WorldWideScience

Sample records for stable concentration gradients

  1. Generation of tunable and pulsatile concentration gradients via microfluidic network

    KAUST Repository

    Zhou, Bingpu

    2014-06-04

    We demonstrate a compact Polydimethylsiloxane microfluidic chip which can quickly generate ten different chemical concentrations simultaneously. The concentration magnitude of each branch can be flexibly regulated based on the flow rate ratios of the two injecting streams. The temporal/pulsatile concentration gradients are achieved by integrating on-chip pneumatic actuated valves controlled by the external signals. The temporal concentration gradients can also be tuned precisely by varying applied frequency and duty cycle of the trigger signal. It is believed that such microdevice will be potentially used for some application areas of producing stable chemical gradients as well as allowing fast, pulsatile gradient transformation in seconds.

  2. Validation of classical density-dependent solute transport theory for stable, high-concentration-gradient brine displacements in coarse and medium sands

    Science.gov (United States)

    Watson, S. J.; Barry, D. A.; Schotting, R. J.; Hassanizadeh, S. M.

    A series of careful laboratory soil column experiments was carried out for the purpose of providing data for testing recently presented theories of miscible density-dependent flow and transport. In particular, modifications to the standard theory involve extensions to both Darcy's (for flow) and Fick's laws (for diffusive/dispersive solute flux). Both coarse- and medium-grained sands were used in the experiments. All experiments concerned upward (i.e., stable) displacement of fresh water within the soil by a brine solution, under either constant head or constant volume flux conditions. The experimental data were analysed using accurate numerical solutions of the standard governing flow and transport model, as well as models with modified Darcy's and Fick's laws. Model parameters were determined by a step-wise fitting procedure based on the least-squares criterion. The results show clearly that, for large density contrasts, an extended Darcy's law was not necessary. On the other hand, an extension to Fick's Law was needed to model the experimental data accurately.

  3. Quantized Concentration Gradient in Picoliter Scale

    Science.gov (United States)

    Hong, Jong Wook

    2010-10-01

    Generation of concentration gradient is of paramount importance in the success of reactions for cell biology, molecular biology, biochemistry, drug-discovery, chemotaxis, cell culture, biomaterials synthesis, and tissue engineering. In conventional method of conducting reactions, the concentration gradients is achieved by using pipettes, test tubes, 96-well assay plates, and robotic systems. Conventional methods require milliliter or microliter volumes of samples for typical experiments with multiple and sequential reactions. It is a challenge to carry out experiments with precious samples that have strict limitations with the amount of samples or the price to pay for the amount. In order to overcome this challenge faced by the conventional methods, fluidic devices with micrometer scale channels have been developed. These devices, however, cause restrictions on changing the concentration due to the fixed gradient set based on fixed fluidic channels.ootnotetextJambovane, S.; Duin, E. C.; Kim, S-K.; Hong, J. W., Determination of Kinetic Parameters, KM and kcat, with a Single Experiment on a Chip. textitAnalytical Chemistry, 81, (9), 3239-3245, 2009.^,ootnotetextJambovane, S.; Hong, J. W., Lorenz-like Chatotic System on a Chip In The 14th International Conference on Miniaturized Systems for Chemistry and Life Sciences (MicroTAS), The Netherlands, October, 2010. Here, we present a unique microfluidic system that can generate quantized concentration gradient by using series of droplets generated by a mechanical valve based injection method.ootnotetextJambovane, S.; Rho, H.; Hong, J., Fluidic Circuit based Predictive Model of Microdroplet Generation through Mechanical Cutting. In ASME International Mechanical Engineering Congress & Exposition, Lake Buena Vista, Florida, USA, October, 2009.^,ootnotetextLee, W.; Jambovane, S.; Kim, D.; Hong, J., Predictive Model on Micro Droplet Generation through Mechanical Cutting. Microfluidics and Nanofluidics, 7, (3), 431-438, 2009

  4. Concentration of stable elements in food products

    Energy Technology Data Exchange (ETDEWEB)

    Montford, M.A.; Shank, K.E.; Hendricks, C.; Oakes, T.W.

    1980-01-01

    Food samples were taken from commercial markets and analyzed for stable element content. The concentrations of most stable elements (Ag, Al, As, Au, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Cu, Fe, Hf, I, K, La, Mg, Mn, Mo, Na, Rb, Sb, Sc, Se, Sr, Ta, Th, Ti, V, Zn, Zr) were determined using multiple-element neutron activation analysis, while the concentrations of other elements (Cd, Hg, Ni, Pb) were determined using atomic absorption. The relevance of the concentrations found are noted in relation to other literature values. An earlier study was extended to include the determination of the concentration of stable elements in home-grown products in the vicinity of the Oak Ridge National Laboratory. Comparisons between the commercial and local food-stuff values are discussed.

  5. Dynamics of Chemotactic Droplets in Salt Concentration Gradients

    DEFF Research Database (Denmark)

    Cejkova, J.; Novak, M.; Stepanek, F.

    2014-01-01

    of the sodium decanoate concentration and the NaCl concentration gradient. The ability of the decanol droplets to migrate in concentration gradients has been demonstrated not only in a linear chemotactic assay but also in a topologically complex environment. Additionally, the ability to reverse the direction...

  6. Lactate uptake against a concentration gradient

    DEFF Research Database (Denmark)

    Nordström, Carl-Henrik; Nielsen, Troels Halfeld; Nielsen, Hans Boye

    2014-01-01

    The recently published article by Jalloh et al (Jalloh I, Helmy A, Shannon RJ, Gallagher CN, Menon D, Carpenter K, Hutchinson P. Lactate uptake by the injured human brain - evidence from an arterio-venous gradient and cerebral microdialysis study. J Neurotrauma. 2013 Aug 22. [Epub ahead of print]...... is of fundamental importance the misconception should be corrected....

  7. Sn Concentration Gradients in Powder-in-tube Superconductors

    CERN Document Server

    Cantoni, M; Pfirter, P Y; de Borman, F; Rossen, J; Arnau, G; Oberli, L; Lee, P

    2010-01-01

    The Sn concentration gradients across the A15 phase have been studied by Energy Dispersive X-ray Spectroscopy (EDS) measurements. High spatial resolution EDS measurements in the Transmission Electron Microscope reveal a comparatively strong Sn concentration gradient from the periphery towards the centre of individual (Nb Ta)3Sn grains.

  8. Complex Surface Concentration Gradients by Stenciled "Electro Click Chemistry"

    DEFF Research Database (Denmark)

    Hansen, Thomas Steen; Lind, Johan Ulrik; Daugaard, Anders Egede

    2010-01-01

    Complex one- or two-dimensional concentration gradients of alkynated molecules are produced on azidized conducting polymer substrates by stenciled "electro click chemistry". The latter describes the local electrochemical generation of catalytically active Cu(I) required to complete a "click...... reaction" between alkynes and azides at room temperature. A stencil on the counter electrode defines the shape and multiplicity of the gradient(s) on the conducting polymer substrate, while the specific reaction conditions control gradient steepness and the maximum concentration deposited. Biologically...

  9. Formation of actin networks in microfluidic concentration gradients

    Directory of Open Access Journals (Sweden)

    Natalja eStrelnikova

    2016-05-01

    Full Text Available The physical properties of cytoskeletal networks are contributors in a number of mechanical responses of cells including cellular deformation and locomotion, and are crucial for the proper action of living cells. Local chemical gradients modulate cytoskeletal functionality including the interactions of the cytoskeleton with other cellular components. Actin is a major constituent of the cytoskeleton. Introducing a microfluidic-based platform, we explored the impact of concentration gradients on the formation and structural properties of actin networks. Microfluidics-controlled flow-free steady state experimental conditions allow for the generation of chemical gradients of different profiles, such as linear or step-like. We discovered specific features of actin networks emerging in defined gradients. In particular, we analyzed the effects of spatial conditions on network properties, bending rigidities of network links, and the network elasticity.

  10. Generation of Local Concentration Gradients by Gas-Liquid Contacting

    NARCIS (Netherlands)

    de Jong, J.; Verheijden, Pascal W.; Lammertink, Rob G.H.; Wessling, Matthias

    2008-01-01

    We present a generic concept to create local concentration gradients, based on the absorption of gases or vapors in a liquid. A multilayer microfluidic device with crossing gas and liquid channels is fabricated by micromilling and used to generate multiple gas-liquid contacting regions, separated by

  11. Metal concentrations in urban riparian sediments along an urbanization gradient

    Science.gov (United States)

    Daniel J. Bain; Ian D. Yesilonis; Richard V. Pouyat

    2012-01-01

    Urbanization impacts fluvial systems via a combination of changes in sediment chemistry and basin hydrology. While chemical changes in urban soils have been well characterized, similar surveys of riparian sediments in urbanized areas are rare. Metal concentrations were measured in sediments collected from riparian areas across the urbanization gradient in Baltimore, MD...

  12. Dynamics of Reactive Microbial Hotspots in Concentration Gradient.

    Science.gov (United States)

    Hubert, A.; Farasin, J.; Tabuteau, H.; Dufresne, A.; Meheust, Y.; Le Borgne, T.

    2017-12-01

    In subsurface environments, bacteria play a major role in controlling the kinetics of a broad range of biogeochemical reactions. In such environments, nutrients fluxes and solute concentrations needed for bacteria metabolism may be highly variable in space and intermittent in time. This can lead to the formation of reactive hotspots where and when conditions are favorable to particular microorganisms, hence inducing biogeochemical reaction kinetics that differ significantly from those measured in homogeneous model environments. To investigate the impact of chemical gradients on the spatial structure and temporal dynamics of subsurface microorganism populations, we develop microfluidic cells allowing for a precise control of flow and chemical gradient conditions, as well as quantitative monitoring of the bacteria's spatial distribution and biofilm development. Using the non-motile Escherichia coli JW1908-1 strain and Gallionella capsiferriformans ES-2 as model organisms, we investigate the behavior and development of bacteria over a range of single and double concentration gradients in the concentrations of nutrients, electron donors and electron acceptors. We measure bacterial activity and population growth locally in precisely known hydrodynamic and chemical environments. This approach allows time-resolved monitoring of the location and intensity of reactive hotspots in micromodels as a function of the flow and chemical gradient conditions. We compare reactive microbial hotspot dynamics in our micromodels to classic growth laws and well-known growth parameters for the laboratory model bacteria Escherichia coli.We also discuss consequences for the formation and temporal dynamics of biofilms in the subsurface.

  13. Fugacity and concentration gradients in a gravity field

    Science.gov (United States)

    May, C. E.

    1986-01-01

    Equations are reviewed which show that at equilibrium fugacity and concentration gradients can exist in gravitational fields. At equilibrium, the logarithm of the ratio of the fugacities of a species at two different locations in a gravitational field is proportional to the difference in the heights of the two locations and the molecular weight of the species. An analogous relation holds for the concentration ratios in a multicomponent system. The ratio is calculated for a variety of examples. The kinetics for the general process are derived, and the time required to approach equilibrium is calculated for several systems. The following special topics are discussed: ionic solutions, polymers, multiphase systems, hydrostatic pressure, osmotic pressure, and solubility gradients in a gravity field.

  14. Quasiconvexity at the boundary and concentration effects generated by gradients

    Czech Academy of Sciences Publication Activity Database

    Kružík, Martin

    2013-01-01

    Roč. 19, č. 3 (2013), s. 679-700 ISSN 1292-8119 R&D Projects: GA ČR GAP201/10/0357; GA ČR(CZ) GAP201/12/0671 Institutional support: RVO:67985556 Keywords : bounded sequences of gradients * concentrations * oscillations Subject RIV: BA - General Mathematics Impact factor: 1.105, year: 2013 http://library.utia.cas.cz/separaty/2013/MTR/kruzik-0394748.pdf

  15. Using nuclear methods for analyzing materials and determining concentration gradients

    International Nuclear Information System (INIS)

    Darras, R.

    After reviewing the various type of nuclear chemical analysis methods, the possibilities of analysis by activation and direct observation of nuclear reactions are specifically described. These methods make it possible to effect analyses of trace-elements or impurities, even as traces, in materials, with selectivity, accuracy and great sensitivity. This latter property makes them advantageous too for determining major elements in small quantities of available matter. Furthermore, they lend themselves to carrying out superficial analyses and the determination of concentration gradients, given the careful choice of the nature and energy of the incident particles. The paper is illustrated with typical examples of analyses on steels, pure iron, refractory metals, etc [fr

  16. Radioactive and stable elements' concentration in medicinal plants from Brazil

    International Nuclear Information System (INIS)

    Sussa, F.V.; Silva, P.S.C.; Damatto, S.R.; Favaro, D.I.T.; Mazzilli, B.P.

    2009-01-01

    Since the early days of mankind, plants have been used as food and for medicinal purposes. Still, little information exists in literature about the activity concentration of 238 U and 232 Th decay products, as well as stable element concentrations in Brazilian plants. Activity concentrations of 226 Ra, 228 Ra and 210 Pb, and chemical concentrations of As, Ba, Br, Cs, Co, Cr, Cu, Eu, Fe, Hf, La, Lu, Rb, Sb, Sc, Sm, Ta, Tb, Yb, Zn and Zr were determined in ten samples commonly used in Brazilian medicinal plants. (author)

  17. Melanin concentration gradients in modern and fossil feathers.

    Directory of Open Access Journals (Sweden)

    Daniel J Field

    Full Text Available In birds and feathered non-avian dinosaurs, within-feather pigmentation patterns range from discrete spots and stripes to more subtle patterns, but the latter remain largely unstudied. A ∼55 million year old fossil contour feather with a dark distal tip grading into a lighter base was recovered from the Fur Formation in Denmark. SEM and synchrotron-based trace metal mapping confirmed that this gradient was caused by differential concentration of melanin. To assess the potential ecological and phylogenetic prevalence of this pattern, we evaluated 321 modern samples from 18 orders within Aves. We observed that the pattern was found most frequently in distantly related groups that share aquatic ecologies (e.g. waterfowl Anseriformes, penguins Sphenisciformes, suggesting a potential adaptive function with ancient origins.

  18. Lowering coefficient of friction in Cu alloys with stable gradient nanostructures.

    Science.gov (United States)

    Chen, Xiang; Han, Zhong; Li, Xiuyan; Lu, K

    2016-12-01

    The coefficient of friction (COF) of metals is usually high, primarily because frictional contacts induce plastic deformation underneath the wear surface, resulting in surface roughening and formation of delaminating tribolayers. Lowering the COF of metals is crucial for improving the reliability and efficiency of metal contacts in engineering applications but is technically challenging. Refining the metals' grains to nanoscale cannot reduce dry-sliding COFs, although their hardness may be elevated many times. We report that a submillimeter-thick stable gradient nanograined surface layer enables a significant reduction in the COF of a Cu alloy under high-load dry sliding, from 0.64 (coarse-grained samples) to 0.29, which is smaller than the COFs of many ceramics. The unprecedented stable low COF stems from effective suppression of sliding-induced surface roughening and formation of delaminating tribolayer, owing to the stable gradient nanostructures that can accommodate large plastic strains under repeated sliding for more than 30,000 cycles.

  19. A model to secure a stable iodine concentration in milk

    Directory of Open Access Journals (Sweden)

    Gisken Trøan

    2015-12-01

    Full Text Available Background: Dairy products account for approximately 60% of the iodine intake in the Norwegian population. The iodine concentration in cow's milk varies considerably, depending on feeding practices, season, and amount of iodine and rapeseed products in cow fodder. The variation in iodine in milk affects the risk of iodine deficiency or excess in the population. Objective: The first goal of this study was to develop a model to predict the iodine concentration in milk based on the concentration of iodine and rapeseed or glucosinolate in feed, as a tool to securing stable iodine concentration in milk. A second aim was to estimate the impact of different iodine levels in milk on iodine nutrition in the Norwegian population. Design: Two models were developed on the basis of results from eight published and two unpublished studies from the past 20 years. The models were based on different iodine concentrations in the fodder combined with either glucosinolate (Model 1 or rapeseed cake/meal (Model 2. To illustrate the impact of different iodine concentrations in milk on iodine intake, we simulated the iodine contribution from dairy products in different population groups based on food intake data in the most recent dietary surveys in Norway. Results: The models developed could predict iodine concentration in milk. Cross-validation showed good fit and confirmed the explanatory power of the models. Our calculations showed that dairy products with current iodine level in milk (200 µg/kg cover 68, 49, 108 and 56% of the daily iodine requirements for men, women, 2-year-old children, and pregnant women, respectively. Conclusions: Securing a stable level of iodine in milk by adjusting iodine concentration in different cow feeds is thus important for preventing excess intake in small children and iodine deficiency in pregnant and non-pregnant women.

  20. Trace element concentrations in soils along urbanization gradients in the city of Wien, Austria.

    Science.gov (United States)

    Simon, Edina; Vidic, Andreas; Braun, Mihály; Fábián, István; Tóthmérész, Béla

    2013-02-01

    Urban soil is an important component of urban ecosystems. This study focuses on heavy metal contamination in soils of Wien (Austria) and results are compared to those for a few large European cities. We analysed the elemental contents of 96 samples of topsoil from urban, suburban and rural areas in Wien along a dynamic (floodplain forest) and a stable (oak-hornbeam forest) urbanization gradient. The following elements were quantified using ICP-OES technique: Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Pb, P, S and Zn. For heavy metals PI (pollution index) values were used to assess the level of pollution. The PI values indicated high level of pollution by Pb in the suburban and rural area of stable gradient and in the urban area of dynamic gradient; moderate level of pollution was indicated for Cd in the urban area of stable gradient. The level of pollution was moderate for Co in the suburban and rural area of the stable gradient, and for Cu in suburban area of stable gradient, and urban area of dynamic gradient. The pollution level of Zn was moderate in all areas. Urban soils, especially in urban parks and green areas may have a direct influence on human health. Thus, the elemental analysis of soil samples is one of the best ways to study the effects of urbanization. Our results indicated that the heavy metal contamination was higher in Wien than in a few large European cities.

  1. Confinement dependent chemotaxis in two-photon polymerized linear migration constructs with highly definable concentration gradients

    DEFF Research Database (Denmark)

    Hjortø, Gertrud Malene; Olsen, Mark Holm; Svane, Inge Marie

    2015-01-01

    Dendritic cell chemotaxis is known to follow chemoattractant concentration gradients through tissue of heterogeneous pore sizes, but the dependence of migration velocity on pore size and gradient steepness is not fully understood. We enabled chemotaxis studies for at least 42 hours at confinement...

  2. A gradient of mercury concentrations in Scottish single malt whiskies.

    Science.gov (United States)

    Rose, Neil L; Yang, Handong; Turner, Simon D

    2016-02-01

    Mercury (Hg) concentrations were measured in 26 Scottish single malt whiskies, and all found to be very low (mercury emissions and deposition over the last 200 years affecting concentrations in local waters used in whisky production. As UK atmospheric emissions of mercury have declined by 90 % since the 1970s, we suggest that whisky being produced today should have even lower Hg concentrations when consumed in 10- to 15-years time. This reduction may be compromised by the remobilisation of contaminants stored in catchment soils being transferred to source waters, but is very unlikely to raise the negligible health risk due to Hg from Scottish single malt whisky consumption.

  3. Stable Isotope Systematics in Grasshopper Assemblages Along an Elevation Gradient, Colorado

    Science.gov (United States)

    Kohn, M. J.; Evans, S.; Dean, J.; Nufio, C.

    2012-12-01

    Insects comprise over three quarters of all animal species, yet studies of body water isotopic composition are limited to only the cockroach, the hoverfly, and chironomid flies. These studies suggest that oxygen and hydrogen isotopic compositions in body water are primarily controlled by dietary water sources, with modification from respiratory and metabolic processes. In particular, outward diffusion of isotopically depleted water vapor through insect spiracles at low humidity enriches residual body water in 18O and 2H (D). Stable isotope compositions (δ18O and δD) also respond to gradients in elevation and humidity, but these influences remain poorly understood. In this study, we measured grasshopper body water and local vegetation isotopic compositions along an elevation gradient in Colorado to evaluate three hypotheses: 1) Insect body water isotopic composition is directly related to food source water composition 2) Water vapor transport alters body water isotopic compositions relative to original diet sources, and 3) Elevation gradients influence isotopic compositions in insect body water. Thirty-five species of grasshopper were collected from 14 locations in Colorado grasslands, ranging in elevation from 450 to 800 meters (n=131). Body water was distilled from previously frozen grasshopper specimens using a vacuum extraction line, furnaces (90 °C), and liquid nitrogen traps. Water samples were then analyzed for δ18O and δD on an LGR Liquid Water Isotope Analyzer, housed in the Department of Geosciences, Boise State University. Grasshopper body water isotopic compositions show wide variation, with values ranging between -76.64‰ to +42.82‰ in δD and -3.06‰ to +26.78‰ in δ18O. Precipitation δ18O values over the entire Earth excluding the poles vary by approximately 30‰, comparable to the total range measured in our single study area. Most grasshopper values deviate from the global meteoric water line relating δ18O and δD in precipitation

  4. Potential impacts of climate change on stable flies, investigated along an altitudinal gradient.

    Science.gov (United States)

    Gilles, J; David, J-F; Duvallet, G; Tillard, E

    2008-03-01

    Adult populations of stable flies were sampled along an altitudinal transect in Reunion Island to determine whether higher temperatures were associated with: (a) higher numbers of flies; (b) a longer season of infestation, and/or (c) different responses to warming in the cosmopolitan Stomoxys calcitrans (L) and the tropical Stomoxys niger niger Macquart (Diptera: Muscidae). Flies of both species were trapped at seven farms situated at four altitudes (100-1600 m a.s.l.) over a 90-week period. For both species, there were no relationships between the maximum or mean fly abundance and altitude. Only minimum abundance in winter was significantly higher at lower altitudes. Maximum and mean abundances differed significantly between nearby farms under similar climatic conditions. Seasonal fluctuations in fly abundance changed along the gradient. At lower altitudes, population growth started earlier after the winter but abundance declined earlier in summer, which resulted in a shift of the season of infestation. Seasonal fluctuations of both species were strongly related to climate variables at high altitude, mainly temperature. However, climate variables explained a decreasing proportion of the variations in abundance at lower altitudes. Stomoxys calcitrans was the most abundant species overall, but the proportion of S. n. niger increased significantly at lower altitudes and this species became predominant at 100 m a.s.l. It is concluded that stable fly infestations are unlikely to worsen in response to global warming. Maximum abundance is limited by local factors, possibly larval resources, which suggests that adequate husbandry practices could override the impact of climate change. Because S. n. niger tends to be the predominant pest at elevated temperatures, it is recommended that this species should not be introduced in areas where climate is changing.

  5. Large concentration changes due to thermal diffusion effects in gas flow microsystems with temperature gradients

    DEFF Research Database (Denmark)

    Quaade, Ulrich; Johannessen, Tue; Jensen, Søren

    Thermal diffusion, or Sorét diffusion, is shown to cause significant concentration changes and transients in gas flow microsystems with temperature gradients. In a silicon microsystem, a temperature gradient of about 100 oC/mm is measured to produce concentration transients of up to 13.7 % in an ......Thermal diffusion, or Sorét diffusion, is shown to cause significant concentration changes and transients in gas flow microsystems with temperature gradients. In a silicon microsystem, a temperature gradient of about 100 oC/mm is measured to produce concentration transients of up to 13.......7 % in an argon/helium mixture, when the flow is abruptly changed from a high value to a low value. Finite element simulations of the thermal diffusion in a geometry similar to the experimental setup reproduce the measurements....

  6. Highly transparent, stable, and superhydrophobic coatings based on gradient structure design and fast regeneration from physical damage

    Science.gov (United States)

    Chen, Zao; Liu, Xiaojiang; Wang, Yan; Li, Jun; Guan, Zisheng

    2015-12-01

    Optical transparency, mechanical flexibility, and fast regeneration are important factors to expand the application of superhydrophobic surfaces. Herein, we fabricated highly transparent, stable, and superhydrophobic coatings through a novel gradient structure design by versatile dip-coating of silica colloid particles (SCPs) and diethoxydimethysiliane cross-linked silica nanoparticles (DDS-SNPs) on polyethylene terephthalate (PET) film and glass, followed by the modification of octadecyltrichlorosiliane (OTCS). When the DDS concentration reached 5 wt%, the modified SCPs/DDS-SNPs coating exhibited a water contact angle (WCA) of 153° and a sliding angle (SA) superhydrophobic coating on PET film and glass was increased by 2.7% and 1% in the visible wavelength, respectively. This superhydrophobic coating also showed good robustness and stability against water dropping impact, ultrasonic damage, and acid solution. Moreover, the superhydrophobic PET film after physical damage can quickly regain the superhydrophobicity by one-step spray regenerative solution of dodecyltrichlorosilane (DTCS) modified silica nanoparticles at room temperature. The demonstrated method for the preparation and regeneration of superhydrophobic coating is available for different substrates and large-scale production at room temperature.

  7. The relation between temperature and concentration gradients in superfluid sup 3 He- sup 4 He solutions

    CERN Document Server

    Zadorozhko, A A; Rudavskij, E Y; Chagovets, V K; Sheshin, G A

    2003-01-01

    The temperature and concentration gradients nabla T and nabla x in a superfluid sup 3 He- sup 4 He mixture with an initial concentration 9,8 % of sup 3 He are measured in a temperature range 70-500 mK. The gradients are produced by a steady thermal flow with heating from below. It is shown that the value of nabla x/nabla T observed in the experiment is in good agreement with the theoretical model derived from the temperature and concentration dependences of osmotic pressure. The experimental data permitted us to obtain a thermal diffusion ratio of the solution responsible for the thermal diffusion coefficient.

  8. Heterostructured electrode with concentration gradient shell for highly efficient oxygen reduction at low temperature

    OpenAIRE

    Zhou, Wei; Liang, Fengli; Shao, Zongping; Chen, Jiuling; Zhu, Zhonghua

    2011-01-01

    Heterostructures of oxides have been widely investigated in optical, catalytic and electrochemical applications, because the heterostructured interfaces exhibit pronouncedly different transport, charge, and reactivity characteristics compared to the bulk of the oxides. Here we fabricated a three-dimensional (3D) heterostructured electrode with a concentration gradient shell. The concentration gradient shell with the composition of Ba0.5-xSr0.5-yCo0.8Fe0.2O3-? (BSCF-D) was prepared by simply t...

  9. Effect of Vertical Concentration Gradient on Globally Planar Detonation with Detailed Reaction Mechanism

    Science.gov (United States)

    Song, Qingguana; Wang, Cheng; Han, Yong; Gao, Dayuan; Duan, Yingliang

    2017-06-01

    Since detonation often initiates and propagates in the non-homogeneous mixtures, investigating its behavior in non-uniform mixtures is significant not only for the industrial explosion in the leakage combustible gas, but also for the experimental investigations with a vertical concentration gradient caused by the difference in the molecular weight of gas mixture. Objective of this work is to show the detonation behavior in the mixture with different concentration gradients with detailed chemical reaction mechanism. A globally planar detonation in H2-O2 system is simulated by a high-resolution code based on the fifth-order weighted essentially non-oscillatory (WENO) scheme in spatial discretization and the third-order Additive Runge-Kutta schemes in time discretization. The different shocked combustion modes appear in the rich-fuel and poor-fuel layers due to the concentration gradient effect. Globally, for the cases with the lower gradient detonation can be sustained in a way of the alternation of the multi-heads mode and single-head mode, whereas for the cases with the higher gradient detonation propagates with a single-head mode. Institute of Chemical Materials, CAEP.

  10. Krebs cycle metabolon formation: metabolite concentration gradient enhanced compartmentation of sequential enzymes.

    Science.gov (United States)

    Wu, Fei; Pelster, Lindsey N; Minteer, Shelley D

    2015-01-25

    Dynamics of metabolon formation in mitochondria was probed by studying diffusional motion of two sequential Krebs cycle enzymes in a microfluidic channel. Enhanced directional co-diffusion of both enzymes against a substrate concentration gradient was observed in the presence of intermediate generation. This reveals a metabolite directed compartmentation of metabolic pathways.

  11. Large polarization gradients and temperature-stable responses in compositionally-graded ferroelectrics

    Science.gov (United States)

    Damodaran, Anoop R.; Pandya, Shishir; Qi, Yubo; Hsu, Shang-Lin; Liu, Shi; Nelson, Christopher; Dasgupta, Arvind; Ercius, Peter; Ophus, Colin; Dedon, Liv R.; Agar, Josh C.; Lu, Hongling; Zhang, Jialan; Minor, Andrew M.; Rappe, Andrew M.; Martin, Lane W.

    2017-05-01

    A range of modern applications require large and tunable dielectric, piezoelectric or pyroelectric response of ferroelectrics. Such effects are intimately connected to the nature of polarization and how it responds to externally applied stimuli. Ferroelectric susceptibilities are, in general, strongly temperature dependent, diminishing rapidly as one transitions away from the ferroelectric phase transition (TC). In turn, researchers seek new routes to manipulate polarization to simultaneously enhance susceptibilities and broaden operational temperature ranges. Here, we demonstrate such a capability by creating composition and strain gradients in Ba1-xSrxTiO3 films which result in spatial polarization gradients as large as 35 μC cm-2 across a 150 nm thick film. These polarization gradients allow for large dielectric permittivity with low loss (εr~775, tan δ<0.05), negligible temperature-dependence (13% deviation over 500 °C) and high-dielectric tunability (greater than 70% across a 300 °C range). The role of space charges in stabilizing polarization gradients is also discussed.

  12. Applicability of Stokes method for measuring viscosity of mixtures with concentration gradient

    Directory of Open Access Journals (Sweden)

    César Medina

    2017-12-01

    Full Text Available After measuring density and viscosity of a mixture of glycerin and water contained in a vertical pipe, a variation of these properties according to depth is observed. These gradients are typical of non-equilibrium states related to the lower density of water and the fact that relatively long times are necessary to achieve homogeneity. In the same pipe, the falling velocity of five little spheres is measured as a function of depth, and then a numerical fit is performed which agrees very well with experimental data. Based on the generalization of these results, the applicability of Stokes method is discussed for measuring viscosity of mixtures with a concentration gradient.

  13. Estimation of pore size distribution using concentric double pulsed-field gradient NMR.

    Science.gov (United States)

    Benjamini, Dan; Nevo, Uri

    2013-05-01

    Estimation of pore size distribution of well calibrated phantoms using NMR is demonstrated here for the first time. Porous materials are a central constituent in fields as diverse as biology, geology, and oil drilling. Noninvasive characterization of monodisperse porous samples using conventional pulsed-field gradient (PFG) NMR is a well-established method. However, estimation of pore size distribution of heterogeneous polydisperse systems, which comprise most of the materials found in nature, remains extremely challenging. Concentric double pulsed-field gradient (CDPFG) is a 2-D technique where both q (the amplitude of the diffusion gradient) and φ (the relative angle between the gradient pairs) are varied. A recent prediction indicates this method should produce a more accurate and robust estimation of pore size distribution than its conventional 1-D versions. Five well defined size distribution phantoms, consisting of 1-5 different pore sizes in the range of 5-25 μm were used. The estimated pore size distributions were all in good agreement with the known theoretical size distributions, and were obtained without any a priori assumption on the size distribution model. These findings support that in addition to its theoretical benefits, the CDPFG method is experimentally reliable. Furthermore, by adding the angle parameter, sensitivity to small compartment sizes is increased without the use of strong gradients, thus making CDPFG safe for biological applications. Copyright © 2013 Elsevier Inc. All rights reserved.

  14. Concentration gradient driven molecular dynamics: a new method for simulations of membrane permeation and separation.

    Science.gov (United States)

    Ozcan, Aydin; Perego, Claudio; Salvalaglio, Matteo; Parrinello, Michele; Yazaydin, Ozgur

    2017-05-01

    In this study, we introduce a new non-equilibrium molecular dynamics simulation method to perform simulations of concentration driven membrane permeation processes. The methodology is based on the application of a non-conservative bias force controlling the concentration of species at the inlet and outlet of a membrane. We demonstrate our method for pure methane, ethane and ethylene permeation and for ethane/ethylene separation through a flexible ZIF-8 membrane. Results show that a stationary concentration gradient is maintained across the membrane, realistically simulating an out-of-equilibrium diffusive process, and the computed permeabilities and selectivity are in good agreement with experimental results.

  15. Observation of Enhanced Hole Extraction in Br Concentration Gradient Perovskite Materials.

    Science.gov (United States)

    Kim, Min-Cheol; Kim, Byeong Jo; Son, Dae-Yong; Park, Nam-Gyu; Jung, Hyun Suk; Choi, Mansoo

    2016-09-14

    Enhancing hole extraction inside the perovskite layer is the key factor for boosting photovoltaic performance. Realization of halide concentration gradient perovskite materials has been expected to exhibit rapid hole extraction due to the precise bandgap tuning. Moreover, a formation of Br-rich region on the tri-iodide perovskite layer is expected to enhance moisture stability without a loss of current density. However, conventional synthetic techniques of perovskite materials such as the solution process have not achieved the realization of halide concentration gradient perovskite materials. In this report, we demonstrate the fabrication of Br concentration gradient mixed halide perovskite materials using a novel and facile halide conversion method based on vaporized hydrobromic acid. Accelerated hole extraction and enhanced lifetime due to Br gradient was verified by observing photoluminescence properties. Through the combination of secondary ion mass spectroscopy and transmission electron microscopy with energy-dispersive X-ray spectroscopy analysis, the diffusion behavior of Br ions in perovskite materials was investigated. The Br-gradient was found to be eventually converted into a homogeneous mixed halide layer after undergoing an intermixing process. Br-substituted perovskite solar cells exhibited a power conversion efficiency of 18.94% due to an increase in open circuit voltage from 1.08 to 1.11 V and an advance in fill-factor from 0.71 to 0.74. Long-term stability was also dramatically enhanced after the conversion process, i.e., the power conversion efficiency of the post-treated device has remained over 97% of the initial value under high humid conditions (40-90%) without any encapsulation for 4 weeks.

  16. A microfluidic device to establish concentration gradients using reagent density differences.

    Science.gov (United States)

    Kong, Qingjun; Able, Richard A; Dudu, Veronica; Vazquez, Maribel

    2010-12-01

    Microfabrication has become widely utilized to generate controlled microenvironments that establish chemical concentration gradients for a variety of engineering and life science applications. To establish microfluidic flow, the majority of existing devices rely upon additional facilities, equipment, and excessive reagent supplies, which together limit device portability as well as constrain device usage to individuals trained in technological disciplines. The current work presents our laboratory-developed bridged μLane system, which is a stand-alone device that runs via conventional pipette loading and can operate for several days without need of external machinery or additional reagent volumes. The bridged μLane is a two-layer polydimethylsiloxane microfluidic device that is able to establish controlled chemical concentration gradients over time by relying solely upon differences in reagent densities. Fluorescently labeled Dextran was used to validate the design and operation of the bridged μLane by evaluating experimentally measured transport properties within the microsystem in conjunction with numerical simulations and established mathematical transport models. Results demonstrate how the bridged μLane system was used to generate spatial concentration gradients that resulted in an experimentally measured Dextran diffusivity of (0.82 ± 0.01) × 10(-6) cm(2)/s.

  17. Total vs. internal element concentrations in Scots pine needles along a sulphur and metal pollution gradient

    International Nuclear Information System (INIS)

    Rautio, Pasi; Huttunen, Satu

    2003-01-01

    Different methods should be used for foliar analyses of trees used as bioindicators of pollution, than those analyses used in nutritional studies of trees. - Analysis of foliar elements is a commonly used method for studying tree nutrition and for monitoring the impacts of air pollutants on forest ecosystems. Interpretations based on the results of foliar element analysis may, however, be different in nutrition vs. monitoring studies. We studied the impacts of severe sulphur and metal (mainly Cu and Ni) pollution on the element concentrations (Al, Ca, Cu, Fe, K, Mg, Mn, Ni, P, Pb, S and Zn) in Scots pine (Pinus sylvestris L.) foliage along an airborne sulphur and metal pollution gradient. Emphasis was put on determining the contribution of air-borne particles that have accumulated on needle surfaces to the total foliage concentrations. A comparison of two soil extraction methods was carried out in order to obtain a reliable estimate of plant-available element concentrations in the soil. Element concentrations in the soil showed only a weak relationship with internal foliar concentrations. There were no clear differences between the total and internal needle S concentrations along the gradient, whereas at the plot closest to the metal smelter complex the total Cu concentrations in the youngest needles were 1.3-fold and Ni concentrations over 1.6-fold higher than the internal needle concentrations. Chloroform-extracted surface wax was found to have Ni and Cu concentrations of as high as 3000 and 600 μg/g of wax, respectively. Our results suggest that bioindicator studies (e.g. monitoring studies) may require different foliar analysis techniques from those used in studies on the nutritional status of trees

  18. DOC concentrations across a depth-dependent light gradient on a Caribbean coral reef

    Directory of Open Access Journals (Sweden)

    Benjamin Mueller

    2017-06-01

    Full Text Available Photosynthates released by benthic primary producers (BPP, such as reef algae and scleractinian corals, fuel the dissolved organic carbon (DOC production on tropical coral reefs. DOC concentrations near BPP have repeatedly been observed to be elevated compared to those in the surrounding water column. As the DOC release of BPP increases with increasing light availability, elevated DOC concentrations near them will, in part, also depend on light availability. Consequently, DOC concentrations are likely to be higher on the shallow, well-lit reef terrace than in deeper sections on the fore reef slope. We measured in situ DOC concentrations and light intensity in close proximity to the reef alga Dictyota sp. and the scleractinian coral Orbicella faveolata along a depth-dependent light gradient from 5 to 20 m depth and compared these to background concentrations in the water column. At 10 m (intermediate light, DOC concentrations near Dictyota sp. were elevated by 15 µmol C L−1 compared to background concentrations in the water column, but not at 5 and 20 m (high and low light, respectively, or near O. faveolata at any of the tested depths. DOC concentrations did not differ between depths and thereby light environments for any of the tested water types. However, water type and depth appear to jointly affect in situ DOC concentrations across the tested depth-dependent light gradient. Corroborative ex situ measurements of excitation pressure on photosystem II suggest that photoinhibition in Dictyota sp. is likely to occur at light intensities that are commonly present on Curaçaoan coral reefs under high light levels at 5 m depth during midday. Photoinhibition may have thereby reduced the DOC release of Dictyota sp. and DOC concentrations in its close proximity. Our results indicate that the occurrence of elevated DOC concentrations did not follow a natural light gradient across depth. Instead, a combination of multiple factors, such as water type

  19. DOC concentrations across a depth-dependent light gradient on a Caribbean coral reef.

    Science.gov (United States)

    Mueller, Benjamin; Meesters, Erik H; van Duyl, Fleur C

    2017-01-01

    Photosynthates released by benthic primary producers (BPP), such as reef algae and scleractinian corals, fuel the dissolved organic carbon (DOC) production on tropical coral reefs. DOC concentrations near BPP have repeatedly been observed to be elevated compared to those in the surrounding water column. As the DOC release of BPP increases with increasing light availability, elevated DOC concentrations near them will, in part, also depend on light availability. Consequently, DOC concentrations are likely to be higher on the shallow, well-lit reef terrace than in deeper sections on the fore reef slope. We measured in situ DOC concentrations and light intensity in close proximity to the reef alga Dictyota sp. and the scleractinian coral Orbicella faveolata along a depth-dependent light gradient from 5 to 20 m depth and compared these to background concentrations in the water column. At 10 m (intermediate light), DOC concentrations near Dictyota sp. were elevated by 15 µmol C L -1 compared to background concentrations in the water column, but not at 5 and 20 m (high and low light, respectively), or near O. faveolata at any of the tested depths. DOC concentrations did not differ between depths and thereby light environments for any of the tested water types. However, water type and depth appear to jointly affect in situ DOC concentrations across the tested depth-dependent light gradient. Corroborative ex situ measurements of excitation pressure on photosystem II suggest that photoinhibition in Dictyota sp. is likely to occur at light intensities that are commonly present on Curaçaoan coral reefs under high light levels at 5 m depth during midday. Photoinhibition may have thereby reduced the DOC release of Dictyota sp. and DOC concentrations in its close proximity. Our results indicate that the occurrence of elevated DOC concentrations did not follow a natural light gradient across depth. Instead, a combination of multiple factors, such as water type, light

  20. Log-stable concentration distributions of trace elements in biomedical samples

    Energy Technology Data Exchange (ETDEWEB)

    Kubala-Kukus, A. [Institute of Physics, Swietokrzyska Academy, Swietokrzyska 15, 25-406 Kielce (Poland)]. E-mail: Aldona.Kubala-Kukus@pu.kielce.pl; Kuternoga, E. [Institute of Physics, Swietokrzyska Academy, Swietokrzyska 15, 25-406 Kielce (Poland); Braziewicz, J. [Institute of Physics, Swietokrzyska Academy, Swietokrzyska 15, 25-406 Kielce (Poland); Pajek, M. [Institute of Physics, Swietokrzyska Academy, Swietokrzyska 15, 25-406 Kielce (Poland)

    2004-10-08

    In the present paper, which follows our earlier observation that the asymmetric and long-tailed concentration distributions of trace elements in biomedical samples, measured by the X-ray fluorescence techniques, can be modeled by the log-stable distributions, further specific aspects of this observation are discussed. First, we demonstrate that, typically, for a quite substantial fraction (10-20%) of trace elements studied in different kinds of biomedical samples, the measured concentration distributions are described in fact by the 'symmetric' log-stable distributions, i.e. the asymmetric distributions which are described by the symmetric stable distributions. This observation is, in fact, expected for the random multiplicative process, which models the concentration distributions of trace elements in the biomedical samples. The log-stable nature of concentration distribution of trace elements results in several problems of statistical nature, which have to be addressed in XRF data analysis practice. Consequently, in the present paper, the following problems, namely (i) the estimation of parameters for stable distributions and (ii) the testing of the log-stable nature of the concentration distribution by using the Anderson-Darling (A{sup 2}) test, especially for symmetric stable distributions, are discussed in detail. In particular, the maximum likelihood estimation and Monte Carlo simulation techniques were used, respectively, for estimation of stable distribution parameters and calculation of the critical values for the Anderson-Darling test. The discussed ideas are exemplified by the results of the study of trace element concentration distributions in selected biomedical samples, which were obtained by using the X-ray fluorescence (XRF, TXRF) methods.

  1. Log-stable concentration distributions of trace elements in biomedical samples

    International Nuclear Information System (INIS)

    Kubala-Kukus, A.; Kuternoga, E.; Braziewicz, J.; Pajek, M.

    2004-01-01

    In the present paper, which follows our earlier observation that the asymmetric and long-tailed concentration distributions of trace elements in biomedical samples, measured by the X-ray fluorescence techniques, can be modeled by the log-stable distributions, further specific aspects of this observation are discussed. First, we demonstrate that, typically, for a quite substantial fraction (10-20%) of trace elements studied in different kinds of biomedical samples, the measured concentration distributions are described in fact by the 'symmetric' log-stable distributions, i.e. the asymmetric distributions which are described by the symmetric stable distributions. This observation is, in fact, expected for the random multiplicative process, which models the concentration distributions of trace elements in the biomedical samples. The log-stable nature of concentration distribution of trace elements results in several problems of statistical nature, which have to be addressed in XRF data analysis practice. Consequently, in the present paper, the following problems, namely (i) the estimation of parameters for stable distributions and (ii) the testing of the log-stable nature of the concentration distribution by using the Anderson-Darling (A 2 ) test, especially for symmetric stable distributions, are discussed in detail. In particular, the maximum likelihood estimation and Monte Carlo simulation techniques were used, respectively, for estimation of stable distribution parameters and calculation of the critical values for the Anderson-Darling test. The discussed ideas are exemplified by the results of the study of trace element concentration distributions in selected biomedical samples, which were obtained by using the X-ray fluorescence (XRF, TXRF) methods

  2. Factors associated with NO2 and NOX concentration gradients near a highway

    Science.gov (United States)

    Richmond-Bryant, J.; Snyder, M. G.; Owen, R. C.; Kimbrough, S.

    2018-02-01

    The objective of this research is to learn how the near-road gradient, in which NO2 and NOX (NO + NO2) concentrations are elevated, varies with changes in meteorological and traffic variables. Measurements of NO2 and NOX were obtained east of I-15 in Las Vegas and fit to functions whose slopes (dCNO2/dx and dCNOX/dx, respectively) characterize the size of the near-road zone where NO2 and NOX concentrations from mobile sources on the highway are elevated. These metrics were used to learn about the near-road gradient by modeling dCNO2/dx and dCNOX/dx as functions of meteorological variables (e.g., wind direction, wind speed), traffic (vehicle count), NOX concentration upwind of the road, and O3 concentration at two fixed-site ambient monitors. Generalized additive models (GAM) were used to model dCNO2/dx and dCNOX/dx versus the independent variables because they allowed for nonlinearity of the variables being compared. When data from all wind directions were included in the analysis, variability in O3 concentration comprised the largest proportion of variability in dCNO2/dx, followed by variability in wind direction. In a second analysis constrained to winds from the west, variability in O3 concentration remained the largest contributor to variability in dCNO2/dx, but the relative contribution of variability in wind speed to variability in dCNO2/dx increased relative to its contribution for the all-wind analysis. When data from all wind directions were analyzed, variability in wind direction was by far the largest contributor to variability in dCNOX/dx, with smaller contributions from hour of day and upwind NOX concentration. When only winds from the west were analyzed, variability in upwind NOX concentration, wind speed, hour of day, and traffic count all were associated with variability in dCNOX/dx. Increases in O3 concentration were associated with increased magnitude near-road dCNO2/dx, possibly shrinking the zone of elevated concentrations occurring near roads

  3. Concentrations of radiocesium and stable elements in different parts of pine tree collected in Chernobyl area

    International Nuclear Information System (INIS)

    Yoshida, Satoshi; Watanabe, Masumi; Suzuki, Akira; Linkov, Igor; Dvornik, Alexander; Zhuchenko, Tatiana

    2007-01-01

    Radial distributions of 137 Cs and related stable elements in a pine tree collected in Chernobyl contaminated area in Belarus were determined, in order to get basic information for dose estimation of pine tree. The concentration of 137 Cs in annual tree rings was the highest in cambium, and decreased sharply toward inside. The highest concentration of 137 Cs in cambium suggests the highest radiation dose to growing part of wood. Distribution of stable Cs was similar as that of 137 Cs, and the 137 Cs/stable Cs ratio was almost constant, indicating the equilibrium of Chernobyl 137 Cs with stable Cs in the pine wood. The similar distributions as Cs were observed for K and Rb. (author)

  4. A gradient stable scheme for a phase field model for the moving contact line problem

    KAUST Repository

    Gao, Min

    2012-02-01

    In this paper, an efficient numerical scheme is designed for a phase field model for the moving contact line problem, which consists of a coupled system of the Cahn-Hilliard and Navier-Stokes equations with the generalized Navier boundary condition [1,2,4]. The nonlinear version of the scheme is semi-implicit in time and is based on a convex splitting of the Cahn-Hilliard free energy (including the boundary energy) together with a projection method for the Navier-Stokes equations. We show, under certain conditions, the scheme has the total energy decaying property and is unconditionally stable. The linearized scheme is easy to implement and introduces only mild CFL time constraint. Numerical tests are carried out to verify the accuracy and stability of the scheme. The behavior of the solution near the contact line is examined. It is verified that, when the interface intersects with the boundary, the consistent splitting scheme [21,22] for the Navier Stokes equations has the better accuracy for pressure. © 2011 Elsevier Inc.

  5. Assessing secondary science students' knowledge of molecule movement, concentration gradients, and equilibrium through multiple contexts

    Science.gov (United States)

    Raven, Sara

    2015-09-01

    Background: Studies have shown that students' knowledge of osmosis and diffusion and the concepts associated with these processes is often inaccurate. This is important to address, as these concepts not only provide the foundation for more advanced topics in biology and chemistry, but are also threaded throughout both state and national science standards. Purpose: In this study, designed to determine the completeness and accuracy of three specific students' knowledge of molecule movement, concentration gradients, and equilibrium, I sought to address the following question: Using multiple evaluative methods, how can students' knowledge of molecule movement, concentration gradients, and equilibrium be characterized? Sample: This study focuses on data gathered from three students - Emma, Henry, and Riley - all of whom were gifted/honors ninth-grade biology students at a suburban high school in the southeast United States. Design and Methods: Using various qualitative data analysis techniques, I analyzed multiple sources of data from the three students, including multiple-choice test results, written free-response answers, think-aloud interview responses, and student drawings. Results: Results of the analysis showed that students maintained misconceptions about molecule movement, concentration gradients, and equilibrium. The conceptual knowledge students demonstrated differed depending on the assessment method, with the most distinct differences appearing on the multiple-choice versus the free-response questions, and in verbal versus written formats. Conclusions: Multiple levels of assessment may be required to obtain an accurate picture of content knowledge, as free-response and illustrative tasks made it difficult for students to conceal any misconceptions. Using a variety of assessment methods within a section of the curriculum can arguably help to provide a deeper understanding of student knowledge and learning, as well as illuminate misconceptions that may have

  6. Caffeine Citrate Dosing Adjustments to Assure Stable Caffeine Concentrations in Preterm Neonates.

    Science.gov (United States)

    Koch, Gilbert; Datta, Alexandre N; Jost, Kerstin; Schulzke, Sven M; van den Anker, John; Pfister, Marc

    2017-12-01

    To identify dosing strategies that will assure stable caffeine concentrations in preterm neonates despite changing caffeine clearance during the first 8 weeks of life. A 3-step simulation approach was used to compute caffeine doses that would achieve stable caffeine concentrations in the first 8 weeks after birth: (1) a mathematical weight change model was developed based on published weight distribution data; (2) a pharmacokinetic model was developed based on published models that accounts for individual body weight, postnatal, and gestational age on caffeine clearance and volume of distribution; and (3) caffeine concentrations were simulated for different dosing regimens. A standard dosing regimen of caffeine citrate (using a 20 mg/kg loading dose and 5 mg/kg/day maintenance dose) is associated with a maximal trough caffeine concentration of 15 mg/L after 1 week of treatment. However, trough concentrations subsequently exhibit a clinically relevant decrease because of increasing clearance. Model-based simulations indicate that an adjusted maintenance dose of 6 mg/kg/day in the second week, 7 mg/kg/day in the third to fourth week and 8 mg/kg/day in the fifth to eighth week assures stable caffeine concentrations with a target trough concentration of 15 mg/L. To assure stable caffeine concentrations during the first 8 weeks of life, the caffeine citrate maintenance dose needs to be increased by 1 mg/kg every 1-2 weeks. These simple adjustments are expected to maintain exposure to stable caffeine concentrations throughout this important developmental period and might enhance both the short- and long-term beneficial effects of caffeine treatment. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Enhanced Vertical Concentration Gradient in Rubbed P3HT:PCBM Graded Bilayer Solar Cells.

    Science.gov (United States)

    Vohra, Varun; Arrighetti, Gianmichele; Barba, Luisa; Higashimine, Koichi; Porzio, William; Murata, Hideyuki

    2012-07-05

    Graded bilayer solar cells have proven to be at least as efficient as the bulk heterojunctions when it comes to the Poly(3-hexylthiophene) (P3HT) - [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) donor-acceptor system. However, control of the vertical concentration gradient using simple techniques has never been reported. We demonstrate that rubbing the P3HT layer prior to PCBM deposition induces major morphological changes in the active layer. Using the newly introduced energy-dispersive X-ray spectroscopy element mapping technique, we found that rubbing P3HT induces the formation of an ideal vertical donor-acceptor concentration gradient. Furthermore, the P3HT crystallites undergo a molecular reorientation from edge-on to face-on configuration inducing a better charge transport in the vertical direction. The combination of these two major morphological changes leads to the fabrication of high-performance solar cells that exhibit, to date, the record efficiencies for spin-coated graded bilayers solar cells.

  8. Heterostructured electrode with concentration gradient shell for highly efficient oxygen reduction at low temperature

    Science.gov (United States)

    Zhou, Wei; Liang, Fengli; Shao, Zongping; Chen, Jiuling; Zhu, Zhonghua

    2011-11-01

    Heterostructures of oxides have been widely investigated in optical, catalytic and electrochemical applications, because the heterostructured interfaces exhibit pronouncedly different transport, charge, and reactivity characteristics compared to the bulk of the oxides. Here we fabricated a three-dimensional (3D) heterostructured electrode with a concentration gradient shell. The concentration gradient shell with the composition of Ba0.5-xSr0.5-yCo0.8Fe0.2O3-δ (BSCF-D) was prepared by simply treating porous Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) backbone with microwave-plasma. Electrochemical impedance spectroscopy reveals that the oxygen surface exchange rate of the BSCF-D is enhanced by ~250% that of the pristine BSCF due to the appearance of the shell. The heterostructured electrode shows an interfacial resistance as low as 0.148 Ω cm2 at 550°C and an unchanged electrochemical performance after heating treatment for 200 h. This method offers potential to prepare heterostructured oxides not only for electrochemical devices but also for many other applications that use ceramic materials.

  9. Cow hair allergen concentrations in dairy farms with automatic and conventional milking systems: From stable to bedroom.

    Science.gov (United States)

    Böhlandt, A; Schierl, R; Heizinger, J; Dietrich-Gümperlein, G; Zahradnik, E; Bruckmaier, L; Sültz, J; Raulf, M; Nowak, D

    2016-01-01

    Bovine hair and dander are considered to be a notable risk factor for sensitization and allergic symptoms in occupationally exposed cattle farmers due to various IgE binding proteins. Farmers are suspected not only to be exposed during their work inside the stables but also inside their homes as allergens could be transferred via hair and clothes resulting in continued bovine allergen exposure in private areas. In recent years a new sensitive sandwich ELISA (enzyme linked immunosorbent assay) test has been developed to measure the cow hair allergen (CHA) concentration in dust. The aim of the present study was to determine the CHA concentration in airborne and settled dust samples in stables and private rooms of dairy cattle farms with automatic milking systems (AM) and conventional milking systems (CM), also with respect to questionnaire data on farming characteristics. For this purpose different sampling techniques were applied, and results and practicability of the techniques were compared. Dust sampling was performed in the stable, computer room (only AM), changing room, living room and bedroom (mattress) of 12 dairy farms with automatic milking systems (AM group) and eight dairy farms with conventional milking systems (CM group). Altogether, 90 samples were taken by ALK filter dust collectors from all locations, while 32 samples were collected by an ion charging device (ICD) and 24 samples by an electronic dust fall collector (EDC) in computer rooms (AM) and/or changing and living rooms (not stables). The dust samples were extracted and analyzed for CHA content with a sandwich ELISA. At all investigated locations, CHA concentrations were above the limit of detection (LOD) of 0.1 ng/ml dust extract. The median CHA concentrations in dust collected by ALK filters ranged from 63 to 7154 μg/g dust in AM farms and from 121 to 5627 μg/g dust in CM farms with a steep concentration gradient from stables to bedrooms. ICD sampling revealed median CHA contents of 112

  10. Cellular effect and efficacy of carfilzomib depends on cellular net concentration gradient.

    Science.gov (United States)

    Schäfer, Julia; Welti, Lukas; Seckinger, Anja; Burhenne, Jürgen; Theile, Dirk; Weiss, Johanna

    2017-07-01

    The cellular interrelation between intracellular concentrations of unbound carfilzomib, a second-generation proteasome inhibitor, and subsequent proteasome inhibition and effect on cell viability are unknown and were evaluated for two different exposure regimens: A high dose bolus regime of 500 nM for 1 h followed by 47 h in drug-free media vs. 48-h continuous exposure to 10 nM. Eight multiple myeloma cell lines were exposed to either one of the two exposure regimens. We quantified the intracellular unbound carfilzomib fraction up to 48 h with a new ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC/MS/MS) method. Intracellular concentrations were compared to simultaneously determined cell viability (AlamarBlue ® assay) and proteasomal subunit activity (ProGlo™ assay). Within the first 10 min, the proportional intracellular enrichment of unbound carfilzomib was higher (313 nM; 62.6%) for the exposure to 500 nM compared to 10 nM (1.93 nM; 19.3%). However, after 1 h, an intracellular/extracellular concentration equilibrium was reached with both settings. At low exposure concentrations, drug removal after 1 h diminished carfilzomib efficacy. Moreover, proteasomal activity recovered when exposed to 10 nM for 48 h. However, when exposure concentration was high (500 nM) proteasome inhibition was complete and sustained even with drug removal after 1 h. We demonstrated that the carfilzomib concentration gradient determines cellular uptake kinetics. The uptake kinetics in turn affects binding, saturation, and activity of the proteasome. Together, these data underscore the importance of steep concentrations for the in vitro efficacy of carfilzomib.

