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Identificação das fontes de Material Particulado Fino ( MP2,5) de Porto Alegre; Identification of sources of Fine Particulate Matter (PM2.5) in Porto Alegre

Machado, Vivian Bauce
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 11/12/2012 PT
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Este trabalho teve como objetivo a identificação e quantificação das fontes do Material Particulado fino (MP2,5) da Região Metropolitana de Porto Alegre (RMPA), em especial, as fontes veiculares. Foram utilizadas amostras coletadas diariamente durante 24 horas, entre junho/2007 a fevereiro/2009 na Universidade Federal de Ciências da Saúde de Porto Alegre, próxima a vias de intenso tráfego. As amostras foram analisadas para determinação da concentração em massa, composição elementar e iônica do MP2,5. A concentração média do particulado fino durante o experimento foi de 13,4 µg m-3 e do Black Carbon foi de 3,8 µg m-3. Os elementos-traço S, K e Fe destacaram-se com concentrações mais elevadas. Através de Modelagem Receptora (Análise de Fatores AF e Fatoração de Matriz Positiva, Positive Matrix Factorization PMF), identificaram-se as possíveis fontes de MP2,5 da região. A utilização do PMF, modelo multivariado mais avançado, embora não tenha mostrado uma clara separação das fontes, possibilitou uma quantificação mais acurada das fontes identificadas. Por essa metodologia foram identificadas como fontes do MP2,5 as emissões veiculares, a ressuspensão do solo e as indústrias. Para ambos os modelos...

Quantificação e caracterização físico-química do material particulado fino (MP2,5): queima de biomassa em fornos de pizzaria na cidade de São Paulo; The chemical quantification and characterization of fine particulate mass (PM2,5): the burning of biomasses in pizza ovens within the city of São Paulo

Lima, Francisco Daniel Mota
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 14/07/2015 PT
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A queima de biomassa em fornos de pizzaria se constitui como importante fonte de poluição do ar. Entre outros tipos de poluentes emitidos, o material particulado finoMP2,5 se destaca como o mais agressivo à saúde humana, além de poder interferir no balanço radiativo global. Objetiva-se, desta forma, através de estudo de caso em três pizzarias na cidade de São Paulo, quantificar e caracterizar o MP2,5 emitido pela queima da biomassa na área interna (indoor) e externa (junto á chaminé). Dentre as três pizzarias, duas fazem uso da lenha de eucalipto e a outra faz uso do briquete, formado a partir da compactação de pedaços de biomassa, serragem, bagaço e outros resíduos madeireiros. As amostras foram coletadas utilizando-se o amostrador Minivol. A análise do material foi realizada por meio de técnicas complementares: gravimetria (para a concentração em massa), refletância (para a concentração de black carbon), fluorescência de raios-X (para a concentração elementar) e utilização do microscópio eletrônico de varredura (MEV) (para identificar a morfologia do material particulado). Além disso, foram feitas inferências na saúde do trabalhador quanto á exposição ao MP2,5, e por fim foi estimada as emissões de MP2...

An Ab Initio MP2 Study of HCN-HX Hydrogen Bonded Complexes

Araújo,Regiane C.M.U.; Ramos,Mozart N.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/1998 EN
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An ab initio MP2/6-311++G** study has been performed to obtain geometries, binding energies and vibrational properties of HCN-HX H-bonded complexes with X = F, Cl, NC, CN and CCH. These MP2/6-311++G** results have revealed that: (i) the calculated H-bond lengths are in very good agreement with the experimental ones; (ii) the H-bond strength is associated with the intermolecular charge transfer and follows the order: HCN-HNC ~ HCN-HF > HCN-HCl ~ HCN-HCN > HCN-HCCH; (iii) BSSE correction introduces an average reduction of 2.4 kJ/mol on the MP2/6-311++G** binding energies, i.e. 11% of the uncorrected binding energy; (iv) the calculated zero-point energies reduce the stability of these complexes and show a good agreement with the available experimental values; (v) the H-X stretching frequency is shifted downward upon H-bond formation. This displacement is associated with the H-bond length; (vi) The more pronounced effect on the infrared intensities occurs with the H-X stretching intensity. It is much enhanced after complexation due to the charge-flux term; (vii) the calculated intermolecular stretching frequencies are in very good agreement with the experimental ones; and, finally, (viii) the results obtained for the HCN-HX complexes follow the same profile as those found for the acetylene-HX series but...

