Heparin‐immobilized poly(2‐hydroxyethylmethacrylate)‐based microspheres

Poly(2‐hydroxyethylmethacrylate) (PHEMA)‐based microspheres (150–200 µm in diameter) were produced by a modified suspension polymerization of different type of comonomers—namely, acrylic acid, dimethylaminoethyl‐methacrylate, and methylmethacrylate. These microspheres were activated with cyanogen bromide (CNBr) at pH 11.5, and heparin molecules were then immobilized through covalent bonds. The amount of immobilized heparin was controlled by changing the initial concentration of CNBr and heparin. The increase in the initial concentrations of both CNBr and heparin caused an increase in the amount of heparin immobilized onto microspheres for all polymer surfaces. The maximum heparin immobilization was observed on the PHEMA homopolymer microspheres (180 mg/g). The plain and heparin‐immobilized microspheres were contacted with blood in in vitro systems and in ex vivo animal experiments. Loss of the blood cells and clotting times were followed. Anticoagulant effect of the immobilized heparin was clearly observed with blood coagulation experiments. Loss of cells in the blood contacting with heparin‐immobilized microspheres was significantly lower than those observed with the plain microspheres. Bovine serum albumin adsorption onto the microspheres containing heparin on their surfaces was also studied. High albumin adsorption values (up to 127 mg/g) were observed in which the heparin‐immobilized PHEMA microspheres were used. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 655–662, 1999     

Carbon nanoparticles/polyvinyl alcohol composites with enhanced optical,thermal, mechanical,and flame-retardant properties

In this work, polyvinyl alcohol (PVA) is chemically bonded to carbon nanoparticles (CNPs) by a very simple and versatile solution casting method. Five different kinds of CNPs/PVA composite films were prepared; 0.5, 1.0, 1.5, 2.0, and 3.0 wt% CNPs dispersed in PVA. The as-prepared samples were characterized using various characterization techniques. The resulting nanocomposites proved to possess homogeneity and better mechanical, thermal, optical, and flame-retardant properties than pure PVA. Most of the CNPs with average particle size ≤100 nm were homogeneously dispersed in the PVA matrix showing fluorescence in the violet color zone. The crystallinity of the nanocomposites show a decline in the diffraction intensity as compared to pure PVA which results from the dwelling of CNPs inside the gaps of stacked-layer chains of PVA. The mechanical properties of nanocomposites indicated enhancement in toughness, elastic modulus and tensile strength with an increase in CNPs contents. The assessment for flame-retardant properties was carried out through cone calorimetry. The results show a decrease in both total heat release rate (THRR) and peak heat release rate (pHRR) of the resulting nanocomposites as compared to pure PVA. The superior properties of the CNPs/PVA composites stemmed from the good interfacial bonding between the CNPs and PVA matrix.     

Reducing heat gain from sheet metal-clad walls by utilizing industrially wasted materials (experimental study)

Buildings' walls are covered to reduce environmental impact and esthetics, and cladding materials vary based on public preference and financial capacity. Metal sheets with glossy surfaces are commonly used, but researchers propose using aluminum sheets and filling gaps with commercial waste materials, like, fabric roll sticks or circular plastic hollow parts. A test room with internal dimensions of 1 × 1 × 2 m used in Baghdad (latitude 33.2° N) was used to study thermal behavior, with a window-type air conditioner providing standard thermal conditions. The air gap attached to the top of the test wall was either left open or closed during the day. Results showed that double-layer bamboo packing preserved 52.1% with a closed-air gap and 49.5% with an open-air gap, but no discernible difference was observed between the two situations.     

Cooling of lithium-ion battery pack using different configurations of flexible baffled channels

The rated temperature and its uniformity of lithium-ion (Li-ion) battery (LIB) pack are the main demands for safe and efficient operation. This paper investigates an air cooling system of a pack of five prismatic LIB's generating considerable heat through discharging energy. The cooling system is a three-dimensional channel with flexible baffles of different arrangements installed on the walls of the channel to lower and regulate the temperature of the batteries. Three arrangements of these baffles are studied, transverse; L-shaped and staggered. The study is formulated as turbulent fluid–structure interaction and solved numerically using the finite elements method. The study was conducted for five spaces between batteries, S = 0, 1, 2, 3 and 4 mm and three different inlet air velocities, U_in = 0.5, 1 and 2 m/s. It was found that the flexible baffles guide the coolant towards the batteries smoothly with less pressure drop and this significantly improves the performance of the battery thermal management system due to the reduction of the maximum temperature and temperature variation as well. The staggered arrangement of the baffles shows the most effective configuration, where the maximum temperature difference between batteries is only 1.85°C for S = 1 mm and U_in = 2 m/s.     

Congo red attached poly(EGDMA–HEMA) microspheres as specific sorbents for removal of cadmium ions

Poly[ethyleneglycoldimethacrylate (EGDMA)–hydroxyethylmethacrylate (HEMA)] microspheres (150–200 μm in diameter) were produced by suspension copolymerization of EGDMA and HEMA in an aqueous medium. Toluene was included in the formulations in order to produce water-swellable microspheres. Poly(vinyl alcohol) and benzoyl peroxide were used as stabilizer and initiator, respectively. Congo red was chemically attached to the microspheres as a metal chelating ligand for specific adsorption of heavy metal ions. These sorbents were characterized by an optical microscopy and a FTIR. Adsorption/desorption of cadmium (Cd²⁺) ions from aqueous solutions on these sorbents were investigated in batch equilibrium experiments by using an atomic absorption spectroscopy with a graphite furnace atomizer. The maximum cadmium adsorption on to the dye-attached microspheres (i.e., by complex formation) was about 18.3 mg Cd²⁺ ions/g polymer, which was observed at pH 6.8. While adsorption onto the plain poly(EGDMA–HEMA) microspheres (i.e., nonspecific adsorption) was about 0.93 mg Cd²⁺ ions/g polymer at the same conditions. More than 90% of the adsorbed cadmium was desorbed in 1 h by using 2M NaCl as an eluant. The resorption capacity of the sorbent did not significantly decrease during repeated sorption–desorption cycling. © 1996 John Wiley & Sons, Inc.     

