Chalcone: A Privileged Structure in Medicinal Chemistry.

Science.gov (United States)

Zhuang, Chunlin; Zhang, Wen; Sheng, Chunquan; Zhang, Wannian; Xing, Chengguo; Miao, Zhenyuan

2017-06-28

Privileged structures have been widely used as an effective template in medicinal chemistry for drug discovery. Chalcone is a common simple scaffold found in many naturally occurring compounds. Many chalcone derivatives have also been prepared due to their convenient synthesis. These natural products and synthetic compounds have shown numerous interesting biological activities with clinical potentials against various diseases. This review aims to highlight the recent evidence of chalcone as a privileged scaffold in medicinal chemistry. Multiple aspects of chalcone will be summarized herein, including the isolation of novel chalcone derivatives, the development of new synthetic methodologies, the evaluation of their biological properties, and the exploration of the mechanisms of action as well as target identification. This review is expected to be a comprehensive, authoritative, and critical review of the chalcone template to the chemistry community.

Chemistry in protoplanetary disks

Science.gov (United States)

Semenov, D. A.

2012-01-01

In this lecture I discuss recent progress in the understanding of the chemical evolution of protoplanetary disks that resemble our Solar system during the first ten million years. At the verge of planet formation, strong variations of temperature, density, and radiation intensities in these disks lead to a layered chemical structure. In hot, dilute and heavily irradiated atmosphere only simple radicals, atoms, and atomic ions can survive, formed and destroyed by gas-phase processes. Beneath the atmosphere a partly UV-shielded, warm molecular layer is located, where high-energy radiation drives rich chemistry, both in the gas phase and on dust surfaces. In a cold, dense, dark disk midplane many molecules are frozen out, forming thick icy mantles where surface chemistry is active and where complex (organic) species are synthesized.

Structure of neutron-rich nuclei

International Nuclear Information System (INIS)

Nazarewicz, W.; Oak Ridge National Lab., TN; Warsaw Univ.

1997-11-01

One of the frontiers of today's nuclear science is the ''journey to the limits'': of atomic charge and nuclear mass, of neutron-to-proton ratio, and of angular momentum. The new data on exotic nuclei are expected to bring qualitatively new information about the fundamental properties of the nucleonic many-body system, the nature of the nuclear interaction, and nucleonic correlations at various energy-distance scales. In this talk, current developments in nuclear structure of neutron-rich nuclei are discussed from a theoretical perspective

CARBON-RICH GIANT PLANETS: ATMOSPHERIC CHEMISTRY, THERMAL INVERSIONS, SPECTRA, AND FORMATION CONDITIONS

Energy Technology Data Exchange (ETDEWEB)

Madhusudhan, Nikku [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Mousis, Olivier [Institut UTINAM, CNRS-UMR 6213, Observatoire de Besancon, BP 1615, F-25010 Besancon Cedex (France); Johnson, Torrence V. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Lunine, Jonathan I., E-mail: nmadhu@astro.princeton.edu [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States)

2011-12-20

The recent inference of a carbon-rich atmosphere, with C/O {>=} 1, in the hot Jupiter WASP-12b motivates the exotic new class of carbon-rich planets (CRPs). We report a detailed study of the atmospheric chemistry and spectroscopic signatures of carbon-rich giant (CRG) planets, the possibility of thermal inversions in their atmospheres, the compositions of icy planetesimals required for their formation via core accretion, and the apportionment of ices, rock, and volatiles in their envelopes. Our results show that CRG atmospheres probe a unique region in composition space, especially at high temperature (T). For atmospheres with C/O {>=} 1, and T {approx}> 1400 K in the observable atmosphere, most of the oxygen is bound up in CO, while H{sub 2}O is depleted and CH{sub 4} is enhanced by up to two or three orders of magnitude each, compared to equilibrium compositions with solar abundances (C/O = 0.54). These differences in the spectroscopically dominant species for the different C/O ratios cause equally distinct observable signatures in the spectra. As such, highly irradiated transiting giant exoplanets form ideal candidates to estimate atmospheric C/O ratios and to search for CRPs. We also find that the C/O ratio strongly affects the abundances of TiO and VO, which have been suggested to cause thermal inversions in highly irradiated hot Jupiter atmospheres. A C/O = 1 yields TiO and VO abundances of {approx}100 times lower than those obtained with equilibrium chemistry assuming solar abundances, at P {approx} 1 bar. Such a depletion is adequate to rule out thermal inversions due to TiO/VO even in the most highly irradiated hot Jupiters, such as WASP-12b. We estimate the compositions of the protoplanetary disk, the planetesimals, and the envelope of WASP-12b, and the mass of ices dissolved in the envelope, based on the observed atmospheric abundances. Adopting stellar abundances (C/O = 0.44) for the primordial disk composition and low-temperature formation conditions

Transition metal chemistry of hydroxy(–OH)-rich molecules ...

Indian Academy of Sciences (India)

Administrator

Appropriately designed hydroxy(–OH) containing Schiff's base and Mannich base molecules have been recently found to be important for development of the coordination chemistry of a number of metal ions in the biomimetic chemistry of metalloenzymes. In this context, our group has studied the coordination role of these ...

Structure and stabilization of hydrogen-rich transverse.

Energy Technology Data Exchange (ETDEWEB)

Lyra, Sgouria [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Wilde, B [Georgia Inst. of Technology, Atlanta, GA (United States); Kolla, Hemanth [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Seitzman, J. [Georgia Inst. of Technology, Atlanta, GA (United States); Lieuwen, T. C. [Georgia Inst. of Technology, Atlanta, GA (United States); Chen, Jacqueline H. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

2014-07-01

This paper reports the results of a joint experimental and numerical study of the ow characteristics and flame stabilization of a hydrogen rich jet injected normal to a turbulent, vitiated cross ow of lean methane combustion products. Simultaneous high-speed stereoscopic PIV and OH PLIF measurements were obtained and analyzed alongside three-dimensional direct numerical simulations of inert and reacting JICF with detailed H₂/CO chemistry. Both the experiment and the simulation reveal that, contrary to most previous studies of reacting JICF stabilized in low-to-moderate temperature air cross ow, the present conditions lead to an autoigniting, burner-attached flame that initiates uniformly around the burner edge. Significant asymmetry is observed, however, between the reaction zones located on the windward and leeward sides of the jet, due to the substantially different scalar dissipation rates. The windward reaction zone is much thinner in the near field, while also exhibiting significantly higher local and global heat release than the much broader reaction zone found on the leeward side of the jet. The unsteady dynamics of the windward shear layer, which largely control the important jet/cross flow mixing processes in that region, are explored in order to elucidate the important flow stability implications arising in the reacting JICF. Vorticity spectra extracted from the windward shear layer reveal that the reacting jet is globally unstable and features two high frequency peaks, including a fundamental mode whose Strouhal number of ~0.7 agrees well with previous non-reacting JICF stability studies. The paper concludes with an analysis of the ignition, ame stabilization, and global structure of the burner-attached flame. Chemical explosive mode analysis (CEMA) shows that the entire windward shear layer, and a large region on the leeward side of the jet, are highly explosive prior to ignition and are dominated by non-premixed flame structures after

Synthetic Strategies towards Fullerene-Rich Dendrimer Assemblies

Directory of Open Access Journals (Sweden)

Jean-François Nierengarten

2012-02-01

Full Text Available The sphere-shaped fullerene has attracted considerable interest not least due to the peculiar electronic properties of this carbon allotrope and the fascinating materials emanating from fullerene-derived structures. The rapid development and tremendous advances in organic chemistry allow nowadays the modification of C60 to a great extent by pure chemical means. It is therefore not surprising that the fullerene moiety has also been part of dendrimers. At the initial stage, fullerenes have been examined at the center of the dendritic structure mainly aimed at possible shielding effects as exerted by the dendritic environment and light-harvesting effects due to multiple chromophores located at the periphery of the dendrimer. In recent years, also many research efforts have been devoted towards fullerene-rich nanohybrids containing multiple C60 units in the branches and/or as surface functional groups. In this review, synthetic efforts towards the construction of dendritic fullerene-rich nanostructures have been compiled and will be summarized herein.

Complex chemistry

International Nuclear Information System (INIS)

Kim, Bong Gon; Kim, Jae Sang; Kim, Jin Eun; Lee, Boo Yeon

2006-06-01

This book introduces complex chemistry with ten chapters, which include development of complex chemistry on history coordination theory and Warner's coordination theory and new development of complex chemistry, nomenclature on complex with conception and define, chemical formula on coordination compound, symbol of stereochemistry, stereo structure and isomerism, electron structure and bond theory on complex, structure of complex like NMR and XAFS, balance and reaction on solution, an organo-metallic chemistry, biology inorganic chemistry, material chemistry of complex, design of complex and calculation chemistry.

Organic chemistry in a CO2 rich early Earth atmosphere

Science.gov (United States)

Fleury, Benjamin; Carrasco, Nathalie; Millan, Maëva; Vettier, Ludovic; Szopa, Cyril

2017-12-01

The emergence of life on the Earth has required a prior organic chemistry leading to the formation of prebiotic molecules. The origin and the evolution of the organic matter on the early Earth is not yet firmly understood. Several hypothesis, possibly complementary, are considered. They can be divided in two categories: endogenous and exogenous sources. In this work we investigate the contribution of a specific endogenous source: the organic chemistry occurring in the ionosphere of the early Earth where the significant VUV contribution of the young Sun involved an efficient formation of reactive species. We address the issue whether this chemistry can lead to the formation of complex organic compounds with CO2 as only source of carbon in an early atmosphere made of N2, CO2 and H2, by mimicking experimentally this type of chemistry using a low pressure plasma reactor. By analyzing the gaseous phase composition, we strictly identified the formation of H2O, NH3, N2O and C2N2. The formation of a solid organic phase is also observed, confirming the possibility to trigger organic chemistry in the upper atmosphere of the early Earth. The identification of Nitrogen-bearing chemical functions in the solid highlights the possibility for an efficient ionospheric chemistry to provide prebiotic material on the early Earth.

Structural and functional rich club organization of the brain in children and adults.

Directory of Open Access Journals (Sweden)

David S Grayson

Full Text Available Recent studies using Magnetic Resonance Imaging (MRI have proposed that the brain's white matter is organized as a rich club, whereby the most highly connected regions of the brain are also highly connected to each other. Here we use both functional and diffusion-weighted MRI in the human brain to investigate whether the rich club phenomena is present with functional connectivity, and how this organization relates to the structural phenomena. We also examine whether rich club regions serve to integrate information between distinct brain systems, and conclude with a brief investigation of the developmental trajectory of rich-club phenomena. In agreement with prior work, both adults and children showed robust structural rich club organization, comprising regions of the superior medial frontal/dACC, medial parietal/PCC, insula, and inferior temporal cortex. We also show that these regions were highly integrated across the brain's major networks. Functional brain networks were found to have rich club phenomena in a similar spatial layout, but a high level of segregation between systems. While no significant differences between adults and children were found structurally, adults showed significantly greater functional rich club organization. This difference appeared to be driven by a specific set of connections between superior parietal, insula, and supramarginal cortex. In sum, this work highlights the existence of both a structural and functional rich club in adult and child populations with some functional changes over development. It also offers a potential target in examining atypical network organization in common developmental brain disorders, such as ADHD and Autism.

The Logical and Psychological Structure of Physical Chemistry and Its Relevance to the Organization/Sequencing of the Major Areas Covered in Physical Chemistry Textbooks

Science.gov (United States)

Tsaparlis, Georgios

2014-01-01

Jensen's scheme for the logical structure of chemistry is taken as reference to study the logical structure of physical chemistry. The scheme distinguishes three dimensions (composition and structure, energy, and time), with each dimension treated at one of the three levels (molar, molecular, and electrical). Such a structure places the outer…

Structural chemistry of superconducting pnictides and pnictide oxides with layered structures

Energy Technology Data Exchange (ETDEWEB)

Johrendt, Dirk [Ludwig-Maximilians-Univ. Muenchen (Germany). Dept. Chemie und Biochemie; Hosono, Hideo [Tokyo Institute of Technology, Yokohama (Japan). Frontier Research Center; Hoffmann, Rolf-Dieter; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie

2011-07-01

The basic structural chemistry of superconducting pnictides and pnictide oxides is reviewed. Crystal chemical details of selected compounds and group subgroup schemes are discussed with respect to phase transitions upon charge-density formation, the ordering of vacancies, or the ordered displacements of oxygen atoms. Furthermore, the influences of doping and solid solutions on the valence electron concentration are discussed in order to highlight the structural and electronic flexibility of these materials. (orig.)

Progress in organic and physical chemistry structures and mechanisms

CERN Document Server

Zaikov, Gennady E; Lobanov, Anton V

2013-01-01

Progress in Organic and Physical Chemistry: Structures and Mechanisms provides a collection of new research in the field of organic and physical properties, including new research on: The physical principles of the conductivity of electrical conducting polymer compounds The dependence on constants of electromagnetic interactions upon electron spacial-energy characteristics Effects of chitosan molecultural weight on rehological behavior of chitosan modified nanoclay at hight hydrated state Bio-structural energy criteria of functional states in normal and pathological conditions Potentiometric study on the international between devalent cations and sodium carboxylates in aqueous solutions Structural characteristic changes in erythrocyte membranes of mice bearing Alzheimer's-like disease caused by the olfactory bulbetomy This volume is intended to provide an overview of new studies and research for engineers, faculty, researchers, and upper-level students in the field of organic and physical chemistry.

Effects of Chemistry on Blunt-Body Wake Structure

Science.gov (United States)

Dogra, Virendra K.; Moss, James N.; Wilmoth, Richard G.; Taylor, Jeff C.; Hassan, H. A.

1995-01-01

Results of a numerical study are presented for hypersonic low-density flow about a 70-deg blunt cone using direct simulation Monte Carlo (DSMC) and Navier-Stokes calculations. Particular emphasis is given to the effects of chemistry on the near-wake structure and on the surface quantities and the comparison of the DSMC results with the Navier-Stokes calculations. The flow conditions simulated are those experienced by a space vehicle at an altitude of 85 km and a velocity of 7 km/s during Earth entry. A steady vortex forms in the near wake for these freestream conditions for both chemically reactive and nonreactive air gas models. The size (axial length) of the vortex for the reactive air calculations is 25% larger than that of the nonreactive air calculations. The forebody surface quantities are less sensitive to the chemistry than the base surface quantities. The presence of the afterbody has no effect on the forebody flow structure or the surface quantities. The comparisons of DSMC and Navier-Stokes calculations show good agreement for the wake structure and the forebody surface quantities.

Interface of Chemistry and Biology

OpenAIRE

I. Kira Astakhova

2013-01-01

Many exciting research studies in Science today lie at the interface between various disciplines. The interface between Chemistry and Biology is particularly rich, since it closely reflects Nature and the origins of Life. Multiple research groups in the Chemistry Departments around the world have made substantial efforts to interweave ideas from Chemistry and Biology to solve important questions related to material science and healthcare, just to name a few. International Journal of Bioorgani...

A General Chemistry Experiment Incorporating Synthesis and Structural Determination

Science.gov (United States)

van Ryswyk, Hal

1997-07-01

An experiment for the general chemistry laboratory is described wherein gas chromatography-mass spectroscopy (GC-MS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) are used to characterize the products of a series of microscale reactions on vanillin. A single sophisticated instrument can be incorporated into the laboratory given sufficient attention to the use of sampling accessories and software macros. Synthetic experiments coupled with modern instrumental techniques can be used in the general chemistry laboratory to illustrate the concepts of synthesis, structure, bonding, and spectroscopy.

From energy-rich phosphate compounds to warfare agents: A review on the chemistry of organic phosphate compounds

Directory of Open Access Journals (Sweden)

Luciano Albino Giusti

2008-12-01

Full Text Available The chemistry of the phosphorus-oxygen bond is widely used in biological systems in many processes, such as energy transduction and the storage, transmission and expression of genetic information, which are essential to living beings in relation to a wide variety of functions. Compounds containing this bond have been designed for many purposes, ranging from agricultural defense systems, in order to increase food production, to nerve agents, for complaining use in warfare. In this review, features related to the chemistry of organic phosphate compounds are discussed, with particular emphasis on the role of phosphate compounds in biochemical events and in nerve agents. To this aim, the energy-rich phosphate compounds are focused, particularly the mode of their use as energy currency in cells. Historical and recent studies carried out by research groups have tried to elucidate the mechanism of action of enzymes responsible for energy transduction through the use of biochemical studies, enzyme models, and artificial enzymes. Finally, recent studies on the detoxification of nerve agents based on phosphorous esters are presented, and on the utilization of chromogenic and fluorogenic chemosensors for the detection of these phosphate species.

Nuclear chemistry on the Czech Technical University in Prague after introduction of structured study and foundation of the Centre for Radiochemistry and Radiation Chemistry

International Nuclear Information System (INIS)

John, J.

2007-01-01

In this presentation the author (head of the Centre for Radiochemistry and Radiation Chemistry) give a short review of history of the Department of Nuclear Chemistry and of the Centre for Radiochemistry and Radiation Chemistry of the Czech Technical University in Prague. Education in structured study in specialisation of nuclear chemistry in bachelor level, master level, as well as post-graduate study in nuclear chemistry with academic degree PhD. are realised. Some scientific results are presented

The atomic structure and chemistry of Fe-rich steps on antiphase boundaries in Ti-doped Bi0.9Nd0.15FeO3

Directory of Open Access Journals (Sweden)

Ian MacLaren

2014-06-01

Full Text Available Stepped antiphase boundaries are frequently observed in Ti-doped Bi0.85Nd0.15FeO3, related to the novel planar antiphase boundaries reported recently. The atomic structure and chemistry of these steps are determined by a combination of high angle annular dark field and bright field scanning transmission electron microscopy imaging, together with electron energy loss spectroscopy. The core of these steps is found to consist of 4 edge-sharing FeO6 octahedra. The structure is confirmed by image simulations using a frozen phonon multislice approach. The steps are also found to be negatively charged and, like the planar boundaries studied previously, result in polarisation of the surrounding perovskite matrix.

Structures of plutonium coordination compounds: A review of past work, recent single crystal x-ray diffraction results, and what we're learning about plutonium coordination chemistry

Science.gov (United States)

Neu, M. P.; Matonic, J. H.; Smith, D. M.; Scott, B. L.

2000-07-01

The compounds we have isolated and characterized include plutonium(III) and plutonium(IV) bound by ligands with a range of donor types and denticity (halide, phosphine oxide, hydroxamate, amine, sulfide) in a variety of coordination geometries. For example, we have obtained the first X-ray structure of Pu(III) complexed by a soft donor ligand. Using a "one pot" synthesis beginning with Pu metal strips and iodine in acetonitrile and adding trithiacyclononane we isolated the complex, PuI3(9S3)(MeCN)2 (Figure 1). On the other end of the coordination chemistry spectrum, we have obtained the first single crystal structure of the Pu(IV) hexachloro anion (Figure 2). Although this species has been used in plutonium purification via anion exchange chromatography for decades, the bond distances and exact structure were not known. We have also characterized the first plutonium-biomolecule complex, Pu(IV) bound by the siderophore desferrioxamine E.In this presentation we will review the preparation, structures, and importance of previously known coordination compounds and of those we have recently isolated. We will show the coordination chemistry of plutonium is rich and varied, well worth additional exploration.

Spallation RI beam facility and heavy element nuclear chemistry

Energy Technology Data Exchange (ETDEWEB)

Nagame, Yuichiro [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

1997-11-01

An outline of the spallation RI (Radioactive Ion) beam facility is presented. Neutron-rich nuclides are produced in the reaction of high intensity (10-1000 {mu}A) protons with energy of 1.5 GeV and an uranium carbide target. Produced nuclides are ionized in an isotope separator on-line (ISOL) and accelerated by the JAERI tandem and the booster linac. Current progress and a future project on the development of the RI beam facility are given. Studies of transactinide elements, including the synthesis of superheavy elements, nuclear structure far from stability, and RI-probed material science are planned with RI beams. An outlook of the transactinide nuclear chemistry studies using neutron-rich RI beams is described. (author)

Click chemistry for the conservation of cellular structures and fluorescent proteins: ClickOx.

Science.gov (United States)

Löschberger, Anna; Niehörster, Thomas; Sauer, Markus

2014-05-01

Reactive oxygen species (ROS), including hydrogen peroxide, are known to cause structural damage not only in living, but also in fixed, cells. Copper-catalyzed azide-alkyne cycloaddition (click chemistry) is known to produce ROS. Therefore, fluorescence imaging of cellular structures, such as the actin cytoskeleton, remains challenging when combined with click chemistry protocols. In addition, the production of ROS substantially weakens the fluorescence signal of fluorescent proteins. This led us to develop ClickOx, which is a new click chemistry protocol for improved conservation of the actin structure and better conservation of the fluorescence signal of green fluorescent protein (GFP)-fusion proteins. Herein we demonstrate that efficient oxygen removal by addition of an enzymatic oxygen scavenger system (ClickOx) considerably reduces ROS-associated damage during labeling of nascent DNA with ATTO 488 azide by Cu(I)-catalyzed click chemistry. Standard confocal and super-resolution fluorescence images of phalloidin-labeled actin filaments and GFP/yellow fluorescent protein-labeled cells verify the conservation of the cytoskeleton microstructure and fluorescence intensity, respectively. Thus, ClickOx can be used advantageously for structure preservation in conventional and most notably in super-resolution microscopy methods. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organizational Information Requirements, Media Richness and Structural Design

OpenAIRE

Richard L. Daft; Robert H. Lengel

1986-01-01

This paper answers the question, "Why do organizations process information?" Uncertainty and equivocality are defined as two forces that influence information processing in organizations. Organization structure and internal systems determine both the amount and richness of information provided to managers. Models are proposed that show how organizations can be designed to meet the information needs of technology, interdepartmental relations, and the environment. One implication for managers i...

Level structures of neutron-rich Xe isotopes

Energy Technology Data Exchange (ETDEWEB)

Ahmad, I.; Lister, C.J.; Morss, L.R. [and others

1995-08-01

The level structures of neutron-rich Xe isotopes were determined by observing prompt gamma-ray coincidences in {sup 248}Cm fission fragments. A 5-mg {sup 248}Cm, in the form of {sup 248}Cm-KCl pellet, was placed inside Eurogam array which consisted of 45 Compton-suppressed Ge detectors and 5 Low-Energy Photon Spectrometers. Transitions in Xe isotopes were identified by the appearance of new peaks in the {gamma}-ray spectra obtained by gating on the gamma peaks of the complementary Mo fragments.

Crystal structures and second-order NLO properties of borogermanates

International Nuclear Information System (INIS)

Zhang, Jian-Han; Kong, Fang; Xu, Xiang; Mao, Jiang-Gao

2012-01-01

Borogermanates are a class of very important compounds in materials chemistry. In this paper, the syntheses, structures, and properties of metal borogermanates are reviewed. Organically templated borogermanates with zeolite-like open-frameworks show potential applications as microporous materials. Many compounds in alkali or alkaline-earth borogermanate systems are structurally acentric or polar, some of which exhibit excellent Second Harmonic Generation (SHG) coefficients, wide transparency regions, and high optical-damage thresholds as well as excellent thermal stability. Most of the lanthanide borogermanates are structurally centrosymmetric and not SHG active; however, they are able to emit strong luminescence in visible or near-IR region. In the B-rich compounds, BO 3 and BO 4 groups can be polymerized into a variety of discrete polynuclear anionic cluster units or extended architectures via B–O–B bridges; whereas in the Ge-rich compounds, GeO 4 and GeO 6 polyhedra can also be polymerized. The combinations of borate and germinate afforded rich structural and topological types. - Graphical abstract: Borogermanates are a class of very important compounds in materials chemistry. Both BO x (x=3, 4) and GeO y (y=4, 6) polyhedra can be polymerized into a variety of discrete polynuclear anionic cluster units or extended architectures. The combinations of borate and germanate groups in the same oxide framework not only give rise to a rich structural chemistry, but also afford many polar compounds with good SHG properties. Highlights: ► Borogermanates are a class of new materials. ► They feature to be the combination of B and Ge atoms into the same oxide framework. ► They can form a large number of novel 2D and 3D framework structures. ► Some of them are acentric or polar with moderate strong SHG responses.

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.

Chemistry and the development of research into the structure of matter

Energy Technology Data Exchange (ETDEWEB)

Coldanskii, V

1977-06-01

Efforts have been made recently to explain the structure of the atomic nucleus and the structure of the electron shell of the atom using a unified quantum mechanics description. The applications are surveyed of the knowledge of the nucleus and electron shell structure in chemistry. Electron paramagnetic resonance, nuclear magnetic resonance and gamma resonance spectrometry are presented as examples.

Coordination chemistry of technetium as related to nuclear medicine

International Nuclear Information System (INIS)

Srivastava, S.C.; Richards, P.

1982-01-01

Significant advances have been made in the area of technetium coordination chemistry during the last five years. The main driving force behind this recent surge of interest in the field has been due to the practical application of technetium-99m in the rapidly growing speciality of nuclear medicine. Technetium-99 is one of the products of nuclear fission reactions, but it was the development of the molybdenum-99-technetium-99m generator about two decades ago that provided the basis for the development of radiopharmaceuticals routinely used in modern diagnostic applications. The chemistry of this element has proven to be quite rich owing to its multiple oxidation states and variable geometry. This can be attributed to its position in the middle of the periodic table. Diagnostic radiopharmaceuticals comprise predominantly III, IV and V oxidation states of Tc and involve a variety of coordination complexes. Even though the chemistry of Tc has been slow to evolve, recent synthetic advances have provided a more scientific basis for the study of a number of compounds with diverse coordination geometries and structures. Ligands with oxygen, nitrogen and sulfur donor atoms have been utilized to elucidate various aspects of the coordination chemistry of Tc. Single crystal X-ray structural analysis has been extensively used to characterize Tc complexes and thus construct a firm foundation for the study of synthetic and mechanistic aspects of the chemistry of this element. (author)

Chemistry and the development of research into the structure of matter

International Nuclear Information System (INIS)

Coldanskij, V.

1977-01-01

Efforts have been made recently to explain the structure of the atomic nucleus and the structure of the electron shell of the atom using a unified quantum mechanics description. The applications are surveyed of the knowledge of the nucleus and electron shell structure in chemistry. Electron paramagnetic resonance, nuclear magnetic resonance and gamma resonance spectrometry are presented as examples. (J.B.)

Geometric structure of chemistry-relevant graphs zigzags and central circuits

CERN Document Server

Deza, Michel-Marie; Shtogrin, Mikhail Ivanovitch

2015-01-01

The central theme of the present book is zigzags and central-circuits of three- or four-regular plane graphs, which allow a double covering or covering of the edgeset to be obtained. The book presents zigzag and central circuit structures of geometric fullerenes and several other classes of graph of interest in the fields of chemistry and mathematics. It also discusses the symmetries, parameterization and the Goldberg–Coxeter construction for those graphs. It is the first book on this subject, presenting full structure theory of such graphs. While many previous publications only addressed particular questions about selected graphs, this book is based on numerous computations and presents extensive data (tables and figures), as well as algorithmic and computational information. It will be of interest to researchers and students of discrete geometry, mathematical chemistry and combinatorics, as well as to lay mathematicians.

Rule of five in 2015 and beyond: Target and ligand structural limitations, ligand chemistry structure and drug discovery project decisions.

Science.gov (United States)

Lipinski, Christopher A

2016-06-01

The rule of five (Ro5), based on physicochemical profiles of phase II drugs, is consistent with structural limitations in protein targets and the drug target ligands. Three of four parameters in Ro5 are fundamental to the structure of both target and drug binding sites. The chemical structure of the drug ligand depends on the ligand chemistry and design philosophy. Two extremes of chemical structure and design philosophy exist; ligands constructed in the medicinal chemistry synthesis laboratory without input from natural selection and natural product (NP) metabolites biosynthesized based on evolutionary selection. Exceptions to Ro5 are found mostly among NPs. Chemistry chameleon-like behavior of some NPs due to intra-molecular hydrogen bonding as exemplified by cyclosporine A is a strong contributor to NP Ro5 outliers. The fragment derived, drug Navitoclax is an example of the extensive expertise, resources, time and key decisions required for the rare discovery of a non-NP Ro5 outlier. Copyright © 2016 Elsevier B.V. All rights reserved.

Chemistry-Nuclear Chemistry Division. Progress report, October 1980-September 1981

International Nuclear Information System (INIS)

Ryan, R.R.

1982-05-01

This report describes major progress in the research and development programs pursued by the Chemistry-Nuclear Chemistry Division of the Los Alamos National Laboratory during FY 1981. Topics covered include advanced analytical methods, atmospheric chemistry and transport, biochemistry, biomedical research, medical radioisotopes research, element migration and fixation, nuclear waste isolation research, inorganic and structural chemistry, isotope separation, analysis and applications, the newly established Nuclear Magnetic Resonance Center, atomic and molecular collisions, molecular spectroscopy, nuclear cosmochemistry, nuclear structure and reactions, pion charge exchange, radiochemical separations, theoretical chemistry, and unclassified weapons research

Chemistry-Nuclear Chemistry Division. Progress report, October 1980-September 1981

Energy Technology Data Exchange (ETDEWEB)

Ryan, R.R. (comp.)

1982-05-01

This report describes major progress in the research and development programs pursued by the Chemistry-Nuclear Chemistry Division of the Los Alamos National Laboratory during FY 1981. Topics covered include advanced analytical methods, atmospheric chemistry and transport, biochemistry, biomedical research, medical radioisotopes research, element migration and fixation, nuclear waste isolation research, inorganic and structural chemistry, isotope separation, analysis and applications, the newly established Nuclear Magnetic Resonance Center, atomic and molecular collisions, molecular spectroscopy, nuclear cosmochemistry, nuclear structure and reactions, pion charge exchange, radiochemical separations, theoretical chemistry, and unclassified weapons research.

The biology and chemistry of the zoanthamine alkaloids.

Science.gov (United States)

Behenna, Douglas C; Stockdill, Jennifer L; Stoltz, Brian M

2008-01-01

Marine natural products have long played an important role in natural products chemistry and drug discovery. Mirroring the rich variety and complicated interactions of the marine environment, the substances isolated from sea creatures tend to be incredibly diverse in both molecular structure and biological activity. The natural products isolated from the polyps of marine zoanthids are no exception. The zoanthamine alkaloids, the first of which were isolated over 20 years ago, are of particular interest to the synthetic community because they feature a novel structural framework and exhibit a broad range of biological activities. In this Review, we summarize the major contributions to understanding the zoanthamine natural products with regard to their isolation and structure determination, as well as studies on their biological activity and total synthesis.

Protactinium and the intersection of actinide and transition metal chemistry

Energy Technology Data Exchange (ETDEWEB)

Wilson, Richard E.; De Sio, Stephanie; Vallet, Valérie

2018-02-12

The role of the 5f and 6d orbitals in the chemistry of the actinide elements has been of considerable interest since their discovery and synthesis. Relativistic effects cause the energetics of the 5f and 6d orbitals to change as the actinide series is traversed left to right imparting a rich and complex chemistry. The 5f and 6d atomic states cross in energy at protactinium (Pa), making it a potential intersection between transition metal and actinide chemistries. Herein, we report the synthesis of a Pa-peroxo cluster, A(6)(Pa4O(O-2)(6)F-12) [A = Rb, Cs, (CH3)(4)N], formed in pursuit of an actinide polyoxometalate. Quantum chemical calculations at the density functional theory level demonstrate equal 5f and 6d orbital participation in the chemistry of Pa and increasing 5f orbital participation for the heavier actinides. Periodic changes in orbital character to the bonding in the early actinides highlights the influence of the 5f orbitals in their reactivity and chemical structure.

Connecting Structure-Property and Structure-Function Relationships across the Disciplines of Chemistry and Biology: Exploring Student Perceptions

Science.gov (United States)

Kohn, Kathryn P.; Underwood, Sonia M.; Cooper, Melanie M.

2018-01-01

While many university students take science courses in multiple disciplines, little is known about how they perceive common concepts from different disciplinary perspectives. Structure-property and structure-function relationships have long been considered important explanatory concepts in the disciplines of chemistry and biology, respectively.…

Of the crystal chemistry of Ruddlesden-Porter type structures in high Tc ceramic superconductors

International Nuclear Information System (INIS)

Dwivedi, A.; Cormack, A.N.

1990-01-01

This paper reports on atomistic computer simulation employed to examine the energetics and crystal chemistry of some Ruddlesden-Popper type oxide superconductors. Similar structural patterns have been noticed in the superconducting oxides. The formation of Ruddlesden-Popper type layers (alternating slabs of rocksalt and perovskite structures) is similar in many respects to that seen in the system Sr-Ti-O. However, there are some significant differences, for example, the rocksalt and perovskite blocks in the new superconducting compounds are not necessarily electrically neutral unlike in the Sr-Ti-O system and this may well lead to significant differences in their structural chemistry

The response of chironomid assemblages to mineral richness gradient in the Western Carpathian helocrenes

Directory of Open Access Journals (Sweden)

Vít Syrovátka

2012-10-01

Full Text Available Chironomid assemblages of helocrene springs were investigated in the Western Carpathians in order to identify potential effect of water mineral richness on the taxonomic structure of the assemblages. A complex gradient considering water chemistry and substratum was used as a measure of basicity (mineral richness. Taxonomic structure, total abundance and abundance of most frequent taxa were related to this gradient with regards to two contrasting habitats: trickle (A and water-loged soil with standing water (B. The variance in chironomid assemblage attributable to basicity was estimated and tested via PERMANOVA as well as the possible effect of the other environmental variables. The response of individual taxa was examined using GAM. The results indicate a strong relationship between basicity and substratum characteristics, with coarser mineral substrata at basic and high amount of organic matter at acidic conditions. Although water chemistry was correlated with and inseparable from these substratum properties, it could not be substituted with them, as they discriminated well only between acidic and basic springs, but did not follow the basicity gradient in either acidic or basic group of springs. Chironomid assemblage showed a strong and systematic response to the complex gradient of mineral richness, which explained the largest portion of variance in both the habitat A and B faunal data and was projected on the first axes of both NMDS ordinations. The assemblage response could be documented by the preference of several taxa for particular mineral richness conditions, while the number of taxa seemed to be highest in the middle of the basicity gradient. As only 17 samples were analysed so far, the results are considered preliminary and, hopefully, more confident results will be available in near future.doi: 10.5324/fn.v31i0.1403.Published online: 17 October 2012.

Structure of neutron-rich nuclei

International Nuclear Information System (INIS)

Nazarewicz, W.

2000-01-01

Complete text of publication follows. The uncharted regions of the (N,Z) plane contain information that can answer many questions of fundamental importance for science: How many protons and neutrons can be clustered together by the strong interaction to form a bound nucleus? What are the proton and neutron magic numbers of the exotic nuclei? What are the properties of very short-lived exotic nuclei with extreme neutron-to-proton ratios? What is the effective nucleon-nucleon interaction in a nucleus that has a very large neutron excess? Nuclear life far from stability is different from that around the stability line; the promised access to completely new combinations of proton and neutron numbers offers prospects for new structural phenomena. The main objective of this talk is to discuss some of the challenges and opportunities of research with exotic nuclei. The covered topics will include: Theoretical challenges; Skins and halos in heavy nuclei; Shape coexistence in exotic nuclei; Beta-decays of neutron-rich nuclei. (author)

Structure of the neutron-rich lithium isotopes in heavy-ion reactions

International Nuclear Information System (INIS)

Bespalova, O.V.; Galakhmatova, B.S.; Romanovskij, E.A.; Shitikova, K.V.; Burov, V.V.; Rzyanin, M.V.; Miller, H.G.; Yen, G.D.

1993-01-01

The structure properties, for factors, angular distributions and interaction cross sections of Li neutron-rich isotopes have been analyzed in the unified way. A good qualitative agreement with the experiment data was obtained. 20 refs.; 11 figs.; 1 tab

Structure, richness and composition of arboreal plants in a cloud thinning forest of Tolima (Colombia)

International Nuclear Information System (INIS)

Campo Kurmen, Juan Manuel

2010-01-01

Structure, richness, and floristic composition of the woody elements of the selective logging forest of the Vereda Dantas, (Ibague, Tolima, Colombia), where studied in a 0.1 ha plot sampled for all individuals ≥2.5 cm dbh. the forest is characterized by scarcity of lianas and hemiepiphytic, absence of typical families of the Colombian cloud forests between 2000 and 2500 m (Araceae, Ericaceae, Myrtaceae, Meliaceae and Aquifoliaceae), and richness increment of the Sabiaceae and Euphorbiaceae. Compared to others cloud forest from the Colombian Andes and the Neotropic, it has, fewer individuals (237 individuals ≥2.5 cm dbh per 0.1 ha) and more large trees (39.7% of individuals ≥10 cm dbh per 0.1 ha). The forest has a lower woody species richness (75 species ≥2.5 cm dbh per 0.1 ha). Apparently, the effects of selective timber extraction on structure, richness, and floristic composition are decrease floristic richness and density of individuals, decrease of lianas density and richness, and more individuals of secondary species, likes: Hedyosmum goudotianum Slms-Laubach var. goudatianum, Miconia resima Naud, and Palicourea calophlebia Standl.

Abnormal rich club organization and impaired correlation between structural and functional connectivity in migraine sufferers.

Science.gov (United States)

Li, Kang; Liu, Lijun; Yin, Qin; Dun, Wanghuan; Xu, Xiaolin; Liu, Jixin; Zhang, Ming

2017-04-01

Because of the unique position of the topologically central role of densely interconnected brain hubs, our study aimed to investigate whether these regions and their related connections would be particularly vulnerable to migraine. In our study, we explored the rich club structure and its role in global functional dynamics in 30 patients with migraine without aura and 30 healthy controls. DTI and resting fMRI were used to construct structural connectivity (SC) and functional connectivity (FC) networks. An independent replication data set of 26 patients and 26 controls was included to replicate and validate significant findings. As compared with the controls, the structural networks of patients exhibited altered rich club organization with higher level of feeder connection density, abnormal small-world organization with increased global efficiency and decreased strength of SC-FC coupling. As these abnormal topological properties and headache attack duration exhibited a significant association with increased density of feeder connections, our results indicated that migraine may be characterized by a selective alteration of the structural connectivity of the rich club regions, tending to have higher 'bridgeness' with non-rich club regions, which may increase the integration among pain-related brain circuits with more excitability but less inhibition for the modulation of migraine.

The latest general chemistry

International Nuclear Information System (INIS)

Ryu, Geun Bae; Choi, Se Yeong; Kim, Chin Yeong; Yoon, Gil Jung; Lee, Eun Seok; Seo, Moon Gyu

1995-02-01

This book deals with the latest general chemistry, which is comprised of twenty-three chapters, the contents of this book are introduction, theory of atoms and molecule, chemical formula and a chemical reaction formula, structure of atoms, nature of atoms and the periodic table, structure of molecule and spectrum, gas, solution, solid, chemical combination, chemical reaction speed, chemical equilibrium, thermal chemistry, oxidation-reduction, electrochemistry, acid-base, complex, aquatic chemistry, air chemistry, nuclear chemistry, metal and nonmetal, organic chemistry and biochemistry. It has exercise in the end of each chapter.

Structure of metal-rich (001) surfaces of III-V compound semiconductors

DEFF Research Database (Denmark)

Kumpf, C.; Smilgies, D.; Landemark, E.

2001-01-01

The atomic structure of the group-III-rich surface of III-V semiconductor compounds has been under intense debate for many years, yet none of the models agrees with the experimental data available. Here we present a model for the three-dimensional structure of the (001)-c(8x2) reconstruction on In......(8 x 2) reconstructions of III-V semiconductor surfaces contain the same essential building blocks....

An Analysis of Prospective Chemistry Teachers' Cognitive Structures through Flow Map Method: The Subject of Oxidation and Reduction

Science.gov (United States)

Temel, Senar

2016-01-01

This study aims to analyse prospective chemistry teachers' cognitive structures related to the subject of oxidation and reduction through a flow map method. Purposeful sampling method was employed in this study, and 8 prospective chemistry teachers from a group of students who had taken general chemistry and analytical chemistry courses were…

Physics and Chemistry of Star and Planet Formation in the Alma ERA

Science.gov (United States)

Bergin, Edwin

2014-06-01

ALMA will open up new avenues of exploration encompassing the wide range of star formation in our galaxy and peering into the central heart of planet-forming circumstellar disks. As we seek to explore the origins of stars and planets molecular emission will be at the front and center of many studies probing gas physics and chemistry. In this talk I will discus some of the areas where we can expect significant advances due to the increased sensitivity and superb spatial resolution of ALMA. In star-forming cores, a rich chemistry is revealed that may be the simpler molecular precursors to more complex organics, such as amino acids, seen within primitive rocks in our own solar system. ALMA will provide new information regarding the relative spatial distribution within a given source for a host of organics, sampling tens to hundreds of transitions of a variety of molecules, including presumably new ones. In this area there is a rich synergy with existing ground and space-based data, including Herschel/Spitzer. Here the increased sampling of sources to be enabled by ALMA should bring greater clarity toward the key products of interstellar chemistry and further constrain processes. On smaller Solar System scales, for over a decade most observations of planet-forming disks focused on the dust thermal continuum emission as a probe of the gas content and structure. ALMA will enable reliable and direct studies of gas to explore the evolving physics of planet-formation, the gas dissipation timescales (i.e. the upper limit to the timescale for giant planet birth), and also the chemistry. It is this chemistry that sets the composition of gas giants and also influences the ultimate composition of water and organic materials that are delivered to terrestrial worlds. Here I will show how we can use molecular emission to determine the gas thermal structure of a disk system and the total gas content - key astrophysical quantities. This will also enable more constrained chemical

The CompTox Chemistry Dashboard: a community data resource for environmental chemistry.

Science.gov (United States)

Williams, Antony J; Grulke, Christopher M; Edwards, Jeff; McEachran, Andrew D; Mansouri, Kamel; Baker, Nancy C; Patlewicz, Grace; Shah, Imran; Wambaugh, John F; Judson, Richard S; Richard, Ann M

2017-11-28

Despite an abundance of online databases providing access to chemical data, there is increasing demand for high-quality, structure-curated, open data to meet the various needs of the environmental sciences and computational toxicology communities. The U.S. Environmental Protection Agency's (EPA) web-based CompTox Chemistry Dashboard is addressing these needs by integrating diverse types of relevant domain data through a cheminformatics layer, built upon a database of curated substances linked to chemical structures. These data include physicochemical, environmental fate and transport, exposure, usage, in vivo toxicity, and in vitro bioassay data, surfaced through an integration hub with link-outs to additional EPA data and public domain online resources. Batch searching allows for direct chemical identifier (ID) mapping and downloading of multiple data streams in several different formats. This facilitates fast access to available structure, property, toxicity, and bioassay data for collections of chemicals (hundreds to thousands at a time). Advanced search capabilities are available to support, for example, non-targeted analysis and identification of chemicals using mass spectrometry. The contents of the chemistry database, presently containing ~ 760,000 substances, are available as public domain data for download. The chemistry content underpinning the Dashboard has been aggregated over the past 15 years by both manual and auto-curation techniques within EPA's DSSTox project. DSSTox chemical content is subject to strict quality controls to enforce consistency among chemical substance-structure identifiers, as well as list curation review to ensure accurate linkages of DSSTox substances to chemical lists and associated data. The Dashboard, publicly launched in April 2016, has expanded considerably in content and user traffic over the past year. It is continuously evolving with the growth of DSSTox into high-interest or data-rich domains of interest to EPA, such

Chemistry-nuclear chemistry division. Progress report, October 1979-September 1980

International Nuclear Information System (INIS)

Ryan, R.R.

1981-05-01

This report presents the research and development programs pursued by the Chemistry-Nuclear Chemistry Division of the Los Alamos National Laboratory. Topics covered include advanced analytical methods, atmospheric chemistry and transport, biochemistry, biomedical research, element migration and fixation, inorganic chemistry, isotope separation and analysis, atomic and molecular collisions, molecular spectroscopy, muonic x rays, nuclear cosmochemistry, nuclear structure and reactions, radiochemical separations, theoretical chemistry, and unclassified weapons research

Chemistry-nuclear chemistry division. Progress report, October 1979-September 1980

Energy Technology Data Exchange (ETDEWEB)

Ryan, R.R. (comp.)

1981-05-01

This report presents the research and development programs pursued by the Chemistry-Nuclear Chemistry Division of the Los Alamos National Laboratory. Topics covered include advanced analytical methods, atmospheric chemistry and transport, biochemistry, biomedical research, element migration and fixation, inorganic chemistry, isotope separation and analysis, atomic and molecular collisions, molecular spectroscopy, muonic x rays, nuclear cosmochemistry, nuclear structure and reactions, radiochemical separations, theoretical chemistry, and unclassified weapons research.

Natural Proline-Rich Cyclopolypeptides from Marine Organisms: Chemistry, Synthetic Methodologies and Biological Status.

Science.gov (United States)

Fang, Wan-Yin; Dahiya, Rajiv; Qin, Hua-Li; Mourya, Rita; Maharaj, Sandeep

2016-10-26

Peptides have gained increased interest as therapeutics during recent years. More than 60 peptide drugs have reached the market for the benefit of patients and several hundreds of novel therapeutic peptides are in preclinical and clinical development. The key contributor to this success is the potent and specific, yet safe, mode of action of peptides. Among the wide range of biologically-active peptides, naturally-occurring marine-derived cyclopolypeptides exhibit a broad range of unusual and potent pharmacological activities. Because of their size and complexity, proline-rich cyclic peptides (PRCPs) occupy a crucial chemical space in drug discovery that may provide useful scaffolds for modulating more challenging biological targets, such as protein-protein interactions and allosteric binding sites. Diverse pharmacological activities of natural cyclic peptides from marine sponges, tunicates and cyanobacteria have encouraged efforts to develop cyclic peptides with well-known synthetic methods, including solid-phase and solution-phase techniques of peptide synthesis. The present review highlights the natural resources, unique structural features and the most relevant biological properties of proline-rich peptides of marine-origin, focusing on the potential therapeutic role that the PRCPs may play as a promising source of new peptide-based novel drugs.

Using Structure-Based Organic Chemistry Online Tutorials with Automated Correction for Student Practice and Review

Science.gov (United States)

O'Sullivan, Timothy P.; Hargaden, Gra´inne C.

2014-01-01

This article describes the development and implementation of an open-access organic chemistry question bank for online tutorials and assessments at University College Cork and Dublin Institute of Technology. SOCOT (structure-based organic chemistry online tutorials) may be used to supplement traditional small-group tutorials, thereby allowing…

Laser-spectroscopy studies of the nuclear structure of neutron-rich radium

Science.gov (United States)

Lynch, K. M.; Wilkins, S. G.; Billowes, J.; Binnersley, C. L.; Bissell, M. L.; Chrysalidis, K.; Cocolios, T. E.; Goodacre, T. Day; de Groote, R. P.; Farooq-Smith, G. J.; Fedorov, D. V.; Fedosseev, V. N.; Flanagan, K. T.; Franchoo, S.; Garcia Ruiz, R. F.; Gins, W.; Heinke, R.; Koszorús, Á.; Marsh, B. A.; Molkanov, P. L.; Naubereit, P.; Neyens, G.; Ricketts, C. M.; Rothe, S.; Seiffert, C.; Seliverstov, M. D.; Stroke, H. H.; Studer, D.; Vernon, A. R.; Wendt, K. D. A.; Yang, X. F.

2018-02-01

The neutron-rich radium isotopes, Ra-233222, were measured with Collinear Resonance Ionization Spectroscopy (CRIS) at the ISOLDE facility, CERN. The hyperfine structure of the 7 s2S10→7 s 7 p P31 transition was probed, allowing measurement of the magnetic moments, quadrupole moments, and changes in mean-square charge radii. These results are compared to existing literature values, and the new moments and change in mean-square charge radii of 231Ra are presented. Low-resolution laser spectroscopy of the very neutron-rich 233Ra has allowed the isotope shift and relative charge radius to be determined for the first time.

Structure of Light Neutron-rich Nuclei

International Nuclear Information System (INIS)

Dlouhy, Zdenek

2007-01-01

In this contribution we searched for irregularities in various separation energies in the frame of mass measurement of neutron-rich nuclei at GANIL. On this basis we can summarize that the new doubly magic nuclei are 8 He, 22 O and 24 O. They are characterized by extra stability and, except 24 O, they cannot accept and bind additional neutrons. However, if we add to these nuclei a proton we obtain 9 Li and 25 F which are the core for two-neutron halo nucleus 11 Li and enables that fluorine can bound even 6 more neutrons, respectively. In that aspect the doubly magic nuclei in the neutron-rich region can form the basis either for neutron halo or very neutron-rich nuclei. (Author)

The Role of Teacher Questions in the Chemistry Classroom

Science.gov (United States)

Dohrn, Sofie Weiss; Dohn, Niels Bonderup

2018-01-01

The purpose of this study was to investigate how a chemistry teacher's questions influence the classroom discourse. It presents a fine-grained analysis of the rich variety of one teacher's questions and the roles they play in an upper secondary chemistry classroom. The study identifies six different functions for the teacher's questions:…

Structurally Based Therapeutic Evaluation: A Therapeutic and Practical Approach to Teaching Medicinal Chemistry.

Science.gov (United States)

Alsharif, Naser Z.; And Others

1997-01-01

Explains structurally based therapeutic evaluation of drugs, which uses seven therapeutic criteria in translating chemical and structural knowledge into therapeutic decision making in pharmaceutical care. In a Creighton University (Nebraska) medicinal chemistry course, students apply the approach to solve patient-related therapeutic problems in…

Chemical sensitive interfacial free volume studies of nanophase Al-rich alloys

International Nuclear Information System (INIS)

Lechner, W.; Puff, W.; Wuerschum, R.; Wilde, G.

2006-01-01

Full text: Al-based nanocrystalline alloys have attracted substantial interest due to their outstanding mechanical properties. These alloys can be obtained by crystallization of melt-spun amorphous precursors or by grain refinement upon repeated cold-rolling of elemental layers. For both synthesis routes, the nanocrystallization process is sensitively affected by interfacial chemistry and free volumes. In order to contribute to an atomistic understanding of the interfacial structure and processes during nanocrystallization, the present work deals with studies of interfacial free volumes by means of positron-annihilation-spectroscopy. In addition to positron lifetime spectroscopy which yields information on the size of free volumes, coincident Doppler broadening of the positron-electron annihilation photons is applied as novel technique for studying the chemistry of interfaces in nanophase materials on an atomistic scale. Al-rich alloys of the above mentioned synthesis routes were studied in this work. (author)

High Temperature Chemistry of Aromatic Hydrocarbons. Final Technical Report

Energy Technology Data Exchange (ETDEWEB)

Scott, Lawrence T. [Boston College, Chestnut Hill, MA (United States). Merkert Chemistry Center, Dept. of Chemistry

2017-05-15

The primary goal of this research was to uncover the principal reaction channels available to polycyclic aromatic hydrocarbons (PAHs) at high temperatures in the gas phase and to establish the factors that determine which channels will be followed in varying circumstances. New structure-property relationships for PAHs were also studied. The efficient production of clean energy from fossil fuels will remain a major component of the DOE mission until alternative sources of energy eventually displace coal and petroleum. Hydrocarbons constitute the most basic class of compounds in all of organic chemistry, and as the dominant species in fossil fuels, they figure prominently into the programs of the DOE. Much is already known about the normal chemistry of hydrocarbons under ambient conditions, but far less is known about their intrinsic chemistry at temperatures close to those reached during combustion. An understanding of the fundamental molecular transformations, rearrangements, and interconversions of PAHs at high temperatures in the gas phase, as revealed by careful studies on small, well-designed, molecular systems, provides insights into the underlying chemistry of many important processes that are more complex, such as the generation of energy by the combustion of fossil fuels, the uncatalyzed gasification and liquefaction of coal, the production of fullerenes in fuel-rich flames, and the formation of soot and carcinogenic pollutants in smoke (e.g., benzo[a]pyrene). The rational control of any of these processes, whether it be the optimization of a desirable process or the minimization of an undesirable one, requires a clear knowledge of the basic chemistry that governs the fate of the species involved. Advances in chemistry at the most fundamental level come about primarily from the discovery of new reactions and from new insights into how reactions occur. Harnessing that knowledge is the key to new technologies. The recent commercialization of a combustion

Chemical Structure and Properties: A Modified Atoms-First, One-Semester Introductory Chemistry Course

Science.gov (United States)

Schaller, Chris P.; Graham, Kate J.; Johnson, Brian J.; Jakubowski, Henry V.; McKenna, Anna G.; McIntee, Edward J.; Jones, T. Nicholas; Fazal, M. A.; Peterson, Alicia A.

2015-01-01

A one-semester, introductory chemistry course is described that develops a primarily qualitative understanding of structure-property relationships. Starting from an atoms-first approach, the course examines the properties and three-dimensional structure of metallic and ionic solids before expanding into a thorough investigation of molecules. In…

Structure activity study on the quinone/quinone methide chemistry of flavonoids

NARCIS (Netherlands)

Awad, H.M.; Boersma, M.G.; Boeren, S.; Bladeren, van P.J.; Vervoort, J.; Rietjens, I.M.C.M.

2001-01-01

A structure-activity study on the quinone/quinone methide chemistry of a series of 3',4'-dihydroxyflavonoids was performed. Using the glutathione trapping method followed by HPLC, 1H NMR, MALDI-TOF, and LC/MS analysis to identify the glutathionyl adducts, the chemical behavior of the

Natural Cr3+-rich ettringite: occurrence, properties, and crystal structure

Science.gov (United States)

Seryotkin, Yurii V.; Sokol, Ella V.; Kokh, Svetlana N.; Murashko, Mikhail N.

