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Louis Pasteur Louis Pasteur ( /ˈluːi pæˈstɜr/, French: [lwi pastœʁ]; December 27, 1822 – September 28, 1895) was a French chemist andmicrobiologist who was one of the most important founders of medical microbiology. He is remembered for his remarkable breakthroughs in the causes and preventions of diseases. His discoveries reduced mortality from puerperal fever, HP Pavilion G6-1223TX Laptop Keyboard and he created the first vaccines for rabies and anthrax. His experiments supported the germ theory of disease. He was best known to the general public for inventing a method to stop milk and wine from causing sickness, a process that came to be calledpasteurization. He is regarded as one of the three main founders of microbiology, HP Pavilion dv6-3180ef Laptop Keyboard together with Ferdinand Cohn and Robert Koch. Pasteur also made many discoveries in the field of chemistry, most notably the molecular basis for the asymmetry of certain crystals.[2] His body lies beneath the Institute Pasteur in Paris in a spectacular vault covered in depictions of his accomplishments in Byzantine mosaics.[3]SONY VAIO VGN-CS16G/Q Laptop Keyboard Louis Pasteur was born on December 27, 1822, in Dole in the Jura region of France, into the family of a poor tanner. Louis grew up in the town of Arbois.[2] This fact probably instilled in the younger Pasteur the strong patriotism that later was a defining element of his character. Louis Pasteur was an average student in his early years, but he was gifted in drawing and painting. SAMSUNG NP-N145-JP04 Laptop Keyboard His pastels and portraits of his parents and friends, made when he was 15, were later kept in the museum of the Pasteur Institute in Paris. He earned his bachelor of arts degree (1840) and bachelor of science degree (1842) at the École Normale Supérieure. After serving briefly as professor of physics at Dijon Lycée in 1848, LENOVO Ideapad U550 Laptop Keyboard he became professor of chemistry at theUniversity of Strasbourg,[2] where he met and courted Marie Laurent, daughter of the university's rector, in 1849. They were married on May 29, 1849, and together had five children, only two of whom survived to adulthood; the other three died of typhoid. These personal tragedies inspired Pasteur to try to find cures for diseases such as typhoid. SAMSUNG N145 Laptop Keyboard In Pasteur's early work as a chemist, he resolved a problem concerning the nature of tartaric acid (1848).[4][5][6][7][8] A solution of this compound derived from living things (specifically, wine lees) rotated the plane of polarization of light passing through it. The mystery was that tartaric acid derived by chemical synthesis had no such effect, even though its chemical reactions were identical and its elemental composition was the same.[9] This was the first time anyone had demonstrated chiral molecules.  ASUS A6M Laptop Keyboard Pasteur's doctoral thesis on crystallography attracted the attention of W. T. Fuillet, and he helped Pasteur garner a position of professor of chemistry at the Faculté (College) of Strasbourg.[2]HP G72-b01SA Laptop Keyboard In 1854, Pasteur was named Dean of the new Faculty of Sciences in Lille. It was on this occasion that Pasteur uttered his oft-quoted remark: "...dans les champs de l'observation, le hasard ne favorise que les esprits préparés" (In the field of observation, chance favors only the prepared mind.[10]) In 1856, he was made administrator and director of scientific studies of the École Normale Supérieure.[2]TOSHIBA Satellite L755-S5169 Laptop Keyboard Pasteur demonstrated fermentation is caused by the growth of micro-organisms, and the emergent growth of bacteria in nutrient broths is not due to spontaneous generation,[2] but rather to biogenesis (Omne vivum ex vivo "all life is from life").SONY VAIO PCG-FR415M Laptop Keyboard He exposed boiled broths to air in vessels that contained a filter to prevent all particles from passing through to the growth medium, and even in vessels with no filter at all, with air being admitted via a long tortuous tube that would not allow dust particles to pass. HP Pavilion dv6-3140sa Laptop Keyboard Nothing grew in the broths unless the flasks were broken open; therefore, the living organisms that grew in such broths came from outside, as spores on dust, rather than spontaneously generated within the broth. This was one of the last and most important experiments disproving the theory of spontaneous generation. The experiment also supported germ theory.[2]ACER Aspire 5553G Laptop Keyboard While Pasteur was not the first to propose germ theory (Girolamo Fracastoro, Agostino Bassi, Friedrich Henle and others had suggested it earlier), he developed it and conducted experiments that clearly indicated its correctness and managed to convince most of Europe it was true. Today, he is often regarded as the father of germ theory and bacteriology, together withRobert Koch.[11] HP Pavilion dv4-1050ee Laptop Keyboard Pasteur's research also showed the growth of micro-organisms was responsible for spoiling beverages, such as beer, wine and milk. With this established, he invented a process in which liquids such as milk were heated to kill most bacteria and moulds already present within them. Claude Bernard and he completed the first test on April 20, 1862. This process was soon afterwards known as pasteurization.[11] DELL Inspiron n7110 Laptop Keyboard Beverage contamination led Pasteur to the idea that micro-organisms infecting animals and humans cause disease. He proposed preventing the entry of micro-organisms into the human body, leading Joseph Lister to develop antiseptic methods in surgery. SONY VAIO VGN-AW11S/B Laptop Keyboard In 1865, two parasitic diseases called pébrine and flacherie were killing great numbers of silkworms at Alais (now Alès). Pasteur worked several years proving it was a microbe attacking silkworm eggs which caused the disease, and eliminating this microbe within silkworm nurseries would eradicate the disease.[2][11]FUJITSU Amilo Mini Ui 3520 Laptop Keyboard Pasteur also discovered anaerobiosis, whereby some micro-organisms can develop and live without air or oxygen, called thePasteur effect.

