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Sample records for organ residence time

  1. Indoor Residence Times of Semivolatile Organic Compounds: Model Estimation and Field Evaluation

    EPA Science Inventory

    Indoor residence times of semivolatile organic compounds (SVOCs) are a major and mostly unavailable input for residential exposure assessment. We calculated residence times for a suite of SVOCs using a fugacity model applied to residential environments. Residence times depend on...

  2. Indoor Residence Times of Semivolatile Organic Compounds: Model Estimation and Field Evaluation

    EPA Science Inventory

    Indoor residence times of semivolatile organic compounds (SVOCs) are a major and mostly unavailable input for residential exposure assessment. We calculated residence times for a suite of SVOCs using a fugacity model applied to residential environments. Residence times depend on...

  3. Chloride and organic chlorine in forest soils: storage, residence times, and influence of ecological conditions.

    PubMed

    Redon, Paul-Olivier; Abdelouas, Abdesselam; Bastviken, David; Cecchini, Sébastien; Nicolas, Manuel; Thiry, Yves

    2011-09-01

    Recent studies have shown that extensive chlorination of natural organic matter significantly affects chlorine (Cl) residence time in soils. This natural biogeochemical process must be considered when developing the conceptual models used as the basis for safety assessments regarding the potential health impacts of 36-chlorine released from present and planned radioactive waste disposal facilities. In this study, we surveyed 51 French forested areas to determine the variability in chlorine speciation and storage in soils. Concentrations of total chlorine (Cl(tot)) and organic chlorine (Cl(org)) were determined in litterfall, forest floor and mineral soil samples. Cl(org) constituted 11-100% of Cl(tot), with the highest concentrations being found in the humus layer (34-689 mg Cl(org) kg(-1)). In terms of areal storage (53 - 400 kg Cl(org) ha(-1)) the mineral soil dominated due to its greater thickness (40 cm). Cl(org) concentrations and estimated retention of organochlorine in the humus layer were correlated with Cl input, total Cl concentration, organic carbon content, soil pH and the dominant tree species. Cl(org) concentration in mineral soil was not significantly influenced by the studied environmental factors, however increasing Cl:C ratios with depth could indicate selective preservation of chlorinated organic molecules. Litterfall contributions of Cl were significant but generally minor compared to other fluxes and stocks. Assuming steady-state conditions, known annual wet deposition and measured inventories in soil, the theoretical average residence time calculated for total chlorine (inorganic (Cl(in)) and organic) was 5-fold higher than that estimated for Cl(in) alone. Consideration of the Cl(org) pool is therefore clearly important in studies of overall Cl cycling in terrestrial ecosystems.

  4. Structure, provenance and residence time of terrestrial organic carbon: insights from Programmed temperature Pyrolysis-Combustion of river sediments

    NASA Astrophysics Data System (ADS)

    Feng, X.; Galy, V.; Rosenheim, B. E.; Roe, K. M.; Williams, E. K.

    2010-12-01

    The terrestrial organic carbon (OC) represents one of the largest reservoirs of C on earth and thus plays a crucial role in the global C cycle, participating to the regulation of atmospheric chemistry. While degradation of sedimentary OC (petrogenic C) is a source of CO2 for the atmosphere, burial of biospheric C (e.g. plant debris and soil OC) is a long-term sequestration of atmospheric CO2. Over short timescales, the atmospheric CO2 level is also sensitive to variations of the residence time of carbon in continental reservoirs. Fluvial transport plays a crucial role in the organic carbon cycle, constituting the connection between the different reservoirs and promoting the transfer of C from one reservoir to the other. Moreover, thanks to the integrating effect of erosion, studying river sediments allows the spatial and temporal integration of organic carbon exchanges occurring in a given basin. OC transported by rivers (riverine OC) is known to be extremely heterogeneous in nature and reactivity, however; ranging from extremely refractory petrogenic C (e.g. graphite) to soil complex OC to labile vegetation debris. Here we use a recently developed method, a programmed-temperature pyrolysis-combustion system (PTP-CS) coupled to multiisotopic analysis, to determine the reactivity, age and nature of OC in river sediments. The method takes advantage of the wide range of reactivity and radiocarbon content of different components of riverine OC. We submitted to PTP-CS a set of river sediments from 1) the Ganges-Brahmputra river system and, 2) the lower Mississippi river. Preliminary results highlight the heterogeneous nature of riverine OC. Different components of the riverine OC pool decompose at different temperature and are characterized by extremely variable isotopic compositions. The decomposition of radiocarbon dead petrogenic C at very high temperature allows estimating the respective contribution of biospheric and petrogenic C. Moreover, biospheric OC appears to

  5. Determination of the hydraulic residence time in a trickling biofilter filled with organic matter.

    PubMed

    Garzón-Zúñiga, M A; Lessard, P; Buelna, G

    2003-05-01

    Biofiltration process using peat as media has been shown to be efficient for the treatment of agroindustrial, chemical and municipal effluents. However, determining the hydraulic retention time of this process is difficult due to many factors. Generally tracer techniques are used, but they measure the molecular retention time instead of the hydraulic retention time; and depending on the case, the results can be wrong. In order to contribute to solving this problem, the objective of this research was to find a trustworthy and adequate technique to determine the hydraulic retention time for a process using a very adsorbent filter bed material (peat). An overview of the hydraulic behaviour of a peat bed filter related to their particular structural composition is presented. Then, based on these characteristics, two different techniques to determine the hydraulic retention time were developed and tested. The first, an indirect modified tracing technique and, the second, a direct one which determines the volume of liquid in treatment into the filter bed through the establishment of a relation between the volume of porosity and the volume of empty spaces (or not occupied by liquid) into the filter bed. The results obtained showed that the proposed techniques gave similar results and proved adequate.

  6. Seasonality in the ``grasshopping'' and atmospheric residence times of persistent organic pollutants over the oceans

    NASA Astrophysics Data System (ADS)

    Jurado, Elena; Dachs, Jordi

    2008-09-01

    Persistent Organic Pollutants (POPs) are toxic, bioaccumulable and semi-volatile compounds that have been detected in all environmental compartments, even in remote pristine regions where they have never been produced or used. Long range atmospheric transport (LRAT) and subsequent deposition is the major route of introduction of POPs to the oceans, including remote regions, and thus to the marine food-webs. It has been suggested that when POPs travel through the atmosphere, they tend to move in stages. This is known as the grasshopper effect, a repeated process of volatilization and deposition, even though the measure of grasshopping potential has been elusive. Here we show the spatial and seasonal variability of the grasshopper and LRAT potentials for polychlorinated biphenyls (PCB), a significant class of POPs. The number of hops that a chemical undergoes during LRAT over the oceans presents an important spatial and seasonal variability driven by biogeochemical processes occurring in the water column. These results have important implications for the understanding of the widespread distribution and fractionation processes of POPs at the global scale, showing that transport events to remote regions, such the Arctic, are maximized during seasons of low primary productivity.

  7. Assessing the potential of stable carbon isotopes to better constrain the residence time of soil organic carbon using a depth-explicit modelling approach

    NASA Astrophysics Data System (ADS)

    Van de Broek, Marijn; Wang, Zhengang; Minella, Jean; Govers, Gerard

    2017-04-01

    The residence time of soil organic carbon (SOC) varies considerably between different ecosystems and is difficult to measure using only field experiments. Therefore, models are often used to assess the residence time of SOC, but the range of optimal model parameters is often poorly constrained. This has important consequences for the reliability with which SOC dynamics are simulated by earth system models, leading to large uncertainties about the contribution of SOC to atmospheric CO2 concentrations. In order to improve the reliability of simulated SOC dynamics, and hence to assess more accurately the residence time of organic carbon (OC) in soils, we constructed a depth-explicit model that simultaneously simulates SOC dynamics and kinetic fractionation of stable carbon isotopes (δ13C). Using stable carbon isotopes as an additional constraint considerably increases our ability to interpret the observed SOC dynamics. For example, it allowed us to accurately assess the fraction of SOC lost after a forest ecosystem (C3 vegetation) was converted to cropland (corn - C4 vegetation). Through the evaluation the modelled depth profiles of δ13C against measured data, we are able to reduce the number of possible model parameters which result in an optimal simulation of SOC depth profiles. Therefore, the reliability of the simulated residence time of SOC increases significantly. We used our model to simulate the residence time of SOC at colluvial landscape positions in a small sub-tropical catchment in southern Brazil. Comparison with colluvial landscape positions in temperate ecosystems shows that the residence time of SOC is much shorter in our sub-tropical ecosystems. In addition, this approach allows us to assess the fate of organic carbon from different sources (e.g. locally produced versus carbon deposited together with sediments), which significantly increases our understanding of SOC dynamics in these environments.

  8. Understanding the diurnal cycle in fluvial dissolved organic carbon - The interplay of in-stream residence time, day length and organic matter turnover

    NASA Astrophysics Data System (ADS)

    Worrall, F.; Howden, N. J. K.; Burt, T. P.

    2015-04-01

    There is increasing interest in characterising the diurnal fluctuation of stream solute concentrations because observed data series derived from spot samples may be highly subjective if such diurnal fluctuations are large. This can therefore lead to large uncertainties, bias or systematic errors in calculation of fluvial solute fluxes, depending upon the particular sampling regime. A simplistic approach would be to assume diurnal fluctuations are constant throughout the water year, but this study proposes diurnal cycles in stream water quality can only be interpreted in the context of stream residence time and changing day length. Three years of hourly dissolved organic carbon (DOC) concentration and flow data from the River Dee catchment (1674 km2) were analysed, and statistical analysis of the entire record shows there is no consistent diurnal cycle in the record. From the 3-year record (1095 days) there were only 96 diurnal cycles could be analysed. Cycles were quantified in terms of their: relative and absolute amplitude; duration; time to maximum concentration; asymmetry; percentile flow and in-stream residence time. The median diurnal cycle showed an amplitude that was 9.2% of the starting concentration; it was not significantly asymmetric; and occurred at the 19th percentile flow. The median DOC removal rate was 0.07 mg C/l/hr with an inter-quartile range of 0.052-0.100 mg C/l/hr. Results were interpreted as controlled by two, separate, zero-order kinetic rate laws, one for the day and one for the night. There was no single diurnal cycle present across the record, rather a number of different cycles controlled by the combination of in-stream residence time and exposure to contrasting light conditions. Over the 3-year period the average in-stream loss of DOC was 32%. The diurnal cycles evident in high resolution DOC data are interpretable, but require contextual information for their influence on in-stream processes to be understood or for them to be utilised.

  9. Solid organ transplant training objectives for residents.

    PubMed

    Masclans, J R; Vicente, R; Ballesteros, M A; Sabater, J; Roca, O; Rello, J

    2012-11-01

    With the aim of analyzing the current state of the educational objectives in the training of medical residents in solid organ transplantation (SOT), we conducted a review of the status of the official programs of the specialities involved in SOT, focusing particularly on lung transplantation. A survey of medical residents was also conducted to allow reflexion about the topic. We obtained 44 surveys from 4 University Hospitals with active programs in SOT, mainly from intensive care medicine and anesthesiology residents. We detected an important number of courses oriented to organ donation but very limited in terms of basic training in the management of the immediate postoperative period, principles of immunosuppression and updates on immunosuppressive therapy and complications (particularly rejection and infection). We also identified that these educational aspects should be directed not only to medical residents from specialities with a close retation to SOT, but also to all who may at some time have a relation to such patients. The use of information and communication techniques (ICTs), on-line courses and also simulations should be instruments to take into account in the biomedical training of medical residents. We conclude that we need a specific training program in complications of SOT, as well as fundamental principles in immunology and immunosuppressor pharmacology. Copyright © 2012 Elsevier España, S.L. y SEMICYUC. All rights reserved.

  10. Curricula and Organization of Primary Care Residencies in Internal Medicine.

    ERIC Educational Resources Information Center

    Eisenberg, John M.

    1980-01-01

    The organization and curricula of internal medicine residencies programs that emphasize primary care are described and compared with traditional residencies in internal medicine. It is noted that primary care residents spend more time in ambulatory care and are allowed more electives in specialties outside of internal medicine. Out-of-hospital…

  11. The Role of Shallow Landslides in the Downslope Transfer of Organic Matter and its Implications on the Residence Time of Carbon in a Tropical Mountain System

    NASA Astrophysics Data System (ADS)

    Restrepo, C.; Ramos-Scharron, C. E.; Joseph-Haines, M.; Miller, M.

    2006-12-01

    Landslides are common features of many tropical mountains, potentially inducing significant changes in land cover and influencing carbon dynamics from local to regional scales. Landslides provide a relatively infrequent but unique mechanism that rapidly transfers organic matter stored in hillslope and low-order channel vegetation and soils to colluvial deposits in fluvial networks and floodplains on higher-order channels. While carbon stored in hillslope vegetation and soil pools may have mean residence times in the order of 10's of years, carbon stored in landslide deposits on floodplains and terraces might have mean residence times in the scale of 100's to 1,000's of years. This study is the first to explore the contribution of landslides in the transfer of organic matter and its consequences on the residence time of carbon within tropical montane watersheds. Focusing in the Sierra de las Minas mountain range in eastern Guatemala we estimated the contribution of landslides to land-cover change and carbon budgets using various remote sensing approaches to create a spatial databases of landslide scars, scoured stream channels, and debris deposits triggered by an earthquake and a rainstorm in 1976 and 1998, respectively. Landslide scars and debris flow scour areas were classified by vegetation types, and their area was converted into units of biomass, soil organic matter, and carbon content based on published data for similar vegetation types in Central America. The net transfer of organic matter and carbon were calculated as the difference between the estimated storage totals, sorted by stream-order, for pre- landslide event conditions and post-event estimates that incorporate the landslides. Even though future field efforts will begin to quantify residence times of carbon within different storage pools, we have attempted to determine an order of magnitude estimate of the residence time of debris deposits in high-order streams by considering their location relative

  12. Variable residence time vortex combustor

    DOEpatents

    Melconian, Jerry O.

    1987-01-01

    A variable residence time vortex combustor including a primary combustion chamber for containing a combustion vortex, and a plurality of louvres peripherally disposed about the primary combustion chamber and longitudinally distributed along its primary axis. The louvres are inclined to impel air about the primary combustion chamber to cool its interior surfaces and to impel air inwardly to assist in driving the combustion vortex in a first rotational direction and to feed combustion in the primary combustion chamber. The vortex combustor also includes a second combustion chamber having a secondary zone and a narrowed waist region in the primary combustion chamber interconnecting the output of the primary combustion chamber with the secondary zone for passing only lower density particles and trapping higher density particles in the combustion vortex in the primary combustion chamber for substantial combustion.

  13. Modeling the rate of turnover of DOC and particulate organic carbon in a UK, peat-hosted stream: Including diurnal cycling in short-residence time systems

    NASA Astrophysics Data System (ADS)

    Worrall, F.; Moody, C. S.

    2014-10-01

    This study proposes a multicomponent, multiprocess scheme to explain the turnover of organic matter (particulate and dissolved organic matter) in streams. The scheme allows for production and degradation of organic matter by both photic and aphotic processes with transformation of dissolved organic carbon (DOC) to increasingly refractory forms. The proposed scheme was compared to 10 months of experimental observations of the turnover and fate of particulate and dissolved organic matter in stream water from a peat-covered catchment. The scheme was able to explain average decline in DOC concentration of 65% over 70 h with a 13% mean average percentage error based on turnover in three types of organic matter (particulate, labile dissolved, and refractory dissolved) although the order and rate of reactions did change between sets of experimental observations. The modeling suggests that activation energies are low for all except the most refractory forms of DOC in turn, suggesting that processes are not sensitive to temperature change. Application of the modeling scheme to organic matter turnover in the River Tees, northern England, showed that annual removal of total organic carbon was equivalent to between 13 and 33 t C/km2/yr from an at source export of between 22 and 56 t C/km2/yr giving a total in-stream loss rate of between 53 and 62% over a median in-stream residence time of 35 h.

  14. Evaluation of quantitative imaging methods for organ activity and residence time estimation using a population of phantoms having realistic variations in anatomy and uptake

    SciTech Connect

    He Bin; Du Yong; Segars, W. Paul; Wahl, Richard L.; Sgouros, George; Jacene, Heather; Frey, Eric C.

    2009-02-15

    Estimating organ residence times is an essential part of patient-specific dosimetry for radioimmunotherapy (RIT). Quantitative imaging methods for RIT are often evaluated using a single physical or simulated phantom but are intended to be applied clinically where there is variability in patient anatomy, biodistribution, and biokinetics. To provide a more relevant evaluation, the authors have thus developed a population of phantoms with realistic variations in these factors and applied it to the evaluation of quantitative imaging methods both to find the best method and to demonstrate the effects of these variations. Using whole body scans and SPECT/CT images, organ shapes and time-activity curves of 111In ibritumomab tiuxetan were measured in dosimetrically important organs in seven patients undergoing a high dose therapy regimen. Based on these measurements, we created a 3D NURBS-based cardiac-torso (NCAT)-based phantom population. SPECT and planar data at realistic count levels were then simulated using previously validated Monte Carlo simulation tools. The projections from the population were used to evaluate the accuracy and variation in accuracy of residence time estimation methods that used a time series of SPECT and planar scans. Quantitative SPECT (QSPECT) reconstruction methods were used that compensated for attenuation, scatter, and the collimator-detector response. Planar images were processed with a conventional (CPlanar) method that used geometric mean attenuation and triple-energy window scatter compensation and a quantitative planar (QPlanar) processing method that used model-based compensation for image degrading effects. Residence times were estimated from activity estimates made at each of five time points. The authors also evaluated hybrid methods that used CPlanar or QPlanar time-activity curves rescaled to the activity estimated from a single QSPECT image. The methods were evaluated in terms of mean relative error and standard deviation of the

  15. A Time Study of Plastic Surgery Residents.

    PubMed

    Lau, Frank H; Sinha, Indranil; Jiang, Wei; Lipsitz, Stuart R; Eriksson, Elof

    2016-05-01

    Resident work hours are under scrutiny and have been subject to multiple restrictions. The studies supporting these changes have not included data on surgical residents. We studied the workday of a team of plastic surgery residents to establish prospective time-study data of plastic surgery (PRS) residents at a single tertiary-care academic medical center. Five trained research assistants observed all residents (n = 8) on a PRS service for 10 weeks and produced minute-by-minute activity logs. Data collection began when the team first met in the morning and continued until the resident being followed completed all non-call activities. We analyzed our data from 3 perspectives: 1) time spent in direct patient care (DPC), indirect patient care, and didactic activities; 2) time spent in high education-value activities (HEAs) versus low education-value activities; and 3) resident efficiency. We defined HEAs as activities that surgeons must master; other activities were LEAs. We quantified resident efficiency in terms of time fragmentation and time spent waiting. A total of 642.4 hours of data across 50 workdays were collected. Excluding call, residents worked an average of 64.2 hours per week. Approximately 50.7% of surgical resident time was allotted to DPC, with surgery accounting for the largest segment of this time (34.8%). Time spent on HEAs demonstrated trended upward with higher resident level (P = 0.086). Time in spent in surgery was significantly associated with higher resident levels (P < 0.0001); 57.7% of activities require 4 minutes or less, suggesting that resident work was highly fragmented. Residents spent 10.7% of their workdays waiting for other services. In this first-time study of PRS residents, we found that compared with medicine trainees, surgical residents spent 3.23 times more time on DPC. High education-value activities comprised most of our residents' workdays. Surgery was the leading component of both DPC and HEAs. Our residents were highly

  16. Soil Organic Carbon Residence Time in Japanese Temperate Forest: Insight From Radiocarbon Analysis of Density Fractionated Soil

    NASA Astrophysics Data System (ADS)

    Kondo, M.; Uchida, M.; Wagai, R.; Suzuki, M.; Shibata, Y.

    2008-12-01

    Soil organic matter is an important carbon reservoir managing CO2 concentration in the atmosphere. However, the mechanism of soil carbon stabilization is little known. To explore the rate of C cycling in a temperate forest soil in Japan, at one of AsiaFlux monitoring sites, we sequentially density fractioned at 1.0, 1.6, 1.8, 2.1 and 2.4 g cm-3 on a soil at surface and deep soil layer and estimated turnover time of these SOC fractions. According to previous study in this site (Uchida et al., in prep.), large amount of light fraction (> 2.1 g cm-3) accounted at 35 - 50 cm depth and its age was significantly old as well as heavy fraction (> 2.1 g cm-3), although light fraction seems to consist of labile carbon. In this study, we investigated more better separation for labile fraction from mineral fraction in volcanic ash soil using different densities ranging from 1.6 to 1.8 g cm-3, excluding the most mineral and organio-mineral material from the light fraction. In surface layer (5 - 10 cm), carbon in lighter fractions (less than 1.8 g cm- 3) accounted for 42% of the total SOC their turnover times were shorter (6 - 43 yrs) than that in 1.8 - 2.1 g cm-3 (150 yrs). While, in deep layer (40 - 45 cm), lighter fraction comprised only small portion of total SOC (1%) but its age was significantly old (2038 yrs BP) as well as 1.8 - 2.1 g cm-3 (2335 yrs BP). The results partially support the previous study that volcanish-based Japanese temperate forest soil might be sequestrating carbon as light fractions semi-permanently.

  17. 13C/Palynological evidence of differential residence times of organic carbon prior to its sedimentation in East African Rift Lakes and peat bogs

    NASA Astrophysics Data System (ADS)

    Hillaire-Marcel, Claude; Aucour, Anne-Marie; Bonnefille, Raymonde; Riollet, Guy; Vincens, Annie; Williamson, David

    Most terrestrial plants producing large amounts of organic matter in the East African Rift follow the Calvin (C3) photosynthetic pathway. Their end products have δ13C values of ca. -27 ± 2‰ (vs. PDB). On the contrary, most Cyperaceae (notably Cyperus papyrus and C. latifolius) are characterized by higher 13C contents ° 13C = -10.5 ± 1‰ ) in relation to their Hatch and Slack (C4) photosynthetic cycle. In consequence, δ13C values in total organic matter (TOM) from peat bog or lake cores essentially responded to the proportion of detritus from C4-Cyperaceae. Immediate evidence of the development or disappearance of Cyperaceae around lake margins or in peat bogs can be found in pollen assemblages. Lag times between pollen signals and correlative ° 13C shifts in TOM from cores are therefore indicative of the residence time of organic matter prior to its sedimentation. Delayed sedimentation of TOM will result in 14C anomalies which depend on several parameters, most of them being site specific as shown by examples from a peat bog in Burundi and from southern Lake Tanganyika. An independent assessment of the chronology by high resolution paleomagnetic correlations indicates a ca. 1.5 ka apparent 14C age of TOM in Lake Tanganyika at the Pleistocene-Holocene transition.

  18. Controlled short residence time coal liquefaction process

    DOEpatents

    Anderson, Raymond P.; Schmalzer, David K.; Wright, Charles H.

    1982-05-04

    Normally solid dissolved coal product and a distillate liquid product are produced by continuously passing a feed slurry comprising raw feed coal and a recycle solvent oil and/or slurry together with hydrogen to a preheating-reaction zone (26, alone, or 26 together with 42), the hydrogen pressure in the preheating-reaction zone being at least 1500 psig (105 kg/cm.sup.2), reacting the slurry in the preheating-reaction zone (26, or 26 with 42) at a temperature in the range of between about 455.degree. and about 500.degree. C. to dissolve the coal to form normally liquid coal and normally solid dissolved coal. A total slurry residence time is maintained in the reaction zone ranging from a finite value from about 0 to about 0.2 hour, and reaction effluent is continuously and directly contacted with a quenching fluid (40, 68) to substantially immediately reduce the temperature of the reaction effluent to below 425.degree. C. to substantially inhibit polymerization so that the yield of insoluble organic matter comprises less than 9 weight percent of said feed coal on a moisture-free basis. The reaction is performed under conditions of temperature, hydrogen pressure and residence time such that the quantity of distillate liquid boiling within the range C.sub.5 -455.degree. C. is an amount at least equal to that obtainable by performing the process under the same conditions except for a longer total slurry residence time, e.g., 0.3 hour. Solvent boiling range liquid is separated from the reaction effluent and recycled as process solvent.

  19. Application of groundwater residence time tracers and broad screening for micro-organic contaminants in the Indo-Gangetic aquifer system

    NASA Astrophysics Data System (ADS)

    Lapworth, Dan; Das, Prerona; Mukherjee, Abhijit; Petersen, Jade; Gooddy, Daren; Krishan, Gopal

    2017-04-01

    Groundwater abstracted from aquifers underlying urban centres across India provide a vital source of domestic water. Abstraction from municipal and private supplies is considerable and growing rapidly with ever increasing demand for water from expanding urban populations. This trend is set to continue. The vulnerability of deeper aquifers (typically >100 m below ground) used for domestic water to contamination migration from often heavily contaminated shallow aquifer systems has not been studies in detail in India. This paper focusses on the occurrence of micro-organic contaminants within sedimentary aquifers beneath urban centres which are intensively pumped for drinking water and domestic use. New preliminary results from a detailed case study undertaken across Varanasi, a city with an estimated population of ca. 1.5 million in Uttar Pradesh. Micro -organic groundwater quality status and evolution with depth is investigated through selection of paired shallow and deep sites across the city. These results are considered within the context of paired groundwater residence time tracers within the top 150m within the sedimentary aquifer system. Groundwater emerging contaminant results are compared with surface water quality from the Ganges which is also used for drinking water supply. Broad screening for >800 micro-organic compounds was undertaken. Age dating tools were employed to constrain and inform a conceptual model of groundwater recharge and contaminant evolution within the sedimentary aquifer system.

  20. Secondary organic aerosol formation by limonene ozonolysis: Parameterizing multi-generational chemistry in ozone- and residence time-limited indoor environments

    NASA Astrophysics Data System (ADS)

    Waring, Michael S.

    2016-11-01

    Terpene ozonolysis reactions can be a strong source of secondary organic aerosol (SOA) indoors. SOA formation can be parameterized and predicted using the aerosol mass fraction (AMF), also known as the SOA yield, which quantifies the mass ratio of generated SOA to oxidized terpene. Limonene is a monoterpene that is at sufficient concentrations such that it reacts meaningfully with ozone indoors. It has two unsaturated bonds, and the magnitude of the limonene ozonolysis AMF varies by a factor of ∼4 depending on whether one or both of its unsaturated bonds are ozonated, which depends on whether ozone is in excess compared to limonene as well as the available time for reactions indoors. Hence, this study developed a framework to predict the limonene AMF as a function of the ozone [O3] and limonene [lim] concentrations and the air exchange rate (AER, h-1), which is the inverse of the residence time. Empirical AMF data were used to calculate a mixing coefficient, β, that would yield a 'resultant AMF' as the combination of the AMFs due to ozonolysis of one or both of limonene's unsaturated bonds, within the volatility basis set (VBS) organic aerosol framework. Then, β was regressed against predictors of log10([O3]/[lim]) and AER (R2 = 0.74). The β increased as the log10([O3]/[lim]) increased and as AER decreased, having the physical meaning of driving the resultant AMF to the upper AMF condition when both unsaturated bonds of limonene are ozonated. Modeling demonstrates that using the correct resultant AMF to simulate SOA formation owing to limonene ozonolysis is crucial for accurate indoor prediction.

  1. Residence times of branching diffusion processes

    NASA Astrophysics Data System (ADS)

    Dumonteil, E.; Mazzolo, A.

    2016-07-01

    The residence time of a branching Brownian process is the amount of time that the mother particle and all its descendants spend inside a domain. Using the Feynman-Kac formalism, we derive the residence-time equation as well as the equations for its moments for a branching diffusion process with an arbitrary number of descendants. This general approach is illustrated with simple examples in free space and in confined geometries where explicit formulas for the moments are obtained within the long time limit. In particular, we study in detail the influence of the branching mechanism on those moments. The present approach can also be applied to investigate other additive functionals of branching Brownian process.

  2. Mean residence time in barchan dunes

    NASA Astrophysics Data System (ADS)

    Zhang, D.; Yang, X.; Rozier, O.; Narteau, C.

    2013-12-01

    A barchan dune migrates when the sediment trapped on its lee side is remobilized by the flow. Then, sand grains may undergo many dune turnover cycles before their ejection along the horns, but the amount of time a sand grain contributes to the dune morphodynamics remains unknown. To estimate such a residence time, we analyze sediment particle motions in steady-state barchan dunes by tracking individual cells of a 3D cellular automaton dune model. The overall sediment flux may be decomposed into advective and dispersive fluxes to estimate the relative contribution of the underlying physical processes to the barchan dune shape. The net lateral sediment transport from the center to the horns indicates that dispersion on the stoss slope is more efficient than avalanches on the lee slope. The combined effect of these two antagonistic dispersive processes restricts the lateral mixing of sediment particles in the central region of barchan dunes. Then, for different flow strengths and dune sizes, we find that the mean residence time of sediment particles in barchan dunes is equal to the surface of the central longitudinal dune slices divided by the input sand flux. We infer that this central slice contains most of the relevant information about barchan dune morphodynamics. Finally, we initiate a discussion about sediment transport and memory in presence of bed forms using the advantages of the particle tracking technique.

  3. Mean sediment residence time in barchan dunes

    NASA Astrophysics Data System (ADS)

    Zhang, D.; Yang, X.; Rozier, O.; Narteau, C.

    2014-03-01

    When a barchan dune migrates, the sediment trapped on its lee side is later mobilized when exposed on the stoss side. Then sand grains may undergo many dune turnover cycles before their ejection along the horns, but the amount of time a sand grain contributes to the dune morphodynamics remains unknown. To estimate such a residence time, we analyze sediment particle motions in steady state barchans by tracking individual cells of a 3-D cellular automaton dune model. The overall sediment flux may be decomposed into advective and dispersive fluxes to estimate the relative contribution of the underlying physical processes to the barchan shape. The net lateral sediment transport from the center to the horns indicates that dispersion on the stoss slope is more efficient than the convergent sediment fluxes associated with avalanches on the lee slope. The combined effect of these two antagonistic dispersive processes restricts the lateral mixing of sediment particles in the central region of barchans. Then, for different flow strengths and dune sizes, we find that the mean residence time of sediment particles in barchans is equal to the surface of the central longitudinal dune slices divided by the input sand flux. We infer that this central slice contains most of the relevant information about barchan morphodynamics. Finally, we initiate a discussion about sediment transport and memory in the presence of bed forms using the advantages of the particle tracking technique.

  4. Many pediatric residents seek and obtain part-time positions.

    PubMed

    Cull, William L; Caspary, Gretchen L; Olson, Lynn M

    2008-02-01

    The goal was to monitor the number of pediatric residents seeking part-time employment after graduation and to examine the difficulty of their job searches, compared with residents seeking full-time employment. As part of the American Academy of Pediatrics Graduating Resident Survey, national random samples of 500 graduating, categorical pediatrics residents were surveyed from 2003 through 2005, between May and August of each year. Responses were pooled to examine resident interest in and experience with part-time employment. Totals of 308 (62%), 307 (61%), and 281 (56%) residents completed the survey in 2003, 2004, and 2005, respectively. Analyses focused on residents who applied for nonfellowship jobs. A total of 51% of residents applied for nonfellowship jobs. Of those who applied for such jobs, 38% reported that they applied for part-time positions and 21% actually accepted part-time positions. Residents who applied for part-time positions were more likely to report moderate or considerable job search difficulty (part-time: 36%; full-time: 25%). The average starting salary for residents who accepted part-time jobs was almost $34,000 less than that for residents working full-time (part-time: $71,615; full-time: $105,598). Residents who accepted part-time positions expected to work 15 hours less per week in practice (38 vs 23 hours) and were more likely to accept a position in the same city/area as their residency (part-time: 60%; full-time: 47%). Approximately 4 of 10 pediatric residents seek part-time employment after graduation, and 2 of 10 accept part-time positions. Strong interest in part-time positions is likely to continue, and this important trend has implications for the pediatric workforce.

  5. The residence time of organic matter in gas hydrate systems: Constraints from iodine and its isotopes at the Blake Ridge and Peru Trench

    NASA Astrophysics Data System (ADS)

    Snyder, G. T.; Dickens, G. R.; Fehn, U.

    2003-04-01

    Large gas hydrate deposits in marine sediment are dynamic systems where substantial amounts of carbon cycle between various solid, gas and dissolved phases over time. Recent modeling exercises, typically grounded with information from boreholes on the Blake Ridge (eastern United States margin), indicate this carbon cycling probably occurs over millions of years, so that while gas hydrate specimens may be very young, the overall deposit is older than surrounding sediment. Here we present measurements of iodine and 129I (half-life = 15.7 Myr) from gas hydrate bearing intervals on the Blake Ridge and Peru Trench, and discuss their significance in terms of carbon cycling. Pore waters on the Blake Ridge contain upwards of 1.7 mM of iodine with 129I/I ratios averaging 166x10-15. By contrast, pore waters from the Peru trench contain upwards of 1.2 mM of iodine with 129I/I ratios averaging 255x10-15. Depth profiles of dissolved iodide concentrations at both locations suggest a cycle whereby iodine is released from organic matter at deep depth, diffused upward, adsorbed onto organic matter at shallow depth, and subsequently buried. Iodine isotopic ratios decrease with depth, and inversely correlate with dissolved iodide, bromide, and dissolved organic carbon concentrations. A straightforward model applied to both sites indicates that iodine-rich organic carbon has accumulated for about 63 Myr on the Blake Ridge and about 42 myr in the Peru Trench. Thus, iodine and carbon cycling in both deposits is indeed very old, with the Blake Ridge possibly representing an extreme case. The longevity of Blake Ridge carbon cycling may explain why this system appears to contain more gas than the Peru Trench despite a lower input of organic carbon.

  6. RESIDENCE TIME DISTRIBUTION OF FLUIDS IN STIRRED ANNULAR PHOTOREACTORS

    EPA Science Inventory

    When gases flow through an annular photoreactor at constant rate, some of the gas spends more or less than the average residence time in the reactor. This spread of residence time can have an important effect on the performance of the reactor. this study tested how the residence...

  7. RESIDENCE TIME DISTRIBUTION OF FLUIDS IN STIRRED ANNULAR PHOTOREACTORS

    EPA Science Inventory

    When gases flow through an annular photoreactor at constant rate, some of the gas spends more or less than the average residence time in the reactor. This spread of residence time can have an important effect on the performance of the reactor. this study tested how the residence...

  8. Protected Time for Research During Orthopaedic Residency Correlates with an Increased Number of Resident Publications.

    PubMed

    Williams, Benjamin R; Agel, Julie A; Van Heest, Ann E

    2017-07-05

    The Accreditation Council for Graduate Medical Education (ACGME) requires orthopaedic residency programs to promote scholarship and research, which manifest differently among programs. We assess the impact of protected research time during orthopaedic residency on the number of resident publications. Rotation schedules and resident names were collected from 125 ACGME-accredited U.S. orthopaedic residency programs. Protected research time was classified as 1 of 3 types: (1) block time, (2) longitudinal time, or (3) no dedicated time. In April 2016, we searched residents in postgraduate year (PGY)-3 to PGY-5 on pubmed.gov to generate all orthopaedic publications with a PubMed identifier published during residency. Each publication's 2015 Thomson Reuters Journal Citation Reports 5-Year Journal Impact Factor and resident first authorship were noted. The number of PubMed identifiers for each program was summed and was divided by the number of residents in PGY-3 to PGY-5, giving a mean number of publications per resident. The relationship between output and program research time was compared using t tests and analysis of variance (ANOVA). A total of 1,690 residents were included, with an overall mean number (and standard deviation) of 1.2 ± 2.4 publications per resident. Eighty-seven programs reported block time, 14 programs reported longitudinal time, and 24 programs reported no time. There was a significant difference (p = 0.02) in the mean number of publications per resident when compared between programs with protected time (1.1 ± 1.2 publications) and programs with no protected time (0.6 ± 0.5 publication). One-way ANOVA demonstrated a significant mean difference across the 3 groups (p < 0.001), with longitudinal time correlating with significantly greater output at 1.9 ± 1.8 publications than block time at 1.0 ± 1.0 publication or no time at 0.6 ± 0.5 publication, a difference that persisted when adjusted to include only impact factors of >0 and exclude case

  9. Prolonged and tunable residence time using reversible covalent kinase inhibitors

    PubMed Central

    Bradshaw, J. Michael; McFarland, Jesse M.; Paavilainen, Ville O.; Bisconte, Angelina; Tam, Danny; Phan, Vernon T.; Romanov, Sergei; Finkle, David; Shu, Jin; Patel, Vaishali; Ton, Tony; Li, Xiaoyan; Loughhead, David G.; Nunn, Philip A.; Karr, Dane E.; Gerritsen, Mary E.; Funk, Jens Oliver; Owens, Timothy D.; Verner, Erik; Brameld, Ken A.; Hill, Ronald J.; Goldstein, David M.; Taunton, Jack

    2015-01-01

    Drugs with prolonged, on-target residence time often show superior efficacy, yet general strategies for optimizing drug-target residence time are lacking. Here, we demonstrate progress toward this elusive goal by targeting a noncatalytic cysteine in Bruton's tyrosine kinase (BTK) with reversible covalent inhibitors. Utilizing an inverted orientation of the cysteine-reactive cyanoacrylamide electrophile, we identified potent and selective BTK inhibitors that demonstrate biochemical residence times spanning from minutes to 7 days. An inverted cyanoacrylamide with prolonged residence time in vivo remained bound to BTK more than 18 hours after clearance from the circulation. The inverted cyanoacrylamide strategy was further utilized to discover fibroblast growth factor receptor (FGFR) kinase inhibitors with residence times of several days, demonstrating generalizability of the approach. Targeting noncatalytic cysteines with inverted cyanoacrylamides may serve as a broadly applicable platform that facilitates “residence time by design”, the ability to modulate and improve the duration of target engagement in vivo. PMID:26006010

  10. Prolonged and tunable residence time using reversible covalent kinase inhibitors.

    PubMed

    Bradshaw, J Michael; McFarland, Jesse M; Paavilainen, Ville O; Bisconte, Angelina; Tam, Danny; Phan, Vernon T; Romanov, Sergei; Finkle, David; Shu, Jin; Patel, Vaishali; Ton, Tony; Li, Xiaoyan; Loughhead, David G; Nunn, Philip A; Karr, Dane E; Gerritsen, Mary E; Funk, Jens Oliver; Owens, Timothy D; Verner, Erik; Brameld, Ken A; Hill, Ronald J; Goldstein, David M; Taunton, Jack

    2015-07-01

    Drugs with prolonged on-target residence times often show superior efficacy, yet general strategies for optimizing drug-target residence time are lacking. Here we made progress toward this elusive goal by targeting a noncatalytic cysteine in Bruton's tyrosine kinase (BTK) with reversible covalent inhibitors. Using an inverted orientation of the cysteine-reactive cyanoacrylamide electrophile, we identified potent and selective BTK inhibitors that demonstrated biochemical residence times spanning from minutes to 7 d. An inverted cyanoacrylamide with prolonged residence time in vivo remained bound to BTK for more than 18 h after clearance from the circulation. The inverted cyanoacrylamide strategy was further used to discover fibroblast growth factor receptor (FGFR) kinase inhibitors with residence times of several days, demonstrating the generalizability of the approach. Targeting of noncatalytic cysteines with inverted cyanoacrylamides may serve as a broadly applicable platform that facilitates 'residence time by design', the ability to modulate and improve the duration of target engagement in vivo.

  11. Residence time determination for adsorbent beds of different configurations

    SciTech Connect

    Otermat, J.E.; Wikoff, W.O.; Kovach, J.L.

    1995-02-01

    The residence time calculations of ASME AG-1 Code, Section FC, currently specify a screen surface area method, that is technically incorrect. Test data has been obtained on Type II adsorber trays of different configurations to establish residence time in the adsorber trays. These data indicate that the air volume/carbon volume ratio or the average screen area are more appropriate for the calculation of the residence time calculation than the currently used, smallest screen area basis.

  12. Supporting organ transplantation in non-resident aliens within limits.

    PubMed

    Bramstedt, Katrina A

    2006-01-01

    It is common knowledge that the supply of cadaveric organs does not meet demand. This shortage is often used as ethical argument against transplantation in Non-Resident Aliens; however, this fact in isolation does not present a comprehensive picture of organ allocation in USA. Even though approximately 153 cadaveric livers, kidneys, and hearts are transplanted into Non-Resident Aliens each year, roughly another 85 livers, kidneys and hearts are recovered as usable for transplantation but are not transplanted due to inability to find a recipient. These organs are also unable to be exported due to logistics or lack of patient matching. Because usable, recovered allografts are discarded on a yearly basis, there is no justification to use "allograft scarcity" as argument against transplantation in Non-Resident Aliens. Further, consistent with other countries, a system of two waiting lists which allocates organs to US Residents with the first right of refusal (with Non-Resident Aliens having to access organs refused by or not matched to US Residents) is ethically appropriate. Justification for this two-list system lies in deconstructing "who" is the transplant community, and who are "guests" of the transplant community.

  13. Reducing natural organic matter and disinfection by-product precursors by alternating oxic and anoxic conditions during engineered short residence time riverbank filtration: A laboratory-scale column study.

    PubMed

    Liu, Peng; Farré, Maria José; Keller, Jurg; Gernjak, Wolfgang

    2016-09-15

    Riverbank filtration (RBF) with days to months of residence time has been successfully used as treatment or pre-treatment process to improve water quality for decades. However, its feasibility depends on the local hydrogeological conditions. Therefore, for sites unsuitable to traditional RBF, a smaller engineered RBF may be an option. This study evaluates the performance of engineered short residence time RBF on improving water quality, focusing on the removal of natural organic matter (NOM) and the reduction of precursors of carbon and nitrogen disinfection by-products (DBP). Lab-scale experiments were conducted with surface feed water from a drinking water plant. The results showed that within 6days hydraulic retention time (HRT), 60-70% dissolved organic carbon (DOC) and 70-80% ultraviolet absorbance at 254nm (UV254) could be removed. During the whole filtration process, biodegradation was responsible for the removal of organic matter, and it was found that alternating redox condition between oxic and anoxic was beneficial for the overall performance of the RBF. Dissolved oxygen (DO) had a substantial impact on the removal of DBP precursors. For carbon-containing DBP (C-DBP) precursors' removal, re-aeration after a sequence of oxic and anoxic conditions could further increase the removal efficiencies from 50%, 60%, and 60% to 80%, 90%, and 80% for trihalomethanes (THMs), chloral hydrate (CH), and haloketones (HKs). Prolonged anoxic conditions were however beneficial for the removal of nitrogen-containing DBP (N-DBP) precursors. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Operative time and cost of resident surgical experience: effect of instituting an otolaryngology residency program.

    PubMed

    Pollei, Taylor R; Barrs, David M; Hinni, Michael L; Bansberg, Stephen F; Walter, Logan C

    2013-06-01

    Describe the procedure length difference between surgeries performed by an attending surgeon alone compared with the resident surgeon supervised by the same attending surgeon. Case series with chart review. Tertiary care center and residency program. Six common otolaryngologic procedures performed between August 1994 and May 2012 were divided into 2 cohorts: attending surgeon alone or resident surgeon. This division coincided with our July 2006 initiation of an otolaryngology-head and neck surgery residency program. Operative duration was compared between cohorts with confounding factors controlled. In addition, the direct result of increased surgical length on operating room cost was calculated and applied to departmental and published resident case log report data. Five of the 6 procedures evaluated showed a statistically significant increase in surgery length with resident involvement. Operative time increased 6.8 minutes for a cricopharyngeal myotomy (P = .0097), 11.3 minutes for a tonsillectomy (P < .0001), 27.4 minutes for a parotidectomy (P = .028), 38.3 minutes for a septoplasty (P < .0001), and 51 minutes for tympanomastoidectomy (P < .0021). Thyroidectomy showed no operative time difference. Cost of increased surgical time was calculated per surgery and ranged from $286 (cricopharyngeal myotomy) to $2142 (mastoidectomy). When applied to reported national case log averages for graduating residents, this resulted in a significant increase of direct training-related costs. Resident participation in the operating room results in increased surgical length and additional system cost. Although residency is a necessary part of surgical training, associated costs need to be acknowledged.

  15. Geological Control of Fractal Groundwater Residence Times

    NASA Astrophysics Data System (ADS)

    Marklund, L.; Wörman, A.

    2009-12-01

    Groundwater transports and distributes heat, particles and solutes both in the subsurface and to and from surficial ecosystems. Therefore, understanding groundwater circulation is a key issue for biogeochemical cycles, water resource management and CO2 sequestration. Fractal scaling relationships have been found in distributions of both land surface topography and solute efflux from watersheds and it have been shown that the fractal nature of the land surface produces fractal distributions of recharge, discharge, and associated subsurface flow patterns in humid regions with low-permeability rock, where the groundwater flow is controlled by landscape topography. In this paper, we relate the groundwater circulation to extensive topographic and geological data sets from Scandinavia and North America using spectral analysis. Especially, we have systematized the spatial distribution of groundwater flow utilizing an exact solution for 3D groundwater flow based on spectral analysis of the topography. This approach is an efficient way to analyze multi-scaled topography-controlled groundwater flow, because the impact of individual topographic scales on the groundwater flow can be analyzed separately. The fractal nature of topography yields a single scale-independent distribution of subsurface water residence times for both near-surface fluvial systems and deeper hydrogeological flows. Large-scale topography mainly controls deeper and larger flow cells and small-scale topography controls smaller and shallower flow cells. This scaling behavior holds at all scales, from small fluvial bedforms (tens of centimeters) to the continental landscape (hundreds of kilometers). However, the geological conditions within a specific region modify the topographic control of the groundwater circulation pattern. For instance, layers of Quaternary deposits and decaying permeability with depth increase the importance of smaller topographic scales. At the groundwater surface, the water flux is

  16. Long residence times - bad tracer tests?

    NASA Astrophysics Data System (ADS)

    Ghergut, Julia; Behrens, Horst; Sauter, Martin

    2015-04-01

    Tracer tests conducted at geothermal well doublets or triplets in the Upper Rhine Rift Valley [1] all face, with very few exceptions so far, one common issue: lack of conclusive tracer test results, or tracer signals still undetectable for longer than one or two years after tracer injection. While the reasons for this surely differ from site to site (Riehen, Landau, Insheim, Bruchsal, ...), its effects on how the usefulness of tracer tests is perceived by the non-tracer community are pretty much the same. The 'poor-signal' frustration keeps nourishing two major 'alternative' endeavours : (I) design and execute tracer tests in single-well injection-withdrawal (push-pull), 'instead of' inter-well flow-path tracing configurations; (II) use 'novel' tracer substances instead of the 'old' ones which have 'obviously failed'. Frustration experienced with most inter-well tracer tests in the Upper Rhine Rift Valley has also made them be regarded as 'maybe useful for EGS' ('enhanced', or 'engineered' geothermal systems, whose fluid RTD typically include a major share of values below one year), but 'no longer worthwhile a follow-up sampling' in natural, large-scale hydrothermal reservoirs. We illustrate some of these arguments with the ongoing Bruchsal case [2]. The inter-well tracer test conducted at Bruchsal was (and still is!) aimed at assessing inter-well connectivity, fluid residence times, and characterizing the reservoir structure [3]. Fluid samples taken at the geothermal production well after reaching a fluid turnover of about 700,000 m3 showed tracer concentrations in the range of 10-8 Minj per m3, in the liquid phase of each sample (Minj being the total quantity of tracer injected as a short pulse at the geothermal re-injection well). Tracer signals might actually be higher, owing to tracer amounts co-precipitated and/or adsorbed onto the solid phase whose accumulation in the samples was unavoidable (due to pressure relief and degassing during the very sampling

  17. Residence time modeling of hot melt extrusion processes.

    PubMed

    Reitz, Elena; Podhaisky, Helmut; Ely, David; Thommes, Markus

    2013-11-01

    The hot melt extrusion process is a widespread technique to mix viscous melts. The residence time of material in the process frequently determines the product properties. An experimental setup and a corresponding mathematical model were developed to evaluate residence time and residence time distribution in twin screw extrusion processes. The extrusion process was modeled as the convolution of a mass transport process described by a Gaussian probability function, and a mixing process represented by an exponential function. The residence time of the extrusion process was determined by introducing a tracer at the extruder inlet and measuring the tracer concentration at the die. These concentrations were fitted to the residence time model, and an adequate correlation was found. Different parameters were derived to characterize the extrusion process including the dead time, the apparent mixing volume, and a transport related axial mixing. A 2(3) design of experiments was performed to evaluate the effect of powder feed rate, screw speed, and melt viscosity of the material on the residence time. All three parameters affect the residence time of material in the extruder. In conclusion, a residence time model was developed to interpret experimental data and to get insights into the hot melt extrusion process. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. The residence time of water in the atmosphere revisited

    NASA Astrophysics Data System (ADS)

    van der Ent, Ruud J.; Tuinenburg, Obbe A.

    2017-02-01

    This paper revisits the knowledge on the residence time of water in the atmosphere. Based on state-of-the-art data of the hydrological cycle we derive a global average residence time of 8.9 ± 0.4 days (uncertainty given as 1 standard deviation). We use two different atmospheric moisture tracking models (WAM-2layers and 3D-T) to obtain atmospheric residence time characteristics in time and space. The tracking models estimate the global average residence time to be around 8.5 days based on ERA-Interim data. We conclude that the statement of a recent study that the global average residence time of water in the atmosphere is 4-5 days, is not correct. We derive spatial maps of residence time, attributed to evaporation and precipitation, and age of atmospheric water, showing that there are different ways of looking at temporal characteristics of atmospheric water. Longer evaporation residence times often indicate larger distances towards areas of high precipitation. From our analysis we find that the residence time over the ocean is about 2 days less than over land. It can be seen that in winter, the age of atmospheric moisture tends to be much lower than in summer. In the Northern Hemisphere, due to the contrast in ocean-to-land temperature and associated evaporation rates, the age of atmospheric moisture increases following atmospheric moisture flow inland in winter, and decreases in summer. Looking at the probability density functions of atmospheric residence time for precipitation and evaporation, we find long-tailed distributions with the median around 5 days. Overall, our research confirms the 8-10-day traditional estimate for the global mean residence time of atmospheric water, and our research contributes to a more complete view of the characteristics of the turnover of water in the atmosphere in time and space.

  19. Otolaryngology resident workflow: a time-motion and efficiency study.

    PubMed

    Victores, Andrew; Roberts, Jess; Sturm-O'Brien, Angela; Victores, Nina; Uecker, Wil; Alford, Bobby; Takashima, Mas

    2011-05-01

    To investigate workflow in an otolaryngology-head and neck surgery residency program over 1 year and identify areas for improvement in the efficiency of resident education and training. Time-motion study. An urban, county hospital and a Veterans Affairs medical center hospital. Subjects and Methods. Eight otolaryngology residents (4 residents at postgraduate year [PGY] 2 and 4 at PGY 4) were studied using direct observations early and late in the 2008-2009 academic year. Resident activities were categorized, and a database program was generated for a handheld computer to facilitate time entry. Resident activities were classified into a taxonomy of tasks and their educational value was assessed. For each PGY level studied, observations were made for clinic and operative days. Residents spent their day on direct patient care (43.5%), indirect patient care (33.7%), didactic education (9.6%), personal activities (7.5%), and transit (5.8%), with activities of marginal educational value consuming 16% of their time. Major inefficiencies included managing administrative tasks, scheduling, and technical difficulties. On average, residents devoted significantly more time to marginal tasks on clinic days (19%) than on operative days (12%; P < .001). These data were compared with previously published data obtained during the pre–Accreditation Council for Graduate Medical Education (ACGME) duty hour mandates era. This study evaluates resident workflow and efficiency over the course of a PGY in an ACGME-accredited otolaryngology residency program. By understanding the time motion of residents, interruptions and inefficiencies in workflow can be identified to direct future changes to enhance resident education and training in the era of the ACGME duty hours mandate.

  20. Short residence time coal liquefaction process including catalytic hydrogenation

    DOEpatents

    Anderson, Raymond P.; Schmalzer, David K.; Wright, Charles H.

    1982-05-18

    Normally solid dissolved coal product and a distillate liquid product are produced by continuously passing a feed slurry comprising raw feed coal and a recycle solvent oil and/or slurry together with hydrogen to a preheating-reaction zone (26, alone, or 26 together with 42), the hydrogen pressure in the preheating-reaction zone being at least 1500 psig (105 kg/cm.sup.2), reacting the slurry in the preheating-reaction zone (26, or 26 with 42) at a temperature in the range of between about 455.degree. and about 500.degree. C. to dissolve the coal to form normally liquid coal and normally solid dissolved coal. A total slurry residence time is maintained in the reaction zone ranging from a finite value from about 0 to about 0.2 hour, and reaction effluent is continuously and directly contacted with a quenching fluid (40, 68) to substantially immediately reduce the temperature of the reaction effluent to below 425.degree. C. to substantially inhibit polymerization so that the yield of insoluble organic matter comprises less than 9 weight percent of said feed coal on a moisture-free basis. The reaction is performed under conditions of temperature, hydrogen pressure and residence time such that the quantity of distillate liquid boiling within the range C.sub.5 -454.degree. C. is an amount at least equal to that obtainable by performing the process under the same condition except for a longer total slurry residence time, e.g., 0.3 hour. Solvent boiling range liquid is separated from the reaction effluent (83) and recycled as process solvent (16). The amount of solvent boiling range liquid is sufficient to provide at least 80 weight percent of that required to maintain the process in overall solvent balance.

  1. Short residence time coal liquefaction process including catalytic hydrogenation

    DOEpatents

    Anderson, R.P.; Schmalzer, D.K.; Wright, C.H.

    1982-05-18

    Normally solid dissolved coal product and a distillate liquid product are produced by continuously passing a feed slurry comprising raw feed coal and a recycle solvent oil and/or slurry together with hydrogen to a preheating-reaction zone, the hydrogen pressure in the preheating-reaction zone being at least 1,500 psig (105 kg/cm[sup 2]), reacting the slurry in the preheating-reaction zone at a temperature in the range of between about 455 and about 500 C to dissolve the coal to form normally liquid coal and normally solid dissolved coal. A total slurry residence time is maintained in the reaction zone ranging from a finite value from about 0 to about 0.2 hour, and reaction effluent is continuously and directly contacted with a quenching fluid to substantially immediately reduce the temperature of the reaction effluent to below 425 C to substantially inhibit polymerization so that the yield of insoluble organic matter comprises less than 9 weight percent of said feed coal on a moisture-free basis. The reaction is performed under conditions of temperature, hydrogen pressure and residence time such that the quantity of distillate liquid boiling within the range C[sub 5]-454 C is an amount at least equal to that obtainable by performing the process under the same condition except for a longer total slurry residence time, e.g., 0.3 hour. Solvent boiling range liquid is separated from the reaction effluent and recycled as process solvent. The amount of solvent boiling range liquid is sufficient to provide at least 80 weight percent of that required to maintain the process in overall solvent balance. 6 figs.

  2. Repeated Hospital Transfers and Associated Outcomes by Residency Time Among Nursing Home Residents in Taiwan.

    PubMed

    Tsai, Hsiu-Hsin; Tsai, Yun-Fang; Liu, Chia-Yih

    2016-11-01

    Nursing home residents' repeated transfers to hospital are costly and can lead to in-hospital complications and high mortality for frail residents. However, no research has examined the trajectory of residents' symptoms over their nursing home residency and its relationship to hospital transfer. The purpose of this retrospective chart-review study was to examine associations between nursing home residents' characteristics, including length of residency, and repeated hospital transfers as well as the trajectory of transfers during residency. For this retrospective study, we reviewed 583 residents' charts in 6 randomly selected nursing homes from northern Taiwan. Data were analyzed by descriptive statistics, chi-squared tests, and 1-way analysis of variance. About half of nursing home residents who had been transferred to hospital (n = 320) were transferred more than twice during their residency (50.97%). Residents who had been transferred 1, 2, 3, or ≥4 times differed significantly in length of residency (F = 3.85, P = .01), physical status (F = 2.65, P = .05), medical history of pneumonia (χ(2) = 13.03, P = .01), and fractures (χ(2) = 8.52, P = .04). Residents with different numbers of transfers differed significantly in their reasons for transfer, that is, falls (χ(2) = 13.01, P = .01) and tube problems (χ(2) = 8.87, P = .03). Among 705 total transfers, fever was the top reason for transfer, and transfer prevalence increased with nursing home residency. To decrease the chance of residents' hospital transfer, nursing home staff should be educated about recognizing and managing fever symptoms, infection-control programs such as influenza vaccination should be initiated, and fall-prevention/education programs should be started when residents first relocate to nursing homes. Copyright © 2016 AMDA – The Society for Post-Acute and Long-Term Care Medicine. Published by Elsevier Inc. All rights reserved.

  3. Radiology report turnaround time: effect on resident education.

    PubMed

    England, Eric; Collins, Jannette; White, Richard D; Seagull, F Jacob; Deledda, John

    2015-05-01

    To compare resident workload from Emergency Department (ED) studies before and after the implementation of a required 1-hour report turnaround time (TAT) and to assess resident and faculty perception of TAT on resident education. Resident study volume will be compared for 3 years before and 1 year after the implementation of a required 1-hour TAT. Changes to resident workload will be compared among the different radiology divisions (body, muscuolskeletal (MSK), chest, and neuro), as well as during different shifts (daytime and overnight). Residents and faculty at two Midwest institutions, both of which have a required report TAT, will be invited to participate in an online survey to query the perceived effect on resident education by implementation of this requirement. A P < .05 was considered statistically significant. A significant decrease in resident involvement in ED studies was noted in the MSK, chest, and neuro sections with average involvement of the 3 years before the 1-hour TAT of 89%, 88%, and 82%, respectively, which decreased to 66%, 68%, and 51% after the 1-hour TAT requirement (P < .05). The resident involvement in ED studies only mildly decreased in the body section from an average before the 1-hour TAT of 87% to 80% after the 1-hour TAT requirement (P < .1). There was an overall significant decrease in resident ED study involvement during the daytime (P = .01) but not after hours during resident call (P = .1). Seventy percent of residents (43 of 61) and 55% of faculty (63 of 114) responded to our surveys. Overall, residents felt their education from ED studies during the daytime and overnight were good. However, residents who were present both before and after the implementation of a required TAT felt their education had been significantly negatively affected. Faculty surveyed thought that the required TAT negatively affected their ability to teach and decreased the quality of resident education. Residents are exposed to fewer ED studies after the

  4. DNA residence time is a regulatory factor of transcription repression.

    PubMed

    Clauß, Karen; Popp, Achim P; Schulze, Lena; Hettich, Johannes; Reisser, Matthias; Escoter Torres, Laura; Uhlenhaut, N Henriette; Gebhardt, J Christof M

    2017-08-21

    Transcription comprises a highly regulated sequence of intrinsically stochastic processes, resulting in bursts of transcription intermitted by quiescence. In transcription activation or repression, a transcription factor binds dynamically to DNA, with a residence time unique to each factor. Whether the DNA residence time is important in the transcription process is unclear. Here, we designed a series of transcription repressors differing in their DNA residence time by utilizing the modular DNA binding domain of transcription activator-like effectors (TALEs) and varying the number of nucleotide-recognizing repeat domains. We characterized the DNA residence times of our repressors in living cells using single molecule tracking. The residence times depended non-linearly on the number of repeat domains and differed by more than a factor of six. The factors provoked a residence time-dependent decrease in transcript level of the glucocorticoid receptor-activated gene SGK1. Down regulation of transcription was due to a lower burst frequency in the presence of long binding repressors and is in accordance with a model of competitive inhibition of endogenous activator binding. Our single molecule experiments reveal transcription factor DNA residence time as a regulatory factor controlling transcription repression and establish TALE-DNA binding domains as tools for the temporal dissection of transcription regulation. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  5. Experimental determination of residence time distribution in continuous dry granulation.

    PubMed

    Mangal, Haress; Kleinebudde, Peter

    2017-05-30

    With increasing importance of continuous manufacturing, the interest in integrating dry granulation into a continuous manufacturing line is growing. Residence time distribution measurements are of importance as they provide information about duration of materials within the process. These data enable traceability and are highly beneficial for developing control strategies. A digital image analysis system was used to determine the residence time distribution of two materials with different deformation behavior (brittle, plastic) in the milling unit of dry granulation systems. A colorant was added to the material (20%w/w iron oxide), which did not affect the material properties excessively, so the milling process could be mimicked well. Experimental designs were conducted to figure out which parameters effect the mean residence time strongly. Moreover, two types of dry granulation systems were contrasted. Longer mean residence times were obtained for the oscillating mill (OM) compared to the conical mill (CM). For co-processed microcrystalline cellulose residence times of 19.8-44.4s (OM) and 11.6-29.1s (CM) were measured, mainly influenced by the specific compaction force, the mill speed and roll speed. For dibasic calcium phosphate anhydrate residence times from 17.7-46.4 (OM) and 5.4-10.2s (CM) were measured, while here the specific compaction force, the mill speed and their interactions with the roll speed had an influence on the mean residence time. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Time-dependent evolution of olive mill wastewater sludge organic and inorganic components and resident microbiota in multi-pond evaporation system.

    PubMed

    Jarboui, Raja; Chtourou, Mohamed; Azri, Chafai; Gharsallah, Néji; Ammar, Emna

    2010-08-01

    The physico-chemical and microbiological characterizations of olive mill wastewater sludge (OMWS) were investigated in five OMW evaporation ponds of the open-pond system in Sfax (Tunisia), during the olive oil production period in 2004. Time-dependent changes in both physico-chemical parameters and the microbiota were investigated. Mathematical models and principal component analysis (PCA) were used to establish the correlations between the studied parameters. During the effluent time-dependent changes in the ponds, the result of OMWS analysis showed an increase of sludge index (SI), ash content, total solids (TS), volatile solids (VS), ethyl acetate extractive (EAE) and total phosphorus (Total P), as well as microbial flora especially the yeasts and moulds. The SI, TS, VS and Total P changes with time fit a simple linear equation, while EAE, phenols and NH(4)(+) fit a second-degree polynomial model. The PCA analysis exhibited three correlated groups. The first group included temperature, ash content, evaporation, SI, TS, VS, Total P, EAE, yeasts and moulds. The second group was made by bacteria and moisture; and the third group by NH(4)(+), oil and phenol. Such modelling might be of help in the prediction of OMW changes in natural evaporation ponds.

  7. Personal time off and residents' career satisfaction, attitudes and emotions.

    PubMed

    Cedfeldt, Andrea S; Bower, Elizabeth A; English, Clea; Grady-Weliky, Tana A; Girard, Donald E; Choi, Dongseok

    2010-10-01

    Doctors who are satisfied with their careers have less stress and burnout and are less likely to make medical errors and more likely to provide a higher quality of patient care. In response to reports that residents experienced barriers to taking time off, Oregon Health and Science University designed a survey to evaluate residents' awareness of their programmes' policies for time off, their ability to find time for personal needs, and associations of both with career satisfaction, emotions and training experience. All 675 residents in a large, urban, tertiary care academic medical centre located in the USA were invited to participate in a confidential, web-based, cross-sectional survey in 2008; 66% completed the survey. The survey instrument consisted of a variety of items including yes/no, multiple choice, Likert scale and narrative response types. Only 41% of respondents were aware of their programmes' policies regarding time off. Residents who reported awareness of a policy were more able to find time to take care of personal needs (odds ratio=1.553, p=0.026). These respondents reported more positive experiences and emotions, fewer negative experiences and emotions, higher levels of career satisfaction and relatively less perceived stress than those who were unaware of a time-off policy. In addition, these respondents reported, on average, fewer work and more sleep hours. Our results highlight the importance of ensuring mechanisms for residents to find time to fulfil personal needs in order to enhance resident well-being and career satisfaction. Ensuring resident awareness of time-off policies is one way to do this. Our study demonstrates that ensuring residents are able to find time for personal needs has significant consequences with respect to resident perceptions of well-being and may be an effective strategy to promote career satisfaction and prevent burnout. © Blackwell Publishing Ltd 2010.

  8. A METHOD TO INCORPORATE ECOLOGY INTO RESIDENCE TIME OF CHEMICALS IN EMBAYMENTS: LOCAL EFFECT TIME

    EPA Science Inventory

    Residence times are classically defined by the physical and chemical aspects of water bodies rather than by their ecological implications. Therefore, a more clear and direct connection between the residence times and ecological effects is necessary to quantitatively relate these ...

  9. A METHOD TO INCORPORATE ECOLOGY INTO RESIDENCE TIME OF CHEMICALS IN EMBAYMENTS: LOCAL EFFECT TIME

    EPA Science Inventory

    Residence times are classically defined by the physical and chemical aspects of water bodies rather than by their ecological implications. Therefore, a more clear and direct connection between the residence times and ecological effects is necessary to quantitatively relate these ...

  10. Residents' perception of skill decay during dedicated research time.

    PubMed

    D'Angelo, Anne-Lise D; Ray, Rebecca D; Jenewein, Caitlin G; Jones, Grace F; Pugh, Carla M

    2015-11-01

    Surgery residents may take years away from clinical responsibilities for dedicated research time. As part of a longitudinal project, the study aim was to investigate residents' perceptions of clinical skill reduction during dedicated research time. Our hypothesis was that residents would perceive a greater potential reduction in skill during research time for procedures they were less confident in performing. Surgical residents engaged in dedicated research training at multiple training programs participated in four simulated procedures: urinary catheterization, subclavian central line, bowel anastomosis, and laparoscopic ventral hernia (LVH) repair. Using preprocedure and postprocedure surveys, participants rated procedures for confidence and difficulty. Residents also indicated the perceived level of skills reduction for the four procedures as a result of time in the laboratory. Thirty-eight residents (55% female) completed the four clinical simulators. Participants had between 0-36 mo in a laboratory (M = 9.29 mo, standard deviation = 9.38). Preprocedure surveys noted lower confidence and higher perceived difficulty for performing the LVH repair followed by bowel anastomosis, central line insertion, and urinary catheterization (P < 0.05). Residents perceived the greatest reduction in bowel anastomosis and LVH repair skills compared with urinary catheterization and subclavian central line insertion (P < 0.001). Postprocedure surveys showed significant effects of the simulation scenarios on resident perception for urinary catheterization (P < 0.05) and LVH repair (P < 0.05). Residents in this study expected greater skills decay for the procedures they had lower confidence performing and greater perceived difficulty. In addition, carefully adapted simulation scenarios had a significant effect on resident perception and may provide a mechanism for maintaining skills and keeping confidence grounded in experience. Copyright © 2015 Elsevier Inc. All

  11. Residence time heating effect in auroral conic generation

    NASA Technical Reports Server (NTRS)

    Horwitz, J. L.

    1984-01-01

    It is pointed out that, in addition to previously considered microscopic aspects of ion perpendicular heating in the auroral region, the effect of mass-dependent resident times in a finite-length perpendicular heating region may be important. In a simple illustrative model, particles are assumed to enter upward into an auroral acceleration region of finite extent along B, in which both parallel electric fields and perpendicular heating exist. In this situation, the particle residence times vary with particle mass as M to the 1/2-power, so that, in addition to effects associated with species-dependent heating rates, the resultant perpendicular energization associated with residence time also varies as M to the 1/2-power. The residence time effect thus favors heating of heavier particles, and may therefore be of some importance in understanding the greater energization of oxygen over hydrogen that has been observed, and also why no electron conics have been observed.

  12. Comparable operative times with and without surgery resident participation.

    PubMed

    Uecker, John; Luftman, Kevin; Ali, Sadia; Brown, Carlos

    2013-01-01

    Both physicians and patients may perceive that having surgical residents participate in operative procedures may prolong operations and worsen outcomes. We hypothesized that resident participation would prolong operative times and potentially adversely affect postoperative outcomes. To evaluate the effect of general surgery resident participation in surgical procedures on operative times and postoperative patient outcomes. Retrospective study of general surgery procedures performed during two 1-year time periods, 2007 without residents and 2011 with residents. Procedures included laparoscopic appendectomy and cholecystectomy, thyroidectomy, breast procedure, hernia repair, lower extremity amputation, tunneled venous catheter, and percutaneous endoscopic gastrostomy. The primary outcome was operative time and secondary outcomes included length of stay (LOS) and mortality. Academic general surgery residency program. There were 2280 operative procedures performed during the 2 periods: 1150 with resident involvement (RES group) and 1130 without residents (NORES group). The RES and NORES groups were similar for patient age (42 vs 41, p = 0.14) and male gender (46% vs 45%, p = 0.68), and there was no difference in overall operative time (68min vs 66min, p = 0.58). More specifically there was no difference in operative time (minutes) for specific procedures including laparoscopic appendectomy (67 vs 71, p = 0.8), thyroidectomy (125 vs 109, p = 0.16), breast procedure (38 vs 26, p = 0.79), hernia repair (61 vs 60, p = 0.74), lower extremity amputation (65 vs 77, p = 0.16), tunneled venous catheter (49 vs 47, p = 0.75), and percutaneous endoscopic gastrostomy (49 vs 46, p = 0.76). However, laparoscopic cholecystectomy took slightly longer in the RES group (71 vs 66, p = 0.02). LOS was shorter during the year with resident involvement (2.6 days vs 3.7 days, p = 0.0004) and there was no difference in mortality (0.17% vs 0.35%, p = 0.45). There is no difference in operative

  13. The Residence Time of Water in the Atmosphere Revisited

    NASA Astrophysics Data System (ADS)

    van der Ent, Ruud; Tuinenburg, Obbe

    2017-04-01

    This paper revisits the knowledge on the residence time of water in the atmosphere. Based on state-of-the-art data of the hydrological cycle we derive a global average residence time of 8.9±0.4 days (uncertainty given as one standard deviation). We use two different atmospheric moisture tracking models (WAM-2layers and 3D-Trajectories) to obtain atmospheric residence time characteristics in time and space. The tracking models estimate the global average residence time to be around 8.5 days based on ERA-Interim data. We conclude that the statement of a recent study that the global average residence time of water in the atmosphere is 4-5 days, is not correct. We derive spatial maps of residence time, attributed to evaporation and precipitation, and age of atmospheric water, showing that there are different ways of looking at temporal characteristics of atmospheric water. Longer evaporation residence times often indicate larger distances towards areas of high precipitation. From our analysis we find that the residence time over the ocean is about 2 days lower than over land. It can be seen that in winter, the age of atmospheric moisture tends to be much lower than in summer. On the Northern Hemisphere, due to the contrast in ocean-to-land temperature and associated evaporation rates, the age of atmospheric moisture increases following atmospheric moisture flow inland in winter, and decreases in summer. Looking at the probability density functions of atmospheric residence time for precipitation and evaporation we find long-tailed distributions with the median around 5 days. Overall, our research confirms the 8-10 days traditional estimate for the global mean residence time of atmospheric water, and our research contributes to a more complete view on the characteristics of the turnover of water in the atmosphere in time and space. In the light of this session, our results show that the turnover of water is relatively fast, but water travels quite far, which explains

  14. Prolonged patient emergence time among clinical anesthesia resident trainees

    PubMed Central

    House, L. McLean; Calloway, Nathan H.; Sandberg, Warren S.; Ehrenfeld, Jesse M.

