Quantum Monte Carlo study of the CO interaction with a dimer model surface for Cr(110)

The chemisorption of CO on a Cr( 110) surface is investigated using the quantum Monte Carlo method in the diffusion Monte Carlo (DMC) variant and a model Cr2CO cluster. The present results are consistent with the earlier ab initio HF study with this model that showed the tilted/ near-parallel orientation as energetically favoured over the perpendicular arrangement. The DMC energy difference between the two orientations is larger (1.9 eV) than that computed in the previous study. The distribution and reorganization of electrons during CO adsorption on the model surface are analysed using the topological electron localization function method that yields electron populations, charge transfer and clear insight on the chemical bonding that occurs with CO adsorption and dissociation on the model surface.

碱金属在[110]单轴应力下的理论强度

<正> 我们知道,晶须的强度远远大于大晶体的强度,很可能接近于理想晶体的理论强度.而晶须的轴线则通常平行于晶体的三个主要方向[100],[110]或[111]。因此当计算理想晶体在单轴应力下的理论强度时,也必须考虑不同的应力方向.七十年代,Milstein等人利用Morse势和Born稳定性判据计算了立方晶体分别在[100],[110]和[111]单轴应力下的理论强度.由于有心力近似受到Cauchy关系的限制,我们在文献

Contribuições sociais estabelecidas pela Lei Complementar nº 110/2001 : razão da instituição e continuidade de exigência

Já se passaram quase doze anos da instituição das contribuições sociais previstas nos arts. 1º e 2º da Lei complementar n. 110/2001. Tais contribuições visavam repor nas contas vinculadas do FGTS os complementos de atualização monetária devida aos trabalhadores em razão de expurgos inflacionários efetuados após a edição dos planos econômicos de janeiro de 1989 (Plano Verão) e de abril de 1990 (Plano Collor I). O presente estudo pretende avaliar se ainda persistem os fatores que justificaram a cobrança da contribuição prevista no art. 1º da referida Lei, em face das razões que justificaram a sua criação. Pela existência de indícios de que os valores recolhidos já atenderam ao seu pressuposto e, com o intuito de responder a essa indagação, a presente pesquisa buscou embasamento na legislação que dá origem ao instituto do FGTS, bem como sua evolução. Nessa ocasião, procurou-se apresentar os antecedentes históricos do Fundo, sua natureza jurídica, prescrição e outras considerações ao regime do FGTS. Teve, também, como fonte de pesquisa, literatura que discute, objetivamente, os expurgos inflacionários nas contas vinculadas do FGTS. Não foi desprezada dos objetos de estudo a jurisprudência dos tribunais superiores, onde foi possível perceber a dimensão que alcançaram as ações judiciais promovidas pelos trabalhadores. Outra fonte de pesquisa de significado relevante na elaboração deste trabalho diz respeito às Demonstrações Financeiras do FGTS somadas aos Relatórios de Gestão, ambos referentes aos exercícios de 2000 a 2011. Por meio desse instrumental, foi possível fazer uma análise do patrimônio do FGTS e identificar o reflexo das contribuições sociais em sua evolução, assim como verificar que o referido Fundo, no decorrer de 2012, já terá amortizado integralmente as despesas decorrentes do pagamento dos complementos de atualização monetária creditados nas contas vinculadas do FGTS. Na metodologia adotada, foram considerados, também, artigos publicados em revistas e em meio eletrônico, leis específicas sobre a matéria, Manual do FGTS e dispositivos constitucionais. Tudo isso, aliado ao método indutivo, favoreceu a aplicação da pesquisa na elucidação da questão em foco.

