Modification of Structure and Strength Properties of Permanent Joints Under Laser Beam Welding with Application of Nanopowder Modifiers

In the paper we present the results of experimental study of specially prepared nanosize metal-ceramic compositions impact upon structure, microhardness and mechanical properties of permanent joints produced by laser-beam welding of steel and titanium alloy plates

New Data on Comparative Cytogenetics of the Mouse-Like Hamsters (Calomyscus Thomas, 1905) from Iran and Turkmenistan.

The taxonomy of the genus Calomyscus remains controversial. According to the latest systematics the genus includes eight species with great karyotypic variation. Here, we studied karyotypes of 14 Calomyscus individuals from different regions of Iran and Turkmenistan using a new set of chromosome painting probes from a Calomyscus sp. male (2n = 46, XY; Shahr-e-Kord-Soreshjan-Cheshme Maiak Province). We showed the retention of large syntenic blocks in karyotypes of individuals with identical chromosome numbers. The only rearrangement (fusion 2/21) differentiated Calomyscus elburzensis, Calomyscus mystax mystax, and Calomyscus sp. from Isfahan Province with 2n = 44 from karyotypes of C. bailwardi, Calomyscus sp. from Shahr-e-Kord, Chahar Mahal and Bakhtiari-Aloni, and Khuzestan-Izeh Provinces with 2n = 46. The individuals from Shahdad tunnel, Kerman Province with 2n = 51-52 demonstrated non-centric fissions of chromosomes 4, 5, and 6 of the 46-chromosomal form with the formation of separate small acrocentrics. A heteromorphic pair of chromosomes in a specimen with 2n = 51 resulted from a fusion of two autosomes. C-banding and chromomycin A3-DAPI staining after G-banding showed extensive heterochromatin variation between individuals

On Nanomodification of Coating Obtained by Laser Cladding of Composite Powder 12NVK-01

The results of an experimental study of the effect of nanomodifying additives on the structure and mechanical properties of a multilayer coating during laser surfacing of a composite powder with a strengthening phase are presented. As a surfacing material, nickel powder 12NVK -01 with a strengthening phase of tungsten carbide was used, and as a modifying additive was a mixture of nanosized refractory powders of titanium nitride and yttrium oxide clad with iron and chromium. It is established that the deposited coating represents a complex system of phases formed during the melting and interaction of the chemical elements of the substrate and the melted powder mixture. The main component of the coating is the combination of nickel with iron and chromium of the type Ni3(Fe,Cr). In the melting process, a partial decomposition of the strengthening phase occurs, depending on the concentration of the nanomodifier. In the case considered, the optimum amount of the modifying additive providing the maximum hardness and wear resistance increase of the composite coatings of the Ni-Cr-B-Si-Fe / WC system is 0.1% by mass of the refractory TiN+Y[2]O[3] nanopowder additive in the composite material

On Nanomodification of Coating Obtained by Laser Cladding of Composite Powder 12NVK-01

The results of an experimental study of the effect of nanomodifying additives on the structure and mechanical properties of a multilayer coating during laser surfacing of a composite powder with a strengthening phase are presented. As a surfacing material, nickel powder 12NVK -01 with a strengthening phase of tungsten carbide was used, and as a modifying additive was a mixture of nanosized refractory powders of titanium nitride and yttrium oxide clad with iron and chromium. It is established that the deposited coating represents a complex system of phases formed during the melting and interaction of the chemical elements of the substrate and the melted powder mixture. The main component of the coating is the combination of nickel with iron and chromium of the type Ni3(Fe,Cr). In the melting process, a partial decomposition of the strengthening phase occurs, depending on the concentration of the nanomodifier. In the case considered, the optimum amount of the modifying additive providing the maximum hardness and wear resistance increase of the composite coatings of the Ni-Cr-B-Si-Fe / WC system is 0.1% by mass of the refractory TiN+Y[2]O[3] nanopowder additive in the composite material

Finding the Cell Center by a Balance of Dynein and Myosin Pulling and Microtubule Pushing: A Computational Study

By comparing computer modeling predictions with observations, we conclude that strong dynein and weaker myosin-generated forces pull the microtubules inward competing with microtubule plus-ends pushing the microtubule aster outward and that the balance of these forces positions the centrosome at the cell center

Data from: Systematics of snow voles (Chionomys, Arvicolinae) revisited

To elucidate the evolutionary history of snow voles, genus Chionomys, we studied the phylogeography of Chionomys nivalis across its range and investigated its relationships with two congeneric species, C. gud and C. roberti, using independent molecular markers. Analyses were based on mitochondrial (~940 bp cyt b) and Y-chromosomal (~2020 bp from three introns) genetic variation. Our data provide conclusive evidence for a Caucasian and Middle Eastern origin for the three species and a subsequent westward expansion of C. nivalis. In addition, we discuss the taxonomic status of the genus Chionomys in relation to the genus Microtus