Celta application form Essay Example

Celta application form Essay Universal Jorge Tattooed Logan, 2007-2010 During my thesis at the university, I worked as a teaching assistant with undergraduate students. I worked on several microbiology laboratories. Activities generally consisted in explaining the theory for a certain technique or procedure, followed by practical exercises. My responsibilities included assisting students with equipment (measuring, handling), reviewing workflow charts and assisting the professor. Microbiology laboratories are quite demanding and due to safety measures, one must make sure the students follow the protocols and workflow precisely. Finch el Highern, Santa Elena, Ecuador From mid-2010 until 2013 lived on the coast of Ecuador near Quailing. During this time I worked on an agricultural project where students from a local school (College tectonic De Santa Elena) visited the farm once a week to practice what they had learned at school. Activities included equipment instructions, agricultural practices, crop planning, plant growth etc. Activities were conducted during a whole school year. What other work experience do you have? Have had several jobs in customer service and logistics. I have worked for English campaigns in the USA such us Compact and Att. Do you have any other professional training? Yes No If Yes, outline here: Customer service Operations Carpentry and Masonry OTHER INFORMATION Please indicate any health concerns that may be pertinent to your application: None Is there any other information you think is worth mentioning? How did you hear about the courses at International House Bogota;? Internet Will you need help with accommodation? Yes OTHER APPLICATIONS Have you previously applied for a CELT course at any centre? Yes If yes what was the outcome of your application/interview? We will write a custom essay sample on Celta application form specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on Celta application form specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on Celta application form specifically for you FOR ONLY $16.38 $13.9/page Hire Writer Approved Are you applying to centers other than II Bogota;? British Council IMPORTANT: Please note that acceptance on a course does not mean a place has been reserved for you. To ensure a place the full fee must be paid no later than six weeks before the start of the course. Fees are not transferable or refundable. I have read and accepted the above conditions. Signed: Arturo Date: 4/15/2015 PLEASE KEEP A COPY OF THIS FORM ONCE YOU HAVE LADLED IT IN. Pre-intent. IEEE task: CELT at II Bogota; Name: Arturo Hypes 1. LEARNING There is a lot to learn about teaching in a very short period of time. How would you characterize yourself as a learner? I believe my learning style is a blend between visual and kinesthesia. As input, like for information to be presented visually; reading written dialogues while Im listening helps retaining information. I am also a hands on person and therefore I learn by doing it. I believe on the effectiveness of an empirical approach depending on the topic. B) W hat is your preferred learning style? For example: 1. Watch it done and copy it 2. Read the theory of it and try to apply it 3. Try it out and get feedback on it 4. Work it out for yourself 5. Or My style would be a combination between number 1 and 2. Depends on the topic and the task. 2. TEACHING Answer the following in 2 or 3 sentences: i. How would you get students talking in class? An effective introduction with positive attitude and a smile is a start. It is important to start with a low level of complexity, start building empathy and provide students with enough information for them to fill confident. Then I would continue asking questions, listening carefully in order to keep asking questions based on what they have said. Ii. What are some of the reasons for and against teaching grammar rules? Reasons Against: grammar based lessons dont lead to oral fluency, language is acquired rather than learned. Reasons for: grammar is De backbone of a language, bringing an idea to its full extension needs the underlying structure of grammar. Iii. How important is listening and reading when learning a foreign language? One needs a massive input of data to learn a language fluently, this helps to develop language intuition, while bringing and incorporating new words into the speech. Iv. What is a good way of teaching vocabulary? Some effective ways for teaching vocabulary are: guessing the meaning wrought the context Of a lecture. The Odd word out, where a list Of 4-5 words contains one that does not fit. Match the opposites. 2 lists of words the first list should contain adjectives and the second the opposite of those adjectives. V. What are the main reasons for and against correcting students mistakes? Reasons for: most students do want to have some of their mistakes corrected as it gives them a basis for improvement. Letting errors pass means that bad habits become persistent. Reasons against: over-correcting may cause a student to lose motivation or to stop talking for fear of being wrong. It can also interrupt the flow of the class or activity, making a pause on every mistake to correct. 3. THE TEACHER a. In your opinion, which of the following jobs would best prepare a person for language teaching (choose one only): sports coach tour group leader driving instructor actor/actress Why? Social worker lecturer sales person nurse Multiple interactions with different kinds of people can lead to learn different accents, words, slang etc. Which helps to develop a more richer language. B. In the light of the above, why do you think YOU are suited to language teaching? Ive been interested in the English language and due to my school and university Ive studying it for most of my life. I am also an open minded individual with excellent interpersonal relationships and lots of stamina, which in my opinion can help develop good relations with students. 4. TEACHER TALK ORe-phrase the following teacher talk in language that an elementary learner might understand. O. If you wouldnt mind opening your books to page 23, please. Please open your books and go to page 23. D. What might you ask someone if you wanted to find out how to get to the cost office? What would you say to someone if you need help finding the post office? O. Jot down the answers and then swap with your neighbor. Write down the answer and then exchange it with the person next to you. 5. LANGUAGE AWARENESS 000000000. Which is the odd one out in each group, and why? O. The babys bottle. The nations struggle. The teachers absent. The nurses pay. The governments defeat. The teachers absent is the odd one out because it refers to something happening in the present. The apostrophe is used as a contraction for the teacher is. While in the others is used as a possessive. 0. 0 The plane was hi-jacked by a woman. The tourists were attacked by a gang. The soldier was hit by a bullet. The trains collided by a river. Three hundred people were killed by the earthquake. Why? The by on the sentence is being used in the sense of beside meaning the trains collided at the side of a river or next to it. The others are using it in the sense of through the action of 0. 0 She must have lost the address. Alan must have been here too. That must have been awful. The thieves must have got in through the window.

