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O impacto da primeira adoção das normas IFRS nas empresas européias químicas e de mineração: pesquisa descritiva; The first impact of the adoption of IFRS in European chemical companies and mining: search descriptive

Cambria, Marcelo
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 20/08/2008 PT
Relevância na Pesquisa
35.91%
A adoção crescente das normas internacionais de contabilidade, as IFRS, é o reflexo de que a comunicação entre empresas, credores, investidores e demais "stakeholders" acompanha as mudanças radicais observadas nos negócios. O trabalho de elaboração de tais normas internacionais ficou a cargo do "Board" do IASB e já se identifica ampla convergência no plano mundial rumo às citadas IFRS. A IFRS 1, denominada "First Time Adoption" refere-se aos requisitos a serem observados no primeiro exercício em que uma empresa publica suas demonstrações em norma contábil local e em IFRS. Este estudo tem por objetivo verificar se, no ano da primeira adoção, há diferença nos grupos de contas patrimoniais do ativo e do passivo nos balanços das empresas dos setores químico e de mineração listadas nas bolsas do Reino Unido, da França e da Alemanha, calculados com base no último balanço em norma contábil local, em relação aos mesmos grupos da primeira demonstração publicada em IFRS. Através da pesquisa nas bolsas de valores destes três países, foram analisadas 42 empresas, sendo 18 empresas de mineração e 24 companhias do segmento químico. Foram utilizados os testes estatísticos t-student para amostras emparelhadas e Wilcoxon para a comparação das médias das diferenças das proporções de cada grupo do patrimônio em relação ao ativo ou passivo total. Os resultados demonstram que existe diferença significativa na estrutura dos grupos do ativo e do passivo pré e pós-adoção das IFRS...

Variability of mercury distribution and exchanges between the Ria de Aveiro and the Atlantic Ocean

Martins, Pedro Emanuel Pato
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
26.1%
A Ria de Aveiro (Portugal) é uma laguna mesotidal que comunica com o Oceano Atlântico através de um único e estreito canal. Durante quatro décadas, foram descarregados num braço da Ria efluentes contaminados com mercúrio provenientes de uma indústria de produção de cloro e soda caustica e estudos anteriores documentam que cerca de 33 toneladas de mercúrio foram retidos nos sedimentos da laguna. O presente trabalho teve como objectivo aumentar o conhecimento dos processos de dispersão e sobre o comportamento do mercúrio durante o percurso estuarino (incluindo a importância do plâncton nestes processos), e a avaliação da extensão da transferência para o Oceano Atlântico. Tirando partido do privilégio da existência de uma única conexão com o Oceano, o canal de interface entre a Ria de Aveiro e o Oceano Atlântico serviu como um ponto ideal para a monitorização da variabilidade do transporte. Para tal, foram recolhidas amostras de água no canal mencionado durante ciclos de maré com amplitudes de maré e descargas fluviais contrastantes. Para estudar os factores que controlam a partição do mercúrio, foi realizada uma caracterização físico-química da fracção dissolvida e dos sólidos suspensos finos e grosseiros. Relativamente à distribuição de mercúrio durante os ciclos de maré...

Química entre a microcamada superficial oceânica e os aerossóis marinhos

Alves,Célia A.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 PT
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26.17%
The sea surface microlayer (SML), although poorly understood, is important in biogeochemical cycling and sea - air exchanges; it is a source or a sink for a range of pollutants. In this paper, an overview of sampling techniques and the role of SML in biogeochemical cycles and climate is presented. The chemical and biological nature of the ocean surface film and its interaction with atmospheric aerosols are discussed. Special attention is given to organic constituents, gel-like compounds, surfactants, halogenated compounds, and metals. Estimates of air - sea exchange fluxes-with focus on organic carbon, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls-are compiled. In addition, research gaps in the chemical composition of marine aerosols and their relationship with SML are described.

