Cationic polymerization of ethylene oxide with Maghnite‐H as a clay catalyst in the presence of ethylene glycol

The activated‐monomer cationic ring‐opening polymerization of ethylene oxide, initiated with ethylene glycol and using an acid‐exchanged montmorillonite clay called Maghnite‐H⁺ as an effective catalyst, was carried out to obtain the corresponding homopolymers with narrow polydispersity ratios. The molecular weights of the obtained polymers were controlled with the feed ratio of the monomer to the initiator. The effects of the amount of the catalyst and time on the polymerization yield and viscosity of the polymers were studied. The structure was confirmed with proton nuclear magnetic resonance and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermal modeling of plasma spray deposition of nanostructured ceramics

A thermal model for plasma spray deposition of ceramic materials onto metallic substrates has been developed. The enthalpy-based control volume formulation of the heat transfer processes has been used to study the temperature evolution in a two-dimensional substrate and in the coating as it is grown. In this paper, additional melting of ceramic splats after deposition is examined, with a view to predicting the retention of nanostructures in a spray consisting of agglomerated, nanometer-sized particles. Initial results for thin coatings indicate that when the mean temperature of the incoming particles is close to the fusion point of the ceramic material, the nanostructure distribution in the coating is largely determined by the composition of the spray. However, with thicker coatings, additional melting due to prolonged plasma gas heating combined with increased thermal resistance in the underlying coating leads to a loss of nanostructure.     

The effect of pH on bioremediation potential for the removal of direct violet textile dye by Aspergillus niger

Alkaline and acidic media have been used in the textile dye industry, depending on the fabric nature. The bioremoval of textile direct violet dye by Aspergillus niger fungal strain was studied. The effect of pH on dye bioremoval was investigated at a pH range from 2 to 11. The direct violet dye bioremoval reached maximum with 92.4%, 64.0%, 91.4%, and 62.3 % at pH values of 2, 3, 8, and 9, respectively, at 24 h of incubation. The percentages of removal rate after 72 h incubation were 98.9, 97.3, 94.0, 95.0, 97.0, and 97.3 at pH 2, 3, 6, 7, 8, and 9, respectively. The optimum pH values were 2, 3, 8, and 9 for direct dye removal. At the end of the experiments, the treatment with fungal strain could reduce COD value of synthetic dye solution by 76-91%. Pseudo first and second order kinetic models were applied to evaluate differences in the biosorption rates and uptakes of textile dye. Pre-equilibrium biosorption of direct violet dye onto fungus under different dye concentrations followed a pseudo second order kinetic model with a high degree of correlation coefficients (R² > 0.99), and the calculated values of q_e nearly matched the experimental values of textile dye during the biotreatment process.     

Optimum Time Diversity and BCH Codes for DS SS-CDMA Cellular Mobile Channels

This paper presents the results of optimum diversity and coding of a cellular radio system using spread-spectrum code division multiple-access (SS-CDMA) and binary phase-shift-keying modulation (BPSK). The base-to-mobile link is considered with the mobile at the boundary between cells. Hence, the received signal is subject to Rayleigh or log-normal fading, as well as to interference from neighbouring cells.First, the probability of error for the fading-interference channel is approximated as a simple, closed-form expression, with one-parameter which signifies the degree of channel fading and interference. It is shown that the approximation is quite satisfactory for a wide range of channel fading and interference. Beside avoiding numerical integration, the use of such simplification offers more insight into the nature of the channel.The use of error-correcting codes to enable increasing the system capacity is then investigated. Since employment of either SS or forward-error correction (FEC) techniques results in bandwidth expansion for a communication system using a fixed alphabet size, there exists a trade-off between how much processing gain and how much coding gain the system should employ such that the bit-error rate is minimum. Two types of coding are analysed, viz. repetitive coding and binary BCH codes. For the repetitive code, Chernoff upper-bound is used to approximate the bit-error rate (BER) and the optimum diversity is then found by a simple minimisation.To find the optimum trade-off between code rate k/n and correction capability t of BCH (n,k,t) codes, the first term of the series representing the BER is used as an estimate of the probability of error. Such approximation is shown to yield a nearly exact estimate of the optimum coding parameters, which minimise the BER. Although exact analysis can be used, the present approach yields a general solution, and optimum design parameters can be related to channel conditions.The essence of the results is as follows: (i) fading and interference channel is approximated as a one parameter family; (ii) optimum diversity increases and processing gain decreases, almost linearly, with the increase of interference and fading severity; (iii) optimum BCH code rate is 0.3 over a wide range of fading and interference conditions, and (iv) optimising coding gain and processing gain can provide substantial increase in system capacity.     

