Data-driven discovery of the governing equations for transport in heterogeneous media by symbolic regression and stochastic optimization.

With advances in instrumentation and the tremendous increase in computational power, vast amounts of data are becoming available for many complex phenomena in macroscopically heterogeneous media, particularly those that involve flow and transport processes, which are problems of fundamental interest that occur in a wide variety of physical systems. The absence of a length scale beyond which such systems can be considered as homogeneous implies that the traditional volume or ensemble averaging of the equations of continuum mechanics over the heterogeneity is no longer valid and, therefore, the issue of discovering the governing equations for flow and transport processes is an open question. We propose a data-driven approach that uses stochastic optimization and symbolic regression to discover the governing equations for flow and transport processes in heterogeneous media.

Resilience of groundwater systems in the presence of Bisphenol A under uncertainty.

Assessing the health risks associated with emerging contaminants in groundwater systems is a complex issue that has been receiving increased attention in indirect potable reuse applications. Among several emerging contaminants, our study focuses on developing a numerical model that aims to compute the transport characteristics of Bisphenol A (BPA) in a 3D spatially heterogeneous aquifer under uncertainty. Traditional approaches that characterize the health risk of BPA to humans rely on the monotonic dose-response (MDR) relationship with a regulatory dose limit.

Toward cost-effective staffing mixes for Veterans Affairs substance use disorder treatment programs.

Background: In fiscal year (FY) 2008, 133,658 patients were provided services within substance use disorders treatment programs (SUDTPs) in the U.S. Department of Veterans Affairs (VA) health care system.

Role of phosphate and Fe-oxides on the acid-aided extraction efficiency and readsorption of As in field-aged soil.

This study was conducted to investigate arsenic (As) readsorption phenomenon in acid-treated soil using phosphate as a competing ion. Three field-aged soils (i.e.

Effect of different soil washing solutions on bioavailability of residual arsenic in soils and soil properties.

The effect of soil washing used for arsenic (As)-contaminated soil remediation on soil properties and bioavailability of residual As in soil is receiving increasing attention due to increasing interest in conserving soil qualities after remediation. This study investigates the effect of different washing solutions on bioavailability of residual As in soils and soil properties after soil washing. Regardless of washing solutions, the sequential extraction revealed that the residual As concentrations and the amount of readily labile As in soils were reduced after soil washing.

Determination of human health risk incorporating experimentally derived site-specific bioaccessibility of arsenic at an old abandoned smelter site.

This study was conducted to investigate the contribution of a site-specific bioavailability of arsenic (As) to human health risk at an old abandoned smelter site in Korea. The site was contaminated with As for over 60 years with the same source (As2O3 in flue gas), but concentration and in vitro bioaccessibility (IVBA) of As differed by operable units (OU), which consequently resulted in difference in estimated risk. Soil samples collected from six OUs showed that aqua regia-extractable As concentrations ranged from 9.

Changes in soil toxicity by phosphate-aided soil washing: effect of soil characteristics, chemical forms of arsenic, and cations in washing solutions.

This study was set to investigate the changes in the toxicity of arsenic (As)-contaminated soils after washing with phosphate solutions. The soil samples collected from two locations (A: rice paddy and B: forest land) of a former smelter site were contaminated with a similar level of As. Soil washing (0.

Sex differences in chronic pain management practices for patients receiving opioids from the Veterans Health Administration.

Background: Women experience chronic pain and use pain-related health care at higher rates than men. It is not known whether the pain-related health care female veterans receive is consistent with clinical practice guideline recommendations or whether receipt of this care differs between men and women.

Objective: The aim of this study was to identify whether sex differences in chronic pain management care exist for patients served by the Veterans Health Administration (VHA).