Sol-Gel Synthesis of Lithium Aluminate

LiAlO₂ was prepared by two sol-gel methods using simultaneous hydrolysis of the reagents: aluminum sec -butoxide/ lithium methoxide and aluminum sec -butoxide/LiOH. The resulting ceramic powders were compared with those prepared by two conventional methods (i.e., solid-state fusion and peroxide). The sol-gel method provided powders with a very high γ-LiAlO₂ content after calcining at temperatures as low as 700°C when LiOH was used. The solids were characterized by AAS, DTA, TGA, XRD, and SEM.     

SOLAR GRAIN DRYING IN HUMID AND HOT-TEMPERATE CLIMATES

A natural solar drying system has been tested with wheat. Simple solar collectors give the small temperature rise needed for low temperature drying. The system, with a capacity of 35 tomes, is placed in a region of humid hot-temperate climate. It has been designed to dry all the locally produced grain (wheat, corn, soybean, sunflower, sorghum, etc.), without a supplemental heat source.

Two different types of solar collectors of the same effective area were tested, with one a storage-collector and the other a bare plate collector

Data from four field tests performed between 1981 and 1983 are given and discussed. The mean mass of water removed from the wheat per hour was of 6.54 kg, under an average air flow of 4.3 m3 /min. tonne     

Evaluation of flow cell detector configurations combining simultaneous preconcentration and scintillation detection for monitoring of pertechnetate in aqueous media

Flow cell detectors were developed for simultaneous concentration and scintillation detection of technetium-99 in water. Evaluated flow cell geometries consisted of a coil and a fountain flow cell design; the latter is based on radial solution flow through a resin bed interfaced with a photomultiplier tube through a polycarbonate window. The sorptive scintillating media investigated were (1) an extractive scintillator combining a porous polystyrene resin with the extractant Aliquat-336 and fluor 2-(1-naphthyl)-5-phenyloxazole, (2) a mixed bed of organic scintillator (BC-400) and Tc-selective resin (TEVA), and (3) a mixed bed of inorganic scintillator particles (CaF2-Eu) with either TEVA resin or strong base anion-exchange resin (Dowex 1 x 8-400(Cl)). Depending on flow cell geometry and medium, the detection efficiencies for 99Tc ranged from 7.26 (BC-400/TEVA in coil geometry) to 50.20% (CaF2(Eu)/Dowex 1 x 8-400(Cl) in fountain flow cell geometry). The configuration with the highest sensitivity, CaF2(Eu)/Dowex 1 x 8-400(Cl) in coil geometry, can detect 99Tc as low as 3.78 Bq L(-1) for a 100-s count interval and a 200-mL sample, which is below the current regulatory level of 33 Bq L(-1). The issue of sensor reusability was addressed in this research, and its potential application at near neutral pH was demonstrated. The optimal sensor design was evaluated with a 99Tc-spiked synthetic groundwater matrix.     

Carrier Frequency Offset Estimation using Data-Dependent Superimposed Training

In this letter we propose, for the first time, a solution to the problem of carrier frequency offset (CFO) estimation within the data dependent superimposed training (DDST) framework for channel estimation. While time division multiplexed (TDM) trained systems can use the TDM sequence to determine the CFO, the original attraction of DDST for channel estimation was that it avoided any TDM training. So in this letter we show how CFO estimation can still be very effectively performed with the DDST algorithm, while continuing to preclude the need for any additional bandwidth-consuming TDM training. Finally, simulations are presented that verify the theoretical results.     

Modeling and hybrid simulation of slow discharge process of adsorbed methane tanks

The slow discharge process of a methane tank filled with porous carbonaceous adsorptive material is modelled and solved by the Integral Transform Method, yielding a hybrid numerical-analytical solution of the related energy equation. A transient one-dimensional nonlinear formulation is adopted, which includes the compressed and adsorbed gas thermal capacitances, the reservoir wall thermal capacitance effect and the gas compressibility influence. The overall mass balance is employed to determine the pressure field evolution, here assumed as spatially uniform. A thorough covalidation analysis is performed, with both numerical and experimental data available in the literature, and the relative importance of some terms in the energy equation formulation is inspected. Finally, different possibilities for the reduction of the adverse effect of the heat of adsorption on storage capacity are proposed and investigated.     