Chris Maccandless Essays

Chris Maccandless Essays Chris Maccandless Essay Chris Maccandless Essay Essay Topic: Into the Wild Happiness is only real when shared. Chris Maccandless decided to leave his ordinary life and explore the wild . He Just graduated with a bachelor and was planning to go to law school. He had a saving of 24000 dollars but gave it to charity . At the beginning of the movie we can see that he had problems with his parents. As the story evolved we understand what the issues were . In his book Walden Henry David Thoreau said that he wanted to live in the wild to learn what it had to teach, to live deliberately and to live deep and suck out all the marrow of life. I think that Maccandless did not go into the wild for the same reasons. Even though he wanted to live deliberately, to front only the essential facts of life he did not go to the wild for the same motives as Henry David Thoreau. Maccandless wanted to live away from his parents. They were not very loving and sometimes violent. In a few scenes, we see how they hated each others but stayed married for money. When he went on his Journey, he could start as a new man and forget about his disturbing past. Thoreau did not mention anything about issues with his family, Just the desire to live free and to learn form the wild. om his family, he realized that happiness is only real when shared which is in contrast to why he decided to live into the wild. The best moment of his experiment was not when he was alone in Alaska but when he met some friends. He had like a son -to-parent relationship with the hippie couple. In theses scenes he was really happy but when went to Alaska he kind of became crazy. (due to loneliness. ) The death scene is hard to watch because he is not happy in his last moments. He realized that he was wrong, that family was the most important thing in life and not living deliberately into the wild.

Impact of Social Networking Evaluation on Travel Websites Essay

Impact of Social Networking Evaluation on Travel Websites - Essay Example The essay "Impact of Social Networking Evaluation on Travel Websites" talks about the research proposal in terms of social networks usage such as MySpace, Facebook, Cyworld and Bebo to promote the travel websites. As a response to changing business environments and to remain competitive, businesses have made investments in IT projects Travel businesses need to invest in IT to face the competition as well to give tough times to its rivals. For example, "fitfortravel" is a website that has been developed by the National Health Service, Scotland for the provision of travel health information for people traveling abroad from the UK. The site has gained immense popularity as travelers find the information provided highly valuable. Illume et al. suggested the potential of virtual communities in tourism research. Enhancing value creation and a creation of brand identity were prerequisites in the creation of social networks in tourism. The advent of â€Å"Web 2.0† has led to a series of new web service. Social Networking has benefited from new internet technologies and new user behavior to become the poster child of web services. Questions on social sites include how they create value for users and how users capture it. Studies have examined revenue generation on social network sites through advertising, subscription and transaction models. Key value drivers include user volume, willingness to pay, trust in peers and the platform. Perceived reciprocity is a pre-requisite for committed relationship and avoiding negative consequences

FM demodulation Essay Example | Topics and Well Written Essays - 1000 words

FM demodulation - Essay Example The PLL has a voltage-controlled oscillator, a phase detector, and a low pass filter connected in a feedback loop. The input voltage determines the frequency of oscillation at the output of the VCO (Sedra 1998). This fosc is equal to the intermediate frequency fi required to be 470 kHz in this case. The circuit is built on a proto board according to the block diagram shown fig1 bellow; The components required are; CD 4046 CMOS Phase-Lock Loop (PLL) integrated circuit Resistors of values; 1k, 10k, 18k (2). Capacitors of values; 0.1?F, 0.01?F, 3900pF and, Breadboard. The actual circuit is realized according to the circuit shown in fig 2 bellow. The circuit components in the PLL providing a centre frequency of 470 kHz are determined according to the equation, fosc = 1/2Ð ¿RC. Therefore 470000Hz*2Ð ¿ = 1/RC and taking R = 100K then 1/C =470000* 2Ð ¿*100000= 3.386pF and the preferred value is 3400nf. The capture range is given by 2fc=1/Ð ¿ (2Ð ¿fL/R1)1/2 and for audio the maximum ran ge is 20 kHz and R1 = 1k therefore the frequency of the filter is given by; (2*20000*Ð ¿) 2 = 2Ð ¿fL/R1 fL= (2*2000*Ð ¿)2*1000/2Ð ¿ = 25.136 GHz and so the filter components are obtained as shown bellow; 25.136*109 = 1/2Ð ¿RfCf and with Rf taken as 18K then Cf = 1/ (25.136*109*2Ð ¿*18000) = 35176.4pF The lock in range is given by fmax – fmin and; fmin= 1/R2(C1+32PF) = 1/10000(3900+32)*10^-12 = 25432.35Hz fmax = 1/R1(C1+32PF) + fmin = 1/1000(3900+32)*10^-12 +25432.35 = 279755.85 Hz Hence lock in range = 254323.5 Hz. Also, capture range 2fc = (2K0fpVDD)1/2 K0 =VDD/2= 15/2 =7.5 2fc = (2*7.5*25432.5*15)1/2 = 7564.6Hz Discussion Did the loop demodulate NBFM? The loop