Separation of proteins from aqueous solution using cellulose acetate/poly (vinyl chloride) blend ultrafiltration membrane

Cellulose acetate (CA) membranes are widely used for ultrafiltration applications. CA and poly (vinyl chloride) (PVC) blend membranes are prepared by using polar solvent of N, N-dimethylformamide (DMF) by phase inversion method. Polyethylene glycol (PEG 600) is used as polymeric additive in the casting solution. The effect of polymer composition and additive concentration on surface morphology, porosity are studied. The morphology of prepared membranes is found to have asymmetric structure with dense skin layer and porous sub-layer. Applications of these membranes are carried out for rejection and permeation of macromolecular proteins such as trypsin, pepsin, egg albumin, bovine serum albumin. On increasing the concentration of PVC and PEG 600, protein rejection decreases whereas permeate flux increases.CA/PVC/PEG (70/30/10 wt%) blend membrane shows the highest permeation flux of 211.1 lm⁻² h⁻¹ for trypsin.     

Investigation of biocatalytic properties of soybean seed hull peroxidase

Soybean seed hull peroxidase (SBP) is an inexpensive oxidoreductive enzyme and could potentially be used to oxidise/polymerise various organic pollutants present in the industrial and petrochemical wastes. SBP is able to retain its catalytic properties under wide ranges of pH and at elevated temperatures. In this study, a systematic evaluation of the biocatalytic properties of SBP was carried out. The optimal pH for SBP activity is pH 6.0 and significant activity was observed between 2.2 and 8.0. SBP also showed three times higher activity at an elevated temperature of 80°C and at pH 6.0 when compared to the activity at room temperature. The pH and temperature of the reaction mixture were found to significantly influence the SBP activity. SBP is fairly active in organic solvents. The enzyme exhibited highest activity in the presence of 16.67% (w/v) ethanol followed by acetone, methanol and acetonitrile. The enzyme activity was reduced with an increase in concentration of the organic solvent. SBP also showed maximum activity at different concentrations of acetone using a phosphate buffer, pH 6.0 than with the other pH buffers. Benzene/acetone mixture seems to be another better solvent system for SBP where it showed about 65% of its activity at 16.67% (w/v) concentration.     

Fabrication,characterization and comparison of DSSC using anatase TiO2 synthesized by various methods

In this study, anatase TiO₂ nanoparticles were synthesized by three techniques, namely, sol–gel, acid-base co-catalyst and room temperature colloidal methods. The synthesized materials were characterized by X-ray diffraction, scanning electron microscopy, pore diameter, pore volume and surface area. The dye-sensitized solar cells were fabricated using the synthesized materials and characterized for incident photon to current conversion efficiency, photocurrent density to photo voltage measurement and electrochemical impedance analysis. Among the studied materials, TiO₂ synthesized by sol–gel method displayed highest photon to current conversion of 76.8% and a maximum solar cell efficiency of 7.85% with J_sc of 14.75 mA/cm², V_oc of 0.76 V and FF of 0.7. This is the first study to report a high power conversion efficiency of DSSC using a sol–gel synthesized titania and its comparison with other two synthesized materials. The high power conversion efficiency of the solar cell using TiO₂ synthesized by sol–gel method is attributed to its characteristic properties such high surface area, larger pore diameter and larger pore volume and highest dye loading capacity.     

Two speaker speech separation by LP residual weighting and harmonics enhancement

This paper presents a method for separating speech of individual speakers from the combined speech of two speakers. The main objective of this work is to demonstrate the significance of the combined excitation source based temporal processing and short-time spectrum based spectral processing method for the separation of speech produced by individual speakers. Speech in a two speaker environment is simultaneously collected over two spatially separated microphones. The speech signals are first subjected to excitation source information (linear prediction residual) based temporal processing. In temporal processing, speech of each speaker is enhanced with respect to the other by relatively emphasizing the speech around the instants of significant excitation of desired speaker by deriving speaker-specific weight function. To further improve the separation, the temporally processed speech is subjected to spectral processing. This involves enhancing the regions around the pitch and harmonic peaks of short time spectra computed from the temporally processed speech. To do so the pitch estimate is obtained from the temporally processed speech. The performance of the proposed method is evaluated using (i) objective quality measures: percentage of energy loss, percentage of noise residue, the signal-to-noise ratio (SNR) gain and perceptual evaluation of speech quality (PESQ), and (ii) subjective quality measure: mean opinion score (MOS). Experimental results are reported for both real and synthetic speech mixtures. The SNR gain and MOS values show that the proposed combined temporal and spectral processing method provides an average improvement in the performance of 5.83% and 8.06% respectively, compared to the best performing individual temporal or spectral processing methods.     