    2016-01-01

    Background and Aims: Emergence time, or the duration between incision closure and extubation, is costly nonoperative time. Efforts to improve operating room efficiency and identify trainee progress make such time intervals of interest. We sought to calculate the incidence of prolonged emergence (i.e., >15 min) for patients under the care of clinical anesthesia (CA) residents. We also sought to identify factors from resident training, medical history, anesthetic use, and anesthesia staffing, which affect emergence. Material and Methods: In this single-center, historical cohort study, perioperative information management systems provided data for surgical cases under resident care at a tertiary care center in the United States from 2006 to 2008. Using multiple logistic regression, the effects of variables on emergence was analyzed. Results: Of 7687 cases under the care of 27 residents, the incidence of prolonged emergence was 13.9%. Emergence prolongation decreased by month in training for 1st-year (CA-1) residents (r2 = 0.7, P < 0.001), but not for CA-2 and CA-3 residents. Mean patient emergence time differed among 27 residents (P < 0.01 for 58.4% or 205/351 paired comparisons). In a model restricted to 1st-year residents, patient male gender, American Society of Anesthesiologists (ASA) physical status >II, emergency surgical case, operative duration ≥2 h, and paralytic agent use were associated with higher frequency of prolonged emergence, while sevoflurane or desflurane use was associated with lower frequency. Attending anesthesiologist handoff was not associated with longer emergence. Conclusion: Incidence of prolonged emergence from general anesthesia differed significantly among trainees, by resident training duration, and for patients with ASA >II. PMID:28096573

  15. The role of topography on catchment-scale water residence time

    USGS Publications Warehouse

    McGuire, K.J.; McDonnell, Jeffery J.; Weiler, M.; Kendall, C.; McGlynn, B.L.; Welker, J.M.; Seibert, J.

    2005-01-01

    The age, or residence time, of water is a fundamental descriptor of catchment hydrology, revealing information about the storage, flow pathways, and source of water in a single integrated measure. While there has been tremendous recent interest in residence time estimation to characterize watersheds, there are relatively few studies that have quantified residence time at the watershed scale, and fewer still that have extended those results beyond single catchments to larger landscape scales. We examined-topographic controls on residence time for seven catchments (0.085-62.4 km2) that represent diverse geologic and geomorphic conditions in the western Cascade Mountains of Oregon. Our primary objective was to determine the dominant physical controls on catchment-scale, water residence time and specifically test the hypothesis that residence time is related to the size of the basin. Residence times were estimated by simple convolution models that described the transfer of precipitation isotopic composition to the stream network. We found that base flow mean residence times for exponential distributions ranged from 0.8 to 3.3 years. Mean residence time showed no correlation to basin area (r2 < 0.01) but instead was correlated (r2 =-0:91) to catchment terrain indices representing the flow path distance and flow path gradient to the stream network. These results illustrate that landscape organization (i.e., topography) rather than basin area controls catchment-scale transport. Results from this study may provide a framework for describing scale-invariant transport across climatic and geologic conditions, whereby the internal form and structure of the basin defines the first-order control on base flow residence time. Copyright 2005 by the American Geophysical Union.

  16. Influence of resident training on anaesthesia induction times.

    PubMed

    Schuster, M; Kotjan, T; Fiege, M; Goetz, A E

    2008-11-01

    The effect of resident training in anaesthesiology on operating room (OR) economics is an issue of debate. Comparisons of anaesthesia process times between residents and consultants might be systematically skewed by interactions of anaesthesia technique and patient factors. In this prospective, observational study, we analysed anaesthesia process times in 599 cases performed for four different surgical services in a University hospital. The following factors were recorded for each case and used in multivariate analyses of process times: age, American Society of Anesthesiologist (ASA) status, BMI, emergency status, the educational level of the anaesthetist, and the anaesthesia technique. In the non-adjusted comparison, only for two of seven anaesthetic techniques did resident cases have statistically significant longer induction times than consultant cases: general anaesthesia with placement of a central venous catheter [mean (sd) anaesthesia time for resident cases 38.2 (17.0) vs 22.3 (10.0) min for consultant cases, P=0.001] and general anaesthesia with a laryngeal mask airway [resident cases 11.3 (5.5) vs consultant cases 7.3 (5.0) min, P=0.003]. Anaesthetic technique had the greatest effect on anaesthesia induction time. Educational level of the anaesthetist and age of the patients had small, but significant effects. Anaesthesia cases performed by residents have in some, but not in all, anaesthesia techniques increased process times compared with cases performed by consultants. This limits a possible negative impact on OR economics by resident education. Patient-based factors including ASA status, BMI, and emergency status have minimal or no effect on anaesthesia process times.

  17. Administrative organization in diagnostic radiology residency program leadership.

    PubMed

    Webber, Grant R; Mullins, Mark E; Chen, Zhengjia; Meltzer, Carolyn C

    2012-04-01

    The aim of this study was to document the current state of administrative structure in US diagnostic radiology (DR) residency program leadership. A secondary objective was to assess for correlation(s), if any, with DR residency programs that equipped positions such as assistant, associate, and emeritus program director (PD) with respect to residency size and region of the country. The Fellowship and Residency Electronic Interactive Database, as well as direct communication and programmatic Web site searches, were used to gather data regarding current US DR residency leadership. Data collected included the presence of additional leadership titles, including assistant PD, associate PD, and PD emeritus, and how many faculty members currently held each position. Programs were excluded if results could not be identified. Analysis of variance and t tests were used to estimate the correlations of the size of a residency with having additional or shared PD positions and the types of positions, respectively. Chi-square tests were used to assess for any regional differences. As of the time of this project, the Fellowship and Residency Electronic Interactive Database defined 186 US DR residency programs. A total of 173 programs (93%) were included in the analysis; the remainder were excluded because of unavailability of relevant data. Seventy-two percent (124 of 173) of programs had additional DR leadership positions. Of these, 30 programs (17%) had more than one such position. There were no significant differences in the sizes of the programs that used these additional positions (mean, 25 ± 12; range, 6-72) compared with those that did not (mean, 24 ± 12; range, 7-51). There were no significant differences between programs that had additional positions with respect to region of the country. The majority of US DR residency programs used some form of additional DR leadership position. In the majority of cases, this was in the form of an assistant or associate PD. Nearly one

  18. Online residence time distribution measurement of thermochemical biomass pretreatment reactors

    DOE PAGES

    Sievers, David A.; Kuhn, Erik M.; Stickel, Jonathan J.; ...

    2015-11-03

    Residence time is a critical parameter that strongly affects the product profile and overall yield achieved from thermochemical pretreatment of lignocellulosic biomass during production of liquid transportation fuels. The residence time distribution (RTD) is one important measure of reactor performance and provides a metric to use when evaluating changes in reactor design and operating parameters. An inexpensive and rapid RTD measurement technique was developed to measure the residence time characteristics in biomass pretreatment reactors and similar equipment processing wet-granular slurries. Sodium chloride was pulsed into the feed entering a 600 kg/d pilot-scale reactor operated at various conditions, and aqueous saltmore » concentration was measured in the discharge using specially fabricated electrical conductivity instrumentation. This online conductivity method was superior in both measurement accuracy and resource requirements compared to offline analysis. Experimentally measured mean residence time values were longer than estimated by simple calculation and screw speed and throughput rate were investigated as contributing factors. In conclusion, a semi-empirical model was developed to predict the mean residence time as a function of operating parameters and enabled improved agreement.« less

  19. Online residence time distribution measurement of thermochemical biomass pretreatment reactors

    SciTech Connect

    Sievers, David A.; Kuhn, Erik M.; Stickel, Jonathan J.; Tucker, Melvin P.; Wolfrum, Edward J.

    2015-11-03

    Residence time is a critical parameter that strongly affects the product profile and overall yield achieved from thermochemical pretreatment of lignocellulosic biomass during production of liquid transportation fuels. The residence time distribution (RTD) is one important measure of reactor performance and provides a metric to use when evaluating changes in reactor design and operating parameters. An inexpensive and rapid RTD measurement technique was developed to measure the residence time characteristics in biomass pretreatment reactors and similar equipment processing wet-granular slurries. Sodium chloride was pulsed into the feed entering a 600 kg/d pilot-scale reactor operated at various conditions, and aqueous salt concentration was measured in the discharge using specially fabricated electrical conductivity instrumentation. This online conductivity method was superior in both measurement accuracy and resource requirements compared to offline analysis. Experimentally measured mean residence time values were longer than estimated by simple calculation and screw speed and throughput rate were investigated as contributing factors. In conclusion, a semi-empirical model was developed to predict the mean residence time as a function of operating parameters and enabled improved agreement.

  20. Air-Parcel Residence Times Within Forest Canopies

    NASA Astrophysics Data System (ADS)

    Gerken, Tobias; Chamecki, Marcelo; Fuentes, Jose D.

    2017-06-01

    We present a theoretical model, based on a simple model of turbulent diffusion and first-order chemical kinetics, to determine air-parcel residence times and the out-of-canopy export of reactive gases emitted within forest canopies under neutral conditions. Theoretical predictions of the air-parcel residence time are compared to values derived from large-eddy simulation for a range of canopy architectures and turbulence levels under neutral stratification. Median air-parcel residence times range from a few sec in the upper canopy to approximately 30 min near the ground and the distribution of residence times is skewed towards longer times in the lower canopy. While the predicted probability density functions from the theoretical model and large-eddy simulation are in good agreement with each other, the theoretical model requires only information on canopy height and eddy diffusivities inside the canopy. The eddy-diffusivity model developed additionally requires the friction velocity at canopy top and a parametrized profile of the standard deviation of vertical velocity. The theoretical model of air-parcel residence times is extended to include first-order chemical reactions over a range of of Damköhler numbers (Da) characteristic of plant-emitted hydrocarbons. The resulting out-of-canopy export fractions range from near 1 for Da =10^{-3} to less than 0.3 at Da = 10 . These results highlight the necessity for dense and tall forests to include the impacts of air-parcel residence times when calculating the out-of-canopy export fraction for reactive trace gases.

  1. Estimation of residence time in a shallow lacustrine embayment

    NASA Astrophysics Data System (ADS)

    Razmi, A. M.; Barry, D. A.; Lemmin, U.; Bakhtyar, R.

    2012-12-01

    Near-shore water quality in lacustrine bays subjected to effluent or stream discharges is affected by, amongst other things, the residence time within a given bay. Vidy Bay, located on the northern shore of Lake Geneva, Switzerland, receives discharge from a wastewater treatment plant, the Chamberonne River and a storm-water drain. The residence time of water in the bay largely depends on water exchanges with the main basin (Grand Lac) of Lake Geneva. Field investigations and modeling of the hydrodynamics of Vidy Bay have shown that currents are variable, due mainly to wind variability over the lake. However, in broad terms there are two main current patterns in the bay, (i) currents are linked to large gyres in the Grand Lac, or (ii) currents are partially independent of the Grand Lac and are controlled by small-scale gyres within the bay. Residence times in Vidy Bay were computed using the hydrodynamic model Delft3D. Since the Vidy Bay shoreline follows a shallow arc, the definition of the off-shore extent of the bay is ambiguous. Here, the largest within-bay gyre is used. Particle tracking was conducted for each of the three discharges into the bay. Model results were computed using meteorological data for 2010, and thus include the natural variability in wind patterns and seasonal stratification. An analysis of the results shows that a water parcel from the waste water outfall has a residence time ranging from hours to days. The water residence time is minimum near to the surface and maximum at the near bottom layer. The results confirmed that wind force, thermal stratification, and water depth are the main factors influencing residence time.

  2. Protected Resident Research Time Does Not Increase the Quantity or Quality of Residency Program Research Publications: A Comparison of 3 Orthopedic Residencies.

    PubMed

    Krueger, Chad A; Hoffman, Jeffery D; Balazs, George C; Johnson, Anthony E; Potter, Benjamin K; Belmont, Philip J

    The effect of dedicated resident research time in terms of residency program research productivity remains largely unknown. We hypothesize that the quantity and quality of a residency program's peer-reviewed publications (PRPs) increase proportionately with the amount of dedicated research time given to residents. Three residency programs (P1, P2, and P3) were examined. P1 has a mandatory research year for all residents between postgraduate years 3 and 4. P2 has an elective research year for 1 resident between postgraduate years 2 and 3. P3 has no dedicated research time for residents. All publications produced by residents and staff at each program from January 2007 through December were recorded from PUBMED. SCImago Journal Rankings were used as a proxy to measure research quality. There was no significant difference in the number of publications produced between the institutions on a per-staff (p = 0.27) and per-resident (p = 0.80) basis. There were no residents at P3 who graduated without at least 1 PRP, whereas there were 7 residents from P1 and 8 residents from P2 who graduated without a PRP. There were no significant differences between programs in terms of the SCImago Journal Ranking for the journals containing their publications (p = 0.135). Residency programs with dedicated research time did not produce significantly (p > 0.05) more, or higher quality, PRPs than residencies without dedicated research time. It may be that the quantity and quality of PRPs is related more to faculty engagement, research interest, and mentorship at individual programs rather than the number of residents given dedicated time to complete research. Level 3. Published by Elsevier Inc.

  3. ON THE RESIDENCE TIME DISTRIBUTION IN IDEALIZED GROUNDWATERSHEDS

    EPA Science Inventory

    The relative cumulative frequency distribution of residence times F(T) is calculated for an entire groundwatershed under steady-state conditions and assuming Dupuit-Forchheimer flow. It appears that F(T) is always the same: , provided that the aquifer recharge rate and are cons...

  4. Comparison of residence time models for cascading rotary dryers

    SciTech Connect

    Cao, W.F.; Langrish, T.A.G.

    1999-04-01

    The predictions of the models of Matchett and Baker (1988), Saeman and Mitchell (1954) and Friedman and Marshall (1949) for the solids residence time in rotary dryers have been compared with both pilot-scale and industrial-scale data. A countercurrent pilot-scale dryer of 0.2m diameter and 2m long has been used with air velocities up to 1.5 m to measure the residence times of sorghum grain. The average discrepancy for the solids residence time between the predictions and the experiments that were carried out in the pilot-scale rotary dryer is {minus}10.4%. Compared with the models of Friedman and Marshall (1949) and Saeman and Mitchell (1954) for the pilot-scale data obtained here, the Matchett and Baker model is more satisfactory for predicting the solids residence time in this pilot-scale dryer. It has also been found that the model of Matchett and Baker describes the industrial data of Saeman and Mitchell (1954) than the correlation of Friedman and Marshall (1949).

  5. Stable, Ultra-Low Residence Time Partial Oxidation

    DOEpatents

    Schmidt, Lanny D.; Hickman, Daniel A.

    1997-07-15

    A process for the catalytic partial oxidation of methane in gas phase at very short residence time (800,000 to 12,000,000 hr.sup.-1) by contacting a gas stream containing methane and oxygen with a metal supported catalyst, such as platinum deposited on a ceramic monolith.

  6. A revised picture of the atmospheric moisture residence time

    NASA Astrophysics Data System (ADS)

    Läderach, Alexander; Sodemann, Harald

    2016-04-01

    The atmospheric branch of the hydrological cycle is a key component of variability in the global water and energy budget. We study the transport of moisture by weather systems using a refined Lagrangian moisture source diagnostics on a global air mass transport climatology calculated with the FLEXPART model for the period 1979-2013. The diagnostics determine source-sink relationships for all precipitation events in the ERA-Interim data set, which provides a new estimate of the atmospheric moisture residence time (defined as the time moisture spends in the atmosphere between evaporation and precipitation). The global mean residence time of 4 to 5 days obtained from our diagnostics is about half the value assumed so far. This is mainly because previous estimates neglect moisture transport, and assume that depletion time constants can be considered as a proxy for the time moisture spends in the atmosphere. We show from different arguments that these assumptions are generally not fulfilled. The revised spatial and temporal picture of the atmospheric moisture residence time reveals patterns that are consistent with the footprints of precipitation producing weather systems in different regions of the earth. This will be exemplified with examples from tropical and extratropical regions.

  7. Modeling the Residence Time of Mobile Bay in Alabama

    NASA Astrophysics Data System (ADS)

    Han, M. M.; Park, K.

    2016-02-01

    The Three-dimensional Hydrodynamic-Eutrophication Model/Environmental Fluid Dynamics Code (HEM3D/EFDC) was used to calculate the residence time of Mobile Bay in Alabama using Eulerian passive tracer method. Mobile Bay is about 50 km long and 20 km wide, so it can be divided into several sections which may have different residence times. Three typical boundary conditions that affect residence time are tide, river discharge, and wind. Mobile Bay is located in the northern Gulf of Mexico and is a micro-tidal region. Two most important tidal components here are K1 and O1, and the maximum tidal range of tropic (spring) tide is less than 0.6 m. There is a difference between the simulation results with and without tidal condition (K1+O1) even though the tidal range is relatively smaller than that in macro-tidal regions. Also the minimum, mean, and maximum of daily mean river discharge for 38 years (1976-2013) in Mobile and Tensaw River are 80.7 m3/s, 1700.8 m3/s, and 14186.7 m3/s respectively, and there are daily, monthly, seasonal, and annual variations. The residence time can be largely affected by the river discharge because of its large deviation. Even though the dominant wind here is southerly in the spring and summer and is northerly in the fall and winter, the wind speed and direction change over time. Continuous winds from similar directions can reduce and increase the residence time such as the southerly, southwesterly, northerly, and northeasterly winds in alignment with the direction of the inlet and outlet of Mobile Bay. Also the short term changes of wind direction and speed can affect it complicatedly. Therefore, the simulations with the combinations of three boundary conditions allow us to understand the water circulation in Mobile Bay well and to predict the residence time when some accidents happen such as contaminations by factories, sewage plants, ships and oil spills.

  8. Real time curriculum map for internal medicine residency

    PubMed Central

    Wong, Roger Y; Roberts, J Mark

    2007-01-01

    Background To manage the voluminous formal curriculum content in a limited amount of structured teaching time, we describe the development and evaluation of a curriculum map for academic half days (AHD) in a core internal medicine residency program. Methods We created a 3-year cyclical curriculum map (an educational tool combining the content, methodology and timetabling of structured teaching), comprising a matrix of topics under various specialties/themes and corresponding AHD hours. All topics were cross-matched against the ACP-ASIM in-training examination, and all hours were colour coded based on the categories of core competencies. Residents regularly updated the map on a real time basis. Results There were 208 topics covered in 283 AHD hours. All topics represented core competencies with minimal duplication (78% covered once in 3 years). Only 42 hours (15%) involved non-didactic teaching, which increased after implementation of the map (18–19 hours/year versus baseline 5 hours/year). Most AHD hours (78%) focused on medical expert competencies. Resident satisfaction (90% response) was high throughout (range 3.64 ± 0.21, 3.84 ± 0.14 out of 4), which improved after 1 year but returned to baseline after 2 years. Conclusion We developed and implemented an internal medicine curriculum map based on real time resident input, with minimal topic duplication and high resident satisfaction. The map provided an opportunity to balance didactic versus non-didactic teaching, and teaching on medical versus non medical expert topics. PMID:17988402

  9. Financial Implications of Residency Programs for Sponsoring Organizations.

    ERIC Educational Resources Information Center

    Heiberger, Michael H.

    1997-01-01

    Explores cost implications of residency programs within the Veterans Administration health care system, particularly the costs and benefits of residencies in family medicine, osteopathic medicine, and general dentistry, because they resemble optometric residencies most closely. Costs of an existing vision therapy residency are examined, and…

  10. The Effect of Tidal Exchange on Residence Time

    NASA Astrophysics Data System (ADS)

    Rynne, P.; Reniers, A.; Van De Kreeke, J.; MacMahan, J. H.

    2014-12-01

    As the conduit between the ocean and an inland body of water such as a lagoon, estuary or harbor, tidal inlets serve an important role in the hydrodynamics of the nearshore environment. As the global population grows in a world where 13% of the coastline is composed of barrier islands, an understanding of the physical processes that influence the transport of inland waters offshore is increasingly paramount. Water renewal, or the replacement of old lagoon water with new seawater has been well studied and is controlled by the tides through the process of tidal exchange or 'tidal pumping'. The magnitude of tidal exchange is influenced by the inlet hydraulics and geometry of the inlet and various physical processes driven by the tide, wind, and waves. To examine the correlation between tidal exchange and the renewal of lagoon water with seawater, a new method to quantify lagoon residence time is explored. Modeling experiments in Delft3D of idealized inlet systems are used to quantify the effect that tidal exchange has on residence time. Tidal exchange is decomposed into two fractions, an ocean exchange fraction and a lagoon exchange fraction. A simple transport model that utilizes both these fractions is compared to both a tidal prism model that neglects the lagoon exchange fraction and Delft3D. The tidal prism model over predicts the seaward transport of lagoon water as compared to Delft3D for all inlet channel geometries studied. The transport model shows good agreement with Delft3D for narrower inlets that support high ocean exchange fractions, but less agreement for wider inlets that support low ocean exchange fractions. Residence time distributions for each geometry are calculated using a new virtual tracer method in Delft3D. The spatially averaged residence time in the lagoon is found to be inversely proportional to the product of the two exchange fractions of each inlet system. Funded by ONR and NDSEG

  11. Mean Residence Time and Emergency Drinking Water Supply.

    NASA Astrophysics Data System (ADS)

    Kralik, Martin; Humer, Franko

    2013-04-01

    Immediately after securing an endangered population, the first priority of aid workers following a disaster is the distribution of drinking water. Such emergency situations are reported from many parts of the world following regional chemical or nuclear pollution accidents, floods, droughts, rain-induced landslides, tsunami, and other extreme events. It is often difficult to organise a replacement water supply when regular water systems with short residence times are polluted, infiltrated or even flooded by natural or man-made disasters. They are either unusable or their restoration may take months or even years. Groundwater resources, proven safe and protected by the geological environment, with long residence times and the necessary infrastructure for their exploitation, would provide populations with timeous replacement of vulnerable water supply systems and make rescue activities more rapid and effective. Such resources have to be identified and investigated, as a substitute for affected drinking water supplies thereby eliminating or reducing the impact of their failure following catastrophic events. Even in many areas such water resources with long residence times in years or decades are difficult to find it should be known which water supply facilities in the region are matching these requirements to allow in emergency situation the transport of water in tankers to the affected regions to prevent epidemics, importing large quantities of bottled water. One should know the residence time of the water supply to have sufficient time to plan and install new safe water supply facilities. Development of such policy and strategy for human security - both long term and short term - is therefore needed to decrease the vulnerability of populations threatened by extreme events and water supplies with short residence times. Generally: The longer the residence time of groundwater in the aquifer, the lower its vulnerability. The most common and economic methods to estimate

  12. Resident fishes display elevated organic pollutants in salmon spawning streams of the great lakes.

    PubMed

    Janetski, David J; Chaloner, Dominic T; Moerke, Ashley H; Rediske, Richard R; O'Keefe, James P; Lamberti, Gary A

    2012-08-07

    Pacific salmon (Oncorhynchus spp.) can transport bioaccumulated organic pollutants to stream ecosystems where they spawn and die. We quantified PCBs, DDE, and PBDEs in resident fishes from 13 Great Lakes tributaries to assess biotransport of pollutants associated with introduced Pacific salmon. Resident fishes sampled from salmon spawning reaches had higher mean pollutant concentrations than those from upstream reaches lacking salmon (93.5 and 4.1 μg x kg(-1) [PCB], 24.0 and 3.1 μg x kg(-1) [DDE], 8.5 and 1.0 μg x kg(-1) [PBDE], respectively), but differences varied substantially among lake basins. In Lake Michigan tributaries, PCB concentrations in resident fishes from salmon reaches were over four times higher than those from salmon reaches in Lake Huron and over 30 times higher than those from Lake Superior. Moreover, resident fish pollutant concentrations were better explained by pollutant inputs from salmon (μg x m(-2); R(2) = 0.76 [PCB], 0.64 [DDE], 0.64 [PBDE]) than by land development/agriculture, watershed area, resident fish species, body length, or lipid content. These results suggest that pollutant dispersal to stream ecosystems via biotransport is an often overlooked consequence of salmon stocking and historical food web contamination in the Great Lakes. Our findings have implications for Great Lakes management, including dam removal and wildlife conservation.

  13. Promoting resident wellness: evaluation of a time-off policy to increase residents' utilization of health care services.

    PubMed

    Cedfeldt, Andrea S; Bower, Elizabeth; Flores, Christine; Brunett, Patrick; Choi, Dongseok; Girard, Donald E

    2015-05-01

    To evaluate awareness and utilization of a new institutional policy to grant residents time off to access personal and family health care. In 2012, two years after policy implementation, an electronic survey was sent to all 546 residents and fellows at a tertiary care academic medical center in the United States. Residents were asked questions regarding awareness of the time-off policy, use of the policy, health care status, reasons for policy use, and barriers to use. A total of 490 (90%) residents responded. Eighty-nine percent of those surveyed were aware of the policy. Of those who were aware, 49.7% used the policy to access health care. Top reasons for policy use were for personal routine or preventive health care, dental care, and urgent health care needs. The most commonly reported barrier to policy use was concern about the impact the resident's absence would have on colleagues. Implementation of policies to prospectively schedule residents' time off during business hours to address health care needs is an important means to promote resident wellness. Such policies remove one commonly cited barrier to residents' access to health care. However, residents still reported concerns about impact on peers and patients as the main reason they were reluctant to take the time off to address their health care needs. More work is needed on both wellness policy implementation practices and on refining the systems that will allow seamless and guiltless transitions of care.

  14. A comment on the use of flushing time, residence time, and age as transport time scales

    USGS Publications Warehouse

    Monsen, N.E.; Cloern, J.E.; Lucas, L.V.; Monismith, Stephen G.

    2002-01-01

    Applications of transport time scales are pervasive in biological, hydrologic, and geochemical studies yet these times scales are not consistently defined and applied with rigor in the literature. We compare three transport time scales (flushing time, age, and residence time) commonly used to measure the retention of water or scalar quantities transported with water. We identify the underlying assumptions associated with each time scale, describe procedures for computing these time scales in idealized cases, and identify pitfalls when real-world systems deviate from these idealizations. We then apply the time scale definitions to a shallow 378 ha tidal lake to illustrate how deviations between real water bodies and the idealized examples can result from: (1) non-steady flow; (2) spatial variability in bathymetry, circulation, and transport time scales; and (3) tides that introduce complexities not accounted for in the idealized cases. These examples illustrate that no single transport time scale is valid for all time periods, locations, and constituents, and no one time scale describes all transport processes. We encourage aquatic scientists to rigorously define the transport time scale when it is applied, identify the underlying assumptions in the application of that concept, and ask if those assumptions are valid in the application of that approach for computing transport time scales in real systems.

  15. The residence time of intensively managed agricultural landscapes

    NASA Astrophysics Data System (ADS)

    Bowling, Laura; Cherkauer, Keith; Chiu, Chun-mei; Rahman, Sanoar

    2015-04-01

    Much of the agricultural landscape across the Midwestern United States is intensively managed through numerous surface and subsurface drainage improvements, and the growing extraction of groundwater resources. The relatively recent glaciation of the North Central region means that the landscape is less dissected and hydrologically connected than older till areas. Low topographic gradients and underlying dense till which restricts vertical water movement, as well as kettle depressions, have led to poorly drained soils and extensive wetlands within the landscape. Large areas of this land could only be farmed once the excess water was removed through artificial surface and subsurface drainage. Conventional wisdom in the region maintains that subsurface tile drainage reduces the occurrence of peak flow events by increasing soil water storage capacity. At the watershed scale, this view does not take into account the coincident increase in surface drainage and reduction in residence time in surface depressions. This paper explores to what degree water management and irrigation has changed surface and subsurface water storage and residence time over the last century and how this has impacted flow duration throughout the Wabash River system in Indiana, USA. The effects of subsurface tile drains, wetlands and aquifer storage are explicitly represented within the Variable Infiltration Capacity (VIC) macroscale hydrology model. We maintain a focus on the entire Wabash River, a river system of historic importance that is also representative of many similar areas in the till plain region of the agricultural Midwest, which contribute to water quality and flood dynamics of the Mississippi river system. By lowering the water table, surface and subsurface drainage improvements have increased the subsurface storage capacity at the beginning of rain events, but this is overwhelmed by the decrease in surface storage capacity for intermediate to large events, decreasing the current

  16. Modelling travel and residence times in the eastern Irish Sea.

    PubMed

    Dabrowski, T; Hartnett, M

    2008-01-01

    The Irish Sea, which lies between 51 degrees N-56 degrees N and 2 degrees 50'W-7 degrees W, provides a sheltered environment to exploit valuable fisheries resource. Anthropogenic activity is a real threat to its water quality. The majority of freshwater input down rivers flows into the eastern Irish Sea. The structure of the water circulation was not well understood during the planning of Sellafield nuclear plant outfall site in the eastern Irish Sea. A three-dimensional primitive equation numerical model was applied to the Irish Sea to simulate both barotropic and baroclinic circulation within the region. High accuracy was achieved with regard to the prediction of both tidal circulation and surface and nearbed water temperatures across the region. The model properly represented the Western Irish Sea Gyre, induced by thermal stratification and not known during planning Sellafield. Passive tracer simulations based on the developed hydrodynamic model were used to deliver residence times of the eastern Irish Sea region for various times of the year as well as travel times from the Sellafield outfall site to various locations within the Irish Sea. The results indicate a strong seasonal variability of travel times from Sellafield to the examined locations. Travel time to the Clyde Sea is the shortest for the autumnal tracer release (90 days); it takes almost a year for the tracer to arrive at the same location if it is released in January. Travel times from Sellafield to Dublin Bay fall within the range of 180-360 days. The average residence time of the entire eastern Irish Sea is around 7 months. The areas surrounding the Isle of Man are initially flushed due to a predominant northward flow; a backwater is formed in Liverpool Bay. Thus, elevated tracer concentrations are predicted in Liverpool Bay in the case of accidental spills at the Sellafield outfall site.

  17. Organize for More Time

    ERIC Educational Resources Information Center

    Thomas, Victoria

    2006-01-01

    This article offers some organizational solutions to help teachers better manage their classrooms and their time. To assist with the room arrangement, notebooks, and file cabinets, teachers may find it helpful to use color coding. Most teachers will have more than one class to teach during the course of a day, and, perhaps, more than one course to…

  18. THE LOCAL EFFECT TIME (LET) AND HOW IT INCORPORATES ECOLOGY INTO RESIDENCE TIME

    EPA Science Inventory

    A clear and direct connection between constituent/water residence times and ecological effects is necessary to quantitatively relate these time scales to ecology. The concept of "local effect time" (LET) is proposed here as a time scale with adequate spatial resolution to relate ...

  19. THE LOCAL EFFECT TIME (LET) AND HOW IT INCORPORATES ECOLOGY INTO RESIDENCE TIME

    EPA Science Inventory

    A clear and direct connection between constituent/water residence times and ecological effects is necessary to quantitatively relate these time scales to ecology. The concept of "local effect time" (LET) is proposed here as a time scale with adequate spatial resolution to relate ...

  20. The determination of residence times in a pilot plant

    NASA Astrophysics Data System (ADS)

    Ramírez, F. Pablo; Cortés, M. Eugenia

    2004-01-01

    It is well known that residence time distributions (RTD) are very important in many chemical processes such as separation, reforming, hydrocracking, fluid catalytic cracking, hydrodesulfuration, hydrogenation among others [3 Procédés de transformation, Editions Technip, Institute Francais du Petrole, Paris, France, 1998]. In addition, tracers can be used to measure the velocity, distribution and residence time of any stream through any part of an industrial [Guidebook on Radioisotope Tracers in Industry, IAEA, Vienna, 1990] or experimental system. Perhaps the best quality of radiotracers is that they do not interfere with normal unit operations or production scheduling. In this paper are presented the RTDs obtained in a pilot plant for a hydrogenation process [IMP, Technical Report, Determinación del tiempo de residencia promedio en el reactor de la planta piloto de hidroagotamiento de crudo, 2002]. The RTDs show a random phenomenon, which is not typical of this type of chemical processes. Several RTDs were determined in order to confirm this random behavior. The data were obtained using as a tracer a radioactive form of sodium iodide containing iodine-131 [The Condensed Chemical Dictionary, 10th Ed., Van Nostrand Reinhold, USA, 1981]. The process works with two phases in a countercurrent flow, inside a packed column. The liquid phase goes down by gravity. The gas phase goes up due to pressure difference [3 Procédés de transformation, Editions Technip, Institute Francais du Petrole, Paris, France, 1998]. The tracer was selected such that it would follow the liquid phase.

  1. Residence time of tropospheric aerosols in association with radioactive nuclides.

    PubMed

    Papastefanou, C

    2006-01-01

    The residence time of atmospheric aerosol particles is a function of various removal processes, such as dry deposition by impaction, diffusion, sedimentation and resuspension as well as wet deposition by rain drops (precipitation scavenging). Estimation of the mean-residence time of atmospheric aerosols could be based on measurements of the activities and ratios of activities of cosmic-ray produced radionuclides, such as (7)Be and the radioactive decay products of radon-222 emanated from soil into the atmosphere, such as (210)Pb, (210)Bi and (210)Po. It was found that a mean value of about 8 days could be applied to aerosol particles in the lower atmosphere below precipitation cloud levels as resulted by the application of two different methods, i.e. the (7)Be-associated atmospheric aerosols and the radon decay product aerosols at two different locations, i.e. at Thessaloniki, Greece 40 degrees 38'N 22 degrees 58'E with dry (precipitation free) climate and at Oak Ridge, Tennessee, USA 35 degrees 58'N 84 degrees 17'W with high precipitation (wet climate), roughly at similar temperate latitudes, but the first one at East longitude and the other at West longitude, respectively.

  2. Residence time estimates for asymmetric simple exclusion dynamics on strips

    NASA Astrophysics Data System (ADS)

    Cirillo, Emilio N. M.; Krehel, Oleh; Muntean, Adrian; van Santen, Rutger; Sengar, Aditya

    2016-01-01

    The target of our study is to approximate numerically and, in some particular physically relevant cases, also analytically, the residence time of particles undergoing an asymmetric simple exclusion dynamics on a two-dimensional vertical strip. The sources of asymmetry are twofold: (i) the choice of boundary conditions (different reservoir levels) and (ii) the strong anisotropy from a drift nonlinear in density with prescribed directionality. We focus on the effect of the choice of anisotropy on residence time. We analyze our results by means of two theoretical models, a Mean Field and a one-dimensional Birth and Death one. For positive drift we find a striking agreement between Monte Carlo and theoretical results. In the zero drift case we still find agreement as long as particles can freely escape the strip through the bottom boundary. Otherwise, the two models give different predictions and their ability to reproduce numerical results depends on the horizontal displacement probability. The topic is relevant for situations occurring in pedestrian flows or biological transport in crowded environments, where lateral displacements of the particles occur predominantly affecting therefore in an essentially way the efficiency of the overall transport mechanism.

  3. Air Parcel Residence Times within Tropical Forest Canopies and Implications for Reactive Gases

    NASA Astrophysics Data System (ADS)

    Gerken, T.; Chamecki, M.; Fuentes, J. D.

    2014-12-01

    The Amazon rainforest is the world's largest natural emitter of reactive trace gases. Due to its dense vegetation (leaf area index > 4), turbulence fluctuations are highly attenuated deep inside the canopy. However, strong coherent eddies that penetrate the upper portion of the canopy can be very effective in transporting gases. Sweeps and ejections act in the order of seconds and transport air parcels into or out of the canopy. The effects of coherent structures on the air parcel residence times and associated chemical processing of reactive gases remain largely unquantified in tropical forests. We combine canopy resolving Large-Eddy Simulation (LES) and field observations in the Brazilian Amazon to study residence times of air parcels in the rainforest as a function of canopy structure and height (h). Good agreement is obtained between simulated and observed turbulence statistics within and above the forest. Coherent structure properties obtained from quadrant analysis are also well reproduced. A Lagrangian particle tracking algorithm is used to quantify the distribution of residence times of air parcels "released" at different heights. Canopy residence times were determined from the particle trajectories. The resulting probability density function (PDF) strongly depended on the particle release height (z). For particles released in the upper canopy (at z/h=0.75) the most frequent residence times were in the order of 30s, with 50% of all particles ejected from the canopy after ~2 minutes. The mean residence time was close to 5 minutes, indicating a very skewed PDF. At z/h=0.25 the PDF was more evenly distributed with its median and mean in the order of ~10 minutes. Due to sweeps, both simulations had a non- negligible fraction of particles transported deep into the canopy, thus increasing greatly their residence times. As the reaction timescales of many biogenic volatile organic compounds (BVOC) are in the order of seconds to minutes, significant chemical

  4. Mineralogical Controls over Carbon Storage and Residence Times in Grassland Soils

    NASA Astrophysics Data System (ADS)

    Dwivedi, D.; Riley, W. J.; Torn, M. S.; Spycher, N.

    2014-12-01

    Globally, soil organic matter (SOM) contains approximately three times more carbon than the atmosphere and terrestrial vegetation contain combined. However, it is not well understood why some SOM persists for a long time while other SOM decomposes quickly. For future climate predictions, representing soil organic matter (SOM) dynamics accurately in Earth system models is essential. Soil minerals stabilize organic carbon in soil; however, there are gaps in our understanding of how soil mineralogy controls the quantity and turnover of long-residence-time organic carbon. To investigate the impact of soil mineralogy on SOM dynamics, we used a new model (Biotic and Abiotic Model of SOM—BAMS1 [Riley et al., 2014]) integrated with a three-dimensional, multiphase reactive transport solver (TOUGHREACT). The model represents bacterial and fungal activity, archetypal polymer and monomer carbon substrate groups, aqueous chemistry, gaseous diffusion, aqueous advection and diffusion, and adsorption and desorption processes. BAMS1 can predict bulk SOM and radiocarbon signatures without resorting to an arbitrary depth-dependent decline in SOM turnover rates. Results show a reasonable match between observed and simulated depth-resolved SOM and ∆14C in grassland ecosystems (soils formed on terraces south of Eureka, California, and the Central Chernozem Region of Russia) and were consistent with expectations of depth-resolved profiles of lignin content and fungi:aerobic bacteria ratios. Results also suggest that clay-mineral surface area and soil sorption coefficients constitute dominant controls over organic carbon stocks and residence times, respectively. Bibliography: Riley, W.J., F.M. Maggi, M. Kleber, M.S. Torn, J.Y. Tang, D. Dwivedi, and N. Guerry (2014), Long residence times of rapidly decomposable soil organic matter: application of a multi-phase, multi-component, and vertically resolved model (BAMS1) to soil carbon dynamics, Geoscientific Model Development, vol. 7, 1335

  5. Are we missing the tail (and the tale) of residence time distributions in watersheds?

    NASA Astrophysics Data System (ADS)

    Frisbee, Marty D.; Wilson, John L.; Gomez-Velez, Jesus D.; Phillips, Fred M.; Campbell, Andrew R.

    2013-09-01

    times provide vital information on hydrological, geochemical, and ecological processes in watersheds. The common perception is that mean residence times in watersheds are very short, on the order of days to years. However, there is growing concern that longer residence times of centuries to millennia are not being captured by traditional surface water age-dating methods. We hypothesize that if mean residence times are biased short, then weathering rates calculated from mean residence times will be forced unrealistically high to match observed solute concentrations. We test this hypothesis by calculating weathering rates from springs based upon residence times estimated using three different age-dating methods. Observed solute concentrations require unrealistically large weathering rates if typical short residence times are employed as compared to rates derived from longer residence times. Residence time distributions in watersheds have substantially longer tails than previously thought, with implications for age-dating methods and their interpretation to infer process behavior.

  6. Age and residence time of terrestrial source water in the northwest Atlantic shelf seas

    NASA Astrophysics Data System (ADS)

    He, R.; Todd, A. C.

    2016-02-01

    Coastal river mouths and bays are the junctions where terrestrial-source water meets and mixes with water from the open ocean. Once the riverine water reaches the coastal ocean, its eventual fate is largely unknown and difficult to trace. Rivers that flow into the ocean may contain high levels of nutrients and organic matter, so understanding the fate of terrestrial source water is important for a variety of biogeochemical processes that occur in the shelf seas. The fate of this terrestrial source water may be described in terms of its mean age (the time since it reached the ocean) and its residence time (the time it remains on the continental shelf). Using a high-resolution ocean model, we apply the constituent-oriented age and residence time (CART) theory to a large region encompassing the northwest Atlantic shelf seas to calculate the mean age of terrestrial source water and its residence time. For this application, 196 river mouths are used as sources of terrestrial water from South America to Nova Scotia. We investigate the spatial and seasonal variability of the water's mean age and compute the residence time within four different shelf regions: the Carribean Sea, the Gulf of Mexico, the South Atlantic Bight, and the Mid-Atlantic Bight/Gulf of Maine. From the estimates of mean age and residence time, we describe the impact of the coastal circulation on the eventual fate of terrestrial waters, and provide conjecture on how varying transport time scales may affect the general biogeochemical processes in the coastal ocean.

  7. Exposure times rather than residence times control redox transformation efficiencies in riparian wetlands

    NASA Astrophysics Data System (ADS)

    Frei, S.; Peiffer, S.

    2016-12-01

    The concept of Damköhler numbers have been extensively used in the discipline of chemical engineering and lately increasingly found its application into environmental science in order to describe the integrated behavior of hydrological systems with respect to their physical transport and biogeochemical transformation capabilities. Defining characteristic time scales of transport and reaction, as part of the Damköhler concept, however is not trivial especially for non-well mixed systems like catchments where physically controlled transport and biogeochemical moderated reactions can be highly variable among individual flow paths. Often, system specific residence times alone are not useful to describe the timescales of transport in the Damköhler concept, because it neglects that degradation of redox-sensitive compounds depend on dynamically changing and non-uniformly distributed hydro-biogeochemical boundary conditions that either facilitate or suppress biogeochemical reactions. In this study an approach is presented that highlights the importance to specifically distinguish between residence and exposure times if system specific transformation efficiencies are evaluated. We investigate the inter-relationship between residence and exposure time distributions for different biogeochemical processes in a virtual wetland environment that is exposed to different hydrological conditions. The relationship between exposure and residence times is mathematically described by a composition matrix that linearly relates the two identities to each other. Composition matrices for different hydrological conditions are analyzed by using the singular value decomposition technique. Results show that especially the type of couplings between the surface and subsurface flow domain control how exposure and residence times are related to each other in the wetland system and that timescales of residence and exposure typically differ by orders of magnitude. Finally, results also indicate

  8. Classifying terrestrial surface water systems using integrated residence time

    NASA Astrophysics Data System (ADS)

    Jones, Allan; Hodges, Ben; McClelland, James; Hardison, Amber; Moffett, Kevan

    2017-04-01

    Linkages between ecology and hydrology in terrestrial surface water often invoke a discussion of lentic (reservoir) vs. lotic (riverine) system behaviors. However, the literature shows a wide range of thresholds separating lentic/lotic regimes and little agreement on a quantitative, repeatable classification metric that can be broadly and reliably applied across a range of systems hosting various flow regimes and suspended/benthic taxa. We propose an integrated Residence Time (iTR) metric as part of a new Freshwater Continuum Classification (FCC) to address this issue. The iTR is computed as the transit time of a water parcel across a system given observed temporal variations in discharge and volume, which creates a temporally-varying metric applicable across a defined system length. This approach avoids problems associated with instantaneous residence times or average residence times that can lead to misleading characterizations in seasonally- or episodically-dynamic systems. The iTR can be directly related to critical flow thresholds and timescales of ecology (e.g., zooplankton growth). The FCC approach considers lentic and lotic to be opposing end-members of a classification continuum and also defines intermediate regimes that blur the line between the two ends of the spectrum due to more complex hydrological system dynamics. We also discover the potential for "oscillic" behavior, where a system switches between lentic and lotic classifications either episodically or regularly (e.g., seasonally). Oscillic behavior is difficult to diagnose with prior lentic/lotic classification schemes, but can be readily identified using iTR. The FCC approach was used to analyze 15 tidally-influenced river segments along the Texas (USA) coast of the Gulf of Mexico. The results agreed with lentic/lotic designations using prior approaches, but also identified more nuanced intermediate and oscillic regimes. Within this set of systems, the oscillic nature of some of the river

  9. Polybrominated diphenyl ethers: Residence time in soils receiving biosolids application.

    PubMed

    Andrade, Natasha A; McConnell, Laura L; Anderson, Marya O; Torrents, Alba; Ramirez, Mark

    2017-03-01

    Polybrominated diphenyl ethers (PBDEs) may enter the environment because of accumulation in biosolids followed by application to agricultural lands. No published dissipation studies are available for PBDEs in agricultural soils after biosolids application. Therefore, we conducted a 3-year study to examine the fate of PBDEs in a small-scale 0.24-ha continuously cropped field after a single biosolids application at 72.3 wet tons/ha and determined dissipation half-lives for BDE-47+BDE-99 and BDE-209. In addition, we conducted a large-scale survey of soils from 26 mostly pasture fields at 10 farms with detailed information on timing and rate of biosolids applications. In the small-scale experiment, maximum soil PBDE concentrations of 43.7 ± 42.7 μg kg(-1) d.w. for BDE-209 and 6.05 ± 7.15 μg kg(-1) d.w. for BDE-47+BDE-99 were reached 1 year after application. We hypothesized that PBDEs were slowly released from the biosolids matrix into the soil over the first year. After 3 years, median BDE-47+BDE-99 concentrations were approximately equal to preapplication levels, whereas median BDE-209 concentrations remained ∼129% above preapplication levels. The estimated residence time from the small-scale experiment was 342 d for BDE-47+BDE-99 and 861 d for BDE-209. In the large-scale study, a subset of fields that received a single biosolids application was used to generate another estimate of residence time: 704 d for BDE-47+BDE-99 and 1440 d for BDE-209. These longer residence time estimates were used in three different first-order decay dissipation scenarios (continuous, limited, and no dissipation) to predict PBDE concentration in fields with single and multiple biosolids applications. Results indicate that dissipation occurs primarily in the first 2 years after application, but residues remaining in the soil after this period are likely to be much more tightly bound and less available for degradation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Formal and Informal Neighborhood Social Organization: Which Promotes Better Resident Health?

    PubMed Central

    Gilster, Megan E.; Meier, Cristian L.

    2016-01-01

    Neighborhood social organization captures how neighborhood residents differently organize to exert social control and enact their vision of their community. Whereas structural aspects of neighborhoods have been found to predict the health of neighborhood residents, we know less about whether neighborhood social characteristics, like social organization, matter for resident health. In their study, authors tested whether two types of social organization—formal and informal—were more predictive of resident self-rated health in a diverse sample of Chicago residents. They used multilevel models with survey weights, ordered dependent variables, and multiple imputation. They found that one measure of formal social organization, organizational participation, was significantly associated with self-rated health even when controlling for other types of social organization and individual participation. The article concludes with a discussion of the implications for macro social work practice to address social determinants of health and improve community health.

  11. Tissue residency of innate lymphoid cells in lymphoid and nonlymphoid organs.

    PubMed

    Gasteiger, Georg; Fan, Xiying; Dikiy, Stanislav; Lee, Sue Y; Rudensky, Alexander Y

    2015-11-20

    Innate lymphoid cells (ILCs) contribute to barrier immunity, tissue homeostasis, and immune regulation at various anatomical sites throughout the body. How ILCs maintain their presence in lymphoid and peripheral tissues thus far has been unclear. We found that in the lymphoid and nonlymphoid organs of adult mice, ILCs are tissue-resident cells that were maintained and expanded locally under physiologic conditions, upon systemic perturbation of immune homeostasis and during acute helminth infection. However, at later time points after infection, cells from hematogenous sources helped to partially replenish the pool of resident ILCs. Thus, ILCs are maintained by self-renewal in broadly different microenvironments and physiological settings. Such an extreme "sedentary" lifestyle is consistent with the proposed roles of ILCs as sentinels and local keepers of tissue function. Copyright © 2015, American Association for the Advancement of Science.

  12. Sediment residence time and landscape evolution in arid Australia

    NASA Astrophysics Data System (ADS)

    Handley, H. K.; Dosseto, A.; Suresh, P. O.; Cohen, T. J.; Turner, S.

    2009-12-01

    Fractionation of Uranium isotopes (234U and 238U) in fine-grained sediment (< 50 µm) can be used to quantify timescales of sediment residence i.e. storage in soils and associated transport in fluvial or aeolian systems. This information is invaluable for understanding the relationships between climate, tectonics and landscape evolution. Previous work has shown it is possible to use this technique to quantify the links between climate change and sediment transport during the last glacial cycle in Australia (Dosseto et al. 2008). In the temperate, tectonically quiescent catchment area studied, Dosseto et al. showed that changes in climatic conditions strongly influence sediment provenance. However, can the same conclusions be drawn for a semi-arid catchment area? (234U/238U) ratios are presented on the fine fraction (2-50 µm) of palaeochannel sediments from the Katipiri Formation in the Strzelecki Desert. The data are combined with sediment deposition ages inferred from optically-stimulated luminescence (OSL) dating in order to constrain the time elapsed since production by physical weathering of the source bedrock (comminution age). These results provide constraint on the evolution of what today is a semi-arid environment and, in particular, how sediment transport and the landscape have responded to climate change over the past 100,000 yrs. The results are compared and contrasted with sediment residence timescales obtained for temperate Australia. Dosseto, A., Turner, S.P., Hesse, P., Maher, K., and Fryirs, K., 2008, Vegetation over hydrologic control of sediment transport over the past 100,000 yr: Geochim. Cosmochim. Acta, v. 72, p. Suppl. 1.

  13. Computing the residence times in the Venice Lagoon

    NASA Astrophysics Data System (ADS)

    Umgiesser, G.; Cucco, A.

    2003-04-01

    The Venice Lagoon is a shallow water body with a total area of about 500 km2. Three inlets govern the water exchanges between the Adriatic Sea and the Venice Lagoon. Water, entering and exiting through these channels during an entire tidal cycle, changes its biogeochemical and physical properties. The aim of this work is to investigate the Venice Lagoon circulation and to quantify the turn over time of the lagoon which mainly influences the water quality of the basin. The study has been carried out with a numerical model. The model computes the main hydrodynamic unknowns on a spatial domain that represents the Venice Lagoon and the Adriatic Sea with a finite element grid. The model considers as open boundary the line of Otranto channel in the southern Adriatic Sea and elsewhere as closed boundary the whole perimeter of the Adriatic Sea and Venice Lagoon. The model has been calibrated using the sea level data measured by more than twelve tide gauges located along the Adriatic Sea and inside the lagoon. The results obtained by the calibrated model have been validated with experimental data such as discharge data collected by botton mounted ADCP probes located at each inlet. The simulations take into account the tidal forcing and the different wind regimes. The instantaneous circulation and the residual current fields have been analyzed and the impact of the most important wind regimes on the circulation has been studied. The turn over time of the lagoon has been computed under different forcing conditions. A passive tracer only subjected to transport mechanism, has been released inside the lagoon. Resolving the time decaying of the tracer concentration for the whole area, the model computes the spatial distribution of the residence time in the basin. The results show that the re-import of water that previously exited the lagoon through the three inlets, plays an important role on the estimation of the turn over time of the lagoon thus influencing the water quality of

  14. Water residence time in Chesapeake Bay for 1980-2012

    NASA Astrophysics Data System (ADS)

    Du, Jiabi; Shen, Jian

    2016-12-01

    Concerns have grown over the increase of nutrients and pollutants discharged into the estuaries and coastal seas. The retention and export of these materials inside a system depends on the residence time (RT). A long-term simulation of time-varying RT of the Chesapeake Bay was conducted over the period from 1980 to 2012. The 33-year simulation results show that the mean RT of the entire Chesapeake Bay system ranges from 110 to 264 days, with an average value of 180 days. The RT was larger in the bottom layers than in the surface layers due to the persistent stratification and estuarine circulation. A clear seasonal cycle of RT was found, with a much smaller RT in winter than in summer, indicating materials discharged in winter would be quickly transported out of the estuary due to the winter-spring high flow. Large interannual variability of the RT was highly correlated with the variability of river discharge (R2 = 0.92). The monthly variability of RT can be partially attributed to the variability of estuarine circulation. A strengthened estuarine circulation results in a larger bottom influx and thus reduces the RT. Wind exerts a significant impact on the RT. The upstream wind is more important in controlling the lateral pattern of RT in the mainstem.

  15. Carbone organique total (COT) et magnésium (Mg2+) : deux traceurs complémentaires du temps de séjour dans l'aquifère karstiqueTotal Organic Carbon (TOC) and magnesium (Mg2+): two complementary tracers of residence time in karstic systems

    NASA Astrophysics Data System (ADS)

    Batiot, Christelle; Emblanch, Christophe; Blavoux, Bernard

    2003-01-01

    The Total Organic Carbon (TOC) is an interesting tracer of fast infiltration within karstic systems [3,7]. Regular sampling on several aquifers, from the experimental site of Vaucluse, made it possible to demonstrate the high sensitivity of this tracer compared with other commonly used chemical and isotopic tracers in karstic hydrogeology. The complementarity of magnesium, indicator of the residence time of water within the system, and TOC appears as a relevant tool in order to characterize the behaviour of the aquifer, to differentiate the water types which participate to the karstic flow (fast infiltration, unsaturated zone, saturated zone) and then, to evaluate their vulnerability.

  16. Resident Involvement in Professional Otolaryngology Organizations: Current Trends in the United States.

    PubMed

    Wong, Kevin; Jang, Minyoung; Gilad, Amir; Levi, Jessica R

    2017-08-01

    Involvement by residents in professional medical organizations can enrich their training, but little data exist regarding the number and types of involvement opportunities available to otolaryngology residents. We sought to fill this gap in knowledge by quantifying the extent to which major otolaryngology-related organizations in the United States provide involvement opportunities to otolaryngology residents. Our analysis included 23 organizations and subspecialty societies. Results showed that many opportunities exist for residents to attend conferences and present research; however, fewer involvement and funding opportunities existed in any other leadership, health policy, or service-learning experiences. These findings were consistent across general and subspecialty societies. Given the many purported benefits of resident involvement in otolaryngology outside of the standard training environment, future efforts may be warranted to increase the number and type of involvement opportunities currently available in professional societies.

  17. Particle tracking and mean residence time in barchan dunes

    NASA Astrophysics Data System (ADS)

    Zhang, Deguo; Narteau, Clement; Rozier, Olivier

    2013-04-01

    We analyze sediment particles motions in steady-state barchan dunes by tracking individual cells of a 3-D cellular automaton dune model. The overall sediment flux may be decomposed into advective and dispersive fluxes to estimate the relative contribution of the underlying physical processes to the barchan dune shape. The net lateral sediment transport from the center to the horns indicates that dispersion on the stoss slope is more efficient than avalanches on the lee slope. The combined effect of these two antagonistic dispersive processes restricts the lateral mixing of sediment particles in the central region of barchan dunes. Then, for different flow strength and dune size, we find that the mean residence time of sediment particles in barchan dunes is equal to the surface of the central longitudinal dune slices divided by the input sand flux. We infer that this central slice contains most of the relevant information about barchan dune morphodynamics. Finally, we initiate a discussion about sediment transport and memory in presence of bedforms using the advantages of the particle tracking technique.

  18. Pathology residency training: time for a new paradigm.

    PubMed

    Domen, Ronald E; Baccon, Jennifer

    2014-06-01

    The exponential growth of the field of pathology over the past several decades has created challenges for residency training programs. These challenges include the ability to train competent pathologists in 4 years, an increased demand for fellowship training, and the structuring and completion of maintenance of certification. The authors feel that pathology residency training has reached a critical point and that a new paradigm for training is required. Copyright © 2014 Elsevier Inc. All rights reserved.

  19. Nonparametric estimation of groundwater residence time distributions: What can environmental tracer data tell us about groundwater residence time?

    NASA Astrophysics Data System (ADS)

    McCallum, James L.; Engdahl, Nicholas B.; Ginn, Timothy R.; Cook, Peter. G.

    2014-03-01

    Residence time distributions (RTDs) have been used extensively for quantifying flow and transport in subsurface hydrology. In geochemical approaches, environmental tracer concentrations are used in conjunction with simple lumped parameter models (LPMs). Conversely, numerical simulation techniques require large amounts of parameterization and estimated RTDs are certainly limited by associated uncertainties. In this study, we apply a nonparametric deconvolution approach to estimate RTDs using environmental tracer concentrations. The model is based only on the assumption that flow is steady enough that the observed concentrations are well approximated by linear superposition of the input concentrations with the RTD; that is, the convolution integral holds. Even with large amounts of environmental tracer concentration data, the entire shape of an RTD remains highly nonunique. However, accurate estimates of mean ages and in some cases prediction of young portions of the RTD may be possible. The most useful type of data was found to be the use of a time series of tritium. This was due to the sharp variations in atmospheric concentrations and a short half-life. Conversely, the use of CFC compounds with smoothly varying atmospheric concentrations was more prone to nonuniqueness. This work highlights the benefits and limitations of using environmental tracer data to estimate whole RTDs with either LPMs or through numerical simulation. However, the ability of the nonparametric approach developed here to correct for mixing biases in mean ages appears promising.

  20. Watershed mean residence times and travel time distributions: how accurately can they be characterized?

    NASA Astrophysics Data System (ADS)

    Godsey, S. E.; Kirchner, J. W.

    2006-12-01

    The average time that rainfall takes to reach the stream - the mean residence time - is a basic parameter used to characterize watersheds. Watersheds are also characterized by the distribution of travel times for individual parcels of precipitation that fall on different points across the catchment. This travel time distribution is an important control on catchment response to contamination events. Catchments with shorter residence times or narrower distributions will have a flashier response to contamination events, whereas catchments with longer residence times or longer-tailed distributions will have a more persistent response to those same contamination events. Catchments' travel time distributions are typically inferred from time series of passive tracers (such as water isotopes, chloride, or bromide) in rainfall and streamflow. Tracer fluctuations in streamflow are typically damped compared to those in preciptation, because precipitation inputs of different ages (and different tracer signatures) are mixed within the catchment. Mathematically, this mixing process is modeled by the convolution of the travel time distribution and the precipitation tracer inputs to generate the stream tracer outputs. The parameters describing the travel time distribution are typically estimated by maximizing the goodness of fit between the modeled and measured tracer outputs. This approach is potentially subject to at least two sources of uncertainty. First, both the input and output tracer concentrations are subject to measurement error. Second, although the catchment mixing process is continuous, the inputs and outputs are only sampled at discrete points in time. Here we test how these two sources of uncertainty may affect travel time distributions that are estimated from catchment monitoring data. We begin by generating synthetic tracer input time series, and convolve these with a specified travel-time distribution to generate a synthetic output time series. We then subsample

  1. Controls on residence time and exchange in a system of shallow coastal bays

    NASA Astrophysics Data System (ADS)

    Safak, I.; Wiberg, P. L.; Richardson, D. L.; Kurum, M. O.

    2015-04-01

    Patterns of transport and residence time influence the morphology, ecology and biogeochemistry of shallow coastal bay systems in important ways. To better understand the factors controlling residence time and exchange in coastal bays, a three-dimensional finite-volume coastal ocean model was set up and validated with field observations of circulation in a system of 14 shallow coastal bays on the Atlantic coast of the USA (Virginia Coast Reserve). Residence times of neutrally buoyant particles as well as exchange among the bays in the system and between the bays and the ocean were examined with Lagrangian particle tracking. There was orders of magnitude variation in the calculated residence time within most of the bays, ranging from hours in the tidally refreshed (repletion) water near the inlets to days-weeks in the remaining (residual) water away from the inlets. Residence time in the repletion waters was most sensitive to the tidal phase (low vs. high) when particles were released whereas residence time in the residual waters was more sensitive to wind forcing. Wind forcing was found to act as a diffuser that shortens particle residence within the bays; its effect was higher away from the inlets and in relatively confined bays. Median residence time in the bays significantly decreased with an increase in the ratio between open water area and total area (open water plus marsh). Exchange among the bays and capture areas of inlets (i.e., exchange between the bays and the ocean) varied considerably but were insensitive to tidal phase of release, wind, and forcing conditions in different years, in contrast to the sensitivity of residence time to these factors. We defined a new quantity, termed shortest-path residence time, calculated as distance from the closest inlet divided by root-mean-square velocity at each point in model domain. A relationship between shortest-path residence time and particle-tracking residence time provides a means of estimating residence time

  2. Time to Talk: Evaluation of a Staff-Resident Quality Time Intervention on the Perceptions of Staff in Aged Care

    ERIC Educational Resources Information Center

    Malins, G. L.; Couchman, L.; Viney, L. L.; Grenyer, B. F. S.

    2004-01-01

    Aged care research has found that relationships between care-providing staff and residents are often not satisfying for either staff or residents. The study evaluated the effects of a simple relationship intervention, Staff-Resident Quality Time, on staff perceptions of relationship satisfaction and control in two aged care facilities. The…

  3. Temporal evolution and variability of dissolved inorganic nitrogen in beach pore water revealed using radon residence times.

    PubMed

    Goodridge, Blair M; Melack, John M

    2014-12-16

    We coupled measurements of beach pore water residence time, determined using the radioisotopic tracer (222)Rn, with dissolved carbon and nitrogen chemistry to identify the temporal evolution and variability of dissolved inorganic nitrogen (DIN) concentrations in beach pore water along the Santa Barbara, California coastline. Pore water dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) ratios (DOC:TDN) were negative exponentially correlated with residence time. Mean pore water residence times were positively correlated with tidal amplitudes, and ranged from 4.4 to 6.4 days. We used this range in mean residence times to model radon residence time distributions (RTDs), and integrated them with modeled DIN vs residence time relationships (DIN-temporal evolution, or DIN-te curves) to derive volume-weighted mean (VWM) DIN concentrations. We observed 1.2-fold and 5.2-fold differences (20% and 420% increases) in VWM DIN concentrations over the range in modeled RTDs and DIN-te curves, respectively, and a maximum 6.4-fold difference (540% increase) in VWM DIN concentrations for an interactive shift in the RTD and the DIN-te curve. Our study suggests that accounting for temporal variability in the RTD and DIN concentration of pore water is necessary to obtain more accurate estimates of DIN delivery to coastal oceans.

  4. Lymphoid Organ-Resident Dendritic Cells Exhibit Unique Transcriptional Fingerprints Based on Subset and Site

    PubMed Central

    Elpek, Kutlu G.; Bellemare-Pelletier, Angelique; Malhotra, Deepali; Reynoso, Erika D.; Lukacs-Kornek, Veronika; DeKruyff, Rosemarie H.; Turley, Shannon J.

    2011-01-01

    Lymphoid organ-resident DC subsets are thought to play unique roles in determining the fate of T cell responses. Recent studies focusing on a single lymphoid organ identified molecular pathways that are differentially operative in each DC subset and led to the assumption that a given DC subset would more or less exhibit the same genomic and functional profiles throughout the body. Whether the local milieu in different anatomical sites can also influence the transcriptome of DC subsets has remained largely unexplored. Here, we interrogated the transcriptional relationships between lymphoid organ-resident DC subsets from spleen, gut- and skin-draining lymph nodes, and thymus of C57BL/6 mice. For this purpose, major resident DC subsets including CD4 and CD8 DCs were sorted at high purity and gene expression profiles were compared using microarray analysis. This investigation revealed that lymphoid organ-resident DC subsets exhibit divergent genomic programs across lymphoid organs. Interestingly, we also found that transcriptional and biochemical properties of a given DC subset can differ between lymphoid organs for lymphoid organ-resident DC subsets, but not plasmacytoid DCs, suggesting that determinants of the tissue milieu program resident DCs for essential site-specific functions. PMID:21886840

  5. Training general surgery residents in pediatric surgery: educational value vs time and cost.

    PubMed

    Lee, Steven L; Sydorak, Roman M; Applebaum, Harry

    2009-01-01

    This study evaluated the educational value of pediatric surgery rotations, the likelihood of performing pediatric operations upon completing general surgery (GS) residency, and time and cost of training GS residents in pediatric surgery. A survey was administered to GS residents that evaluated the pediatric surgery rotation and anticipated practice intentions. A retrospective analysis (2005-2006) of operative times for unilateral inguinal hernia repair, bilateral inguinal hernia repair, and umbilical hernia repair was also performed. Procedure times were compared for operations performed by a pediatric surgeon with and without GS residents. Cost analysis was based on time differences. General surgery residents (n = 19) considered the pediatric surgery rotation to have high educational value (4.7 +/- 0.6 of 5) with extensive teaching (4.6 +/- 0.7) and operative experience (4.4 +/- 0.8). Residents listed pediatric surgery exposure, operative technique, and observed work ethic as most valuable. Upon graduation, residents expect to perform pediatric operations 2 to 3 times annually. Thirty-seven percent of residents felt competent to perform appendectomy (patients >5 years), 32% appendectomy (3-5 years), 21% gastrostomy (>1 year), and 11% inguinal herniorrhaphy (>1 year). Operative times and costs were significantly higher in operative procedures performed with a GS resident. General surgery residents considered pediatric surgery as a valuable educational experience. Residents anticipate performing pediatric operations a few times annually. Training GS residents in pediatric surgery increased operative time and cost. This information may be useful in determining the appropriate setting for resident education as well as budget planning for pediatric surgical practices.

  6. Opportunistic coryneform organisms--residents of human skin.

    PubMed

    Kaźmierczak, Anna K; Szarapińska-Kwaszewska, Jadwiga K; Szewczyk, Eligia M

    2005-01-01

    Opportunistic infections are usually caused by endogenic flora originated from physiological flora. In this context we studied coryneform bacteria recovered from deeper layers of epidermis of the forehead (278 isolates) and the back (196 isolates) of healthy men. It was observed that coryneform bacteria are in dynamic equilibrium with coagulase-negative staphylococci and they amount 4,7% of resident aerobic flora. On the base of biological and metabolic features 49 different biotypes were indicated. Biotypes of lipophilic rods were the basic part of coryneform flora existing for long period. The most frequently isolated taxa were C. jeikeium (31%), CDC group G2 (23,4%), next in order CDC group G1 (11%) and C. afermentans ssp. lipophiluni (7%). These isolates were phenotypically differentiated. Nonlipophilic species did not play significant role in creating resident flora of the skin. The significance of coryneform bacteria in opportunistic infections is growing, especially in immunocompromissed patients. Isolated lipophilic taxa belong to these taxa coryneforms which are described in literature as the main etiologic factors of opportunistic infections.

  7. Residence times in shallow waters help explain regional differences in Wadden Sea eutrophication

    NASA Astrophysics Data System (ADS)

    Schwichtenberg, Fabian; Callies, Ulrich; van Beusekom, Justus E. E.

    2016-11-01

    Regional variations in eutrophication levels of tidal basins in the Wadden Sea can be caused by external factors, like organic matter import, and internal factors like the morphology and hydrodynamics of the receiving tidal basin. For instance, benthic nutrients from remineralized organic matter may be more concentrated in shallow basins or diluted in basins with high exchange rates. In addition, the location of a monitoring station may determine which basin-specific water masses are actually observed. In the present paper a hydrodynamic intertidal imprint (IMP) is estimated for ten stations in various tidal basins of the Wadden Sea. The fraction of time water masses spent in intertidal areas prior to observation is calculated by linking the Lagrangian transport module PELETS to already existing hourly reconstructions of currents between 1959 and 2003. Irrespective of water depth, additional calculations of mean residence times (MRT) in the Wadden Sea indicate whether, in the case of low IMP values, water masses originate from coastal areas or tidal channels. Results show distinct regional differences, with highest values in the eastern part of the Dutch sector of the southern Wadden Sea (IMP=77%, MRT=99%) and lowest values in the German/Danish sector of the northern Wadden Sea (IMP=1.1%, MRT=21%). The IMP correlates positively with observed nutrient levels (R2=0.83). Evidently, this residence time-based intertidal signal is pivotal in explaining regional variations in eutrophication levels revealed by long-term comparative data from different monitoring stations.

  8. Residence times in shallow waters help explain regional differences in Wadden Sea eutrophication

    NASA Astrophysics Data System (ADS)

    Schwichtenberg, Fabian; Callies, Ulrich; van Beusekom, Justus E. E.

    2017-04-01

    Regional variations in eutrophication levels of tidal basins in the Wadden Sea can be caused by external factors, like organic matter import, and internal factors like the morphology and hydrodynamics of the receiving tidal basin. For instance, benthic nutrients from remineralized organic matter may be more concentrated in shallow basins or diluted in basins with high exchange rates. In addition, the location of a monitoring station may determine which basin-specific water masses are actually observed. In the present paper a hydrodynamic intertidal imprint (IMP) is estimated for ten stations in various tidal basins of the Wadden Sea. The fraction of time water masses spent in intertidal areas prior to observation is calculated by linking the Lagrangian transport module PELETS to already existing hourly reconstructions of currents between 1959 and 2003. Irrespective of water depth, additional calculations of mean residence times (MRT) in the Wadden Sea indicate whether, in the case of low IMP values, water masses originate from coastal areas or tidal channels. Results show distinct regional differences, with highest values in the eastern part of the Dutch sector of the southern Wadden Sea (IMP=77%, MRT=99%) and lowest values in the German/Danish sector of the northern Wadden Sea (IMP=1.1%, MRT=21%). The IMP correlates positively with observed nutrient levels (R2=0.83). Evidently, this residence time-based intertidal signal is pivotal in explaining regional variations in eutrophication levels revealed by long-term comparative data from different monitoring stations.

  9. 26 CFR 301.7701(b)-4 - Residency time periods.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... resident test (green card test), described in paragraph (b)(1) of § 301.7701(b)-1, is the first day during... test and the green card test will be the earlier of the first day the individual is physically present... termination date for an alien who meets the green card test is the first day during the calendar year that the...