2017-08-01

Cr3+-rich ettringite with Cr3+→Al substitution and Cr/(Cr + Al) ratios up to 0.40-0.50 was found in mineral assemblages of the Ma'aleh Adumim area of Mottled Zone (Judean Desert). The Cr3+-rich compositions were the latest in the thaumasite → ettringite-thaumasite solid solution → ettringite → ettringite-bentorite solid solution series. The mineral-forming solution was enriched in Cr3+ and had a pH buffered by afwillite at 11-12. Chromium was inherited from larnite rocks produced by high-temperature combustion metamorphic alteration of bioproductive calcareous sediments. The Cr/(Cr + Al) ratios are within 0.10-0.15 in most of the analysed crystals. This degree of substitution imparts pink colouration to the crystals, but does not affect their habit (a combination of monohedra and a prism). The habit changes to pyramid faces in coarse and later Cr3+-bearing crystals as Cr/(Cr + Al) ratios increase abruptly to 0.40-0.50. Single-crystal XRD analysis of one Cr-free and two Cr3+-rich samples and their structure determination and refinement indicate that the Cr-rich crystals (with Cr/(Cr + Al) to 0.3) preserve the symmetry and metrics of ettringite. The Ca-O bonding network undergoes differentiation with increase of Cr3+ concentration at octahedral M sites. The compression of Ca2 and expansion of Ca1 polyhedra sub-networks correlates with the degree of Cr3+→Al substitution.

Compositional and structural variabilities of Mg-rich iron oxide spinels from tuffite

Directory of Open Access Journals (Sweden)

W. N. Mussel

1999-12-01

Full Text Available Maghemite (γFe2O3 from tuffite is exceptionally rich in Mg, relatively to most of those reportedly found in other mafic lithosystems. To investigate in detail the compositional and structural variabilities of this natural magnetic iron oxide, sets of crystals were isolated from samples collected at different positions in a tuffite weathering mantle. These sets of crystal were individually powdered and studied by X-ray diffractometry, Mössbauer spectroscopy, magnetization measurements and chemical analysis. Lattice parameter of the cubic cell (a0 was found to vary from 0.834(1 to 0.8412(1 nm. Lower a0-values are characteristic of maghemite whereas higher ones are related to a magnetite precursor. FeO content ranges up to 17 mass % and spontaneous magnetization ranges from 8 to 32 J T-1 kg-1. Zero-field room temperature Mössbauer spectra are rather complex, indicating that the hyperfine field distributions due to Fe3+ and mixed valence Fe3+/2+ overlap. The structural variabilities of the (Mg, Ti-rich iron oxide spinels is essentially related to the range of chemical composition of its precursor (Mg, Ti-rich magnetite, and probably to the extent to which it has been oxidized during transformation in soil.

Direct Atomic Scale Observation of the Structure and Chemistry of Order/Disorder Interfaces

National Research Council Canada - National Science Library

Srinivasan, R; Banerjee, R; Hwang, J. Y; Viswanathan, G. B; Tiley, J; Fraser, H. L

2008-01-01

... distributed ordered intermetallic precipitates within a disordered matrix. The structure and chemistry at the precipitate/matrix interface plays a critical role in determining the effectiveness of the strengthening mechanism...

High Energy Radical Chemistry Formation of HCN- rich Atmospheres on early Earth

Czech Academy of Sciences Publication Activity Database

Ferus, Martin; Kubelík, Petr; Knížek, Antonín; Pastorek, Adam; Sutherland, J.D.; Civiš, Svatopluk

2017-01-01

Roč. 7, č. 1 (2017), č. článku 6275. ISSN 2045-2322 R&D Projects: GA ČR GA17-05076S; GA MŠk(CZ) LM2015083; GA MŠk LG15013 Grant - others:Akademie věd - GA AV ČR(CZ) R200401521 Institutional support: RVO:61388955 Keywords : high-power laser * transform emission-spectroscopy * induced dielectric-breakdown * prebiotic organic-synthesis * nucleobase formation Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 4.259, year: 2016

Diffusion tractography and graph theory analysis reveal the disrupted rich-club organization of white matter structural networks in early Tourette Syndrome children

Science.gov (United States)

Wen, Hongwei; Liu, Yue; Wang, Shengpei; Zhang, Jishui; Peng, Yun; He, Huiguang

2017-03-01

Tourette syndrome (TS) is a childhood-onset neurobehavioral disorder. At present, the topological disruptions of the whole brain white matter (WM) structural networks remain poorly understood in TS children. Considering the unique position of the topologically central role of densely interconnected brain hubs, namely the rich club regions, therefore, we aimed to investigate whether the rich club regions and their related connections would be particularly vulnerable in early TS children. In our study, we used diffusion tractography and graph theoretical analyses to explore the rich club structures in 44 TS children and 48 healthy children. The structural networks of TS children exhibited significantly increased normalized rich club coefficient, suggesting that TS is characterized by increased structural integrity of this centrally embedded rich club backbone, potentially resulting in increased global communication capacity. In addition, TS children showed a reorganization of rich club regions, as well as significantly increased density and decreased number in feeder connections. Furthermore, the increased rich club coefficients and feeder connections density of TS children were significantly positively correlated to tic severity, indicating that TS may be characterized by a selective alteration of the structural connectivity of the rich club regions, tending to have higher bridging with non-rich club regions, which may increase the integration among tic-related brain circuits with more excitability but less inhibition for information exchanges between highly centered brain regions and peripheral areas. In all, our results suggest the disrupted rich club organization in early TS children and provide structural insights into the brain networks.

Misconception of pre-service chemistry teachers about the concept of resonances in organic chemistry course

Science.gov (United States)

Widarti, Hayuni Retno; Retnosari, Rini; Marfu'ah, Siti

2017-08-01

A descriptive quantitative research has been done to identify the level of understanding and misconceptions of the pre-service chemistry teachers related to the concept of resonance in the organic chemistry course. The subjects of the research were 51 students of State University of Malang, majoring Chemistry Education, currently in their fourth semester, 2015-2016 academic year who have taken the course of Organic Chemistry I. The instruments used in this research is a combination of 8 numbers of multiple choice tests with open answer questions and certainty of response index (CRI). The research findings revealed that there are still misconceptions found in the organic chemistry course, especially about the concept of resonance. There were several misconceptions of the pre-service chemistry teachers, such as resonance structures are in equilibrium with each other; resonance structures are two or more Lewis structures with different in arrangement of both atom and electron; resonance structures are only structures containing charged atoms; formal charge and resonance structures are not related; and the stability of resonance structures are only determined by location of charges in atoms found in such structures. There is also a lack of understanding of curved arrows notation to show electron pair movement.

EGCG Inhibited Lipofuscin Formation Based on Intercepting Amyloidogenic β-Sheet-Rich Structure Conversion.

Directory of Open Access Journals (Sweden)

Shuxian Cai

Full Text Available Lipofuscin (LF is formed during lipid peroxidation and sugar glycosylation by carbonyl-amino crosslinks with biomacrolecules, and accumulates slowly within postmitotic cells. The environmental pollution, modern dietary culture and lifestyle changes have been found to be the major sources of reactive carbonyl compounds in vivo. Irreversible carbonyl-amino crosslinks induced by carbonyl stress are essentially toxiferous for aging-related functional losses in modern society. Results show that (--epigallocatechin gallate (EGCG, the main polyphenol in green tea, can neutralize the carbonyl-amino cross-linking reaction and inhibit LF formation, but the underlying mechanism is unknown.We explored the mechanism of the neutralization process from protein, cell, and animal levels using spectrofluorometry, infrared spectroscopy, conformation antibodies, and electron microscopy. LF demonstrated an amyloidogenic β-sheet-rich with antiparallel structure, which accelerated the carbonyl-amino crosslinks formation and disrupted proteolysis in both PC12 cells and D-galactose (D-gal-induced brain aging mice models. Additionally, EGCG effectively inhibited the formation of the amyloidogenic β-sheet-rich structure of LF, and prevented its conversion into toxic and on-pathway aggregation intermediates, thereby cutting off the carbonyl-amino crosslinks.Our study indicated that the amyloidogenic β-sheet structure of LF may be the core driving force for carbonyl-amino crosslinks further formation, which mediates the formation of amyloid fibrils from native state of biomacrolecules. That EGCG exhibits anti-amyloidogenic β-sheet-rich structure properties to prevent the LF formation represents a novel strategy to impede the development of degenerative processes caused by ageing or stress-induced premature senescence in modern environments.

Species richness and soil properties in Pinus ponderosa forests: A structural equation modeling analysis

Science.gov (United States)

Laughlin, D.C.; Abella, S.R.; Covington, W.W.; Grace, J.B.

2007-01-01

Question: How are the effects of mineral soil properties on understory plant species richness propagated through a network of processes involving the forest overstory, soil organic matter, soil nitrogen, and understory plant abundance? Location: North-central Arizona, USA. Methods: We sampled 75 0.05-ha plots across a broad soil gradient in a Pinus ponderosa (ponderosa pine) forest ecosystem. We evaluated multivariate models of plant species richness using structural equation modeling. Results: Richness was highest at intermediate levels of understory plant cover, suggesting that both colonization success and competitive exclusion can limit richness in this system. We did not detect a reciprocal positive effect of richness on plant cover. Richness was strongly related to soil nitrogen in the model, with evidence for both a direct negative effect and an indirect non-linear relationship mediated through understory plant cover. Soil organic matter appeared to have a positive influence on understory richness that was independent of soil nitrogen. Richness was lowest where the forest overstory was densest, which can be explained through indirect effects on soil organic matter, soil nitrogen and understory cover. Finally, model results suggest a variety of direct and indirect processes whereby mineral soil properties can influence richness. Conclusions: Understory plant species richness and plant cover in P. ponderosa forests appear to be significantly influenced by soil organic matter and nitrogen, which are, in turn, related to overstory density and composition and mineral soil properties. Thus, soil properties can impose direct and indirect constraints on local species diversity in ponderosa pine forests. ?? IAVS; Opulus Press.

Atomic Scale Structure-Chemistry Relationships at Oxide Catalyst Surfaces and Interfaces

Science.gov (United States)

McBriarty, Martin E.

Oxide catalysts are integral to chemical production, fuel refining, and the removal of environmental pollutants. However, the atomic-scale phenomena which lead to the useful reactive properties of catalyst materials are not sufficiently understood. In this work, the tools of surface and interface science and electronic structure theory are applied to investigate the structure and chemical properties of catalytically active particles and ultrathin films supported on oxide single crystals. These studies focus on structure-property relationships in vanadium oxide, tungsten oxide, and mixed V-W oxides on the surfaces of alpha-Al2O3 and alpha-Fe2O 3 (0001)-oriented single crystal substrates, two materials with nearly identical crystal structures but drastically different chemical properties. In situ synchrotron X-ray standing wave (XSW) measurements are sensitive to changes in the atomic-scale geometry of single crystal model catalyst surfaces through chemical reaction cycles, while X-ray photoelectron spectroscopy (XPS) reveals corresponding chemical changes. Experimental results agree with theoretical calculations of surface structures, allowing for detailed electronic structure investigations and predictions of surface chemical phenomena. The surface configurations and oxidation states of V and W are found to depend on the coverage of each, and reversible structural shifts accompany chemical state changes through reduction-oxidation cycles. Substrate-dependent effects suggest how the choice of oxide support material may affect catalytic behavior. Additionally, the structure and chemistry of W deposited on alpha-Fe 2O3 nanopowders is studied using X-ray absorption fine structure (XAFS) measurements in an attempt to bridge single crystal surface studies with real catalysts. These investigations of catalytically active material surfaces can inform the rational design of new catalysts for more efficient and sustainable chemistry.

Investigation of the single Particle Structure of the neutron-rich Sodium Isotopes $^{27-31}\\!$Na

CERN Document Server

2002-01-01

We propose to study the single particle structure of the neutron-rich isotopes $^{27-31}\\!$Na. These isotopes will be investigated via neutron pickup reactions in inverse kinematics on a deuterium and a beryllium target. Scattered beam particles and transfer products are detected in a position sensitive detector located around 0$^\\circ$. De-excitation $\\gamma$-rays emitted after an excited state has been populated will be registered by the MINIBALL Germanium array. The results will shed new light on the structure of the neutron-rich sodium isotopes and especially on the region of strong deformation around the N=20 nucleus $^{31}\\!$Na.

Li-rich layer-structured cathode materials for high energy Li-ion batteries

Science.gov (United States)

Li, Liu; Lee, Kim Seng; Lu, Li

2014-08-01

Li-rich layer-structured xLi2MnO3 ṡ (1 - x)LiMO2 (M = Mn, Ni, Co, etc.) materials have attracted much attention due to their extraordinarily high reversible capacity as the cathode material in Li-ion batteries. To better understand the nature of this type of materials, this paper reviews history of development of the Li-rich cathode materials, and provides in-depth study on complicated crystal structures and reaction mechanisms during electrochemical charge/discharge cycling. Despite the fabulous capability at low rate, several drawbacks still gap this type of high-capacity cathode materials from practical applications, for instance the large irreversible capacity loss at first cycle, poor rate capability, severe voltage decay and capacity fade during electrochemical charge/discharge cycling. This review will also address mechanisms for these inferior properties and propose various possible solutions to solve above issues for future utilization of these cathode materials in commercial Li-ion batteries.

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…

Structure Determination of Unknown Organic Liquids Using NMR and IR Spectroscopy: A General Chemistry Laboratory

Science.gov (United States)

Pavel, John T.; Hyde, Erin C.; Bruch, Martha D.

2012-01-01

This experiment introduced general chemistry students to the basic concepts of organic structures and to the power of spectroscopic methods for structure determination. Students employed a combination of IR and NMR spectroscopy to perform de novo structure determination of unknown alcohols, without being provided with a list of possible…

Physical Chemistry '98: Fourth International Conference on Fundamental and Applied Aspects of Physical Chemistry - Papers

International Nuclear Information System (INIS)

Ribnikar, S.; Anic, S.

1998-01-01

The proceedings has following chapters: Plenary lectures; Chemical Thermodynamics; Spectroscopy, Molecular Structures, Physical Chemistry of Plasma; Kinetics, Catalysis, Nonlinear Dynamics; Electrochemistry; Biophysical Chemistry, Photochemistry, Radiation Chemistry; Radiochemistry, Nuclear Chemistry; Solid State Physical Chemistry, Material Science; Macromolecular Physical Chemistry; Environmental Protection; Phase Boundaries; Complex Compounds; General Physical Chemistry. A separated abstract was prepared for each of the 20 papers selected from the three chapters: Biophysical Chemistry, Photochemistry, Radiation Chemistry; Radiochemistry, Nuclear Chemistry. and Environmental Protection. Refs and figs

Organic chemistry

International Nuclear Information System (INIS)

2003-08-01

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.

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.

Modern electronic structure theory and applications in organic chemistry

CERN Document Server

Davidson, ER

1997-01-01

This volume focuses on the use of quantum theory to understand and explain experiments in organic chemistry. High level ab initio calculations, when properly performed, are useful in making quantitative distinctions between various possible interpretations of structures, reactions and spectra. Chemical reasoning based on simpler quantum models is, however, essential to enumerating the likely possibilities. The simpler models also often suggest the type of wave function likely to be involved in ground and excited states at various points along reaction paths. This preliminary understanding is n

Titan: a laboratory for prebiological organic chemistry

Science.gov (United States)

Sagan, C.; Thompson, W. R.; Khare, B. N.

1992-01-01

When we examine the atmospheres of the Jovian planets (Jupiter, Saturn, Uranus, and Neptune), the satellites in the outer solar system, comets, and even--through microwave and infrared spectroscopy--the cold dilute gas and grains between the stars, we find a rich organic chemistry, presumably abiological, not only in most of the solar system but throughout the Milky Way galaxy. In part because the composition and surface pressure of the Earth's atmosphere 4 x 10(9) years ago are unknown, laboratory experiments on prebiological organic chemistry are at best suggestive; but we can test our understanding by looking more closely at the observed extraterrestrial organic chemistry. The present Account is restricted to atmospheric organic chemistry, primarily on the large moon of Saturn. Titan is a test of our understanding of the organic chemistry of planetary atmospheres. Its atmospheric bulk composition (N2/CH4) is intermediate between the highly reducing (H2/He/CH4/NH3/H2O) atmospheres of the Jovian planets and the more oxidized (N2/CO2/H2O) atmospheres of the terrestrial planets Mars and Venus. It has long been recognized that Titan's organic chemistry may have some relevance to the events that led to the origin of life on Earth. But with Titan surface temperatures approximately equal to 94 K and pressures approximately equal to 1.6 bar, the oceans of the early Earth have no ready analogue on Titan. Nevertheless, tectonic events in the water ice-rich interior or impact melting and slow re-freezing may lead to an episodic availability of liquid water. Indeed, the latter process is the equivalent of a approximately 10(3)-year-duration shallow aqueous sea over the entire surface of Titan.

Crystal structures and second-order NLO properties of borogermanates

Science.gov (United States)

Zhang, Jian-Han; Kong, Fang; Xu, Xiang; Mao, Jiang-Gao

2012-11-01

Borogermanates are a class of very important compounds in materials chemistry. In this paper, the syntheses, structures, and properties of metal borogermanates are reviewed. Organically templated borogermanates with zeolite-like open-frameworks show potential applications as microporous materials. Many compounds in alkali or alkaline-earth borogermanate systems are structurally acentric or polar, some of which exhibit excellent Second Harmonic Generation (SHG) coefficients, wide transparency regions, and high optical-damage thresholds as well as excellent thermal stability. Most of the lanthanide borogermanates are structurally centrosymmetric and not SHG active; however, they are able to emit strong luminescence in visible or near-IR region. In the B-rich compounds, BO3 and BO4 groups can be polymerized into a variety of discrete polynuclear anionic cluster units or extended architectures via B-O-B bridges; whereas in the Ge-rich compounds, GeO4 and GeO6 polyhedra can also be polymerized. The combinations of borate and germinate afforded rich structural and topological types.

Managed forest landscape structure and avian species richness in the southeastern US

Science.gov (United States)

Craig Loehle; T. Bently Wigley; Scott Rutzmoser; John A. Gerwin; Patrick D. Keyser; Richard A. Lancia; Christopher J. Reynolds; Ronald E. Thill; Robert Weih; Don White; Petra Bohall Wood

2005-01-01

Forest structural features at the stand scale (e.g., snags, stem density, species composition) and habitat attributes at larger spatial scales (e.g., landscape pattern, road density) can influence biological diversity and have been proposed as indicators in sustainable forestry programs. This study investigated relationships between such factors and total richness of...

Electrostatics in Chemistry

Indian Academy of Sciences (India)

fundamental concepts of electrostatics as applied to atoms and molecules. The electric ... chemistry, the chemistry of the covalent bond, deals with the structures ..... the position of an asteroid named Ceres ... World Scientific. Singapore, 1992.

Polycyclic aromatic hydrocarbons and molecular hydrogen in oxygen-rich planetary nebulae: the case of NGC 6720.

Science.gov (United States)

Cox, N L J; Pilleri, P; Berné, O; Cernicharo, J; Joblin, C

2016-02-11

Evolved stars are primary sources for the formation of polycyclic aromatic hydrocarbons (PAHs) and dust grains. Their circumstellar chemistry is usually designated as either oxygen-rich or carbon-rich, although dual-dust chemistry objects, whose infrared spectra reveal both silicate- and carbon-dust features, are also known. The exact origin and nature of this dual-dust chemistry is not yet understood. Spitzer -IRS mid-infrared spectroscopic imaging of the nearby, oxygen-rich planetary nebula NGC 6720 reveals the presence of the 11.3 μ m aromatic (PAH) emission band. It is attributed to emission from neutral PAHs, since no band is observed in the 7-8 μ m range. The spatial distribution of PAHs is found to closely follow that of the warm clumpy molecular hydrogen emission. Emission from both neutral PAHs and warm H 2 is likely to arise from photo-dissociation regions associated with dense knots that are located within the main ring. The presence of PAHs together with the previously derived high abundance of free carbon (relative to CO) suggest that the local conditions in an oxygen-rich environment can also become conducive to in-situ formation of large carbonaceous molecules, such as PAHs, via a bottom-up chemical pathway. In this scenario, the same stellar source can enrich the interstellar medium with both oxygen-rich dust and large carbonaceous molecules.

Structure of Ni-rich Ni--Cr--B--Si coating alloys

International Nuclear Information System (INIS)

Knotek, O.; Lugscheider, E.; Reimann, H.

1975-01-01

The structures of quaternary, nickel-rich Ni--Cr--B--Si alloys were analyzed at a constant boron content of 10 at. percent and a temperature of 850 0 C. The composition range for silicide formation was determined. In these quaternary alloys, known binary nickel silicides, nickel and chromium borides, and the ternary silico-boride Ni 6 Si 2 B were confirmed. A new composition for the W 5 Si 3 -type phase in the Ni--B--Si system was proposed. (U.S.)

A qualitative inquiry into the effects of visualization on high school chemistry students' learning process of molecular structure

Science.gov (United States)

Deratzou, Susan

This research studies the process of high school chemistry students visualizing chemical structures and its role in learning chemical bonding and molecular structure. Minimal research exists with high school chemistry students and more research is necessary (Gabel & Sherwood, 1980; Seddon & Moore, 1986; Seddon, Tariq, & Dos Santos Veiga, 1984). Using visualization tests (Ekstrom, French, Harman, & Dermen, 1990a), a learning style inventory (Brown & Cooper, 1999), and observations through a case study design, this study found visual learners performed better, but needed more practice and training. Statistically, all five pre- and post-test visualization test comparisons were highly significant in the two-tailed t-test (p > .01). The research findings are: (1) Students who tested high in the Visual (Language and/or Numerical) and Tactile Learning Styles (and Social Learning) had an advantage. Students who learned the chemistry concepts more effectively were better at visualizing structures and using molecular models to enhance their knowledge. (2) Students showed improvement in learning after visualization practice. Training in visualization would improve students' visualization abilities and provide them with a way to think about these concepts. (3) Conceptualization of concepts indicated that visualizing ability was critical and that it could be acquired. Support for this finding was provided by pre- and post-Visualization Test data with a highly significant t-test. (4) Various molecular animation programs and websites were found to be effective. (5) Visualization and modeling of structures encompassed both two- and three-dimensional space. The Visualization Test findings suggested that the students performed better with basic rotation of structures as compared to two- and three-dimensional objects. (6) Data from observations suggest that teaching style was an important factor in student learning of molecular structure. (7) Students did learn the chemistry concepts

PubChemQC Project: A Large-Scale First-Principles Electronic Structure Database for Data-Driven Chemistry.

Science.gov (United States)

Nakata, Maho; Shimazaki, Tomomi

2017-06-26

Large-scale molecular databases play an essential role in the investigation of various subjects such as the development of organic materials, in silico drug design, and data-driven studies with machine learning. We have developed a large-scale quantum chemistry database based on first-principles methods. Our database currently contains the ground-state electronic structures of 3 million molecules based on density functional theory (DFT) at the B3LYP/6-31G* level, and we successively calculated 10 low-lying excited states of over 2 million molecules via time-dependent DFT with the B3LYP functional and the 6-31+G* basis set. To select the molecules calculated in our project, we referred to the PubChem Project, which was used as the source of the molecular structures in short strings using the InChI and SMILES representations. Accordingly, we have named our quantum chemistry database project "PubChemQC" ( http://pubchemqc.riken.jp/ ) and placed it in the public domain. In this paper, we show the fundamental features of the PubChemQC database and discuss the techniques used to construct the data set for large-scale quantum chemistry calculations. We also present a machine learning approach to predict the electronic structure of molecules as an example to demonstrate the suitability of the large-scale quantum chemistry database.

Relative importance of current and past landscape structure and local habitat conditions for plant species richness in dry grassland-like forest openings.

Science.gov (United States)

Husáková, Iveta; Münzbergová, Zuzana

2014-01-01

In fragmented landscapes, plant species richness may depend not only on local habitat conditions but also on landscape structure. In addition, both present and past landscape structure may be important for species richness. There are, however, only a few studies that have investigated the relative importance of all of these factors. The aim of this study was to examine the effect of current and past landscape structures and habitat conditions on species richness at dry grassland-like forest openings in a forested landscape and to assess their relative importance for species richness. We analyzed information on past and present landscape structures using aerial photographs from 1938, 1973, 1988, 2000 and 2007. We calculated the area of each locality and its isolation in the present and in the past and the continuity of localities in GIS. At each locality, we recorded all vascular plant species (296 species in 110 forest openings) and information on abiotic conditions of the localities. We found that the current species richness of the forest openings was significantly determined by local habitat conditions as well as by landscape structure in the present and in the past. The highest species richness was observed on larger and more heterogeneous localities with rocks and shallow soils, which were already large and well connected to other localities in 1938. The changes in the landscape structure in the past can thus have strong effects on current species richness. Future studies attempting to understand determinants of species diversity in fragmented landscapes should also include data on past landscape structure, as it may in fact be more important than the present structure.

Combustion chemistry of alcohols: Experimental and modeled structure of a premixed 2-methylbutanol flame

KAUST Repository

Lucassen, Arnas; Park, Sungwoo; Hansen, Nils; Sarathy, Mani

2014-01-01

This paper presents a detailed investigation of 2-methylbutanol combustion chemistry in low-pressure premixed flames. This chemistry is of particular interest to study because this compound is potentially a lignocellulosic-based, next-generation biofuel. The detailed chemical structure of a stoichiometric low-pressure (25 Torr) flame was determined using flame-sampling molecular-beam mass spectrometry. A total of 55 species were identified and subsequently quantitative mole fraction profiles as function of distance from the burner surface were determined. In an independent effort, a detailed flame chemistry model for 2-methylbutanol was assembled based on recent knowledge gained from combustion chemistry studies for butanol isomers ([Sarathy et al. Combust. Flame 159 (6) (2012) 2028-2055]) and iso-pentanol (3-methylbutanol) [Sarathy et al. Combust. Flame 160 (12) (2013) 2712-2728]. Experimentally determined and modeled mole fraction profiles were compared to demonstrate the model's capabilities. Examples of individual mole fraction profiles are discussed together with the most significant fuel consumption pathways to highlight the combustion chemistry of 2-methylbutanol. Discrepancies between experimental and modeling results are used to suggest areas where improvement of the kinetic model would be needed. © 2014.

Combustion chemistry of alcohols: Experimental and modeled structure of a premixed 2-methylbutanol flame

KAUST Repository

Lucassen, Arnas

2014-06-14

This paper presents a detailed investigation of 2-methylbutanol combustion chemistry in low-pressure premixed flames. This chemistry is of particular interest to study because this compound is potentially a lignocellulosic-based, next-generation biofuel. The detailed chemical structure of a stoichiometric low-pressure (25 Torr) flame was determined using flame-sampling molecular-beam mass spectrometry. A total of 55 species were identified and subsequently quantitative mole fraction profiles as function of distance from the burner surface were determined. In an independent effort, a detailed flame chemistry model for 2-methylbutanol was assembled based on recent knowledge gained from combustion chemistry studies for butanol isomers ([Sarathy et al. Combust. Flame 159 (6) (2012) 2028-2055]) and iso-pentanol (3-methylbutanol) [Sarathy et al. Combust. Flame 160 (12) (2013) 2712-2728]. Experimentally determined and modeled mole fraction profiles were compared to demonstrate the model\\'s capabilities. Examples of individual mole fraction profiles are discussed together with the most significant fuel consumption pathways to highlight the combustion chemistry of 2-methylbutanol. Discrepancies between experimental and modeling results are used to suggest areas where improvement of the kinetic model would be needed. © 2014.

Principles of Chemistry (by Michael Munowitz)

Science.gov (United States)

Kovac, Reviewed By Jeffrey

2000-05-01

At a time when almost all general chemistry textbooks seem to have become commodities designed by marketing departments to offend no one, it is refreshing to find a book with a unique perspective. Michael Munowitz has written what I can only describe as a delightful chemistry book, full of conceptual insight, that uses a novel and interesting pedagogic strategy. This is a book that has much to recommend it. This is the best-written general chemistry book I have ever read. An editor with whom I have worked recently remarked that he felt his job was to help authors make their writing sing. Well, the writing in Principles of Chemistry sings with the full, rich harmonies and creative inventiveness of the King's Singers or Chanticleer. Here is the first sentence of the introduction: "Central to any understanding of the physical world is one discovery of paramount importance, a truth disarmingly simple yet profound in its implications: matter is not continuous." This is prose to be savored and celebrated. Principles of Chemistry has a distinct perspective on chemistry: the perspective of the physical chemist. The focus is on simplicity, what is common about molecules and reactions; begin with the microscopic and build bridges to the macroscopic. The author's perspective is clear from the organization of the book. After three rather broad introductory chapters, there are four chapters that develop the quantum mechanical theory of atoms and molecules, including a strong treatment of molecular orbital theory. Unlike many books, Principles of Chemistry presents the molecular orbital approach first and introduces valence bond theory later only as an approximation for dealing with more complicated molecules. The usual chapters on descriptive inorganic chemistry are absent (though there is an excellent chapter on organic and biological molecules and reactions as well as one on transition metal complexes). Instead, descriptive chemistry is integrated into the development of

Weakly bound structures in neutron rich Si isotopes

International Nuclear Information System (INIS)

Singh, D.; Saxena, G.; Yadav, H.L.

2009-01-01

Production of radioactive beams have facilitated the nuclear structure studies away from the line of β-stability, especially for the neutron rich drip line nuclei. Theoretical investigations of these nuclei have been carried out by using various approaches viz. few body model or clusters, shell model and mean field theories, both nonrelativistic as well as relativistic mean field (RMF). The advantage of the RMF approach, however, is that in this treatment the spin-orbit interaction is included in a natural way. This is especially advantageous for the description of drip-line nuclei for which the spin-orbit interaction plays an important role. In this communication we report briefly the results of our calculations for the Si isotopes carried out within the framework of RMF + BCS approach

Understanding of the structure activity relationship of PtPd bimetallic catalysts prepared by surface organometallic chemistry and ion exchange during the reaction of iso-butane with hydrogen

KAUST Repository

Al-Shareef, Reem A.; Harb, Moussab; Saih, Youssef; Ould-Chikh, Samy; Roldan, Manuel A.; Anjum, Dalaver H.; Guyonnet, Elodie Bile; Candy, Jean-Pierre; Jan, Deng-Yang; Abdo, Suheil F.; Aguilar-Tapia, Antonio; Proux, Olivier; Hazemann, Jean-Louis; Basset, Jean-Marie

2018-01-01

Well-defined silica supported bimetallic catalysts Pt100-x Pdx were prepared by Surface Organometallic Chemistry (SOMC) and Ionic-Exchange (IE) methods. For all investigated catalysts, iso-butane reaction with hydrogen under differential conditions led to the formation of methane and propane, n-butane, and traces of iso-butylene. The total reaction rate decreased with increasing the Pd loading for both catalysts series as a result of decreasing turnover rate of both isomerization and hydrogenolysis. In the case of Pt100-x Pdx(SOMC) catalysts, the experimental results in combination with DFT calculations suggested a selective coverage of Pt (1 0 0) surface by agglomerated Pd atoms like “islands”, assuming that each metal roughly keeps its intrinsic catalytic properties with relatively small electron transfer from Pt to Pd in the case of Pt-rich sample and from Pd to Pt in the case of Pd-rich sample. For the PtPd catalysts prepared by IE, the catalytic behavior could be explained by the formation of a surface alloy between Pt and Pd in the case of Pd-rich sample and by the segregation of a small amount of Pd on the surface in the case of Pt-rich sample, as demonstrated by TEM, EXAFS and DFT. The catalytic results were explained by a structure activity relationship based on the proposed mechanism of CH bond and CC bond activation and cleavage for iso-butane hydrogenolysis, isomerization, cracking and dehydrogenation.

Understanding of the structure activity relationship of PtPd bimetallic catalysts prepared by surface organometallic chemistry and ion exchange during the reaction of iso-butane with hydrogen

KAUST Repository

Alshareef, Reem Abdul aziz Hamed

2018-04-25

Well-defined silica supported bimetallic catalysts Pt100-x Pdx were prepared by Surface Organometallic Chemistry (SOMC) and Ionic-Exchange (IE) methods. For all investigated catalysts, iso-butane reaction with hydrogen under differential conditions led to the formation of methane and propane, n-butane, and traces of iso-butylene. The total reaction rate decreased with increasing the Pd loading for both catalysts series as a result of decreasing turnover rate of both isomerization and hydrogenolysis. In the case of Pt100-x Pdx(SOMC) catalysts, the experimental results in combination with DFT calculations suggested a selective coverage of Pt (1 0 0) surface by agglomerated Pd atoms like “islands”, assuming that each metal roughly keeps its intrinsic catalytic properties with relatively small electron transfer from Pt to Pd in the case of Pt-rich sample and from Pd to Pt in the case of Pd-rich sample. For the PtPd catalysts prepared by IE, the catalytic behavior could be explained by the formation of a surface alloy between Pt and Pd in the case of Pd-rich sample and by the segregation of a small amount of Pd on the surface in the case of Pt-rich sample, as demonstrated by TEM, EXAFS and DFT. The catalytic results were explained by a structure activity relationship based on the proposed mechanism of CH bond and CC bond activation and cleavage for iso-butane hydrogenolysis, isomerization, cracking and dehydrogenation.

H2O Formation in C-rich AGB Winds

NARCIS (Netherlands)

Lombaert, R.; Decin, L.; Royer, P.; de Koter, A.; Cox, N.L.J.; De Ridder, J.; Khouri, T.; Agúndez, M.; Blommaert, J.A.D.L.; Gernicharo, J.; González-Alfonso, E.; Groenewegen, M.A.T.; Kerschbaum, F.; Neufeld, D.; Vandenbussche, B.; Waelkens, C.

2015-01-01

The Herschel detection of warm H2O vapor emission from C-rich winds of AGB stars challenges the current understanding of circumstellar chemistry. Two mechanisms have been invoked to explain warm H2O formation. In the first, penetration of UV interstellar radiation through a clumpy circumstellar

Structure and chemistry of the Si(111)/AlN interface

Science.gov (United States)

Radtke, G.; Couillard, M.; Botton, G. A.; Zhu, D.; Humphreys, C. J.

2012-01-01

We investigate the atomic structure and the chemistry of the Si(111)/AlN interface for an AlN film grown at low-temperature (735 °C) by metalorganic vapor phase epitaxy. A heterogeneous interface is formed from the alternation of crystallographically abrupt and partly amorphous regions. The polarity of the AlN film, along with the projected atomic structure of the crystalline interface, is retrieved using high-angle annular dark field imaging, and a model, based on these experimental observations, is proposed for the bonding at the interface. Electron energy-loss spectrum-imaging, however, also reveals a chemical intermixing, placing our growth conditions at the onset of SiNx interlayer formation.

Re-Structuring of Marine Communities Exposed to Environmental Change: A Global Study on the Interactive Effects of Species and Functional Richness

Science.gov (United States)

Wahl, Martin; Link, Heike; Alexandridis, Nicolaos; Thomason, Jeremy C.; Cifuentes, Mauricio; Costello, Mark J.; da Gama, Bernardo A. P.; Hillock, Kristina; Hobday, Alistair J.; Kaufmann, Manfred J.; Keller, Stefanie; Kraufvelin, Patrik; Krüger, Ina; Lauterbach, Lars; Antunes, Bruno L.; Molis, Markus; Nakaoka, Masahiro; Nyström, Julia; bin Radzi, Zulkamal; Stockhausen, Björn; Thiel, Martin; Vance, Thomas; Weseloh, Annika; Whittle, Mark; Wiesmann, Lisa; Wunderer, Laura; Yamakita, Takehisa; Lenz, Mark

2011-01-01

Species richness is the most commonly used but controversial biodiversity metric in studies on aspects of community stability such as structural composition or productivity. The apparent ambiguity of theoretical and experimental findings may in part be due to experimental shortcomings and/or heterogeneity of scales and methods in earlier studies. This has led to an urgent call for improved and more realistic experiments. In a series of experiments replicated at a global scale we translocated several hundred marine hard bottom communities to new environments simulating a rapid but moderate environmental change. Subsequently, we measured their rate of compositional change (re-structuring) which in the great majority of cases represented a compositional convergence towards local communities. Re-structuring is driven by mortality of community components (original species) and establishment of new species in the changed environmental context. The rate of this re-structuring was then related to various system properties. We show that availability of free substratum relates negatively while taxon richness relates positively to structural persistence (i.e., no or slow re-structuring). Thus, when faced with environmental change, taxon-rich communities retain their original composition longer than taxon-poor communities. The effect of taxon richness, however, interacts with another aspect of diversity, functional richness. Indeed, taxon richness relates positively to persistence in functionally depauperate communities, but not in functionally diverse communities. The interaction between taxonomic and functional diversity with regard to the behaviour of communities exposed to environmental stress may help understand some of the seemingly contrasting findings of past research. PMID:21611170

MOLECULAR LINE OBSERVATIONS OF THE CARBON-RICH CIRCUMSTELLAR ENVELOPE CIT 6 AT 7 mm WAVELENGTHS

Energy Technology Data Exchange (ETDEWEB)

Chau, Wayne; Zhang Yong; Nakashima, Jun-ichi; Kwok, Sun [Department of Physics, University of Hong Kong (Hong Kong); Deguchi, Shuji [Nobeyama Radio Observatory, National Astronomical Observatory, Minamimaki, Minamisaku, Nagano 384-1305 (Japan)

2012-11-20

We present a {lambda}7 mm spectral line survey of the carbon-rich circumstellar envelope (CSE) CIT 6 using the 45 m telescope at the Nobeyama Radio Observatory. A total of 25 spectral features belonging to five molecular species (HC{sub 3}N, HC{sub 5}N, HC{sub 7}N, SiO, and CS) are detected, enabling us to investigate the chemistry of cyanopolyyne chains. The line strengths are compared with those of the proto-typical carbon-rich CSE IRC+10216. The results show that the cyanopolyyne molecules are enhanced in CIT 6, suggesting that it is more evolved than IRC+10216. In order to investigate the structure of CIT 6, we have constructed a three-dimensional spatiokinematic model. By comparing the observed line profiles with the models, we conclude that this envelope is asymmetric and is composed of several incomplete shells.

Assessing Student Knowledge of Chemistry and Climate Science Concepts Associated with Climate Change: Resources to Inform Teaching and Learning

Science.gov (United States)

Versprille, Ashley; Zabih, Adam; Holme, Thomas A.; McKenzie, Lallie; Mahaffy, Peter; Martin, Brian; Towns, Marcy

2017-01-01

Climate change is one of the most critical problems facing citizens today. Chemistry faculty are presented with the problem of making general chemistry content simultaneously relevant and interesting. Using climate science to teach chemistry allows faculty to help students learn chemistry content in a rich context. Concepts related to…

The chemistry and structure of nickel–tungsten coatings obtained by pulse galvanostatic electrodeposition

International Nuclear Information System (INIS)

Argañaraz, M.P. Quiroga; Ribotta, S.B.; Folquer, M.E.; Zelaya, E.; Llorente, C.; Ramallo-López, J.M.; Benítez, G.; Rubert, A.; Gassa, L.M.; Vela, M.E.; Salvarezza, R.C.

2012-01-01

A detailed characterization of electrodeposited Ni-W coatings prepared by pulse electrodeposition on steel and copper substrates is presented. The coatings were obtained at high current pulse frequency and show high microhardness and absence of brittleness. The surface of the coating consists of nanometer sized crystals forming a cauliflower-like structure protected by a mixture of nickel and tungsten oxides. The cauliflower structure is preserved into the bulk coating that exhibits an average composition ≈70 at% Ni-30 at% W. Different phases are observed in the bulk structure: a W-rich amorphous phase (≈40%) and Ni-rich crystalline phases (≈60%). The crystalline phases consist of crystalline domains ≈7 nm in size of Ni(W) (fcc) solid solution (12 at% W content) and a minor Ni 4 W component (less than 10%). The amorphous phase exhibits a less compact Ni-W structure where some amount of C could also be present. Oxidized W species cannot be detected in the bulk coating, thus discarding the presence of significant amounts of tungsten carbide, tungstates or citrate–tungsten complexes. Our results shed light on controversial points related to the chemical composition and demonstrate the complex structure of this system.

Nuclear chemistry

International Nuclear Information System (INIS)

Vertes, A.; Kiss, I.

1987-01-01

This book is an introduction to the application of nuclear science in modern chemistry. The first group of chapters discuss the basic phenomena and concepts of nuclear physics with emphasis on their relation to chemical problems, including the main properties and the composition of atomic nuclei, nuclear reactions, radioactive decay and interactions of radiation with matter. These chapters provide the basis for understanding the following chapters which encompass the wide scope of nuclear chemistry. The methods of the investigation of chemical structure based on the interaction of nuclear radiation with matter including positronium chemistry and other exotic atoms is elaborated in particular detail. Separate chapters are devoted to the use of radioactive tracers, the chemical consequences of nuclear processes (i.e. hot atom chemistry), radiation chemistry, isotope effects and their applications, and the operation of nuclear reactors

Nuclear chemistry

International Nuclear Information System (INIS)

Vertes, A.; Kiss, I.

1987-01-01

This book is an introduction to the application of nuclear science in modern chemistry. The first group of chapters discuss the basic phenomena and concepts of nuclear physics with emphasis on their relation to chemical problems, including the main properties and the composition of atomic nuclei, nuclear reactions, radioactive decay and interactions of radiation with matter. These chapters provide the basis for understanding the following chapters which encompass the wide scope of nuclear chemistry. The methods of the investigation of chemical structure based on the interaction of nuclear radiation with matter including positronium chemistry and other exotic atoms is elaborated in particular detail. Separate chapters are devoted to the use of radioactive tracers, the chemical consequences of nuclear processes (i.e. hot atom chemistry), radiation chemistry, isotope effects and their applications, and the operation of nuclear reactors. (Auth.)

Tetrahelical structural family adopted by AGCGA-rich regulatory DNA regions

Science.gov (United States)

Kocman, Vojč; Plavec, Janez

2017-05-01

Here we describe AGCGA-quadruplexes, an unexpected addition to the well-known tetrahelical families, G-quadruplexes and i-motifs, that have been a focus of intense research due to their potential biological impact in G- and C-rich DNA regions, respectively. High-resolution structures determined by solution-state nuclear magnetic resonance (NMR) spectroscopy demonstrate that AGCGA-quadruplexes comprise four 5'-AGCGA-3' tracts and are stabilized by G-A and G-C base pairs forming GAGA- and GCGC-quartets, respectively. Residues in the core of the structure are connected with edge-type loops. Sequences of alternating 5'-AGCGA-3' and 5'-GGG-3' repeats could be expected to form G-quadruplexes, but are shown herein to form AGCGA-quadruplexes instead. Unique structural features of AGCGA-quadruplexes together with lower sensitivity to cation and pH variation imply their potential biological relevance in regulatory regions of genes responsible for basic cellular processes that are related to neurological disorders, cancer and abnormalities in bone and cartilage development.

Fundamentals of nuclear chemistry

International Nuclear Information System (INIS)

Majer, V.

1982-01-01

The author of the book has had 25 years of experience at the Nuclear Chemistry of Prague Technical University. In consequence, the book is intended as a basic textbook for students of this field. Its main objectives are an easily understandable presentation of the complex subject and in spite of the uncertainty which still characterizes the definition and subjects of nuclear chemistry - a systematic classification and logical structure. Contents: 1. Introduction (history and definition); 2. General nuclear chemistry (physical fundamentals, hot atom chemistry, interaction of nuclear radiation with matter, radioactive elements, isotope effects, isotope exchange, chemistry of radioactive trace elements); 3. Methods of nuclear chemistry of nuclear chemistry (radiochemical methods, activation, separation and enrichment chemistry); 4. Preparative nuclear chemistry (isotope production, labelled compounds); 5. Analytival nuclear chemistry; 6. Applied nuclear chemistry (isotope applications in general physical and analytical chemistry). The book is supplemented by an annex with tables, a name catalogue and a subject index which will facilitate access to important information. (RB) [de

Heavy metals pollution influence the community structure of Cyanobacteria in nutrient rich tropical estuary

Digital Repository Service at National Institute of Oceanography (India)

Anas, A.; Jasmin, C.; Sheeba V.A.; Gireeshkumar, T.R; Nair, S.

, Mn, Fe, Ni, Cu and Zn) on community structure of cyanobacteria in a nutrient rich tropical estuary, Cochin Estuary (CE), across the southwest coast of India. Dissolved heavy metals were higher in CE during dry season, with Zn as major pollutant...

Variance in water chemistry parameters in isolated wetlands of Florida, USA, and relationships with macroinvertebrate and diatom community structure

Science.gov (United States)

Eighty small isolated wetlands throughout Florida were sampled in 2005 to explore within-site variability of water chemistry parameters and relate water chemistry to macroinvertebrate and diatom community structure. Three samples or measures of water were collected within each si...

Mapping RNA Structure In Vitro with SHAPE Chemistry and Next-Generation Sequencing (SHAPE-Seq).

Science.gov (United States)

Watters, Kyle E; Lucks, Julius B

2016-01-01

Mapping RNA structure with selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) chemistry has proven to be a versatile method for characterizing RNA structure in a variety of contexts. SHAPE reagents covalently modify RNAs in a structure-dependent manner to create adducts at the 2'-OH group of the ribose backbone at nucleotides that are structurally flexible. The positions of these adducts are detected using reverse transcriptase (RT) primer extension, which stops one nucleotide before the modification, to create a pool of cDNAs whose lengths reflect the location of SHAPE modification. Quantification of the cDNA pools is used to estimate the "reactivity" of each nucleotide in an RNA molecule to the SHAPE reagent. High reactivities indicate nucleotides that are structurally flexible, while low reactivities indicate nucleotides that are inflexible. These SHAPE reactivities can then be used to infer RNA structures by restraining RNA structure prediction algorithms. Here, we provide a state-of-the-art protocol describing how to perform in vitro RNA structure probing with SHAPE chemistry using next-generation sequencing to quantify cDNA pools and estimate reactivities (SHAPE-Seq). The use of next-generation sequencing allows for higher throughput, more consistent data analysis, and multiplexing capabilities. The technique described herein, SHAPE-Seq v2.0, uses a universal reverse transcription priming site that is ligated to the RNA after SHAPE modification. The introduced priming site allows for the structural analysis of an RNA independent of its sequence.

Chemistry of superheavy elements

International Nuclear Information System (INIS)

Schaedel, M.

2012-01-01

The chemistry of superheavy elements - or transactinides from their position in the Periodic Table - is summarized. After giving an overview over historical developments, nuclear aspects about synthesis of neutron-rich isotopes of these elements, produced in hot-fusion reactions, and their nuclear decay properties are briefly mentioned. Specific requirements to cope with the one-atom-at-a-time situation in automated chemical separations and recent developments in aqueous-phase and gas-phase chemistry are presented. Exciting, current developments, first applications, and future prospects of chemical separations behind physical recoil separators ('pre-separator') are discussed in detail. The status of our current knowledge about the chemistry of rutherfordium (Rf, element 104), dubnium (Db, element 105), seaborgium (Sg, element 106), bohrium (Bh, element 107), hassium (Hs, element 108), copernicium (Cn, element 112), and element 114 is discussed from an experimental point of view. Recent results are emphasized and compared with empirical extrapolations and with fully-relativistic theoretical calculations, especially also under the aspect of the architecture of the Periodic Table. (orig.)

Chemistry Education: Ten Facets to Shape Us

Science.gov (United States)

Talanquer, Vicente

2013-01-01

The chemistry knowledge that we want our students to develop is rich, complex, and multifaceted. However, some teachers and instructors at the secondary school and college levels approach it in rather rigid and unidimensional ways. The central goal of this contribution is to describe and discuss 10 different complementary perspectives or…

Structure of neutron-rich nuclei around the N = 50 shell-gap closure

Science.gov (United States)

Faul, T.; Duchêne, G.; Thomas, J.-C.; Nowacki, F.; Huyse, M.; Van Duppen, P.

2010-04-01

The structure of neutron-rich nuclei in the vicinity of 78Ni have been investigated via the β-decay of 71,73,75Cu isotopes (ISOLDE, CERN). Experimental results have been compared with shell-model calculations performed with the ANTOINE code using a large (2p3/21f5/22p1/21g9/2) valence space and a 56/28Ni28 core.

General chemistry

International Nuclear Information System (INIS)

Kwon, Yeong Sik; Lee, Dong Seop; Ryu, Haung Ryong; Jang, Cheol Hyeon; Choi, Bong Jong; Choi, Sang Won

1993-07-01

The book concentrates on the latest general chemistry, which is divided int twenty-three chapters. It deals with basic conception and stoichiometry, nature of gas, structure of atoms, quantum mechanics, symbol and structure of an electron of ion and molecule, chemical thermodynamics, nature of solid, change of state and liquid, properties of solution, chemical equilibrium, solution and acid-base, equilibrium of aqueous solution, electrochemistry, chemical reaction speed, molecule spectroscopy, hydrogen, oxygen and water, metallic atom; 1A, IIA, IIIA, carbon and atom IVA, nonmetal atom and an inert gas, transition metals, lanthanons, and actinoids, nuclear properties and radioactivity, biochemistry and environment chemistry.

The role of supramolecular chemistry in stimuli responsive and hierarchically structured functional organic materials

NARCIS (Netherlands)

Schenning, A.P.H.J.; Bastiaansen, C.W.M.; Broer, D.J.; Debije, M.G.

2014-01-01

ABSTRACT: In this review, we show the important role of supramolecular chemistry in the fabrication of stimuli responsive and hierarchically structured liquid crystalline polymer networks. Supramolecular interactions can be used to create three dimensional order or as molecular triggers in materials

Fine-Structure Measurements of Oxygen A Band Absorbance for Estimating the Thermodynamic Average Temperature of the Earth's Atmosphere: An Experiment in Physical and Environmental Chemistry

Science.gov (United States)

Myrick, M. L.; Greer, A. E.; Nieuwland, A.; Priore, R. J.; Scaffidi, J.; Andreatta, Daniele; Colavita, Paula

2006-01-01

The experiment describe the measures of the A band transitions of atmospheric oxygen, a rich series of rotation-electronic absorption lines falling in the deep red portion of the optical spectrum and clearly visible owing to attenuation of solar radiation. It combines pure physical chemistry with analytical and environmental science and provides a…

Rich club analysis in the Alzheimer's disease connectome reveals a relatively undisturbed structural core network.

Science.gov (United States)

Daianu, Madelaine; Jahanshad, Neda; Nir, Talia M; Jack, Clifford R; Weiner, Michael W; Bernstein, Matt A; Thompson, Paul M

2015-08-01

Diffusion imaging can assess the white matter connections within the brain, revealing how neural pathways break down in Alzheimer's disease (AD). We analyzed 3-Tesla whole-brain diffusion-weighted images from 202 participants scanned by the Alzheimer's Disease Neuroimaging Initiative-50 healthy controls, 110 with mild cognitive impairment (MCI) and 42 AD patients. From whole-brain tractography, we reconstructed structural brain connectivity networks to map connections between cortical regions. We tested whether AD disrupts the "rich club" - a network property where high-degree network nodes are more interconnected than expected by chance. We calculated the rich club properties at a range of degree thresholds, as well as other network topology measures including global degree, clustering coefficient, path length, and efficiency. Network disruptions predominated in the low-degree regions of the connectome in patients, relative to controls. The other metrics also showed alterations, suggesting a distinctive pattern of disruption in AD, less pronounced in MCI, targeting global brain connectivity, and focusing on more remotely connected nodes rather than the central core of the network. AD involves severely reduced structural connectivity; our step-wise rich club coefficients analyze points to disruptions predominantly in the peripheral network components; other modalities of data are needed to know if this indicates impaired communication among non rich club regions. The highly connected core was relatively preserved, offering new evidence on the neural basis of progressive risk for cognitive decline. © 2015 Wiley Periodicals, Inc.

Solution structure of the twelfth cysteine-rich ligand-binding repeat in rat megalin

International Nuclear Information System (INIS)

Wolf, Christian A.; Dancea, Felician; Shi Meichen; Bade-Noskova, Veronika; Rueterjans, Heinz; Kerjaschki, Dontscho; Luecke, Christian

2007-01-01

Megalin, an approx. 600 kDa transmembrane glycoprotein that acts as multi-ligand transporter, is a member of the low density lipoprotein receptor gene family. Several cysteine-rich repeats, each consisting of about 40 residues, are responsible for the multispecific binding of ligands. The solution structure of the twelfth cysteine-rich ligand-binding repeat with class A motif found in megalin features two short β-strands and two helical turns, yielding the typical fold with a I-III, II-V and IV-VI disulfide bridge connectivity pattern and a calcium coordination site at the C-terminal end. The resulting differences in electrostatic surface potential compared to other ligand-binding modules of this gene family, however, may be responsible for the functional divergence

Conference 'Chemistry of hydrides' Proceedings

International Nuclear Information System (INIS)

1991-07-01

This collection of thesis of conference of Chemistry hydrides presents the results of investigations concerning of base questions of chemistry of nonorganic hydrides, including synthesis questions, studying of physical and chemical properties, thermodynamics, analytical chemistry, investigation of structure, equilibriums in the systems of metal-hydrogen, behaviour of nonorganic hydrides in non-water mediums and applying investigations in the chemistry area and technology of nonorganic hydrides

Contrasting roles of water chemistry, lake morphology, land-use, climate and spatial processes in driving phytoplankton richness in the Danish landscape

DEFF Research Database (Denmark)

Özkan, Korhan; Jeppesen, Erik; Søndergaard, Martin

2013-01-01

Understanding of the forces driving the structure of biotic communities has long been an important focus for ecology, with implications for applied and conservation science. To elucidate the factors driving phytoplankton genus richness in the Danish landscape, we analyzed data derived from late-s...