A Reinvestigation of the Dimer of para-Benzoquinone with Pyrimidine with MP2, CCSD(T) and DFT using Functionals including those Designed to Describe Dispersion

Marianski, Mateusz; Oliva, Antoni; Dannenberg, J. J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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We reevaluate the interaction of pyridine and p-benzoquinone using functionals designed to treat dispersion. We compare the relative energies of four different structures: stacked, T-shaped (identified for the first time) and two planar H-bonded geometries using these functionals (B97-D, ωB97x-D, M05, M05-2X, M06, M06L, M06-2X), other functionals (PBE1PBE, B3LYP, X3LYP), MP2 and CCSD(T) using basis sets as large as cc-pVTZ. The functionals designed to treat dispersion behave erratically as the predictions of the most stable structure vary considerably. MP2 predicts the experimentally observed structure (H-bonded) to be the least stable, while single point CCSD(T) at the MP2 optimized geometry correctly predicts the observed structure to be most stable. We have confirmed the assignment of the experimental structure using new calculations of the vibrational frequency shifts previously used to identify the structure. The MP2/cc-pVTZ vibrational calculations are in excellent agreement with the observations. All methods used to calculate the energies provide vibrational shifts that agree with the observed structure even though most do not predict this structure to be most stable. The implications for evaluating possible π-stacking in biologically important systems are discussed.

Serine Protease MP2 Activates Prophenoloxidase in the Melanization Immune Response of Drosophila melanogaster

An, Chunju; Zhang, Mingming; Chu, Yuan; Zhao, Zhangwu
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 15/11/2013 EN
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In arthropods, melanization plays a major role in the innate immune response to encapsulate and kill the invasive organisms. It is mediated by a serine protease cascade and is regulated by serpins. The identification of the molecular components of melanization and the regulation of those components are still unclear in Drosophila melanogaster, although some genetic research on the activation of melanization has been reported. Here we report that Drosophila serine protease MP2 directly cleaves both recombinant and native prophenoloxidase-1. Overexpression or repression of MP2 in flies resulted in increased and decreased rates of cleavage, respectively, of prophenoloxidase-1. Moreover, serine protease inhibitor Spn27A formed SDS-stable complexes with MP2, both in vitro and in vivo. The amidase activity of MP2 was inhibited efficiently by Spn27A. Spn27A also prevented MP2 from cleaving prophenoloxidase-1. Taken together, these results indicate that under our experimental conditions MP2 functions as a prophenoloxidase-activating protease, and that this function is inhibited by Spn27A. MP2 and Spn27A thus constitute a regulatory unit in the prophenoloxidase activation cascade in Drosophila. The combination of genetic, molecular genetic and biochemical approaches should allow further advances in our understanding of the prophenoloxidase-activating cascade in insects and indirectly shed further light on protease-cascades in humans and other vertebrates.

Hybrid RHF/MP2 Geometry Optimizations with the Effective Fragment Molecular Orbital Method

Christensen, Anders S.; Steinmann, Casper; Fedorov, Dmitri G.; Jensen, Jan H.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 18/02/2014 EN
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The frozen domain effective fragment molecular orbital method is extended to allow for the treatment of a single fragment at the MP2 level of theory. The approach is applied to the conversion of chorismate to prephenate by Chorismate Mutase, where the substrate is treated at the MP2 level of theory while the rest of the system is treated at the RHF level. MP2 geometry optimization is found to lower the barrier by up to 3.5 kcal/mol compared to RHF optimzations and ONIOM energy refinement and leads to a smoother convergence with respect to the basis set for the reaction profile. For double zeta basis sets the increase in CPU time relative to RHF is roughly a factor of two.

MP2[V] – A simple approximation to second-order Møller–Plesset perturbation theory

Deng, Jia; Gilbert, Andrew T. B.; Gill, Peter M. W.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica Formato: 6 pages
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We propose a simplified variant of the dual-basis MP2[K] scheme [J. Chem. Phys. 2011,134, 081103] that bootstraps a small-basis MP2 result to a large-basis one. This simplified method, which we call MP2[V], assumes the occupied orbitals are adequately described by the smaller basis, and, therefore, only the relaxation of the virtual orbitals is considered when shifting to the larger basis. Numerical tests on several organic reactions and noncovalent interactions show that MP2[V] yields absolute and relative energies that are in excellent agreement with the conventional large-basis MP2 calculations but in a small fraction of the time.; P.M.W.G. thanks the Australian Research Council for funding (Grant Nos. DP1094170 and DP120104740) and APAC for a generous allocation of supercomputer resources. J.D. thanks the ANU/RSC for a Ph.D. scholarship.

