The Picture of Dorian Gray Book Review

Oscar Wildes  only novel The Picture of Dorian Gray (1891) is a classic instance of the aestheticism of the late 19th centurys  Ã¢â‚¬â€¹Ã¢â‚¬â€¹English literature. The maxim of aestheticism art for arts sake is reflected in the opening of the novel, which specifies arts aim to reveal the art and conceal the artist. For greater emphasis, Wilde defines the artist as free of ethical sympathies and morbidity. Even books are seen as only well written or badly written and not as moral or amoral. Following this prelude on art and beauty, Wilde weaves a  Ã¢â‚¬â€¹plot that explores the issue to its core. The plot of The Picture of Dorian Gray, if seen apart from the wit and epigrams of Lord Henry is serious and, at times, even somber. Dorian Gray is a young and handsome man whose well-off friend Lord Henry takes him to an art-loving painter, Basil Hallward. The painter makes a picture of Dorian Gray, a fascinating piece that makes Dorian wish to stop aging. His wish is fulfilled and the picture starts aging instead of young Dorian. The consequence is a disaster. Oscar Wilde has created an amusing tale that does not end very happily but ends beautifully with our easy-going Lord Henry still chirping. Style and Setting Anyone who has read dramatic fiction (Oscar Wilde in particular) will not find it hard to see the style of the storys narrative as closer to drama than a novel. Wilde is not obsessed with describing settings in detail as a novelist with a constructive bent would be. But the brevity of description is masterfully covered in the warm and witty conversations that fill most of the novel. The epigrams of Lord Henry shoot arrows of gentle satire on different elements of society. Women, America, faithfulness, stupidity, marriage, romance, humanity, and weather are just some of the numerous targets of Wildes criticism, which the readers receive from the sharp but sweet tongue of Lord Henry. The twittering lord is thus made an indelible  character for his ease of expression and his envied indifference. Yet, the author does not rely solely on spoken words to impart his impression. He describes some scenes in words that evoke a vivid image in the readers mind. Perhaps the best of these is Dorian Grays brief journey through the dark and filthy streets that stand in an obtrusive contrast to his luxurious entourage but which also bear a remarkable resemblance to the kind of life he has embraced. Characters in The Picture of Dorian Gray Like his stories and plays, Oscar Wilde does not employ many characters to run the story of his novel. Nearly the entire plot is nucleated around Dorian, Lord Henry, and the artist Basil. Minor characters like the Duchess of Harley serve the purpose of initiating or furthering topics that would ultimately be the butt of Lord Henrys repartees. The character description and motivation are again left mainly to the perceptual capacity of the readers. Wilde is always testing the aesthetics of his readers and the easier you go with his characters disposition, the greater insight you gain. Self-Love and the Vulnerability of Beauty The Picture of Dorian Gray addresses more than one theme. The primary appeal of the subject of beauty, as it appears to eyes, is the main focus of the novel. Wilde reveals the tenderness of self-love, or narcissism, which sometimes fails to find an object outside itself. Dorians beauty, unlike Basils art and Lord Henrys social status, is more vulnerable to decay with time. But it is not this weakness of beauty to age that brings the disaster upon our protagonist. It is the consciousness of the owner of beauty to his own wealth that triggers the boundless fear of perishing--fear that causes his doom. Unlike Lord Henrys ease about his rank, Dorians angst about the ephemeral nature of his beauty is shown as the true enemy of a persons self. The philosophical boundaries of Oscar Wildes The Picture of Dorian Gray are too deep to track to their ends. The novel addresses the issue of self-concept as portrayed in art. Further, it connects a persons emotional response to his/her own image. While Dorian remains young and beautiful, the mere sight of an aging picture of him is unbearably painful. It would be too presumptuous to conclude that The Picture of Dorian Gray is a work of beauty with no moralistic purpose. Wilde was not a moralist (as many of us already know) and within the book, there is not much to emphasize a moral code or right conduct. But the novel, in its covert meaning, is not without a moral lesson. We can easily see that beauty is ephemeral and any attempt to deny this fact is amoral. It brings ruin as shows the case of Dorian Gray.

American Family and Traditions - 6646 Words

COLEGIUL NATIONAL â€Å"RADU GRECEANU† [pic] STUDENT: TEACHER: TÄ‚RÄ‚ÅžILÄ‚ ANCA FLORENTINA POPA LIANA SLATINA 2012 Table of Contents 1. INTRODUCTION 3 2. CHAPTER 1: The American Family 4 2.1 A Definition of the Family 4 2.2 What is it Like to be a Young Person in the United States? 4 2.3 Education 5 2.4 The Effects of Divorce in the United States 6 2.5 Interview with an American Teenager 6 3. CHAPTER 2: American Traditions 8 3.1 Christmas Traditions 8 3.2 The Yellow Ribbon 10 3.3 The Window†¦show more content†¦Children in the US start preschool or nursery school at age four or under, kindergarten at five years of age. Schools provide American children with much more than academic education. More than 80 percent of all students participate in extracurricular activities, such as sports, student newspapers, drama clubs, choral groups and bands. During their leisure time, American kids spend much time watching television, listening to music or playing computer games, but many also have after school jobs. One recent study indicated that nine out of 10 teenagers said they either had a job or would like one. Child labor laws set restrictions on the types of work that youths under 16 years can do. Many youths work part-time on weekends or after school at fast-food restaurants, baby-sit for neighbors, hold delivery jobs or work in stores. Many youths are also involved in community service organizations or are active in church and religious-group activities. Other belong to youth groups such as Girl Scouts or Boy Scouts, were they learn about citizenship, arts, camping and other outdoor activities. Thousands of young Americans volunteer to help take care of the elderly, the handicapped and hospital patients, or help clean up the environment. Even though for most American children and teenagers life today is nearly free of serious conflict, young people are still under many types of stress. Peer pressure, changing family conditions, mobility of families, unemploymentShow MoreRelatedMy Grandfather And My Grandmother Essay1359 Words   |  6 PagesMy American roots are made up of my families traditions and history. I interviewed two family members, my grandfather and my grandmother. Each one brings a different background which made them the best option. American roots are a built by families. Each family has its own traditions and ideals. For my gr andparents, their American roots were built completely different from each other. Family has a major impact on an individual s life, it is the starting point of ones American roots. My American rootsRead MoreThe Namesake, A Winner Of The Pulitzer Prize, By Jhumpa Lahiri1026 Words   |  5 Pagesof culture clash between American and Indian tradition. 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Gareth Stokes’s work Robots vs Humans Free Essays

AI and the Future of the Workplace talks about the possibilities of replacing human workers with robots in the near future. Robotisation has the capability to affect employment, reallocate human workers and change business operations as it will play an increasing role in the workplace, making unemployment a big concern in the industry. Businesses need to introduce smaller AI components on their system to be able to get used to the technology and be able to adapt to newer AIs easily. We will write a custom essay sample on Gareth Stokes’s work Robots vs Humans? or any similar topic only for you Order Now Stokes said that AI is an opportunity to explore new things and it should not be feared. He also said that it will generate more opportunities for employment as workers are needed to coach, assist and enhance the thriving AI and machine learning industries. On the other hand, businesses may experience cultural change after the implantation of robots in the workplace and it requires strong leadership to make AI an opportunity and not a threat. Reskilling of employees is also needed for businesses to be able to keep up with technology’s demands and focus their employees on skills that cannot be done by computers. AI’s effect and role on the business industry depends on how people perceive, welcome and approach its idea. Based on what I’ve read I was thinking that AI is not designed with the idea of replacing human workers. Stokes said that robotisation will play a major role in the workplace and we all know that the workplace is composed of human workers. If robotisation is to be embedded in the industry, there is a high possibility of rise in unemployment. Having robots in the system is an edge for businesses since AI has these capabilities that are beyond the human capacity. With the existence of robots, human workers will be of little to no use for businesses and it can result to unemployment. Stokes also said that AI is not something to automatically fear and I am quite disturbed with this remark because it has this tone of finality and I believe that you cannot simply say that AI should not be feared. AI may be an opportunity for businesses to thrive but for employees, AI means being replaced by technology and eventually, unemployment. How to cite Gareth Stokes’s work Robots vs Humans?, Papers

