Exceptionally High Dielectric Constant in Ceramic Pr2CuO4

The pristine layered cuprate Pr₂CuO₄ samples of >95% density were fabricated as thin disks. The samples, analyzed by X‐ray diffraction and Scanning electron microscopy, showed clean T′‐type phase with Rietveld refined lattice parameters a = b = 3.95805(±5) Å and c = 12.2262(±5) Å. The measured dielectric properties of the Pr₂CuO₄ ceramics, in the temperature range ?100°C–150°C and frequencies (ν) 0.1 Hz–1 MHz, showed extremely high ε_r′ > 10⁴ (above ?30°C), and dissipation (tan δ = ε_r′′/ε_r′) between 0.1 and 5 (for 500 Hz ≤ ν ≤ 1 MHz, and ?100 ≤ T ≤ 150°C). The ac conductivity of Pr₂CuO₄ ceramics ranged between 10^?6 and 10^?3 Scm^?1 for the measured frequencies and temperatures, and showed frequency‐dependent double power law behavior akin to a modified Jonscher's power law.     

Synthesis,characterization and application of Azadirachta indica juss (neem oil) fatty amides (AIJFA) based polyurethanes coatings: A renewable novel approach

Number of diethanol amides has been developed by scientist using various vegetable oils and not from neem seed oil. Most of the research work on neem seed oil has explored its applications in pharmaceutical and pesticides fields. This paper representing new area of application of neem seed oil for polymeric resin, in which we attempted to synthesize the neem seed oil based poly(urethane fatty amides) by reaction of neem oil fatty amide (AIJFA) with trimer of isophorone diisocyanate (IPDI). Spectral study of AIJFA was carried out by using FT-IR and ¹H NMR techniques. Molecular weight of AIJFA was determined by gel permeation chromatography (GPC). Fatty acid composition of neem seed oil was obtained by gas chromatographic method. The coatings applied on mild steel plates were evaluated by determining coating properties, chemical and corrosion resistances. TGA study of coatings showed higher thermal stability to AIJFA based PU coatings compared to normal urethane and alkyd coatings.     

Gate All Around Dopingless Nanotube TFET Biosensor with Si0.5Ge0.5 – Based Source

Silicon - Through this paper, we discuss how Tunnel Field Effect Transistors can be utilized for the detection of biomaterials hence acting as a biosensor. The device proposed is a 3-D Doping less...     

An Integrated Controlled-Current PWM Rectifier Chopper Link for Sliding Mode Position Control

Position controllers must handle kinetic energy exchanges during acceleration and deceleration of large inertias. Temporary buffer storage in capacitors is expensive. The system that can manage the power exchange with ease is the integrated controlled-current pulsewidth-modulated (PWM) rectifier/controlled-current PWM chopper link. Bidirectional power is accomplished by bidirectional current flow in the dc link for both modulators. The three-phase currents in the rectifier side are near sinusoidal in waveform at unity power factor. The performance of the system as a position controller in an environment of the sliding mode strategy is studied. The sliding mode strategy offers robust characteristics to the controller.     

A partial Granger causality based method for analysis of parameter interactions in bioreactors

In this article, we utilize the concept of partial Granger causality to study the penicillin production process under several operating conditions. We propose a graph-theoretic template (causal network) based method for intelligent process monitoring. We validate our results with the aid of existing knowledge and available literature. The proposed method is quite general and can be extended to analyze several physical, chemical or biological systems.     

Melt‐mixed polypropylene/acrylonitrile‐butadiene‐styrene blends with multiwall carbon nanotubes: Effect of compatibilizer and modifier on morphology and electrical conductivity

Cocontinuous blends of 45/55 polypropylene (PP)/acrylonitrile‐butadiene‐styrene (ABS) with multiwall carbon nanotubes (MWNT) were prepared by melt‐mixing in a conical twin‐screw microcompounder. PP‐grafted‐maleic anhydride (PP‐g‐MA) and styrene MA were used as compatibilizers for PP/ABS blends. Scanning electron microscopic observations showed phase segregation of PP‐g‐MA in the blends. State of dispersion of MWNT in the presence or absence of the compatibilizers was assessed through AC electrical conductivity measurements and crystallization studies of the blends. An improvement in AC electrical conductivity was observed in blends in presence of either styrene MA or dual compatibilizers. The lowest electrical percolation threshold was achieved at 0.1 wt % of MWNT using sodium salt of 6‐amino hexanoic acid‐modified MWNT. Significant increase in crystallization temperature of PP phase of blends with MWNT was observed in the presence of compatibilizers as compared to blends without compatibilizers. An attempt has been made to address the complex issues of phase segregation, compatibilization, and dispersion of MWNT in cocontinuous blends of PP/ABS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Polymeric sodium alginate interpenetrating network beads for the controlled release of chlorpyrifos

