Tracer Data Research Articles

32. EVOLUTION OF CLINICAL PRACTICE PATTERNS IN LIPOSUCTION: A SIXTEEN-YEAR REVIEW OF CONTINUOUS CERTIFICATION TRACER DATA FROM THE AMERICAN BOARD OF PLASTIC SURGERY

PURPOSE: A sixteen-year review of liposuction tracer data collected from diplomates of the American Board of Plastic Surgery (ABPS) as part of the Continuous Certification process was performed to evaluate for predominant practice patterns and changes in specific practice patterns over this time. METHODS: Liposuction tracer data were collected from 2005-2021, comparing tracer data from 2005-2014 to those from 2015-2021 using Fisher’s exact test and Student’s t-test. RESULTS: 2810 patients with an average age of 42 years were evaluated, of which 84% were female. In the later cohort (2015-2021), in-office procedures increased significantly. Concerning the body area of liposuction, abdomen, flank, and back have increased, while thighs and knees have decreased. Power-assisted lipectomy has grown in popularity, and significant increases were noted in the volume of wetting solution and lipoaspirate. Surgeons are performing procedures concomitantly with liposuction more often, and more mid-surgical position changes from prone to supine were noted. Perioperative heparin and low-molecular-weight heparin (LMWH) use have significantly increased. CONCLUSION: The present study is the first to objectively assess evolving trends in the clinical practice of liposuction over the last sixteen years. These data illustrate an increase in outpatient procedures, a shift in technique towards power-assisted liposuction, and greater surgical focus on the trunk (abdomen, flanks, and back).

61. EVOLVING CLINICAL PRACTICE PATTERNS IN ABDOMINOPLASTY: A 16-YEAR ANALYSIS OF CONTINUOUS CERTIFICATION TRACER DATA FROM THE AMERICAN BOARD OF PLASTIC SURGERY

PURPOSE: This study evaluates changes in practice patterns in abdominoplasty based on a 16-year review of tracer data collected by the American Board of Plastic Surgery (ABPS) as part of the Continuous Certification process. METHODS: ABPS tracer data was reviewed from 2005 to 2020, comparing data between two timeframes with similar case numbers: 2005-2014 versus 2015-2020. Patient demographics, surgical techniques, and complication rates were compared using two-sample t-tests. RESULTS: Cumulative data included 4740 cases from 2005-2014 and 4250 cases from 2015-2020. Comparing patient selection practices, the latter group had significantly increased BMI; however, there was a decrease in pregnancies, previous intra-abdominal surgeries, body scars, and redundant skin over the umbilicus. Among procedure techniques, there has been a significant decline in the use of wide undermining, vertical plication of the abdomen, and surgical drains. Abdominoplasties are increasingly being performed in an outpatient setting (81%) and more surgeons are prescribing heparin instead of postoperative sequential compression devices. Liposuctioning the abdominal flap, hips, and flank is becoming more common while liposuctioning the thighs less common. More abdominoplasties are being performed with no complications (78%vs81%, p<0.001) and without the need for revisionary surgery (90%vs92%, p<0.001). CONCLUSION: Despite surgeons operating on higher BMI patients and performing more aggressive liposuction of the abdominoplasty flap, abdominoplasties are being performed with less complications and increasingly as an outpatient procedure.

Physiologically-based modeling of cholate disposition in beagle dog with and without treatment of the liver transporter inhibitor simeprevir