  11. Seasonal Gradient Patterns of Polycyclic Aromatic Hydrocarbons and Particulate Matter Concentrations near a Highway

    Directory of Open Access Journals (Sweden)

    Francisco Artigas

    2011-09-01

    Full Text Available Close proximity to roadways has been associated with higher exposure to traffic-related air pollutants. However, analyses of the effects of season and meteorological parameters on horizontal gradient patterns of traffic-generated air pollutants still need to be elucidated. Our objectives were to: (1 determine effects of season on horizontal gradient patterns of polycyclic aromatic hydrocarbons (PAHs, total suspended particles (TSP, and PM2.5 near a heavily trafficked highway; and (2 examine the effect of day-of-the-week variations (weekday versus weekend associated with traffic counts on measured airborne-contaminant levels. PAHs (Σ8PAHs [MW 228–278]; gas + particulate, TSP and PM2.5 were monitored at nominal distances (50, 100, and 150 m from the New Jersey Turnpike every 6 days for periods of 24 h, between September 2007 and September 2008. Seasonal variations in the horizontal gradient patterns of Σ8PAHs were observed. In the summer, Σ8PAHs declined significantly between 50–100 m from the highway (23% decrease, but not between the furthermost distances (100–150 m. An inverse pattern was observed in the winter: Σ8PAHs declined between 100–150 m (26% decrease, but not between the closest distances. Σ8PAHs and TSP, but not PM2.5, concentrations measured on weekends were 12–37% lower than those on weekdays, respectively, corresponding to lower diesel traffic volume. This study suggests that people living in the close proximity to highways may be exposed to varying levels of Σ8PAHs, TSP, and PM2.5 depending on distance to highway, season, and day-of-the-week variations.

  12. Perioperative plasma concentrations of stable nitric oxide products are predictive of cognitive dysfunction after laparoscopic cholecystectomy.

    LENUS (Irish Health Repository)

    Iohom, G

    2012-02-03

    In this study our objectives were to determine the incidence of postoperative cognitive dysfunction (POCD) after laparoscopic cholecystectomy under sevoflurane anesthesia in patients aged >40 and <85 yr and to examine the associations between plasma concentrations of i) S-100beta protein and ii) stable nitric oxide (NO) products and POCD in this clinical setting. Neuropsychological tests were performed on 42 ASA physical status I-II patients the day before, and 4 days and 6 wk after surgery. Patient spouses (n = 13) were studied as controls. Cognitive dysfunction was defined as deficit in one or more cognitive domain(s). Serial measurements of serum concentrations of S-100beta protein and plasma concentrations of stable NO products (nitrate\\/nitrite, NOx) were performed perioperatively. Four days after surgery, new cognitive deficit was present in 16 (40%) patients and in 1 (7%) control subject (P = 0.01). Six weeks postoperatively, new cognitive deficit was present in 21 (53%) patients and 3 (23%) control subjects (P = 0.03). Compared with the "no deficit" group, patients who demonstrated a new cognitive deficit 4 days postoperatively had larger plasma NOx at each perioperative time point (P < 0.05 for each time point). Serum S-100beta protein concentrations were similar in the 2 groups. In conclusion, preoperative (and postoperative) plasma concentrations of stable NO products (but not S-100beta) are associated with early POCD. The former represents a potential biochemical predictor of POCD.

  13. Elemental concentrations in deposited dust on leaves along an urbanization gradient.

    Science.gov (United States)

    Simon, Edina; Baranyai, Edina; Braun, Mihály; Cserháti, Csaba; Fábián, István; Tóthmérész, Béla

    2014-08-15

    Environmental health is an essential component of the quality of life in modern societies. Monitoring of environmental quality and the assessment of environmental risks are often species based on the elemental concentration of deposited dust. Our result suggested that stomata size and distribution were the most important factors influencing the accumulation of air contaminants in leaves. We found that the leaves' surfaces of Acer negundo and Celtis occidentalis were covered by a large number of trichomes, and these species have proven to be suitable biomonitors for atmospheric pollution difficult; these can be overcome using bioindicator species. Leaves of Padus serotina, Acer campestre, A. negundo, Quercus robur and C. occidentalis were used to assess the amount of deposited dust and the concentration of contaminants in deposited dust in and around the city of Debrecen, Hungary. Samples were collected from an urban, suburban and rural area along an urbanization gradient. The concentrations of Ba, Cu, Fe, Mn, Ni, Pb, S, Sr and Zn were determined in deposited dust using ICP-OES. Scanning electron microscopy (SEM) was used to explore the morphological structure and dust absorbing capacity of leaves. We found significant differences in dust deposition among species, and dust deposition correlated with trichomes' density. Principal component analysis (PCA) also showed a total separation of tree. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Heavy metal concentration in coat hair and hoof horn in stabled and reserve Polish Konik horses.

    Science.gov (United States)

    Stachurska, A; Wałkuska, G; Chałabis-Mazurek, A; Jaworski, Z; Cebera, M

    2009-01-01

    The objective of the study was to determine if there were differences in Cr, Mn, Cu, Cd, Pb and Ni levels in coat hair and hoof horn between Polish Konik horses maintained in stabled and reserve systems in Roztocze National Park in Poland. Summer and winter feeding seasons (seasons of the year in case of hooves) and age of horses were taken into account. 107 samples of hair and hooves, as well as all kinds of feed and sources of water available for the horses were examined. The results of the study indicate that the concentration of the elements in the coat hair, hoof horn, feeds and water is usually too low to show possible influence of the system of maintenance in feeding seasons and age effect. The reserve horses are not more exposed to heavy metal contamination than the stabled horses. In the hair, solely Mn level is affected by the systems of maintenance in summer and winter feeding seasons: during winter it is higher, particularly in the stabled system, than during summer. In hooves, Cr concentration is higher in stabled horses than in reserve horses and conversely, Cu content is higher in the reserve horses. Mn content is age-affected both in hair and hooves, likewise is Cu content in the hooves. The results indicate a necessity of Cu compound supplementation in feeding the horses in both systems of maintenance.

  15. Decay of the zincate concentration gradient at an alkaline zinc cathode after charging

    Science.gov (United States)

    Kautz, H. E.; May, C. E.

    1979-01-01

    The transport of the zincate ion to the alkaline zinc cathode was studied by observing the decay of the zincate concentration gradient at a horizontal zinc cathode after charging. This decay was found to approximate first order kinetics as expected from a proposed boundary layer model. The concentrations were calculated from polarization voltages. The decay half life was shown to be a linear function of the thickness of porous zinc deposit on the cathode indicating a very rapid transport of zincate through porous zinc metal. The rapid transport is attributed to an electrochemical mechanism. From the linear dependence of the half life on the thickness the boundary layer thickness was found to be about 0.010 cm when the cathode was at the bottom of the cell. No significant dependence of the boundary layer thickness on the viscosity of electrolyte was observed. The data also indicated a relatively sharp transition between the diffusion and convection transport regions. When the cathode was at the top of the cell, the boundary layer thickness was found to be roughly 0.080 cm. The diffusion of zincate ion through asbestos submerged in alkaline electrolyte was shown to be comparable with that predicted from the bulk diffusion coefficient of the zincate ion in alkali.

  16. Ammonia Diffusion through Nalophan Double Bags: Effect of Concentration Gradient Reduction

    Science.gov (United States)

    Capelli, Laura; Boiardi, Emanuela; Del Rosso, Renato

    2014-01-01

    The ammonia loss through Nalophan bags has been studied. The losses observed for storage conditions and times as allowed by the reference standard for dynamic olfactometry (EN 13725:2003) indicate that odour concentration values due to the presence of small molecules may be significantly underestimated if samples are not analysed immediately after sampling. A diffusion model was used in order to study diffusion through the bag. The study discusses the effect of concentration gradient (ΔC) across the polymeric membrane of the analyte. The ΔC was controlled by using a setup bag called “double bags.” Experimental data show a reduction of ammonia percentage losses due to the effect of the external multibarrier. The expedient of the double bag loaded with the same gas mixture allows a reduced diffusion of ammonia into the inner bag. Comparing the inner bag losses with those of the single bag stored in the same conditions (T, P, u) and with equal geometrical characteristics (S/V, z), it was observed that the inner bag of the double bag displays a 16% loss while the single bag displays a 37% loss. Acting on the ΔC it is possible to achieve a gross reduction of 57% in the ammonia leakage due to diffusion. PMID:25506608

  17. Ammonia diffusion through Nalophan double bags: effect of concentration gradient reduction.

    Science.gov (United States)

    Sironi, Selena; Eusebio, Lidia; Capelli, Laura; Boiardi, Emanuela; Del Rosso, Renato

    2014-01-01

    The ammonia loss through Nalophan bags has been studied. The losses observed for storage conditions and times as allowed by the reference standard for dynamic olfactometry (EN 13725:2003) indicate that odour concentration values due to the presence of small molecules may be significantly underestimated if samples are not analysed immediately after sampling. A diffusion model was used in order to study diffusion through the bag. The study discusses the effect of concentration gradient (ΔC) across the polymeric membrane of the analyte. The ΔC was controlled by using a setup bag called "double bags." Experimental data show a reduction of ammonia percentage losses due to the effect of the external multibarrier. The expedient of the double bag loaded with the same gas mixture allows a reduced diffusion of ammonia into the inner bag. Comparing the inner bag losses with those of the single bag stored in the same conditions (T, P, u) and with equal geometrical characteristics (S/V, z), it was observed that the inner bag of the double bag displays a 16% loss while the single bag displays a 37% loss. Acting on the ΔC it is possible to achieve a gross reduction of 57% in the ammonia leakage due to diffusion.

  18. Miniaturized Antimicrobial Susceptibility Test by Combining Concentration Gradient Generation and Rapid Cell Culturing

    Directory of Open Access Journals (Sweden)

    Samuel C. Kim

    2015-10-01

    Full Text Available Effective treatment of bacterial infection relies on timely diagnosis and proper prescription of antibiotic drugs. The antimicrobial susceptibility test (AST is one of the most crucial experimental procedures, providing the baseline information for choosing effective antibiotic agents and their dosages. Conventional methods, however, require long incubation times or significant instrumentation costs to obtain test results. We propose a lab-on-a-chip approach to perform AST in a simple, economic, and rapid manner. Our assay platform miniaturizes the standard broth microdilution method on a microfluidic device (20 × 20 mm that generates an antibiotic concentration gradient and delivers antibiotic-containing culture media to eight 30-nL chambers for cell culture. When tested with 20 μL samples of a model bacterial strain (E. coli ATCC 25922 treated with ampicillin or streptomycin, our method allows for the determination of minimum inhibitory concentrations consistent with the microdilution test in three hours, which is almost a factor of ten more rapid than the standard method.

  19. Dual gradients of light intensity and nutrient concentration for full-factorial mapping of photosynthetic productivity.

    Science.gov (United States)

    Nguyen, Brian; Graham, Percival J; Sinton, David

    2016-08-07

    Optimizing bioproduct generation from microalgae is complicated by the myriad of coupled parameters affecting photosynthetic productivity. Quantifying the effect of multiple coupled parameters in full-factorial fashion requires a prohibitively high number of experiments. We present a simple hydrogel-based platform for the rapid, full-factorial mapping of light and nutrient availability on the growth and lipid accumulation of microalgae. We accomplish this without microfabrication using thin sheets of cell-laden hydrogels. By immobilizing the algae in a hydrogel matrix we are able to take full advantage of the continuous spatial chemical gradient produced by a diffusion-based gradient generator while eliminating the need for chambers. We map the effect of light intensities between 0 μmol m(-2) s(-1) and 130 μmol m(-2) s(-1) (∼28 W m(-2)) coupled with ammonium concentrations between 0 mM and 7 mM on Chlamydomonas reinhardtii. Our data set, verified with bulk experiments, clarifies the role of ammonium availability on the photosynthetic productivity Chlamydomonas reinhardtii, demonstrating the dependence of ammonium inhibition on light intensity. Specifically, a sharp optimal growth peak emerges at approximately 2 mM only for light intensities between 80 and 100 μmol m(-2) s(-1)- suggesting that ammonium inhibition is insignificant at lower light intensities. We speculate that this phenomenon is due to the regulation of the high affinity ammonium transport system in Chlamydomonas reinhardtii as well as free ammonia toxicity. The complexity of this photosynthetic biological response highlights the importance of full-factorial data sets as enabled here.

  20. Elemental concentrations in deposited dust on leaves along an urbanization gradient

    Energy Technology Data Exchange (ETDEWEB)

    Simon, Edina, E-mail: edina.simon@gmail.com [Department of Ecology, University of Debrecen, H-4010 Debrecen, P.O. Box 71 (Hungary); Baranyai, Edina [Department of Inorganic and Analytical Chemistry, University of Debrecen, H-4010 Debrecen, P.O. Box 21 (Hungary); Agilent Atomic Spectroscopy Partner Laboratory, University of Debrecen, Egyetem tér 1, H-4032 Debrecen (Hungary); Braun, Mihály [Institute of Nuclear Research of the Hungarian Academy of Sciences, Herteleni Laboratory of Environmental Studies, 4026 Debrecen, Bem tér 18/C (Hungary); Cserháti, Csaba [Department of Solid State Physics, University of Debrecen, H-4010 Debrecen, P.O. Box 2 (Hungary); Fábián, István [Department of Inorganic and Analytical Chemistry, University of Debrecen, H-4010 Debrecen, P.O. Box 21 (Hungary); Tóthmérész, Béla [HAS-UD Biodiversity and Ecosystem Services Research Group, H-4010 Debrecen, P.O. Box 71 (Hungary)

    2014-08-15

    Environmental health is an essential component of the quality of life in modern societies. Monitoring of environmental quality and the assessment of environmental risks are often species based on the elemental concentration of deposited dust. Our result suggested that stomata size and distribution were the most important factors influencing the accumulation of air contaminants in leaves. We found that the leaves' surfaces of Acer negundo and Celtis occidentalis were covered by a large number of trichomes, and these species have proven to be suitable biomonitors for atmospheric pollution difficult; these can be overcome using bioindicator species. Leaves of Padus serotina, Acer campestre, A. negundo, Quercus robur and C. occidentalis were used to assess the amount of deposited dust and the concentration of contaminants in deposited dust in and around the city of Debrecen, Hungary. Samples were collected from an urban, suburban and rural area along an urbanization gradient. The concentrations of Ba, Cu, Fe, Mn, Ni, Pb, S, Sr and Zn were determined in deposited dust using ICP–OES. Scanning electron microscopy (SEM) was used to explore the morphological structure and dust absorbing capacity of leaves. We found significant differences in dust deposition among species, and dust deposition correlated with trichomes' density. Principal component analysis (PCA) also showed a total separation of tree. - Highlights: • Dust is used as indicators of the accumulation of inorganic pollutants. • Scanning EM was used to explore the morphological structure of leaves. • Amount of dust deposited of leaves correlated with trichomes' density. • A. negundo, C. occidentalis and Q. robur are suitable to indicate air contaminants. • A. negundo and C. occidentalis are suitable to decrease the amount of dust in air.

  1. [Systems with a concentration gradient have no potential energy but have the ability to do useful work].

    Science.gov (United States)

    Bazhin, N M

    2015-01-01

    The systems with the concentration gradient have no potential energy for heat and useful work production. Nevertheless, they have the ability to do useful work due to the heat dragged from the environment using, for instance, electrodes in the concentration cells. The second law of thermodynamics is not violated: work process occurred due to the heat dragged from the environment is coupled with the process of concentration leveling.

  2. Thermoelectric properties of high electron concentration materials under large temperature gradients

    International Nuclear Information System (INIS)

    Bulat, L.P.; Stefansky, V.A.

    1994-01-01

    Theoretical methods of investigating of transport properties in solids under large temperature gradients are grounded. The nonlinear and non-local expressions for current density and heat flow are obtained with degenerated of current carriers gas. A number of new effects with large temperature gradients have been tested. Use of large temperature gradients leads to the increasing of the thermoelectric figure of merit. copyright 1995 American Institute of Physics

  3. Stable isotope and high precision concentration measurements confirm that all humans produce and exhale methane.

    Science.gov (United States)

    Keppler, Frank; Schiller, Amanda; Ehehalt, Robert; Greule, Markus; Hartmann, Jan; Polag, Daniela

    2016-01-29

    Mammalian formation of methane (methanogenesis) is widely considered to occur exclusively by anaerobic microbial activity in the gastrointestinal tract. Approximately one third of humans, depending on colonization of the gut by methanogenic archaea, are considered methane producers based on the classification terminology of high and low emitters. In this study laser absorption spectroscopy was used to precisely measure concentrations and stable carbon isotope signatures of exhaled methane in breath samples from 112 volunteers with an age range from 1 to 80 years. Here we provide analytical evidence that volunteers exhaled methane levels were significantly above background (inhaled) air. Furthermore, stable carbon isotope values of the exhaled methane unambiguously confirmed that this gas was produced by all of the human subjects studied. Based on the emission and stable carbon isotope patterns of various age groups we hypothesize that next to microbial sources in the gastrointestinal tracts there might be other, as yet unidentified, processes involved in methane formation supporting the idea that humans might also produce methane endogenously in cells. Finally we suggest that stable isotope measurements of volatile organic compounds such as methane might become a useful tool in future medical research diagnostic programs.

  4. Studies on concentration of minor stable elements in marine environmental samples

    International Nuclear Information System (INIS)

    Suzuki, Hamaji; Ishii, Toshiaki; Iimura, Mitsue; Koyanagi, Taku

    1978-01-01

    Information on the physico-chemical state and quantity of stable elements in marine environments is frequently required to analyze the radioecological behavior of radionuclides released from nuclear facilities into the sea. In this work, determination of stable Mn, Fe, Co, Zn, Zr, Rb, Cs and some rare earth elements (Ce, Eu, Tb, Yb and Lu) in seawater and marine organisms was carried out and the concentration factors were estimated. Seawater and marine organisms were collected on the seashore of Ibaraki Prefecture and analysed by means of neutron activation analysis or atomic absorption spectrometry depending on the elements or samples. Average concentration factors of the rare earth elements by marine organisms are estimated as 3 x 10 1 : muscle of fish, 5 x 10 2 : soft part of clams, and 2 x 10 2 : algae, respectively. Concentration factors by muscle of fishes were 10 3 : Fe, 2 x 10 2 : Co, 5 x 10 2 : Zn, and 5 x 10 1 : Cs, and those by soft part of shellfishes were 10 4 : Fe, 10 3 : Co, 2 x 10 3 : Zn, and 10 1 : Cs, whereas those by algae were 2 x 10 4 : Fe, 5 x 10 2 : Co, 10 3 : Zn, and 3 x 10 1 : Cs, respectively. The high concentration factors for numerous stable elements by shellfishes and algae suggested their suitabilities to the indicator organisms for monitoring of marine pollution by these heavy metals and corresponding radioisotopes and also their significant contribution to the internal radiation exposure to man as radioactive seafoods. (author)

  5. Beaver ponds increase methylmercury concentrations in Canadian shield streams along vegetation and pond-age gradients.

    Science.gov (United States)

    Roy, Virginie; Amyot, Marc; Carignan, Richard

    2009-08-01

    Beaver impoundments flood forested areas and may be important production sites for methylmercury (MeHg) because of the resulting enhanced microbial activity and oxygen depletion. The influence of 17 beaver impoundments on streamwater chemistry (total mercury (THg), MeHg, nutrients, cations, and anions)] was investigated by sampling sites located along vegetation and pond-age gradients in southwestern Quebec (Canada). Recently inundated beaver ponds (beaver ponds as suggested by depletions of dissolved oxygen, sulfate and nitrite-nitrate concentrations, and increases in nutrients (e.g., dissolved organic carbon, total phosphorus, and total nitrogen) in outlets compared to inlets. Acidic waters at coniferous sites may have stimulated more MeHg production than in mixed woodland regions. Lower methylation efficiencies in older ponds (> 20 years old) may be due to the degradation of less labile organic matter as ponds age. Beavers actively alter watersheds by building impoundments, and our findings indicate that this landscape disturbance may be a significant source of MeHg to downstream water bodies.

  6. Radioactive and stable cobalt concentrations in mussel in Kyushu island, Japan

    International Nuclear Information System (INIS)

    Momoshima, Noriyuki; Shiki, Atsushi; Takashima, Yoshimasa; Maki, Takao; Koriyama, Munehiro; Shimozono, Seika; Imamura, Hiroka; Nakamata, Kojiro.

    1985-01-01

    Two kinds of mussel, Septifer virgatus and Mytilus edulis, were collected from Kyushu island, Japan, in order to elucidate a background level of 60 Co, which is one of the most significant radionuclide for environmental monitoring around a nuclear power plant. The mussels were collected from 7 locations in 1983 and classified 2 or 3 groups depending on their shell size at each location. Activities of 60 Co were measured by a low-background β counter after purified by means of chemical separation and electrodeposition. Stable cobalt concentrations were determined by colorimetric method. The concentrations of cobalt in Septifer virgatus are one order higher level than that in Mytilus edulis. There are not so large difference in cobalt content depending on shell size so long as comparing them at the same location. The radioactivities in mussels show the same trend as stable cobalt. It has become apparent that Septifer virgatus has a tendency to concentrate cobalt with growing but Mytilus edulis is opposite. The cobalt-60 introduced to sea from nuclear explosions seems to be relatively constant in coastal seawater since specific activities are distributed in a narrow range in spite of kind, shell size and location. (author)

  7. Deflagration-to-detonation transition and detonation propagation in H2-air mixtures with transverse concentration gradients

    International Nuclear Information System (INIS)

    Boeck, Lorenz Rupprecht

    2015-01-01

    Explosion of H 2 -air mixtures portrays a major hazard in nuclear reactors during severe loss-of-coolant accidents. Spatial gradients in H 2 concentration prevail in real-world scenarios. Mixture inhomogeneity can lead to significantly stronger explosions as compared to homogeneous mixtures. The present work identifies and quantifies the underlying physical mechanisms.

  8. Finite element modelling and design of a concentration gradient generating bioreactor: application to biological pattern formation and toxicology.

    Science.gov (United States)

    Vozzi, Giovanni; Mazzei, Daniele; Tirella, Annalisa; Vozzi, Federico; Ahluwalia, Arti

    2010-09-01

    This paper describes the use of a microfluidic gradient maker for the toxicological analysis of some conventional biomolecules such as hydrogen peroxide and a local anaesthetic, lidocaine on different cell cultures, human endothelial cells and myoblasts, respectively. The microfluidic device was designed and simulated using COMSOL Multiphysics and the concentration gradient in the microfluidic network was analysed through a fluid-dynamic and mass-transport study. Subsequently the device was fabricated with soft lithography, casting PDMS in a master to obtain channels about 250 microm deep. Hydrogen peroxide was tested on human endothelial cells, while lidocaine was tested on C2C12 myoblasts and an analysis was performed using propidium iodide staining followed by an imaging processing routine to obtain quantitative dose-response profiles in the gradient maker. The results show that the Gradient Maker (GM) bioreactor is a more sensitive method for detection of cell toxicity, and compared with testing of drug toxicity using microwells with individual cell cultures, allows one shot testing with a single cell culture exposed to a large number of concentrations. Moreover, the Gradient Maker was also modelled in order to realise biological pattern formation using two morphogenes acting as activator and inhibitor with varying diffusion rates. Copyright 2010 Elsevier Ltd. All rights reserved.

  9. Concentrations of radionuclides and selected stable elements in fruits and vegetables

    International Nuclear Information System (INIS)

    Oakes, T.W.; Shank, K.E.

    1977-01-01

    Twenty-two types of fruits and vegetables collected from two commercial supermarkets have been analyzed for their radionuclidic and stable-element composition. A specific gamma-emitting isotope analysis was performed on each sample for 40 K, 60 Co, 95 Zr-Nb, 106 Ru, 137 Cs, 226 Ra, and 232 Th. The concentration of the stable elements in each sample were determined using multi-element neutron-activation analysis (Al, Ag, Au, As, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Cu, Eu, Fe, Hf, I, K, La, Mn, Mo, Mg, Na, Rb, Sb, Sc, Se, Sr, Ta, Te, Th, Ti, Zn, Zr) and atomic absorption (Cd, Ni, Pb). Information on the composition of a typical diet is used to estimate the radiological dose to man subsequent to ingestion of these fruits and vegetables. The stable-elemental compositions of the foodstuffs analyzed were compared with estimated values assuming foliar deposition and long-term buildup of effluents from a large modern coal-fired steam plant. It is tentatively concluded that for the general case of a precipitator-equipped, coal-fired steam plant, no toxic levels of trace elements in foodstuffs are expected as a result of the plant operation

  10. Concentrations of radionuclides and selected stable elements in fruits and vegetables

    Energy Technology Data Exchange (ETDEWEB)

    Oakes, T W; Shank, K E

    1977-01-01

    Twenty-two types of fruits and vegetables collected from two commercial supermarkets have been analyzed for their radionuclidic and stable-element composition. A specific gamma-emitting isotope analysis was performed on each sample for /sup 40/K, /sup 60/Co, /sup 95/Zr-Nb, /sup 106/Ru, /sup 137/Cs, /sup 226/Ra, and /sup 232/Th. The concentration of the stable elements in each sample were determined using multi-element neutron-activation analysis (Al, Ag, Au, As, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Cu, Eu, Fe, Hf, I, K, La, Mn, Mo, Mg, Na, Rb, Sb, Sc, Se, Sr, Ta, Te, Th, Ti, Zn, Zr) and atomic absorption (Cd, Ni, Pb). Information on the composition of a typical diet is used to estimate the radiological dose to man subsequent to ingestion of these fruits and vegetables. The stable-elemental compositions of the foodstuffs analyzed were compared with estimated values assuming foliar deposition and long-term buildup of effluents from a large modern coal-fired steam plant. It is tentatively concluded that for the general case of a precipitator-equipped, coal-fired steam plant, no toxic levels of trace elements in foodstuffs are expected as a result of the plant operation.

  11. Vegetative biomass predicts inflorescence production along a CO2 concentration gradient in mesic grassland

    Science.gov (United States)

    Fay, P. A.; Collins, H.; Polley, W.

    2016-12-01

    Atmospheric CO2 concentration will likely exceed 500 µL L-1 by 2050, often increasing plant community productivity in part by increasing abundance of species favored by increased CA . Whether increased abundance translates to increased inflorescence production is poorly understood, and is important because it indicates the potential effects of CO2 enrichment on genetic variability and the potential for evolutionary change in future generations. We examined whether the responses of inflorescence production to CO2 enrichment in four C4 grasses and a C3 forb were predicted their vegetative biomass, and by soil moisture, soil nitrogen, or light availability. Inflorescence production was studied in a long-term CO2 concentration gradient spanning pre-industrial to anticipated mid-21st century values (250 - 500 µL L-1) maintained on clay, silty clay and sandy loam soils common in the U.S. Southern Plains. We expected that CO2 enrichment would increase inflorescence production, and more so with higher water, nitrogen, or light availability. However, structural equation modeling revealed that vegetative biomass was the single consistent direct predictor of flowering for all species (p Solidago canadensis (C3 forb), direct CO2 effects on flowering were only weakly mediated by indirect effects of soil water content and soil NO3-N availability. For the decreasing species (Bouteloua curtipendula, C4 grass), the negative CO2-flowering relationship was cancelled (p = 0.39) by indirect effects of increased SWC and NO3-N on clay and silty clay soils. For the species with no CO2 response, inflorescence production was predicted only by direct water content (p < 0.0001, Schizachyrium scoparius, C4 grass) or vegetative biomass (p = 0.0009, Tridens albescens, C4 grass) effects. Light availability was unrelated to inflorescence production. Changes in inflorescence production are thus closely tied to direct and indirect effects of CO2 enrichment on vegetative biomass, and may either

  12. Spatial variation of the stable nitrogen isotope ratio of woody plants along a topoedaphic gradient in a subtropical savanna.

    Science.gov (United States)

    Bai, Edith; Boutton, Thomas W; Liu, Feng; Wu, X Ben; Archer, Steven R; Hallmark, C Thomas

    2009-03-01

    Variation in the stable N isotope ratio (delta15N) of plants and soils often reflects the influence of environment on the N cycle. We measured leaf delta15N and N concentration ([N]) on all individuals of Prosopis glandulosa (deciduous tree legume), Condalia hookeri (evergreen shrub), and Zanthoxylum fagara (evergreen shrub) present within a belt transect 308 m long x 12 m wide in a subtropical savanna ecosystem in southern Texas, USA in April and August 2005. Soil texture, gravimetric water content (GWC), total N and delta15N were also measured along the transect. At the landscape scale, leaf delta15N was negatively related to elevation for all the three species along this topoedaphic sequence. Changes in soil delta15N, total N, and GWC appeared to contribute to this spatial pattern of leaf delta15N. In lower portions of the landscape, greater soil N availability and GWC are associated with relatively high rates of both N mineralization and nitrification. Both soil delta15N and leaf [N] were positively correlated with leaf delta15N of non-N2 fixing plants. Leaf delta15N of P. glandulosa, an N2-fixing legume, did not correlate with leaf [N]; the delta15N of P. glandulosa's leaves were closer to atmospheric N2 and significantly lower than those of C. hookeri and Z. fagara. Additionally, at smaller spatial scales, a proximity index (which reflected the density and distance of surrounding P. glandulosa trees) was negatively correlated with leaf delta15N of C. hookeri and Z. fagara, indicating the N2-fixing P. glandulosa may be important to the N nutrition of nearby non-N2-fixing species. Our results indicate plant 15N natural abundance can reflect the extent of N retention and help us better understand N dynamics and plant-soil interactions at ecosystem and landscape scales.

  13. Nutrient Concentrations and Stable Isotopes of Runoff from a Midwest Tile-Drained Corn Field

    Science.gov (United States)

    Wilkins, B. P.; Woo, D.; Li, J.; Michalski, G. M.; Kumar, P.; Conroy, J. L.; Keefer, D. A.; Keefer, L. L.; Hodson, T. O.

    2017-12-01

    Tile drains are a common crop drainage device used in Midwest agroecosystems. While efficient at drainage, the tiles provide a quick path for nutrient runoff, reducing the time available for microbes to use nutrients (e.g., NO3- and PO43-) and reduce export to riverine systems. Thus, understanding the effects of tile drains on nutrient runoff is critical to achieve nutrient reduction goals. Here we present isotopic and concentration data collected from tile drain runoff of a corn field located near Monticello, IL. Tile flow samples were measured for anion concentrations and stable isotopes of H2O and NO3-, while precipitation was measured for dual isotopes of H2O. Results demonstrate early tile flow from rain events have a low Cl- concentration (water isotopic values reflecting precipitation, indicating preferential flow (>60% contribution) in the beginning of the hydrograph. As flow continues H2O isotopic values reflect pre-event water (ground and soil water), and Cl- concentrations increase representing a greater influence by matrix flow (60-90% contribution). Nitrate concentrations change dramatically, especially during the growing season, and do not follow a similar trend as the conservative Cl-, often decreasing days before, which represents missing nitrate in the upper surface portion of the soil. Nitrate isotopic data shows significant changes in 15N (4‰) and 18O (4‰) during individual hydrological events, representing that in addition to plant uptake and leaching, considerate NO3- is lost through denitrification. It is notable, that throughout the season d15N and d18O of nitrate change significantly representing that seasonally, substantial denitrification occurs.

  14. Effects of trace element concentration on enzyme controlled stable isotope fractionation during aerobic biodegradation of toluene.

    Science.gov (United States)

    Mancini, Silvia A; Hirschorn, Sarah K; Elsner, Martin; Lacrampe-Couloume, Georges; Sleep, Brent E; Edwards, Elizabeth A; Lollar, Barbara Sherwood

    2006-12-15

    The effects of iron concentration on carbon and hydrogen isotopic fractionation during aerobic biodegradation of toluene by Pseudomonas putida mt-2 were investigated using a low iron medium and two different high iron media. Mean carbon enrichment factors (epsilonc) determined using a Rayleigh isotopic model were smaller in culture grown under high iron conditions (epsilonc = -1.7+/-0.1%) compared to low iron conditions (epsilonc = -2.5+/-0.3%). Mean hydrogen enrichment factors (epsilonH) were also significantly smaller for culture grown under high iron conditions (epsilonH = -77 +/-4%) versus low iron conditions (EpsilonH = -159+/-11%). A mechanistic model for enzyme kinetics was used to relate differences in the magnitude of isotopic fractionation for low iron versus high iron cultures to the efficiency of the enzymatic transformation. The increase of carbon and hydrogen enrichment factors at low iron concentrations suggests a slower enzyme-catalyzed substrate conversion step (k2) relative to the enzyme-substrate binding step (k-l) at low iron concentration. While the observed differences were subtle and, hence, do not significantly impact the ability to use stable isotope analysis in the field, these results demonstrated that resolvable differences in carbon and hydrogen isotopic fractionation were related to low and high iron conditions. This novel result highlights the need to further investigate the effects of other trace elements known to be key components of biodegradative enzymes.

  15. Analysis of the electrolyte convection inside the concentration boundary layer during structured electrodeposition of copper in high magnetic gradient fields.

    Science.gov (United States)

    König, Jörg; Tschulik, Kristina; Büttner, Lars; Uhlemann, Margitta; Czarske, Jürgen

    2013-03-19

    To experimentally reveal the correlation between electrodeposited structure and electrolyte convection induced inside the concentration boundary layer, a highly inhomogeneous magnetic field, generated by a magnetized Fe-wire, has been applied to an electrochemical system. The influence of Lorentz and magnetic field gradient force to the local transport phenomena of copper ions has been studied using a novel two-component laser Doppler velocity profile sensor. With this sensor, the electrolyte convection within 500 μm of a horizontally aligned cathode is presented. The electrode-normal two-component velocity profiles below the electrodeposited structure show that electrolyte convection is induced and directed toward the rim of the Fe-wire. The measured deposited structure directly correlates to the observed boundary layer flow. As the local concentration of Cu(2+) ions is enhanced due to the induced convection, maximum deposit thicknesses can be found at the rim of the Fe-wire. Furthermore, a complex boundary layer flow structure was determined, indicating that electrolyte convection of second order is induced. Moreover, the Lorentz force-driven convection rapidly vanishes, while the electrolyte convection induced by the magnetic field gradient force is preserved much longer. The progress for research is the first direct experimental proof of the electrolyte convection inside the concentration boundary layer that correlates to the deposited structure and reveals that the magnetic field gradient force is responsible for the observed structuring effect.

  16. 3-D thermalhydraulics flow effects on wall concentration gradient profiles of corrosion/precipitation phenomena in LBE loop fittings

    International Nuclear Information System (INIS)

    Armbya, Narain; Li, Guanjun; Chen, Yitung; Moujaes, Samir

    2004-01-01

    Work is ongoing at UNLV to provide a computer simulation framework that will characterize the behavior and effect of thermalhydraulics on the corrosion/precipitation chemical kinetics processes that take place on the inside surfaces of an LBE flow loop. To that end detailed models are being constructed to study these effects first in several expected loop fittings such as sudden expansion and tee-fittings. The typical flow rates chosen for these simulations are typical of design criteria chosen for the loop with Re numbers expected around 200,000 and the usual axial temperature profiles which are being characterized in the DELTA loop at LANL. STAR-CD is the simulation package used to make these predictions which include detailed 3-D velocity, temperature and concentration gradient profiles of the corrosion/precipitation on the inner surface of these fittings initially. The different predicted variables from these simulations indicate that special attention needs to be placed when designing loops with these fittings especially in the regions of sudden velocity changes and stagnation zones. These wall gradients can determine eventually the expected longevity of these fittings in an LBE flow environment. Presently though very little experimental data exists that would be suitable to corroborate the simulation results. Graphs of concentration gradient v/s distance from the inlet of these fittings were plotted. Eventually these individual fitting models will become part of an overall closed loop that will yield more realistic core concentration values and hence more realistic wall gradient values which are dependent on these core values. (author)

  17. Vaspin plasma concentrations and mRNA expressions in patients with stable and unstable angina pectoris.

    Science.gov (United States)

    Li, Hai Ling; Peng, Wen Hui; Cui, Shi Tao; Lei, Hou; Wei, Yi Dong; Li, Wei Ming; Xu, Ya Wei

    2011-09-01

    Vaspin was a recently identified adipokine, playing a protective role in many metabolic diseases. The present study aimed to investigate the association between vaspin plasma level and stable angina pectoris (SAP) and unstable angina pectoris (UAP). A total of 88 patients with angiographically-proved coronary artery disease (CAD) (SAP 47, UAP 41) and 103 control subjects without cardiovascular diseases were enrolled in this study. Circulating vaspin, mRNA expression of vaspin in peripheral blood mononuclear cells (PBMC), clinical parameters, lipid profile and high-sensitivity C-reactive protein (hsCRP) were assayed. The severity of CAD was also assessed according to the number of vessels diseased. There are significant differences in circulating vaspin levels and mRNA levels of PBMC between SAP and UAP groups (SAP 0.91±0.95 ng/mL and UAP 0.43±0.38 ng/mL, p<0.01 in circulating vaspin level; SAP 1.19±0.85 and UAP 0.82±0.56, p<0.05 in mRNA level of PBMC). An inverse correlation between the number of diseased vessels and plasma vaspin concentration was observed (r=-0.350, p<0.01) in the CAD group. Construction of receiver operating characteristic curves confirmed that vaspin plasma concentrations significantly differentiated CAD patients (area under the curve=0.684, p<0.001), as well as UAP (area under the curve=0.640, p<0.05). Decreased vaspin plasma levels and mRNA levels in PBMC were observed in patients with UAP. Low vaspin concentrations correlate with CAD severity. The findings suggested that vaspin could serve as a novel biomarker of CAD as well as UAP.

  18. Impact of Ficoll density gradient centrifugation on major and trace element concentrations in erythrocytes and blood plasma.

    Science.gov (United States)

    Lu, Ying; Ahmed, Sultan; Harari, Florencia; Vahter, Marie

    2015-01-01

    Ficoll density gradient centrifugation is widely used to separate cellular components of human blood. We evaluated the suitability to use erythrocytes and blood plasma obtained from Ficoll centrifugation for assessment of elemental concentrations. We determined 22 elements (from Li to U) in erythrocytes and blood plasma separated by direct or Ficoll density gradient centrifugation, using inductively coupled plasma mass spectrometry. Compared with erythrocytes and blood plasma separated by direct centrifugation, those separated by Ficoll had highly elevated iodine and Ba concentration, due to the contamination from the Ficoll-Paque medium, and about twice as high concentrations of Sr and Mo in erythrocytes. On the other hand, the concentrations of Ca in erythrocytes and plasma were markedly reduced by the Ficoll separation, to some extent also Li, Co, Cu, and U. The reduced concentrations were probably due to EDTA, a chelator present in the Ficoll medium. Arsenic concentrations seemed to be lowered by Ficoll, probably in a species-specific manner. The concentrations of Mg, P, S, K, Fe, Zn, Se, Rb, and Cs were not affected in the erythrocytes, but decreased in plasma. Concentrations of Mn, Cd, and Pb were not affected in erythrocytes, but in plasma affected by EDTA and/or pre-analytical contamination. Ficoll separation changed the concentrations of Li, Ca, Co, Cu, As, Mo, I, Ba, and U in erythrocytes and blood plasma, Sr in erythrocytes, and Mg, P, S, K, Fe, Zn, Se, Rb and Cs in blood plasma, to an extent that will invalidate evaluation of deficiencies or excess intakes. Copyright © 2014 Elsevier GmbH. All rights reserved.

  19. Air pollution assessment based on elemental concentration of leaves tissue and foliage dust along an urbanization gradient in Vienna.

    Science.gov (United States)

    Simon, Edina; Braun, Mihály; Vidic, Andreas; Bogyó, Dávid; Fábián, István; Tóthmérész, Béla

    2011-05-01

    Foliage dust contains heavy metal that may have harmful effects on human health. The elemental contents of tree leaves and foliage dust are especially useful to assess air environmental pollution. We studied the elemental concentrations in foliage dust and leaves of Acer pseudoplatanus along an urbanization gradient in Vienna, Austria. Samples were collected from urban, suburban and rural areas. We analysed 19 elements in both kind of samples: aluminium, barium, calcium, copper, iron, potassium, magnesium, sodium, phosphor, sulphur, strontium and zinc. We found that the elemental concentrations of foliage dust were significantly higher in the urban area than in the rural area for aluminium, barium, iron, lead, phosphor and selenium. Elemental concentrations of leaves were significantly higher in urban than in rural area for manganese and strontium. Urbanization changed significantly the elemental concentrations of foliage dust and leaves and the applied method can be useful for monitoring the environmental load. Copyright © 2011 Elsevier Ltd. All rights reserved.

  20. Effect of raised plasma β endorphin concentrations on peripheral pain and angina thresholds in patients with stable angina

    OpenAIRE

    Jarmukli, N; Ahn, J; Iranmanesh, A; Russell, D

    1999-01-01

    OBJECTIVE—To determine whether changes in plasma concentrations of β endorphins alter angina threshold and peripheral pain threshold in patients with stable angina.
DESIGN—Latin square design comparison of angina thresholds by exercise treadmill test and peripheral pain thresholds using a radiant heat source in eight patients with stable angina under control conditions, after stimulation of pituitary β endorphin release by ketoconazole, after suppression of pituitary β endorphin release by de...

  1. Assessment of Gradient-Based Similarity Functions in the Stable Boundary Layer Derived from a Large-Eddy Simulation

    Science.gov (United States)

    Sorbjan, Zbigniew

    2017-06-01

    Gradient-based similarity functions, evaluated based on data generated by a large-eddy simulation model of the stably stratified boundary layer, are compared with analogous similarity functions, derived from field observations in the surface layer during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment in the Arctic. The comparison is performed in terms of explicit and implicit local scaling systems, for the temperature and momentum fluxes, standard deviations of the vertical velocity and of temperature, as well as dissipation rates for the turbulent kinetic energy and for the temperature variance. The comparison shows the best agreement of the SHEBA-based similarity functions with analogous functions evaluated using the large-eddy simulation data in the range of the Richardson number 0.01<{ Ri}< 0.1.

  2. The concentration gradient flow battery as electricity storage system: Technology potential and energy dissipation

    Science.gov (United States)

    van Egmond, W. J.; Saakes, M.; Porada, S.; Meuwissen, T.; Buisman, C. J. N.; Hamelers, H. V. M.

    2016-09-01

    Unlike traditional fossil fuel plants, the wind and the sun provide power only when the renewable resource is available. To accommodate large scale use of renewable energy sources for efficient power production and utilization, energy storage systems are necessary. Here, we introduce a scalable energy storage system which operates by performing cycles during which energy generated from renewable resource is first used to produce highly concentrated brine and diluate, followed up mixing these two solutions in order to generate power. In this work, we present theoretical results of the attainable energy density as function of salt type and concentration. A linearized Nernst-Planck model is used to describe water, salt and charge transport. We validate our model with experiments over wide range of sodium chloride concentrations (0.025-3 m) and current densities (-49 to +33 A m-2). We find that depending on current density, charge and discharge steps have significantly different thermodynamic efficiency. In addition, we show that at optimal current densities, mechanisms of energy dissipation change with salt concentration. We find the highest thermodynamic efficiency at low concentrate concentrations. When using salt concentrations above 1 m, water and co-ion transport contribute to high energy dissipation due to irreversible mixing.

  3. Using Lead Concentrations and Stable Lead Isotope Ratios to Identify Contamination Events in Alluvial Soils

    Directory of Open Access Journals (Sweden)

    Diane Saint-Laurent

    2010-01-01

    Full Text Available Soils contaminated with hydrocarbons (C10–C50, polycyclic aromatic hydrocarbons (PAHs, and other contaminants (e.g., As, Cd, Cu, Pb were recently discovered on the banks of the Saint-François and Massawippi rivers. Alluvial soils are contaminated over a distance of 100 kilometers, and the level of the contaminated-hydrocarbon layer in the soil profiles is among the highest at the Windsor and Richmond sites. Concentrations of lead and stable lead isotope ratios (204Pb/206Pb, 207Pb/206Pb, 208Pb/206Pb are also used to identify contamination events. The maximum and minimum values detected in soil profiles for arsenic, cadmium, and lead vary from 3.01 to 37.88 mg kg-1 (As, 0.11 to 0.81 mg kg-1 (Cd 12.32 to 149.13 mg kg-1 (Pb, respectively, while the 207Pb/206Pb isotopic ratio values are between 0.8545 and 0.8724 for all the profiles. The highest values of trace elements (As, Pb and Zn were detected in the hydrocarbon layer (C10–C50, most often located at the bottom of the profiles (160, 200, and 220 cm in depth. The various peaks recorded in the soils and the position of the profiles suggest that various contaminants were transported by the river on several occasions and infiltrated the soil matrix or deposited on floodplains during successive floods. Atmospheric particles which entered the river or deposited on riverbanks must also be considered as another source of pollution recorded in soils.

  4. Correlation between Creatinine Clearance and Transtubular Potassium Concentration Gradient in old people and chronic renal disease patients

    International Nuclear Information System (INIS)

    Musso, C.; Imperiali, N.; Algranati, L.; Miguel, R.D.; Liakopoulos, V.; Stefanidis, I.

    2007-01-01

    Senescence and chronic kidney disease (CKD) reduce progressively glomerular filtration rate (GFR) which usually results in an increase in potassium renal secretion. To evaluate whether the transtubular potassium concentration gradient (TTKG) is more accurate parameter for evaluating the renal secretion of this cation than using fractional excretion of potassium as its urinary secretion marker, we studied 55 subjects, 43 of them were healthy elderly volunteers and 12 were CKD patients. Exclusion criteria were: abnormal plasma potassium level or presence of any disease or drug that could induce alteration of balance of this electrolyte levels. All the subjects were on a diet with potassium content around 50 mmol/day. The curves, which demonstrate the relationship between creatinine clearance and TTKG and the grade of correlation between these two parameters were analyzed in both groups. We found that the transtubular potassium concentration gradient had a significant negative correlation with the creatinine clearance level in the healthy elderly group, while there was no correlation in the CKD group. (author)

  5. Stable nitrogen isotope ratios of macrophytes and associated periphyton along a nitrate gradient in two subtropical, spring-fed streams

    DEFF Research Database (Denmark)

    De Brabandere, Loreto; Frazer, Thomas K.; Montoya, Joseph P.

    2007-01-01

    1. An increase in human population and associated changes in land use have caused an increase in groundwater nitrate concentrations throughout central Florida. Within the region, this nitrate-laden groundwater returns to the surface via numerous large springs that serve as the origin of flow for ...

  6. Chloride concentration gradients in tank-stored hydraulic fracturing fluids following flowback

    Science.gov (United States)

    Pamela J. Edwards; Linda L. Tracy; William K. Wilson

    2011-01-01

    A natural gas well in West Virginia was hydraulically fractured and the flowback was recovered and stored in an 18-foot-deep tank. Both in situ field test kit and laboratory measurements of electrical conductivity and chloride concentrations increased substantially with depth, although the laboratory measurements showed a greater increase. The field test kit also...

  7. DOC concentrations across a depth-dependent light gradient on a Caribbean coral reef

    NARCIS (Netherlands)

    Mueller, B.; Meesters, E.H.; van Duyl, F.C.

    2017-01-01

    Photosynthates released by benthic primary producers (BPP), such as reef algae and scleractinian corals, fuel the dissolved organic carbon (DOC) production on tropical coral reefs. DOC concentrations near BPP have repeatedly been observed to be elevated compared to those in the surrounding water

  8. Topsoil dichlorodiphenyltrichloroethane and polychlorinated biphenyl concentrations and sources along an urban-rural gradient in the Yellow River Delta.

    Science.gov (United States)

    Xie, Wenjun; Chen, Aiping; Li, Jianyong; Liu, Qing; Yang, Hongjun; Wu, Tao; Lu, Zhaohua

    2012-01-01

    The Yellow River Delta (YRD) is a typical agricultural and petrochemical industrial area of China. To assess the current status of soil dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyls (PCB) residues, topsoil samples (0-15 cm) (n = 82) were collected in Bincheng District, at the geographic center of the YRD. The total concentrations of six DDT homologues were within 3.3-3819 microg/kg, with a mean concentration of 191 microg/kg, showing significant increase along urban-rural gradient. Soil concentrations of seven indicator PCBs in the area ranged from non-detectable to 87.0 microg/kg, dominated by heavily chlorinated PCBs (PCB-101 and -118). Soil PCBs concentrations were significantly greater in urban than suburban and rural areas. Principal component and multiple linear regression analysis suggest that 86.4% of soil DDTs originate from past DDT usage, and 13.6% originate from dicofol application. Soil PCBs most likely originate from the petrochemical industry (77.1%), municipal solid waste disposal (16.5%), local commercial PCB homologues usage (5.2%), and long-range atmospheric deposition (1.2%). In general, soil DDTs pollution was classified as low level, and mean PCBs concentrations were below the severe contamination classification range. Because PCB-118 is a dioxin-like congener, monitoring and remediation is advised to assess and reduce negative environmental and human health effects from soil DDTs and dioxin-like congeners in the study area.

  9. Spatial Gradients in Trace Metal Concentrations in the Surface Microlayer of the Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    Antonio eTovar-Sanchez

    2014-12-01

    Full Text Available The relationship between dust deposition and surface water metal concentrations is poorly understood. Dissolution, solubility, and partitioning reactions of trace metals from dust particles are governed by complex chemical, biological, and physical processes occurring in the surface ocean. Despite that, the role of the sea surface microlayer (SML, a thin, but fundamental component modulating the air-sea exchange of materials has not been properly evaluated. Our study revealed that the SML of the Mediterranean Sea is enriched with bioactive trace metals (i.e., Cd, Co, Cu and Fe, ranging from 8 (for Cd to 1000 (for Fe times higher than the dissolved metal pool in the underlying water column. The highest enrichments were spatially correlated with the atmospheric deposition of mineral particles. Our mass balance results suggest that the SML in the Mediterranean Sea contains about 2 tonnes of Fe. However, we did not detect any trends between the concentrations of metals in SML with the subsurface water concentrations and biomass distributions. These findings suggest that future studies are needed to quantify the rate of metal exchange between the SML and the bioavailable pool and that the SML should be considered to better understand the effect of atmospheric inputs on the biogeochemistry of trace metals in the ocean.

  10. An enriched stable isotope technique to estimate the availability of soil zinc to Lumbricus terrestris (L.) across a salinization gradient.

    Science.gov (United States)

    Rodgers, Derek W; Lev, Steven M; Snodgrass, Joel W; Ownby, David R; Prince, Lisa M; Casey, Ryan E

    2011-03-01

    An enriched stable isotope approach was developed to evaluate Zn bioavailability to Lumbricus terrestris. The decrease in (68)Zn/(66) Zn in organ tissues was used to assess the relative magnitude of the bioavailable soil Zn pool. This tool was then used to specifically evaluate bioavailability as a function of soil cation distribution. Storm-water pond soils were modified using two treatment regimens whereby H(2)O-extractable Zn was varied either by different ZnCl(2) amendments or by constant ZnCl(2) amendment followed by varying the soil cation distribution through salt amendments (NaCl or CaCl(2)). Earthworms previously equilibrated in (68) Zn-spiked soil were introduced to experimental soils, and after 2 d, removed for analysis of isotopic ratios in specific tissues. Despite a wide range of H(2)O-extractable Zn values produced by the salt treatments (0.007-24.3 mg/kg), a significant relationship between Zn turnover rate in earthworm tissues and H(2)O-extractable Zn in the salt-treated soils was not observed. Rather, considering both treatment regimens, turnover rate better correlated with Zn present in broader pools, such as that extracted by 6M HNO(3). The bioavailability of trace metals to earthworms may be poorly characterized by loosely bound fractions such as the pore water. Additionally, the turnover rate of (68)Zn in anterior organ tissues may be an effective tool to evaluate the relative magnitude of the bioavailable soil Zn pool. Copyright © 2010 SETAC.

  11. Nutrient uptake dynamics across a gradient of nutrient concentrations and ratios at the landscape scale

    Science.gov (United States)

    Gibson, Catherine A.; O'Reilly, Catherine M.; Conine, Andrea L.; Lipshutz, Sondra M.

    2015-02-01

    Understanding interactions between nutrient cycles is essential for recognizing and remediating human impacts on water quality, yet multielemental approaches to studying nutrient cycling in streams are currently rare. Here we utilized a relatively new approach (tracer additions for spiraling curve characterization) to examine uptake dynamics for three essential nutrients across a landscape that varied in absolute and relative nutrient availability. We measured nutrient uptake for soluble reactive phosphorous, ammonium-nitrogen, and nitrate-nitrogen in 16 headwater streams in the Catskill Mountains, New York. Across the landscape, ammonium-nitrogen and soluble reactive phosphorus had shorter uptake lengths and higher uptake velocities than nitrate-nitrogen. Ammonium-nitrogen and soluble reactive phosphorus uptake velocities were tightly correlated, and the slope of the relationship did not differ from one, suggesting strong demand for both nutrients despite the high ambient water column dissolved inorganic nitrogen: soluble reactive phosphorus ratios. Ammonium-nitrogen appeared to be the preferred form of nitrogen despite much higher nitrate-nitrogen concentrations. The uptake rate of nitrate-nitrogen was positively correlated with ambient soluble reactive phosphorus concentration and soluble reactive phosphorus areal uptake rate, suggesting that higher soluble reactive phosphorus concentrations alleviate phosphorus limitation and facilitate nitrate-nitrogen uptake. In addition, these streams retained a large proportion of soluble reactive phosphorus, ammonium-nitrogen, and nitrate-nitrogen supplied by the watershed, demonstrating that these streams are important landscape filters for nutrients. Together, these results (1) indicated phosphorus limitation across the landscape but similarly high demand for ammonium-nitrogen and (2) suggested that nitrate-nitrogen uptake was influenced by variability in soluble reactive phosphorus availability and preference for

  12. The quality control of fruit juices by using the stable isotope ratios and trace metal elements concentrations

    Science.gov (United States)

    Magdas, D. A.; Dehelean, A.; Puscas, R.; Cristea, G.; Tusa, F.; Voica, C.

    2012-02-01

    In the last years, a growing number of research articles detailing the use of natural abundance light stable isotopes variations and trace metal elements concentration as geographic "tracers" to determine the provenance of food have been published. These investigations exploit the systematic global variations of stable hydrogen, oxygen and carbon isotope ratios in (combination) relation with trace metal element concentrations. The trace metal elements content of plants and also their light stable isotopic ratios are mainly related to the geological and pedoclimatic characteristics of the site of growth. The interpretation of such analysis requires an important number of data for authentic natural juices regarding the same seasonal and regional origin, because the isotopic analysis parameters of fruit juices show remarkable variability depending on climatologically factors. In this work was mesured H, C, O stable isotope ratios and the concentrations of 16 elements (P, K, Mg, Na, Ca, Cu, Cr, Ni, Zn, Pb, Co, As, Cd, Mn, Fe and Hg) from 12 single strength juices. The natural variations that appear due to different environmental and climatic conditions are presented and discussed.

  13. Sewage water pollutants removal efficiency correlates to the concentration gradient of amendments

    International Nuclear Information System (INIS)

    Bhatti, Z.A.; Mahmood, Q.; Raja, I.A.

    2009-01-01

    Three coagulants viz. alum, FeCl/sub 3/ and Moringa oleifera seed extract were compared for treating municipal wastewater. The wastewater samples were collected from a drain near the Murree Road in Abbottabad city. The initial treatment depicted that alum was a suitable coagulant, while the other two caused color development and increased chemical oxygen demand in the effluent. Subsequently, wastewater samples were treatment with graded concentrations (4 32 mg.L/sup -1/ of alum in batch series, and shacked at 600-620 rpm for five minutes. The treated samples were analyzed for various water quality parameters to examine the effective coagulation and flocculation process in the wastewater. There was an increase in TDS and electrical conductivity with the increasing levels of alum above the optimized values (22 to 30 mg L/sup -1/). The process primary treatment strategy of wastewater treatment with alum is suitable for reducing the pollutants load in the sewer system. (author)

  14. Combined effect of salt concentration and pressure gradients across charged membranes

    DEFF Research Database (Denmark)

    Benavente, Juana; Jonsson, Gunnar Eigil

    2002-01-01

    to correlate the behaviour of the BP membrane with that corresponding to each sublayer, the same kind of measurements was carried out for both opposite external conditions, this means, applying the pressure on the cation exchanger (CABM) or on the anion exchanger membrane (ACBM), respectively. From values......The combined effect of both concentration and pressure differences on electrical potential (Deltaphi) for two ion-exchanger membranes, one positively charged (AE) and another negatively charged (CE), measured with the membranes in contact with NaCl solutions was studied. Results show a linear...... obtained at DeltaP = 0, the counter-ion transport number in each ion-exchange membrane was obtained and the contribution of membrane potential on Deltaphi values can be evaluated. Results show clear differences on both the membrane potential and the effect of pressure in the bipolar membrane depending...

