Memory effects in gas chromatographic detection with a microwave-induced plasma

Capillary gas chromatography coupled to microwave-inducedplasma detection furnishes sensitivity adequate for trace analysis when the signal is monitored at a carbon emission line. Work performed with one of these systems at high electronic gain for the carbon signal has revealed solvent band widths in excess of four minutes; these impeded quantification of peaks eluting after the solvent. This report discusses two phenomena which could be related to the unexpected intensity of this solvent response: photomultiplier tube saturation and carbon deposits in the quartz plasma discharge tube.     

Growth of InAs nanostructures on InP using atomic-force nanolithography

Atomic-force nanolithography was used to control the nucleation sites of InAs nanostructures on InP substrates. Indentations with a wide range of dimensions were produced on InP. InAs nanostructures were selectively grown by metal organic vapor phase epitaxy. It is shown that the number of active nucleation sites depends on the normal force applied during nanoindentation. Crystalline defects introduced by nanoindentation are shown to be nucleation sites for these nanostructures. The presence of screw dislocations within the grown nanostructures further supports this observation. PACS 81.07.-b; 68.37.Ps; 81.16.Nd     

THE ENERGY ASPECT OF THE RECIPROCAL INTERACTIONS OF PAIRS OF TWO DIFFERENT VIBRATION MODES OF A CLAMPED ANNULAR PLATE

The standardized mutual active and reactive sound power of a clamped plate, representing the energy aspect of the reciprocal interactions of two different in vacuo modes, has been computed. It was assumed that the vibrations are axisymmetric, elastic and time harmonic, the plate's transverse deflection is small as compared with the plate's size, and that the vibration velocity is small as compared with the acoustic wavenumber generated. The Kirchhoff-Love theory of a perfectly elastic plate was used. The integral formulae for the mutual sound power were transformed into their Hankel representations which made possible their subsequent computation. A closed path integral was used to express the integral in its Hankel representation to compute the mutual active sound power. The asymptotic stationary phase method was used to compute the two magnitudes, i.e., the mutual active and reactive sound power. The results obtained are the asymptotic formulae valid for the acoustically fast waves. The oscillating as well as the non-oscillating terms have been identified in the formulae to make possible their further separate analysis. The availability of the asymptotic formulae makes possible some fast numerical computations of the mutual sound power. Moreover, the formulae presented herein, together with those for the individual modes known from the literature, make a complete basis for further computations of the total sound power of the plate's damped and forced vibrations in fluid.     

Two-dimensional antiferromagnet in an external staggered field

We calculate the temperature-dependent energy gap in the magnetic excitations spectrum of the two-dimensional antiferromagnet in the presence of a staggered magnetic field, using the nonlinear sigma model.     

Actinide heterobimetallic oxides (Th, U): reduction studies

In our laboratories we have been studying the synthesis and reactivity of binary actinide and lanthanide intermetallic compounds. In this work, the air-oxidation of ThCu₂ and AnNi₂ (An = Th, U) was followed by thermogravimetry (TG) and the products were characterized by X-ray powder diffraction (XRD). The heterobimetallic oxides obtained are described by the formulas 2MO·ThO₂ (M = Cu, Ni) and 2NiO·UO₃. The thermogravimetric analysis under hydrogen of these heterobimetallic oxides show one mass loss for 2MO·ThO₂ and two mass losses for 2NiO·UO₃ over a wide range of temperature (293–1273 K). The characterization by XRD shows that the reduction products are 2M·ThO₂ (M = Cu, Ni) and 2Ni·UO₂, with all the actinides in the 4+ oxidation state. The actinide heterobimetallic oxides were described as copper or nickel supported catalysts.