demodulates narrow band FM that occupies the frequency range of 0-15kHz as this frequency range lies within the capture range and the lock range of the circuit. Could it be used to demodulate WBFM without any alteration? The loop demodulate the wide band FM as the low pass filter above has a value of 25.136 GHz, which is well above the capture range of WBFM, which is customarily around 10.7 MHz with a system bandwidth of 200 kHz. This bandwidth is within the centre frequency range of 470 kHz (Alencar 2005) What happened to the lock-in and capture range when the loop components were altered? The capture range is low if the cut off frequency of the filter is lower; this is achieved by varying the filter components i.e. using large filter capacitance, and resistor values. On the other hand, the capture range is made large by using lower values of filter components thereby increasing the cut off frequency (Carlson 2002). A wider capture range is desirable as it enables demodulation of WBFM while a small capture range is desirable as it enables the attenuation of high frequency components thereby improving the signal to noise ratio of the system. The lock-in range follows the above relation, as it is also directly proportional to the filter cut off frequency. How would you modify the PLL in ord er to demodulate WBFM? From the relation of WBFM, 2fc = (2K0fpVDD)0.5 it is seen that the capture range 2fc is directly

WWI, Great Depression, WWII, and the Cold War Essay

WWI, Great Depression, WWII, and the Cold War - Essay Example Although there is an uneasy balance in the power relationship between individual states and the federal government, it seems the federal government gained an upperhand in the power equation. The First World War (or WWI) started for no apparent or obvious reasons although it was believed the assassination of the Archduke Franz Ferdinand of Austria triggered it. This war started in 1914 and lasted until 1918 and it was originally mostly a European affair. This war later on became global and America, although leaning towards isolationsm, soon found it got involved in it on the side of the Allies or Triple Entente (Great Britain, France, and Russia against the Central Powers (consisting of Germany, Austria-Hungary, and later on, also Italy). It was the age of imperialism and colonization where countries vied for foreign territories and America entered the war supposedly to safeguard the democratic ideals it espouses but in real terms, America entered a period of its own imperialist ambitions. The federal government grew stronger in this period because of its Manifest Destiny polical doctrine (OSullivan 426). This was a time when America acquired several foreign territories such as Cuba, Puerto Rico, Guam, Hawaii, and the Philippines (in the 1898 Spanish-American War) after it had previously acquired vast territories formerly belonging to Mexico such as Texas, Illinois, Colorado, California, and Arizona. All these territorial acquisitions required a strong federal government for these actions to push through in Congress and in conduct of foreign policy. The expansionist strategy of America was soon followed by the Great Depression in 1929 that was started by a stock market crash on October 29, 1929 but later engulfed an entire world as assets prices collapsed. American citizens lost their life savings while the nations big wealth invested in its stock markets evaporated as panic ensued among the

Natural product chemistry

Natural product chemistry Introduction Of Natural Product Chemistry In the beginning of organic chemistry was natural products chemistry. For a long period, up to the 1960s the structural studies of natural products served as the principle driving force for the discovery of new chemical reactivity. The introduction of spectroscopic techniques, however, removed much of the intellectual challenge involved in structure elucidation. Furthermore, natural products chemistry suffered a dramatic decline from the mid 1990s when major pharmaceutical companies disinvested in this area and switched to more rational combi-chem approaches. Nevertheless, the improvements in spectroscopic methods have historically stimulated natural products chemistry and the efforts to examine new compounds from unusual organisms rapidly and systematically. Natural products chemistry survived and began to flourish again in recent years also through chemical biology and chemical genetics and the realization that natural product structures often explore structural space unavailable t o combi-chem approaches. As a result, challenges for natural product chemists are not diminishing, they are just changing. Natural product chemistry turned to an interdisciplinary science, where the success of a chemist would only be possible in close collaboration with biologists, pharmacologists, and clinicists. Thus many novel biological activities such as beta-tubulin assembly inhibitors for example, could only have emerged from the natural products arena. Contents Of Natural Chemistry Steroids.- Terpenoids.- Fatty Lipids and Prostaglandins.- Alkaloid.- Amino Acids and Proteins.- Nucleic Acids.- Carbohydrates.- Plant and Insect Growth Regulators.- Phenolic Compounds and Natural Dyes.- Marine Natural Products.- Antibacterials.