Mechanisms for Aerobic Degradation of Commercial Naphthenic Acids

Naphthenic acids (NAs) are a class of thousands of carboxylic acids associated with petroleum degradation. They become dissolved in oil sands process waters (OSPW) during the bitumen extraction process, and the resulting process waters can elicit toxicity to aquatic organisms. NAs are weakly biodegradable, but have half-lives of months to years, making it difficult to treat NAs with bioremediation. Two methods for promoting aerobic degradation (cometabolism and mycoremediation) were investigated as proof of concept for effectiveness in degrading commercial NAs. A reciprocating reactor inoculated with a white rot fungus, Pleurotus pulmonaris, was built and compared to an uninoculated reactor to determine the effects of this fungus on NA degradation. Inoculated reactors were more effective than uninoculated reactors in removing NAs, with zero-order half lives of 32 and 39 hours, respectively. This demonstrated the usefulness of both P. pulmonaris and a reciprocating reactor in promoting aerobic NA degradation. Cometabolic NA degradation using different substrates and substrate concentrations was investigated at bench scale. This study confirmed that cometabolic substrate addition increases NA removal rate in comparison to unamended degradation. It also showed that the concentration ratio of substrate to NAs affects the removal rate of NAs. This has important implications to the design of a constructed wetland treatment system for ecological risk mitigation of OSPW, where wetland detritus may serve as a cometabolic substrate to promote NA degradation

Developmental toxic effects of ethylbenzene or toluene alone and in combination with butyl acetate in rats after inhalation exposure

First, the developmental toxic potential of n-butyl acetate (BA) was examined in Sprague-Dawley rats following whole body inhalation exposure, 6 h day-1, from day 6 to 20 of gestation, at concentrations of 0, 500, 1000, 2000 and 3000 ppm. Maternal toxicity was evidenced by significant decreases in body weight gain at 2000 and 3000 ppm, and by reduced food consumption at 1000 ppm and higher concentrations. The effects on prenatal development were limited to a significant decrease in fetal weight at 3000 ppm. Thus, inhaled BA was not a selective developmental toxicant. In the second part of this study, the developmental toxic effects of simultaneous exposures to ethylbenzene (EB) and BA, or to toluene (TOL) and BA were evaluated. Pregnant rats were administered EB (0, 250 or 1000 ppm) and BA (0, 500 or 1500 ppm), or TOL (0, 500 or 1500 ppm) and BA (0, 500, 1500 ppm), separately and in combinations, using a 2 × 2 factorial design. The maternal weight gain was reduced after exposure to 1000 ppm EB, to 1500 ppm BA, or to 1500 ppm TOL, either alone or in binary combinations. A significant reduction of fetal weight was associated with exposure to 1000 ppm EB alone, to either mixtures of EB with BA, or to 1500 ppm TOL alone or combined with BA at either concentration. No embryolethal or teratogenic effects were observed whatever the exposure. There was no evidence of interaction between EB and BA or between TOL and BA in causing maternal or developmental effects. Copyright © 2006 John Wiley & Sons, Ltd

Robust Variable Selection under Cellwise Contamination

Cellwise outliers are widespread in data and traditional robust methods may fail when applied to datasets under such contamination. We propose a variable selection procedure, that uses a pairwise robust estimator to obtain an initial empirical covariance matrix among the response and potentially many predictors. Then we replace the primary design matrix and the response vector with their robust counterparts based on the estimated covariance matrix. Finally, we adopt the adaptive Lasso to obtain variable selection results. The proposed approach is robust to cellwise outliers in regular and high dimensional settings and empirical results show good performance in comparison with recently proposed alternative robust approaches, particularly in the challenging setting when contamination rates are high but the magnitude of outliers is moderate. Real data applications demonstrate the practical utility of the proposed method.Comment: 17 pages, 4 figure

Tailoring the mass distribution and functional group density of dimethylsiloxane-based films by thermal evaporation

The tailoring of molecular weight distribution and the functional group density of vinyl-terminated polydimethylsiloxane (PDMS) by molecular beam deposition is demonstrated herein. Thermally evaporated PDMS and its residue are characterized using gel permeation chromatography and nuclear magnetic resonance. Thermal fragmentation of vinyl groups occurs for evaporation temperatures above 487 K (214 degrees C). At a background pressure of 10(-6) mbar, the maximum molecular weight distribution is adjusted from (700 +/- 100) g/mol to (6100 +/- 100) g/mol with a polydispersity index of 1.06 +/- 0.02. The content of vinyl-termination per repeating unit of PDMS is tailored from (2.8 +/- 0.2)% to (5.6 +/- 0.1)%. Molecular weights of vinyl-terminated PDMS evaporated at temperatures above 388 K (115 degrees C) correspond to those attributed to trimethyl-terminated PDMS. Side groups of linear PDMS dominate intermolecular interactions and vapor pressure

