Evidence of the key role of metal-molecule bonding in metal-molecule-metal transport experiments

The transport properties of two oligothiophene derivatives, that differ only by the chemical group coupling to gold, are compared. It is shown that the role of the coupling group in the transport properties can be decoupled from that of the conjugated body of the molecules and that Se is a better electronic coupling group than S. These results are accounted for semiquantitatively within the frame of the scattering theory of transport, using results from ultraviolet photoemission spectroscopy experiments as inputs for the position in energy of the molecular orbitals with respect to the Fermi level of the electrodes.     

Sound-field reproduction in-room using optimal control techniques: simulations in the frequency domain

This paper describes the simulations and results obtained when applying optimal control to progressive sound-field reproduction (mainly for audio applications) over an area using multiple monopole loudspeakers. The model simulates a reproduction system that operates either in free field or in a closed space approaching a typical listening room, and is based on optimal control in the frequency domain. This rather simple approach is chosen for the purpose of physical investigation, especially in terms of sensing microphones and reproduction loudspeakers configurations. Other issues of interest concern the comparison with wave-field synthesis and the control mechanisms. The results suggest that in-room reproduction of sound field using active control can be achieved with a residual normalized squared error significantly lower than open-loop wave-field synthesis in the same situation. Active reproduction techniques have the advantage of automatically compensating for the room's natural dynamics. For the considered cases, the simulations show that optimal control results are not sensitive (in terms of reproduction error) to wall absorption in the reproduction room. A special surrounding configuration of sensors is introduced for a sensor-free listening area in free field.     

Experiments in mixed-integer linear programming

This paper presents a branch and bound method for solving mixed integer linear programming problems. After briefly discussing the bases of the method, new concepts called pseudo-costs and estimations are introduced. Then, the heuristic rules for generating the tree, which are the main features of the method, are presented. Numerous parameters allow the user for adjusting the search strategy to a given problem.This method has been implemented in the IBM Extended Mathematical Programming System in order to solve large mixed integer L. P. problems. Numerical results making comparisons between different choices of rules are provided and discussed.This paper was presented at the 7th Mathematical Programming Symposium The Hague, The Netherlands.     

Alloying effects on the optical absorption edge of glow-discharge a-Si1-xGex: H

The absorption edge of glow-discharge a-Si_1-xGe_x: H alloys with Ge concentrations varying from 0 to 38% is determined from optical and photoconductivity measurements. The alloying effects on the band edges and the density of localized states in the pseudo-gap are discussed in relation with modifications of the photoconduction response.     

Additions dipolaires-1,3 en serie germaniee: Action de nitrilimines, oxydes de nitrile, et nitrones sur les germanones et germathiones

A new aspect of the reactivity of germanones and germathiones towards nitrilimines, nitriloxides and nitrones is investigated. The regioselectivity of the dipolar 1,3-cycloaddition reactions between germanones or germathiones and diphenylnitrilimine is discussed.

The structure of the adducts is determined from chemical or spectroscopic studies (¹³C NMR, IR).

Germa-oxa- or -thia-diazolines, germaoxathiazoles and germaoxathiazolidines are obtained and the thermal stability of these adducts reported.     

Experimental contribution to the relaxation problem on the (100) and (110) surfaces of aluminum by LEED data reduction

It is shown that low-energy electron diffraction intensities off crystal surfaces can, despite their apparent complexity, be fully understood with such simple and familiar concepts as Bragg reflections, zero-angle scattering phase shifts, electron penetration depth, and intdermediate beams in multiple scattering. Our emphasis is on direct physical understanding rather than on calculational methods.     

Über die Einwirkung von Phosphorpentachlorid auf o-Chinolacetate

Zusammenfassung Die Einwirkung von Phosphorpentachlorid auf o-Chinolacetate führt zur Bildung von Reaktionsprodukten, aus denen durch Hydrolyse m-chlorsubstituierte Phenylphosphorsäuren hervorgehen. Diese liefern bei thermischer Spaltung oder bei alkalischer Hydrolyse entsprechende m-Chlorphenole.     

The graphs with only self-dual signings

Given a graph G, it is possible to attach positive and negative signs to its lines only, to its points only, or to both. The resulting structures are called respectively signed graphs, marked graphs and nets. The dual of each such structure is obtained by changing every sign in it. We determine all graphs G for which every suitable marked graph on G is self-dual (the M-dual graphs), and also the corresponding graphs G for signed graphs (S-dual) and for nets (N-dual.A graph G is M-dual if and only if G or ? is one of the graphs K_2m, 2K_m, mK₂, K_m + K₂ or 2C₄. The S-dual graphs are C₆, 2C₃, 2C₄, 2K_1n, 2nK₂, K_1,2n, nK_1,2, K_2n, K?_n and all graphs obtained from these by the addition of isolated points. Finally, the only N-dual graph other than -K_2n is 2K₂.