Novel polymeric sodium alginate (Na‐Alg) interpenetrating network (IPN) beads have been prepared by crosslinking Na‐Alg blend with gelatin (GE) or egg albumin (EA) using glutaraldehyde (GA) as the crosslinking agent. These beads were used for the controlled release of chlorpyrifos. The swelling experiments were performed in water at different temperatures, and these data were used to calculate the molecular mass (M_C) between crosslinks as well as diffusion coefficients. Diffusion coefficients calculated from desorption data were lower by about two orders of magnitude than those calculated from sorption results. Higher values of M_C were obtained for the gelatin‐based IPNs than the neat Na‐Alg and egg albumin‐based matrices. Size of the beads did not vary significantly either by the network or by increasing the exposure time to the crosslinking agent. The scanning electron microscopy (SEM) was used to understand the surface characteristics of the beads. Differential scanning calorimetry (DSC) indicated a molecular level dispersion of chlorpyrifos in the polymer matrix. The percentage entrapment efficiency showed a dependence on the type of network polymer as well as time of exposure to the crosslinking agent. The encapsulation efficiency decreased with an increase in time of exposure to the crosslinking agent. In vitro release experiments have been performed to follow the release kinetics of chlorpyrifos from the matrices. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 911–918, 2002     

Enzymatically degradable prodrugs: A novel methodology for drug linkage

We have synthesized a novel enzymatically degradable prodrug system based on poly(ethylene glycol) (PEG) and tyrosine units by employing a synthetic methodology which eliminated the use of conventional blocking and deblocking methodology used for chemical linkage of drug molecule to the pendant ? NH₂ group of amino acid. A diester of PEG (6 kDa) and tyrosine hydrochloride was synthesized by dicyclohexyl carbodiimide (DCC)‐mediated condensation. In the second stage, oligomers were prepared by condensing phenolic ? OH groups of tyrosine in the diester with sebacic acid, using DCC. Finally, the hydrochloride salt of tyrosine in the oligomer was treated with triethylamine to activate ? NH₂ groups, which were reacted with benzoyl chloride to obtain a model prodrug system. The products synthesized were characterized by IR, ¹H‐NMR, and GPC. The spectral data were in accordance with the proposed structures of products. Chymotrypsin‐catalyzed degradation of the oligomers was characterized by both MW measurements and Ninhydrin assay for free tyrosine. Degradation studies indicated that the rate of main‐chain degradation (ester hydrolysis) is higher than that of the side chain (amide hydrolysis). This new, simple methodology should be useful for conjugating a variety of bioactive molecules to enzymatically degradable PEG–amino acid based polymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2108–2118, 2002     

Vapor Phase Beckmann Rearrangement of Cyclohexanone Oxime over Different Ferrierite Zeolite Catalysts

Ferrierite zeolite catalysts prepared using different procedures have been tested for their activity for vapor phase Beckmann rearrangement of cyclohexanone oxime to -caprolactam. We report here the results of a study seeking the influence of temperature, nitrogen feed rate, oxime concentration and solvents on the catalyst performance. At low concentration of oxime (2.5 wt%), using acetonitrile as solvent the maximum in the conversion of oxime and selectivity to -caprolactam has been obtained. The presence of weak, medium and strong acid sites as indicated by temperature-programmed desorption of NH₃ corroborates well with the catalytic activities of various ferrierites shown here. Solvent polarity is found to significantly affect the conversion of cyclohexanone oxime.     

Biohydrogen Production from Organic Waste – A Review

Hydrogen fuel is a promising alternative to fossil fuels because of its energy content, clean nature, and fuel efficiency. However, it is not readily available. Most current producion processes are very energy intensive and emit carbon dioxide. Therefore, this article reviews technological options for hydrogen production that are eco-friendly and generate clean hydrogen fuel. Biological methods, such different fermentation processes and photolysis are discussed together with the required substrates and the process efficiency.