- Vitamins and Hormones. Natural product A natural product is a chemical compound or substance produced by a living organism found in nature that usually has a pharmacological or biological activity for use in pharmaceutical drug discovery and drug design. A natural product can be considered as such even if it can be prepared by total synthesis. These small molecules provide the source or inspiration for the majority of FDA-approved agents and continue to be one of the major sources of inspiration for drug discovery. In particular, these compounds are important in the treatment of life-threatening conditions. Natural sources Natural products may be extracted from tissues of terrestrial plants, marine organisms or microorganism fermentation broths. A crude (untreated) extract from any one of these sources typically contains novel, structurally diverse chemical compounds, which the natural environment is a rich source of. Chemical diversity in nature is based on biological and geographical diversity, so researchers travel around the world obtaining samples to analyze and evaluate in drug discovery screens or bioassays. This effort to search for natural products is known as bioprospecting. Animal sources Animals can sometimes be a source of new lead compounds. For example, a series of antibiotic peptides were extracted from the skin of the African clawed frog and a potent analgesic compound called epibatidine was obtained from the skin extracts of the Ecuadorian poison frog. Screening of natural products Pharmacognosy provides the tools to identify, select and process natural products destined for medicinal use. Usually, the natural product compound has some form of biological activity and that compound is known as the active principle such a structure can act as a lead compound (not to be confused with compounds containing the element lead). Many of todays medicines are obtained directly from a natural source. On the other hand, some medicines are developed from a lead compound originally obtained from a natural source. This means the lead compound: can be produced by total synthesis, or can be a starting point (precursor) for a semisynthetic compound, or can act as a template for a structurally different total synthetic compound. This is because most biologically active natural product compounds are secondary metabolites with very complex structures. This has an advantage in that they are extremely novel compounds but this complexity also makes many lead compounds synthesis difficult and the compound usually has to be extracted from its natural source a slow, expensive and inefficient process. As a result, there is usually an advantage in designing simpler analogues. The plant kingdom Plants have always been a rich source of lead compounds (e.g. morphine, cocaine, digitalis, quinine, tubocurarine, nicotine, and muscarine). Many of these lead compounds are useful drugs in themselves (e.g. morphine and quinine), and others have been the basis for synthetic drugs (e.g. local anaesthetics developed from cocaine). Clinically useful drugs which have been recently isolated from plants include the anticancer agent paclitaxel (Taxol) from the yew tree, and the antimalarial agent artemisinin from Artemisia annua. Plants provide a large bank of rich, complex and highly varied structures which are unlikely to be synthesized in laboratories. Furthermore, evolution has already carried out a screening process itself whereby plants are more likely to survive if they contain potent compounds which deter animals or insects from eating them. Even today, the number of plants that have been extensively studied is relatively very few and the vast majority have not been studied at all. The marine world In recent years, there has been a great interest in finding lead compounds from marine sources. Coral, sponges, fish, and marine microorganisms have a wealth of biologically potent chemicals with interesting inflammatory, antiviral, and anticancer activity. For example, curacin A is obtained from a marine cyanobacterium and shows potent antitumor activity. Other antitumor agents derived from marine sources include eleutherobin, discodermolide, bryostatins, dolostatins, and cephalostatins. The microbial world Microorganisms such as bacteria and fungi have been invaluable for discovering drugs and lead compounds. These microorganisms produce a large variety of antimicrobial agents which have evolved to give their hosts an advantage over their competitors in the microbiological world. The screening of microorganisms became highly popular after the discovery of penicillin. Soil and water samples were collected from all over the world in order to study new bacterial or fungal strains, leading to an impressive arsenal of antibacterial agents such as the cephalosporins, tetracyclines, aminoglycosides, rifamycins, and chloramphenicol. Although most of the drugs derived from microorganisms are used in antibacterial therapy, some microbial metabolites have provided lead compounds in other fields of medicine. For example, asperlicin isolated from Aspergillus alliaceus is a novel antagonist of a peptide hormone called cholecystokinin (CCK) which is involved in the control of appetite. CCK also acts as a neurotransmitter in the brain and is thought to be involved in panic attacks. Analogues of asperlicin may therefore have potential in treating anxiety. Other examples include the fungal