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Sample records for mechanistic bioinorganic chemistry

  1. Bioorganic and bioinorganic chemistry.

    Science.gov (United States)

    Constable, Edwin C; Housecroft, Catherine E; Creus, Marc; Gademann, Karl; Giese, Bernd; Ward, Thomas R; Woggon, Wolf D; Chougnet, Antoinette

    2010-01-01

    The interdisciplinary projects in bioinorganic and bioorganic chemistry of the Department of Chemistry, University of Basel led to the preparation of new systems that mimic biologically important processes and to the discovery of compounds from natural sources which are very promising with respect to medical applications. The advances in these areas are reported here.

  2. Bioinorganic Chemistry Modeled with the TPSSh Density Functional

    DEFF Research Database (Denmark)

    Kepp, Kasper Planeta

    2008-01-01

    In this work, the TPSSh density functional has been benchmarked against a test set of experimental structures and bond energies for 80 transition-metal-containing diatomics. It is found that the TPSSh functional gives structures of the same quality as other commonly used hybrid and nonhybrid func...... promising density functional for use and further development within the field of bioinorganic chemistry....

  3. SCOPE OF MEDICINE BIOINORGANIC CHEMISTRY, HYDRO AND MATERIALS SCIENCE

    OpenAIRE

    Beyer, L.; Universidad de Leipzig/Alemania, Facultad de Química y Mineralogía,Instituto de Química Inorgánica.Talstr. 35 041034 Leipzig República Federal Alemana; Angulo Cornejo, J.; Universidad Mayor de San Marcos, Facultad de química e Ingeniería Química. Departamento de Química inorgánica. Av. Venezuela S/N, Ciudad universitaria, Apartado 05-018 Breña, Lima-Perú

    2014-01-01

    The Bioinorganic Chemistry is the newest discipline of Inorganic Chemistry. Despite his youth, has found many applications in various fields such as medicine, Hidrometalugia and Materials Science. in this article an overview of the current status of research in this area is presented through concrete examples of the principles and applications as the study of biominerals, biomineralization processes, bioceramic, bioleaching and metal complexes for medicinal use (therapeutic and diagnostic). T...

  4. The bioinorganic chemistry and associated immunology of chronic beryllium disease.

    Science.gov (United States)

    Scott, Brian L; McCleskey, T Mark; Chaudhary, Anu; Hong-Geller, Elizabeth; Gnanakaran, S

    2008-07-07

    Chronic beryllium disease (CBD) is a debilitating, incurable, and often fatal disease that is caused by the inhalation of beryllium particulates. The growing use of beryllium in the modern world, in products ranging from computers to dental prosthetics (390 tons of beryllium in the US in the year 2000) necessitates a molecular based understanding of the disease in order to prevent and cure CBD. We have investigated the molecular basis of CBD at Los Alamos National Laboratory during the past six years, employing a multidisciplinary approach of bioinorganic chemistry and immunology. The results of this work, including speciation, inhalation and dissolution, and immunology will be discussed.

  5. The bioinorganic chemistry and associated immunology of chronic beryllium disease†

    Science.gov (United States)

    McCleskey, T. Mark; Chaudhary, Anu; Hong-Geller, Elizabeth; Gnanakaran, S.

    2013-01-01

    Chronic beryllium disease (CBD) is a debilitating, incurable, and often fatal disease that is caused by the inhalation of beryllium particulates. The growing use of beryllium in the modern world, in products ranging from computers to dental prosthetics (390 tons of beryllium in the US in the year 2000) necessitates a molecular based understanding of the disease in order to prevent and cure CBD. We have investigated the molecular basis of CBD at Los Alamos National Laboratory during the past six years, employing a multidisciplinary approach of bioinorganic chemistry and immunology. The results of this work, including speciation, inhalation and dissolution, and immunology will be discussed. PMID:18566702

  6. Bioinorganic Chemistry of the Alkali Metal Ions.

    Science.gov (United States)

    Kim, Youngsam; Nguyen, Thuy-Tien T; Churchill, David G

    2016-01-01

    The common Group 1 alkali metals are indeed ubiquitous on earth, in the oceans and in biological systems. In this introductory chapter, concepts involving aqueous chemistry and aspects of general coordination chemistry and oxygen atom donor chemistry are introduced. Also, there are nuclear isotopes of importance. A general discussion of Group 1 begins from the prevalence of the ions, and from a comparison of their ionic radii and ionization energies. While oxygen and water molecule binding have the most relevance to biology and in forming a detailed understanding between the elements, there is a wide range of basic chemistry that is potentially important, especially with respect to biological chelation and synthetic multi-dentate ligand design. The elements are widely distributed in life forms, in the terrestrial environment and in the oceans. The details about the workings in animal, as well as plant life are presented in this volume. Important biometallic aspects of human health and medicine are introduced as well. Seeing as the elements are widely present in biology, various particular endogenous molecules and enzymatic systems can be studied. Sodium and potassium are by far the most important and central elements for consideration. Aspects of lithium, rubidium, cesium and francium chemistry are also included; they help in making important comparisons related to the coordination chemistry of Na(+) and K(+). Physical methods are also introduced.

  7. Carbonic Anhydrase and Metalloderivatives: A Bioinorganic Chemistry Study

    Science.gov (United States)

    McQuate, Robert S.

    1977-01-01

    Discusses selected bioinorganic aspects of carbonic anhydrase and describes experiments that will reinforce the students' understanding of the presence and essential role that metal ions have in some biological systems. (SL)

  8. Integrating Bio-Inorganic and Analytical Chemistry into an Undergraduate Biochemistry Laboratory

    Science.gov (United States)

    Erasmus, Daniel J.; Brewer, Sharon E.; Cinel, Bruno

    2015-01-01

    Undergraduate laboratories expose students to a wide variety of topics and techniques in a limited amount of time. This can be a challenge and lead to less exposure to concepts and activities in bio-inorganic chemistry and analytical chemistry that are closely-related to biochemistry. To address this, we incorporated a new iron determination by…

  9. An Undergraduate Laboratory Experiment in Bioinorganic Chemistry: Ligation States of Myoglobin

    Science.gov (United States)

    Bailey, James A.

    2011-01-01

    Although there are numerous inorganic model systems that are readily presented as undergraduate laboratory experiments in bioinorganic chemistry, there are few examples that explore the inorganic chemistry of actual biological molecules. We present a laboratory experiment using the oxygen-binding protein myoglobin that can be easily incorporated…

  10. Integrating Bio-Inorganic and Analytical Chemistry into an Undergraduate Biochemistry Laboratory

    Science.gov (United States)

    Erasmus, Daniel J.; Brewer, Sharon E.; Cinel, Bruno

    2015-01-01

    Undergraduate laboratories expose students to a wide variety of topics and techniques in a limited amount of time. This can be a challenge and lead to less exposure to concepts and activities in bio-inorganic chemistry and analytical chemistry that are closely-related to biochemistry. To address this, we incorporated a new iron determination by…

  11. Structural and functional models in molybdenum and tungsten bioinorganic chemistry: description of selected model complexes, present scenario and possible future scopes.

    Science.gov (United States)

    Majumdar, Amit

    2014-06-28

    A brief description about some selected model complexes in molybdenum and tungsten bioinorganic chemistry is provided. The synthetic strategies involved and their limitations are discussed. Current status of molybdenum and tungsten bioinorganic modeling chemistry is presented briefly and synthetic problems associated therein are analyzed. Possible future directions which may expand the scope of modeling chemistry are suggested.

  12. Integrating bio-inorganic and analytical chemistry into an undergraduate biochemistry laboratory.

    Science.gov (United States)

    Erasmus, Daniel J; Brewer, Sharon E; Cinel, Bruno

    2015-01-01

    Undergraduate laboratories expose students to a wide variety of topics and techniques in a limited amount of time. This can be a challenge and lead to less exposure to concepts and activities in bio-inorganic chemistry and analytical chemistry that are closely-related to biochemistry. To address this, we incorporated a new iron determination by atomic absorption spectroscopy exercise as part of a five-week long laboratory-based project on the purification of myoglobin from beef. Students were required to prepare samples for chemical analysis, operate an atomic absorption spectrophotometer, critically evaluate their iron data, and integrate these data into a study of myoglobin.

  13. Design of Bioinorganic Materials at the Interface of Coordination and Biosupramolecular Chemistry.

    Science.gov (United States)

    Maity, Basudev; Ueno, Takafumi

    2017-04-01

    Protein assemblies have recently become known as potential molecular scaffolds for applications in materials science and bio-nanotechnology. Efforts to design protein assemblies for construction of protein-based hybrid materials with metal ions, metal complexes, nanomaterials and proteins now represent a growing field with a common aim of providing novel functions and mimicking natural functions. However, the important roles of protein assemblies in coordination and biosupramolecular chemistry have not been systematically investigated and characterized. In this personal account, we focus on our recent progress in rational design of protein assemblies using bioinorganic chemistry for (1) exploration of unnatural reactions, (2) construction of functional protein architectures, and (3) in vivo applications. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Probing bioinorganic chemistry processes in the bloodstream to gain new insights into the origin of human diseases.

    Science.gov (United States)

    Jahromi, Elham Zeini; Gailer, Jürgen

    2010-01-14

    In the context of elucidating the origin of human diseases, past poisoning epidemics have revealed that exceedingly small doses of inorganic environmental pollutants can result in dramatic effects on human health. Today, numerous organic and inorganic pollutants have been quantified in human blood, but the interpretation of these concentrations remains--from a public health point of view--problematic. Conversely, the biomolecular origin for several grievous human diseases is essentially unknown. Taken together and viewed in the context of recent bioinorganic research findings, the established human blood concentrations of toxic metals and metalloids may be functionally connected with the etiology of specific human diseases. To unravel the underlying biomolecular mechanisms, and taking into account the basic flow of dietary matter through mammalian organisms, a better understanding of the bioinorganic chemistry of toxic metals and metalloid compounds in the bloodstream is emerging as a promising avenue for future research. To this end, the concerted application of modern proteomic methodologies, synchrotron-based X-ray absorption spectroscopy and established spectroscopic techniques will contribute to better define the role that blood-based bioinorganic chemistry-related processes play in the origin of human diseases. The application of this and other modern proteomic methodologies could contribute to a better understanding of the role that blood-based bioinorganic chemistry-related processes play in the origin and etiology of human diseases.

  15. Marine Bioinorganic Chemistry: The Role of Trace Metals in the Oceanic Cycles of Major Nutrients

    Science.gov (United States)

    Morel, F. M. M.; Milligan, A. J.; Saito, M. A.

    2003-12-01

    The bulk of living biomass is chiefly made up of only a dozen "major" elements - carbon, hydrogen, oxygen, nitrogen, phosphorus, sodium, potassium, chlorine, calcium, magnesium, sulfur (and silicon in diatoms) - whose proportions vary within a relatively narrow range in most organisms. A number of trace elements, particularly first row transition metals - manganese, iron, nickel, cobalt, copper, and zinc - are also "essential" for the growth of organisms. At the molecular level, the chemical mechanisms by which such elements function as active centers or structural factors in enzymes and by which they are accumulated and stored by organisms is the central topic of bioinorganic chemistry. At the scale of ocean basins, the interplay of physical, chemical, and biological processes that govern the cycling of biologically essential elements in seawater is the subject of marine biogeochemistry. For those interested in the growth of marine organisms, particularly in the one-half of the Earth's primary production contributed by marine phytoplankton, bioinorganic chemistry and marine biogeochemistry are critically linked by the extraordinary paucity of essential trace elements in surface seawater, which results from their biological utilization and incorporation in sinking organic matter. How marine organisms acquire elements that are present at nano- or picomolar concentrations in surface seawater; how they perform critical enzymatic functions when necessary metal cofactors are almost unavailable are the central topics of "marine bioinorganic chemistry." The central aim of this field is to elucidate at the molecular level the metal-dependent biological processes involved in the major biogeochemical cycles.By examining the solutions that emerged from the problems posed by the scarcity of essential trace elements, marine bioinorganic chemists bring to light hitherto unknown ways to take up or utilize trace elements, new molecules, and newer "essential" elements. Focusing on

  16. Invited award contribution for ACS Award in Inorganic Chemistry. Geometric and electronic structure contributions to function in bioinorganic chemistry: active sites in non-heme iron enzymes.

    Science.gov (United States)

    Solomon, E I

    2001-07-16

    Spectroscopy has played a major role in the definition of structure/function correlations in bioinorganic chemistry. The importance of spectroscopy combined with electronic structure calculations is clearly demonstrated by the non-heme iron enzymes. Many members of this large class of enzymes activate dioxygen using a ferrous active site that has generally been difficult to study with most spectroscopic methods. A new spectroscopic methodology has been developed utilizing variable temperature, variable field magnetic circular dichroism, which enables one to obtain detailed insight into the geometric and electronic structure of the non-heme ferrous active site and probe its reaction mechanism on a molecular level. This spectroscopic methodology is presented and applied to a number of key mononuclear non-heme iron enzymes leading to a general mechanistic strategy for O2 activation. These studies are then extended to consider the new features present in the binuclear non-heme iron enzymes and applied to understand (1) the mechanism of the two electron/coupled proton transfer to dioxygen binding to a single iron center in hemerythrin and (2) structure/function correlations over the oxygen-activating enzymes stearoyl-ACP Delta9-desaturase, ribonucleotide reductase, and methane monooxygenase. Electronic structure/reactivity correlations for O2 activation by non-heme relative to heme iron enzymes will also be developed.

  17. Probing the bioinorganic chemistry of toxic metals in the mammalian bloodstream to advance human health.

    Science.gov (United States)

    Gailer, Jürgen

    2012-03-01

    The etiology of numerous grievous human diseases, including Alzheimer's and Parkinson's Disease is not well understood. Conversely, the concentration toxic metals and metalloids, such as As, Cd, Hg and Pb in human blood of the average population is well established, yet we know strikingly little about the role that they might play in the etiology of disease processes. Establishing functional connections between the chronic exposure of humans to these and other inorganic pollutants and the etiology of certain human diseases is therefore viewed by many as one of the greatest challenges in the post-genomic era. Conceptually, this task requires us to uncover hitherto unknown biomolecular mechanisms which must explain how small doses of a toxic metal/metalloid compound (low μg per day) - or mixtures thereof - may eventually result in a particular human disease. The biological complexity that is inherently associated with mammals, however, makes the discovery of these mechanisms a truly monumental task. Recent findings suggest that a better understanding of the bioinorganic chemistry of inorganic pollutants in the mammalian bloodstream represents a fruitful strategy to unravel relevant biomolecular mechanisms. The adverse effect(s) that toxic metals/metalloid compounds exert on the transport of essential ultratrace elements to internal organs appear particularly pertinent. A brief overview of the effect that arsenite and Hg(2+) exert on the mammalian metabolism of selenium is presented. Copyright © 2011 Elsevier Inc. All rights reserved.

  18. Uma visão da química bioinorgânica medicinal Medicinal bioinorganic chemistry

    Directory of Open Access Journals (Sweden)

    Anna Maria Canavarro Benite

    2007-01-01

    Full Text Available Metals play a vital role in human and plant physiology and important research is directed towards exploring the interrelated mechanisms that govern their interactions with biomolecules. Bioinorganic medicinal chemistry studies the functions, processing, storage and applications of metal ions and their complexes in biological systems. This paper presents a brief discussion about on interactions of metals with biomolecules that determine their intracellular accumulation, where metal ions may fulfill essential functions in cellular metabolism or, in certain cases, exert toxic effects towards cells.

  19. The Inorganic Illustrator: A 3-D Graphical Supplement for Inorganic and Bioinorganic Chemistry Courses Distributed on CD-ROM

    Science.gov (United States)

    Childs, Scott L.; Hagen, Karl S.

    1996-10-01

    The visualization of molecular and solid state chemical structures in three dimensions is a particularly difficult problem for students to overcome when the primary means of communication is the two-dimensional world of textbooks, blackboards, and overhead projector screens. Recent editions of popular textbooks in organic, inorganic, and biochemistry have included stereoviews of molecules to aid the student, and stereoviews of crystal structures have been used in inorganic chemistry publications for many years. These are powerful aids for visualizing complex molecules, but with the exception of the biochemistry text mentioned above, they are limited to single, static images generally in black and white. Molecular model kits are routinely used very effectively in organic chemistry but their utility in inorganic chemistry is limited to all but the most simple molecules encountered. Now that personal computers are generally accessible and multimedia tools are starting to make an appearance in chemistry lecture halls (1), we can make our inorganic and bioinorganic chemistry and crystallography lectures come alive with the aid of the computer-based resources, which are the essence of this project. As part of this project we are accumulating a database of representative crystal structures of main group molecules, coordination complexes, organometallic compounds, small metalloproteins, bioinorganic model complexes, clusters, and solid state materials in Chem3D Plus format to be viewed with Chem3D Viewer, which is free software from Cambridge Scientific Computing. We are also generating a library of high-quality graphic images of these same molecules and structures using Cerius2 package from Molecular Simulations. These include polyhedral representations of clusters and solid state structures (see Fig. 1). Figure 1. Representation of the user interface: the title page and an example of polyhedral and ball-and-stick representation of an octanuclear iron-oxo cluster. The

  20. Bioinorganic chemistry of Parkinson's disease: structural determinants for the copper-mediated amyloid formation of alpha-synuclein.

    Science.gov (United States)

    Binolfi, Andrés; Rodriguez, Esaú E; Valensin, Daniela; D'Amelio, Nicola; Ippoliti, Emiliano; Obal, Gonzalo; Duran, Rosario; Magistrato, Alessandra; Pritsch, Otto; Zweckstetter, Markus; Valensin, Gianni; Carloni, Paolo; Quintanar, Liliana; Griesinger, Christian; Fernández, Claudio O

    2010-11-15

    The aggregation of alpha-synuclein (AS) is a critical step in the etiology of Parkinson's disease (PD). A central, unresolved question in the pathophysiology of PD relates to the role of AS-metal interactions in amyloid fibril formation and neurodegeneration. Our previous works established a hierarchy in alpha-synuclein-metal ion interactions, where Cu(II) binds specifically to the protein and triggers its aggregation under conditions that might be relevant for the development of PD. Two independent, non-interacting copper-binding sites were identified at the N-terminal region of AS, with significant difference in their affinities for the metal ion. In this work we have solved unknown details related to the structural binding specificity and aggregation enhancement mediated by Cu(II). The high-resolution structural characterization of the highest affinity N-terminus AS-Cu(II) complex is reported here. Through the measurement of AS aggregation kinetics we proved conclusively that the copper-enhanced AS amyloid formation is a direct consequence of the formation of the AS-Cu(II) complex at the highest affinity binding site. The kinetic behavior was not influenced by the His residue at position 50, arguing against an active role for this residue in the structural and biological events involved in the mechanism of copper-mediated AS aggregation. These new findings are central to elucidate the mechanism through which the metal ion participates in the fibrillization of AS and represent relevant progress in the understanding of the bioinorganic chemistry of PD.

  1. 2013 Gordon Research Conference on metals in biology and seminar on bioinorganic chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Rosenzweig, Amy C. [Northwestern Univ., Evanston, IL (United States)

    2013-01-25

    Typical topics for lectures and posters include: biochemical and biophysical characterization of new metal containing proteins, enzymes, nucleic acids, factors, and chelators from all forms of life; synthesis, detailed characterization, and reaction chemistry of biomimetic compounds; novel crystal and solution structures of biological molecules and synthetic metal-chelates; discussions of the roles that metals play in medicine, maintenance of the environment, and biogeochemical processes; metal homeostasis; application of theory and computations to the structure and mechanism of metal-containing biological systems; and novel applications of spectroscopy to metals in biological systems.

  2. Expanding coordination chemistry from protein to protein assembly.

    Science.gov (United States)

    Sanghamitra, Nusrat J M; Ueno, Takafumi

    2013-05-14

    Bioinorganic chemistry is of growing importance in the fields of nanomaterial science and biotechnology. Coordination of metals by biological systems is a crucial step in intricate enzymatic reactions such as photosynthesis, nitrogen fixation and biomineralization. Although such systems employ protein assemblies as molecular scaffolds, the important roles of protein assemblies in coordination chemistry have not been systematically investigated and characterized. Many researchers are joining the field of bioinorganic chemistry to investigate the inorganic chemistry of protein assemblies. This area is emerging as an important next-generation research field in bioinorganic chemistry. This article reviews recent progress in rational design of protein assemblies in coordination chemistry for integration of catalytic reactions using metal complexes, preparation of mineral biomimetics, and mechanistic investigations of biomineralization processes with protein assemblies. The unique chemical properties of protein assemblies in the form of cages, tubes, and crystals are described in this review.

  3. Does Mechanistic Thinking Improve Student Success in Organic Chemistry?

    Science.gov (United States)

    Grove, Nathaniel P.; Cooper, Melanie M.; Cox, Elizabeth L.

    2012-01-01

    The use of the curved-arrow notation to depict electron flow during mechanistic processes is one of the most important representational conventions in the organic chemistry curriculum. Our previous research documented a disturbing trend: when asked to predict the products of a series of reactions, many students do not spontaneously engage in…

  4. Does Mechanistic Thinking Improve Student Success in Organic Chemistry?

    Science.gov (United States)

    Grove, Nathaniel P.; Cooper, Melanie M.; Cox, Elizabeth L.

    2012-01-01

    The use of the curved-arrow notation to depict electron flow during mechanistic processes is one of the most important representational conventions in the organic chemistry curriculum. Our previous research documented a disturbing trend: when asked to predict the products of a series of reactions, many students do not spontaneously engage in…

  5. Ferritin Diversity: Mechanistic Studies, Disease Implications, and Materials Chemistry

    Science.gov (United States)

    Hilton, Robert J.

    2011-07-01

    The study of ferritin includes a rich history of discoveries and scientific progress. Initially, the composition of ferritin was determined. Soon, it was shown that ferritin is a spherical, hollow protein. Eventually, over several decades of research, the structure and some function of this interesting protein was elucidated. However, the ferritin field was not completely satisfied. Today, for example, researchers are interested in refining the details of ferritin function, in discovering the role of ferritin in a variety of diseases, and in using ferritin for materials chemistry applications. The work presented in this dissertation highlights the progress that we have made in each of these three areas: (1) Mechanistic studies: The buffer used during horse spleen ferritin iron loading significantly influences the mineralization process and the quantity of iron deposited in ferritin. The ferrihydrite core of ferritin is crystalline and ordered when iron is loaded into ferritin in the presence of imidazole buffer. On the other hand, when iron is loaded into ferritin in the presence of MOPS buffer, the ferrihydrite core is less crystalline and less ordered, and a smaller amount of total iron is loaded in ferritin. We also show that iron can be released from the ferritin core in a non-reductive manner. The rate of Fe3+ release from horse spleen ferritin was measured using the Fe3+-specific chelator desferoxamine. We show that iron release occurs by three kinetic events. (2) Disease studies: In order to better understand iron disruption during disease states, we performed in vitro assays that mimicked chronic kidney disease. We tested the hypothesis that elevated levels of serum phosphate interrupted normal iron binding by transferrin and ferritin. Results show that phosphate competes for iron, forming an iron(III)-phosphate complex that is inaccessible to either transferrin or ferritin. Ferritin samples separated from the iron(III)-phosphate complex shows that as the

  6. 2014 Penn State Bioinorganic Workshop

    Energy Technology Data Exchange (ETDEWEB)

    Golbeck, John [Pennsylvania State Univ., State College, PA (United States)

    2015-10-01

    The 3rd Penn State Bioinorganic Workshop took place in early June 2014 and was combined with the 3rd Penn State Frontiers in Metallobiochemistry Symposium. The workshop was even larger than the 2nd Penn State Bioinorganic Workshop we offered in 2012. It had even more participants (162 rather than 123 in 2012). Like the 2012 workshop, the 2014 workshop had three parts. The first part consisted of 16 90-minute lectures presented by faculty experts on the topic of their expertise (see below). Based on the suggestions from the 2012 workshop, we have recorded all 16 lectures professionally and make them available to the entire bioinorganic community via online streaming. In addition, hard copies of the recordings are available as backup.

  7. Science Update: Inorganic Chemistry

    Science.gov (United States)

    Rawls, Rebecca

    1978-01-01

    This first in a series of articles describing the state of the art of various branches of chemistry reviews inorganic chemistry, including bioinorganic, photochemistry, organometallic, and solid state chemistries. (SL)

  8. Computational quantum chemistry and adaptive ligand modeling in mechanistic QSAR.

    Science.gov (United States)

    De Benedetti, Pier G; Fanelli, Francesca

    2010-10-01

    Drugs are adaptive molecules. They realize this peculiarity by generating different ensembles of prototropic forms and conformers that depend on the environment. Among the impressive amount of available computational drug discovery technologies, quantitative structure-activity relationship approaches that rely on computational quantum chemistry descriptors are the most appropriate to model adaptive drugs. Indeed, computational quantum chemistry descriptors are able to account for the variation of the intramolecular interactions of the training compounds, which reflect their adaptive intermolecular interaction propensities. This enables the development of causative, interpretive and reasonably predictive quantitative structure-activity relationship models, and, hence, sound chemical information finalized to drug design and discovery.

  9. Students' Interpretations of Mechanistic Language in Organic Chemistry before Learning Reactions

    Science.gov (United States)

    Galloway, Kelli R.; Stoyanovich, Carlee; Flynn, Alison B.

    2017-01-01

    Research on mechanistic thinking in organic chemistry has shown that students attribute little meaning to the electron-pushing (i.e., curved arrow) formalism. At the University of Ottawa, a new curriculum has been developed in which students are taught the electron-pushing formalism prior to instruction on specific reactions--this formalism is…

  10. TIMES-SS - A mechanistic evaluation of an external validation study using reaction chemistry principles

    DEFF Research Database (Denmark)

    Roberts, David W.; Patlewicz, Grace; Dimitrov, Sabcho D.

    2007-01-01

    -skin metabolism relationships through a number of transformations, some of which are underpinned by mechanistic three-dimensional quantitative structure-activity relationships. Here, we describe an external validation exercise that was recently carried out. As part of this exercise, data were generated for 40 new...... for sensitization. Additional testing on a further four chemicals was carried out to explore some of the specific reaction chemistry findings in more detail. Improvements for TIMES-SS, where appropriate, were put forward together with proposals for further research work. TIMES-SS is a promising tool to aid...

  11. 2010 Gordon Research Conference, Environmental Bioinorganic Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Austin, Rachael [Bates College, Lewiston, ME (United States)

    2010-06-18

    This interdisciplinary meeting will gather together scientists - structural biologists, chemists, geneticists, chemical and biological oceanographers, geochemists, and other specialist - who study the flows of essential and toxic elements through the environment and living systems, on timescales ranging from femptoseconds to eons. Of particular interest are the molecular mechanisms that govern element acquisition and use in organisms, and the tools and techniques used to study these phenomena. The aim of this community is to use these molecular-scale insights to understand the interconnected biotic and abiotic processes that shape the macroscopic environment and its development and change over a range of time scales.

  12. Copper dioxygen (bio)inorganic chemistry.

    Science.gov (United States)

    Solomon, Edward I; Ginsbach, Jake W; Heppner, David E; Kieber-Emmons, Matthew T; Kjaergaard, Christian H; Smeets, Pieter J; Tian, Li; Woertink, Julia S

    2011-01-01

    Cu/O2 intermediates in biological, homogeneous, and heterogeneous catalysts exhibit unique spectral features that reflect novel geometric and electronic structures that make significant contributions to reactivity. This review considers how the respective intermediate electronic structures overcome the spin-forbidden nature of O2 binding, activate O2 for electrophilic aromatic attack and H-atom abstraction, catalyze the 4 e- reduction of O2 to H2O, and discusses the role of exchange coupling between Cu ions in determining reactivity.

  13. Mechanistic Studies at the Interface Between Organometallic Chemistry and Homogeneous Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Casey, Charles P

    2012-11-14

    Mechanistic Studies at the Interface Between Organometallic Chemistry and Homogeneous Catalysis Charles P. Casey, Principal Investigator Department of Chemistry, University of Wisconsin - Madison, Madison, Wisconsin 53706 Phone 608-262-0584 FAX: 608-262-7144 Email: casey@chem.wisc.edu http://www.chem.wisc.edu/main/people/faculty/casey.html Executive Summary. Our goal was to learn the intimate mechanistic details of reactions involved in homogeneous catalysis and to use the insight we gain to develop new and improved catalysts. Our work centered on the hydrogenation of polar functional groups such as aldehydes and ketones and on hydroformylation. Specifically, we concentrated on catalysts capable of simultaneously transferring hydride from a metal center and a proton from an acidic oxygen or nitrogen center to an aldehyde or ketone. An economical iron based catalyst was developed and patented. Better understanding of fundamental organometallic reactions and catalytic processes enabled design of energy and material efficient chemical processes. Our work contributed to the development of catalysts for the selective and mild hydrogenation of ketones and aldehydes; this will provide a modern green alternative to reductions by LiAlH4 and NaBH4, which require extensive work-up procedures and produce waste streams. (C5R4OH)Ru(CO)2H Hydrogenation Catalysts. Youval Shvo described a remarkable catalytic system in which the key intermediate (C5R4OH)Ru(CO)2H (1) has an electronically coupled acidic OH unit and a hydridic RuH unit. Our efforts centered on understanding and improving upon this important catalyst for reduction of aldehydes and ketones. Our mechanistic studies established that the reduction of aldehydes by 1 to produce alcohols and a diruthenium bridging hydride species occurs much more rapidly than regeneration of the ruthenium hydride from the diruthenium bridging hydride species. Our mechanistic studies require simultaneous transfer of hydride from ruthenium to

  14. COMe: the ontology of bioinorganic proteins

    Directory of Open Access Journals (Sweden)

    Contrino Sergio

    2004-02-01

    Full Text Available Abstract Background Many characterised proteins contain metal ions, small organic molecules or modified residues. In contrast, the huge amount of data generated by genome projects consists exclusively of sequences with almost no annotation. One of the goals of the structural genomics initiative is to provide representative three-dimensional (3-D structures for as many protein/domain folds as possible to allow successful homology modelling. However, important functional features such as metal co-ordination or a type of prosthetic group are not always conserved in homologous proteins. So far, the problem of correct annotation of bioinorganic proteins has been largely ignored by the bioinformatics community and information on bioinorganic centres obtained by methods other than crystallography or NMR is only available in literature databases. Results COMe (Co-Ordination of Metals represents the ontology for bioinorganic and other small molecule centres in complex proteins. COMe consists of three types of entities: 'bioinorganic motif' (BIM, 'molecule' (MOL, and 'complex proteins' (PRX, with each entity being assigned a unique identifier. A BIM consists of at least one centre (metal atom, inorganic cluster, organic molecule and two or more endogenous and/or exogenous ligands. BIMs are represented as one-dimensional (1-D strings and 2-D diagrams. A MOL entity represents a 'small molecule' which, when in complex with one or more polypeptides, forms a functional protein. The PRX entities refer to the functional proteins as well as to separate protein domains and subunits. The complex proteins in COMe are subdivided into three categories: (i metalloproteins, (ii organic prosthetic group proteins and (iii modified amino acid proteins. The data are currently stored in both XML format and a relational database and are available at http://www.ebi.ac.uk/come/. Conclusion COMe provides the classification of proteins according to their 'bioinorganic' features

  15. Protective Effects of Dihydromyricetin against •OH-Induced Mesenchymal Stem Cells Damage and Mechanistic Chemistry

    Directory of Open Access Journals (Sweden)

    Xican Li

    2016-05-01

    Full Text Available As a natural flavonoid in Ampelopsis grossedentata, dihydromyricetin (DHM, 2R,3R-3,5,7,3′,4′,5′-hexahydroxy-2,3-dihydroflavonol was observed to increase the viability of •OH-treated mesenchymal stem cells using a MTT [3-(4,5-dimethylthiazol-2-yl-2,5-diphenyl] assay and flow cytometry analysis. This protective effect indicates DHM may be a beneficial agent for cell transplantation therapy. Mechanistic chemistry studies indicated that compared with myricetin, DHM was less effective at ABTS+• (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid radical scavenging and reducing Cu2+, and had higher •O2− and DPPH• (1,1-diphenyl-2-picrylhydrazyl radical scavenging activities. Additionally, DHM could also chelate Fe2+ to give an absorption maximum at 589 nm. Hence, such protective effect of DHM may arise from its antioxidant activities which are thought to occur via direct radical-scavenging and Fe2+-chelation. Direct radical-scavenging involves an electron transfer (ET pathway. The hydrogenation of the 2,3-double bond is hypothesized to reduce the ET process by blocking the formation of a larger π-π conjugative system. The glycosidation of the 3–OH in myricitrin is assumed to sterically hinder atom transfer in the •O2− and DPPH• radical-scavenging processes. In DHM, the Fe2+-chelating effect can actually be attributed to the 5,3′,4′,5′–OH and 4–C=O groups, and the 3–OH group itself can neither scavenge radicals nor chelate metal.

  16. New Mechanistic Insights on the Selectivity of Transition-Metal-Catalyzed Organic Reactions: The Role of Computational Chemistry.

    Science.gov (United States)

    Zhang, Xinhao; Chung, Lung Wa; Wu, Yun-Dong

    2016-06-21

    With new advances in theoretical methods and increased computational power, applications of computational chemistry are becoming practical and routine in many fields of chemistry. In organic chemistry, computational chemistry plays an indispensable role in elucidating reaction mechanisms and the origins of various selectivities, such as chemo-, regio-, and stereoselectivities. Consequently, mechanistic understanding improves synthesis and assists in the rational design of new catalysts. In this Account, we present some of our recent works to illustrate how computational chemistry provides new mechanistic insights for improvement of the selectivities of several organic reactions. These examples include not only explanations for the existing experimental observations, but also predictions which were subsequently verified experimentally. This Account consists of three sections discuss three different kinds of selectivities. The first section discusses the regio- and stereoselectivities of hydrosilylations of alkynes, mainly catalyzed by [Cp*Ru(MeCN)3](+) or [CpRu(MeCN)3](+). Calculations suggest a new mechanism that involves a key ruthenacyclopropene intermediate. This mechanism not only explains the unusual Markovnikov regio-selectivity and anti-addition stereoselectivity observed by Trost and co-workers, but also motivated further experimental investigations. New intriguing experimental observations and further theoretical studies led to an extension of the reaction mechanism. The second section includes three cases of meta-selective C-H activation of aryl compounds. In the case of Cu-catalyzed selective meta-C-H activation of aniline, a new mechanism that involves a Cu(III)-Ar-mediated Heck-like transition state, in which the Ar group acts as an electrophile, was proposed. This mechanism predicted a higher reactivity for more electron-deficient Ar groups, which was supported by experiments. For two template-mediated, meta-selective C-H bond activations catalyzed by

  17. Computational Chemistry in the Undergraduate Laboratory: A Mechanistic Study of the Wittig Reaction

    Science.gov (United States)

    Albrecht, Birgit

    2014-01-01

    The Wittig reaction is one of the most useful reactions in organic chemistry. Despite its prominence early in the organic chemistry curriculum, the exact mechanism of this reaction is still under debate, and this controversy is often neglected in the classroom. Introducing a simple computational study of the Wittig reaction illustrates the…

  18. Effect of surface chemistry of Fe-Ni nanoparticles on mechanistic pathways of azo dye degradation.

    Science.gov (United States)

    Bokare, Alok D; Chikate, Rajeev C; Rode, Chandrashekhar V; Paknikar, Kishore M

    2007-11-01

    The degradation of Orange G, a monoazo dye, in aqueous solutions was investigated using as-synthesized and stored Fe-Ni bimetallic nanoparticles. Batch experiments with a nanocatalyst loading of 3 g/L showed complete dye degradation (150 mg/L) after 10 min of reaction time. HPLC-MS analysis of the degradation products showed that as-synthesized nanoparticles reductively cleaved the azo linkage to produce aniline as the major degradation product. However, 1-year-stored nanoparticles showed an oxidative degradation of Orange G through a hydroxyl-radical induced coupling of parent and/or product molecules. XPS analysis in corroboration with HPLC-MS data showed that the surface chemistry between Fe and Ni in as-synthesized and stored nanoparticles play a crucial role in directing the mode of degradation. Reductive dye degradation using as-synthesized nanoparticles proceeded through hydride transfer from nickel, whereas formation of a Fe2+ -Ni(0) galvanic cell in stored nanoparticles generated hydroxyl radicals from water in a nonFenton type reaction. The latter were responsible for the generation of radical centers on the dye molecule, which led to a coupling-mediated oxidative degradation of Orange G. The generation of hydroxyl radicals is further substantiated with radical quenching experiments using ascorbic acid indicating that stored nanoparticles degrade Orange G through a predominantly oxidative mechanism. HPLC-MS and XPS analysis of dye degradation using as-synthesized nanoparticles exposed to air and water confirmed that the reductive or oxidative degradation capability of Fe-Ni nanoparticles is decided by the time and type of catalyst aging process.

  19. Refinement of the Dermal Sensitisation Threshold (DST) approach using a larger dataset and incorporating mechanistic chemistry domains.

    Science.gov (United States)

    Safford, R J; Aptula, A O; Gilmour, N

    2011-07-01

    An essential step in ensuring the toxicological safety of ingredients in consumer products is the evaluation of their skin sensitising potential. Where skin exposure is low, it is possible to conduct a risk assessment using the Dermal Sensitisation Threshold (DST), a process similar to that of the Threshold of Toxicological Concern. This paper describes work building on that previously published, whose aim was to produce a more robust tool for assessing the safety of consumer products. This consisted of expanding the Local Lymph Node Assay dataset used to define the original DST and classifying chemicals in the dataset according to their mechanistic chemistry domains. A DST of 900μg/cm(2) was derived for chemicals classified as non-reactive and non-proreactive. This value was benchmarked against human potency data for 58 fragrance allergens and was lower than the measured No Expected Sensitisation Levels for those classified as non-reactive. Use of this DST will help to eliminate the need for animal testing of non-reactive and non-proreactive chemicals where skin exposure is sufficiently low. For chemicals where a Quantitative Risk Assessment based on the DST does not give an adequate margin of safety, and those classified as reactive, a case-by-case risk assessment will be required.

  20. Application of isothermal titration calorimetry in bioinorganic chemistry.

    Science.gov (United States)

    Grossoehme, Nicholas E; Spuches, Anne M; Wilcox, Dean E

    2010-11-01

    The thermodynamics of metals ions binding to proteins and other biological molecules can be measured with isothermal titration calorimetry (ITC), which quantifies the binding enthalpy (ΔH°) and generates a binding isotherm. A fit of the isotherm provides the binding constant (K), thereby allowing the free energy (ΔG°) and ultimately the entropy (ΔS°) of binding to be determined. The temperature dependence of ΔH° can then provide the change in heat capacity (ΔC (p)°) upon binding. However, ITC measurements of metal binding can be compromised by undesired reactions (e.g., precipitation, hydrolysis, and redox), and generally involve competing equilibria with the buffer and protons, which contribute to the experimental values (K (ITC), ΔH (ITC)). Guidelines and factors that need to be considered for ITC measurements involving metal ions are outlined. A general analysis of the experimental ITC values that accounts for the contributions of metal-buffer speciation and proton competition and provides condition-independent thermodynamic values (K, ΔH°) for metal binding is developed and validated.

  1. Aqueous vanadium ion dynamics relevant to bioinorganic chemistry: A review.

    Science.gov (United States)

    Kustin, Kenneth

    2015-06-01

    Aqueous solutions of the four highest vanadium oxidation states exhibit four diverse colors, which only hint at the diverse reactions that these ions can undergo. Cationic vanadium ions form complexes with ligands; anionic vanadium ions form complexes with ligands and self-react to form isopolyanions. All vanadium species undergo oxidation-reduction reactions. With a few exceptions, elucidation of the dynamics of these reactions awaited the development of fast reaction techniques before the kinetics of elementary ligation, condensation, reduction, and oxidation of the aqueous vanadium ions could be investigated. As the biological roles played by endogenous and therapeutic vanadium expand, it is appropriate to bring the results of the diverse kinetics studies under one umbrella. To achieve this goal this review presents a systematic examination of elementary aqueous vanadium ion dynamics.

  2. Ecosustainable Development of Novel Bio-inorganic Hybrid Materials as UV Protection Systems for Potential Cosmetic Applications.

    Science.gov (United States)

    Villa, Carla; Lacapra, Chiara; Rosa, Roberto; Veronesi, Paolo; Leonelli, Cristina

    2015-01-01

    A new organoclay, bio-inorganic hybrid material, was successfully prepared following the "green chemistry" principles, exploiting microwave irradiation (as an alternative energetic source) in both the solvent-free synthesis of the organic filler (UVB filter) and in its hydrothermal intercalation in a sodium Bentonite clay (renewable natural inorganic source at low temperature). The organic filler is a benzylidene camphor derivative with the same cationic moiety as the well- known UV filter camphor benzalkonium methosulfate. The aim of the research was the ecosustainable development of a new UV protection model, suitable for use in cosmetic and pharmaceutical products, with potential advantages of stability, efficiency and safety compared to the commercially available UVB sunscreens. The organically modified clay was thoroughly investigated using X-ray diffraction (XRD), infrared spectroscopy (IR), thermo gravimetric analysis and differential thermal analysis (DTA). Results confirmed the complete intercalation of the organic filler in the interlayer region of the smectite clay, leading to a new bio-inorganic hybrid material with potential for cosmetic and pharmaceutical applications in the UV protection field, as confirmed by preliminary photochemical studies. This work represents the first example in the use of Na-Bentonite cationic clay (usually employed as rheological additive) as hosting agent of the synthesized quaternary UVB filter, as well as in the complete MW-assisted preparation of the organoclay, starting from the synthesis of the organic UV sunscreen to its hydrothermal intercalation.

  3. Applications of Density Functional Theory to Iron-Containing Molecules of Bioinorganic Interest

    Directory of Open Access Journals (Sweden)

    Hajime eHirao

    2014-04-01

    Full Text Available The past decades have seen an explosive growth in the application of density functional theory (DFT methods to molecular systems that are of interest in a variety of scientific fields. Owing to its balanced accuracy and efficiency, DFT plays particularly useful roles in the theoretical investigation of large molecules. Even for biological molecules such as proteins, DFT finds application in the form of, e.g., hybrid quantum mechanics and molecular mechanics (QM/MM, in which DFT may be used as a QM method to describe a higher prioritized region in the system, while a MM force field may be used to describe remaining atoms. Iron-containing molecules are particularly important targets of DFT calculations. From the viewpoint of chemistry, this is mainly because iron is abundant on earth, iron plays powerful (and often mysterious roles in enzyme catalysis, and iron thus has the great potential for biomimetic catalysis of chemically difficult transformations. In this paper, we present a brief overview of several recent applications of DFT to iron-containing nonheme synthetic complexes, heme-type cytochrome P450 enzymes, and nonheme iron enzymes, all of which are of particular interest in the field of bioinorganic chemistry. Emphasis will be placed on our own work.

  4. Applications of density functional theory to iron-containing molecules of bioinorganic interest.

    Science.gov (United States)

    Hirao, Hajime; Thellamurege, Nandun; Zhang, Xi

    2014-01-01

    The past decades have seen an explosive growth in the application of density functional theory (DFT) methods to molecular systems that are of interest in a variety of scientific fields. Owing to its balanced accuracy and efficiency, DFT plays particularly useful roles in the theoretical investigation of large molecules. Even for biological molecules such as proteins, DFT finds application in the form of, e.g., hybrid quantum mechanics and molecular mechanics (QM/MM), in which DFT may be used as a QM method to describe a higher prioritized region in the system, while a MM force field may be used to describe remaining atoms. Iron-containing molecules are particularly important targets of DFT calculations. From the viewpoint of chemistry, this is mainly because iron is abundant on earth, iron plays powerful (and often enigmatic) roles in enzyme catalysis, and iron thus has the great potential for biomimetic catalysis of chemically difficult transformations. In this paper, we present a brief overview of several recent applications of DFT to iron-containing non-heme synthetic complexes, heme-type cytochrome P450 enzymes, and non-heme iron enzymes, all of which are of particular interest in the field of bioinorganic chemistry. Emphasis will be placed on our own work.

  5. A theory for bioinorganic chemical reactivity of oxometal complexes and analogous oxidants: the exchange and orbital-selection rules.

    Science.gov (United States)

    Usharani, Dandamudi; Janardanan, Deepa; Li, Chunsen; Shaik, Sason

    2013-02-19

    Over the past decades metalloenzymes and their synthetic models have emerged as an area of increasing research interest. The metalloenzymes and their synthetic models oxidize organic molecules using oxometal complexes (OMCs), especially oxoiron(IV)-based ones. Theoretical studies have helped researchers to characterize the active species and to resolve mechanistic issues. This activity has generated massive amounts of data on the relationship between the reactivity of OMCs and the transition metal's identity, oxidation state, ligand sphere, and spin state. Theoretical studies have also produced information on transition state (TS) structures, reaction intermediates, barriers, and rate-equilibrium relationships. For example, the experimental-theoretical interplay has revealed that nonheme enzymes carry out H-abstraction from strong C-H bonds using high-spin (S = 2) oxoiron(IV) species with four unpaired electrons on the iron center. However, other reagents with higher spin states and more unpaired electrons on the metal are not as reactive. Still other reagents carry out these transformations using lower spin states with fewer unpaired electrons on the metal. The TS structures for these reactions exhibit structural selectivity depending on the reactive spin states. The barriers and thermodynamic driving forces of the reactions also depend on the spin state. H-Abstraction is preferred over the thermodynamically more favorable concerted insertion into C-H bonds. Currently, there is no unified theoretical framework that explains the totality of these fascinating trends. This Account aims to unify this rich chemistry and understand the role of unpaired electrons on chemical reactivity. We show that during an oxidative step the d-orbital block of the transition metal is enriched by one electron through proton-coupled electron transfer (PCET). That single electron elicits variable exchange interactions on the metal, which in turn depend critically on the number of

  6. The Bioinorganic Bridge Between Life and Environment

    Science.gov (United States)

    Anbar, A. D.; Wolfe-Simon, F.

    2008-12-01

    Nearly half the Earth's surface is covered by oligotrophic oceans in which life struggles to survive. These barren ecosystems do not lack water or sunshine, nor the bulk biological elements H, C and O. Instead, they are deficient in one or more of the other elements necessary for life. Hence, the distribution of life on Earth is captive, in part, to the distribution of the 20 or so "bioessential" nutrient elements that are critical components of DNA, RNA, proteins and other biomolecules. Having substantially unraveled this relationship in today's oceans, biogeochemists are beginning to consider how it has evolved over the ~ 4 billion year history of life. A growing body of evidence suggests that major evolutionary transitions are shaped by changes in the availability of bioessential metals. The most striking example is the ecological diversification of eukaryotes. Fossil evidence suggests that this transition roughly coincides with oxygenation of the deep sea, and hence with a hypothetical increase in Cu and Zn coupled to a decrease in Fe in the oceans (Saito et al., 2003). Bioinformatic analyses of protein metal binding sites encoded in whole genomes reveal that the "metallomes" of eukaryotes are systematically enriched in Zn, and depleted in Fe, Mn and Co, compared to those of prokaryotes (DuPont et al., 2006). Arguably, then, eukaryotes rose to ecological prominence because of the advent of oceans that favored organisms with eukaryotic stoichiometry. We are exploring this concept mechanistically by investigating the biochemical responses of representative eukaryotic green algae and cyanobacteria to chronic Fe-deficiency. We observed the intracellular Cu quota of the eukaryotic green alga Chlamydomonas reinhardtii increase under chronic Fe-deficiency. This shift occurs because green algae replace key Fe proteins involved in photosynthetic electron transfer (e.g., cytochrome c6) with analogous Cu-based proteins (e.g., plastocyanin). In contrast, we found that the

  7. Mechanisms before Reactions: A Mechanistic Approach to the Organic Chemistry Curriculum Based on Patterns of Electron Flow

    Science.gov (United States)

    Flynn, Alison B.; Ogilvie, William W.

    2015-01-01

    A significant redesign of the introductory organic chemistry curriculum at the authors' institution is described. There are two aspects that differ greatly from a typical functional group approach. First, organic reaction mechanisms and the electron-pushing formalism are taught before students have learned a single reaction. The conservation of…

  8. Mechanisms before Reactions: A Mechanistic Approach to the Organic Chemistry Curriculum Based on Patterns of Electron Flow

    Science.gov (United States)

    Flynn, Alison B.; Ogilvie, William W.

    2015-01-01

    A significant redesign of the introductory organic chemistry curriculum at the authors' institution is described. There are two aspects that differ greatly from a typical functional group approach. First, organic reaction mechanisms and the electron-pushing formalism are taught before students have learned a single reaction. The conservation of…

  9. Toward mechanistic understanding of nuclear reprocessing chemistries by quantifying lanthanide solvent extraction kinetics via microfluidics with constant interfacial area and rapid mixing.

    Science.gov (United States)

    Nichols, Kevin P; Pompano, Rebecca R; Li, Liang; Gelis, Artem V; Ismagilov, Rustem F

    2011-10-05

    The closing of the nuclear fuel cycle is an unsolved problem of great importance. Separating radionuclides produced in a nuclear reactor is useful both for the storage of nuclear waste and for recycling of nuclear fuel. These separations can be performed by designing appropriate chelation chemistries and liquid-liquid extraction schemes, such as in the TALSPEAK process (Trivalent Actinide-Lanthanide Separation by Phosphorus reagent Extraction from Aqueous Komplexes). However, there are no approved methods for the industrial scale reprocessing of civilian nuclear fuel in the United States. One bottleneck in the design of next-generation solvent extraction-based nuclear fuel reprocessing schemes is a lack of interfacial mass transfer rate constants obtained under well-controlled conditions for lanthanide and actinide ligand complexes; such rate constants are a prerequisite for mechanistic understanding of the extraction chemistries involved and are of great assistance in the design of new chemistries. In addition, rate constants obtained under conditions of known interfacial area have immediate, practical utility in models required for the scaling-up of laboratory-scale demonstrations to industrial-scale solutions. Existing experimental techniques for determining these rate constants suffer from two key drawbacks: either slow mixing or unknown interfacial area. The volume of waste produced by traditional methods is an additional, practical concern in experiments involving radioactive elements, both from disposal cost and experimenter safety standpoints. In this paper, we test a plug-based microfluidic system that uses flowing plugs (droplets) in microfluidic channels to determine absolute interfacial mass transfer rate constants under conditions of both rapid mixing and controlled interfacial area. We utilize this system to determine, for the first time, the rate constants for interfacial transfer of all lanthanides, minus promethium, plus yttrium, under TALSPEAK

  10. Atmospheric chemistry of HFC-134a. Kinetic and mechanistic study of the CF3CFHO2 + NO2 reaction

    DEFF Research Database (Denmark)

    Møgelberg, T.E.; Nielsen, O.J.; Sehested, J.;

    1994-01-01

    A pulse radiolysis system was used to study the kinetics of the reaction of CF3CFHO2 with NO2. By monitoring the rate of the decay of NO2 using its absorption at 400 nm the reaction rate constant was determined to be k = (5.0 +/- 0.5) x 10(-12) cm3 molecule-1 s-1. A long path length Fourier......-transform infrared technique was used to investigate the thermal decomposition of the product CF3CFHO2NO2. At 296 K in the presence of 700 Torr of air, decomposition of CF3CFHO2NO2 was rapid (greater than 90% decomposition within 3 min). The results are discussed in the context of atmospheric chemistry of CF3CFH2...

  11. Applications of Inorganic Chemistry in Biology: An Interdisciplinary Graduate Course

    Science.gov (United States)

    Farrell, Nicholas; Ross, Paul; Roat, Rosette M.

    1998-06-01

    Inorganic chemistry faculty at Virginia Commonwealth University (VCU) are offering an advanced, interdisciplinary, graduate course entitled "Applications of Inorganic Chemistry in Biology". The course utilizes examples from bioinorganic chemistry to introduce advanced topics in synthesis, structural analysis, and analytical methods that are practiced by inorganic chemists. Emphasis is placed on the structure and function of trace and ultratrace transition metals in biological systems and on the use of metals for medicinal purposes. Instrumental techniques such as electron paramagnetic resonance, Mössbauer spectroscopy, and X-ray crystallography are explained in the detail necessary to familiarize students with their use for analysis of bioinorganic systems and their models. Students have take-home examinations during the term and write a term paper describing a metalloprotein whose X-ray structure data is listed in Brookhaven protein data base. The paper follows the same course pattern of classroom discussion of a bioinorganic system, concentrating on the coordination geometry and nearest neighbor contacts of the metal-binding site in the protein, substrate binding site, and relevance to the metalloprotein or enzyme function, mechanism of action of the enzyme or protein, spectroscopic studies on the metal-binding site, and model studies for the protein's metal-binding site. The instructors conclude that their basic goals for the course - introduction to advanced inorganic chemistry topics using bioinorganic examples with emphasis on primary literature sources and computer-assisted displays - are being accomplished.