  15. Plant community and litter composition in temperate deciduous woodlots along two field gradients of soil Ni, Cu and Co concentrations

    International Nuclear Information System (INIS)

    Hale, Beverley; Robertson, Paul

    2016-01-01

    Perennial plant communities in the proximity of metal smelters and refineries may receive substantial inputs of base metal particulate as well as sulphate from the co-emission of sulphur dioxide. The Ni refinery at Port Colborne (Canada) operated by Inco (now Vale Canada Ltd.) emitted Ni, Co and Cu, along with sulphur dioxide, between 1918 and 1984. The objectives were to determine if vascular plant community composition, including standing litter, in twenty-one woodlots on clay or organic soil, were related to soil Ni concentration which decreased in concentration with distance from the Ni refinery. The soil Ni concentration in the clay woodlots ranged from 16 to 4130 mg Ni/kg, and in the organic woodlots, ranged from 98 to 22,700 mg Ni/kg. The concentrations of Co and Cu in the soils were also elevated, and highly correlated with soil Ni concentration. In consequence, each series of woodlots constituted a ‘fixed ratio ray’ of metal mixture exposure. For each of the woodlots, there were 16 independent measurements of ‘woodlot status’ which were correlated with elevated soil Ni concentration. Of the 32 combinations, there were eight linear correlations with soil Ni concentration, considerably more than would be expected by chance alone at a p-value of 0.05. With the exception of mean crown rating for shrubs at the clay sites, the correlations were consistent with the hypothesis that increased soil metal concentrations would be correlated with decreased diversity, plant community health or fitness, and increased accumulation of litter. Only five of the eight linear correlations were from the organic woodlots, suggesting that the observations were not confounded with soil type nor range in soil metal concentrations. - Highlights: • Temperate woodlots on organic or clay soils with gradient of soil Ni were studied. • Soil Ni ranged up to 4100 mg/kg on clay and up to 22,700 mg/kg on organic. • Most indices of plant community status were not correlated

  16. Thermodynamic considerations of arteriovenous gradients of hydrogen ion concentration and carbon dioxide tension.

    Science.gov (United States)

    Rakitzis, E T

    2000-03-01

    It is shown that, in a multicompartmental homeostatic system, the extent of interaction between any two compartments can be assessed by determination of the difference in free energy change of one particular reaction, or a series of coupled reactions, operative in both of the compartments under consideration. Hydrogen ion concentration and carbon dioxide tension have been used to determine free energy change difference relationships between the venous and arterial compartments (-deltadeltaG(a-v)) of the circulatory system. Data from the literature (from two studies of congestive heart failure and one study of experimentally induced cardiac arrest) are used to calculate -deltadeltaG(a-v). It was found that in control subjects -deltadeltaG(a-v) is close to zero, whereas in congestive heart failure or cardiac arrest, the value rises to 150 cal mol(-1) or more, whereas in blood, the approach towards equilibrium between hydrogen and bicarbonate ions and dissolved carbon dioxide (aqueous CO2) is known to be only moderately rapid. It is concluded that, in the system under study, and with respect to the reaction H+ + HCO3- = CO2 + H2O, a high value for the free energy change difference between the two compartments (high -deltadeltaG(a-v)) must be due to an insufficient blood circulation rate. Accordingly, -deltadeltaG(a-v) is probably a quantitative measure of cardiac insufficiency.

  17. Concentration gradient of noradrenaline from the periphery to the centre of the cornea - A clue to its origin.

    Science.gov (United States)

    Figueira, Luis; Ferreira, Carla; Janeiro, Catarina; Serrao, Paula; Falcao-Reis, Fernando; Moura, Daniel

    2018-03-01

    We set out to demonstrate that the major source of corneal catecholamines is its neuronal release from intrinsic sympathetic nerves rather than circulating or non-neuronal local production. Three concentric segments (central, intermediate, peripheral) were obtained by double trephination (9.5-7.25 mm) performed on corneas harvested from 3 to 4 month old rabbits and human corneas rejected for transplantation, along with aqueous humour, full iris tissue and blood samples. Endogenous catecholamines were quantified by high pressure liquid chromatography with electrochemical detection (HPLC-ED), and comparison with the uptake of radio-labelled noradrenaline (3H-NA) before and after incubation with cocaine was performed. Results are means ± SEM. Ratios between enzymatic end products and their substrates were calculated. ANOVA was used for statistical analysis. Catecholamine levels were found to be about one log unit lower in the human cornea than in the rabbit cornea. In the rabbit, dopamine (DA), noradrenaline (NA) and adrenaline (AD) were identified by HPLC-ED in all corneal segments, whilst in the human cornea NA was identified only in the intermediate and peripheral corneal segments, and no AD was found. In the iris and aqueous humour only DA and NA were present. A concentration gradient for NA decreasing from the periphery to the centre of the cornea was identified in both species (NA/DA ratio higher than 1 in the periphery; low AD/NA ratio in all corneal segments), but not for DA or AD. After incubation with 3H-NA all corneal segments and iris tissue showed loading with the aforementioned gradient being reproduced, and a decrease in 3H-NA loading after cocaine was significant only in the peripheral corneal segment and in the iris of both species. Reduction in 3H-NA loading after incubation with cocaine shows that NA in the cornea is mostly of neuronal origin and demonstrates the presence of functional sympathetic nerves (also expectedly found in the iris

  18. Latitudinal Gradients in the Stable Carbon and Oxygen Isotopes of Tree-Ring Cellulose Reveal Differential Climate Influences of the North American Monsoon

    Science.gov (United States)

    Szejner, P.; Wright, W. E.; Babst, F.; Belmecheri, S.; Trouet, V.; Ehleringer, J. R.; Leavitt, S. W.; Monson, R. K.

    2015-12-01

    Summer rainfall plays an important role sustaining different types of ecosystems in the Southwestern US. The arrival of the monsoon breaks the early summer hyper-arid period in the region providing unique seasonal conditions for these ecosystems to thrive. It is unknown to what extent monsoon rainfall is used by Ponderosa pine forests, which occupy many mountain ecosystems in the Western US. While these forests clearly rely on winter snowpack to drive much of their annual net primary productivity, the extent to which they supplement winter moisture, with summer monsoon moisture needs to be clarified. It is likely that there are north-south gradients in the degree to which forests rely on monsoon moisture, as the summer monsoon system tends to become diminished as it moves progressively northward. We addressed these gaps in our knowledge about the monsoon by studying stable Carbon and Oxygen isotopes in earlywood and latewood α-cellulose from cores taken from trees in eleven sites along a latitudinal gradient extending from Southern Arizona and New Mexico toward Utah. Here we show evidence that Ponderosa pine trees from most of these sites use monsoon water to support growth during the late summer, and the fractional use of monsoon precipitation is strongest in the southernmost sites. This study provides new physiological evidence on the influence of the North American monsoon and winter precipitation on tree growth in montane ecosystems of the Western US. Using these results, we predict differences in the susceptibility of southern and northern montane forests to future climate change. ACKNOWLEDGMENTS: This work was funded by an NSF Macrosystems Grant #1065790

  19. Large Eddy Simulation of VOCALS RF06: The Role of Cloud Droplet Number Concentration Gradients in Pockets of Open Cells

    Science.gov (United States)

    Berner, A. H.; Bretherton, C. S.; Wood, R.; Blossey, P. N.

    2009-12-01

    The VAMOS Ocean-Land-Atmosphere Study (VOCALS) REx field campaign sampled several excellent cases of pockets of open cells (POCS) embedded in a fully cloud-covered stratocumulus layer, most notably NSF C-130 flight RF06, which sampled across the boundary of a well defined POC between 0500 and 1000 local time on October 26th, 2008. We present the initial results of Large Eddy Simulation (LES) modeling of RF06 and examine the fidelity of the simulation in reproducing the effects of the observed gradients of cloud droplet concentration, most visibly the difference in cloud characteristics inside vs. outside the POC . The LES simulations were initialized with soundings constructed from aircraft data and NCEP reanalysis. Observations indicated a sharp transition in cloud droplet number concentration across the POC boundary. The SAM LES of Marat Khairoutdinov was run using CAM radiation and Morrison (2005) microphysics, with cloud droplet concentration Nc treated as an advected scalar without microphysical sources and sinks as a first step toward a realistic treatment of aerosols. The simulations were initialized with a step function change in Nc from 60 within the overcast region to 10 within the POC region, and with Nc equal to 10 above the inversion. A doubly periodic ‘bowling alley’ domain with horizontal dimensions of 192km x 24km is used to simulate a transect across the POC. The horizontal resolution is 125m and vertical resolution varies from 20m near the surface to 5m around the inversion, and then stretching to the domain top at 30km. The runs start at 0300 local time and continue for 18 hours across the diurnal cycle of insolation. Mesoscale circulations rapidly develop within the domain, with low level outflow from the POC to overcast regions and inflow near the top of the boundary layer from the overcast region into the POC. Drizzle cells develop within the POC and along its boundaries, consistent with observations, though actual precipitation amounts

  20. Total mercury and methylmercury concentrations over a gradient of contamination in earthworms living in rice paddy soil.

    Science.gov (United States)

    Abeysinghe, Kasun S; Yang, Xiao-Dong; Goodale, Eben; Anderson, Christopher W N; Bishop, Kevin; Cao, Axiang; Feng, Xinbin; Liu, Shengjie; Mammides, Christos; Meng, Bo; Quan, Rui-Chang; Sun, Jing; Qiu, Guangle

    2017-05-01

    Mercury (Hg) deposited from emissions or from local contamination, can have serious health effects on humans and wildlife. Traditionally, Hg has been seen as a threat to aquatic wildlife, because of its conversion in suboxic conditions into bioavailable methylmercury (MeHg), but it can also threaten contaminated terrestrial ecosystems. In Asia, rice paddies in particular may be sensitive ecosystems. Earthworms are soil-dwelling organisms that have been used as indicators of Hg bioavailability; however, the MeHg concentrations they accumulate in rice paddy environments are not well known. Earthworm and soil samples were collected from rice paddies at progressive distances from abandoned mercury mines in Guizhou, China, and at control sites without a history of Hg mining. Total Hg (THg) and MeHg concentrations declined in soil and earthworms as distance increased from the mines, but the percentage of THg that was MeHg, and the bioaccumulation factors in earthworms, increased over this gradient. This escalation in methylation and the incursion of MeHg into earthworms may be influenced by more acidic soil conditions and higher organic content further from the mines. In areas where the source of Hg is deposition, especially in water-logged and acidic rice paddy soil, earthworms may biomagnify MeHg more than was previously reported. It is emphasized that rice paddy environments affected by acidifying deposition may be widely dispersed throughout Asia. Environ Toxicol Chem 2017;36:1202-1210. © 2016 SETAC. © 2016 SETAC.

  1. Fractionation, concentration and flow: A model coupling stable isotope ratios to fluid travel time and chemical reactivity

    Science.gov (United States)

    Druhan, J. L.; Maher, K.

    2014-12-01

    From the point of infiltration to the point of discharge, the chemical signature imparted to fluid flowing through catchments represents the weathering flux from the landscape. The magnitude of this flux is linked to both the time water spends in the system and the time required for reactions to influence fluid chemistry. The ratio of these characteristic times is often represented as a Damköhler number (Da), which links the parameters governing reactivity and flow. Stable isotope ratios are now commonly applied to identify and even quantify the processes and rates of primary mineral weathering, secondary mineral formation and biogeochemical cycling within catchments. Here, we derive a series of fractionation-discharge relationships for a variety of governing chemical rate laws utilizing Da coefficients. These equations can be used to isolate and quantify the effects of (1) fluid travel time distributions and (2) chemical weathering efficiency on observed stable isotope ratios. The analytical solutions are verified against multi-component reactive transport simulations of stable isotope fractionation in homogeneous and spatially correlated heterogeneous flow fields using the CrunchTope code and evaluated against field observations. We demonstrate that for an irreversible reaction, the relationship between stable isotope enrichment and reactant concentration obeys a Rayleigh-type model across a wide range of reaction rates. However, this relationship is violated when a heterogeneous travel time distribution is considered. This observation highlights an important discrepancy in the commonly assumed relationship between fractionation and concentration for irreversible reactions. We further extend our derivation to consider isotope fractionation associated with a reversible reaction (i.e. a kinetically controlled approach to equilibrium) in a steady-state flow field. Due to the dependence of the observed isotope ratio on the flow rate, kinetic enrichment and

  2. Mercury concentrations in Southern Beaufort Sea polar bears: variation based on stable isotopes of carbon and nitrogen.

    Science.gov (United States)

    Cardona-Marek, Tamara; Knott, Katrina K; Meyer, Benjamin E; O'Hara, Todd M

    2009-07-01

    Total Hg concentration was measured in hair and whole blood of 52 adult Southern Beaufort Sea polar bears (Ursus maritimus) captured in the spring of 2005. Stable isotopic signatures (i.e., 13C/12C, delta13C; 15N/14N, delta15N) in hair and two blood compartments (packed blood cells/clot and serum) were determined to assess the variation of Hg concentrations among polar bears in relation to their feeding ecology and other biological factors. Concentrations of Hg in hair and blood (2.2-23.9 microg/g dry wt and 0.007-0.213 microg/g wet wt, respectively) were within the range of values previously reported for polar bears in Canada and East Greenland. Mercury concentration in hair from females was higher than that in hair from males, and concentration was related to interactions between delta13C, delta15N, and longitude of capture location. Mercury concentrations in hair were inversely correlated to delta13C in hair and blood, suggesting that polar bears with greater total Hg concentrations fed more on pelagic prey, such as ringed seals or beluga whale, than on benthic prey. Variability in Hg concentrations in polar bear hair and blood may be the result of intraspecific or regional variation in prey selection rather than strictly trophic level interactions.

  3. The efficacy of scale sampling for monitoring trace element concentrations and stable isotopes in commercially harvested walleye (Sander vitreus).

    Science.gov (United States)

    Ofukany, Amy F A; Hobson, Keith A; Wassenaar, Leonard I; Bond, Alexander L

    2015-01-01

    Commercial and sport fishes are subject to rigorous monitoring for concentrations of elements that could pose threats to human health, with numerous advisories issued by authorities annually for those fisheries with high mercury (Hg) concentrations. In Lake Winnipeg, Manitoba, Canada, the commercial walleye fishery is valued at more than $20 million/year, but has historically been subject to Hg advisories. We used an information theoretic approach to evaluate the utility of non-destructive fish-scale sampling to predict As, Mn and Hg concentrations, as well as stable isotope values in walleye muscle by analysing paired samples. Hg concentrations in scales were significantly related to those in muscle (r(2) = 0.75), but the relationships were weaker for As and Mn. The δ(15)N values in scales predicted δ(15)N in muscle reasonably well (r(2) = 0.72), whereas scale δ(13)C and δ(34)S had less predictive power for estimating their respective muscle stable isotope values. For all three isotope values, sex was a marginal predictor, with parameter confidence intervals bounding zero. Analytical constraints currently limit the utility of non-destructively analysing scales for Hg, but hindcasting trophic changes using archived walleye scales may be useful in understanding shifts in nutrients and production, particularly in impacted lake systems.

  4. Influence of Biopolym Granulat effects on reductionof ammonia concentration in stables of intensive farm animals breeding

    Directory of Open Access Journals (Sweden)

    Bohuslav Čermák

    2014-10-01

    Full Text Available The living environment distress is connected currently not only with industrial production but also agriculture is biggest producer of toxic gas – ammonia (NH3 .Emissions of that gas originate mainly in the farm animals breeding and generate within storage and handling with farmyard manure, slurry, poultry excrements and litter. Agriculture influences considerably landscape. has impact on basic effect on soil, water and air. In assessing experiment the preparation Biopolym Granulat rumen metabolism and N-balance was found positive effects in terms of increased ammonia nitrogen, the number of ciliates and the reduction of N-compounds in feces. Confirmed the impact on the ammonia content in well-ventilated dairy stable. The economic evaluation depends on the exercise price of milk.

  5. Trace metal concentrations in forest and lawn soils of Paris region (France) along a gradient of urban pressure

    Science.gov (United States)

    Ludovic, Foti

    2017-04-01

    concentrations and subsequent risks in soils of Paris and Paris region (Île-de-France). Our study aims at filling this knowledge gap, focusing on contamination and pollution by TMs in lawns and forests that constitute the main types of vegetation in urban areas of Paris region. Considering the rational described above, the aims of the present study were (i) to examine the concentration of eight selected TMs (As, Cd, Cr, Cu, Fe, Ni, Pb, Zn) in soils of two land-uses (public lawns and woods) along an urban pressure gradient in Paris region, (ii) to distinguish origins and sources of contamination or pollution, (iii) to evaluate the individual and overall TM contamination degree as well as the individual and overall TM pollution degree, (iiii) to use soil characteristics to better understand soil origins and histories along the urban pressure gradient and the relationship between these characteristics and TM concentrations. Ultimately, this study provides a baseline TM assessment for the long-term monitoring of the evolution of TM soil contents in urban area of the Paris region.

  6. Concentration and stable carbon isotopic composition of CO2 in cave air of Postojnska jama, Slovenia

    Directory of Open Access Journals (Sweden)

    Magda Mandic

    2013-09-01

    Full Text Available Partial pressure of CO2 (pCO2 and its isotopic composition (δ13CairCO2 were measured in Postojnska jama, Slovenia, at 10 locations inside the cave and outside the cave during a one-year period. At all interior locations the pCO2 was higher and δ13CairCO2 lower than in the outside atmosphere. Strong seasonal fluctuations in both parameters were observed at locations deeper in the cave, which are isolated from the cave air circulation. By using a binary mixing model of two sources of CO2, one of them being the atmospheric CO2, we show that the excess of CO2 in the cave air has a δ13C value of -23.3 ± 0.7 ‰, in reasonable agreement with the previously measured soil-CO2 δ13C values. The stable isotope data suggest that soil CO2 is brought to the cave by drip water.

  7. Impacts of Floods on Organic Carbon Concentrations in Alluvial Soils along Hydrological Gradients Using a Digital Elevation Model (DEM

    Directory of Open Access Journals (Sweden)

    Diane Saint-Laurent

    2016-05-01

    Full Text Available This study examines the spatial distribution of the organic carbon found in alluvial soils affected by successive floods. In flood zones, very little is known of the processes associated with the development of soils subjected to frequent flooding, in particular with respect to the accumulation of litter and organic carbon concentrations. The aim of this study is to better understand the distribution of organic carbon based on various hydrological gradients associated with flood recurrence. A digital elevation model was developed from LIDAR data to assess the microtopography of the site, and further delineate floodplains and no-flood zones. Various soil properties were considered in addition to organic carbon, such as pH, soil bulk density, litter, drainage, and topographic levels (elevation. The results show that the soils in the frequent-flood zones (FFz, recurrence of 0–20 years have significantly less total organic carbon than the soils in the no-flood zones (NFz and the moderate flood zones (MFz, 20–100 years. Average values obtained for the surface horizons (0–20 cm vary by 1.74% ± 0.85% (FFz, 3.34% ± 1.09% (MFz and 3.54% ± 1.77% (NFz, respectively. The absence of ground litter in the frequent flood zones helps decrease the input of organic matter in the surface horizons and progressively results in soil depletion.

  8. Use of passive diffusion sampling method for defining NO2 concentrations gradient in São Paulo, Brazil

    Directory of Open Access Journals (Sweden)

    Meliefste Kees

    2006-06-01

    Full Text Available Abstract Background Air pollution in São Paulo is constantly being measured by the State of Sao Paulo Environmental Agency, however there is no information on the variation between places with different traffic densities. This study was intended to identify a gradient of exposure to traffic-related air pollution within different areas in São Paulo to provide information for future epidemiological studies. Methods We measured NO2 using Palmes' diffusion tubes in 36 sites on streets chosen to be representative of different road types and traffic densities in São Paulo in two one-week periods (July and August 2000. In each study period, two tubes were installed in each site, and two additional tubes were installed in 10 control sites. Results Average NO2 concentrations were related to traffic density, observed on the spot, to number of vehicles counted, and to traffic density strata defined by the city Traffic Engineering Company (CET. Average NO2concentrations were 63μg/m3 and 49μg/m3 in the first and second periods, respectively. Dividing the sites by the observed traffic density, we found: heavy traffic (n = 17: 64μg/m3 (95% CI: 59μg/m3 – 68μg/m3; local traffic (n = 16: 48μg/m3 (95% CI: 44μg/m3 – 52μg/m3 (p Conclusion The differences in NO2 levels between heavy and local traffic sites are large enough to suggest the use of a more refined classification of exposure in epidemiological studies in the city. Number of vehicles counted, traffic density observed on the spot and traffic density strata defined by the CET might be used as a proxy for traffic exposure in São Paulo when more accurate measurements are not available.

  9. Experimental investigation of concentration and stable isotopes signals during organic contaminants back diffusion

    DEFF Research Database (Denmark)

    Jin, Biao; Nika, Chrysanthi-Elisabeth; Rolle, Massimo

    2017-01-01

    -DCE back diffusion from an impervious layer. Intensive sampling (>1000 measurements) was carried out, including the withdrawal of aqueous samples at closely spaced (1 cm) outlet ports, as well as the high-resolution sampling of the source zone (agarose gel) at the end of each experiment. The transient...... behavior of the plumes originated by back diffusion was investigated by sampling the outlet ports at regular intervals in the experiments, each run for a total time corresponding to 15 pore volumes. The high-resolution sampling allowed us to resolve the spatial and temporal evolution of concentration...... [3], provided a good agreement with the experimental data...

  10. Atazanavir intracellular concentrations remain stable during pregnancy in HIV-infected patients.

    Science.gov (United States)

    Focà, Emanuele; Calcagno, Andrea; Bonito, Andrea; Simiele, Marco; Domenighini, Elisabetta; D'Avolio, Antonio; Quiros Roldan, Eugenia; Trentini, Laura; Casari, Salvatore; Di Perri, Giovanni; Castelli, Francesco; Bonora, Stefano

    2017-11-01

    Atazanavir (300 mg) boosted by ritonavir (100 mg) is the preferred third drug in pregnancy. However, there is still discordance on atazanavir dose increase during the third trimester. To evaluate plasma and intracellular atazanavir and ritonavir concentrations in HIV-infected women during pregnancy and after delivery. This was an observational study. HIV-infected pregnant patients treated with atazanavir/ritonavir plus either tenofovir/emtricitabine or abacavir/lamivudine had been prospectively enrolled after having signed a written informed consent form. Plasma and intracellular atazanavir and ritonavir Ctrough (24 ± 3 h after drug intake) were measured at each visit during the first, second and third trimesters and post-partum using validated HPLC-MS and HPLC-photodiode array methods (with direct evaluation of cellular volume). Data are described as median (IQR) and compared through non-parametric tests. Twenty-five patients were enrolled; at baseline, the median age was 32 years (27-35). All patients had plasma HIV RNA  0.05). This is the first demonstration that intracellular atazanavir exposure remains unchanged during pregnancy supporting the standard 300/100 mg atazanavir/ritonavir dosing throughout pregnancy. © The Author 2017. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  11. Peritoneal dialysate effluent and serum CA125 concentrations in stable peritoneal dialysis patients.

    Science.gov (United States)

    Redahan, Lynn; Davenport, Andrew

    2016-06-01

    CA125 in peritoneal dialysis (PD) effluent dialysate has been used as a surrogate biomarker for the health of the peritoneum in PD patients. However CA125 is synthesised by epithelial cells and as such is not specific for the peritoneum, and most studies have only measured peritoneal CA125, without serum CA125 values. As such we wished to determine the factors which influenced PD effluent CA125 in a large contemporaneous cohort. We measured dialysate effluent CA125 in PD patients attending for routine assessment of peritoneal membrane function with a peritoneal equilibration test (PET), with corresponding serum CA125. Serum and dialysate CA125 were measured in 205 PD patients; 59.0 ± 16.8 years, median PD treatment 3 (2-20) months, 59 % male, 42.4 % diabetic, with 31.2 % treated by continuous ambulatory peritoneal dialysis, 22 % by automated overnight peritoneal dialysis cycler (APD) and 46.8 % by APD with a day time exchange. The median serum CA125 was 21 (13-38) U/ml, with an effluent 4 h PD PET effluent of 20 (11.5-36.5) U/ml. PET PD effluent dialysate was associated with PET dialysate total protein (β 12.9, p peritonitis episodes. PD effluent CA125 concentrations were associated with peritoneal protein losses and increased by the usage of higher glucose dialysates to compensate for loss of residual renal function.

  12. Evaluation of NT-proBNP concentrations during exercise in asymptomatic patients with severe high-gradient aortic stenosis.

    Science.gov (United States)

    Dobrowolski, Piotr; Lech, Agnieszka; Klisiewicz, Anna; Hoffman, Piotr

    2016-08-11

    INTRODUCTION The effect of asymptomatic severe aortic stenosis (ASAS) on N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels ar rest and during exercise, as well as their relevance for clinical practice remain controversial.  OBJECTIVES The aim of this study was to test the hypothesis of whether the evaluation of NT-proBNP concentrations during exercise provides additional information about the severity of aortic stenosis and left ventricular remodeling in patients with ASAS. PATIENTS AND METHODS A total of 50 patients with ASAS (mean age, 38.4 ±18.1 years) and 21 healthy subjects (mean age, 43.4 ±10.6 years) were enrolled. Rest and exercise echocardiography was performed to evaluate maximum velocity (Vmax), mean aortic gradient (AG), and aortic valve area (AVA). The left ventricular mass index (LVMI) was calculated. NT-proBNP concentrations at rest and during exercise were assessed, and the difference between the 2 values was calculated (ΔNT-proBNP). RESULTS NT-proBNP and ΔNT-proBNP levels at rest and during exercise were significantly higher in the ASAS group compared with the control group. In the ASAS group, NT-proBNP levels at rest significantly correlated with LVMI (r = 0.432; P <0.0001), AVA (r = -0.408; P <0.0001), Vmax (r = 0.375; P = 0.002), and mean AG (r = 0.257; P = 0.03). NT-proBNP levels during exercise significantly correlated with LVMI (r = 0.432; P <0.0001), mean AG (r = 0.401; P = 0.001), and AVA (r = -0.375; P = 0.001). In the multivariate logistic regression model, the factors independently associated with NT-proBNP both at rest and during exercise were age, AVA, and LVMI. CONCLUSIONS NT-proBNP levels at rest provide valuable information for identifying patients with more advanced left ventricular hypertrophy secondary to severe aortic stenosis. NT-proBNP levels during exercise do not provide new information on the severity of AS.

  13. Climate control on sulphate and nitrate concentrations in alpine streams of Northern Italy along a nitrogen saturation gradient

    Directory of Open Access Journals (Sweden)

    M. Rogora

    2008-03-01

    Full Text Available The role of meteorology, hydrology and atmospheric deposition on the temporal pattern of SO4 and NO3 concentrations was investigated for three streams draining alpine catchments in Northern Italy.

    The study sites lie on a gradient of atmospheric fluxes of SO4 and NO3 (from about 50 to 80 meq m−2 y−1, and from 40 to 90 meq m−2 y−1, respectively. As a consequence of the increasing N input, the three catchments are also representative of aggrading levels of N saturation. Different methods of statistical analysis were applied to monthly data for the period 1997–2005 to identify which variables (temperature, precipitation, hydrology, SO4 and NO3 deposition were the main predictors of water chemistry and its change in time. Hydrological changes and snow cover proved to be the main confounding factors in the response to atmospheric deposition in the River Masino catchment. Its particular characteristics (small catchment area, rapid flushing during runoff and thin soil cover meant that this site responded without a significant delay to SO4 deposition decrease. It also showed a clear seasonal pattern of NO3 concentration, in response to hydrology and biological uptake in the growing season.

    The selected driving variables failed to model the water chemistry at the other study sites. Nevertheless, temperature, especially extreme values, turned out to be important in both SO4 and NO3 export from the catchments. This result might be largely explained by the effect of warm periods on temperature-dependent processes such as mineralization, nitrification and S desorption.

    Our findings suggest that surface waters in the alpine area will be extremely sensitive to a climate warming scenario: higher temperatures and increasing frequency of drought could exacerbate the effects

  14. Optimum concentration gradient of the electrocatalyst, Nafion® and poly(tetrafluoroethylene) in a membrane-electrode-assembly for enhanced performance of direct methanol fuel cells.

    Science.gov (United States)

    Liu, Jing Hua; Jeon, Min Ku; Lee, Ki Rak; Woo, Seong Ihl

    2010-12-14

    A combinatorial library of membrane-electrode-assemblies (MEAs) which consisted of 27 different compositions was fabricated to optimize the multilayer structure of direct methanol fuel cells. Each spot consisted of three layers of ink and a gradient was generated by employing different concentrations of the three components (Pt catalyst, Nafion® and polytetrafluoroethylene (PTFE)) of each layer. For quick evaluation of the library, a high-throughput optical screening technique was employed for methanol electro-oxidation reaction (MOR) activity. The screening results revealed that gradient layers could lead to higher MOR activity than uniform layers. It was found that the MOR activity was higher when the concentrations of Pt catalyst and Nafion ionomer decreased downward from the top layer to the bottom layer. On the other hand, higher MOR activity was observed when PTFE concentration increased downward from the top to the bottom layer.

  15. Carbon and nitrogen stable isotopes and metal concentration in food webs from a mining-impacted coastal lagoon

    Energy Technology Data Exchange (ETDEWEB)

    Marin-Guirao, Lazaro [Departamento de Ecologia e Hidrologia, Facultad de Biologia, Universidad de Murcia, 30100-Murcia (Spain)], E-mail: lamarin@um.es; Lloret, Javier; Marin, Arnaldo [Departamento de Ecologia e Hidrologia, Facultad de Biologia, Universidad de Murcia, 30100-Murcia (Spain)

    2008-04-01

    Two food webs from the Mar Menor coastal lagoon, differing in the distance from the desert-stream through which mining wastes were discharged, were examined by reference to essential (Zn and Cu) and non-essential (Pb and Cd) metal concentrations and stable isotopes content (C and N). The partial extraction technique applied, which reflects the availability of metals to organisms after sediment ingestion, showed higher bioavailable metal concentrations in sediments from the station influenced by the mining discharges, in agreement with the higher metal concentrations observed in organisms, which in many cases exceeded the regulatory limits established in Spanish legislation concerning seafood. Spatial differences in essential metal concentrations in the fauna suggest that several organisms are exposed to metal levels above their regulation capacity. Differences in isotopic composition were found between both food webs, the wadi-influenced station showing higher {delta}{sup 15}N values and lower {delta}{sup 13}C levels, due to the discharge of urban waste waters and by the entrance of freshwater and allochthonous marsh plants. The linear-regressions between trophic levels (as indicated by {delta}{sup 15}N) and the metal content indicated that biomagnification does not occur. In the case of invertebrates, since the 'handle strategy' of the species and the physiological requirements of the organisms, among other factors, determine the final concentration of a specific element, no clear relationships between trophic level and the metal content are to be expected. For their part, fish communities did not show clear patterns in the case of any of the analyzed metals, probably because most fish species have similar metal requirements, and because biological factors also intervened. Finally, since the study deals with metals, assumptions concerning trophic transfer factors calculation may not be suitable since the metal burden originates not only from the prey but

  16. Formation of vertical concentration gradients in poly(3-hexylthiophene-2,5-diyl): Phenyl-C61-butyric acid methyl ester-graded bilayer solar cells

    International Nuclear Information System (INIS)

    Vohra, Varun; Higashimine, Koichi; Tsuzaki, Shogo; Ohdaira, Keisuke; Murata, Hideyuki

    2014-01-01

    In the present work, we demonstrate that graded bilayer solar cells provide a very interesting alternative to the bulk heterojunction active layers commonly used in organic photovoltaic cells. One of the main advantages of this type of active layers is the possibility to optimize independently both donor and acceptor layers. Using various process methods, we obtain active layers that demonstrate a donor–acceptor vertical concentration gradient. These devices exhibit not only a high fill factor but also a remarkable increase in open-circuit voltage (V oc ). In order to understand the influence of the film morphology over the device parameters, we provide a complete study using energy-dispersive x-ray spectroscopy elemental mapping of the device cross sections, showing evidence that ideal donor–acceptor concentration gradient are required to obtain high fill factors. Furthermore, we use a simple equivalent electrical model to extrapolate device parameters such as reverse saturation current for a clearer understanding of the origin of the V oc increase. - Highlights: • Various donor–acceptor concentration-graded devices were fabricated. • Improved donor–acceptor concentration gradient enhances the photovoltaic properties. • The increased open-circuit voltage results from lower reverse saturation currents. • Adjusting the dimensions of buffer and intermixed layers enhances fill factor. • Ideal active layer morphologies lead to an increase of 30% of the efficiency

  17. Integrated Electrokinetics-Adsorption Remediation of Saline-Sodic Soils: Effects of Voltage Gradient and Contaminant Concentration on Soil Electrical Conductivity

    Directory of Open Access Journals (Sweden)

    Mohammed Hussain Essa

    2013-01-01

    Full Text Available In this study, an integrated in situ remediation technique which couples electrokinetics with adsorption, using locally produced granular activated carbon from date palm pits in the treatment zones that are installed directly to bracket the contaminated soils at bench-scale, is investigated. Natural saline-sodic clay soil, spiked with contaminant mixture (kerosene, phenol, Cr, Cd, Cu, Zn, Pb, and Hg, was used in this study to investigate the effects of voltage gradient, initial contaminant concentration, and polarity reversal rate on the soil electrical conductivity. Box-Behnken Design (BBD was used for the experimental design and response surface methodology (RSM was employed to model, optimize, and interpret the results obtained using Design-Expert version 8 platform. The total number of experiments conducted was 15 with voltage gradient, polarity reversal rate, and initial contaminant concentration as variables. The main target response discussed in this paper is the soil electrical conductivity due to its importance in electrokinetic remediation process. Responses obtained were fitted to quadratic models whose R2 ranges from 84.66% to 99.19% with insignificant lack of fit in each case. Among the investigated factors, voltage gradient and initial contaminant concentration were found to be the most significant influential factors.

  18. The meteorology and chemistry of high nitrogen oxide concentrations in the stable boundary layer at the South Pole

    Science.gov (United States)

    Neff, William; Crawford, Jim; Buhr, Marty; Nicovich, John; Chen, Gao; Davis, Douglas

    2018-03-01

    Four summer seasons of nitrogen oxide (NO) concentrations were obtained at the South Pole (SP) during the Sulfur Chemistry in the Antarctic Troposphere (ISCAT) program (1998 and 2000) and the Antarctic Tropospheric Chemistry Investigation (ANTCI) in (2003, 2005, 2006-2007). Together, analyses of the data collected from these studies provide insight into the large- to small-scale meteorology that sets the stage for extremes in NO and the significant variability that occurs day to day, within seasons, and year to year. In addition, these observations reveal the interplay between physical and chemical processes at work in the stable boundary layer of the high Antarctic plateau. We found a systematic evolution of the large-scale wind system over the ice sheet from winter to summer that controls the surface boundary layer and its effect on NO: initially in early spring (Days 280-310) the transport of warm air and clouds over West Antarctica dominates the environment over the SP; in late spring (Days 310-340), the winds at 300 hPa exhibit a bimodal behavior alternating between northwest and southeast quadrants, which is of significance to NO; in early summer (Days 340-375), the flow aloft is dominated by winds from the Weddell Sea; and finally, during late spring, winds aloft from the southeast are strongly associated with clear skies, shallow stable boundary layers, and light surface winds from the east - it is under these conditions that the highest NO occurs. Examination of the winds at 300 hPa from 1961 to 2013 shows that this seasonal pattern has not changed significantly, although the last twenty years have seen an increasing trend in easterly surface winds at the SP. What has also changed is the persistence of the ozone hole, often into early summer. With lower total ozone column density and higher sun elevation, the highest actinic flux responsible for the photolysis of snow nitrate now occurs in late spring under the shallow boundary layer conditions optimum for

  19. In vivo degradation behavior and biological activity of some new Mg–Ca alloys with concentration's gradient of Si for bone grafts

    Energy Technology Data Exchange (ETDEWEB)

    Trincă, Lucia Carmen, E-mail: lctrinca@uaiasi.ro [“Ion Ionescu de la Brad” University of Agricultural Sciences and Veterinary Medicine, Faculty of Horticulture, Str. Aleea M. Sadoveanu, No. 3, 700490 Iasi (Romania); Fântânariu, Mircea, E-mail: mfantanariu@uaiasi.ro [“Ion Ionescu de la Brad” University of Agricultural Sciences and Veterinary Medicine, Faculty of Veterinary Medicine, Str. Aleea M. Sadoveanu, No. 8, 700489 Iasi (Romania); Solcan, Carmen, E-mail: csolcan@yahoo.com [“Ion Ionescu de la Brad” University of Agricultural Sciences and Veterinary Medicine, Faculty of Veterinary Medicine, Str. Aleea M. Sadoveanu, No. 8, 700489 Iasi (Romania); Trofin, Alina Elena, E-mail: aetrofin@yahoo.com [“Ion Ionescu de la Brad” University of Agricultural Sciences and Veterinary Medicine, Faculty of Horticulture, Str. Aleea M. Sadoveanu, No. 3, 700490 Iasi (Romania); Burtan, Liviu, E-mail: lburtan@uaiasi.ro [“Ion Ionescu de la Brad” University of Agricultural Sciences and Veterinary Medicine, Faculty of Veterinary Medicine, Str. Aleea M. Sadoveanu, No. 8, 700489 Iasi (Romania); Acatrinei, Dumitru Mihai, E-mail: dacatrinei@yahoo.com [“Ion Ionescu de la Brad” University of Agricultural Sciences and Veterinary Medicine, Faculty of Veterinary Medicine, Str. Aleea M. Sadoveanu, No. 8, 700489 Iasi (Romania); Stanciu, Sergiu, E-mail: sergiustanciu2003@yahoo.com [“Gheorghe Asachi” Technical University, Faculty of Materials Science and Engineering, Str. Prof. D. Mangeron, No. 67, 700050 Iasi (Romania); and others

    2015-10-15

    Highlights: • A Mg–Ca alloy with Si concentration gradient was obtained as bone graft material. • Degradation rate of the Mg–Ca–Si alloy was investigated by SEM and EDAX techniques. • Subcutaneous and tibiae implants in rats were monitored by Biochemical, histological, RX and CT investigations monitored implant's evolution. • Si concentration gradient decreased the alloy degradation rate during bone healing. - Abstract: Magnesium based alloys, especially Mg–Ca alloys, are biocompatible substrates with mechanical properties similar to those of bones. The biodegradable alloys of Mg–Ca provide sufficient mechanical strength in load carrying applications as opposed to biopolymers and also they avoid stress shielding and secondary surgery inherent with permanent metallic implant materials. The main issue facing a biodegradable Mg–Ca alloy is the fast degradation in the aggressive physiological environment of the body. The alloy's corrosion is proportional with the dissolution of the Mg in the body: the reaction with the water generates magnesium hydroxide and hydrogen. The accelerated corrosion will lead to early loss of the alloy's mechanical integrity. The degradation rate of an alloy can be improved mainly through tailoring the composition and by carrying out surface treatments. This research focuses on the ability to adjust degradation rate of Mg–Ca alloys by an original method and studies the biological activity of the resulted specimens. A new Mg–Ca alloy, with a Si gradient concentration from the surface to the interior of the material, was obtained. The surface morphology was investigated using scanning electron microscopy (VegaTescan LMH II, SE detector, 30 kV), X-ray diffraction (X’Pert equipment) and energy dispersive X-ray (Bruker EDS equipment). In vivo degradation behavior, biological compatibility and activity of Mg–Ca alloys with/without Si gradient concentration were studied with an implant model (subcutaneous

  20. Interactive Effects of CO2 Concentration and Water Regime on Stable Isotope Signatures, Nitrogen Assimilation and Growth in Sweet Pepper

    Science.gov (United States)

    Serret, María D.; Yousfi, Salima; Vicente, Rubén; Piñero, María C.; Otálora-Alcón, Ginés; del Amor, Francisco M.; Araus, José L.

    2018-01-01

    Sweet pepper is among the most widely cultivated horticultural crops in the Mediterranean basin, being frequently grown hydroponically under cover in combination with CO2 fertilization and water conditions ranging from optimal to suboptimal. The aim of this study is to develop a simple model, based on the analysis of plant stable isotopes in their natural abundance, gas exchange traits and N concentration, to assess sweet pepper growth. Plants were grown in a growth chamber for near 6 weeks. Two [CO2] (400 and 800 μmol mol−1), three water regimes (control and mild and moderate water stress) and four genotypes were assayed. For each combination of genotype, [CO2] and water regime five plants were evaluated. Water stress applied caused significant decreases in water potential, net assimilation, stomatal conductance, intercellular to atmospheric [CO2], and significant increases in water use efficiency, leaf chlorophyll content and carbon isotope composition, while the relative water content, the osmotic potential and the content of anthocyanins did change not under stress compared to control conditions support this statement. Nevertheless, water regime affects plant growth via nitrogen assimilation, which is associated with the transpiration stream, particularly at high [CO2], while the lower N concentration caused by rising [CO2] is not associated with stomatal closure. The stable isotope composition of carbon, oxygen, and nitrogen (δ13C, δ18O, and δ15N) in plant matter are affected not only by water regime but also by rising [CO2]. Thus, δ18O increased probably as response to decreases in transpiration, while the increase in δ15N may reflect not only a lower stomatal conductance but a higher nitrogen demand in leaves or shifts in nitrogen metabolism associated with decreases in photorespiration. The way that δ13C explains differences in plant growth across water regimes within a given [CO2], seems to be mediated through its direct relationship with N

  1. Interactive Effects of CO2 Concentration and Water Regime on Stable Isotope Signatures, Nitrogen Assimilation and Growth in Sweet Pepper

    Directory of Open Access Journals (Sweden)

    María D. Serret

    2018-01-01

    Full Text Available Sweet pepper is among the most widely cultivated horticultural crops in the Mediterranean basin, being frequently grown hydroponically under cover in combination with CO2 fertilization and water conditions ranging from optimal to suboptimal. The aim of this study is to develop a simple model, based on the analysis of plant stable isotopes in their natural abundance, gas exchange traits and N concentration, to assess sweet pepper growth. Plants were grown in a growth chamber for near 6 weeks. Two [CO2] (400 and 800 μmol mol−1, three water regimes (control and mild and moderate water stress and four genotypes were assayed. For each combination of genotype, [CO2] and water regime five plants were evaluated. Water stress applied caused significant decreases in water potential, net assimilation, stomatal conductance, intercellular to atmospheric [CO2], and significant increases in water use efficiency, leaf chlorophyll content and carbon isotope composition, while the relative water content, the osmotic potential and the content of anthocyanins did change not under stress compared to control conditions support this statement. Nevertheless, water regime affects plant growth via nitrogen assimilation, which is associated with the transpiration stream, particularly at high [CO2], while the lower N concentration caused by rising [CO2] is not associated with stomatal closure. The stable isotope composition of carbon, oxygen, and nitrogen (δ13C, δ18O, and δ15N in plant matter are affected not only by water regime but also by rising [CO2]. Thus, δ18O increased probably as response to decreases in transpiration, while the increase in δ15N may reflect not only a lower stomatal conductance but a higher nitrogen demand in leaves or shifts in nitrogen metabolism associated with decreases in photorespiration. The way that δ13C explains differences in plant growth across water regimes within a given [CO2], seems to be mediated through its direct

  2. High-Temperature Thermochemical Storage with Redox-Stable Perovskites for Concentrating Solar Power, CRADA Number: CRD-14-554

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Zhiwen [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-09-05

    As part of a Federal Opportunity Announcement (FOA) Award, the project will be led by Colorado School of Mines (CSM) to explore and demonstrate the efficacy of highly reducible, redox-stable oxides to provide efficient thermochemical energy storage for heat release at temperatures of 900 degrees Celcius or more. NREL will support the material development for its application in a concentrating solar power (CSP) plant. In the project, NREL will provide its inventive system design, chemical looping for CSP, and use it as a platform to accommodate the chemical processes using a cost effective perovskite materials identified by CSM. NREL will design a 5-10kW particle receiver for perovskite reduction to store solar energy and help the development of a fluidized-bed reoxidation reactor and system integration. NREL will develop the demonstration receiver for on-sun test in the 5-10 kWt range in NREL's high flux solar furnace. NREL will assist in system analysis and provide techno-economic inputs for the overall system configuration.

  3. Heavy metal concentrations in a soil-plant-snail food chain along a terrestrial soil pollution gradient.

    NARCIS (Netherlands)

    Notten, M.J.M.; Oosthoek, A.; Rozema, J.; Aerts, R.

    2005-01-01

    We investigated concentrations of Zn, Cu, Cd and Pb in the compartments of a soil-plant (Urtica dioica)-snail (Cepaea nemoralis) food chain in four polluted locations in the Biesbosch floodplains, the Netherlands, and two reference locations. Total soil metal concentrations in the polluted locations

  4. In vivo degradation behavior and biological activity of some new Mg-Ca alloys with concentration's gradient of Si for bone grafts

    Science.gov (United States)

    Trincă, Lucia Carmen; Fântânariu, Mircea; Solcan, Carmen; Trofin, Alina Elena; Burtan, Liviu; Acatrinei, Dumitru Mihai; Stanciu, Sergiu; Istrate, Bogdan; Munteanu, Corneliu

    2015-10-01

    Magnesium based alloys, especially Mg-Ca alloys, are biocompatible substrates with mechanical properties similar to those of bones. The biodegradable alloys of Mg-Ca provide sufficient mechanical strength in load carrying applications as opposed to biopolymers and also they avoid stress shielding and secondary surgery inherent with permanent metallic implant materials. The main issue facing a biodegradable Mg-Ca alloy is the fast degradation in the aggressive physiological environment of the body. The alloy's corrosion is proportional with the dissolution of the Mg in the body: the reaction with the water generates magnesium hydroxide and hydrogen. The accelerated corrosion will lead to early loss of the alloy's mechanical integrity. The degradation rate of an alloy can be improved mainly through tailoring the composition and by carrying out surface treatments. This research focuses on the ability to adjust degradation rate of Mg-Ca alloys by an original method and studies the biological activity of the resulted specimens. A new Mg-Ca alloy, with a Si gradient concentration from the surface to the interior of the material, was obtained. The surface morphology was investigated using scanning electron microscopy (VegaTescan LMH II, SE detector, 30 kV), X-ray diffraction (X'Pert equipment) and energy dispersive X-ray (Bruker EDS equipment). In vivo degradation behavior, biological compatibility and activity of Mg-Ca alloys with/without Si gradient concentration were studied with an implant model (subcutaneous and bony) in rats. The organism response to implants was characterized by using radiological (plain X-rays and computed tomography), biochemical and histological methods of investigation. The results sustained that Si gradient concentration can be used to control the rate of degradation of the Mg-Ca alloys for enhancing their biologic activity in order to facilitate bone tissue repair.

  5. Measurement of absolute concentrations of individual compounds in metabolite mixtures by gradient-selective time-zero 1H-13C HSQC with two concentration references and fast maximum likelihood reconstruction analysis.

    Science.gov (United States)

    Hu, Kaifeng; Ellinger, James J; Chylla, Roger A; Markley, John L

    2011-12-15

    Time-zero 2D (13)C HSQC (HSQC(0)) spectroscopy offers advantages over traditional 2D NMR for quantitative analysis of solutions containing a mixture of compounds because the signal intensities are directly proportional to the concentrations of the constituents. The HSQC(0) spectrum is derived from a series of spectra collected with increasing repetition times within the basic HSQC block by extrapolating the repetition time to zero. Here we present an alternative approach to data collection, gradient-selective time-zero (1)H-(13)C HSQC(0) in combination with fast maximum likelihood reconstruction (FMLR) data analysis and the use of two concentration references for absolute concentration determination. Gradient-selective data acquisition results in cleaner spectra, and NMR data can be acquired in both constant-time and non-constant-time mode. Semiautomatic data analysis is supported by the FMLR approach, which is used to deconvolute the spectra and extract peak volumes. The peak volumes obtained from this analysis are converted to absolute concentrations by reference to the peak volumes of two internal reference compounds of known concentration: DSS (4,4-dimethyl-4-silapentane-1-sulfonic acid) at the low concentration limit (which also serves as chemical shift reference) and MES (2-(N-morpholino)ethanesulfonic acid) at the high concentration limit. The linear relationship between peak volumes and concentration is better defined with two references than with one, and the measured absolute concentrations of individual compounds in the mixture are more accurate. We compare results from semiautomated gsHSQC(0) with those obtained by the original manual phase-cycled HSQC(0) approach. The new approach is suitable for automatic metabolite profiling by simultaneous quantification of multiple metabolites in a complex mixture.

  6. Measurement of Absolute Concentrations of Individual Compounds in Metabolite Mixtures by Gradient-Selective Time-Zero 1H-13C HSQC (gsHSQC0) with Two Concentration References and Fast Maximum Likelihood Reconstruction Analysis

    Science.gov (United States)

    Hu, Kaifeng; Ellinger, James J.; Chylla, Roger A.; Markley, John L.

    2011-01-01

    Time-zero 2D 13C HSQC (HSQC0) spectroscopy offers advantages over traditional 2D NMR for quantitative analysis of solutions containing a mixture of compounds because the signal intensities are directly proportional to the concentrations of the constituents. The HSQC0 spectrum is derived from a series of spectra collected with increasing repetition times within the basic HSQC block by extrapolating the repetition time to zero. Here we present an alternative approach to data collection, gradient-selective time-zero 1H-13C HSQC0 in combination with fast maximum likelihood reconstruction (FMLR) data analysis and the use of two concentration references for absolute concentration determination. Gradient-selective data acquisition results in cleaner spectra, and NMR data can be acquired in both constant-time and non-constant time mode. Semi-automatic data analysis is supported by the FMLR approach, which is used to deconvolute the spectra and extract peak volumes. The peak volumes obtained from this analysis are converted to absolute concentrations by reference to the peak volumes of two internal reference compounds of known concentration: DSS (4,4-dimethyl-4-silapentane-1-sulfonic acid) at the low concentration limit (which also serves as chemical shift reference) and MES (2-(N-morpholino)ethanesulfonic acid) at the high concentration limit. The linear relationship between peak volumes and concentration is better defined with two references than with one, and the measured absolute concentrations of individual compounds in the mixture are more accurate. We compare results from semi-automated gsHSQC0 with those obtained by the original manual phase-cycled HSQC0 approach. The new approach is suitable for automatic metabolite profiling by simultaneous quantification of multiple metabolites in a complex mixture. PMID:22029275

  7. Heavy metal concentrations in a soil-plant-snail food chain along a terrestrial soil pollution gradient

    Energy Technology Data Exchange (ETDEWEB)

    Notten, M.J.M. [Institute of Ecological Science, Department of Systems Ecology, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam (Netherlands)]. E-mail: martje.notten@ecology.falw.vu.nl; Oosthoek, A.J.P. [Institute of Ecological Science, Department of Systems Ecology, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam (Netherlands); Rozema, J. [Institute of Ecological Science, Department of Systems Ecology, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam (Netherlands); Aerts, R. [Institute of Ecological Science, Department of Systems Ecology, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam (Netherlands)

    2005-11-15

    We investigated concentrations of Zn, Cu, Cd and Pb in the compartments of a soil-plant (Urtica dioica)-snail (Cepaea nemoralis) food chain in four polluted locations in the Biesbosch floodplains, the Netherlands, and two reference locations. Total soil metal concentrations in the polluted locations were 4-20 times higher than those in the reference locations. Positive relationships between the generally low leaf concentrations and the soil concentrations were found for Zn only (r {sup 2} = 0.20). Bioaccumulation of Zn, Cu and Cd was observed in the snail tissues. We found positive relationships between the snail and leaf concentrations for all metals (range r {sup 2} = 0.19-0.46). The relationships between soil and snail concentrations were also positive, except for Cu (range r {sup 2} = 0.15-0.33). These results suggest transfer of metals to C. nemoralis snails from U. dioica leaves and from the soil. Metal transfer from polluted leaves to C. nemoralis is more important than transfer from the soil. - Bioaccumulation and positive snail-leaf relationships suggest metal transfer from Urtica dioica leaves to Cepaea nemoralis snails.

  8. Heavy metal concentrations in a soil-plant-snail food chain along a terrestrial soil pollution gradient

    International Nuclear Information System (INIS)

    Notten, M.J.M.; Oosthoek, A.J.P.; Rozema, J.; Aerts, R.

    2005-01-01

    We investigated concentrations of Zn, Cu, Cd and Pb in the compartments of a soil-plant (Urtica dioica)-snail (Cepaea nemoralis) food chain in four polluted locations in the Biesbosch floodplains, the Netherlands, and two reference locations. Total soil metal concentrations in the polluted locations were 4-20 times higher than those in the reference locations. Positive relationships between the generally low leaf concentrations and the soil concentrations were found for Zn only (r 2 = 0.20). Bioaccumulation of Zn, Cu and Cd was observed in the snail tissues. We found positive relationships between the snail and leaf concentrations for all metals (range r 2 = 0.19-0.46). The relationships between soil and snail concentrations were also positive, except for Cu (range r 2 = 0.15-0.33). These results suggest transfer of metals to C. nemoralis snails from U. dioica leaves and from the soil. Metal transfer from polluted leaves to C. nemoralis is more important than transfer from the soil. - Bioaccumulation and positive snail-leaf relationships suggest metal transfer from Urtica dioica leaves to Cepaea nemoralis snails

  9. Concentration-Gradient Multichannel Flow-Stream Membrane Capacitive Deionization Cell for High Desalination Capacity of Carbon Electrodes.

    Science.gov (United States)

    Kim, Choonsoo; Lee, Juhan; Srimuk, Pattarachai; Aslan, Mesut; Presser, Volker

    2017-12-22

    We present a novel multichannel membrane flow-stream capacitive deionization (MC-MCDI) concept with two flow streams to control the environment around the electrodes and a middle channel for water desalination. The introduction of side channels to our new cell design allows operation in a highly saline environment, while the feed water stream in the middle channel (conventional CDI channel) is separated from the electrodes with anion- and cation-exchange membranes. At a high salinity gradient between side (1000 mm) and middle (5 mm) channels, MC-MCDI exhibited an unprecedented salt-adsorption capacity (SAC) of 56 mg g -1 in the middle channel with charge efficiency close to unity and low energy consumption. This excellent performance corresponds to a fourfold increase in desalination performance compared to the state-of-the-art in a conventional CDI cell. The enhancement originates from the enhanced specific capacitance in high-molar saline media in agreement with the Gouy-Chapman-Stern theory and from a double-ion desorption/adsorption process of MC-MCDI through voltage operation from -1.2 to +1.2 V. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Vitamin B1 in marine sediments: pore water concentration gradient drives benthic flux with potential biological implications

    Directory of Open Access Journals (Sweden)

    Danielle eMonteverde

    2015-05-01

    Full Text Available Vitamin B1, or thiamin, can limit primary productivity in marine environments, however the major marine environmental sources of this essential coenzyme remain largely unknown. Vitamin B1 can only be produced by organisms that possess its complete synthesis pathway, while other organisms meet their cellular B1 quota by scavenging the coenzyme from exogenous sources. Due to high bacterial cell density and diversity, marine sediments could represent some of the highest concentrations of putative B1 producers, yet these environments have received little attention as a possible source of B1 to the overlying water column. Here we report the first dissolved pore water profiles of B1 measured in cores collected in two consecutive years from Santa Monica Basin, CA. Vitamin B1 concentrations were fairly consistent between the two years ranging from 30 pM up to 770 pM. A consistent maximum at ~5 cm sediment depth covaried with dissolved concentrations of iron. Pore water concentrations were higher than water column levels and represented some of the highest known environmental concentrations of B1 measured to date, (over two times higher than maximum water column concentrations suggesting increased rates of cellular production and release within the sediments. A one dimensional diffusion-transport model applied to the B1 profile was used to estimate a diffusive benthic flux of ~0.7 nmol m 2 d-1. This is an estimated flux across the sediment-water interface in a deep sea basin; if similar magnitude B-vitamin fluxes occur in shallow coastal waters, benthic input could prove to be a significant B1-source to the water column and may play an important role in supplying this organic growth factor to auxotrophic primary producers.

  11. A comparison between evaporation ponds and evaporation surfaces as a source of the concentrated salt brine for salt gradient maintenance at Tajoura solar pond

    International Nuclear Information System (INIS)

    Ramadan, Abdulghani M.; Agha, Khairy R.; Abughres, M.

    2012-01-01

    One of the main problems that negatively affect the operation of salt gradient solar ponds and influence its thermal stability is the maintenance of salt gradient profile. Evaporation pond (EP) is designed to generate the salt which lost upward salt diffusion from the lower convective zone (LCZ) of the solar pond. Another attractive method is the evaporation surface facility (ES). Regions with moderate to high precipitation favor Evaporation Surface over Evaporation Ponds. Dry climates will generally favor Evaporation Ponds for the brine re-concentration. In previous studies [1-3], the authors have shown that the (EP) of Tajoura's Experimental Solar Pond (TESP) is under sized and can provide only about 30% of the salt required by a Salt Gradient Solar Pond (SGSP). The anticipated size of (EP) was estimated and presented in those studies under different design conditions, including Summer, Autumn and Spring designs, while the winter design was excluded due to the low rates of net evaporation during the winter season. In addition, the results presented were predicted for the first three years of operation. The daily variations of brine concentration in the (EP) of (TESP) and those based on different designs were predicted and discussed under different scenarios. The quantities of brine provided by the evaporation pond and that required by SGSP were predicted for both cases of surface water flushing (fresh water and sea-water) under the different design conditions as shown in Table 1. This paper investigates the differences between (EP) and (ES) both as a source for salt brine generation by evaporation. The effect of (EP) depth on the area ratio and daily variations of salt concentrations for three years of operation is shown. Results show that evaporation can be a reasonable method for salt brine generation. Reducing the depth of (EP) improves the capability of (EP) for brine re-concentration. It also increases the (EP) surface area for the same quantity of

  12. Reconstructions of Climatic and Topographic Gradients in the Sierra Nevada during the early Eocene using compound-specific stable isotopes and organic molecular temperature proxies

    Science.gov (United States)

    Hren, M. T.; Pagani, M.; Brandon, M.; Erwin, D. M.

