Bioprocess Scale-up for Acetohydroxamic Acid Production by Hyperactive Acyltransferase of Immobilized Rhodococcus Pyridinivorans

Catalysis Letters - In this study, Rhodococcus pyridinivorans cells containing hyperactive acyltransferase was immobilized on various macromolecules based-polymeric matrices and used to improve...     

Slurry Erosive Wear Evaluation of HVOF-Spray Cr2O3 Coating on Some Turbine Steels

In this study, Cr₂O₃ coatings were deposited on CF8M and CA6NM turbine steels by high-velocity oxy-fuel (HVOF)-spray process and analyzed with regard to their performance under slurry erosion conditions. High Speed Erosion Test Rig was used for slurry erosion tests, and the effects of three parameters, namely, average particle size, speed (rpm), and slurry concentration on slurry erosion of these materials were investigated. SEM micrographs on the surface of samples, before and after slurry erosion tests, were taken to study the erosion mechanism. For the uncoated steels, CA6NM steel showed better erosion resistance in comparison with CF8M steel. The HVOF-sprayed Cr₂O₃-coated CF8M and CA6NM steels showed better slurry erosion resistance in comparison with their uncoated counterparts. It may be due to the higher hardness as a result of HVOF-sprayed Cr₂O₃ coating in comparison with the uncoated CF8M and CA6NM steels.     

Osmium(VIII)/Ruthenium(III) Catalysed Oxidation of l-lysine by Diperiodatocuprate(III) in Aqueous Alkaline Medium: A Comparative Mechanistic Approach by Stopped Flow Technique

Abstract The kinetics of osmium(VIII) and ruthenium(III) catalysed oxidation of l-lysine (l-lys) by diperiodatocuprate(III) (DPC) in alkaline medium at a constant ionic strength of 0.15 mol dm⁻³ was studied spectrophotometrically. The reaction between l-lys and DPC in alkaline medium exhibits 1:2 stoichiometry in both catalysed reaction (l-lys: DPC). The reaction is first order in [DPC] and has less than unit order both in [l-lys] and [alkali]. Increase in periodate concentration decreases the rate. Intervention of free radicals was observed in the reaction. The main products were identified by spot test, IR and GC-MS studies. Probable mechanisms are proposed and discussed. The reaction constants involved in the different steps of the mechanism are calculated. The activation parameters with respect to the slow step of the mechanism are computed and discussed and thermodynamic quantities are also determined. It has been observed that the catalytic efficiency for the present reaction is in the order of Os(VIII) > Ru(III). The active species of catalyst and oxidant have been identified. Graphical Abstract The kinetic and mechanistic investigations of the reaction between DPC and l-lysine has been studied in presence of microamounts of ruthenium(III) and osmium(VIII) in alkaline medium. The monoperiodatoargentate(III), [Ru(H₂O)₅OH]²⁺ and [OsO₄(OH)₂]²⁻ are considered as the active species of oxidant, DPC, ruthenium(III) and osmium(VIII) respectively.      

Study on microhardness,dynamic mechanical,and tribological properties of PEEK/Al2O3 composites

The wear and friction properties of poly (ether‐ether‐ketone) (PEEK) reinforced with 0–33 vol % (60 wt %) micron size Al₂O₃ composites were evaluated at a sliding speed of 1.0 m/s and nominal pressure from 0.5 to 1.25 MPa under dry sliding conditions using a pin‐on‐disk wear tester. The wear resistance of the pure PEEK is 10‐fold higher than that of mild steel under the similar test condition. It is improved to 18‐fold as compared with mild steel at 3.5 vol % Al₂O₃ content. The improvement in wear properties may be attributed to the thin, tenacious, and coherent transfer film formed between the steel countersurface and composite pin. However, the wear resistance of PEEK containing above 3.5 vol % Al₂O₃ was deteriorated, despite their higher hardness and stiffness as compared with that of composites containing lower Al₂O₃ content. This is attributed to the formation of thick and noncoherent transfer film, which does not prevent the wear of the composites from hard asperities of countersurface. Moreover, hard Al₂O₃ particles present in transfer film act as third body wear mechanism. The coefficient of friction of the composites is higher than that of pure PEEK. SEM and optical microscopy have shown that wear of pure PEEK occurs by the mechanism of adhesion mainly whereas of PEEK composites by microploughing and abrasion. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Nanoenergetic Composites of CuO Nanorods,Nanowires, and Al‐Nanoparticles

This paper reports on the synthesis of the nanoenergetic composites containing CuO nanorods and nanowires, and Al‐nanoparticles. Nanorods and nanowires were synthesized using poly(ethylene glycol) templating method and combined with Al‐nanoparticles using ultrasonic mixing and self‐assembly methods. Poly(4‐vinylpyridine) was used for the self‐assembly of Al‐nanoparticles around the nanorods. At the optimized values of equivalence ratio, sonication time, and Al‐particle size, the combustion wave speed of 1650 m s⁻¹ was obtained for the nanorods‐based energetics. For the composite of nanowires and Al‐nanoparticles the speed was increased to 1900 m s⁻¹. The maximum combustion wave speed of 2400 m s⁻¹ was achieved for the self‐assembled composite, which is the highest known so far among the nanoenergetic materials. It is possible that in the self‐assembled composites, the interfacial contact between the oxidizer and fuel is higher and resistance to overall diffusional process is lower, thus enhancing the performance.     