metabolite lovastatin, which was the lead compound for a series of drugs that lower cholesterol levels, and another fungal metabolite called ciclosporin which is used to suppress the immune response after transplantation operations. Venoms and toxins Venoms and toxins from animals, plants, snakes, spiders, scorpions, insects, and microorganisms are extremely potent because they often have very specific interactions with a macromolecular target in the body. As a result, they have proved important tools in studying receptors, ion channels, and enzymes. Many of these toxins are polypeptides (e.g. É‘-bungarotoxin from cobras). However, non-peptide toxins such as tetrodotoxin from the puffer fish are also extremely potent. Venoms and toxins have been used as lead compounds in the development of novel drugs. For example, teprotide, a peptide isolated from the venom of the Brazilian viper, was the lead compound for the development of the antihypertensive agents cilazapril and captopril. The neurotoxins from Clostridium botulinum are responsible for serious food poisoning (botulism), but they have a clinical use as well. They can be injected into specific muscles (such as those controlling the eyelid) to prevent muscle spasm. These toxins prevent cholinergic transmission and could well prove a lead for the development of novel anticholinergic drugs. Traditional Medicine In the past, traditional peoples or ancient civilizations depended greatly on local flora and fauna for their survival. They would experiment with various berries, leaves, roots, animal parts or minerals to find out what effects they had. As a result, many crude drugs were observed by the local healer or shaman to have some medical use. Although some preparations may have been dangerous, or worked by a ceremonial or placebo effect, traditional healing systems usually had a substantial active pharmacopoeia, and in fact most western medicines up until the 1920s were developed this way. Some systems, like traditional Chinese medicine or Ayurveda were fully as sophisticated and as documented systems as western medicine, although they might use different paradigms. Many of these aqueous, ethanolic, distilled, condensed or dried extracts do indeed have a real and beneficial effect, and a study of ethnobotany can give clues as to which plants might be worth studying in more detail. Rhubarb root has been used as a purgative for many centuries. In China, it was called The General because of its galloping charge and was only used for one or two doses unless processed to reduce its purgative qualities. (Bulk laxatives would follow or be used on weaker patients according to the complex laxative protocols of the medical system.[2]) The most significant chemicals in rhubarb root are anthraquinones, which were used as the lead compounds in the design of the laxative dantron. The extensive records of Chinese medicine about response to Artemisia preparations for malaria also provided the clue to the novel antimalarial drug artemisinin. The therapeutic properties of the opium poppy (active principle morphine) were known in Ancient Egypt, were those of the Solanaceae plants in ancient Greece (active principles atropine and hyoscine). The snakeroot plant was well regarded in India (active principle reserpine), and herbalists in medieval England used extracts from the willow tree(salicin) and foxglove (active principle digitalis a mixture of compounds such as digitoxin, digitonin, digitalin). The Aztec and Mayan cultures of Mesoamerica used extracts from a variety of bushes and trees including the ipecacuanha root (active principle emetine), coca bush (active principle cocaine), and cinchona bark (active principle quinine). It can be challenging to obtain information from practitioners of traditional medicine unless a genuine long term relationship is made. Ethnobotanist Richard Schultes approached the Amazonian shamans with respect, dealing with them on their terms. He became a depswa medicine man sharing their rituals while gaining knowledge. They responded to his inquiries in kind, leading to new medicines.[3] On the other hand Cherokee herbalist David Winston recounts how his uncle, a medicine priest, would habitually give misinformation to the visiting ethnobotanists. The acupuncturists who investigated Mayan medicine recounted in Wind in the Blood had something to share with the native healers and thus were able to find information not available to anthropologists.[4] The issue of rights to medicine derived from native plants used and frequently cultivated by native healers complicates this issue. Isolation and purification If the lead compound (or active principle) is present in a mixture of other compounds from a natural source, it has to be isolated and purified. The ease with which the active principle can be isolated and purified depends much on the structure, stability, and quantity of the compound. For example, Alexander Fleming recognized the antibiotic qualities of penicillin and its remarkable non-toxic nature to humans, but he disregarded it as a clinically useful drug because he was unable to purify it. He could isolate it in aqueous solution, but whenever he tried to remove the water, the drug was destroyed. It was not until the development of new experimental procedures such as freeze drying and chromatography that the successful