Clinical assessment of pyloric sphincter function in different variants of denervation

A comparative evaluation of the function of pylorus sphincters was made on the basis of clinical examination of 152 patients after operations performed by the methods of A. E. Zakharov (in 31 patients), A. A. Shalimov-Maki (in 31 patients) and by the author's method (in 90 patients). The variant of the author's operation where only the extraorganic nerve connections were preserved proved to be better in functional respect since no disturbance of the motor-evacuation function took place.     

Effect of Woodward's reagent K on tetrodotoxin-sensitive sodium channels of spinal ganglion neurons of the rat

Currents through "fast" (tetrodotoxin-sensitive) sodium channels in rat sensory neurons were measured before and after external application of solutions containing 10 mM Woodward's reagent K (pH 6.0). The membrane treatment has resulted in irreversible changes of stationary activation and inactivation parameters.     

Salivary lysozyme in the screening for stomach cancer]

The study was concerned with measurement of lysozyme activity of saliva in healthy subjects and patients with different pathologies of the stomach including precancer and cancer. It established a considerable decrease in this parameter in cancer and precancer as compared with healthy controls. Assay of saliva lysozyme activity was found to yield more specific and prognostic data than clinical symptoms and examination of the patient. This procedure proved highly valuable in forming groups at risk for stomach cancer, due to providing significant differences in saliva lysozyme activity indices between "healthy subjects--stomach pathology" and "precancer--precancerous changes--stomach cancer" groups.     

Activation and inactivation of batrachotoxin-modified sodium channels of nerve fiber membranes in the frog

Currents through batrachotoxin (BTX)-modified sodium channels in frog myelinated nerve were measured under voltage-clamp conditions. Nonlinearity of "instantaneous" current-voltage relations was taken into account when determining steady-state parameters of channel activation. BTX induces the shift of voltage dependence of channel activation towards more negative potentials by 67 mV, without changes in its steepness. Current kinetics and effect of preceding depolarization on current size suggest that BTX-modified channels are capable for partial inactivation. High level of steady-state conductance of BTX-modified channels can be explained by suggestion that open state of the channel is energetically more profitable than inactivated one. It is concluded that effect of BTX on inactivation is different in principle from that of pronase and protein reagents.     

Kinetics of sodium current decay during normal axon membrane repolarization and in the presence of scorpion toxin

Decay of sodium currents in repolarization ("tail current") was studied in from axonal membrane. The decay in the membrane repolarization to -40 divided by -60 mV has two exponential components: fast and slow. The fraction of the slow component in the total "tail current" (theta M) decreases as the repolarization potential (Vp) becomes more negative; at Vp more negative than -80 mV "tail" follows practically one-exponential time course. When lengthening the test pulse (at the given Vp) the fraction of the fast component in the "tail" decreases quicker than that of the slow component, following approximately the kinetics of inactivation during the tests pulse. Scorpion toxin treatment results in slowing down "tail" kinetics mainly at the expense of increasing the fraction of the slow component. A kinetic diagram assuming two open state for the channel is suggested. A hypothesis is advanced that scorpion toxin, DDT and trinitrophenol have a common "site" to interact with the gating mechanism of the sodium channel.     

Effect of a water-soluble carbodiimide on the gating mechanism of "fast" sodium channels of the sensory neuron membrane of the rat

Currents through "fast" (tetrodotoxin-sensitive) sodium channels in dorsal root ganglion of rat were measured before and after the 5-6 min. external application of solutions containing 100 mM 1-ethyl-3 (3-dimethylaminopropyl) carbodiimide-HCl (WSC). The WSC treatment (pH 4.8-5.0) resulted in a decrease of the sodium conductance, slowing down of the activation kinetics by the factor of 1.5-2.5 and a decrease of the steepness of the activation curve. Effective charge of activation determined from the limiting logarithmic slope of the activation curve at potentials where channels just begin to open was reduced by the factor of 2.0. At normal pH (7.6) the WSC induced no changes in activation parameters. The results suggest that observed effects are due to the WSC interaction with carboxyl groups, situated at the external membrane surface. These groups may be incorporated in the gating mechanism of the sodium channel.     

