Sucrose is common sugar. It is a molecule composed of two monosaccharides: glucose and fructose. Sucrose is produced in plants, from which table sugar is refined, it has the molecular formula C12H22O11. For human consumption, sucrose is refined from either sugarcane or sugar beet. Sugar mills – located in tropical regions near where sugarcane is grown – crush the cane and produce raw sugar, shipped to other factories for refining into pure sucrose. Sugar beet factories are located in temperate climates where the beet is grown, process the beets directly into refined sugar; the sugar refining process involves washing the raw sugar crystals before dissolving them into a sugar syrup, filtered and passed over carbon to remove any residual colour. The sugar syrup is concentrated by boiling under a vacuum and crystallized as the final purification process to produce crystals of pure sucrose that are clear and sweet. Sugar is an added ingredient in food production and food recipes. About 185 million tonnes of sugar were produced worldwide in 2017.
The word sucrose was coined in 1857 by the English chemist William Miller from the French sucre and the generic chemical suffix for sugars -ose. The abbreviated term Suc is used for sucrose in scientific literature; the name saccharose was coined in 1860 by the French chemist Marcellin Berthelot. Saccharose is an obsolete name for sugars in general sucrose. In sucrose, the components glucose and fructose are linked via an ether bond between C1 on the glucosyl subunit and C2 on the fructosyl unit; the bond is called a glycosidic linkage. Glucose exists predominantly as two isomeric "pyranoses", but only one of these forms links to the fructose. Fructose itself exists as a mixture of "furanoses", each of which having α and β isomers, but only one particular isomer links to the glucosyl unit. What is notable about sucrose is that, unlike most disaccharides, the glycosidic bond is formed between the reducing ends of both glucose and fructose, not between the reducing end of one and the nonreducing end of the other.
This linkage inhibits further bonding to other saccharide units. Since it contains no anomeric hydroxyl groups, it is classified as a non-reducing sugar. Sucrose crystallizes in the monoclinic space group P21 with room-temperature lattice parameters a = 1.08631 nm, b = 0.87044 nm, c = 0.77624 nm, β = 102.938°. The purity of sucrose is measured by polarimetry, through the rotation of plane-polarized light by a solution of sugar; the specific rotation at 20 °C using yellow "sodium-D" light is +66.47°. Commercial samples of sugar are assayed using this parameter. Sucrose does not deteriorate at ambient conditions. Sucrose does not melt at high temperatures. Instead, it decomposes at 186 °C to form caramel. Like other carbohydrates, it combusts to carbon water. Mixing sucrose with the oxidizer potassium nitrate produces the fuel known as rocket candy, used to propel amateur rocket motors. C12H22O11 + 6 KNO3 → 9 CO + 3 N2 + 11 H2O + 3 K2CO3This reaction is somewhat simplified though; some of the carbon does get oxidized to carbon dioxide, other reactions, such as the water-gas shift reaction take place.
A more accurate theoretical equation is: C12H22O11 + 6.288 KNO3 → 3.796 CO2 + 5.205 CO + 7.794 H2O + 3.065 H2 + 3.143 N2 + 2.998 K2CO3 + 0.274 KOH Sucrose burns with chloric acid, formed by the reaction of hydrochloric acid and potassium chlorate: 8 HClO3 + C12H22O11 → 11 H2O + 12 CO2 + 8 HClSucrose can be dehydrated with sulfuric acid to form a black, carbon-rich solid, as indicated in the following idealized equation: H2SO4 + C12H22O11 → 12 C + 11 H2O + Heat. The formula for sucrose's decomposition can be represented as a two-step reaction: the first simplified reaction is dehydration of sucrose to pure carbon and water, carbon oxidises to CO2 with O2 from air. C12H22O11 + heat → 12 C + 11 H2O 12 C + 12 O2 → 12 CO2 Hydrolysis breaks the glycosidic bond converting sucrose into glucose and fructose. Hydrolysis is, however, so slow. If the enzyme sucrase is added, the reaction will proceed rapidly. Hydrolysis can be accelerated with acids, such as cream of tartar or lemon juice, both weak acids.
Gastric acidity converts sucrose to glucose and fructose during digestion, the bond between them being an acetal bond which can be broken by an acid. Given heats of combustion of 1349.6 kcal/mol for sucrose, 673.0 for glucose, 675.6 for fructose, digestion releases about 4 small calories per gram of each of these products. The biosynthesis of sucrose proceeds via the precursors UDP-glucose and fructose 6-phosphate, catalyzed by the enzyme sucrose-6-phosphate synthase; the energy for the reaction is gained by the cleavage of uridine diphosphate. Sucrose is formed by plants and cyanobacteria but not by other organisms. Sucrose is found in many food plants along with the monosaccharide fructose. In many fruits, such as pineapple and apricot, sucrose is the main sugar. In others, such as grapes and pears, fructose is the main sugar. Although sucrose is invariably isolated from natural sources, its chemical synthesis was first achieved in 1953 by Raymond Lemieux. In nature, sucrose is present in many plants, in particular their roots and nectars, because it serves as a way to store energy from photosynthesis.