Theoretical studies for ozonide formation during the ozonolysis of bicyclic endoperoxides

Cain, N.; Hixson, J.; Taylor, D.
Fonte: C S I R O Publishing Publicador: C S I R O Publishing
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
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Theoretical investigations on the treatment of bicyclic endoperoxides (1,2-dioxines) with ozone at the HF/6-31G*, MP2/6-31G*or 6-311G*, and DFT(B3LYP)/6-31G*levels of theory indicate that the estimated activation energies for formation of the possible endo-endo, endo-exo, exo-endo, or exo-exo transition states along with the formation of the primary ozonides and product ozonides are very sensitive to effects of electron correlation and basis set. This study suggests that MP2/6-311G*is the best level of theory for evaluating such systems. At the MP2/6-311G*level of theory it was found that the transition state for primary ozonide formation was lowest in energy when ozone approaches in an endo facial fashion with a further 3kJmol-1 stabilisation seen when the central oxygen within the primary ozonide protrudes outwards (exo) as opposed to inwards (endo). The product ozonides are predicted to be more stable than the combined starting materials by some 380-580kJmol-1 depending on the level of theory, clearly highlighting the substantive exothermic nature of this type of ozonolysis reaction.; Nicole M. Cain, Josh L. Hixson, and Dennis K. Taylor

Atomorbitalbasierte Reformulierung von MP2-Energiegradienten und quantenchemische Untersuchungen zum gauche-Effekt in Prolin- und Polyprolinderivaten; Atomic Orbital-Based Reformulation of MP2 Energy Gradients and Quantum-Chemical Investigations of the gauche-Effect in Proline and Polyproline Compounds

Schweizer, Sabine
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
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Es wird eine auf dem Laplace-Ansatz von Almlöf und Häser basierende Neuformulierung für die Energiegradienten der Møller-Plesset-Störungstheorie zweiter Ordnung (MP2) vorgestellt. Während der Rechenaufwand der konventionellen MP2-Methode mit der fünften Potenz der Molekülgröße ansteigt und deswegen die Anwendbarkeit auf kleine Systemgrößen (etwa 100 Atome) beschränkt ist, eignet sich der vorliegende Ausdruck für eine linear skalierende Umsetzung. Die Reformulierung ist vollständig atomorbitalbasiert, wobei die Berechnung der auftretenden gestörten Einteilchen-Dichtematrix mit Hilfe der Z-Vektor-Technik von Handy und Schaefer umgangen werden kann. Im Rahmen der Arbeit wurde die Z-Vektor-Methode erstmals dichtematrixbasiert formuliert und angewendet. Die Validierung des Ansatzes anhand einer Auswahl kleiner Moleküle deutet auf ein frühes Einsetzen des linearen Skalenverhaltens signifikanter Integralprodukte hin und zeigt, dass bereits vier bis sechs Quadratur-Punkte eine Genauigkeit im µHartree/Bohr-Bereich gewährleisten. Der neue atomorbitalbasierte MP2-Gradientenausdruck liefert eine Grundlage für die Strukturberechnung großer Moleküle unter Berücksichtigung von Elektronenkorrelation, insbesondere von den in der Hartree-Fock-Näherung und in heute gängigen Dichtefunktionalen vernachlässigten dispersiven Wechselwirkungen. Neben den methodischen Entwicklungen werden Untersuchungen zur Konformation und relativen Stabilität von Prolin- und Polyprolinderivaten vorgestellt...

Niedrig-skalierende Møller-Plesset Störungstheorie zweiter Ordnung unter Verwendung von Auxiliarbasen und quantenchemische Berechnung von NMR-Verschiebungen supramolekularer Systeme; Low-Order Scaling Second-Order Møller-Plesset Perturbation Theory Using Auxiliary Basis Sets and Quantum-Chemical Calculation of NMR Chemical Shifts for Supramolecular Systems

