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Theory of nitride oxide adsorption on transition metal (111) surfaces: a first-principles investigation

ZENG, Zhen-Hua; SILVA, Juarez L. F. Da; LI, Wei-Xue
Fonte: ROYAL SOC CHEMISTRY Publicador: ROYAL SOC CHEMISTRY
Tipo: Artigo de Revista Científica
ENG
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In this work, we report a density functional theory study of nitric oxide (NO) adsorption on close-packed transition metal (TM) Rh(111), Ir(111), Pd(111) and Pt(111) surfaces in terms of adsorption sites, binding mechanism and charge transfer at a coverage of Theta(NO) = 0.25, 0.50, 0.75 monolayer (ML). Based on our study, an unified picture for the interaction between NO and TM(111) and site preference is established, and valuable insights are obtained. At low coverage (0.25 ML), we find that the interaction of NO/TM(111) is determined by an electron donation and back-donation process via the interplay between NO 5 sigma/2 pi* and TM d-bands. The extent of the donation and back-donation depends critically on the coordination number (adsorption sites) and TM d-band filling, and plays an essential role for NO adsorption on TM surfaces. DFT calculations shows that for TMs with high d-band filling such as Pd and Pt, hollow-site NO is energetically the most favorable, and top-site NO prefers to tilt away from the normal direction. While for TMs with low d-band filling (Rh and Ir), top-site NO perpendicular to the surfaces is energetically most favorable. Electronic structure analysis show that irrespective of the TM and adsorption site...

Electric field gradients in (111)In-doped (Hf/Zr)(3)Al(2) and (Hf/Zr)(4)Al(3) mixed compounds: ab initio calculations, perturbed angular correlation measurements and site preference

ERRICO, L. A.; Petrilli, Helena Maria; TERRAZOS, L. A.; KULINSKA, A.; WODNIECKI, P.; LIEB, K. P.; UHRMACHER, M.; BELOSEVIC-CAVOR, J.; KOTESKI, V.
Fonte: IOP PUBLISHING LTD Publicador: IOP PUBLISHING LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
35.86%
The quadrupolar hyperfine interactions of in-diffused (111)In -> (111)Cd probes in polycrystalline isostructural Zr(4)Al(3) and Hf(4)Al(3) samples containing small admixtures of the phases (Zr/Hf)(3)Al(2) were investigated. A strong preference of (111)In solutes for the contaminant (Zr/Hf)(3)Al(2) minority phases was observed. Detailed calculations of the electric field gradient (EFG) at the Cd nucleus using the full-potential augmented plane wave + local orbital formalism allowed us to assign the observed EFG fractions to the various lattice sites in the (Zr/Hf)(3)Al(2) compounds and to understand the preferential site occupation of the minority phases by the (111)In atoms. The effects of the size of the supercell and relaxation around the oversized In and Cd probe atoms were investigated in detail.; Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT); ANPCyT Agencia Nacional de Promocion Cientifica y Tecnologica (ANPCyT)[PICT98 0303727]; Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET)[PIP6032]; Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina (CONICET); Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina (CONICET); Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET)[0002]; Antorchas...

The protein LJM 111 from Lutzomyia longipalpis Salivary Gland Extract (SGE) accounts for the SGE-inhibitory effects upon inflammatory parameters in experimental arthritis model

Grespan, Renata; Lemos, Henrique P.; Carregaro, Vanessa; Verri Junior, Waldiceu A.; Souto, Fabricio O.; Oliveira, Carlo J. F. de; Teixeira, Clarissa; Ribeiro, Jose Marcos; Valenzuela, Jesus G.; Cunha, Fernando Q.
Fonte: ELSEVIER SCIENCE BV; AMSTERDAM Publicador: ELSEVIER SCIENCE BV; AMSTERDAM
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
35.74%
Several studies have pointed out the immunomodulatory properties of the Salivary Gland Extract (SGE) from Lutzomyia longipalpis. We aimed to identify the SGE component (s) responsible for its effect on ovalbumin (OVA)-induced neutrophil migration (NM) and to evaluate the effect of SGE and components in the antigen-induced arthritis (AIA) model. We tested the anti-arthritic activities of SGE and the recombinant LJM111 salivary protein (rLJM111) by measuring the mechanical hypernociception and the NM into synovial cavity. Furthermore, we measured IL-17, TNF-alpha and IFN-gamma released by lymph nodes cells stimulated with mBSA or anti-CD3 using enzyme-linked immunosorbent assay (ELISA). Additionally, we tested the effect of SGE and rLJM111 on co-stimulatory molecules expression (MHC-II and CD-86) by flow cytometry. TNF-alpha and IL-10 production (ELISA) of bone marrow-derived dendritic cells (BMDCs) stimulated with LPS, chemotaxis and actin polymerization from neutrophils. Besides, the effect of SGE on CXCR2 and GRK-2 expression on neutrophils was investigated. We identified one plasmid expressing the protein LJM111 that prevented NM in OVA-challenged immunized mice. Furthermore, both SGE and rLJM111 inhibited NM and pain sensitivity in AIA and reduced IL-17...