Many mammals, birds and bacteria accumulate and feed on the sucrose in plants and for some it is their main food source. Seen from a human consumption perspective, honeybees are important because they accumulate sucrose and produce honey, an im
Autoimmunity is the system of immune responses of an organism against its own healthy cells and tissues. Any disease that results from such an aberrant immune response is termed an "autoimmune disease". Prominent examples include celiac disease, post-infectious IBS, diabetes mellitus type 1, Henloch Scholein Pupura sarcoidosis, systemic lupus erythematosus, Sjögren syndrome, eosinophilic granulomatosis with polyangiitis, Hashimoto's thyroiditis, Graves' disease, idiopathic thrombocytopenic purpura, Addison's disease, rheumatoid arthritis, ankylosing spondylitis, polymyositis and multiple sclerosis. Autoimmune diseases are often treated with steroids. In the 19th century it was believed that the immune system was unable to react against the body's own tissues. Paul Ehrlich, at the turn of the 20th century, proposed the concept of horror autotoxicus. Ehrlich adjusted his theory to recognize the possibility of autoimmune tissue attacks, but believed certain innate protection mechanisms would prevent the autoimmune response from becoming pathological.
In 1904 this theory was challenged by the discovery of a substance in the serum of patients with paroxysmal cold hemoglobinuria that reacted with red blood cells. During the following decades, a number of conditions could be linked to autoimmune responses. However, the authoritative status of Ehrlich's postulate hampered the understanding of these findings. Immunology became a biochemical rather than a clinical discipline. By the 1950s the modern understanding of autoantibodies and autoimmune diseases started to spread. More it has become accepted that autoimmune responses are an integral part of vertebrate immune systems. Autoimmunity should not be confused with alloimmunity. While a high level of autoimmunity is unhealthy, a low level of autoimmunity may be beneficial. Taking the experience of a beneficial factor in autoimmunity further, one might hypothesize with intent to prove that autoimmunity is always a self-defense mechanism of the mammal system to survive; the system does not randomly lose the ability to distinguish between self and non-self, the attack on cells may be the consequence of cycling metabolic processes necessary to keep the blood chemistry in homeostasis.
Second, autoimmunity may have a role in allowing a rapid immune response in the early stages of an infection when the availability of foreign antigens limits the response. In their study, Stefanova et al. injected an anti-MHC class II antibody into mice expressing a single type of MHC Class II molecule to temporarily prevent CD4+ T cell-MHC interaction. Naive CD4+ T cells recovered from these mice 36 hours post-anti-MHC administration showed decreased responsiveness to the antigen pigeon cytochrome c peptide, as determined by ZAP70 phosphorylation and interleukin 2 production, thus Stefanova et al. demonstrated that self-MHC recognition maintains the responsiveness of CD4+ T cells when foreign antigens are absent. Pioneering work by Noel Rose and Ernst Witebsky in New York, Roitt and Doniach at University College London provided clear evidence that, at least in terms of antibody-producing B cells, diseases such as rheumatoid arthritis and thyrotoxicosis are associated with loss of immunological tolerance, the ability of an individual to ignore "self", while reacting to "non-self".
This breakage leads to the immune system's mounting an effective and specific immune response against self determinants. The exact genesis of immunological tolerance is still elusive, but several theories have been proposed since the mid-twentieth century to explain its origin. Three hypotheses have gained widespread attention among immunologists: Clonal deletion theory, proposed by Burnet, according to which self-reactive lymphoid cells are destroyed during the development of the immune system in an individual. For their work Frank M. Burnet and Peter B. Medawar were awarded the 1960 Nobel Prize in Physiology or Medicine "for discovery of acquired immunological tolerance". Clonal anergy theory, proposed by Nossal, in which self-reactive T- or B-cells become inactivated in the normal individual and cannot amplify the immune response. Idiotype network theory, proposed by Jerne, wherein a network of antibodies capable of neutralizing self-reactive antibodies exists within the body. In addition, two other theories are under intense investigation: Clonal ignorance theory, according to which autoreactive T cells that are not represented in the thymus will mature and migrate to the periphery, where they will not encounter the appropriate antigen because it is inaccessible tissues.