isolation and purification of penicillin and other natural products became feasible. Synthesis Not all natural products can be fully synthesized and many natural products have very complex structures that are too difficult and expensive to synthesize on an industrial scale. These include drugs such as penicillin, morphine, and paclitaxel (Taxol). Such compounds can only be harvested from their natural source a process which can be tedious, time consuming, and expensive, as well as being wasteful on the natural resource. For example, one yew tree would have to be cut down to extract enough paclitaxel from its bark for a single dose. Furthermore, the number of structural analogues that can be obtained from harvesting is severely limited. A further problem is that isolates often work differently than the original natural products which have synergies and may combine, say, antimicrobial compounds with compounds that stimulate various pathways of the immune system: Many higher plants contain novel metabolites with antimicrobial and antiviral properties. However, in the developed world almost all clinically used chemotherapeutics have been produced by in vitro chemical synthesis. Exceptions, like taxol and vincristine, were structurally complex metabolites that were difficult to synthesize in vitro. Many non-natural, synthetic drugs cause severe side effects that were not acceptable except as treatments of last resort for terminal diseases such as cancer. The metabolites discovered in medicinal plants may avoid the side effect of synthetic drugs, because they must accumulate within living cells. Semisynthetic procedures can sometimes get around these problems. This often involves harvesting a biosynthetic intermediate from the natural source, rather than the final (lead) compound itself. The intermediate could then be converted to the final product by conventional synthesis. This approach can have two advantages. First, the intermediate may be more easily extracted in higher yield than the final product itself. Second, it may allow the possibility of synthesizing analogues of the final product. The semisynthetic penicillins are an illustration of this approach. Another recent example is that of paclitaxel. It is manufactured by extracting 10-deacetylbaccatin III from the needles of the yew tree, then carrying out a four-stage synthesis. Use Of Natural Product Ayurveda Chinese medicine Ethnobotany Journal of Natural Products Pharmacognosy Phytotherapy Secondary metabolite During the last few decades, research into natural products has advanced tremendously thanks to contributions from the fields of chemistry, life sciences, food science and material sciences. Comparisons of natural products from microorganisms, lower eukaryotes, animals, higher plants and marine organisms are now well documented. This book provides an easy-to-read overview of natural products. It includes twelve chapters covering most of the aspects of natural products chemistry. Each chapter covers general introduction, nomenclature, occurrence, isolation, detection, structure elucidation both by degradation and spectroscopic techniques, biosynthesis, synthesis, biological activity and commercial applications, if any, of the compounds mentioned in each topic. Therefore it will be useful for students, other researchers and industry. The introduction to each chapter is brief and attempts only to supply general knowledge in the particular field. Furthermore, at the end of each chapter t here is a list of recommended books for additional study and a list of relevant questions for practice. Combined with pharmacological screening, natural products chemistry has always provided highly useful leads for drug discovery. The searches for new biologically active compounds are most often based on hints coming from ethnobotany but there are still a huge number of unstudied plants, not to speak of mushrooms, marine organisms, insects, and microorganisms. There is a wealth of molecular diversity out there, waiting to be discovered and utilized. The central issue of such type of studies, structure elucidation, although often believed to be trivial, is still a process full of adventure, discovery, and even unavoidable pitfalls. Thus structure elucidation has still much to offer, especially when combined with biological tests. Chemistry Central Journal is waiting for your results to publish. Besides the classic studies connected to pharmacological activities, new developments challenge natural products chemists, such as metabolomics, the large-scale phytochemical analysis in the functional genomics era. Metabolomic requires from a natural product chemist brilliant knowledge of modern analytical techniques and chemometry and close collaboration with biochemists and biologists. Chemical ecology, too, could not advance properly without natural product chemistry. Approximately 60% of the worlds population relies almost entirely on plants for medication. However, if phytopharmaceuticals want to be regarded as rational drugs, they need to be standardized and pharmaceutical quality must be approved. For this reason, another important task for natural products chemistry is connected to standardization: to develop proper analytical methods of quality control, to make sure that medicines obtained from natural sources are safe and of reproducible