  10. 26 CFR 301.7701(b)-4 - Residency time periods.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... resident test (green card test), described in paragraph (b)(1) of § 301.7701(b)-1, is the first day during... test and the green card test will be the earlier of the first day the individual is physically present... termination date for an alien who meets the green card test is the first day during the calendar year that the...

  11. 26 CFR 301.7701(b)-4 - Residency time periods.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... resident test (green card test), described in paragraph (b)(1) of § 301.7701(b)-1, is the first day during... test and the green card test will be the earlier of the first day the individual is physically present... termination date for an alien who meets the green card test is the first day during the calendar year that the...

  12. 26 CFR 301.7701(b)-4 - Residency time periods.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... resident test (green card test), described in paragraph (b)(1) of § 301.7701(b)-1, is the first day during... test and the green card test will be the earlier of the first day the individual is physically present... termination date for an alien who meets the green card test is the first day during the calendar year that the...

  13. 26 CFR 301.7701(b)-4 - Residency time periods.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... resident test (green card test), described in paragraph (b)(1) of § 301.7701(b)-1, is the first day during... test and the green card test will be the earlier of the first day the individual is physically present... termination date for an alien who meets the green card test is the first day during the calendar year that the...

  14. My Time as a Professor in Residence: Lessons Learned

    ERIC Educational Resources Information Center

    Marsh, Josephine Peyton

    2013-01-01

    This commentary is based on two of the lessons the author learned as the professor in residence at ASU Preparatory Academy-Phoenix (ASU Prep), a Title I school operated in partnership with the Phoenix Elementary School District. Her role as a university professor on special assignment as a literacy coach, staff developer, and co-researcher. The…

  15. Groundwater Residence Times: A Key Parameter for Investigating Effects of River Restoration on Riverbank Filtration

    NASA Astrophysics Data System (ADS)

    Vogt, Tobias; Hoehn, Eduard; Schneider, Philipp; Schirmer, Mario; Cirpka, Olaf A.

    2010-05-01

    Many Swiss municipal pumping wells, located near the banks of a losing river, are designed to capture a mixture of freshly infiltrated river water and old alluvial groundwater. Riverbank filtration is assumed to substantially reduce concentrations of pathogens, pesticides, and organic pollutants relative to the river water. Although the number of river restoration projects increases, the effects of river restoration on riverbank filtration are still not well understood. River restoration includes widening of the riverbed and removal of bank armoring in order to establish a more natural sediment transport regime and give the river more space. These measures improve ecological habitat diversity and contribute to flood protection. However, they may cause conflicts with groundwater abstraction for drinking water, because travel times from rivers to pumping stations may be significantly reduced. In Switzerland the minimum mean travel time required for the protection of a drinking-water well is 10 days. Thus, for detailed investigation on river water infiltration into the aquifer, the distribution of groundwater travel times from rivers to observation and production wells and mixing ratios of freshly infiltrated and older alluvial groundwater are key parameters. Due to the high hydraulic conductivity of most Swiss prealpine gravel aquifers, the residence time of water entering many pumping wells is the range of weeks. Therefore, special methods are needed to assess residence times of young groundwater. We analyze time series of electrical conductivity in the river and adjacent groundwater observation wells to investigate travel times of young hyporheic groundwater in adjoining channelized and restored sections of the River Thur in North-East Switzerland. The test site has been established by the RECORD Project (Assessment and Modeling of Coupled Ecological and Hydrological Dynamics in the Restored Corridor of a River (Restored Corridor Dynamics)). To quantify residence

  16. Is mean residence time a useful tool to evaluate carbon sequestration in soils? Limits and potential

    NASA Astrophysics Data System (ADS)

    Abiven, Samuel; Gonzalez-Dominguez, Beatriz; Studer, Mirjam

    2017-04-01

    Soils are increasingly recognized as a serious candidate to store large amounts of carbon. International efforts, like the 4 per mil initiative, are promoting soil-related solutions to retain carbon at long timescales. The options are quite diverse, from biochar or root promoting agricultural techniques to existing large vulnerable soil organic matter stock conservation policies. However, the evaluation of these techniques is not easy. The changes of soil organic carbon stocks are difficult to detect on the short term: carbon stock estimations suffer from technical hurdles, like bulk density estimation or access to the subsoil carbon; the soil is by nature heterogeneous, and generalization of results for a given situation are difficult to upscale. The evaluation of soil organic matter mean residence time (MRT) may be used to describe the potential of these solutions. In soils, MRT is calculated by isotopic techniques (i.e. stable or radioactive isotopes) or by mass balances (i.e. measured or calculated based in CO2 emissions). Depending on the method applied, results may vary greatly and may also describe different facets of the soil organic matter continuum. For example, MRT calculated with 14C data depends on molecules with long residence time while MRT based on mass balance calculations are triggered by fresh inputs that may decompose relatively fast in soils. Based on a comprehensive Swiss forest soils dataset allowing us to calculate soil organic matter MRT by different approaches and a series of recent literature considerations about the MRT, we will discuss the potential of MRT to be applied for carbon storage evaluation.

  17. Seasonal change of residence time in spring water and groundwater at a mountainous headwater catchment

    NASA Astrophysics Data System (ADS)

    Nagano, Kosuke; Tsujimura, Maki; Onda, Yuichi; Iwagami, Sho; Sakakibara, Koichi; Sato, Yutaro

    2017-04-01

    Determination of water age in headwater is important to consider water pathway, source and storage in the catchment. Previous studies showed that groundwater residence time changes seasonally. These studies reported that mean residence time of water in dry season tends to be longer than that in rainy season, and it becomes shorter as precipitation and discharge amount increases. However, there are few studies to clarify factors causing seasonal change in mean residence time in spring water and groundwater based on observed data. Therefore, this study aims to reveal the relationship between mean residence time and groundwater flow system using SFconcentration in spring and 10 minutes interval hydrological data such as discharge volume, groundwater level and precipitation amount in a headwater catchment in Fukushima, Japan. The SF6 concentration data in spring water observed from April 2015 to November 2016 shows the mean residence time of springs ranged from zero to 14 years. We also observed a clear negative correlation between discharge rate and residence time in the spring. The residence time in shallow groundwater in rainy season was younger as compared with that in low rainfall period. Therefore, the shallow groundwater with young residence time seems to contribute to the spring in rainy season, causing shorter residence time. Additionally, the residence time of groundwater ranged from 3 to 5 years even in low rainfall period. The residence time in high groundwater table level in ridge was older as compared with that in low groundwater table level. These suggest that the contribution of groundwater with older age in the ridge becomes dominant in the low discharge.

  18. Iodine-129 constraints on residence times of deep marine brines in the Canadian Shield

    NASA Astrophysics Data System (ADS)

    Bottomley, Dennis J.; Renaud, Robert; Kotzer, Tom; Clark, Ian D.

    2002-07-01

    Canadian Shield brines are characterized by high concentrations of both stable iodine and 129I, the former reflecting its concentrated but diagenetically modified seawater origin, and the latter its long subsurface residence time within its host shield rocks. Stable iodine concentrations in the Yellowknife brine are as high as 18 mg/L, requiring the contribution of iodine from an external marine reservoir. This reservoir likely comprised organic-rich marine sediments in the basin where the brine was produced. Diagenesis of these sediments released iodine to the brine during its infiltration into the subsurface. 129I concentrations in the Yellowknife brine are as high as 3.4 × 108 atom/L and are due to the fission of 238U in the rock matrix and subsequent diffusion of the radiogenic 129I into the fracture fluids. This concentration is close to the predicted secular equilibrium concentration for a fluid in basaltic rock with a uranium concentration of 1 mg/kg after the residence time of ˜80 m.y. required for secular equilibrium has been attained. This time period is interpreted as the minimum residence time of the Yellowknife brine in the shield, but it may be much greater, possibly dating back to Middle Devonian time when most of the present-day shield was covered by seawater. Similarly high stable iodine and 129I concentrations measured in the Sudbury brine support a generic, ancient marine hypothesis for the origin of shield brines. Stable iodine and 129I concentrations in the shallower mine waters are the result of mixing between the brine and low-iodine modern meteoric recharge that is enriched in 129I due to global fallout from nuclear fuel waste reprocessing activities.

  19. Effects of zebra mussels on food webs: Interactions with juvenile bluegill and water residence time

    USGS Publications Warehouse

    Richardson, W.B.; Bartsch, L.A.

    1997-01-01

    We evaluated how water residence time mediated the impact of zebra mussels Dreissena polymorpha and bluegill sunfish Lepomis macrochirus on experimental food webs established in 1100-1 outdoor mesocosms. Water residence time was manipulated as a surrogate for seston resupply - a critical variable affecting growth and survival of suspension-feeding invertebrates. We used a 2 x 2 x 2 factorial experimental design with eight treatment combinations (3 replicates/treatment) including the presence or absence of Dreissena (2000 per m2), juvenile bluegill (40 per mesocosm), and short (1100 1 per d) or long (220 1 per d) water residence time. Measures of seston concentration (chlorophyll a, turbidity and suspended solids) were greater in the short- compared to long water-residence mesocosms, but intermediate in short water-residence mesocosms containing Dreissena. Abundance of rotifers (Keratella and Polyarthra) was reduced in Dreissena mesocosms and elevated in short residence time mesocosms. Cladocera abundance, in general, was unaffected by the presence of Dreissena; densities were higher in short-residence time mesocosms, and reduced in the presence of Lepomis. The growth of juvenile Lepomis were unaffected by Dreissena because of abundant benthic food. The final total mass of Dreissena was significantly greater in short- than long-residence mesocosms. Impacts of Dreissena on planktonic food webs may not only depend on the density of zebra mussels but also on the residence time of the surrounding water and the resupply of seston. ?? 1997 Kluwer Academic Publishers.

  20. Defining and measuring the mean residence time of lateral surface transient storage zones in small streams

    Treesearch

    T.R. Jackson; R. Haggerty; S.V. Apte; A. Coleman; K.J. Drost

    2012-01-01

    Surface transient storage (STS) has functional significance in stream ecosystems because it increases solute interaction with sediments. After volume, mean residence time is the most important metric of STS, but it is unclear how this can be measured accurately or related to other timescales and field-measureable parameters. We studied mean residence time of lateral...

  1. Residence time distributions in sinuosity-driven hyporheic zones and their biogeochemical effects

    NASA Astrophysics Data System (ADS)

    Gomez, Jesus D.; Wilson, John L.; Cardenas, M. Bayani

    2012-09-01

    Hyporheic exchange plays a key role in the biogeochemical evolution of water and in ecosystem functioning at the local, reach, and watershed scales. Residence time is a fundamental metric to describe the possible transformation taking place in this exchange zone. With this in mind, we use a simple conceptual model to explore the residence time distributions (RTDs) of sinuosity-driven hyporheic zones (HZs) and to discriminate the individual effect of sinuosity (σ), valley slope (Jx), hydraulic conductivity (K), aquifer dispersivity (αL), and the biogeochemical timescales (BTSs) that characterize the degradation of dissolved organic carbon in these hydrologic systems. We find that RTDs are characterized by one early mode and a late time power law behavior. For a given aquifer dispersivity, the shape of these distributions is stretched or compressed by changes in Jx, K, and σ, having a strong influence on the net biogeochemical transformations within the HZ. Using BTSs proposed in previous studies and sensitivity analyses, we show the potential of σ, Jx, and K to classify meander HZs as net sinks of nitrates or only modulators of the residence times in the subsurface where nitrate reduction is negligible. These findings can be used as predictive tools to quantify the potential of meanders as biogeochemical reactors at the watershed scale with the aid of remote sensing data and GIS processing techniques. These tools can guide experimental design, suggesting important locations to visit, sample, and/or instrument. Also, hyporheic restoration projects can use them for initial site selection and design of channel modifications.

  2. Matrix Organization of a Residency Program in an Academic Medical Center.

    ERIC Educational Resources Information Center

    Smith, Ellen S.; Eisenberg, John M.

    1980-01-01

    Matrix organization offers a structure that can facilitate coordination and cooperation in health care educational administration. Its application within the health care system is reviewed, the matrix organization of the primary care residency at the University of Pennsylvania is reported, and advantages and disadvantages are discussed.…

  3. Residence time control on hot moments of net nitrate production and uptake in the hyporheic zone

    USGS Publications Warehouse

    Briggs, Martin A.; Lautz, Laura K.; Hare, Danielle K.

    2014-01-01

    moments of net production and uptake, enhancing NO3- production as residence times approach the anaerobic threshold, and changing zones of net NO3- production to uptake as residence times increase past the net sink threshold. The anaerobic and net sink thresholds for beaver-influenced streambed morphology occur at much shorter residence times (1.3 h and 2.3 h, respectively) compared to other documented hyporheic systems, and the net sink threshold compares favorably to the lower boundary of the anaerobic threshold determined for this system with the new oxygen Damkohler number. The consistency of the residence time threshold values of NO3- cycling in this study, despite environmental variability and disparate morphology, indicates that NO3- hot moment dynamics are primarily driven by changes in physical hydrology and associated residence times.

  4. An approach to the residence time distribution for stochastic multi-compartment models.

    PubMed

    Yu, Jihnhee; Wehrly, Thomas E

    2004-10-01

    Stochastic compartmental models are widely used in modeling processes such as drug kinetics in biological systems. This paper considers the distribution of the residence times for stochastic multi-compartment models, especially systems with non-exponential lifetime distributions. The paper first derives the moment generating function of the bivariate residence time distribution for the two-compartment model with general lifetimes and approximates the density of the residence time using the saddlepoint approximation. Then, it extends the distributional approach to the residence time for multi-compartment semi-Markov models combining the cofactor rule for a single destination and the analytic approach to the two-compartment model. This approach provides a complete specification of the residence time distribution based on the moment generating function and thus facilitates an easier calculation of high-order moments than the approach using the coefficient matrix. Applications to drug kinetics demonstrate the simplicity and usefulness of this approach.

  5. Modelling residence-time response to freshwater input in Apalachicola Bay, Florida, USA

    NASA Astrophysics Data System (ADS)

    Huang, Wenrui; Spaulding, M.

    2002-10-01

    Residence time of an estuary can be used to estimate the rate of removal of freshwater and pollutants from river inflow. In this study, a calibrated three-dimensional hydrodynamic model was used to determine residence time in response to the change of freshwater input in Apalachicola Bay. The bay is about 40 km long and 7 km wide, with an average 3 m water depth. Through hydrodynamic model simulations, the spatial and temporal salinity and the total freshwater volume in the bay were calculated. Then the freshwater fraction method was used to estimate the residence time. Results indicate that the residence time in Apalachicola Bay typically ranges between 3 and 10 days for the daily freshwater input ranging from 177 m3/s to 4561 m3/s. Regression analysis of model results shows that an exponential regression equation can be used to correlate the estuarine residence time to changes of freshwater input.

  6. Training for Efficiency: Work, Time and Systems-based Practice in Medical Residency*

    PubMed Central

    Szymczak, Julia E.; Bosk, Charles L.

    2013-01-01

    Medical residency is a period of intense socialization with a heavy workload. Previous sociological studies have identified efficiency as a practical skill necessary for success. However, many contextual features of the training environment have undergone dramatic change since these studies were conducted. What are the consequences of these changes for the socialization of residents to time management and the development of a professional identity? Based on observations of and interviews with internal medicine residents at 3 training programs, we find that efficiency is both a social norm and strategy that residents employ to manage a workload for which the demand for work exceeds the supply of time available to accomplish it. We found that residents struggle to be efficient in the face of seemingly intractable “systems” problems. Residents work around these problems, and in doing so develop a tolerance for organizational vulnerabilities. PMID:22863601

  7. Training for efficiency: work, time, and systems-based practice in medical residency.

    PubMed

    Szymczak, Julia E; Bosk, Charles L

    2012-09-01

    Medical residency is a period of intense socialization with a heavy workload. Previous sociological studies have identified efficiency as a practical skill necessary for success. However, many contextual features of the training environment have undergone dramatic change since these studies were conducted. What are the consequences of these changes for the socialization of residents to time management and the development of a professional identity? Based on observations of and interviews with internal medicine residents at three training programs, we find that efficiency is both a social norm and strategy that residents employ to manage a workload for which the demand for work exceeds the supply of time available to accomplish it. We found that residents struggle to be efficient in the face of seemingly intractable "systems" problems. Residents work around these problems, and in doing so develop a tolerance for organizational vulnerabilities.

  8. Calculation of residence times and radiation doses using the standard PC software Excel.

    PubMed

    Herzog, H; Zilken, H; Niederbremer, A; Friedrich, W; Müller-Gärtner, H W

    1997-12-01

    We developed a program which aims to facilitate the calculation of radiation doses to single organs and the whole body. IMEDOSE uses Excel to include calculations, graphical displays, and interactions with the user in a single general-purpose PC software tool. To start the procedure the input data are copied into a spreadsheet. They must represent percentage uptake values of several organs derived from measurements in animals or humans. To extrapolate these data up to seven half-lives of the radionuclide, fitting to one or two exponentional functions is included and can be checked by the user. By means of the approximate time-activity information the cumulated activity or residence times are calculated. Finally these data are combined with the absorbed fraction doses (S-values) given by MIRD pamphlet No. 11 to yield radiation doses, the effective dose equivalent and the effective dose. These results are presented in a final table. Interactions are realized with push-buttons and drop-down menus. Calculations use the Visual Basic tool of Excel. In order to test our program, biodistribution data of fluorine-18 fluorodeoxyglucose were taken from the literature (Meija et al., J Nucl Med 1991; 32:699-706). For a 70-kg adult the resulting radiation doses of all target organs listed in MIRD 11 were different from the ICRP 53 values by 1%+/-18% on the average. When the residence times were introduced into MIRDOSE3 (Stabin, J Nucl Med 1996; 37:538-546) the mean difference between our results and those of MIRDOSE3 was -3%+/-6%. Both outcomes indicate the validity of the present approach.

  9. Analysis of soil water residence times in a monolith lysimeter at the North Appalachian Experimental Watershed

    SciTech Connect

    Gamble, B.F.; Eckstein, Y.

    1985-01-01

    Estimates of soil water residence times can be made using water budget records. A single average value, referred to as conventional residence time, can be obtained by dividing the mean storage volume by the mean output volume. Using concepts from queuing theory, estimates of residence times can be made by assuming first-in-first-out (FIFO) or last-in-first-out (LIFO) movement of the water. Using such assumption, estimates can be made on the length of time that water remains in the soil, depending on the time of year that water enters the soil. For residence time estimations, monthly water budget data was obtained for the period from 1947 through 1982 for a weighing monolith lysimeter located at the North Appalachian Experimental Watershed near Coshocton, Ohio. The lysimeter encloses an undisturbed block of silt loam soil. The conventional residence time for the record period is 10.2 months. The mean maximum residence time, based on the assumption of all FIFO movement, is 11.1 months with a minimum value of 4 months and a maximum value of 18 months. The assumption of all LIFO movement gives a mean maximum residence time value of 3.8 months with a minimum value of less than one month and a maximum value of 102 months.

  10. Mixing and residence times of stormwater runoff in a detection system

    USGS Publications Warehouse

    Martin, Edward H.

    1989-01-01

    Five tracer runs were performed on a detention pond and wetlands system to determine mixing and residence times in the system. The data indicate that at low discharges and with large amounts of storage, the pond is moderately mixed with residence times not much less than the theoretical maximum possible under complete mixing. At higher discharges and with less storage in the pond, short-circuiting occurs, reducing the amount of mixing in the pond and appreciably reducing the residence times. The time between pond outlet peak concentrations and wetlands outlet peak concentrations indicate that in the wetlands, mixing increases with decreasing discharge and increasing storage.

  11. A study of residence time distribution using radiotracer technique in the large scale plant facility

    NASA Astrophysics Data System (ADS)

    Wetchagarun, S.; Tippayakul, C.; Petchrak, A.; Sukrod, K.; Khoonkamjorn, P.

    2017-06-01

    As the demand for troubleshooting of large industrial plants increases, radiotracer techniques, which have capability to provide fast, online and effective detections to plant problems, have been continually developed. One of the good potential applications of the radiotracer for troubleshooting in a process plant is the analysis of Residence Time Distribution (RTD). In this paper, the study of RTD in a large scale plant facility using radiotracer technique was presented. The objective of this work is to gain experience on the RTD analysis using radiotracer technique in a “larger than laboratory” scale plant setup which can be comparable to the real industrial application. The experiment was carried out at the sedimentation tank in the water treatment facility of Thailand Institute of Nuclear Technology (Public Organization). Br-82 was selected to use in this work due to its chemical property, its suitable half-life and its on-site availability. NH4Br in the form of aqueous solution was injected into the system as the radiotracer. Six NaI detectors were placed along the pipelines and at the tank in order to determine the RTD of the system. The RTD and the Mean Residence Time (MRT) of the tank was analysed and calculated from the measured data. The experience and knowledge attained from this study is important for extending this technique to be applied to industrial facilities in the future.

  12. Children's Perspectives on Everyday Experiences of Shared Residence: Time, Emotions and Agency Dilemmas

    ERIC Educational Resources Information Center

    Haugen, Gry Mette D.

    2010-01-01

    Shared residence is often presented as an arrangement that is in the best interests of the child following the divorce of its parents. Based on in-depth interviews with Norwegian children who have experienced shared residence, this article seeks to explore some dilemmas concerning time, agency and the children's emotions. Three characteristics of…

  13. Surgical council on resident education: a new organization devoted to graduate surgical education.

    PubMed

    Bell, Richard H

    2007-03-01

    The Surgical Council on Resident Education (SCORE) is a voluntary consortium of six organizations with responsibility for resident education in surgery and an interest in improving the training of surgeons. The founding organizations are the American Board of Surgery (ABS), the American College of Surgeons (ACS), the American Surgical Association (ASA), the Association of Program Directors in Surgery (APDS), the Association for Surgical Education (ASE), and the Residency Review Committee for Surgery of the Accreditation Council on Graduate Medical Education (RRC-S). SCORE emerged from a concerted desire to strengthen the graduate education of surgeons and to assure the competence of surgical trainees in the US. SCORE has a unique ability to foster change in resident education because it brings together the major regulatory organizations (ABS and RRC-S), the major professional organization in surgery (ACS), the senior academic organization in surgery (ASA), and the major surgical education organizations (APDS and ASE). SCORE envisions an ambitious agenda. At its meeting in Philadelphia on November 20, 2006, it began developing a standardized curriculum in general surgery to span the period from medical school to practice, and it defined the scope of the curriculum. It approved continued work of building a national Web site to deliver educational content to general surgery residents and to assist program directors. It endorsed continued development of a basic surgery curriculum for all first-year surgery residents and development of a comprehensive technical skills curriculum for all levels of general surgery training, both of which have been initiated by the ACS. In the future, SCORE plans to examine issues such as the assessment of technical competency, the role of simulation in surgical education, the teaching and assessment of professional behaviors, the practicing surgeon's view of the adequacy of residency training, faculty development, and the attrition of

  14. Establishing a community pharmacy residency at an independent pharmacy: Time allocation and valuation.

    PubMed

    Shugart, Katherine; Bryant, Jason; Kress, Dean; Ziegler, Bryan; Connelly, Lynn; Brittain, Kristy

    2015-12-01

    The value of a first-year community pharmacy residency program (CPRP) at an independent pharmacy was estimated based on time allocation for resident responsibilities. Predefined time allocation categories for the pharmacy resident were used to consistently classify and document time completing residency activities. Benefit-to-cost ratio was determined by tabulating total costs and total benefits of the residency program. A retrospective-prospective comparison of overall change in revenue, operating expense, and prescription volume was performed between the preresident time period (July 2012 to June 2013) and the postresident time period (July 2013 to June 2014). This comparison accounted for resident activities that did not directly generate revenue. Time allocations for the resident out of 2,221 total hours logged were dispensing (40%), clinical setup (16%), research (8%), professional meetings (7%), clinical activities (5%), resident education (5%), site precepting (4%), residency meetings (4%), didactic teaching (3%), miscellaneous (3%), marketing (2%), training (2%), and public health promotion (1%). Total costs were $77,422, and total benefits were $118,410. The benefit-to-cost ratio was 1.53. The postresident time interval had $172,451 more revenue and $6,622 more in operating expenses than the preresident time interval, and prescription volume decreased by 2,000 prescriptions compared to the previous year. The benefit-to-cost analysis indicated a $1.53 return for every $1.00 invested into a CPRP. An increase in revenue and operating expenses for the pharmacy was observed after implementation of the CPRP compared to the previous year. Copyright © 2015 by the American Society of Health-System Pharmacists, Inc. All rights reserved.

  15. Control of selectivity in heterogeneous catalysis by tuning nanoparticle properties and reactor residence time

    NASA Astrophysics Data System (ADS)

    Gross, Elad; Liu, Jack Hung-Chang; Toste, F. Dean; Somorjai, Gabor A.

    2012-11-01

    A combination of the advantages of homogeneous and heterogeneous catalysis could enable the development of sustainable catalysts with novel reactivity and selectivity. Although heterogeneous catalysts are often recycled more easily than their homogeneous counterparts, they can be difficult to apply in traditional organic reactions and modification of their properties towards a desired reactivity is, at best, complex. In contrast, tuning the properties of homogeneous catalysts by, for example, modifying the ligands that coordinate a metal centre is better understood. Here, using olefin cyclopropanation reactions catalysed by dendrimer-encapsulated Au nanoclusters as examples, we demonstrate that changing the dendrimer properties allows the catalytic reactivity to be tuned in a similar fashion to ligand modification in a homogeneous catalyst. Furthermore, we show that these heterogeneous catalysts employed in a fixed-bed flow reactor allow fine control over the residence time of the reactants and thus enables the control over product distribution in a way that is not easily available for homogeneous catalysts.

  16. Control of selectivity in heterogeneous catalysis by tuning nanoparticle properties and reactor residence time.

    PubMed

    Gross, Elad; Liu, Jack Hung-Chang; Toste, F Dean; Somorjai, Gabor A

    2012-11-01

    A combination of the advantages of homogeneous and heterogeneous catalysis could enable the development of sustainable catalysts with novel reactivity and selectivity. Although heterogeneous catalysts are often recycled more easily than their homogeneous counterparts, they can be difficult to apply in traditional organic reactions and modification of their properties towards a desired reactivity is, at best, complex. In contrast, tuning the properties of homogeneous catalysts by, for example, modifying the ligands that coordinate a metal centre is better understood. Here, using olefin cyclopropanation reactions catalysed by dendrimer-encapsulated Au nanoclusters as examples, we demonstrate that changing the dendrimer properties allows the catalytic reactivity to be tuned in a similar fashion to ligand modification in a homogeneous catalyst. Furthermore, we show that these heterogeneous catalysts employed in a fixed-bed flow reactor allow fine control over the residence time of the reactants and thus enables the control over product distribution in a way that is not easily available for homogeneous catalysts.

  17. MODELING HOW A HURRICANE BARRIER IN NEW BEDFORD HARBOR, MASSACHUSETTS, AFFECTS THE HYDRODYNAMICS AND RESIDENCE TIMES

    EPA Science Inventory

    Two-dimensional hydrodynamic and transport models were used to simulate tidal and subtidal circulation, residence times, and the longitudinal distributions of conservative constituents in New Bedford Harbor, Massachusetts, before and after a hurricane barrier was constructed. The...

  18. A method of estimating in-stream residence time of water in rivers

    NASA Astrophysics Data System (ADS)

    Worrall, F.; Howden, N. J. K.; Burt, T. P.

    2014-05-01

    This study develops a method for estimating the average in-stream residence time of water in a river channel and across large catchments, i.e. the time between water entering a river and reaching a downstream monitoring point. The methodology uses river flow gauging data to integrate Manning's equation along a length of channel for different percentile flows. The method was developed and tested for the River Tees in northern England and then applied across the United Kingdom (UK). The study developed methods to predict channel width and main channel length from catchment area. For an 818 km2 catchment with a channel length of 79 km, the in-stream residence time at the 50% exceedence flow was 13.8 h. The method was applied to nine UK river basins and the results showed that in-stream residence time was related to the average slope of a basin and its average annual rainfall. For the UK as a whole, the discharge-weighted in-stream residence time was 26.7 h for the median flow. At median flow, 50% of the discharge-weighted in-stream residence time was due to only 6 out of the 323 catchments considered. Since only a few large rivers dominate the in-stream residence time, these rivers will dominate key biogeochemical processes controlling export at the national scale. The implications of the results for biogeochemistry, especially the turnover of carbon in rivers, are discussed.

  19. Evaluation of Residence Time on Nitrogen Oxides Removal in Non-Thermal Plasma Reactor

    PubMed Central

    Talebizadeh, Pouyan; Rahimzadeh, Hassan; Babaie, Meisam; Javadi Anaghizi, Saeed; Ghomi, Hamidreza; Ahmadi, Goodarz; Brown, Richard

    2015-01-01

    Non-thermal plasma (NTP) has been introduced over the last few years as a promising after- treatment system for nitrogen oxides and particulate matter removal from diesel exhaust. NTP technology has not been commercialised as yet, due to its high rate of energy consumption. Therefore, it is important to seek out new methods to improve NTP performance. Residence time is a crucial parameter in engine exhaust emissions treatment. In this paper, different electrode shapes are analysed and the corresponding residence time and NOx removal efficiency are studied. An axisymmetric laminar model is used for obtaining residence time distribution numerically using FLUENT software. If the mean residence time in a NTP plasma reactor increases, there will be a corresponding increase in the reaction time and consequently the pollutant removal efficiency increases. Three different screw thread electrodes and a rod electrode are examined. The results show the advantage of screw thread electrodes in comparison with the rod electrode. Furthermore, between the screw thread electrodes, the electrode with the thread width of 1 mm has the highest NOx removal due to higher residence time and a greater number of micro-discharges. The results show that the residence time of the screw thread electrode with a thread width of 1 mm is 21% more than for the rod electrode. PMID:26496630

  20. Evaluation of Residence Time on Nitrogen Oxides Removal in Non-Thermal Plasma Reactor.

    PubMed

    Talebizadeh, Pouyan; Rahimzadeh, Hassan; Babaie, Meisam; Javadi Anaghizi, Saeed; Ghomi, Hamidreza; Ahmadi, Goodarz; Brown, Richard

    2015-01-01

    Non-thermal plasma (NTP) has been introduced over the last few years as a promising after- treatment system for nitrogen oxides and particulate matter removal from diesel exhaust. NTP technology has not been commercialised as yet, due to its high rate of energy consumption. Therefore, it is important to seek out new methods to improve NTP performance. Residence time is a crucial parameter in engine exhaust emissions treatment. In this paper, different electrode shapes are analysed and the corresponding residence time and NOx removal efficiency are studied. An axisymmetric laminar model is used for obtaining residence time distribution numerically using FLUENT software. If the mean residence time in a NTP plasma reactor increases, there will be a corresponding increase in the reaction time and consequently the pollutant removal efficiency increases. Three different screw thread electrodes and a rod electrode are examined. The results show the advantage of screw thread electrodes in comparison with the rod electrode. Furthermore, between the screw thread electrodes, the electrode with the thread width of 1 mm has the highest NOx removal due to higher residence time and a greater number of micro-discharges. The results show that the residence time of the screw thread electrode with a thread width of 1 mm is 21% more than for the rod electrode.

  1. Using a composite grid approach in a complex coastal domain to estimate estuarine residence time

    USGS Publications Warehouse

    Warner, John C.; Geyer, W. Rockwell; Arango, Herman G.

    2010-01-01

    We investigate the processes that influence residence time in a partially mixed estuary using a three-dimensional circulation model. The complex geometry of the study region is not optimal for a structured grid model and so we developed a new method of grid connectivity. This involves a novel approach that allows an unlimited number of individual grids to be combined in an efficient manner to produce a composite grid. We then implemented this new method into the numerical Regional Ocean Modeling System (ROMS) and developed a composite grid of the Hudson River estuary region to investigate the residence time of a passive tracer. Results show that the residence time is a strong function of the time of release (spring vs. neap tide), the along-channel location, and the initial vertical placement. During neap tides there is a maximum in residence time near the bottom of the estuary at the mid-salt intrusion length. During spring tides the residence time is primarily a function of along-channel location and does not exhibit a strong vertical variability. This model study of residence time illustrates the utility of the grid connectivity method for circulation and dispersion studies in regions of complex geometry.

  2. Feeding assistance needs of long-stay nursing home residents and staff time to provide care.

    PubMed

    Simmons, Sandra F; Schnelle, John F

    2006-06-01

    To describe the staff time requirements to provide feeding assistance to nursing home residents who require three different types of assistance to improve oral food and fluid intake (social stimulation, verbal cuing, or both; physical guidance; or full physical assistance) and to determine whether physically dependent residents require more staff time, as defined in the national Resource Utilization Group System (RUGS) used for reimbursement. Descriptive. Six skilled nursing homes. Ninety-one long-stay residents with low oral intake who responded to improved feeding assistance. Research staff conducted direct observations of usual nursing home care for 2 consecutive days (total of six meals) to measure oral food and fluid consumption (total percentage eaten) and staff time spent providing assistance (minutes and seconds). Research staff then implemented a standardized graduated-assistance protocol on 2 separate days (total of six meals) that enhanced residents' oral food and fluid intake. Staff time to provide feeding assistance that improved food and fluid consumption was comparable across different levels of eating dependency. Across all levels, residents required an average of 35 to 40 minutes of staff time per meal; thus, residents who needed only supervision and verbal cuing required just as much time as those who were physically dependent on staff for eating. The current RUGS system used for reimbursement likely underestimates the staff time required to provide feeding assistance care that improves oral intake.

  3. Dominicans Resident in Spain and the United States Faced With Deceased Organ Donation.

    PubMed

    Ríos, A; López-Navas, A; Ros-Martínez, A; Mikla, M; Martínez-Alarcón, L; Navalón, J C; Ramis, G; Ramírez, P; Parrilla, P

    2015-11-01

    Investigating the attitude of subgroups of populations living in different countries is useful for establishing whether there are differences in opinion in terms of place of residence. The objective of the study was to analyze attitudes toward deceased organ donation in the population from the Dominican Republic who are residing in the southeast of the United States and Spain. A sample was taken of residents of the population from the Dominican Republic residing in Florida (the United States) (n = 63) and in Spain (n = 80), which was stratified by age and sex. A validated questionnaire about psychosocial aspects (PCID-DTO Rios) was self-administered and completed anonymously: the χ(2) test, Student t test, and logistic regression analysis were used. The completion rate was 86% (123 respondents of the 143 selected). Of those surveyed, 54% were in favor, 23% were against, and 23% were undecided. Of the residents in Spain (n = 57) 63% (n = 36) were in favor, 12% (n = 7) were against, and 25% (n = 14) were undecided. Of the residents in the United States (n = 66) 46% (n = 30) were in favor, 33% (n = 22) were against, and 21% (n = 14) were undecided (P < .001). The following factors were found to be associated with attitude: 1) level of education [OR = 12.195 (52.631-2.808); P = .001]; 2) concern about the possible mutilation of the body after donation [OR = 11.363 (47.619-2.695; P = .001]; and 3) rejection of cremation or burial of the body after death [OR = 6.134 (21.276-1.763); P = .004]. Attitude toward the donation of the respondent's own deceased organs after death was more favorable among Dominican residents in Spain compared with those living in the United States. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. The effect of tidal exchange on residence time in a coastal embayment

    NASA Astrophysics Data System (ADS)

    Rynne, Patrick; Reniers, Ad; van de Kreeke, Jacobus; MacMahan, Jamie

    2016-04-01

    Numerical simulations of an idealized lagoon that is connected to the ocean via a tidal inlet show that the mean residence time is inversely proportional to tidal exchange. In the Delft3D model the tidal exchange is controlled by varying the inlet length, width and depth. These changes in the inlet geometry affect the tidal prism and the ebb/flood flow structure, which are shown to control the exchange of lagoon water with seawater. To map residence time within the lagoon, a new method that implements dye tracer is developed and shows that the tidally averaged residence time exhibits significant spatial variability. For inlet systems in which, as a first approximation, the lagoon can be described by a uniformly fluctuating water level, a simple transport model is developed to elucidate the specific processes that control tidal exchange and their effect on residence time. In this transport model tidal exchange is decomposed into two fractions, an ocean exchange fraction and a lagoon exchange fraction. It is shown that both fractions need to be included to better describe tidal exchange. Specifically, inclusion of a lagoon exchange fraction improves previous tidal prism models that assume complete mixing in the lagoon. The assumption of complete mixing results in an under-prediction of residence time. Relating the spatially averaged residence time results to the exchange fractions for each inlet geometry show that the residence time is inversely proportional to the product of the tidal exchange fractions. For these single inlet systems, Keulegan's 0-D hydrodynamic model shows good agreement with Delft3D in predicting the tidal prism, maximum flow velocity, and exchange fractions. With these parameters, estimates of the mean residence time can be reached through a relationship derived from the simple transport model.

  5. Linear and Nonlinear Time-Frequency Analysis for Parameter Estimation of Resident Space Objects

    DTIC Science & Technology

    2017-02-22

    AFRL-AFOSR-UK-TR-2017-0023 Linear and Nonlinear Time-Frequency Analysis for Parameter Estimation of Resident Space Objects Marco Martorella...Nonlinear Time-Frequency Analysis for Parameter Estimation of Resident Space Objects 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA9550-14-1-0183 5c.  PROGRAM...NOTES 14. ABSTRACT Since the first space mission in 1957 (Sputnik 1), artificial objects of different size appeared in orbits around the Earth

  6. How Do Residents Spend Their Time in the Intensive Care Unit?

    PubMed

    Carayon, Pascale; Weinger, Matthew B; Brown, Roger; Cartmill, Randi S; Slagle, Jason; Van Roy, Kara S; Walker, James M; Wood, Kenneth E

    2015-11-01

    To describe the work of residents and the distribution of their time in 6 intensive care units (ICUs) of 2 medical centers (MCs). A total of 242 hours of observation to capture data on tasks performed by residents in 6 ICUs, including adult, pediatric, medical and surgical units, were conducted. For each observation period, the percentages of total time spent on each task and on the aggregated task categories were calculated. Overall, while in the ICUs, residents spent almost half of their time in clinical review and documentation (19%), conversation with team physicians (16%), conversation attendance (6%) and order management (6%). The 2 MCs differed in the time that residents spent on administrative review and documentation (4% in one MC and 15% in the other). The pediatric ICUs were similar in the 2 MCs, whereas the adult ICUs exhibited differences in the time spent on order management and administrative review and documentation. While in the ICUs, residents spent most time performing direct patient care and care coordination activities. The distribution of activities varied across 2 MCs and across ICUs, which highlights the need to consider the local context on residents' work in ICUs.

  7. Residence times of reef-island sediments constrained by post-mortem precipitates

    NASA Astrophysics Data System (ADS)

    Mann, Thomas; Wizemann, André; Kench, Paul; Jompa, Jamaluddin; Westphal, Hildegard

    2017-04-01

    The precipitation of carbonate cements is a rapid process in tropical marine environments. Distinct from calcification, the onset of cementation coincides with the termination of 14C uptake within carbonate-sediment forming organisms. Here we show that this relationship presents new opportunities for examining the temporal lag between organism death and deposition in carbonate systems - the prerequisite for reliable depositional chronologies. We dated skeletal constituents collected from discretely stratified reef-island deposits in Indonesia. In each of the strata, internally least cemented segments of the calcifying green alga Halimeda yield the youngest ages. Complementary mesocosm experiments on cementation rates reveal that post-mortem cement growth initiates within months after transport commences. Continuous pore-filling cementation promptly stabilizes the initially fragile Halimeda skeleton. Furthermore, abrasion experiments show that such cementation significantly increases the durability of segments during transport. Implications of these findings are profound in two respects; first, evaluating residence times of skeletal carbonate constituents based on abrasion features is far from being adequate. Second, the absence of cements within sedimentary Halimeda segments signals that post-mortem transport through the intertidal zone occurred quasi-instantaneously. Radiometric ages from such specimens should minimize the temporal lag between organism death and deposition thus making them reliable indicators of sedimentation in supratidal environments.

  8. Persistent organic pollutants in chinook salmon (Oncorhynchus tshawytscha): implications for resident killer whales of British Columbia and adjacent waters.

    PubMed

    Cullon, Donna L; Yunker, Mark B; Alleyne, Carl; Dangerfield, Neil J; O'Neill, Sandra; Whiticar, Michael J; Ross, Peter S

    2009-01-01

    We measured persistent organic pollutant (POP) concentrations in chinook salmon (Oncorhynchus tshawytscha) in order to characterize dietary exposure in the highly contaminated, salmon-eating northeastern Pacific resident killer whales. We estimate that 97 to 99% of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), dichlorodiphenyltrichloroethane (DDT), and hexachlorocyclohexane (HCH) in returning adult chinook were acquired during their time at sea. Highest POP concentrations (including PCBs, PCDDs, PCDFs, and DDT) and lowest lipids were observed in the more southerly chinook sampled. While feeding by salmon as they enter some more POP-contaminated near-shore environments inevitably contribute to their contamination, relationships observed between POP patterns and both lipid content and delta13C also suggest a migration-related metabolism and loss of the less-chlorinated PCB congeners. This has implications for killer whales, with the more PCB-contaminated salmon stocks in the south partly explaining the 4.0 to 6.6 times higher estimated daily intake for sigmaPCBs in southern resident killer whales compared to northern residents. We hypothesize that the lower lipid content of southerly chinook stocks may cause southern resident killer whales to increase their salmon consumption by as much as 50%, which would further increase their exposure to POPs.

  9. Allocation of Internal Medicine Resident Time in a Swiss Hospital: A Time and Motion Study of Day and Evening Shifts.

    PubMed

    Wenger, Nathalie; Méan, Marie; Castioni, Julien; Marques-Vidal, Pedro; Waeber, Gérard; Garnier, Antoine

    2017-04-18

    Little current evidence documents how internal medicine residents spend their time at work, particularly with regard to the proportions of time spent in direct patient care versus using computers. To describe how residents allocate their time during day and evening hospital shifts. Time and motion study. Internal medicine residency at a university hospital in Switzerland, May to July 2015. 36 internal medicine residents with an average of 29 months of postgraduate training. Trained observers recorded the residents' activities using a tablet-based application. Twenty-two activities were categorized as directly related to patients, indirectly related to patients, communication, academic, nonmedical tasks, and transition. In addition, the presence of a patient or colleague and use of a computer or telephone during each activity was recorded. Residents were observed for a total of 696.7 hours. Day shifts lasted 11.6 hours (1.6 hours more than scheduled). During these shifts, activities indirectly related to patients accounted for 52.4% of the time, and activities directly related to patients accounted for 28.0%. Residents spent an average of 1.7 hours with patients, 5.2 hours using computers, and 13 minutes doing both. Time spent using a computer was scattered throughout the day, with the heaviest use after 6:00 p.m. The study involved a small sample from 1 institution. At this Swiss teaching hospital, internal medicine residents spent more time at work than scheduled. Activities indirectly related to patients predominated, and about half the workday was spent using a computer. Information Technology Department and Department of Internal Medicine of Lausanne University Hospital.

  10. Molecular profile of cochlear immunity in the resident cells of the organ of Corti.

    PubMed

    Cai, Qunfeng; Vethanayagam, R Robert; Yang, Shuzhi; Bard, Jonathan; Jamison, Jennifer; Cartwright, Daniel; Dong, Youyi; Hu, Bo Hua

    2014-10-14

    The cochlea is the sensory organ of hearing. In the cochlea, the organ of Corti houses sensory cells that are susceptible to pathological insults. While the organ of Corti lacks immune cells, it does have the capacity for immune activity. We hypothesized that resident cells in the organ of Corti were responsible for the stress-induced immune response of the organ of Corti. This study profiled the molecular composition of the immune system in the organ of Corti and examined the immune response of non-immune epithelial cells to acoustic overstimulation. Using high-throughput RNA-sequencing and qRT-PCR arrays, we identified immune- and inflammation-related genes in both the cochlear sensory epithelium and the organ of Corti. Using bioinformatics analyses, we cataloged the immune genes expressed. We then examined the response of these genes to acoustic overstimulation and determined how changes in immune gene expression were related to sensory cell damage. The RNA-sequencing analysis reveals robust expression of immune-related genes in the cochlear sensory epithelium. The qRT-PCR array analysis confirms that many of these genes are constitutively expressed in the resident cells of the organ of Corti. Bioinformatics analyses reveal that the genes expressed are linked to the Toll-like receptor signaling pathway. We demonstrate that expression of Toll-like receptor signaling genes is predominantly from the supporting cells in the organ of Corti cells. Importantly, our data demonstrate that these Toll-like receptor pathway genes are able to respond to acoustic trauma and that their expression changes are associated with sensory cell damage. The cochlear resident cells in the organ of Corti have immune capacity and participate in the cochlear immune response to acoustic overstimulation.

  11. The imprint of climate and geology on the residence times of groundwater

    NASA Astrophysics Data System (ADS)

    Maxwell, Reed M.; Condon, Laura E.; Kollet, Stefan J.; Maher, Kate; Haggerty, Roy; Forrester, Mary Michael

    2016-01-01

    Surface and subsurface flow dynamics govern residence time or water age until discharge, which is a key metric of storage and water availability for human use and ecosystem function. Although observations in small catchments have shown a fractal distribution of ages, residence times are difficult to directly quantify or measure in large basins. Here we use a simulation of major watersheds across North America to compute distributions of residence times. This simulation results in peak ages from 1.5 to 10.5 years, in agreement with isotopic observations from bomb-derived radioisotopes, and a wide range of residence times—from 0.1 to 10,000 years. This simulation suggests that peak residence times are controlled by the mean hydraulic conductivity, a function of the prevailing geology. The shape of the residence time distribution is dependent on aridity, which in turn determines water table depth and the frequency of shorter flow paths. These model results underscore the need for additional studies to characterize water ages in larger systems.

  12. Residence time and Posidonia oceanica in Cabrera Archipelago National Park, Spain

    NASA Astrophysics Data System (ADS)

    Orfila, A.; Jordi, A.; Basterretxea, G.; Vizoso, G.; Marbà, N.; Duarte, C. M.; Werner, F. E.; Tintoré, J.

    2005-07-01

    Flushing time and residence time are studied in a small inlet in Cabrera National Park, Western Mediterranean Sea. Flushing time is studied using ADCP in situ data. Observed flushing time data are compared with the simulations from a three-dimensional coastal ocean numerical model. Residence time is assessed using virtual lagrangian particles and studying the number remaining within the analyzed domain. Results show a good agreement between observations and modeling estimations of the flushing time (i.e. 6 days from the ADCP data and 5.6 days from the numerical model). Residence time estimations yield a broad range of values, from 1 h in the Bay to over 30 days depending also on the horizontal and vertical position where particles were released. A continuous stirred tank reactor (CSTR) model for the Port yields a value of 8.7 days. Results obtained for the residence time appear to have a determinant impact over the meadows of the seagrass Posidonia oceanica, present inside the Port. Recirculation patterns and complex flows in coastal environments create a non-uniform distribution of the areas of accumulation of non-conservative properties that indicate that residence time concept is the correct approach when studying the impact of water transport over biological communities.

  13. Combining direct residence time measurements and biogeochemistry to calculate in-situ reaction rates in the hyporheic zone

    NASA Astrophysics Data System (ADS)

    Pittroff, Marco; Gilfedder, Benjamin

    2015-04-01

    The hyporheic zone is an active interface between groundwater, riparian and surface water systems. Exchange and reaction of water, nutrients, and organic matter occur due to variations in surface and groundwater flow regimes, bed topography and active biogeochemistry fuelled by bioavailable carbon. There has been an increasing focus on coupling the residence time of surface water in the hyporheic zone with biogeochemical reactions. However, there are very few tracers that can be used to measure residence times in-situ, especially in complex groundwater-surface water settings. In this work we have used the natural radioisotope Radon (222Rn) as an in-situ tracer for river water residence time in a riffle-pool sequence (Rote Main River), and combined this information with biogeochemical parameters (DOC and C quality, O3, NO3, CO2). We can clearly observe a dependence of reaction progress on the water residence times, with oxygen and nitrate reduction following inverse logarithmic trends as a function of time. By comparing with initial concentrations (the river end member) with riverbed levels we have estimated first-order in-situ reduction rates for nitrate and oxygen. Nitrate reduction rates are at the higher end of published values, which is likely due to the continual supply of bioavailable carbon from the river system. This work helps to better understand the function and efficiency of the hyporheic zone as a natural filter for redox sensitive species such as nitrate at the groundwater - steam interface. It also provides a useful method for estimating residence times in complex, higher order river systems.

  14. [Resident and circulating mast cells in propulsative organs of the frog Rana temporaria].

    PubMed

    Krylova, M I

    2009-01-01

    Mast cells (MCs) of the "blood" and lymph hearts of the adult frog Rana temporaria were investigated at histochemical and ultrastructural levels. Two populations of MCs were revealed in these propulsative organs: population of resident MCs and population of circulating MCs. It has been shown that the resident cardiac MCs have an oval or elongated form and are located between atrial or ventricular myocytes and under endocardial endothelium. The resident cardiac MCs are situated in connective tissue of epicardium, too. Avascular myocardium of the frog ventricle consists of a spongy network of muscle trabeculae. We revealed circulating MCs in intertrabecular spaces and clefts of the spongy myocardium and in the blood of the main central cavity. Circulating MCs are round in shape and contain a large central nucleus enriched with condensed chromatin. They resemble the lymphocytes, but show cytoplasm filled with granules. These granules ultrastructure is much like that of the granules of the cardiac resident MCs. In the lymph heart, oval and somewhat elongated resident MCs are located in the interstitial space among cross-striated muscle fibers and among smooth muscle cells of tubular (afferent and efferent) valves. Sometimes lymphocyte-like circulating MCs are revealed in the cavity of lymph heart. Circulating MCs are also present in the lymphatics located adjacent to the lymph hearts. In certain parts of the lymphatic walls MCs are in close adhesion to the mesothelial cells lining the lymphatic cavity. Our histochemical investigation revealed that both the resident and circulating MCs of the propulsative organs give a strongly positive reaction with alcian blue, but weakly red with safranin and weakly metachromatic with toluidine blue. The presence of population of circulating MCs in the frog suggests that there are differences in biology of MCs between lower and higher vertebrates.

  15. Residence time of buoyant objects in drowning machines

    PubMed Central

    Gioia, Gustavo; Chakraborty, Pinaki; Gary, Stefan F.; Zamalloa, Carlo Zuñiga; Keane, Richard D.

    2011-01-01

    Hydraulic jumps are a common feature of rivers and waterways, where they can be found close to spillways, weirs, rocky ledges, and boulders. People adrift upstream of a hydraulic jump are liable to become trapped in the turbulent roller of the hydraulic jump. For this reason, hydraulic jumps have been termed “drowning machines” and are recognized as a public hazard. We use experiments and theory to show that on average a buoyant object spends a time τ/p trapped in a jump, where τ is the period of a harmonic process inherent in the jump, and p is the probability that the object will escape in any time interval τ. The probability p is governed by the statistical theory of extreme values and depends primarily on the ratio between the density of the object and the density of the fluid. We use our results to draw conclusions that might prove to be useful to public-safety agencies intent on carrying out tests in drowning machines. Our results can also be used to predict the amount of flotsam that accumulates at the toe of a hydraulic jump.

  16. Simulation of Water Age and Residence Time in the New York Bight

    NASA Astrophysics Data System (ADS)

    Zhang, W. G.; Wilkin, J. L.; Schofield, O. M.

    2008-12-01

    Aiming at investigating the time scale of transporting biogeochemical tracers in the New York Bight (NYB), this work looks into the time scale associated with freshwater propagation in NYB. The Constituent-oriented Age and Residence-time Theory is applied in Regional Ocean Modeling System and then verified. Three-year mean age and two-year mean residence time simulations are carried out. Comparison between snapshots of modeled surface freshwater mean age and satellite measured channel ratio, an empirical proxy of age, shows agreement on the general patterns. Least square fit gives the first order estimation of the relationship between channel ratio and mean age. Time series show temporal and spatial variation in mean age, and seasonal averages demonstrate seasonality of surface mean age consistent with surface circulation. Correlation between surface mean age and wind shows major effects wind in different directions has on mean age. Time series of the mean residence time exhibits strong temporal fluctuation in the scale of days, and seasonal averages show seasonality in surface mean residence time, too. The surprising high value of mean residence time along the Long Island coast in spring and summer is caused by the reentry of previously exited water from the eastern boundary after wind changes direction. Correlation between mean residence time and wind shows major effects wind has on the time freshwater and tracers spend in the New York apex area. Results obtained here are very useful for coastal management and studies of local biogeochemical processes and larval dispersal given the ecological and economical importance of the New York Bay.

  17. Methane: Interhemispheric concentration gradient and atmospheric residence time

    PubMed Central

    Mayer, Edward W.; Blake, Donald R.; Tyler, Stanley C.; Makide, Yoshihiro; Montague, Derek C.; Rowland, F. Sherwood

    1982-01-01

    The ground level concentrations of methane in the atmosphere have been measured to be in the range from 1.45 to 1.62 parts per million by volume (ppmv) of dry air in remote locations between 62°N and 54°S latitudes during the time period from November 1977 to July 1979. The average (±rms) concentration for the northern hemisphere was 1.57 ± 0.02 ppmv in January 1978 and 1.59 ± 0.02 in July 1979. The average concentration in the southern hemisphere was lower—1.47 ± 0.02 in January 1978 and 1.51 ± 0.01 in July 1979. The ratio of concentrations between the two hemispheres was 1.068 ± 0.016 in January 1978 and 1.055 ± 0.013 in July 1979, for an average of 1.06 ± 0.01. The higher concentrations in the northern hemisphere require either that the sources of methane lie preferentially in the northern hemisphere or that the removal processes operate more rapidly in the southern hemisphere or both. The primary removal process for CH4 is reaction with tropospheric OH radicals and its estimated atmospheric lifetime is 10.5 ± 1.8 yr. The observed interhemispheric gradient is consistent with this lifetime and preferential release of methane in the northern hemisphere. Measurements taken in the Amazon basin region indicate the presence of a substantial source of methane in that area. PMID:16593168

  18. Observations and modeling of exchange and residence time in tidal inlets

    NASA Astrophysics Data System (ADS)

    Rynne, Patrick Forde

    The exchange of water in a coastal embayment with seawater is forced by tidally driven and gravitational flows. Tidal flows oscillate temporally based on planetary motion, while gravitational flows like those found in rivers act in one direction from high to low altitude. These flows determine the residence time, or the time water will remain within an embayment. At the ocean boundary, many coasts contain barrier islands with inlets through which these flows propagate. The effect that inlets have on the exchange of inland water with the sea has been the subject of research for nearly a century. Residence time is a bulk parameter that can be used to indicate the efficiency of an inlet system to rid itself of contaminants and maintain good water quality. Because coastal embayments are often exposed to anthropogenic pollutants, understanding the processes that control residence time improves our ability to protect coastal ecosystems. Inlet systems, including lagoons and estuaries, are subject to processes of a wide range of spatial and temporal scales. As such, past efforts to identify which processes control the motion and transport of water often rely on assumptions that simplify the kinematics. Today, the rapid evolution of personal computing has enabled the creation of numerical models that resolve the Reynolds Averaged Navier Stokes Equations (RANS) for complex flows found in inlet environments. This dissertation focuses on utilizing such a model to examine the flow in tidal inlet systems and to identify the dominant processes that control exchange and residence time. First, modeling experiments of idealized lagoons are conducted with the aim of quantifying how the shape of an inlet affects residence time. Seventeen different inlet configurations are examined. Methods of quantifying residence time based on previous analytical models are applied to a numerical model for the first time. To better understand the mechanism of exchange, a simple transport model is

  19. How Do Residents Spend Their Time in the Intensive Care Unit?

    PubMed Central

    Carayon, Pascale; Weinger, Matthew B.; Brown, Roger; Cartmill, Randi; Slagle, Jason; Van Roy, Kara Schultz; Walker, James M.; Wood, Kenneth E.

    2015-01-01

    Purpose To describe the work of residents and the distribution of their time in 6 ICUs of 2 medical centers. Methods We conducted a total of 242 hours of observation to capture data on tasks performed by residents in 6 ICUs, including adult, pediatric, medical and surgical units. For each observation period, the percentages of total time spent on each task and on the aggregated task categories were calculated. Results Overall, while in the ICUs, residents spent almost half of their time in clinical review and documentation (19%), conversation with team physicians (16%), conversation attendance (6%) and order management (6%). The two medical centers differed in the time that residents spent on administrative review and documentation (4% in one medical center and 15% in the other one). The pediatric ICUs were similar in the 2 medical centers, whereas the adult ICUs exhibited differences in the time spent on order management and administrative review and documentation. Conclusions While in the ICUs, residents spent most time performing direct patient care and care coordination activities. The distribution of activities varied across 2 medical centers and across ICUs, which highlights the need to consider the local context on residents’ work in ICUs. PMID:26171828

  20. Resident participation in laparoscopic hysterectomy: impact of trainee involvement on operative times and surgical outcomes.

    PubMed

    Igwe, Elena; Hernandez, Enrique; Rose, Stephen; Uppal, Shitanshu

    2014-11-01

    The purpose of this study was to determine the impact of resident involvement on morbidity after total laparoscopic hysterectomy for benign disease. We performed a retrospective review of a National Surgical Quality Improvement Program database of total laparoscopic hysterectomy for benign disease that was performed with resident involvement vs attending alone between Jan. 1, 2008, and Dec. 31, 2011. Surgical operative times and morbidity and mortality rates were compared. Binary logistic regression was used to control for covariates that were significant on univariate analysis (P < .05). A total of 3441 patients were identified as having undergone a total laparoscopic hysterectomy for benign disease. The mean age of patients was 47.4 ± 11.1 years; the mean body mass index was 30.6 ± 7.9 kg/m(2). A resident participated in 1591 of cases (46.2%); 1850 of the procedures (53.8%) were done by an attending physician alone. Cases with resident involvement had higher mean age, Charlson morbidity scoring, and American Society of Anesthesiologists classification and were more likely to be inpatient cases. With resident involvement, the mean operative time was increased (179.29 vs 135.46 minutes; P < .0001). There were no differences in the rates of experiencing at least 1 complication (6.8% for resident involvement vs 5.4% for attending alone; P = .5), composite severe morbidity (1.3% resident vs 1.0% attending alone), or 30-day mortality rate (0% resident vs 0.1% attending alone). Additionally, there were no differences between groups in the infectious, wound, neurorenal, thromboembolic, septic, and cardiopulmonary complications. Cases with resident involvement had significantly increased rates of postoperative transfusion of packed red blood cells (2% vs 0.4%; P < .0001), reoperation (2.2% vs 1.3%; P = .048), and a 30-day readmission (5.5% vs 2.9%; P = .015). In models that were adjusted for factors that differed between the 2 groups, cases with resident involvement had

  1. Residence time of pollutants discharged in the Gulf of Kachchh, northwestern Arabian Sea.

    PubMed

    Patgaonkar, Rupali S; Vethamony, P; Lokesh, K S; Babu, M T

    2012-08-01

    A 2D Hydrodynamic-Particle Analysis model was applied to the Gulf of Kachchh (GoK) to estimate the residence time of pollutants. The tidal currents in the Gulf have a strong E-W component, which prevents the material in the north being transported towards south. In the regions situated very close to the open boundary, where the GoK waters exchange freely with the northern Arabian Sea, dilution takes place rapidly with the incoming waters and hence, the residence time is on the order of 1 day. Influence of eddies and a dynamic barrier across the Sikka-Mundra section on the residence time is apparent. Eastern GoK shows a relatively large residence time, on the order of 2-4 days, warranting caution while releasing industrial wastes in the northeastern Gulf. The region around location-5 behaves like a bay; the dissolved matter gets trapped in this bay and the residence time increases by 3-4 days.

  2. Utilization of decadal tritium variation for assessing the residence time of base flow.

    PubMed

    Rose, S

    2007-01-01

    An iterative algorithm is presented that allows the user to model the subsurface residence time of shallow ground water comprising stream base flow based on decadal scale variation of tritium concentrations. The algorithm accounts for the effects of radioactive decay, the shallow subsurface mixing of ground water with precipitation, and ground water flux. The inverse of the best-fitting modeled flux through the saturated zone is equivalent to the residence time. The data required for this model include at least two measurements of tritium in base flow for a given stream location made at least a decade apart and the long-term tritium input in precipitation for the region of interest. The model is sensitive to relatively small changes in tritium concentrations and is limited by analytic uncertainties to an accuracy of approximately +/-5 years. The algorithm was applied to stream base flow for several basins in the Piedmont Province of Georgia in which tritium concentrations were measured during the early 1990s and again in the 2000s. The model results produced highly concordant residence times for three hydrogeologically similar basins in the Upper Ocmulgee Basin in North Central Georgia. The best estimate of the average residence time for ground water comprising base flow in this Piedmont basin using this new method is between approximately 14 and 18 years. These results are generally consistent with calculations made in previous studies, and these relatively long residence times can be attributed to the storage of water in the clay soils that dominate Piedmont Province watersheds.

  3. Residents' reasons for specialty choice: influence of gender, time, patient and career.

    PubMed

    van der Horst, Klazine; Siegrist, Michael; Orlow, Pascale; Giger, Max

    2010-06-01

    OBJECTIVE This study examined reasons for specialty choice among Swiss residents (post graduate doctors training in specialties). METHODS In 2006, a questionnaire was sent to 8626 Swiss residents registered in postgraduate medical training programmes to obtain specialist qualifications. The response rate was 65% (n = 5631). As residents are allowed to decide on the specialty they want to acquire later in the training process, only residents who had already chosen a specific specialty were included (n = 5038). In responding, residents rated the importance of 19 factors in making their choice of specialty. Categorical principal component analysis was conducted to obtain underlying dimensions within the reasons for choice. A two-way analysis of variance was performed for each dimension to compare the mean object scores for the 10 specialties chosen by the most residents and to examine possible interactions by gender and year of graduation. Contrasts between the specialties were analysed with Scheffe post hoc tests. RESULTS Categorical principal component analyses yielded three factors underlying residents' choice of specialty, which explained 40.8% of the variance in responses: work and time-related aspects; career-related aspects, and patient orientation. Women considered work and time-related aspects and patient orientation to be more important factors in their choice, and career-related aspects to be less important, than did men. Career-related aspects became less important with advancing training status. CONCLUSIONS This study showed that reasons for specialty choice differ according to gender, year of graduation and specialty. With progressing training status, gender differences in reasons for choice and specialty choice may become more pronounced, especially regarding career aspects, which may lead to a change in preferred specialty. Therefore, a modular constructed postgraduate training programme might give residents the flexibility to change from one specialty

  4. Estimation of organ dose equivalents from residents of radiation-contaminated buildings with Rando phantom measurements.

    PubMed

    Lee, J S; Dong, S L; Wu, T H

    1999-05-01

    Since August 1996, a dose reconstruction model has been conducted with thermoluminescent dosimeter (TLD)-embedded chains, belts and badges for external dose measurements on the residents in radiation-contaminated buildings. The TLD dosimeters, worn on the front of the torso, would not be adequate for dose measurement in cases when the radiation is anisotropic or the incident angles of radiation sources are not directed in the front-to-back direction. The shielding and attenuation by the body would result in the dose equivalent estimation being somewhat skewed. An organ dose estimation method with a Rando phantom under various exposure geometries is proposed. The conversion factors, obtained from the phantom study, may be applicable to organ dose estimations for residents in the contaminated buildings if the incident angles correspond to the phantom simulation results. There is a great demand for developing a mathematical model or Monte Carlo calculation to deal with complicated indoor layout geometry problems involving ionizing radiation. Further research should be directed toward conducting laboratory simulation by investigating the relationship between doses delivered from multiple radiation sources. It is also necessary to collaborate with experimental biological dosimetry, such as chromosome aberration analysis, fluorescence in situ hybridization (FISH) and retrospective ESR-dosimetry with teeth, applied to the residents, so that the organ dose equivalent estimations may be more reliable for radio-epidemiological studies.

  5. Attitudes of resident doctors toward different types of organ donation in a Spanish transplant hospital.

    PubMed

    Ríos, A; Conesa, C; Ramírez, P; Galindo, P J; Rodríguez, J M; Rodríguez, M M; Martínez, L; Parrilla, P

    2006-04-01

    Our aim was to analyze acceptance of cadaveric and living organ donation for transplantation among resident doctors, given that they are the new professionals of medicine who will have to encourage and develop transplant programs. A random survey was performed on resident doctors in a third-level hospital with an organ transplant program which is accredited for undergraduate and postgraduate education (n = 171). Attitudes toward cadaveric and living donation were evaluated using a questionnaire including various psychosocial variables that might affect such attitudes. We used the Student t test and the chi-square test. The sample was composed of responses by 171 resident doctors of mean age 28 +/- 4 years with 56% women. Attitudes toward cadaveric donation were favorable in 92% (n = 157). As for living donation, the percentage in favor of nonrelated donation was low: 23% for kidney and 19% for liver. However, when the donation was from a relative, the percentages increased to levels similar to those of cadaveric donation, namely 88% and 85% for kidney and liver, respectively. No differences were observed in attitudes toward cadaveric or living donation according to various psychosocial variables. The trainee doctors showed favorable attitudes toward human cadaveric organ donation as well as living related donation, which suggests a relaunch of living donors in the near future. However, there was not much acceptance of nonrelated donation, as has also been seen in studies of the general public in our geographical area.

  6. Impact of the European Working Time Directive (EWTD) on the operative experience of surgery residents.

    PubMed

    Hopmans, Cornelis J; den Hoed, Pieter T; van der Laan, Lijckle; van der Harst, Erwin; van der Elst, Maarten; Mannaerts, Guido H H; Dawson, Imro; Timman, Reinier; Wijnhoven, Bas P L; IJzermans, Jan N M

    2015-04-01

    In Europe and the United States, work hour restrictions are considered to be particularly burdensome for residents in surgery specialties. The aim of this study was to examine whether reduction of the work week to 48 hours resulting from the implementation of the European Working Time Directive has affected the operative experience of surgery residents. This study was conducted in a general surgery training region in the Netherlands, consisting of 1 university hospital and 6 district training hospitals. Operating records summarizing the surgical procedures performed as "primary surgeon" in the operating theater for different grades of surgeons were retrospectively analyzed for the period 2005-2012 by the use of linear regression models. Operative procedures performed by residents were considered the main outcome measure. In total, 235,357 operative procedures were performed, including 47,458 (20.2%) in the university hospital and 187,899 (79.8%) in the district training hospitals (n = 5). For residents in the university hospital, the mean number of operative procedures performed per 1.0 full-time equivalent increased from 128 operations in 2005 to 204 operations in 2012 (P = .001), whereas for residents in district training hospitals, no substantial differences were found over time. The mean (±SD) operative caseload of 64 residents who completed the 6-year training program between 2005 and 2012 was 1,391 ± 226 (range, 768-1856). A comparison of the operative caseload according to year of board-certification showed no difference. Implementation of the European Working Time Directive has not affected adversely the number of surgical procedures performed by residents within a general surgical training region in the Netherlands. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. Residency Time as an Indicator of Reproductive Restraint in Male Burying Beetles

    PubMed Central

    Smith, Ashlee N.; Belk, Mark C.; Creighton, J. Curtis

    2014-01-01

    The cost of reproduction theory posits that there are trade-offs between current and future reproduction because resources that are allocated to current offspring cannot be used for future reproductive opportunities. Two adaptive reproductive strategies have been hypothesized to offset the costs of reproduction and maximize lifetime fitness. The terminal investment hypothesis predicts that as individuals age they will allocate more resources to current reproduction as a response to decreasing residual reproductive value. The reproductive restraint hypotheses predicts that as individuals age they will allocate fewer resources to current reproduction to increase the chance of surviving for an additional reproductive opportunity. In this study, we test for adaptive responses to advancing age in male burying beetles, Nicrophorus orbicollis. Burying beetles use facultative biparental care, but the male typically abandons the brood before the female. Previous work in male burying beetles has suggested several factors to explain variation in male residency time, but no study has observed male behavior throughout their entire reproductive lifetimes to determine whether males change residency time in an adaptive way with age. We compared residency time of males that reproduced biparentally, uniparentally, and on different-sized carcasses to determine if they used an adaptive reproductive strategy. Males did not increase residency time as they aged when reproducing biparentally, but decreased residency time with age when reproducing uniparentally. A decrease in parental care with age is consistent with a reproductive restraint strategy. When female age increased over time, males did not increase their residency time to compensate for deteriorating female condition. To our knowledge, this is the first test of adaptive reproductive allocation strategies in male burying beetles. PMID:25295755

  8. Lean principles optimize on-time vascular surgery operating room starts and decrease resident work hours.

    PubMed

    Warner, Courtney J; Walsh, Daniel B; Horvath, Alexander J; Walsh, Teri R; Herrick, Daniel P; Prentiss, Steven J; Powell, Richard J

    2013-11-01

    Lean process improvement techniques are used in industry to improve efficiency and quality while controlling costs. These techniques are less commonly applied in health care. This study assessed the effectiveness of Lean principles on first case on-time operating room starts and quantified effects on resident work hours. Standard process improvement techniques (DMAIC methodology: define, measure, analyze, improve, control) were used to identify causes of delayed vascular surgery first case starts. Value stream maps and process flow diagrams were created. Process data were analyzed with Pareto and control charts. High-yield changes were identified and simulated in computer and live settings prior to implementation. The primary outcome measure was the proportion of on-time first case starts; secondary outcomes included hospital costs, resident rounding time, and work hours. Data were compared with existing benchmarks. Prior to implementation, 39% of first cases started on time. Process mapping identified late resident arrival in preoperative holding as a cause of delayed first case starts. Resident rounding process inefficiencies were identified and changed through the use of checklists, standardization, and elimination of nonvalue-added activity. Following implementation of process improvements, first case on-time starts improved to 71% at 6 weeks (P = .002). Improvement was sustained with an 86% on-time rate at 1 year (P < .001). Resident rounding time was reduced by 33% (from 70 to 47 minutes). At 9 weeks following implementation, these changes generated an opportunity cost potential of $12,582. Use of Lean principles allowed rapid identification and implementation of perioperative process changes that improved efficiency and resulted in significant cost savings. This improvement was sustained at 1 year. Downstream effects included improved resident efficiency with decreased work hours. Copyright © 2013 Society for Vascular Surgery. Published by Mosby, Inc. All

  9. Residency time as an indicator of reproductive restraint in male burying beetles.

    PubMed

    Smith, Ashlee N; Belk, Mark C; Creighton, J Curtis

    2014-01-01

    The cost of reproduction theory posits that there are trade-offs between current and future reproduction because resources that are allocated to current offspring cannot be used for future reproductive opportunities. Two adaptive reproductive strategies have been hypothesized to offset the costs of reproduction and maximize lifetime fitness. The terminal investment hypothesis predicts that as individuals age they will allocate more resources to current reproduction as a response to decreasing residual reproductive value. The reproductive restraint hypotheses predicts that as individuals age they will allocate fewer resources to current reproduction to increase the chance of surviving for an additional reproductive opportunity. In this study, we test for adaptive responses to advancing age in male burying beetles, Nicrophorus orbicollis. Burying beetles use facultative biparental care, but the male typically abandons the brood before the female. Previous work in male burying beetles has suggested several factors to explain variation in male residency time, but no study has observed male behavior throughout their entire reproductive lifetimes to determine whether males change residency time in an adaptive way with age. We compared residency time of males that reproduced biparentally, uniparentally, and on different-sized carcasses to determine if they used an adaptive reproductive strategy. Males did not increase residency time as they aged when reproducing biparentally, but decreased residency time with age when reproducing uniparentally. A decrease in parental care with age is consistent with a reproductive restraint strategy. When female age increased over time, males did not increase their residency time to compensate for deteriorating female condition. To our knowledge, this is the first test of adaptive reproductive allocation strategies in male burying beetles.

