The effects of binaural spectral resolution mismatch on Mandarin speech perception in simulated electric hearing

This study assessed the effects of binaural spectral resolution mismatch on the intelligibility of Mandarin speech in noise using bilateral cochlear implant simulations. Noise-vocoded Mandarin speech, corrupted by speech-shaped noise at 0 and 5?dB signal-to-noise ratios, were presented unilaterally or bilaterally to normal-hearing listeners with mismatched spectral resolution between ears. Significant binaural benefits for Mandarin speech recognition were observed only with matched spectral resolution between ears. In addition, the performance of tone identification was more robust to noise than that of sentence recognition, suggesting factors other than tone identification might account more for the degraded sentence recognition in noise.     

Ordinary Papers

This paper deals with the systems of algebraic equations arising in the application of implicit Runge-Kutta methods.Equivalent conditions under which three wide classes of differential equations have unique solutions are presented. In addition, sufficient conditions for their existence are given.     

Spontaneous Metal‐Free Transfer Hydrogenation of Iminoboranes with Ammonia Borane and Amine Boranes

The first spontaneous, metal‐free, room‐temperature hydrogen transfer from ammonia borane to an iminoborane is reported. Mechanistic studies of the reaction indicate a concerted transfer of H⁺ and H^? from donor to acceptor with an activation energy far below those of comparable concerted transfer hydrogenations. This reaction was employed in the syntheses and isolation of new B,N‐disubstituted aminoboranes, a comparatively rare subset within the aminoborane family. This successful transfer hydrogenation to a highly dehydrogenated BN system may serve as a starting point for the design of new systems capable of reversible dehydrogenation/rehydrogenation.     

Hydrogen formation during pyrolysis of polystyrene

Hydrogen was identified as a product of the pyrolysis of polygyrene, especially at high pyrolysis temperatures. With a high interface temperature of the Pyroprobe foil pyrolyser and a high pyrolysis temperature, almost 100% of the pyrolysed polymer could be accounted for. It is then assumed that hydrogen (up to 26%) produces a corresponding amount of carbon, which remains on the foil.     

Continuous production of butanol with immobilized cells ofClostridium acetobutylicum

Spores ofClostridium acetobutylicum were immobilized in calcium alginate. An active gel preparation was obtained after outgrowth of the spores to vegetative cells within the gel matrix. A 100 mL column containing the immobilized cells was used for continuous production. At steady-state conditions the productivity of butanol was 67 g/L reactor volume/day.     

The recognition of nucleotides with model beta-hairpin receptors: investigation of critical contacts and nucleotide selectivity

[reaction: see text] We have investigated the factors that contribute to binding of ATP by a designed 12-residue beta-hairpin peptide, WKWK, and have determined its selectivity for binding to the naturally occurring nucleotide triphosphates. We have previously shown that WKWK creates an ATP binding pocket on one face of the beta-hairpin consisting of two Trp and two Lys residues. Mutation of the two Lys residues on the binding face of the beta-hairpin resulted in a lower affinity, indicating that each is involved in ATP binding and that each residue contributes approximately -1.5 kcal/mol to the energy of complexation. Replacement of either Trp residue of the ATP binding pocket with Phe or Leu destabilizes the complex formed with ATP by approximately 1 kcal/mol, indicating that both Trp residues participate in interactions with ATP. For binding to the nucleotide triphosphates, the order of binding affinity was shown to follow dTTP > GTP > ATP > CTP, with differences in binding energies spanning as much as 1.6 kcal/mol. NMR analysis demonstrates that both aromatic interactions with the Trp side chains and CH-pi interactions between the ribose protons and the Trp residues may contribute significantly to binding. The results from our model system provide useful thermodynamic information regarding protein-nucleic acid interactions that occur at the surface of a beta-sheet.     