Immunology and vaccination

Pasteur's later work on diseases included work on chicken cholera. During this work, a culture of the responsible bacteriahad spoiled and failed to induce the disease in some chickens he was infecting with the disease. Upon reusing these healthy chickens, Pasteur discovered he could not infect them, even with fresh bacteria; the weakened bacteria had caused the chickens to become immune to the disease, though they had caused only mild symptoms.[2][11]ACER NSK-H3V1D Laptop Keyboard His assistant, Charles Chamberland (of French origin), had been instructed to inoculate the chickens after Pasteur went on holiday. Chamberland failed to do this, but instead went on holiday himself. On his return, the month-old cultures made the chickens unwell, but instead of the infection's being fatal, as it usually was, the chickens recovered completely. ASUS X53S Laptop Keyboard Chamberland assumed an error had been made, and wanted to discard the apparently faulty culture when Pasteur stopped him. Pasteur guessed the recovered animals now might be immune to the disease, as were the animals at Eure-et-Loir that had recovered from anthrax.[12] HP pavilion DV7-1000 Laptop Keyboard In the 1870s, he applied this immunization method to anthrax, which affected cattle, and aroused interest in combating other diseases. Pasteur publicly claimed he had made the anthrax vaccine by exposing the bacilli to oxygen. His laboratory notebooks, now in the Bibliothèque Nationale in Paris, in fact show Pasteur used the method of rivalJean-Joseph-Henri Toussaint, a Toulouse veterinary surgeon, to create the anthrax vaccine.[9][13] This method used the oxidizing agent potassium dichromate. Pasteur's oxygen method did eventually produce a vaccine but only after he had been awarded a patent on the production of an anthrax vaccine. The notion of a weak form of a disease causing immunity to the virulent version was not new; this had been known for a long time for smallpox. Inoculation with smallpox was known to result in far less scarring, and greatly reduced mortality, in comparison with the naturally acquired disease. Edward Jenner had also discovered vaccination, using cowpox to give cross-immunity to smallpox (in 1796), HP Pavilion DV7-3065dx Laptop Keyboard DELL Inspiron 1750 Laptop Keyboard and by Pasteur's time this had generally replaced the use of actual smallpox material in inoculation. The difference between smallpox vaccination and anthrax or chicken cholera vaccination was that the weakened form of the latter two disease organisms had been "generated artificially", so a naturally weak form of the disease organism did not need to be found. ACER NSK-H3V1D Laptop Keyboard This discovery revolutionized work in infectious diseases, and Pasteur gave these artificially weakened diseases the generic name of "vaccines", in honour of Jenner's discovery. Pasteur produced the first vaccine for rabies by growing the virus in rabbits, and then weakening it by drying the affected nerve tissue. ASUS X53S Laptop Keyboard The rabies vaccine was initially created by Emile Roux, a French doctor and a colleague of Pasteur who had been working with a killed vaccine produced by desiccating the spinal cords of infected rabbits. The vaccine had been tested only on 11 dogs before its first human trial.[2][9]Compaq Presario CQ57 Series Laptop Keyboard This vaccine was first used on 9-year old Joseph Meister, on July 6, 1885, after the boy was badly mauled by a rabid dog.[9] This was done at some personal risk for Pasteur, since he was not a licensed physician and could have faced prosecution for treating the boy. After consulting with colleagues, Pasteur decided to go ahead with the treatment. HP Envy 15 Laptop Keyboard Meister did not contract the disease. It is sometimes said that Pasteur saved the boy's life, but this cannot be maintained with certainty, since the risk of contracting rabies after such an exposure is estimated at around 15%.[14] Nonetheless, Pasteur was hailed as a hero and the legal matter was not pursued. The treatment's success laid the foundations for the manufacture of many other vaccines. The first of the Pasteur Institutes was also built on the basis of this achievement.[9]HP Pavilion DV6-1014el Laptop Keyboard Legal risk was not the only kind Pasteur undertook. In The Story of San Michele, Axel Munthe writes of the rabies vaccine research: Pasteur himself was absolutely fearless. Anxious to secure a sample of saliva straight from the jaws of a rabid dog, I once saw him with the glass tube held between his lips draw a few drops of the deadly saliva from the mouth of a rabid bull-dog, held on the table by two assistants, their hands protected by leather gloves. TOSHIBA Satellite P300 Laptop Keyboard Because of his study in germs, Pasteur encouraged doctors to sanitize their hands and equipment before surgery. Prior to this, few doctors or their assistants practiced these procedures. Compaq Presario CQ57 Series Laptop Keyboard In 1995, the centennial of the death of Louis Pasteur, the New York Times ran an article titled "Pasteur's Deception". After having thoroughly read Pasteur's lab notes, the science historian Gerald L. Geison declared Pasteur had given a misleading account of the preparation of the anthrax vaccine used in the experiment at Pouilly-le-Fort.[15] Max Perutz published a vigorous defense of Pasteur in the New York Review of Books.[16] HP Probook 4710S Laptop Keyboard  HP Pavilion G6-1223TX Laptop Keyboard

Faith and spirituality

Although his grandson, Louis Pasteur Vallery-Radot, wrote that Pasteur had only kept from his Catholic background a spiritualism without religious practice,[17] Catholic observers often said Louis Pasteur remained throughout his whole life an ardent Christian, and his son-in-law, in perhaps the most complete biography of Louis Pasteur, writes:  FUJITSU Amilo Mini Ui 3520 Laptop Keyboard Absolute faith in God and in Eternity, and a conviction that the power for good given to us in this world will be continued beyond it, were feelings which pervaded his whole life; the virtues of the gospel had ever been present to him. Full of respect for the form of religion which had been that of his forefathers, he came simply to it and naturally for spiritual help in these last weeks of his life.[18] IBM Lenovo ThinkPad X300 Laptop Keyboard Maurice Vallery-Radot, grandson of the brother of the son-in-law of Pasteur and outspoken Catholic, also holds that Pasteur fundamentally remained Catholic.[19] According to both Pasteur Vallery-Radot and Maurice Vallery-Radot, SONY Vaio PCG-K215S Laptop Keyboard the following well-known quotation attributed to Pasteur is apocryphal:[20] "The more I know, the more nearly is my faith that of the Breton peasant. Could I but know all I would have the faith of a Breton peasant's wife".[2] According to Maurice Vallery-Radot,[21] the false quotation appeared for the first time shortly after the death of Pasteur.[22DELL Inspiron 6400 Laptop Keyboard ] However, despite his belief in God, it has been said that his views were that of a freethinker than a Catholic, a spiritual more than a religious man.[23][24][25] He was also against mixing science with religion.[26][27]IBM Lenovo ThinkPad R51 1833 Laptop Keyboard Principal works Pasteur's principal works are: "Etudes sur le Vin", (1866); "Etudes sur le Vinaigre" (1868); "Etudes sur la Maladie des Vers à Soie" (2 vols., 1870); "Quelques Réflexions sur la Science en France" (1871); "Etudes sur la Bière" (1876); "Les Microbes organisés, leur rôle dans la Fermentation, la Putréfaction et la Contagion'" (1878); "Discours de Réception de M.L. Pasteur à l'Académie Française" (1882); and "Traitement de la Rage" (1886).[2]Compaq Presario CQ57 Series Laptop Keyboard Pasteur's death occurred in 1895, near Paris, from complications of a series of strokes that had started in 1868.[9] He died while listening to the story of St Vincent de Paul, whom he admired and sought to emulate.[2] He was buried in the Cathedral of Notre Dame, but his remains were reinterred in a crypt in the Institut Pasteur, Paris, where he is remembered for his life-saving work. ASUS X53S Laptop Keyboard Pasteur won the Leeuwenhoek medal, microbiology's highest Dutch honor in Arts and Sciences, in 1895. Both Institute Pasteur and Université Louis Pasteur were named after him.  HP G42-415DX Laptop Keyboard He was made a Knight of the Legion of Honour in 1853, promoted to Commander in 1868, to Grand Officer in 1878 and made aGrand Croix of the Legion of Honor–one of only 75 in all of France - in 1881. On June 8, 1886, the Ottoman Sultan Abdul Hamid II awarded Pasteur with the Order of the Medjidie (I. Class) and 10000 Ottoman liras.