Thermal properties and two-dimensional photonic band gaps

The effect of temperature on a two-dimensional square lattice photonic crystal composed of Si rods arranged in an air background was investigated theoretically using the plane-wave expansion method. Both the thermal expansion effect and thermo-optical effect are considered simultaneously. We have discussed the role of temperature in creating the complete photonic band gap as a function of temperature. Two different shapes of rods, i.e. square and circular, are considered in the presence of the two polarization states, i.e. TE and TM waves. The numerical results show that the photonic band gap can be significantly enlarged compared to the photonic band gap at room temperature. The effect of temperature on the complete photonic band width in the cylindrical rods case is more significant. Cylindrical and square Si rods may work as a temperature sensor or filter, among many other potential applications.     

Development of novel spray coated soft elastic gelatin capsule sustained release formulations of nifedipine

Nifedipine release from coated commercially available immediate release soft elastic gelatin capsules was investigated. Capsules were spray coated using two different polymeric combinations, ethylcellulose and hydroxypropylmethylcellulose or pectin, at different coating loads. In vitro drug release studies were conducted in three different dissolution media: with gastric pretreatment, without gastric pretreatment, and in water to investigate the pH effect on nifedipine release. Convolution of in vitro dissolution data for selected formulations and commercially available sustained release nifedipine formulations showed that the tested formulations provided release profiles of nifedipine that are very promising in terms of desirable sustained release formulations.     

Biosynthesis and structural characterization of silver nanoparticles from bacterial isolates

This study aimed to develop a green process for biosynthesis of silver nanomaterials by some Egyptian bacterial isolates. This target was achieved by screening an in-house culture collection consists of 300 bacterial isolates for silver nanoparticle formation. Through screening process, it was observed that strains belonging to Escherichia coli (S30, S78), Bacillus megaterium (S52), Acinetobacter sp. (S7) and Stenotrophomonas maltophilia (S54) were potential candidates for synthesis of silver nanoparticles. The extracellular production of silver nanoparticles by positive isolates was investigated by UV-Vis spectroscopy, X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results demonstrated that UV-visible spectrum of the aqueous medium containing silver ion showed a peak at 420 nm corresponding to the plasmon absorbance of silver nanoparticles. Scanning electron microscopy micrograph showed formation of silver nanoparticles in the range of 15-50 nm. XRD-spectrum of the silver nanoparticles exhibited 2θ values corresponding to the silver nanocrystal that produce in hexagonal and cubic crystal configurations with different plane of orientation. In addition, the signals of the silver atoms were observed by EDS-spectrum analysis that confirms the presence of silver nanoparticles (AgNPs) in all positive bacterial isolates.     

Protein Arginine Methyltransferase 1 Is Essential for the Meiosis of Male Germ Cells

Protein arginine methyltransferase 1 (PRMT1) is a major enzyme responsible for the formation of methylarginine in mammalian cells; however, its function in vivo is not well understood due to its early embryonic lethality in null mice exhibiting spontaneous DNA damage, cell cycle delays, and defects in check point activation. Here, we generated germ cell-specific Prmt1 knock-out (KO) mice to evaluate the function of PRMT1 in spermatogenesis. Our findings demonstrate that PRMT1 is vital for male fertility in mice. Spermatogenesis in Prmt1 KO mice was arrested at the zygotene-like stage of the first meiotic division due to an elevated number of DNA double-strand breaks (DSBs). There was a loss of methylation in meiotic recombination 11 (MRE11), the key endonuclease in MRE11/RAD50/NBS 1 (MRN) complex, resulting in the accumulation of SPO11 protein in DSBs. The ATM-mediated negative feedback control over SPO11 was lost and, consequently, the repair pathway of DSBs was highly affected in PRMT1 deficient male germ cells. Our findings provide a novel insight into the role of PRMT1-mediated asymmetric demethylation in mouse spermatogenesis.     

