Alkoxylation of epoxidized polyisoprene by opening of oxirane rings with alcohols

Alkoxylation of epoxidized polyisoprene catalyzed by cerium ammonium nitrate (CAN) was achieved under very mild conditions both in melt and in solution. The cleavage of the epoxidized units with alcohols leads to the formation of alkoxyalcohol units and epoxide rearrangement units in the case of 20 and 38 % epoxidized 1,4‐polyisoprenes. For higher percentage of epoxidation (72 %), cyclization of epoxidized units is observed, which dramatically reduces the alcohol grafting percentage onto the polymer chains. The glass transition temperature increase with the percentage of alkoxylation is attributed to both alkoxy and hydroxyl groups formed after the ring opening of the epoxidized units. However, size‐exclusion chromatography analysis of the modified polymers showed a decrease in the number‐average molecular weight and an increase in the weight‐average molecular weight, which can be interpreted as the degradation and crosslinking of the polymer chains, respectively. Copyright © 2004 Society of Chemical Industry     

Hybrid layered double hydroxides-polypyrrole composites for construction of glucose/O2 biofuel cell

In this work, two layered double hydroxides, Zn₂Cr–ABTS and Zn₂Al–Fe(CN)₆ LDH, have been synthesized and characterized by X ray diffraction and FTIR spectroscopy to confirm the intercalation of redox anions between inorganic layers. These redox active hybrid materials have been used to electrically connect laccase (Lac) and glucose oxidase (GOx) in biofuel cell devices. Co-immobilization of hybrid LDH and enzymes has been performed by entrapment in electropolymerized films of polypyrrole deposited on porous carbon tubular electrodes. Lac/Zn₂Cr–ABTS cathodic electrode allows the electro-enzymatic reduction of O₂, whereas the anodic electrode GOx/Zn₂Al–Fe^III(CN)₆was used for the electro-enzymatic oxidation of glucose. With a two compartment configuration, a maximum power density of 45 μW cm⁻²was obtained at 0.2 V.     

Global trajectory tracking control of VTOL-UAVs without linear velocity measurements

This paper deals with the position control of Vertical Take-Off and Landing (VTOL) Unmanned Aerial Vehicles (UAVs) without linear velocity measurements. We propose a multistage constructive procedure, exploiting the cascade property of the translational and rotational dynamics. More precisely, we consider the force as a virtual control input for the translational dynamics, from which we extract the required (desired) system attitude and thrust achieving the tracking objective. Thereafter, the control torque is designed to drive the actual attitude to the desired one. A nonlinear observer, as well as some instrumental auxiliary variables are used to obviate the need for the linear velocity. Global asymptotic stability of the overall closed loop system is achieved. Simulation results are provided to show the effectiveness of the proposed control scheme.     

Approximated calculation model for plastic deformations of granular waste materials

This paper suggests an approximate model to estimate the total plastic deformation of layers made of granular materials. In this work, the model was designed to calculate the plastic deformations of the cylindrical specimen of monotonic triaxial tests. The model concept is based on the deformation mechanisms of granular material presented in the literature review. These mechanisms assumed that the volume of the whole granular material structure decreases because of particle rearrangements and compressibility of the materials. In triaxial tests, there are three main stages of loading and deformations. A plastic deformation begins in the material due to the post-compaction and tamping effects of the initial loading. This deformation results from compression of the fine material coating between the particles completely or partially depending on its degree of compressibility expressed, herein, by a hardness coefficient. At further loads, the particles contact directly each other and the sample behaves elasticity. When resultant forces on the particle at high levels of loading are more than the confining pressure and shear strength of the material, the particles move or slip laterally causing damage and buckling. The model estimates the total vertical deformations of the material as the sum of the deformation resulting from the post-compaction process and those generated from the re-orientation and horizontal movement of the particles. The model was validated with the results of monotonic triaxial tests of untreated and treated blends made of limestone and Incinerator Bottom Ash Waste (IBAW) to examine the effect of various material properties on the model calculation accuracy. The model results showed that the approximation model depicted the experimental value of the plastic deformations fairly well as the error parentage ranged between 12% and ?15% for treated and untreated blends.     

The level of C‐reactive protein in chronic hemodialysis patients: A comparative study between patients with noninfected catheters and arteriovenous fistula in two large Gulf hemodialysis centers

