Electrical conductivity of (PbO)1−x (SnO) x

Electrical conductivity of lead tin monoxide has been measured as a function of composition (x), temperature and electric field. Heat treatment of samples in vacuum produces an irreversible increase in conductivity and is probably due to chemisorption of oxygen. The thermal activation energies in screen printed layers have been found to be lower than that in pressed pellets and is considered to be due to more grain boundaries being present in the former. The non ohmic electrical conduction in pellets followsJ ∝V ⁿ relationship wheren ranges between 2 and 1·25 for different compositions and temperatures. The theory of space charge limited currents (sclc) in defect insulators has been invoked to explain the observed results.     

Overview of complementary GaAs technology for high-speed VLSIcircuits

A self-aligned complementary GaAs (CGaAs) technology (developed at Motorola) for low-power, portable, digital and mixed-mode circuits is being extended to address high-speed VLSI circuit applications. The process supports full complementary, unipolar (pseudo-DCFL), source-coupled, and dynamic (domino) logic families. Though this technology is not yet mature, it is years ahead of CMOS in terms of fast gate delays at low power supply voltages. Complementary circuits operating at 0.9 V have demonstrated power-delay products of 0.01 μW/MHz/gate. Propagation delays of unipolar circuits are as low as 25 ps. Logic families can be mixed on a chip to trade power for delay. CGaAs is being evaluated for VLSI applications through the design of a PowerPC-architecture microprocessor     

Non-ohmic electric conduction in polycrystalline thulium oxide

The current voltage behaviour of polycrystalline Tm₂O₃ has been investigated at 77 K and 300 K to 350 K. At low voltages, the conduction is ohmic while at higher voltages the current has a quadratic dependence on voltage. The voltageV _T at which the transition from ohmic to non-ohmic conduction takes place changes from 180 V to 100 V as temperature increases from 77 K to 350 K. The results are interpreted in terms of the Rose theory of space charge limited currents (sclc) in defect insulators containing shallow traps.     

Formulation and evaluation of solid self-microemulsifying drug delivery system of chlorthalidone by spray drying technology

The main objective of this study was to prepare a solid self-microemulsifying drug delivery system (S-SMEDDS) by spray drying liquid SMEDDS with an inert solid carrier Aerosil 200 to improve the dissolution rate and permeability of chlorthalidone (CTD). The liquid SMEDDS was composed of CTD, oleic acid, tween 20, and PEG 200. Preliminary screening was performed to select proper component combination. Solubility of CTD was determined in various vehicles. Ternary phase diagram for four series was constructed to delineate the boundaries of the nanoemulsion domain. Optimized S-SMEDDS (S3) was evaluated for dispersibility test (13.30?±?0.95), percentage transmittance (99.50?±?0.002), turbidity (260.43?±?1.02), percent drug content (97.86?±?0.56), droplet size (159.4), polydispersity index (PDI, 0.30), and zeta potential (?12.4). Solid-state characterization was done by scanning electron microscopy (SEM), differential scanning calorimetry, X-ray powder diffraction (XRD), and Fourier transform infrared (FT-IR). The XRD analysis confirmed that there was no crystalline CTD in the S-SMEDDS. SEM study revealed adsorption of liquid SMEDDS on Aerosil 200. In vitro drug release study was performed using water and 0.1N HCl as dissolution medium and compared with plain drug and marketed tablet Thaiklor TM 12.5, and marked increase in rate and extent of dissolution of S-SMEDDS was observed. Ex vivo intestinal permeability study revealed that diffusion of drug was significantly higher from S-SMEDDS than that of suspension of plain drug. The solid SMEDDS formulation was stable. In conclusion, the S-SMEDDS might be an encouraging strategy to improve the oral absorption of CTD.     

An Efficient Quasigroup Block Cipher

Low powered devices, such as smart phones, tablets and sensors, present a particular challenge for advanced encryption systems. In this paper, we present a new quasigroup block encryption system that has low memory and computational requirements and hence suitable for low powered devices. We compare its performance against Advanced Encryption Standard-256 (AES-256) bit algorithm using the NIST statistical test suite (NIST-STS). Since it is well known that a good encryption algorithm must destroy any statistical properties of the input sequence and produce output close to a true random sequence, the NIST-STS suite results provide us a good test bench. In almost all tests from the suite, the proposed algorithm performs better than AES-256.     

