Concatenation of electrochemical grafting with chemical or electrochemical modification for preparing electrodes with specific surface functionality

Surface modified electrodes are used in electro-analysis, electro-catalysis, sensors, biomedical applications, etc. and could also be used in batteries. The properties of modified electrodes are determined by the surface functionality. Therefore, the steps involved in the surface modification of the electrodes to obtain specific functionality are of prime importance. We illustrate here bridging of two routes of surface modifications namely electrochemical grafting, and chemical or electrochemical reduction. First, by electrochemical grafting an organic moiety is covalently immobilized on the surface. Then, either by chemical or by electrochemical route the terminal functional group of the grafted moiety is transformed. Using the former route we prepared lithium alkyl carbonate (–O(CH₂)₃OCO₂Li) modified carbon with potential applications in batteries, and employing the latter we prepared phenyl hydroxyl amine (–C₆H₄NHOH) modified carbon which may find application in biosensors. Benzyl alcohol (–C₆H₄CH₂OH) modified carbon was prepared by both chemical as well as electrochemical route. We report combinations of conjugating the two steps of surface modifications and show how the optimal route of terminal functional group modification depends on the chemical nature of the moiety attached to the surface in the electrochemical grafting step.     

Transient Inclusion Evolution During Modification of Alumina Inclusions by Calcium in Liquid Steel: Part II. Results and Discussion

The formation of intermediate reaction products after calcium addition to aluminum-killed steel was studied. Steel samples were taken from laboratory and industrial heats before and at various times after calcium treatment. Inclusions were characterized by automated and manual scanning electron microscopy and X-ray microanalysis of polished cross sections and inclusions extracted by dissolution of the steel. Industrial and laboratory melts containing more than 40 parts per million (by mass) of dissolved sulfur showed calcium sulfide as the main reaction product after calcium injection, with calcium aluminates appearing later. It is proposed that the calcium aluminates are formed by reaction between the calcium sulfide and the alumina. A laboratory heat containing 7 parts per million of sulfur showed calcium oxide as the main initial calcium reaction product. A simple mechanism is proposed for the modification of alumina inclusions by calcium, considering transient CaO and CaS formation.     

Tight bounds for prefetching and buffer management algorithms forparallel I/O systems

The I/O performance of applications in multiple-disk systems can be improved by overlapping disk accesses. This requires the use of appropriate prefetching and buffer management algorithms that ensure the most useful blocks are accessed and retained in the buffer. In this paper, we answer several fundamental questions on prefetching and buffer management for distributed-buffer parallel I/O systems. First, we derive and prove the optimality of an algorithm, P-min, that minimizes the number of parallel I/Os. Second, we analyze P-con, an algorithm that always matches its replacement decisions with those of the well-known demand-paged MIN algorithm. We show that P-con can become fully sequential in the worst case. Third, we investigate the behavior of on-line algorithms for multiple-disk prefetching and buffer management. We define and analyze P-Iru, a parallel version of the traditional LRU buffer management algorithm. Unexpectedly, we find that the competitive ratio of P-Iru is independent of the number of disks. Finally, we present the practical performance of these algorithms on randomly generated reference strings. These results confirm the conclusions derived from the analysis on worst case inputs     

Classification of drug molecules for oxidative stress signalling pathway

In humans, oxidative stress is involved in the development of diabetes, cancer, hypertension, Alzheimers’ disease, and heart failure. One of the mechanisms in the cellular defence against oxidative stress is the activation of the Nrf2‐antioxidant response element (ARE) signalling pathway. Computation of activity, efficacy, and potency score of ARE signalling pathway and to propose a multi‐level prediction scheme for the same is the main aim of the study as it contributes in a big amount to the improvement of oxidative stress in humans. Applying the process of knowledge discovery from data, required knowledge is gathered and then machine learning techniques are applied to propose a multi‐level scheme. The validation of the proposed scheme is done using the K‐fold cross‐validation method and an accuracy of 90% is achieved for prediction of activity score for ARE molecules which determine their power to refine oxidative stress.Inspec keywords: cancer, cellular biophysics, biochemistry, drugs, molecular biophysics, proteins, learning (artificial intelligence), medical computingOther keywords: oxidative stress, Nrf2‐antioxidant response element signalling pathway, ARE signalling pathway, diabetes, cancer, hypertension, Alzheimers’ disease, heart failure, machine learning techniques, K‐fold cross‐validation method, ARE molecules     

Nanometer MOSFET Variation in Minimum Energy Subthreshold Circuits

Minimum energy operation for digital circuits typically requires scaling the power supply below the device threshold voltage. Advanced technologies offer improved integration, performance, and active-energy efficiency for minimum energy sub-V_t circuits, but are plagued by increased variation and reduced I_ON/I_OFF ratios, which degrade the fundamental device characteristics critical to circuit operation by several orders of magnitude. This paper investigates those characteristics and presents design methodologies and circuit topologies to manage their severe degradation. The issues specific to both general logic and dense static random access memories are analyzed, and solutions that address their distinct design metrics are presented.     