Topological Principles of Borosilicate Glass Chemistry - An Invited Talk

DEFF Research Database (Denmark)

Mauro, J.C.; Smedskjær, Morten Mattrup; Youngman, R. E.

Borosilicate glasses display a rich complexity of chemical behavior depending on the details of their composition and thermal history. We investigate the topological principles of borosilicate glass chemistry covering the extremes from pure borate to pure silicate end members. Based on NMR...

Fundamentals of nuclear chemistry

International Nuclear Information System (INIS)

Matel, L.; Dulanska, S.

2013-01-01

This text-book is an introductory text in nuclear chemistry and radiochemistry, aimed on university undergraduate students in chemistry and related disciplines (physics, nuclear engineering). It covers the key aspects of modern nuclear chemistry. The text begins with basic theories in contemporary physics. It relates nuclear phenomena to key divisions of chemistry such as atomic structure, spectroscopy, equilibria and kinetics. It also gives an introduction to sources of ionizing radiation, detection of ionizing radiation, nuclear power industry and accident on nuclear installations as well as basic knowledge's of radiobiology. This book is essential reading for those taking a first course in nuclear chemistry and is a useful companion to other volumes in physical and analytical chemistry. It will also be of use to those new to working in nuclear chemistry or radiochemistry.

Interstellar chemistry.

Science.gov (United States)

Klemperer, William

2006-08-15

In the past half century, radioastronomy has changed our perception and understanding of the universe. In this issue of PNAS, the molecular chemistry directly observed within the galaxy is discussed. For the most part, the description of the molecular transformations requires specific kinetic schemes rather than chemical thermodynamics. Ionization of the very abundant molecular hydrogen and atomic helium followed by their secondary reactions is discussed. The rich variety of organic species observed is a challenge for complete understanding. The role and nature of reactions involving grain surfaces as well as new spectroscopic observations of interstellar and circumstellar regions are topics presented in this special feature.

Existence of an 16O-rich gaseous reservoir in the solar nebula.

Science.gov (United States)

Krot, Alexander N; McKeegan, Kevin D; Leshin, Laurie A; MacPherson, Glenn J; Scott, Edward R D

2002-02-08

Carbonaceous chondrite condensate olivine grains from two distinct petrographic settings, calcium-aluminum-rich inclusion (CAI) accretionary rims and amoeboid olivine aggregates (AOAs), are oxygen-16 (16O) enriched at the level previously observed inside CAIs. This requires that the gas in the nebular region where these grains condensed was 16O-rich. This contrasts with an 16O-poor gas present during the formation of chondrules, suggesting that CAIs and AOAs formed in a spatially restricted region of the solar nebula containing 16O-rich gas. The 16O-rich gas composition may have resulted either from mass-independent isotopic chemistry or from evaporation of regions with enhanced dust/gas ratios, possibly in an X-wind environment near the young Sun.

Contribution from philosophy of chemistry to chemistry education: In a case of ionic liquids as technochemistry

Science.gov (United States)

Mudzakir, Ahmad; Hernani, Widhiyanti, Tuszie; Sudrajat, Devi Pratiwi

2017-08-01

Traditional chemistry education is commonly handing down of concepts, principles, and theories, such as mechanical properties, the relationship between structure and properties as well as chemical structure and chemical bonding theory, to students without engaging them in the processes of chemical inquiry. This practice leads to the lack of opportunity for the students to construct an appropriate understanding of these concepts, principles, and theories. Students are also rarely facilitated in modeling the structure and function of matter themselves. This situation shows that the philosophy of chemistry has not received as much attention from chemistry educators. The main idea of this paper is to embed philosophy of chemistry through the implementation of technochemistry in chemistry education. One of the most interesting and rapidly developing areas of modern chemistry, technologies and engineering is Ionic Liquids (ILs) as an emerging knowledge on technochemistry which can be applied to chemistry education. The developments between academic researchers and industrial developments in the ILs area are conducted in parallel. In order to overcome the existing problems of scientific development in chemistry education, the science and technology of ILs can be used for reconceptualizing the teaching and learning of chemistry to embrace the epistemology in chemistry. This study promises a potential contribution by philosophy of chemistry. The main objectives of this study are to develop: (i) a perspective based on philosophy of science considerations (rational reconstruction) in order to understand ionic liquids and (ii) teaching materials that can be used to enhance pre-service teacher's view of nature of science and technology (VNOST). The method used in the study is analytical-descriptive (elementarization), i.e. the first step in the model of educational reconstruction (MER). This study concludes that the development of the concepts and their applications of ionic

Three-dimensional structure and cytokine distribution of platelet-rich fibrin.

Science.gov (United States)

Bai, Meng-Yi; Wang, Ching-Wei; Wang, Jyun-Yi; Lin, Ming-Fang; Chan, Wing P

2017-02-01

Previous reports have revealed that several cytokines (including platelet-derived growth factor-BB, transforming growth factors-β1 and insulin-like growth factor-1) can enhance the rate of bone formation and synthesis of extracellular matrix in orthopaedics or periodontology. This study aimed to determine the concentration of cytokines within platelet-rich fibrin microstructures and investigate whether there are differences in the different portions of platelet-rich fibrin, which has implications for proper clinical use of platelet-rich fibrin gel. Whole blood was obtained from six New Zealand rabbits (male, 7 to 39 weeks old, weight 2.7-4 kg); it was then centrifuged for preparation of platelet-rich fibrin gels and harvest of plasma. The resultant platelet-rich fibrin gels were used for cytokine determination, histological analyses and scanning electron microscopy. All plasmas obtained were subject to the same cytokine determination assays for the purpose of comparison. Cytokines platelet-derived growth factor-BB and transforming growth factor-β1 formed concentration gradients from high at the red blood cell end of the platelet-rich fibrin gel (p=1.88×10-5) to low at the plasma end (p=0.19). Insulin-like growth factor-1 concentrations were similar at the red blood cell and plasma ends. The porosities of the platelet-rich fibrin samples taken in sequence from the red blood cell end to the plasma end were 6.5% ± 4.9%, 24.8% ± 7.5%, 30.3% ± 8.5%, 41.4% ± 12.3%, and 40.3% ± 11.7%, respectively, showing a gradual decrease in the compactness of the platelet-rich fibrin network. Cytokine concentrations are positively associated with platelet-rich fibrin microstructure and portion in a rabbit model. As platelet-rich fibrin is the main entity currently used in regenerative medicine, assessing cytokine concentration and the most valuable portion of PRF gels is essential and recommended to all physicians.

Three-dimensional structure and cytokine distribution of platelet-rich fibrin

Directory of Open Access Journals (Sweden)

Meng-Yi Bai

Full Text Available OBJECTIVES: Previous reports have revealed that several cytokines (including platelet-derived growth factor-BB, transforming growth factors-β1 and insulin-like growth factor-1 can enhance the rate of bone formation and synthesis of extracellular matrix in orthopaedics or periodontology. This study aimed to determine the concentration of cytokines within platelet-rich fibrin microstructures and investigate whether there are differences in the different portions of platelet-rich fibrin, which has implications for proper clinical use of platelet-rich fibrin gel. METHODS: Whole blood was obtained from six New Zealand rabbits (male, 7 to 39 weeks old, weight 2.7-4 kg; it was then centrifuged for preparation of platelet-rich fibrin gels and harvest of plasma. The resultant platelet-rich fibrin gels were used for cytokine determination, histological analyses and scanning electron microscopy. All plasmas obtained were subject to the same cytokine determination assays for the purpose of comparison. RESULTS: Cytokines platelet-derived growth factor-BB and transforming growth factor-β1 formed concentration gradients from high at the red blood cell end of the platelet-rich fibrin gel (p=1.88×10-5 to low at the plasma end (p=0.19. Insulin-like growth factor-1 concentrations were similar at the red blood cell and plasma ends. The porosities of the platelet-rich fibrin samples taken in sequence from the red blood cell end to the plasma end were 6.5% ± 4.9%, 24.8% ± 7.5%, 30.3% ± 8.5%, 41.4% ± 12.3%, and 40.3% ± 11.7%, respectively, showing a gradual decrease in the compactness of the platelet-rich fibrin network. CONCLUSION: Cytokine concentrations are positively associated with platelet-rich fibrin microstructure and portion in a rabbit model. As platelet-rich fibrin is the main entity currently used in regenerative medicine, assessing cytokine concentration and the most valuable portion of PRF gels is essential and recommended to all physicians.

Superior activity of non-interacting close acidic protons in Al-rich Pt/H-*BEA zeolite in isomerization of n-hexane

Czech Academy of Sciences Publication Activity Database

Sazama, Petr; Kaucký, Dalibor; Morávková, Jaroslava; Pilař, Radim; Klein, Petr; Pastvová, Jana; Tabor, Edyta; Sklenák, Štěpán; Jakubec, Ivo; Mokrzycki, Lukasz

2017-01-01

Roč. 533, MAR 2017 (2017), s. 28-37 ISSN 0926-860X R&D Projects: GA ČR GA15-12113S; GA MŠk(CZ) LM2015073 Institutional support: RVO:61388955 ; RVO:61388980 Keywords : Isomerization * Alkanes Hexane * Zeolites * Al-rich beta (*BEA) * Mordenite Subject RIV: CF - Physical ; Theoretical Chemistry; CA - Inorganic Chemistry (UACH-T) OBOR OECD: Physical chemistry; Inorganic and nuclear chemistry (UACH-T) Impact factor: 4.339, year: 2016

Click Chemistry in Complex Mixtures: Bioorthogonal Bioconjugation

Science.gov (United States)

McKay, Craig S.; Finn, M.G.

2014-01-01

The selective chemical modification of biological molecules drives a good portion of modern drug development and fundamental biological research. While a few early examples of reactions that engage amine and thiol groups on proteins helped establish the value of such processes, the development of reactions that avoid most biological molecules so as to achieve selectivity in desired bond-forming events has revolutionized the field. We provide an update on recent developments in bioorthogonal chemistry that highlights key advances in reaction rates, biocompatibility, and applications. While not exhaustive, we hope this summary allows the reader to appreciate the rich continuing development of good chemistry that operates in the biological setting. PMID:25237856

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...

Advancing viral RNA structure prediction: measuring the thermodynamics of pyrimidine-rich internal loops.

Science.gov (United States)

Phan, Andy; Mailey, Katherine; Saeki, Jessica; Gu, Xiaobo; Schroeder, Susan J

2017-05-01

Accurate thermodynamic parameters improve RNA structure predictions and thus accelerate understanding of RNA function and the identification of RNA drug binding sites. Many viral RNA structures, such as internal ribosome entry sites, have internal loops and bulges that are potential drug target sites. Current models used to predict internal loops are biased toward small, symmetric purine loops, and thus poorly predict asymmetric, pyrimidine-rich loops with >6 nucleotides (nt) that occur frequently in viral RNA. This article presents new thermodynamic data for 40 pyrimidine loops, many of which can form UU or protonated CC base pairs. Uracil and protonated cytosine base pairs stabilize asymmetric internal loops. Accurate prediction rules are presented that account for all thermodynamic measurements of RNA asymmetric internal loops. New loop initiation terms for loops with >6 nt are presented that do not follow previous assumptions that increasing asymmetry destabilizes loops. Since the last 2004 update, 126 new loops with asymmetry or sizes greater than 2 × 2 have been measured. These new measurements significantly deepen and diversify the thermodynamic database for RNA. These results will help better predict internal loops that are larger, pyrimidine-rich, and occur within viral structures such as internal ribosome entry sites. © 2017 Phan et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

Chemistry

International Nuclear Information System (INIS)

Ferris, L.M.

1975-01-01

The chemical research and development efforts related to the design and ultimate operation of molten-salt breeder reactor systems are concentrated on fuel- and coolant-salt chemistry, including the development of analytical methods for use in these systems. The chemistry of tellurium in fuel salt is being studied to help elucidate the role of this element in the intergranular cracking of Hastelloy N. Studies were continued of the effect of oxygen-containing species on the equilibrium between dissolved UF 3 and dissolved UF 4 , and, in some cases, between the dissolved uranium fluorides and graphite, and the UC 2 . Several aspects of coolant-salt chemistry are under investigation. Hydroxy and oxy compounds that could be formed in molten NaBF 4 are being synthesized and characterized. Studies of the chemistry of chromium (III) compounds in fluoroborate melts were continued as part of a systematic investigation of the corrosion of structural alloys by coolant salt. An in-line voltammetric method for determining U 4+ /U 3+ ratios in fuel salt was tested in a forced-convection loop over a six-month period. (LK)

Ammonia chemistry in a flameless jet

Energy Technology Data Exchange (ETDEWEB)

Zieba, Mariusz; Schuster, Anja; Scheffknecht, Guenter [Institute of Process Engineering and Power Plant Technology, University of Stuttgart, Pfaffenwaldring 23, D-70569 Stuttgart (Germany); Brink, Anders; Hupa, Mikko [Process Chemistry Centre, Aabo Akademi University, Biskopsgatan 8, 20500 Aabo (Finland)

2009-10-15

In this paper, the nitrogen chemistry in an ammonia (NH{sub 3}) doped flameless jet is investigated using a kinetic reactor network model. The reactor network model is used to explain the main differences in ammonia chemistry for methane (CH{sub 4})-containing fuels and methane-free fuels. The chemical pathways of nitrogen oxides (NO{sub x}) formation and destruction are identified using rate-of-production analysis. The results show that in the case of natural gas, ammonia reacts relatively late at fuel lean condition leading to high NO{sub x} emissions. In the pre-ignition zone, the ammonia chemistry is blocked due to the absence of free radicals which are consumed by methane-methyl radical (CH{sub 3}) conversion. In the case of methane-free gas, the ammonia reacted very rapidly and complete decomposition was reached in the fuel rich region of the jet. In this case the necessary radicals for the ammonia conversion are generated from hydrogen (H{sub 2}) oxidation. (author)

Welcome to Inorganics: A New Open Access, Inclusive Forum for Inorganic Chemistry

Directory of Open Access Journals (Sweden)

Duncan H. Gregory

2013-06-01

Full Text Available One of the beauties of inorganic chemistry is its sheer diversity. Just as chemistry sits at the centre of the sciences, inorganic chemistry sits at the centre of chemistry itself. Inorganic chemists are fortunate in having the entire periodic table at their disposal, providing a palette for the creation of a multitude of rich and diverse compounds and materials from the simplest salts to the most complex of molecular species. It follows that the language of inorganic chemistry can thus be a demanding one, accommodating sub-disciplines with very different perspectives and frames of reference. One could argue that it is the unequivocal breadth of inorganic chemistry that empowers inorganic chemists to work at the interfaces, not just between the traditional Inorganic-Organic-Physical boundaries of the discipline, but in the regions where chemistry borders the other physical and life sciences, engineering and socio-economics. [...

Introducing NMR to a General Chemistry Audience: A Structural-Based Instrumental Laboratory Relating Lewis Structures, Molecular Models, and [superscript 13]C NMR Data

Science.gov (United States)

Pulliam, Curtis R.; Pfeiffer, William F.; Thomas, Alyssa C.

2015-01-01

This paper describes a first-year general chemistry laboratory that uses NMR spectroscopy and model building to emphasize molecular shape and structure. It is appropriate for either a traditional or an atoms-first curriculum. Students learn the basis of structure and the use of NMR data through a cooperative learning hands-on laboratory…

Impacts of operating conditions and solution chemistry on osmotic membrane structure and performance

KAUST Repository

Wong, Mavis C.Y.; Martinez, Kristina; Ramon, Guy Z.; Hoek, Eric M.V.

2012-01-01

Herein, we report on changes in the performance of a commercial cellulose triacetate (CTA) membrane, imparted by varied operating conditions and solution chemistries. Changes to feed and draw solution flow rate did not significantly alter the CTA membrane's water permeability, salt permeability, or membrane structural parameter when operated with the membrane skin layer facing the draw solution (PRO-mode). However, water and salt permeability increased with increasing feed or draw solution temperature, while the membrane structural parameter decreased with increasing draw solution, possibly due to changes in polymer intermolecular interactions. High ionic strength draw solutions may de-swell the CTA membrane via charge neutralization, which resulted in lower water permeability, higher salt permeability, and lower structural parameter. This observed trend was further exacerbated by the presence of divalent cations which tends to swell the polymer to a greater extent. Finally, the calculated CTA membrane's structural parameter was lower and less sensitive to external factors when operated in PRO-mode, but highly sensitive to the same factors when the skin layer faced the feed solution (FO-mode), presumably due to swelling/de-swelling of the saturated porous substructure by the draw solution. This is a first attempt aimed at systematically evaluating the changes in performance of the CTA membrane due to operating conditions and solution chemistry, shedding new insight into the possible advantages and disadvantages of this material in certain applications. © 2011 Elsevier B.V.

Some aspects of the chemistry of fast reactor fuel, structural material and decontamination

International Nuclear Information System (INIS)

Ganesan, V.

2012-01-01

The chemistry of materials pertaining to fast reactors is both fascinating and challenging considering the nature of materials involved such as the fuel, coolant, control and shielding materials in addition to the interactions between the structural materials and the fuel/coolant depending on the nature and conditions involved. The different chemical forms of fuel materials, the need to operate up to high burnups with consequent interactions of the fuel with clad materials, the need to close the fuel cycle by recovery of the fuel materials from spent fuels for refabrication and the necessity to manage the waste, throw a host of challenges which make their study scientifically interesting and technologically important. The use of liquid sodium as coolant in fast reactor heat transport systems combined with its inherent chemical reactivity opens up an interesting branch of chemistry involving liquid sodium especially in contact with structural materials during normal operation of the reactor and with fuels in the event of fuel pin failure. The phenomenon of sodium wetting and the associated corrosion of structural materials in contact with it combined with the need to carryout decontamination of such materials make it interesting to examine and evaluate their suitability for reuse without compromising on their structural integrity. Boron being the material of choice for control and shielding applications in fast reactors with varying isotopic enrichment and the technological challenge to produce large quantities of boron carbide makes it unique. Some of these aspects are addressed in this paper. (author)

Impacts of operating conditions and solution chemistry on osmotic membrane structure and performance

KAUST Repository

Wong, Mavis C.Y.

2012-02-01

Herein, we report on changes in the performance of a commercial cellulose triacetate (CTA) membrane, imparted by varied operating conditions and solution chemistries. Changes to feed and draw solution flow rate did not significantly alter the CTA membrane\\'s water permeability, salt permeability, or membrane structural parameter when operated with the membrane skin layer facing the draw solution (PRO-mode). However, water and salt permeability increased with increasing feed or draw solution temperature, while the membrane structural parameter decreased with increasing draw solution, possibly due to changes in polymer intermolecular interactions. High ionic strength draw solutions may de-swell the CTA membrane via charge neutralization, which resulted in lower water permeability, higher salt permeability, and lower structural parameter. This observed trend was further exacerbated by the presence of divalent cations which tends to swell the polymer to a greater extent. Finally, the calculated CTA membrane\\'s structural parameter was lower and less sensitive to external factors when operated in PRO-mode, but highly sensitive to the same factors when the skin layer faced the feed solution (FO-mode), presumably due to swelling/de-swelling of the saturated porous substructure by the draw solution. This is a first attempt aimed at systematically evaluating the changes in performance of the CTA membrane due to operating conditions and solution chemistry, shedding new insight into the possible advantages and disadvantages of this material in certain applications. © 2011 Elsevier B.V.

Nuclear structure far from stability: the neutron-rich 69-79Cu isotopes

International Nuclear Information System (INIS)

Franchoo, Serge

2015-01-01

Far from stability, the nuclear structure that is predicted by the shell model is evolving. Old magic numbers disappear, while new ones appear. Our understanding of the underlying nuclear force that drives these changes is still incomplete. After a short overview across the nuclear chart, we discuss the strength functions of the shell-model orbitals in the neutron-rich copper isotopes towards the 78 Ni doubly-magic nucleus. These were measured in a 72 Zn(d, 3 He) 71 Cu proton pick-up reaction in inverse kinematics with a radioactive beam at the Ganil laboratory in France. We also present the latest results from a 80 Zn(p,2p) 79 Cu knockout experiment at Riken in Japan, leading to selective population of hole states in 79 Cu. Our findings show that the Z=28 shell gap in the neutron-rich copper isotopes is surprisingly steady against the addition of neutrons beyond N=40. (author)

Crystal structure and dimerization equilibria of PcoC, a methionine-rich copper resistance protein from Escherichia coli

Energy Technology Data Exchange (ETDEWEB)

Wernimont, A.K.; Huffman, D.L.; Finney, L.A.; Demeler, B.; O' Halloran, T.V.; Rosenzweig, A.C.

2010-03-08

PcoC is a soluble periplasmic protein encoded by the plasmid-born pco copper resistance operon of Escherichia coli. Like PcoA, a multicopper oxidase encoded in the same locus and its chromosomal homolog CueO, PcoC contains unusual methionine rich sequences. Although essential for copper resistance, the functions of PcoC, PcoA, and their conserved methionine-rich sequences are not known. Similar methionine motifs observed in eukaryotic copper transporters have been proposed to bind copper, but there are no precedents for such metal binding sites in structurally characterized proteins. The high-resolution structures of apo PcoC, determined for both the native and selenomethionine-containing proteins, reveal a seven-stranded barrel with the methionines unexpectedly housed on a solvent-exposed loop. Several potential metal-binding sites can be discerned by comparing the structures to spectroscopic data reported for copper-loaded PcoC. In the native structure, the methionine loop interacts with the same loop on a second molecule in the asymmetric unit. In the selenomethionine structure, the methionine loops are more exposed, forming hydrophobic patches on the protein surface. These two arrangements suggest that the methionine motifs might function in protein-protein interactions between PcoC molecules or with other methionine-rich proteins such as PcoA. Analytical ultracentrifugation data indicate that a weak monomer-dimer equilibrium exists in solution for the apo protein. Dimerization is significantly enhanced upon binding Cu(I) with a measured {Delta}({Delta}G{sup o}) {le} -8.0 kJ/mole, suggesting that copper might bind at the dimer interface.

Hot functional test chemistry - long term experience

International Nuclear Information System (INIS)

Vonkova, K.; Kysela, J.; Marcinsky, M.; Martykan, M.

2010-01-01

Primary circuit materials undergo general corrosion in high temperature, deoxygenated, neutral or mildly alkaline solutions to form thin oxide films. These oxide layers (films) serve as protective film and mitigate the further corrosion of primary materials. Inner chromium-rich oxide layer has low cation diffusion coefficients and thus control iron and nickel transport from the metal surface to the outer layer and their dissolution into the coolant. Much less corrosion products are generated by the compact, integral and stable oxide (passivation) layer. For the latest Czech and Slovak stations commissioned (Temelin and Mochovce) a modified Hot Functional Test (HFT) chemistry was developed in the NRI Rez. Chromium rich surface layer formatted due to modified HTF chemistry ensures lower corrosion rates and radiation field formation and thus also mitigates crud formation during operation. This procedure was also designed to prepare the commissioned unit for the further proper water chemistry practise. Mochovce 1 (SK) was the first station commissioned using these recommendations in 1998. Mochovce 2 (1999) and Temelin 1 and 2 (CZ - 2000 and 2002) were subsequently commissioned using these guidelines too. The main principles of the controlled primary water chemistry applied during the hot functional tests are reviewed and importance of the water chemistry, technological and other relevant parameters is stressed regarding to the quality of the passive layer formed on the primary system surfaces. Samples from Mochovce indicated that duplex oxide layers up to 20 μm thick were produced, which were mainly magnetite substituted with nickel and chromium (e.g. 60-65% Fe, 18-28% Cr, 9-12% Ni, <1% Mn and 1-2% Si on a stainless steel primary circuit sample). Long term operation experience from both nuclear power plants are discussed in this paper. Radiation field, occupational radiation exposure and corrosion layers evolution during the first c. ten years of operation are

Synthesis and study of neutron-rich nuclides

International Nuclear Information System (INIS)

Luo Yixiao

1995-01-01

During the past few years our understanding of the decay properties and nuclear structure has been extended in a systematic fashion for the neutron-rich nuclei. This review will first sketch the production and identification of the neutron-rich nuclei throughout the whole mass region, and will then discuss the impressive progress in the studies of the exotic decay properties and nuclear structure of neutron-rich nuclei. Their astrophysical implications will also be outlined

Polymer chemistry (revised edition)

International Nuclear Information System (INIS)

Kim, Jae Mum

1987-02-01

This book deals with polymer chemistry, which is divided into fourteen chapters. The contents of this book are development of polymer chemistry, conception of polymer, measurement of polymer chemistry, conception of polymer, measurement of polymer, molecule structure of polymer, thermal prosperities of solid polymer, basic theory of polymerization, radical polymerization, ion polymerization, radical polymerization, copolymerization, polymerization by step-reaction, polymer reaction, crown polymer and inorganic polymer on classification and process of creation such as polymeric sulfur and carbon fiber.

Benthic megafaunal community structure of cobalt-rich manganese crusts on Necker Ridge

Science.gov (United States)

Morgan, Nicole B.; Cairns, Stephen; Reiswig, Henry; Baco, Amy R.

2015-10-01

In the North Pacific Ocean, the seamounts of the Hawaiian Archipelago and the Mid-Pacific Mountains are connected by Necker Ridge, a 600 km-long feature spanning a depth range of 1400-4000 m. The Necker Ridge is a part of a large area of the central and western Pacific under consideration for cobalt-rich manganese crust mining. We describe the fauna and community structure of the previously unsampled Necker Ridge based on explorations with the submersible Pisces IV. On five pinnacles and a portion of the Ridge ranging from 1400 to 2000 m deep, 27 transects were recorded using HD video, and voucher specimens were collected to aid in species identification. The video was analyzed to identify and count the megafauna found on each transect and to characterize the substrate. Diversity increased from south to north along the feature. There was a significant difference in community structure between southern and northern pinnacles, with southern pinnacles dominated by crinoids of the Family Charitometridae and northern pinnacles dominated by octocorals, especially the Families Isididae and Chrysogorgiidae. DistLM demonstrated a correlation between community structure on the pinnacles and at least six environmental variables, including latitude, sediment cover, and oxygen concentration, but not including depth. The discontinuous and patchy nature of these distinct megafaunal communities highlights growing evidence that cobalt-rich seamounts are highly heterogeneous habitats, and that managing seamounts may require more complex regulations than treating them as a single ecological unit. These results suggest that extensive community analysis should occur at a given site to determine management priority areas, prior to consideration of that site for exploitation of natural resources.

Bonding, structure and solid-state chemistry

CERN Document Server

Ladd, Mark

2016-01-01

This book is aimed at undergraduate students in both chemistry and those degree subjects in which chemistry forms a significant part. It does not reflect any particular academic year, and so finds a place during the normal span of degree studies in the physical sciences. An A-level standard in science and mathematics is presumed; additional mathematical treatments are discussed in Appendices. An introductory first chapter leads into the main subject matter, which is treated through four chapters in terms of the principle bonding forces of cohesion in the solid state; a further chapter discusses nanosize materials. Important applications of the study topics are interspersed at appropriate points within the text. Each chapter is provided with a set of problems of varying degrees of difficulty, so as to assist the reader in gaining a facility with the subject matter and its applications. The problems are supplemented by detailed tutorial solutions, some of which present additional relevant material that indicate...

New Pathways for Teaching Chemistry: Reflective Judgment in Science.

Science.gov (United States)

Finster, David C.

1992-01-01

The reflective judgment model offers a rich context for analysis of science and science teaching. It provides deeper understanding of the scientific process and its critical thinking and reveals fundamental connections between science and the other liberal arts. Classroom techniques from a college chemistry course illustrate the utility of the…

Rich RNA Structure Landscapes Revealed by Mutate-and-Map Analysis.

Directory of Open Access Journals (Sweden)

Pablo Cordero

2015-11-01

Full Text Available Landscapes exhibiting multiple secondary structures arise in natural RNA molecules that modulate gene expression, protein synthesis, and viral infection [corrected]. We report herein that high-throughput chemical experiments can isolate an RNA's multiple alternative secondary structures as they are stabilized by systematic mutagenesis (mutate-and-map, M2 and that a computational algorithm, REEFFIT, enables unbiased reconstruction of these states' structures and populations. In an in silico benchmark on non-coding RNAs with complex landscapes, M2-REEFFIT recovers 95% of RNA helices present with at least 25% population while maintaining a low false discovery rate (10% and conservative error estimates. In experimental benchmarks, M2-REEFFIT recovers the structure landscapes of a 35-nt MedLoop hairpin, a 110-nt 16S rRNA four-way junction with an excited state, a 25-nt bistable hairpin, and a 112-nt three-state adenine riboswitch with its expression platform, molecules whose characterization previously required expert mutational analysis and specialized NMR or chemical mapping experiments. With this validation, M2-REEFFIT enabled tests of whether artificial RNA sequences might exhibit complex landscapes in the absence of explicit design. An artificial flavin mononucleotide riboswitch and a randomly generated RNA sequence are found to interconvert between three or more states, including structures for which there was no design, but that could be stabilized through mutations. These results highlight the likely pervasiveness of rich landscapes with multiple secondary structures in both natural and artificial RNAs and demonstrate an automated chemical/computational route for their empirical characterization.

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

Managing expectations: assessment of chemistry databases generated by automated extraction of chemical structures from patents.

Science.gov (United States)

Senger, Stefan; Bartek, Luca; Papadatos, George; Gaulton, Anna

2015-12-01

First public disclosure of new chemical entities often takes place in patents, which makes them an important source of information. However, with an ever increasing number of patent applications, manual processing and curation on such a large scale becomes even more challenging. An alternative approach better suited for this large corpus of documents is the automated extraction of chemical structures. A number of patent chemistry databases generated by using the latter approach are now available but little is known that can help to manage expectations when using them. This study aims to address this by comparing two such freely available sources, SureChEMBL and IBM SIIP (IBM Strategic Intellectual Property Insight Platform), with manually curated commercial databases. When looking at the percentage of chemical structures successfully extracted from a set of patents, using SciFinder as our reference, 59 and 51 % were also found in our comparison in SureChEMBL and IBM SIIP, respectively. When performing this comparison with compounds as starting point, i.e. establishing if for a list of compounds the databases provide the links between chemical structures and patents they appear in, we obtained similar results. SureChEMBL and IBM SIIP found 62 and 59 %, respectively, of the compound-patent pairs obtained from Reaxys. In our comparison of automatically generated vs. manually curated patent chemistry databases, the former successfully provided approximately 60 % of links between chemical structure and patents. It needs to be stressed that only a very limited number of patents and compound-patent pairs were used for our comparison. Nevertheless, our results will hopefully help to manage expectations of users of patent chemistry databases of this type and provide a useful framework for more studies like ours as well as guide future developments of the workflows used for the automated extraction of chemical structures from patents. The challenges we have encountered

Computational quantum chemistry website

International Nuclear Information System (INIS)

1997-01-01

This report contains the contents of a web page related to research on the development of quantum chemistry methods for computational thermochemistry and the application of quantum chemistry methods to problems in material chemistry and chemical sciences. Research programs highlighted include: Gaussian-2 theory; Density functional theory; Molecular sieve materials; Diamond thin-film growth from buckyball precursors; Electronic structure calculations on lithium polymer electrolytes; Long-distance electronic coupling in donor/acceptor molecules; and Computational studies of NOx reactions in radioactive waste storage

Circumstellar ammonia in oxygen-rich evolved stars

Science.gov (United States)

Wong, K. T.; Menten, K. M.; Kamiński, T.; Wyrowski, F.; Lacy, J. H.; Greathouse, T. K.

2018-04-01

Context. The circumstellar ammonia (NH3) chemistry in evolved stars is poorly understood. Previous observations and modelling showed that NH3 abundance in oxygen-rich stars is several orders of magnitude above that predicted by equilibrium chemistry. Aims: We would like to characterise the spatial distribution and excitation of NH3 in the oxygen-rich circumstellar envelopes (CSEs) of four diverse targets: IK Tau, VY CMa, OH 231.8+4.2, and IRC +10420. Methods: We observed NH3 emission from the ground state in the inversion transitions near 1.3 cm with the Very Large Array (VLA) and submillimetre rotational transitions with the Heterodyne Instrument for the Far-Infrared (HIFI) aboard Herschel Space Observatory from all four targets. For IK Tau and VY CMa, we observed NH3 rovibrational absorption lines in the ν2 band near 10.5 μm with the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility (IRTF). We also attempted to search for the rotational transition within the excited vibrational state (v2 = 1) near 2 mm with the IRAM 30m Telescope. Non-LTE radiative transfer modelling, including radiative pumping to the vibrational state, was carried out to derive the radial distribution of NH3 in the CSEs of these targets. Results: We detected NH3 inversion and rotational emission in all four targets. IK Tau and VY CMa show blueshifted absorption in the rovibrational spectra. We did not detect vibrationally excited rotational transition from IK Tau. Spatially resolved VLA images of IK Tau and IRC +10420 show clumpy emission structures; unresolved images of VY CMa and OH 231.8+4.2 indicate that the spatial-kinematic distribution of NH3 is similar to that of assorted molecules, such as SO and SO2, that exhibit localised and clumpy emission. Our modelling shows that the NH3 abundance relative to molecular hydrogen is generally of the order of 10-7, which is a few times lower than previous estimates that were made without considering radiative

A simple one-step chemistry model for partially premixed hydrocarbon combustion

Energy Technology Data Exchange (ETDEWEB)

Fernandez-Tarrazo, Eduardo [Instituto Nacional de Tecnica Aeroespacial, Madrid (Spain); Sanchez, Antonio L. [Area de Mecanica de Fluidos, Universidad Carlos III de Madrid, Leganes 28911 (Spain); Linan, Amable [ETSI Aeronauticos, Pl. Cardenal Cisneros 3, Madrid 28040 (Spain); Williams, Forman A. [Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA 92093-0411 (United States)

2006-10-15

This work explores the applicability of one-step irreversible Arrhenius kinetics with unity reaction order to the numerical description of partially premixed hydrocarbon combustion. Computations of planar premixed flames are used in the selection of the three model parameters: the heat of reaction q, the activation temperature T{sub a}, and the preexponential factor B. It is seen that changes in q with equivalence ratio f need to be introduced in fuel-rich combustion to describe the effect of partial fuel oxidation on the amount of heat released, leading to a universal linear variation q(f) for f>1 for all hydrocarbons. The model also employs a variable activation temperature T{sub a}(f) to mimic changes in the underlying chemistry in rich and very lean flames. The resulting chemistry description is able to reproduce propagation velocities of diluted and undiluted flames accurately over the whole flammability limit. Furthermore, computations of methane-air counterflow diffusion flames are used to test the proposed chemistry under nonpremixed conditions. The model not only predicts the critical strain rate at extinction accurately but also gives near-extinction flames with oxygen leakage, thereby overcoming known predictive limitations of one-step Arrhenius kinetics. (author)

A contribution to the study of the structure, reactivity and bioinorganic chemistry of iron

International Nuclear Information System (INIS)

Toma, H.E.

1984-01-01

The research work on inorganic and biological chemistry of iron developed at the University of Sao Paulo (SP, Brazil) is reviewed. Considerations are made about: π interactions, electronic structure and spectroscopy of cyanoferrates; solvation studies and kinetics of substitution reactions involving iron complexes; reactivity of coordinating ligands and iron interactions with biomolecules. (C.L.B.) [pt

Rare Earth Borohydrides—Crystal Structures and Thermal Properties

Directory of Open Access Journals (Sweden)

Christoph Frommen

2017-12-01

Full Text Available Rare earth (RE borohydrides have received considerable attention during the past ten years as possible hydrogen storage materials due to their relatively high gravimetric hydrogen density. This review illustrates the rich chemistry, structural diversity and thermal properties of borohydrides containing RE elements. In addition, it highlights the decomposition and rehydrogenation properties of composites containing RE-borohydrides, light-weight metal borohydrides such as LiBH4 and additives such as LiH.

Structure and chemistry of passivated SiC/SiO{sub 2} interfaces

Energy Technology Data Exchange (ETDEWEB)

Houston Dycus, J.; Xu, Weizong; LeBeau, James M. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7907 (United States); Lichtenwalner, Daniel J.; Hull, Brett; Palmour, John W. [Power Devices R& D, Wolfspeed, A Cree Company, Research Triangle Park, North Carolina 27709 (United States)

2016-05-16

Here, we report on the chemistry and structure of 4H-SiC/SiO{sub 2} interfaces passivated either by nitric oxide annealing or Ba deposition. Using aberration corrected scanning transmission electron microscopy and spectroscopy, we find that Ba and N remain localized at SiC/SiO{sub 2} interface after processing. Further, we find that the passivating species can introduce significant changes to the near-interface atomic structure of SiC. Specifically, we quantify significant strain for nitric oxide annealed sample where Si dangling bonds are capped by N. In contrast, strain is not observed at the interface of the Ba treated samples. Finally, we place these results in the context of field effect mobility.

Comprehensive review in current developments of imidazole-based medicinal chemistry.

Science.gov (United States)

Zhang, Ling; Peng, Xin-Mei; Damu, Guri L V; Geng, Rong-Xia; Zhou, Cheng-He

2014-03-01

Imidazole ring is an important five-membered aromatic heterocycle widely present in natural products and synthetic molecules. The unique structural feature of imidazole ring with desirable electron-rich characteristic is beneficial for imidazole derivatives to readily bind with a variety of enzymes and receptors in biological systems through diverse weak interactions, thereby exhibiting broad bioactivities. The related research and developments of imidazole-based medicinal chemistry have become a rapidly developing and increasingly active topic. Particularly, numerous imidazole-based compounds as clinical drugs have been extensively used in the clinic to treat various types of diseases with high therapeutic potency, which have shown the enormous development value. This work systematically gives a comprehensive review in current developments of imidazole-based compounds in the whole range of medicinal chemistry as anticancer, antifungal, antibacterial, antitubercular, anti-inflammatory, antineuropathic, antihypertensive, antihistaminic, antiparasitic, antiobesity, antiviral, and other medicinal agents, together with their potential applications in diagnostics and pathology. It is hoped that this review will be helpful for new thoughts in the quest for rational designs of more active and less toxic imidazole-based medicinal drugs, as well as more effective diagnostic agents and pathologic probes. © 2013 Wiley Periodicals, Inc.

The Chemistry of Extragalactic Carbon Stars

Science.gov (United States)

Woods, Paul; Walsh, C.; Cordiner, M. A.; Kemper, F.

2013-01-01

Prompted by the ongoing interest in Spitzer Infrared Spectrometer spectra of carbon stars in the Large Magellanic Cloud, we have investigated the circumstellar chemistry of carbon stars in low-metallicity environments. Consistent with observations, our models show that acetylene is particularly abundant in the inner regions of low metallicity carbon-rich asymptotic giant branch stars - more abundant than carbon monoxide. As a consequence, larger hydrocarbons have higher abundances at the metallicities of the Magellanic Clouds than in stars with solar metallicity. We also find that the oxygen and nitrogen chemistry is suppressed at lower metallicity, as expected. Finally, we calculate molecular line emission from carbon stars in the Large and Small Magellanic Cloud and find that several molecules should be readily detectable with the Atacama Large Millimeter Array at Full Science operations.

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.

Understanding surface structure and chemistry of single crystal lanthanum aluminate

KAUST Repository

Pramana, Stevin S.

2017-03-02

The surface crystallography and chemistry of a LaAlO3 single crystal, a material mainly used as a substrate to deposit technologically important thin films (e.g. for superconducting and magnetic devices), was analysed using surface X-ray diffraction and low energy ion scattering spectroscopy. The surface was determined to be terminated by Al-O species, and was significantly different from the idealised bulk structure. Termination reversal was not observed at higher temperature (600 °C) and chamber pressure of 10−10 Torr, but rather an increased Al-O occupancy occurred, which was accompanied by a larger outwards relaxation of Al from the bulk positions. Changing the oxygen pressure to 10−6 Torr enriched the Al site occupancy fraction at the outermost surface from 0.245(10) to 0.325(9). In contrast the LaO, which is located at the next sub-surface atomic layer, showed no chemical enrichment and the structural relaxation was lower than for the top AlO2 layer. Knowledge of the surface structure will aid the understanding of how and which type of interface will be formed when LaAlO3 is used as a substrate as a function of temperature and pressure, and so lead to improved design of device structures.

The Royal Society of Chemistry and the delivery of chemistry data repositories for the community

Science.gov (United States)

Williams, Antony; Tkachenko, Valery

2014-10-01

Since 2009 the Royal Society of Chemistry (RSC) has been delivering access to chemistry data and cheminformatics tools via the ChemSpider database and has garnered a significant community following in terms of usage and contribution to the platform. ChemSpider has focused only on those chemical entities that can be represented as molecular connection tables or, to be more specific, the ability to generate an InChI from the input structure. As a structure centric hub ChemSpider is built around the molecular structure with other data and links being associated with this structure. As a result the platform has been limited in terms of the types of data that can be managed, and the flexibility of its searches, and it is constrained by the data model. New technologies and approaches, specifically taking into account a shift from relational to NoSQL databases, and the growing importance of the semantic web, has motivated RSC to rearchitect and create a more generic data repository utilizing these new technologies. This article will provide an overview of our activities in delivering data sharing platforms for the chemistry community including the development of the new data repository expanding into more extensive domains of chemistry data.

Chemistry in an evolving protoplanetary disk: Effects on terrestrial planet composition

International Nuclear Information System (INIS)

Moriarty, John; Fischer, Debra; Madhusudhan, Nikku

2014-01-01

The composition of planets is largely determined by the chemical and dynamical evolution of the disk during planetesimal formation and growth. To predict the diversity of exoplanet compositions, previous works modeled planetesimal composition as the equilibrium chemical composition of a protoplanetary disk at a single time. However, planetesimals form over an extended period of time, during which elements sequentially condense out of the gas as the disk cools and are accreted onto planetesimals. To account for the evolution of the disk during planetesimal formation, we couple models of disk chemistry and dynamics with a prescription for planetesimal formation. We then follow the growth of these planetesimals into terrestrial planets with N-body simulations of late-stage planet formation to evaluate the effect of sequential condensation on the bulk composition of planets. We find that our model produces results similar to those of earlier models for disks with C/O ratios close to the solar value (0.54). However, in disks with C/O ratios greater than 0.8, carbon-rich planetesimals form throughout a much larger radial range of the disk. Furthermore, our model produces carbon-rich planetesimals in disks with C/O ratios as low as ∼0.65, which is not possible in the static equilibrium chemistry case. These results suggest that (1) there may be a large population of short-period carbon-rich planets around moderately carbon-enhanced stars (0.65 < C/O < 0.8) and (2) carbon-rich planets can form throughout the terrestrial planet region around carbon-rich stars (C/O > 0.8).

Molecular cloning and construction of the coding region for human acetylcholinesterase reveals a G + C-rich attenuating structure

International Nuclear Information System (INIS)

Soreq, H.; Ben-Aziz, R.; Prody, C.A.; Seidman, S.; Gnatt, A.; Neville, L.; Lieman-Hurwitz, J.; Lev-Lehman, E.; Ginzberg, D.; Lapidot-Lifson, Y.; Zakut, H.

1990-01-01

To study the primary structure of human acetylcholinesterase and its gene expression and amplification, cDNA libraries from human tissues expressing oocyte-translatable AcChoEase mRNA were constructed and screened with labeled oligodeoxynucleotide probes. Several cDNA clones were isolated that encoded a polypeptide with ≥50% identically aligned amino acids to Torpedo AcChoEase and human butyrylcholinesterase. However, these cDNA clones were all truncated within a 300-nucleotide-long G + C-rich region with a predicted pattern of secondary structure having a high Gibbs free energy downstream from the expected 5' end of the coding region. Screening of a genomic DNA library revealed the missing 5' domain. When ligated to the cDNA and constructed into a transcription vector, this sequence encoded a synthetic mRNA translated in microinjected oocytes into catalytically active AcChoEase with marked preference for acetylthiocholine over butyrylthiocholine as a substrate, susceptibility to inhibition by the AcChoEase inhibitor BW284C51, and resistance to the AcChoEase inhibitor tetraisopropylpyrophosphoramide. Blot hybridization of genomic DNA from different individuals carrying amplified AcChoEase genes revealed variable intensities and restriction patterns with probes from the regions upstream and downstream from the predicted G + C-rich structure. Thus, the human AcChoEase gene includes a putative G + C-rich attenuator domain and is subject to structural alterations in cases of AcChoEase gene amplification

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...

Spatially Resolved Artificial Chemistry

DEFF Research Database (Denmark)

Fellermann, Harold

2009-01-01

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......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...

Structure of light proton-rich nuclei on the drip-line

International Nuclear Information System (INIS)

Guimaraes, V.; Toyokawa, H.; Yun, C.C.; Niizeki, T.; Ito, K.; Kishida, T.; Kubo, T.; Pu, Y.; Ohura, M.; Orihara, H.; Terakawa, T.; Hamada, S.; Hirai, M.; Miyatake, H.

1995-01-01

Among proton-rich unstable nuclei on the light proton drip-line, nuclear structure of 21 Mg, 17 Ne, 13 O, 11 N and 9 C have been investigated by the three-neutron pick-up reaction ( 3 He, 6 He). The angular distributions measured for this reaction have shown a characteristic feature of a transferred angular-momentum (L) dependence, which provides spin-parity assignments for the new levels in these nuclei. Here, the results on the nuclear structure of 17 Ne and 11 N are reported. The nucleus 17 Ne we almost unknown before, except that the mass excess had been determined and a few states had been suggested. Many T = 3/2 states were known in the other three members ( 17 N, 17 O and 17 F). Thus, the inclusion of the data on 17 Ne levels has enabled an extensive analysis in terms of the Isobaric Multiplet Mass Equation (IMME) for several excited state quartets. This is the first report on such an extensive analysis in the same mass ststem for a wide range in excitation energy. The 11 N nucleus was investigated to learn about the structure of A 11 system. This mass has been intensively studied, specially because of the halo structure observed in 11 Li and the spin parity-inversion of the 11 Be ground-state. The 11 N nucleus was totally unknown before except for the possible ground state

Synthesis and study of neutron-rich nuclides

International Nuclear Information System (INIS)

Luo, Y.X.

1995-01-01

During the past few years our understanding of the decay properties and nuclear structure has been extended in a systematic fashion for the neutron-rich nuclei. This review will discuss the impressive progress in the studies of the exotic decay properties and nuclear structure of n-rich nuclei. Their astrophysical implications will also be outlined. ((orig.))

Structural material anomaly detection system using water chemistry data

International Nuclear Information System (INIS)

Asakura, Yamato; Nagase, Makoto; Uchida, Shunsuke; Ohsumi, Katsumi.

1992-01-01

The concept of an advanced water chemistry diagnosis system for detection of anomalies and preventive maintenance of system components is proposed and put into a concrete form. Using the analogy to a medical inspection system, analyses of water chemistry change will make it possible to detect symptoms of anomalies in system components. Then, correlations between water chemistry change and anomaly occurrence in the components of the BWR primary cooling system are analyzed theoretically. These fragmentary correlations are organized and reduced to an algorithm for the on-line diagnosis system using on-line monitoring data, pH and conductivity. By using actual plant data, the on-line diagnosis model system is verified to be applicable for early and automatic finding of the anomaly cause and for timely supply of much diagnostic information to plant operators. (author)

Structure dependent electrochemical performance of Li-rich layered oxides in lithium-ion batteries

Energy Technology Data Exchange (ETDEWEB)

Fu, Fang; Yao, Yuze; Wang, Haiyan; Xu, Gui-Liang; Amine, Khalil; Sun, Shi-Gang; Shao, Minhua

2017-04-08

Rational and precise control of the structure and dimension of electrode materials is an efficient way to improve their electrochemical performance. In this work, solvothermal or co-precipitation method is used to synthesize lithium-rich layered oxide materials of Li1.2Mn0.56Co0.12Ni0.12O2 (LLO) with various morphologies and structures, including microspheres, microrods, nanoplates, and irregular nanoparticles. These materials exhibit strong structure- dependent electrochemical properties. The porous hierarchical structured LLO microrods exhibit the best performance, delivering a discharge capacity of 264.6 mAh g(-1) at 0.5 C with over 91% retention after 100 cycles. At a high rate of 5 C, a high discharge capacity of 173.6 mAh g(-1) can be achieved. This work reveals the relationship between the morphologies and electrochemical properties of LLO cathode materials, and provides a feasible approach to fabricating robust and high-performance electrode materials for lithium-ion batteries.

Mirror energy difference and the structure of loosely bound proton-rich nuclei around A =20

Science.gov (United States)

Yuan, Cenxi; Qi, Chong; Xu, Furong; Suzuki, Toshio; Otsuka, Takaharu

2014-04-01

The properties of loosely bound proton-rich nuclei around A =20 are investigated within the framework of the nuclear shell model. In these nuclei, the strength of the effective interactions involving the loosely bound proton s1/2 orbit is significantly reduced in comparison with that of those in their mirror nuclei. We evaluate the reduction of the effective interaction by calculating the monopole-based-universal interaction (VMU) in the Woods-Saxon basis. The shell-model Hamiltonian in the sd shell, such as USD, can thus be modified to reproduce the binding energies and energy levels of the weakly bound proton-rich nuclei around A =20. The effect of the reduction of the effective interaction on the structure and decay properties of these nuclei is also discussed.

Nuclear structure studies of neutron-rich heavy nuclei by mass measurements of francium and radium isotopes

Energy Technology Data Exchange (ETDEWEB)

Rosenbusch, Marco [Ernst-Moritz-Arndt-Universitaet, Institut fuer Physik, 17487 Greifswald (Germany); Collaboration: ISOLTRAP-Collaboration

2013-07-01

The mass is a unique property of an atomic nucleus reflecting its binding energy and thus the sum of all interactions at work. Precise measurements of nuclear masses especially of short-lived exotic nuclides provide important input for nuclear structure, nuclear astrophysics, tests of the Standard Model, and weak interaction studies. The Penning-trap mass spectrometer ISOLTRAP at the on-line isotope separator ISOLDE/CERN has been set up for precision mass measurements and continuously improved for accessing more exotic nuclides. The mass uncertainty is typically δm / m=10{sup -8} and the accessible half-life has been reduced to about 50 ms. In this contribution, the results of a measurement campaign of neutron-rich francium and radium isotopes will be presented, i.e. the masses of the isotopic chain of {sup 224-233}Fr and {sup 233,234}Ra, one of the most neutron-rich ensemble obtainable at ISOL facilities. The mass {sup 234}Ra denotes the heaviest mass ever measured with ISOLTRAP. Experimental data in the neutron-rich, heavy mass region is of great interest for studies of structural evolution far from stability, especially because the knowledge from nuclear mass models is scarce. The impact of the new data on the physics in this mass region as well as recent technical developments of ISOLTRAP are discussed.

PHOTOCHEMISTRY IN THE INNER LAYERS OF CLUMPY CIRCUMSTELLAR ENVELOPES: FORMATION OF WATER IN C-RICH OBJECTS AND OF C-BEARING MOLECULES IN O-RICH OBJECTS

International Nuclear Information System (INIS)

Agundez, Marcelino; Cernicharo, Jose; Guelin, Michel

2010-01-01

A mechanism based on the penetration of interstellar ultraviolet photons into the inner layers of clumpy circumstellar envelopes (CSEs) around asymptotic giant branch stars is proposed to explain the non-equilibrium chemistry observed in such objects. We show through a simple modeling approach that in CSEs with a certain degree of clumpiness or with moderately low mass loss rates (a few 10 -7 M sun yr -1 ) a photochemistry can take place in the warm and dense inner layers, inducing important changes in the chemical composition. In carbon-rich objects water vapor and ammonia would be formed with abundances of 10 -8 -10 -6 relative to H 2 , while in oxygen-rich envelopes ammonia and carbon-bearing molecules such as HCN and CS would form with abundances of 10 -9 -10 -7 relative to H 2 . The proposed mechanism would explain the recent observation of warm water vapor in the carbon-rich envelope IRC+10216 with the Herschel Space Observatory and predict that H 2 O should be detectable in other carbon-rich objects.

Preparation and Reaction Chemistry of Novel Silicon-Substituted 1,3-Dienes

Directory of Open Access Journals (Sweden)

Partha P. Choudhury

2015-09-01

Full Text Available 2-Silicon-substituted 1,3-dienes containing non transferrable groups known to promote transmetallation were prepared by Grignard chemistry and enyne metathesis. These dienes participated in one pot metathesis/Diels-Alder reactions in regio- and diastereoselective fashions. Electron-rich alkenes showed the fastest rates in metathesis reactions, and ethylene, a commonly used metathesis promoter slowed enyne metathesis. 2-Pyridyldimethylsilyl and 2-thienyldimethylsilyl substituted Diels-Alder cycloadducts participated in cross-coupling chemistry and the 2-thienyldimethylsilyl substituted cycloadducts underwent cross-coupling under very mild reaction conditions.

Adaptation of quantum chemistry software for the electronic structure calculations on GPU for solid-state systems

International Nuclear Information System (INIS)

Gusakov, V.E.; Bel'ko, V.I.; Dorozhkin, N.N.

2015-01-01

We report on adaptation of quantum chemistry software - Quantum Espresso and LASTO - for the electronic structure calculations for the complex solid-state systems on the GeForce series GPUs using the nVIDIA CUDA technology. Specifically, protective covering based on transition metal nitrides are considered. (authors)

Future in actinoids coordination chemistry

International Nuclear Information System (INIS)

Kitazawa, Takafumi

2006-01-01

Actinoids coordination chemistry is concerned with spent nuclear fuel reprocessing, specifically with solid-state chemistry of nuclear fuels, separation process with radioactive substances, and geological disposal of high-level radioactive substances. In the 21st century, accumulation of minor actinides, Np, Am, Cm, and others will be realized according with the present program of nuclear energy development. The present article briefly introduces general properties of actinide elements, followed by their coordination chemistry compared with rare earths coordination chemistry. Special facility needed to treat actinoids as well as their chemistry is briefly explained, together with the specific experimental apparatus such as X-ray Absorption Fine Structure (XAFS) and time-resolved laser-induced fluorescence spectrometry (TRLFS) with synchrotron radiation facilities. The effect of coordination with actinoids in the environment chemistry is important in underground disposal of high-level radioactive wastes. For theoretical analysis of the results with actinoids chemistry, relativistic calculation is needed. (S. Ohno)

Microdiffraction and CBED crystal structure determination of the Si-rich phase in laser-clad Ni alloy FP-5

International Nuclear Information System (INIS)

Liu, Y.; Mazumder, J.