Stress Fracture Of Lumbar Spine Sample †MyAssignmenthelp.com

Question: Discuss about the Stress Fracture Of Lumbar Spine. Answer: Introduction This report is based on football-associated stress fracture of the lumbar spine. Football is the worlds most loved game. Its history dates back to more than a century. It began in the year 1863 when Football Association of England was first formed. It was the first body formed to govern the sports (Walvin, 2014). The earliest form of the game dates back to the Han dynasty of China. Another variation of the game originated in the Far East as well and this was named the Kemari, which originated in Japan. Moreover, the Greeks and the Romans also had other variations to this game like the Episkryos and the Harpastum, respectively (Ryynnen, 2015). In 1882, the football related associations in England collaborated to create the International Football Association Board (IFAB). FIFA was established in the year 1904 in Paris and it became a part of IFAB in the year 1913. At that time, FIFA had only 7 countries as its members but now it consists of 208 members. This game involves the participa tion of 11 players from each team. The players need to maneuver the ball and hit it inside the oppositions goal post. This game involves the skillful use of ones legs and feet and as a result, it is associated with a number of injuries (Sorez, 2012). Knee injuries are the most common form of injuries associated with football. Knee injuries involve the anterior cruciate ligament and the medial collateral ligament injuries. Others include ankle sprains, torn meniscus, torn hamstrings, muscle contusions, shoulder dislocation and shoulder tendinitis (Whittaker et al., 2015). Stress fracture of the lumbar spine is another type of injury associated with football. This is medically known as Spondylolysis. It is caused due to overuse of ones lower back. It is the most common form of injury to the lower back associated with various games including football. It occurs in the lowermost lumbar vertebra named L5 (Kobayashi et al., 2013). The L5 is situated at the junction of the lumbar spine and the pelvis. This part remains highly stresses during various physical activities, which involves continuous moving and maneuvering. Heavy muscular forces can cause the micro fractures in the lumbar spine. It involves severe pain in the lower back. Thi s causes restrictions in the movement of the player (Murthy, 2012). This report describes the football-associated injury termed Spondylolysis or stress fracture of lumbar spine. Firstly, it provides a classification of stress fractures, diagnosis and the causes associated with this type of injury. Secondly, it provides treatment and rehabilitation programs. Lastly, it provides a prevention measures associated with the injury. Classification and Diagnosis Lumbar spine provides support and stability to the upper part of the body. An injury to this region changes the lumbar vertebral shape, thereby affecting the posture. Spondylolysis can be classified as (1) dysplastic, which is usually congenital, (2) degenerative, which is generally associated with old age, (3) isthmic, which is usually associated with sports, (4) traumatic, which occurs following previous fractures and (5) pathologic, which involves either a localized or generalized disease of the bone. Dysplastic spondylolysis occurs as a result of abnormalities present in the pper scarum or it involves the arch present in the L5. Isthmic Spondylolysis occurs because of lesion development, which can cause a lytic-fatige fracture of pars. Degenerative spondylolysis involves instability of the pars segments (Long Whang, 2015). X-Rays are not useful to detect early stages of stress fractures of the lumbar spine. X-rays can only detect them at the late stages when it is beyond treatment. A radiograph helps to identify compression fracture of the vertebra (Cicala et al., 2013). It also helps to determine the height loss of the vertebra, increase in distance between the pedicles, alignment of the vertebra, among others. However, various scanning techniques can be used to diagnose stress fractures. These are magnetic resonance imaging or MRI, Computed Tomography scan or CT-Scan or a simple bone scan. However, Single Photon Emission Computed Tomography or SPECT is superior to both CT and MRI in the detection of Spondylolysis (Patel et al., 2016). SPECT and CT reveals the presence of number of lesions detected in the pars interarticularis. Unilateral spondylolysis involves the presence of increased bone uptake and sclerosis in the contralateral part of the pars interarticularis as observed by SPECT and CT. Advanc ed stages result in the presence of sclerosis and pedicle, lamina overgrowth. MRI reveals the presence of bony edema, which helps to determine the age of the fracture. CT scan helps to determine the bone anatomy like height loss, canal compromise and fragment retropulsion (Elgazzar, 2017). High amount pressure on the lower vertebra can give rise to stress fractures. This results in the formation of tiny cracks in the lower vertebra, particularly the L5 or the fifth lumbar vertebra. This results in lower back pain as a result of rotation, extension and flexion movements. These movements affect the posterior portions of the spinal column, resulting in the formation of micro fractures in the bone (Gellhorn Katz Suri, 2013). It is particularly observed in young sports players. Overextending or overstretching of the lower back can give rise to can give rise to a lot of stress. These are common among weight lifters, gymnasts and footballers (Sasaji, 2016). Overuse of back muscles results in fatigue and results in its inability to absorb shocks. Repetitive shocks can give rise to tiny cracks in the vertebrae. Chronic pain in the lower back is the most common symptom. This may result from compressive or mechanical pain. Spondylolysis can also lead to Spondylolisthesis. This r esults in slippage of one vertebra over the other. The resulting slipped vertebra can put pressure on the spinal canal space, thereby constraining the nerves (Raastad et al., 2015). This pressure can also lead to back, leg and hip pain. It can also result in numbness of the feet. Other factors that can cause stress fractures are the genetic constitution of an individual and osteoporosis. Treatment and Rehabilitation An effective and acute treatment program is needed for players suffering from stress fractures of the lumbar spine. The treatment usually begins after diagnosis and involves advocating of complete rest to the athlete. The player is needed to stop the various routine exercises and any movements that may cause in pain development. If the pain continues after 3 weeks, it means that the player in getting insufficient rest or may need the support of a back brace. Back braces help to maintain the proper positioning of the back in order to speed up the healing process (Lee et al., 2012). Periodic X-Rays are needed to determine if the back is in proper position. If non-surgical treatment does not help to keep the back in proper position, a spinal fusion is recommended. In this procedure, screws and rods are used which helps to keep the vertebra in the proper position alongside the healing process. This in turn helps to stop the motion of a a vertebral segment, thereby reducing the pain (Wu e t al., 2012). However, there are risks involved with this procedure, which involves infection, bleeding, blood vessel injury and poor healing of wounds. Moreover, ibuprofen, which is an inhibitor of inflammation, can be used to heal the pain. Apart from the use of various nonsteroidal anti-inflammatory drugs (NSAIDs), muscle relaxants can also be used (Patrick, Emanski Knaub, 2016). Medications directed against narcotic pain and against neuropathic pain (like tricyclic antidepressants) can be used. Other techniques for treatment of pain involve analgesic patches, which are localized and intercostals nerve blocks or transcutaneous nerve stimulatory units (Wong McGirt, 2013). The rehabilitation program begins after the treatment phase. If the pain subsides and the player is able to perform daily activities, the athlete is allowed to progress to the rehabilitation program. The rehabilitation program begins in the second month after diagnosis, since the first month is associated with various surgical or non-surgical treatments. The rehabilitation program is characterized by physical therapy with the help of an experienced physiotherapist (Peterson Renstrom, 2016). Physical therapy involves various exercises like the lumbar and core exercises for stabilization, core exercises for generation of core stability, exercises that strengthen the legs and the hips. Other exercises involve postural taping, soft tissue massaging and Spinal Proprioceptive Extension Exercise Dynamic Program (SPEED) (Papa, 2012). Moreover, these exercises also help to make the muscles flexible to allow proper movement. Exercise programs can also be designed to enable the players to prac tice at home. Activities that provide lesser amounts of stress can be introduced. However, activities that put a lot of pressure on the spine like rotation or back arching is avoided. If the player is able to carry out the physical therapy and the low stress activities, then they are allowed to progress to the third phase of the rehabilitation program. The third phase involves continuation of the exercise programs both at home and at the rehabilitation center. Physical therapy exercises are also increased. The players are allowed to return to their sports, however, it is a gradual and progressive return, which involves a set of parameters and guidelines set out by the medical practitioner or physiotherapist (Garet et al., 2013). However, participation in the sport should not be carried out on consecutive days. On reoccurrence of pain, the activities and exercises are needed to be reduced. Prevention measures Stress fracture of the lumbar spine usually causes lower back pain that occurs on one side of the back rather than the center (Lotz, Fields Liebenberg, 2013). It occurs as a mild pain in the beginning and progresses to chronic pain following activities like jumping, running, kicking, among others. This is mostly common among young athletes like footballers. However, various preventative measures can be followed to avoid the development of stress fractures in the lumbar spine. These are: Maintenance of good physical condition during off seasons and not overexerting oneself during the peak seasons. Activities that require high impact like jumping, running, rotation and back arching should be increased in a gradual manner. It is necessary to take day-offs in order to give rest to the back muscles and the body as a whole. It is necessary to avoid participating in the sport throughout the year, as it puts a lot of pressure on the muscles and the vertebra. Maintenance of good flexibility of the hip and hamstring flexors, strength of the core, lumbar and abdominal muscles. Female athletes should be checked to determine their bone mass density (BMD), which helps to understand the quality of their bone health (Chen, Tenforde Fredericson, 2013). Calcium and Vitamin D supplementation can also help to prevent stress fracture. Orthotic devices can prevent lower back stress fractures by shock absorptions. Insoles that absorb shocks are very effective in preventing stress fractures (Kendall, Bird Azari, 2014). Other injuries like those in the ankle can be prevented by the use of balance boards and proprioceptive training. Strengthening programs help to reduce hamstring, knee and groin sprains. Conclusion Lumbar spine generally provides support to the entire upper part of the body. However, continuous strains on the lower vertebra, particularly L5 can give rise to the generation of small fractures. Continuous pressure through various exercises and continuous tournaments lead to the development of a large number of these micro fractures, which eventually results in inability of the vertebrae to absorb shocks causing pain of the lower back. Initially mild pain ensues, which then progresses to severe and chronic pain. The player is unable to carry out normal movements and carry on with their game. With the appearance of mild pain, it is essential for the player to consult a medical practitioner for proper diagnosis. Diagnosis generally involves X-rays, radiographs, MRI, CT scan, SPECT, among others. Such stress fractures of the lumbar spine are generally observed among the athletes who perform gymnastics, weight lifting, footballers, and cricketers, among others. Such athletes require ro tation and arching of their backs continuously. Various treatments that are available involve proper rest and consumption of NSAIDs, in order to relieve the pain. However, back braces can also be used. Surgical treatments involve the spinal fusion technique, which employs screws and rods to keep the vertebra in proper position, preventing it from slipping. Following treatment, the athlete is advised to participate in a rehabilitation program, which involves physical therapy under the guidance of an experienced physiotherapist. Moreover, it involves various exercises that help to stabilize and strengthen the core, lumbar, legs and hip muscles. Other techniques are postural taping, soft tissue massage and SPEED programs. However, it is necessary for the athletes to prevent such occurrence of stress fractures in the future. The athlete needs to provide sufficient rest to his/her body in order to prevent stress. Nutritional supplementations like calcium and vitamin D helps to prevent st ress fractures of the lumbar spine. Moreover, orthotic devices are also known to prevent development of stress fractures in the future. Thus, from the above discussions it can be concluded that stress fractures if severe and not diagnosed properly can give rise to serious consequences and affect the ability of the athlete to participate in the game in the future. References Chen, Y. T., Tenforde, A. S., Fredericson, M. (2013). Update on stress fractures in female athletes: epidemiology, treatment, and prevention.Current reviews in musculoskeletal medicine,6(2), 173-181. Cicala, D., Briganti, F., Casale, L., Rossi, C., Cagini, L., Cesarano, E., Giganti, M. (2013). Atraumatic vertebral compression fractures: differential diagnosis between benign osteoporotic and malignant fractures by MRI.Musculoskeletal surgery,97(2), 169-179. Elgazzar, A. H. (2017). Diagnosis of Traumatic Disorders. InOrthopedic Nuclear Medicine(pp. 147-189). Springer, Cham. Garet, M., Reiman, M. P., Mathers, J., Sylvain, J. (2013). Nonoperative treatment in lumbar spondylolysis and spondylolisthesis: a systematic review.Sports health,5(3), 225-232. Gellhorn, A. C., Katz, J. N., Suri, P. (2013). Osteoarthritis of the spine: the facet joints.Nature Reviews Rheumatology,9(4), 216-224. Kendall, J. C., Bird, A. R., Azari, M. F. (2014). Foot posture, leg length discrepancy and low back painTheir relationship and clinical management using foot orthosesAn overview.The Foot,24(2), 75-80. Kobayashi, A., Kobayashi, T., Kato, K., Higuchi, H., Takagishi, K. (2013). Diagnosis of radiographically occult lumbar spondylolysis in young athletes by magnetic resonance imaging.The American journal of sports medicine,41(1), 169-176. Lee, H. M., Park, S. Y., Lee, S. H., Suh, S. W., Hong, J. Y. (2012). Comparative analysis of clinical outcomes in patients with osteoporotic vertebral compression fractures (OVCFs): conservative treatment versus balloon kyphoplasty.The Spine Journal,12(11), 998-1005. Long III, W. D., Whang, P. G. (2014). Adult Spondylolysis and Isthmic Spondylolisthesis. InSpine Surgery Basics(pp. 229-238). Springer Berlin Heidelberg. Lotz, J. C., Fields, A. J., Liebenberg, E. C. (2013). The role of the vertebral end plate in low back pain.Global spine journal,3(03), 153-164. Murthy, N. S. (2012). Imaging of stress fractures of the spine.Radiologic clinics of North America,50(4), 799-821. Papa, J. A. (2012). Conservative management of a lumbar compression fracture in an osteoporotic patient: a case report.The Journal of the Canadian Chiropractic Association,56(1), 29. Patel, N. D., Broderick, D. F., Burns, J., Deshmukh, T. K., Fries, I. B., Harvey, H. B., OToole, J. E. (2016). ACR appropriateness criteria low back pain.Journal of the American College of Radiology,13(9), 1069-1078. Patrick, N., Emanski, E., Knaub, M. A. (2016). Acute and chronic low back pain.Medical Clinics of North America,100(1), 169-181. Peterson, L., Renstrom, P. A. (2016).Sports Injuries: Prevention, Treatment and Rehabilitation. CRC Press. Raastad, J., Reiman, M., Coeytaux, R., Ledbetter, L., Goode, A. P. (2015, April). The association between lumbar spine radiographic features and low back pain: A systematic review and meta-analysis. InSeminars in arthritis and rheumatism(Vol. 44, No. 5, pp. 571-585). WB Saunders. Ryynnen, J. (2015).The influence of match events on injury incidence during male World Cup football-Epidemiological studies and video analysis of injuries. Sasaji, T., Imaizumi, H., Takano, H., Saitoh, H., Murakami, T., Kanabuchi, R., Sekiya, M. (2016). Sacral Stress Fracture following the Bone Union of Lumbar Spondylolysis.Case reports in medicine,2016. Sorez, J. (2012). A History of Football in Paris: Challenges Faced by Sport Practised within a Capital City (18901940).The International Journal of the History of Sport,29(8), 1125-1140. Walvin, J. (2014).The people's game: the history of football revisited. Random House. Whittaker, J. L., Woodhouse, L. J., Nettel-Aguirre, A., Emery, C. A. (2015). Outcomes associated with early post-traumatic osteoarthritis and other negative health consequences 310 years following knee joint injury in youth sport.Osteoarthritis and cartilage,23(7), 1122-1129. Wong, C. C., McGirt, M. J. (2013). Vertebral compression fractures: a review of current management and multimodal therapy.Journal of multidisciplinary healthcare,6, 205. Wu, Z. X., Gong, F. T., Liu, L., Ma, Z. S., Zhang, Y., Zhao, X., Sang, H. X. (2012). A comparative study on screw loosening in osteoporotic lumbar spine fusion between expandable and conventional pedicle screws.Archives of orthopaedic and trauma surgery,132(4), 471-476.

A Scholar Word Essay Example

A Scholar Word Essay Reflection involves a deep self actualization which contains only the truth. It would only be hypocrisy on my part if I’m going to state that â€Å"being a part of this community service as a way of giving back to the public what they deserve is a privilege for me. † I would be brave and honest enough to tell you that this community service tasked to the scholars is not quite helpful for us.I admit that there are pros and cons of the activity but the negative side outweighs the positive. Voter’s education is a big help for the community especially for the first time voters. We couldn’t deny the fact that this community service including the youth profiling are beneficial for our society. But, just like what I’ve said, there are negative sides of the story First, instead of having our summer job and summer class or even on-the-job training, we are subdued by this activity.The community service will only take a few days or even hours of our time, but that could also be a time for rest after work or after school or even a time for our family after a long strenuous semester. But that won’t happen because any of the statement above is not an excuse of not taking the community service. We are scholars, not robots, we also have a life to live. Second, the reason why we are in this scholarship is because somehow, some of us could not afford the whole tuition of the program we choose, for short we are not that rich.That’s why spending even a few peso on our account without it being reimbursed is a big deal for us. Third, the way of grouping us is somehow a good thing because it teaches us how to socialize with different kinds of people but the problem is throwing these group of people in an unknown barangay that even the Google map could not locate is like throwing scavengers in a remote island waiting to be devoured by sharks and beasts.And lastly, the common issue of all is that maybe the reason why we haven’t hu gged this community service unlike the other activities that we greatly enjoyed is that the foundation of this activity, starting from the orientation, is not right, not proper. Being yelled at the very first meeting is not a great way to start anything and it’s a bit degrading for us scholars. We represent the youth that’s why we a loud and active, and restraining us from doing so is improper and unprofessional especially if ot all of us are involve in the noisy rumble. This is an intellectual criticism, hope you won’t take it personally. I am not speaking in the voice of a selfish, self righteous and self centered scholar, but rather I’m speaking in the voice of those unuttered cries of the scholars who are afraid to speak out what’s in their mind with the fear of losing their scholarship. This is not a complain, this is a reflection.