Interação de moléculas e superfície Au(111); Interactions of molecules and surface Au(111)

Lima, Filipe Camargo Dalmatti Alves
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 15/05/2015 PT
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O estudo de sistemas híbridos compostos por interfaces orgânico/inorgânico, ou sólido/líquido, tem apresentado crescente interesse nas áreas de eletroquímica e nanotecnologia. Além de objetos de pesquisas básicas, estes sistemas apresentam um potencial para inúmeras aplicações, dentre elas: línguas eletrônicas, \emph{self-assembled monolayers} (SAMs), dispositivos fotovoltáicos, baterias alternativas, carreadores de drogas, entre outras. Em especial, o uso de superfícies de ouro em pesquisas ocorre principalmente por causa da natureza inerte deste material, permitindo explorar uma ampla quantidade de potenciais eletrostáticos que induzem a eletrólise ou reações eletroquímicas em outras superfícies. O estudo de voltametria cíclica em SAMs formadas por cadeias polipeptídicas funcionalizadas com ferroceno vem sendo realizado durante as duas últimas décadas. Recentemente, iniciou-se uma controvertida discussão a respeito do mecanismo de transporte eletrônico entre o centro oxidativo e o eletrodo destes sistemas. Alguns grupos argumentam a favor de tunelamento eletrônico do centro oxidativo, enquanto outros grupos têm proposto uma interação de pares \emph{elétron-buraco} dos grupos amida dos peptídeos. Além disto...

In Situ Scanning Tunneling Microscopy Study of 5,6-Dimethyl Uracil on Au (111)

Cunha,Frederico G. C.; Nart,Francisco C.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2001 EN
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The hydrogen evolution mediated 5,6-dimethyluracil (5,6-DMU) film disordering and subsequent reordering was studied in situ in sulfuric acid solution on Au (111) using STM and cyclic voltammetry. A stable, condensed physisorbed film was formed between the limits of the hydrogen evolution (at -0.3 V/SCE) and the lifting of the surface reconstruction (at 0.4 V/SCE) in the bulk solution concentration used in this study. The onset of hydrogen evolution led to the formation of "bubble" like structures which disrupted the stability of the film causing a disordering process which takes place within the whole scanned area. Stepping the potential back to the region of stability allowed the real time observation of the film reorganization. An anisotropic evolution of the film was found. The surface step edges were not found to be preferential nucleation sites. The molecular packing structure was inferred from high-resolution STM images and the existence of two distinct adsorbate states was established.

Evaluation of a bivalent (CVD 103-HgR/CVD 111) live oral cholera vaccine in adult volunteers from the United States and Peru.

Taylor, D N; Tacket, C O; Losonsky, G; Castro, O; Gutierrez, J; Meza, R; Nataro, J P; Kaper, J B; Wasserman, S S; Edelman, R; Levine, M M; Cryz, S J
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1997 EN
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To provide optimum protection against classical and El Tor biotypes of Vibrio cholerae O1, a single-dose, oral cholera vaccine was developed by combining two live, attenuated vaccine strains, CVD 103-HgR (classical, Inaba) and CVD 111 (El Tor, Ogawa). The vaccines were formulated in a double-chamber sachet; one chamber contained lyophilized bacteria, and the other contained buffer. In the first study, 23 U.S. adult volunteers received CVD 103-HgR at 10(8) CFU plus CVD 111 at 10(8), 10(7), or 10(6) CFU, CVD 111 alone at 10(7) CFU, or placebo. In the second study, 275 Peruvian adults were randomized to receive CVD 103-HgR at 10(9) CFU plus CVD 111 at 10(9) or 10(8) CFU, CVD 111 alone at 10(9) CFU, CVD 103-HgR alone at 10(9) CFU, or placebo. Three of 15 U.S. volunteers who received CVD 111 at 10(7) or 10(8) CFU developed mild diarrhea, compared to none of 4 who received CVD 111 at 10(6) CFU and 1 of 4 who received placebo. Twelve (63%) of 19 vaccine recipients shed the El Tor vaccine strain. All but one volunteer developed significant Ogawa and Inaba vibriocidal antibody titers. Volunteers who received CVD 111 at 10(7) CFU had geometric mean Ogawa titers four to five times higher than those of volunteers who received the lower dose. In the second study...

