Axial gas phase dispersion in a molten salt oxidation reactor

Gas phase axial dispersion characteristics were determined in a molten salt oxidation reactor (air-molten sodium carbonate salt two phase system). The effects of the gas velocity (0.05–0.22 m/s) and molten salt bed temperature (870–970 °C) on the gas phase axial dispersion coefficient were studied. The amount of axial gas-phase dispersion was experimentally evaluated by means of residence time distribution (RTD) experiments using an inert gas tracer (CO). The experimentally determined RTD curves were interpreted by using the axial dispersions model, which proved to be a suitable means of describing the axial mixing in the gas phase. The results indicated that the axial dispersion coefficients exhibited an asymptotic value with increasing gas velocity due to the plug-flow like behavior in the higher gas velocity. Temperature had positive effects on the gas phase dispersion. The effect of the temperature on the dispersion intensity was interpreted in terms of the liquid circulation velocity using the drift-flux model.     

Observability and redundancy in process data estimation

By analogy to the development for dynamic systems, concepts of observability and redundancy may be developed with respect to a steady state system. These concepts differ from their counterparts for dynamic systems in that they can be used to characterize individual variables and local behavior as well as system and global behavior. Relations between local observability, global observability, calculability and redundancy are established and explored in this paper. It is shown that these concepts are useful in characterizing the performance of process data estimators with regard to bias and uniqueness of an estimate, convergence of estimation procedures and the feasibility and implications of problem decomposition.     

Investigation on texture evolution during friction stir welding of stainless steel

A two-dimensional Eulerian finite-element formulation is used to model the motion, thermal response, and strain hardening during friction stir welding (FSW) of a stainless steel alloy. Texture evolution is predicted from the computed velocity gradients along streamlines of the flow field. The texture is assumed to be uniform initially and shows monoclinic sample symmetry after deformation. Upstream and downstream of the tool, the deformation is nearly monotonic, causing little change of the texture. Around the tool pin, the texture strengthens, weakens, and restrengthens repeatedly and rapidly. The repeated strengthening and weakening of the texture are explained with the aid of an idealized, circular streamline path and consideration of the relative magnitudes of the deformation rate and spin along the streamline.     

The effect of elastic strain on the optical properties of InGaP/GaAs grown using a valved phosphorus cracker cell in solid source MBE

We report the effect of elastic strain on the optical properties of In_1−xGa_xP grown using a valved phosphorus cracker cell in solid source molecular beam epitaxy (SSMBE). Sample characterization was carried out using photoluminescence (PL) and double-axis X-ray diffraction (XRD). All the In_1−xGa_xP epilayers prepared in this study are gallium-rich (tensile strained) with composition x in the range of 0.516<x<0.559. The unstrained plot of the band-gap as a function of composition x was deduced from the tensile-strained data obtained experimentally by assuming that the valence band splitting is due only to biaxial elastic strain. The unstrained plot of band-gap vs. composition x for our MBE-grown samples was about 10 meV and 20 meV lower than those reported for samples grown by organometallic vapour phase epitaxy (OMVPE) and liquid phase epitaxy (LPE) techniques, respectively. The photoluminescence (PL) full width at half-maximum (FWHM) of the InGaP samples was higher as the composition x increases due to an increase in the lattice mismatch. Compared to other growth techniques involving the use of higher substrate temperature, InGaP of comparable optical quality can be grown using the valved phosphorus cracker cell SSMBE technique.     

Morphological study of heat-sensitive and heat-resistant spores of Clostridium sporogenes, using transmission electron microscopy

