WorldWideScience

Sample records for stream temperature regimes

  1. Influence of Beaver Dams on Channel Complexity, Hydrology, and Temperature Regime in a Mountainous Stream

    Science.gov (United States)

    Majerova, M.; Neilson, B. T.; Schmadel, N. M.; Wheaton, J. M.; Snow, C. J.

    2013-12-01

    Beaver dams and beaver activity affect hydrologic processes, sediment transport, channel complexity and water quality of streams. Beaver ponds, which form behind beaver dams, increase in-channel water storage affecting the timing and volume of flow and resulting in the attenuation and flattening of the hydrograph. Channel complexity also increases the potential for transient storage (both surface and subsurface) and influences stream temperature. Impacts of beaver dams and beaver activity on stream responses are difficult to quantify because responses are dynamic and spatially variable. Few studies have focused on the reach scale temporal influences on stream responses and further research is needed particularly in quantifying the influence of beaver dams and their role in shaping the stream habitat. This study explores the changing hydrology and temperature regime of Curtis Creek, a mountainous stream located in Northern Utah, in a 560 m long reach where groundwater exchanges and temperature differences were observed over a three-year period. We have collected continuous stream discharge, stream temperature data and performed tracer experiments. During the first year, we were able to capture the pre-beaver activity. In the second year, we captured the impacts of some beaver activity with only a few dams built in the reach, while the third year included the effects of an entire active beaver colony. By the end of the study period, a single thread channel had been transformed into a channel with side channels and backwaters at multiple locations therefore increasing channel complexity. The cumulative influence of beaver dams on reach scale discharge resulted in a slightly losing reach that developed into a gaining reach. At the smaller sub-reach scale, both losing to gaining and gaining to losing transformations were observed. Temperature differences showed a warming effect of beaver dams at the reach scale. The reach stream temperature difference increased on

  2. Impacts of beaver dams on hydrologic and temperature regimes in a mountain stream

    Science.gov (United States)

    Majerova, M.; Neilson, B. T.; Schmadel, N. M.; Wheaton, J. M.; Snow, C. J.

    2015-08-01

    Beaver dams affect hydrologic processes, channel complexity, and stream temperature in part by inundating riparian areas, influencing groundwater-surface water interactions, and changing fluvial processes within stream systems. We explored the impacts of beaver dams on hydrologic and temperature regimes at different spatial and temporal scales within a mountain stream in northern Utah over a 3-year period spanning pre- and post-beaver colonization. Using continuous stream discharge, stream temperature, synoptic tracer experiments, and groundwater elevation measurements, we documented pre-beaver conditions in the first year of the study. In the second year, we captured the initial effects of three beaver dams, while the third year included the effects of ten dams. After beaver colonization, reach-scale (~ 750 m in length) discharge observations showed a shift from slightly losing to gaining. However, at the smaller sub-reach scale (ranging from 56 to 185 m in length), the discharge gains and losses increased in variability due to more complex flow pathways with beaver dams forcing overland flow, increasing surface and subsurface storage, and increasing groundwater elevations. At the reach scale, temperatures were found to increase by 0.38 °C (3.8 %), which in part is explained by a 230 % increase in mean reach residence time. At the smallest, beaver dam scale (including upstream ponded area, beaver dam structure, and immediate downstream section), there were notable increases in the thermal heterogeneity where warmer and cooler niches were created. Through the quantification of hydrologic and thermal changes at different spatial and temporal scales, we document increased variability during post-beaver colonization and highlight the need to understand the impacts of beaver dams on stream ecosystems and their potential role in stream restoration.

  3. Predicted median July stream/river temperature regime in New England

    Data.gov (United States)

    U.S. Environmental Protection Agency — This shapefile includes the predicted thermal regime for all NHDPlus version 1 stream and river reaches in New England within the model domain based on the spatial...

  4. Base flow-driven shifts in tropical stream temperature regimes across a mean annual rainfall gradient

    Science.gov (United States)

    Ayron M. Strauch; Richard A. MacKenzie; Ralph W. Tingley

    2017-01-01

    Climate change is expected to affect air temperature and watershed hydrology, but the degree to which these concurrent changes affect stream temperature is not well documented in the tropics. How stream temperature varies over time under changing hydrologic conditions is difficult to isolate from seasonal changes in air temperature. Groundwater and bank storage...

  5. The role of the geophysical template and environmental regimes in controlling stream-living trout populations

    Science.gov (United States)

    Penaluna, Brooke E.; Railsback, Steve F.; Dunham, Jason B.; Johnson, S.; Bilby, Richard E.; Skaugset, Arne E.

    2015-01-01

    The importance of multiple processes and instream factors to aquatic biota has been explored extensively, but questions remain about how local spatiotemporal variability of aquatic biota is tied to environmental regimes and the geophysical template of streams. We used an individual-based trout model to explore the relative role of the geophysical template versus environmental regimes on biomass of trout (Oncorhynchus clarkii clarkii). We parameterized the model with observed data from each of the four headwater streams (their local geophysical template and environmental regime) and then ran 12 simulations where we replaced environmental regimes (stream temperature, flow, turbidity) of a given stream with values from each neighboring stream while keeping the geophysical template fixed. We also performed single-parameter sensitivity analyses on the model results from each of the four streams. Although our modeled findings show that trout biomass is most responsive to changes in the geophysical template of streams, they also reveal that biomass is restricted by available habitat during seasonal low flow, which is a product of both the stream’s geophysical template and flow regime. Our modeled results suggest that differences in the geophysical template among streams render trout more or less sensitive to environmental change, emphasizing the importance of local fish–habitat relationships in streams.

  6. Descriptors of natural thermal regimes in streams and their responsiveness to change in the Pacific Northwest of North America

    Science.gov (United States)

    Ivan Arismendi; Sherri L. Johnson; Jason B. Dunham; Roy Haggerty

    2013-01-01

    1. Temperature is a major driver of ecological processes in stream ecosystems, yet the dynamics of thermal regimes remain poorly described. Most work has focused on relatively simple descriptors that fail to capture the full range of conditions that characterise thermal regimes of streams across seasons or throughout the year.2. To more...

  7. A Statistical Method to Predict Flow Permanence in Dryland Streams from Time Series of Stream Temperature

    Directory of Open Access Journals (Sweden)

    Ivan Arismendi

    2017-12-01

    Full Text Available Intermittent and ephemeral streams represent more than half of the length of the global river network. Dryland freshwater ecosystems are especially vulnerable to changes in human-related water uses as well as shifts in terrestrial climates. Yet, the description and quantification of patterns of flow permanence in these systems is challenging mostly due to difficulties in instrumentation. Here, we took advantage of existing stream temperature datasets in dryland streams in the northwest Great Basin desert, USA, to extract critical information on climate-sensitive patterns of flow permanence. We used a signal detection technique, Hidden Markov Models (HMMs, to extract information from daily time series of stream temperature to diagnose patterns of stream drying. Specifically, we applied HMMs to time series of daily standard deviation (SD of stream temperature (i.e., dry stream channels typically display highly variable daily temperature records compared to wet stream channels between April and August (2015–2016. We used information from paired stream and air temperature data loggers as well as co-located stream temperature data loggers with electrical resistors as confirmatory sources of the timing of stream drying. We expanded our approach to an entire stream network to illustrate the utility of the method to detect patterns of flow permanence over a broader spatial extent. We successfully identified and separated signals characteristic of wet and dry stream conditions and their shifts over time. Most of our study sites within the entire stream network exhibited a single state over the entire season (80%, but a portion of them showed one or more shifts among states (17%. We provide recommendations to use this approach based on a series of simple steps. Our findings illustrate a successful method that can be used to rigorously quantify flow permanence regimes in streams using existing records of stream temperature.

  8. A statistical method to predict flow permanence in dryland streams from time series of stream temperature

    Science.gov (United States)

    Arismendi, Ivan; Dunham, Jason B.; Heck, Michael; Schultz, Luke; Hockman-Wert, David

    2017-01-01

    Intermittent and ephemeral streams represent more than half of the length of the global river network. Dryland freshwater ecosystems are especially vulnerable to changes in human-related water uses as well as shifts in terrestrial climates. Yet, the description and quantification of patterns of flow permanence in these systems is challenging mostly due to difficulties in instrumentation. Here, we took advantage of existing stream temperature datasets in dryland streams in the northwest Great Basin desert, USA, to extract critical information on climate-sensitive patterns of flow permanence. We used a signal detection technique, Hidden Markov Models (HMMs), to extract information from daily time series of stream temperature to diagnose patterns of stream drying. Specifically, we applied HMMs to time series of daily standard deviation (SD) of stream temperature (i.e., dry stream channels typically display highly variable daily temperature records compared to wet stream channels) between April and August (2015–2016). We used information from paired stream and air temperature data loggers as well as co-located stream temperature data loggers with electrical resistors as confirmatory sources of the timing of stream drying. We expanded our approach to an entire stream network to illustrate the utility of the method to detect patterns of flow permanence over a broader spatial extent. We successfully identified and separated signals characteristic of wet and dry stream conditions and their shifts over time. Most of our study sites within the entire stream network exhibited a single state over the entire season (80%), but a portion of them showed one or more shifts among states (17%). We provide recommendations to use this approach based on a series of simple steps. Our findings illustrate a successful method that can be used to rigorously quantify flow permanence regimes in streams using existing records of stream temperature.

  9. Effect of boiling regime on melt stream breakup in water

    International Nuclear Information System (INIS)

    Spencer, B.W.; Gabor, J.D.; Cassulo, J.C.

    1986-01-01

    A study has been performed examining the breakup and mixing behavior of an initially coherent stream of high-density melt as it flows downward through water. This work has application to the quenching of molten core materials as they drain downward during a postulated severe reactor accident. The study has included examination of various models of breakup distances based upon interfacial instabilities dominated either by liquid-liquid contact or by liquid-vapor contact. A series of experiments was performed to provide a data base for assessment of the various modeling approaches. The experiments involved Wood's metal (T/sub m/ = 73 0 C, rho = 9.2 g/cm 3 , d/sub j/ = 20 mm) poured into a deep pool of water. The temperature of the water and wood's metal were varied to span the range from single-phase, liquid-liquid contact to the film boiling regime. Experiment results showed that breakup occurred largely as a result of the spreading and entrainment from the leading edge of the jet. However, for streams of sufficient lengths a breakup length could be discerned at which there was no longer a coherent central core of the jet to feed the leading edge region. The erosion of the vertical trailing column is by Kelvin-Helmoltz instabilities and related disengagement of droplets from the jet into the surrounding fluid. For conditions of liquid-liquid contact, the breakup length has been found to be about 20 jet diameters; when substantial vapor is produced at the interface due to heat transfer from the jet to the water, the breakup distance was found to range to as high as 50 jet diameters. The former values are close to the analytical prediction of Taylor, whereas the latter values are better predicted by the model of Epstein and Fauske

  10. Temperature of the Gulf Stream

    Science.gov (United States)

    2002-01-01

    The Gulf Stream is one of the strong ocean currents that carries warm water from the sunny tropics to higher latitudes. The current stretches from the Gulf of Mexico up the East Coast of the United States, departs from North America south of the Chesapeake Bay, and heads across the Atlantic to the British Isles. The water within the Gulf Stream moves at the stately pace of 4 miles per hour. Even though the current cools as the water travels thousands of miles, it remains strong enough to moderate the Northern European climate. The image above was derived from the infrared measurements of the Moderate-resolution Imaging Spectroradiometer (MODIS) on a nearly cloud-free day over the east coast of the United States. The coldest waters are shown as purple, with blue, green, yellow, and red representing progressively warmer water. Temperatures range from about 7 to 22 degrees Celsius. The core of the Gulf Stream is very apparent as the warmest water, dark red. It departs from the coast at Cape Hatteras, North Carolina. The cool, shelf water from the north entrains the warmer outflows from the Chesapeake and Delaware Bays. The north wall of the Gulf Stream reveals very complex structure associated with frontal instabilities that lead to exchanges between the Gulf Stream and inshore waters. Several clockwise-rotating warm core eddies are evident north of the core of the Gulf Stream, which enhance the exchange of heat and water between the coastal and deep ocean. Cold core eddies, which rotate counter clockwise, are seen south of the Gulf Stream. The one closest to Cape Hatteras is entraining very warm Gulf Stream waters on its northwest circumference. Near the coast, shallower waters have warmed due to solar heating, while the deeper waters offshore are markedly cooler (dark blue). MODIS made this observation on May 8, 2000, at 11:45 a.m. EDT. For more information, see the MODIS-Ocean web page. The sea surface temperature image was created at the University of Miami using

  11. An evaluation of underwater epoxies to permanently install temperature sensors in mountain streams

    Science.gov (United States)

    Daniel J. Isaak; Dona L. Horan

    2011-01-01

    Stream temperature regimes are of fundamental importance in understanding the patterns and processes in aquatic ecosystems, and inexpensive digital sensors provide accurate and repeated measurements of temperature. Most temperature measurements in mountain streams are made only during summer months because of logistical constraints associated with stream access and...

  12. Characteristics of plasma streams and optimization of operational regimes for magnetoplasma compressor

    International Nuclear Information System (INIS)

    Bandura, A.N.; Byrka, O.V.; Garkusha, I.E.; Ladygina, M.S.; Marchenko, A.K.; Petrov, Yu.V.; Solyakov, D.G.; Chebotarev, V.V.; Chuvilo, A.A.

    2011-01-01

    The main objective of these studies is characterization of dense xenon plasma streams generated by magnetoplasma compressor (MPC) in different operational regimes. Optimization of plasma compression in MPC allows increase of the plasma stream pressure up to 22...25 bar, average temperature of electrons of 10...20 eV and plasma stream velocity varied in the range of (2...9)x10 6 cm/s depending on operation regime. Spectroscopy measurements demonstrate that in these conditions most of Xe spectral lines are reabsorbed. In the case of known optical thickness, the real value of electron density can be calculated with accounting self-absorption. Estimations of optical thickness were performed and resulting electron density in focus region was evaluated as 10 18 cm -3 .

  13. Spatial Statistical Network Models for Stream and River Temperatures in the Chesapeake Bay Watershed

    Science.gov (United States)

    Numerous metrics have been proposed to describe stream/river thermal regimes, and researchers are still struggling with the need to describe thermal regimes in a parsimonious fashion. Regional temperature models are needed for characterizing and mapping current stream thermal re...

  14. Simulating the effect of climate change on stream temperature in the Trout Lake Watershed, Wisconsin

    Energy Technology Data Exchange (ETDEWEB)

    Selbig, William R., E-mail: wrselbig@usgs.gov

    2015-07-15

    The potential for increases in stream temperature across many spatial and temporal scales as a result of climate change can pose a difficult challenge for environmental managers, especially when addressing thermal requirements for sensitive aquatic species. This study evaluates simulated changes to the thermal regime of three northern Wisconsin streams in response to a projected changing climate using a modeling framework and considers implications of thermal stresses to the fish community. The Stream Network Temperature Model (SNTEMP) was used in combination with a coupled groundwater and surface water flow model to assess forecasts in climate from six global circulation models and three emission scenarios. Model results suggest that annual average stream temperature will steadily increase approximately 1.1 to 3.2 °C (varying by stream) by the year 2100 with differences in magnitude between emission scenarios. Daily mean stream temperature during the months of July and August, a period when cold-water fish communities are most sensitive, showed excursions from optimal temperatures with increased frequency compared to current conditions. Projections of daily mean stream temperature, in some cases, were no longer in the range necessary to sustain a cold water fishery. - Highlights: • A stream temperature model was calibrated for three streams in northern Wisconsin. • The effect of climate change on stream temperature was simulated in each stream. • Annual average stream temperature was projected to rise from 1 to 3 °C by 2100. • Forecasts of stream temperature exceeded optimal ranges for brook trout.

  15. Alteration of stream temperature by natural and artificial beaver dams.

    Science.gov (United States)

    Weber, Nicholas; Bouwes, Nicolaas; Pollock, Michael M; Volk, Carol; Wheaton, Joseph M; Wathen, Gus; Wirtz, Jacob; Jordan, Chris E

    2017-01-01

    Beaver are an integral component of hydrologic, geomorphic, and biotic processes within North American stream systems, and their propensity to build dams alters stream and riparian structure and function to the benefit of many aquatic and terrestrial species. Recognizing this, beaver relocation efforts and/or application of structures designed to mimic the function of beaver dams are increasingly being utilized as effective and cost-efficient stream and riparian restoration approaches. Despite these verities, the notion that beaver dams negatively impact stream habitat remains common, specifically the assumption that beaver dams increase stream temperatures during summer to the detriment of sensitive biota such as salmonids. In this study, we tracked beaver dam distributions and monitored water temperature throughout 34 km of stream for an eight-year period between 2007 and 2014. During this time the number of natural beaver dams within the study area increased by an order of magnitude, and an additional 4 km of stream were subject to a restoration manipulation that included installing a high-density of Beaver Dam Analog (BDA) structures designed to mimic the function of natural beaver dams. Our observations reveal several mechanisms by which beaver dam development may influence stream temperature regimes; including longitudinal buffering of diel summer temperature extrema at the reach scale due to increased surface water storage, and creation of cool-water channel scale temperature refugia through enhanced groundwater-surface water connectivity. Our results suggest that creation of natural and/or artificial beaver dams could be used to mitigate the impact of human induced thermal degradation that may threaten sensitive species.

  16. ECOLOGICAL ANALYSIS OF HYDROLOGIC DISTURBANCE REGIMES IN STREAMS OF NORTH AND SOUTH DAKOTA

    Science.gov (United States)

    Streamflow variability is an important component of physical disturbance in streams, and is likely to be a major organizing feature of habitat for stream fishes. The disturbance regime in streams is frequently described by the variability in streamflow from both floods and prolo...

  17. Descriptors of natural thermal regimes in streams and their responsiveness to change in the Pacific Northwest of North America

    Science.gov (United States)

    Arismendi, Ivan; Johnson, Sherri L.; Dunham, Jason B.; Haggerty, Roy

    2013-01-01

    1. Temperature is a major driver of ecological processes in stream ecosystems, yet the dynamics of thermal regimes remain poorly described. Most work has focused on relatively simple descriptors that fail to capture the full range of conditions that characterise thermal regimes of streams across seasons or throughout the year. 2. To more completely describe thermal regimes, we developed several descriptors of magnitude, variability, frequency, duration and timing of thermal events throughout a year. We evaluated how these descriptors change over time using long-term (1979–2009), continuous temperature data from five relatively undisturbed cold-water streams in western Oregon, U.S.A. In addition to trends for each descriptor, we evaluated similarities among them, as well as patterns of spatial coherence, and temporal synchrony. 3. Using different groups of descriptors, we were able to more fully capture distinct aspects of the full range of variability in thermal regimes across space and time. A subset of descriptors showed both higher coherence and synchrony and, thus, an appropriate level of responsiveness to examine evidence of regional climatic influences on thermal regimes. Most notably, daily minimum values during winter–spring were the most responsive descriptors to potential climatic influences. 4. Overall, thermal regimes in streams we studied showed high frequency and low variability of cold temperatures during the cold-water period in winter and spring, and high frequency and high variability of warm temperatures during the warm-water period in summer and autumn. The cold and warm periods differed in the distribution of events with a higher frequency and longer duration of warm events in summer than cold events in winter. The cold period exhibited lower variability in the duration of events, but showed more variability in timing. 5. In conclusion, our results highlight the importance of a year-round perspective in identifying the most responsive

  18. Winter-regime surface heat loss from heated streams

    International Nuclear Information System (INIS)

    Paily, P.P.; Macagno, E.O.; Kennedy, J.F.

    1974-01-01

    Evaluation of the rate of surface heat exchange between the water and air is a significant factor in any study of the thermal response of heated streams to heat inputs. Existing methods to determine the amount of heat transfer across the water surface are surveyed, and the different formulas developed for determining the heat exchange components are compiled. Heat-transfer models that have been proposed in the literature are reviewed, and a new linearized model for determining the rate of surface heat exchange is proposed. Generalized relations between the major climatological factors and the coefficients of the linearized heat-loss rate are established by multiple-regression analysis. The analysis is limited to cold-period conditions, in the sense that air temperatures below the freezing point of water only are considered in developing the regression equations. A computer program, using FORTRAN, is presented which enables the computation of the coefficients appearing in the linearized heat-loss rate for all combinations of the various climatological factors

  19. Stream temperature investigations: field and analytic methods

    Science.gov (United States)

    Bartholow, J.M.

    1989-01-01

    This document provides guidance to the user of the U.S. Fish and Wildlife Service’s Stream Network Temperature Model (SNTEMP). Planning a temperature study is discussed in terms of understanding the management objectives and ensuring that the questions will be accurately answered with the modeling approach being used. A sensitivity analysis of SNTEMP is presented to illustrate which input variables are most important in predicting stream temperatures. This information helps prioritize data collection activities, highlights the need for quality control, focuses on which parameters can be estimated rather than measured, and offers a broader perspective on management options in terms of knowing where the biggest temperature response will be felt. All of the major input variables for stream geometry, meteorology, and hydrology are discussed in detail. Each variable is defined, with guidance given on how to measure it, what kind of equipment to use, where to obtain it from another agency, and how to calculate it if the data are in a form other than that required by SNTEMP. Examples are presented for the various forms in which water temperature, discharge, and meteorological data are commonly found. Ranges of values for certain input variables that are difficult to measure of estimate are given. Particular attention is given to those variables not commonly understood by field biologists likely to be involved in a stream temperature study. Pertinent literature is cited for each variable, with emphasis on how other people have treated particular problems and on results they have found.

  20. Three responses to small changes in stream temperature by autumn-emerging aquatic insects

    Science.gov (United States)

    Judith L. Li; Sherri L. Johnson; Janel Banks. Sobota

    2011-01-01

    In this experimental study, conducted in coastal Oregon USA, we examined how small increases in summer water temperatures affected aquatic insect growth and autumn emergence. We maintained naturally fluctuating temperatures from 2 nearby streams and a 3rd regime, naturally fluctuating temperatures warmed by 3-5°C, in flow-through troughs from mid...

  1. Streams in the urban heat island: spatial and temporal variability in temperature

    Science.gov (United States)

    Somers, Kayleigh A.; Bernhardt, Emily S.; Grace, James B.; Hassett, Brooke A.; Sudduth, Elizabeth B.; Wang, Siyi; Urban, Dean L.

    2013-01-01

    Streams draining urban heat islands tend to be hotter than rural and forested streams at baseflow because of warmer urban air and ground temperatures, paved surfaces, and decreased riparian canopy. Urban infrastructure efficiently routes runoff over hot impervious surfaces and through storm drains directly into streams and can lead to rapid, dramatic increases in temperature. Thermal regimes affect habitat quality and biogeochemical processes, and changes can be lethal if temperatures exceed upper tolerance limits of aquatic fauna. In summer 2009, we collected continuous (10-min interval) temperature data in 60 streams spanning a range of development intensity in the Piedmont of North Carolina, USA. The 5 most urbanized streams averaged 21.1°C at baseflow, compared to 19.5°C in the 5 most forested streams. Temperatures in urban streams rose as much as 4°C during a small regional storm, whereas the same storm led to extremely small to no changes in temperature in forested streams. Over a kilometer of stream length, baseflow temperature varied by as much as 10°C in an urban stream and as little as 2°C in a forested stream. We used structural equation modeling to explore how reach- and catchment-scale attributes interact to explain maximum temperatures and magnitudes of storm-flow temperature surges. The best predictive model of baseflow temperatures (R2  =  0.461) included moderately strong pathways directly (extent of development and road density) and indirectly, as mediated by reach-scale factors (canopy closure and stream width), from catchment-scale factors. The strongest influence on storm-flow temperature surges appeared to be % development in the catchment. Reach-scale factors, such as the extent of riparian forest and stream width, had little mitigating influence (R2  =  0.448). Stream temperature is an essential, but overlooked, aspect of the urban stream syndrome and is affected by reach-scale habitat variables, catchment-scale urbanization

  2. The influence of riparian woodland on the spatial and temporal variability of stream water temperatures in an upland salmon stream

    Directory of Open Access Journals (Sweden)

    I. A. Malcolm

    2004-01-01

    Full Text Available The spatio-temporal variability of stream water temperatures was investigated at six locations on the Girnock Burn (30km2 catchment, Cairngorms, Scotland over three hydrological years between 1998 and 2002. The key site-specific factors affecting the hydrology and climatology of the sampling points were investigated as a basis for physical process inference. Particular emphasis was placed on assessing the effects of riparian forest in the lower catchment versus the heather moorland riparian zones that are spatially dominant in the upper catchment. The findings were related to river heat budget studies that provided process detail. Gross changes in stream temperature were affected by the annual cycle of incoming solar radiation and seasonal changes in hydrological and climatological conditions. Inter-annual variation in these controlling variables resulted in inter-annual variability in thermal regime. However, more subtle inter-site differences reflected the impact of site-specific characteristics on various components of the river energy budget. Inter-site variability was most apparent at shorter time scales, during the summer months and for higher stream temperatures. Riparian woodland in the lower catchment had a substantial impact on thermal regime, reducing diel variability (over a period of 24 hours and temperature extremes. Observed inter-site differences are likely to have a substantial effect on freshwater ecology in general and salmonid fish in particular. Keywords: temperature, thermal regime, forest, salmon, hydrology, Girnock Burn, Cairngorm

  3. Modeling Air Temperature/Water Temperature Relations Along a Small Mountain Stream Under Increasing Urban Influence

    Science.gov (United States)

    Fedders, E. R.; Anderson, W. P., Jr.; Hengst, A. M.; Gu, C.

    2017-12-01

    Boone Creek is a headwater stream of low to moderate gradient located in Boone, North Carolina, USA. Total impervious surface coverage in the 5.2 km2 catchment drained by the 1.9 km study reach increases from 13.4% in the upstream half of the reach to 24.3% in the downstream half. Other markers of urbanization, including culverting, lack of riparian shade vegetation, and bank armoring also increase downstream. Previous studies have shown the stream to be prone to temperature surges on short timescales (minutes to hours) caused by summer runoff from the urban hardscaping. This study investigates the effects of urbanization on the stream's thermal regime at daily to yearly timescales. To do this, we developed an analytical model of daily average stream temperatures based on daily average air temperatures. We utilized a two-part model comprising annual and biannual components and a daily component consisting of a 3rd-order Markov process in order to fit the thermal dynamics of our small, gaining stream. Optimizing this model at each of our study sites in each studied year (78 total site-years of data) yielded annual thermal exchange coefficients (K) for each site. These K values quantify the strength of the relationship between stream and air temperature, or inverse thermal stability. In a uniform, pristine catchment environment, K values are expected to decrease downstream as the stream gains discharge volume and, therefore, thermal inertia. Interannual average K values for our study reach, however, show an overall increase from 0.112 furthest upstream to 0.149 furthest downstream, despite a near doubling of stream discharge between these monitoring points. K values increase only slightly in the upstream, less urban, half of the reach. A line of best fit through these points on a plot of reach distance versus K value has a slope of 2E-6. But the K values of downstream, more urbanized sites increase at a rate of 2E-5 per meter of reach distance, an order of magnitude

  4. Mapping spatial and temporal variation of stream water temperature in the upper Esopus Creek watershed

    Science.gov (United States)

    Chien, H.; McGlinn, L.

    2017-12-01

    The upper Esopus Creek and its tributary streams located in the Catskill Mountain region of New York State provide habitats for cold-adapted aquatic species. However, ongoing global warming may change the stream water temperature within a watershed and disturb the persistence of coldwater habitats. Characterizing thermal regimes within the upper Esopus Creek watershed is important to provide information of thermally suitable habitats for aquatic species. The objectives of this study are to measure stream water temperature and map thermal variability among tributaries to the Esopus Creek and within Esopus Creek. These objectives will be achieved by measuring stream water temperature for at least two years. More than 100 water temperature data loggers have been placed in the upper Esopus Creek and their tributaries to collect 30-minute interval water temperatures. With the measured water temperature, we will use spatial interpolation in ArcGIS to create weekly and monthly water temperature surface maps to evaluate the thermal variation over time and space within the upper Esopus Creek watershed. We will characterize responsiveness of water temperature in tributary streams to air temperature as well. This information of spatial and temporal variation of stream water temperature will assist stream managers with prioritizing management practices that maintain or enhance connectivity of thermally suitable habitats in high priority areas.

  5. Interaction between stream temperature, streamflow, and groundwater exchanges in alpine streams

    Science.gov (United States)

    Constantz, James E.

    1998-01-01

    Four alpine streams were monitored to continuously collect stream temperature and streamflow for periods ranging from a week to a year. In a small stream in the Colorado Rockies, diurnal variations in both stream temperature and streamflow were significantly greater in losing reaches than in gaining reaches, with minimum streamflow losses occurring early in the day and maximum losses occurring early in the evening. Using measured stream temperature changes, diurnal streambed infiltration rates were predicted to increase as much as 35% during the day (based on a heat and water transport groundwater model), while the measured increase in streamflow loss was 40%. For two large streams in the Sierra Nevada Mountains, annual stream temperature variations ranged from 0° to 25°C. In summer months, diurnal stream temperature variations were 30–40% of annual stream temperature variations, owing to reduced streamflows and increased atmospheric heating. Previous reports document that one Sierra stream site generally gains groundwater during low flows, while the second Sierra stream site may lose water during low flows. For August the diurnal streamflow variation was 11% at the gaining stream site and 30% at the losing stream site. On the basis of measured diurnal stream temperature variations, streambed infiltration rates were predicted to vary diurnally as much as 20% at the losing stream site. Analysis of results suggests that evapotranspiration losses determined diurnal streamflow variations in the gaining reaches, while in the losing reaches, evapotranspiration losses were compounded by diurnal variations in streambed infiltration. Diurnal variations in stream temperature were reduced in the gaining reaches as a result of discharging groundwater of relatively constant temperature. For the Sierra sites, comparison of results with those from a small tributary demonstrated that stream temperature patterns were useful in delineating discharges of bank storage following

  6. Incorporation of the equilibrium temperature approach in a Soil and Water Assessment Tool hydroclimatological stream temperature model

    Science.gov (United States)

    Du, Xinzhong; Shrestha, Narayan Kumar; Ficklin, Darren L.; Wang, Junye

    2018-04-01

    . However, the NSE values were lower than those of the hydroclimatological model, indicating that more model verification needs to be done. The equilibrium temperature model uses existing SWAT meteorological data as input, can be calibrated using fewer parameters and less effort and has an overall better performance in stream temperature simulation. Thus, it can be used as an effective tool for predicting the changes in stream temperature regimes under varying hydrological and meteorological conditions. In addition, the impact of the stream temperature simulations on chemical reaction rates and concentrations was tested. The results indicate that the improved performance of the stream temperature simulation could significantly affect chemical reaction rates and the simulated concentrations, and the equilibrium temperature model could be a potential tool to model stream temperature in water quality simulations.

  7. Identify the dominant variables to predict stream water temperature

    Science.gov (United States)

    Chien, H.; Flagler, J.

    2016-12-01

    Stream water temperature is a critical variable controlling water quality and the health of aquatic ecosystems. Accurate prediction of water temperature and the assessment of the impacts of environmental variables on water temperature variation are critical for water resources management, particularly in the context of water quality and aquatic ecosystem sustainability. The objective of this study is to measure stream water temperature and air temperature and to examine the importance of streamflow on stream water temperature prediction. The measured stream water temperature and air temperature will be used to test two hypotheses: 1) streamflow is a relatively more important factor than air temperature in regulating water temperature, and 2) by combining air temperature and streamflow data stream water temperature can be more accurately estimated. Water and air temperature data loggers are placed at two USGS stream gauge stations #01362357and #01362370, located in the upper Esopus Creek watershed in Phonecia, NY. The ARIMA (autoregressive integrated moving average) time series model is used to analyze the measured water temperature data, identify the dominant environmental variables, and predict the water temperature with identified dominant variable. The preliminary results show that streamflow is not a significant variable in predicting stream water temperature at both USGS gauge stations. Daily mean air temperature is sufficient to predict stream water temperature at this site scale.

  8. Altered stream-flow regimes and invasive plant species: The Tamarix case

    Science.gov (United States)

    Stromberg, J.C.; Lite, S.J.; Marler, R.; Paradzick, C.; Shafroth, P.B.; Shorrock, D.; White, J.M.; White, M.S.

    2007-01-01

    Aim: To test the hypothesis that anthropogenic alteration of stream-flow regimes is a key driver of compositional shifts from native to introduced riparian plant species. Location: The arid south-western United States; 24 river reaches in the Gila and Lower Colorado drainage basins of Arizona. Methods: We compared the abundance of three dominant woody riparian taxa (native Populus fremontii and Salix gooddingii, and introduced Tamarix) between river reaches that varied in stream-flow permanence (perennial vs. intermittent), presence or absence of an upstream flow-regulating dam, and presence or absence of municipal effluent as a stream water source. Results: Populus and Salix were the dominant pioneer trees along the reaches with perennial flow and a natural flood regime. In contrast, Tamarix had high abundance (patch area and basal area) along reaches with intermittent stream flows (caused by natural and cultural factors), as well as those with dam-regulated flows. Main conclusions: Stream-flow regimes are strong determinants of riparian vegetation structure, and hydrological alterations can drive dominance shifts to introduced species that have an adaptive suite of traits. Deep alluvial groundwater on intermittent rivers favours the deep-rooted, stress-adapted Tamarix over the shallower-rooted and more competitive Populus and Salix. On flow-regulated rivers, shifts in flood timing favour the reproductively opportunistic Tamarix over Populus and Salix, both of which have narrow germination windows. The prevailing hydrological conditions thus favour a new dominant pioneer species in the riparian corridors of the American Southwest. These results reaffirm the importance of reinstating stream-flow regimes (inclusive of groundwater flows) for re-establishing the native pioneer trees as the dominant forest type. ?? 2007 The Authors Journal compilation ?? 2007 Blackwell Publishing Ltd.

  9. Air - water temperature relationships in the trout streams of southeastern Minnesota’s carbonate - sandstone landscape

    Science.gov (United States)

    Krider, Lori A.; Magner, Joseph A.; Perry, Jim; Vondracek, Bruce C.; Ferrington, Leonard C.

    2013-01-01

    Carbonate-sandstone geology in southeastern Minnesota creates a heterogeneous landscape of springs, seeps, and sinkholes that supply groundwater into streams. Air temperatures are effective predictors of water temperature in surface-water dominated streams. However, no published work investigates the relationship between air and water temperatures in groundwater-fed streams (GWFS) across watersheds. We used simple linear regressions to examine weekly air-water temperature relationships for 40 GWFS in southeastern Minnesota. A 40-stream, composite linear regression model has a slope of 0.38, an intercept of 6.63, and R2 of 0.83. The regression models for GWFS have lower slopes and higher intercepts in comparison to surface-water dominated streams. Regression models for streams with high R2 values offer promise for use as predictive tools for future climate conditions. Climate change is expected to alter the thermal regime of groundwater-fed systems, but will do so at a slower rate than surface-water dominated systems. A regression model of intercept vs. slope can be used to identify streams for which water temperatures are more meteorologically than groundwater controlled, and thus more vulnerable to climate change. Such relationships can be used to guide restoration vs. management strategies to protect trout streams.

  10. A stream temperature model for the Peace-Athabasca River basin

    Science.gov (United States)

    Morales-Marin, L. A.; Rokaya, P.; Wheater, H. S.; Lindenschmidt, K. E.

    2017-12-01

    Water temperature plays a fundamental role in water ecosystem functioning. Because it regulates flow energy and metabolic rates in organism productivity over a broad spectrum of space and time scales, water temperature constitutes an important indicator of aquatic ecosystems health. In cold region basins, stream water temperature modelling is also fundamental to predict ice freeze-up and break-up events in order to improve flood management. Multiple model approaches such as linear and multivariable regression methods, neural network and thermal energy budged models have been developed and implemented to simulate stream water temperature. Most of these models have been applied to specific stream reaches and trained using observed data, but very little has been done to simulate water temperature in large catchment river networks. We present the coupling of RBM model, a semi-Lagrangian water temperature model for advection-dominated river system, and MESH, a semi-distributed hydrological model, to simulate stream water temperature in river catchments. The coupled models are implemented in the Peace-Athabasca River basin in order to analyze the variation in stream temperature regimes under changing hydrological and meteorological conditions. Uncertainty of stream temperature simulations is also assessed in order to determine the degree of reliability of the estimates.

  11. How and Why Does Stream Water Temperature Vary at Small Spatial Scales in a Headwater Stream?

    Science.gov (United States)

    Morgan, J. C.; Gannon, J. P.; Kelleher, C.

    2017-12-01

    The temperature of stream water is controlled by climatic variables, runoff/baseflow generation, and hyporheic exchange. Hydrologic conditions such as gaining/losing reaches and sources of inflow can vary dramatically along a stream on a small spatial scale. In this work, we attempt to discern the extent that the factors of air temperature, groundwater inflow, and precipitation influence stream temperature at small spatial scales along the length of a stream. To address this question, we measured stream temperature along the perennial stream network in a 43 ha catchment with a complex land use history in Cullowhee, NC. Two water temperature sensors were placed along the stream network on opposite sides of the stream at 100-meter intervals and at several locations of interest (i.e. stream junctions). The forty total sensors recorded the temperature every 10 minutes for one month in the spring and one month in the summer. A subset of sampling locations where stream temperature was consistent or varied from one side of the stream to the other were explored with a thermal imaging camera to obtain a more detailed representation of the spatial variation in temperature at those sites. These thermal surveys were compared with descriptions of the contributing area at the sample sites in an effort to discern specific causes of differing flow paths. Preliminary results suggest that on some branches of the stream stormflow has less influence than regular hyporheic exchange, while other tributaries can change dramatically with stormflow conditions. We anticipate this work will lead to a better understanding of temperature patterns in stream water networks. A better understanding of the importance of small-scale differences in flow paths to water temperature may be able to inform watershed management decisions in the future.

  12. Leaf litter processing in West Virginia mountain streams: effects of temperature and stream chemistry

    Science.gov (United States)

    Jacquelyn M. Rowe; William B. Perry; Sue A. Perry

    1996-01-01

    Climate change has the potential to alter detrital processing in headwater streams, which receive the majority of their nutrient input as terrestrial leaf litter. Early placement of experimental leaf packs in streams, one month prior to most abscission, was used as an experimental manipulation to increase stream temperature during leaf pack breakdown. We studied leaf...

  13. A model for evaluating stream temperature response to climate change in Wisconsin

    Science.gov (United States)

    Stewart, Jana S.; Westenbroek, Stephen M.; Mitro, Matthew G.; Lyons, John D.; Kammel, Leah E.; Buchwald, Cheryl A.

    2015-01-01

    Expected climatic changes in air temperature and precipitation patterns across the State of Wisconsin may alter future stream temperature and flow regimes. As a consequence of flow and temperature changes, the composition and distribution of fish species assemblages are expected to change. In an effort to gain a better understanding of how climatic changes may affect stream temperature, an approach was developed to predict and project daily summertime stream temperature under current and future climate conditions for 94,341 stream kilometers across Wisconsin. The approach uses a combination of static landscape characteristics and dynamic time-series climatic variables as input for an Artificial Neural Network (ANN) Model integrated with a Soil-Water-Balance (SWB) Model. Future climate scenarios are based on output from downscaled General Circulation Models (GCMs). The SWB model provided a means to estimate the temporal variability in groundwater recharge and provided a mechanism to evaluate the effect of changing air temperature and precipitation on groundwater recharge and soil moisture. The Integrated Soil-Water-Balance and Artificial Neural Network version 1 (SWB-ANNv1) Model was used to simulate daily summertime stream temperature under current (1990–2008) climate and explained 76 percent of the variation in the daily mean based on validation at 67 independent sites. Results were summarized as July mean water temperature, and individual stream segments were classified by thermal class (cold, cold transition, warm transition, and warm) for comparison of current (1990–2008) with future climate conditions.

  14. Validating alternative methodologies to estimate the hydrological regime of temporary streams when flow data are unavailable

    Science.gov (United States)

    Llorens, Pilar; Gallart, Francesc; Latron, Jérôme; Cid, Núria; Rieradevall, Maria; Prat, Narcís

    2016-04-01

    Aquatic life in temporary streams is strongly conditioned by the temporal variability of the hydrological conditions that control the occurrence and connectivity of diverse mesohabitats. In this context, the software TREHS (Temporary Rivers' Ecological and Hydrological Status) has been developed, in the framework of the LIFE Trivers project, to help managers for adequately implement the Water Framework Directive in this type of water bodies. TREHS, using the methodology described in Gallart et al (2012), defines six temporal 'aquatic states', based on the hydrological conditions representing different mesohabitats, for a given reach at a particular moment. Nevertheless, hydrological data for assessing the regime of temporary streams are often non-existent or scarce. The scarcity of flow data makes frequently impossible the characterization of temporary streams hydrological regimes and, as a consequence, the selection of the correct periods and methods to determine their ecological status. Because of its qualitative nature, the TREHS approach allows the use of alternative methodologies to assess the regime of temporary streams in the lack of observed flow data. However, to adapt the TREHS to this qualitative data both the temporal scheme (from monthly to seasonal) as well as the number of aquatic states (from 6 to 3) have been modified. Two alternatives complementary methodologies were tested within the TREHS framework to assess the regime of temporary streams: interviews and aerial photographs. All the gauging stations (13) belonging to the Catalan Internal Catchments (NE, Spain) with recurrent zero flows periods were selected to validate both methodologies. On one hand, non-structured interviews were carried out to inhabitants of villages and small towns near the gauging stations. Flow permanence metrics for input into TREHS were drawn from the notes taken during the interviews. On the other hand, the historical series of available aerial photographs (typically 10

  15. Can air temperature be used to project influences of climate change on stream temperature?

    Science.gov (United States)

    Ivan Arismendi; Mohammad Safeeq; Jason B Dunham; Sherri L Johnson

    2014-01-01

    Worldwide, lack of data on stream temperature has motivated the use of regression-based statistical models to predict stream temperatures based on more widely available data on air temperatures. Such models have been widely applied to project responses of stream temperatures under climate change, but the performance of these models has not been fully evaluated. To...

  16. Exploring new scaling regimes for streaming potential and electroviscous effects in a nanocapillary with overlapping electric double layers.

    Science.gov (United States)

    Das, Siddhartha; Guha, Arnab; Mitra, Sushanta K

    2013-12-04

    In this paper, we unravel new scaling regimes for streaming potential and electroviscous effects in a nanocapillary with thick overlapping Electric Double Layers (EDLs). We observe that the streaming potential, for a given value of the capillary zeta (ζ) potential, varies with the EDL thickness and a dimensionless parameter R, quantifying the conduction current. Depending on the value of R, variation of the streaming potential with the EDL thickness demonstrates distinct scaling regimes: one can witness a Quadratic Regime where the streaming potential varies as the square of the EDL thickness, a Weak Regime where the streaming potential shows a weaker variation with the EDL thickness, and a Saturation Regime where the streaming potential ceases to vary with the EDL thickness. Effective viscosity, characterizing the electroviscous effect, obeys the variation of the streaming potential for smaller EDL thickness values; however, for larger EDL thickness the electroosmotic flow profile dictates the electroviscous effect, with insignificant contribution of the streaming potential. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Metabolic responses of Eucalyptus species to different temperature regimes

    NARCIS (Netherlands)

    Mokochinski, Joao Benhur; Mazzafera, Paulo; Sawaya, Alexandra Christine Helena Frankland; Mumm, Roland; Vos, de Ric Cornelis Hendricus; Hall, Robert David

    2018-01-01

    Species and hybrids of Eucalyptus are the world's most widely planted hardwood trees. They are cultivated across a wide range of latitudes and therefore environmental conditions. In this context, comprehensive metabolomics approaches have been used to assess how different temperature regimes may

  18. Temperature structure function in the Bolgiano regime of thermal convection

    Czech Academy of Sciences Publication Activity Database

    Skrbek, Ladislav; Niemela, J. J.; Sreenivasan, K. R.; Donnelly, J.

    2002-01-01

    Roč. 66, č. 3 (2002), 036303/1-036303/6 ISSN 1063-651X Institutional research plan: CEZ:AV0Z1010914 Keywords : thermal convection * temperature fluctuations * Bolgiano regime Subject RIV: BK - Fluid Dynamics Impact factor: 2.397, year: 2002

  19. Projected warming portends seasonal shifts of stream temperatures in the Crown of the Continent Ecosystem, USA and Canada

    Science.gov (United States)

    Jones, Leslie A.; Muhlfeld, Clint C.; Marshall, Lucy A.

    2017-01-01

    Climate warming is expected to increase stream temperatures in mountainous regions of western North America, yet the degree to which future climate change may influence seasonal patterns of stream temperature is uncertain. In this study, a spatially explicit statistical model framework was integrated with empirical stream temperature data (approximately four million bi-hourly recordings) and high-resolution climate and land surface data to estimate monthly stream temperatures and potential change under future climate scenarios in the Crown of the Continent Ecosystem, USA and Canada (72,000 km2). Moderate and extreme warming scenarios forecast increasing stream temperatures during spring, summer, and fall, with the largest increases predicted during summer (July, August, and September). Additionally, thermal regimes characteristic of current August temperatures, the warmest month of the year, may be exceeded during July and September, suggesting an earlier and extended duration of warm summer stream temperatures. Models estimate that the largest magnitude of temperature warming relative to current conditions may be observed during the shoulder months of winter (April and November). Summer stream temperature warming is likely to be most pronounced in glacial-fed streams where models predict the largest magnitude (> 50%) of change due to the loss of alpine glaciers. We provide the first broad-scale analysis of seasonal climate effects on spatiotemporal patterns of stream temperature in the Crown of the Continent Ecosystem for better understanding climate change impacts on freshwater habitats and guiding conservation and climate adaptation strategies.

  20. Temporal and spatial variability in North Carolina piedmont stream temperature

    Science.gov (United States)

    J.L. Boggs; G. Sun; S.G. McNulty; W. Swartley; Treasure E.; W. Summer

    2009-01-01

    Understanding temporal and spatial patterns of in-stream temperature can provide useful information to managing future impacts of climate change on these systems. This study will compare temporal patterns and spatial variability of headwater in-stream temperature in six catchments in the piedmont of North Carolina in two different geological regions, Carolina slate...

  1. Benthic invertebrate fauna, small streams

    Science.gov (United States)

    J. Bruce Wallace; S.L. Eggert

    2009-01-01

    Small streams (first- through third-order streams) make up >98% of the total number of stream segments and >86% of stream length in many drainage networks. Small streams occur over a wide array of climates, geology, and biomes, which influence temperature, hydrologic regimes, water chemistry, light, substrate, stream permanence, a basin's terrestrial plant...

  2. Stream flow regime of springs in the Mantiqueira Mountain Range region, Minas Gerais State

    Directory of Open Access Journals (Sweden)

    Alisson Souza de Oliveira

    2014-09-01

    Full Text Available The stream flow regime of four springs located in the Mantiqueira Mountain Range region (MG was evaluated and correlated to the respective recharge area, relief characteristics, land cover and physical and hydrologic soil characteristics. The streamflow regime was characterized by monitoring of discharges, calculating the surface runoff and specific discharge and by modeling the discharge over the recession period using the Maillet method. As all recharge areas have similar relief the effect of it on the streamflow was not possible to identify. Analysis included determining the effect of drainage area size, soil characteristics and land cover on the indicators of the streamflow regime. Size of the recharge area had a positive influence on the indicators mean discharge and surface runoff volume and on the regulation of the streamflow regime (springs L4 and L1. The spring under the smallest area of influence provided the worst results for the above mentioned indicators (spring L3. The effect of forest cover (natural and planted, associated with soil characteristics, was evidenced by the indicators surface runoff (in depth and specific yield, both independent of the recharge area size (springs L4 and L2. The interaction of area size, soil characteristics and forest cover (natural and planted provided the best results for all indicators of streamflow regime in the springs studied in the Mantiqueira Mountain Range (spring L4.

  3. Crossing regimes of temperature dependence in animal movement.

    Science.gov (United States)

    Gibert, Jean P; Chelini, Marie-Claire; Rosenthal, Malcolm F; DeLong, John P

    2016-05-01

    A pressing challenge in ecology is to understand the effects of changing global temperatures on food web structure and dynamics. The stability of these complex ecological networks largely depends on how predator-prey interactions may respond to temperature changes. Because predators and prey rely on their velocities to catch food or avoid being eaten, understanding how temperatures may affect animal movement is central to this quest. Despite our efforts, we still lack a mechanistic understanding of how the effect of temperature on metabolic processes scales up to animal movement and beyond. Here, we merge a biomechanical approach, the Metabolic Theory of Ecology and empirical data to show that animal movement displays multiple regimes of temperature dependence. We also show that crossing these regimes has important consequences for population dynamics and stability, which depend on the parameters controlling predator-prey interactions. We argue that this dependence upon interaction parameters may help explain why experimental work on the temperature dependence of interaction strengths has so far yielded conflicting results. More importantly, these changes in the temperature dependence of animal movement can have consequences that go well beyond ecological interactions and affect, for example, animal communication, mating, sensory detection, and any behavioral modality dependent on the movement of limbs. Finally, by not taking into account the changes in temperature dependence reported here we might not be able to properly forecast the impact of global warming on ecological processes and propose appropriate mitigation action when needed. © 2016 John Wiley & Sons Ltd.

  4. Potential Impacts of Climate Change on Stream Water Temperatures Across the United States

    Science.gov (United States)

    Ehsani, N.; Knouft, J.; Ficklin, D. L.

    2017-12-01

    Analyses of long-term observation data have revealed significant changes in several components of climate and the hydrological cycle over the contiguous United States during the twentieth and early twenty-first century. Mean surface air temperatures have significantly increased in most areas of the country. In addition, water temperatures are increasing in many watersheds across the United States. While there are numerous studies assessing the impact of climate change on air temperatures at regional and global scales, fewer studies have investigated the impacts of climate change on stream water temperatures. Projecting increases in water temperature are particularly important to the conservation of freshwater ecosystems. To achieve better insights into attributes regulating population and community dynamics of aquatic biota at large spatial and temporal scales, we need to establish relationships between environmental heterogeneity and critical biological processes of stream ecosystems at these scales. Increases in stream temperatures caused by the doubling of atmospheric carbon dioxide may result in a significant loss of fish habitat in the United States. Utilization of physically based hydrological-water temperature models is computationally demanding and can be onerous to many researchers who specialize in other disciplines. Using statistical techniques to analyze observational data from 1760 USGS stream temperature gages, our goal is to develop a simple yet accurate method to quantify the impacts of climate warming on stream water temperatures in a way that is practical for aquatic biologists, water and environmental management purposes, and conservation practitioners and policy-makers. Using an ensemble of five global climate models (GCMs), we estimate the potential impacts of climate change on stream temperatures within the contiguous United States based on recent trends. Stream temperatures are projected to increase across the US, but the magnitude of the

  5. Stream temperature responses to timber harvest and best management practices—findings from the ODF RipStream project

    Science.gov (United States)

    Jeremy D. Groom

    2013-01-01

    Studies over the past 40 years have established that riparian buff er retention along streams protects against stream temperature increase. Th is protection is neither universal nor complete; some buff ered streams still warm, while other streams’ temperatures remain stable. Oregon Department of Forestry developed riparian rules in the Forest Practices Act (FPA) to...

  6. Can air temperature be used to project influences of climate change on stream temperature?

    Science.gov (United States)

    Arismendi, Ivan; Safeeq, Mohammad; Dunham, Jason B.; Johnson, Sherri L.

    2014-01-01

    Worldwide, lack of data on stream temperature has motivated the use of regression-based statistical models to predict stream temperatures based on more widely available data on air temperatures. Such models have been widely applied to project responses of stream temperatures under climate change, but the performance of these models has not been fully evaluated. To address this knowledge gap, we examined the performance of two widely used linear and nonlinear regression models that predict stream temperatures based on air temperatures. We evaluated model performance and temporal stability of model parameters in a suite of regulated and unregulated streams with 11–44 years of stream temperature data. Although such models may have validity when predicting stream temperatures within the span of time that corresponds to the data used to develop them, model predictions did not transfer well to other time periods. Validation of model predictions of most recent stream temperatures, based on air temperature–stream temperature relationships from previous time periods often showed poor performance when compared with observed stream temperatures. Overall, model predictions were less robust in regulated streams and they frequently failed in detecting the coldest and warmest temperatures within all sites. In many cases, the magnitude of errors in these predictions falls within a range that equals or exceeds the magnitude of future projections of climate-related changes in stream temperatures reported for the region we studied (between 0.5 and 3.0 °C by 2080). The limited ability of regression-based statistical models to accurately project stream temperatures over time likely stems from the fact that underlying processes at play, namely the heat budgets of air and water, are distinctive in each medium and vary among localities and through time.

  7. Detecting climate change oriented and human induced changes in stream temperature across the Southeastern U.S.

    Science.gov (United States)

    Zhang, X.; Voisin, N.; Cheng, Y.; Niemeyer, R. J.; Nijssen, B.; Yearsley, J. R.; Zhou, T.

    2017-12-01

    In many areas, climate change is expected to alter the flow regime and increase stream temperature, especially during summer low flow periods. During these low flow periods, water management increases flows in order to sustain human activities such as water for irrigation and hydroelectric power generation. Water extraction from rivers during warm season can increase stream temperature while reservoir regulation may cool downstream river temperatures by releasing cool water from deep layers. Thus, it is reasonable to hypothesize that water management changes the sensitivity of the stream temperature regime to climate change when compared to unmanaged resources. The time of emergence of change refers to the point in time when observations, or model simulations, show statistically significant changes from a given baseline period, i.e. above natural variability. Here we aim to address two questions by investigating the time of emergence of changes in stream temperature in the southeastern United States: what is the sensitivity of stream temperature under regulated flow conditions to climate change and what is the contribution of water management in increasing or decreasing stream temperature sensitivity to climate change. We simulate regulated flow by using runoff from the Variable Infiltration Capacity (VIC) macroscale hydrological model as input into a large scale river routing and reservoir model MOSART-WM. The River Basin Model (RBM), a distributed stream temperature model, includes a two-layer thermal stratification module to simulate stream temperature in regulated river systems. We evaluate the timing of emergence of changes in flow and stream temperature based on climate projections from two representative concentration pathways (RCPs; RCP4.5 and RCP8.5) from the Coupled Model Intercomparison Project Phase 5 (CMIP5). We analyze the difference in emergence of change between natural and regulated streamflow. Insights will be provided toward applications for

  8. Predictive Models of the Hydrological Regime of Unregulated Streams in Arizona

    Science.gov (United States)

    Anning, David W.; Parker, John T.C.

    2009-01-01

    Three statistical models were developed by the U.S. Geological Survey in cooperation with the Arizona Department of Environmental Quality to improve the predictability of flow occurrence in unregulated streams throughout Arizona. The models can be used to predict the probabilities of the hydrological regime being one of four categories developed by this investigation: perennial, which has streamflow year-round; nearly perennial, which has streamflow 90 to 99.9 percent of the year; weakly perennial, which has streamflow 80 to 90 percent of the year; or nonperennial, which has streamflow less than 80 percent of the year. The models were developed to assist the Arizona Department of Environmental Quality in selecting sites for participation in the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program. One model was developed for each of the three hydrologic provinces in Arizona - the Plateau Uplands, the Central Highlands, and the Basin and Range Lowlands. The models for predicting the hydrological regime were calibrated using statistical methods and explanatory variables of discharge, drainage-area, altitude, and location data for selected U.S. Geological Survey streamflow-gaging stations and a climate index derived from annual precipitation data. Models were calibrated on the basis of streamflow data from 46 stations for the Plateau Uplands province, 82 stations for the Central Highlands province, and 90 stations for the Basin and Range Lowlands province. The models were developed using classification trees that facilitated the analysis of mixed numeric and factor variables. In all three models, a threshold stream discharge was the initial variable to be considered within the classification tree and was the single most important explanatory variable. If a stream discharge value at a station was below the threshold, then the station record was determined as being nonperennial. If, however, the stream discharge was above the threshold

  9. STABILIZATION OF TEMPERATURE REGIMES WHILE SYNTHESIZING DIAMOND POWDERS

    Directory of Open Access Journals (Sweden)

    A. I. Dudiak

    2012-01-01

    Full Text Available The paper considers peculiar features of artificial diamond powder synthesis process and also direct and indirect methods for temperature measurement in a reaction cell of high-pressure apparatus. Differences in temperature regimes of diamond synthesis associated with time fixation of strain and heating power have been analyzed in the paper. The paper  reveals their impracticability.Theoretical methodology for temperature correction in the reaction cell has been proposed in the paper. An algorithm controlling cell material heating has been developed on the basis of a microcontroller and it makes it possible to stabilize temperature in the reaction mixture that permits to improve quality and strength characteristics of the obtained diamond powders. The paper contains a graphic interpretation of calculation results with the help of the proposed algorithm. 

  10. Stream hydraulics and temperature determine the metabolism of geothermal Icelandic streams

    Directory of Open Access Journals (Sweden)

    Demars B. O.L.

    2011-07-01

    Full Text Available Stream ecosystem metabolism plays a critical role in planetary biogeochemical cycling. Stream benthic habitat complexity and the available surface area for microbes relative to the free-flowing water volume are thought to be important determinants of ecosystem metabolism. Unfortunately, the engineered deepening and straightening of streams for drainage purposes could compromise stream natural services. Stream channel complexity may be quantitatively expressed with hydraulic parameters such as water transient storage, storage residence time, and water spiralling length. The temperature dependence of whole stream ecosystem respiration (ER, gross primary productivity (GPP and net ecosystem production (NEP = GPP − ER has recently been evaluated with a “natural experiment” in Icelandic geothermal streams along a 5–25 °C temperature gradient. There remained, however, a substantial amount of unexplained variability in the statistical models, which may be explained by hydraulic parameters found to be unrelated to temperature. We also specifically tested the additional and predicted synergistic effects of water transient storage and temperature on ER, using novel, more accurate, methods. Both ER and GPP were highly related to water transient storage (or water spiralling length but not to the storage residence time. While there was an additional effect of water transient storage and temperature on ER (r2 = 0.57; P = 0.015, GPP was more related to water transient storage than temperature. The predicted synergistic effect could not be confirmed, most likely due to data limitation. Our interpretation, based on causal statistical modelling, is that the metabolic balance of streams (NEP was primarily determined by the temperature dependence of respiration. Further field and experimental work is required to test the predicted synergistic effect on ER. Meanwhile, since higher metabolic activities allow for higher pollutant degradation or uptake

  11. The effects of human land use on flow regime and water chemistry of headwater streams in the highlands of Chiapas

    Directory of Open Access Journals (Sweden)

    Castillo M.M.

    2013-03-01

    Full Text Available We studied the effects of land use changes on flow regime and water chemistry of headwater streams in the highlands of Chiapas, a region in southern Mexico that has experienced high rates of deforestation in the last decades. Samples for water chemistry were collected and discharge was measured between September 2007 and August 2008 at eight streams that differed in the land uses of their riparian and catchment areas, including streams draining protected forested areas. Streams with high forest cover (>70% in their catchments maintained flow through the year. Streams draining more disturbed catchments exhibited reduced or no flow for 4 − 6 months during the dry season. Nitrate concentrations were lower at streams draining forested catchments while highest concentrations were measured where conventional agriculture covered a high proportion of the catchment and riparian zone. Highest phosphorus concentrations occurred at the catchment where poultry manure was applied as fertilizer. Differences between forest streams and those draining disturbed areas were correlated with the proportion of forest and agriculture in the riparian zone. Variation in stream variables among sampling dates was lower at the forest sites than at the more disturbed study streams. Conversion of forest into agriculture and urban areas is affecting flow regime and increasing nutrient concentrations, although the magnitude of the impacts are influenced by the type of agricultural practices and the alteration of the riparian zone.

  12. A quasi-one-dimensional velocity regime of super-thermal electron stream propagation through the solar corona

    International Nuclear Information System (INIS)

    Levin, B.N.

    1984-01-01

    The propagation of an inhomogeneous stream of fast electrons through the corona - the type III radio burst source - is considered. It is shown, that the angular spectrum width of plasma waves excited by the stream is defined both by Landau damping by particles of the diffuse component and by damping (in the region of large phase velocities) by particles of the stream itself having large pitch angles. The regime of quasi-one-dimensional diffusion in the velocity space is realized only in the presence of a sufficiently dense diffuse component of super-thermal particles and only for a sufficiently large inhomogeneity scale of the stream. A large scale of the stream space profile is formed, evidently, close to the region of injection of super-thermal particles. It is the result of 'stripping' of part of the electrons from the stream front to its slower part due to essential non-one-dimensionality of the particle diffusion in velocity space. Results obtained may explain, in particular, the evolution of a stream particle angular spectrum in the generation region of type III radio bursts observed by spacecrafts (Lin et al., 1981). For the relatively low energetic part of the stream, the oblique plasma wave stabilization by a diffuse component results in a quasi-one-dimensional regime of diffusion. The latter conserves the beam-like structure of this part of the stream. (orig.)

  13. Temperature oscillating regimes in Tore Supra diagnosed by MHD activity

    International Nuclear Information System (INIS)

    Maget, P.; Imbeaux, F.; Giruzzi, G.; Udintsev, V.S.; Huysmans, G.T.A.; Segui, J.-L.; Goniche, M.; Moreau, Ph.; Sabot, R.; Garbet, X.

    2006-01-01

    This paper describes what we can learn on the regimes of spontaneous electron temperature oscillations discovered in Tore Supra from the analysis of MHD activity. Since the first observations of this oscillating behaviour of plasma equilibrium, and its interpretation as a predator-prey system involving lower hybrid waves power deposition and electron confinement, analysis of MHD modes has confirmed the reality of safety factor profile oscillations. This points towards the importance of rational values of the safety factor in the transition to transport barriers in reversed magnetic shear plasmas

  14. Solar activity influence on air temperature regimes in caves

    Science.gov (United States)

    Stoeva, Penka; Mikhalev, Alexander; Stoev, Alexey

    Cave atmospheres are generally included in the processes that happen in the external atmosphere as circulation of the cave air is connected with the most general circulation of the air in the earth’s atmosphere. Such isolated volumes as the air of caves are also influenced by the variations of solar activity. We discuss cave air temperature response to climate and solar and geomagnetic activity for four show caves in Bulgaria studied for a period of 46 years (1968 - 2013). Everyday noon measurements in Ledenika, Saeva dupka, Snezhanka and Uhlovitsa cave have been used. Temperatures of the air in the zone of constant temperatures (ZCT) are compared with surface temperatures recorded at meteorological stations situated near about the caves - in the towns of Vratsa, Lovech, Peshtera and Smolyan, respectively. For comparison, The Hansen cave, Middle cave and Timpanogos cave from the Timpanogos Cave National Monument, Utah, USA situated nearly at the same latitude have also been examined. Our study shows that the correlation between cave air temperature time series and sunspot number is better than that between the cave air temperature and Apmax indices; that t°ZCT is rather connected with the first peak in geomagnetic activity, which is associated with transient solar activity (CMEs) than with the second one, which is higher and connected with the recurrent high speed streams from coronal holes. Air temperatures of all examined show caves, except the Ledenika cave, which is ice cave show decreasing trends. On the contrary, measurements at the meteorological stations show increasing trends in the surface air temperatures. The trend is decreasing for the Timpanogos cave system, USA. The conclusion is that surface temperature trends depend on the climatic zone, in which the cave is situated, and there is no apparent relation between temperatures inside and outside the caves. We consider possible mechanism of solar cosmic rays influence on the air temperatures in caves

  15. Developing a novel approach to analyse the regimes of temporary streams and their controls on aquatic biota

    Science.gov (United States)

    Gallart, F.; Prat, N.; García-Roger, E. M.; Latron, J.; Rieradevall, M.; Llorens, P.; Barberá, G. G.; Brito, D.; de Girolamo, A. M.; Lo Porto, A.; Neves, R.; Nikolaidis, N. P.; Perrin, J. L.; Querner, E. P.; Quiñonero, J. M.; Tournoud, M. G.; Tzoraki, O.; Froebrich, J.

    2011-10-01

    Temporary streams are those water courses that undergo the recurrent cessation of flow or the complete drying of their channel. The biological communities in temporary stream reaches are strongly dependent on the temporal changes of the aquatic habitats determined by the hydrological conditions. The use of the aquatic fauna structural and functional characteristics to assess the ecological quality of a temporary stream reach can not therefore be made without taking into account the controls imposed by the hydrological regime. This paper develops some methods for analysing temporary streams' aquatic regimes, based on the definition of six aquatic states that summarize the sets of mesohabitats occurring on a given reach at a particular moment, depending on the hydrological conditions: flood, riffles, connected, pools, dry and arid. We used the water discharge records from gauging stations or simulations using rainfall-runoff models to infer the temporal patterns of occurrence of these states using the developed aquatic states frequency graph. The visual analysis of this graph is complemented by the development of two metrics based on the permanence of flow and the seasonal predictability of zero flow periods. Finally, a classification of the aquatic regimes of temporary streams in terms of their influence over the development of aquatic life is put forward, defining Permanent, Temporary-pools, Temporary-dry and Episodic regime types. All these methods were tested with data from eight temporary streams around the Mediterranean from MIRAGE project and its application was a precondition to assess the ecological quality of these streams using the current methods prescribed in the European Water Framework Directive for macroinvertebrate communities.

  16. Effects of Urbanization on the Flow Regimes of Semi-Arid Southern California Streams

    Science.gov (United States)

    Hawley, R. J.; Bledsoe, B. P.; Stein, E. D.

    2010-12-01

    Stream channel erosion and associated habitat degradation are pervasive in streams draining urban areas in the southwestern US. The prevalence of these impacts results from the inherent sensitivity of streams in semi-arid climates to changes in flow and sediment regimes, and past inattention to management of geomorphically effective flows. Addressing this issue is difficult due to the lack of data linking ranges of flow (from small to large runoff events) to geomorphic channel response. Forty-three U. S. Geological Survey gages with record lengths greater than ~15 yrs and watershed areas less than ~250 square kilometers were used to empirically model the effects of urbanization on streams in southern California. The watersheds spanned a gradient of urban development and ranged from 0 to 23% total impervious area in 2001. With little flow control at the subdivision scale to date, most impervious area in the region is relatively well-connected to surface-drainage networks. Consequently, total impervious area was an effective surrogate for urbanization, and emerged as a significant (p approach expands on previous scaling procedures to produce histogram-style cumulative flow duration graphs for ungaged sites based on urbanization extent and other watershed descriptors. Urbanization resulted in proportionally-longer durations of all geomorphically-effective flows, with a more pronounced effect on the durations of moderate flows. For example, an average watershed from the study domain with ~20% imperviousness could experience five times as many days of mean daily flows on the order of 100 cfs (3 cubic meters per second) and approximately three times as many days on the order of 1,000 cfs (30 cubic meters per second) relative to the undeveloped setting. Increased duration of sediment-transporting flows is a primary driver of accelerated changes in channel form that are often concurrent with urbanization throughout southern California, particularly in unconfined, fine

  17. Low-temperature operating regime of the tokamak evacuating limiter

    International Nuclear Information System (INIS)

    Tokar', M.Z.

    1987-01-01

    The conditions for realizing the regime of strong recycling of a cold dense plasma of an evacuating limiter were determined based on a previously proposed model for describing the limiter layer of a tokamak. The scaling for the dependence of the gas pressure in the evacuation system on the average plasma density in the limiter layer was found, and agreed quantitatively with the results of measurements on the Alcator and ISX-B tokamaks. For the tokamak reactor of the INTOR scale the calculations show that the low-temperature operating regime of the evacuating limiter can be realized with a quite low pumping rate. It has the advantages of reduced erosion of the limiter and small fluxes of impurities into the working volume of the reactor. In addition, the relative concentration of the helium ash in the limiter layer does not exceed 2-3%, but the density of the main plasma is comparable to the proposed average density in the reactor. The concept of a stochastic limiter is of interest for lowering the plasma density in the limiter layer and lowering the thermal loads on the limiter

  18. Method for high temperature mercury capture from gas streams

    Science.gov (United States)

    Granite, Evan J [Wexford, PA; Pennline, Henry W [Bethel Park, PA

    2006-04-25

    A process to facilitate mercury extraction from high temperature flue/fuel gas via the use of metal sorbents which capture mercury at ambient and high temperatures. The spent sorbents can be regenerated after exposure to mercury. The metal sorbents can be used as pure metals (or combinations of metals) or dispersed on an inert support to increase surface area per gram of metal sorbent. Iridium and ruthenium are effective for mercury removal from flue and smelter gases. Palladium and platinum are effective for mercury removal from fuel gas (syngas). An iridium-platinum alloy is suitable for metal capture in many industrial effluent gas streams including highly corrosive gas streams.