Inducing Chaos in Electronic Circuits by Resonant Perturbations

We propose a scheme to induce chaotic attractors in electronic circuits. The applications that we are interested in stipulate the following three constraints: 1) the circuit operates in a stable periodic regime far away from chaotic behavior; 2) no parameters or state variables of the circuit are directly accessible to adjustment and 3) the circuit equations are unknown and the only available information is a time series (or a signal) measured from the circuit. Under these conditions, a viable approach to chaos induction is to use external excitations such as a microwave signal, assuming that a proper coupling mechanism exists which allows the circuit to be perturbed by the excitation. The question we address in this paper is how to choose the waveform of the excitation to ensure that sustained chaos (chaotic attractor) can be generated in the circuit. We show that weak resonant perturbations with time-varying frequency and phase are generally able to drive the circuit into a hierarchy of nonlinear resonant states and eventually into chaos. We develop a theory to explain this phenomenon, provide numerical support, and demonstrate the feasibility of the method by laboratory experiments. In particular, our experimental system consists of a Duffing-type of nonlinear electronic oscillator driven by a phase-locked loop (PLL) circuit. The PLL can track the frequency and phase evolution of the target Duffing circuit and deliver resonant perturbations to generate robust chaotic attractors     

Self-aligned vertical electrostatic combdrives for micromirror actuation

In this paper, we analyze the effect of misalignment in electrostatic combdrives, and describe a fabrication technology that minimizes misalignment in vertical electrostatic combdrives by creating self-aligned, vertically staggered electrodes. Self-alignment of the interdigitated electrodes simplifies fabrication and minimizes failures due to electrostatic instability, thus enabling fabrication of narrow-gap, high-force actuators with high yield. The process is based on deep-reactive ion etching (DRIE) of buried-patterned silicon-on-insulator (SOI) wafers. Measurements on fabricated combdrives show relative misalignment of less than 0.05 /spl mu/m. This corresponds to less than 0.1% misalignment, which, according to our analysis, results in a travel range of 98% of that for perfectly aligned drives. The validity of the process is demonstrated by fabrication of scanning micromirrors measuring 300 /spl mu/m by 100 /spl mu/m. Optical angular deflections from 4/spl deg/ at low frequency to 40/spl deg/ at resonance were measured for an applied voltage of 75 Vpp. Resonant frequencies ranged from 5 kHz to 15 kHz for these devices, making them suitable for high-speed, high-resolution optical scanning and switching.     

A Scalable Distributed Shared Memory Architecture

Scalability of a multiprocessor architecture depends on its ability to manage interconnection network latency with increasing number of processors. Interconnection network latency can be minimized by reducing the distance traversed by a message in terms of number of nodes and wire lengths. Scalability of a DSM architecture also depends on the scalability of the coherency protocol and the associated directory storage requirements. In this paper we describe a DSM architecture based on a fat tree interconnection network with augmented switching nodes. The proposed architecture is CC-NUMA, but supports several important features of COMA architectures. The scalability of this architecture is enhanced by integrating routing and cache coherency operations, which helps in improving locality by trapping requests locally. Scalability of a DSM architecture is defined and evaluated in terms of the asymptotic speedup of an algorithm with increasing number of processors.     

Asymptotic joint normality of the granulometric moments

If a random set (binary image) is composed of randomly sized, disjoint translates arising as homothetics of a finite number of compact primitives and a granulometry is generated by a convex, compact set, then the granulometric moments of the random set can be expressed in terms of model parameters. This paper shows that, under mild conditions, any finite vector of granulometric moments possesses a multivariate distribution that is asymptotically normal. Since Gaussian maximum-likelihood classification is often used when employing the granulometric moments for texture classification, the asymptotic joint normality of the moments gives support to the good results thereby obtained.     

Automatic source-code parallelization using HICOR objects

We show that by using an intermediate representation, which supports a formalized interface on which to construct parallelization tools, the mapping of the representation onto parallel architectures can be performed quickly and efficiently. An intermediate representation called HICOR (Hierarchical Intermediate Code Object Representation) is shown to facilitate the exploitation of parallel operations by providing an abstraction layer for performing high-level intermediate code analysis, scheduling, and code generation. An object-oriented design approach has been employed in the development of HICOR and associated tools. Source language constructs are transformed into specialized object classes. Inheritance properties provided by the object-oriented paradigm are utilized to provide a common interface to each object in the HICOR representation. It is this interface that provides the needed consistency and flexibility in which to construct tools that has since been lacking. In particular, a tool to performCompile-Time Scheduling is presented. The scheduling algorithm employed differs from traditional scheduling problems in that merging of tasks is performed to reduce both task creation and communication costs in determining the final schedule. Architectural parameters are provided as input to the heuristic allowing the scheduler to produce near-optimal results for a wide variety of MIMD architectures. Once the final schedule is determined theTarget Code Generator, also presented, is used to generate the corresponding target code. A prototype system has been implemented in C++ which incorporates the HICOR intermediate representation with the tools described. The target architectures include the Sun 630 MP/4, Sequent Symmetry S81, and Stardent Titan.     

Low–Temperature Hydrogen Sensors Based on Au Nanoclusters and Schottky Contacts on ZnO Films Deposited by Pulsed Laser Deposition on Si and SiO2 Substrates

Unintentionally doped n-type ZnO thin films deposited on Si and SiO₂ substrates by pulsed laser deposition (PLD) techniques, were functionalized as H₂ gas sensors by a) incorporating Au nanoclusters in the surface, and b) developing Au Schottky diodes on ZnO. The influence of the catalytic action of the Au nanoclusters on the sensing properties of the devices was examined and found to provide faster response times at a reduced working temperature of 150 degC. The field-assisted sensing of the Au Schottky diodes demonstrated for the first time in this system, a more dramatic reduction in the working temperature of the sensor to nearly room temperature