Diário da Constituinte [gravação de vídeo] : [programa n. 110]

As grandes cidades brasileiras estão inchadas e a superpopulação causa grandes problemas. Ibsen Pinheiro (PMDB-RS) diz que as regiões ricas são os "primos pobres" do nosso sistema tributário e que a nova Constituição deverá disponibilizar maiores recursos aos grandes centros urbanos para resolver e melhorar a vida de millhões de brasileiros. A Comissão de Ordem Econômica sugere dispositivos para acelerar a reforma urbana, sendo o primeiro deles o que ataca a especulação imobiliária sobre terras urbanas, com a criação de um imposto progressivo nas áreas não construídas e não usadas. Joaquim Bevilacqua (PTB- SP) defende a necessidade de iniciar uma economia de produtividade, em que o capital não seja especulativo, mas que contribua para o desenvolvimento social. Outro dispositivo é o que cria o usucapião urbano, que permite ao cidadão requerer o título de propriedade de uma área de até 250 m2 que ocupar por cinco anos. Gerson Marcondes (PMDB-SP) diz que a proposta atende grande parte das grandes cidades, onde existem não só as favelas, mas também os lotes populares, os loteamentos clandestinos e irregulares. Para evitar problemas urbanos é preciso acabar com o inchaço das cidades grandes e, por isso, os constituintes sugerem o estímulo à povoação de áreas vazias. Renato Bernardi (PMDB-PR) apresenta emenda que estimula o desenvolvimento de áreas pouco povoadas. Jovens a partir de dezesseis anos poderão votar (voto facultativo). Aécio Neves (PMDB-MG) promove campanha para que os jovens de dezesseis aos dezoito anos possam votar. Tito Costa (PMDB-SP) não crê que o cidadão de dezesseis anos esteja apto a votar e a ser votado. Airton Cordeiro (PDT-PR) opina que os jovens podem votar, sobretudo em uma sociedade que impõe a este jovem a necessidade de entrar no mercado de trabalho. Bernardo Cabral (PMDB-AM) entregará relatório da Comissão de Sistematização a Ulysses Guimarães, Presidente da Assembleia Nacional Constituinte (ANC).

Diário da Constituinte [gravação de vídeo] : [programa n. 671]

Os líderes se reúnem para discutir os direitos e deveres individuais e coletivos. Os pontos que estão sem acordo são: direito de propriedade, as formas de indenização para desapropriação, prisão com mandato, apenas com ordem judiciária. Os capítulos polêmicos dos direitos sociais mais polêmicos serão analisados, mas os constituintes acreditam em um acordo para o bem da sociedade.

Unconventional spin texture of a topologically nontrivial semimetal Sb(110)

9 p.

Kinetic investigations of heterogeneously catalyzed reactions on the Ru(001) and Pt(110)-(1x2) surfaces

The initial probabilities of activated, dissociative chemisorption of methane and ethane on Pt(110)-(1 x 2) have been measured. The surface temperature was varied from 450 to 900 K with the reactant gas temperature constant at 300 K. Under these conditions, we probe the kinetics of dissociation via trapping-mediated (as opposed to 'direct') mechanism. It was found that the probabilities of dissociation of both methane and ethane were strong functions of the surface temperature with an apparent activation energies of 14.4 kcal/mol for methane and 2.8 kcal/mol for ethane, which implys that the methane and ethane molecules have fully accommodated to the surface temperature. Kinetic isotope effects were observed for both reactions, indicating that the C-H bond cleavage was involved in the rate-limiting step. A mechanistic model based on the trapping-mediated mechanism is used to explain the observed kinetic behavior. The activation energies for C-H bond dissociation of the thermally accommodated methane and ethane on the surface extracted from the model are 18.4 and 10.3 kcal/mol, respectively.

