Regional selenium cycling in an irrigated agricultural groundwater system: conceptualization, modeling, and mitigation

2012 Summer.Includes bibliographical references.Selenium (Se) is an element that occurs naturally as a trace constituent in geologic formations and associated soils and, although an essential nutrient for animals and humans, can prove detrimental to health at high concentrations. Over the previous decades, the presence of either deficient or elevated concentrations of Se in groundwater, surface water, and associated plants and cultivated crops has emerged as a serious issue in many regions of the world, including the United States, northern and western Europe, the Middle East, and East Asia. Regardless of the nature of concern regarding Se, whether concentrations are deficient or elevated in water supplies and cultivated crops, there is a basic need for a thorough description of the movement and chemical processes of Se within a dynamic soil-aquifer system influenced by agricultural practices, and for the development of numerical simulation tools that allow these processes to be simulated in assessing baseline conditions and exploring remediation best-management practices (BMPs). While the individual processes controlling Se speciation, transformation, and movement within soil systems have been well documented, their synthesis into a comprehensive numerical model of Se fate and transport within an alluvial aquifer system influenced by agricultural practices has not yet been realized. This dissertation presents the development of a numerical model that can simulate the fate and transport of Se species in irrigation-influenced agricultural soil and groundwater systems at a regional scale. The model was developed by first, linking RT3D, modified to handle multi-species reactive transport in variably-saturated porous media, to MODFLOW, which uses the UZF1 (Unsaturated Zone Flow) package to simulate groundwater flow in the unsaturated zone; and second, developing an Se reaction module for RT3D that accounts for the cycling, chemical activity, and transport of Se species in regional-scale agricultural soil and groundwater systems. The module also accounts for the influence of other chemical species such as dissolved oxygen and nitrate (NO3). The resulting model, referred to as UZF-RT3DAG, is applied to a 50,600 ha regional site in the Lower Arkansas River Valley (LARV) in southeastern Colorado for the years 2006 through 2009. Using the calibrated model, multiple BMPs for remediation of Se contamination in the LARV are investigated. These strategies include decreasing annual loading of nitrogen fertilizer, decreasing species concentration in canal water, decreasing applied volume of irrigation water, and increasing chemical activity within riparian areas. Research results are presented through a series of published and submitted articles and modeling results that outline the progression of model development and model application. Results of the BMP scenario testing indicate that alternative land-management practices can have a significant impact in decreasing the concentration of dissolved Se in groundwater by up to 5-8% as well as mass loadings of Se to the Arkansas River by as much as 20-30%. Practices also have a significant impact on decreasing NO3 concentrations and loadings by up to 50% and 45%, respectively. As the alluvial aquifer in the LARV is similar to other Se-contaminated aquifer systems, the results of this research are pertinent to the assessment and remediation of Se contamination world-wide

Constructing and testing a refined groundwater flow model for the LaSalle/Gilcrest area

August 2018.Series and series numbering taken from website.Project Completion Report, Project period: July 1 2017 – June 30 2018

Evaluación de la degradación del suelo y sequías en una región árida utilizando índices de sequía, índice de vegetación ajustado al suelo modificado y datos de sensores remotos Landsat