Nickel-containing nano-sized islands grown on Ge(111)-c(2 × 8) and Ag/Ge(111)-(√3 × √3) surfaces

Fu, Tsu-Yi; Tomaszewska, Agnieszka; Huang, Xiao-Lan; Li, Jhen-Hao; Hsieh, Po-I; Jhou, Ming-Kuan
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 08/10/2013 EN
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The formation of nano-islands on both a Ge(111)-c(2 × 8) surface and an Ag/Ge(111)-(√3 × √3) surface evaporated with 0.1 ML Ni was investigated by scanning tunneling microscopy (STM). We have noticed that at temperatures lower than 670 K, the reaction between Ni and the individual substrate surfaces proceeds to form different structures: flat-topped islands with a 2√7 × 2√7 or a 3 × 3 reconstruction on the Ni/Ge(111)-c(2 × 8) surface vs. islands with a 7 × 7 reconstruction on the Ni/Ag/Ge(111)-(√3 × √3) surface. From this we have inferred that within a temperature range between room temperature and 670 K, the intermediate Ag layer retards mixing between Ni and Ge atoms. As a result, the grown islands are composed of pure Ni atoms. Within a temperature range from 670 to 770 K, most islands produced on the Ag/Ge(111)-(√3 × √3) surface are identical with those formed on the Ni/Ge(111)-c(2 × 8) surface, suggesting that above 670 K, Ni atoms are likely to bind with Ge atoms. However, an essential difference between STM images of the surfaces under study exists in the appearance of large elongated islands on the Ni/Ag/Ge(111)-(√3 × √3) surface. The formation of the latter is explained in terms of a difference in energy for Ni diffusion on the Ge(111)-c(2 × 8) and Ag/Ge(111)-(√3 × √3) surfaces.

Análise teórica da superfície Si(111)-(7x7)

Mikhail, Hanna Degani
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Dissertação
POR
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35.97%
Neste trabalho, realizamos o estudo teórico da reconstrução (7x7) da superfície de Silício crescida na direção [111], denotada por Si(111)–(7x7), utilizando para isto o formalismo da Teoria do Funcional da Densidade, com a Aproximação da Densidade Local (LDA - LocalDensityApproximation) para o termo de troca–correlação. A interação entre os elétrons de valência e o íon de caroço (núcleo mais os elétrons de caroço) foi descrita por meio da Teoria dos Pseudopotenciais não locais de norma conservada, compativel com a LDA. As equações de Kohn–Sham de um–elétron foram resolvidas autoconsistentemente, expandindo as funções de um–elétronemtermos de combinação linear de orbitais atômico numéricos, com base double–. Todos os cálculos foram realizados utilizando o código computacional Siesta. Utilizando o modelo de reconstrução da superfície livre de Si(111)–(7x7), proposto por Takayanagi et al.[1, 2], modelamos a superfície como um slab, cuja célula unitária (7x7) contém 200 átomos de Si distribuidos em uma camada de adatoms (átomos de Si adsorvidos sobre a superfície propriamente dita) e quatro outras camadas, além dos 49 átomos de H usados para saturar as ligações pendentes da camada mais interna ao material. A análise estrutural da superfície reconstruída Si(111)–(7x7) e a análise da estrutura eletrônica mostrou ótima concordância tanto com trabalhos experimentais quanto teóricos...