Thermally stimulated current and electrical conduction in metal (1)-ethyl cellulose-metal (1)/(2) systems

Depolarization current characteristics of solution grown pure ethyl cellulose (EC) films of about 20μm thickness have been studied as a function of electrode materials at constant poling field (5 × 10⁴ V/cm) and poling temperature 40°C. Thermally stimulated current (TSC) thermograms of EC consists of two well resolved peaks (located at 60°C and 140°C) for Al-Al system, which are attributed to the deorientation of strongly attached ethoxy groups of glycosidal units and diffusion of space charges either at electrodes or due to their thermal release at higher temperatures from the defect levels. For dissimilar electrode combinations (Al-Ag/Cu/Au/Sn/Pb), an indication of peak of lower magnitude at around (50–70°C) alongwith a higher temperature peak (140–155°C), have been observed. TSC parameters are found to change with the choice of electrode material. The dependence of dark current at 40°C in metal-ethyl cellulose-metal systems on applied voltage in the range (2·0–5·0) × 10⁴V/cm has also been studied. The results of current-voltage measurement on EC have been interpreted to show that the Schottky-Richardson mechanism is the controlling transport mechanism. Zero field current density extrapolated fromI-E ^1/2 plots are found to vary with metal work function.     

Factorization and the Nehari theorem in time-varying systems

The Nehari Theorem and related results on operator interpolation play an important role in modern system theory. These results are embedded in a function-theoretic conceptual framework and therefore restricted to LTI systems. We give a state space oriented extension of the Nehari Theorem to a time-varying system-theoretic setting. In that setting the theorem addresses the issue of measuring the distance between a noncausal bounded I/O operator and the family of causal I/O operators in stable linear systems. The analysis is based on the recent time-domain LQ optimization approach to robust control. The discussion includes a geometrical analysis of stable and antistable invariant subspaces, a short study of certain types of co-prime factorizations of I/O operators in time-varying systems, and a parametrization of all suboptimal solutions.The research was supported in part by the National Science Foundation under Grant ECS 9108927 and by the U.S. Army Research Office under Contract DAALO3 92 G 0015.The research was supported by NSERC, Canada.     

Kinetics of hydrogenation of D-glucose to sorbitol

The kinetics of the heterogeneous reaction between hydrogen and aqueous solutions of D -glucose to produce sorbitol were studied in a high pressure Parr reactor. Raney-Ni was used as catalyst. The reaction between hydrogen and D -glucose was found to be very slow. In the agitated slurry reactor the diffusional aspects were completely eliminated and the reaction followed homogeneous kinetics. It was found to be first order with respect to both hydrogen and D -glucose. The values of the pseudo-first-order rate constants were found to be 1.5 × 10^?4 and 6.4 × 10^?4s^?1 at 398 and 435 K, respectively. The activation energy was found to be 64.8 kJ mol^?1.     

Influence of different polyesters and their molecular weight on the textural and electrooptical behavior of polymer‐dispersed liquid crystals

The textural and electrooptical behavior of a nematic liquid crystal (LC) dispersed in a flexible and rigid polyester was studied. The dispersion of LC in the polymer matrix and light transmission through the polymer‐dispersed liquid crystal (PDLC) is governed by the nature of the polymer, its molecular weight, and the applied voltage. It was observed that the transmission of light and the dispersion of LC maximizes their respective values at the minimum molecular weight irrespective of the nature of the polymer and at the maximum voltage. The reason is the predominance of chain alignment over entanglement at the minimum molecular weight. As molecular weight increases, the transmission of light as well as the dispersion of LC in the polymer may increase or decrease depending on the predominance of chain entanglement or chain alignment. The alignment of LC droplets in the direction of the applied voltage is increased by an increase in the applied voltage, causing enhancement of the light transmission. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 284–289, 2003     

Renal osmotic stress-induced cotransporter: expression in the newborn, adult and post-ischemic rat kidney

The renal osmotic stress-induced cotransporter (ROSIT), a new putative member of a family of organic solute transporters, is highly expressed in the kidney. Our in situ hybridization data now reveal that large amounts of ROSIT mRNA can be found in the S3 segment of the proximal tubule. In the developing kidney, ROSIT mRNA is expressed after the S-shaped body stage. Because the S3 segment is the major site of damage in the post-ischemic kidney, we evaluated alterations in ROSIT mRNA expression after ischemic acute tubular necrosis. Renal osmotic stress-induced cotransporter mRNA levels were already decreased eight hours post-ischemia. At seven days post-ischemia, ROSIT mRNA reappeared in a mosaic pattern in the regenerating S3 segment, being fully expressed three weeks after the insult except for focal areas. The exact localization of this putative osmolyte transporter in the kidney, together with that of other known osmolyte transporter will contribute to a better understanding of the mechanism of medullary osmolyte accumulation and its vectorial transport.