Nonlinear acoustic waves in channels with variable cross sections

The point symmetry group is studied for the generalized Webster-type equation describing non-linear acoustic waves in lossy channels with variable cross sections. It is shown that, for certain types of cross section profiles, the admitted symmetry group is extended and the invariant solutions corresponding to these profiles are obtained. Approximate analytic solutions to the generalized Webster equation are derived for channels with smoothly varying cross sections and arbitrary initial conditions.Comment: Revtex4, 10 pages, 2 figure. This is an enlarged contribution to Acoustical Physics, 2012, v.58, No.3, p.269-276 with modest stylistic corrections introduced mainly in the Introduction and References. Several typos were also correcte

Contents of heavy metals in fructicose epiphytic lichens of Karelia as indicator of atmospheric transport of pollutants

Results of studies of heavy metals contents in fruticose epiphytic lichens in Karelia are presented and the influence of different sources on the elemental composition of lichens has been estimated. It has been shown, that long-range atmospheric transport influences strongly the accumulation of Pb, Zn, Cd, Sb. For Al, Fe and Co lithogenic source is the main one. In the Northern Karelia atmospheric transport of Cu, Co and Ni from metallurgic enterprises of the Murmansk Region is important source of these elements

Optical properties of graphene-based materials in transparent polymer matrices

This paper was published in the journal, Applied Physics Letters [© American Institute of Physics]. It is also available at: http://dx.doi.org/10.1063/1.4961674Different aspects of graphene-based materials (GBMs) and GBM-nanocomposites have been investigated due to their intriguing features; one of these features is their transparency. Transparency of GBMs has been of an interest to scientists and engineers mainly with regard to electronic devices. In this study, optical transmittance of structural, purpose-made nanocomposites reinforced with GBMs was analyzed to lay a foundation for optical microstructural characterization of nanocomposites in future studies. Two main types of GBM reinforcements were studied, graphene oxide (GO) and graphite nanoplates (GNPs). The nanocomposites investigated are GO/poly(vinyl alcohol), GO/sodium alginate, and GNP/epoxy with different volume fractions of GBMs. Together with UV-visible spectrophotometry, image-processing-assisted micro and macro photography were used to assess the transparency of GBMs embedded in the matrices. The micro and macro photography methods developed were proven to be an alternative way of measuring light transmittance of semi-transparent materials. It was found that there existed a linear relationship between light absorbance and a volume fraction of GBMs embedded in the same type of polymer matrices, provided that the nanocomposites of interest had the same thicknesses. This suggests that the GBM dispersion characteristics in the same type of polymer are similar and any possible change in crystal structure of polymer due to different volumetric contents of GBM does not have an effect on light transmittance of the matrices. The study also showed that the same types of GBMs could display different optical properties in different matrix materials. The results of this study will help to develop practical microstructural characterization techniques for GBM-based nanocomposites

Neutron-capture elements in halo, thick-disk, and thin-disk stars. Strontium, yttrium, zirconium, cerium

We derived Sr, Y, Zr, and Ce abundances for a sample of 74 cool dwarfs and subgiants with iron abundances, [Fe/H], between 0.25 and -2.43. These estimates were obtained using synthetic spectra, assuming local thermodynamic equilibrium (LTE) for Y, Zr, and Ce, allowing for non-LTE conditions for Sr. We used high-resolution (λ/Δλ≈40 000 and 60 000) spectra with signal-to-noise ratios between 50 and 200. We find that the Zr/Y, Sr/Y, and Sr/Zr ratios for the halo stars are the same in a wide metallicity range (-2.43 ≤ [Fe/H] ≤ -0.90), within the errors, indicating a common origin for these elements at the epoch of halo formation. The Zr/Y ratios for thick-disk stars quickly decrease with increasing Ba abundance, indicating a lower rate of production of Zr compared to Y during active thick-disk formation. The thick-disk and halo stars display an increase in the [Zr/Ba] ratio with decreasing Ba abundance and a correlation of the Zr and Eu overabundances relative to Ba. The evolutionary behavior of the abundance ratios found for the thick-disk and halo stars does not agree with current models for the Galaxy's chemical evolution. The abundance ratios of Y and Zr to Fe and Ba for thin-disk stars, as well as the abundance ratios within each group, are, on average, solar, though we note a slight decrease of Zr/Ba and Zr/Y with increasing Ba abundance. These results provide evidence for a dominance of asymptotic-giant-branch stars in the enrichment of the interstellar medium in heavy elements during the thin-disk epoch, in agreement with the predictions of the nucleosynthesis theory for the main s-process component. © 2007 Pleiades Publishing, Ltd

Lattice Boltzmann simulations in microfluidics: probing the no-slip boundary condition in hydrophobic, rough, and surface nanobubble laden microchannels

