Formation constants of copper(I)-olefin complexes in aqueous solution

A simple kinetic method has been applied to measure the formation constants of aqueous copper(I) with fumaronitrile, dimethyl fumarate, and fumaric and maleic acids. At 0.14 M ionic strength, the values of beta(1) are (0.85 +/- 0.02) x 10(3), (6.1 +/- 0.1) x 10(3), (7.3 +/- 0.1) x 10(3), and (2.2 +/- 0.4) x 10(3) M(-1), respectively. The values for the last two olefins are compared to previous results. Values of beta(1) for hydrogen maleate and beta(2) for fumaronitrile also have been determined. A reanalysis of much earlier work has been done, and all the results are discussed in terms of the effect of substituents on the olefin on the beta(1) values. The structure of bis(fumaronitrile)copper(I) nitrate also is reported. The nitrile is N-coordinated to copper(I), which has a distorted tetrahedral geometry, while the overall structure consists of macrocyclic Cu(6)(fumaronitrile)(6) rings which extend in three dimensions.     

Halophilic reactions of a stable silylene with chloro and bromocarbons

A number of disilanes have been synthesized from a stable silylene, 1 (N,N'-di-tert-butyl-1,3-diaza-2-silacyclopent-4-en-2-ylidene), and a variety of halocarbons. It is proposed that disilane formation is a result of an initial halophilic interaction between the silylene and halocarbon. Formation of disilanes from 1 and CCl4, 2a, CHCl3, 2b, CH2Cl2, 2c, benzyl chloride, 2d, and bromobenzene, 5, are described here. An X-ray crystal structure of 2b was determined.     

An investigation of the voltammetric characteristics of the osazone of dihydroxytartaric acid

Differential pulse polarography (d.p.p.), supplemented by other voltammetric techniques, is used to elucidate the tautomeric structures associated with buffered aqueous solutions of the osazone of dihydroxytartaric acid. In particular, d.p.p. is used to evaluate the number of electrons and protons associated with each of seven reduction processes, at pH values ranging from 2.5–11.5. The reversibility of the electrode processes is demonstrated by cyclic voltammetry and d.p.p. All the reduction processes studied are diffusion-controlled. Mechanisms for these reductions are proposed on the basis of the tautomeric equilibrium associated with the osazone in solution.     

An extension of moments calculations for optical absorption bands

In this paper the developments of Henry, Schnatterly and Slichter are extended by using a more general formulation of the principle of spectroscopic stability (for a site of symmetry O_h). The linear effects for any type of stress are obtained next. The expressions indicate how one can test the theory experimentally in a critical manner. This has not been done. The theory shows that one cannot expect to get more information on KCl from stress experiments than is now available. Finally, it is indicated how one may define the irreducible stresses and strains in an unambiguous manner by using the differential strain-energy function.     

Creating permanent 3D arrangements of isolated cells using holographic optical tweezers

We report the creation of permanent 3D configurations of cells, at predefined positions, within a gelatin matrix. The technique used holographic optical tweezers to manipulate individual E. coli within a solution comprising monomer precursors. The matrix was then set and after the laser beam was removed, we were able to demonstrate that the structures remained intact for many days. We were also able to demonstrate that, in the presence of appropriate nutrients, the E. coli survived within the gelatin matrix for several days. The technique could have a number of potential future applications, including the arrangement of a variety of different cell types in complex architectures, as motifs for promoting tissue differentiation and growth within the field of cell engineering.     

Heat conduction paradox involving second-sound propagation in moving media

In this Letter, we revisit the Maxwell-Cattaneo law of finite-speed heat conduction. We point out that the usual form of this law, which involves a partial time derivative, leads to a paradoxical result if the body is in motion. We then show that by using the material derivative of the thermal flux, in lieu of the local one, the paradox is completely resolved. Specifically, that using the material derivative yields a constitutive relation that is Galilean invariant. Finally, we show that under this invariant reformulation, the system of governing equations, while still hyperbolic, cannot be reduced to a single transport equation in the multidimensional case.     

Charge symmetry breaking in np-->dpi(0)

The forward-backward asymmetry in np-->dpi(0), which must be zero in the center-of-mass system if charge symmetry is respected, has been measured to be [17.2+/-8.0(stat)+/-5.5(syst)]x10(-4), at an incident neutron energy of 279.5 MeV. This observable is compared to recent chiral effective field theory calculations, with implications regarding the du quark mass difference.     

Stochastic path integral formulation of full counting statistics

We derive a stochastic path integral representation of counting statistics in semiclassical systems. The formalism is introduced on the simple case of a single chaotic cavity with two quantum point contacts, and then further generalized to find the propagator for charge distributions with an arbitrary number of counting fields and generalized charges. The counting statistics is given by the saddle-point approximation to the path integral, and fluctuations around the saddle point are suppressed in the semiclassical approximation. We use this approach to derive the current cumulants of a chaotic cavity in the hot-electron regime.     

ITQ-12: a new microporous silica polymorph potentially useful for light hydrocarbon separations

The new synthetic form of microporous crystalline silica, denoted as ITQ-12, shows a high potential for the separation of propane and propene from its mixtures.