  12. Catalytic Oxygen Evolution by a Bioinorganic Model of the Photosystem II Oxygen-Evolving Complex

    Science.gov (United States)

    Howard, Derrick L.; Tinoco, Arthur D.; Brudvig, Gary W.; Vrettos, John S.; Allen, Bertha Connie

    2005-01-01

    Bioinorganic models of the manganese Mn4 cluster are important not only as aids in understanding the structure and function of the oxygen-evolving complex (OEC), but also in developing artificial water-oxidation catalysts. The mechanism of water oxidation by photosystem II (PSII) is thought to involve the formation of a high-valent terminal Mn-oxo…

  13. Bioinorganic chemistry of copper coordination to alpha-synuclein: relevance to Parkinson's disease.

    OpenAIRE

    Binolfi, A.; L. Quintanar; Bertoncini, C.; Griesinger, C.; FERNANDEZ, C., LEOZ, J.

    2012-01-01

    Alpha-synuclein (AS) aggregation is associated with neurodegeneration in Parkinson'sdisease (PD). At the same time, alterations in metal ion homeostasis may play a pivotal role in the progression of AS amyloid assembly and the onset of PD. Elucidation of the structural basis directing AS–metal interactions and their effect on AS aggregation constitutes a key step toward understanding the role of metal ions in AS amyloid formation and neurodegeneration. This work provides a comprehensive revie...

  14. Bioinorganic and medicinal chemistry: aspects of gold(I)-protein complexes.

    Science.gov (United States)

    Bhabak, Krishna P; Bhuyan, Bhaskar J; Mugesh, Govindasamy

    2011-03-14

    Gold(I)-based drugs have been used successfully for the treatment of rheumatoid arthritis (RA) for several years. Although the exact mechanism of action of these gold(I) drugs for RA has not been clearly established, the interaction of these compounds with mammalian enzymes has been extensively studied. In this paper, we describe the interaction of therapeutic gold(I) compounds with mammalian proteins that contain cysteine (Cys) and selenocysteine (Sec) residues. Owing to the higher affinity of gold(I) towards sulfur and selenium, gold(I) drugs rapidly react with the activated cysteine or selenocysteine residues of the enzymes to form protein-gold(I)-thiolate or protein-gold(I)-selenolate complexes. The formation of stable gold(I)-thiolate/selenolate complexes generally lead to inhibition of the enzyme activity. The gold-thiolate/selenolate complexes undergo extensive ligand exchange reactions with other nucleophiles and such ligand exchange reactions alter the inhibitory effects of gold(i) complexes. Therefore, the effect of gold(I) compounds on the enzymatic activity of cysteine- or selenocysteine-containing proteins may play important roles in RA. The interaction of gold(I) compounds with different enzymes and the biochemical mechanism underlying the inhibition of enzymatic activities may have broad medicinal implications for the treatment of RA.

  15. Alkali-ion-crown ether in art and conservation: the applied bioinorganic chemistry approach.

    Science.gov (United States)

    Hilfrich, Uwe; Taylor, Harold; Weser, Ulrich

    2004-01-01

    Dried varnish is rich in many ester moieties, which may be broken down into small, soluble compounds by esterase activity or alkaline hydrolysis. Two methods for varnish removal have been developed, including the treatment of either lipase or RbOH / PEG-400 crown ether which allow aged oil varnishes or paint coverings to be removed or thinned. These techniques are designed to proceed in a controlled manner without damaging lower paint or base layers. Unfortunately, lipase did not react with the aged ester groups of dried linseed oil varnish. Surprisingly, the varnish came off in the presence of Tris buffer alone which, in addition, formed reactive metal complexes. A better choice was the use of high M(r) alkali ion polyethylene glycol-400 (PEG-400) crown ether type chelates. PEG-400 complexes alkali ions including rubidium and other alkaliions impeding the diffusion of their basic counter ions into lower varnish or paint layers. Possible migration of alkali metal ions into the paint layer during alkaline varnish removal was determined by labelling the cleansing solutions with (86)Rb. Fortunately, varnish is degraded on the surface only. Lower paint or varnish layers are not attacked even if chemically similar to the varnish or over painting to be removed as virtually no (86)Rb was detected on the paint surface.

  16. Thyroid hormone synthesis and anti-thyroid drugs: A bioinorganic chemistry approach

    Indian Academy of Sciences (India)

    Gouriprasanna Roy; G Mugesh

    2006-11-01

    Hydrogen peroxide, generated by thyroid oxidase enzymes, is a crucial substrate for the thyroid peroxidase (TPO)-catalysed biosynthesis of thyroid hormones, thyroxine (T4) and triiodothyronine (T3) in the thyroid gland. It is believed that the H2O2 generation is a limiting step in thyroid hormone synthesis. Therefore, the control of hydrogen peroxide concentration is one of the possible mechanisms for the inhibition of thyroid hormone biosynthesis. The inhibition of thyroid hormone synthesis is required for the treatment of hyperthyroidism and this can be achieved by one or more anti-thyroid drugs. The most widely used anti-thyroid drug methimazole (MMI) inhibits the production of thyroid hormones by irreversibly inactivating the enzyme TPO. Our studies show that the replacement of sulphur in MMI by selenium leads to a selone, which exists predominantly in its zwitterionic form. In contrast to the sulphur drug, the selenium analogue (MSeI) reversibly inhibits the peroxidase-catalysed oxidation and iodination reactions. Theoretical studies on MSeI reveal that the selenium atom in this compound carries a large negative charge. The carbon-selenium bond length in MSeI is found to be close to single-bond length. As the selenium atom exhibits a large nucleophilic character, the selenium analogue of MMI may scavenge the hydrogen peroxide present in the thyroid cells, which may lead to a reversible inhibition of thyroid hormone biosynthesis.

  17. Development of High Resolution X-Ray spectrometers for the Investigation of Bioinorganic Chemistry in Metalloproteins

    Energy Technology Data Exchange (ETDEWEB)

    Drury, Owen Byron [Univ. of California, Davis, CA (United States)

    2007-01-01

    Metals play as varied a role in biology as the proteins they are part of. They are involved in structure formation, they help transfer material and information, and they catalyze chemical reactions. Other proteins transport material or information, such as hemoglobin that distributes O2 and takes up CO2, or insulin that signals cells to increase glucose uptake in response to high blood glucose levels. Again other proteins promote chemical reactions, such as photosystem II responsible for photosynthetic oxygen evolution or nitrogenase which catalyzes the reduction of N2 to NH3. All of these proteins require the presence of a metal ion for their activity.

  18. Development of high resolution x-ray spectrometers for the investigation of bioinorganic chemistry in metalloproteins

    Science.gov (United States)

    Drury, Owen Byron

    We have built an X-ray spectrometer for synchrotron-based high-resolution soft X-ray spectroscopy. The spectrometer uses four 9-pixel arrays of superconducting tunnel junctions (STJs) as sensors. They infer the energy of an absorbed X-ray from a temporary increase in tunneling current. The STJs are operated in a two-stage adiabatic demagnetization refrigerator (ADR) that uses liquid nitrogen and helium for precooling to 77 K and 4.2 K, and gallium gadolinium garnet and iron ammonium sulfate to attain a base temperature below 0.1 K. The sensors are held at the end of a 40-cm-long cold finger within ˜1 cm of a sample located inside the vacuum chamber of a synchrotron beam line end station. The spectrometer has an energy resolution between 10 eV and 20 eV FWHM below 1 keV, can be operated at rates up to ˜106 counts/s. STJ spectrometers are suited for chemical analysis of dilute samples by fluorescence-detected X-ray absorption spectroscopy (XAS) in cases where conventional germanium detectors do not have enough energy resolution. We have used this STJ spectrometer at the Advanced Light Source synchrotron for spectroscopy on the lower energy X-ray absorption edges of the elements Mo, S, Fe and N. These elements play an important role in biological nitrogen fixation at the metalloprotein nitrogenase, and we have examined if STJ spectrometers can be used to provide new insights into some of the open questions regarding the reaction mechanism of this protein. We have taken X-ray absorption near-edge spectra (XANES) and extended fine structure spectra (EXAFS) of an Fe 6N(CO)15-compound containing a single N atom inside a cluster of six Fe atoms, as postulated to exist inside the Fe-S cluster of the FeMo-cofactor (FeMo-co) in nitrogenase. The STJ detector has enabled the first-ever extended range EXAFS scans on nitrogen through the oxygen K-edge, enabling a comparison with N EXAFS on FeMo-co. We have taken iron L23-edge spectra of the Fe-S cluster in FeMo-co, which can be used to measure its oxidation state despite the very small chemical shifts. We also have taken spectra on the molybdenum M-edges and on the sulfur L-edges of inorganic model compounds.

  19. Silicateins--a novel paradigm in bioinorganic chemistry: enzymatic synthesis of inorganic polymeric silica.

    Science.gov (United States)

    Müller, Werner E G; Schröder, Heinz C; Burghard, Zaklina; Pisignano, Dario; Wang, Xiaohong

    2013-05-03

    The inorganic matrix of the siliceous skeletal elements of sponges, that is, spicules, is formed of amorphous biosilica. Until a decade ago, it remained unclear how the hard biosilica monoliths of the spicules are formed in sponges that live in a silica-poor (<50 μM) aquatic environment. The following two discoveries caused a paradigm shift and allowed an elucidation of the processes underlying spicule formation; first the discovery that in the spicules only one major protein, silicatein, exists and second, that this protein displays a bio-catalytical, enzymatic function. These findings caused a paradigm shift, since silicatein is the first enzyme that catalyzes the formation of an inorganic polymer from an inorganic monomeric substrate. In the present review the successive steps, following the synthesis of the silicatein product, biosilica, and resulting in the formation of the hard monolithic spicules is given. The new insight is assumed to open new horizons in the field of biotechnology and also in biomedicine.

  20. Marine Bioinorganic Chemistry Workshop Held in Heron Island on 28 June - 2nd July 1989

    Science.gov (United States)

    1990-02-09

    know if it is a vanadium-containing enzyme. Hans Vilter reported that they found no bromoperoxidase in sargassum or tubinaria, and thus its occurrence...provided by the of food, cold Antarctic waters are Queensland National Parks and Wildlife unsuitable for reproduction . Young Service on behalf of the Great

  1. Rearrangements of Allylic Sulfinates to Sulfones: A Mechanistic Study

    Science.gov (United States)

    Ball, David B.; Mollard, Paul; Voigtritter, Karl R.; Ball, Jenelle L.

    2010-01-01

    Most current organic chemistry textbooks are organized by functional groups and those of us who teach organic chemistry use functional-group organization in our courses but ask students to learn organic chemistry from a mechanistic approach. To enrich and extend the chemical understanding and knowledge of pericyclic-type reactions for chemistry…

  2. The role of plasma-surface interactions in process chemistry: Mechanistic studies of a-carbon nitride deposition and sulfur fluoride/oxygen etching of silicon

    Science.gov (United States)

    Stillahn, Joshua M.

    The molecular level chemistry of a-CNx deposition in plasma discharges was studied with emphasis on the use of CH 3CN and BrCN as single source precursors for these films. Characterization of the global deposition behavior in these systems indicates that the resulting films are relatively smooth and contain significant levels of N-content, with N/C > 0.3. Notably, films obtained from BrCN plasmas are observed to delaminate upon their exposure to atmosphere, and preliminary investigation of this behavior is presented. Detailed chemical investigation of the deposition process focuses primarily on the contributions of CN radicals, which were characterized from their origin in the gas phase to their reaction at the a-CNx film surface. Laser-induced fluorescence studies suggest that CN is formed through electron impact dissociation of the precursor species and that this breakdown process produces CN with high internal energies, having rotational and vibrational temperatures on the order of 1000 K and 5000 K, respectively. Measurement of CN surface reactivity coefficients in CH3CN plasmas show that CN reacts with a probability of ˜94%, irrespective of the deposition conditions; this information, combined with gas phase and film characterization data, leads to the conclusion that CN internal energies exert a strong influence on their surface reactivity and that these surface reactions favor their incorporation into the a-CN x film. Moreover, this correlation is shown to hold for several other plasma radicals studied in our lab, suggesting the potential for developing a general model for predicting surface interactions of activated gas phase species. This dissertation also presents results from studies of SF6/O 2 etching of Si. Addition of O2 to the feed gas leads to the generation of SO2, among other species, and gas phase characterization data suggest that SO2 may act as a sink for atomic S, preventing the reformation of SOxFy (y > 0) and thus promoting generation of

  3. Biological inorganic chemistry at the beginning of the 21st century.

    Science.gov (United States)

    Gray, Harry B

    2003-04-01

    Advances in bioinorganic chemistry since the 1970s have been driven by three factors: rapid determination of high-resolution structures of proteins and other biomolecules, utilization of powerful spectroscopic tools for studies of both structures and dynamics, and the widespread use of macromolecular engineering to create new biologically relevant structures. Today, very large molecules can be manipulated at will, with the result that certain proteins and nucleic acids themselves have become versatile model systems for elucidating biological function.

  4. Coordination chemistry and applications of versatile 4,5-diazafluorene derivatives.

    Science.gov (United States)

    Annibale, Vincent T; Song, Datong

    2016-01-01

    This perspective review will examine the coordination chemistry and applications of metal complexes of 4,5-diazafluorene derivatives. The versatile derivatives of 4,5-diazafluorene can serve multiple roles, and display a number of coordination modes. The ambidentate derivatives with multiple coordination sites can allow for the syntheses of coordination polymers, multimetallic, and macrocyclic complexes. In addition, certain 4,5-diazafluorene derivatives can serve as spectator ligands to support reactivity at the metal centre, or as reactive actor ligands engaging in atypical reactivity patterns. The applications of metal complexes of 4,5-diazafluorene derivatives in catalysis, photochemistry and photophysics, as well as in bioinorganic chemistry are also surveyed.

  5. Directed synthesis of bio-inorganic vanadium oxide composites using genetically modified filamentous phage

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Michael; Baik, Seungyun [Environmental Safety Group, Korea Institute of Science and Technology Europe (KIST-Europe) Forschungsgesellschaft mbH, Campus E 7 1, Saarbruecken (Germany); Jeon, Hojeong; Kim, Yuchan [Center for Biomaterials, Biomedical Research Institute Korea Institute of Science and Technology (KIST), Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Kim, Jungtae [Environmental Safety Group, Korea Institute of Science and Technology Europe (KIST-Europe) Forschungsgesellschaft mbH, Campus E 7 1, Saarbruecken (Germany); Kim, Young Jun, E-mail: youngjunkim@kist-europe.de [Environmental Safety Group, Korea Institute of Science and Technology Europe (KIST-Europe) Forschungsgesellschaft mbH, Campus E 7 1, Saarbruecken (Germany)

    2015-05-15

    Highlights: • Phage is an excellent seeding for bio-templates for environmentally benign vanadium oxide nanocomposite synthesis. • The synthesized bio-inorganic vanadium oxide showed photodegradation activities. • The fabricated wt phage/vanadium oxide composite exhibited bundle-like structure. • The fabricated RSTB-phage/vanadium oxide composite exhibited a ball with a fiber-like nanostructure. • The virus/vanadium oxide composite could be applied in photocatalysts, sensors and nanoelectronic applications. - Abstract: The growth of crystalline vanadium oxide using a filamentous bacteriophage template was investigated using sequential incubation in a V{sub 2}O{sub 5} precursor. Using the genetic modification of the bacteriophage, we displayed two cysteines that constrained the RSTB-1 peptide on the major coat protein P8, resulting in vanadium oxide crystallization. The phage-driven vanadium oxide crystals with different topologies, microstructures, photodegradation and vanadium oxide composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), quartz microbalance and dissipation (QCM-D) and X-ray photoelectron spectroscopy (XPS). Non-specific electrostatic attraction between a wild-type phage (wt-phage) and vanadium cations in the V{sub 2}O{sub 5} precursor caused phage agglomeration and fiber formation along the length of the viral scaffold. As a result, the addition of recombinant phage (re-phage) in V{sub 2}O{sub 5} precursors formed heterogeneous structures, which led to efficient condensation of vanadium oxide crystal formation in lines, shown by QCM-D analysis. Furthermore, re-phage/V{sub x}O{sub x} composites showed significantly enhanced photodegradation activities compared with the synthesized wt-phage-V{sub 2}O{sub 5} composite under illumination. This study demonstrates that peptide-mediated vanadium oxide mineralization is governed by a complicated interplay of peptide sequence, local structure

  6. Structural characterization of copper(II) binding to α-synuclein: Insights into the bioinorganic chemistry of Parkinson's disease

    OpenAIRE

    Rasia, Rodolfo M.; Carlos W Bertoncini; Marsh, Derek; Hoyer, Wolfgang; Cherny, Dmitry; Zweckstetter, Markus; Griesinger, Christian; Jovin, Thomas M.; Fernández, Claudio O

    2005-01-01

    The aggregation of α-synuclein (AS) is characteristic of Parkinson's disease and other neurodegenerative synucleinopathies. We demonstrate here that Cu(II) ions are effective in accelerating AS aggregation at physiologically relevant concentrations without altering the resultant fibrillar structures. By using numerous spectroscopic techniques (absorption, CD, EPR, and NMR), we have located the primary binding for Cu(II) to a specific site in the N terminus, involving His-50 as the anchoring r...

  7. Structural characterization of copper(II) binding to α-Synuclein: Insights into the bioinorganic chemistry of Parkinson's disease

    OpenAIRE

    Rasia, R.; BERTONCINI, C; Marsh, D; Hoyer, W.; Cherny, D; Zweckstetter, M.; Griesinger, C; Jovin, T.; Fernandez, C.

    2005-01-01

    The aggregation of α -synuclein (AS) is characteristic of Parkinson’s disease and other neurodegenerative synucleinopathies. We demonstrate here that Cu(II) ions are effective in accelerating AS aggregation at physiologically relevant concentrations without altering the resultant fibrillar structures. By using numerous spectroscopic techniques (absorption, CD, EPR, and NMR), we have located the primary binding for Cu(II) to a specific site in the N terminus, involving His-50 as the anchoring ...

  8. Bioinorganic Chemistry in Thyroid Gland: Effect of Antithyroid Drugs on Peroxidase-Catalyzed Oxidation and Iodination Reactions

    Directory of Open Access Journals (Sweden)

    G. Mugesh

    2006-11-01

    Full Text Available Propylthiouracil (PTU and methimazole (MMI are the most commonly used antithyroid drugs. The available data suggest that these drugs may block the thyroid hormone synthesis by inhibiting the thyroid peroxidase (TPO or diverting oxidized iodides away from thyroglobulin. It is also known that PTU inhibits the selenocysteine-containing enzyme ID-1 by reacting with the selenenyl iodide intermediate (E-SeI. In view of the current interest in antithyroid drugs, we have recently carried out biomimetic studies to understand the mechanism by which the antithyroid drugs inhibit the thyroid hormone synthesis and found that the replacement of sulfur with selenium in MMI leads to an interesting compound that may reversibly block the thyroid hormone synthesis. Our recent results on the inhibition of lactoperoxidase (LPO-catalyzed oxidation and iodination reactions by antithyroid drugs are described.

  9. Prion疾病与生物无机化学%Prion Diseases and Bio-inorganic Chemistry

    Institute of Scientific and Technical Information of China (English)

    黄仲贤; 陆君霞; 王韵华

    2000-01-01

    介绍了除病菌、病毒以外的第三种病原体-病蛋白Prion.这种病原蛋白的本质是正常蛋白的异常折叠,因此又被称为蛋白分子的"构象病".还介绍了这种病蛋白的可能致病机理.铜离子对这种病蛋白生成的重要作用,充分显示了生物无机化学这门新兴学科的重要性和前沿性.

  10. Structural characterization of copper(II) binding to alpha-synuclein: Insights into the bioinorganic chemistry of Parkinson's disease.

    Science.gov (United States)

    Rasia, Rodolfo M; Bertoncini, Carlos W; Marsh, Derek; Hoyer, Wolfgang; Cherny, Dmitry; Zweckstetter, Markus; Griesinger, Christian; Jovin, Thomas M; Fernández, Claudio O

    2005-03-22

    The aggregation of alpha-synuclein (AS) is characteristic of Parkinson's disease and other neurodegenerative synucleinopathies. We demonstrate here that Cu(II) ions are effective in accelerating AS aggregation at physiologically relevant concentrations without altering the resultant fibrillar structures. By using numerous spectroscopic techniques (absorption, CD, EPR, and NMR), we have located the primary binding for Cu(II) to a specific site in the N terminus, involving His-50 as the anchoring residue and other nitrogen/oxygen donor atoms in a square planar or distorted tetragonal geometry. The carboxylate-rich C terminus, originally thought to drive copper binding, is able to coordinate a second Cu(II) equivalent, albeit with a 300-fold reduced affinity. The NMR analysis of AS-Cu(II) complexes reveals the existence of conformational restrictions in the native state of the protein. The metallobiology of Cu(II) in Parkinson's disease is discussed by a comparative analysis with other Cu(II)-binding proteins involved in neurodegenerative disorders.

  11. Practical approaches to biological inorganic chemistry

    CERN Document Server

    Louro, Ricardo O

    2012-01-01

    The book reviews the use of spectroscopic and related methods to investigate the complex structures and mechanisms of biological inorganic systems that contain metals. Each chapter presents an overview of the technique including relevant theory, clearly explains what it is and how it works and then presents how the technique is actually used to evaluate biological structures. Practical examples and problems are included to illustrate each technique and to aid understanding. Designed for students and researchers who want to learn both the basics, and more advanced aspects of bioinorganic chemistry. It includes many colour illustrations enable easier visualization of molecular mechanisms and structures. It provides worked examples and problems that are included to illustrate and test the reader's understanding of each technique. It is written by a multi-author team who use and teach the most important techniques used today to analyse complex biological structures.

  12. Solid-State Synthesis, Characterization, and Biological Activity of the Bioinorganic Complex of Aspartic Acid and Arsenic Triiodide

    Directory of Open Access Journals (Sweden)

    Guo-Qing Zhong

    2013-01-01

    Full Text Available The bioinorganic complex of aspartic acid and arsenic triiodide was synthesized by a solid-state reaction at room temperature. The formula of the complex is AsI3[HOOCCH2CH(NH2COOH]2.5. The crystal structure of the complex belongs to monoclinic system with lattice parameters: a=1.0019 nm, b=1.5118 nm, c=2.1971 nm, and β=100.28°. The infrared spectra can demonstrate the complex formation between the arsenic ion and aspartic acid, and the complex may be a dimer with bridge structure. The result of primary biological test indicates that the complex possesses better biological activity for the HL-60 cells of the leukemia than arsenic triiodide.

  13. Mechanistic aspects of ionic reactions in flames

    DEFF Research Database (Denmark)

    Egsgaard, H.; Carlsen, L.

    1993-01-01

    Some fundamentals of the ion chemistry of flames are summarized. Mechanistic aspects of ionic reactions in flames have been studied using a VG PlasmaQuad, the ICP-system being substituted by a simple quartz burner. Simple hydrocarbon flames as well as sulfur-containing flames have been investigated....... The simple hydrocarbon flames are dominated by a series of hydrocarbonic ions and, to a minor extent, protonated oxo-compounds. The introduction of sulfur to the flames leads to significant changes in the ion composition, as sulfur-containing species become dominant. The ability of the technique to study...

  14. Understanding the Impact of a General Chemistry Course on Students' Transition to Organic Chemistry

    Science.gov (United States)

    Collins-Webb, Alexandra; Jeffery, Kathleen A.; Sweeder, Ryan D.

    2016-01-01

    The move from general chemistry to organic chemistry can be a challenge for students as it often involves a transition from quantitatively-oriented to mechanistically-oriented thinking. This study found that the design of the general chemistry course can change the student experience of this transition as assessed by a reflective survey. The…

  15. Understanding the Impact of a General Chemistry Course on Students' Transition to Organic Chemistry

    Science.gov (United States)

    Collins-Webb, Alexandra; Jeffery, Kathleen A.; Sweeder, Ryan D.

    2016-01-01

    The move from general chemistry to organic chemistry can be a challenge for students as it often involves a transition from quantitatively-oriented to mechanistically-oriented thinking. This study found that the design of the general chemistry course can change the student experience of this transition as assessed by a reflective survey. The…

  16. A Perspective on Physical Organic Chemistry

    Science.gov (United States)

    2015-01-01

    A perspective on the development of mechanistic carbene chemistry is presented. The author will point out questions that have been answered, and a next generation of questions will be proposed. PMID:24571434

  17. Advances in analytical methodology for bioinorganic speciation analysis: metallomics, metalloproteomics and heteroatom-tagged proteomics and metabolomics.

    Science.gov (United States)

    Szpunar, Joanna

    2005-04-01

    The recent developments in analytical techniques capable of providing information on the identity and quantity of heteroatom-containing biomolecules are critically discussed. Particular attention is paid to the emerging areas of bioinorganic analysis including: (i) a comprehensive analysis of the entirety of metal and metalloid species within a cell or tissue type (metallomics), (ii) the study of the part of the metallome involving the protein ligands (metalloproteomics), and (iii) the use of a heteroelement, naturally present in a protein or introduced in a tag added by means of derivatisation, for the spotting and quantification of proteins (heteroatom-tagged proteomics). Inductively coupled plasma mass spectrometry (ICP MS), used as detector in chromatography and electrophoresis, and supported by electrospray and MALDI MS, appears as the linchpin analytical technique for these emerging areas. This review focuses on the recent advances in ICP MS in biological speciation analysis including sensitive detection of non-metals, especially of sulfur and phosphorus, couplings to capillary and nanoflow HPLC and capillary electrophoresis, laser ablation ICP MS detection of proteins in gel electrophoresis, and isotope dilution quantification of biomolecules. The paper can be considered as a followup of a previous review by the author on a similar topic (J. Szpunar, Analyst, 2000, 125, 963).

  18. From Source to Sink: Mechanistic Reasoning Using the Electron-Pushing Formalism

    Science.gov (United States)

    Bhattacharyya, Gautam

    2013-01-01

    Since the introduction of Morrison and Boyd's textbook in organic chemistry over 50 years ago, reaction mechanisms and mechanistic reasoning using the electron-pushing formalism (EPF) have become a mainstay of organic chemistry courses. In recent years there have even been several papers in this Journal and others detailing research on how…

  19. Mechanistic studies of olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Grubbs, R.H.

    1979-03-01

    A review covers studies of the olefin metathesis mechanism which indicated that the reaction proceeds by a non-pairwise mechanism; detailed mechanistic studies on the homogeneously and heterogeneously catalyzed metathesis; and stereochemical investigations.

  20. From mechanistic to functional behaviorism.

    Science.gov (United States)

    Moxley, R A

    1992-11-01

    A shift from mechanistic behaviorism to functional behaviorism is presented against the background of two historical traditions, one with an emphasis on form, the other with an emphasis on function. Skinner's work, which made more contributions to a functional behaviorism than to a mechanistic behaviorism, exemplifies this shift. The two traditions and an account of Skinner's development of functional relations are presented in order to show Skinner's contributions to aligning modern behavior analysis with the functional tradition.

  1. Tryptophan oxygenation: mechanistic considerations.

    Science.gov (United States)

    Naismith, James H

    2012-06-01

    From a protein structural viewpoint, tryptophan is often considered an inert structural amino acid, playing a role as a hydrophobic anchor in membrane proteins or as part of the hydrophobic core of soluble proteins. However, tryptophan is the only polyaromatic amino acid and, from a chemical viewpoint, possesses unique reactivity owing to the electron-richness of the indole system. This reactivity is seen in the area of natural products and metabolites which have exquisite modifications of the indole ring system. Enzymes have evolved multiple strategies to break or modify the indole ring; one particular class is the IDO/TDO (indoleamine/tryptophan dioxygenase) superfamily. A new member of this family, PrnB, on the surface catalyses a very different reaction, but actually shares much of the early chemistry with the tryptophan dioxygenases. Studies on PrnB have contributed to our understanding of the wider superfamily. In the present mini-review, recent developments in our understanding of how the TDO class of enzymes use activated molecular oxygen to break the indole ring are discussed.

  2. Applications of Raman Spectroscopy to Inorganic Chemistry

    Institute of Scientific and Technical Information of China (English)

    RobinJHClarkFRS

    1995-01-01

    The renaissance in Raman spectroscopy some 25-30 years ago had particular and immediate impact on Inorganic Chemistry,viz in areas such as the study of deeply coloued compounds,structural changes on change of state,equilibria,vapour phase band contour analysis,Raman band intensities and the nature of the chemical bond,metal-metal bonding,species in melts,identification of species in solution and of radicals by time-resolved techniques,in bioinorganic chemistry,and of linear-chain semiconductors.More recently,much attention has been directed at the quantitative level at the evaluation of geometric changes in molecules on excitation by resonance Raman spectroscopy.At the qualitative level Raman microscopy is now recognised to be the most effective technique for the identification of pigments-particularly the inorganic ones-on medieval manuscripts and especially of the components(down to grain sizes of -1 um)of pigment mixtures,It is thus a very important technique at the Arts/Science borderling in conservation science.

  3. Quantum mechanical methods for the investigation of metalloproteins and related bioinorganic compounds.

    Science.gov (United States)

    Bertini, Luca; Bruschi, Maurizio; Cosentino, Ugo; Greco, Claudio; Moro, Giorgio; Zampella, Giuseppe; De Gioia, Luca

    2014-01-01

    It is well known that transition metal ions are often bound to proteins, conveying very specific functional properties. In fact, metalloproteins play crucial biological roles in the transport and activation of small molecules such as H2, O2, and N2, as well as in several other biochemical processes. However, even if the presence of transition metals in the active site of proteins allows a very rich biochemistry, the experimental disclosure of structure-activity relationships in metalloproteins is generally difficult exactly because of the presence of transition metals, which are intrinsically characterized by a very versatile and often elusive chemistry. For this reason, computational methods are becoming very popular tools in the characterization of metalloproteins. In particular, since computing power is becoming less and less expensive, due to the continuous technological development of CPUs, the computational tools suited to investigate metalloproteins are becoming more accessible and therefore more commonly used also in molecular biology and biochemistry laboratories. Here, we present the main procedures and computational methods based on quantum mechanics, which are commonly used to study the structural, electronic, and reactivity properties of metalloproteins and related bioinspired compounds, with a specific focus on the practical and technical aspects that must be generally tackled to properly study such biomolecular systems.

  4. Mechanistic individualism versus organistic totalitarianism

    Directory of Open Access Journals (Sweden)

    J.J. Venter

    1997-03-01

    Full Text Available Mechanistic individualism versus organistic totalitarianismIn this article it is argued that the organistic world picture, when functioning as a world view, is associated with a totalitarian view of social relationships, usually promoting the interests o f the state or the ethnic group as the interests which should dominate. This is illustrated by referring to the social ideas of Hobbes, Rousseau, D.H. Lawrence and Mussolini. The mechanistic world picture, however, when functioning as a world view, is associated with individualism, according to which the individuals have a relatively independent existence; it suggests that justice and morality are the automatic products of the equilibrating process. Cases in point: Hobbes, Adam Smith, Kant, Darwin, New-Classical and Monetarist economics. Finally (in Neo-Calvinist vein it is argued that the application o f such worldviewish metaphors should be limited, so that justice can be done to both the differentiation of social relationships and their integration.

  5. Recent insights on the medicinal chemistry of metal-based compounds: hints for the successful drug design.

    Science.gov (United States)

    Hernandes, M Z; de S Pontes, F J; Coelho, L C D; Moreira, D R M; Pereira, V R A; Leite, A C L

    2010-01-01

    Although more complex than usually described, the anticancer action mechanism of cisplatin is based on binding to DNA. Following this line of reasoning, most the metal-based compounds discovered soon after cisplatin were designed to acting as DNA-binding agents and their pharmacological properties were thought to be correlated with this mechanism. Apart from the DNA structure, a significant number of proteins and biochemical pathways have been described as drug targets for metal-based compounds. This paper is therefore aimed at discussing the most recent findings on the medicinal chemistry of metal-based drugs. It starts illustrating the design concept behind the bioinorganic chemistry of anticancer complexes. Anticancer metallic compounds that inhibit the protein kinases are concisely discussed as a case study. The accuracy and limitations of molecular docking programs currently available to predict the binding mode of metallic complexes in molecular targets are further discussed. Finally, the advantages and disadvantages of different in vitro screenings are briefly commented.

  6. Semiconductor photocatalysis--mechanistic and synthetic aspects.

    Science.gov (United States)

    Kisch, Horst

    2013-01-14

    Preceding work on photoelectrochemistry at semiconductor single-crystal electrodes has formed the basis for the tremendous growth in the three last decades in the field of photocatalysis at semiconductor powders. The reason for this is the unique ability of inorganic semiconductor surfaces to photocatalyze concerted reduction and oxidation reactions of a large variety of electron-donor and -acceptor substrates. Whereas great attention was paid to water splitting and the exhaustive aerobic degradation of pollutants, only a small amount of research also explored synthetic aspects. After introducing the basic mechanistic principles, standard experiments for the preparation and characterization of visible light active photocatalysts as well as the investigation of reaction mechanisms are discussed. Novel atom-economic C-C and C-N coupling reactions illustrate the relevance of semiconductor photocatalysis for organic synthesis, and demonstrate that the multidisciplinary field combines classical photochemistry with electrochemistry, solid-state chemistry, and heterogeneous catalysis. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Bioinorganic Drugs-2

    Science.gov (United States)

    Williams, David R.

    1974-01-01

    Discusses the metallotherapy approach to viral infection, cadmium poisoning and Wilson's disease. Presents a plan for progress in metallotherapy through more education, more basic research, and more epidemiological studies. (GS)

  8. 2010 INORGANIC CHEMISTRY GORDON RESEARCH CONFERENCE JUNE 20 - 25, 2010

    Energy Technology Data Exchange (ETDEWEB)

    JOHN LOCKEMEYER

    2010-06-25

    The Inorganic Chemistry GRC is one of the longest-standing of the GRCs, originating in 1951. Over the years, this conference has played a role in spawning many other GRCs in specialized fields, due to the involvement of elements from most of the periodic table. These include coordination, organometallic, main group, f-element, and solid state chemistries; materials science, catalysis, computational chemistry, nanotechnology, bioinorganic, environmental, and biomedical sciences just to name a few. The 2010 Inorganic Chemistry GRC will continue this tradition, where scientists at all levels from academic, industrial, and national laboratories meet to define the important problems in the field and to highlight emerging opportunities through exchange of ideas and discussion of unpublished results. Invited speakers will present on a wide variety of topics, giving attendees a look at areas both inside and outside of their specialized areas of interest. In addition to invited speakers, the poster sessions at GRCs are a key feature of the conference. All conferees at the Inorganic Chemistry GRC are invited to present a poster on their work, and here the informal setting promotes the free exchange of ideas and fosters new relationships. As in previous years, we will offer poster presenters the opportunity to compete for one of several program spots in which they can give an oral presentation based on the subject matter of their poster. This is a great way to get your work noticed by the scientists attending the meeting, especially for those early in their career path such as junior faculty members, postdoctoral fellows, and those at comparable ranks. Anyone interested in participating in the poster competition should bring an electronic slide presentation and a small hard copy of their poster to submit to the committee.

  9. HTGR Mechanistic Source Terms White Paper

    Energy Technology Data Exchange (ETDEWEB)

    Wayne Moe

    2010-07-01

    The primary purposes of this white paper are: (1) to describe the proposed approach for developing event specific mechanistic source terms for HTGR design and licensing, (2) to describe the technology development programs required to validate the design methods used to predict these mechanistic source terms and (3) to obtain agreement from the NRC that, subject to appropriate validation through the technology development program, the approach for developing event specific mechanistic source terms is acceptable

  10. Chemistry Notes

    Science.gov (United States)

    School Science Review, 1976

    1976-01-01

    Described are eight chemistry experiments and demonstrations applicable to introductory chemistry courses. Activities include: measure of lattice enthalpy, Le Chatelier's principle, decarboxylation of soap, use of pocket calculators in pH measurement, and making nylon. (SL)

  11. Heterocyclic chemistry

    OpenAIRE

    Hemming, Karl

    2011-01-01

    Recent progress in the synthesis of heterocyclic compounds is presented\\ud 2010 offered highlights in pericyclic chemistry, particularly 1,3-dipolar cycloaddition chemistry, asymmetric synthesis, gold catalysis, organocatalysis, hydroamination, C–H activation and multicomponent reactions.

  12. Chemistry Dashboard

    Science.gov (United States)

    The Chemistry Dashboard is part of a suite of dashboards developed by EPA to help evaluate the safety of chemicals. The Chemistry Dashboard provides access to a variety of information on over 700,000 chemicals currently in use.

  13. Biophysical chemistry.

    Science.gov (United States)

    Häussinger, Daniel; Pfohl, Thomas

    2010-01-01

    Biophysical chemistry at the Department of Chemistry, University of Basel, covers the NMR analysis of protein-protein interaction using paramagnetic tags and sophisticated microscopy techniques investigating the dynamics of biological matter.

  14. Colour Chemistry

    Science.gov (United States)

    Griffiths, J.; Rattee, I. D.

    1973-01-01

    Discusses the course offerings in pure color chemistry at two universities and the three main aspects of study: dyestuff chemistry, color measurement, and color application. Indicates that there exists a constant challenge to ingenuity in the subject discipline. (CC)

  15. Zinc metalloproteins as medicinal targets.

    Science.gov (United States)

    Anzellotti, A I; Farrell, N P

    2008-08-01

    Zinc bioinorganic chemistry has emphasized the role of the metal ion on the structure and function of the protein. There is, more recently, an increasing appreciation of the role of zinc proteins in a variety of human diseases. This critical review, aimed at both bioinorganic and medicinal chemists, shows how apparently widely-diverging diseases share the common mechanistic approaches of targeting the essential function of the metal ion to inhibit activity. Protein structure and function is briefly summarized in the context of its clinical relevance. The status of current and potential inhibitors is discussed along with the prospects for future developments (162 references).

  16. Combinatorial chemistry

    DEFF Research Database (Denmark)

    Nielsen, John

    1994-01-01

    An overview of combinatorial chemistry is presented. Combinatorial chemistry, sometimes referred to as `irrational drug design,' involves the generation of molecular diversity. The resulting chemical library is then screened for biologically active compounds.......An overview of combinatorial chemistry is presented. Combinatorial chemistry, sometimes referred to as `irrational drug design,' involves the generation of molecular diversity. The resulting chemical library is then screened for biologically active compounds....

  17. Combinatorial chemistry

    DEFF Research Database (Denmark)

    Nielsen, John

    1994-01-01

    An overview of combinatorial chemistry is presented. Combinatorial chemistry, sometimes referred to as `irrational drug design,' involves the generation of molecular diversity. The resulting chemical library is then screened for biologically active compounds.......An overview of combinatorial chemistry is presented. Combinatorial chemistry, sometimes referred to as `irrational drug design,' involves the generation of molecular diversity. The resulting chemical library is then screened for biologically active compounds....

  18. Positronium chemistry

    CERN Document Server

    Green, James

    1964-01-01

    Positronium Chemistry focuses on the methodologies, reactions, processes, and transformations involved in positronium chemistry. The publication first offers information on positrons and positronium and experimental methods, including mesonic atoms, angular correlation measurements, annihilation spectra, and statistical errors in delayed coincidence measurements. The text then ponders on positrons in gases and solids. The manuscript takes a look at the theoretical chemistry of positronium and positronium chemistry in gases. Topics include quenching, annihilation spectrum, delayed coincidence

  19. Quantum-chemistry based calibration of the alkali metal cation series (Li(+)-Cs(+)) for large-scale polarizable molecular mechanics/dynamics simulations.

    Science.gov (United States)

    Dudev, Todor; Devereux, Mike; Meuwly, Markus; Lim, Carmay; Piquemal, Jean-Philip; Gresh, Nohad

    2015-02-15

    The alkali metal cations in the series Li(+)-Cs(+) act as major partners in a diversity of biological processes and in bioinorganic chemistry. In this article, we present the results of their calibration in the context of the SIBFA polarizable molecular mechanics/dynamics procedure. It relies on quantum-chemistry (QC) energy-decomposition analyses of their monoligated complexes with representative O-, N-, S-, and Se- ligands, performed with the aug-cc-pVTZ(-f) basis set at the Hartree-Fock level. Close agreement with QC is obtained for each individual contribution, even though the calibration involves only a limited set of cation-specific parameters. This agreement is preserved in tests on polyligated complexes with four and six O- ligands, water and formamide, indicating the transferability of the procedure. Preliminary extensions to density functional theory calculations are reported.

  20. Forensic chemistry.

    Science.gov (United States)

    Bell, Suzanne

    2009-01-01

    Forensic chemistry is unique among chemical sciences in that its research, practice, and presentation must meet the needs of both the scientific and the legal communities. As such, forensic chemistry research is applied and derivative by nature and design, and it emphasizes metrology (the science of measurement) and validation. Forensic chemistry has moved away from its analytical roots and is incorporating a broader spectrum of chemical sciences. Existing forensic practices are being revisited as the purview of forensic chemistry extends outward from drug analysis and toxicology into such diverse areas as combustion chemistry, materials science, and pattern evidence.

  1. Rational and Mechanistic Perspectives on Reinforcement Learning

    Science.gov (United States)

    Chater, Nick

    2009-01-01

    This special issue describes important recent developments in applying reinforcement learning models to capture neural and cognitive function. But reinforcement learning, as a theoretical framework, can apply at two very different levels of description: "mechanistic" and "rational." Reinforcement learning is often viewed in mechanistic terms--as…

  2. Organic chemistry

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2003-08-15

    This book with sixteen chapter explains organic chemistry on linkage isomerism such as alkane, cycloalkane, alkene, aromatic compounds, stereo selective isomerization, aromatic compounds, stereo selective isomerization, organic compounds, stereo selective isomerization, organic halogen compound, alcohol, ether, aldehyde and ketone, carboxylic acid, dicarboxylic acid, fat and detergent, amino, carbohydrate, amino acid and protein, nucleotide and nucleic acid and spectroscopy, a polymer and medical chemistry. Each chapter has introduction structure and characteristic and using of organic chemistry.

  3. Computational chemistry

    OpenAIRE

    2000-01-01

    Computational chemistry has come of age. With significant strides in computer hardware and software over the last few decades, computational chemistry has achieved full partnership with theory and experiment as a tool for understanding and predicting the behavior of a broad range of chemical, physical, and biological phenomena. The Nobel Prize award to John Pople and Walter Kohn in 1998 highlighted the importance of these advances in computational chemistry. With massively parallel computers ...

  4. Chemistry Technology

    Data.gov (United States)

    Federal Laboratory Consortium — Chemistry technology experts at NCATS engage in a variety of innovative translational research activities, including:Design of bioactive small molecules.Development...

  5. Substrate inhibition in the heterogeneous catalyzed aldol condensation: A mechanistic study of supported organocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Kandel, Kapil; Althaus, Stacey M.; Peeraphatdit, Chorthip; Kobayashi, Takeshi; Trewyn, Brian G.; Pruski, Marek; Slowing, Igor I.

    2012-05-23

    In this study, we demonstrate how materials science can be combined with the established methods of organic chemistry to find mechanistic bottlenecks and redesign heterogeneous catalysts for improved performance. By using solid-state NMR, infrared spectroscopy, surface and kinetic analysis, we prove the existence of a substrate inhibition in the aldol condensation catalyzed by heterogeneous amines. We show that modifying the structure of the supported amines according to the proposed mechanism dramatically enhances the activity of the heterogeneous catalyst. We also provide evidence that the reaction benefits significantly from the surface chemistry of the silica support, which plays the role of a co-catalyst, giving activities up to two orders of magnitude larger than those of homogeneous amines. This study confirms that the optimization of a heterogeneous catalyst depends as much on obtaining organic mechanistic information as it does on controlling the structure of the support.

  6. Utilizing Mechanistic Cross-Linking Technology to Study Protein-Protein Interactions: An Experiment Designed for an Undergraduate Biochemistry Lab

    Science.gov (United States)

    Finzel, Kara; Beld, Joris; Burkart, Michael D.; Charkoudian, Louise K.

    2017-01-01

    Over the past decade, mechanistic cross-linking probes have been used to study protein-protein interactions in natural product biosynthetic pathways. This approach is highly interdisciplinary, combining elements of protein biochemistry, organic chemistry, and computational docking. Herein, we described the development of an experiment to engage…

  7. Modeling of iodine radiation chemistry in the presence of organic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Taghipour, Fariborz; Evans, Greg J. E-mail: evansg@chem-eng.toronto.edu

    2002-06-01

    A kinetic-based model was developed that simulates the radiation chemistry of iodine in the presence of organic compounds. The model's mechanistic description of iodine chemistry and generic semi-mechanistic reactions for various classes of organics, provided a reasonable representation of experimental results. The majority of the model and experimental results of iodine volatilization rates were in agreement within an order of magnitude.

  8. Organic chemistry on solid surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Zhen; Zaera, Francisco [Department of Chemistry, University of California, Riverside, CA 92521 (United States)

    2006-07-15

    Chemistry on solid surfaces is central to many areas of practical interest such as heterogeneous catalysis, tribology, electrochemistry, and materials processing. With the development of many surface-sensitive analytical techniques in the past decades, great advances have been possible in our understanding of such surface chemistry at the molecular level. Earlier studies with model systems, single crystals in particular, have provided rich information about the adsorption and reaction kinetics of simple inorganic molecules. More recently, the same approach has been expanded to the study of the surface chemistry of relatively complex organic molecules, in large measure in connection with the selective synthesis of fine chemicals and pharmaceuticals. In this report, the chemical reactions of organic molecules and fragments on solid surfaces, mainly on single crystals of metals but also on crystals of metal oxides, carbides, nitrides, phosphides, sulfides and semiconductors as well as on more complex models such as bimetallics, alloys, and supported particles, are reviewed. A scheme borrowed from the organometallic and organic chemistry literature is followed in which key examples of representative reactions are cited first, and general reactivity trends in terms of both the reactants and the nature of the surface are then identified to highlight important mechanistic details. An attempt has been made to emphasize recent advances, but key earlier examples are cited as needed. Finally, correlations between surface and organometallic and organic chemistry, the relevance of surface reactions to applied catalysis and materials functionalization, and some promising future directions in this area are briefly discussed. (author)

  9. Quantum chemistry

    CERN Document Server

    Lowe, John P

    1993-01-01

    Praised for its appealing writing style and clear pedagogy, Lowe's Quantum Chemistry is now available in its Second Edition as a text for senior undergraduate- and graduate-level chemistry students. The book assumes little mathematical or physical sophistication and emphasizes an understanding of the techniques and results of quantum chemistry, thus enabling students to comprehend much of the current chemical literature in which quantum chemical methods or concepts are used as tools. The book begins with a six-chapter introduction of standard one-dimensional systems, the hydrogen atom,

  10. Introductory Chemistry

    OpenAIRE

    Baron, Mark; Gonzalez-Rodriguez, Jose; Stevens, Gary; Gray, Nathan; Atherton, Thomas; Winn, Joss

    2010-01-01

    Teaching and Learning resources for the 1st Year Introductory Chemistry course (Forensic Science). 30 credits. These are Open Educational Resources (OER), made available for re-use under a Creative Commons license.

  11. Materials Chemistry

    CERN Document Server

    Fahlman, Bradley D

    2011-01-01

    The 2nd edition of Materials Chemistry builds on the strengths that were recognized by a 2008 Textbook Excellence Award from the Text and Academic Authors Association (TAA). Materials Chemistry addresses inorganic-, organic-, and nano-based materials from a structure vs. property treatment, providing a suitable breadth and depth coverage of the rapidly evolving materials field. The 2nd edition continues to offer innovative coverage and practical perspective throughout. After briefly defining materials chemistry and its history, seven chapters discuss solid-state chemistry, metals, semiconducting materials, organic "soft" materials, nanomaterials, and materials characterization. All chapters have been thoroughly updated and expanded with, for example, new sections on ‘soft lithographic’ patterning, ‘click chemistry’ polymerization, nanotoxicity, graphene, as well as many biomaterials applications. The polymer and ‘soft’ materials chapter represents the largest expansion for the 2nd edition. Each ch...

  12. Nuclear Chemistry.

    Science.gov (United States)

    Chemical and Engineering News, 1979

    1979-01-01

    Provides a brief review of the latest developments in nuclear chemistry. Nuclear research today is directed toward increased activity in radiopharmaceuticals and formation of new isotopes by high-energy, heavy-ion collisions. (Author/BB)

  13. Cluster Chemistry

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    @@ Cansisting of eight scientists from the State Key Laboratory of Physical Chemistry of Solid Surfaces and Xiamen University, this creative research group is devoted to the research of cluster chemistry and creation of nanomaterials.After three-year hard work, the group scored a series of encouraging progresses in synthesis of clusters with special structures, including novel fullerenes, fullerene-like metal cluster compounds as well as other related nanomaterials, and their properties study.

  14. Green Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Collison, Melanie

    2011-05-15

    Green chemistry is the science of chemistry used in a way that will not use or create hazardous substances. Dr. Rui Resendes is working in this field at GreenCentre Canada, an offshoot of PARTEQ Innovations in Kingston, Ontario. GreenCentre's preliminary findings suggest their licensed product {sup S}witchable Solutions{sup ,} featuring 3 classes of solvents and a surfactant, may be useful in bitumen oil sands extraction.

  15. Biomimetic oxidation studies. 9. Mechanistic aspects of the oxidation of alcohols with functional,active site methane monooxygenase enzyme models in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Rabion, A. [Lawrence Berkeley National Lab., CA (United States)]|[Univ. of California, Berkeley, CA (United States)]|[Groupement de Recherche de Lacq, Artix (France); Chen, S.; Wang, J.; Buchanan, R.M. [Univ. of Louisville, KY (United States); Seris, J.L. [Groupement de recherche de Lacq, Artix (France); Fish, R.H. [Lawrence Berkeley National Lab., CA (United States)]|[Univ. of California, Berkeley, CA (United States)

    1995-12-13

    The syntheses of biomimetic complexes that mimic the major structural features of the hydroxylase component of methane monooxygenase enzyme (MMO) and, more importantly, that provide similar alkane functionalization activity, in the presence of an oxidant, have been of great interest to the discipline of bioinorganic chemistry. In this communication, we will demonstrate the feasibility of conducting biomimetic oxidation studies in H{sub 2}O with soluble substrates, i.e., alcohols (cyclohexanol, benzyl alcohol), using H{sub 2}O-stable MMO mimics at pH 4.2, and the oxidant, tert-butyl hydroperoxide (TBHP). Both the Mitusunobu procedure and the mesylate displacement reaction proceeded with complete inversion of the stereo-center and provided optically pure penultimate intermediate (>99.9% ee). The synthesis was completed by reduction of the nitro group under standard conditions to deliver LY300164 in 87%. In summary, we have developed an efficient and environmentally benign synthesis of the 5H-2,3-benzodiazepine LY300164 that provides the optically pure compound in 51% overall yield. Intramolecular hydrazone alkylation led to a remarkably facile and selective formation of the benzodiazepine. Furthermore, the application of resins to whole-cell-based biotransformations should find general utility for similar reactions that are complicated by component inhibition and product isolation. 11 refs., 1 fig.

  16. Mechanistic models in computational social science

    Science.gov (United States)

    Holme, Petter; Liljeros, Fredrik

    2015-09-01

    Quantitative social science is not only about regression analysis or, in general, data inference. Computer simulations of social mechanisms have an over 60 years long history. They have been used for many different purposes—to test scenarios, to test the consistency of descriptive theories (proof-of-concept models), to explore emergent phenomena, for forecasting, etc. In this essay, we sketch these historical developments, the role of mechanistic models in the social sciences and the influences from the natural and formal sciences. We argue that mechanistic computational models form a natural common ground for social and natural sciences, and look forward to possible future information flow across the social-natural divide.