  10. Predictive Value of Performance Criteria for First-Time Sophomore Resident Assistants

    ERIC Educational Resources Information Center

    Severance, Dana A.

    2015-01-01

    Housing professionals are increasingly compelled to consider hiring resident assistants (RAs) from a pool of applicants that includes students with less college experience than has traditionally been expected. The purpose of the study is to determine if the success of first-time sophomore RAs differs from that of first-time upper-class RAs…

  11. Residence times and decay rates of downed woody debris biomass/carbon in eastern US forests

    Treesearch

    Matthew B. Russell; Christopher W. Woodall; Shawn Fraver; Anthony W. D' Amato; Grant M. Domke; Kenneth E. Skog

    2014-01-01

    A key component in describing forest carbon (C) dynamics is the change in downed dead wood biomass through time. Specifically, there is a dearth of information regarding the residence time of downed woody debris (DWD), which may be reflected in the diversity of wood (for example, species, size, and stage of decay) and site attributes (for example, climate) across the...

  12. Predictive Value of Performance Criteria for First-Time Sophomore Resident Assistants

    ERIC Educational Resources Information Center

    Severance, Dana A.

    2015-01-01

    Housing professionals are increasingly compelled to consider hiring resident assistants (RAs) from a pool of applicants that includes students with less college experience than has traditionally been expected. The purpose of the study is to determine if the success of first-time sophomore RAs differs from that of first-time upper-class RAs…

  13. Does streambed heterogeneity matter for hyporheic residence time distribution in sand-bedded streams?

    NASA Astrophysics Data System (ADS)

    Tonina, Daniele; de Barros, Felipe P. J.; Marzadri, Alessandra; Bellin, Alberto

    2016-10-01

    Stream water residence times within streambed sediments are key values to quantify hyporheic processes including sediment thermal regime, solute transient storage, dilution rates and biogeochemical transformations, such as those controlling degassing nitrous oxide. Heterogeneity of the streambed sediment hydraulic properties has been shown to be potentially an important factor to characterize hyporheic processes. Here, we quantify the importance of streambed heterogeneity on residence times of dune-like bedform induced hyporheic fluxes at the bedform and reach scales. We show that heterogeneity has a net effect of compression of the hyporheic zone (HZ) toward the streambed, changing HZ volume from the homogenous case and thus inducing remarkable differences in the flow field with respect to the homogeneous case. We unravel the physical conditions for which the commonly used homogenous field assumption is applicable for quantifying hyporheic processes thus explaining why predictive measures based on a characteristic residence time, like the Damköhler number, are robust in heterogeneous sand bedded streams.

  14. Computation of residence time in the simulation of pulsatile ventricular assist devices

    NASA Astrophysics Data System (ADS)

    Long, C. C.; Esmaily-Moghadam, M.; Marsden, A. L.; Bazilevs, Y.

    2014-10-01

    A continuum-based model of particle residence time for moving-domain fluid mechanics and fluid-structure interaction (FSI) computations is proposed, analyzed, and applied to the simulation of an adult pulsatile ventricular assist device (PVAD). Residence time is a quantity of clinical interest for blood pumps because it correlates with thrombotic risk. The proposed technique may be easily implemented in any flow or FSI solver. In the context of PVADs the results of the model may be used to assess how efficiently the pump moves the blood through its interior. Three scalar measures of particle residence time are also proposed. These scalar quantities may be used in the PVAD design with the goal of reducing thrombotic risk.

  15. Strategic Application of Residence-Time Control in Continuous-Flow Reactors

    PubMed Central

    Mándity, István M; Ötvös, Sándor B; Fülöp, Ferenc

    2015-01-01

    As a sustainable alternative for conventional batch-based synthetic techniques, the concept of continuous-flow processing has emerged in the synthesis of fine chemicals. Systematic tuning of the residence time, a key parameter of continuous-reaction technology, can govern the outcome of a chemical reaction by determining the reaction rate and the conversion and by influencing the product selectivity. This review furnishes a brief insight into flow reactions in which high chemo- and/or stereoselectivity can be attained by strategic residence-time control and illustrates the importance of the residence time as a crucial parameter in sustainable method development. Such a fine reaction control cannot be performed in conventional batch reaction set-ups. PMID:26246983

  16. Strategic Application of Residence-Time Control in Continuous-Flow Reactors.

    PubMed

    Mándity, István M; Ötvös, Sándor B; Fülöp, Ferenc

    2015-06-01

    As a sustainable alternative for conventional batch-based synthetic techniques, the concept of continuous-flow processing has emerged in the synthesis of fine chemicals. Systematic tuning of the residence time, a key parameter of continuous-reaction technology, can govern the outcome of a chemical reaction by determining the reaction rate and the conversion and by influencing the product selectivity. This review furnishes a brief insight into flow reactions in which high chemo- and/or stereoselectivity can be attained by strategic residence-time control and illustrates the importance of the residence time as a crucial parameter in sustainable method development. Such a fine reaction control cannot be performed in conventional batch reaction set-ups.

  17. Computational fluid dynamic prediction of the residence time of a vortex separator applied to disinfection.

    PubMed

    Egarr, D; Faram, M G; O'Doherty, T; Phipps, D; Syred, N

    2005-01-01

    A Hydrodynamic Vortex Separator (HDVS) has been modelled using Computational Fluid Dynamics (CFD) in order to predict the residence time of the fluid at the overflow and underflow outlets. A technique which was developed for use in Heating, Ventilation and Air Conditioning (HVAC) was used to determine the residence time and the results have been compared with those determined experimentally. It is shown that in using CFD, it is possible to predict the mean residence time of the fluid and to study the response to a pulse injection of tracer. It is also shown that it is possible to apply these techniques to predict the mean survival rate of bacteria in a combined separation and disinfection process.

  18. Educating pediatric residents about breastfeeding: evaluation of 3 time-efficient teaching strategies.

    PubMed

    Tender, Jennifer A F; Cuzzi, Sandra; Kind, Terry; Simmens, Samuel J; Blatt, Benjamin; Greenberg, Larrie

    2014-11-01

    Previously reported breastfeeding curricula for residents have combined different teaching methods, have focused on knowledge and attitudes, and have been time-intensive. This study aimed to evaluate 3 time-efficient breastfeeding curricula for effectiveness in regard to pediatric residents' knowledge, confidence, and skills in managing a simulated breastfeeding scenario. First-year pediatric residents during their 4-week community hospital newborn nursery rotation were consecutively assigned to 1 of 3 groups. Group 1 shadowed an International Board Certified Lactation Consultant (IBCLC) for 1 hour; group 2 watched a 25-minute case-based breastfeeding DVD; and group 3 observed a 3-hour prenatal parent breastfeeding class (CLS). Residents were assessed by (1) a pretest and posttest evaluating their breastfeeding knowledge and confidence, and (2) a clinical skills scenario managing a breastfeeding standardized patient (SP). Thirty-nine pediatric residents participated in the study (11 in IBCLC, 16 DVD, 12 CLS) over a 1-year period. All groups significantly improved their knowledge scores and confidence in managing breastfeeding problems, with the IBCLC group showing more improvement in knowledge than the other groups (P = .02) and a higher rating of their teaching method (P = .01). All groups performed well on the SP clinical skills scenario, with no significant difference between groups. All 3 teaching methods were time-efficient and produced important gains in knowledge and confidence, with residents in the IBCLC group demonstrating greatest improvement in knowledge and a higher rating of their teaching method. Our study provides support for 3 methods of teaching residents breastfeeding management and demonstrates that IBCLCs are well-received as interprofessional educators. © The Author(s) 2014.

  19. Protected block time for teaching and learning in a postgraduate family practice residency program

    PubMed Central

    Jung, Piera; Kennedy, Maggie; Winder, Mary J.

    2012-01-01

    Abstract Objective To explore the elements necessary for a high-quality educational experience in a family practice residency program with respect to scheduling, learning environment, and approaches to teaching and learning. Design An interpretative, qualitative study using a generative-inquiry approach. Setting The Nanaimo Site of the University of British Columbia Family Practice Residency Program. Participants Fifteen physician instructors and 16 first- and second-year residents. Methods Data were gathered from 2 qualitative focus group interviews with residents; 2 qualitative focus group interviews with physician instructors; and structured and semistructured observation of 2 in-class seminars, with a focus on residents’ engagement with the class. Results were analyzed and categorized into themes independently and collectively by the researchers. Main findings Protected block time for teaching and learning at the Nanaimo Site has been effective in fostering a learning environment that supports collegial relationships and in-depth instruction. Residents and physician instructors benefit from the week-long academic schedule and the opportunity to teach and learn collaboratively. Participants specifically value the connections among learning environment, collegiality, relationships, reflective learning, and the teaching and learning process. Conclusion These findings suggest that strategic planning and scheduling of teaching and learning sessions in residency programs are important to promoting a comprehensive educational experience. PMID:22700741

  20. Catchment travel and residence time distributions: a theoretical framework for solute transport modeling

    NASA Astrophysics Data System (ADS)

    Botter, G.; Bertuzzo, E.; Rinaldo, A.

    2011-12-01

    The probability density functions (pdf's) of travel and residence times are key descriptors of the mechanisms through which catchments retain and release old and event water, transporting solutes to receiving water bodies. In this contribution we derive a general stochastic framework applicable to arbitrary catchment control volumes, where time-variable precipitation, evapotranspiration and discharge are assumed to be the major hydrological drivers for water and solutes. A master equation for the residence time pdf is derived and solved analytically, providing expressions for travel and residence time pdf's as a function of input/output fluxes and of the relevant mixing processes occurring along streamflow production and plant upatke. Our solutions suggest intrinsically time variant travel and residence time pdf's through a direct dependence on the underlying hydrological forcings and soil vegetation dynamics. The proposed framework highlights the dependence of water/solute travel times on eco-hydrological processes (especially transpiration and uptake), and integrates age-dating and tracer hydrology techniques by providing a coherent framework for catchment transport models. An application to the release of pesticides from an agricultural watershead is also discussed.

  1. Residence time distribution and material flow studies in a rotary kiln

    NASA Astrophysics Data System (ADS)

    Sai, P. S. T.; Surender, G. D.; Damodaran, A. D.; Suresh, V.; Philip, Z. G.; Sankaran, K.

    1990-12-01

    Experiments were conducted in a rotary kiln containing ilmenite particles to study the residence time distribution (RTD) of low-density particles, holdup, and bed depth profile. The variables include feed rate of solids, slope and rotational speed of the kiln, type and size of the tracer, and dam height. Correlations are presented for mean residence time, dispersion number, holdup, and steady-state throughput of solids in terms of the process variables. A simple method is proposed to estimate the dam height that gives rise to a flat profile of solids bed along the length of the kiln.

  2. Relating hyporheic fluxes, residence times, and redox-sensitive biogeochemical processes upstream of beaver dams

    USGS Publications Warehouse

    Briggs, Martin A.; Lautz, Laura; Hare, Danielle K.

    2013-01-01

    ¨hler number seemed to overestimate the actual transition as indicated by multiple secondary electron acceptors, illustrating the gradient nature of anaerobic transition. Temporal flux variability in low-flux morphologies generated a much greater range in hyporheic redox conditions compared to high-flux zones, and chemical responses to changing flux rates were consistent with those predicted from the empirical relationship between redox condition and residence time. The Raz tracer revealed that hyporheic flow paths have strong net aerobic respiration, particularly at higher residence time, but this reactive exchange did not affect the net stream signal at the reach scale.

  3. Physiotherapists' perceived motivators and barriers for organizing physical activity for older long-term care facility residents.

    PubMed

    Baert, Veerle; Gorus, Ellen; Guldemont, Nele; De Coster, Sofie; Bautmans, Ivan

    2015-05-01

    Information regarding factors that hinder or stimulate older adults in long-term care facilities (LTCF) for being physically active is available in the literature, but much less is known regarding perceived motivators and barriers among physiotherapists (PTs) to organize physical activity (PA) in LTCF. The main purpose of this study was to examine factors influencing PTs to organize PA in LTCF for older adults. A secondary goal was to examine the PTs' knowledge about and their barriers at the PA guidelines for older adults of the World Health Organization (WHO). A mixed qualitative and quantitative study was carried out using semistructured interviews (n = 24) followed by an online survey (n = 254). As a frame the social-ecological model (McLeroy) was used, distinguishing factors at the intrapersonal, interpersonal, and community level. In the qualitative component the PTs reported 41 motivators and 35 barriers for organizing PA in LTCF. The survey revealed that although the majority of the respondents (71%) are convinced of the usefulness of PA in LTCF, 84% are not familiar with the WHO-guidelines. Seventy-five percent of the respondents believe that the WHO-guidelines are not feasible for LTCF-residents. The strongest motivators on the intrapersonal level were maintaining the independence of the residents (98%), reducing the risk of falling (98%), and improving the physical (93%) and psychological (90%) wellbeing of LTCF-residents. The social interaction among LTCF-residents (91%) during PA was the strongest motivator on the interpersonal level. Motivators on the community level are the belief that PA is the basis of their physiotherapeutic work (89%) and that offering varied activities avoids PA becoming monotonous (71%). Barriers on the intra- and interpersonal level were of less influence. On the community level, they felt hindered to organize PA because of lack of time (38%) and the overload of paperwork (33%). This study described different motivators

  4. Fast Pyrolysis Behavior of Banagrass as a Function of Temperature and Volatiles Residence Time in a Fluidized Bed Reactor.

    PubMed

    Morgan, Trevor James; Turn, Scott Q; George, Anthe

    2015-01-01

    A reactor was designed and commissioned to study the fast pyrolysis behavior of banagrass as a function of temperature and volatiles residence time. Four temperatures between 400 and 600°C were examined as well as four residence times between ~1.0 and 10 seconds. Pyrolysis product distributions of bio-oil, char and permanent gases were determined at each reaction condition. The elemental composition of the bio-oils and chars was also assessed. The greatest bio-oil yield was recorded when working at 450°C with a volatiles residence time of 1.4 s, ~37 wt% relative to the dry ash free feedstock (excluding pyrolysis water). The amounts of char (organic fraction) and permanent gases under these conditions are ~4 wt% and 8 wt% respectively. The bio-oil yield stated above is for 'dry' bio-oil after rotary evaporation to remove solvent, which results in volatiles and pyrolysis water being removed from the bio-oil. The material removed during drying accounts for the remainder of the pyrolysis products. The 'dry' bio-oil produced under these conditions contains ~56 wt% carbon which is ~40 wt% of the carbon present in the feedstock. The oxygen content of the 450°C, 1.4 s 'dry' bio-oil is ~38 wt%, which accounts for ~33 wt% of the oxygen in the feedstock. At higher temperature or longer residence time less bio-oil and char is recovered and more gas and light volatiles are produced. Increasing the temperature has a more significant effect on product yields and composition than increasing the volatiles residence time. At 600°C and a volatiles residence time of 1.2 seconds the bio-oil yield is ~21 wt% of the daf feedstock, with a carbon content of 64 wt% of the bio-oil. The bio-oil yield from banagrass is significantly lower than from woody biomass or grasses such as switchgrass or miscanthus, but is similar to barley straw. The reason for the low bio-oil yield from banagrass is thought to be related to its high ash content (8.5 wt% dry basis) and high concentration of alkali

  5. Fast Pyrolysis Behavior of Banagrass as a Function of Temperature and Volatiles Residence Time in a Fluidized Bed Reactor

    PubMed Central

    Morgan, Trevor James; Turn, Scott Q.; George, Anthe

    2015-01-01

    A reactor was designed and commissioned to study the fast pyrolysis behavior of banagrass as a function of temperature and volatiles residence time. Four temperatures between 400 and 600°C were examined as well as four residence times between ~1.0 and 10 seconds. Pyrolysis product distributions of bio-oil, char and permanent gases were determined at each reaction condition. The elemental composition of the bio-oils and chars was also assessed. The greatest bio-oil yield was recorded when working at 450°C with a volatiles residence time of 1.4 s, ~37 wt% relative to the dry ash free feedstock (excluding pyrolysis water). The amounts of char (organic fraction) and permanent gases under these conditions are ~4 wt% and 8 wt% respectively. The bio-oil yield stated above is for 'dry' bio-oil after rotary evaporation to remove solvent, which results in volatiles and pyrolysis water being removed from the bio-oil. The material removed during drying accounts for the remainder of the pyrolysis products. The 'dry' bio-oil produced under these conditions contains ~56 wt% carbon which is ~40 wt% of the carbon present in the feedstock. The oxygen content of the 450°C, 1.4 s 'dry' bio-oil is ~38 wt%, which accounts for ~33 wt% of the oxygen in the feedstock. At higher temperature or longer residence time less bio-oil and char is recovered and more gas and light volatiles are produced. Increasing the temperature has a more significant effect on product yields and composition than increasing the volatiles residence time. At 600°C and a volatiles residence time of 1.2 seconds the bio-oil yield is ~21 wt% of the daf feedstock, with a carbon content of 64 wt% of the bio-oil. The bio-oil yield from banagrass is significantly lower than from woody biomass or grasses such as switchgrass or miscanthus, but is similar to barley straw. The reason for the low bio-oil yield from banagrass is thought to be related to its high ash content (8.5 wt% dry basis) and high concentration of alkali

  6. Fast Pyrolysis Behavior of Banagrass as a Function of Temperature and Volatiles Residence Time in a Fluidized Bed Reactor

    DOE PAGES

    Morgan, Trevor James; Turn, Scott Q.; George, Anthe

    2015-08-26

    A reactor was designed and commissioned to study the fast pyrolysis behavior of banagrass as a function of temperature and volatiles residence time. Four temperatures between 400 and 600°C were examined as well as four residence times between ~1.0 and 10 seconds. Pyrolysis product distributions of bio-oil, char and permanent gases were determined at each reaction condition. The elemental composition of the bio-oils and chars was also assessed. The greatest bio-oil yield was recorded when working at 450°C with a volatiles residence time of 1.4 s, ~37 wt% relative to the dry ash free feedstock (excluding pyrolysis water). The amountsmore » of char (organic fraction) and permanent gases under these conditions are ~4 wt% and 8 wt% respectively. The bio-oil yield stated above is for 'dry' bio-oil after rotary evaporation to remove solvent, which results in volatiles and pyrolysis water being removed from the bio-oil. The material removed during drying accounts for the remainder of the pyrolysis products. The 'dry' bio-oil produced under these conditions contains ~56 wt% carbon which is ~40 wt% of the carbon present in the feedstock. The oxygen content of the 450°C, 1.4 s 'dry' bio-oil is ~38 wt%, which accounts for ~33 wt% of the oxygen in the feedstock. At higher temperature or longer residence time less bio-oil and char is recovered and more gas and light volatiles are produced. Increasing the temperature has a more significant effect on product yields and composition than increasing the volatiles residence time. At 600°C and a volatiles residence time of 1.2 seconds the bio-oil yield is ~21 wt% of the daf feedstock, with a carbon content of 64 wt% of the bio-oil. The bio-oil yield from banagrass is significantly lower than from woody biomass or grasses such as switchgrass or miscanthus, but is similar to barley straw. In conclusion, the reason for the low bio-oil yield from banagrass is thought to be related to its high ash content (8.5 wt% dry basis) and high

  7. Fast Pyrolysis Behavior of Banagrass as a Function of Temperature and Volatiles Residence Time in a Fluidized Bed Reactor

    SciTech Connect

    Morgan, Trevor James; Turn, Scott Q.; George, Anthe

    2015-08-26

    A reactor was designed and commissioned to study the fast pyrolysis behavior of banagrass as a function of temperature and volatiles residence time. Four temperatures between 400 and 600°C were examined as well as four residence times between ~1.0 and 10 seconds. Pyrolysis product distributions of bio-oil, char and permanent gases were determined at each reaction condition. The elemental composition of the bio-oils and chars was also assessed. The greatest bio-oil yield was recorded when working at 450°C with a volatiles residence time of 1.4 s, ~37 wt% relative to the dry ash free feedstock (excluding pyrolysis water). The amounts of char (organic fraction) and permanent gases under these conditions are ~4 wt% and 8 wt% respectively. The bio-oil yield stated above is for 'dry' bio-oil after rotary evaporation to remove solvent, which results in volatiles and pyrolysis water being removed from the bio-oil. The material removed during drying accounts for the remainder of the pyrolysis products. The 'dry' bio-oil produced under these conditions contains ~56 wt% carbon which is ~40 wt% of the carbon present in the feedstock. The oxygen content of the 450°C, 1.4 s 'dry' bio-oil is ~38 wt%, which accounts for ~33 wt% of the oxygen in the feedstock. At higher temperature or longer residence time less bio-oil and char is recovered and more gas and light volatiles are produced. Increasing the temperature has a more significant effect on product yields and composition than increasing the volatiles residence time. At 600°C and a volatiles residence time of 1.2 seconds the bio-oil yield is ~21 wt% of the daf feedstock, with a carbon content of 64 wt% of the bio-oil. The bio-oil yield from banagrass is significantly lower than from woody biomass or grasses such as switchgrass or miscanthus, but is similar to barley straw. In conclusion, the reason for the low bio-oil yield from banagrass is thought to be related to its high ash content (8.5 wt% dry basis) and high

  8. Radiogenic and Radioactive Isotopic Evidence for a Dynamic Residence Time of the Athabasca Glacier Subglacial Water

    NASA Astrophysics Data System (ADS)

    Arendt, C. A.; Aciego, S.; Sims, K. W.; Aarons, S. M.

    2011-12-01

    Little is known about the time it takes precipitation, input of water from reservoirs, surface melt, and basal melt to migrate to the base of a glacier and discharge. Previous work on the residence time of subglacial water has proven to be either inconclusive or inconsistent. Our research will address the primary subglacial water questions; the flux of subglacial water correlates directly to the mass balance of a glacier but what role does subglacial water storage play in that mass balance? Can we determine residence time of subglacial water? And, how variable is residence time seasonally and on longer time scales? The regional focus of our research is the Athabasca Glacier, part of the Columbia Icefield located in Jasper National Park, Alberta, Canada. Uranium-series (U-series) dating methods based on the ingrowth of daughter isotopes from parents (234U, 230Th and 222Rn from the primary parent 238U) have been used to study the residence time of aquifer systems. Here we show the feasibility of applying these techniques to subglacial water. Samples were collected over two 25-day field periods to account for hydrological and chemical fluctuations between the onset of melt and peak melt. Daily physical observations, 222Rn concentrations (from a Durridge RAD7), conductivity, total alkalinity, pH, maximum velocity, and discharge measurements were taken. Fifty daily 10-40L subglacial water and filtered sediment samples were collected and filtered at our collection site in the main channel at the toe of the Athabasca Glacier. The 238U /234U and 87Sr/86Sr isotopic compositions and U, Th, and Sr concentrations of the filtrate and captured sediments is pending. We will extrapolate the residence time of the water based on the accumulation of 234U and 230Th in our samples from alpha decay, which can be coupled to a radiometric timescale. Given that the 238U /234U and 234U/230Th isotopic composition of subglacial water is dependent on recoil and sediment dissolution processes

  9. Estimation of groundwater residence time using the 36Cl bomb pulse.

    PubMed

    Tosaki, Yuki; Tase, Norio; Sasa, Kimikazu; Takahashi, Tsutomu; Nagashima, Yasuo

    2011-01-01

    We propose a methodology for estimating the residence time of groundwater based on bomb-produced (36)Cl. Water samples were collected from 28 springs and 2 flowing wells located around Mt. Fuji, Central Japan. (36)Cl/Cl ratios in the water samples, determined by accelerator mass spectrometry (AMS), were between 43 × 10(-15) and 412 × 10(-15). A reference time series of the above-background (i.e., bomb-derived) (36)Cl concentration was constructed by linearly scaling the background-corrected Dye-3 data according to the estimated total bomb-produced (36)Cl fallout in the Mt. Fuji area. Assuming piston flow transport, estimates of residence time were obtained by comparing the measured bomb-derived (36)Cl concentrations in spring water with the reference curve. The distribution of (36)Cl-based residence times is basically consistent with that of tritium-based estimates calculated from data presented in previous studies, although the estimated residence times differ between the two tracers. This discrepancy may reflect chlorine recycling via vegetation or the relatively small change in fallout rate, approximately since 1975, which would give rise to large uncertainties in (36)Cl-based estimates of recharge for the period, approximately since 1975. Given the estimated ages for groundwater from flowing wells, dating based on a (36)Cl bomb pulse may be more reliable and sensitive for groundwater recharged before 1975, back as far as the mid-1950s.

  10. OLAND is feasible to treat sewage-like nitrogen concentrations at low hydraulic residence times.

    PubMed

    De Clippeleir, Haydée; Yan, Xungang; Verstraete, Willy; Vlaeminck, Siegfried Elias

    2011-05-01

    Energy-positive sewage treatment can, in principle, be obtained by maximizing energy recovery from concentrated organics and by minimizing energy consumption for concentration and residual nitrogen removal in the main stream. To test the feasibility of the latter, sewage-like nitrogen influent concentrations were treated with oxygen-limited autotrophic nitrification/denitrification (OLAND) in a lab-scale rotating biological contactor at 25°C. At influent ammonium concentrations of 66 and 29 mg N L(-1) and a volumetric loading rate of 840 mg N L(-1) day(-1) yielding hydraulic residence times (HRT) of 2.0 and 1.0 h, respectively, relatively high nitrogen removal rates of 444 and 383 mg N L(-1) day(-1) were obtained, respectively. At low nitrogen levels, adapted nitritation and anammox communities were established. The decrease in nitrogen removal was due to decreased anammox and increased nitratation, with Nitrospira representing 6% of the biofilm. The latter likely occurred given the absence of dissolved oxygen (DO) control, since decreasing the DO concentration from 1.4 to 1.2 mg O(2) L(-1) decreased nitratation by 35% and increased anammox by 32%. Provided a sufficient suppression of nitratation, this study showed the feasibility of OLAND to treat low nitrogen levels at low HRT, a prerequisite to energy-positive sewage treatment.

  11. How are internal medicine residency journal clubs organized, and what makes them successful?

    PubMed

    Sidorov, J

    1995-06-12

    While there has been extensive research on interventions designed to increase knowledge of research methods in the setting of journal clubs, little is known regarding other features that are of potential importance. To my knowledge, no research to date has described the attributes of journal clubs associated with high resident attendance and the avoidance of periodic abandonment. I sought to determine how journal clubs in postgraduate programs in internal medicine are organized and to identify the features associated with high attendance and continuous existence. Mailed cross-sectional survey of the 208 accredited residency programs in internal medicine in the eastern United States. The surveys were mailed to the chief resident in internal medicine in August 1992. Data from 131 residency programs were available (response rate, 64.5%). Mean estimated attendance at the 124 programs with an active journal club was 58.5% (range, 7% to 100%); 86 (65.6%) of the clubs were in continuous existence for 2 years or longer. Fifty-two journal clubs (41.9%) were described as independent of any faculty clubs, and 62 (50.0%) emphasized original research. The number of articles reviewed per session ranged from one to six, but the majority reviewed two articles, usually during a 1-hour period, most often during the lunch hour. Seventy-two programs (58.1%) described club attendance as mandatory. The provision of food was a regular feature of 83 (66.9%) of the journal clubs, and the majority of clubs with food regularly rely on funding support for the food from pharmaceutical companies. Participation of faculty in the scheduling of the club, assigning articles, and overall coordination varied, but in 29 (22.1%) of the clubs, faculty provided formal teaching of critical appraisal skills, clinical epidemiology, and biostatistics. Fewer house staff, a mandatory attendance requirement, being independent of a faculty journal club, and formal teaching were associated with high attendance

  12. Factors Associated with Time to Identify Physical Problems of Nursing Home Residents with Dementia

    PubMed Central

    Kovach, Christine R.; Logan, Brent R.; Simpson, Michelle R.; Reynolds, Sheila

    2010-01-01

    This study describes new problems emerging over six weeks for nursing home residents with advanced dementia and factors associated with time to identify the problems. The sample of 65 developed 149 new acute problems or exacerbations of existing conditions over the six weeks of data collection. The majority of these problems involved uncontrolled pain, new infections and severe psychoses. Nurse assessment skill was associated with a shorter time to identify the new problem and more time spent on the problem. A higher ratio of new to existing interventions was also associated with a shorter time to identify the problem. Other patient characteristics associated with time to identify problems included non-specific vocalizations, physical signs, cognitive status and length of stay. While future research is warranted, findings from this study highlight the frequency of problems requiring treatment and suggest that improved assessment of residents may decrease the time to identify new problems. PMID:20237337

  13. Geospatially Analyzed Groundwater Residence Time as a Tool for Sustainable Groundwater Management

    NASA Astrophysics Data System (ADS)

    Moran, J. E.; Visser, A.; Singleton, M. J.; Hillegonds, D.; Esser, B. K.

    2015-12-01

    Managing groundwater during California's drought and satisfying the requirements of the 2014 Sustainable Groundwater Management Act will require multiple approaches to quantifying rates of change in groundwater storage in the heavily exploited basins around the state. Mean groundwater residence times are useful for developing sustainability goals in that the mean residence time is a measure of the aquifer turnover, or renewal time. The California Groundwater Ambient Monitoring and Assessment program is unique among groundwater monitoring programs in that multiple analyses allow estimation of groundwater residence time. For example, over 4,000 tritium and noble gas analyses have been carried out in wells across California, allowing calculation of tritium-helium groundwater age, spatial analysis of groundwater residence times, and identification of the depth of the transition from modern to pre-modern groundwater. Areas of rapid turnover identified by young ages can be compared with areas that have been identified as being hydrogeologically vulnerable based on physical measures such as mapped permeability, confining conditions, or recharge/discharge rates. Application of groundwater residence time as a tool for sustainable groundwater management has advantages and potential pitfalls. The uncertainty associated with calculated ages and the complexity of broad age distributions in long-screened wells are some of the associated challenges. However, geospatial analysis of isotopic age data prove useful for highlighting areas where isotopic ages are not in agreement with other measures of groundwater renewal time, and where ages may therefore be helpful in setting sustainability goals. Initial comparisons suggest that isotopic ages delineate the extent of influence of artificial recharge more precisely than numerical models and that some areas in the Sierra foothills and Coast Range, identified as active recharge areas, host pre-modern groundwater, suggesting the need for

  14. Residence times in river basins as determined by analysis of long-term tritium records

    NASA Astrophysics Data System (ADS)

    Michel, Robert L.

    1992-01-01

    The US Geological Survey has maintained a network of stations to collect samples for the measurement of tritium concentrations in precipitation and streamflow since the early 1960s. Tritium data from outflow waters of river basins draining 4500-75000 km 2 are used to determine average residence times of water within the basins. The basins studied are the Colorado River above Cisco, Utah; the Kissimmee River above Lake Okeechobee, Florida; the Mississippi River above Anoka, Minnesota; the Neuse River above Streets Ferry Bridge near Vanceboro, North Carolina; the Potomac River above Point of Rocks, Maryland; the Sacramento River above Sacramento, California; the Susquehanna River above Harrisburg, Pennsylvania. The basins are modeled with the assumption that the outflow in the river comes from two sources—prompt (within-year) runoff from precipitation, and flow from the long-term reservoirs of the basin. Tritium concentration in the outflow water of the basin is dependent on three factors: (1) tritium concentration in runoff from the long-term reservoir, which depends on the residence time for the reservoir and historical tritium concentrations in precipitation; (2) tritium concentrations in precipitation (the within-year runoff component); (3) relative contributions of flow from the long-term and within-year components. Predicted tritium concentrations for the outflow water in the river basins were calculated for different residence times and for different relative contributions from the two reservoirs. A box model was used to calculate tritium concentrations in the long-term reservoir. Calculated values of outflow tritium concentrations for the basin were regressed against the measured data to obtain a slope as close as possible to 1. These regressions assumed an intercept of zero and were carried out for different values of residence time and reservoir contribution to maximize the fit of modeled versus actual data for all the above rivers. The final slopes of

  15. Residence times in river basins as determined by analysis of long-term tritium records

    USGS Publications Warehouse

    Michel, R.L.

    1992-01-01

    The US Geological Survey has maintained a network of stations to collect samples for the measurement of tritium concentrations in precipitation and streamflow since the early 1960s. Tritium data from outflow waters of river basins draining 4500-75000 km2 are used to determine average residence times of water within the basins. The basins studied are the Colorado River above Cisco, Utah; the Kissimmee River above Lake Okeechobee, Florida; the Mississippi River above Anoka, Minnesota; the Neuse River above Streets Ferry Bridge near Vanceboro, North Carolina; the Potomac River above Point of Rocks, Maryland; the Sacramento River above Sacramento, California; the Susquehanna River above Harrisburg, Pennsylvania. The basins are modeled with the assumption that the outflow in the river comes from two sources-prompt (within-year) runoff from precipitation, and flow from the long-term reservoirs of the basin. Tritium concentration in the outflow water of the basin is dependent on three factors: (1) tritium concentration in runoff from the long-term reservoir, which depends on the residence time for the reservoir and historical tritium concentrations in precipitation; (2) tritium concentrations in precipitation (the within-year runoff component); (3) relative contributions of flow from the long-term and within-year components. Predicted tritium concentrations for the outflow water in the river basins were calculated for different residence times and for different relative contributions from the two reservoirs. A box model was used to calculate tritium concentrations in the long-term reservoir. Calculated values of outflow tritium concentrations for the basin were regressed against the measured data to obtain a slope as close as possible to 1. These regressions assumed an intercept of zero and were carried out for different values of residence time and reservoir contribution to maximize the fit of modeled versus actual data for all the above rivers. The final slopes of the

  16. Balance and residence times of 210Pb and 210Po in surface waters of the northwestern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Masqué, P.; Sanchez-Cabeza, J. A.; Bruach, J. M.; Palacios, E.; Canals, M.

    2002-10-01

    Concentrations of the naturally occurring radionuclides 210Pb and 210Po were determined in both the dissolved (<0.2 μm) and particulate (>0.2 μm) fractions in surface waters of the northwestern Mediterranean Sea. About 4-8% of the 210Pb activity was observed to be associated to particles, which were determined as being mostly biogenic. The 210Po content in the particulate fraction was generally greater than that of 210Pb, accounting for about 20% of the total activity. Total activities of 210Pb and 210Po were found to be in equilibrium. 226Ra concentrations were also determined in an effort to investigate its occurrence in Mediterranean waters. 226Ra was in excess to both 210Pb and 210Po, with a mean concentration of 1.72±0.03 Bq m -3. Steady-state balance equations of the three radionuclides permit calculation of residence times for 210Pb and 210Po in surface waters (0.8 and 3.0 yr, respectively). 210Po residence times were almost one order of magnitude higher than mostly reported values. Polonium is known to manifest higher affinity and different binding mechanisms (by entering the organic cycle) to biogenic material than 210Pb. Several processes, such as 210Po uptake by buoyant particles and recycling of organic matter in the surface layer, could lead to such long residence times of 210Po and, therefore, of organic particles in surface waters. Larger 210Po atmospheric fluxes than those here considered and inputs from rivers and/or fine-grained sediment resuspension could also help to explain the observation, although presumably to a lesser extent.

  17. Naturalization of central European plants in North America: species traits, habitats, propagule pressure, residence time.

    PubMed

    Pyšek, Petr; Manceur, Ameur M; Alba, Christina; McGregor, Kirsty F; Pergl, Jan; Stajerová, Katerina; Chytrý, Milan; Danihelka, Jiří; Kartesz, John; Klimesova, Jitka; Lucanova, Magdalena; Moravcová, Lenka; Nishino, Misako; Sadlo, Jiri; Suda, Jan; Tichy, Lubomir; Kühn, Ingolf

    2015-03-01

    The factors that promote invasive behavior in introduced plant species occur across many scales of biological and ecological organization. Factors that act at relatively small scales, for example, the evolution of biological traits associated with invasiveness, scale up to shape species distributions among different climates and habitats, as well as other characteristics linked to invasion, such as attractiveness for cultivation (and by extension propagule pressure). To identify drivers of invasion it is therefore necessary to disentangle the contribution of multiple factors that are interdependent. To this end, we formulated a conceptual model describing the process of invasion of central European species into North America based on a sequence of "drivers." We then used confirmatory path analysis to test whether the conceptual model is supported by a statistical model inferred from a comprehensive database containing 466 species. The path analysis revealed that naturalization of central European plants in North America, in terms of the number of North American regions invaded, most strongly depends on residence time in the invaded range and the number of habitats occupied by species in their native range. In addition to the confirmatory path analysis, we identified the effects of various biological traits on several important drivers of the conceptualized invasion process. The data supported a model that included indirect effects of biological traits on invasion via their effect on the number of native range habitats occupied and cultivation in the native range. For example, persistent seed banks and longer flowering periods are positively correlated with number of native habitats, while a stress-tolerant life strategy is negatively correlated with native range cultivation. However, the importance of the biological traits is nearly an order of magnitude less than that of the larger scale drivers and highly dependent on the invasion stage (traits were associated

  18. Recruitment, growth and residence time of fishes in a tropical Australian mangrove system

    NASA Astrophysics Data System (ADS)

    Robertson, Alistar I.; Duke, Norman C.

    1990-11-01

    Twenty fish species accounted for > 96% of the catch by numbers in mangrove habitats in Alligator Creek, in tropical Queensland, Australia. The timing of recruitment, residency status, the period of residence and growth of fish during the time they spent in the mangrove habitat was assessed by examining gonad maturity and following changes in size-frequency plots for each species over 13 months. Five species were permanent residents, completing their life-cycles in mangrove swamps; eight were 'long-term' temporary residents, being present for ˜ 1 year as juveniles before moving to other near-shore habitats; and seven were 'short-term' residents or sporadic users of the mangrove habitat. Amongst the latter group, four species lived in the mangrove habitat for between 1 and 4 consecutive months, while three engraulid species appeared to move rapidly, and often, between mangrove and other near-shore habitats. One of the resident species spawned and recruited throughout the year, but recruitment for most species was highly seasonal, being concentrated in the late dry season (October) to mid wet season (February) period. Temporary resident species dominated the fish community in the wet season (December-April), but resident species comprised more than 90% of total fish numbers in the mid dry season (August) after temporary residents left the mangroves in the early dry season. Several species had more than one peak of recruitment during the wet season. The cohort of 0 + aged Leiognathus equulus which recruited in December grew more rapidly and remained in the mangroves for a shorter period than the cohort which recruited later in the wet season (February). Only nine of the 20 species examined are strictly dependent on mangrove-lined estuaries, the remaining 11 are captured in significant numbers in other near-shore habitats. Only four of the 20 species are of direct commercial importance in Australia, but most are major prey for several valuable, commercial species

  19. Temperature, plant species and residence time effects on nitrogen removal in model treatment wetlands.

    PubMed

    Allen, C R; Stein, O R; Hook, P B; Burr, M D; Parker, A E; Hafla, E C

    2013-01-01

    Total nitrogen (TN) removal in treatment wetlands (TWs) is challenging due to nitrogen cycle complexity and the variation of influent nitrogen species. Plant species, season, temperature and hydraulic loading most likely influence root zone oxygenation and appurtenant nitrogen removal, especially for ammonium-rich wastewater. Nitrogen data were collected from two experiments utilizing batch-loaded (3-, 6-, 9- and 20-day residence times), sub-surface TWs monitored for at least one year during which temperature was varied between 4 and 24 °C. Synthetic wastewater containing 17 mg/l N as NH4 and 27 mg/l amino-N, 450 mg/l chemical oxygen demand (COD), and 13 mg/l SO4-S was applied to four replicates of Carex utriculata, Schoenoplectus acutus and Typha latifolia and unplanted controls. Plant presence and species had a greater effect on TN removal than temperature or residence time. Planted columns achieved approximately twice the nitrogen removal of unplanted controls (40-95% versus 20-50% removal) regardless of season and temperature. TWs planted with Carex outperformed both Typha and Schoenoplectus and demonstrated less temperature dependency. TN removal with Carex was excellent at all temperatures and residence times; Schoenoplectus and Typha TN removal improved at longer residence times. Reductions in TN were not accompanied by increases in NO3, which was consistently below 1 mg/l N.

  20. Water Residence Times and Runoff Sources Across an Urbanizing Gradient (Croton Water Supply Area, New York)

    NASA Astrophysics Data System (ADS)

    Vitvar, T.; Burns, D. A.; Duncan, J. M.; Hassett, J. M.; McDonnell, J. J.

    2002-12-01

    Water residence times and nutrient budgets were measured in 3 small watersheds in the Croton water supply area, NY. The watersheds (less than 1km 2) have different levels of urbanization (natural, semi-developed and fully developed), different mechanisms of runoff generation (quick flow on impervious surfaces and slow flow through the subsurface) and different watershed landscape characteristics (wet zones, hillslopes). Throughfall, stream water, soil water and groundwater in the saturated zone were sampled bi-weekly during a period of up to 2 years and analyzed for major chemical constituents, oxygen-18 content, and nitrogen species. Mean residence times of the stream water of about 30 weeks were estimated using Oxygen-18 and Helium-3/Tritium isotopes for all 3 watersheds. There was no significant difference in mean residence times among the three study watersheds, despite their different levels of urbanization. However, residence times from a few weeks up to ca 2 years vary within the watersheds, depending on the local runoff sources and their geographical conditions (riparian and hillslope topography, aquifer type). The runoff sources were quantified for selected streamwater and groundwater sampling sites using the end member mixing analysis technique (EMMA). The mixing analysis shows the impact of the runoff sources on runoff generation in the selected watersheds, i.e. it shows how big is the impact of urbanization on the runoff generation and how big is the natural control. These results may be useful in watershed management and planning of further urbanization in the Croton water supply area.

  1. Water residence times and nutrient budgets across an urbanizing gradient (Croton water supply area, NY)

    NASA Astrophysics Data System (ADS)

    Vitvar, T.; Burns, D. A.; Duncan, J. M.; Hassett, J. M.; Mitchell, M. J.

    2002-05-01

    Water residence times and nutrient budgets in 3 small watersheds in the Croton water supply area, NY, were examined. The watersheds (less than 1km 2) have different level of urbanization (natural, semi-developed and fully developed), different mechanisms of runoff generation (quick flow on roads and slow flow through subsurface) and different watershed landscape characteristics (wet zones, hillslopes) . Measurements of the comprehensive chemical suite incl. components of nitrogen budget in the throughfall, stream water, soil water and groundwater in the saturated zone were performed bi-weekly over a period up to 2 years. Mean water residence times of the stream water were estimated using Oxygen-18 and Helium-3/Tritium isotopes. There are significant differences in the chemical composition and decrease of nitrification intensity and of mean streamwater residence time along the increasing watershed development. Within each watershed, longer water residence times (up to over 2 years) were estimated in the wetland zones without direct communication with streams in comparison to hillslope areas (up to over 1 year). The results can be used in watershed management and planning of the further urbanization of this water supply area.

  2. Untangling hyporheic residence time distributions and whole stream metabolisms using a hydrological process model

    NASA Astrophysics Data System (ADS)

    Altenkirch, Nora; Mutz, Michael; Molkenthin, Frank; Zlatanovic, Sanja; Trauth, Nico

    2016-04-01

    The interaction of the water residence time in hyporheic sediments with the sediment metabolic rates is believed to be a key factor controlling whole stream metabolism. However, due to the methodological difficulties, there is little data that investigates this fundamental theory of aquatic ecology. Here, we report on progress made to combine numerical modeling with a series of manipulation to laboratory flumes overcoming methodological difficulties. In these flumes, hydraulic conditions were assessed using non-reactive tracer and heat pulse sensor. Metabolic activity was measured as the consumption and production of oxygen and the turnover of reactive tracers. Residence time and metabolic processes were modeled using a multicomponent reactive transport code called Min3P and calibrated with regard to the hydraulic conditions using the results obtained from the flume experiments. The metabolic activity was implemented in the model via Monod type expressions e.g. for aerobic respiration rates. A number of sediment structures differing in residence time distributions were introduced in both, the model and the flumes, specifically to model the biogeochemical performance and to validate the model results. Furthermore, the DOC supply and surface water flow velocity were altered to test the whole stream metabolic response. Using the results of the hydrological process model, a sensitivity analysis of the impact of residence time distributions on the metabolic activity could yield supporting proof of an existing link between the two.

  3. LABORATORY AND NUMERICAL INVESTIGATIONS OF RESIDENCE TIME DISTRIBUTION OF FLUIDS IN LAMINAR FLOW STIRRED ANNULAR PHOTOREACTOR

    EPA Science Inventory

    Laboratory and Numerical Investigations of Residence Time Distribution of Fluids in Laminar Flow Stirred Annular Photoreactor

    E. Sahle-Demessie1, Siefu Bekele2, U. R. Pillai1

    1U.S. EPA, National Risk Management Research Laboratory
    Sustainable Technology Division,...

  4. HOW TO MODEL HYDRODYNAMICS AND RESIDENCE TIMES OF 27 ESTUARIES IN 4 MONTHS

    EPA Science Inventory

    The hydrodynamics and residence times of 27 embayments were modeled during the first year of a project whose goal is to define the relation between nitrogen loadings and ecological responses of 44 systems that range from small to the size of Narragansett Bay and Buzzards Bay. The...

  5. EFFECT OF RESIDENCE TIME ON ANNUAL EXPORT AND DENITRIFICATION OF NITROGEN IN ESTUARIES: A MODEL ANALYSIS

    EPA Science Inventory

    A simple model of annual average response of an estuary to mean nitrogen loading rate and freshwater residence time was developed and tested. It uses nitrogen inputs from land, deposition from the atmosphere, and first-order calculations of internal loss rate and export to perfor...

  6. Residence Time Distribution Measurement and Analysis of Pilot-Scale Pretreatment Reactors for Biofuels Production: Preprint

    SciTech Connect

    Sievers, D.; Kuhn, E.; Tucker, M.; Stickel, J.; Wolfrum, E.

    2013-06-01

    Measurement and analysis of residence time distribution (RTD) data is the focus of this study where data collection methods were developed specifically for the pretreatment reactor environment. Augmented physical sampling and automated online detection methods were developed and applied. Both the measurement techniques themselves and the produced RTD data are presented and discussed.

  7. HOW TO MODEL HYDRODYNAMICS AND RESIDENCE TIMES OF 27 ESTUARIES IN 4 MONTHS

    EPA Science Inventory

    The hydrodynamics and residence times of 27 embayments were modeled during the first year of a project whose goal is to define the relation between nitrogen loadings and ecological responses of 44 systems that range from small to the size of Narragansett Bay and Buzzards Bay. The...

  8. EFFECT OF RESIDENCE TIME ON ANNUAL EXPORT AND DENITRIFICATION OF NITROGEN IN ESTUARIES: A MODEL ANALYSIS

    EPA Science Inventory

    A simple model of annual average response of an estuary to mean nitrogen loading rate and freshwater residence time was developed and tested. It uses nitrogen inputs from land, deposition from the atmosphere, and first-order calculations of internal loss rate and export to perfor...

  9. LABORATORY AND NUMERICAL INVESTIGATIONS OF RESIDENCE TIME DISTRIBUTION OF FLUIDS IN LAMINAR FLOW STIRRED ANNULAR PHOTOREACTOR

    EPA Science Inventory

    Laboratory and Numerical Investigations of Residence Time Distribution of Fluids in Laminar Flow Stirred Annular Photoreactor

    E. Sahle-Demessie1, Siefu Bekele2, U. R. Pillai1

    1U.S. EPA, National Risk Management Research Laboratory
    Sustainable Technology Division,...

  10. Residence times of alluvium in an east Texas stream as indicated by sediment color

    Treesearch

    Jonathan D. Phillips; Daniel A. Marion

    2001-01-01

    The relationships between sediment production, storage, and transport in fluvial systems are complex and variable. Key issues in addressing these relationships are the residence times of sediment delivered to the channel, and the proportion derived from recent upland erosion as opposed to remobilized alluvium. The systematic changes in iron geochemistry often...

  11. Dynamics of nitrate production and removal as a function of residence time in the hyporheic zone

    Treesearch

    Jay P. Zarnetske; Roy Haggerty; Steven M. Wondzell; Michelle A. Baker

    2011-01-01

    Biogeochemical reactions associated with stream nitrogen cycling, such as nitrification and denitrification, can be strongly controlled by water and solute residence times in the hyporheic zone (HZ). We used a whole-stream steady state 15N-Iabeled nitrate and conservative tracer addition to investigate the spatial and temporal physiochemical...

  12. Bridging Home: Building Relationships between Immigrant and Long-Time Resident Youth

    ERIC Educational Resources Information Center

    Dryden-Peterson, Sarah

    2010-01-01

    Background: There is rising evidence that relationships that bridge between immigrants and long-time residents are critical to immigrant integration and to the overall heath of communities. The processes by which this bridging social capital is built are not well understood. Schools in new immigrant destinations, as spaces in which diverse youth…

  13. Conceptual framework for model-based analysis of residence time distribution in twin-screw granulation.

    PubMed

    Kumar, Ashish; Vercruysse, Jurgen; Vanhoorne, Valérie; Toiviainen, Maunu; Panouillot, Pierre-Emmanuel; Juuti, Mikko; Vervaet, Chris; Remon, Jean Paul; Gernaey, Krist V; De Beer, Thomas; Nopens, Ingmar

    2015-04-25

    Twin-screw granulation is a promising continuous alternative for traditional batchwise wet granulation processes. The twin-screw granulator (TSG) screws consist of transport and kneading element modules. Therefore, the granulation to a large extent is governed by the residence time distribution within each module where different granulation rate processes dominate over others. Currently, experimental data is used to determine the residence time distributions. In this study, a conceptual model based on classical chemical engineering methods is proposed to better understand and simulate the residence time distribution in a TSG. The experimental data were compared with the proposed most suitable conceptual model to estimate the parameters of the model and to analyse and predict the effects of changes in number of kneading discs and their stagger angle, screw speed and powder feed rate on residence time. The study established that the kneading block in the screw configuration acts as a plug-flow zone inside the granulator. Furthermore, it was found that a balance between the throughput force and conveying rate is required to obtain a good axial mixing inside the twin-screw granulator. Although the granulation behaviour is different for other excipients, the experimental data collection and modelling methods applied in this study are generic and can be adapted to other excipients.

  14. Racing Against the Clock: Internal Medicine Residents' Time Spent On Electronic Health Records

    PubMed Central

    Chen, Lu; Guo, Uta; Illipparambil, Lijo C.; Netherton, Matt D.; Sheshadri, Bhairavi; Karu, Eric; Peterson, Stephen J.; Mehta, Parag H.

    2016-01-01

    Background Since the late 1980s, resident physicians have spent increasing amounts of time on electronic health record (EHR) data entry and retrieval. Objective longitudinal data measuring time spent on the EHR are lacking. Objective We sought to quantify the time actually spent using the EHR by all first-year internal medicine residents in a single program (N = 41). Methods Active EHR usage data were collected from the audit logs for May, July, and October 2014 and January 2015. Per recommendations from our EHR vendor (Cerner Corporation), active EHR usage time was defined as more than 15 keystrokes, or 3 mouse clicks, or 1700 “mouse miles” per minute. Active EHR usage time was tallied for each patient chart viewed each day and termed an electronic patient record encounter (EPRE). Results In 4 months, 41 interns accumulated 18 322 hours of active EHR usage in more than 33 733 EPREs. Each intern spent on average 112 hours per month on 206 EPREs. Interns spent more time in July compared to January (41 minutes versus 30 minutes per EPRE, P < .001). Time spent on the EHR in January echoed that of the previous May (30 minutes versus 29 minutes, P = .40). Conclusions First-year residents spent a significant amount of time actively using the EHR, achieving maximal proficiency on or before January of the academic year. Decreased time spent on the EHR may reflect greater familiarity with the EHR, growing EHR efficiencies, or other factors. PMID:26913101

  15. The role of residence times in two-patch dengue transmission dynamics and optimal strategies.

    PubMed

    Lee, Sunmi; Castillo-Chavez, Carlos

    2015-06-07

    The reemergence and geographical dispersal of vector-borne diseases challenge global health experts around the world and in particular, dengue poses increasing difficulties in the Americas, due in part to explosive urban and semi-urban growth, increases of within and between region mobility, the absence of a vaccine, and the limited resources available for public health services. In this work, a simple deterministic two-patch model is introduced to assess the impact of dengue transmission dynamics in heterogeneous environments. The two-patch system models the movement (e.g. urban versus rural areas residence times) of individuals between and within patches/environments using residence-time matrices with entries that budget within and between host patch relative residence times, under the assumption that only the human budgets their residence time across regions. Three scenarios are considered: (i) resident hosts in Patch i visit patch j, where i≠j but not the other way around, a scenario referred to as unidirectional motion; (ii) symmetric bi-directional motion; and (iii) asymmetric bi-directional motion. Optimal control theory is used to identify and evaluate patch-specific control measures aimed at reducing dengue prevalence in humans and vectors at a minimal cost. Optimal policies are computed under different residence-matrix configurations mentioned above as well as transmissibility scenarios characterized by the magnitude of the basic reproduction number. Optimal patch-specific polices can ameliorate the impact of epidemic outbreaks substantially when the basic reproduction number is moderate. The final patch-specific epidemic size variation increases as the residence time matrix moves away from the symmetric case (asymmetry). As expected, the patch where individuals spend most of their time or in the patch where transmissibility is higher tend to support larger patch-specific final epidemic sizes. Hence, focusing on intervention that target areas where

  16. Assessing the effect of different river water level interpolation schemes on modeled groundwater residence times

    NASA Astrophysics Data System (ADS)

    Diem, Samuel; Renard, Philippe; Schirmer, Mario

    2014-03-01

    Obtaining a quantitative understanding of river-groundwater interactions is of high practical relevance, for instance within the context of riverbank filtration and river restoration. Modeling interactions between river and groundwater requires knowledge of the river's spatiotemporal water level distribution. The dynamic nature of riverbed morphology in restored river reaches might result in complex river water level distributions, including disconnected river branches, nonlinear longitudinal water level profiles and morphologically induced lateral water level gradients. Recently, two new methods were proposed to accurately and efficiently capture 2D water level distributions of dynamic rivers. In this study, we assessed the predictive capability of these methods with respect to simulated groundwater residence times. Both methods were used to generate surface water level distributions of a 1.2 km long partly restored river reach of the Thur River in northeastern Switzerland. We then assigned these water level distributions as boundary conditions to a 3D steady-state groundwater flow and transport model. When applying either of the new methods, the calibration-constrained groundwater flow field accurately predicted the spatial distribution of groundwater residence times; deviations were within a range of 30% when compared to residence times obtained using a reference method. We further tested the sensitivity of the simulated groundwater residence times to a simplified river water level distribution. The negligence of lateral river water level gradients of 20-30 cm on a length of 200 m caused errors of 40-80% in the calibration-constrained groundwater residence time distribution compared to results that included lateral water level gradients. The additional assumption of a linear water level distribution in longitudinal river direction led to deviations from the complete river water level distribution of up to 50 cm, which caused wide-spread errors in simulated

  17. Burnout syndrome during residency in internal medicine and pediatrics in a country without working time directive.

    PubMed

    Aksoy, Duygu Yazgan; Durusu Tanriover, Mine; Unal, Sule; Dizdar, Omer; Kalyoncu, Umut; Karakaya, Jale; Unal, Serhat; Kale, Gulsev

    2014-01-01

    The purpose of this paper is to demonstrate burnout syndrome among internal medicine and pediatrics residents in a country that does not have the working time directive (WTD) and also to determine the risk factors and consequent impact on efficient functioning in clinical areas. A 57-item questionnaire was given to internal medicine and pediatrics residents. Responses from 22 pediatrics and 33 internal medicine residents were evaluated. Demographic findings, burnout scores, having hobbies, social activities and reading books unrelated to medicine were similar between the two groups. Six pediatrics residents (27.3 per cent) and 11 (33.3 per cent) internal medicine residents met the criteria for clinically significant burnout. Personal accomplishment scores and reading books unrelated to medicine were found to be related to burnout. Burnout is a syndrome characterized by depersonalization, emotional exhaustion and a low sense of personal accomplishment. It is important to document burnout in countries where WTDs are not implemented. Further studies might demonstrate burnout's effect on patient safety, service quality and physician's performance.

  18. Compound Selectivity and Target Residence Time of Kinase Inhibitors Studied with Surface Plasmon Resonance.

    PubMed

    Willemsen-Seegers, Nicole; Uitdehaag, Joost C M; Prinsen, Martine B W; de Vetter, Judith R F; de Man, Jos; Sawa, Masaaki; Kawase, Yusuke; Buijsman, Rogier C; Zaman, Guido J R

    2017-02-17

    Target residence time (τ) has been suggested to be a better predictor of the biological activity of kinase inhibitors than inhibitory potency (IC50) in enzyme assays. Surface plasmon resonance binding assays for 46 human protein and lipid kinases were developed. The association and dissociation constants of 80 kinase inhibitor interactions were determined. τ and equilibrium affinity constants (KD) were calculated to determine kinetic selectivity. Comparison of τ and KD or IC50 values revealed a strikingly different view on the selectivity of several kinase inhibitors, including the multi-kinase inhibitor ponatinib, which was tested on 10 different kinases. In addition, known pan-Aurora inhibitors resided much longer on Aurora B than on Aurora A, despite having comparable affinity for Aurora A and B. Furthermore, the γ/δ-selective PI3K inhibitor duvelisib and the δ-selective drug idelalisib had similar 20-fold selectivity for δ- over γ-isoform but duvelisib resided much longer on both targets.

  19. Influence of temperature on patch residence time in parasitoids: physiological and behavioural mechanisms

    NASA Astrophysics Data System (ADS)

    Moiroux, Joffrey; Abram, Paul K.; Louâpre, Philippe; Barrette, Maryse; Brodeur, Jacques; Boivin, Guy

    2016-04-01

    Patch time allocation has received much attention in the context of optimal foraging theory, including the effect of environmental variables. We investigated the direct role of temperature on patch time allocation by parasitoids through physiological and behavioural mechanisms and its indirect role via changes in sex allocation and behavioural defences of the hosts. We compared the influence of foraging temperature on patch residence time between an egg parasitoid, Trichogramma euproctidis, and an aphid parasitoid, Aphidius ervi. The latter attacks hosts that are able to actively defend themselves, and may thus indirectly influence patch time allocation of the parasitoid. Patch residence time decreased with an increase in temperature in both species. The increased activity levels with warming, as evidenced by the increase in walking speed, partially explained these variations, but other mechanisms were involved. In T. euproctidis, the ability to externally discriminate parasitised hosts decreased at low temperature, resulting in a longer patch residence time. Changes in sex allocation with temperature did not explain changes in patch time allocation in this species. For A. ervi, we observed that aphids frequently escaped at intermediate temperature and defended themselves aggressively at high temperature, but displayed few defence mechanisms at low temperature. These defensive behaviours resulted in a decreased patch residence time for the parasitoid and partly explained the fact that A. ervi remained for a shorter time at the intermediate and high temperatures than at the lowest temperature. Our results suggest that global warming may affect host-parasitoid interactions through complex mechanisms including both direct and indirect effects on parasitoid patch time allocation.

  20. Influence of temperature on patch residence time in parasitoids: physiological and behavioural mechanisms.

    PubMed

    Moiroux, Joffrey; Abram, Paul K; Louâpre, Philippe; Barrette, Maryse; Brodeur, Jacques; Boivin, Guy

    2016-04-01

    Patch time allocation has received much attention in the context of optimal foraging theory, including the effect of environmental variables. We investigated the direct role of temperature on patch time allocation by parasitoids through physiological and behavioural mechanisms and its indirect role via changes in sex allocation and behavioural defences of the hosts. We compared the influence of foraging temperature on patch residence time between an egg parasitoid, Trichogramma euproctidis, and an aphid parasitoid, Aphidius ervi. The latter attacks hosts that are able to actively defend themselves, and may thus indirectly influence patch time allocation of the parasitoid. Patch residence time decreased with an increase in temperature in both species. The increased activity levels with warming, as evidenced by the increase in walking speed, partially explained these variations, but other mechanisms were involved. In T. euproctidis, the ability to externally discriminate parasitised hosts decreased at low temperature, resulting in a longer patch residence time. Changes in sex allocation with temperature did not explain changes in patch time allocation in this species. For A. ervi, we observed that aphids frequently escaped at intermediate temperature and defended themselves aggressively at high temperature, but displayed few defence mechanisms at low temperature. These defensive behaviours resulted in a decreased patch residence time for the parasitoid and partly explained the fact that A. ervi remained for a shorter time at the intermediate and high temperatures than at the lowest temperature. Our results suggest that global warming may affect host-parasitoid interactions through complex mechanisms including both direct and indirect effects on parasitoid patch time allocation.

  1. How Entrustment Is Informed by Holistic Judgments Across Time in a Family Medicine Residency Program: An Ethnographic Nonparticipant Observational Study.

    PubMed

    Sagasser, Margaretha H; Fluit, Cornelia R M G; van Weel, Chris; van der Vleuten, Cees P M; Kramer, Anneke W M

    2017-06-01

    Entrustment has mainly been conceptualized as delegating discrete professional tasks. Because residents provide most of their patient care independently, not all resident performance is visible to supervisors; the entrustment process involves more than granting discrete tasks. This study explored how supervisors made entrustment decisions based on residents' performance in a long-term family medicine training program. A qualitative nonparticipant observational study was conducted in 2014-2015 at competency-based family medicine residency programs in the Netherlands. Seven supervisor-resident pairs participated. During two days, one researcher observed first-year residents' patient encounters, debriefing sessions, and supervisor-resident educational meetings and interviewed them separately afterwards. Data were collected and analyzed using iterative, phenomenological inductive research methodology. The entrustment process developed over three phases. Supervisors based their initial entrustment on prior knowledge about the resident. In the ensuing two weeks, entrustment decisions regarding independent patient care were derived from residents' observed general competencies necessary for a range of health problems (clinical reasoning, decision making, relating to patients); medical knowledge and skills; and supervisors' intuition. Supervisors provided supervision during and after encounters. Once residents performed independently, supervisors kept reevaluating their decisions, informed by residents' overall growth in competencies rather than by adhering to a predefined set of tasks. Supervisors in family medicine residency training took a holistic approach to trust, based on general competencies, knowledge, skills, and intuition. Entrustment started before training and developed over time. Building trust is a mutual process between supervisor and resident, requiring a good working relationship.

  2. Sustained increase in resident meal time hand hygiene through an interdisciplinary intervention engaging long-term care facility residents and staff.

    PubMed

    O'Donnell, Marguerite; Harris, Tony; Horn, Terancita; Midamba, Blondelle; Primes, Vickie; Sullivan, Nancy; Shuler, Rosalyn; Zabarsky, Trina F; Deshpande, Abhishek; Sunkesula, Venkata C K; Kundrapu, Sirisha; Donskey, Curtis J

    2015-02-01

    Hand hygiene by patients may prevent acquisition and dissemination of health care-associated pathogens, but limited efforts have been made to engage patients in hand hygiene interventions. In a long-term care facility, we found that residents were aware of the importance of hand hygiene, but barriers, such as inaccessible products or difficult to use products, limited compliance. A dramatic and sustained improvement in meal time hand hygiene was achieved through engagement of staff and residents.

  3. Microbial Biogeography along an Estuarine Salinity Gradient: Combined Influences of Bacterial Growth and Residence Time

    PubMed Central

    Crump, Byron C.; Hopkinson, Charles S.; Sogin, Mitchell L.; Hobbie, John E.

    2004-01-01

    Shifts in bacterioplankton community composition along the salinity gradient of the Parker River estuary and Plum Island Sound, in northeastern Massachusetts, were related to residence time and bacterial community doubling time in spring, summer, and fall seasons. Bacterial community composition was characterized with denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA. Average community doubling time was calculated from bacterial production ([14C]leucine incorporation) and bacterial abundance (direct counts). Freshwater and marine populations advected into the estuary represented a large fraction of the bacterioplankton community in all seasons. However, a unique estuarine community formed at intermediate salinities in summer and fall, when average doubling time was much shorter than water residence time, but not in spring, when doubling time was similar to residence time. Sequencing of DNA in DGGE bands demonstrated that most bands represented single phylotypes and that matching bands from different samples represented identical phylotypes. Most river and coastal ocean bacterioplankton were members of common freshwater and marine phylogenetic clusters within the phyla Proteobacteria, Bacteroidetes, and Actinobacteria. Estuarine bacterioplankton also belonged to these phyla but were related to clones and isolates from several different environments, including marine water columns, freshwater sediments, and soil. PMID:15006771

  4. Orthopaedic Surgery Residents and Program Directors Agree on How Time Is Currently Spent in Training and Targets for Improvement.

    PubMed

    Camp, Christopher L; Martin, John R; Karam, Matthew D; Ryssman, Daniel B; Turner, Norman S

    2016-04-01

    Although much attention has been paid to the role of deliberate practice as a means of achieving expert levels of performance in other medical specialties, little has been published regarding its role in maximizing orthopaedic surgery resident potential. As an initial step in this process, this study seeks to determine how residents and program directors (PDs) feel current time spent in training is allocated compared with a theoretical ideal distribution of time. According to residents and PDs, (1) how do resident responsibilities change by level of training as perceived and idealized by residents and PDs? (2) How do resident and PD perceptions of current and ideal time distributions compare with one another? (3) Do the current training structures described by residents and PDs differ from what they feel represents an ideal time allocation construct that maximizes the educational value of residency training? A survey was sent to orthopaedic surgery resident and PD members of the Midwest Orthopedic Surgical Skills Consortium asking how they felt residents' time spent in training was distributed across 10 domains and four operating room (OR) roles and what they felt would be an ideal distribution of that time. Responses were compared between residents and PDs and between current schedules and ideal schedules. Both residents and PDs agreed that time currently spent in training differs by postgraduate year with senior-level residents spending more time in the OR (33.7% ± 8.3% versus 17.9% ± 6.2% [interns] and 27.4% ± 10.2% [juniors] according to residents, p < 0.001; and 38.6% ± 8.1% versus 11.8% ± 6.4% [interns] and 26.1% ± 5.7% [juniors] according to PD, p < 0.001). The same holds true for their theoretical ideals. Residents and PDs agree on current resident time allocation across the 10 domains; however, they disagree on multiple components of the ideal program with residents desiring more time spent in the OR than what PDs prefer (residents 40.3% ± 10

  5. Disentangling residence time and temperature sensitivity of microbial decomposition in a global soil carbon model

    NASA Astrophysics Data System (ADS)

    Exbrayat, J.-F.; Pitman, A. J.; Abramowitz, G.

    2014-12-01

    Recent studies have identified the first-order representation of microbial decomposition as a major source of uncertainty in simulations and projections of the terrestrial carbon balance. Here, we use a reduced complexity model representative of current state-of-the-art models of soil organic carbon decomposition. We undertake a systematic sensitivity analysis to disentangle the effect of the time-invariant baseline residence time (k) and the sensitivity of microbial decomposition to temperature (Q10) on soil carbon dynamics at regional and global scales. Our simulations produce a range in total soil carbon at equilibrium of ~ 592 to 2745 Pg C, which is similar to the ~ 561 to 2938 Pg C range in pre-industrial soil carbon in models used in the fifth phase of the Coupled Model Intercomparison Project (CMIP5). This range depends primarily on the value of k, although the impact of Q10 is not trivial at regional scales. As climate changes through the historical period, and into the future, k is primarily responsible for the magnitude of the response in soil carbon, whereas Q10 determines whether the soil remains a sink, or becomes a source in the future mostly by its effect on mid-latitude carbon balance. If we restrict our simulations to those simulating total soil carbon stocks consistent with observations of current stocks, the projected range in total soil carbon change is reduced by 42% for the historical simulations and 45% for the future projections. However, while this observation-based selection dismisses outliers, it does not increase confidence in the future sign of the soil carbon feedback. We conclude that despite this result, future estimates of soil carbon and how soil carbon responds to climate change should be more constrained by available data sets of carbon stocks.

  6. Measurement of Ligand–Target Residence Times by 1H Relaxation Dispersion NMR Spectroscopy

    PubMed Central

    2016-01-01

    A ligand-observed 1H NMR relaxation experiment is introduced for measuring the binding kinetics of low-molecular-weight compounds to their biomolecular targets. We show that this approach, which does not require any isotope labeling, is applicable to ligand–target systems involving proteins and nucleic acids of variable molecular size. The experiment is particularly useful for the systematic investigation of low affinity molecules with residence times in the micro- to millisecond time regime. PMID:27933946

  7. Measurement of Ligand-Target Residence Times by (1)H Relaxation Dispersion NMR Spectroscopy.

    PubMed

    Moschen, Thomas; Grutsch, Sarina; Juen, Michael A; Wunderlich, Christoph H; Kreutz, Christoph; Tollinger, Martin

    2016-12-08

    A ligand-observed (1)H NMR relaxation experiment is introduced for measuring the binding kinetics of low-molecular-weight compounds to their biomolecular targets. We show that this approach, which does not require any isotope labeling, is applicable to ligand-target systems involving proteins and nucleic acids of variable molecular size. The experiment is particularly useful for the systematic investigation of low affinity molecules with residence times in the micro- to millisecond time regime.