BSEP inhibition is one risk factor for Drug-Induced Liver Injury (DILI). While in vitro screening of BSEP inhibition may prevent compounds with BSEP liability from progressing into the clinic, these in vitro data alone can result in false-positives and as such a specific in vivo biomarker would further enhance our BSEP inhibition de-risking strategy. Measurement of endogenous bile acids as biomarkers of BSEP inhibition in vivo is complicated by several factors, including drugs that inhibit BSEP can also inhibit other bile acid transporters such as NTCP. Here, we developed a novel translational framework, including an in vivo biomarker with a corresponding mechanistic model, and attempted to decouple the effect of liver sinusoidal uptake inhibition from efflux inhibition on bile acid disposition in the beagle dog. Specifically, we hypothesized that the change of a stable isotope-labeled (SIL) bile acid tracer’s exposure would yield a toxicodynamic signal that can provide insight into BSEP inhibition and ensuing bile salt accumulation. For this purpose we dosed the stable isotope-labeled cholic acid (13C-CA) and taurocholic acid (D4-TCA) as biomarker tracers in dogs, with and without the liver transporter inhibitor simeprevir, and determined the plasma and bile exposure of 13C-CA, 13C-TCA, D4-CA and D4-TCA in vivo. Key bile acid clearance and transporter inhibition parameters were determined in vitro. We developed a novel Physiologically Based Pharmacokinetic model (PBPK) to integrate the mechanistic physiological understanding, literature knowledge, and in vitro laboratory data to model bile acid disposition. Using modeling and simulation, we provided an increased mechanistic understanding of how to use plasma bile acid tracer data to inform on potential liver transporters inhibition and limitations to in vivo translation. The novel translational framework can enhance the future BSEP inhibition de-risking strategy, particularly if the experimental confounders to studying kinetics in dog hepatocytes in vitro models are solved.

Effects of High-Volume Versus High-Load Resistance Training on Skeletal Muscle Growth and Molecular Adaptations.

We evaluated the effects of higher-load (HL) versus (lower-load) higher-volume (HV) resistance training on skeletal muscle hypertrophy, strength, and muscle-level molecular adaptations. Trained men (n = 15, age: 23 ± 3 years; training experience: 7 ± 3 years) performed unilateral lower-body training for 6 weeks (3× weekly), where single legs were randomly assigned to HV and HL paradigms. Vastus lateralis (VL) biopsies were obtained prior to study initiation (PRE) as well as 3 days (POST) and 10 days following the last training bout (POSTPR). Body composition and strength tests were performed at each testing session, and biochemical assays were performed on muscle tissue after study completion. Two-way within-subject repeated measures ANOVAs were performed on most dependent variables, and tracer data were compared using dependent samples t-tests. A significant interaction existed for VL muscle cross-sectional area (assessed via magnetic resonance imaging; interaction p = 0.046), where HV increased this metric from PRE to POST (+3.2%, p = 0.018) whereas HL training did not (−0.1%, p = 0.475). Additionally, HL increased leg extensor strength more so than HV training (interaction p = 0.032; HV < HL at POST and POSTPR, p < 0.025 for each). Six-week integrated non-myofibrillar protein synthesis (iNon-MyoPS) rates were also higher in the HV versus HL condition, while no difference between conditions existed for iMyoPS rates. No interactions existed for other strength, VL morphology variables, or the relative abundances of major muscle proteins. Compared to HL training, 6 weeks of HV training in previously trained men optimizes VL hypertrophy in lieu of enhanced iNon-MyoPS rates, and this warrants future research.

On the interplay between hillslope and drainage network flow dynamics in the catchment travel time distribution

AbstractTravel time is a robust measure of water transport dynamics in catchments. At a given control section along a drainage network, travel time distribution results from an interplay between two main processes: (i) the transport through the hillslopes and (ii) transport through the drainage network. The main scope of this work is to quantify this interplay, specifically we aim to identify the relative impact of hillslopes and channels on the travel time at the catchment scale. A theoretical framework is developed following a bottom‐up modelling approach that combines a Boussinesq model for water flow and water travel time in hillslopes, with a geomorphological model for water transport in drainage network. Simple semi‐analytical solutions are derived for the first two moments of the travel time distribution within a flow section. We provide some relevant examples based on synthetic rainfall data, exploring the relative impacts of hillslope and channel properties. As expected, the dynamics of the hillslopes control the travel time distribution at the catchment scale. The drainage network typically introduces a lag in the average travel time exiting the hillslopes and reduces the temporal fluctuations of the mean travel time and its variance. Our theoretical model provides meaningful insights on the investigation of the dominant dynamics taking place in catchments: results suggest that hillslopes and their features are the main driver of travel time in catchments. The temporal fluctuations of the travel time moments show a non‐linear dependence with the recharge time‐series and need to be considered as time‐variant. Variability of water ages collected in a single water sample can be very large, the latter feature may have a significant effect on the water quality and on the tracer data analysis, largely governed by the contact times between water and catchment material.