efficacy. The publication of natural product research results in an open access journal is of great importance with respect both to research activities and to effective use of natural resources, removing both price and permission barriers. It is also important to authors, giving them the opportunity to publish their results where they will be most easily accessed by those who mostly need them. Natural Product Chemistry for Drug Discovery provides a comprehensive summary of where natural product chemistry is today in drug discovery. The book covers emerging technologies and case studies and is a source of up-to-date information on the topical subject of natural products. The authors, all experts in their respective fields, provide compelling arguments as to why naturel products should be considered important tools in the drug discovery process. The book will appeal across the board from scientists to professionals, postgraduates and industrial chemists. The case studies selected for inclusion highlight recently marketed drugs and development candidates that have been derived from natural products. These real-life examples show how new technologies, such as advances in screening, isolation, dereplication and prefractionation, have significantly enhanced the discovery process. Introduction Of Synthetic Chemistry In primitive societies, even today, clothes are cleaned by beating them on rocks near a stream. Certain plants, such as soapworts, have leaves that produce sapions, chemical compounds that give a soapy lather. These were probably the first detergents people used. If you look up detergent in a dictionary it is simply defined as cleaning agent. During the last two to three decades, however, the word detergent has tended to imply synthetic detergent, or syndet for short, rather than the older soap. In fact, commercial formulations consist of a number of components, and we shall use the term surface-active agent, or its abbreviation surfactant, to describe the special active ingredients that give detergents their unusual properties. Soap, by this definition, is a surfactant. In fact, it is the oldest one and has been in use for over 4500 years. Some soap manufacture took place in Venice and Savona in the fifteenth century, and in Marseilles in the seventeenth century. By the eighteenth century, manufacture was widespread throughout Europe and North America, and by the nineteenth century the making of soap had become a major industry. As a matter of fact, soap became a detergent in 1907 when a German company put the product Persil on the market. In addition to the carboxylic acid soap, Persil contained sodium perborate, sodium silicate and sodium carbonate. Hence perborate + silicate = PERSIL. Synthetic Surfactant or Soap? You may well ask why soap, which served well for so many years, was eventually displaced. Soaps are cheap and they are manufactured from a renewable source, whereas many of the synthetic detergents are made from petrochemicals. Soaps are also biodegradable; that is, they are readily broken down by bacteria, and thus they do not pollute rivers. However, due to their gelling properties, soaps do have a greater tendency to clog sewerage reticulation systems than synthetic detergents. The grease trap of a non-sewered house was often laden with soap. But the most important reason for the displacement of soap is the fact that, when a carboxylic acid soap is used in hard water, precipitation occurs. The calcium and magnesium ions, which give hardness to the water, form insoluble salts with the fatty acid in soap and a curd-like precipitate occurs and settles, of course, on what ever is being washed. By using a large excess of soap, it is possible to redisperse the precipitate, but it is ext remely sticky and difficult to move. This problem with soap can be demonstrated by a simple experiment in which a concentrated solution of hard-water salts is added to a 0.1% solution of soap and also to a 0.1% solution of synthetic surfactant. The soap precipitates, but the synthetic surfactant remains clear because its salts are water soluble. You may live in an area where the water is extremely soft. But calcium and magnesium ions are present in the dirt that you wash out of your clothes, so that some precipitation still occurs if soap is used, and gradually deposits are built up in the fabric. There are other disadvantages with soap; it deteriorates on storage, and it lacks cleaning power when compared with the modern synthetic surfactants, which can be designed to perform specialised cleaning tasks. Finally and very importantly from a domestic laundry point of view, soap does not rinse out; it tends to leave a residue behind in the fabric that is being washed. A residue gradually builds up and causes bad odour, deterioration of the fabric and other associated problems. Whats the Difference? Whats the difference between a surfactant and soap? In general terms, the difference can be likened to the difference between cotton and nylon. On the one hand, soap and cotton are produced from natural products by a relatively small modification. On the other hand, synthetic surfactants and nylon are produced entirely in a chemical factory. Synthetic surfactants are not very new, either. Back in 1834 the first forerunner of todays synthetic surfactants was produced in the form of a sulfated