  8. A method for calculating the mean residence times of catenary metabolites.

    PubMed

    Cheng, H Y

    1991-07-01

    A method for calculating the mean residence times of metabolites in the body, systemic circulation, and peripheral tissue is described. The calculations require the AUC, AUMC, and derivatives of the plasma concentration versus time curves of the metabolite and its precursor. The method is applicable to metabolites with any precursor order and does not require separate administration of the metabolite. The approach is applied to published data for the primary and secondary metabolites of ketamine.

  9. Hydrothermal carbonisation of poultry litter: Effects of treatment temperature and residence time on yields and chemical properties of hydrochars.

    PubMed

    Ghanim, Bashir M; Pandey, Daya Shankar; Kwapinski, Witold; Leahy, James J

    2016-09-01

    In this study, hydrochars were prepared by hydrothermal carbonisation (HTC) of poultry litter (PL) at temperatures between 150-300°C with residence times of 30, 120 and 480min. The effects of treatment temperature and residence time on the yield and composition of hydrochar were investigated. Both treatment temperature and residence time effects were observed however, the effect of residence time was lower. The results indicated that the HHV was improved by up to 25.17% and the overall ash in hydrochar was significantly lower compared to PL, however this coincided with a lower hydrochar yield. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Residence and Migration of First-Time Freshmen for the State of Hawai'i, Fall 1996. Special Report.

    ERIC Educational Resources Information Center

    Hawaii Univ., Honolulu.

    This report presents information on the residence and migration of first-time freshmen for the State of Hawaii for the Fall 1996 semester. The information presented is for first-time freshmen only. The first-time freshmen population discussed in this report is divided into three groups: (1) those residents of Hawaii who chose to main in the State…

  11. Reducing the residence time of a bouncing drop with spoked macrotexture

    NASA Astrophysics Data System (ADS)

    Patterson, Colin; Bird, James

    2015-11-01

    Liquid drops can bounce when they impact non-wetting surfaces. Recently, studies have demonstrated that the time that the bouncing drop resides at the surface can be adjusted with the presence of ridged macrotextures. When non-parallel macrotextures are present, they intersect to create spoked junctions. At sufficient velocity, a drop impacting a junction might be expected to breakup into smaller droplets; yet it is unclear how many droplets would be produced and the time for these droplets to clear the surface. Here, we show that the number droplets and overall residence time depends on both the number of spokes and the Weber number. We experimentally demonstrate that the center-assisted recoil framework extends beyond superhydrophobic surfaces to those above the Leidenfrost temperature. Finally, we present a physical model that rationalizes our results.

  12. Th-230 - U-238 series disequilibrium of the Olkaria rhyolites Gregory Rift Valley, Kenya: Residence times

    NASA Technical Reports Server (NTRS)

    Black, S.; Macdonald, R.; Kelly, M.

    1993-01-01

    U-series disequilibrium analyses have been conducted on samples from Olkaria rhyolite centers with ages being available for all but one center using both internal and whole rock isochrons. 67 percent of the rhyolites analyzed show U-Th disequilibrium, ranging from 27 percent excess thorium to 36 percent excess uranium. Internal and whole rock isochrons give crystallization/formation ages between 65 ka and 9 ka, in every case these are substantially older than the eruptive dates. The residence times of the rhyolites (U-Th age minus the eruption date) have decreased almost linearly with time, from 45 ka to 7 Ka suggesting a possible increase of activity within the system related to increased basaltic input. The long residence times are mirrored by large Rn-222 fluxes from the centers which cannot be explained by larger U contents.

  13. Estimating Regional Water Residence Time Changes in the Colonial Northeast United States

    NASA Astrophysics Data System (ADS)

    Green, M. B.; Arrigo, J.; Duncan, J.; Parolari, T.

    2008-12-01

    The Northeast United States experienced a fundamental change following colonization by Europeans. During the period from 1600 to 1800 forests were cleared, agricultural lands were expanded, beavers were hunted to near-extinction, wetlands were drained or filled, and cities were built. Such activities had important implications for the stocks of water on and the fluxes of water through that landscape. We have made an early attempt to quantify the changed water stocks and fluxes in the Northeast during this time period using historical information and simple analyses. Simple calculations and estimates of stock and flux uncertainty were used to compute the distribution of land surface water residence times at the beginning and ending of the Colonial Era. Our estimates show that humans shifted water residence towards shorter times, which would have important implications for geomorphology, biogeochemistry, and how humans responded to their alteration of the hydrologic cycle.

  14. Residence time distribution (RTD) of particulate foods in a continuous flow pilot-scale ohmic heater.

    PubMed

    Sarang, Sanjay; Heskitt, Brian; Tulsiyan, Priyank; Sastry, Sudhir K

    2009-08-01

    The residence time distribution (RTD) of a model particulate-fluid mixture (potato in starch solution) in the ohmic heater in a continuous sterilization process was measured using a radio frequency identification (RFID) methodology. The effect of solid concentration and the rotational speed of the agitators on the RTD were studied. The velocity of the fastest particle was 1.62 times the mean product velocity. In general, particle velocity was found to be greater than the product bulk average velocity. Mean particle residence time (MPRT) increased with an increase in the rotational speed of the agitators (P < 0.05), and no particular trend was observed between the MPRT and the solid concentration. The distribution curves E (theta) were skewed to the right suggesting slow moving zones in the system.

  15. Th-230 - U-238 series disequilibrium of the Olkaria rhyolites Gregory Rift Valley, Kenya: Residence times

    NASA Technical Reports Server (NTRS)

    Black, S.; Macdonald, R.; Kelly, M.

    1993-01-01

    U-series disequilibrium analyses have been conducted on samples from Olkaria rhyolite centers with ages being available for all but one center using both internal and whole rock isochrons. 67 percent of the rhyolites analyzed show U-Th disequilibrium, ranging from 27 percent excess thorium to 36 percent excess uranium. Internal and whole rock isochrons give crystallization/formation ages between 65 ka and 9 ka, in every case these are substantially older than the eruptive dates. The residence times of the rhyolites (U-Th age minus the eruption date) have decreased almost linearly with time, from 45 ka to 7 Ka suggesting a possible increase of activity within the system related to increased basaltic input. The long residence times are mirrored by large Rn-222 fluxes from the centers which cannot be explained by larger U contents.

  16. The Pools, Fluxes and Residence Time of Water Across the Amazon Basin

    NASA Astrophysics Data System (ADS)

    Goldsmith, G. R.; Fisher, J. B.; McDonnell, J.; Malhi, Y.

    2014-12-01

    What can ecology tell us about the hydrology of the Amazon? And what can hydrology tell us about the ecology? From a hydrological perspective, plant water storage and use contributes to determining the rate and time scales at which water is recycled from soil to the atmosphere. From an ecological perspective, plant water storage and use contributes to determining the rate and time scales at which water plants can support function. Conceptualized as residence time, the relationship between plant water storage and use can provide fundamental insights into ecohydrology. We explore the spatial variation in the aboveground storage, use, and residence time of water across the Amazon. To do so, we pair estimates of aboveground woody biomass from 413 1-ha old growth forest census plots situated across the Amazon Basin with high resolution estimates of intra- and inter- annual evapotranspiration derived from remote sensing. Aboveground water storage capacity (17.4 ± 6.3 mm) and evapotranspiration (3.7 ± 0.4 mm day-1) result in a residence time of 4.7 ± 1.5 days, equivalent to the use of ca. 24% of stored water day-1. The results indicate that residence time varies due to a predictable relationship between evapotranspiration and biomass at local, regional and landscape scales. The ecohydrology of the Amazon plays a critical role in water and carbon cycling on a global scale. We discuss how our results can help inform our understanding of both the hydrology and ecology of the Amazon Basin in the context of anthropogenic change.

  17. Using continuous underway isotope measurements to map water residence time in hydrodynamically complex tidal environments

    USGS Publications Warehouse

    Downing, Bryan D.; Bergamaschi, Brian; Kendall, Carol; Kraus, Tamara; Dennis, Kate J.; Carter, Jeffery A.; von Dessonneck, Travis

    2016-01-01

    Stable isotopes present in water (δ2H, δ18O) have been used extensively to evaluate hydrological processes on the basis of parameters such as evaporation, precipitation, mixing, and residence time. In estuarine aquatic habitats, residence time (τ) is a major driver of biogeochemical processes, affecting trophic subsidies and conditions in fish-spawning habitats. But τ is highly variable in estuaries, owing to constant changes in river inflows, tides, wind, and water height, all of which combine to affect τ in unpredictable ways. It recently became feasible to measure δ2H and δ18O continuously, at a high sampling frequency (1 Hz), using diffusion sample introduction into a cavity ring-down spectrometer. To better understand the relationship of τ to biogeochemical processes in a dynamic estuarine system, we continuously measured δ2H and δ18O, nitrate and water quality parameters, on board a small, high-speed boat (5 to >10 m s–1) fitted with a hull-mounted underwater intake. We then calculated τ as is classically done using the isotopic signals of evaporation. The result was high-resolution (∼10 m) maps of residence time, nitrate, and other parameters that showed strong spatial gradients corresponding to geomorphic attributes of the different channels in the area. The mean measured value of τ was 30.5 d, with a range of 0–50 d. We used the measured spatial gradients in both τ and nitrate to calculate whole-ecosystem uptake rates, and the values ranged from 0.006 to 0.039 d–1. The capability to measure residence time over single tidal cycles in estuaries will be useful for evaluating and further understanding drivers of phytoplankton abundance, resolving differences attributable to mixing and water sources, explicitly calculating biogeochemical rates, and exploring the complex linkages among time-dependent biogeochemical processes in hydrodynamically complex environments such as estuaries.

  18. Using Continuous Underway Isotope Measurements To Map Water Residence Time in Hydrodynamically Complex Tidal Environments.

    PubMed

    Downing, Bryan D; Bergamaschi, Brian A; Kendall, Carol; Kraus, Tamara E C; Dennis, Kate J; Carter, Jeffery A; Von Dessonneck, Travis S

    2016-12-20

    Stable isotopes present in water (δ(2)H, δ(18)O) have been used extensively to evaluate hydrological processes on the basis of parameters such as evaporation, precipitation, mixing, and residence time. In estuarine aquatic habitats, residence time (τ) is a major driver of biogeochemical processes, affecting trophic subsidies and conditions in fish-spawning habitats. But τ is highly variable in estuaries, owing to constant changes in river inflows, tides, wind, and water height, all of which combine to affect τ in unpredictable ways. It recently became feasible to measure δ(2)H and δ(18)O continuously, at a high sampling frequency (1 Hz), using diffusion sample introduction into a cavity ring-down spectrometer. To better understand the relationship of τ to biogeochemical processes in a dynamic estuarine system, we continuously measured δ(2)H and δ(18)O, nitrate and water quality parameters, on board a small, high-speed boat (5 to >10 m s(-1)) fitted with a hull-mounted underwater intake. We then calculated τ as is classically done using the isotopic signals of evaporation. The result was high-resolution (∼10 m) maps of residence time, nitrate, and other parameters that showed strong spatial gradients corresponding to geomorphic attributes of the different channels in the area. The mean measured value of τ was 30.5 d, with a range of 0-50 d. We used the measured spatial gradients in both τ and nitrate to calculate whole-ecosystem uptake rates, and the values ranged from 0.006 to 0.039 d(-1). The capability to measure residence time over single tidal cycles in estuaries will be useful for evaluating and further understanding drivers of phytoplankton abundance, resolving differences attributable to mixing and water sources, explicitly calculating biogeochemical rates, and exploring the complex linkages among time-dependent biogeochemical processes in hydrodynamically complex environments such as estuaries.

  19. A resident boot camp for reducing door-to-needle times at academic medical centers.

    PubMed

    Ruff, Ilana M; Liberman, Ava L; Caprio, Fan Z; Maas, Matthew B; Mendelson, Scott J; Sorond, Farzaneh A; Bergman, Deborah; Bernstein, Richard A; Curran, Yvonne; Prabhakaran, Shyam

    2017-06-01

    We sought to determine if a structured educational program for neurology residents can lower door-to-needle (DTN) times at an academic institution. A neurology resident educational stroke boot camp was developed and implemented in April 2013. Using a prospective database of 170 consecutive acute ischemic stroke (AIS) patients treated with IV tissue plasminogen activator (tPA) in our emergency department (ED), we evaluated the effect of the intervention on DTN times. We compared DTN times and other process measures preintervention and postintervention. p Values < 0.05 were considered significant. The proportion of AIS patients treated with tPA within 60 minutes of arrival to our ED tripled from 18.1% preintervention to 61.2% postintervention (p < 0.001) with concomitant reduction in DTN time (median 79 minutes vs 58 minutes, p < 0.001). The resident-delegated task (stroke code to tPA) was reduced (75 minutes vs 44 minutes, p < 0.001), while there was no difference in ED-delegated tasks (door to stroke code [7 minutes vs 6 minutes, p = 0.631], door to CT [18 minutes in both groups, p = 0.547]). There was an increase in stroke mimics treated (6.9% vs 18.4%, p = 0.031), which did not lead to an increase in adverse outcomes. DTN times were reduced after the implementation of a stroke boot camp and were driven primarily by efficient resident stroke code management. Educational programs should be developed for health care providers involved in acute stroke patient care to improve rapid access to IV tPA at academic institutions.

  20. Modern Dust Deposition and Dissolved Iron Residence Times in the Eastern Tropical Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Vivancos, S. M.; Anderson, R. F.; Pavia, F. J.; Fleisher, M. Q.; Lu, Y.; Zhang, P.; Cheng, H.; Edwards, R. L.

    2016-02-01

    We use dissolved 230Th and 232Th data along the U.S. GEOTRACES Equatorial Pacific Zonal Transect (EPZT) from Peru to Tahiti to quantify dust input to the region. Dust in the global oceans is a mineral ballast that helps carry organic matter to depth, a reactive particle surface that scavenges trace metals such as Th and Pa from the water column, and through its dissolution dust provides essential micronutrients, such as iron, that stimulate productivity. When integrating Th inventories from the sea surface to 500 meters water depth (Hayes et al., Earth Planet. Sci. Lett., 383 (2013) 16-25), we find that dust fluxes along the EPZT are an order of magnitude lower (0.18-1.61 g/m2/yr) than along the U.S. GEOTRACES Atlantic Transect (Mauritania to Bermuda; 3.22 to 10.56 g/m2/yr). Dust fluxes decrease with distance away from the dust source (i.e., the continents). Using an Fe/Th ratio of 2660 g/g for dust and assuming a Fe/Th solubility ratio of 1.0 (Hayes et al., Geochim. Cosmochim. Acta, 169 (2015) 1-16), we calculate a dissolved iron flux of 12.06 to 109.88 µmol/m2/yr to the EPZT region. Utilizing dissolved iron data along the EPZT (Resing et al., Nature, 523 (2015) 200-203), we calculate a dissolved iron residence time integrated from the sea surface to 500 meters water depth of 4 to 11 years.

  1. Characterizing Drug-Target Residence Time with Metadynamics: How To Achieve Dissociation Rate Efficiently without Losing Accuracy against Time-Consuming Approaches.

    PubMed

    Sun, Huiyong; Li, Youyong; Shen, Mingyun; Li, Dan; Kang, Yu; Hou, Tingjun

    2017-08-28

    Drug-target residence time plays a vital role in drug efficacy. However, there is still no effective strategy to predict drug residence time. Here, we propose to use the optimized (or minimized) structures derived from holo-state proteins to calculate drug residence time, which could give a comparable or even better prediction accuracy compared with those calculated utilizing a large number of molecular dynamics (MD) structures based on the Poisson process. Besides, in addition to the Poisson process, one may use fewer samples for predicting residence time due to the reason that, in a large extent, the calculated drug residence time is stable and independent of the number of samples used for the prediction. With remarkably reduced computational load, the proposed strategy may be promising for large-scale drug residence time prediction, such as post-processing in virtual screening (VS) and lead compound optimization.

  2. Redfield Ratios in Inland Waters: Higher Biological Control of C:N:P Ratios in Tropical Semi-arid High Water Residence Time Lakes

    PubMed Central

    They, Ng H.; Amado, André M.; Cotner, James B.

    2017-01-01

    The canonical Redfield C:N:P ratio for algal biomass is often not achieved in inland waters due to higher C and N content and more variability when compared to the oceans. This has been attributed to much lower residence times and higher contributions of the watershed to the total organic matter pool of continental ecosystems. In this study we examined the effect of water residence times in low latitude lakes (in a gradient from humid to a semi-arid region) on seston elemental ratios in different size fractions. We used lake water specific conductivity as a proxy for residence time in a region of Eastern Brazil where there is a strong precipitation gradient. The C:P ratios decreased in the seston and bacterial size-fractions and increased in the dissolved fraction with increasing water retention time, suggesting uptake of N and P from the dissolved pool. Bacterial abundance, production and respiration increased in response to increased residence time and intracellular nutrient availability in agreement with the growth rate hypothesis. Our results reinforce the role of microorganisms in shaping the chemical environment in aquatic systems particularly at long water residence times and highlights the importance of this factor in influencing ecological stoichiometry in all aquatic ecosystems. PMID:28848518

  3. Redfield Ratios in Inland Waters: Higher Biological Control of C:N:P Ratios in Tropical Semi-arid High Water Residence Time Lakes.

    PubMed

    They, Ng H; Amado, André M; Cotner, James B

    2017-01-01

    The canonical Redfield C:N:P ratio for algal biomass is often not achieved in inland waters due to higher C and N content and more variability when compared to the oceans. This has been attributed to much lower residence times and higher contributions of the watershed to the total organic matter pool of continental ecosystems. In this study we examined the effect of water residence times in low latitude lakes (in a gradient from humid to a semi-arid region) on seston elemental ratios in different size fractions. We used lake water specific conductivity as a proxy for residence time in a region of Eastern Brazil where there is a strong precipitation gradient. The C:P ratios decreased in the seston and bacterial size-fractions and increased in the dissolved fraction with increasing water retention time, suggesting uptake of N and P from the dissolved pool. Bacterial abundance, production and respiration increased in response to increased residence time and intracellular nutrient availability in agreement with the growth rate hypothesis. Our results reinforce the role of microorganisms in shaping the chemical environment in aquatic systems particularly at long water residence times and highlights the importance of this factor in influencing ecological stoichiometry in all aquatic ecosystems.

  4. Estimation of coastal residence time of submarine groundwater discharge using radium progenies.

    PubMed

    Eleftheriou, G; Tsabaris, C; Patiris, D L; Androulakaki, E G; Vlastou, R

    2017-03-01

    A methodology based on γ-spectrometry measurements of untreated coastal water samples is proposed for the direct estimation of coastal residence time of submarine discharged groundwater. The method was applied to a submarine spring at Stoupa Bay covering all seasons. The estimated residence time exhibited an annual mean of 4.6±1.7 d. An additional measurement using the in situ underwater γ-spectrometry technique was performed, in the same site. The in situ method yielded a value of 2.8±0.2 d that was found consistent with the corresponding value derived using the developed lab-based method (3.4±2.0 d) for the same period.

  5. Method for Making Measurements of the Post-Combustion Residence Time in a Gas Turbine Engine

    NASA Technical Reports Server (NTRS)

    Miles, Jeffrey H (Inventor)

    2015-01-01

    A system and method of measuring a residence time in a gas-turbine engine is provided, whereby the method includes placing pressure sensors at a combustor entrance and at a turbine exit of the gas-turbine engine and measuring a combustor pressure at the combustor entrance and a turbine exit pressure at the turbine exit. The method further includes computing cross-spectrum functions between a combustor pressure sensor signal from the measured combustor pressure and a turbine exit pressure sensor signal from the measured turbine exit pressure, applying a linear curve fit to the cross-spectrum functions, and computing a post-combustion residence time from the linear curve fit.

  6. Chaotic itinerancy and power-law residence time distribution in stochastic dynamical systems.

    PubMed

    Namikawa, Jun

    2005-08-01

    Chaotic itinerant motion among varieties of ordered states is described by a stochastic model based on the mechanism of chaotic itinerancy. The model consists of a random walk on a half-line and a Markov chain with a transition probability matrix. The stability of attractor ruin in the model is investigated by analyzing the residence time distribution of orbits at attractor ruins. It is shown that the residence time distribution averaged over all attractor ruins can be described by the superposition of (truncated) power-law distributions if the basin of attraction for each attractor ruin has a zero measure. This result is confirmed by simulation of models exhibiting chaotic itinerancy. Chaotic itinerancy is also shown to be absent in coupled Milnor attractor systems if the transition probability among attractor ruins can be represented as a Markov chain.

  7. An overview of oil palm biomass torrefaction: Effects of temperature and residence time

    NASA Astrophysics Data System (ADS)

    Yaacob, N.; Rahman, N. A.; Matali, S.; Idris, S. S.; Alias, A. B.

    2016-06-01

    Biomass is characterized as high moisture content, low bulk and energy density, possesses hygroscopic behaviour and poor grindability material as compared to the superior coal. A thermal treatment called torrefaction is a heating of biomass in a temperature range between 200°C to 300°C under inert atmosphere in order to upgrade biomass properties. Torrefied biomass has many similar characteristics to coal such as low moisture content, high bulk and energy density, hydrophobic and good grindability. This paper reviews the effects of oil palm biomass torrefaction in terms of temperature and residence time. This is because comprehensive studies on torrefaction parameters need to be carried out since different parameters might affect the chemical and physical characteristic of the torrefied product. Hence, this paper aims to discuss the effects of different torrefaction temperature and residence time towards physicochemical characteristic, mass and energy yield as well as calorific value of torrefied oil palm biomass.

  8. New residence times of the Holocene reworked shells on the west coast of Bohai Bay, China

    NASA Astrophysics Data System (ADS)

    Shang, Zhiwen; Wang, Fu; Li, Jianfen; Marshall, William A.; Chen, Yongsheng; Jiang, Xingyu; Tian, Lizhu; Wang, Hong

    2016-01-01

    Shelly cheniers and shell-rich beds found intercalated in near-shore marine muds and sandy sediments can be used to indicate the location of ancient shorelines, and help to estimate the height of sea level. However, dating the deposition of material within cheniers and shell-rich beds is not straightforward because much of this material is transported and re-worked, creating an unknown temporal off-set, i.e., the residence time, between the death of a shell and its subsequent entombment. To quantify the residence time during the Holocene on a section of the northern Chinese coastline a total 47 shelly subsamples were taken from 17 discrete layers identified on the west coast of Bohai Bay. This material was AMS 14C dated and the calibrated ages were systematically compared. The subsamples were categorized by type as articulated and disarticulated bivalves, gastropod shells, and undifferentiated shell-hash. It was found that within most individual layers the calibrated ages of the subsamples got younger relative to the amount of apparent post-mortem re-working the material had been subject to. For examples, the 14C ages of the bivalve samples trended younger in this order: shell-hash → split shells → articulated shells. We propose that the younger subsample age determined within an individual layer will be the closest to the actual depositional age of the material dated. Using this approach at four Holocene sites we find residence times which range from 100 to 1260 cal yrs, with two average values of 600 cal yrs for the original 14C dates older than 1 ka cal BP and 100 cal yrs for the original 14C dates younger than 1 ka cal BP, respectively. Using this semi-empirical estimation of the shell residence times we have refined the existing chronology of the Holocene chenier ridges on the west coast of Bohai Bay.

  9. Role of Plasma Temperature and Residence Time in Stagnation Plasma Synthesis of c-BN Nanopowders

    DTIC Science & Technology

    2013-01-01

    changing the orientation to parallel which is preferential for the cubic structure . 9 The compressive stresses formed by ion bombardment limit the...bombardment is not needed to synthesize the cubic structure . 11 2.2.3 Effects of voltage bias Voltage bias has been used for years in hopes of...different residence times. As shown in Figure 5.1, the cubic structure of boron nitride does not form in high percentages at relatively low temperatures

  10. Optimisation of polymer foam bubble expansion in extruder by resident time distribution approach

    NASA Astrophysics Data System (ADS)

    Larochette, Mathieu; Graebling, Didier; Léonardi, Frédéric

    2007-04-01

    In this work, we used the Residence Time Distribution (RTD) to study the polystyrene foaming during an extrusion process. The extruder associated with a gear pump is simply and quantitatively described by three continuoustly stirred tank reactors with recycling loops and one plug-flow reactor. The blowing agent used is CO2 and its obtained by thermal decomposition of a chemical blowing agent (CBA). This approach allows to optimize the density of the foam in accordance with the CBA kinetic of decomposition.

  11. Eulerian and Lagrangian Measurements of Water Flow and Residence Time in a Fringing Coral Reef Embayment

    NASA Astrophysics Data System (ADS)

    Storlazzi, C. D.; Messina, A. M.; Cheriton, O. M.; Biggs, T. W.

    2014-12-01

    Hydrodynamic processes on coral reefs are important for nutrient cycling, larval dispersal, temperature variability, and understanding the impacts of terrestrial sediment, nutrients, and contaminants from adjacent impaired watersheds on coral reef ecosystems. Our goal was to understand the spatial and temporal variability in flow velocities and the associated residence time of water in the fringing coral reef flat-lined embayment of Faga'alu, on the island of Tutuila in American Samoa. To accomplish this, data from three bottom-mounted acoustic current profilers and 102 individual Lagrangian ocean surface current drifter deployments (5 drifters x 21 deployments) were combined with meteorologic data and numerical wave model results. These data and model results, collected over nine days, made it possible to evaluate the relative contribution of tidal, wind, and wave forcing on the flow patterns. The high number of drifter deployments made it possible for the velocity data to be binned into 100 m x 100 m grid cells and the resulting residence times computed for the different sets of forcing conditions. Cumulative progressive vectors calculated from the acoustic current profilers closely matched the tracks from concurrently deployed surface current drifters, showing the applicability of this hybrid Lagrangian-Eulerian measurement scheme to understand flow patterns in this geomorphically complex embayment. The bay-wide man current speeds (residence times) varied from 1-37 cm/s (2.78-0.08 hr), 1-36 cm/s (2.78-0.08 hr), and 5-64 cm/s (0.56-0.04 hr) under tidal, wind, and wave forcing, respectively; the highest speeds (shortest residence times) were measured on the outer reef flat closest to where waves were breaking on the reef crest and were slowest (longest) over the inner reef flat close to shore and deep in the embayment.

  12. Asbestos disease at low exposure after long residence time in amphibole miners

    SciTech Connect

    Sluis-Cremer, G.K. )

    1991-01-01

    Short reports of several studies carried out in South Africa which have a bearing on the health effects of low exposures to asbestos are presented. It is stressed that the findings refer solely to amphibole asbestos. Average fiber exposure of 1 or less or a cumulative exposure of less than 2-5 fibers/ml years is associated with the development of asbestosis increasing in frequency with residence time.

  13. Classification of Animal Movement Behavior through Residence in Space and Time.

    PubMed

    Torres, Leigh G; Orben, Rachael A; Tolkova, Irina; Thompson, David R

    2017-01-01

    Identification and classification of behavior states in animal movement data can be complex, temporally biased, time-intensive, scale-dependent, and unstandardized across studies and taxa. Large movement datasets are increasingly common and there is a need for efficient methods of data exploration that adjust to the individual variability of each track. We present the Residence in Space and Time (RST) method to classify behavior patterns in movement data based on the concept that behavior states can be partitioned by the amount of space and time occupied in an area of constant scale. Using normalized values of Residence Time and Residence Distance within a constant search radius, RST is able to differentiate behavior patterns that are time-intensive (e.g., rest), time & distance-intensive (e.g., area restricted search), and transit (short time and distance). We use grey-headed albatross (Thalassarche chrysostoma) GPS tracks to demonstrate RST's ability to classify behavior patterns and adjust to the inherent scale and individuality of each track. Next, we evaluate RST's ability to discriminate between behavior states relative to other classical movement metrics. We then temporally sub-sample albatross track data to illustrate RST's response to less resolved data. Finally, we evaluate RST's performance using datasets from four taxa with diverse ecology, functional scales, ecosystems, and data-types. We conclude that RST is a robust, rapid, and flexible method for detailed exploratory analysis and meta-analyses of behavioral states in animal movement data based on its ability to integrate distance and time measurements into one descriptive metric of behavior groupings. Given the increasing amount of animal movement data collected, it is timely and useful to implement a consistent metric of behavior classification to enable efficient and comparative analyses. Overall, the application of RST to objectively explore and compare behavior patterns in movement data can

  14. Classification of Animal Movement Behavior through Residence in Space and Time

    PubMed Central

    Orben, Rachael A.; Tolkova, Irina; Thompson, David R.

    2017-01-01

    Identification and classification of behavior states in animal movement data can be complex, temporally biased, time-intensive, scale-dependent, and unstandardized across studies and taxa. Large movement datasets are increasingly common and there is a need for efficient methods of data exploration that adjust to the individual variability of each track. We present the Residence in Space and Time (RST) method to classify behavior patterns in movement data based on the concept that behavior states can be partitioned by the amount of space and time occupied in an area of constant scale. Using normalized values of Residence Time and Residence Distance within a constant search radius, RST is able to differentiate behavior patterns that are time-intensive (e.g., rest), time & distance-intensive (e.g., area restricted search), and transit (short time and distance). We use grey-headed albatross (Thalassarche chrysostoma) GPS tracks to demonstrate RST’s ability to classify behavior patterns and adjust to the inherent scale and individuality of each track. Next, we evaluate RST’s ability to discriminate between behavior states relative to other classical movement metrics. We then temporally sub-sample albatross track data to illustrate RST’s response to less resolved data. Finally, we evaluate RST’s performance using datasets from four taxa with diverse ecology, functional scales, ecosystems, and data-types. We conclude that RST is a robust, rapid, and flexible method for detailed exploratory analysis and meta-analyses of behavioral states in animal movement data based on its ability to integrate distance and time measurements into one descriptive metric of behavior groupings. Given the increasing amount of animal movement data collected, it is timely and useful to implement a consistent metric of behavior classification to enable efficient and comparative analyses. Overall, the application of RST to objectively explore and compare behavior patterns in movement data

  15. Simulations of Ground-Water Flow and Residence Time near Woodbury, Connecticut

    USGS Publications Warehouse

    Starn, J. Jeffrey; Brown, Craig J.

    2007-01-01

    Water withdrawn for public use from glacial stratified deposits in Woodbury, Connecticut, is a mixture of water from different source areas, each having a characteristic water-quality signature. The physical processes leading to this mixture were explored using a numerical model to simulate steady-state ground-water source areas and residence times for a public water-supply well (PSW-1) in Woodbury. Upland areas contribute water to the well that is primarily from undeveloped and agricultural land. Valley bottoms contribute water to the well that is primarily from developed land. From 1985 to 2002, 6 percent of the contributing recharge area to the well changed from agricultural and undeveloped to developed land. The pattern of recharge areas and land use causes stratification of ground water by residence time and by characteristic water quality, which is related to land use. As land use changes with time, the water-quality signature of developed land moves deeper into the aquifer. Predicted nitrate concentrations decreased from 1985 to 1995 because of the conversion from agricultural land to developed land, but then began to increase after 1995 because of the conversion of undeveloped land to developed land. Total dissolved solids concentrations, on the other hand, increased from 1985 to 2002 because agriculture is associated with lower total dissolved solids concentrations than is developed land. About 40 percent of the water withdrawn from PSW-1 originated as upland recharge before flowing through glacial deposits in the valley. About 44 percent of the water originated as recharge in either fluvial deposits (mean residence time 7 years) or deltaic deposits (mean residence time 4 years). About 16 percent of the water originated as recharge through storm drains with ground-water discharge (often known as 'dry wells'). The residence time for water that originated as recharge in dry wells is 2 to 4 years, and the mean residence time is 3 years. Dry wells are a fast

  16. Tracing time scales of fluid residence and migration in the crust (Invited)

    NASA Astrophysics Data System (ADS)

    Yokochi, R.; Sturchio, N. C.; Purtschert, R.; Jiang, W.; Lu, Z.; Müller, P.; Yang, G.; Kennedy, B. M.

    2013-12-01

    Crustal fluids (water, gas and oil) mediate chemical reactions, and they may transport, concentrate or disperse elements in the crust; the fluids are often valuable resources in their own right. In this context, determining the time scales of fluid transport and residence time is essential for understanding geochemical cycle of elements, as well as risk and resource management. Crustal fluids contain stable and radioactive noble gases indigenous to the fluid, which may be of magmatic or atmospheric origin of various ages. In addition, radiogenic and nucleogenic noble gases (both stable and radioactive) are continuously produced by the decay of U, Th and K and related nuclear reactions in the crust at known rates and in known relative proportions. They may be released from their production sites and incorporated into the fluid, acting as natural spikes to trace fluid flow. The concentrations of a noble gas isotope in a crustal fluid in a system devoid of phase separation or mixing varies as a function of decay time and supply from the production sites into the fluids. The release rate of noble gases from the production sites in minerals to the fluid phase may be determined uniquely through the studies of noble gas radionuclides (Yokochi et al., 2012), which is fundamental to the behavior of volatile elements in geochemistry. A pilot study of noble gas radionuclides in an active geothermal system was performed at Yellowstone National Park (Yokochi et al., 2013). Prior studies of the Yellowstone system using stable noble gas isotopes show that the thermal fluids contain a mixture of atmospheric, mantle, and crustal components. Noble gas radionuclide measurements provide new chronometric constraints regarding the subsurface residence times of Yellowstone thermal fluids. Upper limits on deep thermal fluid mean residence times, estimated from 39Ar/40Ar* ratios, range from 118 to 137 kyr for features in the Gibbon and Norris Geyser Basin areas, and are about 16 kyr in

  17. Spatial distribution of residence time, microbe and storage volume of groundwater in headwater catchments

    NASA Astrophysics Data System (ADS)

    Tsujimura, Maki; Ogawa, Mahiro; Yamamoto, Chisato; Sakakibara, Koichi; Sugiyama, Ayumi; Kato, Kenji; Nagaosa, Kazuyo; Yano, Shinjiro

    2017-04-01

    Headwater catchments in mountainous region are the most important recharge area for surface and subsurface waters, and time and stock information of the water is principal to understand hydrological processes in the catchments. Also, a variety of microbes are included in the groundwater and spring water, and those varies in time and space, suggesting that information of microbe could be used as tracer for groundwater flow system. However, there have been few researches to evaluate the relationship among the residence time, microbe and storage volume of the groundwater in headwater catchments. We performed an investigation on age dating using SF6 and CFCs, microbe counting in the spring water, and evaluation of groundwater storage volume based on water budget analysis in 8 regions underlain by different lithology, those are granite, dacite, sedimentary rocks, serpentinite, basalt and volcanic lava all over Japan. We conducted hydrometric measurements and sampling of spring water in base flow conditions during the rainless periods 2015 and 2016 in those regions, and SF6, CFCs, stable isotopic ratios of oxygen-18 and deuterium, inorganic solute concentrations and total number of prokaryotes were determined on all water samples. Residence time of spring water ranged from 0 to 16 years in all regions, and storage volume of the groundwater within topographical watershed was estimated to be 0.1 m to 222 m in water height. The spring with the longer residence time tends to have larger storage volume in the watershed, and the spring underlain by dacite tends to have larger storage volume as compared with that underlain by sand stone and chert. Also, total number of prokaryotes in the spring water ranged from 103 to 105 cells/mL, and the spring tends to show clear increasing of total number of prokaryotes with decreasing of residence time. Thus, we observed a certain relationship among residence time, storage volume and total number of prokaryotes in the spring water, and

  18. Error analysis of the residence time of bistable Poisson states obtained by periodic measurements.

    PubMed

    Lee, Jinwoo; Lyo, In-Whan

    2010-06-01

    We performed error analysis on the periodic measurement schemes to obtain the residence time of bistable Poisson states. Experimental data were obtained by periodical level-sensitive samplings of oxygen-induced states on Si(111)-7 x 7 that stochastically switches between two metastable states. Simulated data sequences were created by the Monte Carlo numerical method. The residence times were extracted from the experimental and simulation data sequences by averaging and exponential-fitting methods. The averaging method yields the residence time via the summation of the detected temporal width of each state weighed by the normalized frequency of the state and the exponential fitting via fitting a single exponential function to the frequency histogram of the data. It is found that the averaging method produces consistently more accurate results with no arbitrariness, when compared to the exponential fitting method. For further understanding, data modeling using the first-order approximation was performed; the enhanced accuracy in the averaging method is due to the mutual cancellation of errors associated with detection of zero-width states and long-tail states. We investigated a multi-interval detection scheme as well. Similar analysis shows that the dual-interval scheme produces larger error compared to the single interval one, and has narrower optimum region.

  19. The relative importance of water temperature and residence time in predicting cyanobacteria abundance in regulated rivers.

    PubMed

    Cha, YoonKyung; Cho, Kyung Hwa; Lee, Hyuk; Kang, Taegu; Kim, Joon Ha

    2017-11-01

    Despite a growing awareness of the problems associated with cyanobacterial blooms in rivers, and particularly in regulated rivers, the drivers of bloom formation and abundance in rivers are not well understood. We developed a Bayesian hierarchical model to assess the relative importance of predictors of summer cyanobacteria abundance, and to test whether the relative importance of each predictor varies by site, using monitoring data from 16 sites in the four major rivers of South Korea. The results suggested that temperature and residence time, but not nutrient levels, are important predictors of summer cyanobacteria abundance in rivers. Although the two predictors were of similar significance across the sites, the residence time was marginally better in accounting for the variation in cyanobacteria abundance. The model with spatial hierarchy demonstrated that temperature played a consistently significant role at all sites, and showed no effect from site-specific factors. In contrast, the importance of residence time varied significantly from site to site. This variation was shown to depend on the trophic state, indicated by the chlorophyll-a and total phosphorus levels. Our results also suggested that the magnitude of weir inflow is a key factor determining the cyanobacteria abundance under baseline conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Percolation of clusters with a residence time in the bond definition: Integral equation theory.

    PubMed

    Zarragoicoechea, Guillermo J; Pugnaloni, Luis A; Lado, Fred; Lomba, Enrique; Vericat, Fernando

    2005-03-01

    We consider the clustering and percolation of continuum systems whose particles interact via the Lennard-Jones pair potential. A cluster definition is used according to which two particles are considered directly connected (bonded) at time t if they remain within a distance d, the connectivity distance, during at least a time of duration tau, the residence time. An integral equation for the corresponding pair connectedness function, recently proposed by two of the authors [Phys. Rev. E 61, R6067 (2000)], is solved using the orthogonal polynomial approach developed by another of the authors [Phys. Rev. E 55, 426 (1997)]. We compare our results with those obtained by molecular dynamics simulations.

  1. Theme: Planning, Organization and Time Management.

    ERIC Educational Resources Information Center

    Miller, Larry E.; And Others

    1985-01-01

    This issue focuses upon planning, organization, and time management. Articles discuss program goals, saving failing programs, vocational agriculture program planning under the Perkins Act, program innovation, reviewing the focus of agribusiness education, the changing focus of vocational agriculture at one high school, time management for summer…

  2. A study of the attitude of Latin-American residents in Spain toward organ xenotransplantation.

    PubMed

    Ríos, Antonio; López-Navas, Ana Isabel; Martínez-Alarcón, Laura; Sánchez, José; Ramis, Guillermo; Ramírez, Pablo; Parrilla, Pascual

    2014-01-01

    It is important to find out what would be the level of acceptance of xenotransplantation in society, especially in populations where there are preclinical trials. The Latin-American population is growing in Spain, given the cultural, religious, and language similarities. (i) to analyze attitude toward xenotransplantation in the population born in Latin America and now residing in Spain; and (ii) to establish the variables that affect this attitude. A sample of Latin-American residents in Spain was obtained randomly in 2010 and stratified by the respondent's nationality (n = 1.314). Attitude was evaluated using a validated questionnaire (PCID-XenoTx Rios), which was completed anonymously and self-administered. Student's t-test, the Chi-squared test, Fisher's exact test, and logistic regression analysis. The questionnaire completion rate was 89% (n = 1.165). If it was assumed that xenotransplanted organs functioned as well as human ones, 40% were in favor, 19% against, and 41% undecided. This attitude is related to: age (P = 0.003); sex (P = 0.002); level of education (P < 0.001); descendents (P = 0.003); country of origin (P < 0.001); participation in voluntary prosocial activities (P = 0.006); having spoken about donation and transplantation within the family (P < 0.001); a partner's favorable attitude toward transplantation (P < 0.001); previous experience of donation and/or transplantation (P < 0.001); a belief that one might need a transplant in the future (P < 0.001); and a favorable attitude toward human donation, both deceased as well as living (P < 0.001). In the multivariate analysis, the following variables continue to feature as independent variables: age (older: Odds Ratio = 1.041); sex (male: OR = 1.579); level of education (university: OR = 2.770); descendents (none: OR = 2.386); a partner's attitude toward transplantation (favorable: OR = 2.262); attitude toward deceased organ donation (favorable: OR = 1.587); previous experience of donation and

  3. A new time-space accounting scheme to predict stream water residence time and hydrograph source components at the watershed scale

    Treesearch

    Takahiro Sayama; Jeffrey J. McDonnell

    2009-01-01

    Hydrograph source components and stream water residence time are fundamental behavioral descriptors of watersheds but, as yet, are poorly represented in most rainfall-runoff models. We present a new time-space accounting scheme (T-SAS) to simulate the pre-event and event water fractions, mean residence time, and spatial source of streamflow at the watershed scale. We...

  4. Residence times in a hypersaline lagoon: Using salinity as a tracer

    NASA Astrophysics Data System (ADS)

    Mudge, Stephen M.; Icely, John D.; Newton, Alice

    2008-04-01

    Generally the waters of the Ria Formosa Lagoon, Portugal have a short residence time, in the order of 0.5 days (Tett, P., Gilpin, L., Svendsen, H., Erlandsson, C.P., Larsson, U., Kratzer, S., Fouilland, E., Janzen, C., Lee, J., Grenz, C., Newton, A., Ferreira, J.G., Fernandes, T., Scory, S., 2003. Eutrophication and some European waters of restricted exchange. Continental Shelf Research 23, 1635-1671). This estimation is based on the measurements of currents and the modelling of water exchange at the outlets to the ocean. However, observations of the temperature and salinity in the inner channels imply that residence time is greater in these regions of the lagoon. To resolve this apparent contradiction, spatial measurements of the temperature and salinity were made with a meter for conductivity, temperature and depth along the principal channels of the western portion of the lagoon, with a sampling frequency of two per second. Evaporation rates of 5.4 mm day -1 were measured in a salt extraction pond adjacent to the lagoon and used to determine the residence time through salinity differences with the incoming seawater. In June 2004, the water flooding in from the ocean had an average salinity of 36.07 which contrasted with a maximum of 37.82 at mid ebb on a spring tide, corresponding to a residence time of >7 days; the mean residence time was 2.4 days. As the tide flooded into the channels, the existing water was advected back into the lagoon. Although there was a small amount of mixing with water from another inlet, the water body from the inner lagoon essentially remained distinct with respect to temperature and salinity characteristics. The residence time of the water was further prolonged at the junction between the main channels, where distinct boundaries were observed between the different water masses. As the water ebbed out, the shallow Western Channel was essentially isolated from the rest of the outer lagoon, and the water from this channel was forced

  5. Method for Making Measurements of the Post-Combustion Residence Time in a Gas Turbine Engine

    NASA Technical Reports Server (NTRS)

    Miles, Jeffrey H. (Inventor)

    2017-01-01

    A method of measuring a residence time in a gas-turbine engine is disclosed that includes measuring a combustor pressure signal at a combustor entrance and a turbine exit pressure signal at a turbine exit. The method further includes computing a cross-spectrum function between the combustor pressure signal and the turbine exit pressure signal, calculating a slope of the cross-spectrum function, shifting the turbine exit pressure signal an amount corresponding to a time delay between the measurement of the combustor pressure signal and the turbine exit pressure signal, and recalculating the slope of the cross-spectrum function until the slope reaches zero.

  6. Predicting Polycyclic Aromatic Hydrocarbon Concentrations in Resident Aquatic Organisms Using Passive Samplers and Partial Least-Squares Calibration

    PubMed Central

    2015-01-01

    The current work sought to develop predictive models between time-weighted average polycyclic aromatic hydrocarbon (PAH) concentrations in the freely dissolved phase and those present in resident aquatic organisms. We deployed semipermeable membrane passive sampling devices (SPMDs) and collected resident crayfish (Pacifastacus leniusculus) at nine locations within and outside of the Portland Harbor Superfund Mega-site in Portland, OR. Study results show that crayfish and aqueous phase samples collected within the Mega-site had PAH profiles enriched in high molecular weight PAHs and that freely dissolved PAH profiles tended to be more populated by low molecular weight PAHs compared to crayfish tissues. Results also show that of several modeling approaches, a two-factor partial least-squares (PLS) calibration model using detection limit substitution provided the best predictive power for estimating PAH concentrations in crayfish, where the model explained ≥72% of the variation in the data set and provided predictions within ∼3× of measured values. Importantly, PLS calibration provided a means to estimate PAH concentrations in tissues when concentrations were below detection in the freely dissolved phase. The impact of measurements below detection limits is discussed. PMID:24800862

  7. An influential factor for external radiation dose estimation for residents after the Fukushima Daiichi Nuclear Power Plant accident-time spent outdoors for residents in Iitate Village.

    PubMed

    Ishikawa, Tetsuo; Yasumura, Seiji; Ohtsuru, Akira; Sakai, Akira; Akahane, Keiichi; Yonai, Shunsuke; Sakata, Ritsu; Ozasa, Kotaro; Hayashi, Masayuki; Ohira, Tetsuya; Kamiya, Kenji; Abe, Masafumi

    2016-06-01

    Many studies have been conducted on radiation doses to residents after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. Time spent outdoors is an influential factor for external dose estimation. Since little information was available on actual time spent outdoors for residents, different values of average time spent outdoors per day have been used in dose estimation studies on the FDNPP accident. The most conservative value of 24 h was sometimes used, while 2.4 h was adopted for indoor workers in the UNSCEAR 2013 report. Fukushima Medical University has been estimating individual external doses received by residents as a part of the Fukushima Health Management Survey by collecting information on the records of moves and activities (the Basic Survey) after the accident from each resident. In the present study, these records were analyzed to estimate an average time spent outdoors per day. As an example, in Iitate Village, its arithmetic mean was 2.08 h (95% CI: 1.64-2.51) for a total of 170 persons selected from respondents to the Basic Survey. This is a much smaller value than commonly assumed. When 2.08 h is used for the external dose estimation, the dose is about 25% (23-26% when using the above 95% CI) less compared with the dose estimated for the commonly used value of 8 h.

  8. Root microbiota dynamics of perennial Arabis alpina are dependent on soil residence time but independent of flowering time

    PubMed Central

    Dombrowski, Nina; Schlaeppi, Klaus; Agler, Matthew T; Hacquard, Stéphane; Kemen, Eric; Garrido-Oter, Ruben; Wunder, Jörg; Coupland, George; Schulze-Lefert, Paul

    2017-01-01

    Recent field and laboratory experiments with perennial Boechera stricta and annual Arabidopsis thaliana suggest that the root microbiota influences flowering time. Here we examined in long-term time-course experiments the bacterial root microbiota of the arctic-alpine perennial Arabis alpina in natural and controlled environments by 16S rRNA gene profiling. We identified soil type and residence time of plants in soil as major determinants explaining up to 15% of root microbiota variation, whereas environmental conditions and host genotype explain maximally 11% of variation. When grown in the same soil, the root microbiota composition of perennial A. alpina is largely similar to those of its annual relatives A. thaliana and Cardamine hirsuta. Non-flowering wild-type A. alpina and flowering pep1 mutant plants assemble an essentially indistinguishable root microbiota, thereby uncoupling flowering time from plant residence time-dependent microbiota changes. This reveals the robustness of the root microbiota against the onset and perpetual flowering of A. alpina. Together with previous studies, this implies a model in which parts of the root microbiota modulate flowering time, whereas, after microbiota acquisition during vegetative growth, the established root-associated bacterial assemblage is structurally robust to perturbations caused by flowering and drastic changes in plant stature. PMID:27482927

  9. Root microbiota dynamics of perennial Arabis alpina are dependent on soil residence time but independent of flowering time.

    PubMed

    Dombrowski, Nina; Schlaeppi, Klaus; Agler, Matthew T; Hacquard, Stéphane; Kemen, Eric; Garrido-Oter, Ruben; Wunder, Jörg; Coupland, George; Schulze-Lefert, Paul

    2017-01-01

    Recent field and laboratory experiments with perennial Boechera stricta and annual Arabidopsis thaliana suggest that the root microbiota influences flowering time. Here we examined in long-term time-course experiments the bacterial root microbiota of the arctic-alpine perennial Arabis alpina in natural and controlled environments by 16S rRNA gene profiling. We identified soil type and residence time of plants in soil as major determinants explaining up to 15% of root microbiota variation, whereas environmental conditions and host genotype explain maximally 11% of variation. When grown in the same soil, the root microbiota composition of perennial A. alpina is largely similar to those of its annual relatives A. thaliana and Cardamine hirsuta. Non-flowering wild-type A. alpina and flowering pep1 mutant plants assemble an essentially indistinguishable root microbiota, thereby uncoupling flowering time from plant residence time-dependent microbiota changes. This reveals the robustness of the root microbiota against the onset and perpetual flowering of A. alpina. Together with previous studies, this implies a model in which parts of the root microbiota modulate flowering time, whereas, after microbiota acquisition during vegetative growth, the established root-associated bacterial assemblage is structurally robust to perturbations caused by flowering and drastic changes in plant stature.

  10. Development of Electronic Medical Record-Based "Rounds Report" Results in Improved Resident Efficiency, More Time for Direct Patient Care and Education, and Less Resident Duty Hour Violations.

    PubMed

    Ham, Phillip B; Anderton, Toby; Gallaher, Ryan; Hyrman, Mike; Simmerman, Erika; Ramanathan, Annamalai; Fallaw, David; Holsten, Steven; Howell, Charles Gordon

    2016-09-01

    Surgeons frequently report frustration and loss of efficiency with electronic medical record (EMR) systems. Together, surgery residents and a programmer at Augusta University created a rounds report (RR) summarizing 24 hours of vitals, intake/output, labs, and other values for each inpatient that were previously transcribed by hand. The objective of this study was to evaluate the RR's effect on surgery residents. Surgery residents were queried to assess the RR's impact. Outcome measures were time spent preparing for rounds, direct patient care time, educational activity time, rates of incorrect/incomplete data on rounds, and rate of duty hour violations. Hospital wide, 17,200 RRs were generated in the 1-month study. Twenty-three surgery residents participated. Time spent preparing for rounds decreased per floor patient (15.6 ± 3.0 vs 6.0 ± 1.2, P < 0.0001) and per intensive care unit patient (19.9 ± 2.9 vs 7.5 ± 1.2 P < 0.0001). The work day spent in direct patient care increased from 45.1 ± 5.6 to 54.0 ± 5.7 per cent (P = 0.0044). Educational activity time increased from 35.2 ± 5.4 to 54.7 ± 7.1 minutes per resident per day (P = 0.0004). Reported duty hour violations decreased 58 per cent (P < 0.0001). American Board of Surgery in Training exam scores trended up, and estimates of departmental annual financial savings range from $66,598 to $273,141 per year. Significant improvements occur with surgeon designed EMR tools like the RR. Hospitals and EMR companies should pair interested surgeons with health information technology developers to facilitate EMR enhancements. Improvements like RRs can have broad ranging, multidisciplinary impact and should be standard in all EMRs used for inpatient care at academic medical centers.

  11. Predicting mean residence time and exchange velocity in the hyporheic zone of restored streams

    NASA Astrophysics Data System (ADS)

    Morén, Ida; Wörman, Anders; Riml, Joakim

    2016-04-01

    The hyporheic zones of streams and rivers have been identified as hotspots for biogeochemical reactions in the aquatic environment, making the retention time and exchange velocity of the hyporheic zone essential parameters in the modelling of these processes. However, exact site-specific values of those parameters are often missing in stream restoration projects because there are no well-defined scaling relationships linking them to measurable reach characteristics. In this study we derive semi-analytical solutions for the retention time and exchange velocity in the hyporheic zone. In particular the effect on hyporheic exchange is expressed by the use of physically based models and by superimposing different geomorphologic features of different scales. It is suggested that all exchange phenomena can be modelled as head anomalies expressed with a harmonic distribution along the stream with specific wavelength and head amplitude. The maximum head of an exchange phenomena is either dominated by hydrodynamic or hydrostatic water pressure, depending on the size of the feature causing the exchange. The theory leads to constitutive relationships for exchange velocity and residence time expressed as functions of the distribution of wavelengths, distribution of head amplitude and hydraulic conductivity. In order to validate and evaluate certain empirical coefficients, a number of Rhodamine WT tracer tests were performed in a partly restored agricultural stream in the south of Sweden called the Tullstorps brook. To evaluate the tracer test in sections where remediation actions have been undertaken we used the method of temporal moments. In conjunction with the tracer tests a characterisation of the stream was carried out where hydraulic conductivity of the streambed and stream morphology was measured. The study verifies that the residence time in the hyporheic zone decreases with the maximum hydraulic head of the largest (dominating) geomorphic feature of the reach, and

  12. Treatment of zinc-rich acid mine water in low residence time bioreactors incorporating waste shells and methanol dosing.

    PubMed

    Mayes, W M; Davis, J; Silva, V; Jarvis, A P

    2011-10-15

    Bioreactors utilising bacterially mediated sulphate reduction (BSR) have been widely tested for treating metal-rich waters, but sustained treatment of mobile metals (e.g. Zn) can be difficult to achieve in short residence time systems. Data are presented providing an assessment of alkalinity generating media (shells or limestone) and modes of metal removal in bioreactors receiving a synthetic acidic metal mine discharge (pH 2.7, Zn 15 mg/L, SO(4)(2-) 200mg/L, net acidity 103 mg/L as CaCO(3)) subject to methanol dosing. In addition to alkalinity generating media (50%, v.v.), the columns comprised an organic matrix of softwood chippings (30%), manure (10%) and anaerobic digested sludge (10%). The column tests showed sustained alkalinity generation, which was significantly better in shell treatments. The first column in each treatment was effective throughout the 422 days in removing >99% of the dissolved Pb and Cu, and effective for four months in removing 99% of the dissolved Zn (residence time: 12-14 h). Methanol was added to the feedstock after Zn breakthrough and prompted almost complete removal of dissolved Zn alongside improved alkalinity generation and sulphate attenuation. While there was geochemical evidence for BSR, sequential extraction of substrates suggests that the bulk (67-80%) of removed Zn was associated with Fe-Mn oxide fractions.

  13. The role of buoyancy orientation on bubble residence times and the related critical heat flux

    SciTech Connect

    Brusstar, M.J.; Merte, H. Jr.; Keller, R.B.

    1995-12-31

    Measurements of the effects of buoyancy orientation on the critical heat flux (CHF) in subcooled forced convection boiling of R113 are presented, examining the motion of the vapor above the heater surface and its possible influence on the feed of liquid to the surface. At the low flow velocity of 4 cm/s used, the buoyancy force acting on the vapor dominates over the flow inertia, and the measured CHF values show a strong dependence on the orientation of the heater surface with respect to gravity. The transient and time-averaged behavior of the vapor above the surface at heat flux levels close to the CHF is characterized using hot wire anemometry. Through this, a description of the behavior of the largest vapor bubbles is obtained, which is considered to be of primary importance to the processes by which liquid is fed to the heater surface at these high heat flux levels. The mean residence time of the largest bubbles above the heater surface at a given heater orientation is also determined from the hot wire data. The reciprocal of the mean residence time is found to correlate directly with the measured CHF values for the different orientations and subcoolings, showing that the amount of energy absorbed in the vapor formation process during the bubble residence time is constant for all heater orientations at a given subcooling, and demonstrates that the motion of the largest bubbles determines the CHF. This suggests that the relative effects of buoyancy orientation on the CHF can be modeled by considering only the motion of the largest bubbles in the immediate vicinity of the heater surface.

  14. Geometrical effects on the electron residence time in semiconductor nano-particles

    SciTech Connect

    Koochi, Hakimeh; Ebrahimi, Fatemeh

    2014-09-07

    We have used random walk (RW) numerical simulations to investigate the influence of the geometry on the statistics of the electron residence time τ{sub r} in a trap-limited diffusion process through semiconductor nano-particles. This is an important parameter in coarse-grained modeling of charge carrier transport in nano-structured semiconductor films. The traps have been distributed randomly on the surface (r{sup 2} model) or through the whole particle (r{sup 3} model) with a specified density. The trap energies have been taken from an exponential distribution and the traps release time is assumed to be a stochastic variable. We have carried out (RW) simulations to study the effect of coordination number, the spatial arrangement of the neighbors and the size of nano-particles on the statistics of τ{sub r}. It has been observed that by increasing the coordination number n, the average value of electron residence time, τ{sup ¯}{sub r} rapidly decreases to an asymptotic value. For a fixed coordination number n, the electron's mean residence time does not depend on the neighbors' spatial arrangement. In other words, τ{sup ¯}{sub r} is a porosity-dependence, local parameter which generally varies remarkably from site to site, unless we are dealing with highly ordered structures. We have also examined the effect of nano-particle size d on the statistical behavior of τ{sup ¯}{sub r}. Our simulations indicate that for volume distribution of traps, τ{sup ¯}{sub r} scales as d{sup 2}. For a surface distribution of traps τ{sup ¯}{sub r} increases almost linearly with d. This leads to the prediction of a linear dependence of the diffusion coefficient D on the particle size d in ordered structures or random structures above the critical concentration which is in accordance with experimental observations.

  15. Geometrical effects on the electron residence time in semiconductor nano-particles.

    PubMed

    Koochi, Hakimeh; Ebrahimi, Fatemeh

    2014-09-07

    We have used random walk (RW) numerical simulations to investigate the influence of the geometry on the statistics of the electron residence time τ(r) in a trap-limited diffusion process through semiconductor nano-particles. This is an important parameter in coarse-grained modeling of charge carrier transport in nano-structured semiconductor films. The traps have been distributed randomly on the surface (r(2) model) or through the whole particle (r(3) model) with a specified density. The trap energies have been taken from an exponential distribution and the traps release time is assumed to be a stochastic variable. We have carried out (RW) simulations to study the effect of coordination number, the spatial arrangement of the neighbors and the size of nano-particles on the statistics of τ(r). It has been observed that by increasing the coordination number n, the average value of electron residence time, τ̅(r) rapidly decreases to an asymptotic value. For a fixed coordination number n, the electron's mean residence time does not depend on the neighbors' spatial arrangement. In other words, τ̅(r) is a porosity-dependence, local parameter which generally varies remarkably from site to site, unless we are dealing with highly ordered structures. We have also examined the effect of nano-particle size d on the statistical behavior of τ̅(r). Our simulations indicate that for volume distribution of traps, τ̅(r) scales as d(2). For a surface distribution of traps τ(r) increases almost linearly with d. This leads to the prediction of a linear dependence of the diffusion coefficient D on the particle size d in ordered structures or random structures above the critical concentration which is in accordance with experimental observations.

  16. Residence time and movements of postbreeding shorebirds on the northern coast of Alaska

    USGS Publications Warehouse

    Taylor, Audrey R.; Lanctot, Richard B.; Powell, A.N.; Kendall, S.J.; Nigro, Debora A.

    2011-01-01

    Relatively little is known about shorebird movements across the coast of northern Alaska, yet postbreeding shorebirds use this coastline extensively prior to fall migration. We deployed 346 radio transmitters on 153 breeding and 193 postbreeding shorebirds of five species from 2005 to 2007.We examined two hypotheses regarding postbreeding shorebirds' movements: (1) whether such movements reflect ultimate routes of southbound migration and (2) whether migration strategy (length of flights) or timing of molt in relation to migration (molt occurring in breeding or winter range) are more influential in determining postbreeding shorebirds' behavior. Semipalmated Sandpipers (Calidris pusilla) moved east, consistent with the direction of their ultimate migration, but patterns of other species' movements did not reflect ultimate migration direction. Timing of postnuptial molt appeared to have more influence over residence time and movements than did migration strategy. Postcapture residence time for the Semipalmated Sandpiper was less than for the Western Sandpiper (C. mauri) and significantly less than for Dunlin (C. alpina), and the Semipalmated Sandpiper's movements between were quicker and more frequent than those of the Dunlin. We expected to see the opposite patterns if migration strategy were more influential. Our data shed light on how different shorebird species use the northern Alaska coast after breeding: most species are likely to be stopping over at postbreeding areas, whereas the Dunlin and some Western Sandpipers may be staging. We suggest the coast of northern Alaska be viewed as an interconnected network of postbreeding sites that serve multiple populations of breeding shorebirds. ?? The Cooper Ornithological Society 2011.

  17. In-vivo characterization of 2D residence time maps in the left ventricle

    NASA Astrophysics Data System (ADS)

    Rossini, Lorenzo; Martinez-Legazpi, Pablo; Bermejo, Javier; Benito, Yolanda; Alhama, Marta; Yotti, Raquel; Perez Del Villar, Candelas; Gonzalez-Mansilla, Ana; Barrio, Alicia; Fernandez-Aviles, Francisco; Shadden, Shawn; Del Alamo, Juan Carlos

    2014-11-01

    Thrombus formation is a multifactorial process involving biology and hemodynamics. Blood stagnation and wall shear stress are linked to thrombus formation. The quantification of residence time of blood in the left ventricle (LV) is relevant for patients affected by ventricular contractility dysfunction. We use a continuum formulation to compute 2D blood residence time (TR) maps in the LV using in-vivo 2D velocity fields in the apical long axis plane obtained from Doppler-echocardiography images of healthy and dilated hearts. The TR maps are generated integrating in time an advection-diffusion equation of a passive scalar with a time-source term. This equation represents the Eulerian translation of DTR / D t = 1 and is solved numerically with a finite volume method on a Cartesian grid using an immersed boundary for the LV wall. Changing the source term and the boundary conditions allows us to track blood transport (direct and retained flow) in the LV and the topology of early (E) and atrial (A) filling waves. This method has been validated against a Lagrangian Coherent Structures analysis, is computationally inexpensive and observer independent, making it a potential diagnostic tool in clinical settings.

  18. Delineating Recharge Elevation and Constraining Residence Time of Groundwater on Mount Shasta

    NASA Astrophysics Data System (ADS)

    Moran, J. E.; Peters, E.; Visser, A.; Esser, B. K.; Singleton, M. J.

    2016-12-01

    A warming climate will bring drastic changes to hydrologic systems in the headwater basins of the major rivers in California. Runoff in these rivers fills the reservoirs that sustain cities and agriculture through the dry months, while cool, late season groundwater discharge to streams is critical for sustaining subalpine ecosystems. Despite the important role they play in the larger hydrologic system, groundwater flow paths in headwater basins are typically not well characterized, with recharge and discharge locations largely unidentified, and subsurface residence times unknown. We examined several groundwater residence time tracers, stable isotopes and noble gas recharge temperatures in samples from wells and springs on Mount Shasta at the headwaters of the Sacramento River. The topographic relief in the study area imparts robust signatures of recharge elevation to both stable isotopes of the water molecule (δ18O and δD), and to dissolved noble gases, offering tools to identify recharge areas and delineate groundwater flow paths. This study was carried out during drought years, when the influence of runoff and recent recharge were minimal. Recharge elevations determined using stable isotopes and noble gas recharge temperatures are in close agreement, and indicate that most snowmelt infiltrates at elevations between 2000 and 2900 m (6600 and 9500 ft), which coincides with areas of thin soils and barren land cover. The large springs in Mt Shasta City discharge at an elevation more than 1500 m lower. High elevation springs (>2000 m) yield very young water (< 2 years) while lower elevation wells (1000-1500 m) produce water with a residence time of 6 years or more, based on tritium concentrations in sampled water. Residence time indicators with shorter half-lives (35-Sulfur and 22-Sodium) were not detected, suggesting that very recent recharge was a negligibly small component at the time of sampling. Combined with recharge elevation estimates, ages indicate

  19. Acceptance of organ xenotransplantation among Latin American immigrants resident in the United States.

    PubMed

    Ríos, Antonio; López-Navas, Ana Isabel; Martínez-Alarcón, Laura; Ramis, Guillermo; Hernández, Antonio Miguel; Ayala, Marco Antonio; Garrido, Gregorio; Ramírez, Pablo; Parrilla, Pascual

    2016-07-01

    Making xenotransplantation socially acceptable is the first step in working toward the promotion of this potential therapy option for providing transplant organs. To analyze the attitude toward xenotransplantation among the Latin American population resident in Florida (the USA), and to determine the variables affecting this attitude. A sample of Latin American residents in the state of Florida was randomized and stratified according to nationality, age, and sex (n = 1524). Attitude was assessed using a validated questionnaire (PCID-XenoTx Rios) which was self-completed anonymously. descriptive analysis, Student's t-test, the chi-square test, and a logistic regression analysis. The questionnaire completion rate was 95% (n = 1450). If it was assumed that xenotransplanted organs functioned as well as human ones, 10% (n = 147) would be in favor, 73% (n = 1092) against, and 17% (n = 246) undecided. If the results were worse, only 2% (n = 35) would be in favor. This favorable attitude was related to country of origin (Honduras and Guatemala; P < 0.001); age (P < 0.001); sex (women; P < 0.001); marital status (married; P < 0.001); descendents (yes; P < 0.001); level of formal education (secondary education and university; P < 0.001); participation in voluntary prosocial activities (yes; P < 0.001); having spoken about donation and transplantation within the family (yes; P < 0.001); a partner's favorable attitude toward transplantation (P = 0.040); religion (catholic; P < 0.001); knowing the attitude of one's religion toward donation (yes; P < 0.001); previous experience of donation and/or transplantation (yes; P < 0.001); a belief that one might need a transplant in the future (yes; P < 0.001); and a favorable attitude toward human donation (yes; P < 0.001). The following were associated with attitude in the multivariate analysis: age (≥40 yrs; OR = 1.152); marital status (married; OR = 500); prosocial activities (yes, I

  20. Spatial distribution of triazine residues in a shallow alluvial aquifer linked to groundwater residence time.

    PubMed

    Sassine, Lara; Le Gal La Salle, Corinne; Khaska, Mahmoud; Verdoux, Patrick; Meffre, Patrick; Benfodda, Zohra; Roig, Benoît

    2017-03-01

    At present, some triazine herbicides occurrence in European groundwater, 13 years after their use ban in the European Union, remains of great concern and raises the question of their persistence in groundwater systems due to several factors such as storage and remobilization from soil and unsaturated zone, limited or absence of degradation, sorption in saturated zones, or to continuing illegal applications. In order to address this problem and to determine triazine distribution in the saturated zone, their occurrence is investigated in the light of the aquifer hydrodynamic on the basis of a geochemical approach using groundwater dating tracers ((3)H/(3)He). In this study, atrazine, simazine, terbuthylazine, deethylatrazine, deisopropylatrazine, and deethylterbuthylazine are measured in 66 samples collected between 2011 and 2013 from 21 sampling points, on the Vistrenque shallow alluvial aquifer (southern France), covered by a major agricultural land use. The frequencies of quantification range from 100 to 56 % for simazine and atrazine, respectively (LQ = 1 ng L(-1)). Total triazine concentrations vary between 15 and 350 ng L(-1) and show three different patterns with depth below the water table: (1) low concentrations independent of depth but related to water origin, (2) an increase in concentrations with depth in the aquifer related to groundwater residence time and triazine use prior to their ban, and (3) relatively high concentrations at low depths in the saturated zone more likely related to a slow desorption of these compounds from the soil and unsaturated zone. The triazine attenuation rate varies between 0.3 for waters influenced by surface water infiltration and 4.8 for water showing longer residence times in the aquifer, suggesting an increase in these rates with water residence time in the saturated zone. Increasing triazine concentrations with depth is consistent with a significant decrease in the use of these pesticides for the last 10

  1. Geomorphic Control on Mineral and Fluid Residence Times and Implications for the Hydrochemistry of Weathering

    NASA Astrophysics Data System (ADS)

    Torres, M. A.; West, A. J.; Clark, K. E.; Feakins, S. J.; Ponton, C.

    2014-12-01

    Understanding how hydrologic and geochemical processes are coupled, and how this coupling is linked to geomorphic boundary conditions, remains a fundamental problem in the Geosciences, with implications from hydrology and ecosystem science to the geologic carbon cycle. In this study, we present paired measurements of water chemistry and river runoff in four nested catchments spanning the transition from the Andes Mountains to the foreland floodplain in Peru. These data provide insight into the linkages between catchment hydrology and weathering across a dramatic geomorphic gradient. Along the studied gradient, bedrock-derived solute concentrations range from being nearly constant in the Andes to showing significant dilution in response to increasing runoff in the foreland floodplain. Mean catchment slope appears to be a robust predictor of the power law exponent relating solute concentrations and runoff, which implies that erosional processes are an underlying control on concentration-runoff relationships. A number of factors may explain the observed slope-dependency of concentration-runoff relationships, including both mineral and fluid residence times. Seasonal variation in the δD of the Andean rivers is significantly damped relative to variation in the δD of precipitation. Along with consideration of the annual water budget, these data suggest that water is transiently stored within fractured bedrock in the Andean catchments. Across the entire study area, the seasonal variation in the δD of tributaries (i.e. streams that drain only a narrow range of elevations) increases with decreasing mean catchment elevation, which suggests that fluid residence times are shorter in the foreland floodplain relative to the Andes. Together, we interpret these factors to suggest that erosional processes, by modulating both the residence time of water and minerals in the critical zone, control the hydrologic sensitivity of weathering processes along the Andes-to-Amazon gradient.

