Hydrogen‐Bonding‐Driven Enantioselective Resolution against the Kazlauskas Rule To Afford γ‐Amino Alcohols by Candida rugosa Lipase

Most lipases resolve secondary alcohols in accordance with the “Kazlauskas rule” to give the R enantiomers. In a similar manner to other lipases, Candida rugosa lipase (CRL) exhibits R enantioselectivity towards heptan‐2‐ol, although the enantiomeric ratio (E) is low (E=1.6). However, unexpected enantioselectivity (i.e., S enantioselectivity, E=58) of CRL towards 4‐(tert‐butoxycarbonylamino)butan‐2‐ol, which has a similar chain length to heptan‐2‐ol, has been observed. To develop a deeper understanding of the molecular basis for this unusual enantioselectivity, we have conducted a series of molecular modeling and substrate engineering experiments. The results of these computational and experimental analyses indicated that a hydrogen bond between the Ser450 residue and the nitrogen atom of the carbamate group is critical to stabilize the transition state of the S enantiomer.     

Synthesis of zirconium tungstate–zirconia core–shell composite particles

In this work, ZrW₂O₈–ZrO₂ core–shell composite particles were synthesized. ZrW₂O₈ that was used in the core is a material with negative coefficient of thermal expansion, and it was synthesized from a high-pH precursor based on use of tungstic acid and zirconium acetate. Shell layer was composed of ZrO₂ nanocrystallites and precipitated from an aqueous solution by urea hydrolysis. While volume of the shell was effectively controlled by the initial zirconium ion concentration in the solutions, the rate of precipitation was a function of the ratio of initial concentrations of urea to zirconium ions. It is hypothesized that isolation of the ZrW₂O₈ within a layer of ZrO₂, will be a key element in solving problems associated with reactivity of ZrW₂O₈ towards other components in sintering of ceramic–ceramic composites with tuned or zero thermal expansion coefficient.     

Analytical performance of soft clustering protocols

The success of a mobile ad hoc network (MANET) is strongly related to the protocol used at the medium access control (MAC) layer. Depending on the requirements and the specific network under concern, the protocol parameters at the MAC layer can be arbitrated to make best use of the channel resources. Typically, extensive simulation studies are used to find the best values for these variables. The problem with this approach is the need for excessive amounts of processing power and time. As the dimensions of the decision space increase, the need for processing power grows exponentially. This paper addresses this problem by developing an analytical model that reflects the relationships between protocol parameters and the overall performance of the protocol under various network conditions. Specifically, we model the MH-TRACE cluster-based protocol, which is capable of supporting real-time data transmission. The model is capable of estimating performance measures such as energy consumption and number of receptions while being simple enough to be run for a large set of parameters. The model can be used to optimize parameters of the protocol (such as the number of frames per superframe) as well as to predict the performance variations as the external conditions (such as data generation rate) vary.     

Optical gain in 1.3-μm electrically driven dilute nitride VCSOAs

We report the observation of room-temperature optical gain at 1.3 μm in electrically driven dilute nitride vertical cavity semiconductor optical amplifiers. The gain is calculated with respect to injected power for samples with and without a confinement aperture. At lower injected powers, a gain of almost 10 dB is observed in both samples. At injection powers over 5 nW, the gain is observed to decrease. For nearly all investigated power levels, the sample with confinement aperture gives slightly higher gain.     

Estimation of skin impedance models with experimental data and a proposed model for human skin impedance

The skin is a complex biological tissue whose impedance varies with frequency. The properties and structure of skin changes with the location on the body, age, geographical location and other factors. Considering these factors, skin impedance analysis is a sophisticated data analysis. However, despite all these variations, various researchers have always worked to develop an equivalent electrical model of the skin. The two most important categories of electrical models are RC‐based model and CPE‐based model which focus on the physiological stratification and biological properties of skin, respectively. In this work, experimental skin impedance data is acquired from ten sites on the body to find the fitting model. It is observed that a hybrid of fractional‐order CPE‐based model and higher‐order RC layered‐based model can provide the best fitting electrical model of skin. A new model is developed with this hybrid orders. Genetic algorithm is used for the extraction of parameter components. Least error of fitting has been observed for the proposed model as compared with the other models. This model can be used in correlating many skin problems and in the development of diagnostic tools. It will offer an additional supportive tool in‐vitro to the medical specialist.Inspec keywords: genetic algorithms, skin, data analysis, bioelectric phenomena, medical computing, electric impedance, patient diagnosisOther keywords: skin impedance models, human skin impedance, skin impedance analysis, data analysis, electrical models, RC‐based model, biological properties, experimental skin impedance data, fractional‐order CPE‐based model, skin problems, complex biological tissue, higher‐order RC layered‐based model, genetic algorithm, diagnostic tools     

A Survey of Handover Techniques for Wireless ATM Networks

This paper provides a review and comprehensivecomparison of existing handover schemes proposed forwireless ATM networks. Existing schemes include thoseproposed by NEC, Olivetti, Bell Labs, Cambridge, Stanford, CMU, Berkeley, Michigan, VTT, andColumbia. We highlight the methodologies employed by thevarious schemes and reveal their differences. We discussissues related to the effect of ATM switch architectures on mobility implementation and on futurehandover paradigms.     

