Single-phase current-source-boost inverter for renewable energy sources

This paper presents a new methodology for the operation and control of a single-phase current-source (CS) Boost Inverter, considering that the conventional CS boost inverter has a right-half-plane (RHP) zero in its control-to-output transfer function, and this RHP zero causes the known non-minimum-phase effects. In this context, a special design with low boost inductance and a multi-loop control is developed in order to assure stable and very fast dynamics. Furthermore, the proposed inverter presents output voltage with very low total harmonic distortion (THD), reduced components and high power density. Therefore, this paper presents the inverter operation, the proposed control technique, the main simulation results and a prototype in order to demonstrate the feasibility of the proposal. © 2011 IEEE.

Rumen microbial diversity under influence of a polyclonal antibody preparation against lactate-producing and proteolytic bacteria in cows fed different energy sources

Nine ruminally cannulated cows fed different energy sources were used to evaluate an avianderived polyclonal antibody preparation against specific ruminal bacteria and monensin on microbial community diversity. The experimental design was three Latin squares 3 x 3 distinguished by the main energy source in the diet [dry-ground corn grain, high moisture corn silage or citrus pulp]. Inside each Latin square, animals received one of the feed additives per period [control, monensin or polyclonal antibody preparation]. Each period lasted 21 days where 20 were used for treatments adaptation and the last one for sampling collection. Microbial diversity was evaluated by protozoa counts and denaturing gradient gel electrophoresis. Polyclonal antibodies plus citrus pulp (CiPu) addition in the diet resulted in an increase of relative counting of Isotricha protozoa that indicates a possible effect on this ruminal ciliate population. In general lines, in the present experiment, it was not possible to assign that there was a pattern in the structures of amplification of Bacteria and Archaea communities of the ruminal content. Oral passive immunization is a technology that arises as an effective alternative for feed additive production. Further research is still necessary to better understand its mechanisms of action.

Occurrence of sensitivity during at-home and in-office tooth bleaching therapies with or without use of light sources

The aim of this study was to evaluate the effect of tooth bleaching with 10% carbamide peroxide (CP) or 35% hydrogen peroxide (HP), with or without quartz-tungsten-halogen light or hybrid source LED/infrared laser exposition on the occurrence duration, intensity and location of tooth sensitivity Forty patients were selected and randomly divided into four groups: GI--home bleaching with CP for 4 hours a day, over the course of 3 weeks; GII--three sessions of HP with three 10-minute applications at each session and no light source; GIII--the same procedure as GII with quartz-tungsten-halogen light irradiation; GIV--the same procedure as GII with LED/laser light irradiation. The evaluation included an appointment with each patient before and after each HP bleaching session or each weekly CP bleaching and 7, 30 and 180 days after the end of treatment. The Kruskal-Wallis test revealed that the duration and intensity of post-treatment sensitivity were significantly higher for HP than for CP (p< 0.05), and symptoms were located predominantly in anterior teeth. All bleaching methods generated sensitivity, which was more frequent in anterior teeth. However, treatment with CP generated lower sensitivity than treatment with HP independently of the light sources.

Fermentation characteristics of several carbohydrate sources for dog diets using the in vitro gas production technique

Fermentable carbohydrates are an important part of the canine diet. They can improve gastrointestinal health by modifying gut microbial population and metabolic activity. The present study compared the fermentation characteristics and kinetic patterns of 10 carbohydrate sources using the in vitro gas production technique (IVGPT) with dog faecal inoculum. The substrates tested were: pure cellulose (PC), carboxymethylcellulose (CMC), sugar-cane fibre (SCF), beet pulp (BP), wheat bran (WB), fructooligosaccharides (FOS), inulin, yeast cell wall (YCW), ground psyllium seed (PS), pea hulls (PH). All substrates were incubated at 39°C under anaerobic conditions with faeces collected from dogs as microbial inoculum. Gas production of fermenting cultures was recorded and after 48 h, pH, shortchain fatty acids (SCFA) and organic matter disappearance (OMD) were determined. The results confirm high fermentation by dog faecal bacteria of FOS and inulin that produced high amounts of propionate and that underwent very rapid fermentation. Three substrates (SCF, CMC and PC) were not able to support bacterial growth, with low gas and SCFA production, and high BCFA formation. The PH and BP showed moderate OMD and SCFA production. Wheat bran B underwent rapid fermentation and generated a high proportion of butyrate. Psyllium seeds underwent slow fermentation with delayed gas production, supporting a high formation of SCFA, with an adequate amount of butyrate for bacterial growth while YCW, which showed a delayed fermentation, gave moderate SCFA production. The fermentation characteristics of PS and YCW suggest their potential use in promoting a more distal fermentation on intestinal tract. © Copyright S. Calabrò et al., 2013 Licensee PAGEPress, Italy.

Supplementation of diets for Santa Ines sheep with organic and inorganic zinc sources

This research was conducted with objective to evaluate the effect of different zinc (Zn) sources and doses in the diet for Santa Ines sheep. Forty lambs at weaning, with 18.4 kg of body weight were supplemented with three different sources of zinc (zinc oxide (ZnO), zinc amino acid and zinc proteinate) and three doses of zinc (200, 400 and 600 mg/kg DM) added to the basal diet. At every 28 days, animals were weighted and blood samples were collected for analyses of zinc (Zn), alkaline phosphatase and immunoglobulin G (IgG) and M (IgM). At the end of experiment, liver samples were collected for determination of the hepatic zinc levels. Zinc was analyzed with atomic absorption spectrophotometer, while phosphatase alkaline and immunoglobulins G and M were analyzed using Laborlab and Bioclin kits, respectively. There was no effect of diets on phosphatase alkaline levels and hepatic zinc, but there was difference in the plasmatic zinc levels and IgG and IgM levels. Based on the accumulation of hepatic zinc, the estimate of the zinc bioavailability, through the regression equation, showed that supplementation with organic and inorganic sources of zinc did not differ in the diet of Santa Ines sheep. © 2012 Sociedade Brasileira de Zootecnia.

