Vibrational OH-stretching overtone spectroscopy of jet-cooled resorcinol and hydroquinone rotamers

We have measured the OH-stretching fundamental and overtone spectra of resorcinol and hydroquinone in a supersonic jet using nonresonant ionization detected infrared/near-infrared spectroscopy. Anharmonic oscillator local mode calculations of the OH-stretching frequencies and intensities and Boltzmann populations of the stable rotamers have been calculated at the B3LYP/6-311++G(3df,2pd) level to help interpret the observed spectra. Resorcinol has three stable rotamers and in the recorded second and third OH-stretching overtone spectra there is evidence of two distinguishable rotamers. Hydroquinone has two stable rotamers; however, the OH-stretching oscillators of each rotamer are so similar in nature that even up to the fourth OH-stretching overtone the transitions coincide. These results place a limit on the ability of the jet-cooled overtone spectroscopy technique to distinguish between rotamers.     

Synthetic studies of carbapenem and penem antibiotics. II. Synthesis of 3-acetyl-2-azetidinones by (2 + 2) cycloaddition of diketene and Schiff bases.

It was found that (2 + 2) cycloaddition reaction of diketene with Schiff bases was effectively promoted by imidazole as a catalyst to afford 3-acetyl-2-azetidinone derivatives 4. As an application of this new method, a practical asymmetric synthesis of 4 and its conversion into (3S,4S)-4-carboxy-1-(di-p-anisylmethyl)-3-[(R)-1-hydroxyethyl]-2- azetidinone, which is a key intermediate for the synthesis of carbapenem and penem antibiotics, were accomplished.     

Formation of Superhydrophobic Alumina Coating Films with High Transparency on Polymer Substrates by the Sol-Gel Method

Transparent, superhydrophobic coating films have been prepared on polymer substrates at low temperatures through the sol-gel method. Al₂O₃ gel films were prepared on poly(ethylene terephthalate) substrates from Al(O-sec-C₄H₉)₃ chemically modified with ethyl acetoacetate. A small roughness of about 20–50 nm was found to form on the surface of the Al₂O₃ gel films dried at room temperature and then immersed in hot water at 60°C. The electron diffraction measurements have shown that this roughened surface consists of pseudoboehmite nanocrystals. The coating of hydrolyzed fluoroalkyltrimethoxysilane on the Al₂O₃ gel films with the small roughness produced transparent, superhydrophobic films with contact angle for water larger than 150°.     

Fluorescence resonance energy transfer by quencher adsorption into hydrogels containing fluorophores

We synthesized anionic hydrogels containing fluorophores and investigated the adsorption of a cationic quencher having an amino group into hydrogels by fluorescence resonance energy transfer (FRET). FRET from the fluorophore to the quencher in hydrogels was examined by fluorescence intensity and fluorescence decay using a fluorescence spectrophotometer and femtosecond laser spectroscopy. The fluorescence intensity of the fluorophore‐containing hydrogels decreased rapidly with increasing amounts of adsorbed cationic quencher. The fluorescence emission of the fluorophore in the quencher‐adsorbed hydrogels containing fluorophores decayed more rapidly than that of the original hydrogels. The aforementioned result indicates that the fluorescence of the fluorophore‐containing hydrogels is quenched due to FRET from the fluorophore to the quencher as the cationic quenchers can approach the fluorophores in hydrogels by electrostatic interactions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3245–3252, 2006     

Infrared spectrum of poly(vinylidene fluoride)

Two crystalline forms (α and β) of poly(vinylidene fluoride) were studied by infrared spectroscopy. The spectral differences permitted the study of the transformation and the ratio of the two forms. The ordinary \documentclass{article}\pagestyle{empty}\begin{document}$ \vec G,\vec F $\end{document} matrix method was used to calculate the fundamental mode with a Urey-Bradley type potential field, and a preferred set of the force constants was obtained.     

Combinatorially homogeneous graphs

Gardiner classified ultrahomogeneous graphs and posed the problem of defining “combinatorial homogeneity”. Later, Ronse proved that homogeneous graphs are ultrahomogeneous by classifying such graphs. In this paper, we give a direct proof that (suitably defined) combinatorially homogeneous graphs are ultrahomogeneous. Also, we clasify combinatorially C-homogeneous graphs.     

Investigation on trap distribution and photoelectronic effect due to UV,IR and visible light excitation in self-activated zns crystals

Photoelectronic effects in IR sensitive ZnS crystals are found for IR, UV and visible light excitations. The transient rise characteristic of UV excited photoluminescence (UPL) saturates faster than UV produced photoconductivity (UPC). The UPC shows a typical S-shaped rise curve for any 365 run excitation irradiance and temperature. Simultaneously measured transient behaviors of IR induced photoconductivity (INP) and IR stimulated luminescence (STL) have a strong IR excitation intensity dependence for λ_IR = 2.5?4.6 microm. A unique phenomenon, quick rise followed by quick decay during the initial 20 msec, is found in INP before reaching final maximum but is not observed in STL. During UV steady irradiation, additional photoconductivity and luminescence are quickly induced by an abrupt IR excitation of 2.5 microm. Then, the photoconductivity reaches a new steady state level below UPC steady state. However, the luminescence sets the same UPL steady state level. This means that photoconductivity exhibits an IR optical quenching but not stimulation, while neither optical quenching nor stimulation is found in luminescence. It is also possible to quench the UPC response with visible light excitation at 570 nm. These observations support the previously reported discussion that IR absorbing impurity centers and shallow traps, including recombination (or luminescence) centers must be involved in IR stimulable ZnS crystals. They also indicate the presence of deep trap centers for E_T ≈ 2.18 eV, which have a strong role in slow UPC rise.     

Inversion of enantioselectivity of asymmetric biocatalytic decarboxylation by site-directed mutagenesis based on the reaction mechanism

The introduction of two mutations (G74C/C188S) based on the estimated reaction mechanism resulted in the inversion of enantioselectivity of arylmalonate decarboxylase, which catalyses the asymmetric decarboxylation of arylmethylmalonate to give optically active arylpropionate.     

Extensions by Means of Expansions and Selections

We provide proper mapping-characterizations of some embedding-like properties weaker than -embedding. For instance, we show that a subset A of a space X is -embedded in X if and only if for every continuous map g: A → Y into a Banach space Y of weight w(Y) ⩽ λ, there exists a continuous set-valued mapping φ of X into the nonempty compact subsets of Y such that g is a selection for φ∣A (i.e., g(x) ∈ φ(x) for every x ∈ A). On the other hand, we show that a subset A is C*-embedded in X if and only if for every continuous set-valued mapping φ of X into the non-empty compact subsets of a Banach space Y, every continuous selection g: A → Y for φ∣A is continuously extendable to the whole of X. Combining both results we get the well-known mapping-characterization of -embedding which makes more transparent the relation ‘’. Other weak components of -embedding are described in terms of expansions and selections, possible applications are demonstrated as well.