[28]TOSHIBA Satellite A305 Laptop Keyboard In many localities worldwide, streets are named in his honor. For example, in the USA: the medical school at Stanford University, Palo Alto and Irvine, California, Boston, Massachusetts and Polk, Florida, adjacent to the University of Texas Health Science Center at San Antonio; Jonquière, Québec; San Salvador de Jujuy and Buenos Aires (Argentina), HP G42-363LA Laptop Keyboard Great Yarmouthin Norfolk, in the United Kingdom, Jericho and Wulguru in Queensland, (Australia); Phnom Penh in Cambodia; Ho Chi Minh Cityin Vietnam; Batna in Algeria; Bandung in Indonesia, Tehran in Iran, adjacent to the Odessa State Medical University inOdessa, Ukraine; Milan in Italy and Bucharest, Cluj-Napoca and Timişoara in Romania. A large university hospital is named after him in Košice, Slovakia. Compaq Presario CQ71-430EM Laptop Keyboard In his honor, a statue of him located on the campus of San Rafael High School in San Rafael, California. Also, there is a Pasteur institute in Ootacamund, a hill station in south India, which is involved in vaccine trials and also rabies diagnosis. TOSHIBA Mini NB 505-SP0160 Laptop Keyboard A bronze bust of Pasteur resides on the French Campus of Kaiser Permanente's San Francisco Medical Center in San Francisco, California. The sculpture was designed by Harriet G. Moore and cast in 1984 by Artworks Foundry. In 1992 the Save Outdoor Sculpture! program surveyed the work and described it as being well maintained.[29]SONY VAIO VGN-NR11Z/S Laptop Keyboard Chemist A chemist is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties such as density and acidity. Chemists carefully describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms. Chemists carefully measure substance proportions, reaction rates, and other chemical properties. Lenovo 45N2106 Laptop Keyboard Chemists use this knowledge to learn the composition, and properties of unfamiliar substances, as well as to reproduce and synthesize large quantities of useful naturally occurring substances and create new artificial substances and useful processes. Chemists may specialize in any number of subdisciplines of chemistry. Materials scientists and metallurgists share much of the same education and skills with chemists. ACER Aspire 5742 Laptop Keyboard The work of chemists is often related to the work of chemical engineers, which are primarily concerned with the proper design, construction and evaluation of the most cost-effective large-scale chemical plants and work closely with industrial chemists on the development of new processes and methods for the commercial-scale manufacture of chemicals and related products. SAMSUNG NP-N150-JP01 Laptop Keyboard The roots of chemistry can be traced to the phenomenon of burning. Fire was a mystical force that transformed one substance into another and thus was of primary interest to mankind. It was fire that led to the discovery of iron and glass. After goldwas discovered and became a precious metal, many people were interested to find a method that could convert other substances into gold. COMPAQ Presario C700 Laptop Keyboard This led to the protoscience called Alchemy. The word chemist is derived from the New Latin noun chimista, an abbreviation of alchimista (alchemist). Alchemists discovered many chemical processes that led to the development of modern chemistry. Chemistry as we know it today, was invented by Antoine Lavoisier with his law of Conservation of mass in 1783.  HP 636376-001 Laptop Keyboard Thediscoveries of the chemical elements has a long history culminating in the creation of the periodic table by Dmitri Mendeleev. The Nobel Prize in Chemistry created in 1901 gives an excellent overview of chemical discovery since the start of the 20th century. SONY VAIO VGN-C2S Series Laptop Keyboard Jobs for chemists usually require at least a bachelor's degree, but many positions, especially those in research, require aPh.D. Most undergraduate programs emphasize mathematics and physics as well as chemistry, partly because chemistry is also known as "the central science", thus chemists ought to have a well-rounded knowledge about science. SONY VAIO VGN-NR11Z/S Laptop Keyboard At the Master's level and higher, students tend to specialize in a particular field. Fields of specialization include biochemistry, nuclear chemistry,organic chemistry, inorganic chemistry, polymer chemistry, analytical chemistry, theoretical chemistry, quantum chemistry,environmental chemistry, and physical chemistry. Postdoctoral experience may be required for certain positions. ACER Aspire 5742 Laptop Keyboard Workers whose work involves chemistry, but not at a complexity requiring an education with a chemistry degree, are commonly referred to as chemical technicians. Such technicians commonly do such work as simpler, repetitive analyses for quality control or in clinical laboratories.  TOSHIBA 9J.N7482.901 Laptop Keyboard Pasteur Institute The Pasteur Institute (French: Institut Pasteur) is a French non-profit private foundation dedicated to the study ofbiology, micro-organisms, diseases, and vaccines. It is named after Louis Pasteur, who made some of the greatest breakthroughs in modern medicine at the time, including pasteurization and vaccines for anthrax bacillus and rabies virus. The institute was founded on June 4, 1887, and inaugurated on November 14, 1888. HP 640436-001 Laptop Keyboard For over a century, the Institut Pasteur has been at the forefront of the battle against infectious disease. This worldwidebiomedical research organization based in Paris was the first to isolate HIV, the virus that causes AIDS, in 1983. Over the years, it has been responsible for breakthrough discoveries that have enabled medical science to control such virulent diseases as diphtheria, TOSHIBA Satellite L555-S7929 Laptop Keyboard tetanus, tuberculosis, poliomyelitis, influenza, yellow fever, and plague. Since 1908, eight Pasteur Institute scientists have been awarded the Nobel Prize for medicine and physiology, and the 2008 Nobel Prize in Physiology or Medicine was shared with two Pasteur scientists. HP Envy 15 Laptop Keyboard The Institut Pasteur was founded in 1887 by Louis Pasteur, the French scientist whose early experiments with fermentation led to pioneering research inbacteriology. TOSHIBA Satellite L775D-S7332 Laptop Keyboard A giant in science, Pasteur discovered the principle of sterilization which came to be known as "pasteurization." His discoveries led to the universal practice of surgical antisepsis. He also developed techniques of vaccination to control bacterial infection, as well as a successful vaccine to treatrabies.  ACER Aspire 7720 Laptop Keyboard Louis Pasteur was committed both to basic research and its practical applications. As soon as his institute was created, Pasteur brought together scientists with various specialties. The first five departments were directed by two normaliens (graduates of the École Normale Supérieure): Emile Duclaux (generalmicrobiology research) and Charles Chamberland (microbe research applied to hygiene), HP Probook 4320s Laptop Keyboard as well as a biologist, Ilya Ilyich Mechnikov (morphological microbe research) and two physicians, Jacques-Joseph Grancher (rabies) and Emile Roux (technical microbe research). One year after the inauguration of the Institut Pasteur, Roux set up the first course of microbiology ever taught in the world, then entitled Cours de Microbie Technique (Course of microbe research techniques).  SONY VAIO PCG-FR395EP Laptop Keyboard Although the center against rabies, directed by Jacques-Joseph Grancher and Émile Roux is more than functional, it is also so overcrowded that it becomes necessary to build a structure that Pasteur has been calling with the name “Institute Pasteur” long before it was even built. Since Pasteur can’t, for health reasons, do it himself, he delegates the task of projecting and creating the new building, situated on rue Dutot, to two of his most trusted colleagues, Grancher and Emile Duclaux.[1]HP G62-451SA Laptop Keyboard From the beginning the Institute experiences some economical difficulties that it is able to overcome thanks to the help of the government, some foreign rulers and Madame Boucicaut but this aid won’t in any way restrain its independence, therefore respecting Pasteur’s most important prerogative. The million francs left unused won’t be sufficient to provide for the Institute’s needs for long,  Lenovo ThinkPad T510-4314 Laptop Keyboard HP G62-451SA Laptop Keyboard but the prestigiousness and the social benefits it will bring to France justify and motivate the subsidy it will receive; also the money brought in from selling the vaccines in France and in the rest of the world will help in supporting it. In 1888 this foundation, which has obtained the full approval from the government, begins to function and from the beginning it is involved in the development and changes that France undergoes during the last decades of the XIX century.