Efficient Model of the Interaction of Elastomeric Filler with an Open Shell and a Chrome-Plated Shaft in a Dry Friction Damper

The results of a study of the contact interaction of an open shell and a chrome-plated shaft with elastomeric filler installed coaxially are presented. The considered contact system is a model of the original design of the shell damper of dry friction. The design feature is the following: the bearing link of the damper is a thin-walled cylindrical shell with a cut along the generatrix; the working body of the damper is elastomeric filler; a hollow chrome-plated shaft centers the damper elements and allows it to be used in technological processes with the presence of aggressive and abrasive-containing media. The mechanical-mathematical modeling of the behavior of the presented damper under the conditions of operational loads has been carried out. The idea of identifying the properties of a cut isotropic shell, which bends under the conditions of a nonaxisymmetric contact load, and a strongly orthotropic continuous shell is applied. As a result, dependences were obtained to determine the rigidity and the maximum allowable load of the damper. The effect of the coefficient of friction of the contact pairs elastomer-shell and elastomer-shaft on the damper performance properties has been studied. A technique for the quasi-static analysis of structural damping in non-mobile, non-conservative shell systems with deforming filler has been developed. The hysteresis loops of the damper under a nonmonotonic load are constructed, the dependence of the amount of dissipated energy on the cycle asymmetry coefficient is found. An analysis of the results obtained showed that the use of open shells in friction shock absorbers can significantly reduce their rigidity compared to solid shells and thereby reduce the resonant frequencies of the dynamic system. This circumstance makes such vibration isolators particularly attractive for use in superresonance vibrators as working modules of drilling shock absorbers and elastic hangers of sucker rods in oil and gas production.     

Effect of Different Tool Probe Profiles on Material Flow of Al–Mg–Cu Alloy Joined by Friction Stir Welding

Friction Stir Welding (FSW) was utilized to butt−join 2024–T4 aluminum alloy plates of 1.9 mm thickness, using tools with conical and tapered hexagonal probe profiles. The characteristic effects of FSW using tools with tapered hexagonal probe profiles include an increase in the heat input and a significant modification of material flow, which have a positive effect on the metallurgical characteristics and mechanical performance of the weld. The differences in mechanical properties were interpreted through macrostructural changes and mechanical properties of the welded joints, which were supported by numerical simulation results on temperature distribution and material flow. The material flow resulting from the tapered hexagonal probe was more complicated than that of the conical probe. If in the first case, the dynamic viscosity and strain rate are homogeneously distributed around the probe, but in the case of the tapered hexagonal probe tool, the zones with maximum values of strain rates and minimum values of dynamic viscosity are located along the six tapered edges of the probe.     

Initiation of Free Radical N‐Alkylmaleimide Polymerisation by Monomer Radical Cations. A Low Temperature EPR Study

N‐Alkylmaleimide radical cations were generated by electron beam irradiation of the freon matrix containing the monomers at 77 K. Their transformations with increasing temperature were followed by EPR. The spectra were compared with quantum chemical calculations (density functional B3LYP, Gaussian 98 W). The N‐alkylmaleimide radical cations are found to initiate free radical polymerisation in all cases.     

Analytical Modeling of the Interaction of a Four Implant-Supported Overdenture with Bone Tissue

Today, an interdisciplinary approach to solving the problems of implantology is key to the effective use of intraosseous dental implantations. The functional properties of restoration structures for the dentition depend significantly on the mechanical stresses that occur in the structural elements and bone tissues in response to mastication loads. An orthopedic design with a bar fixation system connected to implants may be considered to restore an edentulous mandible using an overdenture. In this study, the problem of the mechanics of a complete overdenture based on a bar and four implants was formulated. A mathematical model of the interaction between the orthopedic structure and jawbone was developed, and a methodology was established for the analytical study of the stress state of the implants and adjacent bone tissue under the action of a chewing load. The novelty of the proposed model is that it operates with the minimum possible set of input data and provides adequate estimates of the most significant output parameters that are necessary for practical application. The obtained analytical results are illustrated by two examples of calculating the equivalent stresses in implants and the peri-implant tissue for real overdenture designs. To carry out the final assessment of the strength of the implants and bone, the prosthesis was loaded with mastication loads of different localization. In particular, the possibilities of loading the prosthesis in the area of the sixth and seventh teeth were investigated. Recommendations on the configuration of the distal cantilever of the overdenture and the acceptable level and distribution of the mastication load are presented. It was determined that, from a mechanical point of view, the considered orthopedic systems are capable of providing long-term success if they are used in accordance with established restrictions and recommendations.