Polarization induced electronic processes in a quantum well

Analysis of the electronic states in two dimensional systems is of considerable interest for the exclusive use of 2D systems in microelectronic devices as well as for the close relation of this problem to investigations of the some quantum effects. In microelectronic devices, the coupling between the electron 2D subsystem and polarization (induced or spontaneous) is often effectuated by depositing a lattice on the surface of a film with the 2D gas. In this case, the electrons are subjected to an external (or internal) periodic potential, which makes it possible to investigate the electron spectrum in such system. In present paper, the spectrum of the electronic states in an infinitely deep two dimensional asymmetric potential well, where one wall is periodically rough, is investigated theoretically. It is shown that in non-Bragg type resonances arise in such well. The resonances occur in a wide range of energies, starting at values close to the bottom in each 2D sub-band. The resonance interaction splits the energy spectrum and results in the appearance of gaps, giving the electron spectrum a mini-band character. The properties of the electron gas vary substantially in accordance with the new characteristics of the spectrum

Phase transition and energy spectra of some ferroelectrics-ferroelastics

We report the results of electronic structure calculations for several types of MoO4-clusters in the Gd2(MoO4)3 structure in ferroelectric and paraelectric phase by using cluster ab initio restricted Hartree Fock method. The results give a variational approximation to the ground state electron densities of these clusters within the framework of ab initio restricted Hartree Fock (RHF) MO LCAO method

Cluster ab initio calculations of the shape of local potential well and of positions for oxygen atoms in PCN (C=Cd)

Potential relief and equilibrium positions for oxygen atoms in Cd - O - Nb, Cd - O - Cd and Nb - O - Nb chains are studied in Pb(Cd 1/3 Nb 2/3 )O 3 (PCN) and Ba(Cd 1/3 Nb 2/3 )O 3 (BCN). Total energy cluster calculations are performed using ab initio restricted Hartree-Fock method. The electron correlation contribution is calculated within Møller-Plesset method. It is revealed that in PCN the oxygen atoms in Cd - O - Cd and Cd - O - Nb chains move in multi-well potentials with four minima shifted transversely to fourfold [001] axis. Whereas the oxygen atom in Nb - O - Nb chain in PCN and all oxygen atoms in BCN move in single-well potentials. © 2003 Taylor & Francis.?????????? ???? ??????????????? ???????????? (????): 00-02-16919, 01-02-17801We are indebted to L. S. Kamzina and N. T. Krainik for many stimulating and useful discussions. Supported by the TUBITAK (UNISTAR Umbrella Project) and by Russian Foundation for Basic Research (Grants No. 00-02-16919 and No. 01-02-17801)

RImCom: raster-order image compressor for embedded video applications

Due to copyright restrictions, the access to the full text of this article is only available via subscription.This paper presents a real-time, rate controlled, end-to-end (encoder and decoder) hardware solution for memory compression of raster-order video streams—named RImCom (short for Raster-order Image Compression). RImCom offers up to 3x compression that is either lossless or lossy at very reasonable PSNR values. The 180 nm ASIC implementation of RImCom achieves 28 fps at Ultra-HD resolution in the slow corner of synthesis. RImCom can match the fps of the state-of-the-art in the literature with 20 % less area or can achieve twice the fps with 55 % more area. Our FPGA implementation is the only end-to-end FPGA solution in the literature to achieve to this day over 60 fps at Full-HD resolution and to offer rate control. This work was motivated by video processing applications that require the previous frame(s) besides the current frame. When processing HD video streams, even when only one previous frame is required besides the current frame, a significant size and bandwidth of memory is needed. If the current frame is compressed on-the-fly with RImCom or a similar solution and stored on DRAM, and the previous frame is read from DRAM and decompressed with a small IP block, then the overall system cost, power consumption, and electromagnetic radiation are reduced

Vancomycin, high level aminoglycoside and other antimicrobial resistance of enterococci isolated from stools of hospitalized patients

Enterococci are among the principle causative agents of nosocomial infections which could be reliably treated with vancomycin. However, recently vancomycin-resistant strains are reported. Since the gastrointestinal tractus is the reservoir for enterococci we collected stool samples from patients in the intensive care units and other clinics where enterococcal resistance is likely due to frequent antibiotic administration. We isolated 115 strains from 144 stool samples. Resistance percentages were 6.1% to penicillin and imipenem, 8.6% to ciprofloxacin, 6.1% to norfloxacin, 17.3% to nitrofurantoin. None of the strains were to vancomycin-resistant or producing beta-lactamase. High-level aminoglycoside resistance was found 21.7% to streptomycin, 9.5% to gentamicin. Our results showed that enterococcal strains recruited in our hospital are susceptible to vancomycin, but revealed considerable resistance to other antimicrobials

Antimicrobial resistance patterns of the pathogenic bacteria isolated from stool cultures of patients with acute diarrhea in Istanbul, Turkey

We isolated 1153(24.8%) pathogenic bacteria from 4741 stool samples of diarrheic patients. The distribution of bacteria were as follows: 531(46%) Shigella spp., 197(17.1%) non-typhoid Salmonella, 10(0.86%) S. typhi, 140(12%) Aeromonas spp., 120(10.4%) EPEC and 155(13%) Campylobacter. spp. Antimicrobial resistance of these strains except Campylobacter spp. were assessed by disc diffusion method. Many strains of Salmonella, Shigella, Aeromonas genera and EPEC were resistant to ampicillin and sulbactam-ampicillin(20-97%), cotrimoxazole(10-45%). The strains were variably resistant to cefotaxime or ceftriaxone(0-34%), gentamicin(0-30%), tetracycline(20-53%), chloramphenicol (20-48%). All of them were susceptible to ciprofloxacin and imipenem. Our results show that multi-drug resistant Salmonella and Shigella strains are becoming prevalent in Istanbul and that quinolones may be preferred for empirical therapy

Synaptic Organization of the Human Temporal Lobe Neocortex as Revealed by High-Resolution Transmission, Focused Ion Beam Scanning, and Electron Microscopic Tomography

Modern electron microscopy (EM) such as fine-scale transmission EM, focused ion beam scanning EM, and EM tomography have enormously improved our knowledge about the synaptic organization of the normal, developmental, and pathologically altered brain. In contrast to various animal species, comparably little is known about these structures in the human brain. Non-epileptic neocortical access tissue from epilepsy surgery was used to generate quantitative 3D models of synapses. Beside the overall geometry, the number, size, and shape of active zones and of the three functionally defined pools of synaptic vesicles representing morphological correlates for synaptic transmission and plasticity were quantified. EM tomography further allowed new insights in the morphological organization and size of the functionally defined readily releasable pool. Beside similarities, human synaptic boutons, although comparably small (approximately 5 µm), differed substantially in several structural parameters, such as the shape and size of active zones, which were on average 2 to 3-fold larger than in experimental animals. The total pool of synaptic vesicles exceeded that in experimental animals by approximately 2 to 3-fold, in particular the readily releasable and recycling pool by approximately 2 to 5-fold, although these pools seemed to be layer-specifically organized. Taken together, synaptic boutons in the human temporal lobe neocortex represent unique entities perfectly adapted to the “job” they have to fulfill in the circuitry in which they are embedded. Furthermore, the quantitative 3D models of synaptic boutons are useful to explain and even predict the functional properties of synaptic connections in the human neocortex