Lipid and selenium sources on fatty acid composition of intramuscular fat and muscle selenium concentration of Nellore steers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of carbon and nitrogen sources on lipase production by a newly isolated Candida viswanathii strain

Microorganisms can produce lipases with different biochemical characteristics making necessary the screening of new lipase-producing strains for different industrial applications. In this study, 90 microbial strains were screened as potential lipase producers using a sensitive agar plate method with a suitable medium supplemented with Tween 20 and also a liquid culture supplemented with olive oil. The highest cell growth and lipase production for Candida viswanathii were observed in triolein and oleic acid when used as the only pure carbon source. Renewable low-cost triacylglycerols supported the best cell growth, and olive oil was found to be the best inducer for lipase production (19.50 g/L and 58.50 U). The selected conditions for enzyme production were found with yeast extract as nitrogen source and 1.5 % (w/v) olive oil (85.70 U) that resulted in a good cell growth yield (YX/S = 1.234 g/g) and lipase productivity (1.204 U/h) after 72 h of shake-flask cultivation. C. viswanathii lipase presented high hydrolytic activity on esters bonds of triacylglycerols of long-chain, and this strain can be considered an important candidate for future applications in chemical industries. © 2012 Springer-Verlag Berlin Heidelberg and the University of Milan.

Use of different carbon sources in cultivation of baker's yeast for production of glycerol-3-phosphate dehydrogenase

The physiological state of yeast cells changes during culture growth as a consequence of environmental changes (nutrient limitations, pH and metabolic products). Cultures that grow exponentially are heterogeneous cell populations made up of cells regulated by different metabolic and/or genetic control systems. The strain of baker's yeast selected by plating commercial compressed yeast was used for the production of glycerol-3- phosphate dehydrogenase. Glycerol-3-phosphate dehydrogenase (GPD) has been widely used in the enzyme assays with diverse compounds of industrial interest, such as glycerol or glycerol phosphate, as well as a number of important bioanalytical applications. Each cell state determines the level of key enzymes (genetic control), fluxes through metabolic pathways (metabolic control), cell morphology and size. The present study was carried out to determine the effects of environmental conditions and carbon source on GPD production from baker's yeast. Glucose, glycerol, galactose and ethanol were used as carbon sources. Glycerol and ethanol assimilations required agitation, which was dependent on the medium volume in the fermentation flask for the greatest accumulation of intracellular GPD. Enzyme synthesis was also affected by the initial pH of the medium and inoculum size. The fermentation time required for a high level of enzyme formation decreased with the inoculum size. The greatest amount of enzyme (0.45 U/ml) was obtained with an initial pH of 4.5 in the medium containing ethanol or glycerol. The final pH was maintained in YP-ethanol, but in the YP-glycerol the final pH increased to 6.9 during growth.

Photo-Fenton degradation kinetics of low ciprofloxacin concentration using different iron sources and pH

The aim of the present study was to compare the degradation kinetics of low (1 mg L-1) and high (25 mg L-1) concentrations of ciprofloxacin (CIP) aiming to decrease the concentration of additives and evaluate the pH limitation by the use of low iron concentrations and organic ligands. A parameterized kinetic model was satisfactorily fitted to the experimental data in order to study the performance of photo-Fenton process with specific iron sources (iron citrate, iron oxalate, iron nitrate) under different pH medium (2.5, 4.5, 6.5). The process modeling allowed selecting those process conditions (iron source, additives concentrations and pH medium) which maximize the two performance parameters related to the global equilibrium conversion and kinetic rate of the process. For the high CIP concentration, degradation was very influenced by the iron source, resulting in much lower efficiency with iron nitrate. At pH 4.5, highest TOC removal (0.87) was achieved in the presence of iron citrate, while similar CIP conversions were obtained with oxalate and citrate (0.98 after 10 min). For the low CIP concentration, much higher conversion was observed in the presence of citrate or oxalate in relation to iron nitrate up to pH 4.5. This behavior denotes the importance of complexation also at low dosages. Appropriate additives load (320 μM H 2O2; 6 μM Fe) resulted in a CIP conversion of 0.96 after10 min reaction with citrate up to pH 4.5. © 2013 Elsevier B.V. All rights reserved.

Acceso a las fuentes de información estadística sobre el comercio exterior de América Latina = Access to information sources on Latin American foreign trade statistics

Incluye Bibliografía

Resolución 437(XIX): Acceso a las fuentes de información = Resolution 437(XIX): Access to sources of information = Résolution 437(XIX): Accès aux sources d'information

Publicado separadamete en cada idioma

United Nations Conference on New and Renewable Sources of Energy: its relevance for CDCC Member States

Includes bibliography

Lineamientos sobre la utilización de las fuentes estadísticas en cálculos de distribución del ingreso en América Latina = Guidelines for the use of statistical sources in calculations of income distribution in Latin America

Incluye Bibliografía