Biomedical subjects

A G Berezin

Publications and source records attributed to A G Berezin.

3 recordsLinked to original sources

PubMed2006

UF6 enrichment measurements using TDLS techniques.

The objective of this work was investigation of possibility of tunable diode laser spectroscopy (TDLS) technique application for gaseous uranium hexafluoride (UF6) isotope measurement. Spectra of uranium hexafluoride gas mixture were investigated using two different Fourier Transform Spectrometers Vector 22 and Bruker 66v. Observed spectral features were identified and model spectra of different gas mixture components were developed. Optimal spectral range for measurements was determined near maximum of UF6 combination band nu1+nu3. Laboratory prototype of multi-channel instrument under consideration based on tunable diode lasers was built and algorithms were developed to measure gaseous UF6 isotopic ratios. Diode laser used operated at the wavelengths near lambda=7.68 microm. It was placed in a liquid nitrogen cooled cryostat. Three instrument channels were used for laser frequency calibration and spectra recording. Instrument was tested in measurements of real UF6 gas mixtures. Measurement accuracy was analyzed and error sources were identified. The root-mean-square random error in the 235U isotopic content is characterized by a spread of about 0.27% for quick measurements (at times less than 1 min) and 1% for periods of more than an hour. It was estimated that the measurement accuracy could be improved by at least an order of magnitude by minimizing the error sources.

Algorithms↗

PubMed2004

[Molecular mechanisms of cephalosporin resistance in Gram-negative bacteria of the Enterobacteriaceae family].

Extended spectrum beta lactamase genes were detected by the PCR in 87.6% of 231 Enterobacteriaceae strains isolated in medical institutions of Moscow, St. Petersburg, Tomsk and Nazran that showed a decrease in their susceptibility to 3rd generation cephalosporins. Alone or in various combinations TEM type beta lactamases were detected in 43.3% of the isolates, 46.8 and 51.2% of the isolates produced SHV type and CTX type beta lactamases respectively. Combinations of 2 and 3 different determinants were detected in 40 and 14% of the isolates respectively. Production of class C beta lactamases was suspected in 28% of the isolates by their resistance to cefoxitin. The gene of ACT type beta lactamase was detected in 1 strain of Klebsiella pneumoniae and the gene of CMY type beta lactamase was detected in 1 strain of Proteus mirabilis. By the NCCLS 100% of the isolates was susceptible to meropenem, 14% was susceptible to cefotaxime, 64% was susceptible to cefepime, 81% was susceptible to cefoperazone/sulbactam, 47% was susceptible to gentamicin, 57% was susceptible to amikacin and 36% was susceptible to ciprofloxacin.

Anti-Bacterial Agents↗

PubMed2003

[Characteristics and clinical value of extended-spectrum beta-lactamases].

The literature data and the findings of the authors' studies on the role of extended-spectrum bata-lactamases (ESBL) in providing the clinical effect in the treatment of infections due to ESBL-producing organisms were analyzed. The analysis allowed to consider the NCCLS recommendations not sufficiently valid. According to these recommendations the ESBL-producing organisms (among E. coli and Klebsiella spp.) should be regarded as resistant to penicillins, cephalosporins and aztreonam. Susceptibility of 62 Enterobacteriaceae strains that were isolated in 4 therapeutic centres of Tomsk, Nazran and Moscow and proved to be ESBL-producing organisms was tested and it was shown that the 3rd and 4th generation cephalosporins could not be referred to a homogenous group. The same was confirmed by the prospective and retrospective investigations of a multiprofile hospital on the clinical and bacteriological efficacies of the 3rd generation cephalosporins and cefepime in the treatment of hospital-acquired infections due to Enterobacteriaceae strains producing ESBL.

Adolescent↗