Speech enhancement using a generic noise codebook

Although single-microphone noise reduction methods perform well in stationary noise environments, their performance in non-stationary conditions remains unsatisfactory. Use of prior knowledge about speech and noise power spectral densities in the form of trained codebooks has been previously shown to address this limitation. While it is possible to use trained speech codebooks in a practical system, the variety of noise types encountered in practice makes the use of trained noise codebooks less practical. This letter presents a method that uses a generic noise codebook for speech enhancement that can be generated on-the-fly and provides good performance.     

Do current-density nonlinearities cut off the glass transition?

Extended mode-coupling theories for dense fluids predict that nonlinear current-density couplings cut off the singular "ideal glass transition" present in the standard mode-coupling theory where such couplings are ignored. We suggest here that, rather than allowing for activated processes as sometimes supposed, contributions from current-density couplings are always negligible close to a glass transition. We discuss in schematic terms how activated processes can nonetheless cut off the transition by causing the memory function to become linear in correlators at late times.     

Some Tetrahedral Coordination Polymers of Zinc(II), Cadmium(II), and Mercury(II) Involving 4-Aminomethylpyridine

Abstract

Analytical data and infrared spectral measurements down to 200 cm^?1 on the 1:1 compounds formed by the interaction of zinc(II) and cadmium(II) thiocyanates and mercury(II) chloride and bromide with 4-aminomethylpyridine indicate that the compounds are coordination polymers having tetrahedral stereochemistry with bidentate bridging 4-aminomethylpyridine molecules and terminally bonded halogen/pseudohalogen groups in the solid state.     

Bioinspired Nitroalkylation for Selective Protein Modification and Peptide Stapling

Nitroalkanes react specifically with aldehydes, providing rapid, stable, and chemoselective protein bioconjugation. These nitroalkylated proteins mimic key post‐translational modifications (PTMs) of proteins and can be used to understand the role of these PTMs in cellular processes. Demonstrated here is the substrate scope of this bioconjugation by attaching a variety of tags, such as NMR tags, fluorescent tags, affinity tags, and alkyne tags, to proteins. The structure and enzymatic activity of modified proteins remain conserved after labeling. Notably, the nitroalkane group leads to easy characterization of proteins by mass spectrometry because of its distinct fingerprint pattern. Importantly, the nitro‐alkylated peptides provide a new handle for site‐selective fluorination of peptides, thus installing a specific probe to study peptide–protein interactions by ¹⁹F NMR spectroscopy. Furthermore, nitroalkane reagents can be used for the late‐stage diversification of peptides and for the synthesis of peptide staples.     

Bacteriocin PJ4 Active Against Enteric Pathogen Produced by Lactobacillus helveticus PJ4 Isolated from Gut Microflora of Wistar Rat (Rattus norvegicus): Partial Purification and Characterization of Bacteriocin

The increase of multidrug-resistant pathogens and the restriction on the use antibiotics due to its side effects have drawn attention to the search for possible alternatives. Bacteriocins are small antimicrobial peptides produced by numerous bacteria. Much interest has been focused on bacteriocins because they exhibit inhibitory activity against pathogens. Lactic acid bacteria possess the ability to synthesize antimicrobial compounds (like bacteriocin) during their growth. In this study, an antibacterial substance (bacteriocin PJ4) produced by Lactobacillus helveticus PJ4, isolated from rat gut microflora, was identified as bacteriocin. It was effective against wide assay of both Gram-positive and Gram-negative bacteria involved in various diseases, including Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, Enterococcus faecalis, and Staphylococcus aureus. The antimicrobial peptide was relatively heat-resistant and also active over a wide pH range of 2–10. It has been partially purified to homogeneity using ammonium sulfate precipitation and size exclusion chromatography and checked on reverse-phase high-performance liquid chromatography. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis of bacteriocin PJ4 purified through size exclusion chromatography resolved ~6.5 kDa protein with bacteriocin activity. The peptide is inactivated by proteolytic enzymes, trypsin, and lipase but not when treated with catalase, α-amylase, and pepsin. It showed a bactericidal mode of action against the indicator strains E. coli MTCC443, Lactobacillus casei MTCC1423, and E. faecalis DT48. Such characteristics indicate that this bacteriocin may be a potential candidate for alternative agents to control important pathogens.     

