Electrical behavior of the Au/MoS2 interface studied by light emission induced by scanning tunneling microscopy

Light emitted in the tunneling junction of a scanning tunneling microscope has been used to establish the electrical characteristics of nanojunctions made of Au islands deposited on flat MoS₂ surfaces. It is shown that these characteristics are those of rectifying contacts when the gold islands are isolated and that they evolve toward those of ohmic contacts when the island density increases. It is observed that the rectifying behavior also evolves over time as on infinite metal/semiconductor contacts. Using the STM tip, single gold islands can be manipulated on the MoS₂ surface so that their electrical behavior can be changed depending on their position with regard to the other islands.     

Hydrocondensation of CO2 (CO) over supported iron catalysts

Hydrogenation of CO₂ was investigated on iron-copper supported catalysts. Hydrocarbons, except methane, were formed through the CO intermediate, which is formed first in the water gas-shift reaction.

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CO₂ - . CO, , , .

     

Latex Fractionation by Sedimentation and Colloidal Crystallization: The Case of Poly(styrene-co-acrylamide)

Poly(styrene-co-acrylamide) (PS-AAM) latex was prepared, fractionated by sedimentation under gravity, and characterized by PCS, infrared spectra, secondary and backscattered electron imaging in the scanning electron microscope, and electron spectroscopy imaging in an analytical transmission electron microscope. Three latex fractions were obtained. The lower fraction was opalescent and its particles were the more uniform, concerning size, chemical composition, and topochemical features. This lower fraction was still further fractionated by zonal centrifugation in a density gradient, yielding two fractions with similar macrocrystal-forming abilities but different sizes and chemical compositions. These results confirm those previously obtained for the PS-HEMA latex. Copyright 2000 Academic Press.     

Prompt fission induced by antiproton annihilation at rest on heavy nuclei

Antiproton induced fission probabilities of U²³⁸, Bi²⁰⁹, Pb²⁰⁸ and Au¹⁷⁷ are reported together with the mass distribution of the fission fragments in the U²³⁸ and Bi²⁰⁹ cases. The charged particles multiplicities observed in co-incidence with fission have, also, been measured for U and Bi and are presented.Dedicated to Peter Armbruster on the occasion of his 60th birthday in recognition of his important contribution to modern Nuclear Physics     

Experimental and numerical study of shock wave propagation in water generated by pulsed arc electrohydraulic discharges

The objective of this study is to simulate the propagation of the shock wave in water due to an explosion. The study is part of a global research program on the development of an alternative stimulation technique to conventional hydraulic fracturing in tight gas reservoirs aimed at inducing a distributed state of microcracking of rocks instead of localized fracture. We consider the possibility of increasing the permeability of rocks with dynamic blasts. The blast is a shock wave generated in water by pulsed arc electrohydraulic discharges. The amplitude of these shock waves is prescribed by the electrohydraulic discharges which generate high pressures of several kilobars within microseconds. A simplified method has been used to simulate the injected electrical energy as augmentation of enthalpy in water locally. The finite element code EUROPLEXUS is used to perform fluid fast dynamic computation. The predicted pressure is consistent with the experimental results. In addition, shock wave propagation characteristics predicted with simulation can be valuable reference for design of underwater structural elements and engineering of underwater explosion.