Hemodialysis (HD) patients have greater morbidity and mortality when they have a central venous catheter (CVC) rather than an arteriovenous fistula (AVF) access. Inflammation associated with dialysis catheter use and resultant higher C‐reactive protein (CRP) levels could have an independent adverse effect on patient outcomes. In this prospective study, we investigated whether HD catheters induce inflammation independent of infection. We compared the mean levels of the inflammatory marker (CRP) in 67 patients on maintenance HD using noninfected catheters with 86 HD patients using AVFs at Prince Salman Center for Kidney Diseases, Saudi Arabia (KSA), and Jahra Hospital, Kuwait, who met our inclusion criteria. C‐reactive protein levels were measured every 2 months over a period of 6 months using immunoturbidimetric assay. One hundred fifty‐three patients on maintenance HD for more than 6 months were included in the study, with mean age of 52.19 ± 16.06 years; 66% were males and 34% were females. Serial levels of mean CRP were statistically and significantly higher in group with noninfected catheters (1.33, 1.24, and 1.10 mg/dL) compared to those with AVFs (0.65, 0.59, and 0.68 mg/dL) with P value of 0.000. In our study, we found no relation between CRP level and age, sex, hemoglobin, albumin, calcium, phosphorus, and iPTH level in both groups. Hemodialysis patients with a catheter have a heightened state of inflammation independent of infection, and thus our study supports the avoidance of catheters and a timely conversion to AVFs with catheter removal.     

Optimum Design of Passive Shunt Filters for Power Distribution Networks

Static, passive, filters present an economic and simple solution to the harmonic distortion at the distribution level and at the same time supply the required reactive power for voltage support and/or power factor correction. Applying these filters to a distribution network, if not properly designed, may have an adverse effect on the network. This paper presents analysis of the effects of using passive harmonic filters in a power distribution networks. The driving point impedance at the node where the filter installed, as a measure of how harmonic currents would produce harmonic voltages, is determined as function of the filter parameters. Hence, effects of filter parameters on the system impedance, parallel resonant frequency and impedance at resonance are illustrated. The effects of using more than one filter are also examined. A method for the optimal design of a passive filter considering the component limits, harmonic distortion limits and parameter tolerances is also presented. The proposed optimization model has proved its effectiveness through application to measurements at a real distribution feeder.     

New accelerometric method to discriminate between asymptomatic subjects and patients with medial knee osteoarthritis during 3-d gait

This study presents a new method to estimate 3-D linear accelerations at tibial and femoral functional coordinate systems. The method combines the use of 3-D accelerometers, 3-D gyroscopes and reflective markers rigidly fixed on an exoskeleton and, a functional postural calibration method. Marker positions were tracked by a six-camera optoelectronic system (VICON 460, Oxford Metrics). The purpose of this study was to determine if this method could discriminate between medial osteoarthritic and asymptomatic knees during gait. Nine patients with osteoarthritic knees and nine asymptomatic control subjects were included in this study. Eighteen parameters representing maximal, minimal, and range of acceleration values were extracted during the loading and preswing to mid-swing phase periods, and were compared in both groups. Results show good discriminative capacity of the new method. Eight parameters were significantly different between both groups. The proposed method has the potential to be used in comprehending and monitoring gait strategy in patients with osteoarthritic knee.     

CeO2 nanoscale particles: Synthesis,characterization and photocatalytic activity under UVA light irradiation

CeO_2 nanoparticles(NPs) were synthesized in alkaline medium via the homogeneous precipitation method and were subsequently calcined at 80 ℃/24 h(assigned as CeO_2-80) and 500 ℃/2 h(assigned as CeO_2-500). The as-prepared materials and the commercial ceria(assigned as CeO_2-com) were characterized using TGA-MS, XRD, SEM-EDX, UV-vis DRS and IEP techniques. The photocatalytic performances of all obtained photocatalysts were assessed by the degradation of Congo red azo-dye(CR) under UVAlight irradiation at various environmental key factors(e.g., reaction time and calcination temperature).Results reveal that CeO_2 compounds crystalize with cubic phase, CeO_2-500 exhibits smaller crystallite size(9 nm vs 117 nm) than that of bare CeO_2-com. SEM analysis shows that the materials are sphericallike in shape NPs with strong assembly of CeO_2 NPs observed in the CeO_2-500 NPs. EDX analysis confirms the stoichiometry of CeO_2 NPs. UV-vis DRS measurement reveals that, CeO_2-500 NPs exhibits a red-shift of absorption band and a more narrow bandgap(2.6 eV vs 3.20 eV) than that of bare CeO_2-com. On the contrary, Urbach energy of Eu is found to be increased from 0.12 eV(CeO_2-com) to 0.17 eV(CeO_2-500),highlighting an increase of crystalline size and internal microstrain in the CeO_2-500 NPs sample. Zeta potential(IEP) of CeO_2-500 NPs is found to be 7.2. UVA-light-responsive photocatalytic activity is observed with CeO_2-500 NPs at a rate constant of 10×10~(-3) min~(-1), which is four times higher than that of CeO_2-com(K_(app)=2.4×10~(-3) min~(-1)) for the degradation of CR. Pseudo-first-order kinetic model gives the best fit. On the basis of the energy band diagram positions, the enhanced photocatalytic performance of CeO_2-500 nano-catalyst can be ascribed to O_2~-, 'OH and R'~+ as the primary oxidative species involved in the degradation of RC under UVA-light irradiation.