Concomitant Crystallization of Copper(II) Sachharinato Complexes with 2-methylpyrazine as a Monomer and an One-dimensional Polymer: Syntheses,Crystal Structures,Spectroscopic and Thermal Properties

The reaction of [Cu(sac)₂(H₂O)₄] · 2H₂O with 2-methylpyrazine (mpyz) leads two complexes, concomitant crystallization of a mononuclear complex [Cu(sac)₂(mpyz)(H₂O)₂] (1) and a polymeric complex [Cu(sac)₂(μ-mpyz)]_n (2). Both complexes have been characterized by elemental analyses, magnetic measurements, FT-IR and ESR, TG-DTA and single-crystal X-ray diffraction analyses. Single-crystal X-ray analyses show that complex 1 consists of discrete molecules in which the copper(II) ions exhibits a square-pyramidal coordination geometry. The individual molecules of 1 are connected into a hydrogen-bonded chain structure, which is further assembled to form a three-dimensional network by π–π stacking interactions. Complex 2 is an 1D coordination polymer in which copper(II) centers are bridged by the mpyz ligand. The chains are further assembled to form two-dimensional frameworks by π–π and C–H···π stacking interactions.     

Chromatographic performance of monodisperse–macroporous particles produced by “modified seeded polymerization.” I: Effect of monomer/seed latex ratio

In this study, the monodisperse–macroporous particles produced by a relatively new polymerization protocol, the so‐called, “modified seeded polymerization,” were used as column‐packing material in the reversed phase chromatography (RPC) of proteins. The particles were synthesized in the form of styrene‐divinylbenzene copolymer approximately 7.5 μm in size. In the first stage of the synthesis, the monodisperse polystyrene particles 4.4 μm in size were obtained by dispersion polymerization and used as the “seed latex.” The seed particles were swollen by a low‐molecular‐weight organic agent and then by a monomer mixture. The monodisperse–macroporous particles were obtained by the polymerization of monomer mixture in the seed particles. In the proposed polymerization protocol, the number of successive swelling stages was reduced with respect to the present techniques by the use of sufficiently large particles with an appropriate average molecular weight as the seed latex. A series of particles with different porosity properties was obtained by varying the monomer/seed latex ratio. The separation behavior of HPLC columns including the produced particles as packing material was investigated in the RPC mode using a protein mixture including albumin, lysozyme, cytochrome c, and ribonuclease A. The chromatograms were obtained with different flow rates under an acetonitrile–water gradient. The theoretical plate number increased and chromatograms with higher resolutions were obtained with the particles produced by using a lower monomer/seed latex ratio. The separation ability of the column could be protected over a wide range of flow rates (i.e., 0.5–3 mL/min) with most of the materials tested. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 607–618, 2004     

Coverage‐aware connectivity‐constrained unattended sensor deployment in underwater acoustic sensor networks

Careful deployment of nodes in underwater acoustic sensor networks in a distributed manner with the goal of maximized coverage and guaranteed connectivity is a challenging problem because it is very difficult and costly to access the 3D underwater environment. This paper presents a novel algorithm for self‐deployment of nodes in underwater acoustic sensor networks assuming that the nodes are randomly dropped to the water surface and form a densely populated connected network at the water surface. The idea of the algorithm is based on calculating an optimized depth for each node in the network in such a way that the possible sensing coverage overlaps are minimized and the connectivity of final topology is guaranteed. The algorithm has three main phases. In the first phase, nodes are organized in a tree structure that is rooted at the surface station. In the second phase, the depths for all nodes are computed iteratively at surface station. In the final phase, the calculated depths are distributed to nodes so that the nodes start sinking. The performance of the proposed approach is validated through simulation. We observed that the proposed approach performs at least 10% better in terms of network coverage than contemporary schemes in the literature. Copyright © 2016 John Wiley & Sons, Ltd.     

The evaporation rates and mechanisms of cadmium from a bubble-stirred molten copper bath

Experiments to determine the evaporation rates and aerosol formation mechanism of cadmium in molten copper at atmospheric pressure have been carried out. A small amount of cadmium (∼1 wt pct) was added to molten copper at 1473 K and allowed to evaporate while bubbling 750 and 1500 cm³/min of argon through the melt. Melt samples were periodically taken and analyzed by inductively coupled plasma/mass spectroscopy (ICP/MS) to determine their impurity content. A theoretical model to predict the evaporation rates of solutes from molten metals was developed and compared to the experimental results. Excellent correlation between experiment and theory was found for the cadmiumcopper system. The model has been extended to other solutes and also to molten Fe-3 (wt pct) C at 1873 K as a solvent.     

