Template Synthesis of Iminodiacetic Acid Polysiloxane Immobilized Ligand Systems and their Metal Uptake Capacity

Porous solid polysiloxane ligand systems bearing an iminodiacetic acid chelating ligand of the general formula P-IDA (where P- represents [Si-O] _n polysiloxane network and IDA represent an organofunctional group) were achieved in two-step reaction. The first step includes a template synthesis of 3-iodopropylpolysiloxane (P-I) or 3-aminopropylpolysiloxane (P-MA) by hydrolytic polycondensation of TEOS and the corresponding silane agent in the presence of CTAB as a surfactant. The second step includes a modification of 3-iodopropylpolysiloxane with diethyliminodiacetate or 3-aminopropylpolysiloxane with ethylchloroacetate to produce IDA-functionalized polysiloxane ligand systems P-IDA-I & P-IDA-II respectively. It was found that the modified IDA-functionalized polysiloxane ligand systems exhibited higher capacities for uptake of the metal ions (Ni ²⁺, Cu ²⁺ and Pb ²⁺) than those prepared without surfactants.     

Modelling diffusion and adsorption of As species in Fe/GAC adsorbent beds

BACKGROUND: Arsenic decontamination of drinking water by adsorption is a simple and robust operation. When designing packed bed adsorbers for arsenic, the main problems are the slow diffusion kinetics of As in microporous media and the lack of simple equations for predicting the performance of the equipment. Commercial iron‐doped granular activated carbon adsorbents (Fe/GAC) for groundwater arsenic abatement were studied in this work. Basic parameters for arsenate (As^V) adsorption were measured and their performance at larger scale was simulated with an approximate analytical model. RESULTS: In the 0–300 µg_As L^?1 range, the As^V adsorption isotherm on Fe/GAC was found to be approximately linear. Assuming Henry's law for adsorption and homogeneous surface diffusion with constant diffusivity for intrapellet mass transfer, an approximate model for flow and adsorption of arsenate inside packed bed adsorbers was developed, and reduced to an analytic compact solution using the quasi‐lognormal distribution (Q‐LND) approximation. The use of this model with fitted and reported parameters enabled the approximate simulation of industrial adsorbers and home point‐of‐use filters. Results show that industrial adsorbers meet the breakthrough condition with incomplete utilization of the adsorbent unless convenient process configurations are used. In point‐of‐use systems with short residence times intraparticle diffusion would drastically reduce the adsorbent performance. CONCLUSION: Assuming linear adsorption of As^V over Fe/GAC, an analytical approximate solution for flow and adsorption in packed beds can be obtained. The model seems to represent correctly the main features of industrial and home filters, however, more experimental data is necessary for scale‐up purposes. Copyright © 2011 Society of Chemical Industry     

Performance analysis of multiple‐input multiple‐output relay networks based impulse radio ultra‐wideband

In this paper, we study the performance of time hopping pulse position modulation for impulse radio ultra‐wideband. We consider relay network applying decode‐and‐forward protocol. The channels between nodes adopt the IEEE 802.15.4a norms. The bit error rate performance is analyzed considering the effect of interference. Our results show significant improvement due to the diversity gain provided by the relay nodes. However, the performance is limited when multiple access interference (MAI) is present. To combat the MAI effect and further improve the detection reliability, we propose to use antenna selection at the relay. The relay receiver is assumed to be equipped with multiple antennas, and only the best antenna is selected. This is shown to improve the performance in the presence of MAI and improve the diversity gain.Copyright © 2013 John Wiley & Sons, Ltd.     

Trajectory Analysis of Forest Cover Change in the Tropical Dry Forest of Burkina Faso,West Africa

Forest cover decline is one of the most important environmental issues in the tropics. The present study was carried out in Burkina Faso, West Africa, and aimed at assessing the trajectories of forest cover change and measuring landscape metrics of the trajectory classes in order to better understand the processes of change. Landsat and ASTER images acquired over a period of 30 years were used for cover change detection and the Fragstats package was used to compute landscape metrics with five unifying change classes. Results showed a substantial increase in cropland with concurrent decline in forest cover. Deforestation represented 63% of the Percentage of Landscape (PLAND) in 2006, while reforestation accounted for only 28%. Both of these classes had high Normalized Landscape Shape Index (NLSI) values, indicating that they were present as scattered small patches. The old cultivation (30-year permanent cropland) was aggregated (IJI ≈ 0) while deforestation exhibited highly interspersed patches. The old forest and old cultivation presented lower Area Weighted Fractal Dimension Index (FRAC_AM), but deforestation and reforestation had the higher FRAC_AM. These results confirmed that there was a high level of deforestation and fragmentation in southern Burkina Faso and justify the need for a proper management plan to ensure the sustainable use of forest resources.     

Synthesis and application of magnetite polyacrylamide amino-amidoxime nano-composites as adsorbents for water pollutants

In this work, we aimed to develop a feasible method for in situ preparation of a magnetite ionic polymer nanocomposite at room temperature. For this purpose, acrylonitrile (AN) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) monomers were copolymerized and crosslinked using different monomer mol ratios in the presence of N,N-methylenebisacrylamide (MBA) as crosslinker to produce ionic crosslinked polymers P(AN-co-AMPS. The nitrile groups were converted to amine amidoxime by reacting with hydroxylamine to increase the adsorption characteristics of the ionic polymers. The produced polymers were swelled in iron cations produced from the reaction of ferric chloride and potassium iodide, followed by reaction with an ammonium hydroxide solution to produce magnetite nano-polymer composites. We performed FT-IR and XRD analysis to determine the chemical and crystalline structures, and assessed the morphologies and magnetite content using SEM, TEM and TGA analyses. We investigated the adsorption capacity and mechanism of the prepared magnetite nano-composites as adsorbents for methylene blue, Co²⁺ and Ni²⁺ cations from water.     

