Microwave assisted synthesis and characterization of olive oil based polyetheramide as anticorrosive polymeric coatings

Virgin olive oil (VOO) based polyetheramide (PEtA) was developed from N-N′-bis(2-hydroxyl ethyl) olive fatty amide (HEOA) and orcinol through condensation polymerization. PEtA was further treated with toluylene 2,4-diisocynate (TDI) with different percentages (20–30 wt%) via addition polymerization to obtain poly(ether amide urethane) (PEtAU). The structural elucidation of HEOA, PEtA and PEtAU were carried out by FT-IR, ¹H NMR and ¹³C NMR spectroscopic techniques. Physico-chemical and physico-mechanical properties of the material were investigated by standard methods. Thermal stability and curing behavior of virgin olive oil, HEOA, and PEtAU were assessed by thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The corrosion behavior was investigated by potentiodynamic polarization measurements in different corrosive environments (3.5 wt% HCl, 5 wt% NaCl, 3.5 wt% NaOH, tap water) at room temperature. The results showed that UPEtA coatings exhibit good physico-mechanical as well as corrosion resistance performance and can be safely used up to 200 °C. The work is an attempt for alternate utilization of olive oil.     

A 5th-order ΣΔ modulator with combination of op-Amp and CBSC circuit for ADSL applications

In this letter, a 5th-Order single-loop low distortion Sigma–Delta Modulator (SDM) is implemented with the combination of the comparator-based switched-capacitor (CBSC)-based and op-amp-based techniques for asymmetric digital subscriber line (ADSL) applications. This structure, which uses integrator (CBSC-based) and IIR filter (op-amp-based) concurrently, has relatively fewer feed-forward paths and modulator coefficients for sensitivity reduction to mismatch. To lower the power consumption of the modulator, the integrators are implemented with CBSC, the IIR filter block is implemented by single OTA, and a passive adder is used to realize the adder at the input of the 5-bit quantizer. The design purpose is minimizing the power consumption while the dynamic performance maintains high. As shown in the simulation result, for a 2-MHz signal bandwidth, the modulator achieves a dynamic range (DR) of 86.5 dB and a peak signal-to-noise and distortion ratio (SNDR) of 85 dB with an oversampling ratio of 8. In addition it consumes 18.75 mW from a 1.8-V power supply at 32 MS/s, which obtains a figure of merit of 1.6e−3.     

An LC-MS Method for Evaluating Photostability of Naloxone Hydrochloride I.V. Infusion

Naloxone is a well-known opioid antagonist indicated for the treatment of CNS （central nervous system） and respiratory depression induced by natural or synthetic opioid in adults and neonates whose mothers have received opioids. While it has been reported that an injection of 0.2 mg/mL of naloxone hydrochloride is physically and chemically stable, data on photostability on continuous i.v. infusion of 0.2 mg/mL of naloxone hydrochloride has not been reported. Therefore, a method was required for assessment of naloxone hydrochloride photostability. A high performance LC-MS （liquid chromatography/mass spectrometry） method was established to evaluate the photostability of naloxone hydrochloride. Injections of naloxone hydrochloride in 0.9% sodium chloride were exposed to artificial light and stored at room temperature （22 ~C） and 37 ~C. Naloxone losses up to 9.79% of its initial concentration when exposed to light at room temperature for 192 h, but the degradation increased up to 14.91% as the storage temperature increase. The disappearance of naloxone hydrochloride was correlated with the appearance of nor-oxymorphonedegradant. Naloxone hydrochloride is photosensitive and degradation increased at highly temperature and light intensity. Therefore, naloxone i.v. infusion solutions should either be protected from light and/or be frequently replaced when being administered to patients.     