Auto-reactive B cells, that escape deletion, cannot find the antigen or the specific helper T cell. Suppressor population or Regulatory T cell theory, wherein regulatory T-lymphocytes function to prevent, downregulate, or limit autoaggressive immune responses in the immune system. Tolerance can be differentiated into "central" and "peripheral" tolerance, on whether or not the above-stated checking mechanisms operate in the central lymphoid organs or the peripheral lymphoid organs, it must be emphasised that these theories are not mutually exclusive, evidence has been mounting suggesting that all of these mechanisms may contribute to vertebrate immunological tolerance. A puzzling feature of the documented loss of tolerance seen in spontaneous human autoimmunity is that it is entirely restricted
A learning management system is a software application for the administration, tracking and delivery of educational courses, training programs, or learning and development programs. The learning management system concept emerged directly from e-Learning. Although the first LMS appeared in the higher education sector, the majority of the LMSs today focus on the corporate market. Learning Management Systems make up the largest segment of the learning system market; the first introduction of the LMS was in the late 1990s. Learning management systems were designed to identify training and learning gaps, utilizing analytical data and reporting. LMSs are focused on online learning delivery but support a range of uses, acting as a platform for online content, including courses, both asynchronous based and synchronous based. An LMS may offer classroom management for instructor-led training or a flipped classroom, used in higher education, but not in the corporate space. An LMS delivers and manages all types of content, including video and documents.
In the education and higher education markets, an LMS will include a variety of functionality, similar to corporate but will have features such as rubrics and instructor facilitated learning, a discussion board, the use of a syllabus. A syllabus is a feature in the corporate LMS, although courses may start with heading-level index to give learners an overview of topics covered. There are several historical phases of distance education that preceded the development of the LMS: The first known document of correspondence teaching dates back to 1723, through the advertisement in the Boston Gazette of Caleb Phillips, professor of shorthand, offering teaching materials and tutorials; the first testimony of a bi-directional communication organized correspondence course comes from England, in 1840, when Isaac Pitman initiated a shorthand course, wherein he sent a passage of the Bible to students, who would send it back in full transcription. The success of the course resulted in the foundation of the phonographic correspondence society in 1843.
The pioneering milestone in distance language teaching was in 1856 by Charles Toussaint and Gustav Langenscheidt, who began the first European institution of distance learning. This is the first known instance of the use of materials for independent language study. Correspondence institutions in the United States and across Europe were encouraged and fostered by the development in 1680 of the penny post service, which allowed the delivery of letters and parcels for a penny; the concept of eLearning began developing in the early 20th century, marked by the appearance of audio-video communication systems used for remote teaching. In 1909, E. M. Forster published his story'The Machine Stops' and explained the benefits of using audio communication to deliver lectures to remote audiences. In 1920, Sidney L. Pressey developed the first teaching machine which offered multiple types of practical exercises and question formats. Nine years University of Alberta's Professor M. E. Zerte transformed this machine into a problem cylinder able to compare solutions.
This, in a sense was "multimedia", because it made use of several media to reach students and provide instruction. Printed materials would be joined by telephone, radio and TV broadcasts and video tapes; the earliest networked learning system was the Plato Learning Management system developed in the 1970s by Control Data Corporation. In the 1980s the modern telecommunications start to be used in education, with computers more present in the daily use of higher education institutions. Computer aided teaching aim to integrate technical and educational means and instruments to student learning; the trend shifted to video communication, as a result of which Houston University decided to hold telecast classes to their students for 13–15 hours a week. The classes took place in 1953, while in 1956, Robin McKinnon Wood and Gordon Pask released the first adaptive teaching system for corporate environments SAKI; the idea of automating teaching operations inspired the University of Illinois experts to develop their Programmed Logic for Automated Teaching Operations which enabled users to exchange content regardless of their location.
In the period between 1970 and 1980, educational venues were considering the idea of computerizing courses, including the Western Behavioral Sciences Institute from California that introduced the first accredited online-taught degree. The history of the application of computers to education is filled with broadly descriptive terms such as computer-managed instruction, integrated learning systems, computer-based instruction, computer-assisted instruction, computer-assisted learning; these terms describe drill-and-practice programs, more sophisticated tutorials, more individualized instruction, respectively. The term is used to describe a number of different educational computer applications. FirstClass by SoftArc, used by the United Kingdom's Open University in the 1990s and 2000s to deliver online learning across Europe, was one of the earliest internet-based LMSs; the first featured Learning Management System was called EKKO, developed and released by Norway's NKI Distance Education Network in 1991.
Three years New Brunswick's NB Learning Network presented a similar system designed for DOS-based teaching, devoted to business learners. Most modern LMSs are web-based. There are a variety of integration strategies for embedding content into LMSs, including AICC, xAPI, SCORM and LTI. LMSs were designed to be loc