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Luminescence Study of Carbon Doped GaAs Grown on GaAs (311) a Substrate by MOCVD
Cho,S.,Lee,D.,Son,C. S.,Choi,W. C.,Kim,S. I.,Kim,E. K.,Min,S. K. 대한전자공학회 1997 ICVC : International Conference on VLSI and CAD Vol.5 No.1
We investigate the temperature and excitation power density dependence of the photoluminescence (PL) from carbon doped GaAs epilayers grown on GaAs (311)A substrate by atmospheric pressure metalorganic chemical vapor deposition. The measured temperature dependence of the PL peak energy is well expressed by an empirical formula proposed by Varshni. The thermal quenching mechanism of the intensity of 16 K luminescence peak at 1.480 eV is described with the dominant activation energy of 29 ± 2 meV. The activation energy shows an evidence that the emission band involves the carbon acceptor in the recombination process.
Cho, S.‐,Ja,Okabe, S.,Lee, S.‐,J. Informa UK (TaylorFrancis) 2008 Environmental Technology Vol.29 No.4
<P>To investigate the inorganic nitrogen conversion in reactors that were operated under aerobic and micro-aerobic conditions and to identify populations that became acclimated in the reactors under those oxygen conditions, we operated two reactors with 72 h of hydraulic retention time and an artificial medium containing ammonium- and nitrite-nitrogen without any organic compound. We determined the concentration of inorganic nitrogen in samples from the reactors and the microbial community structure in the reactors by using PCR-DGGE of the partial 16S rRNA gene. The results showed that nitrification to nitrate fully progressed in the aerobic reactor within 24 h, but we could not find any obvious reaction in the micro-aerobic reactor. In a view of microbial community structure, the total number of microorganisms composing the communities in the reactors was dramatically decreased compared to those of the initial inoculated sludge that originated from the Jang-lim sewage treatment plant in Busan, Republic of Korea because of the limited nutrients present. One Nitrospira sp. was clearly detected under both aerobic (as DO > 2 mg l(-1)) and micro-aerobic (as DO < 0.7 mg l(-1)) conditions while no AOB-like bacterium was exactly matched among main bands. By the results, nitrite-oxidizing bacteria may be more tolerant to variations in oxygen, or the occupation of ammonia-oxidizing bacteria as dominant groups may have been inhibited by substrate starvation and high concentrations of nitrite-N in influent.</P>
Cho, S.,Kim, S. I.,Kim, Y. H.,Mickevič,ius, J.,Tamulaitis, G.,Shur, M. S. WILEY-VCH Verlag 2006 Physica status solidi. PSS. A, Applications and ma Vol.203 No.15
<P>We report on optimization of growth conditions by studying the structural and optical properties of ZnO films grown on sapphire substrate by pulsed laser deposition at different growth temperatures. The crystallographic structure and surface morphology were studied by X-ray diffraction and atomic force microscopy, respectively. The flattest surface was observed in the sample grown at substrate temperature of 500 °C. The optical characterization was performed by steady state and time resolved photoluminescence spectroscopy. Photoluminescence of the samples was studied at low CW excitation and at high-power-density pulsed excitation in picosecond domain. Stimulated emission was observed at pulsed excitation. Carrier lifetimes were found to significantly depend on the growth temperature reaching the peak value also in the samples grown at approximately 500 °C. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Cho, S.,Choi, C.-W.,Lee, D. H.,Won, C.-H.,Kim, S. M.,Lee, S.,Lee, M.-J.,Chung, J. H. Blackwell Publishing Ltd 2009 Clinical and experimental dermatology Vol.34 No.4
<P>Summary</P><P>Background. </P><P>Evidence for beneficial effects of squalene on ultraviolet (UV)-induced photoageing of the skin is lacking.</P><P>Aim. </P><P>To investigate whether squalene supplementation improves signs and molecular markers of photoageing in human skin <I>in vivo</I>.</P><P>Methods. </P><P>In total, 40 female volunteers aged > 50 years received two different doses [13.5 g/day (low-dose group) and 27 g/day (high-dose group)] of squalene for 90 days. At baseline and at the completion of the study, facial wrinkles were measured using skin replicas. Skin samples were taken to compare type I procollagen and matrix metalloproteinase 1 mRNA levels by real-time reverse-transcriptase PCR, and for type I procollagen immunostaining. Skin samples were also taken 24 h after 2 × minimal erythema dose (MED) of UV irradiation before and after squalene intake to assess UV-induced thymine dimer formation and keratinocytic apoptosis.</P><P>Results. </P><P>In total, 37 subjects completed the trial. Transient loose stool was experienced by 35% of volunteers in the low-dose group and 55% in the high-dose group. Facial wrinkles decreased significantly (<I>P < </I>0.05) in the high-dose group, while procollagen type I mRNA levels and MED increased significantly in the low-dose group. Procollagen immunostaining tended to increase in both groups. Facial erythema decreased and pigmentation increased significantly in both groups. UV-induced keratinocytic apoptosis and thymine dimer staining were substantially reduced in both groups.</P><P>Conclusions. </P><P>Daily ingestion of 13.5 or 27 g of squalene per day resulted in antiageing effects in photoaged skin. However, in view of the frequent incidence of loose stool experienced by the subjects, the risk–benefit ratio of high-dose squalene supplementation is too high to recommend it for treating skin ageing.</P>
Weighted estimates of solutions to second order parabolic equations
Academic Press 2010 Journal of differential equations Vol.248 No.4
We evaluate the rate of decay for solutions to second order parabolic equations, which vanish on the boundary, while the right-hand side is allowed to be unbounded. Our approach is based on a special growth lemma, and it works for both divergence and non-divergence equations, in domains satisfying a general ''exterior measure condition'' (A). The result for elliptic case is published in Cho and Safonov (2007) [2].