Covalent immobilization of penicillin G acylase onto amine-functionalized PVC membranes for 6-APA production from penicillin hydrolysis process. II. Enzyme immobilization and characterization

This article describes the covalent immobilization of penicillin G acylase (PGA) onto glutaraldehyde-activated NH₂-PVC membranes. The immobilized enzyme was used for 6-aminopenicillanic acid production from penicillin hydrolysis. Parameters affecting the immobilization process, which affecting the catalytic activity of the immobilized enzyme, such as enzyme concentration, immobilization's time and temperature were investigated. Enzyme concentration and immobilization's time were found of determine effect. Higher activity was obtained through performing enzyme immobilization at room temperature. Both optimum temperature (35°C) and pH (8.0) of immobilized enzyme have not been altered upon immobilization. However, immobilized enzyme acquires stability against changes in the substrate's pH and temperature values especially in the higher temperature region and lower pH region. The residual relative activities after incubation at 60°C were more than 75% compared to 45% for free enzyme and above 50% compared to 20% for free enzyme after incubation at pH 4.5. The apparent kinetic parameters K_M and V_M were determined. K_M of the immobilized PGA (125.8 mM) was higher than that of the free enzyme (5.4 mM), indicating a lower substrate affinity of the immobilized PGA. Operational stability for immobilized PGA was monitored over 21 repeated cycles. The catalytic membranes were retained up to 40% of its initial activity after 10.5 working h. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Diagnosis of Trypanosoma evansi in Saudi Arabian camels (Camelus dromedarius) by the passive haemagglutination test and Ag-ELISA

The passive haemagglutination test and Ag-ELISA were employed to monitor antibody titres and antigenaemia levels in 4 Najdi camels experimentally infected with Trypanosoma evansi. The two tests were also used to determine the prevalence of trypanosomiasis in a total of 218 Najdi camels in the Gassim region, Central Saudi Arabia, during the period from October 1992 to September 1993. Trypanosoma evansi antibodies in the experimentally infected camels rose after 14-21 days and reached a maximum of between 1:64 and 1:128 by the 12th week post infection. Circulating antigens were detected in the experimentally infected camels one week post infection and antigenaemia levels fluctuated but generally remained above preinfection OD values. The results obtained from the field survey showed that 5.5% of the sampled camels were parasitologically positive for trypanosomes, while 19.7% were serologically positive by the passive haemagglutination test and 13.8% by Ag-ELISA. No significant age difference in seropositivity was observed in the tested camels.     

Enhancing the Performance of Spectrum Mobility in Cognitive Radio Local Area Networks Using KF-ABF-SRE Estimators

Wireless Personal Communications - This paper aims at improving the performance of spectrum mobility in cognitive radio local area networks under a congested environment. Due to the atmospheric...     

Structural, magnetic and magneto-optical properties of ultrathin films of nickel on iridium (001)

A detailed theoretical study of the structural, magnetic and magneto-optical behaviours of ultrathin films of nickel grown by pseudomorphic epitaxy on semi-infinite Ir(001) is given. The crystalline structure is found to be body centered tetragonal. The total energies are calculated by Spin-Polarized Relativistic Linear Muffin-Tin Orbitals with Atomic Sphere Approximation method. The calculation of the magnetic properties shows a ferromagnetic inter-layer coupling. The polar magneto-optical Kerr effect spectra are calculated over a photon energy range extended to 9 eV. The microscopic origin of the most interesting features is explained by the interband transitions between the localized spin projected states. These transitions are characterized by a spin-flip.     

Theory of inclusion controlled grain growth

Different inclusion/grain boundary interactions have been analysed with emphasis on the grain boundary structure and the geometry of the inclusion/boundary profiles. Crystalline inclusions can inhibit grain growth, provided one or more inclusions intersect each boundary. An equation for the limiting grain size, in terms of the volume fraction and the particle size distribution of the inclusions, is derived and is shown to explain the inclusion controlled limiting grain sizes in calcium fluoride and in alumina, as well as grain coarsening in steel. Conditions for the drag of amorphous particles or pores, and for pore isolation are discussed.     