  19. On the Validity of the Streaming Model for the Redshift-Space Correlation Function in the Linear Regime

    Science.gov (United States)

    Fisher, Karl B.

    1995-08-01

    The relation between the galaxy correlation functions in real-space and redshift-space is derived in the linear regime by an appropriate averaging of the joint probability distribution of density and velocity. The derivation recovers the familiar linear theory result on large scales but has the advantage of clearly revealing the dependence of the redshift distortions on the underlying peculiar velocity field; streaming motions give rise to distortions of θ(Ω0.6/b) while variations in the anisotropic velocity dispersion yield terms of order θ(Ω1.2/b2). This probabilistic derivation of the redshift-space correlation function is similar in spirit to the derivation of the commonly used "streaming" model, in which the distortions are given by a convolution of the real-space correlation function with a velocity distribution function. The streaming model is often used to model the redshift-space correlation function on small, highly nonlinear, scales. There have been claims in the literature, however, that the streaming model is not valid in the linear regime. Our analysis confirms this claim, but we show that the streaming model can be made consistent with linear theory provided that the model for the streaming has the functional form predicted by linear theory and that the velocity distribution is chosen to be a Gaussian with the correct linear theory dispersion.

  20. Exploring the persistence of stream-dwelling trout populations under alternative real-world turbidity regimes with an individual-based model

    Science.gov (United States)

    Bret C. Harvey; Steven F. Railsback

    2009-01-01

    We explored the effects of elevated turbidity on stream-resident populations of coastal cutthroat trout Oncorhynchus clarkii clarkii using a spatially explicit individual-based model. Turbidity regimes were contrasted by means of 15-year simulations in a third-order stream in northwestern California. The alternative regimes were based on multiple-year, continuous...

  1. Stream temperature variability: why it matters to salmon

    Science.gov (United States)

    E. Ashley Steel; Brian Beckman; Marie Oliver

    2014-01-01

    Salmon evolved in natural river systems, where temperatures fluctuate daily, weekly, seasonally, and all along a stream’s path—from the mountains to the sea. Climate change and human activities alter this natural variability. Dams, for example, tend to reduce thermal fluctuations.Currently, scientists gauge habitat suitability for aquatic species by...

  2. Hydrological regime as key to the morpho-texture and activity of braided streams

    Science.gov (United States)

    Storz-Peretz, Y.; Laronne, J. B.

    2012-04-01

    recession is responsible for deposition of finer sediment with minimal winnowing in the branch channels. Therefore, channels are finer-grained than the bars. This process is associated with the mid-channel deposition of central bars. However, the steeper chutes and coarser anabranches are associated with erosive braiding processes, such as chute cutoffs and multiple bar dissection, allowing winnowing to occur also during rapid recession. Hence coarser-grained anabranches in drylands are essentially chutes. Lengthy flow recession in humid braided channels allows winnowing of fines, thereby generating armored channels, the finer sedimentary particles often deposited downstream as unit bars. Therefore, channels are coarser-grained than the bars they surround. Even though the steep Saisera is in a humid region, its hydrological regime is ephemeral with rapid and short recessions, responsible for a morpho-texture similar to that of dryland braided streams. Hence, the hydrologic regimen is a key to understanding the morpho-textural character of braided channels and for the higher activity of the ephemeral unarmoured channels in sub-barful events compared to their humid counterparts.

  3. ESTIMATION OF THE TEMPERATURE RISE OF A MCU ACID STREAM PIPE IN NEAR PROXIMITY TO A SLUDGE STREAM PIPE

    International Nuclear Information System (INIS)

    Fondeur, F; Michael Poirier, M; Samuel Fink, S

    2007-01-01

    Effluent streams from the Modular Caustic-Side Solvent Extraction Unit (MCU) will transfer to the tank farms and to the Defense Waste Processing Facility (DWPF). These streams will contain entrained solvent. A significant portion of the Strip Effluent (SE) pipeline (i.e., acid stream containing Isopar(reg s ign) L residues) length is within one inch of a sludge stream. Personnel envisioned the sludge stream temperature may reach 100 C during operation. The nearby SE stream may receive heat from the sludge stream and reach temperatures that may lead to flammability issues once the contents of the SE stream discharge into a larger reservoir. To this end, personnel used correlations from the literature to estimate the maximum temperature rise the SE stream may experience if the nearby sludge stream reaches boiling temperature. Several calculation methods were used to determine the temperature rise of the SE stream. One method considered a heat balance equation under steady state that employed correlation functions to estimate heat transfer rate. This method showed the maximum temperature of the acid stream (SE) may exceed 45 C when the nearby sludge stream is 80 C or higher. A second method used an effectiveness calculation used to predict the heat transfer rate in single pass heat exchanger. By envisioning the acid and sludge pipes as a parallel flow pipe-to-pipe heat exchanger, this method provides a conservative estimation of the maximum temperature rise. Assuming the contact area (i.e., the area over which the heat transfer occurs) is the whole pipe area, the results found by this method nearly matched the results found with the previous calculation method. It is recommended that the sludge stream be maintained below 80 C to minimize a flammable vapor hazard from occurring

  4. Effects of temperature anisotropy on neoclassical transport in the plateau and banana-plateau regimes

    International Nuclear Information System (INIS)

    Taguchi, Masayoshi

    1999-01-01

    The neoclassical transport theory in a presence of temperature anisotropy is investigated in the low to the intermediate collision frequency regimes for a large aspect-ratio tokamak plasma. The standard procedure for an isotropic plasma in the plateau regime is extended to an anisotropic plasma, and the neoclassical transport coefficients in this regime are explicitly calculated. By interpolating the results in the plateau regime and the previously obtained ones in the banana regime, the expressions for the neoclassical transport coefficients which are continuously valid from the banana to the plateau regimes are presented. (author)

  5. Predicting the natural flow regime: Models for assessing hydrological alteration in streams

    Science.gov (United States)

    Carlisle, D.M.; Falcone, J.; Wolock, D.M.; Meador, M.R.; Norris, R.H.

    2009-01-01

    Understanding the extent to which natural streamflow characteristics have been altered is an important consideration for ecological assessments of streams. Assessing hydrologic condition requires that we quantify the attributes of the flow regime that would be expected in the absence of anthropogenic modifications. The objective of this study was to evaluate whether selected streamflow characteristics could be predicted at regional and national scales using geospatial data. Long-term, gaged river basins distributed throughout the contiguous US that had streamflow characteristics representing least disturbed or near pristine conditions were identified. Thirteen metrics of the magnitude, frequency, duration, timing and rate of change of streamflow were calculated using a 20-50 year period of record for each site. We used random forests (RF), a robust statistical modelling approach, to develop models that predicted the value for each streamflow metric using natural watershed characteristics. We compared the performance (i.e. bias and precision) of national- and regional-scale predictive models to that of models based on landscape classifications, including major river basins, ecoregions and hydrologic landscape regions (HLR). For all hydrologic metrics, landscape stratification models produced estimates that were less biased and more precise than a null model that accounted for no natural variability. Predictive models at the national and regional scale performed equally well, and substantially improved predictions of all hydrologic metrics relative to landscape stratification models. Prediction error rates ranged from 15 to 40%, but were 25% for most metrics. We selected three gaged, non-reference sites to illustrate how predictive models could be used to assess hydrologic condition. These examples show how the models accurately estimate predisturbance conditions and are sensitive to changes in streamflow variability associated with long-term land-use change. We also

  6. An evaluation of the relations between flow regime components, stream characteristics, species traits and meta-demographic rates of warmwater stream fishes: Implications for aquatic resource management

    Science.gov (United States)

    Peterson, James T.; Shea, C.P.

    2015-01-01

    Fishery biologists are increasingly recognizing the importance of considering the dynamic nature of streams when developing streamflow policies. Such approaches require information on how flow regimes influence the physical environment and how those factors, in turn, affect species-specific demographic rates. A more cost-effective alternative could be the use of dynamic occupancy models to predict how species are likely to respond to changes in flow. To appraise the efficacy of this approach, we evaluated relative support for hypothesized effects of seasonal streamflow components, stream channel characteristics, and fish species traits on local extinction, colonization, and recruitment (meta-demographic rates) of stream fishes. We used 4 years of seasonal fish collection data from 23 streams to fit multistate, multiseason occupancy models for 42 fish species in the lower Flint River Basin, Georgia. Modelling results suggested that meta-demographic rates were influenced by streamflows, particularly short-term (10-day) flows. Flow effects on meta-demographic rates also varied with stream size, channel morphology, and fish species traits. Small-bodied species with generalized life-history characteristics were more resilient to flow variability than large-bodied species with specialized life-history characteristics. Using this approach, we simplified the modelling framework, thereby facilitating the development of dynamic, spatially explicit evaluations of the ecological consequences of water resource development activities over broad geographic areas. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

  7. Implementation of a subcanopy solar radiation model on a forested headwater basin in the Southern Appalachians to estimate riparian canopy density and stream insolation for stream temperature models

    Science.gov (United States)

    Belica, L.; Petras, V.; Iiames, J. S., Jr.; Caldwell, P.; Mitasova, H.; Nelson, S. A. C.

    2016-12-01

    Water temperature is a key aspect of water quality and understanding how the thermal regimes of forested headwater streams may change in response to climatic and land cover changes is increasingly important to scientists and resource managers. In recent years, the forested mountain watersheds of the Southeastern U.S. have experienced changing climatic patterns as well as the loss of a keystone riparian tree species and anticipated hydrologic responses include lower summer stream flows and decreased stream shading. Solar radiation is the main source of thermal energy to streams and a key parameter in heat-budget models of stream temperature; a decrease in flow volume combined with a reduction in stream shading during summer have the potential to increase stream temperatures. The high spatial variability of forest canopies and the high spatio-temporal variability in sky conditions make estimating the solar radiation reaching small forested headwater streams difficult. The Subcanopy Solar Radiation Model (SSR) (Bode et al. 2014) is a GIS model that generates high resolution, spatially explicit estimates of solar radiation by incorporating topographic and vegetative shading with a light penetration index derived from leaf-on airborne LIDAR data. To evaluate the potential of the SSR model to provide estimates of stream insolation to parameterize heat-budget models, it was applied to the Coweeta Basin in the Southern Appalachians using airborne LIDAR (NCALM 2009, 1m resolution). The LIDAR derived canopy characteristics were compared to current hyperspectral images of the canopy for changes and the SSR estimates of solar radiation were compared with pyranometer measurements of solar radiation at several subcanopy sites during the summer of 2016. Preliminary results indicate the SSR model was effective in identifying variations in canopy density and light penetration, especially in areas associated with road and stream corridors and tree mortality. Current LIDAR data and

  8. Climate and land cover effects on the temperature of Puget Sound streams: Assessment of Climate and Land Use Impacts on Stream Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Qian [Department of Geography, University of California, Los Angeles, Los Angeles CA USA; Sun, Ning [Civil and Environmental Engineering, University of Washington, Seattle WA USA; Pacific Northwest National Laboratory, Richland WA USA; Yearsley, John [Civil and Environmental Engineering, University of Washington, Seattle WA USA; Nijssen, Bart [Civil and Environmental Engineering, University of Washington, Seattle WA USA; Lettenmaier, Dennis P. [Department of Geography, University of California, Los Angeles, Los Angeles CA USA

    2016-03-06

    We apply an integrated hydrology-stream temperature modeling system, DHSVM-RBM, to examine the response of the temperature of the major streams draining to Puget Sound to land cover and climate change. We first show that the model construct is able to reconstruct observed historic streamflow and stream temperature variations at a range of time scales. We then explore the relative effect of projected future climate and land cover change, including riparian vegetation, on streamflow and stream temperature. Streamflow in summer is likely to decrease as the climate warms especially in snowmelt-dominated and transient river basins despite increased streamflow in their lower reaches associated with urbanization. Changes in streamflow also result from changes in land cover, and changes in stream shading result from changes in riparian vegetation, both of which influence stream temperature. However, we find that the effect of riparian vegetation changes on stream temperature is much greater than land cover change over the entire basin especially during summer low flow periods. Furthermore, while future projected precipitation change will have relatively modest effects on stream temperature, projected future air temperature increases will result in substantial increases in stream temperature especially in summer. These summer stream temperature increases will be associated both with increasing air temperature, and projected decreases in low flows. We find that restoration of riparian vegetation could mitigate much of the projected summer stream temperature increases. We also explore the contribution of riverine thermal loadings to the heat balance of Puget Sound, and find that the riverine contribution is greatest in winter, when streams account for up to 1/8 of total thermal inputs (averaged from December through February), with larger effects in some sub-basins. We project that the riverine impact on thermal inputs to Puget Sound will become greater with both urbanization

  9. Morphodynamic regime change induced by riparian vegetation in a restored lowland stream

    NARCIS (Netherlands)

    Eekhout, J.P.C.; Hoitink, A.J.F.

    2013-01-01

    With the aim to establish and understand morphological changes in response to stream restoration measures, a detailed monitoring plan was implemented in a lowland stream called Lunterse Beek, located in the Netherlands. Over a period of 1.5 yr, the monitoring 5 included serial morphological surveys,

  10. The paradox of cooling streams in a warming world: regional climate trends do not parallel variable local trends in stream temperature in the Pacific continental United States

    Science.gov (United States)

    Ivan Arismendi; Sherri L. Johnson; Jason B. Dunham; Roy Haggerty

    2012-01-01

    Temperature is a fundamentally important driver of ecosystem processes in streams. Recent warming of terrestrial climates around the globe has motivated concern about consequent increases in stream temperature. More specifically, observed trends of increasing air temperature and declining stream flow are widely believed to result in corresponding increases in stream...

  11. Unmanned Aerial System Aids Dry-season Stream Temperature Sensing

    Science.gov (United States)

    Chung, M.; Detweiler, C.; Higgins, J.; Ore, J. P.; Dralle, D.; Thompson, S. E.

    2016-12-01

    In freshwater ecosystems, temperature affects biogeochemistry and ecology, and is thus a primary physical determinant of habitat quality. Measuring temperatures in spatially heterogeneous water bodies poses a serious challenge to researchers due to constraints associated with currently available methods: in situ loggers record temporally continuous temperature measurements but are limited to discrete spatial locations, while distributed temperature and remote sensing provide fine-resolution spatial measurements that are restricted to only two-dimensions (i.e. streambed and surface, respectively). Using a commercially available quadcopter equipped with a 6m cable and temperature-pressure sensor system, we measured stream temperatures at two confluences at the South Fork Eel River, where cold water inputs from the tributary to the mainstem create thermal refugia for juvenile salmonids during the dry season. As a mobile sensing platform, unmanned aerial systems (UAS) can facilitate quick and repeated sampling with minimal disturbance to the ecosystem, and their datasets can be interpolated to create a three-dimensional thermal map of a water body. The UAS-derived data was compared to data from in situ data loggers to evaluate whether the UAS is better able to capture fine-scale temperature dynamics at each confluence. The UAS has inherent limitations defined by battery life and flight times, as well as operational constraints related to maneuverability under wind and streamflow conditions. However, the platform is able to serve as an additional field tool for researchers to capture complex thermal structures in water bodies.

  12. Bivariate functional data clustering: grouping streams based on a varying coefficient model of the stream water and air temperature relationship

    Science.gov (United States)

    H. Li; X. Deng; Andy Dolloff; E. P. Smith

    2015-01-01

    A novel clustering method for bivariate functional data is proposed to group streams based on their water–air temperature relationship. A distance measure is developed for bivariate curves by using a time-varying coefficient model and a weighting scheme. This distance is also adjusted by spatial correlation of streams via the variogram. Therefore, the proposed...

  13. Stream temperature monitoring and modeling: Recent advances and new tools for managers

    Science.gov (United States)

    Daniel J. Isaak

    2011-01-01

    Stream thermal regimes are important within regulatory contexts, strongly affect the functioning of aquatic ecosystems, and are a primary determinant of habitat suitability for many sensitive species. The diverse landscapes and topographies inherent to National Forests and Grasslands create mosaics of stream thermal conditions that are intermingled with strong...

  14. Distributed Low Temperature Combustion: Fundamental Understanding of Combustion Regime Transitions

    Science.gov (United States)

    2016-09-07

    behaviour as compared to ethanol. The latter fuel has also been considered along with methane. Work has also been performed on the further assessment of... behaviour as compared to ethanol. The latter fuel has also been considered along with methane. Work has also been performed on the further assess- ment of...identification of various combustion gas states. A range of Damköhler numbers (Da) from the conventional propagating flamelet regime well into the distributed

  15. New methods for modeling stream temperature using high resolution LiDAR, solar radiation analysis and flow accumulated values to predict stream temperature

    Science.gov (United States)

    In-stream temperature directly effects a variety of biotic organisms, communities and processes. Changes in stream temperature can render formally suitable habitat unsuitable for aquatic organisms, particularly native cold water species that are not able to adjust. In order to...

  16. Sensitivity of summer stream temperatures to climate variability in the Pacific Northwest

    Science.gov (United States)

    Charles Luce; Brian Staab; Marc Kramer; Seth Wenger; Dan Isaak; Callie McConnell

    2014-01-01

    Estimating the thermal response of streams to a warming climate is important for prioritizing native fish conservation efforts. While there are plentiful estimates of air temperature responses to climate change, the sensitivity of streams, particularly small headwater streams, to warming temperatures is less well understood. A substantial body of literature correlates...

  17. Fluid temperatures: Modeling the thermal regime of a river network

    Science.gov (United States)

    Rhonda Mazza; Ashley Steel

    2017-01-01

    Water temperature drives the complex food web of a river network. Aquatic organisms hatch, feed, and reproduce in thermal niches within the tributaries and mainstem that comprise the river network. Changes in water temperature can synchronize or asynchronize the timing of their life stages throughout the year. The water temperature fluctuates over time and place,...

  18. Estimation of river and stream temperature trends under haphazard sampling

    Science.gov (United States)

    Gray, Brian R.; Lyubchich, Vyacheslav; Gel, Yulia R.; Rogala, James T.; Robertson, Dale M.; Wei, Xiaoqiao

    2015-01-01

    Long-term temporal trends in water temperature in rivers and streams are typically estimated under the assumption of evenly-spaced space-time measurements. However, sampling times and dates associated with historical water temperature datasets and some sampling designs may be haphazard. As a result, trends in temperature may be confounded with trends in time or space of sampling which, in turn, may yield biased trend estimators and thus unreliable conclusions. We address this concern using multilevel (hierarchical) linear models, where time effects are allowed to vary randomly by day and date effects by year. We evaluate the proposed approach by Monte Carlo simulations with imbalance, sparse data and confounding by trend in time and date of sampling. Simulation results indicate unbiased trend estimators while results from a case study of temperature data from the Illinois River, USA conform to river thermal assumptions. We also propose a new nonparametric bootstrap inference on multilevel models that allows for a relatively flexible and distribution-free quantification of uncertainties. The proposed multilevel modeling approach may be elaborated to accommodate nonlinearities within days and years when sampling times or dates typically span temperature extremes.

  19. Combining multiple approaches and optimized data resolution for an improved understanding of stream temperature dynamics of a forested headwater basin in the Southern Appalachians

    Science.gov (United States)

    Belica, L.; Mitasova, H.; Caldwell, P.; McCarter, J. B.; Nelson, S. A. C.

    2017-12-01

    Thermal regimes of forested headwater streams continue to be an area of active research as climatic, hydrologic, and land cover changes can influence water temperature, a key aspect of aquatic ecosystems. Widespread monitoring of stream temperatures have provided an important data source, yielding insights on the temporal and spatial patterns and the underlying processes that influence stream temperature. However, small forested streams remain challenging to model due to the high spatial and temporal variability of stream temperatures and the climatic and hydrologic conditions that drive them. Technological advances and increased computational power continue to provide new tools and measurement methods and have allowed spatially explicit analyses of dynamic natural systems at greater temporal resolutions than previously possible. With the goal of understanding how current stream temperature patterns and processes may respond to changing landcover and hydroclimatoligical conditions, we combined high-resolution, spatially explicit geospatial modeling with deterministic heat flux modeling approaches using data sources that ranged from traditional hydrological and climatological measurements to emerging remote sensing techniques. Initial analyses of stream temperature monitoring data revealed that high temporal resolution (5 minutes) and measurement resolutions (guide field data collection for further heat flux modeling. By integrating multiple approaches and optimizing data resolution for the processes being investigated, small, but ecologically significant differences in stream thermal regimes were revealed. In this case, multi-approach research contributed to the identification of the dominant mechanisms driving stream temperature in the study area and advanced our understanding of the current thermal fluxes and how they may change as environmental conditions change in the future.

  20. Performance of the air2stream model that relates air and stream water temperatures depends on the calibration method

    Science.gov (United States)

    Piotrowski, Adam P.; Napiorkowski, Jaroslaw J.

    2018-06-01

    A number of physical or data-driven models have been proposed to evaluate stream water temperatures based on hydrological and meteorological observations. However, physical models require a large amount of information that is frequently unavailable, while data-based models ignore the physical processes. Recently the air2stream model has been proposed as an intermediate alternative that is based on physical heat budget processes, but it is so simplified that the model may be applied like data-driven ones. However, the price for simplicity is the need to calibrate eight parameters that, although have some physical meaning, cannot be measured or evaluated a priori. As a result, applicability and performance of the air2stream model for a particular stream relies on the efficiency of the calibration method. The original air2stream model uses an inefficient 20-year old approach called Particle Swarm Optimization with inertia weight. This study aims at finding an effective and robust calibration method for the air2stream model. Twelve different optimization algorithms are examined on six different streams from northern USA (states of Washington, Oregon and New York), Poland and Switzerland, located in both high mountains, hilly and lowland areas. It is found that the performance of the air2stream model depends significantly on the calibration method. Two algorithms lead to the best results for each considered stream. The air2stream model, calibrated with the chosen optimization methods, performs favorably against classical streamwater temperature models. The MATLAB code of the air2stream model and the chosen calibration procedure (CoBiDE) are available as Supplementary Material on the Journal of Hydrology web page.

  1. High frequency Analysis of Stream Chemistry to Establish Elemental Cycling Regimes of High latitude Catchments

    Science.gov (United States)

    2017-02-13

    Precipitation has also increased, and climate models project increased precipitation as snow, a longer snow-free season, and increased frequency... model ( ARIMA ) to differenced data in the package forecast. Given the short (15-minute) time steps in these datasets, exploring autocorrelation...those resulting from fire and climate regimes. Alternatively, installation at a particular location downstream of training activities or

  2. Effect of Temperature Regimes on Seed Germination Asafoetida (Ferula Assafoetida L.

    Directory of Open Access Journals (Sweden)

    Zangoie M.

    2014-12-01

    Full Text Available Asafoetida is a medicinal plant belonging to the Apiaceae family. Gum obtained from the lower part of the stem and roots of this plant has many industrial and pharmaceutical applications. This plant is subject to extinction in its natural habitats due to over-utilization. Understanding the biology of seed germination can help to restore such degradation by implementing agricultural development programs. The present study is an attempt to determine the germination responses to two temperature regimes (constant and fluctuating during the course of the study. The experiment was planned based on a factorial-completely randomized design with two factors (constant and fluctuating temperature regimes at 3 levels each (15, 20 and 25°C with 4 replications. The results showed that the characteristics of germination in asafoetida were significantly improved under the fluctuating temperature as compared with the constant regime. It showed a mean germination time of 1.88 days for the fluctuating regime, while it was 4.88 days for the constant regime. The same results were found on germination rates in favor of fluctuating (0.62 per day in comparison with constant regime (0.33 per day. Under the fluctuating regime, the lowest level of imposed temperature (daily application of 10 and 20 degree during the first and the second 12 hours, respectively was the best for seed germination in this experiment.

  3. A simple prioritization tool to diagnose impairment of stream temperature for coldwater fishes in the Great Basin

    Science.gov (United States)

    Falke, Jeffrey A.; Dunham, Jason B.; Hockman-Wert, David; Pahl, Randy

    2016-01-01

    We provide a simple framework for diagnosing the impairment of stream water temperature for coldwater fishes across broad spatial extents based on a weight-of-evidence approach that integrates biological criteria, species distribution models, and geostatistical models of stream temperature. As a test case, we applied our approach to identify stream reaches most likely to be thermally impaired for Lahontan Cutthroat Trout Oncorhynchus clarkii henshawi in the upper Reese River, located in the northern Great Basin, Nevada. We first evaluated the capability of stream thermal regime descriptors to explain variation across 170 sites, and we found that the 7-d moving average of daily maximum stream temperatures (7DADM) provided minimal among-descriptor redundancy and, based on an upper threshold of 20°C, was also a good indicator of acute and chronic thermal stress. Next, we quantified the range of Lahontan Cutthroat Trout within our study area using a geographic distribution model. Finally, we used a geostatistical model to assess spatial variation in 7DADM and predict potential thermal impairment at the stream reach scale. We found that whereas 38% of reaches in our study area exceeded a 7DADM of 20°C and 35% were significantly warmer than predicted, only 17% both exceeded the biological criterion and were significantly warmer than predicted. This filtering allowed us to identify locations where physical and biological impairment were most likely within the network and that would represent the highest management priorities. Although our approach lacks the precision of more comprehensive approaches, it provides a broader context for diagnosing impairment and is a useful means of identifying priorities for more detailed evaluations across broad and heterogeneous stream networks.

  4. Near-surface temperature gradient in a coastal upwelling regime

    Science.gov (United States)

    Maske, H.; Ochoa, J.; Almeda-Jauregui, C. O.; Ruiz-de la Torre, M. C.; Cruz-López, R.; Villegas-Mendoza, J. R.

    2014-08-01

    In oceanography, a near homogeneous mixed layer extending from the surface to a seasonal thermocline is a common conceptual basis in physics, chemistry, and biology. In a coastal upwelling region 3 km off the coast in the Mexican Pacific, we measured vertical density gradients with a free-rising CTD and temperature gradients with thermographs at 1, 3, and 5 m depths logging every 5 min during more than a year. No significant salinity gradient was observed down to 10 m depth, and the CTD temperature and density gradients showed no pronounced discontinuity that would suggest a near-surface mixed layer. Thermographs generally logged decreasing temperature with depth with gradients higher than 0.2 K m-1 more than half of the time in the summer between 1 and 3 m, 3 and 5 m and in the winter between 1 and 3 m. Some negative temperature gradients were present and gradients were generally highly variable in time with high peaks lasting fractions of hours to hours. These temporal changes were too rapid to be explained by local heating or cooling. The pattern of positive and negative peaks might be explained by vertical stacks of water layers of different temperatures and different horizontal drift vectors. The observed near-surface gradient has implications for turbulent wind energy transfer, vertical exchange of dissolved and particulate water constituents, the interpretation of remotely sensed SST, and horizontal wind-induced transport.

  5. The effectiveness of dispersants under various temperature and salinity regimes

    International Nuclear Information System (INIS)

    Fingas, M.; Fieldhouse, B.; Wang, Z.; Environment Canada, Ottawa, ON

    2005-01-01

    A series of tests were conducted to determine the effectiveness of dispersants in Arctic waters where salinity and temperature interactions play a critical role. In particular, Corexit 9500 was tested on Alaska North Slope oil at different temperatures and salinity using the ASTM standard test and variations of this test. Results were compared to the only historically reported test in which both temperature and salinity were changed over a range of values. This series of tests demonstrated that there is an interaction between salinity, temperature and dispersant effectiveness. It was shown that conventional and currently available dispersants are nearly ineffective at 0 salinity. Dispersant effectiveness peaks at 20 to 40 units of salinity, depending on the type of dispersant. Corexit is less sensitive to salinity, while Corexit 9527 is more sensitive to salinity. There is a smooth gradient of effectiveness with salinity both as the salinity rises to a peak point of effectiveness and as it exceeds this value. Results from the 2 field trials in fresh water suggest that laboratory tests correctly conclude that the effectiveness of dispersants is very low in freshwater. The study also examined several analytical factors such as the total petroleum hydrocarbon (TPH) versus relative petroleum hydrocarbon (RPH) methods, specific versus general calibration curves, and automatic versus manual baseline placement. The analytical variations of effectiveness by RPH or TPH methods do not affect the fundamental relationship between salinity and temperature. 6 refs., 6 tabs., 8 figs

  6. Extreme Temperature Regimes during the Cool Season and their Associated Large-Scale Circulations

    Science.gov (United States)

    Xie, Z.

    2015-12-01

    In the cool season (November-March), extreme temperature events (ETEs) always hit the continental United States (US) and provide significant societal impacts. According to the anomalous amplitudes of the surface air temperature (SAT), there are two typical types of ETEs, e.g. cold waves (CWs) and warm waves (WWs). This study used cluster analysis to categorize both CWs and WWs into four distinct regimes respectively and investigated their associated large-scale circulations on intra-seasonal time scale. Most of the CW regimes have large areal impact over the continental US. However, the distribution of cold SAT anomalies varies apparently in four regimes. In the sea level, the four CW regimes are characterized by anomalous high pressure over North America (near and to west of cold anomaly) with different extension and orientation. As a result, anomalous northerlies along east flank of anomalous high pressure convey cold air into the continental US. To the middle troposphere, the leading two groups feature large-scale and zonally-elongated circulation anomaly pattern, while the other two regimes exhibit synoptic wavetrain pattern with meridionally elongated features. As for the WW regimes, there are some patterns symmetry and anti-symmetry with respect to CW regimes. The WW regimes are characterized by anomalous low pressure and southerlies wind over North America. The first and fourth groups are affected by remote forcing emanating from North Pacific, while the others appear mainly locally forced.

  7. Monitoring strategies of stream phosphorus under contrasting climate-driven flow regimes

    DEFF Research Database (Denmark)

    Goyenola, Guillermo; Meerhoff, Marianna; Teixeira-de Mello, Franco

    2015-01-01

    Climate and hydrology are relevant control factors determining the timing and amount of nutrient losses from land to downstream aquatic systems, in particular of phosphorus (P) from agricultural lands. The main objective of the study was to evaluate the differences in P export patterns and the pe......Climate and hydrology are relevant control factors determining the timing and amount of nutrient losses from land to downstream aquatic systems, in particular of phosphorus (P) from agricultural lands. The main objective of the study was to evaluate the differences in P export patterns...... applied two alternative nutrient sampling programs (high-frequency composite sampling and low-frequency instantaneous-grab sampling) and estimated the contribution derived from point and diffuse sources fitting a source apportionment model. We expected to detect a pattern of higher total and particulate...... program to estimate P exports in flashy streams compared to the less variable streams. We also found signs of interaction between climate/hydrology and land use intensity, in particular in the presence of point sources of P, leading to a bias towards underestimation of P in hydrologically stable streams...

  8. Changes in Stream Water Temperatures in the Chesapeake Bay Region, 1960-2014

    Science.gov (United States)

    This map shows the changes in stream water temperatures in the Chesapeake Bay region from 1960 to 2014. Blue circles represent cooling trends in stream water temperatures, and red circles represent warming trends in stream water temperatures. Data were analyzed by Mike Kolian of EPA in partnership with John Jastram and Karen Rice of the U.S. Geological Survey. For more information: www.epa.gov/climatechange/science/indicators

  9. Local-scale and watershed-scale determinants of summertime urban stream temperatures

    Science.gov (United States)

    Derek B. Booth; Kristin A. Kraseski; C. Rhett. Jackson

    2014-01-01

    The influence of urbanization on the temperature of small streams is widely recognized, but these effects are confounded by the great natural variety of their contributing watersheds. To evaluate the relative importance of local-scale and watershed-scale factors on summer temperatures in urban streams, hundreds of near-instantaneous temperature measurements throughout...

  10. ARIES CATCHMENT UPPER AND MIDDLE COURSE SMALL STREAMS SEASONAL RUNOFF REGIME CHARACTERISTICS

    Directory of Open Access Journals (Sweden)

    CS. HORVATH

    2013-03-01

    Full Text Available The study is based on the processing and interpreting data from 16 gauging stations, of which 10 control catchments smaller than 150 km2 and so reflects more faithfully the local characteristics of the runoff. To highlight the runoff regime features during the year we selected three periods (1950-1967, 1950-2009 and 1970-2009. The geographical features of the central eastern part of the Apuseni Mountains, especially the climatic and geomorphic characteristics, are faithfully reflected in the rivers runoff regime. So, on all rivers the dominant is the spring runoff and the lowest percentage of the total annual average water volume is measured in the winter. Distribution and frequency of the richest (March, April and May and the poorest (January, February, August and September average runoff months vary according to the catchments altitude. The multiannual seasonal and monthly variation of the runoff was highlighted by the coefficients of variation. The study reveals that the rhythmic structure of the runoff regime reflects the local supply, the geological conditions and the reliefs morphological and morphometric characteristics.

  11. Native temperature regime influences soil response to simulated warming

    Science.gov (United States)

    Timothy G. Whitby; Michael D. Madritch

    2013-01-01

    Anthropogenic climate change is expected to increase global temperatures and potentially increase soil carbon (C) mineralization, which could lead to a positive feedback between global warming and soil respiration. However the magnitude and spatial variability of belowground responses to warming are not yet fully understood. Some of the variability may depend...

  12. Method and apparatus for transport, introduction, atomization and excitation of emission spectrum for quantitative analysis of high temperature gas sample streams containing vapor and particulates without degradation of sample stream temperature

    Science.gov (United States)

    Eckels, David E.; Hass, William J.

    1989-05-30

    A sample transport, sample introduction, and flame excitation system for spectrometric analysis of high temperature gas streams which eliminates degradation of the sample stream by condensation losses.

  13. Reconstructing the temperature regime of the Weichselian ice sheet

    International Nuclear Information System (INIS)

    Holmlund, P.

    1997-01-01

    Areas in Sweden are described, where the ice could have been at the pressure melting point during the last ice age. In order to calculate probable degrees of glacial erosion, estimates on the time of ice coverage and the temperature distribution in time are combined data on erosion rates from present day glaciers. An estimate of the extent of ice cover can be made using the proxy temperature record from the Greenland ice cores and a model of the ice sheet. Adding the estimations on climate and ice sheet shape outlined in this contribution, to erosion figures we may conclude that the crucial areas for glaciation erosion are within the mountains and where the present Baltic and the Gulf of Bothnia are situated. At these sites erosion rates of some tens of meters may have occurred. In inland northern Sweden and inland southern Sweden the potential for glacial erosion seems to be small. 14 refs

  14. Reconstructing the temperature regime of the Weichselian ice sheet

    Energy Technology Data Exchange (ETDEWEB)

    Holmlund, P. [Stockholm Univ. (Sweden). Dept. of Physical Geography

    1997-04-01

    Areas in Sweden are described, where the ice could have been at the pressure melting point during the last ice age. In order to calculate probable degrees of glacial erosion, estimates on the time of ice coverage and the temperature distribution in time are combined data on erosion rates from present day glaciers. An estimate of the extent of ice cover can be made using the proxy temperature record from the Greenland ice cores and a model of the ice sheet. Adding the estimations on climate and ice sheet shape outlined in this contribution, to erosion figures we may conclude that the crucial areas for glaciation erosion are within the mountains and where the present Baltic and the Gulf of Bothnia are situated. At these sites erosion rates of some tens of meters may have occurred. In inland northern Sweden and inland southern Sweden the potential for glacial erosion seems to be small. 14 refs.

  15. Temperature response functions introduce high uncertainty in modelled carbon stocks in cold temperature regimes

    Science.gov (United States)

    Portner, H.; Wolf, A.; Bugmann, H.

    2009-04-01

    function of Lloyd&Taylor therefore is an adequate choice to model the temperature dependency of soil organic matter decomposition. The Ticino catchment (300-2300m) in Southern Switzerland was used to study the sensitivity of long-term changes (100 years) in the prediction of carbon storage. The uncertainty in temperature response introduced into the model lead to high uncertainties in long-term soil carbon stocks. Interestingly, the uncertainty increased with decreasing temperature and increasing elevation. The carbon pools in lower elevations (mean annual temperature > 15 °C) turned over faster and little carbon accumulated in the soil. The carbon pools in higher elevations and hence in higher latitudes experiencing colder temperature (mean annual temperature < 15 °C) turned over slower and therefore accumulated more carbon over the simulation period. Therefore, the high elevation soils stored more carbon, but the prediction of the carbon pool size had a much higher uncertainty than the low elevation soils. We concluded that with our model, the predictions of the potential loss of soil carbon in cold temperature regimes is more uncertain than the carbon loss in warmer regions, both due to the higher soil carbon pools, but also due to the higher uncertainty found in our simulations.

  16. Thermal Fluxes and Temperatures in Small Urban Headwater Streams of the BES LTER: Landscape Forest and Impervious Patches and the Importance of Spatial and Temporal Scales

    Science.gov (United States)

    Kim, H.; Belt, K. T.; Welty, C.; Heisler, G.; Pouyat, R. V.; McGuire, M. P.; Stack, W. P.

    2006-05-01

    Water and material fluxes from urban landscape patches to small streams are modulated by extensive "engineered" drainage networks. Small urban headwater catchments are different in character and function from their larger receiving streams because of their extensive, direct connections to impervious surface cover (ISC) and their sometimes buried nature. They need to be studied as unique functional hydrologic units if impacts on biota are to be fully understood. As part of the Baltimore Ecosystem Study LTER project, continuous water temperature data are being collected at 2-minute intervals at over twenty small catchments representing various mixtures of forest and ISC. Suburban stream sites with greater ISC generally have higher summer water temperatures. Suburban catchments with most of their channel drainage contained within storm drain pipes show subdued diurnal variation and cool temperatures, but with very large spikes in summer runoff events. Conversely, high ISC urban piped streams have elevated "baseline" temperatures that stand well above all the other monitoring sites. There is a pronounced upstream-downstream effect; nested small headwater catchments experience more frequent, larger temperature spikes related to runoff events than downstream sites. Also, runoff-initiated temperature elevations at small stream sites unexpectedly last much longer than the storm runoff hydrographs. These observations suggest that for small headwater catchments, urban landscapes not only induce an ambient, "heat island" effect on stream temperatures, but also introduce thermal disturbance regimes and fluxes that are not trivial to aquatic biota.

  17. Spatial patterns of stream temperatures and electric conductivity in a mesoscale catchment

    Science.gov (United States)

    Lieder, Ernestine; Weiler, Markus; Blume, Theresa

    2017-04-01

    Stream temperature and electric conductivity (EC) are both relatively easily measured and can provide valuable information on runoff generation processes and catchment storage.This study investigates the spatial variability of stream temperature and EC in a mesoscale basin. We focus on the mesoscale (sub-catchments and reach scale), and long term (seasonal / annual) stream temperature and EC patterns. Our study basin is the Attert catchment in Luxembourg (288km2), which contains multiple sub-catchments of different geology, topography and land use patterns. We installed 90 stream temperature and EC sensors at sites across the basin in summer 2015. The collected data is complemented by land use and discharge data and an extensive climate data set. Thermal sensitivity was calculated as the slope of daily air temperature-water-temperature regression line and describes the sensitivity of stream temperature to long term environmental change. Amplitude sensitivity was calculated as slope of the daily air and water temperature amplitude regression and describes the short term warming capacity of the stream. We found that groups with similar long term thermal and EC patterns are strongly related to different geological units. The sandstone reaches show the coldest temperatures and lowest annual thermal sensitivity to air temperature. The slate reaches are characterized by comparably low EC and high daily temperature amplitudes and amplitude sensitivity. Furthermore, mean annual temperatures and thermal sensitivities increase exponentially with drainage area, which can be attributed to the accumulation of heat throughout the system. On the reach scale, daily stream temperature fluctuations or sensitivities were strongly influenced by land cover distribution, stream shading and runoff volume. Daily thermal sensitivities were low for headwater streams; peaked for intermediate reaches in the middle of the catchment and then decreased again further downstream with increasing

  18. Observation of a new plasma regime with stationary electron temperature oscillations on Tore Supra

    International Nuclear Information System (INIS)

    Artaud, J.F.; Giruzzi, G.; Imbeaux, F.; Segui, J.L.; Garbet, X.

    2003-01-01

    This document is a copy of the slides presented on the 9. joint US-European Transport Task Force meeting. The first part is devoted to the experimental observations of a new tokamak plasma regime with stationary electron temperature oscillations. The oscillations appear on ECE spontaneously, sometimes associated with a transition to the LHEP regime. The second part presents an interpretation of these oscillations by analogy with a predator-prey system. (A.L.B.)

  19. Effects of wildfire on stream temperatures in the Bitterroot River basin, Montana

    Science.gov (United States)

    Shad K. Mahlum; Lisa A. Eby; Michael K. Young; Chris G. Clancy; Mike Jakober

    2011-01-01

    Wildfire is a common natural disturbance that can influence stream ecosystems. Of particular concern are increases in water temperature during and following fires, but studies of these phenomena are uncommon. We examined effects of wildfires in 2000 on maximum water temperature for a suite of second- to fourth-order streams with a range of burn severities in the...

  20. Stream temperature estimated in situ from thermal-infrared images: best estimate and uncertainty

    International Nuclear Information System (INIS)

    Iezzi, F; Todisco, M T

    2015-01-01

    The paper aims to show a technique to estimate in situ the stream temperature from thermal-infrared images deepening its best estimate and uncertainty. Stream temperature is an important indicator of water quality and nowadays its assessment is important particularly for thermal pollution monitoring in water bodies. Stream temperature changes are especially due to the anthropogenic heat input from urban wastewater and from water used as a coolant by power plants and industrial manufacturers. The stream temperatures assessment using ordinary techniques (e.g. appropriate thermometers) is limited by sparse sampling in space due to a spatial discretization necessarily punctual. Latest and most advanced techniques assess the stream temperature using thermal-infrared remote sensing based on thermal imagers placed usually on aircrafts or using satellite images. These techniques assess only the surface water temperature and they are suitable to detect the temperature of vast water bodies but do not allow a detailed and precise surface water temperature assessment in limited areas of the water body. The technique shown in this research is based on the assessment of thermal-infrared images obtained in situ via portable thermal imager. As in all thermographic techniques, also in this technique, it is possible to estimate only the surface water temperature. A stream with the presence of a discharge of urban wastewater is proposed as case study to validate the technique and to show its application limits. Since the technique analyzes limited areas in extension of the water body, it allows a detailed and precise assessment of the water temperature. In general, the punctual and average stream temperatures are respectively uncorrected and corrected. An appropriate statistical method that minimizes the errors in the average stream temperature is proposed. The correct measurement of this temperature through the assessment of thermal- infrared images obtained in situ via portable

  1. Differences in temperature, organic carbon and oxygen consumption among lowland streams

    DEFF Research Database (Denmark)

    Sand-Jensen, K.; Pedersen, N. L.

    2005-01-01

    1. Temperature, organic carbon and oxygen consumption were measured over a year at 13 sites in four lowlands streams within the same region in North Zealand, Denmark with the objectives of determining: (i) spatial and seasonal differences between open streams, forest streams and streams with or w......1. Temperature, organic carbon and oxygen consumption were measured over a year at 13 sites in four lowlands streams within the same region in North Zealand, Denmark with the objectives of determining: (i) spatial and seasonal differences between open streams, forest streams and streams...... the exponential increase of oxygen consumption rate between 4 and 20 °C averaged 0.121 °C-1 (Q10 of 3.35) in 70 measurements and showed no significant variations between seasons and stream sites or correlations with ambient temperature and organic content. 5. Oxygen consumption rate was enhanced downstream...... at ambient temperature by 30-40% and 80-130%, respectively. Faster consumption of organic matter and dissolved oxygen downstream of point sources should increase the likelihood of oxygen stress of the stream biota and lead to the export of less organic matter but more mineralised nutrients to the coastal...

  2. Comparing stream-specific to generalized temperature models to guide salmonid management in a changing climate

    Science.gov (United States)

    Andrew K. Carlson,; William W. Taylor,; Hartikainen, Kelsey M.; Dana M. Infante,; Beard, Douglas; Lynch, Abigail

    2017-01-01

    Global climate change is predicted to increase air and stream temperatures and alter thermal habitat suitability for growth and survival of coldwater fishes, including brook charr (Salvelinus fontinalis), brown trout (Salmo trutta), and rainbow trout (Oncorhynchus mykiss). In a changing climate, accurate stream temperature modeling is increasingly important for sustainable salmonid management throughout the world. However, finite resource availability (e.g. funding, personnel) drives a tradeoff between thermal model accuracy and efficiency (i.e. cost-effective applicability at management-relevant spatial extents). Using different projected climate change scenarios, we compared the accuracy and efficiency of stream-specific and generalized (i.e. region-specific) temperature models for coldwater salmonids within and outside the State of Michigan, USA, a region with long-term stream temperature data and productive coldwater fisheries. Projected stream temperature warming between 2016 and 2056 ranged from 0.1 to 3.8 °C in groundwater-dominated streams and 0.2–6.8 °C in surface-runoff dominated systems in the State of Michigan. Despite their generally lower accuracy in predicting exact stream temperatures, generalized models accurately projected salmonid thermal habitat suitability in 82% of groundwater-dominated streams, including those with brook charr (80% accuracy), brown trout (89% accuracy), and rainbow trout (75% accuracy). In contrast, generalized models predicted thermal habitat suitability in runoff-dominated streams with much lower accuracy (54%). These results suggest that, amidst climate change and constraints in resource availability, generalized models are appropriate to forecast thermal conditions in groundwater-dominated streams within and outside Michigan and inform regional-level salmonid management strategies that are practical for coldwater fisheries managers, policy makers, and the public. We recommend fisheries professionals reserve resource

  3. Similarities and differences in dissolved organic matter response in two headwater streams under contrasted hydro-climatic regimes

    Science.gov (United States)

    Butturini, Andrea; Guarch, Alba; Battin, Tom

    2017-04-01

    Dissolved organic matter (DOM) concentration and properties in headwater streams are strongly shaped by hydrology. Besides the direct relationship with storms and high flows, seasonal variability of base flow also influences DOM variability. This study focuses on identifying the singularities and similarities in DOM - discharge relationships between an intermittent Mediterranean stream (Fuirosos) and a perennial Alpine stream (Oberer Seebach). Oberer Seebach had a higher discharge mean, but Fuirosos had a higher variability in flow and in magnitude of storm events. During three years we performed an intensive sampling that allows us to satisfactorily capture abrupt and extreme storms. We analysed dissolved organic carbon concentration (DOC) and optical properties of DOM and we calculated the specific ultraviolet absorbance (SUVA), the spectral slopes ratio (SR), the fluorescence index (FI), the biological index (BIX) and the humification index (HIX). DOM in Fuirosos was significantly more concentrated than in Oberer Seebach, and more terrigenous (lower FI), more degraded (lower BIX), more aromatic (higher SUVA) and more humificated (higher HIX). Most of the DOM properties showed a clear relationship with discharge and the sign of the global response was identical in both streams. However, discharge was a more robust predictor of DOM variability in Oberer Seebach than in Fuirosos. In fact, low flow and rewetting periods in Fuirosos introduced considerable dispersion in the relationship. During snowmelt in Oberer Seebach the sensitivity to discharge also decreased (DOC and BIX) or disappeared (SR, FI and HIX). The magnitude of the storm events (DQ) in Fuirosos significantly drove the changes in DOC, FI, BIX and SUVA. This suggests that the flushing/dilution patterns were essentially associated to the occurrence of storm episodes in Fuirosos. In contrast, in Oberer Seebach all DOM qualitative properties were unrelated to DQ and it significantly explained only the

  4. Simultaneous determination of reference free-stream temperature and convective heat transfer coefficients

    International Nuclear Information System (INIS)

    Jeong, Gi Ho; Song, Ki Bum; Kim, Kui Soon

    2001-01-01

    This paper deals with the development of a new method that can obtain heat transfer coefficient and reference free stream temperature simultaneously. The method is based on transient heat transfer experiments using two narrow-band TLCs. The method is validated through error analysis in terms of the random uncertainties in the measured temperatures. It is shown how the uncertainties in heat transfer coefficient and free stream temperature can be reduced. The general method described in this paper is applicable to many heat transfer models with unknown free stream temperature

  5. Ground-based thermal imaging of stream surface temperatures: Technique and evaluation

    Science.gov (United States)

    Bonar, Scott A.; Petre, Sally J.

    2015-01-01

    We evaluated a ground-based handheld thermal imaging system for measuring water temperatures using data from eight southwestern USA streams and rivers. We found handheld thermal imagers could provide considerably more spatial information on water temperature (for our unit one image = 19,600 individual temperature measurements) than traditional methods could supply without a prohibitive amount of effort. Furthermore, they could provide measurements of stream surface temperature almost instantaneously compared with most traditional handheld thermometers (e.g., >20 s/reading). Spatial temperature analysis is important for measurement of subtle temperature differences across waterways, and identification of warm and cold groundwater inputs. Handheld thermal imaging is less expensive and equipment intensive than airborne thermal imaging methods and is useful under riparian canopies. Disadvantages of handheld thermal imagers include their current higher expense than thermometers, their susceptibility to interference when used incorrectly, and their slightly lower accuracy than traditional temperature measurement methods. Thermal imagers can only measure surface temperature, but this usually corresponds to subsurface temperatures in well-mixed streams and rivers. Using thermal imaging in select applications, such as where spatial investigations of water temperature are needed, or in conjunction with stationary temperature data loggers or handheld electronic or liquid-in-glass thermometers to characterize stream temperatures by both time and space, could provide valuable information on stream temperature dynamics. These tools will become increasingly important to fisheries biologists as costs continue to decline.

  6. Regime transitions in near-surface temperature inversions : a conceptual model

    NARCIS (Netherlands)

    van de Wiel, B.J.H.; Vignon, E.; Baas, P.; Bosveld, F.C.; de Roode, S.R.; Moene, A.F.; Genthon, C.; van der Linden, Steven J.A.; van Hooft, J. Antoon; van Hooijdonk, I.G.S.

    2017-01-01

    A conceptual model is used in combination with observational analysis to understand regime transitions of near-surface temperature inversions at night as well as in Arctic conditions. The model combines a surface energy budget with a bulk parameterization for turbulent heat transport. Energy fluxes

  7. Optimal ranking regime analysis of intra- to multidecadal U.S. climate variability. Part I: Temperature

    Science.gov (United States)

    The Optimal Ranking Regime (ORR) method was used to identify intra- to multi-decadal (IMD) time windows containing significant ranking sequences in U.S. climate division temperature data. The simplicity of the ORR procedure’s output – a time series’ most significant non-overlapping periods of high o...

  8. Growth and survival of Apache Trout under static and fluctuating temperature regimes

    Science.gov (United States)

    Recsetar, Matthew S.; Bonar, Scott A.; Feuerbacher, Olin

    2014-01-01

    Increasing stream temperatures have important implications for arid-region fishes. Little is known about effects of high water temperatures that fluctuate over extended periods on Apache Trout Oncorhynchus gilae apache, a federally threatened species of southwestern USA streams. We compared survival and growth of juvenile Apache Trout held for 30 d in static temperatures (16, 19, 22, 25, and 28°C) and fluctuating diel temperatures (±3°C from 16, 19, 22 and 25°C midpoints and ±6°C from 19°C and 22°C midpoints). Lethal temperature for 50% (LT50) of the Apache Trout under static temperatures (mean [SD] = 22.8 [0.6]°C) was similar to that of ±3°C diel temperature fluctuations (23.1 [0.1]°C). Mean LT50 for the midpoint of the ±6°C fluctuations could not be calculated because survival in the two treatments (19 ± 6°C and 22 ± 6°C) was not below 50%; however, it probably was also between 22°C and 25°C because the upper limb of a ±6°C fluctuation on a 25°C midpoint is above critical thermal maximum for Apache Trout (28.5–30.4°C). Growth decreased as temperatures approached the LT50. Apache Trout can survive short-term exposure to water temperatures with daily maxima that remain below 25°C and midpoint diel temperatures below 22°C. However, median summer stream temperatures must remain below 19°C for best growth and even lower if daily fluctuations are high (≥12°C).

  9. Influence of diurnal variations in stream temperature on streamflow loss and groundwater recharge

    Science.gov (United States)

    Constantz, Jim; Thomas, Carole L.; Zellweger, Gary W.

    1994-01-01

    We demonstrate that for losing reaches with significant diurnal variations in stream temperature, the effect of stream temperature on streambed seepage is a major factor contributing to reduced afternoon streamflows. An explanation is based on the effect of stream temperature on the hydraulic conductivity of the streambed, which can be expected to double in the 0° to 25°C temperature range. Results are presented for field experiments in which stream discharge and temperature were continuously measured for several days over losing reaches at St. Kevin Gulch, Colorado, and Tijeras Arroyo, New Mexico. At St. Kevin Gulch in July 1991, the diurnal stream temperature in the 160-m study reach ranged from about 4° to 18°C, discharges ranged from 10 to 18 L/s, and streamflow loss in the study reach ranged from 2.7 to 3.7 L/s. On the basis of measured stream temperature variations, the predicted change in conductivity was about 38%; the measured change in stream loss was about 26%, suggesting that streambed temperature varied less than the stream temperature. At Tijeras Arroyo in May 1992, diurnal stream temperature in the 655-m study reach ranged from about 10° to 25°C and discharge ranged from 25 to 55 L/s. Streamflow loss was converted to infiltration rates by factoring in the changing stream reach surface area and streamflow losses due to evaporation rates as measured in a hemispherical evaporation chamber. Infiltration rates ranged from about 0.7 to 2.0 m/d, depending on time and location. Based on measured stream temperature variations, the predicted change in conductivity was 29%; the measured change in infiltration was also about 27%. This suggests that high infiltration rates cause rapid convection of heat to the streambed. Evapotranspiration losses were estimated for the reach and adjacent flood plain within the arroyo. On the basis of these estimates, only about 5% of flow loss was consumed via stream evaporation and stream-side evapotranspiration

  10. A hierarchical model of daily stream temperature using air-water temperature synchronization, autocorrelation, and time lags

    Directory of Open Access Journals (Sweden)

    Benjamin H. Letcher

    2016-02-01

    Full Text Available Water temperature is a primary driver of stream ecosystems and commonly forms the basis of stream classifications. Robust models of stream temperature are critical as the climate changes, but estimating daily stream temperature poses several important challenges. We developed a statistical model that accounts for many challenges that can make stream temperature estimation difficult. Our model identifies the yearly period when air and water temperature are synchronized, accommodates hysteresis, incorporates time lags, deals with missing data and autocorrelation and can include external drivers. In a small stream network, the model performed well (RMSE = 0.59°C, identified a clear warming trend (0.63 °C decade−1 and a widening of the synchronized period (29 d decade−1. We also carefully evaluated how missing data influenced predictions. Missing data within a year had a small effect on performance (∼0.05% average drop in RMSE with 10% fewer days with data. Missing all data for a year decreased performance (∼0.6 °C jump in RMSE, but this decrease was moderated when data were available from other streams in the network.

  11. A novel approach to analysing the regimes of temporary streams in relation to their controls on the composition and structure of aquatic biota

    Science.gov (United States)

    Gallart, F.; Prat, N.; García-Roger, E. M.; Latron, J.; Rieradevall, M.; Llorens, P.; Barberá, G. G.; Brito, D.; De Girolamo, A. M.; Lo Porto, A.; Buffagni, A.; Erba, S.; Neves, R.; Nikolaidis, N. P.; Perrin, J. L.; Querner, E. P.; Quiñonero, J. M.; Tournoud, M. G.; Tzoraki, O.; Skoulikidis, N.; Gómez, R.; Sánchez-Montoya, M. M.; Froebrich, J.

    2012-09-01

    Temporary streams are those water courses that undergo the recurrent cessation of flow or the complete drying of their channel. The structure and composition of biological communities in temporary stream reaches are strongly dependent on the temporal changes of the aquatic habitats determined by the hydrological conditions. Therefore, the structural and functional characteristics of aquatic fauna to assess the ecological quality of a temporary stream reach cannot be used without taking into account the controls imposed by the hydrological regime. This paper develops methods for analysing temporary streams' aquatic regimes, based on the definition of six aquatic states that summarize the transient sets of mesohabitats occurring on a given reach at a particular moment, depending on the hydrological conditions: Hyperrheic, Eurheic, Oligorheic, Arheic, Hyporheic and Edaphic. When the hydrological conditions lead to a change in the aquatic state, the structure and composition of the aquatic community changes according to the new set of available habitats. We used the water discharge records from gauging stations or simulations with rainfall-runoff models to infer the temporal patterns of occurrence of these states in the Aquatic States Frequency Graph we developed. The visual analysis of this graph is complemented by the development of two metrics which describe the permanence of flow and the seasonal predictability of zero flow periods. Finally, a classification of temporary streams in four aquatic regimes in terms of their influence over the development of aquatic life is updated from the existing classifications, with stream aquatic regimes defined as Permanent, Temporary-pools, Temporary-dry and Episodic. While aquatic regimes describe the long-term overall variability of the hydrological conditions of the river section and have been used for many years by hydrologists and ecologists, aquatic states describe the availability of mesohabitats in given periods that

  12. The paradox of cooling streams in a warming world: Regional climate trends do not parallel variable local trends in stream temperature in the Pacific continental United States

    Science.gov (United States)

    Arismendi, Ivan; Johnson, Sherri; Dunham, Jason B.; Haggerty, Roy; Hockman-Wert, David

    2012-01-01

    Temperature is a fundamentally important driver of ecosystem processes in streams. Recent warming of terrestrial climates around the globe has motivated concern about consequent increases in stream temperature. More specifically, observed trends of increasing air temperature and declining stream flow are widely believed to result in corresponding increases in stream temperature. Here, we examined the evidence for this using long-term stream temperature data from minimally and highly human-impacted sites located across the Pacific continental United States. Based on hypothesized climate impacts, we predicted that we should find warming trends in the maximum, mean and minimum temperatures, as well as increasing variability over time. These predictions were not fully realized. Warming trends were most prevalent in a small subset of locations with longer time series beginning in the 1950s. More recent series of observations (1987-2009) exhibited fewer warming trends and more cooling trends in both minimally and highly human-influenced systems. Trends in variability were much less evident, regardless of the length of time series. Based on these findings, we conclude that our perspective of climate impacts on stream temperatures is clouded considerably by a lack of long-termdata on minimally impacted streams, and biased spatio-temporal representation of existing time series. Overall our results highlight the need to develop more mechanistic, process-based understanding of linkages between climate change, other human impacts and stream temperature, and to deploy sensor networks that will provide better information on trends in stream temperatures in the future.

  13. Headwater stream temperature: interpreting response after logging, with and without riparian buffers, Washington, USA

    Science.gov (United States)

    Jack E. Janisch; Steven M. Wondzell; William J. Ehinger

    2012-01-01

    We examined stream temperature response to forest harvest in small forested headwater catchments in western Washington, USA over a seven year period (2002-2008). These streams have very low discharge in late summer and many become spatially intermittent. We used a before-after, control-impact (BACl) study design to contrast the effect of clearcut logging with two...

  14. Streamflow and nutrient dependence of temperature effects on dissolved oxygen in low-order forest streams

    Science.gov (United States)

    April Mason; Y. Jun Xu; Philip Saksa; Adrienne Viosca; Johnny M. Grace; John Beebe; Richard Stich

    2007-01-01

    Low dissolved oxygen (DO) concentrations in streams can be linked to both natural conditions and human activities. In Louisiana, natural stream conditions such as low flow, high temperature and high organic content, often result in DO levels already below current water quality criteria, making it difficult to develop standards for Best Management Practices (BMPs)....

  15. Dating base flow in streams using dissolved gases and diurnal temperature changes

    Science.gov (United States)

    Sanford, Ward E.; Casile, Gerolamo C.; Haase, Karl B.

    2015-01-01

    A method is presented for using dissolved CFCs or SF6 to estimate the apparent age of stream base flow by indirectly estimating the mean concentration of the tracer in the inflowing groundwater. The mean value is estimated simultaneously with the mean residence times of the gas and water in the stream by sampling the stream for one or both age tracers, along with dissolved nitrogen and argon at a single location over a period of approximately 12–14 h. The data are fitted to an equation representing the temporal in-stream gas exchange as it responds to the diurnal temperature fluctuation. The efficacy of the method is demonstrated by collecting and analyzing samples at six different stream locations across parts of northern Virginia, USA. The studied streams drain watersheds with areas of between 2 and 122 km2 during periods when the diurnal stream temperature ranged between 2 and 5°C. The method has the advantage of estimating the mean groundwater residence time of discharge from the watershed to the stream without the need for the collection of groundwater infiltrating to streambeds or local groundwater sampled from shallow observation wells near the stream.

  16. New England observed and predicted Julian day of maximum growing season stream/river temperature points

    Data.gov (United States)

    U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted Julian day of maximum growing season stream/river temperatures in New England based on a spatial...

  17. New England observed and predicted growing season maximum stream/river temperature points

    Data.gov (United States)

    U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted growing season maximum stream/river temperatures in New England based on a spatial statistical...

  18. New England observed and predicted median July stream/river temperature points

    Data.gov (United States)

    U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted median July stream/river temperatures in New England based on a spatial statistical network...

  19. New England observed and predicted July stream/river temperature daily range points

    Data.gov (United States)

    U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted July stream/river temperature daily ranges in New England based on a spatial statistical network...

  20. New England observed and predicted August stream/river temperature daily range points

    Data.gov (United States)

    U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted August stream/river temperature daily ranges in New England based on a spatial statistical...

  1. New England observed and predicted median August stream/river temperature points

    Data.gov (United States)

    U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted median August stream/river temperatures in New England based on a spatial statistical network...

  2. New England observed and predicted August stream/river temperature maximum daily rate of change points

    Data.gov (United States)

    U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted August stream/river temperature maximum negative rate of change in New England based on a...

  3. Effect of inhomogeneous temperature fields on acoustic streaming structures in resonators.

    Science.gov (United States)

    Červenka, Milan; Bednařík, Michal

    2017-06-01

    Acoustic streaming in 2D rectangular resonant channels filled with a fluid with a spatial temperature distribution is studied within this work. An inertial force is assumed for driving the acoustic field; the temperature inhomogeneity is introduced by resonator walls with prescribed temperature distribution. The method of successive approximations is employed to derive linear equations for calculation of primary acoustic and time-averaged secondary fields including the streaming velocity. The model equations have a standard form which allows their numerical integration using a universal solver; in this case, COMSOL Multiphysics was employed. The numerical results show that fluid temperature variations in the direction perpendicular to the resonator axis influence strongly the streaming field if the ratio of the channel width and the viscous boundary layer thickness is big enough; the streaming in the Rayleigh vortices can be supported as well as opposed, which can ultimately lead to the appearance of additional vortices.

  4. Effects of Forecasted Climate Change on Stream Temperatures in the Nooksack River Basin

    Science.gov (United States)

    Truitt, S. E.; Mitchell, R. J.; Yearsley, J. R.; Grah, O. J.

    2017-12-01

    The Nooksack River in northwest Washington State provides valuable habitat for endangered salmon species, as such it is critical to understand how stream temperatures will be affected by forecasted climate change. The Middle and North Forks basins of the Nooksack are high-relief and glaciated, whereas the South Fork is a lower relief rain and snow dominated basin. Due to a moderate Pacific maritime climate, snowpack in the basins is sensitive to temperature increases. Previous modeling studies in the upper Nooksack basins indicate a reduction in snowpack and spring runoff, and a recession of glaciers into the 21st century. How stream temperatures will respond to these changes is unknown. We use the Distributed Hydrology Soil Vegetation Model (DHSVM) coupled with a glacier dynamics model and the River Basin Model (RBM) to simulate hydrology and stream temperature from present to the year 2100. We calibrate the DHSVM and RBM to the three forks in the upper 1550 km2 of the Nooksack basin, which contain an estimated 3400 hectares of glacial ice. We employ observed stream-temperature data collected over the past decade and hydrologic data from the four USGS streamflow monitoring sites within the basin and observed gridded climate data developed by Linveh et al. (2013). Field work was conducted in the summer of 2016 to determine stream morphology, discharge, and stream temperatures at a number of stream segments for the RBM calibration. We simulate forecast climate change impacts, using gridded daily downscaled data from global climate models of the CMIP5 with RCP4.5 and RCP8.5 forcing scenarios developed using the multivariate adaptive constructed analogs method (MACA; Abatzoglou and Brown, 2011). Simulation results project a trending increase in stream temperature as a result of lower snowmelt and higher air temperatures into the 21st century, especially in the lower relief, unglaciated South Fork basin.

  5. Analysis of stream temperature and heat budget in an urban river under strong anthropogenic influences

    Science.gov (United States)

    Xin, Zhuohang; Kinouchi, Tsuyoshi

    2013-05-01

    Stream temperature variations of the Tama River, which runs through highly urbanized areas of Tokyo, were studied in relation to anthropogenic impacts, including wastewater effluents, dam release and water withdrawal. Both long-term and longitudinal changes in stream temperature were identified and the influences of stream flow rate, temperature and volume of wastewater effluents and air temperature were investigated. Water and heat budget analyses were also conducted for several segments of the mainstream to clarify the relative impacts from natural and anthropogenic factors. Stream temperatures in the winter season significantly increased over the past 20 years at sites affected by intensive and warm effluents from wastewater treatment plants (WWTPs) located along the mainstream. In the summer season, a larger stream temperature increase was identified in the upstream reaches, which was attributable to the decreased flow rate due to water withdrawal. The relationship between air and stream temperatures indicated that stream temperatures at the upstream site were likely to be affected by a dam release, while temperatures in the downstream reaches have deviated more from air temperatures in recent years, probably due to the increased impacts of effluents from WWTPs. Results of the water and heat budget analyses indicated that the largest contributions to water and heat gains were attributable to wastewater effluents, while other factors such as groundwater recharge and water withdrawal were found to behave as energy sinks, especially in summer. The inflow from tributaries worked to reduce the impacts of dam release and the heat exchanges at the air-water interface contributed less to heat budgets in both winter and summer seasons for all river segments.

  6. Geothermal regime of Tarim basin, NW China: insights from borehole temperature logging

    Science.gov (United States)

    Liu, S.; Lei, X.

    2013-12-01

    Geothermal regime of sedimentary basin is vital for understanding basin (de)formation process, hydrocarbon generation status and assessing the resource potential. Located at the Precambrian craton block, the Tarim basin is the largest intermountain basin in China, which is also the ongoing target of oil and gas exploration. Previous knowledge of thermal regime of this basin is from limited oil exploration borehole testing temperature, the inherent deficiency of data of this type makes accurate understanding of its thermal regime impossible. Here we reported our latest steady temperature logging results in this basin and analyze its thermal regime as well. In this study, 10 temperature loggings are conducted in the northern Tarim basin where the major oil and gas fields are discovered. All the boreholes for temperature logging are non-production wells and are shut in at least more than 2~3 years, ensuring the temperature equilibrium after drilling. The derived geothermal gradient varies from 20.2 to 26.1 degree/km, with a mean of 22.0 degree/km. However, some previous reported gradients in this area are obviously lower than our results; for example, the previous gradient of THN2 well is 13.2 degree/km but 23.2 degree/km in this study, and not enough equilibrium time in previous logging accounts for this discrepancy. More important, it is found that high gradients usually occur in the gas field and the gradients of the gas fields are larger than those in other oil fields, indicating higher thermal regime in gas field. The cause of this phenomenon is unclear, and the upward migration of hot fluid along fault conduit is speculated as the possible mechanism for this high geothermal anomaly in the oil and gas fields. Combined with measured thermal conductivity data, 10 new heat flow values are also achieved, and the heat flow of the Tarim basin is between 38mW/m2 and 52mW/m2, with a mean of 43 mW/m2. This relatively low heat flow is coincident with that of typical

  7. Cluster analysis of midlatitude oceanic cloud regimes: mean properties and temperature sensitivity

    Directory of Open Access Journals (Sweden)

    N. D. Gordon

    2010-07-01

    Full Text Available Clouds play an important role in the climate system by reducing the amount of shortwave radiation reaching the surface and the amount of longwave radiation escaping to space. Accurate simulation of clouds in computer models remains elusive, however, pointing to a lack of understanding of the connection between large-scale dynamics and cloud properties. This study uses a k-means clustering algorithm to group 21 years of satellite cloud data over midlatitude oceans into seven clusters, and demonstrates that the cloud clusters are associated with distinct large-scale dynamical conditions. Three clusters correspond to low-level cloud regimes with different cloud fraction and cumuliform or stratiform characteristics, but all occur under large-scale descent and a relatively dry free troposphere. Three clusters correspond to vertically extensive cloud regimes with tops in the middle or upper troposphere, and they differ according to the strength of large-scale ascent and enhancement of tropospheric temperature and humidity. The final cluster is associated with a lower troposphere that is dry and an upper troposphere that is moist and experiencing weak ascent and horizontal moist advection.

