Pressure-Enhanced Crystallization Kinetics of Amorphous Si and Ge: Implications for Point-Defect Mechanisms

The effects of hydrostatic pressure on the solid phase epitaxial growth (SPEG) rate, v, of intrinsic Ge (100) and undoped and doped Si (100) into their respective self-implanted amorphous phases are reported. Samples were annealed in a high-temperature, high-pressure diamond anvil cell. Cryogenically-loaded fluid Ar,used as the pressure transmission medium, ensured a clean and hydrostatic environment.Engineering and Applied Science

A superlinear space decomposition algorithm for constrained nonsmooth convex program

AbstractA class of constrained nonsmooth convex optimization problems, that is, piecewise C2 convex objectives with smooth convex inequality constraints are transformed into unconstrained nonsmooth convex programs with the help of exact penalty function. The objective functions of these unconstrained programs are particular cases of functions with primal–dual gradient structure which has connection with VU space decomposition. Then a VU space decomposition method for solving this unconstrained program is presented. This method is proved to converge with local superlinear rate under certain assumptions. An illustrative example is given to show how this method works

Pressure-Enhanced Solid Phase Epitaxy: Implications for Point Defect Mechanisms

We have measured the effects of hydrostatic pressure on the solid phase epitaxial growth (SPEG) rates of undoped GE(100) into their respective self-implanted amorphous volumes equal to -3.3 +/- 0.3cm3/mole for Si and -6.3 +/- 0.60cm3/mole for Ge. The results of this and other experiments are inconsistent with all bulk point-defect mechanisms, but are consistent with all interface point-defect mechanisms proposed to date for thermal SPEG. A kinetic analysis of the Spaepen-Turnbull bond mechanism shows it to be a highly plausible model for the growth process.Engineering and Applied Science

The Activation Strain Tensor: Nonhydrostatic Stress Effects on Crystal-Growth Kinetics

The solid-phase epitaxial-growth rate of crystalline Si from the amorphous Si on the tensile side is greater than on the compressive side of elastically bent wafers, in marked contrast to the behavior observed under hydrostatic pressure. The phenomenology of an activation strain tensor, the nonhydrostatic analogue of the activation volume, is developed to characterize such measurements. The measurement permits us to characterize to first order the entire activation strain tensor for solid-phase epitaxy of Si(001): The transition state for this process involves an in-plane expansion and a contraction in the direction normal to the interface. Its symmetry is inconsistent with all proposed bulk point-defect mechanisms.Engineering and Applied Science

Effect of Nonhydrostatic Stress on Crystal Growth Kinetics

The effect of nonhydrostatic stresses on the solid phase epitaxial growth rate of crystalline Si(100) into self-implanted amorphous surface layers has been measured. Uniaxial stresses of up to 6 kbar (0.6 GPa) were attained by bending wafers over SiO2 rods and annealing at a temperature too low for plastic deformation to relieve the stress in the crystal, but high enough for solid phase epitaxial growth to proceed. The growth rate on the tensile side was greater than that on the compressive side of the wafer, in marked contrast to the enhancement observed from hydrostatic pressure. The phenomenology of an "activation strain", the nonhydrostatic analogue of the activation volume, has been developed to characterize the results. Combined with the measurement of the activation volume, the measurement reported here permits us to characterize to first order the entire activation strain tensor corresponding to the transition state for solid phase epitaxy of Si(100). We conclude that the transition state for this process is "short and fat"; that is, the fluctuation to the transition state involves an expansion in the two in-plane directions and a contraction in the direction normal to the surface large enough to make the overall volume change negative. The symmetry of the measured activation strain tensor is inconsistent with all bulk point defect mechanisms for solid phase epitaxy. The relevance of the activation strain formalism to heteroepitaxy and vapor phase epitaxy is discussed.Engineering and Applied Science

The synthesis and characterization of 1111-type diluted magnetic semiconductors (La1-xSrx)(Zn1-xTMx)AsO (TM = Mn, Fe, Co)

The doping effect of Sr and transition metals Mn, Fe, Co into the direct-gap semiconductor LaZnAsO has been investigated. Our results indicate that the single phase ZrCuSiAs-type tetragonal crystal structure is preserved in (La1-xSrx)(Zn1-xTMx)AsO (TM = Mn, Fe, Co) with the doping level up to x = 0.1. While the system remains semiconducting, doping with Sr and Mn results in ferromagnetic order with TC ~ 30K, and doping with Sr and Fe results in a spin glass like state below ~6K with a saturation moment of ~0.02 muB/Fe, an order of magnitude smaller than the ~0.4 muB/Mn of Sr and Mn doped samples. The same type of magnetic state is observed neither for (Zn,Fe) substitution without carrier doping, nor for Sr and Co doped specimens.Comment: Accepted for publication in EP

Antitumor activity of mixed heat shock protein/peptide vaccine and cyclophosphamide plus interleukin-12 in mice sarcoma

<p>Abstract</p> <p>Background</p> <p>The immune factors heat shock protein (HSP)/peptides (HSP/Ps) can induce both adaptive and innate immune responses. Treatment with HSP/Ps in cancer cell-bearing mice and cancer patients revealed antitumor immune activity. We aimed to develop immunotherapy strategies by vaccination with a mixture of HSP/Ps (mHSP/Ps, HSP60, HSP70, Gp96 and HSP110) enhanced with cyclophosphamide (CY) and interleukin-12 (IL-12).</p> <p>Methods</p> <p>We extracted mHSP/Ps from the mouse sarcoma cell line S180 using chromatography. The identity of proteins in this mHSP/Ps was assayed using SDS-PAGE and Western blot analysis with antibodies specific to various HSPs. BALB/C mice bearing S180 cells were vaccinated with mHSP/Ps ×3, then were injected intraperitoneally with low-dose CY and subcutaneously with IL-12, 100 μg/day, ×5. After vaccination, T lymphocytes in the peripheral blood were analyzed using FACScan and Cytotoxicity (CTL) was analyzed using lactate dehydrogenase assay. ELISPOT assay was used to evaluate interferon γ (IFN-γ), and immune cell infiltration in tumors was examined in the sections of tumor specimen.</p> <p>Results</p> <p>In mice vaccinated with enhanced vaccine (mHSP/Ps and CY plus IL-12), 80% showed tumor regression and long-term survival, and tumor growth inhibition rate was 82.3% (30 days), all controls died within 40 days. After vaccination, lymphocytes and polymorphonuclear leukocytes infiltrated into the tumors of treated animals, but no leukocytes infiltrated into the tumors of control mice. The proportions of natural killer cells, CD8+, and interferon-γ-secreting cells were all increased in the immune group, and tumor-specific cytotoxic T lymphocyte activity was increased.</p> <p>Conclusions</p> <p>In this mice tumor model, vaccination with mHSP/Ps combined with low-dose CY plus IL-12 induced an immunologic response and a marked antitumor response to autologous tumors. The regimen may be a promising therapeutic agent against tumors.</p