Graph-Laplacian features for neural waveform classification

Analysis of extracellular recordings of neural action potentials (known as spikes) is highly dependent upon the accuracy of neural waveform classification, commonly referred to as spike sorting. Feature extraction is an important stage of this process because it can limit the quality of clustering that is performed in the feature space. Principal components analysis (PCA) is the most commonly used feature extraction method employed for neural spike recordings. To improve upon PCA's feature extraction performance for neural spike sorting, we revisit the PCA procedure to analyze its weaknesses and describe an improved feature extraction method. This paper proposes a linear feature extraction technique that we call graph-Laplacian features, which simultaneously minimizes the graph Laplacian and maximizes variance. The algorithm's performance is compared with PCA and a wavelet-coefficient-based feature extraction algorithm on simulated single-electrode neural data. A cluster-quality metric is proposed to quantitatively measure the algorithm performance. The results show that the proposed algorithm produces more compact and well-separated clusters compared to the other approaches.     

Chemoselective Synthesis of Functionalized 2,5-Dihydro-2-thioxo-1H-imidazoles from 5,5-Diarylthiohydantoins and Activated Acetylenes

Stable crystalline phosphorus ylides are obtained in excellent yields from the 1:1:1 addition reaction between 5,5-diarylthiohydantoins and dialkyl acetylenedicarboxylates in the presence of triphenylphosphine. These phosphoranes undergo a smooth intramolecular Wittig reaction followed by an electrocyclic ring opening to produce dialkyl 2-(2,5-dihydro-5,5-diaryl-2-thioxo-1H-imidazol-4-yl)but-2-enedioates in good yields.     

Synthesis, Characterization, Photoluminescence and Photocatalytic Properties of CeO2 Nanoparticles by the Sonochemical Method

Uniform CeO₂ nanoparticles were synthesized via a facile sonochemical reaction between ceric ammonium nitrate and ammonia. Nanoparticles were synthesized via a surfactant free reaction at room temperature in solvent of water. Products were characterized using X-ray diffraction, scanning electron microscopy, photoluminescence (PL) spectroscopy, and energy dispersive X-ray analysis. The effect of different parameters such as precursor, power of pulsation, surfactant and reaction time on the morphology of the products was investigated. It was found that the as-obtained CeO₂ nanoparticles exhibit a strong PL peak at 381 nm at room temperature that can be ascribed to the high level transition in the CeO₂ semiconductor. The photocatalytic behavior of CeO₂ nanoparticles was evaluated using the degradation of a methyl orange aqueous solution under ultraviolet light irradiation. The results show that CeO₂ nanoparticles are promising materials with excellent performance in photocatalytic applications.     

Simultaneous determination of adrenaline,uric acid,and cysteine using bifunctional electrocatalyst of ruthenium oxide nanoparticles

In this study, ruthenium oxide nanoparticles were electrochemically deposited on the surface of a glassy carbon electrode (RuON-GCE). Electrochemical studies indicate that a modified electrode (RuON-GCE) plays the role of an excellent bifunctional electrocatalyst for the oxidation of adrenaline (AD) and uric acid (UA) in two different potentials. The charge transfer coefficient (α) and the heterogeneous charge transfer rate constant (k′) between the analytes and the electrodeposited nanoparticles were determined using cyclic voltammetry experiments. Through a different pulse voltammetric (DPV) method, the plot of the electrocatalytic current versus AD and UA concentrations emerged to be constituted of two linear segments with different sensitivities. Furthermore, the detection limits of AD and UA were estimated. In DPV, RuON-GCE could separate the oxidation peak potentials of AD, UA, and cysteine (Cys) present in the same solution though, at the bare GCE, the peak potentials were indistinguishable. Finally, the modified electrode activity was studied for the electrocatalytic determination of AD in an injection solution and UA in a human urine sample. The results were found satisfactory.     