  17. Mechanistic Models in Computational Social Science

    CERN Document Server

    Holme, Petter

    2015-01-01

    Quantitative social science is not only about regression analysis or, in general, data inference. Computer simulations of social mechanisms have an over 60 years long history. They have been used for many different purposes -- to test scenarios, to test the consistency of descriptive theories (proof-of-concept models), to explore emerging phenomena, for forecasting, etc. In this essay, we sketch these historical developments, the role of mechanistic models in the social sciences and the influences from natural and formal sciences. We argue that mechanistic computational models form a natural common ground for social and natural sciences, and look forward to possible future information flow across the social-natural divide.

  18. Radiation Chemistry

    Science.gov (United States)

    Wojnárovits, L.

    Ionizing radiation causes chemical changes in the molecules of the interacting medium. The initial molecules change to new molecules, resulting in changes of the physical, chemical, and eventually biological properties of the material. For instance, water decomposes to its elements H2 and O2. In polymers, degradation and crosslinking take place. In biopolymers, e.g., DNS strand breaks and other alterations occur. Such changes are to be avoided in some cases (radiation protection), however, in other cases they are used for technological purposes (radiation processing). This chapter introduces radiation chemistry by discussing the sources of ionizing radiation (radionuclide sources, machine sources), absorption of radiation energy, techniques used in radiation chemistry research, and methods of absorbed energy (absorbed dose) measurements. Radiation chemistry of different classes of inorganic (water and aqueous solutions, inorganic solids, ionic liquids (ILs)) and organic substances (hydrocarbons, halogenated compounds, polymers, and biomolecules) is discussed in concise form together with theoretical and experimental backgrounds. An essential part of the chapter is the introduction of radiation processing technologies in the fields of polymer chemistry, food processing, and sterilization. The application of radiation chemistry to nuclear technology and to protection of environment (flue gas treatment, wastewater treatment) is also discussed.

  19. Handbook of heterocyclic chemistry

    National Research Council Canada - National Science Library

    Katritzky, Alan R

    2010-01-01

    ... Heterocyclic Chemistry I (1984) Comprehensive Heterocyclic Chemistry II (1996) Comprehensive Heterocyclic Chemistry III (2008) Comprehensive Organic Functional Group Transformations I (1995) Compreh...

  20. Polymer Chemistry

    Science.gov (United States)

    Williams, Martha; Roberson, Luke; Caraccio, Anne

    2010-01-01

    This viewgraph presentation describes new technologies in polymer and material chemistry that benefits NASA programs and missions. The topics include: 1) What are Polymers?; 2) History of Polymer Chemistry; 3) Composites/Materials Development at KSC; 4) Why Wiring; 5) Next Generation Wiring Materials; 6) Wire System Materials and Integration; 7) Self-Healing Wire Repair; 8) Smart Wiring Summary; 9) Fire and Polymers; 10) Aerogel Technology; 11) Aerogel Composites; 12) Aerogels for Oil Remediation; 13) KSC's Solution; 14) Chemochromic Hydrogen Sensors; 15) STS-130 and 131 Operations; 16) HyperPigment; 17) Antimicrobial Materials; 18) Conductive Inks Formulations for Multiple Applications; and 19) Testing and Processing Equipment.

  1. Exploring Organic Mechanistic Puzzles with Molecular Modeling

    Science.gov (United States)

    Horowitz, Gail; Schwartz, Gary

    2004-01-01

    The molecular modeling was used to reinforce more general skills such as deducing and drawing reaction mechanisms, analyzing reaction kinetics and thermodynamics and drawing reaction coordinate energy diagrams. This modeling was done through the design of mechanistic puzzles, involving reactions not familiar to the students.

  2. Testing mechanistic models of growth in insects.

    Science.gov (United States)

    Maino, James L; Kearney, Michael R

    2015-11-22

    Insects are typified by their small size, large numbers, impressive reproductive output and rapid growth. However, insect growth is not simply rapid; rather, insects follow a qualitatively distinct trajectory to many other animals. Here we present a mechanistic growth model for insects and show that increasing specific assimilation during the growth phase can explain the near-exponential growth trajectory of insects. The presented model is tested against growth data on 50 insects, and compared against other mechanistic growth models. Unlike the other mechanistic models, our growth model predicts energy reserves per biomass to increase with age, which implies a higher production efficiency and energy density of biomass in later instars. These predictions are tested against data compiled from the literature whereby it is confirmed that insects increase their production efficiency (by 24 percentage points) and energy density (by 4 J mg(-1)) between hatching and the attainment of full size. The model suggests that insects achieve greater production efficiencies and enhanced growth rates by increasing specific assimilation and increasing energy reserves per biomass, which are less costly to maintain than structural biomass. Our findings illustrate how the explanatory and predictive power of mechanistic growth models comes from their grounding in underlying biological processes.

  3. Mechanistic Perspectives on Organic Photoredox Catalysis for Aromatic Substitutions.

    Science.gov (United States)

    Majek, Michal; Jacobi von Wangelin, Axel

    2016-10-18

    Photoredox catalysis has emerged as a powerful tool for the utilization of visible light to drive chemical reactions between organic molecules that exhibit two rather ubiquitous properties: colorlessness and redox-activity. The photocatalyst, however, requires significant absorption in the visible spectrum and reversible redox activity. This very general framework has led to the development of several new modes of reactivity based on electron and energy transfer steps between photoexcited catalyst states and various organic molecules. In the past years, major effort has been devoted to photoredox-catalytic aromatic substitutions involving an initial reductive activation of various aryl electrophiles by the photocatalyst, which opens a new entry into selective arene functionalizations within organic synthesis endeavors. This, however, has led to a unilateral emphasis of synthetic developments including catalyst modifications, substrate scope studies, and combinations with other chemical processes. This Account summarizes recent reports of new protocols for the synthesis of aromatic esters, thioethers, boronates, sulfonates, heterobiaryls, deuteroarenes, and other functionalized arenes under mild photoredox conditions with organic dyes. On the other hand, mechanistic studies were largely neglected. This Account emphasizes the most relevant experiments and techniques, which can greatly assist in the exploration of the mechanistic foundation of aromatic photoredox substitutions and the design of new chemical reactivities. The nature and physicochemical properties of the employed organic dyes, the control of its acid-base chemistry, the choice of the irradiation sources, and the concentrations of substrates and dyes are demonstrated to decisively affect the activity of organic photocatalysts, the chemo- and regioselectivities of reactions, and the operating mechanisms. Several methods of distinction between photocatalytic and radical chain processes are being discussed

  4. Eppur Si Muove! The 2013 Nobel Prize in Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Jeremy C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States); Roux, Benoit [Univ. of Chicago, Chicago, IL (United States)

    2013-12-03

    The 2013 Nobel Prize in Chemistry has been awarded to Martin Karplus, Michael Levitt, and Arieh Warshel for their work on developing computational methods to study complex chemical systems. Hence, their work has led to mechanistic critical insights into chemical systems both large and small and has enabled progress in a number of different fields, including structural biology.

  5. Eppur si muove! The 2013 Nobel Prize in Chemistry.

    Science.gov (United States)

    Smith, Jeremy C; Roux, Benoît

    2013-12-01

    The 2013 Nobel Prize in Chemistry has been awarded to Martin Karplus, Michael Levitt, and Arieh Warshel for their work on developing computational methods to study complex chemical systems. Their work has led to mechanistic critical insights into chemical systems both large and small and has enabled progress in a number of different fields, including structural biology.

  6. Experimental and Theoretical Studies of Atmosphereic Inorganic Chlorine Chemistry

    Science.gov (United States)

    Sander, Stanley P.; Friedl, Randall R.

    1993-01-01

    Over the last five years substantial progress has been made in defining the realm of new chlorine chemistry in the polar stratosphere. Application of existing experimental techniques to potentially important chlorine-containing compounds has yielded quantitative kinetic and spectroscopic data as well as qualitative mechanistic insights into the relevant reactions.

  7. Colorful Chemistry

    Science.gov (United States)

    Sullivan, P. Teal; Carsten Conner, L. D.; Guthrie, Mareca; Pompea, Stephen; Tsurusaki, Blakely K.; Tzou, Carrie

    2017-01-01

    This article describes a chemistry/art activity that originated in an National Science Foundation--funded two-week STEAM (Science, Technology, Engineering, Art, and Math) academy for grade 4-6 girls. The authors recommend using this investigation in conjunction with other activities focusing on chemical change as a step toward fulfilling the…

  8. How phenyl makes a difference: mechanistic insights into the ruthenium( ii )-catalysed isomerisation of allylic alcohols

    KAUST Repository

    Manzini, Simone

    2013-10-16

    [RuCl(η5-3-phenylindenyl)(PPh3)2] (1) has been shown to be a highly active catalyst for the isomerisation of allylic alcohols to the corresponding ketones. A variety of substrates undergo the transformation, typically with 0.25-0.5 mol% of catalyst at room temperature, outperforming commonly-used complexes such as [RuCl(Cp)(PPh3) 2] and [RuCl(η5-indenyl)(PPh3) 2]. Mechanistic experiments and density functional theory have been employed to investigate the mechanism and understand the effect of catalyst structure on reactivity. These investigations suggest a oxo-π-allyl mechanism is in operation, avoiding intermediate ruthenium hydride complexes and leading to a characteristic 1,3-deuterium shift. Important mechanistic insights from DFT and experiments also allowed for the design of a protocol that expands the scope of the transformation to include primary allylic alcohols. © 2013 The Royal Society of Chemistry.

  9. Industrial chemistry engineering

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1993-01-15

    This book on industrial chemistry engineering is divided in two parts. The first part deals with industrial chemistry, inorganic industrial chemistry, organic industrial chemistry, analytical chemistry and practical questions. The last parts explain the chemical industry, a unit parts and thermodynamics in chemical industry and reference. It reveals the test subjects for the industrial chemistry engineering with a written examination and practical skill.

  10. Mechanistic fracture criteria for the failure of human cortical bone

    Energy Technology Data Exchange (ETDEWEB)

    Nalla, Ravi K.; Kinney, John H.; Ritchie, Robert O.

    2002-12-13

    A mechanistic understanding of fracture in human bone is critical to predicting fracture risk associated with age and disease. Despite extensive work, a mechanistic framework for describing how the underlying microstructure affects the failure mode in bone is lacking.

  11. Precision and accuracy of mechanistic-empirical pavement design

    CSIR Research Space (South Africa)

    Theyse, HL

    2006-09-01

    Full Text Available The availability of mechanistic-empirical pavement design methods is increasing internationally. Although mechanistic-empirical design does offer some insight into pavement behaviour and performance, at least more so than empirical design methods...

  12. Evolutionary and mechanistic theories of aging.

    Science.gov (United States)

    Hughes, Kimberly A; Reynolds, Rose M

    2005-01-01

    Senescence (aging) is defined as a decline in performance and fitness with advancing age. Senescence is a nearly universal feature of multicellular organisms, and understanding why it occurs is a long-standing problem in biology. Here we present a concise review of both evolutionary and mechanistic theories of aging. We describe the development of the general evolutionary theory, along with the mutation accumulation, antagonistic pleiotropy, and disposable soma versions of the evolutionary model. The review of the mechanistic theories focuses on the oxidative stress resistance, cellular signaling, and dietary control mechanisms of life span extension. We close with a discussion of how an approach that makes use of both evolutionary and molecular analyses can address a critical question: Which of the mechanisms that can cause variation in aging actually do cause variation in natural populations?

  13. Mechanistic models in computational social science

    Directory of Open Access Journals (Sweden)

    Petter eHolme

    2015-09-01

    Full Text Available Quantitative social science is not only about regression analysis or, in general, data inference. Computer simulations of social mechanisms have an over 60 years long history. They have been used for many different purposes—to test scenarios, to test the consistency of descriptive theories (proof-of-concept models, to explore emergent phenomena, for forecasting, etc. In this essay, we sketch these historical developments, the role of mechanistic models in the social sciences and the influences from the natural and formal sciences. We argue that mechanistic computational models form a natural common ground for social and natural sciences, and look forward to possible future information flow across the social-natural divide.

  14. Mechanistic models in computational social science

    OpenAIRE

    Petter eHolme; Fredrik eLiljeros

    2015-01-01

    Quantitative social science is not only about regression analysis or, in general, data inference. Computer simulations of social mechanisms have an over 60 years long history. They have been used for many different purposes—to test scenarios, to test the consistency of descriptive theories (proof-of-concept models), to explore emergent phenomena, for forecasting, etc. In this essay, we sketch these historical developments, the role of mechanistic models in the social sciences and the influenc...

  15. Mechanistic models in computational social science

    OpenAIRE

    Holme, Petter; Liljeros, Fredrik

    2015-01-01

    Quantitative social science is not only about regression analysis or, in general, data inference. Computer simulations of social mechanisms have an over 60 years long history. They have been used for many different purposes -- to test scenarios, to test the consistency of descriptive theories (proof-of-concept models), to explore emergent phenomena, for forecasting, etc. In this essay, we sketch these historical developments, the role of mechanistic models in the social sciences and the influ...

  16. Tear gas: an epidemiological and mechanistic reassessment

    OpenAIRE

    Rothenberg, Craig; Achanta, Satyanarayana; Svendsen, Erik R.; Jordt, Sven‐Eric

    2016-01-01

    Deployments of tear gas and pepper spray have rapidly increased worldwide. Large amounts of tear gas have been used in densely populated cities, including Cairo, Istanbul, Rio de Janeiro, Manama (Bahrain), and Hong Kong. In the United States, tear gas was used extensively during recent riots in Ferguson, Missouri. Whereas tear gas deployment systems have rapidly improved—with aerial drone systems tested and requested by law enforcement—epidemiological and mechanistic research have lagged behi...

  17. Testing mechanistic models of growth in insects

    OpenAIRE

    Maino, James L.; Kearney, Michael R.

    2015-01-01

    Insects are typified by their small size, large numbers, impressive reproductive output and rapid growth. However, insect growth is not simply rapid; rather, insects follow a qualitatively distinct trajectory to many other animals. Here we present a mechanistic growth model for insects and show that increasing specific assimilation during the growth phase can explain the near-exponential growth trajectory of insects. The presented model is tested against growth data on 50 insects, and compare...

  18. Computational chemistry

    Science.gov (United States)

    Arnold, J. O.

    1987-01-01

    With the advent of supercomputers, modern computational chemistry algorithms and codes, a powerful tool was created to help fill NASA's continuing need for information on the properties of matter in hostile or unusual environments. Computational resources provided under the National Aerodynamics Simulator (NAS) program were a cornerstone for recent advancements in this field. Properties of gases, materials, and their interactions can be determined from solutions of the governing equations. In the case of gases, for example, radiative transition probabilites per particle, bond-dissociation energies, and rates of simple chemical reactions can be determined computationally as reliably as from experiment. The data are proving to be quite valuable in providing inputs to real-gas flow simulation codes used to compute aerothermodynamic loads on NASA's aeroassist orbital transfer vehicles and a host of problems related to the National Aerospace Plane Program. Although more approximate, similar solutions can be obtained for ensembles of atoms simulating small particles of materials with and without the presence of gases. Computational chemistry has application in studying catalysis, properties of polymers, all of interest to various NASA missions, including those previously mentioned. In addition to discussing these applications of computational chemistry within NASA, the governing equations and the need for supercomputers for their solution is outlined.

  19. Kinetic and mechanistic studies of reactive intermediates in photochemical and transition metal-assisted oxidation, decarboxylation and alkyl transfer reactions

    Energy Technology Data Exchange (ETDEWEB)

    Carraher, Jack McCaslin [Iowa State Univ., Ames, IA (United States)

    2014-01-01

    Reactive species like high-valent metal-oxo complexes and carbon and oxygen centered radicals are important intermediates in enzymatic systems, atmospheric chemistry, and industrial processes. Understanding the pathways by which these intermediates form, their relative reactivity, and their fate after reactions is of the utmost importance. Herein are described the mechanistic detail for the generation of several reactive intermediates, synthesis of precursors, characterization of precursors, and methods to direct the chemistry to more desirable outcomes yielding ‘greener’ sources of commodity chemicals and fuels.

  20. Mechanistic Enzymology of the Radical SAM Enzyme DesII.

    Science.gov (United States)

    Ruszczycky, Mark W; Liu, Hung-Wen

    2015-04-01

    DesII is a member of the radical SAM family of enzymes that catalyzes radical-mediated transformations of TDP-4-amino-4,6-didexoy-D-glucose as well as other sugar nucleotide diphosphates. Like nearly all radical SAM enzymes, the reactions begin with the reductive homolysis of SAM to produce a 5'-deoxyadenosyl radical which is followed by regiospecific hydrogen atom abstraction from the substrate. What happens next, however, depends on the nature of the substrate radical so produced. In the case of the biosynthetically relevant substrate, a radical-mediated deamination ensues; however, when this amino group is replaced with a hydroxyl, one instead observes dehydrogenation. The factors that govern the fate of the initially generated substrate radical as well as the mechanistic details underlying these transformations have been a key focus of research into the chemistry of DesII. This review will discuss recent discoveries pertaining to the enzymology of DesII, how it may relate to understanding other radical-mediated lyases and dehydrogenases and the working hypotheses currently being investigated regarding the mechanism of DesII catalysis.

  1. Theoretical chemistry periodicities in chemistry and biology

    CERN Document Server

    Eyring, Henry

    1978-01-01

    Theoretical Chemistry: Periodicities in Chemistry and Biology, Volume 4 covers the aspects of theoretical chemistry. The book discusses the stably rotating patterns of reaction and diffusion; the chemistry of inorganic systems exhibiting nonmonotonic behavior; and population cycles. The text also describes the mathematical modeling of excitable media in neurobiology and chemistry; oscillating enzyme reactions; and oscillatory properties and excitability of the heart cell membrane. Selected topics from the theory of physico-chemical instabilities are also encompassed. Chemists, mechanical engin

  2. Microbial Metallomics: A Bioinorganic Perspective

    Science.gov (United States)

    Elliott, S. J.

    2004-12-01

    The term "metallome", as described by R.J.P. Williams is synonymous with the instantaneously determined concentration of all inorganic species within a cellular system [1]. Here, we refine this definition to specify that metallomics should reflect not only the overall content of inorganic species in cells, but the chemical identity of such species (i.e., in both ligated and unligated states) a well as their location. Of particular interest to the metallobiochemist are the roles inorganic species play in the up- and down-regulation of protein expression in cells. Thus, we consider that a fully realized "metallome" will reflect the biochemical pathways associated with metal ion speciation and localization within cells. Here we will describe currently proposed strategy and methodology that is used by the Elliott Lab of Boston University to capture snapshots of the proteomic and metallomic landscape of a variety of microbial systems. Two such systems will be described in some detail. The first is Methylococcus capsulatus (Bath), a methanotrophic organism that is known to undergo dramatic morphological changes upon the introduction of varying concentrations of Fe and Cu in the growth medium. In particular, the introduction of increasing concentrations of copper induces the expression of extensive intracytosolic membranes [2]. The Fe:Cu ratio also controls the expression of gene transcripts for soluble and particulate methane monooxygenase enzymes. This provides a unique opportunity to explore metal sensing, uptake, speciation and localization in methanotrophs. A developing model of protein expression and metal input will be discussed. Specific metallomic experiments regarding Shewanella oneidensis will also be discussed, in the context of an ongoing effort to understand how this organism can utilize a dazzling array of electron acceptors, including Fe(III), Mn(IV), nitrite, DMSO, TMAO, and fumarate. [1] R.J.P. Williams, Coord. Chem. Rev., 216:583-595 (2001). [2] C.A. Brantner, et al. Arch. Microbiol. 178: 59-64 (2002).

  3. Bioinorganic Activity of Technetium Radiopharmaceuticals.

    Science.gov (United States)

    Pinkerton, Thomas C.; And Others

    1985-01-01

    Technetium radiopharmaceuticals are diagnostic imaging agents used in the field of nuclear medicine to visualize tissues, anatomical structures, and metabolic disorders. Bioavailability of technetium complexes, thyroid imaging, brain imaging, kidney imaging, imaging liver function, bone imaging, and heart imaging are the major areas discussed. (JN)

  4. Upscaling Radionuclide Retardation?Linking the Surface Complexation and Ion Exchange Mechanistic Approach to a Linear Kd Approach

    Energy Technology Data Exchange (ETDEWEB)

    Zavarin, M; Carle, S; Maxwell, R

    2004-05-14

    The LLNL near-field hydrologic source term (HST) model is based on a mechanistic approach to radionuclide retardation-that is, a thermodynamic description of chemical processes governing retardation in the near field, such as aqueous speciation, surface complexation, ion exchange, and precipitation The mechanistic approach allows for radionuclide retardation to vary both in space and time as a function of the complex reaction chemistry of the medium. This level of complexity is necessary for near-field HST transport modeling because of the non-linear reaction chemistry expected close to the radiologic source. Large-scale Corrective Action Unit (CAU) models-into which the near-field HST model results feed-require that the complexity of the mechanistic approach be reduced to a more manageable form (e.g. Linear, Langmuir, or Freundlich sorption isotherms, etc). The linear sorption isotherm (or K{sub d}) approach is likely the most simple approach for large-scale CAU models. It may also be the most appropriate since the reaction chemistry away from the near field is expected to be less complex and relatively steady state. However, if the radionuclide retardation approaches in near-field HST and large-scale CAU models are different, they must be proved consistent. In this report, we develop a method to link the near-field HST and large-scale CAU model radionuclide retardation approaches.

  5. Surface chemistry

    CERN Document Server

    Desai, KR

    2008-01-01

    The surface Chemistry of a material as a whole is crucially dependent upon the Nature and type of surfaces exposed on crystallites. It is therefore vitally important to independently Study different, well - defined surfaces through surface analytical techniques. In addition to composition and structure of surface, the subject also provides information on dynamic light scattering, micro emulsions, colloid Stability control and nanostructures. The present book endeavour to bring before the reader that the understanding and exploitation of Solid state phenomena depended largely on the ability to

  6. Collective cell migration: a mechanistic perspective.

    Science.gov (United States)

    Vedula, Sri Ram Krishna; Ravasio, Andrea; Lim, Chwee Teck; Ladoux, Benoit

    2013-11-01

    Collective cell migration is fundamental to gaining insights into various important biological processes such as wound healing and cancer metastasis. In particular, recent in vitro studies and in silico simulations suggest that mechanics can explain the social behavior of multicellular clusters to a large extent with minimal knowledge of various cellular signaling pathways. These results suggest that a mechanistic perspective is necessary for a comprehensive and holistic understanding of collective cell migration, and this review aims to provide a broad overview of such a perspective.

  7. Mechanistic studies of carbon monoxide reduction

    Energy Technology Data Exchange (ETDEWEB)

    Geoffroy, G.L.

    1990-06-12

    The progress made during the current grant period (1 January 1988--1 April 1990) in three different areas of research is summarized. The research areas are: (1) oxidatively-induced double carbonylation reactions to form {alpha}-ketoacyl complexes and studies of the reactivity of the resulting compounds, (2) mechanistic studies of the carbonylation of nitroaromatics to form isocyanates, carbamates, and ureas, and (3) studies of the formation and reactivity of unusual metallacycles and alkylidene ligands supported on binuclear iron carbonyl fragments. 18 refs., 5 figs., 1 tab.

  8. Chemistry with methane: concepts rather than recipes.

    Science.gov (United States)

    Schwarz, Helmut

    2011-10-17

    Four seemingly simple transformations related to the chemistry of methane will be addressed from mechanistic and conceptual points of view: 1) metal-mediated dehydrogenation to form metal carbene complexes, 2) the hydrogen-atom abstraction step in the oxidative dimerization of methane, 3) the mechanisms of the CH(4)→CH(3)OH conversion, and 4) the initial bond scission (C-H vs. O-H) as well as the rate-limiting step in the selective CH(3)OH→CH(2)O oxidation. State-of-the-art gas-phase experiments, in conjunction with electronic-structure calculations, permit identification of the elementary reactions at a molecular level and thus allow us to unravel detailed mechanistic aspects. Where appropriate, these results are compared with findings from related studies in solution or on surfaces.

  9. Why Teach Environmental Chemistry?

    Science.gov (United States)

    Gardner, Marjorie H.

    1974-01-01

    Discusses the importance of teaching environmental chemistry in secondary school science classes, and outlines five examples of environmental chemistry problems that focus on major concepts of chemistry and have critical implications for human survival and well-being. (JR)

  10. Tear gas: an epidemiological and mechanistic reassessment

    Science.gov (United States)

    Rothenberg, Craig; Achanta, Satyanarayana; Svendsen, Erik R.

    2016-01-01

    Deployments of tear gas and pepper spray have rapidly increased worldwide. Large amounts of tear gas have been used in densely populated cities, including Cairo, Istanbul, Rio de Janeiro, Manama (Bahrain), and Hong Kong. In the United States, tear gas was used extensively during recent riots in Ferguson, Missouri. Whereas tear gas deployment systems have rapidly improved—with aerial drone systems tested and requested by law enforcement—epidemiological and mechanistic research have lagged behind and have received little attention. Case studies and recent epidemiological studies revealed that tear gas agents can cause lung, cutaneous, and ocular injuries, with individuals affected by chronic morbidities at high risk for complications. Mechanistic studies identified the ion channels TRPV1 and TRPA1 as targets of capsaicin in pepper spray, and of the tear gas agents chloroacetophenone, CS, and CR. TRPV1 and TRPA1 localize to pain‐sensing peripheral sensory neurons and have been linked to acute and chronic pain, cough, asthma, lung injury, dermatitis, itch, and neurodegeneration. In animal models, transient receptor potential inhibitors show promising effects as potential countermeasures against tear gas injuries. On the basis of the available data, a reassessment of the health risks of tear gas exposures in the civilian population is advised, and development of new countermeasures is proposed. PMID:27391380

  11. The Mechanistic Approach to Psychiatric Classification

    Directory of Open Access Journals (Sweden)

    Elisabetta Sirgiovanni

    2009-01-01

    Full Text Available A Kuhnian reformulation of the recent debate in psychiatric nosography suggested that the current psychiatric classification system (the DSM is in crisis and that a sort of paradigm shift is awaited (Aragona, 2009. Among possible revolutionary alternatives, the proposed fi ve-axes etiopathogenetic taxonomy (Charney et al., 2002 emphasizes the primacy of the genotype over the phenomenological level as the relevant basis for psychiatric nosography. Such a position is along the lines of the micro-reductionist perspective of E. Kandel (1998, 1999, which sees mental disorders reducible to explanations at a fundamental epistemic level of genes and neurotransmitters. This form of micro-reductionism has been criticized as a form of genetic-molecular fundamentalism (e.g. Murphy, 2006 and a multi-level approach, in the form of the burgeoning Cognitive Neuropsychiatry, was proposed. This article focuses on multi-level mechanistic explanations, coming from Cognitive Science, as a possible alternative etiopathogenetic basis for psychiatric classification. The idea of a mechanistic approach to psychiatric taxonomy is here defended on the basis of a better conception of levels and causality. Nevertheless some critical remarks of Mechanism as a psychiatric general view are also offered.

  12. Tear gas: an epidemiological and mechanistic reassessment.

    Science.gov (United States)

    Rothenberg, Craig; Achanta, Satyanarayana; Svendsen, Erik R; Jordt, Sven-Eric

    2016-08-01

    Deployments of tear gas and pepper spray have rapidly increased worldwide. Large amounts of tear gas have been used in densely populated cities, including Cairo, Istanbul, Rio de Janeiro, Manama (Bahrain), and Hong Kong. In the United States, tear gas was used extensively during recent riots in Ferguson, Missouri. Whereas tear gas deployment systems have rapidly improved-with aerial drone systems tested and requested by law enforcement-epidemiological and mechanistic research have lagged behind and have received little attention. Case studies and recent epidemiological studies revealed that tear gas agents can cause lung, cutaneous, and ocular injuries, with individuals affected by chronic morbidities at high risk for complications. Mechanistic studies identified the ion channels TRPV1 and TRPA1 as targets of capsaicin in pepper spray, and of the tear gas agents chloroacetophenone, CS, and CR. TRPV1 and TRPA1 localize to pain-sensing peripheral sensory neurons and have been linked to acute and chronic pain, cough, asthma, lung injury, dermatitis, itch, and neurodegeneration. In animal models, transient receptor potential inhibitors show promising effects as potential countermeasures against tear gas injuries. On the basis of the available data, a reassessment of the health risks of tear gas exposures in the civilian population is advised, and development of new countermeasures is proposed.

  13. Impacts of mechanistic changes on HOx formation and recycling in the oxidation of isoprene

    Directory of Open Access Journals (Sweden)

    M. E. Jenkin

    2010-03-01

    Full Text Available Recently reported model-measurement discrepancies for the concentrations of the HOx radical species (OH and HO2 in locations characterized by high emission rates of isoprene have indicated possible deficiencies in the representation of OH recycling and formation in isoprene mechanisms currently employed in numerical models; particularly at low levels of NOx. Using version 3.1 of the Master Chemical Mechanism (MCM v3.1 as a base mechanism, the sensitivity of the system to a number of detailed mechanistic changes is examined for a wide range of NOx levels, using a simple box model. These studies place emphasis on processes for which experimental or theoretical evidence has been reported in the peer-reviewed literature, in addition to examining the impact of an intrinsic simplification in the MCM v3.1 chemistry. Although all the considered mechanistic changes lead to simulated increases in the concentrations of OH at low NOx levels, the greatest impact is achieved by implementation of a recently postulated mechanism involving isomerisation of the δ-hydroxyalkenyl peroxy radical isomers, formed from the sequential addition of OH and O2 to isoprene. In conjunction with necessary rapid photolysis of the resultant hydroperoxyaldehyde products, this mechanism yields approximately a factor of three increase in the simulated OH concentration at low NOx, and is the only considered mechanism which achieves enhancements which approach those necessary to explain the reported model-measurement discrepancies. Combination of all the considered mechanistic changes has an effect which is approximately additive, yielding an overall enhancement of about a factor of 3.2 in the simulated OH concentration at the lowest NOx input rate considered, with the simulated mean NOx mixing ratios at this input rate being 42 ppt and 29 ppt with the base case and modified mechanisms respectively. A parameterized representation of the mechanistic changes is optimized and

  14. Induced polarization dependence on pore space geometry: Empirical observations and mechanistic predictions

    Science.gov (United States)

    Weller, A.; Slater, L. D.

    2015-12-01

    We use an extensive database to compare empirical observations and previously proposed empirical models against recently developed mechanistic formulations for the induced polarization (IP) response in porous media as a function of pore space geometry and interfacial chemistry. These comparisons support the argument that the pore-volume normalized internal surface (Spor) is the most important geometric parameter influencing the polarization. The specific polarizability derived from the empirical relationship between imaginary conductivity σ″ and Spor is independent of the porosity. By contrast, equivalent specific polarizability terms in recently proposed mechanistic models are found to be significantly correlated with porosity, and thus do not appear to represent an interfacial chemistry factor independent of the pore space geometry. Furthermore, the database shows no evidence for a significant decrease in the counterion mobility of clayey materials relative to clay-free materials, as postulated in recent studies. On the contrary, a single value of cp is consistent with no significant differences in ionic mobility given that all samples were saturated with a NaCl solution close to a common salinity of about 100 mS/m.

  15. Environmental chemistry. Seventh edition

    Energy Technology Data Exchange (ETDEWEB)

    Manahan, S.E. [Univ. of Missouri, Columbia, MO (United States)

    1999-11-01

    This book presents a basic understanding of environmental chemistry and its applications. In addition to providing updated materials in this field, the book emphasizes the major concepts essential to the practice of environmental chemistry. Topics of discussion include the following: toxicological chemistry; toxicological chemistry of chemical substances; chemical analysis of water and wastewater; chemical analysis of wastes and solids; air and gas analysis; chemical analysis of biological materials and xenobiotics; fundamentals of chemistry; and fundamentals of organic chemistry.

  16. Combustion chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Brown, N.J. [Lawrence Berkeley Laboratory, CA (United States)

    1993-12-01

    This research is concerned with the development and use of sensitivity analysis tools to probe the response of dependent variables to model input variables. Sensitivity analysis is important at all levels of combustion modeling. This group`s research continues to be focused on elucidating the interrelationship between features in the underlying potential energy surface (obtained from ab initio quantum chemistry calculations) and their responses in the quantum dynamics, e.g., reactive transition probabilities, cross sections, and thermal rate coefficients. The goals of this research are: (i) to provide feedback information to quantum chemists in their potential surface refinement efforts, and (ii) to gain a better understanding of how various regions in the potential influence the dynamics. These investigations are carried out with the methodology of quantum functional sensitivity analysis (QFSA).

  17. Astronomical chemistry.

    Science.gov (United States)

    Klemperer, William

    2011-01-01

    The discovery of polar polyatomic molecules in higher-density regions of the interstellar medium by means of their rotational emission detected by radioastronomy has changed our conception of the universe from essentially atomic to highly molecular. We discuss models for molecule formation, emphasizing the general lack of thermodynamic equilibrium. Detailed chemical kinetics is needed to understand molecule formation as well as destruction. Ion molecule reactions appear to be an important class for the generally low temperatures of the interstellar medium. The need for the intrinsically high-quality factor of rotational transitions to definitively pin down molecular emitters has been well established by radioastronomy. The observation of abundant molecular ions both positive and, as recently observed, negative provides benchmarks for chemical kinetic schemes. Of considerable importance in guiding our understanding of astronomical chemistry is the fact that the larger molecules (with more than five atoms) are all organic.

  18. Science Update: Inorganic Chemistry.

    Science.gov (United States)

    Rawls, Rebecca

    1981-01-01

    Describes areas of inorganic chemistry which have changed dramatically in the past year or two, including photochemistry, electrochemistry, organometallic complexes, inorganic reaction theory, and solid state chemistry. (DS)

  19. Advanced Chemistry Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — Description/History: Chemistry laboratory The Advanced Chemistry Laboratory (ACL) is a unique facility designed for working with the most super toxic compounds known...

  20. Wherefore Art Thou Copper? Structures and Reaction Mechanisms of Organocuprate Clusters in Organic Chemistry.

    Science.gov (United States)

    Nakamura; Mori

    2000-11-03

    Organocopper reagents provide the most general synthetic tools in organic chemistry for nucleophilic delivery of hard carbanions to electrophilic carbon centers. A number of structural and mechanistic studies have been reported and have led to a wide variety of mechanistic proposals, some of which might even be contradictory to others. With the recent advent of physical and theoretical methodologies, the accumulated knowledge on organocopper chemistry is being put together into a few major mechanistic principles. This review will summarize first the general structural features of organocopper compounds and the previous mechanistic arguments, and then describe the most recent mechanistic pictures obtained through high-level quantum mechanical calculations for three typical organocuprate reactions, carbocupration, conjugate addition, and S(N)2 alkylation. The unified view on the nucleophilic reactivities of metal organocuprate clusters thus obtained has indicated that organocuprate chemistry represents an intricate example of molecular recognition and supramolecular chemistry, which chemists have long exploited without knowing it. Reasoning about the uniqueness of the copper atom among neighboring metal elements in the periodic table will be presented.

  1. Causation at Different Levels: Tracking the Commitments of Mechanistic Explanations

    DEFF Research Database (Denmark)

    Fazekas, Peter; Kertész, Gergely

    2011-01-01

    This paper tracks the commitments of mechanistic explanations focusing on the relation between activities at different levels. It is pointed out that the mechanistic approach is inherently committed to identifying causal connections at higher levels with causal connections at lower levels. For th...... their autonomy at the same time than standard reductive accounts are, and that what mechanistic explanations are able to do at best is showing that downward causation does not exist....

  2. A Mechanistically-Guided Charpy Embrittlement Correlation For RPV (reactor pressure vessel) Integrity Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Rosinski, S.T. [EPRI, CHARLOTTE, NC (United States); Server, W.L. [ATI Consulting, Pinehurst, NC (United States)

    2002-07-01

    The current neutron irradiation embrittlement trend equation used in the Usa is contained in Nuclear Regulatory Commission (NRC) Regulatory Guide 1.99, Revision 2. The equivalent equation for estimating the mean shift in irradiated Charpy properties is used also in ASTM Standard Guide E 900-87. The three chemistry and irradiation parameters in this old correlation are copper (Cu) content, nickel (Ni) content, and irradiation fluence; base and weld metals are separated also, due to the enhanced embrittlement in welds. The database used to establish this old correlation was compiled in the late 1980's. Today, the database has increased by a multiple of about 5. Through the EPRI Materials Reliability Program a new and improved transition temperature shift embrittlement correlation has been developed. The recommended model is mechanistically-guided, statistically robust, and stems from earlier work on a mechanistic/statistical model proposed by the NRC. From the independent reviews performed on the NRC proposed correlation, the evaluations of mechanistic understanding and statistical testing were combined to assess the most appropriate form for a mean correlation model. The process of evaluating and reducing the number of fitting parameters was not a simple decision. Engineering judgment, through the development of gating criteria and value/magnitude considerations, led to the development of the proposed correlation. This paper discusses the proposed embrittlement correlation and its mechanistic/statistical bases. Predictions using the proposed correlation are compared using the current version of the embrittlement database; comparisons with the predictions with Regulatory Guide 1.99, Revision 2, are also made. (authors)

  3. Applying mechanistic models in bioprocess development

    DEFF Research Database (Denmark)

    Lencastre Fernandes, Rita; Bodla, Vijaya Krishna; Carlquist, Magnus

    2013-01-01

    models should be combined with proper model analysis tools, such as uncertainty and sensitivity analysis. When assuming distributed inputs, the resulting uncertainty in the model outputs can be decomposed using sensitivity analysis to determine which input parameters are responsible for the major part...... of the output uncertainty. Such information can be used as guidance for experimental work; i.e., only parameters with a significant influence on model outputs need to be determined experimentally. The use of mechanistic models and model analysis tools is demonstrated in this chapter. As a practical case study......, experimental data from Saccharomyces cerevisiae fermentations are used. The data are described with the well-known model of Sonnleitner and Käppeli (Biotechnol Bioeng 28:927-937, 1986) and the model is analyzed further. The methods used are generic, and can be transferred easily to other, more complex case...

  4. Reaction Coordinates and Mechanistic Hypothesis Tests.

    Science.gov (United States)

    Peters, Baron

    2016-05-27

    Reaction coordinates are integral to several classic rate theories that can (a) predict kinetic trends across conditions and homologous reactions, (b) extract activation parameters with a clear physical interpretation from experimental rates, and (c) enable efficient calculations of free energy barriers and rates. New trajectory-based rare events methods can provide rates directly from dynamical trajectories without a reaction coordinate. Trajectory-based frameworks can also generate ideal (but abstract) reaction coordinates such as committors and eigenfunctions of the master equation. However, rates and mechanistic insights obtained from trajectory-based methods and abstract coordinates are not readily generalized across simulation conditions or reaction families. We discuss methods for identifying physically meaningful reaction coordinates, including committor analysis, variational transition state theory, Kramers-Langer-Berezhkovskii-Szabo theory, and statistical inference methods that can use path sampling data to screen, mix, and optimize thousands of trial coordinates. Special focus is given to likelihood maximization and inertial likelihood maximization approaches.

  5. Reaction Coordinates and Mechanistic Hypothesis Tests

    Science.gov (United States)

    Peters, Baron

    2016-05-01

    Reaction coordinates are integral to several classic rate theories that can (a) predict kinetic trends across conditions and homologous reactions, (b) extract activation parameters with a clear physical interpretation from experimental rates, and (c) enable efficient calculations of free energy barriers and rates. New trajectory-based rare events methods can provide rates directly from dynamical trajectories without a reaction coordinate. Trajectory-based frameworks can also generate ideal (but abstract) reaction coordinates such as committors and eigenfunctions of the master equation. However, rates and mechanistic insights obtained from trajectory-based methods and abstract coordinates are not readily generalized across simulation conditions or reaction families. We discuss methods for identifying physically meaningful reaction coordinates, including committor analysis, variational transition state theory, Kramers-Langer-Berezhkovskii-Szabo theory, and statistical inference methods that can use path sampling data to screen, mix, and optimize thousands of trial coordinates. Special focus is given to likelihood maximization and inertial likelihood maximization approaches.

  6. Mechanistic issues in asparagine synthetase catalysis.

    Science.gov (United States)

    Richards, N G; Schuster, S M

    1998-01-01

    The enzymatic synthesis of asparagine is an ATP-dependent process that utilizes the nitrogen atom derived from either glutamine or ammonia. Despite a long history of kinetic and mechanistic investigation, there is no universally accepted catalytic mechanism for this seemingly straightforward carboxyl group activating enzyme, especially as regards those steps immediately preceding amide bond formation. This chapter considers four issues dealing with the mechanism: (a) the structural organization of the active site(s) partaking in glutamine utilization and aspartate activation; (b) the relationship of asparagine synthetase to other amidotransferases; (c) the way in which ATP is used to activate the beta-carboxyl group; and (d) the detailed mechanism by which nitrogen is transferred.

  7. Mechanistic curiosity will not kill the Bayesian cat

    NARCIS (Netherlands)

    Borsboom, Denny; Wagenmakers, Eric-Jan; Romeijn, Jan-Willem

    2011-01-01

    Jones & Love (J&L) suggest that Bayesian approaches to the explanation of human behavior should be constrained by mechanistic theories. We argue that their proposal misconstrues the relation between process models, such as the Bayesian model, and mechanisms. While mechanistic theories can answer spe

  8. Industrial Chemistry and School Chemistry: Making Chemistry Studies More Relevant

    Science.gov (United States)

    Hofstein, Avi; Kesner, Miri

    2006-01-01

    In this paper, we present the development and implementation over the period of more than 15 years of learning materials focusing on industrial chemistry as the main theme. The work was conducted in the Department of Science Teaching at the Weizmann Institute of Science, Israel. The project's general goal was to teach chemistry concepts in the…

  9. From Matter to Life:Chemistry?Chemistry!

    Institute of Scientific and Technical Information of China (English)

    Jean-Marie; LEHN

    2007-01-01

    1 Results Animate as well as inanimate matter,living organisms as well as materials,are formed of molecules and of the organized entities resulting from the interaction of molecules with each other.Chemistry provides the bridge between the molecules of inanimate matter and the highly complex molecular architectures and systems which make up living organisms. Synthetic chemistry has developed a very powerful set of methods for constructing ever more complex molecules.Supramolecular chemistry seeks to con...

  10. Green chemistry: A tool in Pharmaceutical Chemistry

    OpenAIRE

    Smita Talaviya; Falguni Majumdar

    2012-01-01

    Green chemistry expresses an area of research developing from scientific discoveries about pollution awareness and it utilizes a set of principles that reduces or eliminates the use or generation of hazardous substances in all steps of particular synthesis or process. Chemists and medicinal scientists can greatly reduce the risk to human health and the environment by following all the valuable principles of green chemistry. The most simple and direct way to apply green chemistry in pharmaceut...

  11. Automaticity: Componential, Causal, and Mechanistic Explanations.

    Science.gov (United States)

    Moors, Agnes

    2016-01-01

    The review first discusses componential explanations of automaticity, which specify non/automaticity features (e.g., un/controlled, un/conscious, non/efficient, fast/slow) and their interrelations. Reframing these features as factors that influence processes (e.g., goals, attention, and time) broadens the range of factors that can be considered (e.g., adding stimulus intensity and representational quality). The evidence reviewed challenges the view of a perfect coherence among goals, attention, and consciousness, and supports the alternative view that (a) these and other factors influence the quality of representations in an additive way (e.g., little time can be compensated by extra attention or extra stimulus intensity) and that (b) a first threshold of this quality is required for unconscious processing and a second threshold for conscious processing. The review closes with a discussion of causal explanations of automaticity, which specify factors involved in automatization such as repetition and complexity, and a discussion of mechanistic explanations, which specify the low-level processes underlying automatization.

  12. Mechanistic insights into type III restriction enzymes.

    Science.gov (United States)

    Raghavendra, Nidhanapati K; Bheemanaik, Shivakumara; Rao, Desirazu N

    2012-01-01

    Type III restriction-modification (R-M) enzymes need to interact with two separate unmethylated DNA sequences in indirectly repeated, head-to-head orientations for efficient cleavage to occur at a defined location next to only one of the two sites. However, cleavage of sites that are not in head-to-head orientation have been observed to occur under certain reaction conditions in vitro. ATP hydrolysis is required for the long-distance communication between the sites prior to cleavage. Type III R-M enzymes comprise two subunits, Res and Mod that form a homodimeric Mod2 and a heterotetrameric Res2Mod2 complex. The Mod subunit in M2 or R2M2 complex recognizes and methylates DNA while the Res subunit in R2M2 complex is responsible for ATP hydrolysis, DNA translocation and cleavage. A vast majority of biochemical studies on Type III R-M enzymes have been undertaken using two closely related enzymes, EcoP1I and EcoP15I. Divergent opinions about how the long-distance interaction between the recognition sites exist and at least three mechanistic models based on 1D- diffusion and/or 3D- DNA looping have been proposed.

  13. Constitutional dynamic chemistry: bridge from supramolecular chemistry to adaptive chemistry.

    Science.gov (United States)

    Lehn, Jean-Marie

    2012-01-01

    Supramolecular chemistry aims at implementing highly complex chemical systems from molecular components held together by non-covalent intermolecular forces and effecting molecular recognition, catalysis and transport processes. A further step consists in the investigation of chemical systems undergoing self-organization, i.e. systems capable of spontaneously generating well-defined functional supramolecular architectures by self-assembly from their components, thus behaving as programmed chemical systems. Supramolecular chemistry is intrinsically a dynamic chemistry in view of the lability of the interactions connecting the molecular components of a supramolecular entity and the resulting ability of supramolecular species to exchange their constituents. The same holds for molecular chemistry when the molecular entity contains covalent bonds that may form and break reversibility, so as to allow a continuous change in constitution by reorganization and exchange of building blocks. These features define a Constitutional Dynamic Chemistry (CDC) on both the molecular and supramolecular levels.CDC introduces a paradigm shift with respect to constitutionally static chemistry. The latter relies on design for the generation of a target entity, whereas CDC takes advantage of dynamic diversity to allow variation and selection. The implementation of selection in chemistry introduces a fundamental change in outlook. Whereas self-organization by design strives to achieve full control over the output molecular or supramolecular entity by explicit programming, self-organization with selection operates on dynamic constitutional diversity in response to either internal or external factors to achieve adaptation.The merging of the features: -information and programmability, -dynamics and reversibility, -constitution and structural diversity, points to the emergence of adaptive and evolutive chemistry, towards a chemistry of complex matter.

  14. Mechanistic Aspects of Aryl-Halide Oxidative Addition, Coordination Chemistry, and Ring-Walking by Palladium.

    Science.gov (United States)

    Zenkina, Olena V; Gidron, Ori; Shimon, Linda J W; Iron, Mark A; van der Boom, Milko E

    2015-11-01

    This contribution describes the reactivity of a zero-valent palladium phosphine complex with substrates that contain both an aryl halide moiety and an unsaturated carbon-carbon bond. Although η(2) -coordination of the metal center to a C=C or C≡C unit is kinetically favored, aryl halide bond activation is favored thermodynamically. These quantitative transformations proceed under mild reaction conditions in solution or in the solid state. Kinetic measurements indicate that formation of η(2) -coordination complexes are not nonproductive side-equilibria, but observable (and in several cases even isolated) intermediates en route to aryl halide bond cleavage. At the same time, DFT calculations show that the reaction with palladium may proceed through a dissociation-oxidative addition mechanism rather than through a haptotropic intramolecular process (i.e., ring walking). Furthermore, the transition state involves coordination of a third phosphine to the palladium center, which is lost during the oxidative addition as the C-halide bond is being broken. Interestingly, selective activation of aryl halides has been demonstrated by adding reactive aryl halides to the η(2) -coordination complexes. The product distribution can be controlled by the concentration of the reactants and/or the presence of excess phosphine.

  15. Identifying mechanistic similarities in drug responses

    KAUST Repository

    Zhao, C.

    2012-05-15

    Motivation: In early drug development, it would be beneficial to be able to identify those dynamic patterns of gene response that indicate that drugs targeting a particular gene will be likely or not to elicit the desired response. One approach would be to quantitate the degree of similarity between the responses that cells show when exposed to drugs, so that consistencies in the regulation of cellular response processes that produce success or failure can be more readily identified.Results: We track drug response using fluorescent proteins as transcription activity reporters. Our basic assumption is that drugs inducing very similar alteration in transcriptional regulation will produce similar temporal trajectories on many of the reporter proteins and hence be identified as having similarities in their mechanisms of action (MOA). The main body of this work is devoted to characterizing similarity in temporal trajectories/signals. To do so, we must first identify the key points that determine mechanistic similarity between two drug responses. Directly comparing points on the two signals is unrealistic, as it cannot handle delays and speed variations on the time axis. Hence, to capture the similarities between reporter responses, we develop an alignment algorithm that is robust to noise, time delays and is able to find all the contiguous parts of signals centered about a core alignment (reflecting a core mechanism in drug response). Applying the proposed algorithm to a range of real drug experiments shows that the result agrees well with the prior drug MOA knowledge. © The Author 2012. Published by Oxford University Press. All rights reserved.

  16. Black tea polyphenols: a mechanistic treatise.

    Science.gov (United States)

    Butt, M S; Imran, A; Sharif, M K; Ahmad, Rabia Shabir; Xiao, Hang; Imran, M; Rsool, H A

    2014-01-01

    Dietary interventions are among the emerging trends to curtail physiological malfunctioning like cancer, diabetes, cardiac complications, etc. The essence of phytonutrients has developed the concept of nutraceuticals at the junction of diet health linkages. In this context, theaflavin & thearubigins are the oxidized derivatives of black tea catechins during fermentation having nutraceutical potential owing to esterification of hydroxyl ring with digallate esters. Theaflavin may influence activation of transcription factors such as NFnB or AP-1 that ultimately hinder the formation of nitric oxide expression gene. Likewise, black tea contains a unique amino acid theanine acts as neurotransmitter owing to its ability to cross the blood-brain barrier. Moreover, it boasts immunity by enhancing the disease-fighting ability of gamma delta T cells. Theaflavin & thearubigins act as safeguard against oxidative stress thereby effective in the cardiac functioning. The mechanistic approach of these antioxidants is likely to be associated with inhibition of redox sensitive transcription factors & pro-oxidant enzymes such as xanthine oxidase or nitric oxide synthase. However, their involvement in antioxidative enzyme induction as in glutathione-S-transferases is also well documented. They act as curative agent against numerous pathological disorders by disrupting the electron chain thus inhibiting the progression of certain ailments. Black tea polyphenols established themselves as strong antioxidants due to their standard one-electron potential, and their vitality is dependent on the concentration of polyphenols and pH for their inclusive execution. Present review is an attempt to enrich the readers regarding the health promoting aspects of black tea polyphenols. Concomitantly, it needs core attention of researchers for the exploitations of black tea flavanols as an important dietary constituent for the vulnerable segment.

  17. Dynamics of forest soil chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Alveteg, M.

    1998-11-01

    Acidification caused by emissions of nitrogen and sulphur and associated adverse effects on forest ecosystems has been an issue on the political agenda for decades. Temporal aspects of soil acidification and/or recovery can be investigated using the soil chemistry model SAFE, a dynamic version of the steady-state model PROFILE used in critical loads assessment on the national level, e.g. for Sweden. In this thesis, possibilities to replace the use of apparent gibbsite solubility coefficients with a more mechanistic Al sub-model are investigated and a reconstruction model, MAKEDEP, is presented which makes hindcasts and forecasts of atmospheric deposition and nutrient uptake and cycling. A regional application of SAFE/MAKEDEP based on 622 sites in Switzerland is also presented. It is concluded that the quantitative information on pools and fluxes of Al in forest ecosystems is very limited and that there currently exists no mechanistic alternative in modelling soil solution Al. MAKEDEP is a valuable and operational tool for deriving input to dynamic soil chemistry models such as SMART, MAGIC and SAFE. For multi-layer models, e.g. the SAFE model, including nutrient cycling in MAKEDEP is shown to be important. The strength of the regional assessment strategy presented in this thesis lies in its transparency and modularity. All sub-modules, including models, transfer functions, assumptions in the data acquisition strategy, etc., can be checked and replaced individually. As the presented assessment strategy is based on knowledge and data from a wide range of scientists and fields it is of vital importance that the research community challenge the assumptions made. The many measurable intermediate results produced by the included models will hopefully encourage scientists to challenge the models through additional measurements at the calculation sites. It is concluded that current reduction plans are not sufficient for all forest ecosystems in Switzerland to recover from

  18. CHINESE JOURNAL OF CHEMISTRY

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@Chinese Journal of Chemistry is an international journal published in English by the Chinese Chemical Society with its editorial office hosted by Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences.