    Since the present balance of reflection of shortwave and absorption of longwave radiation by clouds could change as the atmosphere warms from increasing anthropogenic greenhouse gases, we must also better understand how increasing temperature modifies cloud and radiative properties. We therefore undertake an observational analysis of how midlatitude oceanic clouds change with temperature when dynamical processes are held constant (i.e., partial derivative with respect to temperature. For each of the seven cloud regimes, we examine the difference in cloud and radiative properties between warm and cold subsets. To avoid misinterpreting a cloud response to large-scale dynamical forcing as a cloud response to temperature, we require horizontal and vertical

  8. DETERMINATION ANALYSIS OF TEMPERATURE REGIMES, FUNCTIONAL CHARACTERISTICS AND SLIDING CURVES OF A HYDRODYNAMIC CLUTCH

    Directory of Open Access Journals (Sweden)

    Božidar V Krstić

    2010-01-01

    Full Text Available Analysis of output quality of power transmitters is possible in position when characteristics are determined earlier. This is the reason why we focused on determination of these characteristics for a concrete power hydro-transmitter. This means that the investigation task primarily consisted of determination of functional characteristics, defining of the sliding curves and temperature regimes of a concrete hydrodynamic clutch. Results of velocity and pressure field investigations in the working space of this clutch, obtained by use of the same test setup, are the basis for determination and analysis of the functional characteristics, sliding curves and temperature regimes. In this work we also analyzed function of the hydrodynamic transmitter in assembly with an internal combustion engine, as well as a process of acceleration and deceleration of a vehicle with this assembly in it.

  9. Plasma self-oscillations in the temperature-limited current regime of a hot cathode discharge

    International Nuclear Information System (INIS)

    Arnas Capeau, C.; Bachet, G.; Doveil, F.

    1995-01-01

    Experimental observations of self-oscillations occurring in the so-called ''temperature-limited current regime'' of a hot cathode discharge are presented. Their frequency and amplitude are strongly dependent on the discharge parameters. The scaling laws of their variation and an example of a period-doubling route to chaos are reported. A two probe experiment showing that the plasma behavior is closely related to the hot cathode sheath stability is also reported. copyright 1995 American Institute of Physics

  10. Temperature Response of a Small Mountain Stream to Thunderstorm Cloud-Cover: Application of DTS Fiber-Optic Temperature Sensing

    Science.gov (United States)

    Thayer, D.; Klatt, A. L.; Miller, S. N.; Ohara, N.

    2014-12-01

    From a hydrologic point of view, the critical zone in alpine areas contains the first interaction of living systems with water which will flow to streams and rivers that sustain lowland biomes and human civilization. A key to understanding critical zone functions is understanding the flow of energy, and we can measure temperature as a way of looking at energy transfer between related systems. In this study we installed a Distributed Temperature Sensor (DTS) and fiber-optic cable in a zero-order stream at 9,000 ft in the Medicine Bow National Forest in southern Wyoming. We measured the temperature of the stream for 17 days from June 29 to July 16; the first 12 days were mostly sunny with occasional afternoon storms, and the last 5 experienced powerful, long-lasting storms for much of the day. The DTS measurements show a seasonal warming trend of both minimum and maximum stream temperature for the first 12 days, followed by a distinct cooling trend for the five days that experienced heavy storm activity. To gain insights into the timing and mechanisms of energy flow through the critical zone systems, we analyzed the timing of stream temperature change relative to solar short-wave radiation, and compared the stream temperature temporal response to the temporal response of soil temperature adjacent to the stream. Since convective thunderstorms are a dominant summer weather pattern in sub-alpine regions in the Rocky Mountains, this study gives us further insight into interactions of critical zone processes and weather in mountain ecosystems.

  11. InSTREAM: the individual-based stream trout research and environmental assessment model

    Science.gov (United States)

    Steven F. Railsback; Bret C. Harvey; Stephen K. Jackson; Roland H. Lamberson

    2009-01-01

    This report documents Version 4.2 of InSTREAM, including its formulation, software, and application to research and management problems. InSTREAM is a simulation model designed to understand how stream and river salmonid populations respond to habitat alteration, including altered flow, temperature, and turbidity regimes and changes in channel morphology. The model...

  12. Temperature and moisture regimes in the Enterprise Forest, 1970--1973

    International Nuclear Information System (INIS)

    Crow, T.R.; Buech, R.R.

    1977-01-01

    Within the Enterprise Radiation Forest, measurements of ambient air temperature, humidity, and precipitation were taken from 1970 through 1973. Temperature and moisture stresses that could alter the responses of organisms to gamma radiation were not evident during irradiation (1972) or during the recovery year 1973. Changes in microclimatic regimes as a result of the destruction of vegetation by gamma radiation were also assessed. Although differences in temperature and vapor-pressure deficit (VPD) were small when considering monthly means, mean maximum and mean minimum temperature and standardized plots of mean daily temperature and mean daily VPD indicated greater extremes in the newly created open environment than under the forest canopy. These relationships parallel those reported in comparisons of open environments to forested environments

  13. Developing an Effective Model for Predicting Spatially and Temporally Continuous Stream Temperatures from Remotely Sensed Land Surface Temperatures

    Directory of Open Access Journals (Sweden)

    Kristina M. McNyset

    2015-12-01

    Full Text Available Although water temperature is important to stream biota, it is difficult to collect in a spatially and temporally continuous fashion. We used remotely-sensed Land Surface Temperature (LST data to estimate mean daily stream temperature for every confluence-to-confluence reach in the John Day River, OR, USA for a ten year period. Models were built at three spatial scales: site-specific, subwatershed, and basin-wide. Model quality was assessed using jackknife and cross-validation. Model metrics for linear regressions of the predicted vs. observed data across all sites and years: site-specific r2 = 0.95, Root Mean Squared Error (RMSE = 1.25 °C; subwatershed r2 = 0.88, RMSE = 2.02 °C; and basin-wide r2 = 0.87, RMSE = 2.12 °C. Similar analyses were conducted using 2012 eight-day composite LST and eight-day mean stream temperature in five watersheds in the interior Columbia River basin. Mean model metrics across all basins: r2 = 0.91, RMSE = 1.29 °C. Sensitivity analyses indicated accurate basin-wide models can be parameterized using data from as few as four temperature logger sites. This approach generates robust estimates of stream temperature through time for broad spatial regions for which there is only spatially and temporally patchy observational data, and may be useful for managers and researchers interested in stream biota.

  14. Computational characterization of ignition regimes in a syngas/air mixture with temperature fluctuations

    KAUST Repository

    Pal, Pinaki

    2016-07-27

    Auto-ignition characteristics of compositionally homogeneous reactant mixtures in the presence of thermal non-uniformities and turbulent velocity fluctuations were computationally investigated. The main objectives were to quantify the observed ignition characteristics and numerically validate the theory of the turbulent ignition regime diagram recently proposed by Im et al. 2015 [29] that provides a framework to predict ignition behavior . a priori based on the thermo-chemical properties of the reactant mixture and initial flow and scalar field conditions. Ignition regimes were classified into three categories: . weak (where deflagration is the dominant mode of fuel consumption), . reaction-dominant strong, and . mixing-dominant strong (where volumetric ignition is the dominant mode of fuel consumption). Two-dimensional (2D) direct numerical simulations (DNS) of auto-ignition in a lean syngas/air mixture with uniform mixture composition at high-pressure, low-temperature conditions were performed in a fixed volume. The initial conditions considered two-dimensional isotropic velocity spectrums, temperature fluctuations and localized thermal hot spots. A number of parametric test cases, by varying the characteristic turbulent Damköhler and Reynolds numbers, were investigated. The evolution of the auto-ignition phenomena, pressure rise, and heat release rate were analyzed. In addition, combustion mode analysis based on front propagation speed and computational singular perturbation (CSP) was applied to characterize the auto-ignition phenomena. All results supported that the observed ignition behaviors were consistent with the expected ignition regimes predicted by the theory of the regime diagram. This work provides new high-fidelity data on syngas ignition characteristics over a broad range of conditions and demonstrates that the regime diagram serves as a predictive guidance in the understanding of various physical and chemical mechanisms controlling auto

  15. The development of stream temperature model in a mountainous river of Taiwan.

    Science.gov (United States)

    Tung, Ching-Pin; Lee, Tsung-Yu; Huang, Jr-Chuang; Perng, Po-Wen; Kao, Shih-Ji; Liao, Lin-Yen

    2014-11-01

    Formosan landlocked salmon is an endangered species and is very sensitive to stream temperature change. This study attempts to improve a former stream temperature model (STM) which was developed for the salmon's habitat to simulate stream temperature more realistically. Two modules, solar radiation modification (SRM) and surface/subsurface runoff mixing (RM), were incorporated to overcome the limitation of STM designed only for clear-sky conditions. It was found that daily temperature difference is related to cloud cover and can be used to adjust the effects of cloud cover on incident solar radiation to the ground level. The modified model (STM + SRM) improved the simulation during a baseflow period in both winter and summer with the Nash-Sutcliffe efficiency coefficient improved from 0.37 (by STM only) to 0.71 for the winter and from -0.18 to 0.70 for the summer. On the days with surface/subsurface runoff, the incorporation of the two new modules together (STM + SRM + RM) improved the Nash-Sutcliffe efficiency coefficient from 0.00 to 0.65 and from 0.29 to 0.83 in the winter and the summer, respectively. Meanwhile, the contributions of major thermal sources to stream temperature changes were identified. Groundwater is a major controlling factor for regulating seasonal changes of stream temperature while solar radiation is the primary factor controlling daily stream temperature variations. This study advanced our understanding on short-term stream temperature variation, which could be useful for the authorities to restore the salmon's habitat.

  16. Stream water temperature limits occupancy of salamanders in mid-Atlantic protected areas

    Science.gov (United States)

    Grant, Evan H. Campbell; Wiewel, Amber N. M.; Rice, Karen C.

    2014-01-01

    Stream ecosystems are particularly sensitive to urbanization, and tolerance of water-quality parameters is likely important to population persistence of stream salamanders. Forecasted climate and landscape changes may lead to significant changes in stream flow, chemical composition, and temperatures in coming decades. Protected areas where landscape alterations are minimized will therefore become increasingly important for salamander populations. We surveyed 29 streams at three national parks in the highly urbanized greater metropolitan area of Washington, DC. We investigated relationships among water-quality variables and occupancy of three species of stream salamanders (Desmognathus fuscus, Eurycea bislineata, and Pseudotriton ruber). With the use of a set of site-occupancy models, and accounting for imperfect detection, we found that stream-water temperature limits salamander occupancy. There was substantial uncertainty about the effects of the other water-quality variables, although both specific conductance (SC) and pH were included in competitive models. Our estimates of occupancy suggest that temperature, SC, and pH have some importance in structuring stream salamander distribution.

  17. Fatigue crack growth behavior of RAFM steel in Paris and threshold regimes at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Babu, M. Nani; Sasikala, G., E-mail: gsasi@igcar.gov.in; Dutt, B. Shashank; Venugopal, S.; Bhaduri, A.K.; Jayakumar, T.

    2014-04-01

    Fatigue crack growth (FCG) behavior of a reduced activation ferritic martensitic (indigenous RAFM) steel has been evaluated at 300, 653 and 823 K in Paris and threshold regimes. The effect of temperature on threshold stress intensity factor range and associated crack closure mechanisms is highlighted. The FCG results were compared with those for EUROFER 97. Further, crack tip effective stress intensity factor ranges (ΔK{sub tip,eff}) have been evaluated by taking crack tip shielding into account in order to examine the effect of temperature on true intrinsic FCG behavior.

  18. Increasing synchrony of high temperature and low flow in western North American streams: Double trouble for coldwater biota?

    Science.gov (United States)

    Ivan Arismendi; Mohammad Safeeq; Sherri L. Johnson; Jason B Dunham; Roy Haggerty

    2013-01-01

    Flow and temperature are strongly linked environmental factors driving ecosystem processes in streams. Stream temperature maxima (Tmax_w) and stream flow minima (Qmin) can create periods of stress for aquatic organisms. In mountainous areas, such as western North America, recent shifts toward an earlier spring peak flow and...

  19. Rheology of serpentinite in high-temperature and low-slip-velocity regime

    Science.gov (United States)

    Takahashi, M.; Uehara, S.; Mizoguchi, K.; Takeda, N.; Masuda, K.

    2009-12-01

    This study was designed to clarify the rheology of serpentinite experimentally, related both the sliding velocity and the temperature. The frictional behavior of serpentinite is of particular interest in the study of earthquake generation processes along subducting plates and transform faults. Previous studies [Reinen et al., 1991-93] revealed that the serpentinites indicated two-mechanical behaviors at velocity-step test: ‘state-variable dominated behavior’ at relatively higher velocity (0.1-10 μm/sec) and ‘flow-dominated behavior’ at lower velocity (less than 0.1 μm/sec). Such complexity on the frictional behavior could make it complicated to forecast on the slip acceleration process from the plate motion velocity to the earthquake. Even under the room-temperature condition, those multiple behavior could be observed, thus, serpentinite can be a model substance to present a new constitutive law at the brittle-ductile transition regime. We, therefore, focus to discuss the transient behaviors of serpentinite at the velocity-step test. We used a gas-medium, high-pressure, and high-temperature triaxial testing machine belonging to the National Institute of Advanced Industrial Science and Technology (AIST), Japan. Sliding deformation was applied on the thin zone of the serpentinite gouge (1.0 g of almost pure antigorite powder) sandwiched between two alumina blocks with oblique surfaces at 30° to the axis. All experiments were carried out under a set of constant conditions, 100 MPa of the confining pressure (Ar-gas) and 30 MPa of the pore pressure (distilled water). The temperature conditions were varied from the room-temperature to 500° C, and three sliding velocity-regimes were adopted: low (0.0115 - 0.115 μm/sec), middle (0.115 - 1.15 μm/sec) and high (1.15 - 11.5 μm/sec) velocity regimes. In each velocity regime, the sliding velocity was increased or decreased in a stepwise fashion, and then we observed the transient behaviors until it reached the

  20. Slope Environmental Lapse Rate (SELR of Temperature in the Monsoon Regime of the Western Himalaya

    Directory of Open Access Journals (Sweden)

    Renoj J. Thayyen

    2018-06-01

    Full Text Available The interplay of moisture, temperature, and precipitation forced through the orographic processes sustain and regulate the Himalayan cryospheric system. However, factors influencing the Slope Environmental Lapse Rate (SELR of temperature along the Himalayan mountain slopes and an appropriate modeling solution remain as a key knowledge gaps. The present study evaulates the SELR variations in the monsoon regime of the western Himalaya and proposes a modeling solution for the valley scale SELR assessment. SELR of selected station pairs in the Sutlej and Beas basins ranging between the elevation of 662–3,130 m a.s.l. and that of Garhwal Himalaya between 770 and 3,820 m a.s.l. were assessed in this study. Results suggest that the moisture–temperature interplay is not only forcing the seasonal variations, but also the elevation-depended variability of the temperature SELR. Temperature lapse rate constrianed to the nival–glacier regime is found to be comparable to the saturated adiabatic lapse rate (SALR and lower than the valley scale SELR. The study also suggests that the bi-modal pattern of the annual temperature lapse rates earlier observed in the Nepal Himalaya is extended up to upper Ganga, Sutlej, and Beas basins in the western Himalaya. This seasonal variability of SELR is found to be closly linked with the seasonal variations in the lifting condensation levels (LCLs over the region. Inter-annual variation in SELR of the nival–glacier regime are found to be significant while that of the valley scale SELR are more stable. We propose a simple preliminary but robust model for deriving the valley scale SELR of monsoon regime modifying the equation governing pseudo adiabatic lapse rate. The SELR modeling solution is achieved by deriving monthly SELR indices using the data of two station pairs in the Sutlej and Beas basins during the 1986–2005 period through K-fold cross validation. The model sucessfully captures seasonal SELR variations

  1. Nutrients and temperature additively increase stream microbial respiration

    Science.gov (United States)

    David W. P. Manning; Amy D. Rosemond; Vladislav Gulis; Jonathan P. Benstead; John S. Kominoski

    2017-01-01

    Rising temperatures and nutrient enrichment are co‐occurring global‐change drivers that stimulate microbial respiration of detrital carbon, but nutrient effects on the temperature dependence of respiration in aquatic ecosystems remain uncertain. We measured respiration rates associated with leaf litter, wood, and fine benthic organic matter (FBOM) across...

  2. Application of high temperature superconductors for optimization of regime of the electroenergetic system

    International Nuclear Information System (INIS)

    Manusov, V.Z.; Mikheev, P.A.

    2005-01-01

    Application of the phenomenon of superconductivity in the energetic systems, as in the form of longitudinal engine, also in the transverse appearance (changing of the regime of neutral) is considerate in this article. In the normal regimes of the work of net it is profitable to have less resistance for contraction loss of the capability in the network and decrease of the tension, in emergency state ground return, on the contrary, from the security and safety point of view the work of such resistance will not arrange. Major properties of superconductors are their ability to change electrical parameters (in particular electric resistance) in dependence of the size of current crossing over them, notably nonlinearity of their volt-ampere characteristics. A high temperature superconductor, on the score of economical appropriateness of cooling of superconductor with liquid nitrogen instead of liquid gel is considered

  3. A Regime Diagram for Autoignition of Homogeneous Reactant Mixtures with Turbulent Velocity and Temperature Fluctuations

    KAUST Repository

    Im, Hong G.; Pal, Pinaki; Wooldridge, Margaret S.; Mansfield, Andrew B.

    2015-01-01

    A theoretical scaling analysis is conducted to propose a diagram to predict weak and strong ignition regimes for a compositionally homogeneous reactant mixture with turbulent velocity and temperature fluctuations. The diagram provides guidance on expected ignition behavior based on the thermo-chemical properties of the mixture and the flow/scalar field conditions. The analysis is an extension of the original Zeldovich’s analysis by combining the turbulent flow and scalar characteristics in terms of the characteristic Damköhler and Reynolds numbers of the system, thereby providing unified and comprehensive understanding of the physical and chemical mechanisms controlling ignition characteristics. Estimated parameters for existing experimental measurements in a rapid compression facility show that the regime diagram predicts the observed ignition characteristics with good fidelity.

  4. A Regime Diagram for Autoignition of Homogeneous Reactant Mixtures with Turbulent Velocity and Temperature Fluctuations

    KAUST Repository

    Im, Hong G.

    2015-04-02

    A theoretical scaling analysis is conducted to propose a diagram to predict weak and strong ignition regimes for a compositionally homogeneous reactant mixture with turbulent velocity and temperature fluctuations. The diagram provides guidance on expected ignition behavior based on the thermo-chemical properties of the mixture and the flow/scalar field conditions. The analysis is an extension of the original Zeldovich’s analysis by combining the turbulent flow and scalar characteristics in terms of the characteristic Damköhler and Reynolds numbers of the system, thereby providing unified and comprehensive understanding of the physical and chemical mechanisms controlling ignition characteristics. Estimated parameters for existing experimental measurements in a rapid compression facility show that the regime diagram predicts the observed ignition characteristics with good fidelity.

  5. Influence of maximum water temperature on occurrence of Lahontan cutthroat trout within streams

    Science.gov (United States)

    J. Dunham; R. Schroeter; B. Rieman

    2003-01-01

    We measured water temperature at 87 sites in six streams in two different years (1998 and 1999) to test for association with the occurrence of Lahontan cutthroat trout Oncorhynchus clarki henshawi. Because laboratory studies suggest that Lahontan cutthroat trout begin to show signs of acute stress at warm (>22°C) temperatures, we focused on the...

  6. Assessing the Effects of Water Right Purchases on Stream Temperatures and Fish Habitat

    Science.gov (United States)

    Elmore, L.; Null, S. E.

    2012-12-01

    Warm stream temperature and low flow conditions are limiting factors for native trout species in Nevada's Walker River. Water rights purchases are being considered to increase instream flow and improve habitat conditions. However, the effect of water rights purchases on stream temperatures and fish habitat have yet to be assessed. Manipulating flow conditions affect stream temperatures by altering water depth, velocity, and thermal mass. This study uses the River Modeling System (RMSv4), an hourly, physically-based hydrodynamic and water quality model, to estimate flows and stream temperatures in the Walker River. The model is developed for two wet years (2010-2011). Study results highlight reaches with cold-water habitat that is suitable for native trout species. Previous research on the Walker River has evaluated instream flow changes with water rights purchases. This study incorporates stream temperatures as a proxy for trout habitat, and thus explicitly incorporates water quality and fish habitat into decision-making regarding water rights purchases. Walker River

  7. Classification of Arctic, midlatitude and tropical clouds in the mixed-phase temperature regime

    Directory of Open Access Journals (Sweden)

    A. Costa

    2017-10-01

    Full Text Available The degree of glaciation of mixed-phase clouds constitutes one of the largest uncertainties in climate prediction. In order to better understand cloud glaciation, cloud spectrometer observations are presented in this paper, which were made in the mixed-phase temperature regime between 0 and −38 °C (273 to 235 K, where cloud particles can either be frozen or liquid. The extensive data set covers four airborne field campaigns providing a total of 139 000 1 Hz data points (38.6 h within clouds over Arctic, midlatitude and tropical regions. We develop algorithms, combining the information on number concentration, size and asphericity of the observed cloud particles to classify four cloud types: liquid clouds, clouds in which liquid droplets and ice crystals coexist, fully glaciated clouds after the Wegener–Bergeron–Findeisen process and clouds where secondary ice formation occurred. We quantify the occurrence of these cloud groups depending on the geographical region and temperature and find that liquid clouds dominate our measurements during the Arctic spring, while clouds dominated by the Wegener–Bergeron–Findeisen process are most common in midlatitude spring. The coexistence of liquid water and ice crystals is found over the whole mixed-phase temperature range in tropical convective towers in the dry season. Secondary ice is found at midlatitudes at −5 to −10 °C (268 to 263 K and at higher altitudes, i.e. lower temperatures in the tropics. The distribution of the cloud types with decreasing temperature is shown to be consistent with the theory of evolution of mixed-phase clouds. With this study, we aim to contribute to a large statistical database on cloud types in the mixed-phase temperature regime.

  8. Classification of Arctic, midlatitude and tropical clouds in the mixed-phase temperature regime

    Science.gov (United States)

    Costa, Anja; Meyer, Jessica; Afchine, Armin; Luebke, Anna; Günther, Gebhard; Dorsey, James R.; Gallagher, Martin W.; Ehrlich, Andre; Wendisch, Manfred; Baumgardner, Darrel; Wex, Heike; Krämer, Martina

    2017-10-01

    The degree of glaciation of mixed-phase clouds constitutes one of the largest uncertainties in climate prediction. In order to better understand cloud glaciation, cloud spectrometer observations are presented in this paper, which were made in the mixed-phase temperature regime between 0 and -38 °C (273 to 235 K), where cloud particles can either be frozen or liquid. The extensive data set covers four airborne field campaigns providing a total of 139 000 1 Hz data points (38.6 h within clouds) over Arctic, midlatitude and tropical regions. We develop algorithms, combining the information on number concentration, size and asphericity of the observed cloud particles to classify four cloud types: liquid clouds, clouds in which liquid droplets and ice crystals coexist, fully glaciated clouds after the Wegener-Bergeron-Findeisen process and clouds where secondary ice formation occurred. We quantify the occurrence of these cloud groups depending on the geographical region and temperature and find that liquid clouds dominate our measurements during the Arctic spring, while clouds dominated by the Wegener-Bergeron-Findeisen process are most common in midlatitude spring. The coexistence of liquid water and ice crystals is found over the whole mixed-phase temperature range in tropical convective towers in the dry season. Secondary ice is found at midlatitudes at -5 to -10 °C (268 to 263 K) and at higher altitudes, i.e. lower temperatures in the tropics. The distribution of the cloud types with decreasing temperature is shown to be consistent with the theory of evolution of mixed-phase clouds. With this study, we aim to contribute to a large statistical database on cloud types in the mixed-phase temperature regime.

  9. Effects of different temperature regimes on survival of Diaphorina citri and its endosymbiotic bacterial communities.

    Science.gov (United States)

    Hussain, Mubasher; Akutse, Komivi Senyo; Ravindran, Keppanan; Lin, Yongwen; Bamisile, Bamisope Steve; Qasim, Muhammad; Dash, Chandra Kanta; Wang, Liande

    2017-09-01

    The Asian citrus psyllid, Diaphorina citri, is a major pest of citrus and vector of citrus greening (huanglongbing) in Asian. In our field-collected psyllid samples, we discovered that Fuzhou (China) and Faisalabad (Pakistan), populations harbored an obligate primary endosymbiont Candidatus Carsonella (gen. nov.) with a single species, Candidatus Carsonella ruddii (sp. nov.) and a secondary endosymbiont, Wolbachia surface proteins (WSP) which are intracellular endosymbionts residing in the bacteriomes. Responses of these symbionts to different temperatures were examined and their host survival assessed. Diagnostic PCR assays showed that the endosymbionts infection rates were not significantly reduced in both D. citri populations after 24 h exposure to cold or heat treatments. Although quantitative PCR assays showed significant reduction of WSP relative densities at 40°C for 24 h, a substantial decrease occurred as the exposure duration increased beyond 3 days. Under the same temperature regimes, Ca. C. ruddii density was initially less affected during the first exposure day, but rapidly reduced at 3-5 days compared to WSP. However, the mortality of the psyllids increased rapidly as exposure time to heat treatment increased. The responses of the two symbionts to unfavorable temperature regimes highlight the complex host-symbionts interactions between D. citri and its associated endosymbionts. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  10. STREAM

    DEFF Research Database (Denmark)

    Godsk, Mikkel

    This paper presents a flexible model, ‘STREAM’, for transforming higher science education into blended and online learning. The model is inspired by ideas of active and collaborative learning and builds on feedback strategies well-known from Just-in-Time Teaching, Flipped Classroom, and Peer...... Instruction. The aim of the model is to provide both a concrete and comprehensible design toolkit for adopting and implementing educational technologies in higher science teaching practice and at the same time comply with diverse ambitions. As opposed to the above-mentioned feedback strategies, the STREAM...... model supports a relatively diverse use of educational technologies and may also be used to transform teaching into completely online learning. So far both teachers and educational developers have positively received the model and the initial design experiences show promise....

  11. Guidelines for the collection of continuous stream water-temperature data in Alaska

    Science.gov (United States)

    Toohey, Ryan C.; Neal, Edward G.; Solin, Gary L.

    2014-01-01

    Objectives of stream monitoring programs differ considerably among many of the academic, Federal, state, tribal, and non-profit organizations in the state of Alaska. Broad inclusion of stream-temperature monitoring can provide an opportunity for collaboration in the development of a statewide stream-temperature database. Statewide and regional coordination could reduce overall monitoring cost, while providing better analyses at multiple spatial and temporal scales to improve resource decision-making. Increased adoption of standardized protocols and data-quality standards may allow for validation of historical modeling efforts with better projection calibration. For records of stream water temperature to be generally consistent, unbiased, and reproducible, data must be collected and analyzed according to documented protocols. Collection of water-temperature data requires definition of data-quality objectives, good site selection, proper selection of instrumentation, proper installation of sensors, periodic site visits to maintain sensors and download data, pre- and post-deployment verification against an NIST-certified thermometer, potential data corrections, and proper documentation, review, and approval. A study created to develop a quality-assurance project plan, data-quality objectives, and a database management plan that includes procedures for data archiving and dissemination could provide a means to standardize a statewide stream-temperature database in Alaska. Protocols can be modified depending on desired accuracy or specific needs of data collected. This document is intended to guide users in collecting time series water-temperature data in Alaskan streams and draws extensively on the broader protocols already published by the U.S. Geological Survey.

  12. Evaluation of Macerating Pectinase Enzyme Activity under Various Temperature, pH and Ethanol Regimes

    Directory of Open Access Journals (Sweden)

    Andrew G. Reynolds

    2018-02-01

    Full Text Available The polygalacturonase (PGU, hemicellulase (mannanase and protease enzyme activities in commercial macerating, pectinase-enzyme preparations commonly used by wineries in Ontario (Scottzyme Color X and Color Pro were measured under various simulated process conditions (temperature, pH, and ethanol concentration. Treatments included three temperatures (15, 20 and 30 °C; pH = 3.0, 3.5, 4.0 and 5.0; ethanol = 0%, four pH levels (3.0, 3.5, 4.0 and 5.0; temperature = 15, 20, 30 and 50 °C; ethanol = 0%, and four ethanol concentrations ((2.5, 5, 7.5 and 10%; temperature = 20 °C and pH = 3.5. Polygalacturonase enzyme activity in Color X increased linearly with temperature at all pH levels, and increased with pH at all temperature regimes. Polygalacturonase activity decreased with increasing ethanol. Color X mannanase activity increased with temperatures between 15 and 40 °C, and decreased with increased pH between 3.0 and 5.0. Response of mannanase to ethanol was cubic with a sharp decrease between 8 and 10% ethanol. Protease activity increased linearly with temperatures between 20 and 40 °C. These data suggest that the PGU, mannanase and protease components in these enzyme products provide sufficient activities within the ranges of pH, temperature, and ethanol common during the initial stages of red wine fermentations, although low must temperatures (<20 °C and presence of ethanol would likely lead to sub-optimal enzyme activities.

  13. Classification of Arctic, Mid-Latitude and Tropical Clouds in the Mixed-Phase Temperature Regime

    Science.gov (United States)

    Costa, Anja; Afchine, Armin; Luebke, Anna; Meyer, Jessica; Dorsey, James R.; Gallagher, Martin W.; Ehrlich, André; Wendisch, Manfred; Krämer, Martina

    2016-04-01

    The degree of glaciation and the sizes and habits of ice particles formed in mixed-phase clouds remain not fully understood. However, these properties define the mixed clouds' radiative impact on the Earth's climate and thus a correct representation of this cloud type in global climate models is of importance for an improved certainty of climate predictions. This study focuses on the occurrence and characteristics of two types of clouds in the mixed-phase temperature regime (238-275K): coexistence clouds (Coex), in which both liquid drops and ice crystals exist, and fully glaciated clouds that develop in the Wegener-Bergeron-Findeisen regime (WBF clouds). We present an extensive dataset obtained by the Cloud and Aerosol Particle Spectrometer NIXE-CAPS, covering Arctic, mid-latitude and tropical regions. In total, we spent 45.2 hours within clouds in the mixed-phase temperature regime during five field campaigns (Arctic: VERDI, 2012 and RACEPAC, 2014 - Northern Canada; mid-latitude: COALESC, 2011 - UK and ML-Cirrus, 2014 - central Europe; tropics: ACRIDICON, 2014 - Brazil). We show that WBF and Coex clouds can be identified via cloud particle size distributions. The classified datasets are used to analyse temperature dependences of both cloud types as well as range and frequencies of cloud particle concentrations and sizes. One result is that Coex clouds containing supercooled liquid drops are found down to temperatures of -40 deg C only in tropical mixed clouds, while in the Arctic and mid-latitudes no liquid drops are observed below about -20 deg C. In addition, we show that the cloud particles' aspherical fractions - derived from polarization signatures of particles with diameters between 20 and 50 micrometers - differ significantly between WBF and Coex clouds. In Coex clouds, the aspherical fraction of cloud particles is generally very low, but increases with decreasing temperature. In WBF clouds, where all cloud particles are ice, about 20-40% of the cloud

  14. THE EFFECTS OF WATER TEMPERATURE REGIME FLUCTUATIONS ON THE EMBRYONIC DEVELOPMENT OF SILVER CARP (HYPOPHTHALMICHTHYS MOLITRIX

    Directory of Open Access Journals (Sweden)

    А. Vodyanitskyi

    2015-03-01

    Full Text Available Purpose. To determine the effect of temperature regime fluctuations on the development of silver carp embryos, as well as the activity of enzymatic reactions in fish eggs. Methodology. The studies were conducted at the experimental station of the Institute of Hydrobiology of Bila Tserkov, Ukrainian National Academy of Sciences, from June to July. The biological materials were silver carp eggs, embryos and larvae. The dissolved oxygen content was determined using the Winkler method at four o’clock in the morning. Alkalinity phosphatase and LDG activity were determined using a set of reagents «Alkalinity phosphatase» and «LDG» (Phyllis diagnosis, Ukraine. SDH activity was determined by Vexy. The activity of Na, K-Mg-dependent-activated ATPase was determined as growth of inorganic phosphorus in the incubation medium by Kindratova M.N. et al. Protease activity was determined using immune enzymatic method of Tyurina et al. The obtained results were processed statistically in Statistica 5.5, Epaprobit analysis was used for calculating LC/EC values (Version 1.5. Findings The results showed that a delay of embryonic stages of development occur, the number of abnormal embryos increases, and the reproduction efficiency of fish reduces with an increase in water temperature and decrease in the dissolved oxygen content in water. The temperature factor had a significant effect on the activity of key enzymes, in particular the energetic metabolism changed from aerobic to anaerobic. Originality. It was found a negative effect of abiotic factors of water medium and drastic fluctuations in water temperature and gas regime of water bodies on the course of embryogenesis of silver carp that is especially important in the conditions of climate change. Practical value. The obtained results showed that the level of optimum and unfavorable environmental factors during the change of embryonic stages in embryonic and larval fish can be established based on the

  15. Size effects in olivine control strength in low-temperature plasticity regime

    Science.gov (United States)

    Kumamoto, K. M.; Thom, C.; Wallis, D.; Hansen, L. N.; Armstrong, D. E. J.; Goldsby, D. L.; Warren, J. M.; Wilkinson, A. J.

    2017-12-01

    The strength of the lithospheric mantle during deformation by low-temperature plasticity controls a range of geological phenomena, including lithospheric-scale strain localization, the evolution of friction on deep seismogenic faults, and the flexure of tectonic plates. However, constraints on the strength of olivine in this deformation regime are difficult to obtain from conventional rock-deformation experiments, and previous results vary considerably. We demonstrate via nanoindentation that the strength of olivine in the low-temperature plasticity regime is dependent on the length-scale of the test, with experiments on smaller volumes of material exhibiting larger yield stresses. This "size effect" has previously been explained in engineering materials as a result of the role of strain gradients and associated geometrically necessary dislocations in modifying plastic behavior. The Hall-Petch effect, in which a material with a small grain size exhibits a higher strength than one with a large grain size, is thought to arise from the same mechanism. The presence of a size effect resolves discrepancies among previous experimental measurements of olivine, which were either conducted using indentation methods or were conducted on polycrystalline samples with small grain sizes. An analysis of different low-temperature plasticity flow laws extrapolated to room temperature reveals a power-law relationship between length-scale (grain size for polycrystalline deformation and contact radius for indentation tests) and yield strength. This suggests that data from samples with large inherent length scales best represent the plastic strength of the coarse-grained lithospheric mantle. Additionally, the plastic deformation of nanometer- to micrometer-sized asperities on fault surfaces may control the evolution of fault roughness due to their size-dependent strength.

  16. The Pressure-Temperature Regime of Iraq during the Period of 1948–2013

    Directory of Open Access Journals (Sweden)

    Yu.P. Perevedentsev

    2016-03-01

    Full Text Available We have considered spatiotemporal changes in the pressure-temperature regime at the territory of Iraq and Middle Eastern countries, which is limited by the following geographical coordinates: 27.5–37.5° N, 37.5–50.0° E. The initial data have been obtained from NCEP/NCAR reanalysis in the nodes of 2.5° × 2.5° grids, as well as from the indices of atmospheric circulation during the period of 1948–2013. Statistical processing of the material and construction of the linear trends and composites have allowed to reveal the dynamics of changes in the air temperature and pressure, its dependence on fluctuations in the atmospheric circulation. A tendency has been revealed towards a decrease in the temperature during the cold period and its increase during the warm period. Deviations (anomalies of the distribution of actual temperature and atmospheric pressure from the climatological norm have been estimated. Maps of temperature and pressure distribution in the regions have been created.

  17. Legacy effects of wildfire on stream thermal regimes and rainbow trout ecology: an integrated analysis of observation and individual-based models

    Science.gov (United States)

    Rosenberger, Amanda E.; Dunham, Jason B.; Neuswanger, Jason R.; Railsback, Steven F.

    2015-01-01

    Management of aquatic resources in fire-prone areas requires understanding of fish species’ responses to wildfire and of the intermediate- and long-term consequences of these disturbances. We examined Rainbow Trout populations in 9 headwater streams 10 y after a major wildfire: 3 with no history of severe wildfire in the watershed (unburned), 3 in severely burned watersheds (burned), and 3 in severely burned watersheds subjected to immediate events that scoured the stream channel and eliminated streamside vegetation (burned and reorganized). Results of a previous study of this system suggested the primary lasting effects of this wildfire history on headwater stream habitat were differences in canopy cover and solar radiation, which led to higher summer stream temperatures. Nevertheless, trout were present throughout streams in burned watersheds. Older age classes were least abundant in streams draining watersheds with a burned and reorganized history, and individuals >1 y old were most abundant in streams draining watersheds with an unburned history. Burned history corresponded with fast growth, low lipid content, and early maturity of Rainbow Trout. We used an individual-based model of Rainbow Trout growth and demographic patterns to determine if temperature interactions with bioenergetics and competition among individuals could lead to observed phenotypic and ecological differences among populations in the absence of other plausible mechanisms. Modeling suggested that moderate warming associated with wildfire and channel disturbance history leads to faster individual growth, which exacerbates competition for limited food, leading to decreases in population densities. The inferred mechanisms from this modeling exercise suggest the transferability of ecological patterns to a variety of temperature-warming scenarios.

  18. Effects of dam operation on the endangered Júcar nase, Parachondrostoma arrigonis, related to mesohabitats, microhabitat availability and water temperature regime, in the river Cabriel (Spain)

    Science.gov (United States)

    Martinez-Capel, Francisco; Costa, Rui; Muñoz-Mas, Rafael; Diego Alcaraz-Hernandez, Juan; Hernandez-Mascarell, Aina

    2010-05-01

    The presence of large dams affects habitat availability, often regarded as the primary factor that limits population and community recovery in rivers. Physical habitat is often targeted in restoration, but there is often a paucity of useful information. Habitat degradation has reduced the complexity and connectivity of the Mediterranean streams in Spain. These changes have diminished the historical range of the endangered Júcar nase, Parachondrostoma arrigonis (Steindachner, 1866), isolated the populations of this species, and probably contributed to its risk of extinction. In the Júcar River basin (Spain), where this fish is endemic, the populations are mainly restricted to the river Cabriel, which is fragmented in two segments by the large dam of Contreras. In this river, 3 main lines of research were developed from 2006 to 2008, i.e., microhabitat suitability, mesohabitat suitability, and water temperature, in order to relate such kind of variables with the flow regime. The main goal of the research project, funded by the Spanish Ministry of Environment, was to detect the main reasons of the species decline, and to propose dam operation improvements to contribute to the recovery of the species. The flow and water temperature regimes were also studied in the river Cabriel, upstream and downstream the large dam of Contreras. During the three years of study, below the dam it was observed a small and not significant variation in the proportions of slow and fast habitats; the regulated flow regime was pointed out as the main reason of such variations. At the microhabitat scale, optimal ranges for average depth and velocity were defined; these data allowed us to develop an estimation of weighted useable area under natural and regulated conditions. The Júcar nase were found majorly at depths no greater than 1,15 meters with slow water velocities. It was possible to observe a clear alteration of the flow and water temperature regime below the dam, due to the cold

  19. A model to predict stream water temperature across the conterminous USA

    Science.gov (United States)

    Catalina Segura; Peter Caldwell; Ge Sun; Steve McNulty; Yang Zhang

    2014-01-01

    Stream water temperature (ts) is a critical water quality parameter for aquatic ecosystems. However, ts records are sparse or nonexistent in many river systems. In this work, we present an empirical model to predict ts at the site scale across the USA. The model, derived using data from 171 reference sites selected from the Geospatial Attributes of Gages for Evaluating...

  20. Impact of Black Dust Pollution on Permafrost Temperature Regime in Pechora Basin

    Science.gov (United States)

    Khilimonyuk, V.; Pustovoit, G.; Filatova, M.

    2011-12-01

    Pechora Coal basin locates in North- Easter part of Europe within permafrost zone. The coal mining and post processing lead to emission of black dust (BD) and pollution of Earth surface. The scale of snow pollution surrounding Vorkuta city reaches to 260 g/sq.m of dust that is about 1000 ppmm BD concentration in snow before melting period. Such a large concentration of dust reduces snow reflectivity (Warren and Wiscombe, 1980; Chýlek et al., 1983,Gorbacheva, 1984, Zender et al, 2010) and can thereby trigger albedo feedbacks. The goal of this study is to evaluate the role of dirty surface albedo in the observed changing of permafrost regime in this basin. Two key sites: Workuta (North permafrost zone) and Inta (South permafrost zone) areas were selected for this study. For each site the zoning of territory by typical conditions of permafrost formation was performed. For the selected typical landscapes 1-D vertical heat transfer model coupled with the surface radiation-thermal balance equation at topsoil was simulated. The simulation was performed for the soil profile of 20 m depth during 20 years period with periodical input data at dirty surface averaged on monthly base. The initial measured not disturbed soil temperature profile was used for assessment the soil thermal property for the given landscape and natural surface radiation-thermal balance. The annual cycle of albedo change for dirty surface was taken from experimental measurement (Gorbacheva, 1984) for both sites as the function of the distance from the dust source. The simulation results next were used for mapping the vulnerability of permafrost thermal regime due to black dust pollution. Generally the simulation results show that South permafrost zone with mean temperature of permafrost (-0.5 -0.1C) is more vulnerable to albedo change than North permafrost zone with mean temperature (-2.5 -2C) for the same order of dust impact on albedo.

  1. Downstream changes in spring-fed stream invertebrate communities: the effect of increased temperature range?

    Directory of Open Access Journals (Sweden)

    Russell G. DEATH

    2011-09-01

    Full Text Available Reduced thermal amplitude has been highlighted as a limiting factor for aquatic invertebrate diversity in springs. Moving downstream water temperature range increases and invertebrate richness is expected to change accordingly. In the present study temperature patterns were investigated in seven spring-fed streams, between April 2001 and November 2002, and compared to five run-off-fed streams to assess the degree of crenic temperature constancy. Temperature and physico-chemical characteristics of the water, and food resource levels were measured, and the invertebrate fauna collected at 4 distances (0, 100, 500 m and 1 km from seven springs in the North and South Islands of New Zealand. Temperature variability was greater for run-off-fed streams than for springs, and increased in the spring-fed streams with distance from the source. Periphyton and physico-chemical characteristics of the water did not change markedly over the 1 km studied, with the exception of water velocity and organic matter biomass, which increased and decreased, respectively. The rate of increase in temperature amplitude differed greatly for the studied springs, probably being affected by flow, altitude, and the number and type of tributaries (i.e., spring- or run-off-fed joining the spring-fed stream channel. Longitudinal changes in the number and evenness of invertebrate taxa were positively correlated to thermal amplitude (rs = 0.8. Moving downstream, invertebrate communities progressively incorporated taxa with higher mobility and taxa more common in nearby run-off-fed streams. Chironomids and non-insect taxa were denser at the sources. Chironomid larvae also numerically dominated communities 100 and 500 m downstream from the sources, together with Pycnocentria spp. and Zelolessica spp., while taxa such as Hydora sp. and Hydraenidae beetles, the mayflies Deleatidium spp. and Coloburiscus humeralis, and the Trichoptera Pycnocentrodes spp., all had greater abundances 1 km

  2. Corresponding long-term shifts in stream temperature and invasive fish migration

    Science.gov (United States)

    McCann, Erin L.; Johnson, Nicholas; Pangle, Kevin

    2018-01-01

    By investigating historic trapping records of invasive sea lamprey (Petromyzon marinus) throughout tributaries to the Laurentian Great Lakes, we found that upstream spawning migration timing was highly correlated with stream temperatures over large spatial and temporal scales. Furthermore, several streams in our study exceeded a critical spring thermal threshold (i.e., 15°C) and experienced peak spawning migration up to 30 days earlier since the 1980s, whereas others were relatively unchanged. Streams exhibiting warming trends and earlier migration were spatially clustered and generally found on the leeward side of the Great Lakes where the lakes most affect local climate. These findings highlight that all streams are not equally impacted by climate change and represent, to our knowledge, the first observation linking long-term changes in stream temperatures to shifts in migration timing of an invasive fish. Earlier sea lamprey migration in Great Lakes tributaries may improve young of the year growth and survival, but not limit their spatial distribution, making sea lamprey control more challenging.

  3. Beyond the mean: the role of variability in predicting ecological effects of stream temperature on salmon

    Science.gov (United States)

    E. Ashley Steel; Abby Tillotson; Donald A. Larson; Aimee H. Fullerton; Keith P. Denton; Brian R. Beckman

    2012-01-01

    Alterations in variance of riverine thermal regimes have been observed and are predicted with climate change and human development. We tested whether changes in daily or seasonal thermal variability, aside from changes in mean temperature, could have biological consequences by exposing Chinook salmon (Oncorhynchus tshawytscha) eggs to eight...

  4. Co-occurring Synechococcus ecotypes occupy four major oceanic regimes defined by temperature, macronutrients and iron.

    Science.gov (United States)

    Sohm, Jill A; Ahlgren, Nathan A; Thomson, Zachary J; Williams, Cheryl; Moffett, James W; Saito, Mak A; Webb, Eric A; Rocap, Gabrielle

    2016-02-01

    Marine picocyanobacteria, comprised of the genera Synechococcus and Prochlorococcus, are the most abundant and widespread primary producers in the ocean. More than 20 genetically distinct clades of marine Synechococcus have been identified, but their physiology and biogeography are not as thoroughly characterized as those of Prochlorococcus. Using clade-specific qPCR primers, we measured the abundance of 10 Synechococcus clades at 92 locations in surface waters of the Atlantic and Pacific Oceans. We found that Synechococcus partition the ocean into four distinct regimes distinguished by temperature, macronutrients and iron availability. Clades I and IV were prevalent in colder, mesotrophic waters; clades II, III and X dominated in the warm, oligotrophic open ocean; clades CRD1 and CRD2 were restricted to sites with low iron availability; and clades XV and XVI were only found in transitional waters at the edges of the other biomes. Overall, clade II was the most ubiquitous clade investigated and was the dominant clade in the largest biome, the oligotrophic open ocean. Co-occurring clades that occupy the same regime belong to distinct evolutionary lineages within Synechococcus, indicating that multiple ecotypes have evolved independently to occupy similar niches and represent examples of parallel evolution. We speculate that parallel evolution of ecotypes may be a common feature of diverse marine microbial communities that contributes to functional redundancy and the potential for resiliency.

  5. Improving tribological performance of gray cast iron by laser peening in dynamic strain aging temperature regime

    Science.gov (United States)

    Feng, Xu; Zhou, Jianzhong; Mei, Yufen; Huang, Shu; Sheng, Jie; Zhu, Weili

    2015-09-01

    A high and stable brake disc friction coefficient is needed for automobile safety, while the coefficient degrades due to elevated temperature during the braking process. There is no better solution except changes in material composition and shape design optimization. In the dynamic strain aging(DSA) temperature regime of gray cast iron, micro-dimples with different dimple depth over diameter and surface area density are fabricated on the material surface by laser peening(LP) which is an LST method. Friction behavior and wear mechanism are investigated to evaluate the effects of surface texturing on the tribological performance of specimens under dry conditions. Through LP impacts assisted by DSA, the friction coefficients of the LPed specimens increase noticeably both at room temperature and elevated temperature in comparison to untreated specimens. Moreover, the coefficient of specimen with dimple depth over diameter of 0.03 and surface area density of 30% is up to 0.351 at room temperature, which dramatically rises up to 1.33 times that of untextured specimen and the value is still up to 0.3305 at 400°C with an increasing ratio of 35% compared to that of untreated specimen. The surface of textured specimen shows better wear resistance compared to untreated specimen. Wear mechanism includes adhesive wear, abrasive wear and oxidation wear. It is demonstrated that LP assisted by DSA can substantially improve wear resistance, raise the friction coefficient as well as its stability of gray cast iron under elevated temperatures. Heat fade and premature wear can be effectively relieved by this surface modification method.

  6. Thermal and mechanical properties of selected 3D printed thermoplastics in the cryogenic temperature regime

    International Nuclear Information System (INIS)

    Weiss, K-P; Bagrets, N; Lange, C; Goldacker, W; Wohlgemuth, J

    2015-01-01

    Insulating materials for use in cryogenic boundary conditions are still limited to a proved selection as Polyamid, Glasfiber reinforced resins, PEEK, Vespel etc. These materials are usually formed to parts by mechanical machining or sometimes by cast methods. Shaping complex geometries in one piece is limited. Innovative 3D printing is now an upcoming revolutionary technology to construct functional parts from a couple of thermoplastic materials as ABS, Nylon and others which possess quite good mechanical stability and allow realizing very complex shapes with very subtle details. Even a wide range of material mixtures is an option and thermal treatments can be used to finish the material structure for higher performance. The use of such materials in cryogenic environment is very attractive but so far poor experience exists. In this paper, first investigations of the thermal conductivity, expansion and mechanical strength are presented for a few selected commercial 3D material samples to evaluate their application prospects in the cryogenic temperature regime. (paper)

  7. Finite-element modelling of superconductors in over-critical regime with temperature dependent resistivity

    International Nuclear Information System (INIS)

    Duron, J; Grilli, F; Antognazza, L; Decroux, M; Stavrev, S; Dutoit, B; Fischer, Oe

    2006-01-01

    In this paper, we present a new numerical model, in which both the thermal and the electromagnetic aspects of the over-critical current regime of HTS materials are taken into account. The electromagnetic and thermal equations have been implemented in finite-element method (FEM) software in order to obtain a novel, closer to reality model for investigating the behaviour of the superconductor when the current exceeds I c . This model has been applied for studying the behaviour of strip lines of an YBCO/Au FCL with a sapphire substrate. Simulations with currents largely exceeding I c have been performed, showing that the total current limitation occurs only when the temperature dependence of the electrical parameters is taken into consideration. Such modelling can replace experiments with currents far exceeding I c which may damage or destroy the studied sample or HTS device

  8. New methods for modeling stream temperature using high resolution LiDAR, solar radiation analysis and flow accumulated values

    Science.gov (United States)

    In-stream temperature directly effects a variety of biotic organisms, communities and processes. Changes in stream temperature can render formally suitable habitat unsuitable for aquatic organisms, particularly native cold water species that are not able to adjust. In order to an...

  9. Relative effects of climate change and wildfires on stream temperatures: A simulation modeling approach in a Rocky Mountain watershed

    Science.gov (United States)

    Lisa Holsinger; Robert E. Keane; Daniel J. Isaak; Lisa Eby; Michael K. Young

    2014-01-01

    Freshwater ecosystems are warming globally from the direct effects of climate change on air temperature and hydrology and the indirect effects on near-stream vegetation. In fire-prone landscapes, vegetative change may be especially rapid and cause significant local stream temperature increases but the importance of these increases relative to broader changes associated...

  10. Evaluating links between forest harvest and stream temperature threshold exceedances: the value of spatial and temporal data

    Science.gov (United States)

    Jeremiah D. Groom; Sherri L. Johnson; Joshua D. Seeds; George G. Ice

    2017-01-01

    We present the results of a replicated before-after-control-impact study on 33 streams to test the effectiveness of riparian rules for private and State forests at meeting temperature criteria in streams in western Oregon. Many states have established regulatory temperature thresholds, referred to as numeric criteria, to protect cold-water fishes such as salmon and...

  11. Flat Branch monitoring project: stream water temperature and sediment responses to forest cutting in the riparian zone

    Science.gov (United States)

    Barton D. Clinton; James M. Vose; Dick L. Fowler

    2010-01-01

    Stream water protection during timber-harvesting activities is of primary interest to forest managers. In this study, we examine the potential impacts of riparian zone tree cutting on water temperature and total suspended solids. We monitored stream water temperature and total suspended solids before and after timber harvesting along a second-order tributary of the...

  12. Computational characterization of ignition regimes in a syngas/air mixture with temperature fluctuations

    KAUST Repository

    Pal, Pinaki; Valorani, Mauro; Arias, Paul G.; Im, Hong G.; Wooldridge, Margaret S.; Ciottoli, Pietro P.; Galassi, Riccardo M.

    2016-01-01

    ) was applied to characterize the auto-ignition phenomena. All results supported that the observed ignition behaviors were consistent with the expected ignition regimes predicted by the theory of the regime diagram. This work provides new high-fidelity data

  13. Solar–terrestrial radiant-energy regimes and temperature anomalies of natural and artificial turfs

    International Nuclear Information System (INIS)

    Jim, C.Y.

    2016-01-01

    Highlights: • Solar and terrestrial radian energy regimes affect temperature response of sports turfs. • Adjacent natural and artificial turfs were monitored with replications on sunny days. • Artificial turf has meager albedo, low specific heat and moisture to augment warming. • Artificial turf surface and substrate reach 70 °C but cool down effectively at night. • Artificial turf may induce heat stress on athletes in hot summer afternoon. - Abstract: Artificial turf can develop unusually high surface temperature on hot sunny days. Solar and terrestrial radiant energy regimes as key determinants of thermal performance deserve detailed investigation. This study evaluated six components of the radiant-energy environment of a natural turf (NT) and a contiguous artificial turf (AT) sports fields in Hong Kong: direct solar, reflected solar, net solar, sky thermal, ground thermal, and net thermal. Temperature was monitored at five positions: air at 150 cm, 50 cm and 15 cm height, turf surface, and substrate. The experiment included four replications, namely two summer sunny days, and two duplicated instrument sets at each turf site. The two sites reacted very differently to the same intense daily sum of solar radiation input of 23.70 MW m −2 with 9 h of bright sunshine (>120 W m −2 ), and daily sum of sky thermal radiation input of 38.59 MW m −2 . The maximum direct solar radiation reached 976.1 W m −2 at 1245 h. NT albedo of 0.23 vis-à-vis AT of merely 0.073, and higher moisture content and specific heat of NT materials, presented critical differences. The hydrophobic and generally dry plastic (polyethylene) pile-fibers and black rubber-granule infill materials have low specific heat. Intense incoming shortwave and longwave radiation absorbed readily by AT materials raised turf surface temperature to 70.2 °C and substrate 69.3 °C, in comparison with <40 °C at NT. A cascading warming effect was triggered, beginning with low albedo, high net solar

  14. Harmonic analyses of stream temperatures in the Upper Colorado River Basin

    Science.gov (United States)

    Steele, T.D.

    1985-01-01

    Harmonic analyses were made for available daily water-temperature records for 36 measurement sites on major streams in the Upper Colorado River Basin and for 14 measurement sites on streams in the Piceance structural basin. Generally (88 percent of the station years analyzed), more than 80 percent of the annual variability of temperatures of streams in the Upper Colorado River Basin was explained by the simple-harmonic function. Significant trends were determined for 6 of the 26 site records having 8 years or more record. In most cases, these trends resulted from construction and operation of upstream surface-water impoundments occurring during the period of record. Regional analysis of water-temperature characteristics at the 14 streamflow sites in the Piceance structural basin indicated similarities in water-temperature characteristics for a small range of measurement-site elevations. Evaluation of information content of the daily records indicated that less-than-daily measurement intervals should be considered, resulting in substantial savings in measurement and data-processing costs. (USGS)

  15. Temperature-dependent properties of semiconductor quantum dots in coherent regime; Temperaturabhaengige Eigenschaften einzelner Halbleiter-Quantenpunkte im Kohaerenten Regime

    Energy Technology Data Exchange (ETDEWEB)

    Huebner, Marc C.

    2009-10-15

    Recently, the public has become aware of keywords like ''Quantum computer'' or ''Quantum cryptography''. Regarding their potential application in solid state based quantum information processing and their overall benefit in fundamental research quantum dots have gained more and more public interest. In this context, quantum dots are often referred to as ''artificial atoms'', a term subsuming their physical properties quite nicely and emphasizing the huge potential for further investigations. The basic mechanism to be considered is the theoretical model of a two-level system. A quantum dot itself represents this kind of system quite nicely, provided that only the presence or absence of a single exciton in the ground state of that structure is regarded. This concept can also be expanded to the presence of two excitons (bi-exciton). Transitions between the relevant levels can be induced by optical stimulation. When integrating quantum dots in diode like structures measurements of this phenomena can be accomplished regarding photo currents. This means of detection is highly sensitive and allows for tuning of the energy levels with respect to the energy of an exciting laser utilizing the Stark effect (via an external electric field). The photo current then shows narrow resonances representing those transitions. By this, the system can be used as a highly sensitive nano-spectrometer. The examination of coherent interactions between quantum dots and an electromagnetic field uses laser pulses that are much shorter than the dephasing time of the system (2 ps). The basic study to be done on two level systems is the measurement of Rabi oscillations allowing for the selection of an arbitrary superposition of states. In this work, the existing setup was improved regarding the possibility to control the temperature of the sample. Up to now, only investigations at 4,2 K have been possible. Even at 70 K Rabi oscillations

  16. Effects of forest harvesting on summer stream temperatures in New Brunswick, Canada: an inter-catchment, multiple-year comparison

    Directory of Open Access Journals (Sweden)

    C. P.-A. Bourque

    2001-01-01

    Full Text Available This paper presents a pre- and post-harvest comparison of stream temperatures collected in five neighbouring streams (sub-catchments over a period of five years (1994-1998. The aim of the study was to determine whether land cover changes from clear cutting in areas outside forest buffer zones (applied to streams >0.5 m wide might contribute to an increase in summer mean stream temperatures in buffered streams downslope by infusion of warmed surface and sub-surface water into the streams. Specific relationships were observed in all five forest streams investigated. To assist in the analysis, several spatially-relevant variables, such as land cover change, mid-summer potential solar radiation, flow accumulation, stream location and slope of the land were determined, in part, from existing aerial photographs, GIS-archived forest inventory data and a digital terrain model of the study area. Spatial calculations of insolation levels for July 15th were used as an index of mid-summer solar heating across sub-catchments. Analysis indicated that prior to the 1995 harvest, differences in stream temperature could be attributed to (i topographic position and catchment-to-sun orientation, (ii the level of cutting that occurred in the upper catchment prior to the start of the study, and (iii the average slope within harvested areas. Compared to the pre-harvest mean stream temperatures in 1994, mean temperatures in the three streams downslope from the 1995 harvest areas increased by 0.3 to 0.7°C (representing a 4-8% increase; p-value of normalised temperatures Keywords: terrain attributes, solar radiation, land cover, forest buffers, New Brunswick regulations, spatial modelling, DEM, forest covertypes

  17. Identifying Stream/Aquifer Exchange by Temperature Gradient in a Guarani Aquifer System Outcrop Zone

    Science.gov (United States)

    Wendland, E.; Rosa, D. M. S.; Anache, J. A. A.; Lowry, C.; Lin, Y. F. F.

    2017-12-01

    Recharge of the Guarani Aquifer System (GAS) in South America is supposed to occur mainly in the outcrop zones, where the GAS appears as an unconfined aquifer (10% of the 1.2 Million km2 aquifer extension). Previous evaluations of recharge are based essentially on water balance estimates for the whole aquifer area or water table fluctuations in monitoring wells. To gain a more detailed understanding of the recharge mechanisms the present work aimed to study the stream aquifer interaction in a watershed (Ribeirão da Onça) at an outcrop zone. Two Parshall flumes were installed 1.3 km apart for discharge measurement in the stream. Along this distance an optic fiber cable was deployed to identify stretches with gaining and losing behavior. In order to estimate groundwater discharge in specific locations, 8 temperature sticks were set up along the stream reach to measure continuously the vertical temperature gradient. A temperature probe with 4 thermistors was also used to map the shallow streambed temperature gradient manually along the whole distance. The obtained results show a discharge difference of 250 m3/h between both flumes. Since the last significant rainfall (15 mm) in the watershed occurred 3 months ago, this value can be interpreted as the base flow contribution to the stream during the dry season. Given the temperature difference between groundwater ( 24oC) and surface water ( 17oC) the fiber-optic distributed temperature sensing (FO-DTS) allowed the identification of stretches with gaining behavior. Temperature gradients observed at the streambed varied between 0.67 and 14.33 oC/m. The study demonstrated that heat may be used as natural tracer even in tropical conditions, where the groundwater temperature is higher than the surface water temperature during the winter. The obtained results show that the discharge difference between both flumes can not be extrapolated without detailed analysis. Gaining and loosing stretches have to be identified on order

  18. Temperature Regimes Impact Coral Assemblages along Environmental Gradients on Lagoonal Reefs in Belize.

    Directory of Open Access Journals (Sweden)

    Justin H Baumann

    Full Text Available Coral reefs are increasingly threatened by global and local anthropogenic stressors such as rising seawater temperature, nutrient enrichment, sedimentation, and overfishing. Although many studies have investigated the impacts of local and global stressors on coral reefs, we still do not fully understand how these stressors influence coral community structure, particularly across environmental gradients on a reef system. Here, we investigate coral community composition across three different temperature and productivity regimes along a nearshore-offshore gradient on lagoonal reefs of the Belize Mesoamerican Barrier Reef System (MBRS. A novel metric was developed using ultra-high-resolution satellite-derived estimates of sea surface temperatures (SST to classify reefs as exposed to low (lowTP, moderate (modTP, or high (highTP temperature parameters over 10 years (2003 to 2012. Coral species richness, abundance, diversity, density, and percent cover were lower at highTP sites relative to lowTP and modTP sites, but these coral community traits did not differ significantly between lowTP and modTP sites. Analysis of coral life history strategies revealed that highTP sites were dominated by hardy stress-tolerant and fast-growing weedy coral species, while lowTP and modTP sites consisted of competitive, generalist, weedy, and stress-tolerant coral species. Satellite-derived estimates of Chlorophyll-a (chl-a were obtained for 13-years (2003-2015 as a proxy for primary production. Chl-a concentrations were highest at highTP sites, medial at modTP sites, and lowest at lowTP sites. Notably, thermal parameters correlated better with coral community traits between site types than productivity, suggesting that temperature (specifically number of days above the thermal bleaching threshold played a greater role in defining coral community structure than productivity on the MBRS. Dominance of weedy and stress-tolerant genera at highTP sites suggests that corals

  19. Temperature and Discharge on a Highly Altered Stream in Utah's Cache Valley

    OpenAIRE

    Pappas, Andy

    2013-01-01

    To study the River Continuum Concept (RCC) and the Serial Discontinuity Hypothesis (SDH), I looked at temperature and discharge changes along 52 km of the Little Bear River in Cache Valley, Utah. The Little Bear River is a fourth order stream with one major reservoir, a number of irrigation diversions, and one major tributary, the East Fork of the Little Bear River. Discharge data was collected at six sites on 29 September 2012 and temperature data was collected hourly at eleven sites from 1 ...

  20. Modelling the sporulation of some fungi associated with cheese, at different temperature and water activity regimes.

    Science.gov (United States)

    Camardo Leggieri, Marco; Decontardi, Simone; Battilani, Paola

    2018-08-02

    The objectives of this study were to determine, in-vitro, the influence of temperature (T; 10-30 °C, step 5°), water activity (a w , 0.83-0.99; step 0.04) and time on sporulation (SPO) of some cheese-related fungi belonging to Penicillium spp. and A. versicolor. Overall, sporulation started rapidly (8 h in optimal conditions); it was significantly influenced by T and a w and the fungi studied were clearly distinguished based on their thermo-hydro adaptation. Boundary conditions for sporulation were defined for all the fungi considered and the sporulation rate was successfully modelled, especially based on T and time regimes. Penicillium crustosum, P. nordicum and P. verrucosum showed optimum for SPO at T between 20 and 25 °C and their sporulation continued up to a w  = 0.87 (a w  = 0.83 for P. nordicum). They resulted the fungi best adapted to the environmental conditions of ripening grana cheese storehouses; therefore, it is expected they dominate on the grana cheese surface. Studies on cheese are necessary to validate these results obtained on artificial media and without fungi co-occurrence. Copyright © 2018 Elsevier B.V. All rights reserved.

  1. A hierarchical bayesian model to quantify uncertainty of stream water temperature forecasts.

    Directory of Open Access Journals (Sweden)

    Guillaume Bal

    Full Text Available Providing generic and cost effective modelling approaches to reconstruct and forecast freshwater temperature using predictors as air temperature and water discharge is a prerequisite to understanding ecological processes underlying the impact of water temperature and of global warming on continental aquatic ecosystems. Using air temperature as a simple linear predictor of water temperature can lead to significant bias in forecasts as it does not disentangle seasonality and long term trends in the signal. Here, we develop an alternative approach based on hierarchical Bayesian statistical time series modelling of water temperature, air temperature and water discharge using seasonal sinusoidal periodic signals and time varying means and amplitudes. Fitting and forecasting performances of this approach are compared with that of simple linear regression between water and air temperatures using i an emotive simulated example, ii application to three French coastal streams with contrasting bio-geographical conditions and sizes. The time series modelling approach better fit data and does not exhibit forecasting bias in long term trends contrary to the linear regression. This new model also allows for more accurate forecasts of water temperature than linear regression together with a fair assessment of the uncertainty around forecasting. Warming of water temperature forecast by our hierarchical Bayesian model was slower and more uncertain than that expected with the classical regression approach. These new forecasts are in a form that is readily usable in further ecological analyses and will allow weighting of outcomes from different scenarios to manage climate change impacts on freshwater wildlife.

  2. Methyl halide fluxes from tropical plants under controlled radiation and temperature regimes

    Science.gov (United States)

    Blei, Emanuel; Yokouchi, Yoko; Saito, Takuya; Nozoe, Susumu

    2015-04-01

    Methyl halides (CH3Cl, CH3Br, CH3I) contribute significantly to the halogen burden of the atmosphere and have the potential to influence the stratospheric ozone layer through their catalytic effect in the Chapman cycle. As such they have been studied over the years, and many plants and biota have been examined for their potential to act as a source of these gases. One of the potentially largest terrestrial sources identified was tropical vegetation such as tropical ferns and Dipterocarp trees. Most of these studies concentrated on the identification and quantification of such fluxes rather than their characteristics and often the chambers used in these studies were either opaque or only partially transparent to the full solar spectrum. Therefore it is not certain to which degree emissions of methyl halides are innate to the plants and how much they might vary due to radiation or temperature conditions inside the enclosures. In a separate development it had been proposed that UV-radiation could cause live plant materials to be become emitters of methane even under non-anoxic conditions. As methane is chemically very similar to methyl halides and had been proposed to be produced from methyl-groups ubiquitously found in plant cell material there is a relatively good chance that such a production mechanism would also apply to methyl halides. To test whether radiation can affect elevated emissions of methyl halides from plant materials and to distinguish this from temperature effects caused by heat build-up in chambers a set of controlled laboratory chamber enclosures under various radiation and temperature regimes was conducted on four different tropical plant species (Magnolia grandiflora, Cinnamonum camphora, Cyathea lepifera, Angiopteris lygodiifolia), the latter two of which had previously been identified as strong methyl halide emitters. Abscised leaf samples of these species were subjected to radiation treatments such UV-B, UV-A and broad spectrum radiation

  3. Scaling of spectra in grid turbulence with a mean cross-stream temperature gradient

    Science.gov (United States)

    Bahri, Carla; Arwatz, Gilad; Mueller, Michael E.; George, William K.; Hultmark, Marcus

    2014-11-01

    Scaling of grid turbulence with a constant mean cross-stream temperature gradient is investigated using a combination of theoretical predictions, DNS, and experimental data. Conditions for self-similarity of the governing equations and the scalar spectrum are investigated, which reveals necessary conditions for self-similarity to exist. These conditions provide a theoretical framework for scaling of the temperature spectrum as well as the temperature flux spectrum. One necessary condition, predicted by the theory, is that the characteristic length scale describing the scalar spectrum must vary as √{ t} for a self-similar solution to exist. In order to investigate this, T-NSTAP sensors, specially designed for temperature measurements at high frequencies, were deployed in a heated passive grid turbulence setup together with conventional cold-wires, and complementary DNS calculations were performed to complement and complete the experimental data. These data are used to compare the behavior of different length scales and validate the theoretical predictions.

  4. Influences of wildfire and channel reorganization on spatial and temporal variation in stream temperature and the distribution of fish and amphibians

    Science.gov (United States)

    Jason B. Dunham; Amanda E. Rosenberger; Charlie H. Luce; Bruce E. Rieman

    2007-01-01

    Wildfire can influence a variety of stream ecosystem properties. We studied stream temperatures in relation to wildfire in small streams in the Boise River Basin, located in central Idaho, USA. To examine the spatio-temporal aspects of temperature in relation to wildfire, we employed three approaches: a pre­post fire comparison of temperatures between two sites (one...