    2008-12-01

    Terrestrial sediments from the early Cenozoic provide important records of continental temperature gradients during periods of high global temperatures and PCO2, yet these records are often interpreted in terms of either climatic or orographic effects. As a result, linking models of past global climate with terrestrial temperature information is hampered by a lack of detailed information on paleoelevation. Organic molecular proxies provide new tools to help distinguish between climatic and orographic information in terrestrial sediments. For this study, we used organic molecular proxies to determine paleoelevation and paleotemperature gradients in the Sierra Nevada during the early Eocene warm period. Specifically, we analyzed the hydrogen and carbon isotopes of n-alkanes in bulk sediments and fossil angiosperm leaf cuticle in overbank deposits of major drainages of the Eocene Sierra Nevada to quantify the changes in the isotopic composition of leaf water that potentially reflect changes in paleoelevation. We coupled this data with paleotemperature measurements across this landscape using the MBT/CBT organic molecular temperature proxy, as well as thermodynamic models of the isotopic evolution of rainwater during orographic ascent. Hydrogen isotopes of n-alkanes systematically decrease by more than 30 per mil with distance from the Eocene shoreline and temperature data show a decrease of more than 8 degrees across this ancient range, with temperatures near the ocean margin exceeding 22 degrees. Isotopic and temperature data provide evidence for steep topography and high temperature lapse rates at the California margin during the early Eocene. These results support model estimates of temperature and relative humidity for the early Eocene based on a four time doubling of atmospheric CO2.

  13. A high gradient and strength bioseparator with nano-sized immunomagnetic particles for specific separation and efficient concentration of E. coli O157:H7

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Jianhan, E-mail: jianhan@cau.edu.cn [Ministry of Agriculture Key Laboratory of Agricultural Information Acquisition Technology (Beijing), 17 East Tsinghua Road, China Agricultural University, Mailbox 125, Beijing 100083 (China); Li, Min [College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058 (China); Li, Yanbin [College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058 (China); Department of Biological and Agricultural Engineering, University of Arkansas, Fayetteville, AR 72701 (United States); Chen, Qi [Modern Precision Agriculture System Integration Research Key Laboratory of Ministry of Education, China Agricultural University, Beijing 100083 (China)

    2015-03-15

    Sample pretreatment is a key to rapid screening of pathogens for prevention and control of foodborne diseases. Magnetic immunoseparation is a specific method based on antibody–antigen reaction to capture the target bacteria and concentrate them in a smaller-volume buffer. The use of nano-sized magnetic particles could improve the separation efficiency of bacteria but require much higher gradient and strength magnetic field. In this study, a strong magnetic bioseparator with a mean field strength of 1.35 T and a mean gradient of 90 T/m was developed with the use of the 30 nm and 180 nm magnetic particles to specifically separate and efficiently concentrate foodborne bacterial pathogens using Escherichia coli O157:H7 as a model bacterium. The polyclonal antibodies against E. coli were evaluated using Dot ELISA analysis for their good affinity with the target bacteria and then used to modify the surface of the magnetic nanoparticles by 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) method and streptavidin-biotin binding. The magnetic particle concentrations were optimized to be 40 µg/ml and 100 µg/ml for the 30 nm and 180 nm particles, respectively, the immunoreaction time was optimized to be 45 min for both sizes of particles, and the separation times were optimized to be 60 min and 2 min for the 30 nm and 180 nm particles, respectively. The total magnetic separation time was 2 h and 1 h for the 30 nm and 180 nm particles, respectively. The experimental results demonstrated that the bioseparator with the use of either 30 nm or 180 nm immunomagnetic particles could achieve a separation efficiency of >90% for E. coli O157:H7 at the concentrations ranging from 10{sup 2} to 10{sup 5} cfu/ml. No obvious interferences from non-target foodborne pathogens, such as SalmonellaTyphimurium and Listeria innocua, were found. For overall consideration of the consuming time, the cost, and the separation efficiency, the 180 nm magnetic particles are

  14. Trace Element Concentrations in Tree Leaves and Lichen Collected Along a Metal Pollution Gradient Near Olkusz (Southern Poland).

    Science.gov (United States)

    Zakrzewska, Marta; Klimek, Beata

    2018-02-01

    The aim of the study was to assess the metal pollution in the vicinity of the Bukowno smelter near Olkusz in southern Poland. Birch and oak leaves, pine needles and a lichen Hypogymnia physodes, overgrowing pine bark were collected at stands at different distances from the smelter and analysed for cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) content. Concentrations of metals in the lichen were usually higher than in the tree leaves/needles and decreased with distance from the smelter, apart from the Cu content. The strongest correlation was noticed between Cd and Pb concentrations, which indicates a common pollution source (the smelter). Our results show that birch leaves can be potentially useful as a bioindicator of Zn air pollution since this species was shown to accumulate high amounts of zinc, related to environmental pollution with that metal, in their leaves.

  15. Activity concentration measurements using a conjugate gradient (Siemens xSPECT) reconstruction algorithm in SPECT/CT.

    Science.gov (United States)

    Armstrong, Ian S; Hoffmann, Sandra A

    2016-11-01

    The interest in quantitative single photon emission computer tomography (SPECT) shows potential in a number of clinical applications and now several vendors are providing software and hardware solutions to allow 'SUV-SPECT' to mirror metrics used in PET imaging. This brief technical report assesses the accuracy of activity concentration measurements using a new algorithm 'xSPECT' from Siemens Healthcare. SPECT/CT data were acquired from a uniform cylinder with 5, 10, 15 and 20 s/projection and NEMA image quality phantom with 25 s/projection. The NEMA phantom had hot spheres filled with an 8 : 1 activity concentration relative to the background compartment. Reconstructions were performed using parameters defined by manufacturer presets available with the algorithm. The accuracy of activity concentration measurements was assessed. A dose calibrator-camera cross-calibration factor (CCF) was derived from the uniform phantom data. In uniform phantom images, a positive bias was observed, ranging from ∼6% in the lower count images to ∼4% in the higher-count images. On the basis of the higher-count data, a CCF of 0.96 was derived. As expected, considerable negative bias was measured in the NEMA spheres using region mean values whereas positive bias was measured in the four largest NEMA spheres. Nonmonotonically increasing recovery curves for the hot spheres suggested the presence of Gibbs edge enhancement from resolution modelling. Sufficiently accurate activity concentration measurements can easily be measured on images reconstructed with the xSPECT algorithm without a CCF. However, the use of a CCF is likely to improve accuracy further. A manual conversion of voxel values into SUV should be possible, provided that the patient weight, injected activity and time between injection and imaging are all known accurately.

  16. Compatibility of preparatory procedures for the analysis of cortisol concentrations and stable isotope (δ13C, δ15N) ratios: a test on brown bear hair

    Science.gov (United States)

    Sergiel, Agnieszka; Hobson, Keith A.; Janz, David M.; Cattet, Marc; Selva, Nuria; Kapronczai, Luciene; Gryba, Chantel

    2017-01-01

    Abstract The measurement of naturally occurring glucocorticoids and stable isotopes of several elements has gained importance in wildlife studies in recent decades and opened a myriad of ecological applications. Cortisol and stable isotopes equilibrate in animal tissues over periods of integration related to the growth rate of the tissue, providing information reflecting systemic cortisol secretion and dietary intake. Sample preparation shares the common step of first cleaning the sample of external contamination. However, it is not well understood how different solvents used in sample preparation affect isotopic and cortisol values, and whether it is safe to follow the same procedures for both measures to optimize analyses of the same sample. We conducted an experiment to compare different preparation protocols for the analysis of cortisol concentrations and stable carbon (δ13C) and nitrogen (δ15N) isotope ratios in hair. Hair samples from 12 brown bears (Ursus arctos) were each divided into five aliquots; two aliquots were rinsed with a 2:1 chloroform:methanol (v/v) mixture with one aliquot ground prior to cortisol analysis and the other left intact for stable isotope analyses; two aliquots were washed with methanol with one aliquot ground prior to cortisol analysis and the other left intact for stable isotope analyses; and one aliquot washed with methanol and ground prior to stable isotope analyses. The cortisol, δ13C and δ15N values remained consistent following all treatments. Our results indicate that hair samples rinsed with a 2:1 chloroform:methanol mixture or washed with methanol can be used for both types of analyses. Further, hair that has been ground in a standard hair cortisol procedure can also be used for stable isotope analysis. This information is important for improving laboratory efficiency and compatibility of procedures used for wildlife physiological ecology studies where concurrent measurements of cortisol and stable isotopes in hair are

  17. Solvent micro-evaporation and concentration gradient synergistically induced crystallization of poly(L-lactide) and ring banded supra-structures with radial periodic variation of thickness

    DEFF Research Database (Denmark)

    Huang, Shaoyong; Li, Hongfei; Wen, Huiying

    2014-01-01

    The crystalline morphology and structure of poly(L-lactide) (PLLA) in a PLLA film-chloroform system were investigated by means of wide angle X-ray diffraction (WAXD), polarized optical microscopy (POM) and atomic force microscopy (AFM). Birefringent and nonbirefringent ring banded supra-structure......The crystalline morphology and structure of poly(L-lactide) (PLLA) in a PLLA film-chloroform system were investigated by means of wide angle X-ray diffraction (WAXD), polarized optical microscopy (POM) and atomic force microscopy (AFM). Birefringent and nonbirefringent ring banded supra...... of thicknesses along the radial direction. The formation of the ring banded supra-structures is associated with diffusion and crystal growth induced periodic variation of concentration gradient, which is attributed to diffusion-related rhythmic growth and the competition between diffusion of polymer segments...

  18. Characterization of Growing Soil Bacterial Communities across a pH gradient Using H218O DNA-Stable Isotope Probing

    Science.gov (United States)

    Welty-Bernard, A. T.; Schwartz, E.

    2014-12-01

    Recent studies have established consistent relationships between pH and bacterial diversity and community structure in soils from site-specific to landscape scales. However, these studies rely on DNA or PLFA extraction techniques from bulk soils that encompass metabolically active and inactive, or dormant, communities, and loose DNA. Dormant cells may comprise up to 80% of total live cells. If dormant cells dominate a particular environment, it is possible that previous interpretations of the soil variables assumed to drive communities could be profoundly affected. We used H218O stable isotope probing and bar-coded illumina sequencing of 16S rRNA genes to monitor the response of actively growing communities to changes in soil pH in a soil microcosm over 14 days. This substrate-independent approach has several advantages over 13C or 15N-labelled molecules in that all growing bacteria should be able to make use of water, allowing characterization of whole communities. We hypothesized that Acidobacteria would increasingly dominate the growing community and that Actinobacteria and Bacteroidetes would decline, given previously established responses by these taxa to soil pH. Instead, we observed the reverse. Actinobacteria abundance increased three-fold from 26 to 76% of the overall community as soil pH fell from pH 5.6 to pH 4.6. Shifts in community structure and decreases in diversity with declining soil pH were essentially driven by two families, Streptomyceaca and Microbacteracea, which collectively increased from 2 to 40% of the entire community. In contrast, Acidobacteria as a whole declined although numbers of subdivision 1 remained stable across all soil pH levels. We suggest that the brief incubation period in this SIP study selected for growth of acid-tolerant Actinobacteria over Acidobacteria. Taxa within Actinomycetales have been readily cultured over short time frames, suggesting rapid growth patterns. Conversely, taxa within Acidobacteria have been

  19. Autotrophic and heterotrophic soil respiration determined with trenching, soil CO2 fluxes and 13CO2/12CO2 concentration gradients in a boreal forest ecosystem

    Science.gov (United States)

    Pumpanen, Jukka; Shurpali, Narasinha; Kulmala, Liisa; Kolari, Pasi; Heinonsalo, Jussi

    2017-04-01

    Soil CO2 efflux forms a substantial part of the ecosystem carbon balance, and it can contribute more than half of the annual ecosystem respiration. Recently assimilated carbon which has been fixed in photosynthesis during the previous days plays an important role in soil CO2 efflux, and its contribution is seasonally variable. Moreover, the recently assimilated C has been shown to stimulate the decomposition of recalcitrant C in soil and increase the mineralization of nitrogen, the most important macronutrient limiting gross primary productivity (GPP) in boreal ecosystems. Podzolic soils, typical in boreal zone, have distinctive layers with different biological and chemical properties. The biological activity in different soil layers has large seasonal variation due to vertical gradient in temperature, soil organic matter and root biomass. Thus, the source of CO2 and its components have a vertical gradient which is seasonally variable. The contribution of recently assimilated C and its seasonal as well as spatial variation in soil are difficult to assess without disturbing the system. The most common method of partitioning soil respiration into its components is trenching which entails the roots being cut or girdling where the flow of carbohydrates from the canopy to roots has been isolated by cutting of the phloem. Other methods for determining the contribution of autotrophic (Ra) and heterotrophic (Rh) respiration components in soil CO2 efflux are pulse labelling with 13CO2 or 14CO2 or the natural abundance of 13C and/or 14C isotopes. Also differences in seasonal and short-term temperature response of soil respiration have been used to separate Ra and Rh. We compared the seasonal variation in Ra and Rh using the trenching method and differences between seasonal and short-term temperature responses of soil respiration. I addition, we estimated the vertical variation in soil biological activity using soil CO2 concentration and the natural abundance of 13C and 12C

  20. A high gradient and strength bioseparator with nano-sized immunomagnetic particles for specific separation and efficient concentration of E. coli O157:H7

    Science.gov (United States)

    Lin, Jianhan; Li, Min; Li, Yanbin; Chen, Qi

    2015-03-01

    Sample pretreatment is a key to rapid screening of pathogens for prevention and control of foodborne diseases. Magnetic immunoseparation is a specific method based on antibody-antigen reaction to capture the target bacteria and concentrate them in a smaller-volume buffer. The use of nano-sized magnetic particles could improve the separation efficiency of bacteria but require much higher gradient and strength magnetic field. In this study, a strong magnetic bioseparator with a mean field strength of 1.35 T and a mean gradient of 90 T/m was developed with the use of the 30 nm and 180 nm magnetic particles to specifically separate and efficiently concentrate foodborne bacterial pathogens using Escherichia coli O157:H7 as a model bacterium. The polyclonal antibodies against E. coli were evaluated using Dot ELISA analysis for their good affinity with the target bacteria and then used to modify the surface of the magnetic nanoparticles by 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) method and streptavidin-biotin binding. The magnetic particle concentrations were optimized to be 40 μg/ml and 100 μg/ml for the 30 nm and 180 nm particles, respectively, the immunoreaction time was optimized to be 45 min for both sizes of particles, and the separation times were optimized to be 60 min and 2 min for the 30 nm and 180 nm particles, respectively. The total magnetic separation time was 2 h and 1 h for the 30 nm and 180 nm particles, respectively. The experimental results demonstrated that the bioseparator with the use of either 30 nm or 180 nm immunomagnetic particles could achieve a separation efficiency of >90% for E. coli O157:H7 at the concentrations ranging from 102 to 105 cfu/ml. No obvious interferences from non-target foodborne pathogens, such as SalmonellaTyphimurium and Listeria innocua, were found. For overall consideration of the consuming time, the cost, and the separation efficiency, the 180 nm magnetic particles are practical for rapid

  1. Co/Ti co-substituted layered LiNiO2 prepared using a concentration gradient method as an effective cathode material for Li-ion batteries

    Science.gov (United States)

    Ko, Hyoung Shin; Kim, Jea Han; Wang, Juan; Lee, Jong Dae

    2017-12-01

    The design of Li-ion batteries with high energy storage capacities and efficiencies is a subject of increased research interest, being of key importance for their large-scale applications and further commercialization. However, conventional Li-ion batteries are expensive and have stability-related concerns, which limit their practical applications. In our search for cheaper and safer Li-ion batteries, we use a concentration gradient method to prepare LiNi0.9Co0.1-xTixO2 (0.02 ≤ x ≤ 0.05) cathode materials surface-enriched with Co and Ti that exhibit decreased oxygen loss and improved structural stability. The corresponding crystal structures and morphologies are analyzed by X-ray diffraction and field emission scanning electron microscopy, with the Ni, Co, and Ti concentration distributions determined by energy-dispersive X-ray spectroscopy. The material with the best performance (x = 0.04) exhibits a discharge capacity of 214 mAh g-1 in a charge/discharge voltage range of 3.0-4.3 V (vs. Li/Li+), and possesses an excellent 50-cycle capacity retention of 98.7%. Thermogravimetric analysis shows that partial substitution of Ni with the strongly oxophilic Ti solves the problem of oxygen loss observed in Ni-rich cathode materials such as LiNiO2.

  2. Influence of Biological Agents Effects on Reduction of Ammonia Concentration in Stables of Intensive Farm Animals Breeding

    Directory of Open Access Journals (Sweden)

    Bohuslav Čermák

    2011-05-01

    Full Text Available The living environment distress is connected currently not only with industrial production but also agriculture is biggest producer of toxic gas – ammonia (NH3 .Emissions of that gas originate mainly in the farm animals breeding and generate within storage and handling with farmyard manure, slurry, poultry excrements and litter. Agriculture influences considerably landscape. has impact on basic effect on soil, water and air. In assessing experiment the preparation Biopolym FZT rumen metabolism and N-balance was found positive effects in terms of increased ammonia nitrogen, the number of ciliates and the reduction of N-compounds in feces. Confirmed the impact on the ammonia content in well-ventilated dairy stable. The economic evaluation depends on the exercise price of milk. In the experiments continued.

  3. High-temperature stable absorber coatings for linear concentrating solar thermal power plants; Hochtemperaturstabile Absorberschichten fuer linear konzentrierende solarthermische Kraftwerke

    Energy Technology Data Exchange (ETDEWEB)

    Hildebrandt, Christina

    2009-03-23

    This work describes the development of new absorber coatings for different applications - para-bolic trough and linear Fresnel collectors - and operating conditions - absorber in vacuum or in air. The demand for higher efficiencies of solar thermal power plants using parabolic trough technology results in higher temperatures in the collectors and on the absorber tubes. As heat losses increase strongly with increasing temperatures, the need for a lower emissivity of the absorber coating at constant absorptivity arises. The linear Fresnel application envisions ab-sorber tubes stable in air at high temperatures of about 450 C, which are to date commercially not available. This work comprises the theoretical background, the modeling and the fabrication of absorber tubes including the technology transfer to a production-size inline sputter coater. In annealing tests and accompanying optical measurements, degradation processes have been observed and specified more precisely by material characterization techniques. The simulations provided the capability of different materials used as potential IR-reflector. The highest selectivity can be achieved by applying silver which consequently has been chosen for the application in absorber coatings of the parabolic trough technology. Thin silver films how-ever need to be stabilized when used at high temperatures. Appropriate barrier layers as well as process and layer parameters were identified. A high selectivity was achieved and stability of the absorber coating for 1200 h at 500 C in vacuum has been demonstrated. For the application in air, silver was also analyzed as a potential IR-reflector. Even though the stability could be increased considerably, it nevertheless proved to be insufficient. The main factors influencing stability in a positive way are the use of higher quality polishing, additional barrier layers and adequate process parameters. This knowledge was applied for developing coatings which are stable in air at

  4. Passive dosing of triclosan in multi-generation tests with copepods - Stable exposure concentrations and effects at the low µg l-1 range

    DEFF Research Database (Denmark)

    Ribbenstedt, Anton; Mustajärvi, Lukas; Breitholtz, Magnus

    2017-01-01

    to test the applicability of passive dosing to maintain stable concentrations of the organochlorine bacteriocide triclosan in the water phase during a 6-week multi-generation population development test with the harpacticoid copepod Nitocra spinipes. Triclosan was loaded into silicone (1000 mg), which...... was used as passive dosing phase in the exposure vials. The distribution ratio for triclosan between silicone and water (Dsilicone-water ) was 10466 ± 1927. A population development test was conducted at three concentration levels of triclosan that were measured to be 3-5 µg L(-1) , 7-11 µg L(-1) and 16...... exerted on juvenile development. Progressively lower development index values in the populations exposed to increasing triclosan concentrations suggest developmental retardation. Our results further stress the need for chronic exposure during ecotoxicity testing in chemical risk assessment as even...

  5. Characterizing the production and retention of dissolved iron as Fe(II) across a natural gradient in chlorophyll concentrations in the Southern Drake Passage - Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Katherine Barbeau

    2007-04-10

    . As a co-PI in the NSF/OPP-funded project, I was responsible for iron addition incubation and radiotracer experiments, and analysis of iron chemistry, including iron-organic speciation. This final technical report describes the results of my DOE funded project to analyse reduced iron species using an FeLume flow injection analysis chemiluminescence system as an extension of my work on the NSF/OPP project. On the cruise in 2004, spatial and temporal gradients in Fe(II) were determined, and on-board incubations were conducted to study Fe(II) lifetime and production. Following the cruise a further series of experiments was conducted in my laboratory to study Fe(II) lifetimes and photoproduction under conditions typical of high latitude waters. The findings of this study suggest that, in contrast to results observed during mesoscale iron addition experiments, steady-state levels of Fe(II) are likely to remain low (below detection) even within a significant gradient in dissolved Fe concentrations produced as a result of natural iron enrichment processes. Fe(II) is likely to be produced, however, as a reactive intermediate associated with photochemical reactions in surface waters. While Fe(II) lifetimes measured in the field in this study were commensurate with those determined in previously published Southern Ocean work, Fe(II) lifetimes reflective of realistic Southern Ocean environmental conditions have proven difficult to determine in a laboratory setting, due to contamination by trace levels of H2O2. Laboratory experiments demonstrated that direct ligand-to-metal charge transfer reactions of strong Fe(III)-organic complexes do appear to be a viable source of available Fe(II) in Antarctic waters, and further studies are needed to characterize the temperature dependence of this phenomenon.

  6. The influence of season and leaf age on concentrations of radiocaesium (137Cs), stable caesium (133Cs) and potassium in Agrostis capillaris

    International Nuclear Information System (INIS)

    Salt, C.A.; Kay, J.W.; Jarvis, K.E.

    2004-01-01

    The transfer of radioactive caesium from soils to plants has been well researched. In contrast there is limited knowledge on natural stable 133 Cs and its potential role as a predictor for radiocaesium behaviour. In a pot experiment with Agrostis capillaris close correlations were found between plant 137 Cs and plant 133 Cs concentrations (R 2 90-96%). Season and leaf age had significant effects with concentrations increasing 10-30-fold between June and December. Simultaneously the plant concentrations of K, the nutrient analogue of Cs, decreased to around one third. In the soil the exchangeable fractions of K and 137 Cs declined. No clear relationships were found between 137+133 Cs in the plant and exchangeable K in the soil. However, at the end of the experiment the K content of the above-ground biomass was higher than the exchangeable pool in the soil, suggesting that depletion of soil K could be a key factor in the observed increase of plant 137+133 Cs over time. - Season and leaf age have the same influence on radiocaesium and stable caesium in Agrostis capillaris but affect K differently

  7. Pan-Arctic concentrations of mercury and stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in marine zooplankton

    International Nuclear Information System (INIS)

    Pomerleau, Corinne; Stern, Gary A.; Pućko, Monika; Foster, Karen L.; Macdonald, Robie W.; Fortier, Louis

    2016-01-01

    Zooplankton play a central role in marine food webs, dictating the quantity and quality of energy available to upper trophic levels. They act as “keystone” species in transfer of mercury (Hg) up through the marine food chain. Here, we present the first Pan-Arctic overview of total and monomethylmercury concentrations (THg and MMHg) and stable isotope ratios of carbon (δ 13 C) and nitrogen (δ 15 N) in selected zooplankton species by assembling data collected between 1998 and 2012 from six arctic regions (Laptev Sea, Chukchi Sea, southeastern Beaufort Sea, Canadian Arctic Archipelago, Hudson Bay and northern Baffin Bay). MMHg concentrations in Calanus spp., Themisto spp. and Paraeuchaeta spp. were found to increase with higher δ 15 N and lower δ 13 C. The southern Beaufort Sea exhibited both the highest THg and MMHg concentrations. Biomagnification of MMHg between Calanus spp. and two of its known predators, Themisto spp. and Paraeuchaeta spp., was greatest in the southern Beaufort Sea. Our results show large geographical variations in Hg concentrations and isotopic signatures for individual species related to regional ecosystem features, such as varying water masses and freshwater inputs, and highlight the increased exposure to Hg in the marine food chain of the southern Beaufort Sea. - Highlights: • Assessment of Pan-Arctic variability in zooplankton Hg concentrations • Increased exposure to Hg in the marine food chain of the southern Beaufort Sea • Zooplankton plays a central role in the Hg pathway within Arctic marine food webs.

  8. Stable Binding of Alternative Protein-enriched Food Matrices with Concentrated Cranberry Bioflavonoids for Functional Food Applications

    Science.gov (United States)

    Grace, Mary H.; Guzman, Ivette; Roopchand, Diana E.; Moskal, Kristin; Cheng, Diana M.; Pogrebnyak, Natasha; Raskin, Ilya; Howell, Amy; Lila, Mary Ann

    2013-01-01

    Defatted soy flour (DSF), soy protein isolate (SPI), hemp protein isolate (HPI), medium roast peanut flour (MPF) and pea protein isolate (PPI) stably bind and concentrate cranberry (CB) polyphenols, creating protein/polyphenol-enriched matrices. Proanthocyanidins (PAC) in the enriched matrices ranged from 20.75 mg/g (CB-HPI) to 10.68 mg/g (CB-SPI). Anthocyanins (ANC) ranged from 3.19 mg/g (CB-DSF) to 1.68 mg/g (CB-SPI), while total phenolics (TP) ranged from 37.61 mg/g (CB-HPI) to 21.29 mg/g (CB-SPI). LC-MS indicated that the enriched matrices contained all identifiable ANC, PAC and flavonols present in CB juice. Complexation with SPI stabilized and preserved the integrity of the CB polyphenolic components for at least 15 weeks at 37 °C. PAC isolated from enriched matrices demonstrated comparable anti-adhesion bioactivity to PAC isolated directly from CB juice (MIC 0.4 to 0.16 mg/mL), indicating their potential utility for maintenance of urinary tract health. Approximately 1.0 g of polyphenol-enriched matrix delivered the same amount of PAC available in one cup (300 mL) of commercial CB juice cocktail; which has been shown clinically to be the prophylactic dose for reducing recurring urinary tract infections. CB-SPI inhibited gram- positive and gram-negative bacterial growth. Nutritional and sensory analyses indicated that the targeted CB-matrix combinations have high potential for incorporation in functional food formulations. PMID:23786629

  9. Pan-Arctic concentrations of mercury and stable isotope ratios of carbon (δ{sup 13}C) and nitrogen (δ{sup 15}N) in marine zooplankton

    Energy Technology Data Exchange (ETDEWEB)

    Pomerleau, Corinne, E-mail: corinne.pomerleau@umanitoba.ca [Centre for Earth Observation Science, University of Manitoba, Winnipeg, MB R3T 2N2 (Canada); Greenland Institute of Natural Resources, Kivioq 2, Nuuk 3900, Greenland (Denmark); Stern, Gary A.; Pućko, Monika [Centre for Earth Observation Science, University of Manitoba, Winnipeg, MB R3T 2N2 (Canada); Foster, Karen L. [Foster Environmental, Peterborough, ON K9J 8L2 (Canada); Macdonald, Robie W. [Institute of Ocean Sciences, Fisheries and Oceans Canada, Sidney, BC V8L 4B2 (Canada); Fortier, Louis [Québec-Océan, Département de Biologie, Université Laval, Québec, QC G1V 0A6 (Canada)

    2016-05-01

    Zooplankton play a central role in marine food webs, dictating the quantity and quality of energy available to upper trophic levels. They act as “keystone” species in transfer of mercury (Hg) up through the marine food chain. Here, we present the first Pan-Arctic overview of total and monomethylmercury concentrations (THg and MMHg) and stable isotope ratios of carbon (δ{sup 13}C) and nitrogen (δ{sup 15}N) in selected zooplankton species by assembling data collected between 1998 and 2012 from six arctic regions (Laptev Sea, Chukchi Sea, southeastern Beaufort Sea, Canadian Arctic Archipelago, Hudson Bay and northern Baffin Bay). MMHg concentrations in Calanus spp., Themisto spp. and Paraeuchaeta spp. were found to increase with higher δ{sup 15}N and lower δ{sup 13}C. The southern Beaufort Sea exhibited both the highest THg and MMHg concentrations. Biomagnification of MMHg between Calanus spp. and two of its known predators, Themisto spp. and Paraeuchaeta spp., was greatest in the southern Beaufort Sea. Our results show large geographical variations in Hg concentrations and isotopic signatures for individual species related to regional ecosystem features, such as varying water masses and freshwater inputs, and highlight the increased exposure to Hg in the marine food chain of the southern Beaufort Sea. - Highlights: • Assessment of Pan-Arctic variability in zooplankton Hg concentrations • Increased exposure to Hg in the marine food chain of the southern Beaufort Sea • Zooplankton plays a central role in the Hg pathway within Arctic marine food webs.

  10. Formation of new stable pigments from condensation reaction between malvidin 3-glucoside and (-)-epicatechin mediated by acetaldehyde: Effect of tartaric acid concentration.

    Science.gov (United States)

    Sun, Baoshan; Barradas, Tania; Leandro, Conceição; Santos, Cláudia; Spranger, Isabel

    2008-09-15

    The objective of this work was to study the effect of tartaric acid concentration on the condensation reaction between malvidin 3-glucoside (Mv-glc) and flavanols mediated by acetaldehyde in the model solution. The model wine solutions were prepared by 12% ethanol in water (v/v) with two different l-tartaric acid concentrations (5g/l and 25g/l, respectively) and at two different pH values (3.2 and 1.7, respectively). Four new pigments were detected in model wine solutions containing Mv-glc, (-)-epicatechin and acetaldehyde. By reverse-phase HPLC-DAD, ESI-MS and MS(n) fragmentation analysis, the four new pigments were tentatively identified as four isomers of hydroxyethyl malvidin-3-glucoside-ethyl-flavanol. The decrease in the concentration of Mv-glc and (-)-epicatechin and the increase in the concentration of the new identified pigments were more pronounced at higher tartaric acid concentration. At pH 1.7, although the two well-recognized ethyl-linked Mv-glc-flavanol isomers were quantitatively the major pigmented products in the reaction solution throughout the assay period, they appeared less stable than the four new pigments. At pH 3.2, the rate of formation of ethyl-linked Mv-glc-flavanol pigments was much slower than at pH 1.7, whereas the four new pigments were quantitatively the predominant pigmented products at the latter stage of the reaction. Copyright © 2008 Elsevier Ltd. All rights reserved.

  11. Passive dosing of triclosan in multigeneration tests with copepods - stable exposure concentrations and effects at the low μg/L range.

    Science.gov (United States)

    Ribbenstedt, Anton; Mustajärvi, Lukas; Breitholtz, Magnus; Gorokhova, Elena; Mayer, Philipp; Sobek, Anna

    2017-05-01

    Ecotoxicity testing is a crucial component of chemical risk assessment. Still, due to methodological difficulties related to controlling exposure concentrations over time, data on long-term effects of organic chemicals at low concentrations are limited. The aim of the present study was, therefore, to test the applicability of passive dosing to maintain stable concentrations of the organochlorine bacteriocide triclosan in the water phase during a 6-wk multigeneration population development test with the harpacticoid copepod Nitocra spinipes. Triclosan was loaded into silicone (1000 mg), which was used as passive dosing phase in the exposure vials. The distribution ratio for triclosan between silicone and water (D silicone-water ) was 10466 ± 1927. A population development test was conducted at 3 concentration levels of triclosan that were measured to be 3 μg/L to 5 μg/L, 7 μg/L to 11 μg/L and 16 μg/L to 26 μg/L. The results demonstrate that passive dosing is applicable for long-term ecotoxicity testing of organic chemicals, including during significant growth of the test organism population. Shifts in the demographic structure of the population during exposure suggest the most severe effects were exerted on juvenile development. Progressively lower development index values in the populations exposed to increasing triclosan concentrations suggest developmental retardation. The results further stress the need for chronic exposure during ecotoxicity testing in chemical risk assessment because even the most sensitive endpoint was not significant until after 7 d of exposure. Environ Toxicol Chem 2017;36:1254-1260. © 2016 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC. © 2016 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

  12. Determination of the sulfur and oxygen stable isotopes concentration by mass spectrometry; Determinacao da concentracao (atomos %) dos isotopos estaveis de enxofre e oxigenio por espectrometria de massas

    Energy Technology Data Exchange (ETDEWEB)

    Bendassolli, Jose A.; Trivelin, Paulo C.O. [Centro de Energia Nuclear na Agricultura (CENA), Piracicaba, SP (Brazil); Carneiro Junior, Francisco [Universidade Metodista de Piracicaba (UNIMEP), SP (Brazil)

    1997-10-01

    Two methods to determine the isotope concentrations of {sup 32} S, {sup 33} S, {sup 34} S, {sup 36} S and {sup 18} O in SO{sub 2} samples were evaluated. The isotope analysis were carried out in an C H{sub 4} model, ATLAS MAT mass spectrometer, through the electromagnetic mass scanning of the mass regions 48, 49, 50, 51 and 52. For assessing the effect of {sup 18} O contribution in the determination of the {sup 34} S isotope concentration, two calculation procedures were used. The first involved the resolution of a system of six equations with six unknown quantities, where the values in atoms % for all stable isotopes ({sup 32} S, {sup 33} S, {sup 34} S and {sup 36} S) as well as the most abundant oxygen isotopes ({sup 16} O and {sup 18} O) in SO{sub 2} samples were obtained. The second procedure used a simplified first degree equation, where the O{sub 2} natural abundance was always assumed, to calculate the {sup 34} S concentration only. (author). 11 refs., 2 figs., 3 tabs.

  13. Trends in nitrate concentrations and determination of its origin using stable isotopes (18O and 15N) in groundwater of the Western Central Valley, Costa Rica.

    Science.gov (United States)

    Reynolds-Vargas, Jenny; Fraile-Merino, Julio; Hirata, Ricardo

    2006-08-01

    A study was conducted to evaluate long-term trends in nitrate concentrations and to try to identify the origin of nitrate using stable isotopes (15N(NO3-) and 18O(NO3-)) in the aquifers of the western Central Valley, Costa Rica, where more than 1 million people depend on groundwater to satisfy their daily needs. Data from 20 sites periodically sampled for 4 to 17 years indicate an increasing trend in nitrate concentrations at five sites, which in a period ranging from 10 to 40 years, will exceed recommended maximum concentrations. Results of isotopic analysis indicate a correspondence between land use patterns and the isotopic signature of nitrate in groundwater and suggest that urbanization processes without adequate waste disposal systems, followed by coffee fertilization practices, are threatening water quality in the region. We conclude that groundwater management in this area is not sustainable, and that land use substitution processes from agricultural activity to residential occupation that do not have proper sewage disposal systems may cause a significant increment in the nitrate contaminant load.

  14. Photosynthetic Water Use Efficiency in it Sorghastrum nutans (C4) and it Solidago canadensis (C3) in Three Soils Along a CO2 Concentration Gradient

    Science.gov (United States)

    Fay, P. A.; Hui, D.; Procter, A.; Johnson, H. B.; Polley, H. W.; Jackson, R. B.

    2006-12-01

    The water use efficiency (WUE) of leaf photosynthetic carbon uptake is a key regulator of ecosystem carbon cycles and is strongly sensitive to atmospheric carbon dioxide concentrations [CO2]. However WUE responses to [CO2] typically differ between C3 and C4 species and may differ on varying soil types because of differences in soil moisture retention and plant uptake efficiency. We measured leaf-level photosynthesis (ACO2), stomatal conductance (gS), and transpiration (E) with an infrared gas analyzer to estimate WUE for the C4 grass Sorghastrum nutans and the C3 forb Solidago canadensis in constructed grassland species assemblages growing in three soils arrayed along a 200 560 ppm [CO2] gradient in the LYCOG Experiment, in central Texas, USA. LYCOG consists of eighty intact soil monoliths (1 m X 1 m X 1.5 m) representing 3 soil series, Austin (Udorthentic Haplustolls, a mollisol), Bastrop (Udic Paleustalfs, a sandy loam alfisol) and Houston Black (Udic Haplusterts, a vertisol). The monoliths were vegetated by transplanting 8 native perennial prairie species (5 grasses and 3 forbs), including S. nutans and S. canadensis. Both are abundant and widespread; S. nutans is a dominant species throughout much of North American tallgrass prairie, and S. canadensis is one of the most abundant and widespread forbs in North America. ACO2, gS, and E were measured three times during the growing season. Dark-adapted chlorophyll fluorescence (FvFm) was measured concurrently to assess photosynthetic capacity, and leaf water potential (Ψ leaf) and soil water content were measured to assess plant water status and soil moisture availability. WUE increased strongly (p< 0.0001) at higher [CO2], due to a combination of decreasing E due to decreased gS (p ≤ 0.0005) and increasing ACO2 (p = 0.0055). This pattern was the same in both species (species x [CO2] ns). There was a corresponding increase in Ψ leaf (p = 0.01) at higher [CO2], but no [CO2] effect on FvFm. E and gS were lower on

  15. An assessment of an environmental gradient using coral geochemical records, Whitsunday Islands, Great Barrier Reef, Australia

    International Nuclear Information System (INIS)

    Lewis, S.E.; Brodie, J.E.; McCulloch, M.T.; Mallela, J.; Jupiter, S.D.; Stuart Williams, H.; Lough, J.M.; Matson, E.G.

    2012-01-01

    Coral cores were collected along an environmental and water quality gradient through the Whitsunday Island group, Great Barrier Reef (Australia), for trace element and stable isotope analysis. The primary aim of the study was to examine if this gradient could be detected in coral records and, if so, whether the gradient has changed over time with changing land use in the adjacent river catchments. Y/Ca was the trace element ratio which varied spatially across the gradient, with concentrations progressively decreasing away from the river mouths. The Ba/Ca and Y/Ca ratios were the only indicators of change in the gradient through time, increasing shortly after European settlement. The Mn/Ca ratio responded to local disturbance related to the construction of tourism infrastructure. Nitrogen isotope ratios showed no apparent trend over time. This study highlights the importance of site selection when using coral records to record regional environmental signals.

  16. a Modified Denitrifying Bacteria Method for Dual Stable Isotopic Analysis of of Soil Nitrate in Kcl Extracts: Identification of Bioindicators of Nitrogen Deposition Along a Gradient in the Sonoran Desert

    Science.gov (United States)

    Bell, M. D.; Sickman, J. O.; Allen, E. B.

    2011-12-01

    Previous studies performing dual isotopic analysis of nitrate in KCl soil extracts using denitrifying bacteria have not incorporated alterations in the method to compensate for the increased N2O blank produced when the bacteria are exposed to KCl in solution. When 1M KCl is used as a blank, the amount of N2O released from the concentrated bacteria solution is more than four times as high as when using a DI water blank. The excess N2O produced is not an artifact of nitrate impurity in the KCl, although the blank increases with the molarity of KCl up to 1M. The introduction of N2O gas is significant enough to alter the values of IAEA USGS standards (3 μg in 3ml KCl) which in turn results in an inaccurate regression for unknown samples. We reduced the size of the KCl blank and its effect on the standards by adding 3ml of KCl to the bacteria solution prior to purging the sample with He gas. This removes the N2O gas which is released by the bacteria when they initially come in contact with the KCl, and allows for standards to be calibrated to a precision of ± 0.1 % δ15N and ± 0.2 % δ18O. Using this new method, we measured δ15N and δ18O of nitrate in 1M KCl soil extracts taken from surface soil (5cm cores) along a nitrogen deposition gradient spanning the Coachella Valley in the western Sonoran Desert during the summer. Early germinating winter annual plant species (Schismus barbatus, Chaenactic fremontii, and Malacothrix glabrata) were collected as seedlings early in the growing season and again in late spring before senescence. Leaves from the dominant shrub, Larrea tridentata, were also collected from each site. Soil nitrogen from sites on the eastern edge of the valley had δ18O values between +30 and +41%, indicating an influence of atmospheric nitrate in plant available nitrate. There was an inverse correlation (r2=0.907) between soil δ18O and the δ15N of the C.fremontii leaf tissue, which suggests that in areas of high N deposition, some seedlings are

  17. Irradiance gradients

    International Nuclear Information System (INIS)

    Ward, G.J.; Heckbert, P.S.; Technische Hogeschool Delft

    1992-04-01

    A new method for improving the accuracy of a diffuse interreflection calculation is introduced in a ray tracing context. The information from a hemispherical sampling of the luminous environment is interpreted in a new way to predict the change in irradiance as a function of position and surface orientation. The additional computation involved is modest and the benefit is substantial. An improved interpolation of irradiance resulting from the gradient calculation produces smoother, more accurate renderings. This result is achieved through better utilization of ray samples rather than additional samples or alternate sampling strategies. Thus, the technique is applicable to a variety of global illumination algorithms that use hemicubes or Monte Carlo sampling techniques

  18. Hepatic sinusoid is not well-stirred: estimation of the degree of axial mixing by analysis of lobular concentration gradients formed during uptake of thyroxine by the perfused rat liver

    International Nuclear Information System (INIS)

    Weisiger, R.A.; Mendel, C.M.; Cavalieri, R.R.

    1986-01-01

    Two general models have been proposed for predicting the effects of metabolism, protein binding, and plasma flow on the removal of drugs by the liver. These models differ in the degree of plasma mixing assumed to exist within each hepatic sinusoid. The venous equilibrium model treats the sinusoid as a single well-stirred compartment, whereas the sinusoidal model effectively breaks up the sinusoid into a large number of sequentially perfused compartments which do not exchange their contents except through plasma flow. As a consequence, the sinusoidal model, but not the venous equilibrium model, predicts that the concentration of highly extracted drugs will decline as the plasma flows through the hepatic lobule. To determine which of these alternative models best describes the hepatic uptake process, we looked for evidence that concentration gradients are formed during the uptake of [ 125 I]thyroxine by the perfused rat liver. Autoradiography of tissue slices after perfusion of the portal vein at physiologic flow rates with protein-free buffer containing [ 125 I]thyroxine demonstrated a rapid exponential fall in grain density with distance from the portal venule, declining by half for each 8% of the mean length of the sinusoid. Reversing the direction of perfusate flow reversed the direction of the autoradiographic gradients, indicating that they primarily reflect differences in the concentration of thyroxine within the hepatic sinusoids rather than differences in the uptake capacity of portal and central hepatocytes. Analysis of the data using models in which each sinusoid was represented by different numbers of sequentially perfused compartments (1-20) indicated that at least eight compartments were necessary to account for the magnitude of the gradients seen

  19. Croissance de fibres à gradient de concentration et analyse des processus dynamiques de transitions laser résonnantesdans Y203 dopé Er^{3+}, Yb^{3+} et Ho^{3+}

    Science.gov (United States)

    Laversenne, L.; Goutaudier, C.; Guyot, Y.; Cohen-Adad, M. Th.; Boulon, G.

    2002-06-01

    La croissance et l'exploitation de fibres à gradient de concentration de Y203 dopé par des ions terres rares permet d'étudier les processus dynamiques de transitions laser résonnantes des ions Yb^{3+}, Er^{3+} et Ho^{3+}. Plus particulièrement nous mettons en évidence et analysons les transferts d'énergie radiatifs (self trapping) responsables de l'allongement de la durée de vie expérimentale.

  20. Polychlorinated biphenyl concentrations, accumulation rates in soil from atmospheric deposition and analysis of their affecting landscape variables along an urban-rural gradient in Shanghai, China.

    Science.gov (United States)

    Fang, Shubo; Cui, Qu; Matherne, Brian; Hou, Aixin

    2017-11-01

    This study initiated an in-situ soil experimental system to quantify the annual dynamics of polychlorinated biphenyl (PCB) congener's concentrations and accumulation rates in soil from atmosphere deposition in a rural-urban fringe, and correlated them by landscape physical and demographic variables in the area. The results showed that the concentrations of all PCB congeners significantly increased with the sampling time (p soil PCB concentrations with a threshold effect (p < 0.05). Regression analysis showed that the thresholds were 10-20 km, 1 km/km 2 , 30%, and 20% for distance, road density, population change index, and built-up area percentage, respectively. It was concluded that factors related to industrial development, traffic, and urban sprawling (i.e. built-up areas expanding) were the sources of PCBs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Soil Organic Matter Stores and Dynamics in a Chaparral Ecosystem After Eight Years of Exposure to a Gradient of Atmospheric CO2 Concentrations, From pre-Industrial Level to 750 ppm

    Science.gov (United States)

    del Galdo, I.; Oechel, W. C.; Cotrufo, F.

    2004-12-01

    Due to the continuously increasing concentration of atmospheric CO2, it has become a priority to understand if soil organic matter (SOM) will act as a sink or a source of CO2, under future environmental change. Although many studies have addressed the question, a clear answer, in particular on the long term response, is still missing. Here we report the results of an experiment where we quantified the soil C stores and investigated the dynamics of SOM, its aggregation and pool composition, in a Californian chaparral ecosystem, exposed to a gradient of atmospheric CO2 concentrations. In the study site of Sky Oaks (Warner Springs, CA, USA), twelve closed chambers were installed in 1992, and for 8 years they were fumigated with different concentration of CO2, ranging from pre-industrial levels (250 ppm) to 750 ppm CO2, with step increments of 100 ppm. Fossil fuel-derived CO2, depleted in 13C, was used to fumigate the chambers, thus allowed to trace the C input from the vegetation to the soil at all levels of CO2 exposure. In January 2003, soil were sampled from each chamber and shipped to the SUN (Italy). Here, soil samples were separated by wet sieving into different classes of aggregates, namely, macroaggregates (>250μ m), microaggregates (53-250 μ m) and silt&clay (<53 μ m). Within macroaggregates, we isolated three different structural and functional pools: the coarse particulate organic matter (POM), the microaggregates and the occluded silt&clay. Lastly, a density floatation with Sodium Polytungstate allowed the separation of light fraction contained in the microaggregates from the intra and inter-POM. The isotope mixing-model approach was used to quantify the net C input from the vegetation to the soil along the entire gradient of atmospheric CO2 concentrations.

  2. Acute Toxicity of Ternary Cd-Cu-Ni and Cd-Ni-Zn Mixtures to Daphnia magna: Dominant Metal Pairs Change along a Concentration Gradient.

    Science.gov (United States)

    Traudt, Elizabeth M; Ranville, James F; Meyer, Joseph S

    2017-04-18

    Multiple metals are usually present in surface waters, sometimes leading to toxicity that currently is difficult to predict due to potentially non-additive mixture toxicity. Previous toxicity tests with Daphnia magna exposed to binary mixtures of Ni combined with Cd, Cu, or Zn demonstrated that Ni and Zn strongly protect against Cd toxicity, but Cu-Ni toxicity is more than additive, and Ni-Zn toxicity is slightly less than additive. To consider multiple metal-metal interactions, we exposed D. magna neonates to Cd, Cu, Ni, or Zn alone and in ternary Cd-Cu-Ni and Cd-Ni-Zn combinations in standard 48 h lethality tests. In these ternary mixtures, two metals were held constant, while the third metal was varied through a series that ranged from nonlethal to lethal concentrations. In Cd-Cu-Ni mixtures, the toxicity was less than additive, additive, or more than additive, depending on the concentration (or ion activity) of the varied metal and the additivity model (concentration-addition or independent-action) used to predict toxicity. In Cd-Ni-Zn mixtures, the toxicity was less than additive or approximately additive, depending on the concentration (or ion activity) of the varied metal but independent of the additivity model. These results demonstrate that complex interactions of potentially competing toxicity-controlling mechanisms can occur in ternary-metal mixtures but might be predicted by mechanistic bioavailability-based toxicity models.

  3. Optimization of elution salt concentration in stepwise elution of protein chromatography using linear gradient elution data. Reducing residual protein A by cation-exchange chromatography in monoclonal antibody purification.

    Science.gov (United States)

    Ishihara, Takashi; Kadoya, Toshihiko; Endo, Naomi; Yamamoto, Shuichi

    2006-05-05

    Our simple method for optimization of the elution salt concentration in stepwise elution was applied to the actual protein separation system, which involves several difficulties such as detection of the target. As a model separation system, reducing residual protein A by cation-exchange chromatography in human monoclonal antibody (hMab) purification was chosen. We carried out linear gradient elution experiments and obtained the data for the peak salt concentration of hMab and residual protein A, respectively. An enzyme-linked immunosorbent assay was applied to the measurement of the residual protein A. From these data, we calculated the distribution coefficient of the hMab and the residual protein A as a function of salt concentration. The optimal salt concentration of stepwise elution to reduce the residual protein A from the hMab was determined based on the relationship between the distribution coefficient and the salt concentration. Using the optimized condition, we successfully performed the separation, resulting in high recovery of hMab and the elimination of residual protein A.

  4. Stable isotopes

    International Nuclear Information System (INIS)

    Evans, D.K.

    1986-01-01

    Seventy-five percent of the world's stable isotope supply comes from one producer, Oak Ridge Nuclear Laboratory (ORNL) in the US. Canadian concern is that foreign needs will be met only after domestic needs, thus creating a shortage of stable isotopes in Canada. This article describes the present situation in Canada (availability and cost) of stable isotopes, the isotope enrichment techniques, and related research programs at Chalk River Nuclear Laboratories (CRNL)

  5. Areal-averaged trace gas emission rates from long-range open-path measurements in stable boundary layer conditions

    Directory of Open Access Journals (Sweden)

    K. Schäfer

    2012-07-01

    Full Text Available Measurements of land-surface emission rates of greenhouse and other gases at large spatial scales (10 000 m2 are needed to assess the spatial distribution of emissions. This can be readily done using spatial-integrating micro-meteorological methods like flux-gradient methods which were evaluated for determining land-surface emission rates of trace gases under stable boundary layers. Non-intrusive path-integrating measurements are utilized. Successful application of a flux-gradient method requires confidence in the gradients of trace gas concentration and wind, and in the applicability of boundary-layer turbulence theory; consequently the procedures to qualify measurements that can be used to determine the flux is critical. While there is relatively high confidence in flux measurements made under unstable atmospheres with mean winds greater than 1 m s−1, there is greater uncertainty in flux measurements made under free convective or stable conditions. The study of N2O emissions of flat grassland and NH3 emissions from a cattle lagoon involves quality-assured determinations of fluxes under low wind, stable or night-time atmospheric conditions when the continuous "steady-state" turbulence of the surface boundary layer breaks down and the layer has intermittent turbulence. Results indicate that following the Monin-Obukhov similarity theory (MOST flux-gradient methods that assume a log-linear profile of the wind speed and concentration gradient incorrectly determine vertical profiles and thus flux in the stable boundary layer. An alternative approach is considered on the basis of turbulent diffusivity, i.e. the measured friction velocity as well as height gradients of horizontal wind speeds and concentrations without MOST correction for stability. It is shown that this is the most accurate of the flux-gradient methods under stable conditions.

  6. Assessment of macro-micro element accumulation capabilities of Elodea nuttallii under gradient redox statuses with elevated NH4-N concentrations

    OpenAIRE

    Zaman, Tanjeena; Asaeda, Takashi

    2014-01-01

    Aquatic plants often encounter various redox conditions in their natural environment. Elodea nuttallii (Planch.), a submerged aquatic macrophyte, has a flexile ability to use different nutrient sources from various environments. In the present study, Elodea nuttallii was subjected to various redox conditions (+400 mV to –180 mV) at both normal (2.5 ppm) and high (10 ppm) ammonium concentrations and evaluated for macro and micro element accumulation. A reduced environment was prepared by addin...

  7. Al2O3 Coated Concentration-Gradient Li[Ni0.73Co0.12Mn0.15]O2 Cathode Material by Freeze Drying for Long-Life Lithium Ion Batteries

    International Nuclear Information System (INIS)

    Wang, Jingpeng; Du, Chunyu; Yan, Chunqiu; He, Xiaoshu; Song, Bai; Yin, Geping; Zuo, Pengjian; Cheng, Xinqun

    2015-01-01

    Highlights: • Al 2 O 3 -coated concentration-gradient oxide is synthesized by a freeze drying method. • The effect of Al 2 O 3 -coating on concentration-gradient cathode is firstly studied. • Al 2 O 3 -coated sample exhibits high capacity and significantly enhanced cyclability. • Improved cyclability is ascribed to the effective protection of uniform Al 2 O 3 layer. - Abstract: In order to enhance the electrochemical performance of the high capacity layered oxide cathode with a Ni-rich core and a concentration-gradient shell (NRC-CGS), we use a freeze drying method to coat Al 2 O 3 layer onto the surface of NRC-CGS Li[Ni 0.73 Co 0.12 Mn 0.15 ]O 2 material. The samples are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, charge-discharge measurements and electrochemical impedance spectroscopy. It is revealed that an amorphous Al 2 O 3 layer of about 5 nm in thickness is uniformly formed on the surface of NRC-CGS Li[Ni 0.73 Co 0.12 Mn 0.15 ]O 2 material by the freeze drying procedure. The freeze drying Al 2 O 3 -coated (FD-Al 2 O 3 -coated) sample demonstrates similar discharge capacity and significantly enhanced cycling performances, in comparison to the pristine and conventional heating drying Al 2 O 3 -coated (HD-Al 2 O 3 -coated) samples. The capacity decay rate of FD-Al 2 O 3 -coated Li[Ni 0.73 Co 0.12 Mn 0.15 ]O 2 material is 1.7% after 150 cycles at 55 °C, which is 9 and 12 times lower than that of the pristine and HD-Al 2 O 3 -coated samples. The superior electrochemical stability of the FD-Al 2 O 3 -coated sample is attributed to the synergistic protection of CGS and high-quality Al 2 O 3 coating that effectively protect the active material from electrolyte attack. The freeze drying process provides an effective method to prepare the high performance surface-coated electrode materials

  8. Technical Report on the Behavior of Trace Elements, Stable Isotopes, and Radiogenic Isotopes During the Processing of Uranium Ore to Uranium Ore Concentrate

    Energy Technology Data Exchange (ETDEWEB)

    Marks, N. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Borg, L. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Eppich, G. R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Gaffney, A. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Genneti, V. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hutcheon, I. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Kristo, M. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lindvall, R. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ramon, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Robel, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Roberts, S. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Schorzman, K. C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Sharp, M. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Singleton, M. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Williams, R. W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-07-09

    The goals of this SP-1 effort were to understand how isotopic and elemental signatures behave during mining, milling, and concentration and to identify analytes that might preserve geologic signatures of the protolith ores. The impurities that are preserved through the concentration process could provide useful forensic signatures and perhaps prove diagnostic of sample origin.

  9. Reproducible measurement of vancomycin MICs within the susceptible range in Staphylococcus aureus by a broth microdilution method with a "quasi-continuum" gradient of antibiotic concentrations.

    Science.gov (United States)

    Falcón, R; Mateo, E M; Talaya, A; Giménez, E; Vinuesa, V; Clari, M Á; Navarro, D

    2017-12-01

    The availability of reproducible broth microdilution (BMD) methods including inter log 2 antibiotic dilutions for measuring Staphylococcus aureus (SA) vancomycin minimum inhibitory concentrations (MICs) within the susceptible range is needed to elucidate the impact of vancomycin MICs on clinical outcomes of invasive SA infections. Here, we report on the development of a very precise BMD method that incorporates the following incremental antibiotic concentrations: 0.50, 0.62, 0.75, 0.87, 1.0, 1.25, 1.40, 1.50, 1.60, 1.75, and 2.0 μg/mL. The intra- and inter-assay coefficients of variation of this method were around 20%. The mean of the differences in MIC values for all isolates obtained across two independent runs performed at one center was 0.04 μg/mL [95% confidence interval (CI), 0.011-0.07 μg/mL] and that for ten isolates measured at two different centers was 0.04 μg/mL (95% CI, 0-13 μg/mL). Vancomycin MIC values differed by less than 0.1 μg/mL between runs for most isolates. Storage of isolates at -20 °C for up to 3 months had no impact on the vancomycin MIC values. The mean vancomycin MIC values obtained by the Etest using a standard inoculum (0.5 McFarland) were significantly higher (p ≤ 0.001) than those measured by BMD and the MIC values measured by the two methods correlated poorly (Rho, 0.319; p = 0.148). Nevertheless, the mean MIC values measured by the Etest using lower inocula (10 7 or 10 6  CFU/mL) and those measured by BMD were comparable and correlated significantly (p = 0.004 for 10 7  CFU/mL and p = 0.029 for 10 6  CFU/mL).

  10. Concentrations and Fractionation of Carbon, Iron, Sulfur, Nitrogen and Phosphorus in Mangrove Sediments Along an Intertidal Gradient (Semi-Arid Climate, New Caledonia

    Directory of Open Access Journals (Sweden)

    Jonathan Deborde

    2015-02-01

    Full Text Available In mangrove ecosystems, strong reciprocal interactions exist between plant and substrate. Under semi-arid climate, Rhizophora spp. are usually predominant, colonizing the seashore, and Avicennia marina develops at the edge of salt-flats, which is the highest zone in the intertidal range. Along this zonation, distribution and speciation of C, Fe, S, N, and P in sediments and pore-waters were investigated. From the land-side to the sea-side of the mangrove, sediments were characterized by I/ increase in: (i water content; (ii TOC; (iii mangrove-derived OM; II/ and decrease in: (i salinity; (ii redox; (iii pH; (iv solid Fe and solid P. Beneath Avicennia and Rhizophora, TS accumulated at depth, probably as a result of reduction of iron oxides and sulfate. The loss of total Fe observed towards the sea-side may be related to sulfur oxidation and to more intense tidal flushing of dissolved components. Except the organic forms, dissolved N and P concentrations were very low beneath Avicennia and Rhizophora stands, probably as a result of their uptake by the root systems. However, in the unvegetated salt-flat, NH4+ can accumulate in organic rich and anoxic layers. This study shows: (i the evolution of mangrove sediment biogeochemistry along the intertidal zone as a result of the different duration of tidal inundation and organic enrichment; and (ii the strong links between the distribution and speciation of the different elements.