  19. Advanced Chemistry Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — Description/History: Chemistry laboratoryThe Advanced Chemistry Laboratory (ACL) is a unique facility designed for working with the most super toxic compounds known...

  20. Organometallic Chemistry of Molybdenum.

    Science.gov (United States)

    Lucas, C. Robert; Walsh, Kelly A.

    1987-01-01

    Suggests ways to avoid some of the problems students have learning the principles of organometallic chemistry. Provides a description of an experiment used in a third-year college chemistry laboratory on molybdenum. (TW)

  1. Environmental chemistry: Volume A

    Energy Technology Data Exchange (ETDEWEB)

    Yen, T.F.

    1999-08-01

    This is an extensive introduction to environmental chemistry for engineering and chemical professionals. The contents of Volume A include a brief review of basic chemistry prior to coverage of litho, atmo, hydro, pedo, and biospheres.

  2. Chemistry for Potters.

    Science.gov (United States)

    Denio, Allen A.

    1980-01-01

    Relates pottery making to chemistry by providing chemical information about clay, its origin, composition, properties, and changes that occur during firing; also describes glaze compositions, examples of redox chemistry, salt glazing, crystalline glazes, and problems in toxicity. (CS)

  3. Decorating with Arrows: Toward the Development of Representational Competence in Organic Chemistry

    Science.gov (United States)

    Grove, Nathaniel P.; Cooper, Melanie M.; Rush, Kelli M.

    2012-01-01

    Much effort has been expended in developing improved methods for presenting mechanistic thinking and the curved-arrow notation to organic chemistry students; however, most of these techniques are not research-based. The little research that has been conducted has mainly focused on understanding the meaning that students associate with the…

  4. Green chemistry: A tool in Pharmaceutical Chemistry

    Directory of Open Access Journals (Sweden)

    Smita Talaviya

    2012-07-01

    Full Text Available Green chemistry expresses an area of research developing from scientific discoveries about pollution awareness and it utilizes a set of principles that reduces or eliminates the use or generation of hazardous substances in all steps of particular synthesis or process. Chemists and medicinal scientists can greatly reduce the risk to human health and the environment by following all the valuable principles of green chemistry. The most simple and direct way to apply green chemistry in pharmaceuticals is to utilize eco-friendly, non-hazardous, reproducible and efficient solvents and catalysts in synthesis of drug molecules, drug intermediates and in researches involving synthetic chemistry. Microwave synthesis is also an important tool of green chemistry by being an energy efficient process.

  5. ReactionPredictor: prediction of complex chemical reactions at the mechanistic level using machine learning.

    Science.gov (United States)

    Kayala, Matthew A; Baldi, Pierre

    2012-10-22

    Proposing reasonable mechanisms and predicting the course of chemical reactions is important to the practice of organic chemistry. Approaches to reaction prediction have historically used obfuscating representations and manually encoded patterns or rules. Here we present ReactionPredictor, a machine learning approach to reaction prediction that models elementary, mechanistic reactions as interactions between approximate molecular orbitals (MOs). A training data set of productive reactions known to occur at reasonable rates and yields and verified by inclusion in the literature or textbooks is derived from an existing rule-based system and expanded upon with manual curation from graduate level textbooks. Using this training data set of complex polar, hypervalent, radical, and pericyclic reactions, a two-stage machine learning prediction framework is trained and validated. In the first stage, filtering models trained at the level of individual MOs are used to reduce the space of possible reactions to consider. In the second stage, ranking models over the filtered space of possible reactions are used to order the reactions such that the productive reactions are the top ranked. The resulting model, ReactionPredictor, perfectly ranks polar reactions 78.1% of the time and recovers all productive reactions 95.7% of the time when allowing for small numbers of errors. Pericyclic and radical reactions are perfectly ranked 85.8% and 77.0% of the time, respectively, rising to >93% recovery for both reaction types with a small number of allowed errors. Decisions about which of the polar, pericyclic, or radical reaction type ranking models to use can be made with >99% accuracy. Finally, for multistep reaction pathways, we implement the first mechanistic pathway predictor using constrained tree-search to discover a set of reasonable mechanistic steps from given reactants to given products. Webserver implementations of both the single step and pathway versions of Reaction

  6. Organic chemistry experiment

    Energy Technology Data Exchange (ETDEWEB)

    Mun, Seok Sik

    2005-02-15

    This book deals with organic chemistry experiments, it is divided five chapters, which have introduction, the way to write the experiment report and safety in the laboratory, basic experiment technic like recrystallization and extraction, a lot of organic chemistry experiments such as fischer esterification, ester hydrolysis, electrophilic aromatic substitution, aldol reaction, benzoin condensation, wittig reaction grignard reaction, epoxidation reaction and selective reduction. The last chapter introduces chemistry site on the internet and way to find out reference on chemistry.

  7. Reactivity of γ-Terpinene with NO3 radicals: experimental approach for kinetic and mechanistic study.

    Science.gov (United States)

    Fouqueau, Axel; Cirtog, Manuela; Le Quilleuc, Meryll; Cazaunau, Mathieu; Pangui, Edouard; Duncianu, Marius; Doussin, Jean-François; Picquet-Varrault, Bénédicte

    2017-04-01

    Biogenic Volatile Organic Compounds (BVOC) are highly emitted by vegetation and play a key role in atmospheric chemistry. They are very reactive with atmospheric oxidants (OH, NO3, ozone) and significantly contribute to the formation of Secondary Organic Aerosol (SOA) at the global scale [1]. In addition, night-time chemistry initiated by NO3 radicals leads to the formation of organic nitrates which behave as reservoirs for reactive nitrogen. However, the reactivity of NO3 radical with BVOCs other than isoprene and α- and β-pinene, remains poorly understood. Among the BVOCs, γ-Terpinene is one of the most emitted by vegetation[2]. Two kinetic works were previously published on γ-Terpinene [3] [4], but mechanistic has never been studied. Thus, the aim of this work is to study the reactivity of γ-Terpinene with NO3 by performing experiments in simulation chambers. Kinetic, mechanism and SOA yield will be investigated. For this purpose, two different simulation chambers have been used: - First one, consisting of a Pyrex reactor of 1 m3 [5] coupled to a long path in situ FTIR spectrometer and a Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-ToF-MS) in NO+ mode which was internally developed in LISA, to measure organic nitrates concentration. - Second one, the CESAM chamber (http://cesam.cnrs.fr) [6] is a 4.2 m3 stainless steel chamber which permits to conduct SOA experiments at different temperature and relative humidity. In situ FTIR and PTR-ToF-MS are used to measure gaseous concentrations, and a SMPS was used to characterize particulate phase. Kinetic and mechanistic results will be discussed and compared with the literature values. References [1] Brown S. S., Stutz J., Nighttime radical observations and chemistry. Chem. Soc. Rev. (2012) 41, 6405-6447 [2] Helmig D., Klinger L.F., et al., Biogenic volatile organic compound emissions (BVOCs) I. Identifications from three continental sites in the U.S. Chemosphere. (1999), Vol. 38, No. 9, pp. 2163

  8. American Association for Clinical Chemistry

    Science.gov (United States)

    ... older adolescents and adults. Read more IN CLINICAL CHEMISTRY Eliminating Wild-Type DNA in Liquid Biopsies Researchers ... Online Harmonization.net Commission on Accreditation in Clinical Chemistry American Board of Clinical Chemistry Clinical Chemistry Trainee ...

  9. Green Chemistry and Education.

    Science.gov (United States)

    Hjeresen, Dennis L.; Schutt, David L.; Boese, Janet M.

    2000-01-01

    Many students today are profoundly interested in the sustainability of their world. Introduces Green Chemistry and its principles with teaching materials. Green Chemistry is the use of chemistry for pollution prevention and the design of chemical products and processes that are environmentally benign. (ASK)

  10. Chemistry and Art.

    Science.gov (United States)

    Berry, Martyn

    1999-01-01

    Describes a Chemistry and Art project developed for secondary students and teachers sponsored by the National Gallery and The Royal Society of Chemistry in the United Kingdom. Discusses aspects of the techniques used in creating five paintings as well as the chemistry involved in their making, deterioration, conservation, and restoration.…

  11. Green Chemistry and Education.

    Science.gov (United States)

    Hjeresen, Dennis L.; Schutt, David L.; Boese, Janet M.

    2000-01-01

    Many students today are profoundly interested in the sustainability of their world. Introduces Green Chemistry and its principles with teaching materials. Green Chemistry is the use of chemistry for pollution prevention and the design of chemical products and processes that are environmentally benign. (ASK)

  12. Physical chemistry of surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Adamson, A.

    1990-01-01

    This book covers surface chemistry and selected aspects f colloid chemistry. The text covers such areas as structure and thermodynamics of liquid interfaces; electrical aspects of surface chemistry; microscopy and spectroscopy of solid interfaces; nucleation; contact angle; adsorption from solution; friction and adhesion; lubrication; and chemisorption and catalysis.

  13. Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition

    Directory of Open Access Journals (Sweden)

    Regina Berg

    2013-12-01

    Full Text Available The copper-catalyzed azide–alkyne cycloaddition (CuAAC is one of the most broadly applicable and easy-to-handle reactions in the arsenal of organic chemistry. However, the mechanistic understanding of this reaction has lagged behind the plethora of its applications for a long time. As reagent mixtures of copper salts and additives are commonly used in CuAAC reactions, the structure of the catalytically active species itself has remained subject to speculation, which can be attributed to the multifaceted aggregation chemistry of copper(I alkyne and acetylide complexes. Following an introductory section on common catalyst systems in CuAAC reactions, this review will highlight experimental and computational studies from early proposals to very recent and more sophisticated investigations, which deliver more detailed insights into the CuAAC’s catalytic cycle and the species involved. As diverging mechanistic views are presented in articles, books and online resources, we intend to present the research efforts in this field during the past decade and finally give an up-to-date picture of the currently accepted dinuclear mechanism of CuAAC. Additionally, we hope to inspire research efforts on the development of molecularly defined copper(I catalysts with defined structural characteristics, whose main advantage in contrast to the regularly used precatalyst reagent mixtures is twofold: on the one hand, the characteristics of molecularly defined, well soluble catalysts can be tuned according to the particular requirements of the experiment; on the other hand, the understanding of the CuAAC reaction mechanism can be further advanced by kinetic studies and the isolation and characterization of key intermediates.

  14. Surface chemistry essentials

    CERN Document Server

    Birdi, K S

    2013-01-01

    Surface chemistry plays an important role in everyday life, as the basis for many phenomena as well as technological applications. Common examples range from soap bubbles, foam, and raindrops to cosmetics, paint, adhesives, and pharmaceuticals. Additional areas that rely on surface chemistry include modern nanotechnology, medical diagnostics, and drug delivery. There is extensive literature on this subject, but most chemistry books only devote one or two chapters to it. Surface Chemistry Essentials fills a need for a reference that brings together the fundamental aspects of surface chemistry w

  15. The New Color of Chemistry: Green Chemistry

    Directory of Open Access Journals (Sweden)

    Zuhal GERÇEK

    2012-01-01

    Full Text Available Green chemistry which is the new application of chemistry rules provides solutions to problems that mankind is faced with climate changes, sustainable agriculture, energy, toxics, depletion of natural sources e.g. designing new chemicals and processes that production and utilization of hazardous matters. So, it is the indispensible tool for sustainable development. Current and future chemists should consider the human health and ecological issues in their professional life. In order to provide a solution for this requirement, green chemistry rules and under standings should be primarily taken in the university curriculum and at all educational levels.

  16. Catalytic Chemistry on Oxide Nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Asthagiri, Aravind; Dixon, David A.; Dohnalek, Zdenek; Kay, Bruce D.; Rodriquez, Jose A.; Rousseau, Roger J.; Stacchiola, Dario; Weaver, Jason F.

    2016-05-29

    Metal oxides represent one of the most important and widely employed materials in catalysis. Extreme variability of their chemistry provides a unique opportunity to tune their properties and to utilize them for the design of highly active and selective catalysts. For bulk oxides, this can be achieved by varying their stoichiometry, phase, exposed surface facets, defect, dopant densities and numerous other ways. Further, distinct properties from those of bulk oxides can be attained by restricting the oxide dimensionality and preparing them in the form of ultrathin films and nanoclusters as discussed throughout this book. In this chapter we focus on demonstrating such unique catalytic properties brought by the oxide nanoscaling. In the highlighted studies planar models are carefully designed to achieve minimal dispersion of structural motifs and to attain detailed mechanistic understanding of targeted chemical transformations. Detailed level of morphological and structural characterization necessary to achieve this goal is accomplished by employing both high-resolution imaging via scanning probe methods and ensemble-averaged surface sensitive spectroscopic methods. Three prototypical examples illustrating different properties of nanoscaled oxides in different classes of reactions are selected.

  17. Plasma chemistry in wire chambers

    Energy Technology Data Exchange (ETDEWEB)

    Wise, J.

    1990-05-01

    The phenomenology of wire chamber aging is discussed and fundamentals of proportional counters are presented. Free-radical polymerization and plasma polymerization are discussed. The chemistry of wire aging is reviewed. Similarities between wire chamber plasma (>1 atm dc-discharge) and low-pressure rf-discharge plasmas, which have been more widely studied, are suggested. Construction and use of a system to allow study of the plasma reactions occurring in wire chambers is reported. A proportional tube irradiated by an {sup 55}Fe source is used as a model wire chamber. Condensable species in the proportional tube effluent are concentrated in a cryotrap and analyzed by gas chromatography/mass spectrometry. Several different wire chamber gases (methane, argon/methane, ethane, argon/ethane, propane, argon/isobutane) are tested and their reaction products qualitatively identified. For all gases tested except those containing methane, use of hygroscopic filters to remove trace water and oxygen contaminants from the gas resulted in an increase in the average molecular weight of the products, consistent with results from low-pressure rf-discharge plasmas. It is suggested that because water and oxygen inhibit polymer growth in the gas phase that they may also reduce polymer deposition in proportional tubes and therefore retard wire aging processes. Mechanistic implications of the plasma reactions of hydrocarbons with oxygen are suggested. Unresolved issues in this work and proposals for further study are discussed.

  18. MECHANISTIC STUDIES OF IMPROVED FOAM EOR PROCESSES

    Energy Technology Data Exchange (ETDEWEB)

    William R. Rossen

    2003-03-31

    . We find that such behavior is consistent with earlier models of foam viscosity in tubes, and a modified model for the low-quality regime can account for this behavior. It is not yet clear why this new regime appears in some cases and not in others. Simple modeling suggests that the answer may have to do with the sensitivity of gas trapping to pressure gradient. Research on Task 3 continued to focus on foam generation at limited pressure gradient in sandpacks. We investigated the effects of permeability, surfactant concentration and liquid injection rates on foam generation. In addition, a careful review of published studies showed that repeated snap-off is not a plausible mechanism of foam generation in homogeneous porous media beyond the stage of initial drainage from a fully liquid-saturated state. Snap-off has been the focus of much research on foam generation and is incorporated into most mechanistic foam simulators. This finding should force a reconsideration of its role in foam generation and properties in porous media.

  19. The New Color of Chemistry: Green Chemistry

    OpenAIRE

    Zuhal GERÇEK

    2012-01-01

    Green chemistry which is the new application of chemistry rules provides solutions to problems that mankind is faced with climate changes, sustainable agriculture, energy, toxics, depletion of natural sources e.g. designing new chemicals and processes that production and utilization of hazardous matters. So, it is the indispensible tool for sustainable development. Current and future chemists should consider the human health and ecological issues in their professional life. In order to provid...

  20. Calix 2007:9th International Conference on Calixarene Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Jeffery Davis

    2011-09-09

    The DOE funds helped support an International Conference, Calix 2007, whose focus was on Supramolecular Chemistry. The conference was held at the University of Maryland from August 6-9, 2007 (Figure 1). The conference website is at www.chem.umd.edu/Conferences/Calix2007. This biannual conference had previously been held in the Czech Republic (2005), Canada (2003), Netherlands (2001), Australia (1999), Italy (1997), USA (Fort Worth, 1995) Japan (1993) and Germany (1991). Calixarenes are cup-shaped compounds that are a major part of Supramolecular Chemistry, for which Cram, Lehn and Pederson were awarded a Nobel Prize 20 years ago. Calixarene chemistry has expanded greatly in the last 2 decades, as these compounds are used in synthetic and mechanistic chemistry, separations science, materials science, nanoscience and biological chemistry. The organizing committee was quite happy that Calix 2007 encompassed the broad scope and interdisciplinary nature of the field. Our goal was to bring together leading scientists interested in calixarenes, molecular recognition, nanoscience and supramolecular chemistry. We believe that new research directions and collaborations resulted from an exchange of ideas between conferees. This grant from the DOE was crucial toward achieving that goal, as the funds helped cover some of the registration and accommodations costs for the speakers.

  1. Fast charging technique for high power LiFePO4 batteries: A mechanistic analysis of aging

    Science.gov (United States)

    Anseán, D.; Dubarry, M.; Devie, A.; Liaw, B. Y.; García, V. M.; Viera, J. C.; González, M.

    2016-07-01

    One of the major issues hampering the acceptance of electric vehicles (EVs) is the anxiety associated with long charging time. Hence, the ability to fast charging lithium-ion battery (LIB) systems is gaining notable interest. However, fast charging is not tolerated by all LIB chemistries because it affects battery functionality and accelerates its aging processes. Here, we investigate the long-term effects of multistage fast charging on a commercial high power LiFePO4-based cell and compare it to another cell tested under standard charging. Coupling incremental capacity (IC) and IC peak area analysis together with mechanistic model simulations ('Alawa' toolbox with harvested half-cell data), we quantify the degradation modes that cause aging of the tested cells. The results show that the proposed fast charging technique caused similar aging effects as standard charging. The degradation is caused by a linear loss of lithium inventory, coupled with a less degree of linear loss of active material on the negative electrode. This study validates fast charging as a feasible mean of operation for this particular LIB chemistry and cell architecture. It also illustrates the benefits of a mechanistic approach to understand cell degradation on commercial cells.

  2. Predicting interactions from mechanistic information: can omic data validate theories?

    Science.gov (United States)

    Borgert, Christopher J

    2007-09-01

    To address the most pressing and relevant issues for improving mixture risk assessment, researchers must first recognize that risk assessment is driven by both regulatory requirements and scientific research, and that regulatory concerns may expand beyond the purely scientific interests of researchers. Concepts of "mode of action" and "mechanism of action" are used in particular ways within the regulatory arena, depending on the specific assessment goals. The data requirements for delineating a mode of action and predicting interactive toxicity in mixtures are not well defined from a scientific standpoint due largely to inherent difficulties in testing certain underlying assumptions. Understanding the regulatory perspective on mechanistic concepts will be important for designing experiments that can be interpreted clearly and applied in risk assessments without undue reliance on extrapolation and assumption. In like fashion, regulators and risk assessors can be better equipped to apply mechanistic data if the concepts underlying mechanistic research and the limitations that must be placed on interpretation of mechanistic data are understood. This will be critically important for applying new technologies to risk assessment, such as functional genomics, proteomics, and metabolomics. It will be essential not only for risk assessors to become conversant with the language and concepts of mechanistic research, including new omic technologies, but also, for researchers to become more intimately familiar with the challenges and needs of risk assessment.

  3. Mechanistic Studies of Planetary Haze Formation

    Science.gov (United States)

    Hicks, Raea Kay

    2015-10-01

    Planetary atmospheres can be thought of as global-scale reactors capable of synthesizing large, complex molecules from small gases such as methane (CH4), carbon dioxide (CO2), and nitrogen (N2). The atmosphere of Titan, the largest moon of Saturn covered by a thick organic haze, contains trace amounts (2%) of CH4 in an atmosphere of N2 at a surface pressure of 1.5 bar. This is similar to the Earth's Archaean atmosphere, which possibly contained trace amounts of CH4 and CO2 (˜1,000 ppmv each) in an N2 -dominant atmosphere before the rise of biogenic oxygen. Laboratory simulations of the atmospheric chemistry on Titan and the early Earth have shown that these atmospheres are capable of generating biologically-relevant molecules that condense to form particles which can then settle to the surface of the planetary body, possibly providing the molecules required for the emergence of life. The work presented here examines the mechanisms by which FUV photochemistry initiates incorporation of N atoms into Titan aerosol analogs, and C atoms into early Earth aerosol analogs. Results from the Aerosol Collector and Pyrolyser onboard the Huygens lander reveal the presence of nitrogen in Titan's aerosols. This nitrogen incorporation is thought to occur primarily by extreme-UV photons or energetic electrons. However, recent results from our laboratory indicate a surprising amount of nitrogen incorporation- up to 16% by mass- in Titan aerosol analogs produced by photochemistry initiated by FUV irradiation of CH4/N 2 mixtures. The termolecular reaction CH+N2 +M → HCN2 has been proposed to account for this observation. Here, we test this hypothesis by using a high- resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) to measure the mass loading and chemical composition of aerosol produced at a range of pressures from roughly 0.1 to 1 atm. We report a 10-fold increase in aerosol mass loading across the range of pressures studied, indicating that the mechanism

  4. Orbital interactions in chemistry

    CERN Document Server

    Albright, Thomas A; Whangbo, Myung-Hwan

    2013-01-01

    Explains the underlying structure that unites all disciplines in chemistry Now in its second edition, this book explores organic, organometallic, inorganic, solid state, and materials chemistry, demonstrating how common molecular orbital situations arise throughout the whole chemical spectrum. The authors explore the relationships that enable readers to grasp the theory that underlies and connects traditional fields of study within chemistry, thereby providing a conceptual framework with which to think about chemical structure and reactivity problems. Orbital Interactions

  5. NATO Advanced Study Institute on Fundamental and Technological Aspects of Organo-f-Element Chemistry

    CERN Document Server

    Fragalà, Ignazio

    1985-01-01

    The past decade has seen a dramatic acceleration of activity and interest in phenomena surrounding lanthanide and actinide organo­ metallic compounds. Around the world, active research in organo-f­ element synthesis, chemistry, catalysis, crystallography, and quantum chemistry is in progress. This activity has spanned a remarkably wide range of disciplines, from synthetic/mechanistic inorganic and organic chemistry to radiochemistry, catalytic chemistry, spectroscopy (vibra­ tional, optical, magnetic resonance, photoelectron, Mossbauer), X-ray and neutron diffraction structural analysis, as well as to crystal field and molecular orbital theoretical studies at the interface of chemistry and physics. These investigations have been motivated both by fundamental and applied goals. The evidence that f-element organo­ metallic compounds have unique chemical and physical properties which cannot be duplicated by organometallic compounds of d-block elements has suggested many new areas of endeavor and application....

  6. Advances in quantum chemistry

    CERN Document Server

    Sabin, John R

    2013-01-01

    Advances in Quantum Chemistry presents surveys of current topics in this rapidly developing field that has emerged at the cross section of the historically established areas of mathematics, physics, chemistry, and biology. It features detailed reviews written by leading international researchers. This volume focuses on the theory of heavy ion physics in medicine.Advances in Quantum Chemistry presents surveys of current topics in this rapidly developing field that has emerged at the cross section of the historically established areas of mathematics, physics, chemistry, and biology. It features

  7. Science Update: Analytical Chemistry.

    Science.gov (United States)

    Worthy, Ward

    1980-01-01

    Briefly discusses new instrumentation in the field of analytical chemistry. Advances in liquid chromatography, photoacoustic spectroscopy, the use of lasers, and mass spectrometry are also discussed. (CS)

  8. Group theory and chemistry

    CERN Document Server

    Bishop, David M

    1993-01-01

    Group theoretical principles are an integral part of modern chemistry. Not only do they help account for a wide variety of chemical phenomena, they simplify quantum chemical calculations. Indeed, knowledge of their application to chemical problems is essential for students of chemistry. This complete, self-contained study, written for advanced undergraduate-level and graduate-level chemistry students, clearly and concisely introduces the subject of group theory and demonstrates its application to chemical problems.To assist chemistry students with the mathematics involved, Professor Bishop ha

  9. Green Chemistry Pedagogy

    Science.gov (United States)

    Kolopajlo, Larry

    2017-02-01

    This chapter attempts to show how the practice of chemistry teaching and learning is enriched by the incorporation of green chemistry (GC) into lectures and labs. To support this viewpoint, evidence from a wide range of published papers serve as a cogent argument that GC attracts and engages both science and nonscience students, enhances chemistry content knowledge, and improves the image of the field, while preparing the world for a sustainable future. Published pedagogy associated with green and sustainable chemistry is critically reviewed and discussed.

  10. Elements of environmental chemistry

    National Research Council Canada - National Science Library

    Hites, R. A; Raff, Jonathan D

    2012-01-01

    .... Extensively revised, updated, and expanded, this second edition includes new chapters on atmospheric chemistry, climate change, and polychlorinated biphenyls and dioxins, and brominated flame retardants...

  11. Why did Jacques Monod make the choice of mechanistic determinism?

    Science.gov (United States)

    Loison, Laurent

    2015-06-01

    The development of molecular biology placed in the foreground a mechanistic and deterministic conception of the functioning of macromolecules. In this article, I show that this conception was neither obvious, nor necessary. Taking Jacques Monod as a case study, I detail the way he gradually came loose from a statistical understanding of determinism to finally support a mechanistic understanding. The reasons of the choice made by Monod at the beginning of the 1950s can be understood only in the light of the general theoretical schema supported by the concept of mechanistic determinism. This schema articulates three fundamental notions for Monod, namely that of the rigidity of the sequence of the genetic program, that of the intrinsic stability of macromolecules (DNA and proteins), and that of the specificity of molecular interactions.

  12. Managing mechanistic and organic structure in health care organizations.

    Science.gov (United States)

    Olden, Peter C

    2012-01-01

    Managers at all levels in a health care organization must organize work to achieve the organization's mission and goals. This requires managers to decide the organization structure, which involves dividing the work among jobs and departments and then coordinating them all toward the common purpose. Organization structure, which is reflected in an organization chart, may range on a continuum from very mechanistic to very organic. Managers must decide how mechanistic versus how organic to make the entire organization and each of its departments. To do this, managers should carefully consider 5 factors for the organization and for each individual department: external environment, goals, work production, size, and culture. Some factors may push toward more mechanistic structure, whereas others may push in the opposite direction toward more organic structure. Practical advice can help managers at all levels design appropriate structure for their departments and organization.

  13. Discovering chemistry with an ab initio nanoreactor

    Science.gov (United States)

    Wang, Lee-Ping; Titov, Alexey; McGibbon, Robert; Liu, Fang; Pande, Vijay S.; Martínez, Todd J.

    2014-12-01

    Chemical understanding is driven by the experimental discovery of new compounds and reactivity, and is supported by theory and computation that provide detailed physical insight. Although theoretical and computational studies have generally focused on specific processes or mechanistic hypotheses, recent methodological and computational advances harken the advent of their principal role in discovery. Here we report the development and application of the ab initio nanoreactor—a highly accelerated first-principles molecular dynamics simulation of chemical reactions that discovers new molecules and mechanisms without preordained reaction coordinates or elementary steps. Using the nanoreactor, we show new pathways for glycine synthesis from primitive compounds proposed to exist on the early Earth, which provide new insight into the classic Urey-Miller experiment. These results highlight the emergence of theoretical and computational chemistry as a tool for discovery, in addition to its traditional role of interpreting experimental findings.

  14. Radical behaviorism and scientific frameworks. From mechanistic to relational accounts.

    Science.gov (United States)

    Chiesa, M

    1992-11-01

    A substantial portion of B. F. Skinner's scholarship was devoted to developing methods and terms for a scientific study of behavior. Three concepts central to scientific accounts--cause, explanation, and theory--are examined to illustrate the distinction between mechanistic and relational frameworks and radical behaviorism's relationship to those frameworks. Informed by a scientific tradition that explicitly rejects mechanistic interpretations, radical behaviorism provides a distinctive stance in contemporary psychology. The present analysis suggests that radical behaviorism makes closer contact with the "new world view" advocated by physicists and philosophers of science than does much of contemporary psychology.

  15. An investigation of student understanding in the undergraduate organic chemistry laboratory

    Science.gov (United States)

    Grutsch, John Leo, Jr.

    Laboratory activities in organic chemistry involve a mixture of sophisticated logic and empirical observation that requires the integration of mechanistic thought, laboratory technique, and problem-solving skills. In an effort to understand how students develop the thought processes and problem-solving skills necessary for laboratory work in organic chemistry, student understanding of how the interaction between a reaction system (reactants or starting material(s), reagent(s), and/or solvent), experimental variables (pH, temperature, concentrations, etc), provides a result of interest (yield, selectivity, purity, etc.) for an experiment performed in the organic chemistry laboratory was investigated through the collection of responses to questions posed on pre-laboratory quizzes followed by in-depth interviews during which student volunteers discussed their responses along with their experiences in the laboratory. The conceptual change theory of learning which assumes new conceptions are understood, judged, acquired, or rejected in a conceptual context was used as a theoretical paradigm to examine students responses to questions posed on pre-laboratory quizzes and transcripts of the interviews with student volunteers. Students were found to not have developed a mechanistic understanding of how the interaction between a reaction system (reactants or starting material(s), reagent(s), and/or solvent), experimental variables (pH, temperature, concentrations, etc), provides a result of interest (yield, selectivity, purity, etc.) for an experiment performed in the organic chemistry laboratory. However, students' prior exposure to and understanding of chemical concepts was found to simultaneously assist and hinder in their development of a partial mechanistic understanding of how a reaction system (reactants or starting material(s), reagent(s), and/or solvent), experimental variables (pH, temperature, concentrations, etc), interact to provide a result of interest (yield

  16. Mathematics and Chemistry

    Science.gov (United States)

    Henson, R.; Stumbles, A.

    1977-01-01

    The relationship between mathematics and chemistry has been changing rapidly in recent years. Some chemistry teachers have experienced difficulties in their teaching with the introduction of modern mathematics in the schools. Some suggestions for reinforcing the concepts and language of modern mathematics are put forth. (Author/MA)

  17. Movies in Chemistry Education

    Science.gov (United States)

    Pekdag, Bulent; Le Marechal, Jean-Francois

    2010-01-01

    This article reviews numerous studies on chemistry movies. Movies, or moving pictures, are important elements of multimedia and signify a privileged or motivating means of presenting knowledge. Studies on chemistry movies show that the first movie productions in this field were devoted to university lectures or documentaries. Shorter movies were…

  18. Physical Chemistry of Molecular

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    @@ Established in 2009, the group consists of six researchers and more than 70 research assistants and graduate students from the CAS Key Laboratory of Molecular Nanostructures and Nanotechnologies at the CAS Institute of Chemistry.Its research focuses on the physical chemistry involved in molecular assembly, molecular nanostructures, functional nanomaterials and conceptual nano-devices.

  19. Exercises in Computational Chemistry

    DEFF Research Database (Denmark)

    Spanget-Larsen, Jens

    2016-01-01

    A selection of HyperChem© PC-exercises in computational chemistry. Answers to most questions are appended (Roskilde University 2014-16).......A selection of HyperChem© PC-exercises in computational chemistry. Answers to most questions are appended (Roskilde University 2014-16)....

  20. The Breath of Chemistry

    DEFF Research Database (Denmark)

    Josephsen, Jens

    The present preliminary text is a short thematic presentation in biological inorganic chemistry meant to illustrate general and inorganic (especially coordination) chemistry in biochemistry. The emphasis is on molecular models to explain features of the complicated mechanisms essential to breathing...

  1. Exercises in Computational Chemistry

    DEFF Research Database (Denmark)

    Spanget-Larsen, Jens

    2016-01-01

    A selection of HyperChem© PC-exercises in computational chemistry. Answers to most questions are appended (Roskilde University 2014-16).......A selection of HyperChem© PC-exercises in computational chemistry. Answers to most questions are appended (Roskilde University 2014-16)....

  2. Chemistry in Microfluidic Channels

    Science.gov (United States)

    Chia, Matthew C.; Sweeney, Christina M.; Odom, Teri W.

    2011-01-01

    General chemistry introduces principles such as acid-base chemistry, mixing, and precipitation that are usually demonstrated in bulk solutions. In this laboratory experiment, we describe how chemical reactions can be performed in a microfluidic channel to show advanced concepts such as laminar fluid flow and controlled precipitation. Three sets of…

  3. Chemistry of americium

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, W.W.

    1976-01-01

    Essential features of the descriptive chemistry of americium are reviewed. Chapter titles are: discovery, atomic and nuclear properties, collateral reading, production and uses, chemistry in aqueous solution, metal, alloys, and compounds, and, recovery, separation, purification. Author and subject indexes are included. (JCB)

  4. The roles of dihydrogen bonds in amine borane chemistry.

    Science.gov (United States)

    Chen, Xuenian; Zhao, Ji-Cheng; Shore, Sheldon G

    2013-11-19

    A dihydrogen bond (DHB) is an electrostatic interaction between a protonic hydrogen and a hydridic hydrogen. Over the past two decades, researchers have made significant progress in the identification and characterization of DHBs and their properties. In comparison with conventional hydrogen bonds (HBs), which have been widely used in catalysis, molecular recognition, crystal engineering, and supramolecular synthesis, chemists have only applied DHBs in very limited ways. Considering that DHBs and conventional HBs have comparable strength, DHBs could be more widely applied in chemistry. Over the past several years, we have explored the impact of DHBs on amine borane chemistry and the syntheses and characterization of amine boranes and ammoniated metal borohydrides for hydrogen storage. Through systematic computational and experimental investigations, we found that DHBs play a dominant role in dictating the reaction pathways (and thus different products) of amine boranes where oppositely charged hydrogens coexist for DHB formation. Through careful experiments, we observed, for the first time, a long-postulated reaction intermediate, ammonia diborane (AaDB), whose behavior is essential to mechanistic understanding of the formation of the diammoniate of diborane (DADB) in the reaction of ammonia (NH3) with tetrahydrofuran borane (THF·BH3). The formation of DADB has puzzled the boron chemistry community for decades. Mechanistic insight enabled us to develop facile syntheses of aminodiborane (ADB), ammonia borane (AB), DADB, and an inorganic butane analog NH3BH2NH2BH3 (DDAB). Our examples, together with those in the literature, reinforce the fact that DHB formation and subsequent molecular hydrogen elimination are a viable approach for creating new covalent bonds and synthesizing new materials. We also review the strong effects of DHBs on the stability of conformers and the hydrogen desorption temperatures of boron-nitrogen compounds. We hope that this Account will

  5. Biosynthetic inorganic chemistry.

    Science.gov (United States)

    Lu, Yi

    2006-08-25

    Inorganic chemistry and biology can benefit greatly from each other. Although synthetic and physical inorganic chemistry have been greatly successful in clarifying the role of metal ions in biological systems, the time may now be right to utilize biological systems to advance coordination chemistry. One such example is the use of small, stable, easy-to-make, and well-characterized proteins as ligands to synthesize novel inorganic compounds. This biosynthetic inorganic chemistry is possible thanks to a number of developments in biology. This review summarizes the progress in the synthesis of close models of complex metalloproteins, followed by a description of recent advances in using the approach for making novel compounds that are unprecedented in either inorganic chemistry or biology. The focus is mainly on synthetic "tricks" learned from biology, as well as novel structures and insights obtained. The advantages and disadvantages of this biosynthetic approach are discussed.

  6. Mechanistic Aspects in the Formation, Growth and Surface Functionalization of Metal Oxide Nanoparticles in Organic Solvents.

    Science.gov (United States)

    Niederberger, Markus; Deshmukh, Rupali

    2017-04-04

    The synthesis of metal oxide nanoparticles in organic solvents, so-called nonaqueous (or nonhydrolytic) processes represent powerful alternatives to aqueous approaches and have become an independent research field. 10 years ago, when we published our first review on organic reaction pathways in nonaqueous sol-gel approaches,[1] the number of examples was relatively limited. Nowadays, it is almost impossible to provide an exhaustive overview. Here we review the development of the last few years, without neglecting pioneering examples, which help to follow the historical development. The importance of a profound understanding of mechanistic aspects of nanoparticle crystallization and formation mechanisms can't be overestimated, when it comes to the design of rational synthesis concepts under minimization of trial-and-error experiments. The main reason for the progress in mechanistic understanding lies in the availability of characterization tools that make it possible to monitor chemical reactions from the dissolution of the precursor to the nucleation and growth of the nanoparticles, by ex-situ methods involving sampling after different reaction times, but more and more also by in-situ studies. After a short introduction to experimental aspects of nonaqueous sol-gel routes to metal oxide nanoparticles, we provide an overview of the main and basic organic reaction pathways in these approaches. Afterwards, we summarize the main characterization methods to study formation mechanisms, and then we discuss in great depth the chemical formation mechanisms of many different types of metal oxide nanoparticles. The review concludes with a paragraph on selected crystallization mechanisms reported for nonaqueous systems and a few illustrative examples of nonaqueous sol-gel concepts applied to surface chemistry.

  7. Reduction of Carbon Dioxide by a Molybdenum-Containing Formate Dehydrogenase: A Kinetic and Mechanistic Study.

    Science.gov (United States)

    Maia, Luisa B; Fonseca, Luis; Moura, Isabel; Moura, José J G

    2016-07-20

    Carbon dioxide accumulation is a major concern for the ecosystems, but its abundance and low cost make it an interesting source for the production of chemical feedstocks and fuels. However, the thermodynamic and kinetic stability of the carbon dioxide molecule makes its activation a challenging task. Studying the chemistry used by nature to functionalize carbon dioxide should be helpful for the development of new efficient (bio)catalysts for atmospheric carbon dioxide utilization. In this work, the ability of Desulfovibrio desulfuricans formate dehydrogenase (Dd FDH) to reduce carbon dioxide was kinetically and mechanistically characterized. The Dd FDH is suggested to be purified in an inactive form that has to be activated through a reduction-dependent mechanism. A kinetic model of a hysteretic enzyme is proposed to interpret and predict the progress curves of the Dd FDH-catalyzed reactions (initial lag phase and subsequent faster phase). Once activated, Dd FDH is able to efficiently catalyze, not only the formate oxidation (kcat of 543 s(-1), Km of 57.1 μM), but also the carbon dioxide reduction (kcat of 46.6 s(-1), Km of 15.7 μM), in an overall reaction that is thermodynamically and kinetically reversible. Noteworthy, both Dd FDH-catalyzed formate oxidation and carbon dioxide reduction are completely inactivated by cyanide. Current FDH reaction mechanistic proposals are discussed and a different mechanism is here suggested: formate oxidation and carbon dioxide reduction are proposed to proceed through hydride transfer and the sulfo group of the oxidized and reduced molybdenum center, Mo(6+)═S and Mo(4+)-SH, are suggested to be the direct hydride acceptor and donor, respectively.

  8. Art in Chemistry; Chemistry in Art.

    Science.gov (United States)

    Greenberg, Barbara R.; Patterson, Dianne

    High school teachers are often challenged to motivate students who have little or no interest in a subject and are bored with traditional instruction. This unique book is designed to help educators make chemistry classes more interesting and links art curriculum to practical applications, integrating the two subjects through scores of hands-on…

  9. Korean Kimchi Chemistry: A Multicultural Chemistry Connection

    Science.gov (United States)

    Murfin, Brian

    2009-01-01

    Connecting science with different cultures is one way to interest students in science, to relate science to their lives, and at the same time to broaden their horizons in a variety of ways. In the lesson described here, students make kimchi, a delicious and popular Korean dish that can be used to explore many important chemistry concepts,…

  10. Advanced reach tool (ART) : Development of the mechanistic model

    NARCIS (Netherlands)

    Fransman, W.; Tongeren, M. van; Cherrie, J.W.; Tischer, M.; Schneider, T.; Schinkel, J.; Kromhout, H.; Warren, N.; Goede, H.; Tielemans, E.

    2011-01-01

    This paper describes the development of the mechanistic model within a collaborative project, referred to as the Advanced REACH Tool (ART) project, to develop a tool to model inhalation exposure for workers sharing similar operational conditions across different industries and locations in Europe. T

  11. Mechanistic model for dispersion coefficients in bubble column

    CSIR Research Space (South Africa)

    Skosana, PJ

    2015-05-01

    Full Text Available A mechanistic model describing the mass and momentum exchange in bubble columns is proposed that is based on the observations that the gas distribution in a bubble column is not uniform across the column and that as a consequence large liquid...

  12. A mechanistic assessment of nutrient flushing at the catchment scale

    Science.gov (United States)

    Willem J. van Verseveld; Jeffrey J. McDonnell; Kate Lajtha

    2008-01-01

    This paper mechanistically assesses the flushing mechanism of DOC, DON, and DIN at the hillslope and catchment scales during two storm events, in a small catchment (WS10), H.J. Andrews Experimental Forest in the western Cascade Mountains of Oregon. Using a combination of natural tracer and hydrometric data, and end-member mixing analysis, we were able to describe the...

  13. Mechanistic investigation on the formation of indolizines from 2-enynylpyridines.

    Science.gov (United States)

    Lahoz, Inma R; Sicre, Cristina; Navarro-Vázquez, Armando; Silva López, Carlos; Cid, María-Magdalena

    2009-11-05

    2,3,7-Trisubstituted indolizines were obtained from E- or Z-2-enynyl-4-substituted pyridines. The mechanistic pathway involves a base-catalyzed double-bond isomerization, if the E-isomer is the starting material, followed by a concerted pseudocoarctate cyclization.

  14. Bridging Mechanistic and Phenomenological Models of Complex Biological Systems

    Science.gov (United States)

    Transtrum, Mark K.; Qiu, Peng

    2016-01-01

    The inherent complexity of biological systems gives rise to complicated mechanistic models with a large number of parameters. On the other hand, the collective behavior of these systems can often be characterized by a relatively small number of phenomenological parameters. We use the Manifold Boundary Approximation Method (MBAM) as a tool for deriving simple phenomenological models from complicated mechanistic models. The resulting models are not black boxes, but remain expressed in terms of the microscopic parameters. In this way, we explicitly connect the macroscopic and microscopic descriptions, characterize the equivalence class of distinct systems exhibiting the same range of collective behavior, and identify the combinations of components that function as tunable control knobs for the behavior. We demonstrate the procedure for adaptation behavior exhibited by the EGFR pathway. From a 48 parameter mechanistic model, the system can be effectively described by a single adaptation parameter τ characterizing the ratio of time scales for the initial response and recovery time of the system which can in turn be expressed as a combination of microscopic reaction rates, Michaelis-Menten constants, and biochemical concentrations. The situation is not unlike modeling in physics in which microscopically complex processes can often be renormalized into simple phenomenological models with only a few effective parameters. The proposed method additionally provides a mechanistic explanation for non-universal features of the behavior. PMID:27187545

  15. Directed evolution of aldolases for exploitation in synthetic organic chemistry

    Science.gov (United States)

    Bolt, Amanda; Berry, Alan; Nelson, Adam

    2008-01-01

    This review focuses on the directed evolution of aldolases with synthetically useful properties. Directed evolution has been used to address a number of limitations associated with the use of wild-type aldolases as catalysts in synthetic organic chemistry. The generation of aldolase enzymes with a modified or expanded substrate repertoire is described. Particular emphasis is placed on the directed evolution of aldolases with modified stereochemical properties: such enzymes can be useful catalysts in the stereoselective synthesis of biologically active small molecules. The review also describes some of the fundamental insights into mechanistic enzymology that directed evolution can provide. PMID:18230325

  16. Moderator Chemistry Program

    Energy Technology Data Exchange (ETDEWEB)

    Dewitt, L.V.; Gibbs, A.; Lambert, D.P.; Bohrer, S.R.; Fanning, R.L.; Houston, M.W.; Stinson, S.L.; Deible, R.W.; Abdel-Khalik, S.I.

    1990-11-01

    Over the past fifteen months, the Systems Chemistry Group of the Reactor Engineering Department has undertaken a comprehensive study of the Department`s moderator chemistry program at Savannah River Site (SRS). An internal review was developed to formalize and document this program. Objectives were as outlined in a mission statement and action plan. In addition to the mission statement and action plan, nine separate task reports have been issued during the course of this study. Each of these task reports is included in this document as a chapter. This document is an organized compilation of the individual reports issued by the Systems Chemistry Group in assessment of SRS moderator chemistry to determine if there were significant gaps in the program as ft existed in October, 1989. While these reviews found no significant gaps in that mode of operation, or any items that adversely affected safety, items were identified that could be improved. Many of the items have already been dear with or are in the process of completion under this Moderator Chemistry Program and other Reactor Restart programs. A complete list of the items of improvement found under this assessment is found in Chapter 9, along with a proposed time table for correcting remaining items that can be improved for the chemistry program of SRS reactors. An additional external review of the moderator chemistry processes, recommendations, and responses to/from the Reactor Corrosion Mitigation Committee is included as Appendix to this compilation.

  17. Moderator Chemistry Program

    Energy Technology Data Exchange (ETDEWEB)

    Dewitt, L.V.; Gibbs, A.; Lambert, D.P.; Bohrer, S.R.; Fanning, R.L.; Houston, M.W.; Stinson, S.L.; Deible, R.W.; Abdel-Khalik, S.I.

    1990-11-01

    Over the past fifteen months, the Systems Chemistry Group of the Reactor Engineering Department has undertaken a comprehensive study of the Department's moderator chemistry program at Savannah River Site (SRS). An internal review was developed to formalize and document this program. Objectives were as outlined in a mission statement and action plan. In addition to the mission statement and action plan, nine separate task reports have been issued during the course of this study. Each of these task reports is included in this document as a chapter. This document is an organized compilation of the individual reports issued by the Systems Chemistry Group in assessment of SRS moderator chemistry to determine if there were significant gaps in the program as ft existed in October, 1989. While these reviews found no significant gaps in that mode of operation, or any items that adversely affected safety, items were identified that could be improved. Many of the items have already been dear with or are in the process of completion under this Moderator Chemistry Program and other Reactor Restart programs. A complete list of the items of improvement found under this assessment is found in Chapter 9, along with a proposed time table for correcting remaining items that can be improved for the chemistry program of SRS reactors. An additional external review of the moderator chemistry processes, recommendations, and responses to/from the Reactor Corrosion Mitigation Committee is included as Appendix to this compilation.

  18. Mathematics for physical chemistry

    CERN Document Server

    Mortimer, Robert G

    2013-01-01

    Mathematics for Physical Chemistry is the ideal supplementary text for practicing chemists and students who want to sharpen their mathematics skills while enrolled in general through physical chemistry courses. This book specifically emphasizes the use of mathematics in the context of physical chemistry, as opposed to being simply a mathematics text. This 4e includes new exercises in each chapter that provide practice in a technique immediately after discussion or example and encourage self-study. The early chapters are constructed around a sequence of mathematical topics, wit

  19. Gas phase ion chemistry

    CERN Document Server

    Bowers, Michael T

    1979-01-01

    Gas Phase Ion Chemistry, Volume 1 covers papers on the advances of gas phase ion chemistry. The book discusses the advances in flow tubes and the measurement of ion-molecule rate coefficients and product distributions; the ion chemistry of the earth's atmosphere; and the classical ion-molecule collision theory. The text also describes statistical methods in reaction dynamics; the state selection by photoion-photoelectron coincidence; and the effects of temperature and pressure in the kinetics of ion-molecule reactions. The energy distribution in the unimolecular decomposition of ions, as well

  20. Spatially Resolved Artificial Chemistry

    DEFF Research Database (Denmark)

    Fellermann, Harold

    2009-01-01

    Although spatial structures can play a crucial role in chemical systems and can drastically alter the outcome of reactions, the traditional framework of artificial chemistry is a well-stirred tank reactor with no spatial representation in mind. Advanced method development in physical chemistry has...... made a class of models accessible to the realms of artificial chemistry that represent reacting molecules in a coarse-grained fashion in continuous space. This chapter introduces the mathematical models of Brownian dynamics (BD) and dissipative particle dynamics (DPD) for molecular motion and reaction...

  1. Fluorine in medicinal chemistry.

    Science.gov (United States)

    Swallow, Steven

    2015-01-01

    Since its first use in the steroid field in the late 1950s, the use of fluorine in medicinal chemistry has become commonplace, with the small electronegative fluorine atom being a key part of the medicinal chemist's repertoire of substitutions used to modulate all aspects of molecular properties including potency, physical chemistry and pharmacokinetics. This review will highlight the special nature of fluorine, drawing from a survey of marketed fluorinated pharmaceuticals and the medicinal chemistry literature, to illustrate key concepts exploited by medicinal chemists in their attempts to optimize drug molecules. Some of the potential pitfalls in the use of fluorine will also be highlighted.

  2. Experiments in physical chemistry

    CERN Document Server

    Wilson, J M; Denaro, A R

    1968-01-01

    Experiments in Physical Chemistry, Second Edition provides a compilation of experiments concerning physical chemistry. This book illustrates the link between the theory and practice of physical chemistry. Organized into three parts, this edition begins with an overview of those experiments that generally have a simple theoretical background. Part II contains experiments that are associated with more advanced theory or more developed techniques, or which require a greater degree of experimental skill. Part III consists of experiments that are in the nature of investigations wherein these invest

  3. Enzymes in Analytical Chemistry.

    Science.gov (United States)

    Fishman, Myer M.

    1980-01-01

    Presents tabular information concerning recent research in the field of enzymes in analytic chemistry, with methods, substrate or reaction catalyzed, assay, comments and references listed. The table refers to 128 references. Also listed are 13 general citations. (CS)

  4. Beauty in chemistry

    Directory of Open Access Journals (Sweden)

    Peter Atkins

    2006-03-01

    Full Text Available Though hard going for the general reader and highly personal in its selectivity, Elegant Solutions: Ten Beautiful Experiments in Chemistry provides reflections of a thoughtful author that will delight chemists

  5. Chemistry at large

    Directory of Open Access Journals (Sweden)

    Jeremy. K.M. Sanders

    2007-06-01

    Full Text Available A new book introduces young researchers to supramolecular chemistry, starting from the basics and working up to the more complicated aspects of the topic. While the text is inspiring for new graduates, it lacks a critical view.

  6. Microfluidics in inorganic chemistry.

    Science.gov (United States)

    Abou-Hassan, Ali; Sandre, Olivier; Cabuil, Valérie

    2010-08-23

    The application of microfluidics in chemistry has gained significant importance in the recent years. Miniaturized chemistry platforms provide controlled fluid transport, rapid chemical reactions, and cost-saving advantages over conventional reactors. The advantages of microfluidics have been clearly established in the field of analytical and bioanalytical sciences and in the field of organic synthesis. It is less true in the field of inorganic chemistry and materials science; however in inorganic chemistry it has mostly been used for the separation and selective extraction of metal ions. Microfluidics has been used in materials science mainly for the improvement of nanoparticle synthesis, namely metal, metal oxide, and semiconductor nanoparticles. Microfluidic devices can also be used for the formulation of more advanced and sophisticated inorganic materials or hybrids.

  7. Uncertainty in chemistry.

    Science.gov (United States)

    Menger, Fredric M

    2010-09-01

    It might come as a disappointment to some chemists, but just as there are uncertainties in physics and mathematics, there are some chemistry questions we may never know the answer to either, suggests Fredric M. Menger.

  8. Indicators: Soil Chemistry

    Science.gov (United States)

    The chemical makeup of the soil can provide information on wetland condition, wetland water quality and services being provided by the wetland ecosystem. Analyzing soil chemistry reveals if the soil is contaminated with a toxic chemical or heavy metal.

  9. Chemistry for Kids.

    Science.gov (United States)

    Sato, Sanae; Majoros, Bela

    1988-01-01

    Reports two methods for interesting children in chemistry. Describes a method for producing large soap bubbles and films for study. Examines the use of simple stories to explain common chemical concepts with example given. Lists titles of available stories. (ML)

  10. Supplemental instruction in chemistry

    Science.gov (United States)

    Lundeberg, Mary A.

    This study was designed to measure some effects of supplemental instruction in chemistry. Supplemental instruction is a peer-led cooperative learning program that encourages students to develop conceptual understanding by articulating both understandings and misconceptions in a think-aloud fashion. Supplemental instruction was offered three hours weekly outside of class and lab time for students in four classes of General Organic and Biological Chemistry. Over a two-year period 108 students volunteered to participate in this program; 45 students did not participate. As measured by final grades in chemistry and responses to a questionnaire, supplemental instruction was effective in increasing students' achievement in chemistry. Further research is needed to determine the in-depth effects of supplemental instruction on students' learning, problem solving, and self-esteem.

  11. Water Chemistry: Seeking Information

    Science.gov (United States)

    Delfino, Joseph J.

