Improving the accuracy of four-receiver acoustic Doppler velocimeter (ADV) measurements in turbulent boundary layer flows

Acoustic Doppler instrument measurements suffer from random spikes and Doppler noise. Using a four-receiver ADV (acoustic Doppler velocimeter; Vectrino manufactured by Nortek) that allows recording beam velocities, we combine a spike-removal procedure on the beam velocities with a noise-reduction method on the flow velocities to improve turbulence measurements. We compare the results with those obtained from ADVP (acoustic Doppler velocity profiler) measurements under the same conditions, i.e., in turbulent open-channel flow over a coarse-grained bed. It is shown that spikes are best removed from ADV beam velocity data before calculating flow velocities, thereby correcting all three flow velocity components at the source. Spikes in beam velocities do not correlate with low correlation values. ADVP data generally have few spikes and do not need spike removal treatment, showing that spikes are instrument related. The noise reduction method is based on the decorrelation of the Doppler noise terms contained in two vertical velocities redundantly sampled in the same volume. The combined ADV data treatment is sufficient to significantly extend the resolved frequency range in the velocity spectra. It reduces RMS values by up to a factor of 2, and the corrected values agree with ADVP results and theoretical predictions, indicating that both treatments are needed. Owing to spatial averaging effects over the ADV sample volume, a sampling frequency limit of close to 50 Hz is determined by the deviation of the spectra from the -5/3 slope

International Journal of Molecular and Clinical Microbiology Evaluation of Antibiotic Resistance to Fluoroquinolones and Third Generation Cephalosporines in Iranian Clinical Isolates of Salmonella spp

Salmonella enterica serotypes are one of the most important food borne pathogens and significant public health concerns around the world in humans and other animal species. A total of eighty three epidemiologically unrelated clinical isolates of Salmonella enterica serovars were subjected to antimicrobial susceptibility testing. Eleven isolates (13.1%) which were resistant to at least 4 groups of antimicrobial agents considered as multidrug resistant (MDR) Salmonella serovars. Emergence of MDR Salmonella serovars demonstrates that antimicrobial selection pressure is widespread in our clinical settings. According to the results of antimicrobial susceptibility testing, Salmonella clinical isolates are more susceptible to fluoroquinolones and third generation cephalosporins and these drugs may be used as drugs of choice to treat Salmonella infections