Blends of cardanol-based epoxidized novolac resin and CTBN for application in surface coating: a study on thermal,mechanical, chemical,and morphological characteristics

Blend samples of cardanol-based epoxidized novolac resin and different weight percentages of carboxyl-terminated butadiene acrylonitrile (CTBN) were developed and cured with stoichiometric amounts of aliphatic amine. The formation of various products during the curing of blend samples has been studied by Fourier-transform infrared spectroscopy. The dynamic differential scanning calorimeter scans showed that the pure epoxies and their blend samples with CTBN cured in the temperature range of 100–150°C. The blend sample containing 15 wt% CTBN showed the least cure time (at 120°C) among all other blend samples. Upon evaluation, it was found that blend samples exhibit better properties compared to pure epoxy resin in terms of increase in impact strength and elongation-at-break of the casting and gloss, scratch hardness, adhesion, and flexibility of the film. The improvement in these properties indicates that the rubber modified resin would be more durable than the epoxy based on cardanol. Chemical and morphological properties of the formulated resins were also determined. The thermal stability of the blend samples containing 15 wt% CTBN in epoxy resin was the highest among all other prepared systems. The blend morphology, studied by scanning electron microscope, showed the presence of precipitated discrete rubber particles, which dispersed throughout the epoxy matrix—i.e., they revealed the presence of two-phase morphological features.     

Current efficiency in electro-winning of lanthanum and cerium metals from molten chloride electrolytes

The objective of this study is to prepare lanthanum and cerium metals by fused salt electrolysis of their anhydrous chloride in molten media such as LiCl-KCl, NaCl-KCl, KCl, NaCl, and LiCl and to characterize the metal deposit by X-ray diffraction, energy dispersive X-ray fluorescence, and inductive coupled plasma-atomic emission spectroscopy. Deposit metal of purity more than 99 % was obtained in each of the experiments. The entire process starting from preparation of anhydrous lanthanum/cerium chloride to electrolysis yielding of metal deposits has been described. The effect of process parameters such as temperature, electrolyte composition, and current density on the current efficiency was studied. All these parameters were varied to get the highest current efficiency and metal yield. The major non-rare earth impurities with the deposit are found to be Fe, Cr, and Ni along with ～1×10-3 of total gaseous impurities.     

The location of pyridine in sodium–silver–Y zeolite by powder synchrotron X-ray diffraction

The powder synchrotron X-ray diffraction pattern of a mixed sodium–silver–Y zeolite, Ag_56−xNa_xSi₁₃₆Al₅₆O₃₈₄ x≈19, saturated with pyridine, has been analysed by the Rietveld method to reveal positions for the adsorbed molecules. Cations are distributed over three sites, SII, constrained to 100% occupancy, with 17.2(1) and 14.8(1) Ag(1) and Na(1) ions per unit cell, respectively, SI′ with 18.3(1) Ag(2) ions per cell, and SI with 1.8(1) Ag(3) ions per cell. The refinement suggests that approximately 7.5 pyridine molecules are adsorbed per supercage, located in two sites within the cavities of the zeolite. Pyridine(1) is in the 12-ring window connecting supercages. Three molecules project through each window and approach the SII cations in a supercage, with an average Ag(1)–N distance of 3.17(2) Å. An SII cation can be linked to three pyridine(1) molecules from three separate windows. These sites are full with 5.98(2) molecules per supercage. Pyridine(2) is found in the supercage, oriented with its π electron density towards the SII cations, with its centre at 2.87(2) Å from Ag(1). The average occupancy was fixed at 1.5 molecules per supercage, corresponding to 20% of the pyridine content. A local ordering scheme can be postulated, whereby alternate supercages are filled by pyridine(1) and pyridine(2) molecules, efficiently filling the channels of the zeolite.     

Parametric study of a reverse flat plate absorber cabinet dryer: A new concept

In this communication, the concept of reverse flat plate collector has been used as a heating medium of air for the drying of agricultural products in a cabinet dryer. The reverse flat plate absorber is a non-concentrating collector which can collect solar heat at high temperature unlike conventional nonconcentrating collectors. The thermal performance of the proposed dryer is analyzed by solving the various energy balance equations. An attempt has been made to optimize the vent area of the dryer for speedy flow of humid air from the drying chamber to the atmosphere. In order to have parametric studies, numerical computations have been carried out for a typical day in June for Delhi climatic conditions. The performance of this system is compared with that of conventional cabinet dryers. It is found that the reverse flat plate absorber dryer gives the better performance.