In this contribution we review recent efforts on investigations of the effect of (apparent) boundary slip by utilizing lattice Boltzmann simulations. We demonstrate the applicability of the method to treat fundamental questions in microfluidics by investigating fluid flow in hydrophobic and rough microchannels as well as over surfaces covered by nano- or microscale gas bubbles.Comment: 11 pages, 6 figure

Evaluation of the efficacy and safety of the hybrid scheme for eradication therapy of Helicobacter pylori infection

The aim is to conduct a comprehensive comparative study of the efficacy and safety of the hybrid scheme of eradication therapy (ET) in patients with peptic ulcer of the stomach or duodenum associated with Helicobacter pylori. Materials and methods. In a prospective, randomized comparative study, 180 patients were divided into three equal groups of 60 people, depending on the prescribed 10-day ET regimen. Group 1 - the standard triple scheme (omeprazole, amoxicillin and clarithromycin); group 2 - four-component therapy with preparations of bismuth (omeprazole, tetracycline, metronidazole, bismuth tricalium dicitrate); group 3 - hybrid scheme (first 5 days: omeprazole and amoxicillin, the next 5 days: omeprazole, amoxicillin, clarithromycin, metronidazole). The effectiveness of ET was determined with the help of a breath test a month after the end of therapy. Adverse events were recorded by patients in specially developed diaries. Pharmacoeconomic analysis was carried out using the "cost-effectiveness" method with calculation of the CER coefficient. Results and discussion. The effectiveness of standard triple therapy was 73.3% (ITT), 75.9% (PP); four-component therapy with bismuth preparations - 78.3% (ITT), 82.4% (PP); hybrid scheme - 85% (ITT), 91% (PP). Hybrid therapy proved to be significantly more effective than standard triple therapy with a odds ratio (OR) of 3.25; 95% confidence interval (CI) 1.08-9.73 (p=0.043, χ2=4.75, p-level=0.029298). The incidence of adverse events with the use of triple, four-component and hybrid ET regimens was 15; 18.3 and 28.3% respectively. The OR of at least one adverse event in patients receiving a hybrid ET regimen compared with triple therapy was 2.24 (95% CI 0.91-5.53, p=0.0823, χ2=3.14, p-level=0.076394), and compared with the four-component therapy - 1.76 (95% CI 0.74-4.17, p=0.2804, χ2=1.68, p-level=0.194924). According to the results of the pharmacoeconomic analysis, the most profitable from an economic point of view was a hybrid ET scheme with a CER of 20.1. The conclusion. Hybrid therapy showed the greatest effectiveness in comparison with the triple and four-component ET regimens, however, the incidence of side effects in patients receiving the hybrid ET scheme was higher, although it remained within the acceptable level for use in clinical practice. Pharmacoeconomic analysis also showed the advisability of designating a hybrid ET scheme. The obtained data allow to draw a conclusion about the necessity of further study of the efficiency and safety of the hybrid ET scheme

HYGIENIC VALUE OF VITAMIN D DEFICIENCY IN IRKUTSK REGION AND WAYS OF ITS PREVENTION

The status of vitamin D in the population of Irkutsk region has been determined by the contents of 25(OH)D3 in blood serum of268 people of different age. The highest rates were found in children - 37,78 ± 1,74 ng/ml. In men the level of activity of 25(OH)D3 was equal to 24,64 ± 2,33 ng/ml, in women up to 70years - 21,22 ± 0,85, older than 70 years -15,13 ± 2,24 ng/ml. The lowest rates are found in children with celiac disease -13,43 ± 2,14. More than 60 % of the population suffer from vitamin D deficiency. Yet wide-scale preventive measures are not possible due to limited range offortified food in the trade network

Multifaceted Mechanism of Amicoumacin A Inhibition of Bacterial Translation

Amicoumacin A (Ami) halts bacterial growth by inhibiting the ribosome during translation. The Ami binding site locates in the vicinity of the E-site codon of mRNA. However, Ami does not clash with mRNA, rather stabilizes it, which is relatively unusual and implies a unique way of translation inhibition. In this work, we performed a kinetic and thermodynamic investigation of Ami influence on the main steps of polypeptide synthesis. We show that Ami reduces the rate of the functional canonical 70S initiation complex (IC) formation by 30-fold. Additionally, our results indicate that Ami promotes the formation of erroneous 30S ICs; however, IF3 prevents them from progressing towards translation initiation. During early elongation steps, Ami does not compromise EF-Tu-dependent A-site binding or peptide bond formation. On the other hand, Ami reduces the rate of peptidyl-tRNA movement from the A to the P site and significantly decreases the amount of the ribosomes capable of polypeptide synthesis. Our data indicate that Ami progressively decreases the activity of translating ribosomes that may appear to be the main inhibitory mechanism of Ami. Indeed, the use of EF-G mutants that confer resistance to Ami (G542V, G581A, or ins544V) leads to a complete restoration of the ribosome functionality. It is possible that the changes in translocation induced by EF-G mutants compensate for the activity loss caused by Ami.Russian Foundation for Basic ResearchRevisión por pare