Using Magnetic Levitation To Distinguish Atomic-Level Differences in Chemical Composition of Polymers, and To Monitor Chemical Reactions on Solid Supports

2008 ◽  
Vol 130 (52) ◽  
pp. 17678-17680 ◽  
Author(s):  
Katherine A. Mirica ◽  
Scott T. Phillips ◽  
Sergey S. Shevkoplyas ◽  
George M. Whitesides
Keyword(s):  
Chemical Composition ◽  
Chemical Reactions ◽  
Magnetic Levitation ◽  
Atomic Level ◽  
Solid Supports

Quantitative Hrtem: Measuring Projected Potential, Surface Roughness and Chemical Composition

1994 ◽  
Vol 332 ◽  
Author(s):  
P. Schwander ◽  
C. Kisielowski ◽  
F.H. Baumann ◽  
Y.O. Kim ◽  
A. Ourmazd
Keyword(s):  
Surface Roughness ◽  
Chemical Composition ◽  
Quantum Well ◽  
Cross Section ◽  
Potential Surface ◽  
Atomic Level ◽  
Topographic Map ◽  
Plan View ◽  
Lattice Images ◽  
Imaging Conditions

ABSTRACTWe describe how general lattice images may be used to measure the variation of the potential in crystalline solids in any projection, with no knowledge of the imaging conditions. This approach is applicable to structurally perfect samples, in which interfacial topography, or changes in composition are of interest. We present the first atomic-level topographic map of a Si/SiO2 interface in plan-view, and the first microscopic compositional map of a Si/GeSi/Si quantum well in cross-section.

Multimillion-Atom Simulations of Atomic-Level Surface Stresses and Pressure Distribution on InAs/GaAs Mesas

1999 ◽  
Vol 584 ◽  
Author(s):  
Xiaotao Su ◽  
Rajiv K. Kalia ◽  
Anupam Madhukar ◽  
Aiichiro Nakano ◽  
Priya Vashishta
Keyword(s):  
Molecular Dynamics ◽  
Chemical Composition ◽  
Pressure Distribution ◽  
Molecular Dynamics Simulations ◽  
Large Scale ◽  
Interatomic Potential ◽  
Atomic Level ◽  
Level Surface ◽  
Speed Up ◽  
Dynamics Simulations

AbstractLarge-scale molecular dynamics simulations are performed to investigate the atomiclevel stresses on InAs/GaAs mesas. The simulations are based on an interatomic-potential scheme for InAs/GaAs systems which depends on the local chemical composition. Multiresolution techniques are used to speed up the simulations. InAs/GaAs square mesas with { 101 }-type sidewalls are studied. The atomic-level pressure distribution and surface atomic stresses on the sidewalls with 12, 10, 8 and 6 monolayers of InAs overlayers have been calculated.

Mixture of the Reaction Products during Hardening of the Water Glass Radiation-Protective Composites

2013 ◽  
Vol 746 ◽  
pp. 289-292 ◽  
Author(s):  
Evgeniy Valerjevich Korolev ◽  
Anna Nikolaevna Grishina
Keyword(s):  
Chemical Composition ◽  
Phase Analysis ◽  
Chemical Reactions ◽  
Water Glass ◽  
Building Materials ◽  
Water Resistance ◽  
Barium Chloride ◽  
Reaction Products ◽  
X Ray

The water glass can be used as a binder for the design of water-resistant radiation-protective building materials. In the present work the possibility of hardening of such materials by barium chloride is investigated. The chemical reactions which can take place during the structure forming and lead to the formation of barium hydrosilicates are presented. It is shown by means of X-ray phase analysis that formation of such hydrosilicates of composition BaO·SiO2·6Н2О, BaO·2SiO2·4Н2О, Ba2[SiO2(OH)2]2and BaO·SiO2·Н2О actually occurs. The influence of the quantity of hardener to the chemical composition of the reaction products is examined. The effect of the reaction products to the water resistance of composite is studied. It is shown that water resistance can be increased in case of stochiometric quantity of barium chloride; in such case the primary product of reaction is BaO·2SiO2·4Н2О.

