Characteristic length for pinning force density in Nb3SnNb{_3}Sn

The pinning force density $F{_p}(J{_c},B)=J{_c} \times B$ (where $J_c$ is the critical current density, $B$ is applied magnetic field) is one of main quantities which characterizes the resilience of a superconductor to carry dissipative-free transport current in applied magnetic field. Kramer (1973 J. Appl. Phys. 44 1360) and Dew-Hughes (1974 Phil. Mag. 30 293) proposed a widely used scaling law for the pinning force density amplitude: $F{_p}(B)=F{_{p,max}}((p+q){^{(p+q)}}/({p^p}{q^q}))(B/B_{c2}){^p}(1-B/B{_{c2}})^q$, where $F{_{p,max}}$, $B{_{c2}}$, $p$, and $q$ are free-fitting parameters. Since late 1970-s till now, several research groups reported experimental data for the dependence of $F_{p,max}$ on the average grain size, $d$, in $Nb{_3}Sn$-based conductors. Godeke (2006 Supercond. Sci. Techn. 19 R68) proposed that the dependence obeys the law $|F{_{p,max}}(d)|=A \times log(1/d)+B$. However, this scaling law has several problems, for instance, the logarithm is taken from a non-dimensionless variable, and $|F{_{p,max}}(d)|< 0$ for large grain sizes and $|F{_{p,max}}(d)|\rightarrow \infty$ for $d \rightarrow 0$. Here we reanalysed full inventory of publicly available $|F{_{p,max}}(d)|$ data for $Nb{_3}Sn$ conductors and found that the dependence can be described by $F_{p,max}(d)= F_{p,max}(0)exp(-d/{\delta})$ law, where the characteristic length, ${\delta}$, is varying within a remarkably narrow range, i.e. ${\delta}=(175 \pm 13) nm$, for samples fabricated by different technologies. The interpretation of the result is based on an idea that the in-field supercurrent is flowing within a thin surface layer (the thickness of ${\delta}$) near the grain boundary surfaces. Alternative interpretation is that ${\delta}$ represents characteristic length for the exponentially decay flux pinning potential from dominant defects in $Nb{_3}Sn$ superconductors, which are grain boundaries.Comment: 22 pages, 8 figure

Optimized 3D Segmentation Algorithm for Shelly Sand Images

There is much to be gained from analysing and studying calcareous sediment, with applications ranging from the study of climate change, rock dating, and even building offshore oil rigs and wind farms. One way of performing this analysis is to obtain a µCT scan of the sediment, allowing scientists and engineers to automate much of their analysis using software. Many existing and prospective analysis techniques require handling individual grains. Thus, fast and effective segmentation is an essential first step for any such analysis. Segmentation is non-trivial; these scans hold a lot of information, exhibit ambiguous boundaries between objects, and many objects are hollow, making it even more difficult to apply traditional watershed segmentation. Addressing these issues, in this paper we propose an optimized 3D segmentation (O3DS) algorithm based on watersheds. We make use of branch recursion, partition the image by height prior to segmentation, artificially reducing the size of the largest connected objects. These and additional changes are extremely effective in optimizing performance; O3DS reduces the time to segment a 659x925x932 scan of sediment by 95.4% and produces better or comparable results when compared to similar implementation by our co-author

Traditional and Modern Protective Media for the Low-Temperature Bacteria Preservation

Presented are the literature data on the efficiency of bacteria preservation at temperatures ranging from -20 to -196 °C in the protective media containing such cryoprotectors as glycerol, dimethyl sulfoxide, carbo-hydrates, substances of protein origin specified by regulatory guidelines. Most of the focus is on the publications reporting the results of the long-term bacteria preservation at sub-zero temperatures, optimization of the protective media for pathogenic bacteria, and usage of the compounds with potential cryoprotective activity. Noted is the necessity for approbation of the specified protective media for the conserved bacteria species at the applied preserving temperatures. One of the approaches to the enhancement of the low-temperature preservation techniques is a search for natural protectors, which can provide for surviving of bacteria in the unfavorable conditions, including low temperatures, and a search for possibility to integrate these natural protectors into the cryoprotective media. Displayed are the results of effective application of glycerol-betaine, and polysaccharides of Arctic microorganisms for the low-temperature bacteria preservation

