Microstructural analysis of varistors prepared from nanosize ZnO.

by Pillai, S. C., Kelly, J. M., McCormack, D. E., Ramesh, R. [2004-08-01]

Academic Journal

pages 5

ZnO nanoparticles were prepared by a solid state pyrolysis reaction of zinc acetate dihydrate and oxalic acid dihydrate at 500°C. The course of reaction at various temperatures was followed by XRD. Subsequently varistors were fabricated from this nano-ZnO material by solid state mixing with various oxide additives and sintering to 1050°C. The microstructure of the sintered material was studied using XRD, field emission SEM (FESEM), and EDX, and ZnO grains, bismuth rich regions and spinel phases were identified. Discs made from oxide doped nanoZnO show considerably higher breakdown voltage (656 ± 30 V mm-1) compared to those prepared from micrometre sized ZnO (410 ± 30 V mm-1) and commercial varistors (454 ± 30 V mm-1). However, varistors made from the nano-ZnO show very low densification and high leakage current, making them unsuitable for device fabrication. [ABSTRACT FROM AUTHOR]


Radiative characteristics of aerosol during extreme fire event over Siberia in summer 2012.

by Zhuravleva, Tatiana B., Kabanov, Dmitriy M., Nasrtdinov, Ilmir M., Russkova, Tatiana V., Sakerin, Sergey M., Smirnov, Alexander, Holben, Brent N. [2017-01-01]

Academic Journal

pages 20

Microphysical and optical properties of aerosol were studied during a mega-fire event in summer 2012 over Siberia using ground-based measurements of spectral solar radiation at the AERONET site in Tomsk and satellite observations. The data were analysed using multi-year (2003- 2013) measurements of aerosol characteristics under background conditions and for less intense fires, differing in burning biomass type, stage of fire, remoteness from observation site, etc. ("ordinary" smoke). In June-August 2012, the average aerosol optical depth (AOD, 500 nm) had been 0.95±0.86, about a factor of 6 larger than background values (0.16±0.08), and a factor of 2.5 larger than in ordinary smoke. The AOD values were extremely high on 24- 28 July and reached 3-5. A comparison with satellite observations showed that ground-based measurements in the region of Tomsk not only reflect the local AOD features, but are also characteristic for the territory of Western Siberia as a whole. Single scattering albedo (SSA, 440 nm) in this period ranged from 0.91 to 0.99 with an average of 0.96 in the entire wavelength range of 440-1020 nm. The increase in absorptance of aerosol particles (SSA(440 nm)D0.92) and decrease in SSA with wavelength observed in ordinary smoke agree with the data from multi-year observations in analogous situations in the boreal zone of USA and Canada. Volume aerosol size distribution in extreme and ordinary smoke had a bimodal character with significant prevalence of finemode particles, but in summer 2012 the mean median radius and the width of the fine-mode distribution somewhat increased. In contrast to data from multi-year observations, in summer 2012 an increase in the volume concentration and median radius of the coarse mode was observed with growing AOD. The calculations of the average radiative effects of smoke and background aerosol are presented. Compared to background conditions and ordinary smoke, under the extreme smoke conditions the cooling effect of aerosol considerably intensifies: direct radiative effects (DRE) at the bottom (BOA) and at the top of the atmosphere (TOA) are -13, -35, and -60Wm-2 and -5, -14, and -35Wm-2 respectively. The maximal values of DRE were observed on 27 July (AOD(500 nm)D3.5), when DRE(BOA) reached -150Wm-2, while DRE(TOA) and DRE of the atmosphere were -75Wm-2. During the fire event in summer 2012 the direct radiative effect efficiency varied in range: at the BOA it was -80--40Wm-2, at the TOA it was -50--20Wm-2 and in the atmosphere it was -35--20Wm-2. [ABSTRACT FROM AUTHOR]


Academic Journal

pages 4

The effect of fine grinding of gold-bearing geochemical samples on the representative sample size and the recovery of gold and silver in fire-assay fusion was studied experimentally. A method is proposed for the improvement of grinding and sampling procedures in fire assay. [ABSTRACT FROM AUTHOR]


Applied chemistry.

by Freestone, Nigel [2010-05-10]

Academic Journal

pages 3

The article offers news briefs related to applied chemistry in Great Britain. The radiation badge that measures the low levels of personal exposure received by workers to a range of twenty volatile toxic industrial chemicals has been developed. The fixation of the greenhouse gas is the result of the reaction of carbon dioxide with unsaturated alcohols. The detection of specific anions for water quality assessment still an important chemical challenge.


