Evaluation of both composition and strain distributions in InGaN epitaxial film using x-ray diffraction techniques

The composition and stain distributions in the InGaN epitaxial films are jointly measured by employing various x-ray diffraction (XRD) techniques, including out-of-plane XRD at special planes, in-plane grazing incidence XRD, and reciprocal space mapping (RSM). It is confirmed that the measurement of (204) reflection allows a rapid access to estimate the composition without considering the influence of biaxial strain. The two-dimensional RSM checks composition and degree of strain relaxation jointly, revealing an inhomogeneous strain distribution profile along the growth direction. As the film thickness increases from 100 nm to 450 nm, the strain status of InGaN films gradually transfers from almost fully strained to fully relaxed state and then more in atoms incorporate into the film, while the near-interface region of InGaN films remains pseudomorphic to GaN.

Evaluation of the Effectiveness of Representative Methods for Determining Young's Modulus and Hardness from Instrumented Indentation Data

The effectiveness of Oliver & Pharr's (O&P's) method, Cheng & Cheng's (C&C's) method, and a new method developed by our group for estimating Young's modulus and hardness based on instrumented indentation was evaluated for the case of yield stress to reduced Young's modulus ratio (sigma(y)/E-r) >= 4.55 x 10(-4) and hardening coefficient (n) <= 0.45. Dimensional theorem and finite element simulations were applied to produce reference results for this purpose. Both O&P's and C&C's methods overestimated the Young's modulus under some conditions, whereas the error can be controlled within +/- 16% if the formulation was modified with appropriate correction functions. Similar modification was not introduced to our method for determining Young's modulus, while the maximum error of results was around +/- 13%. The errors of hardness values obtained from all the three methods could be even larger and were irreducible with any correction scheme. It is therefore suggested that when hardness values of different materials are concerned, relative comparison of the data obtained from a single standard measurement technique would be more practically useful. It is noted that the ranges of error derived from the analysis could be different if different ranges of material parameters sigma(y)/E-r and n are considered.

Judd-Ofelt analysis of spectra and experimental evaluation of laser performance of Tm3+ doped Lu2SiO5 crystal

This paper reports that the TM3+:Lu2SiO5 (Tm:LSO) crystal is grown by Czochralski technique. The room-temperature absorption spectra of Tm:LSO crystal are measured on a b-cut sample with 4 at.% thulium. According to the obtained Judd-Ofelt intensity parameters Omega(2)=9.3155 x 10(-20) cm(2), Omega(4)=8.4103 x 10(-20) cm(2), Omega(6)=1.5908 x 10(-20) cm(2), the fluorescence lifetime is calculated to be 2.03 ms for F-3(4) -> H-3(6) transition, and the integrated emission cross section is 5.81 x 10(-18) cm(2). Room-temperature laser action near 2 mu m under diode pumping is experimentally evaluated in Tm:LSO. An optical-optical conversion efficiency of 9.1% and a slope efficiency of 16.2% are obtained with continuous-wave maximum output power of 0.67 W. The emission wavelengths of Tm:LSO laser are centred around 2.06 mu m with spectral bandwidth of similar to 13.6 nm.

Evaluation of estrogenic activities and mechanism of action of perfluorinated chemicals determined by vitellogenin induction in primary cultured tilapia hepatocytes

Perfluorochemicals (PFCs) are emerging persistent organic pollutants (POPs) and are widely present in the environment, wildlife and humans. Recently, reports have suggested that PFCs may have endocrine-disrupting activities. In the present study, we have developed a non-competitive enzyme-linked immunosorbent assay (ELISA) method to investigate estrogenic activities of selected PFCs using vitellogenin (VTG) induction in primary cultured hepatocytes of freshwater male tilapia (Oreochromis niloticus). Cultured hepatocytes were exposed to various concentrations of perfluorooctanyl sulfonate (PFOS), pentadecafluorooctanoic acid (PFOA), 1H, 1H, 2H, 2H-nonafluoro-1-hexanol (4:2 FTOH), 1H, 1H, 2H, 2H-perfluorooctanol (6:2 FTOH) and 1H, 1H, 2H, 2H-perfluoro-1-decanol (8:2 FTOH) for 48h, while 17 beta-estradiol (E2) and 4-nonylphenol (4-NP) were used as positive controls. A dose-dependent induction of VTG was observed in E2-, 4-NP-, PFOS-, PFOA- and 6:2 FrOH-treated cells, whereas VTG levels remained unchanged in the 4:2 FTOH and 8:2 FTOH exposure groups at the concentrations tested. The estimated 48-h EC50 values for E2,4-NP, PFOS, PFOA and 6:2 FTOH were 4.7 x 10(-7), 7.1 x 10(-6), 1.5 x 10(-5), 2.9 x 10(-5) and 2.8 x 10(-5) M, respectively. In the time-course study, significant VTG induction took place at 24 h (E2), 6 It (4-NP), 48 It (PFOS), 48 It (PFOA), 72 It (4:2 FTOH), 12 h (6:2 FTOH), 72 h (8:2 FTOH), and increased further after 96 It of exposure. Co-exposure to binary mixtures of individual PFCs and E2 for 48 It significantly inhibited E2-induced hepatocellular VTG production in a dose-dependent manner except for 4:2 FTOH. The estimated 48-h IC50 (concentration of a compound that elicits 50% inhibition of maximally E2-induced VTG) values for PFOS, PFOA, 6:2 FTOH and 8:2 FTOH were 3.1 x 10(-7), 5.1 X 10(-7), 1.1 X 10(-6) and 7.5 x 10(-7) M, respectively. In order to further investigate the estrogenic mechanism of PFCs, the hepatocytes were co-exposed to binary mixtures of individual chemicals (E2,4-NP, PFOS, PFOA and 6:2 FTOH) and the known estrogen receptor inhibitor tamoxifen for 48 h; tamoxifen significantly inhibited the ability of these chemicals to stimulate vitellogenesis. The overall results demonstrated that PFOS, PFOA and FTOHs have estrogenic activities and that exposure to a combination of E2 and PFCs produced anti-estrogenic effects. The results of the estrogen receptor inhibition assay further suggested that the estrogenic effect of PFCs may be mediated by the estrogen receptor pathway in primary cultured tilapia hepatocytes. (c) 2007 Elsevier B.V. All rights reserved.

