Wrocław University of Technology

About: Wrocław University of Technology is a education organization based out in Wrocław, Poland. It is known for research contribution in the topics: Laser & Computer science. The organization has 13115 authors who have published 31279 publications receiving 338694 citations.

Phenylalanine ammonia-lyase: the use of its broad substrate specificity for mechanistic investigations and biocatalysis--synthesis of L-arylalanines.

Abstract: Several fluoro- and chlorophenylalanines were found to be good substrates of phenylalanine ammonia-lyase (PAL/EC 4.3.1.5) from parsley. The enantiomerically pure L-amino acids were obtained in good yields by reaction of the corresponding cinnamic acids with 5M ammonia solution (buffered to pH 10) in the presence of PAL. The kinetic constants for nine different fluoro- and chlorophenylalanines do not provide a rigorous proof for but are consistent with the previously proposed mechanism comprising an electrophilic attack of the methylidene-imidazolone cofactor of PAL at the aromatic nucleus as a first chemical step. In the resulting Friedel-Crafts-type sigma complex the beta-protons are activated for abstraction and consequently the pro-S is abstracted by an enzymic base. Results from semi-empirical calculations combined with a proposed partial active site model showed a correlation between the experimental kinetic constants and the change in polarization of the pro-S Cbeta-H bond and heat of formation of the sigma complexes, thus making the electrophilic attack at the neutral aromatic ring plausible. Furthermore, while 5-pyrimidinylalanine was found to be a moderately good substrate of PAL, 2-pyrimidinylalanine was an inhibitor.

Conflict Resolution in Free-Ranging Multivehicle Systems: A Resource Allocation Paradigm

Abstract: We propose a novel paradigm for conflict resolution in multivehicle traffic systems, where a number of mobile agents move freely in a finite area, with each agent following a prespecified-motion profile. The key idea behind the proposed method is the tessellation of the underlying motion area in a number of cells and the treatment of these cells as resources that must be acquired by the mobile agents for the execution of their motion profiles, according to an appropriate resource allocation protocol. We capitalize upon the existing literature on the real-time management of sequential resource allocation systems (RASs) and develop such protocols that can formally guarantee the safe and live operation of the underlying traffic system, while they remain scalable with respect to the number of the moving agents. Collective past experience with the considered policies indicates that they also provide a pretty large coverage of the RAS behavioral space that characterizes its safe and live operation. Finally, we also establish that the aforementioned approach is applicable even in traffic systems where all vehicles must be in perpetual motion until their retirement.

``Troublesome'' Vibrations of Aromatic Molecules in Second-Order Möller-Plesset and Density Functional Theory Calculations: Infrared Spectra of Phenol and Phenol-OD Revisited

Abstract: The infrared spectra of phenol and phenol-OD are thoroughly reinvestigated, to resolve the contradictory assignment of some vibrations. The harmonic frequencies, integrated IR intensities, and potential energy distribution (PED) have been calculated by the B3LYP method with the 6-311++G(df,pd) basis set. The Fourier transform infrared (FT-IR) spectra of phenol and phenol-OD have been measured in carbon tetrachloride and cyclohexane solutions, in the frequency range 3700−400 cm-1, and the experimental integrated infrared intensities are reported. On the basis of the results obtained, the detailed assignment of all the fundamental modes of Ph-OH and Ph-OD are presented. The study demonstrates that density functional B3LYP is clearly superior to the ab initio Hartree−Fock (HF) and second-order Moller−Plesset (MP2) methods in reliable prediction of the vibrational spectra of phenol. In particular, it is shown that scaling of the B3LYP-calculated frequencies of the CH and OH(OD) stretching vibrations by the sc...

Power system harmonics estimation using linear least squares method and SVD

Abstract: The paper examines the singular value decomposition (SVD) for estimation of harmonics in signals, in the presence of high noise. The proposed approach results in a linear least squares method. The methods developed for locating the frequencies as closely spaced sinusoidal signals are appropriate tools for the investigation of power system signals containing harmonics and interharmonics differing significantly in their multiplicity. The SVD approach is a numerical algorithm to calculate the linear least squares solution. The methods can also be applied for frequency estimation of heavy distorted periodical signals. To investigate the methods several experiments have been performed using simulated signals and the waveforms of a frequency converter current. For comparison, similar experiments have been repeated using the FFT with the same number of samples and sampling period. The comparison has proved superiority of the SVD for signals buried in the noise. However, the SVD computation is much more complex than FFT, and requires more extensive mathematical manipulations.