Effect of reversible photostructural change on the polarization of photoluminescence in chalcogenide glasses

Optical absorption edge in annealed As₂S₃ films shifts to lower energy after band-gap illumination. In these photodarkened films, polarization memory of photoluminescence was found to increase. In the case of illumination with linearly polarized light, anisotropy is induced in the absorption edge. The polarization memory was larger for larger shift of absorption edge. In contrast with this trend, the memory was smaller in As-rich films, the absorption edge of which was located at lower energy. It is considered that the optical anisotropy of the luminescence centers increases accompanying the reversible photostructural change.     

Magnesium-doped InGaAs using (C2H5C5H4)2Mg: application to InP-based HBTs

Heavily magnesium-doped p-type-InGaAs layers on InP(100) substrates were successfully grown, for the first time, by low-pressure metalorganic chemical vapor deposition (MOCVD) using bis-ethylcyclopentadienyl-magnesium, (C₂H₅C₅H₄)₂Mg (EtCp₂Mg), as organometallic precursor for the Mg. It was experimentally verified that the room-temperature hole concentration of Mg into InGaAs increased with increase of the V/III ratio and decrease of the growth temperature. A maximum hole concentration of over 4 × 10¹⁹ cm⁻³ was obtained. The diffusion coefficient of Mg in InGaAs was experimentally derived to be 10⁻¹² cm²/s at 800°C, which was comparable to that of Be. Finally, InP/InGaAs heterojunction bipolar transistors (HBTs) with Mg-doped bases were fabricated successfully. Measured maximum current gain was about 320 with a 90 nm thick base and a sheet resistance of the base layer of 1.28 kΩ/sq.     

Chemical Synthesis of Interleukin‐2 and Disulfide Stabilizing Analogues

Chemical protein synthesis allows the construction of well‐defined structural variations and facilitates the development of deeper understanding of protein structure–function relationships and new protein engineering strategies. Herein, we report the chemical synthesis of interleukin‐2 (IL‐2) variants on a multimilligram scale and the formation of non‐natural disulfide mimetics that improve stability against reduction. The synthesis was accomplished by convergent KAHA ligations; the acidic conditions of KAHA ligation proved to be valuable for the solubilization of the hydrophobic segments of IL‐2. The bioactivity of the synthetic IL‐2 and its analogues were shown to be equipotent to recombinant IL‐2 and exhibit improved stability against reducing agents.     

Per atom muon capture ratios and effects of molecular structure on muon capture by γ-Fe2O3 and Fe3O4

Journal of Radioanalytical and Nuclear Chemistry - An elemental analysis method utilizing muons has been demonstrated to be effective for non-destructive and quantitative analysis of precious bulk...     

The MTV experiment: a test of time reversal symmetry using polarized 8Li

The MTV (Mott Polarimetry for T-Violation Experiment) experiment at TRIUMF-ISAC (Isotope Separator and ACcelerator), which aims to achieve the highest precision test of time reversal symmetry in polarized nuclear beta decay by measuring a triple correlation (R-correlation), is motivated by the search for a new physics beyond the Standard Model. In this experiment, the existence of non-zero transverse electron polarization is examined utilizing the analyzing power of Mott scattering from a thin metal foil. Backward scattering electron tracks are measured using a multi-wire drift chamber for the first time. The MTV experiment was commissioned at ISAC in 2009 using an 80 % polarized ⁸Li beam at 10⁷ pps, resulting in 0.1 % statistical precision on the R-parameter in the first physics run performed in 2010. Next generation cylindrical drift chamber (CDC) is now being installed for the future run.     

Development of sheath‐flow probe electrospray ionization (SF‐PESI)

Probe electrospray ionization (PESI) uses a sharp solid needle as electrospray emitter. This method was found to be applicable to the analysis of real‐world samples with high concentrations of salts and detergents without sample pretreatment. Since PESI is only applicable to wet samples but not to dry samples, sheath‐flow PESI (SF‐PESI) has been developed. The metal needle was inserted into the fine plastic capillary with a protrusion of 0.1–0.2 mm from the capillary terminus. The solvent was supplied continuously through the capillary. At the lowest position of the probe, solvent flowing out from the capillary makes the sample wet and extracts the analytes from the surface. The extracted analytes were electrosprayed at the highest position of the needle. SF‐PESI was successfully applied to samples such as narcotics, tablets, bill, fruits, potatoes, etc. Copyright © 2013 John Wiley & Sons, Ltd.     

Discrimination of ethylene/vinyl acetate copolymers with different composition and prediction of the content of vinyl acetate in the copolymers and their melting points by near-infrared spectroscopy and chemometrics

Near-infrared (NIR) diffuse reflectance spectra have been measured by use of a rotating drawer for pellets of 12 kinds of ethylene/vinyl acetate (EVA) copolymers with vinyl acetate (VA, the comonomer) varying in the 7–44 wt % range. They are unambiguously discriminated from one another by a score plot of the principal component analysis (PCA) Factor 1 and 2, based upon the NIR spectra pretreated by multiplicative scatter correction (MSC). Principal component (PC) weight loadings for Factor 1 show that the discrimination relies largely upon bands due to the overtone and combination modes arising from the VA unit. We have found one “outlier” in the score plot and elucidated its spectral characteristics based upon PC weight loadings for Factor 2. Partial least-squares (PLS) regression has been applied to propose calibration models which predict the VA content in EVA. The models have been prepared for three kinds of pretreatment, the first derivative, the second derivative, and MSC; and four kinds of wavelength regions. The NIR spectra in the 1100–2200 nm region after the MSC treatment has given the best correlation coefficient and standard error of prediction (SEP) of 0.998 and 0.70%, respectively. The calibration models, prepared by NIR diffuse reflectance spectroscopy for the pellet samples, are compared with previously reported models by NIR transmission spectroscopy for the flowing molten samples, and with those by Raman spectroscopy for the pellet samples. PLS regression has also allowed us to predict melting points of the copolymers with the correlation coefficient and SEP of 0.997 and 0.78°C, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1529–1537, 1998