Conformation of 2,2,2-trifluoroethanol and the solvation structure of its 2-fluoropyridine clusters

The conformation of 2,2,2-trifluoroethanol (TFE) in the 2-fluoropyridine-(TFE)(m)-(H(2)O)(n) clusters in a supersonic jet has been investigated with fluorescence-detected infrared spectroscopy and quantum chemical calculations. It is common to the observed clusters that they form chain structures containing the weak interaction of the pyridyl CH with the fluorine or oxygen atom in the terminal TFE. The detectable conformation of TFE is gauche only even in the case of the existence of the strong base such as 2-fluoropyridine. This result is explained by the change in hyperconjugation among several dominant orbitals. The preference of the terminal TFE in the mixed clusters with TFE and water solvents is observed, which is ascribed to the stronger cooperative effect of TFE than water.     

Spatial coherence measurement of a scanning laser system and applicability of the Zernike’s approximation to the exit pupil on the scan mirror

Spatial coherence of the scanning laser beam was observed on the Young??s experimental set up using 50-??m-wide, 200-??m-separation double slits, which measured the less than unity fringe visibility in the Fraunhofer diffraction pattern of the double slits illuminated by the scanning laser beam at horizontal scan frequency 21 kHz, while approximately unity in case of the illumination by the laser beam at rest. This fact allow us to use the Zernike??s approximation when applying the van Cittert Zernike theorem to the scanning laser system such as the laser pico-projectors in order to estimate its speckle contrast in the projected image on the screen diffuser. The predicted and measured speckle contrasts showed excellent agreement on the screen illuminated by the laser projector.     

Absolute branching fraction measurements for D+ and D0 inclusive semileptonic decays

We present measurements of the inclusive branching fractions for the decays D+-->Xe+ nu(e) and D0-->Xe+ nu(e), using 281 pb(-1) of data collected on the psi(3770) resonance with the CLEO-c detector. We find B(D0-->Xe+ nu(e)) = (6.46+/-0.17+/-0.13)% and B(D+-->Xe+ nu(e)) = (16.13+/-0.20+/-0.33)%. Using the known D meson lifetimes, we obtain the ratio Gamma(D+)sl/Gamma(D0)sl = 0.985+/-0.028+/-0.015, confirming isospin invariance at the level of 3%. The positron momentum spectra from D+ and D0 have consistent shapes.     

Metal Nanoparticle/Polymer Hybrid Particles: The Catalytic Activity of Metal Nanoparticles Formed on the Surface of Polymer Particles by UV-Irradiation

Summary: Polymer particles decorated with metal nanoparticles were prepared by UV-irradiation of polystyrene latex particles incorporating polymethylphenylsilane (PS/PMPS) and P[S-co-NIPAM]/PMPS particles (NIPAM: N-isopropyl acrylamide) in the presence of metal salts. The metal nanoparticle/polymer hybrid particles were used as a catalyst for the reduction of 4-nitrophenol with NaBH₄. The Pd- and Ag-P(S-co-NIPAM)/PMPS hybrid particles had larger metal nanoparticles and the lower catalytic activity than those of Pd- and Ag-PS/PMPS, respectively. The surface functional group of the polymer particles affected the formation of the metal nanoparticles and their catalytic activity.     

Hydrogen-storage properties of solid-solution alloys of immiscible neighboring elements with Pd

Rh and Ag are the elements neighboring Pd, which is well known as a hydrogen-storage metal. Although Rh and Ag do not possess hydrogen-storage properties, can Ag-Rh alloys actually store hydrogen? Ag-Rh solid-solution alloys have not been explored in the past because they do not mix with each other at the atomic level, even in the liquid phase. We have used the chemical reduction method to obtain such Ag-Rh alloys, and XRD and STEM-EDX give clear evidence that the alloys mixed at the atomic level. From the measurements of hydrogen pressure-composition isotherms and solid-state (2)H NMR, we have revealed that Ag-Rh solid-solution alloys absorb hydrogen, and the total amount of hydrogen absorbed reached a maximum at the ratio of Ag:Rh = 50:50, where the electronic structure is expected to be similar to that of Pd.     