Research Needed for Alzheimers Disease essays

Research Needed for Alzheimer's Disease essays Alzheimer's Disorder (AD) is a progressive brain disease which primarily affects older people. The parts of the brain that control memory, language, and even thought gradually decline (ADEAR, date). While AD develops most commonly after the age of sixty, there is a rarer form that can develop at a younger age. Experts estimate that between the ages of 65 and 75, 5% of the population may have AD. By age 85, however, nearly half may have AD (ADEAR, date). In spite of how common the disease is among people who have lived a very long time, AD is not considered a normal consequence of age but a disease process to which one becomes more While scientists are just beginning to untangle the mystery of exactly what causes AD, some facts have been established. The disease was first noticed by a German doctor, Alois Alzheimer. Although doctors had noted dementia in elderly people, Dr. Alzheimer examined the brain of a woman who had died of an unusual mental illness. In the brain he found clumps of matter that should have not been there (called amyloid plaques). He also found tangled figers, now called neurofrbrillary fibers (ADEAR, date). The presence of these formations are definitive signs of Alzheimer's, but since currently they can only be detected after death, their presence is not Since Dr. Alzheimer's first discovery, researchers have noted other brain changes in those with AD. Nerve cells that support memory and cognition die off, and the brains show diminished quantities of the neurotransmitters that allow neurons to communicate with each other (ADEAR, date). Researchers assume that the combination of diminished neurotransmitters and loss of nerve cells contribute to the disruption of thought processes in the patient with AD. The role of neurofrbrillary fiber bundles and the presence of amyloid plaque is less clear. The effects of Alzheimer's Disease on society ...

Does lupron provide a better outcome for first line treatment in Thesis

Does lupron provide a better outcome for first line treatment in advanced prostate cancer - Thesis Example Introduction In spite of all the dramatic advances in the understanding of disease processes, medical science and medical technologies, cancer remains a disease of special focus in present times, because of the challenges that it continues to pose as a life threatening disease. Most of the cancer diseases tend to be chronic, with a strong possibility of causing the death of the individual, yet take years to develop, before presenting any signs and symptoms of the disease. There is limited clarity in how cancer diseases develop and the exact etiology of most cancers is yet to be clearly defined. Treatment of many cancers involves employing repeated interventions and multiple approaches at the different stages of the disease. The treatment strategy in many of the cancer diseases is more of hope at curing the patients and with the more definite aim of managing the disease, so as to extend the period of survival, with better quality of life in terms of comfort alertness, and function. In the United States of America (U.S.A) the disease of cancer continues to remain a major concern in society, as many of the modern diseases show a declining trend, bit in the case of the cancer diseases more people are developing the disease over the few decades (Grenwald, 2002). Prostate cancer is a cancer that affects the male gender only. Widespread use of prostate-specific antigen (PSA) screening is used in U.S.A. to detect prostate cancer, while it is clinically localized, so that the many forms of interventions available for the early stage of prostate cancer may be used in an attempt to cure the patient of the disease. Yet, many patients still present themselves in hospitals demonstrating evidence of progressive, metastatic, or recurrent prostate cancer. Limited effective treatment strategies are possible in advanced prostate cancer, and in many of the cases, the disease progresses to the palliative care stage. In 2008, 28,660 men died in the U.S.A from prostate cancer, making it the most common malignant disease in men. This statistic points to the need for identifying the treatment strategies that provide the best outcomes for advanced prostate cancer in men, so as to improve the outcome for these patients (Phillips & Petrylak, 2010). 2. Literature Review 2.1. Development of Prostrate Cancer Every cancer has been found to be associated or suspected of association with risk factors. In the case of prostate cancer, evidence from studies have shown that the environmental exposures and dietary nutrients, family history, advancement in age and hormonal factors in conjunction act to alter the genetic architecture in the individual, supporting the proliferation of prostate cancer cells. The use of epidemiological data emphasizes the possibility of environmental factors in the development of prostate cancer. For example, Asians as a racial group are less prone to prostate cancer, for which their poor hygiene and diet are believed to be the cause. This can be s een from Asian migrants in the

Public Sector Accounting Essay Example | Topics and Well Written Essays - 2000 words

Public Sector Accounting - Essay Example In order to demonstrate the differences an organization from each sector has been taken. The chosen public sector organization is The Royal Mail Holdings Plc and the publicly listed company is Aviva Plc. Royal Mail is a 100% UK Government owned organization involved with the postal services throughout UK, Ireland and Europe (Royal Mail Group Ltd, 2012). Aviva is a UK-based largest global insurance company and world’s sixth largest (Aviva, 2012). The third section demonstrates the effect of the objectives of public sector accounting and the rules and regulations governing public sector organizations in the form of differences and similarities in the format, style and accounting policies in the annual reports of Royal Mail and Aviva. The fourth section deals with the role of auditor in both the organizations. Overall the four sections in the project analyze if the differences between the two sectors’ accounting practices are prominent or if there is any reduction in their differing frameworks. Accounting Needs & Objectives The public sector encompasses all the organizations that are not owned or operated by private organizations. The organizations’ control lies in the hands of the Government, either national or local. Public sector in UK is diverse and includes nationalized industries, Government agencies and public service organizations. Nationalized industries are commercial organizations that sell goods to market but are mainly governed by government-appointed boards and ministers rather than markets or shareholders. The surplus generated from their operations is expected to enable replacement investment. The government agencies include welfare services and taxation body. These agencies are required to deliver satisfactory services to the claimants and taxpayers by using the resources at their disposal. The public service organization provides health, policing and defence services on behalf of central or local government. These services ar e financed from the tax revenues and therefore not charged from the public directly. Unlike the private sector with a clear objective of profit-making, the public sector has a complex mix of objectives and demands. It is primarily concerned with serving the general public. The importance of public sector accounting and disclosures, and their differences from the private sector accounting is due to the following reasons: Lack of making Profits: The ultimate objective of a private organization if profit making and/or creating wealth for its shareholders. However a public sector organization’s objective is not considered profit making. Sometimes this suggests the possibility of inefficient use of resources or absence of commitment to provide good service to the clients due to no profit-making. Lack of Competition: A private sector organization usually operates in an industry with direct competitors and subject to regulations by oversight regulatory bodies. Contrary to this the p ublic sector organizations are not subject to disciplines of the markets and lack the comparability with other firms. Public Interest: There is a corporate governance framework and audit rules for private organizat

Temperance and The Alcohol Prohibition Essay Example | Topics and Well Written Essays - 1000 words

Temperance and The Alcohol Prohibition - Essay Example In the 1830s and 1840s, temperance movement was gained immense momentum and many people supported it. However, the movement suffered setback during the American Civil War. Both sides in the war were relying on alcohol duty to fund their battles. As a result, numerous states stopped alcohol prohibition (Gately 74). It is worth noting that this was reversed after the war as more and more states and counties embarked to become â€Å"dry†. In the postwar period, the movement grew to become a significant mass movement and was instrumental in encouraging alcohol abstinence. The movement engaged in building alternatives to replace the roles of public bars; the Independent Order of Rechabites was established as a friendly society where no meetings were held in public bars (Tracy 29). Also, there was a movement that introduced temperance fountains around America in order to make sure people have reliably safe drinking water instead of having to go to a saloon and various coffee palaces and temperance halls so as to replace bars. The temperance movement in the United States got a boost as advocacy for alcohol abstinence were emerging in other countries and so its emphasis spreading internationally. For example, the Salvation Army was established in 1864 in London and emphasized heavily on the abstinence from alcohol (Heron 30). A number of local and international prohibitionist groups were created in the postwar period and were instrumental in advocating for alcohol prohibition.

Millennium Development Goals (MDGs)

Millennium Development Goals (MDGs) The Millennium Development Goals (MDG’s) This lesson deals with the Millennium Development Goals (MDGs). MDGs are derived from earlier development targets. The MDG’s originated from the United Nations Millennium Declaration, was the main outcome of the Millennium Summit. The Declaration asserted that every individual has dignity; therefore, the right to freedom, equality, a basic standard of living. MDG’s emphasized the role of developed countries in aiding developing countries, as outlined in Goal Eight, which sets objectives and targets for developed countries to achieve a global partnership for development ________________________________________________________________________________ Objectives After going through this lesson, you should be able to: describe the millennium development goals-(MDGs) Focus on three major areas for improvement. ________________________________________________________________________________________ 7.1Â  Introduction It is not the United Nations that has to achieve millennium development goals; they have to be achieved by every country, by the joint efforts of government and people. The millennium declaration promises people from the dehumanising conditions of extreme poverty, make the right to development a success and reality for everyone. Each goal is easy to understand and implement. The Millennium Development Goals (MDG’s) are the world’s biggest promise – a global agreement through collaborative action. Any happening in one country undoubtedly affects those who live in other countries. We need to have a safe and secure world unless we react all against poverty, injustice and inequality. We can eradicate poverty, since we have the resources, and know how. Let us make best of opportunity. One World One Hope: to achieve our global commitments and vision of the Millennium Development Goals targets by 2015. ________________________________________________________________________________________ 7.3 THE MILLENNIUM DEVELOPMENT GOALS-(MDG’s) The Millennium Development Goals (MDG’s) are the most broadly supported, comprehensive and specific development goals the world has ever agreed upon. These eight time-bound goals provide concrete, numerical benchmarks for tackling extreme poverty in its many dimensions. They include goals and targets on income, poverty, hunger, maternal and child mortality, disease, inadequate shelter, gender inequality, environmental degradation and the Global Partnership for Development. Goal 1: Eradicate extreme poverty and hunger Targets Target 1a: Reduce by half the proportion of people living on less than a dollar a day Target 1b: Achieve full and productive employment and decent work for all, including women and young people Target 1c: Reduce by half the proportion of people who suffer from hunger Goal 2: Achieve universal primary education Targets Target 2a: Ensure that all boys and girls complete a full course of primary schooling Goal 3: Promote gender equality and empower women Target 3a: Eliminate gender disparity in primary and secondary education preferably by 2005, and at all levels by 2015 Goal 4: Reduce child mortality Targets Target 4a: Reduce by two thirds the mortality rate among children under five Goal 5: Improve maternal health Indicators Target 5a: Reduce by three quarters the maternal mortality ratio Target 5b: Achieve, by 2015, universal access to reproductive health Goal 6: Combat HIV/AIDS, malaria and other diseases Targets Target 6a: Halt and begin to reverse the spread of HIV/AIDS Target 6b: Achieve, by 2010, universal access to treatment for HIV/AIDS for all those who need it Goal 7: Ensure environmental sustainability Targets Target 7a: Integrate the principles of sustainable development into country policies and programmes; reverse loss of environmental resources. Target 7b: Reduce biodiversity loss, achieving, by 2010, a significant reduction in the rate of loss. Target 7a and 7b Indicators: Target 7c: Reduce by half the proportion of people without sustainable access to safe drinking water and basic sanitation Goal 8: A global partnership for developments Target 8a: Develop further an open, rule-based, predictable, non-discriminatory trading and financial system Includes a commitment to good governance, development and poverty reduction; both nationally and internationally. Target 8b: Address the special needs of the least developed countries Includes tariff and quota free access for the least developed countries exports; enhanced programme of debt relief for heavily indebted poor countries (HIPC) and cancellation of official bilateral debt; and more generous ODA for countries committed to poverty reduction. Target 8c: Address the special needs of landlocked developing countries and Small Island developing States through the Programme of Action for the Sustainable Development of Small Island Developing States and the outcome of the twenty-second special session of the General Assembly. Target 8d: Deal comprehensively with the debt problems of developing countries through national and international measures in order to make debt sustainable in the long term. _______________________________________________________________________________________ Summing Up: The Millennium Development Goals (MDGs), endorsed by governments at the United Nations in September 2000, aimed to improve human well-being by reducing poverty, hunger, child and maternal mortality, ensuring education for all, controlling and managing diseases, tackling gender disparity, ensuring sustainable development and pursuing global partnerships. This would help to bring underdeveloped and developing nations on the next level of progress.