  2. Microscopic rates of peptide-phospholipid bilayer interactions from single-molecule residence times.

    PubMed

    Myers, Grant A; Gacek, Daniel A; Peterson, Eric M; Fox, Christopher B; Harris, Joel M

    2012-12-05

    The binding of glucagon-like peptide-1 (GLP-1) to a planar phospholipid bilayer is measured using single-molecule total internal reflection fluorescence microscopy. From several reports in the literature, GLP-1 has been shown to be a random coil in free solution, adopting a folded, α-helix conformation when intercalated into membrane environments. Single-molecule fluorescence measurements of GLP-1 binding to supported lipid bilayers show evidence of two populations of membrane-associated molecules having different residence times, suggesting weakly adsorbed peptides and strongly bound peptides in the lipid bilayer. The path to and from a strongly bound (folded, intercalated) state would likely include an adsorbed state as an intermediate, so that the resulting kinetics would correspond to a consecutive first-order reversible three-state model. In this work, the relationships between measured single-molecule residence times and the microscopic rates in a three-state kinetic model are derived and used to interpret the binding of GLP-1 to a supported lipid bilayer. The system of differential equations associated with the proposed consecutive-three state kinetics scheme is solved, and the solution is applied to interpret histograms of single-molecule, GLP-1 residence times in terms of the microscopic rates in the sequential two-step model. These microscopic rates are used to estimate the free energy barrier to adsorption, the fraction of peptides adsorbing to the membrane surface that successfully intercalate in the bilayer, the lifetime of inserted peptides in the membrane, and the free energy change of insertion into the lipid bilayer from the adsorbed state. The transition from a random coil in solution to a folded state in a membrane has been recognized as a common motif for insertion of membrane active peptides. Therefore, the relationships developed here could have wide application to the kinetic analysis of peptide-membrane interactions.

  3. Storage and residence time of suspended sediment in gravel bars of Difficult Run, VA

    NASA Astrophysics Data System (ADS)

    George, J.; Benthem, A.; Pizzuto, J. E.; Skalak, K.

    2016-12-01

    Reducing the export of suspended sediment is an important consideration for restoring water quality to the Chesapeake Bay, but sediment budgets for in-channel landforms are poorly constrained. We quantified fine (< 2 mm) sediment storage and residence times for gravel bars at two reaches along Difficult Run, a 5th order tributary to the Potomac River. Eight gravel bars were mapped in a 150m headwater reach at Miller Heights (bankfull width 11m; total bar volume 114 m3) and 6 gravel bars were mapped in a 160m reach downstream near Leesburg Pike (bankfull width 19m; total bar volume 210 m3). Grain size analyses of surface and subsurface samples from 2 bars at each reach indicate an average suspended sediment content of 55%, suggesting a total volume of suspended sediment stored in the mapped bars to be 178 m3, or 283000 kg, comprising 5% of the average annual suspended sediment load of the two study reaches. Estimates of the annual bedload flux at Miller Heights based on stream gaging records and the Wilcock-Crowe bedload transport equation imply that the bars are entirely reworked at least annually. Scour chains installed in 2 bars at each site (a total of 50 chains) recorded scour and fill events during the winter and spring of 2016. These data indicate that 38% of the total volume of the bars is exchanged per year, for a residence time of 2.6 ± 1.2 years, a value we interpret as the residence time of suspended sediment stored in the bars. These results are supported by mapping of topographic changes derived from structure-from-motion analyses of digital aerial imagery. Storage in alluvial bars therefore represents a significant component of the suspended sediment budget of mid-Atlantic streams.

  4. Experiential Leadership Training for Pediatric Chief Residents: Impact on Individuals and Organizations

    PubMed Central

    Doughty, Robert A.; Williams, Patricia D.; Brigham, Timothy P.; Seashore, Charles

    2010-01-01

    Background The past decade has seen a proliferation of leadership training programs for physicians that teach skills outside the graduate medical education curriculum. Objective To determine the perceived value and impact of an experiential leadership training program for pediatric chief residents on the chief residents and on their programs and institutions. Methods The authors conducted a retrospective study. Surveys were sent to chief residents who completed the Chief Resident Training Program (CRTP) between 1988 and 2003 and to their program directors and department chairs asking about the value of the program, its impact on leadership capabilities, as well as the effect of chief resident training on programs and institutions. Results Ninety-four percent of the chief residents and 94% of program directors and department chairs reported that the CRTP was “very” or “somewhat” relevant, and 92% of the chief residents indicated CRTP had a positive impact on their year as chief resident; and 75% responded it had a positive impact beyond residency. Areas of greatest positive impact included awareness of personality characteristics, ability to manage conflict, giving and receiving feedback, and relationships with others. Fifty-six percent of chief residents reported having held a formal leadership position since chief residency, yet only 28% reported having received additional leadership training. Conclusion The study demonstrates a perceived positive impact on CRTP participants and their programs and institutions in the short and long term. PMID:21975638

  5. Tissue-Resident Memory T Cells and Fixed Immune Surveillance in Nonlymphoid Organs.

    PubMed

    Carbone, Francis R

    2015-07-01

    T cell immunity is often defined in terms of memory lymphocytes that use the blood to access a range of organs. T cells are involved in two patterns of recirculation. In one, the cells shuttle back and forth between blood and secondary lymphoid organs, whereas in the second, memory cells recirculate between blood and nonlymphoid tissues. The latter is a means by which blood T cells control peripheral infection. It is now clear that there exists a distinct memory T cell subset that is absent from blood but found within nonlymphoid tissues. These nonrecirculating tissue-resident memory T (TRM) cells develop within peripheral compartments and never spread beyond their point of lodgement. This review examines fixed immune surveillance by TRM cells, highlighting features that make them potent controllers of infection in nonlymphoid tissues. These features provide clues about TRM cell specialization, such as their ability to deal with sequestered, persisting infections confined to peripheral compartments. Copyright © 2015 by The American Association of Immunologists, Inc.

  6. On solute residence time in the storage zones of small streams - experimental study and scaling law

    NASA Astrophysics Data System (ADS)

    Schmid, Bernhard

    2013-04-01

    Transient storage has a major influence on solute transport in streams, on biogeochemical cycling, water quality and on the functioning of aquatic ecosystems. The first part of the research reported here focuses on surface transient storage (STS) zones between groins along small streams. Such groins are used to protect banks, but also to increase habitat diversity and are, thus, not restricted to large rivers. Repeated tracer dilution experiments on the Mödlingbach, a small stream in Austria some 30 km south of Vienna, have been analyzed to determine the solute residence time between groins and to characterize the exchange processes between dead zones and main stream. Pairs of related breakthrough curves were measured in main stream and storage zones, resp., and used subsequently to estimate the solute residence time in the surface dead zones under study. Following previous work (Weitbrecht et al., 2008; Jackson et al., 2012) these residence times were, in turn, expressed as T = -W-.hD- k ?u hE (1) with W denoting groin length, u main stream flow velocity, hD mean water depth between the groins and hE depth at the interface dead zone - main stream. Coefficient k, finally, is thought to depend on a type of hydraulic radius, RD = W.L/(W+L), with L denoting the distance between the groins, measured in main flow direction. Using both the Mödlingbach STS zone data and the results of the aforementioned study (Weitbrecht et al., 2008) the following regression equation was derived (hS denotes main stream water depth): k = 0.00282? RD + 0.00802 hS (2) The second part of this research focuses on the dependency of solute residence time on flow rate, which is important for an improved understanding of longitudinal solute transport in streams and for the application of mathematical models. The scaling law proposed here is based on a physics-related theory combined with extensive data sets available form a decade of stream tracer experiments on the Mödlingbach stream

  7. The roles of mean residence time on herd behavior in a financial market

    NASA Astrophysics Data System (ADS)

    Li, Jiang-Cheng; Li, Yun-Xian; Tang, Nian-Sheng; Mei, Dong-Cheng

    2016-11-01

    We investigate the herd behavior of stock prices in a finance system with the Heston model. Based on parameter estimation of the Heston model obtained by minimizing the mean square deviation between the theoretical and empirical return distributions, we simulate mean residence time of positive return (MRTPR). Plots of MRTPR against the amplitude or mean reversion of volatility demonstrate a phenomenon of herd behavior for a positive cross correlation between noise sources of the Heston model. Also, for a negative cross correlation, a phenomenon of herd behavior is observed in plots of MRTPR against the long-run variance by increasing amplitude or mean reversion of volatility.

  8. Stable isotope fractionation in response to variable fluid residence time distributions

    NASA Astrophysics Data System (ADS)

    Druhan, J. L.; Maher, K.

    2013-12-01

    Hydrogeochemical processes governing groundwater quantity and quality are often inferred from fluid samples that are the flux-weighted average of a heterogeneous system. This connection has been demonstrated for solutes subject to transport and equilibrium constraints, in which the steady state concentration - discharge relationship is cast in terms of the choice of expression for residence time distribution (Maher, 2011). Here, we examine the extent to which the spatial correlation of the permeability field, which governs the fluid residence time distribution, exerts a principle control on the partitioning of stable isotopes between reactant and product species during heterogeneous reactions in groundwater systems. We demonstrate this relationship using numerical simulations of δ53Cr fractionation due to abiotic CrO42- reduction by Fe2+, implemented in the reactive transport code CrunchFlow. The chemically homogeneous redox reaction generates Cr3+ with an isotope ratio distinct from the reactant pool, and in turn this product species precipitates as a mineral phase Cr(OH)3(s) through a non-fractionating reaction. The corresponding chromate δ53Cr enrichment across a homogeneous domain varies from a maximum value set by the kinetic fractionation factor (αk) at high mean fluid residence times, to a value <αk as fluid velocity increases, demonstrating a transition from reaction-limited to transport-limited regimes. For physically heterogeneous flow fields, the transition in isotopic fractionation from a reaction-limited to a transport-limited regime becomes variable, and falls between the upper and lower bounds set by the homogeneous simulations at slow and fast precipitation rates, respectively. Our results show that while minimal variation occurs in the steady-state isotopic profile of the reactant species (δ53Cr of CrO42-), the combined effects of the precipitation rate and the heterogeneous structure of the porous media lead to a wide range in the steady

  9. Using just-in-time teaching and peer instruction in a residency program's core curriculum: enhancing satisfaction, engagement, and retention.

    PubMed

    Schuller, Mary C; DaRosa, Debra A; Crandall, Marie L

    2015-03-01

    To assess use of the combined just-in-time teaching (JiTT) and peer instruction (PI) instructional strategy in a residency program's core curriculum. In 2010-2011, JiTT/PI was piloted in 31 core curriculum sessions taught by 22 faculty in the Northwestern University Feinberg School of Medicine's general surgery residency program. JiTT/PI required preliminary and categorical residents (n=31) to complete Web-based study questions before weekly specialty topic sessions. Responses were examined by faculty members "just in time" to tailor session content to residents' learning needs. In the sessions, residents answered multiple-choice questions (MCQs) using clickers and engaged in PI. Participants completed surveys assessing their perceptions of JiTT/PI. Videos were coded to assess resident engagement time in JiTT/PI sessions versus prior lecture-based sessions. Responses to topic session MCQs repeated in review sessions were evaluated to study retention. More than 70% of resident survey respondents indicated that JiTT/PI aided in the learning of key points. At least 90% of faculty survey respondents reported positive perceptions of aspects of the JiTT/PI strategy. Resident engagement time for JiTT/PI sessions was significantly greater than for prior lecture-based sessions (z=-2.4, P=.016). Significantly more review session MCQ responses were correct for residents who had attended corresponding JiTT/PI sessions than for residents who had not (chi-square=13.7; df=1; P<.001). JiTT/PI increased learner participation, learner retention, and the amount of learner-centered time. JiTT/PI represents an effective approach for meaningful and active learning in core curriculum sessions.

  10. Are Time-Limited Grants Likely to Stimulate Sustained Growth in Primary Care Residency Training? A Study of the Primary Care Residency Expansion Program.

    PubMed

    Chen, Rossan Melissa; Petterson, Stephen; Bazemore, Andrew; Grumbach, Kevin

    2015-09-01

    To examine the perceived likelihood of sustaining new residency positions funded by five-year (2010-2015) Primary Care Residency Expansion (PCRE) grants from the Health Resources and Services Administration, which aimed to increase training output to address primary care workforce issues. During September-December 2013, the authors administered an online or telephone survey to program directors whose residency programs received PCRE grants. The main outcome measure was perceived likelihood of sustaining the expanded residency positions beyond the expiration of the grant, in the outlying years of 2016 and 2017 (when the positions will be partially supported) and after 2017 (when the positions will be unsupported). Of 78 eligible program directors, 62 responded (response rate = 79.5%). Twenty-eight (45.1%; 95% CI 32.9%-57.9%) reported that their programs were unlikely to, very unlikely to, or not planning to continue the expanded positions after the PCRE grant expires. Overall, 14 (22.5%) reported having secured full funding to support the expanded positions beyond 2017. Family medicine and pediatrics program directors were significantly less likely than internal medicine program directors to report having secured funding for the outlying years (P = .02). This study suggests that an approach to primary care residency training expansion that relies on time-limited grants is unlikely to produce sustainable growth of the primary care pipeline. Policy makers should instead implement systemic reform of graduate medical education (GME) financing and designate reliable sources of funding, such as Medicare and Medicaid GME funds, for new primary care residency positions.

  11. Shear Stress Increases the Residence Time of Adhesion of Pseudomonas aeruginosa

    PubMed Central

    Lecuyer, Sigolene; Rusconi, Roberto; Shen, Yi; Forsyth, Alison; Vlamakis, Hera; Kolter, Roberto; Stone, Howard A.

    2011-01-01

    Although ubiquitous, the processes by which bacteria colonize surfaces remain poorly understood. Here we report results for the influence of the wall shear stress on the early-stage adhesion of Pseudomonas aeruginosa PA14 on glass and polydimethylsiloxane surfaces. We use image analysis to measure the residence time of each adhering bacterium under flow. Our main finding is that, on either surface, the characteristic residence time of bacteria increases approximately linearly as the shear stress increases (∼0–3.5 Pa). To investigate this phenomenon, we used mutant strains defective in surface organelles (type I pili, type IV pili, or the flagellum) or extracellular matrix production. Our results show that, although these bacterial surface features influence the frequency of adhesion events and the early-stage detachment probability, none of them is responsible for the trend in the shear-enhanced adhesion time. These observations bring what we believe are new insights into the mechanism of bacterial attachment in shear flows, and suggest a role for other intrinsic features of the cell surface, or a dynamic cell response to shear stress. PMID:21244830

  12. Sediment residence time and connectivity in non-equilibrium and transient geomorphic systems

    NASA Astrophysics Data System (ADS)

    Hoffmann, Thomas; Hillebrand, Gudrun

    2016-04-01

    Growing empirical evidence shows that sediment delivery in many geomorphic systems is in transient state or out of equilibrium with respect to the external driving forces. The transient state is often related to the (dis)connectivity of the many constituent parts of geomorphic systems as a result of sediment storage along the sediment flow path from its source to the final sink. The response time of geomorphic systems to external changes is thus dependent on the residence time of sediment in various storage compartments. Here, a mathematical concept based on reservoir theory to model residence time of sediment in various depositional environments is presented. The concept allows to reinterpret millennial scale sediment budges, but can be also applied to decal sediment storage in reservoirs and aids sediment management practices in river systems. The framework sheds light on the limitation of the sediment delivery ratio, which is often used as a measure of sediment connectivity in geomorphic systems, and provides analytical information on process type, pace of sediment flux and connectivity of storage compartments along the sediment cascade. Examples will be given using Postglacial sediment budgets from the Canadian Rocky mountains on the one hand and short-term (~15 yrs.) sediment dynamics in the Iffezheim barrage in the Upper Rhine (Germany).

  13. Analysis Of Residence Time Distribution Of Fluid Flow By Axial Dispersion Model

    SciTech Connect

    Sugiharto; Su'ud, Zaki; Kurniadi, Rizal; Waris, Abdul; Abidin, Zainal

    2010-12-23

    Radioactive tracer {sup 82}Br in the form of KBr-82 with activity {+-} 1 mCi has been injected into steel pipeline to qualify the extent dispersion of water flowing inside it. Internal diameter of the pipe is 3 in. The water source was originated from water tank through which the water flow gravitically into the pipeline. Two collimated sodium iodide detectors were used in this experiment each of which was placed on the top of the pipeline at the distance of 8 and 11 m from injection point respectively. Residence time distribution (RTD) curves obtained from injection of tracer are elaborated numerically to find information of the fluid flow properties. The transit time of tracer calculated from the mean residence time (MRT) of each RTD curves is 14.9 s, therefore the flow velocity of the water is 0.2 m/s. The dispersion number, D/uL, for each RTD curve estimated by using axial dispersion model are 0.055 and 0.06 respectively. These calculations are performed after fitting the simulated axial dispersion model on the experiment curves. These results indicated that the extent of dispersion of water flowing in the pipeline is in the category of intermediate.

  14. Residence time distribution as a measure for stochastic resonance in a bistable system

    NASA Astrophysics Data System (ADS)

    Choi, Mee Hyang

    1997-12-01

    We review an alternative measure of Stochastic Resonance (SR), the residence time distribution function (RTDF), in a bistable system, and try to find a legitimate connection between it and either SNR or periodic response. We show that the area of the first peak in the RTDF is not related to SR, and that the exponential decay distribution has to be removed to find any meaningful measure as a response to the input signal. We introduce a model under which we study SR and briefly review the results of response amplitude in linear and nonlinear regimes. We introduce the definitions of the escape time distribution based on a rate equation. We show a useful method for calculating the phase distribution, which is crucial for obtaining the residence time distribution (RTDF). We are focused on the regime where the modulation frequency and the noise- jumping rate are comparable, and the uniform phase averaging does not lead to a correct result for the RTDF. We derive an explicit form for the RTDF, and study the area of the peaks around odd multiples of half of the driving period as a valid measure for SR. We conclude by showing some other statistical quantities which are easily obtained from our analytical results. We compare the numerical solutions of the Langevin equation of our model with our analysis.

  15. Keeping up with the times: revising the dermatology residency curriculum in the era of molecular diagnostics and personalized medicine.

    PubMed

    LaChance, Avery; Murphy, Michael J

    2014-11-01

    The clinical use of molecular diagnostics, genomics, and personalized medicine is increasing and improving rapidly over time. However, medical education incorporating the practical application of these techniques is lagging behind. Although instruction in these areas should be expanded upon and improved at all levels of training, residency provides a concentrated period of time in which to hone in on skills that are practically applicable to a trainee's specialty of choice. Although residencies in some fields, such as pathology, have begun to incorporate practical molecular diagnostics training, this area remains a relative gap in dermatology residency programs. Herein, we advocate for the incorporation of training in molecular diagnostics and personalized medicine into dermatology residency programs and propose a basic curriculum template for how to begin approaching these topics. By incorporating molecular diagnostics into dermatology residency training, dermatologists have the opportunity to lead the way and actively shape the specialty's transition into the era of personalized medicine. © 2014 The International Society of Dermatology.

  16. Residence times of stream-groundwater exchanges due to transient stream stage fluctuations

    NASA Astrophysics Data System (ADS)

    McCallum, James L.; Shanafield, Margaret

    2016-03-01

    The biogeochemical functioning of stream ecosystems is heavily dependent on water and water-borne nutrient fluxes between the stream itself and the streambed and banks (i.e., the hyporheic zone). The travel time of water exchanges through the hyporheic zone has been investigated previously; however, these studies have primarily modeled exchanges under steady state conditions assuming spatial pressure variations. This assumes that the hydraulic gradients that drive the exchanges are maintained the whole time the stream water remains in the bed or banks, which is unrealistic. Therefore, in this study we use a transient approach to investigate residence time distributions (RTDs) of bank inflow and bank outflow during both regular, diurnal stream stage variations and storm flow events. We demonstrate that RTDs reflect the timing and magnitude bank inflows, rather than smooth RTDs. We also show that small percentages of water from a given bank inflow event may be present in bank outflows for long periods of time, due to dispersion and diffusion within the bank, and lower rates of bank outflow, relative to bank inflow. This is apparent in the synthetic model of a single storm flow event, where 10% remained in the bank after 50 days. Additionally, residence times for a given bank inflow event are longer when repeated events occur, because the bank outflows from one event are "interrupted" by an increase in stream stage during a successive event. For example, field data capturing events of variable timing and magnitude showed that 70 days after each of three storm flow events occurred, 40, 12 and 30% of the bank inflow event remained in the banks. These cases indicate that bank exchanges are temporally dynamic and the RTDs of return flows can have significant tailing, which will dictate rates of nutrient exchange within the near-stream environment.

  17. Distribution and residence times of large woody debris along South River, Shenandoah Valley, Virginia

    NASA Astrophysics Data System (ADS)

    Hess, J.; Pizzuto, J.

    2006-12-01

    Numerous studies on large woody debris (LWD) have focused on forested mountain streams located in the Pacific Northwest. Wood in these streams typically form log jams that have a profound impact on stream morphology, promoting channel stability and forcing pools. However, studies are sparse on larger rivers where LWD occurs primarily as individual pieces. Even less is known about the residence times of LWD in these settings. This study focuses on the use of dendrochronology to determine the rates of LWD recruitment and LWD residence times. Located in the Shenandoah Valley of Virginia, the South River is a fourth order stream with a drainage area of over 600 km2 at its confluence with the South Fork Shenandoah River. The riparian zone is dominated by agriculture. Agricultural land use creates a distribution of LWD unlike that of forested streams, consisting primarily of isolated pieces and small jams versus larger jams. Four species of trees are dominant at South River: sycamore (Platanus occidentalis), silver maple (Acer saccharinum), boxelder (Acer negundo) and black walnut (Juglans nigra). Average diameters of LWD are 32 cm with lengths averaging 6-7 m. At the South River, LWD has no influence on channel morphology, but wood traps fine-grained sediment (storing 16% of the river's annual load) and associated contaminants making it the most significant mechanism for storing clay and silt within the channel perimeter. Sixty to seventy-five percent of LWD occurs in pools, while 10-20% occurs in riffles. Most of the wood falls from adjacent banks by both natural processes and agricultural practices. Preliminary dating results indicate that LWD reside in the channel a minimum of 15 years.

  18. Resident involvement in laparoscopic procedures does not worsen clinical outcomes but may increase operative times and length of hospital stay.

    PubMed

    Jolley, Jennifer; Lomelin, Daniel; Simorov, Anton; Tadaki, Carl; Oleynikov, Dmitry

    2016-09-01

    Surgical procedures have a learning curve regarding the number of cases required for proficiency. Consequently, involvement of less experienced resident surgeons may impact patients and the healthcare system. This study examines basic and advanced laparoscopic procedures performed between 2010 and 2011 and evaluates the resident surgeon participation effect. Basic laparoscopic procedures (BL), appendectomy (LA), cholecystectomy (LC), and advanced Nissen fundoplication (LN) were queried from the American College of Surgeons National Surgical Quality Improvement Program database. Cases were identified using Current Procedural Terminology codes. Analyses were performed using IBM SPSS Statistics v.22, α-level = 0.05. Multiple logistic regression was used, accounting for age, race, gender, admission status, wound classification, and ASA classification. In total, 71,819 surgeries were reviewed, 66,327 BL (37,636 LC and 28,691 LA) and 5492 LN. Median age was 48 years for LC and 37 years for LA. In sum, 72.2 % of LC and 49.5 % of LA patients were female. LN median age was 59 years, and 67.7 % of patients were female. For BL, resident involvement was not significantly associated with mortality, morbidity, and return to the OR. Readmission was not related to resident involvement in LC. In LA, resident-involved surgeries had increased readmission and longer OR time, but decreased LOS. In LC, resident involvement was associated with longer LOS and OR time. Resident involvement was not a significant factor in the odds of mortality, morbidity, return to OR, or readmission in LN. Surgeries involving residents had increased odds of having longer LOS, and of lengthier surgery time. We demonstrate resident involvement is safe and does not result in poorer patient outcomes. Readmissions and LOS were higher in BL, and operative times were longer in all surgeries. Resident operations do appear to have real consequences for patients and may impact the healthcare system

  19. Macrotextured spoked surfaces reduce the residence time of a bouncing Leidenfrost drop.

    PubMed

    Patterson, Colin J; Shiri, Samira; Bird, James C

    2017-02-15

    Liquid drops can bounce when they impact non-wetting surfaces. Recently, studies have demonstrated that the time that the bouncing drop contacts a superhydrophobic surface can be reduced by incorporating ridged macrotextures on the surface. Yet the existing models aimed at explaining this phenomenon offer incompatible predictions of the contact time when a drop impacts multiple intersecting macrotextures, or spokes. Furthermore, it is unclear whether the effects of the macrotexture on the drop hydrodynamics extend to non-wetting surfaces in which direct contact is avoided by a thin vapor layer. Here we demonstrate that the phenomenon observed for macrotextured, superhydrophobic surfaces extends to macrotextured, wettable surfaces above the Leidenfrost temperature. We show that the number of droplets and overall residence time both depend on the number of intersecting spokes. Finally, we compare and contrast our results with mechanistic models to rationalize various elements of the phenomenon.

  20. Numerical predictions of residence times behind a rearward facing step with transverse injection

    NASA Technical Reports Server (NTRS)

    Rogers, R. C.; Weidner, E. H.

    1983-01-01

    A numerical investigation of the two-dimensional recirculation zone formed between a rear-ward facing step and a transverse hydrogen jet in a supersonic flow is presented. Calculations were made using an elliptic flow computer code with a time-relaxation finite difference integration algorithm. Cases were examined for jet static pressures between 2 and 5 times mainstream with jets located 3 to 7 step heights downstream of the step. Nominal mainstream flow conditions were Mach 2.4 air at 1 atm pressure and 1000K (1800R) static temperature. Results in the form of mean properties in the recirculation zone and residence time are presented. Calculations of the decay of hydrogen mass from the steady state are presented for selected cases. The combustion potential for each case is assessed by comparison of computed conditions in the recirculation zone with the results from a well-stirred reactor theory.

  1. Numerical predictions of residence times behind a rearward facing step with transverse injection

    NASA Technical Reports Server (NTRS)

    Rogers, R. C.; Weidner, E. H.

    1983-01-01

    A numerical investigation of the two-dimensional recirculation zone formed between a rearward facing step and a transverse hydrogen jet in a supersonic flow is presented. Calculations were made using an elliptic flow computer code with a time-relaxation finite difference integration algorithm. Cases were examined for jet static pressures between 2 and 5 times mainstream with jets located 3 to 7 step heights downstream of the step. Nominal mainstream flow conditions were Mach 2.4 air at 1 atm pressure and 1000 K (1800 R) static temperature. Results in the form of mean properties in the recirculation zone and residence time are presented. Calculations of the decay of hydrogen mass from the steady state are presented for selected cases. The combustion potential for each case is assessed by comparison of computed conditions in the recirculation zone with the results from a well-stirred reactor theory.

  2. Macrotextured spoked surfaces reduce the residence time of a bouncing Leidenfrost drop

    NASA Astrophysics Data System (ADS)

    Patterson, Colin J.; Shiri, Samira; Bird, James C.

    2017-02-01

    Liquid drops can bounce when they impact non-wetting surfaces. Recently, studies have demonstrated that the time that the bouncing drop contacts a superhydrophobic surface can be reduced by incorporating ridged macrotextures on the surface. Yet the existing models aimed at explaining this phenomenon offer incompatible predictions of the contact time when a drop impacts multiple intersecting macrotextures, or spokes. Furthermore, it is unclear whether the effects of the macrotexture on the drop hydrodynamics extend to non-wetting surfaces in which direct contact is avoided by a thin vapor layer. Here we demonstrate that the phenomenon observed for macrotextured, superhydrophobic surfaces extends to macrotextured, wettable surfaces above the Leidenfrost temperature. We show that the number of droplets and overall residence time both depend on the number of intersecting spokes. Finally, we compare and contrast our results with mechanistic models to rationalize various elements of the phenomenon.

  3. Hyporheic Flow and Residence Times in Heterogeneous Cross-Bedded Sediment

    NASA Astrophysics Data System (ADS)

    Sawyer, A. H.; Cardenas, M. B.

    2008-12-01

    The permeability (k) structure of stream sediment influences hyporheic zone depth, flux, and residence time distribution (RTD). We numerically simulate bedform-induced hyporheic exchange using turbulent open channel flow simulations coupled to groundwater flow models that consider high-resolution k fields. The k fields are from the cross-bedded Massillon Sandstone and modern climbing ripple deposits of the Brazos River (Texas). In both cases, k heterogeneity leads to nested scales of hyporheic exchange and increases the depth of exchange relative to equivalent homogeneous sediment. Solute flux and RTDs differ markedly for the Massillon and Brazos cases, although both exhibit power-law RTDs. In the Massillon case, heterogeneity extends the tail of the RTD, relative to equivalent homogeneous sediment. In the Brazos case, heterogeneity leads to earlier breakthrough of solutes and shorter solute residence times along shallow exchange paths, relative to equivalent homogeneous sediment. These complex transport dynamics would presumably influence the fate of biogeochemical constituents and the thermal regime of sediment. Our case studies suggest, however, that the impact of k heterogeneity on hyporheic zone hydrodynamics is small compared with bed topography and channel hydraulics.

  4. A non-discrete method for computation of residence time in fluid mechanics simulations

    NASA Astrophysics Data System (ADS)

    Esmaily-Moghadam, Mahdi; Hsia, Tain-Yen; Marsden, Alison L.

    2013-11-01

    Cardiovascular simulations provide a promising means to predict risk of thrombosis in grafts, devices, and surgical anatomies in adult and pediatric patients. Although the pathways for platelet activation and clot formation are not yet fully understood, recent findings suggest that thrombosis risk is increased in regions of flow recirculation and high residence time (RT). Current approaches for calculating RT are typically based on releasing a finite number of Lagrangian particles into the flow field and calculating RT by tracking their positions. However, special care must be taken to achieve temporal and spatial convergence, often requiring repeated simulations. In this work, we introduce a non-discrete method in which RT is calculated in an Eulerian framework using the advection-diffusion equation. We first present the formulation for calculating residence time in a given region of interest using two alternate definitions. The physical significance and sensitivity of the two measures of RT are discussed and their mathematical relation is established. An extension to a point-wise value is also presented. The methods presented here are then applied in a 2D cavity and two representative clinical scenarios, involving shunt placement for single ventricle heart defects and Kawasaki disease. In the second case study, we explored the relationship between RT and wall shear stress, a parameter of particular importance in cardiovascular disease.

  5. Chemotaxis Increases the Residence Time Distribution of Bacteria in Granular Media Containing Distributed Contaminant Sources

    NASA Astrophysics Data System (ADS)

    Adadevoh, J.; Triolo, S.; Ramsburg, C. A.; Ford, R.

    2015-12-01

    The use of chemotactic bacteria in bioremediation has the potential to increase access to, and biotransformation of, contaminant mass within the subsurface environment. This laboratory-scale study aimed to understand and quantify the influence of chemotaxis on residence times of pollutant-degrading bacteria within homogeneous treatment zones. Focus was placed on a continuous flow sand-packed column system in which a uniform distribution of naphthalene crystals created distributed sources of dissolved phase contaminant. A 10 mL pulse of Pseudomonas putida G7, which is chemotactic to naphthalene, and Pseudomonas putida G7 Y1, a non-chemotactic mutant strain, were simultaneously introduced into the sand-packed column at equal concentrations. Breakthrough curves obtained for the bacteria from column experiments conducted with and without naphthalene were used to quantify the effect of chemotaxis on transport parameters. In the presence of the chemoattractant, longitudinal dispersivity of PpG7 increased by a factor of 3 and percent recovery decreased from 21% to 12%. The results imply that pore-scale chemotaxis responses are evident at an interstitial fluid velocity of 1.7 m/d, which is within the range of typical groundwater flow. Within the context of bioremediation, chemotaxis may work to enhance bacterial residence times in zones of contamination thereby improving treatment.

  6. Tritium activity concentrations and residence times of groundwater collected in Rokkasho, Japan.

    PubMed

    Hasegawa, Hidenao; Ueda, Shinji; Akata, Naofumi; Kakiuchi, Hideki; Hisamatsu, Shun'ichi

    2015-11-01

    Tritium ((3)H) concentrations were measured in groundwater samples from four surface wells (4-10 m deep), four shallow wells (24-26.5 m deep) and a 150-m-deep well in the Futamata River catchment area, which is adjacent to the large-scale commercial spent nuclear fuel reprocessing plant in Rokkasho, Japan. The (3)H concentrations in most of the surface- and shallow-well samples (<0.03-0.57 Bq l(-1)) were similar to those in precipitation (annual mean: 0.31-0.79 Bq l(-1)), suggesting that the residence time of the water in those wells was 0-15 y. The (3)H concentrations in the samples from a 26-m-deep well and the 150-m-deep well were lower than those in the other wells, indicating that groundwater with a long residence time exists in deep aquifers and the estuary area of the catchment. It is not clear whether (3)H released during test operation of the plant with actual spent nuclear fuel affected the (3)H concentrations observed in this study.

  7. Residence time and conversion in the extrusion of chemically reactive materials

    SciTech Connect

    Zhu, W.; Jaluria, Y.

    1999-07-01

    Extrusion is one of the most versatile and energy-efficient processes for the manufacture of polymer products, including food, pharmaceuticals and plastics. Many functions including mixing, cooking and chemical reaction can be performed in an extruder. Here, twin-screw extruders offer improved control of the residence time distribution (RTD) and mixing in materials such as plastics, rubber and food. Based on the flow and the heat transfer characteristics obtained for a self-wiping, co-rotating twin-screw extruder, the residence time and chemical reaction are studied by tracking the particles. For normally starve-fed twin-screw extruders, the length of the completely filled section is calculated as function of the process variables using the coupling of the flow with the die. With a model of the solid conveying section, the RTD for the whole extruder is calculated for corn meal at different screw speeds and flow rates. The calculated variation of RTD with the screw speed and the flow rate yields good agreement with observations from many experiments. The variation of the fully filled section length, chemical conversion and mixing effectiveness are also obtained under different operation conditions. Most of the results are in qualitative agreement with experimental results and may be used as guidelines for extruder design and determination of optimal operating condition.

  8. RANS Simulation of Passive Scalar Residence Times and Exchange Processes in Idealized and Natural Stream Systems

    NASA Astrophysics Data System (ADS)

    Drost, Kevin; Jackson, Tracie; Haggerty, Roy; Apte, Sourabh

    2011-11-01

    Natural stream systems contain a variety of dead zones characterized by flow separation, a mixing layer, and a recirculation zone. These dead zones play an important role in stream solute transport studies. Previous published work has focused on idealized storage zone geometries studied in laboratory flumes. Using RANS simulations, this study first examines these idealized geometries to determine the appropriate scaling relationships between idealized dead zone geometries and the residence times of a passive scalar. These scaling relationships are then applied to measurements from natural systems. The field-measured geometries are located in Oak and Soap creeks near Corvallis, Oregon. Field measurements for the natural systems included: (a) survey measurements to delineate storage zone morphologies; (b) Marsh-McBirney and acoustic Doppler velocimetry measurements for model boundary conditions and computation of turbulence parameters; and (c) continuous salt injections within storage zones and electrical conductivity measurements at point locations in the main channel and storage zones to quantify exchange rates and residence times. This work is sponsored by NSF-EAR project #0943570.

  9. A non-discrete method for computation of residence time in fluid mechanics simulations.

    PubMed

    Esmaily-Moghadam, Mahdi; Hsia, Tain-Yen; Marsden, Alison L

    2013-11-01

    Cardiovascular simulations provide a promising means to predict risk of thrombosis in grafts, devices, and surgical anatomies in adult and pediatric patients. Although the pathways for platelet activation and clot formation are not yet fully understood, recent findings suggest that thrombosis risk is increased in regions of flow recirculation and high residence time (RT). Current approaches for calculating RT are typically based on releasing a finite number of Lagrangian particles into the flow field and calculating RT by tracking their positions. However, special care must be taken to achieve temporal and spatial convergence, often requiring repeated simulations. In this work, we introduce a non-discrete method in which RT is calculated in an Eulerian framework using the advection-diffusion equation. We first present the formulation for calculating residence time in a given region of interest using two alternate definitions. The physical significance and sensitivity of the two measures of RT are discussed and their mathematical relation is established. An extension to a point-wise value is also presented. The methods presented here are then applied in a 2D cavity and two representative clinical scenarios, involving shunt placement for single ventricle heart defects and Kawasaki disease. In the second case study, we explored the relationship between RT and wall shear stress, a parameter of particular importance in cardiovascular disease.

  10. Residence times in subsurface hydrological systems, introduction to the Special Issue

    NASA Astrophysics Data System (ADS)

    de Dreuzy, J.-R.; Ginn, T. R.

    2016-12-01

    Interest in the residence time distribution (RTD) as a comprehensive measure of subsurface hydrologic systems is growing. This focus is resulting from recognition that diverse vadose zone, groundwater flows, and transfer between hydrological compartments, are fundamentally related to the system RTD. Furthermore, transport of chemical or biological species and the biogeochemical activities that govern their fate, is principally reflected by the system RTD. Thus the RTD is used in geochemical interpretation of environmental tracers, in direct reactive transport approaches, and ultimately for sustainability and protection assessments in the consideration of transient boundary flows due to climate change or other causes, anthropogenic and/or natural. The RTD has been handled in the past primarily as a byproduct of models. It is now increasingly viewed as an integrative characteristic for which shape-free and generic distributions are developed, that links conceptual hydrology, characterization data, and mathematical models. Intermediary between mechanistic modeling, geochemical data and predictions, the role for residence time distribution is to represent consistently the flow, transport and reactivity processes while reaching the objective of biogeochemical interpretation and sustainability assessment. After some outline of the scientific context, we introduce the contributions of this special issue and conclude with the emerging challenges.

  11. The reactive transport of trichloroethene is influenced by residence time and microbial numbers

    NASA Astrophysics Data System (ADS)

    Haest, P. J.; Philips, J.; Springael, D.; Smolders, E.

    2011-01-01

    The dechlorination rate in a flow-through porous matrix can be described by the species specific dechlorination rate observed in a liquid batch unless mass transport limitations prevail. This hypothesis was examined by comparing dechlorination rates in liquid batch with that in column experiments at various flow rates (3-9-12 cm day - 1 ). Columns were loaded with an inoculated sand and eluted with a medium containing 1 mM trichloroethene (TCE) for 247 days. Dechlorination in the column treatments increased with decreasing flow rate, illustrating the effect of the longer residence time. Zeroth order TCE or cis-DCE degradation rates were 4-7 folds larger in columns than in corresponding batch systems which could be explained by the higher measured Geobacter and Dehalococcoides numbers per unit pore volume in the columns. The microbial numbers also explained the variability in dechlorination rate among flow rate treatments marked by a large elution of the dechlorinating species' yield as flow increased. Stop flow events did not reveal mass transport limitations for dechlorination. We conclude that flow rate effects on reactive transport of TCE in this coarse sand are explained by residence time and by microbial transport and that mass transport limitations in this porous matrix are limited.

  12. Chemotaxis Increases the Residence Time of Bacteria in Granular Media Containing Distributed Contaminant Sources.

    PubMed

    Adadevoh, Joanna S T; Triolo, Sarah; Ramsburg, C Andrew; Ford, Roseanne M

    2016-01-05

    The use of chemotactic bacteria in bioremediation has the potential to increase access to, and the biotransformation of, contaminant mass within the subsurface. This laboratory-scale study aimed to understand and quantify the influence of chemotaxis on the residence times of pollutant-degrading bacteria within homogeneous treatment zones. Focus was placed on a continuous-flow sand-packed column in which a uniform distribution of naphthalene crystals created distributed sources of dissolved-phase contaminant. A 10 mL pulse of Pseudomonas putida G7, which is chemotactic to naphthalene, and Pseudomonas putida G7 Y1, a nonchemotactic mutant strain, were simultaneously introduced into the sand-packed column at equal concentrations. Breakthrough curves obtained from experiments conducted with and without naphthalene were used to quantify the effect of chemotaxis on transport parameters. In the presence of the chemoattractant, longitudinal dispersion of PpG7 increased by a factor of 3, and percent recovery decreased by 43%. In contrast, PpG7 Y1 transport was not influenced by the presence of naphthalene. The results imply that pore-scale chemotaxis responses are evident at an interstitial velocity of 1.8 m/day, which is within the range of typical groundwater flow. Within the context of bioremediation, chemotaxis may work to enhance bacterial residence times in zones of contamination, thereby improving treatment.

  13. Prevalence and Cost of Full-Time Research Fellowships During General Surgery Residency – A National Survey

    PubMed Central

    Robertson, Charles M.; Klingensmith, Mary E.; Coopersmith, Craig M.

    2009-01-01

    Structured Abstract Objective To quantify the prevalence, outcomes, and cost of surgical resident research. Summary Background Data General surgery is unique among graduate medical education programs because a large percentage of residents interrupt their clinical training to spend 1-3 years performing full-time research. No comprehensive data exists on the scope of this practice. Methods Survey sent to all 239 program directors of general surgery residencies participating in the National Resident Matching Program. Results Response rate was 200/239 (84%). A total of 381 out of 1052 trainees (36%) interrupt residency to pursue full-time research. The mean research fellowship length is 1.7 years, with 72% of trainees performing basic science research. A significant association was found between fellowship length and post-residency activity, with a 14.7% increase in clinical fellowship training and a 15.2% decrease in private practice positions for each year of full-time research (p<0.0001). Program directors at 31% of programs reported increased clinical duties for research fellows as a result of ACGME work hour regulations for clinical residents, while a further 10% of programs are currently considering such changes. It costs $41.5 million to pay the 634 trainees who perform research fellowships each year, the majority of which is paid for by departmental funds (40%) and institutional training grants (24%). Conclusions Interrupting residency to perform a research fellowship is a common and costly practice among general surgery residents. While performing a research fellowship is associated with clinical fellowship training after residency, it is unclear to what extent this practice leads to the development of surgical investigators after post-graduate training. PMID:19106692

  14. Residence Times of Juvenile Salmon and Steelhead in Off-Channel Tidal Freshwater Habitats, Columbia River, USA

    SciTech Connect

    Johnson, Gary E.; Ploskey, Gene R.; Sather, Nichole K.; Teel, D. J.

    2015-05-01

    We estimated seasonal residence times of acoustic-tagged juvenile salmonids in off-channel, tidal freshwater habitats of the Columbia River near the Sandy River delta (rkm 198; 2007, 2008, 2010, and 2011) and Cottonwood Island (rkm 112; 2012).

  15. The effect of residence time on the dynamics of a condensating aerosol in a Hiemenz-type stagnation flow

    NASA Astrophysics Data System (ADS)

    Alshaarawi, Amjad; Zhou, Kun; Scribano, Gianfranco; Attili, Antonio; Bisetti, Fabrizio; Clean Combustion Research Center Team

    2013-11-01

    The effect of residence time on the formation and growth of a condensating aerosol is simulated in a Hiemenz-type stagnation flow setup, for which a unique and well-defined time scale characterizes the velocity field. In this configuration, a hot stream saturated with dibutyle phthalate (DBP) vapor mixes with a cold dry stream. A mixing layer forms at the stagnation plane triggering supersaturation and droplets are generated by homogeneous nucleation. Aerosol dynamics are simulated using the Quadrature Method of Moments (QMOM). Two regimes related to the flow residence time are observed, i.e., a nucleation regime and a condensation regime. The nucleation regime, at short residence times, is characterized by the consumption of DBP vapor into droplets having a negligible effect on the vapor phase. In this regime, both the number density and volume fraction of droplets increase with residence time. In the condensation regime, at long residence times, vapor condensation consumes the vapor phase considerably. For longer residence times, more vapor is consumed, resulting in lower number densities due to the lower nucleation rates, whereas the volume fraction saturates.

  16. Effective denitrification at the groundwater surface-water interface: exposure rather than residence time

    NASA Astrophysics Data System (ADS)

    Peiffer, Stefan; Frei, Sven

    2014-05-01

    Effective processing of material in aquatic systems, e. g. removal of nitrate upon denitrification, requires sufficient reaction time. This statement sounds trivial albeit its implication for biogeochemistry seems to be not fully recognized. The time teff required for effective processing of nitrate is controlled by the underlying biogeochemical rate law. In the simplest case of a 1st order reaction, teff is often calculated as the time when 63% of the initial concentration is consumed setting teff as 1/kreaction. It may, however, be more appropriate to derive teff,90%or teff,99% from the respective rate law. Hence a minimum time t > teff is required that exposes a specific biogeochemical process to conditions favourable for this process, which is anoxia in case of denitrification. This exposure time τexp is not necessarily identical to the residence time τ of water in the particular system or flow path. Rather, the exposure time can be much shorter and may even fluctuate with time. As a consequence, Damköhler numbers (Da = τexp/teff) for denitrification < 1 may be the consequence even though the age of water may be comparatively high. We therefore argue that the key for understanding denitrification efficiency at the groundwater surface-water interface (or in groundwater systems in general) is the quantification of the exposure time. This contribution therefore aims i) to estimate exposure times required for effective denitrification based on an analysis of rate constants for denitrification, ii) to relate these time scales to typical residence time distributions found at the groundwater surface-water interface and iii) to discuss implications for denitrification efficiencies. References: Oldham, C; Farrow, DE; Peiffer, S (2013): A generalized Damköhler number for classifying material processing in hydrological systems, Hydrology and Earth System Sciences, 17, 1133-1148 Frei, S; Knorr, KH; Peiffer, S; Fleckenstein, J (2012): Surface micro-topography causes

  17. Numerical model of circulation and residence times in the Persian Gulf

    NASA Astrophysics Data System (ADS)

    O'Donncha, Fearghal; Ragnoli, Emanuele

    2014-05-01

    parameters. The resultant time-series comprised tidal harmonic constituents and residuals composed of primarily density-driven and wind-driven (near surface) currents. To further decompose the residual currents time series are further filtered based on the differing scaling times of both wind-driven (days) and density-driven (weeks) flows. The resulting datasets enable a comprehensive classification of the relative influence of tides, wind and density effects across the domain. As a summary measure of circulation within the region, the model was used to compute the residence time for a water parcel in the gulf. Several transport time scales were calculated, including the average residence time and variations across the region. Residence statistics provide several insights into circulation in the gulf, in particular, knowledge of circulation patterns through the Straits of Hormuz, regional variation of residence times from North-South, and the impacts of wind and density-driven circulation on particle renewal within the domain.

  18. Coupling groundwater residence time and 234U/238U isotopic ratios in a granitic catchment (Vosges, Eastern France)

    NASA Astrophysics Data System (ADS)

    Viville, Daniel; Aquilina, Luc; Ackerer, Julien; Chatton, Eliot; Labasque, Thierry; Pierret, Marie-Claire; Granet, Mathieu; Perrone, Thierry; Chabaux, François

    2016-04-01

    Weathering processes are active in surface waters but groundwater also represents no neglectable chemical fluxes. As residence-time in groundwater are high, silicate weathering might take place and control Si, Ca and C fluxes. Weathering processes can be deduced from U isotopic ratios but the kinetics of these processes remain relatively poorly constrained. In order to better characterize these processes, we have coupled residence-times deduced from anthropogenic gases (CFC and SF6) analysis and 234U/238U isotopic ratios determination. Samples were collected in the Strengbach catchment (Hydro-geochemical Observatory OHGE, Vosges, eastern France). Two campaigns were carried out in May and August 2015 during two highly contrasted hydro-climatic periods. Both springs and boreholes down to 80 m depth have been sampled. A very clear geochemical distinction is observed between groundwater from surface springs and deeper groundwater from boreholes. Springs show much lower residence-time (few years) and specific chemical composition. Deeper groundwater have residence-time of several decades and different geochemical composition. A clear SF6 production is observed with increasing SF6 concentrations with residence-time. The campaign of May is characterized by highly groundwater levels and spring fluxes. All groundwater show very low residence time, except in the boreholes at depth greater than 40 m. Conversely, during low groundwater-level period in August, the residence times are much higher and CFC concentrations indicate a large mixing process between surface groundwater and deeper levels. The 234U/238U isotopic ratios confirm this vertical zonation in the boreholes, with much higher activity ratios in the deep ground-waters from borehole than in the surface and spring waters; Such high U activity ratios are indicative of long water-rock interactions, which is consistent with the long residence times deducted from the CFC and SF6 data.

  19. Estimates of residence time and related variations in quality of ground water beneath Submarine Base Bangor and vicinity, Kitsap County, Washington

    USGS Publications Warehouse

    Cox, S.E.

    2003-01-01

    screened in the deeper aquifer may be the result of preferential ground-water pathways or induced downward flow caused by pumping stress. Spatial variations in water quality were used to develop a conceptual model of chemical evolution of ground water. Stable isotope ratios of deuterium and oxygen-18 in the 33 ground-water samples were similar, indicating similar climatic conditions and source of precipitation recharge for all of the sampled ground water. Oxidation of organic matter and mineral dissolution increased the concentrations of dissolved inorganic carbon and common ions in downgradient ground waters. However, the largest concentrations were not found near areas of ground-water discharge, but at intermediate locations where organic carbon concentrations were greatest. Dissolved methane, derived from microbial methanogenesis, was present in some ground waters. Methanogenesis resulted in substantial alteration of the carbon isotopic composition of ground water. The NETPATH geochemical model code was used to model mass-transfers of carbon affecting the 14C estimate of ground-water residence time. Carbon sources in ground water include dispersed particulate organic matter present in the confining unit separating the two aquifers and methane present in some ground water. Carbonate minerals were not observed in the lithologic material of the ground-water system but may be present, because they have been found in the bedrock of stream drainages that contribute sediment to the study area.

  20. Residence time dependent desorption of Staphylococcus epidermidis from hydrophobic and hydrophilic substrata.

    PubMed

    Boks, Niels P; Kaper, Hans J; Norde, Willem; Busscher, Henk J; van der Mei, Henny C

    2008-12-01

    Adhesion and desorption are simultaneous events during bacterial adhesion to surfaces, although desorption is far less studied than adhesion. Here, desorption of Staphylococcus epidermidis from substratum surfaces is demonstrated to be residence time dependent. Initial desorption rate coefficients were similar for hydrophilic and hydrophobic dimethyldichlorosilane (DDS)-coated glass, likely because initial desorption is controlled by attractive Lifshitz-Van der Waals interactions, which are comparable on both substratum surfaces. However, significantly slower decay times of the desorption rate coefficients are found for hydrophilic glass than for hydrophobic DDS-coated glass. This difference is suggested to be due to the acid-base interactions between staphylococci and these surfaces, which are repulsive on hydrophilic glass and attractive on hydrophobic DDS-coated glass. Final desorption rate coefficients are higher on hydrophilic glass than on hydrophobic DDS-coated glass, due to the so called hydrophobic effect, facilitating a closer contact on hydrophobic DDS-coated glass.

  1. Automated near-real-time clinical performance feedback for anesthesiology residents: one piece of the milestones puzzle.

    PubMed

    Ehrenfeld, Jesse M; McEvoy, Matthew D; Furman, William R; Snyder, Dylan; Sandberg, Warren S

    2014-01-01

    Anesthesiology residencies are developing trainee assessment tools to evaluate 25 milestones that map to the six core competencies. The effort will be facilitated by development of automated methods to capture, assess, and report trainee performance to program directors, the Accreditation Council for Graduate Medical Education and the trainees themselves. The authors leveraged a perioperative information management system to develop an automated, near-real-time performance capture and feedback tool that provides objective data on clinical performance and requires minimal administrative effort. Before development, the authors surveyed trainees about satisfaction with clinical performance feedback and about preferences for future feedback. Resident performance on 24,154 completed cases has been incorporated into the authors' automated dashboard, and trainees now have access to their own performance data. Eighty percent (48 of 60) of the residents responded to the feedback survey. Overall, residents "agreed/strongly agreed" that they desire frequent updates on their clinical performance on defined quality metrics and that they desired to see how they compared with the residency as a whole. Before deployment of the new tool, they "disagreed" that they were receiving feedback in a timely manner. Survey results were used to guide the format of the feedback tool that has been implemented. The authors demonstrate the implementation of a system that provides near-real-time feedback concerning resident performance on an extensible series of quality metrics, and which is responsive to requests arising from resident feedback about desired reporting mechanisms.

  2. Estimating renewal timescales with residence time and connectivity in an urban man-made lake in China.

    PubMed

    Gao, Xueping; Xu, Liping; Zhang, Chen

    2016-07-01

    Residence times and connectivity are computed for 12 subregions in an urban man-made lake in China using a high-resolution tracer-transport model. The renewal timescales are explicitly defined and computed for two groups of four freshwater inflow scenarios related to water diversion projects. First, the timescale values are computed and compared using different computational criteria for the upper limit of integration in the residence time equation. The sensitivity analysis suggests that a calculation time of 300 days is necessary to satisfy the relative error (0.001) and 5 % cutoff value criteria. Secondly, the residence times can range from 1.5 to 102 and 1.0 to 66 days under low and high flow conditions, respectively. Water in the inner lake would reside in the lake for less than 66 days prior to exiting the region of interest. The timescale values can be applied to impact studies that investigate the extent of sudden water pollution events that initially affect a subdomain of a lake. Finally, the lacustrine residence times are decomposed into the different subregion residence times, resulting in a connectivity matrix. This matrix can illustrate preferential connections among the individual subregions and reveal hidden patterns relating to local hydrodynamics in the lake.

  3. Characteristics of residency training associated with first-time pass rate on the American College of Veterinary Ophthalmologists certifying examination.

    PubMed

    Hendrix, Diane V H; Bentley, Ellison; Rohrbach, Barton W

    2014-07-01

    The aim of this study was to examine the association of various aspects of veterinary ophthalmology residency training with the first-time pass rate (FTPR) of the American College of Veterinary Ophthalmologists (ACVO) examination, as well as the individual written, image recognition, animal examination, and surgical sections of the examination. Program type, resident evaluations, cumulative surgery and case logs, and scores from ACVO examinations from 2007 to 2010 were evaluated. Data were available for 71 candidates. The overall FTPR was 35% (n = 25). For the different sections of the examination, FTPRs were as follows: written (68%), image recognition (76%), intraocular surgery (80%), extraocular surgery (65%), and animal examination (75%). The overall FTPR among candidates from academic residency (AR) programs was 43% (20 of 47), while the FTPR of residents in private practice (PPR) programs was 21% (5 of 24; P = 0.07). The AR candidates were more likely to pass the written portion than PPR residents (P = 0.02), and AR candidates had significantly more time off clinics (median 25%) vs PPR residents (median 18%; P = 0.007). The AR residents also had a higher reported percentage of direct supervision than PPR residents (95% vs 76%, respectively). Although PPR residents did significantly more surgeries and examined significantly more dogs and cats, those from ARs examined significantly more equine, bovine, avian, camelid, and reptile species. Overall, AR residents had a higher FTPR and were more likely to pass the written portion of the examination. Total case and surgery numbers were not associated with FTPR. © 2013 American College of Veterinary Ophthalmologists.

  4. Sources of groundwater nitrate revealed using residence time and isotope methods

    SciTech Connect

    Moore, K B; Ekwurzel, B; Esser, B K; Hudson, G B; Moran, J E

    2004-10-07

    Nitrate concentrations approaching and greater than the maximum contaminant level (MCL) are impairing the viability of many groundwater basins as drinking water sources. Nitrate isotope data are effective in determining contaminant sources, especially when combined with other isotopic tracers such as stable isotopes of water and tritium-helium ages to give insight into the routes and timing of nitrate inputs to the flow system. This combination of techniques is demonstrated in Livermore, CA, where it is determined that low nitrate reclaimed wastewater predominates in the northwest, while two flowpaths with distinct nitrate sources originate in the southeast. Along the eastern flowpath, {delta}{sup 15}N values greater than 10{per_thousand} indicate that animal waste is the primary source. Diminishing concentrations over time suggest that contamination results from historical land use practices. The other flowpath begins in an area where rapid recharge, primarily of low-nitrate imported water (identified by stable isotopes of water and a tritium-helium residence time of less than 1 year), mobilizes a significant local nitrate source, bringing groundwater concentrations up to 53 mg NO{sub 3} L{sup -1}. In this area, artificial recharge of imported water via local arroyos increases the flux of nitrate to the regional aquifer. The low {delta}{sup 15}N value (3.1{per_thousand}) in this location implicates synthetic fertilizer. In addition to these anthropogenic sources, natural nitrate background levels between 15 and 20 mg NO{sub 3} L{sup -1} are found in deep wells with residence times greater than 50 years.

  5. [Organization of a pedodontic residency in the interior of the country].

    PubMed

    Moguillansky, E; Perez, J

    1989-01-01

    Since 1981 there is an Odontopediatric residence in Azul, Pcia. de Bs. As., Argentina. The resident accomplish a three year cycle and obtain a Scholarship payed by Health Ministry of Provincia de Bs. As. The educational curricula is basic and points to the essential aim of health preservation putting aside disease treatment as a way to achieve it.

  6. Drinking water residence time in distribution networks and emergency department visits for gastrointestinal illness in Metro Atlanta, Georgia.

    PubMed

    Tinker, Sarah C; Moe, Christine L; Klein, Mitchel; Flanders, W Dana; Uber, Jim; Amirtharajah, Appiah; Singer, Philip; Tolbert, Paige E

    2009-06-01

    We examined whether the average water residence time, the time it takes water to travel from the treatment plant to the user, for a zip code was related to the proportion of emergency department (ED) visits for gastrointestinal (GI) illness among residents of that zip code. Individual-level ED data were collected from all hospitals located in the five-county metro Atlanta area from 1993 to 2004. Two of the largest water utilities in the area, together serving 1.7 million people, were considered. People served by these utilities had almost 3 million total ED visits, 164,937 of them for GI illness. The relationship between water residence time and risk for GI illness was assessed using logistic regression, controlling for potential confounding factors, including patient age and markers of socioeconomic status (SES). We observed a modestly increased risk for GI illness for residents of zip codes with the longest water residence times compared with intermediate residence times (odds ratio (OR) for Utility 1 = 1.07, 95% confidence interval (CI) = 1.03, 1.10; OR for Utility 2 = 1.05, 95% CI = 1.02, 1.08). The results suggest that drinking water contamination in the distribution system may contribute to the burden of endemic GI illness.

  7. Drinking Water Residence Time in Distribution Networks and Emergency Department Visits for Gastrointestinal Illness in Metro Atlanta, Georgia

    PubMed Central

    Moe, Christine L.; Klein, Mitchel; Flanders, W. Dana; Uber, Jim; Amirtharajah, Appiah; Singer, Philip; Tolbert, Paige E.

    2013-01-01

    We examined whether the average water residence time, the time it takes water to travel from the treatment plant to the user, for a zip code was related to the proportion of emergency department (ED) visits for gastrointestinal (GI) illness among residents of that zip code. Individual-level ED data were collected from all hospitals located in the five-county metro Atlanta area from 1993 to 2004. Two of the largest water utilities in the area, together serving 1.7 million people, were considered. People served by these utilities had almost three million total ED visits, 164,937 of them for GI illness. The relationship between water residence time and risk for GI illness was assessed using logistic regression, controlling for potential confounding factors, including patient age and markers of socioeconomic status (SES). We observed a modestly increased risk for GI illness for residents of zip codes with the longest water residence times compared to intermediate residence times (odds ratio (OR) for Utility 1 = 1.07, 95% confidence interval (CI) = 1.03, 1.10; OR for Utility 2 = 1.05, 95% CI = 1.02, 1.08). The results suggest that drinking water contamination in the distribution system may contribute to the burden of endemic GI illness. PMID:19240359

  8. Residence time revisited: The role of radiocarbon in reactive transport modeling

    NASA Astrophysics Data System (ADS)

    Lawrence, C. R.; Druhan, J. L.; Schulz, M. S.

    2016-12-01

    In recent years, our changing understanding of the dominant controls on soil carbon (C) storage and stability has cast a greater emphasis on the importance of physical and hydrological processes. These shifts in our understanding of C cycling have fostered increasingly commonplace measurements of soil physical and hydrological parameters in soil C studies (e.g. specific surface area, quantitative mineralogy, porosity) that reflect the importance of microbial accessibility to soil C. As a result, we are now poised to reassess the applicability of our approaches for conceptualizing and modeling soil C dynamics, particularly with regard to our representation of soil C pools. The goal of this work is to explore how the quantity and turnover of C, as approximated by radiocarbon measurements, is mechanistically linked to the physical and hydrologic parameters of soils. We utilize a reactive transport (RT) approach to link hydrologic transport, geochemical transformations and microbial activity influencing the magnitude and residence time of different carbon pools under variably saturated conditions. A newly developed version of the CrunchTope software is used to explicitly simulate the coupled transport, transformation, fractionation and decay of the three isotopes of carbon (12C, 13C and 14C) through a mechanistic framework. We constrain this model with a high-resolution dataset of soil carbon content, stable isotope composition and radiocarbon ages as well as physical and hydrologic data measured from a chronosequence of soils located near Santa Cruz, California. The Santa Cruz dataset is highly amenable to this task in that it demonstrates both seasonal and millennial variations in soil C distributions and associated soil properties. We present data from a series of simulations examining the sensitivity of C stocks, fluxes and mean residence times to transient processes spanning a range of temporal scales, including redox conditions, fluid flow and the distribution of

  9. Evaluation of flowpaths and mean resident time of water in a riparian wetland.

    NASA Astrophysics Data System (ADS)

    Augeard, B.; Michelin, J.; Kao, C.

    2003-04-01

    Hydrology is an essential issue to evaluate hydrological, biochemical, or ecological functions of riparian wetlands. Our study focuses on the influence of hydrological processes on subsurface denitrification efficiency. The study site is a riparian wetland (3.2 ha) drained by a temporary stream Les Roises (catchment area 1260 ha) located in Champagne crayeuse 150 km east from Paris, France. This site is characterized by 1-2 m of peat deposits overlying a 10 m depth chalk aquifer. The main wetland inflow is controlled by the chalk aquifer water table level. Measurements of peat permeability indicate the presence of a deep, more decomposed and less permeable layer which isolates the uppermost peat from chalk. A previous study has demonstrated that denitrification occurs in peat during the wetland submersion period. Less intense denitrification has also been observed in the chalk aquifer during the lower water table period. Stream flow and groundwater level monitoring were used to estimate the water budget of peat and to determine the mean resident time of water in peat during both the submersion period and the water table recession. Chalk groundwater flow simulations for the whole catchment have been performed using MODFLOW model to reproduce the observed water table temporal variations. The model also estimates groundwater fluxes bonding the wetland. These fluxes are used as boundary conditions for a wetland profile model developed using HYDRUS 2D. Proportions of ground water flow passing through and under the peat towards the river have been evaluated from steady state simulations. Computed results indicate that 15-25% of the watershed water flows through the peat during the submersion period. The mean resident time of the water in peat soil is about one week. During water table recession only 1% of the water flows through the peatland but the resident time is much higher. Such results suggest that the efficiency of this type of riparian wetland in removing

  10. Trait differences between naturalized and invasive plant species independent of residence time and phylogeny.

    PubMed

    Gallagher, R V; Randall, R P; Leishman, M R

    2015-04-01

    The ability to predict which alien plants will transition from naturalized to invasive prior to their introduction to novel regions is a key goal for conservation and has the potential to increase the efficacy of weed risk assessment (WRA). However, multiple factors contribute to plant invasion success (e.g., functional traits, range characteristics, residence time, phylogeny), and they all must be taken into account simultaneously in order to identify meaningful correlates of invasion success. We compiled 146 pairs of phylogenetically paired (congeneric) naturalized and invasive plant species in Australia with similar minimum residence times (i.e., time since introduction in years). These pairs were used to test for differences in 5 functional traits (flowering duration, leaf size, maximum height, specific leaf area [SLA], seed mass) and 3 characteristics of species' native ranges (biome occupancy, mean annual temperature, and rainfall breadth) between naturalized and invasive species. Invasive species, on average, had larger SLA, longer flowering periods, and were taller than their congeneric naturalized relatives. Invaders also exhibited greater tolerance for different environmental conditions in the native range, where they occupied more biomes and a wider breadth of rainfall and temperature conditions than naturalized congeners. However, neither seed mass nor leaf size differed between pairs of naturalized and invasive species. A key finding was the role of SLA in distinguishing between naturalized and invasive pairs. Species with high SLA values were typically associated with faster growth rates, more rapid turnover of leaf material, and shorter lifespans than those species with low SLA. This suite of characteristics may contribute to the ability of a species to transition from naturalized to invasive across a wide range of environmental contexts and disturbance regimes. Our findings will help in the refinement of WRA protocols, and we advocate the inclusion

  11. Residence time distribution measurements in a pilot-scale poison tank using radiotracer technique.

    PubMed

    Pant, H J; Goswami, Sunil; Samantray, J S; Sharma, V K; Maheshwari, N K

    2015-09-01

    Various types of systems are used to control the reactivity and shutting down of a nuclear reactor during emergency and routine shutdown operations. Injection of boron solution (borated water) into the core of a reactor is one of the commonly used methods during emergency operation. A pilot-scale poison tank was designed and fabricated to simulate injection of boron poison into the core of a reactor along with coolant water. In order to design a full-scale poison tank, it was desired to characterize flow of liquid from the tank. Residence time distribution (RTD) measurement and analysis was adopted to characterize the flow dynamics. Radiotracer technique was applied to measure RTD of aqueous phase in the tank using Bromine-82 as a radiotracer. RTD measurements were carried out with two different modes of operation of the tank and at different flow rates. In Mode-1, the radiotracer was instantaneously injected at the inlet and monitored at the outlet, whereas in Mode-2, the tank was filled with radiotracer and its concentration was measured at the outlet. From the measured RTD curves, mean residence times (MRTs), dead volume and fraction of liquid pumped in with time were determined. The treated RTD curves were modeled using suitable mathematical models. An axial dispersion model with high degree of backmixing was found suitable to describe flow when operated in Mode-1, whereas a tanks-in-series model with backmixing was found suitable to describe flow of the poison in the tank when operated in Mode-2. The results were utilized to scale-up and design a full-scale poison tank for a nuclear reactor.

  12. Local dominance of exotic plants declines with residence time: a role for plant–soil feedback?

    PubMed Central

    Speek, Tanja A.A.; Schaminée, Joop H.J.; Stam, Jeltje M.; Lotz, Lambertus A.P.; Ozinga, Wim A.; van der Putten, Wim H.

    2015-01-01

    Recent studies have shown that introduced exotic plant species may be released from their native soil-borne pathogens, but that they become exposed to increased soil pathogen activity in the new range when time since introduction increases. Other studies have shown that introduced exotic plant species become less dominant when time since introduction increases, and that plant abundance may be controlled by soil-borne pathogens; however, no study yet has tested whether these soil effects might explain the decline in dominance of exotic plant species following their initial invasiveness. Here we determine plant–soil feedback of 20 plant species that have been introduced into The Netherlands. We tested the hypotheses that (i) exotic plant species with a longer residence time have a more negative soil feedback and (ii) greater local dominance of the introduced exotic plant species correlates with less negative, or more positive, plant–soil feedback. Although the local dominance of exotic plant species decreased with time since introduction, there was no relationship of local dominance with plant–soil feedback. Plant–soil feedback also did not become more negative with increasing time since introduction. We discuss why our results may deviate from some earlier published studies and why plant–soil feedback may not in all cases, or not in all comparisons, explain patterns of local dominance of introduced exotic plant species. PMID:25770013

  13. Analysis of catchment behavior using residence time distributions with application to the Thuringian Basin

    NASA Astrophysics Data System (ADS)

    Prykhodko, Vladyslav; Heße, Falk; Kumar, Rohini; Samaniego, Luis; Attinger, Sabine

    2014-05-01

    Residence time distribution (RTD), as presented e.g. by Botter et al., are a novel mathematical framework for a quantitative characterization of hydrological systems. These distributions contain information about water storage, flow pathways and water sources and therefore improve the classical hydrograph methods by allowing both nonlinear as well as time-dependent dynamics. In our study we extend this previous works by applying this theoretical framework on real-world heterogeneous catchments. To that end we use a catchment-scale hydrological model (mHM) and apply the approach of Botter et al. to each spatial grid cell of mHM. To facilitate the coupling we amended Botter's approach by introducing additional fluxes (like runoff from unsaturated zone) and specifying the structure of the groundwater zone. By virtue of this coupling we could then make use of the realistic hydrological fluxes and state variables as provided by mHM. This allowed us to use both observed (precipitation, temperature, soil type etc.) and modeled data sets and asses their impact on the behavior of the resulting RTD's. We extended the aforementioned framework to analyze large catchments by including geomorphic effect due to the actual arrangement of subcatchments around the channel network using the flood routing algorithm of mHM. Additionally we study dependencies of the stochastic characteristics of RTD's on the meteorological and hydrological processes as well as on the morphological structure of the catchment. As a result we gained mean residence times (MRT) of base flow and groundwater flow on the mesoscale (4km x 4km). We compare the spatial distribution of MRT's with land cover and soil moisture maps as well as driving forces like precipitation and temperature. Results showed that land cover is a major predictor for MRT's whereas its impact on the mean evapotranspiration time was much lower. Additionally we determined the temporal evolution of mean travel times by using time series of

  14. Optimal beam pattern to maximize inclusion residence time in an electron beam melting hearth

    SciTech Connect

    Powell, A.; Pal, U.; Avyle, J. van den

    1997-02-01

    Approximate probabilities of inclusion survival through an electron beam melting hearth are computed from nitride dissolution rates, flotation velocities, and residence times. Dissolution rates were determined by measuring shrinkage rates of pure TiN and nitrided sponge in small pools of molten titanium in an electron beam melting hearth. Flotation velocities were calculated using correlations for fluid flow around spheres, and show that particles sink or float unless their densities are extremely close to that of molten titanium. Flow field characteristics which lead to effective inclusion removal are discussed in terms of heat flux pattern required to produce them, based on the electron beam`s unique ability to impart a nearly arbitrary heat flux pattern to the melt surface.

  15. Using Residence Time Distributions (RTDs) to Address the Traceability of Raw Materials in Continuous Pharmaceutical Manufacturing.

    PubMed

    Engisch, William; Muzzio, Fernando

    Continuous processing in pharmaceutical manufacturing is a relatively new approach that has generated significant attention. While it has been used for decades in other industries, showing significant advantages, the pharmaceutical industry has been slow in its adoption of continuous processing, primarily due to regulatory uncertainty. This paper aims to help address these concerns by introducing methods for batch definition, raw material traceability, and sensor frequency determination. All of the methods are based on established engineering and mathematical principles, especially the residence time distribution (RTD). This paper introduces a risk-based approach to address content uniformity challenges of continuous manufacturing. All of the detailed methods are discussed using a direct compaction manufacturing line as the main example, but the techniques can easily be applied to other continuous manufacturing methods such as wet and dry granulation, hot melt extrusion, capsule filling, etc.