Surface morphology and tribological behavior of AlSi10 alloys treated by plasma immersion ion implantation for automotive applications

Plasma immersion ion implantation (PIII) was used to implant nitrogen into Al at a temperature in the range of 320–520 °C. AlN phase was observed for temperatures above 450 °C, whereas no AIN detected by XRD diagnosis at temperatures below 380 °C. It was also observed that there was no effective increase in hardness of the material, but some wear resistance due to formation of AlN.     

Failure Analysis of a Location Axle in Tracked Tractor

In this study, a failure analysis was performed on the location axle (brace axle) of a blade on a tracked tractor used in agricultural areas. The analysis included evaluation of the macrostructure of the damage and the microstructure of the material, as well as a chemical analysis of the material. A commercial finite element method software package was used to determine the behavior of the location axle under the defined boundary conditions. After all the examination steps were completed, the main reason for the damage was determined to be manufacture and material error despite the presence of fatigue tracks in the damaged area. In addition, a heat treatment was carried out with the specimens taken from the damaged area and microstructure was re-examined. The experimental and simulation evaluation results provide a technical basis for suggestions to prevent future damage to the location axle.     

Electrochemical hydrodehalogenation of polychloromethanes at silver and carbon electrodes

The reductive dehalogenation of CCl₄, CHCl₃, CH₂Cl₂ and CH₃Cl has been investigated by cyclic voltammetry and controlled-potential electrolysis at Ag, glassy carbon (GC) and graphite electrodes in dimethylformamide (DMF) + 0.1 M Et₄NClO₄ in the absence and presence of a proton donor. In particular, the study was focused in the evaluation of the intermediates and final products of the reduction process and how their distribution could be affected by tuning relevant chemical and electrochemical parameters. In general, depending on the value of the applied potential, all polychloromethanes (PCMs) can be partially or completely dechlorinated, methane being exclusively formed in the latter case. The nature of the electrode material and the proton availability of the medium affect drastically the distribution of reduction products. The results point out that at both types of electrode, reduction of PCMs takes place through two competing reaction pathways both leading to methane. One reaction route involves a sequence of reductive dehalogenation steps, with the removal of one chlorine atom at a time, whereas the other is based on hydrogenolysis of carbenes and bypasses the intermediacy of partially dechlorinated PCMs. The presence of a proton source affects substantially the hydrodehalogenation efficiency, enhancing the concentration of intermediate PCMs and the final yield of methane. The silver electrode exhibits an extraordinary electrocatalytic effect resulting in remarkable positive shifts of the reduction potentials of all PCMs with respect to GC. The Ag surface strongly affects the kinetics of the dissociative electron transfer to CH_nCl_(4−n) (n = 0–3) as well as the reactivity of the intermediate radicals, carbanions and carbenes.     

First documentation of spawning and nest guarding in the laboratory by the invasive fish,the round goby (Neogobius melanostomus)

Although the round goby, Neogobius melanostomus, is widespread in the Great Lakes and has an extended breeding season with a high reproductive rate; its spawning behaviour remains elusive. We present the first reported accounts of spawning by the round goby in the laboratory. By simulating winter conditions and restoring spring conditions, we induced round gobies to spawn in October 2007, March 2008, May 2008, and January 2009. In one case, fanning by the nest-holding male began 10 days before egg deposition and, during this period, the male rubbed secretions along the ceiling of the nest. Males were choosy about which gravid females entered the nest and prevented entry by some females. Spawning involved repeated inversions by females and males releasing gametes on the ceiling of the nest. Males guarded the nest by blocking the entrance, producing agonistic vocalizations and chasing intruders. Inside the nest, eggs were regularly inspected by the males and constantly ventilated using pectoral and caudal fins. Up to three gravid females spawned sequentially in a nest. Peak ventilation occurred after egg deposition and declined with time until the parental male ate the eggs. The decline of parental care and egg cannibalism was likely an artifact of laboratory conditions and small brood size. Our findings offer new information on the reproductive habits of the invasive round goby. Because the reproductive sequence in the laboratory seems easy to disrupt, the procedures may lead to a management tool to control the spread of the species into new areas.