The role of hydrogen bonding in water-metal interactions

The hydrogen bond interaction between water molecules adsorbed on a Pd <111> surface, a nucleator of two dimensional ordered water arrays at low temperatures, is studied using density functional theory calculations. The role of the exchange and correlation density functional in the characterization of both the hydrogen bond and the water-metal interaction is analyzed in detail. The effect of non local correlations using the van der Waals density functional proposed by Dion et al. [M. Dion, H. Rydberg, E. Schr?der, D. C. Langreth and B. I. Lundqvist, Phys. Rev. Lett., 2004, 92, 246401] is also studied. We conclude that the choice of this potential is critical in determining the cohesive energy of water-metal complexes. We show that the interaction between water molecules and the metal surface is as sensitive to the density functional choice as hydrogen bonds between water molecules are. The reason for this is that the two interactions are very similar in nature. We make a detailed analogy between the water-water bond in the water dimer and the water-Pd bond at the Pd <111> surface. Our results show a strong similarity between these two interactions and based on this we describe the water-Pd bond as a hydrogen bond type interaction. These results demonstrate the need to obtain an accurate and reliable representation of the hydrogen bond interaction in density functional theory.     

Rounded multi-level microchannels with orifices made in one exposure enable aqueous two-phase system droplet microfluidics

Exposure of a negative photoresist-coated glass slide with diffused light from the backside through a mask with disconnected features provides multi-level rounded channels with narrow orifices in one exposure. Using these structures, we construct microfluidic systems capable of creating aqueous two-phase system droplets where one aqueous phase forms droplets and the other aqueous phase forms the surrounding matrix. Unlike water-in-oil droplet systems, aqueous two-phase systems can have very low interfacial tensions that prevent spontaneous droplet formation. The multi-level channels fabricated by backside lithography satisfy two conflicting needs: (i) the requirement to have narrowed channels for efficient valve closure by channel deformation and (ii) the need to have wide channels to reduce the flow velocity, thus reducing the capillary number and enhancing droplet formation.     

Web servers and services for electrostatics calculations with APBS and PDB2PQR

APBS and PDB2PQR are widely utilized free software packages for biomolecular electrostatics calculations. Using the Opal toolkit, we have developed a Web services framework for these software packages that enables the use of APBS and PDB2PQR by users who do not have local access to the necessary amount of computational capabilities. This not only increases accessibility of the software to a wider range of scientists, educators, and students but also increases the availability of electrostatics calculations on portable computing platforms. Users can access this new functionality in two ways. First, an Opal-enabled version of APBS is provided in current distributions, available freely on the web. Second, we have extended the PDB2PQR web server to provide an interface for the setup, execution, and visualization of electrostatic potentials as calculated by APBS. This web interface also uses the Opal framework which ensures the scalability needed to support the large APBS user community. Both of these resources are available from the APBS/PDB2PQR website: http://www.poissonboltzmann.org/.     

Development and validation of a highly sensitive LC-MS/MS method for simultaneous quantitation of acetyl-CoA and malonyl-CoA in animal tissues

A highly sensitive and specific LC‐MS/MS method was developed for simultaneous estimation of acetyl co‐enzyme A (ACoA) and malonyl co‐enzyme A (MCoA) in surrogate matrix using n‐propionyl co‐enzyme A as an internal standard (IS). LC‐MS/MS was operated under the multiple reaction‐monitoring mode using the electrospray ionization technique. Simple acidification followed by dilution using an assay buffer process was used to extract ACoA, MCoA and IS from surrogate matrix and tissue samples. The total run time was 3 min and the elution of both analytes (ACoA, MCoA) and IS occurred at 1.28 min; this was achieved with a mobile phase consisting of 5 mM ammonium formate (pH 7.5)–acetonitrile (30:70, v/v) delivered at a flow rate of 1 mL/min on a monolithic RP‐18e column. A linear response function was established for the range of concentrations 1.09–2187 and 1.09–2193 ng/mL for ACoA and MCoA, respectively. The intra‐ and inter‐day precision values for ACoA and MCoA met the acceptance as per FDA guidelines. ACoA and MCoA were stable in a battery of stability studies viz. bench‐top, auto‐sampler and long‐term. The developed assay was used to quantitate ACoA and MCoA levels in various tissues of rat. Copyright © 2011 John Wiley & Sons, Ltd.