Two‐Microphone Binary Mask Speech Enhancement in Diffuse and Directional Noise Fields

Two‐microphone binary mask speech enhancement (2mBMSE) has been of particular interest in recent literature and has shown promising results. Current 2mBMSE systems rely on spatial cues of speech and noise sources. Although these cues are helpful for directional noise sources, they lose their efficiency in diffuse noise fields. We propose a new system that is effective in both directional and diffuse noise conditions. The system exploits two features. The first determines whether a given time–frequency (T‐F) unit of the input spectrum is dominated by a diffuse or directional source. A diffuse signal is certainly a noise signal, but a directional signal could correspond to a noise or speech source. The second feature discriminates between T‐F units dominated by speech or directional noise signals. Speech enhancement is performed using a binary mask, calculated based on the proposed features. In both directional and diffuse noise fields, the proposed system segregates speech T‐F units with hit rates above 85%. It outperforms previous solutions in terms of signal‐to‐noise ratio and perceptual evaluation of speech quality improvement, especially in diffuse noise conditions.     

Partitioning of Amino Acids in Surfactant Based Aqueous Two-Phase Systems Containing the Nonionic Surfactant (Triton X-100) and Salts

The partitioning of three amino acids, L-phenylalanine, L-tryptophan and L-tyrosine, has been studied in surfactant-based aqueous two-phase systems (ATPS) of Triton X-100 + salts + H₂O at 298.15 K. Sodium citrate as an organic salt and magnesium sulfate as an inorganic salt were used to prepare the ATP systems. The effects of tie-line length and salt type on the partitioning of amino acids have been discussed. The results show that the partitioning behavior of the amino acids in the systems containing MgSO₄ and Na₃C₆H₅O₇ are significantly different, because increasing the tie-line length in MgSO₄ solutions leads to a decrease of the partition coefficient, whereas the opposite trend is found in Na₃C₆H₅O₇ solutions.     

Complexation of 4′-Nitrobenzo-15-crown-5 with Zn<Superscript>2+</Superscript>, Mn<Superscript>2+</Superscript>, Cr<Superscript>3+</Superscript> and Sn<Superscript>4+</Superscript> Cations in Acetonitrile–Ethanol Binary Mixtures

The complexation reactions of 4′-nitrobenzo-15-crown-5 (4′NB15C5) with Zn²⁺, Mn²⁺, Cr³⁺ and Sn⁴⁺ cations were studied in acetonitrile–ethanol (AN–EtOH) binary solvent mixtures at different temperatures by the electrical conductometry method. The stability constants of the resulting 1:1 complexes were determined from computer fitting of the conductance versus mole ratio data. The results show that the selectivity order of 4′NB15C5 for the metal cations in the AN–EtOH (mol-%AN=76) binary solvent at 298.15 K is: Cr³⁺>Mn²⁺≈Zn²⁺>Sn⁴⁺, but the selectivity order changes with the composition of the mixed solvents. A nonlinear relationship was observed between the stability constants (log ₁₀ K _f) of these complexes and the composition of the AN–EtOH binary solvents. The corresponding thermodynamic parameters (DH_c^o, DS_c^o)(\Delta H_{\mathrm{c}}^{\mathrm{o}}, \Delta S_{\mathrm{c}}^{\mathrm{o}}) were obtained from the temperature dependence of the stability constants using van’t Hoff plots. The results show that the values and also the sign of these parameters are influenced by the nature and composition of the mixed solvents.     

Poly(N‐bromobenzene‐1,3‐disulfonamide) and N,N,N′,N′‐tetrabromobenzene‐1,3‐disulfonamide as a mild and efficient catalyst for chemoselective thioacetalization of carbonyl functions and transthioacetalization reactions

Poly(N‐bromobenzene‐1,3‐disulfonamide) and N,N,N′,N′‐tetrabromobenzene‐1,3‐disulfonamide are effective catalysts for chemoselective dithioacetalization of aldehydes in the presence of ketones under neutral conditions. J. Heterocyclic Chem., (2011).     

