Fabrication of Aligned Poly(L‐lactide) Fibers by Electrospinning and Drawing

A new target collector was designed for taking up aligned nanofibers by electrospinning. The collector consists of a rotor around which several fins were attached for winding electrospun filaments continuously in large amounts. The alignment of the nanofibers wound on the collector was affected by the electrospinning conditions, such as the needle‐to‐collector distance and the applied voltage, but not by the rotation speed of the collector. At a voltage of 0.5 kV · cm^?1, about 60% of the fibers were found to be aligned within an angle of ± 5° relative to the rotational direction of the collector. The fiber alignment was improved to 90% by drawing the fiber bundle 2–3 times at 110 °C. The drawing was also effective for crystal orientation of the fibers as revealed by WAXD. The drawn fibers show improved mechanical properties.

     

Ultrasonic and mechanical measurements for the detection of crosslink density of SBR and NBR based on various curing systems

The stress–strain measurements of styrene‐butadiene rubber (SBR) samples based on various curing systems were used to access the crosslink density of various rubber mixes. Same materials were subjected to various uniaxial compression strains. The thicknesses before compression and after recovery were recorded. After recovery, pulse echo method was used to measure the ultrasonic velocity for the dilatational wave and that of shear wave at a frequency of 2 MHz and at room temperature. Both of the ultrasonic velocities were used to determine the elastic moduli of the samples. The relation between the elastic moduli and the corresponding recovery values were used to determine the crosslink density of samples. The crosslink density values obtained from the two techniques were compared. Butadiene‐acrylonitrile (NBR) rubber mix was used to show that the ultrasonic technique is applicable for other rubber compounds. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A fourth-order switched capacitor cascade structure for sigma-delta converters

This paper gives details of the design of a switched capacitor circuit for use in oversampling sigma-delta analogue-to-digital converters. the circuit is a fourth-order cascade of two second-order sections. Comparison with other multistage structures is also presented. It is shown that the proposed design has advantages over the possible alternative cascade of four first-order sections. It is also shown that it gives certain improvements in performance over the popular third-order cascade of a second-order and a first-order section, thus justifying the use of a higher order under the given technology and tolerance constraints.     

Tissue concentrations and pharmacokinetics of florfenicol in broiler chickens

OBJECTIVE: To compare the Bard BTA (bladder tumour antigen) test with voided urine cytology (VUC) in the diagnosis of recurrent bladder cancer (BC). METHODS: Urine specimens for the BTA test and VUC were collected on the same day as before cystoscopy from patients undergoing routine surveillance cystoscopy for recurrent BC. The pathologists performing VUC were blinded to the results of the BTA test. RESULTS: BC was identified by cystoscopy and biopsy in 39 of 164 study participants. The overall sensitivities of the BTA test and VUC were 54 and 28%, respectively (p < 0.05). The BTA test was more sensitive than VUC for all tumour stages and grades. For > or = T2 tumours and grade 3 tumours, respectively, the difference was statistically significant (p < 0.05). The specificities of the BTA test and VUC were 92 and 97%, respectively. Both a false-positive BTA test and VUC were found to predict recurrence. CONCLUSION: The BTA test is equal or superior to VUC in the detection of BC in patients undergoing routine surveillance for recurrent BC.     

Improvement of the compatibility of natural rubber/ethylene–propylene diene monomer rubber blends via natural rubber epoxidation

The longitudinal ultrasonic velocity, longitudinal ultrasonic absorption (attenuation coefficient), glass‐transition temperature, and Mooney viscosity for epoxidized natural rubber/ethylene–propylene diene monomer blends were measured. The variation of the longitudinal ultrasonic velocity with the blend ratios was linear, indicating a compatible system in comparison with the same system without epoxidation (natural rubber/ethylene–propylene diene monomer), which was incompatible. Also, the behavior was confirmed by heat of mixing calculations as well as Mooney viscosity measurements. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2816–2819, 2002     