  5. Stochastic ice stream dynamics.

    Science.gov (United States)

    Mantelli, Elisa; Bertagni, Matteo Bernard; Ridolfi, Luca

    2016-08-09

    Ice streams are narrow corridors of fast-flowing ice that constitute the arterial drainage network of ice sheets. Therefore, changes in ice stream flow are key to understanding paleoclimate, sea level changes, and rapid disintegration of ice sheets during deglaciation. The dynamics of ice flow are tightly coupled to the climate system through atmospheric temperature and snow recharge, which are known exhibit stochastic variability. Here we focus on the interplay between stochastic climate forcing and ice stream temporal dynamics. Our work demonstrates that realistic climate fluctuations are able to (i) induce the coexistence of dynamic behaviors that would be incompatible in a purely deterministic system and (ii) drive ice stream flow away from the regime expected in a steady climate. We conclude that environmental noise appears to be crucial to interpreting the past behavior of ice sheets, as well as to predicting their future evolution.

  6. Quantifying Forested Riparian Buffer Ability to Ameliorate Stream Temperature in a Missouri Ozark Border Stream of the Central U.S

    Science.gov (United States)

    Bulliner, E. A.; Hubbart, J. A.

    2009-12-01

    Riparian buffers play an important role in modulating stream water quality, including temperature. There is a need to better understand riparian form and function to validate and improve contemporary management practices. Further studies are warranted to characterize energy attenuation by forested riparian canopy layers that normally buffer stream temperature, particularly in the central hardwood forest regions of the United States where relationships between canopy density and stream temperature are unknown. To quantify these complex processes, two intensively instrumented hydroclimate stations were installed along two stream reaches of a riparian stream in central Missouri, USA in the winter of 2008. Hydroclimate stations are located along stream reaches oriented in both cardinal directions, which will allow interpolation of results to other orientations. Each station consists of an array of instrumentation that senses the flux of water and energy into and out of the riparian zone. Reference data are supplied from a nearby flux tower (US DOE) located on top of a forested ridge. The study sites are located within a University of Missouri preserved wildland area on the border of the southern Missouri’s Ozark region, an ecologically distinct region in the central United States. Limestone underlies the study area, resulting in a distinct semi-Karst hydrologic system. Vegetation forms a complex, multi-layered canopy extending from the stream edge through the riparian zone and into surrounding hills. Climate is classified as humid continental, with approximate average annual temperature and precipitation of 13.2°C and 970mm, respectively. Preliminary results (summer 2009 data) indicate incoming short-wave radiation is 24.9% higher at the N-S oriented stream reach relative to the E-W oriented reach. Maximum incoming short wave radiation during the period was 64.5% lower at the N-S reach relative to E-W reach. Average air temperature for the E-W reach was 0.3°C lower

  7. New England observed and predicted August stream/river temperature maximum positive daily rate of change points

    Data.gov (United States)

    U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted August stream/river temperature maximum positive daily rate of change in New England based on a...

  8. New England observed and predicted July stream/river temperature maximum positive daily rate of change points

    Data.gov (United States)

    U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted July stream/river temperature maximum positive daily rate of change in New England based on a...

  9. New England observed and predicted July maximum negative stream/river temperature daily rate of change points

    Data.gov (United States)

    U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted July stream/river temperature maximum negative daily rate of change in New England based on a...

  10. Documentation of a daily mean stream temperature module—An enhancement to the Precipitation-Runoff Modeling System

    Science.gov (United States)

    Sanders, Michael J.; Markstrom, Steven L.; Regan, R. Steven; Atkinson, R. Dwight

    2017-09-15

    A module for simulation of daily mean water temperature in a network of stream segments has been developed as an enhancement to the U.S. Geological Survey Precipitation Runoff Modeling System (PRMS). This new module is based on the U.S. Fish and Wildlife Service Stream Network Temperature model, a mechanistic, one-dimensional heat transport model. The new module is integrated in PRMS. Stream-water temperature simulation is activated by selection of the appropriate input flags in the PRMS Control File and by providing the necessary additional inputs in standard PRMS input files.This report includes a comprehensive discussion of the methods relevant to the stream temperature calculations and detailed instructions for model input preparation.

  11. The influence of an interfacial heat release on nonlinear convective regimes under the action of an imposed temperature gradient

    Energy Technology Data Exchange (ETDEWEB)

    Simanovskii, Ilya B, E-mail: cesima@tx.technion.ac.il [Department of Mathematics, Technion—Israel Institute of Technology, 32000 Haifa (Israel)

    2016-12-15

    The influence of an interfacial heat release on nonlinear convective regimes, developed under the action of an imposed temperature gradient in the 47v2 silicone oil–water system, has been studied. Two types of boundary conditions—periodic boundary conditions and rigid heat-insulated lateral walls—have been considered. Transitions between the flows with different spatial structures have been investigated. It is shown that the presence of an interfacial heat release can change the sequence of bifurcations and can lead to the appearance of new oscillatory regimes. The period-three phase trajectory has been found. (paper)

  12. Rising air and stream-water temperatures in Chesapeake Bay region, USA

    Science.gov (United States)

    Rice, Karen C.; Jastram, John D.

    2015-01-01

    Monthly mean air temperature (AT) at 85 sites and instantaneous stream-water temperature (WT) at 129 sites for 1960–2010 are examined for the mid-Atlantic region, USA. Temperature anomalies for two periods, 1961–1985 and 1985–2010, relative to the climate normal period of 1971–2000, indicate that the latter period was statistically significantly warmer than the former for both mean AT and WT. Statistically significant temporal trends across the region of 0.023 °C per year for AT and 0.028 °C per year for WT are detected using simple linear regression. Sensitivity analyses show that the irregularly sampled WT data are appropriate for trend analyses, resulting in conservative estimates of trend magnitude. Relations between 190 landscape factors and significant trends in AT-WT relations are examined using principal components analysis. Measures of major dams and deciduous forest are correlated with WT increasing slower than AT, whereas agriculture in the absence of major dams is correlated with WT increasing faster than AT. Increasing WT trends are detected despite increasing trends in streamflow in the northern part of the study area. Continued warming of contributing streams to Chesapeake Bay likely will result in shifts in distributions of aquatic biota and contribute to worsened eutrophic conditions in the bay and its estuaries.

  13. Low Frequency Modulation of Extreme Temperature Regimes in a Changing Climate

    Energy Technology Data Exchange (ETDEWEB)

    Black, Robert X. [Georgia Inst. of Technology, Atlanta, GA (United States)

    2014-11-24

    studied in (CMIP5) climate model simulations. Although the climate models considered are able to represent the overall behavior of ETEs, the frequency of WWs (CAOs) is too high (low) in many models. While all models qualitatively replicate the overall structure of the PNA pattern, a small minority of models fails to properly simulate the NAO pattern. Model shortcomings in representing the NAO and PNA patterns have important consequences for simulating associated regional variability in surface air temperature and storm track behavior. The influence of PCMs on ETEs is underestimated in most CMIP5 models. In particular, none of the models are able to accurately simulate observed linkages between ETEs and the PDO, due to a gross misrepresentation of the PDO pattern in most models. Our results indicate that predictions of future CAO and WW behavior are currently limited by the ability of climate models to accurately represent PCM characteristics. Our study also considers the behavior of PCMs known as annular modes. It is determined that north-south movements in the stratospheric jet stream (related to the Polar Annular Mode) result in long-lasting impacts upon surface weather conditions including regional air temperature anomalies. The structure and dynamics of the stratospheric northern annular mode (or SNAM, related to changes in the strength of the stratospheric jet stream) was studied in CMIP5 models. In models with poorly-resolved stratospheres, the amplitude of SNAM at stratospheric altitudes is typically too weak, consistent with weaker stratospheric jet variability. However, this distinction does not carry over to the associated tropospheric signature of SNAM. A regional analysis illustrates that most CMIP5 models (regardless of whether the stratosphere is well-resolved) have anomalously weak and eastward shifted (compared to observed SNAM events) storm track and sea level pressure anomaly patterns during SNAM events. Analyses of stratosphere–troposphere coupling

  14. Evaluating the impact of irrigation on surface water - groundwater interaction and stream temperature in an agricultural watershed.

    Science.gov (United States)

    Essaid, Hedeff I; Caldwell, Rodney R

    2017-12-01

    Changes in groundwater discharge to streams caused by irrigation practices can influence stream temperature. Observations along two currently flood-irrigated reaches in the 640-square-kilometer upper Smith River watershed, an important agricultural and recreational fishing area in west-central Montana, showed a downstream temperature decrease resulting from groundwater discharge to the stream. A watershed-scale coupled surface water and groundwater flow model was used to examine changes in streamflow, groundwater discharge to the stream and stream temperature resulting from irrigation practices. The upper Smith River watershed was used to develop the model framework including watershed climate, topography, hydrography, vegetation, soil properties and current irrigation practices. Model results were used to compare watershed streamflow, groundwater recharge, and groundwater discharge to the stream for three scenarios: natural, pre-irrigation conditions (PreIrr); current irrigation practices involving mainly stream diversion for flood and sprinkler irrigation (IrrCurrent); and a hypothetical scenario with only groundwater supplying sprinkler irrigation (IrrGW). Irrigation increased groundwater recharge relative to natural PreIrr conditions because not all applied water was removed by crop evapotranspiration. Groundwater storage and groundwater discharge to the stream increased relative to natural PreIrr conditions when the source of irrigation water was mainly stream diversion as in the IrrCurrent scenario. The hypothetical IrrGW scenario, in which groundwater withdrawals were the sole source of irrigation water, resulted in widespread lowering of the water table and associated decreases in groundwater storage and groundwater discharge to the stream. A mixing analysis using model predicted groundwater discharge along the reaches suggests that stream diversion and flood irrigation, represented in the IrrCurrent scenario, has led to cooling of stream temperatures

  15. High-Temperature Desulfurization of Heavy Fuel-Derived Reformate Gas Streams for SOFC Applications

    Science.gov (United States)

    Flytzani-Stephanopoulos, Maria; Surgenor, Angela D.

    2007-01-01

    Desulfurization of the hot reformate gas produced by catalytic partial oxidation or autothermal reforming of heavy fuels, such as JP-8 and jet fuels, is required prior to using the gas in a solid oxide fuel cell (SOFC). Development of suitable sorbent materials involves the identification of sorbents with favorable sulfidation equilibria, good kinetics, and high structural stability and regenerability at the SOFC operating temperatures (650 to 800 C). Over the last two decades, a major barrier to the development of regenerable desulfurization sorbents has been the gradual loss of sorbent performance in cyclic sulfidation and regeneration at such high temperatures. Mixed oxide compositions based on ceria were examined in this work as regenerable sorbents in simulated reformate gas mixtures and temperatures greater than 650 C. Regeneration was carried out with dilute oxygen streams. We have shown that under oxidative regeneration conditions, high regeneration space velocities (greater than 80,000 h(sup -1)) can be used to suppress sulfate formation and shorten the total time required for sorbent regeneration. A major finding of this work is that the surface of ceria and lanthanan sorbents can be sulfided and regenerated completely, independent of the underlying bulk sorbent. This is due to reversible adsorption of H2S on the surface of these sorbents even at temperatures as high as 800 C. La-rich cerium oxide formulations are excellent for application to regenerative H2S removal from reformate gas streams at 650 to 800 C. These results create new opportunities for compact sorber/regenerator reactor designs to meet the requirements of solid oxide fuel cell systems at any scale.

  16. Using Streamflow and Stream Temperature to Assess the Potential Responses of Freshwater Fish to Climate Change

    Science.gov (United States)

    VanCompernolle, M.; Ficklin, D. L.; Knouft, J.

    2017-12-01

    Streamflow and stream temperature are key variables influencing growth, reproduction, and mortality of freshwater fish. Climate-induced changes in these variables are expected to alter the structure and function of aquatic ecosystems. Using Maxent, a species distribution model (SDM) based on the principal of maximum entropy, we predicted potential distributional responses of 100 fish species in the Mobile River Basin (MRB) to changes in climate based on contemporary and future streamflow and stream temperature estimates. Geologic, topographic, and landcover data were also included in each SDM to determine the contribution of these physical variables in defining areas of suitable habitat for each species. Using an ensemble of Global Climate Model (GCM) projections under a high emissions scenario, predicted distributions for each species across the MRB were produced for both a historical time period, 1975-1994, and a future time period, 2060-2079, and changes in total area and the percent change in historical suitable habitat for each species were calculated. Results indicate that flow (28%), temperature (29%), and geology (29%), on average, contribute evenly to determining areas of suitable habitat for fish species in the MRB, with landcover and slope playing more limited roles. Temperature contributed slightly more predictive ability to SDMs (31%) for the 77 species experiencing overall declines in areas of suitable habitat, but only 21% for the 23 species gaining habitat across all GCMs. Species are expected to lose between 15-24% of their historical suitable habitat, with threatened and endangered species losing 22-30% and those endemic to the MRB losing 19-28%. Sculpins (Cottidae) are expected to lose the largest amount of historical habitat (up to 84%), while pygmy sunfish (Elassomatidae) are expected to lose less than 1% of historical habitat. Understanding which species may be at risk of habitat loss under future projections of climate change can help

  17. Mediating water temperature increases due to livestock and global change in high elevation meadow streams of the Golden Trout Wilderness

    Science.gov (United States)

    Sebastien Nussle; Kathleen R. Matthews; Stephanie M. Carlson

    2015-01-01

    Rising temperatures due to climate change are pushing the thermal limits of many species, but how climate warming interacts with other anthropogenic disturbances such as land use remains poorly understood. To understand the interactive effects of climate warming and livestock grazing on water temperature in three high elevation meadow streams in the Golden Trout...

  18. Seasonal variations in groundwater upwelling zones in a Danish lowland stream analyzed using Distributed Temperature Sensing (DTS)

    DEFF Research Database (Denmark)

    Matheswaran, Karthikeyan; Blemmer, Morten; Rosbjerg, Dan

    2014-01-01

    –night temperature difference were applied to three DTS datasets representing stream temperature responses to the variable meteorological and hydrological conditions prevailing in summer, winter and spring. The standard deviation criterion was useful to identify groundwater discharge zones in summer and spring......-term deployment covering variable meteorological and hydrological scenarios. Copyright © 2012 John Wiley & Sons, Ltd....

  19. Long term variability of the annual hydrological regime and sensitivity to temperature phase shifts in Saxony/Germany

    Science.gov (United States)

    Renner, M.; Bernhofer, C.

    2011-01-01

    The timing of the seasons strongly effects ecosystems and human activities. Recently, there is increasing evidence of changes in the timing of the seasons, such as earlier spring seasons detected in phenological records, advanced seasonal timing of surface temperature, earlier snow melt or streamflow timing. For water resources management there is a need to quantitatively describe the variability in the timing of hydrological regimes and to understand how climatic changes control the seasonal water budget of river basins on the regional scale. In this study, changes of the annual cycle of hydrological variables are analysed for 27 river basins in Saxony/Germany. Thereby monthly series of basin runoff ratios, the ratio of runoff and basin precipitation are investigated for changes and variability of their annual periodicity over the period 1930-2009. Approximating the annual cycle by the means of harmonic functions gave acceptable results, while only two parameters, phase and amplitude, are required. It has been found that the annual phase of runoff ratio, representing the timing of the hydrological regime, is subject to considerable year-to-year variability, being concurrent with basins in similar hydro-climatic conditions. Two distinct basin classes have been identified, whereby basin elevation has been found to be the delimiting factor. An increasing importance of snow on the basin water balance with elevation is apparent and mainly governs the temporal variability of the annual timing of hydrological regimes. Further there is evidence of coincident changes in trend direction (change points in 1971 and 1988) in snow melt influenced basins. In these basins the timing of the runoff ratio is significantly correlated with the timing of temperature, and effects on runoff by temperature phase changes are even amplified. Interestingly, temperature effects may explain the low frequent variability of the second change point until today. However, the first change point can

  20. Two-phase regime in the magnetic field-temperature phase diagram of a type-II superconductor

    International Nuclear Information System (INIS)

    Adams, L.L.A.; Halterman, Klaus; Valls, Oriol T.; Goldman, A.M.

    2004-01-01

    The magnetic field and temperature dependencies of the magnetic moments of superconducting crystals of V 3 Si have been studied. In a constant magnetic field and at temperatures somewhat below the superconducting transition temperature, the moments are hysteretic in temperature. However, the magnetic moment-magnetic field isotherms are reversible and exhibit features that formally resemble the pressure-volume isotherms of the liquid-gas transition. This suggests the existence of a first-order phase transition, a two-phase regime, and a critical point in the superconducting phase diagram. The two phases are disordered vortex configurations with the same magnetization, but with different vortex densities. The entropy change, determined from the data using the Clausius-Clapeyron equation, is consistent with estimates based on the difference in the vortex densities of the two phases

  1. Two-phase regime in the magnetic field-temperature phase diagram of a type-II superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Adams, L.L.A.; Halterman, Klaus; Valls, Oriol T.; Goldman, A.M

    2004-01-01

    The magnetic field and temperature dependencies of the magnetic moments of superconducting crystals of V{sub 3}Si have been studied. In a constant magnetic field and at temperatures somewhat below the superconducting transition temperature, the moments are hysteretic in temperature. However, the magnetic moment-magnetic field isotherms are reversible and exhibit features that formally resemble the pressure-volume isotherms of the liquid-gas transition. This suggests the existence of a first-order phase transition, a two-phase regime, and a critical point in the superconducting phase diagram. The two phases are disordered vortex configurations with the same magnetization, but with different vortex densities. The entropy change, determined from the data using the Clausius-Clapeyron equation, is consistent with estimates based on the difference in the vortex densities of the two phases.

  2. Dynamics of trapped two-component Fermi gas: Temperature dependence of the transition from collisionless to collisional regime

    International Nuclear Information System (INIS)

    Toschi, F.; Vignolo, P.; Tosi, M.P.; Succi, S.

    2003-01-01

    We develop a numerical method to study the dynamics of a two-component atomic Fermi gas trapped inside a harmonic potential at temperature T well below the Fermi temperature T F . We examine the transition from the collisionless to the collisional regime down to T=0.2 T F and find a good qualitative agreement with the experiments of B. DeMarco and D.S. Jin [Phys. Rev. Lett. 88, 040405 (2002)]. We demonstrate a twofold role of temperature on the collision rate and on the efficiency of collisions. In particular, we observe a hitherto unreported effect, namely, the transition to hydrodynamic behavior is shifted towards lower collision rates as temperature decreases

  3. Effect of Different Arbuscular Mycorrhizal Fungi on Growth and Physiology of Maize at Ambient and Low Temperature Regimes

    Directory of Open Access Journals (Sweden)

    Xiaoying Chen

    2014-01-01

    Full Text Available The effect of four different arbuscular mycorrhizal fungi (AMF on the growth and lipid peroxidation, soluble sugar, proline contents, and antioxidant enzymes activities of Zea mays L. was studied in pot culture subjected to two temperature regimes. Maize plants were grown in pots filled with a mixture of sandy and black soil for 5 weeks, and then half of the plants were exposed to low temperature for 1 week while the rest of the plants were grown under ambient temperature and severed as control. Different AMF resulted in different root colonization and low temperature significantly decreased AM colonization. Low temperature remarkably decreased plant height and total dry weight but increased root dry weight and root-shoot ratio. The AM plants had higher proline content compared with the non-AM plants. The maize plants inoculated with Glomus etunicatum and G. intraradices had higher malondialdehyde and soluble sugar contents under low temperature condition. The activities of catalase (CAT and peroxidase of AM inoculated maize were higher than those of non-AM ones. Low temperature noticeably decreased the activities of CAT. The results suggest that low temperature adversely affects maize physiology and AM symbiosis can improve maize seedlings tolerance to low temperature stress.

  4. Development of Atlantic salmon (Salmo salar) eggs and alevins under varied temperature regimes

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, R H; Spinney, H C.E.; Sreedharan, A

    1977-01-01

    Atlantic salmon (Salmo salar) eggs and alevins were raised under conditions where the temperature was systematically varied either at fertilization, at the eyed egg stage, or at hatching. Mortality was more than 20% in eggs started immediately after fertilization at constant incubation temperatures <4/sup 0/C as compared with 5% or less at temperatures >4/sup 0/C. Alevins that eyed at 8/sup 0/C and higher were progressively smaller the higher the temperature. The optimum temperature from fertilization to eye pigmentation was near 6/sup 0/C. Eyed eggs reared at lower temperatures until hatching were larger than those hatched at higher temperatures. This size differential was maintained until the yolk was completely absorbed at all posthatching temperatures investigated. Sudden decreases in temperature at the eyed egg and hatching stages induced severe edema of the alevin yolk sac, resulting in slower growth and increased mortality.

  5. Prediction of temperature and damage in an irradiated human eye-Utilization of a detailed computer model which includes a vectorial blood stream in the choroid.

    Science.gov (United States)

    Heussner, Nico; Holl, Lukas; Nowak, Timo; Beuth, Thorsten; Spitzer, Martin S; Stork, Wilhelm

    2014-08-01

    The work presented here describes the development and use of a three-dimensional thermo-dynamic model of the human eye for the prediction of temperatures and damage thresholds under irradiation. This model takes into account the blood flow by the implementation of a vectorial blood stream in the choroid and also uses the actual physiological extensions and tissue parameters of the eye. Furthermore it considers evaporation, radiation and convection at the cornea as well as the eye lid. The predicted temperatures were successfully validated against existing eye models in terms of corneal and global thermal behaviour. The model׳s predictions were additionally checked for consistency with in-vivo temperature measurements of the cornea, the irradiated retina and its damage thresholds. These thresholds were calculated from the retinal temperatures using the Arrhenius integral. Hence the model can be used to predict the temperature increase and irradiation hazard within the human eye as long as the absorption values and the Arrhenius coefficients are known and the damage mechanism is in the thermal regime. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Climate Change Impacts on Stream Temperature in Regulated River Systems: A Case Study in the Southeastern United States

    Science.gov (United States)

    Cheng, Y.; Niemeyer, R. J.; Zhang, X.; Yearsley, J. R.; Voisin, N.; Nijssen, B.

    2017-12-01

    Climate change and associated changes in air temperature and precipitation are projected to impact natural water resources quantity, quality and timing. In the past century, over 280 major dams were built in the Southeastern United States (SEUS) (GRanD database). Regulation of the river system greatly alters natural streamflow as well as stream temperature. Understanding the impacts of climate change on regulated systems, particularly within the context of the Clean Water Act, can inform stakeholders how to maintain and adapt water operations (e.g. regulation, withdrawals). In this study, we use a new modeling framework to study climate change impacts on stream temperatures of a regulated river system. We simulate runoff with the Variable Infiltration Capacity (VIC) macroscale hydrological model, regulated streamflow and reservoir operations with a large-scale river routing-reservoir model (MOSART-WM), and stream temperature using the River Basin Model (RBM). We enhanced RBM with a two-layer thermal stratification reservoir module. This modeling framework captures both the impact of reservoir regulation on streamflow and the reservoir stratification effects on downstream temperatures. We evaluate changes in flow and stream temperatures based on climate projections from two representative concentration pathways (RCPs; RCP4.5 and RCP8.5) from the Coupled Model Intercomparison Project Phase 5 (CMIP5). We simulate river temperature with meteorological forcings that have been downscaled with the Multivariate Constructed Analogs (MACA) method. We are specifically interested in analyzing extreme periods during which stream temperature exceeds water quality standards. In this study, we focus on identifying whether these extreme temperature periods coincide with low flows, and whether the frequency and duration of these operationally-relevant periods will increase under future climate change.

  7. Effects of ocean acidification, temperature and nutrient regimes on the appendicularian Oikopleura dioica: a mesocosm study

    DEFF Research Database (Denmark)

    Troedsson, Christofer; Bouquet, Jean-Marie; Lobon, Carla M.

    2012-01-01

    , temperature and nutrient levels, consistent with hypotheses concerning gelatinous zooplankton in future oceans. This suggests appendicularians will play more important roles in marine pelagic communities and vertical carbon transport under projected ocean acidification and elevated temperature scenarios....

  8. Long-term monitoring of streambed sedimentation and scour in a dynamic stream based on streambed temperature time series.

    Science.gov (United States)

    Sebok, Eva; Engesgaard, Peter; Duque, Carlos

    2017-08-24

    This study presented the monitoring and quantification of streambed sedimentation and scour in a stream with dynamically changing streambed based on measured phase and amplitude of the diurnal signal of sediment temperature time series. With the applied method, changes in streambed elevation were estimated on a sub-daily scale with 2-h intervals without continuous maintenance of the measurement system, thus making both high temporal resolution and long-term monitoring of streambed elevations possible. Estimates of streambed elevation showed that during base flow conditions streambed elevation fluctuates by 2-3 cm. Following high stream stages, scouring of 2-5 cm can be observed even at areas with low stream flow and weak currents. Our results demonstrate that weather variability can induce significant changes in the stream water and consequently sediment temperatures influencing the diurnal temperature signal in such an extent that the sediment thickness between paired temperature sensors were overestimated by up to 8 cm. These observations have significant consequences on the design of vertical sensor spacing in high-flux environments and in climates with reduced diurnal variations in air temperature.

  9. Responses of quinoa (Chenopodium quinoa Willd.) to salinity and temperature regimes

    DEFF Research Database (Denmark)

    Adolf, Verena Isabelle

    on salt affected soils in the Mediterranean region, it is necessary to evaluate whether these cultivars are also able to thrive under warmer temperatures. Temperatures of the Bolivian highland and Morocco were simulated in climate chambers to evaluate the performance of a very salt tolerant Bolivian...

  10. Secretome weaponries of Cochliobolus lunatus interacting with potato leaf at different temperature regimes reveal a CL[xxxx]LHM - motif.

    Science.gov (United States)

    Louis, Bengyella; Waikhom, Sayanika Devi; Roy, Pranab; Bhardwaj, Pardeep Kumar; Singh, Mohendro Wakambam; Goyari, Sailendra; Sharma, Chandradev K; Talukdar, Narayan Chandra

    2014-03-20

    Plant and animal pathogenic fungus Cochliobolus lunatus cause great economic damages worldwide every year. C. lunatus displays an increased temperature dependent-virulence to a wide range of hosts. Nonetheless, this phenomenon is poorly understood due to lack of insights on the coordinated secretome weaponries produced by C. lunatus under heat-stress conditions on putative hosts. To understand the mechanism better, we dissected the secretome of C. lunatus interacting with potato (Solanum tuberosum L.) leaf at different temperature regimes. C. lunatus produced melanized colonizing hyphae in and on potato leaf, finely modulated the ambient pH as a function of temperature and secreted diverse set of proteins. Using two dimensional gel electrophoresis (2-D) and mass spectrometry (MS) technology, we observed discrete secretomes at 20°C, 28°C and 38°C. A total of 21 differentially expressed peptide spots and 10 unique peptide spots (that did not align on the gels) matched with 28 unique protein models predicted from C. lunatus m118 v.2 genome peptides. Furthermore, C. lunatus secreted peptides via classical and non-classical pathways related to virulence, proteolysis, nucleic acid metabolism, carbohydrate metabolism, heat stress, signal trafficking and some with unidentified catalytic domains. We have identified a set of 5 soluble candidate effectors of unknown function from C. lunatus secretome weaponries against potato crop at different temperature regimes. Our findings demonstrate that C. lunatus has a repertoire of signature secretome which mediates thermo-pathogenicity and share a leucine rich "CL[xxxx]LHM"-motif. Considering the rapidly evolving temperature dependent-virulence and host diversity of C. lunatus, this data will be useful for designing new protection strategies.

  11. Zirconium phosphate waste forms for low-temperature stabilization of cesium-137-containing waste streams

    International Nuclear Information System (INIS)

    Singh, D.; Wagh, A.S.; Tlustochowicz.

    1996-04-01

    Novel chemically bonded phosphate ceramics are being developed and fabricated for low-temperature stabilization and solidification of waste streams that are not amenable to conventional high-temperature stabilization processes because volatiles are present in the wastes. A composite of zirconium-magnesium phosphate has been developed and shown to stabilize ash waste contaminated with a radioactive surrogate of 137 Cs. Excellent retainment of cesium in the phosphate matrix system was observed in Toxicity Characteristic Leaching Procedure tests. This was attributed to the capture of cesium in the layered zirconium phosphate structure by intercalation ion-exchange reaction. But because zirconium phosphate has low strength, a novel zirconium/magnesium phosphate composite waste form system was developed. The performance of these final waste forms, as indicated by compression strength and durability in aqueous environments, satisfy the regulatory criteria. Test results indicate that zirconium-magnesium-phosphate-based final waste forms present a viable technology for treatment and solidification of cesium-contaminated wastes

  12. Simulation of climate-change effects on streamflow, lake water budgets, and stream temperature using GSFLOW and SNTEMP, Trout Lake Watershed, Wisconsin

    Science.gov (United States)

    Hunt, Randall J.; Walker, John F.; Selbig, William R.; Westenbroek, Stephen M.; Regan, R. Steve

    2013-01-01

    2010–2100 showed increases in maximum and minimum temperature over the scenario period. Scenarios of future precipitation did not show a monotonic trend like temperature. Uncertainty in the climate drivers increased over time for both temperature and precipitation. Separate calibration of the uncoupled groundwater and surface-water models did not provide a representative initial parameter set for coupled model calibration. A sequentially linked calibration, in which the uncoupled models were linked by means of utility software, provided a starting parameter set suitable for coupled model calibration. Even with sequentially linked calibration, however, transmissivity of the lower part of the aquifer required further adjustment during coupled model calibration to attain reasonable parameter values for evaporation rates off a small seepage lake (a lake with no appreciable surface-water outlets) with a long history of study. The resulting coupled model was well calibrated to most types of observed time-series data used for calibration. Daily stream temperatures measured during 2002 were successfully simulated with SNTEMP; the model fit was acceptable for a range of groundwater inflow rates into the streams. Forecasts of potential climate change scenarios showed growing season length increasing by weeks, and both potential and actual evapotranspiration rates increasing appreciably, in response to increasing air temperature. Simulated actual evapotranspiration rates increased less than simulated potential evapotranspiration rates as a result of water limitation in the root zone during the summer high-evapotranspiration period. The hydrologic-system response to climate change was characterized by a reduction in the importance of the snow-melt pulse and an increase in the importance of fall and winter groundwater recharge. The less dynamic hydrologic regime is likely to result in drier soil conditions in rainfed wetlands and uplands, in contrast to less drying in groundwater

  13. Temperature Regimes in Traditional Iñupiat Ice Cellars in Barrow, Alaska

    Science.gov (United States)

    Klene, A. E.; Yoshikawa, K.; Streletskiy, D. A.; Brown, J.; Nelson, F. E.; Shiklomanov, N. I.

    2011-12-01

    Historically ice cellars excavated in permafrost (perennially frozen ground) have been essential to Arctic residents and remain so today. These traditional facilities allow secure, year-round frozen storage of subsistence harvests over long periods. Iñupiat peoples in Barrow, Alaska, have many of these cellars, some of which were created more than a century ago. Others were established recently and continue to be enlarged. Temperatures within the cellars are critical because bacteria can damage meat even at temperatures below the freezing point. These cellars generally have temperatures close to those of surrounding permafrost. Climatic change has been suspected of compromising and causing damage to ice cellars in some northern communities, with thaw and spoilage of meat occurring in some cases. Beginning in 2005, local residents and the Native Village of Barrow organization provided access to their ice cellars and miniature temperature data loggers programmed to record at hourly intervals were installed. Cellars at a variety of depths, locations relative to the coast, and age were included in the survey. Analysis of the five years of record revealed seasonal variations within each cellar, temperature changes over time within some cellars, and temperature differences between the five cellars examined. Winter ventilation to artificially cool the cellars, local snow drifting, and proximity to brine-saturated sediments contribute to differences in ambient ground conditions. Long-term temperature measurements in these and other cellars are needed to better understand the observed changes.

  14. Habitat pollution and thermal regime modify molecular stress responses to elevated temperature in freshwater mussels (Anodonta anatina: Unionidae)

    International Nuclear Information System (INIS)

    Falfushynska, H.; Gnatyshyna, L.; Yurchak, I.; Ivanina, A.; Stoliar, O.; Sokolova, I.

    2014-01-01

    Elevated temperature and pollution are common stressors in freshwater ecosystems. We study cellular stress response to acute warming in Anodonta anatina (Unionidae) from sites with different thermal regimes and pollution levels: a pristine area and an agriculturally polluted site with normal temperature regimes (F and A, respectively) and a polluted site with elevated temperature (N) from the cooling pond of an electrical power plant. Animals were exposed to different temperatures for 14 days and stress response markers were measured in gills, digestive gland and hemocytes. Mussels from site N and A had elevated background levels of lactate dehydrogenase activity indicating higher reliance on anaerobic metabolism for ATP production and/or redox maintenance. Exposure to 25 °C and 30 °C induced oxidative stress (indicated by elevated levels of lipid peroxidation products) in digestive gland and gills of mussels from A and F sites, while in mussels from N sites elevated oxidative stress was only apparent at 30 °C. Temperature-induced changes in levels of antioxidants (superoxide dismutase, metallothioneins and glutathione) were tissue- and population-specific. Acute warming led to destabilization of lysosomal membranes and increased frequencies of nuclear lesions in mussels from F and A sites but not in their counterparts from N site. Elevated temperature led to an increase in the frequency of micronuclei in hemocytes in mussels from F and A sites at 25 °C and 30 °C and in mussels from N site at 30 °C. The mussels from N site also demonstrated better survival at elevated temperature (30 °C) than their counterparts from the F and A sites. Taken together, these data indicate that long-term acclimation and/or adaptation of A. anatina to elevated temperatures result in increased thermotolerance and alleviate stress response to moderate temperature rise. In contrast, extreme warming (30 °C) is harmful to mussels from all populations indicating limit to this induced

  15. Habitat pollution and thermal regime modify molecular stress responses to elevated temperature in freshwater mussels (Anodonta anatina: Unionidae)

    Energy Technology Data Exchange (ETDEWEB)

    Falfushynska, H.; Gnatyshyna, L.; Yurchak, I. [Research Laboratory of Comparative Biochemistry and Molecular Biology, Ternopil National Pedagogical University, Kryvonosa Str 2, 46027 Ternopil (Ukraine); Ivanina, A. [Department of Biological Sciences, University of North Carolina at Charlotte, 9201 University City Blvd., Charlotte, NC 28223 (United States); Stoliar, O. [Research Laboratory of Comparative Biochemistry and Molecular Biology, Ternopil National Pedagogical University, Kryvonosa Str 2, 46027 Ternopil (Ukraine); Sokolova, I., E-mail: isokolov@uncc.edu [Department of Biological Sciences, University of North Carolina at Charlotte, 9201 University City Blvd., Charlotte, NC 28223 (United States)

    2014-12-01

    Elevated temperature and pollution are common stressors in freshwater ecosystems. We study cellular stress response to acute warming in Anodonta anatina (Unionidae) from sites with different thermal regimes and pollution levels: a pristine area and an agriculturally polluted site with normal temperature regimes (F and A, respectively) and a polluted site with elevated temperature (N) from the cooling pond of an electrical power plant. Animals were exposed to different temperatures for 14 days and stress response markers were measured in gills, digestive gland and hemocytes. Mussels from site N and A had elevated background levels of lactate dehydrogenase activity indicating higher reliance on anaerobic metabolism for ATP production and/or redox maintenance. Exposure to 25 °C and 30 °C induced oxidative stress (indicated by elevated levels of lipid peroxidation products) in digestive gland and gills of mussels from A and F sites, while in mussels from N sites elevated oxidative stress was only apparent at 30 °C. Temperature-induced changes in levels of antioxidants (superoxide dismutase, metallothioneins and glutathione) were tissue- and population-specific. Acute warming led to destabilization of lysosomal membranes and increased frequencies of nuclear lesions in mussels from F and A sites but not in their counterparts from N site. Elevated temperature led to an increase in the frequency of micronuclei in hemocytes in mussels from F and A sites at 25 °C and 30 °C and in mussels from N site at 30 °C. The mussels from N site also demonstrated better survival at elevated temperature (30 °C) than their counterparts from the F and A sites. Taken together, these data indicate that long-term acclimation and/or adaptation of A. anatina to elevated temperatures result in increased thermotolerance and alleviate stress response to moderate temperature rise. In contrast, extreme warming (30 °C) is harmful to mussels from all populations indicating limit to this induced

  16. Space monitoring of temperature regime of Semipalatinsk nuclear test site: 10 years of observations

    International Nuclear Information System (INIS)

    Spivak, L.F.; Arkhipkin, O.P.; Vitkovskaya, I.S.; Batyrbaeva, M.Zh.; Sagatdinova, G.N.

    2006-01-01

    A brief description of the results of temperature anomaly routine research by specialists from Space Research Institute of Ministry of Education and Science of the Republic of Kazakhstan, revealed in 1997 within Semipalatinsk Test Site in the process of remote sounding of Kazakhstani territory, is given. Results of map analysis for snow cover, day and night temperatures and vegetation (during vegetation season) for the period since 1997 till 2006 testify a hypothesis on natural temperature anomaly, though there is a number of questions to be answered for further complex investigation. (author)

  17. Thermohydraulic modeling of very high temperature reactors in regimes with loss of coolant using CFD

    Energy Technology Data Exchange (ETDEWEB)

    Moreira, Uebert G.; Dominguez, Dany S. [Universidade Estadual de Santa Cruz (UESC), Ilh´eus, BA (Brazil). Programa de P´os-Graduacao em Modelagem Computacional em Ciencia e Tecnologia; Mazaira, Leorlen Y.R.; Lira, Carlos A.B.O. [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Energia Nuclear; Hernandez, Carlos R.G., E-mail: uebert.gmoreira@gmail.com, E-mail: dsdominguez@gmail.com, E-mail: leored1984@gmail.com, E-mail: cabol@ufpe.br, E-mail: cgh@instec.cu [Instituto Superior de Tecnologas y Ciencias Aplicadas (InSTEC), La Habana (Cuba)

    2017-07-01

    The nuclear energy is a good alternative to meet the continuous increase in world energy demand. In this perspective, VHTRs (Very High Temperature Reactors) are serious candidates for energy generation due to its inherently safe performance, low power density and high conversion efficiency. However, the viability of these reactors depends on an efficient safety system in the operation of nuclear plants. The HTR (High Temperature Reactor)-10 model, an experimental reactor of the pebble bed type, is used as a case study in this work to perform the thermohydraulic simulation. Due to the complex patterns flow that appear in the pebble bed reactor core, and advances in computational capacity, CFD (Computational Fluid Dynamics) techniques are used to simulate these reactors. A realistic approach is adopted to simulate the central annular column of the reactor core, which each pebble bed element is modeled in detail. As geometrical model of the fuel elements was selected the BCC (Body Centered Cubic) arrangement. Previous works indicate this arrangement as the configuration that obtain higher fuel temperatures inside the core. Parameters considered for reactor design are available in the technical report of benchmark issues by IAEA (TECDOC-1694). Among the results obtained, we obtained the temperature profiles with different mass flow rates for the coolant. In general, the temperature distributions calculated are consistent with phenomenological behaviour. Even without consider the reactivity changes to reduce the reactor power or other safety procedures, the maximum temperatures do not exceed the recommended limits for fuel elements. (author)

  18. Physical characterization of Rhipsalis (Cactaceae fruits and seeds germination in different temperatures and light regimes

    Directory of Open Access Journals (Sweden)

    A. B. Lone

    Full Text Available Abstract The germination characteristics of the native cactus species are poorly known, being the temperature and the light the factors that the most interferes in that process. Thus, the objective of the present work was to characterize the fruits and evaluate the influence of the temperature and the light in the seed germination of Rhipsalis floccosa, Rhipsalis pilocarpa and Rhipsalis teres. The tested constant temperatures were 15, 20, 25, 30 and 35 °C and the alternate of 20-30 °C and 25-35 °C in a photoperiod of 10 hours, and with determination of the most appropriate temperature, the germination was tested in light absence. The germination percentage, the index of germination speed and medium time of germination were evaluated. For R. floccosa, the highest germination percentage was at 20 °C. For R. pilocarpa and R. teres, the highest germination percentages occurred in 15 °C and 20 °C. There was correlation to germination percentage between the three species, indicating that they had similar germination behavior. Total absence of germination was verified for the three species in condition of light absence. In conclusion, the temperature of 20 °C is the most suitable for the seed germination of R. floccosa. For the species R. pilocarpa and R. teres, the temperatures of 15 and 20 °C are the most suitable.

  19. Physical characterization of Rhipsalis (Cactaceae) fruits and seeds germination in different temperatures and light regimes.

    Science.gov (United States)

    Lone, A B; Colombo, R C; Andrade, B L G; Takahashi, L S A; Faria, R T

    2016-06-01

    The germination characteristics of the native cactus species are poorly known, being the temperature and the light the factors that the most interferes in that process. Thus, the objective of the present work was to characterize the fruits and evaluate the influence of the temperature and the light in the seed germination of Rhipsalis floccosa, Rhipsalis pilocarpa and Rhipsalis teres. The tested constant temperatures were 15, 20, 25, 30 and 35 °C and the alternate of 20-30 °C and 25-35 °C in a photoperiod of 10 hours, and with determination of the most appropriate temperature, the germination was tested in light absence. The germination percentage, the index of germination speed and medium time of germination were evaluated. For R. floccosa, the highest germination percentage was at 20 °C. For R. pilocarpa and R. teres, the highest germination percentages occurred in 15 °C and 20 °C. There was correlation to germination percentage between the three species, indicating that they had similar germination behavior. Total absence of germination was verified for the three species in condition of light absence. In conclusion, the temperature of 20 °C is the most suitable for the seed germination of R. floccosa. For the species R. pilocarpa and R. teres, the temperatures of 15 and 20 °C are the most suitable.

  20. Thermohydraulic modeling of very high temperature reactors in regimes with loss of coolant using CFD

    International Nuclear Information System (INIS)

    Moreira, Uebert G.; Dominguez, Dany S.

    2017-01-01

    The nuclear energy is a good alternative to meet the continuous increase in world energy demand. In this perspective, VHTRs (Very High Temperature Reactors) are serious candidates for energy generation due to its inherently safe performance, low power density and high conversion efficiency. However, the viability of these reactors depends on an efficient safety system in the operation of nuclear plants. The HTR (High Temperature Reactor)-10 model, an experimental reactor of the pebble bed type, is used as a case study in this work to perform the thermohydraulic simulation. Due to the complex patterns flow that appear in the pebble bed reactor core, and advances in computational capacity, CFD (Computational Fluid Dynamics) techniques are used to simulate these reactors. A realistic approach is adopted to simulate the central annular column of the reactor core, which each pebble bed element is modeled in detail. As geometrical model of the fuel elements was selected the BCC (Body Centered Cubic) arrangement. Previous works indicate this arrangement as the configuration that obtain higher fuel temperatures inside the core. Parameters considered for reactor design are available in the technical report of benchmark issues by IAEA (TECDOC-1694). Among the results obtained, we obtained the temperature profiles with different mass flow rates for the coolant. In general, the temperature distributions calculated are consistent with phenomenological behaviour. Even without consider the reactivity changes to reduce the reactor power or other safety procedures, the maximum temperatures do not exceed the recommended limits for fuel elements. (author)

  1. Legacies of stream channel modification revealed using General Land Office surveys, with implications for water temperature and aquatic life

    Directory of Open Access Journals (Sweden)

    Seth M. White

    2017-02-01

    Full Text Available Land use legacies can have a discernible influence in present-day watersheds and should be accounted for when designing conservation strategies for riverine aquatic life. We describe the environmental history of three watersheds within the Grande Ronde subbasin of the Columbia River using General Land Office survey field notes from the 19th century. In the two watersheds severely impacted by Euro-American land use, stream channel widths—a metric representing habitat simplification—increased from an average historical width of 16.8 m to an average present width of 20.8 m in large streams; 4.3 m to 5.5 m in small, confined or partly confined streams; and 3.5 m to 6.5 m in small, laterally unconfined steams. Conversely, we did not detect significant change in stream widths in an adjacent, wilderness stream with minimal human impact. Using a mechanistic water temperature model and restoration scenarios based on the historical condition, we predicted that stream restoration in the impacted watersheds could notably decrease average water temperatures—especially when channel narrowing is coupled with riparian restoration—up to a 6.6°C reduction in the upper Grande Ronde River and 3.0°C in Catherine Creek. These reductions in water temperature translated to substantial changes in the percentage of stream network habitable to salmon and steelhead migration (from 29% in the present condition to 79% in the fully restored scenario and to core juvenile rearing (from 13% in the present condition to 36% in the fully restored scenario. We conclude that land use legacies leave an important footprint on the present landscape and are critical for understanding historic habitat-forming processes as a necessary first step towards restoration.

  2. Length-dependent thermoelectric characteristics of silicon nanowires on plastics in a relatively low temperature regime in ambient air

    International Nuclear Information System (INIS)

    Choi, Jinyong; Cho, Kyoungah; Kim, Sangsig

    2013-01-01

    We report on the thermoelectric characteristics of p-type silicon nanowires (NWs) on plastics in the relatively low temperature regime below 47 ° C, and for temperature differences of less than 10 K in ambient air. Thermal profile images are utilized to directly determine the temperature difference in the NWs generated by Joule heating in air. The Seebeck coefficient of the NWs increases from 294 to 414 μV K −1 as the NW length varies from 40 to 280 μm. For a temperature difference of 7 K, the maximal Seebeck voltage can be estimated to be 2.7 mV for NWs with a length of 280 μm. In contrast, the output power is maximized for NWs length of 240 μm. The maximized output power obtained experimentally in this study is 2.1 pW at a temperature difference of 6 K. The thermoelectric characteristics are analyzed and discussed. (paper)

  3. [Effects of temperature regime on low-light tolerance of Cucumis sativus seedling leaves in their photosynthesis].

    Science.gov (United States)

    Li, Wei; Sui, Xiao-lei; Zhang, Zhen-xian

    2008-12-01

    In a phytotron, the effects of three temperature regimes (day/night 25 degrees C/18 degrees C, optimal temperature; 15 degrees C/9 degrees C, suboptimal temperature; and 9 degrees C/7 degrees C, low temperature) on the low-light (75-85 micromol x m(-2) x s(-1)) tolerance of two Cucumis sativus cultivars (shade-susceptible Jinyan 2 and shade-tolerant Deltastar) seedling leaves in their photosynthesis were studied. The results showed that under low light, the SPAD, net photosynthesis rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), water use efficiency (WUE), actual photochemical efficiency of PS II in the light (phi(PS II)), and photochemical quenching of chlorophyll fluorescence (q(p)) of cucumber leaves decreased, with the decrement getting more with decreasing temperature, while the superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities were in adverse. During the recovery process after low-light stress relieved, the parameters of gas exchange and chlorophyll fluorescence of the leaves recovered gradually, and the recovery of some gas exchange parameters lagged to that of chlorophyll fluorescence parameters. Under low light, the lower the temperature, the more damage the photosynthesis apparatus suffered, and the lesser tolerance to low light the cucumber leaves had in their photosynthesis. During the low temperature and low light treatment period, the decrease of Pn, phi(PS II), and q(p) was more obvious for Jinyan 2 than for Deltastar; and during the relief period, the recovery of these parameters was slower for Jinyan 2 than for Deltastar. It was indicated that Jinyan 2 had weaker tolerance to low temperature and/or low light in its photosynthesis than Deltastar.

  4. Chapter 6: Temperature

    Science.gov (United States)

    Jones, Leslie A.; Muhlfeld, Clint C.; Hauer, F. Richard; F. Richard Hauer,; Lamberti, G.A.

    2017-01-01

    Stream temperature has direct and indirect effects on stream ecology and is critical in determining both abiotic and biotic system responses across a hierarchy of spatial and temporal scales. Temperature variation is primarily driven by solar radiation, while landscape topography, geology, and stream reach scale ecosystem processes contribute to local variability. Spatiotemporal heterogeneity in freshwater ecosystems influences habitat distributions, physiological functions, and phenology of all aquatic organisms. In this chapter we provide an overview of methods for monitoring stream temperature, characterization of thermal profiles, and modeling approaches to stream temperature prediction. Recent advances in temperature monitoring allow for more comprehensive studies of the underlying processes influencing annual variation of temperatures and how thermal variability may impact aquatic organisms at individual, population, and community based scales. Likewise, the development of spatially explicit predictive models provide a framework for simulating natural and anthropogenic effects on thermal regimes which is integral for sustainable management of freshwater systems.

  5. Influences of wildfire and channel reorganization on spatial and temporal variation in stream temperature and the distribution of fish and amphibians

    Science.gov (United States)

    Dunham, J.B.; Rosenberger, A.E.; Luce, C.H.; Rieman, B.E.

    2007-01-01

    Wildfire can influence a variety of stream ecosystem properties. We studied stream temperatures in relation to wildfire in small streams in the Boise River Basin, located in central Idaho, USA. To examine the spatio-temporal aspects of temperature in relation to wildfire, we employed three approaches: a pre-post fire comparison of temperatures between two sites (one from a burned stream and one unburned) over 13 years, a short-term (3 year) pre-post fire comparison of a burned and unburned stream with spatially extensive data, and a short-term (1 year) comparative study of spatial variability in temperatures using a "space for time" substitutive design across 90 sites in nine streams (retrospective comparative study). The latter design included streams with a history of stand-replacing wildfire and streams with severe post-fire reorganization of channels due to debris flows and flooding. Results from these three studies indicated that summer maximum water temperatures can remain significantly elevated for at least a decade following wildfire, particularly in streams with severe channel reorganization. In the retrospective comparative study we investigated occurrence of native rainbow trout (Oncorhynchus mykiss) and tailed frog larvae (Ascaphus montanus) in relation to maximum stream temperatures during summer. Both occurred in nearly every site sampled, but tailed frog larvae were found in much warmer water than previously reported in the field (26.6??C maximum summer temperature). Our results show that physical stream habitats can remain altered (for example, increased temperature) for many years following wildfire, but that native aquatic vertebrates can be resilient. In a management context, this suggests wildfire may be less of a threat to native species than human influences that alter the capacity of stream-living vertebrates to persist in the face of natural disturbance. ?? 2007 Springer Science+Business Media, LLC.

  6. Multiple stressors in agricultural streams: a mesocosm study of interactions among raised water temperature, sediment addition and nutrient enrichment.

    Directory of Open Access Journals (Sweden)

    Jeremy J Piggott

    Full Text Available Changes to land use affect streams through nutrient enrichment, increased inputs of sediment and, where riparian vegetation has been removed, raised water temperature. We manipulated all three stressors in experimental streamside channels for 30 days and determined the individual and pair-wise combined effects on benthic invertebrate and algal communities and on leaf decay, a measure of ecosystem functioning. We added nutrients (phosphorus+nitrogen; high, intermediate, natural and/or sediment (grain size 0.2 mm; high, intermediate, natural to 18 channels supplied with water from a nearby stream. Temperature was increased by 1.4°C in half the channels, simulating the loss of upstream and adjacent riparian shade. Sediment affected 93% of all biological response variables (either as an individual effect or via an interaction with another stressor generally in a negative manner, while nutrient enrichment affected 59% (mostly positive and raised temperature 59% (mostly positive. More of the algal components of the community responded to stressors acting individually than did invertebrate components, whereas pair-wise stressor interactions were more common in the invertebrate community. Stressors interacted often and in a complex manner, with interactions between sediment and temperature most common. Thus, the negative impact of high sediment on taxon richness of both algae and invertebrates was stronger at raised temperature, further reducing biodiversity. In addition, the decay rate of leaf material (strength loss accelerated with nutrient enrichment at ambient but not at raised temperature. A key implication of our findings for resource managers is that the removal of riparian shading from streams already subjected to high sediment inputs, or land-use changes that increase erosion or nutrient runoff in a landscape without riparian buffers, may have unexpected effects on stream health. We highlight the likely importance of intact or restored buffer

  7. Estimation of the effect of thermal convection and casing on the temperature regime of boreholes: a review

    International Nuclear Information System (INIS)

    Eppelbaum, L V; Kutasov, I M

    2011-01-01

    In a vertical borehole, free heat convection arises when the temperature gradient equals or exceeds the so-called critical gradient. The critical temperature gradient is expressed through the critical Rayleigh number and depends on two parameters: (a) the ratio of formation (casings) to fluid (gas) conductivities (λ f /λ) and (b) the convective parameter of the fluid. Both these parameters depend on the temperature (depth). An empirical equation for the critical Rayleigh number as a function of the ratio λ f /λ is suggested. For the 0–100 °C range, empirical equations for convective parameters of water and air are proposed. The analysis of the published results of field investigations in deep boreholes and modelling shows that the temperature disturbances caused by thermal convection do not exceed 0.01–0.05 °C. Thus, in deep wells the temperature deviations due to thermal convection are usually within the accuracy of the temperature surveys. However, due to convection cells the geothermal gradient cannot be determined with sufficient accuracy for short well sections. In shallow boreholes the effect of thermal convection is more essential (up to 3–5 °C). To reduce the effect of convection on the temperature regime in shallow observational wells, it is necessary to reduce the diameter of the wellbores and use well fillers (fluids and gases) with low values of the convective parameters. The field observations and numerical calculations indicate that the distorting effect due to casing pipes is small and its influence is localized to the ends of the pipes, and this effect is independent of time. (topical review)

  8. Distribution of detritivores in tropical forest streams of peninsular Malaysia: role of temperature, canopy cover and altitude variability

    Science.gov (United States)

    Che Salmah, Md Rawi; Al-Shami, Salman Abdo; Abu Hassan, Ahmad; Madrus, Madziatul Rosemahanie; Nurul Huda, Abdul

    2014-07-01

    The diversity and abundance of macroinvertebrate shredders were investigated in 52 forested streams (local scale) from nine catchments (regional scale) covering a large area of peninsular Malaysia. A total of 10,642 individuals of aquatic macroinvertebrates were collected, of which 18.22 % were shredders. Biodiversity of shredders was described by alpha (αaverage ), beta (β) and gamma diversity (γ) measures. We found high diversity and abundance of shredders in all catchments, represented by 1,939 individuals (range 6-115 and average per site of 37.29 ± 3.48 SE) from 31 taxa with 2-13 taxa per site (αaverage = 6.98 ± 0.33 SE) and 10-15 taxa per catchment (γ = 13.33 ± 0.55 SE). At the local scale, water temperature, stream width, depth and altitude were correlated significantly with diversity (Adj- R 2 = 0.205). Meanwhile, dissolved oxygen, stream velocity, water temperature, stream width and altitude were correlated to shredder abundance (Adj- R 2 = 0.242). At regional scale, however, water temperature was correlated negatively with β and γ diversity ( r 2 = 0.161 and 0.237, respectively) as well as abundance of shredders ( r 2 = 0.235). Canopy cover was correlated positively with β diversity ( r 2 = 0.378) and abundance ( r 2 = 0.266), meanwhile altitude was correlated positively with β (quadratic: r 2 = 0.175), γ diversity (quadratic: r 2 = 0.848) as well as abundance (quadratic: r 2 = 0.299). The present study is considered as the first report describing the biodiversity and abundance of shredders in forested headwater streams across a large spatial scale in peninsular Malaysia. We concluded that water temperature has a negative effect while altitude showed a positive relationship with diversity and abundance of shredders. However, it was difficult to detect an influence of canopy cover on shredder diversity.

  9. Temperature dependent transport of two dimensional electrons in the integral quantum Hall regime

    International Nuclear Information System (INIS)

    Wi, H.P.

    1986-01-01

    This thesis is concerned with the temperature dependent electronic transport properties of a two dimensional electron gas subject to background potential fluctuations and a perpendicular magnetic field. The author carried out an extensive temperature dependent study of the transport coefficients, in the region of an integral quantum plateau, in an In/sub x/Ga/sub 1-x/As/InP heterostructure for 4.2K 10 cm -2 meV -1 ) even at the middle between two Landau levels, which is unexpected from model calculations based on short ranged randomness. In addition, the different T dependent behavior of rho/sub xx/ between the states in the tails and those near the center of a Landau level, indicates the existence of different electron states in a Landau level. Additionally, the author reports T-dependent transport measurements in the transition region between two quantum plateaus in several different materials

  10. Preisach modeling of temperature-dependent ferroelectric response of piezoceramics at sub-switching regime

    Science.gov (United States)

    Ochoa, Diego Alejandro; García, Jose Eduardo

    2016-04-01

    The Preisach model is a classical method for describing nonlinear behavior in hysteretic systems. According to this model, a hysteretic system contains a collection of simple bistable units which are characterized by an internal field and a coercive field. This set of bistable units exhibits a statistical distribution that depends on these fields as parameters. Thus, nonlinear response depends on the specific distribution function associated with the material. This model is satisfactorily used in this work to describe the temperature-dependent ferroelectric response in PZT- and KNN-based piezoceramics. A distribution function expanded in Maclaurin series considering only the first terms in the internal field and the coercive field is proposed. Changes in coefficient relations of a single distribution function allow us to explain the complex temperature dependence of hard piezoceramic behavior. A similar analysis based on the same form of the distribution function shows that the KNL-NTS properties soften around its orthorhombic to tetragonal phase transition.

  11. Dielectric relaxation in Li2SO4 in the intermedia-temperature regime

    Science.gov (United States)

    Diosa, J. E.; Vargas, R. A.; Fernández, M. E.; Albinsson, I.; Mellander, B.-E.

    2005-08-01

    The dielectric permittivity of polycrystalline Li2SO4 was measured from 5 Hz to 13 MHz and over the temperature range 235-460 °C. The corrected imaginary part of permittivity, , and its real part vs. frequency clearly show a new dielectric relaxation around fmax = 2 × 104 Hz at T = 256 °C, which shifts to higher frequencies (1 MHz) as the temperatures increases. The relaxation frequency (calculated from the peak position of ) vs. reciprocal T shows an activated relaxation process with activation energy Ea= 0.9 eV, which is very close to that derived from the dc conductivity, E (0.87 eV). We suggest that this dielectric relaxation could be due to the Li+ jump and SO4- reorientation that cause distortion and change of the local lattice polarizability inducing dipoles like LiSO4-.

  12. Space Charge Saturated Sheath Regime and Electron Temperature Saturation in Hall Thrusters

    International Nuclear Information System (INIS)

    Raitses, Y.; Staack, D.; Smirnov, A.; Fisch, N.J.

    2005-01-01

    Secondary electron emission in Hall thrusters is predicted to lead to space charge saturated wall sheaths resulting in enhanced power losses in the thruster channel. Analysis of experimentally obtained electron-wall collision frequency suggests that the electron temperature saturation, which occurs at high discharge voltages, appears to be caused by a decrease of the Joule heating rather than by the enhancement of the electron energy loss at the walls due to a strong secondary electron emission

  13. Development of Colletotrichum gloeosporioides isolated from green pepper in different culture media, temperatures, and light regimes

    Directory of Open Access Journals (Sweden)

    Mello Alexandre Furtado Silveira

    2004-01-01

    Full Text Available Control of anthracnose in green pepper involves the use of resistant varieties and/or fungicides. The selection of varieties and efficient products demands great amounts of conidia as inoculum. It is thus necessary to optimize the production of Colletotrichum gloeosporioides conidia in the laboratory, establishing the best conditions for fungus development. The present study aimed at determining the most favorable culture media, temperature, and light conditions for the production of fungus inoculum. The fungus was isolated from green pepper fruits (Capsicum annuum L. and transferred to four culture media (PDA, oat, filtered pepper extract, and autoclaved pepper extract, under different temperatures (15, 20, 25, 30, and 35ºC and light conditions (24h dark, and 24h light. Colony growth was evaluated after 7 and 12 days of incubation. No differences were found between the culture media. However, the greatest number of conidia was obtained from colonies grown in oat medium at 25ºC. Temperatures of 20 and 25ºC were the most favorable for colony growth and sporulation. Higher sporulation was obtained under incubation in constant light. Cultivation of C. gloeosporioides in oat medium, at 25ºC, and constant light is recommended.

  14. Mediating Water Temperature Increases Due to Livestock and Global Change in High Elevation Meadow Streams of the Golden Trout Wilderness

    Science.gov (United States)

    Nusslé, Sébastien; Matthews, Kathleen R.; Carlson, Stephanie M.

    2015-01-01

    Rising temperatures due to climate change are pushing the thermal limits of many species, but how climate warming interacts with other anthropogenic disturbances such as land use remains poorly understood. To understand the interactive effects of climate warming and livestock grazing on water temperature in three high elevation meadow streams in the Golden Trout Wilderness, California, we measured riparian vegetation and monitored water temperature in three meadow streams between 2008 and 2013, including two “resting” meadows and one meadow that is partially grazed. All three meadows have been subject to grazing by cattle and sheep since the 1800s and their streams are home to the imperiled California golden trout (Oncorhynchus mykiss aguabonita). In 1991, a livestock exclosure was constructed in one of the meadows (Mulkey), leaving a portion of stream ungrazed to minimize the negative effects of cattle. In 2001, cattle were removed completely from two other meadows (Big Whitney and Ramshaw), which have been in a “resting” state since that time. Inside the livestock exclosure in Mulkey, we found that riverbank vegetation was both larger and denser than outside the exclosure where cattle were present, resulting in more shaded waters and cooler maximal temperatures inside the exclosure. In addition, between meadows comparisons showed that water temperatures were cooler in the ungrazed meadows compared to the grazed area in the partially grazed meadow. Finally, we found that predicted temperatures under different global warming scenarios were likely to be higher in presence of livestock grazing. Our results highlight that land use can interact with climate change to worsen the local thermal conditions for taxa on the edge and that protecting riparian vegetation is likely to increase the resiliency of these ecosystems to climate change. PMID:26565706

  15. Dominant bryophyte control over high-latitude soil temperature fluctuations predicted by heat transfer traits, field moisture regime and laws of thermal insulation.

    NARCIS (Netherlands)

    Soudzilovskaia, N.A.; Cornelissen, J.H.C.; van Bodegom, P.M.

    2013-01-01

    Bryophytes cover large territories in cold biomes, where they control soil temperature regime, and therefore permafrost, carbon and nutrient dynamics. The mechanisms of this control remain unclear. We quantified the dependence of soil temperature fluctuations under bryophyte mats on the interplay of

  16. A spatial model for a stream networks of Citarik River with the environmental variables: potential of hydrogen (PH) and temperature

    Science.gov (United States)

    Bachrudin, A.; Mohamed, N. B.; Supian, S.; Sukono; Hidayat, Y.

    2018-03-01

    Application of existing geostatistical theory of stream networks provides a number of interesting and challenging problems. Most of statistical tools in the traditional geostatistics have been based on a Euclidean distance such as autocovariance functions, but for stream data is not permissible since it deals with a stream distance. To overcome this autocovariance developed a model based on the distance the flow with using convolution kernel approach (moving average construction). Spatial model for a stream networks is widely used to monitor environmental on a river networks. In a case study of a river in province of West Java, the objective of this paper is to analyze a capability of a predictive on two environmental variables, potential of hydrogen (PH) and temperature using ordinary kriging. Several the empirical results show: (1) The best fit of autocovariance functions for temperature and potential hydrogen (ph) of Citarik River is linear which also yields the smallest root mean squared prediction error (RMSPE), (2) the spatial correlation values between the locations on upstream and on downstream of Citarik river exhibit decreasingly

  17. Application of Temperature Index Model to Assess the Future Hydrological Regime of the Glacierized Catchments in Nepal.

    Science.gov (United States)

    Kayastha, R.; Kayastha, R. B.

    2017-12-01

    Unavailability of hydro meteorological data in the Himalayan regions is challenging on understanding the flow regimes. Temperature index model is simple yet the powerful glacio-hydrological model to simulate the discharge in the glacierized basin. Modified Positive Degree Day (MPDD) Model Version 2.0 is a grid-ded based semi distributed model with baseflow module is a robust melt modelling tools to estimate the discharge. MPDD model uses temperature and precipitation as a forcing datasets to simulate the discharge and also to obtain the snowmelt, icemelt, rain and baseflow contribution on total discharge. In this study two glacierized, Marsyangdi and Langtang catchment were investigated for the future hydrological regimes. Marsyangdi encompasses an area of 4026.19 sq. km with 20% glaciated area, whereas Langtang catchment with area of 354.64 sq. km with 36% glaciated area is studied to examine for the future climatic scenarios. The model simulates discharge well for the observed period; (1992-1998) in Marsyangdi and from (2007-2013) in Langtang catchment. The Nash-Sutcliffe Efficiency (NSE) for the both catchment were above 0.75 with the volume difference less than - 8 %. The snow and ice melts contribution in Marsyangdi were 4.7% and 10.2% whereas in Langtang the contribution is 15.3% and 23.4%, respectively. Rain contribution ( 40%) is higher than the baseflow contribution in total discharge in both basins. The future river discharge is also predicted using the future climate data from the regional climate models (RCMs) of CORDEX South Asia experiments for the medium stabilization scenario RCP4.5 and very high radiative forcing scenario RCP8.5 after bias correction. The projected future discharge of both catchment shows slightly increase in both scenarios with increase of snow and ice melt contribution on discharge. The result generated from the model can be utilized to understand the future hydrological regimes of the glacierized catchment also the impact of

  18. CADDIS Volume 2. Sources, Stressors and Responses: Temperature - Figure 1. Major Heat Flux Processes in Streams

    Science.gov (United States)

    Introduction to the temperature module, when to list temperature as a candidate cause, ways to measure temperature, simple and detailed conceptual diagrams for temperature, temperature module references and literature reviews.

  19. Variability in stream discharge and temperature: a preliminary assessment of the implications for juvenile and spawning Atlantic salmon

    Directory of Open Access Journals (Sweden)

    D. Tetzlaff

    2005-01-01

    Full Text Available This study focuses on understanding the temporal variability in hydrological and thermal conditions in a small mountain stream and its potential implication for two life stages of Atlantic salmon (Salmo salar – stream resident juveniles and returning adult spawners. Stream discharge and temperature in the Girnock Burn, NE Scotland, were characterised over ten hydrological years (1994/1995–2003/2004. Attention was focussed on assessing variations during particular ecologically 'sensitive' time periods when selected life-stages of salmon behaviour may be especially influenced by hydrological and thermal conditions. Empirical discharge data were used to derive hydraulic parameters to predict the Critical Displacement Velocity (CDV of juvenile salmon. This is the velocity above which fish may no longer be able to hold station in the water column and thus can be used as an index of time periods where feeding behaviour might be constrained. In the Girnock Burn, strong inter- and intra-annual variability in hydrological and thermal conditions may have important implications for feeding opportunities for juvenile fish; both during important growth periods in late winter and early spring, and the emergence of fry in the late spring. Time periods when foraging behaviour of juvenile salmon may be constrained by hydraulic conditions were assessed as the percentage time when CDV for 0+ and 1+ fish were exceeded by mean daily stream velocities. Clear seasonal patterns of CDV were apparent, with higher summer values driven by higher stream temperatures and fish length. Inter-annual variability in the time when mean stream velocity exceeded CDV for 0+ fish ranged between 29.3% (1997/1998 and 44.7% (2000/2001. For 1+ fish mean stream velocity exceeded CDV between 14.5% (1997/1998 and 30.7% (2000/2001 of the time. The movement of adult spawners into the Girnock Burn in preparation for autumn spawning (late October to mid-November exhibited a complex

  20. Influence of myelin proteins on the structure and dynamics of a model membrane with emphasis on the low temperature regime

    Energy Technology Data Exchange (ETDEWEB)

    Knoll, W. [University Joseph Fourier, UFR PhiTEM, Grenoble (France); Institut Laue–Langevin, Grenoble (France); Peters, J. [University Joseph Fourier, UFR PhiTEM, Grenoble (France); Institut Laue–Langevin, Grenoble (France); Institut de Biologie Structurale, Grenoble (France); Kursula, P. [University of Oulu, Oulu (Finland); CSSB–HZI, DESY, Hamburg (Germany); Gerelli, Y. [Institut Laue–Langevin, Grenoble (France); Natali, F., E-mail: natali@ill.fr [Institut Laue–Langevin, Grenoble (France); CNR–IOM–OGG, c/o Institut Laue–Langevin, Grenoble (France)

    2014-11-28

    Myelin is an insulating, multi-lamellar membrane structure wrapped around selected nerve axons. Increasing the speed of nerve impulses, it is crucial for the proper functioning of the vertebrate nervous system. Human neurodegenerative diseases, such as multiple sclerosis, are linked to damage to the myelin sheath through demyelination. Myelin exhibits a well defined subset of myelin-specific proteins, whose influence on membrane dynamics, i.e., myelin flexibility and stability, has not yet been explored in detail. In a first paper [W. Knoll, J. Peters, P. Kursula, Y. Gerelli, J. Ollivier, B. Demé, M. Telling, E. Kemner, and F. Natali, Soft Matter 10, 519 (2014)] we were able to spotlight, through neutron scattering experiments, the role of peripheral nervous system myelin proteins on membrane stability at room temperature. In particular, the myelin basic protein and peripheral myelin protein 2 were found to synergistically influence the membrane structure while keeping almost unchanged the membrane mobility. Further insight is provided by this work, in which we particularly address the investigation of the membrane flexibility in the low temperature regime. We evidence a different behavior suggesting that the proton dynamics is reduced by the addition of the myelin basic protein accompanied by negligible membrane structural changes. Moreover, we address the importance of correct sample preparation and characterization for the success of the experiment and for the reliability of the obtained results.

