Enantiomer separations in capillary electrophoresis in the case of equal binding constants of the enantiomers with a chiral selector: commentary on the feasibility of the concept

It is generally acknowledged that enantiomer separations in capillary electrophoresis are based on differences in the affinities of the analyte enantiomers toward the chiral selector expressed as equilibrium constants of the resulting temporary diastereomeric associates. However, as can be derived from theoretical considerations, a separation of enantiomers by CE is in principle also possible solely based on differences in the mobilities of the temporary diastereomeric complexes per se, when equal binding constants between analyte enantiomers and the chiral selector are assumed and observed.     

Volatile compound analysis of SPME headspace and extract samples from roasted Italian chestnuts (<Emphasis Type="Italic">Castanea sativa</Emphasis> Mill.) using GC-MS

The volatile flavor compounds of roasted Italian chestnuts, which have not been studied prior to this report, were determined by capillary gas-chromatography with a mass selective detector. Samples were obtained by SPME directly from the headspace of freshly roasted and ground chestnuts as well as by previous extraction with dichloromethane. Monoterpenes and derivatives of butane, pentane, hexane, and heptane were identified as important aroma impact compounds. -Butyrolactone (12.8%), -terpinene (9.2%), furfural (6.3%), benzaldehyde (7.2%) and 4-methyl-2-pentanone (5.3%) were found in concentrations higher than 5.0% (calculated as % peak area of GC-MS analysis using a nonpolar column).     

Effect of annealing of poly(3-hexylthiophene)/fullerene bulk heterojunction composites on structural and optical properties

Composite films of P3HT/PCBM-(poly[3-2,5-diyl]/[6,6]-phenyl C₆₁ butyric acid methyl ester) are widely used as an active layer in plastic solar cells. We have studied the influence of thermal annealing on nano-structural and optical properties of thin spin-coated P3HT/PCBM-films. Their structural properties were studied by X-ray diffraction in grazing incidence geometry. It was found that the crystallinity of the investigated films is drastically increased upon annealing. Furthermore, the anisotropic dielectric function of such films was determined by spectroscopic ellipsometry. Significant changes were observed both in parallel and perpendicular components of the dielectric function after annealing. These changes were attributed to the formation of crystalline domains upon annealing.     

On Enhancing SIMD-controlled DSPs for Performing Recursive Filtering

Many digital signal processors (DSPs) and also microprocessors are employing the single-instruction multiple-data (SIMD) paradigm for controlling their data paths. Although the SIMD paradigm can provide high computational power and efficiency, not all applications can profit from this feature. One important application, particularly in audio processing, of DSPs are recursive (IIR) filters. Due to their data-dependencies they can not exploit the capabilities of SIMD-controlled DSPs as non-recursive (FIR) filters can. This paper shows, how the SIMD control scheme can be enhanced to accommodate recursive filters without introducing much hardware overhead. Three methods for calculating recursive filters on SIMD-controlled DSPs and their requirements for control and data transfer are presented. They can be applied to direct-form as well as cascade-form realizations. The performance and hardware requirements of these methods are evaluated to determine the most efficient solution in terms of the AT-product. An erratum to this article is available at .     

Synthesis,Structure, Molecular Orbital Calculations and Decomposition Mechanism for Tetrazolylazide CHN7, its Phenyl Derivative PhCN7 and Tetrazolylpentazole CHN9

Experimental and theoretical data for 5‐azidotetrazole CHN₇ and its phenyl derivative 5‐azido‐1‐phenyltetrazole as well as tetrazolylpentazole are reported. We discuss their syntheses, their properties and the X‐ray structures of 5‐azidotetrazole and its phenyl derivative. The decomposition reactions of tetrazolylpentazole and 5‐azidotetrazole were also investigated. We furthermore calculated the electrostatic potentials of 5‐azidotetrazole, its methyl and phenyl derivatives and of tetrazolylpentazole to determine the relative sensitivity of these compounds.     

Quality-of-Service Analysis for Statistical Multiplexing with Gaussian Distributed and Autoregressive Input

We investigate multiplexers in telecommunication systems with a workload process developing equivalent to that of a service system with semi-Markovian input, which includes fluid flow and time slotted systems. Discrete time methods are used to analyze their waiting time and loss rate.Our focus is on the performance evaluation of statistical multiplexing. Traffic flows are modeled by autoregressive processes producing autocorrelated and Gaussian distributed workload increases. The superposition of on-off voice sources approaches autoregressive processes and they also serve as a basic model for video traffic in an appropriate time scale, although video reveals a more complex autocorrelation structure. Performance results are obtained depending on only two parameters, which allow for clear conclusions about the statistical multiplexing gain with regard to bounds on loss rates as demanded in quality-of-service guarantees.     

SPME/GC/MS analysis of headspace aroma compounds of the Cameroonian fruit Tetrapleura tetraptera (Thonn.) Taub.

The aroma components of fresh and dried fruit shell of Tetrapleura tetraptera (Thonn.) Taub. (Mimosaceae) from Cameroon were analyzed by GC/FID, GC/MS, SPME/GC/FID, SPME/GC/MS, and olfactometry. The headspace is characterized by a high percentage of lower acids and esters. The main compounds in the SPME-headspace samples are 2-methylbutanoic acid (8.1%-14.5%), 2-methylbutenoic acid (3.5%-5.4%), acetic acid (13.0%-48.2%), butanoic acid (1.9-9.5%), 2-methylbutanoic acid ethyl ester (1.4%-3.4%), and 2-methylbutenoic acid ethyl ester (0.9%-10.3%) as well as 3-methylbutanone (0.3%-3.9%), butanol (0.4%-4.6%), 2-hydroxy-3-butanone (8.1%-31.6%), and 2-methylbutanol (3.6%-6.1%). Additional information on volatiles of an oleo-resin and a headspace sample from dried T. tetraptera fruits has been given and the analytical data correlated with olfactoric impressions to provide information about the aroma compounds responsible for the characteristic odour impression of these fruit samples.     

Turbo processing in transmit antenna diversity systems

We consider turbo-trellis-coded transmission over fading multiple-input-multiple-output (M1M0) channels with transmit diversity using space-time block codes. We give a new view on space-time block codes as a transformation of the fading MIMO channel towards a Gaussian single-input-single-output (siso) channel and provide analytical results on the BER of space-time block codes. Furthermore, we describe the concatenation of Turbo-TCM with a space-time block code and show that in addition to the transmit diversity substantial benefits can be obtained by turbo iterations as long as the channel is time-varying during transmission of a coded block or frequency hopping is applied. Finally, a double iterative scheme for turbo equalization and turbo decoding of the concatenation of Turbo-TCM and space-time block code in frequency-selective MIMO channels is described.