Effect of annealing on the structural and electrical properties of In2Te3

Amorphous In2Te3 was prepared in both bulk form, by quenching the molten material, and thin-film form, by the thermal evaporation technique. X-ray diffraction analysis showed that the prepared samples in bulk and as-deposited thin-film forms were in the amorphous state. - and -phases of In2Te3 were prepared by annealing bulk samples at 615 and 813 K, respectively. Films annealed at 573 K give -phase polycrystalline structure. The electrical conductivity for the as-deposited In2Te3 films increases with increasing film thickness. The conduction activation energy, E, of the as-prepared bulk and thin film samples were found to be 0.516 and 0.521 eV. The corresponding values of room-temperature electrical conductivity, RT, for these samples are 1.1×10-6 and 7.15×10-7-1m-1, respectively. The observed change in the value of RT may be due to the difference in the structure of bulk and thin-film samples. The increase of E with annealing temperature for both bulk and thin-film samples is interpreted in terms of the density of states model proposed by Mott and Davis. © 1998 Chapman & Hall     

Utilization of emulsion polymer for preparing bagasse fibers polymer–cement composites

Sugarcane‐bagasse fiber–polymer cement composites were prepared using three lattices namely, styrene butadiene, vinyl ester, and styrene acrylic. The lattices percentages ranged between 3 and 21% from the weight of the mixture. The pressed samples were irradiated at different irradiation doses by using electron beam (EB) accelerator. Comparative studies have been made for physicomechanical properties of unirradiated and irradiated samples. The results indicated that the flexural strength, modulus of elasticity, and impact toughness of the composites increase with the increasing polymer content up to 9.9 and 15% of styrene butadiene, vinyl ester, and acrylic styrene, and then decrease. It was also observed that the maximum values of flexural strength and modulus of elasticity obtained at EB‐irradiation dose 45, 40, and 25 kGy for styrene butadiene, acrylic ester, and vinyl ester, respectively. The impact strength of the composites did not significantly improve above 10 kGy. The average values of hardness of irradiated composites were higher than that those of unirradiated and control composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Cucurbitacins of Cucumis prophetarum and Cucumis prophetarum

Cucurbitacin B, isocucurbitacin B, dihydrocucurbitacin B, cucurbitacin E, dihydrocucurbitacin E, isocucurbitacin D, dihydroisocucurbitacin D, cucurbitacin I, dihydrocucurbitacin I, cucurbitacin Q1, and dihydrocucurbitacin Q1 were identified for the first time as constituents of Cucumis prophetarum L.. Cucurbitacin B, cucurbitacin O, cucurbitacin P, cucurbitacin Q1, dihydrocucurbitacin Q1, isocucurbitacin E, and dihydroisocucurbitacin E also were identified as constituents of C. prophetarum Jusl. ssp. Dissectus. Isocucurbitacin E and dihydroisocucurbitacin E were isolated for the first time in nature. The chemical structures were determined with extensive spectroscopic analysis including 2D NMR, ¹H NMR, ¹³C NMR, correlated spectroscopy (COSY), heteronuclear chemical shift correlation (HETCOR), attached proton test (APT), and distortionless enhancement by polarization transfer (DEPT).     

Sequential chemical treatment of radium species in TENORM waste sludge produced from oil and natural gas production

This paper is dedicated to the treatment of sludge occurring in frame of the Egyptian produced from oil and gas production. The activity levels of three radium isotopes: Ra-226 (of U-series), Ra-228 and Ra-224 (of Th-series) in the solid TENORM waste (sludge) were first evaluated and followed by a sequential treatment for all radium species (fractions) presented in TENORM. The sequential treatment was carried out based on two approaches 'A' and 'B' using different chemical solutions. The results obtained indicate that the activity levels of all radium isotopes (Ra-226, Ra-228 and Ra-224) of the environmental interest in the TENORM waste sludge were elevated with regard to exemption levels established by IAEA [International Atomic Energy Agency (IAEA), International basic safety standards for the protection against ionizing radiation and for the safety of radiation sources. GOV/2715/Vienna, 1994]. Each approach of the sequential treatment was performed through four steps using different chemical solutions to reduce the activity concentration of radium in a large extent. Most of the leached radium was found as an oxidizable Ra species. The actual removal % leached using approach B was relatively efficient compared to A. It is observed that the actual removal percentages (%) of Ra-226, Ra-228 and Ra-224 using approach A are 78+/-2.8, 64.8+/-4.1 and 76.4+/-5.2%, respectively. Whereas in approach A, the overall removal % of Ra-226, Ra-228 and Ra-228 was increased to approximately 91+/-3.5, 87+/-4.1 and 90+/-6.2%, respectively.