Doxycycline Decreases Atherosclerotic Lesions in the Aorta of ApoE-⁄- and Ovariectomized Mice with Correlation to Reduced MMP-2 Activity

Atherogenic events promote changes in vessel walls, with alteration of the redox state, and increased activity of matrix metalloproteinases (MMPs). Thus, this study aims to evaluate aortic remodeling, MMP activity, and reactive oxygen species (ROS) levels after treatment with doxycycline in ApoE^-⁄- and ovariectomized mice (OVX). Female ApoE^-⁄--knockout mice (5 weeks) were submitted to ovariectomy surgery to induce experimental menopause. They then received chow enriched with 1% cholesterol to induce hypercholesterolemia. The animals were divided into two experimental groups: ApoE^-⁄-/OVX vehicle and ApoE^-⁄-/OVX doxycycline (30 mg/kg) administered by gavage once a day for 28 days (15th to the 18th week of life). Blood samples were collected to measure total cholesterol and fractions. The aorta was used for morphometry and to measure the activity and expression of MMP-2 and ROS levels. The ApoE^-⁄-/OVX doxycycline group showed no change in total and fraction cholesterol levels. However, there was a reduction in ROS levels, MMP-2 expression, and activity that correlated with a decrease in atherosclerotic lesions relative to the ApoE^-⁄-/OVX vehicle (p > 0.05). Therefore, we conclude that doxycycline in ApoE^-⁄-/OVX animals promotes a reduction in atherosclerotic lesions by reducing ROS and MMP-2 activity and expression.     

Effects of Sedentarism and Treadmill Training in Mechanical Properties of Muscles of Ovariectomized Rats with High-Fat Diet

The aim of this study is to evaluate the ability of physical training in the maintenance of muscle strength in rats with HFD （high-fat diet） after OVX （ovariectomy）. Eighty Wistar rats are at eight weeks of age and weight 200 g which divided into 8 groups （n = 10） and treated for 12 weeks： GA： OVX ＋ ND （normal diet）, GB： OVX ＋ ND ＋ training, GC： sham ＋ ND, GD： sham ＋ ND ＋ training, GE： OVX ＋ HFD, GF： OVX ＋ HFD ＋ training, GG： sham ＋ HFD and GH： sham ＋ HFD ＋ training. HFD consists of standard ration for rats with addition of 30% lipids. In training groups, physical training five training/week was conducted on a treadmill with adaptation period of three weeks up to 18 m/s for one hour, training were performed for 12 weeks. The sedentary animals remained in individual box. To analyze the effects of training and diet, tensile strength tests of the gastrocnemius muscles were conducted： the speed of 0.1 mm/min. Analysis of variance was performed to compare groups. The mean （SD） obtained for the maximum load （N） were： GA 57.77 （6.89）, GB 62.74 （5.07）, GC 49.45 （6.06）, GD 59.42 （5.26） and GE 55.58 （4.72）, GF 62.50 （4.56）, GG 58.35 （4.54） and GH 56.67 （5.87）, respectively. There were no differences for maximum load between surgeries （p = 0.004） and between treatments （p = 0.000）. Differences were found also for the relationship surgery diet treatment （p = 0.007）. For the variable stiffness （N/mm）, there were not statistically significant differences： GA 5.03 （0.72）, GB 5.08 （1.09）, GC 5.17 （0.53）, GD 5.35 （0.80）, GE 5.52 （1.20）, GF 5.36 （1.07）, GG 4.83 （1.03） and GH 5.40 （0.73）. For the toughness （N/mm）, there were differences between treatments （p = 0.010） and the ratio diet treatment （p = 0.024）： GA 455.00 （107.21）, GB 541.96 （126.80）, GC 394.97 （84.67）, GD 566.90 （157.07）; GE 424.63 （113.03）, GF 478.07 （106.03）; GG 517.44 （98.65?     

Studies on mechanical and biodegradability properties of PVA/lignin blend films

The mechanical and biodegradation properties of polyvinyl alcohol/lignin blended films have been studied. The biodegradable composite films were developed by mechanical mixing followed by film casting method using poly (vinyl alcohol) (PVA), with lignin in different compositions. The progress of biodegradation was evidenced by means of the soil burial test. There was also an evaluation of the weight loss of the samples at the end of the biodegradation process. Blending the PVA with lignin improves tensile strength and the modulus of elasticity and causes a slight decrease in the elongation at break. The best tensile mechanical properties of a PVA/lignin blend were at ratio 2:30 where the tensile strength was 38 MPa, elastic modulus 83.22 MPa and elongation at break 213.9%. Blends of various PVA/lignin ratios have shown transparency, flexibility and good mechanical properties. Film composites also showed good biodegradability. The addition of lignin to the PVA matrix increases the degradation rate of the blends. The weight loss is affected by the composition of the blend, and by the nature of the microorganisms in the soil. PVA/lignin film may be potentially suitable as eco-friendly packaging materials.