    1977-01-01

    A survey of the available literature in water chemistry is presented. Materials surveyed include: texts, reference books, bibliographic resources, journals, American Chemical Society publications, proceedings, unpublished articles, and reports. (BT)

  12. Impact of surface chemistry

    OpenAIRE

    2010-01-01

    The applications of molecular surface chemistry in heterogeneous catalyst technology, semiconductor-based technology, medical technology, anticorrosion and lubricant technology, and nanotechnology are highlighted in this perspective. The evolution of surface chemistry at the molecular level is reviewed, and the key roles of surface instrumentation developments for in situ studies of the gas–solid, liquid–solid, and solid–solid interfaces under reaction conditions are emphasized.

  13. Impact of surface chemistry

    Science.gov (United States)

    Somorjai, Gabor A.; Li, Yimin

    2011-01-01

    The applications of molecular surface chemistry in heterogeneous catalyst technology, semiconductor-based technology, medical technology, anticorrosion and lubricant technology, and nanotechnology are highlighted in this perspective. The evolution of surface chemistry at the molecular level is reviewed, and the key roles of surface instrumentation developments for in situ studies of the gas–solid, liquid–solid, and solid–solid interfaces under reaction conditions are emphasized. PMID:20880833

  14. Applications of supramolecular chemistry

    CERN Document Server

    Schneider, Hans-Jörg

    2012-01-01

    ""The time is ripe for the present volume, which gathers thorough presentations of the numerous actually realized or potentially accessible applications of supramolecular chemistry by a number of the leading figures in the field. The variety of topics covered is witness to the diversity of the approaches and the areas of implementation…a broad and timely panorama of the field assembling an eminent roster of contributors.""-Jean-Marie Lehn, 1987 Noble Prize Winner in Chemistry

  15. Gas phase ion chemistry

    CERN Document Server

    Bowers, Michael T

    1979-01-01

    Gas Phase Ion Chemistry, Volume 2 covers the advances in gas phase ion chemistry. The book discusses the stabilities of positive ions from equilibrium gas-phase basicity measurements; the experimental methods used to determine molecular electron affinities, specifically photoelectron spectroscopy, photodetachment spectroscopy, charge transfer, and collisional ionization; and the gas-phase acidity scale. The text also describes the basis of the technique of chemical ionization mass spectrometry; the energetics and mechanisms of unimolecular reactions of positive ions; and the photodissociation

  16. EPA Environmental Chemistry Laboratory

    Science.gov (United States)

    1993-01-01

    The Environmental Protection Agency's (EPA) Chemistry Laboratory (ECL) is a national program laboratory specializing in residue chemistry analysis under the jurisdiction of the EPA's Office of Pesticide Programs in Washington, D.C. At Stennis Space Center, the laboratory's work supports many federal anti-pollution laws. The laboratory analyzes environmental and human samples to determine the presence and amount of agricultural chemicals and related substances. Pictured, ECL chemists analyze environmental and human samples for the presence of pesticides and other pollutants.

  17. Click chemistry with DNA

    OpenAIRE

    El-Sagheer, Afaf H.; Brown, Tom

    2010-01-01

    The advent of click chemistry has led to an influx of new ideas in the nucleic acids field. The copper catalysed alkyne–azide cycloaddition (CuAAC) reaction is the method of choice for DNA click chemistry due to its remarkable efficiency. It has been used to label oligonucleotides with fluorescent dyes, sugars, peptides and other reporter groups, to cyclise DNA, to synthesise DNA catenanes, to join oligonucleotides to PNA, and to produce analogues of DNA with modified nucleobases and backbone...

  18. Forensic Chemistry Training

    OpenAIRE

    GERÇEK, Zuhal

    2012-01-01

    Increasing the types of terrorism and crime nowadays, the importance of the forensic sciences can be bett er understood. Forensic science is the application of the wide spectrum of science to answer the question of legal system. It contains the application of the principles, techniques and methods of basic sciences and its main aim is the determination of the physical facts which are important in legal situations. Forensic chemistry is the branch of chemistry which performs the chemical analy...

  19. Fundamentals of quantum chemistry

    CERN Document Server

    House, J E

    2004-01-01

    An introduction to the principles of quantum mechanics needed in physical chemistry. Mathematical tools are presented and developed as needed and only basic calculus, chemistry, and physics is assumed. Applications include atomic and molecular structure, spectroscopy, alpha decay, tunneling, and superconductivity. New edition includes sections on perturbation theory, orbital symmetry of diatomic molecules, the Huckel MO method and Woodward/Hoffman rules as well as a new chapter on SCF and Hartree-Fock methods. * This revised text clearly presents basic q

  20. HARNESSING THE CHEMISTRY OF CO2

    Energy Technology Data Exchange (ETDEWEB)

    Louie, Janis

    2010-05-11

    Our research program is broadly focused on activating CO{sub 2} through the use of organic and organometallic based catalysts. Some of our methods have centered on annulation reactions of unsaturated hydrocarbons (and carbonyl substrates) to provide a diverse array of carbocycles and heterocycles. We use a combination of catalyst discovery and optimization in conjunction with classical physical organic chemistry to elucidate the key mechanistic features of the cycloaddition reactions such that the next big advances in catalyst development can be made. Key to all of our cycloaddition reactions is the use of a sterically hindered, electron donating N heterocyclic carbene (NHC) ligand, namely IPr (or SIPr), in conjunction with a low valent nickel pre-catalyst. The efficacy of this ligand is two-fold: (1) the high {delta}-donating ability of the NHC increases the nucleophilicity of the metal center which thereby facilitates interaction with the electrophilic carbonyl and (2) the steric hindrance prevents an otherwise competitive side reaction involving only the alkyne substrate. Such a system has allowed for the facile cycloaddition to prepare highly functionalized pyrones, pyridones, pyrans, as well as novel carbocycles. Importantly, all reactions proceed under extremely mild conditions (room temperature, atmospheric pressures, and short reaction times), require only catalytic amounts of Ni/NHC and readily available starting materials, and afford annulated products in excellent yields. Our current focus revolves around understanding the fundamental processes that govern these cycloadditions such that the next big advance in the cyclization chemistry of CO{sub 2} can be made. Concurrent to our annulation chemistry is our investigation of the potential for imidazolylidenes to function as thermally-actuated CO{sub 2} sequestering and delivery agents.

  1. Mechanistic Fermentation Models for Process Design, Monitoring, and Control

    DEFF Research Database (Denmark)

    Mears, Lisa; Stocks, Stuart M.; Albæk, Mads Orla

    2017-01-01

    Mechanistic models require a significant investment of time and resources, but their application to multiple stages of fermentation process development and operation can make this investment highly valuable. This Opinion article discusses how an established fermentation model may be adapted...... for application to different stages of fermentation process development: planning, process design, monitoring, and control. Although a longer development time is required for such modeling methods in comparison to purely data-based model techniques, the wide range of applications makes them a highly valuable tool...... for fermentation research and development. In addition, in a research environment, where collaboration is important, developing mechanistic models provides a platform for knowledge sharing and consolidation of existing process understanding....

  2. Mechanistic Links Between PARP, NAD, and Brain Inflammation After TBI

    Science.gov (United States)

    2015-10-01

    1 AWARD NUMBER: W81XWH-13-2-0091 TITLE: Mechanistic Links Between PARP, NAD, and Brain Inflammation After TBI PRINCIPAL INVESTIGATOR ...Raymond A. Swanson, M.D CONTRACTING ORGANIZATION: Northern California Institute for Research & Education San Francisco, CA 94121 REPORT DATE: October 2015...STATEMENT Approved for Public Release; Distribution Unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT This project is a pre-clinical evaluation of the

  3. Human Glycinamide Ribonucleotide Transformylase: Active Site Mutants as Mechanistic Probes†

    OpenAIRE

    Manieri, Wanda; Moore, Molly E.; Soellner, Matthew B.; Tsang, Pearl; Caperelli, Carol A.

    2007-01-01

    Human glycinamide ribonucleotide transformylase (GART) (EC2.1.2.2) is a validated target for cancer chemotherapy, but mechanistic studies of this therapeutically important enzyme are limited. Site-directed mutagenesis, initial velocity studies, pH-rate studies, and substrate binding studies have been employed to probe the role of the strictly conserved active site residues, N106, H108, D144, and the semi-conserved K170 in substrate binding and catalysis. Only two conservative substitutions, N...

  4. Nobel Prize in Chemistry. Development of the Olefin Metathesis Method in Organic Synthesis

    Science.gov (United States)

    Casey, Charles P.

    2006-02-01

    The 2005 Nobel Prize in Chemistry was awarded to Yves Chauvin of the Institut Français du Pétrole, Robert H. Grubbs of CalTech, and Richard R. Schrock of MIT "for development of the metathesis method in organic synthesis". The discoveries of the laureates provided a chemical reaction now used daily in the chemical industry for the efficient and more environmentally friendly production of important pharmaceuticals, fuels, synthetic fibers, and many other products. This article tells the story of how olefin metathesis became a truly useful synthetic transformation and a triumph for mechanistic chemistry, and illustrates the importance of fundamental research. See JCE Featured Molecules .

  5. Home range analysis using a mechanistic home range model

    Energy Technology Data Exchange (ETDEWEB)

    Moorcroft, P.R. (Princeton Univ., NJ (United States). Dept. of Ecology and Evolutionary Biology); Lewis, M.A. (Univ. of Utah, Salt Lake City, UT (United States). Dept. of Mathematics) Crabtree, R.L. (Univ. of Idaho, Moscow, ID (United States). Dept. of Fish and Wildlife Resources)

    1999-07-01

    The traditional models used to characterize animal home ranges have no mechanistic basis underlying their descriptions of space use, and as a result, the analysis of animal home ranges has primarily been a descriptive endeavor. In this paper, the authors characterize coyote (Canis latrans) home range patterns using partial differential equations for expected space use that are formally derived from underlying descriptions of individual movement behavior. To the authors' knowledge, this is the first time that mechanistic models have been used to characterize animal home ranges. The results provide empirical support for a model formulation of movement response to scent marks, and suggest that having relocation data for individuals in adjacent groups is necessary to capture the spatial arrangement of home range boundaries. The authors then show how the model fits can be used to obtain predictions for individual movement and scent marking behavior and to predict changes in home range patterns. More generally, the findings illustrate how mechanistic models permit the development of a predictive theory for the relationship between movement behavior and animal spatial distribution.

  6. Numerical simulation in steam injection process by a mechanistic approach

    Energy Technology Data Exchange (ETDEWEB)

    De Souza, J.C.Jr.; Campos, W.; Lopes, D.; Moura, L.S.S. [Petrobras, Rio de Janeiro (Brazil)

    2008-10-15

    Steam injection is a common thermal recovery method used in very viscous oil reservoirs. The method involves the injection of heat to reduce viscosity and mobilize oil. A steam generation and injection system consists primarily of a steam source, distribution lines, injection wells and a discarding tank. In order to optimize injection and improve the oil recovery factor, one must determine the parameters of steam flow such as pressure, temperature and steam quality. This study focused on developing a unified mathematical model by means of a mechanistic approach for two-phase steam flow in pipelines and wells. The hydrodynamic and heat transfer mechanistic model was implemented in a computer simulator to model the parameters of steam injection while trying to avoid the use of empirical correlations. A marching algorithm was used to determine the distribution of pressure and temperature along the pipelines and wellbores. The mathematical model for steam flow in injection systems, developed by a mechanistic approach (VapMec) performed well when the simulated values of pressures and temperatures were compared with the values measured during field tests. The newly developed VapMec model was incorporated in the LinVap-3 simulator that constitutes an engineering supporting tool for steam injection wells operated by Petrobras. 23 refs., 7 tabs., 6 figs.

  7. The milestone of membrane protein research:Nobel Prize in Chemistry for 2003

    Institute of Scientific and Technical Information of China (English)

    ZHAO Wenlong; SUI Senfang

    2004-01-01

    @@ The Nobel Prize in Chemistry for 2003 was awarded to two biologists, Peter Agre in Johns Hopkins School of Medicine and Roderick MacKinnon from Howard Hughes Medical Institute in Rockefeller University, who have made fundamental discoveries concerning channels in cell membranes. Peter Agre discovered and characterized the first water channel protein and Roderick MacKinnon mainly elucidated the structural and mechanistic basis for potassium channels.

  8. Gold-catalyzed formation of heterocycles - an enabling new technology for medicinal chemistry.

    Science.gov (United States)

    Shen, Hong C; Graham, Thomas H

    2013-01-01

    Gold-catalyzed transformations allow efficient access to a wide scope of heterocyclic structures that serve as building blocks and pharmacophores in medicinal chemistry. Compared with other transition metal and Lewis acid catalysis, gold catalysis presents mechanistic divergence, excellent functional group tolerance and/or operational advantages. Emergent applications of gold catalysis have played a key role in the synthesis of biologically active molecules including a drug candidate.

  9. Oxide-ion and proton conducting electrolyte materials for clean energy applications: structural and mechanistic features.

    Science.gov (United States)

    Malavasi, Lorenzo; Fisher, Craig A J; Islam, M Saiful

    2010-11-01

    This critical review presents an overview of the various classes of oxide materials exhibiting fast oxide-ion or proton conductivity for use as solid electrolytes in clean energy applications such as solid oxide fuel cells. Emphasis is placed on the relationship between structural and mechanistic features of the crystalline materials and their ion conduction properties. After describing well-established classes such as fluorite- and perovskite-based oxides, new materials and structure-types are presented. These include a variety of molybdate, gallate, apatite silicate/germanate and niobate systems, many of which contain flexible structural networks, and exhibit different defect properties and transport mechanisms to the conventional materials. It is concluded that the rich chemistry of these important systems provides diverse possibilities for developing superior ionic conductors for use as solid electrolytes in fuel cells and related applications. In most cases, a greater atomic-level understanding of the structures, defects and conduction mechanisms is achieved through a combination of experimental and computational techniques (217 references).

  10. Simple boron removal from seawater by using polyols as complexing agents: A computational mechanistic study

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min-Kyung; Eom, Ki Heon; Lim, Jun-Heok; Lee, Jea-Keun; Lee, Ju Dong; Won, Yong Sun [Pukyong National University, Busan (Korea, Republic of)

    2015-11-15

    The complexation of boric acid (B(OH){sub 3}), the primary form of aqueous boron at moderate pH, with polyols is proposed and mechanistically studied as an efficient way to improve membrane processes such as reverse osmosis (RO) for removing boron in seawater by increasing the size of aqueous boron compounds. Computational chemistry based on the density functional theory (DFT) was used to manifest the reaction pathways of the complexation of B(OH){sub 3} with various polyols such as glycerol, xylitol, and mannitol. The reaction energies were calculated as −80.6, −98.1, and −87.2 kcal/mol for glycerol, xylitol, and mannitol, respectively, indicating that xylitol is the most thermodynamically favorable for the complexation with B(OH){sub 3}. Moreover, the 1 : 2 molar ratio of B(OH)3 to polyol was found to be more favorable than the ratio of 1 : 1 for the complexation. Meanwhile, latest lab-scale actual RO experiments successfully supported our computational prediction that 2 moles of xylitol are the most effective as the complexing agent for 1 mole of B(OH){sub 3} in aqueous solution.

  11. Molecular Targeting of Proteins by l-Homocysteine: Mechanistic Implications for Vascular Disease

    Science.gov (United States)

    Glushchenko, Alla V.; Jacobsen, Donald W.

    2010-01-01

    Hyperhomocysteinemia is an independent risk factor for cardiovascular disease, complications of pregnancy, cognitive impairment, and osteoporosis. That elevated homocysteine leads to vascular dysfunction may be the linking factor between these apparently unrelated pathologies. Although a growing body of evidence suggests that homocysteine plays a causal role in atherogenesis, specific mechanisms to explain the underlying pathogenesis have remained elusive. This review focuses on chemistry unique to the homocysteine molecule to explain its inherent cytotoxicity. Thus, the high pKa of the sulfhydryl group (pKa, 10.0) of homocysteine underlies its ability to form stable disulfide bonds with protein cysteine residues, and in the process, alters or impairs the function of the protein. Studies in this laboratory have identified albumin, fibronectin, transthyretin, and metallothionein as targets for homocysteinylation. In the case of albumin, the mechanism of targeting has been elucidated. Homocysteinylation of the cysteine residues of fibronectin impairs its ability to bind to fibrin. Homocysteinylation of the cysteine residues of metallothionein disrupts zinc binding by the protein and abrogates inherent superoxide dismutase activity. Thus, S-homocysteinylation of protein cysteine residues may explain mechanistically the cytotoxicity of elevated l-homocysteine. PMID:17760510

  12. Impacts of mechanistic changes on HOx formation and recycling in the oxidation of isoprene

    Directory of Open Access Journals (Sweden)

    R. G. Derwent

    2010-09-01

    the mechanism with the reported parameters cannot be fully reconciled with atmospheric observations and existing laboratory data without some degree of parameter refinement and optimisation which would probably include a reduction in the peroxy radical isomerisation rates and a consequent reduction in the OH enhancement propensity. However, an order of magntitude reduction in the isomerisation rates is still found to yield notable enhancements in OH concentrations of up to a factor of about 2, with the maximum impact at the low end of the considered NOx range. A parameterized representation of the mechanistic changes is optimized and implemented into a reduced variant of the Common Representative Intermediates mechanism (CRI v2-R5, for use in the STOCHEM global chemistry-transport model. The impacts of the modified chemistry in the global model are shown to be consistent with those observed in the box model sensitivity studies, and the results are illustrated and discussed with a particular focus on the tropical forested regions of the Amazon and Borneo where unexpectedly elevated concentrations of OH have recently been reported.

  13. Origins of the classical gene concept, 1900-1950: genetics, mechanistic, philosophy, and the capitalization of agriculture.

    Science.gov (United States)

    Allen, Garland E

    2014-01-01

    In the period of "classical genetics" (roughly 1915-950), the common view of the gene was mechanistic--hat is, genes were seen as individual, atomistic units, as material components of the chromosomes. Although it was recognized early on that genes could interact and influence each other's expression, they were still regarded as individually functioning units, much like the chemists' atoms or molecules. Although geneticists in particular knew the story was more complex, the atomistic gene remained the central view for a variety of reasons. It fit the growing philosophy of mechanistic materialism in the life sciences, as biologists tried to make their field more quantitative,rigorous, and predictive, like physics and chemistry. Conceptually and pedagogically, it provided a simple way to depict genes (as beads on a string) that fit with the exciting new work on chromosomal mapping. The atomistic gene also fit well with the increasing drive to move capital into agriculture, both for potential patenting purposes and for ease of experimental manipulation and prediction. It is the latter point that the present essay explores most thoroughly. The rise of agriculture as an industrialized process provided a context and material support that fueled much of the rapid growth of genetics in the first half of the 20th century.

  14. Bioinorganics: synthetic growth factors for bone regeneration

    NARCIS (Netherlands)

    Tahmasebi Birgani, Z.

    2016-01-01

    Bone tissue is naturally able to regenerate when damaged. However, in many large defects caused by fractures due to aging or osteoporosis, trauma, tumor removal, etc., the natural regenerative ability of bone is not sufficient to fully heal the defect. In such cases, a graft is required to support t

  15. Chemistry beyond positivism.

    Science.gov (United States)

    Brandt, Werner W

    2003-05-01

    Chemistry is often thought to be quite factual, and therefore might be considered close to the "positivist" ideal of a value-free science. A closer look, however, reveals that the field is coupled to the invisible realm of values, meanings, and purpose in various ways, and chemists interact with that realm loosely and unevenly. Tacit knowledge is one important locus of such interactions. We are concerned in this essay with two questions. What is the nature of the knowledge when we are in the early stages of discovery? and In what ways does the hidden reality we are seeking affect our search for an understanding of it? The first question is partly answered by Polanyi's theory of tacit knowledge, while the second one leads us to realize the limitations of our language when discussing "reality"-or certain chemical experimental results. A strictly positivist approach is of little use, but so is the opposite, the complete disregard of facts. The contrast between positivism and non-formulable aspects of scientific reasoning amounts to a paradox that needs to be analyzed and can lead to a "connected" chemistry. This in turn resembles networks described by Schweber and is more concerned than the chemistry "as it is" with aspects such as the image of chemistry, the challenges chemists face as citizens, and chemistry in liberal education.

  16. Mathematics for physical chemistry

    CERN Document Server

    Mortimer, Robert G

    2005-01-01

    Mathematics for Physical Chemistry, Third Edition, is the ideal text for students and physical chemists who want to sharpen their mathematics skills. It can help prepare the reader for an undergraduate course, serve as a supplementary text for use during a course, or serve as a reference for graduate students and practicing chemists. The text concentrates on applications instead of theory, and, although the emphasis is on physical chemistry, it can also be useful in general chemistry courses. The Third Edition includes new exercises in each chapter that provide practice in a technique immediately after discussion or example and encourage self-study. The first ten chapters are constructed around a sequence of mathematical topics, with a gradual progression into more advanced material. The final chapter discusses mathematical topics needed in the analysis of experimental data.* Numerous examples and problems interspersed throughout the presentations * Each extensive chapter contains a preview, objectives, and ...

  17. Uranium triamidoamine chemistry.

    Science.gov (United States)

    Gardner, Benedict M; Liddle, Stephen T

    2015-07-01

    Triamidoamine (Tren) complexes of the p- and d-block elements have been well-studied, and they display a diverse array of chemistry of academic, industrial and biological significance. Such in-depth investigations are not as widespread for Tren complexes of uranium, despite the general drive to better understand the chemical behaviour of uranium by virtue of its fundamental position within the nuclear sector. However, the chemistry of Tren-uranium complexes is characterised by the ability to stabilise otherwise reactive, multiply bonded main group donor atom ligands, construct uranium-metal bonds, promote small molecule activation, and support single molecule magnetism, all of which exploit the steric, electronic, thermodynamic and kinetic features of the Tren ligand system. This Feature Article presents a current account of the chemistry of Tren-uranium complexes.

  18. Air Composition and Chemistry

    Science.gov (United States)

    Brimblecombe, Peter

    1996-01-01

    This book is about the atmosphere and humanity's influence on it. For this new edition, Brimblecombe has rewritten and updated much of the book. In the early chapters, he discusses the geochemical, biological and maritime sources of the trace gases. Next, he examines the chemistry of atmospheric gases, suspended particles, and rainfall. After dealing with the natural atmosphere, he examines the sources of air pollution and its effects, with all scenarios updated from the last edition. Scenarios include decline in health, damage to plants and animals, indoor pollution, and acid rain. The final chapters, also revised, are concerned with the chemistry and evolution of the atmospheres of the planets of the solar system. Students with an interest in chemistry and the environmental sciences will find this book highly valuable.

  19. Reaction chemistry of cerium

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-01-01

    It is truly ironic that a synthetic organic chemist likely has far greater knowledge of the reaction chemistry of cerium(IV) than an inorganic colleague. Cerium(IV) reagents have long since been employed as oxidants in effecting a wide variety of organic transformations. Conversely, prior to the late 1980s, the number of well characterized cerium(IV) complexes did not extend past a handful of known species. Though in many other areas, interest in the molecular chemistry of the 4f-elements has undergone an explosive growth over the last twenty years, the chemistry of cerium(IV) has for the most part been overlooked. This report describes reactions of cerium complexes and structure.

  20. Reaction chemistry of cerium

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-01-01

    It is truly ironic that a synthetic organic chemist likely has far greater knowledge of the reaction chemistry of cerium(IV) than an inorganic colleague. Cerium(IV) reagents have long since been employed as oxidants in effecting a wide variety of organic transformations. Conversely, prior to the late 1980s, the number of well characterized cerium(IV) complexes did not extend past a handful of known species. Though in many other areas, interest in the molecular chemistry of the 4f-elements has undergone an explosive growth over the last twenty years, the chemistry of cerium(IV) has for the most part been overlooked. This report describes reactions of cerium complexes and structure.

  1. Spins in chemistry

    CERN Document Server

    McWeeny, Roy

    2004-01-01

    Originally delivered as a series of lectures, this volume systematically traces the evolution of the ""spin"" concept from its role in quantum mechanics to its assimilation into the field of chemistry. Author Roy McWeeny presents an in-depth illustration of the deductive methods of quantum theory and their application to spins in chemistry, following the path from the earliest concepts to the sophisticated physical methods employed in the investigation of molecular structure and properties. Starting with the origin and development of the spin concept, the text advances to an examination of sp

  2. Chemistry in microelectronics

    CERN Document Server

    Le Tiec, Yannick

    2013-01-01

    Microelectronics is a complex world where many sciences need to collaborate to create nano-objects: we need expertise in electronics, microelectronics, physics, optics and mechanics also crossing into chemistry, electrochemistry, as well as biology, biochemistry and medicine. Chemistry is involved in many fields from materials, chemicals, gases, liquids or salts, the basics of reactions and equilibrium, to the optimized cleaning of surfaces and selective etching of specific layers. In addition, over recent decades, the size of the transistors has been drastically reduced while the functionalit

  3. The philosophy of chemistry.

    Science.gov (United States)

    Schummer, Joachim

    2003-03-01

    Although chemistry is by far the largest scientific discipline according to any quantitative measure, it had, until recently, been virtually ignored by professional philosophers of science. They left both a vacuum and a one-sided picture of science tailored to physics. Since the early 1990s, the situation has changed drastically, such that philosophy of chemistry is now one of the most flourishing fields in the philosophy of science, like the philosophy of biology that emerged in the 1970s. This article narrates the development and provides a survey of the main topics and trends.

  4. Chemistry WebBook

    Science.gov (United States)

    SRD 69 NIST Chemistry WebBook (Web, free access)   The NIST Chemistry WebBook contains: Thermochemical data for over 7000 organic and small inorganic compounds; thermochemistry data for over 8000 reactions; IR spectra for over 16,000 compounds; mass spectra for over 33,000 compounds; UV/Vis spectra for over 1600 compounds; electronic and vibrational spectra for over 5000 compounds; constants of diatomic molecules(spectroscopic data) for over 600 compounds; ion energetics data for over 16,000 compounds; thermophysical property data for 74 fluids.

  5. Chemistry and lithography

    CERN Document Server

    Okoroanyanwu, Uzodinma

    2011-01-01

    This is a unique book, combining chemistry and physics with technology and history in a way that is both enlightening and lively. No other book in the field of lithography has as much breadth. Highly recommended for anyone interested in the broad application of chemistry to lithography. --Chris Mack, Gentleman Scientist. This book provides a comprehensive treatment of the chemical phenomena in lithography in a manner that is accessible to a wide readership. The book presents topics on the optical and charged particle physics practiced in lithography, with a broader view of how the marriage bet

  6. The chemistry of silicon

    CERN Document Server

    Rochow, E G; Emeléus, H J; Nyholm, Ronald

    1975-01-01

    Pergamon Texts in Organic Chemistry, Volume 9: The Chemistry of Silicon presents information essential in understanding the chemical properties of silicon. The book first covers the fundamental aspects of silicon, such as its nuclear, physical, and chemical properties. The text also details the history of silicon, its occurrence and distribution, and applications. Next, the selection enumerates the compounds and complexes of silicon, along with organosilicon compounds. The text will be of great interest to chemists and chemical engineers. Other researchers working on research study involving s

  7. Dynamic Combinatorial Chemistry

    DEFF Research Database (Denmark)

    Lisbjerg, Micke

    This thesis is divided into seven chapters, which can all be read individually. The first chapter, however, contains a general introduction to the chemistry used in the remaining six chapters, and it is therefore recommended to read chapter one before reading the other chapters. Chapter 1...... is a general introductory chapter for the whole thesis. The history and concepts of dynamic combinatorial chemistry are described, as are some of the new and intriguing results recently obtained. Finally, the properties of a broad range of hexameric macrocycles are described in detail. Chapter 2 gives...

  8. Dynamic Combinatorial Chemistry

    DEFF Research Database (Denmark)

    Lisbjerg, Micke

    This thesis is divided into seven chapters, which can all be read individually. The first chapter, however, contains a general introduction to the chemistry used in the remaining six chapters, and it is therefore recommended to read chapter one before reading the other chapters. Chapter 1...... is a general introductory chapter for the whole thesis. The history and concepts of dynamic combinatorial chemistry are described, as are some of the new and intriguing results recently obtained. Finally, the properties of a broad range of hexameric macrocycles are described in detail. Chapter 2 gives...

  9. Solvent effects in chemistry

    CERN Document Server

    Buncel, Erwin

    2015-01-01

    This book introduces the concepts, theory and experimental knowledge concerning solvent effects on the rate and equilibrium of chemical reactions of all kinds.  It begins with basic thermodynamics and kinetics, building on this foundation to demonstrate how a more detailed understanding of these effects may be used to aid in determination of reaction mechanisms, and to aid in planning syntheses. Consideration is given to theoretical calculations (quantum chemistry, molecular dynamics, etc.), to statistical methods (chemometrics), and to modern day concerns such as ""green"" chemistry, where ut

  10. Progress in physical chemistry

    CERN Document Server

    Hempelmann, Rolf

    2008-01-01

    Progress in Physical Chemistry is a collection of recent ""Review Articles"" published in the ""Zeitschrift für Physikalische Chemie"". The second volume of Progress in Physical Chemistry is a collection of thematically closely related minireview articles written by the members of the Collaborative Research Centre (SFB) 277 of the German Research Foundation (DFG). These articles are based on twelve years of intense coordinated research efforts. Central topics are the synthesis and the characterization of interface-dominated, i.e. nanostructured materials, mainly in the solid state but also as

  11. Industrial Chemistry Option in MSc Studies in Chemistry.

    Science.gov (United States)

    Shani, Arnon

    1982-01-01

    Discusses the rationale for and development of an industrial chemistry program in chemistry at Ben-Gurion University of the Negev in Israel. Includes an outline of the recommended 2-year curriculum and list of courses in this industrial chemistry option leading to a master of science degree. (Author/JN)

  12. Real World of Industrial Chemistry: Industrial Chemistry Bibliography.

    Science.gov (United States)

    Marmor, Solomon

    1985-01-01

    Presented is a bibliography of articles published in the "Journal of Chemical Education" (1968-1983) which focused on industrial chemistry. Items are listed under these headings: real world of industrial chemistry; industrial notes; subject matter articles; industrial chemistry experiments/demonstrations; academic-industrial interface;…

  13. Turkish Prospective Chemistry Teachers' Beliefs about Chemistry Teaching

    Science.gov (United States)

    Boz, Yezdan; Uzuntiryaki, Esen

    2006-01-01

    In order to study the beliefs of Turkish prospective chemistry teachers about teaching chemistry, semi-structured interviews were conducted with 12 prospective teachers. Analysis of the interviews revealed that most of the prospective teachers held intermediate (transition between constructivist and traditional) beliefs about chemistry teaching.…

  14. Is Chemistry Attractive for Pupils? Czech Pupils' Perception of Chemistry

    Science.gov (United States)

    Kubiatko, Milan

    2015-01-01

    Chemistry is an important subject due to understanding the composition and structure of the things around us. The main aim of the study was to find out the perception of chemistry by lower secondary school pupils. The partial aims were to find out the influence of gender, year of study and favorite subject on the perception of chemistry. The…

  15. Advanced Reach Tool (ART): development of the mechanistic model.

    Science.gov (United States)

    Fransman, Wouter; Van Tongeren, Martie; Cherrie, John W; Tischer, Martin; Schneider, Thomas; Schinkel, Jody; Kromhout, Hans; Warren, Nick; Goede, Henk; Tielemans, Erik

    2011-11-01

    This paper describes the development of the mechanistic model within a collaborative project, referred to as the Advanced REACH Tool (ART) project, to develop a tool to model inhalation exposure for workers sharing similar operational conditions across different industries and locations in Europe. The ART mechanistic model is based on a conceptual framework that adopts a source receptor approach, which describes the transport of a contaminant from the source to the receptor and defines seven independent principal modifying factors: substance emission potential, activity emission potential, localized controls, segregation, personal enclosure, surface contamination, and dispersion. ART currently differentiates between three different exposure types: vapours, mists, and dust (fumes, fibres, and gases are presently excluded). Various sources were used to assign numerical values to the multipliers to each modifying factor. The evidence used to underpin this assessment procedure was based on chemical and physical laws. In addition, empirical data obtained from literature were used. Where this was not possible, expert elicitation was applied for the assessment procedure. Multipliers for all modifying factors were peer reviewed by leading experts from industry, research institutes, and public authorities across the globe. In addition, several workshops with experts were organized to discuss the proposed exposure multipliers. The mechanistic model is a central part of the ART tool and with advancing knowledge on exposure, determinants will require updates and refinements on a continuous basis, such as the effect of worker behaviour on personal exposure, 'best practice' values that describe the maximum achievable effectiveness of control measures, the intrinsic emission potential of various solid objects (e.g. metal, glass, plastics, etc.), and extending the applicability domain to certain types of exposures (e.g. gas, fume, and fibre exposure).

  16. Mechanistic species distribution modeling reveals a niche shift during invasion.

    Science.gov (United States)

    Chapman, Daniel S; Scalone, Romain; Štefanić, Edita; Bullock, James M

    2017-06-01

    Niche shifts of nonnative plants can occur when they colonize novel climatic conditions. However, the mechanistic basis for niche shifts during invasion is poorly understood and has rarely been captured within species distribution models. We quantified the consequence of between-population variation in phenology for invasion of common ragweed (Ambrosia artemisiifolia L.) across Europe. Ragweed is of serious concern because of its harmful effects as a crop weed and because of its impact on public health as a major aeroallergen. We developed a forward mechanistic species distribution model based on responses of ragweed development rates to temperature and photoperiod. The model was parameterized and validated from the literature and by reanalyzing data from a reciprocal common garden experiment in which native and invasive populations were grown within and beyond the current invaded range. It could therefore accommodate between-population variation in the physiological requirements for flowering, and predict the potentially invaded ranges of individual populations. Northern-origin populations that were established outside the generally accepted climate envelope of the species had lower thermal requirements for bud development, suggesting local adaptation of phenology had occurred during the invasion. The model predicts that this will extend the potentially invaded range northward and increase the average suitability across Europe by 90% in the current climate and 20% in the future climate. Therefore, trait variation observed at the population scale can trigger a climatic niche shift at the biogeographic scale. For ragweed, earlier flowering phenology in established northern populations could allow the species to spread beyond its current invasive range, substantially increasing its risk to agriculture and public health. Mechanistic species distribution models offer the possibility to represent niche shifts by varying the traits and niche responses of individual

  17. Development of Improved Mechanistic Deterioration Models for Flexible Pavements

    DEFF Research Database (Denmark)

    Ullidtz, Per; Ertman, Hans Larsen

    1998-01-01

    The paper describes a pilot study in Denmark with the main objective of developing improved mechanistic deterioration models for flexible pavements based on an accelerated full scale test on an instrumented pavement in the Danish Road Tessting Machine. The study was the first in "International...... Pavement Subgrade Performance Study" sponsored by the Federal Highway Administration (FHWA), USA. The paper describes in detail the data analysis and the resulting models for rutting, roughness, and a model for the plastic strain in the subgrade.The reader will get an understanding of the work needed...

  18. Organometallic Reactions Development, Mechanistic Studies and Synthetic Applications

    DEFF Research Database (Denmark)

    Dam, Johan Hygum

    a mechanistic study of the Barbier allylation of benzaldehydes with six different metals (Zn, In, Sb, Sn, Bi and Mg) in aqueous media. The mechanism of the allylation was investigated by means of Hammett plots and the secondary deuterium kinetic isotope effect. It was found that all metals except magnesium form...... a discrete allylmetal species and the rate-determining step is the polar addition to the carbonyl. For magnesium data indicates that the selectivity-determining step is generation of the radical anion of the benzaldehyde. The second project discusses a concise and enantiopure total synthesis...

  19. Top Down Chemistry Versus Bottom up Chemistry

    Science.gov (United States)

    Oka, Takeshi; Witt, Adolf N.

    2016-06-01

    The idea of interstellar top down chemistry (TDC), in which molecules are produced from decomposition of larger molecules and dust in contrast to ordinary bottom up chemistry (BUC) in which molecules are produced synthetically from smaller molecules and atoms in the ISM, has been proposed in the chemistry of PAH and carbon chain molecules both for diffusea,c and dense cloudsb,d. A simple and natural idea, it must have occurred to many people and has been in the air for sometime. The validity of this hypothesis is apparent for diffuse clouds in view of the observed low abundance of small molecules and its rapid decrease with molecular size on the one hand and the high column densities of large carbon molecules demonstrated by the many intense diffuse interstellar bands (DIBs) on the other. Recent identification of C60^+ as the carrier of 5 near infrared DIBs with a high column density of 2×1013 cm-2 by Maier and others confirms the TDC. This means that the large molecules and dust produced in the high density high temperature environment of circumstellar envelopes are sufficiently stable to survive decompositions due to stellar UV radiaiton, cosmic rays, C-shocks etc. for a long time (≥ 10^7 year) of their migration to diffuse clouds and seems to disagree with the consensus in the field of interstellar grains. The stability of molecules and aggregates in the diffuse interstellar medium will be discussed. Duley, W. W. 2006, Faraday Discuss. 133, 415 Zhen,J., Castellanos, P., Paardekooper, D. M., Linnartz, H., Tielens, A. G. G. M. 2014, ApJL, 797, L30 Huang, J., Oka, T. 2015, Mol. Phys. 113, 2159 Guzmán, V. V., Pety, J., Goicoechea, J. R., Gerin, M., Roueff, E., Gratier, P., Öberg, K. I. 2015, ApJL, 800, L33 L. Ziurys has sent us many papers beginning Ziurys, L. M. 2006, PNAS 103, 12274 indicating she had long been a proponent of the idea. Campbell, E. K., Holz, M., Maier, J. P., Gerlich, D., Walker, G. A. H., Bohlender, D, 2016, ApJ, in press Draine, B. T. 2003

  20. Polymer Chemistry in High School.

    Science.gov (United States)

    Stucki, Roger

    1984-01-01

    Discusses why polymer chemistry should be added to the general chemistry curriculum and what topics are appropriate (listing traditional with related polymer topics). Also discusses when and how these topics should be taught. (JN)

  1. Get Cooking with Chemistry!

    Science.gov (United States)

    American Chemical Society, Washington, DC.

    This book presents science activities investigating the chemical changes and reactions with powders that are used in baking. Activities include: (1) Mystery Powders; (2) Find the Fizz: Discover the Secret of Baking Powder; and (3) A Feast for Yeast and Cheese: Behold the Power of Chemistry. (YDS)

  2. Chemistry Is Fun.

    Science.gov (United States)

    Yaniv, D; And Others

    1982-01-01

    Encouraging scientific thinking through open-ended experiments, allowing students access to common chemical instrumentation, and introduction to laboratory techniques are goals of a high school science laboratory program. Course content (general, inorganic, and organic chemistry), limitations, and course evaluation are discussed. (Author/JN)

  3. Microscale Gas Chemistry

    Science.gov (United States)

    Mattson, Bruce; Anderson, Michael P.

    2011-01-01

    The development of syringes having free movement while remaining gas-tight enabled methods in chemistry to be changed. Successfully containing and measuring volumes of gas without the need to trap them using liquids made it possible to work with smaller quantities. The invention of the LuerLok syringe cap also allowed the gas to be stored for a…

  4. Chemistry and Heritage

    Science.gov (United States)

    Vittoria Barbarulo, Maria

    2014-05-01

    Chemistry is the central science, as it touches every aspect of the society we live in and it is intertwined with many aspects of our culture; in particular, the strong link between Chemistry and Archaeology and Art History is being explored, offering a penetrating insight into an area of growing interest from an educational point of view. A series of vital and vibrant examples (i.e., ancient bronzes composition, colour changes due to natural pigment decomposition, marble degradation) has been proposed, on one hand, to improve student understanding of the relationship between cultural and scientific issues arising from the examination, the conservation, and the maintenance of cultural Heritage, on the other, to illustrate the role of the underlying Chemistry. In some case studies, a survey of the most relevant atmospheric factors, which are involved in the deterioration mechanisms, has also been presented to the students. First-hand laboratory experiences have been providing an invaluable means of discovering the full and varied world of Chemistry. Furthermore, the promotion of an interdisciplinary investigation of a famous painting or fresco, involving the study of its nature and significance, the definition of its historical context, any related literature, the chemical knowledge of the materials used, may be an excellent occasion to experiment the Content and Language Integrated Learning (CLIL). The aim of this approach is to convey the important message that everyone has the responsibility to care for and preserve Heritage for the benefit of present and future generations.

  5. The Chemistry of Griseofulvin

    DEFF Research Database (Denmark)

    Petersen, Asger Bjørn; Rønnest, Mads Holger; Larsen, Thomas Ostenfeld;

    2014-01-01

    Specific synthetic routes are presented in schemes to illustrate the chemistry, and the analogs are presented in a table format to give an accessible overview of the structures. Several patents have been published regarding the properties of griseofulvin and its derivatives including synthesis...

  6. Industrial chemistry; Chimie industrielle

    Energy Technology Data Exchange (ETDEWEB)

    Perrin, R. [Universite Claude Bernard, UFR, 69 - Lyon (France); Scharff, J.P. [Universite Claude Bernard, 69 - Lyon (France)]|[Ecole Superieure de Chimie, Physique et Electronique CPE, 69 - Lyon (France)

    1997-12-31

    This book takes stock of the main aspects of the industrial chemistry. It presents all the current chemical aspects concerning the preparation of the main inorganic, metallurgical, organic products and polymers. Are included all the problems related to raw materials, energy, reactions optimization, chemical risk, environment and cleansing, patent rights. It is devoted to students, technical men and engineers. (O.M.) 239 refs.

  7. Nobel Prize in Chemistry

    Science.gov (United States)

    2000-01-01

    The Royal Swedish Academy has awarded the 1999 Nobel Prize in Chemistry to Ahmed H. Zewail (California Institute of Technology, Pasadena, CA) "for his studies of the transition states of chemical reactions using femtosecond spectroscopy". Zewail's work has taken the study of the rates and mechanisms of chemical reactions to the ultimate degree of detail - the time scale of bond making and bond breaking.

  8. Analytical Chemistry Laboratory

    Science.gov (United States)

    Anderson, Mark

    2013-01-01

    The Analytical Chemistry and Material Development Group maintains a capability in chemical analysis, materials R&D failure analysis and contamination control. The uniquely qualified staff and facility support the needs of flight projects, science instrument development and various technical tasks, as well as Cal Tech.

  9. Supramolecular analytical chemistry.

    Science.gov (United States)

    Anslyn, Eric V

    2007-02-02

    A large fraction of the field of supramolecular chemistry has focused in previous decades upon the study and use of synthetic receptors as a means of mimicking natural receptors. Recently, the demand for synthetic receptors is rapidly increasing within the analytical sciences. These classes of receptors are finding uses in simple indicator chemistry, cellular imaging, and enantiomeric excess analysis, while also being involved in various truly practical assays of bodily fluids. Moreover, one of the most promising areas for the use of synthetic receptors is in the arena of differential sensing. Although many synthetic receptors have been shown to yield exquisite selectivities, in general, this class of receptor suffers from cross-reactivities. Yet, cross-reactivity is an attribute that is crucial to the success of differential sensing schemes. Therefore, both selective and nonselective synthetic receptors are finding uses in analytical applications. Hence, a field of chemistry that herein is entitled "Supramolecular Analytical Chemistry" is emerging, and is predicted to undergo increasingly rapid growth in the near future.

  10. Water Chemistry Laboratory Manual.

    Science.gov (United States)

    Jenkins, David; And Others

    This manual of laboratory experiments in water chemistry serves a dual function of illustrating fundamental chemical principles of dilute aqueous systems and of providing the student with some familiarity with the chemical measurements commonly used in water and wastewater analysis. Experiments are grouped in categories on the basis of similar…

  11. Supramolecular Chemistry in Water

    NARCIS (Netherlands)

    Oshovsky, Gennady V.; Reinhoudt, David N.; Verboom, Willem

    2007-01-01

    Supramolecular chemistry in water is a constantly growing research area because noncovalent interactions in aqueous media are important for obtaining a better understanding and control of the major processes in nature. This Review offers an overview of recent advances in the area of water-soluble sy

  12. Chemistry and Popperism.

    Science.gov (United States)

    Akeroyd, F. Michael

    1984-01-01

    Discusses the relationship of Karl Popper's theories to chemistry, examining scientific statements and verisimilitude (which indicates that newer theories should have a higher degree of truth content compared with older theories). Also provides examples illustrating the use of Agassi's criteria for assessing currently fashionable theories. (JN)

  13. Green chemistry metrics

    Science.gov (United States)

    Synthetic chemists have always had an objective to achieve reliable and high-yielding routes to the syntheses of targeted molecules. The importance of minimal waste generation has emphasized the use of green chemistry principles and sustainable development. These directions lead ...

  14. Computational chemistry at Janssen.

    Science.gov (United States)

    van Vlijmen, Herman; Desjarlais, Renee L; Mirzadegan, Tara

    2016-12-19

    Computer-aided drug discovery activities at Janssen are carried out by scientists in the Computational Chemistry group of the Discovery Sciences organization. This perspective gives an overview of the organizational and operational structure, the science, internal and external collaborations, and the impact of the group on Drug Discovery at Janssen.

  15. Chemistry Education and Mythology

    Directory of Open Access Journals (Sweden)

    Sule Aycan

    2005-01-01

    Full Text Available This study aimed to investigate the effect of mythological story in teaching chemistry. To this end the students in the class were divided into two homogenous groups. While the first group was thought in a traditional way, using a mythological story thought the second group. The story used was based on a Mountain just opposite the faculty.

  16. Forensic Chemistry Training

    Directory of Open Access Journals (Sweden)

    Zuhal GERÇEK

    2012-01-01

    Full Text Available Increasing the types of terrorism and crime nowadays, the importance of the forensic sciences can be bett er understood. Forensic science is the application of the wide spectrum of science to answer the question of legal system. It contains the application of the principles, techniques and methods of basic sciences and its main aim is the determination of the physical facts which are important in legal situations. Forensic chemistry is the branch of chemistry which performs the chemical analysis of evidences that used in the courts. Forensic chemist is the professional chemist who analyzes the evidences from crime scene and reaches a result by application of tests. Th us, they have to have a special education. In forensic laboratories candidates who have chemistry/biochemistry undergraduate degree and took biology and forensic chemistry lectures are preferred. It is necessary to design graduate and undergraduate education to train a forensic chemist. Science education should be at the core of the undergraduate education. In addition to this strong laboratory education on both science and forensic science should be given. Th e graduate program of forensic science example should contain forensic science subjects, strong academic lectures on special subjects and research and laboratory components.

  17. Online Organic Chemistry

    Science.gov (United States)

    Janowicz, Philip A.

    2010-01-01

    This is a comprehensive study of the many facets of an entirely online organic chemistry course. Online homework with structure-drawing capabilities was found to be more effective than written homework. Online lecture was found to be just as effective as in-person lecture, and students prefer an online lecture format with shorter Webcasts. Online…

  18. The Chemistry of Griseofulvin

    DEFF Research Database (Denmark)

    Petersen, Asger Bjørn; Rønnest, Mads Holger; Larsen, Thomas Ostenfeld

    2014-01-01

    Specific synthetic routes are presented in schemes to illustrate the chemistry, and the analogs are presented in a table format to give an accessible overview of the structures. Several patents have been published regarding the properties of griseofulvin and its derivatives including synthesis...

  19. Symmetry in chemistry

    CERN Document Server

    Jaffé, Hans H

    1977-01-01

    This book, devoted exclusively to symmetry in chemistry and developed in an essentially nonmathematical way, is a must for students and researchers. Topics include symmetry elements and operations, multiple symmetry operations, multiplication tables and point groups, group theory applications, and crystal symmetry. Extensive appendices provide useful tables.

  20. Evaluating Environmental Chemistry Textbooks.

    Science.gov (United States)

    Hites, Ronald A.

    2001-01-01

    A director of the Indiana University Center for Environmental Science Research reviews textbooks on environmental chemistry. Highlights clear writing, intellectual depth, presence of problem sets covering both the qualitative and quantitative aspects of the material, and full coverage of the topics of concern. Discusses the director's own approach…

  1. Computational chemistry at Janssen

    Science.gov (United States)

    van Vlijmen, Herman; Desjarlais, Renee L.; Mirzadegan, Tara

    2016-12-01

    Computer-aided drug discovery activities at Janssen are carried out by scientists in the Computational Chemistry group of the Discovery Sciences organization. This perspective gives an overview of the organizational and operational structure, the science, internal and external collaborations, and the impact of the group on Drug Discovery at Janssen.

  2. Analytical Chemistry Laboratory

    Science.gov (United States)

    Anderson, Mark

    2013-01-01

    The Analytical Chemistry and Material Development Group maintains a capability in chemical analysis, materials R&D failure analysis and contamination control. The uniquely qualified staff and facility support the needs of flight projects, science instrument development and various technical tasks, as well as Cal Tech.

  3. Array processors in chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Ostlund, N.S.

    1980-01-01

    The field of attached scientific processors (''array processors'') is surveyed, and an attempt is made to indicate their present and possible future use in computational chemistry. The current commercial products from Floating Point Systems, Inc., Datawest Corporation, and CSP, Inc. are discussed.

  4. Online organic chemistry

    Science.gov (United States)

    Janowicz, Philip A.

    This is a comprehensive study of the many facets of an entirely online organic chemistry course. Online homework with structure-drawing capabilities was found to be more effective than written homework. Online lecture was found to be just as effective as in-person lecture, and students prefer an online lecture format with shorter Webcasts. Online office hours were found to be effective, and discussion sessions can be placed online as well. A model was created that explains 36.1% of student performance based on GPA, ACT Math score, grade in previous chemistry course, and attendance at various forms of discussion. Online exams have been created which test problem-solving skills and is instantly gradable. In these exams, students can submit answers until time runs out for different numbers of points. These facets were combined effectively to create an entirely online organic chemistry course which students prefer over the in-person alternative. Lastly, there is a vision for where online organic chemistry is going and what can be done to improve education for all.

  5. Evaluating Environmental Chemistry Textbooks.

    Science.gov (United States)

    Hites, Ronald A.

    2001-01-01

    A director of the Indiana University Center for Environmental Science Research reviews textbooks on environmental chemistry. Highlights clear writing, intellectual depth, presence of problem sets covering both the qualitative and quantitative aspects of the material, and full coverage of the topics of concern. Discusses the director's own approach…

  6. Chemistry in Protoplanetary Disks

    CERN Document Server

    Henning, Thomas

    2013-01-01

    This comprehensive review summarizes our current understanding of the evolution of gas, solids and molecular ices in protoplanetary disks. Key findings related to disk physics and chemistry, both observationally and theoretically, are highlighted. We discuss which molecular probes are used to derive gas temperature, density, ionization state, kinematics, deuterium fractionation, and study organic matter in protoplanetary disks.

  7. systemic chemistry triangle

    African Journals Online (AJOL)

    Temechegn

    This paper describes uses of the systemic chemistry triangle [SCT] in which we get the benefits of both ..... The teachers follows up the following scenario for teaching [Fig.12]:. 1. ... [SATL]: A 10- year's review, AJCE, 1(1) 29-47. 3. Fahmy ...

  8. Mathematical problems for chemistry students

    CERN Document Server

    Pota, Gyorgy

    2011-01-01

    Mathematical Problems for Chemistry Students has been compiled and written (a) to help chemistrystudents in their mathematical studies by providing them with mathematical problems really occurring in chemistry (b) to help practising chemists to activate their applied mathematical skills and (c) to introduce students and specialistsof the chemistry-related fields (physicists, mathematicians, biologists, etc.) intothe world of the chemical applications.Some problems of the collection are mathematical reformulations of those in the standard textbooks of chemistry, others we

  9. Aqueous Solution Chemistry of Plutonium

    Energy Technology Data Exchange (ETDEWEB)

    Clark, David L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-01-28

    Things I have learned working with plutonium: Chemistry of plutonium is complex; Redox equilibria make Pu solution chemistry particularly challenging in the absence of complexing ligands; Understanding this behavior is key to successful Pu chemistry experiments; There is no suitable chemical analog for plutonium.

  10. Industrial Chemistry at Michigan Tech.

    Science.gov (United States)

    Bates, D. K.; Ponter, A. B.

    1985-01-01

    Discusses factors leading to the development of a four-year industrial chemistry program at Michigan Technological University and provides details of its structure. Includes brief descriptions of courses required in industrial chemistry but not in the traditional chemistry program and list of optional courses. (JN)

  11. Division of Analytical Chemistry, 1998

    DEFF Research Database (Denmark)

    Hansen, Elo Harald

    1999-01-01

    The article recounts the 1998 activities of the Division of Analytical Chemistry (DAC- formerly the Working Party on Analytical Chemistry, WPAC), which body is a division of the Federation of European Chemical Societies (FECS). Elo Harald Hansen is the Danish delegate, representing The Danish...... Chemical Society/The Society for Analytical Chemistry....