Zienau, Jan
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
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Neben der ab-initio Berechnung von NMR-Verschiebungen für supramolekulare Systeme befasst sich die vorliegende Dissertation mit der Effiziensteigerung von kürzlich entwickelten linear-skalierenden Methoden im Rahmen der ab-initio Quantenchemie. In diesem Zusammenhang konnte der bei größeren Basissätzen auftretende große Vorfaktor des Rechenzeitaufwandes der in unserer Gruppe entwickelten linear-skalierenden AO-MP2- (Atomorbital-basierte Møller-Plesset Störungstheorie zweiter Ordnung) Methode, welche rigorose Integralschranken verwendet, verkleinert werden. Diese Vorfaktor-Reduktion wird durch Approximation auftretender Integrale unter Verwendung einer Auxiliarbasis im Rahmen des Resolution of the Identity- (RI-) Verfahrens erreicht. Die RI-Approximation wurde weiterhin auf eine ebenfalls linear-skalierende Abwandlung der AO-MP2-Methode angewendet, welche mit einer Cholesky-Zerlegung der bei AO-MP2 auftretenden Pseudodichtematrizen arbeitet (Cholesky-decomposed density-based MP2, CDD-MP2) und durch Beschränkung der Laufindizes auf den besetzten/virtuellen Subraum vor allem für große Basissätze einen inhärent kleineren Vorfaktor als AO-MP2 aufweist. Durch Einführung der RI-Näherung konnte hier eine weitere wesentliche Effizienzsteigerung erzielt werden. Sowohl bei AO-MP2 als auch bei CDD-MP2 wurde die RI-Approximation zunächst nur für die Coulomb-artige Integralkontraktion implementiert. Obwohl beide entwickelten RI-basierten Methoden (RI-AO-MP2 und RI-CDD-MP2) für Basissätze wie SVP und cc-pVTZ gegenüber AO-MP2 beziehungsweise CDD-MP2 einen verkleinerten Vorfaktor aufweisen...

Quantenchemische Berechnung von NMR-Verschiebungen auf MP2-Niveau; Quantum chemical calculations of NMR-shieldings on MP2-Level

Löffler, Martin
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
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Quantenchemisch berechnete NMR-Verschiebungen sind ein wertvolles Hilfsmittel zur Interpretation von NMR-Spektren. Dies ist für die Chemie bei der Strukturaufklärung und zur Untersuchung von Reaktionsmechanismen von großer Bedeutung. Bei einer Vielzahl von Systemen hat sich gezeigt, dass die Berücksichtigung der Elektronenkorrelation notwendig für eine korrekte Beschreibung der NMR-Verschiebung ist. Dies gilt insbesondere bei allen Atomen außer Wasserstoff. In dieser Arbeit wurde eine Implementierung von Routinen zur Berechnung der NMR-Verschiebungen auf dem Niveau der Moeller-Plesset Störungstheorie zweiter Ordnung (MP2) durchgeführt. Diese Methode wird inzwischen aufgrund ihres attraktiven Verhältnisses von Aufwand und Genauigkeit für die Berechnung unterschiedlicher molekularer Eigenschaften verwendet. Die Implementierung erfolgte in einem kommerziellen Quantenchemiepaket. Darüber hinaus wurde die Genauigkeit der Resolution-of-the-Identity(RI)-Approximation für die Berechnung der MP2-NMR-Verschiebungen untersucht. Diese kann eine erhebliche Beschleunigung der Berechnung ermöglichen, das Skalenverhalten des Speicherbedarfs reduzieren und eignet sich für eine praktische Implementierung. Außerdem wurde eine neue Methode zur Abschätzung der Adsorptionsenergie eines Moleküls auf einer Festkörperoberfläche untersucht und auf eine experimentelle Fragestellung angewandt: Die Adsorption des Phthalocyanins CuPcF16 auf einer Metalloberfläche wird wegen der Anwendung dieses Systems als organischen Halbleiter untersucht. Die bislang nur sehr schwer zu berechnende Adsorptionsenergie konnte in dieser Arbeit erstmalig abgeschätzt werden. Die neue Methode beruht auf der quantenchemischen Berechnung der Verzerrungsenergie als untere Schranke der Adsorptionsenergie und kann immer dann verwendet werden...

Contaminación área intradomiciliaria por material particulado fino (MP2,5) e incidencia de infección respiratoria aguda en los primeros 6 meses de vida

