Changes in the Cardiotoxic Effects of Lead Intoxication in Rats Induced by Muscular Exercise

Exposure to lead is associated with an increased risk of cardiovascular diseases. Outbred white male rats were injected with lead acetate intraperitoneally three times a week and/or were forced to run at a speed of 25 m/min for 10 min 5 days a week. We performed noninvasive recording of arterial pressure, electrocardiogram and breathing parameters, and assessed some biochemical characteristics. Electrophoresis in polyacrylamide gel was used to determine the ratio of myosin heavy chains. An in vitro motility assay was employed to measure the sliding velocity of regulated thin filaments on myosin. Isolated multicellular preparations of the right ventricle myocardium were used to study contractility in isometric and physiological modes of contraction. Exercise under lead intoxication normalized the level of calcium and activity of the angiotensin-converting enzyme in the blood serum, normalized the isoelectric line voltage and T-wave amplitude on the electrocardiogram, increased the level of creatine kinase-MB and reduced the inspiratory rate. Additionally, the maximum sliding velocity and the myosin heavy chain ratio were partly normalized. The effect of exercise under lead intoxication on myocardial contractility was found to be variable. In toto, muscular loading was found to attenuate the effects of lead intoxication, as judged by the indicators of the cardiovascular system.     

Microstructural characteristics of an ultrafine grain metal processed with equal-channel angular pressing

Equal-channel angular pressing is a procedure for producing a fully dense material with an ultrafine grain size, typically in the submicrometer or nanometer range, by subjecting the material to a very high plastic strain. This paper describes the principle of equal-channel angular pressing and illustrates the capability of the technique by reference to a series of detailed experiments conducted on an Al-3%Mg solid solution alloy in which the grain size was successfully reduced by equal-channel angular pressing from an initial size of ˜500 μm in the hot-rolled condition to a final size of ˜0.2 μm.     

Robust nonlinear sampled‐data system analysis based on Fridman's method and S‐procedure

This paper is devoted to the evaluation of sampling interval providing robust exponential stability of nonlinear system with sector‐bounded nonlinearities. It extends our previous results (R. E. Seifullaev, A. L. Fradkov. Sampled‐data control of nonlinear oscillations based on LMIs and Fridman's method. In 5th IFAC International Workshop on Periodic Control Systems, 95‐100. Caen, France. 2013). The proposed approach exploits E. Fridman's method for linear systems based on a general time‐dependent Lyapunov–Krasovskii functional. With classical results of V. A. Yakubovich about S‐procedure, the problem is reduced to feasibility analysis of linear matrix inequalities. The results are illustrated by example: the pendulum system with friction and sector‐bounded multiple nonlinearities. Copyright © 2015 John Wiley & Sons, Ltd.     

Receptivity of boundary layers to distributed wall vibrations

Linear three-dimensional receptivity of boundary layers to distributed wall vibrations in the large Reynolds number limit (Re-->infinity) is studied in this paper. The fluid motion is analysed by means of the multiscale asymptotic technique combined with the method of matched asymptotic expansions. The body surface is assumed to be perturbed by small-amplitude oscillations being tuned in resonance with the neutral Tollmien-Schlichting wave at a certain point on the wall. The characteristic length of the resonance region is found to be O(Re-3/16), which follows from the condition that the boundary-layer non-parallelism and the wave amplitude growth have the same order of magnitude. The amplitude equation is derived as a solvability condition for the inhomogeneous boundary-value problem. Investigating detuning effects, we consider perturbations in the form of a wave packet with a narrow O(Re-3/16) discrete or continuous spectrum concentrated near the resonant wavenumber and frequency. The boundary-layer laminarization based on neutralizing the oncoming Tollmien-Schlichting waves (or wave packets) is also discussed.     