  12. New web-based applications for mechanistic case diagramming

    Directory of Open Access Journals (Sweden)

    Fred R. Dee

    2014-07-01

    Full Text Available The goal of mechanistic case diagraming (MCD is to provide students with more in-depth understanding of cause and effect relationships and basic mechanistic pathways in medicine. This will enable them to better explain how observed clinical findings develop from preceding pathogenic and pathophysiological events. The pedagogic function of MCD is in relating risk factors, disease entities and morphology, signs and symptoms, and test and procedure findings in a specific case scenario with etiologic pathogenic and pathophysiological sequences within a flow diagram. In this paper, we describe the addition of automation and predetermined lists to further develop the original concept of MCD as described by Engelberg in 1992 and Guerrero in 2001. We demonstrate that with these modifications, MCD is effective and efficient in small group case-based teaching for second-year medical students (ratings of ~3.4 on a 4.0 scale. There was also a significant correlation with other measures of competency, with a ‘true’ score correlation of 0.54. A traditional calculation of reliability showed promising results (α =0.47 within a low stakes, ungraded environment. Further, we have demonstrated MCD's potential for use in independent learning and TBL. Future studies are needed to evaluate MCD's potential for use in medium stakes assessment or self-paced independent learning and assessment. MCD may be especially relevant in returning students to the application of basic medical science mechanisms in the clinical years.

  13. Novel catalytic and mechanistic studies on wastewater denitrification with hydrogen.

    Science.gov (United States)

    Theologides, C P; Olympiou, G G; Savva, P G; Pantelidou, N A; Constantinou, B K; Chatziiona, V K; Valanidou, L Y; Piskopianou, C T; Costa, C N

    2014-01-01

    The present work reports up-to-date information regarding the reaction mechanism of the catalytic hydrogenation of nitrates in water media. In the present mechanistic study, an attempt is made, for the first time, to elucidate the crucial role of several catalysts and reaction parameters in the mechanism of the NO(3)(-)/H(2) reaction. Steady-state isotopic transient kinetic analysis (SSITKA) experiments coupled with ex situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were performed on supported Pd-Cu catalysts for the NO(3)(-)/H(2) and NO(3)(-)/H(2)/O(2) reactions. The latter experiments revealed that the formation and surface coverage of various adsorbed active intermediate N-species on the support or Pd/Cu metal surface is significantly favored in the presence of TiO(2) in the support mixture and in the presence of oxygen in the reaction's gaseous feed stream. The differences in the reactivity of these adsorbed N-species, found in the present work, adequately explain the large effect of the chemical composition of the support and the gas feed composition on catalyst behaviour (activity and selectivity). The present study leads to solid mechanistic evidence concerning the presence of a hydrogen spillover process from the metal to the support. Moreover, this study shows that Cu clusters are active sites for the reduction of nitrates to nitrites.

  14. Surgery for malignant gliomas: mechanistic reasoning and slippery statistics.

    Science.gov (United States)

    Mitchell, Patrick; Ellison, David W; Mendelow, A David

    2005-07-01

    Current surgical treatment of malignant gliomas largely depends on mechanistic reasoning and data collected in non-randomised studies. Technological advance has enabled more accurate resection of tumours and preservation of eloquent brain areas but ethical considerations have restricted randomised trials on the efficacy of surgery to one small trial that found a 3 month survival advantage for patients over age 65 years who received surgery and interim analysis of a larger trial. There is an argument for surgery as a palliative measure in patients with symptoms caused by mechanisms that are surgically remediable. Whether there is any survival advantage from surgery in patients other than those with immediately life-threatening, surgically remediable complications, such as raised intracranial pressure, is unclear. The available data show that if such an advantage does exist, it is modest at best. Adjuvant treatments given surgically are being studied. Chemotherapy wafers are the most prominent of the adjuvant treatments but the evidence available is insufficient to recommend their use in routine practice. In this review we examine the prevailing mechanistic model and observational data; we assess how these are applied and the priorities they indicate for future research.

  15. Noncanonical IFN Signaling: Mechanistic Linkage of Genetic and Epigenetic Events

    Directory of Open Access Journals (Sweden)

    Howard M. Johnson

    2016-01-01

    Full Text Available The canonical model of cytokine signaling via the JAK/STAT pathway dominates our view of signal transduction but provides no insight into the significance of the simultaneous presence of activated JAKs and STATs in the nucleus of cells treated with cytokines. Such a mechanistic shortcoming challenges the usefulness of the model in its present form. Focusing on the interferon (IFN cytokines, we have developed a noncanonical model of IFN signaling that naturally connects activated JAKs and STATs at or near response elements of genes that are activated by the IFNs. Specifically, cells treated with IFNγ showed association of activated STAT1α and JAK2 at the GAS element of genes activated by IFNγ. For IFNα treated cells, the association involved activated STAT1α and TYK2 JAK kinase at the ISRE promoter. The power of the noncanonical model is that it provides mechanistic insight into specific gene activation at the level of the associated epigenetics, akin to that of steroid/steroid receptor signaling.

  16. Trichloroethylene: Mechanistic, Epidemiologic and Other Supporting Evidence of Carcinogenic Hazard

    Science.gov (United States)

    Rusyn, Ivan; Chiu, Weihsueh A.; Lash, Lawrence H.; Kromhout, Hans; Hansen, Johnni; Guyton, Kathryn Z.

    2013-01-01

    The chlorinated solvent trichloroethylene (TCE) is a ubiquitous environmental pollutant. The carcinogenic hazard of TCE was the subject of a 2012 evaluation by a Working Group of the International Agency for Research on Cancer (IARC). Information on exposures, relevant data from epidemiologic studies, bioassays in experimental animals, and toxicity and mechanism of action studies was used to conclude that TCE is carcinogenic to humans (Group 1). This article summarizes the key evidence forming the scientific bases for the IARC classification. Exposure to TCE from environmental sources (including from hazardous waste sites and contaminated water) is common throughout the world. While workplace use of TCE has been declining, occupational exposures remain of concern, especially in developing countries. Strongest human evidence is from studies of occupational TCE exposure and kidney cancer. Positive, although less consistent, associations were reported for liver cancer and non-Hodgkin's lymphoma. TCE is carcinogenic at multiple sites in multiple species and strains of experimental animals. The mechanistic evidence includes extensive data on the toxicokinetics and genotoxicity of TCE and its metabolites. Together, available evidence provided a cohesive database supporting the human cancer hazard of TCE, particularly in the kidney. For other target sites of carcinogenicity, mechanistic and other data were found to be more limited. Important sources of susceptibility to TCE toxicity and carcinogenicity were also reviewed by the Working Group. In all, consideration of the multiple evidence streams presented herein informed the IARC conclusions regarding the carcinogenicity of TCE. PMID:23973663

  17. Trichloroethylene: Mechanistic, epidemiologic and other supporting evidence of carcinogenic hazard.

    Science.gov (United States)

    Rusyn, Ivan; Chiu, Weihsueh A; Lash, Lawrence H; Kromhout, Hans; Hansen, Johnni; Guyton, Kathryn Z

    2014-01-01

    The chlorinated solvent trichloroethylene (TCE) is a ubiquitous environmental pollutant. The carcinogenic hazard of TCE was the subject of a 2012 evaluation by a Working Group of the International Agency for Research on Cancer (IARC). Information on exposures, relevant data from epidemiologic studies, bioassays in experimental animals, and toxicity and mechanism of action studies was used to conclude that TCE is carcinogenic to humans (Group 1). This article summarizes the key evidence forming the scientific bases for the IARC classification. Exposure to TCE from environmental sources (including hazardous waste sites and contaminated water) is common throughout the world. While workplace use of TCE has been declining, occupational exposures remain of concern, especially in developing countries. The strongest human evidence is from studies of occupational TCE exposure and kidney cancer. Positive, although less consistent, associations were reported for liver cancer and non-Hodgkin lymphoma. TCE is carcinogenic at multiple sites in multiple species and strains of experimental animals. The mechanistic evidence includes extensive data on the toxicokinetics and genotoxicity of TCE and its metabolites. Together, available evidence provided a cohesive database supporting the human cancer hazard of TCE, particularly in the kidney. For other target sites of carcinogenicity, mechanistic and other data were found to be more limited. Important sources of susceptibility to TCE toxicity and carcinogenicity were also reviewed by the Working Group. In all, consideration of the multiple evidence streams presented herein informed the IARC conclusions regarding the carcinogenicity of TCE.

  18. Splicing in immune cells-mechanistic insights and emerging topics.

    Science.gov (United States)

    Schaub, Annalisa; Glasmacher, Elke

    2017-04-01

    Differential splicing of mRNAs not only enables regulation of gene expression levels, but also ensures a high degree of gene-product diversity. The extent to which splicing of mRNAs is utilized as a mechanism in immune cells has become evident within the last few years. Still, only a few of these mechanisms have been well studied. In this review, we discuss some of the best-understood mechanisms, for instance the differential splicing of CD45 in T cells, as well as immunoglobulin genes in B cells. Beyond that we provide general mechanistic insights on how, when and where this process takes place and discuss the current knowledge regarding these topics in immune cells. We also highlight some of the reported links to immune-related diseases, genome-wide sequencing studies that revealed thousands of differentially spliced transcripts, as well as splicing studies on immune cells that remain mechanistically not fully understood. We thereby display potential emerging topics for future studies centered on splicing mechanisms in immune cells. © The Author 2017. Published by Oxford University Press on behalf of The Japanese Society for Immunology.

  19. Mechanistic and Economical Characteristics of Asphalt Rubber Mixtures

    Directory of Open Access Journals (Sweden)

    Mena I. Souliman

    2016-01-01

    Full Text Available Load associated fatigue cracking is one of the major distress types occurring in flexible pavement systems. Flexural bending beam fatigue laboratory test has been used for several decades and is considered to be an integral part of the new superpave advanced characterization procedure. One of the most significant solutions to prolong the fatigue life for an asphaltic mixture is to utilize flexible materials as rubber. A laboratory testing program was performed on a conventional and Asphalt Rubber- (AR- gap-graded mixtures to investigate the impact of added rubber on the mechanical, mechanistic, and economical attributes of asphaltic mixtures. Strain controlled fatigue tests were conducted according to American Association of State Highway and Transportation Officials (AASHTO procedures. The results from the beam fatigue tests indicated that the AR-gap-graded mixtures would have much longer fatigue life compared with the reference (conventional mixtures. In addition, a mechanistic analysis using 3D-Move software coupled with a cost analysis study based on the fatigue performance on the two mixtures was performed. Overall, analysis showed that AR modified asphalt mixtures exhibited significantly lower cost of pavement per 1000 cycles of fatigue life per mile compared to conventional HMA mixture.

  20. New web-based applications for mechanistic case diagramming

    Science.gov (United States)

    Dee, Fred R.; Haugen, Thomas H.; Kreiter, Clarence D.

    2014-01-01

    The goal of mechanistic case diagraming (MCD) is to provide students with more in-depth understanding of cause and effect relationships and basic mechanistic pathways in medicine. This will enable them to better explain how observed clinical findings develop from preceding pathogenic and pathophysiological events. The pedagogic function of MCD is in relating risk factors, disease entities and morphology, signs and symptoms, and test and procedure findings in a specific case scenario with etiologic pathogenic and pathophysiological sequences within a flow diagram. In this paper, we describe the addition of automation and predetermined lists to further develop the original concept of MCD as described by Engelberg in 1992 and Guerrero in 2001. We demonstrate that with these modifications, MCD is effective and efficient in small group case-based teaching for second-year medical students (ratings of ~3.4 on a 4.0 scale). There was also a significant correlation with other measures of competency, with a ‘true’ score correlation of 0.54. A traditional calculation of reliability showed promising results (α =0.47) within a low stakes, ungraded environment. Further, we have demonstrated MCD's potential for use in independent learning and TBL. Future studies are needed to evaluate MCD's potential for use in medium stakes assessment or self-paced independent learning and assessment. MCD may be especially relevant in returning students to the application of basic medical science mechanisms in the clinical years. PMID:25059836

  1. Examination on Expert Chemistry Teachers’ Secondary School Chemistry Textbook Usage

    Directory of Open Access Journals (Sweden)

    Canan NAKİBOĞLU

    2009-04-01

    Full Text Available The purpose of the study is to determine how chemistry textbooks used by expert chemistry teachers are used during teaching process in secondary education, and to find how prospective chemistry teachers evaluate the situation mentioned. Thus, a project concerned with how expert chemistry teachers use them in their classes was carried out. Based on the research context, an interview that was used to interview with expert chemistry teachers by prospective chemistry teachers was prepared by the author. Next, prospective chemistry teachers were asked to evaluate how expert chemistry teachers used textbooks. The sample group of the study consisted of 21 expert high school chemistry teachers working at schools in Balıkesir and 21 prospective chemistry teachers studying at Education Faculty of Balıkesir University during 2007-2008 academic years. The findings of the study revealed that expert chemistry teachers did not use textbooks during their teaching process while they used them as the sources of problems and exercises at the end of units. Furthermore, it was found that University Entrance Exam (OSS had an effect on how to use the textbooks by teachers.

  2. A review of the electrophilic reaction chemistry involved in covalent DNA binding.

    Science.gov (United States)

    Enoch, S J; Cronin, M T D

    2010-09-01

    The need to assess the ability of a chemical to act as a mutagen or a genotoxic carcinogen (collectively termed genotoxicity) is one of the primary requirements in regulatory toxicology. Several pieces of legislation have led to an increased interest in the use of in silico methods, specifically the formation of chemical categories for the assessment of toxicological endpoints. A key step in the development of chemical categories for genotoxicity is defining the organic chemistry associated with the formation of a covalent bond between DNA and an exogenous chemical. This organic chemistry is typically defined as structural alerts. To this end, this article has reviewed the literature defining the structural alerts associated with covalent DNA binding. Importantly, this review article also details the mechanistic organic chemistry associated with each of the structural alerts. This information is extremely important in terms of meeting regulatory requirements for the acceptance of the chemical category approach. The structural alerts and associated mechanistic chemistry have been incorporated into the Organisation for Economic Co-operation and Development (OECD) (Q)SAR Application Toolbox.

  3. Towards "Bildung"-Oriented Chemistry Education

    Science.gov (United States)

    Sjöström, Jesper

    2013-01-01

    This paper concerns "Bildung"-oriented chemistry education, based on a reflective and critical discourse of chemistry. It is contrasted with the dominant type of chemistry education, based on the mainstream discourse of chemistry. "Bildung"-oriented chemistry education includes not only content knowledge in chemistry, but also…

  4. Toward a mechanistic understanding of patterns in biomineralization and new insights for old dogmas in geological settings (Invited)

    Science.gov (United States)

    Dove, P. M.; Hamm, L.; Giuffre, A. J.; Han, N.; De Yoreo, J. J.

    2013-12-01

    The ability of organisms to mineralize tissues into skeletons and other functional structures is a remarkable achievement of biology. Yet, the physical basis for how macromolecules regulate the placement and onset of mineral formation is not well established. Efforts to understand nucleation onto organic substrates have produced two, seemingly contradictory, lines of thought: The biomineralization community widely assumes the organic matrix promotes nucleation through stereochemical matching to guide the organization of solute ions, while materials synthesis groups use simple binding assays to correlate high binding strength with good promoters of nucleation. This study reconciles the two views and provides a mechanistic explanation for template-directed nucleation by correlating heterogeneous nucleation barriers with crystal-substrate binding free energies. Using surface assembled monolayers (SAM) as simple model systems, we first measure the kinetics of calcite nucleation onto model substrates that present different functional group chemistries (carboxyl, thiol, phosphate, hydroxyl) and conformations (C11, C16 chain lengths). We find rates are substrate-specific and obey predictions of classical nucleation theory at supersaturations that extend above the solubility of amorphous calcium carbonate (ACC). Analysis of the kinetic data shows the thermodynamic barrier to nucleation is reduced by minimizing the interfacial free energy of the system, γ. We then use dynamic force spectroscopy to independently measure calcite-substrate binding free energies, ΔGb. Moreover, we show that within the classical theory of nucleation, γ and ΔGb should be linearly related. The results bear out this prediction and demonstrate that low energy barriers to nucleation correlate with strong crystal-substrate binding. This relationship is general to all functional group chemistries and conformations. These findings reconcile the long-standing concept of templated nucleation through

  5. Carbohydrates in Supramolecular Chemistry.

    Science.gov (United States)

    Delbianco, Martina; Bharate, Priya; Varela-Aramburu, Silvia; Seeberger, Peter H

    2016-02-24

    Carbohydrates are involved in a variety of biological processes. The ability of sugars to form a large number of hydrogen bonds has made them important components for supramolecular chemistry. We discuss recent advances in the use of carbohydrates in supramolecular chemistry and reveal that carbohydrates are useful building blocks for the stabilization of complex architectures. Systems are presented according to the scaffold that supports the glyco-conjugate: organic macrocycles, dendrimers, nanomaterials, and polymers are considered. Glyco-conjugates can form host-guest complexes, and can self-assemble by using carbohydrate-carbohydrate interactions and other weak interactions such as π-π interactions. Finally, complex supramolecular architectures based on carbohydrate-protein interactions are discussed.

  6. Bubble and foam chemistry

    CERN Document Server

    Pugh, Robert J

    2016-01-01

    This indispensable guide will equip the reader with a thorough understanding of the field of foaming chemistry. Assuming only basic theoretical background knowledge, the book provides a straightforward introduction to the principles and properties of foams and foaming surfactants. It discusses the key ideas that underpin why foaming occurs, how it can be avoided and how different degrees of antifoaming can be achieved, and covers the latest test methods, including laboratory and industrial developed techniques. Detailing a variety of different kinds of foams, from wet detergents and food foams, to polymeric, material and metal foams, it connects theory to real-world applications and recent developments in foam research. Combining academic and industrial viewpoints, this book is the definitive stand-alone resource for researchers, students and industrialists working on foam technology, colloidal systems in the field of chemical engineering, fluid mechanics, physical chemistry, and applied physics.

  7. Tropical Soil Chemistry

    DEFF Research Database (Denmark)

    Borggaard, Ole K.

    and environmental protection. Tropical Soil Chemistry by Ole K. Borggaard provides an overview of the composition, occurrence, properties, processes, formation, and environmental vulnerability of various tropical soil types (using American Soil Taxonomy for classification). The processes and the external factors......A new book that is particularly relevant as tropical countries experience increased pressure on land resources to improve agricultural production. To ensure sustainable land use, the potentials and limitations of different kinds of tropical soils must be known in relation to crop production...... soil chemical issues are also presented to assess when, why, and how tropical soils differ from soils in other regions. This knowledge can help agricultural specialists in the tropics establish sustainable crop production. Readers are assumed to be familiar with basic chemistry, physics...

  8. Chemistry space–time

    Directory of Open Access Journals (Sweden)

    David A. Winkler

    2015-12-01

    Full Text Available As Einstein identified so clearly, space and time are intimately related. We discuss the relationship between time and Euclidean space using spectroscopic and radioastronomical studies of interstellar chemistry as an example. Given the finite speed of light, we are clearly studying chemical reactions occurring tens of thousands of years ago that may elucidate the primordial chemistry of this planet several billion years ago. We also explore space of a different kind – chemical space, with many more dimensions than the four we associate as space–time. Vast chemical spaces also need very efficient (computational methods for their exploration to overcome this ‘curse of dimensionality’. We discuss methods by which the time to explore these new spaces can be very substantially reduced, opening the discovery useful new materials that are the key to our future.

  9. Organic Chemistry in Space

    Science.gov (United States)

    Charnley, Steven

    2009-01-01

    Astronomical observations, theoretical modeling, laboratory simulation and analysis of extraterrestrial material have enhanced our knowledge of the inventory of organic matter in the interstellar medium (ISM) and on small bodies such as comets and asteroids (Ehrenfreund & Charnley 2000). Comets, asteroids and their fragments, meteorites and interplanetary dust particles (IDPs), contributed significant amounts of extraterrestrial organic matter to the young Earth. This material degraded and reacted in a terrestrial prebiotic chemistry to form organic structures that may have served as building blocks for life on the early Earth. In this talk I will summarize our current understanding of the organic composition and chemistry of interstellar clouds. Molecules of astrobiological relevance include the building blocks of our genetic material: nucleic acids, composed of subunits such as N-heterocycles (purines and pyrimidines), sugars and amino acids. Signatures indicative of inheritance of pristine and modified interstellar material in comets and meteorites will also be discussed.

  10. Nuclear analytical chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Brune, D.; Forkman, B.; Persson, B.

    1984-01-01

    This book covers the general theories and techniques of nuclear chemical analysis, directed at applications in analytical chemistry, nuclear medicine, radiophysics, agriculture, environmental sciences, geological exploration, industrial process control, etc. The main principles of nuclear physics and nuclear detection on which the analysis is based are briefly outlined. An attempt is made to emphasise the fundamentals of activation analysis, detection and activation methods, as well as their applications. The book provides guidance in analytical chemistry, agriculture, environmental and biomedical sciences, etc. The contents include: the nuclear periodic system; nuclear decay; nuclear reactions; nuclear radiation sources; interaction of radiation with matter; principles of radiation detectors; nuclear electronics; statistical methods and spectral analysis; methods of radiation detection; neutron activation analysis; charged particle activation analysis; photon activation analysis; sample preparation and chemical separation; nuclear chemical analysis in biological and medical research; the use of nuclear chemical analysis in the field of criminology; nuclear chemical analysis in environmental sciences, geology and mineral exploration; and radiation protection.

  11. Quo vadis, analytical chemistry?

    Science.gov (United States)

    Valcárcel, Miguel

    2016-01-01

    This paper presents an open, personal, fresh approach to the future of Analytical Chemistry in the context of the deep changes Science and Technology are anticipated to experience. Its main aim is to challenge young analytical chemists because the future of our scientific discipline is in their hands. A description of not completely accurate overall conceptions of our discipline, both past and present, to be avoided is followed by a flexible, integral definition of Analytical Chemistry and its cornerstones (viz., aims and objectives, quality trade-offs, the third basic analytical reference, the information hierarchy, social responsibility, independent research, transfer of knowledge and technology, interfaces to other scientific-technical disciplines, and well-oriented education). Obsolete paradigms, and more accurate general and specific that can be expected to provide the framework for our discipline in the coming years are described. Finally, the three possible responses of analytical chemists to the proposed changes in our discipline are discussed.

  12. [Gaubius and medical chemistry].

    Science.gov (United States)

    van Gijn, Jan; Gijselhart, Joost P

    2011-01-01

    Hieronymus David Gaub (1705-1780) was the son of a protestant cloth merchant in Heidelberg. Disliking a pietistic boarding school in Halle, Germany, he came to stay with a paternal uncle who was a physician in Amsterdam. Hieronymus studied medicine in Harderwijk and in Leiden, under the guidance of Herman Boerhaave (1668-1738). In 1731 he was appointed reader (and in 1734 professor) in chemistry at the Leiden medical faculty. After Boerhaave's death he also taught medicine, but without access to hospital beds. Gaubius correctly envisaged that chemistry would become an important discipline in medicine, but was limited by the technical constraints of his time. In his textbook of general pathology (1758) he attributed disease to disturbances of not only fluids, but also solid parts, although symptoms remained the basis of his classification. The book would remain influential for several decades, until the advent of pathological anatomy.

  13. Storylines in intercalation chemistry.

    Science.gov (United States)

    Lerf, A

    2014-07-21

    Intercalation chemistry will soon be a hundred years old. The period of greatest activity in this field of solid state chemistry and physics was from about 1970 to 1990. The intercalation reactions are defined as topotactic solid state reactions and the products--the intercalation compounds--are clearly distinguished from inclusion and interstitial compounds. After a short historical introduction emphasizing the pioneering work of Ulrich Hofmann, the central topics and concepts will be reviewed and commented on. The most important ones, in my view, are: dichalcogenide intercalation compounds, the electrochemical intercalation and the search for new battery electrodes, the physics of graphite intercalation compounds, and the staging and interstratification phenomena. The relation to other fields of actual research and the demands for forthcoming research will also be addressed.

  14. Organic Chemistry in Space

    Science.gov (United States)

    Charnley, Steven

    2009-01-01

    Astronomical observations, theoretical modeling, laboratory simulation and analysis of extraterrestrial material have enhanced our knowledge of the inventory of organic matter in the interstellar medium (ISM) and on small bodies such as comets and asteroids (Ehrenfreund & Charnley 2000). Comets, asteroids and their fragments, meteorites and interplanetary dust particles (IDPs), contributed significant amounts of extraterrestrial organic matter to the young Earth. This material degraded and reacted in a terrestrial prebiotic chemistry to form organic structures that may have served as building blocks for life on the early Earth. In this talk I will summarize our current understanding of the organic composition and chemistry of interstellar clouds. Molecules of astrobiological relevance include the building blocks of our genetic material: nucleic acids, composed of subunits such as N-heterocycles (purines and pyrimidines), sugars and amino acids. Signatures indicative of inheritance of pristine and modified interstellar material in comets and meteorites will also be discussed.

  15. Pharmaceutical process chemistry: evolution of a contemporary data-rich laboratory environment.

    Science.gov (United States)

    Caron, Stéphane; Thomson, Nicholas M

    2015-03-20

    Over the past 20 years, the industrial laboratory environment has gone through a major transformation in the industrial process chemistry setting. In order to discover and develop robust and efficient syntheses and processes for a pharmaceutical portfolio with growing synthetic complexity and increased regulatory expectations, the round-bottom flask and other conventional equipment familiar to a traditional organic chemistry laboratory are being replaced. The new process chemistry laboratory fosters multidisciplinary collaborations by providing a suite of tools capable of delivering deeper process understanding through mechanistic insights and detailed kinetics translating to greater predictability at scale. This transformation is essential to the field of organic synthesis in order to promote excellence in quality, safety, speed, and cost efficiency in synthesis.

  16. Conservative or reactive? Mechanistic chemical perspectives on organic matter stability

    Science.gov (United States)

    Koch, Boris

    2016-04-01

    Carbon fixation by terrestrial and marine primary production has a fundamental seasonal effect on the atmospheric carbon content and it profoundly contributes to long-term carbon storage in form of organic matter (OM) in soils, water, and sediments. The efficacy of this sequestration process strongly depends on the degree of OM persistence. Therefore, one of the key issues in dissolved and particulate OM research is to assess the stability of reservoirs and to quantify their contribution to global carbon fluxes. Incubation experiments are helpful to assess OM stability during the first, early diagenetic turnover induced by sunlight or microbes. However, net carbon fluxes within the global carbon cycle also act on much longer time scales, which are not amenable in experiments. It is therefore critical to improve our mechanistic understanding to be able to assess potential future changes in the organic matter cycle. This session contribution highlights some achievements and open questions in the field. An improved mechanistic understanding of OM turnover particularly depends on the molecular characterization of biogeochemical processes and their kinetics: (i) in soils and sediments, aggregation/disaggregation of OM is primarily controlled by its molecular composition. Hence, the chemical composition determines the transfer of organic carbon from the large particulate to the small dissolved organic matter reservoir - an important substrate for microbial metabolism. (ii) In estuaries, dissolved organic carbon gradients usually suggest conservative behavior, whereas molecular-level studies reveal a substantial chemical modification of terrestrial DOM along the land-ocean interface. (iii) In the ocean, previous studies have shown that the recalcitrance of OM depends on bulk concentration and energy yield. However, ultrahigh resolution mass spectrometry in combination with radiocarbon analyses also emphasized that stability is tightly connected to molecular composition

  17. A new mechanistic framework to predict OCS fluxes in soils

    Science.gov (United States)

    Sauze, Joana; Ogee, Jérôme; Launois, Thomas; Kesselmeier, Jürgen; Van Diest, Heidi; Wingate, Lisa

    2015-04-01

    A better description of the amplitude of photosynthetic and respiratory gross CO2 fluxes at large scales is needed to improve our predictions of the current and future global CO2 cycle. Carbonyl sulfide (COS) is the most abundant sulphur gas in the atmosphere and has been proposed as a new tracer of gross photosynthesis, as the uptake of COS from the atmosphere is dominated by the activity of carbonic anhydrase (CA), an enzyme abundant in leaves that also catalyses CO2 hydration during photosynthesis. However, soils also exchange COS with the atmosphere and there is growing evidence that this flux must also be accounted for in atmospheric budgets. In this context a new mechanistic description of soil-atmosphere COS exchange is clearly needed. Soils can take up COS from the atmosphere as the soil biota also contain CA, and COS emissions from soils have also been reported in agricultural fields or anoxic soils. Previous studies have also shown that soil COS fluxes present an optimum soil water content and soil temperature. Here we propose a new mechanistic framework to predict the fluxes of COS between the soils and the atmosphere. We describe the COS soil budget by a first-order reaction-diffusion-production equation, assuming that the hydrolysis of COS by CA is total and irreversible. To describe COS diffusion through the soil matrix, we use different formulations of soil air-filled pore space and temperature, depending on the turbulence level above the soil surface. Using this model we are able to explain the observed presence of an optimum temperature for soil COS uptake and show how this optimum can shift to cooler temperatures in the presence of soil COS emissions. Our model can also explain the observed optimum with soil moisture content previously described in the literature (e.g. Van Diest & Kesselmeier, 2008) as a result of diffusional constraints on COS hydrolysis. These diffusional constraints are also responsible for the response of COS uptake to soil

  18. Quantum mechanics in chemistry

    CERN Document Server

    Schatz, George C

    2002-01-01

    Intended for graduate and advanced undergraduate students, this text explores quantum mechanical techniques from the viewpoint of chemistry and materials science. Dynamics, symmetry, and formalism are emphasized. An initial review of basic concepts from introductory quantum mechanics is followed by chapters examining symmetry, rotations, and angular momentum addition. Chapter 4 introduces the basic formalism of time-dependent quantum mechanics, emphasizing time-dependent perturbation theory and Fermi's golden rule. Chapter 5 sees this formalism applied to the interaction of radiation and matt

  19. Transferases in Polymer Chemistry

    Science.gov (United States)

    van der Vlist, Jeroen; Loos, Katja

    Transferases are enzymes that catalyze reactions in which a group is transferred from one compound to another. This makes these enzymes ideal catalysts for polymerization reactions. In nature, transferases are responsible for the synthesis of many important natural macromolecules. In synthetic polymer chemistry, various transferases are used to synthesize polymers in vitro. This chapter reviews some of these approaches, such as the enzymatic polymerization of polyesters, polysaccharides, and polyisoprene.

  20. Green chemistry: development trajectory

    Science.gov (United States)

    Moiseev, I. I.

    2013-07-01

    Examples of applications of green chemistry methods in heavy organic synthesis are analyzed. Compounds, which can be produced by the processing of the biomass, and the criteria for the selection of the most promising products are summarized. The current status of the ethanol production and processing is considered. The possibilities of the use of high fatty acid triglycerides, glycerol, succinic acid, and isoprene are briefly discussed. The bibliography includes 67 references.

  1. Analytical Chemistry in Russia.

    Science.gov (United States)

    Zolotov, Yuri

    2016-09-06

    Research in Russian analytical chemistry (AC) is carried out on a significant scale, and the analytical service solves practical tasks of geological survey, environmental protection, medicine, industry, agriculture, etc. The education system trains highly skilled professionals in AC. The development and especially manufacturing of analytical instruments should be improved; in spite of this, there are several good domestic instruments and other satisfy some requirements. Russian AC has rather good historical roots.

  2. Exploring soil organic matter-mineral interactions: mechanistic insights at the nanometer and molecular length scales

    Science.gov (United States)

    Newcomb, C.; Qafoku, N. P.; Grate, J. W.; Hufschmid, R.; Browning, N.; De Yoreo, J. J.

    2015-12-01

    With elevated levels of carbon dioxide in the atmosphere due to anthropogenic emissions and disruption to the carbon cycle, the effects of climate change are being accelerated. Approximately 80% of Earth's terrestrial organic carbon is stored in soil, and the residence time of this carbon can range from hours to millenia. Understanding the dynamics of this carbon pool in the carbon cycle is crucial to both predicting climate and sustaining ecosystem services. Soil organic carbon is known to be strongly associated with high surface area clay minerals. The nature of these interactions is not well understood primarily due to the heterogeneity of soil, as much of the current knowledge relies on experiments that take a top-down approach using bulk experimental measurements. Our work seeks to probe physical, chemical, and molecular-level interactions at the organic-mineral interface using a bottom-up approach that establishes a model system where complexity can be built in systematically. By performing in situ techniques such as dynamic force spectroscopy, a technique where organic molecules can be brought into contact with mineral surfaces in a controlled manner using an atomic force microscope, we demonstrate the ability to mechanistically probe the energy landscape of individual organic molecules with mineral surfaces. We demonstrate the ability to measure the binding energies of soil-inspired organic functional groups (including carboxylic acid, amine, methyl, and phosphate) with clay and mineral surfaces as a function of solution chemistry. This effort can provide researchers with both guiding principles about carbon dynamics at the sub-nanometer length scale and insights into early aggregation events, where organic-mineral interactions play a significant role.

  3. Premixed flame chemistry of a gasoline primary reference fuel surrogate

    KAUST Repository

    Selim, Hatem

    2017-03-10

    Investigating the combustion chemistry of gasoline surrogate fuels promises to improve detailed reaction mechanisms used for simulating their combustion. In this work, the combustion chemistry of one of the simplest, but most frequently used gasoline surrogates – primary reference fuel 84 (PRF 84, 84 vol% iso-octane and 16 vol% n-heptane), has been examined in a stoichiometric premixed laminar flame. Time-of-flight mass spectrometry coupled with a vacuum ultraviolet (VUV) synchrotron light source for species photoionization was used. Reactants, major end-products, stable intermediates, free radicals, and isomeric species were detected and quantified. Numerical simulations were conducted using a detailed chemical kinetic model with the most recently available high temperature sub-mechanisms for iso-octane and heptane, built on the top of an updated pentane isomers model and AramcoMech 2.0 (C0C4) base chemistry. A detailed interpretation of the major differences between the mechanistic pathways of both fuel components is given. A comparison between the experimental and numerical results is depicted and rate of production and sensitivity analyses are shown for the species with considerable disagreement between the experimental and numerical findings.

  4. From China to the world: Science China Chemistry celebrates the International Year of Chemistry

    Institute of Scientific and Technical Information of China (English)

    ZHU XiaoWen; XUE Zi-Ling

    2012-01-01

    1 Introduction Science China Chemistry is considered the best and most comprehensive chemistry journal in China,Its primary mission is to communicate the results of basic and innovative chemistry research.The subject areas include physical chemistry,organic chemistry,inorganic chemistry,polymer chemistry,biological chemistry,environmental chemistry,and chemical engineering in the form of Feature Articles,Reviews,Communications,Articles,and News & Comments.

  5. Mechanistic failure mode investigation and resolution of parvovirus retentive filters.

    Science.gov (United States)

    LaCasse, Daniel; Lute, Scott; Fiadeiro, Marcus; Basha, Jonida; Stork, Matthew; Brorson, Kurt; Godavarti, Ranga; Gallo, Chris

    2016-07-01

    Virus retentive filters are a key product safety measure for biopharmaceuticals. A simplistic perception is that they function solely based on a size-based particle removal mechanism of mechanical sieving and retention of particles based on their hydrodynamic size. Recent observations have revealed a more nuanced picture, indicating that changes in viral particle retention can result from process pressure and/or flow interruptions. In this study, a mechanistic investigation was performed to help identify a potential mechanism leading to the reported reduced particle retention in small virus filters. Permeate flow rate or permeate driving force were varied and analyzed for their impact on particle retention in three commercially available small virus retentive filters. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:959-970, 2016.

  6. Mechanistic modeling confronts the complexity of molecular cell biology.

    Science.gov (United States)

    Phair, Robert D

    2014-11-05

    Mechanistic modeling has the potential to transform how cell biologists contend with the inescapable complexity of modern biology. I am a physiologist-electrical engineer-systems biologist who has been working at the level of cell biology for the past 24 years. This perspective aims 1) to convey why we build models, 2) to enumerate the major approaches to modeling and their philosophical differences, 3) to address some recurrent concerns raised by experimentalists, and then 4) to imagine a future in which teams of experimentalists and modelers build-and subject to exhaustive experimental tests-models covering the entire spectrum from molecular cell biology to human pathophysiology. There is, in my view, no technical obstacle to this future, but it will require some plasticity in the biological research mind-set.

  7. Mechanistic study of ZnO nanorod array electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    El Belghiti, H.; Pauporte, T.; Lincot, D. [Laboratoire d' Electrochimie et Chimie Analytique, UMR7575, Ecole Nationale Superieure de Chimie de Paris-Universite Paris 6 (France)

    2008-10-15

    The growth of ZnO nanorods by electrodeposition from oxygenated aqueous mixture of zinc chloride and potassium chloride is studied experimentally as a function of the deposition time, zinc concentration and the substrate. These parameters influence markedly the characteristics of the deposits (rod density, aspect ratio, orientation). A mechanistic model is presented in order to explain the formation of ZnO nanorod arrays by electrodeposition. The model is based on the effect of zinc concentration on the interfacial pH at the electrode surface and then on the charged stable zinc species able to react with the growing film. The charge of the complex seems to be the key parameter which stops the lateral growth and then significantly increases the aspect ratio of the single crystalline nanorods. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Serum Albumin Binding and Esterase Activity: Mechanistic Interactions with Organophosphates

    Directory of Open Access Journals (Sweden)

    Nikolay V. Goncharov

    2017-07-01

    Full Text Available The albumin molecule, in contrast to many other plasma proteins, is not covered with a carbohydrate moiety and can bind and transport various molecules of endogenous and exogenous origin. The enzymatic activity of albumin, the existence of which many scientists perceive skeptically, is much less studied. In toxicology, understanding the mechanistic interactions of organophosphates with albumin is a special problem, and its solution could help in the development of new types of antidotes. In the present work, the history of the issue is briefly examined, then our in silico data on the interaction of human serum albumin with soman, as well as comparative in silico data of human and bovine serum albumin activities in relation to paraoxon, are presented. Information is given on the substrate specificity of albumin and we consider the possibility of its affiliation to certain classes in the nomenclature of enzymes.

  9. Obesity, energy balance, and cancer: a mechanistic perspective.

    Science.gov (United States)

    Hursting, Stephen D

    2014-01-01

    Nearly 36 % of adults and 20 % of children in the USA are obese, defined as a body mass index (BMI) ≥30 kg/m(2). Obesity, which is accompanied by metabolic dysregulation often manifesting in the metabolic syndrome, is an established risk factor for many cancers. Within the growth-promoting, proinflammatory environment of the obese state, cross talk between macrophages, adipocytes, and epithelial cells occurs via obesity-associated hormones, cytokines, and other mediators that may enhance cancer risk and/or progression. This chapter synthesizes the evidence on key biological mechanisms underlying the obesity-cancer link, with particular emphasis on obesity-associated enhancements in growth factor signaling, inflammation, and vascular integrity processes, as well as obesity-dependent microenvironmental perturbations, including the epithelial-to-mesenchymal transition. These interrelated pathways represent possible mechanistic targets for disrupting the obesity-cancer link.

  10. Mechanistic Multidimensional Modeling of Forced Convection Boiling Heat Transfer

    Directory of Open Access Journals (Sweden)

    Michael Z. Podowski

    2009-01-01

    Full Text Available Due to the importance of boiling heat transfer in general, and boiling crisis in particular, for the analysis of operation and safety of both nuclear reactors and conventional thermal power systems, extensive efforts have been made in the past to develop a variety of methods and tools to evaluate the boiling heat transfer coefficient and to assess the onset of temperature excursion and critical heat flux (CHF at various operating conditions of boiling channels. The objective of this paper is to present mathematical modeling concepts behind the development of mechanistic multidimensional models of low-quality forced convection boiling, including the mechanisms leading to temperature excursion and the onset of CHF.

  11. From patterns to emerging processes in mechanistic urban ecology.

    Science.gov (United States)

    Shochat, Eyal; Warren, Paige S; Faeth, Stanley H; McIntyre, Nancy E; Hope, Diane

    2006-04-01

    Rapid urbanization has become an area of crucial concern in conservation owing to the radical changes in habitat structure and loss of species engendered by urban and suburban development. Here, we draw on recent mechanistic ecological studies to argue that, in addition to altered habitat structure, three major processes contribute to the patterns of reduced species diversity and elevated abundance of many species in urban environments. These activities, in turn, lead to changes in animal behavior, morphology and genetics, as well as in selection pressures on animals and plants. Thus, the key to understanding urban patterns is to balance studying processes at the individual level with an integrated examination of environmental forces at the ecosystem scale.

  12. Mechanistic modelling of the drying behaviour of single pharmaceutical granules

    DEFF Research Database (Denmark)

    Thérèse F.C. Mortier, Séverine; Beer, Thomas De; Gernaey, Krist

    2012-01-01

    The trend to move towards continuous production processes in pharmaceutical applications enhances the necessity to develop mechanistic models to understand and control these processes. This work focuses on the drying behaviour of a single wet granule before tabletting, using a six...... of b on the drying behaviour. Experimental data with the six-segmented fluidised bed dryer were collected to calibrate b. An exponential dependence on the drying air temperature was found. Independent experiments were done for the validation of the drying model.......-segmented fluidised bed drying system, which is part of a fully continuous from-powder-to-tablet manufacturing line. The drying model is based on a model described by Mezhericher et al. [1] and consists of two submodels. In the first drying phase (submodel 1), the surface water evaporates, while in the second drying...

  13. A General Mechanistic Model of Solid Oxide Fuel Cells

    Institute of Scientific and Technical Information of China (English)

    SHI Yixiang; CAI Ningsheng

    2006-01-01

    A comprehensive model considering all forms of polarization was developed. The model considers the intricate interdependency among the electrode microstructure, the transport phenomena, and the electrochemical processes. The active three-phase boundary surface was expressed as a function of electrode microstructure parameters (porosity, coordination number, contact angle, etc.). The exchange current densities used in the simulation were obtained by fitting a general formulation to the polarization curves proposed as a function of cell temperature and oxygen partial pressure. A validation study shows good agreement with published experimental data. Distributions of overpotentials, gas component partial pressures, and electronic/ionic current densities have been calculated. The effects of a porous electrode structure and of various operation conditions on cell performance were also predicted. The mechanistic model proposed can be used to interpret experimental observations and optimize cell performance by incorporating reliable experimental data.

  14. Structure determines medication errors in nursing units: a mechanistic approach.

    Science.gov (United States)

    Hung, Chang-Chiao; Lee, Bih-O; Tsai, Shu-Ling; Tseng, Yun Shan; Chang, Chia-Hao

    2015-03-01

    Medication errors have long been considered critical in global health care systems. However, few studies have been conducted to explore the effects of nursing unit structure on medication errors. The purpose of this study, therefore, was to determine the effects of structural factors on medication errors in nursing units. A total of 977 staff nurses and 62 head nurses participated in this cross-sectional design study. The findings show that professional autonomy (β = .53, t = 6.03, p nursing experts (β = .52, t = 5.99, p medication error rates. This study shows that the structural factors influence medication administration and the mechanistic approach is specifically in relation of low medication error rates. The author suggests that head nurses should consider strategies that require adjustments to unit control mechanisms.

  15. Parameter and uncertainty estimation for mechanistic, spatially explicit epidemiological models

    Science.gov (United States)

    Finger, Flavio; Schaefli, Bettina; Bertuzzo, Enrico; Mari, Lorenzo; Rinaldo, Andrea

    2014-05-01

    Epidemiological models can be a crucially important tool for decision-making during disease outbreaks. The range of possible applications spans from real-time forecasting and allocation of health-care resources to testing alternative intervention mechanisms such as vaccines, antibiotics or the improvement of sanitary conditions. Our spatially explicit, mechanistic models for cholera epidemics have been successfully applied to several epidemics including, the one that struck Haiti in late 2010 and is still ongoing. Calibration and parameter estimation of such models represents a major challenge because of properties unusual in traditional geoscientific domains such as hydrology. Firstly, the epidemiological data available might be subject to high uncertainties due to error-prone diagnosis as well as manual (and possibly incomplete) data collection. Secondly, long-term time-series of epidemiological data are often unavailable. Finally, the spatially explicit character of the models requires the comparison of several time-series of model outputs with their real-world counterparts, which calls for an appropriate weighting scheme. It follows that the usual assumption of a homoscedastic Gaussian error distribution, used in combination with classical calibration techniques based on Markov chain Monte Carlo algorithms, is likely to be violated, whereas the construction of an appropriate formal likelihood function seems close to impossible. Alternative calibration methods, which allow for accurate estimation of total model uncertainty, particularly regarding the envisaged use of the models for decision-making, are thus needed. Here we present the most recent developments regarding methods for parameter and uncertainty estimation to be used with our mechanistic, spatially explicit models for cholera epidemics, based on informal measures of goodness of fit.

  16. Antidepressants and gabapentinoids in neuropathic pain: Mechanistic insights.

    Science.gov (United States)

    Kremer, Mélanie; Salvat, Eric; Muller, André; Yalcin, Ipek; Barrot, Michel

    2016-12-03

    Neuropathic pain arises as a consequence of a lesion or disease affecting the somatosensory system. It is generally chronic and challenging to treat. The recommended pharmacotherapy for neuropathic pain includes the use of some antidepressants, such as tricyclic antidepressants (TCAs) (amitriptyline…) or serotonin and noradrenaline re-uptake inhibitors (duloxetine…), and/or anticonvulsants such as the gabapentinoids gabapentin or pregabalin. Antidepressant drugs are not acute analgesics but require a chronic treatment to relieve neuropathic pain, which suggests the recruitment of secondary downstream mechanisms as well as long-term molecular and neuronal plasticity. Noradrenaline is a major actor for the action of antidepressant drugs in a neuropathic pain context. Mechanistic hypotheses have implied the recruitment of noradrenergic descending pathways as well as the peripheral recruitment of noradrenaline from sympathetic fibers sprouting into dorsal root ganglia; and importance of both α2 and β2 adrenoceptors have been reported. These monoamine re-uptake inhibitors may also indirectly act as anti-proinflammatory cytokine drugs; and their therapeutic action requires the opioid system, particularly the mu (MOP) and/or delta (DOP) opioid receptors. Gabapentinoids, which target the voltage-dependent calcium channels α2δ-1 subunit, inhibit calcium currents, thus decreasing the excitatory transmitter release and spinal sensitization. Gabapentinoids also activate the descending noradrenergic pain inhibitory system coupled to spinal α2 adrenoceptors. Gabapentinoid treatment may also indirectly impact on neuroimmune actors, like proinflammatory cytokines. These drugs are effective against neuropathic pain both with acute administration at high dose and with repeated administration. This review focuses on mechanistic knowledge concerning chronic antidepressant treatment and gabapentinoid treatment in a neuropathic pain context. Copyright © 2016 IBRO. Published by

  17. Spotlight on medicinal chemistry education.

    Science.gov (United States)

    Pitman, Simone; Xu, Yao-Zhong; Taylor, Peter; Turner, Nicholas; Coaker, Hannah; Crews, Kasumi

    2014-05-01

    The field of medicinal chemistry is constantly evolving and it is important for medicinal chemists to develop the skills and knowledge required to succeed and contribute to the advancement of the field. Future Medicinal Chemistry spoke with Simone Pitman (SP), Yao-Zhong Xu (YX), Peter Taylor (PT) and Nick Turner (NT) from The Open University (OU), which offers an MSc in Medicinal Chemistry. In the interview, they discuss the MSc course content, online teaching, the future of medicinal chemistry education and The OU's work towards promoting widening participation. SP is a Qualifications Manager in the Science Faculty at The OU. She joined The OU in 1993 and since 1998 has been involved in the Postgraduate Medicinal Chemistry provision at The OU. YX is a Senior Lecturer in Bioorganic Chemistry at The OU. He has been with The OU from 2001, teaching undergraduate courses of all years and chairing the master's course on medicinal chemistry. PT is a Professor of Organic Chemistry at The OU and has been involved with the production and presentation of The OU courses in Science and across the university for over 30 years, including medicinal chemistry modules at postgraduate level. NT is a Lecturer in Analytical Science at The OU since 2009 and has been involved in the production of analytical sciences courses, as well as contributing to the presentation of a number of science courses including medicinal chemistry.

  18. Glassy state on the undergraduate course in chemistry (physical chemistry).

    OpenAIRE

    Yamaki, SB; Pedroso, AG; ATVARS, TDZ

    2002-01-01

    We consider the relevance of the study of the glassy state properties and the glass transition as important topics of the physical chemistry for undergraduate courses of Chemistry. Two of the most important theoretical approaches for the description of the glassy state, the thermodynamic and the kinetic models, are summarized with emphasis on the physical chemistry aspects. Examples illustrating the glass transition of some materials are also presented.

  19. Green Chemistry Metrics with Special Reference to Green Analytical Chemistry

    OpenAIRE

    Marek Tobiszewski; Mariusz Marć; Agnieszka Gałuszka; Jacek Namieśnik

    2015-01-01

    The concept of green chemistry is widely recognized in chemical laboratories. To properly measure an environmental impact of chemical processes, dedicated assessment tools are required. This paper summarizes the current state of knowledge in the field of development of green chemistry and green analytical chemistry metrics. The diverse methods used for evaluation of the greenness of organic synthesis, such as eco-footprint, E-Factor, EATOS, and Eco-Scale are described. Both the well-establis...

  20. The mechanistically significant coordination chemistry of dinitrogen at FeMo-co, the catalytic site of nitrogenase.

    Science.gov (United States)

    Dance, Ian

    2007-02-07

    Reported here is a comprehensive theoretical investigation of the binding of N(2) to the Fe(7)MoS(9)N(homocitrate)(cysteine)(histidine) active site (FeMo-co) of the enzyme nitrogenase, as a prerequisite to elucidation of the chemical mechanism of the catalyzed reduction to NH(3). The degree and type of hydrogenation of FeMo-co, with H atoms and possibly an H(2) molecule, are key variables, following the Thorneley-Lowe kinetic scheme. Ninety-four local energy minima were located for N(2) coordinated in eta(2) (side) and eta(1) (end) modes at the endo and exo coordination positions of Fe2 and Fe6. The stabilities of 57 representative structures are assessed by calculation of the reaction profiles and activation energies for the association and dissociation of N(2). Barriers to association of N(2) depend mainly on the location of the hydrogenation and the location of N(2) coordination, while dissociation barriers depend primarily on whether N(2) is eta(2)- and eta(1)-coordinated, and secondarily on the location of the hydrogenation. Increased negative charge on FeMo-co increases the barriers, while C in place of N at the center of FeMo-co has little effect. The interactions of the models of ligated FeMo-co with the surrounding protein, including proteins with mutations of key amino acids, are assessed by in silico cofactor transplantations and calculations of protein strain energies. From these results, which identify models involving contacts and interactions with the surrounding residues that have been shown by mutation to affect the N(2) activity of nitrogenase, and from the N(2) coordination profiles, it is concluded that endo-eta(1)-N(2) coordination at Fe6 is most probable. There is strong reason to believe that the mechanism of nitrogenase will involve one or more of the preferred models presented here, and a detailed foundation of structures and principles is now available for postulation and calculation of the profiles of the steps in which H atoms bound to FeMo-co are transferred to bound N(2).

  1. Mechanistic chemistry of oxidation of balsalazide with acidic chloramine-T and bromamine-T: A comparative spectrophotometric kinetic study

    Indian Academy of Sciences (India)

    Puttaswamy; S Dakshayani

    2014-11-01

    Balsalazide (BSZ) belongs to a class of non-steroidal anti-inflammatory drugs. Kinetics and mechanism of oxidation of BSZ with sodium N-halo-p-toluenesulfonamides viz., chloramine-T(CAT) and bromamine-T(BAT) in HClO4 medium have been spectrophotometrically investigated (max =357nm) at 303 K. Under comparable experimental conditions, reactions with both the oxidants follow a first-order dependence of rate on [BSZ] and fractional-order dependence on each [oxidant] and [HClO4]. Activation parameters and reaction constants have been computed. 2-hydroxy-5-nitroso-benzoic acid and 3-(4-nitroso-benzoylamino)-propionic acid are identified as the oxidation products of BSZ with both CAT and BAT. The rate of oxidation of BSZ is about five-fold faster with BAT than with CAT. Plausible mechanism and related rate law have been deduced for the observed kinetics.