Equilibrium and kinetic studies on the extraction of gadolinium(III) from nitrate medium by di‐2‐ethylhexylphosphoric acid in kerosene using a single drop technique

The liquid–liquid extraction of Gd(III) from aqueous nitrate medium was studied using di‐2‐ethylhexylphosphoric acid (HDEHP) in kerosene. On the basis of the slope analysis data, the composition of the extracted species was found to be [Gd A₃(HA)] with the extraction equilibrium constant (K_ex) = (1.48 ± 0.042) × 10^?12 mol dm^?3. The results of the effect of temperature on the value of the equilibrium extraction constant indicated the endothermic character of the extraction system. The kinetics of the forward extraction of Gd³⁺ from nitrate medium by HDEHP in kerosene was investigated using the single drop column technique. The rate of flux (mass transfer per unit area) was found to be proportional to [Gd(III)], [H₂A₂]_(o), [NO₃^?], and [H⁺]^?1 in the liquid drop organic phase. The forward extraction rate constant, k_f, was 2.24 × 10^?3 m s^?1 using the equation: Copyright © 2005 Society of Chemical Industry     

Hybrid nanocomposite coating by sol–gel method: a review

The development of environmentally friendly process for pretreatments of metallic substrates is a field of growing research due to the ban against chromates used as protective pretreatments. Among the possible candidates for environmentally friendly pretreatments of aluminum alloys are the silica-based sol–gel coatings. Such coatings are able to form an Si–O–Al conversion layer providing a stable alumina/sol–gel film interface, which inhibits the onset of corrosion. Sol–gel technology offers a wide range of chemical mechanisms and exhibits high potential substitutes for the environmentally unfriendly chromate metal-surface pretreatment. Sol–gel derived organo-silicate hybrid coatings, preloaded with organic corrosion inhibitors, have been developed to provide active corrosion protection when integrity of the coating is compromised. The incorporation of organic corrosion inhibitors into hybrid coatings has been achieved as a result of physical entrapment of the inhibitor within the coating material at the stage of film formation and cross-linking. Sol–gel derived coatings, especially the hybrid films, provide a dense barrier against electrolyte uptake, and offer a wide range of applications as corrosion protective, hydrophilic coatings, hydrophobic anti-reflective coatings, migration barriers against liquid and volatile compounds, antibacterial modification of textiles and water-repellent antistatic textiles. In this paper, the novel applications of the sol–gel derived coatings are presented and discussed.     

On the Role of Both Polypropylene Fibers and Silica Nanoparticles on the Viscoelastic Behavior of Silicone Rubber Nanocomposites

In the present study, silica nanoparticles and polypropylene fibers were added to silicone rubber matrix and their effect was investigated on the viscoelastic behavior of silicone rubber composites by dynamic mechanical analysis and compression set test. Bonding of the reinforcements with silicone rubber matrix was studied by Fourier transform infrared spectroscopy (FTIR). The results proved that the role of silica particles on the elastic modulus of silicone rubber was more effective than that of polypropylene at room temperature because of higher stiffness and also partial interaction of polypropylene with matrix.     

Study of chain sequence in the controlled radical telomerization of vinyl acetate with Co(acac)2 catalyst in bulk

A series of porphyrin-containing polymers with triazole rings as linkers have been successfully synthesized by click polymerization. The polycycloadditions of porphyrin-containing dialkyne 1 and 1,4-diazidobenzene 2 were initiated either by simple heating or by Cu(I)-catalyst, affording polymers P1-P8 with relatively high molecular weight. The polymerization process was monitored by gel permeation chromatography analysis. The polymer prepared by thermally initiated click polymerization has unimodal molecular weight distribution and moderate polydispersity index after prolonging reaction time to 170?h. Compared with the metal-free click polymerization, the rate of molecular weight growth in Cu(I)-catalyzed click polymerization declined, leading to relatively low molecular weight of the resulting polymer. The as-synthesized polymers are soluble in common organic solvents and stable at a temperature up to 350?°C. The photophysical properties of the porphyrin monomer and the polymer were investigated by UV?Cvis and fluorescence spectroscopy. This approach offers practical advantages over other synthetic methods used to prepare main-chain porphyrin-containing polymers with regard to the absence of byproducts generated during the polymerization reaction.     

Influence of strain rate on the toughening effect of CaCO3 in polypropylene/CaCO3 composites

The effects of 40 and 50 wt% of calcium carbonate on the mechanical properties of polypropylene were investigated by uniaxial tensile deformation at room temperature and at loading rates of 5, 50, and 125 mm/min. The results showed that the addition of calcium carbonate to polypropylene decreased yield strength while increasing modulus. The decreases yield strength was attributed to the poor adhesion between filler and matrix. The tensile toughness of polypropylene was improved by the addition of calcium carbonate particles at constant strain rate because of the plastic deformation of interparticle ligaments following particle‐matrix debonding. The (strain rate) sensitive behavior of the composites (at constant calcium carbonate content) was observed. J. VINYL ADDIT. TECHNOL., 19:271–275, 2013. © 2013 Society of Plastics Engineers