Glutaraldehyde release from heat-polymerized acrylic resins after disinfection and chemical and mechanical polishing

Orsi,Iara Augusta; Andrade,Vanessa Gomes; Bonato,Pierina Sueli; Raimundo,Lariça Barbosa; Herzog,Daniella Silva; Borie,Eduardo
Fonte: Fundação Odontológica de Ribeirão Preto Publicador: Fundação Odontológica de Ribeirão Preto
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 EN
Relevância na Pesquisa
26.27%
This study evaluated the release of glutaraldehyde from heat-polymerized acrylic resins subjected to disinfection followed by chemical and mechanical polishing. Ninety disc-shaped specimens (15 x 4 mm), 30 per resin (Lucitone 550, QC-20 and Classico), were made and assigned to 2 groups according to the type of polishing. One side of each specimen was not polished and the other was either mechanically (n=45) or chemically (n=45) polished, and immersed in water at 50°C for 1 h to allow the release of intrinsic substances and then kept in distilled water for 7 days. The specimens were disinfected by immersion in 2% glutaraldehyde for 10 min. After this period, 3 specimens from each group were immersed in water for 15, 30, 60, 120 and 240 min. For the 15-, 30-, 60-min immersions, 4 water exchanges were done at the end of period. High performance liquid chromatography (HPLC) was used to detect and quantify the glutaraldehyde released after each period. Data were analyzed statistically by two-way ANOVA and multiple comparisons were done by Tukey’s and Scheffé’s tests (α=0.05). No glutaraldehyde release was observed from the specimens with chemical polishing at any of the immersion periods, while the mechanically polished specimens released glutaraldehyde. In the groups with water exchanges...

Induction of Ouabain-resistant Mutation and Sister Chromatid Exchanges in Chinese Hamster Cells with Chemical Carcinogens Mediated by Human Pulmonary Macrophages

Hsu, Ih Chang; Harris, Curtis C.; Yamaguchi, Maria; Trump, Benjamin F.; Schafer, Paul W.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1979 EN
Relevância na Pesquisa
26.33%
Pulmonary macrophages (PAM) metabolically activated benzo[a]pyrene [B(a)P] and its proximate carcinogenic metabolite, (±)trans 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (7,8-diol), to ultimate mutagens that were detected in cocultivated Chinese hamster V79 cells. Increases in the frequency of ouabainresistant (Or) mutations and sister chromatid exchanges were found in V79 cells only when they were cocultivated with both PAM and the chemical procarcinogens. 7,8-Diol caused higher frequencies of both Or mutations and sister chromatid exchanges than did the parent compound, B(a)P. When metabolically activated by PAM the mean Or mutation frequency caused by B(a)P was 9 Or mutants/106 surviving V79 cells per 106 PAM and a 10-fold interindividual variation (range, 2-21) was found. The mean Or mutation frequency caused by 7,8-diol was 64 and a ninefold interindividual variation (range, 14-120) was found. In the absence of PAM, the Or mutation frequency in V79 cells was one or less Or mutant per 106 survivors. 7,8-Benzoflavone, an inhibitor of mixed function oxidases, reduced the frequencies of Or mutations and of sister chromatid exchanges in V79 cells caused by 7,8-diol and B(a)P. As expected 7,8-benzoflavone did not influence the frequency of Or mutations caused by one of the ultimate mutagens derived from B(a)P and 7...

Involvement of HbPIP2;1 and HbTIP1;1 Aquaporins in Ethylene Stimulation of Latex Yield through Regulation of Water Exchanges between Inner Liber and Latex Cells in Hevea brasiliensis1[C][W]

