Evidence for the critical role of nanoscale surface roughness on the retention and release of silver nanoparticles in porous media.

Although nanoscale surface roughness has been theoretically demonstrated to be a crucial factor in the interaction of colloids and surfaces, little experimental research has investigated the influence of roughness on colloid or silver nanoparticle (AgNP) retention and release in porous media. This study experimentally examined AgNP retention and release using two sands with very different surface roughness properties over a range of solution pH and/or ionic strength (IS). AgNP transport was greatly enhanced on the relatively smooth sand in comparison to the rougher sand, at higher pH, and lower IS and fitted model parameters showed systematic changes with these physicochemical factors. Complete release of the retained AgNPs was observed from the relatively smooth sand when the solution IS was decreased from 40 mM NaCl to deionized (DI) water and then the solution pH was increased from 6.5 to 10. Conversely, less than 40% of the retained AgNPs was released in similar processes from the rougher sand. These observations were explained by differences in the surface roughness of the two sands which altered the energy barrier height and the depth of the primary minimum with solution chemistry. Limited numbers of AgNPs apparently interacted in reversible, shallow primary minima on the smoother sand, which is consistent with the predicted influence of a small roughness fraction (e.g., pillar) on interaction energies. Conversely, larger numbers of AgNPs interacted in deeper primary minima on the rougher sand, which is consistent with the predicted influence at concave locations. These findings highlight the importance of surface roughness and indicate that variations in sand surface roughness can greatly change the sensitivity of nanoparticle transport to physicochemical factors such as IS and pH due to the alteration of interaction energy and thus can strongly influence nanoparticle mobility in the environment

Modeling Virus Transport and Removal during Storage and Recovery in Heterogeneous Aquifers

A quantitative understanding of virus removal during aquifer storage and recovery (ASR) in physically and geochemically heterogeneous aquifers is needed to accurately assess human health risks from viral infections. A two-dimensional axisymmetric numerical model incorporating processes of virus attachment, detachment, and inactivation in aqueous and solid phases was developed to systematically evaluate the virus removal performance of ASR schemes. Physical heterogeneity was considered as either layered or randomly distributed hydraulic conductivities (with selected variance and horizontal correlation length). Geochemical heterogeneity in the aquifer was accounted for using Colloid Filtration Theory to predict the spatial distribution of attachment rate coefficient. Simulation results demonstrate that the combined effects of aquifer physical heterogeneity and spatial variability of attachment rate resulted in higher virus concentrations in the recovered water at the ASR well (i.e. reduced virus removal). While the sticking efficiency of viruses to aquifer sediments was found to significantly influence virus concentration in the recovered water, the solid phase inactivation under realistic field conditions combined with the duration of storage phase had a predominant influence on the overall virus removal. The relative importance of physical heterogeneity increased under physicochemical conditions that reduced virus removal (e.g. lower value of sticking efficiency or solid phase inactivation rate). This study provides valuable insight on site selection of ASR projects and an approach to optimize ASR operational parameters (e.g. storage time) for virus removal and to minimize costs associated with post-recovery treatment

Anaerobic Transformation Kinetics and Mechanism of Steroid Estrogenic Hormones in Dairy Lagoon Water

Dairy products are a staple of the American diet. The main ingredient of the dairy industry, milk, has a byproduct even before it reaches the pasteurizing factory. For cows to produce milk, they need to have given birth recently. Pregnancy and lactation hormones include estrogen compounds. These hormones are excreted through urine and feces. Liquid manure and wastewater from precipitation and washing processes of the herd end up in a series of dairy farm lagoons designed to remove solids from the water. What happens to the estrogen compounds? How can we prevent hormones from contaminating the environment and causing detrimental effects in aquatic species? One research query is to determine if the lagoons have long enough retention times for hormones to degrade. Results appear in Wei Zheng, Xiaolin Li, Scott R. Yates, and Scott A. Bradford (2012). Environmental Science & Technology 46(10), 5471-5478. DOI: 10.1021/es301551hOpe

Fate and Transport of Steroid Hormones and Veterinary Antibiotics Derived from Cattle Farms

Concentrated animal feeding operations (CAFOs) have been identified as one of the most important sources for the release of animal hormones and veterinary antibiotics into the aquatic environment. Funded by a USDA research grant, Dr. Wei Zheng set out to identify and quantify the environmental fate and transport of several commonly-occurring steroid hormones, veterinary antibiotics, and their metabolites. Findings were published in the following papers: Xiaolin Li, Wei Zheng, Michael L. Machesky, Scott R. Yates, and Michael Katterhenry (2011). Journal of Agricultural and Food Chemistry 2011 59 (18), 10176-10181 DOI: 10.1021/jf202325c Wei Zheng, Xiaolin Li, Scott R. Yates, and Scott A. Bradford (2012). Environmental Science & Technology 46 (10), 5471-5478. DOI: 10.1021/es301551h Xiaolin Li, Wei Zheng, Walton R. Kelly (2013). Science of the Total Environment 445-446, 22-28. DOI: 10.1016/j.scitotenv.2012.12.035 Wei Zheng, Yonghong Zou, Xiaolin Li, Michael L. Machesky (2013). Journal of Hazardous Materials 258-259, 109-115. DOI: 10.1016/j.jhazmat.2013.04.038 Yonghong Zou and Wei Zheng Environmental Science & Technology 2013 47 (10), 5185-5192 DOI: 10.1021/es400624w.U.S. Department of AgricultureOpe

