Comparative Investigation on the Concentration-Dependences of the Half-Band Widths of Infrared Absorption and Raman Bands

It is demonstrated that the fashions of the concentration-dependences of half-band widths are markedly different between the corresponding bands in i.r. absorption and Raman spectra when the i.r. absorption intensities of the bands are extremely large. On the other hand, when the i.r. intensities are not so great, the similar behaviour is observed for the changes in the half-band widths. In this study, these phenomena have been discussed in terms of the vibrational relaxation of resonance type and the local field effect.     

Magnetic Circularly Polarized Luminescence from PtIIOEP and F2-ppyPtII(acac) under North-up and South-up Faraday Geometries

The magnetic circularly polarized luminescence (MCPL) and photoluminescence (PL) spectra of achiral (2,3,7,8,12,13,17,18-octaethylporphyrinato)platinum(II), PtOEP , and [2-(4′,6′-difluorophenyl)pyridinato-N,C^2′]platinum(II) acetylacetonate-O,O, F₂-ppyPt(acac) , in toluene and dichloromethane solutions were recorded under an external magnetic field of 1.6 T with N-up and S-up Faraday geometries. The MCPL signs of PtOEP and F₂-ppyPt(acac) were controlled solely by changing the N-up and S-up geometries. The MCPL/PL wavelengths of F₂-ppyPt(acac) in solutions were varied by the ratio of the monomeric and excimeric species.     

Multi‐scaled microstructures in natural rubber characterized by synchrotron X‐ray scattering and optical microscopy

Multi‐scaled microstructures induced by natural impurities (i.e., proteins, phospholipids, carbohydrates) in natural rubber (NR) were investigated by synchrotron small‐angle X‐ray scattering (SAXS), wide‐angle X‐ray diffraction (WAXD), and optical microscopy using several kinds of untreated and chemically treated un‐vulcanized samples. These microstructures include large aggregates (size less than 50 μm), well‐defined crystals (size less than a few 10 μm), and micelles (size much less than 10 μm). In un‐vulcanized NR samples, even though the concentrations of natural impurities are relatively low, the dispersion of these microstructures significantly affects the mechanical properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2456–2464, 2008     

Cell surface-anchored fluorescent aptamer sensor enables imaging of chemical transmitter dynamics

A fluorescent aptamer sensor was applied to the analysis of extracellular chemical transmitter dynamics. We utilized a tocopherol-labeled aptamer, which allowed the direct anchoring of the fluorescent aptamer on the cell surface while retaining its performance as a fluorescent sensor. The fast-responsive fluorescent DNA aptamer sensor, which targets adenine compounds, was anchored on the surface of brain astrocytes. Fluorescence imaging of the aptamer-anchored astrocytes enabled the real-time monitoring of release of adenine compounds as a gliotransmitter, which was synchronized with calcium wave propagation in neighboring cells.     

Synthesis, crystal structure, spectroscopic and electrochemical properties, and H2-evolving activity of a new [PtCl(terpyridine)]+ derivative with viologen-like redox properties

A new Pt(II)-based metalloviologen analog, [PtCl(Mepytpy)](2+) (abbreviated as PV(2+); Mepytpy(+) = 4'-(4-methyl-pyridinio)-2,2':6',2'-terpyridine), was synthesized and its spectroscopic and electrochemical properties were investigated. The structures of Mepytpy(+) and PV(2+) were solved by single-crystal X-ray diffraction analysis. Electrochemical studies in DMF (N,N-dimethylformamide) revealed that both the first and second reduction potentials of PV(2+) (E = -0.87 V vs. Fc/Fc(+) for PV(2+)/PV(+)˙; E = -1.31 V vs. Fc/Fc(+) for PV(+)˙/PV(0)) are nearly consistent with those of methylviologen (N,N'-dimetyl-4,4'-bipyridinium, MV(2+)) (E = -0.90 V vs. Fc/Fc(+) for MV(2+)/MV(+)˙; E = -1.28 V vs. Fc/Fc(+) for MV(+)˙/MV(0)), where the first reduction of PV(2+) is assigned as the reduction at the Mepytpy(+) ligand bound to the Pt(ii) ion. Upon the addition of a reducing agent Na(2)S(2)O(4) into an aqueous acetate buffer solution (pH = 5.0) of PV(2+), the generation of one-electron-reduced radical species (PV(+)˙) was spectrophotometrically observed and was assigned based on the time-dependent density functional theory (TD-DFT) calculations. The H(2)-evolving activity of PV(2+) was evaluated in the presence of a sacrificial electron donor (EDTA) in an aqueous acetate buffer solution (pH = 5.0). It was found that the stability of the metalloviologen PV(2+) during the photolysis is much higher than that of the parent compound [PtCl(tpy)](+).     

Kinetics and DFT studies on water oxidation by Ce4+ catalyzed by [Ru(terpy)(bpy)(OH2)]2+

The Ru(V)==O species and other intermediates in O(2) evolution from water catalyzed by [Ru(terpy)(bpy)(OH(2))](2+) were spectrophotometrically characterized, and the spectral components observed were identified based on the TD-DFT calculations. Moreover, important insights into the rapid paths after the RDS were given by the DFT studies.     

Parameter estimation for von Mises–Fisher distributions

When analyzing high-dimensional data, it is often appropriate to pay attention only to the direction of each datum, disregarding its norm. The von Mises–Fisher (vMF) distribution is a natural probability distribution for such data. When we estimate the parameters of vMF distributions, parameter κ which corresponds to the degree of concentration is difficult to obtain, and some approximations are necessary. In this article, we propose an iterative algorithm using fixed points to obtain the maximum likelihood estimate (m.l.e.) for κ. We prove that there is a unique local maximum for κ. Besides, using a specific function to calculate the m.l.e., we obtain the upper and lower bounds of the interval in which the exact m.l.e. exists. In addition, based on these bounds, a new and good approximation is derived. The results of numerical experiments demonstrate the new approximation exhibits higher precision than traditional ones.