1995-01-01

This paper demonstrates an example of using kinematical microdiffraction to solve an unknown Si-rich phase of micrometer size in a laser-clad Ni alloy FP-5 on Al alloy AA333. The composition of the Si-rich phase obtained by energy-dispersice X-ray spectroscopy (EDX) analysis in a transmission electron microscope is approximately 0.7wt%Al, 71wt%Si, 3.3wt%Cr, 0.8wt%Fe, 21wt%Ni and 2.8wt%Cu. The point group was identified by the standard convergent-beam symmetry analysis to be P6 3 /mmc (No. 194). Structure analysies by microdiffraction (MD) indicates that the Si-rich phase is a close-packed structure.The intensity distribution in the microdiffraction pattern of the [1120] zone axis taken with a very thin area showed a close match with kinematical calculation. A close-packed-structure model specified as ABCACB was deduced from the [1120] zone axis MD pattern. The randomly distributed atoms of all the elements in the unit cell are at 2/3, 1/3-1/12; 1/3, 1/12; 0, 0, 3/12, 1/3, 2/3, 5/12, 2/3, 1/3, 7/12; 0,0, 9/12. The model was checked by comparison with a simulated diffraction pattern map and with a simulated [0001] zone-axis CBED pattern, which showed complete agreement with the proposed model. (orig.)

DOE fundamentals handbook: Chemistry

International Nuclear Information System (INIS)

1993-01-01

The Chemistry Handbook was developed to assist nuclear facility operating contractors in providing operators, maintenance personnel, and the technical staff with the necessary fundamentals training to ensure a basic understanding of chemistry. The handbook includes information on the atomic structure of matter; chemical bonding; chemical equations; chemical interactions involved with corrosion processes; water chemistry control, including the principles of water treatment; the hazards of chemicals and gases, and basic gaseous diffusion processes. This information will provide personnel with a foundation for understanding the chemical properties of materials and the way these properties can impose limitations on the operation of equipment and systems

Medicinal Chemistry Projects Requiring Imaginative Structure-Based Drug Design Methods.

Science.gov (United States)

Moitessier, Nicolas; Pottel, Joshua; Therrien, Eric; Englebienne, Pablo; Liu, Zhaomin; Tomberg, Anna; Corbeil, Christopher R

2016-09-20

Computational methods for docking small molecules to proteins are prominent in drug discovery. There are hundreds, if not thousands, of documented examples-and several pertinent cases within our research program. Fifteen years ago, our first docking-guided drug design project yielded nanomolar metalloproteinase inhibitors and illustrated the potential of structure-based drug design. Subsequent applications of docking programs to the design of integrin antagonists, BACE-1 inhibitors, and aminoglycosides binding to bacterial RNA demonstrated that available docking programs needed significant improvement. At that time, docking programs primarily considered flexible ligands and rigid proteins. We demonstrated that accounting for protein flexibility, employing displaceable water molecules, and using ligand-based pharmacophores improved the docking accuracy of existing methods-enabling the design of bioactive molecules. The success prompted the development of our own program, Fitted, implementing all of these aspects. The primary motivation has always been to respond to the needs of drug design studies; the majority of the concepts behind the evolution of Fitted are rooted in medicinal chemistry projects and collaborations. Several examples follow: (1) Searching for HDAC inhibitors led us to develop methods considering drug-zinc coordination and its effect on the pKa of surrounding residues. (2) Targeting covalent prolyl oligopeptidase (POP) inhibitors prompted an update to Fitted to identify reactive groups and form bonds with a given residue (e.g., a catalytic residue) when the geometry allows it. Fitted-the first fully automated covalent docking program-was successfully applied to the discovery of four new classes of covalent POP inhibitors. As a result, efficient stereoselective syntheses of a few screening hits were prioritized rather than synthesizing large chemical libraries-yielding nanomolar inhibitors. (3) In order to study the metabolism of POP inhibitors by

Enzymatic synthesis of capric acid-rich structured lipids (MUM type) using Candida antarctica lipase.

Science.gov (United States)

SilRoy, Sumita; Ghosh, Mahua

2011-01-01

The objective of the work was to produce capric acid rich structured lipids starting from various Indian indigenous vegetable oils, such as rice bran, ground nut and mustard oils. Acidolysis reaction between individual vegetable oils and capric acid in one is to three molar ratios at 45 degree centigrade temperature was carried out using position specific Candida antarctica lipase so as to protect the Sn-2 position of the oils which are rich in unsaturated fatty acids. The incorporation of capric acid depended on the reaction time showing 6 % within 6 h and 30.8 % in 72 h with rice bran oil. Similarly, in ground nut oil incorporation of capric acid was 34.2 % in 72 h compared to 5.3 % in 6 h. Thus mustard oil showed much lower incorporation than the other two oils, with 3.3 % and 19.5 % in 6 and 72 h respectively. The incorporation of capric acid was influenced by the nature of the fatty acids present in the original oil. The fatty acid composition of Sn-2 position of the structured triacylglycerols of the three oils revealed that capric acid was mainly replacing the fatty acids occupying the Sn-1 and 3 positions of the triglyceride molecule.

Chemistry Division annual progress report for period ending January 31, 1984

Energy Technology Data Exchange (ETDEWEB)

1984-05-01

Progress is reported in the following fields: coal chemistry, aqueous chemistry at high temperatures and pressures, geochemistry, high-temperature chemistry and thermodynamics of structural materials, chemistry of transuranium elements and compounds, separations chemistry, elecrochemistry, catalysis, chemical physics, theoretical chemistry, nuclear waste chemistry, chemistry of hazardous chemicals, and thermal energy storage.

Extraterrestrial Radiation Chemistry and Molecular Astronomy

Science.gov (United States)

Hudson, Reggie L.; Moore, Marla H.

2009-01-01

Astronomical observations of both solar system and interstellar regions have revealed a rich chemical inventory that includes most classes of organic molecules and selected inorganics. For example, gas-phase ethylene glycol and SOz have been observed by astronomers, while solidphase detections include OCS, H2O2 , and the cyanate anion.' All of these are found in environments that are, by earthly standards, exceedingly hostile: temperatures of 10 - 100 K, miniscule densities, and near-ubiquitous ionizing-radiation fields. Beyond the simplest chemical species, these conditions have made it difficult-to-impassible to account for the observed molecular abundances using gas-phase chemistry, suggesting solid-phase reactions play an important role. In extraterrestrial environments, cosmic rays, UV photons, and magnetospheric radiation all drive chemical reactions, even at cryogenic temperatures. To study this chemistry, radiation astrochemists conduct experiments on icy materials, frozen under vacuum and exposed to sources such as keV electrons and MeV protons. Compositional changes usually are followed with IR spectroscopy and, in selected cases, more-sensitive mass-spectral techniques. This talk will review some recent results on known and suspected extraterrestrial molecules and ions. Spectra and reaction pathways will be presented, and predictions made for interstellar chemistry and the chemistry of selected solar system objects. Some past radiation-chemical contributions, and future needs, will be explored.

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…

Structural manifestations of aging in Se-rich glasses

Science.gov (United States)

Dash, S.; Ravindren, S.; Chen, P.; Boolchand, P.

2015-03-01

We examine weakly cross-linked GexSe100-x (0%modulated DSC and Raman scattering experiments. Homogeneity of melts was carefully verified using FT-Raman line profiling. Upon aging at RT for 4 months, we find the width of the glass transition W(x) steadily decreasing from 10C at 7% Ge to 2C for pure Se. The 5-fold reduction of W(x) with a decrease of Ge content is accompanied by a 2-fold increase in the non-reversing enthalpy. Rejuvenation of the aged glasses changes W(x) from 15C at 7% Ge to 7C for pure Se. Tg is found to decrease upon rejuvenation with the difference (Tg(aged)-Tg(rejuv)) showing a maximum near 3% Ge and vanishing for pure Se and 6% of Ge, which are topological thresholds. These results in Se-rich glasses are consistent with aging induced decoupling of Se8 crowns and growth of extended range structural correlations between polymeric Sen chains due to lone pair interactions. At higher x, near 8-10% of Ge, eutectic effects are manifested. Work supported by NSF Grant DMR 08-53957.

Scandium Terminal Imido Chemistry.

Science.gov (United States)

Lu, Erli; Chu, Jiaxiang; Chen, Yaofeng

2018-02-20

Research into transition metal complexes bearing multiply bonded main-group ligands has developed into a thriving and fruitful field over the past half century. These complexes, featuring terminal M═E/M≡E (M = transition metal; E = main-group element) multiple bonds, exhibit unique structural properties as well as rich reactivity, which render them attractive targets for inorganic/organometallic chemists as well as indispensable tools for organic/catalytic chemists. This fact has been highlighted by their widespread applications in organic synthesis, for example, as olefin metathesis catalysts. In the ongoing renaissance of transition metal-ligand multiple-bonding chemistry, there have been reports of M═E/M≡E interactions for the majority of the metallic elements of the periodic table, even some actinide metals. In stark contrast, the largest subgroup of the periodic table, rare-earth metals (Ln = Sc, Y, and lanthanides), have been excluded from this upsurge. Indeed, the synthesis of terminal Ln═E/Ln≡E multiple-bonding species lagged behind that of the transition metal and actinide congeners for decades. Although these species had been pursued since the discovery of a rare-earth metal bridging imide in 1991, such a terminal (nonpincer/bridging hapticities) Ln═E/Ln≡E bond species was not obtained until 2010. The scarcity is mainly attributed to the energy mismatch between the frontier orbitals of the metal and the ligand atoms. This renders the putative terminal Ln═E/Ln≡E bonds extremely reactive, thus resulting in the formation of aggregates and/or reaction with the ligand/environment, quenching the multiple-bond character. In 2010, the stalemate was broken by the isolation and structural characterization of the first rare-earth metal terminal imide-a scandium terminal imide-by our group. The double-bond character of the Sc═N bond was unequivocally confirmed by single-crystal X-ray diffraction. Theoretical investigations revealed the presence

Dust evolution, a global view: III. Core/mantle grains, organic nano-globules, comets and surface chemistry

Science.gov (United States)

2016-01-01

Within the framework of The Heterogeneous dust Evolution Model for Interstellar Solids (THEMIS), this work explores the surface processes and chemistry relating to core/mantle interstellar and cometary grain structures and their influence on the nature of these fascinating particles. It appears that a realistic consideration of the nature and chemical reactivity of interstellar grain surfaces could self-consistently and within a coherent framework explain: the anomalous oxygen depletion, the nature of the CO dark gas, the formation of ‘polar ice’ mantles, the red wing on the 3 μm water ice band, the basis for the O-rich chemistry observed in hot cores, the origin of organic nano-globules and the 3.2 μm ‘carbonyl’ absorption band observed in comet reflectance spectra. It is proposed that the reaction of gas phase species with carbonaceous a-C(:H) grain surfaces in the interstellar medium, in particular the incorporation of atomic oxygen into grain surfaces in epoxide functional groups, is the key to explaining these observations. Thus, the chemistry of cosmic dust is much more intimately related with that of the interstellar gas than has previously been considered. The current models for interstellar gas and dust chemistry will therefore most likely need to be fundamentally modified to include these new grain surface processes. PMID:28083090

Isotope and Nuclear Chemistry Division annual report, FY 1983

International Nuclear Information System (INIS)

Heiken, J.H.; Lindberg, H.A.

1984-05-01

This report describes progress in the major research and development programs carried out in FY 1983 by the Isotope and Nuclear Chemistry Division. It covers radiochemical diagnostics of weapons tests; weapons radiochemical diagnostics research and development; other unclassified weapons research; stable and radioactive isotope production, separation, and applications (including biomedical applications); element and isotope transport and fixation; actinide and transition metal chemistry; structural chemistry, spectroscopy, and applications; nuclear structure and reactions; irradiation facilities; advanced analytical techniques; development and applications; atmospheric chemistry and transport; and earth and planetary processes

Isotope and Nuclear Chemistry Division annual report, FY 1983

Energy Technology Data Exchange (ETDEWEB)

Heiken, J.H.; Lindberg, H.A. (eds.)

1984-05-01

This report describes progress in the major research and development programs carried out in FY 1983 by the Isotope and Nuclear Chemistry Division. It covers radiochemical diagnostics of weapons tests; weapons radiochemical diagnostics research and development; other unclassified weapons research; stable and radioactive isotope production, separation, and applications (including biomedical applications); element and isotope transport and fixation; actinide and transition metal chemistry; structural chemistry, spectroscopy, and applications; nuclear structure and reactions; irradiation facilities; advanced analytical techniques; development and applications; atmospheric chemistry and transport; and earth and planetary processes.

Isotope and Nuclear Chemistry Division annual report, FY 1984

International Nuclear Information System (INIS)

Heiken, J.H.

1985-04-01

This report describes progress in the major research and development programs carried out in FY 1984 by the Isotope and Nuclear Chemistry Division. It covers radiochemical diagnostics of weapons tests; weapons radiochemical diagnostics research and development; other unclassified weapons research; stable and radioactive isotope production, separation, and applications (including biomedical applications); element and isotope transport and fixation; actinide and transition metal chemistry; structural chemistry, spectroscopy, and applications; nuclear structure and reactions; irradiation facilities; advanced analytical techniques: development and applications; atmospheric chemistry and transport; and earth and planetary processes. 287 refs

The radiation chemistry of macromolecules

CERN Document Server

1973-01-01

The Radiation Chemistry of Macromolecules, Volume II is a collection of papers that discusses radiation chemistry of specific systems. Part 1 deals with radiation chemistry of substituted vinyl polymers, particularly polypropylene (PP) as its structure is intermediate between polyethylene and polyisobutylene. This part also discusses polypropylene oxide (PPOx) for it can be prepared in the atactic, isotactic, and optically active forms. One paper focuses on the fundamental chemical processes and the changes in physical properties that give rise to many different applications of polystyrene. An

Experimental and Analytical Studies of Solar System Chemistry

Science.gov (United States)

Burnett, Donald S.

2003-01-01

The cosmochemistry research funded by this grant resulted in the publications given in the attached Publication List. The research focused in three areas: (1) Experimental studies of trace element partitioning. (2) Studies of the minor element chemistry and O isotopic compositions of MgAlO4 spinels from Ca-Al-Rich Inclusions in carbonaceous chondrite meteorites, and (3) The abundances and chemical fractionations of Th and U in chondritic meteorites.

200 years of lithium and 100 years of organolithium chemistry

International Nuclear Information System (INIS)

Wietelmann, Ulrich; Klett, Jan

2018-01-01

The element lithium has been discovered 200 years ago. Due to its unique properties it has emerged to play a vital role in industry, esp. for energy storage, and lithium-based products and processes support sustainable technological developments. In addition to the many uses of lithium in its inorganic forms, lithium has a rich organometallic chemistry. The development of organometallic chemistry has been hindered by synthetic problems from the start. When Wilhelm Schlenk developed the basic principles to handle and synthesize air- and moisture-sensitive compounds, the road was open to further developments. After more information was available about the stability and solubility of such compounds, they started to play an essential role in other fields of chemistry as alkyl or aryl transfer reagents. (copyright 2018 The Authors. Published by Wiley-VCH Verlag GmbH and Co. KGaA.)

200 years of lithium and 100 years of organolithium chemistry

Energy Technology Data Exchange (ETDEWEB)

Wietelmann, Ulrich [Albemarle Germany GmbH, Synthesis Solutions, Industriepark Hoechst, Frankfurt am Main (Germany); Klett, Jan [Institut fuer Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universitaet Mainz (Germany)

2018-03-01

The element lithium has been discovered 200 years ago. Due to its unique properties it has emerged to play a vital role in industry, esp. for energy storage, and lithium-based products and processes support sustainable technological developments. In addition to the many uses of lithium in its inorganic forms, lithium has a rich organometallic chemistry. The development of organometallic chemistry has been hindered by synthetic problems from the start. When Wilhelm Schlenk developed the basic principles to handle and synthesize air- and moisture-sensitive compounds, the road was open to further developments. After more information was available about the stability and solubility of such compounds, they started to play an essential role in other fields of chemistry as alkyl or aryl transfer reagents. (copyright 2018 The Authors. Published by Wiley-VCH Verlag GmbH and Co. KGaA.)

Investigating Students' Similarity Judgments in Organic Chemistry

Science.gov (United States)

Graulich, N.; Bhattacharyya, G.

2017-01-01

Organic chemistry is possibly the most visual science of all chemistry disciplines. The process of scientific inquiry in organic chemistry relies on external representations, such as Lewis structures, mechanisms, and electron arrows. Information about chemical properties or driving forces of mechanistic steps is not available through direct…

An ezrin-rich, rigid uropod-like structure directs movement of amoeboid blebbing cells.

Science.gov (United States)

Lorentzen, Anna; Bamber, Jeffrey; Sadok, Amine; Elson-Schwab, Ilan; Marshall, Christopher J

2011-04-15

Melanoma cells can switch between an elongated mesenchymal-type and a rounded amoeboid-type migration mode. The rounded 'amoeboid' form of cell movement is driven by actomyosin contractility resulting in membrane blebbing. Unlike elongated A375 melanoma cells, rounded A375 cells do not display any obvious morphological front-back polarisation, although polarisation is thought to be a prerequisite for cell movement. We show that blebbing A375 cells are polarised, with ezrin (a linker between the plasma membrane and actin cytoskeleton), F-actin, myosin light chain, plasma membrane, phosphatidylinositol (4,5)-bisphosphate and β1-integrin accumulating at the cell rear in a uropod-like structure. This structure does not have the typical protruding shape of classical leukocyte uropods, but, as for those structures, it is regulated by protein kinase C. We show that the ezrin-rich uropod-like structure (ERULS) is an inherent feature of polarised A375 cells and not a consequence of cell migration, and is necessary for cell invasion. Furthermore, we demonstrate that membrane blebbing is reduced at this site, leading to a model in which the rigid ezrin-containing structure determines the direction of a moving cell through localised inhibition of membrane blebbing.

Structure of proton-rich nuclei of astrophysical interest

Energy Technology Data Exchange (ETDEWEB)

Roeckl, E [Gesellschaft fuer Schwerionenforschung (GSI), Darmstadt (Germany)

1998-06-01

Recent experimental data concerning proton-rich nuclei between A=20 and A=100 are presented and discussed with respect to their relevance to the astrophysical rp process and to the calibration of solar neutrino detectors. (orig.)

PROTO-PLANETARY DISK CHEMISTRY RECORDED BY D-RICH ORGANIC RADICALS IN CARBONACEOUS CHONDRITES

International Nuclear Information System (INIS)

Remusat, Laurent; Robert, Francois; Meibom, Anders; Mostefaoui, Smail; Delpoux, Olivier; Binet, Laurent; Gourier, Didier; Derenne, Sylvie

2009-01-01

Insoluble organic matter (IOM) in primitive carbonaceous meteorites has preserved its chemical composition and isotopic heterogeneity since the solar system formed ∼4.567 billion years ago. We have identified the carrier moieties of isotopically anomalous hydrogen in IOM isolated from the Orgueil carbonaceous chondrite. Data from high spatial resolution, quantitative isotopic NanoSIMS mapping of Orgueil IOM combined with data from electron paramagnetic resonance spectroscopy reveals that organic radicals hold all the deuterium excess (relative to the bulk IOM) in distinct, micrometer-sized, D-rich hotspots. Taken together with previous work, the results indicate that an isotopic exchange reaction took place between pre-existing organic compounds characterized by low D/H ratios and D-rich gaseous molecules, such as H 2 D + or HD 2 + . This exchange reaction most likely took place in the diffuse outer regions of the proto-planetary disk around the young Sun, offering a model that reconciles meteoritic and cometary isotopic compositions of organic molecules.

Proto-Planetary Disk Chemistry Recorded by D-Rich Organic Radicals in Carbonaceous Chondrites

Science.gov (United States)

Remusat, Laurent; Robert, François; Meibom, Anders; Mostefaoui, Smail; Delpoux, Olivier; Binet, Laurent; Gourier, Didier; Derenne, Sylvie

2009-06-01

Insoluble organic matter (IOM) in primitive carbonaceous meteorites has preserved its chemical composition and isotopic heterogeneity since the solar system formed ~4.567 billion years ago. We have identified the carrier moieties of isotopically anomalous hydrogen in IOM isolated from the Orgueil carbonaceous chondrite. Data from high spatial resolution, quantitative isotopic NanoSIMS mapping of Orgueil IOM combined with data from electron paramagnetic resonance spectroscopy reveals that organic radicals hold all the deuterium excess (relative to the bulk IOM) in distinct, micrometer-sized, D-rich hotspots. Taken together with previous work, the results indicate that an isotopic exchange reaction took place between pre-existing organic compounds characterized by low D/H ratios and D-rich gaseous molecules, such as H2D+ or HD2 +. This exchange reaction most likely took place in the diffuse outer regions of the proto-planetary disk around the young Sun, offering a model that reconciles meteoritic and cometary isotopic compositions of organic molecules.

Introductory quantum chemistry

International Nuclear Information System (INIS)

Chandra, A.K.

1974-01-01

This book on quantum chemistry is primarily intended for university students at the senior undergraduate level. It serves as an aid to the basic understanding of the important concepts of quantum mechanics introduced in the field of chemistry. Various chapters of the book are devoted to the following : (i) Waves and quanta, (ii) Operator concept in quantum chemistry, (iii) Wave mechanics of some simple systems, (iv) Perturbation theory, (v) Many-electron atoms and angular momenta (vi) Molecular orbital theory and its application to the electronic structure of diatomic molecules, (vii) Chemical bonding in polyatomic molecules and (viii) Chemical applications of Hellmann-Feynman theorem. At the end of each chapter, a set of problems is given and the answers to these problems are given at the end of the book. (A.K.)

itube, Youtube, Wetube: Social Media Videos in Chemistry Education and Outreach

Science.gov (United States)

Smith, David K.

2014-01-01

Social media provide a unique arena in which chemists can communicate directly with an international audience from a wide range of backgrounds. In particular, YouTube offers a rich environment through which students of chemistry and members of the general public can be engaged, and chemophobia can be addressed. This article describes the…

Selective host molecules obtained by dynamic adaptive chemistry.

Science.gov (United States)

Matache, Mihaela; Bogdan, Elena; Hădade, Niculina D

2014-02-17

Up till 20 years ago, in order to endow molecules with function there were two mainstream lines of thought. One was to rationally design the positioning of chemical functionalities within candidate molecules, followed by an iterative synthesis-optimization process. The second was the use of a "brutal force" approach of combinatorial chemistry coupled with advanced screening for function. Although both methods provided important results, "rational design" often resulted in time-consuming efforts of modeling and synthesis only to find that the candidate molecule was not performing the designed job. "Combinatorial chemistry" suffered from a fundamental limitation related to the focusing of the libraries employed, often using lead compounds that limit its scope. Dynamic constitutional chemistry has developed as a combination of the two approaches above. Through the rational use of reversible chemical bonds together with a large plethora of precursor libraries, one is now able to build functional structures, ranging from quite simple molecules up to large polymeric structures. Thus, by introduction of the dynamic component within the molecular recognition processes, a new perspective of deciphering the world of the molecular events has aroused together with a new field of chemistry. Since its birth dynamic constitutional chemistry has continuously gained attention, in particular due to its ability to easily create from scratch outstanding molecular structures as well as the addition of adaptive features. The fundamental concepts defining the dynamic constitutional chemistry have been continuously extended to currently place it at the intersection between the supramolecular chemistry and newly defined adaptive chemistry, a pivotal feature towards evolutive chemistry. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Vanadium-rich tourmaline from graphitic rocks at Bítovánky, Czech republic; compositional variation, crystal structure

Czech Academy of Sciences Publication Activity Database

Cempírek, J.; Houzar, S.; Novák, M.; Selway, J.B.; Šrein, Vladimír

2006-01-01

Roč. 28, Spec. pap. (2006), s. 39-41 ISSN 1896-2203. [Central European Mineralogical Conference /1./. Vyšná Boca, 11.09.2006-15.09.2006] Institutional research plan: CEZ:AV0Z30460519 Keywords : V-rich tourmaline * compositional variation * crystal structure Subject RIV: DB - Geology ; Mineralogy

Chemistry Division annual progress report for period ending April 30, 1993

Energy Technology Data Exchange (ETDEWEB)

Poutsma, M.L.; Ferris, L.M.; Mesmer, R.E.

1993-08-01

The Chemistry Division conducts basic and applied chemical research on projects important to DOE`s missions in sciences, energy technologies, advanced materials, and waste management/environmental restoration; it also conducts complementary research for other sponsors. The research are arranged according to: coal chemistry, aqueous chemistry at high temperatures and pressures, geochemistry, chemistry of advanced inorganic materials, structure and dynamics of advanced polymeric materials, chemistry of transuranium elements and compounds, chemical and structural principles in solvent extraction, surface science related to heterogeneous catalysis, photolytic transformations of hazardous organics, DNA sequencing and mapping, and special topics.

Systems chemistry: All in a spin

Science.gov (United States)

Clark, Lucy; Lightfoot, Philip

2016-05-01

A fundamental challenge in systems chemistry is to engineer the emergence of complex behaviour. The collective structures of metal cyanide chains have now been interpreted in the same manner as the myriad of magnetic phases displayed by frustrated spin systems, highlighting a symbiotic approach between systems chemistry and magnetism.

Comparative assessment of university chemistry undergraduate ...

African Journals Online (AJOL)

A comparative analysis of the structure of undergraduate chemistry curricula of universities in the southwest of Nigeria with a view to establishing the relative proportion of the different areas of chemistry each curriculum accommodates. It is a qualitative research, involving content analysis with a partial quantitative analysis ...

Probing the chemistry, electronic structure and redox energetics in pentavalent organometallic actinide complexes

Energy Technology Data Exchange (ETDEWEB)

Graves, Christopher R [Los Alamos National Laboratory; Vaughn, Anthony E [Los Alamos National Laboratory; Morris, David E [Los Alamos National Laboratory; Kiplinger, Jaqueline L [Los Alamos National Laboratory

2008-01-01

Complexes of the early actinides (Th-Pu) have gained considerable prominence in organometallic chemistry as they have been shown to undergo chemistries not observed with their transition- or lanthanide metal counterparts. Further, while bonding in f-element complexes has historically been considered to be ionic, the issue of covalence remains a subject of debate in the area of actinide science, and studies aimed at elucidating key bonding interactions with 5f-orbitals continue to garner attention. Towards this end, our interests have focused on the role that metal oxidation state plays in the structure, reactivity and spectral properties of organouranium complexes. We report our progress in the synthesis of substituted U{sup V}-imido complexes using various routes: (1) Direct oxidation of U{sup IV}-imido complexes with copper(I) salts; (2) Salt metathesis with U{sup V}-imido halides; (3) Protonolysis and insertion of an U{sup V}-imido alkyl or aryl complex with H-N{double_bond}CPh{sub 2} or N{triple_bond}C-Ph, respectively, to form a U{sup V}-imido ketimide complex. Further, we report and compare the crystallographic, electrochemical, spectroscopic and magnetic characterization of the pentavalent uranium (C{sub 5}Me{sub 5}){sub 2}U({double_bond}N-Ar)(Y) series (Y = OTf, SPh, C{triple_bond}C-Ph, NPh{sub 2}, OPh, N{double_bond}CPh{sub 2}) to further interrogate the molecular, electronic, and magnetic structures of this new class of uranium complexes.

Rich structure in the correlation matrix spectra in non-equilibrium steady states.

Science.gov (United States)

Biswas, Soham; Leyvraz, Francois; Monroy Castillero, Paulino; Seligman, Thomas H

2017-01-17

It has been shown that, if a model displays long-range (power-law) spatial correlations, its equal-time correlation matrix will also have a power law tail in the distribution of its high-lying eigenvalues. The purpose of this paper is to show that the converse is generally incorrect: a power-law tail in the high-lying eigenvalues of the correlation matrix may exist even in the absence of equal-time power law correlations in the initial model. We may therefore view the study of the eigenvalue distribution of the correlation matrix as a more powerful tool than the study of spatial Correlations, one which may in fact uncover structure, that would otherwise not be apparent. Specifically, we show that in the Totally Asymmetric Simple Exclusion Process, whereas there are no clearly visible correlations in the steady state, the eigenvalues of its correlation matrix exhibit a rich structure which we describe in detail.

Structural and Chemical Evolution of Li- and Mn-rich Layered Cathode Material

Energy Technology Data Exchange (ETDEWEB)

Zheng, Jianming; Xu, Pinghong; Gu, Meng; Xiao, Jie; Browning, Nigel D.; Yan, Pengfei; Wang, Chong M.; Zhang, Jiguang

2015-02-24

Lithium (Li)- and manganese-rich (LMR) layered-structure materials are very promising cathodes for high energy density lithium-ion batteries. However, their voltage fading mechanism and its relationships with fundamental structural changes are far from being sufficiently understood. Here we report the detailed phase transformation pathway in the LMR cathode (Li[Li0.2Ni0.2Mn0.6]O2) during cycling for the samples prepared by hydro-thermal assistant method. It is found the transformation pathway of LMR cathode is closely correlated to its initial structure and preparation conditions. The results reveal that LMR cathode prepared by HA approach experiences a phase transformation from the layered structure to a LT-LiCoO2 type defect spinel-like structure (Fd-3m space group) and then to a disordered rock-salt structure (Fm-3m space group). The voltage fade can be well correlated with the Li ion insertion into octahedral sites, rather than tetrahedral sites, in both defect spinel-like structure and disordered rock-salt structure. The reversible Li insertion/removal into/from the disordered rock-salt structure is ascribed to the Li excess environment that can satisfy the Li percolating in the disordered rock-salt structure despite the increased kinetic barrier. Meanwhile, because of the presence of a great amount of oxygen vacancies, a significant decrease of Mn valence is detected in the cycled particle, which is below that anticipated for a potentially damaging Jahn-Teller distortion (+3.5). Clarification of the phase transformation pathway, cation redistribution, oxygen vacancy and Mn valence change undoubtedly provides insights into a profound understanding on the voltage fade, and capacity degradation of LMR cathode. The results also inspire us to further enhance the reversibility of LMR cathode via improving its surface structural stability.

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.

Summer Ephemeroptera, Plecoptera, and Trichoptera (EPT) species richness and community structure in the lower Illinois River basin of Illinois

Science.gov (United States)

DeWalt, R.E.; Webb, D.W.; Harris, M.A.

1999-01-01

Ephemeroptera, Plecoptera, and Trichoptera (EPT) species richness is useful for monitoring stream health, but no published studies in Illinois quantitatively document EPT richness or assemblage structure. The objectives of this study were to characterize adult EPT richness and structure and relate these to relative water quality at eight stream sites (160-69,300 km3 area) in the lower Illinois River basin. Adults were ultra-violet light trapped in June, July, and August 1997. Nutrient enrichment by nitrate and nitrite nitrogen was strongly evident, especially in smaller drainages, while critical loss of stable habitat was observed in larger water bodies. Seventy EPT species were identified from 17,889 specimens. Trichoptera were by far the most speciose (41 species), followed by Ephemeroptera (26), and Plecoptera (3). Caddisflies also dominated species richness across sites, contributing 18.0 of the average 28.9 total EPT species collected. Site EPT richness varied significantly (F = 5.51, p = 0.003, df = 7), with smaller drainages supporting greater richness, generally. Differences were also evident for months (F = 21.7, p = 0.0001, df = 2), with June being lower (11.8 average) than either July (20.6) or August (18.1) values. Hilsenhoff biotic index (HBI) scores did not vary significantly across sites (F = 0.7, p = 0.7, df = 7), but were different across months (F = 5.4, p = 0.02, df = 2). June (4.23) and July (4.53) means were not different, but both were lower (of better quality) than August (5.33) scores. The relationship of EPT to HBI scores was not investigated statistically due to problems of sample size and interdependence of monthly samples, but graphical analysis suggested no consistent relationship. This suggested a decoupling of the HBI from the EPT and implied that the gain in taxonomic resolution achieved by using adults outstripped the resolution of the HBI. Use of the HBI to characterize adult aquatic insect communities is discouraged. New state

Structural Analyses of Phase Stability in Amorphous and Partially Crystallized Ge-Rich GeTe Films Prepared by Atomic Layer Deposition.

Science.gov (United States)

Gwon, Taehong; Mohamed, Ahmed Yousef; Yoo, Chanyoung; Park, Eui-Sang; Kim, Sanggyun; Yoo, Sijung; Lee, Han-Koo; Cho, Deok-Yong; Hwang, Cheol Seong

2017-11-29

The local bonding structures of Ge x Te 1-x (x = 0.5, 0.6, and 0.7) films prepared through atomic layer deposition (ALD) with Ge(N(Si(CH 3 ) 3 ) 2 ) 2 and ((CH 3 ) 3 Si) 2 Te precursors were investigated using Ge K-edge X-ray absorption spectroscopy (XAS). The results of the X-ray absorption fine structure analyses show that for all of the compositions, the as-grown films were amorphous with a tetrahedral Ge coordination of a mixture of Ge-Te and Ge-Ge bonds but without any signature of Ge-GeTe decomposition. The compositional evolution in the valence band electronic structures probed through X-ray photoelectron spectroscopy suggests a substantial chemical influence of additional Ge on the nonstoichiometric GeTe. This implies that the ALD process can stabilize Ge-abundant bonding networks like -Te-Ge-Ge-Te- in amorphous GeTe. Meanwhile, the XAS results on the Ge-rich films that had undergone post-deposition annealing at 350 °C show that the parts of the crystalline Ge-rich GeTe became separated into Ge crystallites and rhombohedral GeTe in accordance with the bulk phase diagram, whereas the disordered GeTe domains still remained, consistent with the observations of transmission electron microscopy and Raman spectroscopy. Therefore, amorphousness in GeTe may be essential for the nonsegregated Ge-rich phases and the low growth temperature of the ALD enables the achievement of the structurally metastable phases.

A Methane-Rich Early Mars: Implications for Habitability and the Emergence of Life

Science.gov (United States)

Wong, Michael L.; Friedson, Andrew James; Willacy, Karen; Shia, Run-Lie; Yung, Yuk; Russell, Michael J.

2017-10-01

We investigate the radiation and chemistry of a ~4.0 Ga, CH4-rich martian atmosphere in an effort to assess whether or not Mars was once habitable and suitable for the emergence of life. High atmospheric CH4 may be consistent with a mantle that does not reach the requisite pressure (24 GPa) and temperature (1900 K) for the silicate spinel-to-perovskite transition (Dale et al., 2012; McCammon, 1997; Wadhwa, 2001; Wood et al., 2006). Impact degassing from chondritic material can also contribute substantial amounts of CH4 to the atmosphere (Schaefer and Fegley, 2007). CH4 plays an important role in atmospheric radiation. Atmospheric models have demonstrated that a purely CO2 atmosphere, even one as massive as 7 bars, is incapable of heating Mars above an annual-mean surface temperature of 273 K (Forget et al., 2013), although recent studies show that recurring wet states could have been induced in an H2-rich atmosphere (Batalha et al., 2015, 2016). We show that CH4 alone is insufficient to warm early Mars above freezing—in fact it produces an anti-greenhouse effect—but it substantially raises middle atmospheric temperatures. We determine whether or not such high temperatures could prolong the photochemical lifetime of SO2, another potent greenhouse gas. We use RC1D, a non-gray 1-D radiative-convective equilibrium model, to calculate the atmospheric thermal structure consistent with the radiative heating and cooling associated with the composition computed at each chemical model time step. KINETICS, the Caltech/JPL chemistry transport model (e.g. Nair et al., 1994), determines the chemical makeup of the atmosphere, evaluating steady-state chemical profiles and the synthesis of astrobiologically relevant molecules. H2O is in vapor pressure equilibrium at the surface. We consider conditions forced by the faint-young Sun’s spectrum and luminosity. By coupling RC1D and KINETICS, we are able to paint a more realistic picture of Mars’s early climate, calculating the

Structural and functional characterization of EIAV gp45 fusion peptide proximal region and asparagine-rich layer

Energy Technology Data Exchange (ETDEWEB)

Duan, Liangwei; Du, Jiansen [State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin 300071 (China); Wang, Xuefeng; Zhou, Jianhua; Wang, Xiaojun [State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001 (China); Liu, Xinqi, E-mail: liu2008@nankai.edu.cn [State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin 300071 (China)

2016-04-15

Equine infectious anaemia virus (EIAV) and human immunodeficiency virus (HIV) are members of the lentiviral genus. Similar to HIV gp41, EIAV gp45 is a fusogenic protein that mediates fusion between the viral particle and the host cell membrane. The crystal structure of gp45 reported reveals a different conformation in the here that includes the fusion peptide proximal region (FPPR) and neighboring asparagine-rich layer compared with previous HIV-1 gp41 structures. A complicated hydrogen-bond network containing a cluster of solvent molecules appears to be critical for the stability of the gp45 helical bundle. Interestingly, viral replication was relatively unaffected by site-directed mutagenesis of EIAV, in striking contrast to that of HIV-1. Based on these observations, we speculate that EIAV is more adaptable to emergent mutations, which might be important for the evolution of EIAV as a quasi-species, and could potentially contribute to the success of the EIAV vaccine. - Highlights: • The crystal structure of EIAV gp45 was determined. • The fusion peptide proximal region adopts a novel conformation different to HIV-1. • The asparagine-rich layer includes an extensive hydrogen-bond network. • These regions of EIAV are highly tolerant to mutations. • The results provide insight into the mechanism of gp41/gp45-mediated membrane fusion.

A Structural View on Medicinal Chemistry Strategies against Drug Resistance.

Science.gov (United States)

Agnello, Stefano; Brand, Michael; Chellat, Mathieu F; Gazzola, Silvia; Riedl, Rainer

2018-05-30

The natural phenomenon of drug resistance represents a generic impairment that hampers the benefits of drugs in all major clinical indications. Antibacterials and antifungals are affected as well as compounds for the treatment of cancer, viral infections or parasitic diseases. Despite the very diverse set of biological targets and organisms involved in the development of drug resistance, underlying molecular processes have been identified to understand the emergence of resistance and to overcome this detrimental mechanism. Detailed structural information of the root causes for drug resistance is nowadays frequently available to design next generation drugs anticipated to suffer less from resistance. This knowledge-based approach is a prerequisite in the fight against the inevitable occurrence of drug resistance to secure the achievements of medicinal chemistry in the future. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Developing and Implementing a Reorganized Undergraduate Chemistry Curriculum Based on the Foundational Chemistry Topics of Structure, Reactivity, and Quantitation

Science.gov (United States)

Schaller, Chris P.; Graham, Kate J.; Johnson, Brian J.; Fazal, M. A.; Jones, T. Nicholas; McIntee, Edward J.; Jakubowski, Henry V.

2014-01-01

The recent revision of undergraduate curricular guidelines from the American Chemical Society Committee on Professional Training (ACS-CPT) has generated interest in examining new ways of organizing course sequences both for chemistry majors and for nonmajors. A radical reconstruction of the foundation-level chemistry curriculum is presented in…

High-spin structure of neutron-rich Dy isotopes

Indian Academy of Sciences (India)

Neutron-rich Dy isotopes; high-spin states; g-factors; cranked HFB theory. ... for 164Dy marking a clear separation in the behaviour as a function of neutron ... cipal x-axis as the cranking axis) in this mass region we have planned to make a sys-.

Spectroscopy and chemistry of uranium IV

International Nuclear Information System (INIS)

Folcher, G.; Rigny, P.

1980-06-01

Different fundamental research papers on uranium IV are presented, some were never edited. Molecular spectroscopy was used for identification and structural study of uranium IV in aqueous or organic solutions. The fields studied are: coordination, stereochemistry, electronic structure and chemical properties. For interpretation of results some studies were made with solid compounds or with thorium compounds or thorium complexes. Knowledge of actinides chemistry is improved, uranium and thorium being models for 5 f ions, extractive chemistry is better understood and new applications are possible [fr

Relative influence of soil chemistry and topography on soil available micronutrients by structural equation modeling

OpenAIRE

Zhu, Hongfen; Zhao, Ying; Nan, Feng; Duan, Yonghong; Bi, Rutian

2016-01-01

Soil chemical and topographic properties are two important factors influencing available micronutrient distribution of soil in the horizontal dimension. The objective of this study was to explore the relative influence of soil chemistry (including soil pH, soil organic matter, total nitrogen, available phosphorus, and available potassium) and topography (including elevation, slope, aspect, and wetness index) on the availability of micronutrients (Fe, Mn, Cu, Zn, and B) using structural equati...

Impact of the Fused Deposition (FDM Printing Process on Polylactic Acid (PLA Chemistry and Structure

Directory of Open Access Journals (Sweden)

Michael Arthur Cuiffo

2017-06-01

Full Text Available Polylactic acid (PLA is an organic polymer commonly used in fused deposition (FDM printing and biomedical scaffolding that is biocompatible and immunologically inert. However, variations in source material quality and chemistry make it necessary to characterize the filament and determine potential changes in chemistry occurring as a result of the FDM process. We used several spectroscopic techniques, including laser confocal microscopy, Fourier transform infrared (FTIR spectroscopy and photoacousitc FTIR spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS in order to characterize both the bulk and surface chemistry of the source material and printed samples. Scanning electron microscopy (SEM and differential scanning calorimetry (DSC were used to characterize morphology, cold crystallinity, and the glass transition and melting temperatures following printing. Analysis revealed calcium carbonate-based additives which were reacted with organic ligands and potentially trace metal impurities, both before and following printing. These additives became concentrated in voids in the printed structure. This finding is important for biomedical applications as carbonate will impact subsequent cell growth on printed tissue scaffolds. Results of chemical analysis also provided evidence of the hygroscopic nature of the source material and oxidation of the printed surface, and SEM imaging revealed micro- and submicron-scale roughness that will also impact potential applications.

Chemistry Division annual progress report for period ending July 31, 1981

International Nuclear Information System (INIS)

1982-01-01

Research is reported on: chemistry of coal liquefaction, aqueous chemistry at high temperatures, geosciences, high-temperature chemistry and thermodynamics of structural materials, chemistry of TRU elements and compounds, separations chemistry, electrochemistry, nuclear waste chemistry, chemical physics, theoretical chemistry, inorganic chemistry of hydrogen cycles, molten salt systems, and enhanced oil recovery. Separate abstracts were prepared for the sections dealing with coal liquefaction, TRU elements and compounds, separations, nuclear wastes, and enhanced oil recovery

Chemistry Division annual progress report for period ending July 31, 1981

Energy Technology Data Exchange (ETDEWEB)

1982-01-01

Research is reported on: chemistry of coal liquefaction, aqueous chemistry at high temperatures, geosciences, high-temperature chemistry and thermodynamics of structural materials, chemistry of TRU elements and compounds, separations chemistry, electrochemistry, nuclear waste chemistry, chemical physics, theoretical chemistry, inorganic chemistry of hydrogen cycles, molten salt systems, and enhanced oil recovery. Separate abstracts were prepared for the sections dealing with coal liquefaction, TRU elements and compounds, separations, nuclear wastes, and enhanced oil recovery. (DLC)

Unprecedented propane–SCR-NOx activity over template-free synthesized Al-rich Co-BEA* zeolite

Czech Academy of Sciences Publication Activity Database

Sazama, Petr; Mokrzycki, Lukasz; Wichterlová, Blanka; Vondrová, Alena; Pilař, Radim; Dědeček, Jiří; Sklenák, Štěpán; Tabor, Edyta

2015-01-01

Roč. 332, DEC 2015 (2015), s. 201-211 ISSN 0021-9517 R&D Projects: GA TA ČR(CZ) TH01021259; GA ČR GA15-13876S Institutional support: RVO:61388955 Keywords : beta zeolite * Al-rich BEA* * OSDA-free synthesis Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 7.354, year: 2015

Structural evolution of Ge-rich Si1−xGex films deposited by jet-ICPCVD

Directory of Open Access Journals (Sweden)

Yu Wang

2015-11-01

Full Text Available Amorphous Ge-rich Si1−xGex films with local Ge-clustering were deposited by dual-source jet-type inductively coupled plasma chemical-vapor deposition (jet-ICPCVD. The structural evolution of the deposited films annealed at various temperatures (Ta is investigated. Experimental results indicate that the crystallization occurs to form Ge and Si clusters as Ta = 500 °C. With raising Ta up to 900 °C, Ge clusters percolate together and Si diffuses and redistributes to form a Ge/SiGe core/shell structure, and some Ge atoms partially diffuse to the surface as a result of segregation. The present work will be helpful in understanding the structural evolution process of a hybrid SiGe films and beneficial for further optimizing the microstructure and properties.

The Materials Chemistry of Atomic Oxygen with Applications to Anisotropic Etching of Submicron Structures in Microelectronics and the Surface Chemistry Engineering of Porous Solids

Science.gov (United States)

Koontz, Steve L.; Leger, Lubert J.; Wu, Corina; Cross, Jon B.; Jurgensen, Charles W.

1994-01-01

Neutral atomic oxygen is the most abundant component of the ionospheric plasma in the low Earth orbit environment (LEO; 200 to 700 kilometers altitude) and can produce significant degradation of some spacecraft materials. In order to produce a more complete understanding of the materials chemistry of atomic oxygen, the chemistry and physics of O-atom interactions with materials were determined in three radically different environments: (1) The Space Shuttle cargo bay in low Earth orbit (the EOIM-3 space flight experiment), (2) a high-velocity neutral atom beam system (HVAB) at Los Alamos National Laboratory (LANL), and (3) a microwave-plasma flowing-discharge system at JSC. The Space Shuttle and the high velocity atom beam systems produce atom-surface collision energies ranging from 0.1 to 7 eV (hyperthermal atoms) under high-vacuum conditions, while the flowing discharge system produces a 0.065 eV surface collision energy at a total pressure of 2 Torr. Data obtained in the three different O-atom environments referred to above show that the rate of O-atom reaction with polymeric materials is strongly dependent on atom kinetic energy, obeying a reactive scattering law which suggests that atom kinetic energy is directly available for overcoming activation barriers in the reaction. General relationships between polymer reactivity with O atoms and polymer composition and molecular structure have been determined. In addition, vacuum ultraviolet photochemical effects have been shown to dominate the reaction of O atoms with fluorocarbon polymers. Finally, studies of the materials chemistry of O atoms have produced results which may be of interest to technologists outside the aerospace industry. Atomic oxygen 'spin-off' or 'dual use' technologies in the areas of anisotropic etching in microelectronic materials and device processing, as well as surface chemistry engineering of porous solid materials are described.

Nuclear chemistry research for the safe disposal of nuclear waste

International Nuclear Information System (INIS)

Fanghaenel, Thomas

2011-01-01

The safe disposal of high-level nuclear waste and spent nuclear fuel is of key importance for the future sustainable development of nuclear energy. Concepts foresee the isolation of the nuclear waste in deep geological formations. The long-term radiotoxicity of nuclear waste is dominated by plutonium and the minor actinides. Hence it is essential for the performance assessment of a nuclear waste disposal to understand the chemical behaviour of actinides in a repository system. The aqueous chemistry and thermodynamics of actinides is rather complex in particular due to their very rich redox chemistry. Recent results of our detailed study of the Plutonium and Neptunium redox - and complexation behaviour are presented and discussed. (author)

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

ANT International chemistry update and best practices

International Nuclear Information System (INIS)

Nordmann, F.; Odar, S.; Venz, H.; Kysela, J.; Ruehle, W.; Riess, R.

2010-01-01

There is an increasing number of Nuclear Power Plants (NPP) in various countries. Their chemistry practices are different due to the variety of designs and experiences while in the past the view was more monolithic. This is allowing a very rich experience that is extremely difficult to fully be aware of. ANT International is now collecting and evaluating these data as well as related R and D Information. This allows interested parties to have an easier access to the various sources of information. The chemistry experts associated to ANT International have been gathering a comprehensive detailed view of: The numerous laboratory data gained all over the world during the past decades; The extensive plant operating experiences with various types of chemistry strategies, crosschecked for various types of reactors designs and materials; An experienced international knowledge able to give the comprehensive overview that young engineers now in charge of many other activities are unable to fully cover. This paper gives the core conclusions of the detailed ANT International reports and results that have recently been gathered in the area of chemistry. It particularly covers: The primary water chemistry and its relation with radionuclides, dose rates and fuel behaviour; The secondary water chemistry focusing on its rationale selection depending on materials, design and other constraints; The start up and shutdown chemistry with it large variety of practices hardly understandable even for some experts; and, The maintenance remedies such as decontamination, steam generator cleaning and its alternate options. Various types of Reactor designs (PWR, VVER, BWR, CANDU®) are considered. The different materials, for example the impact of steam generator tubing and its evolution on the secondary water chemistry rationale or on the radioactivity built-up in the primary coolant, are described. The ways to improve the plant operation with a long term reliability as well as the most

Titan's organic chemistry: Results of simulation experiments

Science.gov (United States)

Sagan, Carl; Thompson, W. Reid; Khare, Bishun N.

1992-01-01

Recent low pressure continuous low plasma discharge simulations of the auroral electron driven organic chemistry in Titan's mesosphere are reviewed. These simulations yielded results in good accord with Voyager observations of gas phase organic species. Optical constants of the brownish solid tholins produced in similar experiments are in good accord with Voyager observations of the Titan haze. Titan tholins are rich in prebiotic organic constituents; the Huygens entry probe may shed light on some of the processes that led to the origin of life on Earth.

Measurements of local chemistry and structure in Ni(O)-YSZ composites during reduction using energy-filtered environmental TEM

DEFF Research Database (Denmark)

Jeangros, Quentin; Hansen, Thomas Willum; Wagner, Jakob Birkedal

2014-01-01

Energy-filtered transmission electron microscopy images are acquired during the reduction of a NiO-YSZ composite in H-2 up to 600 degrees C. Temperature-resolved quantitative information about both chemistry and structure is extracted with nm spatial resolution from the data, paving the way...

Structures of pseudechetoxin and pseudecin, two snake-venom cysteine-rich secretory proteins that target cyclic nucleotide-gated ion channels: implications for movement of the C-terminal cysteine-rich domain

International Nuclear Information System (INIS)

Suzuki, Nobuhiro; Yamazaki, Yasuo; Brown, R. Lane; Fujimoto, Zui; Morita, Takashi; Mizuno, Hiroshi

2008-01-01

The structures of pseudechetoxin and pseudecin suggest that both proteins bind to cyclic nucleotide-gated ion channels in a manner in which the concave surface occludes the pore entrance. Cyclic nucleotide-gated (CNG) ion channels play pivotal roles in sensory transduction by retinal photoreceptors and olfactory neurons. The elapid snake toxins pseudechetoxin (PsTx) and pseudecin (Pdc) are the only known protein blockers of CNG channels. These toxins belong to a cysteine-rich secretory protein (CRISP) family containing an N-terminal pathogenesis-related proteins of group 1 (PR-1) domain and a C-terminal cysteine-rich domain (CRD). PsTx and Pdc are highly homologous proteins, but their blocking affinities on CNG channels are different: PsTx blocks both the olfactory and retinal channels with ∼15–30-fold higher affinity than Pdc. To gain further insights into their structure and function, the crystal structures of PsTx, Pdc and Zn 2+ -bound Pdc were determined. The structures revealed that most of the amino-acid-residue differences between PsTx and Pdc are located around the concave surface formed between the PR-1 domain and the CRD, suggesting that the concave surface is functionally important for CNG-channel binding and inhibition. A structural comparison in the presence and absence of Zn 2+ ion demonstrated that the concave surface can open and close owing to movement of the CRD upon Zn 2+ binding. The data suggest that PsTx and Pdc occlude the pore entrance and that the dynamic motion of the concave surface facilitates interaction with the CNG channels

Structures of pseudechetoxin and pseudecin, two snake-venom cysteine-rich secretory proteins that target cyclic nucleotide-gated ion channels: implications for movement of the C-terminal cysteine-rich domain

Energy Technology Data Exchange (ETDEWEB)

Suzuki, Nobuhiro [Department of Applied Biochemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8572 (Japan); Department of Biochemistry, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602 (Japan); Yamazaki, Yasuo [Department of Biochemistry, Meiji Pharmaceutical University, Kiyose, Tokyo 204-8588 (Japan); Brown, R. Lane [Neurological Science Institute, Oregon Health and Science University, Beaverton, Oregon 97006 (United States); Fujimoto, Zui [Department of Biochemistry, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602 (Japan); Morita, Takashi, E-mail: tmorita@my-pharm.ac.jp [Department of Biochemistry, Meiji Pharmaceutical University, Kiyose, Tokyo 204-8588 (Japan); Mizuno, Hiroshi, E-mail: tmorita@my-pharm.ac.jp [Department of Biochemistry, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602 (Japan); VALWAY Technology Center, NEC Soft Ltd, Koto-ku, Tokyo 136-8627 (Japan); Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology, Central 6, Tsukuba, Ibaraki 305-8566 (Japan); Department of Applied Biochemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8572 (Japan)

2008-10-01

The structures of pseudechetoxin and pseudecin suggest that both proteins bind to cyclic nucleotide-gated ion channels in a manner in which the concave surface occludes the pore entrance. Cyclic nucleotide-gated (CNG) ion channels play pivotal roles in sensory transduction by retinal photoreceptors and olfactory neurons. The elapid snake toxins pseudechetoxin (PsTx) and pseudecin (Pdc) are the only known protein blockers of CNG channels. These toxins belong to a cysteine-rich secretory protein (CRISP) family containing an N-terminal pathogenesis-related proteins of group 1 (PR-1) domain and a C-terminal cysteine-rich domain (CRD). PsTx and Pdc are highly homologous proteins, but their blocking affinities on CNG channels are different: PsTx blocks both the olfactory and retinal channels with ∼15–30-fold higher affinity than Pdc. To gain further insights into their structure and function, the crystal structures of PsTx, Pdc and Zn{sup 2+}-bound Pdc were determined. The structures revealed that most of the amino-acid-residue differences between PsTx and Pdc are located around the concave surface formed between the PR-1 domain and the CRD, suggesting that the concave surface is functionally important for CNG-channel binding and inhibition. A structural comparison in the presence and absence of Zn{sup 2+} ion demonstrated that the concave surface can open and close owing to movement of the CRD upon Zn{sup 2+} binding. The data suggest that PsTx and Pdc occlude the pore entrance and that the dynamic motion of the concave surface facilitates interaction with the CNG channels.