A Man with a Vision :: essays research papers

My search began with personal interest about a man by the name of Howard Coffin. I knew him as the founder of Pirates of the Spanish Main, a local organization that he established in 1931. His purpose in founding the club was to welcome dignitaries, promote the Golden Isles, and aid the community. As a member of the club today, I thought it might be interesting to trace the roots back to the founder. Little did I know, Mr. Coffin was much more than just the founder of a club. He was also a man with a vision, who made huge strides in developing much of the Golden Isles.   Ã‚  Ã‚  Ã‚  Ã‚  Mr. Coffin was born in 1873 and grew up on an Ohio farm, and in Ann Harbor, Michigan. He first discovered one of his visions while attending the University of Michigan. His vision was somehow to produce a low cost car, which would sell for less than a thousand dollars and that would attract a mass market. In 1902, Howard Coffin went to work for the Old Motor Works of Detroit, where he began his phenomenal career as an automobile builder. After the Olds Company decided to stay with their expensive car, he worked at other companies until he was finally able to achieve his dream. With the financial support of the Hudson Department Stores of Detroit, he invented the Hudson Car. The car was the first model of a four-cylinder roadster that sold for about $900.   Ã‚  Ã‚  Ã‚  Ã‚  The first visit that Mr. Coffin made to the coast of Georgia was in 1910 to attend the Savannah Road Race. Early automobile manufacturers liked to watch their cars perform, but also they made it a vacation trip. While attending the races and enjoying their vacation, Mr. and Mrs. Coffin fell in love with the beauty and history of the Golden Isles of the Georgia coast. Since Mr. Coffin was well able to afford just about anything he wanted, he and his wife decided to purchase the 20,000 acres that made up Sapelo Island. They would have a place to vacation, a wonderful place to entertain, and a reason to return to the Georgia coast.   Ã‚  Ã‚  Ã‚  Ã‚  Howard Coffin’s real importance to Golden Isles history was in the vision that he had for development with the ongoing process of automobile roads. After the end of World War I, the sales of automobiles far surpassed the condition of roads for their travel.

Advantages and Disadvantages of a Multi-Racial Society Essay

Nowadays 99% of the modern world countries have become a multiracial society, whether it is relative to their language, religion , culture, or traditions . Also universities , schools and other societies have become multiracial, it is not necessary for the whole country . And today with all aspects of economical, social and other types of growth , it is distinguishably linked to the globalization and the immigration of people to other countries, which has become more and more common . But can a multiracial community exist with no problems attached ? A multiracial society is very rich in culture heritage , where you get the opportunity to learn about other cultures. A multi-racial society is also a multi-linguist society so people living in such societies benefit from the richness of languages and are thus able to speak different languages , there is also a wide variety of traditions, customs and festivals that are being carried out in such countries. In addition with the fusion of cultures food becomes national, people are able to eat a wider variety of food, learning to prepare them in different ways, even celebrations of festivals become national. In addition a multi-racial society teaches people how to respect and understand the religion and cultures of others. Therefore this leads to tolerance. Moreover multi nationality makes the country more dynamic because there are people who come from different places and this can help to develop new ideas about how to make our lives better. In these multi-racial societies very often there are misunderstandings, which lead to conflict . Fanaticism is another factor, which creates conflicts in a multi-racial society. These conflicts and divisions between people is further increased by politicians who practice racial and ethnic politics, only to obtain votes. Fanaticism also encourages people in becoming racist which then leads to intolerance and misunderstandings. Not to mention that sometimes some religions in some societies get stereotyped in an insulting way, which creates clashes between two cultures or more . To conclude I will say that peace remains very fragile, it can break at any time. So we should not let anyone gamble with it. We should neither allow ourselves to be manipulated by the governments nor the people in power.

Heat of Formation Worked Example Problem

Heat of Formation Worked Example Problem Heat of formation is the enthalpy change that occurs when a pure substance forms from its elements under conditions of constant pressure. These are worked example problems calculating the heat of formation. Review The symbol for the standard heat of formation (also known as the standard enthalpy of formation) is ΔHf or ΔHf ° where: Δ indicates a change H indicates enthalpy, which is only measured as a change, not as an instantaneous value  ° indicates a thermal energy (heat or temperature) f means formed or that a compound is being formed from its component elements You may wish to review the Laws of Thermochemistry and endothermic and exothermic reactions before you begin. Tables are available for heats of formation of common compounds and ions in aqueous solution. Remember, heat of formation will tell you whether heat was absorbed or released and the quantity of heat. Problem 1 Calculate ΔH for the following reaction: 8 Al(s) 3 Fe3O4(s) → 4 Al2O3(s) 9 Fe(s) Solution ΔH for a reaction is equal to the sum of the heats of formation of the product compounds minus the sum of the heats of formation of the reactant compounds: ΔH ÃŽ £ ΔHf products - ÃŽ £ ΔHf reactants Omitting terms for the elements, the equation becomes: ΔH 4 ΔHf Al2O3(s) - 3 ΔHf Fe3O4(s) The values for ΔHf may be found in the Heats of Formation of Compounds table. Plugging in these numbers: ΔH 4(-1669.8 kJ) - 3(-1120.9 kJ) ΔH -3316.5 kJ Answer ΔH -3316.5 kJ Problem 2 Calculate ΔH for the ionization of hydrogen bromide: HBr(g) → H(aq) Br-(aq) Solution ΔH for a reaction is equal to the sum of the heats of formation of the product compounds minus the sum of the heats of formation of the reactant compounds: ΔH ÃŽ £ ΔHf  products - ÃŽ £ ΔHf  reactants Remember, the heat of formation of H  is zero. The equation becomes: ΔH ΔHf  Br-(aq) - ΔHf  HBr(g) The values for ΔHf  may be found in the Heats of Formation of Compounds of Ions  table. Plugging in these numbers: ΔH -120.9 kJ - (-36.2 kJ) ΔH -120.9 kJ 36.2 kJ ΔH -84.7 kJ Answer ΔH -84.7 kJ

Westnile Disease essays

Westnile Disease essays About the Virus, the Disease, and Its Spread West Nile virus is spread by the bite of an infected mosquito, and can infect people, horses, many types of birds, and some other animals. Most people who become infected with West Nile virus will have either no symptoms or only mild ones. However, on rare occasions, West Nile virus infection can result in severe and sometimes fatal illnesses. There is no evidence to suggest that West Nile virus can be spread from person to person or from animal to person. Overview of West Nile Virus Updated Q: What are West Nile virus, West Nile fever, and West Nile encephalitis? A.West Nile Virus is a flavivirus commonly found in Africa, West Asia, and the Middle East. It is closely related to St. Louis encephalitis virus found in the United States. The virus can infect humans, birds, mosquitoes, horses and some other mammals. West Nile fever is a case of mild disease in people, characterized by flu-like symptoms. West Nile fever typically lasts only a few days and does not appear to cause any long-term health effects. More severe disease due to a person being infected with this virus can be West Nile encephalitis, West Nile meningitis or West Nile meningoencephalitis. Encephalitis refers to an inflammation of the brain, meningitis is an inflammation of the membrane around the brain and the spinal cord, and meningoencephalitis refers to inflammation of the brain and the membrane surrounding it. Q. Where did West Nile virus come from? A. West Nile virus has been commonly found in humans and birds and other vertebrates in Africa, Eastern Europe, West Asia, and the Middle East, but until 1999 had not previously been documented in the Western Hemisphere. It is not known from where the U.S. virus originated, but it is most closely related genetically to strains found in the Middle East. Q. Historically, where has West Nile encephalit...

Intercultur Article Example | Topics and Well Written Essays - 500 words

Intercultur - Article Example These included questions about what type of boss the respondent preferred and what factors describe their ideal job. Findings Among Hofstede’s findings were the conclusion that Asian countries generally have a power-distance, USA and other Western countries are generally individualistic, South American and Asian countries are generally collectivistic, Asian countries are generally highly masculine while Nordic countries are highly feminine. Research Implications/Limitations Hofstede’s methodology and the conclusions drawn from it have been strongly criticized by a number of other sociologists, such as McSweeney (2002); a common criticism is that Hofstede has inferred broad aspects of national cultures from the situationaly specific replies of a handful of questionnaire responses received from the employees of just one company. Value Hofstede’s work seems to be deeply flawed with respect to methodology and as such can only be of limited value to the reader. It would probably be wise for a manager not to base their cross cultural communication upon a work based on such flimsy evidence. While it may be valid to classify individuals as being more individualistic or masculine, attributing cultures with such attribute is just a more subtle form of stereotyping. Hofstede’s study has not produced any great insights about people and their culture but serve merely to confirm existing crude racial and cultural stereotypes for example that Asians are servile toward their despotic leaders, that Americans are individualists, that South Americans are very family oriented people, that Nordic societies are highly liberal and progressive societies where the differences in status between men and women have largely been eliminated while Asians oppress their women and keep them chained in their homes. Design/Methodology/Approach Hall and Hall espouse their theories regarding the differences between

Between Self expression and commercialization - the sixth generation Essay

Between Self expression and commercialization - the sixth generation - Essay Example Many of the Fifth Generation filmmakers also felt this†¦.self-sufficiency and commercialization, and had to reconsider their positions† (13). From an ideology-centered position, the directors were moving toward to a more individual centered stance. Individuals’ well and woe, as the subject, began to occupy the central place more and more in a movie. Referring to this new orientation, Peterson says, â€Å"The so called 5th generation – included Chen Kaige and Zhang Yimou, the filmmakers we now associate with China’s cinematic revival† (Peterson 3). Though they felt the impulse to explore their ‘self’ as a nation, they, unlike the Sixth Generation Film directors, carefully avoid any direct collision with the dominant political culture. Struggle between Self-expression and Commercialization Choosing to follow their own ways posed a number of risks for these film makers in the 1990s. First, they had to depend on private finance, since d epending on the governmental budget necessarily would bind them to follow the political guidance that often appeared to be contradictory to their free self-expressive zeal, as Peisa says, â€Å"For the cinema, the beginning of the 1990’s was, on the one hand a time of ever intensifying commercialism and on the other hand a politically sensitive time.† (13) Also depending on private financing was not that easy since it often was not as sufficient as the governmental allowances were. Second, commercializing posed to be a potential challenge for them. Shifting from the government fund to private sponsorship necessarily demanded a significant return from the making cost. There were challenges too for the self-expressionist film makers of the 1990s. The most common challenge was to win a market that had already been overly saturated with the supply of ideological but cheaply popular movies in that decade. Movies enriched with elegant theme and taste needed to be fully self- expressionist and self exploring in order to be popular among the majority of the moviegoers: a strategy that was bound to go against the political interests and culture of the era. Therefore avoiding the political wrath, these directors â€Å"began, for the first time in China, to realize their movies with private capital and without submitting the work for the censorship approval; hence they had to find alternative ways to show those works† (Gagliardi). In the beginning of the 1990s, one of crucial alternatives for the moviemakers was to enter into international market, as Gagliardi says, â€Å"One of these ways was the international film festival circuit where the movies found positive criticism and foreign producers† (Gagliardi). In spite of the government’s ban and censorship, the Sixth Generation movies that were critically appraised by the West made a massive infiltration into the country through mostly piracy. With the modernization of

Summary about the Rwanda Genocide Essay Example | Topics and Well Written Essays - 500 words

Summary about the Rwanda Genocide - Essay Example The majority called Hutu and the minority the Tutsi. Tutsi held the majority of the political power despite their small population as compared to the Hutu. In 1984, the Germans became the first colonial power in Rwanda. They realized that the Tutsi had light skins, and they were tall. To the Germans, the characteristics resembled Europeans hence they favoured them in issuing responsibilities. The First World War made the Germans lose their colonies including Rwanda (Mamdani, 2001). Belgium took over Rwanda and introduced the identity cards. The Tutsi continued to receive favour from the Belgians, leaving the Hutu behind. the Belgians gave the Tutsi leadership positions which made the majority of the population, the Hutu terribly angry. However, during Rwanda’s’ struggle for independence, the Belgians made the new self-dependent government in the hands of the Hutu. This further increased the tension between the two ethnic communities. In 1994, the year which the genocide took place, President Habyarimana while coming back from Tanzania, was assassinated. A surface-to-air missile shot the presidents plane killing everyone on board. This made the Hutu extremely angry, and within 24 hours of the assassination the slaughter had started. In Kigali, the Hutu blocked the roads and interrogated the road users. They were supposed to produce their identity cards to prove that they were Hutus. The Tutsi were killed instantly. The killings were done by the use of clubs, machete and knives. The Hutu youths who doing the killings called themselves interahamwe, this means those who strike as one. They also went after the government officials who were Tutsi and the Hutu officials who supported the Tutsi (Mamdani, 2001). This included the prime minister. Ten Belgians UN peacekeepers tried to protect the prime minister and were killed in the process. The Tutsi started running towards the hills

