Xem 1-20 trên 185 kết quả Several chemical
  • 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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  • Severe chemical contamination was found in ash contaminated soil samples from open burning sites at both Agbogbloshie and Korforidua, as well as in sediment from a shallow lagoon at the Agbogbloshie site. Most samples contained numerous toxic and persistent organic chemical pollutants, as well as very high levels of many toxic metals, the majority of which are either known to be used in electronic devices, or are likely to be formed during the open- burning of materials used in such devices.

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  • The Chemical Weapons Convention requires, among other things, that the signatories to the convention--which includes the United States--destroy by April 29, 2007, or as soon possible thereafter, any chemical warfare materiel that has been recovered from sites where it has been buried once discovered. For several years the United States and several other countries have been developing and using technologies to dispose of this non-stockpile materiel. To determine whether international efforts have resulted in technologies that would benefit the U.S. program, the U.S.

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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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  • Polymers are materials of very high molecular weight that are found to have multifarious applications in our modern society. They usually consist of several structural units bound together by covalent bonds [1,2]. For example, polyethy- lene is a long-chain polymer and is represented by

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  • A compilation of the most important aerosol chemical processes involved in known scientific and technological disciplines, Aerosol Chemical Processes in the Environment serves as a handbook for aerosol chemistry. Aerosol science is interdisciplinary, interfacing with many environmental, biological and technological research fields. Aerosols and aerosol research play an important role in both basic and applied scientific and technological fields. Interdisciplinary cooperation is useful and necessary.

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  • Weeds severely affect crop quality and yield. Therefore, successful farming relies on their control by coordinated management approaches. Among these, chemical herbicides are of key importance. Their development and commercialization began in the 1940's and they allowed for a qualitative increase in crop yield and quality when it was most needed. This book blends review chapters with scientific studies, creating an overview of some the current trends in the field of herbicides.

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  • I was pleased to respond to Ventus Publishing to write a textbook (which is split into 3 more manageable books, “Chemistry Maths 1”, “Chemistry Maths 2”, and “Chemistry Maths 3” which should be studied in sequence) that would help Chemistry students survive, and even enjoy, the Maths required for a Chemistry degree. I developed and presented tutorials on Maths to our first year Chemistry students over several years at the Chemistry Department, Heriot-Watt University, Edinburgh, Scotland. These tutorials have formed the basis for this workbook.

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  • Chuck Schoeffler, Ph.D., authored portions of the v1.2 text in conjunction with Parallax, Inc. At that time, Dr Schoeffler was a professor at University of Idaho's Industrial Technology Education department. He designed the original Board of Education Robot (Boe-Bot) shown here along with many similar robot derivatives with unique functions. After several revisions, Chuck's design was adopted as the basis of the Parallax Boe-Bot that is used in this Text. Russ Miller of Parallax designed the Boe-Bot based on this prototype....

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  • Wide agreement as to a clear and useful nomenclature is of great benefit in any field of science. The nomenclature here presented merits wide acceptance among terpene and other interested chemists because of the thorough way in which the careful work was done. Many versed in the chemistry of terpenes and many others experienced in naming chemical compounds were consulted. Full opportunity for criticism was offered.

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  • These days, it is impossible to think of an area of knowledge that can keep on developing without a collaboration in interdisciplinary fields. Electromotive force is a type of energy per unit of electric charge that is converted reversibly from chemical, mechanical, or other forms of energy into electrical energy by a dynamo, battery, electrochemical cells, thermoelectric devices, solar cells, transformers, and so on. The theory of electromotive Force is currently one of the most important research topics within the electrical engineering domain.

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  • “Be it deep or shallow, red or black, sand or clay, the soil is the link between the rock core of the earth and the living things on its surface. It is the foothold for the plants we grow. Therein lays the main reason for our interest in soils.” --- Roy W. Simonson, USDA Yearbook of Agriculture, 1957. The British naturalist Charles Darwin (1809–1882) was probably the first scientist to examine a soil profile and suggest factors responsible for the structure of the various layers.

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  • This book presents the selection of various high level contributions involving thermodynamics. The book goes from the fundamentals up to several applications in different scientific fields. The content of the book has been classified in six sections: Classical Thermodynamics, Statistical Thermodynamics, Property Prediction in Thermodynamics, Material and Products, Non Equilibrium and Thermodynamics in Diverse Areas. The classification of the book aims to provide to the reader the facility of finding the desired topic included in the book.

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  • Corn is the major cereal crop of the U.S. and the second most important cereal crop worldwide. The diversity of potential uses for corn was realized by the Native Americans prior to the first voyage of Columbus. Today, corn production in the U.S. provides feed, food, and a resource for many unique industrial and commercial products. The potential to enhance use of corn for specialty purposes based on existing uses, and develop new products to meet the needs of future generations, provides the plant breeder/plant scientist with unique challenges.

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  • Cerium, an element in the lanthanide series, has a number of radioactive isotopes. Several of these are produced in abundance in nuclear fission reactions associated with nuclear industry operations or detonation of nuclear devices. This report summarizes our present knowledge of the relevant physical, chemical, and biological properties of radiocerium as a basis for establishing radiation protection guidelines.

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  • Chemometric Techniques for Quantitative Analysis shows how to produce and use quantitative analytical calibrations in a laboratory or production environment following a variety of methods, how to estimate the time and resources needed to develop analytical calibrations, and how to employ the quantitative software provided with a wide range of instruments and commercial software packages. Among several, this bestselling volume covers basic and classical approaches, component regression; PCR in action; partial least squares; PLS in action.

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  • This book is an outgrowth of research done by Dr. Gamt Dijsterhuis for his doctoral thesis at the University of Leiden. However, there are also contributions by several other authors, as well, including Eeke van der Burg, John Gower, Pieter Punter, Els van den Broek, and Margo Flipsen.

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  • Unlike natural disasters, where any disruption to business service provision is likely to be hardware-related, disruption to business operation in the event of a pandemic is anticipated to be mainly human-resource oriented. Individual employers must consider their workforces and their particular circumstances. However, most should plan for up to 50% staff absences for periods of about two weeks at the height of a severe pandemic wave, and lower levels of staff absence for a few weeks either side of the peak. Overall, a pandemic wave may last about 8 weeks.

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  • This book is an outgrowth of research done by Dr. Gamt Dijsterhuis for his doctoral thesis at the University of Leiden. However, there are also contributions by several other authors, as well, including Eeke van der Burg, John Gower, Pieter Punter, Els van den Broek, and Margo Flipsen. SCIENCE Garmt B. Dijksterhuis, Ph.D. ID-DLO, Institute for Animal Science and Health Food Science Department Lely stad The Netherlands FOOD & NUTRITION PRESS, INC. TRUMBULL, CONNECTICUT 06611 USA .MULTIVARIATE DATA ANALYSIS IN SENSORY AND CONSUMER SCIENCE .

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  • In this study, structural features of Tricholoma matsutake polysaccharide (TMP-A) were investigated by a combination of infrared (IR) spectra, gas chromatography–mass spectrometry (GC–MS), nuclear magnetic resonance (NMR) spectroscopy. The results indicated that TMP-A had a backbone of 1,4-- d-glucopyranose residue which branches at O-6 based on the experimental results. The branches were mainly composed of an (1→3)--d-galactopyranose residue, and terminated with -d-xylopyranose residue.

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