Science.gov

Sample records for distant residence times

  1. Use of videophones for distant caregiving: an enriching experience for families and residents in long-term care.

    PubMed

    Demiris, George; Oliver, Debra R Parker; Hensel, Brian; Dickey, Geraldine; Rantz, Marilyn; Skubic, Marjorie

    2008-07-01

    The objective of this study was to explore the role of videophone technology in enhancing the distant caregiving experience of and communication between residents of a long-term care facility and their family members. Ten participants-4 residents of an independent retirement facility and 6 family members-were recruited. A videophone was installed in each resident's apartment, and another was mailed to the remote family member. Participants were asked to conduct a videocall at least once per week for 3 months. Exit interviews assessed general impressions of videophone communication, the relationship between residents and family members, stress, burden, and isolation. Participants were enthusiastic and emphasized a sense of closeness, the inclusion of the resident in family interactions, and reduced feelings of guilt and isolation as key benefits. New models of care are needed to challenge the existing paradigm, which often excludes distant caregivers from the care process. Technology can facilitate this process by bridging geographic distance. PMID:18649824

  2. 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.

  3. [Part-time residency training in Israel].

    PubMed

    Fishbain, Dana; Levi, Baruch; Borow, Malke; Ashkenazi, Shai; Lindner, Arie

    2012-08-01

    Full-time work has long been perceived as a cornerstone of medical residency, the consensus being that a resident must apply the bulk of his time and attention to his professional training. Demographic and cultural changes that have taken place over the last several years, specifically the rise in the number of female doctors and the importance of leisure time to the younger generation, have intensified the need to find new and innovative ways to deal with the plight of the resident population. One idea, already in effect in many Western countries, is the institution of part-time residency programs. The possibility of fulfilling residency requirements on a part-time basis is intended to assist medical residents in integrating their professional development with their personal and family life, without compromising the quality of their training. A number of research studies conducted over the last several years in countries that allow part-time residency, among them the United States, England and Switzerland, aimed to examine the quality of part-time training. The various studies evinced a high level of satisfaction from the program both by the residents themselves and their supervisors, and in many aspects those doing residency part-time received higher appraisals than their full-time colleagues. Some of the residents polled noted that they would have totally foregone the practice of medicine had there not been an option to complete residency part-time. In light of the experience throughout the world and the changing landscape in Israel, the Scientific Council of the Israeli Medical Association decided to examine the issue and its various aspects, and weighed all the considerations in favor and against part-time residency. Recently, the Scientific Council approved the launch of a pilot program to allow part-time residency in several fields that were carefully selected according to specific criteria. Once the Ministry of Health completes the LegisLation process, part-time

  4. Residence Time Statistics for N Renewal Processes

    NASA Astrophysics Data System (ADS)

    Burov, S.; Barkai, E.

    2011-10-01

    We present a study of residence time statistics for N renewal processes with a long tailed distribution of the waiting time. Such processes describe many nonequilibrium systems ranging from the intensity of N blinking quantum dots to the residence time of N Brownian particles. With numerical simulations and exact calculations, we show sharp transitions for a critical number of degrees of freedom N. In contrast to the expectation, the fluctuations in the limit of N→∞ are nontrivial. We briefly discuss how our approach can be used to detect nonergodic kinetics from the measurements of many blinking chromophores, without the need to reach the single molecule limit.

  5. Carbon Residence Times in Pedogenic Carbonate Pools

    NASA Astrophysics Data System (ADS)

    Monger, H.; Feng, Y.; Karnjanapiboonwang, A.

    2013-12-01

    Soil carbonate is a huge pool of terrestrial carbon that contains at least 930 to 940 Pg C and has influx rates on the order of 1 to 12 g CaCO3/m2/yr. Such large mass to flux ratios yield long mean residence times for carbon (e.g., 85,000 years)--assuming steady state. Like other global carbon pools, the soil carbonate pool has smaller sub-pools with higher influx rates and shorter mean residence times. For example, pedogenic carbonate in coppice dunes known to have formed since 1858 and carbonate formed on lithic artifacts in soils at archaeology sites suggests mean residence times can be as short as 120 years--again assuming steady state. Harder to assess are efflux rates as CO2 emissions or bicarbonate leaching. Some Bowen-ratio studies have nevertheless found evidence for CO2 emissions resulting from carbonate dissolution, and other studies have found evidence for bicarbonate leaching based on dissolution pipes through calcic horizons using soil morphology studies. Since an understanding of mean residence times are prerequisite for a better understanding of soil carbonate in the global carbon cycle, especially in a scenario of an expanding Aridosphere, more influx and efflux measurements are needed to evaluate the possibility of carbon sequestration by soil carbonate in hyperarid, arid, semiarid, or subhumid soils.

  6. 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.

  7. Residence times of branching diffusion processes.

    PubMed

    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. PMID:27575100

  8. Atmospheric Residence Times of Continental Aerosols.

    NASA Astrophysics Data System (ADS)

    Balkanski, Yves Jacques

    The global atmospheric distributions of ^{222}Rn and ^{210 }Pb are simulated with a three-dimensional model of atmospheric transport based on the meteorology of the NASA GISS^1>=neral circulation model. The short-lived radioactive gas ^ {222}Rn (half-life = 3.8d) is emitted almost exclusively from land, at a relatively uniform rate; hence it is an excellent tracer of continental influences. Lead -210 is produced by decay of ^{222} Rn and immediately condenses to preexisting aerosol surfaces. It provides an excellent measure of aerosol residence times in the atmosphere because its source is accurately defined by the ^{222} Rn distribution. Results from the three-dimensional model are compared to measurements of ^ {222}Rn and ^{210 }Pb atmospheric concentrations to evaluate model's long-range transport over oceanic regions and to study the deposition mechanisms of atmospheric aerosols. Model results for ^{222} Rn are used to examine the long-range transport of continental air over two selected oceanic regions, the subantartic Indian Ocean and the North Pacific. It is shown that fast transport of air from southern Africa causes substantial continental pollution at southern mid-latitudes, a region usually regarded as pristine. Air over the North Pacific is heavily impacted by continental influences year round, but the altitude at which the transport occurs varies seasonally. Observations of aerosols at island sites, which are commonly used as diagnostics of continental influences, may be misleading because they do not account for influences at high altitude and because aerosols are efficiently scavenged by deposition during transport. The study of ^{210}Pb focuses on defining the residence times of submicron aerosols in the troposphere. Scavenging in wet convective updrafts is found to provide the dominant sink on a global scale. The globally averaged residence time for ^{210 }Pb-containing aerosols in the troposphere is 7 days. The average increase in residence time

  9. 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.

  10. A method of real-time detection for distant moving obstacles by monocular vision

    NASA Astrophysics Data System (ADS)

    Jia, Bao-zhi; Zhu, Ming

    2013-12-01

    In this paper, we propose an approach for detection of distant moving obstacles like cars and bicycles by a monocular camera to cooperate with ultrasonic sensors in low-cost condition. We are aiming at detecting distant obstacles that move toward our autonomous navigation car in order to give alarm and keep away from them. Method of frame differencing is applied to find obstacles after compensation of camera's ego-motion. Meanwhile, each obstacle is separated from others in an independent area and given a confidence level to indicate whether it is coming closer. The results on an open dataset and our own autonomous navigation car have proved that the method is effective for detection of distant moving obstacles in real-time.

  11. 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...

  12. Time- versus Competency-Based Residency Training.

    PubMed

    Nguyen, Vu T; Losee, Joseph E

    2016-08-01

    Graduate medical education is at the brink of a paradigm shift in educating the next generation of physicians. Over 100 years ago, the Flexner report helped usher in the Halstedian residency, based on timed exposure and knowledge assessment as the cornerstones of medical education. The addition of operative case logs and respective board examinations to the current model of surgical education has served to establish practice minimums; however, they do not provide any assessment of actual operative capability or clinical competence. Although these facets have been tempered over time, one could argue that they currently exist only as surrogates for the true goal of all graduate medical education: the development of competent, graduating physicians, capable of independent and ethical practice. There now exists a growing body of evidence that competency-based medical education is this century's Flexnerian revolution. By the objective, subjective, and global assessment of competence, it is thought that we can more effectively and efficiently educate our trainees, provide much needed accountability to our individual patients and to the public as a whole, and establish a lasting model of self-motivated, lifelong learning.

  13. Timely Completion of Paperwork: Are Some Residents Consistently Late Responders?

    PubMed Central

    Metheny, William P.

    2014-01-01

    Background One element of competence in professionalism entails the timely completion of paperwork. Early identification of residents who are consistently late in completing their assignments might be the first step in helping them change this habit. Objective This study sought to determine if program coordinators' ratings of residents' response habits to completing assignments were associated with existing measures of resident response times tracked by the institution. Methods Program coordinators rated residents as early, mid, or late responders based on their experience with them. We compared coordinators' ratings with the response time of these same residents in returning orientation materials to the institution, completing a patient safety survey and duty hour logs, and providing their required countersignature on telephone and verbal orders. A total of 196 residents enrolled at this institution were eligible for this comparison in the 2012–2013 academic year. Results Program coordinators rated 23% (40 of 177) of the residents as late responders. These ratings were significantly associated with the response time of residents in returning orientation materials and the completed patient safety survey. Residents identified as late responders were 2.45 times (confidence interval, 1.09 ± 5.64) more likely to have delinquent medical records. Conclusions This exploratory study suggests that residents who are late responders can be identified as early as orientation and that they likely maintain this response habit in completing assignments throughout residency. To address this professionalism issue, programs should track and counsel residents on their timeliness in completing paperwork. PMID:24949137

  14. TIMING AND INTERSTELLAR SCATTERING OF 35 DISTANT PULSARS DISCOVERED IN THE PALFA SURVEY

    SciTech Connect

    Nice, D. J.; Altiere, E.; Farrington, D.; Popa, L.; Wang, Y.; Bogdanov, S.; Camilo, F.; Cordes, J. M.; Brazier, A.; Chatterjee, S.; Hessels, J. W. T.; Kaspi, V. M.; Lyne, A. G.; Stappers, B. W.; Ransom, S. M.; Sanpa-arsa, S.; Allen, B.; Bhat, N. D. R.; Champion, D. J.; Crawford, F.; and others

    2013-07-20

    We have made extensive observations of 35 distant slow (non-recycled) pulsars discovered in the ongoing Arecibo PALFA pulsar survey. Timing observations of these pulsars over several years at Arecibo Observatory and Jodrell Bank Observatory have yielded high-precision positions and measurements of rotation properties. Despite being a relatively distant population, these pulsars have properties that mirror those of the previously known pulsar population. Many of the sources exhibit timing noise, and one underwent a small glitch. We have used multifrequency data to measure the interstellar scattering properties of these pulsars. We find scattering to be higher than predicted along some lines of sight, particularly in the Cygnus region. Finally, we present XMM-Newton and Chandra observations of the youngest and most energetic of the pulsars, J1856+0245, which has previously been associated with the GeV-TeV pulsar wind nebula HESS J1857+026.

  15. 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

  16. 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.

  17. 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

  18. Catchment residence and travel time distributions: The master equation

    NASA Astrophysics Data System (ADS)

    Botter, Gianluca; Bertuzzo, Enrico; Rinaldo, Andrea

    2011-06-01

    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 paper we analyze theoretically such pdf's, whose proper characterization reveals important conceptual and practical differences. A general stochastic framework applicable to arbitrary catchment control volumes is adopted, where time-variable precipitation, evapotranspiration and discharge are assumed to be the major hydrological drivers. The 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. Our solutions suggest intrinsically time-variant travel and residence time pdf's through a direct dependence on hydrological forcings and soil-vegetation dynamics. The proposed framework integrates age-dating and tracer hydrology techniques, and provides a coherent framework for catchment transport models based on travel times.

  19. 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 ...

  20. The relationship between attending alcohol serving venues nearby versus distant to one’s residence and sexual risk taking in a South African township

    PubMed Central

    Eaton, Lisa A.; Kalichman, Seth C.; Pitpitan, Eileen V.; Cain, Demetria N.; Watt, Melissa H.; Sikkema, Kathleen J.; Skinner, Donald; Pieterse, Desiree

    2013-01-01

    BACKGROUND South Africa remains a country with one of the highest prevalence rates of HIV/AIDS at 18% among 15–49 year olds. Underdeveloped urban areas, or townships, are particularly hard hit by the HIV/AIDS epidemic. Alcohol use in these townships has been established as an important risk factor for HIV transmission. Likewise, alcohol serving venues (shebeens) have been identified as sites where substance abuse and sexual risk taking occur. However, little is known about how proximity of alcohol serving establishments (shebeens) to one's residence may be related to sexual risk-taking. METHODS We surveyed 3,261 men and women attending shebeens in a township located in Cape Town, South Africa. We investigated the relationships between attending nearby (< 15 minute walk) versus distant (>15 minute walk) shebeens, and sex and substance abuse related risk-taking. RESULTS Women who attended distant shebeens versus nearby shebeens relative to their residence were approximately twice as likely to report HIV positive status. Bivariate analyses demonstrated that these women were also more likely to report other sexually transmitted infections, greater numbers of sex partners, higher rates of alcohol and drug use, and seeking out new sex partners at shebeen. No differences in sex behavior, substance use or HIV/STI were identified among men. DISCUSSION Proximity of shebeens appears to be an important contextual factor in explaining HIV/STI transmission risk-taking. Future studies should focus on how anonymity may be related to sexual risk and substance use behaviors among women in South African townships. PMID:23404137

  1. Effect of residence time on the efficacy of antidandruff shampoos.

    PubMed

    Piérard-Franchimont, C; Uhoda, E; Loussouarn, G; Saint-Léger, D; Piérard, G E

    2003-12-01

    Dandruff is known to be controlled by fungistatic shampoos active against Malassezia spp. These products also remove the loosely attached scales. This study was performed to assess the effect of a 5-min residence time on the efficacy of antidandruff shampoos. Two commercially available shampoos were used in two groups of 21 panelists with severe dandruff. They contained either 1% ketoconazole or 1% piroctone olamine. In each group, intraindividual comparisons were made by a split-scalp design between the effect of a 5-min residence time versus no residence time. Both shampoos induced significant reductions in scaliness and yeast colonization. The beneficial effects were obvious immediately after one single shampooing and 3 days later as well. The improvement was greater with a 5-min residence time. The piroctone olamine treatment benefited more than the ketoconazole treatment from the extension of shampoo-exposure time. In conclusion, the benefit of a residence time in treating dandruff is documented. The level of improvement in efficacy may vary according to the nature of the shampoo.

  2. Effect of residence time on the efficacy of antidandruff shampoos.

    PubMed

    Piérard-Franchimont, C; Uhoda, E; Loussouarn, G; Saint-Léger, D; Piérard, G E

    2003-12-01

    Dandruff is known to be controlled by fungistatic shampoos active against Malassezia spp. These products also remove the loosely attached scales. This study was performed to assess the effect of a 5-min residence time on the efficacy of antidandruff shampoos. Two commercially available shampoos were used in two groups of 21 panelists with severe dandruff. They contained either 1% ketoconazole or 1% piroctone olamine. In each group, intraindividual comparisons were made by a split-scalp design between the effect of a 5-min residence time versus no residence time. Both shampoos induced significant reductions in scaliness and yeast colonization. The beneficial effects were obvious immediately after one single shampooing and 3 days later as well. The improvement was greater with a 5-min residence time. The piroctone olamine treatment benefited more than the ketoconazole treatment from the extension of shampoo-exposure time. In conclusion, the benefit of a residence time in treating dandruff is documented. The level of improvement in efficacy may vary according to the nature of the shampoo. PMID:18494909

  3. 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.

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

    DOE PAGES

    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 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

  5. Nonlinear sensors: an approach to the residence time detection strategy.

    PubMed

    Dari, A; Bosi, L; Gammaitoni, L

    2010-01-01

    The monitoring of the residence time difference in bistable sensors has been recently proposed as a valid scheme for improving the detection capabilities of sensors as diverse as fluxgate magnetometers, ferroelectric sensors and mechanical sensors. In this paper we propose an approach to the residence time based detection strategy based on the measurement of the slope m of the sensor output integral. We demonstrate that such a method, far from degrading the detection performances can provide an easier way to realize fast and reliable sensors without the computationally demanding task related with the computation of the residence time difference. We introduce the receiver operating characteristic curve as a quantitative estimator for the comparison of the two methods and show that the detector performances increase with increasing the periodic bias amplitude A up to a maximum value. This condition has potentially relevant consequences in the future detectors design. PMID:20365331

  6. 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...

  7. 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.

  8. 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...

  9. Oxygen depletion in relation to water residence times.

    PubMed

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

    2007-11-01

    The relationship between residence time and oxygen saturation was investigated in a mesotidal lagoon in southern Portugal. The system receives no significant freshwater input during the summer months and has a high evaporation rate. These features enable an estimate of residence time from the salinity differences between ocean water entering the system and lagoon water. More than 10,000 GPS referenced measurements of oxygen saturation, temperature and salinity were made during large spring tides in September, 2006. The lowest oxygen saturation ( approximately 44%) was measured in the waters with the highest calculated residence times (7 days). There was a significant linear decrease in the oxygen saturation with increasing residence time of approximately 16% per day. This was similar to the rate measured on a neap tide in August, 2005. The high salinity, low oxygen saturated water was spatially confined to one inner channel, except at high water when this water was pushed into other channels. Although the tides investigated were the largest for several years, the oxygen saturation did not exceed 70% in this inner region. It is proposed that the direct discharge of oxygen consuming effluent, including domestic sewage, into this inner channel is responsible for this persistent oxygen deficit. PMID:17968445

  10. The residence time of carbon in Amazonian primary forests

    NASA Astrophysics Data System (ADS)

    Trumbore, S.; Vieira, S. A.; Camargo, P.; Chambers, J. Q.; Higuchi, N.; Selhorst, D.; Martinelli, L. A.

    2004-12-01

    The residence time of carbon is a major determiner of the capacity of an ecosystem to function as a source or sink of carbon. The overall residence time of carbon in primary forests is determined by (1) what fraction of photosynthetic products get respired quickly and (2) the residence time of C allocated to living plant tissues, and (3) the time each of these components takes to decay, including what fraction is oxidized to CO2 versus what becomes stabilized in soil organic matter. Using radiocarbon to determine the age of carbon in various pools in forests, we conclude that: (1) carbon use efficiency of these forests is low, with ~70% of photosynthetic products respired within a year, and only 30% allocated to growth of wood, root and leaf tissues; (2) carbon resides on average for 2-3 years in leaves and 3-10 years in fine roots; very rapid or ephemeral root turnover is assigned in our budgets to AƒAøAøâ_sA¬A<Å"autotrophicAƒAøAøâ_sA¬Aøâ_zAø respiration (3) the mean age of carbon in living trees is longer (200-260 years) than the mean residence time of carbon derived from the biomass stock divided by annual wood growth increment (40-100 years) because most of the biomass is in the largest, fastest growing, trees, while most of the individuals are smaller, slower growing, shaded trees; (4) decomposition rates are rapid, but potentially recycling of carbon in the microbial community leads to a significant decadally cycling pool in near-surface organic matter. We will summarize these findings and use them with models of carbon dynamics to estimate carbon storage and loss potential on interannual to decadal timescales. The overall age of heterotrophically respired carbon (carbon derived from microbial decomposition) is 6-10 years, with much of the time lag due to the time spent by C in living leaf and root tissues. Even when combined with 70% autotrophically respired C with residence times of <1 year, this significant time lag can lead to large

  11. 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.

  12. Predictors of Nursing Home Residents' Time to Hospitalization

    PubMed Central

    O'Malley, A James; Caudry, Daryl J; Grabowski, David C

    2011-01-01

    Objectives To model the predictors of the time to first acute hospitalization for nursing home residents, and accounting for previous hospitalizations, model the predictors of time between subsequent hospitalizations. Data Sources Merged file from New York State for the period 1998–2004 consisting of nursing home information from the minimum dataset and hospitalization information from the Statewide Planning and Research Cooperative System. Study Design Accelerated failure time models were used to estimate the model parameters and predict survival times. The models were fit to observations from 50 percent of the nursing homes and validated on the remaining observations. Principal Findings Pressure ulcers and facility-level deficiencies were associated with a decreased time to first hospitalization, while the presence of advance directives and facility staffing was associated with an increased time. These predictors of the time to first hospitalization model had effects of similar magnitude in predicting the time between subsequent hospitalizations. Conclusions This study provides novel evidence suggesting modifiable patient and nursing home characteristics are associated with the time to first hospitalization and time to subsequent hospitalizations for nursing home residents. PMID:20849556

  13. On ground water residence time in karst aquifers

    NASA Astrophysics Data System (ADS)

    Gabrovsek, Franci; Petric, Metka; Kogovšek, Janja; Dreybrodt, Wolfgang

    2015-04-01

    Residence time of groundwater in karst aquifers span several orders of magnitude. To demonstrate some parts of this wide spectrum, several approaches are presented here. First, a genetic numerical model is used to study the spreading of plumes through confined telogenetic karst aquifer. Digital models of fractured karst aquifer at different stages of early karstification with well defined flow velocities are used as a "test sites". A particle tracking algorithm is applied to study the advective spreading of plumes caused by instantaneous input into selected region of the modelling domain. The simulations shows high variability of the resulting transfer functions, depending on the stage of evolution, the structure of initial network, the boundary conditions and the location of particle injection. Besides idealistic modelling scenario, several field studies in Dinaric karst systems in Slovenia are reviewed with focus to the ground water residence time. The methods include dye tracing experiments and continuous monitoring of ground water in epiphreatic caves. The studied systems have evolved in complex tectonic settings and are characterised by the network of epiphreatic conduits, interrupted by large collapse chambers and dolines. Dye tracing experiments revealed surprising flow paths and high variations of residence time at different hydrological conditions. Important information on the velocity of groundwater flow in large epiphreatic conduits can be obtained from continuous and simultaneous monitoring of ground water parameters in active caves in a selected system. Such cases from Reka - Timavo system and Postojna - Planina cave system are presented, where temperature is used as a ground water tracer and the results were compared to the results of dye tracing. Vadose zone presents the biggest challenge for characterisation of groundwater flow in karst. Many different flow paths show extremely high variability in flow velocities/residence times. These is

  14. Inferring residence time distributions from hillslope tracer experiments

    NASA Astrophysics Data System (ADS)

    McGuire, K. J.; Weiler, M.; McDonnell, J. J.

    2003-12-01

    Water residence time in catchments is typically determined by black-box modeling of environmental tracers (e.g., 18O and 2H), in which input (rainfall) and output (discharge) tracer concentrations are used to estimate parameters of an assumed distribution that represents the residence time. In this study, a different approach was taken, where the residence time distribution (RTD) was determined directly from an artificial tracer experiment. Two tracers (Amino G acid and bromide) were applied as line sources (20 and 40 m from the stream, respectively) to the soil surface of a steep forested hillslope in the H.J. Andrews Experimental Forest. Tracer concentrations and seepage flow were monitored for approximately 100 days. The resulting breakthrough curves were modeled using a simple, process-based hillslope model conditional on spatially varying soil depth and depth-varying drainable porosity and hydraulic conductivity. The model preserved internal hydrological behavior such as water table dynamics and satisfactorily reproduced seepage discharge and tracer concentrations. Using the model and assuming the same parameterization, we infer the RTD of conservative tracers applied to the entire hillslope. The derived RTDs were then compared to functions that represent RTDs used in black-box models.

  15. 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

  16. Abuse of residents: it's time to take action.

    PubMed Central

    Myers, M F

    1996-01-01

    The scientific study of the sexual dynamics that come into play during residency training seems to both fascinate and repel trainees and their supervisors. One of the more provocative and shameful dimensions of this area of inquiry, the abuse of residents, causes a good deal of distress. How do we respond to findings of significant psychological abuse, discrimination on the basis of sex or sexual orientation and sexual harassment in medical settings? How can we ignore over a decade of research? How can we not heed the experience of so many young physicians? Given the uncertain times in Canadian medicine and the insecurity in our professional and personal lives, we must work together to improve the culture of our teaching institutions and implement measures nationally and locally to close this dark chapter. PMID:8646658

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. Residence time distributions of gas flowing through rotating drum bioreactors.

    PubMed

    Hardin, M T; Howes, T; Mitchell, D A

    2001-07-20

    Residence time distribution studies of gas through a rotating drum bioreactor for solid-state fermentation were performed using carbon monoxide as a tracer gas. The exit concentration as a function of time differed considerably from profiles expected for plug flow, plug flow with axial dispersion, and continuous stirred tank reactor (CSTR) models. The data were then fitted by least-squares analysis to mathematical models describing a central plug flow region surrounded by either one dead region (a three-parameter model) or two dead regions (a five-parameter model). Model parameters were the dispersion coefficient in the central plug flow region, the volumes of the dead regions, and the exchange rates between the different regions. The superficial velocity of the gas through the reactor has a large effect on parameter values. Increased superficial velocity tends to decrease dead region volumes, interregion transfer rates, and axial dispersion. The significant deviation from CSTR, plug flow, and plug flow with axial dispersion of the residence time distribution of gas within small-scale reactors can lead to underestimation of the calculation of mass and heat transfer coefficients and hence has implications for reactor design and scale-up. PMID:11370003

  2. 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.

  3. Soil residence time: A window into landscape morphologic steady state

    NASA Astrophysics Data System (ADS)

    Almond, P. C.; Roering, J. J.

    2005-12-01

    For a landscape in true morphologic steady state the erosion rate and the average residence time of the debris mantle regolith (including the soils) are everywhere equal. Where other factors influencing soil properties such as climate, organisms and parent material are relatively invariant the degree of weathering and extent of pedological development in the debris mantle regolith should be spatially invariant. The corollary to this argument, commonly exploited in soil-geomorphic analysis, is that variation in debris mantle regolith development in a landscape reflects inheritance of older geomorphic surfaces and hence departure from steady state, at least over some time and space scale. The Oregon Coast Range (OCR) experiences a constant rate of rock uplift and has escaped the effects of Pleistocene glacial and periglacial processes. Furthermore, rock uplift and denudation rates have been shown to be approximately in balance, and consequently the OCR is promoted as being a good candidate for a (flux) steady state landscape. This is, however, not a sufficient condition for morphologic steady state, which is often assumed in numerical landscape simulations. The rock underlying the OCR is relatively homogeneous turbidites of the Tyee formation, and climatic and vegetation factors are relatively uniform over large areas. The degree of weathering and pedological development of the regolith on hillslopes should therefore dominantly reflect variation in regolith residence time, such that significant variation implies non-morphologic-steady state conditions. Indeed, spatial variation in soil/regolith age indicates the extent of departure from morphologic steady state. We have observed ubiquitous but localised deep, highly weathered regoliths and soils on ridge tops in the OCR. The extent, depth, geometry and elevational distribution of these deep regolith patches combined with relative measures of their age derived from total element and meteoric 10Be inventory will enable

  4. Distribution and timing of distant metastasis after local therapy in large cohort of patients with esophageal and esophagogastric junction cancer

    PubMed Central

    Shiozaki, Hironori; Sudo, Kazuki; Xiao, Lianchun; Wadhwa, Roopma; Elimova, Elena; Hofstetter, Wayne L.; Skinner, Heath D.; Lee, Jeffrey H.; Weston, Brian; Bhutani, Manoop S.; Blum, Mariela A.; Maru, Dipen M.; Ajani, Jaffer A.

    2014-01-01

    Background Patients with localized esophageal and esophagogastric junction cancer (EAC) receive chemoradiation then surgery (trimodality; TMT) or definitive chemoradiation (bimodality; BMT). Since distant metastases (DMs) are common but the details of the DM distribution and timing in a large cohort have not been described. Methods 629 patients with localized EAC who had TMT or BMT were analyzed. Standard statistical methods were used to define the endpoints. Results The median follow-up time was 37.2 months (interquartile range: 17.8–65.0). Among 356 TMT patients, 33% (119) developed DM as their first relapse and among 273 patients with BMT, 40% (109) developed DM. 91% (TMT) and 96% (BMT) of DMs were diagnosed within 2 years of local therapy. The most common sites of DMs were: lung, distant nodes, liver, peritoneal cavity, bone, brain, and pleura in the order of frequency. The median overall survival of TMT patients with DM was 10.2 months (95% CI: 7.8–12.7) and that for BMT patients with DM was 7.8 months (95% CI: 5.7–9.9). Conclusions Following TMT or BMT, ≥33% of patients developed DMs and most DM occurred within 2 years (>90%) of local therapy. A clinical model that highly associates with high-risk for DM in TMT-eligible patients, prior to surgery, is desirable. PMID:24925190

  5. TIME STRUCTURE OF GAMMA-RAY SIGNALS GENERATED IN LINE-OF-SIGHT INTERACTIONS OF COSMIC RAYS FROM DISTANT BLAZARS

    SciTech Connect

    Prosekin, Anton; Aharonian, Felix; Essey, Warren; Kusenko, Alexander

    2012-10-01

    Blazars are expected to produce both gamma rays and cosmic rays. Therefore, observed high-energy gamma rays from distant blazars may contain a significant contribution from secondary gamma rays produced along the line of sight by the interactions of cosmic-ray protons with background photons. Unlike the standard models of blazars that consider only the primary photons emitted at the source, models that include the cosmic-ray contribution predict that even {approx}10 TeV photons should be detectable from distant objects with redshifts as high as z {>=} 0.1. Secondary photons contribute to signals of point sources only if the intergalactic magnetic fields are very small, B {approx}< 10{sup -14} G, and their detection can be used to set upper bounds on magnetic fields along the line of sight. Secondary gamma rays have distinct spectral and temporal features. We explore the temporal properties of such signals using a semi-analytical formalism and detailed numerical simulations, which account for all the relevant processes, including magnetic deflections. In particular, we elucidate the interplay of time delays coming from the proton deflections and from the electromagnetic cascade, and we find that, at multi-TeV energies, secondary gamma rays can show variability on timescales of years for B {approx} 10{sup -15} G.

  6. Ligand Release Pathways Obtained with WExplore: Residence Times and Mechanisms.

    PubMed

    Dickson, Alex; Lotz, Samuel D

    2016-06-23

    The binding of ligands with their molecular receptors is of tremendous importance in biology. Although much emphasis has been placed on characterizing binding sites and bound poses that determine the binding thermodynamics, the pathway by which a ligand binds importantly determines the binding kinetics. The computational study of entire unbiased ligand binding and release pathways is still an emerging field, made possible only recently by advances in computational hardware and sampling methodologies. We have developed one such method (WExplore) that is based on a weighted ensemble of trajectories, which we apply to ligand release for the first time, using a set of three previously characterized interactions between low-affinity ligands and the protein FKBP-12 (FK-506 binding protein). WExplore is found to be more efficient that conventional sampling, even for the nanosecond-scale unbinding events observed here. From a nonequilibrium ensemble of unbinding trajectories, we obtain ligand residence times and release pathways without using biasing forces or a Markovian assumption of transitions between regions. We introduce a set of analysis tools for unbinding transition pathways, including using von Mises-Fisher distributions to model clouds of ligand exit points, which provide a quantitative proxy for ligand surface diffusion. Differences between the transition pathway ensembles of the three ligands are identified and discussed.

  7. Ligand Release Pathways Obtained with WExplore: Residence Times and Mechanisms.

    PubMed

    Dickson, Alex; Lotz, Samuel D

    2016-06-23

    The binding of ligands with their molecular receptors is of tremendous importance in biology. Although much emphasis has been placed on characterizing binding sites and bound poses that determine the binding thermodynamics, the pathway by which a ligand binds importantly determines the binding kinetics. The computational study of entire unbiased ligand binding and release pathways is still an emerging field, made possible only recently by advances in computational hardware and sampling methodologies. We have developed one such method (WExplore) that is based on a weighted ensemble of trajectories, which we apply to ligand release for the first time, using a set of three previously characterized interactions between low-affinity ligands and the protein FKBP-12 (FK-506 binding protein). WExplore is found to be more efficient that conventional sampling, even for the nanosecond-scale unbinding events observed here. From a nonequilibrium ensemble of unbinding trajectories, we obtain ligand residence times and release pathways without using biasing forces or a Markovian assumption of transitions between regions. We introduce a set of analysis tools for unbinding transition pathways, including using von Mises-Fisher distributions to model clouds of ligand exit points, which provide a quantitative proxy for ligand surface diffusion. Differences between the transition pathway ensembles of the three ligands are identified and discussed. PMID:27231969

  8. 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.

  9. Inpatient Performance of Primary Care Residents: Impact of Reduction in Time on the Ward.

    ERIC Educational Resources Information Center

    And Others; Goroll, Allan H.

    1979-01-01

    The inpatient (ward/intensive care unit) performance of primary care medical residents was compared with that of their peers in the standard internal medicine residency program. Nearly identical performances of the two groups suggests that substantial time in the first two years of residency can be devoted successfully to ambulatory training.…

  10. 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

  11. Does unsaturated flow drive soil carbon residence times?

    NASA Astrophysics Data System (ADS)

    Lawrence, C. R.; Mnich, M.; Druhan, J. L.; Schulz, M. S.; Stonestrom, D. A.; Maher, K.; Harden, J. W.

    2015-12-01

    Soil moisture is widely recognized as a driver of many important biogeochemical processes. For example, ecosystem productivity, microbial lifecycles, soil organic matter decomposition, soil secondary mineralogy, the development and persistence of redox gradients, and the export of dissolved carbon are all sensitive to soil-water content and potential. In turn, each of these processes is recognized as an important control on the turnover of soil organic carbon. These dependencies raise a key question: Is the flux of water through unsaturated soils the dominant driver of soil organic carbon turnover across broad spatial scales? To better characterize the importance of soil moisture fluxes, we synthesize data from a number of soil studies to evaluate how total soil carbon storage, carbon residence time, and depth dependent gradients vary in relation to soil hydrologic fluxes. Specifically, we compare soil carbon storage and stability to measured and/or modeled infiltration ([precipitation + condensation] - [evapotranspiration + runoff]) and long-term soil water flux estimates from chloride mass balance, or other techniques. Additionally, we consider the interaction of soil age and hydrology, as the development of secondary mineral horizons during pedogenesis represents a critical threshold in both soil water flux and soil organic carbon turnover. We focus on data from 3 previously descried soil chronosequences, including the Santa Cruz, Mattole, and Merced terraces, which together span a wide range of age and soil moisture conditions. Across these sites, organic carbon accumulates to greater depths in the soils with highest infiltration but the relationship between turnover and soil moisture is not as straightforward. To help interpret these results, we compare field data against simulations of biogeochemical reactions involving soil carbon and the resulting isotopic gradients using the reactive transport model CrunchTope. Overall, this effort provides for an improved

  12. 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…

  13. Hyporheic zone exchange fluxes and residence times inferred from riverbed temperature and radon data

    NASA Astrophysics Data System (ADS)

    Cranswick, Roger H.; Cook, Peter G.; Lamontagne, Sebastien

    2014-11-01

    Vertical profiles of temperature, radon and electrical conductivity are used to characterise downwelling, neutral and upwelling hyporheic zones along a pool-riffle sequence in the Haughton River in north-eastern Australia. Water residence times and vertical fluxes are derived from temperature and radon data and then directly compared for downwelling profiles. Temperature and radon-derived fluxes in downwelling zones ranged from 0.02 to 24 m day-1 with a mean of 1.69 m day-1 while residence times across the study site ranged from tens of minutes to greater than 15 days. The radon approach has the lowest uncertainty for residence times between 0.1 and 15 days while the uncertainty of the temperature approach (using a diel river signal) is lowest for residence times that are less than a few days. For 83% of depths in downwelling profiles, radon-derived residence times were greater (some up to two orders of magnitude greater) than temperature-derived residence times. When the error bounds of the residence time estimates were accounted for, 57% of radon-derived residence times were considerably greater than temperature-derived residence times in downwelling profiles. We suggest that this disparity is due to the different influence of small scale heterogeneity on temperature and radon transport. These field based results indicate that small scale heterogeneity may play a far more important role than has been previously considered in groundwater-surface water interaction studies.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. The drug-target residence time model: a 10-year retrospective.

    PubMed

    Copeland, Robert A

    2016-02-01

    The drug-target residence time model was first introduced in 2006 and has been broadly adopted across the chemical biology, biotechnology and pharmaceutical communities. While traditional in vitro methods view drug-target interactions exclusively in terms of equilibrium affinity, the residence time model takes into account the conformational dynamics of target macromolecules that affect drug binding and dissociation. The key tenet of this model is that the lifetime (or residence time) of the binary drug-target complex, and not the binding affinity per se, dictates much of the in vivo pharmacological activity. Here, this model is revisited and key applications of it over the past 10 years are highlighted.

  1. 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

  2. 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. PMID:26496630

  3. 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.

  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. Peak Alert Time and Rapport between Residence Hall Roommates.

    ERIC Educational Resources Information Center

    Carey, John C.; And Others

    1988-01-01

    Examined whether peak alert time is related to compatibility for college roommates. Data from 66 male pairs and from 55 female pairs of roommates revealed that pairs who were similar on self-reported peak circadian alertness had higher levels of rapport. (Author/NB)

  6. 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.

  7. 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.

  8. 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

  9. Experimental study of residence time distributions of ball-mill circuits grinding coal-water mixtures

    SciTech Connect

    Shoji, K.; Takahashi, Y.; Ohtake, A.; Austin, L.G.

    2008-08-15

    Residence time distributions (RTDs) were estimated by water tracing in a number of wet overflow ball mills (diameters 0.38 to 4.65 m) producing dense, coal-water slurries. In open-circuit mills of 0.38 m diameter and various length-diameter (LID) ratios, the mean residence times of solid were also determined from measured mill holdups. Holdup increased with increased mill feed rate, but the mean residence times of coal and water were still equal to each other. The experimental residence time distributions were fitted to the Mori-Jimbo-Yamazaki semi-infinite, axial mixing model, and the dimensionless mixing coefficient was determined for each of 25 tests in single- and two-compartment mills. This coefficient was found to be independent to the feed rate but linearly proportional to the D/L ratio. The mixing coefficient was smaller for two-compartment mills than for single-compartment mills, showing that there was reduced mixing introduced by the diaphragm separating the compartments. Equations are given to scale residence time distributions for changes in mill diameter and length.

  10. 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.

  11. Water residence times around copper plastocyanin: a molecular dynamics simulation approach

    NASA Astrophysics Data System (ADS)

    Rocchi, Claudia; Rita Bizzarri, Anna; Cannistraro, Salvatore

    1997-01-01

    In order to study the dynamical properties of the solvent-protein interface, a detailed analysis of the time-relaxation behaviour of the hydration shells around each atom of copper plastocyanin has been performed by means of a time correlation function technique. In computing the function, which allowed us to extract average water residence times and coordination numbers within atomic shells of a given radius, we focused on the short and long time limits of the function itself, also in connection with a detailed analysis of the statistical uncertainty. Water residence times distribution around plastocyanin has been calculated for the first coordination shell. Water residence times near charged and polar atoms were found to be longer than those of non-polar ones; moreover side-chain oxygens and nitrogens, which form hydrogen bonds with solvent molecules, show larger water residence times than other atom types and, for negatively and positively charged residues, these times correlate to the hydrogen bond average duration. The accessibility of the solvent to protein atoms, investigated in terms of coordination numbers, has been compared to the more standard Solvent Accessible Surface. The active site, including the copper atom and its ligands, has been studied in greater detail to better understand the connections between the water molecule dynamical properties and the protein biological functionality. In particular for copper site, which was believed to be inaccessible to the solvent, it has been found that at least one water molecule which does not exchange with bulk has permanent contact with the metal.

  12. 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.

  13. 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

  14. Planting intensity, residence time, and species traits determine invasion success of alien woody species.

    PubMed

    Pysek, Petr; Krivánek, Martin; Jarosík, Vojtech

    2009-10-01

    We studied the relative importance of residence time, propagule pressure, and species traits in three stages of invasion of alien woody plants cultivated for about 150 years in the Czech Republic, Central Europe. The probability of escape from cultivation, naturalization, and invasion was assessed using classification trees. We compared 109 escaped-not-escaped congeneric pairs, 44 naturalized-not-naturalized, and 17 invasive-not-invasive congeneric pairs. We used the following predictors of the above probabilities: date of introduction to the target region as a measure of residence time; intensity of planting in the target area as a proxy for propagule pressure; the area of origin; and 21 species-specific biological and ecological traits. The misclassification rates of the naturalization and invasion model were low, at 19.3% and 11.8%, respectively, indicating that the variables used included the major determinants of these processes. The probability of escape increased with residence time in the Czech Republic, whereas the probability of naturalization increased with the residence time in Europe. This indicates that some species were already adapted to local conditions when introduced to the Czech Republic. Apart from residence time, the probability of escape depends on planting intensity (propagule pressure), and that of naturalization on the area of origin and fruit size; it is lower for species from Asia and those with small fruits. The probability of invasion is determined by a long residence time and the ability to tolerate low temperatures. These results indicate that a simple suite of factors determines, with a high probability, the invasion success of alien woody plants, and that the relative role of biological traits and other factors is stage dependent. High levels of propagule pressure as a result of planting lead to woody species eventually escaping from cultivation, regardless of biological traits. However, the biological traits play a role in later

  15. 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.

  16. Numerical estimation of the noncompartmental pharmacokinetic parameters variance and coefficient of variation of residence times.

    PubMed

    Purves, R D

    1994-02-01

    Noncompartmental investigation of the distribution of residence times from concentration-time data requires estimation of the second noncentral moment (AUM2C) as well as the area under the curve (AUC) and the area under the moment curve (AUMC). The accuracy and precision of 12 numerical integration methods for AUM2C were tested on simulated noisy data sets representing bolus, oral, and infusion concentration-time profiles. The root-mean-squared errors given by the best methods were only slightly larger than the corresponding errors in the estimation of AUC and AUMC. AUM2C extrapolated "tail" areas as estimated from a log-linear fit are biased, but the bias is minimized by application of a simple correction factor. The precision of estimates of variance of residence times (VRT) can be severely impaired by the variance of the extrapolated tails. VRT is therefore not a useful parameter unless the tail areas are small or can be shown to be estimated with little error. Estimates of the coefficient of variation of residence times (CVRT) and its square (CV2) are robust in the sense of being little affected by errors in the concentration values. The accuracy of estimates of CVRT obtained by optimum numerical methods is equal to or better than that of AUC and mean residence time estimates, even in data sets with large tail areas.

  17. 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

  18. 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

  19. Extra-regional residence time as a correlate of plant invasiveness: European archaeophytes in North America.

    PubMed

    La Sorte, Frank A; Pysek, Petr

    2009-09-01

    Human activities have degraded biogeographical barriers to dispersal resulting in the spread and naturalization of increasing numbers of nonnative invasive species. One correlate of invasiveness within a region is residence time or time since introduction. Plant species that were introduced into Europe prior to AD 1500 (European archaeophytes) that were subsequently introduced into North America provide a unique opportunity to examine the effect of extra-regional residence time (i.e., residence time that occurred in a nonnative region before a species was introduced into a new region). Here, we examine how nonnative species with extensive extra-regional residence times have affected beta diversity among states in the contiguous United States of America based on an analysis of occupancy and distance decay of similarity. State floras contained an average of 3106 +/- 922 species (mean +/- SD) with 2318 +/- 757 species classified as native, 180 +/- 43 species as European archaeophyte, and 608 -236 species as other exotic with no European archaeophyte association. For European archaeophytes, 42% were identified as noxious weeds in the United States with 8% identified as agricultural and 14% as natural-area weeds (20%, 2%, and 13% for other exotics, respectively). In strong contrast to natives and other exotics, European archaeophytes were more widespread and presented weaker distance-decay patterns. Thus, European archaeophytes were more likely to become noxious weeds, particularly within agricultural areas, and were associated with significant losses in beta diversity. We suggest that this outcome is a consequence of extra-regional residence time, which allowed for the selection of species or the evolution of traits that favored the colonization of arable habitats associated with early agricultural activities in Europe, habitats that are widespread, resource rich, and uniformly distributed in the United States. Our findings suggest that a long-term trajectory can be

  20. 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

  1. 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

  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. 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. PMID:25698071

  4. 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...

  5. Short residence time coal liquefaction. Topical report, May 1978-July 1982

    SciTech Connect

    Not Available

    1984-02-01

    This report is the second in a series of topical reports describing work conducted for the US Department of Energy at Gulf Oil Corporation's Merriam Coal Liquefaction Laboratory. It reviews research carried out over several years to determine the role of process variables in an SRC I type coal dissolution process. The data reported describe the effects of temperature (440 to 500/sup 0/C), pressure (1000 to 3000 psig) and residence time (1 to 10 minutes) using bituminous coal (Kentucky 9/14, Indiana V, and Pittsburgh seams) in the short residence time solvent refined coal (SRC) process. All of the research was conducted using a continuous bench scale unit. The short residence time SRC process was originally envisioned as a stand-alone process which would produce a low cost solid SRC I type product. With interest shifting toward the production of higher quality products, the short residence time SRC process can now be thought of as a minimum cost first stage of a multi-staged process. 9 references, 16 figures, 23 tables.

  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. 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.

  8. 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.

  9. Molecular Dynamics Simulations and Kinetic Measurements to Estimate and Predict Protein-Ligand Residence Times.

    PubMed

    Mollica, Luca; Theret, Isabelle; Antoine, Mathias; Perron-Sierra, Françoise; Charton, Yves; Fourquez, Jean-Marie; Wierzbicki, Michel; Boutin, Jean A; Ferry, Gilles; Decherchi, Sergio; Bottegoni, Giovanni; Ducrot, Pierre; Cavalli, Andrea

    2016-08-11

    Ligand-target residence time is emerging as a key drug discovery parameter because it can reliably predict drug efficacy in vivo. Experimental approaches to binding and unbinding kinetics are nowadays available, but we still lack reliable computational tools for predicting kinetics and residence time. Most attempts have been based on brute-force molecular dynamics (MD) simulations, which are CPU-demanding and not yet particularly accurate. We recently reported a new scaled-MD-based protocol, which showed potential for residence time prediction in drug discovery. Here, we further challenged our procedure's predictive ability by applying our methodology to a series of glucokinase activators that could be useful for treating type 2 diabetes mellitus. We combined scaled MD with experimental kinetics measurements and X-ray crystallography, promptly checking the protocol's reliability by directly comparing computational predictions and experimental measures. The good agreement highlights the potential of our scaled-MD-based approach as an innovative method for computationally estimating and predicting drug residence times. PMID:27391254

  10. 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...

  11. 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,...

  12. 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.

  13. Residence time controls on nitrogen transformations in a permeable nearshore aquifer

    NASA Astrophysics Data System (ADS)

    Robinson, C. E.

    2015-12-01

    Permeable nearshore aquifers are an important biogeochemical hotspot for nitrogen (N) cycling. Located at the land-sea interface this hotspot has been shown to regulate N fluxes to coastal waters via submarine groundwater discharge. N transformations in a nearshore aquifer may result in either a net production or net removal of NO3- with the transformations controlled by complex interacting physical transport and biogeochemical kinetic processes. Oceanic forcing including tides and waves cause large quantities of seawater and chemical constituents, including dissolved oxygen and organic matter, to recirculate through the nearshore aquifer. There is currently limited understanding of the impact of the oceanic forcing on the residence time of recirculating constituents and the subsequent implications on N transformations in the aquifer. A numerical model was applied to quantify the influence of varying tidal and wave conditions on residence times and evaluate how the interactions between the coupled transport and reaction kinetics control N transformations and fluxes. Simulations were performed using the variable-density groundwater flow model SEAWAT-2005 combined with the reactive multi-component transport model PHT3D v2.10. The model simulated the transport and transformation of both marine- and land-derived chemical consitituents and considered oxic DOM mineralization, nitrification and denitrification. Simulations demonstrate that the recirculation residence times, combined with oxygen removal rates, regulate whether a nearshore aquifer will act as a net source or sink of NO3. Dimensionless Damköhler numbers calculated as the ratio of the characteristic residence time to characterisitic oxygen reaction time were determined and provide valuable insight into the residence time controls on the ultimate flux of N to the sea.

  14. 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.

  15. 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. PMID:26961124

  16. 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.