Electrochemical approach for monitoring the effect of anti tubulin drugs on breast cancer cells based on silicon nanograss electrodes

One of the most interested molecular research in the field of cancer detection is the mechanism of drug effect on cancer cells. Translating molecular evidence into electrochemical profiles would open new opportunities in cancer research. In this manner, applying nanostructures with anomalous physical and chemical properties as well as biocompatibility would be a suitable choice for the cell based electrochemical sensing. Silicon based nanostructure are the most interested nanomaterials used in electrochemical biosensors because of their compatibility with electronic fabrication process and well engineering in size and electrical properties. Here we apply silicon nanograss (SiNG) probing electrodes produced by reactive ion etching (RIE) on silicon wafer to electrochemically diagnose the effect of anticancer drugs on breast tumor cells. Paclitaxel (PTX) and mebendazole (MBZ) drugs have been used as polymerizing and depolymerizing agents of microtubules. PTX would perturb the anodic/cathodic responses of the cell-covered biosensor by binding phosphate groups to deformed proteins due to extracellular signal-regulated kinase (ERK^1/2) pathway. MBZ induces accumulation of Cytochrome C in cytoplasm. Reduction of the mentioned agents in cytosol would change the ionic state of the cells monitored by silicon nanograss working electrodes (SiNGWEs). By extending the contacts with cancer cells, SiNGWEs can detect minor signal transduction and bio recognition events, resulting in precise biosensing. Effects of MBZ and PTX drugs, (with the concentrations of 2 nM and 0.1 nM, respectively) on electrochemical activity of MCF-7 cells are successfully recorded which are corroborated by confocal and flow cytometry assays.     

A Mild,Simple, Efficient,and Selective Protection of Hydroxyl Groups Using Silica-Supported Sodium Hydrogen Sulfate as a Heterogeneous Catalyst

A mild, simple, novel, and highly efficient method for the rapid protection of various primary, secondary, tertiary aliphatic alcohols, aromatic alcohols, and oximes using hexamethyldisilazane (HMDS) in the presence of silica-supported sodium hydrogen sulfate (NaHSO ₄ -SiO ₂ ), as an active, inexpensive, nontoxic, heterogeneous, and readily available catalyst under ambient conditions is described. Timethylsilyl ethers were prepared in high to excellent yields, with short reaction times under mild and almost neutral reaction conditions at room temperature.     

Performance enhancement of bimetallic Co-Ru/CNTs nano catalysts using microemulsion technique

Bimetallic cobalt-ruthenium nano catalysts supported on carbon nanotubes(CNTs)are prepared using microemultion technique with water-to-surfactant ratios of 0.5—1.5.The nano catalysts were extensively characterized by different methods and their activity and selectivity in Fischer-Tropsch synthesis(FTS)have been assessed in a fixed-bed microreactor.The physicochemical properties and performance of the nanocatalysts were compared with the catalyst prepared by impregnation method.Very narrow particle size distribution has been produced by the microemulsion technique at relatively high loadings of active metals(15 wt%Co and 1 wt%Ru).According to TEM images,small Co particles(2—7 nm)were mostly confined inside the CNTs.Comparing with the catalyst prepared by impregnation,the use of microemulsion technique with water to surfactant ratio of 0.5 decreased the average cobalt oxide particle size to 4.8 nm,the dispersion was almost doubled and the reduction increased by 28%.Activity and selectivity were found to be dependent on the catalyst preparation method and water-to-surfactant ratio(as well as cobalt particle sizes).CO conversion increased from 59.1%to 75.1%and the FTS rate increased from 0.291 to0.372 gHC/(gcath).C5+liquid hydrocarbons selectivity decreased from 92.4%to 87.6%.     

Easily prepared azopyridines as potent and recyclable reagents for facile esterification reactions. An efficient modified mitsunobu reaction

The 2,2'-, 3,3'-, and 4,4'-azopyridines (azpy) and their alkyl pyridinium ionic liquids were studied as a new class of electron-deficient reagents for Mitsunobu esterification reactions. Among these compounds, 4,4'-azopyridine was found to be the most suitable one for esterification and thioesterification reactions. This new reagent promises to provide general and complementary solutions for separation problems in Mitsunobu reactions without restricting the reaction scope and facilitates the isolation of its hydrazine byproduct. The pyridine hydrazine byproduct can be simply recycled to its azopyridine by an oxidation reaction.     

Kinetic-spectrophotometric determination of sulfide by its reaction with resazurin

A sensitive, rapid and selective method for the determination of sulfide based on its reaction with resazurin at pH 7 is described. The method is simple and has the great advantage of being free from interference of other sulfur anions and thus sulfide can be easily determined at trace levels in the presence of other sulfur compounds. The method has been applied to some synthetic samples and a spring water sample. The importance of sulfide compounds in biological processes has been widely demonstrated [1]. However, most of the methods used so far are either not sensitive enough or require complicated and expensive instruments; or are subjected to interferences from other sulfur compounds. Therefore, more sensitive, simple and selective methods are still required.