General Chemistry for Engineers.

Science.gov (United States)

Kybett, B. D.

1982-01-01

Discusses the relationship between molecular structure, intermolecular forces, and tensile strengths of a polymer and suggests that this is a logical way to introduce polymers into a general chemistry course. (Author/JN)

Millimeter wave studies of circumstellar chemistry

Science.gov (United States)

Tenenbaum, Emily Dale

2010-06-01

Millimeter wave studies of molecules in circumstellar envelopes and a planetary nebula have been conducted. Using the Submillimeter Telescope (SMT) of the Arizona Radio Observatory (ARO) on Mt. Graham, a comparative spectral survey from 215-285 GHz was carried out of the carbon-rich asymptotic giant branch star IRC +10216 and the oxygen-rich supergiant VY Canis Majoris. A total of 858 emission lines were observed in both objects, arising from 40 different molecules. In VY Canis Majoris, AlO, AlOH, and PO were detected for the first time in interstellar space. In IRC +10216, PH3 was detected for the first time beyond the solar system, and C3O, and CH2NH were found for the first time in a circumstellar envelope. Additionally, in the evolved planetary nebula, the Helix, H2CO, C2H, and cyclic-C3H2 were observed using the SMT and the Kitt Peak 12 m telescopes. The presence of these three molecules in the Helix suggests that relatively complex chemistry occurs in planetary nebulae, despite the harsh ultraviolet field. Overall, the research on molecules in circumstellar and planetary nebulae furthers our understanding of the nature of the material that is fed back into the interstellar medium from evolved stars. Besides telescope work, laboratory research was also conducted -- the rotational spectrum of ZnCl was measured and its bond length and rotational constants were determined. Lastly, in partial fulfillment of a graduate certificate in entrepreneurial chemistry, the commercial applications of terahertz spectroscopy were explored through literature research.

Predictive Modeling in Actinide Chemistry and Catalysis

Energy Technology Data Exchange (ETDEWEB)

Yang, Ping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-05-16

These are slides from a presentation on predictive modeling in actinide chemistry and catalysis. The following topics are covered in these slides: Structures, bonding, and reactivity (bonding can be quantified by optical probes and theory, and electronic structures and reaction mechanisms of actinide complexes); Magnetic resonance properties (transition metal catalysts with multi-nuclear centers, and NMR/EPR parameters); Moving to more complex systems (surface chemistry of nanomaterials, and interactions of ligands with nanoparticles); Path forward and conclusions.

Is torrefaction of polysaccharides-rich biomass equivalent to carbonization of lignin-rich biomass?

Science.gov (United States)

Bilgic, E; Yaman, S; Haykiri-Acma, H; Kucukbayrak, S

2016-01-01

Waste biomass species such as lignin-rich hazelnut shell (HS) and polysaccharides-rich sunflower seed shell (SSS) were subjected to torrefaction at 300°C and carbonization at 600°C under nitrogen. The structural variations in torrefied and carbonized biomasses were compared. Also, the burning characteristics under dry air and pure oxygen (oxy-combustion) conditions were investigated. It was concluded that the effects of carbonization on HS are almost comparable with the effects of torrefaction on SSS in terms of devolatilization and deoxygenation potentials and the increases in carbon content and the heating value. Consequently, it can be proposed that torrefaction does not provide efficient devolatilization from the lignin-rich biomass while it is relatively more efficient for polysaccharides-rich biomass. Heat-induced variations in biomass led to significant changes in the burning characteristics under both burning conditions. That is, low temperature reactivity of biomass reduced considerably and the burning shifted to higher temperatures with very high burning rates. Copyright © 2015 Elsevier Ltd. All rights reserved.

Popular Science Articles for Chemistry Teaching

Directory of Open Access Journals (Sweden)

Ketevan Kupatadze

2017-07-01

Full Text Available The presented paper reviews popular science articles (these articles are published in online magazine “The Teacher” as one of the methods of chemistry teaching. It describes which didactic principles they are in line with and how this type of articles can be used in order to kindle the interest of pupils, students and generally, the readers of other specialties, in chemistry.  The articles review the main topics of inorganic/organic chemistry, biochemistry and ecological chemistry in a simple and entertaining manner. A part of the articles is about "household" chemistry. Chemical topics are related to poetry, literature, history of chemistry or simply, to fun news. The paper delineates the structure of popular science articles and the features of engaging students. It also reviews the teachers' and students' interview results about the usage of popular science articles in chemistry teaching process. The aforementioned pedagogical study revealed that the popular science articles contain useful information not only for the students of other specialties, but also for future biologists and ecologists (having chemistry as a mandatory subject at their universities. The articles are effectively used by teachers on chemistry lessons to kindle students' interest in this subject. DOI: http://dx.doi.org/10.17807/orbital.v9i3.960 

Ice Chemistry in Interstellar Dense Molecular Clouds, Protostellar Disks, and Comets

Science.gov (United States)

Sandford, Scott A.

2015-01-01

Despite the low temperatures (T less than 20K), low pressures, and low molecular densities found in much of the cosmos, considerable chemistry is expected to occur in many astronomical environments. Much of this chemistry happens in icy grain mantles on dust grains and is driven by ionizing radiation. This ionizing radiation breaks chemical bonds of molecules in the ices and creates a host of ions and radicals that can react at the ambient temperature or when the parent ice is subsequently warmed. Experiments that similar these conditions have demonstrated a rich chemistry associated with these environments that leads to a wide variety of organic products. Many of these products are of considerable interest to astrobiology. For example, the irradiation of simple ices has been shown to abiotically produce amino acids, nucleobases, quinones, and amphiphiles, all compounds that play key roles in modern biochemistry. This suggests extraterrestrial chemistry could have played a role in the origin of life on Earth and, by extension, do so on planets in other stellar systems.

Structure of Se-rich As-Se glasses by high-resolution x-ray photoelectron spectroscopy

International Nuclear Information System (INIS)

Golovchak, R.; Kovalskiy, A.; Miller, A. C.; Jain, H.; Shpotyuk, O.

2007-01-01

To establish the validity of various proposed structural models, we have investigated the structure of the binary As x Se 100-x chalcogenide glass family (x≤40) by high-resolution x-ray photoelectron spectroscopy. From the composition dependence of the valence band, the contributions to the density of states from the 4p lone pair electrons of Se and the 4p bonding states and 4s electrons of Se and As are identified in the top part of the band. The analysis of Se 3d and As 3d core-level spectra supports the so-called chain crossing model for the atomic structure of Se-rich As x Se 100-x bulk glasses. The results also indicate small deviations (∼3-8%) from this model, especially for glass compositions with short Se chains (25 40 Se 60 and of Se-Se-Se fragments in a glass with composition x=30 is established

Advances in high temperature chemistry 1

CERN Document Server

Eyring, Leroy

2013-01-01

Advances in High Temperature Chemistry, Volume 1 describes the complexities and special and changing characteristics of high temperature chemistry. After providing a brief definition of high temperature chemistry, this nine-chapter book goes on describing the experiments and calculations of diatomic transition metal molecules, as well as the advances in applied wave mechanics that may contribute to an understanding of the bonding, structure, and spectra of the molecules of high temperature interest. The next chapter provides a summary of gaseous ternary compounds of the alkali metals used in

New insights into methane-oxygen ion chemistry

KAUST Repository

Alquaity, Awad B.S.; Chen, Bingjie; Han, Jie; Selim, Hatem; Belhi, Memdouh; Karakaya, Yasin; Kasper, Tina; Sarathy, Mani; Bisetti, Fabrizio; Farooq, Aamir

2016-01-01

External electric fields may reduce emissions and improve combustion efficiency by active control of combustion processes. In-depth, quantitative understanding of ion chemistry in flames enables predictive models to describe the effect of external electric fields on combustion plasma. This study presents detailed cation profile measurements in low-pressure, burner-stabilized, methane/oxygen/argon flames. A quadrupole molecular beam mass spectrometer (MBMS) coupled to a low-pressure (P =30Torr) combustion chamber was utilized to measure ion signals as a function of height above the burner. Lean, stoichiometric and rich flames were examined to evaluate the dependence of ion chemistry on flame stoichiometry. Additionally, for the first time, cataloging of flame cations is performed using a high mass resolution time-of-flight mass spectrometer (TOF-MS) to distinguish ions with the same nominal mass. In the lean and stoichiometric flames, the dominant ions were HO, CHO , CHO, CHO and CHO, whereas large signals were measured for HO, CH and CHO in the rich flame. The spatial distribution of cations was compared with results from numerical simulations constrained by thermocouple-measured flame temperatures. Across all flames, the predicted HO decay rate was noticeably faster than observed experimentally. Sensitivity analysis showed that the mole fraction of HO is most sensitive to the rate of chemi-ionization CH+O↔CHO +E. To our knowledge, this work represents the first detailed measurements of positive ions in canonical low-pressure methane flames.

New insights into methane-oxygen ion chemistry

KAUST Repository

Alquaity, Awad B.S.

2016-06-15

External electric fields may reduce emissions and improve combustion efficiency by active control of combustion processes. In-depth, quantitative understanding of ion chemistry in flames enables predictive models to describe the effect of external electric fields on combustion plasma. This study presents detailed cation profile measurements in low-pressure, burner-stabilized, methane/oxygen/argon flames. A quadrupole molecular beam mass spectrometer (MBMS) coupled to a low-pressure (P =30Torr) combustion chamber was utilized to measure ion signals as a function of height above the burner. Lean, stoichiometric and rich flames were examined to evaluate the dependence of ion chemistry on flame stoichiometry. Additionally, for the first time, cataloging of flame cations is performed using a high mass resolution time-of-flight mass spectrometer (TOF-MS) to distinguish ions with the same nominal mass. In the lean and stoichiometric flames, the dominant ions were HO, CHO , CHO, CHO and CHO, whereas large signals were measured for HO, CH and CHO in the rich flame. The spatial distribution of cations was compared with results from numerical simulations constrained by thermocouple-measured flame temperatures. Across all flames, the predicted HO decay rate was noticeably faster than observed experimentally. Sensitivity analysis showed that the mole fraction of HO is most sensitive to the rate of chemi-ionization CH+O↔CHO +E. To our knowledge, this work represents the first detailed measurements of positive ions in canonical low-pressure methane flames.

Supramolecular chemistry-general principles and selected examples from anion recognition and metallosupramolecular chemistry.

Science.gov (United States)

Albrecht, Markus

2007-12-01

This review gives an introduction into supramolecular chemistry describing in the first part general principles, focusing on terms like noncovalent interaction, molecular recognition, self-assembly, and supramolecular function. In the second part those will be illustrated by simple examples from our laboratories. Supramolecular chemistry is the science that bridges the gap between the world of molecules and nanotechnology. In supramolecular chemistry noncovalent interactions occur between molecular building blocks, which by molecular recognition and self-assembly form (functional) supramolecular entities. It is also termed the "chemistry of the noncovalent bond." Molecular recognition is based on geometrical complementarity based on the "key-and-lock" principle with nonshape-dependent effects, e.g., solvatization, being also highly influential. Self-assembly leads to the formation of well-defined aggregates. Hereby the overall structure of the target ensemble is controlled by the symmetry features of the certain building blocks. Finally, the aggregates can possess special properties or supramolecular functions, which are only found in the ensemble but not in the participating molecules. This review gives an introduction on supramolecular chemistry and illustrates the fundamental principles by recent examples from our group.

The Effect of Aqueous Alteration in Antarctic Carbonaceous Chondrites from Comparative ICP-MS Bulk Chemistry

Science.gov (United States)

Alonso-Azcarate, J.; Trigo-Rodriguez, J. M.; Moyano-Cambero, C. E.; Zolensky, M.

2014-01-01

Terrestrial ages of Antarctic carbonaceous chondrites (CC) indicate that these meteorites have been preserved in or on ice for, at least, tens of thousands of years. Due to the porous structure of these chondrites formed by the aggregation of silicate-rich chondrules, refractory inclusions, metal grains, and fine-grained matrix materials, the effect of pervasive terrestrial water is relevant. Our community defends that pristine CC matrices are representing samples of scarcely processed protoplanetary disk materials as they contain stellar grains, but they might also trace parent body processes. It is important to study the effects of terrestrial aqueous alteration in promoting bulk chemistry changes, and creating distinctive alteration minerals. Particularly because it is thought that aqueous alteration has particularly played a key role in some CC groups in modifying primordial bulk chemistry, and homogenizing the isotopic content of fine-grained matrix materials. Fortunately, the mineralogy produced by parent-body and terrestrial aqueous alteration processes is distinctive. With the goal to learn more about terrestrial alteration in Antarctica we are obtaining reflectance spectra of CCs, but also performing ICP-MS bulk chemistry of the different CC groups. A direct comparison with the mean bulk elemental composition of recovered falls might inform us on the effects of terrestrial alteration in finds. With such a goal, in the current work we have analyzed some members representative of CO and CM chondrite groups.

Electronic structure and fine structural features of the air-grown UNxOy on nitrogen-rich uranium nitride

Science.gov (United States)

Long, Zhong; Zeng, Rongguang; Hu, Yin; Liu, Jing; Wang, Wenyuan; Zhao, Yawen; Luo, Zhipeng; Bai, Bin; Wang, Xiaofang; Liu, Kezhao

2018-06-01

Oxide formation on surface of nitrogen-rich uranium nitride film/particles was investigated using X-ray photoelectron spectroscopy (XPS), auger electron spectroscopy (AES), aberration-corrected transmission electron microscopy (TEM), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) coupled with electron energy-loss spectroscopy (EELS). XPS and AES studies indicated that the oxidized layer on UN2-x film is ternary compound uranium oxynitride (UNxOy) in 5-10 nm thickness. TEM/HAADF-STEM and EELS studies revealed the UNxOy crystallizes in the FCC CaF2-type structure with the lattice parameter close to the CaF2-type UN2-x matrix. The work can provide further information to the oxidation mechanism of uranium nitride.

Consequences of buffelgrass pasture development for primary productivity, perennial plant richness, and vegetation structure in the drylands of Sonora, Mexico.

Science.gov (United States)

Franklin, Kimberly; Molina-Freaner, Francisco

2010-12-01

In large parts of northern Mexico native plant communities are being converted to non-native buffelgrass (Pennisetum ciliare) pastures, and this conversion could fundamentally alter primary productivity and species richness. In Sonora, Mexico land conversion is occurring at a regional scale along a rainfall-driven gradient of primary productivity, across which native plant communities transition from desert scrub to thorn scrub. We used a paired sampling design to compare a satellite-derived index of primary productivity, richness of perennial plant species, and canopy-height profiles of native plant communities with buffelgrass pastures. We sampled species richness across a gradient of primary productivity in desert scrub and thorn scrub vegetation to examine the influence of site productivity on the outcomes of land conversion. We also examined the influence of pasture age on species richness of perennial plants. Index values of primary productivity were lower in buffelgrass pastures than in native vegetation, which suggests a reduction in primary productivity. Land conversion reduced species richness by approximately 50% at local and regional scales, reduced tree and shrub cover by 78%, and reduced canopy height. Land conversion disproportionately reduced shrub species richness, which reflects the common practice among Sonoran ranchers of conserving certain tree and cactus species. Site productivity did not affect the outcomes of land conversion. The age of a buffelgrass pasture was unrelated to species richness within the pasture, which suggests that passive recovery of species richness to preconversion levels is unlikely. Our findings demonstrate that land conversion can result in large losses of plant species richness at local and regional scales and in substantial changes to primary productivity and vegetation structure, which casts doubt on the feasibility of restoring native plant communities without active intervention on the part of land managers. �

Crystal structure of modular sodium-rich and low-iron eudialyte from Lovozero alkaline massif

Energy Technology Data Exchange (ETDEWEB)

Rozenberg, K. A.; Rastsvetaeva, R. K., E-mail: rast@ns.crys.ras.ru; Aksenov, S. M. [Federal Scientific Research Center “Crystallography and Photonics”, Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2016-09-15

The structure of the sodium-rich representative of the eudialyte group found by A.P. Khomyakov at the Lovozero massif (Kola Peninsula) is studied by X-ray diffraction. The trigonal cell parameters are: a = 14.2032(1) and c = 60.612(1) Å, V = 10589.13 Å3, space group R3m. The structure is refined to the final R = 5.0% in the anisotropic approximation of atomic displacement parameters using 3742|F| > 3σ(F). The idealized formula (Z = 3) is Na{sub 37}Ca{sub 10}Mn{sub 2}FeZr{sub 6}Si{sub 50}(Ti, Nb){sub 2}O{sub 144}(OH){sub 5}Cl{sub 3} · H{sub 2}O. Like other 24-layer minerals of the eudialyte group, this mineral has a modular structure. Its structure contains two modules, namely, “alluaivite” (with an admixture of “eudialyte”) and “kentbrooksite,” called according to the main structural fragments of alluaivite, eudialyte, and kentbrooksite. The mineral found at the Lovozero alkaline massif shows some chemical and symmetry-structural distinctions from the close-in-composition labyrinthite modular mineral from the Khibiny massif. The difference between the minerals stems from different geochemical conditions of mineral formation in the two regions.

On the transition from tin-rich to antimony-rich European white soda-glass trade beads for the Senecas of Northeastern North America

International Nuclear Information System (INIS)

Sempowski, M.L.; Nohe, A.W.; Moreau, J.F.; Karklins, K.; Aufreiter, S.; Toronto Univ. ON; Hancock, R.G.V.; Royal Military College, Kingston, ON

2000-01-01

It has been shown that several modifications occurred, over the span of the 17th to 19th centuries, in the agents used to opacify European-made white soda-glass beads that were transmitted as trade goods to northeastern North America. Tin was used at the beginning of the 17th century, followed by Sb later in the century, and then by As during the 18th and 19th centuries. In an attempt to define more closely the transition from Sn-rich to Sb-rich white beads, 198 white glass beads from a number of archaeological sites in western New York State were analyzed. It was shown that the arrival of Sb-white soda-glass trade beads began in this region during the period from approximately A.D. 1625-1640, and that they had completely replaced Sn-white beads by A.D. 1675. Specific bead chemistries link a number of the archaeological sites. (author)

COMPARATIVE SPECTRA OF OXYGEN-RICH VERSUS CARBON-RICH CIRCUMSTELLAR SHELLS: VY CANIS MAJORIS AND IRC +10216 AT 215-285 GHz

International Nuclear Information System (INIS)

Tenenbaum, E. D.; Dodd, J. L.; Woolf, N. J.; Ziurys, L. M.; Milam, S. N.

2010-01-01

A sensitive (1σ rms at 1 MHz resolution ∼3 mK) 1 mm spectral line survey (214.5-285.5 GHz) of VY Canis Majoris (VY CMa) and IRC +10216 has been conducted to compare the chemistries of oxygen- and carbon-rich circumstellar envelopes. This study was carried out using the Submillimeter Telescope of the Arizona Radio Observatory with a new Atacama Large Millimeter Array type receiver. This survey is the first to chemically characterize an O-rich circumstellar shell at millimeter wavelengths. In VY CMa, 128 emission features were detected arising from 18 different molecules; and in IRC +10216, 720 lines were observed, assigned to 32 different species. The 1 mm spectrum of VY CMa is dominated by SO 2 and SiS; in IRC +10216, C 4 H and SiC 2 are the most recurrent species. Ten molecules were common to both sources: CO, SiS, SiO, CS, CN, HCN, HNC, NaCl, PN, and HCO + . Sulfur plays an important role in VY CMa, but saturated/unsaturated carbon dominates the molecular content of IRC +10216, producing CH 2 NH, for example. Although the molecular complexity of IRC +10216 is greater, VY CMa supports a unique 'inorganic' chemistry leading to the oxides PO, AlO, and AlOH. Only diatomic and triatomic compounds were observed in VY CMa, while species with four or more atoms are common in IRC +10216, reflecting carbon's ability to form multiple strong bonds, unlike oxygen. In VY CMa, a new water maser (v 2 = 2) has been found, as well as vibrationally excited NaCl. Toward IRC +10216, vibrationally excited CCH was detected for the first time.

Comparative Spectra of Oxygen-rich Versus Carbon-rich Circumstellar Shells: VY Canis Majoris and IRC +10216 at 215-285 GHz

Science.gov (United States)

Tenenbaum, E. D.; Dodd, J. L.; Milam, S. N.; Woolf, N. J.; Ziurys, L. M.

2010-09-01

A sensitive (1σ rms at 1 MHz resolution ~3 mK) 1 mm spectral line survey (214.5-285.5 GHz) of VY Canis Majoris (VY CMa) and IRC +10216 has been conducted to compare the chemistries of oxygen- and carbon-rich circumstellar envelopes. This study was carried out using the Submillimeter Telescope of the Arizona Radio Observatory with a new Atacama Large Millimeter Array type receiver. This survey is the first to chemically characterize an O-rich circumstellar shell at millimeter wavelengths. In VY CMa, 128 emission features were detected arising from 18 different molecules; and in IRC +10216, 720 lines were observed, assigned to 32 different species. The 1 mm spectrum of VY CMa is dominated by SO2 and SiS; in IRC +10216, C4H and SiC2 are the most recurrent species. Ten molecules were common to both sources: CO, SiS, SiO, CS, CN, HCN, HNC, NaCl, PN, and HCO+. Sulfur plays an important role in VY CMa, but saturated/unsaturated carbon dominates the molecular content of IRC +10216, producing CH2NH, for example. Although the molecular complexity of IRC +10216 is greater, VY CMa supports a unique "inorganic" chemistry leading to the oxides PO, AlO, and AlOH. Only diatomic and triatomic compounds were observed in VY CMa, while species with four or more atoms are common in IRC +10216, reflecting carbon's ability to form multiple strong bonds, unlike oxygen. In VY CMa, a new water maser (v 2 = 2) has been found, as well as vibrationally excited NaCl. Toward IRC +10216, vibrationally excited CCH was detected for the first time.

The role of teacher questions in the chemistry classroom

DEFF Research Database (Denmark)

Dohrn, Sofie Weiss; Dohn, Niels Bonderup

2018-01-01

, the students become highly accomplished in recalling facts but have difficulties when higher order thinking is required. The findings suggest that an interactive classroom can be created by using many engaging teacher questions. The six different categories of questions promote the students' learning process......The purpose of this study was to investigate how a chemistry teacher's questions influence the classroom discourse. It presents a fine-grained analysis of the rich variety of one teacher's questions and the roles they play in an upper secondary chemistry classroom. The study identifies six...... different functions for the teacher's questions: Student Knowledge, Request, Monologic Discourse, Clarification, Relations and Interaction of Contexts. Overall, these questions create a safe and interactive learning environment. However, the questions are predominantly closed in form. As a result...

Multiscale pore structure and its effect on gas transport in organic-rich shale

Science.gov (United States)

Wu, Tianhao; Li, Xiang; Zhao, Junliang; Zhang, Dongxiao

2017-07-01

A systematic investigation of multiscale pore structure in organic-rich shale by means of the combination of various imaging techniques is presented, including the state-of-the-art Helium-Ion-Microscope (HIM). The study achieves insight into the major features at each scale and suggests the affordable techniques for specific objectives from the aspects of resolution, dimension, and cost. The pores, which appear to be isolated, are connected by smaller pores resolved by higher-resolution imaging. This observation provides valuable information, from the microscopic perspective of pore structure, for understanding how gas accumulates and transports from where it is generated. A comprehensive workflow is proposed based on the characteristics acquired from the multiscale pore structure analysis to simulate the gas transport process. The simulations are completed with three levels: the microscopic mechanisms should be taken into consideration at level I; the spatial distribution features of organic matter, inorganic matter, and macropores constitute the major issue at level II; and the microfracture orientation and topological structure are dominant factors at level III. The results of apparent permeability from simulations agree well with the values acquired from experiments. By means of the workflow, the impact of various gas transport mechanisms at different scales can be investigated more individually and precisely than conventional experiments.

Research for the advancement of green chemistry practice: Studies in atmospheric and educational chemistry

Science.gov (United States)

Cullipher, Steven Gene

Green chemistry is a philosophy of chemistry that emphasizes a decreasing dependence on limited non-renewable resources and an increasing focus on preventing pollution byproducts of the chemical industry. In short, it is the discipline of chemistry practiced through the lens of environmental stewardship. In an effort to advance the practice of green chemistry, three studies will be described that have ramifications for the practice. The first study examines the atmospheric oxidation of a hydrofluorinated ether, a third-generation CFC replacement compound with primarily unknown atmospheric degradation products. Determination of these products has the potential to impact decisions on refrigerant usage in the future. The second study examines chemistry students' development of understanding benefits-costs-risks analysis when presented with two real-world scenarios: refrigerant choice and fuel choice. By studying how benefits-costs-risks thinking develops, curricular materials and instructional approaches can be designed to better foster the development of an ability that is both necessary for green chemists and important in daily decision-making for non-chemists. The final study uses eye tracking technology to examine students' abilities to interpret molecular properties from structural information in the context of global warming. Such abilities are fundamental if chemists are to appropriately assess risks and hazards of chemistry practice.

Long-Term Trends and Temporal Synchrony in Plankton Richness, Diversity and Biomass Driven by Re-Oligotrophication and Climate across 17 Danish Lakes

Directory of Open Access Journals (Sweden)

Korhan Özkan

2016-09-01

Full Text Available A two-decade (1989–2008 time series of lake phyto- and zooplankton, water characteristics and climate in 17 Danish lakes was analysed to examine the long term changes and the effects of lake restoration efforts. The analyses of the pair-wise correlations across time series revealed a strong synchrony in climatic variables among the lakes. A significant, but weak increase in air temperature was observed and resulted in a corresponding increase in surface water temperature only in summer. Lake physico-chemical variables had weaker synchrony than climatic variables. Synchrony in water temperature and stratification was stronger than lake chemistry as the former is mostly affected by atmospheric energy flux. Synchrony in the taxonomic richness of the plankton groups and phytoplankton biomass was apparent, to a similar degree as observed for lake chemistry. The synchrony and the temporal trends in lake chemistry and plankton were more pronounced for the lakes with strong re-oligotrophication. Phytoplankton biomass decreased and plankton richness increased in these lakes, with a shift from Chlorophyta dominance towards more heterogeneous phytoplankton communities. Notably, a widespread significant positive trend in plankton richness was observed not only in lakes with strong re-oligotrophication but across all lakes. The widespread increase in plankton richness coincided with widespread decrease in phosphate and total nitrogen concentrations, as well as with the trends in climate indicating a likely joint effect of nutrient reduction and climate in driving lake plankton. However, temporal changes and synchrony as well as the recovery of richness and composition of lake plankton more coherently corresponded with the nutrient loading reduction across the Danish landscape, while the role of climate control of the lake plankton was less pronounced.

Dragonfly: In Situ Exploration of Titan's Organic Chemistry and Habitability

Science.gov (United States)

Turtle, E. P.; Barnes, J. W.; Trainer, M. G.; Lorenz, R. D.

2017-12-01

Titan's abundant complex carbon-rich chemistry, interior ocean, and past presence of liquid water on the surface make it an ideal destination to study prebiotic chemical processes and document the habitability of an extraterrestrial environment. Titan exploration is a high science priority due to the level of organic synthesis that it supports. Moreover, opportunities for organics to have interacted with liquid water at the surface (e.g., in impact melt sheets) increase the potential for chemical processes to progress further, providing an unparalleled opportunity to investigate prebiotic chemistry, as well as to search for signatures of potential water-based or even hydrocarbon-based life. The diversity of Titan's surface materials and environments drives the scientific need to be able to sample a variety of locations, thus mobility is key for in situ measurements. Titan's atmosphere is 4 times denser than Earth's reducing the wing/rotor area required to generate a given amount of lift, and the low gravity reduces the required magnitude of lift, making heavier-than-air mobility highly efficient. Dragonfly is a rotorcraft lander mission proposed to NASA's New Frontiers Program to take advantage of Titan's unique natural laboratory to understand how far chemistry can progress in environments that provide key ingredients for life. Measuring the compositions of materials in different environments will reveal how far organic chemistry has progressed. Surface material can be sampled into a mass spectrometer to identify the chemical components available and processes at work to produce biologically relevant compounds. Bulk elemental surface composition can be determined by a neutron-activated gamma-ray spectrometer. Meteorology measurements can characterize Titan's atmosphere and diurnal and spatial variations therein. Geologic features can be characterized via remote-sensing observations, which also provide context for samples. Seismic sensing can probe subsurface

Chemistry Division: Annual progress report for period ending March 31, 1987

International Nuclear Information System (INIS)

1987-08-01

This report is divided into the following sections: coal chemistry; aqueous chemistry at high temperatures and pressures; geochemistry of crustal processes to high temperatures and pressures; chemistry of advanced inorganic materials; structure and dynamics of advanced polymeric materials; chemistry of transuranium elements and compounds; separations chemistry; reactions and catalysis in molten salts; surface science related to heterogeneous catalysis; electron spectroscopy; chemistry related to nuclear waste disposal; computational modeling of security document printing; and special topics

Quantum Chemistry; A concise introduction for students of physics, chemistry, biochemistry and materials science

Science.gov (United States)

Thakkar, Ajit J.

2017-09-01

This book provides non-specialists with a basic understanding of the underlying concepts of quantum chemistry. It is both a text for second- or third-year undergraduates and a reference for researchers who need a quick introduction or refresher. All chemists and many biochemists, materials scientists, engineers, and physicists routinely use spectroscopic measurements and electronic structure computations in their work. The emphasis of Quantum Chemistry on explaining ideas rather than enumerating facts or presenting procedural details makes this an excellent foundation text/reference.

Low temperature nitrogen chemistry. Final report

Energy Technology Data Exchange (ETDEWEB)

Glarborg, P.; Dam-Johansen, K.; Kristensen, P.G.; Alzueta, M.; Roejel, H.

1997-04-01

The results of a two tasks program on Natural Gas Reburning are reported. The work involved an experimental and theoretical study of the reburning and hybrid reburning/SNCR chemistry in the 1000-1500 K range. The interactions between hydrocarbon and nitrogen chemistry under fuel-rich conditions were investigated in order to assess the NO{sub x} reduction potential of low temperature reburning. The effect of reburn fuel(carbon monoxide, methane, acetylene, ethylene, ethane, and methane/ethane mixture), temperature, stoichiometry, reactant dilution, reaction time, and inlet NO level were studied. The results indicate a significant NO reduction potential even below 1400 K, but extrapolation to practical conditions are complicated by inadequate knowledge of the detailed chemistry as well as of the effect of mixing. The possibilities of enhancing the conversion to N{sub 2} instead of NO by adding selective reducing agents (hybrid reburning/SNCR) were evaluated. Our results indicate little synergistic effect between reburn and SNCR. The most simple configuration, where the selective reducing agent is injected together with the burnout air, is not expected to be effective, unless the N-agent is injected in form of an aqueous solution. A chemical kinetic model for reburning and reburn/SNCR is listed and can be obtained by e-mail from pgl(commerical at)kt.dtu.dk.(au) 145 refs.

Neutron rich nuclei around 132Sn

International Nuclear Information System (INIS)

Bhattacharya, Sarmishtha

2016-01-01

The neutron rich nuclei with few particles or holes in 132 Sn have various experimental and theoretical interest to understand the evolution of nuclear structure around the doubly magic shell closure Z=50 and N=82. Some of the exotic neutron rich nuclei in this mass region are situated near waiting points in the r-process path and are of special astrophysical interest. Neutron rich nuclei near 132 Sn have been studied using fission fragment spectroscopy. The lifetime of low lying isomeric states have been precisely measured and the beta decay from the ground and isomeric states have been characterized using gamma-ray spectroscopy

Implementation and Evaluation of Web-Based Learning Activities on Bonding and the Structure of Matter for 10-th Grade Chemistry

Science.gov (United States)

Frailich, Marcel

This study deals with the development, implementation, and evaluation of web-based activities associated with the topic of chemical bonding , as taught in 10th grade chemistry. A website was developed entitled: "Chemistry and the Chemical Industry in the Service of Mankind", its URL is: http://stwww.weizmann.ac.il/g-chem/learnchem (Kesner, Frailich, & Hofstein, 2003). The main goal of this study was to assess the educational effectiveness of website activities dealing with the chemical bonding concept. These activities include visualization tools, as well as topics relevant to daily life and industrial applications. The study investigated the effectiveness of a web-based learning environment regarding the understanding of chemical bonding concepts, students' perceptions of the classroom learning environment, their attitudes regarding the relevance of learning chemistry to everyday life, and their interest in chemistry studies. As mentioned before, in the present study we focused on activities (from the website), all of which deal with chemical bonding concept. The following are the reasons for the decision to focus on this topic: (1) Chemical bonding is a key concept that is taught in 10th grade chemistry in high school. It provides the basis for many other chemistry topics that are taught later, and (2) Chemical bonding is a difficult for students using existing tools (e. g., static models in books, ball-and- stick models), which are insufficient to demonstrate the abstract nature phenomena associated with this topic. The four activities developed for this study are (1) models of the atomic structure, (2) metals -- structure and properties, (3) ionic substances in everyday life and in industry, and (4) molecular substances -- structure, properties, and uses. The study analyzed both quantitative and qualitative research. The quantitative tools of the study included: A Semantic Differential questionnaire and a Chemistry Classroom Web-Based Learning Environment

Pressure-induced chemistry in a nitrogen-hydrogen host-guest structure

Science.gov (United States)

Spaulding, Dylan K.; Weck, Gunnar; Loubeyre, Paul; Datchi, Fréderic; Dumas, Paul; Hanfland, Michael

2014-12-01

New topochemistry in simple molecular systems can be explored at high pressure. Here we examine the binary nitrogen/hydrogen system using Raman spectroscopy, synchrotron X-ray diffraction, synchrotron infrared microspectroscopy and visual observation. We find a eutectic-type binary phase diagram with two stable high-pressure van der Waals compounds, which we identify as (N2)6(H2)7 and N2(H2)2. The former represents a new type of van der Waals host-guest compound in which hydrogen molecules are contained within channels in a nitrogen lattice. This compound shows evidence for a gradual, pressure-induced change in bonding from van der Waals to ionic interactions near 50 GPa, forming an amorphous dinitrogen network containing ionized ammonia in a room-temperature analogue of the Haber-Bosch process. Hydrazine is recovered on decompression. The nitrogen-hydrogen system demonstrates the potential for new pressure-driven chemistry in high-pressure structures and the promise of tailoring molecular interactions for materials synthesis.

The Aro 1 mm Survey of the Oxygen-Rich Envelope of Supergiant Star NML Cygnus

Science.gov (United States)

Edwards, Jessica L.; Ziurys, L. M.; Woolf, N. J.

2011-06-01

Although a number of molecular line surveys of carbon-rich circumstellar envelopes (CSE) have been performed, only one oxygen-rich CSE, that of VY Canis Majoris (VY CMa), has been studied in depth. The Arizona Radio Observatory (ARO) 1 mm survey of VY CMa showed a very different and interesting chemistry dominated by sulfur- and silicon-bearing compounds as well as a number of more exotic species. A similar survey of the oxygen rich star NML Cygnus (NML Cyg) from 215 to 285 GHz is currently under way using the ARO Sub-millimeter Telescope. Initial observations show that this circumstellar envelope appears to be as chemically rich as that of VY CMa. Molecules including 12CO, 13CO, 12CN, 13CN, HCN, HCO+, CS, SO{_2}, SiO and 30SiO have been observed in NML Cyg. Line profiles of this source also suggest that there may be multiple outflows and that the circumstellar envelope is not spherically symmetric. Current results will be presented.

Chemistry Division: Annual progress report for period ending March 31, 1987

Energy Technology Data Exchange (ETDEWEB)

1987-08-01

This report is divided into the following sections: coal chemistry; aqueous chemistry at high temperatures and pressures; geochemistry of crustal processes to high temperatures and pressures; chemistry of advanced inorganic materials; structure and dynamics of advanced polymeric materials; chemistry of transuranium elements and compounds; separations chemistry; reactions and catalysis in molten salts; surface science related to heterogeneous catalysis; electron spectroscopy; chemistry related to nuclear waste disposal; computational modeling of security document printing; and special topics. (DLC)

Structure vs chemistry: friction and wear of Pt-based metallic surfaces.

Science.gov (United States)

Caron, A; Louzguine-Luzguin, D V; Bennewitz, R

2013-11-13

In comparison of a Pt57.5Cu14.7Ni5.3P22.5 metallic glass with a Pt(111) single crystal we find that wearless friction is determined by chemistry through bond formation alloying, while wear is determined by structure through plasticity mechanisms. In the wearless regime, friction is affected by the chemical composition of the counter body and involves the formation of a liquid-like neck and interfacial alloying. The wear behavior of Pt-based metallic surfaces is determined by their structural properties and corresponding mechanisms for plastic deformation. In the case of Pt(111) wear occurs by dislocation-mediated homogeneous plastic deformation. In contrast the wear of Pt57.5Cu14.7Ni5.3P22.5 metallic glass occurs through localized plastic deformation in shear bands that merge together in a single shear zone above a critical load and corresponds to the shear softening of metallic glasses. These results open a new route in the control of friction and wear of metals and are relevant for the development of self-lubricated and wear-resistant mechanical devices.

Third Chemistry Conference on Recent Trends in Chemistry

International Nuclear Information System (INIS)

Saeed, M.M.; Wheed, S.

2011-01-01

The third chemistry conference 2011 on recent trends in chemistry was held from October 17-19, 2001 at Islamabad, Pakistan. More than 65 papers and oral presentation. The scope of the conference was wide open and provides and opportunity for participation of broad spectrum of chemists. This forum provided a platform for the dissemination of the latest research followed by discussion pertaining to new trends in chemistry. This con fence covered different aspects of subjects including analytical chemistry, environmental chemistry, polymer chemistry, industrial chemistry, biochemistry and nano chemistry etc. (A.B.)

Purification, structure and immunobiological activity of an arabinan-rich pectic polysaccharide from the cell walls of Prunus dulcis seeds.

Science.gov (United States)

Dourado, Fernando; Madureira, Pedro; Carvalho, Vera; Coelho, Ricardo; Coimbra, Manuel A; Vilanova, Manuel; Mota, Manuel; Gama, Francisco M

2004-10-20

The structure and bioactivity of a polysaccharide extracted and purified from a 4M KOH + H3BO3 solution from Prunus dulcis seed cell wall material was studied. Anion-exchange chromatography of the crude extract yielded two sugar-rich fractions: one neutral (A), the other acidic (E). These fractions contain a very similar monosaccharide composition: 5:2:1 for arabinose, uronic acids and xylose, respectively, rhamnose and galactose being present in smaller amounts. As estimated by size-exclusion chromatography, the acidic fraction had an apparent molecular mass of 762 kDa. Methylation analysis (from the crude and fractions A and E), suggests that the polysaccharide is an arabinan-rich pectin. In all cases, the polysaccharides bear the same type of structural Ara moieties with highly branched arabinan-rich pectic polysaccharides. The average relative proportions of the arabinosyl linkages is 3:2:1:1 for T-Araf:(1-->5)-Araf:(1-->3,5)-Araf:(1-->2,3,5)-Araf. The crude polysaccharide extract and fractions A and E induced a murine lymphocyte stimulatory effect, as evaluated by the in vitro and in vivo expression of lymphocyte activation markers and spleen mononuclear cells culture proliferation. The lymphocyte stimulatory effect was stronger on B- than on T-cells. No evidence of cytotoxic effects induced by the polysaccharide fractions was found.

The structural chemistry of metallocorroles: combined X-ray crystallography and quantum chemistry studies afford unique insights.

Science.gov (United States)

Thomas, Kolle E; Alemayehu, Abraham B; Conradie, Jeanet; Beavers, Christine M; Ghosh, Abhik

2012-08-21

Although they share some superficial structural similarities with porphyrins, corroles, trianionic ligands with contracted cores, give rise to fundamentally different transition metal complexes in comparison with the dianionic porphyrins. Many metallocorroles are formally high-valent, although a good fraction of them are also noninnocent, with significant corrole radical character. These electronic-structural characteristics result in a variety of fascinating spectroscopic behavior, including highly characteristic, paramagnetically shifted NMR spectra and textbook cases of charge-transfer spectra. Although our early research on corroles focused on spectroscopy, we soon learned that the geometric structures of metallocorroles provide a fascinating window into their electronic-structural characteristics. Thus, we used X-ray structure determinations and quantum chemical studies, chiefly using DFT, to obtain a comprehensive understanding of metallocorrole geometric and electronic structures. This Account describes our studies of the structural chemistry of metallocorroles. At first blush, the planar or mildly domed structure of metallocorroles might appear somewhat uninteresting particularly when compared to metalloporphyrins. Metalloporphyrins, especially sterically hindered ones, are routinely ruffled or saddled, but the missing meso carbon apparently makes the corrole skeleton much more resistant to nonplanar distortions. Ruffling, where the pyrrole rings are alternately twisted about the M-N bonds, is energetically impossible for metallocorroles. Saddling is also uncommon; thus, a number of sterically hindered, fully substituted metallocorroles exhibit almost perfectly planar macrocycle cores. Against this backdrop, copper corroles stand out as an important exception. As a result of an energetically favorable Cu(d(x2-y2))-corrole(π) orbital interaction, copper corroles, even sterically unhindered ones, are inherently saddled. Sterically hindered substituents

Comparative Spectra of Oxygen-Rich Versus Carbon-Rich Circumstellar Shells: VY Canis Majoris and IRC(plus)10216 at 215-285 GHz

Science.gov (United States)

Tenebaum, E. D.; Dodd, J. L.; Milam, S. N.; Woolf, N. J.; Ziurys, L. M.

2010-01-01

A sensitive (1sigma rms at 1 MHz resolution approx.3 mK) 1 mm spectral line survey (214.5-285.5 GHz) of VY Canis Majoris (VY CMa) and IRC +10216 has been conducted to compare the chemistries of oxygen- and carbon-rich circumstellar envelopes. This study was carried out using the Submillimeter Telescope of the Arizona Radio Observatory with a new Atacama Large Millimeter Array type receiver. This survey is the first to chemically characterize an O-rich circumstellar shell at millimeter wavelengths. In VY CMa, 128 emission features were detected arising from 18 different molecules; and in IRC +10216, 720 lines were observed, assigned to 32 different species. The 1 mm spectrum of VY CMa is dominated by SO, and SiS; in IRC +10216, C4H and SiC2 are the most recurrent species. Ten molecules were common to both sources: CO, SiS, SiO, CS, CN, HCN, HNC, NaCl, PN, and HCO(+). Sulfur plays an important role in VY CMa, but saturated/ unsaturated carbon dominates the molecular content of IRC +102.16, producing CH2NH, for example. Although the molecular complexity of IRC +10216 is greater, VY CMa supports a unique "inorganic" chemistry leading to the oxides PO, AlO, and AlOH. Only diatomic and triatomic compounds were observed in VY CMa, while species with four or more atoms are common in IRC +10216, reflecting carbon's ability to form multiple strong bonds, unlike oxygen. In VY CMa, a new water maser (v2 = 2) has been found, as well as vibrationally excited NaCl. Toward IRC +10216, vibrationally excited CCH was detected for the first time.

Medicinal chemistry and the pharmacy curriculum.

Science.gov (United States)

Khan, M O Faruk; Deimling, Michael J; Philip, Ashok

2011-10-10

The origins and advancements of pharmacy, medicinal chemistry, and drug discovery are interwoven in nature. Medicinal chemistry provides pharmacy students with a thorough understanding of drug mechanisms of action, structure-activity relationships (SAR), acid-base and physicochemical properties, and absorption, distribution, metabolism, excretion, and toxicity (ADMET) profiles. A comprehensive understanding of the chemical basis of drug action equips pharmacy students with the ability to answer rationally the "why" and "how" questions related to drug action and it sets the pharmacist apart as the chemical expert among health care professionals. By imparting an exclusive knowledge base, medicinal chemistry plays a vital role in providing critical thinking and evidence-based problem-solving skills to pharmacy students, enabling them to make optimal patient-specific therapeutic decisions. This review highlights the parallel nature of the history of pharmacy and medicinal chemistry, as well as the key elements of medicinal chemistry and drug discovery that make it an indispensable component of the pharmacy curriculum.

The Role of Cesium Cation in Controlling Interphasial Chemistry on Graphite Anode in Propylene Carbonate-Rich Electrolytes

Energy Technology Data Exchange (ETDEWEB)

Xiang, Hongfa; Mei, Donghai; Yan, Pengfei; Bhattacharya, Priyanka; Burton, Sarah D.; Cresce, Arthur V.; Cao, Ruiguo; Engelhard, Mark H.; Bowden, Mark E.; Zhu, Zihua; Polzin, Bryant; Wang, Chong M.; Xu, Kang; Zhang, Jiguang; Xu, Wu

2015-09-10

Propylene carbonate (PC) is seldom used in lithium-ion batteries (LIBs) due to its sustained co-intercalation into graphene structure and the eventual graphite exfoliation, despite potential advantages it brings, such as wider liquid range and lower cost. Here we discover that cesium cation (Cs+), originally used to suppress dendrite growth of Li metal anode, directs the formation of solid electrolyte interphase (SEI) on graphitic anode in PC-rich electrolytes through preferential solvation. Effective suppression of PC-decomposition and graphite-exfoliation was achieved when the ratio of ethylene carbonate (EC)/PC in electrolytes was so adjusted that the reductive decomposition of Cs+-(EC)m (1≤m≤2) complex precedes that of Li+-(PC)n (3≤n≤5). The interphase directed by Cs+ is stable, ultrathin and compact, leading to significant improvements in LIB performances. In a broader context, the accurate tailoring of SEI chemical composition by introducing a new solvation center represents a fundamental breakthrough in manipulating interfacial reactions processes that once were elusive.

Are carnivore digestive separation mechanisms revealed on structure-rich diets?: Faecal inconsistency in dogs (Canis familiaris) fed day old chicks

NARCIS (Netherlands)

Cuyper, De Annelies; Clauss, M.; Hesta, Myriam; Cools, An; Bosch, G.; Hendriks, W.H.; Janssens, Geert P.J.

2018-01-01

Pronounced variations in faecal consistency have been described anecdotally for some carnivore species fed a structure-rich diet. Typically two faecal consistencies are distinguished, namely hard and firm versus liquid and viscous faeces. It is possible that a separation mechanism is operating in

Unusual Amino Acids in Medicinal Chemistry.

Science.gov (United States)

Blaskovich, Mark A T

2016-12-22

Unusual amino acids are fundamental building blocks of modern medicinal chemistry. The combination of readily functionalized amine and carboxyl groups attached to a chiral central core along with one or two potentially diverse side chains provides a unique three-dimensional structure with a high degree of functionality. This makes them invaluable as starting materials for syntheses of complex molecules, highly diverse elements for SAR campaigns, integral components of peptidomimetic drugs, and potential drugs on their own. This Perspective highlights the diversity of unnatural amino acid structures found in hit-to-lead and lead optimization campaigns and clinical stage and approved drugs, reflecting their increasingly important role in medicinal chemistry.

Radiation chemistry

International Nuclear Information System (INIS)

Rodgers, F.; Rodgers, M.A.

1987-01-01

The contents of this book include: Interaction of ionizing radiation with matter; Primary products in radiation chemistry; Theoretical aspects of radiation chemistry; Theories of the solvated electron; The radiation chemistry of gases; Radiation chemistry of colloidal aggregates; Radiation chemistry of the alkali halides; Radiation chemistry of polymers; Radiation chemistry of biopolymers; Radiation processing and sterilization; and Compound index

Developmental programming of aortic and renal structure in offspring of rats fed fat-rich diets in pregnancy

DEFF Research Database (Denmark)

Armitage, James A.; Lakasing, Lorin; Taylor, Paul D.

2005-01-01

Evidence from human and animal studies suggests that maternal nutrition can induce developmental programming of adult hypertension in offspring. We have previously described a model of maternal dietary imbalance in Sprague-Dawley rats whereby administration of a maternal diet rich in animal lard......-Dawley rats fed a control diet (OC) or lard-rich diet (OHF) during pregnancy and suckling followed by a control diet post-weaning. To gain further insight, we assessed aortic reactivity and elasticity in an organ bath preparation and renal renin and Na+,K+-ATPase activity. Plasma aldosterone concentration...... weight, glomerular number or volume in OHF compared with OC, but renin and Na+,K+-ATPase activity were significantly reduced in OHF compared with controls. Programmed alterations to aortic structure and function are consistent with previous observations that exposure to maternal high fat diets produces...

Chemistry and structure of giant molecular clouds in energetic environments

Science.gov (United States)

Anderson, Crystal Nicole

2016-09-01

Throughout the years many studies on Galactic star formation have been conducted. This resulted in the idea that giant molecular clouds (GMCs) are hierarchical in nature with substructures spanning a large range of sizes. The physical processes that determine how molecular clouds fragment, form clumps/cores and then stars depends strongly on both recent radiative and mechanical feed- back from massive stars and, on longer term, from enhanced cooling due to the buildup of metals. Radiative and mechanical energy input from stellar populations can alter subsequent star formation over a large part of a galaxy and hence is relevant to the evolution of galaxies. Much of our knowledge of star formation on galaxy wide scales is based on scaling laws and other parametric descriptions. But to understand the overall evolution of star formation in galaxies we need to watch the feedback processes at work on giant molecular cloud (GMC) scales. By doing this we can begin to answer how strong feedback environments change the properties of the substructure in GMCs. Tests of Galactic star formation theory to other galaxies has been a challenging process due to the lack of resolution with current instruments. Thus, only the nearest galaxies allow us to resolve GMCs and their substructures. The Large Magellanic Cloud (LMC), is one of the closest low metallicity dwarf galaxies (D˜ 50 kpc) and is close enough that current instruments can resolve the sub- structure of its GMCs to molecular gas tracers (e.g. HCO+, HCN, HNC, CS, C2H, N2H+) detected in the LMC at 1.5-40 pc scales and in NGC 5253 at 40 pc scales. I then compare the molecular gas detections to the Central Molecular Zone in our Galaxy. Dense molecular gas was detected in all of the sources. For the regions in the LMC, molecular lines of CS, N2H+, C 2H, HNC, HCO+ and HCN were all detected in N159W and N113 while only HCN, HCO+, HNC, and C2H were detected in 30Dor-10. Toward NGC 5253 only HCO+, HCN, C2H and CS were detected. I

Chemistry with bigger, better atoms

Indian Academy of Sciences (India)

DELL

Anshu Pandey. Solid State and Structural Chemistry Unit. Indian Institute of Science. H. Cd. Hg. U ? Page 2. Quantum Dots: A Coarse-grained view. • Quantum Dot Electronic Structure can be approximated remarkably well as a Spherical. Particle in a Box Problem ... The concept of stoichiometry still holds!!! Rekha M. et. al.

Crystal chemistry of Ruddlesden-Popper type structures in high Tc ceramic superconductors

International Nuclear Information System (INIS)

Dwivedi, Anurag; Cormack, A.N.

1991-01-01

Similar structural patterns have been noticed in the systems La-Cu-O, La-Ni-O and Bi and Tl-containing superconducting oxides. The formation of Ruddlesden-Popper type layers (alternating slabs of rocksalt and perovskite strucutres) is seen in these oxides which is similar in many respects to what is seen in the system Sr-Ti-O. However, there are some significant differences, for example the rocksalt and perovskite blocks in new superconducting compounds are not necessarily electrically neutral, unlike in the Sr-Ti-O system. It, thus, becomes necessary to create oxygen vacancies in the basic perovskite structure of Bi-containing compounds, when the width of the perovskite slab changes on addition of extra Cu-O planes. Results of atomistic simulations suggest that these missing oxygen ions allows the Cu-O planes to buckle in Bi-series of compounds. This is also supported by the absence of buckling in the Sr-Ti-O series of compounds and the first member of Bi-containing compounds in which there are no missing oxygen ions. Additional results on the phase stability of polytypoid structure in la-Cu-O system and defect chemistry of compounds of La N i-O system are presented. (author). 14 re fs., 7 figs., 4 tabs

Rapid automated nuclear chemistry

International Nuclear Information System (INIS)

Meyer, R.A.

1979-01-01

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

Incorporating Modeling and Simulations in Undergraduate Biophysical Chemistry Course to Promote Understanding of Structure-Dynamics-Function Relationships in Proteins

Science.gov (United States)

Hati, Sanchita; Bhattacharyya, Sudeep

2016-01-01

A project-based biophysical chemistry laboratory course, which is offered to the biochemistry and molecular biology majors in their senior year, is described. In this course, the classroom study of the structure-function of biomolecules is integrated with the discovery-guided laboratory study of these molecules using computer modeling and…

Innovation Developments of Coal Chemistry Science in L.M. Litvinenko Institute of Physical-Organic Chemistry and Coal Chemistry of NAS of Ukraine

Directory of Open Access Journals (Sweden)

Shendrik, T.G.