  1. In situ TEM and synchrotron characterization of U–10Mo thin specimen annealed at the fast reactor temperature regime

    International Nuclear Information System (INIS)

    Yun, Di; Mo, Kun; Mohamed, Walid; Ye, Bei; Kirk, Marquis A.; Baldo, Peter; Xu, Ruqing; Yacout, Abdellatif M.

    2015-01-01

    U–Mo metallic alloys have been extensively used for the Reduced Enrichment for Research and Test Reactors (RERTR) program, which is now known as the Office of Material Management and Minimization under the Conversion Program. This fuel form has also recently been proposed as fast reactor metallic fuels in the recent DOE Ultra-high Burnup Fast Reactor project. In order to better understand the behavior of U–10Mo fuels within the fast reactor temperature regime, a series of annealing and characterization experiments have been performed. Annealing experiments were performed in situ at the Intermediate Voltage Electron Microscope (IVEM-Tandem) facility at Argonne National Laboratory (ANL). An electro-polished U–10Mo alloy fuel specimen was annealed in situ up to 700 °C. At an elevated temperature of about 540 °C, the U–10Mo specimen underwent a relatively slow microstructure transition. Nano-sized grains were observed to emerge near the surface. At the end temperature of 700 °C, the near-surface microstructure had evolved to a nano-crystalline state. In order to clarify the nature of the observed microstructure, Laue diffraction and powder diffraction experiments were carried out at beam line 34-ID of the Advanced Photon Source (APS) at ANL. Phases present in the as-annealed specimen were identified with both Laue diffraction and powder diffraction techniques. The U–10Mo was found to recrystallize due to thermally-induced recrystallization driven by a high density of pre-existing dislocations. A separate in situ annealing experiment was carried out with a Focused Ion Beam processed (FIB) specimen. A similar microstructure transition occurred at a lower temperature of about 460 °C with a much faster transition rate compared to the electro-polished specimen. - Highlights: • TEM annealing experiments were performed in situ at the IVEM facility up to fast reactor temperature. • At 540 °C, the U-10Mo specimen underwent a slow microstructure transition

  2. In situ TEM and synchrotron characterization of U–10Mo thin specimen annealed at the fast reactor temperature regime

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Di, E-mail: diyun1979@xjtu.edu.cn [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Xi' an Jiao Tong University, 28 Xian Ning West Road, Xi' an 710049 (China); Mo, Kun; Mohamed, Walid; Ye, Bei; Kirk, Marquis A.; Baldo, Peter; Xu, Ruqing; Yacout, Abdellatif M. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)

    2015-12-15

    U–Mo metallic alloys have been extensively used for the Reduced Enrichment for Research and Test Reactors (RERTR) program, which is now known as the Office of Material Management and Minimization under the Conversion Program. This fuel form has also recently been proposed as fast reactor metallic fuels in the recent DOE Ultra-high Burnup Fast Reactor project. In order to better understand the behavior of U–10Mo fuels within the fast reactor temperature regime, a series of annealing and characterization experiments have been performed. Annealing experiments were performed in situ at the Intermediate Voltage Electron Microscope (IVEM-Tandem) facility at Argonne National Laboratory (ANL). An electro-polished U–10Mo alloy fuel specimen was annealed in situ up to 700 °C. At an elevated temperature of about 540 °C, the U–10Mo specimen underwent a relatively slow microstructure transition. Nano-sized grains were observed to emerge near the surface. At the end temperature of 700 °C, the near-surface microstructure had evolved to a nano-crystalline state. In order to clarify the nature of the observed microstructure, Laue diffraction and powder diffraction experiments were carried out at beam line 34-ID of the Advanced Photon Source (APS) at ANL. Phases present in the as-annealed specimen were identified with both Laue diffraction and powder diffraction techniques. The U–10Mo was found to recrystallize due to thermally-induced recrystallization driven by a high density of pre-existing dislocations. A separate in situ annealing experiment was carried out with a Focused Ion Beam processed (FIB) specimen. A similar microstructure transition occurred at a lower temperature of about 460 °C with a much faster transition rate compared to the electro-polished specimen. - Highlights: • TEM annealing experiments were performed in situ at the IVEM facility up to fast reactor temperature. • At 540 °C, the U-10Mo specimen underwent a slow microstructure transition

  3. Influence of water temperature and feeding regime on otolith growth in Anguilla japonica glass eels and elvers: does otolith growth cease at low temperatures?

    Science.gov (United States)

    Fukuda, N; Kuroki, M; Shinoda, A; Yamada, Y; Okamura, A; Aoyama, J; Tsukamoto, K

    2009-06-01

    The influences of water temperature and feeding regime on otolith growth in Anguilla japonica glass eels and elvers were investigated using individuals reared at 5, 10, 15, 20, 25 and 30 degrees C and in fed or unfed conditions at salinity 32 after their otoliths were marked with alizarin complexone (ALC). To eliminate the difficulty of observing the edges of otoliths with optical (OM) or scanning electron (SEM) microscopes, three to 10 individuals were sampled from each tank at 10, 20 and 30 days during the experiment and reared for an additional 10 days at 25 degrees C after their otoliths were marked a second time. Otolith growth and the number of increments were measured using both OM and SEM. Most A. japonica commenced feeding after 10 days at 20-30 degrees C or after 20 days at 15 degrees C, but no feeding occurred at 5 and 10 degrees C. No otolith growth occurred at 5 and 10 degrees C except in two individuals with minimal increment deposition at 10 degrees C. Otolith growth was proportional to water temperature within 15-25 degrees C and not different between 25 and 30 degrees C. At 15, 25 and 30 degrees C, the mean otolith growth rate in fed conditions was higher than in unfed conditions. The number of increments per day was significantly different among water temperatures (0.00-0.01 day(-1) at 5 and 10 degrees C, 0.43-0.48 day(-1) at 15 degrees C and 0.94-1.07 day(-1) at 20-30 degrees C). These results indicated that otolith growth in A. japonica glass eels and elvers was affected by temperature and ceased at otoliths of wild-caught A. japonica glass eels and elvers need to carefully consider the water temperatures potentially experienced by the juveniles in the wild.

  4. Identify temporal trend of air temperature and its impact on forest stream flow in Lower Mississippi River Alluvial Valley using wavelet analysis.

    Science.gov (United States)

    Ouyang, Ying; Parajuli, Prem B; Li, Yide; Leininger, Theodor D; Feng, Gary

    2017-08-01

    Characterization of stream flow is essential to water resource management, water supply planning, environmental protection, and ecological restoration; while air temperature variation due to climate change can exacerbate stream flow and add instability to the flow. In this study, the wavelet analysis technique was employed to identify temporal trend of air temperature and its impact upon forest stream flows in Lower Mississippi River Alluvial Valley (LMRAV). Four surface water monitoring stations, which locate near the headwater areas with very few land use disturbances and the long-term data records (60-90 years) in the LMRAV, were selected to obtain stream discharge and air temperature data. The wavelet analysis showed that air temperature had an increasing temporal trend around its mean value during the past several decades in the LMRAV, whereas stream flow had a decreasing temporal trend around its average value at the same time period in the same region. Results of this study demonstrated that the climate in the LMRAV did get warmer as time elapsed and the streams were drier as a result of warmer air temperature. This study further revealed that the best way to estimate the temporal trends of air temperature and stream flow was to perform the wavelet transformation around their mean values. Published by Elsevier Ltd.

  5. Computational study of collisions between O(3P) and NO(2Π) at temperatures relevant to the hypersonic flight regime

    International Nuclear Information System (INIS)

    Castro-Palacio, Juan Carlos; Nagy, Tibor; Meuwly, Markus; Bemish, Raymond J.

    2014-01-01

    Reactions involving N and O atoms dominate the energetics of the reactive air flow around spacecraft when reentering the atmosphere in the hypersonic flight regime. For this reason, the thermal rate coefficients for reactive processes involving O( 3 P) and NO( 2 Π) are relevant over a wide range of temperatures. For this purpose, a potential energy surface (PES) for the ground state of the NO 2 molecule is constructed based on high-level ab initio calculations. These ab initio energies are represented using the reproducible kernel Hilbert space method and Legendre polynomials. The global PES of NO 2 in the ground state is constructed by smoothly connecting the surfaces of the grids of various channels around the equilibrium NO 2 geometry by a distance-dependent weighting function. The rate coefficients were calculated using Monte Carlo integration. The results indicate that at high temperatures only the lowest A-symmetry PES is relevant. At the highest temperatures investigated (20 000 K), the rate coefficient for the “O1O2+N” channel becomes comparable (to within a factor of around three) to the rate coefficient of the oxygen exchange reaction. A state resolved analysis shows that the smaller the vibrational quantum number of NO in the reactants, the higher the relative translational energy required to open it and conversely with higher vibrational quantum number, less translational energy is required. This is in accordance with Polanyi's rules. However, the oxygen exchange channel (NO2+O1) is accessible at any collision energy. Finally, this work introduces an efficient computational protocol for the investigation of three-atom collisions in general

  6. Computational study of collisions between O(3P) and NO(2Π) at temperatures relevant to the hypersonic flight regime.

    Science.gov (United States)

    Castro-Palacio, Juan Carlos; Nagy, Tibor; Bemish, Raymond J; Meuwly, Markus

    2014-10-28

    Reactions involving N and O atoms dominate the energetics of the reactive air flow around spacecraft when reentering the atmosphere in the hypersonic flight regime. For this reason, the thermal rate coefficients for reactive processes involving O((3)P) and NO((2)Π) are relevant over a wide range of temperatures. For this purpose, a potential energy surface (PES) for the ground state of the NO2 molecule is constructed based on high-level ab initio calculations. These ab initio energies are represented using the reproducible kernel Hilbert space method and Legendre polynomials. The global PES of NO2 in the ground state is constructed by smoothly connecting the surfaces of the grids of various channels around the equilibrium NO2 geometry by a distance-dependent weighting function. The rate coefficients were calculated using Monte Carlo integration. The results indicate that at high temperatures only the lowest A-symmetry PES is relevant. At the highest temperatures investigated (20,000 K), the rate coefficient for the "O1O2+N" channel becomes comparable (to within a factor of around three) to the rate coefficient of the oxygen exchange reaction. A state resolved analysis shows that the smaller the vibrational quantum number of NO in the reactants, the higher the relative translational energy required to open it and conversely with higher vibrational quantum number, less translational energy is required. This is in accordance with Polanyi's rules. However, the oxygen exchange channel (NO2+O1) is accessible at any collision energy. Finally, this work introduces an efficient computational protocol for the investigation of three-atom collisions in general.

  7. Honey locust (Gleditsia triacanthos l. (Fabaceae)) invasion effect on temperature, light and metabolism of a Pampean Stream

    International Nuclear Information System (INIS)

    Giorgi, Adonis David; Vilches, Carolina; Rodriguez Castro, Maria Carolina; Zunino, Eduardo; Debandi, Juan; Kravetz, Sebastian; Torremorell, Ana

    2014-01-01

    The establishment of invader species in a region generally modifies the ecosystems where they are introduced. In this study we analyze the effect produced by a gleditsia triacanthos (Honey locust) invasion on a Pampean Stream. This organism modifies the temperature and the light reaching the stream. Thermal range shows significant differences between reaches but mean tem between 85 and 95 % down the trees. These modifications reduce the primary gross production of 2.7 to 1.7 g 02. M"2 at spring and of 25 to 20 g 02. M"2 at summer. Respiration in spring and summer is halved at invaded reaches, but net ecosystem metabolism is similar in both reach and seasons. Moreover, the reach invaded by honey locust show scarce macrophytes. We argue that the honey locust reduces the diversity by reduction of macrophytes and their associated organisms but also reduce the primary production causing changes in the food web

  8. Riparian microclimate and stream temperature: thinning and buffer-width influences

    Science.gov (United States)

    Paul D. Anderson

    2013-01-01

    Th inning of 30- to 70-year-old Douglas-fir (Pseudotsuga menziesii) stands is a common silvicultural activity on federal forest lands in Washington and Oregon west of the Cascade Range crest. Decreases in forest cover lead to alterations of site energy balances resulting in changes to understory and stream channel microclimates. Uncut vegetative...

  9. The influence of drawing temperature on mechanical properties and organisation of melt spun polyethylene solid-state drawn in the pseudo-affine regime

    NARCIS (Netherlands)

    Hu, Xin; Alcock, B.; Loos, J.

    2006-01-01

    Mechanical properties of high density polyethylene (HDPE) solid-state drawn with fixed draw ratio at different temperatures in a fiber/tape spin line were investigated. All drawing experiments were performed in the pseudo-affine regime, i.e. no effective relaxation of the molecules occurs during

  10. Rethinking the longitudinal stream temperature paradigm: region-wide comparison of thermal infrared imagery reveals unexpected complexity of river temperatures

    Science.gov (United States)

    We used an extensive dataset of remotely sensed summertime river temperature to compare longitudinal profiles (temperature versus distance) for 54 rivers in the Pacific Northwest. We evaluated (1) how often profiles fit theoretical expectations of asymptotic downstream warming, a...

  11. SUPPLEMENTARY FEEDING ON THE NUTRIENT BALANCE OF LACTATING DAIRY COW AT CONTRASTING TEMPERATURE REGIMES: ASSESSMENT USING CORNELL NET CARBOHYDRATE AND PROTEIN SYSTEM (CNCPS) MODEL

    OpenAIRE

    A. Jayanegara; A. Sofyan

    2014-01-01

    Dairy cows often do not receive adequate nutrient supply during their lactation period. This condition caneven be worse if the environmental temperature is not in comfortable range which may occur especially intropical regions. The present research was aimed to simulate the effect of supplementary feeding on nutrientbalance of lactating dairy cow at contrasting temperature regimes using Cornell Net Carbohydrate andProtein System (CNCPS) model. Treatments consisted of feeds (R1: Pennisetum pur...

  12. Germinação e vigor de sementes de Crataeva tapia L. em diferentes temperaturas e regimes de luz Germination and vigor of Crataeva tapia L. seeds in different temperatures and light regimes

    Directory of Open Access Journals (Sweden)

    Evio Alves Galindo

    2012-03-01

    Full Text Available O comportamento germinativo das sementes de diferentes espécies varia em função da temperatura e luminosidade, o que pode fornecer informações de interesse biológico, ecológico e da tecnologia de sementes, pois muito pouco se conhece com relação às exigências de sementes de espécies tropicais quanto aos diversos fatores envolvidos na germinação. O trabalho foi realizado com o objetivo de avaliar o efeito de diferentes temperaturas e condições de luminosidade sobre a germinação e vigor das sementes de Crataeva tapia L. No Laboratório de Análise de Sementes (LAS, do Centro de Ciências Agrárias, da Universidade Federal da Paraíba (CCA - UFPB, em Areia - PB foram avaliadas a influência das temperaturas de 25 °C; 30 °C e 35 °C constantes e 20-30 °C alternada, sob regimes de luz branca (sem papel celofane, verde (com papel celofane verde, vermelha (com papel celofane vermelho, vermelha-distante (com duas folhas de papel celofane vermelho intercaladas por duas folhas azuis e ausência de luz (com plástico preto, adotando-se o delineamento inteiramente ao acaso, em esquema fatorial 4 x 5 (temperaturas e regimes de luz, em quatro repetições de 25 sementes cada. As características analisadas foram: porcentagem de germinação, primeira contagem de germinação, índice de velocidade de germinação, comprimento e massa seca das plântulas. A temperatura alternada de 20-30 °C, seguida da temperatura constante de 30 °C, podem ser recomendadas para testes de germinação e vigor de sementes de C. tapia. As combinações de temperatura e regimes de luz influenciam o potencial germinativo e o vigor de sementes de Crataeva tapia L.The germination behavior of seeds of different species varies on function of the temperature and luminosity, which can provide information of biological and ecological interest, and technology of seeds, because very little is known with respect to the requirements of seeds of tropical species as the

  13. Impact of wildfire on stream nutrient chemistry and ecosystem metabolism in boreal forest catchments of interior Alaska

    Science.gov (United States)

    Emma F. Betts; Jeremy B. Jones

    2009-01-01

    With climatic warming, wildfire occurrence is increasing in the boreal forest of interior Alaska. Loss of catchment vegetation during fire can impact streams directly through altered solute and debris inputs and changed light and temperature regimes. Over longer time scales, fire can accelerate permafrost degradation, altering catchment hydrology and stream nutrient...

  14. Direct and indirect toxicity of the fungicide pyraclostrobin to Hyalella azteca and effects on leaf processing under realistic daily temperature regimes.

    Science.gov (United States)

    Willming, Morgan M; Maul, Jonathan D

    2016-04-01

    Fungicides in aquatic environments can impact non-target bacterial and fungal communities and the invertebrate detritivores responsible for the decomposition of allochthonous organic matter. Additionally, in some aquatic systems daily water temperature fluctuations may influence these processes and alter contaminant toxicity, but such temperature fluctuations are rarely examined in conjunction with contaminants. In this study, the shredding amphipod Hyalella azteca was exposed to the fungicide pyraclostrobin in three experiments. Endpoints included mortality, organism growth, and leaf processing. One experiment was conducted at a constant temperature (23 °C), a fluctuating temperature regime (18-25 °C) based on field-collected data from the S. Llano River, Texas, or an adjusted fluctuating temperature regime (20-26 °C) based on possible climate change predictions. Pyraclostrobin significantly reduced leaf shredding and increased H. azteca mortality at concentrations of 40 μg/L or greater at a constant 23 °C and decreased leaf shredding at concentrations of 15 μg/L or greater in the fluctuating temperatures. There was a significant interaction between temperature treatment and pyraclostrobin concentration on H. azteca mortality, body length, and dry mass under direct aqueous exposure conditions. In an indirect exposure scenario in which only leaf material was exposed to pyraclostrobin, H. azteca did not preferentially feed on or avoid treated leaf disks compared to controls. This study describes the influence of realistic temperature variation on fungicide toxicity to shredding invertebrates, which is important for understanding how future alterations in daily temperature regimes due to climate change may influence the assessment of ecological risk of contaminants in aquatic ecosystems. Copyright © 2016. Published by Elsevier Ltd.

  15. Investigating spatial variability of vertical water fluxes through the streambed in distinctive stream morphologies using temperature and head data

    Science.gov (United States)

    Wang, Liping; Jiang, Weiwei; Song, Jinxi; Dou, Xinyi; Guo, Hongtao; Xu, Shaofeng; Zhang, Guotao; Wen, Ming; Long, Yongqing; Li, Qi

    2017-08-01

    Investigating the interaction of groundwater and surface water is key to understanding the hyporheic processes. The vertical water fluxes through a streambed were determined using Darcian flux calculations and vertical sediment temperature profiles to assess the pattern and magnitude of groundwater/surface-water interaction in Beiluo River, China. Field measurements were taken in January 2015 at three different stream morphologies including a meander bend, an anabranching channel and a straight stream channel. Despite the differences of flux direction and magnitude, flux directions based on vertical temperature profiles are in good agreement with results from Darcian flux calculations at the anabranching channel, and the Kruskal-Wallis tests show no significant differences between the estimated upward fluxes based on the two methods at each site. Also, the upward fluxes based on the two methods show similar spatial distributions on the streambed, indicating (1) that higher water fluxes at the meander bend occur from the center of the channel towards the erosional bank, (2) that water fluxes at the anabranching channel are higher near the erosional bank and in the center of the channel, and (3) that in the straight channel, higher water fluxes appear from the center of the channel towards the depositional bank. It is noted that higher fluxes generally occur at certain locations with higher streambed vertical hydraulic conductivity ( K v) or where a higher vertical hydraulic gradient is observed. Moreover, differences of grain size, induced by stream morphology and contrasting erosional and depositional conditions, have significant effects on streambed K v and water fluxes.

  16. Instream habitat restoration and stream temperature reduction in a whirling disease-positive Spring Creek in the Blackfoot River Basin, Montana

    Science.gov (United States)

    Pierce, Ron; Podner, Craig; Marczak, Laurie B; Jones, Leslie A.

    2014-01-01

    Anthropogenic warming of stream temperature and the presence of exotic diseases such as whirling disease are both contemporary threats to coldwater salmonids across western North America. We examined stream temperature reduction over a 15-year prerestoration and postrestoration period and the severity of Myxobolus cerebralisinfection (agent of whirling disease) over a 7-year prerestoration and postrestoration period in Kleinschmidt Creek, a fully reconstructed spring creek in the Blackfoot River basin of western Montana. Stream restoration increased channel length by 36% and reduced the wetted surface area by 69% by narrowing and renaturalizing the channel. Following channel restoration, average maximum daily summer stream temperatures decreased from 15.7°C to 12.5°C, average daily temperature decreased from 11.2°C to 10.0°C, and the range of daily temperatures narrowed by 3.3°C. Despite large changes in channel morphology and reductions in summer stream temperature, the prevalence and severity of M. cerebralis infection for hatchery Rainbow Trout Oncorhynchus mykiss remained high (98–100% test fish with grade > 3 infection) versus minimal for hatchery Brown Trout Salmo trutta (2% of test fish with grade-1 infection). This study shows channel renaturalization can reduce summer stream temperatures in small low-elevation, groundwater-dominated streams in the Blackfoot basin to levels more suitable to native trout. However, because of continuous high infections associated with groundwater-dominated systems, the restoration of Kleinschmidt Creek favors brown trout Salmo trutta given their innate resistance to the parasite and the higher relative susceptibility of other salmonids.

  17. Can riparian vegetation shade mitigate the expected rise in stream temperatures due to climate change during heat waves in a human-impacted pre-alpine river?

    Directory of Open Access Journals (Sweden)

    H. Trimmel

    2018-01-01

    Full Text Available Global warming has already affected European rivers and their aquatic biota, and climate models predict an increase of temperature in central Europe over all seasons. We simulated the influence of expected changes in heat wave intensity during the 21st century on water temperatures of a heavily impacted pre-alpine Austrian river and analysed future mitigating effects of riparian vegetation shade on radiant and turbulent energy fluxes using the deterministic Heat Source model. Modelled stream water temperature increased less than 1.5 °C within the first half of the century. Until 2100, a more significant increase of around 3 °C in minimum, maximum and mean stream temperatures was predicted for a 20-year return period heat event. The result showed clearly that in a highly altered river system riparian vegetation was not able to fully mitigate the predicted temperature rise caused by climate change but would be able to reduce water temperature by 1 to 2 °C. The removal of riparian vegetation amplified stream temperature increases. Maximum stream temperatures could increase by more than 4 °C even in annual heat events. Such a dramatic water temperature shift of some degrees, especially in summer, would indicate a total shift of aquatic biodiversity. The results demonstrate that effective river restoration and mitigation require re-establishing riparian vegetation and emphasize the importance of land–water interfaces and their ecological functioning in aquatic environments.

  18. Can riparian vegetation shade mitigate the expected rise in stream temperatures due to climate change during heat waves in a human-impacted pre-alpine river?

    Science.gov (United States)

    Trimmel, Heidelinde; Weihs, Philipp; Leidinger, David; Formayer, Herbert; Kalny, Gerda; Melcher, Andreas

    2018-01-01

    Global warming has already affected European rivers and their aquatic biota, and climate models predict an increase of temperature in central Europe over all seasons. We simulated the influence of expected changes in heat wave intensity during the 21st century on water temperatures of a heavily impacted pre-alpine Austrian river and analysed future mitigating effects of riparian vegetation shade on radiant and turbulent energy fluxes using the deterministic Heat Source model. Modelled stream water temperature increased less than 1.5 °C within the first half of the century. Until 2100, a more significant increase of around 3 °C in minimum, maximum and mean stream temperatures was predicted for a 20-year return period heat event. The result showed clearly that in a highly altered river system riparian vegetation was not able to fully mitigate the predicted temperature rise caused by climate change but would be able to reduce water temperature by 1 to 2 °C. The removal of riparian vegetation amplified stream temperature increases. Maximum stream temperatures could increase by more than 4 °C even in annual heat events. Such a dramatic water temperature shift of some degrees, especially in summer, would indicate a total shift of aquatic biodiversity. The results demonstrate that effective river restoration and mitigation require re-establishing riparian vegetation and emphasize the importance of land-water interfaces and their ecological functioning in aquatic environments.

  19. Direct and indirect toxicity of the fungicide pyraclostrobin to Hyalella azteca and effects on leaf processing under realistic daily temperature regimes

    International Nuclear Information System (INIS)

    Willming, Morgan M.; Maul, Jonathan D.

    2016-01-01

    Fungicides in aquatic environments can impact non-target bacterial and fungal communities and the invertebrate detritivores responsible for the decomposition of allochthonous organic matter. Additionally, in some aquatic systems daily water temperature fluctuations may influence these processes and alter contaminant toxicity, but such temperature fluctuations are rarely examined in conjunction with contaminants. In this study, the shredding amphipod Hyalella azteca was exposed to the fungicide pyraclostrobin in three experiments. Endpoints included mortality, organism growth, and leaf processing. One experiment was conducted at a constant temperature (23 °C), a fluctuating temperature regime (18–25 °C) based on field-collected data from the S. Llano River, Texas, or an adjusted fluctuating temperature regime (20–26 °C) based on possible climate change predictions. Pyraclostrobin significantly reduced leaf shredding and increased H. azteca mortality at concentrations of 40 μg/L or greater at a constant 23 °C and decreased leaf shredding at concentrations of 15 μg/L or greater in the fluctuating temperatures. There was a significant interaction between temperature treatment and pyraclostrobin concentration on H. azteca mortality, body length, and dry mass under direct aqueous exposure conditions. In an indirect exposure scenario in which only leaf material was exposed to pyraclostrobin, H. azteca did not preferentially feed on or avoid treated leaf disks compared to controls. This study describes the influence of realistic temperature variation on fungicide toxicity to shredding invertebrates, which is important for understanding how future alterations in daily temperature regimes due to climate change may influence the assessment of ecological risk of contaminants in aquatic ecosystems. - Highlights: • Pyraclostrobin was directly toxic to Hyalella azteca and reduced leaf processing. • Indirect exposure via leaf material did not change H

  20. Response to multi-generational selection under elevated [CO2] in two temperature regimes suggests enhanced carbon assimilation and increased reproductive output in Brassica napus L

    DEFF Research Database (Denmark)

    Frenck, Georg; van der Linden, Leon; Mikkelsen, Teis Nørgaard

    2013-01-01

    different temperature regimes. To reveal phenotypic divergence at the manipulated [CO2] and temperature conditions, a full-factorial natural selection regime was established in a phytotron environment over the range of four generations. It is demonstrated that a directional response to selection at elevated......Functional plant traits are likely to adapt under the sustained pressure imposed by environmental changes through natural selection. Employing Brassica napus as a model, a multi-generational study was performed to investigate the potential trajectories of selection at elevated [CO2] in two...... subjected to increased levels of CO2 over the generational range investigated. The results of this study suggest that phenotypic divergence of plants selected under elevated atmospheric CO2 concentration may drive the future functions of plant productivity to be different from projections that do...

  1. Summer temperature metrics for predicting brook trout (Salvelinus fontinalis) distribution in streams

    Science.gov (United States)

    Parrish, Donna; Butryn, Ryan S.; Rizzo, Donna M.

    2012-01-01

    We developed a methodology to predict brook trout (Salvelinus fontinalis) distribution using summer temperature metrics as predictor variables. Our analysis used long-term fish and hourly water temperature data from the Dog River, Vermont (USA). Commonly used metrics (e.g., mean, maximum, maximum 7-day maximum) tend to smooth the data so information on temperature variation is lost. Therefore, we developed a new set of metrics (called event metrics) to capture temperature variation by describing the frequency, area, duration, and magnitude of events that exceeded a user-defined temperature threshold. We used 16, 18, 20, and 22°C. We built linear discriminant models and tested and compared the event metrics against the commonly used metrics. Correct classification of the observations was 66% with event metrics and 87% with commonly used metrics. However, combined event and commonly used metrics correctly classified 92%. Of the four individual temperature thresholds, it was difficult to assess which threshold had the “best” accuracy. The 16°C threshold had slightly fewer misclassifications; however, the 20°C threshold had the fewest extreme misclassifications. Our method leveraged the volumes of existing long-term data and provided a simple, systematic, and adaptable framework for monitoring changes in fish distribution, specifically in the case of irregular, extreme temperature events.

  2. Sensitivities of dry season runoff to precipitation and temperature in southern Sierra Nevada streams

    Science.gov (United States)

    Safeeq, M.; Hunsaker, C. T.; Bales, R. C.

    2016-12-01

    In a mediterranean climate, dry season runoff sustains water supply and supports aquatic habitat and other ecosystems. Precipitation and temperature directly, by regulating recharge and evapotranspiration (ET), and indirectly, by regulating amount and timing of snowmelt, control the dry season runoff in the Sierra Nevada. Here, we explored relative impacts of precipitation and temperature variability on dry season runoff using path analysis. Specific objectives include: (i) to quantify the direct and indirect impacts of precipitation and temperature on 7-day average minimum flow (Qmin) and (ii) to explore the role of preceding year Qmin on fall season runoff (QF). We used daily runoff, air temperature, precipitation, and snow water equivalent (SWE) over 2004-2015 for the ten catchments in the Kings River Experimental Watersheds. For path analysis model of Qmin, we defined annual precipitation and temperature as exogenous variables and peak SWE, day of snow disappearance, and Qmin as endogenous variables. For QF, we defined current year fall precipitation and preceding year Qmin as exogenous variables and current year QF as an endogenous variable. Path analysis results for Qmin show precipitation as a dominant driver when compared to temperature, peak SWE, and day of snow disappearance. However, in half of the catchments that are mostly located at higher elevations the impact of temperature on Qmin was either comparable or exceeded that of precipitation. This relatively high sensitivity of Qmin to air temperature in high elevation catchments is consistent with the earlier findings of increased ET in proportion to warming. The direct effects of peak SWE and day of snow disappearance on Qmin were limited, and indirect effects of temperature and precipitation via peak SWE and day of snow disappearance were not significant. The preceding year Qmin and fall precipitation showed comparable impacts on QF, indicating that the storage in the preceding year modulates current

  3. The hydrological cycle in the high Pamir Mountains: how temperature and seasonal precipitation distribution influence stream flow in the Gunt catchment, Tajikistan

    Science.gov (United States)

    Pohl, E.; Knoche, M.; Gloaguen, R.; Andermann, C.; Krause, P.

    2014-12-01

    Complex climatic interactions control hydrological processes in high mountains that in their turn regulate the erosive forces shaping the relief. To unravel the hydrological cycle of a glaciated watershed (Gunt River) considered representative of the Pamirs' hydrologic regime we developed a remote sensing-based approach. At the boundary between two distinct climatic zones dominated by Westerlies and Indian summer monsoon, the Pamir is poorly instrumented and only a few in situ meteorological and hydrological data are available. We adapted a suitable conceptual distributed hydrological model (J2000g). Interpolations of the few available in situ data are inadequate due to strong, relief induced, spatial heterogeneities. Instead we use raster data, preferably from remote sensing sources depending on availability and validation. We evaluate remote sensing-based precipitation and temperature products. MODIS MOD11 surface temperatures show good agreement with in situ data, perform better than other products and represent a good proxy for air temperatures. For precipitation we tested remote sensing products as well as the HAR10 climate model data and the interpolation-based APHRODITE dataset. All products show substantial differences both in intensity and seasonal distribution with in-situ data. Despite low resolutions, the datasets are able to sustain high model efficiencies (NSE ≥0.85). In contrast to neighbouring regions in the Himalayas or the Hindukush, discharge is dominantly the product of snow and glacier melt and thus temperature is the essential controlling factor. 80% of annual precipitation is provided as snow in winter and spring contrasting peak discharges during summer. Hence, precipitation and discharge are negatively correlated and display complex hysteresis effects that allow to infer the effect of inter-annual climatic variability on river flow. We infer the existence of two subsurface reservoirs. The groundwater reservoir (providing 40% of annual

  4. Bonding to dentin as a function of air-stream temperatures for solvent evaporation

    Directory of Open Access Journals (Sweden)

    Andréia Aquino Marsiglio

    2012-06-01

    Full Text Available This study evaluated the influence of solvent evaporation conditions of acid-etching adhesives. The medium dentin of thirty extracted human third molars was exposed and bonded to different types of etch-and-rinse adhesives: 1 Scotchbond Multi-Purpose (SBMP ; water-based; 2 Adper Single Bond 2 (SB ; ethanol/water-based, and 3 Prime & Bond 2.1 (PB ; acetone-based. Solvents were evaporated at air-drying temperatures of 21ºC or 38ºC. Composite buildups were incrementally constructed. After storage in water for 24 h at 37ºC, the specimens were prepared for bond strength testing. Data were analyzed by two-way ANOVA and Tukey's test (5%. SBMP performed better when the solvents were evaporated at a higher temperature (p < 0.05. Higher temperatures did not affect the performance of SB or PB. Bond strength at room temperature was material-dependent, and air-drying temperatures affected bonding of the water-based, acid-etching adhesive.

  5. Low-temperature plasma-catalytic oxidation of formaldehyde in atmospheric pressure gas streams

    International Nuclear Information System (INIS)

    Ding Huixian; Zhu Aimin; Lu Fugong; Xu Yong; Zhang Jing; Yang Xuefeng

    2006-01-01

    Formaldehyde (HCHO) is a typical air pollutant capable of causing serious health disorders in human beings. This work reports plasma-catalytic oxidation of formaldehyde in gas streams via dielectric barrier discharges over Ag/CeO 2 pellets at atmospheric pressure and 70 0 C. With a feed gas mixture of 276 ppm HCHO, 21.0% O 2 , 1.0% H 2 O in N 2 , ∼99% of formaldehyde can be effectively destructed with an 86% oxidative conversion into CO 2 at GHSV of 16500 h -1 and input discharge energy density of 108 J l -1 . At the same experimental conditions, the conversion percentages of HCHO to CO 2 from pure plasma-induced oxidation (discharges over fused silica pellets) and from pure catalytic oxidation over Ag/CeO 2 (without discharges) are 6% and 33% only. The above results and the CO plasma-catalytic oxidation experiments imply that the plasma-generated short-lived gas phase radicals, such as O and HO 2 , play important roles in the catalytic redox circles of Ag/CeO 2 to oxidize HCHO and CO to CO 2

  6. Determination of the Glass-Transition Temperature of GRPS and CFRPS Using a Torsion Pendulum in Regimes of Freely Damped Vibrations and Quasi-Stastic Torsion of Specimens

    Science.gov (United States)

    Startsev, V. O.; Lebedev, M. P.; Molokov, M. V.

    2018-03-01

    A method to measure the glass-transition temperature of polymers and polymeric matrices of composite materials with the help of an inverse torsion pendulum over a wide range of temperatures is considered combining the method of free torsional vibrations and a quasi-static torsion of specimens. The glass-transition temperature Tg of a KMKS-1-80. T10 fiberglass, on increasing the frequency of freely damped torsional vibrations from 0.7 to 9.6 Hz, was found to increase from 132 to 140°C. The value of Tg of these specimens, determined by measuring the work of their torsion through a small fixed angle was 128.6°C ± 0.8°C. It is shown that the use of a torsion pendulum allows one to determine the glass-transition temperature of polymeric or polymer matrices of PCMs in dynamic and quasi-static deformation regimes of specimens.

  7. New methodology to investigate potential contaminant mass fluxes at the stream-aquifer interface by combining integral pumping tests and streambed temperatures

    International Nuclear Information System (INIS)

    Kalbus, E.; Schmidt, C.; Bayer-Raich, M.; Leschik, S.; Reinstorf, F.; Balcke, G.U.; Schirmer, M.

    2007-01-01

    The spatial pattern and magnitude of mass fluxes at the stream-aquifer interface have important implications for the fate and transport of contaminants in river basins. Integral pumping tests were performed to quantify average concentrations of chlorinated benzenes in an unconfined aquifer partially penetrated by a stream. Four pumping wells were operated simultaneously for a time period of 5 days and sampled for contaminant concentrations. Streambed temperatures were mapped at multiple depths along a 60 m long stream reach to identify the spatial patterns of groundwater discharge and to quantify water fluxes at the stream-aquifer interface. The combined interpretation of the results showed average potential contaminant mass fluxes from the aquifer to the stream of 272 μg m -2 d -1 MCB and 71 μg m -2 d -1 DCB, respectively. This methodology combines a large-scale assessment of aquifer contamination with a high-resolution survey of groundwater discharge zones to estimate contaminant mass fluxes between aquifer and stream. - We provide a new methodology to quantify the potential contaminant mass flux from an aquifer to a stream

  8. Computational thermal-fluid dynamics analysis of the laminar flow regime in the meander flow geometry characterizing the heat exchanger used in high temperature superconducting current leads

    International Nuclear Information System (INIS)

    Rizzo, Enrico; Heller, Reinhard; Richard, Laura Savoldi; Zanino, Roberto

    2013-01-01

    Highlights: • The laminar regime in the meander flow geometry has been analysed with a previously validated computational strategy. • Several meander flow geometries as well as flow conditions have been analysed. • A range for the Reynolds number has been defined in which the flow can be considered laminar. • Correlations for the pressure drop and the heat transfer coefficients in the laminar regime have been derived. • A comparison between the computed the experimental pressure drop of the W7-X HTS current lead prototype is presented. -- Abstract: The Karlsruhe Institute of Technology and the Politecnico di Torino have developed and validated a computational thermal-fluid dynamics (CtFD) strategy for the systematic analysis of the thermal-hydraulics inside the meander flow heat exchanger used in high-temperature superconducting current leads for fusion applications. In the recent past, the application of this CtFD technique has shown that some operating conditions occurring in these devices may not reach the turbulent regime region. With that motivation, the CtFD analysis of the helium thermal-fluid dynamics inside different meander flow geometries is extended here to the laminar flow regime. Our first aim is to clarify under which operative conditions the flow regime can be considered laminar and how the pressure drop as well as the heat transfer are related to the geometrical parameters and to the flow conditions. From the results of this analysis, correlations for the pressure drop and for the heat transfer coefficient in the meander flow geometry have been derived, which are applicable with good accuracy to the design of meander flow heat exchangers over a broad range of geometrical parameters

  9. Computational thermal-fluid dynamics analysis of the laminar flow regime in the meander flow geometry characterizing the heat exchanger used in high temperature superconducting current leads

    Energy Technology Data Exchange (ETDEWEB)

    Rizzo, Enrico, E-mail: enrico.rizzo@kit.edu [Institute for Technical Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe (Germany); Heller, Reinhard [Institute for Technical Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe (Germany); Richard, Laura Savoldi; Zanino, Roberto [Dipartimento Energia, Politecnico di Torino, 10129 Torino (Italy)

    2013-11-15

    Highlights: • The laminar regime in the meander flow geometry has been analysed with a previously validated computational strategy. • Several meander flow geometries as well as flow conditions have been analysed. • A range for the Reynolds number has been defined in which the flow can be considered laminar. • Correlations for the pressure drop and the heat transfer coefficients in the laminar regime have been derived. • A comparison between the computed the experimental pressure drop of the W7-X HTS current lead prototype is presented. -- Abstract: The Karlsruhe Institute of Technology and the Politecnico di Torino have developed and validated a computational thermal-fluid dynamics (CtFD) strategy for the systematic analysis of the thermal-hydraulics inside the meander flow heat exchanger used in high-temperature superconducting current leads for fusion applications. In the recent past, the application of this CtFD technique has shown that some operating conditions occurring in these devices may not reach the turbulent regime region. With that motivation, the CtFD analysis of the helium thermal-fluid dynamics inside different meander flow geometries is extended here to the laminar flow regime. Our first aim is to clarify under which operative conditions the flow regime can be considered laminar and how the pressure drop as well as the heat transfer are related to the geometrical parameters and to the flow conditions. From the results of this analysis, correlations for the pressure drop and for the heat transfer coefficient in the meander flow geometry have been derived, which are applicable with good accuracy to the design of meander flow heat exchangers over a broad range of geometrical parameters.

  10. Effect of different arbuscular mycorrhizal fungi on growth and physiology of maize at ambient and low temperature regimes

    DEFF Research Database (Denmark)

    Chen, Xiaoying; Song, Fengbin; Liu, Fulai

    2014-01-01

    and soluble sugar contents under low temperature condition. The activities of catalase (CAT) and peroxidase of AM inoculated maize were higher than those of non-AM ones. Low temperature noticeably decreased the activities of CAT. The results suggest that low temperature adversely affects maize physiology...

  11. High mortality of Zostera marina under high temperature regimes but minor effects of the invasive macroalgae Gracilaria vermiculophylla

    DEFF Research Database (Denmark)

    Höffle, Hannes; Thomsen, M.S.; Holmer, M.

    2011-01-01

    The present study tested for density-dependent effects of the invasive drift macroalgae Gracilaria vermiculophylla (Ohmi) Papenfuss on growth and survival of the native eelgrass, Zostera marina L., under different temperature levels. Three weeks laboratory experiments were conducted in Odense......, Denmark, combining three algae densities (control, low 1.9 kg WW m2, high 4.5 kg WW m2) with typical Danish summer temperatures (18 C) and elevated temperatures (21 C and 27 C). There was a significant effect of temperature on shoot survival with on average 68% mortality in the high temperature treatment...... but almost no mortality at the two lower temperatures. The higher mortality was probably caused by high sulphide levels in the sediment pore water (0.6 mmol l1 at 18 C compared to 3.7 mmol l1 at 27 C). Above-ground growth of the surviving shoots was also significantly affected by temperature, with leaf...

  12. On natural circulation in High Temperature Gas-Cooled Reactors and pebble bed reactors for different flow regimes and various coolant gases

    International Nuclear Information System (INIS)

    Melesed'Hospital, G.

    1983-01-01

    The use of CO 2 or N 2 (heavy gas) instead of helium during natural circulation leads to improved performance in both High Temperature Gas-Cooled Reactors (HTGR) and in Pebble Bed Reactors (PBR). For instance, the coolant temperature rise corresponding to a coolant pressure level and a rate of afterheat removal could be only 18% with CO 2 as compared to He, for laminar flow in HTGR; this value would be 40% in PBR. There is less difference between HTGR and PBR for turbulent flows; CO 2 is found to be always better than N 2 . These types of results derived from relationships between coolant properties, coolant flow, temperature rise, pressure, afterheat levels and core geometry, are obtained for HTGR and PBR for various flow regimes, both within the core and in the primary loop

  13. Pretreatment of Sesame Seed (Sesamum indicum L. with Proline and its Effective on Seed Germination and Plant Physiological Defense Systems under Different Temperature Regimes

    Directory of Open Access Journals (Sweden)

    Nasibeh Tavakoli

    2016-06-01

    Full Text Available To study the effects of proline and temperature on the rates of antioxidant enzymes and germination index, a factorial laboratory experiment based on completely randomized design was conducted with three replications at the Mohaghegh Ardabili University in 2014. Treatments cinsisted of three levels of proline (0, 5 and 10 mM and different temperature regimes (15, 25 and 35°C. Results showed that proline significantly increased germination index, rates of antioxidant enzymes, proline, protein and mobility of food reserves. Exogenous application of proline increased assimilates in the seedlings. However, proline synthesis was decreased at temrature regimes of 15 and35°C as compared to 25 °C. Peroxidase enzyme rate at 25°C was lowere than of 15 and 35 °C and addition of proline increased levels of enzymes at these temperature regemes. Application of 10 mM proline at 25 °C showed the highest activity of catalase and polyphenol oxidase rates. However, rates of these enzymes at 15 and 35°C decreased as compared with that of 25°C. The length of radicle increased at all temperatures regemes and the length of plumule increased by proline, but reduced at temperatures of 15 and 35°C. According to the positive effects of proline on food reserves and seed vigor index, speed and rate of germination, proline, protein and antioxidant enzymes contents of seedlings, it seems that pretreatment of seeds with proline is an appropriate method for better seed germination attributs under these temperatures regemes.

  14. High mortality of Zostera marina under high temperature regimes but minor effects of the invasive macroalgae Gracilaria vermiculophylla

    Science.gov (United States)

    Höffle, H.; Thomsen, M. S.; Holmer, M.

    2011-03-01

    The present study tested for density-dependent effects of the invasive drift macroalgae Gracilaria vermiculophylla (Ohmi) Papenfuss on growth and survival of the native eelgrass, Zostera marina L., under different temperature levels. Three weeks laboratory experiments were conducted in Odense, Denmark, combining three algae densities (control, low 1.9 kg WW m -2, high 4.5 kg WW m -2) with typical Danish summer temperatures (18 °C) and elevated temperatures (21 °C and 27 °C). There was a significant effect of temperature on shoot survival with on average 68% mortality in the high temperature treatment but almost no mortality at the two lower temperatures. The higher mortality was probably caused by high sulphide levels in the sediment pore water (0.6 mmol l -1 at 18 °C compared to 3.7 mmol l -1 at 27 °C). Above-ground growth of the surviving shoots was also significantly affected by temperature, with leaf elongation rates being negatively affected, while the leaf plastochrone interval increased. Relative growth rate was significantly higher at 21 °C than at 18 °C or 27 °C, whereas rhizome elongation was significantly lowest at 27 °C. Elemental sulphur content in the plant tissues increased significantly with temperature and was up to 34 times higher (S 0 in rhizomes) at 27 °C compared to the lower temperatures. In contrast to the temperature effects, cover by G. vermiculophylla did not cause significant effects on any seagrass responses. However, there was a (non-significant) negative effect of algal cover at the highest temperature, where the seagrass is already stressed. The latter results suggest that more studies should test for interaction effects between temperature and other anthropogenic stressors given that temperature is predicted to increase in the near future.

  15. Investigation of the Low-Temperature Behavior of FD-SOI MOSFETs in the Saturation Regime Using Y and Z Functions

    Directory of Open Access Journals (Sweden)

    A. Karsenty

    2014-01-01

    Full Text Available The saturation regime of two types of fully depleted (FD SOI MOSFET devices was studied. Ultrathin body (UTB and gate recessed channel (GRC devices were fabricated simultaneously on the same silicon wafer through a selective “gate recessed” process. They share the same W/L ratio but have a channel film thickness of 46 nm and 2.2 nm, respectively. Their standard characteristics (IDS-VDS and IDS-VGS of the devices were measured at room temperature before cooling down to 77 K. Surprisingly, their respective temperature dependence is found to be opposite. In this paper, we focus our comparative analysis on the devices' conduction using a Y-function applied to the saturation domain. The influence of the temperature in this domain is presented for the first time. We point out the limits of the Y-function analysis and show that a new function called Z can be used to extract the series resistance in the saturation regime.

  16. Little Cross-Feeding of the Mycorrhizal Networks Shared Between C3-Panicum bisulcatum and C4-Panicum maximum Under Different Temperature Regimes

    Directory of Open Access Journals (Sweden)

    Veronika Řezáčová

    2018-04-01

    Full Text Available Common mycorrhizal networks (CMNs formed by arbuscular mycorrhizal fungi (AMF interconnect plants of the same and/or different species, redistributing nutrients and draining carbon (C from the different plant partners at different rates. Here, we conducted a plant co-existence (intercropping experiment testing the role of AMF in resource sharing and exploitation by simplified plant communities composed of two congeneric grass species (Panicum spp. with different photosynthetic metabolism types (C3 or C4. The grasses had spatially separated rooting zones, conjoined through a root-free (but AMF-accessible zone added with 15N-labeled plant (clover residues. The plants were grown under two different temperature regimes: high temperature (36/32°C day/night or ambient temperature (25/21°C day/night applied over 49 days after an initial period of 26 days at ambient temperature. We made use of the distinct C-isotopic composition of the two plant species sharing the same CMN (composed of a synthetic AMF community of five fungal genera to estimate if the CMN was or was not fed preferentially under the specific environmental conditions by one or the other plant species. Using the C-isotopic composition of AMF-specific fatty acid (C16:1ω5 in roots and in the potting substrate harboring the extraradical AMF hyphae, we found that the C3-Panicum continued feeding the CMN at both temperatures with a significant and invariable share of C resources. This was surprising because the growth of the C3 plants was more susceptible to high temperature than that of the C4 plants and the C3-Panicum alone suppressed abundance of the AMF (particularly Funneliformis sp. in its roots due to the elevated temperature. Moreover, elevated temperature induced a shift in competition for nitrogen between the two plant species in favor of the C4-Panicum, as demonstrated by significantly lower 15N yields of the C3-Panicum but higher 15N yields of the C4-Panicum at elevated as

  17. Flow regimes

    International Nuclear Information System (INIS)

    Kh'yuitt, G.

    1980-01-01

    An introduction into the problem of two-phase flows is presented. Flow regimes arizing in two-phase flows are described, and classification of these regimes is given. Structures of vertical and horizontal two-phase flows and a method of their identification using regime maps are considered. The limits of this method application are discussed. The flooding phenomena and phenomena of direction change (flow reversal) of the flow and interrelation of these phenomena as well as transitions from slug regime to churn one and from churn one to annular one in vertical flows are described. Problems of phase transitions and equilibrium are discussed. Flow regimes in tubes where evaporating liquid is running, are described [ru

  18. Application of multi-pass high pressure homogenization under variable temperature regimes to induce autolysis of wine yeasts.

    Science.gov (United States)

    Comuzzo, Piergiorgio; Calligaris, Sonia; Iacumin, Lucilla; Ginaldi, Federica; Voce, Sabrina; Zironi, Roberto

    2017-06-01

    The effects of the number of passes and processing temperature management (controlled vs. uncontrolled) were investigated during high pressure homogenization-induced autolysis of Saccharomyces bayanus wine yeasts, treated at 150MPa. Both variables were able to affect cell viability, and the release of soluble molecules (free amino acids, proteins and glucidic colloids), but the effect of temperature was more important. S. bayanus cells were completely inactivated in 10 passes without temperature control (corresponding to a processing temperature of 75°C). The two processing variables also affected the volatile composition of the autolysates produced: higher temperatures led to a lower concentration of volatile compounds. The management of the operating conditions may allow the compositional characteristics of the products to be modulated, making them suitable for different winemaking applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. The thermal regime in the resurgent dome of Long Valley Caldera, California: Inferences from precision temperature logs in deep wells

    Science.gov (United States)

    Hurwitz, S.; Farrar, C.D.; Williams, C.F.

    2010-01-01

    Long Valley Caldera in eastern California formed 0.76Ma ago in a cataclysmic eruption that resulted in the deposition of 600km3 of Bishop Tuff. The total current heat flow from the caldera floor is estimated to be ~290MW, and a geothermal power plant in Casa Diablo on the flanks of the resurgent dome (RD) generates ~40MWe. The RD in the center of the caldera was uplifted by ~80cm between 1980 and 1999 and was explained by most models as a response to magma intrusion into the shallow crust. This unrest has led to extensive research on geothermal resources and volcanic hazards in the caldera. Here we present results from precise, high-resolution, temperature-depth profiles in five deep boreholes (327-1,158m) on the RD to assess its thermal state, and more specifically 1) to provide bounds on the advective heat transport as a guide for future geothermal exploration, 2) to provide constraints on the occurrence of magma at shallow crustal depths, and 3) to provide a baseline for future transient thermal phenomena in response to large earthquakes, volcanic activity, or geothermal production. The temperature profiles display substantial non-linearity within each profile and variability between the different profiles. All profiles display significant temperature reversals with depth and temperature gradients <50??C/km at their bottom. The maximum temperature in the individual boreholes ranges between 124.7??C and 129.5??C and bottom hole temperatures range between 99.4??C and 129.5??C. The high-temperature units in the three Fumarole Valley boreholes are at the approximate same elevation as the high-temperature unit in borehole M-1 in Casa Diablo indicating lateral or sub-lateral hydrothermal flow through the resurgent dome. Small differences in temperature between measurements in consecutive years in three of the wells suggest slow cooling of the shallow hydrothermal flow system. By matching theoretical curves to segments of the measured temperature profiles, we calculate

  20. The influence of temperature and moisture contents regimes on the aerobic microbial activity of a biosolids composting blend.

    Science.gov (United States)

    Liang, C; Das, K C; McClendon, R W

    2003-01-01

    To understand the relationships between temperature, moisture content, and microbial activity during the composting of biosolids (municipal wastewater treatment sludge), well-controlled incubation experiments were conducted using a 2-factor factorial design with six temperatures (22, 29, 36, 43, 50, and 57 degrees C) and five moisture contents (30, 40, 50, 60, and 70%). The microbial activity was measured as O2 uptake rate (mg g(-1) h(-1)) using a computer controlled respirometer. In this study, moisture content proved to be a dominant factor impacting aerobic microbial activity of the composting blend. Fifty percent moisture content appeared to be the minimal requirement for obtaining activities greater than 1.0 mg g(-1) h(-1). Temperature was also documented to be an important factor for biosolids composting. However, its effect was less influential than moisture content. Particularly, the enhancement of composting activities induced by temperature increment could be realized by increasing moisture content alone.

  1. Dry matter production, radiation interception and radiation use efficiency of potato in response to temperature and nitrogen application regimes

    DEFF Research Database (Denmark)

    Zhenjiang, Zhou; Plauborg, Finn; Kristensen, Kristian

    2017-01-01

    while N rate varied from 0 to 180 kg ha−1. Statistical analysis using mixed modelling detected two clear features: Both temperature and N supply were important factors for dry matter production. Higher temperatures were associated with decreased dry matter production mainly through its negative effect...... on radiation use efficiency (RUE) when comparing inter-annual variation in dry matter production. The loss of tuber dry matter was c. 10% per °C, which is higher than estimated in previous studies. Specifically, compared to mean air temperature from end of tuber initiation to maturity, mean air temperature...... from emergence to end of tuber initiation was more important for dry matter production. N supply promoted dry matter production (p

  2. Flow regimes

    International Nuclear Information System (INIS)

    Liles, D.R.

    1982-01-01

    Internal boundaries in multiphase flow greatly complicate fluid-dynamic and heat-transfer descriptions. Different flow regimes or topological configurations can have radically dissimilar interfacial and wall mass, momentum, and energy exchanges. To model the flow dynamics properly requires estimates of these rates. In this paper the common flow regimes for gas-liquid systems are defined and the techniques used to estimate the extent of a particular regime are described. Also, the current computer-code procedures are delineated and introduce a potentially better method is introduced

  3. Thermal regime of a continental permafrost associated gas hydrate occurrence a continuous temperature profile record after drilling

    Science.gov (United States)

    Henninges, J.; Huenges, E.; Mallik Working Group

    2003-04-01

    Both the size and the distribution of natural methane hydrate occurrences, as well as the release of gaseous methane through the dissociation of methane hydrate, are affected by the subsurface pressure and temperature conditions. During a field experiment, which was carried out in the Mackenzie Delta, NWT, Canada, within the framework of the Mallik 2002 Production Research Well Program*, the variation of temperature within three 40 m spaced, 1200 m deep wells was measured deploying the Distributed Temperature Sensing (DTS) technology. An innovative experimental design for the monitoring of spatial and temporal variations of temperature along boreholes was developed and successfully applied under extreme arctic conditions. A special feature is the placement of the fibre-optic sensor cable inside the cement annulus between the casing and the wall of the borehole. Temperature profiles were recorded with a sampling interval of 0.25 m and 5 min, and temperatures can be determined with a resolution of 0.3 °C. The observed variation of temperature over time shows the decay of the thermal disturbances caused by the drilling and construction of the wells. An excellent indicator for the location of the base of the ice-bonded permafrost layer, which stands out as a result of the latent heat of the frozen pore fluid, is a sharp rise in temperature at 604 m depth during the period of equilibration. A similar effect can be detected in the depth interval between 1105 m and 1110 m, which is interpreted as an indicator for the depth to the base of the methane hydrate stability zone. Nine months after the completion of the wells the measured borehole temperatures are close to equilibrium. The mean temperature gradient rises from 9.4 K/km inside the permafrost to 25.4 K/km in the ice-free sediment layers underneath. The zone of the gas hydrate occurrences between 900 m and 1100 m shows distinct variations of the geothermal gradient, which locally rises up to 40 K/km. At the lower

  4. Fretting wear behaviour of TiC/Ti(C,N)/TiN multi-layer coatings at elevated temperature in gross slip regime

    International Nuclear Information System (INIS)

    Liu Hanwei; Huang Kunpeng; Zhu Minhao; Zhou Zhongrong

    2005-01-01

    Tic/Ti(C,N)/TiN multi-layer coatings are prepared on the 1Cr13 stainless steel substrate by the technique of Chemical Vapour Deposition, and the fretting wear behaviour of 1Cr13 stainless steel and TiC/Ti(C,N)/TiN coatings are investigated and studied controversially from 25 degree C to 400 degree C in the gross slip regime. It shows that the temperature has great influence on the fretting wear in the gross slip regime for the 1Cr13 stainless steel but little for Ti/C/Ti(C,N)/TiN multi-layer coatings. With the temperature increasing, the friction coefficient and the wear volume of the 1Cr13 alloy decreases and the wear volume of TiC/Ti(C, N)/TiN multi-layer coatings is invariant. TiC/Ti(C,N)/TiN multi-layer coatings have better wear-resistant capability than the 1Cr13 stainless steel, but the wear volume of the substrate increases greatly because of the grain-abrasion resulted from hard debris when TiC/Ti(C,N)/TiN multi-layer coatings are ground off. (authors)

  5. Investigating heat and temperature regime of the combustion chamber furnace screen of the TP 100A steam generator in the Varna thermal power plant

    Energy Technology Data Exchange (ETDEWEB)

    Mikhlevski, A; Buchinski, B; Dashkiev, Yu; Radzievski, V; Petkov, Kh [Kievski Politekhnicheski Institut (USSR)

    1988-01-01

    In the course of 10 year operation of six TP 100A steam generators 72 emergency operation interruptions occurred due to the piercing of screen pipes in the combustion chamber. According to investigations carried out by the NPO, CKT, VTI, KPI and Soyuzenergo institutes, the damage occurred mainly because of the destructive influence of external gas corrosion processes, overheating and fatigue of metallic pipes, as well as unstable heat and temperature regime in the combustion chamber. Large-scale measurements of the main thermodynamic parameters of the combustion chamber of the TP-100A steam generator were carried out in order to increase service life of screen pipes. It was found that the temperature of screen pipes increases 2.5 C/month because of deposition of sediments. Regular cleaning of screen pipes in intervals of 18 months is recommended as a very efficient means of prolonging their service life. 1 ref.

  6. Diagnostic system for measuring temperature, pressure, CO.sub.2 concentration and H.sub.2O concentration in a fluid stream

    Science.gov (United States)

    Partridge, Jr., William P.; Jatana, Gurneesh Singh; Yoo, Ji Hyung; Parks, II, James E.

    2017-12-26

    A diagnostic system for measuring temperature, pressure, CO.sub.2 concentration and H.sub.2O concentration in a fluid stream is described. The system may include one or more probes that sample the fluid stream spatially, temporally and over ranges of pressure and temperature. Laser light sources are directed down pitch optical cables, through a lens and to a mirror, where the light sources are reflected back, through the lens to catch optical cables. The light travels through the catch optical cables to detectors, which provide electrical signals to a processer. The processer utilizes the signals to calculate CO.sub.2 concentration based on the temperatures derived from H.sub.2O vapor concentration. A probe for sampling CO.sub.2 and H.sub.2O vapor concentrations is also disclosed. Various mechanical features interact together to ensure the pitch and catch optical cables are properly aligned with the lens during assembly and use.

  7. Analysis of the effect of implemented low temperature overpressure regimes on the reactor pressure vessel resistance to damage

    International Nuclear Information System (INIS)

    Pistora, V.

    1995-12-01

    The temperature and stress fields of the Dukovany WWER-440 reactor pressure vessel (RPV) were calculated based on a two-dimensional model using the finite element method. Two pressurized thermal shock events occurred at Dukovany in 1992: the temperature in 3 loops dropped rapidly while the primary circuit was fully pressurized. The calculation revealed that the first event was intolerable with respect to the RPV resistance to brittle fracture; had the two events occurred towards the end of the RPV lifetime, both would have been intolerable. (M.D.). 6 tabs., 15 figs., 6 refs

  8. Correlations of metabolic rate and body acceleration in three species of coastal sharks under contrasting temperature regimes.

    Science.gov (United States)

    Lear, Karissa O; Whitney, Nicholas M; Brewster, Lauran R; Morris, Jack J; Hueter, Robert E; Gleiss, Adrian C

    2017-02-01

    The ability to produce estimates of the metabolic rate of free-ranging animals is fundamental to the study of their ecology. However, measuring the energy expenditure of animals in the field has proved difficult, especially for aquatic taxa. Accelerometry presents a means of translating metabolic rates measured in the laboratory to individuals studied in the field, pending appropriate laboratory calibrations. Such calibrations have only been performed on a few fish species to date, and only one where the effects of temperature were accounted for. Here, we present calibrations between activity, measured as overall dynamic body acceleration (ODBA), and metabolic rate, measured through respirometry, for nurse sharks (Ginglymostoma cirratum), lemon sharks (Negaprion brevirostris) and blacktip sharks (Carcharhinus limbatus). Calibrations were made at a range of volitional swimming speeds and experimental temperatures. Linear mixed models were used to determine a predictive equation for metabolic rate based on measured ODBA values, with the optimal model using ODBA in combination with activity state and temperature to predict metabolic rate in lemon and nurse sharks, and ODBA and temperature to predict metabolic rate in blacktip sharks. This study lays the groundwork for calculating the metabolic rate of these species in the wild using acceleration data. © 2017. Published by The Company of Biologists Ltd.

  9. Intraspecies variation in a widely distributed tree species regulates the responses of soil microbiome to different temperature regimes.

    Science.gov (United States)

    Zhang, Cui-Jing; Delgado-Baquerizo, Manuel; Drake, John E; Reich, Peter B; Tjoelker, Mark G; Tissue, David T; Wang, Jun-Tao; He, Ji-Zheng; Singh, Brajesh K

    2018-04-01

    Plant characteristics in different provenances within a single species may vary in response to climate change, which might alter soil microbial communities and ecosystem functions. We conducted a glasshouse experiment and grew seedlings of three provenances (temperate, subtropical and tropical origins) of a tree species (i.e., Eucalyptus tereticornis) at different growth temperatures (18, 21.5, 25, 28.5, 32 and 35.5°C) for 54 days. At the end of the experiment, bacterial and fungal community composition, diversity and abundance were characterized. Measured soil functions included surrogates of microbial respiration, enzyme activities and nutrient cycling. Using Permutation multivariate analysis of variance (PerMANOVA) and network analysis, we found that the identity of tree provenances regulated both structure and function of soil microbiomes. In some cases, tree provenances substantially affected the response of microbial communities to the temperature treatments. For example, we found significant interactions of temperature and tree provenance on bacterial community and relative abundances of Chloroflexi and Zygomycota, and inorganic nitrogen. Microbial abundance was altered in response to increasing temperature, but was not affected by tree provenances. Our study provides novel evidence that even a small variation in biotic components (i.e., intraspecies tree variation) can significantly influence the response of soil microbial community composition and specific soil functions to global warming. © 2018 Society for Applied Microbiology and John Wiley & Sons Ltd.

  10. High-temperature creep of equiaxed Cd-26.5 at % Zn eutectic in the superplastic regime

    International Nuclear Information System (INIS)

    Tonejc, Anton; Poirier, J.-P.

    1976-01-01

    The temperature and stress dependence on the secondary creep rate of the Cd+26.5Zn eutectoid in the superplastic domain was studied in constant-stress compression creep. Experiments were performed in the following ranges of temperature, stress and grain size: 170C 2 , 1<10μm. In all cases secondary creep was established after a strain approximately equal to 4%. For temperatures higher than 200C all the techniques yielded the same value for m (m=0.49+-0.03) in the whole investigated range of stresses. For T=170C a lower value of m was found (m=0.33). The activation energy was determined and found equal to 25Kcal/mol. Micrographic examinations were performed on sectioned samples at several stages of deformation. The grain size was found to be identical for various conditions of temperature and stress and very stable with respect to deformation. The experimental results of the creep tests are discussed in relation with the microstructural aspects

  11. Comparison of three inert markers in measuring apparent nutrient digestibility of juvenile abalone under different culture condition and temperature regimes

    Science.gov (United States)

    Nur, K. U.; Adams, L.; Stone, D.; Savva, N.; Adams, M.

    2018-03-01

    A comparative research using three inert markers, chromic oxide, yttrium and ytterbium to measure the apparent nutrient digestibility of experimental feed in juvenile Hybrid abalone (Haliotis rubra X H. laevigata) and Greenlip abalone (H.laevigata) revealed that apparent digestibility of crude protein (ADCP) measured using yttrium and ytterbium in hybrid abalone were significantly different across the treatments. Protein digestibility measured in experimental tanks was higher than those measured in indoor and outdoor commercial tanks, regardless of inert marker used. Chromic oxide led to overestimated ADCP compared to when measured using yttrium and ytterbium. There were no significant interactions between temperature and inert markers when measuring ADCP and apparent digestibility of gross energy (ADGE). However, there was a significant difference of ADCP amongst inert markers when measured in greenlip abalone cultured at two temperatures. While measurements of ADge calculated using three inert markers shared the same value.

  12. Relative Linkages of Stream Dissolved Oxygen with the Climatic, Hydrological, and Biogeochemical Drivers across the East Coast of U.S.A.

    Science.gov (United States)

    Abdul-Aziz, O. I.; Ahmed, S.

    2017-12-01

    Dissolved oxygen (DO) is a key indicator of stream water quality and ecosystem health. However, the temporal dynamics of stream DO is controlled by a multitude of interacting environmental drivers. The relative linkages of stream DO with the relevant environmental drivers were determined in this study across the U.S. East Coast by employing a systematic data analytics approach. The study analyzed temporal data for 51 water quality monitoring stations from USGS NWIS and EPA STORET databases. Principal component analysis and factor analysis, along with Pearson's correlation analysis, were applied to identify the interrelationships and unravel latent patterns among DO and the environmental drivers. Power law based partial least squares regression models with a bootstarp Monte-Carlo procedure (1000 iterations) were developed to reliably estimate the environmental linkages of DO by resolving multicollinearity. Based on the similarity of dominant drivers, the streams were categorized into three distinct environmental regimes. Stream DO in the northern part of temperate zone (e.g., northeast coast) had the strongest linkage with water temperature; suggesting an environmental regime with dominant climatic control. However, stream DO in the tropical zones (e.g., southeast Florida) was mostly driven by pH; indicating an environmental regime likely controlled by redox chemistry. Further, a transitional regime was found between the temperate and tropical zones, where stream DO was controlled by both water temperature and pH. The results suggested a strong effect of the climatic gradient (temperate to tropical) on stream DO along the East Coast. The identified environmental regimes and the regime-specific relative linkages provided new information on the dominant controls of coastal stream water quality dynamics. The findings would guide the planning and management of coastal stream water quality and ecosystem health across the U.S. East Coast and around the world.

  13. Petroleum hydrocarbon biodegradation under seasonal freeze-thaw soil temperature regimes in contaminated soils from a sub-Arctic site.

    Science.gov (United States)

    Chang, Wonjae; Klemm, Sara; Beaulieu, Chantale; Hawari, Jalal; Whyte, Lyle; Ghoshal, Subhasis

    2011-02-01

    Several studies have shown that biostimulation in ex situ systems such as landfarms and biopiles can facilitate remediation of petroleum hydrocarbon contaminated soils at sub-Arctic sites during summers when temperatures are above freezing. In this study, we examine the biodegradation of semivolatile (F2: C10-C16) and nonvolatile (F3: C16-C34) petroleum hydrocarbons and microbial respiration and population dynamics at post- and presummer temperatures ranging from -5 to 14 °C. The studies were conducted in pilot-scale tanks with soils obtained from a historically contaminated sub-Arctic site in Resolution Island (RI), Canada. In aerobic, nutrient-amended, unsaturated soils, the F2 hydrocarbons decreased by 32% during the seasonal freeze-thaw phase where soils were cooled from 2 to -5 °C at a freezing rate of -0.12 °C d(-1) and then thawed from -5 to 4 °C at a thawing rate of +0.16 °C d(-1). In the unamended (control) tank, the F2 fraction only decreased by 14% during the same period. Biodegradation of individual hydrocarbon compounds in the nutrient-amended soils was also confirmed by comparing their abundance over time to that of the conserved diesel biomarker, bicyclic sesquiterpanes (BS). During this period, microbial respiration was observed, even at subzero temperatures when unfrozen liquid water was detected during the freeze-thaw period. An increase in culturable heterotrophs and 16S rDNA copy numbers was noted during the freezing phase, and the (14)C-hexadecane mineralization in soil samples obtained from the nutrient-amended tank steadily increased. Hydrocarbon degrading bacterial populations identified as Corynebacterineae- and Alkanindiges-related strains emerged during the freezing and thawing phases, respectively, indicating there were temperature-based microbial community shifts.