Einfluß der absoluten Oberflächenspannung auf die Form dünner Einkristalle: Eine Analyse am Beispiel Si(111); Influence of absolute surface stress on the deformation of thin single crystal sheets: an analysis for Si(111)

Kaiser, Stefan
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
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Obwohl die absolute Oberflächenspannung eine für viele Anwendungen relevante, fundamentale Eigenschaft von Festkörperoberflächen ist, existiert bisher kein Verfahren, mit dem diese makroskopische Größe mit akzeptabler Genauigkeit gemessen werden kann. Änderungen der Oberflächenspannung lassen sich mit der sogenannten Biegebalkenmethode ermitteln, Absolutwerte dagegen nicht. Nach einem von Müller und Kern 1994 aufgestellten Modell hat die absolute Oberflächenspannung einen nicht vernachlässigbaren Einfluß auf die durch die Schwerkraft verursachte Deformation von sehr dünnen, waagerecht aufgehängten Einkristallen. Eine Messung des Effektes ist allerdings technisch anspruchsvoll und wurde in der vorliegenden Arbeit erstmals realisiert. Durch den Einsatz von Phasenschiebungs-Interferometrie ist es gelungen, die Biegelinie eines 25,4 mm langen und ca. 50 Mikrometer dicken Si(111)-Streifen zu bestimmen. Dabei zeigte sich jedoch, daß die Deformation von der absoluten Oberflächenspannung unabhängig ist. Dieses Verhalten konnte durch eine ausführliche theoretische Analyse erklärt werden, wobei das Modell von Müller und Kern widerlegt wurde. Tatsächlich tritt die vorhergesagte Abhängigkeit nur unter speziellen Randbedingungen auf. Aus einem überarbeiteten Modell konnte eine neue Probengeometrie abgeleitet werden...

Density functional study of acrolein adsorption on Pt (111)

Pirillo, Silvina; López Corral, Ignacio; German, Estefania; Juan, Alfredo
Fonte: Elsevier Publicador: Elsevier
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
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The electronic structure and bonding of acrolein (propenal) adsorption on Pt (111) were studied by density functional calculations (DFT). We optimized different adsorption configurations on the surface using the VASP code. The energetic study indicates that acrolein trans isomers are less stable on the Pt surface than cis configurations, which have a similar stability in all cases. We found that the inclusion of Van der Waals (vdW) corrections does not change the obtained adsorption geometries or preferential sites relative energies. We also analyzed the evolution of the chemical bonding changes in the adsorbate and the metal surface by crystal orbital overlap population (COOP) and overlap population (OP) analysis of selected bonds. Except for the h1 configuration, the adsorption of acrolein on the surface is mainly due to the formation of CePt bonds. We also found that the acrolein C pz orbital, perpendicular to the surface, play an important role in the adsorption, as well as Pt pz and dz 2 orbitals, whose lobes are well oriented to overlap with the adsorbate orbitals.; Fil: Pirillo, Silvina. Universidad Nacional del Sur. Departamento de Física; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Química del Sur; Argentina.;; Fil: López Corral...

Surface Chemistry of 4-Mercaptobenzoic Acid Self-Assembled on Ag(111) and Ag Nanoparticles.

Maya Giron, Julie Viviana; Zelaya, Maria Eugenia; Rubert, Aldo Alberto; Benitez, Guillermo Alfredo; Carro, Pilar; Salvarezza, Roberto Carlos; Vela, Maria Elena
Fonte: Amer Chemical Soc Publicador: Amer Chemical Soc
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
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The adsorption of 4-mercaptobenzoic acid (MBA) on Ag(111) and Ag nanoparticles (AgNPs) has been studied by Xray photoelectron spectroscopy (XPS), electrochemical techniques, high-resolution transmission electron microscopy (HRTEM), and density functional theory (DFT) calculations. Results show that MBA molecules adsorb intact on the Ag (111) surface via a thiolate bond, arranged in a (√3 × 4) lattice with coverage θ = 0.25. The phase diagram built using DFT data shows that this lattice is more stable than the dense (√7 × √7)R19.1° MBA lattices on reconstructed Ag(111) surfaces. No significant amounts of sulfide were found neither on the Ag(111) surfaces nor on MBA-protected AgNPs, suggesting that the Ag core@Ag-sulfide shell structure where thiolates could be grafted cannot be applied to the MBAprotected AgNPs. Slow degradation of the MBA protective layer in ambient conditions on the AgNPs results in disulfide formation and AgNP sintering.; Fil: Maya Giron, Julie Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicaciones; Argentina;; Fil: Zelaya, E.. Comisión Nacional de Energía Atómica. Gerencia del área Investigaciones y Aplicaciones No Nucleares. Gerencia de Fisica (cab). División Física de Metales; Argentina; Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina;; Fil: Rubert...