Australias Population Distribution and Density Essay Example for Free

Australias Population Distribution and Density Essay The physical environment has determined to some extent, the distribution and density of Australia’s population. Discuss. People do not live evenly spread through the world. Australia is one of the counties that considered has a low population density. This is due to approximately 23 million population were distributed unevenly. Besides the physical environment, there are also a variety of other factors that have actually worked together to distribute in the Australia’s population that cannot be neglected. These included the economic and history factors. The physical environment is one of the well-known factors that affect the distribution and density of Australia’s population. This refers to the landforms, climate, flora and fauna and of course the components including people constantly interact and affect each other. Australia is very famous with its diversity of animals and plants that are able to survive in the harsh and extreme climate such as the marsupials and eucalypts, which had, actually attracts many people to live in this unique land. The climate is rather dry due to the little rainfall, and this caused mass migration of people to other places. Therefore, this results in the different population density in different region. Australia’s economic has also contributed to the distribution and density of its population. This is due to the reliance on maritime trade in the past. The first European settlement was located on the coast. Therefore, most of the industries were attracted to these centres. This provides a variety of job opportunities to the people. Therefore, many people have settled down there. In the early days, coastal shipping was the main transportation to them because the land routes were difficult to construct and take time to cross. The main function of that is to transport commodities to ports for the exportation to all over the world. This has directly influenced many of the employers and they have found that it is easier to attract labour to coastal location, which has also significantly increased the number of population in that region. The most significant point is, Australia is rich with its natural resources such as iron ore and coal. These are mainly exported to all over the world and hence planted many business and investment opportunities. Colonial historical factor tends to affect the distribution and density of Australia’s population too. In the past, the vegetation patterns and agricultural regions are the most significant points. Most of the interior of the country is uninhabitable so people mainly lived on the coast, especially on the east coast where conditions are better. Besides that, most of the major urban cities have developed on the sites that first settled by the European invaders and settlers. The capital city is the main area of dense population while the rural areas are considered as a very low dense populated region in each state and territory. This is because people can easily get food from the coastal area, which has now been adopted to be the city of the state. Australia is meant to be a very sparsely populated country. This is due to the many factors present which actually played a role in it. It includes the physical environment, economic and history factors. However, some statistics show that there is a sudden growth in the distribution and density of Australia’s population since 1990s as people started to migrate into Australia from all over the world. In a nutshell, there will be an ongoing growth in the distribution and density of Australia’s long-term population that will also brings a lot of goods such as financial and social benefits. (575 words)