[2]TOSHIBA Satellite L775-S7243 Laptop Keyboard The statutes drawn by Pasteur and later approved by Duclaux and Grancher define, besides its absolute freedom and independence, the Institutes internal repartition: a rabies division controlled by Grancher, an anthrax one in Chamberland’s hands, who will also supervise the department of microbiology while Emile Roux will deal with microbial methods applied to medicine. ACER Aspire 5741Z Laptop Keyboard The Institute during World War I and World War II During the First World War the Institute was not only involved in the prevention of sanitary risks but also had to deal with the demands of the moment. The most urgent matter was to vaccinate the troops against typhoid fever, easily contracted by the soldiers who often had no choice but to drink from small streams or puddles from the last rain. By September 1914, ACER Aspire 5810T Laptop Keyboard the Institute was able to provide 670000 doses of the needed vaccine and continued to produce it throughout the conflict. It is important to note that the war brought to light germs that during times of peace were concealed deep within the soil or in pockets of putrefaction and therefore it revealed the true nature and severity of some types of pathologens that would otherwise have remained unknown. TOSHIBA NSK-TN0SC Laptop Keyboard That's howWeinberg[disambiguation needed], Metchnikoff’s scholar, disclosed the complex etiology of gas gangrene and created a vaccine for each one of the anaerobes associated with it.[3] The First World War involved science in warfare: a movement of active participation arose among researchers who felt the need to help France win the war. Lenovo Thinkpad X220 Laptop Keyboard This is why Gabriel Bertrand, with Roux’s authorization, crafted a grenade based on chloropicrin and Fourneau discovered the chemical reaction that led to the formation of methylarsine chloride whose effects are even worse than the ones of other poisonous gases used during the war. Lenovo laptop keyboard In 1938 the Institute, despite its relative poverty, builds and edifice that hosts a biochemical division and another one dedicated to cellular pathology, whose direction is entrusted to the hands of Boivin (who will discover the endotoxines -more appropriately called glucid- lipo- polipeptidic toxines- that are contained in the germ’s body and are freed after its death) and during the same period Andre Lwoff assumes the direction of a new microbial physiology branch built on rue Dutot.[4] The general mobilitation determined by France’s war declaration against Germany, in September 1939, empties the Institute, SAMSUNG N145 Laptop Keyboard also significantly reducing its activities, of the members in the age or condition appropriate for being recruited in the army but the almost total absence of battles during the first months of the conflict keeps the sanitary situation on the front in the norm. The Germans never tried to gather information on the Institute’s research: SONY VAIO VGN-N21M/W Laptop Keyboard their confidence in Germany’s advantage in this field decreased their curiosity and their only interest was in the serums and vaccines that it could provide to their troops or the European auxiliaries they recluted. This – in the lack of a better term- freedom allowes the Institute to become, during the two years after the occupation, the greatest pharmacy for the Resistance thanks to the initiative of Vallery-Radot, Pasteur’s nephew. ACER Aspire 5741Z Laptop Keyboard The Germans become suspicious of the Institute’s staff only after the outbreak of a typhoid epidemic in a division of the Wehrmacht that was stationed in the parisian region before being sent to the Russian front.[5] The cause of the epidemy will be exposed later by some French men: a member of the Institute had stolen a culture of the germ responsible for the disease and, TOSHIBA Satellite 1800-921 Laptop Keyboard with the collaboration of an accomplice situated near the German troops, infected a large quantity of butter with it. The fact that, after the Germans sold some of the butter to the enemy, the epidemy spread to the civil population is proof that the illness’s breakout was not caused by the local waters. Afterwards the German authorities ordered that the Institute’s stoves containing microbial cultures could be opened only by authorized members of the personnel; a similar security problem also induces them to demand complete lists of the staff’s names and functions: TOSHIBA Satellite L775-S7243 Laptop Keyboard the reason behind some absences is well known to the German’s who sent two very valuable biologists, Doctor Wolmann and his wife, as well as other three lab assistants to a concentration camp. The Institute won’t constitute a location for entrenchment even after the burst of the battles for Paris’s liberation because its inviolability and sacredness as well as the fear that involving it in any type of conflict might “free the ghosts of long defeated diseases”.[6]HP Mini 110-3135dx Laptop Keyboard The Institute's economical difficulties during the Seventies At the end of 1973 the Institute’s economic status is so worrisome that its troubles arouse the public’s interest: no one can believe that an institution which has to provide vaccines and serums for more that fifty million people can be undergoing such big economic problems, an institution that furthermore is believed to be under the government protection –like the Bank of France- and therefore shielded from bankruptcy. The causes of the decadence that is bringing the Institute to ruins are multiple, ASUS X53S Laptop Keyboard but most of them can be identified with its commercial and industrial activities and its management. Both the research and production branch have to endure the recoil caused by financial issues: the research doesn’t receive enough funds and the production, which keeps losing market ground to the new private labs, is immobilized by the antiquated mechanical supplies. Compaq Presario CQ57 Series Laptop Keyboard When in 1968, after disappearing for a long period, rabies comes back to France, the Institute, who owes its original celebrity to this disease’s vaccine, is replaced by other pharmaceutical industries in the production of the vaccines; yet, despite the deficiencies in the production’s organization, its members are able to produce, in 1968, over 400000 doses of vaccine against the Hong Kong influenza. ACER Aspire 5610Z Laptop Keyboard In 1971 Jacques Monod announces a new era of modernization and development: this new awakening is symbolized by the construction of a new factory where all the production’s departments are going to be reunited. Its construction will cost forty five millions and the Government, positively impressed by the Institute’s will to change, will grant it a sum of twenty million francs to bridge the deficit, followed by the people’s initiative to also accept a role in the division of the financial responsibilities.[7]TOSHIBA NSK-TBD01 Laptop Keyboard Not long after the Institute’s inauguration, Roux, now less occupied in the fight against rabies, resumes in a new lab and with the help of a new addition, Yersin, his experiments on diphtheria. This disease used to kill every year thousands of children: commonly called “croup” because it creates fake membranes in the small patient’s throat, HP 597635-001 Laptop Keyboard therefore killing him by suffocation, deserves to be called “Horrible monster, sparrow hawk of the shadows” by Victor Hugo in his “Art of being a grandfather”. The painter Albert Gustaf Aristides Edelfelt has drawn a famous painting portraying Pasteur in his laboratory while he is trying to cure this illness that was handled at the times through procedures that were just as cruel as the illness itself.  HP 516884-001 Laptop Keyboard Roux and Yersin grow the bacillus that causes it and study, thanks to various experiments they do on rabbits, its pathogenic power and symptoms, like the paralysis of the respiratory muscles.[8]SONY VAIO VGN-FS115Z Laptop Keyboard It is this last consequence of the diphtheria that provides the two researchers with a valuable clue of the nature of the disease since it is caused by an intoxication due to a toxin introduced into the organism by the bacillus, that while secreting this particular venom is able to multiply itself: they are therefore inclined to think that the bacillus owes its virulence to the toxin.  ASUS X53S Laptop Keyboard After filtrating the microbial culture of the Corynebacterium diphtheriae and injecting it into the lab animals, they are able to observe all the typical signs of the sickness. Roux and Yersin establish that they are dealing with a new type of bacillus, not only able to proliferate and abundantly reproduce itself, but also capable of spreading at the same time a powerful venom and they deduce that it can play the role of antigen, TOSHIBA Satellite L775D-S7305 Laptop Keyboard that is if they can overcome the delicate moment of its injection, made especially dangerous by the toxin.