2015-11-01

Full Text Available The article presents short historical review and innovation developments of Coal Chemistry Department of L.M. Litvinenko Institute, NAS of Ukraine connected with coal mine exploitation problems, search for decisions toward prevention of spontaneous combustion, dust control in mines, establishing structural chemical features of coal with different genesis and stages of metamorphism with the aim to develop new methods of their modification and rational use. The methods of obtaining inexpensive sorbents from Ukrainian raw materials (including carbon containing waste are proposed. The problems of modern coal chemistry science in IPOCC of NAS of Ukraine are outlined.

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...

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

Abnormal rich club organization and functional brain dynamics in schizophrenia.

Science.gov (United States)

van den Heuvel, Martijn P; Sporns, Olaf; Collin, Guusje; Scheewe, Thomas; Mandl, René C W; Cahn, Wiepke; Goñi, Joaquín; Hulshoff Pol, Hilleke E; Kahn, René S

2013-08-01

The human brain forms a large-scale structural network of regions and interregional pathways. Recent studies have reported the existence of a selective set of highly central and interconnected hub regions that may play a crucial role in the brain's integrative processes, together forming a central backbone for global brain communication. Abnormal brain connectivity may have a key role in the pathophysiology of schizophrenia. To examine the structure of the rich club in schizophrenia and its role in global functional brain dynamics. Structural diffusion tensor imaging and resting-state functional magnetic resonance imaging were performed in patients with schizophrenia and matched healthy controls. Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, the Netherlands. Forty-eight patients and 45 healthy controls participated in the study. An independent replication data set of 41 patients and 51 healthy controls was included to replicate and validate significant findings. MAIN OUTCOME(S) AND MEASURES: Measures of rich club organization, connectivity density of rich club connections and connections linking peripheral regions to brain hubs, measures of global brain network efficiency, and measures of coupling between brain structure and functional dynamics. Rich club organization between high-degree hub nodes was significantly affected in patients, together with a reduced density of rich club connections predominantly comprising the white matter pathways that link the midline frontal, parietal, and insular hub regions. This reduction in rich club density was found to be associated with lower levels of global communication capacity, a relationship that was absent for other white matter pathways. In addition, patients had an increase in the strength of structural connectivity-functional connectivity coupling. Our findings provide novel biological evidence that schizophrenia is characterized by a selective

Global volcanic emissions: budgets, plume chemistry and impacts

Science.gov (United States)

Mather, T. A.

2012-12-01

Over the past few decades our understanding of global volcanic degassing budgets, plume chemistry and the impacts of volcanic emissions on our atmosphere and environment has been revolutionized. Global volcanic emissions budgets are needed if we are to make effective use of regional and global atmospheric models in order to understand the consequences of volcanic degassing on global environmental evolution. Traditionally volcanic SO2 budgets have been the best constrained but recent efforts have seen improvements in the quantification of the budgets of other environmentally important chemical species such as CO2, the halogens (including Br and I) and trace metals (including measurements relevant to trace metal atmospheric lifetimes and bioavailability). Recent measurements of reactive trace gas species in volcanic plumes have offered intriguing hints at the chemistry occurring in the hot environment at volcanic vents and during electrical discharges in ash-rich volcanic plumes. These reactive trace species have important consequences for gas plume chemistry and impacts, for example, in terms of the global fixed nitrogen budget, volcanically induced ozone destruction and particle fluxes to the atmosphere. Volcanically initiated atmospheric chemistry was likely to have been particularly important before biological (and latterly anthropogenic) processes started to dominate many geochemical cycles, with important consequences in terms of the evolution of the nitrogen cycle and the role of particles in modulating the Earth's climate. There are still many challenges and open questions to be addressed in this fascinating area of science.

Medicinal Chemistry and Molecular Modeling: An Integration to Teach Drug Structure-Activity Relationship and the Molecular Basis of Drug Action

Science.gov (United States)

Carvalho, Ivone; Borges, Aurea D. L.; Bernardes, Lilian S. C.

2005-01-01

The use of computational chemistry and the protein data bank (PDB) to understand and predict the chemical and molecular basis involved in the drug-receptor interactions is discussed. A geometrical and chemical overview of the great structural similarity in the substrate and inhibitor is provided.

Structural landscape of the proline-rich domain of Sos1 nucleotide exchange factor.

Science.gov (United States)

McDonald, Caleb B; Bhat, Vikas; Kurouski, Dmitry; Mikles, David C; Deegan, Brian J; Seldeen, Kenneth L; Lednev, Igor K; Farooq, Amjad

2013-01-01

Despite its key role in mediating a plethora of cellular signaling cascades pertinent to health and disease, little is known about the structural landscape of the proline-rich (PR) domain of Sos1 guanine nucleotide exchange factor. Herein, using a battery of biophysical tools, we provide evidence that the PR domain of Sos1 is structurally disordered and adopts an extended random coil-like conformation in solution. Of particular interest is the observation that while chemical denaturation of PR domain results in the formation of a significant amount of polyproline II (PPII) helices, it has little or negligible effect on its overall size as measured by its hydrodynamic radius. Our data also show that the PR domain displays a highly dynamic conformational basin in agreement with the knowledge that the intrinsically unstructured proteins rapidly interconvert between an ensemble of conformations. Collectively, our study provides new insights into the conformational equilibrium of a key signaling molecule with important consequences on its physiological function. Copyright © 2013 Elsevier B.V. All rights reserved.

Structural, mechanical and corrosion studies of Cr-rich inclusions in 152 cladding of dissimilar metal weld joint

Science.gov (United States)

Li, Yifeng; Wang, Jianqiu; Han, En-Hou; Yang, Chengdong

2018-01-01

Cr-rich inclusions were discovered in 152 cladding at the inner wall of domestic dissimilar metal weld joint, and their morphologies, microstructures, mechanical properties and corrosion behaviors were systematically characterized by SEM, TEM, nanoindentation and FIB. The results indicate that the Cr-rich inclusions originate from large-size Cr particles in 152 welding electrode flux, and they are 50-150 μm in size in most cases, and there is a continuous transition zone of 2-5 μm in width between the Cr inclusion core and 152 cladding matrix, and the transition zone consists of Ni & Fe-rich dendritic austenite and Cr23C6 and Cr matrix. The transition zone has the highest nanoindentation hardness (7.66 GPa), which is much harder than the inclusion core (5.14 GPa) and 152 cladding (3.71 GPa). In-situ microscopic tensile tests show that cracks initialize preferentially in transition zone, and then propagate into the inclusion core, and creep further into 152 cladding after penetrating the core area. The inclusion core and its transition zone both share similar oxide film structure with nickel-base 152 cladding matrix in simulated primary water, while those two parts present better general corrosion resistance than 152 cladding matrix due to higher Cr concentration.

Isotope and Nuclear Chemistry Division annual report FY 1986, October 1985-September 1986

International Nuclear Information System (INIS)

Heiken, J.H.

1987-06-01

This report describes progress in the major research and development programs carried out in FY 1986 by the Isotope and Nuclear Chemistry Division. The report includes articles on radiochemical diagnostics and weapons tests; weapons radiochemical diagnostics research and development; other unclassified weapons research; stable and radioactive isotope production and separation; chemical biology and nuclear medicine; element and isotope transport and fixation; actinide and transition metal chemistry; structural chemistry, spectroscopy, and applications; nuclear structure and reactions; irradiation facilities; advanced concepts and technology; and atmospheric chemistry

Isotope and Nuclear Chemistry Division annual report FY 1986, October 1985-September 1986

Energy Technology Data Exchange (ETDEWEB)

Heiken, J.H. (ed.)

1987-06-01

This report describes progress in the major research and development programs carried out in FY 1986 by the Isotope and Nuclear Chemistry Division. The report includes articles on radiochemical diagnostics and weapons tests; weapons radiochemical diagnostics research and development; other unclassified weapons research; stable and radioactive isotope production and separation; chemical biology and nuclear medicine; element and isotope transport and fixation; actinide and transition metal chemistry; structural chemistry, spectroscopy, and applications; nuclear structure and reactions; irradiation facilities; advanced concepts and technology; and atmospheric chemistry.

Improving Information Literacy Skills through Learning to Use and Edit Wikipedia: A Chemistry Perspective

Science.gov (United States)

Walker, Martin A.; Li, Ye

2016-01-01

Our students rely on Wikipedia on their mobile devices or laptops, since it is an extremely rich and broad resource. This article overviews the Chemistry content on Wikipedia and how students can learn to use it effectively as an information resource, critically evaluating content, and learning key information literacy skills. We also discuss how…

Structural Diversity in Alkali Metal and Alkali Metal Magnesiate Chemistry of the Bulky 2,6-Diisopropyl-N-(trimethylsilyl)anilino Ligand.

Science.gov (United States)

Fuentes, M Ángeles; Zabala, Andoni; Kennedy, Alan R; Mulvey, Robert E

2016-10-10

Bulky amido ligands are precious in s-block chemistry, since they can implant complementary strong basic and weak nucleophilic properties within compounds. Recent work has shown the pivotal importance of the base structure with enhancement of basicity and extraordinary regioselectivities possible for cyclic alkali metal magnesiates containing mixed n-butyl/amido ligand sets. This work advances alkali metal and alkali metal magnesiate chemistry of the bulky arylsilyl amido ligand [N(SiMe 3 )(Dipp)] - (Dipp=2,6-iPr 2 -C 6 H 3 ). Infinite chain structures of the parent sodium and potassium amides are disclosed, adding to the few known crystallographically characterised unsolvated s-block metal amides. Solvation by N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA) or N,N,N',N'-tetramethylethylenediamine (TMEDA) gives molecular variants of the lithium and sodium amides; whereas for potassium, PMDETA gives a molecular structure, TMEDA affords a novel, hemi-solvated infinite chain. Crystal structures of the first magnesiate examples of this amide in [MMg{N(SiMe 3 )(Dipp)} 2 (μ-nBu)] ∞ (M=Na or K) are also revealed, though these breakdown to their homometallic components in donor solvents as revealed through NMR and DOSY studies. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

A Study of Faculty Approaches to Teaching Undergraduate Physical Chemistry Courses

Science.gov (United States)

Mack, Michael Ryan

Chemistry education researchers have not adequately studied teaching and learning experiences at all levels in the undergraduate chemistry curriculum leaving gaps in discipline-based STEM education communities understanding about how the upper- division curricula works (National Research Council, 2012b; Towns, 2013). This study explored faculty approaches to teaching in upper-division physical chemistry course settings using an interview-based methodology. Two conceptualizations of approaches to teaching emerged from a phenomenographic analysis of interview transcripts: (1) faculty beliefs about the purposes for teaching physical chemistry and (2) their conceptions of their role as an instructor in these course settings. Faculty who reported beliefs predominantly centered on helping students develop conceptual knowledge and problem-solving skills in physical chemistry often worked with didactic models of teaching, which emphasized the transfer of expert knowledge to students. When faculty expressed beliefs that were more inclusive of conceptual, epistemic, and social learning goals in science education they often described more student-centered models of teaching and learning, which put more responsibilities on them to facilitate students' interactive engagement with the material and peers during regularly scheduled class time. Knowledge of faculty thinking, as evinced in a rich description of their accounts of their experience, provides researchers and professional developers with useful information about the potential opportunities or barriers that exist for helping faculty align their beliefs and goals for teaching with research-based instructional strategies.

Structure correlation and chemistry

International Nuclear Information System (INIS)

Buergi, H.B.

1998-01-01

The main goal of crystal and molecular structure determination is to provide a starting point for understanding the physical, chemical and biological properties of matter. At present, results from nearly 300000 crystal structure studies are available in computer-readable form. Structure correlation attempts to extract knowledge and understanding from this body of information, which is not available from its parts. This article reviews some typical examples: libraries of prototypal molecular dimensions, mappings of chemical reaction pathways, correlations between structure on one hand and energy, reaction rate, catalytic activity or magnetism on the other. The knowledge gained from structure-correlation studies, together with quantum-chemical and other modeling techniques, provides conceptual and practical tools for designing molecules and materials with tailor-made properties. (orig.)

Chemistry of the actinide elements. Second edition

International Nuclear Information System (INIS)

Katz, J.J.; Seaborg, G.T.; Morss, L.R.

1987-01-01

This is an exhaustive, updated discourse on the chemistry of Actinides, Volume 1 contains a systematic coverage of the elements Ac, Th, Pa, U, Np, and Pu, which constitutes Part 1 of the work. The characterization of each element is discussed in terms of its nuclear properties, occurrence, preparation, atomic and metallic properties, chemistry of specific compounds, and solution chemistry. The first part of Volume 2 follows the same format as Volume 1 but is confined to the elements Am, Cm, Bk, Cf, and Es, plus a more condensed coverage of the Transeinsteinium elements (Fm, Md, No, Lw, and 104-109). Part 2 of this volume is devoted to a discussion of the actinide elements in general, with a specific focus on electronic spectra, thermodynamic and magnetic properties, the metallic state, structural chemistry, solution kinetics, organometallic chemistry for σ- and π-bonded compounds, and some concluding remarks on the superheavy elements

Isotope and Nuclear Chemistry Division annual report, FY 1988

International Nuclear Information System (INIS)

1989-06-01

This report describes some of the major research and development programs of the Isotope and Nuclear Chemistry Division during FY 1988. The report includes articles on weapons chemistry, biochemistry and nuclear medicine, nuclear structure and reactions, and the INC Division facilities and laboratories

Substrate availability drives spatial patterns in richness of ammonia-oxidizing bacteria and archaea in temperate forest soils

Science.gov (United States)

J.S. Norman; J.E. Barrett

2016-01-01

We sought to investigate the drivers of richness of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in temperate forest soils. We sampled soils across four experimental watersheds in the Coweeta Hydrologic Laboratory, North Carolina USA. These watersheds are geographically close, but vary in soil chemistry due to differences in land use history. While we...

Effects of wood fiber surface chemistry on strength of wood–plastic composites

Energy Technology Data Exchange (ETDEWEB)

Migneault, Sébastien, E-mail: sebastien.migneault@uqat.ca [University of Quebec in Abitibi-Temiscamingue (UQAT), 445 boulevard de l’Université, Rouyn-Noranda, Québec J9X 5E4 (Canada); Koubaa, Ahmed, E-mail: ahmed.koubaa@uqat.ca [UQAT (Canada); Perré, Patrick, E-mail: patrick.perre@ecp.fr [École centrale de Paris, Grande Voie des Vignes, F-92 295 Chatenay-Malabry Cedex (France); Riedl, Bernard, E-mail: Bernard.Riedl@sbf.ulaval.ca [Université Laval, 2425 rue de la Terrasse, Québec City, Québec G1V 0A6 (Canada)

2015-07-15

Highlights: • Infrared spectroscopy and X-ray photoelectron spectroscopy analyses showed variations of surface chemical characteristics according to fiber origin. • Surface chemical characteristics of fibers could partly explain the differences in mechanical properties of the wood–plastic composites. • Fibers with carbohydrate rich surface led to stronger wood–plastic composites because the coupling between the matrix and fibers using coupling agent is achieved with polar sites mostly available on carbohydrates. • Conversely, lignin or extractives rich surface do not have oxidized functions for the esterification reaction with coupling agent and thus led to wood–plastic composites with lower mechanical properties. • Other factors such as mechanical interlocking and fiber morphology interfere with the effects of fiber surface chemistry. - Abstract: Because wood–plastic composites (WPC) strength relies on fiber-matrix interaction at fiber surface, it is likely that fiber surface chemistry plays an important role in WPC strength development. The objective of the present study is to investigate the relationships between fiber surface chemical characteristics and WPC mechanical properties. Different fibers were selected and characterized for surface chemical characteristics using X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR). WPC samples were manufactured at 40% fiber content and with six different fibers. High density polyethylene was used as matrix and maleated polyethylene (MAPE) was used as compatibility agent. WPC samples were tested for mechanical properties and fiber-matrix interface was observed with scanning electron microscope. It was found WPC strength decreases as the amount of unoxidized carbon (assigned to lignin and extractives) measured with XPS on fiber surface increases. In the opposite case, WPC strength increases with increasing level of oxidized carbon (assigned to carbohydrates) on fiber surface. The same

Effects of wood fiber surface chemistry on strength of wood–plastic composites

International Nuclear Information System (INIS)

Migneault, Sébastien; Koubaa, Ahmed; Perré, Patrick; Riedl, Bernard

2015-01-01

Highlights: • Infrared spectroscopy and X-ray photoelectron spectroscopy analyses showed variations of surface chemical characteristics according to fiber origin. • Surface chemical characteristics of fibers could partly explain the differences in mechanical properties of the wood–plastic composites. • Fibers with carbohydrate rich surface led to stronger wood–plastic composites because the coupling between the matrix and fibers using coupling agent is achieved with polar sites mostly available on carbohydrates. • Conversely, lignin or extractives rich surface do not have oxidized functions for the esterification reaction with coupling agent and thus led to wood–plastic composites with lower mechanical properties. • Other factors such as mechanical interlocking and fiber morphology interfere with the effects of fiber surface chemistry. - Abstract: Because wood–plastic composites (WPC) strength relies on fiber-matrix interaction at fiber surface, it is likely that fiber surface chemistry plays an important role in WPC strength development. The objective of the present study is to investigate the relationships between fiber surface chemical characteristics and WPC mechanical properties. Different fibers were selected and characterized for surface chemical characteristics using X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR). WPC samples were manufactured at 40% fiber content and with six different fibers. High density polyethylene was used as matrix and maleated polyethylene (MAPE) was used as compatibility agent. WPC samples were tested for mechanical properties and fiber-matrix interface was observed with scanning electron microscope. It was found WPC strength decreases as the amount of unoxidized carbon (assigned to lignin and extractives) measured with XPS on fiber surface increases. In the opposite case, WPC strength increases with increasing level of oxidized carbon (assigned to carbohydrates) on fiber surface. The same

In-situ Evaluation of Soil Organic Molecules: Functional Group Chemistry Aggregate Structures, Metal and Surface Complexation Using Soft X-Ray

International Nuclear Information System (INIS)

Myneni, Satish C.

2008-01-01

Organic molecules are common in all Earth surface environments, and their composition and chemistry play an important role in a variety of biogeochemical reactions, such as mineral weathering, nutrient cycling and the solubility and transport of contaminants. However, most of what we know about the chemistry of these molecules comes from spectroscopy and microscopy studies of organic molecules extracted from different natural systems using either inorganic or organic solvents. Although all these methods gave us clues about the composition of these molecules, their composition and structure change with the extraction and the type of ex-situ analysis, their true behavior is less well understood. The goal of this project is to develop synchrotron instrumentation for studying natural organics, and to apply these recently developed synchrotron X-ray spectroscopy and microscopy techniques for understanding the: (1) functional group composition of naturally occurring organic molecules; (2) macromolecular structures of organic molecules; and (3) the nature of interactions of organic molecules with mineral surfaces in different environmental conditions.

Relative Importance of Current and Past Landscape Structure and Local Habitat Conditions for Plant Species Richness in Dry Grassland-Like Forest Openings

Czech Academy of Sciences Publication Activity Database

Husáková, I.; Münzbergová, Zuzana

2014-01-01

Roč. 9, č. 5 (2014), s. 1-15 E-ISSN 1932-6203 Institutional support: RVO:67985939 Keywords : landscape structure * species richness * dry grassland Subject RIV: EF - Botanics Impact factor: 3.234, year: 2014

Stabilized Lithium-Metal Surface in a Polysulfide-Rich Environment of Lithium-Sulfur Batteries.

Science.gov (United States)

Zu, Chenxi; Manthiram, Arumugam

2014-08-07

Lithium-metal anode degradation is one of the major challenges of lithium-sulfur (Li-S) batteries, hindering their practical utility as next-generation rechargeable battery chemistry. The polysulfide migration and shuttling associated with Li-S batteries can induce heterogeneities of the lithium-metal surface because it causes passivation by bulk insulating Li2S particles/electrolyte decomposition products on a lithium-metal surface. This promotes lithium dendrite formation and leads to poor lithium cycling efficiency with complicated lithium surface chemistry. Here, we show copper acetate as a surface stabilizer for lithium metal in a polysulfide-rich environment of Li-S batteries. The lithium surface is protected from parasitic reactions with the organic electrolyte and the migrating polysulfides by an in situ chemical formation of a passivation film consisting of mainly Li2S/Li2S2/CuS/Cu2S and electrolyte decomposition products. This passivation film also suppresses lithium dendrite formation by controlling the lithium deposition sites, leading to a stabilized lithium surface characterized by a dendrite-free morphology and improved surface chemistry.

Physics and Chemistry of Earth Materials

Science.gov (United States)

Navrotsky, Alexandra

1994-11-01

Stressing the fundamental solid state behavior of minerals, and emphasizing both theory and experiment, this text surveys the physics and chemistry of earth materials. The author begins with a systematic tour of crystal chemistry of both simple and complex structures (with completely new structural drawings) and discusses how to obtain structural and thermodynamic information experimentally. Dr. Navrotsky also reviews the quantitative concepts of chemical bonding--band theory, molecular orbit and ionic models. She then covers physical properties and relates microscopic features to macroscopic thermodynamic behavior and treats high pressure phase transitions, amorphous materials and solid state reactions. The author concludes with a look at the interface between mineral physics and materials science. Highly illustrated throughout, this book fills the gap between undergraduate texts and specialized review volumes and is appropriate for students and researchers in earth science and materials science.

Synthesis of polybenzoxazine based nitrogen-rich porous carbons for carbon dioxide capture

Science.gov (United States)

Wan, Liu; Wang, Jianlong; Feng, Chong; Sun, Yahui; Li, Kaixi

2015-04-01

Nitrogen-rich porous carbons (NPCs) were synthesized from 1,5-dihydroxynaphthalene, urea, and formaldehyde based on benzoxazine chemistry by a soft-templating method with KOH chemical activation. They possess high surface areas of 856.8-1257.8 m2 g-1, a large pore volume of 0.15-0.65 cm3 g-1, tunable pore structure, high nitrogen content (5.21-5.32 wt%), and high char yields. The amount of the soft-templating agent F127 has multiple influences on the textural and chemical properties of the carbons, affecting the surface area and pore structure, impacting the compositions of nitrogen species and resulting in an improvement of the CO2 capture performance. At 1 bar, high CO2 uptake of 4.02 and 6.35 mmol g-1 at 25 and 0 °C was achieved for the sample NPC-2 with a molar ratio of F127 : urea = 0.010 : 1. This can be attributed to its well-developed micropore structure and abundant pyridinic nitrogen, pyrrolic nitrogen and pyridonic nitrogen functionalities. The sample NPC-2 also exhibits a remarkable selectivity for CO2/N2 separation and a fast adsorption/desorption rate and can be easily regenerated. This suggests that the polybenzoxazine-based NPCs are desirable for CO2 capture because of possessing a high micropore surface area, a large micropore volume, appropriate pore size distribution, and a large number of basic nitrogen functionalities.Nitrogen-rich porous carbons (NPCs) were synthesized from 1,5-dihydroxynaphthalene, urea, and formaldehyde based on benzoxazine chemistry by a soft-templating method with KOH chemical activation. They possess high surface areas of 856.8-1257.8 m2 g-1, a large pore volume of 0.15-0.65 cm3 g-1, tunable pore structure, high nitrogen content (5.21-5.32 wt%), and high char yields. The amount of the soft-templating agent F127 has multiple influences on the textural and chemical properties of the carbons, affecting the surface area and pore structure, impacting the compositions of nitrogen species and resulting in an improvement of the

A study of how precursor key concepts for organic chemistry success are understood by general chemistry students

Science.gov (United States)

Meyer, Patrick Gerard

This study examines college student understanding of key concepts that will support future organic chemistry success as determined by university instructors. During four one-hour individual interviews the sixteen subjects attempted to solve general chemistry problems. A think-aloud protocol was used along with a whiteboard where the students could draw and illustrate their ideas. The protocols for the interviews were adapted from the Covalent Structure and Bonding two-tiered multiple choice diagnostic instrument (Peterson, Treagust, & Garnett, 1989) and augmented by the Geometry and Polarity of Molecules single-tiered multiple choice instrument (Furio & Calatayud, 1996). The interviews were videotaped, transcribed, and coded for analysis to determine the subjects' understanding of the key ideas. The subjects displayed many misconceptions that were summarized into nine assertions about student conceptualization of chemistry. (1) Many students misunderstand the location and nature of intermolecular forces. (2) Some think electronegativity differences among atoms in a molecule are sufficient to make the molecule polar, regardless of spatial arrangement. (3) Most know that higher phase change temperatures imply stronger intermolecular attractions, but many do not understand the difference between covalent molecular and covalent network substances. (4) Many have difficulty deciding whether a molecule is polar or non-polar, often confusing bilateral symmetry with spatial symmetry in all three dimensions. (5) Many cannot reliably draw correct Lewis structures due to carelessness and overuse of flawed algorithms. (6) Many are confused by how electrons can both repel one other and facilitate bonding between atoms via orbitals---this seems oxymoronic to them. (7) Many cannot explain why the atoms of certain elements do not follow the octet rule and some believe the octet rule alone can determine the shape of a molecule. (8) Most do know that electronegativity and polarity

Isotope and Nuclear Chemistry Division annual report FY 1985, October 1984-September 1985

International Nuclear Information System (INIS)

Heiken, J.H.

1986-04-01

This report describes progress in the major research and development programs carried out in FY 1985 by the Isotope and Nuclear Chemistry Division. It covers radiochemical diagnostics of weapons tests; weapons radiochemical diagnostics research and development; other unclassified weapons research; stable and radioactive isotope production, separation, and applications (including biomedical applications); element and isotope transport and fixation; actinide and transition metal chemistry; structural chemistry, spectroscopy, and applications; nuclear structure and reactions; irradiations facilities; advanced analytical techniques; development and applications; atmospheric chemistry and transport; and earth and planetary processes

Machine learning of single molecule free energy surfaces and the impact of chemistry and environment upon structure and dynamics.

Science.gov (United States)

Mansbach, Rachael A; Ferguson, Andrew L

2015-03-14

The conformational states explored by polymers and proteins can be controlled by environmental conditions (e.g., temperature, pressure, and solvent) and molecular chemistry (e.g., molecular weight and side chain identity). We introduce an approach employing the diffusion map nonlinear machine learning technique to recover single molecule free energy landscapes from molecular simulations, quantify changes to the landscape as a function of external conditions and molecular chemistry, and relate these changes to modifications of molecular structure and dynamics. In an application to an n-eicosane chain, we quantify the thermally accessible chain configurations as a function of temperature and solvent conditions. In an application to a family of polyglutamate-derivative homopeptides, we quantify helical stability as a function of side chain length, resolve the critical side chain length for the helix-coil transition, and expose the molecular mechanisms underpinning side chain-mediated helix stability. By quantifying single molecule responses through perturbations to the underlying free energy surface, our approach provides a quantitative bridge between experimentally controllable variables and microscopic molecular behavior, guiding and informing rational engineering of desirable molecular structure and function.

Selectivity on-target of bromodomain chemical probes by structure-guided medicinal chemistry and chemical biology.

Science.gov (United States)

Galdeano, Carles; Ciulli, Alessio

2016-09-01

Targeting epigenetic proteins is a rapidly growing area for medicinal chemistry and drug discovery. Recent years have seen an explosion of interest in developing small molecules binding to bromodomains, the readers of acetyl-lysine modifications. A plethora of co-crystal structures has motivated focused fragment-based design and optimization programs within both industry and academia. These efforts have yielded several compounds entering the clinic, and many more are increasingly being used as chemical probes to interrogate bromodomain biology. High selectivity of chemical probes is necessary to ensure biological activity is due to an on-target effect. Here, we review the state-of-the-art of bromodomain-targeting compounds, focusing on the structural basis for their on-target selectivity or lack thereof. We also highlight chemical biology approaches to enhance on-target selectivity.

Bryophyte species richness on retention aspens recovers in time but community structure does not.

Science.gov (United States)

Oldén, Anna; Ovaskainen, Otso; Kotiaho, Janne S; Laaka-Lindberg, Sanna; Halme, Panu

2014-01-01

Green-tree retention is a forest management method in which some living trees are left on a logged area. The aim is to offer 'lifeboats' to support species immediately after logging and to provide microhabitats during and after forest re-establishment. Several studies have shown immediate decline in bryophyte diversity after retention logging and thus questioned the effectiveness of this method, but longer term studies are lacking. Here we studied the epiphytic bryophytes on European aspen (Populus tremula L.) retention trees along a 30-year chronosequence. We compared the bryophyte flora of 102 'retention aspens' on 14 differently aged retention sites with 102 'conservation aspens' on 14 differently aged conservation sites. We used a Bayesian community-level modelling approach to estimate the changes in bryophyte species richness, abundance (area covered) and community structure during 30 years after logging. Using the fitted model, we estimated that two years after logging both species richness and abundance of bryophytes declined, but during the following 20-30 years both recovered to the level of conservation aspens. However, logging-induced changes in bryophyte community structure did not fully recover over the same time period. Liverwort species showed some or low potential to benefit from lifeboating and high potential to re-colonise as time since logging increases. Most moss species responded similarly, but two cushion-forming mosses benefited from the logging disturbance while several weft- or mat-forming mosses declined and did not re-colonise in 20-30 years. We conclude that retention trees do not function as equally effective lifeboats for all bryophyte species but are successful in providing suitable habitats for many species in the long-term. To be most effective, retention cuts should be located adjacent to conservation sites, which may function as sources of re-colonisation and support the populations of species that require old-growth forests.

Bryophyte species richness on retention aspens recovers in time but community structure does not.

Directory of Open Access Journals (Sweden)

Anna Oldén

Full Text Available Green-tree retention is a forest management method in which some living trees are left on a logged area. The aim is to offer 'lifeboats' to support species immediately after logging and to provide microhabitats during and after forest re-establishment. Several studies have shown immediate decline in bryophyte diversity after retention logging and thus questioned the effectiveness of this method, but longer term studies are lacking. Here we studied the epiphytic bryophytes on European aspen (Populus tremula L. retention trees along a 30-year chronosequence. We compared the bryophyte flora of 102 'retention aspens' on 14 differently aged retention sites with 102 'conservation aspens' on 14 differently aged conservation sites. We used a Bayesian community-level modelling approach to estimate the changes in bryophyte species richness, abundance (area covered and community structure during 30 years after logging. Using the fitted model, we estimated that two years after logging both species richness and abundance of bryophytes declined, but during the following 20-30 years both recovered to the level of conservation aspens. However, logging-induced changes in bryophyte community structure did not fully recover over the same time period. Liverwort species showed some or low potential to benefit from lifeboating and high potential to re-colonise as time since logging increases. Most moss species responded similarly, but two cushion-forming mosses benefited from the logging disturbance while several weft- or mat-forming mosses declined and did not re-colonise in 20-30 years. We conclude that retention trees do not function as equally effective lifeboats for all bryophyte species but are successful in providing suitable habitats for many species in the long-term. To be most effective, retention cuts should be located adjacent to conservation sites, which may function as sources of re-colonisation and support the populations of species that require old

Expression, purification and preliminary biochemical and structural characterization of the leucine rich repeat namesake domain of leucine rich repeat kinase 2.

Science.gov (United States)

Vancraenenbroeck, Renée; Lobbestael, Evy; Weeks, Stephen D; Strelkov, Sergei V; Baekelandt, Veerle; Taymans, Jean-Marc; De Maeyer, Marc

2012-03-01

Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common cause of familial Parkinson's disease. Much research effort has been directed towards the catalytic core region of LRRK2 composed of GTPase (ROC, Ras of complex proteins) and kinase domains and a connecting COR (C-terminus of ROC) domain. In contrast, the precise functions of the protein-protein interaction domains, such as the leucine-rich repeat (LRR) domain, are not known. In the present study, we modeled the LRRK2 LRR domain (LRR(LRRK2)) using a template assembly approach, revealing the presence of 14 LRRs. Next, we focused on the expression and purification of LRR(LRRK2) in Escherichia coli. Buffer optimization revealed that the protein requires the presence of a zwitterionic detergent, namely Empigen BB, during solubilization and the subsequent purification and characterization steps. This indicates that the detergent captures the hydrophobic surface patches of LRR(LRRK2) thereby suppressing its aggregation. Circular dichroism (CD) spectroscopy measured 18% α-helices and 21% β-sheets, consistent with predictions from the homology model. Size exclusion chromatography (SEC) and dynamic light scattering measurements showed the presence of a single species, with a Stokes radius corresponding to the model dimensions of a protein monomer. Furthermore, no obvious LRR(LRRK2) multimerization was detected via cross-linking studies. Finally, the LRR(LRRK2) clinical mutations did not influence LRR(LRRK2) secondary, tertiary or quaternary structure as determined via SEC and CD spectroscopy. We therefore conclude that these mutations are likely to affect putative LRR(LRRK2) inter- and intramolecular interactions. Copyright © 2011 Elsevier B.V. All rights reserved.

Progress report 1981-1982. Reactor Chemistry Department

International Nuclear Information System (INIS)

1983-08-01

Review of the activities performed by the Reactor Chemistry Department of the National Atomic Energy Commission of Argentina during 1981-1982. This Department provides services and assistance in all matters related to water chemistry and nuclear reactors chemistry, in all their phases: design, construction, commissioning and decommissioning. During this period, the following tasks were performed: study of the metallic oxide-water interphases; determination of the goethite and magnetite surficial charges; synthesis of the monodispersed nickel ferrites; study of the iron oxides dissolution mechanism in presence of different complexing agents; chemical decontamination of structural metals; thermodynamics of the water-nitrogen system; physico-chemical studies of aqueous solutions at high temperatures; hydrothermal decomposition of ionic exchange resines and study of the equilibria of the anionic exchange for the chemistry of pressurized reactor's primary loops. The appendix includes information on the Reactor Chemistry Department staff, its publications, services, seminars, courses and conferences performed during 1981-1982. (R.J.S.) [es

Flame chemistry of alkane-rich gasoline fuels and a surrogate using photoionization mass spectrometry: I. Primary reference fuel

KAUST Repository

Selim, H.

2015-03-30

Improving the gasoline engines performance requires thorough understanding of their fundamental chemistry of combustion. Since the actual gasoline fuels are difficult to examine, due to the lack of knowledge about their exact composition as well as their numerous fuel components, the approach of using simpler gasoline fuels with limited number of components or using surrogate fuels has become more common. In this study, the combustion chemistry of laminar premixed flame of different gasoline fuels/surrogate has been examined. In this particular paper, the primary reference fuel, PRF84, has been examined at equivalence ratio of 1 and pressure of 20 Torr. The gas analysis was conducted using vacuum ultraviolet photoionization mass spectrometry.

Flame chemistry of alkane-rich gasoline fuels and a surrogate using photoionization mass spectrometry: I. Primary reference fuel

KAUST Repository

Selim, H.; Lucassen, A.; Hansen, N.; Sarathy, Mani

2015-01-01

Improving the gasoline engines performance requires thorough understanding of their fundamental chemistry of combustion. Since the actual gasoline fuels are difficult to examine, due to the lack of knowledge about their exact composition as well as their numerous fuel components, the approach of using simpler gasoline fuels with limited number of components or using surrogate fuels has become more common. In this study, the combustion chemistry of laminar premixed flame of different gasoline fuels/surrogate has been examined. In this particular paper, the primary reference fuel, PRF84, has been examined at equivalence ratio of 1 and pressure of 20 Torr. The gas analysis was conducted using vacuum ultraviolet photoionization mass spectrometry.

Structural and Chemical Properties of the Nitrogen-Rich Energetic Material Triaminoguanidinium 1-methyl-5-nitriminotetrazolate under Pressure

Science.gov (United States)

2012-08-01

ABSTRACT 16. SECURITY CLASSIFICATION OF: The structural and chemical properties of the bi-molecular, hydrogen-bonded, nitrogen-rich ener- getic...School Apprenticeship Program (ARO-HSAP), and the Depart- ment of Energy National Nuclear Security Administration (Carnegie/DOE Alliance Center; DE-FC52...B. J. Baer, H. Cynn, W. J. Evans, V. Iota , and C. S. Yoo, Phys. Rev. B 76(1), 014113 (2007). 9T. M. Klapötke, J. Stierstorfer, and A. U. Wallek, Chem

Structural Analysis of Lexical Bundles in University Lectures of Politics and Chemistry

Directory of Open Access Journals (Sweden)

Hadi Kashiha

2014-01-01

Full Text Available Referred to as extended collocations, lexical bundles are considered as a main factor in building fluency in academic discourse; helping to shape meaning and coherence in a text or speech. For decades, lexical bundles have attracted considerable amount of attention in corpus-based research in English for Academic Purposes (EAP. While, the focus of the most of the studies on lexical bundles was to explore the use of these multi-word expressions in academic written registers such as research articles, academic spoken registers such as university lectures have not received that amount of attention from the scholars. In this vein, there is still an open question of how they are structurally different across disciplines. With these concerns in mind, this study aimed to explore how lexical bundles are used structurally in a 50291 words corpus of 8 university lectures across two disciplines: chemistry and politics. To this aim, the most frequent four-word bundles in the corpus were classified according to their grammatical types to see the possible disciplinary variations in their frequency of use as well as the structure involved in their use. Results of the analysis revealed that noun phrase and prepositional phrase fragments were the most common structures in the lectures of the two disciplines, accounting for more than half of the bundles in politics. University lecturers appear to apply a variety of structures in the use of lexical bundles often peculiar to the discipline in order to convey their disciplinary messages.  This would lead to the need to emphasize the instruction of the most common structures in that discipline in a way for the lectures to be as comprehensive as possible for the intended audiences.

Organic Chemistry of Southern Sources: Microwave Spectroscopy of Cha-MMS1 and IRAS 15194-5115

Science.gov (United States)

Cordiner, Martin; Charnley, Steven

2011-01-01

We report new spectra of molecule-rich sources in the southern hemisphere obtained using the 22-meter Mopra telescope. Spectra and maps are presented of organic molecules detected between 30 and 50 GHz in the young Class 0 protostar Chamaeleon MMS-1. The large abundances of polyynes, cyanopolyynes and methanol may be indicative of a warm carbon chemistry in the dense gas surrounding this protostar. Spectra are also presented from a 78-96 GHz scan of the carbon-rich AGB star IRAS 15194-5115, including new detections of HC5N, CCS and C13CH.

Synthesis, crystal structure investigation and magnetism of the complex metal-rich boride series Crx(Rh1-yRuy)7-xB3 (x=0.88-1; y=0-1) with Th7Fe3-type structure

Science.gov (United States)

Misse, Patrick R. N.; Mbarki, Mohammed; Fokwa, Boniface P. T.

2012-08-01

Powder samples and single crystals of the new complex boride series Crx(Rh1-yRuy)7-xB3 (x=0.88-1; y=0-1) have been synthesized by arc-melting the elements under purified argon atmosphere on a water-cooled copper crucible. The products, which have metallic luster, were structurally characterized by single-crystal and powder X-ray diffraction as well as EDX measurements. Within the whole solid solution range the hexagonal Th7Fe3 structure type (space group P63mc, no. 186, Z=2) was identified. Single-crystal structure refinement results indicate the presence of chromium at two sites (6c and 2b) of the available three metal Wyckoff sites, with a pronounced preference for the 6c site. An unexpected Rh/Ru site preference was found in the Ru-rich region only, leading to two different magnetic behaviors in the solid solution: The Rh-rich region shows a temperature-independent (Pauli) paramagnetism whereas an additional temperature-dependent paramagnetic component is found in the Ru-rich region.

Optimization of reactor coolant shutdown chemistry practices for crud inventory management

International Nuclear Information System (INIS)

Fellers, B.; Barnette, J.; Stevens, J.; Perkins, D.

2002-01-01

This report describes reactor coolant shutdown chemistry control practices at Comanche Peak Steam Electric Station (CPSES, TXU-Generation, USA). The shutdown evolution is managed from a process control perspective to achieve conditions most favorable to crud decomposition and to avoiding re-precipitation of metals. The report discusses the evolution of current industry practices and the necessity for greater emphasis on shutdown chemistry control in response to Axial Offset Anomaly and growth of ex-core radiation fields during outage conditions. Nuclear Industry experience with axial offset anomaly (AOA), radiation field growth and unexpected behavior of crud during reactor shutdowns has encouraged the refinement of chemistry control practices during plant shutdown and startup. The strong implication of nickel rich crud as a cause of AOA and unexpected crud behavior has resulted in a focus on nickel inventory management. The goals for Comanche Peak Steam Electric Station (CPSES) include maintaining solubility of metals and radioisotopes, maximizing nickel removal and effective cleanup with demineralizers. This paper provides results and lessons learned from long term efforts to optimize the shutdown process. (authors)

Annual Report of Institute of Nuclear Chemistry and Technology 1999

International Nuclear Information System (INIS)

2000-06-01

The INCT 1999 Annual Report is the review of scientific activities in all branches being developed in the Institute of Nuclear Chemistry and Technology, Warsaw. The studies are connected in general with the following fields: radiation chemistry and physics, radiation technologies, radiochemistry, stable isotopes, nuclear analytical methods, chemistry in general, radiobiology, process engineering, material engineering, structural studies and diagnostics and nucleonic control systems and accelerators

Annual Report of Institute of Nuclear Chemistry and Technology 2002

International Nuclear Information System (INIS)

2003-06-01

The INCT 2002 Annual Report is the review of scientific activities in all branches being developed in the Institute of Nuclear Chemistry and Technology, Warsaw. The studies are connected in general with the following fields: radiation chemistry and physics, radiation technologies, radiochemistry, stable isotopes, nuclear analytical methods, chemistry in general, radiobiology, process engineering, material engineering, structural studies and diagnostics, nucleonic control systems and accelerators

Annual Report of Institute of Nuclear Chemistry and Technology 2002

Energy Technology Data Exchange (ETDEWEB)

NONE

2003-06-01

The INCT 2002 Annual Report is the review of scientific activities in all branches being developed in the Institute of Nuclear Chemistry and Technology, Warsaw. The studies are connected in general with the following fields: radiation chemistry and physics, radiation technologies, radiochemistry, stable isotopes, nuclear analytical methods, chemistry in general, radiobiology, process engineering, material engineering, structural studies and diagnostics, nucleonic control systems and accelerators.

Annual Report of Institute of Nuclear Chemistry and Technology 1999

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-06-01

The INCT 1999 Annual Report is the review of scientific activities in all branches being developed in the Institute of Nuclear Chemistry and Technology, Warsaw. The studies are connected in general with the following fields: radiation chemistry and physics, radiation technologies, radiochemistry, stable isotopes, nuclear analytical methods, chemistry in general, radiobiology, process engineering, material engineering, structural studies and diagnostics and nucleonic control systems and accelerators.

Cerium intermetallics with TiNiSi-type structure

Energy Technology Data Exchange (ETDEWEB)

Janka, Oliver; Niehaus, Oliver; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Chevalier, Bernard [Bordeaux Univ. CNRS (UPR 9048), Pessac (France). Inst. de Chimie de la Matiere Condensee de Bordeaux (ICMCB)

2016-08-01

Intermetallic compounds with the equiatomic composition CeTX that crystallize with the orthorhombic TiNiSi-type structure can be synthesized with electron-rich transition metals (T) and X = Zn, Al, Ga, Si, Ge, Sn, As, Sb, and Bi. The present review focusses on the crystal chemistry and chemical bonding of these CeTX phases and on their physical properties, {sup 119}Sn and {sup 121}Sb Moessbauer spectra, high-pressure effects, hydrogenation reactions and the formation of solid solutions in order to elucidate structure-property relationships. This paper is the final one of a series of four reviews on equiatomic intermetallic cerium compounds [Part I: Z. Naturforsch. 2015, 70b, 289; Part II: Z. Naturforsch. 2015, 70b, 695; Part III: Z. Naturforsch. 2016, 71b, 165].

Integrating Chemistry: Crossing the Millennium Divide.

Science.gov (United States)

Housecroft, Catherine E

2018-02-01

A personal account of the development of two University level chemistry books is presented. The account focuses on ways to integrate the traditional branches of chemistry into a textbook that captures the imagination of students and relates chemical principles and fundamental topics to environmental, medicinal, biological and industrial applications. The ways in which teaching methods have changed over two decades and how web-based resources can be used to improve the communication of chemical (in particular structural) concepts are highlighted.

Evolving knowledge of sex differences in brain structure, function, and chemistry.

Science.gov (United States)

Cosgrove, Kelly P; Mazure, Carolyn M; Staley, Julie K

2007-10-15

Clinical and epidemiologic evidence demonstrates sex differences in the prevalence and course of various psychiatric disorders. Understanding sex-specific brain differences in healthy individuals is a critical first step toward understanding sex-specific expression of psychiatric disorders. Here, we evaluate evidence on sex differences in brain structure, chemistry, and function using imaging methodologies, including functional magnetic resonance imaging (fMRI), positron emission tomography (PET), single photon emission computed tomography (SPECT), and structural magnetic resonance imaging (MRI) in mentally healthy individuals. MEDLINE searches of English-language literature (1980-November 2006) using the terms sex, gender, PET, SPECT, MRI, fMRI, morphometry, neurochemistry, and neurotransmission were performed to extract relevant sources. The literature suggests that while there are many similarities in brain structure, function, and neurotransmission in healthy men and women, there are important differences that distinguish the male from the female brain. Overall, brain volume is greater in men than women; yet, when controlling for total volume, women have a higher percentage of gray matter and men a higher percentage of white matter. Regional volume differences are less consistent. Global cerebral blood flow is higher in women than in men. Sex-specific differences in dopaminergic, serotonergic, and gamma-aminobutyric acid (GABA)ergic markers indicate that male and female brains are neurochemically distinct. Insight into the etiology of sex differences in the normal living human brain provides an important foundation to delineate the pathophysiological mechanisms underlying sex differences in neuropsychiatric disorders and to guide the development of sex-specific treatments for these devastating brain disorders.

A materials informatics approach for crystal chemistry

Science.gov (United States)

Kong, Chang Sun

This thesis addresses one of the fundamental questions in materials crystal chemistry, namely why do atoms arrange themselves in the way they do? The ability to broadly design and predict new phases [i.e. crystal structures] can be partly met using concepts that employ phase homologies. Homologous series of compounds are those that seem chemically diverse but can be expressed in terms of a mathematical formula that is capable of producing each chemical member in that crystal structure. A well-established strategy to help discover new compounds -- or at least to try to develop chemical design strategies for discovery -- is to search, organize and classify homologous compounds from known data. These classification schemes are developed with the hope that they can provide sufficient insight to help us forecast with some certainty, specific new phases or compounds. Yet, while the classification schemes (over a dozen have been reported in the last 50 years) have proved to be instructive, mostly in hindsight, but they have had limited impact, if at all, on the a priori design of materials chemistry. The aim of this research project is to develop a totally new approach to the study of chemical complexity in materials science using the tools of information theory and data science, which link diverse and high dimensional data derived from physical modeling and experiments. A very large scale binary AB2 crystallographic database is used as a data platform to develop a new data mining/informatics protocol based on high dimensional recursive partitioning schemes coupled to information theoretic measures to: (1) Identify which type of structure prototype is preferred over another for a given chemistry of compound; (2) discover new classification schemes of structure/chemistry/property relationships that classical homologies do not detect and finally we; (3) Extract and organize the underlying design rules for the formation of a given structure by quantitatively assessing the

Pre-Service Physics and Chemistry Teachers' Conceptual Integration of Physics and Chemistry Concepts

Science.gov (United States)

Tuysuz, Mustafa; Bektas, Oktay; Geban, Omer; Ozturk, Gokhan; Yalvac, Bugrahan

2016-01-01

This study examines the pre-service teachers' opinions about conceptual integration (CI) and their understanding of it. A qualitative phenomenology design was used in the study. Data was collected through in-depth semi-structured interviews comprising ten guiding questions. Three pre-service physics and three pre-service chemistry teachers…

Structure and chemistry of epitaxial ceria thin films on yttria-stabilized zirconia substrates, studied by high resolution electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Sinclair, Robert, E-mail: bobsinc@stanford.edu [Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States); Lee, Sang Chul, E-mail: sclee99@stanford.edu [Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States); Shi, Yezhou; Chueh, William C. [Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States); Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States)

2017-05-15

We have applied aberration-corrected transmission electron microscopy (TEM) imaging and electron energy loss spectroscopy (EELS) to study the structure and chemistry of epitaxial ceria thin films, grown by pulsed laser deposition onto (001) yttria-stabilized zirconia (YSZ) substrates. There are few observable defects apart from the expected mismatch interfacial dislocations and so the films would be expected to have good potential for applications. Under high electron beam dose rate (above about 6000 e{sup -}/Å{sup 2}s) domains of an ordered structure appear and these are interpreted as being created by oxygen vacancy ordering. The ordered structure does not appear at lower lose rates (ca. 2600 e{sup -}/Å{sup 2}s) and can be removed by imaging under 1 mbar oxygen gas in an environmental TEM. EELS confirms that there is both oxygen deficiency and the associated increase in Ce{sup 3+} versus Ce{sup 4+} cations in the ordered domains. In situ high resolution TEM recordings show the formation of the ordered domains as well as atomic migration along the ceria thin film (001) surface. - Highlights: • The local structure and chemistry of ceria can be studied by TEM combined with EELS. • At lower electron, there are no observable changes in the ceria thin films. • At higher dose rates, an ordered phase is created due to oxygen vacancy ordering. • In situ HRTEM shows the oxygen vacancy ordering and the movement of surface atoms.

Variation in fish community structure, richness, and diversity in 56 Danish lakes with contrasting depth, size, and trophic state: does the method matter?

DEFF Research Database (Denmark)

Menezes, Rosemberg; Borchsenius, Finn; Svenning, J.-C.

2013-01-01

a better understanding of fish communities. We compare fish community composition, richness, and diversity in 56 Danish lakes using data obtained by gillnetting in different lake zones and near-shore electrofishing, respectively. On average, electrofishing captured more species than offshore gillnets......, but not more than littoral gillnets. Overall, the different fish sampling methods showed consistency as to fish community structure, but noticeable differences in community–environment relationships. Lake area was the best predictor for fish species richness in the littoral samplings, while it was poor...... community, as all methods miss some important species that other methods capture. However, electrofishing seems to be a fast alternative to gillnets for monitoring fish species richness and composition in littoral habitats of Danish lakes....

Ethnobotany, chemistry, and biological activities of the genus Tithonia (Asteraceae).

Science.gov (United States)

Chagas-Paula, Daniela A; Oliveira, Rejane B; Rocha, Bruno A; Da Costa, Fernando B

2012-02-01

The genus Tithonia is an important source of diverse natural products, particularly sesquiterpene lactones, diterpenes, and flavonoids. The collected information in this review attempts to summarize the recent developments in the ethnobotany, biological activities, and secondary metabolite chemistry of this genus. More than 100 structures of natural products from Tithonia are reported in this review. The species that has been most investigated in this genus is T. diversifolia, from which ca. 150 compounds were isolated. Biological studies are described to evaluate the anti-inflammatory, analgesic, antimalarial, antiviral, antidiabetic, antidiarrhoeal, antimicrobial, antispasmodic, vasorelaxant, cancer-chemopreventive, cytotoxic, toxicological, bioinsecticide, and repellent activities. A few of these studies have been carried out with isolated compounds from Tithonia species, but the majority has been conducted with different extracts. The relationship between the biological activity and the toxicity of compounds isolated from the plants of this genus as well as T. diversifolia extracts still remains unclear, and mechanisms of action remain to be determined. Copyright © 2012 Verlag Helvetica Chimica Acta AG, Zürich.

Understanding of catalysis on early transition metal oxide-based catalysts through exploration of surface structure and chemistry during catalysis using in-situ approaches

Energy Technology Data Exchange (ETDEWEB)

Tao, Franklin [Univ. of Kansas, Lawrence, KS (United States). Dept. of Chemical and Petroleum Engineering. Dept. of Chemistry

2015-09-14

Two main categories of heterogeneous catalysts are metal and metal oxide which catalyze 80% chemical reactions at solid-gas and solid-liquid interfaces. Metal oxide catalysts are much more complicated than metal catalysts. The reason is that the cations of the metal atoms could exhibit a few different oxidation states on surface of the same catalyst particle such as Co₃O₄ or change of their oxidation states under different reactive environments. For a metal catalyst, there is only one oxidation state typically. In addition, surface of a metal oxide can be terminated with multiple surface functionalities including O atoms with different binding configurations and OH group. For metal, only metal atoms are exposed typically. Obviously, the complication of surface chemistry and structure of a metal oxide makes studies of surface of an oxide catalyst very challenging. Due to the complication of surface of a meal oxide, the electronic and geometric structures of surface of a metal oxide and the exposed species have received enormous attention since oxide catalysts catalyze at least 1/3 chemical reactions in chemical and energy industries. Understanding of catalytic reactions on early transition metal oxide-based catalysts is fundamentally intriguing and of great practical interest in energy- and environment-related catalysis. Exploration of surface chemistry of oxide-based catalysts at molecular level during catalysis has remained challenging though it is critical in deeply understanding catalysis on oxide-based catalysts and developing oxide-based catalysts with high activity and selectivity. Thus, the overall objective of this project is to explore surface chemistry and structure of early transition metal oxide-based catalysts through in-situ characterization of surface of catalysts, measurements of catalytic performances, and then build an intrinsic correlation of surface chemistry and structure with their catalytic performances in a few

Nano-phase separation and structural ordering in silica-rich mixed network former glasses.

