Bioindication of natural waters using a histological analysis of the <Emphasis Type="Italic">Carassius Auratus</Emphasis> mesonephros structure

The paper has investigated bioindicator properties of mesonephrosa of goldfish Carassius gibelio Bloch 1782. It has been found a broad spectrum of the action of water-soluble insecticide Bulldog-ES on organs and tissues. The possibility of using a histological criterion for assessing the state of water area has been studied.     

Maximum Average Tangential Stress Criterion for Prediction of the Crack Path

The concept of the average stress has been employed to propose the maximum average tangential stress (MATS) criterion for predicting the direction of fracture angle. This criterion states that a crack grows when the maximum average tangential stress in the fracture process zone ahead of the crack tip reaches its critical value and the crack growth direction coincides with the direction of the maximum average tangential stress along a constant radius around the crack tip. The tangential stress is described by the singular and non-singular (T-stress) terms in the Williams series solution. The predicted directions of fracture angle are consistent with the experimental data for the mixed mode I/II crack growth behavior of Guiting limestone.     

Optothermophysical properties of demineralized human dental enamel determined using photothermally generated diffuse photon density and thermal-wave fields

Noninvasive dental diagnostics is a growing discipline since it has been established that early detection and quantification of tooth mineral loss can reverse caries lesions in their incipient state. A theoretical coupled diffuse photon density and thermal-wave model was developed and applied to photothermal radiometric frequency responses, fitted to experimental data using a multiparameter simplex downhill minimization algorithm for the extraction of optothermophysical properties from artificially demineralized human enamel. The aim of this study was to evaluate the reliability and robustness of the advanced fitting algorithm. The results showed a select group of optical and thermal transport parameters and thicknesses were reliably extracted from the computational fitting algorithm. Theoretically derived thicknesses were accurately predicted, within about 20% error, while the estimated error in the optical and thermal property evaluation was within the values determined from early studies using destructive analyses. The high fidelity of the theoretical model illustrates its efficacy, reliability, and applicability toward the nondestructive characterization of depthwise inhomogeneous sound enamel and complex enamel caries lesions.     

The effective T-stress estimation and crack paths emanating from U-notches

The concept of the T-stress as a local constraint factor has been extended to U-notch tip stress distribution as the effective T-stress. The effective T-stress has been estimated as the average value of the T-stress in the region corresponding to the effective (characteristic) distance ahead of the notch tip. The T-stress is evaluated by finite element method using the experimental load for crack initiation and computing the difference between principal stresses along ligament. A large range of critical effective T-stress values is investigated for different specimen configurations and notch aspect ratios. Crack stabilisation and crack bifurcation for fracture emanating from notches according to the critical effective T-stress is discussed. A model involving the influence of the critical effective T-stress on void growth for ductile failure in the vicinity of the notch tip has been proposed.     

Detection of discontinuities of a metal and a protective coating on pipelines

A technique of diagnostic nondestructive testing is proposed that ensures reliable detection of flaws in the interface of the protective coating on pipelines based on discrimination between discontinuities in the coating and the tube metal.     

Spatial kinetics in fast reactors

The analysis of the solution to the spatial nonstationary equation of neutron transport is presented by the example of a fast reactor. Experiments in spatial kinetics conducted recently at the complex of critical assemblies (fast physical stand) and computations of their data using the TIMER code (for solving the nonstationary equation in multidimensional diffusion approximation for direct and inverse problems of reactor kinetics) have shown that kinetics of fast reactors substantially differs from kinetics of thermal reactors. The difference is connected with influence of the delayed neutron spectrum on rates of the process in a fast reactor.     

The cohesive zone model in a problem of delayed hydride cracking of zirconium alloys

The crack tip model with the cohesive zone ahead of a finite crack tip has been presented. The estimation of the length of the cohesive zone and the crack tip opening displacement is based on the comparison of the local stress concentration, according to Westergaard's theory, with the cohesive stress. To calculate the cohesive stress, von Mises yield condition at the boundary of the cohesive zone is employed for plane strain and plane stress. The model of the stress distribution with the maximum stress within the cohesive zone is discussed. Local criterion of brittle fracture and modelling of the fracture process zone by cohesive zone were used to describe fracture initiation at the hydride platelet in the process zone ahead of the crack tip. It was shown that the theoretical K _IH-estimation applied to the case of mixed plane condition within the process zone is qualitatively consistent with experimental data for unirradiated Zr-2.5Nb alloy. In the framework of the proposed model, the theoretical value of K ^H _IC for a single hydride platelet at the crack tip has been also estimated.     

Polymeric Copper Oxide: Preparation and Investigation of Its Structure and Optical Properties

A complex of polyvinyl alcohol (PVA) with copper hydroxide was used as a precursor to obtain polymeric copper oxide through thermal decomposition. The absence of Cu(OH)₂ crystalline phase was observed for the component ratio up to 1 Cu(OH)₂ molecular unit to 3 PVA residuals. The formation of crystalline copper oxide was not observed after the dehydration of this material. UV–VIS and IR spectroscopy, and computational modeling were used to study the structure and properties of the obtained materials. A comparison with other similar materials was drawn. It was found that experimental data are in general accordance with the computations based on the polymeric model for copper hydroxide/oxide as a component of hybrid interpolymeric complex with PVA. A distinctive feature observed for polymeric copper oxide is strong broadening of the optical absorption band at 400 nm. It is suggested that this effect is caused by strong electron–phonon interaction, which is also responsible for superconductivity of copper oxide based systems.     

Generalized Equation of the Opening of a Through-Thickness Ring Crack in a Clad Thick-Wall Pipeline

Based on numerical-analytical analysis of a straight pipeline section produced of pearlitic steel clad by buttering of austenitic steel, a crack opening was investigated. These steels have different line expansion coefficients. The generalized equation of an opening of a through-thickness ring crack in a thick-wall clad pipeline was obtained taking into account the internal pressure and thermal stresses. The need to take into account the thermal stresses in the evaluation of an opening of a through-thickness ring crack in the clad pipeline was shown. The investigation results can be used effectively when the foundation of the “leak before break” concept in pipeline transport.