Barria Pailaquilen, Rene Mauricio
Fonte: Universidad de Chile Publicador: Universidad de Chile
Tipo: Tesis
ES
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Doctorado en Salud Pública; No disponible a texto completo; Objetivo Evaluar la asociación entre contaminación intradomiciliaria por MP2,5 e IRA en los primeros seis meses de vida. . Método Cohorte de 207 neonatos de dos ciudades del sur de Chile. Dentro del primer mes posparto se midió la concentración intradomiciliaria de MP2,5 y evaluó factores ambientales (temperatura, humedad, calefacción, ventilación, tabaquismo y aseo). Se realizó seguimiento por seis meses para constatar eventos IRA en centros de atención primaria y por contacto telefónico. La asociación entre la exposición y desenlace fue evaluada con regresión logística. Resultados La [MP2,5] mediana fue 107,5 μg/m3 mientras la incidencia de IRA global, alta y baja (IRAB) fue 59,9, 40,1 y 39,1%, respectivamente. No se demostró asociación entre [MP2,5] e incidencia de IRA. IRA alta se asoció sólo a presencia ocasional de mascota en el hogar (OR=2,43; IC95% 1,02-5,08), en tanto IRA baja se asoció con mayor riesgo al tercer nivel de exposición de MP2,5 (OR=2,50; IC95% 1,07-5,85) y un significativo efecto protector con la presencia del padre en el hogar (OR=0,48; IC95% 0,25-0,93). Conclusiones Se detectó niveles elevados de MP2,5. La falta de asociación observada entre la exposición y desenlace pudo estar determinada por condiciones favorables de los lactantes estudiados y por evaluación de efecto a corto plazo. No obstante...

Efectos del material particulado (MP10 y MP2,5) sobre las hospitalizaciones por enfermedades respiratorias en niños, en Santiago de Chile, estudio caso control alterno (case crossover)

Matus Correa, Patricia Isabel
Fonte: Universidad de Chile Publicador: Universidad de Chile
Tipo: Tesis
ES
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Doctorado en Salud Pública; No disponible a texto completo; Contexto La contaminación atmosférica afecta a alrededor de 6 millones de habitantes de la Región Metropolitana de Chile. Su impacto a nivel de la salud respiratoria de los niños ha sido escasamente evaluado. Objetivo Determinar si la exposición a material particulado respirable se asocia a un mayor número de hospitalizaciones por enfermedades respiratorias en niños menores de 15 años, independiente de la situación viral imperante, durante los años 2001 a 2005. Diseño Caso control alternante, con estratificación temporal. Análisis de Componentes Principales. Material Todas las hospitalizaciones del sistema público y privado de la Región Metropolitana con diagnostico de egreso por causa respiratoria (CIE-10 J00 a J99) durante el período de estudio, que cumplieron con los criterios de ser de menores de 15 años y residentes en comunas de la Región Metropolitana. Participantes Un total de 72 479 hospitalizaciones de menores de 15 años, residentes de la Región Metropolitana. Mediciones Se evaluaron todas las hospitalizaciones respiratorias (CIE10 J00-J99), las hospitalizaciones por neumonía (CIE-10 J12-J18); por asma (CIE-10 J21.0 – J21.9) y por bronquiolitis (CIE-10J45 – J46) del registro de egresos hospitalarios del Ministerio de Salud. Se evaluó la exposición por MP10...

G4(MP2)-6X: A cost-effective improvement to G4(MP2)

Chan, Bun; Deng, Jia; Radom, Leo
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
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G4(MP2)-6X is developed as a composite procedure with a cost comparable to that of G4(MP2) but performance approaching that of G4. The new procedure is a variant of G4(MP2) that employs BMK/6-31+G(2df,p) geometries and has six additional scaling factors f

MP2[V] - A simple approximation to second-order møller-plesset perturbation theory

Deng, Jia; Gilbert, Andrew; Gill, Peter
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We propose a simplified variant of the dual-basis MP2[K] scheme [ J. Chem. Phys. 2011, 134, 081103 ] that bootstraps a small-basis MP2 result to a large-basis one. This simplified method, which we call MP2[V], assumes the occupied orbitals are adequately

G4-SP, G4(MP2)-SP, G4-sc, and G4(MP2)-sc: modifications to G4 and G4(MP2) for the treatment of medium-sized radicals

Chan, B; Coote, Michelle; Radom, Leo
Fonte: Singapore University Press and World Scientific Publishing Co Pty Ltd Publicador: Singapore University Press and World Scientific Publishing Co Pty Ltd
Tipo: Artigo de Revista Científica
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The G4-SP and G4(MP2)-SP procedures are introduced, as alternatives to G4 and G4(MP2), to overcome shortcomings associated with the treatment of spin polarization (SP) in large open-shell systems. The new methods employ a converging SP term, to replace th

Hybrid RHF/MP2 geometry optimizations with the Effective Fragment Molecular Orbital Method