Polynuclear Metallic Architectures Based on Fluorinated Functionalized Diketonates

K.Y.S. is thankful to the Council for grants of the President of Russian Federation (grant no. 1453.2019.3)

Dihydroazolopyrimidine crownophanes. Synthesis and tuberculostatic activity

Azolo[1,5-a]pyrimidines are considered to be purine analogues and they form one of the most promising groups of biologically active compounds[1-16] in medicinal chemistry. One of the strategies enhancing biochemical activity of azolo[1,5-a]pyrimidines is introduction of functional groups responsible for solubility and transport into their pharmacophore nucleus.[1,16] In this study, we wish to report ultrasound- and microwave-assisted one-pot cascade synthesis of macroheterocyclic 1-phenyl-2-(21-phenyl-10,11,13,14,20,20a-hexahydro-4aH-dibenzo-[13,14: 8,9][1,4,7] trioxacyclotetradecino[11,10-e]azolo[1,5-a]pyrimidin-20-yl)-1-ethanones. US and MV irradiation of the reaction mixtures under alkaline catalysis was found to promote a significant reduction of the reaction times (from 35 to 2 hours) and shift of the equilibrium in favor of 6,7-dihydroazolo[1,5-a]pyrimidine crownophanes in excellent yields (from 18[24] to 75 %). The high regio and stereoselectivity of the (R,S,R)-macroheterocyclic diastereomer formation was established by means of X-ray crystallography, 1H NMR spectroscopy, as well as HPLC and preparative chromatography. The aq. DMF appeared to be an acceptable solvent for stabilization of the important template-assisted pseudo-cyclic complex of the chalcone podand in this synthesis. Introduction of the dibenzo-crown ether transport moiety into 6,7-dihydroazolo[1,5-a]pyrimidines proved to increase their tuberculostatic activity in order to MIC 3.15 mg/ml. © ISUCT Publishing

Comparison of 2D Optical Imaging and 3D Microtomography Shape Measurements of a Coastal Bioclastic Calcareous Sand

This article compares measurements of particle shape parameters from three-dimensional (3D) X-ray micro-computed tomography (μCT) and two-dimensional (2D) dynamic image analysis (DIA) from the optical microscopy of a coastal bioclastic calcareous sand from Western Australia. This biogenic sand from a high energy environment consists largely of the shells and tests of marine organisms and their clasts. A significant difference was observed between the two imaging techniques for measurements of aspect ratio, convexity, and sphericity. Measured values of aspect ratio, sphericity, and convexity are larger in 2D than in 3D. Correlation analysis indicates that sphericity is correlated with convexity in both 2D and 3D. These results are attributed to inherent limitations of DIA when applied to platy sand grains and to the shape being, in part, dependent on the biology of the grain rather than a purely random clastic process, like typical siliceous sands. The statistical data has also been fitted to Johnson Bounded Distribution for the ease of future use. Overall, this research demonstrates the need for high-quality 3D microscopy when conducting a micromechanical analysis of biogenic calcareous sand

A Rare Example of Discrete Lanthanide–Lithium Tetrakis-β-Diketonates: Synthesis, Structures, and Luminescence Properties

Abstract: The reactions of functionalized lithium CF3-β-diketonate (LiL) with europium(III) and terbium(III) chlorides in acetonitrile afford heterobimetallic complexes with the general formula [LiL-nL4(H2O)](CH3CN) (Ln = Eu (IIIa) and Tb (IIIb)). It is found that Ln–Li tetrakis-β-diketonates can also be prepared by the crystallization from acetonitrile of the previously synthesized complexes [(LnL3)(LiL)(MeOH)] (I) and [(LnL3)(LiL)(H2O)] (II). For the first time, the single crystals of the compounds in a series of Ln–Li tetrakis-β-diketonates are characterized by X-ray diffraction analysis (CIF files CCDC nos. 1973632 (IIIa) and 1973633 (IIIb)). The photoluminescence properties of the synthesized heterometallic complexes in the solid state are studied. © 2020, Pleiades Publishing, Ltd.This work was supported by the Russian Foundation for Basic Research (project no. 18-33-20124), Council for Grants of President of the Russian Federation (grant no. MK-1453.2019.3), and basic themes of the Russian Academy of Sciences (state registration nos. AAAA-A19-119011790132-7 and AAAA-A19-119012490006-1)

