Aerobic biological treatment of wastewaters containing dichloromethane

BACKGROUND: Volatilization has been advanced as one of the predominant phenomena contributing to volatile organic carbon emissions from wastewater treatment plants (WWTPs). In this study, strategies for minimizing such air stripping losses when treating a liquid stream containing dichloromethane (DCM), aiming at decreasing the overall emission inventory from WWTPs, were investigated. RESULTS: System R1, consisting of a continuous flow stirred tank reactor (CSTR) treating a liquid stream containing DCM at a concentration of 12 mmol dm−3 presented a biodegradation efficiency (BE) of 68%, based upon chloride release, with 10% of measurable losses, mainly due to volatilization, and 22% of unmeasurable losses. System R2 introduced operational designs aiming at decreasing DCM volatilization. In Experiment R2.1, a biotrickling filter, through which the air stripped from the CSTR was driven, was introduced leading to a reduction from 10% to 7% on the measurable losses. In Experiment R2.2, the air stripped from the CSTR was recirculated at a flow rate of 2.4 dm3 h−1 through the reactormedium before entering the biotrickling filter. The BE was improved from 69% to 82% and the losses associated with air stripping were successfully reduced to 2%. The proposed design, including air recirculation and the biotrickling filter, increased the ratio between the biodegradation rate and the volatilization rate from 7 to 41. CONCLUSIONS: Recirculation of the gaseous effluent through the reactor medium, which allowed for higher residence time within the bioreactor, was shown to be a successful strategy for improving the treatment process, thus minimizing DCM volatilization losses

GENERACIÓN DE HAZ CON MOMENTO ANGULAR ORBITAL REGISTRADO EN CRISTAL FOTORREFRACTIVO

En este trabajo se presenta una técnica novedosa para la generación de haces de luz con momento angular orbital (MAO), utilizando un cristal fotorrefractivo Bi12TiO20 (BTO) en un arreglo experimental donde un haz con MAO y un haz de referencia generan un registro holográfico interferométrico del haz. Una de las posibles aplicaciones, si se consigue fijar el holograma, podría ser el estudio de fenómenos de óptica y óptica no lineal utilizando haces con altas potencias

n-3 polyunsaturated fatty acids in milk is associate to weight gain and growth in premature infants

<p>Abstract</p> <p>Background</p> <p>Linoleic 18:2 (n-6) and α-linolenic 18:3 (n-3) essential fatty acids and long-chain polyunsaturated fatty acids (LC-PUFA) are essential nutrients for growth and neonatal development. Consumption of preformed n-3 LC-PUFA has been shown to increase gestational duration and to decrease the incidence of premature birth in human studies. This study evaluated the association of essential fatty acids and LC-PUFA in breast milk on the growth of premature children (weight, height and head circumference).</p> <p>Study design</p> <p>Thirty-seven premature infants with a gestational age of 37 weeks or less were followed until 6 months of gestational age, adjusted for prematurity. The milk from mothers, weight, height and head circumference measures of children were collected during the follow up. The breast milk fatty acids were quantified by gas-liquid chromatography.</p> <p>Results</p> <p>Our results showed that total n-3 PUFA was positively associated with weight gain (<it>p </it>= 0.05), height (<it>p </it>= 0.04) and body mass index (BMI) of children (<it>p </it>= 0.05). Our results also indicate that both linoleic acid and total essential fatty acids were positively associated with BMI and head circumference, whereas oleic acid was positively associated only with head circumference.</p> <p>Conclusion</p> <p>These results suggest that the n-3 PUFA composition of milk may be associated with weight gain and growth. Considering the advantages of n-3 LC-PUFA consumption on infant growth and visual function and its association with reduced incidence of premature birth, dietitians should advise pregnant women to increase their intake of foods high in n-3 LC-PUFA.</p

Inclusión laboral para personas con discapacidad

Expone en una primera parte las reflexiones en los marcos legislativos y curriculares en torno al ámbito laboral de las personas con discapacidad y, en una segunda parte las recomendaciones finales que realizó el grupo de expertos reunidos en la mesa de trabajo sobre la inclusión laboral de las personas con discapacidad, los días 12, 13 y 14 de noviembre de 2008, en la ciudad de Lima, Perú, con la intención de influir positivamente en el reto de hacer efectivo el derecho al trabajo de estas personas

Mycobacterium tuberculosis Glucosyl-3-Phosphoglycerate Synthase: Structure of a Key Enzyme in Methylglucose Lipopolysaccharide Biosynthesis

Tuberculosis constitutes today a serious threat to human health worldwide, aggravated by the increasing number of identified multi-resistant strains of Mycobacterium tuberculosis, its causative agent, as well as by the lack of development of novel mycobactericidal compounds for the last few decades. The increased resilience of this pathogen is due, to a great extent, to its complex, polysaccharide-rich, and unusually impermeable cell wall. The synthesis of this essential structure is still poorly understood despite the fact that enzymes involved in glycosidic bond synthesis represent more than 1% of all M. tuberculosis ORFs identified to date. One of them is GpgS, a retaining glycosyltransferase (GT) with low sequence homology to any other GTs of known structure, which has been identified in two species of mycobacteria and shown to be essential for the survival of M. tuberculosis. To further understand the biochemical properties of M. tuberculosis GpgS, we determined the three-dimensional structure of the apo enzyme, as well as of its ternary complex with UDP and 3-phosphoglycerate, by X-ray crystallography, to a resolution of 2.5 and 2.7 Å, respectively. GpgS, the first enzyme from the newly established GT-81 family to be structurally characterized, displays a dimeric architecture with an overall fold similar to that of other GT-A-type glycosyltransferases. These three-dimensional structures provide a molecular explanation for the enzyme's preference for UDP-containing donor substrates, as well as for its glucose versus mannose discrimination, and uncover the structural determinants for acceptor substrate selectivity. Glycosyltransferases constitute a growing family of enzymes for which structural and mechanistic data urges. The three-dimensional structures of M. tuberculosis GpgS now determined provide such data for a novel enzyme family, clearly establishing the molecular determinants for substrate recognition and catalysis, while providing an experimental scaffold for the structure-based rational design of specific inhibitors, which lay the foundation for the development of novel anti-tuberculosis therapies

Positive Selection Results in Frequent Reversible Amino Acid Replacements in the G Protein Gene of Human Respiratory Syncytial Virus

Human respiratory syncytial virus (HRSV) is the major cause of lower respiratory tract infections in children under 5 years of age and the elderly, causing annual disease outbreaks during the fall and winter. Multiple lineages of the HRSVA and HRSVB serotypes co-circulate within a single outbreak and display a strongly temporal pattern of genetic variation, with a replacement of dominant genotypes occurring during consecutive years. In the present study we utilized phylogenetic methods to detect and map sites subject to adaptive evolution in the G protein of HRSVA and HRSVB. A total of 29 and 23 amino acid sites were found to be putatively positively selected in HRSVA and HRSVB, respectively. Several of these sites defined genotypes and lineages within genotypes in both groups, and correlated well with epitopes previously described in group A. Remarkably, 18 of these positively selected tended to revert in time to a previous codon state, producing a “flip-flop” phylogenetic pattern. Such frequent evolutionary reversals in HRSV are indicative of a combination of frequent positive selection, reflecting the changing immune status of the human population, and a limited repertoire of functionally viable amino acids at specific amino acid sites