  17. 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. PMID:25637117

  18. Inverse dependency of particle residence times in ponds to the concentration of phosphate, the limiting nutrient.

    PubMed

    Roberts, Kimberly A; Santschi, Peter H

    2004-01-01

    234Th, a commonly used short-lived particle-reactive tracer in marine systems, was measured in three different holding pond series at the Rocky Flats Environmental Technology Site (RFETS), Colorado, along with its parent nuclide 238U, to determine steady-state residence times of particle-reactive actinides such as Pu, and of particles. Series B ponds, which received industrial effluent that includes ortho-phosphate (PO4) and actinides, differed from series A and C ponds, which did not. This difference was also evident in the calculated particle residence times, which were <1 day for the ponds B4 and B5, where PO4 concentrations were higher (1.4 and 1.8 mg/l), and 3 and 3.4 days for ponds A3 and C2, respectively, where ortho-phosphate concentrations were lower (<0.1 mg/l). Particle residence times thus showed an inverse relationship with the concentration of ortho-phosphate, the limiting nutrient in fresh water systems. The same relationship to the concentration of ortho-phosphate or any of the other nutrient elements was not evident for the residence times of dissolved 234Th, which ranged between 0.1 and 2 days. This can be attributed to higher concentrations of dissolved and particulate ligands with greater binding potential for actinides such as four-valent Th and Pu in ponds with higher ortho-phosphate concentrations. Regardless of actual ortho-phosphate concentration, however, at water residence (holding) times of 1 month in these ponds, particles and associated actinides would be expected to be completely removed from the pond water to sediments. PMID:15261419

  19. Inverse dependency of particle residence times in ponds to the concentration of phosphate, the limiting nutrient.

    PubMed

    Roberts, Kimberly A; Santschi, Peter H

    2004-01-01

    234Th, a commonly used short-lived particle-reactive tracer in marine systems, was measured in three different holding pond series at the Rocky Flats Environmental Technology Site (RFETS), Colorado, along with its parent nuclide 238U, to determine steady-state residence times of particle-reactive actinides such as Pu, and of particles. Series B ponds, which received industrial effluent that includes ortho-phosphate (PO4) and actinides, differed from series A and C ponds, which did not. This difference was also evident in the calculated particle residence times, which were <1 day for the ponds B4 and B5, where PO4 concentrations were higher (1.4 and 1.8 mg/l), and 3 and 3.4 days for ponds A3 and C2, respectively, where ortho-phosphate concentrations were lower (<0.1 mg/l). Particle residence times thus showed an inverse relationship with the concentration of ortho-phosphate, the limiting nutrient in fresh water systems. The same relationship to the concentration of ortho-phosphate or any of the other nutrient elements was not evident for the residence times of dissolved 234Th, which ranged between 0.1 and 2 days. This can be attributed to higher concentrations of dissolved and particulate ligands with greater binding potential for actinides such as four-valent Th and Pu in ponds with higher ortho-phosphate concentrations. Regardless of actual ortho-phosphate concentration, however, at water residence (holding) times of 1 month in these ponds, particles and associated actinides would be expected to be completely removed from the pond water to sediments.

  20. Residency time, migration route and survival of Atlantic salmon Salmo salar smolts in a Canadian fjord.

    PubMed

    Dempson, J B; Robertson, M J; Pennell, C J; Furey, G; Bloom, M; Shears, M; Ollerhead, L M N; Clarke, K D; Hinks, R; Robertson, G J

    2011-06-01

    Atlantic salmon Salmo salar smolts (n = 181) from two rivers were surgically implanted with acoustic transmitters and released to determine migration route, residency time and survival in a 50 km long estuarine fjord located on the south coast of Newfoundland, Canada. Data obtained from automated receivers placed throughout the Bay d'Espoir fjord indicated that migrating smolts used different routes to reach the outer areas of the fjord. The duration of time that smolts spent in the immediate estuary zone also differed between the two localities (7 and 17 days) although the total time smolts were resident in the fjord was similar and extensive (40 days). Many smolts were resident for periods of 4-8 weeks moving back and forth in the outer part of the fjord where maximum water depths range from 300 to 700 m. Survival in the estuary zone was greater for smolts with prolonged residency in estuarine habitat. Overall smolt survival to the fjord exit was moderately high (54-85%), indicating that the initial phase of migration did not coincide with a period of unusually high mortality. PMID:21651545

  1. Beyond Sedna: Probing the Distant Solar System

    NASA Astrophysics Data System (ADS)

    Schwamb, Megan E.

    This thesis presents studies in observational planetary astronomy probing the structure of the Kuiper belt and beyond. The discovery of Sedna on a highly eccentric orbit beyond Neptune challenges our understanding of the solar system and suggests the presence of a population of icy bodies residing past the Kuiper belt. With a perihelion of 76 AU, Sedna is well beyond the reach of the gas-giants and could not be scattered onto its highly eccentric orbit from interactions with Neptune alone. Sedna's aphelion at ˜1000 AU is too far from the edge of the solar system to feel the perturbing effects of passing stars or galactic tides in the present-day solar neighborhood. Sedna must have been emplaced in its orbit at an earlier time when massive unknown bodies were present in or near the solar system. The orbits of distant Sedna-like bodies are dynamically frozen and serve as the relics of their formation process. We have performed two surveys to search for additional members of the Sedna population. In order to find the largest and brightest Sedna-like bodies we have searched ˜12,000 deg² within +/-30 degrees of the ecliptic to a limiting R magnitude of 21.3 using the QUEST camera on the 1.2m Samuel Oschin Telescope. To search for the fainter, more common members of this distant class of solar system bodies, we have performed an deep survey using the Subaru Prime Focus Camera on the 8.2m Subaru telescope covering 43 deg² to a limiting R magnitude of 25.3. Searching over a two-night baseline, we were sensitive to motions out to distances of approximately 1000 AU. We present the results of these surveys. We discuss the implications for a distant Sedna-like population beyond the Kuiper belt and discuss future prospects for detecting and studying these distant bodies, focusing in particular on the constraints we can place on the embedded stellar cluster environment the early Sun may have been born in, where the location and distribution of Sedna-like orbits sculpted by

  2. 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.

  3. 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.

  4. 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.

  5. 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. PMID:19723195

  6. 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.

  7. Seasonal Short-Lived Radium Activity in the Venice Lagoon: The Role of Residence Time

    NASA Astrophysics Data System (ADS)

    Rapaglia, J.; Ferrarin, C.; Zaggia, L.; Umgiesser, G.; Zuppi, G.; Manfe', G.

    2008-12-01

    Radium is considered to be an excellent tracer of submarine groundwater discharge (SGD) and, therefore, has been used in many studies of this process in the past decade. Comprehensive surveys of excess 223,224Ra activity were completed in the surface waters of the Venice Lagoon over 6 seasons in order to quantify seasonal variation of SGD into the lagoon. The mass balance of radium found that SGD was 5-26 times greater than total river discharge (35.5 m3 s-1), and that total SGD could differ by almost an order of magnitude pending season. Several possible parameters, which may cause the seasonal variation, were tested. These included precipitation events, average tidal elevation, average tidal excursion, wind speed and direction, yet none provided a satisfactory explanation for the difference. Residence time based on a hydrodynamic model, however, was very strongly correlated with the observed variation. When the average residence time in the lagoon was low (5 days) the SGD was calculated to be 930 m3 s-1 and when the average residence time was high (9 days) the SGD was quantified as 160 m3 s-1. Radioactive decay is already accounted for in the mass balance model and therefore this correlation must be explained by another process. The Venice Lagoon is characterized by low residence time during periods of spring tides and bora or northerly winds, both of which create exceptionally strong currents in the Venice Lagoon. The currents as well as the large tidal excursion which occurs at spring tides drive a recirculation of seawater through the surface sediments, which greatly increases short-lived Ra activity in the surface waters. This evidence suggests, therefore, that short-lived Ra mass balance studies, which are based on a single survey, may under or overestimate the mean annual SGD pending the hydrodynamics of the investigated location.

  8. Radiochemical constraints on the crustal residence time of submarine hydrothermal fluids: Endeavour Ridge

    SciTech Connect

    Kadko, D. ); Moore, W. )

    1988-03-01

    The {sup 210}Pb/Pb and {sup 228}Ra/{sup 226}Ra ratios measured in fluids and particles venting from the Endeavour Ridge are used to constrain the crustal residence time of the convecting hydrothermal fluid from the initiation of basalt alteration where Mg{sup +2} loss from seawater results in rapidly falling pH conditions, to termination at seafloor venting. The {sup 210}Pb/Pb ratios of hot, low Mg fluids are close to that of the basalts, suggesting a residence time of no greater than ten years. Particles associated with these vents have slightly higher ratios which may in part be due to scavenging of seawater {sup 210}Pb. The {sup 228}Ra/{sup 226}Ra ratios of the fluids and an associated Ba-rich particle samples were also close to the basalt ratios, further constraining the residence time to 3 years or less. These estimates indicate that the mass of fluid interacting with newly formed crust at any one time is less than 9 x 10{sup 13}kg, if the axial heat flux is to be no greater than 30% of the total advective heat loss from the oceanic crust.

  9. Estimation of divergence times from multiprotein sequences for a few mammalian species and several distantly related organisms.

    PubMed

    Nei, M; Xu, P; Glazko, G

    2001-02-27

    When many protein sequences are available for estimating the time of divergence between two species, it is customary to estimate the time for each protein separately and then use the average for all proteins as the final estimate. However, it can be shown that this estimate generally has an upward bias, and that an unbiased estimate is obtained by using distances based on concatenated sequences. We have shown that two concatenation-based distances, i.e., average gamma distance weighted with sequence length (d(2)) and multiprotein gamma distance (d(3)), generally give more satisfactory results than other concatenation-based distances. Using these two distance measures for 104 protein sequences, we estimated the time of divergence between mice and rats to be approximately 33 million years ago. Similarly, the time of divergence between humans and rodents was estimated to be approximately 96 million years ago. We also investigated the dependency of time estimates on statistical methods and various assumptions made by using sequence data from eubacteria, protists, plants, fungi, and animals. Our best estimates of the times of divergence between eubacteria and eukaryotes, between protists and other eukaryotes, and between plants, fungi, and animals were 3, 1.7, and 1.3 billion years ago, respectively. However, estimates of ancient divergence times are subject to a substantial amount of error caused by uncertainty of the molecular clock, horizontal gene transfer, errors in sequence alignments, etc.

  10. 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.

  11. 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.

  12. Towards the reliable calculation of residence time for off-lattice kinetic Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Alexander, Kathleen C.; Schuh, Christopher A.

    2016-08-01

    Kinetic Monte Carlo (KMC) methods have the potential to extend the accessible timescales of off-lattice atomistic simulations beyond the limits of molecular dynamics by making use of transition state theory and parallelization. However, it is a challenge to identify a complete catalog of events accessible to an off-lattice system in order to accurately calculate the residence time for KMC. Here we describe possible approaches to some of the key steps needed to address this problem. These include methods to compare and distinguish individual kinetic events, to deterministically search an energy landscape, and to define local atomic environments. When applied to the ground state  ∑5(2 1 0) grain boundary in copper, these methods achieve a converged residence time, accounting for the full set of kinetically relevant events for this off-lattice system, with calculable uncertainty.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. Impacts of residence time during storage on potential of water saving for grey water recycling system.

    PubMed

    Liu, S; Butler, D; Memon, F A; Makropoulos, C; Avery, L; Jefferson, B

    2010-01-01

    Grey water recycling has been generally accepted and is about to move into practice in terms of sustainable development. Previous research has revealed the bacteria re-growth in grey water and reclaimed municipal water during storage. However, in most present grey water recycling practices, impacts of water quality changes during storage on the system's performance and design regulation have not been addressed. In this paper, performance of a constructed wetland based grey water recycling system was analysed by taking the constraint of residence time during storage into account using an object based household water cycle model. Two indicators, water saving efficiency (WSE) and residence time index (RTI), are employed to reflect the system's performance and residence time during storage respectively. Results show that WSE and RTI change with storage tank volumes oppositely. As both high WSE and RTI cannot be achieved simultaneously, it is concluded that in order to achieve the most cost-effective and safe solution, systems with both small grey and green tanks are needed, whilst accepting that only relatively modest water saving efficiency targets can be achieved. Higher efficiencies will only be practicable if water quality deterioration in the green water tank can be prevented by some means (e.g. disinfection).

  19. Impact of enzyme concentration and residence time on apparent activity recovery in jump dilution analysis.

    PubMed

    Copeland, Robert A; Basavapathruni, Aravind; Moyer, Mikel; Scott, Margaret Porter

    2011-09-15

    Jump dilution analysis is commonly used to evaluate the reversibility of inhibition and to quantify the residence time of the inhibitor-enzyme complex. During hit and lead characterization, one sometimes observes apparently linear progress curves after jump dilution that display activity recoveries that are intermediate between those expected for fully reversible and irreversible inhibition. Computer simulations of progress curves after jump dilution indicate that seemingly linear progress curves can result when dealing with tight-binding inhibitors if substoichiometric concentrations of inhibitor are preincubated with enzyme. In this situation, the activity recovered is comparable to that expected for instantaneously reversible inhibitors. In addition, simulations demonstrate that intermediate values of activity recovery may be observed for compounds with modestly slow dissociation rates (i.e., residence times >0min but ≤20min) when the attending curvature of the data is not accounted for. The observation of intermediate values of recovery can, thus, serve as an indication of either modest residence time or a contaminating inactivator within an inhibitor sample, in either case prompting greater scrutiny of the test compound.

  20. Fertilizer residence time affects nitrogen uptake efficiency and growth of sweet corn.

    PubMed

    Zotarelli, L; Scholberg, J M; Dukes, M D; Muñoz-Carpena, R

    2008-01-01

    Understanding plant N uptake dynamics is critical for increasing fertilizer N uptake efficiency (FUE) and minimize the risk of N leaching. The objective of this research was to determine the effect of residence time of N fertilizer on N uptake and FUE of sweet corn. Plants were grown in 25 L columns during the fall and spring to mimic short-term N uptake dynamics. Nitrogen was applied either 1, 3, or 7 d before a weekly leaching event, using KNO3 solution (total of 393 kg N ha(-1)). Residence times (tR) were tR-1, tR-3, and tR-7 d before weekly removal of residual soil N. Plant N uptake was calculated by comparing weekly N recovery from planted with non-planted columns. During the fall, N uptake values at 70 d after emergence were 59, 73, and 126 kg N ha(-1). During the spring, corresponding values were 54, 108, and 159 kg N ha(-1). A linear response of plant growth and yield to the tR was observed under cooler conditions, whereas a quadratic response occurred under warmer conditions. There was correlation between root length density and yield. It is concluded that increasing N fertilizer residence time, which is indicative of better irrigation practices, enhanced overall sweet corn growth, yield, N uptake, and FUE, consequently reduced the risk of N being leached below the root zone before complete N uptake. PMID:18453447

  1. Fertilizer residence time affects nitrogen uptake efficiency and growth of sweet corn.

    PubMed

    Zotarelli, L; Scholberg, J M; Dukes, M D; Muñoz-Carpena, R

    2008-01-01

    Understanding plant N uptake dynamics is critical for increasing fertilizer N uptake efficiency (FUE) and minimize the risk of N leaching. The objective of this research was to determine the effect of residence time of N fertilizer on N uptake and FUE of sweet corn. Plants were grown in 25 L columns during the fall and spring to mimic short-term N uptake dynamics. Nitrogen was applied either 1, 3, or 7 d before a weekly leaching event, using KNO3 solution (total of 393 kg N ha(-1)). Residence times (tR) were tR-1, tR-3, and tR-7 d before weekly removal of residual soil N. Plant N uptake was calculated by comparing weekly N recovery from planted with non-planted columns. During the fall, N uptake values at 70 d after emergence were 59, 73, and 126 kg N ha(-1). During the spring, corresponding values were 54, 108, and 159 kg N ha(-1). A linear response of plant growth and yield to the tR was observed under cooler conditions, whereas a quadratic response occurred under warmer conditions. There was correlation between root length density and yield. It is concluded that increasing N fertilizer residence time, which is indicative of better irrigation practices, enhanced overall sweet corn growth, yield, N uptake, and FUE, consequently reduced the risk of N being leached below the root zone before complete N uptake.

  2. 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.

  3. Distant Cities, Travelling Tales and Segmented Young Lives: Making and Remaking Youth Exclusion across Time and Place

    ERIC Educational Resources Information Center

    Dillabough, Jo-Anne; McLeod, Julie; Oliver, Caroline

    2015-01-01

    A substantial body of research suggests that incipient moral anxiety is growing in relation to excluded youth, and is manifestly cross-national in nature. While these anxieties are often assumed to be most evident in recent times, historians of childhood and youth persistently remind us of the long history of anxiety recorded in the public record…

  4. 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

  5. Structure and composition of the distant lunar exosphere: Constraints from ARTEMIS observations of ion acceleration in time-varying fields

    NASA Astrophysics Data System (ADS)

    Halekas, J. S.; Poppe, A. R.; Farrell, W. M.; McFadden, J. P.

    2016-06-01

    By analyzing the trajectories of ionized constituents of the lunar exosphere in time-varying electromagnetic fields, we can place constraints on the composition, structure, and dynamics of the lunar exosphere. Heavy ions travel slower than light ions in the same fields, so by observing the lag between field rotations and the response of ions from the lunar exosphere, we can place constraints on the composition of the ions. Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) provides an ideal platform to utilize such an analysis, since its two-probe vantage allows precise timing of the propagation of field discontinuities in the solar wind, and its sensitive plasma instruments can detect the ion response. We demonstrate the utility of this technique by using fully time-dependent charged particle tracing to analyze several minutes of ion observations taken by the two ARTEMIS probes ~3000-5000 km above the dusk terminator on 25 January 2014. The observations from this time period allow us to reach several interesting conclusions. The ion production at altitudes of a few hundred kilometers above the sunlit surface of the Moon has an unexpectedly significant contribution from species with masses of 40 amu or greater. The inferred distribution of the neutral source population has a large scale height, suggesting that micrometeorite impact vaporization and/or sputtering play an important role in the production of neutrals from the surface. Our observations also suggest an asymmetry in ion production, consistent with either a compositional variation in neutral vapor production or a local reduction in solar wind sputtering in magnetic regions of the surface.

  6. Probabilistic approach of water residence time and connectivity using Markov chains with application to tidal embayments

    NASA Astrophysics Data System (ADS)

    Bacher, C.; Filgueira, R.; Guyondet, T.

    2016-01-01

    Markov chain analysis was recently proposed to assess the time scales and preferential pathways into biological or physical networks by computing residence time, first passage time, rates of transfer between nodes and number of passages in a node. We propose to adapt an algorithm already published for simple systems to physical systems described with a high resolution hydrodynamic model. The method is applied to bays and estuaries on the Eastern Coast of Canada for their interest in shellfish aquaculture. Current velocities have been computed by using a 2 dimensional grid of elements and circulation patterns were summarized by averaging Eulerian flows between adjacent elements. Flows and volumes allow computing probabilities of transition between elements and to assess the average time needed by virtual particles to move from one element to another, the rate of transfer between two elements, and the average residence time of each system. We also combined transfer rates and times to assess the main pathways of virtual particles released in farmed areas and the potential influence of farmed areas on other areas. We suggest that Markov chain is complementary to other sets of ecological indicators proposed to analyse the interactions between farmed areas - e.g., depletion index, carrying capacity assessment. Markov chain has several advantages with respect to the estimation of connectivity between pair of sites. It makes possible to estimate transfer rates and times at once in a very quick and efficient way, without the need to perform long term simulations of particle or tracer concentration.

  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. 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. PMID:27034103

  9. Determining Timing of Hepatectomy for Colorectal Cancer with Distant Metastasis According to Imaging-Based Tumor Shrinkage Ratio

    PubMed Central

    Sasaki, Yoshiyuki; Osada, Shinji; Mori, Ryuutarou; Imai, Hisashi; Tanaka, Yoshihiro; Matsuhashi, Nobuhiro; Okumura, Naoki; Nonaka, Kenichi; Takahashi, Takao; Yoshida, Kazuhiro

    2013-01-01

    Background: The optimal timing of surgical resection of liver metastasis remains controversial, and guidelines regarding the upper limits of operative indications have not yet been defined. Surgical indication for metastasis from colorectal cancer (CLM) based on results of preoperative chemotherapy and RNF8 was investigated. Methods: Differences in CLM size on CT were evaluated as shrinkage rate/day by dividing tumor shrinkage rates by the interval in days between CT. Levels of RNF8 of resected colorectal cancer and CLM frozen specimen were detected. Results: When the cut line for shrinkage rate at 12 weeks was set at 0.35%, disease-free survival was significantly better in patients with a shrinkage rate >0.35% vs. ≤0.35% (p=0.003). RNF8 expression was significantly higher in Tis (p=0.001). In liver metastasis, RNF8 expression level was significantly lower in patients with partial response to FOLFOX than with stable disease, (p=0.017). Conclusions: A strategy of FOLFOX administration for 12 weeks to patients with low RNF8 expression and hepatectomy planned after 4 weeks rest may be accepted as the best therapeutic option for treating CLM. PMID:23935401

  10. 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

  11. 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. PMID:27670576

  12. 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

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

    PubMed

    Koochi, Hakimeh; Ebrahimi, Fatemeh

    2014-09-01

    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.

  14. Noble gas residence times of saline waters within crystalline bedrock, Outokumpu Deep Drill Hole, Finland

    NASA Astrophysics Data System (ADS)

    Kietäväinen, Riikka; Ahonen, Lasse; Kukkonen, Ilmo T.; Niedermann, Samuel; Wiersberg, Thomas

    2014-11-01

    Noble gas residence times of saline groundwaters from the 2516 m deep Outokumpu Deep Drill Hole, located within the Precambrian crystalline bedrock of the Fennoscandian Shield in Finland, are presented. The accumulation of radiogenic (4He, 40Ar) and nucleogenic (21Ne) noble gas isotopes in situ together with the effects of diffusion are considered. Fluid samples were collected from depths between 180 and 2480 m below surface, allowing us to compare the modelled values with the measured concentrations along a vertical depth profile. The results show that while the concentrations in the upper part are likely affected by diffusion, there is no indication of diffusive loss at or below 500 m depth. Furthermore, no mantle derived gases were found unequivocally. Previous studies have shown that distinct vertical variation occurs both in geochemistry and microbial community structuring along the drill hole, indicating stagnant waters with no significant exchange of fluids between different fracture systems or with surface waters. Therefore in situ accumulation is the most plausible model for the determination of noble gas residence times. The results show that the saline groundwaters in Outokumpu are remarkably old, with most of the samples indicating residence times between ∼20 and 50 Ma. Although being first order approximations, the ages of the fluids clearly indicate that their formation must predate more recent events, such as Quaternary glaciations. Isolation within the crust since the Eocene-Miocene epochs has also direct implications to the deep biosphere found at Outokumpu. These ecosystems must have been isolated for a long time and thus very likely rely on energy and carbon sources such as H2 and CO2 from groundwater and adjacent bedrock rather than from the ground surface.

  15. 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.

  16. Fluxes and residence times of hydrocarbons in the coastal Mediterranean: How important are the biota?

    NASA Astrophysics Data System (ADS)

    Burns, K. A.; Villeneuve, J.-P.; Fowler, S. W.

    1985-03-01

    Settling particles collected in semi-permanent particle interceptor traps (PITs) moored at 100 m depth in a water column of 250 m at a distance of 2 km from the Monaco coast in the north western Mediterranean were analyzed for petroleum and chlorinated hydrocarbons. Time series observations of material collected between 1979 and 1982 showed that vertical mass and organic contaminant fluxes varied seasonally by an order of magnitude and corresponded with general cycles of zooplankton biomass and primary productivity in surface waters. Analyses of surface seawater including surface microlayer, dissolved and particulate phases are reported along with data from zooplankton, fecal material, and sediments collected near the trap station. Settling particles displayed two predominant patterns of petroleum hydrocarbons similar to the patterns of both 'dissolved' and 'particulate' hydrocarbons seen in surface seawater. Residence times of hydrocarbons in surface waters were computed according to recent partitioning models and compared with those calculated from the fluxes of actually settling particles and from sediment data. PCB fluxes calculated from sediment and settling particles averaged 2 to 4 ng cm -2 yr -1 with good agreement between data bases. Petroleum fluxes on settling particles averaged 8 μg cm -2 yr -1 but fluxes based on sediment concentrations showed that 90% of the petroleum hydrocarbons transported to depth were degraded before incorporation into compacted sediments. By evaluating fluxes and residence times with three independent data bases we conclude that the biota are effective in transporting both particulate and dissolved organic contaminants to ocean sediments. Furthermore, the residence times of these materials in surface waters do not vary as much as would be predicted on the basis of their widely differing solubilities.

  17. 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.

  18. 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.

  19. 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.

  20. HUBBLE PINPOINTS DISTANT SUPERNOVAE

    NASA Technical Reports Server (NTRS)

    2002-01-01

    These Hubble Space Telescope images pinpoint three distant supernovae, which exploded and died billions of years ago. Scientists are using these faraway light sources to estimate if the universe was expanding at a faster rate long ago and is now slowing down. Images of SN 1997cj are in the left hand column; SN 1997ce, in the middle; and SN 1997ck, on the right. All images were taken by the Hubble telescope's Wide Field and Planetary Camera 2. The top row of images are wider views of the supernovae. The supernovae were discovered in April 1997 in a ground-based survey at the Canada-France-Hawaii Telescope on Mauna Kea, Hawaii. Once the supernovae were discovered, the Hubble telescope was used to distinguish the supernovae from the light of their host galaxies. A series of Hubble telescope images were taken in May and June 1997 as the supernovae faded. Six Hubble telescope observations spanning five weeks were taken for each supernova. This time series enabled scientists to measure the brightness and create a light curve. Scientists then used the light curve to make an accurate estimate of the distances to the supernovae. Scientists combined the estimated distance with the measured velocity of the supernova's host galaxy to determine the expansion rate of the universe in the past (5 to 7 billion years ago) and compare it with the current rate. These supernovae belong to a class called Type Ia, which are considered reliable distance indicators. Looking at great distances also means looking back in time because of the finite velocity of light. SN 1997ck exploded when the universe was half its present age. It is the most distant supernova ever discovered (at a redshift of 0.97), erupting 7.7 billion years ago. The two other supernovae exploded about 5 billion years ago. SN 1997ce has a redshift of 0.44; SN 1997cj, 0.50. SN 1997ck is in the constellation Hercules, SN 1997ce is in Lynx, just north of Gemini; and SN 1997cj is in Ursa Major, near the Hubble Deep Field

  1. Activity in distant comets

    NASA Technical Reports Server (NTRS)

    Luu, Jane X.

    1992-01-01

    Activity in distant comets remains a mystery in the sense that we still have no complete theory to explain the various types of activity exhibited by different comets at large distances. This paper explores the factors that should play a role in determining activity in a distant comet, especially in the cases of comet P/Tempel 2, comet Schwassmann-Wachmann 1, and 2060 Chiron.

  2. 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

  3. 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

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    Radioactive tracer 82Br 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.

  6. 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.

  7. Does Be10 Underestimate Residence Time of Critical Zones in Acid Environments?

    NASA Astrophysics Data System (ADS)

    Richter, D., Jr.

    2014-12-01

    Meteoric 10Be inventories were coupled with with mass balance of 9Be (bedrock to 18.3 meters soil-saprolite profile) to estimate the soil residence time (SRT) of a biogeomorphically stable Ultisol. We estimate SRT after correcting for observed9Be losses, which indicate that more than half of the 9Be weathered from primary minerals had been leached from the soil and saprolite. Our estimates of minimum SRT range between 1.3-1.4 Ma and between 2.6-3.1 Ma under high and low (2.0 and 1.3 × 106 atoms cm-2 yr-1, respectively) estimates of atmospheric 10Be deposition. Denudation rates of the physiographic region corroborate our residence time estimates. We double to quadruple the pedogenic time constraints of interfluves on the Southern Piedmont, and demonstrate that assumptions of complete meteoric 10Be retention in acidic soil systems need questioning. The results may have far-reaching consequences for soil, sediment, river, and ocean research using meteoric 10Be.

  8. 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).

  9. 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.

  10. 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.

  11. 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

    2016-01-01

    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.

  12. Thiolated α-Cyclodextrin: The Invisible Choice to Prolong Ocular Drug Residence Time.

    PubMed

    Ijaz, Muhammad; Ahmad, Mahmood; Akhtar, Naveed; Laffleur, Flavia; Bernkop-Schnürch, Andreas

    2016-09-01

    It was the aim of this study to develop cysteamine-conjugated α-cyclodextrin (α-CD) enabled to form disulfide bonds with cysteine-rich substructures of the ocular mucus layer to provide a prolonged residence time of incorporated drugs at the site of action. Cysteamine was covalently attached to oxidized α-CD via reductive amination. The resulting α-CD-cysteamine conjugates (α-CD-Cys) were characterized regarding the amount of free thiol groups attached to the oligomer backbone via Ellman's reagent; resazurin assay was conducted for cytotoxicity, and mucoadhesive properties were evaluated on porcine intestinal and ocular mucosal tissues. Furthermore, albino rabbits were used for assessing the irritation-masking effects of α-CD-Cys. Free thiol groups attached to the backbone were in the range of 558 ± 24-1143 ± 92 μmol/g. None of these α-CD-Cys unduly affected the viability of Caco-2 cells in a concentration of 0.5%. Mucoadhesive properties of α-CD-Cys were up to 32-fold improved compared to unmodified α-CD. Encapsulation of cetirizine into α-CD-Cys resulted in significantly reduced local ocular mucosal irritation of this model drug. According to these results, α-CD-Cys is a promising new tool to prolong drug residence time on the ocular mucosal surface. PMID:27233687

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Fluid flow pattern and water residence time in waste stabilisation ponds.

    PubMed

    Badrot-Nico, F; Guinot, V; Brissaud, F

    2009-01-01

    As treatment processes are kinetic-dependent, a consistent description of water residence times is essential to the prediction of waste stabilization ponds performance. A physically-based 3D transient CFD model simulating the water velocity, temperature and concentration fields as a function of all influent meteorological factors--wind speed and direction, solar radiation, air temperature and relative humidity--was used to identify the relationships between the meteorological conditions and the hydrodynamic patterns and water residence times distributions in a polishing pond. The required meteorological data were recorded on site and water temperatures recorded at 10 sampling sites for 141 days. Stratification events appear on very calm days for wind speeds lower than 3 m s(-1) and on sunny days for wind speeds lower than 5 m s(-1). De-stratification is related to two mixing processes: nightly convection cells and global mixing patterns. Numerical tracer experiments show that the results of the flow patterns can be evaluated using the dispersed flow regime approximation and, for wind speeds exceeding 6 m s(-1), the completely stirred tank reactor assumption. PMID:19342800

  18. 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.

  19. 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.

  20. Evaluation of membrane bioreactor performance via residence time distribution: effects of membrane configuration and mixing.

    PubMed

    Wang, Y; Ong, K W; Brannock, M W D; Leslie, G L

    2008-01-01

    Unlike conventional wastewater treatment systems that have a single effluent discharge point, membrane bioreactors (MBR) may have multiple extraction points resulting from the location of the membrane element in the reactor. This leads to multiple residence time distributions for an MBR system. One method to characterise the mixing is based on the concept of residence time distribution (RTD). A set of RTDs were generated using the conservative tracer, lithium chloride, for pilot plant MBRs with capacity up to 300 m3/day. Flat sheet and hollow fibre pilot plant MBR systems were operated in parallel on primary effluent collected at the Bedok Water Reclamation Plant in the republic of Singapore. Analysis of the RTD profiles indicated that membrane geometry did not impact on the kinetic conversion associated with nitrification because both MBRs were in well mixed conditions. However, the energy required to achieve perfect mixing with a hollow fibre module MBR, as defined by the velocity gradient, was lower than that with a flat sheet module MBR. The implication is that energy input associated with reactor mixing will depend on the configuration of the membrane. The difference in energy requirements between flat sheets and hollow fibres is such that careful consideration should be given to membrane selection in larger municipal installations. PMID:18309212

  1. 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.

  2. A DISTANT QUASAR'S BRILLIANT LIGHT

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The arrow in this image, taken by a ground-based telescope, points to a distant quasar, the brilliant core of an active galaxy residing billions of light-years from Earth. As light from this faraway object travels across space, it picks up information on galaxies and the vast clouds of material between galaxies as it moves through them. The Space Telescope Imaging Spectrograph aboard NASA's Hubble Space Telescope decoded the quasar's light to find the spectral 'fingerprints' of highly ionized (energized) oxygen, which had mixed with invisible clouds of hydrogen in intergalactic space. The quasar's brilliant beam pierced at least four separate filaments of the invisible hydrogen laced with the telltale oxygen. The presence of oxygen between the galaxies implies there are huge quantities of hydrogen in the universe. Credits: WIYN Telescope at Kitt Peak National Observatory in Arizona. The telescope is owned and operated by the University of Wisconsin, Indiana University, Yale University, and the National Optical Astronomy Observatories.

  3. 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).

  4. 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.

  5. 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.

  6. Signal detection via residence-time asymmetry in noisy bistable devices.

    PubMed

    Bulsara, A R; Seberino, C; Gammaitoni, L; Karlsson, M F; Lundqvist, B; Robinson, J W C

    2003-01-01

    We introduce a dynamical readout description for a wide class of nonlinear dynamic sensors operating in a noisy environment. The presence of weak unknown signals is assessed via the monitoring of the residence time in the metastable attractors of the system, in the presence of a known, usually time-periodic, bias signal. This operational scenario can mitigate the effects of sensor noise, providing a greatly simplified readout scheme, as well as significantly reduced processing procedures. Such devices can also show a wide variety of interesting dynamical features. This scheme for quantifying the response of a nonlinear dynamic device has been implemented in experiments involving a simple laboratory version of a fluxgate magnetometer. We present the results of the experiments and demonstrate that they match the theoretical predictions reasonably well. PMID:12636577

  7. 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.

  8. 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.

  9. 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. PMID:27040544

  10. Controlled by Distant Explosions

    NASA Astrophysics Data System (ADS)

    2007-03-01

    VLT Automatically Takes Detailed Spectra of Gamma-Ray Burst Afterglows Only Minutes After Discovery A time-series of high-resolution spectra in the optical and ultraviolet has twice been obtained just a few minutes after the detection of a gamma-ray bust explosion in a distant galaxy. The international team of astronomers responsible for these observations derived new conclusive evidence about the nature of the surroundings of these powerful explosions linked to the death of massive stars. At 11:08 pm on 17 April 2006, an alarm rang in the Control Room of ESO's Very Large Telescope on Paranal, Chile. Fortunately, it did not announce any catastrophe on the mountain, nor with one of the world's largest telescopes. Instead, it signalled the doom of a massive star, 9.3 billion light-years away, whose final scream of agony - a powerful burst of gamma rays - had been recorded by the Swift satellite only two minutes earlier. The alarm was triggered by the activation of the VLT Rapid Response Mode, a novel system that allows for robotic observations without any human intervention, except for the alignment of the spectrograph slit. ESO PR Photo 17a/07 ESO PR Photo 17a/07 Triggered by an Explosion Starting less than 10 minutes after the Swift detection, a series of spectra of increasing integration times (3, 5, 10, 20, 40 and 80 minutes) were taken with the Ultraviolet and Visual Echelle Spectrograph (UVES), mounted on Kueyen, the second Unit Telescope of the VLT. "With the Rapid Response Mode, the VLT is directly controlled by a distant explosion," said ESO astronomer Paul Vreeswijk, who requested the observations and is lead-author of the paper reporting the results. "All I really had to do, once I was informed of the gamma-ray burst detection, was to phone the staff astronomers at the Paranal Observatory, Stefano Bagnulo and Stan Stefl, to check that everything was fine." The first spectrum of this time series was the quickest ever taken of a gamma-ray burst afterglow

  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. 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

  13. Setting, distant view looking east/southeast toward north and west elevations ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Setting, distant view looking east/southeast toward north and west elevations of Ranger's Residence, with rock formations in the background - Toney Residence, 10700 Escondido Canyon Road, Agua Dulce, Los Angeles County, CA

  14. 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

  15. Constructed wetlands dye study to determine flow patterns and residence time

    SciTech Connect

    Cano, M.L.; Dorn, P.B.; Vipond, T.E.; Dunn, A.N.; Hawkins, B.F.

    1995-12-31

    Two pilot-scale wetlands (30 m x 6 m) were constructed for tertiary treatment for refinery effluent to remove divalent cationic metals and chronic toxicity. The wetlands have free water surface flow ({approximately}30 cm depth) and are populated with bulrush. To understand the removal of specific pollutants by the biological system and design full scale systems, it is necessary to determine the flow pattern and residence time for each of the wetland cells. A tracer study using a slug injection technique was conducted with rhodamine WT dye. An engineering approach was used to determine retention times by measuring the dye effluent concentration as a function of time and analyzing this profile. Dispersion indexes for the wetlands were also calculated. In addition, flow patterns were determined by periodically sampling a grid within each of the wetland cells. The dye study results indicated: (1) the actual retention time was less than the theoretical retention time (based on volume and flow rate) and (2) partial plug flow regime with a dispersion index of 3.74 was present. These data will be useful for future modeling of pollutant removal by the wetland cells and for the design of full scale systems.

  16. 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

  17. Residence time of contaminants released in surface coal mines -- a wind-tunnel study

    SciTech Connect

    Thompson, R.S.

    1994-12-31

    Surface coal mining operations (blasting, shoveling, loading, trucking, etc.) are sources of airborne particles. The 1990 Clean Air Act Amendments direct the EPA to analyze the accuracy of the Industrial Source Complex model and the AP-42 emission factors, and to make revisions as may be necessary to eliminate any significant over-prediction of air concentration of fugitive particles from surface coal mines. A wind-tunnel study was performed at the US EPA`s Fluid Modeling Facility to investigate dispersion from surface coal mines in support of the dispersion modeling activities. Described here is the portion of the study directed at determining the residence time that material released near the floor of a mine will stay within the mine.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. TSPO ligand residence time influences human glioblastoma multiforme cell death/life balance.

    PubMed

    Costa, Barbara; Da Pozzo, Eleonora; Giacomelli, Chiara; Taliani, Sabrina; Bendinelli, Sara; Barresi, Elisabetta; Da Settimo, Federico; Martini, Claudia

    2015-03-01

    Ligands addressed to the mitochondrial Translocator Protein (TSPO) have been suggested as cell death/life and steroidogenesis modulators. Thus, TSPO ligands have been proposed as drug candidates in several diseases; nevertheless, a correlation between their binding affinity and in vitro efficacy has not been demonstrated yet, questioning the specificity of the observed effects. Since drug-target residence time is an emerging parameter able to influence drug pharmacological features, herein, the interaction between TSPO and irDE-MPIGA, a covalent TSPO ligand, was investigated in order to explore TSPO control on death/life processes in a standardized glioblastoma cell setting. After 90 min irDE-MPIGA cell treatment, 25 nM ligand concentration saturated irreversibly all TSPO binding sites; after 24 h, TSPO de-novo synthesis occurred and about 40 % TSPO binding sites resulted covalently bound to irDE-MPIGA. During cell culture treatments, several dynamic events were observed: (a) early apoptotic markers appeared, such as mitochondrial membrane potential collapse (at 3 h) and externalization of phosphatidylserine (at 6 h); (b) cell viability was reduced (at 6 h), without cell cycle arrest. After digitonin-permeabilized cell suspension treatment, a modulation of mitochondrial permeability transition pore was evidenced. Similar effects were elicited by the reversible TSPO ligand PIGA only when applied at micromolar dose. Interestingly, after 6 h, irDE-MPIGA cell exposure restored cell survival parameters. These results highlighted the ligand-target residence time and the cellular setting are crucial parameters that should be taken into account to understand the drug binding affinity and efficacy correlation and, above all, to translate efficiently cellular drug responses from bench to bedside.

  3. 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.

  4. 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. PMID:21761932

  5. Activity size distribution and residence time of 7Be aerosols in the Arctic atmosphere

    NASA Astrophysics Data System (ADS)

    Ioannidou, Alexandra; Paatero, Jussi

    2014-05-01

    The activity size distributions of the natural radionuclide tracer 7Be in different size range fractions (<0.39 μm, 0.39-0.69 μm, 0.69-1.3 μm, 1.3-2.1 μm, 2.1-4.2 μm, 4.2-10.2 μm and >10.2 μm) were determined in the boreal atmosphere in the Arctic Research Centre of the Finnish Meteorological Institute (FMI) at Sodankylä, Finland (67°22‧ N, 26°38‧ E, 180 m asl). The activity median aerodynamic diameter (AMAD) ranged from 0.54 μm to 1.05 μm (average 0.83 μm). A residence time of about 8 days applies to aerosols of 0.83 μm diameter, representing the residence of aerosol particles in arctic environment. The observed positive correlation between AMAD values and RH% can be explained by the fact that condensation during high relative humidity conditions becomes more intense, resulting in increased particle sizes of atmospheric aerosols. However, greater aerosol particle sizes means higher wet scavenging rate of aerosols and as a result lower activity concentration of 7Be in the atmosphere, explaining the anti-correlation between the AMAD values and activity concentrations of 7Be. But this associated with possibly higher scavenging rates of aerosols does not necessarily alone explain the anti-correlation between the AMAD and the 7Be activities. The air mass origin associated with synoptic scale weather phenomena may contribute to that too. The Flextra model was used to assess the transport pattern and to explain the deviation in radionuclide activity concentrations and AMAD values observed in the site of investigation.

  6. PEGylation of antibody fragments greatly increases their local residence time following delivery to the respiratory tract.

    PubMed

    Koussoroplis, Salome Juliette; Paulissen, Geneviève; Tyteca, Donatienne; Goldansaz, Hadi; Todoroff, Julie; Barilly, Céline; Uyttenhove, Catherine; Van Snick, Jacques; Cataldo, Didier; Vanbever, Rita

    2014-08-10

    Inhalation aerosols offer a targeted therapy for respiratory diseases. However, the therapeutic efficacy of inhaled biopharmaceuticals is limited by the rapid clearance of macromolecules in the lungs. The aim of this research was to study the effects of the PEGylation of antibody fragments on their local residence time after administration to the respiratory tract. We demonstrate that the conjugation of a two-armed 40-kDa polyethylene glycol (PEG) chain to anti-interleukin-17A (IL-17A) F(ab')2 and anti-IL-13 Fab' greatly prolonged the presence of these fragments within the lungs of mice. The content of PEGylated antibody fragments within the lungs plateaued up to 4h post-delivery, whereas the clearance of unconjugated proteins started immediately after administration. Forty-eight hours post-delivery, F(ab')2 and Fab' contents in the lungs had decreased to 10 and 14% of the dose initially deposited, respectively. However, this value was 40% for both PEG40-F(ab')2 and PEG40-Fab'. The prolonged pulmonary residency of the anti-IL-17A PEG40-F(ab')2 translated into an improved efficacy in reducing lung inflammation in a murine model of house dust mite-induced lung inflammation. We demonstrate that PEGylated proteins were principally retained within the lung lumen rather than the nasal cavities or lung parenchyma. In addition, we report that PEG increased pulmonary retention of antibody fragments through mucoadhesion and escape from alveolar macrophages rather than increased hydrodynamic size or improved enzymatic stability. The PEGylation of proteins might find broad application in the local delivery of therapeutic proteins to diseased airways. PMID:24845126

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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…

  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. TSPO ligand residence time: a new parameter to predict compound neurosteroidogenic efficacy.

    PubMed

    Costa, Barbara; Da Pozzo, Eleonora; Giacomelli, Chiara; Barresi, Elisabetta; Taliani, Sabrina; Da Settimo, Federico; Martini, Claudia

    2016-01-11

    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.

  16. 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.

  17. 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

  18. 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

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. 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

  4. 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

  5. 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

  6. Tidal Circulation and Residence Time in a Macrotidal Estuary: Cobscook Bay, Maine

    NASA Astrophysics Data System (ADS)

    Brooks, D. A.; Baca, M. W.; Lo, Y.-T.

    1999-11-01

    Cobscook Bay is a macrotidal estuary situated near the entrance to the Bay of Fundy, where the mean semi-diurnal tidal range is 5·7 m. Vigorous tidal currents in the bay maintain cold water temperatures year-round and effectively exchange nutrients and other dissolved matter with offshore waters. Partly because of the cold water and tidal exchange, a net-pen salmon aquaculture industry has rapidly expanded in the last decade, raising questions about sustainable levels of production in the environmentally pristine bay. The present study addresses the question of dispersion and flushing of materials in the bay, using a three-dimensional numerical model to simulate the circulation driven by the semi-diurnal tide and runoff from principal rivers. With initialization based on May 1995 cruise data, the results show that the tidal-mean flushing times for neutral surface particles vary from less than one day in the main channel near the entrance to more than a week in the extremities of the inner arms of the bay. A bay-wide average flushing time is about two days, or four tidal cycles, but the detailed distribution is strongly influenced by a pair of counter-rotating eddies that forms in the central bay during each flooding tide. The eddy pattern preferentially directs the initial flood into a southern arm of the bay, where particles and dissolved materials are sequestered. The effective horizontal mixing coefficient in the main channel of the central bay is 300-400 m 2 s -1, leading to rapid dispersal of particles and pollutants in the along-channel direction and into the shallow inner arms of the bay where they tend to accumulate. A map of tidal-mean residence time indicates that most current aquaculture sites are located in reasonably well flushed regions.

  7. 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.

  8. 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

  9. The effect of solids residence time on phosphorus adsorption to hydrous ferric oxide floc.

    PubMed

    Conidi, Daniela; Parker, Wayne J

    2015-11-01

    The impact of solids residence time (SRT) on phosphate adsorption to hydrous ferric oxide (HFO) floc when striving for ultra-low P concentrations was characterized and an equilibrium model that describes the adsorption of P onto HFO floc of different ages was developed. The results showed that fresh HFO had a higher adsorption capacity in comparison to aged (2.8, 7.4, 10.8 and 22.8 days) HFO and contributed substantially to P removal at steady state. P adsorption onto HFO solids was determined to be best described by the Freundlich isotherm. P desorption from HFO solids was negligible supporting the hypothesis that chemisorption is the mechanism of P adsorption on HFO solids. A model that included the contribution of different classes of HFO solids (i.e. High, Low or Old, containing high concentration, low concentration or no active surface sites, respectively) to adsorption onto HFO from a sequencing batch reactor (SBR) system was found to adequately describe P adsorption onto HFO solids of different ages. From the model it was determined that the fractions of High and Low HFO decreased with SRT while the fraction of Old HFO increased with SRT. The transformation of High HFO to Low HFO did not limit the overall production of Old HFO and the fresh HFO solids contributed more to P removal at steady state than the aged solids.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. RESIDENCE TIMES OF PARTICLES IN DIFFUSIVE PROTOPLANETARY DISK ENVIRONMENTS. I. VERTICAL MOTIONS

    SciTech Connect

    Ciesla, F. J.

    2010-11-01

    The chemical and physical evolution of primitive materials in protoplanetary disks are determined by the types of environments they are exposed to and their residence times within each environment. Here, a method for calculating representative paths of materials in diffusive protoplanetary disks is developed and applied to understanding how the vertical trajectories that particles take impact their overall evolution. The methods are general enough to be applied to disks with uniform diffusivity, the so-called constant-{alpha} cases, and disks with a spatially varying diffusivity, such as expected in 'layered-disks'. The average long-term dynamical evolution of small particles and gaseous molecules is independent of the specific form of the diffusivity in that they spend comparable fractions of their lifetimes at different heights in the disk. However, the paths that individual particles and molecules take depend strongly on the form of the diffusivity leading to a different range of behavior of particles in terms of deviations from the mean. As temperatures, gas densities, chemical abundances, and photon fluxes will vary with height in protoplanetary disks, the different paths taken by primitive materials will lead to differences in their chemical and physical evolution. Examples of differences in gas phase chemistry and photochemistry are explored here. The methods outlined here provide a powerful tool that can be integrated with chemical models to understand the formation and evolution of primitive materials in protoplanetary disks on timescales of 10{sup 5}-10{sup 6} years.

  16. 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. PMID:26047352

  17. Tubular biofilter for toluene removal under various organic loading rates and gas empty bed residence times.

    PubMed

    Chen, Hong; Yang, Chunping; Zeng, Guangming; Luo, Shenglian; Yu, Guanlong

    2012-10-01

    A tubular biofilter (TBF) which consisted of a closed chamber, a polyurethane sponge tube and a nutrient solution distributor was developed and evaluated under organic loading rates (OL) ranging from 18.7 to 149.3 gm(-3)h(-1) and gas empty bed residence times (EBRTs) of 30-5.0 s. Using toluene as model VOC, the startup of the TBF lasted approximately 7 weeks. The removal efficiency decreased from 99% to 52.2% when OL was increased from 18.7 to 149.3g toluene m(-3)h(-1) at 15s, but did not decline significantly when the EBRT was reduced from 30 to 5.0 s at 18.7 gm(-3)h(-1). Biomass concentration did not increase significantly within the sponge tube during the 391 days' operation as observed through the Plexiglas pipe of the TBF. The TBF is suitable for treating waste gases with low toluene concentrations even at high gas flow and over long periods.

  18. Sand residence times of one million years in the Namib Sand Sea from cosmogenic nuclides

    NASA Astrophysics Data System (ADS)

    Vermeesch, P.; Fenton, C. R.; Kober, F.; Wiggs, G. F. S.; Bristow, C. S.; Xu, S.