  11. Effects of Boundary Layer Height on the Model of Ground-Level PM2.5 Concentrations from AOD: Comparison of Stable and Convective Boundary Layer Heights from Different Methods

    Directory of Open Access Journals (Sweden)

    Zengliang Zang

    2017-06-01

    Full Text Available The aerosol optical depth (AOD from satellites or ground-based sun photometer spectral observations has been widely used to estimate ground-level PM2.5 concentrations by regression methods. The boundary layer height (BLH is a popular factor in the regression model of AOD and PM2.5, but its effect is often uncertain. This may result from the structures between the stable and convective BLHs and from the calculation methods of the BLH. In this study, the boundary layer is divided into two types of stable and convective boundary layer, and the BLH is calculated using different methods from radiosonde data and National Centers for Environmental Prediction (NCEP reanalysis data for the station in Beijing, China during 2014–2015. The BLH values from these methods show significant differences for both the stable and convective boundary layer. Then, these BLHs were introduced into the regression model of AOD-PM2.5 to seek the respective optimal BLH for the two types of boundary layer. It was found that the optimal BLH for the stable boundary layer is determined using the method of surface-based inversion, and the optimal BLH for the convective layer is determined using the method of elevated inversion. Finally, the optimal BLH and other meteorological parameters were combined to predict the PM2.5 concentrations using the stepwise regression method. The results indicate that for the stable boundary layer, the optimal stepwise regression model includes the factors of surface relative humidity, BLH, and surface temperature. These three factors can significantly enhance the prediction accuracy of ground-level PM2.5 concentrations, with an increase of determination coefficient from 0.50 to 0.68. For the convective boundary layer, however, the optimal stepwise regression model includes the factors of BLH and surface wind speed. These two factors improve the determination coefficient, with a relatively low increase from 0.65 to 0.70. It is found that the

  12. Short communication: Relationship between serum cortisol concentration and defensive behavioral responses of dairy cows exposed to natural infestation by stable fly, Stomoxys calcitrans.

    Science.gov (United States)

    Vitela-Mendoza, I; Cruz-Vázquez, C; Solano-Vergara, J; Orihuela-Trujillo, A

    2016-12-01

    The aim of this study was conducted to evaluate the effect of natural infestation by Stomoxys calcitrans on the behavioral and adrenocortical responses of dairy cattle. Twenty Holstein cows randomly selected were individually sprayed with insecticide once every 7d, whereas no insecticide was applied to the other 20 animals. The average number of flies per cow was estimated daily, and the frequency of fly-avoidance behaviors was measured daily; plasma cortisol concentration was measured each morning. No flies were ever counted on the treated cows at any time during the experiment, whereas an average of 17.13±1.14 (±standard error) flies/d were recorded on untreated cows. Tail movement was the most frequent behavior displayed, with stamps or kicks showing the highest increment rate (41.2×) when fly population increased from zero to greater than 51 flies/cow. Cortisol concentration increased to a maximum of 56.81±39.53ng/mL with 26 to 30 flies/cow per day. Coefficients of determination between the number of flies, cortisol concentration, tail movements, and stamps or kicks were 0.73, 0.78, and 0.81, respectively. The multiple correlation coefficient was 0.90, with 81% of the variation in cortisol concentration explainable by variation in the number of flies per cow and the frequency of fly-avoidance behaviors. It was concluded that plasma cortisol concentration is linearly related to a combination of the number of flies and the frequency of fly-dislodging behaviors, producing a maximum response before reaching maximum fly loads. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  13. Stability of gradient semigroups under perturbations

    Science.gov (United States)

    Aragão-Costa, E. R.; Caraballo, T.; Carvalho, A. N.; Langa, J. A.

    2011-07-01

    In this paper we prove that gradient-like semigroups (in the sense of Carvalho and Langa (2009 J. Diff. Eqns 246 2646-68)) are gradient semigroups (possess a Lyapunov function). This is primarily done to provide conditions under which gradient semigroups, in a general metric space, are stable under perturbation exploiting the known fact (see Carvalho and Langa (2009 J. Diff. Eqns 246 2646-68)) that gradient-like semigroups are stable under perturbation. The results presented here were motivated by the work carried out in Conley (1978 Isolated Invariant Sets and the Morse Index (CBMS Regional Conference Series in Mathematics vol 38) (RI: American Mathematical Society Providence)) for groups in compact metric spaces (see also Rybakowski (1987 The Homotopy Index and Partial Differential Equations (Universitext) (Berlin: Springer)) for the Morse decomposition of an invariant set for a semigroup on a compact metric space).

  14. Determination of trace element concentrations and stable lead, uranium and thorium isotope ratios by quadrupole-ICP-MS in NORM and NORM-polluted sample leachates

    Energy Technology Data Exchange (ETDEWEB)

    Mas, J.L., E-mail: ppmasb@us.es [Dpto. Fisica Aplicada I, EPS, Universidad de Sevilla, 41012 Sevilla (Spain); Villa, M. [Servicio de Radioisotopos, Centro de Investigacion, Tecnologia e Innovacion (CITIUS), Universidad de Sevilla, Avda. Reina Mercedes 4b, 41012 Sevilla (Spain); Dpto. Fisica Aplicada II, ETS de Arquitectura, Universidad de Sevilla, Avda. Reina Mercedes 2, 41012 Sevilla (Spain); Hurtado, S. [Servicio de Radioisotopos, Centro de Investigacion, Tecnologia e Innovacion (CITIUS), Universidad de Sevilla, Avda. Reina Mercedes 4b, 41012 Sevilla (Spain); Garcia-Tenorio, R. [Dpto. Fisica Aplicada II, ETS de Arquitectura, Universidad de Sevilla, Avda. Reina Mercedes 2, 41012 Sevilla (Spain)

    2012-02-29

    Highlights: Black-Right-Pointing-Pointer Polluted sediment and NORM samples. Black-Right-Pointing-Pointer An efficient yet fast process allowing multi-parametric determinations in <3 days. Black-Right-Pointing-Pointer Trace element concentrations, Pb, Th and U isotope ratios with a single instrument. - Abstract: This work focuses on the monitoring of the potential pollution in scenarios that involve NORM-related industrial activities (environmental or in-door scenarios). The objective was to develop a method to determine extent and origin of the contamination, suitable for monitoring (i.e. simple, fast and economical) and avoiding the use of too many different instruments. It is presented a radiochemical method that allows the determination of trace element concentrations and {sup 206}Pb/{sup 207}Pb/{sup 208}Pb, {sup 238}U/{sup 234}U and {sup 232}Th/{sup 230}Th isotope ratios using a single sample aliquot and a single instrument (ICP-QMS). Eichrom UTEVA{sup Registered-Sign} extraction chromatography minicolumns were used to separate uranium and thorium in sample leachates. Independent ICP-MS determinations of uranium and thorium isotope ratios were carried out afterwards. Previously a small aliquot of the leachate was used for the determination of trace element concentrations and lead isotope ratios. Several radiochemical arrangements were tested to get maximum performances and simplicity of the method. The performances of the method were studied in terms of chemical yields of uranium and thorium and removal of the potentially interfering elements. The established method was applied to samples from a chemical industry and sediments collected in a NORM-polluted scenario. The results obtained from our method allowed us to infer not only the extent, but also the sources of the contamination in the area.

  15. Conducta alimentaria de Daphnia ambigua Scourfield 1947, Moina micrura Kurz 1874 y Ceriodaphnia dubia Richard 1895 (Cladocera frente a un gradiente de concentración de alimento Feeding behaviour of Daphnia ambigua Scourfield 1947, Moina micrura Kurz 1874 and Ceriodaphnia dubia Richard 1895 (Cladocera under a food concentration gradient

    Directory of Open Access Journals (Sweden)

    GINGER MARTINEZ

    2000-03-01

    Full Text Available Debido a que Cladocera es el grupo de microfiltradores más abundante del zooplancton límnico y cuyas poblaciones se encuentran usualmente limitadas por alimento, la respuesta de los individuos frente a un gradiente de concentración de recursos tendría significativas implicancias sobre los patrones poblacionales y comunitarios. Se comparó la conducta alimentaria de Moina micrura, Ceriodaphnia dubia y Daphnia ambigua (Cladocera frente a las microalgas Chlorella sp. y Oocystis sp. (Chlorophyceae mediante los siguientes parámetros: Tasa de Ingesta Máxima (Imax, Concentración Limitante Incipiente (CLI y Eficiencia de Consumo (b, los cuales fueron obtenidos a través de un modelo de respuesta funcional. Los resultados mostraron que D. ambigua presentó las mayores Imax y CLI sobre ambos recursos, sin embargo, esta especie presentó la menor b. Mientras que D. ambigua no presentó diferencias en b sobre Chlorella sp. y Oocystis sp., M. micrura presentó una mayor b sobre Chlorella sp. y C. dubia sobre Oocystis sp. Estos resultados revelan significativas diferencias interespecíficas en la respuesta alimentaria de Cladocera, grupo que presentó un complejo comportamiento frente a variaciones en la disponibilidad de recursos alimentariosBecause Cladocera is the most abundant group of filter-feeders in the freshwater zooplankton and their populations are usually found under limited resources conditions, the individual response under a resources concentration gradient has important consequences on the population and community patterns. Feeding behavior of Moina micrura, Ceriodaphnia dubia and Daphnia ambigua (Cladocera on the microalgae Chlorella sp. and Oocystis sp. (Chlorophyceae was compared by using the following parameters: Maximum Ingestion Rate (Imax, Incipient Limiting Concentration (ILC and Consumption Efficiency (b, which were obtained through a model of functional response. Results indicated that D. ambigua showed the highest Imax and

  16. Concentration quenching of Eu2+ in a thermal-stable yellow phosphor Ca2BO3Cl:Eu2+ for LED application

    International Nuclear Information System (INIS)

    Zhang Xinguo; Zhang Jilin; Dong Zhiyue; Shi Jianxin; Gong Menglian

    2012-01-01

    A piece-shaped phosphor Ca 2 BO 3 Cl: Eu 2+ was synthesized by solid-state reaction method. This phosphor exhibited wide absorption in ultra-violet and visible range, and bright yellow emission band centering at 570 nm. The concentration quenching mechanism was verified to be a dipole–dipole interaction, and its critical transfer distance was about 17 Å by both calculated crystal structural method and experimental spectral method. This phosphor has a good thermal stability with a quenching temperature (T 1/2 ) of 200 °C. Yellow and white LEDs were fabricated with this phosphor and near UV chips, and the yellow LED has a high color purity of 97.0% and promising current tolerant property, while the white LED shows a luminous efficiency of 11.68 lm/W. - Highlights: ► Broadband excitable and strong yellow-emitting Ca 2 BO 3 Cl: Eu 2+ phosphor is obtained by solid state reaction. ► Concentration quenching mechanism of Ca 2 BO 3 Cl: Eu 2+ is dipole–dipole interaction. ► Quenching temperature (T 1/2 ) of Ca 2 BO 3 Cl: Eu 2+ is at 200 °C. ► As synthesized material can be used for LED phosphor application.

  17. Stable particles

    International Nuclear Information System (INIS)

    Samios, N.P.

    1994-01-01

    I have been asked to review the subject of stable particles, essentially the particles that eventually comprised the meson and baryon octets, with a few more additions - with an emphasis on the contributions made by experiments utilizing the bubble chamber technique. In this activity, much work had been done by the photographic emulsion technique and cloud chambers - exposed to cosmic rays as well as accelerator based beams. In fact, many if not most of the stable particles were found by these latter two techniques, however, the foree of the bubble chamber (coupled with the newer and more powerful accelerators) was to verify, and reinforce with large statistics, the existence of these states, to find some of the more difficult ones, mainly neutrals and further to elucidate their properties, i.e., spin, parity, lifetimes, decay parameters, etc. (orig.)

  18. Stable particles

    International Nuclear Information System (INIS)

    Samios, N.P.

    1993-01-01

    I have been asked to review the subject of stable particles, essentially the particles that eventually comprised the meson and baryon octets. with a few more additions -- with an emphasis on the contributions made by experiments utilizing the bubble chamber technique. In this activity, much work had been done by the photographic emulsion technique and cloud chambers-exposed to cosmic rays as well as accelerator based beams. In fact, many if not most of the stable particles were found by these latter two techniques, however, the forte of the bubble chamber (coupled with the newer and more powerful accelerators) was to verify, and reinforce with large statistics, the existence of these states, to find some of the more difficult ones, mainly neutrals and further to elucidate their properties, i.e., spin, parity, lifetimes, decay parameters, etc

  19. Up-gradient transport in a probabilistic transport model

    DEFF Research Database (Denmark)

    Gavnholt, J.; Juul Rasmussen, J.; Garcia, O.E.

    2005-01-01

    The transport of particles or heat against the driving gradient is studied by employing a probabilistic transport model with a characteristic particle step length that depends on the local concentration or heat gradient. When this gradient is larger than a prescribed critical value, the standard....... These results supplement recent works by van Milligen [Phys. Plasmas 11, 3787 (2004)], which applied Levy distributed step sizes in the case of supercritical gradients to obtain the up-gradient transport. (c) 2005 American Institute of Physics....

  20. Elemental gradients in macrophytes from a reactor effluent gradient

    International Nuclear Information System (INIS)

    Grace, J.B.; Tilly, L.J.

    1978-01-01

    The tissues of submersed macrophtes from along the thermal gradient were analyzed for phosphorus to determine whether any pattern correspondent to standing crop distributions could be detected. Although water concentrations of phosphorus showed no detectable relationship to the thermal effluent, tissue concentrations of this element in submersed macrophytes declined with distance from the effluent entry point. The occurrence of this concentration pattern suggests that phosphorus availability is greater near the discharge. Because phosphorus is the element most often determined to limit aquatic productivity, its greater availability may partially account for the apparent enhancement of macrophte growth near the thermal discharge. A patter of macrophyte abundance which indicated enchancement related to the discharge gradient in the reactor-cooling reservoir, Par Pond is reported. Correlative data tended to implicate light and temperature as important in influencing the differential abundance pattern

  1. Determination of trace element concentrations and stable lead, uranium and thorium isotope ratios by quadrupole-ICP-MS in NORM and NORM-polluted sample leachates

    International Nuclear Information System (INIS)

    Mas, J.L.; Villa, M.; Hurtado, S.; García-Tenorio, R.

    2012-01-01

    Highlights: ► Polluted sediment and NORM samples. ► An efficient yet fast process allowing multi-parametric determinations in 206 Pb/ 207 Pb/ 208 Pb, 238 U/ 234 U and 232 Th/ 230 Th isotope ratios using a single sample aliquot and a single instrument (ICP-QMS). Eichrom UTEVA ® extraction chromatography minicolumns were used to separate uranium and thorium in sample leachates. Independent ICP-MS determinations of uranium and thorium isotope ratios were carried out afterwards. Previously a small aliquot of the leachate was used for the determination of trace element concentrations and lead isotope ratios. Several radiochemical arrangements were tested to get maximum performances and simplicity of the method. The performances of the method were studied in terms of chemical yields of uranium and thorium and removal of the potentially interfering elements. The established method was applied to samples from a chemical industry and sediments collected in a NORM-polluted scenario. The results obtained from our method allowed us to infer not only the extent, but also the sources of the contamination in the area.

  2. Stable beams

    CERN Multimedia

    2015-01-01

    Stable beams: two simple words that carry so much meaning at CERN. When LHC page one switched from "squeeze" to "stable beams" at 10.40 a.m. on Wednesday, 3 June, it triggered scenes of jubilation in control rooms around the CERN sites, as the LHC experiments started to record physics data for the first time in 27 months. This is what CERN is here for, and it’s great to be back in business after such a long period of preparation for the next stage in the LHC adventure.   I’ve said it before, but I’ll say it again. This was a great achievement, and testimony to the hard and dedicated work of so many people in the global CERN community. I could start to list the teams that have contributed, but that would be a mistake. Instead, I’d simply like to say that an achievement as impressive as running the LHC – a machine of superlatives in every respect – takes the combined effort and enthusiasm of everyone ...

  3. A case study for sustainable development action using financial gradients

    International Nuclear Information System (INIS)

    Bose, Arnab; Ramji, Aditya; Singh, Jarnail; Dholakia, Dhairya

    2012-01-01

    Energy access is critical for sustainable development and therefore financing energy access is a necessity. The key is whether to focus on grants or public finance for sustainable development projects or move to a more diffused financing mechanism, involving investment grade financing sources like debt and equity. In other words, financing sustainable development action via grants is becoming a constraint. To address this constraint, it is important to consider the relationship between the nature and sources of financial flows. The concept of ‘financial gradients’ emerged while analysing the financial and business strategy developed for Lighting a Billion Lives (LaBL) campaign. This paper espouses the idea of ‘financial gradients’ which is a potential financial mechanism for sustainable development action. Financial gradients, can contribute in three different ways—first, as an approach to analyse financial flows in projects; second, as a tool to generate a single, long term and stable inflow of finance; third, as a financial mechanism to help in creating long term strategies to sustain projects. This paper will concentrate on financial gradients as a potential approach to analyse financial flows in a sustainable development programme. - Highlights: ► Financial stability is a key challenge for sustainable development programmes. ► Development action via public funds is limited, need for investment grade finance. ► Need to understand financial flows with relation to nature and sources of finance. ► Financial gradients is an innovative tool for ensuring health of programmes.

  4. Self-organization of intracellular gradients during mitosis

    Directory of Open Access Journals (Sweden)

    Fuller Brian G

    2010-01-01

    Full Text Available Abstract Gradients are used in a number of biological systems to transmit spatial information over a range of distances. The best studied are morphogen gradients where information is transmitted over many cell lengths. Smaller mitotic gradients reflect the need to organize several distinct events along the length of the mitotic spindle. The intracellular gradients that characterize mitosis are emerging as important regulatory paradigms. Intracellular gradients utilize intrinsic auto-regulatory feedback loops and diffusion to establish stable regions of activity within the mitotic cytosol. We review three recently described intracellular mitotic gradients. The Ran GTP gradient with its elaborate cascade of nuclear transport receptors and cargoes is the best characterized, yet the dynamics underlying the robust gradient of Ran-GTP have received little attention. Gradients of phosphorylation have been observed on Aurora B kinase substrates both before and after anaphase onset. In both instances the phosphorylation gradient appears to result from a soluble gradient of Aurora B kinase activity. Regulatory properties that support gradient formation are highlighted. Intracellular activity gradients that regulate localized mitotic events bare several hallmarks of self-organizing biologic systems that designate spatial information during pattern formation. Intracellular pattern formation represents a new paradigm in mitotic regulation.

  5. Comparison of Corneal Riboflavin Gradients Using Dextran and HPMC Solutions.

    Science.gov (United States)

    Ehmke, Tobias; Seiler, Theo G; Fischinger, Isaak; Ripken, Tammo; Heisterkamp, Alexander; Frueh, Beatrice E

    2016-12-01

    To determine the riboflavin concentration gradient in the anterior corneal stroma when using hydroxypropyl methylcellulose (HPMC) or dextran as the carrier agent. Four different groups of porcine corneas (5 each) were compared regarding the riboflavin concentration in the anterior stroma. Prior to all experiments, stable hydration conditions were established for the corresponding solution. The dextran groups were treated with 0.1% riboflavin in 20% dextran for 10 and 30 minutes and the HPMC groups with 0.1% riboflavin in 1.1% HPMC for 10 and 30 minutes. After imbibition, nonlinear microscopy and consecutive image analysis were used to determine two-photon fluorescence intensities. To determine the riboflavin concentration, corneas were saturated and measured a second time by two-photon microscopy. With this measurement, a proper correction for absorption and scattering could be performed. Ultraviolet-A (UVA) transmission was measured after the application time for each group. Riboflavin concentration decreased with increasing depth and increased with longer application times in all groups. Comparing the dextran for 30 minutes and HPMC for 10 minutes groups, a significantly higher stromal riboflavin concentration was found within the most anterior 70 µm in the dextran group for 30 minutes, whereas deeper than 260 µm HPMC-assisted imbibition for 10 minutes yielded higher concentrations. In dextran-treated corneas, values obtained from pachymetry were substantially reduced, whereas HPMC-assisted imbibition led to a decent swelling. UVA transmission values were higher in dextran-assisted imbibition than in HPMC-assisted imbibition. Stromal riboflavin gradients are similar when applied in dextran for 30 minutes and HPMC for 10 minutes. When using HPMC solutions, a shallower cross-linked volume is expected due to a higher corneal hydration. [J Refract Surg. 2016;32(12):798-802.]. Copyright 2016, SLACK Incorporated.

  6. Concentration gradient driven molecular dynamics: a new method for simulations of membrane permeation and separation† †Electronic supplementary information (ESI) available: Additional simulation settings, results and snapshots. See DOI: 10.1039/c6sc04978h Click here for additional data file.

    Science.gov (United States)

    Ozcan, Aydin; Perego, Claudio; Salvalaglio, Matteo; Parrinello, Michele

    2017-01-01

    In this study, we introduce a new non-equilibrium molecular dynamics simulation method to perform simulations of concentration driven membrane permeation processes. The methodology is based on the application of a non-conservative bias force controlling the concentration of species at the inlet and outlet of a membrane. We demonstrate our method for pure methane, ethane and ethylene permeation and for ethane/ethylene separation through a flexible ZIF-8 membrane. Results show that a stationary concentration gradient is maintained across the membrane, realistically simulating an out-of-equilibrium diffusive process, and the computed permeabilities and selectivity are in good agreement with experimental results. PMID:28966778

  7. Mercury contamination and stable isotopes reveal variability in foraging ecology of generalist California gulls

    Science.gov (United States)

    Peterson, Sarah; Ackerman, Joshua T.; Eagles-Smith, Collin A.

    2017-01-01

    Environmental contaminants are a concern for animal health, but contaminant exposure can also be used as a tracer of foraging ecology. In particular, mercury (Hg) concentrations are highly variable among aquatic and terrestrial food webs as a result of habitat- and site-specific biogeochemical processes that produce the bioaccumulative form, methylmercury (MeHg). We used stable isotopes and total Hg (THg) concentrations of a generalist consumer, the California gull (Larus californicus), to examine foraging ecology and illustrate the utility of using Hg contamination as an ecological tracer under certain conditions. We identified four main foraging clusters of gulls during pre-breeding and breeding, using a traditional approach based on light stable isotopes. The foraging cluster with the highest δ15N and δ34S values in gulls (cluster 4) had mean blood THg concentrations 614% (pre-breeding) and 250% (breeding) higher than gulls with the lowest isotope values (cluster 1). Using a traditional approach of stable-isotope mixing models, we showed that breeding birds with a higher proportion of garbage in their diet (cluster 2: 63–82% garbage) corresponded to lower THg concentrations and lower δ15N and δ34S values. In contrast, gull clusters with higher THg concentrations, which were more enriched in 15N and 34S isotopes, consumed a higher proportion of more natural, estuarine prey. δ34S values, which change markedly across the terrestrial to marine habitat gradient, were positively correlated with blood THg concentrations in gulls. The linkage we observed between stable isotopes and THg concentrations suggests that Hg contamination can be used as an additional tool for understanding animal foraging across coastal habitat gradients.

  8. An assessment of an environmental gradient using coral geochemical records, Whitsunday Islands, Great Barrier Reef, Australia.

    Science.gov (United States)

    Lewis, S E; Brodie, J E; McCulloch, M T; Mallela, J; Jupiter, S D; Williams, H Stuart; Lough, J M; Matson, E G

    2012-01-01

    Coral cores were collected along an environmental and water quality gradient through the Whitsunday Island group, Great Barrier Reef (Australia), for trace element and stable isotope analysis. The primary aim of the study was to examine if this gradient could be detected in coral records and, if so, whether the gradient has changed over time with changing land use in the adjacent river catchments. Y/Ca was the trace element ratio which varied spatially across the gradient, with concentrations progressively decreasing away from the river mouths. The Ba/Ca and Y/Ca ratios were the only indicators of change in the gradient through time, increasing shortly after European settlement. The Mn/Ca ratio responded to local disturbance related to the construction of tourism infrastructure. Nitrogen isotope ratios showed no apparent trend over time. This study highlights the importance of site selection when using coral records to record regional environmental signals. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

  9. Realizable planar gradient-index solar lenses.

    Science.gov (United States)

    Kotsidas, Panagiotis; Modi, Vijay; Gordon, Jeffrey M

    2012-04-01

    The design of single element planar hemispherical gradient-index solar lenses that can accommodate the constraints of realistic materials and fabrication techniques are presented, and simulated with an extended and polychromatic solar source for concentrator photovoltaics at flux concentration values exceeding 1000 suns. The planar hemispherical far-field lens is created from a near-field unit magnification spherical gradient-index design, and illustrated with an f/1.40 square solar lens that allows lossless packing within a concentrator module.

  10. Extracellular Processing of Molecular Gradients by Eukaryotic Cells Can Improve Gradient Detection Accuracy

    Science.gov (United States)

    Segota, Igor; Franck, Carl

    2017-12-01

    Eukaryotic cells sense molecular gradients by measuring spatial concentration variation through the difference in the number of occupied receptors to which molecules can bind. They also secrete enzymes that degrade these molecules, and it is presently not well understood how this affects the local gradient perceived by cells. Numerical and analytical results show that these enzymes can substantially increase the signal-to-noise ratio of the receptor difference and allow cells to respond to a much broader range of molecular concentrations and gradients than they would without these enzymes.

  11. Extracellular Processing of Molecular Gradients by Eukaryotic Cells Can Improve Gradient Detection Accuracy.

    Science.gov (United States)

    Segota, Igor; Franck, Carl

    2017-12-15

    Eukaryotic cells sense molecular gradients by measuring spatial concentration variation through the difference in the number of occupied receptors to which molecules can bind. They also secrete enzymes that degrade these molecules, and it is presently not well understood how this affects the local gradient perceived by cells. Numerical and analytical results show that these enzymes can substantially increase the signal-to-noise ratio of the receptor difference and allow cells to respond to a much broader range of molecular concentrations and gradients than they would without these enzymes.

  12. Bathymetric influence on dissolved methane in hydrothermal plumes revealed by concentration and stable carbon isotope measurements at newly discovered venting sites on the Central Indian Ridge (11-13°S)

    Science.gov (United States)

    You, Ok-Rye; Son, Seung Kyu; Baker, Edward T.; Son, Juwon; Kim, Mi Jin; Barcelona, Michael J.; Kim, Moonkoo

    2014-09-01

    Methane is a useful tracer for studying hydrothermal discharge, especially where the source fluids are of low temperature and lack metal precipitates. However, the dual origins of deep-sea methane, both chemical and biological, complicate the interpretation of methane observations. Here, we use both the concentration and stable carbon isotopic composition (δ13C) of dissolved methane to trace hydrothermal plumes and identify the source and behavior of methane at two sites of newly discovered hydrothermal activity on the Central Indian Ridge (11-13°S). At both sites, methane and optical anomalies between 2500 and 3500 m at all stations indicate active hydrothermal discharge. We compared methane concentrations and δ13C at three stations, two (CTIR110136 and CTIR110208) with the most prominent anomalies at each site, and a third (CTIR110140) with near-background methane values. At stations CTIR110136 and CTIR110208, the concentration and δ13C of methane in distinct plumes ranged from 3.3 to 42.3 nmol kg-1 and -30.0 to -15.4‰, respectively, compared to deep-water values of 0.5 to 1.2 nmol kg-1 and -35.1 to -28.9‰ at the station with a near-background distal plume (CTIR110140). δ13C was highest in the center of the plumes at CTIR110136 (-15.4‰) and CTIR110208 (-17.8‰). From the plume values we estimate that the δ13C of methane in the hydrothermal fluids at these stations was approximately -19‰ and thus the methane was most likely derived from magmatic outgassing or the chemical synthesis of inorganic matter. We used the relationship between δ13C and methane concentration to examine the behavior of methane at the plume stations. In the CTIR110208 plume, simple physical mixing was likely the major process controlling the methane profile. In the CTIR110136 plume we interpret a more complicated relationship as resulting from microbial oxidation as well as physical mixing. We argue that this difference in methane behavior between the two areas stems from a

  13. Stereo vision with distance and gradient recognition

    Science.gov (United States)

    Kim, Soo-Hyun; Kang, Suk-Bum; Yang, Tae-Kyu

    2007-12-01

    Robot vision technology is needed for the stable walking, object recognition and the movement to the target spot. By some sensors which use infrared rays and ultrasonic, robot can overcome the urgent state or dangerous time. But stereo vision of three dimensional space would make robot have powerful artificial intelligence. In this paper we consider about the stereo vision for stable and correct movement of a biped robot. When a robot confront with an inclination plane or steps, particular algorithms are needed to go on without failure. This study developed the recognition algorithm of distance and gradient of environment by stereo matching process.

  14. Subduction zones seen by GOCE gravity gradients

    DEFF Research Database (Denmark)

    Švarc, Mario; Herceg, Matija; Cammarano, Fabio

    . Few pattern recognition methods were tested on all 6 gravity gradient tensor components represented as global scale maps with resolution of 100km (corresponds to the resolution of the GOCE satellite data). By adjusting pattern recognition methods’ features and optimizing various input patterns...... and used as starting point for analysis based on image processing. On obtained maps, locations of known subduction zones were represented with characteristic elongated patterns and cross-sections. Cross sections of well-known subduction zones were used as input patterns for pattern recognition method......, the best method was applied. That is a combination of methods based on SURF (Speeded Up Robust Features) and MSER (Maximally Stable Extremal Regions) algorithms provided in MATLAB’s Computer Vision System Toolbox. Based on 6 gravity gradient components, the global gradient anomaly maps were produced...

  15. Inversion gradients for acoustic VTI wavefield tomography

    KAUST Repository

    Li, Vladimir

    2017-03-21

    Wavefield tomography can handle complex subsurface geology better than ray-based techniques and, ultimately, provide a higher resolution. Here, we implement forward and adjoint wavefield extrapolation for VTI (transversely isotropic with a vertical symmetry axis) media using a generalized pseudospectral operator based on a separable approximation for the P-wave dispersion relation. This operator is employed to derive the gradients of the differential semblance optimization (DSO) and modified image-power objective functions. We also obtain the gradient expressions for a data-domain objective function that can more easily incorporate borehole information necessary for stable VTI velocity analysis. These gradients are similar to the ones obtained with a space-time finite-difference (FD) scheme for a system of coupled wave equations but the pseudospectral method is not hampered by the imprint of the shear-wave artifact. Numerical examples also show the potential advantages of the modified image-power objective function in estimating the anellipticity parameter η.

  16. Travelling gradient thermocouple calibration

    International Nuclear Information System (INIS)

    Broomfield, G.H.

    1975-01-01

    A short discussion of the origins of the thermocouple EMF is used to re-introduce the idea that the Peltier and Thompson effects are indistinguishable from one another. Thermocouples may be viewed as devices which generate an EMF at junctions or as integrators of EMF's developed in thermal gradients. The thermal gradient view is considered the more appropriate, because of its better accord with theory and behaviour, the correct approach to calibration, and investigation of service effects is immediately obvious. Inhomogeneities arise in thermocouples during manufacture and in service. The results of travelling gradient measurements are used to show that such effects are revealed with a resolution which depends on the length of the gradient although they may be masked during simple immersion calibration. Proposed tests on thermocouples irradiated in a nuclear reactor are discussed

  17. Colloid and Phosphorus Leaching From Undisturbed Soil Cores Sampled Along a Natural Clay Gradient

    DEFF Research Database (Denmark)

    Vendelboe, Anders Lindblad; Møldrup, Per; Heckrath, Goswin Johann

    2011-01-01

    was to correlate easily measurable soil properties, such as clay content and water-dispersible colloids, to colloid and phosphorus leaching. The clay contents across the gradient ranged from 0.11 to 0.23 kg kgj1. Irrigating with artificial rainwater, all samples showed a high first flush of colloids and phosphorus......The presence of strongly sorbing compounds in groundwater and tile drains can be a result of colloid-facilitated transport. Colloid and phosphorus leaching from macropores in undisturbed soil cores sampled across a natural clay gradient at Aarup, Denmark, were studied. The aim of the study...... followed by lower and stable colloid and phosphorus concentrations. The mass of particles leached at first flush was independent of clay content and was attributed to the instant release of particles associated with the macropore walls and released upon contact with flowing water. Below a clay content of È...

  18. Gradient Alloy for Optical Packaging

    Data.gov (United States)

    National Aeronautics and Space Administration — Advances in additive manufacturing, such as Laser Engineered Net Shaping (LENS), enables the fabrication of compositionally gradient microstructures, i.e. gradient...

  19. Stable Isotope Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Tissue samples (skin, bone, blood, muscle) are analyzed for stable carbon, stable nitrogen, and stable sulfur analysis. Many samples are used in their entirety for...

  20. Stable, precise, and reproducible patterning of bicoid and hunchback molecules in the early Drosophila embryo.

    Directory of Open Access Journals (Sweden)

    Yurie Okabe-Oho

    2009-08-01

    Full Text Available Precise patterning of morphogen molecules and their accurate reading out are of key importance in embryonic development. Recent experiments have visualized distributions of proteins in developing embryos and shown that the gradient of concentration of Bicoid morphogen in Drosophila embryos is established rapidly after fertilization and remains stable through syncytial mitoses. This stable Bicoid gradient is read out in a precise way to distribute Hunchback with small fluctuations in each embryo and in a reproducible way, with small embryo-to-embryo fluctuation. The mechanisms of such stable, precise, and reproducible patterning through noisy cellular processes, however, still remain mysterious. To address these issues, here we develop the one- and three-dimensional stochastic models of the early Drosophila embryo. The simulated results show that the fluctuation in expression of the hunchback gene is dominated by the random arrival of Bicoid at the hunchback enhancer. Slow diffusion of Hunchback protein, however, averages out this intense fluctuation, leading to the precise patterning of distribution of Hunchback without loss of sharpness of the boundary of its distribution. The coordinated rates of diffusion and transport of input Bicoid and output Hunchback play decisive roles in suppressing fluctuations arising from the dynamical structure change in embryos and those arising from the random diffusion of molecules, and give rise to the stable, precise, and reproducible patterning of Bicoid and Hunchback distributions.

  1. Coaxial two-channel high-gradient dielectric wakefield accelerator

    Directory of Open Access Journals (Sweden)

    G. V. Sotnikov

    2009-06-01

    Full Text Available A new scheme for a dielectric wakefield accelerator is proposed that employs a cylindrical multizone dielectric structure configured as two concentric dielectric tubes with outer and inner vacuum channels for drive and accelerated bunches. Analytical and numerical studies have been carried out for such coaxial dielectric-loaded structures (CDS for high-gradient acceleration. An analytical theory of wakefield excitation by particle bunches in a multizone CDS has been formulated. Numerical calculations are presented for an example of a CDS using dielectric tubes with dielectric permittivity 5.7, having external diameters of 2.121 and 0.179 mm with inner diameters of 2.095 and 0.1 mm. An annular 5 GeV, 6 nC electron bunch with rms length of 0.035 mm energizes a wakefield on the structure axis having an accelerating gradient of ∼600  MeV/m with a transformer ratio ∼8∶1. The period of the accelerating field is ∼0.33  mm. If the width of the drive bunch channel is decreased, it is possible to obtain an accelerating gradient of >1  GeV/m while keeping the transformer ratio approximately the same. Full numerical simulations using a particle-in-cell code have confirmed results of the linear theory and furthermore have shown the important influence of the quenching wave that restricts the region of the wakefield to within several periods following the drive bunch. Numerical simulations for another example have shown nearly stable transport of drive and accelerated bunches through the CDS, using a short train of drive bunches.

  2. Uniform gradient expansions

    Directory of Open Access Journals (Sweden)

    Massimo Giovannini

    2015-06-01

    Full Text Available Cosmological singularities are often discussed by means of a gradient expansion that can also describe, during a quasi-de Sitter phase, the progressive suppression of curvature inhomogeneities. While the inflationary event horizon is being formed the two mentioned regimes coexist and a uniform expansion can be conceived and applied to the evolution of spatial gradients across the protoinflationary boundary. It is argued that conventional arguments addressing the preinflationary initial conditions are necessary but generally not sufficient to guarantee a homogeneous onset of the conventional inflationary stage.

  3. Uniform gradient expansions

    CERN Document Server

    Giovannini, Massimo

    2015-01-01

    Cosmological singularities are often discussed by means of a gradient expansion that can also describe, during a quasi-de Sitter phase, the progressive suppression of curvature inhomogeneities. While the inflationary event horizon is being formed the two mentioned regimes coexist and a uniform expansion can be conceived and applied to the evolution of spatial gradients across the protoinflationary boundary. It is argued that conventional arguments addressing the preinflationary initial conditions are necessary but generally not sufficient to guarantee a homogeneous onset of the conventional inflationary stage.

  4. High gradient superconducting quadrupoles

    International Nuclear Information System (INIS)

    Lundy, R.A.; Brown, B.C.; Carson, J.A.; Fisk, H.E.; Hanft, R.H.; Mantsch, P.M.; McInturff, A.D.; Remsbottom, R.H.

    1987-07-01

    Prototype superconducting quadrupoles with a 5 cm aperture and gradient of 16 kG/cm have been built and tested as candidate magnets for the final focus at SLC. The magnets are made from NbTi Tevatron style cable with 10 inner and 14 outer turns per quadrant. Quench performance and multipole data are presented. Design and data for a low current, high gradient quadrupole, similar in cross section but wound with a cable consisting of five insulated conductors are also discussed

  5. Generating substrate bound functional chemokine gradients in vitro

    DEFF Research Database (Denmark)

    Hjortø, Gertrud Malene; Hansen, Morten; Larsen, Niels Bent

    2009-01-01

    Microcontact printing (mCP) is employed to generate discontinuous microscale gradients of active fractalkine, a chemokine expressed by endothelial cells near sites of inflammation where it is believed to form concentration gradients descending away from the inflamed area. In vivo, fractalkine is ...... surface-bound chemokines (haptotactic gradients). The use of a capture antibody facilitates control of the orientation of tagged molecules, thereby ensuring a high degree of bio-functionality through correct presentation and reduced protein denaturation....

  6. Adaptive microfluidic gradient generator for quantitative chemotaxis experiments

    Science.gov (United States)

    Anielski, Alexander; Pfannes, Eva K. B.; Beta, Carsten

    2017-03-01

    Chemotactic motion in a chemical gradient is an essential cellular function that controls many processes in the living world. For a better understanding and more detailed modelling of the underlying mechanisms of chemotaxis, quantitative investigations in controlled environments are needed. We developed a setup that allows us to separately address the dependencies of the chemotactic motion on the average background concentration and on the gradient steepness of the chemoattractant. In particular, both the background concentration and the gradient steepness can be kept constant at the position of the cell while it moves along in the gradient direction. This is achieved by generating a well-defined chemoattractant gradient using flow photolysis. In this approach, the chemoattractant is released by a light-induced reaction from a caged precursor in a microfluidic flow chamber upstream of the cell. The flow photolysis approach is combined with an automated real-time cell tracker that determines changes in the cell position and triggers movement of the microscope stage such that the cell motion is compensated and the cell remains at the same position in the gradient profile. The gradient profile can be either determined experimentally using a caged fluorescent dye or may be alternatively determined by numerical solutions of the corresponding physical model. To demonstrate the function of this adaptive microfluidic gradient generator, we compare the chemotactic motion of Dictyostelium discoideum cells in a static gradient and in a gradient that adapts to the position of the moving cell.

  7. Stable convergence and stable limit theorems

    CERN Document Server

    Häusler, Erich

    2015-01-01

    The authors present a concise but complete exposition of the mathematical theory of stable convergence and give various applications in different areas of probability theory and mathematical statistics to illustrate the usefulness of this concept. Stable convergence holds in many limit theorems of probability theory and statistics – such as the classical central limit theorem – which are usually formulated in terms of convergence in distribution. Originated by Alfred Rényi, the notion of stable convergence is stronger than the classical weak convergence of probability measures. A variety of methods is described which can be used to establish this stronger stable convergence in many limit theorems which were originally formulated only in terms of weak convergence. Naturally, these stronger limit theorems have new and stronger consequences which should not be missed by neglecting the notion of stable convergence. The presentation will be accessible to researchers and advanced students at the master's level...

  8. Density-dependent adaptive resistance allows swimming bacteria to colonize an antibiotic gradient

    NARCIS (Netherlands)

    Hol, F.J.H.; Hubert, A.W.R.; Dekker, C.; Keymer Vergara, J.E.

    2016-01-01

    During antibiotic treatment, antibiotic concentration gradients develop. Little is know regarding the effects of antibiotic gradients on populations of nonresistant bacteria. Using a microfluidic device, we show that high-density motile Escherichia coli populations composed of nonresistant

  9. Sodium setpoint and gradient in bicarbonate hemodialysis.

    Science.gov (United States)

    Basile, Carlo; Libutti, Pasquale; Lisi, Piero; Vernaglione, Luigi; Casucci, Francesco; Losurdo, Nicola; Teutonico, Annalisa; Lomonte, Carlo

    2013-01-01

    The demonstration of an individual osmolar setpoint in hemodialysis (HD) is crucial to individualize dialysate sodium concentrations. Furthermore, the diffusive gradient between plasma and dialysate sodium is important in the "fine tuning" of the intradialytic sodium mass balance (MB). The design of this study included part A: a retrospective analysis of predialysis plasma sodium concentrations extracted from a 6-year database in our HD population (147 prevalent white anuric patients); and part B: study of intradialytic sodium kinetics in 48 patients undergoing one 4-hour bicarbonate HD session. Direct potentiometry with an ion-selective electrode was used for sodium measurements. Study part A: the mean number of plasma sodium measurements per patient was 16.06 ± 14.03 over a mean follow-up of 3.55 ± 1.76 years. The mean of the averaged plasma sodium concentrations was 136.7 ± 2.1 mmol/L, with a low mean intraindividual coefficient of variation (1.39 ± 0.4). Study part B: mean predialysis and postdialysis plasma sodium concentrations were 135.8 ± 0.9 and 138.0 ± 0.9 mmol/L (p<0.001). Mean inlet dialyzer sodium concentration was 138.7 ± 1.1 mmol/L; the hourly diffusion concentration gradients showed a statistically significant transfer from dialysate to plasma (Wilks ? <0.0001). A statistically significant relationship was found between sodium MB and diffusion gradient (p<0.02), and between sodium MB and ultrafiltration volume (p<0.01). A relatively "fixed" and individual osmolar setpoint in HD patients was shown for the first time in a long-term follow-up. A dialysate sodium concentration of 140 mmol/L determined a dialysate to plasma sodium gradient.

  10. Gradient computation for VTI acoustic wavefield tomography

    KAUST Repository

    Li, Vladimir

    2016-09-06

    Wavefield tomography can handle complex subsurface geology better than ray-based techniques and, ultimately, provide a higher resolution. Here, we implement forward and adjoint wavefield extrapolation for VTI (transversely isotropic with a vertical symmetry axis) media using a pseudospectral operator that employes a separable approximation of the P-wave dispersion relation. This operator is employed to derive the gradients of the differential semblance optimization (DSO) and modified stack-power objective functions. We also obtain the gradient expressions for the data-domain objective function, which can incorporate borehole information necessary for stable VTI velocity analysis. These gradients are compared to the ones obtained with a space-time finite-difference (FD) scheme for a system of coupled wave equations. Whereas the kernels computed with the two wave-equation operators are similar, the pseudospectral method is not hampered by the imprint of the shear-wave artifact. Numerical examples also show that the modified stack-power objective function produces cleaner gradients than the more conventional DSO operator.

  11. Colloidal attraction induced by a temperature gradient.

    Science.gov (United States)

    Di Leonardo, R; Ianni, F; Ruocco, G

    2009-04-21

    Colloidal crystals are of extreme importance for applied research and for fundamental studies in statistical mechanics. Long-range attractive interactions, such as capillary forces, can drive the spontaneous assembly of such mesoscopic ordered structures. However, long-range attractive forces are very rare in the colloidal realm. Here we report a novel strong, long-ranged attraction induced by a thermal gradient in the presence of a wall. By switching the thermal gradient on and off, we can rapidly and reversibly form stable hexagonal 2D crystals. We show that the observed attraction is hydrodynamic in nature and arises from thermally induced slip flow on particle surfaces. We used optical tweezers to measure the force law directly and compare it to an analytical prediction based on Stokes flow driven by Marangoni-like forces.

  12. stableGP

    Data.gov (United States)

    National Aeronautics and Space Administration — The code in the stableGP package implements Gaussian process calculations using efficient and numerically stable algorithms. Description of the algorithms is in the...

  13. Temperature-gradient-induced

    Science.gov (United States)

    Park, Cheol; Glaser, Matt; Maclennan, Joe; Clark, Noel; Trittel, Torsten; Stannarius, Ralf

    Freely-suspended smectic films of sub-micrometer thickness and lateral extensions of several millimeters were used to study thermally driven migration and convection in the film plane. Film experiments were performed during the 6 minute microgravity phase of a TEXUS suborbital rocket flight (Texus 52, launched April 27, 2015). We have found an attraction of the smectic material towards the cold edge of the film in a temperature gradient, similar to the Soret effect. This process is reversed when this edge is heated up again. Thermal convection driven by two thermocontacts in the film is practically absent, even at temperature gradients up to 10 K/mm, with thermally driven convection only setting in when the hot post reaches the transition temperature to the nematic phase. The Observation and Analysis of Smectic Islands in Space (OASIS) flight hardware was launched on SpaceX-6 in April 2015 and experiments on smectic bubbles were carried out on the International Space Station using four different smectic A and C liquid crystal materials in separate sample chambers. We observed that smectic islands on the surface of the bubbles migrated towards the colder part of the bubble in a temperature gradient. This work was supported by NASA Grant No. NNX-13AQ81G, by the Soft Materials Research Center under NSF MRSEC Grants No. DMR-0820579 and No. DMR-1420736, and by DLR Grants 50WM1127 and 50WM1430.

  14. Nort-South gradients in plasma concentrations of B-vitamins and other components of one-carbon metabolism in Western Europe: results from the European Prospective Investigation into Cancer and Nutrition (EPIC) Study

    NARCIS (Netherlands)

    Eussen, S.J.P.M.; Nilsen, R.M.; Midttun, O.; Hustad, S.; IJssenagger, N.; Meyer, K.; Fredriksen, A.; Ulvik, A.; Ueland, P.M.; Brennan, P.; Johansson, M.; Bueno-de-Mesquita, B.; Vineis, P.; Chuang, S.C.; Boutron-Ruault, M.C.; Dossus, L.; Perquier, F.; Overvad, K.; Teucher, B.; Grote, V.A.; Trichopoulou, A.; Adarakis, G.; Plada, M.; Sieri, S.; Tumino, R.; Santucci de Magistris, M.; Ros, M.M.; Peeters, P.H.M.; Redondo, M.L.; Zamora-Ros, R.; Chirlaque, M.D.; Ardanaz, E.; Sonestedt, E.; Ericson, U.; Schneede, J.; Guelpen, B.; Wark, P.A.; Gallo, V.; Norat, T.; Riboli, E.; Vollset, S.E.

    2013-01-01

    Different lifestyle patterns across Europe may influence plasma concentrations of B-vitamins and one-carbon metabolites and their relation to chronic disease. Comparison of published data on one-carbon metabolites in Western European regions is difficult due to differences in sampling procedures and

  15. North-south gradients in plasma concentrations of B-vitamins and other components of one-carbon metabolism in Western Europe: results from the European Prospective Investigation into Cancer and Nutrition (EPIC) Study

    NARCIS (Netherlands)

    Eussen, S.J.; Nilsen, R.M.; Midttun, O.; Hustad, S.; N, I.J.; Meyer, K.; Fredriksen, A.; Ulvik, A.; Ueland, P.M.; Brennan, P.; Johansson, M.; Bueno-de-Mesquita, B.; Vineis, P.; Chuang, S.C.; Boutron-Ruault, M.C.; Dossus, L.; Perquier, F.; Overvad, K.; Teucher, B.; Grote, V.A.; Trichopoulou, A.; Adarakis, G.; Plada, M.; Sieri, S.; Tumino, R.; Magistris, M.S. de; Ros, M.M.; Peeters, P.H.M.; Redondo, M.L.; Zamora-Ros, R.; Chirlaque, M.D.; Ardanaz, E.; Sonestedt, E.; Ericson, U.; Schneede, J.; Guelpen, B. van; Wark, P.A.; Gallo, V.; Norat, T.; Riboli, E.; Vollset, S.E.

    2013-01-01

    Different lifestyle patterns across Europe may influence plasma concentrations of B-vitamins and one-carbon metabolites and their relation to chronic disease. Comparison of published data on one-carbon metabolites in Western European regions is difficult due to differences in sampling procedures and

  16. The Galactic metallicity gradient

    Science.gov (United States)

    Rolleston, W. R. J.; Smartt, S. J.; Dufton, P. L.; Ryans, R. S. I.

    2000-11-01

    We have previously published intermediate to high resolution spectroscopic observations of approximately 80 early B-type main-sequence stars situated in 19 Galactic open clusters/associations with Galactocentric distances distributed over 6Twarog et al. \\cite{twa97}). However, there is no evidence to suggest that our data would be better fitted with a two-zone model. Moreover, we observe a N/O gradient of -0.04+/-0.02 dex kpc-1 which is consistent with that found for other spiral galaxies (Vila-Costas & Edmunds \\cite{vil93}).

  17. [Translaminar Gradient and Glaucoma].

    Science.gov (United States)

    Čmelo, J

    2017-01-01

    The cribriform plate is a threshold of the intraocular pressure (VOT) and of the intracranial pressure (IKT). The difference between the VOT and IKT is referred to as translaminar gradient (TLG). The goal was to evaluate the Glaucoma progression (visual field, fundus examination, HRT) with / without topical anti-glaucomatous therapy) in relation to the TLG. the significance of TLG has been studied in two groups. I. Group: 57 patients diagnosed and treatment of Primary Open-Angle Glaucoma (PGOU), 10 patients with Ocular hypertension (OH), 7 patients with Normal-Tension Glaucoma (NTG), and 75 healthy without glaucoma. The examinations of TLG were carried out once and retrospectively. In II. group there were prospectively studied 14 patients with OH and 24 patients with newly detected PGOU without local therapy. The examinations were performed 4 times at intervals of 10 to 11 months. All tests included a basic eye examination, ORA tonometry, HRT examination, gonioscopy, Color Doppler sonography of blood vessels of the eye and orbit. Venous pulsation pressure (VPT) has been recorded by the Ophthalmodynamometer Meditron (D-ODM). In case of spontaneous retinal venous pulsation, VPT was considered as the same pressure as the VOT. The TLG was calculated with formula of Querfurth: ICT = 0.29 + 0.74 (VOT / PI (AO)). [PI(AO) - Pulsatility index of the Ophthalmic artery (AO)]. I. group: TLG was in the control group without Glaucoma: 12.2 ± 2.0 torr. The NTG group: 9.0 ± 1.70 mm Hg. PGOU: 11.1 ± 1.91 mm Hg. OH: 12.6 ± 0.85 mm Hg. IKT alone does not show a significant relationship to the presence of glaucoma, ocular hypertension. II. Group: The average TLG in Ocular Hypertension (14 patients) has been 3.8 ± 1.2 torr. 2 patients (OH) had TLG 10 torr. and 15 torr. After 4 years in one of them (TLG = 15 torr.) there was recorded Glaucoma progression. In the PGOU group before antiglaucoma therapy, TLG was 15.0 ± 4.8 torr for all patients. After setting up local anti

  18. Potential use of gradient denaturing gel electrophoresis in obtaining mutational spectra from human cells

    International Nuclear Information System (INIS)

    Thilly, W.G.

    1985-01-01

    A method is described to isolate mutations in DNA in human cells. When a double-stranded DNA migrates through an electric field on an electrophoretic gel, it is compact hydrodynamic structure relative to the same material in a melted form. Normally the solution in electrophoretic gels is uniform, but a way has been devised to set up a stable gradient of increasing solute concentration in the direction of DNA motion. Thus, as a double-stranded DNA molecule is drawn by the electric field into higher and higher concentrations of urea/formamide, it will eventually reach a point at which the concentration is high enough to melt the lower-melting-point region. The melting results in an essentially immobile structure within the gel so that the position at which the DNA molecule stops on the gradient gel is determined by its melting point, which is uniquely determined by its nucleotide sequence. A single base pair substitution within a low melting point sequence of some 100 base pairs changed the expected melting point by 0.4 0 C and resulted in about a 2-cm displacement under appropriate denaturing gel conditions. This expectation leads to the idea that if a mixture of DNA sequences derived from point mutations within the same restriction fragment were permitted to anneal with a complementary wild-type sequence, the melting point of each type of heteroduplex would differ depending on the kind and position of each mutation

  19. Evaluation of Thermal Stability of RNA Nanoparticles by Temperature Gradient Gel Electrophoresis (TGGE) in Native Condition.

    Science.gov (United States)

    Benkato, Kheiria; O'Brien, Benjamin; Bui, My N; Jasinski, Daniel L; Guo, Peixuan; Khisamutdinov, Emil F

    2017-01-01

    Temperature gradient gel electrophoresis (TGGE) is a powerful tool used to analyze the thermal stabilities of nucleic acids. While TGGE is a decades-old technique, it has recently gained favor in the field of RNA nanotechnology, notably in assessing the thermal stabilities of RNA nanoparticles (NPs). With TGGE, an electrical current and a linear temperature gradient are applied simultaneously to NP-loaded polyacrylamide gel, separating the negatively charged NPs based on their thermal behavior (a more stable RNA complex will remain intact through higher temperature ranges). The linear temperature gradient can be set either perpendicular or parallel to the electrical current, as either will make the NPs undergo a transition from native to denatured conformations. Often, the melting transition is influenced by sequence variations, secondary/tertiary structures, concentrations, and external factors such as the presence of a denaturing agent (e.g., urea), the presence of monovalent or divalent metal ions, and the pH of the solvent. In this chapter, we describe the experimental setup and the analysis of the thermal stability of RNA NPs in native conditions using a modified version of a commercially available TGGE system.

  20. Quantitation of 4-Methyl-4-sulfanylpentan-2-one (4MSP) in Hops by a Stable Isotope Dilution Assay in Combination with GC×GC-TOFMS: Method Development and Application To Study the Influence of Variety, Provenance, Harvest Year, and Processing on 4MSP Concentrations.

    Science.gov (United States)

    Reglitz, Klaas; Steinhaus, Martin

    2017-03-22

    A stable isotope dilution assay was developed for quantitation of 4-methyl-4-sulfanylpentan-2-one (4MSP) in hops. The approach included the use of 4-( 13 C)methyl-4-sulfanyl(1,3,5- 13 C 3 )pentan-2-one as internal standard, selective isolation of hop thiols by mercurated agarose, and GC×GC-TOFMS analysis. Application of the method to 53 different hop samples revealed 4MSP concentrations between Hop processing such as drying and pelletizing had only a minor impact on 4MSP concentrations. Like the majority of other hop volatiles, 4MSP is predominantly located in the lupulin glands.

  1. Transport of nanoparticles in a temperature gradient

    Science.gov (United States)

    Putnam, Shawn; Cahill, David

    2006-03-01

    Thermodiffusion, mass transport in a temperature gradient, is commonly characterized by either the thermodiffusion coefficient DT or the Soret coefficient ST; e.g., at low particle concentration c, the particle flux of a colloidal suspension subjected to a temperature gradient ∇T is J=- cDT∇T-Dc∇c, where Dc is the diffusion coefficient and the Soret coefficient is ST= DT/Dc. We present our measured DT data for aqueous suspensions of charged polystyrene spheres, alumina nanoparticles, and globular proteins of lysozyme. Special emphasis is given to our published work on charged polystyrene spheres with different surface functionalities. For example, in solutions with large concentrations of monovalent salts, 100 mM, DT for 26 nm spheres with carboxyl functionality can be varied within the range -0.9 x10^- 7 cm^2 s-1 K-1 protein solutions of lysozyme.

  2. Relationships among Mercury Concentration, and Stable Isotope Ratios of Carbon and Nitrogen in the Scalp Hair of Residents from Seven Countries: Effects of Marine Fish and C4 Plants Consumption

    OpenAIRE

    Endo, Tetsuya; Hayasaka, Moriaki; Ogasawra, Hideki; Kimura, Osamu; Kotaki, Yuichi; Haraguchi, Koichi

    2015-01-01

    We analyzed the Hg concentration, and δ¹³C and δ¹⁵N values in the scalp hair of residents from seven countries; Vietnam, New Zealand, Spain, the USA, South Korea, Brazil and Japan. Relationships among the data in each country and among the seven countries were then examined. The highest Hg concentration as well as the highest or higher δ¹⁵N value in each country was found in the hair of a heavy marine fish-eater, whereas the lowest Hg concentration and δ¹⁵N value were found in the hair of a v...

  3. Comparison of Metabolite Concentrations in the Left Dorsolateral Prefrontal Cortex, the Left Frontal White Matter, and the Left Hippocampus in Patients in Stable Schizophrenia Treated with Antipsychotics with or without Antidepressants. ¹H-NMR Spectroscopy Study.