Simultaneous effects of polymer concentration,jet-stretching,and hot-drawing on microstructural development of wet-spun poly(acrylonitrile) fibers

Investigation of structural development of acrylic fibers during the early stages of the wet-spinning process has great importance both in carbon fiber and textile industries. The simultaneous effects of increasing polymer concentration, jet-stretching and hot-drawing on porosity, morphology, and mechanical properties of wet-spun poly(acrylonitrile) fibers were studied. The detailed microstructure of the voids was characterized by electron microscopy, porosimetry, and thermoporometry. The effects of jet-stretching/hot-drawing on the overall porosity of the fibers were negligible below a threshold polymer concentration. Increasing polymer concentration from 10 to 20 vol.% reduced the total porosity. Hot-drawing was more effective in reducing the overall porosity of the fibers in comparison with jet-stretching. Stretching and drawing replaced the macrovoids by dense ligaments but did not change the volume fraction of nanovoids, however, shifted nanovoids size distribution toward smaller values. In general, Young’s modulus and elongation at break increased by decreasing overall porosity, however, they depended also on the distribution of voids size and chain orientation along the fiber axis. Strength–diameter correlation showed a good agreement with the Griffith’s theory.     

A mathematical model for prediction of microporosity in aluminum alloy A356

In the present work, a mathematical model was developed based on finite difference method to predict the microporosity distribution in A356 aluminum alloy casting. Heat, mass, and gas conservation equations were solved in this model. Moreover, Darcy’s equation was considered in the mushy zone. Results show that the distribution and concentration of microporosities in cast parts vary with both cooling rate and initial gas content. Simulation results were compared with experimental data where proportionally good agreement with experimental results was found. Finally, a complex cast part was simulated presenting the ability of the model to predict the porosities in industrial cast parts.     

Copper recovery improvement in an industrial flotation circuit: A case study of Sarcheshmeh copper mine

Obtaining high recovery in copper flotation plants has been always under investigation in recent years. Misreported copper into tailing dramatically declines copper recovery. This study aims to find the possible reasons of copper loss to tailing and present the methods to improve the performance of the Sarcheshmeh copper plant flotation circuit. This work was performed in two phases. In the first stage, two surveys were carried out in an industrial plant for evaluation of floatability of two different types of copper ore (sulfide and mixed copper ores comprising sulfide and oxide minerals) and investigation of misreported copper into tailing. In the second stage, influence of particle size distribution in different levels, the collector (Z11 + R407), and sulfidisation agent (NaHS) dosages were investigated on the floatability of mixed copper ore, and possible improvement of copper recovery ores was evaluated by a series of batch flotation experiments.

Almost 95% of overall copper loss in final tailing took place in the rougher circuit. The overall recovery of mixed copper ores was obtained 8% less than the other survey. It was found that an important factor of recovery reduction was due to increasing oxide copper proportion in rougher feed. Results of size-by-size recovery analysis showed that the highest sulfide copper loss occurred in coarse particles (>74 µm) and the highest oxide copper loss happened in fine particles (<9 µm). From batch flotation experiments, it was found that the ultimate recovery increased to a certain value with increasing the collector dosage (50 g/t) and thereafter reduced. Increasing the NaHS dosage to 800 g/t resulted in 4.5% increase in recovery from 79.3% to 83.8% with a significant increase in grade. It is observed that size reduction of coarse particles (>74 μm) of rougher tailing and then their flotation have significant effect on increasing overall recovery from 79.3% to 82.2%. Experimental studies showed that the use of the proposed methods with considering the optimized conditions in the plant can be led to an increase in copper recovery from 79% to 87% without any decrease in grade.     

Production of butanol and polyhydroxyalkanoate from industrial waste by Clostridium beijerinckii ASU10