    2010-12-01

    The Namib Sand Sea is one of the world's oldest and largest sand deserts, yet little is known about the source of the sand in this, or other large deserts. In particular, it is unclear whether the sand is derived from local sediment or comes from remote sources. The relatively uniform appearance of dune sands and low compositional variability within dune fields make it difficult to address this question. Here we combine cosmogenic-nuclide measurements and geochronological techniques to assess the provenance and migration history of sand grains in the Namib Sand Sea. We use U-Pb geochronology of detrital zircons to show that the primary source of sand is the Orange River at the southern edge of the Namib desert. Our burial ages obtained from measurements of the cosmogenic nuclides 10Be, 26Al and 21Ne suggest that the residence time of sand within the sand sea is at least one million years. We therefore conclude that, despite large climatic changes in the Namib region associated with Quaternary glacial-interglacial cycles, the area currently occupied by the Namib Sand Sea has never been entirely devoid of sand during the past million years.

  19. Subunit stabilization and polyethylene glycolation of cocaine esterase improves in vivo residence time.

    PubMed

    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

    2011-12-01

    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

  20. 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.

  1. [Distant mental influence on living organisms].

    PubMed

    Bonilla, Ernesto

    2013-12-01

    This article reviews studies of distant mental influence on living organisms, including mental suggestions of sleeping and awakening, mental influence at long distances, mental interactions with remote biological systems, mental effects on physiological activity and the sense of being stared at. Significant effects of distant mental influence have been shown in several randomized controlled trials in humans, animals, plants, bacteria and cells in the laboratory. Although distant mental influence on living organisms appears to contradict our ordinary sense of reality and the laws defined by conventional science, several hypotheses have been proposed to explain the observed effects; they include skeptical, signal transfer, field, multidimensional space/time and quantum mechanics hypotheses. In conclusion, as the progress of physics continues to expand our comprehension of reality, a rational explanation for distant mind-matter interaction will emerge and, as history has shown repeatedly, the supernatural events will evolve into paranormal and then, into normal ones, as the scientific frontiers expand. PMID:24502184

  2. [Distant mental influence on living organisms].

    PubMed

    Bonilla, Ernesto

    2013-12-01

    This article reviews studies of distant mental influence on living organisms, including mental suggestions of sleeping and awakening, mental influence at long distances, mental interactions with remote biological systems, mental effects on physiological activity and the sense of being stared at. Significant effects of distant mental influence have been shown in several randomized controlled trials in humans, animals, plants, bacteria and cells in the laboratory. Although distant mental influence on living organisms appears to contradict our ordinary sense of reality and the laws defined by conventional science, several hypotheses have been proposed to explain the observed effects; they include skeptical, signal transfer, field, multidimensional space/time and quantum mechanics hypotheses. In conclusion, as the progress of physics continues to expand our comprehension of reality, a rational explanation for distant mind-matter interaction will emerge and, as history has shown repeatedly, the supernatural events will evolve into paranormal and then, into normal ones, as the scientific frontiers expand.

  3. Impact of model geometry and recharge rates on catchment's residence time distributions - numerical experiments

    NASA Astrophysics Data System (ADS)

    Neubauer, M.; Musolff, A.; Fleckenstein, J. H.

    2013-12-01

    Residence time distributions (RTD) of water in catchments are promising tools to characterize and model solute transport on a larger scale. In the last decade, much research has been conducted on the estimation and the application of RTD's. However, there are still some major issues to be addressed to complex derivation, parameterization and transient behavior. Through improved remote sensing data, the surface elevation can mostly be resolved in detail, while subsurface volumes and boundaries remain highly undetermined. Our objectives are to systematically evaluate the impact of different depths and geometries of the domain bottom and groundwater recharge rates on RTD's. The study site is a small (1.6 km2) headwater catchment located within the Harz Mountains, Germany. For this catchment long time series of climate, discharge and hydrochemistry are available while groundwater flow field and subsurface structure are less known. The site is intensively influenced by agricultural land use and exhibits strong seasonal dynamics of water flow and hydrochemistry due to the snowmelt. The modeling was performed using HydroGeoSphere, a coupled surface and subsurface model, which solves the Richards Equation for variable saturated soils. The Open Source software Paraview and R was chosen as postprocessors to perform and analyze forward particle tracking algorithms under steady state conditions. Ten depth and geometry scenarios of the domain bottom were created (5 horizontal bottom geometries - constant base and 5 variable bottom geometries - parallel to surface topography; both minimum depths ranging from 2 m to 50 m). The model's internal structure was discretized by two homogenous layers (averaged catchment representation) parallel to the input digital elevation model (2x2 m). The geometry scenarios were combined with fifteen steady state simulations for different groundwater recharge rate scenarios (0.1 mm up to 15 mm per day). Model results indicate a strong influence of

  4. Flow residence time and regions of intraluminal thrombus deposition in intracranial aneurysms.

    PubMed

    Rayz, V L; Boussel, L; Ge, L; Leach, J R; Martin, A J; Lawton, M T; McCulloch, C; Saloner, D

    2010-10-01

    Thrombus formation in intracranial aneurysms, while sometimes stabilizing lesion growth, can present additional risk of thrombo-embolism. The role of hemodynamics in the progression of aneurysmal disease can be elucidated by patient-specific computational modeling. In our previous work, patient-specific computational fluid dynamics (CFD) models were constructed from MRI data for three patients who had fusiform basilar aneurysms that were thrombus-free and then proceeded to develop intraluminal thrombus. In this study, we investigated the effect of increased flow residence time (RT) by modeling passive scalar advection in the same aneurysmal geometries. Non-Newtonian pulsatile flow simulations were carried out in base-line geometries and a new postprocessing technique, referred to as "virtual ink" and based on the passive scalar distribution maps, was used to visualize the flow and estimate the flow RT. The virtual ink technique clearly depicted regions of flow separation. The flow RT at different locations adjacent to aneurysmal walls was calculated as the time the virtual ink scalar remained above a threshold value. The RT values obtained in different areas were then correlated with the location of intra-aneurysmal thrombus observed at a follow-up MR study. For each patient, the wall shear stress (WSS) distribution was also obtained from CFD simulations and correlated with thrombus location. The correlation analysis determined a significant relationship between regions where CFD predicted either an increased RT or low WSS and the regions where thrombus deposition was observed to occur in vivo. A model including both low WSS and increased RT predicted thrombus-prone regions significantly better than the models with RT or WSS alone. PMID:20499185

  5. Flow Residence Time and Regions of Intraluminal Thrombus Deposition in Intracranial Aneurysms

    PubMed Central

    Boussel, L.; Ge, L.; Leach, J. R.; Martin, A. J.; Lawton, M. T.; McCulloch, C.; Saloner, D.

    2010-01-01

    Thrombus formation in intracranial aneurysms, while sometimes stabilizing lesion growth, can present additional risk of thrombo-embolism. The role of hemodynamics in the progression of aneurysmal disease can be elucidated by patient-specific computational modeling. In our previous work, patient-specific computational fluid dynamics (CFD) models were constructed from MRI data for three patients who had fusiform basilar aneurysms that were thrombus-free and then proceeded to develop intraluminal thrombus. In this study, we investigated the effect of increased flow residence time (RT) by modeling passive scalar advection in the same aneurysmal geometries. Non-Newtonian pulsatile flow simulations were carried out in base-line geometries and a new postprocessing technique, referred to as “virtual ink” and based on the passive scalar distribution maps, was used to visualize the flow and estimate the flow RT. The virtual ink technique clearly depicted regions of flow separation. The flow RT at different locations adjacent to aneurysmal walls was calculated as the time the virtual ink scalar remained above a threshold value. The RT values obtained in different areas were then correlated with the location of intra-aneurysmal thrombus observed at a follow-up MR study. For each patient, the wall shear stress (WSS) distribution was also obtained from CFD simulations and correlated with thrombus location. The correlation analysis determined a significant relationship between regions where CFD predicted either an increased RT or low WSS and the regions where thrombus deposition was observed to occur in vivo. A model including both low WSS and increased RT predicted thrombus-prone regions significantly better than the models with RT or WSS alone. PMID:20499185

  6. 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.

  7. 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

  8. 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.

  9. Distant Kuiper Belt Objects

    NASA Astrophysics Data System (ADS)

    Allen, R. Lynne; Bernstein, Gary; Malhotra, Renu

    2001-02-01

    Kuiper Belt Object surveys indicate a lack of objects with semi- major axis a⪆50 AU in low eccentricity, low inclination orbits. This presents a problem for the simplest theories of Kuiper Belt evolution, which predict a dense, primordial outer Kuiper Belt. A possible solution is that the outer Belt is very dynamically cold, appearing as a razor-thin plane on the sky. If this disk was inclined only 0.5° from the ecliptic, present surveys could fail to detect it since the deep surveys (limiting magnitude R~26) lack sufficient sky coverage and the shallow surveys (limiting mag R~24.4) lack sufficient depth to see small (radius ⪉130 km) objects beyond 50 AU. If this cold, dense disk were to cross a Mosaic field with a limiting magnitude R=25.8, we would expect to see at least 15 distant KBOs. By observing strategically placed large fields we could detect any cold, dense distant disk inclined at up to 0.7° from the invariable plane. This would place a strong constraint on the location of a cold, dense outer Kuiper Belt.

  10. 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.

  11. 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.

  12. 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.

  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. Carbon residence time dominates uncertainty in terrestrial vegetation responses to future climate and atmospheric CO2

    PubMed Central

    Friend, Andrew D.; Lucht, Wolfgang; Rademacher, Tim T.; Keribin, Rozenn; Betts, Richard; Cadule, Patricia; Ciais, Philippe; Clark, Douglas B.; Dankers, Rutger; Falloon, Pete D.; Ito, Akihiko; Kahana, Ron; Kleidon, Axel; Lomas, Mark R.; Nishina, Kazuya; Ostberg, Sebastian; Pavlick, Ryan; Peylin, Philippe; Schaphoff, Sibyll; Vuichard, Nicolas; Warszawski, Lila; Wiltshire, Andy; Woodward, F. Ian

    2014-01-01

    Future climate change and increasing atmospheric CO2 are expected to cause major changes in vegetation structure and function over large fractions of the global land surface. Seven global vegetation models are used to analyze possible responses to future climate simulated by a range of general circulation models run under all four representative concentration pathway scenarios of changing concentrations of greenhouse gases. All 110 simulations predict an increase in global vegetation carbon to 2100, but with substantial variation between vegetation models. For example, at 4 °C of global land surface warming (510–758 ppm of CO2), vegetation carbon increases by 52–477 Pg C (224 Pg C mean), mainly due to CO2 fertilization of photosynthesis. Simulations agree on large regional increases across much of the boreal forest, western Amazonia, central Africa, western China, and southeast Asia, with reductions across southwestern North America, central South America, southern Mediterranean areas, southwestern Africa, and southwestern Australia. Four vegetation models display discontinuities across 4 °C of warming, indicating global thresholds in the balance of positive and negative influences on productivity and biomass. In contrast to previous global vegetation model studies, we emphasize the importance of uncertainties in projected changes in carbon residence times. We find, when all seven models are considered for one representative concentration pathway × general circulation model combination, such uncertainties explain 30% more variation in modeled vegetation carbon change than responses of net primary productivity alone, increasing to 151% for non-HYBRID4 models. A change in research priorities away from production and toward structural dynamics and demographic processes is recommended. PMID:24344265

  15. Estimation of ground water residence times in the Critical zone: insight from U activity ratios

    NASA Astrophysics Data System (ADS)

    Chabaux, Francois; Ackerer, Julien; Lucas, Yann; viville, Daniel

    2016-04-01

    The use of radioactive disequilibria as tracers and chronometers of weathering processes and related mass transfers has been recognized since the 60'. The development, over the last two decades, of analytical methods for measuring very precisely U-series nuclides (especially, 234U, 230Th and 226Ra) in environmental samples has opened up new scientific applications in Earth Surface Sciences. Here, we propose to present the potential of U activity ratios in surface waters as chronometer of water transfers at a watershed scale. This will be illustrated from studies performed at different scales, with the analysis of U activity ratios in surface waters from small watersheds (Strengbach and Ringelbach watersheds in the Vosges Mountain, France) but also from watersheds of much more regional extension (e.g., the Upper Rhine basin or the Ganges basin). These various studies show that variations of U activity ratios in surface waters are mainly associated with 234U-238U fractionations occurring during the water transfer within the bedrock, which intensity depends on two main parameters: the petro-physical characteristics of the aquifer, principally the geometry of water-rock interfaces and the duration of the water-rock interactions. This readily explains why different U activity ratios (UAR) can be observed in the different aquifers of a continental hydrosystem and hence why UAR can be used to trace the source of river waters. For a hydrological system developed on a substratum marked by fairly homogeneous petro-physical characteristics, the main parameter controlling the UAR in waters draining such a system would be the duration of the water-rock interactions. Variations of UAR in stream or spring waters of such a system can therefore be modeled using simple reactive transport model, which allows the estimation of both the dissolution rate of the bedrock and the residence time of the waters within the aquifer.

  16. River delta network hydraulic residence time distributions and their role in coastal nutrient biogeochemistry

    NASA Astrophysics Data System (ADS)

    Hiatt, M. R.; Castaneda, E.; Twilley, R.; Hodges, B. R.; Passalacqua, P.

    2015-12-01

    River deltas have the potential to mitigate increased nutrient loading to coastal waters by acting as biofilters that reduce the impact of nutrient enrichment on downstream ecosystems. Hydraulic residence time (HRT) is known to be a major control on biogeochemical processes and deltaic floodplains are hypothesized to have relatively long HRTs. Hydrological connectivity and delta floodplain inundation induced by riverine forces, tides, and winds likely alter surface water flow patterns and HRTs. Since deltaic floodplains are important elements of delta networks and receive significant fluxes of water, sediment, and nutrients from distributary channels, biogeochemical transformations occurring within these zones could significantly reduce nutrient loading to coastal receiving waters. However, network-scale estimates of HRT in river deltas are lacking and little is known about the effects of tides, wind, and the riverine input on the HRT distribution. Subsequently, there lacks a benchmark for evaluating the impact of engineered river diversions on coastal nutrient ecology. In this study, we estimate the HRT of a coastal river delta by using hydrodynamic modeling supported by field data and relate the HRT to spatial and temporal patterns in nitrate levels measured at discrete stations inside a delta island at Wax Lake Delta. We highlight the control of the degree of hydrological connectivity between distributary channels and interdistributary islands on the network HRT distribution and address the roles of tides and wind on altering the shape of the distribution. We compare the observed nitrate concentrations to patterns of channel-floodplain hydrological connectivity and find this connectivity to play a significant role in the nutrient removal. Our results provide insight into the potential role of deltaic wetlands in reducing the nutrient loading to near-shore waters in response to large-scale river diversions.

  17. Isotopic metrics for structure, connectivity, and residence time in urban water supply systems

    NASA Astrophysics Data System (ADS)

    Bowen, Gabriel; Kennedy, Casey; Good, Stephen; Ehleringer, James

    2014-05-01

    Public water supply systems are the life-blood of urban areas, accessing, managing, and distributing water from an often complex array of sources to provide on-demand access to safe, potable water at the point-of-use. Water managers are faced with a wide range of potential threats, ranging from climate change to infrastructure failure to supply contamination. Information on the structure of supply and conveyance systems, connectivity within these systems, and links between the point-of-use and environmental water sources are thus critical to assessing the stability of water supplies and responding efficiently and effectively to water supply threats. We report datasets documenting stable hydrogen and oxygen isotope ratios of public supply water in cities of the United States across a range of scales. The data show a wide range of spatial and temporal variability that can be attributed to a combination of regional hydroclimate and water supply characteristics. Comparisons of public supply waters with model-based estimates of the isotopic composition of regional water sources suggests that major factors reflected in the tap water data include the degree of fragmentation of natural and man-made storage and conveyance systems, inter-basinal transfer of water, evaporative losses, and the total residence time of the natural and artificial systems being exploited. Because each of these factors contributes to determining the sustainability of water supply systems and their sensitivity to environmental disturbance, we propose a set of isotope-based metrics that can be used to efficiently assess and monitor the characteristics of public-supply systems in water security assessments and in support of management, planning, and outreach activities.

  18. 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

  19. Carbon residence time dominates uncertainty in terrestrial vegetation responses to future climate and atmospheric CO2.

    PubMed

    Friend, Andrew D; Lucht, Wolfgang; Rademacher, Tim T; Keribin, Rozenn; Betts, Richard; Cadule, Patricia; Ciais, Philippe; Clark, Douglas B; Dankers, Rutger; Falloon, Pete D; Ito, Akihiko; Kahana, Ron; Kleidon, Axel; Lomas, Mark R; Nishina, Kazuya; Ostberg, Sebastian; Pavlick, Ryan; Peylin, Philippe; Schaphoff, Sibyll; Vuichard, Nicolas; Warszawski, Lila; Wiltshire, Andy; Woodward, F Ian

    2014-03-01

    Future climate change and increasing atmospheric CO2 are expected to cause major changes in vegetation structure and function over large fractions of the global land surface. Seven global vegetation models are used to analyze possible responses to future climate simulated by a range of general circulation models run under all four representative concentration pathway scenarios of changing concentrations of greenhouse gases. All 110 simulations predict an increase in global vegetation carbon to 2100, but with substantial variation between vegetation models. For example, at 4 °C of global land surface warming (510-758 ppm of CO2), vegetation carbon increases by 52-477 Pg C (224 Pg C mean), mainly due to CO2 fertilization of photosynthesis. Simulations agree on large regional increases across much of the boreal forest, western Amazonia, central Africa, western China, and southeast Asia, with reductions across southwestern North America, central South America, southern Mediterranean areas, southwestern Africa, and southwestern Australia. Four vegetation models display discontinuities across 4 °C of warming, indicating global thresholds in the balance of positive and negative influences on productivity and biomass. In contrast to previous global vegetation model studies, we emphasize the importance of uncertainties in projected changes in carbon residence times. We find, when all seven models are considered for one representative concentration pathway × general circulation model combination, such uncertainties explain 30% more variation in modeled vegetation carbon change than responses of net primary productivity alone, increasing to 151% for non-HYBRID4 models. A change in research priorities away from production and toward structural dynamics and demographic processes is recommended.

  20. Magnetic field effects on the dynamics of a Rydberg electron: The residence time near the core

    NASA Astrophysics Data System (ADS)

    Kono, Hirohiko; Tazaki, Takayuki; Kawata, Isao; Fujimura, Yuichi

    1999-12-01

    Using symplectic integrator schemes, we calculate the classical trajectory of a Rydberg electron in external electric and magnetic fields. We also solve the equation of motion obtained by taking the mean values over one revolution of the electron in the undisturbed motion. The resulting secular motion is periodic. When only an electric field F is applied, as long as the modulation period in the orbital angular momentum l is longer than the revolution period, the motion agrees with the secular one and the duration for which l is much larger than its low initial value is stretched. The residence time (RT), namely, the probability of finding the electron at the distance r, is hence smaller than that at F=0. In crossed electric and magnetic fields, the secular motion predicts that an additional time stretching due to a magnetic field occurs up to the critical value of magnetic field strength, Bc=3√3 nF (n is the principal action). In the actual simulations, the RT near the core is smaller than that at B=0 even beyond Bc, regardless of the magnitude of the non-Coulombic interaction C2/r2. Slow modulations in l are generated by transitions to secular motions that maintain high l, in addition to the fast modulation originating from the secular motion. When the magnetic field is so strong as to induce chaotic motion (˜4000 G for the energy of -5 cm-1), the RT is one order of magnitude as large as those in weak field cases around 40 G. In the intermediate region (> a few hundred Gauss), without a non-Coulombic interaction, the RT monotonically increases as B increases. In the presence of C2/r2, transitions from low l states to high l states occur: the RT decreases. The motions in high l states can be explained by the well-known model in which an electron bound to the core by a harmonic force moves in a magnetic field.

  1. Linking granulation performance with residence time and granulation liquid distributions in twin-screw granulation: An experimental investigation.

    PubMed

    Kumar, Ashish; Alakarjula, Maija; Vanhoorne, Valérie; Toiviainen, Maunu; De Leersnyder, Fien; Vercruysse, Jurgen; Juuti, Mikko; Ketolainen, Jarkko; Vervaet, Chris; Remon, Jean Paul; Gernaey, Krist V; De Beer, Thomas; Nopens, Ingmar

    2016-07-30

    Twin-screw granulation is a promising wet granulation technique for the continuous manufacturing of pharmaceutical solid dosage forms. A twin screw granulator displays a short residence time. Thus, the solid-liquid mixing must be achieved quickly by appropriate arrangement of transport and kneading elements in the granulator screw allowing the production of granules with a size distribution appropriate for tableting. The distribution of residence time and granulation liquid is governed by the field conditions (such as location and length of mixing zones) in the twin-screw granulator, thus contain interesting information on granulation time, mixing and resulting sub-processes such as wetting, aggregation and breakage. In this study, the impact of process (feed rate, screw speed and liquid-to-solid ratio) and equipment parameters (number of kneading discs and stagger angle) on the residence time (distribution), the granulation liquid-powder mixing and the resulting granule size distributions during twin-screw granulation were investigated. Residence time and axial mixing data was extracted from tracer maps and the solid-liquid mixing was quantified from moisture maps, obtained by monitoring the granules at the granulator outlet using near infra-red chemical imaging (NIR-CI). The granule size distribution was measured using the sieving method. An increasing screw speed dominantly reduced the mean residence time. Interaction of material throughput with the screw speed and with the number of kneading discs led to most variation in the studied responses including residence time and mixing capacity. At a high screw speed, granulation yield improved due to high axial mixing. However, increasing material throughput quickly lowers the yield due to insufficient mixing of liquid and powder. Moreover, increasing liquid-to-solid ratio resulted in more oversized granules, and the fraction of oversized granules further increased at higher throughput. Although an increasing number

  2. Linking granulation performance with residence time and granulation liquid distributions in twin-screw granulation: An experimental investigation.

    PubMed

    Kumar, Ashish; Alakarjula, Maija; Vanhoorne, Valérie; Toiviainen, Maunu; De Leersnyder, Fien; Vercruysse, Jurgen; Juuti, Mikko; Ketolainen, Jarkko; Vervaet, Chris; Remon, Jean Paul; Gernaey, Krist V; De Beer, Thomas; Nopens, Ingmar

    2016-07-30

    Twin-screw granulation is a promising wet granulation technique for the continuous manufacturing of pharmaceutical solid dosage forms. A twin screw granulator displays a short residence time. Thus, the solid-liquid mixing must be achieved quickly by appropriate arrangement of transport and kneading elements in the granulator screw allowing the production of granules with a size distribution appropriate for tableting. The distribution of residence time and granulation liquid is governed by the field conditions (such as location and length of mixing zones) in the twin-screw granulator, thus contain interesting information on granulation time, mixing and resulting sub-processes such as wetting, aggregation and breakage. In this study, the impact of process (feed rate, screw speed and liquid-to-solid ratio) and equipment parameters (number of kneading discs and stagger angle) on the residence time (distribution), the granulation liquid-powder mixing and the resulting granule size distributions during twin-screw granulation were investigated. Residence time and axial mixing data was extracted from tracer maps and the solid-liquid mixing was quantified from moisture maps, obtained by monitoring the granules at the granulator outlet using near infra-red chemical imaging (NIR-CI). The granule size distribution was measured using the sieving method. An increasing screw speed dominantly reduced the mean residence time. Interaction of material throughput with the screw speed and with the number of kneading discs led to most variation in the studied responses including residence time and mixing capacity. At a high screw speed, granulation yield improved due to high axial mixing. However, increasing material throughput quickly lowers the yield due to insufficient mixing of liquid and powder. Moreover, increasing liquid-to-solid ratio resulted in more oversized granules, and the fraction of oversized granules further increased at higher throughput. Although an increasing number

  3. Training for Efficiency: Work, Time, and Systems-Based Practice in Medical Residency

    ERIC Educational Resources Information Center

    Szymczak, Julia E.; Bosk, Charles L.

    2012-01-01

    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…

  4. An integrated approach for determining sources and residence times of fine sediment transported through a river network

    NASA Astrophysics Data System (ADS)

    Smith, H. G.; Blake, W. H.

    2012-04-01

    Fine sediment and associated contaminants transported through river networks can have important impacts on water quality, aquatic habitat and ecosystem function long after catchment remediation measures have been implemented. In this context, the potential role of fine sediment as a secondary source of pollution requires attention. Knowledge of fine sediment transfer and storage in river basins is essential for predicting recovery times of rivers affected by historic or contemporary industrial pollution e.g. mining. It is also vital for determining the effectiveness of management actions in reducing the supply of contaminated sediment to coastal ecosystems. Against this background, we aim to determine the residence/travel times of fine sediment through a river network in south-west England. The approach utilises fallout radionuclides (Cs-137, excess Pb-210, Be-7) to (i) infer diffuse sources of sediment and associated contaminants transported in suspension over event and seasonal timescales and (ii) estimate fine sediment residence times based on differences in radioactive decay rates. Information on downstream changes in sediment sources within basins is critical for interpreting residence times using fallout radionuclide data since changes in source type (e.g. surface versus subsurface) may influence residence time signals. Consequently, analysis of sediment sources for a set of nested monitoring sites is coupled with methods for estimating residence time e.g. comparison of Be-7/excess Pb-210 ratios and a two-compartment radionuclide mass balance model comprising slow and rapid transport components. The present study focuses on the River Tamar (917 km2), an agricultural basin with an extensive history of metal mining and legacy of fine sediment contamination. Sampling of land use and channel bank source material across the basin has been undertaken for the sediment source analysis in conjunction with integrated suspended sediment sampling over monthly intervals

  5. Sediment residence times constrained by uranium-series isotopes: A critical appraisal of the comminution approach

    NASA Astrophysics Data System (ADS)

    Handley, Heather K.; Turner, Simon; Afonso, Juan C.; Dosseto, Anthony; Cohen, Tim

    2013-02-01

    Quantifying the rates of landscape evolution in response to climate change is inhibited by the difficulty of dating the formation of continental detrital sediments. We present uranium isotope data for Cooper Creek palaeochannel sediments from the Lake Eyre Basin in semi-arid South Australia in order to attempt to determine the formation ages and hence residence times of the sediments. To calculate the amount of recoil loss of 234U, a key input parameter used in the comminution approach, we use two suggested methods (weighted geometric and surface area measurement with an incorporated fractal correction) and typical assumed input parameter values found in the literature. The calculated recoil loss factors and comminution ages are highly dependent on the method of recoil loss factor determination used and the chosen assumptions. To appraise the ramifications of the assumptions inherent in the comminution age approach and determine individual and combined comminution age uncertainties associated to each variable, Monte Carlo simulations were conducted for a synthetic sediment sample. Using a reasonable associated uncertainty for each input factor and including variations in the source rock and measured (234U/238U) ratios, the total combined uncertainty on comminution age in our simulation (for both methods of recoil loss factor estimation) can amount to ±220-280 ka. The modelling shows that small changes in assumed input values translate into large effects on absolute comminution age. To improve the accuracy of the technique and provide meaningful absolute comminution ages, much tighter constraints are required on the assumptions for input factors such as the fraction of α-recoil lost 234Th and the initial (234U/238U) ratio of the source material. In order to be able to directly compare calculated comminution ages produced by different research groups, the standardisation of pre-treatment procedures, recoil loss factor estimation and assumed input parameter values

  6. A model to predict CWD residence times in tropical forests along an altitudinal gradient in Australia

    NASA Astrophysics Data System (ADS)

    Torello-Raventos, Mireia; Ford, Andrew; Saiz, Gus; Bloomfield, Keith; Lloyd, Jon; Bird, Michael

    2014-05-01

    More reliable knowledge on the complex responses of vegetation to climate change is one of the most urgent needs for tropical forest preservation and recent data models indicate an increase of tree mortality in tropical forests as a consequence of climate change1. Coarse woody debris dynamics in tropical forests remain poorly understood2. Tropical forests are known for possessing a wide range of wood densities- with different wood traits and secondary wood chemical components-, adding complexity to the accurate estimations of coarse woody debris residence times (τ). Quantifying τ in these ecosystems along an altitudinal gradient provides a way to improve our understanding of carbon dynamics in the face of climate change. This study examines τ from different tree tropical forest species -ranging from soft to hardwoods- and under different decay status, to understand the effects of climate on the chemical and physical decay of CWD on an elevation gradient from 102 m above sea level (MAT = 23.7° C) to 1500 m above sea level (MAT = 16.7° C) in Australia. Wood density together with Carbon:Nitrogen ratio enabled prediction of the variation in τ between decay classes within tree species, between tree species and along the elevation gradient. τ increased with decreasing the decay status, increasing wood density and temperature also played an important role as τ increased with increasing site elevation. The study also highlighted the importance of including seasonal variation of climate in short term field studies, as a single wet season reduced the τ of the CWD compared to τ after a year of exposure. Intraspecific variation of plant traits and secondary wood chemicals explained the observed range in τ for species with similar wood densities, decreasing with increasing decayed status of the samples. This study will aid in the development of predictive relationships between wood density and environmental variables to infer carbon dynamics at local and global scale

  7. Chemical composition profiles during alkaline flooding at different temperatures and extended residence times

    SciTech Connect

    Aflaki, R.; Handy, L.L.

    1992-12-01

    The objective of this work was to investigate whether or not caustic sweeps the major portion of the reservoir efficiently during an alkaline flood process. It was also the objective of this work to study the state of final equilibrium during a caustic flood through determination of the pH and chemical composition profiles along the porous medium. For this purpose, a long porous medium which provided extended residence times was required. It was necessary to set up the porous medium such that the changes in the pH and chemical composition of the solution could be monitored. Four Berea sandstone cores (8 in. length and1 in. diameter) placed in series provided the desired length and the opportunity for sampling in-between cores. This enabled establishment of pH and chemical composition profiles. The experiments were run at, temperatures up.to 180{degrees}C, and the flow rates varied from 4.8 to 0.2 ft/day. The samples were analyzed for pH and for Si and Al concentrations.The results show that caustic consumption is insignificant for temperatures up to 100{degrees}C. Above 100{degrees}C consumption increases and is accompanied by a significant decrease in pH. The sharp decline in pH also coincides with a sharp decline in concentration of silica in solution. The results also show that alumina is removed from the solution and solubility of alumina ultimately reaches zero. Sharp silica and pH declines take place even in the absence of any alumina in solution. As a result, removal of silica from solution is attributed to the irreversible caustic/rock interaction. This interaction is in the form of chemisorption reactions in which silica is adsorbed onto the rock surface consuming hydroxyl ion. Once these reactions were satisfied, caustic breakthrough occurs at a high pH. However, significant pore volumes of caustic must be injected for completion of the chemisorption.

  8. Chemical composition profiles during alkaline flooding at different temperatures and extended residence times

    SciTech Connect

    Aflaki, R.; Handy, L.L.

    1992-12-01

    The objective of this work was to investigate whether or not caustic sweeps the major portion of the reservoir efficiently during an alkaline flood process. It was also the objective of this work to study the state of final equilibrium during a caustic flood through determination of the pH and chemical composition profiles along the porous medium. For this purpose, a long porous medium which provided extended residence times was required. It was necessary to set up the porous medium such that the changes in the pH and chemical composition of the solution could be monitored. Four Berea sandstone cores (8 in. length and1 in. diameter) placed in series provided the desired length and the opportunity for sampling in-between cores. This enabled establishment of pH and chemical composition profiles. The experiments were run at, temperatures up.to 180[degrees]C, and the flow rates varied from 4.8 to 0.2 ft/day. The samples were analyzed for pH and for Si and Al concentrations.The results show that caustic consumption is insignificant for temperatures up to 100[degrees]C. Above 100[degrees]C consumption increases and is accompanied by a significant decrease in pH. The sharp decline in pH also coincides with a sharp decline in concentration of silica in solution. The results also show that alumina is removed from the solution and solubility of alumina ultimately reaches zero. Sharp silica and pH declines take place even in the absence of any alumina in solution. As a result, removal of silica from solution is attributed to the irreversible caustic/rock interaction. This interaction is in the form of chemisorption reactions in which silica is adsorbed onto the rock surface consuming hydroxyl ion. Once these reactions were satisfied, caustic breakthrough occurs at a high pH. However, significant pore volumes of caustic must be injected for completion of the chemisorption.

  9. Trait differences between naturalized and invasive plant species independent of residence time and phylogeny

    PubMed Central

    Gallagher, R V; Randall, R P; Leishman, M R

    2015-01-01

    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

  10. Trait differences between naturalized and invasive plant species independent of residence time and phylogeny

    PubMed Central

    Gallagher, R V; Randall, R P; Leishman, M R

    2015-01-01

    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

  11. Decoupling the effects of primary production and residence time variation on nitrogen retention in a tidally-influenced spring run

    NASA Astrophysics Data System (ADS)

    Hensley, R. T.; Cohen, M. J.; Korhnak, L. V.

    2013-12-01

    Models of nitrogen (N) retention in river networks suggest biogeochemical as well as hydraulic properties exert considerable control on reach scale nutrient retention rates. Freshwater tidally influenced rivers provide a model system for decoupling metabolic vs. hydraulic controls on retention. The clear diurnal N retention signal in response to assimilatory uptake observed in other rivers becomes convoluted as the solar day moves in and out of phase with the semi-diurnal (~12.5 hr) tidal cycle. We used an upstream-downstream mass balance approach to estimate N retention at 15 minute intervals over an entire lunar month in Manatee Springs, a tidally varying, spring-fed stream in North Florida. Retention rates varied markedly with tidal forcing. Contrary to our expectations, higher retention rates and shorter uptake lengths were observed at low tide, corresponding to the shortest residence times, which varied between 22 and 71 minutes in this 350m reach. By profiling a continuously injected conservative tracer under both high and low tide conditions, we determined this was not the result of variation in lateral inflow (e.g., dilution from denitrified hyporheic porewater at lower channel stage). This increased retention at shorter residence times (and hence higher velocity) may be the result of greater turbulent mixing, which drives river water into the benthic reactive zone where the principal retention pathway, denitrification, occurs. After controlling for residence time effects, the residual retention signal exhibited a strong diel pattern. This assimilatory N retention was highly correlated with daily primary production (using the diel oxygen method), and estimated ecosystem molar C:N ratios (8.55×0.83:1) were comparable to observed tissue stoichiometry of the dominant autotrophs (9:1). N retention (blue) and residence time (red) calculated at 15 minute intervals. Note the inverse correlation; highest retention rates occur at the shortest residence times. N

  12. 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

  13. 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

  14. Patterns and processes of fluvial discontinuity and sediment residence times on the lower Macquarie River, Murray-Darling Basin, Australia

    NASA Astrophysics Data System (ADS)

    Larkin, Zacchary; Ralph, Timothy; Hesse, Paul

    2014-05-01

    The supply, transport and deposition of fine-grained sediment are important factors determining the morphology of lowland rivers that experience channel breakdown and have wetlands on their lower reaches. Sediment supply and residence time determine whether reaches accumulate sediment (wetland areas) or erode sediment (channelised areas). This research investigated how processes of sedimentation and erosion drive channel breakdown and reformation in the Macquarie Marshes, a large anastomosing wetland system in the Murray-Darling Basin, Australia. Channel breakdown is attributed to a dominance of in-stream sedimentation that leads to a point where single-thread river channels cannot be maintained and so avulsion and floodout processes create smaller distributary channels and wetlands. Avulsions may reconnect channels, changing the sediment supply regime in those particular channels. Channel reformation occurs on the trunk stream where the floodplain gradient steepens enough to allow convergence of small tributaries, locally increasing stream power (and erosive energy in channels). As each river reach reforms following channel breakdown, the channel is smaller, shallower and straighter than the previous reach. One reach in this system recently (in the 1970s) became connected with a parallel channel through avulsion and has morphological characteristics that indicate a significant change in flow and sediment supply. In a pilot study using uranium-series disequilibrium methods and OSL dating, a sediment residence time of 58 +/- 2 ka was determined for sediment in the base of the active channel and a sediment residence time of 153 +/- 5 ka was determined for sediment buried in an adjacent meander that was cut off from the main channel 1,000 years ago. The apparent dramatic decrease in sediment residence time to this active channel poses an interesting question about the role of relatively new channels in transporting and depositing sediment more rapidly than the

  15. 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

  16. 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

  17. Estimation of baseflow residence times in watersheds from the runoff hydrograph recession: method and application in the Neversink watershed, Catskill Mountains, New York

    NASA Astrophysics Data System (ADS)

    Vitvar, Tomas; Burns, Douglas A.; Lawrence, Gregory B.; McDonnell, Jeffrey J.; Wolock, David M.

    2002-06-01

    A method for estimation of mean baseflow residence time in watersheds from hydrograph runoff recession characteristics was developed. Runoff recession characteristics were computed for the period 1993-96 in the 2 km2 Winnisook watershed, Catskill Mountains, southeastern New York, and were used to derive mean values of subsurface hydraulic conductivity and the storage coefficient. These values were then used to estimate the mean baseflow residence time from an expression of the soil contact time, based on watershed soil and topographic characteristics. For comparison, mean baseflow residence times were calculated for the same period of time through the traditional convolution integral approach, which relates rainfall 18O to 18O values in streamflow. Our computed mean baseflow residence time was 9 months by both methods. These results indicate that baseflow residence time can be calculated accurately using recession analysis, and the method is less expensive than using environmental and/or artificial tracers. Published in 2002 by John Wiley & Sons, Ltd.

  18. Highly efficient indoor air purification using adsorption-enhanced-photocatalysis-based microporous TiO2 at short residence time.

    PubMed

    Lv, Jinze; Zhu, Lizhong

    2013-01-01

    A short residence time is a key design parameter for the removal of organic pollutants in catalyst-based indoor air purification systems. In this study, we synthesized a series of TiO2 with different micropore volumes and studied their removal efficiency of indoor carbonyl pollutants at a short residence time. Our results indicated that the superior adsorption capability of TiO2 with micropores improved its performance in the photocatalytic degradation of cyclohexanone, while the photocatalytic removal of the pollutant successfully kept porous TiO2 from becoming saturated. When treated with 1 mg m(-3) cyclohexanone at a relatively humidity of 18%, the adsorption amount on microporous TiO2 was 5.4-7.9 times higher than that on P25. Removal efficiency via photocatalysis followed'the same order as the adsorption amount: TiO2-5 > TiO2-20 > TiO2-60 > TiO2-180 > P25. The advantage of microporous TiO2 over P25 became more pronounced when the residence time declined from 0.072 to 0.036 s. Moreover, as the concentration of cyclohexanone deceased from 1000 ppb to 500 ppb, removal efficiency by microporous TiO2 increased more rapidly than P25.

  19. Synchronous network of distant telescopes

    NASA Astrophysics Data System (ADS)

    Zhilyaev, B.; Svyatogorov, O.; Verlyuk, I.; Andreev, M.; Sergeev, A.; Lovkaya, M.; Antov, A.; Konstantinova-Antova, R.; Bogdanovski, R.; Avgoloupis, S.; Seiradakis, J.; Contadakis, M. E.

    The Synchronous Network of distant Telescopes (SNT) represents an innovative approach in observational astrophysics. The authors present an unique existing realization of the SNT-conception. It was founded within the international collaboration between astronomical observatories of Ukraine, Russia, Bulgaria and Greece. All the telescopes of the Network are equipped with standardized photometric systems (based on photo-multipliers). The unified timing systems (based on GPS-receivers) synchronize all the apertures to UTC with an accuracy of 1 microsecond and better. The essential parts of the SNT are the original software for operating and data processing. The described international Network successfully works for more than 10 years. The obtained unique observational data made it possible to discover new fine-scale features and flare-triggered phenomena in flaring red dwarfs, as well as the recently found high-frequency variability in some chromospherically active stars.

  20. Calculation of surface diffusivity and residence time by molecular dynamics with application to nanoscale selective-area growth

    NASA Astrophysics Data System (ADS)

    Almeida, S.; Ochoa, E.; Chavez, J. J.; Zhou, X. W.; Zubia, D.

    2015-08-01

    The surface diffusivity and residence time were calculated by molecular dynamics simulations in order to solve the surface diffusion equations for selective-area growth. The calculations for CdTe/CdS material system were performed in substrates with Cd termination and S termination. The surface diffusivity and residence time were obtained at different temperatures (600 K, 800 K, 1000 K, 1200 K, and 1400 K). The thermal activation energies were extracted from Arrhenius equation for each substrate termination. Thereafter, values obtained by molecular dynamics were used in a surface diffusion model to calculate the surface concentration profile of adatoms. Alternating the surface termination has the potential to achieve nanoscale selective-area growth without the need of a dielectric film as a mask.

  1. Atmospheric residence time of (210)Pb determined from the activity ratios with its daughter radionuclides (210)Bi and (210)Po.

    PubMed

    Semertzidou, P; Piliposian, G T; Appleby, P G

    2016-08-01

    The residence time of (210)Pb created in the atmosphere by the decay of gaseous (222)Rn is a key parameter controlling its distribution and fallout onto the landscape. These in turn are key parameters governing the use of this natural radionuclide for dating and interpreting environmental records stored in natural archives such as lake sediments. One of the principal methods for estimating the atmospheric residence time is through measurements of the activities of the daughter radionuclides (210)Bi and (210)Po, and in particular the (210)Bi/(210)Pb and (210)Po/(210)Pb activity ratios. Calculations used in early empirical studies assumed that these were governed by a simple series of equilibrium equations. This approach does however have two failings; it takes no account of the effect of global circulation on spatial variations in the activity ratios, and no allowance is made for the impact of transport processes across the tropopause. This paper presents a simple model for calculating the distributions of (210)Pb, (210)Bi and (210)Po at northern mid-latitudes (30°-65°N), a region containing almost all the available empirical data. By comparing modelled (210)Bi/(210)Pb activity ratios with empirical data a best estimate for the tropospheric residence time of around 10 days is obtained. This is significantly longer than earlier estimates of between 4 and 7 days. The process whereby (210)Pb is transported into the stratosphere when tropospheric concentrations are high and returned from it when they are low, significantly increases the effective residence time in the atmosphere as a whole. The effect of this is to significantly enhance the long range transport of (210)Pb from its source locations. The impact is illustrated by calculations showing the distribution of (210)Pb fallout versus longitude at northern mid-latitudes. PMID:27132252

  2. Regional oxygen reduction and denitrification rates in groundwater from multi-model residence time distributions, San Joaquin Valley, USA

    USGS Publications Warehouse

    Green, Christopher T.; Jurgens, Bryant; Zhang, Yong; Starn, Jeffrey; Singleton, Michael J.; Esser, Bradley K.

    2016-01-01

    Rates of oxygen and nitrate reduction are key factors in determining the chemical evolution of groundwater. Little is known about how these rates vary and covary in regional groundwater settings, as few studies have focused on regional datasets with multiple tracers and methods of analysis that account for effects of mixed residence times on apparent reaction rates. This study provides insight into the characteristics of residence times and rates of O2 reduction and denitrification (NO3− reduction) by comparing reaction rates using multi-model analytical residence time distributions (RTDs) applied to a data set of atmospheric tracers of groundwater age and geochemical data from 141 well samples in the Central Eastern San Joaquin Valley, CA. The RTD approach accounts for mixtures of residence times in a single sample to provide estimates of in-situ rates. Tracers included SF6, CFCs, 3H, He from 3H (tritiogenic He),14C, and terrigenic He. Parameter estimation and multi-model averaging were used to establish RTDs with lower error variances than those produced by individual RTD models. The set of multi-model RTDs was used in combination with NO3− and dissolved gas data to estimate zero order and first order rates of O2 reduction and denitrification. Results indicated that O2 reduction and denitrification rates followed approximately log-normal distributions. Rates of O2 and NO3− reduction were correlated and, on an electron milliequivalent basis, denitrification rates tended to exceed O2 reduction rates. Estimated historical NO3− trends were similar to historical measurements. Results show that the multi-model approach can improve estimation of age distributions, and that relatively easily measured O2 rates can provide information about trends in denitrification rates, which are more difficult to estimate.

  3. Hydrodynamics, temperature/salinity variability and residence time in the Chilika lagoon during dry and wet period: Measurement and modeling

    NASA Astrophysics Data System (ADS)

    Mahanty, M. M.; Mohanty, P. K.; Pattnaik, A. K.; Panda, U. S.; Pradhan, S.; Samal, R. N.

    2016-08-01

    This paper investigated the hydrodynamics, spatio-temporal variability of temperature/salinity and the residence time of tracer concentrations in a largest brackish water coastal lagoon in Asia, namely the Chilika lagoon, India. An integrated approach combined the measurement and 2D hydrodynamic-advection/dispersion model is used to simulate circulation and temperature/salinity, and estimated the water residence time in lagoon under different forcing mechanisms, such as tide, wind and freshwater discharge during the dry and wet periods. Water circulation inside the lagoon is simulated when wind is included with the tide only forcing during dry period, and freshwater influx is included with the tide and wind forcing during wet period. Under the realistic forcing conditions, the computed temporal variability of water temperature and salinity are well correlated with the measurements in both the periods. The spatial variations of water temperature within the lagoon is influenced by the meteorological conditions, tide and freshwater influx as well as the shallowness of the lagoon, whereas the salinity is spatially controlled by the freshwater influx from the riverine system and seawater intrusion through the tidal inlets. The numerical model results show that in the Chilika lagoon tidal and river influx affect significantly the residence time spatially, and is site specific. The residence time varies from values of 4-5 days in the outer channel (OC) and 132 days at the northern sector (NS) in the main body of lagoon. The current study represents a first attempt to use a combined model approach, which is therefore, a useful tool to support the ecological implication of the lagoon ecosystem.

  4. Influence of substrate heterogeneity on the hydraulic residence time and removal efficiency of horizontal subsurface flow constructed wetlands

    NASA Astrophysics Data System (ADS)

    Carranza-Diaz, O.; Brovelli, A.; Rossi, L.; Barry, D. A.

    2009-04-01

    Horizontal, subsurface flow constructed wetlands are wastewater treatment devices. The influent polluted water flows through a porous substrate where the contaminants are removed, for example by microbial oxidation, surface adsorption and mineral precipitation. These systems are widely used with varying degrees of success to treat municipal and agricultural contaminated waters and remove the organic carbon and nutrient load. Constructed wetlands are an appealing and promising technology, because they (i) are potentially very efficient in removing the pollutants, (ii) require only a small external energy input and (iii) require low maintenance. However, practical experience has shown that the observed purification rate is highly variable and is often much smaller than expected. One of the numerous reasons proposed to explain the variable efficiency of constructed wetlands is the existence of highly conductive zones within the porous substrate, which produce a dramatic reduction of the hydraulic residence time and therefore directly decreases the overall water purification rate. This work aims to understand quantitatively the relationship between the spatial variability in the hydraulic properties of the substrate and the effective residence time in constructed wetlands. We conducted two suites of stochastic numerical simulations, modelling the transport of a conservative tracer in a three-dimensional simulated constructed wetland in one case, and the microbial oxidation of a carbon source in the other. Within each group of simulations, different hydraulic conductivity fields were tested. These were based on a log-normal, spatially correlated random field (with exponential spatial correlation). The amount of heterogeneity was varied by changing the variance correlation length in the three directions. For each set of parameters, different realizations are considered to deduce both the expected residence time for a certain amount of heterogeneity, and its range of

  5. Atmospheric residence time of (210)Pb determined from the activity ratios with its daughter radionuclides (210)Bi and (210)Po.

    PubMed

    Semertzidou, P; Piliposian, G T; Appleby, P G

    2016-08-01

    The residence time of (210)Pb created in the atmosphere by the decay of gaseous (222)Rn is a key parameter controlling its distribution and fallout onto the landscape. These in turn are key parameters governing the use of this natural radionuclide for dating and interpreting environmental records stored in natural archives such as lake sediments. One of the principal methods for estimating the atmospheric residence time is through measurements of the activities of the daughter radionuclides (210)Bi and (210)Po, and in particular the (210)Bi/(210)Pb and (210)Po/(210)Pb activity ratios. Calculations used in early empirical studies assumed that these were governed by a simple series of equilibrium equations. This approach does however have two failings; it takes no account of the effect of global circulation on spatial variations in the activity ratios, and no allowance is made for the impact of transport processes across the tropopause. This paper presents a simple model for calculating the distributions of (210)Pb, (210)Bi and (210)Po at northern mid-latitudes (30°-65°N), a region containing almost all the available empirical data. By comparing modelled (210)Bi/(210)Pb activity ratios with empirical data a best estimate for the tropospheric residence time of around 10 days is obtained. This is significantly longer than earlier estimates of between 4 and 7 days. The process whereby (210)Pb is transported into the stratosphere when tropospheric concentrations are high and returned from it when they are low, significantly increases the effective residence time in the atmosphere as a whole. The effect of this is to significantly enhance the long range transport of (210)Pb from its source locations. The impact is illustrated by calculations showing the distribution of (210)Pb fallout versus longitude at northern mid-latitudes.

  6. River Incision, Sediment Storage, and Sediment Residence Times at the Western Tibetan Plateau Margin

    NASA Astrophysics Data System (ADS)

    Bloethe, J. H.; Munack, H.; Fülling, A.; Resentini, A.; Garzanti, E.; Kubik, P.; Korup, O.

