Application of Copper Thermal Spraying for Electrical Joints between Superconducting Nb3Sn Cables

This manuscript reports on the application of copper thermal spraying in the manufacturing process of an electrical connection between Nb3Sn cables for superconducting magnets of fusion reactors. The joint is realized through diffusion bonding of the sprayed coating of the two cables. The main requirement for such a connection is its electrical resistance, which must be below 1 nΩ at B = 8 T, I = 63.3 kA and T = 4.5 K. Micrographs of the joint prototype were taken to relate the joint resistance with its microstructure and to provide feedback on the manufacturing process. Optical microscopy (OM) was used to evaluate the grain size of the coating, presence of oxide phases and to analyze the jointed surfaces. Scanning electron microscopy (SEM) and, in particular, energy-dispersive X-ray spectroscopy (EDX) were used to confirm the elemental composition of specimens extracted from the prototype. It is shown that the copper coating has an oxide concentration of 40%. Despite this, the resistance of the prototype is 0.48 nΩ in operating conditions, as the oxides are in globular form. The contact ratio between the jointed surfaces is about 95%. In addition, residual resistivity ratio (RRR) measurements were carried out to quantify the electrical quality of the Cu coating.

Exogenous Vimentin Supplementation Transiently Affects Early Steps during HPV16 Pseudovirus Infection

Understanding and modulating the early steps in oncogenic Human Papillomavirus (HPV) infection has great cancer-preventative potential, as this virus is the etiological agent of virtually all cervical cancer cases and is associated with many other anogenital and oropharyngeal cancers. Previous work from our laboratory has identified cell-surface-expressed vimentin as a novel HPV16 pseudovirus (HPV16-PsVs)-binding molecule modulating its infectious potential. To further explore its mode of inhibiting HPV16-PsVs internalisation, we supplemented it with exogenous recombinant human vimentin and show that only the globular form of the molecule (as opposed to the filamentous form) inhibited HPV16-PsVs internalisation in vitro. Further, this inhibitory effect was only transient and not sustained over prolonged incubation times, as demonstrated in vitro and in vivo, possibly due to full-entry molecule engagement by the virions once saturation levels have been reached. The vimentin-mediated delay of HPV16-PsVs internalisation could be narrowed down to affecting multiple steps during the virus’ interaction with the host cell and was found to affect both heparan sulphate proteoglycan (HSPG) binding as well as the subsequent entry receptor complex engagement. Interestingly, decreased pseudovirus internalisation (but not infection) in the presence of vimentin was also demonstrated for oncogenic HPV types 18, 31 and 45. Together, these data demonstrate the potential of vimentin as a modulator of HPV infection which can be used as a tool to study early mechanisms in infectious internalisation. However, further refinement is needed with regard to vimentin’s stabilisation and formulation before its development as an alternative prophylactic means.

Increasing the service life of pellet car grate bars made of 40Х24Н12СЛ steel

Intercrystallite corrosion (ICC) is the main reason to decrease service life of pellet car grate bars made of steel 40Х24Н12СЛ. In the process of the study of microstructure of pellet car grate bars manufactured according to GOST 977–88, the structure defects were established that increase the tendency to ICC. To prevent the ICC of the bars, a mode of heat treatment was elaborated, consisting of two basic operations: air hardening with preliminary exposure within 80 minutes at the temperature 1100 °С, followed by tempering within 150 minutes at the temperature 900 °С. The study of the structure of the pilot grate bar showed that the selected mode of the hardening enables to dissolve the carbide network in the structure of the detail and crash large carbides, and the subsequent tempering contributes to the growth of the carbide phase in the entire volume of metal, partially remaining in the structure after hardening. It was shown that the proposed mode of the heat treatment contributes to bringing the structure of the metal to a more “equilibrium” state, which will allow to exclude the formation of large carbides and carbide network, growth and coagulation along the grain boundary. Results of tests of a pilot batch of grate bars installed at an industrial induration machine with a working area of 768 m2 and operating temperature of 20–1310°С presented. It was established that the elaborated technology ensures absence of casting defects in the grate bars – cracks and warping, inclination of the grate bars to ICC, increased by 23.13% heat resistance compared to the reference grate bars of foreign supply due to the globular form of carbide secretions with a minimum length of borders along which the metal matrix is depleted by chrome. Industrial testing of the grate bars manufactured under the experimental technology has proved the practical significance and applicability of the performed research.

