A capacitor cell of a capacitive energy storage with a switch based on reverse switch-on dynistors

A capacitor cell of a capacitive energy storage designed for operating with an arc load is described. The cell that stores an energy of 64 kJ is based on a high-voltage (18 kV) capacitor and allows formation of current pulses with an amplitude of up to 60 kA. The discharge circuit of the cell contains a semiconductor switch in the form of an assembly of reverse switch-on dynistors (RSDs) connected in series, a crowbar diode switch, and a replaceable toroidal inductor. An assembly of protecting diodes connected in series to the RSD switch excludes the possibility of a flow of reverse-current pulses through dynistors. All elements of the cell are mounted on the capacitor and occupy a volume of 120 dm³.     

Influence of Landau level mixing on the properties of elementary excitations in graphene in strong magnetic field

ABSTRACT: Massless Dirac electrons in graphene fill Landau levels with energies scaled as square roots of their numbers. Coulomb interaction between electrons leads to mixing of different Landau levels. The relative strength of this interaction depends only on dielectric susceptibility of surrounding medium and can be large in suspended graphene. We consider influence of Landau level mixing on the properties of magnetoexcitons and magnetoplasmons-elementary electron-hole excitations in graphene in quantizing magnetic field. We show that, at small enough background dielectric screening, the mixing leads to very essential change of magnetoexciton and magnetoplasmon dispersion laws in comparison with the lowest Landau level approximation.PACS: 73.22.Pr; 71.35.Ji; 73.43.Mp; 71.70.Gm.     

Tunable order in colloids of hard magnetic hexaferrite nanoplatelets

Structural ordering in the concentrated magnetic colloids containing 50×5 nm hard magnetic disc-like SrFe₁₂O₁₉ nanoparticles was investigated by cryogenic scanning electron microscopy,optical microscopy,magnetic measurements,and small-angle X-ray scattering.It was revealed that macroscopically homogeneous magnetic liquid consists of dynamic threads of stacked nanoparticles.The threads align into quasiperiodic arrays with the distances between individual threads of a few micrometers.They also can form pseudodomain structures with -90°domain boundaries realized through T-type thread interconnects.The effects of magnetic attraction and electrostatic repulsion on the equilibrium interplatelet distance in the threads were studied.It was demonstrated that this distance can be tuned by the control of the particles charge and electric double layer screening from Stern layer thickness(-1 nm)to tens of nanometers.It was shown that the permanent magnetic field is not able to cause any structural changes in the ordered magnetic liquid phase,while alternating field draws particles apart by their vibrations.External variation of interparticle distance up to 6%was achieved using an alternating magnetic field of low intensity.Experimental data were complemented by the theoretical models of screened electrostatic interactions between spherical and platelike magnetic particles.The last model provides good predictive power and correlates with the experimental data.The stabilization energy of the condensed phase in the order of 1-10 kBT was derived from the model.An approach allows controlling of an equilibrium interparticle distance and interparticle distance distribution by adjusting the magnetization and surface charge of the particles as well as the ionic strength of the solvent.     

Calculation of Some Properties of the Cubic Oxides of II-VIII Group Metals

Experimental data on the bulk modulus of elasticity, thermal expansion coefficient, specific heat capacity, specific volume, Grueneisen constant, and atomization energy of the cubic monoxides of Mg, Ca, Sr, Cd, Ba, Eu, Th, U, Pu, Ti, Zr, V, Nb, Ta, Cr, Mn, Fe, Co, and Ni were analyzed. Using six correlation relationships values of unknown properties and adjusted values of known properties at 298 K were calculated.

     

Probing Cell‐Type‐Specific Intracellular Nanoscale Barriers Using Size‐Tuned Quantum Dots

The compartmentalization of size‐tuned luminescent semiconductor nanocrystal quantum dots (QDs) in four distinctive cell lines, which would be representative of the most likely environmental exposure routes to nanoparticles in humans, is studied. The cells are fixed and permeabilized prior to the addition of the QDs, thus eliminating any cell‐membrane‐associated effects due to active QD uptake mechanisms or to specificity of signaling routes in different cell types, but leaving intact the putative physical subcellular barriers. All quantitative assays are performed using a high content analysis (HCA) platform, thereby obtaining robust data on large cell populations. While smaller QDs 2.1 nm in diameter enter the nuclei and localize to the nucleoli in all cell types, the rate and dynamics of their passage vary depending on the cell origin. As the QD size is increased to 4.4 nm, penetration into the cell is reduced but each cell line displays its own cutoff size thresholds reflecting cell‐type‐determined cytoplasmic and nuclear pore penetration specificity. These results give rise to important considerations regarding the differential compartmentalization and susceptibility of organs, tissues, and cells to nanoparticles, and may be of prime importance for biomedical imaging and drug‐delivery research employing nanoparticle‐based probes and systems.     

Quasi-probability distributions for the simplest dynamical groups

We prove that the Wigner-Stratonovich-Agarwal operator that defines the quasi-probability distribution on the sphere [for the SU(2) dynamical group] can be written as an integral of the SU(2) (irreducible unitary) representation element with respect to a single variable that labels the orbits in the coadjoint representation. This allows us to consider contractions of the SU(2) quasi-probability distribution to the cases of the Heisenberg-Weyl group and the two-dimensional Euclidean group.     

Comparing Five and Lower-Dimensional Grain Boundary Character and Energy Distributions in Copper: Experiment and Molecular Statics Simulation

Metallurgical and Materials Transactions A - The misorientation of 515 grain boundaries has been determined using electron backscatter diffraction data from an 18 μm thick copper foil with...     

Influence of Titanium Excess in a Ti–Si Reaction Mixture on the Synthesis of a Composite in a Combustion Wave

Theoretical Foundations of Chemical Engineering - On the basis of the classic concepts of the theory of solid-phase combustion, for the first time, a model with a detailed scheme of chemical...     

Comparative Characteristics of the Structure and Physicochemical Properties of Silica Synthesized by Pyrogenic and Fluoride Methods

Silicon - This paper presents the comparative analysis of the properties of highly dispersed silicas synthesized by pyrogenic and fluoride methods. Raw materials and synthesis conditions differ...