Dynamic Contributions of Stratified Groundwater to Streams Controls Seasonal Variations of Streamwater Transit Times

AbstractStreamwater transit time distributions display a variable proportion of old waters (≥1 year). We hypothesize that the corresponding long transit times result from groundwater contributions to the stream and that seasonal streamwater transit time variations result from (a) the variable contributions of different flowpaths (overland flow, seepage flow and baseflow) and (b) the stratification of groundwater residence times. We develop a parsimonious model to capture the groundwater contribution to the stream discharge and its effect on transient transit times. Infiltration is partitioned according to the aquifer saturation between Boussinesq groundwater flow and overland flow. Time‐variable transit time distributions are obtained with a new 2D particle tracking algorithm. Hydraulic conductivity, total and drainable porosities are calibrated by using discharge and CFC tracer data on a crystalline catchment located in Brittany (France). The calibrated models succeed in reproducing CFCs concentrations and discharge dynamics. The groundwater flow contribution to the stream is controlled by the aquifer hydraulic conductivity, while its age is controlled by the drainable and total porosities. Old groundwater (≥1 year) is the source for approximately 75% of the streamflow with strong seasonal variations (between 40% and 95%). Mean transit times are approximately 13 years, varying between 6 and 20 years, proportional to the groundwater contribution. These seasonal variations are driven by the groundwater versus overland flow partitioning. The stratification of groundwater residence times in the aquifer plays a minor role in the streamwater transit times but is key for the transit time dynamics of the groundwater contribution to the stream.

Advanced workflow for multi-well tracer test analysis in a geothermal reservoir

Interpretation of tracer tests in geothermal reservoirs is carried out by fitting the measured data either with simplified two-dimensional (2-D) analytical solutions or with complex numerical models. Available analytical solutions commonly only describe isotropic conditions in 1-D or 2-D, which is generally unsatisfactory to construct realistic reservoir models. Moreover, due to the large spatial and temporal scale of a tracer test in deep reservoirs, the concentration levels measured in the field are relatively low due to dispersion that complicates the assessment of breakthrough curve tailing and residence time. Fitting tracer data with fully resolving 3-D numerical models thus may be more appropriate, but even with a rich set of field data, reliable calibration is often compromised by the high computational effort and data hunger of such models. In this study, an advanced workflow is presented for evaluating tracer test data. Firstly, a 3-D analytical model in which solute transport is considered in anisotropic porous media is developed. Green's function method is applied to obtain a moving line source solution of the convection-dispersion-diffusion equation for solute transport in a 3-D porous medium. In addition, Green's function equation is analytically convoluted with a rectangular pulse function, which represents tracer injection. Secondly, the analytical model results are fitted to the tracer test data by Monte-Carlo simulations to obtain feasible ranges of flow velocities, as well as longitudinal and transversal dispersivities. Finally, the derived parameter values are implemented in a 3-D numerical model to evaluate the solute residence time in a large-scale reservoir. The results applied to field data from the Kızıldere field in Turkey demonstrate that the workflow provides robust estimates of effective parameters from well-to-well data in complex reservoir systems with anisotropic flow paths. Thus, despite the higher effort of applying convolution and stochastic parameter estimation, the preceding analytical step of the workflow substantially eases numerical model set-up.