    Science.gov (United States)

    Strzelecki, Dominik; Grzelak, Piotr; Podgórski, Michał; Kałużyńska, Olga; Stefańczyk, Ludomir; Kotlicka-Antczak, Magdalena; Gmitrowicz, Agnieszka

    2015-10-15

    Managing affective, negative, and cognitive symptoms remains the most difficult therapeutic problem in stable phase of schizophrenia. Efforts include administration of antidepressants. Drugs effects on brain metabolic parameters can be evaluated by means of proton nuclear magnetic resonance (¹H-NMR) spectroscopy. We compared spectroscopic parameters in the left prefrontal cortex (DLPFC), the left frontal white matter (WM) and the left hippocampus and assessed the relationship between treatment and the spectroscopic parameters in both groups. We recruited 25 patients diagnosed with schizophrenia (DSM-IV-TR), with dominant negative symptoms and in stable clinical condition, who were treated with antipsychotic and antidepressive medication for minimum of three months. A group of 25 patients with schizophrenia, who were taking antipsychotic drugs but not antidepressants, was matched. We compared metabolic parameters (N-acetylaspartate (NAA), myo-inositol (mI), glutamatergic parameters (Glx), choline (Cho), and creatine (Cr)) between the two groups. All patients were also assessed with the Positive and Negative Syndrome Scale (PANSS) and the Calgary Depression Scale for Schizophrenia (CDSS). In patients receiving antidepressants we observed significantly higher NAA/Cr and NAA/Cho ratios within the DLPFC, as well as significantly higher mI/Cr within the frontal WM. Moreover, we noted significantly lower values of parameters associated with the glutamatergic transmission--Glx/Cr and Glx/Cho in the hippocampus. Doses of antipsychotic drugs in the group treated with antidepressants were also significantly lower in the patients showing similar severity of psychopathology.

  4. Comparison of Metabolite Concentrations in the Left Dorsolateral Prefrontal Cortex, the Left Frontal White Matter, and the Left Hippocampus in Patients in Stable Schizophrenia Treated with Antipsychotics with or without Antidepressants. 1H-NMR Spectroscopy Study

    Science.gov (United States)

    Strzelecki, Dominik; Grzelak, Piotr; Podgórski, Michał; Kałużyńska, Olga; Stefańczyk, Ludomir; Kotlicka-Antczak, Magdalena; Gmitrowicz, Agnieszka

    2015-01-01

    Managing affective, negative, and cognitive symptoms remains the most difficult therapeutic problem in stable phase of schizophrenia. Efforts include administration of antidepressants. Drugs effects on brain metabolic parameters can be evaluated by means of proton nuclear magnetic resonance (1H-NMR) spectroscopy. We compared spectroscopic parameters in the left prefrontal cortex (DLPFC), the left frontal white matter (WM) and the left hippocampus and assessed the relationship between treatment and the spectroscopic parameters in both groups. We recruited 25 patients diagnosed with schizophrenia (DSM-IV-TR), with dominant negative symptoms and in stable clinical condition, who were treated with antipsychotic and antidepressive medication for minimum of three months. A group of 25 patients with schizophrenia, who were taking antipsychotic drugs but not antidepressants, was matched. We compared metabolic parameters (N-acetylaspartate (NAA), myo-inositol (mI), glutamatergic parameters (Glx), choline (Cho), and creatine (Cr)) between the two groups. All patients were also assessed with the Positive and Negative Syndrome Scale (PANSS) and the Calgary Depression Scale for Schizophrenia (CDSS). In patients receiving antidepressants we observed significantly higher NAA/Cr and NAA/Cho ratios within the DLPFC, as well as significantly higher mI/Cr within the frontal WM. Moreover, we noted significantly lower values of parameters associated with the glutamatergic transmission—Glx/Cr and Glx/Cho in the hippocampus. Doses of antipsychotic drugs in the group treated with antidepressants were also significantly lower in the patients showing similar severity of psychopathology. PMID:26501256

  5. Generalized conjugate gradient squared

    Energy Technology Data Exchange (ETDEWEB)

    Fokkema, D.R.; Sleijpen, G.L.G. [Utrecht Univ. (Netherlands)

    1994-12-31

    In order to solve non-symmetric linear systems of equations, the Conjugate Gradient Squared (CGS) is a well-known and widely used iterative method. In practice the method converges fast, often twice as fast as the Bi-Conjugate Gradient method. This is what you may expect, since CGS uses the square of the BiCG polynomial. However, CGS may suffer from its erratic convergence behavior. The method may diverge or the approximate solution may be inaccurate. BiCGSTAB uses the BiCG polynomial and a product of linear factors in an attempt to smoothen the convergence. In many cases, this has proven to be very effective. Unfortunately, the convergence of BiCGSTAB may stall when a linear factor (nearly) degenerates. BiCGstab({ell}) is designed to overcome this degeneration of linear factors. It generalizes BiCGSTAB and uses both the BiCG polynomial and a product of higher order factors. Still, CGS may converge faster than BiCGSTAB or BiCGstab({ell}). So instead of using a product of linear or higher order factors, it may be worthwhile to look for other polynomials. Since the BiCG polynomial is based on a three term recursion, a natural choice would be a polynomial based on another three term recursion. Possibly, a suitable choice of recursion coefficients would result in method that converges faster or as fast as CGS, but less erratic. It turns out that an algorithm for such a method can easily be formulated. One particular choice for the recursion coefficients leads to CGS. Therefore one could call this algorithm generalized CGS. Another choice for the recursion coefficients leads to BiCGSTAB. It is therefore possible to mix linear factors and some polynomial based on a three term recursion. This way one may get the best of both worlds. The authors will report on their findings.

  6. Stable isotopes labelled compounds

    International Nuclear Information System (INIS)

    1982-09-01

    The catalogue on stable isotopes labelled compounds offers deuterium, nitrogen-15, and multiply labelled compounds. It includes: (1) conditions of sale and delivery, (2) the application of stable isotopes, (3) technical information, (4) product specifications, and (5) the complete delivery programme

  7. Stable Boundary Layer Issues

    NARCIS (Netherlands)

    Steeneveld, G.J.

    2012-01-01

    Understanding and prediction of the stable atmospheric boundary layer is a challenging task. Many physical processes are relevant in the stable boundary layer, i.e. turbulence, radiation, land surface coupling, orographic turbulent and gravity wave drag, and land surface heterogeneity. The

  8. Evolutionary Stable Strategy

    Indian Academy of Sciences (India)

    IAS Admin

    After Maynard-Smith and Price [1] mathematically derived why a given behaviour or strategy was adopted by a certain proportion of the population at a given time, it was shown that a strategy which is currently stable in a population need not be stable in evolutionary time (across generations). Additionally it was sug-.

  9. Relationships among Mercury Concentration, and Stable Isotope Ratios of Carbon and Nitrogen in the Scalp Hair of Residents from Seven Countries: Effects of Marine Fish and C4 Plants Consumption.

    Directory of Open Access Journals (Sweden)

    Tetsuya Endo

    Full Text Available We analyzed the Hg concentration, and δ¹³C and δ¹⁵N values in the scalp hair of residents from seven countries; Vietnam, New Zealand, Spain, the USA, South Korea, Brazil and Japan. Relationships among the data in each country and among the seven countries were then examined. The highest Hg concentration as well as the highest or higher δ¹⁵N value in each country was found in the hair of a heavy marine fish-eater, whereas the lowest Hg concentration and δ¹⁵N value were found in the hair of a vegetarian or non (marginal-fish eater. Hg concentrations were positively correlated with the δ¹⁵N values in each country, and increased markedly in samples with δ¹⁵N values exceeding 9.0 ‰, probably due to fish consumption. The highest Hg concentration could be found in sample, with a δ¹³C value between -19 and -18‰, probably reflecting the δ¹³C value of the marine food web.

  10. Relationships among Mercury Concentration, and Stable Isotope Ratios of Carbon and Nitrogen in the Scalp Hair of Residents from Seven Countries: Effects of Marine Fish and C4 Plants Consumption.

    Science.gov (United States)

    Endo, Tetsuya; Hayasaka, Moriaki; Ogasawra, Hideki; Kimura, Osamu; Kotaki, Yuichi; Haraguchi, Koichi

    2015-01-01

    We analyzed the Hg concentration, and δ¹³C and δ¹⁵N values in the scalp hair of residents from seven countries; Vietnam, New Zealand, Spain, the USA, South Korea, Brazil and Japan. Relationships among the data in each country and among the seven countries were then examined. The highest Hg concentration as well as the highest or higher δ¹⁵N value in each country was found in the hair of a heavy marine fish-eater, whereas the lowest Hg concentration and δ¹⁵N value were found in the hair of a vegetarian or non (marginal)-fish eater. Hg concentrations were positively correlated with the δ¹⁵N values in each country, and increased markedly in samples with δ¹⁵N values exceeding 9.0 ‰, probably due to fish consumption. The highest Hg concentration could be found in sample, with a δ¹³C value between -19 and -18‰, probably reflecting the δ¹³C value of the marine food web.

  11. Gradient Boosting Machines, A Tutorial

    Directory of Open Access Journals (Sweden)

    Alexey eNatekin

    2013-12-01

    Full Text Available Gradient boosting machines are a family of powerful machine-learning techniques that have shown considerable success in a wide range of practical applications. They are highly customizable to the particular needs of the application, like being learned with respect to different loss functions. This article gives a tutorial introduction into the methodology of gradient boosting methods. A theoretical information is complemented with many descriptive examples and illustrations which cover all the stages of the gradient boosting model design. Considerations on handling the model complexity are discussed. A set of practical examples of gradient boosting applications are presented and comprehensively analyzed.

  12. Biochemical and Spectroscopic Characterization of Highly Stable Photosystem II Supercomplexes from Arabidopsis.

    Science.gov (United States)

    Crepin, Aurelie; Santabarbara, Stefano; Caffarri, Stefano

    2016-09-02

    Photosystem II (PSII) is a large membrane supercomplex involved in the first step of oxygenic photosynthesis. It is organized as a dimer, with each monomer consisting of more than 20 subunits as well as several cofactors, including chlorophyll and carotenoid pigments, lipids, and ions. The isolation of stable and homogeneous PSII supercomplexes from plants has been a hindrance for their deep structural and functional characterization. In recent years, purification of complexes with different antenna sizes was achieved with mild detergent solubilization of photosynthetic membranes and fractionation on a sucrose gradient, but these preparations were only stable in the cold for a few hours. In this work, we present an improved protocol to obtain plant PSII supercomplexes that are stable for several hours/days at a wide range of temperatures and can be concentrated without degradation. Biochemical and spectroscopic properties of the purified PSII are presented, as well as a study of the complex solubility in the presence of salts. We also tested the impact of a large panel of detergents on PSII stability and found that very few are able to maintain the integrity of PSII. Such new PSII preparation opens the possibility of performing experiments that require room temperature conditions and/or high protein concentrations, and thus it will allow more detailed investigations into the structure and molecular mechanisms that underlie plant PSII function. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  13. Normal modified stable processes

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole Eiler; Shephard, N.

    2002-01-01

    This paper discusses two classes of distributions, and stochastic processes derived from them: modified stable (MS) laws and normal modified stable (NMS) laws. This extends corresponding results for the generalised inverse Gaussian (GIG) and generalised hyperbolic (GH) or normal generalised inverse...... Gaussian (NGIG) laws. The wider framework thus established provides, in particular, for added flexibility in the modelling of the dynamics of financial time series, of importance especially as regards OU based stochastic volatility models for equities. In the special case of the tempered stable OU process...

  14. Applications of stable isotopes

    International Nuclear Information System (INIS)

    Letolle, R.; Mariotti, A.; Bariac, T.

    1991-06-01

    This report reviews the historical background and the properties of stable isotopes, the methods used for their measurement (mass spectrometry and others), the present technics for isotope enrichment and separation, and at last the various present and foreseeable application (in nuclear energy, physical and chemical research, materials industry and research; tracing in industrial, medical and agronomical tests; the use of natural isotope variations for environmental studies, agronomy, natural resources appraising: water, minerals, energy). Some new possibilities in the use of stable isotope are offered. A last chapter gives the present state and forecast development of stable isotope uses in France and Europe

  15. Denaturing gradient gel electrophoresis

    International Nuclear Information System (INIS)

    Kocherginskaya, S.A.; Cann, I.K.O.; Mackie, R.I.

    2005-01-01

    It is worthwhile considering that only some 30 species make up the bulk of the bacterial population in human faeces at any one time based on the classical cultivation-based approach. The situation in the rumen is similar. Thus, it is practical to focus on specific groups of interest within the complex community. These may be the predominant or the most active species, specific physiological groups or readily identifiable (genetic) clusters of phylogenetically related organisms. Several 16S rDNA fingerprinting techniques can be invaluable for selecting and monitoring sequences or phylogenetic groups of interest and are described below. Over the past few decades, considerable attention was focussed on the identification of pure cultures of microbes on the basis of genetic polymorphisms of DNA encoding rRNA such as ribotyping, amplified fragment length polymorphism and randomly amplified polymorphic DNA. However, many of these methods require prior cultivation and are less suitable for use in analysis of complex mixed populations although important in describing cultivated microbial diversity in molecular terms. Much less attention was given to molecular characterization of complex communities. In particular, research into diversity and community structure over time has been revolutionized by the advent of molecular fingerprinting techniques for complex communities. Denaturing or temperature gradient gel electrophoresis (DGGE/TGGE) methods have been successfully applied to the analysis of human, pig, cattle, dog and rodent intestinal populations

  16. Color Gradient in the King Type Globular Cluster NGC 7089

    Directory of Open Access Journals (Sweden)

    Young-Jong Sohn

    1999-12-01

    Full Text Available We use BV CCD images to investigate the reality of the color gradient within a King type globular cluster NGC 7089. Surface photometry shows that there is a strong radial color gradient in the central region of the cluster in the sense of bluer center with the amplitude of -0.39 +/- 0.07 mag/arcsec2 in (B - V. In the outer region of the cluster, however, the radial color gradient shows a reverse case, i.e., redder toward the center. (B - V color profile which was derived from resolved stars in VGC 7089 field also shows a significant color gradient in the central region of the clusters, indicating that lights from the combination of red giant stars and blue horizontal branch stars cause the radial color gradient. Color gradient of the outer region of NGC 7089 may be due to the unresolved background of the cluster. Similar color gradients in the central area of clusters have been previously observed exserved exclusively in highly concentrated systems classified as post core collapse clusters. We caution, however, to confirm the reality of the color gradient from resolved stars, we need more accurate imaging data of the cluster with exceptional seeing condition because the effect of completeness correlates with local density of stars.

  17. Characterization of gradient control systems

    NARCIS (Netherlands)

    Cortés, Jorge; van der Schaft, Arjan; Crouch, Peter E.

    2005-01-01

    Given a general nonlinear affine control system with outputs and a torsion-free affine connection defined on its state space, we investigate the gradient realization problem: we give necessary and sufficient conditions under which the control system can be written as a gradient control system

  18. Sobolev gradients and differential equations

    CERN Document Server

    Neuberger, J W

    2010-01-01

    A Sobolev gradient of a real-valued functional on a Hilbert space is a gradient of that functional taken relative to an underlying Sobolev norm. This book shows how descent methods using such gradients allow a unified treatment of a wide variety of problems in differential equations. For discrete versions of partial differential equations, corresponding Sobolev gradients are seen to be vastly more efficient than ordinary gradients. In fact, descent methods with these gradients generally scale linearly with the number of grid points, in sharp contrast with the use of ordinary gradients. Aside from the first edition of this work, this is the only known account of Sobolev gradients in book form. Most of the applications in this book have emerged since the first edition was published some twelve years ago. What remains of the first edition has been extensively revised. There are a number of plots of results from calculations and a sample MatLab code is included for a simple problem. Those working through a fair p...

  19. Rainbow refractometry on particles with radial refractive index gradients

    Energy Technology Data Exchange (ETDEWEB)

    Saengkaew, Sawitree [CNRS/Universite et INSA de Rouen, UMR 6614/CORIA, BP12, 76 800, Saint Etienne du Rouvray CEDEX (France); Chulalongkorn University, Center of Excellence in Particle Technology, Faculty of Engineering, Bangkok (Thailand); Charinpanitkul, Tawatchai; Vanisri, Hathaichanok; Tanthapanichakoon, Wiwut [Chulalongkorn University, Center of Excellence in Particle Technology, Faculty of Engineering, Bangkok (Thailand); Biscos, Yves; Garcia, Nicolas; Lavergne, Gerard [ONERA/DMAE, Toulouse (France); Mees, Loic; Gouesbet, Gerard; Grehan, Gerard [CNRS/Universite et INSA de Rouen, UMR 6614/CORIA, BP12, 76 800, Saint Etienne du Rouvray CEDEX (France)

    2007-10-15

    The rainbow refractrometry, under its different configurations (classical and global), is an attractive technique to extract information from droplets in evaporation such as diameter and temperature. Recently a new processing strategy has been developed which increases dramatically the size and refractive index measurements accuracy for homogeneous droplets. Nevertheless, for mono component as well as for multicomponent droplets, the presence of temperature and/or of concentration gradients induce the presence of a gradient of refractive index which affects the interpretation of the recorded signals. In this publication, the effect of radial gradient on rainbow measurements with a high accuracy never reached previously is quantified. (orig.)

  20. Development and characterization of 430L matrix composites gradient materials

    Directory of Open Access Journals (Sweden)

    Elisa Maria Ruiz-Navas

    2005-03-01

    Full Text Available This paper deals with a new concept that is Functionally Gradient Materials (FGM. The materials developed in this work are constituted by a 430L matrix core and composite materials with this matrix and gradient concentration with NbC reinforcement, from the core to the surface, through different steps. Composite powders of different content in NbC were produced through high energy milling in order to obtain the gradient composition. The morphology and microhardness of these powders were characterised and subsequently were processed through conventional P/M techniques, pressing and sintering. The materials obtained show improved wear behaviour.

  1. The geomagnetic field gradient tensor

    DEFF Research Database (Denmark)

    Kotsiaros, Stavros; Olsen, Nils

    2012-01-01

    We develop the general mathematical basis for space magnetic gradiometry in spherical coordinates. The magnetic gradient tensor is a second rank tensor consisting of 3 × 3 = 9 spatial derivatives. Since the geomagnetic field vector B is always solenoidal (∇ · B = 0) there are only eight independent...... tensor elements. Furthermore, in current free regions the magnetic gradient tensor becomes symmetric, further reducing the number of independent elements to five. In that case B is a Laplacian potential field and the gradient tensor can be expressed in series of spherical harmonics. We present properties...... of the magnetic gradient tensor and provide explicit expressions of its elements in terms of spherical harmonics. Finally we discuss the benefit of using gradient measurements for exploring the Earth’s magnetic field from space, in particular the advantage of the various tensor elements for a better determination...

  2. Analysing Stable Time Series

    National Research Council Canada - National Science Library

    Adler, Robert

    1997-01-01

    We describe how to take a stable, ARMA, time series through the various stages of model identification, parameter estimation, and diagnostic checking, and accompany the discussion with a goodly number...

  3. Investigation of the stress distribution around a mode 1 crack with a novel strain gradient theory

    Science.gov (United States)

    Lederer, M.; Khatibi, G.

    2017-01-01

    Stress concentrations at the tip of a sharp crack have extensively been investigated in the past century. According to the calculations of Inglis, the stress ahead of a mode 1 crack shows the characteristics of a singularity. This solution is exact in the framework of linear elastic fracture mechanics (LEFM). From the viewpoint of multiscale modelling, however, it is evident that the stress at the tip of a stable crack cannot be infinite, because the strengths of atomic bonds are finite. In order to prevent the problem of this singularity, a new version of strain gradient elasticity is employed here. This theory is implemented in the commercial FEM code ABAQUS through user subroutine UEL. Convergence of the model is proved through consecutive mesh refinement. In consequence, the stresses ahead of a mode 1 crack become finite. Furthermore, the model predicts a size effect in the sense “smaller is stronger”.

  4. Gradient zone boundary control in salt gradient solar ponds

    Energy Technology Data Exchange (ETDEWEB)

    Hull, John R. (Downers Grove, IL)

    1984-01-01

    A method and apparatus for suppressing zone boundary migration in a salt gradient solar pond includes extending perforated membranes across the pond at the boundaries, between the convective and non-convective zones, the perforations being small enough in size to prevent individual turbulence disturbances from penetrating the hole, but being large enough to allow easy molecular diffusion of salt thereby preventing the formation of convective zones in the gradient layer. The total area of the perforations is a sizable fraction of the membrane area to allow sufficient salt diffusion while preventing turbulent entrainment into the gradient zone.

  5. Gross nitrous oxide production and consumption along a salt marsh redox gradient

    Science.gov (United States)

    Yang, W. H.; Silver, W. L.

    2012-12-01

    Coastal wetlands denitrify nitrate (NO3-)-rich urban and agricultural runoff, and thus decrease anthropogenic nitrogen loading on downslope aquatic ecosystems. Elevation gradients in coastal wetlands likely create redox gradients that result in a range of denitrification dynamics. Our objective was to determine if this redox gradient could elucidate the controls on nitrous oxide (N2O) production and consumption in a salt marsh bordering Tomales Bay, CA. We installed soil equilibration chambers to measure soil oxygen (O2) at 10 cm depth along a transect in each of three marsh zones: high, mid, and low (n=4 per zone). We used the stable isotope trace gas pool dilution technique to measure gross rates of N2O production and consumption over three hour sampling periods at low tide when the surface soils were not saturated. Intact soil cores (0-10 cm depth) taken from the flux chamber footprints were extracted for ammonium, NO3-, and ferric and ferrous iron (Fe(III) and Fe(II)) concentrations as well as assayed for denitrifying enzyme activity (DEA). We sampled on four dates to characterize N2O dynamics across a range of environmental conditions. Bulk soil O2 concentrations in the soil equilibration chambers were higher in the high marsh than in the mid and low marshes (pconcentrations were significantly lower and HCl-extractable Fe(II) concentrations were significantly higher in the low marsh compared to the high and mid marshes (NO3- psalt marsh was neither an N2O source nor sink, with net N2O fluxes averaging 51 ± 40 μg-N m-2 d-1 across all marsh zones and sampling dates. However, net N2O fluxes were negative in 29 out of 44 measurements. Sub-atmospheric soil N2O concentrations at 10 cm depth together with the quantification of significant gross N2O consumption rates suggest that the net uptake of atmospheric N2O by the soil occurred in all marsh zones. Boxplots of (1) gross N2O production rates and (2) gross N2O consumption rates along a salt marsh elevation

  6. Effect of composition gradient on magnetothermal instability modified by shear and rotation

    Science.gov (United States)

    Gupta, Himanshu; Chaudhuri, Anya; Sadhukhan, Shubhadeep; Chakraborty, Sagar

    2018-02-01

    We model the intracluster medium as a weakly collisional plasma that is a binary mixture of the hydrogen and the helium ions, along with free electrons. When, owing to the helium sedimentation, the gradient of the mean-molecular weight (or equivalently, composition or helium ions' concentration) of the plasma is not negligible, it can have appreciable influence on the stability criteria of the thermal convective instabilities, e.g. the heat-flux-buoyancy instability and the magnetothermal instability (MTI). These instabilities are consequences of the anisotropic heat conduction occurring preferentially along the magnetic field lines. In this paper, without ignoring the magnetic tension, we first present the mathematical criterion for the onset of composition gradient modified MTI. Subsequently, we relax the commonly adopted equilibrium state in which the plasma is at rest, and assume that the plasma is in a sheared state which may be due to differential rotation. We discuss how the concentration gradient affects the coupling between the Kelvin-Helmholtz instability and the MTI in rendering the plasma unstable or stable. We derive exact stability criterion by working with the sharp boundary case in which the physical variables - temperature, mean-molecular weight, density and magnetic field - change discontinuously from one constant value to another on crossing the boundary. Finally, we perform the linear stability analysis for the case of the differentially rotating plasma that is thermally and compositionally stratified as well. By assuming axisymmetric perturbations, we find the corresponding dispersion relation and the explicit mathematical expression determining the onset of the modified MTI.

  7. The concentration gradient flow battery as electricity storage system

    NARCIS (Netherlands)

    Egmond, Van W.J.; Saakes, M.; Porada, S.; Meuwissen, T.; Buisman, C.J.N.; Hamelers, H.V.M.

    2016-01-01

    Unlike traditional fossil fuel plants, the wind and the sun provide power only when the renewable resource is available. To accommodate large scale use of renewable energy sources for efficient power production and utilization, energy storage systems are necessary. Here, we introduce a scalable

  8. High-k 3D-barium titanate foam/phenolphthalein poly(ether sulfone)/cyanate ester composites with frequency-stable dielectric properties and extremely low dielectric loss under reduced concentration of ceramics

    Science.gov (United States)

    Zheng, Longhui; Yuan, Li; Guan, Qingbao; Liang, Guozheng; Gu, Aijuan

    2018-01-01

    Higher dielectric constant, lower dielectric loss and better frequency stability have been the developing trends for high dielectric constant (high-k) materials. Herein, new composites have been developed through building unique structure by using hyperbranched polysiloxane modified 3D-barium titanate foam (BTF) (BTF@HSi) as the functional fillers and phenolphthalein poly(ether sulfone) (cPES)/cyanate ester (CE) blend as the resin matrix. For BTF@HSi/cPES/CE composite with 34.1 vol% BTF, its dielectric constant at 100 Hz is as high as 162 and dielectric loss is only 0.007; moreover, the dielectric properties of BTF@HSi/cPES/CE composites exhibit excellent frequency stability. To reveal the mechanism behind these attractive performances of BTF@HSi/cPES/CE composites, three kinds of composites (BTF/CE, BTF/cPES/CE, BTF@HSi/CE) were prepared, their structure and integrated performances were intensively investigated and compared with those of BTF@HSi/cPES/CE composites. Results show that the surface modification of BTF is good for preparing composites with improved thermal stability; while introducing flexible cPES to CE is beneficial to fabricate composites with good quality through effectively blocking cracks caused by the stress concentration, and then endowing the composites with good dielectric properties at reduced concentration of ceramics.

  9. Leaf water stable isotopes and water transport outside the xylem.

    Science.gov (United States)

    Barbour, M M; Farquhar, G D; Buckley, T N

    2017-06-01

    How water moves through leaves, and where the phase change from liquid to vapour occurs within leaves, remain largely mysterious. Some time ago, we suggested that the stable isotope composition of leaf water may contain information on transport pathways beyond the xylem, through differences in the development of gradients in enrichment within the various pathways. Subsequent testing of this suggestion provided ambiguous results and even questioned the existence of gradients in enrichment within the mesophyll. In this review, we bring together recent theoretical developments in understanding leaf water transport pathways and stable isotope theory to map a path for future work into understanding pathways of water transport and leaf water stable isotope composition. We emphasize the need for a spatially, anatomically and isotopically explicit model of leaf water transport. © 2016 John Wiley & Sons Ltd.

  10. Drift in Diffusion Gradients

    Directory of Open Access Journals (Sweden)

    Fabio Marchesoni

    2013-08-01

    Full Text Available The longstanding problem of Brownian transport in a heterogeneous quasi one-dimensional medium with space-dependent self-diffusion coefficient is addressed in the overdamped (zero mass limit. A satisfactory mesoscopic description is obtained in the Langevin equation formalism by introducing an appropriate drift term, which depends on the system macroscopic observables, namely the diffuser concentration and current. The drift term is related to the microscopic properties of the medium. The paradoxical existence of a finite drift at zero current suggests the possibility of designing a Maxwell demon operating between two equilibrium reservoirs at the same temperature.

  11. Calcium stable isotope geochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Gausonne, Nikolaus [Muenster Univ. (Germany). Inst. fuer Mineralogie; Schmitt, Anne-Desiree [Strasbourg Univ. (France). LHyGeS/EOST; Heuser, Alexander [Bonn Univ. (Germany). Steinmann-Inst. fuer Geologie, Mineralogie und Palaeontologie; Wombacher, Frank [Koeln Univ. (Germany). Inst. fuer Geologie und Mineralogie; Dietzel, Martin [Technische Univ. Graz (Austria). Inst. fuer Angewandte Geowissenschaften; Tipper, Edward [Cambridge Univ. (United Kingdom). Dept. of Earth Sciences; Schiller, Martin [Copenhagen Univ. (Denmark). Natural History Museum of Denmark

    2016-08-01

    This book provides an overview of the fundamentals and reference values for Ca stable isotope research, as well as current analytical methodologies including detailed instructions for sample preparation and isotope analysis. As such, it introduces readers to the different fields of application, including low-temperature mineral precipitation and biomineralisation, Earth surface processes and global cycling, high-temperature processes and cosmochemistry, and lastly human studies and biomedical applications. The current state of the art in these major areas is discussed, and open questions and possible future directions are identified. In terms of its depth and coverage, the current work extends and complements the previous reviews of Ca stable isotope geochemistry, addressing the needs of graduate students and advanced researchers who want to familiarize themselves with Ca stable isotope research.

  12. Modeling chemical gradients in sediments under losing and gaining flow conditions: The GRADIENT code

    Science.gov (United States)

    Boano, Fulvio; De Falco, Natalie; Arnon, Shai

    2018-02-01

    Interfaces between sediments and water bodies often represent biochemical hotspots for nutrient reactions and are characterized by steep concentration gradients of different reactive solutes. Vertical profiles of these concentrations are routinely collected to obtain information on nutrient dynamics, and simple codes have been developed to analyze these profiles and determine the magnitude and distribution of reaction rates within sediments. However, existing publicly available codes do not consider the potential contribution of water flow in the sediments to nutrient transport, and their applications to field sites with significant water-borne nutrient fluxes may lead to large errors in the estimated reaction rates. To fill this gap, the present work presents GRADIENT, a novel algorithm to evaluate distributions of reaction rates from observed concentration profiles. GRADIENT is a Matlab code that extends a previously published framework to include the role of nutrient advection, and provides robust estimates of reaction rates in sediments with significant water flow. This work discusses the theoretical basis of the method and shows its performance by comparing the results to a series of synthetic data and to laboratory experiments. The results clearly show that in systems with losing or gaining fluxes, the inclusion of such fluxes is critical for estimating local and overall reaction rates in sediments.

  13. Strain gradients in epitaxial ferroelectrics

    International Nuclear Information System (INIS)

    Catalan, G.; Noheda, B.; McAneney, J.; Sinnamon, L.J.; Gregg, J.M.

    2005-01-01

    X-ray analysis of ferroelectric thin layers of Ba 1/2 Sr 1/2 TiO 3 with different thicknesses reveals the presence of strain gradients across the films and allows us to propose a functional form for the internal strain profile. We use this to calculate the influence of strain gradient, through flexoelectric coupling, on the degradation of the ferroelectric properties of films with decreasing thickness, in excellent agreement with the observed behavior. This paper shows that strain relaxation can lead to smooth, continuous gradients across hundreds of nanometers, and it highlights the pressing need to avoid such strain gradients in order to obtain ferroelectric films with bulklike properties

  14. Diffusiophoresis in one-dimensional solute gradients

    Energy Technology Data Exchange (ETDEWEB)

    Ault, Jesse T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Warren, Patrick B. [Unilever R& D Port Sunlight, Bebington (United Kingdom); Shin, Sangwoo [Univ. of Hawaii at Manoa, Honolulu, HI (United States); Stone, Howard A. [Princeton Univ., Princeton, NJ (United States)

    2017-11-06

    Here, the diffusiophoretic motion of suspended colloidal particles under one-dimensional solute gradients is solved using numerical and analytical techniques. Similarity solutions are developed for the injection and withdrawal dynamics of particles into semi-infinite pores. Furthermore, a method of characteristics formulation of the diffusion-free particle transport model is presented and integrated to realize particle trajectories. Analytical solutions are presented for the limit of small particle diffusiophoretic mobility Γp relative to the solute diffusivity Ds for particle motions in both semi-infinite and finite domains. Results confirm the build up of local maxima and minima in the propagating particle front dynamics. The method of characteristics is shown to successfully predict particle motions and the position of the particle front, although it fails to accurately predict suspended particle concentrations in the vicinity of sharp gradients, such as at the particle front peak seen in some injection cases, where particle diffusion inevitably plays an important role. Results inform the design of applications in which the use of applied solute gradients can greatly enhance particle injection into and withdrawal from pores.

  15. Impact of Ozone Gradient on Grapevine Leaves

    Science.gov (United States)

    Alebic-Juretic, Ana; Bokan-Vucelic, Itana; Mifka, Boris; Zatezalo, Marija; Zubak, Velimir

    2017-04-01

    Due to complex orography and air mass circulation, the Rijeka Bay area is characterized by O3 gradient, with concentrations risen with the altitude (1). Therefore AOT40 values were often exceeded and should result in harmful effects on vegetation. Based on previous controlled experiments (2), we examined the possible effect of atmospheric ozone on grape leaves under natural O3 gradient. Grapevine leaves (2-5) were collected from May to September 2016 at two sampling points in the proximity of two AQM stations: Site 1 in the city centre (20m asl) and Site 2 (186m asl) in the suburban settlement. Subsequent to weighing and determination of surface area, the leaves (0,5 g) were extracted in 95% ethanol and analysed on chlorophyl a (Chla), chlorophyl b (Chlb) and carotene (Car) content by UV-VIS spectrometry on 3 wavelengths (664, 649, 470 nm) (3) In summer 2016 O3 gradient was not that pronounced as usual (1), but stil the concentrations differed by approx. 20%, exceeding national AOT40 value at both sites (22.360 and 28.061 μg m-3 h, respectively, at Sites 1 and 2). The concentrations of other pollutants were bellow limit values (LV). The Cha and Chb in a sample leaves collected at the end of May at Site 2 are equal to that with filtered O3 in control experiment (2), i.e. without damage caused by ozone, while the Car content is lower approx. 50% and is kept at the same level. The con-centrations of pigments obtained in July prooved the possible damage by O3, while in subsequent months could speed up natural ageing. This is the first evidence of O3 damage on plants in the Rijeka Bay area, in spite of weaker O3 gradient and lacking visible signs of damage. Preliminary results indicate the need for more frequent sampling, particularly in the period included in AOT40 (May-July). References: 1. Alebić-Juretić A (2012) Int J Remote Sensing, 33(2): 335-345 2. Britvec M, Reichenauer T, Soja G., Ljubešić N, Pećina M (2001) Biologia (Bratislava),56/4: 417-424 3. Sumanata

  16. New Techniques for Studying Calcium Gradients

    Science.gov (United States)

    Tsien, R. Y.

    1985-01-01

    Improved techniques for detecting and manipulating spatial gradients of cytosolic free Ca(2+) concentrations (Ca(2)) sub i and intracellular stores are discussed. Three areas of progress are: (1) development of new fluorescent indicators for Ca(2+) that are the first to be suitable for measuring Ca(2+)) sub i and its inhomogeneities in individual cells; (2) invention of photolabile chelators which shift irreversibly from high to low affinity for Ca(2+) upon illumination, permitting light-controlled jumps in (Ca(2+)) sub i; and (3) fixation methods to trap dynamic intraorganellar Ca stores in a form readily visible by electron microscopy.

  17. Gradient Index Optics at DARPA

    Science.gov (United States)

    2013-11-01

    sodium, is submerged into a bath of molten salt containing a different ion, such as lithium bromide. Ions from the salt bath diffuse into the glass...molecules, creating a gradient of index of refraction (Mohr et al. 1979). • Crystal growing. From a silver- chloride /sodium- chloride bath, starting with a...sodium chloride seed, a crystal is pulled that begins to deplete the sodium in the bath and starts to pull silver, forming a gradient (Houde-Walter

  18. Stochastic Gradient Monomial Gamma Sampler

    OpenAIRE

    Zhang, Yizhe; Chen, Changyou; Gan, Zhe; Henao, Ricardo; Carin, Lawrence

    2017-01-01

    Recent advances in stochastic gradient techniques have made it possible to estimate posterior distributions from large datasets via Markov Chain Monte Carlo (MCMC). However, when the target posterior is multimodal, mixing performance is often poor. This results in inadequate exploration of the posterior distribution. A framework is proposed to improve the sampling efficiency of stochastic gradient MCMC, based on Hamiltonian Monte Carlo. A generalized kinetic function is leveraged, delivering ...

  19. Evolutionary Stable Strategy

    Indian Academy of Sciences (India)

    2016-08-26

    Aug 26, 2016 ... Home; Journals; Resonance – Journal of Science Education; Volume 21; Issue 9. Evolutionary Stable Strategy: Application of Nash Equilibrium in Biology. General ... Using some examples of classical games, we show how evolutionary game theory can help understand behavioural decisions of animals.

  20. The Stable Concordance Genus

    OpenAIRE

    Kearney, M. Kate

    2013-01-01

    The concordance genus of a knot is the least genus of any knot in its concordance class. Although difficult to compute, it is a useful invariant that highlights the distinction between the three-genus and four-genus. In this paper we define and discuss the stable concordance genus of a knot, which describes the behavior of the concordance genus under connected sum.

  1. Manifolds admitting stable forms

    Czech Academy of Sciences Publication Activity Database

    Le, Hong-Van; Panák, Martin; Vanžura, Jiří

    2008-01-01

    Roč. 49, č. 1 (2008), s. 101-11 ISSN 0010-2628 R&D Projects: GA ČR(CZ) GP201/05/P088 Institutional research plan: CEZ:AV0Z10190503 Keywords : stable forms * automorphism groups Subject RIV: BA - General Mathematics

  2. Stable isotope studies

    International Nuclear Information System (INIS)

    Ishida, T.

    1992-01-01

    The research has been in four general areas: (1) correlation of isotope effects with molecular forces and molecular structures, (2) correlation of zero-point energy and its isotope effects with molecular structure and molecular forces, (3) vapor pressure isotope effects, and (4) fractionation of stable isotopes. 73 refs, 38 figs, 29 tabs

  3. Interactive Stable Ray Tracing

    DEFF Research Database (Denmark)

    Dal Corso, Alessandro; Salvi, Marco; Kolb, Craig

    2017-01-01

    Interactive ray tracing applications running on commodity hardware can suffer from objectionable temporal artifacts due to a low sample count. We introduce stable ray tracing, a technique that improves temporal stability without the over-blurring and ghosting artifacts typical of temporal post-pr...

  4. The stable subgroup graph

    Directory of Open Access Journals (Sweden)

    Behnaz Tolue

    2018-07-01

    Full Text Available In this paper we introduce stable subgroup graph associated to the group $G$. It is a graph with vertex set all subgroups of $G$ and two distinct subgroups $H_1$ and $H_2$ are adjacent if $St_{G}(H_1\\cap H_2\

  5. Mercury Bioaccumulation in Estuarine Fishes: Novel Insights from Sulfur Stable Isotopes.

    Science.gov (United States)

    Willacker, James J; Eagles-Smith, Collin A; Ackerman, Joshua T

    2017-02-21

    Estuaries are transitional habitats characterized by complex biogeochemical and ecological gradients that result in substantial variation in fish total mercury concentrations (THg). We leveraged these gradients and used carbon (δ 13 C), nitrogen (δ 15 N), and sulfur (δ 34 S) stable isotopes to examine the ecological and biogeochemical processes underlying THg bioaccumulation in fishes from the San Francisco Bay Estuary. We employed a tiered approach that first examined processes influencing variation in fish THg among wetlands, and subsequently examined the roles of habitat and within-wetland processes in generating larger-scale patterns in fish THg. We found that δ 34 S, an indicator of sulfate reduction and habitat specific-foraging, was correlated with fish THg at all three spatial scales. Over the observed ranges of δ 34 S, THg concentrations in fish increased by up to 860% within wetlands, 560% among wetlands, and 291% within specific impounded wetland habitats. In contrast, δ 13 C and δ 15 N were not correlated with THg among wetlands and were only important in low salinity impounded wetlands, possibly reflecting more diverse food webs in this habitat. Together, our results highlight the key roles of sulfur biogeochemistry and ecology in influencing estuarine fish THg, as well as the importance of fish ecology and habitat in modulating the relationships between biogeochemical processes and Hg bioaccumulation.

  6. Mercury bioaccumulation in estuarine fishes: Novel insights from sulfur stable isotopes

    Science.gov (United States)

    Willacker, James J.; Eagles-Smith, Collin A.; Ackerman, Joshua T.

    2017-01-01

    Estuaries are transitional habitats characterized by complex biogeochemical and ecological gradients that result in substantial variation in fish total mercury concentrations (THg). We leveraged these gradients and used carbon (δ13C), nitrogen (δ15N), and sulfur (δ34S) stable isotopes to examine the ecological and biogeochemical processes underlying THg bioaccumulation in fishes from the San Francisco Bay Estuary. We employed a tiered approach that first examined processes influencing variation in fish THg among wetlands, and subsequently examined the roles of habitat and within-wetland processes in generating larger-scale patterns in fish THg. We found that δ34S, an indicator of sulfate reduction and habitat specific-foraging, was correlated with fish THg at all three spatial scales. Over the observed ranges of δ34S, THg concentrations in fish increased by up to 860% within wetlands, 560% among wetlands, and 291% within specific impounded wetland habitats. In contrast, δ13C and δ15N were not correlated with THg among wetlands and were only important in low salinity impounded wetlands, possibly reflecting more diverse food webs in this habitat. Together, our results highlight the key roles of sulfur biogeochemistry and ecology in influencing estuarine fish THg, as well as the importance of fish ecology and habitat in modulating the relationships between biogeochemical processes and Hg bioaccumulation.

  7. Traits and climate are associated with first flowering day in herbaceous species along elevational gradients.

    Science.gov (United States)

    Bucher, Solveig Franziska; König, Patrizia; Menzel, Annette; Migliavacca, Mirco; Ewald, Jörg; Römermann, Christine

    2018-01-01

    Phenological responses to changing temperatures are known as "fingerprints of climate change," yet these reactions are highly species specific. To assess whether different plant characteristics are related to these species-specific responses in flowering phenology, we observed the first flowering day (FFD) of ten herbaceous species along two elevational gradients, representing temperature gradients. On the same populations, we measured traits being associated with (1) plant performance (specific leaf area), (2) leaf biochemistry (leaf C, N, P, K, and Mg content), and (3) water-use efficiency (stomatal pore area index and stable carbon isotopes concentration). We found that as elevation increased, FFD was delayed for all species with a highly species-specific rate. Populations at higher elevations needed less temperature accumulation to start flowering than populations of the same species at lower elevations. Surprisingly, traits explained a higher proportion of variance in the phenological data than elevation. Earlier flowering was associated with higher water-use efficiency, higher leaf C, and lower leaf P content. In addition to that, the intensity of shifts in FFD was related to leaf N and K. These results propose that traits have a high potential in explaining phenological variations, which even surpassed the effect of temperature changes in our study. Therefore, they have a high potential to be included in future analyses studying the effects of climate change and will help to improve predictions of vegetation changes.

  8. Growth and deformation structure of gradient and layer-gradient Ti-Al-Si-Cu-N coatings

    Energy Technology Data Exchange (ETDEWEB)

    Ovchinnikov, Stanislav V., E-mail: ovm@spti.tsu.ru; Pinzhin, Yurii P., E-mail: pinzhin@phys.tsu.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); Korotaev, Alexandr D., E-mail: korotaev@phys.tsu.ru [National Research Tomsk State University, Tomsk, 634050 (Russian Federation)

    2014-11-14

    The features of the growth structure and modification of gradient and layer-gradient Ti-Al-Si-Cu-N coatings in the areas of deformation and fracture during indentation and scratch testing were investigated using transmission and scanning electron microscopy methods. The influence of the concentration of alloying elements and displacement potential in the substrate on the secondary sputtering, phase composition and the level of combined torsion and bending of the crystal lattice of doped TiN were determined. It was found out that the size of the crystals in deformation location bands grows with deformation of gradient nanocrystal coatings. The article shows that layer-gradient coatings combining submicrocrystalline and nanocrystalline structures have the increased plasticity and fracture toughness due to enhanced density of interfaces and formation of the soft metal phase (Cu) in the surface layer.

  9. Growth and deformation structure of gradient and layer-gradient Ti-Al-Si-Cu-N coatings

    International Nuclear Information System (INIS)

    Ovchinnikov, Stanislav V.; Pinzhin, Yurii P.; Korotaev, Alexandr D.

    2014-01-01

    The features of the growth structure and modification of gradient and layer-gradient Ti-Al-Si-Cu-N coatings in the areas of deformation and fracture during indentation and scratch testing were investigated using transmission and scanning electron microscopy methods. The influence of the concentration of alloying elements and displacement potential in the substrate on the secondary sputtering, phase composition and the level of combined torsion and bending of the crystal lattice of doped TiN were determined. It was found out that the size of the crystals in deformation location bands grows with deformation of gradient nanocrystal coatings. The article shows that layer-gradient coatings combining submicrocrystalline and nanocrystalline structures have the increased plasticity and fracture toughness due to enhanced density of interfaces and formation of the soft metal phase (Cu) in the surface layer

  10. Visualization of an endogenous retinoic acid gradient across embryonic development.

    Science.gov (United States)

    Shimozono, Satoshi; Iimura, Tadahiro; Kitaguchi, Tetsuya; Higashijima, Shin-Ichi; Miyawaki, Atsushi

    2013-04-18

    In vertebrate development, the body plan is determined by primordial morphogen gradients that suffuse the embryo. Retinoic acid (RA) is an important morphogen involved in patterning the anterior-posterior axis of structures, including the hindbrain and paraxial mesoderm. RA diffuses over long distances, and its activity is spatially restricted by synthesizing and degrading enzymes. However, gradients of endogenous morphogens in live embryos have not been directly observed; indeed, their existence, distribution and requirement for correct patterning remain controversial. Here we report a family of genetically encoded indicators for RA that we have termed GEPRAs (genetically encoded probes for RA). Using the principle of fluorescence resonance energy transfer we engineered the ligand-binding domains of RA receptors to incorporate cyan-emitting and yellow-emitting fluorescent proteins as fluorescence resonance energy transfer donor and acceptor, respectively, for the reliable detection of ambient free RA. We created three GEPRAs with different affinities for RA, enabling the quantitative measurement of physiological RA concentrations. Live imaging of zebrafish embryos at the gastrula and somitogenesis stages revealed a linear concentration gradient of endogenous RA in a two-tailed source-sink arrangement across the embryo. Modelling of the observed linear RA gradient suggests that the rate of RA diffusion exceeds the spatiotemporal dynamics of embryogenesis, resulting in stability to perturbation. Furthermore, we used GEPRAs in combination with genetic and pharmacological perturbations to resolve competing hypotheses on the structure of the RA gradient during hindbrain formation and somitogenesis. Live imaging of endogenous concentration gradients across embryonic development will allow the precise assignment of molecular mechanisms to developmental dynamics and will accelerate the application of approaches based on morphogen gradients to tissue engineering and

  11. Stable isotope analysis

    International Nuclear Information System (INIS)

    Tibari, Elghali; Taous, Fouad; Marah, Hamid

    2014-01-01

    This report presents results related to stable isotopes analysis carried out at the CNESTEN DASTE in Rabat (Morocco), on behalf of Senegal. These analyzes cover 127 samples. These results demonstrate that Oxygen-18 and Deuterium in water analysis were performed by infrared Laser spectroscopy using a LGR / DLT-100 with Autosampler. Also, the results are expressed in δ values (‰) relative to V-SMOW to ± 0.3 ‰ for oxygen-18 and ± 1 ‰ for deuterium.

  12. Forensic Stable Isotope Biogeochemistry

    Science.gov (United States)

    Cerling, Thure E.; Barnette, Janet E.; Bowen, Gabriel J.; Chesson, Lesley A.; Ehleringer, James R.; Remien, Christopher H.; Shea, Patrick; Tipple, Brett J.; West, Jason B.

    2016-06-01

    Stable isotopes are being used for forensic science studies, with applications to both natural and manufactured products. In this review we discuss how scientific evidence can be used in the legal context and where the scientific progress of hypothesis revisions can be in tension with the legal expectations of widely used methods for measurements. Although this review is written in the context of US law, many of the considerations of scientific reproducibility and acceptance of relevant scientific data span other legal systems that might apply different legal principles and therefore reach different conclusions. Stable isotopes are used in legal situations for comparing samples for authenticity or evidentiary considerations, in understanding trade patterns of illegal materials, and in understanding the origins of unknown decedents. Isotope evidence is particularly useful when considered in the broad framework of physiochemical processes and in recognizing regional to global patterns found in many materials, including foods and food products, drugs, and humans. Stable isotopes considered in the larger spatial context add an important dimension to forensic science.

  13. Polyacrylamide temperature gradient gel electrophoresis.

    Science.gov (United States)

    Viglasky, Viktor

    2013-01-01

    Temperature Gradient Gel Electrophoresis (TGGE) is a form of electrophoresis in which temperature gradient is used to denature molecules as they move through either acrylamide or agarose gel. TGGE can be applied to analyze DNA, RNA, protein-DNA complexes, and, less commonly, proteins. Separation of double-stranded DNA molecules during TGGE relies on temperature-dependent melting of the DNA duplex into two single-stranded DNA molecules. Therefore, the mobility of DNA reflects not only the size of the molecule but also its nucleotide composition, thereby allowing separation of DNA molecules of similar size with different sequences. Depending on the relative orientation of electric field and temperature gradient, TGGE can be performed in either a parallel or a perpendicular mode. The former is used to analyze multiple samples in the same gel, whereas the later allows detailed analysis of a single sample. This chapter is focused on analysis of DNA by polyacrylamide TGGE using the perpendicular mode.

  14. The Potential of Tropospheric Gradients for Regional Precipitation Prediction

    Science.gov (United States)

    Boisits, Janina; Möller, Gregor; Wittmann, Christoph; Weber, Robert

    2017-04-01

    Changes of temperature and humidity in the neutral atmosphere cause variations in tropospheric path delays and tropospheric gradients. By estimating zenith wet delays (ZWD) and gradients using a GNSS reference station network the obtained time series provide information about spatial and temporal variations of water vapour in the atmosphere. Thus, GNSS-based tropospheric parameters can contribute to the forecast of regional precipitation events. In a recently finalized master thesis at TU Wien the potential of tropospheric gradients for weather prediction was investigated. Therefore, ZWD and gradient time series at selected GNSS reference stations were compared to precipitation data over a period of six months (April to September 2014). The selected GNSS stations form two test areas within Austria. All required meteorological data was provided by the Central Institution for Meteorology and Geodynamics (ZAMG). Two characteristics in ZWD and gradient time series can be anticipated in case of an approaching weather front. First, an induced asymmetry in tropospheric delays results in both, an increased magnitude of the gradient and in gradients pointing towards the weather front. Second, an increase in ZWD reflects the increased water vapour concentration right before a precipitation event. To investigate these characteristics exemplary test events were processed. On the one hand, the sequence of the anticipated increase in ZWD at each GNSS station obtained by cross correlation of the time series indicates the direction of the approaching weather front. On the other hand, the corresponding peak in gradient time series allows the deduction of the direction of movement as well. To verify the results precipitation data from ZAMG was used. It can be deduced, that tropospheric gradients show high potential for predicting precipitation events. While ZWD time series rather indicate the orientation of the air mass boundary, gradients rather indicate the direction of movement

  15. Gram-scale fractionation of nanodiamonds by density gradient ultracentrifugation

    KAUST Repository

    Peng, Wei

    2013-01-01

    Size is a defining characteristic of nanoparticles; it influences their optical and electronic properties as well as their interactions with molecules and macromolecules. Producing nanoparticles with narrow size distributions remains one of the main challenges to their utilization. At this time, the number of practical approaches to optimize the size distribution of nanoparticles in many interesting materials systems, including diamond nanocrystals, remains limited. Diamond nanocrystals synthesized by detonation protocols-so-called detonation nanodiamonds (DNDs)-are promising systems for drug delivery, photonics, and composites. DNDs are composed of primary particles with diameters mainly <10 nm and their aggregates (ca. 10-500 nm). Here, we introduce a large-scale approach to rate-zonal density gradient ultracentrifugation to obtain monodispersed fractions of nanoparticles in high yields. We use this method to fractionate a highly concentrated and stable aqueous solution of DNDs and to investigate the size distribution of various fractions by dynamic light scattering, analytical ultracentrifugation, transmission electron microscopy and powder X-ray diffraction. This fractionation method enabled us to separate gram-scale amounts of DNDs into several size ranges within a relatively short period of time. In addition, the high product yields obtained for each fraction allowed us to apply the fractionation method iteratively to a particular size range of particles and to collect various fractions of highly monodispersed primary particles. Our method paves the way for in-depth studies of the physical and optical properties, growth, and aggregation mechanism of DNDs. Applications requiring DNDs with specific particle or aggregate sizes are now within reach. © 2013 The Royal Society of Chemistry.

  16. Gram-scale fractionation of nanodiamonds by density gradient ultracentrifugation.

    Science.gov (United States)

    Peng, Wei; Mahfouz, Remi; Pan, Jun; Hou, Yuanfang; Beaujuge, Pierre M; Bakr, Osman M

    2013-06-07

    Size is a defining characteristic of nanoparticles; it influences their optical and electronic properties as well as their interactions with molecules and macromolecules. Producing nanoparticles with narrow size distributions remains one of the main challenges to their utilization. At this time, the number of practical approaches to optimize the size distribution of nanoparticles in many interesting materials systems, including diamond nanocrystals, remains limited. Diamond nanocrystals synthesized by detonation protocols - so-called detonation nanodiamonds (DNDs) - are promising systems for drug delivery, photonics, and composites. DNDs are composed of primary particles with diameters mainly <10 nm and their aggregates (ca. 10-500 nm). Here, we introduce a large-scale approach to rate-zonal density gradient ultracentrifugation to obtain monodispersed fractions of nanoparticles in high yields. We use this method to fractionate a highly concentrated and stable aqueous solution of DNDs and to investigate the size distribution of various fractions by dynamic light scattering, analytical ultracentrifugation, transmission electron microscopy and powder X-ray diffraction. This fractionation method enabled us to separate gram-scale amounts of DNDs into several size ranges within a relatively short period of time. In addition, the high product yields obtained for each fraction allowed us to apply the fractionation method iteratively to a particular size range of particles and to collect various fractions of highly monodispersed primary particles. Our method paves the way for in-depth studies of the physical and optical properties, growth, and aggregation mechanism of DNDs. Applications requiring DNDs with specific particle or aggregate sizes are now within reach.

  17. Subcellular partitioning of metals in Aporrectodea caliginosa along a gradient of metal exposure in 31 field-contaminated soils

    Energy Technology Data Exchange (ETDEWEB)

    Beaumelle, Léa [INRA, UR 251 PESSAC, 78026 Versailles Cedex (France); Gimbert, Frédéric [Laboratoire Chrono-Environnement, UMR 6249 University of Franche-Comté/CNRS Usc INRA, 16 route de Gray, 25030 Besançon Cedex (France); Hedde, Mickaël [INRA, UR 251 PESSAC, 78026 Versailles Cedex (France); Guérin, Annie [INRA, US 0010 LAS Laboratoire d' analyses des sols, 273 rue de Cambrai, 62000 Arras (France); Lamy, Isabelle, E-mail: lamy@versailles.inra.fr [INRA, UR 251 PESSAC, 78026 Versailles Cedex (France)

    2015-07-01

    Subcellular fractionation of metals in organisms was proposed as a better way to characterize metal bioaccumulation. Here we report the impact of a laboratory exposure to a wide range of field-metal contaminated soils on the subcellular partitioning of metals in the earthworm Aporrectodea caliginosa. Soils moderately contaminated were chosen to create a gradient of soil metal availability; covering ranges of both soil metal contents and of several soil parameters. Following exposure, Cd, Pb and Zn concentrations were determined both in total earthworm body and in three subcellular compartments: cytosolic, granular and debris fractions. Three distinct proxies of soil metal availability were investigated: CaCl{sub 2}-extractable content dissolved content predicted by a semi-mechanistic model and free ion concentration predicted by a geochemical speciation model. Subcellular partitionings of Cd and Pb were modified along the gradient of metal exposure, while stable Zn partitioning reflected regulation processes. Cd subcellular distribution responded more strongly to increasing soil Cd concentration than the total internal content, when Pb subcellular distribution and total internal content were similarly affected. Free ion concentrations were better descriptors of Cd and Pb subcellular distribution than CaCl{sub 2} extractable and dissolved metal concentrations. However, free ion concentrations and soil total metal contents were equivalent descriptors of the subcellular partitioning of Cd and Pb because they were highly correlated. Considering lowly contaminated soils, our results raise the question of the added value of three proxies of metal availability compared to soil total metal content in the assessment of metal bioavailability to earthworm. - Highlights: • Earthworms were exposed to a wide panel of historically contaminated soils • Subcellular partitioning of Cd, Pb and Zn was investigated in earthworms • Three proxies of soil metal availability were

  18. Patterns and controls of seasonal variability of carbon stable isotopes of particulate organic matter in lakes.

    Science.gov (United States)

    Gu, Binhe; Schelske, Claire L; Waters, Matthew N

    2011-04-01

    Carbon stable isotopes (δ(13)C) of particulate organic matter (POM) have been used as indicators for energy flow, primary productivity and carbon dioxide concentration in individual lakes. Here, we provide a synthesis of literature data from 32 freshwater lakes around the world to assess the variability of δ(13)C(POM) along latitudinal, morphometric and biogeochemical gradients. Seasonal mean δ(13)C(POM), a temporally integrated measure of the δ(13)C(POM), displayed weak relationships with all trophic state indices [total phosphorus (TP), total nitrogen (TN), and chlorophyll a (Chl a)], but decreased significantly with the increase in latitude, presumably in response to the corresponding decrease in water temperature and increase in CO(2) concentration. The seasonal minimum δ(13)C(POM) also correlated negatively with latitude while seasonal maximum δ(13)C(POM) correlated positively with all trophic state indices, pH, and δ(13)C of dissolved inorganic carbon (DIC). Seasonal amplitude of δ(13)C(POM) (the difference between seasonal maximum and minimum values) correlated significantly with pH, TP and Chl a concentrations and displayed small variations in oligotrophic, mesotrophic and low latitude eutrophic lakes, which is attributed to low primary productivity and abundant non-living POM in the low trophic state lakes and relatively stable environmental conditions in the subtropics. Seasonal amplitude of δ(13)C(POM) was the greatest in high latitude eutrophic lakes. Greater seasonal changes in solar energy and light regime may be responsible for the large seasonal variability in high latitude productive lakes. This synthesis provides new insights on the factors controlling variations in stable carbon isotopes of POM among lakes on the global scale.