Possible involvement of plasmids in degradation of malathion and chlorpyriphos by Micrococcus sp

Culture is the basic method in bacteriology. It allowed the discovery of Helicobacter pylori. Problems in the culture of this fragile, slow-growing bacterium concern transport and processing in the laboratory, but they can be solved. Culture has a 100% specificity. When performed properly, it has a sensitivity in the range of the other best diagnostic methods for Helicobacter pylori. It allows strain typing and, most importantly, susceptibility testing to antibiotics, because an increased rate of acquired resistance of Helicobacter pylori is currently observed. Culture must be performed in clinical trials, at least when antibiotics, to which Helicobacter pylori may be resistant, are used. In clinical practice, culture and susceptibility testing can generally be restricted to treatment failures. However, it is important to monitor Helicobacter pylori susceptibility to antibiotics at a national or regional level in order to give recommendations for primary treatment.     

Design and Analysis of an Interference Cancellation Algorithm for AF,DF and DMF Relay Protocol in Multiuser MIMO Scenario Based on the LTE-Advanced System

The analysis and design of relay protocols is a hot issue in 3GPP Long Term Evolution—Advanced. In this paper, we discuss interference cancellation in a multiuser MIMO environment using Amplify-and-Forward (AF), Decode-and-Forward (DF) and De-Modulate-and-Forward (DMF) as relay protocols, and using Thomilson Harashima Precoding and Dirty Paper Coding as precoding techniques, with Zero-Forcing, Minimum Mean Square Error, Successive Interference Cancellation and Ordered Successive Interference Cancellation detection techniques. By using a combination of classical precoding schemes and detection techniques with weighted matrix, we propose a new interference cancellation technique that is capable of cancelling interference. The interference cancellation is managed by AF, DF and DMF relay node protocols and the interference free codeword is transmitted to the selected User Equipment. The proposed algorithm when used with DMF protocol shows best performance, compared to the conventional system or the no-relay system case, it gives best performance. The observation results shows that DMF protocol gives the best results for BER and Throughput performance in a high interference environment.     

Synthesis of gold nanoparticles using aqueous extract of Calotropis procera latex

This is an account of the use of aqueous extract of the latex of Calotropis procera for the synthesis of gold nanoparticles. UV-Vis spectroscopic studies of the products resulting from reaction between the aqueous latex extract and chlorauric acid indicated the successful synthesis of gold nanoparticles. Reaction parameters viz. concentration of latex extract and reaction time were optimized for maximum yield of gold nanoparticles. Effect of reaction temperature on the synthesis rate of the particles and their optical properties was also studied. Transmission electron microscopic (TEM) studies of the particles revealed the dominance of spherical particles. Mean particle size distribution was found to be 22 ± 10 nm. Crystalline nature of the particles was confirmed from X-ray diffractrograms. FT-IR analysis and protein coagulation test of the gold nanoparticles confirmed capping behaviour of the latex proteins that contributed to their long term stability (6 months) in aqueous medium. Toxicity of the particles was tested on three cell lines, HeLa, A549 and BHK21. The method exploits a cheap and easily available biomaterial not explored so far for the synthesis of metallic nanoparticles.     

A review: Fibre metal laminates,background, bonding types and applied test methods

During the past decades, increasing demand in aircraft industry for high-performance, lightweight structures have stimulated a strong trend towards the development of refined models for fibre-metal laminates (FMLs). Fibre metal laminates are hybrid composite materials built up from interlacing layers of thin metals and fibre reinforced adhesives. The most commercially available fibre metal laminates (FMLs) are ARALL (Aramid Reinforced Aluminium Laminate), based on aramid fibres, GLARE (Glass Reinforced Aluminium Laminate), based on high strength glass fibres and CARALL (Carbon Reinforced Aluminium Laminate), based on carbon fibres. Taking advantage of the hybrid nature from their two key constituents: metals (mostly aluminium) and fibre-reinforced laminate, these composites offer several advantages such as better damage tolerance to fatigue crack growth and impact damage especially for aircraft applications. Metallic layers and fibre reinforced laminate can be bonded by classical techniques, i.e. mechanically and adhesively. Adhesively bonded fibre metal laminates have been shown to be far more fatigue resistant than equivalent mechanically bonded structures.