Late Summer Water Sources in Rivers and Lakes of the Upper Yana River Basin, Northern Eurasia, Inferred from Hydrological Tracer Data

Major ions, stable isotopes, and trace elements, including rare earth elements (REEs), are used as natural tracers in the qualitative assessment of potential water sources in lakes and rivers of the upper Yana River basin, between Verkhoyansk and Chersky Ranges, during the late summer period. Three distinct regions were sampled, and a dominant water source in each region was qualitatively inferred from water chemistry data. The REE distribution pattern was found to be highly regional and controlled by pH and carbonate contents. Mountain headwater stream at the Verkhoyansk Range north slope, the Dulgalakh River, shows an input from a mixture of shallow groundwater and icing meltwater, with a depleted isotopic signature (δ18O below –21‰), d-excess (dex = δ2H − 8·δ18O) above 18, enrichment in Mg and Sr, and depletion in heavy REEs. The Derbeke Depression lakes and streams are fed by rainfall having ultra-low total dissolved solids (TDS) content, below 25 mg/L, and a convex-up REE pattern. In a medium mountainous river at the Chersky Range flank, the Dogdo River, leaching through fissured Jurassic carbonates is a dominant runoff pathway. Riverine water is heavily depleted in light REEs, but enriched in Mo, Rb, Sb, W and U. In the Dulgalakh River water, high positive Sm and Gd anomalies were observed, attributed either to local geology (greenshists), historical mining legacy, or contemporary winter road operations.

Addendum to “Quantifying Uncertainty in Tracer‐Based Hydrograph Separations” for Three‐Component Mixing Problems

AbstractWater mixing problems are common in hydrology. A 1998 paper describing uncertainty analysis in tracer‐based mixing problems is widely cited but does not present the equations needed for three‐component problems. This Commentary presents the equations needed to compute the uncertainties in the mixing fractions for a three‐component water mixing problem based on tracer data.

A Pointwise Conservative Method for Thermochemical Convection Under the Compressible Anelastic Liquid Approximation

AbstractIn prior work we found that precise approximation of the continuity constraint is crucial for accurate propagation of tracer data when advected through a background incompressible velocity field (Sime et al., 2021, https://doi.org/10.1029/2020gc009349). Here we extend this investigation to compressible flows using the anelastic liquid approximation (ALA) and address four related issues: (a) Exact conservation of tracer discretized fields through a background compressible velocity; (b) Exact mass conservation; (c) Addition and removal of tracers without affecting (exact) conservation to preserve a consistent number of tracers per cell; and (d) the diffusion of tracer data, for example, as induced by thermal or chemical effects. In this process we also present an abstract formulation of the interior penalty hybrid discontinuous Galerkin (HDG) finite element formulation for diffusion problems and apply it to the advection‐diffusion and compressible Stokes systems. Finally we present numerical experiments exhibiting the HDG compressible Stokes momentum formulation's superconvergent compressibility approximation and reproduce examples of a community benchmark for the ALA.

A Fourteen-year Review of Practice Patterns and Evidence-based Medicine in Operative Metacarpal Fracture Repair.

Background:The American Board of Plastic Surgery has been collecting practice data on metacarpal fracture operative repair since 2006 as part of its Continuous Certification process. These data allow plastic surgeons to compare their surgical experience to national trends. Additionally, these data present the opportunity to analyze those trends in relation to evidence-based medicine.Methods:Data on metacarpal fracture operative repair from May 2006 to December 2014 were reviewed and compared with those from January 2015 to March 2020. National practice trends observed in these data were evaluated and reviewed alongside published literature and evidence-based medicine.Results:In total, 1160 metacarpal fracture repair cases were included. Outpatient (as opposed to inpatient) operative repairs have been trending upward, from 50% to 61% (P < 0.001). Most repairs were performed under general anesthesia (68%), and there was a decrease in the use of regional anesthesia between our two cohorts (14%–9%; P = 0.01). An open reduction with internal fixation was the most popular technique (51%), and a decrease in the use of closed reduction with splinting was observed (16%–10%; P = 0.001). Stiffness was the most commonly reported adverse event. Topics addressed in evidence-based medicine articles but not tracer data included interosseous wiring, which has shown success in spiral shaft fracture treatment with minimal complications, and nonoperative management.Conclusion:As evidence-based recommendations continue to change with additional research inquiry, tracer data can provide an excellent overview of the current practice of metacarpal fracture repair and how effectively physicians adapt to remain aligned with best practices.

