A method is proposed to calculate thermal effects induced by the heat treatment of high-entropy metallic glasses within the general thermodynamic approach. The experimental verification of the ...proposed method shows that the exothermic effect observed below the calorimetric glass transition temperature, the endothermic effect in the glass transition region, and the exothermic effect during the crystallization of a metallic glass can be quantitatively described using the general thermodynamic equation for the change in the entropy of the glass including the diaelastic effect.
The poly-l-proline type II (PPII) helix in recent years has emerged clearly as a structural class not only of fibrillar proteins (in collagen, PPII is a dominant conformation) but also of the folded ...and unfolded proteins. Although much less abundant in folded proteins than the α-helix and β-structure, the left-handed, extended PPII helix represents the only frequently occurring regular structure apart from these two structure classes. Natively unfolded proteins have a high content of the PPII helices identified by spectroscopic methods. Apart from the structural function, PPII is favorable for protein–protein and protein–nucleic acid interactions and plays a major role in signal transduction and protein complex assembly, as this structure is often found in binding sites, specifically binding sites of widely spread SH3 domains. PPII helices do not necessarily contain proline, but proline has high PPII propensity. Commonly occurring proline-rich regions, serving as recognition sites, are likely to have PPII structure. PPII helices are involved in transcription, cell motility, self-assembly, elasticity, and bacterial and viral pathogenesis, and has an important structural role in amyloidogenic proteins. However, PPII helices are not always assigned in experimentally solved structures, and they are rarely used in protein structure modeling. We aim to give an overview of this structural class and of the place it holds in our current understanding of protein structure and function. This review is subdivided into three main parts: the first part covers PPII helices in unfolded peptides and proteins, the second part includes studies of the PPII helices in folded proteins, and the third part discusses the functional role of the PPII.
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► The PPII helix is an extended, flexible left-handed helix without regular hydrogen bonds. ► PPII commonly occurs in folded proteins; it is abundant in unfolded proteins. ► PPII helices do not necessarily contain proline but proline has high PPII propensity. ► PPII has an important structural role and forms protein binding motifs. ► The PPII helix is a structure class comparable with the α-helix and β-structure.
Recent advances in recording and real-time analysis of surface electromyographic signals (sEMG) have fostered the use of sEMG human-machine interfaces for controlling personal computers, prostheses ...of upper limbs, and exoskeletons among others. Despite a relatively high mean performance, sEMG-interfaces still exhibit strong variance in the fidelity of gesture recognition among different users. Here, we systematically study the latent factors determining the performance of sEMG-interfaces in synthetic tests and in an arcade game. We show that the degree of muscle cooperation and the amount of the body fatty tissue are the decisive factors in synthetic tests. Our data suggest that these factors can only be adjusted by long-term training, which promotes fine-tuning of low-level neural circuits driving the muscles. Short-term training has no effect on synthetic tests, but significantly increases the game scoring. This implies that it works at a higher decision-making level, not relevant for synthetic gestures. We propose a procedure that enables quantification of the gestures' fidelity in a dynamic gaming environment. For each individual subject, the approach allows identifying "problematic" gestures that decrease gaming performance. This information can be used for optimizing the training strategy and for adapting the signal processing algorithms to individual users, which could be a way for a qualitative leap in the development of future sEMG-interfaces.
In this paper, anisotropic classes of well-posed Cauchy problems and boundary-value problems for systems of convolutions equations are obtained. For a particular case of differential equations, a ...hypersurface of conjugate orders of the corresponding polynomial is used, and various classes of well-posed problems are obtained.
We have solved the long-standing problem of the mechanism of terahertz (THz) generation by a two-color filament in air and found that both neutrals and plasma contribute to the radiation. We reveal ...that the contribution from neutrals by four-wave mixing is much weaker and higher in frequency than the distinctive plasma lower-frequency contribution. The former is in the forward direction while the latter is in a cone and reveals an abrupt down-shift to the plasma frequency. Ring-shaped spatial distributions of the THz radiation are shown to be of universal nature and they occur in both collimated and focusing propagation geometries. Experimental measurements of the frequency-angular spectrum generated by 130-fs laser pulses agree with numerical simulations based on a unidirectional pulse propagation model.
Consideration of the issues of improving the accuracy of digital prediction of the deformation modes of operation of polymer textile materials, which are important both from the scientific and ...research side and from the practical side, allows deriving recommendations for the creation of new promising materials with specified functional properties. A method for optimizing mathematical simulation of the fundamental operation modes of polymer textile materials is also considered.
This paper presents the results of experimental studies of heat transfer in electric arc furnaces, which showed that heat fluxes incident from arcs on a heating surface comprise 85%–95% of thermal ...radiation fluxes. The thermal radiation laws of ionized and nonionized gas volumes are stated, according to which the heat transfer in electric arc furnaces is calculated. The experimental and calculated data on the heat fluxes of arc radiation on a heating surface differ by no more than 5%–8%, indicating that the thermal radiation laws of gas volumes correspond to real heat transfer processes in electric arc furnaces. The heat exchange of arcs in an electric arc furnace bath was calculated. When the arcs are completely buried in the recesses of the bath, their slag and heat radiation fluxes are converted in the recesses into convective heat fluxes and heat conduction flows, heating the entire volume of the metal bath and slag.
This article presents the calculation results of the heat transfer in a high-power electric arc steel-making furnace EAF-100. With an increase in the slag layer height, the radiation heat fluxes from ...arcs to the walls decrease, while the surface of the bath and spherical segments under the arcs increase. With the full penetration of the arcs into the bath and slag, the density of the thermal radiation fluxes of the arcs is reduced by three times over the entire height of the walls compared with an insignificant embedding of the arcs. Thermal loads on the water-cooled wall panels in the absorbing furnace atmosphere are reduced by four times compared to those in the transparent furnace atmosphere.
Issues with mathematical modeling of relaxation processes of polymeric textile materials are discussed. Application of an optimality criterion of the mathematical modeling of the viscoelasticity ...allows the accuracy of determining the relaxation characteristics and the reliability of predicting the relaxation processes to be controlled. The proposed method allows the problem of the technological direction of choosing materials with the optimal relaxation characteristics to be solved with respect to the operational properties.
A method for calculating the heat fluxes of arc rays on a metal bath and the heat transfer thereof is described. The heat fluxes of arc rays distributed unevenly over the surface of the metal bath ...are 6–60 times greater in the bath areas opposite the arcs than those in the bath areas located near the slopes and between the arcs. With an increase in the height of a slag layer, the thermal radiation of arcs on the surface of walls, arches, and metal baths decreases, while increasing on the surface of the spherical segments under the arcs. Due to the electrodynamic forces, the slag and metal in the spherical segments under the arcs are constantly renewed, with the convective heat exchange of metal and slag being intensified. The efficiency of arcs at a complete immersion in slag in high-power electric arc furnaces reaches 78–80%.
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