Detonation nanodiamonds are produced at utilization of high explosives. When an explosive blasts in a water environment, the detonation products contain microdiamonds, and in a gaseous medium, ...nanodiamonds. It is known that with decreasing size the influence of the surface energy of particles on their properties increases. Thus, it is interesting to compare the properties of detonation nano and microdiamonds. In this study, we have examined the thermal stability of diamond materials by synchronous thermal analysis. The experiments were performed at atmospheric pressure in argon flow for different heating rates in a range from room temperature to 1500 °C. Samples of initial and annealed micro and nanomaterials were studied using electron microscopy, x-ray and x-ray-fluorescence analysis. It was established that thermal and structural properties of micro and nanodiamonds differ substantially.
A mass spectrometric method has been developed for determining the content of dopamine and serotonin derivatives, which allows evaluating the efficiency of their penetration through artificial ...membranes depending on the structure of their peptide fragment. In this case, the diffusion of dopamine and serotonin derivatives through the membrane occurred as a result of competitive interactions. It was shown which compounds in this mixture more easily penetrate through artificial membranes. It was found that the most promising in terms of overcoming the BBB are Boc–Pro–Srt and Boc–Pro–DOPA.
We studied the effects of Selank on intestinal microbiota in Wistar male rats subjected to chronic restraint stress. Selank was injected intraperitoneally in doses of 80, 250 and 750 μg/kg 15 min ...before stress exposure. Chronic restraint stress led to a decrease in the content of obligate microflora, while the content of opportunistic microorganisms increased. Selank restored intestinal microbiota presumably via central (neurotropic) and peripheral (immunotropic) mechanisms.
Effect of temperature on the efficiency of deuterium introduction into a new biologically active compound salicylcarnosine (SC) has been studied. Gaseous deuterium and heavy water were used as ...deuterium sources. The synthesis of labelled SC by a solid-phase method at 190°C leads to formation of DSC in 53% yield and deuterium content about 4.8 atoms per molecule. It has been shown that isotope exchange between SC protons and deuterium water proceeds more efficiently after preliminary treatment of catalyst with gaseous deuterium at ambient temperature. DSC forms in 46% yield and contains about 7.3 deuterium atoms per molecule. The preparative synthesis of labelled SC by this procedure at 190°C results in DSC yield of 60–70% at deuterium content about 6.2 atoms per molecule. The new procedure for the activation of deuterium inclusion in peptides opens additional opportunities for preparing highly labelled compounds.
Recommendations were developed for estimating the size of computational grid cells in the numerical modeling of external and internal flows in relation to aeronautical engineering problems. ...Recommendations are obtained in the form of criterial relations connecting the dimensionless scale of the global grid element with regime and geometric characteristics, which make it possible to a priori estimate the cell size that ensures grid convergence of the solution. The paper presents the results of developing correlations for typical channels of a turbine blade cooling system as well as for a typical airfoil.
A procedure was developed for introducing tritium into the side chain of the abscisic acid (ABA) molecule. The reaction was carried out in dioxane in the presence of the Lindlar catalyst. The yield ...of the labeled product was 70% and the molar radioactivity was 44 Ci/mol. The tritium-labeled abscisic acid analogue was found to be a growth substrate for soil bacteria that incorporate a radioactive label into cellular metabolites. The absorption of the label by bacteria from the side chain of abscisic acid is more than an order of magnitude higher than that for labeling in the cyclohexene moiety. The results indicate the existence of a previously unknown metabolism pathway of ABA in microorganisms.
In this study, we accurately measured the breakdown thresholds in four atmospheric gases using the high-power terahertz radiation of the Novosibirsk free electron laser (NovoFEL). The breakdown ...intensities of the 130-μm radiation in a form of 74-ps pulses were equal to 1.1–1.4 GW/cm
2
. These data have been compared with calculations based on a phenomenological criterion for a breakdown and the classical theory of stochastic microwave heating of electrons. Presented are threshold conditions for a quasi-continuous plasma discharge that is maintained by means of a sequence of pulses of the NovoFEL. At a pulse repetition rate of 5.6 MHz, the discharge quenching thresholds are 15–60% lower than the breakdown thresholds depending on the amount of plasma emerging.
The paper discusses the geochemical and Sr–Nd–Pb-isotope data on ice-rafted sediments (IRS) from different areas of the Arctic Ocean. Samples were collected during the Cruise of R/V
Polarstern
...between Spitsbergen and North Pole, Yermak Plateau, as well as in Fram Strait. It is shown that the studied IRS samples in terms of La
N
/Yb
N
and εNd values are close to the composition of suspended particulate matter (SPM) from the mouth parts of large rivers and rivers transporting the sedimentary erosion products. This also follows from their Th/Sc, Th/Co, La/Sc, La/Sm, Sc/Th ratios and Sc content and from the position of their data points in the Sc–Th/Sc, La/Sc–Th/Co, and La/Sm–Sc/Th diagrams between the average SPM compositions of the Ob and Lena rivers. The values of
207
Pb/
206
Pb and εNd in IRS samples give grounds to suggest that the rock complexes of the European, North American, and Asian continental margins could be potential sources for this sedimentary material. In the
207
Pb/
206
Pb–εNd diagram, the IRS samples from all three studied areas define a compact cluster and are mainly confined to the triangle with corners represented by the Mackenzie River, Okhotsk–Chukotka volcanic area, and Lena River, being closer to the latter. In the Sm/Nd–εNd diagram, IRS points also form a compact field, being located almost in the middle between the average SPM compositions of the Yenisei and Ob rivers, on the one hand, and Lena River, on the other. In all diagrams, IRS samples from the different West Arctic areas show no significant scatter. With allowance for the fact that sediments are not subjected to significant homogenization during ice rafting, sediments from all three areas were obtained from a common source. As seen from the position of IRS data points in the
87
Sr/
86
Sr–εNd diagram, this source was the Asian continental margin.
Necessary precursors for obtaining tritium-labeled Z-Gly-Pro-DOPA, Z-Gly-Pro-SRT, Z-Gly-Pro-Dox, OL-Gly-Pro-DOPA,Ol-Gly-Pro-Srt were synthesized for the first time (Gly stands for glycine; Pro, ...proline; Ol, Oleic acid, DOPA, dopamine; Dox, Doxorubicin; Srt, Serotonin; and Z, benzyloxycarbonyl protection). The tritium-labeled proline and glycine were used to synthesize peptide derivatives of DOPA, Dox, and Srt with different tritium distributions.
Pharmacokinetics and relative bioavailability of antidepressant GSB-106 (hexamethylendiamide
bis
-(
N
-monosuccinyl-
L
-seryl-
L
-lysine) were determined in rabbits after single oral administration ...of the pharmaceutical substance and tablet mass. GSB-106 concentrations in the blood plasma were determined by HPLC-mass spectrometry. Relative bioavailability of GSB-106 tablet form was 160.79±24.33%.
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