This study demonstrated a biotechnological approach for simultaneous production of low‐cost H₂, liquid biofuels, and polyhydroxyalkanoates (PHAs) by solventogenic bacterium (Clostridium beijerinckii) from renewable industrial wastes such as molasses and crude glycerol. C beijerinckii ASU10 (KF372577) exhibited considerable performance for hydrogen production of 5.1 ± 0.84 and 11 ± 0.44 mL H₂ h^?1 on glycerol and sugarcane molasses, respectively. The total acetone‐butanol‐ethanol (ABE) generation from glycerol and molasses was 9.334 ± 2.98 and 10.831 ± 4.1 g L^?1, respectively. ABE productivity (g L^?1 h^?1) was 0.0486 and 0.0564 with a yield rate (g g^?1) up to 0.508 and 0.493 from glycerol and molasses fermentation, respectively. The PHA yields from glycerol and sugarcane molasses were 84.37% and 37.97% of the dried bacterial biomass, respectively. Additionally, the ultrathin section of C beijerinckii ASU10 showed that PHA granules were accumulated more densely on glycerol than molasses. Gas chromatography–mass spectrometry (GC‐MS) analysis confirmed that the PHAs obtained from molasses fermentation included 3‐hydroxybutyrate (47.3%) and 3‐hydroxyoctanoate (52.7%) as the main constituents. Meanwhile, 3‐hydroxybutyrate represented the sole monomer of PHA produced from glycerol fermentation. This study demonstrated that C beijerinckii ASU10 (KF372577) is a potent strain for low‐cost PHA production depending on its high potential to produce high‐energy biofuel and other valuable compounds from utilization of organic waste materials.     

Theoretical estimation of the apparent rate constants for ozone decomposition in gas and aqueous phases using ab initio calculations

An ab initio study, using the coupled cluster calculations (CCSD) method was conducted to investigate the kinetics of the ozone degradation in gas and aqueous phases considering the reaction of ozone with the hydroperoxyl radical. Two potential transition state paths, oxygen and hydrogen transfer, are studied and compared. It was revealed by the ab initio quantum chemical calculations that the calculated overall rate constant in the gas phase differs by approximately an order of magnitude from measured values. However, the calculated selectivity (branching fraction), which was measured directly with isotope studies of hydrogen atom transfer, is almost exactly equal to the experimental value at 298.15 K. The sensitivity analysis showed that adding the reaction between ozone and hydroperoxyl radical to the kinetic model accelerates the decomposition process by more than four times in the aqueous phase (pH = 7–8.5), and for an order of magnitude change in the rate constant of this reaction, the decomposition half-life changes by 20–45 %. This result might affect our understanding of atmospheric ozone chemistry.     

Strength and Wear Behavior of Mg Alloy AE42 Reinforced with Carbon Short Fibers

In addition to the advantage of the lightweight of magnesium alloys, magnesium composites have moderate strength and elastic modulus. The proposed application of magnesium composites as diesel truck pistons makes it necessary to assess their wear performance. Little research data have been discussed on wear behavior of Mg alloy AE42 matrix and its composites. Thus, this paper reports wear behavior of magnesium alloy AE42(Mg–Al–Mn—RE; rare earth) and its composite AE42-C, which contains 23 vol% of randomly oriented carbon short fibers. Materials characterization, including density measurements, hardness testing, microstructures investigation, and compression testing at temperatures of 25, 150,and 300 °C, were conducted. Wear tests were performed under various loads and sliding distances. Wear mechanisms were also proposed based on the examination of worn surfaces using optical microscopy and scanning electron microscopy equipped with EDX(energy-dispersive X-ray spectrometry) analysis system. The hardness of AE42-23 vol% C composite is twice the hardness of the Mg matrix alloy AE42. Significant improvements to yield stress and compressive strength at temperatures of 25, 150, and 300 °C of the composite versus the AE42 alloy are achieved. Wear resistance of the composite is improved considerably versus that of the Mg alloy AE42 at the various sliding distances. Smearing of graphite on the worn surface produces a lubricating film that delays change from mild to severe wear of the composite, especially at high loads. EDX analysis of the worn surface shows oxidation of the matrix alloy at higher wear loads, and this mechanism decreases in the presence of carbon fibers under the same loads. Abrasive wear, oxidation, and plastic deformation are the dominant wear mechanisms for the alloy matrix AE42, whereas mainly abrasive wear is the wear mechanism of AE42-23 vol% C composite under the proposed testing conditions.