1,715 research outputs found
Characterization and analysis of azimuthally sensitive correlations
A unified framework for describing the azimuthal dependence of two-particle
correlations in heavy-ion collisions is introduced, together with the methods
for measuring the corresponding observables. The generalization to azimuthal
correlations between more than two particles is presented.Comment: 7 pages; talk given at Hot Quarks 2004, Taos (NM), July 18-24,200
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Effects of Surface Roughness on the Electrochemical Reduction of CO2 over Cu
We have investigated the role of surface roughening on the CO2 reduction reaction (CO2RR) over Cu. The activity and product selectivity of Cu surfaces roughened by plasma pretreatment in Ar, O2, or N2 were compared with that of electrochemically polished Cu samples. Differences in total and product current densities, the ratio of current densities for HER (the hydrogen evolution reaction) to CO2RR, and the ratio of current densities for C2+ to C1 products depend on the electrochemically active surface and are nearly independent of plasma composition. Theoretical analysis of an electropolished and roughened Cu surface reveals a higher fraction of undercoordinated Cu sites on the roughened surface, sites that bind CO preferentially. Roughened surfaces also contain square sites similar to those on a Cu(100) surface but with neighboring step sites, which adsorb OC-COH, a precursor to C2+ products. These findings explain the increases in the formation of oxygenates and hydrocarbons relative to CO and the ratio of oxygenates to hydrocarbons observed with increasing surface roughness
Variability in the Lambda Orionis cluster substellar domain
We present the first results on variability of very low mass stars and brown
dwarfs belonging to the 5 Myr Lambda Orionis cluster (Collinder 69). We have
monitored almost continuously in the J filter a small area of the cluster which
includes 12 possible members of the cluster during one night. Some members have
turned to be short-term variable. One of them, LOri167, has a mass close to the
planetary mass limit and its variability might be due to instabilities produced
by the deuterium burning, although other mechanism cannot be ruled out.Comment: Accepted for Astronomische Nachrichten. Workshop "Ultra-low-mass star
formation and evolution", La Palma June 200
Logarithmic Moduli Spaces for Surfaces of Class VII
In this paper we describe logarithmic moduli spaces of pairs (S,D) consisting
of minimal surfaces S of class VII with positive second Betti number b_2
together with reduced divisors D of b_2 rational curves. The special case of
Enoki surfaces has already been considered by Dloussky and Kohler. We use
normal forms for the action of the fundamental group of the complement of D and
for the associated holomorphic contraction germ from (C^2,0) to (C^2,0).Comment: Minor correction of the dimension of the moduli spac
Electronic conduction and electrocatalysis by supramolecular tetraruthenated copper porphyrazine films
A new tetraruthenated copper(II)-tetra(3,4-pyridyl)porphyrazine species, [CuTRPyPz]4+, has been synthesized and fully characterized by means of analytical, spectroscopic and electrochemical techniques. This À-conjugated system contrasts with the related meso-tetrapyridylporphyrins by exhibiting strong electronic interaction between the coordinated peripheral complexes and the central ring. Based on favorable À-stacking and electrostatic interactions, layer-by-layer assembled films were successfully generated from the appropriate combination of [CuTRPyPz]4+ with copper(II)-tetrasulfonated phtalocyanine, [CuTSPc]4-. Their conducting and electrocatalytic properties were investigated by means of impedance spectroscopy and rotating disc voltammetry, exhibiting metallic behavior near the Ru(III/II) redox potential, as well as enhanced catalytic activity for the oxidation of nitrite and sulphite ions.Uma nova espécie cobre(II)-tetra(3,4-piridil) porfirazina tetrarrutenada, [CuTRPyPz]4+ foi sintetizada e sua caracterização conduzida por meio de métodos analíticos, espectroscópicos e eletroquímicos. Sua extensa conjugação-À a distingue dos derivados análogos da meso-tetrapiridilporfirina, levando à ocorrência de interações eletrônicas mais fortes entre os complexos periféricos e o anel porfirazínico central. Com base nas interações eletrostáticas e de empilhamento-À, foram realizadas montagens, camada-por-camada, de filmes funcionais, combinando-se a [CuTRPyPz]4+ com a ftalocianina de cobre(II) tetrassulfonada, [CuTSPc]4-. As propriedades condutoras e eletrocatalíticas desses filmes foram investigadas através de técnicas de impedância e de voltametria de disco rotatório, observando-se um comportamento metálico nas proximidades do potencial do par redox Ru(III)/(II), bem como uma pronunciada atividade catalítica na oxidação de íons nitrito e sulfito, em meio aquoso.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Instituto do Milênio de Materiais Complexo
Etude expérimentale de la maladie de Talfan en France. Isolement et identification du Virus
Richard Y., Toma Bernard, Goret Pierre. Étude expérimentale de la maladie de Talfan en France. Isolement et identification du virus. In: Bulletin de l'Académie Vétérinaire de France tome 126 n°2, 1973. pp. 73-81
Explosions of water clusters in intense laser fields
Energetic, highly-charged oxygen ions, (), are copiously
produced upon laser field-induced disassembly of highly-charged water clusters,
and , 60, that are formed by seeding high-pressure
helium or argon with water vapor. clusters (n40000) formed under
similar experimental conditions are found undergo disassembly in the Coulomb
explosion regime, with the energies of ions showing a
dependence. Water clusters, which are argued to be considerably smaller in
size, should also disassemble in the same regime, but the energies of fragment
O ions are found to depend linearly on which, according to
prevailing wisdom, ought to be a signature of hydrodynamic expansion that is
expected of much larger clusters. The implication of these observations on our
understanding of the two cluster explosion regimes, Coulomb explosion and
hydrodynamic expansion, is discussed. Our results indicate that charge state
dependences of ion energy do not constitute an unambiguous experimental
signature of cluster explosion regime.Comment: Submitted to Phys. Rev.
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