Personality dimensions, psychosocial-demographic variables, and English language competency in predicting level of acculturative stress among Turkish international students.

A sample of 229 Turkish international students studying in 17 universities throughout the United States participated in this online study. The main purpose of the study was to investigate acculturative stress based on students' demographics, personality, level of social connectedness, and English language competency. A hierarchical regression analysis indicated that marital status, English language competency, social connectedness, adjustment difficulties, neuroticism, and openness to experience were predictors of acculturative stress. Analysis of variance results showed that acculturative stress did not significantly differ by students' gender or age. Implications are discussed and suggestions for interventions and future research are provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Filtration characteristics of aluminium hydroxide mixtures (alumina hydrates)

The specific cake resistance of the alumina hydrates obtained from sodium aluminate solutions was investigated against the caustic ratio, ageing and filtration pressure using a laboratory test filter at constant pressure filtration conditions. The alumina hydrate product was produced from sodium aluminate solutions by seeding the aluminium hydroxide crystals of definite size distribution at constant solution temperature. The specific cake resistance was found to increase with the caustic ratio and filtration pressure and to decrease with the ageing of alumina hydrates in aluminate solutions.     

Detecting and connecting disjoint sub-networks in wireless sensor and actor networks

Wireless sensor and actor networks (WSANs) can be considered as a combination of a sensor network and an actor network in which powerful and mobile actor nodes can perform application specific actions based on the received data from the sensors. As most of these actions are performed collaboratively among the actors, inter-actor connectivity is one of the desirable features of WSANs. In this paper, we propose a novel distributed algorithm for establishing a connected inter-actor network topology. Considering initially disjoint sets of actors, our algorithm first initiates a search process by using the underlying sensor network in order to detect the possible sub-networks of actors in the region. After these sub-networks are detected, our algorithm pursues a coordinated actor movement in order to connect the sub-networks and thus achieve inter-actor connectivity for all the actors. This coordinated movement approach exploits the minimum connected dominating set of each sub-network when picking the appropriate actor to move so that the connectivity of each sub-network is not violated. In addition, the approach strives to minimize the total travel distance of actors and the messaging cost on both sensors and actors in order to extend the lifetime of WSAN. We analytically study the performance of our algorithm. Extensive simulation experiments validate the analytical results and confirm the effectiveness of our approach.     

Thermoresponsive isopropylacrylamide-vinylpyrrolidone copolymer by radiation polymerization

In this study, a random copolymer of N-isopropylacrylamide and N-vinyl-pyrrolidone [poly(NIPAM-co-NVP)] having a thermoresponsive character was prepared by a radiation copolymerization method. Poly(ethylene glycol), PEG 4000, was included in the copolymerization recipe to increase the thermoresponsivity of the resultant copolymeric structures. NIPAM-co-NVP copolymers with different thermoresponsive properties were obtained by changing the initial NIPAM/NVP mol ratio, total monomer, and PEG 4000 concentrations. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1775–1784, 1997     

The effect of oxygen content on the temperature dependent tribological behavior of Cr-O-N coatings

CrN, Cr-O-N and Cr-O coatings with different oxygen contents were produced with reactive cathodic arc physical vapor deposition on high speed steel substrates. The temperature dependent friction and wear behaviours of these coatings were investigated within the temperature range of 25-100 °C. The results of the study showed that it is possible to produce CrN coatings with temperature independent, low coefficient of friction (CoF) and wear behavior by introducing oxygen into them. The amount of oxygen in the coating played a critical role on the tribological behavior. Only, in the coatings produced with oxygen content higher than 46%, a temperature independent wear behavior was observed. The structure and chemistry of the coatings and wear tracks were investigated with XRD and micro Raman spectroscopy. The coatings, with an oxygen content higher than 46%, consisted of Cr₂O₃ and other compounds that are giving broad Raman shifts between 675-834 cm^− 1. With the presence of compounds giving Raman shifts at 675-834 cm^− 1, in the film and/or in the wear track, it became possible to achieve films with temperature independent, low CoF and wear behavior.