To investigate the primary structural determinants affecting heat resistance of Clostridium sporogenes spores, electron micrographs of heat-sensitive (D121 degrees C = 0.56 min) and heat-resistant (D121 degrees C = 0.93 min) spores of C. sporogenes were taken with a transmission electron microscope. The mean thickness (+/- standard deviation [SD]) of coat layers and cortex regions of heat-sensitive spores were 82.9 +/- 14.5 and 86.0 +/- 22.7 nm, while those of heat-resistant spores were 106.9 +/- 45.7 and 111.7 +/- 32.1 nm, respectively. The thickness of coat (P = 0.031) and cortex (P = 0.006) showed statistically significant differences, suggesting that heat-resistant spores have a thicker coat and cortex than do heat-sensitive spores. The mean sizes (+/- SD) of cores were 467.0 +/- 88.7 nm for heat-sensitive spores and 460.2 +/- 98.5 nm for heat-resistant spores, respectively, which showed no statistically significant differences. The ratios (+/- SD) of the core size to the sporoplast size were 0.84 +/- 0.05 for heat-sensitive spores and 0.80 +/- 0.07 for heat-resistant spores, respectively, showing statistically significant differences (P = 0.030), which indicated that the ratio is negatively related to heat resistance. Accordingly, the structural components of heat-sensitive spores were severely damaged by heat treatment, whereas those of heat-resistant spores were unlysed under the same conditions. Based on the structural analyses of spores, it was elucidated that the thickness of coat layer and cortex region are significantly correlated with heat resistance of C. sporogenes spores, and that cortex region plays a major role in protecting the spore from heat damage.     

Effects of zirconium doping on the characteristics of tin oxide thin film transistors

Thin-film transistors (TFTs) with zirconium-doped tin oxide (ZSO) channels were fabricated by co-sputtering Sn and Zr metal targets. The effect of Zr on the performance of SnO_x-based TFTs was studied. TFTs with an intrinsic SnO_x channel did not show promising performance. However, ZSO TFTs exhibited improved electrical properties, with increased I_ON/I_OFF and decreased subthreshold swing. The influence of zirconium doping on bias stability in tin oxide TFTs was also investigated. ZSO TFTs exhibited turn-on voltage (V_ON) shifts of +9 V for positive stress bias, compared with +18 V for intrinsic SnO_x TFTs. The improvements in device performance and stability were attributed to reduced carrier concentration induced by carrier trapping at Zr impurity sites.     

Investigation of VOPcPhO as an acceptor material for bulk heterojunction solar cells

In this study, we have successfully demonstrated a new system of donor–acceptor blend for bulk heterojunction solar cells of poly(3-hexylthiophene) (P3HT) by using vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine (VOPcPhO) as acceptor material. A broad absorption over the whole visible range (450–750 nm) is achieved. Utilizing this blend system in solar cell fabrication, ITO/PEDOT:PSS/P3HT:VOPcPhO/Al solar cells have been fabricated and characterized in open air. A maximum power conversation efficiency up to 1.09% has been recorded. To confirm the charge transport, the electron and hole mobility of VoPcPhO has been measured. The results show that the VoPcPhO has bipolar transport and can act as an electron as well as hole transporting material. The electron mobility is comparable with hole mobility.     

Expression of apoptosis regulators in cutaneous malignant melanoma

Metastatic malignant melanoma (MM) is usually incurable and responds poorly to chemotherapy. Because many cytotoxic drugs cause cell death by inducing apoptosis, an imbalance of apoptosis regulatory proteins may contribute to MM treatment resistance. We have previously shown reduced expression of Bcl-2 protein, a negative regulator of apoptosis, in MM as compared with benign nevi. It is hypothesized that other apoptosis regulators may be involved in survival of MM cells. We examined the expression of Bax, Bcl-2, Bcl-X, and Mcl-1 in human benign nevi, primary MM, and metastatic MM using immunohistochemistry. Results were confirmed with Western blotting. The proapoptotic protein, Bax, was surprisingly overexpressed in all MM samples compared with benign nevi. Interestingly, in most MM samples there was overexpression of Mcl-1 or Bcl-XL, both negative regulators of apoptosis. Increased expression of Mcl-1 and Bcl-XL was first observed in thin primary melanomas, suggesting that up-regulation of these proteins represents a relatively early event associated with malignant transformation in MM. As published previously, the majority of primary and metastatic MM exhibited reduced Bcl-2 levels. We conclude that the apoptosis inhibitors Bcl-XL or Mcl-1, alone or in combination, may circumvent the normal cell death pathway, contributing to the pathogenesis and treatment resistance in metastatic MM.     

The stress-corrosion cracking of aluminum-coated U-4.5 wt% Nb

Room temperature ($\text{26 ± 2}$°C) tests show that the aged (80 h at 260°C) U-4.5 wt% Nb alloy can be protected from stress-corrosion cracking in aqueous chloride environments by coating the alloy with aluminum.