Modelling pollution transport dynamics and mixing in square manhole overflows

Detailed knowledge of the dynamic interactions between incoming sewerage and an overflowing manhole, and the resulting pollutant concentrations from manhole flooding, are critical for robust design and operations of wastewater infrastructures, especially during extreme climatic events. This study investigates the mixing and dispersion of solute in square manhole overflow using laboratory tracer experiment and analytical modelling. Tests are conducted with three flow rates to examine mixing characteristics over a wide range of operational conditions. Two overflowing scenarios including blocked pipe exit, and overflow in combination with pipe exit are studied. The Residence Time Distributions (RTD) and longitudinal dispersion coefficients are determined to understand the characteristics of pollutant transport. The analysis of the fluorometric tracer data show the appropriateness and robustness of the deconvolution model adopted in this study for determining the mixing characteristics and RTDs (R2 > 0.95). Similarly, the Taylor's model was shown to be capable of predicting advective and dispersive mixing mechanisms within the manhole, for the range of flow conditions tested in this study. New empirical predictive formulae are derived to characterize the pollutant mixing in square manholes under different operational conditions.

Predicting Thermal Performance of an Enhanced Geothermal System From Tracer Tests in a Data Assimilation Framework

AbstractPredicting the thermal performance of an enhanced geothermal system (EGS) requires a comprehensive characterization of the underlying fracture flow patterns from practically available data such as tracer data. However, due to the inherent complexities of subsurface fractures and the generally insufficient geological/geophysical data, interpreting tracer data for fracture flow characterization and thermal prediction remains a challenging task. The present study aims to tackle the challenge by leveraging a data assimilation method to maximize the utilization of information inherently contained in tracer data, and meanwhile maintain the flexibility to handle various uncertainties. A tracer data interpretation framework was proposed with the following three components integrated: (a) We use principal component analysis (PCA) to reduce the dimensionality of model parameter space. (b) We use ES‐MDA (ensemble smoother with multiple data assimilation) to invert for fracture aperture/flow fields and obtain posterior model ensembles for uncertainty quantification. Various data types are assimilated jointly to improve the predictive ability of the posterior ensemble. (c) The inverted fracture aperture fields are then incorporated into reservoir models to predict thermal performance. We developed a field‐scale EGS model to verify the ability of the framework to characterize highly heterogeneous fracture aperture/flow fields and predicting thermal performance. We also applied the framework to a mesoscale field experiment to demonstrate its potential application in real‐world geothermal reservoirs. The results indicate that the proposed framework can effectively retrieve fracture flow information from tracer data for thermal prediction and uncertainty quantification, and thus provide informative guidance for EGS optimization and risk management.

Going digital: added value of electronic data collection in 2018 Afghanistan Health Survey