  16. Target engagement and drug residence time can be observed in living cells with BRET

    PubMed Central

    Robers, Matthew B.; Dart, Melanie L.; Woodroofe, Carolyn C.; Zimprich, Chad A.; Kirkland, Thomas A.; Machleidt, Thomas; Kupcho, Kevin R.; Levin, Sergiy; Hartnett, James R.; Zimmerman, Kristopher; Niles, Andrew L.; Ohana, Rachel Friedman; Daniels, Danette L.; Slater, Michael; Wood, Monika G.; Cong, Mei; Cheng, Yi-Qiang; Wood, Keith V.

    2015-01-01

    The therapeutic action of drugs is predicated on their physical engagement with cellular targets. Here we describe a broadly applicable method using bioluminescence resonance energy transfer (BRET) to reveal the binding characteristics of a drug with selected targets within intact cells. Cell-permeable fluorescent tracers are used in a competitive binding format to quantify drug engagement with the target proteins fused to Nanoluc luciferase. The approach enabled us to profile isozyme-specific engagement and binding kinetics for a panel of histone deacetylase (HDAC) inhibitors. Our analysis was directed particularly to the clinically approved prodrug FK228 (Istodax/Romidepsin) because of its unique and largely unexplained mechanism of sustained intracellular action. Analysis of the binding kinetics by BRET revealed remarkably long intracellular residence times for FK228 at HDAC1, explaining the protracted intracellular behaviour of this prodrug. Our results demonstrate a novel application of BRET for assessing target engagement within the complex milieu of the intracellular environment. PMID:26631872

  17. Target engagement and drug residence time can be observed in living cells with BRET.

    PubMed

    Robers, Matthew B; Dart, Melanie L; Woodroofe, Carolyn C; Zimprich, Chad A; Kirkland, Thomas A; Machleidt, Thomas; Kupcho, Kevin R; Levin, Sergiy; Hartnett, James R; Zimmerman, Kristopher; Niles, Andrew L; Ohana, Rachel Friedman; Daniels, Danette L; Slater, Michael; Wood, Monika G; Cong, Mei; Cheng, Yi-Qiang; Wood, Keith V

    2015-12-03

    The therapeutic action of drugs is predicated on their physical engagement with cellular targets. Here we describe a broadly applicable method using bioluminescence resonance energy transfer (BRET) to reveal the binding characteristics of a drug with selected targets within intact cells. Cell-permeable fluorescent tracers are used in a competitive binding format to quantify drug engagement with the target proteins fused to Nanoluc luciferase. The approach enabled us to profile isozyme-specific engagement and binding kinetics for a panel of histone deacetylase (HDAC) inhibitors. Our analysis was directed particularly to the clinically approved prodrug FK228 (Istodax/Romidepsin) because of its unique and largely unexplained mechanism of sustained intracellular action. Analysis of the binding kinetics by BRET revealed remarkably long intracellular residence times for FK228 at HDAC1, explaining the protracted intracellular behaviour of this prodrug. Our results demonstrate a novel application of BRET for assessing target engagement within the complex milieu of the intracellular environment.

  18. Effects of age, sex and reproductive status on persistent organic pollutant concentrations in "Southern Resident" killer whales.

    PubMed

    Krahn, Margaret M; Hanson, M Bradley; Schorr, Gregory S; Emmons, Candice K; Burrows, Douglas G; Bolton, Jennie L; Baird, Robin W; Ylitalo, Gina M

    2009-10-01

    "Southern Resident" killer whales (Orcinus orca) that comprise three fish-eating "pods" (J, K and L) were listed as "endangered" in the US and Canada following a 20% population decline between 1996 and 2001. Blubber biopsy samples from Southern Resident juveniles had statistically higher concentrations of certain persistent organic pollutants than were found for adults. Most Southern Resident killer whales, including the four juveniles, exceeded the health-effects threshold for total PCBs in marine mammal blubber. Maternal transfer of contaminants to the juveniles during rapid development of their biological systems may put these young whales at greater risk than adults for adverse health effects (e.g., immune and endocrine system dysfunction). Pollutant ratios and field observations established that two of the pods (K- and L-pod) travel to California to forage. Nitrogen stable isotope values, supported by field observations, indicated possible changes in the diet of L-pod over the last decade.

  19. An Ophthalmic Formulation of Disulfiram Nanoparticles Prolongs Drug Residence Time in Lens.

    PubMed

    Nagai, Noriaki; Mano, Yu; Ito, Yoshimasa

    2016-01-01

    Disulfiram (DSF) is a dimer of diethyldithiocarbamate (DDC) that we previously added to a solution of 2-hydroxypropyl-β-cyclodextrin (DSF solution). We found that the instillation of this DSF solution delayed lens opacification in a hereditary cataractous ICR/f rat. In this study, we attempted to design an ophthalmic formulation containing DSF nanoparticles for use as a lens targeted drug delivery system (nano-DSF suspension), and investigated the changes in drug content in the lens after the instillation of DSF solution or nano-DSF suspension. The nano-DSF suspension was prepared by a bead mill method to yield a mean particle size of nano-DSF of 181 nm. Following the instillation of 1.4% DSF solution or the nano-DSF suspension, DDC was detected only in the aqueous humor and lens; in both, the area under the curve (AUC) and mean residence time (MRT) for the nano-DSF suspension were higher than for the DSF solution. In addition, we found that the DDC residence time in the cortex and nucleus of the lens was higher than in the capsule-epithelium. Although DDC was not detected in the cortex and nucleus of lenses following the instillation of the 1.4% DSF solution, the instillation of a 1.4% nano-DSF suspension led to the accumulation of DDC in both areas. In conclusion, it is possible that the instillation of a nano-DSF suspension can supply more DDC into the aqueous humor and lens than a conventional formulation, and these findings provide information significant for the prevention of cataracts and the design of a lens targeted drug delivery system.

  20. Multi-scale field investigation of water flow pathways and residence times in mountainous catchments

    NASA Astrophysics Data System (ADS)

    Lyon, S. W.; Troch, P. A.; Desilets, S. E.

    2006-12-01

    The "sky islands" of Arizona and New Mexico in the southwestern United States form a unique complex of about 27 mountain ranges whose ecosystems support many perennial and ephemeral streams in an arid climate. Among these sky islands are the Santa Catalina Mountains near Tucson, AZ, with a peak elevation of 9157 ft at Mt. Lemmon. Sabino Canyon Creek is the main stream which runs on the south face of the mountain range. It usually flows from July through April with an average daily flow of approximately 0.28 m3/s (10 cfs). However, flash floods are common both during summer as a result of intense monsoon rains and during spring because of rapid snowmelt. During these events, flow increases rapidally, reaching peak flows up to 480 m3/s (16,000 cfs, July 2006). Characterizing water flow pathways and residence times in these complex catchments is important for improving flash flood warning systems, estimating mountain front recharge, managing forest and wild fires, and understanding ecosystem functions. In the summer of 2006, we set up an extensive hydrometrical and hydro-chemical monitoring network in Sabino Canyon Creek, comprising 40 tipping bucket rain gauges (two of which were equipped to automatically collect rainwater samples), 5 automatic surface water level stations (three of which were equipped with auto samplers), and 8 manual soil lysimeters. In addition, several rain and stream water grab samples were collected manually during intensive rain events. Water samples are analyzed for major ions and liquid water isotopic concentration (2H and 18O) in rain, soil, ground and surface water. The data allows for a detailed reconstruction of water flow pathways and residence times at 3 different catchment scales (2 km2, 8 km2, and 91 km2) during the recorded flow events, including the highest monsoon rainfall-runoff event ever recorded in these mountains.

  1. A nanoparticle formulation of disulfiram prolongs corneal residence time of the drug and reduces intraocular pressure.

    PubMed

    Nagai, Noriaki; Yoshioka, Chiaki; Mano, Yu; Tnabe, Wataru; Ito, Yoshimasa; Okamoto, Norio; Shimomura, Yoshikazu

    2015-03-01

    The goal in the search for successful therapies for glaucoma is the reduction of intraocular pressure (IOP), and the search for effective eye drops that reduce IOP is a high priority. We previously reported the potential of a 2-hydroxypropyl-β-cyclodextrin (HPβCD) solution containing 0.5% DSF (DSF solution) to provide effective anti-glaucoma treatment in eye drop form. In this study, we designed new ophthalmic formulations containing 0.5% DSF nanoparticles prepared by a bead mill method (DSFnano dispersion; particle size 183 ± 92 nm, mean ± S.D.), and compared the IOP-reducing effects of a DSFnano dispersion with those of a DSF solution. The high stability of the DSFnano dispersion was observed until 7 days after preparation, and the DSFnano dispersion showed high antimicrobial activity against Escherichia coli (ATCC 8739). In transcorneal penetration experiments using rabbit corneas, only diethyldithiocarbamate (DDC) was detected in the aqueous humor, while no DSF was detected. The DDC penetration level (area under the curve, AUC) and corneal residence time (mean residence time, MRT) of the DSFnano dispersion were approximately 1.45- and 1.44-fold higher than those of the DSF, respectively. Moreover, the IOP-reducing effects of the DSFnano dispersion were significantly greater than those of the DSF solution in rabbits (the IOP was enhanced by placing the rabbits in a dark room for 5 h). In addition, DSFnano dispersion are tolerated better by a corneal epithelial cell than DSF solution and commercially available timolol maleate eye drops. It is possible that dispersions containing DSF nanoparticles will provide new possibilities for the effective treatment of glaucoma, and that an ocular drug delivery system using drug nanoparticles may expand their usage as therapy in the ophthalmologic field. These findings provide significant information that can be used to design further studies aimed at developing anti-glaucoma drugs. Copyright © 2015 Elsevier Ltd

  2. Residence time distributions for hydrologic systems: Mechanistic foundations and steady-state analytical solutions

    NASA Astrophysics Data System (ADS)

    Leray, Sarah; Engdahl, Nicholas B.; Massoudieh, Arash; Bresciani, Etienne; McCallum, James

    2016-12-01

    This review presents the physical mechanisms generating residence time distributions (RTDs) in hydrologic systems with a focus on steady-state analytical solutions. Steady-state approximations of the RTD in hydrologic systems have seen widespread use over the last half-century because they provide a convenient, simplified modeling framework for a wide range of problems. The concept of an RTD is useful anytime that characterization of the timescales of flow and transport in hydrologic systems is important, which includes topics like water quality, water resource management, contaminant transport, and ecosystem preservation. Analytical solutions are often adopted as a model of the RTD and a broad spectrum of models from many disciplines has been applied. Although these solutions are typically reduced in dimensionality and limited in complexity, their ease of use makes them preferred tools, specifically for the interpretation of tracer data. Our review begins with the mechanistic basis for the governing equations, highlighting the physics for generating a RTD, and a catalog of analytical solutions follows. This catalog explains the geometry, boundary conditions and physical aspects of the hydrologic systems, as well as the sampling conditions, that altogether give rise to specific RTDs. The similarities between models are noted, as are the appropriate conditions for their applicability. The presentation of simple solutions is followed by a presentation of more complicated analytical models for RTDs, including serial and parallel combinations, lagged systems, and non-Fickian models. The conditions for the appropriate use of analytical solutions are discussed, and we close with some thoughts on potential applications, alternative approaches, and future directions for modeling hydrologic residence time.

  3. Flowpaths, source water contributions and water residence times in a Mexican tropical dry forest catchment

    NASA Astrophysics Data System (ADS)

    Farrick, Kegan K.; Branfireun, Brian A.

    2015-10-01

    Runoff in forested tropical catchments has been frequently described in the literature as dominated by the rapid translation of rainfall to runoff through surface and shallow subsurface pathways. However, studies examining runoff generation in tropical catchments with highly permeable soils have received little attention, particularly in tropical dry forests. We present a study focused on identifying the dominant flowpaths, water sources and stream water residence times in a tropical dry forest catchment near the Pacific coast of central Mexico. During the wet season, pre-event water contributions to stormflow ranged from 72% to 97%, with the concentrations of calcium, magnesium, sodium and potassium closely coupling the geochemistry of baseflow and groundwater from the narrow riparian/near-stream zone. Baseflow from the intermittent stream showed a strongly damped isotopic signature and a mean baseflow residence time of 52-110 days was estimated. These findings all suggest that instead of the surface and near-surface subsurface lateral pathways observed over many tropical catchments, runoff is generated through vertical flow processes and the displacement and discharge of stored water from the saturated zone. As the wet season progressed, contributions from the saturated zone persisted; however, the stormflow and baseflow geochemistry suggests that the contributing area of the catchment increased. Our results show that during the early part of the wet season, runoff originated primarily from the headwater portion of the catchment. As the wet season progressed and catchment wetness increased, connectivity among sub-basin was improved, resulting in runoff contributions from across the entire catchment.

  4. Sources and Residence Times of Groundwater in Shasta County, CA Determined by Isotopic Tracers

    NASA Astrophysics Data System (ADS)

    Peters, E.; Moran, J. E.; Deinhart, A.; Roberts, S. K.; Esser, B.; Visser, A.

    2015-12-01

    Large-volume springs are a significant source of water to communities in Shasta County. Aquifers in this region are developed in young volcanic formations and the age and flow of groundwater is not well characterized, making predicting the impact of drought and climate change on spring flow difficult. To better understand the water resources and the hydrogeology of the region and to better constrain the age of water produced by springs, we have sampled water from wells, springs, and streams for a suite of geochemical and isotopic tracers. We are using isotopic tracers because of the limited number of sampling points over a large area, leaving traditional hydrogeologic methods such as water levels and pump tests inadequate for a regional study. We analyzed samples for sulfur-35 (87.4 day half-life) and found detections in two springs, confirming the presence of a fraction of recently (1-2 years) recharged groundwater. Tritium (12.3 year half-life) activities show that some wells produce water recharged more than 5 decades ago, but most produce more recently recharged water. We will also report results for sodium-22 (2.6 year half-life), krypton-85 (10.8 year half-life), carbon-14 (5,730 year half-life), dissolved noble gases, stable isotopes of water, and helium isotopic composition. These isotopes are applied to determine the age (residence time) of groundwater over a broad age distribution, from less than one year to tens of thousands of years. These tracers should also provide information on aquifer volumes, help delineate groundwater flow, and help to identify recharge areas. A collection of groundwater ages from springs at high elevations to wells in the upper Sacramento Valley will help delineate groundwater flowpaths. Finally, groundwater residence times will help determine groundwater volume and recharge rates, and resolve questions related to drought vulnerability and effective adjustments in water resource management.

  5. Residence time of water discharging from the Hanging Gardens of Zion Park

    USGS Publications Warehouse

    Kimball, B.A.; Christensen, P.K.

    1996-01-01

    The Hanging Gardens are a unique feature of Zion National Park. Knowledge of the source and residence time of water discharging from the Hanging Gardens is necessary to help preserve these features. Ground-water chemical and isotopic data distinguish the discharge from seeps and springs into two groups, one of low and one of high conductivity. Water with low conductivity likely originates as recharge near the steps and springs, and it only interacts with the Navajo Sandstone. High conductivity water, on the other hand, originates as recharge on the tops of plateaus to the east, where it interacts with marine rocks of the Carmel Formation. Carbon dating of these ground waters indicates that the low conductivity water is essentially modern recharge, while the high conductivity water was recharged 1,000 to 4,000 years ago.The Hanging Gardens are a unique feature of Zion National Park. Knowledge of the source and residence time of water discharging from the Hanging Gardens is necessary to help preserve these features. Ground-water chemical and isotopic data distinguish the discharge from seeps and springs into two groups, one of low and one of high conductivity. Water with low conductivity likely originates as recharge near the seeps and springs, and it only interacts with the Navajo Sandstone. High conductivity water, on the other hand, originates as recharge on the tops of plateaus to the cast, where it interacts with marine rocks of the Carmel Formation. Carbon dating of these ground waters indicates that the low conductivity water is essentially modern recharge, while the high conductivity water was recharged 1,000 to 4,000 years ago.

  6. Influence of forestry, environmental change and climatic variability on the hydrology, hydrochemistry and residence times of upland catchments

    NASA Astrophysics Data System (ADS)

    Tetzlaff, D.; Malcolm, I. A.; Soulsby, C.

    2007-11-01

    SummaryLong-term (>25 year) hydrological and hydrochemical data sets for two small afforested catchments at Loch Ard, Central Scotland, are analysed to assess the effects of forest management, environmental change and climatic variability. The two catchments, B10 (0.9 km 2) and B11 (1.4 km 2) are dominated by acidic gley soils. Their streams have responsive hydrological regimes and acidic surface waters with pH ranging from ˜5.5 at low flows to 4.0 at high flows. Partial clear-felling appeared to have limited effects on the catchment water balances, though flood peaks and low flows might be enhanced for short periods of a few years. Felling had a notable, short-term, perturbation on stream water chemistry, with both NO 3 and K concentrations being increased. Stream chemistry also exhibited marked variability in response to climatic conditions and changing atmospheric inputs, which resulted in strong inter-annual and seasonal variation of precipitation quantity and quality. These influence annual stream flows and chemistry, with marine-derived Cl and Na being the dominant anion and cation. Emission controls of acidic oxides from fossil fuel burning have reduced SO 4 concentrations in precipitation; a trend that has been exacerbated by felling and mirrored in the two streams. This has corresponded to declining levels of inorganic aluminium. In contrast, dissolved organic carbon concentrations have increased possibly in response to warmer drier summers and felling operations. Chemically-based hydrograph separations indicated that groundwater comprised 25-35% of annual runoff in both catchments, with no evidence of any change relating to forest management. Cl data were used to estimate mean catchment residence times by applying lumped parameter models. Both catchments have mean residence times on the order of a few months, though they are about 1 month shorter in B10 which is consistent with differences in soils and topography, though this might also reflect

  7. The decadal state of the terrestrial carbon cycle: Global retrievals of terrestrial carbon allocation, pools, and residence times.

    PubMed

    Bloom, A Anthony; Exbrayat, Jean-François; van der Velde, Ivar R; Feng, Liang; Williams, Mathew

    2016-02-02

    The terrestrial carbon cycle is currently the least constrained component of the global carbon budget. Large uncertainties stem from a poor understanding of plant carbon allocation, stocks, residence times, and carbon use efficiency. Imposing observational constraints on the terrestrial carbon cycle and its processes is, therefore, necessary to better understand its current state and predict its future state. We combine a diagnostic ecosystem carbon model with satellite observations of leaf area and biomass (where and when available) and soil carbon data to retrieve the first global estimates, to our knowledge, of carbon cycle state and process variables at a 1° × 1° resolution; retrieved variables are independent from the plant functional type and steady-state paradigms. Our results reveal global emergent relationships in the spatial distribution of key carbon cycle states and processes. Live biomass and dead organic carbon residence times exhibit contrasting spatial features (r = 0.3). Allocation to structural carbon is highest in the wet tropics (85-88%) in contrast to higher latitudes (73-82%), where allocation shifts toward photosynthetic carbon. Carbon use efficiency is lowest (0.42-0.44) in the wet tropics. We find an emergent global correlation between retrievals of leaf mass per leaf area and leaf lifespan (r = 0.64-0.80) that matches independent trait studies. We show that conventional land cover types cannot adequately describe the spatial variability of key carbon states and processes (multiple correlation median = 0.41). This mismatch has strong implications for the prediction of terrestrial carbon dynamics, which are currently based on globally applied parameters linked to land cover or plant functional types.

  8. The decadal state of the terrestrial carbon cycle: Global retrievals of terrestrial carbon allocation, pools, and residence times

    PubMed Central

    Bloom, A. Anthony; Exbrayat, Jean-François; van der Velde, Ivar R.; Feng, Liang; Williams, Mathew

    2016-01-01

    The terrestrial carbon cycle is currently the least constrained component of the global carbon budget. Large uncertainties stem from a poor understanding of plant carbon allocation, stocks, residence times, and carbon use efficiency. Imposing observational constraints on the terrestrial carbon cycle and its processes is, therefore, necessary to better understand its current state and predict its future state. We combine a diagnostic ecosystem carbon model with satellite observations of leaf area and biomass (where and when available) and soil carbon data to retrieve the first global estimates, to our knowledge, of carbon cycle state and process variables at a 1° × 1° resolution; retrieved variables are independent from the plant functional type and steady-state paradigms. Our results reveal global emergent relationships in the spatial distribution of key carbon cycle states and processes. Live biomass and dead organic carbon residence times exhibit contrasting spatial features (r = 0.3). Allocation to structural carbon is highest in the wet tropics (85–88%) in contrast to higher latitudes (73–82%), where allocation shifts toward photosynthetic carbon. Carbon use efficiency is lowest (0.42–0.44) in the wet tropics. We find an emergent global correlation between retrievals of leaf mass per leaf area and leaf lifespan (r = 0.64–0.80) that matches independent trait studies. We show that conventional land cover types cannot adequately describe the spatial variability of key carbon states and processes (multiple correlation median = 0.41). This mismatch has strong implications for the prediction of terrestrial carbon dynamics, which are currently based on globally applied parameters linked to land cover or plant functional types. PMID:26787856

  9. NMR-based estimates of the molecular dimensions in wildfire charcoal: Implications for predictions of biochar residence time

    NASA Astrophysics Data System (ADS)

    Hockaday, William; Kane, Evan; Huang, Rixiang; Von Bargen, Justin; Davis, Rebecca; Ohlson, Mikael

    2014-05-01

    The thermochemical conversion of biomass to energy and fuels generates charcoal as a co-product. Charcoals derived from sustainable biomass sources—biochars—are an inherently stable form of carbon, relatively long residence times in the environment. Biochars can have potentially beneficial properties as soil fertility amendments, which has further stimulated research on the use of biochars for soil carbon sequestration as a climate change mitigation strategy. However, it is challenging to assess the long-term stability of biochar carbon using laboratory or field incubations because these are comprised of short-term observations. In this study, we make use of ancient charcoals from the boreal forests of Alaska and Scandanavia. We have deliberately selected charcoals from organic soil horizons, as to investigate the inherent biological and chemical stability of charcoal C without the protective influence of soil minerals. We use 14C radiocarbon dating to determine the age of the charcoals, differential scanning calorimetry to assess thermal stability, and solid-state 13C NMR to assess the chemical structure. Specifically, we employ C-H dipolar-dephasing NMR experiments to estimate the relative abundance and molecular dimensions of condensed aromatic domains and aliphatic structures. We test the hypothesis that the environmental stability, as determined by apparent 14C age and thermal stability, is related to the extent of ring condensation in the charcoal structure. Preliminary results suggest that the dimension of the condensed aromatic ring clusters may be an important molecular parameter to include in algorithms used to model/predict the residence time of charcoal and biochar C in soil.

  10. Levels and profiles of persistent organic pollutants in resident and migratory birds from an urbanized coastal region of South Korea.

    PubMed

    Hong, Sang Hee; Shim, Won Joon; Han, Gi Myung; Ha, Sung Yong; Jang, Mi; Rani, Manviri; Hong, Sunwook; Yeo, Gwang Yeong

    2014-02-01

    Persistent organic pollutants (POPs) levels in resident and migratory birds collected from an urbanized coastal region of South Korea were investigated. As target species, resident birds that reside in different habitats-such as inland and coastal regions-were selected and their POP contamination status and accumulation features evaluated. Additionally, winter and summer migratory species were analysed for comparison with resident birds. Black-tailed gull and domestic pigeon were selected as the coastal and inland resident birds, respectively, and pacific loon and heron/egret were selected as the winter and summer migratory birds, respectively. The overall POP concentrations (unit: ng/g lipid) in resident birds were 14-131,000 (median: 13,400) for PCBs, 40-284,000 (11,200) for DDTs, <1.0-2850 (275) for CHLs, 23-2020 (406) for HCHs, 2-1520 (261) for HCB, <0.2-48 (5) for pentachlorobenzene (PeCB), 71-7120 (1840) for PBDEs, and <1.8-2300 (408) for HBCDs. In resident birds, the overall level of POPs was higher in seagull compared to pigeon. The stable isotope ratio of nitrogen and carbon indicates that seagull occupies a higher trophic position in the environment than pigeon. However, the POP accumulation profiles in these species differed. Pigeon tends to accumulate more recently used POPs such as PBDEs than seagull. The high-brominated BDE congeners, γ-HBCDs and γ-HCH (also called lindane) were enriched in pigeon compared to seagull, implying the widespread use of Deca-BDE, technical HBCDs, and lindane in the terrestrial environment of South Korea. The different accumulation profile of POPs in both resident species would be related to their habitat difference and trophic positions. For urban resident bird such as pigeon, an intentional intake of dust or soils during feeding is likely to be an additional route of exposure to POPs. Resident birds generally accumulated higher POPs concentrations than migratory birds, the exceptions being relatively volatile compounds

  11. On-site residence time in a driven diffusive system: Violation and recovery of a mean-field description.

    PubMed

    Messelink, J; Rens, R; Vahabi, M; MacKintosh, F C; Sharma, A

    2016-01-01

    We investigate simple one-dimensional driven diffusive systems with open boundaries. We are interested in the average on-site residence time defined as the time a particle spends on a given site before moving on to the next site. Using mean-field theory, we obtain an analytical expression for the on-site residence times. By comparing the analytic predictions with numerics, we demonstrate that the mean-field significantly underestimates the residence time due to the neglect of time correlations in the local density of particles. The temporal correlations are particularly long-lived near the average shock position, where the density changes abruptly from low to high. By using domain wall theory, we obtain highly accurate estimates of the residence time for different boundary conditions. We apply our analytical approach to residence times in a totally asymmetric exclusion process (TASEP), TASEP coupled to Langmuir kinetics (TASEP+LK), and TASEP coupled to mutually interactive LK (TASEP+MILK). The high accuracy of our predictions is verified by comparing these with detailed Monte Carlo simulations.

  12. Transit and residence times in the Adriatic Sea surface as derived from drifter data and Lagrangian numerical simulations

    NASA Astrophysics Data System (ADS)

    Poulain, P.-M.; Hariri, S.

    2013-08-01

    Statistics of transit and residence times in the Adriatic Sea surface, a semi-enclosed basin of the Mediterranean, are estimated from drifter data and Lagrangian numerical simulations. The results obtained from the drifters are generally underestimated given their short operating lifetimes (half life of ∼40 days) compared to the transit and residence times. This bias can be removed by considering a large amount of numerical particles whose trajectories are integrated over a long time (750 days) with a statistical advection-dispersion model of the Adriatic surface circulation. Numerical particles indicate that the maximum transit time to exit the basin is about 216-260 days for particles released near the northern tip of the Adriatic, and that a particle entering on the eastern Otranto Channel will typically exit on the other side of the channel after 170-185 days. A duration of 150-168 days is estimated as the residence time in the Adriatic Basin.

  13. Transit and residence times in the surface Adriatic Sea as derived from drifter data and Lagrangian numerical simulations

    NASA Astrophysics Data System (ADS)

    Poulain, P.-M.; Hariri, S.

    2013-01-01

    Statistics of transit and residence times in the surface Adriatic Sea, a semi-enclosed basin of the Mediterranean, are estimated from drifter data and Lagrangian numerical simulations. The results obtained from the drifters are generally underestimated given their short operating lifetimes (half life of ~ 40 days) compared to the transit and residence times. This bias can be removed by considering a large amount of numerical particles whose trajectories are integrated over a long time (750 days) with a statistical advection-diffusion model of the Adriatic surface circulation. Numerical particles indicate that the maximum transit time to exit the basin is about 216-260 days for objects released near the northern tip of the Adriatic, and that a particle entering on the eastern Otranto Channel will typically exit on the other side of the Channel after 170-185 days. A value of 150-168 days is estimated for the residence time in the Adriatic basin.

  14. The Role of Noble Gases in Defining the Mean Residence Times of Fluids within Precambrian Crustal Systems

    NASA Astrophysics Data System (ADS)

    Warr, O.; Sherwood Lollar, B.; Fellowes, J.; Sutcliffe, C. N.; McDermott, J. M.; Holland, G.; Mabry, J.; Ballentine, C. J.

    2015-12-01

    Brines rich in N2, H2, CH4 and He hosted within Precambrian crustal rocks are known to sustain microbial life [1]. The geological systems containing these brines have the potential to isolate organisms over planetary timescales and so can provide unique insight into the diversity and evolution of terrestrial life [1-3]. Long considered geological outliers, the prevalence of systems containing these ancient, deep fracture waters is only now being revealed. Recent studies demonstrate the Precambrian crust which accounts for ~70% of total crustal surface area has a global hydrogen production comparable to marine systems [2]. In addition to H2-producing reactions (e.g. radiolysis and serpentinization), a diversity of CH4-producing reactions also occur in these systems through both microbial and water-rock interactions [1, 2]. However, the role these Precambrian systems have in global hydrogen and carbon cycles is poorly understood. For this we need good constraints on the origins, residence times and degree of microbial activity of the fluids within these systems as well as the degree of interaction with external systems. Fortunately, noble gases are ideal for this role [1,3]. Previous noble gas analysis of N2, H2, CH4 and He-rich fluid samples collected at 2.4 km depth from a Cu-Zn mine in Timmins, Ontario, identified isolated fracture fluids with the oldest residence times ever observed (>1.1 Ga) [3]. This study has been significantly expanded now to fluids from an even greater depth (3 km) at Timmins, and from two new mines in the Sudbury Basin. Preliminary data from the deeper Timmins level indicate a new closed system with 136Xe/130Xe ratios 93% above modern air values (20% at 2.4 km) and an early atmosphere 124Xe/130Xe signal approaching the age of the host rock (~2.7 Ga) [4]. In comparison, the Sudbury system indicates exchange with an external source, being highly enriched in helium (30% gas volume) but with a low fissiogenic 136Xe/130Xe excess (10-38% above

  15. Assessing the Benefits Provided by SWOT Data Towards Estimating Reservoir Residence Time in the Mekong River Basin

    NASA Astrophysics Data System (ADS)

    Bonnema, M.; Hossain, F.

    2016-12-01

    The Mekong River Basin is undergoing rapid hydropower development. Nine dams are planned on the main stem of the Mekong and many more on its extensive tributaries. Understanding the effects that current and future dams have on the river system and water cycle as a whole is vital for the millions of people living in the basin. reservoir residence time, the amount of time water spends stored in a reservoir, is a key parameter in investigating these impacts. The forthcoming Surface Water and Ocean Topography (SWOT) mission is poised to provide an unprecedented amount of surface water observations. SWOT, when augmented by current satellite missions, will provide the necessary information to estimate the residence time of reservoirs across the entire basin in a more comprehensive way than ever before. In this study, we first combine observations from current satellite missions (altimetry, spectral imaging, precipitation) to estimate the residence times of existing reservoirs. We then use this information to project how future reservoirs will increase the residence time of the river system. Next, we explore how SWOT observations can be used to improve residence time estimation by examining the accuracy of reservoir surface area and elevation observations as well as the accuracy of river discharge observations.

  16. Real time in situ detection of organic nitrates in atmospheric aerosols.

    PubMed

    Rollins, Andrew W; Smith, Jared D; Wilson, Kevin R; Cohen, Ronald C

    2010-07-15

    A novel instrument is described that quantifies total particle-phase organic nitrates in real time with a detection limit of 0.11 microg m(-3) min(-1), 45 ppt min(-1) (-ONO(2)). Aerosol nitrates are separated from gas-phase nitrates with a short residence time activated carbon denuder. Detection of organic molecules containing -ONO(2) subunits is accomplished using thermal dissociation coupled to laser induced fluorescence detection of NO(2). This instrument is capable of high time resolution (seconds) measurements of particle-phase organic nitrates, without interference from inorganic nitrate. Here we use it to quantify organic nitrates in secondary organic aerosol generated from high-NO(x) photooxidation of limonene, alpha-pinene, Delta-3-carene, and tridecane. In these experiments the organic nitrate moiety is observed to be 6-15% of the total SOA mass.

  17. Ross ice shelf cavity circulation, residence time, and melting: Results from a model of oceanic chlorofluorocarbons

    NASA Astrophysics Data System (ADS)

    Reddy, Tasha E.; Holland, David M.; Arrigo, Kevin R.

    2010-04-01

    Despite their harmful effects in the upper atmosphere, anthropogenic chlorofluorocarbons dissolved in seawater are extremely useful for studying ocean circulation and ventilation, particularly in remote locations. Because they behave as a passive tracer in seawater, and their atmospheric concentrations are well-mixed, well-known, and have changed over time, they are ideal for gaining insight into the oceanographic characteristics of the isolated cavities found under Antarctic ice shelves, where direct observations are difficult to obtain. Here we present results from a modeling study of air-sea chlorofluorocarbon exchange and ocean circulation in the Ross Sea, Antarctica. We compare our model estimates of oceanic CFC-12 concentrations along an ice shelf edge transect to field data collected during three cruises spanning 16 yr. Our model produces chlorofluorocarbon concentrations that are quite similar to those measured in the field, both in magnitude and distribution, showing high values near the surface, decreasing with depth, and increasing over time. After validating modeled circulation and air-sea gas exchange through comparison of modeled temperature, salinity, and chlorofluorocarbons with field data, we estimate that the residence time of water in the Ross Ice Shelf cavity is approximately 2.2 yr and that basal melt rates for the ice shelf average 10 cm yr -1. The model predicts a seasonal signature to basal melting, with highest melt rates in the spring and also the fall.

  18. Residence and transit times of MinD in E. coli bacterial cells

    NASA Astrophysics Data System (ADS)

    Giuliani, Maximiliano; Kelly, Corey; Dutcher, John

    2012-02-01

    A key step in the life of a bacterial cell is its division into two daughters cells of equal size. This process is carefully controlled and regulated so that an equal partitioning of the main cell components is obtained, which is critical for the viability of the daughter cells. In E. coli this regulation is accomplished in part by the Min protein system, that determines the localization of the division machinery. Of particular interest is the MinD protein that exhibits an oscillation between the poles in the rod shaped bacteria. The oscillation relies on a ATP mediated dimerization of the MinD protein that allows its insertion into the inner membrane at one of the poles of the cell, followed by an interaction with the MinE protein, which releases the MinD from the membrane, allowing it to travel to the other pole of the cell where the cycle is repeated. We have studied the spatio-temporal characteristics of the MinD oscillation from which we extract the average times for the two main processes that determine the oscillation period: the residence time in the membrane and the transit time to travel the length of the cell. Additionally, we explore how these two timescales are affected by stresses on the bacterial cells due to unfavorable physiological conditions.

  19. Biofilm growth in gravel bed streams controls solute residence time distributions

    NASA Astrophysics Data System (ADS)

    Aubeneau, A. F.; Hanrahan, Brittany; Bolster, Diogo; Tank, Jennifer

    2016-07-01

    Streambed substrates harbor a rich biome responsible for biogeochemical processing in riverine waters. Beyond their biological role, the presence of benthic and hyporheic biofilms can play an important role in influencing large-scale transport of solutes, even for conservative tracers. As biofilms grow and accumulate biomass, they actively interact with and influence surface and subsurface flow patterns. To explore this effect, we conducted experiments at the Notre Dame Linked Ecosystems Experimental Facility in four outdoor streams, each with different gravel beds. Over the course of 20 weeks we conducted transport experiments in each of these streams and observed different patterns in breakthrough curves as biofilms grew on the substrate. Biofilms played a major role in shaping the observed conservative transport patterns. Overall, while the presence of biofilms led to a decreased exchange rate between the fast (mobile) and slow (immobile) parts of the flow domain, water that was exchanged tended to be stored in the slow regions for longer times once biofilms had established. More specifically, we observed enhanced longitudinal dispersion in breakthrough curves as well as broader residence time distributions when biofilms were present. Biofilm colonization over time homogenized transport patterns across the four streams that were originally very distinct. These results indicate that stream biofilms exert a strong control on conservative solute transport in streams, a role that to date has not received enough attention.

  20. Residency times and patterns of movement of postbreeding dunlin on a subarctic staging area in Alaska

    USGS Publications Warehouse

    Warnock, Nils; Handel, Colleen M.; Gill, Robert E.; McCaffery, Brian J.

    2013-01-01

    Understanding how individuals use key resources is critical for effective conservation of a population. The Yukon-Kuskokwim Delta (YKD) in western Alaska is the most important postbreeding staging area for shorebirds in the subarctic North Pacific, yet little is known about movements of shorebirds there during the postbreeding period. To address this information gap, we studied residency times and patterns of movement of 17 adult and 17 juvenile radio-marked Dunlin (Calidris alpina) on the YKD between early August and early October 2005. Throughout this postbreeding period, during which Dunlin were molting, most birds were relocated within a 130 km radius of their capture site on the YKD, but three birds were relocated more than 600 km to the south at estuaries along the Alaska Peninsula. On average, juvenile Dunlin were relocated farther away from the banding site (median relocation distance = 36.3 km) than adult Dunlin (median relocation distance = 8.8 km). Post-capture, minimum lengths of stay by Dunlin on the YKD were not significantly different between juveniles (median = 19 days) and adults (median = 23 days), with some birds staging for more than 50 days. Body mass at time of capture was the best single variable explaining length of stay on the YKD, with average length of stay decreasing by 2.5 days per additional gram of body mass at time of capture. Conservation efforts for postbreeding shorebirds should consider patterns of resource use that may differ not only by age cohort but also by individual condition.

  1. Determination of the Residence Time of Food Particles During Aseptic Sterilization

    NASA Technical Reports Server (NTRS)

    Carl, J. R.; Arndt, G. D.; Nguyen, T. X.

    1994-01-01

    The paper describes a non-invasive method to measure the time an individual particle takes to move through a length of stainless steel pipe. The food product is in two phase flow (liquids and solids) and passes through a pipe with pressures of approximately 60 psig and temperatures of 270-285 F. The proposed problem solution is based on the detection of transitory amplitude and/or phase changes in a microwave transmission path caused by the passage of the particles of interest. The particles are enhanced in some way, as will be discussed later, such that they will provide transitory changes that are distinctive enough not to be mistaken for normal variations in the received signal (caused by the non-homogeneous nature of the medium). Two detectors (transmission paths across the pipe) will be required and place at a known separation. A minimum transit time calculation is made from which the maximum velocity can be determined. This provides the minimum residence time. Also average velocity and statistical variations can be computed so that the amount of 'over-cooking' can be determined.

  2. U Isotope Systematics on Groundwaters from Southwestern France : Mixing Processes and Residence Times

    NASA Astrophysics Data System (ADS)

    Innocent, C.; Malcuit, E.; Négrel, P.

    2011-12-01

    The Eocene Sands Aquifer of the Aquitanian Basin (Southwestern France) has been extensively studied for its hydrology, hydrogeochemistry and also for stable isotopes (André, 2002; André et al., 2005). 14C dates were also obtained in the southern part of the aquifer (André, 2002). Recently, in the framework of the CARISMEAU research project (Négrel et al., 2007), groundwaters have been analyzed for their U activity ratio in order to put some constraints on their residence time in the aquifer. A excellent correlation has been found between 234U/238U ratios (which can be as high as 13.5) and 14C dates, which allowed to propose residence times for the analyzed groundwaters at the scale of the whole aquifer (including the city of Bordeaux and its suburb) (Innocent and Négrel, 2008; submitted). The second step of the CARISMEAU research project (CARISMEAU 2) now focusses on the restricted "Entre-Deux-Mers" area. New groundwaters have been recovered and analyzed for their U isotopic composition. As for previous data, U activity ratios are typically very high, ranging from 2.9 to 8.6. Owing to additional 14C ages from the northern part of the aquifer, it is shown that most of the measured uranium activity ratios correlate with these 14C dates and fall on or close to the straight line defined previously (see above). As a consequence, residence times derived from U isotopic compositions fairly agree with 14C data, with only one exception from a groundwater which plots apart from the correlation line. Pumping tests have been done at a selected site (EMZM 7), involving pumping times of 1 hour, 8 hours and 16 hours. For each pumping time, waters have been recovered at different, increasing pumping rates of 80 m3 per hour, 120 m3 per hour, 160 m3 per hour, and 120 m3 per hour. The chemical composition of these twelve waters has not been found to vary significantly. Uranium activities are constant for ten of the twelve groundwaters (around 6.5, with a U concentration around

  3. Impact of climate change on mean groundwater residence time in several Mediterranean Spanish aquifers

    NASA Astrophysics Data System (ADS)

    Pulido-Velazquez, David; Marín-Lechado, Carlos; Martos-Rosillo, Sergio; Collados-Lara, Antonio-Juan; Ruíz-Constan, Ana

    2017-04-01

    The mean residence time in an aquifer, also known as natural turnover time or renewable period, can be obtained as the relation (R / St) between its storage capacity (St) and its recharge (R). It is an excellent indicator of the aquifer response capacity to its exploitation. Aquifers in which R is close to St values are extremely vulnerable to exploitation, even when it is less than the average recharge. This is especially relevant in Mediterranean climate areas, where long and intensive drought periods appear and will be exacerbated in future scenarios of global change. The natural turnover time depends on the recharge and the Global Change can produce important changes on it in the future. In this research we propose a method for a detailed estimation of natural turnover time by combining detailed 3D geological modelling of the case studies, estimated fields of specific yield for the aquifers (based on the analysis of multiple field sample), and rainfall-recharge models in several aquifer with different ratios of natural turnover time. These detailed 3D geological models have been defined by integrating information coming from seismic profiles, boreholes, magnetotelluric, electromagnetic and electrical sounding, digital elevation models, previous geological maps and new structural dates. They also allow us to deduce the reserve curve as a function of the elevation. On the other hand, different ensemble and downscaling techniques will be used to define potential future global climate change scenarios for the test-regions based on the data coming from simulations with different Regional Circulation Models (RCMs). These precipitation and temperature scenarios will be employed to feed the previously calibrated rainfall-recharge models in order to estimated future recharge and turnover time values. The methodology applied in this work could be a tool of special interest to identify at regional level which aquifers are most vulnerable to exploitation considering

  4. Determining the residence time distribution of various screw elements in a co-rotating twin-screw extruder by means of fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Lepschi, Alexander; Gerstorfer, Gregor; Miethlinger, Jürgen

    2015-05-01

    The Residence Time Distribution (RTD) is key to optimizing the mixing ability of an extruder. For both sensitive and reactive materials, it is important to know how long particles remain in the barrel and how long the polymer remains, for instance, in a kneading element. To assess the influence of different screw configurations on the RTD, a low-concentration tracer particle was injected into the feeding section and measured inline by fluorescence spectroscopy1 both inside the barrel and at the extruder exit. The measurements were conducted using polypropylene with different amounts of organic peroxide. Measuring the residence time at various positions along the screw allows the RTD to be determined for just one screw element. Furthermore, we show the influence of different screw configurations on the polydispersity of polypropylene.

  5. Dedicated Research Time During Surgery Residency Leads to a Significant Decline In Self-Assessed Clinical Aptitude and Surgical Skills.

    PubMed

    Grova, Monica M; Yang, Anthony D; Humphries, Misty D; Galante, Joseph M; Salcedo, Edgardo S

    2017-05-19

    The surgical community commonly perceives a decline in surgical and patient care skills among residents who take dedicated time away from clinical activity to engage in research. We hypothesize that residents perceive a decline in their skills because of dedicated research time. UC Davis Medical Center, Sacramento, CA, an institutional tertiary care center. General surgery residents and graduates from UC Davis general surgery residency training program, who had completed at least 1 year of research during their training. A total of 35 people were asked to complete the survey, and 19 people submitted a completed survey. Participants were invited to complete an online survey. Factors associated with the decline in skills following their research years were examined. All statistical analyses were performed with IBM SPSS Statistics software. A total of 19 current or former general surgery residents responded to the survey (54% response rate). Overall, 42% described their research as "basic science." Thirteen residents (68%) dedicated 1 year to research, while the remainder spent 2 or more years. Basic science researchers were significantly more likely to report a decrease in clinical judgment (75% vs. 22%, p = 0.013) as well as a decrease in patient care skills (63% vs. 0%, p = 0.002). Residents who dedicated at least 2 years to research were more likely to perceive a decline in overall aptitude and surgical skills (100% vs. 46%, p = 0.02), and a decline in patient care skills (67% vs. 8%, p = 0.007). Most residents who dedicate time for research perceive a decline in their overall clinical aptitude and surgical skills. This can have a dramatic effect on the confidence of these residents in caring for patients and leading a care team once they re-enter clinical training. Residents who engaged in 2 or more years of research were significantly more likely to perceive these problems. Further research should determine how to keep residents who are interested in academics

  6. Organizational and Individual Conditions Associated with Depressive Symptoms among Nursing Home Residents over Time

    ERIC Educational Resources Information Center

    Cassie, Kimberly M.; Cassie, William E.

    2012-01-01

    Purpose: To examine the effect of organizational culture and climate on depressive symptoms among nursing home residents. Design and Methods: Using a pooled cross-sectional design, this study examines a sample of 23 nursing homes, 1,114 employees, and 5,497 residents. Depressive symptoms were measured using the Minimum Data Set, Depression Rating…

  7. Organizational and Individual Conditions Associated with Depressive Symptoms among Nursing Home Residents over Time

    ERIC Educational Resources Information Center

    Cassie, Kimberly M.; Cassie, William E.

    2012-01-01

    Purpose: To examine the effect of organizational culture and climate on depressive symptoms among nursing home residents. Design and Methods: Using a pooled cross-sectional design, this study examines a sample of 23 nursing homes, 1,114 employees, and 5,497 residents. Depressive symptoms were measured using the Minimum Data Set, Depression Rating…

  8. Are Prior Experience and Subspecialty Training Time Predictive of Pediatric Anesthesia Exit Exam Scores for Rotating CA-2 Residents?

    PubMed

    Nelson, Jonathon H; Deutsch, Nina; Cohen, Ira T; Reddy, Srijaya K

    2017-01-01

    Anesthesiology residency programs commonly have rotations at free-standing children's hospitals to provide and/or supplement their residents' training in pediatric anesthesia. Length and timing of these rotations differ from program to program as can their residents' existing medical knowledge and clinical skills. We predicted that residents with prior pediatric anesthesia experience, who rotate at our pediatric institution for two consecutive months, will score higher on an exit exam compared to residents without prior pediatric experience or those that only rotate for one month. A 50-question multiple choice test was created using pediatric questions released from The American Board of Anesthesiology (ABA) written examinations. The test was administered and proctored at the end of each rotation. Study participants came from three different programs: Program A offers prior pediatric anesthesia experience and a one month rotation; Program B - offers prior pediatric anesthesia experience and a two month rotation; and Program C - does not offer prior pediatric anesthesia experience but includes a two month rotation. The 2014-2015 cohort consisted of 26 rotating second-year clinical anesthesia (CA-2) residents. One resident's exam scores were excluded from this study due to protocol violation. Mean exam scores for Program A, B, and C were 70.5% ± 5.7, 64.2% ± 7.0, and 67.3% ± 4.3, respectively. There was no statistically significant difference in the exit exam scores among the three groups. Prior pediatric anesthesia experience or length of time for subspecialty rotation was not associated with any significant difference in exit exam scores for CA-2 residents.

  9. Residence times and alluvial architecture of a sediment superslug in response to different flow regimes

    USGS Publications Warehouse

    Moody, John A.

    2017-01-01

    A superslug was deposited in a basin in the Colorado Front Range Mountains as a consequence of an extreme flood following a wildfire disturbance in 1996. The subsequent evolution of this superslug was measured by repeat topographic surveys (31 surveys from 1996 through 2014) of 18 cross sections approximately uniformly spaced over 1500 m immediately above the basin outlet. These surveys allowed the identification within the superslug of chronostratigraphic units deposited and eroded by different geomorphic processes in response to different flow regimes.Over the time period of the study, the superslug went through aggradation, incision, and stabilization phases that were controlled by a shift in geomorphic processes from generally short-duration, episodic, large-magnitude floods that deposited new chronostratigraphic units to long-duration processes that eroded units. These phases were not contemporaneous at each channel cross section, which resulted in a complex response that preserved different chronostratigraphic units at each channel cross section having, in general, two dominant types of alluvial architecture—laminar and fragmented. Age and transit-time distributions for these two alluvial architectures evolved with time since the extreme flood. Because of the complex shape of the distributions they were best modeled by two-parameter Weibull functions. The Weibull scale parameter approximated the median age of the distributions, and the Weibull shape parameter generally had a linear relation that increased with time since the extreme flood. Additional results indicated that deposition of new chronostratigraphic units can be represented by a power-law frequency distribution, and that the erosion of units decreases with depth of burial to a limiting depth. These relations can be used to model other situations with different flow regimes where vertical aggradation and incision are dominant processes, to predict the residence time of possible contaminated

  10. Residence times and alluvial architecture of a sediment superslug in response to different flow regimes

    NASA Astrophysics Data System (ADS)

    Moody, John A.

    2017-10-01

    A superslug was deposited in a basin in the Colorado Front Range Mountains as a consequence of an extreme flood following a wildfire disturbance in 1996. The subsequent evolution of this superslug was measured by repeat topographic surveys (31 surveys from 1996 through 2014) of 18 cross sections approximately uniformly spaced over 1500 m immediately above the basin outlet. These surveys allowed the identification within the superslug of chronostratigraphic units deposited and eroded by different geomorphic processes in response to different flow regimes. Over the time period of the study, the superslug went through aggradation, incision, and stabilization phases that were controlled by a shift in geomorphic processes from generally short-duration, episodic, large-magnitude floods that deposited new chronostratigraphic units to long-duration processes that eroded units. These phases were not contemporaneous at each channel cross section, which resulted in a complex response that preserved different chronostratigraphic units at each channel cross section having, in general, two dominant types of alluvial architecture-laminar and fragmented. Age and transit-time distributions for these two alluvial architectures evolved with time since the extreme flood. Because of the complex shape of the distributions they were best modeled by two-parameter Weibull functions. The Weibull scale parameter approximated the median age of the distributions, and the Weibull shape parameter generally had a linear relation that increased with time since the extreme flood. Additional results indicated that deposition of new chronostratigraphic units can be represented by a power-law frequency distribution, and that the erosion of units decreases with depth of burial to a limiting depth. These relations can be used to model other situations with different flow regimes where vertical aggradation and incision are dominant processes, to predict the residence time of possible contaminated

  11. Accessing doctors at times of need-measuring the distance tolerance of rural residents for health-related travel.

    PubMed

    McGrail, Matthew Richard; Humphreys, John Stirling; Ward, Bernadette

    2015-05-29

    Poor access to doctors at times of need remains a significant impediment to achieving good health for many rural residents. The two-step floating catchment area (2SFCA) method has emerged as a key tool for measuring healthcare access in rural areas. However, the choice of catchment size, a key component of the 2SFCA method, is problematic because little is known about the distance tolerance of rural residents for health-related travel. Our study sought new evidence to test the hypothesis that residents of sparsely settled rural areas are prepared to travel further than residents of closely settled rural areas when accessing primary health care at times of need. A questionnaire survey of residents in five small rural communities of Victoria and New South Wales in Australia was used. The two outcome measures were current travel time to visit their usual doctor and maximum time prepared to travel to visit a doctor, both for non-emergency care. Kaplan-Meier charts were used to compare the association between increased distance and decreased travel propensity for closely-settled and sparsely-settled areas, and ordinal multivariate regression models tested significance after controlling for health-related travel moderating factors and town clustering. A total of 1079 questionnaires were completed with 363 from residents in closely-settled locations and 716 from residents in sparsely-settled areas. Residents of sparsely-settled communities travel, on average, 10 min further than residents of closely-settled communities (26.3 vs 16.9 min, p < 0.001), though this difference was not significant after controlling for town clustering. Differences were more apparent in terms of maximum time prepared to travel (54.1 vs 31.9 min, p < 0.001). Differences of maximum time remained significant after controlling for demographic and other constraints to access, such as transport availability or difficulties getting doctor appointments, as well as after controlling for town

  12. TSPO ligand residence time: a new parameter to predict compound neurosteroidogenic efficacy

    PubMed Central

    Costa, Barbara; Da Pozzo, Eleonora; Giacomelli, Chiara; Barresi, Elisabetta; Taliani, Sabrina; Da Settimo, Federico; Martini, Claudia

    2016-01-01

    The pharmacological activation of the cholesterol-binding Translocator Protein (TSPO) leads to an increase of endogenous steroids and neurosteroids determining benefic pleiotropic effects in several pathological conditions, including anxiety disorders. The relatively poor relationship between TSPO ligand binding affinities and steroidogenic efficacies prompted us to investigate the time (Residence Time, RT) that a number of compounds with phenylindolylglyoxylamide structure (PIGAs) spends in contact with the target. Here, given the poor availability of TSPO ligand kinetic parameters, a kinetic radioligand binding assay was set up and validated for RT determination using a theoretical mathematical model successfully applied to other ligand-target systems. TSPO ligand RT was quantified and the obtained results showed a positive correlation between the period for which a drug interacts with TSPO and the compound ability to stimulate steroidogenesis. Specifically, the TSPO ligand RT significantly fitted both with steroidogenic efficacy (Emax) and with area under the dose-response curve, a parameter combining drug potency and efficacy. A positive relation between RT and anxiolytic activity of three compounds was evidenced. In conclusion, RT could be a relevant parameter to predict the steroidogenic efficacy and the in vivo anxiolytic action of new TSPO ligands. PMID:26750656

  13. Plan for radionuclide tracer studies of the residence time distribution in the Wilsonville dissolver and preheater

    SciTech Connect

    Jolley, R.L.; Begovich, J.M.; Brashear, H.R.; Case, N.; Clark, T.G.; Emery, J.F.; Patton, B.D.; Rodgers, B.R.; Villiers-Fisher, J.F.; Watson, J.S.

    1983-12-01

    Stimulus-response measurements using radiotracers to measure residence time distribution (RTD) and hydrodynamic parameters for the preheaters and dissolvers at the Ft. Lewis Solvent Refined Coal (SRC) and the Exxon Donor Solvent (EDS) coal conversion pilot plants are reviewed. A plan is also presented for a series of radioactive tracer studies proposed for the Advanced Coal Liquefaction Facility at Wilsonville, Alabama, to measure the RTD for the preheater and dissolvers in the SRC-I mode. The tracer for the gas phase will be /sup 133/Xe, and /sup 198/Au (on carbonized resin or as an aqueous colloidal suspension) will be used as the slurry tracer. Four experimental phases are recommended for the RTD tracer studies: (1) preheater; (2) dissolver with 100% takeoff; (3) dissolver with 100% takeoff and solids withdrawal; and (4) dissolver with 50% takeoff. Eighteen gas-tracer and 22 liquid-tracer injections are projected to accomplish the four experimental phases. Two to four tracer injections are projected for preliminary tests to ensure the capability of safe injection of the radiotracers and the collection of statistically significant data. A complete projected cost and time schedule is provided, including procurement of necessary components, preparation of the radiotracers, assembly and testing of tracer injection apparatus and detection systems, onsite work and tracer injections, laboratory experimentation, data analysis, and report writing.

  14. Determining the True Residence Time Distribution Curve of Phase I System

    SciTech Connect

    Robinson, Bruce A.

    1982-08-24

    Previous engineering analysis of the Br82 tracer experiments failed to account for the fact that the fluid was being recirculated during these tests. Thus, the concentration vs. volume curves shown in the Run Segments 4 and 5 reports and elsewhere are not really the response of the system to a pulse of tracer. These data are complicated by the fact that at later times most of the tracer being measured was not the original pulse, but the tracer on its second or third pass through the reservoir. When this recirculation effect is subtracted out of the original concentration vs. volume curves, the true residence time distribution (RTD) for the Phase I system indicates that the "long tail" on these curves is not caused by dispersion but results almost entirely from recirculation. The RTD curve for this system cannot be modeled precisely using a one parameter model, but can probably be described by a combination of hydrodynamic and turbulent dispersion in a single fracture. Alternatively, flow through multiple fractures could easily result in the RTD curves determined during Run Segments 4 and 5.

  15. Residence and Migration of First-Time Freshmen Enrolled in Higher Education Institutions: Fall 1994. E.D. TABS.

    ERIC Educational Resources Information Center

    Barbett, Samuel

    This report presents 23 tables of data on residence and migration of first-time freshmen based on the 1994 "Fall Enrollment" survey, part of the Integrated Postsecondary Education Data System. The survey counted 2.14 million first-time freshmen. More than 366,000 (17 percent) migrated between states. The percent of freshmen who left…

  16. Seasonal variation of residence time in spring and groundwater evaluated by CFCs and numerical simulation in mountainous headwater catchment

    NASA Astrophysics Data System (ADS)

    Tsujimura, Maki; Watanabe, Yasuto; Ikeda, Koichi; Yano, Shinjiro; Abe, Yutaka

    2016-04-01

    Headwater catchments in mountainous region are the most important recharge area for surface and subsurface waters, additionally time information of the water is principal to understand hydrological processes in the catchments. However, there have been few researches to evaluate variation of residence time of subsurface water in time and space at the mountainous headwaters especially with steep slope. We investigated the temporal variation of the residence time of the spring and groundwater with tracing of hydrological flow processes in mountainous catchments underlain by granite, Yamanashi Prefecture, central Japan. We conducted intensive hydrological monitoring and water sampling of spring, stream and ground waters in high-flow and low-flow seasons from 2008 through 2013 in River Jingu Watershed underlain by granite, with an area of approximately 15 km2 and elevation ranging from 950 m to 2000 m. The CFCs, stable isotopic ratios of oxygen-18 and deuterium, inorganic solute constituent concentrations were determined on all water samples. Also, a numerical simulation was conducted to reproduce of the average residence times of the spring and groundwater. The residence time of the spring water estimated by the CFCs concentration ranged from 10 years to 60 years in space within the watershed, and it was higher (older) during the low flow season and lower (younger) during the high flow season. We tried to reproduce the seasonal change of the residence time in the spring water by numerical simulation, and the calculated residence time of the spring water and discharge of the stream agreed well with the observed values. The groundwater level was higher during the high flow season and the groundwater dominantly flowed through the weathered granite with higher permeability, whereas that was lower during the low flow season and that flowed dominantly through the fresh granite with lower permeability. This caused the seasonal variation of the residence time of the spring

  17. Residence time, mineralization processes and groundwater origin within a carbonate coastal aquifer with a thick unsaturated zone

    NASA Astrophysics Data System (ADS)

    Santoni, S.; Huneau, F.; Garel, E.; Vergnaud-Ayraud, V.; Labasque, T.; Aquilina, L.; Jaunat, J.; Celle-Jeanton, H.

    2016-09-01

    This study aims at establishing groundwater residence times, identifying mineralization processes and determining groundwater origins within a carbonate coastal aquifer with thick unsaturated zone and lying on a granitic depression. A multi-tracer approach (major ions, SiO2, Br-, Ba+, Sr2+, 18O, 2H, 13C, 3H, Ne, Ar) combined with a groundwater residence time determination using CFCs and SF6 allows defining the global setting of the study site. A typical mineralization conditioned by the sea sprays and the carbonate matrix helped to validate the groundwater weighted residence times from using a binary mixing model. Terrigenic SF6 excesses have been detected and quantified, which permits to identify a groundwater flow from the surrounding fractured granites towards the lower aquifer principally. The use of CFCs and SF6 as a first hydrogeological investigation tool is possible and very relevant despite the thick unsaturated zone and the hydraulic connexion with a granitic environment.

  18. Watershed Influences on Residence Time and Oxygen Reduction Rates in an Agricultural Landscape

    NASA Astrophysics Data System (ADS)

    Shope, C. L.; Tesoriero, A. J.

    2015-12-01

    Agricultural use of synthetic fertilizers and animal manure has led to increased crop production, but also elevated nitrogen concentrations in groundwater, resulting in impaired water quality. Groundwater oxygen concentrations are a key indicator of potential biogeochemical processes, which control water/aquifer interactions and contaminant transport. The U.S. Geological Survey's National Water-Quality Assessment Program has a long-history of studying nutrient transport and processing across the United States and the Glacial Aquifer system in particular. A series of groundwater well networks in Eastern Wisconsin is being used to evaluate the distribution of redox reaction rates over a range of scales with a focus on dissolved O2 reduction rates. An analysis of these multi-scale networks elucidates the influence of explanatory variables (i.e.: soil type, land use classification) on reduction rates and redox reactions throughout the Fox-Wolf-Peshtigo watersheds. Multiple tracers including dissolved gasses, tritium, helium, chlorofluorocarbons, sulfur hexafluoride, and carbon-14 were used to estimate groundwater ages (0.8 to 61.2 yr) at over 300 locations. Our results indicate O2 reduction rates along a flowpath study area (1.2 km2) of 0.15 mg O2 L-1 yr-1 (0.12 to 0.18 mg O2 L-1 yr-1) up to 0.41 mg O2 L-1 yr-1 (0.23 to 0.89 mg O2 L-1 yr-1) for a larger scale land use study area (3,300 km2). Preliminary explanatory variables that can be used to describe the variability in reduction rates include soil type (hydrologic group, bulk density) and chemical concentrations (nitrite plus nitrate, silica). The median residence time expected to reach suboxic conditions (≤ 0.4 mg O2 L-1) for the flowpath and the land use study areas was 66 and 25 yr, respectively. These results can be used to elucidate and differentiate the impact of residence time on groundwater quality vulnerability and sustainability in agricultural regions without complex flow models.

  19. Influence of operational parameters (sludge retention time and hydraulic residence time) on the removal of estrogens by membrane bioreactor.

    PubMed

    Estrada-Arriaga, Edson B; Mijaylova, Petia N

    2011-08-01

    This paper deals with the removal of two natural estrogens, estrone (E1) and 17β-estradiol (E2) and a synthetic one 17α ethinylestradiol (EE2) from wastewater in a laboratory-scale membrane bioreactor (MBR). The effects of both solid retention time (SRT) and hydraulic residence time (HRT) were studied using synthetic wastewater in the MBR. At 35, 45, 60, 75, and 95 days, SRT was studied. The HRT was varied in the range of 7-12 h. The results showed that the increases in HRT and SRT enhanced the biodegradation process after adaptation to microorganisms. At HRT of 12 h, the estrogen removals were close to 100% in the MBR. The highest estrogen removals were obtained at SRT of 60 days. Continuous tests showed a linear relationship between nitrification and estrogen removal rates. The most biodegradable compound was the E2. The membrane fouling rates increased with the decreased of SRT and HRT. Optimal process conditions in this work was obtained at the SRT and HRT of 60 days and 12 h, respectively, with high efficient of estrogen removal, nitrification efficiencies, as well as a minimum membrane fouling rate.

  20. The Influence of Sitting Time and Physical Activity on Health Outcomes in Public Housing Residents

    PubMed Central

    Leach, Heather J.; Mama, Scherezade K.; Soltero, Erica G.; Lee, Rebecca E.

    2015-01-01

    Objectives Examine differences between levels of physical activity and sitting time for residents of public housing developments located in high vs low income neighborhoods, and whether physical activity or sitting time had a greater influence on health outcomes. Design Secondary data analysis from the Healthful Options Using Streets and Transportation in Our Neighborhoods (HOUSTON) project. Setting Public housing developments located in Houston, TX. Participants African American, adult males and females. Main Outcome Measures Self-reported PA and time spent sitting on weekdays were measured using the International Physical Activity Questionnaire (IPAQ) short form. Participants completed measures of BMI (kg/m2), % body fat (%BF) and resting blood pressure to assess health outcomes. Neighborhood income was defined as the median household income at the census block group level, obtained from the 2006–2010 American Community Survey. Results All participants (N=216) had an annual household income of ≤$19,350, and neighborhood income ranged from $9,226 to $57,618. Participants reported an average of 4342.2 ± 4828.3 MET-min/wk of physical activity, and 4.5 ± 3.2 hours of sitting per weekday. Time spent sitting was associated with BMI (β=.50, t=2.4, P=.018), %BF (β=.87, t=3.6, P=.000), and diastolic blood pressure (β=.62, t=2.1, P=.041). Physical activity was not significantly associated with any health outcomes. Conclusion Our findings indicate that public housing residents’ health statuses are vulnerable to sedentary behaviors regardless of the affluence of the neighborhood surrounding the housing development. PMID:25065081

  1. Simultaneously Assessing Climate and Vegetation Drivers of Carbon Residence Time and Net Primary Productivity across Six US Grasslands

    NASA Astrophysics Data System (ADS)

    Wilcox, K.; Collins, S. L.; Knapp, A.; Pockman, W.; Smith, M. D.; Luo, Y.

    2016-12-01

    Carbon (C) storage is an important ecosystem service which buffers global C emissions, including 30% from anthropogenic sources. To predict how much C is stored within ecosystems, we need knowledge of both C inputs through net primary productivity (NPP) and how long C remains in an ecosystem until being released back to the atmosphere (C residence time). Currently, earth system models have difficulty accurately projecting C storage at spatial scales relevant for land management decisions (i.e., in individual ecosystems). One reason underlying the limited scalability of these models is that, although climate is incorporated into model projections of NPP and C residence time, the functional composition of vegetation (e.g., annual versus perennial abundance) is not as well represented at finer spatial scales. Quantifying the importance of climate versus vegetation as drivers of C cycling is particularly important in the context of global change, which will likely alter climatic and vegetation characteristics at different rates. To address this, we estimated NPP and ecosystem C residence time across 6 US grasslands spanning various climate and vegetation gradients. NPP was measured at each site, while C residence time was estimated via inverse modeling. For C residence time, we used three years of carbon pool and flux observations at each site in conjunction with a six-pool C model in a Bayesian framework to estimate C turnover, C transfer and environmental scaling parameters for each ecosystem. These parameters were then used to estimate residence times of individual C pools and the entire ecosystem. Using numerous climatic and vegetation characteristics for each grassland, we determined that the variability of NPP across the six grasslands was determined primarily by mean annual precipitation (MAP). Alternately, although ecosystem C residence time across sites was partially explained by climate, it was more strongly linked with the abundances of annual plant species

  2. Variability of Residence Time tracer Concentrations at the Southern Sierra Critical Zone Observatory during the California Drought

    NASA Astrophysics Data System (ADS)

    Visser, A.; Thaw, M.; Stacy, E.; Hunsaker, C. T.; Bibby, R. K.; Deinhart, A.; Schorzman, K.; Egnatuk, C. M.; Conklin, M. H.; Esser, B.

    2015-12-01

    California water supply from high elevation snow melt is vulnerable to climate change and prolonged drought conditions. Reduced snow pack and earlier snow melt will result in a greater reliance on man-made reservoirs and subsurface catchment storage. To gain insight into the subsurface storage volume of high elevation catchments, we studied the residence time distribution of surface water leaving the Southern Sierra Critical Zone Observatory. Since October 2014, we have collected monthly samples of two residence time tracers with contrasting half-lives: sulfur-35 (87.5 days) and tritium (12.32 years). Upstream catchment area at the three nested sampling locations is 1 km2 (P301 sub-catchment), 4 km2 (Providence Creek) and ~50 km2 (Big Creek). Samples were analyzed at LLNL by low level liquid scintillation counting and noble gas mass spectrometry after helium accumulation. Variations in tracer concentrations in precipitation, both for tritium (11-24 pCi/L) and sulfur-35 (24-100 mBq/L), complicate straightforward interpretation of residence times. Sulfur-35 concentrations show that last year precipitation contributes 1% - 10% of total stream flow, even during peak snowmelt. Tritium concentrations in stream flow vary between 40% and 60% of the initial concentration in precipitation (15.5 pCi/L), indicating that water leaving the catchment has a residence time on the order of years to decades. Additional analyses of sodium-22 (2.6 year half-life) will aid in deconvoluting the residence time distribution. These low tracer concentrations can be attributed to current severe drought conditions, resulting in low discharge rates and longer residence times. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-675107

  3. Continuous, high-resolution spatial mapping of water isotopes: improving tools for quantifying local evaporation and residence times

    NASA Astrophysics Data System (ADS)

    Dennis, Kate J.; Carter, Jeffrey A.; Winkler, Renato; Downing, Brian; Kendall, Carol; Bergamaschi, Brian

    2015-04-01

    Stable isotopes of water (d2H, d18O) are unique tracers of many hydrological processes including evaporation, precipitation, reservoir mixing and residence time. Historically, discrete water samples have been collected and analyzed via either Isotope Ratio Mass Spectrometry, or more recently laser-based spectroscopic methods, such as Cavity Ring-Down Spectroscopy (CRDS). However, the analysis of discrete samples precludes the ability to construct high resolution water isotope data sets through time and space. By coupling a recently developed front-end peripheral device (Continuous Water Sampler or CWS) to a CRDS analyzer (Picarro L2130-i), we continuously measured and spatially mapped water isotopes on a transect of the Sacramento River Delta following an extended period of drought. More than two-thousand five-second average d18O and d2H measurements were made aboard the R/V King (USGS) over a six-hour period. In addition to water isotopes, nitrate, chlorophyll, dissolved organic matter (DOM) fluorescence, and other water quality parameters were also measured continuously. As you travel northeast up the delta, surface waters become progressively more enriched in 18O and 2H, while nitrate decreased in concentration and chlorophyll and DOM increased. We utilize the spatially-mapped isotope data within a single transect to understand local evaporation and residence time by (i) utilizing the secondary parameter, d-excess, and (ii) using a simple mass balance model of water moving through the system (inflow, outflow and evaporation). Additional transects, to be conducted during the rainy season, should highlight how the Delta system evolves seasonally. In concert with other data previously collected from the Sacramento River Delta, we suggest the lower region represents a mixture of river waters derived from the Sierra Nevada Mountains and the more marine waters from the mouth of the San Francisco Bay. Moving NE up the Delta into shallow sloughs through flooded wetlands

  4. How Do Residents Spend Their Shift Time? A Time and Motion Study With a Particular Focus on the Use of Computers.

    PubMed

    Mamykina, Lena; Vawdrey, David K; Hripcsak, George

    2016-06-01

    To understand how much time residents spend using computers compared with other activities, and what residents use computers for. This time and motion study was conducted in June and July 2010 at NewYork-Presbyterian/Columbia University Medical Center with seven residents (first-, second-, and third-year) on the general medicine service. An experienced observer shadowed residents during a single day shift, captured all their activities using an iPad application, and took field notes. The activities were captured using a validated taxonomy of clinical activities, expanded to describe computer-based activities with a greater level of detail. Residents spent 364.5 minutes (50.6%) of their shift time using computers, compared with 67.8 minutes (9.4%) interacting with patients. In addition, they spent 292.3 minutes (40.6%) talking with others in person, 186.0 minutes (25.8%) handling paper notes, 79.7 minutes (11.1%) in rounds, 80.0 minutes (11.1%) walking or waiting, and 54.0 minutes (7.5%) talking on the phone. Residents spent 685 minutes (59.6%) multitasking. Computer-based documentation activities amounted to 189.9 minutes (52.1%) of all computer-based activities time, with 128.7 minutes (35.3%) spent writing notes and 27.3 minutes (7.5%) reading notes composed by others. The study showed that residents spent considerably more time interacting with computers (over 50% of their shift time) than in direct contact with patients (less than 10% of their shift time). Some of this may be due to an increasing reliance on computing systems for access to patient data, further exacerbated by inefficiencies in the design of the electronic health record.

