Synthesis and characterization of monomeric and polymeric pyridinylimine‐based Ni(II) complexes and their catalytic activities in ethylene oligomerization

A new polymeric ligand was synthesized through the reaction of 4‐(pyridinylimine)phenol and formaldehyde in a basic medium, and its corresponding polymer–nickel complexes were formed in a 1:1 molar ratio. The synthesized compounds were characterized using elemental and spectral analyses. The monomeric and polymeric Ni(II) complexes (C₁ and C₂, respectively) were evaluated as catalyst precursors for ethylene oligomerization, using methylaluminoxane as an activator at two different ethylene pressures. C₂ was found to be a more effective pre‐catalyst than C₁, with the co‐catalyst having a similar effect in both cases. C₂ exhibited an activity of 1.282 × 10⁶ g (mol Ni)^?1 h^?1 bar^?1, with an Al:Ni ratio of 2000:1 at room temperature and 1 atm ethylene pressure. Meanwhile C₁ exhibited an activity of 1.126 × 10⁶ g (mol Ni)^?1 h^?1 bar^?1 under similar experimental conditions. At 5 atm ethylene pressure, C₁ favoured the formation of high‐density polyethylene, whereas C₂ favoured the formation of branched low‐density polyethylene. Copyright © 2012 Society of Chemical Industry     

Hybrid clustering analysis using improved krill herd algorithm

In this paper, a novel text clustering method, improved krill herd algorithm with a hybrid function, called MMKHA, is proposed as an efficient clustering way to obtain promising and precise results in this domain. Krill herd is a new swarm-based optimization algorithm that imitates the behavior of a group of live krill. The potential of this algorithm is high because it performs better than other optimization methods; it balances the process of exploration and exploitation by complementing the strength of local nearby searching and global wide-range searching. Text clustering is the process of grouping significant amounts of text documents into coherent clusters in which documents in the same cluster are relevant. For the purpose of the experiments, six versions are thoroughly investigated to determine the best version for solving the text clustering. Eight benchmark text datasets are used for the evaluation process available at the Laboratory of Computational Intelligence (LABIC). Seven evaluation measures are utilized to validate the proposed algorithms, namely, ASDC, accuracy, precision, recall, F-measure, purity, and entropy. The proposed algorithms are compared with the other successful algorithms published in the literature. The results proved that the proposed improved krill herd algorithm with hybrid function achieved almost all the best results for all datasets in comparison with the other comparative algorithms.     

Inhibition of mild steel corrosion in acid solution by Pheniramine drug: Experimental and theoretical study

Inhibition of mild steel corrosion in 1 M HCl solution by Pheniramine drug was studied using weight loss, electrochemical impedance spectroscopy, linear polarization resistance, and potentiodynamic polarization measurements. The values of activation energy (E_a) and different thermodynamic parameters such as adsorption equilibrium constant (K_ads), free energy of adsorption , adsorption enthalpy and adsorption entropy were calculated and discussed. The adsorption process of studied drug on mild steel surface obeys the Langmuir adsorption isotherm. Potentiodynamic polarization measurements showed that Pheniramine is mixed-type inhibitor. Further, theoretical calculations were carried out and relations between computed parameters and experimental inhibition efficiency were discussed.     

Superior electrocatalytic activity of mesoporous Au film templated from diblock copolymer micelles

Mesoporous Au films consisting of a network of interconnected Au ligaments around ultra-large pores were found to exhibit a promising electrocatalytic activity towards sluggish reactions. Mesoporous Au films with pore sizes up to 25 nm were successfully fabricated using a polymeric micelle approach. A superior catalytic activity of the mesoporous Au films towards methanol oxidation was confirmed, which was thoroughly analyzed and compared with that of other Au materials. An intrinsic investigation on the high catalytic activity revealed that the superior performance of the as-prepared mesoporous Au film was related to its unique atomic structures around the mesopores with well-crystallized facets and several step/kink sites on the Au surfaces. These findings showcase a strategic and feasible design for preparing highly active Au-based catalysts that could be used as promising candidates in electrocatalytic applications.

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Transmission electron microscopy study of Ni–Si nanocomposite films

Nickel induced crystallization of amorphous Si (a-Si) films is investigated using transmission electron microscopy. Metal-induced crystallization was achieved on layered films deposited onto thermally oxidized Si(3 1 1) substrates by electron beam evaporation of a-Si (400 nm) over Ni (50 nm). The multi-layer stack was subjected to post-deposition annealing at 200 and 600 °C for 1 h after the deposition. Microstructural studies reveal the formation of nanosized grains separated by dendritic channels of 5 nm width and 400 nm length. Electron diffraction on selected points within these nanostructured regions shows the presence of face centered cubic NiSi₂ and diamond cubic structured Si. Z-contrast scanning transmission electron microscopy images reveal that the crystallization of Si occurs at the interface between the grains of NiSi₂ and a-Si. X-ray absorption fine structure spectroscopy analysis has been carried out to understand the nature of Ni in the Ni–Si nanocomposite film. The results of the present study indicate that the metal induced crystallization is due to the diffusion of Ni into the a-Si matrix, which then reacts to form nickel silicide at temperatures of the order of 600 °C leading to crystallization of a-Si at the silicide–silicon interface.     