Tungngoen, Kessarin; Kongsawadworakul, Panida; Viboonjun, Unchera; Katsuhara, Maki; Brunel, Nicole; Sakr, Soulaiman; Narangajavana, Jarunya; Chrestin, Hervé
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Publicado em /10/2009 EN
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26%
Natural rubber is synthesized in specialized articulated cells (laticifers) located in the inner liber of Hevea brasiliensis. Upon bark tapping, the laticifer cytoplasm (latex) is expelled due to liber tissue turgor pressure. In mature virgin (untapped) trees, short-term kinetic studies confirmed that ethylene, the rubber yield stimulant used worldwide, increased latex yield, with a concomitant decrease in latex total solid content, probably through water influx in the laticifers. As the mature laticifers are devoid of plasmodesmata, the rapid water exchanges with surrounding liber cells probably occur via the aquaporin pathway. Two full-length aquaporin cDNAs (HbPIP2;1 and HbTIP1;1, for plasma membrane intrinsic protein and tonoplast intrinsic protein, respectively) were cloned and characterized. The higher efficiency of HbPIP2;1 than HbTIP1;1 in increasing plasmalemma water conductance was verified in Xenopus laevis oocytes. HbPIP2;1 was insensitive to HgCl2. In situ hybridization demonstrated that HbPIP2;1 was expressed in all liber tissues in the young stem, including the laticifers. HbPIP2;1 was up-regulated in both liber tissues and laticifers, whereas HbTIP1;1 was down-regulated in liber tissues but up-regulated in laticifers in response to bark Ethrel treatment. Ethylene-induced HbPIP2;1 up-regulation was confirmed by western-blot analysis. The promoter sequences of both genes were cloned and found to harbor...

Spin-locking vs. chemical exchange saturation transfer MRI for investigating chemical exchange process between water and labile metabolite protons

Jin, Tao; Autio, Joonas; Obata, Takayuki; Kim, Seong-Gi
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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36.05%
Chemical exchange saturation transfer (CEST) and spin-locking (SL) experiments were both able to probe the exchange process between protons of non-equivalent chemical environments. To compare the characteristics of the CEST and SL approaches in the study of chemical exchange effects, we performed CEST and SL experiments at varied pH and concentrated metabolites with exchangeable amide, amine, and hydroxyl protons at 9.4 T. Our results show that: i) On-resonance SL is most sensitive to chemical exchanges in the intermediate exchange regime and is able to detect hydroxyl and amine protons on a millimolar concentration scale. Off-resonance SL and CEST approaches are sensitive to slow-exchanging protons when an optimal SL or saturation pulse power matches the exchanging rate, respectively. ii) Offset frequency-dependent SL and CEST spectra are very similar, and can be explained well with an SL model recently developed by Trott and Palmer. iii) The exchange rate and population of metabolite protons can be determined from offset-dependent SL or CEST spectra or from on-resonance SL relaxation dispersion measurements. iv) The asymmetry of the magnetization transfer ratio (MTRasym) is highly dependent on the choice of saturation pulse power. In the intermediate exchange regime...

Quantitative chemical exchange sensitive MRI using irradiation with toggling inversion preparation (iTIP)

Jin, Tao; Kim, Seong-Gi
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
35.97%
Chemical exchange (CE) sensitive MRI contrast acquired with an off-resonance irradiation pulse is affected by other relaxation mechanisms, such as longitudinal and transverse relaxations. In particular, for intermediate chemical exchanges, the effect of transverse relaxation often dominates CE contrast. Since water relaxation rates can change significantly in many pathological conditions or during physiological challenge, it is crucial to separate these relaxation effects in order to obtain pure CE contrast. Here we proposed a novel acquisition scheme in which a toggling inversion pulse is applied prior to the off-resonance irradiation. By combined acquisition of irradiation images with and without an inversion pulse at both the labile proton frequency and the reference frequency, longitudinal and transverse relaxation contributions are cancelled; and the quantification of CE parameters, such as the exchange rate and the labile proton concentration, can be simplified. Furthermore, the CE mediated relaxation rate can be readily determined with a relatively short irradiation pulse and without approaching the steady state, therefore, reducing the limitations on hardware and specific absorption rate requirements. The signal characteristics of the proposed method are evaluated by numerical simulations and phantom experiments.