BackgroundThrough a nationally representative household survey in Afghanistan, we conducted an operational study in two relatively secure provinces comparing effectiveness of computer-aided personal interviewing (CAPI) with paper-and-pencil interviewing (PAPI).MethodsIn Panjshir and Parwan provinces, household survey data were collected using paper questionnaires in 15 clusters, and OpenDataKit (ODK) software on electronic tablets in 15 other clusters. Added value was evaluated from three perspectives: efficient implementation, data quality, and acceptability. Efficiency was measured through financial expenditures and time stamped data. Data quality was measured by examining completeness. Acceptability was studied through focus group discussions with survey staff.ResultsSurvey costs were 68% more expensive in CAPI clusters compared to PAPI clusters, due primarily to the upfront one-time investment for survey programming. Enumerators spent significantly less time administering surveys in CAPI cluster households (248 min survey time) compared to PAPI (289 min), for an average savings of 41 min per household (95% CI 25–55). CAPI offered a savings of 87 days for data management over PAPI.Among 49 tracer variables (meaning responses were required from all respondents), small differences were observed between PAPI and CAPI. 2.2% of the cleaned dataset’s tracer data points were missing in CAPI surveys (1216/ 56,073 data points), compared to 3.2% in PAPI surveys (1953/ 60,675 data points). In pre-cleaned datasets, 3.9% of tracer data points were missing in CAPI surveys (2151/ 55,092 data points) compared to 3.2% in PAPI surveys (1924/ 60,113 data points).Enumerators from Panjsher and Parwan preferred CAPI over PAPI due to time savings, user-friendliness, improved data security, and less conspicuity when traveling; however approximately half of enumerators trained from all 34 provinces reported feeling unsafe due to Taliban presence. Community and household respondent skepticism could be resolved by enumerator reassurance. Enumerators shared that in the future, they prefer collecting data using CAPI when possible.ConclusionsCAPI offers clear gains in efficiency over PAPI for data collection and management time, although costs are relatively comparable even without the programming investment. However, serious field staff concerns around Taliban threats and general insecurity mean that CAPI should only be conducted in relatively secure areas.

Comparing the clinical performance and cost efficacy of [68Ga]Ga-PSMA-11 and [18F]PSMA-1007 in the diagnosis of recurrent prostate cancer: a Markov chain decision analysis

PurposeAmongst others, [68Ga]Ga-PSMA-11 and [18F]PSMA-1007 are available for the detection of recurrent prostate cancer (rPC). There are currently limited data comparing the performance of these two radioligands with respect to clinical outcomes or their cost efficacy, which this study aims to address.MethodsTwo hundred and forty-four patients undergoing PSMA PET/CT for rPC were retrospectively analysed for this study (one hundred and twenty two with each radiopharmaceutical) to generate rates of PET positivity, negativity and unclear findings. Patients underwent follow-up to determine the rate of additional examinations and to confirm PET findings. A Markov chain decision analysis was implemented to model clinical decision-making processes and to analyse clinical performance of the two tracers. We determine their clinical cost efficacies using cost data from several countries where both radiotracers are in routine use.ResultsThe PET positivity rate was non-significantly higher for [18F]PSMA-1007 compared to [68Ga]Ga-PSMA-11 (91.8% vs. 86.9%, p = 0.68), whereas the rate of uncertain findings was significantly greater (17.2% vs. 8.25%, p = 0.02). The probability of a true positive finding was higher for [68Ga]Ga-PSMA-11 (0.90, 95% CI 0.70-0.98) vs. [18F]PSMA-1007 (0.81, 95% CI 0.66–0.91). A significantly (p < 0.0001) higher PPV for [68Ga]Ga-PSMA-11 (0.99, 95% CI 0.99–1.0 vs. 0.86) was found compared to [18F]PSMA-1007 (0.86, 95% CI 0.82–1.00). Intervention efficacy analysis favoured [68Ga]Ga-PSMA-11, where the number needed to image (to achieve a true positive finding) was 10.58 and the number needed to image to harm (to achieve a false positive finding) was − 8.08. A cost efficacy analysis favours [68Ga]Ga-PSMA-11 in three of the four jurisdictions analysed where health economic data was available (Switzerland, Israel, Australia) and [18F]PSMA-1007 in one jurisdiction (Denmark).ConclusionThe analysis reveals a non-significantly higher PET positivity rate for [18F]PSMA-1007, but finds significantly greater rates of uncertain findings and false positive findings when compared to [68Ga]Ga-PSMA-11. We find differences in the two tracers in terms of clinical performance and cost efficacy. The method presented herein is generalisable and can be used with clinical or cost data for other countries or tracers.