[9] Some German researchers have also discovered the diphtheria toxin and are trying to immunize some guinea pigs through the use of a vaccine: one of them, Von Behring, Robert Koch's student states that he was able to weaken small doses of the toxin.  HP G62-225NR Laptop Keyboard Nonetheless Roux is not convinced by this result since no one knows the collateral effects of the procedure and prefers to use serotherapy since more than one lab research- like the one accomplished by Charles Richet- demonstrated that the serum of an animal vaccinated against the disease includes the antibodies needed to defeat it. HP 599572-001 Laptop Keyboard The antidiphtheria serum which is able to agglutinate the bacteria and neutralize the toxin is supplied by a horse inoculated with the viral germs and it is separated from the blood drawn from the horses’ jugular vein. Like it happened for his teacher with the antirabies vaccine, Roux will need to test the effectiveness of the product he elaborated and endure all the stress and ethical dilemmas that the first use of such a risky HP pavilion DV7-1000 Laptop Keyboard but also groundbreaking procedure implies. To test the serum two groups of children are chosen from two different hospitals: in the first one, which receives the serum, 338 out of 449 children survive, in the latter one, treated with the custom therapies, only 204 out of 520 do. Once the results are made public by “Figaro`” newspaper a subscription is opened to raise the money needed to provide the Institute the amount of horses necessary to produce enough serum to satisfy the national demand.[10] SONY VAIO VGN-C2S Series Laptop Keyboard After Duclaux’s death, Roux takes his place as head of the Institute and the last research he carries out is the one on syphilis, a dangerous disease because of its immediate effects and the hereditary ripercussions that result from it. Despite Fournier’s considerable work Van Swieten’s liquid mercury is still the only known cure, although its results are doubtful and uncertain. SONY VAIO PCG-FR415M Laptop Keyboard The search for a stronger remedy against this disease is made more difficult because most animals are immune to it: it is thus not possible to experiment possible cures and study their likely side effects.[11] The sexually transmittable Treponema pallidum ( the syphlis germ), detected by two german biologists, Schaudinne and Hoffmann[disambiguation needed], HP pavilion DV7-1000 Laptop Keyboard affects only the human race – where it resides in sperm, ulceration and cancers that it is able to cause- and, as it will be later discovered, some anthropoid apes, especially chimpanzees. Both Roux and Metchnikoff, consequently to the discovery that this type of ape can be contaminated with the illness, contributed with their research in creating a vaccine ( while Bordet and Wasserman[disambiguation needed]HP 597635-001 Laptop Keyboard elaborate a solution that is able to expose the germ’s presence in human blood): even though it is not yet a completely reliable solution it represents a noteworthy evolution compared to the previous medicines used against syphilis.[12]HP Mini 110-3118cl Laptop Keyboard

Metchnikoff’s phagocytosis theory

Ilya Ilyich Mechnikov already enounced the “principle of immunization” during this voluntary exile in Italy where he went to undertake some studies, the results of which he had promptly communicated to Pasteur. The phagocytosis theory is based on the notion that phagocytes are cells that have the power to englobe foreign bodies- and above all bacteria- introduced inside an organism. HP 636191-001 Laptop Keyboard German biologists opposed to his doctrine the humoral theory: they claimed to have found in Roux's serum some substances able to reveal the presence of microbes and to ensure their destruction if properly stimulated. The German scientistEduard Buchner referred to this substances as “alexine” and two other biologists, Von Behring and Kitasato, demonstrated their lytic power towards bacteria.[13]  ASUS X53S Laptop Keyboard In 1894 one of these scientist published the result of an experiment that appeared to completely refute Metchnikoff’s ideas: using the cholera vibrio, discovered ten years before by Robert Koch, as an antigen,  HP 636191-001 Laptop Keyboard Richard F. J. Pfeiffer introduced it in the abdomen of a guinea pig already vaccinated against this disease and was able to observe the destruction of the vibrio in the local blood plasma, without the participation of the phagocytes. Not even this study is able to shake Metchnikoff’s belief and faith in his theory and his ideas, as well as Pfeiffer’s and Buchner’s will all contribute to the elaboration of the current theory of the immune system. Compaq Presario CQ42-219TU Laptop Keyboard Yersin's studies on the plague Yersin, after his research with Roux, leaves abruptly the Institute for personal reasons, without losing Pasteur’s benevolence, who never doubts that the young man is destined to great things in the scientific area and will contribute in spreading the pastorian spirit around the world. The news of a violent plague outburst in Yunman enables Yersin to truly show and reach his potential as he is called, SONY V-0709BIAS1-US Laptop Keyboard as Pasteur’s scholar, to conduct a microbiological research of the disease. The plague he has to deal with is the “bubonic plague” which is recognizable most of the time through the abscesses, “buboes”, it provokes in its victims.  ACER Aspire 5735 Laptop Keyboard Yersin looks for the germ responsible for the infection specifically in this plague-spots, tumors caused by the inflammation of the lymphatic glands which become black because of the necrosis of the tissue.[14] After many microscopic exams he is able to state that in most of the cases the bubonic plague bacterium is located in these buboes; but in the meanwhile the Japanese scientist Kitasato also declares that he has isolated the bacterium, DELL Inspiron N4110 Laptop Keyboard even though the description he provides is dissimilar to the one given by Yersin. Therefore, although at first named “Kitasato-Yersin bacillus” by the scientific community, the microbe will later assume only the latter’s name because the one identified by Kitasato, a type of streptococcus, cannot be found in the lymphatic glands. TOSHIBA Satellite pro 4600 Laptop Keyboard However it is Paul-Louis Simond the first to understand and describe the etiology of the plague and its modality of contamination: he observes all over the bodies of the people affected by it small flea bites, which he also found on the bodies of the dead rats that were always linked to the plague and then deduced that the fleas, which carried the bacteria, were its true cause and that they transmitted the illness by jumping from the dead rat's body to the human one and biting it.[15]TOSHIBA Satellite L40-18Z Laptop Keyboard In the beginning of the twentieth century the improvement of the general life conditions and the development of a more extensive conception of hygiene determines in France a slight regression in consumption cases: nonetheless the Institute’s labs, like many other ones, keeps trying to find among Koch’s bacillus many singularities the one that will allow them to find an antidote to its terrible consequences。HP Pavilion dv6-2113sa Laptop Keyboard . Right after he had discovered the bacillus, Koch had tried in vain to create a vaccine against it, however the injection of the filtrate he had prepared, later called old tubercolin had the effect of revealing who was phthisic from who wasn’t by causing in the latter-and not in the former-fever and light trembing. DELL Inspiron N4050 Laptop Keyboard The Institute’s newspaper was filled at the time with articles regarding tubercolosis, some of which written by Albert Calmette, who extended his research to a socio- professional category which was extremely affected by it, that is the miners in whom this disease is often anticipated or accompanied by silicosis and anchylostomiasis ( caused by a small intestinal worm that creates a state of anemia propitious to tubercolosis).[16] SONY VAIO VGN-NW240F Laptop Keyboard After finding a better solution to anchylostomiasis, he focused on creating a vaccine using the bacillus responsible for bovine tubercolosis, very similar to the human one as it causes almost the same symptoms. Having observed that most actinomycetales are saprophytes, that is able to survive outside of living organisms, with the help of a veterinary, HP G42-381TX Laptop Keyboard Camille Guerin, he attempted to create a special nutritious environment for the bacillus that, in time, altered its features by eliminating the virulence and leaving only the antigenic power. Both of the scientist knew that this arduous task would require a lot of effort and time because it was necessary to act on a large number of generations to change the genetic foundation of a species, TOSHIBA Satellite L40-139 Laptop Keyboard nevertheless the velocity of the bacteria’s reproduction allowed, since it was constantly monitored, to interfere with an important phase of its evolution. The environment deemed appropriate for the denaturation of the Mycobacterium bovis was a compost of potatoes cooked in the bile of an ox treated with glycerine and Calmette reinseminated it every three weeks for thirteen years, DELL Inspiron M5030 Laptop Keyboard while checking for an enfeeblement of the pathogenic power of the bacillus. Having finally lost completely its virulence, the bovine tubercolosis germ grown with their method was the principal prophylactic weapon against human tubercolosis and it helped to reduce considerably the frequency of this disease. SONY VAIO VGN-CR14GN Laptop Keyboard While experimenting on chimpanzees in Kindia, on whom he was able to test exhaustively his vaccine, Calmette also discovered that it can notably weaken some leprosy- its bacillus presents some similarities with Koch’s one- manifestations.[17]DELL Vostro 1015 Laptop Keyboard

