Xem 1-20 trên 221 kết quả Chemical compounds
  • Mapping and classification of chemical compound names are important aspects of the tasks of BioNLP. This paper introduces the architecture of a system for the syntactic and semantic analysis of such names. Our system aims at yielding both the denoted chemical structure and a classification of a given name. We employ a novel approach to the task which promises an elegant and efficient way of solving the problem. The proposed system differs significantly from existing systems, in that it is also able to deal with underspecifying names and class names. ...

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  • Chemical substances (also called pure substances) may well be defined as "any material with a definite chemical composition" in an introductory general chemistry textbook.[2] According to this definition a chemical substance can either be a pure chemical element or a pure chemical compound. But, there are exceptions to this definition; a pure substance can also be defined as a form of matter that has both definite composition and distinct properties.[3] The chemical substance index published by CAS also includes several alloys of uncertain composition.

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  • Project Gutenberg's The Chemical History Of A Candle, by Michael Faraday This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.net Title: The Chemical History Of A Candle Author: Michael Faraday Release Date: December 26, 2004

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  • Chemists frequently refer to chemical compounds using chemical formulae or molecular structure of the compound. There has been a phenomenal growth in the number of chemical compounds being synthesized (or isolated), and then reported in the scientific literature by professional chemists around the world.[13] An enormous number of chemical compounds are possible through the chemical combination of the known chemical elements. As of May 2011, about sixty million chemical compounds are known.

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  • Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory. Other chemical substances commonly encountered in pure form are diamond (carbon), gold, table salt (sodium chloride) and refined sugar (sucrose). However, simple or seemingly pure substances found in nature can in fact be mixtures of chemical substances.

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  • This handbook is an encyclopedic treatment of chemical elements and their most important compounds intended for professionals and students in many areas of chemistry throughout the manufacturing, academic, and consulting communities.

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  • As early as the middle of the 19th century, scientists were beginning to isolate and characterize organic compounds from nature. Modern studies of the nature of natural products, those compounds not involved in primary metabolic processes, began in the 1930s and 1940s. In the decades that followed, scientists began to focus on why organisms produce these compounds.

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  • The Project Gutenberg EBook of An Introductory Course of Quantitative Chemical Analysis, by Henry P. Talbot This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.net Title: An Introductory Course of Quantitative Chemical Analysis With Explanatory Notes Author: Henry P. Talbot Release Date: June 30, 2004

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  • Environmental Chemistry is a relatively young science. Interest in this subject, however, is growing very rapidly and, although no agreement has been reached as yet about the exact content and limits of this interdisciplinary discipline, there appears to be increasing interest in seeing environmental topics which are based on chemistry embodied in this subject. One of the first objectives of Environmental Chemistry must be the study of the environment and of natural chemical processes which occur in the environment.

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  • This book is written primarily to engineering students in the fields of basic chemistry, environmental chemistry, food production, chemical and biochemical engineering who in the beginning of their university studies receive education in inorganic chemistry and applied chemistry in general. The aim of this book is to explain and clarify important terms and concepts which the students are supposed to be familiar with. The book can not replace existing educational textbooks but it gives a great supplement to the education within chemistry.

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  • Preparations derived from Lentinula edodes (Berk.) Pegl. mycelium are worldwide used as dietary supplements containing compounds active as immune system enhancers, demonstrating chemopreventive and anticancer activity. L. edodes mycelium enriched with organic forms of selenium like selenized yeast possess putative, higher cancer preventive properties. The objective of this study was to test the effect of enrichment in selenium on antioxidant, reducing and free radical scavenging activity of water and alcohol extracts from mycelium of L. edodes (Berk.).

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  • content decreased (Agblevor et al. 1994). The equivalents of chlorine per equivalent of alkali or alkaline earth metals increased from 3.4 to 8.5 during this filtration. This suggests that the residual inorganics may be present as chlorides and that much of the chlorine may be in solution. Chloride ions in solution will have an adverse effect on corrosion of many metals, including stainless steels such as SS304. Compared to coal and many crude oils, biomass has a low sulfur content.

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  • Plants defend themselves from other organisms by elaborating bioactive chemical defences. This is the essential basis of the use of herbal medicines that still represents a major therapeutic resort for much of humanity However, at the outset, it must be stated that any plant that is not part of our evolved dietary cultures is potentially dangerous. Commercial herbal medicinal preparations approved by expert regulatory authorities have a significant place in mainstream conventional medicine and in complementary medicine.

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  • Tham khảo sách 'project gutenberg's the chemical history of a candle, by michael faraday', khoa học tự nhiên, hoá học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả

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  • VNU Journal of Science, Natural Sciences and Technology 26 (2010) 161-164 Fresh leaves of Litsea glutinosa (Lour.) C. B. Rob. from Ha Tinh were steam distilled to produce an oil in 0.15% yield. The essential oil was analysis by a combination of capillary GC and GC/MS. Seventy eight compounds were detected in the oil, of which more than 95.18% were terpenoids. The major components were (E)-β-ocimene (13.35%), β-caryophyllene (27.20%) and bicyclogermacrene (18.16%).

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  • Electrolytes: solutes which carry electrical charge - these compounds are at least partially ionized 1. Strong Electrolytes = solutes almost completely ionized 2. Weak Electrolytes = solutes only partially ionized .Acids and Bases - electrolytes (can be weak or strong) 1. Bronsted-Lowery Theory: acids are proton donors bases are proton acceptors 2. Strong Acids and bases almost completely ionized 3. Weak acids and bases (poorly ionized). See Table 6-2 (memorize strong acids and bases)

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  • 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), also called dioxin, is among the most toxic anthropogenic substance ever identified. TCDD and a number of similar polychlorinated dioxins, dibenzofurans, and coplanar polychlorinated biphenyls (dioxin-like compounds [DLCs]) have been the subject of intense scientific research and frequently controversial environmental and health policies.

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  • The toxicity or carcinogenicity of each reagent used in this method has not been precisely defined; however, each chemical compound should be treated as a potential health hazard. From this viewpoint, exposure to these chemicals must be reduced to the lowest possible level by whatever means available. The laboratory is responsible for maintaining a current awareness file of OSHA regulations regarding the safe handling of the chemicals specified in this method.

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  • In our studies on the phytochemistry and biological activities of Croton tonkinensis Gagnep. (Euphorbiaceae) oriented by traditional medicine interesting biological activities of the plant were demonstrated in correlation with the ent-kaurane-type diterpenoid constituents. The high accumulation of the active principle ent-18-acetoxy-7-hydroxykaur-16-en-15-one (1) led to our recent study on the chemical modification of this lead compound. In this paper the transformations of 1 into several derivatives by hydrolysis, acetylation, and oxydation were reported.

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  • People of four generations ago lived at the turn of the 20th Century, before the invention and widespread use in agriculture and industry of thousands of synthetic chemicals. Those of us living in the early 21st Century inhabit a world where some of these substances – which were introduced as far back as the 1920s and employed more and more in the 1940s and '50s – have been around for decades. Now they are everywhere . . . including in the tissues of every human being on Earth.

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