Study of effect of wheel steel microalloying by calcium and barium on nonmetallic inclusions modification

The increase in freight cars axis loads, dynamic loads and heat impact on the wheels, change of other factors, stipulated by railway transport traffic intensification lead to considerable decrease of service life of solid-rolled wheels. To increase the service life of them, provision of the transport metal purity in non-deformed oxide nonmetallic inclusions with high content of Al2O3, decrease of general steel pollution by nonmetallic inclusions by micro-alloying and modification is an actual task. The purpose of the study was elaboration of wheel steel ladle treatment technology, including the steel micro-alloying and modification by barium-containing alloys to create material, which could meet high operation requirements, made to the railway wheels of new generation, intended to operate under increased axis loads conditions at the modern high-speed rolling-stock. It was shown, that replacement of everywhere applied silicocalcium by barium-based alloys is one of perspective ways of modification mechanism perfection. Results of industrial tests of micro-alloying of wheel steel by barium during ladle treatment presented. It was shown, that application for modification of cored wire with silicobarium filler instead of cored wire with silicocalsium filler СК-30, enabled to transform the nonmetallic inclusions into globular form practically completely, to raise the steel purity for all kinds of inclusions in both middle and maximum points range and to refine to some extent the grain size by 1-2 points. In the pilot metal at the depth of 40 mm from the surface, the gain was somewhat finer and more uniform (number 7), comparing with the existing technology (number 5-6). The pollution of the pilot metal by nonmetallic inclusions meets requirements of GOST 10791—2011 for category A and those of the standard EN 13262: 2004+А2:2011 for category 1.

Maturation of the functional mouse CRES amyloid from globular form

The epididymal lumen contains a complex cystatin-rich nonpathological amyloid matrix with putative roles in sperm maturation and sperm protection. Given our growing understanding for the biological function of this and other functional amyloids, the problem still remains: how functional amyloids assemble including their initial transition to early oligomeric forms. To examine this, we developed a protocol for the purification of nondenatured mouse CRES, a component of the epididymal amyloid matrix, allowing us to examine its assembly to amyloid under conditions that may mimic those in vivo. Herein we use X-ray crystallography, solution-state NMR, and solid-state NMR to follow at the atomic level the assembly of the CRES amyloidogenic precursor as it progressed from monomeric folded protein to an advanced amyloid. We show the CRES monomer has a typical cystatin fold that assembles into highly branched amyloid matrices, comparable to those in vivo, by forming β-sheet assemblies that our data suggest occur via two distinct mechanisms: a unique conformational switch of a highly flexible disulfide-anchored loop to a rigid β-strand and by traditional cystatin domain swapping. Our results provide key insight into our understanding of functional amyloid assembly by revealing the earliest structural transitions from monomer to oligomer and by showing that some functional amyloid structures may be built by multiple and distinctive assembly mechanisms.

Structure and characteristics of boron-containing steels for fasteners

According to TU 14-1-4486-88 and TU 14-1-5490-2004, in accordance with international standards DIN EN 10263-4, OJSC «BSW – Management Company of the Holding «BMC» produces hot-rolled products of the following grades of steel: 20Г2Р, 30Г1Р, 20MnB4, 30MnB4 and 32CrB4 microalloyed with boron. They are used for the manufacture of fasteners instead of previously used steels 35X, 38X and 40X. The use of boron-containing steels reduces the surface defects of hardware; to increase the stability of the mechanical properties of bolts, screws, studs, strength class 8.8 and 10.9 by GOST 1759.4-87; to achieve a high level of toughness at negative temperatures. It is shown that steel 20Г2Р provides stable mechanical properties of products up to M27 (in contrast to steel grades 35X, which are designed exclusively for bolts of class M16 8.8). The boron-containing steels in the delivery state with the structure of granular perlite have high technological plasticity – in the cold, the bolt head is formed and the thread is rolled without tearing in the thread hollows, as is the case with chromium steels of type 40X. It was found that their ductility increases due to the low content of carbon and chromium, as well as the formation of dispersed carbonitride-boride phases of a globular form.