Hydrogels for Wound Healing Applications

Hydrogels for Wound Healing Applications Abstract This chapter discusses about the hydrogels both natural and synthetic that can be used for wound healing applications. Also it discusses briefly about the various novel techniques that have been developed recently. Keywords: Hydrogels; Chitosan, Antimicrobial; Grafting; Blending; Wound dressing; Wound healing; Gene therapy, Stem cell therapy, Skin Engineering, pH and Thermosensitive polymers. 1 Introduction Healthcare is an essential aspect of human survival. So many biopolymers have generated interest in a number of biomedical applications. Wound management is one such area where management of cuts, ulcers, and sores needs dressings which help in promoting rapid wound healing in order to obtain both functional and cosmetic results. [45] There are different kinds of wound management products: staples or sutures, dressings or bandages, surgical sealants and adhesives, skin substitutes, and other biomaterials. [51] Human skin provides an effective barrier to microbial penetration and subsequent infection. However, once the wound has been developed in this barrier, the infection chances increases. In case of chronic wounds, the colonization and infection potential increases as the result of the presence of avascular eschar which provides an environment for the uninhibited growth of microorganisms. [89] The rate of infection is related to the type of wound, general wound care, and local health of the patient. [88, 90] For avoiding infection, good clinical practices are needed. The management of chronic wounds is a very costly practice and it also places an enormous drain on healthcare resources; studies have calculated the cost of wounds to the NHS to be about  £1bn a year. [166] So for lowering this cost such wound management products are needed that are more economical and effective. Out of all the above wound management products, here in this chapter we will discuss more about the wound dressings that will provide an optimal healing environment to the wound. A dressing is an adjunct used by a person for application to a wound in order to promote healing and/or prevent further harm. It is designed to be in direct contact with the wound, so it is different from the bandage in the manner that bandages are normally used to hold dressing in place. A wound is a break in the epithelial integrity of the skin and may be accompanied by disruption of the structure and function of underlying normal tissue. Wounds can be divided into four categories based on their appearance and stage of healing: Necrotic, sloughing, granulating and epithelializing wounds. [87] Wounds cause discomfort and are more prone to infection and other troublesome complications. [75] Some diseases like diabetes, ischaemia and conditions like malnourishment, ageing, local infection, local tissue damage due to burn leads to delay in wound healing. Infection is a major complication of burn injury and is responsible for 50-75% of hospital deaths. [76] Human skin has one of the greatest capacities to regenerate itself amongst all of the tissues in our body. It constantly replaces old cells with new cells, enabling it to repair itself when damaged. Wound healing is a complex-physiologic process, which consists of three overlapping phases: inflammatory, proliferative and remodeling phases. The normal healing response begins the moment the tissue is injured. As the blood components spill into the site of injury, the platelets come into contact with exposed collagen and other elements of the extracellular matrix. This contact triggers the platelets to release clotting factors as well as essential growth factors. During the inflammation process, neutrophils are the first leukocytes which come at the site of injury to rid it from bacterial contamination. Then, the monocytes and their conversion to macrophages initiate tissue repair by releasing a number of biologically active substances and growth factors that are necessary for the initi ation of tissue formation process. In the third process, fibroblasts proliferate and migrate into the wound space and started the deposition of the loose extracellular matrix. Endothelial cells grow into a wound simultaneously with fibroblasts and undergo angiogenesis. Finally, tissue remodeling takes place to reconstruct the basement membrane by the differentiation of keratinocytes as well as the formation of follicle cells. [43, 49, 50] A scar is an essential part of this natural healing process following any type of damage to the skin. This can occur after a surgical incision or the healing of a wound. As your body makes an effort to close an open wound and protect itself from infection, it replaces injured skin tissue with rapidly generated scar tissue. Scarring is slight when the damaged outer layer of skin is healed by rebuilt tissue. When we damage the thick layer of tissue beneath the skin, rebuilding is more complicated. Our bodies lay down collagen fibers (a protein which is naturally produced by the body) and this usually results in a highly obvious scar. A permanent reminder of the injury is left behind. So, a dressing that can induce scarless healing is needed. Historically, a dressing was usually a piece of material, sometimes cloth, but the use of cobwebs, dung, leaves and honey has also been described. However, modern dressings include gauzes, semipermeable films, low adherent dressings, gels, foams, hydrocolloids, alginates, hydrogels and polysaccharide pastes. Wound dressings are passive, active or interactive. Passive dressings simply provide cover while active or interactive dressings are capable of modifying the physiology of the wound environment. Interactive dressings include hydrocolloids, hydrogels, alginates, foam dressings and antimicrobial dressings. [17, 20, 85] Traditionally dry wound dressings are considered to be good for healing wounds i.e. the wound should be covered with gauze or left open. But it has been observed by Winter [191] that when wound is left open to air without any dressing, a scab i.e. a dry covering covers the wound and decreases the rate of epithelialization. On the other hand, if moist dressing is used in place of dry dressings scab will not form and rate of healing increases as moist dressings provide low oxygen tension which helps in wound healing, these dressings not only keep cells viable which enables them to release growth factors while maintaining contact between them and the healing tissues, but may also modulate or stimulate their proliferation, these dressings decrease the pain at rest, during ambulation and during dressing changes also moist environment allows rapid and efficient delivery of any added antimicrobial agent thus prevent the wound from infection. So, the dressings that create and maintain a mois t environment, however, are now considered to provide the optimal conditions for wound healing. 2 Requirements of an ideal wound care system These characteristics should be present in the ideal wound care system (a) it should be capable of maintaining a high humidity at the wound site, (b) it should be non-toxic, (c) non-allergenic, (d) it can be removed without causing trauma to the wound, (e) it should pe impermeable to bacteria, (f) Thermally insulating, (g) it should be soft to touch, (h) it should allow proper gaseous exchange, (i) it should be free from particulate and toxic product, (j) promote tissue reconstruction processes and (k) it should be cost effective. [20, 165, 177] Out of all the dressings hydrocolloids, alginates and hydrogels each one has its own advantages and limitations but hydrogels are best and have all the characteristics that are needed in an ideal wound dressing. All the above mentioned characteristics can be achieved in hydrogel wound dressings. 3 Hydrogels for Wound Healing Applications Hydrogels are natural or synthetic cross-linked polymers used in a variety of medical and biomedical applications. Hydrogels consist of a matrix of insoluble polymers with up to 96% water content enabling them to donate water molecules to the wound surface and to maintain a moist environment at the wound bed. They are used in the construction of contact lenses, drug-delivery vehicles, wound dressings and as physiological electrodes or sensors. [17] Examples of hydrogel include Aquaform, Intrasite, GranuGel, Nu-Gel, Purilon, Sterigel. These also have the ability to absorb a degree of wound exudate. They transmit moisture vapour and oxygen, but their bacterial and fluid permeability is dependent on the type of secondary dressing used. [20] Hydrogels swell or shrink in aqueous solutions due to the association, dissociation and binding of various ions to polymer chains. These systems may swell in water until an equilibrium state is reached and retain their original shape. The interactions responsible for water sorption by hydrogels include the process of hydration, which is connected to the presence of such chemical groups as -OH, -COOH, -CONH2, -CONH-, and -SO3H and the existence of capillary areas and differences in osmotic pressure. The forces that make hydrogel dissolution impossible are presence of covalent bonds between individual polymer chains, hydrophobic and electrostatic interactions. [46] These are hydrophilic polymer networks which may absorb from 10-20% (an arbitrary lower limit) up to thousands of times their dry weight in water. These may be chemically stable or they may degrade and dissolve. They are called ‘reversible, or ‘physical gels when the networks are held together by molecular entanglements, and/or secondary forces including ionic, H-bonding or hydrophobic forces. [13, 14, 15] Hydrogels are called ‘permanent or ‘chemicalgels when they are covalently-crosslinked networks as shown in 1. Hydrogels can be made by irradiation, freeze-thawing or chemical methods. Out of all the methods, irradiation is considered as a suitable tool for the formation of hydrogels as in this method there is easy control of processing, no need of adding initiators or cross-linkers which are harmful, and have the possibility of formation and sterilization in one step. But as everything has its own advantages and disadvantages this method also has a disadvantage which is hydrogels formed by this method have poor mechanical strength. Nowadays, Freeze thawing technique is generally used to prepare hydrogels having good strength, stability and no crosslinkers and initiators. But the main disadvantage is that the prepared hydrogels have opaque appearance and limited swelling and thermal stability. [120] In comparison to the traditional gauze therapy the application of a hydrogel seems to significantly stimulate wound healing. [11] Various natural and synthetic polymers having good biocompatibility are used to develop hydrogel wound dressing. These polymers include natural polymers such as alginate, chitosan, gelatin and collagen and synthetic polymers such as polyurethane, poly(ethylene glycol), polycaprolactone, poly vinyl pyrrolidone, poly(lactide-co-glycolide), polyacrylonitrile , poly(amino acid), etc. Table 1 below shows different hydrophilic polymers used to synthesize hydrogel matrices. Table 1 Hydrophilic polymers used to synthesize hydrogel matrices. [13] Hydrogels may be classified as homopolymer hydrogels, copolymer hydrogels, multipolymer hydrogels, and interpenetrating polymeric hydrogels. Homopolymer hydrogels are crosslinked networks of one type of hydrophilic monomer unit, whereas copolymer hydrogels are produced by the crosslinking of two comonomer units, one of which must be hydrophilic. Multipolymer hydrogels are produced by the crosslinking of more than three monomers. Finally, interpenetrating polymeric hydrogels are produced by the swelling of a first network in a monomer and the reaction of the latter to form a second intermeshing network structure. [46, 47] Also, it has been shown that the blending of a natural polymer with a synthetic polymer seems to be a good method for obtaining materials having required mechanical and thermal properties in comparison to pure components. It is also a simple method by which suitable shapes such as films, sponges and hydrogels can be obtained easily to realize a variety of biomedical devices. 2 shows healing is faster with the hydrogel dressing than with the gauze dressing. Wound area covered by hydrogel decreases faster with increasing healing period. On the contrary, the wound covered by gauze dressing reduces by only half a percent even after 14 days. [192] 3.1 Natural Hydrogels Natural polymers, such as chitin, chitosan, alginate, collagen, elastin, genipin, gelatin, cellulose etc. have been used for dressing wounds because they play an important role in the healing process. [47] Chitosan is a partially deacetylated form of chitin. Chitin as BeschitinÃ’, Unitika, is also commercially available as dressing in Japan. [28] But as far as chitosan is concerned it is biocompatible, biodegradable, haemostatic, fungistatic [54] and non-toxic and can be successfully used as gels, films, fibres etc. This polymer also show antibacterial properties and possess good wound healing properties. [60, 61, 62] It has many applications as wound dressing, drug delivery device and as scaffold for tissue engineering. [63, 64] Some of the examples of wound dressings are given below which use chitosan as one of the biomaterial. Asymmetric chitosan membranes have been developed by using immersion-precipitation phase-inversion method. [123, 124, 125] These asymmetric chitosan membranes are homogeneous and have porous structure. This membrane was prepared by preheating casted chitosan solution in oven for different time periods for dry phase separation and then immersed in to coagulant tank for wet phase separation and were subsequently freeze-dried. The skin layer acts as the rate controlling barrier for the release of drug and the porous layer provide mechanical support to the skin layer. The water vapor transmission rate, gas permeability, PBS solution absorption, in-vitro degradation, cell culture, bacterial penetration and wound healing test of this dressing were carried out. These membranes are effective in controlling evaporative water loss, showed excellent oxygen permeability and also antibacterial in nature. These are also found to be an urgent hemostat. In another study, silver sulphadiazine was inc orporated as an antimicrobial agent to this asymmetric dressing. The release behaviour of both silver and sulphadiazine ions were studied and found to be significantly different from one another. Silver ions displayed a slow release behavior while sulphadiazine ions exhibited burst effect on first day of the drug release and then slowly tapered off. It is because of the interaction of silver with amino group of chitosan leading to its slow release throughout whereas, as the sulphadiazine ions were free to diffuse through the membrane to reach the wound site thus they showed a burst release. The membranes were further found effective against P. aerugniosa and S. aureus. In one of the papers, novel wound dressings were formed that composed of chitosan film and Minocycline Hydrochloride (MH) and commercial polyurethane film (Tegaderm) as a backing. It is also a useful formulation for the treatment of severe burn wounds. Water vapor and oxygen can permeate the Tegaderm film but water cannot. The tegaderm film support the polymer membrane. [126] In one of the studies, a silver nanocrystalline chitosan (SNC) wound dressing composed of nano-silver and chitosan was constructed by self-assembly and nanotechnology and used for treating deep partial-thickness wounds. In this, sterility and pyrogen testing were performed to ensure biosafety. These dressings promote wound healing and combat infection, and also decrease the risk of silver absorption in comparison with silver sulphadiazine (SSD) dressings. [127] There is also one more method of forming wound dressing composed of chitosan i.e. the formation of polyelectrolyte complex of gum kondagogu (GKG) and chitosan. This complex is formed by the electrostatic interaction between carboxyl group of gum and amine group of chitosan. This method is more advantageous as it avoids the use of organic solvents, chemical crosslinking agents and thus reduces the toxicity and undesirable side effects. In this, diclofenac sodium is used as model drug. The diclofenac loaded complex of gum kondagogu/ chitosan shows drug release which changes with change in pH. The drug release was higher at pH 6.8 as compared to pH 1.2, due to higher swelling of complex at higher pH. This holds a great potential as a natural polymer based delivery device for controlled delivery of drugs like diclofenac sodium for two reasons: (i) to reduce dosing frequency and (ii) lower the gastric toxicity. [152] Semi-interpenetrating polymer networks (SIPNs) composed of chitosan (CS) and poloxamer were prepared in order to improve the mechanical strength of CS. The WVTR was found to be 2508.2 ±65.7 gm−2 day−1, i.e. these can maintain a moist environment at wound site which enhance epithelial cell migration. Also, the in vitro assessment of SIPNs showed proper biodegradation and low cytotoxicity and in vivo is carried out on experimental full thickness wounds in a mouse model and found that the wounds covered with these were completely filled with new epithelium without any significant adverse reactions after 3 weeks. In one of the papers, a kind of surgical wound dressing, the chitosan-gelatin sponge wound dressing (CGSWD) having good antibacterial property is prepared. The in vitro test showed that the antibacterial effect of CGSWD on E. coli K88 is better than that of penicillin, and the effect on S. aureus is also better than that of cefradine. [137] One more wound dressing consists of two separate layers were prepared in which the upper layer is a swellable hydrogel material which can absorb exudates and also serve as mechanical and microbial barrier while lower layer is a chitosan acetate foam incorporated with the anti-microbial agent chlorherxidine gluconate. [183] The antimicrobial activity is checked by the Bauer-Kirby Disk Diffusion Test, inhibition zones can be clearly seen around the discs of chitosan acetate foams incorporated with chlorhexidine gluconate, in culture plates inoculated with either Gram-negative or positive bacteria showing that the dressing is antimicrobial in nature. Blending is a convenient and effective method to improve physical and mechanical properties of hydrogels. So modification of chitosan is done by blending with other polymers like cellulose. [178] In this, E. coli and S. aureus were used as the test bacteria to examine the antibacterial properties of chitosan, cellulose and chitosan/cellulose blends. The numbers of colony of these bacteria formed on the test membranes are shown in s 5 and 6. It was noted that the numbers of colony of all test bacteria formed on the chitosan/cellulose blend membranes were decreased with the increase of chitosan concentration. These blends are more effective against E. coli than that of S. aureus, as indicated by the lower colony unit. Thus these dressings are suitable to use as an antimicrobial wound dressing. Chitosan due to its structural properties has the ability to heal wounds without scar formation. [198] Since chitosan is composed of D-glucosamine, which is also the component present in the disaccharide subunits of hyaluronic acid, chitosan tries to structurally mimic hyaluronic acid and exerts similar effects. [197] It has been known that the fetal wound healing takes place without fibrosis or scar formation due to the presence of hyaluronic acid. [199] In one of the studies, Chitosan as a semi-permeable biological dressing maintains a moist environment and prevent the wound site from dehydration and contamination. In addition, digital colour separation analysis of donor site scars demonstrated an earlier return to normal skin colour at chitosan-treated areas as shown in 7. [196] Collagen is also a biopolymer that is used as a polymer for making wound dressing and drug delivery devices as it is biocompatible and biocompatibility of a material applied to wound tissue is a prerequisite for optimal wound environment and facilitation of the healing processes. A new collagen dressing with gentamycin or amikacin was prepared in one of the research work and these follow the basic requirement of antibacterial bandages. The dressing is composed of two collagen biomaterials—membrane and sponge—both possessing good tissue biocompatibility. These dressing released antibiotics slowly and show the antibacterial treatment in experimentally infected superficial wounds in mice. Thus, it can be used for the treatment of infected wounds in humans. [26] As discussed previously that both chitosan and collagen are excellent materials that can be used as wound dressing materials. So it has been seen that if both are used simultaneously then what will be the effect. It is found that the wound dressings composed of chitosan crosslinked collagen sponge (CCCS) enhance the diabetic wound healing. Collagen crosslinked with chitosan showed several advantages required for wound dressing, including the uniform and porous ultrastructure, less water imbibition, small interval porosity, and high resistance to collagenase digestion and slow release of FGF from CCCS/FGF. [138] Following moist healing concept, alginates which are able to absorb exudates from wound have become one of the most important materials for wound management. [52, 53, 54, 55, 56] In this particular field, the properties of alginate fibers are unparalleled in many respects. Alginate based products form a gel and effective in removing out of the wound on the contrary to traditional cotton and viscose fibres, which can entrap in the wound developing discomfort during dressing removal. [55] Also, the alginate fibres are non-toxic, non-carcinogenic, non-allergic, haemostatic, biocompatible, of reasonable strength, capable of being sterilized and easily processable. Sorbsanâ„ ¢ was first commercialized in 1981 and after that there were many dressings launched. The alginate fibers can be converted into wound dressings by using a number of textile processes. Because of its simplicity and also the high absorbency of the product, nonwoven is the main form of alginate wound dressings. [19] The antimicrobial action of alginate dressing can be seen as in 8 which shows the antimicrobial action of silver containing alginate fibers against E. Coli. There was 100% reduction in bacteria count within 5 hr after the fibers were placed in contact with solutions containing the bacteria. Sorbsan alginate fibers showed some antimicrobial activity while AquacelTM (made of carboxymethyl cellulose), does not show any antimicrobial effect. [18] Gelatin widely found in nature and is the major constituent of skin, bones, and connective tissue. Gelatin can easily be obtained by a controlled hydrolysis of the fibrous insoluble protein, collagen. [195] This is also used in number of biomedical applications like wound dressings. Hydrogel wound dressing from gelatin, oxidized alginate and borax were prepared and the composite matrix promotes wound healing because of alginate, has haemostatic effect of gelatin and is antiseptic because of borax. The water vapour transmission rate (WVTR) of the hydrogel was calculated and found to be 2686 ±124 g/m2/day indicating that this hydrogel can maintain a proper fluid balance at the wound site which helps in cell migration. 