Hydrocarbon chain length induces surface structure transitions in alkanethiolate-Au adatom self-assembled monolayers on Au(111)

Carro, Pilar; Pensa, Evangelina Laura; Vericat, Carolina; Salvarezza, Roberto Carlos
Fonte: Amer Chemical Soc Publicador: Amer Chemical Soc
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
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A detailed density functional calculation (DFT) study including van der Waals (vdW) dispersion forces of different adatom-containing models (RS−Auad−SR) at saturation coverage for methanethiol (MT), butanethiol (BT), and hexanethiol (HT) on Au(111) is presented. The stability analysis of these lattices shows a transition from the (3 × 4) to the c(4 × 2) surface structure when the number of C atoms in the alkanethiol chain is larger than 2, fairly predicting recent experimental observations for these systems. The transition takes place when the smaller energy needed to reconstruct the Au(111) surface and the larger binding energy for MT in the (3 × 4) MT lattice is compensated by a larger interaction energy between hydrocarbon chains in the c(4 × 2) lattice for BT and HT. Our calculations therefore explain why the (3 × 4) lattice is more stable for MT and ethanethiol (ET) while the c(4 × 2) lattice predominates for longer alkanethiols, thus shedding light on the behavior of alkanethiol self-assembled monolayers (SAMs) on Au(111).; Fil: Carro, P.. Universidad de La Laguna. Instituto de Materiales y Nanotecnología. Departamento de Química Física; España;; Fil: Pensa, Evangelina Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicaciones; Argentina;; Fil: Vericat...

Growth of epitaxially oriented Ag nanoislands on air-oxidized Si(111)-(7x7) surfaces: Influence of short range order on the substrate

Roy, Anupam; Bhattacharjee, K.; Ghatak, J.; Dev, B. N.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 14/09/2010
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Clean Si(111)-(7{x7) surfaces, followed by air-exposure, have been investigated by reflection high energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). Fourier transforms (FTs) of STM images show the presence of short range (7x7) order on the air-oxidized surface. Comparison with FTs of STM images from a clean Si(111)-(7x7) surface shows that only the 1/7th order spots are present on the air-oxidized surface. The oxide layer is ~ 2-3 nm thick, as revealed by cross-sectional transmission electron microscopy (XTEM). Growth of Ag islands on these air-oxidized Si(111)-(7x7) surfaces has been investigated by in-situ RHEED and STM and ex-situ XTEM and scanning electron microscopy. Ag deposition at room temperature leads to the growth of randomly oriented Ag islands while preferred orientation evolves when Ag is deposited at higher substrate temperatures. For deposition at 550{\deg}C face centered cubic Ag nanoislands grow with a predominant epitaxial orientation [1 -1 0]Ag || [1 -1 0]Si, (111)Ag || (111)Si along with its twin [-1 1 0]Ag || [1 -1 0]Si, (111)Ag || (111)Si, as observed for epitaxial growth of Ag on Si(111) surfaces. The twins are thus rotated by a 180{\deg} rotation of the Ag unit cell about the Si [111] axis. It is intriguing that Ag nanoislands follow an epitaxial relationship with the Si(111) substrate in spite of the presence of a 2-3 nm thick oxide layer between Ag and Si. Apparently the short range order on the oxide surface influences the crystallographic orientation of the Ag nanoislands.; Comment: 10 figures

Anatomy of HH 111 from CO Observations: a Bow-shock-driven Molecular Outflow

Lefloch, Bertrand; Cernicharo, José; Reipurth, Jo; Pardo Carrión, Juan Ramón; Neri, Roberto
Fonte: American Astronomical Society; University of Chicago Press Publicador: American Astronomical Society; University of Chicago Press
Tipo: Artículo Formato: 1373320 bytes; application/pdf
ENG
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We present single-dish and interferometric millimeter line observations of the HH 111 outflow and its driving source. The physical conditions of the core have been determined from the emission of the millimeter line of CO and its isotopomers and CS with the IRAM 30 m telescope, and the CO J=7-->6 line with the Caltech Submillimeter Observatory. The emission reveals a small condensation of cold (T=20-25 K) and dense gas [n(H2)=3x10^5 cm^-3]. The outflow has been mapped with the IRAM Plateau de Bure Interferometer (PdBI). The cold gas is distributed in a hollow cylinder surrounding the optical jet. The formation of this cavity and its kinematics are well accounted for in the frame of outflow gas entrainment by jet bow shocks. Evidence of gas acceleration is found along the cavity walls, correlated with the presence of optical bow shocks. The separation of the inner walls reaches 8"-10", which matches the transverse size of the wings in the bow shock. CSO observations of the J=7-->6 line show evidence of a high-velocity and hot gas component (T=300-1000 K) with a low filling factor. This emission probably arises from shocked gas in the jet. Observations of the 3P2-3P1 [CI] line are consistent with C-type nondissociative shocks. Mapping of the high-velocity molecular bullets B1-B3...

