Antibacterial activity against Escherichia coli and characterization of ZnO and ZnO–Al2O3 mixed oxide nanoparticles

In order to achieve better antibacterial water insoluble nanoparticles (Nanoparticles) of ZnO and ZnO–Al2O3 were studied. ZnO–Al2O3 mixed oxide nanoparticles were produced from a solution containing Zn(AC)2⋅2H2O and AlCl3 by Solvothermal method. The calcination process of the ZnO–Al2O3 composite nanoparticles brought forth polycrystalline one phase ZnO–Al2O3 nanoparticles of 30–50 nm in diameters. ZnO and ZnO–Al2O3 were crystallized into würtzite and rock salt structures, respectively. The structural properties of this sample were analyzed by XRD and compared with bulk case of these samples. Antibacterial effectiveness of the ZnO and ZnO–Al2O3 nanoparticles were tested against general Escherichia coli (E. coli ATCC 25922) and E. coli O157:H7 by measuring the growth through optical density and digital counting of live–dead cells. Minimum inhibitory concentration values against four representative bacteria along with E. coli O157:H7 were also obtained

Hierarchal Grouping Strategy with Adaptive Power Tuning in ZigBee Wireless Sensor Networks

Designing wireless sensor networks should meet appropriate parameters such as quality of service (QoS) defined by different users. The variable physical conditions of the environment, processing and transmission power limitations and limited communication capabilities are the most important obstacles that influence QoS parameters such as throughput, delay, reliability and network lifetime. The most important problems that directly have destructive effects on these parameters are hidden and exposed node problems. These problems extremely decrease throughput and increase delay and power consumption in the network. In this paper, we propose a new and efficient method that relies on clustering, grouping and subgrouping strategy to create smaller zones and avoid collisions. By allocating different transmission powers to different nodes depending on their hierarchy level in the network, the mentioned problems decrease and as a result power consumption decreases due to reduction in the retransmissions. This mechanism has been simulated by OPNET on IEEE802.15.4/Zigbe

A survey on the handover management in 5G-NR cellular networks: aspects, approaches and challenges

Abstract With the purpose of providing higher data rate and ultra-reliable and low-latency communications for the users, employing the small cells in the upcoming Fifth-Generation-New Radio (5G-NR) cellular networks and beyond is leading to the serious challenges in mobility management due to dynamicity of the user equipments (UEs). Among different issues related to the mobility of the UEs, the handover management is one of the key procedures to let the UEs experience a high quality of service (QoS)/quality of experience (QoE). So far, many protocols and algorithms have been proposed to enhance the mobility management in 5G-NR from various aspects, but still a thorough survey has not been incorporated to summarize the recent advances and future directions of the mentioned issue. Thus, the handover management and the corresponding challenges stand in the center of concentrations in this paper, with a glance on 4G to the advancements of 5G-NR. The challenges include QoS/QoE, throughput, delay, traffic load, the attacks during authentication process and resource allocation. To overcome the mentioned challenges, the handover procedure is evaluated by some key performance indicators such as handover ratio, handover failure, radio link failure and such like which depend on the received signal quality. The lack of new advancements and novel aspects of handover plus the separation of security and handover issues in previous works are perceived as research gaps and motivations for the current paper. In this regard, this paper aims to specify and analyze the technical issues, to provide an overview on the proposed methods and recent advances and to bring the future directions into the limelight. We categorize the concurrent standards and methods about the handover, and then, we survey the proposed algorithms including theoretical, algorithm-based and pattern-capturing approaches following the authentication process along with the vulnerabilities and the algorithms to counteract the attacks during handover. Also, we study various issues corresponding to network performance during the handover procedure. Finally, we discuss the open problems and future research directions

Offer a novel method for size appraise of NiO nanoparticles by PL analysis: Synthesis by sonochemical method

In this work, we will discuss the optical properties of NiO nanoparticles that we have investigated recently by photoluminescence (PL) spectroscopy. In particular, we will show the blue-shifts of PL, originating from the electron–hole recombination of the self-trapped exciton (STE), observed in smaller-sized NiO nanoparticles. To explain the size effect in relating to the STE PL shift, a question has been raised on whether it is appropriate to apply him quantum confinement (QC) theory usually used for the Mott-Winner type excitons in semiconductors to wide band-gap material, such as silica. Variations in several parameters and their effects on the structural (crystal size and morphology) properties of nanoparticles were investigated. Characterizations were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal stability (TGA and DTA), solid state UV and solid state florescent (PL)

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