Using Multiple Environmental Tracers to Estimate Field-Scale Longitudinal Dispersivity

In this study, we seek to reduce parameter uncertainty in groundwater modeling systems, particularly in reactive transport models, by quantifying effective field-scale longitudinal dispersivity using anthropogenic environmental tracers. We generate synthetic aquifer fields and model transport of atmospheric tracers and test whether tracers can be used to determine an effective aquifer-scale dispersion coefficient. We generate synthetic datasets by simulating transport of chlorofluorocarbons (CFC11, CFC12, CFC113), sulfur-hexafluoride (SF6) and tritium (3H) with input functions derived from known atmospheric concentrations, through a three-dimensional, stochastic, heterogeneous synthetic aquifer developed using sequential Gaussian simulation using the PFLOTRAN reactive transport model. Flux-averaged concentrations calculated from model output are used as synthetic observation datasets to calibrate effective dispersivity for simplified homogeneous models with the PEST parameter estimation software. Tracer-derived effective dispersivity values are compared with theoretical and empirical values reasonable for our stochastic structure. We assess the ability of our homogenous model with tracer-derived effective dispersion coefficients to reproduce transport of a synthetic contaminant through the heterogeneous 3D field with two new boundary conditions. The ratio of CFC11/SF6 displays less than a 10% difference between the full (4.12m) and single-time (4.43m) series derived effective dispersivity. The ratio of CFC12/SF6 displays less than a 10% difference between the full (4.09m) and single-time (4.43m) series value. While all tracer-derived values from both the full-time and single-time series (1.96 m to 10.75 m) were within reason compared to the theoretically and empirically derived values (1.01 m to 5.32 m), dispersivity values derived from CFC11/SF6 and CFC12/SF6 for the full and single-time series display quantitatively smaller residuals compared to our heterogeneous truth model for our new boundary conditions. Our results indicate that environmental tracers can be useful in estimating effective dispersion coefficients for reactive transport models over longer length and time scales than traditional applied tracer studies. This new method of utilizing multiple environmental tracers over a limited time series could be an easy, inexpensive, and effective solution in quantifying field-scale longitudinal dispersivity and reduce parameter uncertainty in groundwater/contamination transport models

Effect of food concentration and type of diet on Acartia survival and naupliar development

We have performed life table experiments to investigate the effects of different food types and concentrations on the larval development and survival up to adulthood of Acartia tonsa. The food species offered comprised a wide taxonomic spectrum: the pigmented flagellates Isochrysis galbana, Emiliania huxleyi, Rhodomonas sp., Prorocentrum minimum, the diatom Thalassiosira weissflogii, grown on medium offering enriched macronutrient concentrations and the ciliate Euplotes sp. initially cultured on Rhodomonas. For the ciliate species, also the functional response was studied. In order to avoid limitation by mineral nutrients, food algae have been taken from the exponential growth phase of the nutrient replete cultures. The suitability of Rhodomonas as a food source throughout the entire life cycle was not a surprise. However, in contrast to much of the recent literature about the inadequacy or even toxicity of diatoms, we found that also Thalassiosira could support Acartia-development through the entire life cycle. On the other hand, Acartia could not complete its life cycle when fed with the other food items, Prorocentrum having adverse effects even when mixed with Rhodomonas and Thalassiosira. Isochrysis well supported naupliar survival and development, but was insufficient to support further development until reproduction. With Emiliania and Euplotes, nauplii died off before most of them could reach the first copepodite stages. Acartia-nauplii showed a behavioral preference for Euplotes-feeding over diatom feeding, but nevertheless Euplotes was an insufficient diet to complete development beyond the naupliar stages

Grazing Rates of Calanus finmarchicus on Thalassiosira weissflogii Cultured under Different Levels of Ultraviolet Radiation

UVB alters photosynthetic rate, fatty acid profiles and morphological characteristics of phytoplankton. Copepods, important grazers of primary production, select algal cells based upon their size, morphological traits, nutritional status, and motility. We investigated the grazing rates of the copepod Calanus finmarchicus on the diatom Thalassiosira weissflogii cultured under 3 levels of ultraviolet radiation (UVR): photosynthetically active radiation (PAR) only (4 kJ-m−2/day), and PAR supplemented with UVR radiation at two intensities (24 kJ-m−2/day and 48 kJ-m−2/day). There was no significant difference in grazing rates between the PAR only treatment and the lower UVR treatment. However, grazing rates were significantly (∼66%) higher for copepods feeding on cells treated with the higher level of UVR. These results suggest that a short-term increase in UVR exposure results in a significant increase in the grazing rate of copepods and, thereby, potentially alters the flow rate of organic matter through this component of the ecosystem

Using multiple environmental tracers to quantify field-scale hydrodynamic dispersion and reduce parameter uncertainty in reactive transport models.