Academic Journal

pages 3

The author reflects on the learning regarding advanced statistics and analysis of data in laboratory medicine. He argues that the dependence of laboratory results on several different influence factors such as age, is evident before the establishment of the concept of reference values introduced by Gräsbeck and Saris. He states that disciplines of laboratory medicine serves as interface between basic biological and natural sciences such as chemistry, and the clinical disciplines.


Chemistry Atoms First

by Paul Flowers [2016]

Book

pages unknown

Chemistry: Atoms First is a peer-reviewed, openly licensed introductory textbook produced through a collaborative publishing partnership between OpenStax and the University of Connecticut and UConn Undergraduate Student Government Association. This title is an adaptation of the OpenStax Chemistry text and covers scope and sequence requirements of the two-semester general chemistry course. Reordered to fit an atoms first approach, this title introduces atomic and molecular structure much earlier than the traditional approach, delaying the introduction of more abstract material so students have time to acclimate to the study of chemistry. Chemistry: Atoms First also provides a basis for understanding the application of quantitative principles to the chemistry that underlies the entire course


Key Elements of Green Chemistry

by Lucian Lucia [2018]

Book

pages unknown

Green chemistry, in addition to being a science, it is also a philosophy and nearly a religion. Attendance at American Chemical Society Green Chemistry & Engineering Conferences will instill such an ideal into any attendant because of the nearly universal appeal and possibilities in this novel approach to radicalizing the business of doing science and engineering


Introductory Chemistry

by David Ball [2011]

Book

pages unknown

ntroductory Chemistry is intended for a one-semester introductory or preparatory chemistry course. Throughout the chapters, David presents two features that reinforce the theme of the textbook, that chemistry is everywhere. The first is the boxed feature titled, appropriately, ”Chemistry is Everywhere“. This feature takes a topic of the chapter and demonstrates how this topic shows up in everyday life. In the introductory chapter, ”Chemistry is Everywhere“ focuses on the personal hygiene products that students may use every morning: toothpaste, soap, shampoo among others. The second boxed feature focuses on chemistry that students likely indulge in every day: eating and drinking. In the ”Food and Drink App“, David discusses how the chemistry of the chapter applies to things that students eat and drink every day


Book

pages unknown

The overall goal of the authors with General Chemistry: Principles, Patterns, and Applications was to produce a text that introduces the students to the relevance and excitement of chemistry. Although much of first-year chemistry is taught as a service course, Bruce and Patricia feel there is no reason that the intrinsic excitement and potential of chemistry cannot be the focal point of the text and the course. So, they emphasize the positive aspects of chemistry and its relationship to students’ lives, which requires bringing in applications early and often. In addition, the authors feel that many first year chemistry students have an enthusiasm for biologically and medically relevant topics, so they use an integrated approach in their text that includes explicit discussions of biological and environmental applications of chemistry


Chemistry

by Paul Flowers [2015]

Book

pages unknown

Chemistry is designed for the two-semester general chemistry course. For many students, this course provides the foundation to a career in chemistry, while for others, this may be their only college-level science course. As such, this textbook provides an important opportunity for students to learn the core concepts of chemistry and understand how those concepts apply to their lives and the world around them. The text has been developed to meet the scope and sequence of most general chemistry courses. At the same time, the book includes a number of innovative features designed to enhance student learning. A strength of Chemistry is that instructors can customize the book, adapting it to the approach that works best in their classroom


Review

pages 2

Reviews the book 'From Medical Chemistry to Biochemistry. The Making of a Biomedical Discipline,' by R.E. Kohler.