A Simple Chemical Method for Synthesis of NiFe2O4 Nanoparticles and Polystyrene-Based Magnetic Nanocomposites

Magnetic NiFe₂O₄ (NiFe) nanoparticles were synthesized via a facile chemical reaction between Ni(NO₃)₂ and Fe(NO₃)₃. Different percents of NiFe nanoparticles were then added to polystyrene (PS) matrix. Nanoparticles were characterized using X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. The magnetic properties of the samples were also investigated using an alternating gradient force magnetometer. The nanoparticles exhibit ferromagnetic behaviour at room temperature, with a saturation magnetization of 20.8 emu/g and a coercivity of 99.6 Oe. Preparation of NiFe₂O₄ -PS nanocomposite leads to decrease in the coercivity.     

The Effect of Aminated Carbon Nanotube and Phosphorus Pentoxide on the Thermal Stability and Flame Retardant Properties of the Acrylonitrile–Butadiene–Styrene

Multi-walled carbon nanotubes (MWCNT) have been successfully functionalized with amino groups. In order to improve the thermal stability of the polymer nanocomposite, aminated-MWCNTs were added to acrylonitrile–butadiene–styrene (ABS). The influence of MWCNT and phosphorus pentoxide nanostructures on the flame retardancy of the ABS matrix was studied using UL-94 test. The results show that the MWCNT nanostructure can’t enhance the flame retardancy of the ABS matrix but synergism of MWCNT and P₂O₅ can effectively improve the flame retardancy of the nanocomposite.     

Synergistic Effect Between Sb2O3 Nanoparticles–Trichloromelamine and Carbon Nanotube on the Flame Retardancy and Thermal Stability of the Cellulose Acetate

Sb₂O₃ nanoparticles were synthesized via a simple surfactant-free sonochemical reaction. Multi-walled carbon nanotubes (MWCNT) have been successfully functionalized with amino groups. Cellulose acetate (CA) as a polymeric matrix was choosing in this work. In order to improve the thermal stability and flame retardancy of the CA, nanoparticles, aminated-MWCNT and trichloromelamine (TCM) were added to the polymeric matrix. The nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy and UL-94 analysis. Flame retardancy of the nanocomposite was improved as a result of synergistic effect between Sb₂O₃ and TCM. Result show that thermal decomposition of the nanocomposites was shifted towards higher temperatures.     

Synthesis and thermogravimetric analysis of inclusion complexes of O2N2-donor Aza-crown macrocyclic ligands with [60]fullerene

A simple method for the formation of inclusion complex of [60]fullerene with two O₂N₂-donor aza-crown macrocyclic ligands was introduced. The products were characterized using UV–vis and IR spectroscopies as well as HPLC, and ESI mass spectrometry. The ESI mass and elemental analysis data revealed that the ratio of macroring:[60]fullerene were not the same. The binding capability of the macrorings as well as the number of the macroring addends to [60]fullerene were investigated using thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). Considering percentage mass loss in different steps of TG and the enthalpy changes in DSC found for each of these products, the number of their addends on [60]fullerene were calculated. Theoretical calculations in semi-empirical level using AM1 suggested that proper orientation of the nitrogen-donor groups on the aza-crown macrorings toward [60]fullerene could be the main factor for the observed difference in the number of macroring addends attached to [60]fullerene.     

From Nef‐Isocyanide Adducts toward Functionalized 5‐Iminothiazolidines Containing Polarized CC Bonds

An efficient synthesis of alkyl 5‐(alkylimino)‐3‐aryl(alkyl)‐2‐(dicyanomethylene)‐4‐hydroxythiazolidine‐4‐carboxylates, containing polarized C?C bonds, via reaction of malononitrile, arylisothiocyanates, and the Nef‐isocyanide adducts, under basic conditions, is described.     

Best packetisation scheme for H.263 Internet video communication

The H.263 codec is an efficient way to stream variable bit-rate video sequences. It is proposed that, for equivalent bandwidth and frame rate, a two-slice packetisation scheme results in superior peak signal-to-noise ratio, rather than the conventional one-slice scheme, and that constant inter-packet gap rather than 'bursty' delivery is preferable.