Ain Sefra is part of the Ksour Mountains and it's situated in southwestern Algeria, where the climate is arid. The study area is progressively facing regression and degradation exacerbated by climate change. These trends point to a significant acceleration of desertification and drought and the loss of production systems that play a critical social, ecological, and economic role in the region. To better understand the natural hazard of dryness in Ain Sefra and the impact of climate change, we used various drought indices and remote sensing data. Hence, analyzing precipitation records from 1965 to 2021, through several drought indices, droughts were identified as a recurring phenomenon. Moreover, the frequency of successive dry years is relatively high. There were three most extended continuous dry periods. The first phase lasted seven years from 1980 to 1987, the second twelve years from 1994 to 2006, and the third nine years from 2012 to 2021. Calculation of the Modified Soil-Adjusted Vegetation Index (MSAVI) for five multidate satellite images allowed us to follow the evolution of land use elements in this region from 1977 to 2017. Indeed, the study of these multi-temporal images reveals a considerable growth of sands, moving towards the north and northeast of the zone during the last decades. The combination of drought indices and remote sensing seems to be most promising; whose results are valuable tools for guidance and decision support to local and regional authorities.Ain Sefr, en las montañas Ksour, está situada en el suroeste de Argelia, donde el clima es árido. El área de estudio se enfrenta progresivamente a la regresión y degradación exacerbada por el cambio climático. Estas tendencias apuntan a una aceleración significativa de la desertificación y la sequía y a la pérdida de sistemas de producción que desempeñan un papel social, ecológico y económico crítico en la región. Para comprender mejor el peligro natural de la sequía en Ain Sefra y el impacto del cambio climático, se varios índices de sequía y datos de teledetección. Al analizar los registros de precipitación desde 1965 hasta 2021, a través de varios índices de sequía, se identificaron las sequías como un fenómeno recurrente. Además, la frecuencia de años secos sucesivos es relativamente alta. Hubo tres períodos secos continuos más prolongados. La primera fase duró siete años, de 1980 a 1987, la segunda doce años, de 1994 a 2006, y la tercera nueve años, de 2012 a 2021. El cálculo del Índice de Vegetación Ajustado al Suelo Modificado (MSAVI) para cinco imágenes satelitales multifecha nos permitió seguir la evolución de los elementos de uso del suelo en esta región desde 1977 hasta 2017. De hecho, el estudio de estas imágenes multitemporales revela un crecimiento considerable de arenas, moviéndose hacia el norte y noreste de la zona durante las últimas décadas. La combinación de índices de sequía y sensores remotos parece ser muy prometedores, pues sus resultados son valiosas herramientas de orientación y apoyo a la decisión de los entes locales y regionales.Financial support to perform this study was provided partially by the University Center Salhi Ahmed Naama (Argelia). Antonio Jodar-Abellan acknowledges financial support received form the XTREME Spanish National Project (Ref: PID2019-109381RB-I00/AEI/10.13039/501100011033)

Cyclotron modeling phase-resolved infrared spectroscopy of polars I: EF Eridani

We present phase-resolved low resolution infrared spectra of the polar EF Eridani obtained over a period of 2 years with SPEX on the IRTF. The spectra, covering the wavelength range 0.8 to 2.4 microns, are dominated by cyclotron emission at all phases. We use a ``Constant Lambda'' prescription to attempt to model the changing cyclotron features seen in the spectra. A single cyclotron emission component with B = 12.6 MG, and a plasma temperature of kT = 5.0 keV, does a reasonable job in matching the features seen in the H and K bands, but fails to completely reproduce the morphology shortward of 1.6 microns. We find that a two component model, where both components have similar properties, but whose contributions differ with viewing geometry, provides an excellent fit to the data. We discuss the implications of our models and compare them with previously published results. In addition, we show that a cyclotron model with similar properties to those used for modeling the infrared spectra, but with a field strength of B = 115 MG, can explain the GALEX observations of EF Eri.Comment: 25 pages, 5 figures, to appear in Ap

#OrthoTwitter: Relationship between author Twitter utilization and academic impact in orthopaedic surgery

Background #OrthoTwitter has evolved to disseminate findings and engage the public. However, the academic impact of Twitter utilization in orthopaedic surgery is unknown. Questions/purposes The purpose of the study was to evaluate relationships between the author and manuscript Twitter activity and citations. Methods Manuscripts in 17 orthopaedic journals from 2018 were identified. Citations, online mentions, impact factors, and subspecialties were obtained. H-index and Twitter account details for authors were obtained for a subset of manuscripts. Relationships between Twitter activity and citations were evaluated. Results 2,473/4,224 (58.5%) manuscripts were mentioned on Twitter (n=29,958 mentions), with Twitter manuscripts cited more frequently (median 10 vs. 7, p\u3c0.0001). Twitter mentions, impact factors, non-open-access status, and subspecialties were associated with citation counts. Articles mentioned in 10, 100, and 1,000 Tweets were observed to have a 1.1-fold, 1.7-fold, and 245-fold increase in citations. In author-level analyses, 156 (20.0%) first and 216 (27.7%) senior authors had Twitter accounts. Citation count was associated with increasing senior author H-index