Nanoparticle–Plant Interactions: Two‐Way Traffic

In this Review, an effort is made to discuss the most recent progress and future trend in the two‐way traffic of the interactions between plants and nanoparticles (NPs). One way is the use of plants to synthesize NPs in an environmentally benign manner with a focus on the mechanism and optimization of the synthesis. Another way is the effects of synthetic NPs on plant fate with a focus on the transport mechanisms of NPs within plants as well as NP‐mediated seed germination and plant development. When NPs are in soil, they can be adsorbed at the root surface, followed by their uptake and inter/intracellular movement in the plant tissues. NPs may also be taken up by foliage under aerial deposition, largely through stomata, trichomes, and cuticles, but the exact mode of NP entry into plants is not well documented. The NP–plant interactions may lead to inhibitory or stimulatory effects on seed germination and plant development, depending on NP compositions, concentrations, and plant species. In numerous cases, radiation‐absorbing efficiency, CO₂ assimilation capacity, and delay of chloroplast aging have been reported in the plant response to NP treatments, although the mechanisms involved in these processes remain to be studied.     

Unsupervised text feature selection technique based on hybrid particle swarm optimization algorithm with genetic operators for the text clustering

The text clustering technique is an appropriate method used to partition a huge amount of text documents into groups. The documents size affects the text clustering by decreasing its performance. Subsequently, text documents contain sparse and uninformative features, which reduce the performance of the underlying text clustering algorithm and increase the computational time. Feature selection is a fundamental unsupervised learning technique used to select a new subset of informative text features to improve the performance of the text clustering and reduce the computational time. This paper proposes a hybrid of particle swarm optimization algorithm with genetic operators for the feature selection problem. The k-means clustering is used to evaluate the effectiveness of the obtained features subsets. The experiments were conducted using eight common text datasets with variant characteristics. The results show that the proposed algorithm hybrid algorithm (H-FSPSOTC) improved the performance of the clustering algorithm by generating a new subset of more informative features. The proposed algorithm is compared with the other comparative algorithms published in the literature. Finally, the feature selection technique encourages the clustering algorithm to obtain accurate clusters.     

Indigo: user-level support for building distributed shared abstractions

Distributed systems that consist of workstations connected by high performance interconnects offer computational power comparable to moderate size parallel machines. Middleware like distributed shared memory (DSM) or distributed shared objects (DSO) attempts to improve the programmability of such hardware by presenting to application programmers interfaces similar to those offered by shared memory machines. This paper presents the portable Indigo data sharing library which provides a small set of primitives with which arbitrary shared abstractions are easily and efficiently implemented across distributed hardware platforms. Sample shared abstractions implemented with Indigo include DSM as well as fragmented objects, where the object state is split across different machines and where interfragment communications may be customized to application-specific consistency needs. The Indigo library's design and implementation are evaluated on two different target platforms: a workstation cluster and an IBM SP2 machine. As part of this evaluation, a novel DSM system and consistency protocol are implemented and evaluated with several high performance applications. Application performance attained with the DSM system is compared to the performance experienced when utilizing the underlying basic message-passing facilities or when employing Indigo to construct customized fragmented objects implementing the application's shared state. Such experimentation results in insights concerning the efficient implementation of DSM systems (e.g. how to deal with false sharing). It also leads to the conclusion that Indigo provides a sufficiently rich set of abstractions for efficient implementation of the next generation of parallel programming models for high performance machines. © 1998 John Wiley & Sons, Ltd.     

Synthesis and characterization of first‐ and second‐generation polyamide pyridylimine nickel dihalide metallodendrimers and their uses as catalysts for ethylene polymerization

First‐ and second‐generation pyridylimine‐terminated dendrimeric ligands were prepared by the reaction of the corresponding amine‐terminated aromatic polyamide dendrimers with 2‐acetylpyridine. The pyridylimine terminal groups were used as bidentate N,N ligands of nickel halide to prepare the corresponding first‐generation and second‐generation nickel dihalide metallodendrimers C1 and C2 , respectively. The synthesized dendrimers and metallodendrimers were characterized by elemental and spectral analyses. C1 and C2 were evaluated as catalyst precursors for ethylene oligomerization after being activated with methylaluminoxane (MAO) and diethylaluminum chloride (Et₂AlCl) under 1 atm and 5 atm pressure of ethylene. In both cases, the use of 1 atm or 5 atm pressure of ethylene and a 1500:1 Al:Ni molar ratio for C1 and C2 resulted in high catalytic activities toward ethylene polymerization. Upon activation with MAO and Et₂AlCl, C1 exhibited promising activities toward ethylene polymerization and produced linear chain structures that were associated with high density polyethylene. In contrast, C2 produced a polymer with the branching nature of low density polyethylene under similar conditions. © 2014 Society of Chemical Industry     

IP address allocation protocols in vehicular ad hoc networks

In vehicular ad hoc networks (VANETs), communication takes place between vehicles to vehicles, the vehicles to the road side units, and vice-versa. The basic purpose of these communications is to share and exchange tremendous amount of data and information. For efficient information sharing, a systematic and structured connection establishment algorithm is needed. In VANETs, each connected node of the network need to be assigned a unique address. Hence, an algorithm is needed for the proper assignment of unique address to all nodes in the network. This paper explains different types of IP address protocols in VANETs. We have also explained advantage and disadvantage of existing IP address allocation protocols in VANETs.