    2012-12-01

    Intermediate sediment storage protects underlying bedrock from incision, buffers sediment delivery from adjacent hillslopes and provides the source for potentially catastrophic sediment release. Along the western Tibetan plateau margin, broad alluviated valleys host large valley fills. Besides sediment storage in major valleys, deeply incised bedrock gorges also have the potential to store sediment for > 104 yrs, even though they are typically portrayed as conveyor belts for incoming sediment. Here we report on cyclic aggradation and re-incision of fluvial terraces near the Tibetan plateau margin in the Ladakh and Zanskar Ranges, NW Himalaya, India. Recently reported 10Be-derived bedrock incision rates of up to 3 mm/yr suggest locally focused fast incision that contrasts with the low (~0.02 mm/yr) denudation rates of this dry high-altitude mountain desert. We combine Optically Stimulated Luminescence (OSL) and 10Be dating techniques, provenance analyses and morphometric analyses of digital elevation models (DEMs), in order to understand the Quaternary evolution of the region and to estimate sediment storage and residence times. We present the first OSL-derived dataset of fluvial fill terrace ages in the lower Zanskar gorge, a major tributary of the upper Indus River. These data are complemented by new 10Be exposure ages from fluvially polished surfaces and a 10Be depth profile of a fluvial terrace situated at the Zanskar-Indus confluence. Our data indicate at least two cycles of aggradation and re-incision. OSL ages from a terrace level 35 m above the river point to a phase of aggradation between 50 ka and 20 ka, which we attribute either to a late- or postglacial sediment pulse from the Zanskar headwaters, and/or to natural damming downstream. Preliminary results for the 10Be depth profile from the top of a terrace ~160 m above river level suggest a deposition age of > 100 ka, dating an older aggradation cycle. This higher terrace level is also present in the

  7. Receptor residence time trumps drug-likeness and oral bioavailability in determining efficacy of complement C5a antagonists

    NASA Astrophysics Data System (ADS)

    Seow, Vernon; Lim, Junxian; Cotterell, Adam J.; Yau, Mei-Kwan; Xu, Weijun; Lohman, Rink-Jan; Kok, W. Mei; Stoermer, Martin J.; Sweet, Matthew J.; Reid, Robert C.; Suen, Jacky Y.; Fairlie, David P.

    2016-04-01

    Drug discovery and translation are normally based on optimizing efficacy by increasing receptor affinity, functional potency, drug-likeness (rule-of-five compliance) and oral bioavailability. Here we demonstrate that residence time of a compound on its receptor has an overriding influence on efficacy, exemplified for antagonists of inflammatory protein complement C5a that activates immune cells and promotes disease. Three equipotent antagonists (3D53, W54011, JJ47) of inflammatory responses to C5a (3nM) were compared for drug-likeness, receptor affinity and antagonist potency in human macrophages, and anti-inflammatory efficacy in rats. Only the least drug-like antagonist (3D53) maintained potency in cells against higher C5a concentrations and had a much longer duration of action (t1/2 ~ 20 h) than W54011 or JJ47 (t1/2 ~ 1–3 h) in inhibiting macrophage responses. The unusually long residence time of 3D53 on its receptor was mechanistically probed by molecular dynamics simulations, which revealed long-lasting interactions that trap the antagonist within the receptor. Despite negligible oral bioavailability, 3D53 was much more orally efficacious than W54011 or JJ47 in preventing repeated agonist insults to induce rat paw oedema over 24 h. Thus, residence time on a receptor can trump drug-likeness in determining efficacy, even oral efficacy, of pharmacological agents.

  8. Natural radionuclides (210)Po and (210)Pb in the Delaware and Chesapeake Estuaries: modeling scavenging rates and residence times.

    PubMed

    Marsan, D; Rigaud, S; Church, T

    2014-12-01

    During the spring and summer months of 2012, (210)Po and (210)Pb activity were measured in the dissolved and particulate phases from the Delaware and upper Chesapeake estuaries. The upper Delaware estuary, near the freshwater end member, was characterized by high-suspended matter concentrations that scavenged dissolved (210)Po and (210)Pb. Box models were applied using mass balance calculations to assess the nuclides residence times in each estuary. Only 60% of the dissolved (210)Po and 55% of the dissolved (210)Pb from the Delaware estuary were exported to coastal waters. A large fraction of soluble (210)Po and (210)Pb within the estuary was either reversibly adsorbed onto suspended particles, trapped in sediment accumulation zones (such as intertidal marshes), bioaccumulated into phytoplankton and discharged to the coastal ocean. The upper Chesapeake estuary was largely characterized by sub-oxic bottom waters that contained higher concentrations of dissolved (210)Po and (210)Pb, hypothesized to be subjected to redox cycling of manganese. The Delaware and Chesapeake estuary mean residence times for (210)Po differed significantly at 86 ± 7 and 126 ± 10 days respectively, while they were similar for (210)Pb (67 ± 6-55 ± 5 days). The difference in residence times corresponds to the greater extent of biogeochemical scavenging and regeneration processes within the upper Chesapeake. PMID:25239647

  9. Natural radionuclides (210)Po and (210)Pb in the Delaware and Chesapeake Estuaries: modeling scavenging rates and residence times.

    PubMed

    Marsan, D; Rigaud, S; Church, T

    2014-12-01

    During the spring and summer months of 2012, (210)Po and (210)Pb activity were measured in the dissolved and particulate phases from the Delaware and upper Chesapeake estuaries. The upper Delaware estuary, near the freshwater end member, was characterized by high-suspended matter concentrations that scavenged dissolved (210)Po and (210)Pb. Box models were applied using mass balance calculations to assess the nuclides residence times in each estuary. Only 60% of the dissolved (210)Po and 55% of the dissolved (210)Pb from the Delaware estuary were exported to coastal waters. A large fraction of soluble (210)Po and (210)Pb within the estuary was either reversibly adsorbed onto suspended particles, trapped in sediment accumulation zones (such as intertidal marshes), bioaccumulated into phytoplankton and discharged to the coastal ocean. The upper Chesapeake estuary was largely characterized by sub-oxic bottom waters that contained higher concentrations of dissolved (210)Po and (210)Pb, hypothesized to be subjected to redox cycling of manganese. The Delaware and Chesapeake estuary mean residence times for (210)Po differed significantly at 86 ± 7 and 126 ± 10 days respectively, while they were similar for (210)Pb (67 ± 6-55 ± 5 days). The difference in residence times corresponds to the greater extent of biogeochemical scavenging and regeneration processes within the upper Chesapeake.

  10. Receptor residence time trumps drug-likeness and oral bioavailability in determining efficacy of complement C5a antagonists

    PubMed Central

    Seow, Vernon; Lim, Junxian; Cotterell, Adam J.; Yau, Mei-Kwan; Xu, Weijun; Lohman, Rink-Jan; Kok, W. Mei; Stoermer, Martin J.; Sweet, Matthew J.; Reid, Robert C.; Suen, Jacky Y.; Fairlie, David P.

    2016-01-01

    Drug discovery and translation are normally based on optimizing efficacy by increasing receptor affinity, functional potency, drug-likeness (rule-of-five compliance) and oral bioavailability. Here we demonstrate that residence time of a compound on its receptor has an overriding influence on efficacy, exemplified for antagonists of inflammatory protein complement C5a that activates immune cells and promotes disease. Three equipotent antagonists (3D53, W54011, JJ47) of inflammatory responses to C5a (3nM) were compared for drug-likeness, receptor affinity and antagonist potency in human macrophages, and anti-inflammatory efficacy in rats. Only the least drug-like antagonist (3D53) maintained potency in cells against higher C5a concentrations and had a much longer duration of action (t1/2 ~ 20 h) than W54011 or JJ47 (t1/2 ~ 1–3 h) in inhibiting macrophage responses. The unusually long residence time of 3D53 on its receptor was mechanistically probed by molecular dynamics simulations, which revealed long-lasting interactions that trap the antagonist within the receptor. Despite negligible oral bioavailability, 3D53 was much more orally efficacious than W54011 or JJ47 in preventing repeated agonist insults to induce rat paw oedema over 24 h. Thus, residence time on a receptor can trump drug-likeness in determining efficacy, even oral efficacy, of pharmacological agents. PMID:27094554

  11. SUBSURFACE RESIDENCE TIMES AS AN ALGORITHM FOR AQUIFER SENSITIVITY MAPPING: TESTING THE CONCEPT WITH ANALYTIC ELEMENT GROUND WATER MODELS IN THE CONTENTNEA CREEK BASIN, NORTH CAROLINA, USA

    EPA Science Inventory

    The objective of this research is to test the utility of simple functions of spatially integrated and temporally averaged ground water residence times in shallow "groundwatersheds" with field observations and more detailed computer simulations. The residence time of water in the...

  12. Impact of Timing of Birth and Resident Duty-Hour Restrictions on Outcome of Small Preterm Infants

    PubMed Central

    Bell, Edward F.; Hansen, Nellie I.; Morriss, Frank H.; Stoll, Barbara J.; Ambalavanan, Namasivayam; Gould, Jeffrey B.; Laptook, Abbot R.; Walsh, Michele C.; Carlo, Waldemar A.; Shankaran, Seetha; Das, Abhik; Higgins, Rosemary D.

    2010-01-01

    OBJECTIVE To examine the impact of birth at night, on the weekend, and during July or August – the first months of the academic year – and the impact of resident duty-hour restrictions on mortality and morbidity of VLBW infants. METHODS Outcomes were analyzed for 11,137 infants with birth weight 501–1250 grams enrolled in the NICHD Neonatal Research Network registry 2001–2005. Approximately half were born before the introduction of resident duty-hour restrictions in 2003. Follow-up assessment at 18–22 months was completed for 4,508 infants. Mortality (7-day and 28-day), short-term morbidities, and neurodevelopmental outcome were examined with respect to the timing of birth: night vs day, weekend vs weekday, and July or August vs other months, and after vs before implementation of resident duty-hour restrictions. RESULTS There was no effect of hour, day, or month of birth on mortality and no impact on the risks of short-term morbidities except the risk of ROP requiring operative treatment was lower for infants born during the late night hours than during the day. There was no impact of timing of birth on neurodevelopmental outcome except the risk of hearing impairment or death was slightly lower among infants born in July or August compared with other months. The introduction of resident and fellow duty-hour restrictions had no impact on mortality or neurodevelopmental outcome. The only change in short-term morbidity after duty-hour restrictions were introduced was an increase in the risk of ROP (stage 2 or higher). CONCLUSION In this network of academic centers, the timing of birth and the introduction of duty-hour restrictions had little effect on the risks of mortality and morbidity of VLBW infants, suggesting that staffing patterns were adequate to provide consistent care. PMID:20643715

  13. Residence times and nitrate transport in ground water discharging to streams in the Chesapeake Bay Watershed

    USGS Publications Warehouse

    Lindsey, Bruce D.; Phillips, Scott; Donnelly, Colleen A.; Speiran, Gary K.; Plummer, L. Niel; Bohlke, John-Karl; Focazio, Michael J.; Burton, William C.; Busenberg, Eurybiades

    2003-01-01

    One of the major water-quality problems in the Chesapeake Bay is an overabundance of nutrients from the streams and rivers that discharge to the Bay. Some of these nutrients are from nonpoint sources such as atmospheric deposition, agricultural manure and fertilizer, and septic systems. The effects of efforts to control nonpoint sources, however, can be difficult to quantify because of the lag time between changes at the land surface and the response in the base-flow (ground water) component of streams. To help resource managers understand the lag time between implementation of management practices and subsequent response in the nutrient concentrations in the base-flow component of streamflow, a study of ground-water discharge, residence time, and nitrate transport in springs throughout the Chesapeake Bay Watershed and in four smaller watersheds in selected hydrogeomorphic regions (HGMRs) was conducted. The four watersheds were in the Coastal Plain Uplands, Piedmont crystalline, Valley and Ridge carbonate, and Valley and Ridge siliciclastic HGMRs. A study of springs to estimate an apparent age of the ground water was based on analyses for concentrations of chlorofluorocarbons in water samples collected from 48 springs in the Chesapeake Bay Watershed. Results of the analysis indicate that median age for all the samples was 10 years, with the 25th percentile having an age of 7 years and the 75th percentile having an age of 13 years. Although the number of samples collected in each HGMR was limited, there did not appear to be distinct differences in the ages between the HGMRs. The ranges were similar between the major HGMRs above the Fall Line (modern to about 50 years), with only two HGMRs of small geographic extent (Piedmont carbonate and Mesozoic Lowland) having ranges of modern to about 10 years. The median values of all the HGMRs ranged from 7 to 11 years. Not enough samples were collected in the Coastal Plain for comparison. Spring samples showed slightly

  14. Cosmogenic, radiogenic, and stable isotopic constraints on groundwater residence time in the nubian aquifer, western desert of egypt

    SciTech Connect

    Patterson, Leslie J.; Sturchio, Neil C.; Kennedy, B.Mack; van Soest, Matthias C.; Sultan, Mohamed; Lu, Zheng-Tian; Lehmann, Bernhard; Purtschert, Roland; El Alfy, Zeinhom; El Kaliouby, Baher; Dawood, Yehia; Abdallah, Ali

    2004-06-01

    Measurements of radiochlorine ({sup 36}Cl), radiogenic noble gases ({sup 4}He and {sup 40}Ar), and stable chlorine isotope ratios were obtained to assess the residence time of groundwater in the Nubian Aquifer of the Western Desert of Egypt. Measured {sup 36}Cl/Cl ratios yield apparent residence times from {approx}0.2 to 1.2 x 10{sup 6} years in the deep (600-1200 m) groundwater (assuming constant Cl) and {le} 0.16 x 10{sup 6} years in the shallow (<600 m) groundwater. Values of {delta}{sup 37}Cl in the groundwater strengthen the application of the {sup 36}Cl dating method by constraining Cl sources and identifying groundwater mixing. Dissolved gases were measured in some of the deep groundwater samples. Measured {sup 4}He concentrations indicate accumulation of radiogenic {sup 4}He that is qualitatively consistent with the age progression indicated by the {sup 36}Cl/Cl ratios, but the flux of external {sup 4}He from the underlying crust has not been quantified and is not constant throughout the aquifer. Concentrations of {sup 40}Ar range from 3.3 to 6.7 x 10{sup -4} ccSTP/g and indicate excess air incorporation at recharge. Measured {sup 40}Ar/{sup 36}Ar ratios do not exceed the atmospheric ratio. A two-dimensional numerical hydrodynamic transect of the aquifer was modeled from the area of the Uweinat Uplift to the northern Bahariya Oasis. Predicted groundwater velocities in the deep portion of the aquifer are 0.5-3.5 m/yr with groundwater residence times up to 9 x 10{sup 5} years; residence times up to 1.3 x 10{sup 6} years are predicted in the confining shale. Aquifer properties are estimated by using the model to fit the measured {sup 36}Cl/Cl ratios. Under these conditions, hydrodynamic residence times are within about 30 percent of those calculated from {sup 36}Cl when mixing of Cl{sup -} is accounted for in the highest-Cl{sup -} deep groundwaters. By mutually calibrating multiple methods (hydrodynamic, {sup 36}Cl, and {sup 4}He), a consistent picture of the

  15. Heralded Quantum Entanglement between Distant Matter Qubits

    PubMed Central

    Yang, Wen-Juan; Wang, Xiang-Bin

    2015-01-01

    We propose a scheme to realize heralded quantum entanglement between two distant matter qubits using two Λ atom systems. Our proposal does not need any photon interference. We also present a general theory of outcome state of non-monochromatic incident light and finite interaction time. PMID:26041259

  16. Multimedia level-III partitioning and residence times of xenobiotics in water-rich and water-poor environments

    SciTech Connect

    Breitkopf, C.; Kuehne, R.; Schueuermann, G.

    2000-05-01

    The environmental fate of 10 compounds covering a wide range of intrinsic persistence and volatility is studied with a multimedia level-III fugacity model at two system temperatures (293 and 282 K) using water-rich and water-poor model environments and standard emission scenarios to air and water, respectively. The resultant level-III partitionings depend significantly on the entry mode and on the relative compartment sizes, and the variation with system temperature is more pronounced for polar compounds and when air is the primary discharge compartment. For example, the steady-state portion in soil of airborne phenol varies from 21 to 89%, whereas waterborne phenol resides in water at a rate of 100% in both water-rich and water-poor environments. For some compounds, the residence time (considering both advection and degradation) is substantially affected by intermedia transport processes such as rainfall. With airborne atrazine, the regional residence time is comparable to that of DDT and significantly greater than the ones of hexachlorobenzene, polychlorinated biphenyl 28, and lindane, although the latter have much longer media-specific half-lives and much greater hydrophobicity. The discussion includes detailed analyses of the compound properties and their impact on the level-III environmental fate.

  17. Latitude of residence and position in time zone are predictors of cancer incidence, cancer mortality, and life expectancy at birth.

    PubMed

    Borisenkov, Mikhail F

    2011-03-01

    According to the hypothesis of circadian disruption, external factors that disturb the function of the circadian system can raise the risk of malignant neoplasm and reduce life span. Recent work has shown that the functionality of the circadian system is dependent not only on latitude of residence but also on the region's position in the time zone. The purpose of the present research was to examine the influence of latitude and time zone on cancer incidence, cancer mortality, and life expectancy at birth. A stepwise multiple regression analysis was carried out on residents of 59 regions of the European part of the Russian Federation (EPRF) using age-standardized parameters (per 100,000) of cancer incidence (CI), cancer mortality (CM), and life expectancy at birth (LE, yrs) as dependent variables. The geographical coordinates (latitude and position in the time zone) of the regions were used as independent variables, controlling for the level of economic development in the regions. The same analysis was carried out for LE in 31 regions in China. Latitude was the strongest predictor of LE in the EPRF population; it explained 48% and 45% of the variability in LE of women and men, respectively. Position within the time zone accounted for an additional 4% and 3% variability of LE in women and men, respectively. The highest values for LE were observed in the southeast of the EPRF. In China, latitude was not a predictor of LE, whereas position in the time zone explained 15% and 18% of the LE variability in women and men, respectively. The highest values of LE were observed in the eastern regions of China. Both latitude and position within the time zone were predictors for CI and CM of the EPRF population. Latitude was the best predictor of stomach CI and CM; this predictor explained 46% and 50% of the variability, respectively. Position within the time zone was the best predictor of female breast CM; it explained 15% of the variability. In most cases, CI and CM increased

  18. Observations of Distant Clusters

    NASA Technical Reports Server (NTRS)

    Donahue, Megan

    2004-01-01

    The is the proceedings and papers supported by the LTSA grant: Homer, D. J.\\& Donahue, M. 2003, in "The Emergence of Cosmic Structure": 13'h Astrophysics Conference Proceedings, Vol. 666,3 1 1-3 14, (AIP). Baumgartner, W. H., Loewenstein, M., Horner, D. J., Mushotzky, R. F. 2003, HEAD- AAS, 35.3503. Homer, D. J. , Donahue, M., Voit G. M. 2003, HEAD-AAS, 35.1309. Nowak, M. A., Smith, B., Donahue, M., Stocke, J. 2003, HEAD-AAS, 35.1316. Scott, D., Borys, C., Chapman, S. C., Donahue, M., Fahlman, G. G., Halpem, M. Newbury, P. 2002, AAS, 128.01. Jones, L. R. et al. 2002, A new era in cosmology, ASP Conference Proceedings, Vol. 283, p. 223 Donahue, M., Daly, R. A., Homer, D. J. 2003, ApJ, 584, 643, Constraints on the Cluster Environments and Hotspot magnetic field strengths for radio sources 3280 and 3254. Donahue, M., et al. 2003, ApJ, 598, 190. The mass, baryonic fraction, and x-ray temperature of the luminous, high-redshift cluster of galaxies MS045 1.6-0305 Perlman, E. S. et al. 2002, ApJS, 140, 256. Smith, B. J., Nowak, M., Donahue, M., Stocke, J. 2003, AJ, 126, 1763. Chandra Observations of the Interacting NGC44 10 Group of Galaxies. Postman, M., Lauer, T. R., Oegerle, W., Donahue, M. 2002, ApJ, 579, 93. The KPNO/deep-range cluster survey I. The catalog and space density of intermediate-redshift clusters. Molnar, S. M., Hughes, J. P., Donahue, M., Joy, M. 2002, ApJ, 573, L91, Chandra Observations of Unresolved X-Ray Sources around Two Clusters of Galaxies. Donahue, M., Mack, J., 2002 NewAR, 46, 155, HST NIcmos and WFPC2 observations of molecular hydrogen and dust around cooling flows. Koekemoer, A. M. et al. 2002 NewAR, 46, 149, Interactions between the A2597 central radio source and dense gas host galaxy. Donahue, M. et al. 2002 ApJ, 569,689, Distant cluster hunting II.

  19. Maintaining social cohesion is a more important determinant of patch residence time than maximizing food intake rate in a group-living primate, Japanese macaque (Macaca fuscata).

    PubMed

    Kazahari, Nobuko

    2014-04-01

    Animals have been assumed to employ an optimal foraging strategy (e.g., rate-maximizing strategy). In patchy food environments, intake rate within patches is positively correlated with patch quality, and declines as patches are depleted through consumption. This causes patch-leaving and determines patch residence time. In group-foraging situations, patch residence times are also affected by patch sharing. Optimal patch models for groups predict that patch residence times decrease as the number of co-feeding animals increases because of accelerated patch depletion. However, group members often depart patches without patch depletion, and their patch residence time deviates from patch models. It has been pointed out that patch residence time is also influenced by maintaining social proximity with others among group-living animals. In this study, the effects of maintaining social cohesion and that of rate-maximizing strategy on patch residence time were examined in Japanese macaques (Macaca fuscata). I hypothesized that foragers give up patches to remain in the proximity of their troop members. On the other hand, foragers may stay for a relatively long period when they do not have to abandon patches to follow the troop. In this study, intake rate and foraging effort (i.e., movement) did not change during patch residency. Macaques maintained their intake rate with only a little foraging effort. Therefore, the patches were assumed to be undepleted during patch residency. Further, patch residence time was affected by patch-leaving to maintain social proximity, but not by the intake rate. Macaques tended to stay in patches for short periods when they needed to give up patches for social proximity, and remained for long periods when they did not need to leave to keep social proximity. Patch-leaving and patch residence time that prioritize the maintenance of social cohesion may be a behavioral pattern in group-living primates.

  20. Residence Times and Pathway Analysis Using a Coupled Three-Dimensional Variably Saturated Groundwater Flow and Land Surface Model

    NASA Astrophysics Data System (ADS)

    Kollet, S. J.; Maxwell, R. M.

    2007-12-01

    The analysis of residence times and pathways of solutes in the subsurface is important in the characterization of biogeochemical processes and contaminant transport. Recent theoretical and experimental studies have shown power law (fractal) residence time distributions because of the fractal character of the topography. The theoretical studies focused on a steady-state analysis of the flow field utilizing an undulating water table boundary condition that follows the topography. However, processes of the vadose zone including root water uptake and evaporation have been neglected until this work. In this study, the three-dimensional variably saturated groundwater flow model ParFlow, coupled to a land surface model, is used to study the influence of processes of the vadose zone on pathways and residence time distributions. A small catchment is simulated incorporating topography; land and soil cover information; and one year of realistic atmospheric forcing. Transient Lagrangian transport simulations of a conservative tracer are performed, also including dispersion (i.e. heterogeneity), to develop spectral transforms of the arrival time distributions. The resulting power spectra show power law behavior over a wide range of scales. While the spectral scaling exponent (SSP) decreases with increasing heterogeneity, the influence of the vadose zone appears to cause an increase in the SSP. Additionally, the effect of explicit representation of subsurface heterogeneity and spatial model resolution on the scaling behavior is studied. This work was conducted under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory (LLNL) under contract W-7405-Eng-48. This project was funded by the Laboratory Directed Research and Development Program at LLNL.

  1. Slow-Onset Inhibition of Mycobacterium tuberculosis InhA: Revealing Molecular Determinants of Residence Time by MD Simulations

    PubMed Central

    Merget, Benjamin; Sotriffer, Christoph A.

    2015-01-01

    An important kinetic parameter for drug efficacy is the residence time of a compound at a drug target, which is related to the dissociation rate constant koff. For the essential antimycobacterial target InhA, this parameter is most likely governed by the ordering of the flexible substrate binding loop (SBL). Whereas the diphenyl ether inhibitors 6PP and triclosan (TCL) do not show loop ordering and thus, no slow-binding inhibition and high koff values, the slightly modified PT70 leads to an ordered loop and a residence time of 24 minutes. To assess the structural differences of the complexes from a dynamic point of view, molecular dynamics (MD) simulations with a total sampling time of 3.0 µs were performed for three ligand-bound and two ligand-free (perturbed) InhA systems. The individual simulations show comparable conformational features with respect to both the binding pocket and the SBL, allowing to define five recurring conformational families. Based on their different occurrence frequencies in the simulated systems, the conformational preferences could be linked to structural differences of the respective ligands to reveal important determinants of residence time. The most abundant conformation besides the stable EI* state is characterized by a shift of Ile202 and Val203 toward the hydrophobic pocket of InhA. The analyses revealed potential directions for avoiding this conformational change and, thus, hindering rapid dissociation: (1) an anchor group in 2'-position of the B-ring for scaffold stabilization, (2) proper occupation of the hydrophobic pocket, and (3) the introduction of a barricade substituent in 5'-position of the diphenyl ether B-ring. PMID:25996598

  2. Modeling sediment transport processes and residence times in the shallow coastal bay complex of the Virginia Coast Reserve

    NASA Astrophysics Data System (ADS)

    Safak, I.; Wiberg, P. L.

    2011-12-01

    Patterns of sediment transport and particle residence times influence the morphology and ecology of shallow coastal bays in important ways. The Virginia Coast Reserve (VCR), a barrier island-lagoon-marsh system on the Eastern Shore of Virginia, is typical of many shallow coastal bay complexes that lack a significant fluvial source of freshwater and sediment. Sediment redistribution within the bays in response to storms and sea-level rise, together with the dynamics of marsh and lagoon-bottom plants, largely governs the morphological evolution of this system. There are also important feedbacks between sediment and ecosystem dynamics. This is particularly true in the VCR, which is relatively unaffected by human activities. As a step towards evaluating the impact of hydrodynamics on sediment and ecological processes in the VCR, a single unified model that accounts for circulation, surface waves, wave-current interaction, and sediment processes is employed. This three-dimensional unstructured grid finite-volume coastal ocean model (FVCOM) is validated with field observations of wind- and tide-induced water flow (water level and current velocities) in Hog Island Bay, centrally located within the VCR. Here, the resulting patterns of sediment transport and particle residence times over event and seasonal time scales are presented. Water and particle exchange within the VCR and between the VCR and the ocean is examined with the Lagrangian particle-tracking module in FVCOM. We focus on three bays with strongly varying bathymetry and coastline geometry, which are also located along a gradient of nitrogen input to the system. The results indicate that residence time of particles within the system vary greatly depending on the location of particle release, bay morphology, and wind conditions. The implications for morphologic evolution and ecosystem response to climate and land-use changes are evaluated.

  3. Groundwater residence time and palaeohydrology in the Otway Basin, South Australia: 2H, 18O and 14C data

    NASA Astrophysics Data System (ADS)

    Love, A. J.; Herczeg, A. L.; Leaney, F. W.; Stadter, M. F.; Dighton, J. C.; Armstrong, D.

    1994-01-01

    Stable isotopes (δ 2H, δ 18O and δ 13C) and radiocarbon ( 14C) have been used in conjunction with chemical data to evaluate recharge mechanisms, groundwater residence time and palaeohydrology within the confined Dilwyn sand aquifer in the Gambier Embayment of the Otway Basin. This aquifer does not receive recharge down-gradient of the hydraulic hinge-line and data have been interpreted along two discrete flow lines. The mean residence time of groundwater (determined by 14C) in the confined aquifer from the hydraulic hinge position to the sea (a distance of about 50 km) along an inferred flow path is approximately 12 800 years. The corresponding hydraulic travel time calculated from Darcy's law is approximately 49 000 years. The apparent discrepancy may be a result of eustatic sea-level lowering during the last glacial. Because the groundwater system is hydraulically connected to the sea, lower sea-level would result in increased gradients and a decrease in groundwater residence time. Variations in stable isotopic composition along flow lines suggest a number of recharge mechanisms. Stable isotope data indicate progressive depletion of 2H and 18O in the groundwaters over the past 30 000 years. Groundwaters older than about 10 000 years B.P. were recharged either during a cooler climate climatic regime (lower precipitation/evapotranspiration and temperature) and/or the vapour source(s) had travelled over greater continental mass than those recharged over the past 10 000 years. Lower chloride concentrations in some of the older groundwaters indicate lower evapotranspiration rates in the recharge areas before 10 000 years ago.

  4. Quest for the most distant objects in the universe

    SciTech Connect

    Kanipe, J.

    1988-06-01

    Far out in the distant universe, between 10 billion and 11 billion years away in space and time, lies a region where the majority of known quasars resides. Astronomers have known about this stratum of quasars for over two decades and have spent the better part of that time trying to understand why these objects seem predisposed to congregate at this distance. The most plausible explanation is that there were more quasars 10 billion or 11 billion years ago than there are now and that this region represents, in effect, the quasar spawning grounds. For astronomers this quasar stratum has played an important role in demarcating the edge of the observable universe. Beyond lies only a handful of more distant quasars, and beyond that lies a vast, impenetrable region that extends back to a time before the quasars formed, when matter and photons went their separate ways 700,000 years after the Big Bang. But a recent flurry of back-to-back quasar discoveries may spell the beginning of the end of this theory. Between August 1986 and late September 1987 more than a half-dozen quasars were detected at 12 billion light-years, which is beyond what astronomers had considered the edge of the universe. Although the new quasars may not seem to be too far out of bounds, a little distance translates into a lot of time in the development of the young universe. The final stroke would be the discovery of quasars or possibly primeval galaxies in a region of space thought to predate the formation of galaxies. Theorists would then be forced to discard established models that explain how galaxies formed and evolved and to devise new theories that better reflect observations. This would cause a major revolution in astronomy.

  5. Redeposition in plasma-assisted atomic layer deposition: Silicon nitride film quality ruled by the gas residence time

    SciTech Connect

    Knoops, Harm C. M. E-mail: w.m.m.kessels@tue.nl; Peuter, K. de; Kessels, W. M. M. E-mail: w.m.m.kessels@tue.nl

    2015-07-06

    The requirements on the material properties and growth control of silicon nitride (SiN{sub x}) spacer films in transistors are becoming ever more stringent as scaling of transistor structures continues. One method to deposit high-quality films with excellent control is atomic layer deposition (ALD). However, depositing SiN{sub x} by ALD has turned out to be very challenging. In this work, it is shown that the plasma gas residence time τ is a key parameter for the deposition of SiN{sub x} by plasma-assisted ALD and that this parameter can be linked to a so-called “redeposition effect”. This previously ignored effect, which takes place during the plasma step, is the dissociation of reaction products in the plasma and the subsequent redeposition of reaction-product fragments on the surface. For SiN{sub x} ALD using SiH{sub 2}(NH{sup t}Bu){sub 2} as precursor and N{sub 2} plasma as reactant, the gas residence time τ was found to determine both SiN{sub x} film quality and the resulting growth per cycle. It is shown that redeposition can be minimized by using a short residence time resulting in high-quality films with a high wet-etch resistance (i.e., a wet-etch rate of 0.5 nm/min in buffered HF solution). Due to the fundamental nature of the redeposition effect, it is expected to play a role in many more plasma-assisted ALD processes.

  6. Dissolved organic carbon lability increases with water residence time in the alluvial aquifer of a river floodplain ecosystem

    NASA Astrophysics Data System (ADS)

    Helton, Ashley M.; Wright, Meredith S.; Bernhardt, Emily S.; Poole, Geoffrey C.; Cory, Rose M.; Stanford, Jack A.

    2015-04-01

    We assessed spatial and temporal patterns of dissolved organic carbon (DOC) lability and composition throughout the alluvial aquifer of the 16 km2 Nyack Floodplain in northwest Montana, USA. Water influx to the aquifer derives almost exclusively from the Middle Fork of the Flathead River, and water residence times within the aquifer range from days to months. Across seasons and channel discharge conditions, we measured DOC concentration, lability, and optical properties of aquifer water sampled from 12 wells, both near and ~3 m below the water table. Concentrations of DOC were typically low (542 ± 22.7 µg L-1; mean ± se), and the percentage of labile DOC averaged 18 ± 12% during 3 day laboratory assays. Parallel factor analysis of fluorescence excitation-emission matrices revealed two humic-like and two amino acid-like fluorescence groups. Total DOC, humic-like components, and specific UV absorbance decreased with water residence time, consistent with sorption to aquifer sediments. However, labile DOC (both concentration and fraction) increased with water residence time, suggesting a concurrent influx or production of labile DOC. Thus, although the carbon-poor, oxygen-rich aquifer is a net sink for DOC, recalcitrant DOC appears to be replaced with more labile DOC along aquifer flow paths. Our observation of DOC production in long flow paths contrasts with studies of hyporheic DOC consumption along short (centimeters to meters) flow paths and highlights the importance of understanding the role of labile organic matter production and/or influx in alluvial aquifer carbon cycling.

  7. Detection of cancer before distant metastasis

    PubMed Central

    2013-01-01

    Background To establish a distant metastasis (DM) cells must disseminate from the primary tumor and overcome a series of obstacles, the metastatic cascade. In this study we develop a mathematical model for this cascade to estimate the tumor size and the circulating tumor cell (CTC) load before the first metastasis has formed from a primary breast cancer tumor. Methods The metastatic cascade is described in discrete steps: 1. local tumor growth; 2. dissemination into circulation; 3. survival in circulation; 4. extravasation into tissue; and 5. growth into a metastasis. The model was built using data and relationships described in the literature to predict the relationship between tumor size and probability of distant metastasis for 38715 patients with surgically removed TXNXM0 primary breast cancer from the Netherlands Cancer Registry. The model was calibrated using primary tumor size, probability of distant metastasis and time to distant metastasis for 1489 patients with stage T1BNXM0 (25% of total patients with T1BNXM0). Validation of the model was done with data for all patients. Results From the time to distant metastasis of these 38715 breast cancer patients, we determined a tumor doubling time of 1.7 ± 0.9 months. Fitting the data for 25% of T1B patients estimates a metastatic efficiency of 1 metastasis formed per 60 million disseminated tumor cells. Validation of the model to data of patients in all T-stages shows good agreement between model and epidemiological data. To reduce the 5-year risk of distant metastasis for TXNXM0 from 9.2% to 1.0%, the primary tumor needs to be detected and removed before it reaches a diameter of 2.7 ± 1.6 mm. At this size, the model predicts that there will be 9 ± 6 CTC/L blood. Conclusions To reduce the rate of distant metastasis in surgically treated TXNXM0 breast cancer to 1%, imaging technology will need to be able to detect lesions of 2.7 mm in diameter or smaller. Before CTC detection can be applied in

  8. Impact of Temperature and Hydrological Residence Time on the Fate and Transport of Iron and Organic Carbon in Subalpine Wetlands

    NASA Astrophysics Data System (ADS)

    Schneider, L. M.; Borch, T.; Rhoades, C.; Pallud, C. E.

    2015-12-01

    Wetlands contain one third of the planet's soil carbon (C) and are characterized by markedly different chemical and physical environments than terrestrial ecosystems. The hydrologic residence time and temperature in wetlands influences their redox conditions and thus biogeochemical reaction rates. In these environments, transformation and movement of C and iron (Fe) are closely linked due to the sorption of organic C by solid Fe(III)-phases. Therefore, changes in Fe biogeochemical cycling will influence the size and turnover rate of soil C pools, which could negatively impact water quality and C storage. We examined the effects of hydrologic residence time and temperature on reduction of autochtonous Fe(III)-oxides. Fe(II)-export rates, used as a lower bound for bulk Fe(III)-reduction rates, and dissolved organic carbon (DOC) export rates were measured on intact mineral soil cores using flow-through reactor experiments exposed to temperatures based on mean annual conditions (6°, 12°, and 18°C). Soils were from a slope and a depressional subalpine wetland (USDA Fraser Experimental Forest, CO, USA), characterized by different hydrologic residence times, were compared. In the depressional wetland we observed the shallower soil depths have higher overall Fe(II)-export rates than the deeper soil depths. As temperature increases, Fe(II)-export rate increases, with a more than doubling in magnitude from 12 to 18° C. In comparing sites that are continuously inundated to those that are seasonally inundated, surprisingly we see higher Fe(II)-export rates in the seasonally inundated sites for all temperatures and depths. In the slope wetland we observed an opposite trend with depth and with temperature, with Fe(II)-export rates declining by almost an order of magnitude between 6 and 12°C. In addition, our results showed a positive correlation between Fe(II)-export rates and DOC export rates suggesting Fe(III)-reduction exerts a biogeochemical control on water quality

  9. Application of radium isotopes to determine crustal residence times of hydrothermal fluids from two sites on the Reykjanes Peninsula, Iceland

    NASA Astrophysics Data System (ADS)

    Kadko, David; Gronvold, Karl; Butterfield, David

    2007-12-01

    Radium isotopes were used to determine the crustal residence times of hydrothermal fluids from two geothermal wells (Svartsengi and Reykjanes) from the Reykjanes Peninsula, Iceland. The availability of rock samples from the subsurface (to depths of 2400 m) allowed direct comparison of the radium isotopic characteristics of the fluids with those of the rocks within the high temperature and pressure reaction zone. The 226Ra activity of the Svartsengi fluid was ˜one-fourth of the Reykjanes fluid and the 228Ra/ 226Ra ratio of the Svartsengi fluid was ˜twice that of Reykjanes. The fluid isotopic characteristics were relatively stable for both sites over the 6 years (2000-2006) of the study. It was determined, using a model that predicts the evolution of the fluid 228Ra/ 226Ra ratio with time, that both sites had fluid residence times, from the onset of high temperature water-rock reaction, of less than 5 years. Measurement of the short-lived 224Ra and 223Ra allowed estimation of the recoil input parameter used in the model. The derived timescale is consistent with results from similar studies of fluids from submarine systems, and has implications for the use of terrestrial systems in Iceland as an exploited energy resource.

  10. Interactive distance learning in orthodontic residency programs: problems and potential solutions.

    PubMed

    Klein, Katherine P; Hannum, Wallace H; Fields, Henry W; Proffit, William R

    2012-03-01

    Sharing resources through distance education has been proposed as one way to deal with a lack of full-time faculty members and maintain high-quality content in orthodontic residency programs. To keep distance education for orthodontic residents cost-effective while retaining interaction, a blended approach was developed that combines observation of web-based seminars with live post-seminar discussions. To evaluate this approach, a grant from the American Association of Orthodontists (AAO) opened free access during the 2009-10 academic year to twenty-five recorded seminars in four instructional sequences to all sixty-three orthodontic programs in the United States and Canada. The only requirement was to also participate in the evaluation. Just over half (52 percent) of the U.S. programs chose to participate; the primary reason for participating was because faculty members wanted their residents to have exposure to other faculty members and ideas. The non-participating programs cited technical and logistical problems and their own ability to teach these subjects satisfactorily as reasons. Although participating distant faculty members and residents were generally pleased with the experience, problems in both educational and technical aspects were observed. Educationally, the biggest problem was lack of distant resident preparation and expectation of a lecture rather than a seminar. Technically, the logistics of scheduling distant seminars and uneven quality of the audio and video recordings were the major concerns of both residents and faculty members. Proposed solutions to these educational and technical problems are discussed.

  11. A new methodology for measurement of sludge residence time distribution in a paddle dryer using X-ray fluorescence analysis.

    PubMed

    Charlou, Christophe; Milhé, Mathieu; Sauceau, Martial; Arlabosse, Patricia

    2015-02-01

    Drying is a necessary step before sewage sludge energetic valorization. Paddle dryers allow working with such a complex material. However, little is known about sludge flow in this kind of processes. This study intends to set up an original methodology for sludge residence time distribution (RTD) measurement in a continuous paddle dryer, based on the detection of mineral tracers by X-ray fluorescence. This accurate analytical technique offers a linear response to tracer concentration in dry sludge; the protocol leads to a good repeatability of RTD measurements. Its equivalence to RTD measurement by NaCl conductivity in sludge leachates is assessed. Moreover, it is shown that tracer solubility has no influence on RTD: liquid and solid phases have the same flow pattern. The application of this technique on sludge with different storage duration at 4 °C emphasizes the influence of this parameter on sludge RTD, and thus on paddle dryer performances: the mean residence time in a paddle dryer is almost doubled between 24 and 48 h of storage for identical operating conditions.

  12. Sewage sludge ash to phosphate fertilizer by chlorination and thermal treatment: residence time requirements for heavy metal removal.

    PubMed

    Nowak, Benedikt; Wegerer, Harald; Aschenbrenner, Philipp; Rechberger, Helmut; Winter, Franz

    2012-01-01

    Heavy metal removal from sewage sludge ash can be performed by mixing the ash with environmentally compatible chlorides (e.g. CaCl2 or MgCl2) and water, pelletizing the mixture and treating the pellets in a rotary reactor at about 1000 degrees C. Thermogravimetry-mass spectroscopy, muffle oven tests (500-1150 degrees C) and investigations in a laboratory-scale rotary reactor (950-1050 degrees C, residence time 1-25 min) were carried out. In the rotary reactor, up to 97% of Cu, 95% Pb and 95% Zn can be removed at 1050 degrees C. As Cl release starts from 400 degrees C (obtained from thermogravimetry-mass spectrometry experiments), heavy metals are already removed partially within the heating period. This heavy metal removal can be described as being similar to a first-order rate law. To meet the limit values specified in the Austrian and German fertilizer ordinances, residence times of the order of minutes are sufficient at 950 degrees C. PMID:23393980

  13. Measurements of liquid phase residence time distributions in a pilot-scale continuous leaching reactor using radiotracer technique.

    PubMed

    Pant, H J; Sharma, V K; Shenoy, K T; Sreenivas, T

    2015-03-01

    An alkaline based continuous leaching process is commonly used for extraction of uranium from uranium ore. The reactor in which the leaching process is carried out is called a continuous leaching reactor (CLR) and is expected to behave as a continuously stirred tank reactor (CSTR) for the liquid phase. A pilot-scale CLR used in a Technology Demonstration Pilot Plant (TDPP) was designed, installed and operated; and thus needed to be tested for its hydrodynamic behavior. A radiotracer investigation was carried out in the CLR for measurement of residence time distribution (RTD) of liquid phase with specific objectives to characterize the flow behavior of the reactor and validate its design. Bromine-82 as ammonium bromide was used as a radiotracer and about 40-60MBq activity was used in each run. The measured RTD curves were treated and mean residence times were determined and simulated using a tanks-in-series model. The result of simulation indicated no flow abnormality and the reactor behaved as an ideal CSTR for the range of the operating conditions used in the investigation.

  14. A [32P]-NAD+-based method to identify and quantitate long residence time enoyl-ACP reductase inhibitors

    PubMed Central

    Yu, Weixuan; Neckles, Carla; Chang, Andrew; Bommineni, Gopal Reddy; Spagnuolo, Lauren; Zhang, Zhuo; Liu, Nina; Lai, Christina; Truglio, James; Tonge, Peter J.

    2015-01-01

    The classical methods for quantifying drug-target residence time (tR) use loss or regain of enzyme activity in progress curve kinetic assays. However, such methods become imprecise at very long residence times, mitigating the use of alternative strategies. Using the NAD(P)H-dependent FabI enoyl-ACP reductase as a model system, we developed a Penefsky column-based method for direct measurement of tR, where the off-rate of the drug was determined with radiolabeled [adenylate-32P] NAD(P+) cofactor. Twenty-three FabI inhibitors were analyzed and a mathematical model was used to estimate limits to the tR values of each inhibitor based on percent drug-target complex recovery following gel filtration. In general, this method showed good agreement with the classical steady state kinetic methods for compounds with tR values of 10-100 min. In addition, we were able to identify seven long tR inhibitors (100-1500 min) and to accurately determine their tR values. The method was then used to measure tR as a function of temperature, an analysis not previously possible using the standard kinetic approach due to decreased NAD(P)H stability at elevated temperatures. In general, a 4-fold difference in tR was observed when the temperature was increased from 25 °C to 37 °C . PMID:25684450

  15. Residence times of shallow groundwater in West Africa: implications for hydrogeology and resilience to future changes in climate

    NASA Astrophysics Data System (ADS)

    Lapworth, D. J.; MacDonald, A. M.; Tijani, M. N.; Darling, W. G.; Gooddy, D. C.; Bonsor, H. C.; Araguás-Araguás, L. J.

    2013-05-01

    Although shallow groundwater (<50 mbgl) sustains the vast majority of improved drinking-water supplies in rural Africa, there is little information on how resilient this resource may be to future changes in climate. This study presents results of a groundwater survey using stable isotopes, CFCs, SF6, and 3H across different climatic zones (annual rainfall 400-2,000 mm/year) in West Africa. The purpose was to quantify the residence times of shallow groundwaters in sedimentary and basement aquifers, and investigate the relationship between groundwater resources and climate. Stable-isotope results indicate that most shallow groundwaters are recharged rapidly following rainfall, showing little evidence of evaporation prior to recharge. Chloride mass-balance results indicate that within the arid areas (<400 mm annual rainfall) there is recharge of up to 20 mm/year. Age tracers show that most groundwaters have mean residence times (MRTs) of 32-65 years, with comparable MRTs in the different climate zones. Similar MRTs measured in both the sedimentary and basement aquifers suggest similar hydraulic diffusivity and significant groundwater storage within the shallow basement. This suggests there is considerable resilience to short-term inter-annual variation in rainfall and recharge, and rural groundwater resources are likely to sustain diffuse, low volume abstraction.

  16. Residence times and mixing of water in river banks: implications for recharge and groundwater - surface water exchange

    NASA Astrophysics Data System (ADS)

    Unland, N. P.; Cartwright, I.; Cendón, D. I.; Chisari, R.

    2014-02-01

    The residence time of groundwater within 50 m of the Tambo River, South East Australia, has been estimated through the combined use of 3H and 14C. Groundwater residence times increase towards the Tambo River which implies a gaining river system and not increasing bank storage with proximity to the Tambo River. Major ion concentrations and δ2H and δ18O values of bank water also indicate that bank infiltration does not significantly impact groundwater chemistry under baseflow and post-flood conditions, suggesting that the gaining nature of the river may be driving the return of bank storage water back into the Tambo River within days of peak flood conditions. The covariance between 3H and 14C indicates the leakage and mixing between old (~17 200 yr) groundwater from a semi-confined aquifer and younger groundwater (<100 yr) near the river where confining layers are less prevalent. The presence of this semi-confined aquifer has also been used to help explain the absence of bank storage, as rapid pressure propagation into the semi-confined aquifer during flooding will minimise bank infiltration. This study illustrates the complex nature of river groundwater interactions and the potential downfall in assuming simple or idealised conditions when conducting hydrogeological studies.

  17. The role of residence time in diagnostic models of global carbon storage capacity: model decomposition based on a traceable scheme

    PubMed Central

    Yizhao, Chen; Jianyang, Xia; Zhengguo, Sun; Jianlong, Li; Yiqi, Luo; Chengcheng, Gang; Zhaoqi, Wang

    2015-01-01

    As a key factor that determines carbon storage capacity, residence time (τE) is not well constrained in terrestrial biosphere models. This factor is recognized as an important source of model uncertainty. In this study, to understand how τE influences terrestrial carbon storage prediction in diagnostic models, we introduced a model decomposition scheme in the Boreal Ecosystem Productivity Simulator (BEPS) and then compared it with a prognostic model. The result showed that τE ranged from 32.7 to 158.2 years. The baseline residence time (τ′E) was stable for each biome, ranging from 12 to 53.7 years for forest biomes and 4.2 to 5.3 years for non-forest biomes. The spatiotemporal variations in τE were mainly determined by the environmental scalar (ξ). By comparing models, we found that the BEPS uses a more detailed pool construction but rougher parameterization for carbon allocation and decomposition. With respect to ξ comparison, the global difference in the temperature scalar (ξt) averaged 0.045, whereas the moisture scalar (ξw) had a much larger variation, with an average of 0.312. We propose that further evaluations and improvements in τ′E and ξw predictions are essential to reduce the uncertainties in predicting carbon storage by the BEPS and similar diagnostic models. PMID:26541245

  18. Increasing functional modularity with residence time in the co-distribution of native and introduced vascular plants

    PubMed Central

    Hui, Cang; Richardson, David M.; Pyšek, Petr; Le Roux, Johannes J.; Kučera, Tomáš; Jarošík, Vojtěch

    2013-01-01

    Species gain membership of regional assemblages by passing through multiple ecological and environmental filters. To capture the potential trajectory of structural changes in regional meta-communities driven by biological invasions, one can categorize species pools into assemblages of different residence times. Older assemblages, having passed through more environmental filters, should become more functionally ordered and structured. Here we calculate the level of compartmentalization (modularity) for three different-aged assemblages (neophytes, introduced after 1500 AD; archaeophytes, introduced before 1500 AD, and natives), including 2,054 species of vascular plants in 302 reserves in central Europe. Older assemblages are more compartmentalized than younger ones, with species composition, phylogenetic structure and habitat characteristics of the modules becoming increasingly distinctive. This sheds light on two mechanisms of how alien species are functionally incorporated into regional species pools: the settling-down hypothesis of diminishing stochasticity with residence time, and the niche-mosaic hypothesis of inlaid neutral modules in regional meta-communities. PMID:24045305

  19. HUBBLE SPIES MOST DISTANT SUPERNOVA EVER SEEN

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Using NASA's Hubble Space Telescope, astronomers pinpointed a blaze of light from the farthest supernova ever seen, a dying star that exploded 10 billion years ago. The detection and analysis of this supernova, called 1997ff, is greatly bolstering the case for the existence of a mysterious form of dark energy pervading the cosmos, making galaxies hurl ever faster away from each other. The supernova also offers the first glimpse of the universe slowing down soon after the Big Bang, before it began speeding up. This panel of images, taken with the Wide Field and Planetary Camera 2, shows the supernova's cosmic neighborhood; its home galaxy; and the dying star itself. Astronomers found this supernova in 1997 during a second look at the northern Hubble Deep Field [top panel], a tiny region of sky first explored by the Hubble telescope in 1995. The image shows the myriad of galaxies Hubble spied when it peered across more than 10 billion years of time and space. The white box marks the area where the supernova dwells. The photo at bottom left is a close-up view of that region. The white arrow points to the exploding star's home galaxy, a faint elliptical. Its redness is due to the billions of old stars residing there. The picture at bottom right shows the supernova itself, distinguished by the white dot in the center. Although this stellar explosion is among the brightest beacons in the universe, it could not be seen directly in the Hubble images. The stellar blast is so distant from Earth that its light is buried in the glow of its host galaxy. To find the supernova, astronomers compared two pictures of the 'deep field' taken two years apart. One image was of the original Hubble Deep Field; the other, the follow-up deep-field picture taken in 1997. Using special computer software, astronomers then measured the light from the galaxies in both images. Noting any changes in light output between the two pictures, the computer identified a blob of light in the 1997 picture

  20. Transport and residence times of tropospheric aerosols inferred from a global three-dimensional simulation of Pb-210

    NASA Technical Reports Server (NTRS)

    Balkanski, Yves J.; Jacob, Daniel J.; Gardner, Geraldine M.; Graustein, William C.; Turekian, Karl K.