Praise of Biochemistry.

by Pennazio, Sergio [2008-03-01]

Academic Journal

pages 20

The interplay of chemistry and biology that occurred after Lavoisier's revolution gave the possibility of analysing the first organic molecules present in animals and plants. The will of learning of the first biologists enabled them to gain the biological meaning of many organic molecules and, towards the mid-19th century, to introduce the concept of "metabolism" for explaining the transformation of food into heat and products for both animal and plant tissues. This concept changed the course of both the experimental biology and medicine and made official, almost in an obvious way, the success of biochemistry as the most appropriate discipline for studying cell metabolism. After the discovery of proteins and nucleic acids as the macromolecules of the genetic code, the words "molecular biology" replaced the word biochemistry but this replacement was nominalistic, because the molecular mechanisms involved in growth and development of the organisms are fundamentally of biochemical nature. In this context, life represents a biochemical phenomenon endowed with a specific internal coherence, resting on two fundamental processes: i) a program, expressed by the genetic code, and ii) a modulation of the complex cell metabolism, with the production of chemical work, heat and homeostasis. This conception of life excludes any external planning design, as well as any deterministic and teleological interpretation, and may be considered of validity for the whole evolutionist span, from the formation of the first protocells to the appearance of man. [ABSTRACT FROM AUTHOR]


Application of Thermodynamic Models for Better Understanding and Optimizing the Hall-Heroult Process.

by Coursol, Pascal, Dufour, Gilles, Coté, Jules, Chartrand, Patrice, Mackey, Phillip [2012-11-01]

Academic Journal

pages 8

During the last decade, important improvements have been made in the application of thermodynamic models for studying the molten cryolite system used in the Hall-Heroult process. This approach allows a better understanding and paves the way for furthering developments in bath chemistry and molten metal processing. In this article, thermodynamic modeling is used to explore the operating windows in the reduction of alumina in molten cryolite. The impact of a range of concentrations of AlF, CaF, and AlO in conventional or 'lithium-free' baths is also discussed. Subsequently, the model was also used to evaluate the impact of additions of lithium fluoride to the bath. Conditions allowing an operation at lower cell voltages and lower bath temperatures were identified. The modeling approach described in this article is considered as an important innovation to revisit fundamentals, to constantly re-examine paradigms, and to identify potential modifications in bath chemistry for improving energy efficiency and productivity of modern prebaked Hall-Heroult cells. [ABSTRACT FROM AUTHOR]


CHEMISTRY.

No author [2003-12-01]

Periodical

pages 7

Presents several books related to chemistry. "Chemistry Resources in the Electronic Age," by Judith A. Bazler; "Chemistry Fundamentals; An Environmental Perspective," Second Edition, by Phyllis Buell and James Girard; "Biochemistry and Chemistry; Research and Development," edited by G. E. Zaikov and V. M. M. Lobo; Others.


Biochemical Properties of Soluble and Bound Peroxidases from Artichoke Heads and Leaves.

by Sergio, Lucrezia, Cardinali, Angela, De Paola, Angela, Di Venere, Donato [2009-01-01]

Academic Journal

pages 7

Soluble (SP), ionically bound (IBP) and covalently bound (CBP) peroxidases (POD) from artichoke leaves and heads have been characterized for the main biochemical parameters. The three PODs, in both leaves and heads, showed the major apparent catalytic efficiency (vmax,app/Km,app) towards ferulic acid, even though, in some cases, they showed higher affinity (Km,app) for other substrates. In leaves, SP and IBP showed higher Km,app for ferulic and chlorogenic acids, and CBP for ferulic and caffeic acids. In heads, SP showed higher Km,app for chlorogenic acid, IBP for caffeic and ferulic acids, and CBP for ferulic acid. It was shown that pH optimum for PODs ranged between 5.0 and 6.0 in leaves. In heads, pH optimum for SP and IBP was 5.5, while CBP presented a very low activity in a wide pH range. All PODs showed high thermal stability but different ability to regenerate: the bound forms were more able to regenerate than the soluble one. The results obtained show that (i) CBP from heads is able to work under very different cellular conditions, (ii) all PODs, in both tissues, have a high apparent catalytic efficiency for ferulic acid, which could explain the effective involvement of POD in lignin biosynthesis, (iii) in heads, high Km,app of SP for chlorogenic acid, particularly abundant in artichoke, could justify the possible involvement of PODs in browning mechanism, and (iv) in heat-processed artichoke, the ability of PODs to regenerate could contribute to oxidation and loss of product quality. [ABSTRACT FROM AUTHOR]


Academic Journal

pages 10

Varieties of chemical and phase equilibria are controlled by the minimum Gibbs energy principle, according to which the Gibbs energy for a system will have the minimum value at any given temperature and pressure. It is understood that the minimum is with respect to all nonequilibrium states at the same temperature and pressure. The abstract relation between Gibbs energy and the equilibrium constant is deduced from fundamental laws of thermodynamics. However, actual use of this relation calls for the Gibbs energy as a function of concentrations of the chemicals. Since thermodynamics is formulated without any reference to materials, how does one get that relation? This article provides the answer, and in the process shows that application of theory to experiments requires several intermediate layers where theory and experiment commingle. Reprinted by permission of the publisher.