Science.gov (United States)

Liu, Hao; Youngman, Randall E; Kapoor, Saurabh; Jensen, Lars R; Smedskjaer, Morten M; Yue, Yuanzheng

2018-06-13

We investigate the structure, phase separation, glass transition, and crystallization in a mixed network former glass series, i.e., B2O3-Al2O3-SiO2-P2O5 glasses with varying SiO2/B2O3 molar ratio. All the studied glasses exhibit two separate glassy phases: droplet phase (G1) with the size of 50-100 nm and matrix phase (G2), corresponding to a lower calorimetric glass transition temperature (Tg1) and a higher one (Tg2), respectively. Both Tg values decrease linearly with the substitution of B2O3 for SiO2, but the magnitude of the decrease is larger for Tg1. Based on nuclear magnetic resonance and Raman spectroscopy results, we infer that the G1 phase is rich in boroxol rings, while the G2 phase mainly involves the B-O-Si network. Both phases contain BPO4- and AlPO4-like units. Ordered domains occur in G2 upon isothermal and dynamic heating, driven by the structural heterogeneity in the as-prepared glasses. The structural ordering lowers the activation energy of crystal growth, thus promoting partial crystallization of G2. These findings are useful for understanding glass formation and phase separation in mixed network former oxide systems, and for tailoring their properties.

Organic chemistry as a language and the implications of chemical linguistics for structural and retrosynthetic analyses.

Science.gov (United States)

Cadeddu, Andrea; Wylie, Elizabeth K; Jurczak, Janusz; Wampler-Doty, Matthew; Grzybowski, Bartosz A

2014-07-28

Methods of computational linguistics are used to demonstrate that a natural language such as English and organic chemistry have the same structure in terms of the frequency of, respectively, text fragments and molecular fragments. This quantitative correspondence suggests that it is possible to extend the methods of computational corpus linguistics to the analysis of organic molecules. It is shown that within organic molecules bonds that have highest information content are the ones that 1) define repeat/symmetry subunits and 2) in asymmetric molecules, define the loci of potential retrosynthetic disconnections. Linguistics-based analysis appears well-suited to the analysis of complex structural and reactivity patterns within organic molecules. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multistep continuous-flow synthesis in medicinal chemistry: discovery and preliminary structure-activity relationships of CCR8 ligands.

Science.gov (United States)

Petersen, Trine P; Mirsharghi, Sahar; Rummel, Pia C; Thiele, Stefanie; Rosenkilde, Mette M; Ritzén, Andreas; Ulven, Trond

2013-07-08

A three-step continuous-flow synthesis system and its application to the assembly of a new series of chemokine receptor ligands directly from commercial building blocks is reported. No scavenger columns or solvent switches are necessary to recover the desired test compounds, which were obtained in overall yields of 49-94%. The system is modular and flexible, and the individual steps of the sequence can be interchanged with similar outcome, extending the scope of the chemistry. Biological evaluation confirmed activity on the chemokine CCR8 receptor and provided initial structure-activity-relationship (SAR) information for this new ligand series, with the most potent member displaying full agonist activity with single-digit nanomolar potency. To the best of our knowledge, this represents the first published example of efficient use of multistep flow synthesis combined with biological testing and SAR studies in medicinal chemistry. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Correlations between age, kinematics, and chemistry as seen by the RAVE survey

Science.gov (United States)

Wojno, Jennifer; Kordopatis, Georges; Steinmetz, Matthias; McMillan, Paul; Binney, James; Famaey, Benoit; Monari, Giacomo; Minchev, Ivan; Wyse, Rosemary F. G.; Antoja, Teresa; Siebert, Arnaud; Carrillo, Ismael; Bland-Hawthorn, Joss; K Grebel, Eva; Zwitter, Tomaž; Bienaymé, Olivier; Gibson, Brad; Kunder, Andrea; Munari, Ulisse; Navarro, Julio; Parker, Quentin; Reid, Warren; Seabroke, George

2018-04-01

We explore the connections between stellar age, chemistry, and kinematics across a Galactocentric distance of 7.5 ages for RAVE stars are determined using a Bayesian method, taking TGAS parallaxes as a prior. We divide our sample into young (0 age groups. We find significant differences in kinematic trends of young and old, metal-poor and metal-rich, stellar populations. In particular, we find a strong metallicity dependence in the mean Galactocentric radial velocity as a function of radius (∂VR/∂R) for young stars, with metal-rich stars having a much steeper gradient than metal-poor stars. For ∂Vϕ/∂R, young, metal-rich stars significantly lag the LSR with a slightly positive gradient, while metal-poor stars show a negative gradient above the LSR. We interpret these findings as correlations between metallicity and the relative contributions of the non-axisymmetries in the Galactic gravitational potential (the spiral arms and the bar) to perturb stellar orbits.

Change in soil fungal community structure driven by a decline in ectomycorrhizal fungi following a mountain pine beetle (Dendroctonus ponderosae) outbreak.

Science.gov (United States)

Pec, Gregory J; Karst, Justine; Taylor, D Lee; Cigan, Paul W; Erbilgin, Nadir; Cooke, Janice E K; Simard, Suzanne W; Cahill, James F

2017-01-01

Western North American landscapes are rapidly being transformed by forest die-off caused by mountain pine beetle (Dendroctonus ponderosae), with implications for plant and soil communities. The mechanisms that drive changes in soil community structure, particularly for the highly prevalent ectomycorrhizal fungi in pine forests, are complex and intertwined. Critical to enhancing understanding will be disentangling the relative importance of host tree mortality from changes in soil chemistry following tree death. Here, we used a recent bark beetle outbreak in lodgepole pine (Pinus contorta) forests of western Canada to test whether the effects of tree mortality altered the richness and composition of belowground fungal communities, including ectomycorrhizal and saprotrophic fungi. We also determined the effects of environmental factors (i.e. soil nutrients, moisture, and phenolics) and geographical distance, both of which can influence the richness and composition of soil fungi. The richness of both groups of soil fungi declined and the overall composition was altered by beetle-induced tree mortality. Soil nutrients, soil phenolics and geographical distance influenced the community structure of soil fungi; however, the relative importance of these factors differed between ectomycorrhizal and saprotrophic fungi. The independent effects of tree mortality, soil phenolics and geographical distance influenced the community composition of ectomycorrhizal fungi, while the community composition of saprotrophic fungi was weakly but significantly correlated with the geographical distance of plots. Taken together, our results indicate that both deterministic and stochastic processes structure soil fungal communities following landscape-scale insect outbreaks and reflect the independent roles tree mortality, soil chemistry and geographical distance play in regulating the community composition of soil fungi. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Structural Search for High Pressure CS2 and Xe-Cl Compounds

Science.gov (United States)

Zarifi, Niloofar; Tse, John S.

2018-04-01

The recent successful implementation of several methodologies for the prediction of crystal structures based on the first-principles electronic structure have ushered in a new area of computational chemistry. In this study, the two most popular methods, namely genetic evolution and particle swarm optimization, were applied to the investigation of stable crystalline polymorphs of solid carbon disulfide and xenon halides at high pressure. It was found that both methods have their own merits. However, there are subtleties that need to be considered for the proper execution of the methods. We found a two-dimensional (2D) layered structure that may be responsible for the superconductivity in CS2. Except for XeCl2, no thermodynamically stable crystalline Xe halides were found under 60 GPa in the halide-rich region of the phase diagram.

Recent development in computational actinide chemistry

International Nuclear Information System (INIS)

Li Jun

2008-01-01

Ever since the Manhattan project in World War II, actinide chemistry has been essential for nuclear science and technology. Yet scientists still seek the ability to interpret and predict chemical and physical properties of actinide compounds and materials using first-principle theory and computational modeling. Actinide compounds are challenging to computational chemistry because of their complicated electron correlation effects and relativistic effects, including spin-orbit coupling effects. There have been significant developments in theoretical studies on actinide compounds in the past several years. The theoretical capabilities coupled with new experimental characterization techniques now offer a powerful combination for unraveling the complexities of actinide chemistry. In this talk, we will provide an overview of our own research in this field, with particular emphasis on applications of relativistic density functional and ab initio quantum chemical methods to the geometries, electronic structures, spectroscopy and excited-state properties of small actinide molecules such as CUO and UO 2 and some large actinide compounds relevant to separation and environment science. The performance of various density functional approaches and wavefunction theory-based electron correlation methods will be compared. The results of computational modeling on the vibrational, electronic, and NMR spectra of actinide compounds will be briefly discussed as well [1-4]. We will show that progress in relativistic quantum chemistry, computer hardware and computational chemistry software has enabled computational actinide chemistry to emerge as a powerful and predictive tool for research in actinide chemistry. (authors)

Structure analysis of molecular systems in the Institute of Macromolecular Chemistry of the Czech Academy of Sciences

Czech Academy of Sciences Publication Activity Database

Hašek, Jindřich

2010-01-01

Roč. 17, 2a (2010), k32-k34 ISSN 1211-5894. [Struktura 2010. Soláň, 14.06.2010-17.06.2010] R&D Projects: GA AV ČR IAA500500701; GA ČR GA305/07/1073 Institutional research plan: CEZ:AV0Z40500505 Keywords : Academy of Sciences of the Czech Republic * X-ray structure analysis * crystallography Subject RIV: CD - Macromolecular Chemistry http:// xray .cz/ms/bul2010-2a/hasek.pdf

Conformational Analysis of Drug Molecules: A Practical Exercise in the Medicinal Chemistry Course

Science.gov (United States)

Yuriev, Elizabeth; Chalmers, David; Capuano, Ben

2009-01-01

Medicinal chemistry is a specialized, scientific discipline. Computational chemistry and structure-based drug design constitute important themes in the education of medicinal chemists. This problem-based task is associated with structure-based drug design lectures. It requires students to use computational techniques to investigate conformational…

Templated Chemistry for Sequence-Specific Fluorogenic Detection of Duplex DNA

Science.gov (United States)

Li, Hao; Franzini, Raphael M.; Bruner, Christopher; Kool, Eric T.

2015-01-01

We describe the development of templated fluorogenic chemistry for detection of specific sequences of duplex DNA in solution. In this approach, two modified homopyrimidine oligodeoxynucleotide probes are designed to bind by triple helix formation at adjacent positions on a specific purine-rich target sequence of duplex DNA. One fluorescein-labeled probe contains an α-azidoether linker to a fluorescence quencher; the second (trigger) probe carries a triarylphosphine, designed to reduce the azide and cleave the linker. The data showed that at pH 5.6 these probes yielded a strong fluorescence signal within minutes on addition to a complementary homopurine duplex DNA target. The signal increased by a factor of ca. 60, and was completely dependent on the presence of the target DNA. Replacement of cytosine in the probes with pseudoisocytosine allowed the templated chemistry to proceed readily at pH 7. Single nucleotide mismatches in the target oligonucleotide slowed the templated reaction considerably, demonstrating high sequence selectivity. The use of templated fluorogenic chemistry for detection of duplex DNAs has not been previously reported and may allow detection of double stranded DNA, at least for homopurine-homopyrimidine target sites, under native, non-disturbing conditions. PMID:20859985

Probing chemistry within the membrane structure of wood with soft X-ray spectral microscopy

International Nuclear Information System (INIS)

Cody, George D.

2000-01-01

Scanning Transmission Soft X-ray spectral microscopy on Carbon's 1s absorption edge reveals the distribution of structural biopolymers within cell membrane regions of modern cedar and oak. Cellulose is extremely susceptible to beam damage. Spectroscopic studies of beam damage reveals that the chemical changes resulting from secondary electron impact may be highly selective and is consistent with hydroxyl eliminations and structural rearrangement of pyranose rings in alpha-cellulose to hydroxyl substituted γ pyrones. A study of acetylated cellulose demonstrates significantly different chemistry; principally massive decarboxylation. Defocusing the beam to a 2 μm spot size allows for the acquisition of 'pristine' cellulose spectra. Spectral deconvolution is used to assess the distribution of lignin and cellulose in the different regions of the cell membrane. Using the intensity of the hydroxylated aromatic carbons 1s-π * transition, the ratio of coniferyl and syringyl based lignin within the middle lamellae and secondary cell wall of oak, an angiosperm can be determined

Secondary structures of rRNAs from all three domains of life.

Directory of Open Access Journals (Sweden)

Anton S Petrov

Full Text Available Accurate secondary structures are important for understanding ribosomes, which are extremely large and highly complex. Using 3D structures of ribosomes as input, we have revised and corrected traditional secondary (2° structures of rRNAs. We identify helices by specific geometric and molecular interaction criteria, not by co-variation. The structural approach allows us to incorporate non-canonical base pairs on parity with Watson-Crick base pairs. The resulting rRNA 2° structures are up-to-date and consistent with three-dimensional structures, and are information-rich. These 2° structures are relatively simple to understand and are amenable to reproduction and modification by end-users. The 2° structures made available here broadly sample the phylogenetic tree and are mapped with a variety of data related to molecular interactions and geometry, phylogeny and evolution. We have generated 2° structures for both large subunit (LSU 23S/28S and small subunit (SSU 16S/18S rRNAs of Escherichia coli, Thermus thermophilus, Haloarcula marismortui (LSU rRNA only, Saccharomyces cerevisiae, Drosophila melanogaster, and Homo sapiens. We provide high-resolution editable versions of the 2° structures in several file formats. For the SSU rRNA, the 2° structures use an intuitive representation of the central pseudoknot where base triples are presented as pairs of base pairs. Both LSU and SSU secondary maps are available (http://apollo.chemistry.gatech.edu/RibosomeGallery. Mapping of data onto 2° structures was performed on the RiboVision server (http://apollo.chemistry.gatech.edu/RiboVision.

Nanofat-derived stem cells with platelet-rich fibrin improve facial contour remodeling and skin rejuvenation after autologous structural fat transplantation

Science.gov (United States)

Liang, Zhi-Jie; Chen, Hai; Zhu, Mao-Guang; Xu, Fang-Tian; He, Ning; Wei, Xiao-Juan; Li, Hong-Mian

2017-01-01

Traditional autologous fat transplantation is a common surgical procedure for treating facial soft tissue depression and skin aging. However, the transplanted fat is easily absorbed, reducing the long-term efficacy of the procedure. Here, we examined the efficacy of nanofat-assisted autologous fat structural transplantation. Nanofat-derived stem cells (NFSCs) were isolated, mechanically emulsified, cultured, and characterized. Platelet-rich fibrin (PRF) enhanced proliferation and adipogenic differentiation of NFSCs in vitro. We then compared 62 test group patients with soft tissue depression or signs of aging who underwent combined nanofat, PRF, and autologous fat structural transplantation to control patients (77 cases) who underwent traditional autologous fat transplantation. Facial soft tissue depression symptoms and skin texture were improved to a greater extent after nanofat transplants than after traditional transplants, and the nanofat group had an overall satisfaction rate above 90%. These data suggest that NFSCs function similarly to mesenchymal stem cells and share many of the biological characteristics of traditional fat stem cell cultures. Transplants that combine newly-isolated nanofat, which has a rich stromal vascular fraction (SVF), with PRF and autologous structural fat granules may therefore be a safe, highly-effective, and long-lasting method for remodeling facial contours and rejuvenating the skin. PMID:28978136

Annual Report of Institute of Nuclear Chemistry and Technology 2001

International Nuclear Information System (INIS)

2002-06-01

The INCT 2001 Annual Report is the review of scientific activities in all branches being developed in the Institute of Nuclear Chemistry and Technology in Warsaw. The studies are connected in general with the following fields: radiation chemistry and physics, radiation technologies, radiochemistry, stable isotopes, nuclear analytical methods, chemistry in general, radiobiology, process engineering, material engineering, structural studies and diagnostics, nucleonic control systems and accelerators and nuclear analytical methods

Annual Report 2004 of Institute of Nuclear Chemistry and Technology

International Nuclear Information System (INIS)

Michalik, J.; Smulek, W.; Godlewska-Para, E.

2005-06-01

The INCT 2004 Annual Report is the review of scientific activities in all branches being developed in the Institute of Nuclear Chemistry and Technology Warsaw. The studies are connected in general with the following fields: radiation chemistry and physics, radiation technologies, radiochemistry, stable isotopes, nuclear analytical methods, chemistry in general, radiobiology, process engineering, material engineering, structural studies and diagnostics, nucleonic control systems and accelerators, radiobiology and nuclear analytical methods

Annual Report 2004 of Institute of Nuclear Chemistry and Technology

Energy Technology Data Exchange (ETDEWEB)

Michalik, J; Smulek, W; Godlewska-Para, E [eds.

2005-06-01

The INCT 2004 Annual Report is the review of scientific activities in all branches being developed in the Institute of Nuclear Chemistry and Technology Warsaw. The studies are connected in general with the following fields: radiation chemistry and physics, radiation technologies, radiochemistry, stable isotopes, nuclear analytical methods, chemistry in general, radiobiology, process engineering, material engineering, structural studies and diagnostics, nucleonic control systems and accelerators, radiobiology and nuclear analytical methods.

Annual Report of Institute of Nuclear Chemistry and Technology 2001

Energy Technology Data Exchange (ETDEWEB)

NONE

2002-06-01

The INCT 2001 Annual Report is the review of scientific activities in all branches being developed in the Institute of Nuclear Chemistry and Technology in Warsaw. The studies are connected in general with the following fields: radiation chemistry and physics, radiation technologies, radiochemistry, stable isotopes, nuclear analytical methods, chemistry in general, radiobiology, process engineering, material engineering, structural studies and diagnostics, nucleonic control systems and accelerators and nuclear analytical methods.

CAREM-25: considerations about primary coolant chemistry

International Nuclear Information System (INIS)

Chocron, Mauricio; Iglesias, Alberto M.; Raffo Calderon, Maria C.; Villegas, Marina

2000-01-01

World operating experience, in conjunction with basic studies has been modifying chemistry specifications for the primary coolant of water cooled nuclear reactors along with the reactor type and structural materials involved in the design. For the reactor CAREM-25, the following sources of information have been used: 1) Experience gained by the Chemistry Department of the National Atomic Energy Commission (CNEA, Argentina); 2) Participation of the Chemistry Department (CNEA) in international cooperation projects; 3) Guidelines given by EPRI, Siemens-KWU, AECL, etc. Given the main objectives: materials integrity, low radiation levels and personnel safety, which are in turn a balance between the lowest corrosion and activity transport achievable and considering that the CAREM-25 is a pressurized vessel integrated reactor, a group of guidelines for the chemistry and additives for the primary coolant have been given in the present work. (author)

chemf: A purely functional chemistry toolkit.

Science.gov (United States)

Höck, Stefan; Riedl, Rainer

2012-12-20

Although programming in a type-safe and referentially transparent style offers several advantages over working with mutable data structures and side effects, this style of programming has not seen much use in chemistry-related software. Since functional programming languages were designed with referential transparency in mind, these languages offer a lot of support when writing immutable data structures and side-effects free code. We therefore started implementing our own toolkit based on the above programming paradigms in a modern, versatile programming language. We present our initial results with functional programming in chemistry by first describing an immutable data structure for molecular graphs together with a couple of simple algorithms to calculate basic molecular properties before writing a complete SMILES parser in accordance with the OpenSMILES specification. Along the way we show how to deal with input validation, error handling, bulk operations, and parallelization in a purely functional way. At the end we also analyze and improve our algorithms and data structures in terms of performance and compare it to existing toolkits both object-oriented and purely functional. All code was written in Scala, a modern multi-paradigm programming language with a strong support for functional programming and a highly sophisticated type system. We have successfully made the first important steps towards a purely functional chemistry toolkit. The data structures and algorithms presented in this article perform well while at the same time they can be safely used in parallelized applications, such as computer aided drug design experiments, without further adjustments. This stands in contrast to existing object-oriented toolkits where thread safety of data structures and algorithms is a deliberate design decision that can be hard to implement. Finally, the level of type-safety achieved by Scala highly increased the reliability of our code as well as the productivity of

Natural analogue study of CO2 storage monitoring using probability statistics of CO2-rich groundwater chemistry

Science.gov (United States)

Kim, K. K.; Hamm, S. Y.; Kim, S. O.; Yun, S. T.

2016-12-01

For confronting global climate change, carbon capture and storage (CCS) is one of several very useful strategies as using capture of greenhouse gases like CO2 spewed from stacks and then isolation of the gases in underground geologic storage. CO2-rich groundwater could be produced by CO2 dissolution into fresh groundwater around a CO2 storage site. As consequence, natural analogue studies related to geologic storage provide insights into future geologic CO2 storage sites as well as can provide crucial information on the safety and security of geologic sequestration, the long-term impact of CO2 storage on the environment, and field operation and monitoring that could be implemented for geologic sequestration. In this study, we developed CO2 leakage monitoring method using probability density function (PDF) by characterizing naturally occurring CO2-rich groundwater. For the study, we used existing data of CO2-rich groundwaters in different geological regions (Gangwondo, Gyeongsangdo, and Choongchungdo provinces) in South Korea. Using PDF method and QI (quantitative index), we executed qualitative and quantitative comparisons among local areas and chemical constituents. Geochemical properties of groundwater with/without CO2 as the PDF forms proved that pH, EC, TDS, HCO3-, Ca2+, Mg2+, and SiO2 were effective monitoring parameters for carbonated groundwater in the case of CO2leakage from an underground storage site. KEY WORDS: CO2-rich groundwater, CO2 storage site, monitoring parameter, natural analogue, probability density function (PDF), QI_quantitative index Acknowledgement This study was supported by the "Basic Science Research Program through the National Research Foundation of Korea (NRF), which is funded by the Ministry of Education (NRF-2013R1A1A2058186)" and the "R&D Project on Environmental Management of Geologic CO2 Storage" from KEITI (Project number: 2014001810003).

Chemistry and physics

International Nuclear Information System (INIS)

Broerse, J.J.; Barendsen, G.W.; Kal, H.B.; Kogel, A.J. van der

1983-01-01

This book contains the extended abstracts of the contributions of the poster workshop sessions on chemistry and physics of the 7th international congress of radiation research. They cover the following main topics: primary processes in radiation physics and chemistry, general chemistry in radiation chemistry, DNA and model systems in radiation chemistry, molecules of biological interest in radiation chemistry, techniques in radiation chemistry, hot atom chemistry. refs.; figs.; tabs

Chemistry--The Big Picture

Science.gov (United States)

Cassell, Anne

2011-01-01

Chemistry produces materials and releases energy by ionic or electronic rearrangements. Three structure types affect the ease with which a reaction occurs. In the Earth's crust, "solid crystals" change chemically only with extreme heat and pressure, unless their fixed ions touch moving fluids. On the other hand, in living things, "liquid crystals"…

Isotope and nuclear chemistry division. Annual report, FY 1987. Progress report, October 1986-September 1987

International Nuclear Information System (INIS)

Barr, D.W.; Heiken, J.H.

1988-05-01

This report describes progress in the major research and development programs carried out in FY 1987 by the Isotope and Nuclear Chemistry Division. The report includes articles on radiochemical weapons diagnostics and research and development; other unclassified weapons research; stable and radioactive isotope production and separation; chemical biology and nuclear medicine; element and isotope transport and fixation; actinide and transition metal chemistry; structural chemistry, spectroscopy, and applications; nuclear structure and reactions; irradiation facilities; advanced concepts and technology; and atmospheric chemistry

Pharmacophore screening of the protein data bank for specific binding site chemistry.

Science.gov (United States)

Campagna-Slater, Valérie; Arrowsmith, Andrew G; Zhao, Yong; Schapira, Matthieu

2010-03-22

A simple computational approach was developed to screen the Protein Data Bank (PDB) for putative pockets possessing a specific binding site chemistry and geometry. The method employs two commonly used 3D screening technologies, namely identification of cavities in protein structures and pharmacophore screening of chemical libraries. For each protein structure, a pocket finding algorithm is used to extract potential binding sites containing the correct types of residues, which are then stored in a large SDF-formatted virtual library; pharmacophore filters describing the desired binding site chemistry and geometry are then applied to screen this virtual library and identify pockets matching the specified structural chemistry. As an example, this approach was used to screen all human protein structures in the PDB and identify sites having chemistry similar to that of known methyl-lysine binding domains that recognize chromatin methylation marks. The selected genes include known readers of the histone code as well as novel binding pockets that may be involved in epigenetic signaling. Putative allosteric sites were identified on the structures of TP53BP1, L3MBTL3, CHEK1, KDM4A, and CREBBP.

The complex metal-rich boride Ti{sub 1+x}Rh{sub 2-x+y}Ir{sub 3-y}B{sub 3} (x=0.68, y=1.06) with a new structure type containing B{sub 4} zigzag fragments: Synthesis, crystal chemistry and theoretical calculations

Energy Technology Data Exchange (ETDEWEB)

Goerens, Christian [Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52064 Aachen (Germany); Fokwa, Boniface P.T., E-mail: boniface.fokwa@ac.rwth-aachen.de [Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52064 Aachen (Germany)

2012-08-15

Polycrystalline samples and single crystals of the new complex boride Ti{sub 1+x}Rh{sub 2-x+y}Ir{sub 3-y}B{sub 3} (x=0.68; y=1.06) were synthesized by arc-melting the elements in a water-cooled copper crucible under an argon atmosphere and characterized by X-Ray diffraction as well as EDX measurements. The crystal structure was refined on the basis of single crystal data. The new phase, which represents a new structure type containing trans zigzag B{sub 4} fragments as well as isolated boron atoms crystallizes in the orthorhombic space group Pbam (Nr. 55) with the lattice parameters a=8.620(1) A, b=14.995(2) A and c=3.234(1) A. First-principles density functional theory calculations using the Vienna ab-initio simulation package (VASP) were performed on an appropriate structural model (using a supercell approach) and the experimental crystallographic data could be reproduced accurately. Based on this model, the density of states and crystal orbital Hamilton population (for bonding analysis) were calculated, using the linear muffin-tin orbital atomic sphere approximation (LMTO-ASA) method. According to these calculations, this metal-rich compound should be metallic, as expected. Furthermore, very strong boron-boron interactions are observed in the trans zigzag B{sub 4} fragment, which induce a clear differentiation of two types of metal-boron contacts with different strength. The observed three-dimensional metal-metal interaction is in good agreement with the predicted metallic behavior. - graphical abstract: The structure of Ti{sub 1.68(2)}Rh{sub 2.38(6)}Ir{sub 1.94(4)} B{sub 3}, a new structure type containing planar trans zigzag B{sub 4} units, is another example which illustrates the tendency of metal-rich borides to form B-B bonds with increasing boron content. Beside the B{sub 4} fragment it exhibits one-dimensional chains of titanium atoms and hold one-dimensional strings of face-sharing empty tetrahedral and square pyramidal clusters (see figure). Highlights

Origin of the latitudinal richness gradient

DEFF Research Database (Denmark)

Engemann, Kristine; Sandel, Brody Steven; Enquist, Brian J.

2015-01-01

Spatial variation in richness patterns must be due to variation in rates of speciation, extinction, immigration and emigration. Hotspots of diversity can occur either because they are hotspots of speciation (cradles) or cold spots of extinction (museums) – two major hypotheses that make contrasting...... predictions for the phylogenetic structure of communities. We test these hypotheses by comparing centers of species richness and phylogenetic clustering for vascular plants in the New World. Range maps for 88,417 plant species were extracted from the Botanical Information and Ecology Network (BIEN) database...... and combined with the BIEN mega phylogeny of >80,000 species. We calculated the Phylogenetic Diversity Index (PDI) and Net Relatedness Index (NRI) for each cell in a 100×100 km grid using a new computationally efficient algorithm. Species richness patterns were compared to patterns of PDI and NRI. We found...

Isotope and Nuclear Chemistry Division annual report, FY 1990, October 1, 1989--September 30, 1990

International Nuclear Information System (INIS)

Heiken, J.; Minahan, M.

1991-06-01

This report describes some of the major research and development programs of the Isotope and Nuclear Chemistry Division during FY 1990. The report includes articles on weapons chemistry, environmental chemistry, actinide and transition metal chemistry, geochemistry, nuclear structure and reactions, biochemistry and nuclear medicine, materials chemistry, and INC Division facilities and laboratories

Annual Report 2003 of the Institute of Nuclear Chemistry and Technology

Energy Technology Data Exchange (ETDEWEB)

NONE

2004-07-01

The INCT 2003 Annual Report is the review of scientific activities in all branches being developed in the Institute of Nuclear Chemistry and Technology Warsaw. The studies are connected in general with the following fields: radiation chemistry and physics, radiation technologies, radiochemistry, stable isotopes, nuclear analytical methods, chemistry in general, radiobiology, process engineering, material engineering, structural studies, nucleonic control systems and accelerators.

Annual Report 2003 of the Institute of Nuclear Chemistry and Technology

International Nuclear Information System (INIS)

2004-01-01

The INCT 2003 Annual Report is the review of scientific activities in all branches being developed in the Institute of Nuclear Chemistry and Technology Warsaw. The studies are connected in general with the following fields: radiation chemistry and physics, radiation technologies, radiochemistry, stable isotopes, nuclear analytical methods, chemistry in general, radiobiology, process engineering, material engineering, structural studies, nucleonic control systems and accelerators

Dietary safety assessment of genetically modified rice EH rich in β-carotene.

Science.gov (United States)

Wu, Yangyang; Xu, Yan; Du, Yanan; Zhao, Xiao; Hu, Ruili; Fan, Xiaorui; Ren, Fangfang; Yao, Quanhong; Peng, Rihe; Tang, Xueming; Zhao, Kai

2017-08-01

This 90-day study aimed to assess the dietary safety of transgenic rice EH which is rich in β-carotene. Two experimental groups of Sprague-Dawley rats were fed diets containing 45% rice flour of Zhonghua 11 rice and transgenic rice EH rich in β-carotene, respectively. The reference group was fed a diet containing standard feed nutrition. During the trial period, each rat was weighed and the food intake was recorded twice a week. Their behaviors were observed daily. In the end, blood samples were obtained from all anesthetized rats to measure the hematologic and serum chemistry indicators. Growth performance, anatomy and pathology of all organs in each group were analyzed. Although a few parameters were found to be statistically significantly different across groups, they were within the normal reference range for this breed and age of rats. Therefore, the changes were not considered to be diet related. The results revealed that the transgenic rice EH rich in β-carotene was as nutritious as Zhonghua 11 rice and showed a lack of biologically meaningful unintended effects. Copyright © 2017 Elsevier Inc. All rights reserved.

Vacancy enhanced formation and phase transition of Cu-rich precipitates in α - iron under neutron irradiation

Energy Technology Data Exchange (ETDEWEB)

Lv, G. C. [Basic Experimental Center of Natural Science, University of Science and Technology Beijing, Beijing, 100083 (China); Corrosion and Protection Center, Key Laboratory of Environmental Fracture (MOE), University of Science and Technology Beijing, Beijing, 100083 (China); Zhang, H. [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Canada, T6G2V4 (Canada); He, X. F.; Yang, W. [China Institute of Atomic Energy, Beijing, 102413 (China); Su, Y. J., E-mail: yjsu@ustb.edu.cn [Corrosion and Protection Center, Key Laboratory of Environmental Fracture (MOE), University of Science and Technology Beijing, Beijing, 100083 (China)

2016-04-15

In this paper, we employed both molecular statics and molecular dynamics simulation methods to investigate the role of vacancies in the formation and phase transition of Cu-rich precipitates in α-iron. The results indicated that vacancies promoted the diffusion of Cu atoms to form Cu-rich precipitates. After Cu-rich precipitates formed, they further trapped vacancies. The supersaturated vacancy concentration in the Cu-rich precipitate induced a shear strain, which triggered the phase transition from bcc to fcc structure by transforming the initial bcc (110) plane into fcc (111) plane. In addition, the formation of the fcc-twin structure and the stacking fault structure in the Cu-rich precipitates was observed in dynamics simulations.

Structure and function of ABCG2-rich extracellular vesicles mediating multidrug resistance.

Directory of Open Access Journals (Sweden)

Vicky Goler-Baron

2011-01-01

Full Text Available Multidrug resistance (MDR is a major impediment to curative cancer chemotherapy. The ATP-Binding Cassette transporters ABCG2, ABCB1 and ABCC2 form a unique defense network against multiple structurally and functionally distinct chemotherapeutics, thereby resulting in MDR. Thus, deciphering novel mechanisms of MDR and their overcoming is a major goal of cancer research. Recently we have shown that overexpression of ABCG2 in the membrane of novel extracellular vesicles (EVs in breast cancer cells results in mitoxantrone resistance due to its dramatic sequestration in EVs. However, nothing is known about EVs structure, biogenesis and their ability to concentrate multiple antitumor agents. To this end, we here found that EVs are structural and functional homologues of bile canaliculi, are apically localized, sealed structures reinforced by an actin-based cytoskeleton and secluded from the extracellular milieu by the tight junction proteins occludin and ZO-1. Apart from ABCG2, ABCB1 and ABCC2 were also selectively targeted to the membrane of EVs. Moreover, Ezrin-Radixin-Moesin protein complex selectively localized to the border of the EVs membrane, suggesting a key role for the tethering of MDR pumps to the actin cytoskeleton. The ability of EVs to concentrate and sequester different antitumor drugs was also explored. Taking advantage of the endogenous fluorescence of anticancer drugs, we found that EVs-forming breast cancer cells display high level resistance to topotecan, imidazoacridinones and methotrexate via efficient intravesicular drug concentration hence sequestering them away from their cellular targets. Thus, we identified a new modality of anticancer drug compartmentalization and resistance in which multiple chemotherapeutics are actively pumped from the cytoplasm and highly concentrated within the lumen of EVs via a network of MDR transporters differentially targeted to the EVs membrane. We propose a composite model for the structure and

Ocean-Continent Transition Structure of the Pelotas Magma-Rich Continental Margin, South Atlantic

Science.gov (United States)

Harkin, Caroline; Kusznir, Nick; Roberts, Alan; Manatschal, Gianreto; McDermott, Ken

2017-04-01

Rifted continental margins in the southern South Atlantic are magma-rich showing well developed volcanic extrusives known as seaward dipping reflectors (SDRs). Here we examine the magma-rich continental rifted margin of the Pelotas Basin, offshore Brazil. Deep seismic reflection data displays a large package of seaward dipping reflectors with an approximate width of 200 km and a varying thickness of 10 km to 17 km that have previously been interpreted as volcanic SDRs. We examine these SDRs to explore if they are composed predominantly of basaltic or sedimentary-volcaniclastic material. We also study the thickness of the crustal basement beneath the SDRs. Additionally we investigate if these SDRs are underlain by thin 'hyper-extended' continental crust or if they have been deposited on new magmatic basement. The answers to these questions are important in understanding the structure and formation processes of magma-rich continental margins. We use gravity inversion to investigate SDR composition by varying the proportion of basalt to sediments-volcaniclastics (basalt fraction) which determines the SDR densities in the gravity inversion. By matching the Moho depth and two-way travel time from gravity inversion and deep seismic reflection data, we determine the lateral variation in basalt fraction of the SDRs. Our analysis suggests: 1) There is an overall pattern of SDR basalt fraction and bulk density decreasing oceanward. This could be due to increasing sediment content oceanward or it could result from the change in basalt flows to hyaloclastites as water depth increases. 2) The SDR package can be split into two distinct sub packages based on the basalt fraction results, where the proximal side of each package has a higher basalt fraction and density. 3) The inner SDR package contains reflectors that bear a resemblance to the SDRs described by Hinz (1981) corresponding to syn-tectonic volcanic eruptions into an extensional basin, while the outer SDR package has

Low temperature surface chemistry and nanostructures

Science.gov (United States)

Sergeev, G. B.; Shabatina, T. I.

2002-03-01

The new scientific field of low temperature surface chemistry, which combines the low temperature chemistry (cryochemistry) and surface chemistry approaches, is reviewed in this paper. One of the most exciting achievements in this field of science is the development of methods to create highly ordered hybrid nanosized structures on different organic and inorganic surfaces and to encapsulate nanosized metal particles in organic and polymer matrices. We consider physical and chemical behaviour for the systems obtained by co-condensation of the components vapours on the surfaces cooled down to 4-10 and 70-100 K. In particular the size effect of both types, the number of atoms in the reactive species structure and the thickness of growing co-condensate film, on the chemical activity of the system is analysed in detail. The effect of the internal mechanical stresses on the growing interfacial co-condensate film formation and on the generation of fast (explosive) spontaneous reactions at low temperatures is discussed. The examples of unusual chemical interactions of metal atoms, clusters and nanosized particles, obtained in co-condensate films on the cooled surfaces under different conditions, are presented. The examples of highly ordered surface and volume hybrid nanostructures formation are analysed.

From hot atom chemistry to epithermal chemistry

International Nuclear Information System (INIS)

Roessler, K.

2004-01-01

The rise and fall of hot atom chemistry (HAC) over the years from 1934 to 2004 is reviewed. Several applications are discussed, in particular to astrophysics and the interaction of energetic ions and atoms in space. Epithermal chemistry (ETC) is proposed to substitute the old name, since it better fits the energy range as well as the non-thermal and non-equilibrium character of the reactions. ETC also avoids the strong connexion of HAC to nuclear chemistry and stands for the opening of the field to physical chemistry and astrophysics. (orig.)

Ectomycorrhizal Community Structure and Soil Characteristics of Mature Lodgepole Pine (Pinus Contorta) and Adjacent Stands of Old Growth Mixed Conifer in Yellowstone National Park, Wyoming USA

Science.gov (United States)

Douglas, Robert B.; Parker, V. Thomas; Cullings, Kenneth W.; Sun, Sidney (Technical Monitor)

2003-01-01

Forest development patterns following disturbance are known to influence the physical and chemical attributes of soils at different points in time. Changes in soil resources are thought to have a corresponding effect on ectomycorrhizal (ECM) community structure. We used molecular methods to compare below-ground ECM species richness, composition, and abundance between adjacent stands of homogenous lodgepole pine and old growth mixed conifer in Yellowstone National Park (YNP). In each stand-type we collected soil cores to both identify mycorrhizae and assess soil chemistry. Although no statistical difference was observed in the mean number of ECM root tips per core between stand types, the total number of species identified (85 versus 35) and the mean number of species per core (8.8 +/- 0.6 versus 2.5 +/- 0.3) were significantly higher in lodgepole pine. Differences between the actual and estimated species richness levels indicated that these forest types support a high number of ECM species and that undersampling was severe. Species compositions were widely disparate between stands where only four species were shared out of a total of 116. Soil analysis also revealed that mixed conifer was significantly lower in pH, but higher in organic matter, potassium, phosphorus, and ammonium when compared to lodgepole pine stands. Species richness per core was correlated with these chemical data, however, analysis of covariance indicated that stand type was the only statistically significant factor in the observed difference in species richness. Our data suggest that ECM fungal richness increases as homogenous lodgepole pine stands grow and mature, but declines after Engelmann spruce and subalpine fir colonize. Despite difficulties linking species composition with soil chemistry, there are a variety of physical and chemical factors that could be influencing ECM community structure. Future field experiments are necessary to test some of the mechanisms potentially operating

Mathematical Chemistry

OpenAIRE

Trinajstić, Nenad; Gutman, Ivan

2002-01-01

A brief description is given of the historical development of mathematics and chemistry. A path leading to the meeting of these two sciences is described. An attempt is made to define mathematical chemistry, and journals containing the term mathematical chemistry in their titles are noted. In conclusion, the statement is made that although chemistry is an experimental science aimed at preparing new compounds and materials, mathematics is very useful in chemistry, among other things, to produc...

Synthesis, electronic structure, elastic properties, and interfacial behavior of icosahedral boron-rich solids

Energy Technology Data Exchange (ETDEWEB)

Hunold, Oliver

2017-08-01

Boron-rich solids are commonly characterized by icosahedral clusters, where 12 B atoms form an icosahedron, giving rise to outstanding mechanical and transport properties. However, broader applications are limited due to the high synthesis temperature required to obtain the icosahedra-based crystalline structure. Utilizing high power pulsed magnetron sputtering (HPPMS), the deposition temperature may be lowered as compared to direct current magnetron sputtering by enhanced surface diffusion. Therefore, HPPMS was utilized to investigate the influence of the substrate temperature on the structural evolution of B-rich Al-Y-B thin films. The formation of the intended AlYB{sub 14} phase together with the (Y,Al)B{sub 6} impurity phase, containing 1.8 at.% less B than AlYB{sub 14}, was observed at a growth temperature of 800 C and hence 600 C below the bulk synthesis temperature. Based on density functional theory (DFT) calculations it is inferred that minute compositional variations may lead to formation of competing phases, such as (Y,Al)B{sub 6}. Furthermore, 800 C still limits the usage significantly. Therefore, quantum mechanical material design was applied to identify phases with even higher phase stabilities compared to AlYB{sub 14}. Phase stability of T{sub 0.75}Y{sub 0.75}B{sub 14} (T= Sc, Ti, V, Y, Zr, Nb, Si) critically depends on the exact magnitude of charge transferred by T and Y to the B icosahedra. The highest phase stabilities have been identified for Sc{sub 0.75}Y{sub 0.75}B{sub 14}, Ti{sub 0.75}Y{sub 0.75}B{sub 14}, and Zr{sub 0.75}Y{sub 0.75}B{sub 14}. ln combination with Young's modulus values up to 517 GPa these phases are very interesting from a wear-resistance point of view. Still high synthesis temperatures limit the use of such systems onto technologically relevant substrate materials. However, amorphous B-rich solids, which can be synthesized without additional heating, exhibit attractive mechanical and electrical properties. Within these

Acid-generating salts and their relationship to the chemistry of groundwater and storm runoff at an abandoned mine site in southwestern Indiana, USA

International Nuclear Information System (INIS)

Bayless, E.R.; Olyphant, G.A.

1993-01-01

Cation distributions in twenty samples of acid-generating salts were compared to those in groundwater and storm runoff from a coal-refuse deposit in an effort to identify source-product relationships. Two mineral suites, one primarily composed of melanterite, rozenite and szomolnokite, and the other composed almost entirely of copiapite, were found to be most abundant at the study site. Comparisons of cation distributions in salts with those in water samples led to an hypothesis that a copiapite-rich suite precipitated from vadose-zone groundwater that was brought to the surface by evaporative forcing. The copiapite-rich suite, which contained larger concentrations of aluminum, calcium and zinc than the melanterite-rozenite-szomolnokite mineral suite, was the primary source of solutes in captured storm runoff. An analysis of samples collected during a summer thunderstorm indicated that the chemistry of surface runoff varied little with time or with distance downstream. The cation distributions in samples of groundwater indicated that iron-rich pore waters observed near the surface in late autumn may have influenced water chemistry in the deeper portions of the unsaturated zone during the 1989 recharge season. The results of this study show that the solutes produced by the two observed salt suites can be distinguished by their mole percent iron and that the source-product relationships can explain observed variability in mine drainage chemistry at the study site

A new titanium-bearing calcium aluminosilicate phase. 2: Crystallography and crystal chemistry of grains formed in slowly cooled melts with bulk compositions of calcium-aluminium-rich inclusions

Science.gov (United States)

Barber, David J.; Beckett, John R.; Paque, Julie M.; Stolper, Edward

1994-01-01

The crystallography and crystal chemistry of a new calcium- titanium-aluminosilicate mineral (UNK) observed in synthetic analogs to calcium-aluminum-rich inclusions (CAIs) from carbonaceous chondrites was studied by electron diffraction techniques. The unit cell is primitive hexagonal or trigonal, with a = 0.790 +/- 0.02 nm and c = 0.492 +/- 0.002 nm, similar to the lattice parameters of melilite and consistent with cell dimensions for crystals in a mixer furnace slag described by Barber and Agrell (1994). The phase frequently displays an epitactic relationship in which melilite acts as the host, with (0001)(sub UNK) parallel (001)(sub mel) and zone axis group 1 0 -1 0(sub UNK) parallel zone axis group 1 0 0(sub mel). If one of the two space groups determined by Barber and Agrell (1994) for their sample of UNK is applicable (P3m1 or P31m), then the structure is probably characterized by puckered sheets of octahedra and tetrahedra perpendicular to the c-axis with successive sheets coordinated by planar arrays of Ca. In this likely structure, each unit cell contains three Ca sites located in mirror planes, one octahedrally coordinated cation located along a three-fold axis and five tetrahedrally coordinated cations, three in mirrors and two along triads. The octahedron contains Ti but, because there are 1.3-1.9 cations of Ti/formula unit, some of the Ti must also be in tetrahedral coordination, an unusual but not unprecedented situation for a silicate. Tetrahedral sites in mirror planes would contain mostly Si, with lesser amounts of Al while those along the triads correspondingly contain mostly Al with subordinate Ti. The structural formula, therefore, can be expressed as Ca(sub 3)(sup VIII)(Ti,Al)(sup VI)(Al,Ti,Si)(sub 2)(sup IV)(Si,Al)(sub 3)(sup IV)O14 with Si + Ti = 4. Compositions of meteoritic and synthetic Ti-bearing samples of the phase can be described in terms of a binary solid solution between the end-members Ca3TiAl2Si3O14 and Ca3Ti(AlTi)(AlSi2)O14. A Ti

THE REACH AND RICHNESS OF WIKINOMICS: IS THE FREE WEB-BASED ENCYCLOPEDIA WIKIPEDIA ONLY FOR RICH COUNTRIES?

DEFF Research Database (Denmark)

Rask, Morten

2007-01-01

In this article, a model of the patterns of correlation in Wikipedia, reach and richness, lays the foundation for studying whether the free Web-based encyclopedia Wikipedia is only for developed countries. Based on data from 12 different Wikipedia language editions, the author finds that the cent......In this article, a model of the patterns of correlation in Wikipedia, reach and richness, lays the foundation for studying whether the free Web-based encyclopedia Wikipedia is only for developed countries. Based on data from 12 different Wikipedia language editions, the author finds...... that the central structural effect is on the level of human development in the current country. In other words, Wikipedia is in general more for rich countries than for less developed countries. It is suggested that policy makers make investments in increasing the general level of literacy, education, and standard...

Cooperative studyware development of organic chemistry module by experts, teachers, and students

Science.gov (United States)

Dori, Yehudit J.

1995-06-01

Experts, teachers, and students took active part in a process of organic chemistry studyware development. A unique characteristic of this process was the active involvement of three different groups of people in the authoring process: science educators, chemistry teachers, and chemistry students studying towards an education certificate. The science educators—the experts—advised the team on new methods of presenting the subject matter in an appealing way, using 3D computerized molecular modeling. The in-service chemistry teachers contributed from their rich field experience to constructing the studyware. This mutual development helped maintain the balance between expert requirements and expectations from students on one hand, and the actual student capabilities, as perceived by teachers through constant contact with the students, on the other. Finally, the preservice teachers—the undergraduate chemistry students—were often zealous, enthusiastic, and willing to put in the extra time and effort needed to produce quality studyware, while following the guidelines of the experts and teachers. Feedback on the qualities and shortcomings of the studyware was obtained in two cycles. The first one was done while the studyware was still under development by peers, and the second by individual target students, serving as a beta-site. This double feedback helped improve the studyware, mainly by elaborating on portions that require more detail and explanation. The paper describes the process as well as representative parts of the studyware. The combination of experts, teachers, and students in the development team seems to have the potential to yield studyware that is appropriate for effective science education in general and chemistry teaching in particular.

Proceedings of the 37. Brazilian Congress on Chemistry. Abstracts

International Nuclear Information System (INIS)

1997-01-01

This volume contains the summaries of the papers presented at the 37. Brazilian Congress on Chemistry. The topics include subjects about new technologies in the field of relevance for nuclear interest and energy field, involving environmental aspects, analytical chemistry and electrochemistry. The chemistry of elements of nuclear interest has been presented, and dissertations about rare earth elements were discussed. Studies about fuels, mainly petroleum, their products and biomass fuels, including their production, physical-chemical properties, structure studies and feasibility studies has also been comprehended

Learning Organic Chemistry Through Natural Products

Indian Academy of Sciences (India)

Higher Learning. ... The Series on "learning Organic Chemistry Through Natural Products". Nature is a remarkable ... skeletal structure to the interior electronic configu- ration ... Among the advantages of this approach are the fact that unlike the.

Ab initio valence calculations in chemistry

CERN Document Server

Cook, D B

1974-01-01

Ab Initio Valence Calculations in Chemistry describes the theory and practice of ab initio valence calculations in chemistry and applies the ideas to a specific example, linear BeH2. Topics covered include the Schrödinger equation and the orbital approximation to atomic orbitals; molecular orbital and valence bond methods; practical molecular wave functions; and molecular integrals. Open shell systems, molecular symmetry, and localized descriptions of electronic structure are also discussed. This book is comprised of 13 chapters and begins by introducing the reader to the use of the Schrödinge

Water Chemistry Section: progress report (1981-82)

International Nuclear Information System (INIS)

Dharwadkar, S.R.; Ramshesh, V.

1983-01-01

The activities of the Water Chemistry Section of the Bhabha Atomic Research Centre (BARC), Bombay, during the years 1981 and 1982 are reported in the form of individual summaries. The research activities of the Section cover the following areas: (1) chemistry and thermodynamics of nuclear materials, (2) crystal structure of organo-metallic complexes using X-ray diffraction, (3) thermophysical and phase transition studies, (4) solid state chemistry and thermochemical studies, (5) water and steam chemistry of heavy water plants and phwr type reactors, and (6) uranium isotope exchange studies. A survey is also given of: (i) the Section's participation in advisory and consultancy services in nuclear and thermal power stations, (ii) training activities, and (iii) assistance in chemical analysis by various techniques to other units of BARC and outside agencies. A list of publications and lectures by the staff during the report period is included. (M.G.B.)

C,N-Chelated Organotin(IV) Azides: Synthesis, Structure and Use within the Click Chemistry.

Czech Academy of Sciences Publication Activity Database

Švec, P.; Bartoš, K.; Růžičková, Z.; Cuřínová, Petra; Dušek, L.; Turek, J.; de Proft, F.; Růžička, A.

2016-01-01

Roč. 40, č. 7 (2016), s. 5808-5817 ISSN 1144-0546 Grant - others:FWO(BE) 12T6615N Institutional support: RVO:67985858 Keywords : organotin(IV)azides * click chemistry * chelation Subject RIV: CC - Organic Chemistry Impact factor: 3.269, year: 2016

Annual Report of the Institute of Nuclear Chemistry and Technology 2000

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-06-01

The INCT 2000 Annual Report is the review of scientific activities in all branches being developed in the Institute of Nuclear Chemistry and Technology Warsaw. The studies are connected in general with the following fields: radiation chemistry and physics, radiation technologies, radiochemistry, stable isotopes, nuclear analytical methods, chemistry in general, radiobiology, process engineering, material engineering, structural studies and diagnostics and nucleonic control systems and accelerators.

Annual Report of the Institute of Nuclear Chemistry and Technology 2000

International Nuclear Information System (INIS)

2001-06-01

The INCT 2000 Annual Report is the review of scientific activities in all branches being developed in the Institute of Nuclear Chemistry and Technology Warsaw. The studies are connected in general with the following fields: radiation chemistry and physics, radiation technologies, radiochemistry, stable isotopes, nuclear analytical methods, chemistry in general, radiobiology, process engineering, material engineering, structural studies and diagnostics and nucleonic control systems and accelerators

High pressure in solid state chemistry: Combined experimental and modeling approaches for assessing and predicting properties

Science.gov (United States)

Etourneau, Jean; Matar, Samir F.

2018-06-01

The thermodynamic pressure parameter has been thoroughly used with mastership by Gérard Demazeau throughout his rich career in solid state chemistry and materials sciences and more recently in biosciences. After a review of such works, focus is made in this topical article on his contribution together with his team in the field of hard materials based on light elements B, C, N with a proposition of a new ultra-hard carbon nitride C2N on one hand and on the structural transformations under high pressures of perovskite into postperovskite with a change of dimensionality from 3D to 2D and related oxides, regarding the arrangement of octahedra, on the other hand. Investigation and concepts first arising from experimental observables are shown to be aided and accelerated via first principles calculations of energy and energy-related quantities.

Normal Science Education and Its Dangers: The Case of School Chemistry.

Science.gov (United States)

Van Berkel, Berry; De Vos, Wobbe; Verdonk, Adri H.; Pilot, Albert

2000-01-01

Attempts to solve the problem of hidden structure in school chemistry. Argues that normal chemistry education is isolated from common sense, everyday life and society, the history and philosophy of science, technology, school physics, and chemical research. (Author/CCM)

Cryogenic ion chemistry and spectroscopy.

Science.gov (United States)

Wolk, Arron B; Leavitt, Christopher M; Garand, Etienne; Johnson, Mark A

2014-01-21

The use of mass spectrometry in macromolecular analysis is an incredibly important technique and has allowed efficient identification of secondary and tertiary protein structures. Over 20 years ago, Chemistry Nobelist John Fenn and co-workers revolutionized mass spectrometry by developing ways to non-destructively extract large molecules directly from solution into the gas phase. This advance, in turn, enabled rapid sequencing of biopolymers through tandem mass spectrometry at the heart of the burgeoning field of proteomics. In this Account, we discuss how cryogenic cooling, mass selection, and reactive processing together provide a powerful way to characterize ion structures as well as rationally synthesize labile reaction intermediates. This is accomplished by first cooling the ions close to 10 K and condensing onto them weakly bound, chemically inert small molecules or rare gas atoms. This assembly can then be used as a medium in which to quench reactive encounters by rapid evaporation of the adducts, as well as provide a universal means for acquiring highly resolved vibrational action spectra of the embedded species by photoinduced mass loss. Moreover, the spectroscopic measurements can be obtained with readily available, broadly tunable pulsed infrared lasers because absorption of a single photon is sufficient to induce evaporation. We discuss the implementation of these methods with a new type of hybrid photofragmentation mass spectrometer involving two stages of mass selection with two laser excitation regions interfaced to the cryogenic ion source. We illustrate several capabilities of the cryogenic ion spectrometer by presenting recent applications to peptides, a biomimetic catalyst, a large antibiotic molecule (vancomycin), and reaction intermediates pertinent to the chemistry of the ionosphere. First, we demonstrate how site-specific isotopic substitution can be used to identify bands due to local functional groups in a protonated tripeptide designed to

Final Report - Low Temperature Combustion Chemistry And Fuel Component Interactions

Energy Technology Data Exchange (ETDEWEB)

Wooldridge, Margaret [Univ. of Michigan, Ann Arbor, MI (United States)

2017-02-24

Recent research into combustion chemistry has shown that reactions at “low temperatures” (700 – 1100 K) have a dramatic influence on ignition and combustion of fuels in virtually every practical combustion system. A powerful class of laboratory-scale experimental facilities that can focus on fuel chemistry in this temperature range is the rapid compression facility (RCF), which has proven to be a versatile tool to examine the details of fuel chemistry in this important regime. An RCF was used in this project to advance our understanding of low temperature chemistry of important fuel compounds. We show how factors including fuel molecular structure, the presence of unsaturated C=C bonds, and the presence of alkyl ester groups influence fuel auto-ignition and produce variable amounts of negative temperature coefficient behavior of fuel ignition. We report new discoveries of synergistic ignition interactions between alkane and alcohol fuels, with both experimental and kinetic modeling studies of these complex interactions. The results of this project quantify the effects of molecular structure on combustion chemistry including carbon bond saturation, through low temperature experimental studies of esters, alkanes, alkenes, and alcohols.