Backbone Dynamics of an Atypical Orphan Response Regulator Protein, Helicobacter pylori 1043

Jeong, Ki-Woong; Ko, Hyunsook; Lee, Sung-Ah; Hong, Eunmi; Ko, Sunggeon; Cho, Hyun-Soo; Lee, Weontae; Kim, Yangmee
Fonte: Korea Society for Molecular and Cellular Biology Publicador: Korea Society for Molecular and Cellular Biology
Tipo: Artigo de Revista Científica
EN
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26%
An atypical orphan response regulator protein, HP1043 (HP-RR) in Helicobacter pylori, is proven to be essential for cell growth and does not require the well known phosphorelay scheme. HP-RR was identified as a symmetric dimer with two functional domains, an N-terminal regulatory domain (HP-RRr) and a C-terminal effector domain (HP-RRe). HP-RR is a new class of response regulator, as a phosphorylation-independent regulator. Previously, we have presented a detailed three-dimensional structure of HP-RR using NMR spectroscopy and X-ray crystallography. In this study, in order to understand the functional importance of flexibilities in HP-RRr and HP-RRe, T1, T2, heteronuclear NOE experiments have been performed and backbone dynamics of HP-RRr and HP-RRe were investigated. HP-RRr is a symmetric dimer and the interface region, α4-β5-α5 of dimer, showed high rigidity (high S2 values). Site of rearrangements associated with phosphorylation of HP-RRr (Ser75: Rex = 3.382, Ile95: Rex = 5.228) showed slow chemical exchanges. HP-RRe is composed of three α-helices flanked on two sides by anti-parallel β-sheets. Low order parameters as well as conformational exchanges in the centers of loop regions known as the DNA binding site and transcription site of HP-RRe suggested that flexibility of HP-RRe is essential for interaction with DNA. In conclusion...

Constraining Subduction Zone Processes Through Local, Regional, and Global Chemical Systematics

Turner, Stephen
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation; text Formato: application/pdf
EN
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26.09%
Subduction zones recycle material from Earth’s surface into the mantle, and are an important means of continent building. The subduction system serves as a stamp, imprinting the distinct chemical characteristics of our planet’s geological reservoirs, and distinguishing it within the solar system. As such, the elemental exchanges mediated by this system are a long-standing focus of geochemical and geophysical research. Advances in geochemical techniques and improved geophysical models of subduction have illuminated the processes which give rise to arc volcanism. Great strides have been made in answering the question of what goes down, and what comes back up, though much remains unknown. Arc volcanoes provide a valuable window into the complex subduction environment, and so a comprehensive understanding of arc magma petrogenesis provides a means to resolve significant outstanding questions. The processes that regulate the compositions of erupted arc magmas are complicated, however. In order to use arc magmas as a tool for constraining elemental fluxes across large-scale geochemical reservoirs, we must trace the path of lavas sampled on Earth’s surface back down through the lithosphere. Once we reach the asthenosphere...

Vibrational and Chemical Relaxation Rates of Diatomic Gases

Kewley, Douglas John
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
EN
Relevância na Pesquisa
35.91%
A theoretical and experimental study of the vibrational and chemical relaxation rates of diatomic gases, in flows behind shock waves and along nozzles,is made here. ¶ The validity of the conventional relaxation rate models, which are generally used to analyse experiments, is tested by developing a detailed microscopic description of the diatomic relaxation processes. ...; yes

Coordinating Links among Research, Standardisation and Policy in Support of Water Framework Directive Chemical Monitoring Requirements