Structural evaluation of polycrystalline silicon thin films by hot-wire-assisted PECVD

Tungsten wires were introduced into a plasma-enhanced chemical vapor deposition (PECVD) system as a catalyzer: we name this technique 'hot-wire-assisted PECVD' (HW-PECVD). Under constant deposition pressure (p(g)), gas flow ratio and catalyzer position, the effects of the hot wire temperature (T-f) on the structural properties of the poly-Si films have been characterized by X-ray diffraction (XRD), Raman scattering and Fourier-transform infrared (FTIR) spectroscopy. Compared with conventional PECVD, the grain size, crystalline volume fraction (X-e) and deposition rate were all enhanced when a high T-f was used. The best poly-Si film exhibits a preferential (220) orientation, with a full width at half-maximum (FWHM) of 0.2 degrees. The Si-Si TO peak of the Raman scattering spectrum is located at 519.8 cm(-1) with a FWHM of 7.1 cm(-1). The X-c is 0.93. These improvements are mainly the result of promotion of the dissociation of SiH4 and an increase in the atomic H concentration in the gas phase. (C) 2001 Elsevier Science B.V. All rights reserved.

Evaluation of thermal radiation dependent performance of GaSb thermophotovoltaic cell based on an analytical absorption coefficient model

Applying the model dielectric function method, we have expressed the absorption coefficient of GaSb analytically at room temperature relating to the contribution of various critical points of its electronic band structure. The calculated absorption spectrum shows good agreement with the reported experimental data obtained by spectral ellipsometry on nominally undoped sample. Based on this analytical absorption spectrum, we have qualitatively evaluated the response of active absorbing layer structure and its photoelectric conversion properties of GaSb thermophotovoltaic device on the perturbation of external thermal radiation induced by the varying radiator temperature or emissivity. Our calculation has demonstrated that desirable thickness to achieve the maximum conversion efficiency should be decreased with the increment of radiator temperature and the performance degradation brought by any structure deviation from its optimal one would be stronger meanwhile. For the popular radiator temperature, no more than 1500 K in a real solar thermophotovoltaic system, and typical doping profile in GaSb cell, a reasonable absorbing layer structure parameter should be controlled within 100-300 nm for the emitter while 3000-5000 nm for the base.

Structural evaluation of polycrystalline silicon thin films by hot-wire-assisted PECVD

Tungsten wires were introduced into a plasma-enhanced chemical vapor deposition (PECVD) system as a catalyzer: we name this technique 'hot-wire-assisted PECVD' (HW-PECVD). Under constant deposition pressure (p(g)), gas flow ratio and catalyzer position, the effects of the hot wire temperature (T-f) on the structural properties of the poly-Si films have been characterized by X-ray diffraction (XRD), Raman scattering and Fourier-transform infrared (FTIR) spectroscopy. Compared with conventional PECVD, the grain size, crystalline volume fraction (X-e) and deposition rate were all enhanced when a high T-f was used. The best poly-Si film exhibits a preferential (220) orientation, with a full width at half-maximum (FWHM) of 0.2 degrees. The Si-Si TO peak of the Raman scattering spectrum is located at 519.8 cm(-1) with a FWHM of 7.1 cm(-1). The X-c is 0.93. These improvements are mainly the result of promotion of the dissociation of SiH4 and an increase in the atomic H concentration in the gas phase. (C) 2001 Elsevier Science B.V. All rights reserved.

Evaluation of the thermal/optical reflectance method for discrimination between char- and soot-EC

IEECAS SKLLQG

Evaluation of the thermal/optical reflectance method for quantification of elemental carbon in sediments

IEECAS SKLLQG

Evaluation of the interaction between netropsin and double stranded DNA by capillary zone electrophoresis

Capillary zone electrophoresis (CZE) was applied to study the interaction between netropsin and a 14mer double stranded DNA (dsDNA). The binding constant of this interaction calculated from Scatchard plot was (1.07+/-0.10) X 10(5) (mol/L)(-1). The binding stoichiometry was 1:1. The use of polyacrylamide coated capillary showed better effect in the analysis of DNA than noncoated capillary.

Quantitative evaluation of the interaction between pUC19DNA and ovalbumin by capillary zone electrophoresis

Capillary zone electrophoresis (CZE) was used to study the interaction between pUC19DNA (pUC19) and ovalbumin (Ova). Samples containing pUC19 and Ova at various ratios were incubated at room temperature and were then separated by CZE with tris-acetate buffer at pH 7.2. Reduction in ultraviolet (UV) absorbance of pUC19 was due to the decrease of free pUC19 after binding to Ova. The binding constant of the interaction calculated from the Scatchard plot was (1.46+/-0.15) x 10(5) M-1. The use of polyacrylamide-coated capillary showed better effects than that of uncoated capillary. The results show that it is important to keep a constant ionic strength in the samples in order to obtain accurate quantitative data in binding assays by CZE.