  14. An experimental study of soil temperature regimes associated with solar disinfestation techniques under greenhouse conditions in Greece.

    Science.gov (United States)

    Garofalakis, I; Tsiros, I; Frangoudakis, A; Chronopoulos, K; Flouri, F

    2006-01-01

    This paper deals with an experimental study of various techniques that have been applied for soil disinfestation purposes under greenhouse conditions. Various meteorological parameters and soil temperatures were measured for four different experimental soil segments (three associated with different disinfestation techniques and one as a reference) at depths varying between 0-1 m and with a time interval of 5 min in a greenhouse located in the Agricultural University of Athens Campus, Greece. Results showed that plastic polyethylene films such as covers, metallic conductors or a combination of both were able to enhance heat transfer and temperature increase in greenhouse soil. For typical disinfestation conditions, the depth-averaged temperature values for plastic covers, metallic conductors, and the combination of both were found to be higher than those for the reference of about 5 degrees C, 12 degrees C and 15 micro C, respectively. Moreover, the remained population percentages 50 days after the initiation of the experiment were found to be 19.3%, 25.3%, 37.3% Kcat 94% of the initial population, for the combination of metallic conductors and plastic covers, metallic conductors, plastic cover, and for the reference, respectively.

  15. Experimental evolution across different thermal regimes yields genetic divergence in recombination fraction but no divergence in temperature associated plastic recombination.

    Science.gov (United States)

    Kohl, Kathryn P; Singh, Nadia D

    2018-04-01

    Phenotypic plasticity is pervasive in nature. One mechanism underlying the evolution and maintenance of such plasticity is environmental heterogeneity. Indeed, theory indicates that both spatial and temporal variation in the environment should favor the evolution of phenotypic plasticity under a variety of conditions. Cyclical environmental conditions have also been shown to yield evolved increases in recombination frequency. Here, we use a panel of replicated experimental evolution populations of D. melanogaster to test whether variable environments favor enhanced plasticity in recombination rate and/or increased recombination rate in response to temperature. In contrast to expectation, we find no evidence for either enhanced plasticity in recombination or increased rates of recombination in the variable environment lines. Our data confirm a role of temperature in mediating recombination fraction in D. melanogaster, and indicate that recombination is genetically and plastically depressed under lower temperatures. Our data further suggest that the genetic architectures underlying plastic recombination and population-level variation in recombination rate are likely to be distinct. © 2018 The Author(s). Evolution © 2018 The Society for the Study of Evolution.

  16. Impacts of projected mid-century temperatures on thermal regimes for select specialty and fieldcrops common to the southwestern U.S.

    Science.gov (United States)

    Elias, E.; Lopez-Brody, N.; Dialesandro, J.; Steele, C. M.; Rango, A.

    2015-12-01

    The impacts of projected temperature increases in agricultural ecosystems are complex, varyingby region, cropping system, crop growth stage and humidity. We analyze the impacts of mid-century temperature increases on crops grown in five southwestern states: Arizona, California,New Mexico, Nevada and Utah. Here we present a spatial impact assessment of commonsouthwestern specialty (grapes, almonds and tomatoes) and field (alfalfa, cotton and corn)crops. This analysis includes three main components: development of empirical temperaturethresholds for each crop, classification of predicted future climate conditions according to thesethresholds, and mapping the probable impacts of these climatic changes on each crop. We use30m spatial resolution 2012 crop distribution and seasonal minimum and maximumtemperature normals (1970 to 2000) to define the current thermal envelopes for each crop.These represent the temperature range for each season where 95% of each crop is presentlygrown. Seasonal period change analysis of mid-century temperatures changes downscaled from20 CMIP5 models (RCP8.5) estimate future temperatures. Change detection maps representareas predicted to become more or less suitable, or remain unchanged. Based upon mid-centurytemperature changes, total regional suitable area declined for all crops except cotton, whichincreased by 20%. For each crop there are locations which change to and from optimal thermalenvelope conditions. More than 80% of the acres currently growing tomatoes and almonds willshift outside the present 95% thermal range. Fewer acres currently growing alfalfa (14%) andcotton (20%) will shift outside the present 95% thermal range by midcentury. Crops outsidepresent thermal envelopes by midcentury may adapt, possibly aided by adaptation technologiessuch as misters or shade structures, to the new temperature regime or growers may elect togrow alternate crops better suited to future thermal envelopes.

  17. Energy harvesting through gas dynamics in the free molecular flow regime between structured surfaces at different temperatures

    DEFF Research Database (Denmark)

    Baier, Tobias; Dölger, Julia; Hardt, Steffen

    2014-01-01

    For a gas confined between surfaces held at different temperatures the velocity distribution shows a significant deviation from the Maxwell distribution when the mean free path of the molecules is comparable to or larger than the channel dimensions. If one of the surfaces is suitably structured...... from the thermal creep flow that has gained more attention so far. This situation is studied in the limit of free-molecular flow for the case that an unstructured surface is allowed to move tangentially with respect to a structured surface. Parameter studies are conducted, and configurations...

  18. Energy harvesting through gas dynamics in the free molecular flow regime between structured surfaces at different temperatures

    Science.gov (United States)

    Baier, Tobias; Dölger, Julia; Hardt, Steffen

    2014-05-01

    For a gas confined between surfaces held at different temperatures the velocity distribution shows a significant deviation from the Maxwell distribution when the mean free path of the molecules is comparable to or larger than the channel dimensions. If one of the surfaces is suitably structured, this nonequilibrium distribution can be exploited for momentum transfer in a tangential direction between the two surfaces. This opens up the possibility to extract work from the system which operates as a heat engine. Since both surfaces are held at constant temperatures, the mode of momentum transfer is different from the thermal creep flow that has gained more attention so far. This situation is studied in the limit of free-molecular flow for the case that an unstructured surface is allowed to move tangentially with respect to a structured surface. Parameter studies are conducted, and configurations with maximum thermodynamic efficiency are identified. Overall, it is shown that significant efficiencies can be obtained by tangential momentum transfer between structured surfaces.

  19. Contribution of the actomyosin motor to the temperature-dependent translational diffusion of water by cytoplasmic streaming in Elodea canadensis cells.

    Science.gov (United States)

    Vorob'ev, V N; Anisimov, A V; Dautova, N R

    2004-12-01

    The extent to which the actomyosin motor responsible for cytoplasmic streaming contributes to the translational diffusion of water in Elodea canadensis cells was studied by a nuclear magnetic resonance (NMR) spin-echo technique. The relative contribution of the actomyosin motor was determined from the corresponding apparent diffusion coefficient by the Einstein-Smolukhovsky relation. It is equal to the difference between the diffusional displacements of the cytoplasmic and the bulk water (deltaX). The NMR data show that the temperature dependence of deltaX is humpshaped, which is characteristic of enzyme reactions. At the same time, the apparent diffusion coefficient of cytoplasmic water increases with an increase in temperature. The most significant contribution of the actomyosin motor to deltaX is observed at temperatures below 20 degrees C. Within the temperature range of 20 to 33 degrees C, deltaX changes only slightly, and a further increase in temperature reduces deltaX to zero.

  20. Application of Distributed Temperature Sensing for coupled mapping of sedimentation processes and spatio-temporal variability of groundwater discharge in soft-bedded streams

    DEFF Research Database (Denmark)

    Sebok, Eva; Duque, C; Engesgaard, Peter

    2015-01-01

    , maximum and mean streambed temperatures as well as the daily amplitude and standard deviation of temperatures. The identified potential high-discharge areas were mostly located near the channel banks, also showing temporal variability because of the scouring and redistribution of streambed sediments......The delineation of groundwater discharge areas based on Distributed Temperature Sensing (DTS) data of the streambed can be difficult in soft-bedded streams where sedimentation and scouring processes constantly change the position of the fibre optic cable relative to the streambed. Deposition...... variability in streambed temperatures between October 2011 and January 2012. Detailed monthly streambed elevation surveys were carried out to monitor the position of the fibre optic cable relative to the streambed and to quantify the effect of sedimentation processes on streambed temperatures. Based...

  1. Nonlinear magnetic electron tripolar vortices in streaming plasmas.

    Science.gov (United States)

    Vranjes, J; Marić, G; Shukla, P K

    2000-06-01

    Magnetic electron modes in nonuniform magnetized and unmagnetized streaming plasmas, with characteristic frequencies between the ion and electron plasma frequencies and at spatial scales of the order of the collisionless skin depth, are studied. Two coupled equations, for the perturbed (in the case of magnetized plasma) or self-generated (for the unmagnetized plasma case) magnetic field, and the temperature, are solved in the strongly nonlinear regime and stationary traveling solutions in the form of tripolar vortices are found.

  2. Investigations of Pulsed Plasma Streams Generated by 'Prosvet' device Operated with Different Gases

    International Nuclear Information System (INIS)

    Byrka, O.V.; Bandura, A.N.; Chebotarev, V.V. and others

    2006-01-01

    The paper presents the investigations of plasma streams generated by pulsed plasma gun 'Prosvet' operated with different gases: krypton (m=84) and helium (m=4). Contour parameters of working gas spectral lines (full intensities and half-widths) are used for determination of spatial distributions of the electron density and temperature. Temporal distributions of the spectral lines intensities (both neutrals and ions of working gas), impurity spectral lines and continuum intensities are analyzed. Plasma stream velocity was estimated by time-of-flight method between two monochromators (MUM) connected with photo-multiplier. longitudinal distributions of the plasma pressure for different time moments and varied distances from the accelerator output have been used for investigation of the plasma stream dynamics and study the plasma compression in the focus region for different operational regimes of plasma accelerator. Experiments show that operation regime of the accelerator and plasma stream parameters strongly depend on the gas atomic mass

  3. Regime change?

    International Nuclear Information System (INIS)

    Pilat, Joseph F.; Budlong-Sylvester, K.W.

    2004-01-01

    Following the 1998 nuclear tests in South Asia and later reinforced by revelations about North Korean and Iraqi nuclear activities, there has been growing concern about increasing proliferation dangers. At the same time, the prospects of radiological/nuclear terrorism are seen to be rising - since 9/11, concern over a proliferation/terrorism nexus has never been higher. In the face of this growing danger, there are urgent calls for stronger measures to strengthen the current international nuclear nonproliferation regime, including recommendations to place civilian processing of weapon-useable material under multinational control. As well, there are calls for entirely new tools, including military options. As proliferation and terrorism concerns grow, the regime is under pressure and there is a temptation to consider fundamental changes to the regime. In this context, this paper will address the following: Do we need to change the regime centered on the Treaty on the Nonproliferation of Nuclear Weapons (NPT) and the International Atomic Energy Agency (IAEA)? What improvements could ensure it will be the foundation for the proliferation resistance and physical protection needed if nuclear power grows? What will make it a viable centerpiece of future nonproliferation and counterterrorism approaches?

  4. Tests on wall temperatures of the moderator cell of the D2 cold source in equilibrium and transient regimes

    International Nuclear Information System (INIS)

    Hoffmann, H.

    1989-01-01

    A second cold source is planned in the high flux reactor inside an available horizontal channel. A volume exceeding 5 liters of liquid D 2 at a temperature of 25 K is required for good moderation. The moderator is near the core in the glove finger 23 cm in diameter and 5 m long. Thermal insulation of the cold structures from the environment is assured by a vacuum (Fig. 1). A facility near the core means a high heat liberation (3000 W) in the moderating cell, two-thirds of which is liberated in the material (aluminum) and one-third in the moderator itself. The moderator must handle the heat transfer. This can only be achieved with cooling by boiling the moderator in the cell which is in a state of saturation (25 K; 1.5 bars). It evaporates under the effect of the power liberated. The vapor is eliminated from the source in a monophase form, or in a diphase form as a mixture of fluid and vapor and then liquefied outside the glove finger in a condenser in a high position, cooled with helium. The condensed fluid then returns into the cell. This D 2 circuit is supposed to operate without pumps according to the principle of a thermisiphon. That is, the density differences in the input and outlet tubes give rise to circulation of the fluid. 6 refs., 24 figs

  5. Reactive collisions for NO(2Π) + N(4S) at temperatures relevant to the hypersonic flight regime.

    Science.gov (United States)

    Denis-Alpizar, Otoniel; Bemish, Raymond J; Meuwly, Markus

    2017-01-18

    The NO(X 2 Π) + N( 4 S) reaction which occurs entirely in the triplet manifold of N 2 O is investigated using quasiclassical trajectories and quantum simulations. Fully-dimensional potential energy surfaces for the 3 A' and 3 A'' states are computed at the MRCI+Q level of theory and are represented using a reproducing kernel Hilbert space. The N-exchange and N 2 -formation channels are followed by using the multi-state adiabatic reactive molecular dynamics method. Up to 5000 K these reactions occur predominantly on the N 2 O 3 A'' surface. However, for higher temperatures the contributions of the 3 A' and 3 A'' states are comparable and the final state distributions are far from thermal equilibrium. From the trajectory simulations a new set of thermal rate coefficients of up to 20 000 K is determined. Comparison of the quasiclassical trajectory and quantum simulations shows that a classical description is a good approximation as determined from the final state analysis.

  6. Thermal discharges from Paducah Gaseous Diffusion Plant outfalls: Impacts on stream temperatures and fauna of Little Bayou and Big Bayou Creeks

    Energy Technology Data Exchange (ETDEWEB)

    Roy, W.K.; Ryon, M.G.; Hinzman, R.L. [Oak Ridge National Lab., TN (United States). Computer Science and Mathematics Div.

    1996-03-01

    The development of a biological monitoring plan for the receiving streams of the Paducah Gaseous Diffusion Plant (PGDP) began in the late 1980s, because of an Agreed Order (AO) issued in September 1987 by the Kentucky Division of Water (KDOW). Five years later, in September 1992, more stringent effluent limitations were imposed upon the PGDP operations when the KDOW reissued Kentucky Pollutant Discharge Elimination System permit No. KY 0004049. This action prompted the US Department of Energy (DOE) to request a stay of certain limits contained in the permit. An AO is being negotiated between KDOW, the US Enrichment Corporation (USEC), and DOE that will require that several studies be conducted, including this stream temperature evaluation study, in an effort to establish permit limitations. All issues associated with this AO have been resolved, and the AO is currently being signed by all parties involved. The proposed effluent temperature limit is 89 F (31.7 C) as a mean monthly temperature. In the interim, temperatures are not to exceed 95 F (35 C) as a monthly mean or 100 F (37.8 C) as a daily maximum. This study includes detailed monitoring of instream temperatures, benthic macroinvertebrate communities, fish communities, and a laboratory study of thermal tolerances.

  7. Thermal discharges from Paducah Gaseous Diffusion Plant outfalls: Impacts on stream temperatures and fauna of Little Bayou and Big Bayou Creeks

    International Nuclear Information System (INIS)

    Roy, W.K.; Ryon, M.G.; Hinzman, R.L.

    1996-03-01

    The development of a biological monitoring plan for the receiving streams of the Paducah Gaseous Diffusion Plant (PGDP) began in the late 1980s, because of an Agreed Order (AO) issued in September 1987 by the Kentucky Division of Water (KDOW). Five years later, in September 1992, more stringent effluent limitations were imposed upon the PGDP operations when the KDOW reissued Kentucky Pollutant Discharge Elimination System permit No. KY 0004049. This action prompted the US Department of Energy (DOE) to request a stay of certain limits contained in the permit. An AO is being negotiated between KDOW, the US Enrichment Corporation (USEC), and DOE that will require that several studies be conducted, including this stream temperature evaluation study, in an effort to establish permit limitations. All issues associated with this AO have been resolved, and the AO is currently being signed by all parties involved. The proposed effluent temperature limit is 89 F (31.7 C) as a mean monthly temperature. In the interim, temperatures are not to exceed 95 F (35 C) as a monthly mean or 100 F (37.8 C) as a daily maximum. This study includes detailed monitoring of instream temperatures, benthic macroinvertebrate communities, fish communities, and a laboratory study of thermal tolerances

  8. Thermal Discharges from Paducah Gaseous Diffusion Plant Outfalls: Impacts on Stream Temperatures and Fauna of Little Bayou and Big Bayou Creeks

    International Nuclear Information System (INIS)

    Roy, W.K.

    1999-01-01

    The development of a biological monitoring plan for the receiving streams of the Paducah Gaseous Diffusion Plant (PGDP) began in the late 1980s, because of an Agreed Order (AO) issued in September 1987 by the Kentucky Division of Water (KDOW). Five years later, in September 1992, more stringent effluent limitations were imposed upon the PGDP operations when the KDOW reissued Kentucky Pollutant Discharge Elimination System permit No. KY 0004049. This action prompted the US Department of Energy (DOE) to request a stay of certain limits contained in the permit. An AO is being negotiated between KDOW, the United States Enrichment Corporation (USEC), and DOE that will require that several studies be conducted, including this stream temperature evaluation study, in an effort to establish permit limitations. All issues associated with this AO have been resolved, and the AO is currently being signed by all parties involved. The proposed effluent temperature limit is 89 F (31.7C) as a mean monthly temperature. In the interim, temperatures are not to exceed 95 F (35 C) as a monthly mean or 100 F (37.8 C) as a daily maximum. This study includes detailed monitoring of instream temperatures, benthic macroinvertebrate communities, fish communities, and a laboratory study of thermal tolerances

  9. Thermal Discharges from Paducah Gaseous Diffusion Plant Outfalls: Impacts on Stream Temperatures and Fauna of Little Bayou and Big Bayou Creeks

    Energy Technology Data Exchange (ETDEWEB)

    Roy, W.K.

    1999-01-01

    The development of a biological monitoring plan for the receiving streams of the Paducah Gaseous Diffusion Plant (PGDP) began in the late 1980s, because of an Agreed Order (AO) issued in September 1987 by the Kentucky Division of Water (KDOW). Five years later, in September 1992, more stringent effluent limitations were imposed upon the PGDP operations when the KDOW reissued Kentucky Pollutant Discharge Elimination System permit No. KY 0004049. This action prompted the US Department of Energy (DOE) to request a stay of certain limits contained in the permit. An AO is being negotiated between KDOW, the United States Enrichment Corporation (USEC), and DOE that will require that several studies be conducted, including this stream temperature evaluation study, in an effort to establish permit limitations. All issues associated with this AO have been resolved, and the AO is currently being signed by all parties involved. The proposed effluent temperature limit is 89 F (31.7C) as a mean monthly temperature. In the interim, temperatures are not to exceed 95 F (35 C) as a monthly mean or 100 F (37.8 C) as a daily maximum. This study includes detailed monitoring of instream temperatures, benthic macroinvertebrate communities, fish communities, and a laboratory study of thermal tolerances.

  10. SUPPLEMENTARY FEEDING ON THE NUTRIENT BALANCE OF LACTATING DAIRY COW AT CONTRASTING TEMPERATURE REGIMES: ASSESSMENT USING CORNELL NET CARBOHYDRATE AND PROTEIN SYSTEM (CNCPS MODEL

    Directory of Open Access Journals (Sweden)

    A. Jayanegara

    2014-10-01

    Full Text Available Dairy cows often do not receive adequate nutrient supply during their lactation period. This condition caneven be worse if the environmental temperature is not in comfortable range which may occur especially intropical regions. The present research was aimed to simulate the effect of supplementary feeding on nutrientbalance of lactating dairy cow at contrasting temperature regimes using Cornell Net Carbohydrate andProtein System (CNCPS model. Treatments consisted of feeds (R1: Pennisetum purpureum, R2: P.purpureum + concentrate (60:40, R3: P. purpureum + Gliricidia sepium + Leucaena leucocephala(60:20:20, R4: P. purpureum + concentrate + G. sepium + L. leucocephala (60:20:10:10 and environmentaltemperatures (T1: 20 oC, T2: 30 oC. The dairy cow inputs in CNCPS were Holstein breed, body weight of500 kg, feed intake of 15 kg (dry matter basis per day and produced milk 15 kg/day. Based on the CNCPSmodel, there were negative balances of metabolisable energy (ME and metabolisable protein (MP if alactating dairy cow fed only by P. purpureum. The ME balance was worse at higher temperature, while theMP balance was remain unchanged. Addition of concentrate mixture (R2 fulfilled the ME and MPrequirements as well as other nutrients. Addition of leguminous tree leaves (R3 and R4 improved thenutritional status of the lactating cow model compared to R1, but did not better than R2. It was concludedthat supplementary feeding is necessary for improving the nutrient balance of lactating dairy cow, especiallywhen the cow is maintained under uncomfortable environmental temperature.

  11. The contribution of Distributed Temperature Sensing (DTS) in streams to assess spatial runoff processes in a moraine dominated agricultural catchment

    DEFF Research Database (Denmark)

    Boegh, Eva; Blemmer, Morten; Holmes, Esbern

    Evaluating impacts of site-specific changes in land use and land cover on catchment processes is significantly complicated by spatial heterogeneity and the long and variable time lags between precipitation and the responses of streams and groundwater. In this study, a 1-D soil-plant-atmosphere mo......Evaluating impacts of site-specific changes in land use and land cover on catchment processes is significantly complicated by spatial heterogeneity and the long and variable time lags between precipitation and the responses of streams and groundwater. In this study, a 1-D soil...

  12. Competition Regime

    Directory of Open Access Journals (Sweden)

    Danilo Icaza Ortiz

    2013-01-01

    Full Text Available This paper is a review of the competition regime works of various authors, published under the auspices of the University of the Hemispheres and the Corporation for Studies and Publications. Analyzes the structure, the general concepts, case law taken for development. Includes comments on the usefulness of this work for the study of competition law and the contribution to the lawyers who want to practice in this branch of economic law.

  13. Linking Stream Dissolved Oxygen with the Dynamic Environmental Drivers across the Pacific Coast of U.S.A.

    Science.gov (United States)

    Araya, F. Z.; Abdul-Aziz, O. I.

    2017-12-01

    This study utilized a systematic data analytics approach to determine the relative linkages of stream dissolved oxygen (DO) with the hydro-climatic and biogeochemical drivers across the U.S. Pacific Coast. Multivariate statistical techniques of Pearson correlation matrix, principal component analysis, and factor analysis were applied to a complex water quality dataset (1998-2015) at 35 water quality monitoring stations of USGS NWIS and EPA STORET. Power-law based partial least squares regression (PLSR) models with a bootstrap Monte Carlo procedure (1000 iterations) were developed to reliably estimate the relative linkages by resolving multicollinearity (Nash-Sutcliffe Efficiency, NSE = 0.50-0.94). Based on the dominant drivers, four environmental regimes have been identified and adequately described the system-data variances. In Pacific North West and Southern California, water temperature was the most dominant driver of DO in majority of the streams. However, in Central and Northern California, stream DO was controlled by multiple drivers (i.e., water temperature, pH, stream flow, and total phosphorus), exhibiting a transitional environmental regime. Further, total phosphorus (TP) appeared to be the limiting nutrient for most streams. The estimated linkages and insights would be useful to identify management priorities to achieve healthy coastal stream ecosystems across the Pacific Coast of U.S.A. and similar regions around the world. Keywords: Data analytics, water quality, coastal streams, dissolved oxygen, environmental regimes, Pacific Coast, United States.

  14. Stream Classification Tool User Manual: For Use in Applications in Hydropower-Related Evironmental Mitigation

    Energy Technology Data Exchange (ETDEWEB)

    McManamay, Ryan A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Troia, Matthew J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); DeRolph, Christopher R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Samu, Nicole M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-01-01

    Stream classifications are an inventory of different types of streams. Classifications help us explore similarities and differences among different types of streams, make inferences regarding stream ecosystem behavior, and communicate the complexities of ecosystems. We developed a nested, layered, and spatially contiguous stream classification to characterize the biophysical settings of stream reaches within the Eastern United States (~ 900,000 reaches). The classification is composed of five natural characteristics (hydrology, temperature, size, confinement, and substrate) along with several disturbance regime layers, and each was selected because of their relevance to hydropower mitigation. We developed the classification at the stream reach level using the National Hydrography Dataset Plus Version 1 (1:100k scale). The stream classification is useful to environmental mitigation for hydropower dams in multiple ways. First, it creates efficiency in the regulatory process by creating an objective and data-rich means to address meaningful mitigation actions. Secondly, the SCT addresses data gaps as it quickly provides an inventory of hydrology, temperature, morphology, and ecological communities for the immediate project area, but also surrounding streams. This includes identifying potential reference streams as those that are proximate to the hydropower facility and fall within the same class. These streams can potentially be used to identify ideal environmental conditions or identify desired ecological communities. In doing so, the stream provides some context for how streams may function, respond to dam regulation, and an overview of specific mitigation needs. Herein, we describe the methodology in developing each stream classification layer and provide a tutorial to guide applications of the classification (and associated data) in regulatory settings, such as hydropower (re)licensing.

  15. Streams with Strahler Stream Order

    Data.gov (United States)

    Minnesota Department of Natural Resources — Stream segments with Strahler stream order values assigned. As of 01/08/08 the linework is from the DNR24K stream coverages and will not match the updated...

  16. Relations between fish abundances, summer temperatures, and forest harvest in a northern Minnesota stream system from 1997 to 2007

    Science.gov (United States)

    Eric Merten; Nathaniel Hemstad; Susan Eggert; Lucinda Johnson; Randall Kolka; Bruce Vondracek; Raymond. Newman

    2010-01-01

    Short-term effects of forest harvest on fish habitat have been well documented, including sediment inputs, leaf litter reductions, and stream warming. However, few studies have considered changes in local climate when examining postlogging changes in fish communities. To address this need, we examined fish abundances between 1997 and 2007 in a basin in a northern...

  17. Solar wind stream interfaces

    International Nuclear Information System (INIS)

    Gosling, J.T.; Asbridge, J.R.; Bame, S.J.; Feldman, W.C.

    1978-01-01

    Measurements aboard Imp 6, 7, and 8 reveal that approximately one third of all high-speed solar wind streams observed at 1 AU contain a sharp boundary (of thickness less than approx.4 x 10 4 km) near their leading edge, called a stream interface, which separates plasma of distinctly different properties and origins. Identified as discontinuities across which the density drops abruptly, the proton temperature increases abruptly, and the speed rises, stream interfaces are remarkably similar in character from one stream to the next. A superposed epoch analysis of plasma data has been performed for 23 discontinuous stream interfaces observed during the interval March 1971 through August 1974. Among the results of this analysis are the following: (1) a stream interface separates what was originally thick (i.e., dense) slow gas from what was originally thin (i.e., rare) fast gas; (2) the interface is the site of a discontinuous shear in the solar wind flow in a frame of reference corotating with the sun; (3) stream interfaces occur at speeds less than 450 km s - 1 and close to or at the maximum of the pressure ridge at the leading edges of high-speed streams; (4) a discontinuous rise by approx.40% in electron temperature occurs at the interface; and (5) discontinuous changes (usually rises) in alpha particle abundance and flow speed relative to the protons occur at the interface. Stream interfaces do not generally recur on successive solar rotations, even though the streams in which they are embedded often do. At distances beyond several astronomical units, stream interfaces should be bounded by forward-reverse shock pairs; three of four reverse shocks observed at 1 AU during 1971--1974 were preceded within approx.1 day by stream interfaces. Our observations suggest that many streams close to the sun are bounded on all sides by large radial velocity shears separating rapidly expanding plasma from more slowly expanding plasma

  18. Evaluation of statistically downscaled GCM output as input for hydrological and stream temperature simulation in the Apalachicola–Chattahoochee–Flint River Basin (1961–99)

    Science.gov (United States)

    Hay, Lauren E.; LaFontaine, Jacob H.; Markstrom, Steven

    2014-01-01

    The accuracy of statistically downscaled general circulation model (GCM) simulations of daily surface climate for historical conditions (1961–99) and the implications when they are used to drive hydrologic and stream temperature models were assessed for the Apalachicola–Chattahoochee–Flint River basin (ACFB). The ACFB is a 50 000 km2 basin located in the southeastern United States. Three GCMs were statistically downscaled, using an asynchronous regional regression model (ARRM), to ⅛° grids of daily precipitation and minimum and maximum air temperature. These ARRM-based climate datasets were used as input to the Precipitation-Runoff Modeling System (PRMS), a deterministic, distributed-parameter, physical-process watershed model used to simulate and evaluate the effects of various combinations of climate and land use on watershed response. The ACFB was divided into 258 hydrologic response units (HRUs) in which the components of flow (groundwater, subsurface, and surface) are computed in response to climate, land surface, and subsurface characteristics of the basin. Daily simulations of flow components from PRMS were used with the climate to simulate in-stream water temperatures using the Stream Network Temperature (SNTemp) model, a mechanistic, one-dimensional heat transport model for branched stream networks.The climate, hydrology, and stream temperature for historical conditions were evaluated by comparing model outputs produced from historical climate forcings developed from gridded station data (GSD) versus those produced from the three statistically downscaled GCMs using the ARRM methodology. The PRMS and SNTemp models were forced with the GSD and the outputs produced were treated as “truth.” This allowed for a spatial comparison by HRU of the GSD-based output with ARRM-based output. Distributional similarities between GSD- and ARRM-based model outputs were compared using the two-sample Kolmogorov–Smirnov (KS) test in combination with descriptive

  19. Seeing the light: the effects of particles, dissolved materials, and temperature on in situ measurements of DOM fluorescence in rivers and streams

    Science.gov (United States)

    Downing, Bryan D.; Pellerin, Brian A.; Bergamaschi, Brian A.; Saraceno, John Franco; Kraus, Tamara E.C.

    2012-01-01

    Field-deployable sensors designed to continuously measure the fluorescence of colored dissolved organic matter (FDOM) in situ are of growing interest. However, the ability to make FDOM measurements that are comparable across sites and over time requires a clear understanding of how instrument characteristics and environmental conditions affect the measurements. In particular, the effects of water temperature and light attenuation by both colored dissolved material and suspended particles may be significant in settings such as rivers and streams. Using natural standard reference materials, we characterized the performance of four commercially-available FDOM sensors under controlled laboratory conditions over ranges of temperature, dissolved organic matter (DOM) concentrations, and turbidity that spanned typical environmental ranges. We also examined field data from several major rivers to assess how often attenuation artifacts or temperature effects might be important. We found that raw (uncorrected) FDOM values were strongly affected by the light attenuation that results from dissolved substances and suspended particles as well as by water temperature. Observed effects of light attenuation and temperature agreed well with theory. Our results show that correction of measured FDOM values to account for these effects is necessary and feasible over much of the range of temperature, DOM concentration, and turbidity commonly encountered in surface waters. In most cases, collecting high-quality FDOM measurements that are comparable through time and between sites will require concurrent measurements of temperature and turbidity, and periodic discrete sample collection for laboratory measurement of DOM.

  20. Stream Crossings

    Data.gov (United States)

    Vermont Center for Geographic Information — Physical measurements and attributes of stream crossing structures and adjacent stream reaches which are used to provide a relative rating of aquatic organism...

  1. Akamai Streaming

    OpenAIRE

    ECT Team, Purdue

    2007-01-01

    Akamai offers world-class streaming media services that enable Internet content providers and enterprises to succeed in today's Web-centric marketplace. They deliver live event Webcasts (complete with video production, encoding, and signal acquisition services), streaming media on demand, 24/7 Webcasts and a variety of streaming application services based upon their EdgeAdvantage.

  2. Juvenile coho salmon growth and health in streams across an urbanization gradient

    Science.gov (United States)

    Spanjer, Andrew R.; Moran, Patrick W.; Larsen, Kimberly; Wetzel, Lisa; Hansen, Adam G.; Beauchamp, David A.

    2018-01-01

    Expanding human population and urbanization alters freshwater systems through structural changes to habitat, temperature effects from increased runoff and reduced canopy cover, altered flows, and increased toxicants. Current stream assessments stop short of measuring health or condition of species utilizing these freshwater habitats and fail to link specific stressors mechanistically to the health of organisms in the stream. Juvenile fish growth integrates both external and internal conditions providing a useful indicator of habitat quality and ecosystem health. Thus, there is a need to account for ecological and environmental influences on fish growth accurately. Bioenergetics models can simulate changes in growth and consumption in response to environmental conditions and food availability to account for interactions between an organism's environmental experience and utilization of available resources. The bioenergetics approach accounts for how thermal regime, food supply, and food quality affect fish growth. This study used a bioenergetics modeling approach to evaluate the environmental factors influencing juvenile coho salmon growth among ten Pacific Northwest streams spanning an urban gradient. Urban streams tended to be warmer, have earlier emergence dates and stronger early season growth. However, fish in urban streams experienced increased stress through lower growth efficiencies, especially later in the summer as temperatures warmed, with as much as a 16.6% reduction when compared to fish from other streams. Bioenergetics modeling successfully characterized salmonid growth in small perennial streams as part of a more extensive monitoring program and provides a powerful assessment tool for characterizing mixed life-stage specific responses in urban streams.

  3. Ranking site vulnerability to increasing temperatures in southern Appalachian brook trout streams in Virginia: An exposure-sensitivity approach

    Science.gov (United States)

    Bradly A. Trumbo; Keith H. Nislow; Jonathan Stallings; Mark Hudy; Eric P. Smith; Dong-Yun Kim; Bruce Wiggins; Charles A. Dolloff

    2014-01-01

    Models based on simple air temperature–water temperature relationships have been useful in highlighting potential threats to coldwater-dependent species such as Brook Trout Salvelinus fontinalis by predicting major losses of habitat and substantial reductions in geographic distribution. However, spatial variability in the relationship between changes...

  4. Thinking beyond the Bioreactor Box: Incorporating Stream Ecology into Edge-of-Field Nitrate Management.

    Science.gov (United States)

    Goeller, Brandon C; Febria, Catherine M; Harding, Jon S; McIntosh, Angus R

    2016-05-01

    Around the world, artificially drained agricultural lands are significant sources of reactive nitrogen to stream ecosystems, creating substantial stream health problems. One management strategy is the deployment of denitrification enhancement tools. Here, we evaluate the factors affecting the potential of denitrifying bioreactors to improve stream health and ecosystem services. The performance of bioreactors and the structure and functioning of stream biotic communities are linked by environmental parameters like dissolved oxygen and nitrate-nitrogen concentrations, dissolved organic carbon availability, flow and temperature regimes, and fine sediment accumulations. However, evidence of bioreactors' ability to improve waterway health and ecosystem services is lacking. To improve the potential of bioreactors to enhance desirable stream ecosystem functioning, future assessments of field-scale bioreactors should evaluate the influences of bioreactor performance on ecological indicators such as primary production, organic matter processing, stream metabolism, and invertebrate and fish assemblage structure and function. These stream health impact assessments should be conducted at ecologically relevant spatial and temporal scales. Bioreactors have great potential to make significant contributions to improving water quality, stream health, and ecosystem services if they are tailored to site-specific conditions and implemented strategically with land-based and stream-based mitigation tools within watersheds. This will involve combining economic, logistical, and ecological information in their implementation. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  5. Relative Linkages of Stream Dissolved Oxygen with the Hydroclimatic and Biogeochemical Drivers across the Gulf Coast of U.S.A.

    Science.gov (United States)

    Gebreslase, A. K.; Abdul-Aziz, O. I.

    2017-12-01

    Dynamics of coastal stream water quality is influenced by a multitude of interacting environmental drivers. A systematic data analytics approach was employed to determine the relative linkages of stream dissolved oxygen (DO) with the hydroclimatic and biogeochemical variables across the Gulf Coast of U.S.A. Multivariate pattern recognition techniques of PCA and FA, alongside Pearson's correlation matrix, were utilized to examine the interrelation of variables at 36 water quality monitoring stations from USGS NWIS and EPA STORET databases. Power-law based partial least square regression models with a bootstrap Monte Carlo procedure (1000 iterations) were developed to estimate the relative linkages of dissolved oxygen with the hydroclimatic and biogeochemical variables by appropriately resolving multicollinearity (Nash-Sutcliffe efficiency = 0.58-0.94). Based on the dominant drivers, stations were divided into four environmental regimes. Water temperature was the dominant driver of DO in the majority of streams, representing most the northern part of Gulf Coast states. However, streams in the southern part of Texas and Florida showed a dominant pH control on stream DO. Further, streams representing the transition zone of the two environmental regimes showed notable controls of multiple drivers (i.e., water temperature, stream flow, and specific conductance) on the stream DO. The data analytics research provided profound insight to understand the dynamics of stream DO with the hydroclimatic and biogeochemical variables. The knowledge can help water quality managers in formulating plans for effective stream water quality and watershed management in the U.S. Gulf Coast. Keywords Data analytics, coastal streams, relative linkages, dissolved oxygen, environmental regimes, Gulf Coast, United States.

  6. Characterizing snowmelt regime of the river swat - a case study

    International Nuclear Information System (INIS)

    Malik, M.A.

    2015-01-01

    Snowmelt generates 70 to 80% of runoff of Indus River and its tributaries. Forecasting snowmelt generated flow is important for water management, reservoir operation and channel diversion. River Swat being not direct contributor to the existing reservoirs remained out of focus for characterizing its snowmelt regime. Thirty years (1971-2000) data of upper Swat catchment above Kalam gauging station was acquired from WAPDA. Normal monthly values over the period and average monthly values of each year were determined for stream flow, precipitation and temperature together with average monthly values of weighted and maximum temperature. Snowmelt regime was ascertained from plot of normal values of flow, precipitation and temperature. Using temperature index approach, average monthly flow over the snowmelt months (April, May and June) in terms of mm depth over the catchment was regressed on all the temperature indices using exponential, power and third degree polynomial functions. Tmax was found the best index for snowmelt with R2 as 0.902 for the third degree polynomial function. Runoff coefficient (ROC) for the total precipitation was conceptualized and through iteration was found as T max 100. The optimized value of ROC was used to segregate rain induced and snowmelt induced runoff. The segregated snowmelt induced runoff was again regressed on Tmax using the same function which slightly improved R2 to 0.916. The model was tested for four years of data and forecasted flow was found reasonable in the context of simplicity of the approach. (author)

  7. HydroClim: a Continental-Scale Database of Contemporary and Future Streamflow and Stream Temperature Estimates for Aquatic Ecosystem Studies

    Science.gov (United States)

    Knouft, J.; Ficklin, D. L.; Bart, H. L.; Rios, N. E.

    2017-12-01

    Streamflow and water temperature are primary factors influencing the traits, distribution, and diversity of freshwater species. Ongoing changes in climate are causing directional alteration of these environmental conditions, which can impact local ecological processes. Accurate estimation of these variables is critical for predicting the responses of species to ongoing changes in freshwater habitat, yet ecologically relevant high-resolution data describing variation in streamflow and water temperature across North America are not available. Considering the vast amount of web-accessible freshwater biodiversity data, development and application of appropriate hydrologic data are critical to the advancement of our understanding of freshwater systems. To address this issue, we are developing the "HydroClim" database, which will provide web-accessible (www.hydroclim.org) historical and projected monthly streamflow and water temperature data for stream sections in all major watersheds across the United States and Canada from 1950-2099. These data will also be integrated with FishNet 2 (www.fishnet2.net), an online biodiversity database that provides open access to over 2 million localities of freshwater fish species in the United States and Canada, thus allowing for the characterization of the habitat requirements of freshwater species across this region. HydroClim should provide a vast array of opportunities for a greater understanding of water resources as well as information for the conservation of freshwater biodiversity in the United States and Canada in the coming century.

  8. Chironomid-based reconstructions of summer air temperature from lake deposits in Lyndon Stream, New Zealand spanning the MIS 3/2 transition

    Science.gov (United States)

    Woodward, C. A.; Shulmeister, J.

    2007-01-01

    We present chironomid-based temperature reconstructions from lake sediments deposited between ca 26,600 cal yr BP and 24,500 cal yr BP from Lyndon Stream, South Island, New Zealand. Summer (February mean) temperatures averaged 1 °C cooler, with a maximum inferred cooling of 3.7 °C. These estimates corroborate macrofossil and beetle-based temperature inferences from the same site and suggest climate amelioration (an interstadial) at this time. Other records from the New Zealand region also show a large degree of variability during the late Otiran glacial sequence (34,000-18,000 cal yr BP) including a phase of warming at the MIS 2/3 transition and a maximum cooling that did not occur until the global LGM (ca 20,000 cal yr BP). The very moderate cooling identified here at the MIS 2/3 transition confirms and enhances the long-standing discrepancy in New Zealand records between pollen and other proxies. Low abundances (<20%) of canopy tree pollen in records from late MIS 3 to the end of MIS 2 cannot be explained by the minor (<5 °C) cooling inferred from this and other studies unless other environmental parameters are considered. Further work is required to address this critical issue.

  9. PALLADIUM/COPPER ALLOY COMPOSITE MEMBRANES FOR HIGH TEMPERATURE HYDROGEN SEPARATION FROM COAL-DERIVED GAS STREAMS; F

    International Nuclear Information System (INIS)

    J. Douglas Way; Robert L. McCormick

    2001-01-01

    Recent advances have shown that Pd-Cu composite membranes are not susceptible to the mechanical, embrittlement, and poisoning problems that have prevented widespread industrial use of Pd for high temperature H(sub 2) separation. These membranes consist of a thin ((approx)10(micro)m) film of metal deposited on the inner surface of a porous metal or ceramic tube. Based on preliminary results, thin Pd(sub 60)Cu(sub 40) films are expected to exhibit hydrogen flux up to ten times larger than commercial polymer membranes for H(sub 2) separation, and resist poisoning by H(sub 2)S and other sulfur compounds typical of coal gas. Similar Pd-membranes have been operated at temperatures as high as 750 C. The overall objective of the proposed project is to demonstrate the feasibility of using sequential electroless plating to fabricate Pd(sub 60)Cu(sub 40) alloy membranes on porous supports for H(sub 2) separation. These following advantages of these membranes for processing of coal-derived gas will be demonstrated: High H(sub 2) flux; Sulfur tolerant, even at very high total sulfur levels (1000 ppm); Operation at temperatures well above 500 C; and Resistance to embrittlement and degradation by thermal cycling. The proposed research plan is designed to providing a fundamental understanding of: Factors important in membrane fabrication; Optimization of membrane structure and composition; Effect of temperature, pressure, and gas composition on H(sub 2) flux and membrane selectivity; and How this membrane technology can be integrated in coal gasification-fuel cell systems

  10. Analysis of Influence of Heat Insulation on the Thermal Regime of Storage Tanks with Liquefied Natural Gas

    OpenAIRE

    Maksimov Vyacheslav I.; Nagornova Tatiana A.; Glazyrin Viktor P.; Shestakov Igor A.

    2016-01-01

    Is numerically investigated the process of convective heat transfer in the reservoirs of liquefied natural gas (LNG). The regimes of natural convection in a closed rectangular region with different intensity of heat exchange at the external borders are investigated. Is solved the time-dependent system of energy and Navier-Stokes equations in the dimensionless variables "vorticity – the stream function". Are obtained distributions of the hydrodynamic parameters and temperatures, that character...

  11. Salmonids, stream temperatures, and solar loading--modeling the shade provided to the Klamath River by vegetation and geomorphology

    Science.gov (United States)

    Forney, William M.; Soulard, Christopher E.; Chickadel, C. Christopher

    2013-01-01

    The U.S. Geological Survey is studying approaches to characterize the thermal regulation of water and the dynamics of cold water refugia. High temperatures have physiological impacts on anadromous fish species. Factors affecting the presence, variability, and quality of thermal refugia are known, such as riverine and watershed processes, hyporheic flows, deep pools and bathymetric factors, thermal stratification of reservoirs, and other broader climatic considerations. This research develops a conceptual model and methodological techniques to quantify the change in solar insolation load to the Klamath River caused by riparian and floodplain vegetation, the morphology of the river, and the orientation and topographic characteristics of its watersheds. Using multiple scales of input data from digital elevation models and airborne light detection and ranging (LiDAR) derivatives, different analysis methods yielded three different model results. These models are correlated with thermal infrared imagery for ground-truth information at the focal confluence with the Scott River. Results from nonparametric correlation tests, geostatistical cross-covariograms, and cross-correlograms indicate that statistical relationships between the insolation models and the thermal infrared imagery exist and are significant. Furthermore, the use of geostatistics provides insights to the spatial structure of the relationships that would not be apparent otherwise. To incorporate a more complete representation of the temperature dynamics in the river system, other variables including the factors mentioned above, and their influence on solar loading, are discussed. With similar datasets, these methods could be applied to any river in the United States—especially those listed as temperature impaired under Section 303(d) of the Clean Water Act—or international riverine systems. Considering the importance of thermal refugia for aquatic species, these methods can help investigate opportunities

  12. Stream systems.

    Science.gov (United States)

    Jack E. Williams; Gordon H. Reeves

    2006-01-01

    Restored, high-quality streams provide innumerable benefits to society. In the Pacific Northwest, high-quality stream habitat often is associated with an abundance of salmonid fishes such as chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch), and steelhead (O. mykiss). Many other native...

  13. Temperature, salinity, and oxygen; measured with a Seabird CTD system; The Anatomy of Gulf Stream Meanders; Fall of 1988 and Spring of 1989; Gulf Stream region South of Cape Cod (NODC Accession 9900100)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The object was to probe in greater detail than has been possible in the past, the dynamical balances of Gulf Stream meanders and their change with time....

  14. Thermal and hydrologic responses to climate change predict marked alterations in boreal stream invertebrate assemblages.

    Science.gov (United States)

    Mustonen, Kaisa-Riikka; Mykrä, Heikki; Marttila, Hannu; Sarremejane, Romain; Veijalainen, Noora; Sippel, Kalle; Muotka, Timo; Hawkins, Charles P

    2018-06-01

    Air temperature at the northernmost latitudes is predicted to increase steeply and precipitation to become more variable by the end of the 21st century, resulting in altered thermal and hydrological regimes. We applied five climate scenarios to predict the future (2070-2100) benthic macroinvertebrate assemblages at 239 near-pristine sites across Finland (ca. 1200 km latitudinal span). We used a multitaxon distribution model with air temperature and modeled daily flow as predictors. As expected, projected air temperature increased the most in northernmost Finland. Predicted taxonomic richness also increased the most in northern Finland, congruent with the predicted northwards shift of many species' distributions. Compositional changes were predicted to be high even without changes in richness, suggesting that species replacement may be the main mechanism causing climate-induced changes in macroinvertebrate assemblages. Northern streams were predicted to lose much of the seasonality of their flow regimes, causing potentially marked changes in stream benthic assemblages. Sites with the highest loss of seasonality were predicted to support future assemblages that deviate most in compositional similarity from the present-day assemblages. Macroinvertebrate assemblages were also predicted to change more in headwaters than in larger streams, as headwaters were particularly sensitive to changes in flow patterns. Our results emphasize the importance of focusing protection and mitigation on headwater streams with high-flow seasonality because of their vulnerability to climate change. © 2018 John Wiley & Sons Ltd.

  15. Suspended sediment, turbidity, and stream water temperature in the Sauk River Basin, western Washington, water years 2012-16

    Science.gov (United States)

    Jaeger, Kristin L.; Curran, Christopher A.; Anderson, Scott W.; Morris, Scott T.; Moran, Patrick W.; Reams, Katherine A.

    2017-11-01

    The Sauk River is a federally designated Wild and Scenic River that drains a relatively undisturbed landscape along the western slope of the North Cascade Mountain Range, Washington, which includes the glaciated volcano, Glacier Peak. Naturally high sediment loads characteristic of basins draining volcanoes like Glacier Peak make the Sauk River a dominant contributor of sediment to the downstream main stem river, the Skagit River. Additionally, the Sauk River serves as important spawning and rearing habitat for several salmonid species in the greater Skagit River system. Because of the importance of sediment to morphology, flow-conveyance, and ecosystem condition, there is interest in understanding the magnitude and timing of suspended sediment and turbidity from the Sauk River system and its principal tributaries, the White Chuck and Suiattle Rivers, to the Skagit River.Suspended-sediment measurements, turbidity data, and water temperature data were collected at two U.S. Geological Survey streamgages in the upper and middle reaches of the Sauk River over a 4-year period extending from October 2011 to September 2015, and at a downstream location in the lower river for a 5-year period extending from October 2011 to September 2016. Over the collective 5-year study period, mean annual suspended-sediment loads at the three streamgages on the upper, middle, and lower Sauk River streamgages were 94,200 metric tons (t), 203,000 t, and 940,000 t streamgages, respectively. Fine (smaller than 0.0625 millimeter) total suspended-sediment load averaged 49 percent at the upper Sauk River streamgage, 42 percent at the middle Sauk River streamgage, and 34 percent at the lower Sauk River streamgage.

  16. Stream Evaluation

    Data.gov (United States)

    Kansas Data Access and Support Center — Digital representation of the map accompanying the "Kansas stream and river fishery resource evaluation" (R.E. Moss and K. Brunson, 1981.U.S. Fish and Wildlife...

  17. High-temperature incineration of radioactive waste. Exploitation of the FLK-60 slagging incinerator for the treatment of different waste streams contaminated with plutonium

    International Nuclear Information System (INIS)

    Voorde Van de, N.; Taeymans, A.; Hennart, D.; Vanbrabant, R.; Balleux, W.; Geenen, G.; Gijbels, J.

    1986-01-01

    During the years 1983 and 1984 the FLK-60 high-temperature slagging incinerator at Mol was used for incineration of simulated plutonium waste and BWR power-station waste after extensive technical adaptations. A total of 10 tons of simulated waste containing 15 g of plutonium and 6 tons of simulated waste containing 624 MBq of 60 Co and 393 MBq of cesium isotopes was successfully treated. The average volume reduction factor was 18. Global decontamination factors of 280 000 for 137 Cs and 22 000 000 for 239 Pu were measured. Routine working and interventions for maintenance and repair could be carried out safely in alpha-conditions. The report describes in detail the technical adaptations and the behaviour of the various parts of the installation during the 39 runs carried out in the contract period. It also gives the chemical and radiochemical composition of the granules and secondary waste streams. The plutonium-based leach rate of the granules is in the range of 2 x 10 -5 to 3.5 x 10 -4 g/cm 2 . d. Finally typical mass, energy and radioactivity balances of the installation are given and various options for the final conditioning of the granules are briefly discussed. 6 refs, 6 figs, 29 tables

  18. Subsurface Controls on Stream Intermittency in a Semi-Arid Landscape

    Science.gov (United States)

    Dohman, J.; Godsey, S.; Thackray, G. D.; Hale, R. L.; Wright, K.; Martinez, D.

    2017-12-01

    Intermittent streams currently constitute 30% to greater than 50% of the global river network. In addition, the number of intermittent streams is expected to increase due to changes in land use and climate. These streams provide important ecosystem services, such as water for irrigation, increased biodiversity, and high rates of nutrient cycling. Many hydrological studies have focused on mapping current intermittent flow regimes or evaluating long-term flow records, but very few have investigated the underlying causes of stream intermittency. The disconnection and reconnection of surface flow reflects the capacity of the subsurface to accommodate flow, so characterizing subsurface flow is key to understanding stream drying. We assess how subsurface flow paths control local surface flows during low-flow periods, including intermittency. Water table dynamics were monitored in an intermittent reach of Gibson Jack Creek in southeastern Idaho. Four transects were delineated with a groundwater well located in the hillslope, riparian zone, and in the stream, for a total of 12 groundwater wells. The presence or absence of surface flow was determined by frequent visual observations as well as in situ loggers every 30m along the 200m study reach. The rate of surface water drying was measured in conjunction with temperature, precipitation, subsurface hydraulic conductivity, hillslope-riparian-stream connectivity and subsurface travel time. Initial results during an unusually wet year suggest different responses in reaches that were previously observed to occasionally cease flowing. Flows in the intermittent reaches had less coherent and lower amplitude diel variations during base flow periods than reaches that had never been observed to dry out. Our findings will help contribute to our understanding of mechanisms driving expansion and contraction cycles in intermittent streams, increase our ability to predict how land use and climate change will affect flow regimes, and

  19. Development and assessment of indices to determine stream fish vulnerability to climate change and habitat alteration

    Science.gov (United States)

    Sievert, Nicholas A.; Paukert, Craig P.; Tsang, Yin-Phan; Infante, Dana M.

    2016-01-01

    Understanding the future impacts of climate and land use change are critical for long-term biodiversity conservation. We developed and compared two indices to assess the vulnerability of stream fish in Missouri, USA based on species environmental tolerances, rarity, range size, dispersal ability and on the average connectivity of the streams occupied by each species. These two indices differed in how environmental tolerance was classified (i.e., vulnerability to habitat alteration, changes in stream temperature, and changes to flow regimes). Environmental tolerance was classified based on measured species responses to habitat alteration, and extremes in stream temperatures and flow conditions for one index, while environmental tolerance for the second index was based on species’ traits. The indices were compared to determine if vulnerability scores differed by index or state listing status. We also evaluated the spatial distribution of species classified as vulnerable to habitat alteration, changes in stream temperature, and change in flow regimes. Vulnerability scores were calculated for all 133 species with the trait association index, while only 101 species were evaluated using the species response index, because 32 species lacked data to analyze for a response. Scores from the trait association index were greater than the species response index. This is likely due to the species response index's inability to evaluate many rare species, which generally had high vulnerability scores for the trait association index. The indices were consistent in classifying vulnerability to habitat alteration, but varied in their classification of vulnerability due to increases in stream temperature and alterations to flow regimes, likely because extremes in current climate may not fully capture future conditions and their influence on stream fish communities. Both indices showed higher mean vulnerability scores for listed species than unlisted species, which provided a coarse

  20. Damage-spreading and out-of-equilibrium dynamics in the low-temperature regime of the two-dimensional ± J Edwards–Anderson model

    International Nuclear Information System (INIS)

    Rubio Puzzo, M L; Romá, F; Bustingorry, S; Gleiser, P M

    2010-01-01

    We present results showing the correlation between the out-of-equilibrium dynamics and the equilibrium damage-spreading process in the two-dimensional ± J Edwards–Anderson model at low temperatures. A key ingredient in our analysis is the projection of finite temperature spin configurations onto the ground state topology of the system. In particular, through numerical simulations we correlate ground state information with the out-of-equilibrium dynamics. We also analyse how the propagation of a small perturbation in equilibrated systems is related to the ground state topology. This damage-spreading study unveils the presence of rigid clusters of spins. We claim that these clusters give rise to the slow out-of-equilibrium dynamics observed in the temperature range between the glass temperature T g = 0 of the two-dimensional ± J Edwards–Anderson model and the critical temperature T c of the pure ferromagnetic Ising model

  1. Single-scattering properties of ice particles in the microwave regime: Temperature effect on the ice refractive index with implications in remote sensing

    International Nuclear Information System (INIS)

    Ding, Jiachen; Bi, Lei; Yang, Ping; Kattawar, George W.; Weng, Fuzhong; Liu, Quanhua; Greenwald, Thomas

    2017-01-01

    An ice crystal single-scattering property database is developed in the microwave spectral region (1 to 874 GHz) to provide the scattering, absorption, and polarization properties of 12 ice crystal habits (10-plate aggregate, 5-plate aggregate, 8-column aggregate, solid hexagonal column, hollow hexagonal column, hexagonal plate, solid bullet rosette, hollow bullet rosette, droxtal, oblate spheroid, prolate spheroid, and sphere) with particle maximum dimensions from 2 µm to 10 mm. For each habit, four temperatures (160, 200, 230, and 270 K) are selected to account for temperature dependence of the ice refractive index. The microphysical and scattering properties include projected area, volume, extinction efficiency, single-scattering albedo, asymmetry factor, and six independent nonzero phase matrix elements (i.e. P_1_1, P_1_2, P_2_2, P_3_3, P_4_3 and P_4_4). The scattering properties are computed by the Invariant Imbedding T-Matrix (II-TM) method and the Improved Geometric Optics Method (IGOM). The computation results show that the temperature dependence of the ice single-scattering properties in the microwave region is significant, particularly at high frequencies. Potential active and passive remote sensing applications of the database are illustrated through radar reflectivity and radiative transfer calculations. For cloud radar applications, ignoring temperature dependence has little effect on ice water content measurements. For passive microwave remote sensing, ignoring temperature dependence may lead to brightness temperature biases up to 5 K in the case of a large ice water path. - Highlights: • Single-scattering properties of ice crystals are computed from 1 to 874 GHz. • Ice refractive index temperature dependence is considered at 160, 200, 230 and 270 K. • Potential applications of the database to microwave remote sensing are illustrated. • Ignoring temperature dependence of ice refractive index can lead to 5 K difference in IWP retrieval

  2. Communication: Equilibrium rate coefficients from atomistic simulations: The O(3P) + NO(2Π) → O2(X3Σg−) + N(4S) reaction at temperatures relevant to the hypersonic flight regime

    International Nuclear Information System (INIS)

    Castro-Palacio, Juan Carlos; Bemish, Raymond J.; Meuwly, Markus

    2015-01-01

    The O( 3 P) + NO( 2 Π) → O 2 (X 3 Σ g − ) + N( 4 S) reaction is among the N- and O- involving reactions that dominate the energetics of the reactive air flow around spacecraft during hypersonic atmospheric re-entry. In this regime, the temperature in the bow shock typically ranges from 1000 to 20 000 K. The forward and reverse rate coefficients for this reaction derived directly from trajectory calculations over this range of temperature are reported in this letter. Results compare well with the established equilibrium constants for the same reaction from thermodynamic quantities derived from spectroscopy in the gas phase which paves the way for large-scale in silico investigations of equilibrium rates under extreme conditions

  3. Communication: Equilibrium rate coefficients from atomistic simulations: The O((3)P) + NO((2)Π) → O2(X(3)Σg(-)) + N((4)S) reaction at temperatures relevant to the hypersonic flight regime.

    Science.gov (United States)

    Castro-Palacio, Juan Carlos; Bemish, Raymond J; Meuwly, Markus

    2015-03-07

    The O((3)P) + NO((2)Π) → O2(X(3)Σg(-)) + N((4)S) reaction is among the N- and O- involving reactions that dominate the energetics of the reactive air flow around spacecraft during hypersonic atmospheric re-entry. In this regime, the temperature in the bow shock typically ranges from 1000 to 20,000 K. The forward and reverse rate coefficients for this reaction derived directly from trajectory calculations over this range of temperature are reported in this letter. Results compare well with the established equilibrium constants for the same reaction from thermodynamic quantities derived from spectroscopy in the gas phase which paves the way for large-scale in silico investigations of equilibrium rates under extreme conditions.

  4. Seismic activity and thermal regime of low temperature fumaroles at Mt. Vesuvius in 2004-2011: distinguishing among seismic, volcanic and hydrological signals

    Directory of Open Access Journals (Sweden)

    Paola Cusano

    2013-11-01

    Full Text Available Seismological, soil temperature and hydrological data from Mt. Vesuvius are collected to characterize the present-day activity of the volcanic/hydrothermal system and to detect possible unrest-related phenomena. We present patterns of seismicity and soil temperature in the crater area during the period February 2004-December 2011. The temporal distribution of number and depth of Volcano-Tectonic earthquakes and the energy release are considered. Hourly data of soil temperature have been acquired since January 2004 in different locations along the rim and within the crater. The observed changes of temperature are studied to establish a temporal-based correlation with the volcanic activity and/or with external forcing, as variations of the regional and local stress field acting on the volcano or meteorological phenomena. The comparison between seismic activity and temperature data highlights significant variations possibly related to changes in fluid circulation in the hydrothermal system of the volcano. The common continuous observations start just before a very shallow earthquake occurred in August 2005, which was preceded by a thermal anomaly. This coincidence has been interpreted as related to fluid-driven rock fracturing, as observed in other volcanoes. For the successive temporal patterns, the seismicity rate and energy release are characterized by slight variations accompanied by changes in temperature. This evidence of reactivity of the fumarole thermal field to seismic strain can be used to discriminate between tectonic and volcanic signals at Mt. Vesuvius.

  5. The behavior of ZrO_2/20%Y_2O_3 and Al_2O_3 coatings deposited on aluminum alloys at high temperature regime

    International Nuclear Information System (INIS)

    Pintilei, G.L.; Crismaru, V.I.; Abrudeanu, M.; Munteanu, C.; Baciu, E.R.; Istrate, B.; Basescu, N.

    2015-01-01

    Highlights: • In both the ZrO_2/20%Y_2O_3 and Al_2O_3 coatings the high temperature caused a decrease of pores volume and a lower thickness of the interface between successive splats. • The NiCr bond layer in the sample with a ZrO_2/20%Y_2O_3 suffered a fragmentation due to high temperature exposure and thermal expansion which can lead to coating exfoliation. • The NiCr bond layer in the sample with an Al_2O_3 coating showed an increase of pore volume due to high temperature. - Abstract: Aluminum alloy present numerous advantages like lightness, high specific strength and diversity which recommend them to a high number of applications from different fields. In extreme environments the protection of aluminum alloys is difficult and requires a high number of requirements like high temperature resistance, thermal fatigue resistance, corrosion fatigue resistance and galvanic corrosion resistance. To obtain these characteristics coatings can be applied to the surfaces so they can enhance the mechanical and chemical properties of the parts. In this paper two coatings were considered for deposition on an AA2024 aluminum alloy, ZrO_2/20%Y_2O_3 and Al_2O_3. To obtain a better adherence of the coating to the base material an additional bond layer of NiCr is used. Both the coatings and bond layer were deposited by atmospheric plasma spraying on the samples. The samples were subjected to a temperature of 500 °C and after that slowly cooled to room temperature. The samples were analyzed by electron microscopy and X-ray diffraction to determine the morphological and phase changes that occurred during the temperature exposure. To determine the stress level in the parts due to thermal expansion a finite element analysis was performed in the same conditions as the tests.

  6. Evaluation of novel thermo-resistant Micractinium and Scenedesmus sp. for efficient biomass and lipid production under different temperature and nutrient regimes.

    Science.gov (United States)

    Sonmez, Cagla; Elcin, Evrim; Akın, Dilan; Oktem, Huseyin Avni; Yucel, Meral

    2016-07-01

    Despite the vast interest in microalgae as feedstock for biodiesel production, relatively few studies examined their response to diurnal temperature fluctuation. Here, we describe biomass and lipid productivities and fatty acid profiles of thermo-resistant Micractinium sp. and Scenedesmus sp. grown in batch cultures in a laboratory set-up that mimics a typically warm summer day in Central Anatolia with a 16-h light temperature of 30°C and 8-h dark temperature of 16°C (30°C (day)/16°C (night)). Both strains can survive a temperature range of 10-50°C. We found the lipid productivities of Micractinium sp. and Scenedesmus sp. as 30/21mgL(-1)d(-1) and 6/7mgL(-1)d(-1), respectively during the 30°C (day)/16°C (night) cycle. Saturated fatty acid content increased with increasing temperature. Additionally, we cultured Micractinium sp. under Nitrogen (N) and Phosphorus (P) limiting conditions. Highest lipid productivity of 85.4±2mgL(-1)d(-1) was obtained under P-depletion during exponential growth phase. Oleic acid amount also increased eight fold during P-deplete. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Comparison of information content of temporal response of chemoresistive gas sensor under three different temperature modulation regimes for gas detection of different feature reduction methods

    Science.gov (United States)

    Hosseini-Golgoo, S. M.; Salimi, F.; Saberkari, A.; Rahbarpour, S.

    2017-12-01

    In the present work the feature extraction of transient response of a resistive gas sensor under temperature cycling, temperature transient, and temperature combination methods were compared. So, the heater were stimulated by three pulse (cycling), ramp (transient) and staircase (combination) waveforms. The period or duration of all waves was equal to 40 s. Methanol, ethanol, 1-propanol, 1-butanol, toluene and acetone each at 11 different concentration levels in the range of 100 to 2000 ppm were used as the target gases. The utilized sensor was TGS-813 that made by Figaro Company. Recorded results were studied and heuristic features such as peak, rise time, slope and curvature of recorded responses were extracted for each heater waveform. Results showed that although application of this feature extraction method to all waveforms led to gas diagnoses, best results were achieved in the case of staircase waveform. The combination waveform had enough information to separate all examined target gases.

  8. Communication: Vibrational relaxation of CO(1Σ) in collision with Ar(1S) at temperatures relevant to the hypersonic flight regime.

    Science.gov (United States)

    Denis-Alpizar, Otoniel; Bemish, Raymond J; Meuwly, Markus

    2017-03-21

    Vibrational energy relaxation (VER) of diatomics following collisions with the surrounding medium is an important elementary process for modeling high-temperature gas flow. VER is characterized by two parameters: the vibrational relaxation time τ vib and the state relaxation rates. Here the vibrational relaxation of CO(ν=0←ν=1) in Ar is considered for validating a computational approach to determine the vibrational relaxation time parameter (pτ vib ) using an accurate, fully dimensional potential energy surface. For lower temperatures, comparison with experimental data shows very good agreement whereas at higher temperatures (up to 25 000 K), comparisons with an empirically modified model due to Park confirm its validity for CO in Ar. Additionally, the calculations provide insight into the importance of Δν>1 transitions that are ignored in typical applications of the Landau-Teller framework.

  9. The interactive effects of climate change, riparian management, and a non-native predators on stream-rearing salmon

    Science.gov (United States)

    Lawrence, David J.; Stewart-Koster, Ben; Olden, Julian D.; Ruesch, Aaron S.; Torgersen, Christian E.; Lawler, Joshua J.; Butcher, Don P.; Crown, Julia K.

    2014-01-01

    Predicting how climate change is likely to interact with myriad other stressors that threaten species of conservation concern is an essential challenge in aquatic ecosystems. This study provides a framework to accomplish this task in salmon-bearing streams of the northwestern United States, where land-use related reductions in riparian shading have caused changes in stream thermal regimes, and additional warming from projected climate change may result in significant losses of coldwater fish habitat over the next century. Predatory non-native smallmouth bass have also been introduced into many northwestern streams and their range is likely to expand as streams warm, presenting an additional challenge to the persistence of threatened Pacific salmon. The goal of this work was to forecast the interactive effects of climate change, riparian management, and non-native species on stream-rearing salmon, and to evaluate the capacity of restoration to mitigate these effects. We intersected downscaled global climate forecasts with a local-scale water temperature model to predict mid- and end-of-century temperatures in streams in the Columbia River basin; we compared one stream that is thermally impaired due to the loss of riparian vegetation and another that is cooler and has a largely intact riparian corridor. Using the forecasted stream temperatures in conjunction with fish-habitat models, we predicted how stream-rearing Chinook salmon and bass distributions would change as each stream warmed. In the highly modified stream, end-of-century warming may cause near total loss of Chinook salmon rearing habitat and a complete invasion of the upper watershed by bass. In the less modified stream, bass were thermally restricted from the upstream-most areas. In both systems, temperature increases resulted in higher predicted spatial overlap between stream-rearing Chinook salmon and potentially predatory bass in the early summer (2-4-fold increase) and greater abundance of bass. We

  10. The interactive effects of climate change, riparian management, and a nonnative predator on stream-rearing salmon.

    Science.gov (United States)

    Lawrence, David J; Stewart-Koster, Ben; Olden, Julian D; Ruesch, Aaron S; Torgersen, Christian E; Lawler, Joshua J; Butcher, Don P; Crown, Julia K

    2014-06-01

    Predicting how climate change is likely to interact with myriad other stressors that threaten species of conservation concern is an essential challenge in aquatic ecosystems. This study provides a framework to accomplish this task in salmon-bearing streams of the northwestern United States, where land-use-related reductions in riparian shading have caused changes in stream thermal regimes, and additional warming from projected climate change may result in significant losses of coldwater fish habitat over the next century. Predatory, nonnative smallmouth bass have also been introduced into many northwestern streams, and their range is likely to expand as streams warm, presenting an additional challenge to the persistence of threatened Pacific salmon. The goal of this work was to forecast the interactive effects of climate change, riparian management, and nonnative species on stream-rearing salmon and to evaluate the capacity of restoration to mitigate these effects. We intersected downscaled global climate forecasts with a local-scale water temperature model to predict mid- and end-of-century temperatures in streams in the Columbia River basin. We compared one stream that is thermally impaired due to the loss of riparian vegetation and another that is cooler and has a largely intact riparian corridor. Using the forecasted stream temperatures in conjunction with fish-habitat models, we predicted how stream-rearing chinook salmon and bass distributions would change as each stream warmed. In the highly modified stream, end-of-century warming may cause near total loss of chinook salmon-rearing habitat and a complete invasion of the upper watershed by bass. In the less modified stream, bass were thermally restricted from the upstream-most areas. In both systems, temperature increases resulted in higher predicted spatial overlap between stream-rearing chinook salmon and potentially predatory bass in the early summer (two- to fourfold increase) and greater abundance of

  11. The impact of temperature regimes on development, dormancy breaking and germination of dwarf shrub seeds from arctic, alpine and boreal sites

    DEFF Research Database (Denmark)

    Graae, Bente Jessen; Alsos, Inger Greve; Ejrnæs, Rasmus

    2008-01-01

    It has been suggested that the infrequent sexual reproduction of arctic dwarf shrubs might be related to the harsh environmental conditions in which they live. If this is the case, then increases in temperature resulting from global climate change might drastically affect regeneration of arctic...