    1993-01-01

    A global three-dimensional model is used to investigate the transport and tropospheric residence time of Pb-210, an aerosol tracer produced in the atmosphere by radioactive decay of Rn-222 emitted from soils. The model uses meteorological input with 4 deg x 5 deg horizontal resolution and 4-hour temporal resolution from the Goddard Institute for Space Studies general circulation model (GCM). It computes aerosol scavenging by convective precipitation as part of the wet convective mass transport operator in order to capture the coupling between vertical transport and rainout. Scavenging in convective precipitation accounts for 74% of the global Pb-210 sink in the model; scavenging in large-scale precipitation accounts for 12%, and scavenging in dry deposition accounts for 14%. The model captures 63% of the variance of yearly mean Pb-210 concentrations measured at 85 sites around the world with negligible mean bias, lending support to the computation of aerosol scavenging. There are, however, a number of regional and seasonal discrepancies that reflect in part anomalies in GCM precipitation. Computed residence times with respect to deposition for Pb-210 aerosol in the tropospheric column are about 5 days at southern midlatitudes and 10-15 days in the tropics; values at northern midlatitudes vary from about 5 days in winter to 10 days in summer. The residence time of Pb-210 produced in the lowest 0.5 km of atmosphere is on average four times shorter than that of Pb-210 produced in the upper atmosphere. Both model and observations indicate a weaker decrease of Pb-210 concentrations between the continental mixed layer and the free troposphere than is observed for total aerosol concentrations; an explanation is that Rn-222 is transported to high altitudes in wet convective updrafts, while aerosols and soluble precursors of aerosols are scavenged by precipitation in the updrafts. Thus Pb-210 is not simply a tracer of aerosols produced in the continental boundary layer, but

  1. Role of trimethylated chitosan (TMC) in nasal residence time, local distribution and toxicity of an intranasal influenza vaccine.

    PubMed

    Hagenaars, Niels; Mania, Marta; de Jong, Pascal; Que, Ivo; Nieuwland, Rob; Slütter, Bram; Glansbeek, Harrie; Heldens, Jacco; van den Bosch, Han; Löwik, Clemens; Kaijzel, Eric; Mastrobattista, Enrico; Jiskoot, Wim

    2010-05-21

    The nose is a promising immunization site and intranasal (i.n.) vaccination studies with whole inactivated influenza virus (WIV) adjuvanted with N,N,N-trimethylchitosan (TMC-WIV) have shown promising results. In this study, the influence of TMC on the i.n. delivery of WIV was studied in mice by comparing the nasal residence time and the specific location in the nasal cavity of WIV and TMC-WIV. Additionally, the local toxicity profile of the WIV formulations was assessed. In vivo fluorescence imaging was used to study the nasal residence time and the fate of the bulk vaccine in mice that received vaccines fluorescently labeled with IRDye800CW. An immunohistochemical (IHC) staining method for nasal cross-sections was developed to visualize the antigen in the nasal cavity. Therefore, mice were sacrificed at different time points after vaccination with various vaccine formulations and nasal cross-sections were made. The local toxicity was assessed using hematoxylin and eosin staining for the nasal cross-sections. No significant differences in the nasal residence time between WIV and TMC-WIV were observed. However, IHC revealed a striking difference in the location and distribution of WIV in the nasal cavity. When formulated as plain WIV, positive staining was mainly found in the nasal cavity, presumably in mucus blobs. TMC-coated WIV, on the other hand, was mostly present as a thin layer on the epithelial surfaces of the naso- and maxilloturbinates. This difference in staining pattern correlates with the observed differences in immunogenicity of these two vaccines and indicates that TMC-WIV results in a much closer interaction of WIV with the epithelial surfaces than WIV alone, potentially leading to enhanced uptake and induction of immune responses. This study further shows that both WIV and TMC-WIV formulations induce minimal local toxicity. Taken altogether, these results provide more insight in the mode of action and safety of TMC and justify further research to

  2. Limits on the time variation of the electromagnetic fine-structure constant in the low energy limit from absorption lines in the spectra of distant quasars.

    PubMed

    Srianand, R; Chand, H; Petitjean, P; Aracil, B

    2004-03-26

    We present the results of a detailed many-multiplet analysis performed on a new sample of Mg ii systems observed in high quality quasar spectra obtained using the Very Large Telescope. The weighted mean value of the variation in alpha derived from our analysis over the redshift range 0.4time of 9.7 Gyr in the most favored cosmological model today. This gives a 3sigma limit, -2.5 x 10(-16)time variation of alpha, that forms the strongest constraint obtained based on high redshift quasar absorption line systems.

  3. Standards for permanent teeth emergence time and sequence in Lithuanian children, residents of Vilnius city.

    PubMed

    Almonaitiene, Ruta; Balciuniene, Irena; Tutkuviene, Janina

    2012-01-01

    BACKGROUND. Up-to-date population specific standards on the timing and sequence of emergence of the permanent teeth are essential in planning medical care for children. To the best of authors' knowledge, data about emergence time of permanent teeth in Lithuanian children has not been provided. OBJECTIVE. To provide the first standards of permanent teeth emergence time and sequence in Lithuanian children, citizens of Vilnius. MATERIAL AND METHODS. In a cross-sectional study, data were collected from 3596 Lithuanian children, 4 to 16 years of age in randomly selected kindergartens and secondary schools of Vilnius city. During dental examination all erupted permanent teeth, except third molars, were recorded. MiniTab15 statistical software was used to calculate clinical eruption time of permanent teeth. Different comparisons were made to detect inter-jaw, inter-gender and inter-population differences. RESULTS. The earliest teeth to erupt in both genders are lower central incisors around the age of six. The first stage of mixed dentition ends with the eruption of upper lateral incisors around the age of 8 in boys and a half of year earlier in girls. Second transitional period starts after the emergence of first premolars or lower canine in girls and upper first premolar in boys at the age of 9.5. The last tooth to erupt in both genders is the upper second molar at the age of twelve. No significant differences have been found between right and left sides in either jaw. Lower permanent teeth tended to emerge significantly earlier than the upper ones, except for premolars and first molars. Girls preceded boys by 4 to 5 months on average. Lithuanian children on average showed earlier emergence time, especially in premolars, but resemble German and Finnish populations more closely. CONCLUSIONS. No significant asymmetry in permanent teeth emergence time has been found in either jaw. Lower permanent teeth, showed earlier clinical eruption than in the upper jaw in both genders

  4. Groundwater residence times in Shenandoah National Park, Blue Ridge Mountains, Virginia, USA: A multi-tracer approach

    USGS Publications Warehouse

    Plummer, L.N.; Busenberg, E.; Böhlke, J.K.; Nelms, D.L.; Michel, R.L.; Schlosser, P.

    2001-01-01

    Chemical and isotopic properties of water discharging from springs and wells in Shenandoah National Park (SNP), near the crest of the Blue Ridge Mountains, VA, USA were monitored to obtain information on groundwater residence times. Investigated time scales included seasonal (wet season, April, 1996; dry season, August-September, 1997), monthly (March through September, 1999) and hourly (30-min interval recording of specific conductance and temperature, March, 1999 through February, 2000). Multiple environmental tracers, including tritium/helium-3 (3H/3He), chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6), sulfur-35 (35S), and stable isotopes (??18O and ??2H) of water, were used to estimate the residence times of shallow groundwater discharging from 34 springs and 15 wells. The most reliable ages of water from springs appear to be based on SF6 and 3H/3He, with most ages in the range of 0-3 years. This range is consistent with apparent ages estimated from concentrations of CFCs; however, CFC-based ages have large uncertainties owing to the post-1995 leveling-off of the CFC atmospheric growth curves. Somewhat higher apparent ages are indicated by 35S (> 1.5 years) and seasonal variation of ??18O (mean residence time of 5 years) for spring discharge. The higher ages indicated by the 35S and ??18O data reflect travel times through the unsaturated zone and, in the case of 35S, possible sorption and exchange of S with soils or biomass. In springs sampled in April, 1996, apparent ages derived from the 3H/3He data (median age of 0.2 years) are lower than those obtained from SF6 (median age of 4.3 years), and in contrast to median ages from 3H/3He (0.3 years) and SF6 (0.7 years) obtained during the late summer dry season of 1997. Monthly samples from 1999 at four springs in SNP had SF6 apparent ages of only 1.2 to 2.5 ?? 0.8 years, and were consistent with the 1997 SF6 data. Water from springs has low excess air (0-1 cm3 kg-1) and N2-Ar temperatures that vary

  5. Determination of residence time and mixing processes of the Ubatuba, Brazil, inner shelf waters using natural Ra isotopes

    NASA Astrophysics Data System (ADS)

    Moore, Willard S.; de Oliveira, Joselene

    2008-02-01

    Coastal waters contain elevated dissolved activities of short-lived radium isotopes, 223Ra and 224Ra, having half-lives of 11.4 and 3.66 days, respectively. The input of these isotopes near the coast must be balanced by decay and mixing into the open ocean, where excess activities are zero. Since the decay rate is known, in the ideal case the mixing rate may be determined from the offshore distribution of these isotopes. This study found that samples collected in June 2000 followed the expected exponential decrease with distance offshore. We assign a dispersion coefficient of 28-39 m 2 s -1 for this study. During January 2002 and November 2003, there was not a consistent decrease of activity with distance offshore. This is likely due to the ruggedness of the coastline, where many bays and small islands interrupt simple mixing patterns. To estimate exchange rates during 2002 and 2003, we used a model based on the decrease in the 224Ra/ 223Ra activity ratio (AR) with time for samples isolated from fresh inputs of Ra. This model yielded residence times of 1-2 weeks for samples collected within 20 km of the coast. We used this residence time to calculate the flux of 228Ra (half-life = 5.7 years) to the study area necessary to maintain the enrichment relative to ocean water. This enrichment is a factor of ten greater than the flux of 228Ra expected from submarine groundwater discharge (SGD) occurring within 50 m of shore.

  6. Can we differentiate alpine groundwater storages regarding volume and residence time by recession observations, ion composition and tracer balance?

    NASA Astrophysics Data System (ADS)

    Floriancic, Marius; Smoorenburg, Maarten; Margreth, Michael; Naef, Felix

    2015-04-01

    Research on how catchments store and release water is essential to improve flood and low flow prediction in (un)gauged watersheds. Despite their importance for catchment scale assessments on runoff generation, knowledge on storage properties and residence times is still limited. Here we present some approaches to separate different storage types regarding their residence time and a quantification of the volumes of these storages based on a dataset of winter recession observation in the alpine Poschiavino headwater area. This spatially highly resolved dataset of discharge, electric conductivity and ion composition from a watershed with strongly contrasting storage properties, allowed separating three main contributing sources: continuous discharge from bedrock cracks, strongly delayed discharge from thick sediment deposits and fractured rock and rapid discharge from shallow layers. The gradients of the recession curves, the variation of electric conductivity in the river network and calculated tracer balance were used to separate contribution from different sources. Additionally contribution from sedimentary rocks and crystalline layers could be separated based on the variation of ion composition in the water samples. We derived recession curves for a period of four months for the separated storages in different parts of the catchment allowing estimation of the contributed volumes in this time period. Finally the spatial distribution of the storage types could be mapped throughout the catchment based on information like geo(morpho)logical maps, aerial photographs, DEM and field observations. We found significant variation comparing the discharged volume and specific discharge throughout the winter season in the different subcatchments. Constant discharge from bedrock cracks is similar in all catchment parts. Storage in the shallow deposits depleted quickly. High winter discharge could be attributed to thick quaternary deposits contributing during the whole

  7. Foraging strategy of a neotropical primate: how intrinsic and extrinsic factors influence destination and residence time.

    PubMed

    Plante, Sabrina; Colchero, Fernando; Calmé, Sophie

    2014-01-01

    Most animals need to actively search for food to meet energetic requirements and live in heterogeneous environments where food resources have complex spatio-temporal patterns of availability. Consequently, foraging animals need to find a balance between effort and resource allocation while accounting for intrinsic and extrinsic factors, which are often overlooked when modelling foraging behaviour. We identified the decision rules for foraging in black howler monkeys (Alouatta pigra), according to food preferences, locations of high-quality patches and previously eaten trees, phenology of food resources and hunger state. We depicted foraging in two stages: (i) the choice of the immediate next tree and (ii) the time spent on this tree. We used a recently developed model for inference of movement processes, incorporating resource selection functions into a Markov chain framework. We found that monkeys tend to move to preferred tree species at each step. However, we did not find conclusively that, at each step, monkeys direct their movements to reach high-quality patches. In fact, they were using these patches intensively, thus limiting the possibility to move towards other high-quality patches. Time spent on a tree was positively and strongly affected by the presence of preferred food items, but not by its species. We also showed that time spent on trees increased as a function of satiation state. We suggest that the strategy adopted by black howlers tends to be efficient because choosing preferred trees at each step and spending spend more time where preferred resources are available should favour energy intake and restrain movement costs. This study showcases a modelling framework that can be widely used in ecology to describe movements as a combination of multiple attraction and repulsion sources, such as mates and competitors. PMID:23957316

  8. Use of isotopic data to estimate water residence times of the Finger Lakes, New York

    NASA Astrophysics Data System (ADS)

    Michel, Robert L.; Kraemer, Thomas F.

    1995-01-01

    Water retention times in the Finger Lakes, a group of 11 lakes in central New York with similar hydrologic and climatic characteristics, were estimated by use of a tritium-balance model. During July 1991, samples were collected from the 11 lakes and selected tributary streams and were analyzed for tritium, deuterium, and oxygen-18. Additional samples from some of the sites were collected in 1990, 1992 and 1993. Tritium concentration in lake water ranged from 24.6 Tritium Units (TU) (Otisco Lake) to 43.2 TU (Seneca Lake).The parameters in the model used to obtain water retention time (WRT) included relative humidity, evaporation rate, tritium concentrations of inflowing water and lake water, and WRT of the lake. A historical record of tritium concentrations in precipitation and runoff was obtained from rainfall data at Ottawa, Canada, analyses of local wines produced during 1977-1991, and streamflow samples collected in 1990-1991. The model was simulated in yearly steps for 1953-1991, and the WRT was varied to reproduce tritium concentrations measured in each lake in 1991. Water retention times obtained from model simulations ranged from 1 year for Otisco Lake to 12 years for Seneca Lake, and with the exception of Seneca Lake and Skaneateles Lake, were in agreement with earlier estimates obtained from runoff estimates and chloride balances. The sensitivity of the model to parameter changes was tested to determine possible reasons for the differences calculated for WRT's for Seneca Lake and Skaneateles Lake. The shorter WRT obtained from tritium data for Lake Seneca (12 years as compared to 18 years) can be explained by a yearly addition of less than 3% by lake volume of ground water to the lake, the exact percentage depending on tritium concentration in the ground water.

  9. Short residence time hydropyrolysis of coal. Technical progress report, 1 January-31 March 1980

    SciTech Connect

    Saville, D. A.; Russel, W. B.

    1980-01-01

    This report sets forth the current status of our efforts to model the hydropyrolysis process on the scale of a single coal particle. Several oversimplifications of the original model have been identified and the more general analysis begun. As emphasized in the literature, the effect of time-temperature history, or nonisothermal reaction conditions, appears to be important and is being incorporated into the model. An increased internal pressure due to the restricted escape of volatiles can increase the rate of deposition and also cause the swelling of plastic coal particles. Our efforts reported here should lead to realistic descriptions of these processes.

  10. Polymer binding to carbon nanotubes in aqueous dispersions: residence time on the nanotube surface as obtained by NMR diffusometry.

    PubMed

    Frise, Anton E; Pagès, Guilhem; Shtein, Michael; Pri Bar, Ilan; Regev, Oren; Furó, István

    2012-03-01

    The binding of block copolymer Pluronic F-127 in aqueous dispersions of single- (SWCNT) and multiwalled (MWCNT) carbon nanotubes has been studied by pulsed-field-gradient (PFG) (1)H NMR spectroscopy. We show that a major fraction of polymers exist as a free species while a minor fraction is bound to the carbon nanotubes (CNT). The polymers exchange between these two states with residence times on the nanotube surface of 24 ± 5 ms for SWCNT and of 54 ± 11 ms for MWCNT. The CNT concentration in the solution was determined by improved thermal gravimetric analysis (TGA) indicating that the concentration of SWCNT dispersed by F-127 was significantly higher than that for MWCNT. For SWCNT, the area per adsorbed Pluronic F-127 molecule is estimated to be about 40 nm(2).

  11. 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

  12. In vivo Target Residence Time and Kinetic Selectivity: The Association Rate Constant as Determinant.

    PubMed

    de Witte, Wilhelmus E A; Danhof, Meindert; van der Graaf, Piet H; de Lange, Elizabeth C M

    2016-10-01

    It is generally accepted that, in conjunction with pharmacokinetics, the first-order rate constant of target dissociation is a major determinant of the time course and duration of in vivo target occupancy. Here we show that the second-order rate constant of target association can be equally important. On the basis of the commonly used mathematical models for drug-target binding, it is shown that a high target association rate constant can increase the (local) concentration of the drug, which decreases the rate of decline of target occupancy. The increased drug concentration can also lead to increased off-target binding and decreased selectivity. Therefore, the kinetics of both target association and dissociation need to be taken into account in the selection of drug candidates with optimal pharmacodynamic properties.

  13. In vivo Target Residence Time and Kinetic Selectivity: The Association Rate Constant as Determinant.

    PubMed

    de Witte, Wilhelmus E A; Danhof, Meindert; van der Graaf, Piet H; de Lange, Elizabeth C M

    2016-10-01

    It is generally accepted that, in conjunction with pharmacokinetics, the first-order rate constant of target dissociation is a major determinant of the time course and duration of in vivo target occupancy. Here we show that the second-order rate constant of target association can be equally important. On the basis of the commonly used mathematical models for drug-target binding, it is shown that a high target association rate constant can increase the (local) concentration of the drug, which decreases the rate of decline of target occupancy. The increased drug concentration can also lead to increased off-target binding and decreased selectivity. Therefore, the kinetics of both target association and dissociation need to be taken into account in the selection of drug candidates with optimal pharmacodynamic properties. PMID:27394919

  14. Changing restoration rules: exotic bivalves interact with residence time and depth to control phytoplankton productivity

    USGS Publications Warehouse

    Lucas, Lisa V.; Thompson, Janet K.

    2012-01-01

    Non-native species are a prevalent ecosystem stressor that can interact with other stressors to confound resource management and restoration. We examine how interactions between physical habitat attributes and a particular category of non-native species (invasive bivalves) influence primary production in aquatic ecosystems. Using mathematical models, we show how intuitive relationships between phytoplankton productivity and controllable physical factors (water depth, hydraulic transport time) that hold in the absence of bivalves can be complicated—and even reversed—by rapid bivalve grazing. In light-limited environments without bivalves, shallow, hydrodynamically “slow” habitats should generally have greater phytoplankton biomass and productivity than deeper, “faster” habitats. But shallower, slower environments can be less productive than deeper, faster ones if benthic grazing is strong. Moreover, shallower and slower waters exhibit a particularly broad range of possible productivity outcomes that can depend on whether bivalves are present. Since it is difficult to predict the response of non-native bivalves to habitat restoration, outcomes for new shallow, slow environments can be highly uncertain. Habitat depth and transport time should therefore not be used as indicators of phytoplankton biomass and production where bivalve colonization is possible. This study provides for ecosystem management a particular example of a broad lesson: abiotic ecosystem stressors should be managed with explicit consideration of interactions with other major (including biotic) stressors. We discuss the applicability and management implications of our models and results for a range of aquatic system types, with a case study focused on the Sacramento-San Joaquin Delta (California, USA). Simple mathematical models like those used here can illuminate interactions between ecosystem stressors and provide process-based guidance for resource managers as they develop strategies

  15. 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.

  16. 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

  17. 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

    2016-02-01

    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.

  18. 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

    2016-02-01

    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

  19. Rural Outreach: Connecting Distant Networks.

    ERIC Educational Resources Information Center

    Kenkel, Mary Beth

    Rural outreach in community mental health centers involves staff commuting from a central agency to surrounding rural towns to provide clinical and/or community service. The problem for outreach staff is how to best provide services to a rural network that is distant and different from the urban network. In general the greater the distance, the…

  20. The dependence of estuarine turbidity on tidal intrusion length, tidal range and residence time

    NASA Astrophysics Data System (ADS)

    Uncles, R. J.; Stephens, J. A.; Smith, R. E.

    2002-07-01

    times for solutes than shorter systems and that larger tides tend to reduce flushing times, although the tidal influence is secondary. Short, rapidly flushed estuaries quickly lose their erodable fine sediment to the coastal zone during freshets and during the ebbing currents of spring tides. Turbidity is therefore small during low runoff, low wave activity conditions. Very long, very slowly flushed estuaries are unlikely to lose a significant fraction of their resuspended sediments during freshets or individual ebb tides and are therefore able to accumulate large and increasing amounts of fine sediment in the long-term. Turbidity within them is therefore high during the fast currents of large spring tides.

  1. The dependence of estuarine turbidity on tidal intrusion length, tidal range and residence time

    USGS Publications Warehouse

    Uncles, R.J.; Stephens, J.A.; Smith, R.E.

    2002-01-01

    times for solutes than shorter systems and that larger tides tend to reduce flushing times, although the tidal influence is secondary. Short, rapidly flushed estuaries quickly lose their erodable fine sediment to the coastal zone during freshets and during the ebbing currents of spring tides. Turbidity is therefore small during low runoff, low wave activity conditions. Very long, very slowly flushed estuaries are unlikely to lose a significant fraction of their resuspended sediments during freshets or individual ebb tides and are therefore able to accumulate large and increasing amounts of fine sediment in the long-term. Turbidity within them is therefore high during the fast currents of large spring tides. ?? 2002 Elsevier Science Ltd. All rights reserved.

  2. Integrated modeling of flow and residence times at the catchment scale with multiple interacting pathways

    NASA Astrophysics Data System (ADS)

    Davies, J.; Beven, K.; Rodhe, A.; Nyberg, L.; Bishop, K.

    2013-08-01

    There is still a need for catchment hydrological and transport models that properly integrate the effects of preferential flows while accounting for differences in velocities and celerities. A modeling methodology is presented here which uses particle tracking methods to simulate both flow and transport in multiple pathways in a single consistent solution. Water fluxes and storages are determined by the volume and density of particles and transport is attained by labeling the particles with information that may be tracked throughout the lifetime of that particle in the catchment. The methodology allows representation of preferential flows through the use of particle velocity distributions, and mixing between pathways can be achieved with pathway transition probabilities. A transferable 3-D modeling methodology is presented for the first time and applied to a unique step-shift isotope experiment that was carried out at the 0.63 ha G1 catchment in Gårdsjön, Sweden. This application highlights the importance of combining flow and transport in hydrological representations, and the importance of pathway velocity distributions and interactions in obtaining a satisfactory representation of the observations.

  3. Residence times of fine tropospheric aerosols as determined by {sup 210}Pb progeny.

    SciTech Connect

    Marley, N. A.; Gaffney, J. S.; Drayton, P. J.; Cunningham, M. M.; Mielcarek, C.; Ravelo, R.; Wagner, C.

    1999-10-05

    Fine tropospheric aerosols can play important roles in the radiative balance of the atmosphere. The fine aerosols can act directly to cool the atmosphere by scattering incoming solar radiation, as well as indirectly by serving as cloud condensation nuclei. Fine aerosols, particularly carbonaceous soots, can also warm the atmosphere by absorbing incoming solar radiation. In addition, aerosols smaller than 2.5 {micro}m have recently been implicated in the health effects of air pollution. Aerosol-active radioisotopes are ideal tracers for the study of atmospheric transport processes. The source terms of these radioisotopes are relatively well known, and they are removed from the atmosphere only by radioactive decay or by wet or dry deposition of the host aerosol. The progeny of the primordial radionuclide {sup 238}U are of particular importance to atmospheric studies. Uranium-238 is common throughout Earth's crust and decays to the inert gas {sup 222}Rn, which escapes into the atmosphere. Radon-222 decays by the series of alpha and beta emissions shown in Figure 1 to the long-lived {sup 210}Pb. Once formed, {sup 210}Pb becomes attached to aerosol particles with average attachment times of 40 s to 3 min.

  4. Infectious Diseases in Immigrant Population Related to the Time of Residence in Spain.

    PubMed

    Cobo, Fernando; Salas-Coronas, Joaquín; Cabezas-Fernández, M Teresa; Vázquez-Villegas, José; Cabeza-Barrera, M Isabel; Soriano-Pérez, Manuel J

    2016-02-01

    The aim of this study was to evaluate the data on the main imported infectious diseases and public health issues arising from the risk of transmission of tropical and common diseases in the immigrant population. During the period of study, 2,426 immigrants were attended in the Tropical Medicine Unit of the Hospital of Poniente. For each patient, a complete screening for common and tropical diseases was performed. The prevalence and main features of intestinal and urinary parasites, microfilarias, Chagas disease, malaria, hepatitis B (HBV) and C (HCV) viruses, extrapulmonary tuberculosis and syphilis was investigated taking into account the length of stay in Spain. Sub-Saharan Africa patients who had lived for <3 years in Spain had a high significantly number of infections produced by hookworms, Ascaris lumbricoides, Trichuris trichiura, Schistosoma mansoni, Giardia lamblia, Entamoeba histolytica/dispar and Plasmodium spp. In patients who had lived for more than 3 years, there were significantly high rates of HBV infections, although HBV rates in sub-Saharan African patients are high even if the patients have been in Spain for <3 years. However, patients with large stays in Spain had also an important number of parasitological diseases. The main objective of the diagnosis is to avoid important public health problems and further complications in patients. It is advisable to carry out a screening of the main transmissible infections in all immigrant population regardless of the time outside their country. This screening should be individualized according to the geographical area of origin. PMID:25466580

  5. Time variant cross correlation to assess residence time of water and implication for hydraulics of a sink-rise karst system

    NASA Astrophysics Data System (ADS)

    Bailly-Comte, V.; Martin, Jonathan B.; Screaton, E. J.

    2011-05-01

    Transport rates and residence time in the subsurface are critical parameters for understanding water-rock interactions for efficient contaminant remediation. This paper presents a methodology for assessing flow and transit time of water through hydrological systems, with specific applications to karst systems and implication for hydraulics of a conduit system surrounded by a porous and permeable intergranular matrix. A time variant cross-correlation function analysis is applied to bivariate time series that characterize mass transfer, assuming a stationary system using sliding windows of various sizes. We apply the method to 1 year long temperature records in the Santa Fe River (north central Florida) measured at (1) the River Sink, where all the incoming surface water drains into a sinkhole, (2) Sweetwater Lake, where the river resurges into a 500 m long karst window, and (3) the River Rise, where the water discharges from a first-magnitude karst spring. Results are compared with those obtained using specific conductivity. Estimated residence time ranges from less than 1 day during floods to more than 15 days during base flow within the 8000 m flow path between the River Sink and the River Rise. Results are used to characterize geometric, hydraulic, and hydrodynamic properties of this sink-rise system with strong matrix-conduit interactions. These properties are critical to the chemical and physical behavior of surface water-groundwater mixing. Our results also have direct implications for sampling strategies and hydrograph separation of many karst systems with different degrees and types of matrix porosity and permeability.

  6. Characterization of surface and ground water δ18O seasonal variation and its use for estimating groundwater residence times

    USGS Publications Warehouse

    Reddy, Michael M.; Schuster, Paul F.; Kendall, Carol; Reddy, Micaela B.

    2006-01-01

    18O is an ideal tracer for characterizing hydrological processes because it can be reliably measured in several watershed hydrological compartments. Here, we present multiyear isotopic data, i.e. 18O variations (δ18O), for precipitation inputs, surface water and groundwater in the Shingobee River Headwaters Area (SRHA), a well-instrumented research catchment in north-central Minnesota. SRHA surface waters exhibit δ18O seasonal variations similar to those of groundwaters, and seasonal δ18O variations plotted versus time fit seasonal sine functions. These seasonal δ18O variations were interpreted to estimate surface water and groundwater mean residence times (MRTs) at sampling locations near topographically closed-basin lakes. MRT variations of about 1 to 16 years have been estimated over an area covering about 9 km2 from the basin boundary to the most downgradient well. Estimated MRT error (±0·3 to ±0·7 years) is small for short MRTs and is much larger (±10 years) for a well with an MRT (16 years) near the limit of the method. Groundwater transit time estimates based on Darcy's law, tritium content, and the seasonal δ18O amplitude approach appear to be consistent within the limits of each method. The results from this study suggest that use of the δ18O seasonal variation method to determine MRTs can help assess groundwater recharge areas in small headwaters catchments.

  7. RESIDENCE TIMES OF PARTICLES IN DIFFUSIVE PROTOPLANETARY DISK ENVIRONMENTS. II. RADIAL MOTIONS AND APPLICATIONS TO DUST ANNEALING

    SciTech Connect

    Ciesla, F. J.

    2011-10-10

    The origin of crystalline grains in comets and the outer regions of protoplanetary disks remains a mystery. It has been suggested that such grains form via annealing of amorphous precursors in the hot, inner region of a protoplanetary disk, where the temperatures needed for such transformations were found, and were then transported outward by some dynamical means. Here we develop a means of tracking the paths that dust grains would have taken through a diffusive protoplanetary disk and examine the types and ranges of environments that particles would have seen over a 10{sup 6} yr time period in the dynamic disk. We then combine this model with three annealing laws to examine how the dynamic evolution of amorphous grains would have led to their physical restructuring and their delivery to various regions of the disk. It is found that 'sibling particles' - those particles that reside at the same location at a given period of time-take a wide range of unique and independent paths through the disk to arrive there. While high temperatures can persist in the disk for very long time periods, we find that those grains that are delivered to the cold outer regions of the disk are largely annealed in the first few x10{sup 5} yr of disk history. This suggests that the crystallinity of grains in the outer disk would be determined early and remain unchanged for much of disk history, in agreement with recent astronomical observations.

  8. Belowground carbon allocation in a temperate beech forest: new insight into carbon residence time using whole tree 13C labelling

    NASA Astrophysics Data System (ADS)

    Epron, D.; Ngao, J.; Plain, C.; Longdoz, B.; Granier, A.

    2011-12-01

    Belowground carbon allocation is an important component of forest carbon budget, affecting tree growth (competition between aboveground and belowground carbon sinks), acquisition of belowground resources (nutrients and water) that are often limiting forest ecosystems and soil carbon sequestration. Total belowground carbon flow can be estimated using a mass-balance approach as cumulative soil CO2 efflux minus the carbon input from aboveground litter plus the changes in the C stored in roots, in the forest floor, and in the soil, and further compared to gross annual production. While this approach is useful for understanding the whole ecosystem carbon budget, uncertainties remain about the contribution of the different belowground pools of carbon to ecosystem respiration and carbon sequestration. New insights into transfer rate and residence time of carbon in belowground compartments can be gained from in situ whole-crown 13C labelling experiments. We combined both approaches in a young temperate beech forest in north-eastern France where ecosystem carbon fluxes are recorded since a decade. Carbon allocated belowground represented less than 40% of gross primary production in this young beech forest. Autotrophic respiration assessed by comparing soil CO2 efflux measured on normal and on root exclusion plots, accounted for 60% of the total belowground carbon flow. This indicated a rather short mean residence time of carbon allocated belowground in the soil compartments. The recovery of 13C in soil CO2 efflux after pulse-labelling entire crowns of tree with 13CO2 at several occasions during the growing season was observed a few couple of hours after the labelling. That indicates a rapid transfer of 13C belowground with a maximum occurring within 2 to 4 days after labelling. Label was recovered at the same time in the respiration and in the biomass of both fine roots and soil microbes. Allocation of recently assimilated carbon to soil microbial respiration was greater in

  9. A model of environmental behaviour of contaminated dust and its application to determining dust fluxes and residence times

    NASA Astrophysics Data System (ADS)

    Allott, R. W.; Kelly, M.; Nicholas Hewitt, C.

    A model has been developed to describe the temporal behaviour of the concentrations of a pollutant tracer within the urban environment of Barrow-in-Furness, NW England. The tracer used was 137Cs derived primarily from wet deposition, on 3 May 1986, of the radioactive cloud from the Chernobyl reactor accident (28 April 1986). The 137Cs activity deposited during this primary event was supplemented by a small secondary atmospheric deposition input of resuspended activity. The model was validated against the measured temporal behaviour of 137Cs in urban dust for two outdoor reservoirs in which the only observed input of dust and activity was by atmospheric deposition. Further modelling studies on other reservoirs (both outdoors and indoors) confirmed the existence of additional input fluxes of dust and activity; the most significant of these being the mechanical transport of soil and degradation of construction material (outdoors) and the mechanical transport of outdoor dust and soil and incorporation of organic material (indoors). The model enabled estimates of the magnitudes of these additional fluxes to be made and mean dust mass residence times to be calculated (outdoors, 250 ± 110 d; indoors 29 ± 1 d, indicating the length of time that conservative dust-bound pollutants would be expected to remain in urban reservoirs with no secondary inputs following the primary contamination event. These residence times correspond to environmental half-lives of 170 ± 70 d outdoors and 20 ± 1 d indoors, for reservoirs which only receive a single primary input of a contaminant. Where secondary inputs of pollutants occur, such as the atmospheric deposition of resuspended activity or the mechanical transport of contaminated dust indoors, the mean environmental half-lives of the pollutants increase by 50% for outdoor dust reservoirs and over 18-times for indoor reservoirs. This re-contamination of indoor dusts has implications for decontamination programmes in that attention

  10. 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

  11. Quantifying the residence time and flushing characteristics of a shallow, back-barrier estuary: Application of hydrodynamic and particle tracking models

    USGS Publications Warehouse

    Defne, Zafer; Ganju, Neil K.

    2015-01-01

    Estuarine residence time is a major driver of eutrophication and water quality. Barnegat Bay-Little Egg Harbor (BB-LEH), New Jersey, is a lagoonal back-barrier estuary that is subject to anthropogenic pressures including nutrient loading, eutrophication, and subsequent declines in water quality. A combination of hydrodynamic and particle tracking modeling was used to identify the mechanisms controlling flushing, residence time, and spatial variability of particle retention. The models demonstrated a pronounced northward subtidal flow from Little Egg Inlet in the south to Pt. Pleasant Canal in the north due to frictional effects in the inlets, leading to better flushing of the southern half of the estuary and particle retention in the northern estuary. Mean residence time for BB-LEH was 13 days but spatial variability was between ∼0 and 30 days depending on the initial particle location. Mean residence time with tidal forcing alone was 24 days (spatial variability between ∼0 and 50 days); the tides were relatively inefficient in flushing the northern end of the Bay. Scenarios with successive exclusion of physical processes from the models revealed that meteorological and remote offshore forcing were stronger drivers of exchange than riverine inflow. Investigations of water quality and eutrophication should take into account spatial variability in hydrodynamics and residence time in order to better quantify the roles of nutrient loading, production, and flushing.

  12. Program Directors' Responses to a Survey on Variables Used To Select Residents in a Time of Change.

    ERIC Educational Resources Information Center

    Wagoner, Norma E.; Suriano, J. Robert

    1999-01-01

    A survey of 794 program directors in 14 specialties assessed actual and projected changes in the selection process for medical residents and determined the relative weights the directors assigned to personal and academic criteria. Results indicate significant changes in the selection process, including a continuing decrease in residency positions…

  13. The Evolution and Increasing Complexity of the Resident Assistant Role in the United States from Colonial to Modern Times

    ERIC Educational Resources Information Center

    Boone, Katherine B.; Davidson, Denise L.; Bauman, Mark

    2016-01-01

    The evolution of the resident assistant position and its history are important to understanding its increasing complexities. In this article we examine how court cases and federal legislation, along with changes in popular culture, have altered and shaped the role of the resident assistant. Our premise is that this role, originally relatively…

  14. Flow pattern and residence time of groundwater within the south-eastern Taoudeni sedimentary basin (Burkina Faso, Mali)

    NASA Astrophysics Data System (ADS)

    Huneau, F.; Dakoure, D.; Celle-Jeanton, H.; Vitvar, T.; Ito, M.; Traore, S.; Compaore, N. F.; Jirakova, H.; Le Coustumer, P.

    2011-10-01

    SummaryThe knowledge about groundwater flow conditions within the Southeastern Taoudeni Basin Aquifer shared by Burkina Faso and Mali is relatively limited with very little information on potentiometric heads, recharge processes, residence time and water quality. A better evaluation of groundwater resources in this area is a strategic point for water resources management in the entire Soudano-Sahelian region which endures since the beginning of the twentieth century a continuous decrease in precipitation amount. This paper provides a transboundary synthesis using water ( 18O, 2H and 3H) and carbon isotopes ( 13C and 14C) in conjunction with hydrogeological and hydrochemical data. The objectives are to improve the conceptual model of groundwater recharge and flow within this sandstone reservoir, and to assess the changes in the aquifer due to water abstraction and recent climate changes including an insight into Sahelian aquifers palaeorecharge processes. The local meteoric water line for the Bobo-Dioulasso station is proposed: δ 2H = 8.0 (±0.5)δ 18O + 10.2 (±2.1). Two main tendencies can be derived from groundwater chemistry. First, a slight evolution from the Ca-Mg-HCO 3 type towards a Na-K-HCO 3 type that indicates developed interactions between groundwater and clay minerals related to the residence time of groundwater. A second tendency towards Cl-NO 3-SO 4-HCO 3 water types indicates the anthropogenic influence on groundwater related to the poor sanitary conditions observed around wells. The carbon-14 activity measured on the TDIC varies between 0.3 and 122 pmC, so our record contains samples covering a wide period from Actual to Pleistocene suggesting a continuous recharge of the system through time even if the Sahel region has endured many different climate phases which have influenced the infiltration and recharge processes. All groundwater samples have stable isotope compositions in the range of the present day regional and global meteoric water line

  15. Seasonal recharge and mean residence times of soil and epikarst water in a small karst catchment of southwest China.

    PubMed

    Hu, Ke; Chen, Hongsong; Nie, Yunpeng; Wang, Kelin

    2015-01-01

    Soil and epikarst play an important role in the hydrological cycle in karst regions. This paper focuses on investigating the seasonal recharge and mean residence time (MRT) of soil water and epikarst water in a small karst catchment of southwest China. The deuterium contents in precipitation, creek, soil baseflow (direct recharge of the saturated soil water to the stream), epikarst spring, and soil waters were monitored weekly for two years, and MRT was calculated by an exponential model (EM) and a dispersion model (DM). The obvious seasonal variation of deuterium in rainfall was buffered in epikarst water, indicating sufficient water mixing. Soil baseflow contained less rainy-season rainwater than epikarst spring discharge, reflecting the retarded effect of soil thickness on rainwater recharge. MRTs of all water bodies were 41-71 weeks, and soils in the depression extended those of shallow groundwater. This demonstrated that the deep soil layer played an important role in karst hydrological processes in the study catchment. The creek was recharged mostly by rainfall through epikarst, indicating its crucial role in water circulation. These results showed epikarst had a strong water-holding capacity and also delayed water contact time with dolomite. PMID:25959092

  16. Seasonal recharge and mean residence times of soil and epikarst water in a small karst catchment of southwest China.

    PubMed

    Hu, Ke; Chen, Hongsong; Nie, Yunpeng; Wang, Kelin

    2015-05-11

    Soil and epikarst play an important role in the hydrological cycle in karst regions. This paper focuses on investigating the seasonal recharge and mean residence time (MRT) of soil water and epikarst water in a small karst catchment of southwest China. The deuterium contents in precipitation, creek, soil baseflow (direct recharge of the saturated soil water to the stream), epikarst spring, and soil waters were monitored weekly for two years, and MRT was calculated by an exponential model (EM) and a dispersion model (DM). The obvious seasonal variation of deuterium in rainfall was buffered in epikarst water, indicating sufficient water mixing. Soil baseflow contained less rainy-season rainwater than epikarst spring discharge, reflecting the retarded effect of soil thickness on rainwater recharge. MRTs of all water bodies were 41-71 weeks, and soils in the depression extended those of shallow groundwater. This demonstrated that the deep soil layer played an important role in karst hydrological processes in the study catchment. The creek was recharged mostly by rainfall through epikarst, indicating its crucial role in water circulation. These results showed epikarst had a strong water-holding capacity and also delayed water contact time with dolomite.

  17. Seasonal recharge and mean residence times of soil and epikarst water in a small karst catchment of southwest China

    NASA Astrophysics Data System (ADS)

    Hu, Ke; Chen, Hongsong; Nie, Yunpeng; Wang, Kelin

    2015-05-01

    Soil and epikarst play an important role in the hydrological cycle in karst regions. This paper focuses on investigating the seasonal recharge and mean residence time (MRT) of soil water and epikarst water in a small karst catchment of southwest China. The deuterium contents in precipitation, creek, soil baseflow (direct recharge of the saturated soil water to the stream), epikarst spring, and soil waters were monitored weekly for two years, and MRT was calculated by an exponential model (EM) and a dispersion model (DM). The obvious seasonal variation of deuterium in rainfall was buffered in epikarst water, indicating sufficient water mixing. Soil baseflow contained less rainy-season rainwater than epikarst spring discharge, reflecting the retarded effect of soil thickness on rainwater recharge. MRTs of all water bodies were 41-71 weeks, and soils in the depression extended those of shallow groundwater. This demonstrated that the deep soil layer played an important role in karst hydrological processes in the study catchment. The creek was recharged mostly by rainfall through epikarst, indicating its crucial role in water circulation. These results showed epikarst had a strong water-holding capacity and also delayed water contact time with dolomite.

  18. Seasonal recharge and mean residence times of soil and epikarst water in a small karst catchment of southwest China

    PubMed Central

    Hu, Ke; Chen, Hongsong; Nie, Yunpeng; Wang, Kelin

    2015-01-01

    Soil and epikarst play an important role in the hydrological cycle in karst regions. This paper focuses on investigating the seasonal recharge and mean residence time (MRT) of soil water and epikarst water in a small karst catchment of southwest China. The deuterium contents in precipitation, creek, soil baseflow (direct recharge of the saturated soil water to the stream), epikarst spring, and soil waters were monitored weekly for two years, and MRT was calculated by an exponential model (EM) and a dispersion model (DM). The obvious seasonal variation of deuterium in rainfall was buffered in epikarst water, indicating sufficient water mixing. Soil baseflow contained less rainy-season rainwater than epikarst spring discharge, reflecting the retarded effect of soil thickness on rainwater recharge. MRTs of all water bodies were 41-71 weeks, and soils in the depression extended those of shallow groundwater. This demonstrated that the deep soil layer played an important role in karst hydrological processes in the study catchment. The creek was recharged mostly by rainfall through epikarst, indicating its crucial role in water circulation. These results showed epikarst had a strong water-holding capacity and also delayed water contact time with dolomite. PMID:25959092

  19. Soil Organic Matter Mean Residence Time Measurement: Characterization of Analyitical and Numerical Approaches for the Bombspike Model Resolution

    NASA Astrophysics Data System (ADS)

    Marzaioli, F.; Lubritto, C.; Del Galdo, I.; D'Onofrio, A.; Cotrufo, M.; Terrasi, F.

    2008-12-01

    Anthropogenic actions, fossil fuel use and land use change, are drastically altering the global carbon cycle. CO2 in the atmosphere, the most sensitive compartment of the entire cycle, has never been exceeded in the last 650 ka. Terrestrial ecosystems preserve in the soil organic matter(SOM) 1600 PgC, an amount of C twice with respect to the atmosphere. The amounts of carbon in SOM, its exchange fluxes with the atmosphere, the observed sequestering times(ranging from years to centuries)and the possibility of regulation of C in future land management, has led the scientific community to look at a more precise soil C cycle. Recent studies pointed out how, because of the multi compartment nature of soils, SOM cannot be considered as a homogeneous reservoir. The coexistence of several phases in the soil compartment is evidenced by the presence of different SOM carbon pools (fractions) each one characterized by a homogeneous C mean residence time. Considering SOM as a composite compartment drastically increases difficulties in the methodological approach to the study of these pools resulting in complex feedback responses to changing climate conditions. Atmospheric tests of nuclear weapons (banned in 1963 after the test ban treaty) enriched atmospheric 14CO2 doubling its background levels. The signal (bombspike) decreases over time, with an exponential trend (annual rate of 0.4%), because of the net uptake of CO2 from oceans and vegetation; and the dilution caused by fossil CO2 releases. Observed bombspike decrease rate allows dating of atmospheric CO2 with a precision of ± 1 year. Once globally distributed in the atmosphere the bombcarbon signal becomes a SOM marker allowing a sensitive mean residence time measurement of C by means of dynamic models simulating its fate in the soil (bombspike models). Bombspike models rely on the SOM box model, in which first derivative of soil C content over time is expressed by the net balance between net inputs of C and outputs

  20. Estimation of groundwater residence times in watersheds using the runoff recession hydrograph: Application and comparison with the isotopic approach in two headwater watersheds

    NASA Astrophysics Data System (ADS)

    Vitvar, T.; Burns, D. A.; McDonnell, J. J.

    2001-05-01

    A need exists for a method to estimate groundwater residence time in watersheds that uses readily available data. Current methods require intensive and expensive collection of isotope or other tracer data. We have developed a method for estimation of mean baseflow residence time in watersheds based on runoff recession characteristics in the Winnisook watershed, Catskill Mts, New York, USA, and in the Maimai watershed, New Zealand. We first derived mean transmissivity and storativity of the dynamic subsurface water storage based on calculated runoff recession characteristics, and then we used these to estimate mean baseflow residence time. The two selected watersheds represent two different geomorphic, climatic and hydrological regimes: the Winnisook is an upland forested catchment with 20\\deg mean slope angles, thin soils (<1.0 m) developed in glacial till, 1570 mm annual rainfall and is underlain by permeable layered sedimentary bedrock. The Maimai watershed is a steep humid catchment with 35\\deg mean slope angles, thin soils (<0.5 m), 2700 mm annual rainfall and is underlain by impermeable bedrock. To test the new approach, mean baseflow residence times were calculated using the convolution integral approach relating rainfall to sampled streamflow 18O values. Mean baseflow residence time for the 2 km&^{2}$ Winnisook watershed was about 9 months using both the convolution integral approach and the recession hydrograph approach. The mean baseflow residence time for the 0.3 ha Maimai watershed was 3 months based on the convolution integral approach. The recession hydrograph method yields a slightly different result dependent on the variable shape of the recession hydrograph in this wet climatic regime. This new baseflow recession method may be an alternative to the convolution integral approach, and can delineate dynamic and static reservoirs for solving mixing problems at the watershed scale.

  1. Residence times and diel passage distributions of radio-tagged juvenile spring chinook salmon and steelhead in a gatewell and fish collection channel of a Columbia River Dam

    USGS Publications Warehouse

    Beeman, J.W.; Maule, A.G.

