Features of electrochemical and thermal properties of CsHSO<Subscript>4</Subscript>-C<Subscript>60</Subscript> composite materials

New composite proton-conducting materials based on cesium hydrosulfate with fullerite C₆₀ were synthesized. The concentration dependence of the proton conductivity and thermal properties of synthesized materials with C₆₀ contents from 0 to 50 vol % was studied. It was found that these dependences are nonmonotonic with extrema at C₆₀ contents of ～2 and 30 vol %. The conductivity of the composite material with a C₆₀ content of ～2 vol % is almost twice higher than the conductivity of pure CsHSO₄ due to the formation of a new surface phase, which is confirmed by thermal analysis methods.     

Evolution of Anolyte Composition in the Oxidative Electrolysis of Sodium Bromide in a Sulfuric Acid Medium

The oxidation of a 10 mM aqueous solution of sodium bromide in a sulfuric acid medium on the surface of a platinum electrode in a cell with separated spaces was studied. The process is important in view of the use of the bromine–bromide redox couple in redox flow batteries. The study was performed by cyclic voltammetry, potentiostatic chronoamperometry with optical absorption spectrum recording, and measurements of the potential of the redox reference electrode. A numerical procedure for processing the experimental spectra of the solution was developed to separate them into the spectrum of molecular bromine and the residual signal. The latter was attributed to the absorption of the tribromide anion based on the literature data. The experimental dependences of the Br₂ and Br₃^- concentrations for the oxidative electrolysis of the NaBr solution in the sulfuric acid medium agreed well with the theoretical predictions. The current efficiency of bromine formation was evaluated.

     

A monopole mass filter with a hyperbolic V-shaped electrode

In this article we compare the classical monopole mass filter of von Zahn and the monopole mass filter with a hyperbolic V-shaped electrode. The experimental results and those of computer simulation for both mass spectrometers are presented. We show that the replacement of a conventional 90 degrees V-shaped electrode by an electrode with a hyperbolic profile substantially improves the peak shape of any given mass, and increases the mass resolution by a factor of 3-4 and the abundance sensitivity by a factor of 100. The potential of high analytical performance combined with electroforming techniques for electrode manufacture indicate future practical uses of such instruments. Copyright 1999 John Wiley & Sons, Ltd.     

Resonance Energy Transfer Reveals the Presence of Multiple Luminescence Emission Centers within a Carbon Nanodot

JETP Letters - Carbon nanodots are an emerging class of nanomaterials which exhibit visible photoluminescence, commonly attributed to luminescent organic groups within their structure. A question...     

Fabrication and characterization of Al nanomechanical resonators for coupling to nanoelectronic devices

We report on a suspension technique for Al doubly clamped beams. The technique is based on two consecutive reactive ion etching processes in CF₄ plasma, anisotropic and isotropic, of SiO _x on which Al layer is deposited. With this technique, Al doubly clamped beams were fabricated. One of the beams was characterized using a magnetomotive measurement scheme at low temperatures. The developed suspension technique is suitable for the fabrication of Al nanoelectronic devices with a mechanical degree of freedom, in particular, superconducting flux qubits with partly suspended loops.     

Single FIR-photon detection using a quantum dot

We study single-electron-transistor (SET) operation of the quantum dot (QD) in a strong magnetic field under weak illumination of far-infrared (FIR) radiation, which causes cyclotron resonance (CR) excitation inside the QD. We find that the SET conductance resonance is exceedingly sensitive to the FIR: It switches on (off) upon the excitation of just one electron to a higher Landau level inside the QD, whereby enabling us to detect individual events of FIR-photon (hν 6 meV) absorption.     

Justification of the Kirchhoff hypotheses and error estimation for two-dimensional models of anisotropic and inhomogeneous plates, including laminated plates

Asymptotic analysis of the problem describing deformation ofa thin cylindrical plate with clamped lateral side is performed.The problem is considered under the most general statement withthe plate being laminated and consisting of an arbitrary numberof nonhomogeneous and anisotropic (21 elastic moduli) layers.Explicit integral representations of the differential operatorswhich form the two-dimensional model of the plate are derived.In the case when the elastic moduli of each of the layers areconstant, these integral representations turn into algebraicones. The asymptotic procedure is justified with the help ofa weighted inequality of Korn's type. The error estimates obtainedgive a rigorous mathematical proof of both of Kirchhoff's hypotheses(kinematic and static) and shed light on the well-known intrinsicinconsistency of two of the hypotheses.     

Multicomponent Al-Si-based composites

The rapid quenching from melt was used to synthesize high-alloyed hypereutectic silumins with antimony and copper. The silumins were natural composites whose structure consisted mostly of dispersed intermetallic crystals uniformly distributed in the Al matrix. It was found that by selecting the optimum phase composition of the alloy and synthesizing multicomponent compounds, including fusible and refractory components, the linear thermal expansion coefficient can be reduced to 7.8 × 10⁻⁶ K⁻¹, or one-third of the corresponding coefficient for unalloyed silumin.     

Effect of femtosecond laser radiation on mammalian oocytes

Nucleolus-like bodies (NLBs) of mammalian oocytes are a convenient object for studying the effects of laser radiation on cellular organelles during laser surgery operations. NLBs in mouse germinal vesicle oocytes (GV oocytes) were subject to nanosurgery by means of tightly focused femtosecond laser pulses at near-infrared wavelength. The damage threshold of the NLB material was one-half orders of magnitude below the threshold for the water breakdown by femtosecond pulses. An incision of NLB material with submicron resolution was obtained at a threshold pulse energy. At the pulse energy one order of magnitude higher than the threshold level, significant deformation and rupture of NLBs were observed. Anisotropic deformations of the NLBs and the dynamics of their relaxation indicate the presence of granular structure in these organelles. Mechanical strain and the formation of cavitation and steam-gas bubbles in the place of impact of laser pulses can be described with the help of a model of the laser breakdown of medium.