Sumant Avasarala - Academia.edu (original) (raw)

Papers by Sumant Avasarala

Journal of Hazardous Materials

Environmental Science & Technology

Cardiovascular Toxicology

ACS Sustainable Chemistry & Engineering

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Environmental science & technology, Jan 21, 2018

This research focused on synthesis, characterization, and application of point-of-use catalytic r... more This research focused on synthesis, characterization, and application of point-of-use catalytic reactive electrochemical membranes (REMs) for electrocatalytic NO reduction. Deposition of Pd-Cu and Pd-In catalysts to the REMs produced catalytic REMs (i.e., Pd-Cu/REM and Pd-In/REM) that were active for NO reduction. Optimal performance was achieved with a Pd-Cu/REM and upstream counter electrode, which reduced NO from 1.0 mM to below the EPAs regulatory MCL (700 μM) in a single pass through the REM (residence time ∼2 s), obtaining product selectivity of <2% toward NO/NH. Nitrate reduction was not affected by dissolved oxygen and carbonate species and only slightly decreased in a surface water sample due to Ca and Mg scaling. Energy consumption to treat surface water was 1.1 to 1.3 kWh mol for 1 mM NO concentrations, and decreased to 0.19 and 0.12 kWh mol for 10 and 100 mM NaNO solutions, respectively. Electrocatalytic reduction kinetics were shown to be an order of magnitude higher...

Toxicological sciences : an official journal of the Society of Toxicology, 2018

Exposure to windblown particulate matter (PM) arising from legacy uranium (U) mine sites in the N... more Exposure to windblown particulate matter (PM) arising from legacy uranium (U) mine sites in the Navajo Nation may pose a human health hazard due to their potentially high metal content, including U and vanadium (V). To assess the toxic impact of PM derived from Claim 28 (a priority U mine) compared with background PM, and consider the putative role of metal species U and V. Two representative sediment samples from Navajo Nation sites (Background PM and Claim 28 PM) were obtained, characterized in terms of chemistry and morphology, and fractioned to the respirable (≤ 10 μm) fraction. Mice were dosed with either PM sample, uranyl acetate, or vanadyl sulfate via aspiration (100 µg), with assessments of pulmonary and vascular toxicity 24 h later. Particulate matter samples were also examined for in vitro effects on cytotoxicity, oxidative stress, phagocytosis, and inflammasome induction. Claim 28 PM10 was highly enriched with U and V and exhibited a unique nanoparticle ultrastructure co...

Environmental science & technology, Jan 7, 2017

The reactive transport of uranium (U) and vanadium(V) from abandoned mine wastes collected from t... more The reactive transport of uranium (U) and vanadium(V) from abandoned mine wastes collected from the Blue Gap/Tachee Claim-28 mine site in Arizona was investigated by integrating flow-through column experiments with reactive transport modeling, and electron microscopy. The mine wastes were sequentially reacted in flow-through columns at pH 7.9 (10 mM HCO) and pH 3.4 (10 mM CHCOOH) to evaluate the effect of environmentally relevant conditions encountered at Blue Gap/Tachee on the release of U and V. The reaction rate constants (k) for the dissolution of uranyl-vanadate (U-V) minerals predominant at Blue Gap/Tachee were obtained from simulations with the reactive transport software, PFLOTRAN. The estimated reaction rate constants were within 1 order of magnitude for pH 7.9 (k= 4.8 × 10mol cms) and pH 3.4 (k= 3.2 × 10mol cms). However, the estimated equilibrium constants (K) for U-V bearing minerals were more than 6 orders of magnitude different for reaction at circumneutral pH (K= 10) ...

Environmental science. Processes & impacts, Jan 29, 2017

The mobility and accumulation of uranium (U) along the Rio Paguate, adjacent to the Jackpile Mine... more The mobility and accumulation of uranium (U) along the Rio Paguate, adjacent to the Jackpile Mine, in Laguna Pueblo, New Mexico was investigated using aqueous chemistry, electron microprobe, X-ray diffraction and spectroscopy analyses. Given that it is not common to identify elevated concentrations of U in surface water sources, the Rio Paguate is a unique site that concerns the Laguna Pueblo community. This study aims to better understand the solid chemistry of abandoned mine waste sediments from the Jackpile Mine and identify key hydrogeological and geochemical processes that affect the fate of U along the Rio Paguate. Solid analyses using X-ray fluorescence determined that sediments located in the Jackpile Mine contain ranges of 320 to 9200 mg kg(-1) U. The presence of coffinite, a U(iv)-bearing mineral, was identified by X-ray diffraction analyses in abandoned mine waste solids exposed to several decades of weathering and oxidation. The dissolution of these U-bearing minerals fr...

Environmental science & technology, Nov 1, 2016

We applied spectroscopy, microscopy, diffraction, and aqueous chemistry methods to investigate th... more We applied spectroscopy, microscopy, diffraction, and aqueous chemistry methods to investigate the persistence of metals in water and sediments from the Animas River 13 days after the Gold King Mine spill (August 5, 2015). The Upper Animas River watershed, located in San Juan Colorado, is heavily mineralized and impacted by acid mine drainage, with low pH water and elevated metal concentrations in sediments (108.4 ± 1.8 mg kg(-1) Pb, 32.4 ± 0.5 mg kg(-1) Cu, 729.6 ± 5.7 mg kg(-1) Zn, and 51 314.6 ± 295.4 mg kg(-1) Fe). Phosphate and nitrogen species were detected in water and sediment samples from Farmington, New Mexico, an intensive agricultural area downstream from the Animas River, while metal concentrations were low compared to those observed upstream. Solid-phase analyses of sediments suggest that Pb, Cu, and Zn are associated with metal-bearing jarosite and other minerals (e.g., clays, Fe-(oxy)hydroxides). The solubility of jarosite at near-neutral pH and biogeochemical proces...