Processing Video Images of Chemical Reactions

1990 ◽  
Vol 48 (1) ◽  
pp. 538-539
Author(s):  
Eyring LeRoy ◽  
W.J. de Ruijter
Keyword(s):  
Electron Microscope ◽  
Chemical Reactions ◽  
Chemical Reactivity ◽  
Scientific Information ◽  
Chemical Change ◽  
Atomic Level ◽  
Storage Medium ◽  
Video Images ◽  
Transmission Electron ◽  
Pertinent Information

The high-resolution transmission electron microscope is unique in its capacity to provide direct images of bulk matter at the atomic level. This suggests the electron microscope as a nanochemical laboratory in which elementary reaction mechanisms can be observed and deciphered. The nature, disposition, and evolution of defects, the agents of chemical change, must be studied intimately if the fundamentals of chemical reactivity in solids are to be understood fully. Chemical change during microscopical observation is inevitable since alterations in the electronic associations of the atoms are produced by the electron beam. For a chemist this presents an extraordinary opportunity for investigating the atomic-level mechanism of a chemical reaction.Chemical reactions observed at near atomic resolution can be recorded on videotape at the rate of 30 images per second. Since the onset, extent and rapidity of a reaction varies over many orders of magnitude and is not predictable it is sometimes necessary to record for hours. The videotape provides a convenient storage medium for this immense quantity of information. The tapes can then be edited for those stretches bearing pertinent information and can be processed as needed. The purpose may simply be clear communication of scientific information to peers or more extensive processing may be desired for pedagogical use.

From disk midplanes to exoplanet atmospheres. The volatile chemical link.

2020 ◽  
Author(s):  
Christian Eistrup
Keyword(s):  
Chemical Composition ◽  
Gas Phase ◽  
Chemical Reactions ◽  
Chemical Evolution ◽  
Protoplanetary Disks ◽  
Solid Material ◽  
Comprehensive Treatment ◽  
Large Network ◽  
Grain Interaction ◽  
Grain Surface

<p>Exoplanetary science is now pushing to constrain the atmospheric compositions of exoplanets. This quest will be further aided by the next generation of facilities, such as the JWST and ground-based ELTs. Linking the observed composition of exoplanet atmospheres to where and how these atmospheres formed in their natal protoplanetary disks often involves comparing the observed exoplanetary atmospheric carbon-to-oxygen (C/O) ratio to a model of a disk midplane with a fixed chemical composition. In this scenario, chemical evolution in the midplane prior to and during the planet formation era is not considered. The C/O ratios of gas and ice in the disk midplane are simply defined by icelines of volatile molecules such as water and CO in the midplane. However, kinetic chemical evolution during the lifetime of the gaseous disk can change the relative abundances of volatile molecules, thus altering the C/O ratios of the planet-forming material. In my chemical evolution models, I utilize a large network of gas-phase, grain-surface and gas-grain interaction reactions, thus providing a comprehensive treatment of chemistry. In my talk, I will outline how such chemical reactions can cause the chemical composition in the disk midplane to evolve, how this affects the C/O ratios of the gas and solid material that form planets, and how such changes to the midplane chemical composition can lead to differences in exoplanet atmospheric compositions. These differences in exoplanet atmospheric compositions may be discernible with JWST observations.</p>

Chemical production of essential Cheddar flavour compounds

1979 ◽  
Vol 46 (3) ◽  
pp. 531-537 ◽  
Author(s):  
Donald J. Manning
Keyword(s):  
Chemical Composition ◽  
Chemical Reactions ◽  
Cheddar Cheese ◽  
Reducing Agents ◽  
Chemical Production ◽  
Sulphur Compounds ◽  
Similar Treatment ◽  
Flavour Compounds ◽  
Volatile Sulphur Compounds

