No abstract available

[en] There are three major research activities involved in this thesis. The first is to improve and adapt the existing inverse algorithms, filtering techniques and lead field analysis that are required to deconvolve the current distribution from the measured magnetic field. We accomplished the improvements of the filtering technique by incorporating the current continuity condition to deal with a discontinuous current source and by using optimal filters to gain better noise control. Furthermore, we extended the filtering technique to the deconvolution of the magnetization distribution from the magnetic field measured in the vicinity of diamagnetic and paramagnetic objects. By adapting lead field analysis, we reconstructed the current distribution on a cylindrical surface, rather than for two-dimensional planar current distributions as done before. As the second major objective, and through this extensive research on inverse algorithms, we developed an algorithm, based upon the finite element method, to reconstruct a bounded and discontinuous current source. The significance of the finite element method to successfully interpret the magnetic field produced by a high temperature superconducting (HTS) thin film. We designed and built a nonmagnetic cooling system for a one inch square HTS thin. We performed several experiments to study the magnetic properties, the transport properties, and flux noise for a thin film with large area. With the help of the finite element method, we successfully reconstructed the supercurrent patterns of the thin film, and found that the conductivity of the HTS thin film is either nonuniform or anisotropic at both room and liquid nitrogen temperature. The flux noise of the thin film was much higher at the critical temperature than below or above that temperature. Overall, this research succeeded in the development o general methods to analyze magnetic field data, not only for HTS, but also for normal conductors and weakly-magnetic materials

No abstract available

[en] Purpose: To combine total variation (TV) and Hessian penalty in a structure adaptive way for cone-beam CT (CBCT) reconstruction. Methods: TV is a widely used first order penalty with good ability in suppressing noise and preserving edges but leads to the staircase effect in regions with smooth intensity transition. The second order Hessian penalty can effectively suppress the staircase effect with extra cost of blurring object edges. To take the best of both penalties we proposed a novel method to combine both for CBCT reconstruction in a structure adaptive way. The proposed method adaptively determined the weight of each penalty according to the geometry of local regions. An specially-designed exponent term with image gradient involved was used to characterize the local geometry such that the weights for Hessian and TV were 1 and 0 respectively at uniform local regions and 0 and 1 at edge regions. For other local regions the weights varied from 0 to 1. The objective functional was minimized using the majorzationminimization approach. We evaluated the proposed method on a modified 3D shepp-logan and a CatPhan 600 phantom. The full-width-at-halfmaximum (FWHM) and contrast-to-noise (CNR) were calculated. Results: For 3D shepp-logan the reconstructed images using TV had an obvious staircase effect while those using the proposed method and Hessian preserved the smooth transition regions well. FWHMs of the proposed method TV and Hessian penalty were 1.75 1.61 and 3.16 respectively, indicating that both TV and the proposed method is able to preserve edges. For CatPhan 600 CNR values of the proposed method were similar to those of TV and Hessian. Conclusion: The proposed method retains favorable properties of TV like preserving edges and also has the ability in better preserving gradual transition structure as Hessian does. All methods performs similarly in suppressing noise. This work was supported in part by National Natural Science Foundation of China (NNSFC) under Grant Nos.60971112 and 61375018 grants from the Cancer Prevention and Research Institute of Texas (RP130109 and RP110562-P2) National Institute of Biomedical Imaging and Bioengineering (R01 EB020366) and a grant from the American Cancer Society (RSG-13-326-01-CCE).

[en] A treatment of kinetic Monte Carlo method is devised that incorporates strain effects in a direct and natural way. The submonolayer growth (θ<0.3) of islands, in the cases of negative misfits (-10% and -32%) and of positive misfits (+10%, +20%, and +32%), is considered. The case of negative misfits leads to smaller islands, whereas the case of positive misfits leads to larger islands. It is inferred, from these drastic effects of strain on heteroepitaxial nucleation, that the adatom, at low coverage (θ<0.3), is subject, during the growth regime (0.05<θ<0.2), to a bias force generated by compressive or tensile strain at interface, which promotes detachment or attachment from islands, respectively. copyright 1999 The American Physical Society