The studies of the catalytic decomposition of formic acid on the Ru(001) surface with thermal desorption mass spectrometry following the adsorption of DCOOH and HCOOH on the surface at 130 and 310 K are described. Formic acid (DCOOH) chemisorbs dissociatively on the surface via both the cleavage of its O-H bond to form a formate and a hydrogen adatom, and the cleavage of its C-O bond to form a carbon monoxide, a deuterium adatom and an hydroxyl (OH). The former is the predominant reaction. The rate of desorption of carbon dioxide is a direct measure of the kinetics of decomposition of the surface formate. It is characterized by a kinetic isotope effect, an increasingly narrow FWHM, and an upward shift in peak temperature with Ɵ_T, the coverage of the dissociatively adsorbed formic acid. The FWHM and the peak temperature change from 18 K and 326 K at Ɵ_T = 0.04 to 8 K and 395 K at Ɵ_T = 0.89. The increase in the apparent activation energy of the C-D bond cleavage is largely a result of self-poisoning by the formate, the presence of which on the surface alters the electronic properties of the surface such that the activation energy of the decomposition of formate is increased. The variation of the activation energy for carbon dioxide formation with Ɵ_T accounts for the observed sharp carbon dioxide peak. The coverage of surface formate can be adjusted over a relatively wide range so that the activation energy for C-D bond cleavage in the case of DCOOH can be adjusted to be below, approximately equal to, or well above the activation energy for the recombinative desorption of the deuterium adatoms. Accordingly, the desorption of deuterium was observed to be governed completely by the desorption kinetics of the deuterium adatoms at low Ɵ_T, jointly by the kinetics of deuterium desorption and C-D bond cleavage at intermediate Ɵ_T, and solely by the kinetics of C-D bond cleavage at high Ɵ_T. The overall branching ratio of the formate to carbon dioxide and carbon monoxide is approximately unity, regardless the initial coverage Ɵ_T, even though the activation energy for the production of carbon dioxide varies with Ɵ_T. The desorption of water, which implies C-O bond cleavage of the formate, appears at approximately the same temperature as that of carbon dioxide. These observations suggest that the cleavage of the C-D bond and that of the C-O bond of two surface formates are coupled, possibly via the formation of a short-lived surface complex that is the precursor to to the decomposition.

The measurement of steady-state rate is demonstrated here to be valuable in determining kinetics associated with short-lived, molecularly adsorbed precursor to further reactions on the surface, by determining the kinetic parameters of the molecular precursor of formaldehyde to its dissociation on the Pt(110)-(1 x 2) surface.

Overlayers of nitrogen adatoms on Ru(001) have been characterized both by thermal desorption mass spectrometry and low-energy electron diffraction, as well as chemically via the postadsorption and desorption of ammonia and carbon monoxide.

The nitrogen-adatom overlayer was prepared by decomposing ammonia thermally on the surface at a pressure of 2.8 x 10^(-6) Torr and a temperature of 480 K. The saturated overlayer prepared under these conditions has associated with it a (√247/10 x √247/10)R22.7° LEED pattern, has two peaks in its thermal desorption spectrum, and has a fractional surface coverage of 0.40. Annealing the overlayer to approximately 535 K results in a rather sharp (√3 x √3)R30° LEED pattern with an associated fractional surface coverage of one-third. Annealing the overlayer further to 620 K results in the disappearance of the low-temperature thermal desorption peak and the appearance of a rather fuzzy p(2x2) LEED pattern with an associated fractional surface coverage of approximately one-fourth. In the low coverage limit, the presence of the (√3 x √3)R30° N overlayer alters the surface in such a way that the binding energy of ammonia is increased by 20% relative to the clean surface, whereas that of carbon monoxide is reduced by 15%.

A general methodology for the indirect relative determination of the absolute fractional surface coverages has been developed and was utilized to determine the saturation fractional coverage of hydrogen on Ru(001). Formaldehyde was employed as a bridge to lead us from the known reference point of the saturation fractional coverage of carbon monoxide to unknown reference point of the fractional coverage of hydrogen on Ru(001), which is then used to determine accurately the saturation fractional coverage of hydrogen. We find that ƟSAT/H = 1.02 (±0.05), i.e., the surface stoichiometry is Ru : H = 1 : 1. The relative nature of the method, which cancels systematic errors, together with the utilization of a glass envelope around the mass spectrometer, which reduces spurious contributions in the thermal desorption spectra, results in high accuracy in the determination of absolute fractional coverages.

Investigations into the structure and function of the exocrine pancreas of lampreys. [Translation from: Morph.Jb. 110 245-269, 1967.]

As representatives of the most primitive of recent vertebrate groups, lampreys show fundamental differences in different features of organisation to the species of the remaining classes of vertebrates. The topical distinction between exocrine and endocrine pancreas is also considered among the morphological peculiarities of Petromyzontida. This study aims to contribute to a further explanation of this phenomenon. 50 brook lampreys were histologically examined.