castor oil, which was used in the textile industry. The development of the first detergents in an effort to overcome the reaction of soaps with hard water provides a good illustration of one of the standard chemical approaches. If a useful substance has some undesirable property, an attempt is made to prepare an analogue, a near chemical relation, which will prove more satisfactory. The petroleum industry had, as a waste product, the compound propylene, CH3-CH=CH2, which used to be burnt off. By joining four of these propylene molecules together and if benzene is attached at the double bond, the resulting compound reacts with sulphuric acid. Then sodium hydroxide is added to neutralise the sulfonic acid and a sodium salt is obtained. The new substance is closely related to an ordinary soap, and is an excellent detergent. Detergent Foam Level The relationship between foaming power and detergency has always been of interest, and foaming power has become associated in many consumers minds with high detergent power. The first liquid detergent on the Australian market was Trix. It was non-foaming, so was soon replaced because of consumer resistance. However, it is generally conceded by detergent technologists that foam height has no direct relationship to cleaning power in ordinary fabric washing systems. In systems where the amount of washing fluid is low, foam may play an important role. The individual foam films tend to take up and hold particles of soil that have been removed from the item, preventing them from being re-deposited and allowing them to be washed or scraped away. Front loading washing machines work by bashing clothes against the side of the tub the high tech version of beating clothes on rocks. Front loaders clean clothes better than top loaders, but only if a low-suds detergent is used, because the suds cushion the impact and reduce the cleaning action. Chemical Characteristics Of Synthetic Chemistry Synthetic detergents dissolve or tend to dissolve in water or other solvents. To enable them to do this, they require distinct chemical characteristics. Hydrophilic (water loving) groupings in their molecular structure, and hydrophobic (water hating) groupings, help the detergent in its â€Å"detergency† action. This detergency depends on the balance of the molecular weight of the hydrophobic to the hydrophilic portion. This is called the HLB value, and can range from 1 upwards. HLB is Hydrophilic-Lypophilic Balance. As the 0HLB value increases, the product can tend towards being a paste or solid. The lower number HLB values tend to be less water soluble, and more oil soluble. The higher the HLB the more water soluble the product. Mixtures of low and high HLB detergents produce good detergents to handle oil, fat and grease, the higher HLB detergent helps solubilise the less water soluble, low HLB detergent into an aqueous system.

gay literature :: essays research papers

While sexual difference may not exist between lesbians all other forms of difference do. These include differences of identity: race, class origins, employment status, age, religion, physical abilities - and while we may struggle against these differences within our individual ‘spaces’ they have a material and institutional reality that cannot be wished away What, to you, seems important about the terms gay and lesbian in literature? In the face of a homophobic society we need creative and critical processes that draw out the complexity of lesbian lives and same sex choices, not a retreat into the comforting myths of heroines and unfractured, impeachable identities This quote addresses directly the primary difficulty of the issue. The terms gay and lesbian are useful in literature in that they allow a group of people who have been marginalised and even persecuted to become visible. They enable a way of life and a set of identities, harmonious or conflicting, to be presented, to be questioned, to be understood and accepted. As categories they create ‘space’ in which there may develop a more evolved understanding of texts and they also create a genre within which many lesbian and gay writers are comfortable with being placed. A gendered reading of a text can reveal undercurrents and depths which might otherwise not be apparent. These categories also make ‘space’ for the author within the text which leads to a closer tie between the author and the reader in the reading process. However the danger which this sort of terminology presents is that of homogenising ways both of reading and writing a text. In creating a category one is always not only creating an inclusive zone but in doing so also excluding certain elements. The risk is run of stultifying the creative process through the exclusion by a minority group of the minority groups within. As Bonnie Zimmerman writes in her essay ‘Lesbians like this and that’ By positing the lesbian as ‘excess’ in the patriarchal system we may fail to note the identities that function as ‘excess’ within our own newly created lesbian community. There is a risk of adopting a separatist approach, of placing the categories of gay and lesbian literature outside the mainstream and creating a gay canon but in doing so retaining the underlying values of that ‘patriarchal system.’ How does one avoid replicating the masculinist cultural error of taking the dominant for the universal