2 shows the loss of water vapour with time through the hydrogel when placed in a moisture rich environment. [119] Genipin has been used to crosslink chitosan membranes to control swelling ratio and mechanical properties. It increased its ultimate tensile strength but significantly reduced its strain-at-fracture and swelling ratio. It had significantly less cytotoxicity for human fibroblasts and slower degradation rate compared to the glutaraldehyde-crosslinked membrane. This genipin crosslinked chitosan membrane can be successfully used as a wound dressing. [132] Bacterial cellulose is a natural polymer consisting of microfibrils containing glucan chains bound together by hydrogen bonds. Bacterial cellulose with chitosan combines properties such as bioactivity, biocompatibility, and biodegradability of the two biopolymers and form an ideal material for dressing wounds. [66, 67] These are antibacterial and scar preventive in nature too. Since natural polymers have been considered limited in their applications for wound-dressing materials as their low mechanical properties and shortage of processing. So we move towards the synthetic polymers that can be used for wound healing applications. 3.2 Synthetic Hydrogels Synthetic polymers are also being used successfully in biomedical applications as one of the materials because of their wide range of mechanical properties, suitability for easily forming into a variety of different shapes, and low production costs. In an ideal dressing both the characteristics i.e. antimicrobial ability and moist healing environment should be present, so in order to prevent the wound from dehydration and bacterial penetration a new dressing composed of polyurethane is designed in such a way that the upper layer of the dressing is microporous (pore size Polyvinyl pyrrolidone (PVP) is one of the most widely used synthetic polymers in medicine because of its solubility in water and its extremely low cytotoxicity. Hydrogels prepared by radiation crosslinking of an aqueous solution of polyvinyl pyrrolidone (PVP) have been used as wound dressing. [21] These are biocompatible, reduces pain, easily replacable, permeable to oxygen, maintain moist environment at the wound site. Polyvinyl alcohol (PVA) is a well-known polymer because it is biocompatible and have required mechanical properties and polyethylene oxide (PEO) is a hydrophilic semicrystalline polyether which is biocompatible, non toxic, non polar, non antigenic and non immunogenic and is highly desirable in most biomedical applications requiring contact with physiological fluids. A hydrogel composed of PEO for wound dressing is prepared and PVA is added to give toughness to the hydrogel by electron beam irradiation and found that these hydrogels showed satisfactory properties for wound dressing that has been evaluated by creating wound on the back of the marmots. [157] The hydrogel gives a wet environment to wounds which causes faster healing compared with the gauze dressing with a dry environment. The weight of the hydrogel increases quickly at the earlier stages, up to 4 days, due to absorption of effusion produced from the wound as shown in Table 2. After that, the production of effusion from the wound ceases and the weight of the hydrogel decreases due to evaporation of the water in the hydrogel. This means that the healing of wound proceeds smoothly with time. The hydrogel can be peeled off easily from the wound at the time of removal. Table 2 Absorption of effusion from wound of dressing during healing. [157] The toughness of PEO hydrogel is improved by the addition of PVA and tensile strength is measured and found that as shown in 10 and 11, the tensile strength and elongation decrease with increasing dose because of the increase of crosslinking. Various synthetic polymers as discussed above are used for wound dressing applications. But the major problem with these materials is their biocompatibility characteristics are often unsatisfactory and their interaction with living tissues is a major problem. So a combination of both natural and synthetic polymers is the better option to make a hydrogel having biocompatibility and desired mechanical strength. 3.3 Blended hydrogels Since both the natural and synthetic polymers have their own advantages and disadvantages so a combination of natural and synthetic polymers can endow the optimal properties necessary for wound repair. [47] The combination of natural and synthetic polymers is used in the biomedical, bioengineering and biotechnology field nowadays because of their great potential. A blended hydrogel composed of polyvinyl alcohol/polyvinyl pyrrolidone and charcoal were prepared by single ‘‘freezing and thawing or two-step ‘‘freezing and thawing and ÃŽ ³-ray irradiation and applied as wound dressing. It is found that the absorption of S. aureus and P. aeruginosa by charcoal/PVA/PVP hydrogels was larger than those by PVA/PVP hydrogels, this is due to the absorption and attachment capability of bacteria by charcoal, this can be shown in 12 given below. [22] The most classical way of fabricating a CS based wound dressing has been to design an asymmetric composite structure. In this method, the Cotton fabric was coated with chitosan (CS) and polyethylene glycol (PEG) followed by freeze-drying. The outer dense layer helps in preventing the microbial passage across the dressing and provides a rate controlling barrier for water vapor permeation, while the inner porous layer provides a high surface area for the exudates absorption. For the absorption of wound exudates porosity is the prime requirement in a dressing. It has been found that these dressings have the porosity 54-70% and the pore size was in the range of 75-120 µm. [45] The increase in the PEG content in the blend composition led to an enhanced destabilization of pores, leading to an increase in the pore size with elongated morphology. There seems to be phase separation between the two components which is an important factor for the observed behavior of the porous structure. Cot ton fabric has been used as the support layer for the CS-PEG layer and leads to very thin and light weight structures. The structure of the dressing has been designed in such a way that it leads to the high porosity of the bulk structure. The thickness of CS coating plays an important role in the development of the porosity on the surface. The influence of the CS thickness on the surface morphology is presented in 13 given below. PEG addition to CS makes significant alteration in the surface morphology of this CS-PEG/cotton membrane (freeze-dried), henceforth known as CPC membrane. There is a distinct trend in the loss of inherent elongated porous structure in membranes and formation of the partially collapsed porosity takes place due to the PEG addition. This suggests that a very limited interaction between CS and PEG exists which is reflected in the observed surface morphology. It has been observed that higher the amount of PEG, the higher is the pore destabilization leading to larger pores. This is evident from the morphology of the CPC membrane at 50% PEG-20 content as shown in 14.45 On the above matrix, the addition of PVP and drug followed by coating on the cotton fabric and freeze drying of the coated matrix is also done. It has been found that the drug Hydrogels for Wound Healing Applications Hydrogels for Wound Healing Applications Abstract This chapter discusses about the hydrogels both natural and synthetic that can be used for wound healing applications. Also it discusses briefly about the various novel techniques that have been developed recently. Keywords: Hydrogels; Chitosan, Antimicrobial; Grafting; Blending; Wound dressing; Wound healing; Gene therapy, Stem cell therapy, Skin Engineering, pH and Thermosensitive polymers. 1 Introduction Healthcare is an essential aspect of human survival. So many biopolymers have generated interest in a number of biomedical applications. Wound management is one such area where management of cuts, ulcers, and sores needs dressings which help in promoting rapid wound healing in order to obtain both functional and cosmetic results. [45] There are different kinds of wound management products: staples or sutures, dressings or bandages, surgical sealants and adhesives, skin substitutes, and other biomaterials. [51] Human skin provides an effective barrier to microbial penetration and subsequent infection. However, once the wound has been developed in this barrier, the infection chances increases. In case of chronic wounds, the colonization and infection potential increases as the result of the presence of avascular eschar which provides an environment for the uninhibited growth of microorganisms. [89] The rate of infection is related to the type of wound, general wound care, and local health of the patient. [88, 90] For avoiding infection, good clinical practices are needed. The management of chronic wounds is a very costly practice and it also places an enormous drain on healthcare resources; studies have calculated the cost of wounds to the NHS to be about  £1bn a year. [166] So for lowering this cost such wound management products are needed that are more economical and effective. Out of all the above wound management products, here in this chapter we will discuss more about the wound dressings that will provide an optimal healing environment to the wound. A dressing is an adjunct used by a person for application to a wound in order to promote healing and/or prevent further harm. It is designed to be in direct contact with the wound, so it is different from the bandage in the manner that bandages are normally used to hold dressing in place. A wound is a break in the epithelial integrity of the skin and may be accompanied by disruption of the structure and function of underlying normal tissue. Wounds can be divided into four categories based on their appearance and stage of healing: Necrotic, sloughing, granulating and epithelializing wounds. [87] Wounds cause discomfort and are more prone to infection and other troublesome complications. [75] Some diseases like diabetes, ischaemia and conditions like malnourishment, ageing, local infection, local tissue damage due to burn leads to delay in wound healing. Infection is a major complication of burn injury and is responsible for 50-75% of hospital deaths. [76] Human skin has one of the greatest capacities to regenerate itself amongst all of the tissues in our body. It constantly replaces old cells with new cells, enabling it to repair itself when damaged. Wound healing is a complex-physiologic process, which consists of three overlapping phases: inflammatory, proliferative and remodeling phases. The normal healing response begins the moment the tissue is injured. As the blood components spill into the site of injury, the platelets come into contact with exposed collagen and other elements of the extracellular matrix. This contact triggers the platelets to release clotting factors as well as essential growth factors. During the inflammation process, neutrophils are the first leukocytes which come at the site of injury to rid it from bacterial contamination. Then, the monocytes and their conversion to macrophages initiate tissue repair by releasing a number of biologically active substances and growth factors that are necessary for the initi ation of tissue formation process. In the third process, fibroblasts proliferate and migrate into the wound space and started the deposition of the loose extracellular matrix. Endothelial cells grow into a wound simultaneously with fibroblasts and undergo angiogenesis. Finally, tissue remodeling takes place to reconstruct the basement membrane by the differentiation of keratinocytes as well as the formation of follicle cells. [43, 49, 50] A scar is an essential part of this natural healing process following any type of damage to the skin. This can occur after a surgical incision or the healing of a wound. As your body makes an effort to close an open wound and protect itself from infection, it replaces injured skin tissue with rapidly generated scar tissue. Scarring is slight when the damaged outer layer of skin is healed by rebuilt tissue. When we damage the thick layer of tissue beneath the skin, rebuilding is more complicated. Our bodies lay down collagen fibers (a protein which is naturally produced by the body) and this usually results in a highly obvious scar. A permanent reminder of the injury is left behind. So, a dressing that can induce scarless healing is needed. Historically, a dressing was usually a piece of material, sometimes cloth, but the use of cobwebs, dung, leaves and honey has also been described. However, modern dressings include gauzes, semipermeable films, low adherent dressings, gels, foams, hydrocolloids, alginates, hydrogels and polysaccharide pastes. Wound dressings are passive, active or interactive. Passive dressings simply provide cover while active or interactive dressings are capable of modifying the physiology of the wound environment. Interactive dressings include hydrocolloids, hydrogels, alginates, foam dressings and antimicrobial dressings. [17, 20, 85] Traditionally dry wound dressings are considered to be good for healing wounds i.e. the wound should be covered with gauze or left open. But it has been observed by Winter [191] that when wound is left open to air without any dressing, a scab i.e. a dry covering covers the wound and decreases the rate of epithelialization. On the other hand, if moist dressing is used in place of dry dressings scab will not form and rate of healing increases as moist dressings provide low oxygen tension which helps in wound healing, these dressings not only keep cells viable which enables them to release growth factors while maintaining contact between them and the healing tissues, but may also modulate or stimulate their proliferation, these dressings decrease the pain at rest, during ambulation and during dressing changes also moist environment allows rapid and efficient delivery of any added antimicrobial agent thus prevent the wound from infection. So, the dressings that create and maintain a mois t environment, however, are now considered to provide the optimal conditions for wound healing. 2 Requirements of an ideal wound care system These characteristics should be present in the ideal wound care system (a) it should be capable of maintaining a high humidity at the wound site, (b) it should be non-toxic, (c) non-allergenic, (d) it can be removed without causing trauma to the wound, (e) it should pe impermeable to bacteria, (f) Thermally insulating, (g) it should be soft to touch, (h) it should allow proper gaseous exchange, (i) it should be free from particulate and toxic product, (j) promote tissue reconstruction processes and (k) it should be cost effective. [20, 165, 177] Out of all the dressings hydrocolloids, alginates and hydrogels each one has its own advantages and limitations but hydrogels are best and have all the characteristics that are needed in an ideal wound dressing. All the above mentioned characteristics can be achieved in hydrogel wound dressings. 3 Hydrogels for Wound Healing Applications Hydrogels are natural or synthetic cross-linked polymers used in a variety of medical and biomedical applications. Hydrogels consist of a matrix of insoluble polymers with up to 96% water content enabling them to donate water molecules to the wound surface and to maintain a moist environment at the wound bed. They are used in the construction of contact lenses, drug-delivery vehicles, wound dressings and as physiological electrodes or sensors. [17] Examples of hydrogel include Aquaform, Intrasite, GranuGel, Nu-Gel, Purilon, Sterigel. These also have the ability to absorb a degree of wound exudate. They transmit moisture vapour and oxygen, but their bacterial and fluid permeability is dependent on the type of secondary dressing used. [20] Hydrogels swell or shrink in aqueous solutions due to the association, dissociation and binding of various ions to polymer chains. These systems may swell in water until an equilibrium state is reached and retain their original shape. The interactions responsible for water sorption by hydrogels include the process of hydration, which is connected to the presence of such chemical groups as -OH, -COOH, -CONH2, -CONH-, and -SO3H and the existence of capillary areas and differences in osmotic pressure. The forces that make hydrogel dissolution impossible are presence of covalent bonds between individual polymer chains, hydrophobic and electrostatic interactions. [46] These are hydrophilic polymer networks which may absorb from 10-20% (an arbitrary lower limit) up to thousands of times their dry weight in water. These may be chemically stable or they may degrade and dissolve. They are called ‘reversible, or ‘physical gels when the networks are held together by molecular entanglements, and/or secondary forces including ionic, H-bonding or hydrophobic forces. [13, 14, 15] Hydrogels are called ‘permanent or ‘chemicalgels when they are covalently-crosslinked networks as shown in 1. Hydrogels can be made by irradiation, freeze-thawing or chemical methods. Out of all the methods, irradiation is considered as a suitable tool for the formation of hydrogels as in this method there is easy control of processing, no need of adding initiators or cross-linkers which are harmful, and have the possibility of formation and sterilization in one step. But as everything has its own advantages and disadvantages this method also has a disadvantage which is hydrogels formed by this method have poor mechanical strength. Nowadays, Freeze thawing technique is generally used to prepare hydrogels having good strength, stability and no crosslinkers and initiators. But the main disadvantage is that the prepared hydrogels have opaque appearance and limited swelling and thermal stability. [120] In comparison to the traditional gauze therapy the application of a hydrogel seems to significantly stimulate wound healing. [11] Various natural and synthetic polymers having good biocompatibility are used to develop hydrogel wound dressing. These polymers include natural polymers such as alginate, chitosan, gelatin and collagen and synthetic polymers such as polyurethane, poly(ethylene glycol), polycaprolactone, poly vinyl pyrrolidone, poly(lactide-co-glycolide), polyacrylonitrile , poly(amino acid), etc. Table 1 below shows different hydrophilic polymers used to synthesize hydrogel matrices. Table 1 Hydrophilic polymers used to synthesize hydrogel matrices. [13] Hydrogels may be classified as homopolymer hydrogels, copolymer hydrogels, multipolymer hydrogels, and interpenetrating polymeric hydrogels. Homopolymer hydrogels are crosslinked networks of one type of hydrophilic monomer unit, whereas copolymer hydrogels are produced by the crosslinking of two comonomer units, one of which must be hydrophilic. Multipolymer hydrogels are produced by the crosslinking of more than three monomers. Finally, interpenetrating polymeric hydrogels are produced by the swelling of a first network in a monomer and the reaction of the latter to form a second intermeshing network structure. [46, 47] Also, it has been shown that the blending of a natural polymer with a synthetic polymer seems to be a good method for obtaining materials having required mechanical and thermal properties in comparison to pure components. It is also a simple method by which suitable shapes such as films, sponges and hydrogels can be obtained easily to realize a variety of biomedical devices. 