484 research outputs found
Distribution of deformations and parameters of stress-strain state in steel Kh18N10T
Parameters of the laws of distribution of fields of micro- and submicrodeformations in steel Kh18N10T are determined under uniaxial tension of specimens. The components of the plastic strain tensor and their statistics are determined for grain arrays and in the plane of four individual grains. The intensities of the major micro-and submicrodeformations are computed. The correlation relations between the deformations of individual volumes of metal inside grains are estimated. The parameters of the strain-stress states of structural components (grains) of a polycrystal are determined. Qualitative analysis of the microstructural features of deformation of the steel studied is performed. © 2013 Springer Science+Business Media New York
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Critical Role of Methylammonium Librational Motion in Methylammonium Lead Iodide (CH3NH3PbI3) Perovskite Photochemistry.
Raman and photoluminescence (PL) spectroscopy are used to investigate dynamic structure-function relationships in methylammonium lead iodide (MAPbI3) perovskite. The intensity of the 150 cm-1 methylammonium (MA) librational Raman mode is found to be correlated with PL intensities in microstructures of MAPbI3. Because of the strong hydrogen bond between hydrogens in MA and iodine in the PbI6 perovskite octahedra, the Raman activity of MA is very sensitive to structural distortions of the inorganic framework. The structural distortions directly influence PL intensities, which in turn have been correlated with microstructure quality. Our measurements, supported with first-principles calculations, indicate how excited-state MA librational displacements mechanistically control PL efficiency and lifetime in MAPbI3-material parameters that are likely important for efficient photovoltaic devices
Maser Oscillation in a Whispering-Gallery-Mode Microwave Resonator
We report the first observation of above-threshold maser oscillation in a
whispering-gallery(WG)-mode resonator, whose quasi-transverse-magnetic, 17th
azimuthal-order WG mode, at a frequency of approx. 12.038 GHz, with a loaded Q
of several hundred million, is supported on a cylinder of mono-crystalline
sapphire. An electron spin resonance (ESR) associated with Fe3+ ions, that are
substitutively included within the sapphire at a concentration of a few parts
per billion, coincides in frequency with that of the (considerably narrower) WG
mode. By applying a c.w. `pump' to the resonator at a frequency of approx.
31.34 GHz, with no applied d.c. magnetic field, the WG (`signal') mode is
energized through a three-level maser scheme. Preliminary measurements
demonstrate a frequency stability (Allan deviation) of a few times 1e-14 for
sampling intervals up to 100 s.Comment: REVTeX v.4, 3 pages, with a separate .bbl file and 3 .eps figure
Surgical treatment of secondary postuveal glaucoma by microinvasive non-penetrating deep sclerectomy with Healaflow implant injection: clinical case
The study aim was to evaluate the effectiveness of treatment of postveal uncompensated glaucoma in a patient with chronic infectious uveitis by microinvasive non-penetrating deep sclerectomy using drainage implant Healaflow. Material and methods. In a patient with the history of chronic uveitis, for the purpose of surgical treatment of secondary uncompensated post-uveal glaucoma, a microinvasive non-penetrating deep sclerectomy with the introduction of Healaflow has been performed in order to stabilize intraocular pressure, visual acuity and visual field. Healaflow was used to prevent proliferation and scarring in the early postoperative period. Results. At the follow-up period of 6 months after the operation, the drainage outflow tracts were preserved; intraocular pressure was stabilized. Conclusions. Microinvasive non-penetrating sclerectomy with Healaflow injection is the safe and effective method of surgical treatment of patients with postveal uncompensated glaucoma. The use of Healaflow is an effective method for preventing scarring of formed drainage outflow tracts
Controlling the Frequency-Temperature Sensitivity of a Cryogenic Sapphire Maser Frequency Standard by Manipulating Fe3+ Spins in the Sapphire Lattice
To create a stable signal from a cryogenic sapphire maser frequency standard,
