Xem 1-20 trên 58 kết quả Material substances
  • The definition for dielectric constant relates to the permittivity of the material (symbol use here ε). The permittivity expresses the ability of a material to polarise in response to an applied field. It is the ratio of the permittivity of the dielectric to the permittivity of a vacuum. Physically it means the greater the polarisation developed by a material in an applied field of given strength, the greater the dielectric constant will be. Traditionally dielectric materials are made from inorganic substances eg. mica and silicon dioxide.

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  • Decisions as to which machine and method to use must marry design intent with machine capability. It has therefore become necessary for digitally savvy architects to understand how these tools work, what materials they are best suited for, and where in the tooling process the possibilities lie. Along these lines, architects have begun to couple form with method and revisit tectonic systems as a means to produce material effect. They seek to elevate standard building materials perceptually through nonstandard fabrication processes.

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  • Chemistry is the scientific study of matter, method and variable nature of the substance applied in life. About chemical elements, compounds, atoms, molecules, and the chemical reactions occurring among the component.Chemistry developed from alchemy, has been practiced for thousands of years ago in China, Europe and India

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  • Physics is as well as basic science because the physical laws governing all other natural sciences. This means that the natural sciences as biology, chemistry, geography ... study only specific parts of nature and must comply with the laws of physics. For example, the chemistry of these substances are governed by the physical laws of quantum mechanics, thermodynamics and electromagnetism.

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  • Synthesis has a central role in the development of Science especially in Chemistry. The strategies adopted in synthesis of molecules and materials have undergone considerable changes in recent times and it was felt that it may be necessary to assess and assimilate information on this topic in a single place. Though, no originality is claimed to the contents on this topic, the very fact that the available information on this topic is available in one place itself is considered to be a major step forward.

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  • Through the studies, we can deduce that most of the industrial discharge carries toxic substances. Due to the presence of high amount of toxic, carcinogen, and teratogen of metals, researchers are highly concerned with its effect on the environment and health of mankind. Rigorous investigations are currently being carried out to study the consequences of the contamination on the surface water, groundwater, and surface land due to industrial discharge.

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  • Chemical substances have become an essential part of human activities. Proper use of chemical substances help human society protect itself from hunger, thirst, famine, disease, and infection with good grains, fruits, and vegetables. Synthesis, formulations, and proper use of newer drugs and pharmaceuticals have offered the benefits of improved health care to society.

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  • Metabolism of pesticides denotes that any foreign substance that enters in the living system and how it will be changed into non-toxic and thrown out due to the enzymatic activity and other mode of action. When chemical toxins applied to nonliving substance (soil and water) that will lose the toxic principles by degradation process due to the action of biotic and abiotic factors. The time to nullify the toxicity is of prime importance and it vary depending upon the chemical molecule and environmental conditions.

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  • There are many contents in this book: physical properties of pure substances, vapor pressures of pure substances, vapor pressures of solutions, physical and chemical data, water-vapor content of gases, densities of pure substances, densities of aqueous inorganic solutions at 1 atm, densities of aqueous organic solutions, densities of miscellaneous materials, physical and chemical data, specific heats of miscellaneous materials, properties of formation and, combustion reactions.

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  • A biosensor is defined as a detecting device that combines a transducer with a biologically sensitive and selective component. When a specific target molecule interacts with the biological component, a signal is produced, at transducer level, proportional to the concentration of the substance. Therefore biosensors can measure compounds present in the environment, chemical processes, food and human body at low cost if compared with traditional analytical techniques.

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  • Anthropogenic air pollution constitutes of many substances. Greenhouse gases absorb and reflect some of the infrared parts of solar radiation reflected from the earth surface thus causing the troposphere to be warmer. Among others, these substances are carbone-dioxide, water vapour, hydrogen oxides, nitrogen-oxides and methane. Beyond causing warming, most of these gases are poisonous to the Earth’s biosphere. Besides greenhouse gases, there are a few more poisonous substances which have anthropogenic sources.

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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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  • Analysis was conducted on all nutrients or nutrient groups for which numeric data were provided in at least 10 of the 137 crop studies that reported comparisons between organic and conventional crops (see Appendix 10).

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  • Metal in sediment is affected by mineralogical and chemical composition of suspended material, anthropogenic influences by deposition, sorption, and enrichment in living organism or aquatic plant (Jain et al., 2005). Naturally, suspended and bed sediment are an important compartment to buffer metal concentration in an aquatic system especially by adsorption or precipitation (Jain & Ali, 2000; Jain, 2001; Jain & Sharma, 2002; Jain et al., 2004).

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  • FC01 CELLS Cells are tiny building blocks that make up all living things. Cells are so small that you need a microscope to see them. ANIMAL CELL This is the control centre of the cell. It contains chromosomes with DNA instructions for all the cell’s activities, including instructions to make new cells. This is a jelly like substance, in which many of the cell’s activities, e.g. respiration and protein synthesis occur. This is a thin skin around the cell. It is selectivelt permeable, controlling what goes in and out of the cell....

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  • The objective of waste water treatment is to prevent large quantities of substances to reach and impact the environment in high doses and concentrations. Areas of high population densitiy naturally are areas were production of sewage sludge is high (see Figure 1-1). Presently about 8 million t of sewage sludges (MAGOAROU 2000) are produced each year in the EU member states (Table 1-1). Its high content of organic materials, of nitrogen and phosphorous suggest their use as soil conditioner and fertilizer in agriculture.

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  • Piezoelectricity from the Greek word "piezo" means pressure electricity. Certain crystalline substances generate electric charges under mechanical stress and conversely experience a mechanical strain in the presence of an electric field. The piezoelectric effect was discovered in some naturally occurring materials in the 1880s. However it was not until the Second World War that man-made polycrystalline ceramic ma‐ terials were produced that also showed piezoelectric properties.

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  • R.A.M. Must be defect free Most at risk during in flight fueling High maintenance $14.5 million (F-117) Affected by weather conditions Reason for B-2 Bomber stationed only in USA References www.f-22raptor.com/st_getstealthy.php People.howstuffworks.com/stealth-bomber.htm People.howstuffworks.com/news-intem67.htm

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  • The systematic review search process identified 162 relevant articles published, with an English abstract, in peer-reviewed journals since 1st January 1958 until 29th February 2008. A total of 3558 comparisons of content of nutrients and other substances in organically and conventionally produced foodstuffs were extracted for analysis.

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  • The small number of livestock product studies identified in the review necessitated the use of more modest criteria for nutrient selection. Analysis was conducted on all nutrients or nutrient groups for which numeric data were provided in at least 5 of the 25 livestock product studies which reported comparisons between organic and conventional livestock products (see Appendix 11).

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