2 shows healing is faster with the hydrogel dressing than with the gauze dressing. Wound area covered by hydrogel decreases faster with increasing healing period. On the contrary, the wound covered by gauze dressing reduces by only half a percent even after 14 days. [192] 3.1 Natural Hydrogels Natural polymers, such as chitin, chitosan, alginate, collagen, elastin, genipin, gelatin, cellulose etc. have been used for dressing wounds because they play an important role in the healing process. [47] Chitosan is a partially deacetylated form of chitin. Chitin as BeschitinÃ’, Unitika, is also commercially available as dressing in Japan. [28] But as far as chitosan is concerned it is biocompatible, biodegradable, haemostatic, fungistatic [54] and non-toxic and can be successfully used as gels, films, fibres etc. This polymer also show antibacterial properties and possess good wound healing properties. [60, 61, 62] It has many applications as wound dressing, drug delivery device and as scaffold for tissue engineering. [63, 64] Some of the examples of wound dressings are given below which use chitosan as one of the biomaterial. Asymmetric chitosan membranes have been developed by using immersion-precipitation phase-inversion method. [123, 124, 125] These asymmetric chitosan membranes are homogeneous and have porous structure. This membrane was prepared by preheating casted chitosan solution in oven for different time periods for dry phase separation and then immersed in to coagulant tank for wet phase separation and were subsequently freeze-dried. The skin layer acts as the rate controlling barrier for the release of drug and the porous layer provide mechanical support to the skin layer. The water vapor transmission rate, gas permeability, PBS solution absorption, in-vitro degradation, cell culture, bacterial penetration and wound healing test of this dressing were carried out. These membranes are effective in controlling evaporative water loss, showed excellent oxygen permeability and also antibacterial in nature. These are also found to be an urgent hemostat. In another study, silver sulphadiazine was inc orporated as an antimicrobial agent to this asymmetric dressing. The release behaviour of both silver and sulphadiazine ions were studied and found to be significantly different from one another. Silver ions displayed a slow release behavior while sulphadiazine ions exhibited burst effect on first day of the drug release and then slowly tapered off. It is because of the interaction of silver with amino group of chitosan leading to its slow release throughout whereas, as the sulphadiazine ions were free to diffuse through the membrane to reach the wound site thus they showed a burst release. The membranes were further found effective against P. aerugniosa and S. aureus. In one of the papers, novel wound dressings were formed that composed of chitosan film and Minocycline Hydrochloride (MH) and commercial polyurethane film (Tegaderm) as a backing. It is also a useful formulation for the treatment of severe burn wounds. Water vapor and oxygen can permeate the Tegaderm film but water cannot. The tegaderm film support the polymer membrane. [126] In one of the studies, a silver nanocrystalline chitosan (SNC) wound dressing composed of nano-silver and chitosan was constructed by self-assembly and nanotechnology and used for treating deep partial-thickness wounds. In this, sterility and pyrogen testing were performed to ensure biosafety. These dressings promote wound healing and combat infection, and also decrease the risk of silver absorption in comparison with silver sulphadiazine (SSD) dressings. [127] There is also one more method of forming wound dressing composed of chitosan i.e. the formation of polyelectrolyte complex of gum kondagogu (GKG) and chitosan. This complex is formed by the electrostatic interaction between carboxyl group of gum and amine group of chitosan. This method is more advantageous as it avoids the use of organic solvents, chemical crosslinking agents and thus reduces the toxicity and undesirable side effects. In this, diclofenac sodium is used as model drug. The diclofenac loaded complex of gum kondagogu/ chitosan shows drug release which changes with change in pH. The drug release was higher at pH 6.8 as compared to pH 1.2, due to higher swelling of complex at higher pH. This holds a great potential as a natural polymer based delivery device for controlled delivery of drugs like diclofenac sodium for two reasons: (i) to reduce dosing frequency and (ii) lower the gastric toxicity. [152] Semi-interpenetrating polymer networks (SIPNs) composed of chitosan (CS) and poloxamer were prepared in order to improve the mechanical strength of CS. The WVTR was found to be 2508.2 ±65.7 gm−2 day−1, i.e. these can maintain a moist environment at wound site which enhance epithelial cell migration. Also, the in vitro assessment of SIPNs showed proper biodegradation and low cytotoxicity and in vivo is carried out on experimental full thickness wounds in a mouse model and found that the wounds covered with these were completely filled with new epithelium without any significant adverse reactions after 3 weeks. In one of the papers, a kind of surgical wound dressing, the chitosan-gelatin sponge wound dressing (CGSWD) having good antibacterial property is prepared. The in vitro test showed that the antibacterial effect of CGSWD on E. coli K88 is better than that of penicillin, and the effect on S. aureus is also better than that of cefradine. [137] One more wound dressing consists of two separate layers were prepared in which the upper layer is a swellable hydrogel material which can absorb exudates and also serve as mechanical and microbial barrier while lower layer is a chitosan acetate foam incorporated with the anti-microbial agent chlorherxidine gluconate. [183] The antimicrobial activity is checked by the Bauer-Kirby Disk Diffusion Test, inhibition zones can be clearly seen around the discs of chitosan acetate foams incorporated with chlorhexidine gluconate, in culture plates inoculated with either Gram-negative or positive bacteria showing that the dressing is antimicrobial in nature. Blending is a convenient and effective method to improve physical and mechanical properties of hydrogels. So modification of chitosan is done by blending with other polymers like cellulose. [178] In this, E. coli and S. aureus were used as the test bacteria to examine the antibacterial properties of chitosan, cellulose and chitosan/cellulose blends. The numbers of colony of these bacteria formed on the test membranes are shown in s 5 and 6. It was noted that the numbers of colony of all test bacteria formed on the chitosan/cellulose blend membranes were decreased with the increase of chitosan concentration. These blends are more effective against E. coli than that of S. aureus, as indicated by the lower colony unit. Thus these dressings are suitable to use as an antimicrobial wound dressing. Chitosan due to its structural properties has the ability to heal wounds without scar formation. [198] Since chitosan is composed of D-glucosamine, which is also the component present in the disaccharide subunits of hyaluronic acid, chitosan tries to structurally mimic hyaluronic acid and exerts similar effects. [197] It has been known that the fetal wound healing takes place without fibrosis or scar formation due to the presence of hyaluronic acid. [199] In one of the studies, Chitosan as a semi-permeable biological dressing maintains a moist environment and prevent the wound site from dehydration and contamination. In addition, digital colour separation analysis of donor site scars demonstrated an earlier return to normal skin colour at chitosan-treated areas as shown in 7. [196] Collagen is also a biopolymer that is used as a polymer for making wound dressing and drug delivery devices as it is biocompatible and biocompatibility of a material applied to wound tissue is a prerequisite for optimal wound environment and facilitation of the healing processes. A new collagen dressing with gentamycin or amikacin was prepared in one of the research work and these follow the basic requirement of antibacterial bandages. The dressing is composed of two collagen biomaterials—membrane and sponge—both possessing good tissue biocompatibility. These dressing released antibiotics slowly and show the antibacterial treatment in experimentally infected superficial wounds in mice. Thus, it can be used for the treatment of infected wounds in humans. [26] As discussed previously that both chitosan and collagen are excellent materials that can be used as wound dressing materials. So it has been seen that if both are used simultaneously then what will be the effect. It is found that the wound dressings composed of chitosan crosslinked collagen sponge (CCCS) enhance the diabetic wound healing. Collagen crosslinked with chitosan showed several advantages required for wound dressing, including the uniform and porous ultrastructure, less water imbibition, small interval porosity, and high resistance to collagenase digestion and slow release of FGF from CCCS/FGF. [138] Following moist healing concept, alginates which are able to absorb exudates from wound have become one of the most important materials for wound management. [52, 53, 54, 55, 56] In this particular field, the properties of alginate fibers are unparalleled in many respects. Alginate based products form a gel and effective in removing out of the wound on the contrary to traditional cotton and viscose fibres, which can entrap in the wound developing discomfort during dressing removal. [55] Also, the alginate fibres are non-toxic, non-carcinogenic, non-allergic, haemostatic, biocompatible, of reasonable strength, capable of being sterilized and easily processable. Sorbsanâ„ ¢ was first commercialized in 1981 and after that there were many dressings launched. The alginate fibers can be converted into wound dressings by using a number of textile processes. Because of its simplicity and also the high absorbency of the product, nonwoven is the main form of alginate wound dressings. [19] The antimicrobial action of alginate dressing can be seen as in 8 which shows the antimicrobial action of silver containing alginate fibers against E. Coli. There was 100% reduction in bacteria count within 5 hr after the fibers were placed in contact with solutions containing the bacteria. Sorbsan alginate fibers showed some antimicrobial activity while AquacelTM (made of carboxymethyl cellulose), does not show any antimicrobial effect. [18] Gelatin widely found in nature and is the major constituent of skin, bones, and connective tissue. Gelatin can easily be obtained by a controlled hydrolysis of the fibrous insoluble protein, collagen. [195] This is also used in number of biomedical applications like wound dressings. Hydrogel wound dressing from gelatin, oxidized alginate and borax were prepared and the composite matrix promotes wound healing because of alginate, has haemostatic effect of gelatin and is antiseptic because of borax. The water vapour transmission rate (WVTR) of the hydrogel was calculated and found to be 2686 ±124 g/m2/day indicating that this hydrogel can maintain a proper fluid balance at the wound site which helps in cell migration. 2 shows the loss of water vapour with time through the hydrogel when placed in a moisture rich environment. [119] Genipin has been used to crosslink chitosan membranes to control swelling ratio and mechanical properties. It increased its ultimate tensile strength but significantly reduced its strain-at-fracture and swelling ratio. It had significantly less cytotoxicity for human fibroblasts and slower degradation rate compared to the glutaraldehyde-crosslinked membrane. This genipin crosslinked chitosan membrane can be successfully used as a wound dressing. [132] Bacterial cellulose is a natural polymer consisting of microfibrils containing glucan chains bound together by hydrogen bonds. Bacterial cellulose with chitosan combines properties such as bioactivity, biocompatibility, and biodegradability of the two biopolymers and form an ideal material for dressing wounds. [66, 67] These are antibacterial and scar preventive in nature too. Since natural polymers have been considered limited in their applications for wound-dressing materials as their low mechanical properties and shortage of processing. So we move towards the synthetic polymers that can be used for wound healing applications. 3.2 Synthetic Hydrogels Synthetic polymers are also being used successfully in biomedical applications as one of the materials because of their wide range of mechanical properties, suitability for easily forming into a variety of different shapes, and low production costs. In an ideal dressing both the characteristics i.e. antimicrobial ability and moist healing environment should be present, so in order to prevent the wound from dehydration and bacterial penetration a new dressing composed of polyurethane is designed in such a way that the upper layer of the dressing is microporous (pore size Polyvinyl pyrrolidone (PVP) is one of the most widely used synthetic polymers in medicine because of its solubility in water and its extremely low cytotoxicity. Hydrogels prepared by radiation crosslinking of an aqueous solution of polyvinyl pyrrolidone (PVP) have been used as wound dressing. [21] These are biocompatible, reduces pain, easily replacable, permeable to oxygen, maintain moist environment at the wound site. Polyvinyl alcohol (PVA) is a well-known polymer because it is biocompatible and have required mechanical properties and polyethylene oxide (PEO) is a hydrophilic semicrystalline polyether which is biocompatible, non toxic, non polar, non antigenic and non immunogenic and is highly desirable in most biomedical applications requiring contact with physiological fluids. A hydrogel composed of PEO for wound dressing is prepared and PVA is added to give toughness to the hydrogel by electron beam irradiation and found that these hydrogels showed satisfactory properties for wound dressing that has been evaluated by creating wound on the back of the marmots. [157] The hydrogel gives a wet environment to wounds which causes faster healing compared with the gauze dressing with a dry environment. The weight of the hydrogel increases quickly at the earlier stages, up to 4 days, due to absorption of effusion produced from the wound as shown in Table 2. After that, the production of effusion from the wound ceases and the weight of the hydrogel decreases due to evaporation of the water in the hydrogel. This means that the healing of wound proceeds smoothly with time. The hydrogel can be peeled off easily from the wound at the time of removal. Table 2 Absorption of effusion from wound of dressing during healing. [157] The toughness of PEO hydrogel is improved by the addition of PVA and tensile strength is measured and found that as shown in 10 and 11, the tensile strength and elongation decrease with increasing dose because of the increase of crosslinking. Various synthetic polymers as discussed above are used for wound dressing applications. But the major problem with these materials is their biocompatibility characteristics are often unsatisfactory and their interaction with living tissues is a major problem. So a combination of both natural and synthetic polymers is the better option to make a hydrogel having biocompatibility and desired mechanical strength. 3.3 Blended hydrogels Since both the natural and synthetic polymers have their own advantages and disadvantages so a combination of natural and synthetic polymers can endow the optimal properties necessary for wound repair. [47] The combination of natural and synthetic polymers is used in the biomedical, bioengineering and biotechnology field nowadays because of their great potential. A blended hydrogel composed of polyvinyl alcohol/polyvinyl pyrrolidone and charcoal were prepared by single ‘‘freezing and thawing or two-step ‘‘freezing and thawing and ÃŽ ³-ray irradiation and applied as wound dressing. It is found that the absorption of S. aureus and P. aeruginosa by charcoal/PVA/PVP hydrogels was larger than those by PVA/PVP hydrogels, this is due to the absorption and attachment capability of bacteria by charcoal, this can be shown in 12 given below. [22] The most classical way of fabricating a CS based wound dressing has been to design an asymmetric composite structure. In this method, the Cotton fabric was coated with chitosan (CS) and polyethylene glycol (PEG) followed by freeze-drying. The outer dense layer helps in preventing the microbial passage across the dressing and provides a rate controlling barrier for water vapor permeation, while the inner porous layer provides a high surface area for the exudates absorption. For the absorption of wound exudates porosity is the prime requirement in a dressing. It has been found that these dressings have the porosity 54-70% and the pore size was in the range of 75-120 µm. [45] The increase in the PEG content in the blend composition led to an enhanced destabilization of pores, leading to an increase in the pore size with elongated morphology. There seems to be phase separation between the two components which is an important factor for the observed behavior of the porous structure. Cot ton fabric has been used as the support layer for the CS-PEG layer and leads to very thin and light weight structures. The structure of the dressing has been designed in such a way that it leads to the high porosity of the bulk structure. The thickness of CS coating plays an important role in the development of the porosity on the surface. The influence of the CS thickness on the surface morphology is presented in 13 given below. PEG addition to CS makes significant alteration in the surface morphology of this CS-PEG/cotton membrane (freeze-dried), henceforth known as CPC membrane. There is a distinct trend in the loss of inherent elongated porous structure in membranes and formation of the partially collapsed porosity takes place due to the PEG addition. This suggests that a very limited interaction between CS and PEG exists which is reflected in the observed surface morphology. It has been observed that higher the amount of PEG, the higher is the pore destabilization leading to larger pores. This is evident from the morphology of the CPC membrane at 50% PEG-20 content as shown in 14.45 On the above matrix, the addition of PVP and drug followed by coating on the cotton fabric and freeze drying of the coated matrix is also done. It has been found that the drug