B-cell and T-cell immunoblastic lymphomas of baboons

The results of morphological study of B- and T-cellular immunoblast baboon lymphomas are presented. Differences are found both in the structure of tumour cells and in the histostructure of tumours as a whole. The tumor cells of B-immunoblastic lymphomas expressed mainly IgM. The tumour cells of certain T-immunoblastic lymphomas being investigated by means of monoclonal OKT4 antibodies had a surface phenotype peculiar to T-helper cells.     

Kinetics of chlorination of tantalum pentoxide in mixture with sucrose carbon by chlorine gas

The mechanism and kinetics of β-Ta₂O₅ chlorination, mixed with sucrose carbon, have been studied by a thermogravimetric technique. The investigated temperature range was 500 °C to 850 °C. The reactants and reaction residues were analyzed by scanning electronic microscopy (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller method for surface area (BET). The effect of various experimental parameters was studied, such as carbon percentage, temperature, chlorine partial pressure, and flow, use of the multiple sample method, and carbon previous oxidation. The carbon percentage and previous treatment have an effect on the system reactivity. The temperature has a marked effect on the reaction rate. In the 500 °C to 600 °C temperature interval, the apparent activation energy is 144 kJ/mol of oxide, while at higher temperatures, the activation energy decreases. With high chorine partial pressures, the order of reaction is near zero. The kinetic contractile plate model, X=kt, considering carbon oxidation as the controlling stage, is the one with the best fit to the experimental data. A probable mechanism for the carbochlorination of β-Ta₂O₅ is proposed: (1) activation of chlorine on the carbon surface, (2) chlorination of Ta₂O₅, (3) oxidation of carbon, and (4) recrystallization of β-Ta₂O₅.     

N-Type Field-Effect Transistors Using Multiple Mg-Doped ZnO Nanorods

Nanorod field-effect transistors (FETs) that use multiple Mg-doped ZnO nanorods and a SiO₂ gate insulator were fabricated and characterized. The use of multiple nanorods provides higher on-currents without significant degradation in threshold voltage shift and subthreshold slopes. It has been observed that the on-currents of the multiple ZnO nanorod FETs increase approximately linearly with the number of nanorods, with on-currents of ~1 muA per nanorod and little change in off-current (~4times10^-12). The subthreshold slopes and on-off ratios typically improve as the number of nanorods within the device channel is increased, reflecting good uniformity of properties from nanorod to nanorod. It is expected that Mg dopants contribute to high n-type semiconductor characteristics during ZnO nanorod growth. For comparison, nonintentionally doped ZnO nanorod FETs are fabricated, and show low conductivity to compare with Mg-doped ZnO nanorods. In addition, temperature-dependent current-voltage characteristics of single ZnO nanorod FETs indicate that the activation energy of the drain current is very low (0.05-0.16 eV) at gate voltages both above and below threshold     

Interaction of optical radiation with GaAs nanowhisker arrays

We have studied the reflectivity spectra of doped GaAs nanowhiskers (NWs) with various morphologies, which were grown by molecular-beam epitaxy. It is established that the character of the reflectivity spectra of NWs is determined by the shape of nanocrystals. NWs with droplike and pointlike vertices differently interact with electromagnetic radiation. Laser radiation produces a spectraly selective action on the NW array, which leads to a change in the NW height and induces “caking” of their vertices, thus modifying the reflectivity of the sample. This phenomenon can be used for the creation of local microstructures with preset characteristics in large NW arrays.     

Application of holographic interferometry for determining the solubility of gases in liquids

The effect of a gas dissolved in a liquid on the variation of the refractive index of the compressed mixture was studied. The compression process was monitored with the aid of a holographic interferometer. The sensitivity of this method allows the compressibility of water and the solubility of helium and nitrogen to be studied at pressures below 4 atm. A procedure for obtaining qualitative and quantitative data on the solubility of gases in liquids is proposed.     

Fermi–Bose Correspondence and Bose–Einstein Condensation in the Two-Dimensional Ideal Gas

The ideal uniform two-dimensional (2D) Fermi and Bose gases are considered both in the thermodynamic limit and the finite case. We derive May's Theorem, viz. the correspondence between the internal energies of the Fermi and Bose gases in the thermodynamic limit. This results in both gases having the same heat capacity. However, as we shall show, the thermodynamic limit is never truly reached in two dimensions and so it is essential to consider finite-size effects. We show in an elementary manner that for the finite 2D Bose gas, a pseudo-Bose–Einstein condensate forms at low temperatures, incompatible with May's Theorem. The two gases now have different heat capacities, dependent on the system size and tending to the same expression in the thermodynamic limit.     

Surface Films on Zinc-Plated Steel Formed on Holding in Aqueous Extracts of Anticorrosion Pigments

The methods of X-ray photoelectron spectroscopy and Auger spectroscopy are used to study surface films formed on zinc and zinc-plated steel in the process of holding in aqueous extracts of mixtures of phosphate and calcium-containing pigments. It is shown that protective films formed mainly of zinc and calcium phosphates of different chemical structure are deposited in inhibited solutions on specimens of pure zinc and zinc-plated steel. The protective properties of these films are much better than the protective properties of the surface layers formed on the metal in the extracts of a single phosphate (or calcium-containing) pigment. The mixture of these pigments may serve as a promising substitution of chromate inhibitors in anticorrosive organic coatings.     

Influence of the model for random birefringence on the differential group delay of periodically spun fibers

We consider the two Wai-Menyuk models of birefringence in periodically spun fibers, and we show that the differential group delay differs significantly for the two models when the spin period approaches or exceeds the fiber beat length. When the fiber correlation length is large, we explain this difference quantitatively, and we explain it qualitatively for any fiber correlation length.     

A mechanistic analysis of the correlation between overall strength and indentation hardness in discontinuously reinforced aluminum

It is well established that the indentation hardness of metallic alloys shows a reasonable correlation with their yield strength or ultimate strength. Experiments illustrate that such a unique correlation is nonexistent for discontinuously reinforced metal matrix composites, even when the indentation size is much greater than the reinforcement size. For aluminum alloys reinforced with silicon carbide particles, the same composite yield strength and tensile strength with different reinforcement fractions do not lead to similar hardness, or vice versa. Finite element analyses are carried out to rationalize the experimental findings. The modeling utilizes a two-dimensional plane-strain formulation. Discrete particles are included in the material model, and the overall stress-strain response and the indentation response are numerically simulated. The results confirm the lack of unique correspondence between the composite hardness and strength. The alteration of local heterogeneity in the composite is found to affect the indentation response. Effects of the geometrical arrangement of particles and thermal residual stresses on the indentation response are also investigated numerically.