High-Performance Liquid Chromatography Method for the Monitoring of the <Emphasis Type="Italic">Allium</Emphasis> Derivative Propyl Propane Thiosulfonate Used as Natural Additive in Animal Feed

A new simple analytical method for monitoring propyl propane thiosulfonate (PTSO) in animal feed is presented. PTSO is an active ingredient from Allium spp. (like onion and shallot), proposed as a natural additive for feed being an efficient alternative to antibiotics used as growth promoter due to its efficiency improving animal health. Reversed-phase liquid chromatography with UV detection has been used and a previous sample treatment based on solid-liquid extraction has been developed and optimized in order to extract PTSO from a feed for laying hens using acetone as extraction solvent. The method has been characterized obtaining limits of detection and quantification of 11.2 and 37.3 mg kg^?1, respectively, which are lower than the concentrations expected in samples containing this additive. The intra- and interday relative standard deviations (RSDs) were lower than 8.3 % in all the cases, and recoveries varied from 90.2 to 94.6 %. Finally, in order to check the unequivocal identification of PTSO, mass spectrometry detection was applied. The proposed method is a simple procedure for monitoring PTSO in commercial feed, being possible to implement it in routine laboratories for quantification purposes and stability studies of the distributed products.     

Resistance of Vigna unguiculata (cowpea) seeds to Callosobruchus maculatus is restricted to cotyledonary tissues

We have investigated the survival of Callosobruchus maculatus larvae when reared on resistant IT81D 1045 Vigna unguiculata seeds, whose resistance has been associated with variant forms of vicilins. Here, we present data which show that larvae of C. maculatus feeding on embryonic axis of resistant cowpea reach a mass of around 28 times higher than those feeding on cotyledonary tissues. Additionally, incorporation of 5–10% of embryonic axis flour on artificial seeds made of resistant flour restores toxicity of seeds to the bruchid. Vicilins purified from both susceptible and resistant embryonic axis had no deleterious effects either on insect development or on insect survival until a level of 4% of incorporation. In contrast, vicilins from resistant cotyledons show an LD₅₀ (50% lethal dose) and WD₅₀ (half weight dose) of 2%. Total vicilin contents of embryonic axes were around two times lower than in cotyledonary tissues, while proteolytic activities of all four proteinase classes were always higher in the former tissues. By 2D‐PAGE we visualized eight protein spots, which seem to be exclusively found on resistant cotyledons. Copyright © 2006 Society of Chemical Industry     

A Comparative Biochemical Characterization of Microbial Transglutaminases: Commercial vs. a Newly Isolated Enzyme from <Emphasis Type="Italic">Streptomyces</Emphasis> Sp.

A new microbial transglutaminase (MTGase or MTG, EC 2.3.2.13) from a Streptomyces sp. strain isolated from Brazilian soil samples was characterized in crude and purified forms. The aim of this work is to provide relevant information about a new transglutaminase and to compare its characteristics with the well-known commercial transglutaminase from Ajinomoto Co. Inc. (Activa® TG-BP). The enzyme from Streptomyces sp., in both crude and pure forms, exhibited optimal activity in the 6.0–6.5 pH range and at 35–40°C. The results for the commercial enzyme were the same. A second maximum of activity was observed at pH 10.0 with both the crude Streptomyces sp. enzyme and the commercial enzyme. This interesting fact has not been reported in the literature previously. The fact that this second maximum of activity does not appear on the purified form of the enzyme may suggest the presence of an isoenzyme on the crude extract. All of the enzymes tested were stable over the pH range from 4.5 to 8.0 and up to 45°C. The decline in activity of the commercial transglutaminase above 45°C and pH 8.0 was more gradual. The activities of all the MTG samples were independent of Ca⁺² concentration, but they were elevated in the presence of K⁺, Ba²⁺, and Co²⁺ and inhibited by Cu²⁺ and Hg²⁺, which suggests the presence of a thiol group in the MTG’s active site. The purified enzyme presented a K _m of 6.37 mM and a V _max of 1.7 U/mL, while the crude enzyme demonstrated a K _m of 6.52 mM and a V _max of 1.35 U/mL.