[en] Several herbicide-tolerant crops have been developed and commercialized from herbicide-tolerant mutants obtained through chemical mutagenesis followed by herbicide selection or direct herbicide selection of spontaneous mutations. All mutations used in commercial herbicide-tolerant crops are derived from a single nucleotide substitution of genes that encode enzymes or proteins targeted by herbicides. The alleles of all commercial herbicide-tolerant mutations are incompletely-dominant except for the triazine-tolerant mutation. (author)

[en] A study was carried out into the formation of aluminium foams via powder processing route. Aluminum powder compacts both in pure form and AI-5%TiO₂ were foamed at temperatures ranging from 675 to 800^oC. Foaming agent TiH₂ was mixed with powders typically with 0.6 wt % in two different sizes. Experiments have shown that foaming in excess of 120 % is possible both with pure AI as well as in AI-TiO₂. It is found that with coarse TiH₂, with and without TiO₂, Al expands more, implying that there may be a certain size below which particles may not participate in the foaming process. It is further found that with the use of high temperature there are internal reactions between foaming agent and aluminium as well as between TiO₂ and AI. This is with the result that with TiO₂ added system foaming becomes more temperature dependant than the pure AI. (Original)

[en] Cyclosporine I.V. (CIV), in its vehicle, Cremophor EL, (CEL), is a potent immunosuppressive agent which prolongs survival of allogeneic transplants. NKCC is postulated to be involved in allograft rejection. This study was designed to investigate the effect of CEL, a polyoxyethylated castor oil, on in vitro spontaneous cytotoxicity induced by human natural killer cells. NKCC was measured by a standard ⁵¹Cr release assay with K562 target cells. After a 4 hr NKCC assay, both CIV at 10^-3M to 10^-7M and CEL at the equivalent dilution, suppressed NKCC 46 to 6%, relative to control lysis (p 0.05). There was no significant suppression of NKCC at dilutions greater than 10^-7M. The differences in NKCC between CIV and CEL at all dilutions tested were not significant. Both CIV and CEL with increasing dilutions correlated negatively with NKCC (r = -0.67, p < 0.0001; r = -0.74, p < 0.0001, respectively). With a 4 hr preincubation, both CIV at 10^-4M and CEL at the equivalent dilution suppressed NKCC (p < 0.01). However, after a 24 hr preincubation of CIV and CEL, NKCC did not differ from control lysis. These data suggest that the CIV vehicle CEL transiently suppresses in vitro NKCC and, therefore, may play a role in the survival of allogeneic transplants

[en] Multiferroic ceramics with the general formula (x)MgFe₂O₄-(1-x)BaTiO₃ (x=0.4, 0.5, and 0.6) were synthesized by solid-state sintering process. From the x-ray diffraction analysis, it was observed that almost no chemical reaction occurs between the ferrite and the ferroelectric materials used to form the diphase composite systems. No impure phase was observed in all the sintered composite systems. Leakage current density, ferroelectric properties and dielectric properties were found to improve with the addition of the ferroelectric phase. For the composite with the least amount of ferrite, the values of remnant polarization (2P_r) before and after dc magnetic poling at 7 kOe for 1 h were found to be 1.35 and 2.12 μC/cm², respectively. This showed marked improvement as high as 57% and confirmed the coupling of the electrical dipoles with the magnetic field applied. All the studied composite systems proved to be multiferroic in nature. The highest magnetoelectric coupling coefficient of 50.2 mV/cm Oe was measured at dc magnetic field of 10 kOe along with ac frequency of 50 Hz at room temperature for the 0.6MgFe₂O₄-0.4BaTiO₃ composite system. Magnetoelectric effect at resonance frequency increases by a factor of 80 compared to the other frequencies for such composite systems

[en] This paper reports on the infrared optical absorption properties near and above the fundamental absorption edge of MBE grown undoped GaInAsSb quaternary semiconductor alloy deposited on GaSb and GaAs substrates measured and analyzed at room temperature by means of a Fourier Transform Infrared Spectrometer, and were found to be fully characterized by the interband transition theory and Urbach's rule. The optical band gap of MBE-GaInAsSb has been determined using a linear extrapolation of (αhν)² as a function of the photon energy hν, and the refractive index n deduced from the interference pattern, which shows good agreement with the theory of Sadao Adachi's