    2001-01-01

    The amount of time radio-tagged juvenile spring chinook salmon Oncorhynchus tshawytscha and juvenile steelhead O. mykiss spent within a gatewell and the juvenile collection channel at McNary Dam, Columbia River, USA, was measured to determine the diel passage behavior and residence times within these portions of the juvenile bypass system. The median gatewell residence times were 8.9 h for juvenile chinook salmon and 3.2 h for steelhead. Juvenile spring chinook salmon spent 83% of their time in the 18-m-deep gatewell at depths of 9 m or less, and juvenile steelhead spent 96% of their time in the upper 11 m. Fish released during midday and those released in the evening generally exited the gatewell in the evening, indicating that fish entering the gatewell during daylight will have prolonged residence times. Median collection-channel residence times of juvenile chinook salmon were much shorter (2.3 min) than those of steelhead (28.0 min), most likely because of the greater size of the steelhead and the high water velocities within the channel (2.1 m/s). This and other studies indicate most juvenile salmonids enter gatewells of several Columbia and Snake river dams in the evening and pass into the collection channels quickly. However, this is not consistent with the natural in-river migration patterns of these species and represents a delay in dam passage.

  2. Xenobiotic removal efficiencies in wastewater treatment plants: residence time distributions as a guiding principle for sampling strategies.

    PubMed

    Majewsky, Marius; Gallé, Tom; Bayerle, Michael; Goel, Rajeev; Fischer, Klaus; Vanrolleghem, Peter A

    2011-11-15

    The effect of mixing regimes and residence time distribution (RTD) on solute transport in wastewater treatment plants (WWTPs) is well understood in environmental engineering. Nevertheless, it is frequently neglected in sampling design and data analysis for the investigation of polar xenobiotic removal efficiencies in WWTPs. Most studies on the latter use 24-h composite samples in influent and effluent. The effluent sampling period is often shifted by the mean hydraulic retention time assuming that this allows a total coverage of the influent load. However, this assumption disregards mixing regime characteristics as well as flow and concentration variability in evaluating xenobiotic removal performances and may consequently lead to biased estimates or even negative elimination efficiencies. The present study aims at developing a modeling approach to estimate xenobiotic removal efficiencies from monitoring data taking the hydraulic RTD in WWTPs into consideration. For this purpose, completely mixed tanks-in-series were applied to address hydraulic mixing regimes in a Luxembourg WWTP. Hydraulic calibration for this WWTP was performed using wastewater conductivity as a tracer. The RTD mixing approach was coupled with first-order biodegradation kinetics for xenobiotics covering three classes of biodegradability during aerobic treatment. Model simulations showed that a daily influent load is distributed over more than one day in the effluent. A 24-h sampling period with an optimal time offset between influent and effluent covers less than the half of the influent load in a dry weather scenario. According to RTD calculations, an optimized sampling strategy covering four consecutive measuring days in the influent would be necessary to estimate the full-scale elimination efficiencies with sufficient accuracy. Daily variations of influent flow and concentrations can substantially affect the reliability of these sampling results. Commonly reported negative removal

  3. Xenobiotic removal efficiencies in wastewater treatment plants: residence time distributions as a guiding principle for sampling strategies.

    PubMed

    Majewsky, Marius; Gallé, Tom; Bayerle, Michael; Goel, Rajeev; Fischer, Klaus; Vanrolleghem, Peter A

    2011-11-15

    The effect of mixing regimes and residence time distribution (RTD) on solute transport in wastewater treatment plants (WWTPs) is well understood in environmental engineering. Nevertheless, it is frequently neglected in sampling design and data analysis for the investigation of polar xenobiotic removal efficiencies in WWTPs. Most studies on the latter use 24-h composite samples in influent and effluent. The effluent sampling period is often shifted by the mean hydraulic retention time assuming that this allows a total coverage of the influent load. However, this assumption disregards mixing regime characteristics as well as flow and concentration variability in evaluating xenobiotic removal performances and may consequently lead to biased estimates or even negative elimination efficiencies. The present study aims at developing a modeling approach to estimate xenobiotic removal efficiencies from monitoring data taking the hydraulic RTD in WWTPs into consideration. For this purpose, completely mixed tanks-in-series were applied to address hydraulic mixing regimes in a Luxembourg WWTP. Hydraulic calibration for this WWTP was performed using wastewater conductivity as a tracer. The RTD mixing approach was coupled with first-order biodegradation kinetics for xenobiotics covering three classes of biodegradability during aerobic treatment. Model simulations showed that a daily influent load is distributed over more than one day in the effluent. A 24-h sampling period with an optimal time offset between influent and effluent covers less than the half of the influent load in a dry weather scenario. According to RTD calculations, an optimized sampling strategy covering four consecutive measuring days in the influent would be necessary to estimate the full-scale elimination efficiencies with sufficient accuracy. Daily variations of influent flow and concentrations can substantially affect the reliability of these sampling results. Commonly reported negative removal

  4. Charge and energy dependence of the residence time of cosmic ray nuclei below 15 GeV/nucleon

    NASA Technical Reports Server (NTRS)

    Soutoul, A.; Engelmann, J. J.; Ferrando, P.; Koch-Miramond, L.; Masse, P.; Webber, W. R.

    1985-01-01

    The relative abundance of nuclear species measured in cosmic rays at Earth has often been interpreted with the simple leaky box model. For this model to be consistent an essential requirement is that the escape length does not depend on the nuclear species. The discrepancy between escape length values derived from iron secondaries and from the B/C ratio was identified by Garcia-Munoz and his co-workers using a large amount of experimental data. Ormes and Protheroe found a similar trend in the HEAO data although they questioned its significance against uncertainties. They also showed that the change in the B/C ratio values implies a decrease of the residence time of cosmic rays at low energies in conflict with the diffusive convective picture. These conclusions crucially depend on the partial cross section values and their uncertainties. Recently new accurate cross sections of key importance for propagation calculations have been measured. Their statistical uncertainties are often better than 4% and their values significantly different from those previously accepted. Here, these new cross sections are used to compare the observed B/C+O and (Sc to Cr)/Fe ratio to those predicted with the simple leaky box model.

  5. A 2002-2008 hydrological budget and phosphorus residence times for Shark River Slough, Everglades National Park

    NASA Astrophysics Data System (ADS)

    Saha, A. K.; Price, R. M.; Fitz, H.; Engel, V.

    2010-12-01

    A monthly and annual water budget has been created for Shark River Slough (SRS) within the Everglades National Park (ENP) over 2002-2008. Inputs considered are surface water inflows via water delivery structures (S12s and S333) and precipitation, while outputs consist of evapotranspiration, discharge to the Gulf of Mexico (Lostman, Shark, Broad, Harney and North rivers) and seepage losses from the eastern part of the slough under levee L31. Using a mass balance approach, monthly change in volume of SRS (from water level changes) is equated to the sum of inputs, outputs and a residual term, that includes error in each of the inputs and outputs as well as net groundwater exchange. Results for 2002-2008 indicate that precipitation is the largest input to the SRS, while ET is the largest output, with ET being equal to or greater than precipitation. A net groundwater discharge to freshwater flow is predicted that is also lag correlated with surface water salinity by 1 month, thereby supporting earlier hydrological and geochemical findings of coastal groundwater discharge in the mangrove zone. The small quantity of inflows relative to precipitation and ET highlights the necessity of gradually increasing surface water inflows to restore ecosystem processes in terrestrial, freshwater and marine portions of the ENP. Water flow measurement data and the Ecological Landscape Model (ELM) is used in conjunction with Phosphorus concentration data to calculate phosphorus residence times in different parts of SRS that has been found to vary seasonally.

  6. 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.

  7. Refined assessment of associations between drinking water residence time and emergency department visits for gastrointestinal illness in Metro Atlanta, Georgia.

    PubMed

    Levy, Karen; Klein, Mitchel; Sarnat, Stefanie Ebelt; Panwhar, Samina; Huttinger, Alexandra; Tolbert, Paige; Moe, Christine

    2016-08-01

    Recent outbreak investigations suggest that a substantial proportion of waterborne disease outbreaks are attributable to water distribution system issues. In this analysis, we examine the relationship between modeled water residence time (WRT), a proxy for probability of microorganism intrusion into the distribution system, and emergency department visits for gastrointestinal (GI) illness for two water utilities in Metro Atlanta, USA during 1993-2004. We also examine the association between proximity to the nearest distribution system node, based on patients' residential address, and GI illness using logistic regression models. Comparing long (≥90th percentile) with intermediate WRTs (11th to 89th percentile), we observed a modestly increased risk for GI illness for Utility 1 (OR = 1.07, 95% CI: 1.02-1.13), which had substantially higher average WRT than Utility 2, for which we found no increased risk (OR = 0.98, 95% CI: 0.94-1.02). Examining finer, 12-hour increments of WRT, we found that exposures >48 h were associated with increased risk of GI illness, and exposures of >96 h had the strongest associations, although none of these associations was statistically significant. Our results suggest that utilities might consider reducing WRTs to <2-3 days or adding booster disinfection in areas with longer WRT, to minimize risk of GI illness from water consumption.

  8. Performance linked to residence time distribution by a novel wool-based bioreactor for tertiary sewage treatment.

    PubMed

    Hu, Bibo; Wheatley, Andrew; Ishtchenko, Vera; Huddersman, Katherine

    2012-05-01

    Laboratory-scale experiments were carried out using up-flow 7 L Submerged Aerated Filter reactors packed with wool fibre or commercial plastic pall rings, Kaldnes, (70% by volume) support media for the tertiary treatment of sewage. The performance of the wool bioreactor was more consistent than that with Kaldnes medium, for both TOC removal (93%) and SS removal (90%). Both plastic and wool-packed bioreactors achieved complete nitrification at the load of about 0.4 kgCOD/m(3)/day. The sludge yield of the wool bioreactor was almost half that of the bioreactor with Kaldnes suggesting that wool could retain residual organics and particulates. The wool however was degraded and it was concluded that wool would have to be considered as additional sacrificial adsorption capacity rather than an alternative medium. The performance was linked to the residence time distribution studies and these changes in the wool structure. Biomass growth increased the retention of the tracer in the wool reactor by, it was suggested, exposing a greater surface area. Results from the plastic media on the other hand showed increased mixing possibly by increasing the mobility of the plastic. Aeration increased the mixing in both reactors, and patterns were in all cases predominantly well-mixed.

  9. Size of spawning population, residence time, and territory shifts of individuals in the spawning aggregation of a riverine catostomid

    USGS Publications Warehouse

    Grabowski, T.B.; Isely, J.J.

    2008-01-01

    Little is known about the behavior of individual fish in a spawning aggregation, specifically how long an individual remains in an aggregation. We monitored Moxostoma robustum (Cope) (Robust Redhorse) in a Savannah River spawning aggregation during spring 2004 and 2005 to provide an estimate of the total number of adults and the number of males comprising the aggregation and to determine male residence time and movements within a spawning aggregation. Robust Redhorse were captured using prepostioned grid electrofishers, identified to sex, weighed, measured, and implanted with a passive integrated transponder. Spawning aggregation size was estimated using a multiple census mark-and-recapture procedure. The spawning aggregation seemed to consist of approximately the same number of individuals (82-85) and males (50-56) during both years of this study. Individual males were present for a mean of 3.6 ?? 0.24 days (?? SE) during the 12-day spawning period. The mean distance between successive recaptures of individual males was 15.9 ?? 1.29 m (?? SE). We conclude that males establish spawning territories on a daily basis and are present within the spawning aggregation for at least 3-4 days. The relatively short duration of the aggregation may be the result of an extremely small population of adults. However, the behavior of individuals has the potential to influence population estimates made while fish are aggregated for spawning.

  10. Residence times and mixing of water in river banks: implications for recharge and groundwater-surface water exchange

    NASA Astrophysics Data System (ADS)

    Unland, N. P.; Cartwright, I.; Cendón, D. I.; Chisari, R.

    2014-12-01

    Bank exchange processes within 50 m of the Tambo River, southeast Australia, have been investigated through the combined use of 3H and 14C. Groundwater residence times increase towards the Tambo River, which suggests the absence of significant bank storage. Major ion concentrations and δ2H and δ18O values of bank water also indicate that bank infiltration does not significantly impact groundwater chemistry under baseflow and post-flood conditions, suggesting that the gaining nature of the river may be driving the return of bank storage water back into the Tambo River within days of peak flood conditions. The covariance between 3H and 14C indicates the leakage and mixing between old (~17 200 years) groundwater from a semi-confined aquifer and younger groundwater (<100 years) near the river, where confining layers are less prevalent. It is likely that the upward infiltration of deeper groundwater from the semi-confined aquifer during flooding limits bank infiltration. Furthermore, the more saline deeper groundwater likely controls the geochemistry of water in the river bank, minimising the chemical impact that bank infiltration has in this setting. These processes, coupled with the strongly gaining nature of the Tambo River are likely to be the factors reducing the chemical impact of bank storage in this setting. This study illustrates the complex nature of river groundwater interactions and the potential downfall in assuming simple or idealised conditions when conducting hydrogeological studies.

  11. T-3364366 Targets the Desaturase Domain of Delta-5 Desaturase with Nanomolar Potency and a Multihour Residence Time.

    PubMed

    Miyahisa, Ikuo; Suzuki, Hideo; Mizukami, Atsushi; Tanaka, Yukiya; Ono, Midori; Hixon, Mark S; Matsui, Junji

    2016-09-01

    Delta-5 desaturase (D5D) catalyzes the conversion from dihomo-gamma linoleic acid (DGLA) to arachidonic acid (AA). DGLA and AA are common precursors of anti- and pro-inflammatory eicosanoids, respectively, making D5D an attractive drug target for inflammatory-related diseases. Despite several reports on D5D inhibitors, their biochemical mechanisms of action (MOAs) remain poorly understood, primarily due to the difficulty in performing quantitative enzymatic analysis. Herein, we report a radioligand binding assay to overcome this challenge and characterized T-3364366, a thienopyrimidinone D5D inhibitor, by use of the assay. T-3364366 is a reversible, slow-binding inhibitor with a dissociation half-life in excess of 2.0 h. The long residence time was confirmed in cellular washout assays. Domain swapping experiments between D5D and D6D support [(3)H]T-3364366 binding to the desaturase domain of D5D. The present study is the first to demonstrate biochemical MOA of desaturase inhibitors, providing important insight into drug discovery of desaturase enzymes. PMID:27660693

  12. In vitro and ex vivo methods predict the enhanced lung residence time of liposomal ciprofloxacin formulations for nebulisation.

    PubMed

    Ong, Hui Xin; Benaouda, Faiza; Traini, Daniela; Cipolla, David; Gonda, Igor; Bebawy, Mary; Forbes, Ben; Young, Paul M

    2014-01-01

    Liposomal ciprofloxacin formulations have been developed with the aim of enhancing lung residence time, thereby reducing the burden of inhaled antimicrobial therapy which requires multiple daily administration due to rapid absorptive clearance of antibiotics from the lungs. However, there is a lack of a predictive methodology available to assess controlled release inhalation delivery systems and their effect on drug disposition. In this study, three ciprofloxacin formulations were evaluated: a liposomal formulation, a solution formulation and a 1:1 combination of the two (mixture formulation). Different methodologies were utilised to study the release profiles of ciprofloxacin from these formulations: (i) membrane diffusion, (ii) air interface Calu-3 cells and (iii) isolated perfused rat lungs. The data from these models were compared to the performance of the formulations in vivo. The solution formulation provided the highest rate of absorptive transport followed by the mixture formulation, with the liposomal formulation providing substantially slower drug release. The rank order of drug release/transport from the different formulations was consistent across the in vitro and ex vivo methods, and this was predictive of the profiles in vivo. The use of complimentary in vitro and ex vivo methodologies provided a robust analysis of formulation behaviour, including mechanistic insights, and predicted in vivo pharmacokinetics.

  13. A non-discrete method for residence time calculation as an indicator of thrombus formation in cardiovascular applications

    NASA Astrophysics Data System (ADS)

    Esmaily Moghadam, Mahdi; Marsden, Alison

    2012-11-01

    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 fully understood, recent findings suggest that thrombosis risk correlates with the presence of recirculation regions with high residence time (RT). Current approaches for calculating RT are often based on releasing a finite number of Lagrangian particles in the flow and calculating RT by tracking their pathways. However, this method requires several simulations for a single case study, each of which requires releasing a significant number of particles, to obtain temporal and spatial convergence. In this work, we introduce a new non-discrete method, in which RT is calculated in an Eulerian non-discrete framework, using the advection-diffusion equation. Starting with an existing and a newly developed intuitive definition for the RT, the formulation for calculating RT in a region of interest is presented. The physical significance and sensitivity of each measure of RT is discussed and an extension of these definitions to a point-wise value is presented. Application to simulations of shunt insertion for single ventricle heart patients is demonstrated.

  14. Refined assessment of associations between drinking water residence time and emergency department visits for gastrointestinal illness in Metro Atlanta, Georgia.

    PubMed

    Levy, Karen; Klein, Mitchel; Sarnat, Stefanie Ebelt; Panwhar, Samina; Huttinger, Alexandra; Tolbert, Paige; Moe, Christine

    2016-08-01

    Recent outbreak investigations suggest that a substantial proportion of waterborne disease outbreaks are attributable to water distribution system issues. In this analysis, we examine the relationship between modeled water residence time (WRT), a proxy for probability of microorganism intrusion into the distribution system, and emergency department visits for gastrointestinal (GI) illness for two water utilities in Metro Atlanta, USA during 1993-2004. We also examine the association between proximity to the nearest distribution system node, based on patients' residential address, and GI illness using logistic regression models. Comparing long (≥90th percentile) with intermediate WRTs (11th to 89th percentile), we observed a modestly increased risk for GI illness for Utility 1 (OR = 1.07, 95% CI: 1.02-1.13), which had substantially higher average WRT than Utility 2, for which we found no increased risk (OR = 0.98, 95% CI: 0.94-1.02). Examining finer, 12-hour increments of WRT, we found that exposures >48 h were associated with increased risk of GI illness, and exposures of >96 h had the strongest associations, although none of these associations was statistically significant. Our results suggest that utilities might consider reducing WRTs to <2-3 days or adding booster disinfection in areas with longer WRT, to minimize risk of GI illness from water consumption. PMID:27441862

  15. Resident recruitment.

    PubMed

    Longmaid, H Esterbrook

    2003-02-01

    This article has introduced the reader to the critical components of successful recruitment of radiology residents. With particular attention to the ACGME institutional and program requirements regarding resident recruitment, and an explanation of the support systems (ERAS and NRMP) currently available to those involved in applicant review and selection, the article has sought to delineate a sensible approach to recruitment. Successful recruiters have mastered the essentials of these programs and have learned to adapt the programs to their needs. As new program directors work with their departments' resident selection committees, they will identify the factors that faculty and current residents cite as most important in the successful selection of new residents. By structuring the application review process, exploiting the power of the ERAS, and crafting a purposeful and friendly interview process, radiology residency directors can find and recruit the residents who best match their programs. PMID:12585436

  16. Contrasting residence times and fluxes of water and sulfate in two small forested watersheds in Virginia, USA.

    PubMed

    Böhlke, John Karl; Michel, Robert L

    2009-07-01

    Watershed mass balances for solutes of atmospheric origin may be complicated by the residence times of water and solutes at various time scales. In two small forested headwater catchments in the Appalachian Mountains of Virginia, USA, mean annual export rates of SO(4)(=) differ by a factor of 2, and seasonal variations in SO(4)(=) concentrations in atmospheric deposition and stream water are out of phase. These features were investigated by comparing (3)H, (35)S, delta(34)S, delta(2)H, delta(18)O, delta(3)He, CFC-12, SF(6), and chemical analyses of open deposition, throughfall, stream water, and spring water. The concentrations of SO(4)(=) and radioactive (35)S were about twice as high in throughfall as in open deposition, but the weighted composite values of (35)S/S (11.1 and 12.1x10(-15)) and delta(34)S (+3.8 and +4.1 per thousand) were similar. In both streams (Shelter Run, Mill Run), (3)H concentrations and delta(34)S values during high flow were similar to those of modern deposition, delta(2)H and delta(18)O values exhibited damped seasonal variations, and (35)S/S ratios (0-3x10(-15)) were low throughout the year, indicating inter-seasonal to inter-annual storage and release of atmospheric SO(4)(=) in both watersheds. In the Mill Run watershed, (3)H concentrations in stream base flow (10-13 TU) were consistent with relatively young groundwater discharge, most delta(34)S values were approximately the same as the modern atmospheric deposition values, and the annual export rate of SO(4)(=) was equal to or slightly greater than the modern deposition rate. In the Shelter Run watershed, (3)H concentrations in stream base flow (1-3 TU) indicate that much of the discharging ground water had been deposited prior to the onset of atmospheric nuclear bomb testing in the 1950s, base flow delta(34)S values (+1.6 per thousand) were significantly lower than the modern deposition values, and the annual export rate of SO(4)(=) was less than the modern deposition rate

  17. Contrasting residence times and fluxes of water and sulfate in two small forested watersheds in Virginia, USA

    USGS Publications Warehouse

    Böhlke, J.K.; Michel, R.L.

    2009-01-01

    Watershed mass balances for solutes of atmospheric origin may be complicated by the residence times of water and solutes at various time scales. In two small forested headwater catchments in the Appalachian Mountains of Virginia, USA, mean annual export rates of SO4= differ by a factor of 2, and seasonal variations in SO4= concentrations in atmospheric deposition and stream water are out of phase. These features were investigated by comparing 3H, 35S, ??34S, ??2H, ??18O, ??3He, CFC-12, SF6, and chemical analyses of open deposition, throughfall, stream water, and spring water. The concentrations of SO4= and radioactive 35S were about twice as high in throughfall as in open deposition, but the weighted composite values of 35S/S (11.1 and 12.1 ?? 10- 15) and ??34S (+ 3.8 and + 4.1???) were similar. In both streams (Shelter Run, Mill Run), 3H concentrations and ??34S values during high flow were similar to those of modern deposition, ??2H and ??18O values exhibited damped seasonal variations, and 35S/S ratios (0-3 ?? 10- 15) were low throughout the year, indicating inter-seasonal to inter-annual storage and release of atmospheric SO4= in both watersheds. In the Mill Run watershed, 3H concentrations in stream base flow (10-13??TU) were consistent with relatively young groundwater discharge, most ??34S values were approximately the same as the modern atmospheric deposition values, and the annual export rate of SO4= was equal to or slightly greater than the modern deposition rate. In the Shelter Run watershed, 3H concentrations in stream base flow (1-3??TU) indicate that much of the discharging ground water had been deposited prior to the onset of atmospheric nuclear bomb testing in the 1950s, base flow ??34S values (+ 1.6???) were significantly lower than the modern deposition values, and the annual export rate of SO4= was less than the modern deposition rate. Concentrations of 3H and 35S in Shelter Run base flow, and of 3H, 3He, CFC-12, SF6, and 35S in a spring

  18. Whale shark (Rhincodon typus) seasonal presence, residence time and habitat use at darwin island, galapagos marine reserve.

    PubMed

    Acuña-Marrero, David; Jiménez, Jesús; Smith, Franz; Doherty, Paul F; Hearn, Alex; Green, Jonathan R; Paredes-Jarrín, Jules; Salinas-de-León, Pelayo

    2014-01-01

    The life history of the whale shark (Rhincodon typus), including its reproductive ecology, still remains largely unknown. Here, we present results from the first whale shark population study around Darwin Island, Galapagos Marine Reserve. Following a diversified approach we characterized seasonal occurrence, population structure and size, and described habitat use of whale sharks based on fine scale movements around the island. Whale shark presence at Darwin Island was negatively correlated with Sea Surface Temperature (SST), with highest abundance corresponding to a cool season between July and December over six years of monitoring. From 2011 to 2013 we photo-identified 82 whale sharks ranging from 4 to 13.1 m Total Length (TL). Size distribution was bimodal, with a great majority (91.5%) of adult female individuals averaging 11.35 m±0.12 m (TL±SE), all but one showing signs of a potential pregnancy. Population dynamics models for apparently pregnant sharks estimated the presence of 3.76±0.90 (mean ± SE) sharks in the study area per day with an individual residence time of 2.09±0.51 (mean ± SE) days. Movement patterns analysis of four apparently pregnant individuals tracked with acoustic tags at Darwin Island revealed an intense use of Darwin's Arch, where no feeding or specific behavior has been recorded, together with periodic excursions around the island's vicinity. Sharks showed a preference for intermediate depths (20-30 m) with occasional dives mostly to mid-water, remaining the majority of their time at water temperatures between 24-25°C. All of our results point to Darwin Island as an important stopover in a migration, possibly with reproductive purposes, rather than an aggregation site. Current studies carried out in this area to investigate regional scale movement patterns may provide essential information about possible pupping grounds for this enigmatic species. PMID:25551553

  19. Whale shark (Rhincodon typus) seasonal presence, residence time and habitat use at darwin island, galapagos marine reserve.

    PubMed

    Acuña-Marrero, David; Jiménez, Jesús; Smith, Franz; Doherty, Paul F; Hearn, Alex; Green, Jonathan R; Paredes-Jarrín, Jules; Salinas-de-León, Pelayo

    2014-01-01

    The life history of the whale shark (Rhincodon typus), including its reproductive ecology, still remains largely unknown. Here, we present results from the first whale shark population study around Darwin Island, Galapagos Marine Reserve. Following a diversified approach we characterized seasonal occurrence, population structure and size, and described habitat use of whale sharks based on fine scale movements around the island. Whale shark presence at Darwin Island was negatively correlated with Sea Surface Temperature (SST), with highest abundance corresponding to a cool season between July and December over six years of monitoring. From 2011 to 2013 we photo-identified 82 whale sharks ranging from 4 to 13.1 m Total Length (TL). Size distribution was bimodal, with a great majority (91.5%) of adult female individuals averaging 11.35 m±0.12 m (TL±SE), all but one showing signs of a potential pregnancy. Population dynamics models for apparently pregnant sharks estimated the presence of 3.76±0.90 (mean ± SE) sharks in the study area per day with an individual residence time of 2.09±0.51 (mean ± SE) days. Movement patterns analysis of four apparently pregnant individuals tracked with acoustic tags at Darwin Island revealed an intense use of Darwin's Arch, where no feeding or specific behavior has been recorded, together with periodic excursions around the island's vicinity. Sharks showed a preference for intermediate depths (20-30 m) with occasional dives mostly to mid-water, remaining the majority of their time at water temperatures between 24-25°C. All of our results point to Darwin Island as an important stopover in a migration, possibly with reproductive purposes, rather than an aggregation site. Current studies carried out in this area to investigate regional scale movement patterns may provide essential information about possible pupping grounds for this enigmatic species.

  20. Estimation of groundwater residence time using environmental radioisotopes (14C,T) in carbonate aquifers, southern Poland.

    PubMed

    Samborska, Katarzyna; Różkowski, Andrzej; Małoszewski, Piotr

    2013-01-01

    Triassic carbonate aquifers in the Upper Silesia region, affected by intense withdrawal, have been investigated by means of isotopic analyses of (14)C, δ(13)C, δ(2)H, δ(18)O and (3)H. The isotopic examinations were carried out in the 1970s and in the early 1980s, and it was the first application of tracers to estimate age and vulnerability for the contamination of groundwater in this region. Similar isotopic analyses were conducted in 2007 and 2008 with the same Triassic carbonate formation. The isotopic examinations were performed within the confined part of the carbonate formation, wherein aquifers are covered by semi-permeable deposits. The direct recharge of the aquifer occurs in the outcrop areas, but it mainly takes place due to percolation of the water through aquitards and erosional windows. The Triassic aquifer has been intensively drained by wells and by lead-zinc mines. Nowadays, the declining water demand and closure of some mines have induced a significant increase in the water table level. The detailed analysis of the results, including the radiocarbon age corrections and the comparison of radioisotope activities, has made it possible to estimate the range of residence time within the carbonate Triassic aquifer. This range from several tens to several tens of thousands indicates that the recharge of aquifers might have occurred between modern times and the Pleistocene. The apparent age of the water estimated on the basis of (14)C activity was corrected considering the carbon isotope exchange and the diffusion between mobile water in fractures and stagnant water in micropores. The obtained corrected period of recharge corresponds to the result of investigations of noble gases, which were carried out in the 1990s. In almost half of the cases, groundwater is a mixture of young and old water. The mixing processes occur mainly in areas of heavy exploitation of the aquifer. PMID:22607326

  1. Estimation of groundwater residence time using environmental radioisotopes (14C,T) in carbonate aquifers, southern Poland.

    PubMed

    Samborska, Katarzyna; Różkowski, Andrzej; Małoszewski, Piotr

    2013-01-01

    Triassic carbonate aquifers in the Upper Silesia region, affected by intense withdrawal, have been investigated by means of isotopic analyses of (14)C, δ(13)C, δ(2)H, δ(18)O and (3)H. The isotopic examinations were carried out in the 1970s and in the early 1980s, and it was the first application of tracers to estimate age and vulnerability for the contamination of groundwater in this region. Similar isotopic analyses were conducted in 2007 and 2008 with the same Triassic carbonate formation. The isotopic examinations were performed within the confined part of the carbonate formation, wherein aquifers are covered by semi-permeable deposits. The direct recharge of the aquifer occurs in the outcrop areas, but it mainly takes place due to percolation of the water through aquitards and erosional windows. The Triassic aquifer has been intensively drained by wells and by lead-zinc mines. Nowadays, the declining water demand and closure of some mines have induced a significant increase in the water table level. The detailed analysis of the results, including the radiocarbon age corrections and the comparison of radioisotope activities, has made it possible to estimate the range of residence time within the carbonate Triassic aquifer. This range from several tens to several tens of thousands indicates that the recharge of aquifers might have occurred between modern times and the Pleistocene. The apparent age of the water estimated on the basis of (14)C activity was corrected considering the carbon isotope exchange and the diffusion between mobile water in fractures and stagnant water in micropores. The obtained corrected period of recharge corresponds to the result of investigations of noble gases, which were carried out in the 1990s. In almost half of the cases, groundwater is a mixture of young and old water. The mixing processes occur mainly in areas of heavy exploitation of the aquifer.

  2. Whale Shark (Rhincodon typus) Seasonal Presence, Residence Time and Habitat Use at Darwin Island, Galapagos Marine Reserve

    PubMed Central

    Acuña-Marrero, David; Jiménez, Jesús; Smith, Franz; Doherty, Paul F.; Hearn, Alex; Green, Jonathan R.; Paredes-Jarrín, Jules; Salinas-de-León, Pelayo

    2014-01-01

    The life history of the whale shark (Rhincodon typus), including its reproductive ecology, still remains largely unknown. Here, we present results from the first whale shark population study around Darwin Island, Galapagos Marine Reserve. Following a diversified approach we characterized seasonal occurrence, population structure and size, and described habitat use of whale sharks based on fine scale movements around the island. Whale shark presence at Darwin Island was negatively correlated with Sea Surface Temperature (SST), with highest abundance corresponding to a cool season between July and December over six years of monitoring. From 2011 to 2013 we photo-identified 82 whale sharks ranging from 4 to 13.1 m Total Length (TL). Size distribution was bimodal, with a great majority (91.5%) of adult female individuals averaging 11.35 m±0.12 m (TL±SE), all but one showing signs of a potential pregnancy. Population dynamics models for apparently pregnant sharks estimated the presence of 3.76±0.90 (mean ± SE) sharks in the study area per day with an individual residence time of 2.09±0.51 (mean ± SE) days. Movement patterns analysis of four apparently pregnant individuals tracked with acoustic tags at Darwin Island revealed an intense use of Darwin's Arch, where no feeding or specific behavior has been recorded, together with periodic excursions around the island's vicinity. Sharks showed a preference for intermediate depths (20–30 m) with occasional dives mostly to mid-water, remaining the majority of their time at water temperatures between 24–25°C. All of our results point to Darwin Island as an important stopover in a migration, possibly with reproductive purposes, rather than an aggregation site. Current studies carried out in this area to investigate regional scale movement patterns may provide essential information about possible pupping grounds for this enigmatic species. PMID:25551553

  3. Gaseous activity of distant comets

    NASA Astrophysics Data System (ADS)

    Womack, Maria; Sarid, Gal; Wierzchos, Kacper

    2016-10-01

    The activity of most comets within 3AU of the Sun is dominated by the sublimation of frozen water, the most abundant ice in comets. Some comets, however, are active well beyond the water-ice sublimation limit. Studying distantly active comets provides valuable opportunities to explore primitive bodies when water-ice sublimation is largely dormant, which is the case for most of a comet's lifetime. Beyond 4 AU, super-volatiles such as CO or CO2 are thought to play a major role in driving observed activity. Carbon monoxide is of special interest because it is a major contributor to comae and has a very low sublimation temperature. Three bodies dominate the observational record and modeling efforts for distantly active small bodies: the long-period comet C/1995 O1 Hale-Bopp and the short-period comets (with centaur orbits) 29P/Schwassmann Wachmann 1 and 2060 Chiron. Hale-Bopp's long-period orbit means it has experienced very little solar heating in its lifetime and is analogous to dynamically new comets making their first approach to the Sun. Because Chiron and 29P have much smaller orbits closer to the Sun, they have experienced much more thermal processing than Hale-Bopp and this is expected to have changed their chemical composition from their original state. We point out that the observed CO production rates and line-widths in these three distantly active objects are consistent with each other when adjusted for heliocentric distance. This is particularly interesting for Hale-Bopp and 29P, which have approximately the same radius. The consistent CO production rates may point to a similar CO release mechanism in these objects. We also discuss how observed radio line profiles support that the development and sublimation of icy grains in the coma at about 5-6 AU is probably a common feature in distantly active comets, and an important source of other volatiles within 6 AU, including H2O, HCN, CH3OH, and H2CO.

  4. SUBSURFACE RESIDENCE TIMES AS AN ALGORITHM FOR AQUIFER SENSITIVITY MAPPING: TESTING THE CONCEPT WITH GROUND WATER MODELS IN THE CONTENTNEA CREEK BASIN, NORTH CAROLINA, USA

    EPA Science Inventory

    This poster will present a modeling and mapping assessment of landscape sensitivity to non-point source pollution as applied to a hierarchy of catchment drainages in the Coastal Plain of the state of North Carolina. Analysis of the subsurface residence time of water in shallow a...

  5. Subsurface Residence Times as an Algorithm for Aquifer Sensitivity Mapping: testing the concept with analytic element ground water models in the Contentnea Creek Basin, North Carolina, USA

    NASA Astrophysics Data System (ADS)

    Kraemer, S. R.

    2002-05-01

    The objective of this research is to test the utility of simple functions of spatially integrated and temporally averaged ground water residence times in shallow groundwatersheds with field observations and detailed computer simulations. The residence time of water in the subsurface is arguably a surrogate of aquifer sensitivity to contamination --- short contact time in subsurface media may result in reduced contaminant assimilation prior to discharge to a well or stream. Residence time is an established criterion for the delineation of wellhead protection areas. The residence time of water may also have application in assessing the connection between landscape and fair weather loadings of non-point source pollution to streams, such as the drainage of nitrogen-nitrate from agricultural fields as base flow. The field setting of this study includes a hierarchy of catchments in the Contentnea Creek basin (2600 km2) of North Carolina, USA, centered on the intensive coastal plain field study site at Lizzie, NC (1.2+km^2), run by the US Geological Survey and the NC Department of Environment and Natural Resources of Raleigh, NC. Analytic element models are used to define the advective flow field and regional boundary conditions. The issues of conceptual model complexity are explored using the multi-layer object oriented analytic element model Tim, and by embedding the finite difference model MODFLOW within the analytic element model GFLOW copyright. The models are compared to observations of hydraulic head, base flow separations, and aquifer geochemistry and age dating evidence. The resulting insights are captured and mapped across the basin as zones of average aquifer residence time using ArcView copyright GIS tools. Preliminary results and conclusions will be presented. Mention of commercial software does not constitute endorsement or recommendation for use.

  6. PARTIAL REPRODUCTIVE ISOLATION OF A RECENTLY DERIVED RESIDENT-FRESHWATER POPULATION OF THREESPINE STICKLEBACK (GASTEROSTEUS ACULEATUS) FROM ITS PUTATIVE ANADROMOUS ANCESTOR

    PubMed Central

    Furin, Christoff G.; Von Hippel, Frank A.; Bell, Michael A.

    2012-01-01

    We used no-choice mating trials to test for assortative mating between a newly derived resident-freshwater population (8 – 22 generations since founding) of threespine stickleback (Gasterosteus aculeatus) in Loberg Lake, Alaska and its putative anadromous ancestor as well as a morphologically convergent but distantly related resident-freshwater population. Partial reproductive isolation has evolved between the Loberg Lake population and its ancestor within a remarkably short time period. However, Loberg stickleback readily mate with morphologically similar, but distantly related resident-freshwater stickleback. Partial pre-mating isolation is asymmetrical; anadromous females and smaller, resident-freshwater males from Loberg Lake readily mate, but the anadromous males and smaller Loberg females do not. Our results indicate that pre-mating isolation can begin to evolve in allopatry within a few generations after isolation as a correlated effect of evolution of reduced body size. PMID:23025615

  7. Origin and residence time of groundwater in the Tadla basin (Morocco) using multiple isotopic and geochemical tools

    NASA Astrophysics Data System (ADS)

    Bouchaou, L.; Michelot, J. L.; Qurtobi, M.; Zine, N.; Gaye, C. B.; Aggarwal, P. K.; Marah, H.; Zerouali, A.; Taleb, H.; Vengosh, A.

    2009-12-01

    SummaryGroundwater resources in the Tadla basin stem from surface water recharge and different groundwater inflows, forming a multilayered aquifer system, which hosts one of Morocco's most important groundwater reservoirs. The hydrodynamic infrastructure; i.e. the relationship between all regional aquifers, recharge, and the residence time of waters poses a serious challenge for current water management and future exploitation in aiming for a long-term sustainable utilization. A combined hydrogeologic and isotopic investigation using hydrochemical and isotopic tracers such as 18O, 2H, 3H, 13C and 14C was carried out in order to determine the sources of water recharge to the aquifers, the groundwater flow system, and the residence time of these waters. More than one hundred point measurements throughout the study area in varying wells, boreholes, springs and rivers were investigated. Chemical compositions of the groundwater indicate an important influence by the host carbonate rocks from each of the Tadla aquifers. Stable isotope results indicate the existence of two groups of groundwater corresponding to the unconfined aquifer in the north and the confined aquifer in the south. The δ18O, δ2H, 3H, and 14C data indicate that the High Atlas Mountains in the south and east of the basin, which are characterized by high rainfall and low δ18O and δ2H values, are currently the major source of recharge for the Tadla aquifers. A significant recharge zone lies in the northern part of the basin where all the aquifers outcrop. The confined zones show depleted 18O values, corresponding to the signature of recharge water from the Atlas Mountains. Moreover, all isotope data demonstrated clearly that the Tassaout springs, which are located in the southwest of the basin and were previously interpreted as representing natural outlet of the deep aquifers, are comprised of young waters with depleted 18O and 2H signatures, suggesting a high altitude recharge from the Atlas Mountain

  8. Nitrogen transport and transformations in a coastal plain watershed: Influence of geomorphology on flow paths and residence times

    USGS Publications Warehouse

    Tesoriero, A.J.; Spruill, T.B.; Mew, H.E.; Farrell, K.M.; Harden, S.L.

    2005-01-01

    Nitrogen transport and groundwater-surface water interactions were examined in a coastal plain watershed in the southeastern United States. Groundwater age dates, calculated using chlorofluorocarbon and tritium concentrations, along with concentrations of nitrogen species and other redox-active constituents, were used to evaluate the fate and transport of nitrate. Nitrate is stable only in recently recharged (<10 years) water found in the upper few meters of saturated thickness in the upland portion of a surficial aquifer. Groundwater with a residence time between 10 and 30 years typically has low nitrate and elevated excess N2 concentrations, indications that denitrification has reduced nitrate concentrations. Groundwater older than 30 years also has low nitrate concentrations but contains little or no excess N2, suggesting that this water did not contain elevated concentrations of nitrate along its flow path. Nitrate transport to streams varies between first- and third-order streams. Hydrologic, lithologic, and chemical data suggest that the surficial aquifer is the dominant source of flow and nitrate to a first-order stream. Iron-reducing conditions occur in groundwater samples from the bed and banks of the first-order stream, suggesting that direct groundwater discharge is denitrified prior to entering the stream. However, nitrogen from the surficial aquifer is transported directly to the stream via a tile drain that bypasses these reduced zones. In the alluvial valley of a third-order stream the erosion of a confining layer creates a much thicker unconfined alluvial aquifer with larger zones of nitrate stability. Age dating and chemical information (SiO 2, Na/K ratios) suggest that water in the alluvial aquifer is derived from short flow paths through the riparian zone and/or from adjacent streams during high-discharge periods. Copyright 2005 by the American Geophysical Union.

  9. Carbon Residence Time Explains Changes in Predicted 21st Century Vegetation Carbon across CMIP5 Earth System Models

    NASA Astrophysics Data System (ADS)

    Jiang, L.; Liang, J.; Luo, Y.

    2015-12-01

    Global averaged surface temperature has increased by 0.6 °C over the period 1986 to 2005; and will continue rising 1.0-3.7 °C during the last 30 years of this century. Land ecosystems can sequester approximately one third of annual anthropogenic carbon dioxide emission. Therefore, dynamics of land sink is one of the key components to determine the future atmospheric CO2 concentration and accordingly surface temperature. The accuracy of predicted surface temperature will largely depend on the uncertainty of predicted land carbon uptake. Unfortunately, the uncertainties of future land sink predicted by Earth System Models (ESMs) involved in CMIP5 turned out to be very large. The spread of the land carbon uptake within a specific Representative Concentration Pathway (RCP) scenario was larger than those variation between the four scenarios. Moreover, predicted soil carbon stocks by the end of this century extended to a wide range. Quantifying the uncertainties in predicted vegetation carbon and identifying the causes for the uncertainties will help improve ESMs' performance and give the priorities for model development. In this study, we investigated uncertainties in projections of vegetation carbon by twelve CMIP5 ESMs during the twenty-first century and explored the sources of uncertainties across the models. We found that the predicted changes of vegetation carbon by the end of this century varied quite much across the ESMs under the RCP8.5 scenario, from declining of 190 Pg C to increasing of 320 Pg C. These changes of vegetation carbon can be attributed mostly to the changes in carbon residence time, rather than net primary productivity. We further investigated model's differences in their responses of vegetation carbon to temperature, precipitation and CO2 among the ESMs. Our results have the potential to help improve CMIP5 ESMs for more reliable predictions.

  10. Effect of temperature, hydraulic residence time and elevated PCO2 on acid neutralization within a pulsed limestone bed reactor

    USGS Publications Warehouse

    Watten, B.J.; Lee, P.C.; Sibrell, P.L.; Timmons, M.B.

    2007-01-01

    Limestone has potential for reducing reagent costs and sludge volume associated with treatment of acid mine drainage, but its use is restricted by slow dissolution rates and the deposition of Fe, Al and Mn-based hydrolysis products on reactive surfaces. We evaluated a pulsed limestone bed (PLB) reactor (15 L/min capacity) that uses a CO2 pretreatment step to accelerate dissolution and hydraulic shearing forces provided by intermittent fluidization to abrade and carry away surface scales. We established the effects of hydraulic residence time (HRT, 5.1-15.9 min), temperature (T, 12-22 ??C) and CO2 tension (PCO2, 34.5-206.8 kPa) on effluent quality when inlet acidity (Acy) was fixed at 440 mg/L (pH=2.48) with H2SO4. The PLB reactor neutralized all H+ acidity (N=80) while concurrently providing unusually high levels of effluent alkalinity (247-1028 mg/L as CaCO3) that allow for side-stream treatment with blending. Alkalinity (Alk) yields rose with increases in PCO2, HRT and settled bed height (BH, cm) and decreased with T following the relationship (R2=0.926; p<0.001): (Alk)non-filtered=-548.726+33.571??(PCO2)0.5+33.671??(HRT)+7.734??(BH)-5.197??(T). Numerical modeling showed CO2 feed requirements for a target Alk yield decrease with increases in HRT, T and the efficiency of off-gas (CO2) recycling. ?? 2007 Elsevier Ltd. All rights reserved.

  11. Residence time of carbon substrate for autotrophic respiration of a grassland ecosystem correlates with the carbohydrate status of its vegetation

    NASA Astrophysics Data System (ADS)

    Ostler, Ulrike; Lehmeier, Christoph A.; Schleip, Inga; Schnyder, Hans

    2016-04-01

    Ecosystem respiration is composed of two component fluxes: (1) autotrophic respiration, which comprises respiratory activity of plants and plant-associated microbes that feed on products of recent photosynthetic activity and (2) heterotrophic respiration of microbes that decompose organic matter. The mechanistic link between the availability of carbon (C) substrate for ecosystem respiration and its respiratory activity is not well understood, particularly in grasslands. Here, we explore, how the kinetic features of the supply system feeding autotrophic ecosystem respiration in a temperate humid pasture are related to the content of water-soluble carbohydrates and remobilizable protein (as potential respiratory substrates) in vegetation biomass. During each September 2006, May 2007 and September 2007, we continuously labeled 0.8 m2 pasture plots with 13CO2/12CO2 and observed ecosystem respiration and its tracer content every night during the 14-16 day long labeling periods. We analyzed the tracer kinetics with a pool model, which allowed us to precisely partition ecosystem respiration into its autotrophic and heterotrophic flux components. At the end of a labeling campaign, we harvested aboveground and belowground plant biomass and analyzed its non-structural C contents. Approximately half of ecosystem respiration did not release any significant amount of tracer during the labeling period and was hence characterized as heterotrophic. The other half of ecosystem respiration was autotrophic, with a mean residence time of C in the respiratory substrate pool between 2 and 6 d. Both the rate of autotrophic respiration and the turnover of its substrate supply pool were correlated with plant carbohydrate content, but not with plant protein content. These findings are in agreement with studies in controlled environments that revealed water-soluble carbohydrates as the main substrate and proteins as a marginal substrate for plant respiration under favorable growth conditions

  12. Systematic Analysis of the Effect of Small Scale Permeability Heterogeneity on Hyporheic Exchange Flux and Residence Times

    NASA Astrophysics Data System (ADS)

    Laube, G.; Schmidt, C.; Fleckenstein, J. H.

    2014-12-01

    The hyporheic zone (HZ) contributes significantly to whole stream biogeochemical cycling. Biogeochemical reactions within the HZ are often transport limited, thus, understanding these reactions requires knowledge about the magnitude of hyporheic fluxes (HF) and the residence time (RT) of these fluxes within the HZ. While the hydraulics of HF are relatively well understood, studies addressing the influence of permeability heterogeneity lack systematic analysis and have even produced contradictory results (e.g. [1] vs. [2]). In order to close this gap, this study uses a statistical numerical approach to elucidate the influence of permeability heterogeneity on HF and RT. We simulated and evaluated 3750 2D-scenarios of sediment heterogeneity by means of Gaussian random fields with focus on total HF and RT distribution. The scenarios were based on ten realizations of each of all possible combinations of 15 different correlation lengths, 5 dipping angles and 5 permeability variances. Roughly 500 hyporheic stream traces were analyzed per simulation, for a total of almost two million stream traces analyzed for correlations between permeability heterogeneity, HF, and RT. Total HF and the RT variance positively correlated with permeability variance while the mean RT negatively correlated with permeability variance. In contrast, changes in correlation lengths and dipping angles had little effect on the examined properties RT and HF. These results provide a possible explanation of the seemingly contradictory conclusions of recent studies, given that the permeability variances in these studies differ by several orders of magnitude. [1] Bardini, L., Boano, F., Cardenas, M.B, Sawyer, A.H, Revelli, R. and Ridolfi, L. "Small-Scale Permeability Heterogeneity Has Negligible Effects on Nutrient Cycling in Streambeds." Geophysical Research Letters, 2013. doi:10.1002/grl.50224. [2] Zhou, Y., Ritzi, R. W., Soltanian, M. R. and Dominic, D. F. "The Influence of Streambed Heterogeneity on

  13. Laundry greywater treatment using a fluidized bed reactor: a proposed model based on greywater biodegradation and residence time distribution approach.

    PubMed

    David, Pierre-luc; Bulteau, Gaëlle; Humeau, Philippe; Gérente, Claire; Andrès, Yves

    2013-01-01

    The increasing demand for water and the decrease in global water resources require research into alternative solutions to preserve them. The present study deals with the optimization of a treatment process, i.e. an aerobic fluidized bed reactor and the modelling of the degradation that takes place within it. The methodology employed is based on the hydrodynamics of the treatment process linked to the biodegradation kinetics of greywater coming from a washing machine. The residence time distribution (RTD) approach is selected for the hydrodynamic study. Biodegradation kinetics are quantified by respirometry and dissolved organic carbon (DOC) analysis on several mass quantities of colonized particles. RTD determinations show that there are no dysfunctions in the fluidized bed. Its hydrodynamic behaviour is similar to the one of a continuous stirred-tank reactor. A first-order reaction is obtained from the DOC biodegradation study. A model describing the degradation that takes place into the reactor is proposed, and from a sensitive study, the influence of the operating conditions on DOC biodegradation is defined. The theoretical results calculated from the first-order equation C(t) = 0.593 x C(0) x e(-kt) are compared with the experimental results and validated by a Student test. The value of the kinetic constant k is 0.011 h(-1) in the presence of a biomass carrier. The results highlight that it is possible to design a reactor in order to obtain a carbon content lower than 15 mg C L(-1) when the characteristics of raw greywater are known.