Transmission Infrared Spectra of CH_3-, CD_3-, and C_(10)H_(21)-Ge(111) Surfaces

Knapp, David; Brunschwig, Bruce S.; Lewis, Nathan S.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 25/08/2011
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The surface chemistry of CH_3–, CD_3–, and C_(10)H_(21)–Ge(111) surfaces prepared through a bromination/alkylation method have been investigated by infrared spectroscopy. Well-ordered CH_3–Ge(111) surfaces could be prepared only if, prior to bromination, the surface was etched with 6.0 M HCl or with a two-step etch of H_2O_2 (1.5 M)/HF (5.1 M) followed by a short HF (6.0 M) etch. The etching method used to make the Ge precursor surface, and the formation of a bromine-terminated intermediate Ge surface, were of critical importance to obtain clear, unambiguous infrared absorption peaks on the methyl-terminated Ge surfaces. Polarization-dependent absorption peaks observed at 1232 cm^(–1) for CH_3–Ge(111) surfaces and at 951 cm^(–1) for CD_3–Ge(111) surfaces were assigned to the methyl “umbrella” vibrational mode. A polarization-dependent peak at 2121 cm^(–1) for CD_3–Ge(111) surfaces was assigned to the symmetric methyl stretching mode. Polarization-independent absorption peaks at 755 cm^(–1) for CH_3–Ge(111) and at 577 cm^(–1) for CD_3–Ge(111) were assigned to the methyl rocking mode. These findings provide spectroscopic evidence that the methyl monolayer structure on the alkylated Ge is well-ordered and similar to that on analogous Si(111) surfaces...

Comparison of the Photoelectrochemical Behavior of H‑Terminated and Methyl-Terminated Si(111) Surfaces in Contact with a Series of One-Electron, Outer-Sphere Redox Couples in CH_3CN

Grimm, Ronald L.; Bierman, Matthew J.; O'Leary, Leslie E.; Strandwitz, Nicholas C.; Brunschwig, Bruce S.; Lewis, Nathan S.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 08/11/2012
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The photoelectrochemical behavior of methyl-terminated p-type and n-type Si(111) surfaces was determined in contact with a series of one-electron, outer-sphere, redox couples that span >1 V in the Nernstian redox potential, E(A/A^−), of the solution. The dependence of the current vs potential data, as well as of the open-circuit photovoltage, V_(OC), on E(A/A^−) was compared to the behavior of H-terminated p-type and n-type Si(111) surfaces in contact with these same electrolytes. For a particular E(A/A^−) value, CH_3-terminated p-Si(111) electrodes showed lower V_(OC) values than Hterminated p-Si(111) electrodes, whereas CH_3-terminated n-Si(111) electrodes showed higher V_(OC) values than H-terminated n-Si(111) electrodes. Under 100 mW cm^(−2) of ELH-simulated Air Mass 1.5 illumination, n-type H−Si(111) and CH_3−Si(111) electrodes both demonstrated nonrectifying behavior with no photovoltage at very negative values of E(A/A^−) and produced limiting V_(OC) values of >0.5 V at very positive values of E(A/A^−). Illuminated p-type H−Si(111) and CH_3−Si(111) electrodes produced no photovoltage at positive values of E(A/A^−) and produced limiting V_(OC) values in excess of 0.5 V at very negative values of E(A/A^−). In contact with CH_3CN-octamethylferrocene^(+/0)...

How Can Multi-State Compliance Programs in State Implementation Plans under Section 110 of the Clean Air Act Inform the Potential Use of Multi-State, Market-Based Mechanisms for Compliance with Section 111 of the Clean Air Act?