Calmette's work in Saigon

In Saigon Albert Calmette also created the first over seas branch of the Institute where he produced an amount of smallpox and rabies vaccines sufficient to satisfy the needs of the population and started a study on venomous snakes, particularly cobras. During these studies Calmette discovered that the power of the venom as well as the tetanus’ one could be annihilated by the use of alkaline hypochlorites and was able therefore to create a serum, effective if injected right after the cobra’s bite. Back in France, he acquired enough snakes to continue his work and create serum for the local population.[18] HP 519265-001 Laptop Keyboard The scientist and writer Charles Nicolle while in Tunisi studied how epidemic typhus- known for the red spots it left on sick people that disappeared before their death- was transmitted. He noted that no matter how many sick people were hospitalized with typhus, the disease would not be transmitted to people who had other disease. HP Pavilion dv6-2112sa Laptop Keyboard The brilliant intuition that enabled him to guess how the contamination happened occurred to him while he was visiting the hospital: to get in he had to climb over the cadaver of a native located not far from where the in-patients left all their clothes and this is how he suddenly understood that the vector of the disease are louse. Nevertheless it wasn’t him who discovered the bacterium responsible for the disease but three other scientists,Ricketts[disambiguation needed], Wilder[disambiguation needed] and Prowazeki who called it Rickettsia prowazekii.[19]HP Pavilion DV6-6B00 Laptop Keyboard TOSHIBA Satellite L300 Laptop Keyboard During the summer of 1900, the extremely hot weather and scarcity of the hydric supply in Paris, usually insured by the Ourcq channel and by the "aqueduc de la Dhuis" force the authorities to pump water from the Seine, direct it towards the channels and to filter it in order to make it usable, a measure that in those times inevitably led to a sudden and alarming growth of the typhoid cases in Paris.  HP Pavilion DV6-6B00 Laptop Keyboard The cause of the disease, a bacillus that was discovered almost twenty years before by the German bacteriologist Karl Joseph Eberth and that looks like a bodyless spider, is constantly present in this river and not even pouring extensive quantities of ozone and of lime permanganate into its water is enough to exterminate the bacteria.[20] ASUS X53S Laptop Keyboard The difficulty in creating a vaccine is caused by the nature of the germ’s toxine: while the diphtheria bacillus secretes its toxine, the typhoid one contains inside its body the toxin which is therefore an endotoxine that is able to preserve its pathogenic power even after the death of the bacillus. COMPAQ Presario CQ60-260ES Laptop Keyboard The doctor André Chantemesse, who works in the Institute, unlike most of his colleagues is positive that “the XX century will see the disappearance of the typhoid fever like the XIX century has the smallpoxes’ one”. After working in the rabies division of Rue Vaquelin and studying the microbe that causes dysentery, he seeks the collaboration of a younger bacteriologist, TOSHIBA Mini NB 505-SP0160 Laptop Keyboard Fernald Widal: together they are able to immunize some guinea pigs by inoculating them with Eberth bacilluses previously killed by the heat, hence questioning the basis of the conventional vaccination method, built on the notion that only weakened -but not dead- bacteria can be used to immunize.[21]DELL Inspiron 1750 Laptop Keyboard After an extensive experimentation they develop a thorough process of immunization: three or four injections of germs treated at a temperature of 55 Celsius degrees can prevent and – if not done to late- effectively fight the fever. The bacillus doesn’t survive the heat, but the toxin it contains, adequately weakened, maintains its antigenic power and induces the production of antibodies. HP Pavilion dv6-2112sa Laptop Keyboard The Hospital Pasteur is built during the first year of the twentieth century in front of the Institute and is employed for a long time by the members as a field for clinical observation and experimentations of therapeutical processes elaborated by themselves. Since in the beginning it was provided with only 120 beds, every patient was so well isolated in his private room that each one could be almost considered a small pest house, TOSHIBA Satellite L775D-S7226 Laptop Keyboard ideal for quarantines. The construction of the Hospital was enabled by the gift of a rich benefactor, Madame Leabudy, while the money offered by another rich woman, the baroness Hirsch, was used to build a vast pavilion that accommodated the department of chemical biology of the Institute.[22]HP G62-b25SA Laptop Keyboard The work done in the new pavilion by Duclaux clarified how the human body accomplished some of its vital functions and brought to light the role of a diastaseand was finalized in resolving a controversy aroused between Pasteur and Berthelot after the publication of Claude Bernard’s posthumous essay regarding the nature of the agents impli

cated in some transformations that happen inside the plants like fermentation.  HP Pavilion DV7-3065dx Laptop Keyboard While Pasteur believed that the only substance implied in the process of fermentation was yeast, Bernard- and Berthelot in his own way- believed that some other soluble ferment was involved: a German chemist will demonstrate the existence of this “ferment”, a intracellular diastase and will call “zymase” what we know now as enzymes. TOSHIBA Satellite A205-S5805 Laptop Keyboard Duclaux’s study on the metabolism of nutrients will not have immediate practical applications but will reveal how extensive is the field of enzymes and open new roads that will lead biology to extend the knowledge on life’s mechanisms on a molecular level.[23]SONY VAIO VGN-AR170P Laptop Keyboard

Germ theory of disease

The ancient historical view was that disease was spontaneously generated instead of being created by microorganisms that grow by reproduction.[1] TheAtharvaveda, a sacred text of Hinduism, is one of the earliest ancient texts dealing with medicine. It identifies the causes of disease as living causative agents such as the yatudhānya, the kimīdi, DELL Inspiron N4050 Laptop Keyboard the kimi, and the durama. The atharvāns seek to kill them with a variety of drugs in order to counter the disease.[citation needed] One of the earliest western references to this latter theory appears in On Agriculture by Marcus Terentius Varro (published in 36 BC), wherein there is a warning about locating a homestead in the proximity of swamps: HP Pavilion dv6-2113sa Laptop Keyboard "...and because there are bred certain minute creatures that cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and there cause serious diseases."[2]IBM 39T0581 Laptop Keyboard\ Girolamo Fracastoro proposed in 1546 that epidemic diseases are caused by transferable seed-like entities that could transmit infection by direct or indirect contact or even without contact over long distances. The Italian Agostino Bassi is often credited with having stated the germ theory of disease for the first time, based on his observations on the lethal and epidemic muscardine disease of silkworms. ACER Aspire 5739G Laptop Keyboard In 1835, he specifically blamed the deaths of the insects on a contagious, living agent that was visible to the naked eye as powdery spore masses; this microscopic fungus was subsequently called Beauveria bassiana in his honor. ACER Aspire 5742Z Laptop Keyboard Microorganisms were first directly observed by Anton van Leeuwenhoek, who is considered the father of microbiology. Building on Leeuwenhoek's work, physicianNicolas Andry argued in 1700 that microorganisms he called "worms" were responsible for smallpox and other diseases.