  5. Dependence of atmospheric refractive index structure parameter (Cn2) on the residence time and vertical distribution of aerosols.

    PubMed

    Anand, N; Satheesh, S K; Krishna Moorthy, K

    2017-07-15

    Effects of absorbing atmospheric aerosols in modulating the tropospheric refractive index structure parameter (Cn2) are estimated using high resolution radiosonde and multi-satellite data along with a radiative transfer model. We report the influence of variations in residence time and vertical distribution of aerosols in modulating Cn2 and why the aerosol induced atmospheric heating needs to be considered while estimating a free space optical communication link budget. The results show that performance of the link is seriously affected if large concentrations of absorbing aerosols reside for a long time in the atmospheric path.

  6. Estimation of sediment residence times in subtropical highland catchments of central Mexico combining river gauging and fallout radionuclides

    NASA Astrophysics Data System (ADS)

    Evrard, Olivier; Némery, Julien; Gratiot, Nicolas; Duvert, Clément; Lefèvre, Irène; Ayrault, Sophie; Esteves, Michel; Bonté, Philippe

    2010-05-01

    Subtropical regions of the world are affected by intense soil erosion associated with deforestation, overgrazing and cropping intensification. This land degradation leads to important on-site (e.g. decrease in soil fertility) and off-site impacts (e.g. reservoir sedimentation, water pollution). This study determined the mean sediment residence times in soils and rivers of three catchments (3 - 12 km²) with contrasted land uses (i.e. cropland, forests, rangelands, extended gully networks) located in highlands of the transvolcanic belt of central Mexico. Calculations were based on rainfall and river gauging as well as on fallout radionuclide measurements (Be-7, Cs-137, Pb-210). Atmospheric deposition of Be-7 and Pb-210 was estimated based on the analysis of rainfall precipitated samples. Rainfall samples were collected all throughout the rainy season in order to take account of the temporal variations of the radionuclide fluxes. Furthermore, sampling of suspended sediment was conducted at the outlet of each catchment during most of the storms that occurred throughout the 2009 rainy season. Be-7, Cs-137 and Pb-210 concentrations of this sediment were determined by gamma-spectrometry. A two-box balance model was then used to estimate the sediment residence time and the inventory of radionuclides in the three selected catchments. This model subdivided each catchment into two boxes: (i) a "soil-box" characterised by low transport velocities and hence long radionuclide residence times and (ii) a "river-box" covering the river surface and its surroundings characterised by quicker exchanges and shorter radionuclide residence times. Input and output fluxes of sediment and radionuclides were taken into account in each box. Radioactive decay during the residence time of sediment was also considered. The mean residence time of sediment in soils ranged between 13,300 - 28,500 years. In contrast, sediment residence time in rivers was much shorter, fluctuating between 28 and 393

  7. Groundwater residence time : tell me who you are and I will tell which information you may provide

    NASA Astrophysics Data System (ADS)

    Aquilina, Luc; Labasque, Thierry; Kolbe, Tamara; Marçais, Jean; Leray, Sarah; Abbott, Ben; de Dreuzy, Jean-Raynald

    2016-04-01

    Groundwater residence-time or ages have been widely used in hydrogeology during the last decades. Following tritium measurements, anthropogenic gases (CFC, SF6, 35Kr) have been developed. They provide information at the aquifer scale on long residence times. They complement the more localized data obtained from sparse boreholes with hydraulic and geophysical methods. Anthropogenic tracer concentrations are most generally considered as "Groundwater ages" using a piston flow model providing an order of magnitude for the residence time. More advanced information can however be derived from the combined analysis of the tracer concentrations. For example, the residence time distribution over the last 50 years can be well approached by the concentration of two sufficient different anthropogenic tracers in the group (CFC, SF6, 35Kr), i.e. tracers whose anthropogenic chronicles are sufficiently different. And, with additional constrains on geological and hydraulic properties, groundwater ages contribute to characterize the aquifer structures and the groundwater resources. Complex geological environments also include old groundwater bodies in extremely confined aquifer sections. In such cases, various tracers are related to highly different processes. CFCs can be taken as a marker of modern contamination to track exchanges between shallower and deeper aquifers, leakage processes, and modification of circulations linked to recent anthropogenic changes. 14C or 36Cl can be used to evidence much older processes but have to be related to the history of the chemical element itself. Numerous field studies in fact demonstrate the broad-range extent of the residence time distribution spanning in some cases several orders of magnitude. Flow and transport models in heterogeneous structures confirm such wide residence times and help to characterize their distribution. Residence times also serve as a privileged interface to the fate of some contaminants in aquifers or to trace

  8. Rn as a geochemical tool for estimating residence times in the hyporheic zone and its application to biogeochemical processes

    NASA Astrophysics Data System (ADS)

    Gilfedder, Benjamin; Dörner, Sebastian; Ebertshäuser, Marlene Esther; Glaser, Barbara; Klug, Maria; Pittroff, Marco; Pieruschka, Ines; Waldemer, Carolin

    2014-05-01

    The hyporheic zone is at the interface between groundwater and surface water systems. It is also often a geochemical and redox boundary between typically reduced groundwater and oxic surface water. It experiences dynamic physical and chemical conditions as both groundwater fluxes and surface water levels vary in time and space. This can be particularly important for processes such as biogeochemical processing of nutrients and carbon. There has recently been an increasing focus on coupling residence times of surface water in the hyporheic zone with biogeochemical reactions. While geochemical profiles can be readily measured using established geochemical sampling techniques (e.g. peepers), quantifying surface water residence times and flow paths within the hyporheic zone is more elusive. The nobel gas radon offers a method for quantification of surface water residence times in the hyporheic zone. Radon activities are typically low in surface waters due to degassing to the atmosphere and decay. However once the surface water flows into the hyporheic zone radon accumulates along the flow path due to emanation from the sediments. Using simple analytical equations the water residence time can be calculated based on the difference between measured 222Rn activities and 222Rn activities at secular equilibrium, with a maximum limit of about 20 days (depending on measurement precision). Rn is particularly suited to residence time measurements in the hyporheic zone since it does not require addition of tracers to the stream nor does it require complex simulations and assumptions (such as 1D vertical flow) as for temperature measurements. As part of the biogeochemistry course at the University of Bayreuth, we have investigated the coupling of redox processes and water residence times in the hyporheic zone using 222Rn as a tracer for residence time. Of particular interest were nitrate and sulfate reduction and methane and CO2 production. Measurements were made in a sandy section

  9. Effects of residence time on summer nitrate uptake in Mississippi River flow-regulated backwaters

    USGS Publications Warehouse

    James, W.F.; Richardson, W.B.; Soballe, D.M.

    2008-01-01

    Nitrate uptake may be improved in regulated floodplain rivers by increasing hydrological connectivity to backwaters. We examined summer nitrate uptake in a series of morphologically similar backwaters on the Upper Mississippi River receiving flow-regulated nitrate loads via gated culverts. Flows into individual backwaters were held constant over a summer period but varied in the summers of 2003 and 2004 to provide a range of hydraulic loads and residence times (??). The objectives were to determine optimum loading and ?? for maximum summer uptake. Higher flow adjustment led to increased loading but lower ?? and contact time for uptake. For highest flows, ?? was less than 1 day resulting in lower uptake rates (Unet, 4000 m). For low flows, ?? was greater than 5 days and U% approached 100%, but Unet was 200 mg m-2 day-1. Snet was < half the length of the backwaters under these conditions indicating that most of the load was assimilated in the upper reaches, leading to limited delivery to lower portions. Unet was maximal (384-629 mg m-2 day-1) for intermediate flows and ?? ranging between 1 and 1.5 days. Longer Snet (2000-4000 m) and lower U% (20-40%) reflected limitation of uptake in upper reaches by contact time, leading to transport to lower reaches for additional uptake. Uptake by ???10 000 ha of reconnected backwaters along the Upper Mississippi River (13% of the total backwater surface area) at a Unet of ???630 mg m-2 day-1 would be the equivalent of ???40% of the summer nitrate load (155 mg day-1) discharged from Lock and Dam 4. These results indicate that backwater nitrate uptake can play an important role in reducing nitrate loading to the Gulf of Mexico. Copyright ?? 2008 John Wiley & Sons, Ltd.

  10. Impact of Relative Residence Times in Highly Distinct Environments on the Distribution of Heavy Drinkers

    PubMed Central

    Mubayi, Anuj; Greenwood, Priscilla E.; Castillo-Chávez, Carlos; Gruenewald, Paul; Gorman, Dennis M.

    2009-01-01

    Alcohol consumption is a function of social dynamics, environmental contexts, individuals’ preferences and family history. Empirical surveys have focused primarily on identification of risk factors for high-level drinking but have done little to clarify the underlying mechanisms at work. Also, there have been few attempts to apply nonlinear dynamics to the study of these mechanisms and processes at the population level. A simple framework where drinking is modeled as a socially contagious process in low- and high-risk connected environments is introduced. Individuals are classified as light, moderate (assumed mobile), and heavy drinkers. Moderate drinkers provide the link between both environments, that is, they are assumed to be the only individuals drinking in both settings. The focus here is on the effect of moderate drinkers, measured by the proportion of their time spent in “low-” versus “high-” risk drinking environments, on the distribution of drinkers. A simple model within our contact framework predicts that if the relative residence times of moderate drinkers is distributed randomly between low- and high-risk environments then the proportion of heavy drinkers is likely to be higher than expected. However, the full story even in a highly simplified setting is not so simple because “strong” local social mixing tends to increase high-risk drinking on its own. High levels of social interaction between light and moderate drinkers in low-risk environments can diminish the importance of the distribution of relative drinking times on the prevalence of heavy drinking. PMID:20161388

  11. Structure-guided residence time optimization of a dabigatran reversal agent.

    PubMed

    Schiele, Felix; van Ryn, Joanne; Litzenburger, Tobias; Ritter, Michael; Seeliger, Daniel; Nar, Herbert

    2015-01-01

    Novel oral anticoagulants are effective and safe alternatives to vitamin-K antagonists for anticoagulation therapy. However, anticoagulation therapy in general is associated with an elevated risk of bleeding. Idarucizumab is a reversal agent for the direct thrombin inhibitor, dabigatran etexilate (Pradaxa®) and is currently in Phase 3 studies. Here, we report data on the antibody fragment aDabi-Fab2, a putative backup molecule for idarucizumab. Although aDabi-Fab2 completely reversed effects of dabigatran in a rat model in vivo, we observed significantly reduced duration of action compared to idarucizumab. Rational protein engineering, based on the X-ray structure of aDabi-Fab2, led to the identification of mutant Y103W. The mutant had optimized shape complementarity to dabigatran while maintaining an energetically favored hydrogen bond. It displayed increased affinity for dabigatran, mainly driven by a slower off-rate. Interestingly, the increased residence time translated into longer duration of action in vivo. It was thus possible to further enhance the efficacy of aDabi-Fab2 based on rational design, giving it the potential to serve as a back-up candidate for idarucizumab.

  12. Effects of residence time distribution and packing on methanol oxidation in biotrickling filter

    SciTech Connect

    Yuanita W. Hutomo; K.L. Pinder

    2006-03-15

    The effects of residence time distribution (RTD) on biotrickling filter systems and the comparison of the maximum elimination capacity (EC) and poisoning limits as functions of loadings of two packing media, Celite Biocatalyst Carrier R-635 and a subbituminous coal (Hat Creek coal from British Columbia), were studied. To alter the RTD patterns in the two reactor columns, two baffle designs were chosen. The RTD tests were done under dry conditions, over a range of airflow rates, with zero baffle, one baffle, and two baffles added into each column. Mixed culture from compost was used to acclimate the bed for the methanol removal efficiency study. No nutrients were added in the coal column. To study the poisoning limit, the inlet methanol concentration was randomly increased until a severe drop in removal efficiency occurred. From the RTD tests and the removal efficiency runs, which did not result in 100% conversion, number of tank-in-series (N) values, maximum EC values, and rate constants of each column with different baffle configurations could be obtained. Results from duplicate runs showed that addition of baffles decreased the N values of the columns and increased the back mixing in both systems. Maximum EC values, critical loadings, and poisoning limits also increased with increasing back mixing. Coal was superior to Celite Biocatalyst Carrier R-635 because it gave good conversions without additional nutrients. In all runs, the rate of methanol removal was controlled by a zero order process. 14 refs., 10 figs., 7 tabs.

  13. Subunit Stabilization and Polyethylene Glycolation of Cocaine Esterase Improves In Vivo Residence Time

    SciTech Connect

    Narasimhan, Diwahar; Collins, Gregory T.; Nance, Mark R.; Nichols, Joseph; Edwald, Elin; Chan, Jimmy; Ko, Mei-Chuan; Woods, James H.; Tesmer, John J.G.; Sunahara, Roger K.

    2012-03-15

    No small-molecule therapeutic is available to treat cocaine addiction, but enzyme-based therapy to accelerate cocaine hydrolysis in serum has gained momentum. Bacterial cocaine esterase (CocE) is the fastest known native enzyme that hydrolyzes cocaine. However, its lability at 37 C has limited its therapeutic potential. Cross-linking subunits through disulfide bridging is commonly used to stabilize multimeric enzymes. Herein we use structural methods to guide the introduction of two cysteine residues within dimer interface of CocE to facilitate intermolecular disulfide bond formation. The disulfide-crosslinked enzyme displays improved thermostability, particularly when combined with previously described mutations that enhance stability (T172R-G173Q). The newly modified enzyme yielded an extremely stable form of CocE (CCRQ-CocE) that retained greater than 90% of its activity after 41 days at 37 C, representing an improvement of more than 4700-fold over the wild-type enzyme. CCRQ-CocE could also be modified by polyethylene glycol (PEG) polymers, which improved its in vivo residence time from 24 to 72 h, as measured by a cocaine lethality assay, by self-administration in rodents, and by measurement of inhibition of cocaine-induced cardiovascular effects in rhesus monkeys. PEG-CCRQ elicited negligible immune response in rodents. Subunit stabilization and PEGylation has thus produced a potential protein therapeutic with markedly higher stability both in vitro and in vivo.

  14. Predictive Model for Particle Residence Time Distributions in Riser Reactors. Part 1: Model Development and Validation

    DOE PAGES

    Foust, Thomas D.; Ziegler, Jack L.; Pannala, Sreekanth; ...

    2017-02-28

    Here in this computational study, we model the mixing of biomass pyrolysis vapor with solid catalyst in circulating riser reactors with a focus on the determination of solid catalyst residence time distributions (RTDs). A comprehensive set of 2D and 3D simulations were conducted for a pilot-scale riser using the Eulerian-Eulerian two-fluid modeling framework with and without sub-grid-scale models for the gas-solids interaction. A validation test case was also simulated and compared to experiments, showing agreement in the pressure gradient and RTD mean and spread. For simulation cases, it was found that for accurate RTD prediction, the Johnson and Jackson partialmore » slip solids boundary condition was required for all models and a sub-grid model is useful so that ultra high resolutions grids that are very computationally intensive are not required. Finally, we discovered a 2/3 scaling relation for the RTD mean and spread when comparing resolved 2D simulations to validated unresolved 3D sub-grid-scale model simulations.« less

  15. The Effect of Solids Residence Time on Chemical Phosphorus Removal in Low Concentration Applications.

    PubMed

    Conidi, Daniela; Parker, Wayne J

    2016-11-01

      The effect of solids residence time (SRT) on steady state phosphorus (P) removal when striving for ultralow concentrations through metal salt addition was studied. Lab-scale continuous flow sequencing batch reactors (SBRs) were operated under high (6.4 mg P/L; 1.4 mol Fe/mol P) and low (3.4 mg P/L; 2.6 mol Fe/mol P) influent phosphate concentrations to characterize P removal. Residual P concentrations, particle size distribution, and microscopy analyses were determined over a range of SRTs. A majority of P removal (94% with 3.4 mg P/L; 83% with 6.4 mg P/L) occurred immediately after iron (Fe) addition with additional removal in the SBRs (3.3-4.8% with 3.4 mg P/L; 5.5-8.8% with 6.4 mg P/L). Soluble P uptake was higher for SRTs ≤ 7.4 days with 3.4 mg P/L and ≤ 14.3 days with 6.4 mg P/L. Normalized P uptake (μg P/mg total suspended solids [TSS]) decreased with SRT providing evidence that aging changed floc properties relevant to P removal. Floc size was found to have no distinguishable influence on P removal. However, changes in floc morphology were consistent with P removal trends.

  16. Liquid flow residence time in a fibrous fixed bed reactor with recycle.

    PubMed

    Martinov, Martin; Hadjiev, Dimiter; Vlaev, Serafim

    2010-02-01

    Waste removal efficiency of gas-liquid biofilter reactors for waste water treatment depends on its flow regime and residence time distribution (RTD) as key parameters of bio-reactor performance. The present study reports RTD regime in a fibrous fixed bed biofilm reactor related to a fluid velocity range appropriate for biofilm operation. The data from tracer experiments are correlated in terms of the one-parameter "tanks-in-series" model. The aerated fibrous bed reactor RTD function is found to be dependent on net liquid and gas phase superficial velocity U(L) and U(G). Liquid internal recirculation exhibited small effect comparable with the effect of net liquid flow. A power law relationship relating the number of perfectly mixed cells with liquid and gas superficial velocity is elaborated. Assuming similarity of the prototype and real vessels' flow fields, the equation as well as its corresponding range of fluid velocity can be used for bio-reactor design and scale-up. Comparison over the model parameters obtained in fixed bed bubble columns at low fluid velocity shows the results of this study to be comparable with previous data of mesh wire packing.

  17. Scrutinizing the carbon cycle and CO2 residence time in the atmosphere

    NASA Astrophysics Data System (ADS)

    Harde, Hermann

    2017-05-01

    Climate scientists presume that the carbon cycle has come out of balance due to the increasing anthropogenic emissions from fossil fuel combustion and land use change. This is made responsible for the rapidly increasing atmospheric CO2 concentrations over recent years, and it is estimated that the removal of the additional emissions from the atmosphere will take a few hundred thousand years. Since this goes along with an increasing greenhouse effect and a further global warming, a better understanding of the carbon cycle is of great importance for all future climate change predictions. We have critically scrutinized this cycle and present an alternative concept, for which the uptake of CO2 by natural sinks scales proportional with the CO2 concentration. In addition, we consider temperature dependent natural emission and absorption rates, by which the paleoclimatic CO2 variations and the actual CO2 growth rate can well be explained. The anthropogenic contribution to the actual CO2 concentration is found to be 4.3%, its fraction to the CO2 increase over the Industrial Era is 15% and the average residence time 4 years.

  18. Mean water residence times in the pre-alpine Rietholzbach catchment

    NASA Astrophysics Data System (ADS)

    Lehner, I.; Bernasconi, S.; Seneviratne, S. I.

    2009-04-01

    The Rietholzbach catchment is a small, hilly pre-alpine basin in the north-eastern part of Switzerland. Its area is 3.31 km2 and it covers an altitude range between 682 and 950 m. The area is only sparsely populated and primarily used as pasture land (67 %), on steep slopes the land use is forest (25 %). A hydrological peculiarity is the congruence of surface and sub-surface catchment area. In 1975 measurements were initiated to determine and understand the water balance and its processes. Isotope measurements of all components of the water cycle started in 1994. The water samples of precipitation, soil water (discharge of a lysimeter), ground water, and river water are taken approximately bi-weekly. All samples are prepared by the CO2 gas equilibration technique and are analysed in terms of the oxygen isotopes by mass spectrometry. The samples are taken either at the gauge at the outflow of the catchment or next to the main measurement site in the upper third of the catchment where an other gauge, three groundwater wells, the lysimeter and the meteorological sensors are installed in close vicinity. Based on these data series this contribution will present estimates of the mean water residence times in the different components of the catchment.

  19. Investigation of residence time and groundwater flux in Venice Lagoon: comparing radium isotope and hydrodynamic models.

    PubMed

    Rapaglia, John; Ferrarin, Christian; Zaggia, Luca; Moore, Willard S; Umgiesser, Georg; Garcia-Solsona, Ester; Garcia-Orellana, Jordi; Masqué, Pere

    2010-07-01

    The four naturally-occurring isotopes of radium were coupled with a previously evaluated hydrodynamic model to determine the apparent age of surface waters and to quantify submarine groundwater discharge (SGD) into the Venice Lagoon, Italy. Mean apparent age of water in the Venice Lagoon was calculated using the ratio of 224Ra to 228Ra determined from 30 monitoring stations and a mean pore water end member. Average apparent age was calculated to be 6.0 d using Ra ratios. This calculated age was very similar to average residence time calculated for the same period using a hydrodynamic model (5.8 d). A mass balance of Ra was accomplished by quantifying each of the sources and sinks of Ra in the lagoon, with the unknown variable being attributed to SGD. Total SGD were calculated to be 4.1 +/- 1.5, 3.8 +/- 0.7, 3.0 +/- 1.3, and 3.5 +/- 1.0 x 10(10) L d(-1) for (223,224,226, 228)Ra, respectively, which are an order of magnitude larger than total mean fluvial discharge into the Venice Lagoon (3.1 x 10(9) L d(-1)). The SGD as a source of nutrients in the Venice Lagoon is also discussed and, though significant to the nutrient budget, is likely to be less important as the dominant control on SGD is recirculated seawater rather than freshwater. 2009 Elsevier Ltd. All rights reserved.

  20. Structure-guided residence time optimization of a dabigatran reversal agent

    PubMed Central

    Schiele, Felix; van Ryn, Joanne; Litzenburger, Tobias; Ritter, Michael; Seeliger, Daniel; Nar, Herbert

    2015-01-01

    Novel oral anticoagulants are effective and safe alternatives to vitamin-K antagonists for anticoagulation therapy. However, anticoagulation therapy in general is associated with an elevated risk of bleeding. Idarucizumab is a reversal agent for the direct thrombin inhibitor, dabigatran etexilate (Pradaxa®) and is currently in Phase 3 studies. Here, we report data on the antibody fragment aDabi-Fab2, a putative backup molecule for idarucizumab. Although aDabi-Fab2 completely reversed effects of dabigatran in a rat model in vivo, we observed significantly reduced duration of action compared to idarucizumab. Rational protein engineering, based on the X-ray structure of aDabi-Fab2, led to the identification of mutant Y103W. The mutant had optimized shape complementarity to dabigatran while maintaining an energetically favored hydrogen bond. It displayed increased affinity for dabigatran, mainly driven by a slower off-rate. Interestingly, the increased residence time translated into longer duration of action in vivo. It was thus possible to further enhance the efficacy of aDabi-Fab2 based on rational design, giving it the potential to serve as a back-up candidate for idarucizumab. PMID:26047352

  1. Quantifying the residence time distribution of surface transient storage in streams: A computational fluid dynamics approach

    NASA Astrophysics Data System (ADS)

    Jackson, T. R.; Drost, K. J.; Haggerty, R.; Apte, S. V.

    2011-12-01

    Transient storage is the sum of surface transient storage (STS) and hyporheic transient storage (HTS) and separating the two storage components is challenging. A number of studies have attempted to determine the relationship between transient storage and stream channel properties; however, difficulties ensue when attempting to calculate STS. The present study attempts to develop a predictive relationship between a stream's STS residence time distribution (RTD) to physically-based and field-measureable properties of natural streams. Our approach is to use field measurements to constrain a computational fluid dynamics (CFD) model of STS and use both to develop and test a predictive model of STS RTD. Field sites were located on Oak and Soap creeks in the Willamette Valley near Corvallis, Oregon. Data collection included: (1) obtaining detailed stream and STS zone morphologies through dense survey measurements; (2) determining turbulence parameters and CFD model boundary inputs from stream and storage zone velocity measurements with a Marsh-McBirney and acoustic Doppler velocimeter; (3) quantifying the RTD and its mean using salt tracer injections and electrical conductivity probes; and (4) estimating mixing layer parameters using velocity measurements and a visual dye. Preliminary results from the CFD model and comparison to field data will be presented, and resulting insights into the RTD.

  2. Treating Stormwater with Green Infrastructure: Plants, Residence Time Distributions, and the Removal of Fecal Indicator Bacteria

    NASA Astrophysics Data System (ADS)

    Parker, E.; Grant, S. B.; Rippy, M.; Winfrey, B.; Mehring, A.

    2015-12-01

    In many cities, green infrastructure is increasingly used to capture and treat stormwater runoff, due to the many opportunities these systems afford for protecting receiving water quality and ecology while mitigating water scarcity. Here, we focus on how plants affect the removal of fecal indicator bacteria (FIB) in newly-constructed stormwater biofilters, a type of green infrastructure consisting of unconsolidated granular media containing one or more plant species. Input-response experiments were carried out using both non-reactive (salt) and reactive (sewage) tracers on six laboratory-scale (~1m long by 24 cm diameter) biofilters, half of which were planted with the sedge Carex appressa (treatment replicates) and half of which were unplanted (control replicates). C. appressa modifies the residence time distribution (RTD) in a biofilter by creating preferential flow paths along which water and mass can move quickly, but does not appear to alter the intrinsic rate at which FIB are removed. Thus, the "green" component of green infrastructure can alter pollutant removal by changing the RTD, with or without a concomitant change in pollutant reactivity.

  3. Drug-target residence time--a case for G protein-coupled receptors.

    PubMed

    Guo, Dong; Hillger, Julia M; IJzerman, Adriaan P; Heitman, Laura H

    2014-07-01

    A vast number of marketed drugs act on G protein-coupled receptors (GPCRs), the most successful category of drug targets to date. These drugs usually possess high target affinity and selectivity, and such combined features have been the driving force in the early phases of drug discovery. However, attrition has also been high. Many investigational new drugs eventually fail in clinical trials due to a demonstrated lack of efficacy. A retrospective assessment of successfully launched drugs revealed that their beneficial effects in patients may be attributed to their long drug-target residence times (RTs). Likewise, for some other GPCR drugs short RT could be beneficial to reduce the potential for on-target side effects. Hence, the compounds' kinetics behavior might in fact be the guiding principle to obtain a desired and durable effect in vivo. We therefore propose that drug-target RT should be taken into account as an additional parameter in the lead selection and optimization process. This should ultimately lead to an increased number of candidate drugs moving to the preclinical development phase and on to the market. This review contains examples of the kinetics behavior of GPCR ligands with improved in vivo efficacy and summarizes methods for assessing drug-target RT. © 2014 Wiley Periodicals, Inc.

  4. Optimized Inhibitors of Soluble Epoxide Hydrolase Improve in Vitro Target Residence Time and in Vivo Efficacy

    PubMed Central

    2015-01-01

    Diabetes is affecting the life of millions of people. A large proportion of diabetic patients suffer from severe complications such as neuropathic pain, and current treatments for these complications have deleterious side effects. Thus, alternate therapeutic strategies are needed. Recently, the elevation of epoxy-fatty acids through inhibition of soluble epoxide hydrolase (sEH) was shown to reduce diabetic neuropathic pain in rodents. In this report, we describe a series of newly synthesized sEH inhibitors with at least 5-fold higher potency and doubled residence time inside both the human and rodent sEH enzyme than previously reported inhibitors. These inhibitors also have better physical properties and optimized pharmacokinetic profiles. The optimized inhibitor selected from this new series displayed improved efficacy of almost 10-fold in relieving pain perception in diabetic neuropathic rats as compared to the approved drug, gabapentin, and previously published sEH inhibitors. Therefore, these new sEH inhibitors could be an attractive alternative to treat diabetic neuropathy in humans. PMID:25079952

  5. Effects of residence time distribution and packing on methanol oxidation in biotrickling filter.

    PubMed

    Hutomo, Yuanita W; Pinder, K L

    2006-03-01

    The effects of residence time distribution (RTD) on biotrickling filter systems and the comparison of the maximum elimination capacity (EC) and poisoning limits as functions of loadings of two packing media, Celite Biocatalyst Carrier R-635 and a subituminous coal, were studied. To alter the RTD patterns in the two reactor columns, two baffle designs were chosen. The RTD tests were done under dry conditions, over a range of airflow rates, with zero baffle, one baffle, and two baffles added into each column. Mixed culture from compost was used to acclimate the bed for the methanol removal efficiency study. No nutrients were added in the coal column. To study the poisoning limit, the inlet methanol concentration was randomly increased until a severe drop in removal efficiency occurred. From the RTD tests and the removal efficiency runs, which did not result in 100% conversion, number of tank-in-series (N) values, maximum EC values, and rate constants of each column with different baffle configurations could be obtained. Results from duplicate runs showed that addition of baffles decreased the N values of the columns and increased the back mixing in both systems. Maximum EC values, critical loadings, and poisoning limits also increased with increasing back mixing. Coal was superior to Celite Biocatalyst Carrier R-635 because it gave good conversions without additional nutrients. In all runs, the rate of methanol removal was controlled by a zero order process.

  6. Transport in lymphatic capillaries. I. Macroscopic measurements using residence time distribution theory.

    PubMed

    Swartz, M A; Berk, D A; Jain, R K

    1996-01-01

    We present a novel integrative method for characterizing transport in the lymphatic capillaries in the tail of the anesthetized mouse, which is both sensitive and reproducible for quantifying uptake and flow. Interstitially injected, fluorescently labeled macromolecules were used to visualize and quantify these processes. Residence time distribution (RTD) theory was employed to measure net flow velocity in the lymphatic network as well as to provide a relative measure of lymphatic uptake of macromolecules from the interstitium. The effects of particle size and injection pressure were determined. The uptake rate was found to be independent of particle size in the range of a 6- to 18-nm radius; beyond this size, the interstitial matrix seemed to pose a greater barrier. A comparison of 10 vs. 40 cmH2O injection pressure showed a significant influence on the relative uptake rate but not on the net velocity within the network (3.3 +/- 0.8 vs. 3.8 +/- 1.0 micron/s). This suggested the presence of a systemic driving force for baseline lymph propulsion that is independent of the local pressure gradients driving the uptake. This model can be used to examine various aspects of transport physiology of the initial lymphatics.

  7. Subunit Stabilization and Polyethylene Glycolation of Cocaine Esterase Improves In Vivo Residence TimeS⃞

    PubMed Central

    Narasimhan, Diwahar; Collins, Gregory T.; Nance, Mark R.; Nichols, Joseph; Edwald, Elin; Chan, Jimmy; Ko, Mei-Chuan; Woods, James H.; Tesmer, John J. G.

    2011-01-01

    No small-molecule therapeutic is available to treat cocaine addiction, but enzyme-based therapy to accelerate cocaine hydrolysis in serum has gained momentum. Bacterial cocaine esterase (CocE) is the fastest known native enzyme that hydrolyzes cocaine. However, its lability at 37°C has limited its therapeutic potential. Cross-linking subunits through disulfide bridging is commonly used to stabilize multimeric enzymes. Herein we use structural methods to guide the introduction of two cysteine residues within dimer interface of CocE to facilitate intermolecular disulfide bond formation. The disulfide-crosslinked enzyme displays improved thermostability, particularly when combined with previously described mutations that enhance stability (T172R-G173Q). The newly modified enzyme yielded an extremely stable form of CocE (CCRQ-CocE) that retained greater than 90% of its activity after 41 days at 37°C, representing an improvement of more than 4700-fold over the wild-type enzyme. CCRQ-CocE could also be modified by polyethylene glycol (PEG) polymers, which improved its in vivo residence time from 24 to 72 h, as measured by a cocaine lethality assay, by self-administration in rodents, and by measurement of inhibition of cocaine-induced cardiovascular effects in rhesus monkeys. PEG-CCRQ elicited negligible immune response in rodents. Subunit stabilization and PEGylation has thus produced a potential protein therapeutic with markedly higher stability both in vitro and in vivo. PMID:21890748

  8. Towards a Fully Distributed Characterization of Water Residence and Transit Time by Coupled Hydrology-Transport Modeling

    NASA Astrophysics Data System (ADS)

    Remondi, F.; Fatichi, S.; Burlando, P.

    2015-12-01

    Water residence and transit time are crucial elements in flow pathways and catchment response characterization. The temporal distribution of catchment transit times has been generally studied and modelled with lumped parameter approaches. However, understanding the dominant controls in a more holistic manner requires attention to the spatially distributed catchment properties also in relation to their control on the basin response to different type of precipitation events. A tool that looks both at the time and space distribution of water residence and transport can be useful for predicting water and solute fluxes and ultimately for better understanding the dependence of catchment transit and residence times on geomorphological and climatic factors. To this purpose we couple a fully distributed, yet essential, process-based watershed model with a component to simulate solute transport. Key features of the developed tool include: (a) reduced complexity spatially-distributed hydrological model; (b) spatially-distributed water age and conservative tracer concentration; (c) possibility to explicitly compute transit time distributions for different precipitation events and locations. The presented framework is tested on the Plynlimon watershed (UK), where long-term records of hydrological variables are available. Among them, discharge and chloride concentration are used to investigate the model behavior. We present the integrated model concept, the underlying methodologies, the results from the case study application, as well as preliminary virtual experiments that allow exploring the full statistical space of travel and residence times.

  9. The Feasibility and Effectiveness of a Pilot Resident-Organized and -Led Knowledge Base Review

    ERIC Educational Resources Information Center

    Vautrot, Victor J.; Festin, Fe E.; Bauer, Mark S.

    2010-01-01

    Objective: The Accreditation Council for Graduate Medical Education (ACGME) requires a sufficient medical knowledge base as one of the six core competencies in residency training. The authors judged that an annual "short-course" review of medical knowledge would be a useful adjunct to standard seminar and rotation teaching, and that a…

  10. The Feasibility and Effectiveness of a Pilot Resident-Organized and -Led Knowledge Base Review

    ERIC Educational Resources Information Center

    Vautrot, Victor J.; Festin, Fe E.; Bauer, Mark S.

    2010-01-01

    Objective: The Accreditation Council for Graduate Medical Education (ACGME) requires a sufficient medical knowledge base as one of the six core competencies in residency training. The authors judged that an annual "short-course" review of medical knowledge would be a useful adjunct to standard seminar and rotation teaching, and that a…

  11. Impact of TimeSlips, a creative expression intervention program, on nursing home residents with dementia and their caregivers.

    PubMed

    Fritsch, Thomas; Kwak, Jung; Grant, Stacey; Lang, Josh; Montgomery, Rhonda R; Basting, Anne D

    2009-02-01

    Creative expression (CE) programs are emerging interventions to improve the quality of care and life of persons with dementia (PWDs) in long-term care settings. However, limited empirical evidence exists to support the effectiveness of these programs. Here, we report the findings from an assessment of the impact of TimeSlips (TS), a group storytelling program that encourages CE among PWDs and those who care for them. Instruction in TS was provided through a 10-week on-site training. An observational study using an experimental design was conducted in 20 nursing home facilities in 2 states, 10 of which were randomly selected to implement TS. Two weeks after the implementation of TS at the intervention sites, we conducted 4 days of direct observation, using a time-sampling approach, of residents and staff in each facility. Using surveys, we also assessed staff job satisfaction, attitudes toward residents, and burnout. Compared with residents in the control facilities, those in the TS facilities were more engaged and more alert. In TS facilities, there were more frequent staff-resident interactions, social interactions, and social engagement. Also, staff who participated in the TS program had more positive views of residents with dementia and devalued residents less than did the control group staff. There were no differences in staff job satisfaction and burnout among staff in the TS and non-TS facilities. Implementing the TS program in nursing facilities improves the care environment for PWDs. However, additional studies are needed to offer further insights into the mechanisms by which TS improves both staff and resident outcomes.

  12. Preliminary estimates of residence times and apparent ages of ground water in the Chesapeake Bay watershed, and water-quality data from a survey of springs

    USGS Publications Warehouse

    Focazio, Michael J.; Plummer, L. Neil; Bohlke, John K.; Busenberg, Eurybiades; Bachman, L. Joseph; Powars, David S.

    1998-01-01

    Knowledge of the residence times of the ground-water systems in Chesapeake Bay watershed helps resource managers anticipate potential delays between implementation of land-management practices and any improve-ments in river and estuary water quality. This report presents preliminary estimates of ground-water residence times and apparent ages of water in the shallow aquifers of the Chesapeake Bay watershed. A simple reservoir model, published data, and analyses of spring water were used to estimate residence times and apparent ages of ground-water discharge. Ranges of aquifer hydraulic characteristics throughout the Bay watershed were derived from published literature and were used to estimate ground-water residence times on the basis of a simple reservoir model. Simple combinations of rock type and physiographic province were used to delineate hydrogeomorphic regions (HGMR?s) for the study area. The HGMR?s are used to facilitate organization and display of the data and analyses. Illustrations depicting the relation of aquifer characteristics and associated residence times as a continuum for each HGMR were developed. In this way, the natural variation of aquifer characteristics can be seen graphically by use of data from selected representative studies. Water samples collected in September and November 1996, from 46 springs throughout the watershed were analyzed for chlorofluorocarbons (CFC?s) to estimate the apparent age of ground water. For comparison purposes, apparent ages of water from springs were calculated assuming piston flow. Additi-onal data are given to estimate apparent ages assuming an exponential distribution of ages in spring discharge. Additionally, results from previous studies of CFC-dating of ground water from other springs and wells in the watershed were compiled. The CFC data, and the data on major ions, nutrients, and nitrogen isotopes in the water collected from the 46 springs are included in this report. The apparent ages of water

  13. Reflections in a time of transition: orthopaedic faculty and resident understanding of accreditation schemes and opinions on surgical skills feedback

    PubMed Central

    Gundle, Kenneth R.; Mickelson, Dayne T.; Hanel, Doug P.

    2016-01-01

    Introduction Orthopaedic surgery is one of the first seven specialties that began collecting Milestone data as part of the Accreditation Council for Graduate Medical Education's Next Accreditation System (NAS) rollout. This transition from process-based advancement to outcome-based education is an opportunity to assess resident and faculty understanding of changing paradigms, and opinions about technical skill evaluation. Methods In a large academic orthopaedic surgery residency program, residents and faculty were anonymously surveyed. A total of 31/32 (97%) residents and 29/53 (55%) faculty responded to Likert scale assessments and provided open-ended responses. An internal end-of-rotation audit was conducted to assess timeliness of evaluations. A mixed-method analysis was utilized, with nonparametric statistical testing and a constant-comparative qualitative method. Results There was greater familiarity with the six core competencies than with Milestones or the NAS (p<0.05). A majority of faculty and residents felt that end-of-rotation evaluations were not adequate for surgical skills feedback. Fifty-eight per cent of residents reported that end-of-rotation evaluations were rarely or never filled out in a timely fashion. An internal audit demonstrated that more than 30% of evaluations were completed over a month after rotation end. Qualitative analysis included themes of resident desire for more face-to-face feedback on technical skills after operative cases, and several barriers to more frequent feedback. Discussion The NAS and outcome-based education have arrived. Residents and faculty need to be educated on this changing paradigm. This transition period is also a window of opportunity to address methods of evaluation and feedback. In our orthopaedic residency, trainees were significantly less satisfied than faculty with the amount of technical and surgical skills feedback being provided to trainees. The quantitative and qualitative analyses converge on one

  14. Assessment of the vaginal residence time of biomarkers of semen exposure☆,☆☆,★

    PubMed Central

    Thurman, Andrea; Jacot, Terry; Melendez, Johan; Kimble, Thomas; Snead, Margaret; Jamshidi, Roxanne; Wheeless, Angie; Archer, David F.; Doncel, Gustavo F.; Mauck, Christine

    2016-01-01

    Objective The primary objective of this pilot study is to determine and compare the residence time in the vagina of biomarkers of semen exposure for up to 15 days post exposure. The biomarkers are prostate-specific antigen (PSA), Y chromosome DNA, the sex determining region of the Y chromosome (SRY) and testis-specific protein Y-encoded 4 (TSPY4). The secondary objectives are to determine if biomarker concentrations differed between intercourse and inoculation groups, to establish whether the sampling frequency post exposure affected biomarker concentrations and decay profile and to determine if biomarker concentrations in vaginal swabs obtained by the participant at home were similar to swabs obtained by the nurse in the clinic. Study design We randomized healthy women to unprotected intercourse (n=17) versus vaginal inoculation with the male partner’s semen in the clinic (n=16). Women were then further randomized to have vaginal swabs obtained at either 7 or 4 time points after semen exposure, up to 15 days post exposure, either obtained at home by the participant or in the clinic by the research nurse. Results PSA and SRY were markers of recent semen exposure. TSPY4 was detectable in approximately 50% of participants at 15 days post exposure. Unprotected intercourse resulted in significantly higher concentrations of select biomarkers. Sampling frequency and home versus clinic sampling had no significant effect on biomarker concentrations. Conclusions Objective biomarkers of recent or distant semen exposure may have great utility for verifying protocol compliance in a variety of clinical trials. PMID:27259675

  15. Alongshore Variation in the Depth of Activation: Implications of Oil Residence Time

    NASA Astrophysics Data System (ADS)

    Flores, P.; Houser, C.

    2016-12-01

    In 2010 the Deepwater Horizon Oil Spill released approximately 5 million barrels of oil into the Gulf of Mexico just as the nearshore and beach profile were recovering from winter storms. As a consequence, oil mats and tar balls were trapped at depth within the beach and nearshore profile. Excavation of this buried oil during subsequent storms creates the potential for the contamination of adjacent beaches and the degradation of marine ecosystems, which can in turn negatively impact local economies that depend on fisheries and tourism. The potential for oil burial and persistence is dependent on four things: the physio-chemical nature of the oil as it reaches the nearshore environment, the pre-existing morphology of the beach and nearshore, and the evolution of that morphology after the oil is deposited. The depth at which the oil is buried is also dependent on the beach profile during the time of the spill. The purpose of this study is to characterize the alongshore variation in depth of activation on a Deepwater Horizon impacted section of Pensacola Beach, Florida with regards to the implications of oil residence time. Ground- Penetrating Radar (GPR) surveys were conducted along two parallel 1-km transects adjacent to the swash zone and the dune. Additional cross- shore transects were completed every 150 m from the base of the dune to the top of the swash zone. Sediments cores were taken at the crossing points of the alongshore and cross-shore transects, to calibrate the GPR surveys and complete an elemental analysis for the identification of storm layers. The cores were also analyzed for the presence of buried oil.

  16. Phosphorus as indicator of magmatic olivine residence time, morphology and growth rate

    NASA Astrophysics Data System (ADS)

    Sobolev, Alexander; Batanova, Valentina

    2015-04-01

    Phosphorus is among of slowest elements by diffusion rate in silicate melts and crystals (e.g. Spandler et al, 2007). In the same time it is moderately incompatible to compatible with olivine (Brunet & Chazot, 2001; Grant & Kohn, 2013). This makes phosphorus valuable tracer of olivine crystallization in natural conditions. Indeed, it is shown that natural magmatic olivine crystals commonly posses strong and complicated zoning in phosphorus (Milman-Barris et al, 2008; Welsch et al, 2014). In this paper we intend to review phosphorus behavior in olivine in published experimental and natural olivine studies and present large set of new EPMA data on phosphorus zoning in olivine phenocrysts from MORBs, OIBs, komatiites and kimberlites. We will show that sharp olivine zones enriched in phosphorus by a factor of 10-20 over prediction by equilibrium partition may be due to formation of P-rich boundary layer on the interface of fast growing olivine. This is proved by finding of small-size (normally 10 mkm or less) exceptionally P-rich melt inclusions in olivine, which are otherwise similar in composition to typical melt. These observations could provide potential olivine growth speedometer. We will also demonstrate, that sharp zoning in phosphorus may provide valuable information on the residence time of olivine crystals in different environments: magma chambers and conduits as well as mantle sources. This study has been founded by Russian Science Foundation grant 14-17-00491. References: Spandler, et al, 2007, Nature, v. 447, p. 303-306; Brunet & Chazot, 2001, Chemical Geology, v. 176, p. 51-72; Grant & Kohn, 2013, American Mineralogist, v. 98, p. 1860-1869; Milman-Barris et al, 2008, Contr. Min. Petrol. v. 155, p.739-765; Welsch et al, 2014, Geology, v. 42, p.867-870.

  17. Slow-Onset Inhibition of the FabI Enoyl Reductase from Francisella Tularensis: Residence Time and In Vivo Activity

    PubMed Central

    Lu, Hao; England, Kathleen; Ende, Christopher am; Truglio, James J.; Luckner, Sylvia; Reddy, B. Gopal; Marlenee, Nikki; Knudson, Susan E.; Knudson, Dennis L.; Bowen, Richard A.; Kisker, Caroline; Slayden, Richard A.; Tonge, Peter J.

    2009-01-01

    Francisella tularensis is a highly virulent and contagious gram-negative intracellular bacterium that causes the disease tularemia in mammals. The high infectivity and the ability of the bacterium to survive for weeks in a cool, moist environment have raised the possibility that this organism could be exploited deliberately as a potential biological weapon. Fatty acid biosynthesis (FAS-II) is essential for bacterial viability and has been validated as a target for the discovery of novel antibacterials. The FAS-II enoyl reductase ftuFabI has been cloned and expressed, and a series of diphenyl ethers have been identified that are subnanomolar inhibitors of the enzyme with MIC90 values as low as 0.00018 μg/ml. The existence of a linear correlation between the Ki and MIC values strongly suggests that the antibacterial activity of the diphenyl ethers results from direct inhibition of ftuFabI within the cell. The compounds are slow onset inhibitors of ftuFabI, and the residence time of the inhibitors on the enzyme correlates with their in vivo activity in a mouse model of tularemia infection. Significantly, the rate of breakdown of the enzyme-inhibitor complex is a better predictor of in vivo activity than the overall thermodynamic stability of the complex, a concept that has important implications for the discovery of novel chemotherapeutics that normally rely on equilibrium measurements of potency. PMID:19206187

  18. Slow-Onset Inhibition of the FabI Enoyl Reductase from Francisella tularensis: Residence Time and in Vivo Activity

    SciTech Connect

    Lu, H.; England, K; Ende, C; Truglio, J; Luckner, S; Reddy, B; Marlenee, N; Knudson, S; Knudson, D; et. al.

    2009-01-01

    Francisella tularensis is a highly virulent and contagious Gram-negative intracellular bacterium that causes the disease tularemia in mammals. The high infectivity and the ability of the bacterium to survive for weeks in a cool, moist environment have raised the possibility that this organism could be exploited deliberately as a potential biological weapon. Fatty acid biosynthesis (FAS-II) is essential for bacterial viability and has been validated as a target for the discovery of novel antibacterials. The FAS-II enoyl reductase ftuFabI has been cloned and expressed, and a series of diphenyl ethers have been identified that are subnanomolar inhibitors of the enzyme with MIC90 values as low as 0.00018 ?g mL-1. The existence of a linear correlation between the Ki and MIC values strongly suggests that the antibacterial activity of the diphenyl ethers results from direct inhibition of ftuFabI within the cell. The compounds are slow-onset inhibitors of ftuFabI, and the residence time of the inhibitors on the enzyme correlates with their in vivo activity in a mouse model of tularemia infection. Significantly, the rate of breakdown of the enzyme-inhibitor complex is a better predictor of in vivo activity than the overall thermodynamic stability of the complex, a concept that has important implications for the discovery of novel chemotherapeutics that normally rely on equilibrium measurements of potency.

  19. Evaluation of CAESAR-Lisflood as a tool for modelling river channel change and floodplain sediment residence times.

    NASA Astrophysics Data System (ADS)

    Feeney, Christopher; Smith, Hugh; Chiverrell, Richard; Hooke, Janet; Cooper, James

    2017-04-01

    Sediment residence time represents the duration of particle storage, from initial deposition to remobilisation, within reservoirs such as floodplains. Residence time influences rates of downstream redistribution of sediment and associated contaminants and is a useful indicator of landform stability and hence, preservation potential of alluvial archives of environmental change. River channel change controls residence times, reworking sediments via lateral migration, avulsion and incision through floodplain deposits. As reworking progresses, the floodplain age distribution is 'updated', reflecting the time since 'older' sediments were removed and replaced with 'younger' ones. The relationship between ages and the spatial extents they occupy can be used to estimate the average floodplain sediment residence times. While dating techniques, historic maps and remote sensing can reconstruct age distributions from historic reworking, modelling provides advantages, including: i) capturing detailed river channel changes and resulting floodplain ages over longer timescales and higher resolutions than from historic mapping, and ii) control over inputs to simulate hypothetical scenarios to investigate the effects of different environmental drivers on residence times. CAESAR-Lisflood is a landform evolution model capable of simulating variable channel width, divergent flow, and both braided and meandering planforms. However, the model's ability to accurately simulate channel changes requires evaluation if it is to be useful for quantitative evaluation of floodplain sediment residence times. This study aims to simulate recent historic river channel changes along ten 1 km reaches in northern England. Simulation periods were defined by available overlapping historic map and mean daily flow datasets, ranging 27-39 years. LiDAR-derived 2 m DEMs were modified to smooth out present-day channels and burn in historic channel locations. To reduce run times, DEMs were resampled to coarser

  20. Atmospheric residence times from transpiration and evaporation to precipitation: An age-weighted regional evaporation tagging approach

    NASA Astrophysics Data System (ADS)

    Wei, Jianhui; Knoche, Hans Richard; Kunstmann, Harald

    2016-06-01

    The atmospheric water residence time is a fundamental descriptor that provides information on the timescales of evaporation and precipitation. In this study, a regional climate model-based evaporation tagging algorithm is extended with an age tracer approach to calculate moisture residence times, defined as time between the original evaporation and the returning of water masses to the land surface as precipitation. Our case study addresses how long this time is for the transpired and for the direct evaporated moisture. Our study region is the Poyang Lake region in Southeast China, the largest freshwater lake in the country. We perform simulations covering the period from October 2004 to December 2005. In 2005, 11% of direct evaporated water (10% of transpired water) precipitates locally. Direct evaporated water accounts for 64% and transpired water for 36% of the total tagged moisture with a mean age of around 36 h for both. Considering precipitation, a large proportion (69%) originates from direct evaporated water with a mean atmospheric residence time of 6.6 h and a smaller amount from transpired water with a longer residence time of 10.7 h. Modulated by the East Asian monsoon, the variation of the meteorological conditions, the magnitude of the partitioned moisture, and the corresponding residence time patterns change seasonally and spatially and reveal the different fate of transpired and direct evaporated water in the atmospheric hydrological cycle. We conclude that our methodological approach has the potential to be used for addressing how timescales of the hydrological cycle changes regionally under global warming.

  1. Characterization and source profiling of volatile organic compounds in indoor air of private residences in Selangor State, Malaysia.

    PubMed

    Sakai, Nobumitsu; Yamamoto, Shuta; Matsui, Yasuto; Khan, Md Firoz; Latif, Mohd Talib; Ali Mohd, Mustafa; Yoneda, Minoru

    2017-05-15

    Volatile Organic Compounds (VOCs) in indoor air were investigated at 39 private residences in Selangor State, Malaysia to characterize the indoor air quality and to identify pollution sources. Twenty-two VOCs including isomers (14 aldehydes, 5 aromatic hydrocarbons, acetone, trichloroethylene and tetrachloroethylene) were collected by 2 passive samplers for 24h and quantitated using high performance liquid chromatography and gas chromatography mass spectrometry. Source profiling based on benzene/toluene ratio as well as statistical analysis (cluster analysis, bivariate correlation analysis and principal component analysis) was performed to identify pollution sources of the detected VOCs. The VOCs concentrations were compared with regulatory limits of air quality guidelines in WHO/EU, the US, Canada and Japan to clarify the potential health risks to the residents. The 39 residences were classified into 2 groups and 2 ungrouped residences based on the dendrogram in the cluster analysis. Group 1 (n=30) had mainly toluene (6.87±2.19μg/m(3)), formaldehyde (16.0±10.1μg/m(3)), acetaldehyde (5.35±4.57μg/m(3)) and acetone (11.1±5.95μg/m(3)) at background levels. Group 2 (n=7) had significantly high values of formaldehyde (99.3±10.7μg/m(3)) and acetone (35.8±12.6μg/m(3)), and a tendency to have higher values of acetaldehyde (23.7±13.5μg/m(3)), butyraldehyde (3.35±0.41μg/m(3)) and isovaleraldehyde (2.30±0.39μg/m(3)). The 2 ungrouped residences showed particularly high concentrations of BTX (benzene, toluene and xylene: 235μg/m(3) in total) or acetone (133μg/m(3)). The geometric mean value of formaldehyde (19.2μg/m(3)) exceeded an 8-hour regulatory limit in Canada (9μg/m(3)), while those in other compounds did not exceed any regulatory limits, although a few residences exceeded at least one regulatory limit of benzene or acetaldehyde. Thus, the VOCs in the private residences were effectively characterized from the limited number of monitoring, and the

  2. Time in U.S. Residency and the Social, Behavioral, and Emotional Adjustment of Latino Immigrant Families

    ERIC Educational Resources Information Center

    Martinez, Charles R., Jr.; McClure, Heather H.; Eddy, J. Mark; Wilson, D. Molloy

    2011-01-01

    Little is known about contributors to positive social, behavioral, and emotional adjustment among foreign-born youth at different stages of adapting to life in the United States. Using baseline data from the Adolescent Latino Acculturation Study (N = 217), this article examines the effects of time in residency on parent adjustment, family stress,…

  3. Water Residence Times and Their Relation to Soil and Aquifer Properties and Degree of Urbanization (Croton Water Supply Area, NY)

    NASA Astrophysics Data System (ADS)

    Vitvar, T.; Burns, D.; Kendall, C.; McDonnell, J.

    2002-05-01

    Water residence times were determined in 3 small watersheds in the Croton water supply area, NY. The watersheds (less than 1 km2 drainage area) have different amounts of urbanization (natural, semi-developed and fully developed), different mechanisms of runoff generation (quick flow on roads and slow flow through subsurface) and different watershed landscape characteristics (wetlands, hillslopes) . Measurements of the Oxygen-18 content of throughfall, stream water, soil water and groundwater in the saturated zone were performed bi-weekly over a period of 2 years. Mean water residence times of the stream water, soil water and groundwater were estimated using Oxygen-18 and Helium-3/Tritium isotopes. There are small but significant differences in the isotopic content of waters in each watershed, along with soil and aquifer properties as a function of the level of urbanization. Longer groundwater residence times (up to more than 2 years) were estimated in wetland zones without direct communication with streams in comparison to hillslope areas (up to more than 1 year). In highly urbanized areas, mixing of natural runoff generation processes with urbanization effects such as the influence of septic plumes results in a complex spectrum of residence times in soil waters and groundwaters. We illustrate the possibilities of using stable isotope measurements to describe small-scale complex runoff generation processes in watersheds.

  4. Residence Times of Molecular Complexes in Solution from NMR Data of Intermolecular Hydrogen-Bond Scalar Coupling.

    PubMed

    Zandarashvili, Levani; Esadze, Alexandre; Kemme, Catherine A; Chattopadhyay, Abhijnan; Nguyen, Dan; Iwahara, Junji

    2016-03-03

    The residence times of molecular complexes in solution are important for understanding biomolecular functions and drug actions. We show that NMR data of intermolecular hydrogen-bond scalar couplings can yield information on the residence times of molecular complexes in solution. The molecular exchange of binding partners via the breakage and reformation of a complex causes self-decoupling of intermolecular hydrogen-bond scalar couplings, and this self-decoupling effect depends on the residence time of the complex. For protein-DNA complexes, we investigated the salt concentration dependence of intermolecular hydrogen-bond scalar couplings between the protein side-chain (15)N and DNA phosphate (31)P nuclei, from which the residence times were analyzed. The results were consistent with those obtained by (15)Nz-exchange spectroscopy. This self-decoupling-based kinetic analysis is unique in that it does not require any different signatures for the states involved in the exchange, whereas such conditions are crucial for kinetic analyses by typical NMR and other methods.

  5. Implementation and evaluation of a simulation curriculum for paediatric residency programs including just-in-time in situ mock codes

    PubMed Central

    Sam, Jonathan; Pierse, Michael; Al-Qahtani, Abdullah; Cheng, Adam

    2012-01-01

    OBJECTIVE: To develop, implement and evaluate a simulation-based acute care curriculum in a paediatric residency program using an integrated and longitudinal approach. DESIGN: Curriculum framework consisting of three modular, year-specific courses and longitudinal just-in-time, in situ mock codes. SETTING: Paediatric residency program at BC Children’s Hospital, Vancouver, British Columbia. INTERVENTIONS: The three year-specific courses focused on the critical first 5 min, complex medical management and crisis resource management, respectively. The just-in-time in situ mock codes simulated the acute deterioration of an existing ward patient, prepared the actual multidisciplinary code team, and primed the surrounding crisis support systems. Each curriculum component was evaluated with surveys using a five-point Likert scale. RESULTS: A total of 40 resident surveys were completed after each of the modular courses, and an additional 28 surveys were completed for the overall simulation curriculum. The highest Likert scores were for hands-on skill stations, immersive simulation environment and crisis resource management teaching. Survey results also suggested that just-in-time mock codes were realistic, reinforced learning, and prepared ward teams for patient deterioration. CONCLUSIONS: A simulation-based acute care curriculum was successfully integrated into a paediatric residency program. It provides a model for integrating simulation-based learning into other training programs, as well as a model for any hospital that wishes to improve paediatric resuscitation outcomes using just-in-time in situ mock codes. PMID:23372405

  6. Residence and Migration of First-Time Freshmen Enrolled in Degree-Granting Institutions: Fall 1996. E.D. Tabs.

    ERIC Educational Resources Information Center

    Barbett, Samuel

    This report presents detailed tabulations of data on the residence and migration of first-time freshmen enrolled in degree-granting institutions in the Fall of 1996 based on data from the Integrated Postsecondary Education Data System's Fall Enrollment survey. Tables are presented by state, control (public/private), and level of institution, for…

  7. Tracer travel and residence time distributions in highly heterogeneous aquifers: Coupled effect of flow variability and mass transfer

    NASA Astrophysics Data System (ADS)

    Cvetkovic, V.; Fiori, A.; Dagan, G.

    2016-12-01

    The driving mechanism of tracer transport in aquifers is groundwater flow which is controlled by the heterogeneity of hydraulic properties. We show how hydrodynamics and mass transfer are coupled in a general analytical manner to derive a physically-based (or process-based) residence time distribution for a given integral scale of the hydraulic conductivity; the result can be applied for a broad class of linear mass transfer processes. The derived tracer residence time distribution is a transfer function with parameters to be inferred from combined field and laboratory measurements. It is scalable relative to the correlation length and applicable for an arbitrary statistical distribution of the hydraulic conductivity. Based on the derived residence time distribution, the coefficient of variation and skewness of residence time are illustrated assuming a log-normal hydraulic conductivity field and first-order mass transfer. We show that for a low Damkohler number the coefficient of variation is more strongly influenced by mass transfer than by heterogeneity, whereas skewness is more strongly influenced by heterogeneity.

  8. Examination of residence time and its relevance to water quality within a coastal mega-structure: The Palm Jumeirah Lagoon

    NASA Astrophysics Data System (ADS)

    Cavalcante, Geórgenes H.; Kjerfve, Björn; Feary, David A.

    2012-10-01

    SummaryA numerical modeling study was carried out to compute average residence time in the semi-enclosed lagoon formed by the man-made island Palm Jumeirah (Dubai, United Arab Emirates), termed Palm Jumeirah Lagoon (PJL). The PJL encompasses a main island axis with 17 'fronds' radiating from this axis, all encapsulated within a semi-circular breakwater system. A coupled hydrodynamic and solute transport model was developed for the waters of the PJL, based on depth-integrated conservation equations. Numerical model predictions were then verified against a set of field-measured hydrodynamic data. Model-predicted water elevations and velocities were in good agreement with field measurements. Residence times for this tidal dominated system were investigated through numerical experiments using a conservative tracer as a surrogate. The results indicated that average residence time varied spatially throughout the PJL depending on tidal flushing. Average residence time was unequally distributed throughout the PJL, with the eastern side showing higher flushing times than the western side. In addition, there were also differences between sections of the PJL in average residence time of a tracer: between frond tips and the surrounding breakwater the tracer was reduced to 30-40% of its original value after approximately 1 week, while a tracer placed between the fronds was reduced to 30-40% of its value after 20 days. The findings of this research provide vital information for understanding the water transport process in this man-made lagoon, and will be important in assessing the potential impact on coastal water quality conditions in coastal developments within the Middle East.

  9. Temperature and residence time controls on an estuarine harmful algal bloom: Modeling hydrodynamics and Alexandrium fundyense in Nauset estuary

    PubMed Central

    Ralston, David K.; Brosnahan, Michael L.; Fox, Sophia E.; Lee, Krista; Anderson, Donald M.

    2015-01-01

    A highly resolved, 3-d model of hydrodynamics and Alexandrium fundyense in an estuarine embayment has been developed to investigate the physical and biological controls on a recurrent harmful algal bloom. Nauset estuary on Cape Cod (MA, USA) consists of three salt ponds connected to the ocean through a shallow marsh and network of tidal channels. The model is evaluated using quantitative skill metrics against observations of physical and biological conditions during three spring blooms. The A. fundyense model is based on prior model applications for the nearby Gulf of Maine, but notable modifications were made to be consistent with the Nauset observations. The dominant factors controlling the A. fundyense bloom in Nauset were the water temperature, which regulates organism growth rates, and the efficient retention of cells due to bathymetric constraints, stratification, and cell behavior (diel vertical migration). Spring-neap variability in exchange altered residence times, but for cell retention to be substantially longer than the cell doubling time required both active vertical migration and stratification that inhibits mixing of cells into the surface layer by wind and tidal currents. Unlike in the Gulf of Maine, the model results were relatively insensitive to cyst distributions or germination rates. Instead, in Nauset, high apparent rates of vegetative cell division by retained populations dictated bloom development. Cyst germination occurred earlier in the year than in the Gulf of Maine, suggesting that Nauset cysts have different controls on germination timing. The model results were relatively insensitive to nutrient concentrations, due to eutrophic conditions in the highly impacted estuary or due to limitations in the spatial and temporal resolution of nutrient sampling. Cell loss rates were inferred to be extremely low during the growth phase of the bloom, but increased rapidly during the final phase due to processes that remain uncertain. The validated

  10. Temperature and residence time controls on an estuarine harmful algal bloom: Modeling hydrodynamics and Alexandrium fundyense in Nauset estuary.

    PubMed

    Ralston, David K; Brosnahan, Michael L; Fox, Sophia E; Lee, Krista; Anderson, Donald M

    2015-11-01

    A highly resolved, 3-d model of hydrodynamics and Alexandrium fundyense in an estuarine embayment has been developed to investigate the physical and biological controls on a recurrent harmful algal bloom. Nauset estuary on Cape Cod (MA, USA) consists of three salt ponds connected to the ocean through a shallow marsh and network of tidal channels. The model is evaluated using quantitative skill metrics against observations of physical and biological conditions during three spring blooms. The A. fundyense model is based on prior model applications for the nearby Gulf of Maine, but notable modifications were made to be consistent with the Nauset observations. The dominant factors controlling the A. fundyense bloom in Nauset were the water temperature, which regulates organism growth rates, and the efficient retention of cells due to bathymetric constraints, stratification, and cell behavior (diel vertical migration). Spring-neap variability in exchange altered residence times, but for cell retention to be substantially longer than the cell doubling time required both active vertical migration and stratification that inhibits mixing of cells into the surface layer by wind and tidal currents. Unlike in the Gulf of Maine, the model results were relatively insensitive to cyst distributions or germination rates. Instead, in Nauset, high apparent rates of vegetative cell division by retained populations dictated bloom development. Cyst germination occurred earlier in the year than in the Gulf of Maine, suggesting that Nauset cysts have different controls on germination timing. The model results were relatively insensitive to nutrient concentrations, due to eutrophic conditions in the highly impacted estuary or due to limitations in the spatial and temporal resolution of nutrient sampling. Cell loss rates were inferred to be extremely low during the growth phase of the bloom, but increased rapidly during the final phase due to processes that remain uncertain. The validated

  11. Improving residents' handovers through just-in-time training for structured communication

    PubMed Central

    Rourke, Liam; Amin, Aditi; Boyington, Curtiss; Ao, Peter; Frolova, Natalia

    2016-01-01

    In a recent quality assurance project we learned that nearly half of the handovers we examined were characterized as unsatisfactory by our residents, who provided examples in which their anxiety had been piqued and patient care had been affected. These reports substantiated a growing body of literature on the relationship between the quality of handover and the quality of patient care, so we sought to improve the quality and consistency of the in-hosptial handovers undertaken by our internal medicine residents. Senior residents attended morning report for three consecutive month long blocks and evaluated the quality of the handovers using an observational protocol comprised of 16 aspects of effective handover. During the first block, the resident observed a median of eight of the 16 practices occurring across the 46 handovers, and a large amount of variability. At the beginning of the subsequent block we presented a concise introduction to a structured handover procedure (SBARR). The median quality of the subsequent 33 handovers rose to 11, and the variability decreased considerably. In the next block we refined the SBARR orientation to focus on the errors observed in the previous blocks, and the improvement in the quality and variability was sustained. The minor change, which requires few resources to sustain, had a favourable impact on the quality of our residents' in-hospital handovers. PMID:26893890

  12. Improving residents' handovers through just-in-time training for structured communication.

    PubMed

    Rourke, Liam; Amin, Aditi; Boyington, Curtiss; Ao, Peter; Frolova, Natalia

    2016-01-01

    In a recent quality assurance project we learned that nearly half of the handovers we examined were characterized as unsatisfactory by our residents, who provided examples in which their anxiety had been piqued and patient care had been affected. These reports substantiated a growing body of literature on the relationship between the quality of handover and the quality of patient care, so we sought to improve the quality and consistency of the in-hosptial handovers undertaken by our internal medicine residents. Senior residents attended morning report for three consecutive month long blocks and evaluated the quality of the handovers using an observational protocol comprised of 16 aspects of effective handover. During the first block, the resident observed a median of eight of the 16 practices occurring across the 46 handovers, and a large amount of variability. At the beginning of the subsequent block we presented a concise introduction to a structured handover procedure (SBARR). The median quality of the subsequent 33 handovers rose to 11, and the variability decreased considerably. In the next block we refined the SBARR orientation to focus on the errors observed in the previous blocks, and the improvement in the quality and variability was sustained. The minor change, which requires few resources to sustain, had a favourable impact on the quality of our residents' in-hospital handovers.

  13. Residence times of groundwater and nitrate transport in coastal aquifer systems: Daweijia area, northeastern China.

    PubMed

    Han, Dongmei; Cao, Guoliang; McCallum, James; Song, Xianfang

    2015-12-15

    Groundwater within the coastal aquifer systems of the Daweijia area in northeastern China is characterized by a large of variations (33-521mg/L) in NO3(-) concentrations. Elevated nitrate concentrations, in addition to seawater intrusion in the Daweijia well field, both attributable to anthropogenic activities, may impact future water-management practices. Chemical and stable isotopic (δ(18)O, δ(2)H) analysis, (3)H and CFCs methods were applied to provide a better understanding of the relationship between the distribution of groundwater mean residence time (MRT) and nitrate transport, and to identify sources of nitrate concentrations in the complex coastal aquifer systems. There is a relatively narrow range of isotopic composition (ranging from -8.5 to -7.0‰) in most groundwater. Generally higher tritium contents observed in the wet season relative to the dry season may result from rapid groundwater circulation in response to the rainfall through the preferential flow paths. In the well field, the relatively increased nitrate concentrations of groundwater, accompanied by the higher tritium contents in the wet season, indicate the nitrate pollution can be attributed to domestic wastes. The binary exponential and piston-flow mixing model (BEP) yielded feasible age distributions based on the conceptual model. The good inverse relationship between groundwater MRTs (92-467years) and the NO3(-) concentrations in the shallow Quaternary aquifers indicates that elevated nitrate concentrations are attributable to more recent recharge for shallow groundwater. However, there is no significant relationship between the MRTs (8-411years) and the NO3(-) concentrations existing in the carbonate aquifer system, due to the complex hydrogeological conditions, groundwater age distributions and the range of contaminant source areas. Nitrate in the groundwater system without denitrification effects could accumulate and be transported for tens of years, through the complex carbonate

  14. Radiotracer method for residence time distribution study in multiphase flow system.

    PubMed

    Sugiharto, S; Su'ud, Z; Kurniadi, R; Wibisono, W; Abidin, Z

    2009-01-01

    [(131)I] isotope in different chemical compounds have been injected into 24in hydrocarbon transmission pipeline containing approximately 95% water, 3% crude oil, 2% gas and negligible solid material, respectively. The system is operated at the temperature around 70 degrees C enabling fluids flow is easier in the pipeline. The segment of measurement was chosen far from the junction point of the pipeline, therefore, it was reasonably to assume that the fluids in such multiphase system were separated distinctively. Expandable tubing of injector was used to ensure that the isotopes were injected at the proper place in the sense that [(131)I]Na isotope was injected into water layer and iodo-benzene, ([131])IC(6)H(5,) was injected into crude oil regime. The radiotracer selection was based on the compatibility of radiotracer with each of fluids under investigation. [(131)I]Na was used for measuring flow of water while iodo-benzene, ([131])IC(6)H(5,) was used for measuring flow of crude oil. Two scintillation detectors were used and they are put at the distances 80 and 100m, respectively, from injection point. The residence time distribution data were utilized for calculation water and crude oil flows. Several injections were conducted in the experiments. Although the crude oil density is lighter than the density of water, the result of measurement shows that the water flow is faster than the crude oil flow. As the system is water-dominated, water may act as carrier and the movement of crude oil is slowed due to friction between crude oil with water and crude oil with gas at top layer. Above of all, this result was able to give answer on the question why crude oil always arrives behind water as it is checked at gathering station. In addition, the flow patterns of the water in the pipeline calculated by Reynolds number and predicted by simple tank-in-series model is turbulence in character.

  15. Seasonal variations of aerosol residence time in the lower atmospheric boundary layer.

    PubMed

    Ahmed, A A; Mohamed, A; Ali, A E; Barakat, A; Abd El-Hady, M; El-Hussein, A

    2004-01-01

    During a one year period, from Jan. 2002 up to Dec. 2002, approximately 130 air samples were analyzed to determine the atmospheric air activity concentrations of short- and long-lived (222Rn) decay products 214Pb and 210Pb. The samples were t