  14. The residence times of surface water-groundwater exchange from 10-3 - 103 m and why long tails matter

    NASA Astrophysics Data System (ADS)

    Bayani Cardenas, M.

    2014-05-01

    The age and residence time of water and their distribution (ADs and RTDs) integrate information about processes that are useful for many hydrologic problems. In this presentation, I will discuss examples of ADs and RTDs associated with a process that is ubiquitous across the hydrosphere -- surface water-groundwater exchange. At the decimeter scale, bedforms induce dynamic pressure gradients which drive exchange between rivers and the hyporheic zone. The RTDs for this exchange follow power-laws which also imply broad ADs. The AD for hyporheic exchange controls redox processes such as denitrification, which is critical for local and watershed-scale nutrient dynamics. Local-scale heterogeneity enhances the power-law RTDs but relative to equivalent homogeneous media, this appears to have minimal impacts on biogeochemical processes. At the channel-floodplain scale, hyporheic exchange is induced by hydrostatic pressure gradients along sinuous river channels. The ADs/RTDs for this exchange are highly sensitive to planform river morphology but may also exhibit power-law tails. Similarly to decimeter-scale exchange, the ADs/RTDs correspond to cascading redox processes which culminate with denitrification. Thus, the biogeochemical processes are linked to landscape form. At the basin scale, regional exchange from recharge to discharge zones are driven by regional topography. These Tothian flow systems also have power-law RTDs and broad ADs. The distributions have direct implications on sustainability of regional groundwater resources and can be used as guide for management and exploitation of aquifers. Thus, ADs and RTDs are useful concepts for myriad hydrologic problems from 10^(-3) to 103 meters.

  15. 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

    Estimates of residence time of ground water beneath Submarine Base Bangor and vicinity ranged from less than 50 to 4,550 years before present, based on analysis of the environmental tracers tritium, chlorofluorocarbons (CFCs), and carbon-14 (14C), in 33 ground-water samples collected from wells tapping the ground-water system. The concentrations of multiple environmental tracers tritium, CFCs, and 14C were used to classify ground water as modern (recharged after 1953), pre-modern (recharged prior to 1953), or indeterminate. Estimates of the residence time of pre-modern ground water were based on evaluation of 14C of dissolved inorganic carbon present in ground water using geochemical mass-transfer modeling to account for the interactions of the carbon in ground water with carbon of the aquifer sediments. Ground-water samples were obtained from two extensive aquifers and from permeable interbeds within the thick confining unit separating the sampled aquifers. Estimates of ground-water residence time for all ground-water samples from the shallow aquifer were less than 45 years and were classified as modern. Estimates of the residence time of ground water in the permeable interbeds within the confining unit ranged from modern to 4,200 years and varied spatially. Near the recharge area, residence times in the permeable interbeds typically were less than 800 years, whereas near the discharge area residence times were in excess of several thousand years. In the deeper aquifers, estimates of ground-water residence times typically were several thousand years but ranged from modern to 4,550 years. These estimates of ground-water residence time based on 14C were often larger than estimates of ground-water residence time developed by particle-tracking analysis using a ground-water flow model. There were large uncertainties?on the order of 1,000-2,000 years?in the estimates based on 14C. Modern ground-water tracers found in some samples from large-capacity production wells

  16. A computational model of wall shear and residence time of particles conveyed by steady flow in a curved tube

    NASA Astrophysics Data System (ADS)

    Thiriet, M.; Graham, J. M. R.; Issa, R. I.

    1993-01-01

    A finite-volume model of steady flow of an incompressible viscous fluid has been carried out in a smooth rigid 90° bend of circular cross-section. The inlet boundary conditions for laminar flow are either an entry Poiseuille regime or a constant injection velocity for a range of Dean number 140 leq De leq 430. A numerical test of turbulent flow was performed for De sim 22 100 with a flat velocity profile at the model entry. The lower the role played by the viscous forces, the larger the distance necessary to set an outer shift of the peak axial velocity. The axial velocity of laminar flow depends not only on the value of the Dean number, but also on separate effects of the Reynolds number and of the tube curvature. The larger the laminar boundary layer at the bend inlet, the nearer from the entry the bend segment where the strongest secondary motion is located. With increasing Reynolds number, the secondary flow develops over a longer bend region and the wall shear rises. Upstream and downstream effect of the bend on the shear stress, as well as flow disturbances induced by very small curvature, were observed. The residence time of conveyed particles is enhanced by the presence of a curved section in the conduit with respect to a straight pipe only at the inner edge of the straight section located downstream from the bend. When the Reynolds number rises, the flow regime remaining laminar, the residence time is smaller in the whole pipe. However for turbulent flow, the residence time, which has much smaller values, takes its highest values in the exit straight section. Les équations de conservation de la masse et de la quantité de mouvement ont été résolues pour un écoulement stationnaire d'un fluide incompressible visqueux dans un coude (angle de 90°), de parois lisses et rigides et de section droite uniforme et circulaire, par la méthode des volumes finis. Les conditions limites en entrée pour l'écoulement laminaire sont soit un profil parabolique, soit

  17. Characterization of the Gacka River basin karst aquifer (Croatia): hydrochemistry, stable isotopes and tritium-based mean residence times.

    PubMed

    Ozyurt, Nur N; Lutz, Hans O; Hunjak, Tamara; Mance, Diana; Roller-Lutz, Zvjezdana

    2014-07-15

    The Gacka River basin aquifer is a highly-developed karst system, located in the Croatian Dinarides. It is mostly composed of permeable Jurassic and Cretaceous carbonate rocks, and clastic sedimentary rocks of Paleogene age. Gacka River provides high quality water for the town of Otočac and several villages; together with the neighboring Lika River, the water is used for the Hydroelectric Power Plant at Senj on the coast. About 10 perennial and over 20 seasonal springs are located at 450 to 460 ma.s.l. (above sea level). Three major springs (Pećina, Majerovo and Tonkovića) provide 57% of the mean annual river flow. Similarities between the average groundwater temperatures as well as between the average specific electrical conductivity values (9.0°C-328 μS/cm, 9.6°C-350 μS/cm and 8.9°C-312 μS/cm) of the springs imply that they are fed from aquifers with similar mean residence times (MRTs). The mean δ(18)O contents of Majerovo, Tonkovića, and Pećina are around -10.1‰, -9.2‰ and -8.9‰, respectively, revealing differences in the mean recharge area elevations. Compared to the temporal amplitude of the(18)O signal of precipitation, the (18)O signal variations of the springs are substantially attenuated because the recharges occurring at different times are well mixed within the aquifers. This indicates MRTs of more than just a few years. The average tritium contents of Pećina, Majerovo and Tonkovića are 5.48 TU, 6.13 TU and 6.17 TU, respectively. Serially connected exponential-plug type unsteady lumped-parameter models run on an annual time scale resulted in rather satisfactory matches between the observed and calculated tritium contents for all studied springs. The models revealed similar MRTs (and corresponding reservoir volumes) for Pećina, Tonkovića and Majerovo of 12 years (470 Mm(3)), 12 years (1,190 Mm(3)), and 12.2 years (1,210 Mm(3)), respectively. Plug flow conditions dominate in about 90% of the total aquifer volumes. PMID:24784749

  18. Characterization of the Gacka River basin karst aquifer (Croatia): hydrochemistry, stable isotopes and tritium-based mean residence times.

    PubMed

    Ozyurt, Nur N; Lutz, Hans O; Hunjak, Tamara; Mance, Diana; Roller-Lutz, Zvjezdana

    2014-07-15

    The Gacka River basin aquifer is a highly-developed karst system, located in the Croatian Dinarides. It is mostly composed of permeable Jurassic and Cretaceous carbonate rocks, and clastic sedimentary rocks of Paleogene age. Gacka River provides high quality water for the town of Otočac and several villages; together with the neighboring Lika River, the water is used for the Hydroelectric Power Plant at Senj on the coast. About 10 perennial and over 20 seasonal springs are located at 450 to 460 ma.s.l. (above sea level). Three major springs (Pećina, Majerovo and Tonkovića) provide 57% of the mean annual river flow. Similarities between the average groundwater temperatures as well as between the average specific electrical conductivity values (9.0°C-328 μS/cm, 9.6°C-350 μS/cm and 8.9°C-312 μS/cm) of the springs imply that they are fed from aquifers with similar mean residence times (MRTs). The mean δ(18)O contents of Majerovo, Tonkovića, and Pećina are around -10.1‰, -9.2‰ and -8.9‰, respectively, revealing differences in the mean recharge area elevations. Compared to the temporal amplitude of the(18)O signal of precipitation, the (18)O signal variations of the springs are substantially attenuated because the recharges occurring at different times are well mixed within the aquifers. This indicates MRTs of more than just a few years. The average tritium contents of Pećina, Majerovo and Tonkovića are 5.48 TU, 6.13 TU and 6.17 TU, respectively. Serially connected exponential-plug type unsteady lumped-parameter models run on an annual time scale resulted in rather satisfactory matches between the observed and calculated tritium contents for all studied springs. The models revealed similar MRTs (and corresponding reservoir volumes) for Pećina, Tonkovića and Majerovo of 12 years (470 Mm(3)), 12 years (1,190 Mm(3)), and 12.2 years (1,210 Mm(3)), respectively. Plug flow conditions dominate in about 90% of the total aquifer volumes.

  19. A proposed solution to integrating cognitive-affective neuroscience and neuropsychiatry in psychiatry residency training: The time is now.

    PubMed

    Torous, John; Stern, Adam P; Padmanabhan, Jaya L; Keshavan, Matcheri S; Perez, David L

    2015-10-01

    Despite increasing recognition of the importance of a strong neuroscience and neuropsychiatry education in the training of psychiatry residents, achieving this competency has proven challenging. In this perspective article, we selectively discuss the current state of these educational efforts and outline how using brain-symptom relationships from a systems-level neural circuit approach in clinical formulations may help residents value, understand, and apply cognitive-affective neuroscience based principles towards the care of psychiatric patients. To demonstrate the utility of this model, we present a case of major depressive disorder and discuss suspected abnormal neural circuits and therapeutic implications. A clinical neural systems-level, symptom-based approach to conceptualize mental illness can complement and expand residents' existing psychiatric knowledge. PMID:26054985

  20. A proposed solution to integrating cognitive-affective neuroscience and neuropsychiatry in psychiatry residency training: The time is now.

    PubMed

    Torous, John; Stern, Adam P; Padmanabhan, Jaya L; Keshavan, Matcheri S; Perez, David L

    2015-10-01

    Despite increasing recognition of the importance of a strong neuroscience and neuropsychiatry education in the training of psychiatry residents, achieving this competency has proven challenging. In this perspective article, we selectively discuss the current state of these educational efforts and outline how using brain-symptom relationships from a systems-level neural circuit approach in clinical formulations may help residents value, understand, and apply cognitive-affective neuroscience based principles towards the care of psychiatric patients. To demonstrate the utility of this model, we present a case of major depressive disorder and discuss suspected abnormal neural circuits and therapeutic implications. A clinical neural systems-level, symptom-based approach to conceptualize mental illness can complement and expand residents' existing psychiatric knowledge.

  1. The Cosmic Dance of Distant Galaxies

    NASA Astrophysics Data System (ADS)

    2006-03-01

    detail, since they had to select a single slit, i.e. a single direction, across the galaxy. Things changed with the availability of the multi-object GIRAFFE spectrograph [2], now installed on the 8.2-m Kueyen Unit Telescope of ESO's Very Large Telescope (VLT) at the Paranal Observatory (Chile). In one mode, known as "3-D spectroscopy" or "integral field", this instrument can obtain simultaneous spectra of smaller areas of extended objects like galaxies or nebulae. For this, 15 deployable fibre bundles, the so-called Integral Field Units (IFUs) , cf. ESO PR 01/02 , are used to make meticulous measurements of distant galaxies. Each IFU is a microscopic, state-of-the-art two-dimensional lens array with an aperture of 3 x 2 arcsec2 on the sky. It is like an insect's eye, with twenty micro-lenses coupled with optical fibres leading the light recorded at each point in the field to the entry slit of the spectrograph. ESO PR Photo 10c/06 ESO PR Photo 10c/06 Dark Matter and Stellar Mass in Distant Galaxies "GIRAFFE on ESO's VLT is the only instrument in the world that is able to analyze simultaneously the light coming from 15 galaxies covering a field of view almost as large as the full moon," said Mathieu Puech, lead author of one the papers presenting the results [3]. "Every galaxy observed in this mode is split into continuous smaller areas where spectra are obtained at the same time." The astronomers used GIRAFFE to measure the velocity fields of several tens of distant galaxies, leading to the surprising discovery that as much as 40% of distant galaxies were "out of balance" - their internal motions were very disturbed - a possible sign that they are still showing the aftermath of collisions between galaxies. When they limited themselves to only those galaxies that have apparently reached their equilibrium, the scientists found that the relation between the dark matter and the stellar content did not appear to have evolved during the last 6 billions years. Thanks to its

  2. SU-E-T-45: Antibody Mean Residence Time in Blood and Its Correlation with Protein Molecular Weight

    SciTech Connect

    Kwok, C; Williams, L

    2014-06-01

    Purpose: Animal biodistribution data are required prior to introducing a new radiopharmaceutical into clinical trials. Protein engineering, using recombinant DNA techniques can produce a large number of related (cognate) antibodies to a given molecular target. Thus, it is important that these constructs be numerically related to one another via a single criterion. In the following, we use the mean residence time (MRT) in murine blood as this criterion. Methods: Five cognate anti-CEA (Carcinoembryonic Antigen) antibodies were compared with regard to their MRT in whole blood of CEA-positive tumor-bearing (LS174T) mice. MRT was defined by blood AUC (area under the curve) divided by the initial blood uptake value; all in units of percent injected dose per gram (%ID/g). Cognates included single chain scFv (25 kDa), diabody (50 kDa), minibody (80 kDa), F(ab')2 (120 kDa), and intact (155 kDa) forms of the murine cT84.66 antibody against CEA. All were labeled with radioactive iodine. Results: The agents, in the sequence listed, exhibited MRT values of 1.16 +/- 0.01 h, 0.99 h, 5.06 +/- 0.70 h, 6.61 +/- 0.36 h, and 59.3 +/- 2.4 h respectively. Because of the monotonic nature of the sequence, a linear correlation analysis was performed between molecular weight (MW) and MRT or ln(MRT) of the 5 proteins. Probability of random correlation was 0.10 for MRT and 0.01 for ln(MRT). Conclusion: MRT values of cognate anti-CEA antibodies were found to be a monotonically increasing sequence with respect to MW. Cognate MW values correlated best to ln(MRT) of the protein species. Thus MRT was proportional to an exponential function of molecular weight. The extended intact antibody circulation time presumably reflected its relatively maximal MW. Presence of an intact FC segment on this native antibody may also have influenced these results.

  3. Perspective: call to action: it is time for academic institutions to appoint a resident quality and patient safety officer.

    PubMed

    Fleischut, Peter M; Evans, Adam S; Nugent, William C; Faggiani, Susan L; Kerr, Gregory E; Lazar, Eliot J

    2011-07-01

    In meeting the Accreditation Council for Graduate Medical Education (ACGME) core competency requirements, teaching hospitals often find it challenging to ensure effective involvement of housestaff in the area of quality and patient safety (QPS). Because housestaff are the frontline providers of care to patients, and medical errors occasionally occur based on their actions, it is essential for health care organizations to engage them in QPS processes.In early 2008 a Housestaff Quality Council (HQC) was established at New York-Presbyterian Hospital, Weill Cornell Medical Center, to improve QPS by engaging housestaff in policy and decision-making processes and to promote greater housestaff participation in QPS initiatives. It was quickly realized that the success of the HQC was highly contingent on alignment with the institution's overall QPS agenda. To this end, the position of resident QPS officer was created to strengthen the relationship between the hospital's strategic goals and the HQC. The authors describe the success of the resident QPS officers at their institution and observe that by appointing and supporting resident QPS officers, hospitals will be better able to meet their quality and safety goals, residency programs will be able to fulfill their required ACGME core competencies, and the overall quality and safety of patient care can be improved. Simultaneously, the creation of this position will help to create a new cadre of physician leaders needed to further the goals of QPS in health care. PMID:21617508

  4. Distant Massive Clusters and Cosmology

    NASA Technical Reports Server (NTRS)

    Donahue, Megan

    1999-01-01

    We present a status report of our X-ray study and analysis of a complete sample of distant (z=0.5-0.8), X-ray luminous clusters of galaxies. We have obtained ASCA and ROSAT observations of the five brightest Extended Medium Sensitivity (EMSS) clusters with z > 0.5. We have constructed an observed temperature function for these clusters, and measured iron abundances for all of these clusters. We have developed an analytic expression for the behavior of the mass-temperature relation in a low-density universe. We use this mass-temperature relation together with a Press-Schechter-based model to derive the expected temperature function for different values of Omega-M. We combine this analysis with the observed temperature functions at redshifts from 0 - 0.8 to derive maximum likelihood estimates for the value of Omega-M. We report preliminary results of this analysis.

  5. 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

  6. Is Eruption Style Linked to Magma Residence Time at Kilauea Volcano? Results from Chemical Zoning in Olivine

    NASA Astrophysics Data System (ADS)

    Lynn, K. J.; Costa Rodriguez, F.; Shea, T.; Garcia, M. O.

    2015-12-01

    Kilauea is generally characterized by its modern effusive activity, but the past 2500 years were dominated by cycles of explosive and effusive eruptions lasting 100's of years (Swanson et al. 2012). These different eruption styles may reflect variable volatile contents in the source that control magma ascent rate and storage durations (e.g., Sides et al. 2014). A detailed petrological study of the dominantly explosive Keanakako'i tephras (1500-1820 CE) was undertaken to better understand the storage and transport conditions preceding high-energy eruptions. Here, we focus on preliminary results for olivine from the 1500 CE Basal Reticulite (>600 m fountain; May et al. 2015). Olivine major (Fe, Mg), minor (Mn, Ca, Ni) and trace (Li, Na, Al, P, Sc, Ti, V, Cr, Co, Zn) element traverses and 2D maps were collected for 10 crystals and reveal two major populations. The dominant population has homogeneous Fo89 and Fo87 cores with thin (3-12 μm) rims of intermediate composition (Fo87.5-88.5). Normal, reverse, and complex trace element zoning (Al, P, Ti, Cr) is prominent in these otherwise homogenous (Fo, Ni, Ca, Mn) crystals. 2D maps reveal early skeletal growth and the progressive decrease of Cr from core to rim suggests olivine and Cr-spinel crystallization, which should produce significant Fo zoning. Absence of Fo zoning could imply significant storage time in a reservoir allowing homogenization. The majority of rim compositions are out of equilibrium with adhering glass, and Fe-Mg modeling indicates that their residence within the carrier melt was of a few days. A second population consists of strongly zoned (normal and reverse) crystals with a wide range of core Fo (78 to 89) and Fo82-84 rims. Timescales from Fe-Mg zoning are up to 1 year, and may record storage histories before interaction with the carrier melt. The diversity in olivine zoning suggests at least two stages of magma mixing, and a more complex evolution for the magmas that fed the reticulite eruptions

  7. Einstein Ring in Distant Universe

    NASA Astrophysics Data System (ADS)

    2005-06-01

    Using ESO's Very Large Telescope, Rémi Cabanac and his European colleagues have discovered an amazing cosmic mirage, known to scientists as an Einstein Ring. This cosmic mirage, dubbed FOR J0332-3557, is seen towards the southern constellation Fornax (the Furnace), and is remarkable on at least two counts. First, it is a bright, almost complete Einstein ring. Second, it is the farthest ever found. ESO PR Photo 20a/05 ESO PR Photo 20a/05 Deep Image of a Region in Fornax (FORS/VLT) [Preview - JPEG: 400 x 434 pix - 60k] [Normal - JPEG: 800 x 867 pix - 276k] [Full Res - JPEG: 1859 x 2015 pix - 3.8M] ESO PR Photo 20b/05 ESO PR Photo 20b/05 Zoom-in on the Newly Found Einstein Ring (FORS/VLT) [Preview - JPEG: 400 x 575 pix - 168k] [Normal - JPEG: 630 x 906 pix - 880k] Caption: ESO PR Photo 20a/05 is a composite image taken in two bands (B and R) with VLT/FORS1 of a small portion of the sky (field-of-view 7x7' or 1/15th of the area of the full moon). The faintest object seen in the image has a magnitude 26, that is, it is 100 million times fainter than what can be observed with the unaided eye. The bright elliptical galaxy on the lower-left quadrant is a dwarf galaxy part of a large nearby cluster in the Fornax constellation. As for all deep images of the sky, this field shows a variety of objects, the brightest ponctual sources being stars from our Galaxy. By far the field is dominated by thousands of faint background galaxies the colours of which are related to the age of their dominant stellar population, their dust content and their distance. The newly found Einstein ring is visible in the top right part of the image. ESO PR Photo 20b/05 zooms-in on the position of the newly found cosmic mirage. ESO PR Photo 20c/05 ESO PR Photo 20c/05 Einstein Ring in Distant Universe (FORS/VLT) [Preview - JPEG: 400 x 584 pix - 104k] [Normal - JPEG: 800 x 1168 pix - 292k] [Full Res - JPEG: 1502 x 2192 pix - 684k] Caption of ESO PR Photo 20c/05: The left image is magnified and centred

  8. Climate impacts on groundwater storage, hydrochemistry and residence time in geologically variable, snowmelt-dominated mountain catchments, Front Range, Colorado

    NASA Astrophysics Data System (ADS)

    Zeliff, M. M.; Williams, M. W.

    2012-12-01

    Groundwater storage, hydrochemistry and residence time are all known to vary widely depending on hydrogeologic conditions. In mountainous terrain hydrogeology can vary greatly over short distances, from bedrock aquifers on ridge tops to colluvial and fluvial aquifers in valleys. Determining how climate alters groundwater in the context of variable hydrogeologic conditions is needed to understand in-stream flows and biogeochemical cycles in these climactically sensitive alpine settings. In 2005 at the Niwot LTER six piezometers were installed in surficial diamicton and colluvium at the base of a semi-permanent snowfield at the Martinelli site (3440 m). Eight piezometers were also installed at the Saddle on a ridge-top in the alpine tundra (3528 m). In 2010 12 piezometers were installed at the C1 site (3025 m) in the subalpine atop moraine deposits. Groundwater monitoring for all sites is year-round and is comprised of depth-to-water measurements by hand and pressure transducers for select wells, as well as chemistry samples for major solutes including dissolved organic matter and stable isotopes of water, δ18O and δD. Across the Niwot LTER precipitation falls predominately as snow creating a strongly snowmelt-dominated hydrograph. Groundwater response to this seasonality is reflected in both physical and hydrochemical groundwater measurements. Snowmelt leads to sharp increases in water level in all piezometers including up to 7 m of water table change at the Saddle, up to 3 m of change at Martinelli and up to 5 m of water table change at C1. Minimum water table levels are not always measureable as the water table can drop below the extent of the piezometers, however, at the Saddle there are decreasing trends in annual minimum groundwater level in 3 of the 4 deep piezometers, possibly reflecting a decrease in total aquifer storage. Hydrochemical groundwater response to snowmelt is evident in distinct harmonic trends in major solute and isotope chemistry. Time

  9. Distant intentionality and healing: assessing the evidence.

    PubMed

    Schlitz, M; Braud, W

    1997-11-01

    Since the 1950s, researchers have attempted to understand reports of distant or "psychic" healing, developing experimental protocols that test the distant healing hypothesis by measuring biological changes in a target system while ruling out suggestion or self-regulation as counterexplanations. This article provides a brief overview of these "healing analog" experiments. It also provides a summary and meta-analysis of 30 formal experiments in which self-reported healers, "psychics," and other self-selected volunteers attempted to influence autonomic nervous system activity in a distant person. Results across the experiments showed a significant and characteristic variation during distant intentionality periods, compared with randomly interspersed control periods. Possible alternative explanations for the reported effects are considered. Finally the implications of distant intentionality are discussed for an understanding of the possible mechanisms of distant healing, the nature of the mind-body relationship, and the role of consciousness in the physical world.

  10. Galactic Teamwork Makes Distant Bubbles

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-03-01

    During the period of reionization that followed the dark ages of our universe, hydrogen was transformed from a neutral state, which is opaque to radiation, to an ionized one, which is transparent to radiation. But what generated the initial ionizing radiation? The recent discovery of multiple distant galaxies offers evidence for how this process occurred.Two Distant GalaxiesWe believe reionization occurred somewhere between a redshift of z = 6 and 7, because Ly-emitting galaxies drop out at roughly this redshift. Beyond this distance, were generally unable to see the light from these galaxies, because the universe is no longer transparent to their emission. This is not always the case, however: if a bubble of ionized gas exists around a distant galaxy, the radiation can escape, allowing us to see the galaxy.This is true of two recently-discovered Ly-emitting galaxies, confirmed to be at a redshift of z~7 and located near one another in a region known as the Bremer Deep Field. The fact that were able to see the radiation from these galaxies means that they are in an ionized HII region presumably one of the earlier regions to have become reionized in the universe.But on their own, neither of these galaxies is capable of generating an ionized bubble large enough for their light to escape. So what ionized the region around them, and what does this mean for our understanding of how reionization occurred in the universe?A Little Help From FriendsLocation in different filters of the objects in the Hubble Bremer Deep Field catalog. The z~7 selection region is outlined by the grey box. BDF-521 and BDF-3299 were the two originally discovered galaxies; the remaining red markers indicate the additional six galaxies discovered in the same region. [Castellano et al. 2016]A team of scientists led by Marco Castellano (Rome Observatory, INAF) investigated the possibility that there are other, faint galaxies near these two that have helped to ionize the region. Performing a survey

  11. Leprosy in six isolated residents of northern Louisiana. Time-clustered cases in an essentially nonendemic area.

    PubMed

    West, B C; Todd, J R; Lary, C H; Blake, L A; Fowler, M E; King, J W

    1988-09-01

    Northern Louisiana has been essentially free of indigenous leprosy, and now it is not. Six new cases of leprosy have been diagnosed: three in 1986, the other three in 1985, 1983, and 1982, respectively. The patients had been lifelong residents of six scattered rural parishes. Leprosy had never been reported from five of them. No patient had had contact with human leprosy. The patients were white; four were women; the mean +/- SD age at onset was 60.3 +/- 16.4 years (age range, 31 to 80 years); and the mean +/- SD interval to diagnosis was 1.2 +/- 1.4 years. One patient had Hodgkin's disease at the age of 25 years and leprosy at the age of 31 years; another patient had cervical carcinoma. All rural northern Louisiana residents coexist with armadillos (Dasypus novemcinctus), some of which are infected with Mycobacterium leprae, the significance of which is unknown. Hypothetically, exposure to an unknown human case, reactivation of "asymptomatic" leprosy through immunosenescence or immunosuppression, or infection from an environmental source might have occurred. Because the patients lacked contact, travel, residence, and exposure risk factors, the origin of leprosy in the new indigenous cases is noteworthy and is not understood.

  12. The Cosmic Dance of Distant Galaxies

    NASA Astrophysics Data System (ADS)

    2006-03-01

    detail, since they had to select a single slit, i.e. a single direction, across the galaxy. Things changed with the availability of the multi-object GIRAFFE spectrograph [2], now installed on the 8.2-m Kueyen Unit Telescope of ESO's Very Large Telescope (VLT) at the Paranal Observatory (Chile). In one mode, known as "3-D spectroscopy" or "integral field", this instrument can obtain simultaneous spectra of smaller areas of extended objects like galaxies or nebulae. For this, 15 deployable fibre bundles, the so-called Integral Field Units (IFUs) , cf. ESO PR 01/02 , are used to make meticulous measurements of distant galaxies. Each IFU is a microscopic, state-of-the-art two-dimensional lens array with an aperture of 3 x 2 arcsec2 on the sky. It is like an insect's eye, with twenty micro-lenses coupled with optical fibres leading the light recorded at each point in the field to the entry slit of the spectrograph. ESO PR Photo 10c/06 ESO PR Photo 10c/06 Dark Matter and Stellar Mass in Distant Galaxies "GIRAFFE on ESO's VLT is the only instrument in the world that is able to analyze simultaneously the light coming from 15 galaxies covering a field of view almost as large as the full moon," said Mathieu Puech, lead author of one the papers presenting the results [3]. "Every galaxy observed in this mode is split into continuous smaller areas where spectra are obtained at the same time." The astronomers used GIRAFFE to measure the velocity fields of several tens of distant galaxies, leading to the surprising discovery that as much as 40% of distant galaxies were "out of balance" - their internal motions were very disturbed - a possible sign that they are still showing the aftermath of collisions between galaxies. When they limited themselves to only those galaxies that have apparently reached their equilibrium, the scientists found that the relation between the dark matter and the stellar content did not appear to have evolved during the last 6 billions years. Thanks to its

  13. Using heat as a tracer to estimate spatially distributed mean residence times in the hyporheic zone of a riffle-pool sequence

    USGS Publications Warehouse

    Naranjo, Ramon C.

    2013-01-01

    Biochemical reactions that occur in the hyporheic zone are highly dependent on the time solutes that are in contact with sediments of the riverbed. In this investigation, we developed a 2-D longitudinal flow and solute-transport model to estimate the spatial distribution of mean residence time in the hyporheic zone. The flow model was calibrated using observations of temperature and pressure, and the mean residence times were simulated using the age-mass approach for steady-state flow conditions. The approach used in this investigation includes the mixing of different ages and flow paths of water through advection and dispersion. Uncertainty of flow and transport parameters was evaluated using standard Monte Carlo and the generalized likelihood uncertainty estimation method. Results of parameter estimation support the presence of a low-permeable zone in the riffle area that induced horizontal flow at a shallow depth within the riffle area. This establishes shallow and localized flow paths and limits deep vertical exchange. For the optimal model, mean residence times were found to be relatively long (9–40.0 days). The uncertainty of hydraulic conductivity resulted in a mean interquartile range (IQR) of 13 days across all piezometers and was reduced by 24% with the inclusion of temperature and pressure observations. To a lesser extent, uncertainty in streambed porosity and dispersivity resulted in a mean IQR of 2.2 and 4.7 days, respectively. Alternative conceptual models demonstrate the importance of accounting for the spatial distribution of hydraulic conductivity in simulating mean residence times in a riffle-pool sequence.

  14. Flotation rate and residence time distribution in continuous coal froth flotation circuits and an evaluation of reagents and circuit variations for pyritic sulfur removal

    SciTech Connect

    Arnold, B.J.

    1989-01-01

    This thesis gives the results of research conducted on several aspects of coal froth flotation. The effect of operating variables on the residence time distribution in coal froth flotation cells is discussed, and a model of the residence time distribution is presented for use with flotation rate models in scaling up from laboratory to plant scale. Flotation rate models are also investigated in detail for continuous coal froth flotation circuits. Changes in operating variables were found to affect the mean residence time in cells, but they did not have much effect on the mixing behavior. The use of a time lag was found to be an important part of rate models for continuous froth flotation cells. An important aspect of the use of such rate and residence time equations is their application to the flotation of gangue constituents, which often enter the froth by water carry-over in addition to natural flotation or flotation as slime coatings. As such, water carry-over is also investigated in this thesis for the laboratory and the plant and for both ash-forming minerals and pyrite. Maintaining a constant froth factor, the percentage of froth above the weir, in both laboratory and plant tests is believed to be a critical factor in predicting plant results using a kinetic factor ratio documented in the literature. Removing the pyrite and ash-forming minerals from coal that may be recovered by the water carry-over or other mechanisms is an important goal in coal froth flotation. This thesis also contains the results of tests with pyrite depressants and circuit variations for removal of pyritic sulfur.

  15. 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.

  16. Coagulation effect on the activity size distributions of long lived radon progeny aerosols and its application to atmospheric residence time estimation techniques.

    PubMed

    Anand, S; Mayya, Y S

    2015-03-01

    The long lived naturally occurring radon progeny species in the atmosphere, namely (210)Pb, (210)Bi and (210)Po, have been used as important tracers for understanding the atmospheric mixing processes and estimating aerosol residence times. Several observations in the past have shown that the activity size distribution of these species peaks at larger particle sizes as compared to the short lived radon progeny species - an effect that has been attributed to the process of coagulation of the background aerosols to which they are attached. To address this issue, a mathematical equation is derived for the activity-size distribution of tracer species by formulating a generalized distribution function for the number of tracer atoms present in coagulating background particles in the presence of radioactive decay and removal. A set of these equations is numerically solved for the progeny chain using Fuchs coagulation kernel combined with a realistic steady-state aerosol size spectrum that includes nucleation, accumulation and coarse mode components. The important findings are: (i) larger shifts in the modal sizes of (210)Pb and (210)Po at higher aerosol concentrations such as that found in certain Asian urban regions (ii) enrichment of tracer specific activity on particles as compared to that predicted by pure attachment laws (iii) sharp decline of daughter-to-parent activity ratios for decreasing particle sizes. The implication of the results to size-fractionated residence time estimation techniques is highlighted. A coagulation corrected graphical approach is presented for estimating the residence times from the size-segregated activity ratios of (210)Bi and (210)Po with respect to (210)Pb. The discrepancy between the residence times predicted by conventional formula and the coagulation corrected approach for specified activity ratios increases at higher atmospheric aerosol number concentrations (>10(10) #/m(3)) for smaller sizes (<1 μm). The results are further

  17. Hillslope lowering rates and mobile-regolith residence times from in situ and meteoric 10Be analysis: Boulder Creek Critical Zone Observatory, Colorado

    NASA Astrophysics Data System (ADS)

    Foster, M. A.; Anderson, R. S.; Wyshnytzky, C.; Ouimet, W. B.; Dethier, D. P.

    2014-12-01

    Mobile regolith is produced as weathered saprolite is entrained into the mobile layer. The rate of mobile-regolith production and its residence time on hillslopes shapes the topography and evolution of hillslopes. We calculate the production rate of mobile regolith and the mobile-regolith residence times on active hillslopes in Gordon Gulch, within the Boulder Creek Critical Zone Observatory (CZO), Colorado. We find mobile-regolith production rates (average 3.1 cm/ka) and residence times (average 10-20 ka) derived from both in situand meteoric methods agree. Lowering-rates derived from our study are also comparable to basin-averaged denudation rates for small basins in the Colorado Front Range (Dethier and Lazarus, 2006). In this study, we have measured both in situ and meteoric 10Be in saprolite and mobile regolith separately. We find that, on average, two-thirds of in situ 10Be is produced within saprolite, and that at least one-tenth of the meteoric 10Be inventories are stored in saprolite. In the case of in situ 10Be, this simply reflects the exponential fall-off in production rates through a thin mobile-regolith cover. In the case of meteoric 10Be, our calculations suggest that >40% of the meteoric 10Be deposition occurs within the saprolite. Most studies that utilize 10Be report residence times and soil-production rates based on concentrations in either the mobile regolith or saprolite; therefore, our 10Be data highlight the importance of clearly identifying mobile and immobile portions of the regolith, constraining its 10Be inventory, and use of consistent terminology for the mobile-layer.

  18. Coagulation effect on the activity size distributions of long lived radon progeny aerosols and its application to atmospheric residence time estimation techniques.

    PubMed

    Anand, S; Mayya, Y S

    2015-03-01

    The long lived naturally occurring radon progeny species in the atmosphere, namely (210)Pb, (210)Bi and (210)Po, have been used as important tracers for understanding the atmospheric mixing processes and estimating aerosol residence times. Several observations in the past have shown that the activity size distribution of these species peaks at larger particle sizes as compared to the short lived radon progeny species - an effect that has been attributed to the process of coagulation of the background aerosols to which they are attached. To address this issue, a mathematical equation is derived for the activity-size distribution of tracer species by formulating a generalized distribution function for the number of tracer atoms present in coagulating background particles in the presence of radioactive decay and removal. A set of these equations is numerically solved for the progeny chain using Fuchs coagulation kernel combined with a realistic steady-state aerosol size spectrum that includes nucleation, accumulation and coarse mode components. The important findings are: (i) larger shifts in the modal sizes of (210)Pb and (210)Po at higher aerosol concentrations such as that found in certain Asian urban regions (ii) enrichment of tracer specific activity on particles as compared to that predicted by pure attachment laws (iii) sharp decline of daughter-to-parent activity ratios for decreasing particle sizes. The implication of the results to size-fractionated residence time estimation techniques is highlighted. A coagulation corrected graphical approach is presented for estimating the residence times from the size-segregated activity ratios of (210)Bi and (210)Po with respect to (210)Pb. The discrepancy between the residence times predicted by conventional formula and the coagulation corrected approach for specified activity ratios increases at higher atmospheric aerosol number concentrations (>10(10) #/m(3)) for smaller sizes (<1 μm). The results are further

  19. Using radium isotopes to estimate the residence time and the contribution of submarine groundwater discharge (SGD) in the Changjiang effluent plume, East China Sea

    NASA Astrophysics Data System (ADS)

    Gu, Hequan; Moore, Willard S.; Zhang, Lei; Du, Jinzhou; Zhang, Jing

    2012-03-01

    This paper reports the initial result of the flux of submarine groundwater discharge (SGD) into the Changjiang effluent plume (CEP). A radium mass balance model and a 224Ra/223Ra activity ratio (AR) apparent age model were applied to estimate the residence time of water above the pycnocline in the CEP. These two approaches gave similar results, yielding residence times of 5.4 d and 7.0 d, respectively, in the inner and outer plume zones. The nonconservative inventory of 226Ra was established in the CEP, and converted to a 226Ra flux by dividing by the water residence time and assuming steady state conditions. After subtracting the desorption of 226Ra from suspended sediment and the diffusion from the bottom sediment, the 226Ra flux from SGD was converted to a total SGD flux by dividing by the measured activity of 226Ra in local groundwater. The SGD flux in the CEP is estimated to be 0.2-1.0×109 m3 d-1, which is equivalent to 6-30% of the Changjiang water discharge during flood season. This large flux indicates that SGD may be another important nutrient source to the East China Sea.

  20. Mixing interfaces, fluxes, residence times and redox conditions of the hyporheic zones induced by dune-like bedforms and ambient groundwater flow

    NASA Astrophysics Data System (ADS)

    Marzadri, Alessandra; Tonina, Daniele; Bellin, Alberto; Valli, Alberto

    2016-02-01

    Recent studies highlighted the importance of the interface between streams and their surrounding sediment, known as the hyporheic zone, where stream waters flow through the alluvium. These pore water fluxes stem from the interaction among streambed morphology, stream hydraulics and surrounding groundwater flow. We analytically model the hyporheic hydraulics induced by a spatially uniform ambient groundwater flow made of a horizontal, underflow, and a vertical, basal, component, which mimics gaining and losing stream conditions. The proposed analytical solution allows to investigate the control of simple hydromorphological quantities on the extent, residence time and redox conditions of the hyporheic zone, and the thickness of the mixing interface between hyporheic and groundwater cells. Our analysis shows that the location of the mixing zone shallows or deepens in the sediment as a function of bedform geometry, surface hydraulic and groundwater flow. The point of stagnation, where hyporheic flow velocities vanish and where the separation surface passes through, is shallower than or coincides with the deepest point of the hyporheic zone only due to underflow. An increase of the ambient flow causes a reduction of the hyporheic zone volume similarly in both losing and gaining conditions. The hyporheic residence time is lognormally distributed under neutral, losing and gaining conditions, with the residence time moments depending on the same set of parameters describing dune morphology and stream flow.

  1. Distant retrograde orbits for the Moon's exploration

    NASA Astrophysics Data System (ADS)

    Sidorenko, Vladislav

    We discuss the properties of the distant retrograde orbits (which are called quasi-satellite orbits also) around Moon. For the first time the distant retrograde orbits were described by J.Jackson in studies on restricted three body problem at the beginning of 20th century [1]. In the synodic (rotating) reference frame distant retrograde orbit looks like an ellipse whose center is slowly drifting in the vicinity of minor primary body while in the inertial reference frame the third body is orbiting the major primary body. Although being away the Hill sphere the third body permanently stays close enough to the minor primary. Due to this reason the distant retrograde orbits are called “quasi-satellite” orbits (QS-orbits) too. Several asteroids in solar system are in a QS-orbit with respect to one of the planet. As an example we can mention the asteroid 2002VE68 which circumnavigates Venus [2]. Attention of specialists in space flight mechanics was attracted to QS-orbits after the publications of NASA technical reports devoted to periodic moon orbits [3,4]. Moving in QS-orbit the SC remains permanently (or at least for long enough time) in the vicinity of small celestial body even in the case when the Hill sphere lies beneath the surface of the body. The properties of the QS-orbit can be studied using the averaging of the motion equations [5,6,7]. From the theoretical point of view it is a specific case of 1:1 mean motion resonance. The integrals of the averaged equations become the parameters defining the secular evolution of the QS-orbit. If the trajectory is robust enough to small perturbations in the simplified problem (i.e., restricted three body problem) it may correspond to long-term stability of the real-world orbit. Our investigations demonstrate that under the proper choice of the initial conditions the QS-orbits don’t escape from Moon or don’t impact Moon for long enough time. These orbits can be recommended as a convenient technique for the large

  2. Characterizing the trophic niches of stocked and resident cyprinid fishes: consistency in partitioning over time, space and body sizes.

    PubMed

    Bašić, Tea; Britton, J Robert

    2016-07-01

    Hatchery-reared fish are commonly stocked into freshwaters to enhance recreational angling. As these fishes are often of high trophic position and attain relatively large sizes, they potentially interact with functionally similar resident fishes and modify food-web structure. Hatchery-reared barbel Barbus barbus are frequently stocked to enhance riverine cyprinid fish communities in Europe; these fish can survive for over 20 years and exceed 8 kg. Here, their trophic consequences for resident fish communities were tested using cohabitation studies, mainly involving chub Squalius cephalus, a similarly large-bodied, omnivorous and long-lived species. These studies were completed over three spatial scales: pond mesocosms, two streams and three lowland rivers, and used stable isotope analysis. Experiments in mesocosms over 100 days revealed rapid formation of dietary specializations and discrete trophic niches in juvenile B. barbus and S. cephalus. This niche partitioning between the species was also apparent in the streams over 2 years. In the lowland rivers, where fish were mature individuals within established populations, this pattern was also generally apparent in fishes of much larger body sizes. Thus, the stocking of these hatchery-reared fish only incurred minor consequences for the trophic ecology of resident fish, with strong patterns of trophic niche partitioning and diet specialization. Application of these results to decision-making frameworks should enable managers to make objective decisions on whether cyprinid fish should be stocked into lowland rivers according to ecological risk. PMID:27547336

  3. Permanent resident

    PubMed Central

    Fisher, John F.

    2016-01-01

    The training of physicians in the past century was based primarily on responsibility and the chain-of-command. Those with the bulk of that responsibility in the fields of pediatrics and internal medicine were residents. Residents trained the medical students and supervised them carefully in caring for patients. Most attending physicians supervised their teams at arm's length, primarily serving as teachers of the finer points of diagnosis and treatment during set periods of the day or week with a perfunctory signature on write-ups or progress notes. Residents endeavored to protect the attending physician from being heavily involved unless they were unsure about a clinical problem. Before contacting the attending physician, a more senior resident would be called. Responsibility was the ultimate teacher. The introduction of diagnosis-related groups by the federal government dramatically changed the health care delivery system, placing greater emphasis on attending physician visibility in the medical record, ultimately resulting in more attending physician involvement in day-to-day care of patients in academic institutions. Without specified content in attending notes, hospital revenues would decline. Although always in charge technically, attending physicians increasingly have assumed the role once dominated by the resident. Using biographical experiences of more than 40 years, the author acknowledges and praises the educational role of responsibility in his own training and laments its declining role in today's students and house staff. PMID:27193992

  4. Permanent resident.

    PubMed

    Fisher, John F

    2016-01-01

    The training of physicians in the past century was based primarily on responsibility and the chain-of-command. Those with the bulk of that responsibility in the fields of pediatrics and internal medicine were residents. Residents trained the medical students and supervised them carefully in caring for patients. Most attending physicians supervised their teams at arm's length, primarily serving as teachers of the finer points of diagnosis and treatment during set periods of the day or week with a perfunctory signature on write-ups or progress notes. Residents endeavored to protect the attending physician from being heavily involved unless they were unsure about a clinical problem. Before contacting the attending physician, a more senior resident would be called. Responsibility was the ultimate teacher. The introduction of diagnosis-related groups by the federal government dramatically changed the health care delivery system, placing greater emphasis on attending physician visibility in the medical record, ultimately resulting in more attending physician involvement in day-to-day care of patients in academic institutions. Without specified content in attending notes, hospital revenues would decline. Although always in charge technically, attending physicians increasingly have assumed the role once dominated by the resident. Using biographical experiences of more than 40 years, the author acknowledges and praises the educational role of responsibility in his own training and laments its declining role in today's students and house staff.

  5. Relationship Between the Number of Residency Applications and the Yearly Match Rate: Time to Start Thinking About an Application Limit?

    PubMed Central

    Weissbart, Steven J.; Kim, Soo Jeong; Feinn, Richard S.; Stock, Jeffrey A.

    2015-01-01

    Background There has been an increase in the number of applications medical students have submitted for the National Residency Matching Program (NRMP). These additional applications are associated with significant costs and may contribute to match inefficiency. Objective We explored if match rates improved in years when an increased number of applications were submitted. Methods We analyzed yearly published data from the NRMP and the Electronic Residency Application Service for 13 specialties. A generalized linear model was used to assess the relationship between the annual match rate and the mean number of applications submitted per applicant, while controlling for the number of positions available and the number of applicants in the given year. Results Over the last 13 years there has been an increase in the mean number of applications submitted per applicant (P < .001). For the 13 assessed medical specialties, there was no statistically significant relationship between the mean number of applications per applicant per year submitted to the NRMP, and the annual match rate (odds ratios near 1.00 and nonsignificant, P values > .05). Conclusions There was no improvement in the match rate in years when medical students submitted an increased number of applications. Therefore, it would appear that the applicants do not benefit from the larger number of applications submitted. Further study is required to assess the cost and benefit of these additional applications. PMID:26217428

  6. Distant Operational Care Centre: Design Project Report

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The goal of this project is to outline the design of the Distant Operational Care Centre (DOCC), a modular medical facility to maintain human health and performance in space, that is adaptable to a range of remote human habitats. The purpose of this project is to outline a design, not to go into a complete technical specification of a medical facility for space. This project involves a process to produce a concise set of requirements, addressing the fundamental problems and issues regarding all aspects of a space medical facility for the future. The ideas presented here are at a high level, based on existing, researched, and hypothetical technologies. Given the long development times for space exploration, the outlined concepts from this project embodies a collection of identified problems, and corresponding proposed solutions and ideas, ready to contribute to future space exploration efforts. In order to provide a solid extrapolation and speculation in the context of the future of space medicine, the extent of this project's vision is roughly within the next two decades. The Distant Operational Care Centre (DOCC) is a modular medical facility for space. That is, its function is to maintain human health and performance in space environments, through prevention, diagnosis, and treatment. Furthermore, the DOCC must be adaptable to meet the environmental requirements of different remote human habitats, and support a high quality of human performance. To meet a diverse range of remote human habitats, the DOCC concentrates on a core medical capability that can then be adapted. Adaptation would make use of the DOCC's functional modularity, providing the ability to replace, add, and modify core functions of the DOCC by updating hardware, operations, and procedures. Some of the challenges to be addressed by this project include what constitutes the core medical capability in terms of hardware, operations, and procedures, and how DOCC can be adapted to different remote

  7. Comparison of Shoulder Range of Motion, Strength, and Playing Time in Uninjured High School Baseball Pitchers Who Reside in Warm- and Cold-Weather Climates

    PubMed Central

    Kaplan, Kevin M.; ElAttrache, Neal S.; Jobe, Frank W.; Morrey, Bernard F.; Kaufman, Kenton R.; Hurd, Wendy J.