Hauser, Janie
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Masters' project
Publicado em 19/04/2013 EN_US
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The Environmental Protection Agency (“EPA”) has committed to regulating greenhouse gas (“GHG”) emissions from stationary sources under section 111(d) of the Clean Air Act (“CAA”). There are only a few established regulatory programs under section 111(d) that EPA can reference as guidance during this process. Furthermore, the courts have not ruled on whether EPA may authorize the use of multi-state or market-based compliance mechanisms under section 111(d). However, section 111(d) explains that the regulatory process in 111(d) should be “similar to that provided by [section] 110.” Many states use multi-state, market-based compliance mechanisms to meet the requirements of section 110. Three section 110 programs, specifically, the NOx SIP Call, the Regional Haze program, and the Transportation Conformity program, serve as legal and structural examples of how EPA could develop regulations for GHG emissions under 111(d). Based on experiences with these 110 programs, EPA can learn valuable lessons for the development of a regulatory program that provides flexibility for states to use multi-state, market-based mechanisms for compliance. First, the NOx SIP Call and Clean Air Interstate Rule (“CAIR”) litigation demonstrate the D.C. Circuit’s commitment to the exact language in the CAA. The court was...

Heat Reductions and Carbon Emissions: A Policy Mechanism for Regulating Coal Plants under 111(d) of the Clean Air Act

Hansel, Peter
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Masters' project
Publicado em 24/04/2014
Relevância na Pesquisa
35.83%
The Clean Air Act requires the EPA to regulate carbon dioxide and greenhouse gases to protect public health and welfare. Currently the agency is in the process of developing standards for existing coal power plants under section 111(d) of the CAA and are expected to issue the proposed rule this summer. These regulations have the potential to drastically reduce emissions in the United States. Of the policy proposals and recommendations that have been submitted to the EPA, most advocate for including flexibility mechanisms, such as emissions trading, crediting and offsets, in the guidance policy. However, such broad mechanisms have limited precedence under 111(d) and their legality is untested. This paper explores a more conservative approach by regulating coal units within-the-fence-line. Specifically, the proposed policy would require uniform mandatory heat rate reductions for all coal units, regardless of initial heat rate. All coal units would be required to lower heat rates by 740-810 Btu/kWh, resulting in an 8% fleet-wide average. Inefficient units would be allowed to continue to operate alongside more efficient ones as long as each reduces their heat rate by the given amount. The policy was modeled and this analysis finds that despite costs associated with installing heat-rate reducing technology...

Heat Rate Reductions and Carbon Emissions: A Policy Mechanism for Regulating Coal Plants under 111(d) of the Clean Air Act

Hansel, Peter
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Masters' project
Publicado em 24/04/2014
Relevância na Pesquisa
35.83%
The Clean Air Act requires the EPA to regulate carbon dioxide and greenhouse gases to protect public health and welfare. Currently the agency is in the process of developing standards for existing coal power plants under section 111(d) of the CAA and are expected to issue the proposed rule this summer. These regulations have the potential to drastically reduce emissions in the United States. Of the policy proposals and recommendations that have been submitted to the EPA, most advocate for including flexibility mechanisms, such as emissions trading, crediting and offsets, in the guidance policy. However, such broad mechanisms have limited precedence under 111(d) and their legality is untested. This paper explores a more conservative approach by regulating coal units within-the-fence-line. Specifically, the proposed policy would require uniform mandatory heat rate reductions for all coal units, regardless of initial heat rate. All coal units would be required to lower heat rates by 740-810 Btu/kWh, resulting in an 8% fleet-wide average. Inefficient units would be allowed to continue to operate alongside more efficient ones as long as each reduces their heat rate by the given amount. The policy was modeled and this analysis finds that despite costs associated with installing heat-rate reducing technology...

A one-sided knot ejection at the core of the HH 111 outflow

Gómez,L.; Rodríguez,L. F.; Loinard,L.
Fonte: Instituto de Astronomía, UNAM Publicador: Instituto de Astronomía, UNAM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2013 EN
Relevância na Pesquisa
35.79%
We present an astrometry study of the radio source VLA 1 at the core of the HH 111 outflow using new data (2007) as well as archival observations (1992-1996). All data were taken at 3.6 cm with the Very Large Array in its most extended (A) configuration. The source VLA 1 has undergone a dramatic morphological change, showing a one-sided knot ejection in the 2007 epoch. We also report the detection of a 3.6 cm compact continuum source (VLA 3) located at ( -10.''6, 98.''7) from VLA 1. No significant absolute proper motions were found for VLA 1 and VLA 3 and the upper limits are consistent with those found for (embedded) radio sources in the Orion Nebula. We favor the interpretation that in the continuum at 3.6 cm we are observing two nearly perpendicular jets. HH 111 presents a new case of one-sided jet ejection in a young stellar object. The galactic (or extragalactic) nature of VLA 3 remains unclear.