Constant velocity pulling and unfolding of thyroid hormone receptor by steered molecular dynamics

Unfolding pathways of T3 liganded thyroid hormone receptor (THRT3) can be studied by using the protocols of steered molecular dynamics (SMD). Theory of constant velocity pulling has been implemented to the structure of THRT3 in a neutral water-ion solution equilibrated up to 20 ns. The globular form of THRT3 is completely unfolded extending N-C termini from 38 Å to 876 Å at a constant speed of 0.1 Å/ps by means of 8.5 ns long SMD simulations. The peak force measured in the intermediate conformations is related to a burst of backbone H-bonds among a-helices and b-hairpins. With decrease in H-bonds, electrostatic energy increases by losing gradually the secondary structure and separating a and b-strands in solution. The force at the end (t > 8.5 ns) increases steeply with the large increase in bond-angle and bond-length potentials when the system becomes completely unfolded. The hydrophobic ligand binding domain (LBD) of THR-b with load bearing H-bonds protects T3 from water attack. Even after complete unfolding of THR-b LBD, the position of T3 is not deviated more than 2.5 Å and a large number of water molecules remain in the surrounding of this domain area. This is a strong evidence for the mechanochemical stability of a receptor protein’s LBD towards hormone activated gene expressions followed by ligand binding and dissociation. BIBECHANA 17 (2020) 50-57

Mechanochemistry of von Willebrand factor

Von Willebrand factor (VWF), a blood multimeric protein with a very high molecular weight, plays a crucial role in the primary haemostasis, the physiological process characterized by the adhesion of blood platelets to the injured vessel wall. Hydrodynamic forces are responsible for extensive conformational transitions in the VWF multimers that change their structure from a globular form to a stretched linear conformation. This feature makes this protein particularly prone to be investigated by mechanochemistry, the branch of the biophysical chemistry devoted to investigating the effects of shear forces on protein conformation. This review describes the structural elements of the VWF molecule involved in the biochemical response to shear forces. The stretched VWF conformation favors the interaction with the platelet GpIb and at the same time with ADAMTS-13, the zinc-protease that cleaves VWF in the A2 domain, limiting its prothrombotic capacity. The shear-induced conformational transitions favor also a process of self-aggregation, responsible for the formation of a spider-web like network, particularly efficient in the trapping process of flowing platelets. The investigation of the biophysical effects of shear forces on VWF conformation contributes to unraveling the molecular mechanisms of many types of thrombotic and haemorrhagic syndromes.

Technical and economic aspects of development and running ladle treatment aggregates

Modern ladle treatment of liquid steel represents a wide set of technological processes and aggregates, as well as units and systems, many of them having significant cost and need expensive maintenance. Technical and economic advantages, obtained at various variants of steel ladle treatment considered, the advantages being at both metal products producers and consumers. Factors of production expenses saving at the stage of steel smelting due to transferring of the steel refining operation from melting aggregates to the stage of ladle treatment considered. It was noted, that in the process of continuous casting of metal, subjected to ladle refining, the steel casting improves considerably due to keeping the narrow temperature interval, decreased content and globular form of nonmetallic inclusions. In its turn it results in a decrease of rejects, an increase of billet drawing speed possibility and correspondent increase of production capacity, reduction of the number of the casted billet shell breaks. Technical and economic advantages of melt treatment by cored wire or by all-metal injection wire with stuff shown. Decrease of rejects is an important factor for cost decreasing. For example, application of calcium-aluminum cored wire at a steel-works enabled to decrease the rejects of well-casings made of 20ГЮ steel by a factor of 1.5–2. In many cases production of state-of-the-art steel grades, for example IF-steels, being the base of the modern motor-car construction, is not possible without ladle treatment. Therefore, absence of ladle treatment elements at a big steelworks can lead to considerable losses.

Water Effects on Molecular Adsorption of Poly(N-vinyl-2-pyrrolidone) on Cellulose Nanocrystals Surfaces: Molecular Dynamics Simulations

Models of interaction between a poly(N-vinyl-2-pyrrolidone) macromolecule and a fragment of Iβ-cellulose were built in a vacuum and water environment. The models were made to interpret the mechanism of interaction of the polymer and cellulose nanocrystals by the classical molecular dynamics method. The structural behavior of a poly(N-vinyl-2-pyrrolidone) macromolecule in water has been studied in terms of the radius of gyration, atom–atom radial distribution functions and number of hydrogen bonds. It was found that the polymer has a high affinity with the solvent and each monomer unit has on average 0.5 hydrogen bonds. The structural and energy characteristics of the polymer adsorption were investigated at different initial positions of the poly(N-vinyl-2-pyrrolidone) macromolecule relative to the cellulose fragment. It was observed that the polymer macromolecule was mainly adsorbed on the cellulose fragment in the globular form. Moreover, in the solvent the interaction of poly(N-vinyl-2-pyrrolidone) with the cellulose hydrophobic surface was stronger than that with the hydrophilic one. This study will show that the presence of water makes the interaction between the polymer and cellulose weaker than in a vacuum, and the polymer and cellulose mainly interact through their solvation shells.