Energy Dispersive X-Ray Microanalysis of Elemental Distribution in Raw and Germinated Brown Rice Varieties

In this study, the mineral composition of germinated brown rice, brown rice, and white rice was evaluated. Brown rice grain was processed through a combination of chemical pretreatment and low oxygen treatment, after which germination was confirmed through imaging under a microscope. Using energy dispersive X-ray analysis, Mg, Al, and Cl were found to be slightly higher in germinated brown rice than in brown rice and white rice. These variations in the mineral content of germinated brown rice were attributed to the joint effect of the germination process and the prior soaking. The inability of energy dispersive X-ray to detect other minerals suggested that it was not sensitive and, hence, it was not suitable for studying elemental distribution in rice grains, or maybe the elements were not present in the rice grains studied.     

Preparation, characterization and in vitro biological study of biomimetic three-dimensional gelatin–montmorillonite/cellulose scaffold for tissue engineering

This work focused on studying the effect of blending gelatin (Gel) with Cellulose (Cel), in the presence of montmorillonite (MMT), on the swelling behavior, in vitro degradation and surface morphology. Additionally, the effect of the prepared biocomposites on the characteristics of the human osteosarcoma cells (Saos-2), including proliferation, scaffold/cells interactions, apoptosis and their potential of the cells to induce osteogenesis and differentiation was evaluated. The crosslinked biocomposites with glutaraldehyde (GA) or N,N-methylene-bisacrylamide (MBA) was prepared via an intercalation process and freeze-drying technique. Properties including SEM morphology, X-ray diffraction characterization and in vitro biodegradation were investigated. The successful generation of 3-D biomimetic porous scaffolds incorporating Saos-2 cells indicated their potential for de novo bone formation that exploits cell–matrix interactions. In vitro studies revealed that the scaffolds containing 12 and 6% MMT crosslinked by 5 and 0.5% GA seem to be the two most efficient and effective biodegradable scaffolds, which promoted Saos-2 cells proliferation, migration, expansion, adhesion, penetration, spreading, and differentiation, respectively. MMT improved cytocompatibility between the osteoblasts and the biocomposite. In vitro analysis indicated good biocompatibility of the scaffold and presents the scaffold as a new potential candidate as suitable biohybrid material for tissue engineering.     

Theoretical study of methane adsorption on perfect and defective Ni(1 1 1) surfaces

We employ periodic density functional theory (DFT-GGA-PW91) calculations to study the adsorption of CH₄, on a perfect and defective (1 1 1) face of nickel, at a coverage of 0.25 monolayer (ML). As a surface defect, we consider a Ni adatom. We investigate systematically the site preference for CH₄, for various molecular orientations with 1, 2 or 3 H pointing toward the surface. Whatever the CH₄ adsorption site could be, the most stable configurations are obtained when 2 H atoms are directed to the surface. CH₄ stabilises weakly on the flat Ni surface, the adsorption energies being at best in the 50 meV range. However, beside a dominating physical interaction, some features are indicative of a chemical interaction through the Ni d-band. In presence of a Ni adatom, the chemical nature of the interaction manifests plainly, with sizeable adsorption energies up to 0.37 eV. The molecular restructuring and the mechanism of the interaction are examined.     

Towards an efficient failure detection in MANETs

Mobile ad hoc networks (MANETs) are characterized by a dynamic topology and generally deployed in a hostile environment with limited resources. As a result, the nodes are more vulnerable and are often subject to failures. Therefore, the design of an efficient failure detector in MANETs is a very challenging issue as the detection is proved to be unreliable. Such an achievement amounts to balance between the performances of the accuracy, the completeness and the resource consumption. We present and discuss in this paper a solution for an efficient failure detection in MANETs. This new protocol, called efficient failure detection for MANETs, exploits different mechanisms to improve the completeness and the accuracy of the detection while reducing the traffic overhead. The number of used timers are limited to two for each node thus reducing the complexity of the algorithm. The simulations performed on NS2 platform show the efficiency of efficient failure detection for MANETs comparing with other protocols. Copyright © 2016 John Wiley & Sons, Ltd.     

Modelling outflow following rupture in pipeline networks

A numerical model for simulating the fluid dynamics following rupture in pressurised pipeline networks containing multi-component hydrocarbon mixtures is described. Based on the solution of the conservation equations using the method of characteristics, the model accounts for pipeline bends, branches and couplings. Modelling of hypothetical full bore ruptures in straight and branched pipelines indicate the importance of accounting for pipeline system configuration complexity when simulating such type of failure.