SummaryPossible mechanisms for the production of volatile sulphur compounds during the ripening of Cheddar cheese have been studied. Slurries of cheese made with and without starter organisms were treated with dithiothreitol (DTT) and the chemical composition of the headspace examined. Cheeses were also pressed from curd treated with DTT and glutathione (GSH). Reactions occurring between methionine, cystine and Na caseinate and reducing agents cysteine, DTT and GSH were also studied. In addition, the reactions of H2S with methionine and Na casein. ate were investigated.Treatment of cheeses with DTT and GSH resulted in the production of H2S and methanethiol (CH3SH) together with the development of Cheddar flavour. Similar treatment of methionine and Na caseinate also yielded H2S and CH3SH whereas Cystine produced only H2S. H2S reacted with both Na caseinate and methionine to yield CH3SH.These results are consistent with the occurrence of some of the chemical reactions studied during the ripening of Cheddar cheese.

scholarly journals An Overview of the Biolubricant Production Process: Challenges and Future Perspectives

Processes ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 257 ◽  
Author(s):  
Juan Antonio Cecilia ◽  
Daniel Ballesteros Plata ◽  
Rosana Maria Alves Saboya ◽  
Francisco Murilo Tavares de Luna ◽  
Celio L. Cavalcante ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Environmental Impact ◽  
Research And Development ◽  
Chemical Reactions ◽  
Vegetable Oils ◽  
Future Perspectives ◽  
Mineral Oils ◽  
Natural Oils ◽  
Polyol Esters ◽  
Branched Chain

The term biolubricant applies to all lubricants that are easily biodegradable and non-toxic to humans and the environment. The uses of biolubricant are still very limited when compared to those of mineral oils, although this trend is increasing and depends on investment in research and development (R&D). The increase in demand for biodegradable lubricants is related to the evolution of environmental regulations, with more restrictive rules being implemented to minimize environmental impact caused by inappropriate disposal. This study provides an overview of the types, production routes, properties, and applications of biolubricants. Biolubricants are classified as either natural or synthetic oils according to chemical composition. Natural oils are of animal or vegetable origin and are rarely used because they are unstable at high temperatures and form compounds that are harmful to equipment and machines. Synthetic oils are obtained from chemical reactions and are the best lubricants for demanding applications. They are obtained by various routes, mainly by obtaining straight or branched-chain monoesters, diesters, triesters, and polyol esters from vegetable oils. The conversion of triglyceride to esters can be followed or preceded by one or more reactions to improve reactions such as epoxidation and hydrogenation.

Relations between the Quality of Latex and Its Chemical Composition

1946 ◽  
Vol 19 (2) ◽  
pp. 494-500
Author(s):  
George Martin
Keyword(s):  
Chemical Composition ◽  
Chemical Reactions ◽  
Chemical Properties ◽  
The Other ◽  
Rubber Content ◽  
Total Solids ◽  
Two Samples ◽  
Acceptable Method

Abstract One of the chief technical difficulties when latex is used industrially for the manufacture of rubber articles is that there is no method available for determining whether or not successive shipments of latex are suitable for any particular process of manufacture. Two samples of latex may be similar in appearance and have nearly the same chemical properties with respect to dry rubber content, total solids and alkalinity, yet one sample may be in excellent condition, whereas the other sample is on the point of coagulating. When these two samples are mixed with compounding ingredients, one remains quite fluid, while the other thickens or even coagulates. Then again, when treated with a coagulant, one sample gels in a normal way and under conditions compatible with good processing, whereas the other sample gels either too rapidly or too slowly, or coagulates to an unusable mass. It is safe to say that there is no generally acceptable method with which it is possible to judge the quality of latex, and the different procedures which have been suggested cannot be regarded as satisfactory. Rubber planters have called attention many times to the large variations in the properties of natural latex. Preserved latex is perhaps even more variable, for new factors then enter and influence its properties, e.g., the effects of bacteria before any preservatives are added to the latex, and chemical reactions which take place between certain components of the latex and the preservatives. In addition, the properties of latex change continuously with age, which is extremely limited compared with that of dry rubber.

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