RNA interference (RNAi) promotes silencing of gene expression in a post-transcriptional manner. R... more RNA interference (RNAi) promotes silencing of gene expression in a post-transcriptional manner. RNAi-is a potential therapeutic in the treatment of several medically relevant pulmonary diseases, such as lung cancer, cystic fibrosis, asthma, chronic obstructive pulmonary disease, respiratory syncytial virus, and severe acute respiratory syndrome viral infection, and there are several ongoing clinical trials related to lung and siRNA. However, progress in this area has been hindered largely by the lack of efficient carriers capable of overcoming the lung architecture, extra and intracellular barriers present in the lung tissue to the efficient delivery of siRNA to the cell cytosol, and also due to formulation challenges. In this work we report the preparation and characterization of dendriplexes between siRNA and poly(amidoamine) (PAMAM) dendrimers, and their in vitro gene knockdown efficiency in a model lung alveolar epithelium cell line stably expressing eGFP. We also show strategie...

Environmental Science & Technology, 2015

The chemical interactions of U and co-occurring metals in abandoned mine wastes in a Native Ameri... more The chemical interactions of U and co-occurring metals in abandoned mine wastes in a Native American community in northeastern Arizona were investigated using spectroscopy, microscopy and aqueous chemistry. The concentrations of U (67-169 μg L(-1)) in spring water samples exceed the EPA maximum contaminant limit of 30 μg L(-1). Elevated U (6,614 mg kg(-1)), V (15,814 mg kg(-1)), and As (40 mg kg(-1)) concentrations were detected in mine waste solids. Spectroscopy (XPS and XANES) solid analyses identified U (VI), As (-I and III) and Fe (II, III). Linear correlations for the release of U vs V and As vs Fe were observed for batch experiments when reacting mine waste solids with 10 mM ascorbic acid (∼pH 3.8) after 264 h. The release of U, V, As, and Fe was at least 4-fold lower after reaction with 10 mM bicarbonate (∼pH 8.3). These results suggest that U-V mineral phases similar to carnotite [K2(UO2)2V2O8] and As-Fe-bearing phases control the availability of U and As in these abandoned mine wastes. Elevated concentrations of metals are of concern due to human exposure pathways and exposure of livestock currently ingesting water in the area. This study contributes to understanding the occurrence and mobility of metals in communities located close to abandoned mine waste sites.

Molecular Pharmaceutics, 2014

In order to determine the minimum RNase A concentration to degrade siRNA completely, siRNA (300 n... more In order to determine the minimum RNase A concentration to degrade siRNA completely, siRNA (300 ng) was incubated with different amounts of RNase A in TE 1X pH 8 buffer (0.02, 0.07, 0.162, 0.348, 0.7, and 3.3 g RNase A per 1 g siRNA) for 45 min at 37C, in presence or absence of RiboLock ® RNase Inhibitor (RI, 1L = 40U). The concentration of 0.35 g RNase A per 1 g siRNA has been reported in literature to be enough to degrade a large fraction of siRNA in polyplexes, 1, 2 and based on that, the amount of RNase A was varied in this experiment. Next, samples were frozen at -20C overnight, and loaded in the slots of casted agarose gel (1.5 % w/v in TAE 1X pH 8.2 buffer) stained with ethidium bromide (0.5 g  mL -1 ). The electrophoresis was performed at 60V (E0160-VWR Mini Gel Electrophoresis) for 40 min, and the siRNA-dye migration was visualized under UV irradiation (FOTO/Analyst ® Investigator/Eclipse with UV Transilluminator Fotodyne Inc.) and the images were recorded using the FOTO/Analyst ® PC Image software (v.5). The result is shown in , and clearly indicates that free siRNA (not protected by RNase inhibitor) was completely degraded by RNAse A starting at concentration 0.162 g RNase A per 1 g siRNA, since no siRNA band was observed in lane 6 compared to lane 7 and lane 1.

ASME 2010 4th International Conference on Energy Sustainability, Volume 2, 2010

ABSTRACT The world is currently dependant on fossil fuels as a fuel source for transportation and... more ABSTRACT The world is currently dependant on fossil fuels as a fuel source for transportation and fuelling the industrial sector. The increasing awareness of the depletion of fossil fuel resources and the environmental benefits of bio-diesel has made it more attractive in recent times. Many researches are being made to commercialize the production. However the cost of bio-diesel is the major obstacle to its commercialization in comparison to conventional diesel fuels. The objective of this paper is to produce biodiesel from Used cooking oil using a two stage process of acid and base catalyzed Transesterification reaction and optimizing the process variable such as Methanol to oil ratio, Catalyst to oil ratio, Reaction temperature and Reaction time as these process variable has adverse effect on the Transesterification reaction. The optimized parameters gave an yield of about 96%. Also an attempt had been made to examine the effect of temperature, moisture and storage time on the accumulation of free fatty acids in Used cooking oil. The results showed that the triacylglycerides was hydrolysed and the free fatty acid content was raised.