The xraylib library for X-ray–matter interactions. Recent developments

This work presents the recent developments of xraylib, an ANSI C library that provides convenient access to a large number of X-ray related databases, with a focus on quantitative X-ray fluorescence applications. The enhancements include improved X-ray fluorescence production cross sections that take into account cascade effects and M-lines, as well as revised line energies, atomic level widths, Compton broadening profiles etc. A full overview of the complete application programming interface is presented.     

Linear and non-linear conduction regimes in broken down gate oxides

We have investigated conduction properties of gate oxides in metal-oxide–semiconductor structures in which dielectric breakdown has occurred. The measurements were performed on p- and n-type substrate samples with oxide thickness ranging from 2.0 to 13.5 nm. It is shown that the post-breakdown differential conductance has two typical modes, which, in terms of the physics of mesoscopic conducting systems, are referred to as linear and non-linear conduction regimes. In this work, we propose an analytic model for the conductance based on the electron transmission properties of quantum point contacts, which captures the essential features and consistently explains both breakdown modes.     

Pentafluorobenzaldehyde and its utilizing in organic synthesis

Over the past 50 years, pentafluorobenzaldehyde has received much attention due to its unique chemical and physical properties as well as its real or potential applications in chemistry of porphyrines, additives, drug delivery and in analytical chemistry. Pentafluorobenzaldehyde is multifunctional aromatic compound containing five atoms of fluorine and one aldehydic function. That is why it can provide nucleophilic substitutions of all or some atoms of fluorine, nucleophilic additions of aldehydic function, “haloform reaction” and some cyclization reactions. This year, it is being the 50th year, since the first synthesis of this compound was published.     

On the Statistical Mechanics and Surface Tensions of Binary Mixtures

Within a lattice model describing a binary mixture with fixed concentrations of the species we discuss the relationship between the surface tension of the mixture and the concentrations.     

Crystalline structure of sequential poly(ester amide)s derived from glycolic acid, 1,6‐hexanediamine,and even aliphatic dicarboxylic acids

Basic structural data of two sequential poly(ester amide)s derived from glycolic acid, 1,6‐hexanediamine, and adipic acid or dodecanodioic acid have been determined by means of X‐ray and electron diffraction patterns from fibers and single crystals. Chain‐folded lamellar crystals were obtained by isothermal crystallization from diol or glycerine solutions, and the crystalline habit was investigated by real space electron microscopy. Polyethylene decoration techniques were applied to evaluate the regularity of the folding surfaces. Spherulites prepared from evaporation of formic acid solutions were also studied. The two sequential poly(ester amide)s crystallized according to triclinic and monoclinic unit cells, in which the a crystallographic parameter was close to the typical distance between hydrogen‐bonded chains. Projections viewed down the chain axis revealed differences in the packing mode since oblique and rectangular cells were found for the adipic acid and dodecanodioic acid derivatives, respectively. Both structures can be envisaged as a stacking of hydrogen‐bonded sheets although clear differences concerning the shift between consecutive sheets and the number of layers comprising the unit cell were found. The large unit cells that have been deduced seem to be a consequence of the different packing preferences of the diester and diamide moieties. Both polymers have a molecular conformation that deviates from the all‐trans conformation typical of aliphatic polyamides and polyesters with a large number of methylene groups. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 194–206, 2009     

Analysis of a pressure-stabilized finite element approximation of the stationary Navier-Stokes equations

Summary. The purpose of this paper is to analyze a finite element approximation of the stationary Navier-Stokes equations that allows the use of equal velocity-pressure interpolation. The idea is to introduce as unknown of the discrete problem the projection of the pressure gradient (multiplied by suitable algorithmic parameters) onto the space of continuous vector fields. The difference between these two vectors (pressure gradient and projection) is introduced in the continuity equation. The resulting formulation is shown to be stable and optimally convergent, both in a norm associated to the problem and in the norm for both velocities and pressure. This is proved first for the Stokes problem, and then it is extended to the nonlinear case. All the analysis relies on an inf-sup condition that is much weaker than for the standard Galerkin approximation, in spite of the fact that the present method is only a minor modification of this. Received May 25, 1998 / Revised version received August 31, 1999 / Published online July 12, 2000     

Gasuntersuchungen

Ohne Zusammenfassung