COMBSS: Best Subset Selection via Continuous Optimization

The problem of best subset selection in linear regression is considered with the aim to find a fixed size subset of features that best fits the response. This is particularly challenging when the total available number of features is very large compared to the number of data samples. Existing optimal methods for solving this problem tend to be slow while fast methods tend to have low accuracy. Ideally, new methods perform best subset selection faster than existing optimal methods but with comparable accuracy, or, being more accurate than methods of comparable computational speed. Here, we propose a novel continuous optimization method that identifies a subset solution path, a small set of models of varying size, that consists of candidates for the single best subset of features, that is optimal in a specific sense in linear regression. Our method turns out to be fast, making the best subset selection possible when the number of features is well in excess of thousands. Because of the outstanding overall performance, framing the best subset selection challenge as a continuous optimization problem opens new research directions for feature extraction for a large variety of regression models

Facilitators and barriers to the implementation of a Mobile Health Wallet for pregnancy-related health care: A qualitative study of stakeholders’ perceptions in Madagascar

Financial barriers are a major obstacle to accessing maternal health care services in low-resource settings. In Madagascar, less than half of live births are attended by skilled health staff. Although mobile money-based savings and payment systems are often used to pay for a variety of services, including health care, data on the implications of a dedicated mobile money wallet restricted to health-related spending during pregnancy–a mobile health wallet (MHW)–are not well understood. In cooperation with the Madagascan Ministry of Health, this study aims to elicit the perceptions, experiences, and recommendations of key stakeholders in relation to a MHW amid a pilot study in 31 state-funded health care facilities. We conducted a two-stage qualitative study using semi-structured in-depth interviews with stakeholders (N = 21) representing the following groups: community representatives, health care providers, health officials and representatives from phone provider companies. Interviews were conducted in Atsimondrano and Renivohitra districts, between November and December of 2017. Data was coded thematically using inductive and deductive approaches, and found to align with a social ecological model. Key facilitators for successful implementation of the MHW, include (i) close collaboration with existing communal structures and (ii) creation of an incentive scheme to reward pregnant women to save. Key barriers to the application of the MHW in the study zone include (i) disruption of informal benefits for health care providers related to the current cash-based payment system, (ii) low mobile phone ownership, (iii) illiteracy among the target population, and (iv) failure of the MHW to overcome essential access barriers towards institutional health care services such as fear of unpredictable expenses. The MHW was perceived as a potential solution to reduce disparities in access to maternal health care. To ensure success of the MHW, direct demand-side and provider-side financial incentives merit consideration

Fuentes de fósforo con promotores de crecimiento (pgpr) en cultivo de maíz chipa (Zea mays L. var. amylacea Sturtev.)

La limitada disponibilidad de P en los suelos de la Región Oriental restringe la productividad del maíz chipa. La fertilización con fosfatos solubles es una de las alternativas para compensar ese déficit nutricional del cultivo. El ensayo tuvo lugar en el Departamento de Canindeyú, Distrito de Yvyrarovaná, con el objetivo de evaluar el efecto de fuentes de fósforo con promotores de crecimiento (PGPR) en el cultivo de maíz chipa. Se utilizó un diseño de bloques completos al azar con arreglo factorial en parcelas divididas. Los factores fueron fuentes de fósforo (5 niveles) y PGPR (2 niveles: con y sin), dando lugar a 10 tratamientos con 4 repeticiones. Las fuentes de fosfato utilizados fueron el superfosfato triple (SFT), superfosfato simple (SFS), fosfato termomagnesiano (TFM) y roca molida (RM), aplicados a dosis de 80 kg ha-1 de P2O5, a excepción de la roca molida que fue aplicada en una dosis de 300 kg ha-1 . Los PGPR fueron aplicados a dosis de 3 mL kg -1 de semilla. Las variables evaluadas fueron: altura de planta y de inserción de mazorca, número de hojas, diámetro del tallo, longitud y diámetro de mazorca, hilera de granos por mazorca, granos por hilera de mazorca, masa de 1.000 granos, rendimiento, masa seca aérea, índice de cosecha, eficiencia agronómica y económica, así como rentabilidad. Los resultados fueron sometidos a análisis de varianza. No se encontró diferencia significativa respecto a la utilización de PGPR, pero si entre fuentes fosfatadas, todos los parámetros estudiados, excepto masa de 1.000 granos, diámetro de mazorca, índice de cosecha y eficiencia agronómica, tuvieron mejores resultados con las fuentes de P más solubles (SFT y SFS), donde medias más altas se obtuvieron con el SFT, con rendimiento de 3.870 kg ha-1 y eficiencia agronómica de 18,9 kg de granos por kg de P2O5 aplicado, generando una rentabilidad de hasta 176 % a nivel de mercado. Existe una efectividad diferenciada para las diferentes fuentes de P, donde SFT>SFS>TFM>RM.CONACYT – Consejo Nacional de Ciencia y TecnologíaPROCIENCI