Raman study of InAs/GaAs quantum dot solar cells

We report polarized and resonant Raman study of InAs/GaAs quantum dot solar cell (QDSC) structures. Raman spectra obtained from the top surfaces of the samples suggested that the formation of InAs QDs induced tensile strain in the overgrown GaAs layers. Furthermore, a longitudinal optical phonon-plasmon (LPP) coupled modes were observed in the p-type GaAs layers. The tensile strain was increased with an increase in the QD size. The hole concentrations estimated by fitting the individual LPP coupled modes were in the range of 2.4–3.5 × 10¹⁸ cm^?3. Resonant Raman spectra obtained from the cleaved sides, where the QDs were located, showed a 225 cm^?1 mode in parallel polarization configurations. Based on accurate analysis, this mode was identified as the LA(X) phonon of GaAs.     

Amperometric proton selective sensors utilizing ion transfer reactions across a microhole liquid/gel interface

A new cost-effective amperometric proton selective sensor utilizing a single microhole interface between two immiscible electrolyte solutions (ITIES) is developed. The sensing methodology is based on measuring currents associated with proton transfer across the interface assisted by a proton selective ionophore. The ellipse shaped micro-interface was first fabricated by simple mechanical punching with a sharp needle on a thin PVC film (12 μm thick) commercially available as a food wrapping material. The microhole was then filled up with a gellified polyvinylchloride (PVC)-2-nitrophenyloctylether (NPOE) to create a single microhole liquid/liquid interface. Direct ion transfer reactions across the polarized interface serving as ion sensing platforms were studied using cyclic voltammetry. In order to enhance the selectivity of proton sensing, a proton selective ionophore, octadecyl isonicotinate (ETH1778), was incorporated into the organic gel layer and their electrochemical sensing characteristics were investigated using cyclic voltammetry and differential pulse stripping voltammetry. As an example, we employed the proton selective sensor for the determination of glucose concentrations. The detection scheme involves two steps: (i) protons are first generated by the oxidation of glucose with glucose oxidase in the aqueous phase; and (ii) the current associated with the proton transfer across the interface is then measured for correlating the concentration of glucose.     

Synthesis of α-Diketones from α,β-Dihydroxy Ketones

Treatment of α,β-dihydroxy ketones with carbonyldiimidazole resulted in the formation of α-diketones based on the elimination of the cyclic carbonates formed in situ.     

Retinoic acid inhibits inducible nitric oxide synthase expression in 3T3-L1 adipocytes

The present study was undertaken to explore whether retinoids, which are known to have immunomodulatory actions, could attenuate tumor necrosis factor-alpha (TNF)-stimulated inducible nitric oxide synthase (iNOS) expression in 3T3-L1 adipocytes. Adipocytes incubated with TNF induced dose- and time-dependent accumulation of nitrite in the culture medium through the iNOS induction as confirmed by Western blotting. Treatment of cells with TNF in the presence of all-trans-retinoic acid (RA) significantly decreased their ability to produce nitrite and iNOS induction. Both 13-cis- and all- trans-RA-induced suppression was dose-dependent, and all-trans-RA was somewhat potent than 13-cis-RA. The inhibitory effect of RA on TNF-induced iNOS induction was reversible, completely recovered after 2 days, and was exerted through the inhibition of NF-kappaB activation. TNF also suppressed the lipoprotein lipase (LPL) activity of 3T3-L1 adipocytes. RA could not reverse the TNF- induced LPL suppression at RA levels causing near complete inhibition of the TNF-induced NO production. These results indicate that RAs attenuate iNOS expression reversibly in TNF-stimulated 3T3-L1 adipocytes, and that the TNF-induced LPL suppression is not the result of NO overproduction.     

Probing the pion field in nuclei

It is suggested that muon absorption and doubly radiative pion absorption in nuclei can complement each other in probing the pion field in the nuclear medium. The relevant issues we consider are possible pion condensation and nuclear “renormalization” of weak and electromagnetic vertices, the adequate understanding of which is necessary to extract from nuclear experiments useful information on basic form factors in the weak Hamiltonian.     

Evolution of magnetic polarons and spin-carrier interactions through the metal-insulator transition in Eu(1-x)Gd(x)O

Raman scattering studies as functions of temperature, magnetic field, and Gd substitution are used to investigate the evolution of magnetic polarons and spin-carrier interactions through the metal-insulator transition in Eu(1-x)Gd(x)O. These studies reveal a spin-fluctuation-dominated paramagnetic (PM) regime for T>T*>T(C), and a coexistence regime for T相似文献   

Rapid determination of 99Tc in environmental samples by high resolution ICP-MS coupled with on-line flow injection system

High resolution inductively coupled plasma mass spectrometry coupled with an on-line flow injection system (FI-HR-ICP-MS) was applied to determine the ultra-trace level ⁹⁹Tc in soil. The flow injection system (PrepLab) was composed of two TEVA-Spec^Òresins, reduced remarkably the sample amounts and the analysis time, compared to the conventional analytical methods. In the flow injection system, Mo and Ru were sufficiently eliminated by using the flow injection system, with the decontamination factors of 1.6^.10⁴ and 9.9^.10⁵, respectively. With the present method, it was possible to determine ultra-low level of ⁹⁹Tc in 3-6 g soil at 3–5 hours of analysis time per sample. The relative standard deviation for each sample was less than 4%. The detection limits for ⁹⁹Tc was 85 fg^.ml^–1 (0.05 mBq^.ml^–1), which was calculated from the three times standard deviation of the count rate of the blank.     

Recent progress on dense nuclear matter in skyrmion approaches

The Skyrme model provides a novel unified approach to nuclear physics. In this approach, single baryon, baryonic matter and medium-modified hadron properties are treated on the same footing. Intrinsic density dependence (IDD) reflecting the change of vacuum by compressed baryonic matter figures naturally in the approach. In this article, we review the recent progress on accessing dense nuclear matter by putting baryons treated as solitons, namely, skyrmions, on crystal lattice with accents on the implications in compact stars.