[3] Ignaz Semmelweis was a Hungarianobstetrician working at Vienna's Allgemeines Krankenhaus in 1847,  DELL Studio 1558 Laptop Keyboard when he noticed the dramatically high incidence of death from puerperal fever among women who delivered at the hospital with the help of the doctors and medical students. Births attended by the midwives were relatively safe. Investigating further, Semmelweis made the connection between puerperal fever and examinations of delivering women by doctors, and further realized that these physicians had usually come directly from autopsies.  Lenovo 45N2240 Laptop Keyboard Asserting that puerperal fever was a contagious disease and that matter from autopsies were implicated in its development, Semmelweis made doctors wash their hands with chlorinated lime water before examining pregnant women, thereby reducing mortality from childbirth from 18% to 2.2% at his hospital. Nevertheless, he and his theories were viciously attacked by most of the Viennese medical establishment. SAMSUNG NP-N150-KA03 Laptop Keyboard John Snow contributed to the formation of the germ theory when he traced the source of the 1854 cholera outbreak in Soho, London. The statistical analysis of the affected cases showed that the outbreak was not consistent with the miasma theory, which was prevalent at the time. HP Pavilion dv6-2170us Laptop Keyboard Contrary to the miasma model, he identified drinking water as the vessel for transmission of the disease. He found that cases occurred in the homes that obtained their water from the Broad Street pump, which was at the geographical center of the outbreak. Lenovo 04W0872 Laptop Keyboard Italian physician Francesco Redi provided early evidence against spontaneous generation. He devised an experiment in 1668 in which he used three jars. He placed a meatloaf and egg in each of the three jars. He had one of the jars open, another one tightly sealed, and the last one covered with gauze. After a few days, he observed that the meat loaf in the open jar was covered by maggots, HP Mini 311-1035TU Laptop Keyboard and the jar covered with gauze had maggots on the surface of the gauze. However, the tightly sealed jar had no maggots inside or outside it. He also noticed that the maggots were found only on surfaces that were accessible by flies. From this he concluded that spontaneous generation is not a plausible theory. Louis Pasteur further demonstrated between 1860 and 1864 that fermentation and the growth of microorganisms in nutrient broths did not proceed by spontaneous IBM Lenovo Thinkpad X201 Laptop Keyboard generation. He exposed freshly boiled broth to air in vessels that contained a filter to stop all particles passing through to the growth medium: and even with no filter at all, with air being admitted via a long tortuous tube that would not pass dust particles. Nothing grew in the broths, therefore the living organisms that grew in such broths came from outside, as spores on dust, rather than being generated within the broth. HP 640436-001 Laptop Keyboard In the 1870s, Joseph Lister was instrumental in developing practical applications of the germ theory of disease with respect to surgical techniques. Robert Koch was the first scientist to devise a series of tests used to assess the germ theory of disease.[1] Koch's Postulates were published in 1890, and derived from his work demonstrating that anthrax was caused by the bacterium Bacillus anthracis. These postulates are still used today to help determine whether a newly discovered disease is caused by a microorganism. SONY Vaio PCG-K215S Laptop Keyboardcrystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an ordered pattern extending in all three spatial dimensions. In addition to their microscopic structure, large crystals are usually identifiable by their macroscopic geometrical shape, consisting of flat faces with specific, characteristic orientations.[citation needed]ACER Aspire 5742 Laptop Keyboard The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms ofcrystal growth is called crystallization or solidification. The word crystal is derived from the Ancient Greek word κρύσταλλος(krustallos), meaning both “ice” and “rock crystal”,[1] from κρύος (kruos), "icy cold, frost".[2][3]HP 634139-001 Laptop Keyboard Common crystals include snowflakes, diamonds, and table salt; however, most common inorganic solids are polycrystals. Crystals are often symmetrically intergrown to form crystal twins. TOSHIBA Satellite L775D-S7305 Laptop Keyboard The scientific definition of a "crystal" is based on the microscopic arrangement of atoms inside it, called thecrystal structure. A crystal is a solid where the atoms form a periodic arrangement. (Quasicrystals are an exception, see below.) TOSHIBA Satellite L300 Laptop Keyboard Not all solids are crystals. For example, when liquid water starts freezing, the phase change begins with small ice crystals that grow until they fuse, forming a polycrystalline structure. In the final block of ice, each of the small crystals (called "crystallites" or "grains") is a true crystal with a periodic arrangement of atoms, but the whole polycrystal does not have a periodic arrangement of atoms, HP G62-a60EV Laptop Keyboard because the periodic pattern is broken at the grain boundaries. Most macroscopic inorganic solids are polycrystalline, including almost all metals,ceramics, ice, rocks, etc. Solids that are neither crystalline nor polycrystalline, such as glass, are calledamorphous solids, also called glassy, vitreous, or noncrystalline. SONY VAIO PCG-792L Laptop Keyboard These have no periodic order, even microscopically. There are distinct differences between crystalline solids and amorphous solids: most notably, the process of forming a glass does not release the latent heat of fusion, but forming a crystal does.  SONY VAIO VGN-FS415E Laptop Keyboard A crystal structure (an arrangement of atoms in a crystal) is characterized by its unit cell, a small imaginary box containing one or more atoms in a specific spatial arrangement. The unit cells are stacked in three-dimensional space to form the crystal.  HP G61-321NR Laptop Keyboard The symmetry of a crystal is constrained by the requirement that the unit cells stack perfectly with no gaps. There are 219 possible crystal symmetries, called crystallographic space groups. These are grouped into 7 crystal systems, such as cubic crystal system (where the crystals may form cubes or rectangular boxes, such as halite shown at right) or hexagonal crystal system (where the crystals may form hexagons, such asordinary water ice). SONY VAIO VGN-CR520E Laptop Keyboard Crystals are commonly recognized by their shape, consisting of flat faces with sharp angles. These shape characteristics are not necessary for a crystal—a crystal is scientifically defined by its microscopic atomic arrangement, not its macroscopic shape—but the characteristic macroscopic shape is often present and easy to see. HP 519265-001 Laptop Keyboard Euhedral crystals are those with obvious, well-formed flat faces. Anhedral crystals do not, usually because the crystal is one grain in a polycrystalline solid. The flat faces (also called facets) of a euhedral crystal are oriented in a specific way relative to the underlying atomic arrangement of the crystal: They are planes of relatively low Miller index.[4] TOSHIBA Satellite C650-182 Laptop Keyboard This occurs because some surface orientations are more stable than others (lower surface energy). As a crystal grows, new atoms attach easily to the rougher and less stable parts of the surface, but less easily to the flat, stable surfaces. Therefore, the flat surfaces tend to grow larger and smoother, until the whole crystal surface consists of these plane surfaces. (See diagram on right.) HP AEAT5U00010 Laptop Keyboard One of the oldest techniques in the science of crystallography consists of measuring the three-dimensional orientations of the faces of a crystal, and using them to infer the underlying crystal symmetry. SONY Vaio PCG-K215S Laptop Keyboard A crystal's habit is its visible external shape. This is determined by the crystal structure (which restricts the possible facet orientations), the specific crystal chemistry and bonding (which may favor some facet types over others), and the conditions under which the crystal formed. SONY VAIO VGN-NR11Z/S Laptop Keyboard Some crystals have formed by magmatic and metamorphic processes, giving origin to large masses of crystalline rock. The vast majority of igneous rocks are formed from molten magma and the degree of crystallization depends primarily on the conditions under which they solidified. Such rocks as granite, which have cooled very slowly and under great pressures, ASUS X53S Laptop Keyboard have completely crystallized; but many kinds of lava were poured out at the surface and cooled very rapidly, and in this latter group a small amount of amorphous or glassy matter is common. Other crystalline rocks, the metamorphic rocks such as marbles, mica-schistsand quartzites, are recrystallized. This means that they were at first fragmental rocks like limestone,  FUJITSU Amilo Mini Ui 3520 Laptop Keyboard shale and sandstoneand have never been in a molten condition nor entirely in solution, but the high temperature and pressure conditions ofmetamorphism have acted on them by erasing their original structures and inducing recrystallization in the solid state.