Impact Toughness of Ultrafine‐Grained Commercially Pure Titanium for Medical Application

This study aims at achieving the best combination of strength, ductility, and impact toughness in ultrafine‐grained (UFG) Ti Grade 4 produced by equal‐channel angular pressing via Conform scheme (ECAP‐C) with subsequent cold drawing. UFG structures with various parameters (e.g., size and shape of grains, dislocation density, conditions of boundaries) are formed by varying the treatment procedures (deformation temperature and speed at drawing, annealing temperature). The tensile and impact toughness tests were performed on samples with a V‐shaped notch and different structures of commercially pure Ti Grade 4 in the coarse‐grained and UFG states. The results demonstrated that grain refinement, higher dislocation density, and their elongated shape were obtained as a result of drawing at 200 °С, which led to a decrease in both the uniform elongation at tension and the impact toughness of Ti Grade 4. Short‐term annealing at 400–450 °C could improve the impact toughness of UFG Ti with a non‐significant decrease in strength. This short‐term annealing contributes to the dislocation density decrease without considerable grain growth as a result of the recovery and redistribution of dislocations. The dependence of impact toughness on the strain hardening ability of UFG Ti was discussed.

     

Hybrid Organic–Inorganic Halide Post-Perovskite 3-Cyanopyridinium Lead Tribromide for Optoelectronic Applications

2D halide perovskite-like semiconductors are attractive materials for various optoelectronic applications, from photovoltaics to lasing. To date, the most studied families of such low-dimensional halide perovskite-like compounds are Ruddlesden–Popper, Dion–Jacobson, and other phases that can be derived from 3D halide perovskites by slicing along different crystallographic directions, which leads to the spatially isotropic corner-sharing connectivity type of metal-halide octahedra in the 2D layer plane. In this work, a new family of hybrid organic–inorganic 2D lead halides is introduced, by reporting the first example of the hybrid organic–inorganic post-perovskite 3-cyanopyridinium lead tribromide (3cp)PbBr₃. The post-perovskite structure has unique octahedra connectivity type in the layer plane: a typical “perovskite-like” corner-sharing connectivity pattern in one direction, and the rare edge-sharing connectivity pattern in the other. Such connectivity leads to significant anisotropy in the material properties within the inorganic layer plane. Moreover, the dense organic cation packing results in the formation of 1D fully organic bands in the electronic structure, offering the prospects of the involvement of the organic subsystem into material's optoelectronic properties. The (3cp)PbBr₃ clearly shows the 2D quantum size effect with a bandgap around 3.2 eV and typical broadband self-trapped excitonic photoluminescence at temperatures below 200 K.     

Concentrations and Source Identification of Polycyclic Aromatic Hydrocarbons (PAHs) in Mangrove Sediments from North of Persian Gulf

The concentrations of 16 Environmental Protection Agency (EPA) priority polyaromatic hydrocarbons (PAHs) were quantified in surface sediments from Hormozgan Province mangroves, south of Iran in dry and wet seasons. Sampling stations were selected in Laft and Khamir mangroves with international importance. Polyaromatic hydrocarbons varied from 75.24 ± 11.24 to 581.94 ± 637.39 ng/g dry weight basis. Pollution sources and their contribution for polyaromatic hydrocarbons pollution in sediments of Hormozgan mangroves were appointed based on molecular ratios and statistical methods, including principal components analysis (PCA) and multiple linear regression/principal components analysis (PCA/MLR) tests. Both of pyrogenic and petrogenic sources contributed in detected concentrations of PAHs. Contribution percentages of pyrogenic and petrogenic origins were estimated at 73.20 and 26.79%, respectively. Temporal variations showed that sediments contained higher levels of ∑PAHs in wet season than dry time. However, the mean detected ∑PAHs was lower than international quality guidelines; the high concentration of PAHs was found in Laft mangrove, suggesting the presence of PAH polluted localized area.     

Grain refinement in nanostructured Al–Mg alloys subjected to high pressure torsion

Nanostructures of three binary Al–Mg alloys and a commercial AA5182 alloy subjected to high pressure torsion at room temperature were comparatively investigated using transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray line profile analysis. Grain size distributions, dislocation densities, and densities of planar defects including stacking faults and microtwins were quantified. The average subgrain size decreased considerably from 120 to 55 nm as the Mg content increased from 0.5 to 4.1 wt%. The average dislocation density in the alloys first increased to a maximum and then decreased as the Mg content increased and the average subgrain size decreased. The role of Mg solute on these features and the refinement mechanisms associated with the typical nanostructures and faults were interpreted.