Christensen, Anders S.; Steinmann, Casper; Fedorov, Dmitri G.; Jensen, Jan H.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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The frozen domain effective fragment molecular orbital method is extended to allow for the treatment of a single fragment at the MP2 level of theory. The approach is applied to the conversion of chorismate to prephenate by chorismate mutase, where the substrate is treated at the MP2 level of theory while the rest of the system is treated at the RHF level. MP2 geometry optimization is found to lower the barrier by up to 3.5 kcal/mol compared to RHF optimzations and ONIOM energy refinement and leads to a smoother convergence with respect to the basis set for the reaction profile. For double zeta basis sets the increase in CPU time relative to RHF is roughly a factor of two.; Comment: 11 pages, 3 figures

Simple non-empirical procedure for spin-component-scaled MP2 methods applied to the calculation of dissociation energy curve of noncovalently-interacting systems

Grabowski, I.; Fabiano, E.; Della Sala, F.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/08/2013
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We present a simple and non-empirical method to determine optimal scaling coefficients, within the (spin-component)-scaled MP2 approach, for calculating intermolecular potential energies of noncovalently-interacting systems. The method is based on an observed proportionality between (spin-component) MP2 and CCSD(T) energies for a wide range of intermolecular distances and allows to compute with high accuracy a large portion of the dissociation curve at the cost of a single CCSD(T) calculation. The accuracy of the present procedure is assessed for a series of noncovalently-interacting test systems: the obtained results reproduce CCSD(T) quality in all cases and definitely outperform conventional MP2, CCSD and SCS-MP2 results. The difficult case of the Beryllium dimer is also considered.; Comment: 9 pages, 7 figures

Multipath level evaluation in the GPS relative positioning and its atenuation through multiresolution analysis; AVALIAÇÃO DO NÍVEL DE MULTICAMINHO NO POSICIONAMENTO RELATIVO GPS E SUA ATENUAÇÃO ATRAVÉS DA ANÁLISE DE MULTIRESOLUÇÃO

DE SOUZA, ENIUCE MENEZES; POLEZEL, WESLEY GILDO CANDUCCI; MONICO, JOÃO FRANCISCO GALERA
Fonte: Universidade Federal do Paraná-UFPR Publicador: Universidade Federal do Paraná-UFPR
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Artigo Avaliado pelos Pares Formato: application/pdf
Publicado em 25/01/2006 POR
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The multipath effect affects the differential and relative positioning, even that one involving short baselines. So it is necessary to detect this effect, check the caused error level, and mainly, its removal. This paper aims at analysing and comparing some useful components in the detection of this effect. These components are the Signal to Noise Ratio (SNR), the values of MP1 and MP2 obtained from the TEQC software that indicates the multipath level in the carriers L1 and L2, the multipath repeatability in consecutive days and the elevation angle and the azimuth of the satellites. For this purpose, an experiment is carried out, comparing such components in the presence and the absence of reflector objects that cause the multipath. Not only there is clear multipath repeatability in the residuals, but it also appears in the measures SNR, MP1 and MP2, reaching up 99% of correlation. For reduction, at least, of the high frequency multipath effect, the Multi-Resolution Analysis using wavelets is applied in the double differences (DD) measures. Some statistical tests were accomplished, which indicate results improvement, and mainly, larger reliability in the solution of the ambiguities, reaching up 49% of improvement concerning the Ratio test without applying the proposed method.; O efeito do multicaminho afeta os posicionamentos diferencial e relativo...

The Role of the Linearity on the Hydrogen Bond in the Formamide Dimer: a BLYP, B3LYP, and MP2 Study

Ramírez,José-Zeferino; Vargas,Rubicelia; Garza,Jorge
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2008 EN
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Quantum chemistry methods have been proven to be a very useful tool to study chemical systems stabilized by hydrogen bonds. The two theoretical methodologies most frequently used are the Density Functional Theory (DFT), in its Kohn-Sham version, and the second order Maller-Plesset Perturbation Theory (MP2). Lately, many studies have been focused on weak hydrogen bonds (binding energies < 4 kcal/mol) because such contacts might have a relevant role in the molecular ensemble. However, there are some results about this type of interactions where the Kohn-Sham model and MP2 give different answers. By testing two exchange-correlation functionals, BLYP and B3LYP, we are proposing in this paper that such a discrepancy will happen mainly when the hydrogen bond is far from the linearity; we present this hypothesis on the formamide dimer as an example. We found that, even when this dimer exhibits two hydrogen bonds (N-H... O) with moderate strength, the MP2 and the two exchange-correlation functionals, considered in this work, predict different potential energy surfaces when the geometrical parameters of the hydrogen bond are distorted and a limited basis set is used.