EFFECTS OF PACKING AND ASPECT RATIO ON MIXING AND HETEROGENEOUS CATALYSIS IN MICROCHANNELS

ABSTRACT Many industrial chemical processes involve the mixing of two or more liquids. By reducing chemical reactors to microscale dimensions, engineers seek to take advantage of decreased diffusion lengths, leading to increased effectiveness (e.g., higher purity of product) over larger process components. In this study, computational models developed using the commercial multiphysics code CFD-ACE+ are used to predict flow within microreactor channels. Two aqueous streams enter a channel-one containing a contaminant and the other devoid of the contaminant. Changes in two geometric attributes are investigated with respect to their effect on mixing of the streams: 1) packing feature layout within the channel and 2) channel aspect ratio. Reynolds numbers (Re) for the simulations range between 0.1 and 100. Results indicate that both packing feature position within the channel and channel aspect ratio can have a substantial impact on mixing. Between Re = 0.1 and Re = 1, mixing efficiency generally decreases with increasing Re; however, as the Re is increased from 1 to 100, fluid flow patterns in the channel are altered, and wake regions and streamline changes created by the packing features lead to improved mixing. Examples showing enhanced chemical conversion during heterogeneous catalysis as a result of better mixing are also presented

Netrin-3 Avoidance and Mitotic Inhibition in \u3cem\u3eTetrahymena thermophila\u3c/em\u3e Involves Intracellular Calcium and Serine/Threonine Kinase Activity

Netrins are a family of signaling proteins ubiquitously expressed throughout the animal kingdom. While netrin-1 has been well characterized, other netrins, such as netrin-3, remain less well understood. In our current study, we characterize the behavior of two netrin-3 peptides, one derived from the N-terminal and one derived from the C-terminal of netrin-3. Both peptides cause avoidance behavior and mitotic inhibition in Tetrahymena thermophila at concentrations as low as 0.5 micrograms (μg) per milliliter. These effects can be reversed by addition of the calcium chelator, EGTA; the intracellular calcium chelator, BAPTA-AM, or the serine/threonine kinase inhibitor, apigenin. The broad spectrum tyrosine kinase inhibitor, genistein, has no effect on netrin-3 signaling, indicating that netrin-3 signaling in this organism uses a different pathway than the previously described netrin-1 pathway. Further studies will allow us to better describe the netrin-3 signaling pathway in this organism

Anthropometric indices of Gambian children after one or three annual rounds of mass drug administration with azithromycin for trachoma control.

BACKGROUND: Mass drug administration (MDA) with azithromycin, carried out for the control of blinding trachoma, has been linked to reduced mortality in children. While the mechanism behind this reduction is unclear, it may be due, in part, to improved nutritional status via a potential reduction in the community burden of infectious disease. To determine whether MDA with azithromycin improves anthropometric indices at the community level, we measured the heights and weights of children aged 1 to 4 years in communities where one (single MDA arm) or three annual rounds (annual MDA arm) of azithromycin had been distributed. METHODS: Data collection took place three years after treatment in the single MDA arm and one year after the final round of treatment in the annual MDA arm. Mean height-for-age, weight-for-age and weight-for-height z scores were compared between treatment arms. RESULTS: No significant differences in mean height-for-age, weight-for-age or weight-for-height z scores were found between the annual MDA and single MDA arms, nor was there a significant reduction in prevalence of stunting, wasting or underweight between arms. CONCLUSIONS: Our data do not provide evidence that community MDA with azithromycin improved anthropometric outcomes of children in The Gambia. This may suggest reductions in mortality associated with azithromycin MDA are due to a mechanism other than improved nutritional status