3D confocal Raman imaging of oil-rich emulsion from enzyme-assisted aqueous extraction of extruded soybean powder.

Science.gov (United States)

Wu, Longkun; Wang, Limin; Qi, Baokun; Zhang, Xiaonan; Chen, Fusheng; Li, Yang; Sui, Xiaonan; Jiang, Lianzhou

2018-05-30

The understanding of the structure morphology of oil-rich emulsion from enzyme-assisted extraction processing (EAEP) was a critical step to break the oil-rich emulsion structure in order to recover oil. Albeit EAEP method has been applied as an alternative way to conventional solvent extraction method, the structure morphology of oil-rich emulsion was still unclear. The current study aimed to investigate the structure morphology of oil-rich emulsion from EAEP using 3D confocal Raman imaging technique. With increasing the enzymatic hydrolysis duration from 1 to 3 h, the stability of oil-rich emulsion was decreased as visualized in the 3D confocal Raman images that the protein and oil were mixed together. The subsequent Raman spectrum analysis further revealed that the decreased stability of oil-rich emulsion was due to the protein aggregations via SS bonds or protein-lipid interactions. The conformational transfer in protein indicated the formation of a compact structure. Copyright © 2017 Elsevier Ltd. All rights reserved.

Variability in chemistry of surface and soil waters of an ...

African Journals Online (AJOL)

Water chemistry is important for the maintenance of wetland structure and function. Interpreting ecological patterns in a wetland system therefore requires an in-depth understanding of the water chemistry of that system. We investigated the spatial distribution of chemical solutes both in soil pore water and surface water, ...

The Importance of Medicinal Chemistry Knowledge in the Clinical Pharmacist's Education.

Science.gov (United States)

Fernandes, João Paulo S

2018-03-01

Objective. To show why medicinal chemistry must be a key component of the education of pharmacy students, as well as in the pharmacist's practice. Findings. Five case reports were selected by their clinically relevant elements of medicinal chemistry and were explained using structure-activity relationship data of the drugs involved in the case easily obtained from primary literature and in medicinal chemistry textbooks. Summary. This paper demonstrates how critical clinical decisions can be addressed using medicinal chemistry knowledge. While such knowledge may not explain all clinical decisions, medicinal chemistry concepts are essential for the education of pharmacy students to explain drug action in general and clinical decisions.

Industrial chemistry engineering

International Nuclear Information System (INIS)

1993-01-01

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.

Chemistry Teacher Candidates' Acceptance and Opinions about Virtual Reality Technology for Molecular Geometry

Science.gov (United States)

Saritas, M. T.

2015-01-01

The meaningful knowledge creation about molecular geometry has always been the challenge of chemistry learning. In particular, microscopic world of chemistry science (example, atoms, molecules, structures) used in traditional two dimensional way of chemistry teaching can lead to such problem as students create misconceptions. In recent years,…

A Comparison of How Undergraduates, Graduate Students, and Professors Organize Organic Chemistry Reactions

Science.gov (United States)

Galloway, Kelli R.; Leung, Min Wah; Flynn, Alison B.

2018-01-01

To explore the differences between how organic chemistry students and organic chemistry professors think about organic chemistry reactions, we administered a card sort task to participants with a range of knowledge and experience levels. Beginning students created a variety of categories ranging from structural similarities to process oriented…

Advanced chemistry management system to optimize BWR chemistry control

International Nuclear Information System (INIS)

Maeda, K.; Nagasawa, K.

2002-01-01

BWR plant chemistry control has close relationships among nuclear safety, component reliability, radiation field management and fuel integrity. Advanced technology is required to improve chemistry control [1,3,6,7,10,11]. Toshiba has developed TACMAN (Toshiba Advanced Chemistry Management system) to support BWR chemistry control. The TACMAN has been developed as response to utilities' years of requirements to keep plant operation safety, reliability and cost benefit. The advanced technology built into the TACMAN allows utilities to make efficient chemistry control and to keep cost benefit. TACMAN is currently being used in response to the needs for tools those plant chemists and engineers could use to optimize and identify plant chemistry conditions continuously. If an incipient condition or anomaly is detected at early stage, root causes evaluation and immediate countermeasures can be provided. Especially, the expert system brings numerous and competitive advantages not only to improve plant chemistry reliability but also to standardize and systematize know-how, empirical knowledge and technologies in BWR chemistry This paper shows detail functions of TACMAN and practical results to evaluate actual plant. (authors)

Experimental study of the structure of rich premixed 1,3-butadiene/CH4/O2/Ar flame

OpenAIRE

Gueniche, Hadj-Ali; Glaude, Pierre-Alexandre; Fournet, René; Battin-Leclerc, Frédérique

2007-01-01

The structure of a laminar rich premixed 1,3-C4H6/CH4/O2/Ar flame have been investigated. 1,3-Butadiene, methane, oxygen and argon mole fractions are 0.033; 0.2073; 0.3315, and 0.4280, respectively, for an equivalent ratio of 1.80. The flame has been stabilized on a burner at a pressure of 6.7 kPa (50 Torr). The concentration profiles of stable species were measured by gas chromatography after sampling with a quartz probe. Quantified species included carbon monoxide and dioxide, methane, oxyg...

Hyperfine structure and isotope shift of the neutron-rich barium isotopes 139-146Ba and 148Ba

International Nuclear Information System (INIS)

Wendt, K.; Ahmad, S.A.; Klempt, W.; Neugart, R.; Otten, E.W.

1988-01-01

The hyperfine structure and isotope shift in the 6s 2 S 1/2 -6p 2 P 3/2 line of Ba II (455.4 nm) have been measured by collinear fast-beam laser spectroscopy for the neutron-rich isotopes 139-146 Ba and 148 Ba. Nuclear moments and mean square charge radii of these isotopes have been recalculated. The isotope shift of the isotope 148 Ba (T 1/2 = 0.64 s) could be studied for the first time, yielding δ 2 > 138,148 = 1.245(3) fm 2 . (orig.)

Chemical complexity in the winds of the oxygen-rich supergiant star VY Canis Majoris

Science.gov (United States)

Ziurys, L. M.; Milam, S. N.; Apponi, A. J.; Woolf, N. J.

2007-06-01

The interstellar medium is enriched primarily by matter ejected from old, evolved stars. The outflows from these stars create spherical envelopes, which foster gas-phase chemistry. The chemical complexity in circumstellar shells was originally thought to be dominated by the elemental carbon to oxygen ratio. Observations have suggested that envelopes with more carbon than oxygen have a significantly greater abundance of molecules than their oxygen-rich analogues. Here we report observations of molecules in the oxygen-rich shell of the red supergiant star VY Canis Majoris (VY CMa). A variety of unexpected chemical compounds have been identified, including NaCl, PN, HNC and HCO+. From the spectral line profiles, the molecules can be distinguished as arising from three distinct kinematic regions: a spherical outflow, a tightly collimated, blue-shifted expansion, and a directed, red-shifted flow. Certain species (SiO, PN and NaCl) exclusively trace the spherical flow, whereas HNC and sulphur-bearing molecules (amongst others) are selectively created in the two expansions, perhaps arising from shock waves. CO, HCN, CS and HCO+ exist in all three components. Despite the oxygen-rich environment, HCN seems to be as abundant as CO. These results suggest that oxygen-rich shells may be as chemically diverse as their carbon counterparts.

General chemistry courses that can affect achievement: An action research study in developing a plan to improve undergraduate chemistry courses

Science.gov (United States)

Shweikeh, Eman

Over the past 50 years, considerable research has been dedicated to chemistry education. In evaluating principal chemistry courses in higher education, educators have noted the learning process for first-year general chemistry courses may be challenging. The current study investigated perceptions of faculty, students and administrators on chemistry education at three institutions in Southern California. Via action research, the study sought to develop a plan to improve student engagement in general chemistry courses. A mixed method was utilized to analyze different perceptions on key factors determining the level of commitment and engagement in general chemistry education. The approach to chemistry learning from both a faculty and student perspective was examined including good practices, experiences and extent of active participation. The research study considered well-known measures of effective education with an emphasis on two key components: educational practices and student behavior. Institutional culture was inclusively assessed where cognitive expectations of chemistry teaching and learning were communicated. First, the extent in which faculty members are utilizing the "Seven Principles for Good Practice in Undergraduate Education" in their instruction was explored. Second, student attitudes and approaches toward chemistry learning were examined. The focus was on investigating student understanding of the learning process and the structure of chemistry knowledge. The seven categories used to measure students' expectations for learning chemistry were: effort, concepts, math link, reality link, outcome, laboratory, and visualization. This analysis represents the views of 16 faculty and 140 students. The results validated the assertion that students need some competencies and skills to tackle the challenges of the chemistry learning process to deeply engage in learning. A mismatch exists between the expectations of students and those of the faculty

Organic carbamates in drug design and medicinal chemistry.

Science.gov (United States)

Ghosh, Arun K; Brindisi, Margherita

2015-04-09

The carbamate group is a key structural motif in many approved drugs and prodrugs. There is an increasing use of carbamates in medicinal chemistry and many derivatives are specifically designed to make drug-target interactions through their carbamate moiety. In this Perspective, we present properties and stabilities of carbamates, reagents and chemical methodologies for the synthesis of carbamates, and recent applications of carbamates in drug design and medicinal chemistry.

Learning Organic Chemistry Through Natural Products

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education; Volume 1; Issue 7. Learning Organic Chemistry Through Natural engine Products - Structure and Biological Functions. N R Krishnaswamy. Series Article Volume 1 Issue 7 July 1996 pp 23-30 ...

New Perspectives in the Chemistry of Marine Pyridoacridine Alkaloids

Directory of Open Access Journals (Sweden)

Alois Plodek

2016-01-01

Full Text Available Secondary metabolites from marine organisms are a rich source of novel leads for drug development. Among these natural products, polycyclic aromatic alkaloids of the pyridoacridine type have attracted the highest attention as lead compounds for the development of novel anti-cancer and anti-infective drugs. Numerous sophisticated total syntheses of pyridoacridine alkaloids have been worked out, and many of them have also been extended to the synthesis of libraries of analogues of the alkaloids. This review summarizes the progress in the chemistry of pyridoacridine alkaloids that was made in the last one-and-a-half decades.

The Chemistry of Superheavy Elements

CERN Document Server

Schädel, M

2003-01-01

The chemistry of transactinide or superheavy elements has reached element 108. Preparations are under way to leap to element 112 and beyond. The current status of this atom-at-a-time chemical research and its future perspectives are reviewed from an experimental point of view together with some of the interesting results from n -rich nuclides near and at the N=162 neutron shell. Experimental techniques and important results enlightening typical chemical properties of elements 104 through 108 are presented in an exemplary way. From the results of these experiments it is justified to place these elements in the Periodic Table of the Elements in to groups 4 through 8, respectively. However, mainly due to the influence of relativistic effects, it is no longer possible to deduce detailed chemical properties of these superheavy elements simply from this position.

Electronic structure and photocatalytic activity of wurtzite Cu–Ga–S nanocrystals and their Zn substitution

KAUST Repository

Kandiel, Tarek

2015-03-23

Stoichiometric and gallium-rich wurtzite Cu-Ga-S ternary nanocrystals were synthesized via a facile solution-based hot injection method using 1-dodecanethiol as a sulfur source. The use of 1-dodecanethiol was found to be essential not only as a sulfur source but also as a structure-directing reagent to form a metastable wurtzite structure. In addition, the substitution of zinc in the wurtzite gallium-rich Cu-Ga-S nanocrystals was also investigated. The obtained nanocrystals were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and inductively coupled plasma atomic emission spectroscopy (ICP-OES). Electronic structures of pristine and the Zn-substituted Cu-Ga-S system were investigated using density functional theory (DFT) with HSE06 exchange-correlation functional. The calculated bandgaps accurately reflect the measured ones. The allowed electronic transitions occur upon the photon absorption from the (Cu + S) band towards the (Ga + S) one. The Zn substitution was found not to contribute to the band edge structure and hence altered the bandgaps only slightly, the direct transition nature remaining unchanged with the Zn substitution. The photocatalytic activities of H2 evolution from an aqueous Na2S/Na2SO3 solution under visible-light illumination on the synthesized nanocrystals were investigated. While the stoichiometric CuGaS2 exhibited negligible activity, the gallium-rich Cu-Ga-S ternary nanocrystals displayed reasonable activity. The optimum Zn substitution in the gallium-rich Cu-Ga-S ternary nanocrystals enhanced the H2 evolution rate, achieving an apparent quantum efficiency of >6% at 400 nm. © 2015 The Royal Society of Chemistry.

Current organic chemistry

National Research Council Canada - National Science Library

1997-01-01

Provides in depth reviews on current progress in the fields of asymmetric synthesis, organometallic chemistry, bioorganic chemistry, heterocyclic chemistry, natural product chemistry, and analytical...

The Medicinal Chemistry of Dengue Virus.

Science.gov (United States)

Behnam, Mira A M; Nitsche, Christoph; Boldescu, Veaceslav; Klein, Christian D

2016-06-23

The dengue virus and related flaviviruses are an increasing global health threat. In this perspective, we comment on and review medicinal chemistry efforts aimed at the prevention or treatment of dengue infections. We include target-based approaches aimed at viral or host factors and results from phenotypic screenings in cellular assay systems for viral replication. This perspective is limited to the discussion of results that provide explicit chemistry or structure-activity relationship (SAR), or appear to be of particular interest to the medicinal chemist for other reasons. The discovery and development efforts discussed here may at least partially be extrapolated toward other emerging flaviviral infections, such as West Nile virus. Therefore, this perspective, although not aimed at flaviviruses in general, should also be able to provide an overview of the medicinal chemistry of these closely related infectious agents.

Aquatic Chemistry

International Nuclear Information System (INIS)

Kim, Dong Yeun; Kim, Oh Sik; Kim, Chang Guk; Park, Cheong Gil; Lee, Gwi Hyeon; Lee, Cheol Hui

1987-07-01

This book deals aquatic chemistry, which treats water and environment, chemical kinetics, chemical balance like dynamical characteristic, and thermodynamics, acid-base chemistry such as summary, definition, kinetics, and PH design for mixture of acid-base chemistry, complex chemistry with definition, and kinetics, precipitation and dissolution on summary, kinetics of precipitation and dissolution, and balance design oxidation and resolution with summary, balance of oxidation and resolution.

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....

Turkish Prospective Chemistry Teachers' Alternative Conceptions about Acids and Bases

Science.gov (United States)

Boz, Yezdan

2009-01-01

The purpose of this study was to obtain prospective chemistry teachers' conceptions about acids and bases concepts. Thirty-eight prospective chemistry teachers were the participants. Data were collected by means of an open-ended questionnaire and semi-structured interviews. Analysis of data indicated that most prospective teachers did not have…

Ion-molecule reactions: their role in radiation chemistry

International Nuclear Information System (INIS)

Lias, S.G.; Ausloos, P.

1975-01-01

A comprehensive review of ion--molecule reactions is presented, including information from mass spectrometric, organic chemistry, and NMR studies, from theoretical calculations, and from gas and liquid phase radiation chemistry. Special emphasis is placed on interpreting the role of ion--molecule reactions in systems under high energy irradiation. The discussion is presented under the following chapter headings: ion--molecule reactions and their role in radiation chemistry; unimolecular processes: the nature and structure of ionic intermediates in radiolysis; ion lifetimes and the fate of unreactive ions; kinetics and mechanisms of ion--molecule reactions; proton transfer reactions; negative atom and two-atom transfer reactions; condensation reactions; and, association or clustering reactions

Porous structure and surface chemistry of phosphoric acid activated carbon from corncob

Science.gov (United States)

Sych, N. V.; Trofymenko, S. I.; Poddubnaya, O. I.; Tsyba, M. M.; Sapsay, V. I.; Klymchuk, D. O.; Puziy, A. M.

2012-11-01

Active carbons have been prepared from corncob using chemical activation with phosphoric acid at 400 °C using varied ratio of impregnation (RI). Porous structure of carbons was characterized by nitrogen adsorption and scanning electron microscopy. Surface chemistry was studied by IR and potentiometric titration method. It has been shown that porosity development was peaked at RI = 1.0 (SBET = 2081 m2/g, Vtot = 1.1 cm3/g), while maximum amount of acid surface groups was observed at RI = 1.25. Acid surface groups of phosphoric acid activated carbons from corncob includes phosphate and strongly acidic carboxylic (pK = 2.0-2.6), weakly acidic carboxylic (pK = 4.7-5.0), enol/lactone (pK = 6.7-7.4; 8.8-9.4) and phenol (pK = 10.1-10.7). Corncob derived carbons showed high adsorption capacity to copper, especially at low pH. Maximum adsorption of methylene blue and iodine was observed for carbon with most developed porosity (RI = 1.0).

Forensic Chemistry

Science.gov (United States)

Bell, Suzanne

2009-07-01

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.

The Brazilian medicinal chemistry from 1998 to 2008 in the Journal of Medicinal Chemistry, Bioorganic and Medicinal Chemistry, Bioorganic and Medicinal Chemistry Letters and European Journal of Medicinal Chemistry [A química medicinal brasileira de 1998 a 2008 nos periódicos Journal of Medicinal Chemistry, Bioorganic and Medicinal Chemistry, Bioorganic and Medicinal Chemistry Letters e European Journal of Medicinal Chemistry

OpenAIRE

Bárbara Vasconcellos da Silva; Renato Saldanha Bastos; Angelo da Cunha Pinto

2009-01-01

In this article we present the Brazilian publications, the research groups involved, the contributions per states and the main diseases studied from 1998 to 2008 in the following periodicals: Journal of Medicinal Chemistry, Bioorganic and Medicinal Chemistry, Bioorganic and Medicinal Chemistry Letters and European Journal of Medicinal Chemistry.

Magnetic properties of tetrataenite-rich meteorites. Pt. 2

International Nuclear Information System (INIS)

Nagata, T.; Funaki, M.; Danon, J.

1985-01-01

Magnetic hysteresis and thermomagnetic characteristics of St. Severin (LL 6 ), Appley Bridge (LL 6 ) and Tuxtuac (LL 5 ) chondrites, which contain tetrataenite in their metallic components, are measured and analyzed in comparison with another tetrataenite-rich chondrite, Yamato 74160. The magnetic properties of tetrataenite-rich meteorites are characterized by (a) high magnetic coercive force (H sub(C)) which amounts to 520 Oe for St. Severin and 160 Oe for Appley Bridge, (b) essential flatness up to about 500 0 C and then a sharp irreversible drop down to Curie point of the first-run heating thermomagnetic curve. Both characteristic features are broken down to the ordinary features of disordered taenite by a breakdown of tetrataenite structure at elevated temperatures beyond the order-disorder transition temperature. The natural remanent magnetization (NRM) of tetrataenite-rich meteorites is extremely stable against AF-demagnetization and other magnetic disturbances because of the high magnetic coercivity of tetrataenite. The breakdown processes of ordered tetrataenite structure by heat treatments are experimentally pursued for the purpose of research of a possible formation process of tetrataenite phase in meteorites. (Author) [pt

The effect of peatland drainage and restoration on Odonata species richness and abundance.

Science.gov (United States)

Elo, Merja; Penttinen, Jouni; Kotiaho, Janne S

2015-04-09

Restoration aims at reversing the trend of habitat degradation, the major threat to biodiversity. In Finland, more than half of the original peatland area has been drained, and during recent years, restoration of some of the drained peatlands has been accomplished. Short-term effects of the restoration on peatland hydrology, chemistry and vegetation are promising but little is known about how other species groups apart from vascular plants and bryophytes respond to restoration efforts. Here, we studied how abundance and species richness of Odonata (dragonflies and damselflies) respond to restoration. We sampled larvae in three sites (restored, drained, pristine) on each of 12 different study areas. We sampled Odonata larvae before restoration (n = 12), during the first (n = 10) and the third (n = 7) year after restoration and used generalized linear mixed models to analyze the effect of restoration. Drained sites had lower abundance and species richness than pristine sites. During the third year after restoration both abundance and species richness had risen in restored sites. Our results show that Odonata suffer from drainage, but seem to benefit from peatland restoration and are able to colonize newly formed water pools already within three years after restoration.

Diverse applications of radiation chemistry

International Nuclear Information System (INIS)

Cooper, R.

1998-01-01

Radiation chemistry began as early radiotherapists needed a reliable and appropriate dosimeter. The iron sulphate dosimeter, using ferrous iron in sulphuric acid and oxidation by irradiation, was a nasty brew of chemicals but it was sensitive, reliable and conveniently had the same density as human tissue. Water irradiation chemistry studies were driven by the need to understand the fundamental processes in radiotherapy; to control the corrosion problems in the cooling/ heat exchange systems of nuclear reactors and to find stable solvents and reagents for use in spent fuel element processing. The electrical and mechanical stability of materials in high radiation fields stimulated the attention of radiation chemists to the study of defects in solids. The coupled use of radiation and Electron Spin Resonance (ESR) enabled the identity of defect structures to be probed. This research led to the development of the sensitive Thermoluminescent Dosimeters, TLD's and a technique for dating of archaeological pottery artefacts. Radiation chemistry in the area of medicine is very active with fundamental studies of the mechanism of DNA strand breakage and the development of radiation sensitisers and protectors for therapeutic purposes. The major area of polymer radiation chemistry is one which Australia commands great international respect

Impaired rich club and increased local connectivity in children with traumatic brain injury: Local support for the rich?

Science.gov (United States)

Verhelst, Helena; Vander Linden, Catharine; De Pauw, Toon; Vingerhoets, Guy; Caeyenberghs, Karen

2018-03-12

Recent evidence has shown the presence of a "rich club" in the brain, which constitutes a core network of highly interconnected and spatially distributed brain regions, important for high-order cognitive processes. This study aimed to map the rich club organization in 17 young patients with moderate to severe TBI (15.71 ± 1.75 years) in the chronic stage of recovery and 17 age- and gender-matched controls. Probabilistic tractography was performed on diffusion weighted imaging data to construct the edges of the structural connectomes using number of streamlines as edge weight. In addition, the whole-brain network was divided into a rich club network, a local network and a feeder network connecting the latter two. Functional outcome was measured with a parent questionnaire for executive functioning. Our results revealed a significantly decreased rich club organization (p values < .05) and impaired executive functioning (p < .001) in young patients with TBI compared with controls. Specifically, we observed reduced density values in all three subnetworks (p values < .005) and a reduced mean strength in the rich club network (p = .013) together with an increased mean strength in the local network (p = .002) in patients with TBI. This study provides new insights into the nature of TBI-induced brain network alterations and supports the hypothesis that the local subnetwork tries to compensate for the biologically costly subnetwork of rich club nodes after TBI. © 2018 Wiley Periodicals, Inc.

Medicinal chemistry for 2020

Science.gov (United States)

Satyanarayanajois, Seetharama D; Hill, Ronald A

2011-01-01

Rapid advances in our collective understanding of biomolecular structure and, in concert, of biochemical systems, coupled with developments in computational methods, have massively impacted the field of medicinal chemistry over the past two decades, with even greater changes appearing on the horizon. In this perspective, we endeavor to profile some of the most prominent determinants of change and speculate as to further evolution that may consequently occur during the next decade. The five main angles to be addressed are: protein–protein interactions; peptides and peptidomimetics; molecular diversity and pharmacological space; molecular pharmacodynamics (significance, potential and challenges); and early-stage clinical efficacy and safety. We then consider, in light of these, the future of medicinal chemistry and the educational preparation that will be required for future medicinal chemists. PMID:22004084

Chemistry of the organic-rich hot core G327.3-0.6

Science.gov (United States)

Gibb, E.; Nummelin, A.; Irvine, W. M.; Whittet, D. C.; Bergman, P.; Ferris, J. P. (Principal Investigator)

2000-01-01

We present gas-phase abundances of species found in the organic-rich hot core G327.3-0.6. The data were taken with the Swedish-ESO Submillimetre Telescope (SEST). The 1-3 mm spectrum of this source is dominated by emission features of nitrile species and saturated organics, with abundances greater than those found in many other hot cores, including Sgr B2 and OMC-1. Population diagram analysis indicates that many species (CH3CN, C2H3CN, C2H5CN, CH3OH, etc.) have hot components that originate in a compact (2") region. Gas-phase chemical models cannot reproduce the high abundances of these molecules found in hot cores, and we suggest that they originate from processing and evaporation of icy grain mantle material. In addition, we report the first detection of vibrationally excited ethyl cyanide and the first detection of methyl mercaptan (CH3SH) outside the Galactic center.

Learning Organic Chemistry Through Natural Products

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education; Volume 1; Issue 5. Learning Organic Chemistry Through Natural Products From Molecular and Electronic Structures to Reactivity. N R Krishnaswamy. Series Article Volume 1 Issue 5 May 1996 pp 12-18 ...

Modeling local chemistry in PWR steam generator crevices

International Nuclear Information System (INIS)

Millett, P.J.

1997-01-01

Over the past two decades steam generator corrosion damage has been a major cost impact to PWR owners. Crevices and occluded regions create thermal-hydraulic conditions where aggressive impurities can become highly concentrated, promoting localized corrosion of the tubing and support structure materials. The type of corrosion varies depending on the local conditions, with stress corrosion cracking being the phenomenon of most current concern. A major goal of the EPRI research in this area has been to develop models of the concentration process and resulting crevice chemistry conditions. These models may then be used to predict crevice chemistry based on knowledge of bulk chemistry, thereby allowing the operator to control corrosion damage. Rigorous deterministic models have not yet been developed; however, empirical approaches have shown promise and are reflected in current versions of the industry-developed secondary water chemistry guidelines

The richness and reach of Wikinomics: Is the free web-based encyclopedia Wikipedia only for the rich countries?

DEFF Research Database (Denmark)

Rask, Morten

2007-01-01

In this paper, a model of the patterns of correlation in Wikipedia, reach and richness, lays the foundation for studying whether or not the free web-based encyclopedia Wikipedia is only for developed countries. Based upon data from 12 different Wikipedia language editions, we find that the central...... structural effect is on the level of human development in the current country. In other words, Wikipedia is in general, more for rich countries than for less developed countries. It is suggested that policy makers make investments in increasing the general level of literacy, education, and standard of living...

Bad chemistry

OpenAIRE

Petsko, Gregory A

2004-01-01

General chemistry courses haven't changed significantly in forty years. Because most basic chemistry students are premedical students, medical schools have enormous influence and could help us start all over again to create undergraduate chemistry education that works.

Web-Based Job Submission Interface for the GAMESS Computational Chemistry Program

Science.gov (United States)

Perri, M. J.; Weber, S. H.

2014-01-01

A Web site is described that facilitates use of the free computational chemistry software: General Atomic and Molecular Electronic Structure System (GAMESS). Its goal is to provide an opportunity for undergraduate students to perform computational chemistry experiments without the need to purchase expensive software.

The link between physics and chemistry in track modelling

International Nuclear Information System (INIS)

Green, N.J.B.; Bolton, C.E.; Spencer-Smith, R.D.

1999-01-01

The physical structure of a radiation track provides the initial conditions for the modelling of radiation chemistry. These initial conditions are not perfectly understood, because there are important gaps between what is provided by a typical track structure model and what is required to start the chemical model. This paper addresses the links between the physics and chemistry of tracks, with the intention of identifying those problems that need to be solved in order to obtain an accurate picture of the initial conditions for the purposes of modelling chemistry. These problems include the reasons for the increased yield of ionisation relative to homolytic bond breaking in comparison with the gas phase. A second area of great importance is the physical behaviour of low-energy electrons in condensed matter (including thermolisation and solvation). Many of these processes are not well understood, but they can have profound effects on the transient chemistry in the track. Several phenomena are discussed, including the short distance between adjacent energy loss events, the molecular nature of the underlying medium, dissociative attachment resonances and the ability of low-energy electrons to excite optically forbidden molecular states. Each of these phenomena has the potential to modify the transient chemistry substantially and must therefore be properly characterised before the physical model of the track can be considered to be complete. (orig.)

Yearly scientific meeting: chemistry in human health and environment protection. Bialystok'92

International Nuclear Information System (INIS)

1992-01-01

The conference has been divided into 12 sections devoted to following topics: analytical chemistry; environmental chemistry; chemistry of natural compounds; chemistry of pharmaceutics and toxic compounds; chemistry in medicine; electrochemistry; young scientists forum; didactics and history of chemistry; chemistry and industry - technologies environment friendly; new trends in polymer science; crystallochemistry; pro-ecological actions in leather industry. Different analytical methods for determination of heavy methods and rare earths have been presented. Some of them have been successfully applied for the examination of environmental and biological materials. The basic chemical and physico-chemical studies including thermodynamic, crystal structure, coordination chemistry, sorption properties etc. have been extensively resented. The existence of radioactive elements in environment has been also investigated, especially in respect to municipal and industrial wastes and products of their processing. The radiation effects for different materials have been reported and discussed as well

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

Chemistry and biology by new multiple choice

International Nuclear Information System (INIS)

Seo, Hyeong Seok; Kim, Seong Hwan

2003-02-01

This book is divided into two parts, the first part is about chemistry, which deals with science of material, atom structure and periodic law, chemical combination and power between molecule, state of material and solution, chemical reaction and an organic compound. The second part give description of biology with molecule and cell, energy in cells and chemical synthesis, molecular biology and heredity, function on animal, function on plant and evolution and ecology. This book has explanation of chemistry and biology with new multiple choice.

Physicists bag Chemistry Nobel for microscopy method

Science.gov (United States)

Johnston, Hamish

2017-11-01

The 2017 Nobel Prize for Chemistry has been given to Jacques Dubochet, Joachim Frank and Richard Henderson “for developing cryo-electron microscopy for the high-resolution structure determination of biomolecules in solution”.

Electron spin interactions in chemistry and biology fundamentals, methods, reactions mechanisms, magnetic phenomena, structure investigation

CERN Document Server

Likhtenshtein, Gertz

2016-01-01

This book presents the versatile and pivotal role of electron spin interactions in nature. It provides the background, methodologies and tools for basic areas related to spin interactions, such as spin chemistry and biology, electron transfer, light energy conversion, photochemistry, radical reactions, magneto-chemistry and magneto-biology. The book also includes an overview of designing advanced magnetic materials, optical and spintronic devices and photo catalysts. This monograph appeals to scientists and graduate students working in the areas related to spin interactions physics, biophysics, chemistry and chemical engineering.

Non-thermally activated chemistry

International Nuclear Information System (INIS)

Stiller, W.

1987-01-01

The subject is covered under the following headings: state-of-the art of non-thermally activated chemical processes; basic phenomena in non-thermal chemistry including mechanochemistry, photochemistry, laser chemistry, electrochemistry, photo-electro chemistry, high-field chemistry, magneto chemistry, plasma chemistry, radiation chemistry, hot-atom chemistry, and positronium and muonium chemistry; elementary processes in non-thermal chemistry including nuclear chemistry, interactions of electromagnetic radiations, electrons and heavy particles with matter, ionic elementary processes, elementary processes with excited species, radicalic elementary processes, and energy-induced elementary processes on surfaces and interfaces; and comparative considerations. An appendix with historical data and a subject index is given. 44 figs., 41 tabs., and 544 refs

Sulfonimidamides in Medicinal and Agricultural Chemistry

DEFF Research Database (Denmark)

Chinthakindi, Praveen K; Naicker, Tricia; Thota, Niranjan

2017-01-01

The synthesis and evaluation of structural analogues and isosteres are of central importance in medicinal and agricultural chemistry. The sulfonamide functional group represents one of the most important amide isosteres in contemporary drug design, and about 500 such compounds have overcome both ...

Cyclodextrin chemistry

International Nuclear Information System (INIS)

Khan, M.Z.; Chuaqui, C.A.

1990-05-01

The chemistry of cyclodextrins was studied. This study included synthesising some cyclodextrin derivatives, preparing selected inclusion complexes with cyclodextrin and investigating the effects of gamma irradiation on cyclodextrins and certain linear oligosaccharides. This report presents a brief review of the structure and properties of cyclodextrins, the synthesis of cyclodextrin derivatives, their complexation and applications. This is followed by a description of the synthesis of some cyclodextrin derivatives and the preparation of inclusion complexes of cyclodextrin with some organic compounds. Finally, the effects of gamma irradiation on cyclodextrins, some of their derivatives and certain structurally related carbohydrates are discussed. The gamma irradiation studies were carried out for two reasons: to study the effects of gamma irradiation on cyclodextrins and their derivatives; and to investigate selectivity during the gamma irradiation of cyclodextrin derivatives

CARBON CHEMISTRY IN THE ENVELOPE OF VY CANIS MAJORIS: IMPLICATIONS FOR OXYGEN-RICH EVOLVED STARS

International Nuclear Information System (INIS)

Ziurys, L. M.; Tenenbaum, E. D.; Pulliam, R. L.; Woolf, N. J.; Milam, S. N.

2009-01-01

Observations of the carbon-bearing molecules CO, HCN, CS, HNC, CN, and HCO + have been conducted toward the circumstellar envelope of the oxygen-rich red supergiant star, VY Canis Majoris (VY CMa), using the Arizona Radio Observatory (ARO). CO and HCN were also observed toward the O-rich shells of NML Cyg, TX Cam, IK Tau, and W Hya. Rotational transitions of these species at 1 mm, 0.8 mm, and 0.4 mm were measured with the ARO Submillimeter Telescope, including the J = 6 → 5 line of CO at 691 GHz toward TX Cam and W Hya. The ARO 12 m was used for 2 mm and 3 mm observations. Four transitions were observed for HCO + in VY CMa, the first definitive identification of this ion in a circumstellar envelope. Molecular line profiles from VY CMa are complex, indicating three separate outflows: a roughly spherical flow and separate red- and blueshifted winds, as suggested by earlier observations. Spectra from the other sources appear to trace a single outflow component. The line data were modeled with a radiative transfer code to establish molecular abundances relative to H 2 and source distributions. Abundances for CO derived for these objects vary over an order of magnitude, f ∼ 0.4-5 x 10 -4 , with the lower values corresponding to the supergiants. For HCN, a similar range in abundance is found (f ∼ 0.9-9 x 10 -6 ), with no obvious dependence on the mass-loss rate. In VY CMa, HCO + is present in all three outflows with f ∼ 0.4-1.6 x 10 -8 and a spatial extent similar to that of CO. HNC is found only in the red- and blueshifted components with [HCN]/[HNC] ∼ 150-190, while [CN]/[HCN] ∼ 0.01 in the spherical flow. All three velocity components are traced in CS, which has a confined spatial distribution and f ∼ 2-6 x 10 -7 . These observations suggest that carbon-bearing molecules in O-rich shells are produced by a combination of photospheric shocks and photochemistry. Shocks may play a more prominent role in the supergiants because of their macroturbulent

Carbon Chemistry in the Envelope of VY Canis Majoris: Implications for Oxygen-Rich Evolved Stars

Science.gov (United States)

Ziurys, L. M.; Tenenbaum, E. D.; Pulliam, R. L.; Woolf, N. J.; Milam, S. N.

2009-04-01

Observations of the carbon-bearing molecules CO, HCN, CS, HNC, CN, and HCO+ have been conducted toward the circumstellar envelope of the oxygen-rich red supergiant star, VY Canis Majoris (VY CMa), using the Arizona Radio Observatory (ARO). CO and HCN were also observed toward the O-rich shells of NML Cyg, TX Cam, IK Tau, and W Hya. Rotational transitions of these species at 1 mm, 0.8 mm, and 0.4 mm were measured with the ARO Submillimeter Telescope, including the J = 6 → 5 line of CO at 691 GHz toward TX Cam and W Hya. The ARO 12 m was used for 2 mm and 3 mm observations. Four transitions were observed for HCO+ in VY CMa, the first definitive identification of this ion in a circumstellar envelope. Molecular line profiles from VY CMa are complex, indicating three separate outflows: a roughly spherical flow and separate red- and blueshifted winds, as suggested by earlier observations. Spectra from the other sources appear to trace a single outflow component. The line data were modeled with a radiative transfer code to establish molecular abundances relative to H2 and source distributions. Abundances for CO derived for these objects vary over an order of magnitude, f ~ 0.4-5 × 10-4, with the lower values corresponding to the supergiants. For HCN, a similar range in abundance is found (f ~ 0.9-9 × 10-6), with no obvious dependence on the mass-loss rate. In VY CMa, HCO+ is present in all three outflows with f ~ 0.4-1.6 × 10-8 and a spatial extent similar to that of CO. HNC is found only in the red- and blueshifted components with [HCN]/[HNC] ~ 150-190, while [CN]/[HCN] ~ 0.01 in the spherical flow. All three velocity components are traced in CS, which has a confined spatial distribution and f ~ 2-6 × 10-7. These observations suggest that carbon-bearing molecules in O-rich shells are produced by a combination of photospheric shocks and photochemistry. Shocks may play a more prominent role in the supergiants because of their macroturbulent velocities.

Current status of regulatory aspects relating to water chemistry in Japanese NPPs

International Nuclear Information System (INIS)

Sato, Masatoshi

2014-01-01

In nuclear power plants, water chemistry of cooling water is carefully monitored and controlled to keep integrity of structures, systems and components, and to reduce occupational radiation exposures. As increasing demand for advanced application of light water cooled reactors, water chemistry control plays more important roles on plant reliability. The road maps on R and D for water chemistry of nuclear power systems have been proposed along with promotion of R and D related water chemistry in Japan. In academic and engineering societies, non-governmental standards for water chemistry are going to be established. In the present paper, recent trends of water chemistry in Japan have been surveyed. The effects of water chemistry on plant safety and radiation exposures have been discussed. In addition, possible contributions of regulation regarding water chemistry control have been confirmed. Major water chemistry regulatory aspects relating to reactor safety and radiation safety are also outlined in this paper. (author)

Eighteenth annual West Coast theoretical chemistry conference

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-05-01

Abstracts are presented from the eighteenth annual west coast theoretical chemistry conference. Topics include molecular simulations; quasiclassical simulations of reactions; photodissociation reactions; molecular dynamics;interface studies; electronic structure; and semiclassical methods of reactive systems.

American Chemical Society. Division of Nuclear Chemistry and Technology

International Nuclear Information System (INIS)

Anon.

1991-01-01

The meeting of the 201st American Chemical Society Division of Nuclear Chemistry and Technology was comprised from a variety of topics in this field including: nuclear chemistry, nuclear physics, and nuclear techniques for environmental studies. Particular emphasis was given to fundamental research concerning nuclear structure (seven of the nineteen symposia) and studies of airborne particle monitoring and transport (five symposia). 105 papers were presented

Structural and optical properties of silicon rich oxide films in graded-stoichiometric multilayers for optoelectronic devices

Energy Technology Data Exchange (ETDEWEB)

Palacios-Huerta, L.; Aceves-Mijares, M. [Electronics Department, INAOE, Apdo. 51, Puebla, Pue. 72000, México (Mexico); Cabañas-Tay, S. A.; Cardona-Castro, M. A.; Morales-Sánchez, A., E-mail: alfredo.morales@cimav.edu.mx [Centro de Investigación en Materiales Avanzados S.C., Unidad Monterrey-PIIT, Apodaca, NL 66628, México (Mexico); Domínguez-Horna, C. [Instituto de Microelectrónica de Barcelona, IMB-CNM (CSIC), Bellaterra 08193, Barcelona (Spain)

2016-07-18

Silicon nanocrystals (Si-ncs) are excellent candidates for the development of optoelectronic devices. Nevertheless, different strategies are still necessary to enhance their photo and electroluminescent properties by controlling their structural and compositional properties. In this work, the effect of the stoichiometry and structure on the optical properties of silicon rich oxide (SRO) films in a multilayered (ML) structure is studied. SRO MLs with silicon excess gradually increased towards the top and bottom and towards the center of the ML produced through the variation of the stoichiometry in each SRO layer were fabricated and confirmed by X-ray photoelectron spectroscopy. Si-ncs with three main sizes were observed by a transmission electron microscope, in agreement with the stoichiometric profile of each SRO layer. The presence of the three sized Si-ncs and some oxygen related defects enhances intense violet/blue and red photoluminescence (PL) bands. The SRO MLs were super-enriched with additional excess silicon by Si{sup +} implantation, which enhanced the PL intensity. Oxygen-related defects and small Si-ncs (<2 nm) are mostly generated during ion implantation enhancing the violet/blue band to become comparable to the red band. The structural, compositional, and luminescent characteristics of the multilayers are the result of the contribution of the individual characteristics of each layer.

"Drug" Discovery with the Help of Organic Chemistry.

Science.gov (United States)

Itoh, Yukihiro; Suzuki, Takayoshi

2017-01-01

The first step in "drug" discovery is to find compounds binding to a potential drug target. In modern medicinal chemistry, the screening of a chemical library, structure-based drug design, and ligand-based drug design, or a combination of these methods, are generally used for identifying the desired compounds. However, they do not necessarily lead to success and there is no infallible method for drug discovery. Therefore, it is important to explore medicinal chemistry based on not only the conventional methods but also new ideas. So far, we have found various compounds as drug candidates. In these studies, some strategies based on organic chemistry have allowed us to find drug candidates, through 1) construction of a focused library using organic reactions and 2) rational design of enzyme inhibitors based on chemical reactions catalyzed by the target enzyme. Medicinal chemistry based on organic chemical reactions could be expected to supplement the conventional methods. In this review, we present drug discovery with the help of organic chemistry showing examples of our explorative studies on histone deacetylase inhibitors and lysine-specific demethylase 1 inhibitors.

Large-scale micromagnetic simulation of Nd-Fe-B sintered magnets with Dy-rich shell structures

Directory of Open Access Journals (Sweden)

T. Oikawa

2016-05-01

Full Text Available Large-scale micromagnetic simulations have been performed using the energy minimization method on a model with structural features similar to those of Dy grain boundary diffusion (GBD-processed sintered magnets. Coercivity increases as a linear function of the anisotropy field of the Dy-rich shell, which is independent of Dy composition in the core as long as the shell thickness is greater than about 15 nm. This result shows that the Dy contained in the initial sintered magnets prior to the GBD process is not essential for enhancing coercivity. Magnetization reversal patterns indicate that coercivity is strongly influenced by domain wall pinning at the grain boundary. This observation is found to be consistent with the one-dimensional pinning theory.

New experimental investigation of cluster structures in 10 Be and 16 C neutron-rich nuclei

Science.gov (United States)

Dell'Aquila, L.; Acosta, D.; Auditore, L.; Cardella, G.; De Filippo, E.; De Luca, S.; Francalanza, L.; Gnoffo, B.; Lanzalone, G.; Lombardo, I.; Martorana, N. S.; Norella, S.; Pagano, A.; Pagano, E. V.; Papa, M.; Pirrone, S.; Politi, G.; Quattrocchi, L.; Rizzo, F.; Russotto, P.; Trifirò, A.; Trimarchi, M.; Verde, G.; Vigilante, M.

2017-11-01

The existence of cluster structures in ^{10} Be and ^{16} C neutron-rich isotopes is investigated via projectile break-up reactions induced on polyethylene (CH _2 target. We used a fragmentation beam constituted by 55MeV/u ^{10} Be and 49MeV/u ^{16} C beams provided by the FRIBs facility at INFN-LNS. Invariant mass spectra of 4{He}+ 6 He and 6{He} + ^{10} Be breakup fragments are reconstructed by means of the CHIMERA 4π detector to investigate the presence of excited states of projectile nuclei characterized by cluster structure. In the first case, we suggest the presence of a new state in ^{10} Be at 13.5MeV. A non-vanishing yield corresponding to 20.6MeV excitation energy of ^{16} C was observed in the 6{He} + ^{10} Be cluster decay channel. To improve the results of the present analysis, a new experiment has been performed recently, taking advantage of the coupling of CHIMERA and FARCOS. In the paper we describe the data reduction process of the new experiment together with preliminary results.

Cycloadditions in modern polymer chemistry.

Science.gov (United States)

Delaittre, Guillaume; Guimard, Nathalie K; Barner-Kowollik, Christopher

2015-05-19

Synthetic polymer chemistry has undergone two major developments in the last two decades. About 20 years ago, reversible-deactivation radical polymerization processes started to give access to a wide range of polymeric architectures made from an almost infinite reservoir of functional building blocks. A few years later, the concept of click chemistry revolutionized the way polymer chemists approached synthetic routes. Among the few reactions that could qualify as click, the copper-catalyzed azide-alkyne cycloaddition (CuAAC) initially stood out. Soon, many old and new reactions, including cycloadditions, would further enrich the synthetic macromolecular chemistry toolbox. Whether click or not, cycloadditions are in any case powerful tools for designing polymeric materials in a modular fashion, with a high level of functionality and, sometimes, responsiveness. Here, we wish to describe cycloaddition methodologies that have been reported in the last 10 years in the context of macromolecular engineering, with a focus on those developed in our laboratories. The overarching structure of this Account is based on the three most commonly encountered cycloaddition subclasses in organic and macromolecular chemistry: 1,3-dipolar cycloadditions, (hetero-)Diels-Alder cycloadditions ((H)DAC), and [2+2] cycloadditions. Our goal is to briefly describe the relevant reaction conditions, the advantages and disadvantages, and the realized polymer applications. Furthermore, the orthogonality of most of these reactions is highlighted because it has proven highly beneficial for generating unique, multifunctional polymers in a one-pot reaction. The overview on 1,3-dipolar cycloadditions is mostly centered on the application of CuAAC as the most travelled route, by far. Besides illustrating the capacity of CuAAC to generate complex polymeric architectures, alternative 1,3-dipolar cycloadditions operating without the need for a catalyst are described. In the area of (H)DA cycloadditions

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...

Two genetic loci produce distinct carbohydrate-rich structural components of the Pseudomonas aeruginosa biofilm matrix.

Science.gov (United States)

Friedman, Lisa; Kolter, Roberto

2004-07-01

Pseudomonas aeruginosa forms biofilms, which are cellular aggregates encased in an extracellular matrix. Molecular genetics studies of three common autoaggregative phenotypes, namely wrinkled colonies, pellicles, and solid-surface-associated biofilms, led to the identification of two loci, pel and psl, that are involved in the production of carbohydrate-rich components of the biofilm matrix. The pel gene cluster is involved in the production of a glucose-rich matrix material in P. aeruginosa strain PA14 (L. Friedman and R. Kolter, Mol. Microbiol. 51:675-690, 2004). Here we investigate the role of the pel gene cluster in P. aeruginosa strain ZK2870 and identify a second genetic locus, termed psl, involved in the production of a mannose-rich matrix material. The 11 predicted protein products of the psl genes are homologous to proteins involved in carbohydrate processing. P. aeruginosa is thus able to produce two distinct carbohydrate-rich matrix materials. Either carbohydrate-rich matrix component appears to be sufficient for mature biofilm formation, and at least one of them is required for mature biofilm formation in P. aeruginosa strains PA14 and ZK2870. Copyright 2004 American Society for Microbiology

Radiation chemistry of biologically compatible polymers

International Nuclear Information System (INIS)

Hill, D.J. T.; Pomery, P.J.; Saadat, G.; Whittaker, A.K.

1996-01-01

Full text: Poly (2-hydroxy ethyl methacrylate) [PHEMA] and poly (2-ethoxy ethyl methacrylate) [PEEMA] are of biomedical and industrial interest due to their biocompatibility with living tissue. In this paper the effect of high energy radiation on these polymers is reported. PHEMA and PEEMA have similar molecular structures to poly (methyl methacrylate)[PMMA], and the γ irradiation of this polymer is well understood. Hence the radiation chemistry of PMMA is used as model system for the the analysis of the radiation chemistry of these polymers. The mechanism of the radiation induced chemistry of the polymers has been investigated using a range of techniques including electron spin resonance spectroscopy (ESR) to establish free radical pathways, GC to identify small molecule volatile products, NMR to identify small molecule radiation products and Gel Permeation Chromatography (GPC) to determine molecular weight changes. Whilst much of the major part of the radiation chemistry can be attributed to similar reactions which can be observed in PMMA, there are a number of new radicals which are present as a result of the influence of the side chain interactions which reduces the mobility of the polymer chain

An ideal teaching program of nuclear chemistry in the undergraduate chemistry curriculum

International Nuclear Information System (INIS)

Uenak, T.

2009-01-01

It is well known that several reports on the common educational problems of nuclear chemistry have been prepared by certain groups of experts from time to time. According to very important statements in these reports, nuclear chemistry and related courses generally do not take sufficient importance in undergraduate chemistry curricula and it was generally proposed that nuclear chemistry and related courses should be introduced into undergraduate chemistry curricula at universities worldwide. Starting from these statements, an ideal program in an undergraduate chemistry curriculum was proposed to be introduced into the undergraduate chemistry program at the Department of Chemistry, Ege University, in Izmir, Turkey during the regular updating of the chemistry curriculum. Thus, it has been believed that this Department of Chemistry has recently gained an ideal teaching program in the field of nuclear chemistry and its applications in scientific, industrial, and medical sectors. In this contribution, the details of this program will be discussed. (author)

The structure of neutron-rich nuclei explored via in-beam gamma-ray spectroscopy of fast beams

International Nuclear Information System (INIS)

Glasmacher, T.; Campbell, C.M.; Church, J.A.; Dinca, D.C.; Hansen, P.G.; Olliver, H.; Perry, B.C.; Sherrill, B.M.; Terry, J.R.; Bazin, D.; Enders, J.; Gade, A.; Hu, Z.; Mueller, W.F.

2003-01-01

In-beam gamma-ray spectroscopy with fast exotic beams provides an efficient tool to study bound states in exotic neutron-rich nuclei. Specialized experimental techniques have been developed and explore different aspects of nuclear structure. Inelastic scattering experiments with γ-ray detection can measure the response of exotic nuclei to electromagnetic (Coulomb excitation with a heavy target) or hadronic probes (proton scattering with hydrogen target). In-beam fragmentation populates higher-lying bound states to establish levels. Single- and two-nucleon knockout reactions allow for detailed wavefunction spectroscopy of individual levels and for the measurement of spectroscopic factors. Experimental programs employing these techniques are now underway at all projectile-fragmentation facilities around the world. Here we report on several successful in-beam gamma-ray spectroscopy experiments that have been performed at the Coupled Cyclotron Facility at Michigan State University with an emphasis on elucidating the evolution of nuclear structure around neutron numbers N=16, N=20, and N=28 in the π(sd) shell. (orig.)

Simulations of the structure and dynamics of nanoparticle-based ionic liquids

KAUST Repository

Hong, Bingbing

2012-01-01

We use molecular dynamics simulations over microsecond time scales to study the structure and dynamics of coarse-grained models for nanoparticle-based ionic liquids. The systems of interest consist of particles with charged surface groups and linear or three-arm counterions, which also act as the solvent. A comparable uncharged model of nanoparticles with tethered chains is also studied. The pair correlation functions display a rich structure resulting from the packing of cores and chains, as well as electrostatic effects. Even though electrostatic interactions between oppositely charged ions at contact are much greater than the thermal energy, we find that chain dynamics at intermediate time scales are dominated by chain hopping between core particles. The uncharged core particles with tethered chains diffuse faster than the ionic core particles. © 2012 The Royal Society of Chemistry.

Experimental study of the structure of rich premixed 1,3-butadiene/CH4/O2/Ar flame.

OpenAIRE

Gueniche , Hadj-Ali; Glaude , Pierre-Alexandre; Fournet , René; Battin-Leclerc , Frédérique

2006-01-01

traduit de Fizika Goreniya I Vzryva, 2006, 42, 89-95.; The structure of a laminar rich premixed 1,3-C4H6/CH4/O2/Ar flame have been investigated. 1,3-Butadiene, methane, oxygen and argon mole fractions are 0.033; 0.2073; 0.3315, and 0.4280, respectively, for an equivalent ratio of 1.80. The flame has been stabilized on a burner at a pressure of 6.7 kPa (50 Torr). The concentration profiles of stable species were measured by gas chromatography after sampling with a quartz probe. Quantified spec...

Coolant circuit water chemistry of the Paks Nuclear Power Plant

International Nuclear Information System (INIS)

Tilky, Peter; Doma, Arpad

1985-01-01

The numerous advantages of the proper selection of water chemistry parameters including low corrosion rate of the structural materials, hence the low-level activity build-up, depositions, radiation doses were emphasized. Major characteristics of water chemistry applied to the primary coolant of pressurized water reactors including neutral, slightly basic and strong basic ones are discussed. Boric acid is widely used to control reactivity. Primary coolant water chemistry of WWER type reactors which is based on the addition of ammonia and potassium hydroxide to boric acid is compared with that of other reactors. The demineralization of the total condensate of the steam turbines became a general trend in the water chemistry of the secondary coolant circuits. (V.N.)

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