First order phase transition from the vortex liquid to an amorphous solid

We present a systematic study of the topology of the vortex solid phase in superconducting Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ samples with low doses of columnar defects. A new state of vortex matter imposed by the presence of geometrical contours associated with the random distribution of columns is found. The results show that the first order liquid-solid transition in this vortex matter does not require a structural symmetry change.Comment: 4 pages, 5 figure

The in vitro influence of different factors on the indicators of human ejaculate

The paper presents the results of investigations dealing with the impact of experimental exposures (to chemical substances and electromagnetic radiation) on human sperm. The radiation is shown to suppress sperm motility. High hydrogen peroxide concentrations and ejaculate cryopreservation have also a negative effect on sperm motility and viability. Low hydrogen peroxide levels cause the opposite effect on sperm motility. The use of some regulatory mechanisms also yields positive results. Antioxidants increase the number of mobile sex cells in an experiment. Clinical observations using antioxidants support the results of laboratory tests

Effects of glyprolines on free-radical oxidation in the brain neocortex of white rats in mild traumatic brain injury

The aim of the study was to compare the effect of glyproline peptides RGRGP (Arg-Gly-Arg-Gly-Pro), RGP (Arg-GlyPro), PRPGP (Pro-Arg-Pro-Gly-Pro) and PGPL (Pro-Gly-Pro-Leu) peptide substances at various concentrations on the free radical oxidation intensity of the brain tissues of Wistar males after intraperitoneal administration of peptide solutions after traumatic brain injury.Material and methods. The brain tissue of Wistar males aged 2–3 months (n = 126) were used in the experiment. RGRGP, RGP, PRPGP, and PGPL peptides were provided by Academician N.F. Myasoyedov. Traumatic brain injury (TBI) was modeled by free fall of a load. From the second to the fifth day of the experiment, the animals were injected intraperitoneally with peptides. On the sixth day, the animals were taken out of the experiment. The activity of free radical oxidation was determined in freshly prepared homogenates of sections of the cerebral cortex by chemiluminescence (CL).Results. TBI significantly enhance free-radical oxidation intensity of the neocortex in brain tissue of Wistar rats, and the studied peptides affect it in different ways - from a decrease in CL intensity (the minimum value in TBI + RGP 0.1 group) to its increase (the maximum value in TBI + RGPGP 0.1 group). The effect depends on the dose of glyproline.Conclusions. The results obtained, based on the analysis of the free radical oxidation intensity of tissues, mainly indicate a different degree of correction of tissue homeostasis indicators. It can be assumed that Arg-Pro-Gly peptide can be the basis for the development of new drugs for post-stress rehabilitation after injuries of various levels and genesis

Instabilities and disorder-driven first-order transition of the vortex lattice

Transport studies in a Corbino disk geometry suggest that the Bragg glass phase undergoes a first-order transition into a disordered solid. This transition shows a sharp reentrant behavior at low fields. In contrast, in the conventional strip configuration, the phase transition is obscured by the injection of the disordered vortices through the sample edges, which results in the commonly observed vortex instabilities and smearing of the peak effect in NbSe2 crystals. These features are found to be absent in the Corbino geometry, in which the circulating vortices do not cross the sample edges.Comment: 12 pages 3 figures. Accepted for publication in Physical Review Letter

Oxidation state and coordination environment of uranium in sodium iron aluminophosphate glasses

An analysis of the X-ray absorption near edge structure (XANES) and the extended X-ray absorption fine structure (EXAFS) of uranium determined the oxidation state and coordination environment of uranium atoms in glasses containing 40 mol % Na$_2$O, 10 mol % Al2O3, 10 mol % Fe$_2$O$_3$, and 40 mol % P$_2$O$_5$ to which uranium oxides were added to a concentration of 50 wt % (above 100%). If the added amount of UO2 was small, uranium occurred as U(IV) in a near-octahedral oxygen environment with an average U–O distance in the first coordination sphere of 2.25 Å. At higher concentrations of uranium oxides introduced both as UO$_2$ and as UO$_3$, uranium occurred as U(V) and U(VI); the first coordination sphere is split; shorter (~1.7–1.8 Å) and longer (2.2–2.3 Å) distances were observed, which corresponded to the axial and equatorial U–O bonds in uranyl ions, respectively; and the redox equilibrium shifted toward U(VI). The glass with the maximal (~33 wt %) UO$_3$ concentration contained mainly U(VI). The existence of low-valence uranium species can be related to the presence of Fe(II) in glasses. The second coordination sphere of uranium manifests itself only at high concentrations of uranium oxides

Effect of regulatory peptides on the parametres of human ejaculate

The results of the impact of some biologically active synthetic substances, antioxidants, and regulatory oligopeptides. Application Semax as stimulating agent in the experiment showed a positive effect, which is expressed in increasing overall sperm motility and much more in actively movind population. Selank also has a stimulating effect on sperm motility, improving the overall mobility by 18 %, and active – 39 %. Have a significant positive effect of regulatory peptides. Used in a concentration of all three peptides showed similar results, improving the overall mobility in the first hour of incubation at 21–36 % for the 3rd hour – 25–42 %. Active mobility increased by 39–79% and 63– 88%, respectively. Meksidol showed noticeable changes in sperm motility in the experiment, and in patients with patospermia. Thus, the use of biologically active peptides in an experiment can serve as a basis for their introduction into clinical practice andrology and reproduction.</em