Achieving Equilibrium as a Semi‐Alluvial Channel: Anthropogenic, Bedrock, and Colluvial Controls on the White Clay Creek, PA, USA

AbstractBased on well‐developed hydraulic geometry relations for width and depth, classic studies initially interpreted the Mid‐Atlantic White Clay Creek (WCC) as a quasi‐equilibrium, alluvial channel. Subsequent studies document the legacy of colonial‐age watershed disturbances and urban development, confounding earlier classifications. To investigate this matter, we contribute new data from reach‐scale geomorphic mapping, and observations and modeling of bed material transport. WCC's longitudinal profile reflects a history of bedrock incision, while hydraulic geometry equations for width and depth indicate quasi‐equilibrium cross‐sectional adjustment. Alluvial landforms such as pools and riffles, bars, and actively forming floodplains occur at all 12 study sites, but exposures of bedrock and colluvium are also common. The ratio of bankfull to threshold Shields stress averages 1.41 (range: 0.41–2.63), suggesting that WCC is an alluvial, threshold, gravel‐bed river. However, a numerical model of WCC bed material transport and grain size, calibrated to bedload tracer data, demonstrates that 22% (range: 8%–73%) of bed material is composed of immobile, locally sourced cobbles and boulders, while the remaining bed material represents mobile, sand to cobble‐sized alluvium; this leads us to classify WCC as a semi‐alluvial river. Additional computations suggest that channel morphology is insensitive to bed material supply. Field observations imply that bankfull Shields stresses do not represent channel adjustments to achieve stable banks; rather, width adjustment likely reflects cohesive bank processes. Despite the numerous and contradictory labels applied to WCC (i.e., quasi‐equilibrium, Anthropocene, bedrock, semi‐alluvial, and gravel‐bed), each term contributes insight that any single conceptual model would be unable to provide alone.

Integrated Fracture Characterization of Thamama Reservoirs in Abu Dhabi Oil Field, United Arab Emirates

Summary Volumetric maximum curvature attribute computed from 3D ocean bottom cable (OBC) seismic data, production logging tool (PLT), inorganic chemical tracer data, and fractures observed from core and full-bore formation microimager (FMI) logs were integrated to characterize fractured carbonate reservoirs of an offshore oil field in Abu Dhabi, United Arab Emirates (UAE). The extracted maximum curvature anomalies are predominantly orientated in NNE-SSW and NE-SW, a trend perpendicular to the dominant fault direction in the oil field and similar to the dominant strike directions of fractures measured from core data and FMI logs. Because the fracture strike directions of well data mimic the strike directions of curvature anomalies at corresponding reservoir levels, we interpreted the maximum curvature anomalies to represent dilatational fractured zones or fracture corridors. Integration of dynamic data, such as PLT and chemical tracers, and maximum curvature anomalies demonstrate that the inferred fracture zones can determine water breakthroughs as well as inter- and intrareservoir communications. As a result, this study highlights possible fracture zones and their internal architecture, as well as their potential flow capabilities. These results play a key role in reservoir management and monitoring of water movement through structural pathways.

The role of spatial embedding in mouse brain networks constructed from diffusion tractography and tracer injections