QUEVAUVILLER PHILLIPPE; BORCHERS Ulrich; GAWLIK BERND
Fonte: ROYAL SOC CHEMISTRY Publicador: ROYAL SOC CHEMISTRY
Tipo: Articles in Journals Formato: Printed
ENG
Relevância na Pesquisa
26.11%
The need for coordination among scientific and policy activities is an old debate in which respective communities have often confronted their views rather than reflecting on concrete solutions. In the last few years, however, constructive exchanges have taken place in the context of expert groups linked to the implementation of the Water Framework Directive (WFD) and related EU funded research projects, which have resulted in a better understanding of communication and knowledge transfer gaps. These exchanges concern not only the way research is being interfaced with water policies, but also how improved coordination could be organised regarding technical specifications linked to standardisation. This paper discusses on-going efforts to improve coordination among research, standardisation and policy in support of WFD implementation, with emphasis on chemical monitoring requirements.; JRC.H.5-Rural, water and ecosystem resources

Chemical vapor deposition of alumina-based thin films

Fahlman, Bradley Dean
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
35.97%
Deposition of highly conformal alumina thin films onto various substrates was carried out by hydrolysis of AlH3(NMe2Et) in a hot-wall atmospheric pressure chemical vapor deposition (APCVD) system. Optimum growth conditions were at 165°C with a AlH3(NMe 2Et):H2O ratio of less than 1:25. Films were characterized by SEM, microprobe and electrical conductivity measurements. Deposition of hermetic coatings onto ZnS EL-phosphor particles was accomplished in a simple fluidized-bed APCVD reactor. Chromium-doped alumina (ruby) thin films were deposited onto sapphire substrates using a mixture of Al(acac)3 and Cr(acac)3 precursors with added oxygen sources. APCVD with water vapor resulted in smooth films that were visibly colored following thermal annealing. Substituting water vapor with [Me2Al(mu-OiPr)]2 in vacuo increased growth rates and produced films with improved color homogeneity. The observed intensity of the ruby fluorescence was found to increase with post-deposition annealing. The sublimation enthalpies for a variety of metal beta-diketonate compounds were determined using thermogravimetric analysis. Replacing methyl groups with CF3 units increased the volatility of the particular complex in the order acac < tfac < hfac. The refinement of the Al:Cr site occupancy in mixed AlxCr y(acac)3 crystals was accomplished by various methods. Refinement of occupancy with common displacement parameters and refinement of both occupancy and displacement parameters were found to agree with WDS data within experimental error for all crystals studied. A facile chalcogenide exchange is observed for the reaction of [( tBu)Ga(mu3-Te)]4 with elemental sulfur or selenium...

PUG-SOAP and PUG-REST: web services for programmatic access to chemical information in PubChem

Kim, Sunghwan; Thiessen, Paul A.; Bolton, Evan E.; Bryant, Stephen H.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.03%
PubChem (http://pubchem.ncbi.nlm.nih.gov) is a public repository for information on chemical substances and their biological activities, developed and maintained by the US National Institutes of Health (NIH). PubChem contains more than 180 million depositor-provided chemical substance descriptions, 60 million unique chemical structures and 225 million bioactivity assay results, covering more than 9000 unique protein target sequences. As an information resource for the chemical biology research community, it routinely receives more than 1 million requests per day from an estimated more than 1 million unique users per month. Programmatic access to this vast amount of data is provided by several different systems, including the US National Center for Biotechnology Information (NCBI)'s Entrez Utilities (E-Utilities or E-Utils) and the PubChem Power User Gateway (PUG)—a common gateway interface (CGI) that exchanges data through eXtended Markup Language (XML). Further simplifying programmatic access, PubChem provides two additional general purpose web services: PUG-SOAP, which uses the simple object access protocol (SOAP) and PUG-REST, which is a Representational State Transfer (REST)-style interface. These interfaces can be harnessed in combination to access the data contained in PubChem...

Saccharomyces cerevisiae rad51 mutants are defective in DNA damage-associated sister chromatid exchanges but exhibit increased rates of homology-directed translocations.