A study of the stereochemistry of 2-aryl-4,5-dimethyl-1,3-dioxolanes by cholesteric induction in nematic phases and circular dichroism spectroscopy

[Chemical reaction: See text] The circular dichroism spectra and the twisting ability of a series of 2-aryl-4,5-dimethyl-1,3-dioxolanes used as dopants in nematic solvents have been related to their absolute configuration. Whereas the circular dichroism (CD) spectra are deeply affected by the substituents present in the aromatic ring, which in several cases cause sign inversion, the helical twisting power beta is only marginally influenced. The values of beta also seem not very sensitive to the rotamer population around the aromatic ring; this indicates the predominant importance of the chiral dioxolane ring in determining the cholesteric induction. These facts can be explained by the different nature of the two observables: in CD, the chirality is read by the absorbing chromophore and is deeply influenced even by small changes of this group. In cholesteric induction we are dealing instead with chiral solute-solvent interactions that determine a twist in the solvent. In light of the present and previous results, this process seems predominantly determined by short-range interactions, which are modulated by the molecular shape. From a practical point of view, a configurational correlation using CD for the present series of compounds seems problematic, while the values of beta are nicely correlated to the absolute configurations. Calculations with the surface chirality method predict well the sign and order of magnitude of beta and their limited sensitivity to the phenyl substituents and rotamer population.     

An acid-catalyzed Michael-aldol reaction

A tricyclic ketone is formed from cyclohexanone and cyclohexenone in strong acid solutions. The structure is confirmed by X-ray crystallography.     

Structure and catalytic properties of nanosized alumina supported platinum and palladium particles synthesized by reaction in microemulsion

Mixtures of nanosized platinum and palladium particles have been prepared by reduction of salt-containing microemulsion droplets using hydrazine as the reducing agent. To avoid possible negative effects of the presence of sulfur compounds during the preparation the microemulsion was made using the sulfur-free nonionic polyoxyethylene 4 lauryl ether surfactant. Transmission electron microscopy showed that the as-prepared mixtures contained crystalline platinum particles of fairly homogeneous size (20 to 40 nm) with adsorbed amorphous palladium particles 2 to 5 nm in size. Catalyst samples were prepared by depositing the nanoparticles on a gamma-Al(2)O(3) support followed by heating in air at 600 degrees C. Alloyed particles of platinum and palladium with sizes ranging from 5 to 80 nm were obtained during the heating. The majority of the particles had the fcc structure and their compositional range was dependent upon the Pt:Pd molar ratio of the microemulsion. A catalyst prepared from a microemulsion with a 20:80 Pt:Pd molar ratio showed the highest catalytic activity for CO oxidation, while pure platinum and palladium catalysts showed higher sulfur resistance. These results differ from the performance of conventional wet-impregnated catalysts, where a 50:50 Pt:Pd molar ratio resulted in the highest catalytic activity as well as the highest sulfur resistance.     

Electrocatalysis of a Europium-Dependent Bacterial Methanol Dehydrogenase with Its Physiological Electron-Acceptor Cytochrome cGJ

We report the first electrochemical study of a lanthanoid-dependent methanol dehydrogenase (Eu-MDH) from the acidophilic verrucomicrobial methanotroph Methylacidiphilum fumariolicum SolV with its own physiological cytochrome c_GJ electron acceptor. Eu-MDH harbours a redox active 2,7,9-tricarboxypyrroloquinoline quinone (PQQ) cofactor which is non-covalently bound but coordinates trivalent lanthanoid elements including Eu³⁺. Eu-MDH and the cytochrome were co-adsorbed with the biopolymer chitosan and cast onto a mercaptoundecanol (MU) monolayer modified Au working electrode. Cyclic voltammetry of cytochrome c_GJ reveals a well-defined quasi-reversible Fe^III/II redox couple at +255 mV vs. NHE at pH 7.5 and this response is pH independent. The reversible one-electron response of the cytochrome c_GJ transforms into a sigmoidal catalytic wave in the presence of Eu-MDH and its substrates (methanol or formaldehyde). The catalytic current was pH-dependent and pH 7.3 was found to be optimal. Kinetic parameters (pH dependence, activation energy) obtained by electrochemistry show the same trends as those obtained from an artificial phenazine ethosulfate/dichlorophenol indophenol assay.