Academic Journal

pages 21

Eighteenth-century scientific translation was not just a linguistic or intellectual affair. It included numerous material aspects requiring a social organization to marshal the indispensable human and non-human actors. Paratexts and actors' correspondences provide a good observatory to get information about aspects such as shipments and routes, processes of translation and language acquisition (dictionaries, grammars and other helpful materials, such as translated works in both languages), texts acquisition and dissemination (including author's additions and corrections, oral presentations in academic meetings and announcements of forthcoming translations). The nature of scientific translation changed in France during the second half of the eighteenth century. Beside solitary translators, it also happened to become a collective enterprise, dedicated to providing abridgements (Collection académique, 1755–79) or enriching the learned journals with full translations of the most recent foreign texts (Guyton de Morveau's ‘Bureau de traduction de Dijon’, devoted to chemistry and mineralogy, 1781–90). That new trend clearly had a decisive influence on the nature of the scientific press itself. A way to set up science as a social activity in the provincial capital of Dijon, translation required a local and international network for acquiring the linguistic and scientific expertise, along with the original texts, as quickly as possible. Laboratory results and mineralogical observations were used to compare material facts (colour, odour, shape of crystals, etc.) with those described in the original text. By providing a double kind of validation – with both the experiments and the translations – the laboratory thus happened to play a major role in translation. [ABSTRACT FROM AUTHOR]


Periodical

pages unknown

Reports on the publication of predicted molecular properties of chemical structures by Advanced Chemistry Development Inc. and Chemical Abstracts Service (CAS) company as of August 2002. List of calculated properties which are available in the CAS Registry; Addition of calculated property data to the CAS Registry.


Application of a computer-assisted structure elucidation program for the structural determination of a new terpenoid aldehyde with an unusual skeleton.

by Li, Xing-Nuo, Ridge, Clark D., Mazzola, Eugene P., Sun, Jianghao, Gutierrez, Osvaldo, Moser, Arvin, DiMartino, Joseph C., MacDonald, Scott A., Chen, Pei [2017-03-01]

Academic Journal

pages 4

The structure of a novel compound from Adansonia digitata has been elucidated, and its 1H and 13C NMR spectra have been assigned employing a variety of one-dimensional and two-dimensional NMR techniques without degradative chemistry. The Advanced Chemistry Development ACD/Structure Elucidator software was important for determining part of this structure that contained a fused bicyclic system with very few hydrogen atoms, which in turn, exhibited essentially no discriminating HMBC connectivities throughout that portion of the molecule. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]


Chemistry software.

No author [2006-02-01]

Periodical

pages unknown

The article describes the ACD/Web Librarian version 9 chemistry software from Toronto, Ontario-based Advanced Chemistry Development Inc. The software is designed to be browser-based and can be use for sharing and viewing spectal, chromatographic and chemical data. Interested parties may visit the company's Web site.


Advanced Chemistry Development Inc.

No author [2000-12-01]

Periodical

pages 1

Provides information on Advanced Chemistry Development Inc. which specializes in chemistry software. Objective of the company; Target markets; Products and services offered; Details of its facilities.


Periodical

pages 1

Features Toronto, Ontario-based chemistry software company Advanced Chemistry Development Inc. Company description; Number of employees; Date founded; Chief spectroscopic techniques supported; Markets served; Major products and services; Facilities; Contact information.


Periodical

pages 1

Provides information about Toronto, Ontario-based Advanced Chemistry Development Inc., a company that designs and manufactures software for molecular spectroscopic, analytical, structural and property-driven chemistry applications. Spectroscopic techniques supported; Markets served; Major products and services; Facilities.