Catalysis of Thermostable Alcohol Dehydrogenase Improved by Engineering the Microenvironment through Fusion with Supercharged Proteins

The enzymatic microenvironment can impact biocatalytic activity; however, these effects can be difficult to investigate as mutations and fusions can introduce multiple variables and overlapping effects. The fusion of a supercharged protein is a potentially facile means to alter the enzymatic microenvironment. We have investigated complexes made between a thermostable alcohol dehydrogenase (AdhD) and superfolding green fluorescent protein (sfGFP) mutants with extreme surface charges. Three charged sfGFP variants, −30, 0, and +36 were covalently attached to AdhD through the SpyCatcher/SpyTag system. Specific rates for the NAD⁺-dependent oxidation of butane-2,3-diol were significantly increased in the −30 sfGFP complex, a mixed effect was seen for the 0 sfGFP complexes, and the rates were unaffected by +36 sfGFP complexation. Reactions performed at various pH values (7.8–9.8) and salt concentrations (7.75–500 mm ) showed that there was a complex interplay between these effects that was consistent with fusion proteins affecting the local ionic strength, as opposed to the local pH. Steady-state kinetic analyses were performed with the −30 and 0 AdhD–sfGFP complexes. The overall catalytic efficiency was dependent on the charge of the fused sfGFP variant; the −30 sfGFP fusions exhibited the largest beneficial effects at pH 8.8. The impact of the fusions on the apparent ionic strength provides further insight into the effects of charged patches observed on metabolon-forming enzyme complexes.     

Cooperative amplify‐and‐forward partial relay selection with outdated channel information in spectrum‐sharing systems

Recently, cooperative relaying techniques have been integrated into spectrum‐sharing systems in an effort to yield higher spectral efficiency. Many investigations on such systems have assumed that the channel state information between the secondary transmitter and primary receiver used to calculate the maximum allowable transmit secondary user transmit power to limit the interference is known to be perfect. However, because of feedback delay from the primary receiver or the time‐varying properties of the channel, the channel information may be outdated, which is an important scenario to cognitive radio systems. In this paper, we investigate the impact of outdated channel state information for relay selection on the performance of partial relay selection with amplify and forward in underlay spectrum‐sharing systems. We begin by deriving a closed‐form expression for the outage probability of the secondary network in a Rayleigh fading channel along with peak received interference power constraint and maximum allowable secondary user transmit power. We also provide a closed‐form expression for the average bit‐error rate of the underlying system. Moreover, we present asymptotic expressions for both the outage probability and average bit‐error rate in the high signal‐to‐noise ratio regime that reveal practical insights on the achievable diversity gain. Finally, we confirm our results through comparisons with computer simulations. Copyright © 2016 John Wiley & Sons, Ltd.     

A Multifunctional Electronic Skin Empowered with Damage Mapping and Autonomic Acceleration of Self-Healing in Designated Locations

Integrating self-healing capabilities into soft electronic devices and sensors is important for increasing their reliability, longevity, and sustainability. Although some advances in self-healing soft electronics have been made, many challenges have been hindering their integration in digital electronics and their use in real-world conditions. Herein, an electronic skin (e-skin) with high sensing performance toward temperature, pressure, and pH levels—both at ambient and/or in underwater conditions is reported. The e-skin is empowered with a novel self-repair capability that consists of an intrinsic mechanism for efficient self-healing of small-scale damages as well as an extrinsic mechanism for damage mapping and on-demand self-healing of big-scale damages in designated locations. The overall design is based on a multilayered structure that integrates a neuron-like nanostructured network for self-monitoring and damage detection and an array of electrical heaters for selective self-repair. This system has significantly enhanced self-healing capabilities; for example, it can decrease the healing time of microscratches from 24 h to 30 s. The electronic platform lays down the foundation for the development of a new subcategory of self-healing devices in which electronic circuit design is used for self-monitoring, healing, and restoring proper device function.     

Simple new correlation for the prediction of equilibrium constant (KP) of Haber reaction covering the industrial conditions

Ammonia is an important industrial chemical, and its production is one of the highest of all inorganic chemicals. It is synthesized, in principal, from nitrogen and hydrogen by Haber process. It was found that the equilibrium constant (K_P) of Haber reaction is strongly pressure dependent. Many correlations were developed in order to rigorously express this (K_P); however, the most reliable expressions involved are inherently complex. This paper illustrates a simple correlation which was developed to express the value of (K_P) of Haber reaction at temperatures from 350 to 600 °C and pressures from 50 to 300 atm, which covers today’s industrial range. In this correlation, K_P is expressed in terms of temperature and pressure of equilibrium mixture which is the direct data measured. The effects of temperature and pressure are not separated allowing K_P to be calculated directly, without iterations; using spreadsheet. Results were compared to that of Gillespie and Beattie method showing very good match. The new simple correlation can be used easily in commercial simulation packages, e.g. Hysys, using its embedded spreadsheet to build reliable ammonia synthesis reactor modeling benefiting from featured analysis methods of these packages.     