Comparison of β-galactosidase immobilization by entrapment in and adsorption on poly(2-hydroxyethylmethacrylate) membranes

β-Galactosidase was immobilized in/on poly(2-hydroxyethyl methacrylate) (pHEMA) membranes by two different methods: adsorption on Cibacron F3GA derivatized pHEMA membranes (pHEMA-CB), and entrapment in the bulk of the pHEMA membranes. The maximum β-galactosidase adsorption on pHEMA-CB membranes was obtained as 95·6μgcm^-2 in 2·0mgcm^-3 enzyme solution. The adsorption phenomena appeared to follow a typical Langmuir isotherm. In the entrapment, an increase in β-galactosidase loading resulted in a consistent increase in membrane activity from 3·3×10^-2 to 17·8×10^-2Ucm^-2 pHEMA membranes. The K_m values for both immobilized β-galactosidase (adsorbed 0·32mM and entrapped 0·81mM ) were higher than that of the free enzyme (0·26mM ). The optimum reaction temperature of the adsorbed enzyme was 5°C higher than that of both the free and the entrapped enzyme. The optimum reaction pH was 7·5 for free and both immobilized preparations. After 15 successive uses the retained activity of the adsorbed and the entrapped enzymes was 80% and 95%, respectively. The storage stability of the enzyme was found to increase upon immobilization. ©1997 SCI     

New generation polymeric nanospheres for catalase immobilization

Monosize poly(2‐hydroxyethyl methacrylate‐co‐N‐methacryloly‐L ‐histidinemethylester) [mon‐poly(HEMA‐MAH)] nanospheres were prepared via surfactant‐free emulsion polymerization method. L ‐Histidine groups of the mon‐poly(HEMA‐MAH) nanospheres were chelated with Fe³⁺ ions. Mon‐poly(HEMA‐MAH) nanospheres were characterized by Fourier transform infrared spectroscopy, proton NMR, and scanning electron microscopy. Particle size of the mon‐poly(HEMA‐MAH) nanospheres was measured by Zeta Sizer. Elemental analysis of MAH for nitrogen was estimated as 0.94 mmol/g polymer. The catalase immobilized onto the mon‐poly(HEMA‐MAH)–Fe³⁺ nanospheres resulted in increasing the enzyme stability with time. Optimum operational temperature for both immobilized preparations was the same, and the temperature profiles of the immobilized preparations were significantly broader. It was observed that enzyme could be repeatedly adsorbed and desorbed on the mon‐poly(HEMA‐MAH)–Fe³⁺ nanospheres without loss of adsorption capacity or enzymic activity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Compound conical concentrators with elliptical receivers

Geometrical analysis of the compound conical concentrator (CCC) with a receiver of a general shape is given. Special emphasis is given to the concentrator with a receiver of an elliptical shape. Circular and strip receivers emerge as special cases in a generalized treatment. The CCC with a circular receiver has a quasi-parabolic profile, and the CCC with a strip receiver is made up of tangents to a system of confocal parabolas. Various intensity distributions may be obtained with the different receivers. Uniformly distributed concentrated-flux, most suitable for use with photovoltaic systems, can be easily obtained with CCC trough-type reflectors with strip receivers.     

Mechanical and Thermal Properties of Thermoset–Graphene Nanocomposites

Graphene has resulted in significant research effort to generate polymer nanocomposites with improved mechanical, thermal as electrical properties as compared to pure polymers. A large number of studies have been undertaken using different graphene derivatives, filler loadings, synthesis methods, and so on to obtain optimum filler dispersion as well as filler–matrix interactions, which are crucial for achieving significant enhancement in the properties, especially at low filler fraction. This review summarizes the mechanical and thermal properties of numerous studies carried out for the property enhancements of commercially relevant thermosetting materials such as epoxy, polyurethane, natural rubber, melamine formaldehyde, phenol formaldehyde, silicones, vinyl ester, cyanate ester, and unsaturated polyester resin.

     

Suppression of 3D mobility of carrier and superconductivity by Y substitution in Cu0.5Tl0.5Ba2(Ca2−xYx)Cu3O10−δ samples

Bulk Cu_0.5Tl_0.5Ba₂(Ca_2−xY_x)Cu₃O_10−δ superconductor ceramic samples were synthesized by the conventional solid-state method and characterized by X-ray diffraction, dc-resistivity, ac-susceptibility and Fourier Transform Infrared spectroscopy. The main purpose of this study was to investigate the role of charge carriers and the effect of Y substitution at Ca sites in between the CuO₂ planes on superconductivity. The superconducting properties are suppressed by Y substitution at Ca sites in between the CuO₂ planes of Cu_0.5Tl_0.5Ba₂(Ca_2−xY_x)Cu₃O_10−δ samples. It is most likely that Y³⁺ may create correlated domains in between the CuO₂ planes and localizes the carriers, which lowers the diamagnetic screening and suppresses the superconductivity. Therefore, cationic substitution reduces the three dimensional (3D) mobility of carriers, resulting in the reduction of the Fermi vector and velocity of the carriers, which in turn suppresses the superconducting properties of the material.