  12. The behavior of ZrO2/20%Y2O3 and Al2O3 coatings deposited on aluminum alloys at high temperature regime

    Science.gov (United States)

    Pintilei, G. L.; Crismaru, V. I.; Abrudeanu, M.; Munteanu, C.; Baciu, E. R.; Istrate, B.; Basescu, N.

    2015-10-01

    Aluminum alloy present numerous advantages like lightness, high specific strength and diversity which recommend them to a high number of applications from different fields. In extreme environments the protection of aluminum alloys is difficult and requires a high number of requirements like high temperature resistance, thermal fatigue resistance, corrosion fatigue resistance and galvanic corrosion resistance. To obtain these characteristics coatings can be applied to the surfaces so they can enhance the mechanical and chemical properties of the parts. In this paper two coatings were considered for deposition on an AA2024 aluminum alloy, ZrO2/20%Y2O3 and Al2O3. To obtain a better adherence of the coating to the base material an additional bond layer of NiCr is used. Both the coatings and bond layer were deposited by atmospheric plasma spraying on the samples. The samples were subjected to a temperature of 500 °C and after that slowly cooled to room temperature. The samples were analyzed by electron microscopy and X-ray diffraction to determine the morphological and phase changes that occurred during the temperature exposure. To determine the stress level in the parts due to thermal expansion a finite element analysis was performed in the same conditions as the tests.

  13. Plant litter dynamics in the forest-stream interface: precipitation is a major control across tropical biomes.

    Science.gov (United States)

    Tonin, Alan M; Gonçalves, José F; Bambi, Paulino; Couceiro, Sheyla R M; Feitoza, Lorrane A M; Fontana, Lucas E; Hamada, Neusa; Hepp, Luiz U; Lezan-Kowalczuk, Vânia G; Leite, Gustavo F M; Lemes-Silva, Aurea L; Lisboa, Leonardo K; Loureiro, Rafael C; Martins, Renato T; Medeiros, Adriana O; Morais, Paula B; Moretto, Yara; Oliveria, Patrícia C A; Pereira, Evelyn B; Ferreira, Lidiane P; Pérez, Javier; Petrucio, Mauricio M; Reis, Deusiano F; S Rezende, Renan; Roque, Nadia; Santos, Luiz E P; Siegloch, Ana E; Tonello, Gabriela; Boyero, Luz

    2017-09-07

    Riparian plant litter is a major energy source for forested streams across the world and its decomposition has repercussions on nutrient cycling, food webs and ecosystem functioning. However, we know little about plant litter dynamics in tropical streams, even though the tropics occupy 40% of the Earth's land surface. Here we investigated spatial and temporal (along a year cycle) patterns of litter inputs and storage in multiple streams of three tropical biomes in Brazil (Atlantic forest, Amazon forest and Cerrado savanna), predicting major differences among biomes in relation to temperature and precipitation regimes. Precipitation explained most of litter inputs and storage, which were generally higher in more humid biomes (litterfall: 384, 422 and 308 g m -2 y -1 , storage: 55, 113 and 38 g m -2 , on average in Atlantic forest, Amazon and Cerrado, respectively). Temporal dynamics varied across biomes in relation to precipitation and temperature, with uniform litter inputs but seasonal storage in Atlantic forest streams, seasonal inputs in Amazon and Cerrado streams, and aseasonal storage in Amazon streams. Our findings suggest that litter dynamics vary greatly within the tropics, but point to the major role of precipitation, which contrasts with the main influence of temperature in temperate areas.

  14. Average-atom model for two-temperature states and ionic transport properties of aluminum in the warm dense matter regime

    Science.gov (United States)

    Hou, Yong; Fu, Yongsheng; Bredow, Richard; Kang, Dongdong; Redmer, Ronald; Yuan, Jianmin

    2017-03-01

    The average-atom model combined with the hyper-netted chain approximation is an efficient tool for electronic and ionic structure calculations for warm dense matter. Here we generalize this method in order to describe non-equilibrium states with different electron and ion temperature as produced in laser-matter interactions on ultra-short time scales. In particular, the electron-ion and ion-ion correlation effects are considered when calculating the electron structure. We derive an effective ion-ion pair-potential using the electron densities in the framework of temperature-depended density functional theory. Using this ion-ion potential we perform molecular dynamics simulations in order to determine the ionic transport properties such as the ionic diffusion coefficient and the shear viscosity through the ionic velocity autocorrelation functions.

  15. Effects of Temperature and Axial Strain on Four-Wave Mixing Parametric Frequencies in Microstructured Optical Fibers Pumped in the Normal Dispersion Regime

    Directory of Open Access Journals (Sweden)

    Javier Abreu-Afonso

    2014-10-01

    Full Text Available A study of the effect of temperature and axial strain on the parametric wavelengths produced by four-wave mixing in microstructured optical fibers is presented. Degenerate four-wave mixing was generated in the fibers by pumping at normal dispersion, near the zero-dispersion wavelength, causing the appearance of two widely-spaced four-wave mixing spectral bands. Temperature changes, and/or axial strain applied to the fiber, affects the dispersion characteristics of the fiber, which can result in the shift of the parametric wavelengths. We show that the increase of temperature causes the signal and idler wavelengths to shift linearly towards shorter and longer wavelengths, respectively. For the specific fiber of the experiment, the band shift at rates ­–0.04 nm/ºC and 0.3 nm/ºC, respectively. Strain causes the parametric bands to shift in the opposite way. The signal band shifted 2.8 nm/me and the idler -5.4 nm/me. Experimental observations are backed by numerical simulations.

  16. Full-scale model development of the WWER-440 reactor fuel rod bundle for core temperature regime study under reflooding conditions

    International Nuclear Information System (INIS)

    Bezrukov, Yu.A.; Logvinov, S.A.; Levchuk, S.V.; Nakladnov, V.D.; Onshin, V.P.; Sokolov, A.S.

    1982-01-01

    Consideration is given to the issues of a full scale WWER-440 fuel rod bundle imitation. An imitator contains a molybdenum heating rod inclosed in stainless steel shell. The shell diameter is 9 mm, the heated length is 2500 mm, the total len.o.th is 2855 mm. 125 fuel rod imitators are set in the bundle mock-up. The experiments were run on a test facility imitating the WWER-440 reactor primary loop, providing the conditions of the loop breaking. The mock-up thermal hydraulics has been studied during the refloodino. stage. The mock-up was heated up to predetermined initial temperature at a low power level with saturated steam cooling. Then the steam input was stopped, the power level rarapidly rised up to a given value and the cooling water injected. Simultaneously with water injection all the measured parameters monitoring was started. Both at the top spraying and combined cooling temperature oscillations in the upper and middle parts of the mock-up were observed. At the bottom reflooding the mock-up cooling down took more time, thereat temperature inthe upper part first slowly rised during reflooding then decreased and then dropped abruptly at thefront coming up [ru

  17. Estimating survival rates of quagga mussel (Dreissena rostriformis bugensis veliger larvae under summer and autumn temperature regimes in residual water of trailered watercraft at Lake Mead, USA

    Directory of Open Access Journals (Sweden)

    Wook Jin Choi

    2013-01-01

    Full Text Available On 6 January 2007, invasive quagga mussels [Dreissena rostriformis bugensis (Andrusov, 1897] were discovered in the Boulder Basin ofLake Mead, Nevada, a popular site for recreational boating in the southwestern United States. Recreational watercraft are considered aprimary vector for overland dispersal of quagga mussel veliger larvae between water bodies. Thus, effective decontamination of veligers inresidual water carried by trailered recreation boats is critical to controlling this species’ spread. The survival rate of quagga mussel veligerswas measured during exposure to environmental temperature conditions mimicking those experienced in the residual water of traileredvessels during warm summer and cooler autumn months in the semi-arid southwestern United States. Under warm summer conditions,quagga mussel veligers survived approximately five days while under cooler autumn conditions they survived 27 days. When tested underautumn temperature conditions veliger survival times increased with increased level of larval development. The results suggested a greaterlikelihood of veliger transport in the residual water of trailered watercraft during autumn months. The results indicated that presentlyrecommended vessel quarantine times to kill all externally attached juvenile and adult dreissenid mussels prior to launching in an uninfested water body should be increased to generate 100% veliger mortality in residual water unable to be fully drained from the internal areas of watercraft.

  18. Predicting predatory impact of juvenile invasive lionfish (Pterois volitans) on a crustacean prey using functional response analysis: effects of temperature, habitat complexity and light regimes

    KAUST Repository

    South, Josie

    2017-07-01

    The ecological implications of biotic interactions, such as predator-prey relationships, are often context-dependent. Comparative functional responses analysis can be used under different abiotic contexts to improve understanding and prediction of the ecological impact of invasive species. Pterois volitans (Lionfish) [Linnaeus 1758] is an established invasive species in the Caribbean and Gulf of Mexico, with a more recent invasion into the Mediterranean. Lionfish are generalist predators that impact a wide range of commercial and non-commercial species. Functional response analysis was employed to quantify interaction strength between lionfish and a generic prey species, the shrimp (Paleomonetes varians) [Leach 1814], under the contexts of differing temperature, habitat complexity and light wavelength. Lionfish have prey population destabilising Type II functional responses under all contexts examined. Significantly more prey were consumed at 26 °C than at 22 °C. Habitat complexity did not significantly alter the functional response parameters. Significantly more prey were consumed under white light and blue light than under red light. Attack rate was significantly higher under white light than under blue or red light. Light wavelength did not significantly change handling times. The impacts on prey populations through feeding rates may increase with concomitant temperature increase. As attack rates are very high at low habitat complexity this may elucidate the cause of high impact upon degraded reef ecosystems with low-density prey populations, although there was little protection conferred through habitat complexity. Only red light (i.e. dark) afforded any reduction in predation pressure. Management initiatives should account for these environmental factors when planning mitigation and prevention strategies.

  19. Aeroacoustics of Three-Stream Jets

    Science.gov (United States)

    Henderson, Brenda S.

    2012-01-01

    Results from acoustic measurements of noise radiated from a heated, three-stream, co-annular exhaust system operated at subsonic conditions are presented. The experiments were conducted for a range of core, bypass, and tertiary stream temperatures and pressures. The nozzle system had a fan-to-core area ratio of 2.92 and a tertiary-to-core area ratio of 0.96. The impact of introducing a third stream on the radiated noise for third-stream velocities below that of the bypass stream was to reduce high frequency noise levels at broadside and peak jet-noise angles. Mid-frequency noise radiation at aft observation angles was impacted by the conditions of the third stream. The core velocity had the greatest impact on peak noise levels and the bypass-to-core mass flow ratio had a slight impact on levels in the peak jet-noise direction. The third-stream jet conditions had no impact on peak noise levels. Introduction of a third jet stream in the presence of a simulated forward-flight stream limits the impact of the third stream on radiated noise. For equivalent ideal thrust conditions, two-stream and three-stream jets can produce similar acoustic spectra although high-frequency noise levels tend to be lower for the three-stream jet.

  20. Predicting thermal reference conditions for USA streams and rivers

    Science.gov (United States)

    Hill, Ryan A.; Hawkins, Charles P.; Carlisle, Daren M.

    2013-01-01

    Temperature is a primary driver of the structure and function of stream ecosystems. However, the lack of stream temperature (ST) data for the vast majority of streams and rivers severely compromises our ability to describe patterns of thermal variation among streams, test hypotheses regarding the effects of temperature on macroecological patterns, and assess the effects of altered STs on ecological resources. Our goal was to develop empirical models that could: 1) quantify the effects of stream and watershed alteration (SWA) on STs, and 2) accurately and precisely predict natural (i.e., reference condition) STs in conterminous USA streams and rivers. We modeled 3 ecologically important elements of the thermal regime: mean summer, mean winter, and mean annual ST. To build reference-condition models (RCMs), we used daily mean ST data obtained from several thousand US Geological Survey temperature sites distributed across the conterminous USA and iteratively modeled ST with Random Forests to identify sites in reference condition. We first created a set of dirty models (DMs) that related STs to both natural factors (e.g., climate, watershed area, topography) and measures of SWA, i.e., reservoirs, urbanization, and agriculture. The 3 models performed well (r2 = 0.84–0.94, residual mean square error [RMSE] = 1.2–2.0°C). For each DM, we used partial dependence plots to identify SWA thresholds below which response in ST was minimal. We then used data from only the sites with upstream SWA below these thresholds to build RCMs with only natural factors as predictors (r2 = 0.87–0.95, RMSE = 1.1–1.9°C). Use of only reference-quality sites caused RCMs to suffer modest loss of predictor space and spatial coverage, but this loss was associated with parts of ST response curves that were flat and, therefore, not responsive to further variation in predictor space. We then compared predictions made with the RCMs to predictions made with the DMs with SWA set to 0. For most

  1. Peak-Temperature (Tp) estimates with Raman micro-spectroscopy on carbonaceous material (RSCM) as a tool for distinguishing tectometamorphic regimes in the Tauern Window (Eastern Alps, Austria)

    Science.gov (United States)

    Scharf, A.; Ziemann, M. A.; Handy, M. R.

    2012-04-01

    Raman micro-spectroscopy of CM in 201 samples from the eastern part of the Tauern Window reveal the overprinting of HP subduction metamorphism, post-nappe HT metamorphism and late orogenic crustal attenuation during exhumation. The following patterns of our CM data lend insight into this evolution, especially when considered in the context of the distribution of mineral parageneses, radiometric ages and structures in the Tauern Window: (1) a continuous increase in Tp (330-500°C) across nappe boundaries between two oceanic units (Valais, Piemont) in the NE part of the Tauern Window indicates that temperatures equilibrated after accretion and nappe stacking. The Tp gradient preserved in this area is ca. 10°C/km; (2) a higher Tp gradient (20-25°C/km) in the footwall of a major top-SE extensional shear zone affecting the same units at the E end of the Tauern Window reveals that the previously equilibrated Tp gradient was attenuated during doming and exhumation; (3) identical Tp estimates (500°C) -within error and for a given calibration (ref. below) - are recorded at the top and bottom of a moderately E-dipping basement nappe (Storz Nappe) within a foreland-dipping duplex (the Venediger Nappe Complex, VNC) forming the basement core of the Tauern Window. The Tp value at the top of this nappe occurs at the base of the attenuated Tp gradient described in (2), whereas the Tp at the bottom of the nappe is typical for high Tp values (530-640°C) in the core of the duplex that is exposed in a post-nappe dome (Hochalm) in the SE part of the Tauern Window. We intepret Tp values in the central part of the Tauern Window (530°C) that contain relict HP assemblages and are unaffected by doming as the maximum temperature of subduction-related metamorphism. Existing radiometric data in the area as well as from related units in other parts of the Tauern Window indicate that the thermal peak of HP metamorphism occurred at 38-40 Ma (Kurz et al. 2008, refs therein), followed by HT

  2. Sustainable urban regime adjustments

    DEFF Research Database (Denmark)

    Quitzau, Maj-Britt; Jensen, Jens Stissing; Elle, Morten

    2013-01-01

    The endogenous agency that urban governments increasingly portray by making conscious and planned efforts to adjust the regimes they operate within is currently not well captured in transition studies. There is a need to acknowledge the ambiguity of regime enactment at the urban scale. This direc...

  3. Flux scaling: Ultimate regime

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Flux scaling: Ultimate regime. With the Nusselt number and the mixing length scales, we get the Nusselt number and Reynolds number (w'd/ν) scalings: and or. and. scaling expected to occur at extremely high Ra Rayleigh-Benard convection. Get the ultimate regime ...

  4. Long-term dynamics of biological indicators of navaga Eleginus nawaga (Walbaum, 1792 of the White Sea in relation to changes of the reservoir temperature regime

    Directory of Open Access Journals (Sweden)

    Stasenkov V. A.

    2017-06-01

    Full Text Available Systematic studies of navagа of the White Sea were initiated in the late 1960-ies. Data sets on dimensional indicators, age composition of populations of navaga of the Onega, Dvina, Mezen Bays and Voronka of the White Sea have been accumulated during 45 years of observations. The aim of this work is to identify the causes of the interannual and long-term changes of biological population parameters of navaga. As investigated interannual changes reflecting fish growth, the length and mass of 2 and 3 years old specimens have been chosen. It has been proved that interannual fluctuations in length and weight may depend on the length of the feeding season, as well as the number of populations. Climate warming has resulted that over the past 45 years since the beginning of observations the water temperature in the White Sea in April on average has increased by one degree, and some years – even more. Due to lengthening of the feeding period the seasonal growth of navaga has increased, respectively the annual rates of its length and weight have increased as well. The increase in the growth rate of navaga in the Onega and Dvina Bays has led to its mass mature and joining the fishing (commercial herd at the age of two years. In the Mezen Bay and Voronka the trend on the increase in annual average length and weight navaga of only younger age groups has kept. Growth rate of large size navaga has decreased due to the almost complete cessation of fishing and the increase of older fish number. The revealed regularities in the change of the navaga population parameters of the White Sea should be used for preparing the forecast data on the state of its reserves.

  5. A spatial assessment of stream-flow characteristics and hydrologic ...

    African Journals Online (AJOL)

    The global hydrologic regime has been intensively altered through activities such as dam construction, water abstraction, and inter-basin transfers. This paper uses the Range of Variability Approach (RVA) and daily stream flow records from nine gauging stations to characterize stream-flow post dam construction in the ...

  6. Mathematical Simulation of Convective Heat Transfer in the Low-Temperature Storage of Liquefied Natural Gas

    OpenAIRE

    Shestakov, Igor; Dolgova, Anastasia; Maksimov, Vyacheslav Ivanovich

    2015-01-01

    The article shows the results of mathematical modeling of convective heat transfer in the low-temperature storage of liquefied natural gas. Regime of natural convection in an enclosure with different intensity of the heat flux at the external borders are investigated. Was examined two-dimensional nonstationary problem within the model of Navier-Stokes in dimensionless variables “vorticity - stream function - temperature”. Distributions of hydrodynamic parameters and temperatures that characte...

  7. Thermal Variability in Gravel Bars and its Potential Consequences for CO2 Evasion from Alpine Coldwater Streams

    Science.gov (United States)

    Boodoo, K. S.; Schelker, J.; Battin, T. J.

    2016-12-01

    Gravel bars (GB) are ubiquitous in-stream structures with relatively large exposed surfaces, capable of absorbing heat and possibly acting as a heat source to the underlying hyporheic zone (HZ). The distinctive mixing of groundwater and surface water within their HZ largely determines its characteristic physical and biogeochemical properties, including temperature distribution. To study thermal variability within GBs and its possible consequences for CO2 evasion fluxes we analysed high frequency spatio-temporal data for a range of stream and atmospheric physical parameters including the vertical GB temperature, in an Alpine cold water stream (Oberer Seebach, Austria) over the course of a year. We found the vertical temperature profiles within the GB to vary seasonally and with discharge. During warm summer months, diurnal vertical temperature patterns were most pronounced and were detected throughout all one-meter-depth profiles. Furthermore, permanently wetted GB sediment (-56 cm depth) temperatures above that of stream and groundwater occurred 17% of the year, particularly during summer. This is further evidence for downward heat transfer to the wetted HZ. Average CO2 flux from the GB was significantly higher than that of streamwater during summer and winter, with significantly higher temperatures and CO2 outgassing rates occurring at the GB tail as compared to streamwater and the head and mid of the GB throughout the year. Higher cumulative (over 6 h) GB temperatures were associated with increased CO2 evasion fluxes; the strength of the relationship increased with depth (max. r2 = 0.61 at -100cm depth). This enhanced CO2 flux may result from the input of warmer CO2-rich groundwater into the HZ in autumn and winter, while downward heat transfer in summer may enhance GB metabolism and therefore CO2 evasion. The importance of these processes is likely to increase, particularly in cold-water streams, due to the occurrence of more frequent and intense warm

  8. Investigation of helium plasma stream parameters in experiments on surface modification

    International Nuclear Information System (INIS)

    Bandura, A.N.; Byrka, O.V.; Chebotarev, V.V.; Garkusha, I.E.; Tsarenko, A.V. and eds.

    2005-01-01

    The main objection of this study is adjustment of plasma treatment regimes for different materials that allows achieving optimal thickness of modified layer with simultaneously minimal value of surface roughness. With use of optical spectroscopy, detailed information about the basic plasma parameters - electron density, electron and ion temperatures, plasma stream duration and velocity, was obtained. Integrated spectra of plasma radiation were analyzed. The majority of helium and impurity spectral lines were investigated on a subject of Stark broadening. Plasma pressure and energy density values measured with piezodetectors and calorimeters are in good agreement with plasma parameters obtained by optical techniques

  9. 'CANDLE' burnup regime after LWR regime

    International Nuclear Information System (INIS)

    Sekimoto, Hiroshi; Nagata, Akito

    2008-01-01

    CANDLE (Constant Axial shape of Neutron flux, nuclide densities and power shape During Life of Energy producing reactor) burnup strategy can derive many merits. From safety point of view, the change of excess reactivity along burnup is theoretically zero, and the core characteristics, such as power feedback coefficients and power peaking factor, are not changed along burnup. Application of this burnup strategy to neutron rich fast reactors makes excellent performances. Only natural or depleted uranium is required for the replacing fuels. About 40% of natural or depleted uranium undergoes fission without the conventional reprocessing and enrichment. If the LWR produced energy of X Joules, the CANDLE reactor can produce about 50X Joules from the depleted uranium left at the enrichment facility for the LWR fuel. If we can say LWRs have produced energy sufficient for full 20 years, we can produce the energy for 1000 years by using the CANDLE reactors with depleted uranium. We need not mine any uranium ore, and do not need reprocessing facility. The burnup of spent fuel becomes 10 times. Therefore, the spent fuel amount per produced energy is also reduced to one-tenth. The details of the scenario of CANDLE burnup regime after LWR regime will be presented at the symposium. (author)

  10. Application of the Hydroecological Integrity Assessment Process for Missouri Streams

    Science.gov (United States)

    Kennen, Jonathan G.; Henriksen, James A.; Heasley, John; Cade, Brian S.; Terrell, James W.

    2009-01-01

    Natural flow regime concepts and theories have established the justification for maintaining or restoring the range of natural hydrologic variability so that physiochemical processes, native biodiversity, and the evolutionary potential of aquatic and riparian assemblages can be sustained. A synthesis of recent research advances in hydroecology, coupled with stream classification using hydroecologically relevant indices, has produced the Hydroecological Integrity Assessment Process (HIP). HIP consists of (1) a regional classification of streams into hydrologic stream types based on flow data from long-term gaging-station records for relatively unmodified streams, (2) an identification of stream-type specific indices that address 11 subcomponents of the flow regime, (3) an ability to establish environmental flow standards, (4) an evaluation of hydrologic alteration, and (5) a capacity to conduct alternative analyses. The process starts with the identification of a hydrologic baseline (reference condition) for selected locations, uses flow data from a stream-gage network, and proceeds to classify streams into hydrologic stream types. Concurrently, the analysis identifies a set of non-redundant and ecologically relevant hydrologic indices for 11 subcomponents of flow for each stream type. Furthermore, regional hydrologic models for synthesizing flow conditions across a region and the development of flow-ecology response relations for each stream type can be added to further enhance the process. The application of HIP to Missouri streams identified five stream types ((1) intermittent, (2) perennial runoff-flashy, (3) perennial runoff-moderate baseflow, (4) perennial groundwater-stable, and (5) perennial groundwater-super stable). Two Missouri-specific computer software programs were developed: (1) a Missouri Hydrologic Assessment Tool (MOHAT) which is used to establish a hydrologic baseline, provide options for setting environmental flow standards, and compare past and

  11. A Four-Level Hierarchy for Organizing Wildland Stream Resource Information

    Science.gov (United States)

    Harry Parrott; Daniel A. Marion; R. Douglas Perkinson

    1989-01-01

    An analysis of current USDA Forest Service methods of collecting and using wildland stream resource data indicates that required information can be organized into a four-level hierarchy. Information at each level is tiered with information at the preceding level. Level 1 is the ASSOCIATION, which is differentiated by stream size and flow regime. Level 2, STREAM TYPE,...

  12. Distribution, abundance, and diversity of stream fishes under variable environmental conditions

    Science.gov (United States)

    Christopher M. Taylor; Thomas L. Holder; Richard A. Fiorillo; Lance R. Williams; R. Brent Thomas; Melvin L. Warren

    2006-01-01

    The effects of stream size and flow regime on spatial and temporal variability of stream fish distribution, abundance, and diversity patterns were investigated. Assemblage variability and species richness were each significantly associated with a complex environmental gradient contrasting smaller, hydrologically variable stream localities with larger localities...

  13. Enrolment regimes and gender differences in university of mines ...

    African Journals Online (AJOL)

    These perceptions, the general dislike for engineering courses by most females for fear of mathematics and the knowledge of the fact that engineering is quite difficult, explain the phenomenon of female under-representation in the mines. Though the progressive feminine enrolment regimes, due to gender main streaming ...

  14. Electron and ion energy distribution functions in slide-away regime of TRIAM-1 tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Kazuo; Satoh, Takemichi; Toi, Kazuo; Hiraki, Naoji; Nakamura, Yukio; Itoh, Satoshi

    1983-02-01

    The plasma properties, and the electron and ion energy distribution functions in particular, are studied in the slide-away regime of the TRIAM-1 tokamak, with the streaming parameter averaged over the plasma cross-section being varied up to 0.4. In the range >= 0.1, the soft X-ray spectrum has a tail component, and the electrical resistivity derived from the loop voltage/plasma current characteristics is lower than the Spitzer-Harm resistivity, which is estimated from the experimentally-obtained Zsub(eff)-value, electron temperature and electron density. Anomalous ion heating, however, does not occur, and the ion temperature agrees well with Artsimovich's scaling law.

  15. Arctic circulation regimes.

    Science.gov (United States)

    Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L

    2015-10-13

    Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. © 2015 The Authors.

  16. THE INFLUENCED FLOW REGIMES

    Directory of Open Access Journals (Sweden)

    Gavril PANDI

    2011-03-01

    Full Text Available The influenced flow regimes. The presence and activities ofhumanity influences the uniform environmental system, and in this context, therivers water resources. In concordance with this, the natural runoff regime suffersbigger and deeper changes. The nature of these changes depending on the type anddegree of water uses. The multitude of the use cause different types of influence,whit different quantitative aspects. In the same time, the influences havequalitative connotations, too, regarding to the modifications of the yearly watervolume runoff. So the natural runoff regime is modified. After analyzing thedistribution laws of the monthly runoff, there have been differenced four types ofinfluenced runoff regimes. In the excess type the influenced runoff is bigger thanthe natural, continuously in the whole year. The deficient type is characterized byinverse rapports like the first type, in the whole year. In the sinusoidal type, theinfluenced runoff is smaller than the natural in the period when the water isretained in the lake reservoirs, and in the depletion period the situation inverts. Atthe irregular type the ratio between influenced and natural runoff is changeable ina random meaner monthly. The recognition of the influenced regime and the gradeof influence are necessary in the evaluation and analysis of the usable hydrologicalriver resources, in the flood defence activities, in the complex scheme of thehydrographic basins, in the environment design and so on.

  17. Coldwater fish in wadeable streams [Chapter 8

    Science.gov (United States)

    Jason B. Dunham; Amanda E. Rosenberger; Russell F. Thurow; C. Andrew Dolloff; Philip J. Howell

    2009-01-01

    Small, wadeable streams comprise the majority of habitats available to fishes in fluvial networks. Wadeable streams are generally less than 1 m deep, and fish can be sampled without the use of water craft. Cold waters are defined as having mean 7-d summer maximum water temperatures of less than 20°C and providing habitat for coldwater fishes.

  18. Hall effect in hopping regime

    International Nuclear Information System (INIS)

    Avdonin, A.; Skupiński, P.; Grasza, K.

    2016-01-01

    A simple description of the Hall effect in the hopping regime of conductivity in semiconductors is presented. Expressions for the Hall coefficient and Hall mobility are derived by considering averaged equilibrium electron transport in a single triangle of localization sites in a magnetic field. Dependence of the Hall coefficient is analyzed in a wide range of temperature and magnetic field values. Our theoretical result is applied to our experimental data on temperature dependence of Hall effect and Hall mobility in ZnO. - Highlights: • Expressions for Hall coefficient and mobility for hopping conductivity are derived. • Theoretical result is compared with experimental curves measured on ZnO. • Simultaneous action of free and hopping conduction channels is considered. • Non-linearity of hopping Hall coefficient is predicted.

  19. Hall effect in hopping regime

    Energy Technology Data Exchange (ETDEWEB)

    Avdonin, A., E-mail: avdonin@ifpan.edu.pl [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa (Poland); Skupiński, P. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa (Poland); Grasza, K. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa (Poland); Institute of Electronic Materials Technology, ul. Wólczyńska 133, 01-919 Warszawa (Poland)

    2016-02-15

    A simple description of the Hall effect in the hopping regime of conductivity in semiconductors is presented. Expressions for the Hall coefficient and Hall mobility are derived by considering averaged equilibrium electron transport in a single triangle of localization sites in a magnetic field. Dependence of the Hall coefficient is analyzed in a wide range of temperature and magnetic field values. Our theoretical result is applied to our experimental data on temperature dependence of Hall effect and Hall mobility in ZnO. - Highlights: • Expressions for Hall coefficient and mobility for hopping conductivity are derived. • Theoretical result is compared with experimental curves measured on ZnO. • Simultaneous action of free and hopping conduction channels is considered. • Non-linearity of hopping Hall coefficient is predicted.

  20. Supply regimes in fisheries

    DEFF Research Database (Denmark)

    Nielsen, Max

    2006-01-01

    Supply in fisheries is traditionally known for its backward bending nature, owing to externalities in production. Such a supply regime, however, exist only for pure open access fisheries. Since most fisheries worldwide are neither pure open access, nor optimally managed, rather between the extremes......, the traditional understanding of supply regimes in fisheries needs modification. This paper identifies through a case study of the East Baltic cod fishery supply regimes in fisheries, taking alternative fisheries management schemes and mesh size limitations into account. An age-structured Beverton-Holt based bio......-economic supply model with mesh sizes is developed. It is found that in the presence of realistic management schemes, the supply curves are close to vertical in the relevant range. Also, the supply curve under open access with mesh size limitations is almost vertical in the relevant range, owing to constant...

  1. Simulation of climate change effects on streamflow, groundwater, and stream temperature using GSFLOW and SNTEMP in the Black Earth Creek Watershed, Wisconsin

    Science.gov (United States)

    Hunt, Randall J.; Westenbroek, Stephen M.; Walker, John F.; Selbig, William R.; Regan, R. Steven; Leaf, Andrew T.; Saad, David A.

    2016-08-23

    A groundwater/surface-water model was constructed and calibrated for the Black Earth Creek watershed in south-central Wisconsin. The model was then run to simulate scenarios representing common societal concerns in the basin, focusing on maintaining a cold-water resource in an urbanizing fringe near its upper stream reaches and minimizing downstream flooding. Although groundwater and surface water are considered a single resource, many hydrologic models simplistically simulate feedback loops between the groundwater system and other hydrologic processes. These feedbacks include timing and rates of evapotranspiration, surface runoff, soil-zone flow, and interactions with the groundwater system; however, computer models can now routinely and iteratively couple the surface-water and groundwater systems—albeit with longer model run times. In this study, preliminary calibrations of uncoupled transient surface-water and steady-state groundwater models were used to form the starting point for final calibration of one transient computer simulation that iteratively couples groundwater and surface water. The computer code GSFLOW (Groundwater/Surface-water FLOW) was used to simulate the coupled hydrologic system; a surface-water model represented hydrologic processes in the atmosphere, at land surface, and within the soil zone, and a groundwater-flow model represented the unsaturated zone, saturated zone, and streams. The coupled GSFLOW model was run on a daily time step during water years 1985–2007. Early simulation times (1985–2000) were used for spin-up to make the simulation results less sensitive to initial conditions specified; the spin-up period was not included in the model calibration. Model calibration used observed heads, streamflows, solar radiation, and snowpack measurements from 2000 to 2007 for history matching. Calibration was performed by using the PEST parameter estimation software suite.

  2. Determination of the Hall Thruster Operating Regimes

    International Nuclear Information System (INIS)

    L. Dorf; V. Semenov; Y. Raitses; N.J. Fisch

    2002-04-01

    A quasi one-dimensional (1-D) steady-state model of the Hall thruster is presented. For the same discharge voltage two operating regimes are possible -- with and without the anode sheath. For given mass flow rate, magnetic field profile and discharge voltage a unique solution can be constructed, assuming that the thruster operates in one of the regimes. However, we show that for a given temperature profile the applied discharge voltage uniquely determines the operating regime: for discharge voltages greater than a certain value, the sheath disappears. That result is obtained over a wide range of incoming neutral velocities, channel lengths and widths, and cathode plane locations. It is also shown that a good correlation between the quasi 1-D model and experimental results can be achieved by selecting an appropriate electron mobility and temperature profile

  3. Human impacts on river ice regime in the Carpathian Basin

    Science.gov (United States)

    Takács, Katalin; Nagy, Balázs; Kern, Zoltán

    2014-05-01

    River ice is a very important component of the cryosphere, and is especially sensitive to climatic variability. Historical records of appearance or disappearance and timing of ice phenomena are useful indicators for past climatic variations (Williams, 1970). Long-term observations of river ice freeze-up and break-up dates are available for many rivers in the temperate or cold region to detect and analyze the effects of climate change on river ice regime. The ice regime of natural rivers is influenced by climatic, hydrological and morphological factors. Regular ice phenomena observation mostly dates back to the 19th century. During this long-term observation period, the human interventions affecting the hydrological and morphological factors have become more and more intensive (Beltaos and Prowse, 2009). The anthropogenic effects, such as river regulation, hydropower use or water pollution causes different changes in river ice regime (Ashton, 1986). To decrease the occurrence of floods and control the water discharge, nowadays most of the rivers are regulated. River regulation changes the morphological parameters of the river bed: the aim is to create solid and equable bed size and stream gradient to prevent river ice congestion. For the satisfaction of increasing water demands hydropower is also used. River damming results a condition like a lake upstream to the barrage; the flow velocity and the turbulence are low, so this might be favourable for river ice appearance and freeze-up (Starosolsky, 1990). Water pollution affects ice regime in two ways; certain water contaminants change the physical characteristics of the water, e.g. lessens the freezing point of the water. Moreover the thermal stress effect of industrial cooling water and communal wastewater is also important; in winter these water sources are usually warmer, than the water body of the river. These interventions result different changes in the characteristic features of river ice regime. Selected

  4. Estimating thermal regimes of bull trout and assessing the potential effects of climate warming on critical habitats

    Science.gov (United States)

    Jones, Leslie A.; Muhlfeld, Clint C.; Marshall, Lucy A.; McGlynn, Brian L.; Kershner, Jeffrey L.

    2013-01-01

    Understanding the vulnerability of aquatic species and habitats under climate change is critical for conservation and management of freshwater systems. Climate warming is predicted to increase water temperatures in freshwater ecosystems worldwide, yet few studies have developed spatially explicit modelling tools for understanding the potential impacts. We parameterized a nonspatial model, a spatial flow-routed model, and a spatial hierarchical model to predict August stream temperatures (22-m resolution) throughout the Flathead River Basin, USA and Canada. Model comparisons showed that the spatial models performed significantly better than the nonspatial model, explaining the spatial autocorrelation found between sites. The spatial hierarchical model explained 82% of the variation in summer mean (August) stream temperatures and was used to estimate thermal regimes for threatened bull trout (Salvelinus confluentus) habitats, one of the most thermally sensitive coldwater species in western North America. The model estimated summer thermal regimes of spawning and rearing habitats at <13 C° and foraging, migrating, and overwintering habitats at <14 C°. To illustrate the useful application of such a model, we simulated climate warming scenarios to quantify potential loss of critical habitats under forecasted climatic conditions. As air and water temperatures continue to increase, our model simulations show that lower portions of the Flathead River Basin drainage (foraging, migrating, and overwintering habitat) may become thermally unsuitable and headwater streams (spawning and rearing) may become isolated because of increasing thermal fragmentation during summer. Model results can be used to focus conservation and management efforts on populations of concern, by identifying critical habitats and assessing thermal changes at a local scale.

  5. Cargo liability regimes

    Science.gov (United States)

    2001-01-01

    There are at present at least three international regimes of maritime cargo liability in force in different countries of the world - the original Hague rules (1924), the updated version known as the Hague-Visby rules (1968, further amended 1979), and...

  6. Trust in regulatory regimes

    NARCIS (Netherlands)

    Six, Frédérique; Verhoest, Koen

    2017-01-01

    Within political and administrative sciences generally, trust as a concept is contested, especially in the field of regulatory governance. This groundbreaking book is the first to systematically explore the role and dynamics of trust within regulatory regimes. Conceptualizing, mapping and analyzing

  7. East Asian welfare regime

    DEFF Research Database (Denmark)

    Abrahamson, Peter

    2017-01-01

    The paper asks if East Asian welfare regimes are still productivist and Confucian? And, have they developed public care policies? The literature is split on the first question but (mostly) confirmative on the second. Care has to a large, but insufficient extent, been rolled out in the region...

  8. Removal of sulfur from process streams

    International Nuclear Information System (INIS)

    Brignac, D.G.

    1984-01-01

    A process wherein water is added to a non-reactive gas stream, preferably a hydrogen or hydrogen-containing gas stream, sufficient to raise the water level thereof to from about 0.2 percent to about 50 percent, based on the total volume of the process gas stream, and the said moist gas stream is contacted, at elevated temperature, with a particulate mass of a sulfur-bearing metal alumina spinel characterized by the formula MAl 2 O 4 , wherein M is chromium, iron, cobalt, nickel, copper, cadmium, mercury, or zinc to desorb sulfur thereon. In the sulfur sorption cycle, due to the simultaneous adsorption of water and sulfur, the useful life of the metal alumina spinel for sulfur adsorption can be extended, and the sorbent made more easily regenerable after contact with a sulfur-bearing gas stream, notably sulfur-bearing wet hydrogen or wet hydrogen-rich gas streams

  9. International Food Regime

    Directory of Open Access Journals (Sweden)

    A. V. Malov

    2018-01-01

    Full Text Available The review article reveals the content of the concept of Food Regime, which is little-known in the Russian academic reference. The author monitored and codified the semantic dynamic of the terminological unit from its original interpretations to modern formulations based on the retrospective analysis. The rehabilitation of the academic merits of D. Puchala and R. Hopkins — authors who used the concept Food Regime for a few years before its universally recognized origin and official scientific debut, was accomplished with help of historical and comparative methods. The author implemented the method of ascension from the abstract to the concrete to demonstrating the classification of Food Regimes compiled on the basis of geopolitical interests in the sphere of international production, consumption, and distribution of foodstuffs. The characteristic features of historically formed Food Regime were described in the chronological order, as well as modern tendencies possessing reformist potential were identified. In particular, it has been established that the idea of Food Sovereignty (which is an alternative to the modern Corporate Food Regime is the subject for acute academic disputes. The discussion between P. McMichael P. and H. Bernstein devoted to the “peasant question” — mobilization frame of the Food Sovereignty strategy was analyzed using the secondary data processing method. Due to the critical analysis, the author comes to the conclusion that it is necessary to follow the principles of the Food Sovereignty strategy to prevent the catastrophic prospects associated with ecosystem degradation, accelerated erosion of soils, the complete disappearance of biodiversity and corporate autoc racy successfully. The author is convinced that the idea of Food Sovereignty can ward off energetic liberalization of nature, intensive privatization of life and rapid monetization of unconditioned human reflexes.

  10. Photosynthesis of amphibious and obligately submerged plants in CO2-rich lowland streams.

    Science.gov (United States)

    Sand-Jensen, Kaj; Frost-Christensen, Henning

    1998-11-01

    Small unshaded streams in lowland regions receive drainage water with high concentrations of free␣CO 2 , and they support an abundant growth of amphibious and obligately submerged plants. Our first objective was to measure the CO 2 regime during summer in a wide range of small alkaline Danish streams subject to wide variation in temperature, O 2 and CO 2 during the day. The second objective was to determine the effect of these variations on daily changes in light-saturated photosynthesis in water of a homophyllous and a heterophyllous amphibious species that only used CO 2 , and an obligately submerged species capable of using both HCO - 3 and CO 2 . We found that the median CO 2 concentrations of the streams were 11 and 6 times above air saturation in the morning and the afternoon, respectively, but stream sites with dense plant growth had CO 2 concentrations approaching air saturation in the afternoon. In contrast, outlets from lakes had low CO 2 concentrations close to, or below, air saturation. The amphibious species showed a reduction of photosynthesis in water from morning to afternoon along with the decline in CO 2 concentrations, while increasing temperature and O 2 had little effect on photosynthesis. Photosynthesis of the obligately submerged species varied little with the change of CO 2 because of HCO 3 - - use, and variations were mostly due to changes in O 2 concentration. Independent measurements showed that changes in temperature, O 2 and CO 2 could account for the daily variability of photosynthesis of all three species in water. The results imply that CO 2 supersaturation in small lowland streams is important for the rich representation of amphibious species and their contribution to system photosynthesis.

  11. Stream Response to an Extreme Defoliation Event

    Science.gov (United States)

    Gold, A.; Loffredo, J.; Addy, K.; Bernhardt, E. S.; Berdanier, A. B.; Schroth, A. W.; Inamdar, S. P.; Bowden, W. B.

    2017-12-01

    Extreme climatic events are known to profoundly impact stream flow and stream fluxes. These events can also exert controls on insect outbreaks, which may create marked changes in stream characteristics. The invasive Gypsy Moth (Lymantria dispar dispar) experiences episodic infestations based on extreme climatic conditions within the northeastern U.S. In most years, gypsy moth populations are kept in check by diseases. In 2016 - after successive years of unusually warm, dry spring and summer weather -gypsy moth caterpillars defoliated over half of Rhode Island's 160,000 forested ha. No defoliation of this magnitude had occurred for more than 30 years. We examined one RI headwater stream's response to the defoliation event in 2016 compared with comparable data in 2014 and 2015. Stream temperature and flow was gauged continuously by USGS and dissolved oxygen (DO) was measured with a YSI EXO2 sonde every 30 minutes during a series of deployments in the spring, summer and fall from 2014-2016. We used the single station, open channel method to estimate stream metabolism metrics. We also assessed local climate and stream temperature data from 2009-2016. We observed changes in stream responses during the defoliation event that suggest changes in ET, solar radiation and heat flux. Although the summer of 2016 had more drought stress (PDSI) than previous years, stream flow occurred throughout the summer, in contrast to several years with lower drought stress when stream flow ceased. Air temperature in 2016 was similar to prior years, but stream temperature was substantially higher than the prior seven years, likely due to the loss of canopy shading. DO declined dramatically in 2016 compared to prior years - more than the rising stream temperatures would indicate. Gross Primary Productivity was significantly higher during the year of the defoliation, indicating more total fixation of inorganic carbon from photo-autotrophs. In 2016, Ecosystem Respiration was also higher and Net

  12. Analysis of the influence of the plasma thermodynamic regime in the spectrally resolved and mean radiative opacity calculations of carbon plasmas in a wide range of density and temperature

    International Nuclear Information System (INIS)

    Gil, J.M.; Rodriguez, R.; Martel, P.; Florido, R.; Rubiano, J.G.; Mendoza, M.A.; Minguez, E.

    2013-01-01

    In this work the spectrally resolved, multigroup and mean radiative opacities of carbon plasmas are calculated for a wide range of plasma conditions which cover situations where corona, local thermodynamic and non-local thermodynamic equilibrium regimes are found. An analysis of the influence of the thermodynamic regime on these magnitudes is also carried out by means of comparisons of the results obtained from collisional-radiative, corona or Saha–Boltzmann equations. All the calculations presented in this work were performed using ABAKO/RAPCAL code. -- Highlights: ► Spectrally resolved, multigroup and mean radiative opacities of carbon plasmas are calculated. ► Corona, local thermodynamic and non-local thermodynamic equilibrium regimes are analyzed. ► Simulations performed using the computational package ABAKO/RAPCAL. ► A criterion for the establishment of the thermodynamic regime is proposed.

  13. Analysis of Influence of Heat Insulation on the Thermal Regime of Storage Tanks with Liquefied Natural Gas

    Science.gov (United States)

    Maksimov, Vyacheslav I.; Nagornova, Tatiana A.; Glazyrin, Viktor P.; Shestakov, Igor A.

    2016-02-01

    Is numerically investigated the process of convective heat transfer in the reservoirs of liquefied natural gas (LNG). The regimes of natural convection in a closed rectangular region with different intensity of heat exchange at the external borders are investigated. Is solved the time-dependent system of energy and Navier-Stokes equations in the dimensionless variables "vorticity - the stream function". Are obtained distributions of the hydrodynamic parameters and temperatures, that characterize basic regularities of the processes. The special features of the formation of circulation flows are isolated and the analysis of the temperature distribution in the solution region is carried out. Is shown the influence of geometric characteristics and intensity of heat exchange on the outer boundaries of reservoir on the temperature field in the LNG storage.

  14. Analysis of Influence of Heat Insulation on the Thermal Regime of Storage Tanks with Liquefied Natural Gas

    Directory of Open Access Journals (Sweden)

    Maksimov Vyacheslav I.

    2016-01-01

    Full Text Available Is numerically investigated the process of convective heat transfer in the reservoirs of liquefied natural gas (LNG. The regimes of natural convection in a closed rectangular region with different intensity of heat exchange at the external borders are investigated. Is solved the time-dependent system of energy and Navier-Stokes equations in the dimensionless variables “vorticity – the stream function”. Are obtained distributions of the hydrodynamic parameters and temperatures, that characterize basic regularities of the processes. The special features of the formation of circulation flows are isolated and the analysis of the temperature distribution in the solution region is carried out. Is shown the influence of geometric characteristics and intensity of heat exchange on the outer boundaries of reservoir on the temperature field in the LNG storage.

  15. Flow regime alterations under changing climate in two river basins: Implications for freshwater ecosystems

    Science.gov (United States)

    Gibson, C.A.; Meyer, J.L.; Poff, N.L.; Hay, L.E.; Georgakakos, A.

    2005-01-01

    We examined impacts of future climate scenarios on flow regimes and how predicted changes might affect river ecosystems. We examined two case studies: Cle Elum River, Washington, and Chattahoochee-Apalachicola River Basin, Georgia and Florida. These rivers had available downscaled global circulation model (GCM) data and allowed us to analyse the effects of future climate scenarios on rivers with (1) different hydrographs, (2) high future water demands, and (3) a river-floodplain system. We compared observed flow regimes to those predicted under future climate scenarios to describe the extent and type of changes predicted to occur. Daily stream flow under future climate scenarios was created by either statistically downscaling GCMs (Cle Elum) or creating a regression model between climatological parameters predicted from GCMs and stream flow (Chattahoochee-Apalachicola). Flow regimes were examined for changes from current conditions with respect to ecologically relevant features including the magnitude and timing of minimum and maximum flows. The Cle Elum's hydrograph under future climate scenarios showed a dramatic shift in the timing of peak flows and lower low flow of a longer duration. These changes could mean higher summer water temperatures, lower summer dissolved oxygen, and reduced survival of larval fishes. The Chattahoochee-Apalachicola basin is heavily impacted by dams and water withdrawals for human consumption; therefore, we made comparisons between pre-large dam conditions, current conditions, current conditions with future demand, and future climate scenarios with future demand to separate climate change effects and other anthropogenic impacts. Dam construction, future climate, and future demand decreased the flow variability of the river. In addition, minimum flows were lower under future climate scenarios. These changes could decrease the connectivity of the channel and the floodplain, decrease habitat availability, and potentially lower the ability

  16. Fish populations in Plynlimon streams

    Directory of Open Access Journals (Sweden)

    D. T. Crisp

    1997-01-01

    Full Text Available In Plynlimon streams, brown trout (Salmo trutta L. are widespread in the upper Wye at population densities of 0.03 to 0.32 fish m-2 and show evidence of successful recruitment in most years. In the upper Severn, brown trout are found only in an area of c. 1670 -2 downstream of Blaenhafren Falls at densities of 0.03 to 0.24 fish -2 and the evidence suggests very variable year to year success in recruitment (Crisp & Beaumont, 1996. Analyses of the data show that temperature differences between afforested and unafforested streams may affect the rates of trout incubation and growth but are not likely to influence species survival. Simple analyses of stream discharge data suggest, but do not prove, that good years for recruitment in the Hafren population were years of low stream discharge. This may be linked to groundwater inputs detected in other studies in this stream. More research is needed to explain the survival of the apparently isolated trout population in the Hafren.

  17. Floating Exchange Rate Regime

    OpenAIRE

    Quader, Syed Manzur

    2004-01-01

    In recent years, many developing countries having a history of high inflation, unfavorable balance of payment situation and a high level of foreign currencies denominated debt, have switched or are in the process of switching to a more flexible exchange rate regime. Therefore, the stability of the exchange rate and the dynamics of its volatility are more crucial than before to prevent financial crises and macroeconomic disturbances. This paper is designed to find out the reasons behind Bangla...

  18. Biotic Responses of Headwater Streams to Geophysical Alteration and Disturbance Related to Climate Change

    Science.gov (United States)

    Gresswell, R. E.; Sedell, E. R.; Cannon, S.; Hostetler, S. W.; Williams, J. E.; Haak, A. L.; Kershner, J. L.

    2009-12-01

    Climate change will potentially alter physical habitat availability for trout species (both native and nonnative) in the western USA, and ultimately affect population distribution and abundance in watersheds across the region. To understand the biological consequences of habitat alteration associated with climate change, we have developed models linking contemporary patterns of occurrence and abundance to geomorphic variables (e.g., aspect, elevation, and slope) and stream conditions derived from the habitat (e.g., temperature, discharge, and flood regimes). Because headwater streams may be especially susceptible to catastrophic disturbances in the form of debris flow torrents that have the potential to radically alter the physical structure of channels and sometimes extirpate local fish populations, we are focusing fine-scale spatial analyses in the high elevation systems. Risks of such disturbances increase exponentially in landscapes that have experienced recent wildfires when high-intensity precipitation or runoff events occur. Although predicting the timing, extent, and severity of future wildfires or subsequent precipitation and runoff events is difficult, it is possible to identify channels within stream networks that may be prone to debris flows. These channels can be identified using models based on characteristic storm and burn scenarios and geographic information describing topographic, soil, and vegetation characteristics. At-risk channels are being mapped throughout the stream networks within the study areas in the headwaters of the Colorado River to provide information about the potential for catastrophic population disturbance in response to variety of wildfire and post-wildfire storm scenarios.

  19. Continental slope sea level and flow variability induced by lateral movements of the Gulf Stream in the Middle Atlantic Bight

    Science.gov (United States)

    Böhm, E.; Hopkins, T. S.; Pietrafesa, L. J.; Churchill, J. H.

    2006-08-01

    As described by [Csanady, G.T., Hamilton, P., 1988. Circulation of slope water. Continental Shelf Research 8, 565-624], the flow regime over the slope of the southern Middle Atlantic Bight (MAB) includes a current reversal in which southwestward flow over the upper and middle slope becomes entrained in the northeastward current adjacent to the Gulf Stream. In this paper we use satellite-derived data to quantify how lateral motions of the Gulf Stream impact this current system. In our analysis, the Gulf Stream’s thermal front is delineated using a two-year time series of sea surface temperature derived from NOAA/AVHRR satellite data. Lateral motions of the Gulf Stream are represented in terms of temporal variations of the area, east of 73°W, between the Gulf Stream thermal front and the shelf edge. Variations of slope water flow within this area are represented by anomalies of geostrophic velocity as derived from the time series of the sea level anomaly determined from TOPEX/POSEIDON satellite altimeter data. A strong statistical relationship is found between Gulf Stream displacements and parabathic flow over the continental slope. It is such that the southwestward flow over the slope is accelerated when the Gulf Stream is relatively far from the shelf edge, and is decelerated (and perhaps even reversed) when the Gulf Stream is close to the shelf edge. This relationship between Gulf Stream displacements and parabathic flow is also observed in numerical simulations produced by the Miami Isopycnic Coordinate Model. In qualitative terms, it is consistent with the notion that when the Gulf Stream is closer to the 200-m isobath, it is capable of entraining a larger fraction of shelf water masses. Alternatively, when the Gulf Stream is far from the shelf-break, more water is advected into the MAB slope region from the northeast. Analysis of the diabathic flow indicates that much of the cross-slope transport by which the southwestward flow entering the study region is

  20. In-stream biogeochemical processes of a temporary river.

    Science.gov (United States)

    Tzoraki, Ourania; Nikolaidis, Nikolaos P; Amaxidis, Yorgos; Skoulikidis, Nikolaos Th

    2007-02-15

    A reach at the estuary of Krathis River in Greece was used to assess how in-stream processes alter its hydrologic and biogeochemical regime. Krathis River exhibited high annual flow variability and its transmission losses become significant, especially during the dry months. These transmission losses are enhanced in chemistry due to release of nutrients from river sediments. These fluxes are significant because they correspond to 11% of the dissolved inorganic nitrogen flux of the river. Release of nitrogen species was influenced by temperature, while release of phosphate was not because phosphate levels were below the equilibrium concentration. There is a significant amount of sediments with fine composition that create "hot spot" areas in the river reach. These sediments are mobilized during the first flush events in the fall carrying with them a significant load of nutrient and suspended matter to the coastal zone. The nutrient organic content of sediments was also significant and it was studied in terms of its mineralization capacity. The capacity for mineralization was influenced by soil moisture, exhibiting significant capacity even at moisture levels of 40%. Temporary rivers are sensitive ecosystems, vulnerable to climate changes. In-stream processes play a significant role in altering the hydrology and biogeochemistry of the water and its impacts to the coastal zone.

  1. StreamCat

    Data.gov (United States)

    U.S. Environmental Protection Agency — The StreamCat Dataset provides summaries of natural and anthropogenic landscape features for ~2.65 million streams, and their associated catchments, within the...

  2. Prioritized Contact Transport Stream

    Science.gov (United States)

    Hunt, Walter Lee, Jr. (Inventor)

    2015-01-01

    A detection process, contact recognition process, classification process, and identification process are applied to raw sensor data to produce an identified contact record set containing one or more identified contact records. A prioritization process is applied to the identified contact record set to assign a contact priority to each contact record in the identified contact record set. Data are removed from the contact records in the identified contact record set based on the contact priorities assigned to those contact records. A first contact stream is produced from the resulting contact records. The first contact stream is streamed in a contact transport stream. The contact transport stream may include and stream additional contact streams. The contact transport stream may be varied dynamically over time based on parameters such as available bandwidth, contact priority, presence/absence of contacts, system state, and configuration parameters.

  3. Experimental study of steam condensation regime map for simplified spargers

    International Nuclear Information System (INIS)

    Kim, Y. S.; Yoon, Y. J.; Song, C. H.; Park, C. K.; Kang, H. S.; Jun, H. K.

    2003-01-01

    An experimental study was conducted to produce a condensation regime map for single-hole and 4-hole steam spargers using GIRLS facility. The regime map for a single-hole sparger was derived using parameters such as the frequency and magnitude of the dynamic pressure. For 4-hole sparager, the regime map was derived using the trends of sound and dynamic pressure. Using the single-hole and 4-hole data, a steam jet condensation regime map was suggested with respect to pool temperature and steam mass flux

  4. Integrated flow and temperature modeling at the catchment scale

    DEFF Research Database (Denmark)

    Loinaz, Maria Christina; Davidsen, Hasse Kampp; Butts, Michael

    2013-01-01

    –groundwater dynamics affect stream temperature. A coupled surface water–groundwater and temperature model has therefore been developed to quantify the impacts of land management and water use on stream flow and temperatures. The model is applied to the simulation of stream temperature levels in a spring-fed stream...

  5. GAGES: A stream gage database for evaluating natural and alteredflow conditions in the conterminous United States

    Science.gov (United States)

    Falcone, James A.; Carlisle, Daren M.; Wolock, David M.; Meador, Michael R.

    2010-01-01

    Stream flow is a controlling element in the ecology of rivers and streams. Knowledge of the natural flow regime facilitates the assessment of whether specific hydrologic attributes have been altered by humans in a particular stream and the establishment of specific goals for stream-flow restoration. Because most streams are ungaged or have been altered by human influences, characterizing the natural flow regime is often only possible by estimating flow characteristics based on nearby stream gages of reference quality, i.e., gaged locations that are least disturbed by human influences. The ability to evaluate natural stream flow, that which is not altered by human activities, would be enhanced by the existence of a nationally consistent and up-to-date database of gages in relatively undisturbed watersheds.

  6. Productivity of Stream Definitions

    NARCIS (Netherlands)

    Endrullis, Jörg; Grabmayer, Clemens; Hendriks, Dimitri; Isihara, Ariya; Klop, Jan

    2007-01-01

    We give an algorithm for deciding productivity of a large and natural class of recursive stream definitions. A stream definition is called ‘productive’ if it can be evaluated continuously in such a way that a uniquely determined stream is obtained as the limit. Whereas productivity is undecidable

  7. Productivity of stream definitions

    NARCIS (Netherlands)

    Endrullis, J.; Grabmayer, C.A.; Hendriks, D.; Isihara, A.; Klop, J.W.

    2008-01-01

    We give an algorithm for deciding productivity of a large and natural class of recursive stream definitions. A stream definition is called ‘productive’ if it can be evaluated continually in such a way that a uniquely determined stream in constructor normal form is obtained as the limit. Whereas

  8. THE INFLUENCE OF MONK EQUIPPED PONDS ON THE QUALITY OF BASIN HEAD STREAMS, THE EXAMPLE OF WATER TEMPERATURE IN LIMOUSIN AND BERRY (FRANCE

    Directory of Open Access Journals (Sweden)

    Laurent TOUCHART

    2010-12-01

    Full Text Available In the centre-west regions of France, the deep water outlet system known as a “monk” is used in 13% of bodies of water. The authorities are strongly encouraging this to increase, arguing that this system would reduce pond induced warming of the hydrographical network. We have measured the water temperature in four monk equipped ponds for 13 years to such an extent that this paper draws on an analysis of 142,200 original measurements. Compared to a surface outflow, a monk is a system which shifts the warming of the emissary water course to the end of summer and the autumn which reduces average annual warming by about 1°C. This reduces the heating of diurnal maxima but increases warming of the minima. A monk equipped pond warms the river with deep water which has acquired its heat by mechanical convection generated by the wind, as opposed to a weir equipped pond which provides surface water warmed by insolation. In winter the monk equipped pond does not damage the thermal living conditions for Fario trout embryos and larvae under the gravel. In summer, the monk prevents night time cooling of the emissary and increases the temperature of the minima excessively for sensitive species.

  9. MODELING OF CONVECTIVE STREAMS IN PNEUMOBASIC OBJECTS (Part 2

    Directory of Open Access Journals (Sweden)

    B. M. Khroustalev

    2015-01-01

    Full Text Available The article presents modeling for investigation of aerodynamic processes on area sections (including a group of complex constructional works for different regimes of drop and wind streams  and  temperature  conditions  and  in  complex  constructional  works  (for  different regimes of heating and ventilation. There were developed different programs for innovation problems solution in the field of heat and mass exchange in three-dimensional space of pres- sures-speeds-temperatures of оbjects.The field of uses of pneumobasic objects: construction and roof of tennis courts, hockey pitches, swimming pools , and also exhibitions’ buildings, circus buildings, cafes, aqua parks, studios, mobile objects of medical purposes, hangars, garages, construction sites, service sta- tions and etc. Advantages of such objects are the possibility and simplicity of multiple instal- lation and demolition works. Their large-scale implementation is determined by temperature- moisture conditions under the shells.Analytical and calculating researches, real researches of thermodynamic parameters of heat and mass exchange, multifactorial processes of air in pneumobasic objects, their shells in a wide range of climatic parameters of air (January – December in the Republic of Belarus, in many geographical latitudes of many countries have shown that the limit of the possibility of optimizing wind loads, heat flow, acoustic effects is infinite (sports, residential, industrial, warehouse, the military-technical units (tanks, airplanes, etc.. In modeling of convective flows in pneumobasic objects (part 1 there are processes with higher dynamic parameters of the air flow for the characteristic pneumobasic object, carried out the calculation of the velocity field, temperature, pressure at the speed of access of air through the inflow holes up to 5 m/sec at the moments of times (20, 100, 200, 400 sec. The calculation was performed using the developed mathematical

  10. Flow Regime Classification and Hydrological Characterization: A Case Study of Ethiopian Rivers

    Directory of Open Access Journals (Sweden)

    Belete Berhanu

    2015-06-01

    Full Text Available The spatiotemporal variability of a stream flow due to the complex interaction of catchment attributes and rainfall induce complexity in hydrology. Researchers have been trying to address this complexity with a number of approaches; river flow regime is one of them. The flow regime can be quantified by means of hydrological indices characterizing five components: magnitude, frequency, duration, timing, and rate of change of flow. Similarly, this study aimed to understand the flow variability of Ethiopian Rivers using the observed daily flow data from 208 gauging stations in the country. With this process, the Hierarchical Ward Clustering method was implemented to group the streams into three flow regimes (1 ephemeral, (2 intermittent, and (3 perennial. Principal component analysis (PCA is also applied as the second multivariate analysis tool to identify dominant hydrological indices that cause the variability in the streams. The mean flow per unit catchment area (QmAR and Base flow index (BFI show an incremental trend with ephemeral, intermittent and perennial streams. Whereas the number of mean zero flow days ratio (ZFI and coefficient of variation (CV show a decreasing trend with ephemeral to perennial flow regimes. Finally, the streams in the three flow regimes were characterized with the mean and standard deviation of the hydrological variables and the shape, slope, and scale of the flow duration curve. Results of this study are the basis for further understanding of the ecohydrological processes of the river basins in Ethiopia.

  11. Unsteady mixed convection of a micropolar fluid past a circular cylinder due to time-dependent free stream velocity and temperature

    Directory of Open Access Journals (Sweden)

    Nepal C. Roy

    2016-06-01

    Full Text Available Unsteady mixed convection boundary-layer flow of an electrically conducting micropolar fluid past a circular cylinder is investigated taking into account the effect of thermal radiation and heat generation or absorption. The reduced non-similar boundary-layer equations are solved using the finite difference method. It is found that the magnitude of the friction factor and the couple stress significantly increases due to the increase of the mixed convection parameter, the conduction-radiation parameter, the surface temperature parameter, the heat absorption parameter and the frequency parameter. However the magnitude of the heat transfer rate decreases with these parameters. The converse characteristics are observed for the Prandtl number. The magnitude of the couple stress and the heat transfer rate is seen to decrease whereas the magnitude of the skin factor increases with increasing the vortex viscosity parameter. The magnetic field parameter reduces the skin factor, couple stress and heat transfer rate. The amplitude of oscillation of the transient skin factor and couple stress gradually increases owing to an increase of $\\xi$. But the transient heat transfer rate is found to be oscillating with almost the same amplitude for any value of $\\xi$. The amplitude of oscillation of the transient skin factor and couple stress increases with an increase of $S$ and $\\xi$ while the amplitude of the transient heat transfer rate increases with increasing Pr and $S$.

  12. Characteristics of regulatory regimes

    Directory of Open Access Journals (Sweden)

    Noralv Veggeland

    2013-03-01

    Full Text Available The overarching theme of this paper is institutional analysis of basic characteristics of regulatory regimes. The concepts of path dependence and administrative traditions are used throughout. Self-reinforcing or positive feedback processes in political systems represent a basic framework. The empirical point of departure is the EU public procurement directive linked to OECD data concerning use of outsourcing among member states. The question is asked: What has caused the Nordic countries, traditionally not belonging to the Anglo-Saxon market-centred administrative tradition, to be placed so high on the ranking as users of the Market-Type Mechanism (MTM of outsourcing in the public sector vs. in-house provision of services? A thesis is that the reason may be complex, but might be found in an innovative Scandinavian regulatory approach rooted in the Nordic model.

  13. Improving Prediction of Large-scale Regime Transitions

    Science.gov (United States)

    Gyakum, J. R.; Roebber, P.; Bosart, L. F.; Honor, A.; Bunker, E.; Low, Y.; Hart, J.; Bliankinshtein, N.; Kolly, A.; Atallah, E.; Huang, Y.

    2017-12-01

    Cool season atmospheric predictability over the CONUS on subseasonal times scales (1-4 weeks) is critically dependent upon the structure, configuration, and evolution of the North Pacific jet stream (NPJ). The NPJ can be perturbed on its tropical side on synoptic time scales by recurving and transitioning tropical cyclones (TCs) and on subseasonal time scales by longitudinally varying convection associated with the Madden-Julian Oscillation (MJO). Likewise, the NPJ can be perturbed on its poleward side on synoptic time scales by midlatitude and polar disturbances that originate over the Asian continent. These midlatitude and polar disturbances can often trigger downstream Rossby wave propagation across the North Pacific, North America, and the North Atlantic. The project team is investigating the following multiscale processes and features: the spatiotemporal distribution of cyclone clustering over the Northern Hemisphere; cyclone clustering as influenced by atmospheric blocking and the phases and amplitudes of the major teleconnection indices, ENSO and the MJO; composite and case study analyses of representative cyclone clustering events to establish the governing dynamics; regime change predictability horizons associated with cyclone clustering events; Arctic air mass generation and modification; life cycles of the MJO; and poleward heat and moisture transports of subtropical air masses. A critical component of the study is weather regime classification. These classifications are defined through: the spatiotemporal clustering of surface cyclogenesis; a general circulation metric combining data at 500-hPa and the dynamic tropopause; Self Organizing Maps (SOM), constructed from dynamic tropopause and 850 hPa equivalent potential temperature data. The resultant lattice of nodes is used to categorize synoptic classes and their predictability, as well as to determine the robustness of the CFSv2 model climate relative to observations. Transition pathways between these

  14. Regimes of mini black hole abandoned to accretion

    Science.gov (United States)

    Paik, Biplab

    2018-01-01

    Being inspired by the Eddington’s idea, along with other auxiliary arguments, it is unveiled that there exist regimes of a black hole that would prohibit accretion of ordinary energy. In explicit words, there exists a lower bound to black hole mass below which matter accretion process does not run for black holes. Not merely the baryonic matter, but, in regimes, also the massless photons could get prohibited from rushing into a black hole. However, unlike the baryon accretion abandoned black hole regime, the mass-regime of a black hole prohibiting accretion of radiation could vary along with its ambient temperature. For example, we discuss that earlier to 10‑8 s after the big-bang, as the cosmological temperature of the Universe grew above ˜ 1014 K, the mass range of black hole designating the radiation accretion abandoned regime, had to be in varying state being connected with the instantaneous age of the evolving Universe by an “one half” power law. It happens to be a fact that a black hole holding regimes prohibiting accretion of energy is gigantic by its size in comparison to the Planck length-scale. Hence the emergence of these regimes demands mini black holes for not being viable as profound suckers of energy. Consideration of accretion abandoned regimes could be crucial for constraining or judging the evolution of primordial black holes over the age of the Universe.

  15. Flow of a stream through a reservoir

    International Nuclear Information System (INIS)

    Sauerwein, K.

    1967-01-01

    If a reservoir is fed from a single source, which may not always be pure, the extent to which the inflowing stream mixes with the water in the reservoir is important for the quality of the water supplied by the reservoir. This question was investigated at the Lingese Reservoir, containing between one and two million cubic metres of water, in the Bergisches Land (North Rhine-Westphalia). The investigation was carried out at four different seasons so that the varying effects of the stream-water temperatures could be studied in relation to the temperature of the reservoir water. The stream was radioactively labelled at the point of inflow into the reservoir, and its flow through the reservoir was measured in length and depth from boats, by means of 1-m-long Geiger counters. In two cases the radioactivity of the outflowing water was also measured at fixed points. A considerable variety of intermixing phenomena were observed; these were mainly of limnological interest. The results of four experiments corresponding to the four different seasons are described in detail. They were as follows: (1) The mid-October experiment where the stream, with a temperature of 8.0 deg. C, was a good 5 deg. C colder than the water of the reservoir, whose temperature was almost uniform, ranging from 13.2 deg. C at the bed to 13.6 deg. C at the surface. (2) The spring experiment (second half of March), when the stream temperature was only 0.3 deg. C below that of the reservoir surface (7.8 deg. C), while the temperature of the bed was 5.8 deg. C. (3) The winter experiment (early December) where at first the temperature of the stream was approximately the same as that of the surface so that, once again, the stream at first flowed 1/2 - 1 m below the surface. During the almost wind-free night a sudden fall in temperature occurred, and the air temperature dropped from 0 deg. C to -12 deg. C. (4) The summer experiment (end of July to mid-August) when the stream was nearly 1 deg. C colder than

  16. Influence of pulsed plasma streams processing on wear behavior of steels in different friction conditions

    International Nuclear Information System (INIS)

    Bandura, A.N.; Byrka, O.V.; Tereshin, V.I.; Bovda, A.M.; Tortika, A.S.