Fasullo, M; Giallanza, P; Dong, Z; Cera, C; Bennett, T
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/2001 EN
Relevância na Pesquisa
26.11%
Saccharomyces cerevisiae Rad51 is structurally similar to Escherichia coli RecA. We investigated the role of S. cerevisiae RAD51 in DNA damage-associated unequal sister chromatid exchanges (SCEs), translocations, and inversions. The frequency of these rearrangements was measured by monitoring mitotic recombination between two his3 fragments, his3-Delta5' and his3-Delta3'::HOcs, when positioned on different chromosomes or in tandem and oriented in direct or inverted orientation. Recombination was measured after cells were exposed to chemical agents and radiation and after HO endonuclease digestion at his3-Delta3'::HOcs. Wild-type and rad51 mutant strains showed no difference in the rate of spontaneous SCEs; however, the rate of spontaneous inversions was decreased threefold in the rad51 mutant. The rad51 null mutant was defective in DNA damage-associated SCE when cells were exposed to either radiation or chemical DNA-damaging agents or when HO endonuclease-induced double-strand breaks (DSBs) were directly targeted at his3-Delta3'::HOcs. The defect in DNA damage-associated SCEs in rad51 mutants correlated with an eightfold higher spontaneous level of directed translocations in diploid strains and with a higher level of radiation-associated translocations. We suggest that S. cerevisiae RAD51 facilitates genomic stability by reducing nonreciprocal translocations generated by RAD51-independent break-induced replication (BIR) mechanisms.

Direct measurements of the energy flux due to chemical reactions at the surface of a silicon sample interacting with a SF6 plasma

Dussart, Remi; Thomann, Anne-Lise; Pichon, Laurianne E.; Bedra, Larbi; Semmar, Nadjib; Lefaucheux, Philippe; Mathias, Jacky; Tessier, Yves
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 04/11/2008
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26.01%
Energy exchanges due to chemical reactions between a silicon surface and a SF6 plasma were directly measured using a heat flux microsensor (HFM). The energy flux evolution was compared with those obtained when only few reactions occur at the surface to show the part of chemical reactions. At 800 W, the measured energy flux due to chemical reactions is estimated at about 7 W.cm\^{-2} against 0.4 W.cm\^{-2} for ion bombardment and other contributions. Time evolution of the HFM signal is also studied. The molar enthalpy of the reaction giving SiF4 molecules was evaluated and is consistent with values given in literature.; Comment: 3 pages

Microreversible recycled chemical systems. Comment on "A Re-Examination of Reversibility in Reaction Models for the Spontaneous Emergence of Homochirality"

Plasson, Raphael
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.01%
The question of the onset of the homochirality on prebiotic Earth still remains a fundamental question in the quest for the origin of life. Recent works in this field introduce the concept of recycling, rather than the traditional open-flow system described by Frank. This approach has been criticized by Blackmond et al. They claimed that such systems are thermodynamically impossible, except in the cases where non-microreversible reactions are introduced, like in photochemical reactions, or under the influence of physical actions (e.g. by crystal crushing). This point of view reveals misunderstandings about this model of a recycled system, overlooks the possibility of energy exchanges that could take place in prebiotic systems, and leads the authors to unawarely remove the activation reaction and energy source from their "non-equilibrium" models. It is especially important to understand what are the concepts behind the notion of recycled systems, and of activation reactions. These points are fundamental to comprehending how chemical systems -- and especially prebiotic chemical systems -- can be maintained in non-equilibrium steady states, and how free energy can be used and exchanged between systems. The proposed approach aims at the decomposition of the problem...

Collisional and photoinitiated reaction dynamics in the ground electronic state of Ca–HCl