Diffusion MRI tractography is the only noninvasive method to measure the structural connectome in humans. However, recent validation studies have revealed limitations of modern tractography approaches, which lead to significant mistracking caused in part by local uncertainties in fiber orientations that accumulate to produce larger errors for longer streamlines. Characterizing the role of this length bias in tractography is complicated by the true underlying contribution of spatial embedding to brain topology. In this work, we compare graphs constructed with ex vivo tractography data in mice and neural tracer data from the Allen Mouse Brain Connectivity Atlas to random geometric surrogate graphs which preserve the low-order distance effects from each modality in order to quantify the role of geometry in various network properties. We find that geometry plays a substantially larger role in determining the topology of graphs produced by tractography than graphs produced by tracers. Tractography underestimates weights at long distances compared to neural tracers, which leads tractography to place network hubs close to the geometric center of the brain, as do corresponding tractography-derived random geometric surrogates, while tracer graphs place hubs further into peripheral areas of the cortex. We also explore the role of spatial embedding in modular structure, network efficiency and other topological measures in both modalities. Throughout, we compare the use of two different tractography streamline node assignment strategies and find that the overall differences between tractography approaches are small relative to the differences between tractography- and tracer-derived graphs. These analyses help quantify geometric biases inherent to tractography and promote the use of geometric benchmarking in future tractography validation efforts.

Influence of redox gradients on nitrate transport from the landscape to groundwater and streams

Increases in nitrogen applications to the land surface since the 1950s have led to a cascade of negative environmental impacts, including degradation of drinking water supplies, nutrient enrichment of aquatic ecosystems and contributions to global climate change. In this study, groundwater, streambed porewater, and stream sampling were used to establish trends in nitrate concentrations and how redox gradients influence nitrate transport across diverse glacial terranes. Decadal sampling has found that elevated nitrate concentrations in shallow groundwater beneath cropland have been sustained for decades. Redox gradients established in the saturated zone using dissolved O2, iron, nitrate and excess N2 from denitrification suggest that nitrate-bearing zones are thin in glacial terranes dominated by fine materials. These thin nitrate-bearing zones lead to suboxic, low nitrate streambed porewater and limit the contributions of nitrate to streams from slow-flow groundwater. In contrast, thick oxic zones in more coarse-grained glacial terranes allow nitrate to reach deeper groundwater, resulting in streambed porewater with elevated nitrate concentrations and causing a large portion of stream nitrate to be derived from slow-flow groundwater. Groundwater age tracer data indicate that denitrification occurs more quickly in the terrane dominated by fine material than in the more coarse-grained terrane. The quicker depletion of nitrate in the more fine-grained terrane suggests that the thinner oxic zone in this terrane is due, in part, to the greater availability and reactivity of electron donors in this terrane than in the more coarse-grained terrane. Groundwater age tracer data and hydrograph separation analysis suggest that saturated zone lag times between when changes in land use practices occur and when changes in stream water are fully observed may vary widely across hydrogeologic settings.

Using nitrate as a tracer to constrain age selection preferences in catchments with strong seasonality

Excess export of nitrate to streams has been an environmental issue attracting attention across the world. Lumped models based on StorAge Selection (SAS) functions have been used widely to investigate this export processes in terms of hydrological and chemical responses in catchment outflux – both in discharge (Q) and in evapotranspiration (ET). The validity of these models depends on the appropriate choice of water age selection preferences, i.e. the parameterization of the SAS functions of Q and ET, which are often calibrated against observed in-stream tracer data. This study attempted to assess the usefulness of in-stream nitrate (N-NO3) concentrations for resolving the SAS functions in terms of plausibility (being physically meaningful) and parameter uncertainty, in a small agricultural catchment in central Germany that experiences strong seasonality. A spatially implicit model was built to simulate the dynamics of nitrate export. The data sets of in-stream nitrate concentrations, nitrogen surplus in the soil, and the median age of Q were used to constrain the model. The best-fit (to all data sets) results indicate high plausibility of the calibrated, temporally dynamic age selection preferences for Q for most time of a year, however, not for ET. The uncertainty analysis using a Monte Carlo approach suggests that lower uncertainty is associated with the SAS functions for Q than that for ET. The uncertainties of the SAS functions can be reduced by 60% combining the three datasets instead of using only in-stream concentration data. This study demonstrated the usefulness of combined data sets for adequately determining dynamic age selection preferences for Q, but not for ET. Better constraining selection preferences will require better in-stream concentration data for the dry period and additional data sets for ET (e.g. age of ET).