  2. (CO/sub 2/ chemistry and biochemistry, Ginosa Marina, Italy, June 17-28, 1989): Foreign trip report

    Energy Technology Data Exchange (ETDEWEB)

    Hartman, F.C.

    1989-07-11

    The traveler attended a conference organized by the NATO Advanced Study Institute on plant molecular biology and presented two invited addresses entitled ''Rubisco: Active-site characterization and mechanistic implications.'' Presentations concerning biological CO/sub 2/ fixation, chemical modifications of proteins, site-directed mutagenesis, CO/sub 2/ chemistry, carbonic anhydrase, biotin-requiring enzymes, and the greenhouse effect were relevant to ongoing investigations of the Protein Chemistry Group and the Protein Engineering Program at ORNL's Biology Division.

  3. Sixty Years of Chemistry at CAS

    Institute of Scientific and Technical Information of China (English)

    WAN Li-Jun

    2011-01-01

    @@ As one of the fundamental and key disciplines of natural sciences, chemistry deals with the properties, composition, structure, transformation and applications of substances.It could be further divided into several branches, such as inorganic chemistry, organic chemistry, physical chemistry, polymer chemistry, analytical chemistry and chemical engineering.In recent years, many new branches and fields have emerged amide the continuous development of chemistry and its interdisciplinary research with mathematics, physics, astronomy, earth science, biology, medical science, materials science, and environmental science.

  4. From organic chemistry to fat and oil chemistry*

    OpenAIRE

    Deffense Etienne

    2009-01-01

    With his work on animal fat and identification of fatty acids, Chevreul was a pioneer in organic chemistry. As Chevreul, I had a passion for organic chemistry too. It was then, an honour and a pleasure to present in 2008 at EFL in Athens this presentation entitled “From organic chemistry to fat and oil chemistry” because my background in organic chemistry helped me all along my professional career to understand and implement new developments related to oil and fat technology and processing. A...

  5. An Evaluation of Chemistry I Textbook by Chemistry Teachers

    Directory of Open Access Journals (Sweden)

    Abdullah AYDIN

    2010-04-01

    Full Text Available Textbooks are one of the most consulted sources in the processes of teaching- learning and assessment. It is indispensable to prepare textbooks in accordance with the curriculum to ensure effective teaching and learning. “Teacher evaluation questionnaire” consistingof 20 questions has been prepared to evaluate secondary level IXth class chemistry textbook in terms of its content. This questionnaire was carried out with 31 secondary level chemistry teachers who work in the public schools and 19 chemistry teachers who work in the private courses. According to the results obtained, chemistry teachers think that there are some deficiencies and obstacles in the application of this textbook.

  6. Green Chemistry: Progress and Barriers

    Science.gov (United States)

    Green, Sarah A.

    2016-10-01

    Green chemistry can advance both the health of the environment and the primary objectives of the chemical enterprise: to understand the behavior of chemical substances and to use that knowledge to make useful substances. We expect chemical research and manufacturing to be done in a manner that preserves the health and safety of workers; green chemistry extends that expectation to encompass the health and safety of the planet. While green chemistry may currently be treated as an independent branch of research, it should, like safety, eventually become integral to all chemistry activities. While enormous progress has been made in shifting from "brown" to green chemistry, much more effort is needed to effect a sustainable economy. Implementation of new, greener paradigms in chemistry is slow because of lack of knowledge, ends-justify-the-means thinking, systems inertia, and lack of financial or policy incentives.

  7. Mechanistic understanding of calcium-phosphonate solid dissolution and scale inhibitor return behavior in oilfield reservoir: formation of middle phase.

    Science.gov (United States)

    Zhang, Ping; Shen, Dong; Ruan, Gedeng; Kan, Amy T; Tomson, Mason B

    2016-08-03

    Phosphonates are an important class of mineral scale inhibitors used for oilfield scale control. By injecting the phosphonate into an oilfield reservoir, calcium-phosphonate precipitate will form and subsequently release the phosphonate into produced water for scale control. In this study, a systematic procedure is developed to mechanistically characterize an acidic calcium-phosphonate amorphous material that is later developed into a middle phase and eventually a crystalline phase. The phosphonate used in this study is diethylenetriamine pentakis (methylene phosphonic acid) (DTPMP). An amorphous calcium-DTPMP solid is precipitated by mixing a calcium-containing solution with a DTPMP solution. The stoichiometry of this initially formed solid can be experimentally confirmed via a static dissolution test. Following another dynamic development test, two additional Ca-DTPMP solid phases, i.e., a middle phase and a crystalline phase have been observed. Electron microscopy and X-ray diffraction were employed to characterize the morphology and crystallinity of different Ca-DTPMP solids of interest. Evidently, the dynamic brine flushing of the Ca-DTPMP solid developed the initially amorphous material into a middle phase solid with an amorphous/microcrystalline structure and eventually into a crystalline material. Furthermore, a dissolution characterization study was carried out to determine the solubility product of the middle phase solid at different conditions. The obtained mechanistic understanding of the Ca-DTPMP solid related to precipitation chemistry, dissolution behavior and phase transition is critical to elucidate oilfield DTPMP return data and more importantly, can optimize the oilfield scale squeeze design to achieve an extended squeeze lifetime.

  8. NUCLEAR CHEMISTRY ANNUAL REPORT 1970

    Energy Technology Data Exchange (ETDEWEB)

    Authors, Various

    1971-05-01

    Papers are presented for the following topics: (1) Nuclear Structure and Nuclear Properties - (a) Nuclear Spectroscopy and Radioactivity; (b) Nuclear Reactions and Scattering; (c) Nuclear Theory; and (d) Fission. (2) Chemical and Atomic Physics - (a) Atomic and Molecular Spectroscopy; and (b) Hyperfine Interactions. (3) Physical, Inorganic, and Analytical Chemistry - (a) X-Ray Crystallography; (b) Physical and Inorganic Chemistry; (c) Radiation Chemistry; and (d) Chemical Engineering. (4) Instrumentation and Systems Development.

  9. Process Analytical Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Veltkamp, David J.(VISITORS); Doherty, Steve D.(BCO); Anderson, B B.(VISITORS); Koch, Mel (University of Washington); Bond, Leonard J.(BATTELLE (PACIFIC NW LAB)); Burgess, Lloyd W.(VISITORS); Ullman, Alan H.(UNKNOWN); Bamberger, Judith A.(BATTELLE (PACIFIC NW LAB)); Greenwood, Margaret S.(BATTELLE (PACIFIC NW LAB))

    1999-06-15

    This review of process analytical chemistry is an update to the previous review on this subject published in 1995(A2). The time period covered for this review includes publications written or published from late 1994 until early 1999, with the addition of a few classic references pointing to background information critical to an understanding of a specific topic area. These older references have been critically included as established fundamental works. New topics covered in this review not previously treated as separate subjects in past reviews include sampling systems, imaging (via optical spectroscopy), and ultrasonic analysis.

  10. Chemistry in aircraft plumes

    Energy Technology Data Exchange (ETDEWEB)

    Kraabol, A.G.; Stordal, F.; Knudsen, S. [Norwegian Inst. for Air Research, Kjeller (Norway); Konopka, P. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Wessling (Germany). Inst. fuer Physik der Atmosphaere

    1997-12-31

    An expanding plume model with chemistry has been used to study the chemical conversion of NO{sub x} to reservoir species in aircraft plumes. The heterogeneous conversion of N{sub 2}O{sub 5} to HNO{sub 3}(s) has been investigated when the emissions take place during night-time. The plume from an B747 has been simulated. During a ten-hour calculation the most important reservoir species was HNO{sub 3} for emissions at noon. The heterogeneous reactions had little impact on the chemical loss of NO{sub x} to reservoir species for emissions at night. (author) 4 refs.

  11. Phoenix's Wet Chemistry Lab

    Science.gov (United States)

    2008-01-01

    This is an illustration of the analytical procedure of NASA's Phoenix Mars Lander's Wet Chemistry Lab (WCL) on board the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) instrument. By dissolving small amounts of soil in water, WCL can determine the pH, the abundance of minerals such as magnesium and sodium cations or chloride, bromide and sulfate anions, as well as the conductivity and redox potential. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  12. Radiochemistry and nuclear chemistry

    CERN Document Server

    Choppin, Gregory; RYDBERG, JAN; Ekberg, Christian

    2013-01-01

    Radiochemistry or nuclear chemistry is the study of radiation from an atomic and molecular perspective, including elemental transformation and reaction effects, as well as physical, health and medical properties. This revised edition of one of the earliest and best-known books on the subject has been updated to bring into teaching the latest developments in research and the current hot topics in the field. To further enhance the functionality of this text, the authors have added numerous teaching aids, examples in MathCAD with variable quantities and options, hotlinks to relevant text secti

  13. Analytical chemistry in space

    CERN Document Server

    Wainerdi, Richard E

    1970-01-01

    Analytical Chemistry in Space presents an analysis of the chemical constitution of space, particularly the particles in the solar wind, of the planetary atmospheres, and the surfaces of the moon and planets. Topics range from space engineering considerations to solar system atmospheres and recovered extraterrestrial materials. Mass spectroscopy in space exploration is also discussed, along with lunar and planetary surface analysis using neutron inelastic scattering. This book is comprised of seven chapters and opens with a discussion on the possibilities for exploration of the solar system by

  14. Nuclear Chemistry and Services

    Energy Technology Data Exchange (ETDEWEB)

    Vandevelde, L

    2002-04-01

    The objectives, the programme, and the achievements of R and D at the Belgian Nuclear Research Centre SCK-CEN in the field of nuclear chemistry and analytical techniques are summarized. Major achievement in 2001 included the completion of a project on the measurement of critical radionuclides in reactor waste fluxes (the ARIANE project), the radiochemical characterisation of beryllium material originating from the second matrix of the BR2 reactor as well as to a the organisation of a workshop on the analysis of thorium and its isotopes in workplace materials.

  15. Physical chemistry II essentials

    CERN Document Server

    REA, The Editors of

    1992-01-01

    REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Physical Chemistry II includes reaction mechanisms, theoretical approaches to chemical kinetics, gravitational work, electrical and magnetic work, surface work, kinetic theory, collisional and transport properties of gases, statistical mechanics, matter and waves, quantum mechanics, and rotations and vibrations of atoms and molecules.

  16. Introduction to Coordination Chemistry

    CERN Document Server

    Lawrance, Geoffrey Alan

    2010-01-01

    Introduction to Coordination Chemistry examines and explains how metals and molecules that bind as ligands interact, and the consequences of this assembly process. This book describes the chemical and physical properties and behavior of the complex assemblies that form, and applications that may arise as a result of these properties. Coordination complexes are an important but often hidden part of our world?even part of us?and what they do is probed in this book. This book distills the essence of this topic for undergraduate students and for research scientists.

  17. Organic iodine chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Dickinson, S. E-mail: shirley.dickinson@aeat.co.uk; Sims, H.E.; Belval-Haltier, E.; Jacquemain, D.; Poletiko, C.; Funke, F.; Hellmann, S.; Karjunen, T.; Zilliacus, R

    2001-11-01

    A shared-cost action on Organic Iodine Chemistry has been completed as part of the CEC 4th Framework programme on Nuclear Fission Safety. Organisations from four EC countries are involved in an integrated programme of experiments and analysis to help clarify the phenomenology, and to increase confidence in the modelling of iodine behaviour in containment. The project is focused on identifying the main routes for organic iodine formation, and providing new experimental kinetic data which will be used to improve existing models and to stimulate code development.

  18. Phoenix's Wet Chemistry Lab

    Science.gov (United States)

    2008-01-01

    This is an illustration of soil analysis on NASA's Phoenix Mars Lander's Wet Chemistry Lab (WCL) on board the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) instrument. By dissolving small amounts of soil in water, WCL will attempt to determine the pH, the abundance of minerals such as magnesium and sodium cations or chloride, bromide and sulfate anions, as well as the conductivity and redox potential. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  19. Nuclear Chemistry and Services

    Energy Technology Data Exchange (ETDEWEB)

    Vandevelde, L

    2002-04-01

    The objectives, the programme, and the achievements of R and D at the Belgian Nuclear Research Centre SCK-CEN in the field of nuclear chemistry and analytical techniques are summarized. Major achievement in 2001 included the completion of a project on the measurement of critical radionuclides in reactor waste fluxes (the ARIANE project), the radiochemical characterisation of beryllium material originating from the second matrix of the BR2 reactor as well as to a the organisation of a workshop on the analysis of thorium and its isotopes in workplace materials.

  20. Sustainable chemistry metrics.

    Science.gov (United States)

    Calvo-Flores, Francisco García

    2009-01-01

    Green chemistry has developed mathematical parameters to describe the sustainability of chemical reactions and processes, in order to quantify their environmental impact. These parameters are related to mass and energy magnitudes, and enable analyses and numerical diagnoses of chemical reactions. The environmental impact factor (E factor), atom economy, and reaction mass efficiency have been the most influential metrics, and they are interconnected by mathematical equations. The ecodesign concept must also be considered for complex industrial syntheses, as a part of the sustainability of manufacturing processes. The aim of this Concept article is to identify the main parameters for evaluating undesirable environmental consequences.

  1. Chemistry in Bioinformatics

    Science.gov (United States)

    Murray-Rust, Peter; Mitchell, John BO; Rzepa, Henry S

    2005-01-01

    Chemical information is now seen as critical for most areas of life sciences. But unlike Bioinformatics, where data is openly available and freely re-usable, most chemical information is closed and cannot be re-distributed without permission. This has led to a failure to adopt modern informatics and software techniques and therefore paucity of chemistry in bioinformatics. New technology, however, offers the hope of making chemical data (compounds and properties) free during the authoring process. We argue that the technology is already available; we require a collective agreement to enhance publication protocols. PMID:15941476

  2. Chemistry in Bioinformatics

    Directory of Open Access Journals (Sweden)

    Mitchell John

    2005-06-01

    Full Text Available Abstract Chemical information is now seen as critical for most areas of life sciences. But unlike Bioinformatics, where data is openly available and freely re-usable, most chemical information is closed and cannot be re-distributed without permission. This has led to a failure to adopt modern informatics and software techniques and therefore paucity of chemistry in bioinformatics. New technology, however, offers the hope of making chemical data (compounds and properties free during the authoring process. We argue that the technology is already available; we require a collective agreement to enhance publication protocols.

  3. Chemistry and Science Fiction

    Science.gov (United States)

    Stocker, Jack H.

    1998-11-01

    This lively collection looks at science as filtered through literature, film, and television. It discusses classic works in science fiction and provides an in-depth look at the chemistry depicted in popular culture, particularly in Start Trek , Star Wars , and Doctor Who . It includes an examination by Nebula Award winner Connie Willis of how science fiction authors use science, and reprints two tongue-in-cheek short stories by Isaac Asimov. The book also includes suggestions for using science fiction as an educational resource.

  4. Chemistry in space

    CERN Document Server

    Rehder, Dieter

    2010-01-01

    The dynamic field of extraterrestrial chemistry brings together ideas of chemistr, astrophysics, and biology to the study of molecules between stars, around stars, and on plantes. This book serves as an introduction to chemial processes under ?unearthly? and hence usually extreme conditions (temperature, pressure, high or low density, bombardment by cosmic rays), and their impact on the early development of our solar system, as well as providing a deeper understanding of processes in earthly regions where conditions approach those of extraterrestrial areas.A unique and extraordinary perspe

  5. Principles of quantum chemistry

    CERN Document Server

    George, David V

    2013-01-01

    Principles of Quantum Chemistry focuses on the application of quantum mechanics in physical models and experiments of chemical systems.This book describes chemical bonding and its two specific problems - bonding in complexes and in conjugated organic molecules. The very basic theory of spectroscopy is also considered. Other topics include the early development of quantum theory; particle-in-a-box; general formulation of the theory of quantum mechanics; and treatment of angular momentum in quantum mechanics. The examples of solutions of Schroedinger equations; approximation methods in quantum c

  6. Quantum chemistry an introduction

    CERN Document Server

    Kauzmann, Walter

    2013-01-01

    Quantum Chemistry: An Introduction provides information pertinent to the fundamental aspects of quantum mechanics. This book presents the theory of partial differentiation equations by using the classical theory of vibrations as a means of developing physical insight into this essential branch of mathematics.Organized into five parts encompassing 16 chapters, this book begins with an overview of how quantum mechanical deductions are made. This text then describes the achievements and limitations of the application of quantum mechanics to chemical problems. Other chapters provide a brief survey

  7. Podcasts in the Chemistry Teaching

    Directory of Open Access Journals (Sweden)

    Bruno Silva Leite

    2016-12-01

    Full Text Available Information and Communication Technologies (ICT provide facilities in teaching through education. There are many new tools and methodologies that use ICT as a knowledge-building support, but that are not always related to pedagogical practice. The Podcast is an important technology that can be used in the classroom. Using this tool, it can make the most interactive chemistry class, fleeing the classroom routine. However, it is necessary to point out that the podcast is just one feature that should be incorporated into education and not a substitute. This paper describes the development of Chemistry Podcasts by teachers and chemistry students in three disciplines in 2015. This study took place over a one-year period in a public University, in Pernambuco, Brazil. In the discipline of "Computer applied to the teaching of chemistry" participated 21 Chemistry teachers. In the disciplines of "Information and Communication Technologies in the teaching of chemistry" and "Informatics, Chemistry and Education" was composed of 54 undergraduate students in chemistry. Twelve podcasts were elaborated by students and five by teachers in this paper we present only nine. The results showed the contribution of podcasts produced by teachers and students in teaching and learning process chemistry. DOI: http://dx.doi.org/10.17807/orbital.v0i0.898

  8. Green chemistry: principles and practice.

    Science.gov (United States)

    Anastas, Paul; Eghbali, Nicolas

    2010-01-01

    Green Chemistry is a relatively new emerging field that strives to work at the molecular level to achieve sustainability. The field has received widespread interest in the past decade due to its ability to harness chemical innovation to meet environmental and economic goals simultaneously. Green Chemistry has a framework of a cohesive set of Twelve Principles, which have been systematically surveyed in this critical review. This article covers the concepts of design and the scientific philosophy of Green Chemistry with a set of illustrative examples. Future trends in Green Chemistry are discussed with the challenge of using the Principles as a cohesive design system (93 references).

  9. Green Chemistry for Chemical Synthesis

    National Research Council Canada - National Science Library

    Chao-Jun Li; Barry M. Trost

    2008-01-01

    Green chemistry for chemical synthesis addresses our future challenges in working with chemical processes and products by inventing novel reactions that can maximize the desired products and minimize...

  10. Solid state chemistry an introduction

    CERN Document Server

    Smart, Lesley E

    2012-01-01

    ""Smart and Moore are engaging writers, providing clear explanations for concepts in solid-state chemistry from the atomic/molecular perspective. The fourth edition is a welcome addition to my bookshelves. … What I like most about Solid State Chemistry is that it gives simple clear descriptions for a large number of interesting materials and correspondingly clear explanations of their applications. Solid State Chemistry could be used for a solid state textbook at the third or fourth year undergraduate level, especially for chemistry programs. It is also a useful resource for beginning graduate

  11. The physical basis of chemistry

    CERN Document Server

    Warren, Warren S

    2000-01-01

    If the text you're using for general chemistry seems to lack sufficient mathematics and physics in its presentation of classical mechanics, molecular structure, and statistics, this complementary science series title may be just what you're looking for. Written for the advanced lower-division undergraduate chemistry course, The Physical Basis of Chemistry, Second Edition, offers students an opportunity to understand and enrich the understanding of physical chemistry with some quantum mechanics, the Boltzmann distribution, and spectroscopy. Posed and answered are questions concerning eve

  12. The land-use legacy effect: Towards a mechanistic understanding of time-lagged water quality responses to land use/cover.

    Science.gov (United States)

    Martin, Sherry L; Hayes, Daniel B; Kendall, Anthony D; Hyndman, David W

    2017-02-01

    Numerous studies have linked land use/land cover (LULC) to aquatic ecosystem responses, however only a few have included the dynamics of changing LULC in their analysis. In this study, we explicitly recognize changing LULC by linking mechanistic groundwater flow and travel time models to a historical time series of LULC, creating a land-use legacy map. We then illustrate the utility of legacy maps to explore relationships between dynamic LULC and lake water chemistry. We tested two main concepts about mechanisms linking LULC and lake water chemistry: groundwater pathways are an important mechanism driving legacy effects; and, LULC over multiple spatial scales is more closely related to lake chemistry than LULC over a single spatial scale. We applied statistical models to twelve water chemistry variables, ranging from nutrients to relatively conservative ions, to better understand the roles of biogeochemical reactivity and solubility on connections between LULC and aquatic ecosystem response. Our study illustrates how different areas can have long groundwater pathways that represent different LULC than what can be seen on the landscape today. These groundwater pathways delay the arrival of nutrients and other water quality constituents, thus creating a legacy of historic land uses that eventually reaches surface water. We find that: 1) several water chemistry variables are best fit by legacy LULC while others have a stronger link to current LULC, and 2) single spatial scales of LULC analysis performed worse for most variables. Our novel combination of temporal and spatial scales was the best overall model fit for most variables, including SRP where this model explained 54% of the variation. We show that it is important to explicitly account for temporal and spatial context when linking LULC to ecosystem response. Copyright © 2016. Published by Elsevier B.V.

  13. Elucidating the coordination chemistry and mechanism of biological nitrogen fixation.

    Science.gov (United States)

    Dance, Ian

    2007-08-03

    How does the enzyme nitrogenase reduce the inert molecule N2 to NH3 under ambient conditions that are so different from the energy-expensive conditions of the best industrial practices? This review focuses on recent theoretical investigations of the catalytic site, the iron-molybdenum cofactor FeMo-co, and the way in which it is hydrogenated by protons and electrons and then binds N2. Density functional calculations provide reaction profiles and activation energies for possible mechanistic steps. This establishes a conceptual framework and the principles for the coordination chemistry of FeMo-co that are essential to the chemical mechanism of catalysis. The model advanced herein explains relevant experimental data.

  14. Art in Chemistry: Chemistry in Art. Second Edition

    Science.gov (United States)

    Greenberg, Barbara R.; Patterson, Dianne

    2008-01-01

    This textbook integrates chemistry and art with hands-on activities and fascinating demonstrations that enable students to see and understand how the science of chemistry is involved in the creation of art. It investigates such topics as color integrated with electromagnetic radiation, atoms, and ions; paints integrated with classes of matter,…

  15. Introducing Chemistry Students to the "Real World" of Chemistry

    Science.gov (United States)

    Brown, Michael E.; Cosser, Ronald C.; Davies-Coleman, Michael T.; Kaye, Perry T.; Klein, Rosalyn; Lamprecht, Emmanuel; Lobb, Kevin; Nyokong, Tebello; Sewry, Joyce D.; Tshentu, Zenixole R.; van der Zeyde, Tino; Watkins, Gareth M.

    2010-01-01

    A majority of chemistry graduates seek employment in a rapidly changing chemical industry. Our attempts to provide the graduates with skills in entrepreneurship and the ability to understand and communicate with their chemical engineering colleagues, in addition to their fundamental knowledge of chemistry, are described. This is done at…

  16. Medicinal Chemistry/Pharmacology in Sophomore Organic Chemistry.

    Science.gov (United States)

    Harrison, Aline M.

    1989-01-01

    Discussed is a series of lectures designed to illustrate the use of general organic chemical principles in molecular biology, introduce current research in interdisciplinary areas to the beginner, increase interest in organic chemistry, and bridge the gap between traditional organic chemistry, biology, and the consumer. An outline is presented.…

  17. A Quantum Chemistry Concept Inventory for Physical Chemistry Classes

    Science.gov (United States)

    Dick-Perez, Marilu; Luxford, Cynthia J.; Windus, Theresa L.; Holme, Thomas

    2016-01-01

    A 14-item, multiple-choice diagnostic assessment tool, the quantum chemistry concept inventory or QCCI, is presented. Items were developed based on published student misconceptions and content coverage and then piloted and used in advanced physical chemistry undergraduate courses. In addition to the instrument itself, data from both a pretest,…

  18. Art in Chemistry: Chemistry in Art. Second Edition

    Science.gov (United States)

    Greenberg, Barbara R.; Patterson, Dianne

    2008-01-01

    This textbook integrates chemistry and art with hands-on activities and fascinating demonstrations that enable students to see and understand how the science of chemistry is involved in the creation of art. It investigates such topics as color integrated with electromagnetic radiation, atoms, and ions; paints integrated with classes of matter,…

  19. Introducing Chemistry Students to the "Real World" of Chemistry

    Science.gov (United States)

    Brown, Michael E.; Cosser, Ronald C.; Davies-Coleman, Michael T.; Kaye, Perry T.; Klein, Rosalyn; Lamprecht, Emmanuel; Lobb, Kevin; Nyokong, Tebello; Sewry, Joyce D.; Tshentu, Zenixole R.; van der Zeyde, Tino; Watkins, Gareth M.

    2010-01-01

    A majority of chemistry graduates seek employment in a rapidly changing chemical industry. Our attempts to provide the graduates with skills in entrepreneurship and the ability to understand and communicate with their chemical engineering colleagues, in addition to their fundamental knowledge of chemistry, are described. This is done at…

  20. A Quantum Chemistry Concept Inventory for Physical Chemistry Classes

    Science.gov (United States)

    Dick-Perez, Marilu; Luxford, Cynthia J.; Windus, Theresa L.; Holme, Thomas

    2016-01-01

    A 14-item, multiple-choice diagnostic assessment tool, the quantum chemistry concept inventory or QCCI, is presented. Items were developed based on published student misconceptions and content coverage and then piloted and used in advanced physical chemistry undergraduate courses. In addition to the instrument itself, data from both a pretest,…

  1. Development of a mechanistic model for forced convection subcooled boiling

    Science.gov (United States)

    Shaver, Dillon R.

    The focus of this work is on the formulation, implementation, and testing of a mechanistic model of subcooled boiling. Subcooled boiling is the process of vapor generation on a heated wall when the bulk liquid temperature is still below saturation. This is part of a larger effort by the US DoE's CASL project to apply advanced computational tools to the simulation of light water reactors. To support this effort, the formulation of the dispersed field model is described and a complete model of interfacial forces is formulated. The model has been implemented in the NPHASE-CMFD computer code with a K-epsilon model of turbulence. The interfacial force models are built on extensive work by other authors, and include novel formulations of the turbulent dispersion and lift forces. The complete model of interfacial forces is compared to experiments for adiabatic bubbly flows, including both steady-state and unsteady conditions. The same model is then applied to a transient gas/liquid flow in a complex geometry of fuel channels in a sodium fast reactor. Building on the foundation of the interfacial force model, a mechanistic model of forced-convection subcooled boiling is proposed. This model uses the heat flux partitioning concept and accounts for condensation of bubbles attached to the wall. This allows the model to capture the enhanced heat transfer associated with boiling before the point of net generation of vapor, a phenomenon consistent with existing experimental observations. The model is compared to four different experiments encompassing flows of light water, heavy water, and R12 at different pressures, in cylindrical channels, an internally heated annulus, and a rectangular channel. The experimental data includes axial and radial profiles of both liquid temperature and vapor volume fraction, and the agreement can be considered quite good. The complete model is then applied to simulations of subcooled boiling in nuclear reactor subchannels consistent with the

  2. Modeling Bird Migration under Climate Change: A Mechanistic Approach

    Science.gov (United States)

    Smith, James A.

    2009-01-01

    How will migrating birds respond to changes in the environment under climate change? What are the implications for migratory success under the various accelerated climate change scenarios as forecast by the Intergovernmental Panel on Climate Change? How will reductions or increased variability in the number or quality of wetland stop-over sites affect migratory bird species? The answers to these questions have important ramifications for conservation biology and wildlife management. Here, we describe the use of continental scale simulation modeling to explore how spatio-temporal changes along migratory flyways affect en-route migration success. We use an individually based, biophysical, mechanistic, bird migration model to simulate the movement of shorebirds in North America as a tool to study how such factors as drought and wetland loss may impact migratory success and modify migration patterns. Our model is driven by remote sensing and climate data and incorporates important landscape variables. The energy budget components of the model include resting, foraging, and flight, but presently predation is ignored. Results/Conclusions We illustrate our model by studying the spring migration of sandpipers through the Great Plains to their Arctic breeding grounds. Why many species of shorebirds have shown significant declines remains a puzzle. Shorebirds are sensitive to stop-over quality and spacing because of their need for frequent refueling stops and their opportunistic feeding patterns. We predict bird "hydrographs that is, stop-over frequency with latitude, that are in agreement with the literature. Mean stop-over durations predicted from our model for nominal cases also are consistent with the limited, but available data. For the shorebird species simulated, our model predicts that shorebirds exhibit significant plasticity and are able to shift their migration patterns in response to changing drought conditions. However, the question remains as to whether this

  3. A new mechanistic framework to predict OCS fluxes from soils

    Science.gov (United States)

    Ogée, Jérôme; Sauze, Joana; Kesselmeier, Jürgen; Genty, Bernard; Van Diest, Heidi; Launois, Thomas; Wingate, Lisa

    2016-04-01

    Estimates of photosynthetic and respiratory fluxes at large scales are needed to improve our predictions of the current and future global CO2 cycle. Carbonyl sulfide (OCS) is the most abundant sulfur gas in the atmosphere and has been proposed as a new tracer of photosynthetic gross primary productivity (GPP), as the uptake of OCS from the atmosphere is dominated by the activity of carbonic anhydrase (CA), an enzyme abundant in leaves that also catalyses CO2 hydration during photosynthesis. However soils also exchange OCS with the atmosphere, which complicates the retrieval of GPP from atmospheric budgets. Indeed soils can take up large amounts of OCS from the atmosphere as soil microorganisms also contain CA, and OCS emissions from soils have been reported in agricultural fields or anoxic soils. To date no mechanistic framework exists to describe this exchange of OCS between soils and the atmosphere, but empirical results, once upscaled to the global scale, indicate that OCS consumption by soils dominates OCS emission and its contribution to the atmospheric budget is large, at about one third of the OCS uptake by vegetation, also with a large uncertainty. Here, we propose a new mechanistic model of the exchange of OCS between soils and the atmosphere that builds on our knowledge of soil CA activity from CO2 oxygen isotopes. In this model the OCS soil budget is described by a first-order reaction-diffusion-production equation, assuming that the hydrolysis of OCS by CA is total and irreversible. Using this model we are able to explain the observed presence of an optimum temperature for soil OCS uptake and show how this optimum can shift to cooler temperatures in the presence of soil OCS emission. Our model can also explain the observed optimum with soil moisture content previously described in the literature as a result of diffusional constraints on OCS hydrolysis. These diffusional constraints are also responsible for the response of OCS uptake to soil weight and

  4. Modeling Bird Migration under Climate Change: A Mechanistic Approach

    Science.gov (United States)

    Smith, James A.

    2009-01-01

    How will migrating birds respond to changes in the environment under climate change? What are the implications for migratory success under the various accelerated climate change scenarios as forecast by the Intergovernmental Panel on Climate Change? How will reductions or increased variability in the number or quality of wetland stop-over sites affect migratory bird species? The answers to these questions have important ramifications for conservation biology and wildlife management. Here, we describe the use of continental scale simulation modeling to explore how spatio-temporal changes along migratory flyways affect en-route migration success. We use an individually based, biophysical, mechanistic, bird migration model to simulate the movement of shorebirds in North America as a tool to study how such factors as drought and wetland loss may impact migratory success and modify migration patterns. Our model is driven by remote sensing and climate data and incorporates important landscape variables. The energy budget components of the model include resting, foraging, and flight, but presently predation is ignored. Results/Conclusions We illustrate our model by studying the spring migration of sandpipers through the Great Plains to their Arctic breeding grounds. Why many species of shorebirds have shown significant declines remains a puzzle. Shorebirds are sensitive to stop-over quality and spacing because of their need for frequent refueling stops and their opportunistic feeding patterns. We predict bird "hydrographs that is, stop-over frequency with latitude, that are in agreement with the literature. Mean stop-over durations predicted from our model for nominal cases also are consistent with the limited, but available data. For the shorebird species simulated, our model predicts that shorebirds exhibit significant plasticity and are able to shift their migration patterns in response to changing drought conditions. However, the question remains as to whether this

  5. Complex Protostellar Chemistry

    Science.gov (United States)

    Nuth, Joseph A., III; Johnson, Natasha M.

    2012-01-01

    Two decades ago, our understanding of the chemistry in protostars was simple-matter either fell into the central star or was trapped in planetary-scale objects. Some minor chemical changes might occur as the dust and gas fell inward, but such effects were overwhelmed by the much larger scale processes that occurred even in bodies as small as asteroids. The chemistry that did occur in the nebula was relatively easy to model because the fall from the cold molecular cloud into the growing star was a one-way trip down a well-known temperature-pressure gradient; the only free variable was time. However, just over 10 years ago it was suggested that some material could be processed in the inner nebula, flow outward, and become incorporated into comets (1, 2). This outward flow was confirmed when the Stardust mission returned crystalline mineral fragments (3) from Comet Wild 2 that must have been processed close to the Sun before they were incorporated into the comet. In this week's Science Express, Ciesla and Sandford (4) demonstrate that even the outermost regions of the solar nebula can be a chemically active environment. Their finding could have consequences for the rest of the nebula.

  6. Complex Protostellar Chemistry

    Science.gov (United States)

    Nuth, Joseph A., III; Johnson, Natasha M.

    2012-01-01

    Two decades ago, our understanding of the chemistry in protostars was simple-matter either fell into the central star or was trapped in planetary-scale objects. Some minor chemical changes might occur as the dust and gas fell inward, but such effects were overwhelmed by the much larger scale processes that occurred even in bodies as small as asteroids. The chemistry that did occur in the nebula was relatively easy to model because the fall from the cold molecular cloud into the growing star was a one-way trip down a well-known temperature-pressure gradient; the only free variable was time. However, just over 10 years ago it was suggested that some material could be processed in the inner nebula, flow outward, and become incorporated into comets (1, 2). This outward flow was confirmed when the Stardust mission returned crystalline mineral fragments (3) from Comet Wild 2 that must have been processed close to the Sun before they were incorporated into the comet. In this week's Science Express, Ciesla and Sandford (4) demonstrate that even the outermost regions of the solar nebula can be a chemically active environment. Their finding could have consequences for the rest of the nebula.

  7. From organic chemistry to fat and oil chemistry*

    Directory of Open Access Journals (Sweden)

    Deffense Etienne

    2009-01-01

    Full Text Available With his work on animal fat and identification of fatty acids, Chevreul was a pioneer in organic chemistry. As Chevreul, I had a passion for organic chemistry too. It was then, an honour and a pleasure to present in 2008 at EFL in Athens this presentation entitled “From organic chemistry to fat and oil chemistry” because my background in organic chemistry helped me all along my professional career to understand and implement new developments related to oil and fat technology and processing. Among the topics which I worked out, I highlighted more particularly the following subjects: the degumming chemistry of oil and fat; the improvement of physical refining; a new chemical analytical tool for the dry fractionation; new development in the dry fractionation

  8. Green Chemistry Metrics with Special Reference to Green Analytical Chemistry.

    Science.gov (United States)

    Tobiszewski, Marek; Marć, Mariusz; Gałuszka, Agnieszka; Namieśnik, Jacek

    2015-06-12

    The concept of green chemistry is widely recognized in chemical laboratories. To properly measure an environmental impact of chemical processes, dedicated assessment tools are required. This paper summarizes the current state of knowledge in the field of development of green chemistry and green analytical chemistry metrics. The diverse methods used for evaluation of the greenness of organic synthesis, such as eco-footprint, E-Factor, EATOS, and Eco-Scale are described. Both the well-established and recently developed green analytical chemistry metrics, including NEMI labeling and analytical Eco-scale, are presented. Additionally, this paper focuses on the possibility of the use of multivariate statistics in evaluation of environmental impact of analytical procedures. All the above metrics are compared and discussed in terms of their advantages and disadvantages. The current needs and future perspectives in green chemistry metrics are also discussed.

  9. Green Chemistry Metrics with Special Reference to Green Analytical Chemistry

    Directory of Open Access Journals (Sweden)

    Marek Tobiszewski

    2015-06-01

    Full Text Available The concept of green chemistry is widely recognized in chemical laboratories. To properly measure an environmental impact of chemical processes, dedicated assessment tools are required. This paper summarizes the current state of knowledge in the field of development of green chemistry and green analytical chemistry metrics. The diverse methods used for evaluation of the greenness of organic synthesis, such as eco-footprint, E-Factor, EATOS, and Eco-Scale are described. Both the well-established and recently developed green analytical chemistry metrics, including NEMI labeling and analytical Eco-scale, are presented. Additionally, this paper focuses on the possibility of the use of multivariate statistics in evaluation of environmental impact of analytical procedures. All the above metrics are compared and discussed in terms of their advantages and disadvantages. The current needs and future perspectives in green chemistry metrics are also discussed.

  10. Computational organic chemistry: bridging theory and experiment in establishing the mechanisms of chemical reactions.

    Science.gov (United States)

    Cheng, Gui-Juan; Zhang, Xinhao; Chung, Lung Wa; Xu, Liping; Wu, Yun-Dong

    2015-02-11

    Understanding the mechanisms of chemical reactions, especially catalysis, has been an important and active area of computational organic chemistry, and close collaborations between experimentalists and theorists represent a growing trend. This Perspective provides examples of such productive collaborations. The understanding of various reaction mechanisms and the insight gained from these studies are emphasized. The applications of various experimental techniques in elucidation of reaction details as well as the development of various computational techniques to meet the demand of emerging synthetic methods, e.g., C-H activation, organocatalysis, and single electron transfer, are presented along with some conventional developments of mechanistic aspects. Examples of applications are selected to demonstrate the advantages and limitations of these techniques. Some challenges in the mechanistic studies and predictions of reactions are also analyzed.

  11. Significant steps in the evolution of analytical chemistry--is the today's analytical chemistry only chemistry?

    Science.gov (United States)

    Karayannis, Miltiades I; Efstathiou, Constantinos E

    2012-12-15

    In this review the history of chemistry and specifically the history and the significant steps of the evolution of analytical chemistry are presented. In chronological time spans, covering the ancient world, the middle ages, the period of the 19th century, and the three evolutional periods, from the verge of the 19th century to contemporary times, it is given information for the progress of chemistry and analytical chemistry. During this period, analytical chemistry moved gradually from its pure empirical nature to more rational scientific activities, transforming itself to an autonomous branch of chemistry and a separate discipline. It is also shown that analytical chemistry moved gradually from the status of exclusive serving the chemical science, towards serving, the environment, health, law, almost all areas of science and technology, and the overall society. Some recommendations are also directed to analytical chemistry educators concerning the indispensable nature of knowledge of classical analytical chemistry and the associated laboratory exercises and to analysts, in general, why it is important to use the chemical knowledge to make measurements on problems of everyday life.

  12. Rapid Discrimination Among Putative Mechanistic Models of Biochemical Systems.

    Science.gov (United States)

    Lomnitz, Jason G; Savageau, Michael A

    2016-08-31

    An overarching goal in molecular biology is to gain an understanding of the mechanistic basis underlying biochemical systems. Success is critical if we are to predict effectively the outcome of drug treatments and the development of abnormal phenotypes. However, data from most experimental studies is typically noisy and sparse. This allows multiple potential mechanisms to account for experimental observations, and often devising experiments to test each is not feasible. Here, we introduce a novel strategy that discriminates among putative models based on their repertoire of qualitatively distinct phenotypes, without relying on knowledge of specific values for rate constants and binding constants. As an illustration, we apply this strategy to two synthetic gene circuits exhibiting anomalous behaviors. Our results show that the conventional models, based on their well-characterized components, cannot account for the experimental observations. We examine a total of 40 alternative hypotheses and show that only 5 have the potential to reproduce the experimental data, and one can do so with biologically relevant parameter values.

  13. Ancient Chinese medicine and mechanistic evidence of acupuncture physiology.

    Science.gov (United States)

    Yang, Edward S; Li, Pei-Wen; Nilius, Bernd; Li, Geng

    2011-11-01

    Acupuncture has been widely used in China for three millennia as an art of healing. Yet, its physiology is not yet understood. The current interest in acupuncture started in 1971. Soon afterward, extensive research led to the concept of neural signaling with possible involvement of opioid peptides, glutamate, adenosine and identifying responsive parts in the central nervous system. In the last decade scientists began investigating the subject with anatomical and molecular imaging. It was found that mechanical movements of the needle, ignored in the past, appear to be central to the method and intracellular calcium ions may play a pivotal role. In this review, we trace the technique of clinical treatment from the first written record about 2,200 years ago to the modern time. The ancient texts have been used to introduce the concepts of yin, yang, qi, de qi, and meridians, the traditional foundation of acupuncture. We explore the sequence of the physiological process, from the turning of the needle, the mechanical wave activation of calcium ion channel to beta-endorphin secretion. By using modern terminology to re-interpret the ancient texts, we have found that the 2nd century B.C.: physiologists were meticulous investigators and their explanation fits well with the mechanistic model derived from magnetic resonance imaging (MRI) and confocal microscopy. In conclusion, the ancient model appears to have withstood the test of time surprisingly well confirming the popular axiom that the old wine is better than the new.

  14. Fine particulate matter air pollution and atherosclerosis: Mechanistic insights.

    Science.gov (United States)

    Bai, Yuntao; Sun, Qinghua

    2016-12-01

    Atherosclerosis is a progressive disease characterized by the accumulation of lipids and fibrous plaque in the arteries. Its etiology is very complicated and its risk factors primarily include genetic defects, smoking, hyperlipidemia, hypertension, lack of exercise, and infection. Recent studies suggest that fine particulate matter (PM2.5) air pollution may also contribute to the development of atherosclerosis. The present review integrates current experimental evidence with mechanistic pathways whereby PM2.5 exposure can promote the development of atherosclerosis. PM2.5-mediated enhancement of atherosclerosis is likely due to its pro-oxidant and pro-inflammatory effects, involving multiple organs, different cell types, and various molecular mediators. Studies about the effects of PM2.5inhalation on atherosclerosis may yield a better understanding of the link between air pollution and major cardiovascular diseases, and provide useful information for policy makers to determine acceptable levels of PM2.5 air quality. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Analytical techniques for mechanistic characterization of EUV photoresists

    Science.gov (United States)

    Grzeskowiak, Steven; Narasimhan, Amrit; Murphy, Michael; Ackerman, Christian; Kaminsky, Jake; Brainard, Robert L.; Denbeaux, Greg

    2017-03-01

    Extreme ultraviolet (EUV, 13.5 nm) lithography is the prospective technology for high volume manufacturing by the microelectronics industry. Significant strides towards achieving adequate EUV source power and availability have been made recently, but a limited rate of improvement in photoresist performance still delays the implementation of EUV. Many fundamental questions remain to be answered about the exposure mechanisms of even the relatively well understood chemically amplified EUV photoresists. Moreover, several groups around the world are developing revolutionary metal-based resists whose EUV exposure mechanisms are even less understood. Here, we describe several evaluation techniques to help elucidate mechanistic details of EUV exposure mechanisms of chemically amplified and metal-based resists. EUV absorption coefficients are determined experimentally by measuring the transmission through a resist coated on a silicon nitride membrane. Photochemistry can be evaluated by monitoring small outgassing reaction products to provide insight into photoacid generator or metal-based resist reactivity. Spectroscopic techniques such as thin-film Fourier transform infrared (FTIR) spectroscopy can measure the chemical state of a photoresist system pre- and post-EUV exposure. Additionally, electrolysis can be used to study the interaction between photoresist components and low energy electrons. Collectively, these techniques improve our current understanding of photomechanisms for several EUV photoresist systems, which is needed to develop new, better performing materials needed for high volume manufacturing.

  16. Mechanistic Perspectives of Maslinic Acid in Targeting Inflammation

    Directory of Open Access Journals (Sweden)

    Wei Hsum Yap

    2015-01-01

    Full Text Available Chronic inflammation drives the development of various pathological diseases such as rheumatoid arthritis, atherosclerosis, multiple sclerosis, and cancer. The arachidonic acid pathway represents one of the major mechanisms for inflammation. Prostaglandins (PGs are lipid products generated from arachidonic acid by the action of cyclooxygenase (COX enzymes and their activity is blocked by nonsteroidal anti-inflammatory drugs (NSAIDS. The use of natural compounds in regulation of COX activity/prostaglandins production is receiving increasing attention. In Mediterranean diet, olive oil and table olives contain significant dietary sources of maslinic acid. Maslinic acid is arising as a safe and novel natural pentacyclic triterpene which has protective effects against chronic inflammatory diseases in various in vivo and in vitro experimental models. Understanding the anti-inflammatory mechanism of maslinic acid is crucial for its development as a potential dietary nutraceutical. This review focuses on the mechanistic action of maslinic acid in regulating the inflammation pathways through modulation of the arachidonic acid metabolism including the nuclear factor-kappa B (NF-κB/COX-2 expression, upstream protein kinase signaling, and phospholipase A2 enzyme activity. Further investigations may provide insight into the mechanism of maslinic acid in regulating the molecular targets and their associated pathways in response to specific inflammatory stimuli.

  17. A brief review of exercise, bipolar disorder and mechanistic pathways

    Directory of Open Access Journals (Sweden)

    Daniel eThomson

    2015-03-01

    Full Text Available Despite evidence that exercise has been found to be effective in the treatment of depression, it is unclear whether these data can be extrapolated to bipolar disorder. Available evidence for bipolar disorder is scant, with no existing randomised controlled trials having tested the impact of exercise on depressive, manic or hypomanic symptomatology. Although exercise is often recommended in bipolar disorder, this is based on extrapolation from the unipolar literature, theory and clinical expertise and not empirical evidence. In addition, there are currently no available empirical data on program variables, with practical implications on frequency, intensity and type of exercise derived from unipolar depression studies. The aim of the current paper is to explore the relationship between exercise and bipolar disorder and potential mechanistic pathways. Given the high rate of medical co-morbidities experienced by people with bipolar disorder, it is possible that exercise is a potentially useful and important intervention with regard to general health benefits; however, further research is required to elucidate the impact of exercise on mood symptomology.

  18. Warming will affect phytoplankton differently: evidence through a mechanistic approach.

    Science.gov (United States)

    Huertas, I Emma; Rouco, Mónica; López-Rodas, Victoria; Costas, Eduardo

    2011-12-07

    Although the consequences of global warming in aquatic ecosystems are only beginning to be revealed, a key to forecasting the impact on aquatic communities is an understanding of individual species' vulnerability to increased temperature. Despite their microscopic size, phytoplankton support about half of the global primary production, drive essential biogeochemical cycles and represent the basis of the aquatic food web. At present, it is known that phytoplankton are important targets and, consequently, harbingers of climate change in aquatic systems. Therefore, investigating the capacity of phytoplankton to adapt to the predicted warming has become a relevant issue. However, considering the polyphyletic complexity of the phytoplankton community, different responses to increased temperature are expected. We experimentally tested the effects of warming on 12 species of phytoplankton isolated from a variety of environments by using a mechanistic approach able to assess evolutionary adaptation (the so-called ratchet technique). We found different degrees of tolerance to temperature rises and an interspecific capacity for genetic adaptation. The thermal resistance level reached by each species is discussed in relation to their respective original habitats. Our study additionally provides evidence on the most resistant phytoplankton groups in a future warming scenario.

  19. Stem cell guidance through the mechanistic target of rapamycin

    Institute of Scientific and Technical Information of China (English)

    Kenneth; Maiese

    2015-01-01

    Stem cells offer great promise for the treatment of multiple disorders throughout the body. Critical to this premise is the ability to govern stem cell pluripotency, proliferation, and differentiation. The mechanistic target of rapamycin(mT OR), 289-kD a serine/threonine protein kinase, that is a vital component of mT OR Complex 1 and mT OR Complex 2 represents a critical pathway for the oversight of stem cell maintenance. mT OR can control the programmed cell death pathways of autophagy andapoptosis that can yield variable outcomes in stem cell survival and be reliant upon proliferative pathways that include Wnt signaling, Wnt1 inducible signaling pathway protein 1(WISP1), silent mating type information regulation 2 homolog 1(Saccharomyces cerevisiae)(SIRT1), and trophic factors. mT OR also is a necessary component for the early development and establishment of stem cells as well as having a significant impact in the regulation of the maturation of specific cell phenotypes. Yet, as a proliferative agent, mT OR can not only foster cancer stem cell development and tumorigenesis, but also mediate cell senescence under certain conditions to limit invasive cancer growth. mT OR offers an exciting target for the oversight of stem cell therapies but requires careful consideration of the diverse clinical outcomes that can be fueled by mT OR signaling pathways.

  20. Palladium Catalyzed Allylic C-H Alkylation: A Mechanistic Perspective

    Directory of Open Access Journals (Sweden)

    Casper Junker Engelin

    2011-01-01

    Full Text Available The atom-efficiency of one of the most widely used catalytic reactions for forging C-C bonds, the Tsuji-Trost reaction, is limited by the need of preoxidized reagents. This limitation can be overcome by utilization of the recently discovered palladium-catalyzed C-H activation, the allylic C-H alkylation reaction which is the topic of the current review. Particular emphasis is put on current mechanistic proposals for the three reaction types comprising the overall transformation: C-H activation, nucleophillic addition, and re-oxidation of the active catalyst. Recent advances in C-H bond activation are highlighted with emphasis on those leading to C-C bond formation, but where it was deemed necessary for the general understanding of the process closely related C-H oxidations and aminations are also included. It is found that C-H cleavage is most likely achieved by ligand participation which could involve an acetate ion coordinated to Pd. Several of the reported systems rely on benzoquinone for re-oxidation of the active catalyst. The scope for nucleophilic addition in allylic C-H alkylation is currently limited, due to demands on pKa of the nucleophile. This limitation could be due to the pH dependence of the benzoquinone/hydroquinone redox couple. Alternative methods for re-oxidation that does not rely on benzoquinone could be able to alleviate this limitation.

  1. Mechanistic Features of Nanodiamonds in the Lapping of Magnetic Heads

    Directory of Open Access Journals (Sweden)

    Xionghua Jiang

    2014-01-01

    Full Text Available Nanodiamonds, which are the main components of slurry in the precision lapping process of magnetic heads, play an important role in surface quality. This paper studies the mechanistic features of nanodiamond embedment into a Sn plate in the lapping process. This is the first study to develop mathematical models for nanodiamond embedment. Such models can predict the optimum parameters for particle embedment. From the modeling calculations, the embedded pressure satisfies p0=3/2·W/πa2 and the indentation depth satisfies δ=k1P/HV. Calculation results reveal that the largest embedded pressure is 731.48 GPa and the critical indentation depth δ is 7 nm. Atomic force microscopy (AFM, scanning electron microscopy (SEM, and Auger electron spectroscopy (AES were used to carry out surface quality detection and analysis of the disk head. Both the formation of black spots on the surface and the removal rate have an important correlation with the size of nanodiamonds. The results demonstrate that an improved removal rate (21 nm·min−1 can be obtained with 100 nm diamonds embedded in the plate.

  2. AIR POLLUTION, INFLAMMATION AND PRETERM BIRTH: A POTENTIAL MECHANISTIC LINK

    Science.gov (United States)

    Vadillo-Ortega, Felipe; Osornio-Vargas, Alvaro; Buxton, Miatta A.; Sánchez, Brisa N.; Rojas-Bracho, Leonora; Viveros-Alcaráz, Martin; Castillo-Castrejón, Marisol; Beltrán-Montoya, Jorge; Brown, Daniel G.; O´Neill, Marie S.