    2014-01-01

    Background There is an assumption that baseball athletes who reside in warm-weather climates experience larger magnitude adaptations in throwing shoulder motion and strength compared with their peers who reside in cold-weather climates. Hypotheses (1) The warm-weather climate (WWC) group would exhibit more pronounced shoulder motion and strength adaptations than the cold-weather climate (CWC) group, and (2) the WWC group would participate in pitching activities for a greater proportion of the year than the CWC group, with the time spent pitching predicting throwing shoulder motion and strength in both groups. Study Design Cross-sectional study; Level of evidence, 3. Methods One hundred uninjured high school pitchers (50 each WWC, CWC) were recruited. Rotational shoulder motion and isometric strength were measured and participants reported the number of months per year they pitched. To identify differences between groups, t tests were performed; linear regression was used to determine the influence of pitching volume on shoulder motion and strength. Results The WWC group pitched more months per year than athletes from the CWC group, with the number of months spent pitching negatively related to internal rotation motion and external rotation strength. The WWC group exhibited greater shoulder range of motion in all planes compared with the CWC group, as well as significantly lower external rotation strength and external/internal rotation strength ratios. There was no difference in internal rotation strength between groups, nor a difference in the magnitude of side-to-side differences for strength or motion measures. Conclusion Athletes who reside in cold- and warm-weather climates exhibit differences in throwing shoulder motion and strength, related in part to the number of months spent participating in pitching activities. The amount of time spent participating in pitching activities and the magnitude of range of motion and strength adaptations in athletes who reside

  8. NEARBY GALAXIES IN MORE DISTANT CONTEXTS

    SciTech Connect

    Eskew, Michael; Zaritsky, Dennis E-mail: dzaritsky@as.arizona.edu

    2011-02-15

    We use published reconstructions of the star formation history (SFH) of the Large Magellanic Cloud (LMC), Small Magellanic Cloud, and NGC 300 from the analysis of resolved stellar populations to investigate where such galaxies might land on well-known extragalactic diagnostic plots over the galaxies' lifetime (assuming that nothing other than their stellar populations change). For example, we find that the evolution of these galaxies implies a complex evolution in the Tully-Fisher relation with look-back time and that the observed scatter is consistent with excursions these galaxies take as their stellar populations evolve. We find that the growth of stellar mass is weighted to early times, despite the strongly star-forming current nature of the three systems. Lastly, we find that these galaxies can take circuitous paths across the color-magnitude diagram. For example, it is possible, within the constraints provided by the current determination of its SFH, that the LMC reached the red sequence at intermediate age prior to ending back up on the blue cloud at the current time. Unfortunately, this behavior happens at sufficiently early times that our resolved SFH is crude and insufficiently constraining to convincingly demonstrate that this was the actual evolutionary path. The limited sample size precludes any general conclusions, but we present these as examples how we can bridge the study of resolved populations and the more distant universe.

  9. Cold Gas in Distant Galaxies

    NASA Astrophysics Data System (ADS)

    Carilli, Christopher; Walter, Fabian

    2015-08-01

    Over the past decade, observations of the cool interstellar medium (ISM) in distant galaxies via molecular and atomic fine structure line (FSL) emission have gone from a curious look into a few extreme, rare objects to a mainstream tool for studying galaxy formation out to the highest redshifts. Molecular gas has been observed in about 200 galaxies at z > 1 to z ~ 7, including AGN host-galaxies, highly star-forming submillimeter galaxies, and increasing samples of main-sequence color-selected star-forming galaxies. Studies have moved well beyond simple detections to dynamical imaging at kpc resolution and multiline, multispecies studies that determine the physical conditions in the ISM in early galaxies. Observations of the cool gas are the required complement to studies of the stellar density and star-formation history of the Universe as they reveal the phase of the ISM that immediately precedes star formation in galaxies.Current observations suggest that the order of magnitude increase in the cosmic star-formation rate density from z ~ 0 to 2 is commensurate with a similar increase in the gas-to-stellar mass ratio in star-forming disk galaxies. Progress has been made in determining the CO luminosity to H2 mass conversion factor at high z. The dichotomy between high versus low values for the conversion factor for main-sequence versus starburst galaxies, respectively, appears to persist with increasing redshift, with a likely dependence on metalicity and other local physical conditions. There may also be two sequences in the relationship between star-formation rate and gas mass: one for starbursts, in which the gas consumption timescale is short (~ few e7 years), and one for main sequence galaxies, with an order of magnitude longer gas consumption timescale.With the advent of ALMA, studies of atomic FSL emission are rapidly progressing, with ~ 50 galaxies detected in the exceptionally bright [CII] 158 um line to date, 50% in the last year or so. The [CII] line is

  10. Residence time as a key for comprehensive assessment of the relationship between changing land use and nitrates in regional groundwater systems.

    PubMed

    Cao, Yingjie; Tang, Changyuan; Song, Xianfang; Liu, Changming; Zhang, Yinghua

    2013-04-01

    In this study, an approach is put forward to study the relationship between changing land use and groundwater nitrate contamination in the Sanjiang Plain. This approach emphasizes the importance of groundwater residence time when relating the nitrates to the changing land use. The principles underlying the approach involve the assessment of groundwater residence time by CFCs and the Vogel age model and the reconstruction of the land use at the groundwater recharge time by interpolation. Nitrate trend analysis shows that nitrates have begun to leach into the aquifers since agricultural activities boomed after the 1950s. Hydrochemical analysis implies that the possible process relating to the nitrate reduction in the groundwater is the oxidation of Fe(ii)-silicates. However, the chemical kinetics of the oxidation of Fe(ii)-silicates is slow, so this denitrification process contributes little to the nitrate variations. Stepwise regression shows that the nitrate concentrations of samples had no direct relationship with the land use at the groundwater sampling time, but had a relatively strong relationship with the land use at the groundwater recharge time. Dry land is recognized as the dominant factor contributing to the elevated concentration of nitrates. The nitrogen isotope for nitrate (δ(15)N-NO3) gives a more direct result of the identification of nitrate sources: the use of manure in agricultural activities. Principle component (PC) regression shows that the process of the dry land exploitation is the major process that controls the nitrate contamination in the Sanjiang Plain.

  11. Crystal residence times from trace element zoning in plagioclase reveal changes in magma transfer dynamics at Mt. Etna during the last 400 years

    NASA Astrophysics Data System (ADS)

    Viccaro, Marco; Barca, Donatella; Bohrson, Wendy A.; D'Oriano, Claudia; Giuffrida, Marisa; Nicotra, Eugenio; Pitcher, Bradley W.

    2016-04-01

    Trace element zoning in plagioclase of selected alkaline lavas from the historic (1607-1892 AD) and recent (1983-2013 AD) activity of Mt. Etna volcano has been used to explore the possible role that volcano-tectonics exert on magma transfer dynamics. The observed textural characteristics of crystals include near-equilibrium textures (i.e., oscillatory zoning) and textures with variable extent of disequilibrium (patchy zoning, coarse sieve textures and dissolved cores). Historic crystals exhibit lower K concentrations at lower anorthite contents, a feature in agreement with the general more potassic character of the recent lavas if compared to the historic products. Historic plagioclases have statistically higher Ba and lower Sr concentrations than the recent crystals, which result in different Sr/Ba ratios for the two suites of plagioclase. Variations in the anorthite content along core-to-rim profiles obtained on crystals with different types of textures for both the historic and recent eruptive periods were evaluated particularly versus Sr/Ba. At comparable average An contents, crystals characterized by oscillatory zoning, which are representative of near-equilibrium crystallization from the magma, display distinct Sr/Ba ratios. We suggest that these features are primarily related to recharge of a new, geochemically-distinct magma into the storage and transport system of the volcano. In addition to distinct trace element and textural characteristics of plagioclase, Sr diffusion modeling for plagioclase suggests that residence times are generally shorter for crystals found in recently erupted lavas (25-77 years, average 43 years) compared to those of the historic products (43-163 years, average 99 years). Shorter residences times correlate with gradual increases in eruption volume and eruption frequency rates through time. We attribute these features to an increasing influence, since the 17th century, of extensional tectonic structures within the upper 10 km of

  12. DISTANT CLUSTER OF GALAXIES [left

    NASA Technical Reports Server (NTRS)

    2002-01-01

    One of the deepest images to date of the universe, taken with NASA's Hubble Space Telescope (HST), reveals thousands of faint galaxies at the detection limit of present day telescopes. Peering across a large volume of the observable cosmos, Hubble resolves thousands of galaxies from five to twelve billion light-years away. The light from these remote objects has taken billions of years to cross the expanding universe, making these distant galaxies fossil evidence' of events that happened when the universe was one-third its present age. A fraction of the galaxies in this image belong to a cluster located nine billion light-years away. Though the field of view (at the cluster's distance) is only two million light-years across, it contains a multitude of fragmentary objects. (By comparison, the two million light-years between our Milky Way galaxy and its nearest large companion galaxy, in the constellation Andromeda, is essentially empty space!) Very few of the cluster's members are recognizable as normal spiral galaxies (like our Milky Way), although some elongated members might be edge-on disks. Among this zoo of odd galaxies are ``tadpole-like'' objects, disturbed and apparently merging systems dubbed 'train-wrecks,' and a multitude of faint, tiny shards and fragments, dwarf galaxies or possibly an unknown population of objects. However, the cluster also contains red galaxies that resemble mature examples of today's elliptical galaxies. Their red color comes from older stars that must have formed shortly after the Big Bang. The image is the full field view of the Wide Field and Planetary Camera-2. The picture was taken in intervals between May 11 and June 15, 1994 and required an 18-hour long exposure, over 32 orbits of HST, to reveal objects down to 29th magnitude. [bottom right] A close up view of the peculiar radio galaxy 3C324 used to locate the cluster. The galaxy is nine billion light-years away as measured by its spectral redshift (z=1.2), and located in the

  13. Aquifer residence times for recycled water estimated using chemical tracers and the propagation of temperature signals at a managed aquifer recharge site in Australia

    NASA Astrophysics Data System (ADS)

    Bekele, Elise; Patterson, Bradley; Toze, Simon; Furness, Andrew; Higginson, Simon; Shackleton, Mark

    2014-09-01

    A prerequisite for minimizing contamination risk whilst conducting managed aquifer recharge (MAR) with recycled water is estimating the residence time in the zone where pathogen inactivation and biodegradation processes occur. MAR in Western Australia's coastal aquifers is a potential major water source. As MAR with recycled water becomes increasingly considered in this region, better knowledge of applied and incidental tracer-based options from case studies is needed. Tracer data were collected at a MAR site in Floreat, Western Australia, under a controlled pumping regime over a distance of 50 m. Travel times for bromide-spiked groundwater were compared with two incidental tracers in recycled water: chloride and water temperature. The average travel time using bromide was 87 ± 6 days, whereas the estimates were longer based on water temperature (102 ± 17 days) and chloride (98 ± 60 days). The estimate of average flow velocity based on water temperature data was identical to the estimate based on bromide within a 25-m section of the aquifer (0.57 ± 0.04 m day-1). This case study offers insights into the advantages, challenges and limitations of using incidental tracers in recycled water as a supplement to a controlled tracer test for estimating aquifer residence times.

  14. Residence times and age distributions of spring waters at the Semmering catchment area, Eastern Austria, as inferred from tritium, CFCs and stable isotopes.

    PubMed

    Han, Liangfeng; Hacker, Peter; Gröning, Manfred

    2007-03-01

    The groundwater system in the mountainous area of Semmering, Austria, was studied by environmental tracers in several karst springs. The tracers used included stable isotopes ((18)O, (2)H), tritium ((3)H) and chlorofluorocarbons (CFCs). The tracers provided valuable information in regard to (1) the mean altitude of the spring catchment areas; (2) the residence time and age distribution of the spring waters; and (3) the interconnection of the springs to a sinkhole. The combination of the stable isotopic data and the topography/geology provided the estimates of the mean altitudes of the catchment areas. Based on the stable isotopic data the recharge temperature of the spring waters was estimated. The smoothing of precipitation's isotopic signal in spring discharge provided information on the minimum transit time of the spring waters. Due to short observation time, (3)H data alone cannot be used for describing the mean residence time of the karst waters. CFCs, though useful in recognizing the co-existence of young (post-1993) water with old (CFC-free) water, could not be used to resolve age distribution models. It is shown in this article, however, that the combined use of tritium and CFCs can provide a better assessment of models to account for different groundwater age distributions. In Appendix A, a simplified method for collecting groundwater samples for the analysis of CFCs is described. The method provides a real facilitation for fieldwork. Test data are given for this sampling method in regard to potential contamination by atmospheric CFCs.

  15. Modeling duration of time lived in a residence, a community and mobility in rural areas of Merced and Ventura, California to assess potential health risks to airborne contaminants.

    PubMed

    Driver, Jeffrey; Price, Paul; vanWesenbeeck, Ian; Kaplan, William; Holden, Larry; Ross, John; Landenberger, Bryce

    2016-11-01

    A de novo population mobility survey of 800 households (random digit dialing-based phone interviews) was conducted in high demand areas of the agricultural fumigant, 1,3-dichloropropene (1,3-D) in Merced and Ventura counties of California. The survey included approximately 20 questions relating to the length of time individuals had lived in the high demand areas in each county, and also relating to weekly and annual mobility patterns. Lifetime inhalation exposures to 1,3-D are determined, in part, by the number of years individuals spend in an area where the fumigant is used. The purpose of the survey was to provide location-specific data for probabilistic modeling of long-term inhalation exposures to 1,3-D. The survey found that the majority of residents do not live in a high demand area or in the same house (99.99%) for 70years (a default assumption used by some regulatory agencies). It was also observed that residents move frequently and are mobile day-to-day and week-to-week, within the use area. Finally, estimates of total residency duration, derived from the survey results indicate that median times spent within a high demand area (which could include more than one residential location) were 18 and 26years for Ventura and Merced high demand areas, respectively. The average time spent in the high demand areas was 22 and 27years for the Ventura and Merced community, respectively. Less than 0.01% of the populations in either of the high demand areas spend 70years in the same house. PMID:27436777

  16. Modeling duration of time lived in a residence, a community and mobility in rural areas of Merced and Ventura, California to assess potential health risks to airborne contaminants.

    PubMed

    Driver, Jeffrey; Price, Paul; vanWesenbeeck, Ian; Kaplan, William; Holden, Larry; Ross, John; Landenberger, Bryce

    2016-11-01

    A de novo population mobility survey of 800 households (random digit dialing-based phone interviews) was conducted in high demand areas of the agricultural fumigant, 1,3-dichloropropene (1,3-D) in Merced and Ventura counties of California. The survey included approximately 20 questions relating to the length of time individuals had lived in the high demand areas in each county, and also relating to weekly and annual mobility patterns. Lifetime inhalation exposures to 1,3-D are determined, in part, by the number of years individuals spend in an area where the fumigant is used. The purpose of the survey was to provide location-specific data for probabilistic modeling of long-term inhalation exposures to 1,3-D. The survey found that the majority of residents do not live in a high demand area or in the same house (99.99%) for 70years (a default assumption used by some regulatory agencies). It was also observed that residents move frequently and are mobile day-to-day and week-to-week, within the use area. Finally, estimates of total residency duration, derived from the survey results indicate that median times spent within a high demand area (which could include more than one residential location) were 18 and 26years for Ventura and Merced high demand areas, respectively. The average time spent in the high demand areas was 22 and 27years for the Ventura and Merced community, respectively. Less than 0.01% of the populations in either of the high demand areas spend 70years in the same house.

  17. Numerical model of hyporheic exchange and reactive transport dynamics from the perspective of residence time on upwelling and downwelling zones at River Bure, UK

    NASA Astrophysics Data System (ADS)

    Gokdemir, C.; Heppell, K.; Tonina, D.; Harvey, G.; Bellin, A.

    2013-12-01

    The hyporheic zone is often defined as where mixing of surface water and groundwater occurs in shallow sediments beneath and adjacent to rivers. This mixing is credited with creating unique biogeochemical conditions that can attenuate contaminants from either upstream surface water or groundwater under gaining and losing conditions. Hyporheic exchange often results from differences in the channel near-bed total pressures as they vary in response to interactions between the surface flow and bed topography and the nearby water table. Reactions of contaminants in groundwater also dependent on mixing from surface water. Therefore, representation of the profile of upwelling and downwelling exchange between surface water and groundwater have important consequences for contaminant transport. Here we are studying nitrogen fate within a restored reach of the River Bure, Norfolk, United Kingdom. We combine field measurements of surface flow properties, nearby groundwater table and nitrogen compound concentration with numerical simulation of the hyporheic flow path. We numerically model mixing between hyporheic flow paths induced by sediment, bedform, meanders on riverbed, and flow paths of adjacent upwelling of deeper groundwater. Preliminary results indicate that with the coarse topographical data and with limited surface water hydraulic data it is possible to define the spatial extent of hyporheic exchange and potential mixing zones for contaminants as a function of residence time. The proposed work has the potential to depict high residence time zones and biogeochemical reactivity in homogeneous and heterogeneous sediments. Furthermore, our results aim to clarify hyporheic zone definitions from the perspective of residence time and of upwelling and downwelling contaminants in order to understand real case biogeochemical dynamics.

  18. Extracellular amylases of starch-fermenting yeast: pH effect on export and residence time in the periplasm

    SciTech Connect

    Calleja, G.B.; Levy-Rick, S.R.; Nasim, A.; Lusena, C.V.

    1987-01-01

    Aerobic cultures of S. alluvius in Wickerham's yeast-nitrogen-base medium with starch as sole carbon source become strongly acidic and contain no detectable extra-cellular amylolytic activity during stationary phase, when the activity in buffered cultures is maximal. The extracellular amylases are irreversibly inactivated at the low pH value (less than 3.5) attained by the cultures. When adequately buffered, the medium yields maximal extracellular amylolytic activity. About 0.2 M phosphate buffer is adequate for substrate concentrations of up to 0.5% starch; higher starch concentrations require more buffer. Unbuffered cultures that are adjusted once with alkali to pH 5.5 also allow maximal extracellular amylolytic activity, provided the adjustment is made prior to the end of exponential growth. Automatic pH control allows use of high starch concentrations of up to 4%. Export is optimal at pH values higher than the optima for enzyme activity and stability and for population growth. The need for pH adjustment prior to the appearance of amylolytic activity in the medium suggests pH dependence of the export process itself and/or acid inactivation of enzymes transiently resident in the periplasm. (Refs. 23).

  19. Arming and firing system for DISTANT RUNNER

    SciTech Connect

    Skenandore, L.H.; Johnson, J.P.

    1982-03-01

    Sandia A and F systems Division 1132 provided arming and firing support for the DISTANT RUNNER Test Program at White Sands Missile Range. This report describes the field support and the firing system that was used.

  20. 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

  1. Gene Transfers Between Distantly Related Organisms

    NASA Technical Reports Server (NTRS)

    Doolittle, Russell F.

    2003-01-01

    With the completion of numerous microbial genome sequences, reports of individual gene transfers between distantly related prokaryotes have become commonplace. On the other hand, transfers between prokaryotes and eukaryotes still excite the imagination. Many of these claims may be premature, but some are certainly valid. In this chapter, the kinds of supporting data needed to propose transfers between distantly related organisms and cite some interesting examples are considered.

  2. Derivation of a Multiparameter Gamma Model for Analyzing the Residence-Time Distribution Function for Nonideal Flow Systems as an Alternative to the Advection-Dispersion Equation

    DOE PAGES

    Embry, Irucka; Roland, Victor; Agbaje, Oluropo; Watson, Valetta; Martin, Marquan; Painter, Roger; Byl, Tom; Sharpe, Lonnie

    2013-01-01

    A new residence-time distribution (RTD) function has been developed and applied to quantitative dye studies as an alternative to the traditional advection-dispersion equation (AdDE). The new method is based on a jointly combined four-parameter gamma probability density function (PDF). The gamma residence-time distribution (RTD) function and its first and second moments are derived from the individual two-parameter gamma distributions of randomly distributed variables, tracer travel distance, and linear velocity, which are based on their relationship with time. The gamma RTD function was used on a steady-state, nonideal system modeled as a plug-flow reactor (PFR) in the laboratory to validate themore » effectiveness of the model. The normalized forms of the gamma RTD and the advection-dispersion equation RTD were compared with the normalized tracer RTD. The normalized gamma RTD had a lower mean-absolute deviation (MAD) (0.16) than the normalized form of the advection-dispersion equation (0.26) when compared to the normalized tracer RTD. The gamma RTD function is tied back to the actual physical site due to its randomly distributed variables. The results validate using the gamma RTD as a suitable alternative to the advection-dispersion equation for quantitative tracer studies of non-ideal flow systems.« less

  3. Voyager observations of jupiter's distant magnetotail. Progress report

    SciTech Connect

    Kurth, W.S.; Gurnett, D.A.; Scarf, F.L.; Poynter, R.L.; Sullivan, J.D.

    1980-08-01

    Observations of nonthermal continuum radiation by Voyager 1 and 2 at large distances from Jupiter have led to the identification of brief encounters with the Jovian magnetosphere at distances greater than 700 RJ and in directions substantially far from the Jupiter-Sun line. In addition, a number of examples of continuum radiation apparently trapped in local density depressions in the solar wind are observed. Simultaneous measurements by the Voyager plasma instrument have verified the distant magnetotail crossings and are used to correlate the occurrence of trapped continuum radiation events within solar wind density rarefractions. The Voyager observations of the distant Jovian magnetotail are compared with observations in the distant terrestrial magnetosphere and also with observations of the plasma tails of comets. One variable explanation of the observations is that the Jovian tail consists of filamentary structures, some of which extend to large distances in the pre-dawn direction. The observations of continuum radiation trapped in low-density regions of the solar wind suggest that Voyager may at times be connected to the distant tail by a low-density trough which acts as a wave guide and allows radiation from the tail to reach the spacecraft. This may provide an indirect method of detecting the tail extending more than 2 AU downstream from Jupiter.

  4. Using Distant Sources in Local Seismic Tomography

    NASA Astrophysics Data System (ADS)

    Julian, Bruce; Foulgr, Gillian

    2014-05-01

    Seismic tomography methods such as the 'ACH' method of Aki, Christoffersson & Husebye (1976, 1977) are subject to significant bias caused by the unknown wave-speed structure outside the study volume, whose effects are mathematically of the same order as the local-structure effects being studied. Computational experiments using whole-mantle wave-speed models show that the effects are also of comparable numerical magnitude (Masson & Trampert, 1997). Failure to correct for these effects will significantly corrupt computed local structures. This bias can be greatly reduced by solving for additional parameters defining the shapes, orientations, and arrival times of the incident wavefronts. The procedure is exactly analogous to solving for hypocentral locations in local-earthquake tomography. For planar incident wavefronts, each event adds three free parameters and the forward problem is surprisingly simple: The first-order change in the theoretical arrival time at observation point B resulting from perturbations in the incident-wave time t0 and slowness vector s is δtB ≡ δt0 + δs · rA = δtA, the change in the time of the plane wave at the point A where the un-perturbed ray enters the study volume (Julian and Foulger, submitted). This consequence of Fermat's principle apparently has not previously been recognized. In addition to eliminating the biasing effect of structure outside the study volume, this formalism enables us to combine data from local and distant events in studies of local structure, significantly improving resolution of deeper structure, particularly in places such as volcanic and geothermal areas where seismicity is confined to shallow depths. Many published models that were derived using ACH and similar methods probably contain significant artifacts and are in need of re-evaluation.

  5. Active Tobacco Smoking and Distant Metastasis in Patients With Oropharyngeal Cancer

    SciTech Connect

    McBride, Sean M.; Ali, Nawal N.; Margalit, Danielle N.; Chan, Annie W.

    2012-09-01

    Purpose: Distant metastasis is the site of first relapse in approximately one-third of patients with locally advanced oropharyngeal carcinoma, irrespective of human papillomavirus status. Yet the risk factors associated with distant metastasis are not well characterized. We sought to characterize the relationship between smoking status and distant metastasis. Methods and Materials: We evaluated the association between tobacco smoking status and distant metastasis in a retrospective cohort study of 132 patients who underwent definitive radiation therapy and chemotherapy for Stage III-IVA/B oropharyngeal cancer. Information on tobacco smoking was prospectively collected by patient questionnaires and physician notes at the time of diagnosis. Thirty-three percent of the patients were nonsmokers, 51% were former smokers, 16% were active smokers. The cumulative lifetime tobacco smoking in pack-years was 20 (range, 0-150). Results: With a median follow-up time of 52 months, the overall rate of distant metastasis at 4 years was 8%. Distant metastasis was the most common first site of relapse, occurring in 56% of the patients with recurrences. Active smokers had higher rates of distant metastasis than non-active smokers (including never- and former smokers; 31% vs. 4%, p < 0.001) and former smokers (31% vs. 3%, p < 0.001). There was no statistically significant difference in the risk of distant metastasis for patients with lifetime cumulative pack-years >20 and {<=}20 (10% vs. 4%, p = 0.19). In univariate analysis, active smoking (p = 0.0004) and N category (p = 0.009) were predictive of increased risk of distant metastasis. In multivariate analysis, active smoking was the most significant predictive factor for increased risk of distant metastasis (hazard ratio, 12.7, p < 0.0001). Conclusions: This study identified a strong association between active smoking and distant metastasis in patients with oropharyngeal cancer.

  6. Application of a novel type impinging streams reactor in solid-liquid enzyme reactions and modeling of residence time distribution using GDB model.

    PubMed

    Fatourehchi, Niloufar; Sohrabi, Morteza; Dabir, Bahram; Royaee, Sayed Javid; Haji Malayeri, Adel

    2014-02-01

    Solid-liquid enzyme reactions constitute important processes in biochemical industries. The isomerization of d-glucose to d-fructose, using the immobilized glucose isomerase (Sweetzyme T), as a typical example of solid-liquid catalyzed reactions has been carried out in one stage and multi-stage novel type of impinging streams reactors. Response surface methodology was applied to determine the effects of certain pertinent parameters of the process namely axial velocity (A), feed concentration (B), nozzles' flow rates (C) and enzyme loading (D) on the performance of the apparatus. The results obtained from the conversion of glucose in this reactor were much higher than those expected in conventional reactors, while residence time was decreased dramatically. Residence time distribution (RTD) in a one-stage impinging streams reactor was investigated using colored solution as the tracer. The results showed that the flow pattern in the reactor was close to that in a continuous stirred tank reactor (CSTR). Based on the analysis of flow region in the reactor, gamma distribution model with bypass (GDB) was applied to study the RTD of the reactor. The results indicated that RTD in the impinging streams reactor could be described by the latter model.

  7. Aerosol residence times and changes in radioiodine-131I and radiocaesium-137 Cs activity over Central Poland after the Fukushima-Daiichi Nuclear reactor accident.

    PubMed

    Długosz-Lisiecka, Magdalena; Bem, Henryk

    2012-05-01

    The first detectable activities of radioiodine (131)I, and radiocaesium (134)Cs and (137)Cs in the air over Central Poland were measured in dust samples collected by the ASS-500 station in the period of 21(st) to 24(th) of March, 2011. However, the highest activity of both fission products, (131)I and (137)Cs: 8.3 mBq m(-3) and 0.75 mBq m(-3), respectively, were obtained in the samples collected on 30(th) March, i.e.∼18 days after the beginning of the fission products' discharge from the damaged units of the Fukushima Daiichi Nuclear Power Plant. The simultaneously determined corrected aerosol residence time for the same samples by (210)Pb/(210)Bi and (210)Pb/(210)Po methods was equal to 10 days. Additionally, on the basis of the activity ratio of two other natural cosmogenic radionuclides, (7)Be and (22)Na in these aerosol samples, it was possible to estimate the aerosol residence time at ∼150 days for the solid particles coming from the stratospheric fallout. These data, as well as the differences in the activity size distribution of (7)Be and (131)I in the air particulate matter, show, in contrast to the Chernobyl discharge, a negligible input of stratospheric transport of Fukushima-released fission products.

  8. Synthesis and photocatalytic activity of TiO2 nanoparticles prepared by chemical vapor condensation method with different precursor concentration and residence time.

    PubMed

    Chin, Sungmin; Park, Eunseuk; Kim, Minsu; Bae, Gwi-Nam; Jurng, Jongsoo

    2011-10-15

    Nanosized TiO(2) photocatalysts were synthesized using a chemical vapor condensation method under a range of synthesis conditions (precursor vapor concentration and residence time in a tubular electric furnace). X-ray diffraction showed that the prepared TiO(2) powders consisted mainly of anatase (>94%) with a small amount of rutile. The mean particle diameter from the Brunauer-Emmett-Teller surface area and transmission electron microscopy measurements ranged from 9.4 to 16.6 nm. The specific surface area (92.5-163.5 m(2) g(-1)) of the prepared TiO(2) powders was found to be dependent on the synthesis conditions. The content of hydroxyl groups on the surface of the prepared TiO(2) sample was higher than those on commercial TiO(2), resulting in increased photocatalytic oxidation. The photocatalytic activity of the TiO(2) samples prepared in a methylene blue solution was strongly dependent on the crystallinity and specific surface area, which were affected by the TTIP vapor concentration and residence time. PMID:21802692

  9. Non-proportional bioaccumulation of trace metals and metalloids in the planktonic food web of two Singapore coastal marine inlets with contrasting water residence times.

    PubMed

    Calbet, Albert; Schmoker, Claire; Russo, Francesca; Trottet, Aurore; Mahjoub, Mohamed-Sofiane; Larsen, Ole; Tong, Hor Yee; Drillet, Guillaume

    2016-08-01

    We analyzed the concentrations of trace metals/metalloids (TMs) in the water, sediment and plankton of two semi-enclosed marine coastal inlets located north of Jurong Island and separated by a causeway (SW Singapore; May 2012-April 2013). The west side of the causeway (west station) has residence times of approximately one year, and the east side of the causeway (east station) has residence times of one month. The concentrations of most of the TMs in water and sediment were higher in the west than in the east station. In the water column, most of the TMs were homogeneously distributed or had higher concentrations at the surface. Preliminary evidence suggests that the TMs are primarily derived from aerosol depositions from oil combustion and industry. Analyses of TMs in seston (>0.7μm; mostly phytoplankton) and zooplankton (>100μm) revealed that the seston from the west station had higher concentrations of most TMs; however, the concentrations of TMs in zooplankton were similar at the two stations. Despite the high levels of TMs in water, sediment and seston, the bioaccumulation detected in zooplankton was moderate, suggesting either the presence of effective detoxification mechanisms or/and the inefficient transfer of TMs from primary producers to higher trophic levels as a result of the complexity of marine planktonic food webs. In summary, the TM concentrations in water and seston are not reliable indicators of the bioaccumulation at higher trophic levels of the food web.

  10. Application of a novel type impinging streams reactor in solid-liquid enzyme reactions and modeling of residence time distribution using GDB model.

    PubMed

    Fatourehchi, Niloufar; Sohrabi, Morteza; Dabir, Bahram; Royaee, Sayed Javid; Haji Malayeri, Adel

    2014-02-01

    Solid-liquid enzyme reactions constitute important processes in biochemical industries. The isomerization of d-glucose to d-fructose, using the immobilized glucose isomerase (Sweetzyme T), as a typical example of solid-liquid catalyzed reactions has been carried out in one stage and multi-stage novel type of impinging streams reactors. Response surface methodology was applied to determine the effects of certain pertinent parameters of the process namely axial velocity (A), feed concentration (B), nozzles' flow rates (C) and enzyme loading (D) on the performance of the apparatus. The results obtained from the conversion of glucose in this reactor were much higher than those expected in conventional reactors, while residence time was decreased dramatically. Residence time distribution (RTD) in a one-stage impinging streams reactor was investigated using colored solution as the tracer. The results showed that the flow pattern in the reactor was close to that in a continuous stirred tank reactor (CSTR). Based on the analysis of flow region in the reactor, gamma distribution model with bypass (GDB) was applied to study the RTD of the reactor. The results indicated that RTD in the impinging streams reactor could be described by the latter model. PMID:24411440

  11. Investigations on polyplex stability during the freezing step of lyophilization using controlled ice nucleation--the importance of residence time in the low-viscosity fluid state.

    PubMed

    Kasper, Julia C; Pikal, Michael J; Friess, Wolfgang

    2013-03-01

    The aim of the study was to comprehensively investigate the influence of the freezing step during lyophilization on the stability of gene-delivery particles in order to better understand particle stabilization during freezing. Particle size of plasmid/linear polyethylenimine (LPEI) polyplexes at two DNA concentrations and at increasing sucrose-DNA ratios was investigated separately as a function of freezing procedure, ice-nucleation temperature, residence time of the particles in a partially frozen state, or incomplete freezing. Using a numerical model, the increase in sucrose concentration and system viscosity and corresponding bimolecular reaction rates were theoretically estimated. Freezing with a temperature-hold step after ice nucleation negatively influenced particle stability. Ice-nucleation temperature had an impact only at low DNA concentrations. Particle stability was highly reduced during the early part of freezing (<-3°C), especially at low shelf-ramp rates. In this phase, bimolecular reaction rates increase greatly at still low system viscosity. Below a critical temperature (≤∼-18°C) and at high system viscosity, no further particle aggregation occurred. In conclusion, the initial sample viscosity rather than the unfrozen volume and the residence time of particles in the low-viscosity state are the predominant factors in particle stabilization, which likely apply to aggregation in any system.

  12. Tracer ages along a section between Ellesmere Island and the North Pole: Implications for circulation and mean residence times of the upper water colum

    NASA Astrophysics Data System (ADS)

    Schlosser, P.; Smethie, W. M., Jr.; Newton, R.; Friedrich, R.

    2014-12-01

    We present age tracer distributions (Tritium/He-3 and SF6) from a section between Ellesmere Island and the North Pole as part of the Switchyard project. The sections cover the period between 2008 and 2013. The tracers are interpreted in the context of circulation patterns and mean residence times of the main water masses. Mixed layer tracer ages range from close to zero to ca. 5 years with most of the ages grouping around 2.5 years. The tracer ages increase rapidly through the halocline waters (roughly 10 years at about 100 and 20 years close to 200 meters depth, respectively) and typically reach their maximum values close to the depth of the core of the Atlantic Water (up to 35 years). Within the AW there are large lateral gradients with higher ages found in the boundary current along the slope of the Canadian Archipelago, and lower ages prevalent close to the North Pole. We also observe temporal variability in the age tracer distributions, mainly in the lateral gradient of the ages in the AW layer. We discuss the age tracer results in the context of the circulation and mean residence times of waters in the Switchyard region of the Arctic Ocean and their variability. We also discuss possible systematic differences between the Tritium/He-3 and SF6 ages and their relevance for our main conclusions.

  13. Preliminary simulation of hyporheic hydrology suggests systematic changes in hyporheic flow path length and residence time in response to reach-scale channel restoration in Meacham Creek, OR

    NASA Astrophysics Data System (ADS)

    Amerson, B. E.; Poole, G.

    2011-12-01

    Hyporheic hydrologic response to stream restoration has typically focused on hydrodynamics associated with individual features or habitat units rather than whole reaches. Here we present preliminary results from MODFLOW simulations that compare modeled hyporheic hydrology prior to and after major channel reconfiguration associated with a recently completed reach-scale channel restoration on Meacham Creek in northeastern Oregon. Our model was parameterized using LiDAR floodplain surface elevation data and empirically-derived estimates of aquifer properties. Results show that groundwater flow path length and cumulative residence time distributions are apt to be altered by channel reconfiguration. For example, our model shows that the relatively high-gradient and straight baseline channel is dominated by either short or long flow path lengths, with relatively few medium length flow paths. In contrast, the proposed restoration channel is more sinuous and has a lower gradient. Our modeling suggests that the restoration channel will have a broader distribution of flow path lengths and residence times. We used model results to select well locations for intensive monitoring of groundwater surface elevation and temperature. Monitoring will continue through 2012 and is designed to evaluate model predictions as well as to document the effects of the channel restoration on surface water-groundwater interactions and concomitant effects on water temperature.

  14. Real-Time Imaging of Resident T Cells in Human Lung and Ovarian Carcinomas Reveals How Different Tumor Microenvironments Control T Lymphocyte Migration.

    PubMed

    Bougherara, Houcine; Mansuet-Lupo, Audrey; Alifano, Marco; Ngô, Charlotte; Damotte, Diane; Le Frère-Belda, Marie-Aude; Donnadieu, Emmanuel; Peranzoni, Elisa

    2015-01-01

    T cells play a key role in the battle against cancer. To perform their antitumor activities, T cells need to adequately respond to tumor antigens by establishing contacts with either malignant cells or antigen-presenting cells. These latter functions rely on a series of migratory steps that go from entry of T cells into the tumor followed by their locomotion in the tumor stroma. Our knowledge of how T cells migrate within tumors mainly comes from experiments performed in mouse models. Whereas such systems have greatly advanced our understanding, they do not always faithfully recapitulate the disease observed in cancer patients. We previously described a technique based on tissue slices that enables to track with real-time imaging microscopy the motile behavior of fluorescent T cells plated onto fresh sections of human lung tumors. We have now refined this approach to monitor the locomotion of resident tumor-infiltrating CD8 T cells labeled with fluorescently coupled antibodies. Using this approach, our findings reveal that CD8 T cells accumulate in the stroma of ovarian and lung carcinomas but move slowly in this compartment. Conversely, even though less populated, tumors islets were found to be zones of faster migration for resident CD8 T cells. We also confirm the key role played by collagen fibers, which, by their orientation, spacing and density, control the distribution and migration of resident CD8 T cells within the tumor stroma. We have subsequently demonstrated that, under some physical tissue constraints, CD8 T cells exhibited a mode of migration characterized by alternate forward and backward movements. In sum, using an ex vivo assay to track CD8 T cells in fresh human tumor tissues, we have identified the extracellular matrix as a major stromal component in influencing T cell migration, thereby impacting the control of tumor growth. This approach will aid in the development and testing of novel immunotherapy strategies to promote T cell migration in

  15. Application of electron stimulated desorption techniques to measure the isotherm and the mean residence time of hydrogen physisorbed on a metal surface

    SciTech Connect

    Arakawa, Ichiro Shimizu, Hideyuki; Kawarabuki, Taku; Yamakawa, Koichiro; Miura, Takashi

    2015-03-15

    Electron stimulated desorption techniques were applied to probe the density of H{sub 2} physisorbed on a cold surface. The adsorption isotherm of H{sub 2} on a copper surface was measured in the equilibrium pressure range between 10{sup −9} and 10{sup −4} Pa at surface temperatures of 6.5 and 4.2 K. The mean residence times of H{sub 2} on copper were obtained from the observation of the time development of the surface density in a transitional state approaching equilibrium, and are 50–500 s for the coverage between 1 and 0.18 at 4.2 K of the substrate temperature. The adsorption energies of 1.18–1.27 kJ/mol, and the condensation coefficient of 0.074–0.018 were also deduced.

  16. 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.

  17. Interpreting the Clustering of Distant Red Galaxies

    SciTech Connect

    Tinker, Jeremy L.; Wechsler, Risa H.; Zheng, Zheng; /Princeton, Inst. Advanced Study

    2009-08-03

    We analyze the angular clustering of z {approx} 2.3 distant red galaxies (DRGs) measured by Quadri et al. (2008). We find that, with robust estimates of the measurement errors and realistic halo occupation distribution modeling, the measured clustering can be well fit within standard halo occupation models, in contrast to previous results. However, in order to fit the strong break in w({theta}) at {theta} = 10{double_prime}, nearly all satellite galaxies in the DRG luminosity range are required to be DRGs. Within this luminosity-threshold sample, the fraction of galaxies that are DRGs is {approx} 44%, implying that the formation of DRGs is more efficient for satellite galaxies than for central galaxies. Despite the evolved stellar populations contained within DRGs at z = 2.3, 90% of satellite galaxies in the DRG luminosity range have been accreted within 500 Myr. Thus, satellite DRGs must have known they would become satellites well before the time of their accretion. This implies that the formation of DRGs correlates with large-scale environment at fixed halo mass, although the large-scale bias of DRGs can be well fit without such assumptions. Further data are required to resolve this issue. Using the observational estimate that {approx} 30% of DRGs have no ongoing star formation, we infer a timescale for star formation quenching for satellite galaxies of 450 Myr, although the uncertainty on this number is large. However, unless all non-star forming satellite DRGs were quenched before accretion, the quenching timescale is significantly shorter than z {approx} 0 estimates. Down to the completeness limit of the Quadri et al sample, we find that the halo masses of central DRGs are {approx} 50% higher than non-DRGs in the same luminosity range, but at the highest halo masses the central galaxies are DRGs only {approx} 2/3 of the time.

  18. ISEE 3 observations during the CDAW 8 intervals - Case studies of the distant geomagnetic tail covering a wide range of geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Richardson, I. G.; Slavin, J. A.; Owen, C. J.; Cowley, S. W. H.; Galvin, A. B.; Sanderson, T. R.; Scholer, M.

    1989-01-01

    Observations made by the ISEE 3 spacecraft in the distant geomagnetic tail during the eight CDAW 8 intervals are discussed, along with their relation to concurrent geomagnetic activity. This extensive multiinstrument case study of distant tail data covers a wide range of geomagnetic conditions from extended intervals of magnetic quiet with isolated substorms to prolonged periods of intense disturbance. Plasmoids are observed in the distant tail following disturbance enhancements, the time of their appearance being generally consistent with disconnection from the near-earth region at the time of the enhancement. Their structure is entirely consistent with the neutral line model. However, not all enhancements in geomagnetic activity result in the observation of plasmoids. In particular, the CDAW 8 data suggest that, during extended intervals of strong activity, a continuous neutral line may reside in the near-earth tail and some disturbance enhancements may then relate to an increase in the reconnection rate at a preexisting neutral line, rather than to new neutral line and plasmoid formation.

  19. Impact of TimeSlips, a Creative Expression Intervention Program, on Nursing Home Residents with Dementia and their Caregivers

    ERIC Educational Resources Information Center

    Fritsch, Thomas; Kwak, Jung; Grant, Stacey; Lang, Josh; Montgomery, Rhonda R.; Basting, Anne D.

    2009-01-01

    Purpose: 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…

  20. Application of multiple isotopic and geochemical tracers for investigation of recharge, salinization, and residence time of water in the Souss Massa aquifer, southwest of Morocco

    NASA Astrophysics Data System (ADS)

    Bouchaou, L.; Michelot, J. L.; Vengosh, A.; Hsissou, Y.; Qurtobi, M.; Gaye, C. B.; Bullen, T. D.; Zuppi, G. M.

    2008-05-01

    SummaryGroundwater and surface water in Souss-Massa basin in the west-southern part of Morocco is characterized by a large variation in salinity, up to levels of 37 g L-1. The high salinity coupled with groundwater level decline pose serious problems for current irrigation and domestic water supplies as well as future exploitation. A combined hydrogeologic and isotopic investigation using several chemical and isotopic tracers such as Br/Cl, δ18O, δ2H, 3H, 87Sr/86Sr, δ11B, and 14C was carried out in order to determine the sources of water recharge to the aquifer, the origin of salinity, and the residence time of water. Stable isotope, 3H and 14C data indicate that the high Atlas mountains in the northern margin of the Souss-Massa basin with high rainfall and low δ18O and δ2H values (-6 to -8‰ and -36 to -50‰) is currently constitute the major source of recharge to the Souss-Massa shallow aquifer, particularly along the eastern part of the basin. Localized stable isotope enrichments offset meteoric isotopic signature and are associated with high nitrate concentrations, which infer water recycling via water agricultural return flows. The 3H and 14C data suggest that the residence time of water in the western part of the basin is in the order of several thousands of years; hence old water is mined, particularly in the coastal areas. The multiple isotope analyses and chemical tracing of groundwater from the basin reveal that seawater intrusion is just one of multiple salinity sources that affect the quality of groundwater in the Souss-Massa aquifer. We differentiate between modern seawater intrusion, salinization by remnants of seawater entrapped in the middle Souss plains, recharge of nitrate-rich agricultural return flow, and dissolution of evaporate rocks (gypsum and halite minerals) along the outcrops of the high Atlas mountains. The data generated in this study provide the framework for a comprehensive management plan in which water exploitation should

  1. Application of multiple isotopic and geochemical tracers for investigation of recharge, salinization, and residence time of water in the Souss-Massa aquifer, southwest of Morocco

    USGS Publications Warehouse

    Bouchaou, L.; Michelot, J.L.; Vengosh, A.; Hsissou, Y.; Qurtobi, M.; Gaye, C.B.; Bullen, T.D.; Zuppi, G.M.

    2008-01-01

    Groundwater and surface water in Souss-Massa basin in the west-southern part of Morocco is characterized by a large variation in salinity, up to levels of 37 g L-1. The high salinity coupled with groundwater level decline pose serious problems for current irrigation and domestic water supplies as well as future exploitation. A combined hydrogeologic and isotopic investigation using several chemical and isotopic tracers such as Br/Cl, ??18O, ??2H, 3H, 87Sr/86Sr, ??11B, and 14C was carried out in order to determine the sources of water recharge to the aquifer, the origin of salinity, and the residence time of water. Stable isotope, 3H and 14C data indicate that the high Atlas mountains in the northern margin of the Souss-Massa basin with high rainfall and low ??18O and ??2H values (-6 to -8??? and -36 to -50???) is currently constitute the major source of recharge to the Souss-Massa shallow aquifer, particularly along the eastern part of the basin. Localized stable isotope enrichments offset meteoric isotopic signature and are associated with high nitrate concentrations, which infer water recycling via water agricultural return flows. The 3H and 14C data suggest that the residence time of water in the western part of the basin is in the order of several thousands of years; hence old water is mined, particularly in the coastal areas. The multiple isotope analyses and chemical tracing of groundwater from the basin reveal that seawater intrusion is just one of multiple salinity sources that affect the quality of groundwater in the Souss-Massa aquifer. We differentiate between modern seawater intrusion, salinization by remnants of seawater entrapped in the middle Souss plains, recharge of nitrate-rich agricultural return flow, and dissolution of evaporate rocks (gypsum and halite minerals) along the outcrops of the high Atlas mountains. The data generated in this study provide the framework for a comprehensive management plan in which water exploitation should shift

  2. Distribution of 7Be, 210Pb and 137Cs in watersheds of different scales in the Seine River basin: inventories and residence times.

    PubMed

    Le Cloarec, Marie-Françoise; Bonté, Philippe; Lefèvre, Irène; Mouchel, Jean-Marie; Colbert, Steven

    2007-04-01

    The activity of environmental radionuclides ((7)Be, (210)Pb and (137)Cs) was monitored in nested catchments, inside the Seine River basin. Suspended matter data was collected at 8 different watersheds, ranging from order 1 to order 7, and ranging in size over 4 orders of magnitude. Suspended matter was analyzed for (210)Pb, (137)Cs and (7)Be, and used to calculate the flux of sediments out of each watershed. Monthly atmospheric flux data of (210)Pb and (7)Be was analyzed to assess the input flux of each into the watersheds, taking into account the rainfall during sampling periods. Taking advantage of the different half-lives of (7)Be (53 days) and (210)Pb (22 years), a two-box model was built for each of the catchments following a methodology previously developed by Dominik et al. [Dominik J, Burrus D, Vernet JP. Transport of the environmental radionuclides in alpine watershed. Earth Planet Sci Letters 1987; 84: 165-180.]. The model divides the watershed into a soil box and a rapid reservoir and provides insight into the removal rate of suspended matter from the surrounding watershed. The model enables the assessment of the surface area and the residence time of slow and rapid reservoirs to describe the fate of contaminants of atmospheric origin inside the river basin. The model was improved by considering the dissolved fraction in the total flux and adding the (137)Cs inventory as an additional constraint. The effects of these changes are discussed. Residence times in the soil box, characterized by low transport velocity, range between 4800 years at Melarchez (order 1) to about 30000 years at Andresy and Poses (order 7). They remain constant in each watershed over a large range of variation of atmospheric fluxes of (7)Be and (210)Pb during the whole study, but are sensitive to SM variations. The residence time in the rapid box, which includes the surface of the river and immediate surroundings, is less than one year, while its surface area is in the range 0.6% to

  3. Nutrient Loads and Ground-Water Residence Times in an Agricultural Basin in North-Central Connecticut

    USGS Publications Warehouse

    Mullaney, John R.

    2007-01-01

    Nutrient loads from ground-water discharge were studied in Broad Brook Basin, a 15.8-square mile basin in north-central Connecticut, dominated by agricultural activity. Loads were calculated, along with the travel times of ground water from recharge to discharge areas, to estimate the time required for the effects of Best Management Practices (BMPs) to be observed. Most concentrations of nitrogen and phosphorus in Broad Brook exceeded U.S. Environmental Protection Agency Ecoregion XIV nutrient criteria for streams. During the study period (1993-2004), annual loads of nitrogen from Broad Brook Basin ranged from 117,000 to 270,000 pounds (lb), and yields were about 10 times larger than those from forested basins in Connecticut. Ground-water discharge from the aquifer to the streams (base flow) during the study period was estimated with hydrograph separation and accounted for 82 percent of the total runoff from the basin. Nitrate nitrogen in base flow averaged 71 percent of the annual load of total nitrogen discharged from the basin, indicating that the largest source of nitrogen was likely from ground-water discharge. Annual loads of total phosphorus from the basin ranged from 2,330 to 14,400 lb, and yields were about five times higher than those from forested basins in Connecticut. Dissolved phosphorus averaged about 71 percent of the total phosphorus load, and ground-water discharge accounted for only as much as 40 percent of the annual load of dissolved phosphorus; therefore, phosphorus loads are dominated by stormwater-runoff events. Ground-water samples collected from 11 wells in the basin contained elevated concentrations of nitrite plus nitrate nitrogen. Dissolved gas analyses indicated that little denitrification was occurring in the aquifer. Appar