In this study, we seek to reduce parameter uncertainty in groundwater modeling systems, particularly in reactive transport models, by developing a new technique to quantify field-scale hydrodynamic dispersion using anthropogenic environmental tracer concentrations and numerical groundwater modeling. We generate a series of synthetic aquifer fields using known heterogeneous aquifer parameters to model spatial variability using known atmospheric tracer datasets to determine if a single, unique value of dispersion can be applied field-wide. The atmospheric data is comprised of publicly available Chlorofluorocarbons (CFC11, CFC12, CFC113) and Sulfur-hexafluoride (SF6) concentration atmospheric data. A 2D heterogeneous synthetic truth aquifer developed using synthetic Gaussian simulations is compared with 2D homogeneous synthetic aquifers with varying hydrodynamic dispersion values. Breakthrough curves of tracer concentrations, and ratios thereof, through our synthetic aquifers over time are fit to curves produced through our heterogeneous truth model to assess whether a single field-scale dispersivity value can be adequately identified. The same methodology is applied to 3D simulations to assess the ability to estimate reasonable field-scale hydrodynamic dispersion coefficients in a 3D flow field. To evaluate the accuracy of our method, we compare the observed tracer-derived dispersivity values to dispersivity values calculated from theoretical estimates. This new method of utilizing multiple environmental tracers over a limited time series could be an easy, inexpensive, and effective solution in quantifying field-scale hydrodynamic dispersion and reduce parameter uncertainty in groundwater/contamination transport models

\u27No Pink Ribbons\u27: How Women\u27s Lived Experiences With Breast Atypia Inform Decisions Involving Risk-Reducing Medications

Purpose: Atypical hyperplasia (AH) is associated with a nearly 4-fold elevation of lifetime risk for breast cancer, and lobular carcinoma in situ (LCIS) is associated with a 7- to 8-fold risk. Women with AH/LCIS make numerous decisions in the course of treatment, including whether to take a risk-reducing medication, an option relatively few women pursue. We explored women’s decision-making processes through patient narratives in an effort to inform decision supports for AH/LCIS. Methods: We conducted in-depth interviews with 20 English-speaking women with AH/LCIS and no subsequent diagnosis of invasive breast cancer who had enrolled in the Rays of Hope Center for Breast Cancer Research patient registry between April 5, 2012, and March 31, 2016. Interviews were audiotaped, professionally transcribed, and qualitatively analyzed using thematic qualitative content analysis. Results: We identified three major narrative themes: 1) experiences with medical care; 2) decision-making; and 3) making sense of AH/LCIS. Each major theme had several subthemes, many of which map onto existing decisional theories and heuristics. Subthemes included the impact of life context on diagnosis meaning, emotional responses, changes in self-concept and body image, and understanding of the risk-benefit of risk-reducing medications. Conclusions: This narrative analysis offers important insights into how lived experience may influence decision-making for women with AH/LCIS. Decision supports that focus not only on analytic decisional processes, but also patients’ subjectivities and decisional heuristics, could prove useful for women and their health care providers

'No Pink Ribbons': How Women's Lived Experiences With Breast Atypia Inform Decisions Involving Risk-Reducing Medications

Purpose: Atypical hyperplasia (AH) is associated with a nearly 4-fold elevation of lifetime risk for breast cancer, and lobular carcinoma in situ (LCIS) is associated with a 7- to 8-fold risk. Women with AH/LCIS make numerous decisions in the course of treatment, including whether to take a risk-reducing medication, an option relatively few women pursue. We explored women’s decision-making processes through patient narratives in an effort to inform decision supports for AH/LCIS. Methods: We conducted in-depth interviews with 20 English-speaking women with AH/LCIS and no subsequent diagnosis of invasive breast cancer who had enrolled in the Rays of Hope Center for Breast Cancer Research patient registry between April 5, 2012, and March 31, 2016. Interviews were audiotaped, professionally transcribed, and qualitatively analyzed using thematic qualitative content analysis. Results: We identified three major narrative themes: 1) experiences with medical care; 2) decision-making; and 3) making sense of AH/LCIS. Each major theme had several subthemes, many of which map onto existing decisional theories and heuristics. Subthemes included the impact of life context on diagnosis meaning, emotional responses, changes in self-concept and body image, and understanding of the risk-benefit of risk-reducing medications. Conclusions: This narrative analysis offers important insights into how lived experience may influence decision-making for women with AH/LCIS. Decision supports that focus not only on analytic decisional processes, but also patients’ subjectivities and decisional heuristics, could prove useful for women and their health care providers

TRACER: an ‘eye-opener’ to the patient experience across the transition of care in an internal medicine resident program

Background: A safe patient transition requires a complex set of physician skills within the interprofessional practice. Objective: To evaluate a rotation which applies self-reflection and workplace learning in a TRAnsition of CarE Rotation (TRACER) for internal medicine (IM) residents. TRACER is a 2-week required IM resident rotation where trainees join a ward team as a quality officer and follow patients into postacute care. Methods: In 2010, residents participated in semistructured, one-on-one interviews as part of ongoing program evaluation. They were asked what they had learned on TRACER, the year prior, and how they used those skills in their practice. Using transcripts, the authors reviewed and coded each transcript to develop themes. Results: Five themes emerged from a qualitative, grounded theory analysis: seeing things from the other side, the ‘ah ha’ moment of fragmented care, team collaboration including understanding nursing scope of practice in different settings, patient understanding, and passing the learning on. TRACER gives residents a moment to breathe and open their eyes to the interprofessional practice setting and the patient's experience of care in transition. Conclusions: Residents learn about transitions of care through self-reflection. This learning is sustained over time and is valued enough to teach to their junior colleagues