Synthesis and chiroptical properties of amino acid-derived poly(methylpropargyl ester)s

Chiral methylpropargyl ester monomers containing amino acid moieties, N-(tert-butoxycarbonyl)-l-alanine (R)-1-methylpropargyl ester (1), N-(benzyloxycarbonyl)-l-valine (R)-1-methylpropargyl ester (2), and N-(tert-butoxycarbonyl)-l-O-cyclohexyl-l-glutamic acid (R)-1-methylpropargyl ester (3) were synthesized and polymerized with (nbd)Rh⁺[η⁶-C₆H₅B⁻(C₆H₅)₃] to give the corresponding polymers with number-average molecular weights ranging from 32 700 to 64 100 in 84-85% yields. The polymers were soluble in toluene, CHCl₃, CH₂Cl₂, THF, DMF, and DMSO, but insoluble in hexane, diethyl ether, and MeOH. The specific rotation and circular dichroism (CD) spectroscopic studies revealed that poly(1)-poly(3) took predominantly one-handed helical structures in the solvents, wherein the degree of one-handedness and tightness of the helix depended on the solvent. The helical structure of the polymers was stable to the addition of MeOH and heat.     

(η5‐Cyclopentadienyl)[(1,2,3,4,4a,10a‐η)‐1‐methylthianthrene]iron(II) hexafluoridophosphate acetone 0.33‐solvate

The title complex salt, [Fe(C₅H₅)(C₁₃H₁₀S₂)]PF₆·0.33C₃H₆O, obtained from an acetone–diethyl ether–dichloromethane mixture at 280 (2) K, has three cationic molecules (A–C), three hexafluoridophosphate counter‐anions and one acetone solvent molecule in the asymmetric unit. Two of the three cations contain FeCp (Cp is cyclopentadienyl) inside the fold of the heterocycle. The dihedral angles between the planes of the external (complexed and uncomplexed) benzene rings in the thianthrene molecule are 146.5 (2)° for FeCp‐out‐of‐fold molecule A, and 139.0 (3) and 142.5 (2)° for the two FeCp‐in‐fold molecules B and C, respectively. The complexed Cp and benzene rings in each molecule are almost parallel, with a dihedral angle between the planes of 0.2 (5)° for molecule A, 2.8 (5)° for B, and 2.19 (4) and 6.86 (6)° for the disordered Cp ring in C.     

Temperature and current coefficients of lasing wavelength in tunable diode laser spectroscopy

The factors determining temperature and current coefficients of lasing wavelength are investigated and discussed under monitoring CO₂-gas absorption spectra. The diffusion rate of Joule heating at the active layer to the surrounding region is observed by monitoring the change in the junction voltage, which is a function of temperature and the wavelength (frequency) deviation under sinusoidal current modulation. Based on the experimental results, the time interval of monitoring the wavelength after changing the ambient temperature or injected current (scanning rate) has to be constant at least to eliminate the monitoring error induced by the deviation of lasing wavelength, though the temperature and current coefficients of lasing wavelength differ with the rate.     

Efficient estimation of stable Lévy process with symmetric jumps

Efficient estimation of a non-Gaussian stable Lévy process with drift and symmetric jumps observed at high frequency is considered. For this statistical experiment, the local asymptotic normality of the likelihood is proved with a non-singular Fisher information matrix through the use of a non-diagonal norming matrix. The asymptotic normality and efficiency of a sequence of roots of the associated likelihood equation are shown as well. Moreover, we show that a simple preliminary method of moments can be used as an initial estimator of a scoring procedure, thereby conveniently enabling us to bypass numerically demanding likelihood optimization. Our simulation results show that the one-step estimator can exhibit quite similar finite-sample performance as the maximum likelihood estimator.     

p-Phenylenediamine Epoxy Resin Film for Redox Enzyme Detection

Summary: Phenylenediamine derivatives (PDs) are environmentally hazardous, though very useful for chemical analysis. To minimize release into the environment, a PD-containing epoxy resin film was developed that retained redox enzyme activity. p-Phenylenediamine and 2,2-bis(4-glycidyloxyphenyl)-propane were cured to produce a violet film. This film was reactive against peroxidase, a redox enzyme that oxidizes phenylenediamine to afford an imine. Enzymatic oxidation caused the film to change color from violet to deep green. The film exhibited fluorescence at 394 nm under excitation at 350 nm, and the fluorescent intensity decreased with greater oxidation. Thus, the film could be used to detect redox enzyme activity.     

Scanning tunneling microscopy and abinitio studies of precursor states of Ga-induced cluster on Si(0 0 1) surface

The growth processes and structures of Ga layers formed on a Si(0 0 1) surface have been studied by scanning tunneling microscopy (STM) and abinitio calculation. The precursor states of the Ga clusters that compose the Si(0 0 1) 8 × n-Ga (n = 4, 5, 6) structures are observed in addition to the 2 × 2- and 4 × 2-Ga structures at a Ga coverage of 0.55 ML at 300 °C. There are two types of precursor clusters whose protrusions are observed as different shapes in filled-state STM images. We compare the observed STM images with the simulated ones to identify the possible structural models. From the results, we determine the structure of each precursor cluster. On the basis of the results, the formation processes of the cluster are discussed.     

Effects of polyethylenimine on morphology and property of ZnO films grown in aqueous solutions

Morphologies and properties of well-aligned ZnO films were controlled using zinc nitrate-hexamethylenetetramine aqueous solutions with the addition of polyethylenimine as a surfactant. Porous and dense ZnO films were fabricated with and without polyethylenimine, respectively. The addition of polyethylenimine proceeded to form porous ZnO whiskers film by preferential adsorption to nonpolar crystal faces and modifications of the surface free energy and growth rate. Dense ZnO film showed high transmittance of 80%, and low intensity of fluorescence and photo-induced current. Porous ZnO whiskers film showed low transmittance of 70%, while high intensity of fluorescence and high photo-induced current were detected because the porous ZnO nanowhisker film possessed a large interior surface area which can capture large amounts of DNA molecules labeled with dye molecules on the surface of ZnO crystals. High performance dye-sensitized sensors can be produced using ZnO whisker films prepared from an aqueous solution.     

Control of nanogap junction resistance by imposed pulse voltage

The resistance switching effect of a simple gold nanogap junction was investigated. This device exhibits highly reproducible switching and nonvolatile characteristics. The resistance switching was developed for dependence of the resistance on the applied voltage level. Four separate ranges of resistance were repeatedly controlled by programmed sequential application of voltage pulses, including the operation of data verification.