  19. Computational Strain Gradient Crystal Plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2011-01-01

    element solution method is presented, which delivers the slip-rate field and the velocity-field based on two minimum principles. Some plane deformation problems relevant for certain specific orientations of a face centered cubic crystal under plane loading conditions are studied, and effective in......A model for strain gradient crystal visco-plasticity is formulated along the lines proposed by Fleck andWillis (2009) for isotropic plasticity. Size-effects are included in the model due to the addition of gradient terms in both the free energy as well as through a dissipation potential. A finite...

  20. Development and propagation of a pollution gradient in the marine ...

    Indian Academy of Sciences (India)

    latitude over the Arabian Sea. Latitudinal gradients in anthropogenic gases have been observed over the Arabian Sea and the Indian Ocean. Higher marine boundary layer ozone concentrations were observed over the Indian. Ocean in the northern hemisphere during the northeast monsoon season (Johnson et al 1990).

  1. Compositional gradients in Gramineae genes

    DEFF Research Database (Denmark)

    Wong, Gane Ka-Shu; Wang, Jun; Tao, Lin

    2002-01-01

    In this study, we describe a property of Gramineae genes, and perhaps all monocot genes, that is not observed in eudicot genes. Along the direction of transcription, beginning at the junction of the 5'-UTR and the coding region, there are gradients in GC content, codon usage, and amino-acid usage...

  2. Stable patterns for fourth-order parabolic equations

    OpenAIRE

    van den Berg, J. B.; Vandervorst, R. C.

    2002-01-01

    We consider fourth-order parabolic equations of gradient type. For the sake of simplicity, the analysis is carried out for the specific equation $u\\sb t=-\\gamma\\ u\\sb {xxxx}+\\beta u\\sb {xx}-F\\sp \\prime(u)$ with $(t,x)\\in (0,\\infty)\\times(0, L)$ and $\\gamma,\\beta>0$ and where $F(u)$ is a bistable potential. We study its stable equilibria as a function of the ratio $\\gamma/beta\\sp 2$. As the ratio $\\gamma/beta\\sp 2$ crosses an explicit threshold value, the number of stable ...

  3. Systematic interpolation method predicts protein chromatographic elution with salt gradients, pH gradients and combined salt/pH gradients.

    Science.gov (United States)

    Creasy, Arch; Barker, Gregory; Carta, Giorgio

    2017-03-01

    A methodology is presented to predict protein elution behavior from an ion exchange column using both individual or combined pH and salt gradients based on high-throughput batch isotherm data. The buffer compositions are first optimized to generate linear pH gradients from pH 5.5 to 7 with defined concentrations of sodium chloride. Next, high-throughput batch isotherm data are collected for a monoclonal antibody on the cation exchange resin POROS XS over a range of protein concentrations, salt concentrations, and solution pH. Finally, a previously developed empirical interpolation (EI) method is extended to describe protein binding as a function of the protein and salt concentration and solution pH without using an explicit isotherm model. The interpolated isotherm data are then used with a lumped kinetic model to predict the protein elution behavior. Experimental results obtained for laboratory scale columns show excellent agreement with the predicted elution curves for both individual or combined pH and salt gradients at protein loads up to 45 mg/mL of column. Numerical studies show that the model predictions are robust as long as the isotherm data cover the range of mobile phase compositions where the protein actually elutes from the column. Copyright © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Gradient-driven flux-tube simulations of ion temperature gradient turbulence close to the non-linear threshold

    Energy Technology Data Exchange (ETDEWEB)

    Peeters, A. G.; Rath, F.; Buchholz, R.; Grosshauser, S. R.; Strintzi, D.; Weikl, A. [Physics Department, University of Bayreuth, Universitätsstrasse 30, Bayreuth (Germany); Camenen, Y. [Aix Marseille Univ, CNRS, PIIM, UMR 7345, Marseille (France); Candy, J. [General Atomics, PO Box 85608, San Diego, California 92186-5608 (United States); Casson, F. J. [CCFE, Culham Science Centre, Abingdon OX14 3DB, Oxon (United Kingdom); Hornsby, W. A. [Max Planck Institut für Plasmaphysik, Boltzmannstrasse 2 85748 Garching (Germany)

    2016-08-15

    It is shown that Ion Temperature Gradient turbulence close to the threshold exhibits a long time behaviour, with smaller heat fluxes at later times. This reduction is connected with the slow growth of long wave length zonal flows, and consequently, the numerical dissipation on these flows must be sufficiently small. Close to the nonlinear threshold for turbulence generation, a relatively small dissipation can maintain a turbulent state with a sizeable heat flux, through the damping of the zonal flow. Lowering the dissipation causes the turbulence, for temperature gradients close to the threshold, to be subdued. The heat flux then does not go smoothly to zero when the threshold is approached from above. Rather, a finite minimum heat flux is obtained below which no fully developed turbulent state exists. The threshold value of the temperature gradient length at which this finite heat flux is obtained is up to 30% larger compared with the threshold value obtained by extrapolating the heat flux to zero, and the cyclone base case is found to be nonlinearly stable. Transport is subdued when a fully developed staircase structure in the E × B shearing rate forms. Just above the threshold, an incomplete staircase develops, and transport is mediated by avalanche structures which propagate through the marginally stable regions.

  5. Marginally Stable Nuclear Burning

    Science.gov (United States)

    Strohmayer, Tod E.; Altamirano, D.

    2012-01-01

    Thermonuclear X-ray bursts result from unstable nuclear burning of the material accreted on neutron stars in some low mass X-ray binaries (LMXBs). Theory predicts that close to the boundary of stability oscillatory burning can occur. This marginally stable regime has so far been identified in only a small number of sources. We present Rossi X-ray Timing Explorer (RXTE) observations of the bursting, high- inclination LMXB 4U 1323-619 that reveal for the first time in this source the signature of marginally stable burning. The source was observed during two successive RXTE orbits for approximately 5 ksec beginning at 10:14:01 UTC on March 28, 2011. Significant mHz quasi- periodic oscillations (QPO) at a frequency of 8.1 mHz are detected for approximately 1600 s from the beginning of the observation until the occurrence of a thermonuclear X-ray burst at 10:42:22 UTC. The mHz oscillations are not detected following the X-ray burst. The average fractional rms amplitude of the mHz QPOs is 6.4% (3 - 20 keV), and the amplitude increases to about 8% below 10 keV.This phenomenology is strikingly similar to that seen in the LMXB 4U 1636-53. Indeed, the frequency of the mHz QPOs in 4U 1323-619 prior to the X-ray burst is very similar to the transition frequency between mHz QPO and bursts found in 4U 1636-53 by Altamirano et al. (2008). These results strongly suggest that the observed QPOs in 4U 1323-619 are, like those in 4U 1636-53, due to marginally stable nuclear burning. We also explore the dependence of the energy spectrum on the oscillation phase, and we place the present observations within the context of the spectral evolution of the accretion-powered flux from the source.

  6. Consolidation by Prefabricated Vertical Drains with a Threshold Gradient

    Directory of Open Access Journals (Sweden)

    Xiao Guo

    2014-01-01

    Full Text Available This paper shows the development of an approximate analytical solution of radial consolidation by prefabricated vertical drains with a threshold gradient. To understand the effect of the threshold gradient on consolidation, a parametric analysis was performed using the present solution. The applicability of the present solution was demonstrated in two cases, wherein the comparisons with Hansbo’s results and observed data were conducted. It was found that (1 the flow with the threshold gradient would not occur instantaneously throughout the whole unit cell. Rather, it gradually occurs from the vertical drain to the outside; (2 the moving boundary would never reach the outer radius of influence if R+1stable value at the end of consolidation; (4 the larger the threshold gradient is, the greater the long-term excess pore pressure will be; and (5 the present solution could predict the consolidation behavior in soft clay better than previous methods.

  7. A gradient enhanced plasticity-damage microplane model for concrete

    Science.gov (United States)

    Zreid, Imadeddin; Kaliske, Michael

    2018-03-01

    Computational modeling of concrete poses two main types of challenges. The first is the mathematical description of local response for such a heterogeneous material under all stress states, and the second is the stability and efficiency of the numerical implementation in finite element codes. The paper at hand presents a comprehensive approach addressing both issues. Adopting the microplane theory, a combined plasticity-damage model is formulated and regularized by an implicit gradient enhancement. The plasticity part introduces a new microplane smooth 3-surface cap yield function, which provides a stable numerical solution within an implicit finite element algorithm. The damage part utilizes a split, which can describe the transition of loading between tension and compression. Regularization of the model by the implicit gradient approach eliminates the mesh sensitivity and numerical instabilities. Identification methods for model parameters are proposed and several numerical examples of plain and reinforced concrete are carried out for illustration.

  8. Vertebrate pressure-gradient receivers

    DEFF Research Database (Denmark)

    Christensen-Dalsgaard, Jakob

    2011-01-01

    The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum and stro......The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum....... Recent vertebrates form a continuum from perfect interaural transmission (0 dB in a certain frequency band) and pronounced eardrum directionality (30-40 dB) in the lizards, over somewhat attenuated transmission and limited directionality in birds and frogs, to the strongly attenuated interaural...

  9. Diffusiophoresis in one-dimensional solute gradients

    Science.gov (United States)

    Ault, Jesse; Warren, Patrick; Shin, Sangwoo; Stone, Howard

    2017-11-01

    We solve for the diffusiophoretic motion of suspended colloidal particles that are exposed to 1D solute gradients using numerical and analytical techniques. Similarity solutions are developed that govern the particle dynamics in a semi-infinite domain. The method of characteristics is also used to describe a diffusion-free transport model for the particles. In the limit of small particle diffusiophoretic mobility, relative to the solute diffusivity, analytical solutions are determined for the particle motions in both finite and semi-infinite domains. Results demonstrate the presence of local maxima and minima in the particle concentrations and confirm the traveling particle front dynamics. Results can inform the design of particle injection and withdrawal applications in pores and other quasi-1D geometries.

  10. Physisorbed Polymer-Tethered Lipid Bilayer with Lipopolymer Gradient

    Directory of Open Access Journals (Sweden)

    Christoph A. Naumann

    2012-11-01

    Full Text Available Physisorbed polymer-tethered lipid bilayers consisting of phospholipids and lipopolymers represent an attractive planar model membrane platform, in which bilayer fluidity and membrane elastic properties can be regulated through lipopolymer molar concentration. Herein we report a method for the fabrication of such a planar model membrane system with a lateral gradient of lipopolymer density. In addition, a procedure is described, which leads to a sharp boundary between regions of low and high lipopolymer molar concentrations. Resulting gradients and sharp boundaries are visualized on the basis of membrane buckling structures at elevated lipopolymer concentrations using epifluorescence microscopy and atomic force microscopy. Furthermore, results from spot photobleaching experiments are presented, which provide insight into the lipid lateral fluidity in these model membrane architectures. The presented experimental data highlight a planar, solid-supported membrane characterized by fascinating length scale-dependent dynamics and elastic properties with remarkable parallels to those observed in cellular membranes.

  11. Primordial vorticity and gradient expansion

    CERN Document Server

    Giovannini, Massimo

    2012-01-01

    The evolution equations of the vorticities of the electrons, ions and photons in a pre-decoupling plasma are derived, in a fully inhomogeneous geometry, by combining the general relativistic gradient expansion and the drift approximation within the Adler-Misner-Deser decomposition. The vorticity transfer between the different species is discussed in this novel framework and a set of general conservation laws, connecting the vorticities of the three-component plasma with the magnetic field intensity, is derived. After demonstrating that a source of large-scale vorticity resides in the spatial gradients of the geometry and of the electromagnetic sources, the total vorticity is estimated to lowest order in the spatial gradients and by enforcing the validity of the momentum constraint. By acknowledging the current bounds on the tensor to scalar ratio in the (minimal) tensor extension of the $\\Lambda$CDM paradigm the maximal comoving magnetic field induced by the total vorticity turns out to be, at most, of the or...

  12. Reaction Gradients Viewed Inside Single Photoactive Particles

    Science.gov (United States)

    Alpert, P.; Corral Arroyo, P.; Dou, J.; Kreiger, U.; Luo, B.; Peter, T.; Ammann, M.

    2017-12-01

    In terms of chemical selectivity and spatial resolution, a technique known as scanning transmission X-ray microscopy coupled to near-edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS) is unmatched and will remain so for years into the future. We present a recent development coupling STXM/NEXAFS to a custom-built photochemical environmental reactor in which aerosol particles reside allowing for in situ chemical imaging. A laboratory investigation of metal-organic complex photochemistry was conducted. Transition metals are of great importance to atmospheric chemistry and aerosol photochemical aging due to their ability to catalyze oxidation reactions. Aerosol particles composed of mixtures of citric acid and iron citrate were probed for their organic carbon composition and iron oxidation state under atmospherically relevant conditions. At 40% relative humidity, oxygen diffusion and reaction was severely limited. Fe was reoxidized in the first 200 nm of the particle surface leaving reduced iron in the core. Similar gradients were observed at 60% RH, however waiting approximately 2 hours in the dark resulted in a recovery of the initial Fe(III) concentration. We draw two main conclusions from our findings. Frist, the oxidation gradients must have been the result of anoxic conditions at the interior of aerosol particles. This was predicted using a newly developed model for molecular diffusion through multiple layers with a reaction framework describing the photochemical processing of the metal organic matrix. Second, the lifetime of organic radicals in an anoxic diffusion limited organic matrix must be considerably long ( hours) to completely reoxidize iron as they wait for molecular oxygen. Long radical lifetimes in viscous organic aerosol in turn, could create high radical concentrations or favor radical-radical reactions in particles typically not considered when oxygen is plentiful. Our results impact predictions of aerosol physiochemical properties, e

  13. Evaluation of the Field Gradient Lattice Detector

    CERN Document Server

    AUTHOR|(CDS)2072983

    A novel Micro Pattern Gas Detector, named the Field Gradient Lattice Detector, has been implemented using technologies available to CERN’s Printed Circuit Workshop. Numerous prototypes based on various materials were constructed in different geometries and their gain performance has been studied using 55Fe and 109Cd X-ray sources in Argon-CO2 gas mixtures. Two axis (2D) prototype structures have been shown to provide stable gains of around 1000 while a 3D design, based on the same polyimide foils used in other MPGD elements, holds a gain of 5000 for 8.9 keV X-rays even at high rates of 22 kHz/mm2. At a gain of 3100, the device has been tested up to 1 MHz/mm2 and shows no signs of degradation in performance. The energy resolution of the 3D-in-polyimide is modest, around 40% for 5.9 keV X-rays and 30% if the source is collimated indicating a variation in gain over the 3x3 cm2 active area. Having the most promise for future applications, the 3D-in-polyimide design has been selected for testing with a custom-bu...

  14. Mercury biomagnification through food webs along a salinity gradient down-estuary from a biological hotspot

    Science.gov (United States)

    Rumbold, Darren G.; Lange, Ted R.; Richard, Doug; DelPizzo, Gina; Hass, Nicole

    2018-01-01

    To examine down-estuary effects and how differences in food webs along a salinity gradient might influence mercury (Hg) biomagnification, we conducted a study from 2010 to 2015 in an estuary with a known biological hotspot at its headwaters. Over 907 samples of biota, representing 92 different taxa of fish and invertebrates, seston and sediments were collected from the upper, middle and lower reach for Hg determination and for stable nitrogen and carbon isotope analyses. Trophic magnification slopes (TMS; log Hg versus δ15N), as a measure of biomagnification efficiency, ranged from 0.23 to 0.241 but did not differ statistically among reaches. Hg concentrations were consistently highest, ranging as high as 4.9 mg/kg in top predatory fish, in the upper-reach of the estuary where basal Hg entering the food web was also highest, as evidenced by methylmercury concentrations in suspension feeders. Top predatory fish at the mouth of the estuary contained relatively low [THg], likely due to lower basal Hg. This was nonetheless surprising given the potential for down-estuary biotransport.

  15. Color Gradients Within Globular Clusters: Restricted Numerical Simulation

    Directory of Open Access Journals (Sweden)

    Young-Jong Sohn

    1997-06-01

    Full Text Available The results of a restricted numerical simulation for the color gradients within globular clusters have been presented. The standard luminosity function of M3 and Salpeter's initial mass functions were used to generate model clusters as a fundamental population. Color gradients with the sample clusters for both King and power law cusp models of surface brightness distributions are discussed in the case of using the standard luminosity function. The dependence of color gradients on several parameters for the simulations with Salpeter's initial mass functions, such as slope of initial mass functions, cluster ages, metallicities, concentration parameters of King model, and slopes of power law, are also discussed. No significant radial color gradients are shown to the sample clusters which are regenerated by a random number generation technique with various parameters in both of King and power law cusp models of surface brightness distributions. Dynamical mass segregation and stellar evolution of horizontal branch stars and blue stragglers should be included for the general case of model simulations to show the observed radial color gradients within globular clusters.

  16. Mathematical modelling of digit specification by a sonic hedgehog gradient

    KAUST Repository

    Woolley, Thomas E.

    2013-11-26

    Background: The three chick wing digits represent a classical example of a pattern specified by a morphogen gradient. Here we have investigated whether a mathematical model of a Shh gradient can describe the specification of the identities of the three chick wing digits and if it can be applied to limbs with more digits. Results: We have produced a mathematical model for specification of chick wing digit identities by a Shh gradient that can be extended to the four digits of the chick leg with Shh-producing cells forming a digit. This model cannot be extended to specify the five digits of the mouse limb. Conclusions: Our data suggest that the parameters of a classical-type morphogen gradient are sufficient to specify the identities of three different digits. However, to specify more digit identities, this core mechanism has to be coupled to alternative processes, one being that in the chick leg and mouse limb, Shh-producing cells give rise to digits; another that in the mouse limb, the cellular response to the Shh gradient adapts over time so that digit specification does not depend simply on Shh concentration. Developmental Dynamics 243:290-298, 2014. © 2013 Wiley Periodicals, Inc.

  17. Instabilities in power law gradient hardening materials

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    2005-01-01

    Tension and compression instabilities are investigated for specimens with dimensions in the micron range. A finite strain generalization of a higher order strain gradient plasticity theory is implemented in a finite element scheme capable of modeling power law hardening materials. Effects...... of gradient hardening are found to delay the onset of localization under plane strain tension, and significantly reduce strain gradients in the localized zone. For plane strain compression gradient hardening is found to increase the load-carrying capacity significantly....

  18. Conjugate gradient heat bath for ill-conditioned actions.

    Science.gov (United States)

    Ceriotti, Michele; Bussi, Giovanni; Parrinello, Michele

    2007-08-01

    We present a method for performing sampling from a Boltzmann distribution of an ill-conditioned quadratic action. This method is based on heat-bath thermalization along a set of conjugate directions, generated via a conjugate-gradient procedure. The resulting scheme outperforms local updates for matrices with very high condition number, since it avoids the slowing down of modes with lower eigenvalue, and has some advantages over the global heat-bath approach, compared to which it is more stable and allows for more freedom in devising case-specific optimizations.

  19. Bistable gradient networks. II. Storage capacity and behavior near saturation

    Science.gov (United States)

    McGraw, Patrick N.; Menzinger, Michael

    2003-01-01

    We examine numerically the storage capacity and the behavior near saturation of an attractor neural network consisting of bistable elements with an adjustable coupling strength, the bistable gradient network. For strong coupling, we find evidence of a first-order “memory blackout” phase transition, as in the Hopfield network. For weak coupling, on the other hand, there is no evidence of such a transition and memorized patterns can be stable even at high levels of loading. The enhanced storage capacity comes, however, at the cost of imperfect retrieval of the patterns from corrupted versions.

  20. Gradient remediability in linear distributed parabolic systems ...

    African Journals Online (AJOL)

    The aim of this paper is the introduction of a new concept that concerned the analysis of a large class of distributed parabolic systems. It is the general concept of gradient remediability. More precisely, we study with respect to the gradient observation, the existence of an input operator (gradient efficient actuators) ensuring ...

  1. Estimation of gradients from scattered data

    Energy Technology Data Exchange (ETDEWEB)

    Stead, S.E.

    1984-01-01

    Many techniques for producing a surface from scattered data require gradients at the data points. Since only positional data are usually known, the gradients must be estimated before the surface can be computed. The quality of the surface depends on the estimated gradients; so it is important to compute accurate estimates.

  2. An education gradient in health, a health gradient in education, or a confounded gradient in both?

    Science.gov (United States)

    Lynch, Jamie L; von Hippel, Paul T

    2016-04-01

    There is a positive gradient associating educational attainment with health, yet the explanation for this gradient is not clear. Does higher education improve health (causation)? Do the healthy become highly educated (selection)? Or do good health and high educational attainment both result from advantages established early in the life course (confounding)? This study evaluates these competing explanations by tracking changes in educational attainment and Self-rated Health (SRH) from age 15 to age 31 in the National Longitudinal Study of Youth, 1997 cohort. Ordinal logistic regression confirms that high-SRH adolescents are more likely to become highly educated. This is partly because adolescent SRH is associated with early advantages including adolescents' academic performance, college plans, and family background (confounding); however, net of these confounders adolescent SRH still predicts adult educational attainment (selection). Fixed-effects longitudinal regression shows that educational attainment has little causal effect on SRH at age 31. Completion of a high school diploma or associate's degree has no effect on SRH, while completion of a bachelor's or graduate degree have effects that, though significant, are quite small (less than 0.1 points on a 5-point scale). While it is possible that educational attainment would have greater effect on health at older ages, at age 31 what we see is a health gradient in education, shaped primarily by selection and confounding rather than by a causal effect of education on health. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Comparison of two different anaerobic feeding strategies to establish a stable aerobic granulated sludge bed.

    Science.gov (United States)

    Rocktäschel, T; Klarmann, C; Helmreich, B; Ochoa, J; Boisson, P; Sørensen, K H; Horn, H

    2013-11-01

    Two different anaerobic feeding strategies were compared to optimize the development and performance of aerobic granules. A stable aerobic granulation of activated sludge was achieved with an anaerobic plug flow operation (PI) and a fast influent step followed by an anaerobic mixing phase (PII). Two lab scale sequencing batch reactors (SBRs) were operated to test the different operation modes. PI with plug flow and a reactor H/D (height/diameter) ratio of 9 achieved a biomass concentration of 20 g(TSS)/L and an effluent TSS concentration of 0.10 g(TSS)/L. PII with the mixed anaerobic phase directly after feeding and a reactor H/D ratio of 2 achieved a biomass concentration of 9 g(TSS)/L and an effluent quality of 0.05 g(TSS)/L. Furthermore, it is shown that the plug flow regime during anaerobic feeding together with the lower H/D ratio of 2 led to channeling effects, which resulted in lower storage of organic carbon and a general destabilization of the granulation process. Compared to the plug flow regime (PI), the anaerobic mixing (PII) provided lower substrate gradients within the biofilm. However, these disadvantages could be compensated by higher mass transfer coefficients in PII (k(L) = 0.3 m/d for PI; k(L) = 86 m/d for PII) during the anaerobic phase. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. Concentration device

    DEFF Research Database (Denmark)

    2013-01-01

    A concentration device (2) for filter filtration concentration of particles (4) from a volume of a fluid (6). The concentration device (2) comprises a filter (8) configured to filter particles (4) of a predefined size in the volume of the fluid (6). The concentration device (2) comprises...

  5. High precision and stable structures for particle detectors

    CERN Document Server

    Da Mota Silva, S; Hauviller, Claude

    1999-01-01

    The central detectors used in High Energy Physics Experiments require the use of light and stable structures capable of supporting delicate and precise radiation detection elements. These structures need to be highly stable under environmental conditions where external vibrations, high radiation levels, temperature and humidity gradients should be taken into account. Their main design drivers are high dimension and dynamic stability, high stiffness to mass ratio and large radiation length. For most applications, these constraints lead us to choose Carbon Fiber Reinforced Plastics ( CFRP) as structural element. The construction of light and stable structures with CFRP for these applications can be achieved by careful design engineering and further confirmation at the prototyping phase. However, the experimental environment can influence their characteristics and behavior. In this case, theuse of adaptive structures could become a solution for this problem. We are studying structures in CFRP with bonded piezoel...

  6. Shape reconstruction from gradient data.

    Science.gov (United States)

    Ettl, Svenja; Kaminski, Jürgen; Knauer, Markus C; Häusler, Gerd

    2008-04-20

    We present a generalized method for reconstructing the shape of an object from measured gradient data. A certain class of optical sensors does not measure the shape of an object but rather its local slope. These sensors display several advantages, including high information efficiency, sensitivity, and robustness. For many applications, however, it is necessary to acquire the shape, which must be calculated from the slopes by numerical integration. Existing integration techniques show drawbacks that render them unusable in many cases. Our method is based on an approximation employing radial basis functions. It can be applied to irregularly sampled, noisy, and incomplete data, and it reconstructs surfaces both locally and globally with high accuracy.

  7. Temperature Gradient in Hall Thrusters

    International Nuclear Information System (INIS)

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

    2003-01-01

    Plasma potentials and electron temperatures were deduced from emissive and cold floating probe measurements in a 2 kW Hall thruster, operated in the discharge voltage range of 200-400 V. An almost linear dependence of the electron temperature on the plasma potential was observed in the acceleration region of the thruster both inside and outside the thruster. This result calls into question whether secondary electron emission from the ceramic channel walls plays a significant role in electron energy balance. The proportionality factor between the axial electron temperature gradient and the electric field is significantly smaller than might be expected by models employing Ohmic heating of electrons

  8. On Nonconvex Decentralized Gradient Descent

    Science.gov (United States)

    2016-08-01

    difference between each local point and their global average is subject to a bound proportional to the step size. This note then establishes similar...estimation, and control. When fi’s are convex, the existing algorithms include the (sub)gradient meth- ods [5], [7], [10], [11], [18], [14], [15], and the...set of n nodes and E is the edge set. Any edge (i, j) ∈ E represents an arc between node i and node j. Let x(i) ∈ Rp denote the local copy of x at node

  9. Stringy bounces and gradient instabilities

    CERN Document Server

    Giovannini, Massimo

    2017-01-01

    Bouncing solutions are obtained from a generally covariant action characterized by a potential which is a nonlocal functional of the dilaton field at two separated space-time points. Gradient instabilities are shown to arise in this context but they are argued to be nongeneric. After performing a gauge-invariant and frame-invariant derivation of the evolution equations of the fluctuations, a heuristic criterium for the avoidance of pathological instabilities is proposed and corroborated by a number of explicit examples that turn out to be compatible with a quasi-flat spectrum of curvature inhomogeneities for typical wavelengths larger than the Hubble radius.

  10. Generalized Gradient Approximation Made Simple

    International Nuclear Information System (INIS)

    Perdew, J.P.; Burke, K.; Ernzerhof, M.

    1996-01-01

    Generalized gradient approximations (GGA close-quote s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. copyright 1996 The American Physical Society

  11. Factors influencing stable isotopes and growth of algae in oil sands aquatic reclamation.

    Science.gov (United States)

    Boutsivongsakd, Monique; Farwell, Andrea J; Chen, Hao; Dixon, D George

    2015-01-01

    Previous studies reported (15)N enrichment of biota in reclamation wetlands that contain oil sands processed material (e.g., processed water and tailings); however, there is little information on the factors controlling (15)N enrichment in these systems. In this microcosm study, the aim was to examine stable C and N isotopes and growth (chlorophyll a [chl a] and dry weight) of algae as a function of exposure to different sources and concentrations of water-soluble fractions (WSF) derived from tailings. Two sources of tailings including mature fine tailings (MFT) and consolidated tailings (CT) and peat-mineral overburden were utilized to generate separate WSF that differed in water quality. In general, there was (15)N enrichment of filamentous algae along the increasing gradient of WSF/nutrient concentrations in both CT and peat microcosms, and among the different sources, algae were more (15)N enriched in CT WSF than in peat WSF. Growth of filamentous algae was inhibited at higher WSF concentrations, possibly due to reduced light availability at elevated levels of fine clay particles in MFT microcosms and colored dissolved organic carbon (DOC) in peat microcosms. Filamentous algae displayed lower biomass and (15)N depletion in 100% peat WSF. This study indicated that both the quality (source) and quantity of WSF affected algal growth and directly and/or indirectly influenced δ(15)N of algae. The distinct (15)N enrichment of primary producers derived from tailings suggest that stable N isotopes might be useful to trace exposure to oil sands processed material in biota that utilize these resources in reclaimed systems constructed with tailings or natural systems that receive tailings dyke seepage.

  12. Bacterial Response to Antibiotic Gradients in a Porous Microfluidic Device

    Science.gov (United States)

    Deng, J.; Shechtman, L. A.; Sanford, R. A.; Dong, Y.; Werth, C. J.; Fouke, B. W.

    2015-12-01

    Microorganisms in nature have evolved survival strategies to cope with a wide variety of environmental stresses, including gradients in temperature, pH, substrate availability and aqueous chemistry. Microfluidic devices provide a consistently reliable real-time means to quantitatively measure, control and reproduce the dynamic nature of these stresses. As an example, accelerated adaptation from genetic mutations have been observed in E. coli as it responds to gradients of Ciprofloxacin (Zhang et. al. 2011). However, the mechanisms by which bacteria respond to antibiotic gradients, as well as the effect of changes in how the stressor is applied, have not been systematically studied. In this study, newly designed and fabricated microfluidic devices with porous media have been utilized to determine the chemical stress fields that enhance adaptation and thus to test how E. coli bacterial communities adapt to antibiotic stresses. By applying antibiotic and nutrient into inlet channels adjacent to either side of the porous media inoculated with E. coli, a gradient of antibiotic was formed. Hydrogel barriers were selectively photo-polymerized in between of the inlet channels and the porous media to prevent any undesired convection. Hence, chemical solute can only be transported by diffusion, creating a reproducible antibiotic gradient over the porous media. The bacteria were also constrained by the hydrogel boundary barriers from escaping the porous media. Preliminary results suggest that E. coli moves freely with respect to Ciprofloxacin concentrations. In addition, and unexpectedly, the E. coli colonies exhibit a concentric pulsed growth front radiating away from the point of inoculation within the micromodel ecosystem and pulse over the porous media containing antibiotic. The bacteria at the growth front grow into long filaments (up to 100μm) while the bacteria in the inner concentric area are normal size. We hypothesize that the frontier bacteria, which are first

  13. Dynamical attraction to stable processes

    OpenAIRE

    Fisher, Albert M.; Talet, Marina

    2012-01-01

    We apply dynamical ideas within probability theory, proving an almost-sure invariance principle in log density for stable processes. The familiar scaling property (self-similarity) of the stable process has a stronger expression, that the scaling flow on Skorokhod path space is a Bernoulli flow. We prove that typical paths of a random walk with i.i.d. increments in the domain of attraction of a stable law can be paired with paths of a stable process so that, after applying a non-random regula...

  14. Strain gradient effects on cyclic plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Legarth, Brian Nyvang

    2010-01-01

    Size effects on the cyclic shear response are studied numerically using a recent higher order strain gradient visco-plasticity theory accounting for both dissipative and energetic gradient hardening. Numerical investigations of the response under cyclic pure shear and shear of a finite slab between...... rigid platens have been carried out, using the finite element method. It is shown for elastic–perfectly plastic solids how dissipative gradient effects lead to increased yield strength, whereas energetic gradient contributions lead to increased hardening as well as a Bauschinger effect. For linearly...... hardening materials it is quantified how dissipative and energetic gradient effects promote hardening above that of conventional predictions. Usually, increased hardening is attributed to energetic gradient effects, but here it is found that also dissipative gradient effects lead to additional hardening...

  15. Biogeochemical gradients above a coal tar DNAPL

    Energy Technology Data Exchange (ETDEWEB)

    Scherr, Kerstin E., E-mail: kerstin.brandstaetter-scherr@boku.ac.at [University of Natural Resources and Life Sciences Vienna (BOKU), Department IFA-Tulln, Institute for Environmental Biotechnology, Konrad Lorenz Strasse 20, 3430 Tulln (Austria); Backes, Diana [University of Natural Resources and Life Sciences Vienna (BOKU), Department IFA-Tulln, Institute for Environmental Biotechnology, Konrad Lorenz Strasse 20, 3430 Tulln (Austria); Scarlett, Alan G. [University of Plymouth, Petroleum and Environmental Geochemistry Group, Biogeochemistry Research Centre, Drake Circus, Plymouth, Devon PL4 8AA (United Kingdom); Lantschbauer, Wolfgang [Government of Upper Austria, Directorate for Environment and Water Management, Division for Environmental Protection, Kärntner Strasse 10-12, 4021 Linz (Austria); Nahold, Manfred [GUT Gruppe Umwelt und Technik GmbH, Ingenieurbüro für Technischen Umweltschutz, Plesching 15, 4040 Linz (Austria)

    2016-09-01

    Naturally occurring distribution and attenuation processes can keep hydrocarbon emissions from dense non aqueous phase liquids (DNAPL) into the adjacent groundwater at a minimum. In a historically coal tar DNAPL-impacted site, the de facto absence of a plume sparked investigations regarding the character of natural attenuation and DNAPL resolubilization processes at the site. Steep vertical gradients of polycyclic aromatic hydrocarbons, microbial community composition, secondary water quality and redox-parameters were found to occur between the DNAPL-proximal and shallow waters. While methanogenic and mixed-electron acceptor conditions prevailed close to the DNAPL, aerobic conditions and very low dissolved contaminant concentrations were identified in three meters vertical distance from the phase. Comprehensive two-dimensional gas chromatography–mass spectrometry (GC × GC–MS) proved to be an efficient tool to characterize the behavior of the present complex contaminant mixture. Medium to low bioavailability of ferric iron and manganese oxides of aquifer samples was detected via incubation with Shewanella alga and evidence for iron and manganese reduction was collected. In contrast, 16S rDNA phylogenetic analysis revealed the absence of common iron reducing bacteria. Aerobic hydrocarbon degraders were abundant in shallow horizons, while nitrate reducers were dominating in deeper aquifer regions, in addition to a low relative abundance of methanogenic archaea. Partial Least Squares – Canonical Correspondence Analysis (PLS-CCA) suggested that nitrate and oxygen concentrations had the greatest impact on aquifer community structure in on- and offsite wells, which had a similarly high biodiversity (H’ and Chao1). Overall, slow hydrocarbon dissolution from the DNAPL appears to dominate natural attenuation processes. This site may serve as a model for developing legal and technical strategies for the treatment of DNAPL-impacted sites where contaminant plumes are

  16. Control of colloids with gravity, temperature gradients, and electric fields

    CERN Document Server

    Sullivan, M; Harrison, C; Austin, R H; Megens, M; Hollingsworth, A; Russel, W B; Cheng Zhen; Mason, T; Chaikin, P M

    2003-01-01

    We have used a variety of different applied fields to control the density, growth, and structure of colloidal crystals. Gravity exerts a body force proportional to the buoyant mass and in equilibrium produces a height-dependent concentration profile. A similar body force can be obtained with electric fields on charged particles (electrophoresis), a temperature gradient on all particles, or an electric field gradient on uncharged particles (dielectrophoresis). The last is particularly interesting since its magnitude and sign can be changed by tuning the applied frequency. We study these effects in bulk (making 'dielectrophoretic bottles' or traps), to control concentration profiles during nucleation and growth and near surfaces. We also study control of non-spherical and optically anisotropic particles with the light field from laser tweezers.

  17. Concentration risk

    Directory of Open Access Journals (Sweden)

    Matić Vesna

    2016-01-01

    Full Text Available Concentration risk has been gaining a special dimension in the contemporary financial and economic environment. Financial institutions are exposed to this risk mainly in the field of lending, mostly through their credit activities and concentration of credit portfolios. This refers to the concentration of different exposures within a single risk category (credit risk, market risk, operational risk, liquidity risk.

  18. Convection induced by thermal gradients on thin reaction fronts

    Science.gov (United States)

    Ruelas Paredes, David R. A.; Vasquez, Desiderio A.

    2017-09-01

    We present a thin front model for the propagation of chemical reaction fronts in liquids inside a Hele-Shaw cell or porous media. In this model we take into account density gradients due to thermal and compositional changes across a thin interface. The front separating reacted from unreacted fluids evolves following an eikonal relation between the normal speed and the curvature. We carry out a linear stability analysis of convectionless flat fronts confined in a two-dimensional rectangular domain. We find that all fronts are stable to perturbations of short wavelength, but they become unstable for some wavelengths depending on the values of compositional and thermal gradients. If the effects of these gradients oppose each other, we observe a range of wavelengths that make the flat front unstable. Numerical solutions of the nonlinear model show curved fronts of steady shape with convection propagating faster than flat fronts. Exothermic fronts increase the temperature of the fluid as they propagate through the domain. This increment in temperature decreases with increasing speed.

  19. Novel Techniques for Pulsed Field Gradient NMR Measurements

    Science.gov (United States)

    Brey, William Wallace

    Pulsed field gradient (PFG) techniques now find application in multiple quantum filtering and diffusion experiments as well as in magnetic resonance imaging and spatially selective spectroscopy. Conventionally, the gradient fields are produced by azimuthal and longitudinal currents on the surfaces of one or two cylinders. Using a series of planar units consisting of azimuthal and radial current elements spaced along the longitudinal axis, we have designed gradient coils having linear regions that extend axially nearly to the ends of the coil and to more than 80% of the inner radius. These designs locate the current return paths on a concentric cylinder, so the coils are called Concentric Return Path (CRP) coils. Coils having extended linear regions can be made smaller for a given sample size. Among the advantages that can accrue from using smaller coils are improved gradient strength and switching time, reduced eddy currents in the absence of shielding, and improved use of bore space. We used an approximation technique to predict the remaining eddy currents and a time-domain model of coil performance to simulate the electrical performance of the CRP coil and several reduced volume coils of more conventional design. One of the conventional coils was designed based on the time-domain performance model. A single-point acquisition technique was developed to measure the remaining eddy currents of the reduced volume coils. Adaptive sampling increases the dynamic range of the measurement. Measuring only the center of the stimulated echo removes chemical shift and B_0 inhomogeneity effects. The technique was also used to design an inverse filter to remove the eddy current effects in a larger coil set. We added pulsed field gradient and imaging capability to a 7 T commercial spectrometer to perform neuroscience and embryology research and used it in preliminary studies of binary liquid mixtures separating near a critical point. These techniques and coil designs will find

  20. Latitudinal Gradients in Induced and Constitutive Resistance against Herbivores.

    Science.gov (United States)

    Anstett, Daniel N; Chen, Wen; Johnson, Marc T J

    2016-08-01

    Plants are hypothesized to evolve increased defense against herbivores at lower latitudes, but an increasing number of studies report evidence that contradicts this hypothesis. Few studies have examined the evolution of constitutive and induced resistance along latitudinal gradients. When induction is not considered, underlying patterns of latitudinal clines in resistance can be obscured because plant resistance represents a combination of induced and constitutive resistance, which may show contrasting patterns with latitude. Here, we asked if there are latitudinal gradients in constitutive versus induced resistance by using genotypes of Oenothera biennis (Onagraceae) sampled along an 18° latitudinal gradient. We conducted two bioassay experiments to compare the resistance of plant genotypes against one generalist (Spodoptera exigua) and one specialist (Acanthoscelidius acephalus) herbivore. These insects were assayed on: i) undamaged control plants, ii) plants that had been induced with jasmonic acid, and iii) plants induced with herbivore damage. Additionally, we examined latitudinal gradients of constitutive and induced chemical resistance by measuring the concentrations of total phenolics, the concentration of oxidized phenolics, and the percentage of phenolics that were oxidized. Spodoptera exigua showed lower performance on plants from lower latitudes, whereas A. acephalus showed no latitudinal pattern. Constitutive total phenolics were greater in plants from lower latitudes, but induced plants showed higher total phenolics at higher latitudes. Oxidative activity was greatest at higher latitudes regardless of induction. Overall, both latitude and induction have an impact on different metrics of plant resistance to herbivory. Further studies should consider the effect of induction and herbivore specialization more explicitly, which may help to resolve the controversy in latitudinal gradients in herbivory and defense.

  1. Stable carbon isotope time series from tropical tree rings indicate a precipitation signal

    OpenAIRE

    E. Fichtler; Gerhard Helle; M. Worbes

    2010-01-01

    Although studies on stable-carbon isotopes in trees from temperate zones provide abundant paleoclimatic data, tropical trees are still understudied in this context. Therefore this study examined the variability of intra- and inter-annual stable-carbon isotopic pattern in several tree species from various tropical climates. The delta C-13 Values of samples of 12 broadleaved trees (seven species) from various paleotropical and neotropical sites along a climatic moisture gradient were investigat...

  2. Concentrator Photovoltaics

    CERN Document Server

    Luque, Antonio L

    2007-01-01

    Photovoltaic solar-energy conversion is one of the most promising technologies for generating renewable energy, and conversion of concentrated sunlight can lead to reduced cost for solar electricity. In fact, photovoltaic conversion of concentrated sunlight insures an efficient and cost-effective sustainable power resource. This book gives an overview of all components, e.g. cells, concentrators, modules and systems, for systems of concentrator photovoltaics. The authors report on significant results related to design, technology, and applications, and also cover the fundamental physics and market considerations. Specific contributions include: theory and practice of sunlight concentrators; an overview of concentrator PV activities; a description of concentrator solar cells; design and technology of modules and systems; manufacturing aspects; and a market study.

  3. Wavefront reconstruction from its gradients.

    Science.gov (United States)

    Talmi, Amos; Ribak, Erez N

    2006-02-01

    Wavefronts reconstructed from measured gradients are composed of a straightforward integration of the measured data, plus a correction term that disappears when there are no measurement errors. For regions of any shape, this term is a solution of Poisson's equation with Dirichlet conditions (V = 0 on the boundaries). We show that for rectangular regions, the correct solution is not a periodic one, but one expressed with Fourier cosine series. The correct solution has a lower variance than the periodic Fourier transform solution. Similar formulas exist for a circular region with obscuration. We present a near-optimal solution that is much faster than fast-Fourier-transform methods. By use of diagonal multigrid methods, a single iteration brings the correction term to within a standard deviation of 0.08, two iterations, to within 0.0064, etc.

  4. Carotenoids in a food chain along a pollution gradient.

    Science.gov (United States)

    Sillanpää, Saila; Salminen, Juha-Pekka; Lehikoinen, Esa; Toivonen, Eija; Eeva, Tapio

    2008-11-15

    Carotenoids are synthesized by plants, therefore insects and birds must obtain them from their diet. They function in pigmentation and as antioxidants. We studied the carotenoid profiles in a model food chain (plant-insect-bird) in an air pollution gradient to find out whether heavy metal pollution affects the transfer of carotenoids across the trophic levels. Birch leaves showed higher beta-carotene and, one of the birch species (Betula pendula), higher total carotenoids levels in the polluted area. There was no difference in the lutein concentration of caterpillars' food source, birch leaves, between the study areas. Autumnal moth larvae accumulated lutein more efficiently than beta-carotene while sawfly larvae accumulated beta-carotene over lutein. Because of different antioxidant profiles in different leaf chewing insects their sensitivity to pollution stress may differ. The lutein concentration of plasma and feathers of Great tit nestlings did not differ along the pollution gradient. The lack of difference in lutein concentration of autumnal moth larvae along pollution gradient may partly explain the lutein concentrations of Great tit nestlings, since the abundance of autumnal moth larvae peak during the nestling phase of Great tit. The lutein concentration of autumnal moth larvae was positively associated to circulating plasma lutein level of Great tit indicating the importance of carotenoid rich diet during the nestling phase. In addition, the higher the plasma lutein concentration the more lutein was deposited to feathers, irrespective of the other possible functions of lutein in nestlings. We found that carotenoid levels differed between the polluted and the unpolluted area especially at lower levels of food chain: in birches and in caterpillars.

  5. Stable isotope separation

    International Nuclear Information System (INIS)

    Botter, F.; Molinari, Ph.; Dirian, G.

    1964-01-01

    Pure deuterium has been separated from gaseous mixtures of hydrogen and deuterium by band displacement chromatography, using columns of palladium on a support. The best results were obtained with columns of Pd on sintered α alumina. With a column of this type, of total capacity about 2 liters, a preparative apparatus of low dead volume has been built which produces 1 liter of pure D 2 from a 50 p. 100 D 2 , 50 p. 100 100 H 2 mixture in about 12 minutes. As a first approximation chromatography is likened theoretically to counter current fractionation, neglecting superficial resistance to the exchange. and also longitudinal diffusions. The number of theoretical plates required necessary for a certain enrichment of the gas phase is determined graphically or by calculation, enabling comparisons to be made between the efficiencies of columns containing different amounts of palladium. Thermal Diffusion: For the separation of hydrogen isotopes a thermal diffusion installation, made of stainless steel and entirely tele-commanded has been constructed. The separation cascade is made up of two identical pairs of hot wire columns. Each pair can work separately or they may be connected by a thermosyphon. The temperature of the hot wire is kept at around 1000 deg C by direct current. With this installation, hydrogen samples with a deuterium content lower than o,5 ppm were obtained from a gas originally containing 32 ppm. It was thus possible to prepare tritium of 99,3 p. 100 concentration from gas with an initial content of 6 p. 100. For quantitative separation of xenon enriched five time in 124 Xe by thermal diffusion, two identical cascades were constructed, each consisting of 5 columns, working in parallel and the two being connected by thermosyphon or by a capillary tube linked to a thermal gas oscillation. The central tungsten wire is heated to 1200 deg C. The columns are grouped like cluster of a heat exchanger, in shell of 30 cm diameter through which cooling water

  6. [Content trends of pollutants in street dust of Beijing along the urban-rural gradient and road density gradient].

    Science.gov (United States)

    Tang, Rong-Li; Ma, Ke-Ming; Zhang, Yu-Xin; Mao, Qi-Zheng

    2013-01-01

    In the article, pollutant content of 220 road dust samples within the sixth ring road of Beijing have been investigated by using grid stationing sampling method. The changing characteristics of road nude number per unit area, road network density and pollutant content within buffering areas along urban to rural gradient were also studied. Three following variation trends are presented as each index varies widely within the research areas. Firstly, road nude number per unit area, road network density and Cu, Cr, Pb content decrease along urban to rural gradient, and they decrease sharply in the beginning. Secondly, Mn, Cd content change a little along urban to rural gradient, and mean value remains stable. Thirdly, the content of Ni, TOC, TN decreases along with the distance fluctuations in the beginning and their mean values are then rising slowly in the suburbs. The turning point of pollutant content are found in places 15-20 km away from city center. The article shows that the road index and Cd content are irrelevant, and weak correlations are found between road index, TS, Mn and pH. And other relevance ranking are described as follows: Cu > TN > TOC > Pb > Ni > Cr. In contrast with road network density, higher correlations between road nude number per unit area and each element are fond, and element pollution of Cu, TN, TOC, Pb, Ni and Cr could be indicated by these indicators.

  7. Do low-mercury terrestrial resources subsidize low-mercury growth of stream fish? Differences between species along a productivity gradient.

    Directory of Open Access Journals (Sweden)

    Darren M Ward

    Full Text Available Low productivity in aquatic ecosystems is associated with reduced individual growth of fish and increased concentrations of methylmercury (MeHg in fish and their prey. However, many stream-dwelling fish species can use terrestrially-derived food resources, potentially subsidizing growth at low-productivity sites, and, because terrestrial resources have lower MeHg concentrations than aquatic resources, preventing an increase in diet-borne MeHg accumulation. We used a large-scale field study to evaluate relationships among terrestrial subsidy use, growth, and MeHg concentrations in two stream-dwelling fish species across an in-stream productivity gradient. We sampled young-of-the-year brook trout (Salvelinus fontinalis and Atlantic salmon (Salmo salar, potential competitors with similar foraging habits, from 20 study sites in streams in New Hampshire and Massachusetts that encompassed a wide range of aquatic prey biomass. Stable isotope analysis showed that brook trout used more terrestrial resources than Atlantic salmon. Over their first growing season, Atlantic salmon tended to grow larger than brook trout at sites with high aquatic prey biomass, but brook grew two-fold larger than Atlantic salmon at sites with low aquatic prey biomass. The MeHg concentrations of brook trout and Atlantic salmon were similar at sites with high aquatic prey biomass and the MeHg concentrations of both species increased at sites with low prey biomass and high MeHg in aquatic prey. However, brook trout had three-fold lower MeHg concentrations than Atlantic salmon at low-productivity, high-MeHg sites. These results suggest that differential use of terrestrial resource subsidies reversed the growth asymmetry between potential competitors across a productivity gradient and, for one species, moderated the effect of low in-stream productivity on MeHg accumulation.

  8. Jupiter's evolution with primordial composition gradients

    OpenAIRE

    Vazan, A.; Helled, R.; Guillot, T.

    2018-01-01

    Recent formation and structure models of Jupiter suggest that the planet can have composition gradients and not be fully convective (adiabatic). This possibility directly affects our understanding of Jupiter's bulk composition and origin. In this Letter we present Jupiter's evolution with a primordial structure consisting of a relatively steep heavy-element gradient of 40 Earth masses. We show that for a primordial structure with composition gradients, most of the mixing occurs in the outer p...

  9. Thermal conduction down steep temperature gradients

    International Nuclear Information System (INIS)

    Bell, A.R.; Evans, R.G.; Nicholas, D.J.

    1980-08-01

    The Fokker-Planck equation has been solved numerically in one spatial and two velocity dimensions in order to study thermal conduction in large temperature gradients. An initially cold plasma is heated at one end of the spatial grid producing temperature gradients with scale lengths of a few times the electron mean free path. The heat flow is an order of magnitude smaller than that predicted by the classical theory which is valid in the limit of small temperature gradients. (author)

  10. Testing the limits of gradient sensing.

    Directory of Open Access Journals (Sweden)

    Vinal Lakhani

    2017-02-01

    Full Text Available The ability to detect a chemical gradient is fundamental to many cellular processes. In multicellular organisms gradient sensing plays an important role in many physiological processes such as wound healing and development. Unicellular organisms use gradient sensing to move (chemotaxis or grow (chemotropism towards a favorable environment. Some cells are capable of detecting extremely shallow gradients, even in the presence of significant molecular-level noise. For example, yeast have been reported to detect pheromone gradients as shallow as 0.1 nM/μm. Noise reduction mechanisms, such as time-averaging and the internalization of pheromone molecules, have been proposed to explain how yeast cells filter fluctuations and detect shallow gradients. Here, we use a Particle-Based Reaction-Diffusion model of ligand-receptor dynamics to test the effectiveness of these mechanisms and to determine the limits of gradient sensing. In particular, we develop novel simulation methods for establishing chemical gradients that not only allow us to study gradient sensing under steady-state conditions, but also take into account transient effects as the gradient forms. Based on reported measurements of reaction rates, our results indicate neither time-averaging nor receptor endocytosis significantly improves the cell's accuracy in detecting gradients over time scales associated with the initiation of polarized growth. Additionally, our results demonstrate the physical barrier of the cell membrane sharpens chemical gradients across the cell. While our studies are motivated by the mating response of yeast, we believe our results and simulation methods will find applications in many different contexts.

  11. Disentangling dissolved oxygen sources in shallow riparian groundwater by stable isotope analysis

    Science.gov (United States)

    Mader, Michael; Porst, David; Schmidt, Christian; van Geldern, Robert; Barth, Johannes

    2017-04-01

    Dissolved oxygen (DO) is one of the strongest oxidation agents in aquatic environments. Besides gas-water-exchange, mixing and mineral oxidation, it is a key player in fundamental biogeochemical processes such as respiration and photosynthesis. These processes also systematically influence stable isotope ratios of DO and of dissolved inorganic carbon (DIC). Simultaneous measurements of DO and DIC concentrations in conjunction with their stable isotope ratios (δ18ODO and δ13CDIC) can thus provide useful tools to quantify oxygen and carbon sources and sinks in natural waters. This study focused on the Selke River in the Harz Mountains (Germany) with steep DO gradients between the stream water and the shallow, adjacent groundwater and associated stable isotope shifts. δ13CDIC values decreased from -13 ‰ to -18 ‰ versus the Vienna Pee Dee Belemnite standard (VPDB) from May to November 2016 and indicated the dominant influence of microbial respiration on the observed DO gradients. With such respiration dominance, we have expected a simultaneous enrichment of δ18ODOto values higher than the one of atmospheric O2 (+23.9 ‰ versus Vienna Standard Mean Ocean Water standard - VSMOW). However, our measurements revealed anomalously low δ18ODO values between +22 ‰ and +18 ‰ versus VSMOW for the same time period. These δ18ODO values were lower than those found in the river. Latter were close to equilibrium with the atmosphere (24.9 ‰ versus VSMOW). The observed δ18ODO ratios in the shallow groundwater can be explained with DO from the river that is subject to fractionation by microbial respiration with a typical fractionation factor (αr) of 0.995. In addition, mass balances revealed that this oxygen pool receives contributions of up to 25 % by diffused oxygen from the vadose zone. Consequently, isotope shifts by respiration and admixture with surface water are masked by diffusion effects that result in a decoupling of carbon and oxygen isotope systematics in

  12. STOCHASTIC GRADIENT METHODS FOR UNCONSTRAINED OPTIMIZATION

    Directory of Open Access Journals (Sweden)

    Nataša Krejić

    2014-12-01

    Full Text Available This papers presents an overview of gradient based methods for minimization of noisy functions. It is assumed that the objective functions is either given with error terms of stochastic nature or given as the mathematical expectation. Such problems arise in the context of simulation based optimization. The focus of this presentation is on the gradient based Stochastic Approximation and Sample Average Approximation methods. The concept of stochastic gradient approximation of the true gradient can be successfully extended to deterministic problems. Methods of this kind are presented for the data fitting and machine learning problems.

  13. Wireless SAW Based Temperature Gradient Sensor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Prime Photonics proposes design and development of a surface acoustic wave (SAW) based temperature gradient sensor for instrumentation of thermal protection systems...

  14. Community and ecosystem responses to elevational gradients

    DEFF Research Database (Denmark)

    Sundqvist, Maja K.; Sanders, Nate; Wardle, David A.

    2013-01-01

    elevational gradients for understanding community and ecosystem responses to global climate change at much larger spatial and temporal scales than is possible through conventional ecological experiments. However, future studies that integrate elevational gradient approaches with experimental manipulations...... will provide powerful information that can improve predictions of climate change impacts within and across ecosystems.......Community structure and ecosystem processes often vary along elevational gradients. Their responses to elevation are commonly driven by changes in temperature, and many community- and ecosystem-level variables therefore frequently respond similarly to elevation across contrasting gradients...

  15. On lower order strain gradient plasticity theories

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Hutchinson, J. W.

    2003-01-01

    the tangent moduli governing increments of stress and strain. It is shown that the modification is far from benign from a mathematical standpoint, changing the qualitative character of solutions and leading to a new type of localization that is at odds with what is expected from a strain gradient theory......By way of numerical examples, this paper explores the nature of solutions to a class of strain gradient plasticity theories that employ conventional stresses, equilibrium equations and boundary conditions. Strain gradients come into play in these modified conventional theories only to alter....... The findings raise questions about the physical acceptability of this class of strain gradient theories....

  16. Factors controlling soil organic carbon stability along a temperate forest altitudinal gradient

    Science.gov (United States)

    Tian, Qiuxiang; He, Hongbo; Cheng, Weixin; Bai, Zhen; Wang, Yang; Zhang, Xudong

    2016-01-01

    Changes in soil organic carbon (SOC) stability may alter carbon release from the soil and, consequently, atmospheric CO2 concentration. The mean annual temperature (MAT) can change the soil physico-chemical characteristics and alter the quality and quantity of litter input into the soil that regulate SOC stability. However, the relationship between climate and SOC stability remains unclear. A 500-day incubation experiment was carried out on soils from an 11 °C-gradient mountainous system on Changbai Mountain in northeast China. Soil respiration during the incubation fitted well to a three-pool (labile, intermediate and stable) SOC decomposition model. A correlation analysis revealed that the MAT only influenced the labile carbon pool size and not the SOC stability. The intermediate carbon pool contributed dominantly to cumulative carbon release. The size of the intermediate pool was strongly related to the percentage of sand particle. The decomposition rate of the intermediate pool was negatively related to soil nitrogen availability. Because both soil texture and nitrogen availability are temperature independent, the stability of SOC was not associated with the MAT, but was heavily influenced by the intrinsic processes of SOC formation and the nutrient status. PMID:26733344

  17. Constant fields and constant gradients in open ionic channels.

    Science.gov (United States)

    Chen, D P; Barcilon, V; Eisenberg, R S

    1992-05-01

    Ions enter cells through pores in proteins that are holes in dielectrics. The energy of interaction between ion and charge induced on the dielectric is many kT, and so the dielectric properties of channel and pore are important. We describe ionic movement by (three-dimensional) Nemst-Planck equations (including flux and net charge). Potential is described by Poisson's equation in the pore and Laplace's equation in the channel wall, allowing induced but not permanent charge. Asymptotic expansions are constructed exploiting the long narrow shape of the pore and the relatively high dielectric constant of the pore's contents. The resulting one-dimensional equations can be integrated numerically; they can be analyzed when channels are short or long (compared with the Debye length). Traditional constant field equations are derived if the induced charge is small, e.g., if the channel is short or if the total concentration gradient is zero. A constant gradient of concentration is derived if the channel is long. Plots directly comparable to experiments are given of current vs voltage, reversal potential vs. concentration, and slope conductance vs. concentration. This dielectric theory can easily be tested: its parameters can be determined by traditional constant field measurements. The dielectric theory then predicts current-voltage relations quite different from constant field, usually more linear, when gradients of total concentration are imposed. Numerical analysis shows that the interaction of ion and channel can be described by a mean potential if, but only if, the induced charge is negligible, that is to say, the electric field is spatially constant.