Effect of alcohols on the degradation of crosslinked unsaturated polyester in sub-critical water

The effect of alcohols on the degradation of unsaturated polyesters crosslinked with styrene was studied in sub-critical water at 300 °C. The de-crosslinked polymer was obtained by degradation of polyester chains in sub-critical water, and the de-crosslinking was enhanced by adding alcohols and phenols having a long alkyl chain such as 1-tetradecanol and 3-pentadecylphenol. However, the enhancement was not observed in the presence of diols even when they had a long alkyl chain. This finding suggests that transesterification enhanced the de-crosslinking of the polymer in sub-critical water.     

A Virtual Active Compound Produced from the Negative Image of a Ligand-binding Pocket, and its Application to in-silico Drug Screening

We developed a new structure-based in-silico screening method using a negative image of a ligand-binding pocket and a multi-protein–compound interaction matrix. Based on the structure of the ligand pocket of the target protein, we designed a negative image, which consists of virtual atoms whose radii are close to those of carbon atoms. The virtual atoms fit the pocket ideally and achieve an optimal Coulomb interaction. A protein–compound docking program calculates the protein–compound interaction matrix for many proteins and many compounds including the negative image, which can be treated as a virtual compound. With specific attention to a vector of docking scores for a single compound with many proteins, we selected a compound whose score vector was similar to that of the negative image as a candidate hit compound. This method was applied to representative target proteins and showed high database enrichment with a relatively quick procedure.     

Amperometric determination of chloroguaiacol at submicromolar levels after on-line preconcentration with molecularly imprinted polymers

In this study, a sorbent flow preconcentration system coupled to amperometric detector for the chloroguaiacol (4-chloro-2-methoxyphenol) determination at submicromolar levels is described. The satisfactory selectivity of the proposed method was attained by means of the use of a chloroguaiacol-imprinted polymer, whose the synthesis was carried out by bulk polymerization. Flow and chemical parameters associated to the preconcentration system, such as sample pH, preconcentration and elution flow rates, concentration of the carrier solution (KCl) and eluent volume were investigated through multivariate analysis. The flow preconcentration of chloroguaiacol was not affect by equimolar presence of structurally similar phenolic compounds including catechol, 4-chloro-3-methylphenol, 4-aminophenol and 2-cresol, thus showing the good performance of the imprinted polymer. Under the best experimental conditions, it was obtained a preconcentration factor of 110-fold and low detection and quantification limits of 27 and 78 nmol L⁻¹, respectively. The analytical curve covered a wide linear range from 0.05 up to 5.0 μmol L⁻¹ (r > 0.999) and satisfactory precision (n = 8) evaluated by relative standard deviation (R.S.D.) were respectively, 5.5 and 4.2%, for solutions of 1.0 and 5.0 μmol L⁻¹ chloroguaiacol. Other parameters related to the performance of the flow system were also evaluated including concentration efficiency of 27.5 min⁻¹ and consumptive index of 0.09 mL. Recoveries varying from 93 up to 112% for water samples (tap water and river water) spiked with chloroguaiacol concentration were achieved, thus assuring the accuracy of the proposed flow preconcentration system.     

Examination of (e,2e) scattering models by comparison of momentum profiles of noble gases between experiment and theory

Momentum profiles have been measured for the two outermost atomic orbitals of noble gases, Ar, Kr and Xe, at incident electron energy of about 2 keV using a newly developed multichannel (e,2e) spectrometer. The experimental results exhibit significantly improved statistics compared with those achieved in previous studies while covering a wide range of momenta up to 3.6 a.u. The results are compared with theoretical calculations using four (e,2e) scattering models, the plane-wave impulse and Born approximations (PWIA and PWBA), and the distorted-wave impulse and Born approximations (DWIA and DWBA). The DWIA and DWBA scattering models have been found to satisfactorily reproduce the experimental momentum profiles in terms of both shape and intensity over the entire momentum range covered, indicating the importance of distorted wave effects for quantitatively describing (e,2e) reaction.