110-W fiber laser with homemade double-clad fiber

A high-power ytterbium-doped fiber laser (YDFL) with homemade double-clad fiber (DCF) is introduced in this letter. The geometric parameter and laser characteristics of the fiber have been studied. With one-end-pumping scheme, pumped by a high-power laser diode with launching power of 280 W, a maximum continuous wave (CW) output of 110 W is obtained with an optical-to-optical efficiency of 40%.

Comment on "Acoustic chaos in a duct with two separate sound sources" [J. Acoust. Soc. Am. 110, 120-126 (2001)] (L)

In a paper published in this journal in 2001 by Dong [W. G. Dong, X. Y. Huang, and Q. L. Wo, J. Acoust. Soc. Am. 110, 120-126 (2001)] it was claimed that acoustic chaos was obtained experimentally by the nonlinear interaction of two acoustic waves in a duct. In this comment a simple experimental setup and an analytical model is used to show that the dynamics of such systems corresponds to a quasiperiodic motion, and not to a chaotic one. © 2008 Acoustical Society of America.

Vertically standing Ge nanowires on GaAs(110) substrates.

The growth of epitaxial Ge nanowires is investigated on (100), (111) B and (110) GaAs substrates in the growth temperature range from 300 to 380 °C. Unlike epitaxial Ge nanowires on Ge or Si substrates, Ge nanowires on GaAs substrates grow predominantly along the [Formula: see text] direction. Using this unique property, vertical [Formula: see text] Ge nanowires epitaxially grown on GaAs(110) surface are realized. In addition, these Ge nanowires exhibit minimal tapering and uniform diameters, regardless of growth temperatures, which is an advantageous property for device applications. Ge nanowires growing along the [Formula: see text] directions are particularly attractive candidates for forming nanobridge devices on conventional (100) surfaces.

Structural and electrical properties of (110) ZnO epitaxial thin films on (001) SrTiO3 substrates

(110) oriented ZnO thin films were epitaxially prepared on (001) SrTiO3 single crystal substrates by a pulsed laser deposition method. The evolution of structure, surface morphology, and electrical conductivity of ZnO films was investigated on changing the growth temperature. Two domain configurations with 90 degrees rotation to each other in the film plane were found to exist to reduce the lattice mismatch between the films and substrates. In the measured temperature range between 80 K and 300 K, the electrical conductivity can be perfectly fitted by a formula of a (T) = sigma(0) + aT(b/2). implying that the electron-phonon scattering might have a significant contribution to the conductivity. (C) 2008 Elsevier Ltd. All rights reserved.

Cleaved-edge overgrowth of aligned InAs islands on GaAs(110)

A novel approach for positioning InAs islands on GaAs(110) by cleaved-edge overgrowth is reported. The first growth sample contains a strained InxGa1-xAs/GaAs superlattice of varying indium fraction and thickness, which acts as a strain nanopattern for the cleaved edge overgrowth. The formation of aligned islands is observed by means of atomic force microscopy. The ordering of the aligned islands and the structure of a single InAs island are found to depend on the properties of the underlying InxGa1-xAs/GaAs superlattice and molecular beam epitaxy growth conditions.

A novel method for positioning of InAs islands on GaAs(110)

A novel method for positioning of InAs islands on GaAs (110) by cleaved edge overgrowth is reported. The first growth sample contains strained InxGa1-xAs/GaAs superlattice (SL) of varying indium fraction, which acts as a strain nanopattern for the cleaved-edge overgrowth. Atoms incident on the cleaved edge will preferentially migrate to InGaAs regions where favorable bonding sites are available. By this method InAs island chains with lateral periodicity defined by the thickness of InGaAs and GaAs of SL have been realized by molecular beam epitaxy (MBE). They are observed by means of atomic force microscopy (AFM). The strain nanopattern's effect is studied by the different indium fraction of SL and MBE growth conditions. (c) 2005 Elsevier B.V. All rights reserved.