the frequency-temperature dependence of the supporting Whispering Gallery mode
must be annulled. We report the ability to control this dependence by
manipulating the paramagnetic susceptibility of Fe3+ ions in the sapphire
lattice. We show that the maser signal depends on other Whispering Gallery
modes tuned to the pump signal near 31 GHz, and the annulment point can be
controlled to exist between 5 to 10 K depending on the Fe3+ ion concentration
and the frequency of the pump. This level of control has not been achieved
previously, and will allow improvements in the stability of such devices.Comment: 17 pages, 10 figure
Structural features of Ni-Cr-Si-B materials obtained by different technologies
This study considers the structural features of Ni-Cr-Si-B (Ni - base; 15.1 % Cr; 2 % Si; 2 % B; 0.4 % C) materials obtained by different methods. The self-fluxing coatings were deposited by plasma spraying on the tubes from low carbon steel. Bulk cylinder specimens of 20 mm diameter and 15 mm height were obtained by spark plasma sintering (SPS). The structure and phase composition of these materials were investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The major phases of coatings and sintered materials are [gamma]-Ni, Ni[3]B, CrB and Cr[7]C[3]. We demonstrate that the particle unmelted in the process of plasma spraying or SPS consist of [gamma]-Ni-NEB eutectic and also CrB and Cr[7]C[3] inclusions. The prolonged exposure of powder to high temperatures as well as slow cooling rates by SPS provide for the growth of the structural components as compared to those of plasma coatings materials. High cooling rates at the plasma spraying by melted particles contribute to the formation of supersaturated solid solution of Cr, Si and Fe in [gamma]-Ni. The structure of the melted particles in sintering material has gradient composition: the core constituted of Ni grains of 10 μm with [gamma]-Ni-Ni[3]B eutectic on the edges. The results of the experiment demonstrate that the sintering material has a smaller microhardness in comparison with plasma coatings (650 and 850 MPa, respectively), but at the same time the material has higher density (porosity less than 1 %) than plasma coatings (porosity about 2.. .3 %)
The problem of wellbeing within the framework of quality management
The idea of common well-being suggests the dissolution of the state’s monopoly in social welfare for the benefit o
Computer prediction of biological activity spectra of substituted and fused methylxanthines
Based on the chemical structure and mathematical algorithm of the Prediction of Activity Spectra for Substances software, computer prediction of
possible types of biological activity of 121 substances substituted and fused derivatives of methylxanthine, has been done. The structure of compounds
synthesized has been confirmed by modern physical and chemical methods: elemental analysis, UV-, IR-, HNMR- and mass-spectrometry, counter
synthesis. The purity of the synthesized compounds has been controlled by thin layer chromatography. These substances are white crystalline powders,
odorless, of a bitter taste, insoluble in water, soluble in dimethylformamide and dimethylsulfoxide and practically insoluble in alcohol, ether, chloroform,
glacial acetic acid. Chemical structures of tested compounds have been introduced by a computer program “Java 6 Standart Edition” and posted on the
official site of biological spectra prediction (http://195.178.207.233/PASSNew/predsct.php) in the form of the original multi-atomic orbital descriptors
(Multilevel Neighborhoods of Atoms). The results of the computer prediction of the diuretic activity have been considered positive if the predicted activity probability of the substance Pa has been > 0.5. It has been specified that the newly synthesized derivatives of methylxanthine are able to demonstrate
the following pharmacological activities: diuretic, neurotropic, antihypoxic, analgesic, anti-inflammatory and metabolic. By the method of computer
prediction for substituted and fused methylxanthine derivatives it has been found that the highest diuretic activity is characteristic of the compound
g-6713 - pyrrolidine 1,7-dimethylimidazo[1,2-f]xanthinyl acetate. The substituted and fused derivatives of methylxanthine present a promising group
of compounds for further synthesis and screening of new pharmacological substances with diuretic properties
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