    2014-01-01

    Preterm birth is a public health issue of global significance, which may result in mortality during the perinatal period or may lead to major health and financial consequences due to lifelong impacts. Even though several risk factors for preterm birth have been identified, prevention efforts have failed to halt the increasing rates of preterm birth. Epidemiological studies have identified air pollution as an emerging potential risk factor for preterm birth. However, many studies were limited by study design and inadequate exposure assessment. Due to the ubiquitous nature of ambient air pollution and the potential public health significance of any role in causing preterm birth, a novel focus investigating possible causal mechanisms influenced by air pollution is therefore a global health priority. We hypothesize that air pollution may act together with other biological factors to induce systemic inflammation and influence the duration of pregnancy. Evaluation and testing of this hypothesis is currently being conducted in a prospective cohort study in Mexico City and will provide an understanding of the pathways that mediate the effects of air pollution on preterm birth. The important public health implication is that crucial steps in this mechanistic pathway can potentially be acted on early in pregnancy to reduce the risk of preterm birth. PMID:24382337

  3. Mechanistic evaluation of virus clearance by depth filtration.

    Science.gov (United States)

    Venkiteshwaran, Adith; Fogle, Jace; Patnaik, Purbasa; Kowle, Ron; Chen, Dayue

    2015-01-01

    Virus clearance by depth filtration has not been well-understood mechanistically due to lack of quantitative data on filter charge characteristics and absence of systematic studies. It is generally believed that both electrostatic interactions and sized based mechanical entrapment contribute to virus clearance by depth filtration. In order to establish whether the effectiveness of virus clearance correlates with the charge characteristics of a given depth filter, a counter-ion displacement technique was employed to determine the ionic capacity for several depth filters. Two depth filters (Millipore B1HC and X0HC) with significant differences in ionic capacities were selected and evaluated for their ability to eliminate viruses. The high ionic capacity X0HC filter showed complete porcine parvovirus (PPV) clearance (eliminating the spiked viruses to below the limit of detection) under low conductivity conditions (≤2.5 mS/cm), achieving a log10 reduction factor (LRF) of > 4.8. On the other hand, the low ionic capacity B1HC filter achieved only ∼2.1-3.0 LRF of PPV clearance under the same conditions. These results indicate that parvovirus clearance by these two depth filters are mainly achieved via electrostatic interactions between the filters and PPV. When much larger xenotropic murine leukemia virus (XMuLV) was used as the model virus, complete retrovirus clearance was obtained under all conditions evaluated for both depth filters, suggesting the involvement of mechanisms other than just electrostatic interactions in XMuLV clearance.

  4. Mechanistic understanding of monosaccharide-air flow battery electrochemistry

    Science.gov (United States)

    Scott, Daniel M.; Tsang, Tsz Ho; Chetty, Leticia; Aloi, Sekotilani; Liaw, Bor Yann

    Recently, an inexpensive monosaccharide-air flow battery configuration has been demonstrated to utilize a strong base and a mediator redox dye to harness electrical power from the partial oxidation of glucose. Here the mechanistic understanding of glucose oxidation in this unique glucose-air power source is further explored by acid-base titration experiments, 13C NMR, and comparison of results from chemically different redox mediators (indigo carmine vs. methyl viologen) and sugars (fructose vs. glucose) via studies using electrochemical techniques. Titration results indicate that gluconic acid is the main product of the cell reaction, as supported by evidence in the 13C NMR spectra. Using indigo carmine as the mediator dye and fructose as the energy source, an abiotic cell configuration generates a power density of 1.66 mW cm -2, which is greater than that produced from glucose under similar conditions (ca. 1.28 mW cm -2). A faster transition from fructose into the ene-diol intermediate than from glucose likely contributed to this difference in power density.

  5. Mechanistic aspects of photooxidation of polyhydroxylated molecules on metal oxides.

    Energy Technology Data Exchange (ETDEWEB)

    Shkrob, I. A.; Marin, T. M.; Sevilla, M. D.; Chemerisov, S. (Chemical Sciences and Engineering Division); (Benedictine Univ.); (Oakland Univ.)

    2011-03-24

    Polyhydroxylated molecules, including natural carbohydrates, are known to undergo photooxidation on wide-gap transition-metal oxides irradiated by ultraviolet light. In this study, we examine mechanistic aspects of this photoreaction on aqueous TiO{sub 2}, {alpha}-FeOOH, and {alpha}-Fe{sub 2}O{sub 3} particles using electron paramagnetic resonance (EPR) spectroscopy and site-selective deuteration. We demonstrate that the carbohydrates are oxidized at sites involved in the formation of oxo bridges between the chemisorbed carbohydrate molecule and metal ions at the oxide surface. This bridging inhibits the loss of water (which is the typical reaction of the analogous free radicals in bulk solvent) promoting instead a rearrangement that leads to elimination of the formyl radical. For natural carbohydrates, the latter reaction mainly involves carbon-1, whereas the main radical products of the oxidation are radical arising from H atom loss centered on carbon-1, -2, and -3 sites. Photoexcited TiO{sub 2} oxidizes all of the carbohydrates and polyols, whereas {alpha}-FeOOH oxidizes some of the carbohydrates, and {alpha}-Fe{sub 2}O{sub 3} is unreactive. These results serve as a stepping stone for understanding the photochemistry on mineral surfaces of more complex biomolecules such as nucleic acids.

  6. Mechanistic aspects of photooxidation of polyhydroxylated molecules on metal oxides

    Science.gov (United States)

    Shkrob, Ilya A.; Marin, Timothy M.; Chemerisov, Sergey D.; Sevilla, Michael D.

    2011-01-01

    Polyhydroxylated molecules, including natural carbohydrates, are known to undergo photooxidation on wide-gap transition metal oxides irradiated by ultraviolet light. In this study, we examine mechanistic aspects of this photoreaction on aqueous TiO2, α-FeOOH, and α-Fe2O3 particles using electron paramagnetic resonance (EPR) spectroscopy and site-selective deuteration. We demonstrate that the carbohydrates are oxidized at sites involved in the formation of oxo-bridges between the chemisorbed carbohydrate molecule and metal ions at the oxide surface. This bridging inhibits the loss of water (which is the typical reaction of the analogous free radicals in bulk solvent) promoting instead a rearrangement that leads to elimination of the formyl radical. For natural carbohydrates, the latter reaction mainly involves carbon-1, whereas the main radical products of the oxidation are radical arising from H atom loss centered on carbon-1, -2, and -3 sites. Photoexcited TiO2 oxidizes all of the carbohydrates and polyols, whereas α-FeOOH oxidizes some of the carbohydrates, and α-Fe2O3 is unreactive. These results serve as a stepping stone for understanding the photochemistry on mineral surfaces of more complex biomolecules such as nucleic acids. PMID:21532934

  7. Mechanistic insight into sonochemical biodiesel synthesis using heterogeneous base catalyst.

    Science.gov (United States)

    Choudhury, Hanif A; Chakma, Sankar; Moholkar, Vijayanand S

    2014-01-01

    The beneficial effect of ultrasound on transesterification reaction is well known. Heterogeneous (or solid) catalysts for biodiesel synthesis have merit that they do not contaminate the byproduct of glycerol. In this paper, we have attempted to identify the mechanistic features of ultrasound-enhanced biodiesel synthesis with the base-catalyst of CaO. A statistical design of experiments (Box-Behnken) was used to identify the influence of temperature, alcohol to oil molar ratio and catalyst loading on transesterification yield. The optimum values of these parameters for the highest yield were identified through Response Surface Method (with a quadratic model) and ANOVA. These values are: temperature=62 °C, molar ratio=10:1 and catalyst loading=6 wt.%. The activation energy was determined as 82.3 kJ/mol, which is higher than that for homogeneous catalyzed system (for both acidic and basic catalyst). The experimental results have been analyzed vis-à-vis simulations of cavitation bubble dynamics. Due to 3-phase heterogeneity of the system, the yield was dominated by intrinsic kinetics, and the optimum temperature for the highest yield was close to boiling point of methanol. At this temperature, the influence of cavitation bubbles (in terms of both sonochemical and sonophysical effect) is negligible, and ultrasonic micro-streaming provided necessary convection in the system. The influence of all parameters on the reaction system was found to be strongly inter-dependent.

  8. Mechanistic modeling of aberrant energy metabolism in human disease

    Directory of Open Access Journals (Sweden)

    Vineet eSangar

    2012-10-01

    Full Text Available Dysfunction in energy metabolism—including in pathways localized to the mitochondria—has been implicated in the pathogenesis of a wide array of disorders, ranging from cancer to neurodegenerative diseases to type II diabetes. The inherent complexities of energy and mitochondrial metabolism present a significant obstacle in the effort to understand the role that these molecular processes play in the development of disease. To help unravel these complexities, systems biology methods have been applied to develop an array of computational metabolic models, ranging from mitochondria-specific processes to genome-scale cellular networks. These constraint-based models can efficiently simulate aspects of normal and aberrant metabolism in various genetic and environmental conditions. Development of these models leverages—and also provides a powerful means to integrate and interpret—information from a wide range of sources including genomics, proteomics, metabolomics, and enzyme kinetics. Here, we review a variety of mechanistic modeling studies that explore metabolic functions, deficiency disorders, and aberrant biochemical pathways in mitochondria and related regions in the cell.

  9. Equation-free mechanistic ecosystem forecasting using empirical dynamic modeling.

    Science.gov (United States)

    Ye, Hao; Beamish, Richard J; Glaser, Sarah M; Grant, Sue C H; Hsieh, Chih-Hao; Richards, Laura J; Schnute, Jon T; Sugihara, George

    2015-03-31

    It is well known that current equilibrium-based models fall short as predictive descriptions of natural ecosystems, and particularly of fisheries systems that exhibit nonlinear dynamics. For example, model parameters assumed to be fixed constants may actually vary in time, models may fit well to existing data but lack out-of-sample predictive skill, and key driving variables may be misidentified due to transient (mirage) correlations that are common in nonlinear systems. With these frailties, it is somewhat surprising that static equilibrium models continue to be widely used. Here, we examine empirical dynamic modeling (EDM) as an alternative to imposed model equations and that accommodates both nonequilibrium dynamics and nonlinearity. Using time series from nine stocks of sockeye salmon (Oncorhynchus nerka) from the Fraser River system in British Columbia, Canada, we perform, for the the first time to our knowledge, real-data comparison of contemporary fisheries models with equivalent EDM formulations that explicitly use spawning stock and environmental variables to forecast recruitment. We find that EDM models produce more accurate and precise forecasts, and unlike extensions of the classic Ricker spawner-recruit equation, they show significant improvements when environmental factors are included. Our analysis demonstrates the strategic utility of EDM for incorporating environmental influences into fisheries forecasts and, more generally, for providing insight into how environmental factors can operate in forecast models, thus paving the way for equation-free mechanistic forecasting to be applied in management contexts.

  10. Applying Mechanistic Dam Breach Models to Historic Levee Breaches

    Directory of Open Access Journals (Sweden)

    Risher Paul

    2016-01-01

    Full Text Available Hurricane Katrina elevated levee risk in the US national consciousness, motivating agencies to assess and improve their levee risk assessment methodology. Accurate computation of the flood flow magnitude and timing associated with a levee breach remains one of the most difficult and uncertain components of levee risk analysis. Contemporary methods are largely empirical and approximate, introducing substantial uncertainty to the damage and life loss models. Levee breach progressions are often extrapolated to the final width and breach formation time based on limited experience with past breaches or using regression equations developed from a limited data base of dam failures. Physically based embankment erosion models could improve levee breach modeling. However, while several mechanistic embankment breach models are available, they were developed for dams. Several aspects of the levee breach problem are distinct, departing from dam breach assumptions. This study applies three embankments models developed for dam breach analysis (DL Breach, HR BREACH, and WinDAM C to historic levee breaches with observed (or inferred breach rates, assessing the limitations, and applicability of each model to the levee breach problem.

  11. Mechanistic insights into acyclovir-polyethylene glycol 20000 binary dispersions

    Science.gov (United States)

    Venkateskumar, Krishnamoorthy; Parasuraman, Subramani; Gunasunderi, Raju; Sureshkumar, Krishnan; Nayak, M. Muralidhar; Shah, Syed Adnan Ali; Kassen, Khoo; Kai, Heng Wei

    2016-01-01

    Objective: The objective of this study is to provide a mechanistic insight into solubility enhancement and dissolution of acyclovir (ACY) by polyethylene glycol20000 (PEG20000). Materials and Methods: Solid dispersions with differing ratios of drug (ACY) and carrier (PEG20000) were prepared and evaluated by phase solubility, in vitro release studies, kinetic analysis, in situ perfusion, and in vitro permeation studies. Solid state characterization was also done by Powder X-Ray Diffraction (PXRD), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared spectroscopy (FT-IR) analysis and surface morphology was assessed by Polarizing Microscopic Image (PMI) analysis, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and Nuclear Magnetic Resonance (NMR) analysis. Results: Thermodynamic parameters proved the solubilization effect of carrier. The aqueous solubility and dissolution of ACY were increased in all samples. Formation of solid solution, crystallinity reduction, and absence of interaction between drug and carrier was proved by XRD, DSC, and FTIR analysis. The particle size reduction and change in surface morphology were confirmed by SEM and AFM and analysis. The permeation coefficient and amount of drug diffused was higher in samples as compared to ACY. The stability was high in dispersions, and it was proved by NMR analysis. Conclusion: The mechanical insights into the enhancement of solubility and dissolution could be used as a platform to improve the aqueous solubility for other poor water soluble drugs. PMID:28123988

  12. Mechanistic rationales for targeting interleukin-17A in spondyloarthritis.

    Science.gov (United States)

    Raychaudhuri, Siba P; Raychaudhuri, Smriti K

    2017-03-08

    The term spondyloarthritis (SpA) is used to describe a group of inflammatory autoimmune diseases, including ankylosing spondylitis and psoriatic arthritis, with common genetic risk factors and clinical features. SpA is clinically distinct from rheumatoid arthritis and typically affects the spine, sacroiliac joints, entheses, and, less commonly, peripheral joints. Although the pathogenesis of SpA is not fully understood, recent findings have identified the interleukin (IL)-17 pathway as a key mediator of disease pathogenesis. Clinical evidence for the efficacy of IL-17A inhibition by biologic agents was initially shown in patients with chronic plaque psoriasis, another autoimmune disease mediated by the IL-17 pathway. Subsequently, similar positive efficacy for inhibition of IL-17A was seen in patients with ankylosing spondylitis and psoriatic arthritis. Inhibition of IL-17A may also improve cardiovascular and metabolic comorbidities often found in patients with SpA because studies have linked these disorders to the IL-17 pathway. In this review, we will examine key preclinical studies that demonstrated the mechanistic role of IL-17A in the development SpA and discuss how these observations were translated into clinical practice.

  13. A Mechanistic Model of a Passive Autocatalytic Hydrogen Recombiner

    Directory of Open Access Journals (Sweden)

    Rożeń Antoni

    2015-03-01

    Full Text Available : A passive autocatalytic hydrogen recombiner (PAR is a self-starting device, without operator action or external power input, installed in nuclear power plants to remove hydrogen from the containment building of a nuclear reactor. A new mechanistic model of PAR has been presented and validated by experimental data and results of Computational Fluid Dynamics (CFD simulations. The model allows to quickly and accurately predict gas temperature and composition, catalyst temperature and hydrogen recombination rate. It is assumed in the model that an exothermic recombination reaction of hydrogen and oxygen proceeds at the catalyst surface only, while processes of heat and mass transport occur by assisted natural and forced convection in non-isothermal and laminar gas flow conditions in vertical channels between catalyst plates. The model accounts for heat radiation from a hot catalyst surface and has no adjustable parameters. It can be combined with an equation of chimney draft and become a useful engineering tool for selection and optimisation of catalytic recombiner geometry.

  14. Turix, a dynamic mechanistic model for feed evaluation

    Directory of Open Access Journals (Sweden)

    Luis Manuel Vargas-Villamil

    2013-04-01

    Full Text Available The objective of this study was to use the Turix model (a new mechanistic dynamic model that can be used for feed evaluation under tropical conditions, along with in situ and in vitro sugar cane experimental data from a previous study, to evaluate sugar cane kinetics through estimation of three parameters associated with ruminal bacterial growth: kM,SmL, the substrate uptake; kLM, the bacterial growth from intermediate metabolite; and Y VFAP,FS, the products related to volatile fatty acid yield. Values of these parameters for the whole sugar cane and its neutral detergent fiber (NDF and acid detergent fiber (ADF fractions were: a kM, SmL, 16.20, 50.47 and 21.97 mL h-1 (mg M-1 ; b kLM, 96.00, 543.00 and 1,680.00 h-1 ; and, 1.02, 0.40 and 0.23 g g-1 , respectively. Results from the model adjustment showed a slow microbial substrate uptake c Y VFAP, FS and a low biomass yield for whole sugar cane. The highest substrate uptake was obtained for NDF, while the highest biomass yield was obtained for ADF. The interrelation between the parameters kM, SmL showed to be important for biological and Y VFAP, FS description of microorganism growth and VFAP and biomass production.

  15. A Mechanistic Link between Olfaction and Autism Spectrum Disorder.

    Science.gov (United States)

    Rozenkrantz, Liron; Zachor, Ditza; Heller, Iris; Plotkin, Anton; Weissbrod, Aharon; Snitz, Kobi; Secundo, Lavi; Sobel, Noam

    2015-07-20

    Internal action models (IAMs) are brain templates for sensory-motor coordination underlying diverse behaviors. An emerging theory suggests that impaired IAMs are a common theme in autism spectrum disorder (ASD). However, whether impaired IAMs occur across sensory systems and how they relate to the major phenotype of ASD, namely impaired social communication, remains unclear. Olfaction relies on an IAM known as the sniff response, where sniff magnitude is automatically modulated to account for odor valence. To test the failed IAM theory in olfaction, we precisely measured the non-verbal non-task-dependent sniff response concurrent with pleasant and unpleasant odors in 36 children--18 with ASD and 18 matched typically developing (TD) controls. We found that whereas TD children generated a typical adult-like sniff response within 305 ms of odor onset, ASD children had a profoundly altered sniff response, sniffing equally regardless of odor valance. This difference persisted despite equal reported odor perception and allowed for 81% correct ASD classification based on the sniff response alone (binomial, p 0.18), impairment. These results uncover a novel ASD marker implying a mechanistic link between the underpinnings of olfaction and ASD and directly linking an impaired IAM with impaired social abilities.

  16. Mechanistic basis of infertility of mouse intersubspecific hybrids.

    Science.gov (United States)

    Bhattacharyya, Tanmoy; Gregorova, Sona; Mihola, Ondrej; Anger, Martin; Sebestova, Jaroslava; Denny, Paul; Simecek, Petr; Forejt, Jiri

    2013-02-01

    According to the Dobzhansky-Muller model, hybrid sterility is a consequence of the independent evolution of related taxa resulting in incompatible genomic interactions of their hybrids. The model implies that the incompatibilities evolve randomly, unless a particular gene or nongenic sequence diverges much faster than the rest of the genome. Here we propose that asynapsis of heterospecific chromosomes in meiotic prophase provides a recurrently evolving trigger for the meiotic arrest of interspecific F1 hybrids. We observed extensive asynapsis of chromosomes and disturbance of the sex body in >95% of pachynemas of Mus m. musculus × Mus m. domesticus sterile F1 males. Asynapsis was not preceded by a failure of double-strand break induction, and the rate of meiotic crossing over was not affected in synapsed chromosomes. DNA double-strand break repair was delayed or failed in unsynapsed autosomes, and misexpression of chromosome X and chromosome Y genes was detected in single pachynemas and by genome-wide expression profiling. Oocytes of F1 hybrid females showed the same kind of synaptic problems but with the incidence reduced to half. Most of the oocytes with pachytene asynapsis were eliminated before birth. We propose the heterospecific pairing of homologous chromosomes as a preexisting condition of asynapsis in interspecific hybrids. The asynapsis may represent a universal mechanistic basis of F1 hybrid sterility manifested by pachytene arrest. It is tempting to speculate that a fast-evolving subset of the noncoding genomic sequence important for chromosome pairing and synapsis may be the culprit.

  17. A mechanistic stochastic framework for regulating bacterial cell division.

    Science.gov (United States)

    Ghusinga, Khem Raj; Vargas-Garcia, Cesar A; Singh, Abhyudai

    2016-07-26

    How exponentially growing cells maintain size homeostasis is an important fundamental problem. Recent single-cell studies in prokaryotes have uncovered the adder principle, where cells add a fixed size (volume) from birth to division, irrespective of their size at birth. To mechanistically explain the adder principle, we consider a timekeeper protein that begins to get stochastically expressed after cell birth at a rate proportional to the volume. Cell-division time is formulated as the first-passage time for protein copy numbers to hit a fixed threshold. Consistent with data, the model predicts that the noise in division timing increases with size at birth. Intriguingly, our results show that the distribution of the volume added between successive cell-division events is independent of the newborn cell size. This was dramatically seen in experimental studies, where histograms of the added volume corresponding to different newborn sizes collapsed on top of each other. The model provides further insights consistent with experimental observations: the distribution of the added volume when scaled by its mean becomes invariant of the growth rate. In summary, our simple yet elegant model explains key experimental findings and suggests a mechanism for regulating both the mean and fluctuations in cell-division timing for controlling size.

  18. Mechanistic Differences Leading to Infectious and Sterile Inflammation.

    Science.gov (United States)

    Behnia, Faranak; Sheller, Samantha; Menon, Ramkumar

    2016-05-01

    Inflammation is a physiologic component of pregnancy and parturition. Overwhelming intrauterine inflammatory load promotes quiescent feto-maternal tissues into a contractile phenotype. Like inflammation, oxidative stress is an inevitable component of both pregnancy and parturition. Pathologic activation of host innate immune response to adverse pregnancy conditions can lead to premature activation of inflammatory and oxidative stress. Inflammation and oxidative stress markers seen with both sterile and infectious inflammation are often similar; therefore, it is difficult to understand causality of conditions like spontaneous preterm birth. This review demonstrates potential mechanistic pathways of activation of sterile and infectious inflammation. We demonstrate the activation of two unique pathways of inflammation by factors that are well-documented proxies for oxidative stress (cigarette smoke extract) and infection (lipopolysaccharide). Sterile inflammation seen after exposure to an oxidative stress inducer is due to cellular elemental damage resulting in p38 mitogen-activated protein kinase (MAPK) induced cellular senescence. Infectious inflammation is through activation of transcription factor NF-κB and independent of oxidative stress-associated damages and p38 MAPK-induced senescence. Understanding the differences in the inflammatory pathway activation by various risk factors is important to design better screening, diagnostic and intervention strategies to reduce the risks of adverse pregnancy outcomes.

  19. Diffusion theory in biology: a relic of mechanistic materialism.

    Science.gov (United States)

    Agutter, P S; Malone, P C; Wheatley, D N

    2000-01-01

    Diffusion theory explains in physical terms how materials move through a medium, e.g. water or a biological fluid. There are strong and widely acknowledged grounds for doubting the applicability of this theory in biology, although it continues to be accepted almost uncritically and taught as a basis of both biology and medicine. Our principal aim is to explore how this situation arose and has been allowed to continue seemingly unchallenged for more than 150 years. The main shortcomings of diffusion theory will be briefly reviewed to show that the entrenchment of this theory in the corpus of biological knowledge needs to be explained, especially as there are equally valid historical grounds for presuming that bulk fluid movement powered by the energy of cell metabolism plays a prominent note in the transport of molecules in the living body. First, the theory's evolution, notably from its origins in connection with the mechanistic materialist philosophy of mid nineteenth century physiology, is discussed. Following this, the entrenchment of the theory in twentieth century biology is analyzed in relation to three situations: the mechanism of oxygen transport between air and mammalian tissues; the structure and function of cell membranes; and the nature of the intermediary metalbolism, with its implicit presumptions about the intracellular organization and the movement of molecules within it. In our final section, we consider several historically based alternatives to diffusion theory, all of which have their precursors in nineteenth and twentieth century philosophy of science.

  20. Organic Chemistry Software from COMPress.

    Science.gov (United States)

    Ball, Sister Isabel

    1982-01-01

    Reviews three organic chemistry computer programs for TRS-80 and Apple microcomputers. Programs include "Introduction to Organic Chemistry,""Qualitative Organic Analysis," and a game called "Chemrain." Indicates that all three produce a readable screen, require exact responses, use graphics in an appealingly and…

  1. News from Online: Green Chemistry

    Science.gov (United States)

    Uffelman, Erich S.

    2004-01-01

    Green chemistry closely relates to energy and environmental problems, and includes the promotion of environmental friendly products and systems within the framework of renewable resources. Various websites on green chemistry are reviewed, one of which lists the 12 commandments of this particular subject.

  2. Annual Report 1984. Chemistry Department

    DEFF Research Database (Denmark)

    Funck, Jytte; Nielsen, Ole John

    This report contains a brief survey of the main activities in the Chemistry Department. All articles and reports published and lectures given in 1984 are presented. The facilities and equipment are mentioned briefly. The activities are divided into the following groups: radioisotope chemistry...

  3. Contextualising Nanotechnology in Chemistry Education

    Science.gov (United States)

    O'Connor, Christine; Hayden, Hugh

    2008-01-01

    In recent years nanotechnology has become part of the content of many undergraduate chemistry and physics degree courses. This paper deals with the role of contextualisation of nanotechnology in the delivery of the content, as nanotechnology is only now being slowly integrated into many chemistry degree courses in Ireland and elsewhere. An…

  4. 750 Reasons To Celebrate Chemistry!

    Science.gov (United States)

    Compton, Neville

    2017-06-12

    Time to reflect: This issue marks the 750th issue of Chemistry-A European Journal. The journal has played a significant role in changing chemistry. Its history has featured top papers from top authors for more than 20 years. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Chemistry Teachers' Views of Creativity

    Science.gov (United States)

    Akkanat, Çigdem; Gökdere, Murat

    2015-01-01

    The purpose of this study was to determine chemistry teachers' views of creativity. In this study, phenomenology method, one of the qualitative research patterns, was used. The participants of this study were 13 chemistry teachers working in Amasya. A semi-structured interview form was used for data collection. By using NVivo 9 qualitative…

  6. Fundamentals of Aqueous Microwave Chemistry

    Science.gov (United States)

    The first chemical revolution changed modern life with a host of excellent amenities and services, but created serious problems related to environmental pollution. After 150 years of current chemistry principles and practices, we need a radical change to a new type of chemistry k...

  7. Introducing Relativity into Quantum Chemistry

    Science.gov (United States)

    Li, Wai-Kee; Blinder, S. M.

    2011-01-01

    It is not often realized by chemists that the special theory of relativity is behind several aspects of quantum chemistry. The Schrdinger equation itself is based on relations between space-time and energy-momentum four vectors. Electron spin is, of course, the most obvious manifestation of relativity. The chemistry of some heavy elements is…

  8. Contextualising Nanotechnology in Chemistry Education

    Science.gov (United States)

    O'Connor, Christine; Hayden, Hugh

    2008-01-01

    In recent years nanotechnology has become part of the content of many undergraduate chemistry and physics degree courses. This paper deals with the role of contextualisation of nanotechnology in the delivery of the content, as nanotechnology is only now being slowly integrated into many chemistry degree courses in Ireland and elsewhere. An…

  9. [Photonic crystals for analytical chemistry].

    Science.gov (United States)

    Chen, Yi; Li, Jincheng

    2009-09-01

    Photonic crystals, originally created to control the transmission of light, have found their increasing value in the field of analytical chemistry and are probable to become a hot research area soon. This review is hence composed, focusing on their analytical chemistry-oriented applications, including especially their use in chromatography, capillary- and chip-based electrophoresis.

  10. Remedial Mathematics for Quantum Chemistry

    Science.gov (United States)

    Koopman, Lodewijk; Brouwer, Natasa; Heck, Andre; Buma, Wybren Jan

    2008-01-01

    Proper mathematical skills are important for every science course and mathematics-intensive chemistry courses rely on a sound mathematical pre-knowledge. In the first-year quantum chemistry course at this university, it was noticed that many students lack basic mathematical knowledge. To tackle the mathematics problem, a remedial mathematics…

  11. Introducing Relativity into Quantum Chemistry

    Science.gov (United States)

    Li, Wai-Kee; Blinder, S. M.

    2011-01-01

    It is not often realized by chemists that the special theory of relativity is behind several aspects of quantum chemistry. The Schrdinger equation itself is based on relations between space-time and energy-momentum four vectors. Electron spin is, of course, the most obvious manifestation of relativity. The chemistry of some heavy elements is…

  12. Crocodile Chemistry. [CD-ROM].

    Science.gov (United States)

    1999

    This high school chemistry resource is an on-screen chemistry lab. In the program, students can experiment with a huge range of chemicals, choosing the form, quantity and concentrations. Dangerous or difficult experiments can be investigated safely and easily. A vast range of equipment can be set up, and complex simulations can be put together and…

  13. Chemistry Teachers' Views of Creativity

    Science.gov (United States)

    Akkanat, Çigdem; Gökdere, Murat

    2015-01-01

    The purpose of this study was to determine chemistry teachers' views of creativity. In this study, phenomenology method, one of the qualitative research patterns, was used. The participants of this study were 13 chemistry teachers working in Amasya. A semi-structured interview form was used for data collection. By using NVivo 9 qualitative…

  14. Rethinking Undergraduate Physical Chemistry Curricula

    Science.gov (United States)

    Miller, Stephen R.

    2016-01-01

    A summary of fundamental changes made to the undergraduate physical chemistry curriculum in the Chemistry Department at Gustavus Adolphus College (beginning in the 2013-2014 academic year) is presented. The yearlong sequence now consists of an introductory semester covering both quantum mechanics and thermodynamics/kinetics, followed by a second…

  15. Rethinking Undergraduate Physical Chemistry Curricula

    Science.gov (United States)

    Miller, Stephen R.

    2016-01-01

    A summary of fundamental changes made to the undergraduate physical chemistry curriculum in the Chemistry Department at Gustavus Adolphus College (beginning in the 2013-2014 academic year) is presented. The yearlong sequence now consists of an introductory semester covering both quantum mechanics and thermodynamics/kinetics, followed by a second…

  16. Chemistry of Art and Color Sudoku Puzzles

    Science.gov (United States)

    Welsh, Michael J.

    2007-01-01

    Sudoku puzzle format was used to teach light science and chemistry terms to students of Chemistry of Art and Color. The puzzles were used to motivate and encourage students to learn chemistry in an easier and in friendly fashion.

  17. Learning Environment as Correlates of Chemistry Students ...

    African Journals Online (AJOL)

    gold

    2012-07-26

    Jul 26, 2012 ... together predict students‟ achievement in chemistry as well as their relative contribution to the ... secondary certificate examinations in 2010/2011 school year, and their 241 chemistry ... LEQI had 11 sections- chemistry ...

  18. Dynamic imine chemistry.

    Science.gov (United States)

    Belowich, Matthew E; Stoddart, J Fraser

    2012-03-21

    Formation of an imine--from an amine and an aldehyde--is a reversible reaction which operates under thermodynamic control such that the formation of kinetically competitive intermediates are, in the fullness of time, replaced by the thermodynamically most stable product(s). For this fundamental reason, the imine bond has emerged as an extraordinarily diverse and useful one in the hands of synthetic chemists. Imine bond formation is one of a handful of reactions which define a discipline known as dynamic covalent chemistry (DCC), which is now employed widely in the construction of exotic molecules and extended structures on account of the inherent 'proof-reading' and 'error-checking' associated with these reversible reactions. While both supramolecular chemistry and DCC operate under the regime of reversibility, DCC has the added advantage of constructing robust molecules on account of the formation of covalent bonds rather than fragile supermolecules resulting from noncovalent bonding interactions. On the other hand, these products tend to require more time to form--sometimes days or even months--but their formation can often be catalysed. In this manner, highly symmetrical molecules and extended structures can be prepared from relatively simple precursors. When DCC is utilised in conjunction with template-directed protocols--which rely on the use of noncovalent bonding interactions between molecular building blocks in order to preorganise them into certain relative geometries as a prelude to the formation of covalent bonds under equilibrium control--an additional level of control of structure and topology arises which offers a disarmingly simple way of constructing mechanically-interlocked molecules, such as rotaxanes, catenanes, Borromean rings, and Solomon knots. This tutorial review focuses on the use of dynamic imine bonds in the construction of compounds and products formed with and without the aid of additional templates. While synthesis under thermodynamic

  19. Complex Autocatalysis in Simple Chemistries.

    Science.gov (United States)

    Virgo, Nathaniel; Ikegami, Takashi; McGregor, Simon

    2016-01-01

    Life on Earth must originally have arisen from abiotic chemistry. Since the details of this chemistry are unknown, we wish to understand, in general, which types of chemistry can lead to complex, lifelike behavior. Here we show that even very simple chemistries in the thermodynamically reversible regime can self-organize to form complex autocatalytic cycles, with the catalytic effects emerging from the network structure. We demonstrate this with a very simple but thermodynamically reasonable artificial chemistry model. By suppressing the direct reaction from reactants to products, we obtain the simplest kind of autocatalytic cycle, resulting in exponential growth. When these simple first-order cycles are prevented from forming, the system achieves superexponential growth through more complex, higher-order autocatalytic cycles. This leads to nonlinear phenomena such as oscillations and bistability, the latter of which is of particular interest regarding the origins of life.

  20. Handbook of relativistic quantum chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wenjian (ed.) [Peking Univ., Beijing (China). Center for Computational Science and Engineering

    2017-03-01

    This handbook focuses on the foundations of relativistic quantum mechanics and addresses a number of fundamental issues never covered before in a book. For instance: How can many-body theory be combined with quantum electrodynamics? How can quantum electrodynamics be interfaced with relativistic quantum chemistry? What is the most appropriate relativistic many-electron Hamiltonian? How can we achieve relativistic explicit correlation? How can we formulate relativistic properties? - just to name a few. Since relativistic quantum chemistry is an integral component of computational chemistry, this handbook also supplements the ''Handbook of Computational Chemistry''. Generally speaking, it aims to establish the 'big picture' of relativistic molecular quantum mechanics as the union of quantum electrodynamics and relativistic quantum chemistry. Accordingly, it provides an accessible introduction for readers new to the field, presents advanced methodologies for experts, and discusses possible future perspectives, helping readers understand when/how to apply/develop the methodologies.

  1. Pollution prevention through chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Breen, J.J.; Anastas, P.T.; Hassur, S.M.; Tobin, P.S. [Environmental Protection Agency, Washington, DC (United States). Office of Pollution Prevention and Toxics

    1995-09-01

    Prosperity without pollution, and the consideration of how to achieve this economic and environmental imperative, has become the fundamental environmental theme of the 1990s. The new strategy--pollution prevention--will serve s the keystone of federal, state, and local environmental policy. The challenge is to switch from two decades of environmental policy based on pollution controls and government-mandated regulations to a future environmental policy based on pollution prevention, source reduction, recycling, and waste minimization. To make this change will require a new social compact among environmental, industrial, and regulatory interests. This chapter focuses on the role of chemistry and the contributions of synthetic and process analytical chemists. It also describes the implementation of pollution prevention concepts into the premanufacturing notice review process mandated by Section 5 of the Toxic Substances Control Act (TSCA) and discusses the implications of pollution prevention for chemical safety. 55 refs.

  2. Rapid automated nuclear chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, R.A.

    1979-05-31

    Rapid Automated Nuclear Chemistry (RANC) can be thought of as the Z-separation of Neutron-rich Isotopes by Automated Methods. The range of RANC studies of fission and its products is large. In a sense, the studies can be categorized into various energy ranges from the highest where the fission process and particle emission are considered, to low energies where nuclear dynamics are being explored. This paper presents a table which gives examples of current research using RANC on fission and fission products. The remainder of this text is divided into three parts. The first contains a discussion of the chemical methods available for the fission product elements, the second describes the major techniques, and in the last section, examples of recent results are discussed as illustrations of the use of RANC.

  3. Getting Hooked on Chemistry

    Science.gov (United States)

    Mason, Diana S.

    2002-04-01

    Other fun things in this issue include three Quote Boxes by Olney (3) that will allow your students to engage in deductive reasoning to solve the puzzles. Kelkar (4) presents a slightly more difficult but very clever mystery element game; it provides clues to element symbols that all fit into a single matrix. Ibanez's game (5) lists popular sayings or proverbs and the student's job is to match each with an analogous chemical phenomenon. As always, answers are provided. For the more sophisticated among us, there is Who Wants to Be a Chemist Extraordinaire? devised by Campbell and Muzyka (6), who describe their use of online chemistry game shows patterned on popular TV programs. Examples of the HTML files with sample questions are available through JCE Online. These are just some of the many suggestions that can be found in this issue of JCE. Try a few, you might like them!

  4. Beryllium chemistry and processing

    CERN Document Server

    Walsh, Kenneth A

    2009-01-01

    This book introduces beryllium; its history, its chemical, mechanical, and physical properties including nuclear properties. The 29 chapters include the mineralogy of beryllium and the preferred global sources of ore bodies. The identification and specifics of the industrial metallurgical processes used to form oxide from the ore and then metal from the oxide are thoroughly described. The special features of beryllium chemistry are introduced, including analytical chemical practices. Beryllium compounds of industrial interest are identified and discussed. Alloying, casting, powder processing, forming, metal removal, joining and other manufacturing processes are covered. The effect of composition and process on the mechanical and physical properties of beryllium alloys assists the reader in material selection. The physical metallurgy chapter brings conformity between chemical and physical metallurgical processing of beryllium, metal, alloys, and compounds. The environmental degradation of beryllium and its all...

  5. Multiresolution computational chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Harrison, Robert J [Oak Ridge National Laboratory, PO Box 2008 MS6367, Oak Ridge, TN 37831 (United States); University of Tennessee, Knoxville (United States); Fann, George I [Oak Ridge National Laboratory, PO Box 2008 MS6367, Oak Ridge, TN 37831 (United States); Gan Zhengting [Oak Ridge National Laboratory, PO Box 2008 MS6367, Oak Ridge, TN 37831 (United States); Yanai, Takeshi [Oak Ridge National Laboratory, PO Box 2008 MS6367, Oak Ridge, TN 37831 (United States); Sugiki, Shinichiro [Oak Ridge National Laboratory, PO Box 2008 MS6367, Oak Ridge, TN 37831 (United States); Beste, Ariana [Oak Ridge National Laboratory, PO Box 2008 MS6367, Oak Ridge, TN 37831 (United States); Beylkin, Gregory [University of Tennessee, Knoxville (United States)

    2005-01-01

    Multiresolution techniques in multiwavelet bases, made practical in three and higher dimensions by separated representations, have enabled significant advances in the accuracy and manner of computation of molecular electronic structure. The mathematical and numerical techniques are described in the article by Fann. This paper summarizes the major accomplishments in computational chemistry which represent the first substantial application of most of these new ideas in three and higher dimensions. These include basis set limit computation with linear scaling for Hartree-Fock and Density Functional Theory with a wide variety of functionals including hybrid and asymptotically corrected forms. Current capabilities include energies, analytic derivatives, and excitation energies from linear response theory. Direct solution in 6-D of the two-particle wave equation has also been demonstrated. These methods are written using MADNESS which provides a high level of composition using functions and operators with guarantees of speed and precision.

  6. Organic chemistry on Titan

    Science.gov (United States)

    Chang, S.; Scattergood, T.; Aronowitz, S.; Flores, J.

    1979-01-01

    Features taken from various models of Titan's atmosphere are combined in a working composite model that provides environmental constraints within which different pathways for organic chemical synthesis are determined. Experimental results and theoretical modeling suggest that the organic chemistry of the satellite is dominated by two processes: photochemistry and energetic particle bombardment. Photochemical reactions of CH4 in the upper atmosphere can account for the presence of C2 hydrocarbons. Reactions initiated at various levels of the atmosphere by cosmic rays, Saturn 'wind', and solar wind particle bombardment of a CH4-N2 atmospheric mixture can account for the UV-visible absorbing stratospheric haze, the reddish appearance of the satellite, and some of the C2 hydrocarbons. In the lower atmosphere photochemical processes will be important if surface temperatures are sufficiently high for gaseous NH3 to exist. It is concluded that the surface of Titan may contain ancient or recent organic matter (or both) produced in the atmosphere.

  7. Introduction to structural chemistry

    CERN Document Server

    Batsanov, Stepan S

    2014-01-01

    A concise description of models and quantitative parameters in structural chemistry and their interrelations, with 280 tables and >3000 references giving the most up-to-date experimental data on energy characteristics of atoms, molecules and crystals (ionisation potentials, electron affinities, bond energies, heats of phase transitions, band and lattice energies), optical properties (refractive index, polarisability), spectroscopic characteristics and geometrical parameters (bond distances and angles, coordination numbers) of substances in gaseous, liquid and solid states, in glasses and melts, for various thermodynamic conditions. Systems of metallic, covalent, ionic and van der Waals radii, effective atomic charges and other empirical and semi-empirical models are critically revised. Special attention is given to new and growing areas: structural studies of solids under high pressures and van der Waals molecules in gases. The book is addressed to researchers, academics, postgraduates and advanced-course stu...

  8. Chemistry of Aviation Fuels

    Science.gov (United States)

    Knepper, Bryan; Hwang, Soon Muk; DeWitt, Kenneth J.

    2004-01-01

    Minimum ignition energies of various methanol/air mixtures were measured in a temperature controlled constant volume combustion vessel using a spark ignition method with a spark gap distance of 2 mm. The minimum ignition energies decrease rapidly as the mixture composition (equivalence ratio, Phi) changes from lean to stoichiometric, reach a minimum value, and then increase rather slowly with Phi. The minimum of the minimum ignition energy (MIE) and the corresponding mixture composition were determined to be 0.137 mJ and Phi = 1.16, a slightly rich mixture. The variation of minimum ignition energy with respect to the mixture composition is explained in terms of changes in reaction chemistry.

  9. Prebiotic phosphorus chemistry reconsidered

    Science.gov (United States)

    Schwartz, A. W.; Orgel, L. E. (Principal Investigator)

    1997-01-01

    The available evidence indicates that the origin of life on Earth certainly occurred earlier than 3.5 billion years ago and perhaps substantially earlier. The time available for the chemical evolution which must have preceded this event is more difficult to estimate. Both endogenic and exogenic contributions to chemical evolution have been considered; i.e., from chemical reactions in a primitive atmosphere, or by introduction in the interiors of comets and/or meteorites. It is argued, however, that the phosphorus chemistry of Earth's earliest hydrosphere, whether primarily exogenic or endogenic in origin, was most likely dominated by compounds less oxidized than phosphoric acid and its esters. A scenario is presented for the early production of a suite of reactive phosphonic acid derivatives, the properties of which may have foreshadowed the later appearance of biophosphates.

  10. Prebiotic chemistry in clouds

    Science.gov (United States)

    Oberbeck, Verne R.; Marshall, John; Shen, Thomas

    1991-01-01

    The chemical evolution hypothesis of Woese (1979), according to which prebiotic reactions occurred rapidly in droplets in giant atmospheric reflux columns was criticized by Scherer (1985). This paper proposes a mechanism for prebiotic chemistry in clouds that answers Scherer's concerns and supports Woese's hypothesis. According to this mechanism, rapid prebiotic chemical evolution was facilitated on the primordial earth by cycles of condensation and evaporation of cloud drops containing clay condensation nuclei and nonvolatile monomers. For example, amino acids supplied by, or synthesized during entry of meteorites, comets, and interplanetary dust, would have been scavenged by cloud drops containing clay condensation nuclei and would be polymerized within cloud systems during cycles of condensation, freezing, melting, and evaporation of cloud drops.

  11. Rapid automated nuclear chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, R.A.

    1979-05-31

    Rapid Automated Nuclear Chemistry (RANC) can be thought of as the Z-separation of Neutron-rich Isotopes by Automated Methods. The range of RANC studies of fission and its products is large. In a sense, the studies can be categorized into various energy ranges from the highest where the fission process and particle emission are considered, to low energies where nuclear dynamics are being explored. This paper presents a table which gives examples of current research using RANC on fission and fission products. The remainder of this text is divided into three parts. The first contains a discussion of the chemical methods available for the fission product elements, the second describes the major techniques, and in the last section, examples of recent results are discussed as illustrations of the use of RANC.

  12. Keeping Current with Chemistry

    Science.gov (United States)

    Moore, John W.

    2003-05-01

    Chemistry content changes continually. Everyone involved in chemical education should evaluate on a regular schedule the content and emphasis of our courses. Not to do so almost guarantees that we will not be serving the best interests of our students—and ourselves. If we shy away from new material because we are unfamiliar with it, we are poor modelers of the process by which we hope our students will become self-sufficient learners. Moreover, we are unlikely to attract to our discipline those students who already have some knowledge of where in modern science the action really is. Both of these would be costly mistakes. Let’s resolve not to make them.

  13. Advances in analytical chemistry

    Science.gov (United States)

    Arendale, W. F.; Congo, Richard T.; Nielsen, Bruce J.

    1991-01-01

    Implementation of computer programs based on multivariate statistical algorithms makes possible obtaining reliable information from long data vectors that contain large amounts of extraneous information, for example, noise and/or analytes that we do not wish to control. Three examples are described. Each of these applications requires the use of techniques characteristic of modern analytical chemistry. The first example, using a quantitative or analytical model, describes the determination of the acid dissociation constant for 2,2'-pyridyl thiophene using archived data. The second example describes an investigation to determine the active biocidal species of iodine in aqueous solutions. The third example is taken from a research program directed toward advanced fiber-optic chemical sensors. The second and third examples require heuristic or empirical models.

  14. Chemistry for whom? Gender awareness in teaching and learning chemistry

    Science.gov (United States)

    Andersson, Kristina

    2016-11-01

    Marie Ståhl and Anita Hussénius have defined what discourses dominate national tests in chemistry for Grade 9 in Sweden by using feminist, critical didactic perspectives. This response seeks to expand the results in Ståhl and Hussénius's article Chemistry inside an epistemological community box!—Discursive exclusions and inclusions in the Swedish national tests in chemistry, by using different facets of gender awareness. The first facet—Gender awareness in relations to the test designers' own conceptions—highlighted how the gender order where women are subordinated men becomes visible in the national tests as a consequence of the test designers internalized conceptions. The second facet—Gender awareness in relation to chemistry—discussed the hierarchy between discourses within chemistry. The third facet—Gender awareness in relation to students—problematized chemistry in relation to the students' identity formation. In summary, I suggest that the different discourses can open up new ways to interpret chemistry and perhaps dismantle the hegemonic chemistry discourse.

  15. Chemistry for whom? Gender awareness in teaching and learning chemistry

    Science.gov (United States)

    Andersson, Kristina

    2017-06-01

    Marie Ståhl and Anita Hussénius have defined what discourses dominate national tests in chemistry for Grade 9 in Sweden by using feminist, critical didactic perspectives. This response seeks to expand the results in Ståhl and Hussénius's article Chemistry inside an epistemological community box!— Discursive exclusions and inclusions in the Swedish national tests in chemistry, by using different facets of gender awareness. The first facet—Gender awareness in relations to the test designers' own conceptions—highlighted how the gender order where women are subordinated men becomes visible in the national tests as a consequence of the test designers internalized conceptions. The second facet—Gender awareness in relation to chemistry—discussed the hierarchy between discourses within chemistry. The third facet—Gender awareness in relation to students—problematized chemistry in relation to the students' identity formation. In summary, I suggest that the different discourses can open up new ways to interpret chemistry and perhaps dismantle the hegemonic chemistry discourse.

  16. Nanoplasmonics tuned ``click chemistry''

    Science.gov (United States)

    Tijunelyte, I.; Guenin, E.; Lidgi-Guigui, N.; Colas, F.; Ibrahim, J.; Toury, T.; Lamy de La Chapelle, M.

    2016-03-01

    Nanoplasmonics is a growing field of optical condensed matter science dedicated to optical phenomena at the nanoscale level in metal systems. Extensive research on noble metallic nanoparticles (NPs) has emerged within the last two decades due to their ability to keep the optical energy concentrated in the vicinity of NPs, in particular, the ability to create optical near-field enhancement followed by heat generation. We have exploited these properties in order to induce a localised ``click'' reaction in the vicinity of gold nanostructures under unfavourable experimental conditions. We demonstrate that this reaction can be controlled by the plasmonic properties of the nanostructures and we propose two physical mechanisms to interpret the observed plasmonic tuning of the ``click'' chemistry.Nanoplasmonics is a growing field of optical condensed matter science dedicated to optical phenomena at the nanoscale level in metal systems. Extensive research on noble metallic nanoparticles (NPs) has emerged within the last two decades due to their ability to keep the optical energy concentrated in the vicinity of NPs, in particular, the ability to create optical near-field enhancement followed by heat generation. We have exploited these properties in order to induce a localised ``click'' reaction in the vicinity of gold nanostructures under unfavourable experimental conditions. We demonstrate that this reaction can be controlled by the plasmonic properties of the nanostructures and we propose two physical mechanisms to interpret the observed plasmonic tuning of the ``click'' chemistry. Electronic supplementary information (ESI) available: NMR study on reaction initiation, SERS spectra and temperature calculations. See DOI: 10.1039/c5nr09018k

  17. DEVELOPMENT OF PHYSICAL CHEMISTRY (SELECTED ARTICLES),

    Science.gov (United States)

    Reviews are presented on the historical background of three areas of physical chemistry : Chemical kinetics (418 references); Thermochemistry (217 references); and Radiation chemistry (271 references).

  18. More Chemistry with Light! More Light in Chemistry!

    Science.gov (United States)

    Bach, Thorsten

    2015-09-21

    "…︁ Why is chemistry overlooked when talking about light? Is the photon a physical particle per se? Are all important light-induced processes biological? Maybe the role of light for chemistry and the role of chemistry for light may be far less important than a few eccentric scientists would like to believe. From the perspective of a synthetically oriented photochemist, however, the facts are different …︁" Read more in the Editorial by Thorsten Bach. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Cellular copper distribution: a mechanistic systems biology approach.

    Science.gov (United States)

    Banci, Lucia; Bertini, Ivano; Cantini, Francesca; Ciofi-Baffoni, Simone

    2010-08-01

    Copper is an essential but potentially harmful trace element required in many enzymatic processes involving redox chemistry. Cellular copper homeostasis in mammals is predominantly maintained by regulating copper transport through the copper import CTR proteins and the copper exporters ATP7A and ATP7B. Once copper is imported into the cell, several pathways involving a number of copper proteins are responsible for trafficking it specifically where it is required for cellular life, thus avoiding the release of harmful free copper ions. In this study we review recent progress made in understanding the molecular mechanisms of copper transport in cells by analyzing structural features of copper proteins, their mode of interaction, and their thermodynamic and kinetic parameters, thus contributing to systems biology of copper within the cell.

  20. Mechanistic features of isomerizing alkoxycarbonylation of methyl oleate

    KAUST Repository

    Roesle, Philipp

    2012-10-24

    The weakly coordinated triflate complex [(P̂P)Pd(OTf)] +(OTf)- (1) (P̂P = 1,3-bis(di-tert- butylphosphino)propane) is a suitable reactive precursor for mechanistic studies of the isomerizing alkoxcarbonylation of methyl oleate. Addition of CH 3OH or CD3OD to 1 forms the hydride species [(P ̂P)PdH(CH3OH)]+(OTf)- (2-CH3OH) or the deuteride [(P̂P)PdD(CD 3OD)]+(OTf)- (2D-CD3OD), respectively. Further reaction with pyridine cleanly affords the stable and isolable hydride [(P̂P)PdH(pyridine)]+(OTf) - (2-pyr). This complex yields the hydride fragment free of methanol by abstraction of pyridine with BF3OEt2, and thus provides an entry to mechanistic observations including intermediates reactive toward methanol. Exposure of methyl oleate (100 equiv) to 2D-CD 3OD resulted in rapid isomerization to the thermodynamic isomer distribution, 94.3% of internal olefins, 5.5% of α,β-unsaturated ester and <0.2% of terminal olefin. Reaction of 2-pyr/BF3OEt 2 with a stoichiometric amount of 1-13C-labeled 1-octene at -80 °C yields a 50:50 mixture of the linear alkyls [(P ̂P)Pd13CH2(CH2) 6CH3]+ and [(P̂P)PdCH 2(CH2)6 13CH3] + (4a and 4b). Further reaction with 13CO yields the linear acyls [(P̂P)Pd13C(=O)12/13CH 2(CH2)6 12/13CH3(L)] + (5-L; L = solvent or 13CO). Reaction of 2-pyr/BF 3·OEt2 with a stoichiometric amount of methyl oleate at -80 °C also resulted in fast isomerization to form a linear alkyl species [(P̂P)PdCH2(CH2) 16C(=O)OCH3]+ (6) and a branched alkyl stabilized by coordination of the ester carbonyl group as a four membered chelate [(P̂P)PdCH{(CH2)15CH 3}C(=O)OCH3]+ (7). Addition of carbon monoxide (2.5 equiv) at -80 °C resulted in insertion to form the linear acyl carbonyl [(P̂P)PdC(=O)(CH2)17C(=O)OCH 3(CO)]+ (8-CO) and the five-membered chelate [(P ̂P)PdC(=O)CH{(CH2)15CH3}C(=O) OCH3]+ (9). Exposure of 8-CO and 9 to 13CO at -50 °C results in gradual incorporation of the 13C label. Reversibility of 7 + CO ⇄ 9 is also evidenced by ΔG = -2.9 kcal mol-1 and