An extended access control model for permissioned blockchain frameworks

Wireless Networks - In distributed environment, a digital transaction or operation requires transparency and trust among multiple stakeholders. Several approches address such...     

Discussing Arab Spring’s effect on scientific productivity and research performance in Arab countries

Scientometrics - This research letter discusses whether Arab Spring explains the changes in research productivity and impact of Arab countries by identifying non-sociopolitical factors that can be...     

Evaluation of a cocktail of three bacteriophages for the biocontrol of Salmonella of wastewater

Salmonella serovars are increasing in importance as significant pathogens of both human and animals. Although water and wastewater are treated to eliminate pathogenic microorganisms, they still play an important role in the transmission of Salmonella spp. In this study, bacteriophages infecting Salmonella spp. were isolated from wastewater and evaluated; for their potential to lyse environmental Salmonella strains in vitro at different MOIs and temperatures; and to control the wastewater bacterial community. Three distinct phages designated sww65, sww275, and sww297; as defined by plaque morphology, electron microscopy and host range; were obtained from wastewater. Challenge tests were performed at 37, and 30 °C with the infection of the Salmonella cultures with individual phage, a mixture of two phages, and cocktail of three phages at MOIs of 10⁰, 10², and 10⁴ PFU/CFU. At 30, and 37 °C, a cocktail of three phages reduced all of the Salmonella cultures tested. These results required a high multiplicity of infection. However, when infected with only one phage or a mixture of two phages at MOIs of 10⁰ or 10 ² PFU/CFU, an emergence of bacterial resistance was observed. The dynamic monitoring of wastewater enterobacterial community was conducted using Enterobacterial Repetitive Intergenic Consensus-PCR (ERIC-PCR). The number of bands decreased gradually with the use of individual phage or phage cocktails. Moreover, the dynamic monitoring of Salmonella community during wastewater treatment was performed using PCR detection of virulence gene invA. The results correlated with the ERIC-PCR fingerprints, and suggested that Salmonella community was affected by the phage treatment. Indeed, in wastewater, bacteriophages are reducing Salmonella and other members of the Enterobacteriaceae. These results indicated that dynamic changes are closely related with the process of treatment. The introduction of wide host range bacteriophages in wastewater can have a potential impact on the dynamics of the microbial communities, manifested by the reduction or the elimination of microbial species.     

Characterization of β-In2−xAlxS3 thin films prepared by chemical spray pyrolysis technique

Indium sulfide (In₂S₃) is a good window or buffer layer for photovoltaic application. In this work, β-In_2?xAl_xS₃ thin films with different thicknesses (400, 442, 646 and 714 nm) are successfully synthesized on heated glass substrates using a chemical spray pyrolysis technique. The thin film thickness effect on the structural, optical and photoluminescence (PL) properties of β-In_2?xAl_xS₃ material is studied. The X-ray diffraction patterns suggest the formation of β-In₂S₃ cubic phase preferentially oriented towards (400) direction. The level of the residual dislocation seems to be reduced to 3.12 × 10⁹ lines mm^?2 for the optimum thickness (646 nm) for which the β-In_2?xAl_xS₃ film crystallinity is the best one. In order to enhance the electrical properties, β-In_2?xAl_xS₃ layers are annealed in air at 400 °C for different annealing times (15, 30 and 45 min). The minimum resistivity, maximum Hall mobility and carrier concentration are found for β-In_2?xAl_xS₃ films annealed for 30 min. All samples have high transmittance of about 75 % but the wide band gap (E_g = 3.32 eV) is obtained for this optimum thickness. This result indicates good optical quality of β-In_2?xAl_xS₃ layers. Defects-related PL properties are also discussed.     

Microstructure,physical and mechanical properties of mortar–rubber aggregates mixtures

This work focuses on the feasibility of reusing and valorising rubber aggregates from shredded worn tyres in cement composites. Our purpose is to study the influence of both microstructures of matrix and of interfacial transition zone (ITZ) on mechanical properties of mortar–rubber aggregates mixtures. The same volume of rubber aggregates substituted volume fractions of sand. Volume ratios of rubber aggregates were ranged from 0% to 50%. Micro structural morphology of various samples was observed by means of scanning electron microscopy (SEM). The matrix porosity and the evolution of hydration products (CSH, CaOH₂, CaCO₃) were estimated for specimens that had been curing for 28 days at constant temperature and constant relative humidity. An energy dispersive X-ray analyser and X-ray diffraction were used together with SEM in order to quantify these results.     

A comparative study on the starting methods of three phasewound-rotor induction motors. I

This paper presents a comparative study on the starting performance of three phase wound-rotor induction motors under different methods of starting. These methods are online direct starting, variable rotor resistance starting and double feed starting. In the double feed starting, the rotor winding is connected in parallel with the stator winding across the supply for a predetermined short period. By this connection, the motor produces an extremely high starting torque. For carrying out the investigations sought, a rigorous state space mathematical model has been developed and simulated. The effect of torsional dynamics has been taken into considerations     

Starting transients of three phase reluctance motors as affected bytorsional dynamics

In this paper, a rigorous mathematical model describing the transient behavior of three-phase reluctance motors under the effect of torsional dynamics is developed. Provisions are made to allow the analysis of both the three-phase balanced mode of operation and the single-phase mode of operation of such motors. The resulting state-space equations are then solved numerically in order to yield the required transient response curves. The outcome of this study will help in devising techniques to deal with the dangerous consequences of the electromechanical resonance phenomenon that may arise