Redshift Determination and CO Line Excitation Modeling for the Multiply Lensed Galaxy HLSW-01

We report on the redshift measurement and CO line excitation of HERMES J105751.1+573027 (HLSW-01), a strongly lensed submillimeter galaxy discovered in Herschel/SPIRE observations as part of the Herschel Multi-tiered Extragalactic Survey (HerMES). HLSW-01 is an ultra-luminous galaxy with an intrinsic far-infrared luminosity of L _(FIR) = 1.4 × 10^(13) L _⊙, and is lensed by a massive group of galaxies into at least four images with a total magnification of μ = 10.9 ± 0.7. With the 100 GHz instantaneous bandwidth of the Z-Spec instrument on the Caltech Submillimeter Observatory, we robustly identify a redshift of z = 2.958 ± 0.007 for this source, using the simultaneous detection of four CO emission lines (J = 7 → 6, J = 8 → 7, J = 9 → 8, and J = 10 → 9). Combining the measured line fluxes for these high-J transitions with the J = 1 → 0, J = 3 → 2, and J = 5 → 4 line fluxes measured with the Green Bank Telescope, the Combined Array for Research in Millimeter Astronomy, and the Plateau de Bure Interferometer, respectively, we model the physical properties of the molecular gas in this galaxy. We find that the full CO spectral line energy distribution is described well by warm, moderate-density gas with T _(kin) = 86-235 K and n_H_2 = (1.1-3.5)x10^3 cm^(–3). However, it is possible that the highest-J transitions are tracing a small fraction of very dense gas in molecular cloud cores, and two-component models that include a warm/dense molecular gas phase with T _(kin) ~ 200 K, n_H_2 ~ 10^5 cm^(–3) are also consistent with these data. Higher signal-to-noise measurements of the J _(up) ≥ 7 transitions with high spectral resolution, combined with high spatial resolution CO maps, are needed to improve our understanding of the gas excitation, morphology, and dynamics of this interesting high-redshift galaxy

100 Years of Training and Development Research: What We Know and Where We Should Go

Training and development research has a long tradition within applied psychology dating back to the early 1900’s. Over the years, not only has interest in the topic grown but there have been dramatic changes in both the science and practice of training and development. In the current article, we examine the evolution of training and development research using articles published in the Journal of Applied Psychology (JAP) as a primary lens to analyze what we have learned and to identify where future research is needed. We begin by reviewing the timeline of training and development research in JAP from 1918 to the present in order to elucidate the critical trends and advances that define each decade. These trends include the emergence of more theory-driven training research, greater consideration of the role of the trainee and training context, examination of learning that occurs outside the classroom, and understanding training’s impact across different levels of analysis. We then examine in greater detail the evolution of four key research themes: training criteria, trainee characteristics, training design and delivery, and the training context. In each area, we describe how the focus of research has shifted over time and highlight important developments. We conclude by offering several ideas for future training and development research

Using the ionospheric response to the solar eclipse on 20th March 2015 to detect spatial structure in the solar corona

Long-term variability has previously been observed in the relative magnitude of annual and semi-annual variations in the critical frequency (related to the peak electron concentration) of the ionospheric F2 layer (foF2). In this paper we investigate the global patterns in such variability by calculating the time varying power ratio of semi-annual to annual components seen in ionospheric foF2 data sequences from 77 ionospheric monitoring stations around the world. The temporal variation in power ratios observed at each station was then correlated with the same parameter calculated from similar epochs for the Slough/Chilton data set (for which there exists the longest continuous sequence of ionospheric data). This technique reveals strong regional variation in the data, which bears a striking similarity to the regional variation observed in long-term changes to the height of the ionospheric F2 layer. We argue that since both the height and peak density of the ionospheric F2 region are influenced by changes to thermospheric circulation and composition, the observed long-term and regional variability can be explained by such changes. In the absence of long-term measurements of thermospheric composition, detailed modelling work is required to investigate these processes

Total versus superficial parotidectomy for stage III melanoma

BackgroundThe primary purpose of this study was to describe the parotid recurrence rates after superficial and total parotidectomy.MethodsA retrospective cohort study was performed on patients with cutaneous melanoma metastatic to the parotid gland who underwent parotidectomy from 1998 through 2014. Primary outcome was parotid bed recurrence. Secondary outcomes were facial nerve function postoperatively and at last follow‐up.ResultsOne hundred twenty‐nine patients were included in the study. Thirty‐four patients (26%) underwent a total parotidectomy and 95 patients underwent superficial parotidectomy. Twelve patients (13%) developed parotid bed recurrence after superficial parotidectomy alone versus zero after total parotidectomy (P = .035). Facial nerve function, clinically detected disease, stage, and adjuvant treatment were not statistically different between the groups (P = .32, .32, .13, and 0.99, respectively).ConclusionParotid bed melanoma recurrence was more common after superficial parotidectomy compared to total parotidectomy, and recurrence resulted in significant facial nerve functional deficit. Our results support total parotidectomy when metastatic melanoma involves the parotid nodal basin.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137735/1/hed24810_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137735/2/hed24810.pd