    2000-01-01

    Pulsed plasma streams processing was applied for surface modification of industrial steel samples. Different types of wear tests (pin-on-disk,flat-on-flat, abrasive,cavitation) were carried out for samples irradiated by pulsed nitrogen plasma streams. There was achieved essential decrease of wear and tear of processed surfaces of all kinds of steels including previously thermally quenched ones. Obtained results are of importance for both determination of optimal regimes of plasma streams processing and the most resulting use of pulsed plasma streams for technology purpose, i.e. for identification of wear modes and optimal friction conditions for steels processed by plasma streams

  17. How climate change will affect sessile stages of brown trout (Salmo trutta) in mountain streams of the Iberian Peninsula

    Science.gov (United States)

    Santiago, José M.; Alonso, Carlos; García de Jalón, Diego; Solana, Joaquín

    2017-04-01

    Streamflow and temperature regimes are determinant for the availability of suitable physical habitat for instream biological communities. Iberian brown trout (Salmo trutta) populations live in a climatic border in which summer water scarcity and raising temperatures will compromise their viability throughout the current century. Due to their impaired mobility, sessile stages of trout life cycle (i.e. eggs and larvae) are among the most sensitive organisms to environmental changing conditions. At a given spawning redd, thermal habitat is limited by the length of the period at which suitable temperatures occur. At the same time, suitable physical habitat is limited by the instream flow regime during spawning and incubation of eggs and larvae. Temperature and flow do also interact, thus producing synergistic effects on both physical and thermal habitats. This study is aimed at quantitatively predicting thermal and physical habitat loss for the sessile stages of brown trout life cycle due to clime change, in mountain streams at the rear edge of the species natural distribution using high-resolution spatial-temporal simulations of the thermal and physical habitat. Two streams of Central Spain have been studied (Cega and Lozoya streams). Daily temperature and flow data from ad hoc downscaled IPCC (RCP4.5 and RCP8.5) predictions were used as input variables. Physical habitat changes were simulated from previously predicted stream flow data by means of hydraulic simulation tools (River2D). By taking into account the thermal tolerance limits and the proportion of lost physical habitat, limiting factors for the reproduction of brown trout in the study area were determined. The general increase of mean temperatures shortens the duration of the early developmental stages. This reduction of the sessile period is rather similar in both RCP4.5 and RCP8.5 scenarios by 2050. Differences between both scenarios become greater by 2099. The duration of sessile developmental is reduced

  18. Resource subsidies between stream and terrestrial ecosystems under global change

    Science.gov (United States)

    Larsen, Stefano; Muehlbauer, Jeffrey D.; Marti Roca, Maria Eugenia

    2016-01-01

    Streams and adjacent terrestrial ecosystems are characterized by permeable boundaries that are crossed by resource subsidies. Although the importance of these subsidies for riverine ecosystems is increasingly recognized, little is known about how they may be influenced by global environmental change. Drawing from available evidence, in this review we propose a conceptual framework to evaluate the effects of global change on the quality and spatiotemporal dynamics of stream–terrestrial subsidies. We illustrate how changes to hydrological and temperature regimes, atmospheric CO2 concentration, land use and the distribution of nonindigenous species can influence subsidy fluxes by affecting the biology and ecology of donor and recipient systems and the physical characteristics of stream–riparian boundaries. Climate-driven changes in the physiology and phenology of organisms with complex life cycles will influence their development time, body size and emergence patterns, with consequences for adjacent terrestrial consumers. Also, novel species interactions can modify subsidy dynamics via complex bottom-up and top-down effects. Given the seasonality and pulsed nature of subsidies, alterations of the temporal and spatial synchrony of resource availability to consumers across ecosystems are likely to result in ecological mismatches that can scale up from individual responses, to communities, to ecosystems. Similarly, altered hydrology, temperature, CO2 concentration and land use will modify the recruitment and quality of riparian vegetation, the timing of leaf abscission and the establishment of invasive riparian species. Along with morphological changes to stream–terrestrial boundaries, these will alter the use and fluxes of allochthonous subsidies associated with stream ecosystems. Future research should aim to understand how subsidy dynamics will be affected by key drivers of global change, including agricultural intensification, increasing water use and biotic

  19. Inventory of miscellaneous streams

    International Nuclear Information System (INIS)

    Lueck, K.J.

    1995-09-01

    On December 23, 1991, the US Department of Energy, Richland Operations Office (RL) and the Washington State Department of Ecology (Ecology) agreed to adhere to the provisions of the Department of Ecology Consent Order. The Consent Order lists the regulatory milestones for liquid effluent streams at the Hanford Site to comply with the permitting requirements of Washington Administrative Code. The RL provided the US Congress a Plan and Schedule to discontinue disposal of contaminated liquid effluent into the soil column on the Hanford Site. The plan and schedule document contained a strategy for the implementation of alternative treatment and disposal systems. This strategy included prioritizing the streams into two phases. The Phase 1 streams were considered to be higher priority than the Phase 2 streams. The actions recommended for the Phase 1 and 2 streams in the two reports were incorporated in the Hanford Federal Facility Agreement and Consent Order. Miscellaneous Streams are those liquid effluents streams identified within the Consent Order that are discharged to the ground but are not categorized as Phase 1 or Phase 2 Streams. This document consists of an inventory of the liquid effluent streams being discharged into the Hanford soil column

  20. Hydrography - Streams and Shorelines

    Data.gov (United States)

    California Natural Resource Agency — The hydrography layer consists of flowing waters (rivers and streams), standing waters (lakes and ponds), and wetlands -- both natural and manmade. Two separate...

  1. Substrate homogenization affects survival and fitness in the lowland stream caddisflies Micropterna sequax and Potamophylax rotundipennis

    NARCIS (Netherlands)

    Westveer, Judith J.; Verdonschot, Piet F.M.; Verdonschot, Ralf C.M.

    2017-01-01

    Loss of substrate heterogeneity or patchiness is common in lowland streams with disturbed hydrological regimes. At the reach scale, peak discharges tend to homogenize the stream bed and decrease the availability of specific microhabitat types. This spatial shift in habitats toward a more

  2. Riparian indicators of flow frequency in a tropical montante stream network

    Science.gov (United States)

    Andrew S. Pike; Frederick N. Scatena

    2010-01-01

    Many field indicators have been used to approximate the magnitude and frequency of flows in a variety of streams and rivers, yet due to a scarcity of long-term flow records in tropical mountain streams, little to no work has been done to establish such relationships between field features and the flow regime in these environments. Furthermore, the transition between...

  3. Hydrology and substrates: determinants of oligochaete distribution in lowland streams (the Netherlands)

    NARCIS (Netherlands)

    Verdonschot, P.F.M.

    2001-01-01

    In most soft-bottomed, lowland streams in the Netherlands discharge regimes largely follow the precipitation pattern. Winter discharges are higher and much more dynamic then summer discharges, although rain storms throughout the year cause unexpected peak flows. Minimal precipitation, reduced stream

  4. Numerical study of acoustic streaming and radiation forces on micro particles

    DEFF Research Database (Denmark)

    Jensen, Mads Jakob Herring; Muller, Peter Barkholt; Barnkob, Rune

    2012-01-01

    , and 2) Stokes drag from the induced acoustic streaming flow. Both effects are second order and require the solution of the full linearized Navier-Stokes equation in order to be captured correctly. The model shows the transition from streaming drag to radiation force dominated regimes. The transition...

  5. Optimal ranking regime analysis of U.S. climate variablility. Part II: Precipitation and streamflow

    Science.gov (United States)

    In a preceding companion paper the Optimal Ranking Regime (ORR) method was used to identify intra- to multi-decadal (IMD) regimes in U.S. climate division temperature data during 1896-2012. Here, the method is used to test for annual and seasonal precipitation regimes during that same period. In add...

  6. Spatial simulation of smallmouth bass in streams

    International Nuclear Information System (INIS)

    Jager, H.I.; Schmoyer, D.D.; Sale, M.J.; Van Winkle, W.; DeAngelis, D.L.; Sabo, M.J.

    1993-01-01

    The hydropower industry and its regulators are hampered by the inability to predict the relationship between alternative flow regimes and fish population response. We have developed a spatially explicit, individual-based model of populations of small-mouth bass in streams as part of the Compensatory Mechanisms in Fish Populations Program (see Sale and Otto 1991). In the model, the profitability of alternative stream locations varies in response to habitat depth and velocity through changes in the frequency of prey encounters and the metabolic costs experienced by fish. We conducted an evaluation of our hydraulic simulation at the scale of individual stream cells. The potential error in predictions for individual cell velocities suggests that larger-scale model predictions for the representative reach are most appropriate. At this scale, the model appears to produce realistic patterns in the growth and dispersal of young-of-year small-mouth bass. This verification step allows us to proceed with greater confidence in evaluating the original question of how small-mouth bass populations respond to alternative flow regimes

  7. High resolution stream water quality assessment in the Vancouver, British Columbia region: a citizen science study.

    Science.gov (United States)

    Shupe, Scott M

    2017-12-15

    Changing land cover and climate regimes modify water quantity and quality in natural stream systems. In regions undergoing rapid change, it is difficult to effectively monitor and quantify these impacts at local to regional scales. In Vancouver, British Columbia, one of the most rapidly urbanizing areas in Canada, 750 measurements were taken from a total of 81 unique sampling sites representing 49 streams located in urban, forest, and agricultural-dominant watersheds at a frequency of up to 12 times per year between 2013 and 2016. Dissolved nitrate (NO 3 -N) and phosphate (PO 4 -P) concentrations, turbidity, water temperature, pH and conductivity were measured by citizen scientists in addition to observations of hydrology, vegetation, land use, and visible stream impacts. Land cover was mapped at a 15-m resolution using Landsat 8 OLI imagery and used to determine dominant land cover for each watershed in which a sample was recorded. Regional, seasonal, and catchment-type trends in measurements were determined using statistical analyses. The relationships of nutrients to land cover varied seasonally and on a catchment-type basis. Nitrate showed seasonal highs in winter and lows in summer, though phosphate had less seasonal variation. Overall, nitrate concentrations were positively associated to agriculture and deciduous forest and negatively associated with coniferous forest. In contrast, phosphate concentrations were positively associated with agricultural, deciduous forest, and disturbed land cover and negatively associated with urban land cover. Both urban and agricultural land cover were significantly associated with an increase in water conductivity. Increased forest land cover was associated with better water quality, including lower turbidity, conductivity, and water temperature. This study showed the importance of high resolution sampling in understanding seasonal and spatial dynamics of stream water quality, made possible with the large number of

  8. Winter feeding, growth and condition of brown trout Salmo trutta in a groundwater-dominated stream

    Science.gov (United States)

    French, William E.; Vondracek, Bruce C.; Ferrington, Leonard C.; Finlay, Jacques C.; Dieterman, Douglas J.

    2014-01-01

    Winter can be a stressful period for stream-dwelling salmonid populations, often resulting in reduced growth and survival. Stream water temperatures have been identified as a primary mechanism driving reductions in fitness during winter. However, groundwater inputs can moderate water temperature and may reduce winter severity. Additionally, seasonal reductions in prey availability may contribute to decreased growth and survival, although few studies have examined food webs supporting salmonids under winter conditions. This study employed diet, stable isotope, and mark-recapture techniques to examine winter (November through March) feeding, growth, and condition of brown troutSalmo trutta in a groundwater-dominated stream (Badger Creek, Minnesota, USA). Growth was greater for fish ≤ 150 mm (mean = 4.1 mg g−1 day−1) than for those 151–276 mm (mean = 1.0 mg g−1 day−1) during the winter season. Overall condition from early winter to late winter did not vary for fish ≤150 mm (mean relative weight (Wr) = 89.5) and increased for those 151–276 mm (mean Wr = 85.8 early and 89.4 late). Although composition varied both temporally and by individual, brown trout diets were dominated by aquatic invertebrates, primarily Amphipods, Dipterans, and Trichopterans. Stable isotope analysis supported the observations of the dominant prey taxa in stomach contents and indicated the winter food web was supported by a combination of allochthonous inputs and aquatic macrophytes. Brown trout in Badger Creek likely benefited from the thermal regime and increased prey abundance present in this groundwater-dominated stream during winter.

  9. Effects of urban stream burial on nitrogen uptake and ...

    Science.gov (United States)

    Urbanization has resulted in extensive burial and channelization of headwater streams, yet little is known about impacts on stream ecosystem functions critical for reducing downstream nitrogen pollution. To characterize the biogeochemical impact of stream burial, we measured NO3- uptake, using 15N-NO3- isotope tracer releases, and whole stream metabolism, during four seasons in three paired buried and open streams reaches within the Baltimore Ecosystem Study Long-term Ecological Research Network. Stream burial increased NO3- uptake lengths, by a factor of 7.5 (p < 0.01) and decreased nitrate uptake velocity and areal nitrate uptake rate by factors of 8.2 (p = 0.01) and 9.6 (p < 0.001), respectively. Stream burial decreased gross primary productivity by a factor of 9.2 (p < 0.05) and decreased ecosystem respiration by a factor of 4.2 (p = 0.06). From statistical analysis of Excitation Emissions Matrices (EEMs), buried streams were also found to have significantly less labile dissolved organic matter. Furthermore, buried streams had significantly lower transient storage and water temperatures. Overall, differences in NO3- uptake and metabolism were primarily explained by decreased transient storage and light availability in buried streams. We estimate that stream burial increases daily watershed nitrate export by as much as 500% due to decreased in-stream retention and may considerably decrease carbon export via decreased primary production. These results

  10. LHCb trigger streams optimization

    Science.gov (United States)

    Derkach, D.; Kazeev, N.; Neychev, R.; Panin, A.; Trofimov, I.; Ustyuzhanin, A.; Vesterinen, M.

    2017-10-01

    The LHCb experiment stores around 1011 collision events per year. A typical physics analysis deals with a final sample of up to 107 events. Event preselection algorithms (lines) are used for data reduction. Since the data are stored in a format that requires sequential access, the lines are grouped into several output file streams, in order to increase the efficiency of user analysis jobs that read these data. The scheme efficiency heavily depends on the stream composition. By putting similar lines together and balancing the stream sizes it is possible to reduce the overhead. We present a method for finding an optimal stream composition. The method is applied to a part of the LHCb data (Turbo stream) on the stage where it is prepared for user physics analysis. This results in an expected improvement of 15% in the speed of user analysis jobs, and will be applied on data to be recorded in 2017.

  11. Asteroid/meteorite streams

    Science.gov (United States)

    Drummond, J.

    The independent discovery of the same three streams (named alpha, beta, and gamma) among 139 Earth approaching asteroids and among 89 meteorite producing fireballs presents the possibility of matching specific meteorites to specific asteroids, or at least to asteroids in the same stream and, therefore, presumably of the same composition. Although perhaps of limited practical value, the three meteorites with known orbits are all ordinary chondrites. To identify, in general, the taxonomic type of the parent asteroid, however, would be of great scientific interest since these most abundant meteorite types cannot be unambiguously spectrally matched to an asteroid type. The H5 Pribram meteorite and asteroid 4486 (unclassified) are not part of a stream, but travel in fairly similar orbits. The LL5 Innisfree meteorite is orbitally similar to asteroid 1989DA (unclassified), and both are members of a fourth stream (delta) defined by five meteorite-dropping fireballs and this one asteroid. The H5 Lost City meteorite is orbitally similar to 1980AA (S type), which is a member of stream gamma defined by four asteroids and four fireballs. Another asteroid in this stream is classified as an S type, another is QU, and the fourth is unclassified. This stream suggests that ordinary chondrites should be associated with S (and/or Q) asteroids. Two of the known four V type asteroids belong to another stream, beta, defined by five asteroids and four meteorite-dropping (but unrecovered) fireballs, making it the most probable source of the eucrites. The final stream, alpha, defined by five asteroids and three fireballs is of unknown composition since no meteorites have been recovered and only one asteroid has an ambiguous classification of QRS. If this stream, or any other as yet undiscovered ones, were found to be composed of a more practical material (e.g., water or metalrich), then recovery of the associated meteorites would provide an opportunity for in-hand analysis of a potential

  12. Characterization of fluidization regime in circulating fluidized bed reactor with high solid particle concentration using computational fluid dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Chalermsinsuwan, Benjapon; Thummakul, Theeranan; Piumsomboon, Pornpote [Chulalongkorn University, Bangkok (Thailand); Gidaspow, Dimitri [Armour College of Engineering, Chicago (United States)

    2014-02-15

    The hydrodynamics inside a high solid particle concentration circulating fluidized bed reactor was investigated using computational fluid dynamics simulation. Compared to a low solid particle reactor, all the conventional fluidization regimes were observed. In addition, two unconventional fluidization regimes, circulating-turbulent and dense suspension bypassing regimes, were found with only primary gas injection. The circulating-turbulent fluidization regime showed uniformly dense solid particle distribution in all the system directions, while the dense suspension bypassing fluidization regime exhibited the flow of solid particles at only one side system wall. Then, comprehensive fluidization regime clarification and mapping were evaluated using in-depth system parameters. In the circulating-turbulent fluidization regime, the total granular temperature was low compared to the adjacent fluidization regimes. In the dense suspension bypassing fluidization regime, the highest total granular temperature was obtained. The circulating-turbulent and dense suspension bypassing fluidization regimes are suitable for sorption and transportation applications, respectively.

  13. Process-based humidity control regime for greenhouse crops

    NARCIS (Netherlands)

    Korner, O.; Challa, H.

    2003-01-01

    Modern greenhouses in The Netherlands are designed for efficient use of energy. Climate control traditionally aims at optimal crop performance. However, energy saving is a major issue for the development of new temperature regimes. Temperature integration (TI) results in fluctuating and often high

  14. Deforestation and stream warming affect body size of Amazonian fishes.

    Science.gov (United States)

    Ilha, Paulo; Schiesari, Luis; Yanagawa, Fernando I; Jankowski, KathiJo; Navas, Carlos A

    2018-01-01

    Declining body size has been suggested to be a universal response of organisms to rising temperatures, manifesting at all levels of organization and in a broad range of taxa. However, no study to date evaluated whether deforestation-driven warming could trigger a similar response. We studied changes in fish body size, from individuals to assemblages, in streams in Southeastern Amazonia. We first conducted sampling surveys to validate the assumption that deforestation promoted stream warming, and to test the hypothesis that warmer deforested streams had reduced fish body sizes relative to cooler forest streams. As predicted, deforested streams were up to 6 °C warmer and had fish 36% smaller than forest streams on average. This body size reduction could be largely explained by the responses of the four most common species, which were 43-55% smaller in deforested streams. We then conducted a laboratory experiment to test the hypothesis that stream warming as measured in the field was sufficient to cause a growth reduction in the dominant fish species in the region. Fish reared at forest stream temperatures gained mass, whereas those reared at deforested stream temperatures lost mass. Our results suggest that deforestation-driven stream warming is likely to be a relevant factor promoting observed body size reductions, although other changes in stream conditions, like reductions in organic matter inputs, can also be important. A broad scale reduction in fish body size due to warming may be occurring in streams throughout the Amazonian Arc of Deforestation, with potential implications for the conservation of Amazonian fish biodiversity and food supply for people around the Basin.

  15. Deforestation and stream warming affect body size of Amazonian fishes

    Science.gov (United States)

    Yanagawa, Fernando I.; Jankowski, KathiJo; Navas, Carlos A.

    2018-01-01

    Declining body size has been suggested to be a universal response of organisms to rising temperatures, manifesting at all levels of organization and in a broad range of taxa. However, no study to date evaluated whether deforestation-driven warming could trigger a similar response. We studied changes in fish body size, from individuals to assemblages, in streams in Southeastern Amazonia. We first conducted sampling surveys to validate the assumption that deforestation promoted stream warming, and to test the hypothesis that warmer deforested streams had reduced fish body sizes relative to cooler forest streams. As predicted, deforested streams were up to 6 °C warmer and had fish 36% smaller than forest streams on average. This body size reduction could be largely explained by the responses of the four most common species, which were 43–55% smaller in deforested streams. We then conducted a laboratory experiment to test the hypothesis that stream warming as measured in the field was sufficient to cause a growth reduction in the dominant fish species in the region. Fish reared at forest stream temperatures gained mass, whereas those reared at deforested stream temperatures lost mass. Our results suggest that deforestation-driven stream warming is likely to be a relevant factor promoting observed body size reductions, although other changes in stream conditions, like reductions in organic matter inputs, can also be important. A broad scale reduction in fish body size due to warming may be occurring in streams throughout the Amazonian Arc of Deforestation, with potential implications for the conservation of Amazonian fish biodiversity and food supply for people around the Basin. PMID:29718960

  16. Gravel bar thermal variability and its potential consequences for CO2 evasion from Alpine coldwater streams

    Science.gov (United States)

    Boodoo, Kyle; Battin, Tom; Schelker, Jakob

    2017-04-01

    CO2 evasion. Furthermore, catchment CO2 outgassing fluxes significantly exceeded that of the stream, with higher diurnal CO2 outgassing fluxes observed for all 13 GBs within the Ybbs and Erlauf catchments as compared to their respective streams. We found DOC concentration did not significantly correlate to CO2 outgassing. But, vertical temperature gradient as a measure of heat flux to the hyporheic zone explained 55% and 69% of the variability in observed CO2 efflux from the OSB gravel bar (seasonal samplings during summer 2015 - winter 2016) and 11 catchment gravel bars (2 GBs excluded due to equipment malfunction) respectively. These results highlight the effect of temperature on physical and biochemical stream processes, particularly in cold-water streams, due to the occurrence of more frequent and intense warm temperature events, as well as altered flow regimes, likely consequences of climatic change.

  17. Principles for urban stormwater management to protect stream ecosystems

    Science.gov (United States)

    Walsh, Christopher J.; Booth, Derek B.; Burns, Matthew J.; Fletcher, Tim D.; Hale, Rebecca L.; Hoang, Lan N.; Livingston, Grant; Rippy, Megan A.; Roy, Allison; Scoggins, Mateo; Wallace, Angela

    2016-01-01

    Urban stormwater runoff is a critical source of degradation to stream ecosystems globally. Despite broad appreciation by stream ecologists of negative effects of stormwater runoff, stormwater management objectives still typically center on flood and pollution mitigation without an explicit focus on altered hydrology. Resulting management approaches are unlikely to protect the ecological structure and function of streams adequately. We present critical elements of stormwater management necessary for protecting stream ecosystems through 5 principles intended to be broadly applicable to all urban landscapes that drain to a receiving stream: 1) the ecosystems to be protected and a target ecological state should be explicitly identified; 2) the postdevelopment balance of evapotranspiration, stream flow, and infiltration should mimic the predevelopment balance, which typically requires keeping significant runoff volume from reaching the stream; 3) stormwater control measures (SCMs) should deliver flow regimes that mimic the predevelopment regime in quality and quantity; 4) SCMs should have capacity to store rain events for all storms that would not have produced widespread surface runoff in a predevelopment state, thereby avoiding increased frequency of disturbance to biota; and 5) SCMs should be applied to all impervious surfaces in the catchment of the target stream. These principles present a range of technical and social challenges. Existing infrastructural, institutional, or governance contexts often prevent application of the principles to the degree necessary to achieve effective protection or restoration, but significant potential exists for multiple co-benefits from SCM technologies (e.g., water supply and climate-change adaptation) that may remove barriers to implementation. Our set of ideal principles for stream protection is intended as a guide for innovators who seek to develop new approaches to stormwater management rather than accept seemingly

  18. Percent Forest Adjacent to Streams

    Data.gov (United States)

    U.S. Environmental Protection Agency — The type of vegetation along a stream influences the water quality in the stream. Intact buffer strips of natural vegetation along streams tend to intercept...

  19. Percent Agriculture Adjacent to Streams

    Data.gov (United States)

    U.S. Environmental Protection Agency — The type of vegetation along a stream influences the water quality in the stream. Intact buffer strips of natural vegetation along streams tend to intercept...

  20. Influence of Flow Regulation on Summer Water Temperature: Sauce Grande River, Argentina

    Science.gov (United States)

    Casado, A.; Hannah, D. M.; Peiry, J.; Campo, A. M.

    2012-12-01

    This study quantifies the effects of the Paso de las Piedras Dam on the thermal behaviour of the Sauce Grande River, Argentina, during a summer season. A 30-day data set of continuous hourly data was assembled for eight stream temperature gauging sites deployed above and below the impoundment. Time series span the hottest period recorded during summer 2009 to evaluate variations in river water temperature under strong meteorological influence. The methods include: (i) analysis of the time series by inspecting the absolute differences in daily data (magnitude, timing, frequency, duration and rate of change), (ii) classification of diurnal regimes by using a novel regime 'shape' and 'magnitude' classifying method (RSMC), and (ii) quantification of the sensitivity of water temperature regimes to air temperature by computation of a novel sensitivity index (SI). Results showed that fluctuations in daily water temperatures were linked to meteorological drivers; however, spatial variability in the shape and the magnitude of the thermographs revealed the effects of the impoundment in regulating the thermal behaviour of the river downstream. An immediate cooling effect below the dam was evident. Mean daily temperatures were reduced in up to 4 °C, and described a warming trend in the downstream direction over a distance of at least 15 km (up to +2.3 °C). Diurnal cycles were reduced in amplitude and delayed in timing, and revealed a dominance of regime magnitude stability and regime shape climatic insensitivity over a distance of 8 km downstream. These findings provide new information about the water quality of the Sauce Grande River and inform management of flows to maintain the ecological integrity of the river system. Also, they motivate further analysis of potential correlates under varying hydrological and meteorological conditions. The methods presented herein have wider applicability for quantifying river thermal regimes and their sensitivity to climate and other

  1. On the dynamics of stream piracy

    Science.gov (United States)

    Goren, L.; Willett, S. D.

    2012-04-01

    Drainage network reorganization by stream piracy is invoked repeatedly to explain the morphology of unique drainage patterns and as a possible mechanism inducing abrupt variations of sediment accumulation rates. However, direct evidence of stream piracy is usually rare, and is highly interpretation dependent. As a first step in assessing how probable capture events are and establishing the conditions that favor stream piracy versus the those that favor stable landscapes, we formulate analytically the physics of divide migration and capture events and study this formulation from a dynamical system point of view. The formulation is based on a one-dimensional topographic cross section between two channels that share a water divide. Two hillslope profiles diverge from the divide and drain into two fluvial bedrock tributaries, whose erosion rate is controlled by a stream power law. The rate of erosion at the bounding channels is thus a function of the upstream drainage area and local slope. A tectonically induced downward perturbation of the elevation of one of the bounding channels lowers the channel slope but at the same time increases the drainage area due to outward migration of the water divide. The changes in slope and area have opposing effect on the erosion rate at the bounding channels, so that the perturbation may either grow or be damped. We define the geomorphic and tectonic parameters that control the behavior of the system and find the regimes that lead to stable landscapes and to capture events.

  2. Transient regimes in a heavy water reactor; Regimes transitoires dans un reacteur a eau lourde

    Energy Technology Data Exchange (ETDEWEB)

    Raievski, V [Commissariat a l' Energie Atomique, Saclay(France). Centre d' Etudes Nucleaires

    1953-07-01

    We studied the variations of power and reactivity of a reactor when we raise in a continuous way the starting plates. During the subcritical regime (negative reactivity), the power is determined by reactivity and by the intensity of the sources of photo neutrons, produced during the previous work of the reactor. When, during the rise of the plates, the reactor, pass by the critical regime (zero reactivity), one notes that the reached power is independent of the initial reactivity. During the sur-critical regime (positive reactivity), the elevation of temperature of the uranium bars slows down the growth of reactivity due to the movements of the plates. The power stretches then toward a value that depends only on the regime of cooling of the reactor and the excess of the available reactivity. This survey permits to choose such a rise speed, that reactivity remains constantly lower to a value beyond which the piloting of the reactor becomes difficult. This result is not more valid, if the intensity of the sources is insufficient, what takes place during the first divergences and after a stop of long length. (author) [French] On etudie les variations de puissance et de reactivite d'un reacteur quand on leve d'une facon continue les plaques de demarrage. Pendant le regime subcritique (reactivite negative), la puissance est determinee par la reactivite et par l'intensite des sources de photoneutrons, produites pendant la marche anterieure du reacteur. Quand, au cours de la montee des plaques, le reacteur passe par le regime critique (reactivite nulle), on constate que la puissance atteinte est independante de la reactivite initiale. Pendant le regime surcritique (reactivite positive), l'elevation de temperature des barres d'uranium ralentit l'accroissement de reactivite due aux mouvements des plaques. La puissance tend alors vers une valeur qui ne depend plus que du regime de refroidissement du reacteur et de l'exces de la reactivite disponible. Cette etude permet de

  3. Wadeable Streams Assessment Data

    Science.gov (United States)

    The Wadeable Streams Assessment (WSA) is a first-ever statistically-valid survey of the biological condition of small streams throughout the U.S. The U.S. Environmental Protection Agency (EPA) worked with the states to conduct the assessment in 2004-2005. Data for each parameter sampled in the Wadeable Streams Assessment (WSA) are available for downloading in a series of files as comma separated values (*.csv). Each *.csv data file has a companion text file (*.txt) that lists a dataset label and individual descriptions for each variable. Users should view the *.txt files first to help guide their understanding and use of the data.

  4. Current US nuclear liability regime

    International Nuclear Information System (INIS)

    Brown, O.F.

    2000-01-01

    The Price-Anderson Act Adopted by US Congress in 1957 as the world's first national nuclear liability regime. It is a comprehensive, complicated and unique system and stems from special features of US legal regime and federal system of government. It differs from other systems by providing for 'economic', not legal; channeling of liability to facility operator and not recommended as model for other states, but most features adopted by other states and international conventions

  5. Totalitäre Regimes

    OpenAIRE

    Merkel, Wolfgang

    2004-01-01

    "The development of the term and the analytical concept of totalitarianism have gone through several stages since the 1920s. However, even in its most sophisticated form, the version seen in Friedrich/ Brzezinski, the concept exhibits substantial systematic classification problems and analytical weaknesses. This article attempts to frame the type of totalitarian regime within a general typology of political regimes. Special attention is dedicated to the problem of distinguishing autocra...

  6. Endogenous Monetary Policy Regime Change

    OpenAIRE

    Troy Davig; Eric M. Leeper

    2006-01-01

    This paper makes changes in monetary policy rules (or regimes) endogenous. Changes are triggered when certain endogenous variables cross specified thresholds. Rational expectations equilibria are examined in three models of threshold switching to illustrate that (i) expectations formation effects generated by the possibility of regime change can be quantitatively important; (ii) symmetric shocks can have asymmetric effects; (iii) endogenous switching is a natural way to formally model preempt...

  7. Future Roads Near Streams

    Data.gov (United States)

    U.S. Environmental Protection Agency — Roads are a source of auto related pollutants (e.g. gasoline, oil and other engine fluids). When roads are near streams, rain can wash these pollutants directly into...

  8. Channelized Streams in Iowa

    Data.gov (United States)

    Iowa State University GIS Support and Research Facility — This draft dataset consists of all ditches or channelized pieces of stream that could be identified using three input datasets; namely the1:24,000 National...

  9. Roads Near Streams

    Data.gov (United States)

    U.S. Environmental Protection Agency — Roads are a source of auto related pollutants (e.g. gasoline, oil and other engine fluids). When roads are near streams, rain can wash these pollutants directly into...

  10. Streaming tearing mode

    Science.gov (United States)

    Shigeta, M.; Sato, T.; Dasgupta, B.

    1985-01-01

    The magnetohydrodynamic stability of streaming tearing mode is investigated numerically. A bulk plasma flow parallel to the antiparallel magnetic field lines and localized in the neutral sheet excites a streaming tearing mode more strongly than the usual tearing mode, particularly for the wavelength of the order of the neutral sheet width (or smaller), which is stable for the usual tearing mode. Interestingly, examination of the eigenfunctions of the velocity perturbation and the magnetic field perturbation indicates that the streaming tearing mode carries more energy in terms of the kinetic energy rather than the magnetic energy. This suggests that the streaming tearing mode instability can be a more feasible mechanism of plasma acceleration than the usual tearing mode instability.

  11. DNR 24K Streams

    Data.gov (United States)

    Minnesota Department of Natural Resources — 1:24,000 scale streams captured from USGS seven and one-half minute quadrangle maps, with perennial vs. intermittent classification, and connectivity through lakes,...

  12. Trout Stream Special Regulations

    Data.gov (United States)

    Minnesota Department of Natural Resources — This layer shows Minnesota trout streams that have a special regulation as described in the 2006 Minnesota Fishing Regulations. Road crossings were determined using...

  13. Scientific stream pollution analysis

    National Research Council Canada - National Science Library

    Nemerow, Nelson Leonard

    1974-01-01

    A comprehensive description of the analysis of water pollution that presents a careful balance of the biological,hydrological, chemical and mathematical concepts involved in the evaluation of stream...

  14. Acoustic and streaming velocity components in a resonant waveguide at high acoustic levels.

    Science.gov (United States)

    Daru, Virginie; Reyt, Ida; Bailliet, Hélène; Weisman, Catherine; Baltean-Carlès, Diana

    2017-01-01

    Rayleigh streaming is a steady flow generated by the interaction between an acoustic wave and a solid wall, generally assumed to be second order in a Mach number expansion. Acoustic streaming is well known in the case of a stationary plane wave at low amplitude: it has a half-wavelength spatial periodicity and the maximum axial streaming velocity is a quadratic function of the acoustic velocity amplitude at antinode. For higher acoustic levels, additional streaming cells have been observed. Results of laser Doppler velocimetry measurements are here compared to direct numerical simulations. The evolution of axial and radial velocity components for both acoustic and streaming velocities is studied from low to high acoustic amplitudes. Two streaming flow regimes are pointed out, the axial streaming dependency on acoustics going from quadratic to linear. The evolution of streaming flow is different for outer cells and for inner cells. Also, the hypothesis of radial streaming velocity being of second order in a Mach number expansion, is not valid at high amplitudes. The change of regime occurs when the radial streaming velocity amplitude becomes larger than the radial acoustic velocity amplitude, high levels being therefore characterized by nonlinear interaction of the different velocity components.

  15. Collaborative Media Streaming

    OpenAIRE

    Kahmann, Verena

    2008-01-01

    Mit Hilfe der IP-Technologie erbrachte Multimedia-Dienste wie IPTV oder Video-on-Demand sind zur Zeit ein gefragtes Thema. Technisch werden solche Dienste unter dem Begriff "Streaming" eingeordnet. Ein Server sendet Mediendaten kontinuierlich an Empfänger, welche die Daten sofort weiterverarbeiten und anzeigen. Über einen Rückkanal hat der Kunde die Möglichkeit der Einflussnahme auf die Wiedergabe. Eine Weiterentwicklung dieser Streaming-Dienste ist die Möglichkeit, gemeinsam mit anderen dens...

  16. Jet Noise Scaling in Dual Stream Nozzles

    Science.gov (United States)

    Khavaran, Abbas; Bridges, James

    2010-01-01

    Power spectral laws in dual stream jets are studied by considering such flows a superposition of appropriate single-stream coaxial jets. Noise generation in each mixing region is modeled using spectral power laws developed earlier for single stream jets as a function of jet temperature and observer angle. Similarity arguments indicate that jet noise in dual stream nozzles may be considered as a composite of four single stream jets representing primary/secondary, secondary/ambient, transition, and fully mixed zones. Frequency filter are designed to highlight spectral contribution from each jet. Predictions are provided at an area ratio of 2.0--bypass ratio from 0.80 to 3.40, and are compared with measurements within a wide range of velocity and temperature ratios. These models suggest that the low frequency noise in unheated jets is dominated by the fully mixed region at all velocity ratios, while the high frequency noise is dominated by the secondary when the velocity ratio is larger than 0.80. Transition and fully mixed jets equally dominate the low frequency noise in heated jets. At velocity ratios less than 0.50, the high frequency noise from primary/bypass becomes a significant contributing factor similar to that in the secondary/ambient jet.

  17. Rotenone persistence model for montane streams

    Science.gov (United States)

    Brown, Peter J.; Zale, Alexander V.

    2012-01-01

    The efficient and effective use of rotenone is hindered by its unknown persistence in streams. Environmental conditions degrade rotenone, but current label instructions suggest fortifying the chemical along a stream based on linear distance or travel time rather than environmental conditions. Our objective was to develop models that use measurements of environmental conditions to predict rotenone persistence in streams. Detailed measurements of ultraviolet radiation, water temperature, dissolved oxygen, total dissolved solids (TDS), conductivity, pH, oxidation–reduction potential (ORP), substrate composition, amount of organic matter, channel slope, and travel time were made along stream segments located between rotenone treatment stations and cages containing bioassay fish in six streams. The amount of fine organic matter, biofilm, sand, gravel, cobble, rubble, small boulders, slope, pH, TDS, ORP, light reaching the stream, energy dissipated, discharge, and cumulative travel time were each significantly correlated with fish death. By using logistic regression, measurements of environmental conditions were paired with the responses of bioassay fish to develop a model that predicted the persistence of rotenone toxicity in streams. This model was validated with data from two additional stream treatment reaches. Rotenone persistence was predicted by a model that used travel time, rubble, and ORP. When this model predicts a probability of less than 0.95, those who apply rotenone can expect incomplete eradication and should plan on fortifying rotenone concentrations. The significance of travel time has been previously identified and is currently used to predict rotenone persistence. However, rubble substrate, which may be associated with the degradation of rotenone by adsorption and volatilization in turbulent environments, was not previously considered.

  18. Transition from weak wave turbulence regime to solitonic regime

    Science.gov (United States)

    Hassani, Roumaissa; Mordant, Nicolas

    2017-11-01

    The Weak Turbulence Theory (WTT) is a statistical theory describing the interaction of a large ensemble of random waves characterized by very different length scales. For both weak non-linearity and weak dispersion a different regime is predicted where solitons propagate while keeping their shape unchanged. The question under investigation here is which regime between weak turbulence or soliton gas does the system choose ? We report an experimental investigation of wave turbulence at the surface of finite depth water in the gravity-capillary range. We tune the wave dispersion and the level of nonlinearity by modifying the depth of water and the forcing respectively. We use space-time resolved profilometry to reconstruct the deformed surface of water. When decreasing the water depth, we observe a drastic transition between weak turbulence at the weakest forcing and a solitonic regime at stronger forcing. We characterize the transition between both states by studying their Fourier Spectra. We also study the efficiency of energy transfer in the weak turbulence regime. We report a loss of efficiency of angular transfer as the dispersion of the wave is reduced until the system bifurcates into the solitonic regime. This project has recieved funding from the European Research Council (ERC, Grant Agreement No. 647018-WATU).

  19. Measurements of the movement of the jet streams at mid-latitudes, in the Northern and Southern Hemispheres, 1979 to 2010

    Directory of Open Access Journals (Sweden)

    R. D. Hudson

    2012-08-01

    Full Text Available Previous studies have shown that the mean latitude of the sub-tropical jet streams in both hemispheres have shifted toward the poles over the last few decades. This paper presents a study of the movement of both the subtropical and Polar fronts, the location of the respective jet streams, between 1979 and 2010 at mid-latitudes, using total ozone measurements to identify the sharp horizontal boundary that occurs at the position of the fronts. Previous studies have shown that the two fronts are the boundaries of three distinct regimes in the stratosphere, corresponding to the Hadley, Ferrel, and polar meridionally overturning circulation cells in the troposphere. Over the period of study the horizontal area of the Hadley cell has increased at latitudes between 20 and 60 degrees while the area of the Polar cell has decreased. A linear regression analysis was performed to identify the major factors associated with the movement of the subtropical jet streams. These were: (1 changes in the Tropical land plus ocean temperature, (2 direct radiative forcing from greenhouse gases in the troposphere, (3 changes in the temperature of the lower tropical stratosphere, (4 the Quasi-Biennial Oscillation, and (5 volcanic eruptions. The dominant mechanism was the direct radiative forcing from greenhouse gases. Between 1979 and 2010 the poleward movement of the subtropical jet streams was 3.7 ± 0.3 degrees in the Northern Hemisphere and 6.5 ± 0.2 degrees in the Southern Hemisphere. Previous studies have shown that weather systems tend to follow the jet streams. The observed poleward movement in both hemispheres over the past thirty years represents a significant change in the position of the sub-tropical jet streams, which should lead to significant latitudinal shifts in the global weather patterns and the hydrologic cycle.

  20. Streaming Pool: reuse, combine and create reactive streams with pleasure

    CERN Multimedia

    CERN. Geneva

    2017-01-01

    When connecting together heterogeneous and complex systems, it is not easy to exchange data between components. Streams of data are successfully used in industry in order to overcome this problem, especially in the case of "live" data. Streams are a specialization of the Observer design pattern and they provide asynchronous and non-blocking data flow. The ongoing effort of the ReactiveX initiative is one example that demonstrates how demanding this technology is even for big companies. Bridging the discrepancies of different technologies with common interfaces is already done by the Reactive Streams initiative and, in the JVM world, via reactive-streams-jvm interfaces. Streaming Pool is a framework for providing and discovering reactive streams. Through the mechanism of dependency injection provided by the Spring Framework, Streaming Pool provides a so called Discovery Service. This object can discover and chain streams of data that are technologically agnostic, through the use of Stream IDs. The stream to ...

  1. Wind-Driven Ecological Flow Regimes Downstream from Hydropower Dams

    Science.gov (United States)

    Kern, J.; Characklis, G. W.

    2012-12-01

    Conventional hydropower can be turned on and off quicker and less expensively than thermal generation (coal, nuclear, or natural gas). These advantages enable hydropower utilities to respond to rapid fluctuations in energy supply and demand. More recently, a growing renewable energy sector has underlined the need for flexible generation capacity that can complement intermittent renewable resources such as wind power. While wind power entails lower variable costs than other types of generation, incorporating it into electric power systems can be problematic. Due to variable and unpredictable wind speeds, wind power is difficult to schedule and must be used when available. As a result, integrating large amounts of wind power into the grid may result in atypical, swiftly changing demand patterns for other forms of generation, placing a premium on sources that can be rapidly ramped up and down. Moreover, uncertainty in wind power forecasts will stipulate increased levels of 'reserve' generation capacity that can respond quickly if real-time wind supply is less than expected. These changes could create new hourly price dynamics for energy and reserves, altering the short-term financial signals that hydroelectric dam operators use to schedule water releases. Traditionally, hourly stream flow patterns below hydropower dams have corresponded in a very predictable manner to electricity demand, whose primary factors are weather (hourly temperature) and economic activity (workday hours). Wind power integration has the potential to yield more variable, less predictable flows at hydro dams, flows that at times could resemble reciprocal wind patterns. An existing body of research explores the impacts of standard, demand-following hydroelectric dams on downstream ecological flows; but weighing the benefits of increased reliance on wind power against further impacts to ecological flows may be a novel challenge for the environmental community. As a preliminary step in meeting this

  2. Pasture size effects on the ability of off-stream water or restricted stream access to alter the spatial/temporal distribution of grazing beef cows.

    Science.gov (United States)

    Bisinger, J J; Russell, J R; Morrical, D G; Isenhart, T M

    2014-08-01

    For 2 grazing seasons, effects of pasture size, stream access, and off-stream water on cow distribution relative to a stream were evaluated in six 12.1-ha cool-season grass pastures. Two pasture sizes (small [4.0 ha] and large [12.1 ha]) with 3 management treatments (unrestricted stream access without off-stream water [U], unrestricted stream access with off-stream water [UW], and stream access restricted to a stabilized stream crossing [R]) were alternated between pasture sizes every 2 wk for 5 consecutive 4-wk intervals in each grazing season. Small and large pastures were stocked with 5 and 15 August-calving cows from mid May through mid October. At 10-min intervals, cow location was determined with Global Positioning System collars fitted on 2 to 3 cows in each pasture and identified when observed in the stream (0-10 m from the stream) or riparian (0-33 m from the stream) zones and ambient temperature was recorded with on-site weather stations. Over all intervals, cows were observed more (P ≤ 0.01) frequently in the stream and riparian zones of small than large pastures regardless of management treatment. Cows in R pastures had 24 and 8% less (P cows in or near pasture streams regardless of pasture size. In 2011, the probability of cow presence in the stream and riparian zones increased at greater (P cow presence in the stream and riparian zones increased at greater (P cow presence in the stream and riparian zone increased less (P cow presence in shade (within 10 m of tree drip lines) in the total pasture with increasing temperatures did not differ between treatments. However, probability of cow presence in riparian shade increased at greater (P cows in or near pasture streams with unrestricted access.

  3. Streams and their future inhabitants

    DEFF Research Database (Denmark)

    Sand-Jensen, K.; Friberg, Nikolai

    2006-01-01

    In this fi nal chapter we look ahead and address four questions: How do we improve stream management? What are the likely developments in the biological quality of streams? In which areas is knowledge on stream ecology insuffi cient? What can streams offer children of today and adults of tomorrow?...

  4. A climatology of low level wind regimes over Central America using a weather type classification approach.

    Directory of Open Access Journals (Sweden)

    Fernán eSáenz

    2015-04-01

    Full Text Available Based on the potential of the weather types classification method to study synoptic features, this study proposes the application of such methodology for the identification of the main large scale patterns related with weather in Central America. Using ERA Interim low-level winds in a domain that encompasses the intra-Americas sea, the eastern tropical Pacific, southern North America, Central America and northern South America; the K-means clustering algorithm was applied to find recurrent regimes of low-level winds. Eleven regimes were identified and good coherency between the results and known features of regional circulation was found. It was determined that the main large scale patterns can be either locally forced or a response to tropical-extratropical interactions. Moreover, the local forcing dominates the summer regimes whereas mid latitude interactions lead winter regimes. The study of the relationship between the large scale patterns and regional precipitation shows that winter regimes are related with the Caribbean-Pacific precipitation seesaw. Summer regimes, on the other hand, enhance the Caribbean-Pacific precipitation contrasting distribution as a function of the dominant regimes. A strong influence of ENSO on the frequency and duration of the regimes was found. It was determined that the specific effect of ENSO on the regimes depends on whether the circulation is locally forced or lead by the interaction between the tropics and the mid-latitudes. The study of the cold surges using the information of the identified regimes revealed that three regimes are linkable with the occurrence of cold surges that affect Central America and its precipitation. As the winter regimes are largely dependent of mid-latitude interaction with the tropics, the effect that ENSO has on the Jet Stream is reflected in the winter regimes. An automated analysis of large scale conditions based on reanalysis and/or model data seems useful for both dynamical

  5. Monitoring Streambed Scour/Deposition Under Nonideal Temperature Signal and Flood Conditions

    Science.gov (United States)

    DeWeese, Timothy; Tonina, Daniele; Luce, Charles

    2017-12-01

    Streambed erosion and deposition are fundamental geomorphic processes in riverbeds, and monitoring their evolution is important for ecological system management and in-stream infrastructure stability. Previous research showed proof of concept that analysis of paired temperature signals of stream and pore waters can simultaneously provide monitoring scour and deposition, stream sediment thermal regime, and seepage velocity information. However, it did not address challenges often associated with natural systems, including nonideal temperature variations (low-amplitude, nonsinusoidal signal, and vertical thermal gradients) and natural flooding conditions on monitoring scour and deposition processes over time. Here we addressed this knowledge gap by testing the proposed thermal scour-deposition chain (TSDC) methodology, with laboratory experiments to test the impact of nonideal temperature signals under a range of seepage velocities and with a field application during a pulse flood. Both analyses showed excellent match between surveyed and temperature-derived bed elevation changes even under very low temperature signal amplitudes (less than 1°C), nonideal signal shape (sawtooth shape), and strong and changing vertical thermal gradients (4°C/m). Root-mean-square errors on predicting the change in streambed elevations were comparable with the median grain size of the streambed sediment. Future research should focus on improved techniques for temperature signal phase and amplitude extractions, as well as TSDC applications over long periods spanning entire hydrographs.

  6. A model for the origin of solar wind stream interfaces

    International Nuclear Information System (INIS)

    Hundhausen, A.J.; Burlaga, L.F.

    1975-01-01

    The basic variations in solar wind properties that have been observed at 'stream interfaces' near 1 AU are explained by a gas dynamic model in which a radially propagating stream, produced by a temperature variation in the solar envelope, steepens nonlinearly while moving through interplanetary space. The region thus identified with the stream interface separates the ambient solar wind from the fresh hot material originally in the stream. However, the interface regions given by the present model are thicker than most stream interfaces observed in the solar wind, a fact suggesting that some additional physical process may be important in determining that thickness. Variations in the density, speed, or Alfven pressure alone appear not to produce streams with such an interface

  7. Response to multi-generational selection under elevated [CO2] in two temperature regimes suggests enhanced carbon assimilation and increased reproductive output in Brassica napus L

    DEFF Research Database (Denmark)

    Frenck, Georg; van der Linden, Leon; Mikkelsen, Teis Nørgaard

    2013-01-01

    Functional plant traits are likely to adapt under the sustained pressure imposed by environmental changes through natural selection. Employing Brassica napus as a model, a multi-generational study was performed to investigate the potential trajectories of selection at elevated [CO2] in two differ...... ameliorate depressions in plant reproductive fitness caused by higher temperatures in situations where both factors co-occur....

  8. The behavior of ZrO{sub 2}/20%Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3} coatings deposited on aluminum alloys at high temperature regime

    Energy Technology Data Exchange (ETDEWEB)

    Pintilei, G.L., E-mail: laura_rares082008@yahoo.com [Pitesti University, Faculty of Mechanics and Technology, Str. Targu din Vale nr.1, 110040 Pitesti, Arges (Romania); Technical University “Gheorghe Asachi” of Iasi, Faculty of Mechanics, Bld D. Mangeron nr. 61, 700050 Iasi (Romania); Crismaru, V.I. [Technical University “Gheorghe Asachi” of Iasi, Faculty of Mechanics, Bld D. Mangeron nr. 61, 700050 Iasi (Romania); Abrudeanu, M. [Pitesti University, Faculty of Mechanics and Technology, Str. Targu din Vale nr.1, 110040 Pitesti, Arges (Romania); Munteanu, C. [Technical University “Gheorghe Asachi” of Iasi, Faculty of Mechanics, Bld D. Mangeron nr. 61, 700050 Iasi (Romania); Baciu, E.R. [University of Medicine and Pharmacy “Gr.T.Popa”, Department Implantology, Removable Restorations, Technology, Str. Universitatii nr. 16, 700115 Iasi (Romania); Istrate, B.; Basescu, N. [Technical University “Gheorghe Asachi” of Iasi, Faculty of Mechanics, Bld D. Mangeron nr. 61, 700050 Iasi (Romania)

    2015-10-15

    Highlights: • In both the ZrO{sub 2}/20%Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3} coatings the high temperature caused a decrease of pores volume and a lower thickness of the interface between successive splats. • The NiCr bond layer in the sample with a ZrO{sub 2}/20%Y{sub 2}O{sub 3} suffered a fragmentation due to high temperature exposure and thermal expansion which can lead to coating exfoliation. • The NiCr bond layer in the sample with an Al{sub 2}O{sub 3} coating showed an increase of pore volume due to high temperature. - Abstract: Aluminum alloy present numerous advantages like lightness, high specific strength and diversity which recommend them to a high number of applications from different fields. In extreme environments the protection of aluminum alloys is difficult and requires a high number of requirements like high temperature resistance, thermal fatigue resistance, corrosion fatigue resistance and galvanic corrosion resistance. To obtain these characteristics coatings can be applied to the surfaces so they can enhance the mechanical and chemical properties of the parts. In this paper two coatings were considered for deposition on an AA2024 aluminum alloy, ZrO{sub 2}/20%Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3}. To obtain a better adherence of the coating to the base material an additional bond layer of NiCr is used. Both the coatings and bond layer were deposited by atmospheric plasma spraying on the samples. The samples were subjected to a temperature of 500 °C and after that slowly cooled to room temperature. The samples were analyzed by electron microscopy and X-ray diffraction to determine the morphological and phase changes that occurred during the temperature exposure. To determine the stress level in the parts due to thermal expansion a finite element analysis was performed in the same conditions as the tests.

  9. Relative importance of temperature and diet to larval development and adult size of the winter stonefly, Soyedina carolinensis (Plecoptera: Nemouridae)

    Energy Technology Data Exchange (ETDEWEB)

    Sweeney, B.W.; Vannote, R.L.; Dodds, P.J.

    1986-02-01

    Soyedina carolinensis Claassen, a leaf shredding stonefly, was reared in a series of three laboratory experiments from early instar to adult on different species of deciduous leaves and at various constant and fluctuating temperature regimes. Experiment 1, which involved rearing larvae on fourteen different leaf diets at ambient stream temperatures, showed that diet significantly affected larval growth and adult size but did not affect overall developmental time. Experiment 2, which involved rearing larvae on five different leaf diets at each of three fluctuating temperature regimes, showed that: adding 6/sup 0/C to the normal temperature regime of WCC was lethal to 99% of the larvae regardless of diet; and warming WCC by 3/sup 0/C did not affect developmental time but did significantly reduce adult size relative to adults reared at WCC temperatures on certain diets. Experiment 3, which involved rearing larvae on five different leaf diets at each of five constant temperatures showed that: temperature significantly affected the mortality, growth, and development time of larvae whereas diet only affected larval growth and mortality; temperatures at or near 10/sup 0/C yielded maximum larval growth and survival for most diets; at 5/sup 0/C, larval mortality was high and growth was low resulting in a few small adults for most diets; larval mortality was at or near 100% at 15/sup 0/C regardless of diet; and no larvae survived at 20 and 25/sup 0/C.

  10. ANALYTICAL MODELS OF EXOPLANETARY ATMOSPHERES. II. RADIATIVE TRANSFER VIA THE TWO-STREAM APPROXIMATION

    Energy Technology Data Exchange (ETDEWEB)

    Heng, Kevin; Mendonça, João M.; Lee, Jae-Min, E-mail: kevin.heng@csh.unibe.ch, E-mail: joao.mendonca@csh.unibe.ch, E-mail: lee@physik.uzh.ch [University of Bern, Center for Space and Habitability, Sidlerstrasse 5, CH-3012 Bern (Switzerland)

    2014-11-01

    We present a comprehensive analytical study of radiative transfer using the method of moments and include the effects of non-isotropic scattering in the coherent limit. Within this unified formalism, we derive the governing equations and solutions describing two-stream radiative transfer (which approximates the passage of radiation as a pair of outgoing and incoming fluxes), flux-limited diffusion (which describes radiative transfer in the deep interior), and solutions for the temperature-pressure profiles. Generally, the problem is mathematically underdetermined unless a set of closures (Eddington coefficients) is specified. We demonstrate that the hemispheric (or hemi-isotropic) closure naturally derives from the radiative transfer equation if energy conservation is obeyed, while the Eddington closure produces spurious enhancements of both reflected light and thermal emission. We concoct recipes for implementing two-stream radiative transfer in stand-alone numerical calculations and general circulation models. We use our two-stream solutions to construct toy models of the runaway greenhouse effect. We present a new solution for temperature-pressure profiles with a non-constant optical opacity and elucidate the effects of non-isotropic scattering in the optical and infrared. We derive generalized expressions for the spherical and Bond albedos and the photon deposition depth. We demonstrate that the value of the optical depth corresponding to the photosphere is not always 2/3 (Milne's solution) and depends on a combination of stellar irradiation, internal heat, and the properties of scattering in both the optical and infrared. Finally, we derive generalized expressions for the total, net, outgoing, and incoming fluxes in the convective regime.

  11. On the regimes of premixing

    Energy Technology Data Exchange (ETDEWEB)

    Angelini, S.; Theofanous, T.G.; Yuen, W.W. [California Univ., Santa Barbara, CA (United States). Center for Risk Studies and Safety

    1998-01-01

    The conditions of the MAGICO-2000 experiment are extended to more broadly investigate the regimes of premixing, and the corresponding internal structures of mixing zones. With the help of the data and numerical simulations using the computer code PM-ALPHA, we can distinguish extremes of behavior dominated by inertia and thermal effects - we name these the inertia and thermal regimes, respectively. This is an important distinction that should guide future experiments aimed at code verification in this area. Interesting intermediate behaviors are also delineated and discussed. (author)

  12. Direct numerical simulations of exhaust gas recirculation effect on multistage autoignition in the negative temperature combustion regime for stratified HCCI flow conditions by using H2O2 addition

    Science.gov (United States)

    El-Asrag, Hossam A.; Ju, Yiguang

    2013-04-01

    Direct numerical simulations (DNSs) of a stratified flow in a homogeneous compression charge ignition (HCCI) engine are performed to investigate the exhaust gas recirculation (EGR) and temperature/mixture stratification effects on the autoignition of synthetic dimethyl ether (DME) in the negative temperature combustion region. Detailed chemistry for a DME/air mixture is employed and solved by a hybrid multi-time scale (HMTS) algorithm to reduce the computational cost. The effect of ? to mimic the EGR effect on autoignition are studied. The results show that adding ? enhances autoignition by rapid OH radical pool formation (34-46% reduction in ignition delay time) and changes the ignition heat release rates at different ignition stages. Sensitivity analysis is performed and the important reactions pathways affecting the autoignition are specified. The DNS results show that the scales introduced by thermal and mixture stratifications have a strong effect after the low temperature chemistry (LTC) ignition especially at the locations of high scalar dissipation rates. Compared to homogenous ignition, stratified ignitions show similar first autoignition delay times, but 18% reduction in the second and third ignition delay times. The results also show that molecular transport plays an important role in stratified low temperature ignition, and that the scalar mixing time scale is strongly affected by local ignition in the stratified flow. Two ignition-kernel propagation modes are observed: a wave-like, low-speed, deflagrative mode and a spontaneous, high-speed, ignition mode. Three criteria are introduced to distinguish these modes by different characteristic time scales and Damkhöler numbers using a progress variable conditioned by an ignition kernel indicator. The low scalar dissipation rate flame front is characterized by high displacement speeds and high mixing Damkhöler number. The proposed criteria are applied successfully at the different ignition stages and

  13. Transition from the constant ion mobility regime to the ion-atom charge-exchange regime for bounded collisional plasmas

    International Nuclear Information System (INIS)

    Poggie, Jonathan; Sternberg, Natalia

    2005-01-01

    A numerical and analytical study of a planar, collisional, direct-current, plasma-wall problem is presented. The fluid model for the problem is first validated by comparing numerical solutions with experimental data for low-pressure (∼0.1 Pa) electrode sheaths with wall potentials on the order of -100 V. For electric potential, ion number density, and ion velocity, good agreement was found between theory and experiment from within the sheath out to the bulk plasma. The frictional drag resulting from ion-neutral collisions is described by a model incorporating both linear and quadratic velocity terms. In order to study the transition from the constant ion mobility regime (linear friction) to the ion-atom charge-exchange collision regime (quadratic friction), the theoretical model was examined numerically for a range of ion temperatures and ion-neutral collision rates. It was found that the solution profiles in the quasineutral plasma depend on the ion temperature. For low ion temperatures they are governed mainly by the ion-atom charge-exchange regime, whereas for high temperatures they are governed by the constant ion mobility regime. Quasineutral plasma models corresponding to these two limiting cases were solved analytically. In particular, an analytical plasma solution is given for the ion-atom charge exchange regime that includes the effects of ion inertia. In contrast to the quasineutral plasma, the sheath is always governed for low to moderate collision rates by the ion-atom charge-exchange regime, independent of the ion temperature. Varying the collision rate, it was shown that when the wall potential is sufficiently high, the sheath cannot be considered collisionless, even if the collision rate is quite small

  14. Spatio-temporal variation in stream water chemistry in a tropical urban watershed

    Science.gov (United States)

    A. Ramirez; K.G. Rosas; A.E. Lugo; O.M. Ramos-Gonzalez

    2014-01-01

    Urban activities and related infrastructure alter the natural patterns of stream physical and chemical conditions. According to the Urban Stream Syndrome, streams draining urban landscapes are characterized by high concentrations of nutrients and ions, and might have elevated water temperatures and variable oxygen concentrations. Here, we report temporal and spatial...

  15. Determination of the Hall Thruster Operating Regimes; TOPICAL

    International Nuclear Information System (INIS)

    L. Dorf; V. Semenov; Y. Raitses; N.J. Fisch

    2002-01-01

    A quasi one-dimensional (1-D) steady-state model of the Hall thruster is presented. For the same discharge voltage two operating regimes are possible - with and without the anode sheath. For given mass flow rate, magnetic field profile and discharge voltage a unique solution can be constructed, assuming that the thruster operates in one of the regimes. However, we show that for a given temperature profile the applied discharge voltage uniquely determines the operating regime: for discharge voltages greater than a certain value, the sheath disappears. That result is obtained over a wide range of incoming neutral velocities, channel lengths and widths, and cathode plane locations. It is also shown that a good correlation between the quasi 1-D model and experimental results can be achieved by selecting an appropriate electron mobility and temperature profile

  16. Defense Waste Processing Facility Recycle Stream Evaporation

    International Nuclear Information System (INIS)

    STONE, MICHAEL

    2006-01-01

    The Defense Waste Processing Facility (DWPF) at the Savannah River Site (SRS) stabilizes high level radioactive waste (HLW) by vitrification of the waste slurries. DWPF currently produces approximately five gallons of dilute recycle for each gallon of waste vitrified. This recycle stream is currently sent to the HLW tank farm at SRS where it is processed through the HLW evaporators with the concentrate eventually sent back to the DWPF for stabilization. Limitations of the HLW evaporators and storage space constraints in the tank farm have the potential to impact the operation of the DWPF and could limit the rate that HLW is stabilized. After an evaluation of various alternatives, installation of a dedicated evaporator for the DWPF recycle stream was selected for further evaluation. The recycle stream consists primarily of process condensates from the pretreatment and vitrification processes. Other recycle streams consist of process samples, sample line flushes, sump flushes, and cleaning solutions from the decontamination and filter dissolution processes. The condensate from the vitrification process contains some species, such as sulfate, that are not appreciably volatile at low temperature and could accumulate in the system if 100% of the evaporator concentrate was returned to DWPF. These species are currently removed as required by solids washing in the tank farm. The cleaning solutions are much higher in solids content than the other streams and are generated 5-6 times per year. The proposed evaporator would be required to concentrate the recycle stream by a factor of 30 to allow the concentrate to be recycled directly to the DWPF process, with a purge stream sent to the tank farm as required to prevent buildup of sulfate and similar species in the process. The overheads are required to meet stringent constraints to allow the condensate to be sent directly to an effluent treatment plant. The proposed evaporator would nearly de-couple the DWPF process from the

  17. Streaming potential measurements of biosurfaces

    Science.gov (United States)

    Van Wagenen, R. A.; Andrade, J. D.; Hibbs, J. B., Jr.

    1976-01-01

    A technique based on the measurement of streaming potentials has been developed to evaluate the electrokinetic region of the cell periphery. This approach is feasible for cell lines propagated in in-vitro cell cultures in monolayer form. The advantage of this system is that cells may be evaluated in the living state atttached to a substrate; it is not necessary to subject the cells to enzymatic, chemical, or mechanical trauma required to obtain monodisperse suspensions which are then normally evaluated by microelectrophoresis. In this manner, it should be possible to study the influence of substrate and environmental factors on the charge density and potential at the cell periphery. The apparatus and procedure are described as well as some results concerning the electrokinetic potential of borosilicate capillaries as a function of ionic strength, pH, and temperature. The effect that turbulence and entrance flow conditions have on accurate streaming-potential measurements is discussed. The electrokinetic potential of BALB/c 3T12 fibroblasts has been quantified as a function of pH, ionic strength, glutaraldehyde fixation, and Giemsa staining.

  18. Method of purifying zirconium tetrachloride and hafnium tetrachloride in a vapor stream

    International Nuclear Information System (INIS)

    Snyder, T.S.; Stolz, R.A.

    1992-01-01

    This patent describes a method of purifying zirconium tetrachloride and hafnium tetrachloride in a vapor stream from a sand chlorinator in which the silicon and metals present in sand fed to the chlorinator are converted to chlorides at temperatures over about 800 degrees C. It comprises cooling a vapor stream from a sand chlorinator, the vapor stream containing principally silicon tetrachloride, zirconium tetrachloride, and hafnium tetrachloride contaminated with ferric chloride, to a temperature of from about 335 degrees C to about 600 degrees C; flowing the vapor stream through a gaseous diffusion separative barrier to produce a silicon tetrachloride-containing vapor stream concentrated in zirconium tetrachloride and hafnium tetrachloride and a silicon tetrachloride-containing vapor stream depleted in zirconium tetrachloride and hafnium tetrachloride; adsorbing the ferric chloride in the separative barrier; and recovering the silicon tetrachloride stream concentrated in zirconium tetrachloride and hafnium tetrachloride separately from the silicon tetrachloride stream depleted in zirconium tetrachloride and hafnium tetrachloride

  19. Fish diversity in adjacent ambient, thermal, and post-thermal freshwater streams

    International Nuclear Information System (INIS)

    McFarlane, R.W.

    1976-01-01

    The Savannah River Plant area is drained by five streams of various sizes and thermal histories. One has never been thermally stressed, two presently receive thermal effluent, and two formerly received thermal effluent from nuclear production reactors. Sixty-four species of fishes are known to inhabit these streams; 55 species is the highest number obtained from any one stream. Thermal effluent in small streams excludes fish during periods of high temperatures, but the streams are rapidly reinvaded when temperatures subside below lethal limits. Some cyprinids become extinct in nonthermal tributaries upstream from the thermal effluents after extended periods of thermal stress. This extinction is similar to that which follows stream impoundment. Post-thermal streams rapidly recover their fish diversity and abundance. The alteration of the streambed and removal of overhead canopy may change the stream characteristics and modify the post-thermal fish fauna

  20. Land degradation and property regimes

    Science.gov (United States)

    Paul M. Beaumont; Robert T. Walker

    1996-01-01

    This paper addresses the relationship between property regimes and land degradation outcomes, in the context of peasant agriculture. We consider explicitly whether private property provides for superior soil resource conservation, as compared to common property and open access. To assess this we implement optimization algorithms on a supercomputer to address resource...

  1. Regime identification in ASDEX Upgrade

    International Nuclear Information System (INIS)

    Giannone, L; Sips, A C C; Kardaun, O; Spreitler, F; Suttrop, W

    2004-01-01

    The ability to recognize the transition from the L-mode to the H-mode or from the H-mode to the improved H-mode reliably from a conveniently small number of measurements in real time is of increasing importance for machine control. Discriminant analysis has been applied to regime identification of plasma discharges in the ASDEX Upgrade tokamak. An observation consists of a set of plasma parameters averaged over a time slice in a discharge. The data set consists of all observations over different discharges and time slices. Discriminant analysis yields coefficients allowing the classification of a new observation. The results of a frequentist and a formal Bayesian approach to discriminant analysis are compared. With five plasma variables, a failure rate of 1.3% for predicting the L-mode and the H-mode confinement regime was achieved. With five plasma variables, a failure rate of 5.3% for predicting the H-mode and the improved H-mode confinement regime was achieved. The coefficients derived by discriminant analysis have been applied subsequently to discharges to illustrate the operation of regime identification in a real time control system

  2. Monetary regimes in open economies

    NARCIS (Netherlands)

    Korpos, A.

    2006-01-01

    This thesis presents a two-country open economy framework for the analysis of strategic interactions among monetary authorities and wage bargaining institutions. From this perspective, the thesis investigates the economic consequences of replacing flexible and fixed exchange rate regimes with a

  3. Low temperature destructive distillation

    Energy Technology Data Exchange (ETDEWEB)

    1938-07-05

    A process is given and apparatus is described for the destructive distillation at low temperature of coal, oil shale, and the like by subjection to the action of a stream of hot gases or superhearted steam, flowing in a closed circuit. Subsequent treatment of the distillation residues with a gas stream containing oxygen results in combustion of the carbon-containing material therein brings to a high temperature the solid residue, in which the process comprises subsequently contacting the hot solid residue with the fluid stream effecting the distillation.

  4. Sputtering of Ge(001): transition between dynamic scaling regimes

    DEFF Research Database (Denmark)

    Smilgies, D.-M.; Eng, P.J.; Landemark, E.

    1997-01-01

    We have studied the dynamic behavior of the Ge(001) surface during sputtering in situ and in real time using synchrotron X-ray diffraction. We find two dynamic regimes as a function of surface temperature and sputter current which are separated by a sharp transition. The boundary between these two...

  5. The Rabbit Stream Cipher

    DEFF Research Database (Denmark)</