[5]ACER Aspire 5742 Laptop Keyboard Other rock crystals have formed out of precipitation from fluids, commonly water, to form druses or quartz veins. Theevaporites such as rock salt, gypsum and some limestones have been deposited from aqueous solution, mostly owing toevaporation in arid climates. TOSHIBA Satellite L775D-S7226 Laptop Keyboard The same group of atoms can often solidify in many different ways. Polymorphism is the ability of a solid to exist in more than one crystal form. For example, water ice is ordinarily found in the hexagonal form Ice Ih, but can also exist as the cubic Ice Ic, the rhombohedral ice II, and many other forms. The different polymorphs are usually called different phases. HP 640436-001 Laptop Keyboard In addition, the same atoms may be able to form noncrystalline phases. For example, water can also form amorphous ice, while SiO2 can form both fused silica (an amorphous glass) and quartz (a crystal). Likewise, if a substance can form crystals, it can also form polycrystals.  HP QT6D Laptop Keyboard For pure chemical elements, polymorphism is known as allotropy. For example, diamond and graphite are two crystalline forms of carbon, while amorphous carbon is a noncrystalline form. Polymorphs, despite having the same atoms, may have wildly different properties. For example, diamond is among the hardest substances known, while graphite is so soft that it is used as a lubricant. SONY 148701322 Laptop Keyboard Polyamorphism is a similar phenomenon where the same atoms can exist in more than one amorphous solid form. Crystallization is the process of forming a crystalline structure from a fluid or from materials dissolved in a fluid. (More rarely, crystals may be deposited directly from gas; see thin-film deposition and epitaxy.) SONY VAIO VGN-CS16G/Q Laptop Keyboard Crystallization is a complex and extensively-studied field, because depending on the conditions, a single fluid can solidify into many different possible forms. It can form a single crystal, perhaps with various possible phases, stoichiometries, impurities, defects, HP G62-100SL Laptop Keyboard andhabits. Or, it can form a polycrystal, with various possibilities for the size, arrangement, orientation, and phase of its grains. The final form of the solid is determined by the conditions under which the fluid is being solidified, such as the chemistry of the fluid, the ambient pressure, the temperature, and the speed with which all these parameters are changing. Compaq Presario CQ71-420ER Laptop Keyboard Specific industrial techniques to produce large single crystals (called boules) include the Czochralski process and the Bridgman technique. Other less exotic methods of crystallization may be used, depending on the physical properties of the substance, includinghydrothermal synthesis, sublimation, or simply solvent-based crystallization. TOSHIBA Satellite C655-S5132 Laptop Keyboard Large single crystals can be created by geological processes. For example, selenite crystals in excess of 10 meters are found in theCave of the Crystals in Naica, Mexico.[6] For more details on geological crystal formation, see above. SONY VAIO VGN-CR31S Laptop Keyboard Crystals can also be formed by biological processes, see above. Conversely, some organisms have special techniques to preventcrystallization from occurring, such as antifreeze proteins. ACER Aspire 5810T Laptop Keyboard A few examples of crystallographic defects include vacancy defects (an empty space where an atom should fit),interstitial defects (an extra atom squeezed in where it does not fit), and dislocations (see figure at right). Dislocations are especially important in materials science, because they help determine the mechanical strength of materials.  HP COMPAQ NX6120 Laptop Keyboard Another common type of crystallographic defect is an impurity, meaning that the "wrong" type of atom is present in a crystal. For example, a perfect crystal of diamond would only contain carbon atoms, but a real crystal might perhaps contain a few boron atoms as well. These boron impurities change the diamond's color to slightly blue. Likewise, the only difference between ruby and sapphire is the type of impurities present in a corundum crystal. Compaq Presario CQ56-105TU Laptop Keyboard In semiconductors, a special type of impurity, called a dopant, drastically changes the crystal's electrical properties. Semiconductor devices, such as transistors, are made possible largely by putting different semiconductor dopants into different places, in specific patterns. TOSHIBA Satellite C655D-SP5003M Laptop Keyboard Twinning is a phenomenon somewhere between a crystallographic defect and a grain boundary. Like a grain boundary, a twin boundary has different crystal orientations on its two sides. But unlike a grain boundary, the orientations are not random, but related in a specific, mirror-image way. COMPAQ Presario CQ60-307EA Laptop Keyboard Crystalline structures occur in all classes of materials, with all types of chemical bonds. Almost all metal exists in a polycrystalline state; amorphous or single-crystal metals must be produced synthetically, often with great difficulty. Ionically bonded crystals can form upon solidification ofsalts, either from a molten fluid or upon crystallization from a solution.  FUJITSU Amilo Mini Ui 3520 Laptop Keyboard Covalently bonded crystals are also very common, notable examples being diamond,silica, and graphite. Polymer materials generally will form crystalline regions, but the lengths of the molecules usually prevent complete crystallization. Weakvan der Waals forces can also play a role in a crystal structure; for example, this type of bonding loosely holds together the hexagonal-patterned sheets ingraphite. Compaq Presario CQ71-420ER Laptop Keyboard A quasicrystal consists of arrays of atoms that are ordered but not strictly periodic. They have many attributes in common with ordinary crystals, such as displaying a discrete pattern in x-ray diffraction, and the ability to form shapes with smooth, flat faces. HP Pavilion dv6-2113sa Laptop Keyboard HP G72-b15SA Laptop Keyboard Quasicrystals are most famous for their ability to show five-fold symmetry, which is impossible for an ordinary periodic crystal (see crystallographic restriction theorem). The International Union of Crystallography has redefined the term "crystal" to include both ordinary periodic crystals and quasicrystals ("any solid having an essentially discrete diffraction diagram"[7]). Compaq Presario CQ42-228LA Laptop Keyboard Quasicrystals, first discovered in 1982, are quite rare in practice. Only about 100 solids are known to form quasicrystals, compared to about 400,000 periodic crystals measured to date.[8] The 2011 Nobel Prize in Chemistry was awarded to Dan Shechtman for the discovery of quasicrystals.[9]SONY Vaio PCG-K315S Laptop Keyboard Crystals can have certain special electrical, optical, and mechanical properties that glass and polycrystals normally cannot. These properties are related to the anisotropy of the crystal, i.e. the lack of rotational symmetry in its atomic arrangement. One such property is thepiezoelectric effect, where a voltage across the crystal can shrink or stretch it. FUJITSU Amilo Mini Ui 3520 Laptop Keyboard Another is birefringence, where a double image appears when looking through a crystal. Moreover, various properties of a crystal, including electrical conductivity, electrical permittivity, and Young's modulus, may be different in different directions in a crystal. For example, graphite crystals consist of a stack of sheets, and although each individual sheet is mechanically very strong, the sheets are rather loosely bound to each other. Therefore, the mechanical strength of the material is quite different depending on the direction of stress. HP Pavilion G6-1B59WM Laptop Keyboard Not all crystals have all of these properties. Conversely, these properties are not quite exclusive to crystals. They can appear in glasses or polycrystals that have been made anisotropic by working or stress--for example, stress-induced birefringence. HP Envy 15  Keyboard COMPAQ 367777-001  Keyboard

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