Assessment of the cardiovascular system characteristics for preschool children (5-6 years old) following dif-ferent physical education programs

В статье проанализированы следующие показатели: процент изменения пульса и пульсового давления после физической нагрузки, показатель качества реакции (ПКР) на физическую нагрузку детей дошкольного возраста, занимающихся по разным программам физического воспитанияThe following characteristics are analyzed in the article: the pulse percentage change and pulse pressure after exercise load, reaction quality factor (RQF) on exercise load for preschool children following different physical education program

Perfluoroalkyl Chain Length Effect on Crystal Packing and [LnO8] Coordination Geometry in Lanthanide-Lithium β-Diketonates: Luminescence and Single-Ion Magnet Behavior

Functionalized perfluoroalkyl lithium β-diketonates (LiL) react with lanthanide(III) salts (Ln = Eu, Gd, Tb, Dy) in methanol to give heterobimetallic Ln-Li complexes of general formula [(LnL3)(LiL)(MeOH)]. The length of fluoroalkyl substituent in ligand was found to affect the crystal packing of complexes. Photoluminescent and magnetic properties of heterobimetallic β-diketonates in the solid state are reported. The effect of the geometry of the [LnO8] coordination environment of heterometallic β-diketonates on the luminescent properties (quantum yields, phosphorescence lifetimes for Eu, Tb, Dy complexes) and single-ion magnet behavior (Ueff for Dy complexes) is revealed. © 2023 by the authors.Russian Academy of Sciences, РАН: AAAA-A19-119011790132-7This work carried out in the framework of the basic theme of the Russian Academy of Sciences (state registration № AAAA-A19-119011790132-7)

Effect of the Silica–Magnetite Nanocomposite Coating Functionalization on the Doxorubicin Sorption/Desorption

A series of new composite materials based on Fe3O4 magnetic nanoparticles coated with SiO2 (or aminated SiO2) were synthesized. It has been shown that the use of N-(phosphonomethyl)iminodiacetic acid (PMIDA) to stabilize nanoparticles before silanization ensures the increased content of a SiO2 phase in the Fe3O4@SiO2 nanocomposites (NCs) in comparison with materials obtained under similar conditions, but without PMIDA. It has been demonstrated for the first time that the presence of PMIDA on the surface of NCs increases the level of Dox loading due to specific binding, while surface modification with 3-aminopropylsilane, on the contrary, significantly reduces the sorption capacity of materials. These regularities were in accordance with the results of quantum chemical calculations. It has been shown that the energies of Dox binding to the functional groups of NCs are in good agreement with the experimental data on the Dox sorption on these NCs. The mechanisms of Dox binding to the surface of NCs were proposed: simultaneous coordination of Dox on the PMIDA molecule and silanol groups at the NC surface leads to a synergistic effect in Dox binding. The synthesized NCs exhibited pH-dependent Dox release, as well as dose-dependent cytotoxicity in in vitro experiments. The cytotoxic effects of the studied materials correspond to their calculated IC50 values. NCs with a SiO2 shell obtained using PMIDA exhibited the highest effect. At the same time, the presence of PMIDA in NCs makes it possible to increase the Dox loading, as well as to reduce its desorption rate, which may be useful in the design of drug delivery vehicles with a prolonged action. We believe that the data obtained can be further used to develop stimuli-responsive materials for targeted cancer chemotherapy. © 2022 by the authors.Ministry of Education and Science of the Russian Federation, Minobrnauka, (075-15-2020-777)This research was funded by the Ministry of Science and Higher Education of the Russian Federation, grant number 075-15-2020-777