Rodent nerve-muscle cell culture system for studies of neuromuscular junction development: refinements and applications

Understanding of vertebrate neuromuscular junction (NMJ) development has been advanced by experimentation with cultures of dissociated embryonic nerve and skeletal muscle cells, particularly those derived from Xenopus and chick embryos. We previously developed a rodent (rat) nerve-muscle coculture system that is characterized by extensive induction of acetylcholine receptor (AChR) aggregation at sites of axonal contact with myotubes (Dutton et al., 1995). In this article, we report modifications of this culture system and examples of its application to the study of NMJ development: (1) We describe improved methods for the enrichment of myoblasts to give higher yields of myotubes with equal or greater purity. (2) We demonstrate lipophilic dye labeling of axons in cocultures by injection of dye into neuron aggregates and show the feasibility of studying the growth of living axons on myotubes during synapse formation. (3) We describe the preparation of a better-defined coculture system containing myotubes with purified rat motoneurons and characterize the system with respect to axon-induced AChR aggregation. (4) We demonstrate dependence of the pattern of axon-induced AChR aggregation on muscle cell species, by the use of chick-rat chimeric co-cultures. (5) We provide evidence for the role of alternatively-spliced agrin isoforms in synapse formation by using single cell RT-PCR with neurons collected from co-cultures after observation of axon-induced AChR aggregation. Microsc. Res. Tech. 49:26-37, 2000. Published 2000 Wiley-Liss, Inc.     

Development of self-microemulsifying drug delivery system of mebendazole by spray drying technology: Characterization,in vitro and in vivo evaluation

In this study, a novel liquid self-microemulsifying drug delivery system (SMEDDS) containing mebendazole was formulated and further developed into a solid form by a spray drying method using Aerosil 200 as the solid carrier. The optimum liquid SMEDDS consisted of Labrafil 2125 CS, Tween 20, and Maisine 35-1 as the oil phase, the surfactant, and the cosurfactant, respectively. The formulated SMEDDS was completely emulsified or dispersed within a minute. All formulations were dissolved within 1 h using 0.1 N HCl as dissolution medium, whereas pure drug was less significantly dissolved in this time period. The droplet size was found to be within 250 nm for solid forms of SMEDDS. Solid state characterization was performed by scanning electron micrograph, differential scanning calorimetry, and X-ray powder diffraction. After oral administration to Wistar rats, mebendazole in the solid SMEDDS resulted in the significant improvement in bioavailability compared with that of pure drug analyzed by RP-HPLC. The optimized formulation showed 24.87 folds increase in bioavailability as compared to pure drug and 8.39 folds increase in bioavailability in comparison to marketed tablet of mebendazole. The optimized batch has found to be 3.1726 years of shelf life. In conclusion, the solid SMEDDS is a promising solid dosage form for poorly water-soluble and low bioavailability drugs.     

Oblivious Transfer Using Elliptic Curves

Abstract

In this article we propose an algorithm for oblivious transfer using elliptic curves. Also, we present its application to chosen one-out-of-two oblivious transfer.     

Anomalous pressure-dependence in surface-modified silicon-derived nanoparticles

Surfaces can significantly alter the optical properties of nanomaterials, but they are difficult to control and their roles are hard to understand in highly reactive materials such as silicon nanomaterials. In this work, we investigate the role of the surface in controlling the optical transitions in highly luminescent silicon-derived nanoparticles. By combining high-pressure and low-temperature experiments, we experimentally correlate the anomalously intense and narrow transitions in the UV range with the surface oxides, while the visible transition and the photoluminescence (PL) are verified to originate from the Si-ligand charge transfer band. We find that the high-pressure absorption and PL depends on the rigidity of the surface ligand. This indicates that the surface plays a dominant role on the optical properties of these silicon-derived nanoparticles, and is different than other semiconductor nanomaterials, in which pressure-dependent optical transitions depend on lattice strain or phase transformations. This work presents a comprehensive understanding of the optical transitions and the effect of surface ligands and surface oxidation in these highly luminescent Si-derived nanoparticles. The new insight into the oxidation-activated and ligand-mediated transitions, and the pressure-dependent PL may help with engineering the band structure of other highly-reactive optical nanomaterials.

     

Spray-Dried Solid Self-Emulsifying Delivery System of Ketoprofen: Development and Its Characterization

Ketoprofen is classified as BCS class II drug with low aqueous solubility, short half-life (2–2.5 h), and low oral bioavailability and also causes gastric irritation. The systems intended for oral administration were prepared by using soybean oil, Cremophor EL, and Maisine 35-1 and its adsorption on Aerosil 200. The spray-dried product demonstrated high process yield (52.2–68.3%) with good loading capacity (83.13–93.69%) and significant drug release compared to pure drug. The smooth spherical particles produced had no interaction with the excipients as demonstrated by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). Differential scanning calorimetry (DSC) indicated the complete miscibility of the drug with excipients and X-ray diffraction (XRD) demonstrated the transformation from crystalline to amorphous form.