Sheep and goats are reservoirs of colistin resistant Escherichia coli that co-resist critically important antimicrobials: First study from Jordan

There is a knowledge gap on colistin-resistant and mobilized colistin-resistant (mcr) Escherichia coli in sheep and goats worldwide. This study determined the prevalence and antimicrobial resistance of mobilized colistin-resistant (mcr) E. coli in dairy sheep and goat flocks in Jordan. A total of 948 milk samples were collected from 155 flocks across Jordan. The milk samples were pre-enriched in MacConkey broth and then plated on MacConkey agar supplemented with 8 mg/l colistin and the presence of mcr-1 gene in the isolates was tested by polymerase chain reaction. In total, 1,158 E. coli isolates were colistin resistant, with 74.8% herd-level prevalence and 39.5% individual animal prevalence. Sixty-one (5.3%) of 1,158 phenotypically colistin-resistant E. coli harbored mcr-1, with 23.9% herd-level prevalence and 6.6% individual animal prevalence. About 77.1% of the mcr-1 E. coli resisted one or more antimicrobial classes and 37.7% were multidrug resistant. More than 30% of the mcr-1 positive E. coli isolates were resistant to nalidixic acid, tetracycline, ceftazidime, cefpodoxime and ampicillin, whereas 8–20% of the isolates were resistant to cefotaxime, ceftriaxone, gentamicin, tobramycin, sulfamethoxazole-trimethoprim, and amoxicillin-clavulanic acid. This study indicates that small ruminants are reservoirs of colistin-resistant and mcr-1 positive E. coli that exhibit co-resistance to critically important antimicrobials which would pose public health issue and calls for the necessary banning of the use of colistin in small ruminants.     

An integrated building information modelling-based environmental impact assessment framework

The application of Environmental Impact Assessment (EIA) studies faces many challenges, especially in developing countries. This problem was investigated in the existing literature and via a designed questionnaire among local practitioners. The reasons were mainly attributed to the seclusion of the EIA process across the project’s phases, as well as the complexity of the EIA procedures. Hence, the research argues that Building Information Modelling (BIM) applications can be the key to resolve several associated problems to EIA either directly, or indirectly by streamlining Environmental Management System (EMS). Thus, a keyword-based scientometric analysis was used to define parameters and interrelations and establish network analysis for a proposed BIM-based EIA framework. The proposed framework presents scoring schemes to support three types of assessments: the efficiency of applying BIM techniques for an EIA process (Score A), proper integration of BIM techniques for different EIA steps (Score I) and proper integration of BIM techniques across project phases (Score B). It also shows the interplay of points between the three schemes via a Sankey diagram. The proposed framework was applied to compare three major construction projects in a developing country, the case of Egypt to pinpoint areas of drawbacks. The results pinpointed poor application of advanced BIM models to support sustainability analysis for EIA studies. This is in addition to imbalance of applying BIM applications across different project phases, it was notably less pronounced for the operation and maintenance stage as well as end of life scenarios. Also, poor integration of BIM tools could not support decisions related to the mitigation step. Hence, applying 6-dimensional BIM model shall enable developing mitigation measures and shall support design optimization during building operation and end of life phase. This novel approach presents the required level of verification and quality control procedure needed by decision-makers and environmental engineers to perform EIA studies and pave the way for further related research.

Graphical Abstract

     

Performance of MIMO cross‐layer MAC protocol based on antenna selection in ad hoc networks

In this paper, we investigate the performance of a cross‐layer (physical and MAC) design for multiple‐input multiple‐output (MIMO) system that aims at maximizing the throughput of ad hoc networks by selecting the optimum antenna combination. Employing this cross‐layer design is shown to improve the overall network performance relative to the case where no antenna selection (AS) is used. To solve the node blocking problem associated with the IEEE 802.11 medium‐access control (MAC) protocol, the proposed protocol leverage the available degrees of freedom offered by the MIMO system to allow neighboring nodes to simultaneously communicate using the zero‐forcing (ZF) Bell‐labs layered space‐time (BLAST) architecture. Using the cross‐layer design, neighboring nodes share their optimum antenna selection (AS) information through control messages. Given this shared information, nodes set their decisions on the number of selected antennas based on the available spatial channels that guarantees collision‐free transmissions. At the destination node, the ZF receiver is employed to extract the desired user data while treating the data from neighboring users as interference. The performance of the proposed cross‐layer design is examined through simulations, where we show that the network throughput is significantly improved compared to conventional MAC protocols. Copyright © 2010 John Wiley & Sons, Ltd.