Sanz, Cristina; Avoird, Ad van der; Roncero, Octavio
Fonte: American Institute of Physics Publicador: American Institute of Physics
Tipo: Artículo Formato: 203135 bytes; application/pdf
ENG
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11 pages, 14 figures, 1 table.-- PACS nrs.: 82.30.Cf; 82.50.-m; 82.20.Kh; 82.30.Fi; 82.20.Rp; 82.20.Fd; 33.20.Ea; 33.15.Ry; 33.15.Dj; 82.30.Hk.; Ca+HCl(ν,j) reactive collisions were studied for different rovibrational states of the HCl reactant using wave-packet calculations in reactant Jacobi coordinates. A recently proposed potential-energy surface was used with a barrier of ≈ 0.4 eV followed by a deep well. The possibility of an insertion mechanism due to this last well has been analyzed and it was found that once the wave packet passes over the barrier most of it goes directly to CaCl+H products, which shows that the reaction dynamics is essentially direct. It was also found that there is no significant change in the reaction efficiency as a function of the initial HCl rovibrational state, because CaHCl at the barrier has an only little elongated HCl bond. Near the threshold for reaction with HCl(ν=0), however, the reaction shows significant steric effects for j>0. In a complementary study, the infrared excitation from the Ca–HCl van der Waals well was simulated. The spectrum thus obtained shows several series of resonances which correspond to quasibound states correlating to excited HCl(ν) vibrations. The Ca–HCl binding energies of these quasibound states increase dramatically with ν...

A detailed quantum mechanical and quasiclassical trajectory study on the dynamics of the H(+) + H2 --> H2 + H(+) exchange reaction

González Lezana, Tomás; Roncero, Octavio; Honvault, Pascal; Launay, Jean-Michel; Bulut, Niyazi; Aoiz, F. Javier; Bañares, Luis
Fonte: American Institute of Physics Publicador: American Institute of Physics
Tipo: Artículo Formato: 1181895 bytes; application/pdf
ENG
Relevância na Pesquisa
26.17%
13 pages, 11 figures.-- PACS nrs.: 82.30.Hk; 82.30.Nr.; The H(+) + H2 exchange reaction has been studied theoretically by means of a different variety of methods as an exact time independent quantum mechanical, approximate quantum wave packet, statistical quantum, and quasiclassical trajectory approaches. Total and state-to-state reaction probabilities in terms of the collision energy for different values of the total angular momentum obtained with these methods are compared. The dynamics of the reaction is extensively studied at the collision energy of E(coll) = 0.44 eV. Integral and differential cross sections and opacity functions at this collision energy have been calculated. In particular, the fairly good description of the exact quantum results provided by the statistical quantum method suggests that the dynamics of the process is governed by an insertion mechanism with the formation of a long-lived collision complex.; Two of the authors (O.R. and T.G.L.) thank the Spanish Ministry of Education (MEC) for financial support through Grants Nos. FIS2004-02461 and CTQ2004-02415. One of the authors (T.G.L.) would like to acknowledge support from the program Ramón y Cajal of Spanish MEC and EU Grant No. MERG-CT-2004-513600. Two other authors (F.J.A. and L.B.) acknowledge financial support through MEC Grant No. CTQ2005-08493-C02-01 and Universidad Complutense- Comunidad de Madrid Grant No. 910729. Another author (N.B.) thanks a postdoctoral fellowship by Spanish MEC under the program "Estancias de jóvenes doctores y tecnólogos extranjeros en España". One of the authors (F.J.A.) thanks the financial support by the programme of "Sabáticos Complutenses" of the Universidad Complutense de Madrid. The EQM calculations were performed on a NEC-SX5 vector supercomputer...

Critical success factors for the development of trade exchanges

Cook, Jack
Fonte: APICS E&R Foundation Academic Program Proceedings Publicador: APICS E&R Foundation Academic Program Proceedings
Tipo: Proceedings
EN_US
Relevância na Pesquisa
26.1%
Inefficiencies exist throughout the supply chain. Everyday business operations are often tedious and time-consuming. Transactions may be significant delayed due to limitations associated with asynchronous communications. Electronic marketplaces provide a means for improving supply chain efficiency. They enhance liquidity by permitting a large number of buyers and sellers to connect with each other. Estimates indicate that B2B trade exchanges with facilitate $600 billion to $3 trillion (U.S. revenues) in trade by 2003 (Tumolo, 2001). Exchanges are found in a variety of industries including aerospace, agriculture, automotive, banking, chemical, education, energy, food, hospitality, paper, and steel...