  18. Shelf-Stable Food Safety

    Science.gov (United States)

    ... is an MRE? Is an MRE shelf stable? What foods are packaged in retort packages? What is aseptic ... type of package is used for aseptic processing? What foods are packaged in aseptic packages? Can I microwave ...

  19. Stable emulsions in extraction systems containing zirconium and silicic acid

    International Nuclear Information System (INIS)

    Sinegribova, O.A.; Chizhevskaya, S.V.; Kotenko, A.A.

    1989-01-01

    The effect of zirconium nitrate compound nature and silicic acid on the rate of emulsions stratification in extraction systems depending on the components concentration, solution acidity, its past history, is studied. It is stated that stable multinuclear zirconium compounds have an influence on formation of stable emulsions in systems containing silicic acid. On the basis of results of chemical analysis and properties of interphase precipitates, being part of stable emulsion, suppositions on mechanism of interaction of zirconium nitrate compounds with silicic acid β-form are made

  20. Pharmaceuticals labelled with stable isotopes

    International Nuclear Information System (INIS)

    Krumbiegel, P.

    1986-11-01

    The relatively new field of pharmaceuticals labelled with stable isotopes is reviewed. Scientific, juridical, and ethical questions are discussed concerning the application of these pharmaceuticals in human medicine. 13 C, 15 N, and 2 H are the stable isotopes mainly utilized in metabolic function tests. Methodical contributions are given to the application of 2 H, 13 C, and 15 N pharmaceuticals showing new aspects and different states of development in the field under discussion. (author)

  1. Stable isotope research pool inventory

    International Nuclear Information System (INIS)

    1984-03-01

    This report contains a listing of electromagnetically separated stable isotopes which are available at the Oak Ridge National Laboratory for distribution for nondestructive research use on a loan basis. This inventory includes all samples of stable isotopes in the Research Materials Collection and does not designate whether a sample is out on loan or is in reprocessing. For some of the high abundance naturally occurring isotopes, larger amounts can be made available; for example, Ca-40 and Fe-56

  2. Oxygen gradients for open well cellular cultures via microfluidic substrates.

    Science.gov (United States)

    Lo, Joe F; Sinkala, Elly; Eddington, David T

    2010-09-21

    Controlling oxygen concentration at a microscale level can benefit experimental investigations involving oxidative stress, ischemia, and reactive oxygen species (ROS) mediated cellular pathways. Here, we report the application of microfluidic gradient generation in an open-well culture model, in which a gradient of gas is delivered via diffusion through a gas permeable substrate that separates cells from the gas microchannels below. By using diffusion to localize oxygen delivery, microgradients of oxygen concentrations can be rapidly and controllably applied without exposing cells to mechanical stresses or reducing culture volumes inside microfluidic culture chambers. Furthermore, we demonstrate the modulation of intracellular ROS levels in Madin-Darby Canine Kidney (MDCK) cells by applying these oxygen microgradients. Increases in ROS levels consistent with both oxidative stress and hypoxic exposures were observed in MDCK cells. The measured ROS increases were comparable to 100 microM hydrogen peroxide exposure in a control comparison, which is within the range of standard ROS induction methods. Incubation with 200 microM vitamin C was able to demodulate the ROS response at both hypoxic and hyperoxic exposures. By providing microfluidic controlled gradients, constant ROS exposure, and a shear-free open well design, the devices introduced here greatly improve upon standard oxygen-based culturing methods.

  3. A model for sedimentation in inhomogeneous media. I. Dynamic density gradients from sedimenting co-solutes.

    Science.gov (United States)

    Schuck, Peter

    2004-03-01

    Macromolecular sedimentation in inhomogeneous media is of great practical importance. Dynamic density gradients have a long tradition in analytical ultracentrifugation, and are frequently used in preparative ultracentrifugation. In this paper, a new theoretical model for sedimentation in inhomogeneous media is presented, based on finite element solutions of the Lamm equation with spatial and temporal variation of the local solvent density and viscosity. It is applied to macromolecular sedimentation in the presence of a dynamic density gradient formed by the sedimentation of a co-solute at high concentration. It is implemented in the software SEDFIT for the analysis of experimental macromolecular concentration distributions. The model agrees well with the measured sedimentation profiles of a protein in a dynamic cesium chloride gradient, and may provide a measure for the effects of hydration or preferential solvation parameters. General features of protein sedimentation in dynamic density gradients are described.

  4. Growth and chemosensory behavior of sulfate-reducing bacteria in oxygen-sulfide gradients

    DEFF Research Database (Denmark)

    Sass, Andrea M.; Wieland, Andrea Eschemann; Kühl, Michael

    2002-01-01

    Growth and chemotactic behavior in oxic–anoxic gradients were studied with two freshwater and four marine strains of sulfate-reducing bacteria related to the genera Desulfovibrio, Desulfomicrobium or Desulfobulbus. Cells were grown in oxygen–sulfide counter-gradients within tubes filled with agar...... to actively change the extension and slope of the gradients by oxygen reduction with lactate or even sulfide as electron donor. Generally, the chemotactic behavior was in agreement with a defense strategy that re-establishes anoxic conditions, thus promoting anaerobic growth and, in a natural community...... chemotactically to lactate, nitrate, sulfate and thiosulfate, and even sulfide functioned as an attractant. In oxic–anoxic gradients the bacteria moved away from high oxygen concentrations and formed bands at the outer edge of the oxic zone at low oxygen concentration (

  5. Canonical trivialization of gravitational gradients

    International Nuclear Information System (INIS)

    Niedermaier, Max

    2017-01-01

    A one-parameter family of canonical transformations is constructed that reduces the Hamiltonian form of the Einstein–Hilbert action to its strong coupling limit where dynamical spatial gradients are absent. The parameter can alternatively be viewed as the overall scale of the spatial metric or as a fractional inverse power of Newton’s constant. The generating function of the canonical transformation is constructed iteratively as a powerseries in the parameter to all orders. The algorithm draws on Lie–Deprit transformation theory and defines a ‘trivialization map’ with several bonus properties: (i) Trivialization of the Hamiltonian constraint implies that of the action while the diffeomorphism constraint is automatically co-transformed. (ii) Only a set of ordinary differential equations needs to be solved to drive the iteration via a homological equation where no gauge fixing is required. (iii) In contrast to (the classical limit of) a Lagrangian trivialization map the algorithm also produces series solutions of the field equations. (iv) In the strong coupling theory temporal gauge variations are abelian, nevertheless the map intertwines with the respective gauge symmetries on the action, the field equations, and their solutions. (paper)

  6. Canonical trivialization of gravitational gradients

    Science.gov (United States)

    Niedermaier, Max

    2017-06-01

    A one-parameter family of canonical transformations is constructed that reduces the Hamiltonian form of the Einstein-Hilbert action to its strong coupling limit where dynamical spatial gradients are absent. The parameter can alternatively be viewed as the overall scale of the spatial metric or as a fractional inverse power of Newton’s constant. The generating function of the canonical transformation is constructed iteratively as a powerseries in the parameter to all orders. The algorithm draws on Lie-Deprit transformation theory and defines a ‘trivialization map’ with several bonus properties: (i) Trivialization of the Hamiltonian constraint implies that of the action while the diffeomorphism constraint is automatically co-transformed. (ii) Only a set of ordinary differential equations needs to be solved to drive the iteration via a homological equation where no gauge fixing is required. (iii) In contrast to (the classical limit of) a Lagrangian trivialization map the algorithm also produces series solutions of the field equations. (iv) In the strong coupling theory temporal gauge variations are abelian, nevertheless the map intertwines with the respective gauge symmetries on the action, the field equations, and their solutions.

  7. Gradient Flow Convolutive Blind Source Separation

    DEFF Research Database (Denmark)

    Pedersen, Michael Syskind; Nielsen, Chinton Møller

    2004-01-01

    Experiments have shown that the performance of instantaneous gradient flow beamforming by Cauwenberghs et al. is reduced significantly in reverberant conditions. By expanding the gradient flow principle to convolutive mixtures, separation in a reverberant environment is possible. By use of a circ...

  8. Microinstabilities in weak density gradient tokamak systems

    International Nuclear Information System (INIS)

    Tang, W.M.; Rewoldt, G.; Chen, L.

    1986-04-01

    A prominent characteristic of auxiliary-heated tokamak discharges which exhibit improved (''H-mode type'') confinement properties is that their density profiles tend to be much flatter over most of the plasma radius. Depsite this favorable trend, it is emphasized here that, even in the limit of zero density gradient, low-frequency microinstabilities can persist due to the nonzero temperature gradient

  9. Preconditioning the modified conjugate gradient method ...

    African Journals Online (AJOL)

    In this paper, the convergence analysis of the conventional conjugate Gradient method was reviewed. And the convergence analysis of the modified conjugate Gradient method was analysed with our extension on preconditioning the algorithm. Convergence of the algorithm is a function of the condition number of M-1A.

  10. 40 CFR 230.25 - Salinity gradients.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Salinity gradients. 230.25 Section 230.25 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) OCEAN DUMPING SECTION 404(b... Physical and Chemical Characteristics of the Aquatic Ecosystem § 230.25 Salinity gradients. (a) Salinity...

  11. Patterns of macromycete community assemblage along an elevation gradient: options for fungal gradient and metacommunity analyse

    Science.gov (United States)

    Marko Gómez-Hernández; Guadalupe Williams-Linera; Roger Guevara; D. Jean Lodge

    2012-01-01

    Gradient analysis is rarely used in studies of fungal communities. Data on macromycetes from eight sites along an elevation gradient in central Veracruz, Mexico, were used to demonstrate methods for gradient analysis that can be applied to studies of communities of fungi. Selected sites from 100 to 3,500 m altitude represent tropical dry forest, tropical montane cloud...

  12. Density Gradient Stabilization of Electron Temperature Gradient Driven Turbulence in a Spherical Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Y; Mazzucato, E; Guttenfelder, W; Bell, R E; Domier, C W; LeBlanc, B P; Lee, K C; Luhmann Jr, N C; Smith, D R

    2011-03-21

    In this letter we report the first clear experimental observation of density gradient stabilization of electron temperature gradient driven turbulence in a fusion plasma. It is observed that longer wavelength modes, k⊥ρs ≤10, are most stabilized by density gradient, and the stabilization is accompanied by about a factor of two decrease in the plasma effective thermal diffusivity.

  13. Boundary value problems of the circular cylinders in the strain-gradient theory of linear elasticity

    International Nuclear Information System (INIS)

    Kao, B.G.

    1979-11-01

    Three boundary value problems in the strain-gradient theory of linear elasticity are solved for circular cylinders. They are the twisting of circular cylinder, uniformly pressuring of concentric circular cylinder, and pure-bending of simply connected cylinder. The comparisons of these solutions with the solutions in classical elasticity and in couple-stress theory reveal the differences in the stress fields as well as the apparent stress fields due to the influences of the strain-gradient. These aspects of the strain-gradient theory could be important in modeling the failure behavior of structural materials

  14. Approximate error conjugation gradient minimization methods

    Science.gov (United States)

    Kallman, Jeffrey S

    2013-05-21

    In one embodiment, a method includes selecting a subset of rays from a set of all rays to use in an error calculation for a constrained conjugate gradient minimization problem, calculating an approximate error using the subset of rays, and calculating a minimum in a conjugate gradient direction based on the approximate error. In another embodiment, a system includes a processor for executing logic, logic for selecting a subset of rays from a set of all rays to use in an error calculation for a constrained conjugate gradient minimization problem, logic for calculating an approximate error using the subset of rays, and logic for calculating a minimum in a conjugate gradient direction based on the approximate error. In other embodiments, computer program products, methods, and systems are described capable of using approximate error in constrained conjugate gradient minimization problems.

  15. Development of Gradient Cemented Carbides Through ICME Strategy

    Science.gov (United States)

    Du, Yong; Peng, Yingbiao; Zhang, Weibin; Chen, Weimin; Zhou, Peng; Xie, Wen; Cheng, Kaiming; Zhang, Lijun; Wen, Guanghua; Wang, Shequan

    An integrated computational materials engineering (ICME) including CALPHAD method is a powerful tool for materials process optimization and alloy design. The quality of CALPHAD-type calculations is strongly dependent on the quality of the thermodynamic and diffusivity databases. The development of a thermodynamic database, CSUTDCC1, and a diffusivity database, CSUDDCC1, for cemented carbides is described. Several gradient cemented carbides sintered under vacuum and various partial pressures of N2 have been studied via experiment and simulation. The microstructure and concentration profile of the gradient zones have been investigated via SEM and EPMA. Examples of ICME applications in design and manufacture for different kinds of cemented carbides are shown using the databases and comparing where possible against experimental data, thereby validating its accuracy.

  16. Respiratory depression by stable xenon in goats

    International Nuclear Information System (INIS)

    Winkler, S.S.

    1986-01-01

    Regional cerebral blood flow (rCBF) studies with stable xenon have recently become practical. Xenon pharmacology is thus a more than academic interest. The authors studied the respiratory response of three trained goats to a mixture of 70% xenon, 30% oxygen. The relatively high xenon concentration was used because of the animals' resistance to anesthetic effects. Two other goats were treated with equivalent anesthetic concentration of nitrous oxide and halothane. The xenon-treated animals showed respiratory depression, in contrast to the stimulating effects observed with halothane and nitrous oxide. Elevation of PaCO/sub 2/ was significant and would substantially increase cRBF. Their findings emphasize the need to monitor ventilation and respond appropriately if necessary

  17. Concentrating Radioactivity

    Science.gov (United States)

    Herrmann, Richard A.

    1974-01-01

    By concentrating radioactivity contained on luminous dials, a teacher can make a high reading source for classroom experiments on radiation. The preparation of the source and its uses are described. (DT)

  18. Dependence of bacterial chemotaxis on gradient shape and adaptation rate.

    Directory of Open Access Journals (Sweden)

    Nikita Vladimirov

    2008-12-01

    Full Text Available Simulation of cellular behavior on multiple scales requires models that are sufficiently detailed to capture central intracellular processes but at the same time enable the simulation of entire cell populations in a computationally cheap way. In this paper we present RapidCell, a hybrid model of chemotactic Escherichia coli that combines the Monod-Wyman-Changeux signal processing by mixed chemoreceptor clusters, the adaptation dynamics described by ordinary differential equations, and a detailed model of cell tumbling. Our model dramatically reduces computational costs and allows the highly efficient simulation of E. coli chemotaxis. We use the model to investigate chemotaxis in different gradients, and suggest a new, constant-activity type of gradient to systematically study chemotactic behavior of virtual bacteria. Using the unique properties of this gradient, we show that optimal chemotaxis is observed in a narrow range of CheA kinase activity, where concentration of the response regulator CheY-P falls into the operating range of flagellar motors. Our simulations also confirm that the CheB phosphorylation feedback improves chemotactic efficiency by shifting the average CheY-P concentration to fit the motor operating range. Our results suggest that in liquid media the variability in adaptation times among cells may be evolutionary favorable to ensure coexistence of subpopulations that will be optimally tactic in different gradients. However, in a porous medium (agar such variability appears to be less important, because agar structure poses mainly negative selection against subpopulations with low levels of adaptation enzymes. RapidCell is available from the authors upon request.

  19. Stable Boundary Layer Education (STABLE) Final Campaign Summary

    Energy Technology Data Exchange (ETDEWEB)

    Turner, David D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-03-01

    The properties of, and the processes that occur in, the nocturnal stable boundary layer are not well understood, making it difficult to represent adequately in numerical models. The nocturnal boundary layer often is characterized by a temperature inversion and, in the Southern Great Plains region, a low-level jet. To advance our understanding of the nocturnal stable boundary layer, high temporal and vertical resolution data on the temperature and wind properties are needed, along with both large-eddy simulation and cloud-resolving modeling.

  20. Shifts in the Source and Composition of Dissolved Organic Matter in Southwest Greenland Lakes Along a Regional Hydro-climatic Gradient

    Science.gov (United States)

    Osburn, Christopher L.; Anderson, Nicholas J.; Stedmon, Colin A.; Giles, Madeline E.; Whiteford, Erika J.; McGenity, Terry J.; Dumbrell, Alex J.; Underwood, Graham J. C.

    2017-12-01

    Dissolved organic matter (DOM) concentration and quality were examined from Arctic lakes located in three clusters across south-west (SW) Greenland, covering the regional climatic gradient: cool, wet coastal zone; dry inland interior; and cool, dry ice-marginal areas. We hypothesized that differences in mean annual precipitation between sites would result in a reduced hydrological connectivity between lakes and their catchments and that this concentrates degraded DOM. The DOM in the inland lake group was characterized by a lower aromaticity and molecular weight, a low soil-like fluorescence, and carbon stable isotope (δ13C-DOC) values enriched by 2‰ relative to the coastal group. DOC-specific absorbance (SUVA254) and DOC-specific soil-like fluorescence (SUVFC1) revealed seasonal and climatic gradients across which DOM exhibited a dynamic we term "pulse-process": Pulses of DOM exported from soils to lakes during snow and ice melt were followed by pulses of autochthonous DOM inputs (possibly from macrophytes), and their subsequent photochemical and microbial processing. These effects regulated the dynamics of DOM in the inland lakes and suggested that if circumpolar lakes currently situated in cool wetter climatic regimes with strong hydrological connectivity have reduced connectivity under a drier future climate, they may evolve toward an end-point of large stocks of highly degraded DOC, equivalent to the inland lakes in the present study. The regional climatic gradient across SW Greenland and its influence on DOM properties in these lakes provide a model of possible future changes to lake C cycling in high-latitude systems where climatic changes are most pronounced.

  1. Intracellular chemical gradients: morphing principle in bacteria

    Directory of Open Access Journals (Sweden)

    Endres Robert G

    2012-09-01

    Full Text Available Abstract Advances in computational biology allow systematic investigations to ascertain whether internal chemical gradients can be maintained in bacteria – an open question at the resolution limit of fluorescence microscopy. While it was previously believed that the small bacterial cell size and fast diffusion in the cytoplasm effectively remove any such gradient, a new computational study published in BMC Biophysics supports the emerging view that gradients can exist. The study arose from the recent observation that phosphorylated CtrA forms a gradient prior to cell division in Caulobacter crescentus, a bacterium known for its complicated cell cycle. Tropini et al. (2012 postulate that such gradients can provide an internal chemical compass, directing protein localization, cell division and cell development. More specifically, they describe biochemical and physical constraints on the formation of such gradients and explore a number of existing bacterial cell morphologies. These chemical gradients may limit in vitro analyses, and may ensure timing control and robustness to fluctuations during critical stages in cell development.

  2. Satellite gravity gradient grids for geophysics.

    Science.gov (United States)

    Bouman, Johannes; Ebbing, Jörg; Fuchs, Martin; Sebera, Josef; Lieb, Verena; Szwillus, Wolfgang; Haagmans, Roger; Novak, Pavel

    2016-02-11

    The Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite aimed at determining the Earth's mean gravity field. GOCE delivered gravity gradients containing directional information, which are complicated to use because of their error characteristics and because they are given in a rotating instrument frame indirectly related to the Earth. We compute gravity gradients in grids at 225 km and 255 km altitude above the reference ellipsoid corresponding to the GOCE nominal and lower orbit phases respectively, and find that the grids may contain additional high-frequency content compared with GOCE-based global models. We discuss the gradient sensitivity for crustal depth slices using a 3D lithospheric model of the North-East Atlantic region, which shows that the depth sensitivity differs from gradient to gradient. In addition, the relative signal power for the individual gradient component changes comparing the 225 km and 255 km grids, implying that using all components at different heights reduces parameter uncertainties in geophysical modelling. Furthermore, since gravity gradients contain complementary information to gravity, we foresee the use of the grids in a wide range of applications from lithospheric modelling to studies on dynamic topography, and glacial isostatic adjustment, to bedrock geometry determination under ice sheets.

  3. Advanced Gradient Heating Facility (AGHF)

    Science.gov (United States)

    1998-01-01

    This section of the publication includes papers entitled: (1) Coupled growth in hypermonotectics; (2) Directional solidification of refined Al-4 wt.% Cu alloys; (3) Effects of convection on interface curvature during growth of concentrated ternary compounds; (4) Directional solidification of Al-1.5 wt.% Ni alloys; (5) Interactive response of advancing phase boundaries to particles; (6) INTeractive Response of Advancing Phase boundaries to Particles-INTRAPP; and (7) Particle engulfment and pushing by solidifying interfaces.

  4. Free water transport, small pore transport and the osmotic pressure gradient.

    Science.gov (United States)

    Parikova, Alena; Smit, Watske; Zweers, Machteld M; Struijk, Dirk G; Krediet, Raymond T

    2008-07-01

    Water transport in peritoneal dialysis (PD) patients occurs through the small pores and water channels, the latter allowing free water transport (FWT). The osmotic gradient is known to be one of the major determinants of water transport. The objective of the study was to analyse the relation between each transport route and the osmotic gradient. The 4-h standard peritoneal permeability analyses of 80 stable PD patients were studied. Small pore transport (SPT) was calculated based on the transported amount of sodium. FWT was calculated by subtracting SPT from transcapillary ultrafiltration (TCUF). Water transport rates were determined. The osmotic gradient was calculated. The slope of the relation between FWT rate and osmotic gradient (slope(FWT)), and the elimination constant (K(e)) of the exponential relation between SPT rate and osmotic gradient (K(SPT)) were calculated for every patient. The FWT rate was related to the osmotic gradient (P = 0.001). A similar correlation was also found between the SPT rate and osmotic gradient when fitted exponentially (P = 0.005). The rates of FWT decreased significantly between each time point during the whole dwell. The SPT rates decreased significantly within the first half of the dwell and levelled off thereafter. No correlations were found between the slope(FWT), K(SPT) and PD duration. The slope(FWT) of the relationship between the FWT and the osmotic gradient is an indirect measurement of the amount of functioning water channels. Similarly, the K(SPT) value represents the number of functioning small pores. The absence of a relationship of these parameters with the duration of PD suggests opposing mechanisms, for instance a lower number of functioning pores in combination with an increased vascular surface area. Conclusion. The curves of the relationship between FWR, SPT and OG support the assumption that FWR is much more dependent on the OG than SPT. Non-osmotic determinants are likely to be important in small pore fluid

  5. Sound beam manipulation based on temperature gradients

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Feng [Key Laboratory of Modern Acoustics, Institute of Acoustics and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); School of Physics & Electronic Engineering, Changshu Institute of Technology, Changshu 215500 (China); Quan, Li; Liu, Xiaozhou, E-mail: xzliu@nju.edu.cn; Gong, Xiufen [Key Laboratory of Modern Acoustics, Institute of Acoustics and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-10-28

    Previous research with temperature gradients has shown the feasibility of controlling airborne sound propagation. Here, we present a temperature gradients based airborne sound manipulation schemes: a cylindrical acoustic omnidirectional absorber (AOA). The proposed AOA has high absorption performance which can almost completely absorb the incident wave. Geometric acoustics is used to obtain the refractive index distributions with different radii, which is then utilized to deduce the desired temperature gradients. Since resonant units are not applied in the scheme, its working bandwidth is expected to be broadband. The scheme is temperature-tuned and easy to realize, which is of potential interest to fields such as noise control or acoustic cloaking.

  6. On fracture in finite strain gradient plasticity

    DEFF Research Database (Denmark)

    Martínez Pañeda, Emilio; Niordson, Christian Frithiof

    2016-01-01

    predictions. These differences increase significantly when large strains are taken into account, as a consequence of the contribution of strain gradients to the work hardening of the material. The magnitude of stress elevation at the crack tip and the distance ahead of the crack where GNDs significantly alter......In this work a general framework for damage and fracture assessment including the effect of strain gradients is provided. Both mechanism-based and phenomenological strain gradient plasticity (SGP) theories are implemented numerically using finite deformation theory and crack tip fields...

  7. Speciation gradients and the distribution of biodiversity.

    Science.gov (United States)

    Schluter, Dolph; Pennell, Matthew W

    2017-05-31

    Global patterns of biodiversity are influenced by spatial and environmental variations in the rate at which new species form. We relate variations in speciation rates to six key patterns of biodiversity worldwide, including the species-area relationship, latitudinal gradients in species and genetic diversity, and between-habitat differences in species richness. Although they sometimes mirror biodiversity patterns, recent rates of speciation, at the tip of the tree of life, are often highest where species richness is low. Speciation gradients therefore shape, but are also shaped by, biodiversity gradients and are often more useful for predicting future patterns of biodiversity than for interpreting the past.

  8. Sound beam manipulation based on temperature gradients

    International Nuclear Information System (INIS)

    Qian, Feng; Quan, Li; Liu, Xiaozhou; Gong, Xiufen

    2015-01-01

    Previous research with temperature gradients has shown the feasibility of controlling airborne sound propagation. Here, we present a temperature gradients based airborne sound manipulation schemes: a cylindrical acoustic omnidirectional absorber (AOA). The proposed AOA has high absorption performance which can almost completely absorb the incident wave. Geometric acoustics is used to obtain the refractive index distributions with different radii, which is then utilized to deduce the desired temperature gradients. Since resonant units are not applied in the scheme, its working bandwidth is expected to be broadband. The scheme is temperature-tuned and easy to realize, which is of potential interest to fields such as noise control or acoustic cloaking

  9. Stable carbon isotope ratios and intrinsic water-use efficiency of Miocene fossil leaves compared to modern congeners

    Energy Technology Data Exchange (ETDEWEB)

    Marshall, J.D.; Zhang, J.; Rember, W.C.; Jennings, D.; Larson, P. (Univ. of Idaho, Moscow, ID (United States))

    1994-06-01

    Miocene fossil leaves of forest trees were extracted from the Clarkia, Idaho fossil beds and their stable carbon isotope ratios were analyzed. Fossils had higher lignin concentrations and lower cellulose concentrations that modern leaves due to diagenesis and the HF used to extract the fossils. Therefore, [delta][sup 13]C of extracted fossil lignin was compared to that of modern lignin. Fossil lignin [delta][sup 13]C was significantly different from that of congeneric modern leaves (paired t-test, P<0.0001), but was 1.9% less negative. Gymnosperms (Metasequoia, Taxodium) were less negative than angiosperms (e.g., Magnolia, Quercus, Acer, Persea), but no difference between evergreen and deciduous species was detected. Using published estimates of the concentration and [delta][sup 13]C of atmospheric CO[sub 2] during the Miocene was estimated the CO[sub 2] partial pressure gradient across the stomata (intrinsic water-use efficiency). Intrinsic water-use efficiency was at least 70% higher during this past [open quotes]greenhouse[close quotes] period than at present.

  10. High-gradient two-beam accelerator structure

    Directory of Open Access Journals (Sweden)

    S. Yu Kazakov

    2010-07-01

    Full Text Available A novel cavity structure is described that could be the basis for a two-beam, high-gradient, accelerator. Versions of the structure could be used for acceleration of beams of electrons, positrons, muons, protons, or heavier ions; with either electron or proton drive beams. The structure embodies cavities that are excited in several harmonically related eigenmodes, such that rf fields reach their peak values only during small portions of each basic rf period. This feature could help raise breakdown and pulse heating thresholds. The two-beam accelerator structure comprises chains of these cavities. In this configuration, no transfer elements are needed to couple rf energy from the drive beam to the accelerated beam, since both beams traverse the same cavities. Purposeful cavity detuning is used to provide much smaller deceleration for a high-current drive beam, than acceleration for a low-current accelerated beam, i.e., to provide a high transformer ratio. A self-consistent theory is presented to calculate idealized acceleration gradient, transformer ratio, and efficiency for energy transfer from the drive beam to the accelerated beam, for either parallel or antiparallel motion of the beams. The theory has been cast in dimensionless quantities so as to facilitate optimization with respect to efficiency, acceleration gradient, or transformer ratio, and to illuminate the interdependence of these parameters. Means for dramatically shortening the structure fill time are also described. However, no beam dynamics analysis is presented, so the range of parameters within which this new acceleration concept can be used will remain uncertain until it is established that stable beam transport along the structure using an appropriate focusing system is possible.

  11. Molecular fractionation of starch by density-gradient ultracentrifugation.

    Science.gov (United States)

    Yoon, Jae Wook; Lim, Seung Taik

    2003-03-28

    Amylose and amylopectin in corn and potato starches were fractionated by centrifugation at 124,000g for 3-72 h at 40 degrees C in a gradient media, Nycodenz, based on their sedimentation rate differences. The fractions were collected from a centrifuge tube, and then analyzed by the phenol-sulfuric acid method and iodine-binding test. Amylopectin, a large and highly branched starch molecule, migrated faster than amylose and quickly reached its isopycnic point with a buoyant density of about 1.25 g/mL, exhibiting a sharp and stable carbohydrate peak. Amylose, which is a relatively small and linear molecule, however, migrated slowly in a broad density range and continued moving to higher density regions, eventually overlapping with amylopectin peak as the centrifugation continued. This could indicate that the buoyant density of amylose is similar to that of amylopectin. Under centrifugal conditions of 3 h and 124,000g, amylose and amylopectin molecules were clearly separated, and the presence of intermediate starch molecules (11.5 and 7.7% for corn and potato starch, respectively) was also observed between amylose and amylopectin fractions. The amylose content of corn and potato starches was 22.6 and 21.1%, respectively, based on the total carbohydrate analysis after the ultracentrifugation for 3 h. In alkaline gradients (pH 11 or 12.5), the sedimentation rate of starch molecules and the buoyant density of amylopectin were reduced, possibly due to the structural changes induced by alkali.

  12. Radiation-stable polyolefin compositions

    International Nuclear Information System (INIS)

    Rekers, J.W.

    1986-01-01

    This invention relates to compositions of olefinic polymers suitable for high energy radiation treatment. In particular, the invention relates to olefinic polymer compositions that are stable to sterilizing dosages of high energy radiation such as a gamma radiation. Stabilizers are described that include benzhydrol and benzhydrol derivatives; these stabilizers may be used alone or in combination with secondary antioxidants or synergists

  13. Monitoring of stable glaucoma patients

    NARCIS (Netherlands)

    K.M. Holtzer-Goor (Kim); N.S. Klazinga (Niek); M.A. Koopmanschap (Marc); H.G. Lemij (Hans); T. Plochg; E. van Sprundel (Esther)

    2010-01-01

    textabstractA high workload for ophthalmologists and long waiting lists for patients challenge the organization of ophthalmic care. Tasks that require less specialized skills, like the monitoring of stable (well controlled) glaucoma patients could be substituted from ophthalmologists to other

  14. A new type of descent conjugate gradient method with exact line search

    Science.gov (United States)

    Hajar, Nurul; Mamat, Mustafa; Rivaie, Mohd.; Jusoh, Ibrahim

    2016-06-01

    Nowadays, conjugate gradient (CG) methods are impressive for solving nonlinear unconstrained optimization problems. In this paper, a new CG method is proposed and analyzed. This new CG method satisfies descent condition and its global convergence is established using exact line search. Numerical results show that this new CG method substantially outperforms the previous CG methods. This new CG method is considered robust, efficient and provided faster and stable convergence.

  15. Formation of compositional gradient profiles by using shear-induced polymer migration phenomenon under Couette flow field

    Energy Technology Data Exchange (ETDEWEB)

    Im, Sang Hyuk; Lee, Su Jin [Kyung Hee University, Yongin (Korea, Republic of); Suh, Duck Jong; Park, O Ok [Korea Advanced Institute of Science and Technology (KAIST), Daejeon (Korea, Republic of); Kwon, Moo Hyun [Woosuk University, Wanju (Korea, Republic of)

    2015-07-15

    We investigated whether a graded-index profile, specified by the polymer compositional gradient, could be formed using shear-induced polymer migration phenomenon in a polymer solution. For the presented model system, we generated a shear flow by rotating a glass rod at the center of a polystyrene/methylmethacrylate (PS/MMA) solution and measured the degree of polymer migration by the shear flow field by examining the concentration of polymer solution along the radial direction from the rotating axis to the periphery. Through model experiments, we formed a compositional gradient and controlled its profile in the solution by varying the concentration of polymer solution, molecular weight of polymer, and shear rate. Finally, we solidified the gradient profiles by the polymerization of the PS/MMA solution and confirmed that the gradient profiles were maintained with a compositional gradient twice larger than the mother PS/MMA solution.

  16. Convergence of soil nitrogen isotopes across global climate gradients

    Science.gov (United States)

    Craine, Joseph M.; Elmore, Andrew J.; Wang, Lixin; Augusto, Laurent; Baisden, W. Troy; Brookshire, E. N. J.; Cramer, Michael D.; Hasselquist, Niles J.; Hobbie, Erik A.; Kahmen, Ansgar; Koba, Keisuke; Kranabetter, J. Marty; Mack, Michelle C.; Marin-Spiotta, Erika; Mayor, Jordan R.; McLauchlan, Kendra K.; Michelsen, Anders; Nardoto, Gabriela B.; Oliveira, Rafael S.; Perakis, Steven S.; Peri, Pablo L.; Quesada, Carlos A.; Richter, Andreas; Schipper, Louis A.; Stevenson, Bryan A.; Turner, Benjamin L.; Viani, Ricardo A. G.; Wanek, Wolfgang; Zeller, Bernd

    2015-01-01

    Quantifying global patterns of terrestrial nitrogen (N) cycling is central to predicting future patterns of primary productivity, carbon sequestration, nutrient fluxes to aquatic systems, and climate forcing. With limited direct measures of soil N cycling at the global scale, syntheses of the 15 N: 14 N ratio of soil organic matter across climate gradients provide key insights into understanding global patterns of N cycling. In synthesizing data from over 6000 soil samples, we show strong global relationships among soil N isotopes, mean annual temperature (MAT), mean annual precipitation (MAP), and the concentrations of organic carbon and clay in soil. In both hot ecosystems and dry ecosystems, soil organic matter was more enriched in 15 N than in corresponding cold ecosystems or wet ecosystems. Below a MAT of 9.8°C, soil δ15N was invariant with MAT. At the global scale, soil organic C concentrations also declined with increasing MAT and decreasing MAP. After standardizing for variation among mineral soils in soil C and clay concentrations, soil δ15N showed no consistent trends across global climate and latitudinal gradients. Our analyses could place new constraints on interpretations of patterns of ecosystem N cycling and global budgets of gaseous N loss.

  17. Improving GOCE cross-track gravity gradients

    Science.gov (United States)

    Siemes, Christian

    2018-01-01

    The GOCE gravity gradiometer measured highly accurate gravity gradients along the orbit during GOCE's mission lifetime from March 17, 2009, to November 11, 2013. These measurements contain unique information on the gravity field at a spatial resolution of 80 km half wavelength, which is not provided to the same accuracy level by any other satellite mission now and in the foreseeable future. Unfortunately, the gravity gradient in cross-track direction is heavily perturbed in the regions around the geomagnetic poles. We show in this paper that the perturbing effect can be modeled accurately as a quadratic function of the non-gravitational acceleration of the satellite in cross-track direction. Most importantly, we can remove the perturbation from the cross-track gravity gradient to a great extent, which significantly improves the accuracy of the latter and offers opportunities for better scientific exploitation of the GOCE gravity gradient data set.

  18. Vegetation patterns and environmental gradients in Benin

    NARCIS (Netherlands)

    Adomou, A.

    2005-01-01

    Key words: West Africa, Benin, vegetation patterns, floristic areas, phytogeography, chorology, floristic gradients, climatic factors, water availability, Dahomey Gap, threatened plants, biodiversity, conservation.Understanding plant species distribution patterns and the underlying factors is a

  19. Flexoelectricity: strain gradient effects in ferroelectrics

    Energy Technology Data Exchange (ETDEWEB)

    Ma Wenhui [Department of Physics, Shantou Unversity, Shantou, Guangdong 515063 (China)

    2007-12-15

    Mechanical strain gradient induced polarization effect or flexoelectricity in perovskite-type ferroelectric and relaxor ferroelectric ceramics was investigated. The flexoelectric coefficients measured at room temperature ranged from about 1 {mu} C m{sup -1} for lead zirconate titanate to 100 {mu} C m{sup -1} for barium strontium titanate. Flexoelectric effects were discovered to be sensitive to chemical makeup, phase symmetry, and domain structures. Based on phenomenological discussion and experimental data on flexoelectricity, the present study proposed that mechanical strain gradient field could influence polarization responses in a way analogous to electric field. Flexoelectric coefficients were found to be nonlinearly enhanced by dielectric permittivity and strain gradient. Interfacial mismatch in epitaxial thin films can give rise to high strain gradients, enabling flexoelectric effects to make a significant impact in properly engineered ferroelectric heterostructure systems.

  20. Flexoelectricity: strain gradient effects in ferroelectrics

    International Nuclear Information System (INIS)

    Ma Wenhui

    2007-01-01

    Mechanical strain gradient induced polarization effect or flexoelectricity in perovskite-type ferroelectric and relaxor ferroelectric ceramics was investigated. The flexoelectric coefficients measured at room temperature ranged from about 1 μ C m -1 for lead zirconate titanate to 100 μ C m -1 for barium strontium titanate. Flexoelectric effects were discovered to be sensitive to chemical makeup, phase symmetry, and domain structures. Based on phenomenological discussion and experimental data on flexoelectricity, the present study proposed that mechanical strain gradient field could influence polarization responses in a way analogous to electric field. Flexoelectric coefficients were found to be nonlinearly enhanced by dielectric permittivity and strain gradient. Interfacial mismatch in epitaxial thin films can give rise to high strain gradients, enabling flexoelectric effects to make a significant impact in properly engineered ferroelectric heterostructure systems

  1. Integral Field Spectroscopy Surveys: Oxygen Abundance Gradients

    Science.gov (United States)

    Sánchez, S. F.; Sánchez-Menguiano, L.

    2017-07-01

    We present here the recent results on our understanding of oxygen abundance gradients derived using Integral Field Spectroscopic surveys. In particular we analyzed more than 2124 datacubes corresponding to individual objects observed by the CALIFA (˜ 734 objects) and the public data by MaNGA (˜ 1390 objects), deriving the oxygen abundance gradient for each galaxy. We confirm previous results that indicate that the shape of this gradient is very similar for all galaxies with masses above 109.5M⊙, presenting in average a very similar slope of ˜ -0.04 dex within 0.5-2.0 re, with a possible drop in the inner regions (r109.5M⊙) the gradient seems to be flatter than for more massive ones. All these results agree with an inside-out growth of massive galaxies and indicate that low mass ones may still be growing in an outside in phase.

  2. Unimodal and crossmodal gradients of spatial attention

    DEFF Research Database (Denmark)

    Föcker, J.; Hötting, K.; Gondan, Matthias

    2010-01-01

    Behavioral and event-related potential (ERP) studies have shown that spatial attention is gradually distributed around the center of the attentional focus. The present study compared uni- and crossmodal gradients of spatial attention to investigate whether the orienting of auditory and visual...... spatial attention is based on modality specific or supramodal representations of space. Auditory and visual stimuli were presented from five speaker locations positioned in the right hemifield. Participants had to attend to the innermost or outmost right position in order to detect either visual...... or auditory deviant stimuli. Detection rates and event-related potentials (ERPs) indicated that spatial attention is distributed as a gradient. Unimodal spatial ERP gradients correlated with the spatial resolution of the modality. Crossmodal spatial gradients were always broader than the corresponding...

  3. Photosynthetic and gas exchange characteristics of dominant woody plants on a moisture gradient in an African savanna

    NARCIS (Netherlands)

    Midgley, G.F.; Aranibar, J.N.; Mantlana, K.B.; Macko, S.

    2004-01-01

    We determined key photosynthetic gas exchange parameters, and their temperature dependence, in dominant woody plants at four savanna sites on a moisture gradient in Botswana, southern Africa. Leaf stable carbon and nitrogen (N) isotope and morphological measures were made concurrently. Sampling of

  4. Microinstabilities in weak density gradient tokamak systems

    Energy Technology Data Exchange (ETDEWEB)

    Tang, W.M.; Rewoldt, G.; Chen, L.

    1986-04-01

    A prominent characteristic of auxiliary-heated tokamak discharges which exhibit improved (''H-mode type'') confinement properties is that their density profiles tend to be much flatter over most of the plasma radius. Depsite this favorable trend, it is emphasized here that, even in the limit of zero density gradient, low-frequency microinstabilities can persist due to the nonzero temperature gradient.

  5. Tolman temperature gradients in a gravitational field

    OpenAIRE

    Santiago, Jessica; Visser, Matt

    2018-01-01

    Tolman's relation for the temperature gradient in an equilibrium self-gravitating general relativistic fluid is broadly accepted within the general relativity community. However, the concept of temperature gradients in thermal equilibrium continues to cause confusion in other branches of physics, since it contradicts naive versions of the laws of classical thermodynamics. In this paper we discuss the crucial role of the universality of free fall, and how thermodynamics emphasises the great di...

  6. Ultimate gradient in solid-state accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Whittum, D.H.

    1998-08-01

    The authors recall the motivation for research in high-gradient acceleration and the problems posed by a compact collider. They summarize the phenomena known to appear in operation of a solid-state structure with large fields, and research relevant to the question of the ultimate gradient. They take note of new concepts, and examine one in detail, a miniature particle accelerator based on an active millimeter-wave circuit and parallel particle beams.

  7. Ultimate gradient in solid-state accelerators

    International Nuclear Information System (INIS)

    Whittum, D.H.

    1998-08-01

    The authors recall the motivation for research in high-gradient acceleration and the problems posed by a compact collider. They summarize the phenomena known to appear in operation of a solid-state structure with large fields, and research relevant to the question of the ultimate gradient. They take note of new concepts, and examine one in detail, a miniature particle accelerator based on an active millimeter-wave circuit and parallel particle beams

  8. Intratumoral oxygen gradients mediate sarcoma cell invasion

    Science.gov (United States)

    Lewis, Daniel M.; Park, Kyung Min; Tang, Vitor; Xu, Yu; Pak, Koreana; Eisinger-Mathason, T. S. Karin; Simon, M. Celeste; Gerecht, Sharon

    2016-01-01

    Hypoxia is a critical factor in the progression and metastasis of many cancers, including soft tissue sarcomas. Frequently, oxygen (O2) gradients develop in tumors as they grow beyond their vascular supply, leading to heterogeneous areas of O2 depletion. Here, we report the impact of hypoxic O2 gradients on sarcoma cell invasion and migration. O2 gradient measurements showed that large sarcoma mouse tumors (>300 mm3) contain a severely hypoxic core [≤0.1% partial pressure of O2 (pO2)] whereas smaller tumors possessed hypoxic gradients throughout the tumor mass (0.1–6% pO2). To analyze tumor invasion, we used O2-controllable hydrogels to recreate the physiopathological O2 levels in vitro. Small tumor grafts encapsulated in the hydrogels revealed increased invasion that was both faster and extended over a longer distance in the hypoxic hydrogels compared with nonhypoxic hydrogels. To model the effect of the O2 gradient accurately, we examined individual sarcoma cells embedded in the O2-controllable hydrogel. We observed that hypoxic gradients guide sarcoma cell motility and matrix remodeling through hypoxia-inducible factor-1α (HIF-1α) activation. We further found that in the hypoxic gradient, individual cells migrate more quickly, across longer distances, and in the direction of increasing O2 tension. Treatment with minoxidil, an inhibitor of hypoxia-induced sarcoma metastasis, abrogated cell migration and matrix remodeling in the hypoxic gradient. Overall, we show that O2 acts as a 3D physicotactic agent during sarcoma tumor invasion and propose the O2-controllable hydrogels as a predictive system to study early stages of the metastatic process and therapeutic targets. PMID:27486245

  9. The luminescent concentrator. Stability issues

    Energy Technology Data Exchange (ETDEWEB)

    Slooff, L.H.; Budel, T.; Burgers, A.R.; Bakker, N.J. [ECN Solar Energy, P.O.Box 1, 1755 ZG Petten (Netherlands); Buechtemann, A.; Danz, R. [Fraunhofer-Institute for Applied Polymer Research, Geiselbergstr.69, D-14476 Golm (Germany); Meyer, T.; Meyer, A. [Solaronix SA, Rue de l' Ouriette 129, CH-1170 Aubonne (Switzerland)

    2007-08-15

    One of the major challenges in the research on luminescent concentrators is the lifetime of the luminescent polymer plates. There are some commercial plates available, but data on lifetime are very limited, especially when dedicated to applications like the luminescent concentrator. In this paper we report stability experiments on luminescent concentrator plates, aged under continuous white light illumination, outdoor conditions and high intensity monochromatic illumination. The results show that the lifetime strongly depends on the organic luminescent dye in the plate. The best materials exhibit an initial decrease in performance of about 20% and then remain more or less stable. It is shown that the degradation is not caused by UV illumination.

  10. Behavioural plasticity in wintering Mediterranean ospreys revealed by stable isotopes analyses and GPS tracking.

    Science.gov (United States)

    Monti, Flavio; Robert, Aloïs; Dominici, Jean-Marie; Sforzi, Andrea; Triay Bagur, Rafel; Muñoz Navarro, Antoni; Guillou, Gaël; Bentaleb, Ilham; Duriez, Olivier

    2015-04-01

    To infer wintering ecology in Mediterranean ospreys (Pandion haliaetus) we relied on a dual and complementary approach, using both GPS tracking and multi stable isotope tracer approaches. A control sample of feathers from 80 individuals (mostly chicks) was collected over a large latitudinal gradient (from Lapland to Africa) to assess the variability of carbon, nitrogen and sulphur stable isotope ratios between breeding sites and habitat types across the Western Palearctic. Then, C, N and S isotopic compositions from an experimental set of 18 Mediterranean adults were examined to infer wintering ground locations and habitat types used during the inter-breeding period. Additionally, 12 adult ospreys were fitted with GPS devices and tracked during migration and the wintering season. By combining the two techniques we evidenced a partial migratory population with 41.7% of tagged individuals being resident and 58.3% that actually migrated. Ospreys spent the winter at temperate latitudes and showed a high plasticity in habitat selection. They made use of marine bays, coastal lagoons/marshland and inland freshwater sites. Movements and home range areas were reduced during the season. Wintering grounds were largely spread over the coasts of different countries of the basin, rather than concentrated in one single area. Such behavioural plasticity in the choice of location and habitat type suggests the implementing of broad-scale approaches for the protection of important areas for ospreys in winter. To contribute at assuring a right level of conservation of the osprey populations in the Mediterranean basin, a harmonization of the management protocols of wetland sites among countries is necessary.

  11. Nitrate stable isotopes and major ions in snow and ice samples from four Svalbard sites

    Directory of Open Access Journals (Sweden)

    Carmen P. Vega

    2015-04-01

    Full Text Available Increasing reactive nitrogen (Nr deposition in the Arctic may adversely impact N-limited ecosystems. To investigate atmospheric transport of Nr to Svalbard, Norwegian Arctic, snow and firn samples were collected from glaciers and analysed to define spatial and temporal variations (1–10 years in major ion concentrations and the stable isotope composition (δ15N and δ18O of nitrate (NO3- across the archipelago. The δ15N NO3- and δ18ONO3- averaged −4‰ and 67‰ in seasonal snow (2010–11 and −9‰ and 74‰ in firn accumulated over the decade 2001–2011. East–west zonal gradients were observed across the archipelago for some major ions (non-sea salt sulphate and magnesium and also for δ15NNO3- and δ18ONO3- in snow, which suggests a different origin for air masses arriving in different sectors of Svalbard. We propose that snowfall associated with long-distance air mass transport over the Arctic Ocean inherits relatively low δ15NNO3- due to in-transport N isotope fractionation. In contrast, faster air mass transport from the north-west Atlantic or northern Europe results in snowfall with higher δ15NNO3- because in-transport fractionation of N is then time-limited.

  12. Microfluidic synthesis of composite cross-gradient materials for investigating cell-biomaterial interactions.

    Science.gov (United States)

    He, Jiankang; Du, Yanan; Guo, Yuqi; Hancock, Matthew J; Wang, Ben; Shin, Hyeongho; Wu, Jinhui; Li, Dichen; Khademhosseini, Ali

    2011-01-01

    Combinatorial material synthesis is a powerful approach for creating composite material libraries for the high-throughput screening of cell-material interactions. Although current combinatorial screening platforms have been tremendously successful in identifying target (termed "hit") materials from composite material libraries, new material synthesis approaches are needed to further optimize the concentrations and blending ratios of the component materials. Here we employed a microfluidic platform to rapidly synthesize composite materials containing cross-gradients of gelatin and chitosan for investigating cell-biomaterial interactions. The microfluidic synthesis of the cross-gradient was optimized experimentally and theoretically to produce quantitatively controllable variations in the concentrations and blending ratios of the two components. The anisotropic chemical compositions of the gelatin/chitosan cross-gradients were characterized by Fourier transform infrared spectrometry and X-ray photoelectron spectrometry. The three-dimensional (3D) porous gelatin/chitosan cross-gradient materials were shown to regulate the cellular morphology and proliferation of smooth muscle cells (SMCs) in a gradient-dependent manner. We envision that our microfluidic cross-gradient platform may accelerate the material development processes involved in a wide range of biomedical applications. © 2010 Wiley Periodicals, Inc.

  13. Production and use of stable isotopes in France

    International Nuclear Information System (INIS)

    Roth, E.; Letolle, R.

    1991-01-01

    This paper can not cover the field of production and use of stable isotopes in France exhaustively within six pages. We have chosen to concentrate on highlights of the subject and on recent work, and to give references for further reading. 26 refs

  14. Magnetoelectric Transverse Gradient Sensor with High Detection Sensitivity and Low Gradient Noise

    OpenAIRE

    Zhang, Mingji; Or, Siu Wing

    2017-01-01

    We report, theoretically and experimentally, the realization of a high detection performance in a novel magnetoelectric (ME) transverse gradient sensor based on the large ME effect and the magnetic field gradient (MFG) technique in a pair of magnetically-biased, electrically-shielded, and mechanically-enclosed ME composites having a transverse orientation and an axial separation. The output voltage of the gradient sensor is directly obtained from the transverse MFG-induced difference in ME vo...

  15. Microbiological characterization of stable resuspended dust

    Directory of Open Access Journals (Sweden)

    Nora Kováts

    2016-06-01

    Full Text Available Objectives: Air quality in the stables is characterized by elevated level of dust and aeroallergens which are supposed to directly cause or exacerbate several respiratory disorders. The most often recognized problem is recurrent airway obstruction (RAO, previously known as chronic obstructive pulmonary disease (COPD. There is some indication that aeroallergens (among them endotoxins may also cause inflammation in human airways and may exceed safe levels in stables. Monitoring studies have covered mainly the determination of the concentration of respirable particles and of culturable fungi and their toxins. However, these particles do not only directly affect the respiratory system, but might act as a carrier conveying toxic contaminants and biological agents such as bacteria. In a typical, 20-horse Hungarian stable, microbial community of respirable fraction of resuspended dust has been characterized to reveal if these particles convey hazardous pathogenic bacteria, posing risk to either horses or staff. Material and Methods: Resuspended dust was sampled using a mobile instrument. The instrument contains a PARTISOL-FRM model 2000 sampler that was operated at a flow rate of 16.7 l/min and a cyclone separator which collected the particulate matter with an aerodynamic size between 1 μm and 10 μm (PM1–10 fraction. Microbial taxa were identified by culture-independent next generation sequencing (NGS of variable 16S ribosomal ribonucleic acid (rRNA gene regions. Results: In total, 1491 different taxa were identified, of them 384 were identified to species level, 961 to genus level. The sample was dominated by common ubiquitous soil and organic material-dwelling taxa. Conclusions: Pathogens occurred at low abundance, and were represented by mostly facultative human pathogens, with the prevalence of Staphylococcus species.

  16. Toward Practical Secure Stable Matching

    Directory of Open Access Journals (Sweden)

    Riazi M. Sadegh

    2017-01-01

    Full Text Available The Stable Matching (SM algorithm has been deployed in many real-world scenarios including the National Residency Matching Program (NRMP and financial applications such as matching of suppliers and consumers in capital markets. Since these applications typically involve highly sensitive information such as the underlying preference lists, their current implementations rely on trusted third parties. This paper introduces the first provably secure and scalable implementation of SM based on Yao’s garbled circuit protocol and Oblivious RAM (ORAM. Our scheme can securely compute a stable match for 8k pairs four orders of magnitude faster than the previously best known method. We achieve this by introducing a compact and efficient sub-linear size circuit. We even further decrease the computation cost by three orders of magnitude by proposing a novel technique to avoid unnecessary iterations in the SM algorithm. We evaluate our implementation for several problem sizes and plan to publish it as open-source.

  17. Variation in wood nutrients along a tropical soil fertility gradient.

    Science.gov (United States)

    Heineman, Katherine D; Turner, Benjamin L; Dalling, James W

    2016-07-01

    Wood contains the majority of the nutrients in tropical trees, yet controls over wood nutrient concentrations and their function are poorly understood. We measured wood nutrient concentrations in 106 tree species in 10 forest plots spanning a regional fertility gradient in Panama. For a subset of species, we quantified foliar nutrients and wood density to test whether wood nutrients scale with foliar nutrients at the species level, or wood nutrient storage increases with wood density as predicted by the wood economics spectrum. Wood nutrient concentrations varied enormously among species from fourfold in nitrogen (N) to > 30-fold in calcium (Ca), potassium (K), magnesium (Mg) and phosphorus (P). Community-weighted mean wood nutrient concentrations correlated positively with soil Ca, K, Mg and P concentrations. Wood nutrients scaled positively with leaf nutrients, supporting the hypothesis that nutrient allocation is conserved across plant organs. Wood P was most sensitive to variation in soil nutrient availability, and significant radial declines in wood P indicated that tropical trees retranslocate P as sapwood transitions to heartwood. Wood P decreased with increasing wood density, suggesting that low wood P and dense wood are traits associated with tree species persistence on low fertility soils. Substantial variation among species and communities in wood nutrient concentrations suggests that allocation of nutrients to wood, especially P, influences species distributions and nutrient dynamics in tropical forests. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  18. Towards stable acceleration in LINACS

    CERN Document Server

    Dubrovskiy, A D

    2014-01-01

    Ultra-stable and -reproducible high-energy particle beams with short bunches are needed in novel linear accelerators and, in particular, in the Compact Linear Collider CLIC. A passive beam phase stabilization system based on a bunch compression with a negative transfer matrix element R56 and acceleration at a positive off-crest phase is proposed. The motivation and expected advantages of the proposed scheme are outlined.

  19. The long range migration of hydrogen through Zircaloy in response to tensile and compressive stress gradients

    International Nuclear Information System (INIS)

    Kammenzind, B.F.; Berquist, B.M.; Bajaj, R.; Kreyns, P.H.; Franklin, D.G.

    1998-01-01

    Zircaloy-4, which is used widely as a core structural material in pressurized water reactors (PWRs), picks up hydrogen during service. Hydrogen solubility in Zircaloy-4 is low and zirconium hydride phases precipitate after the Zircaloy-4 lattice becomes supersaturated with hydrogen. These hydrides embrittle the Zircaloy-4, degrading its mechanical performance as a structural material. Because hydrogen can move rapidly through the Zircaloy-4 lattice, the potential exists for large concentrations of hydride to accumulate in local regions of a Zircaloy component remote from its point of entry into the component. Much has been reported in the literature regarding the long range migration of hydrogen through Zircaloy under concentration gradients and temperature gradients. Relatively little has been reported, however, regarding the long range migration of hydrogen under stress gradients. This paper presents experimental results regarding the long range migration of hydrogen through Zircaloy in response to both tensile and compressive stress gradients. The importance of this driving force for hydrogen migration relative to concentration and thermal gradients is discussed

  20. Jupiter's evolution with primordial composition gradients

    Science.gov (United States)

    Vazan, Allona; Helled, Ravit; Guillot, Tristan

    2018-02-01

    Recent formation and structure models of Jupiter suggest that the planet can have composition gradients and not be fully convective (adiabatic). This possibility directly affects our understanding of Jupiter's bulk composition and origin. In this Letter we present Jupiter's evolution with a primordial structure consisting of a relatively steep heavy-element gradient of 40 M⊕. We show that for a primordial structure with composition gradients, most of the mixing occurs in the outer part of the gradient during the early evolution (several 107 yr), leading to an adiabatic outer envelope (60% of Jupiter's mass). We find that the composition gradient in the deep interior persists, suggesting that 40% of Jupiter's mass can be non-adiabatic with a higher temperature than the one derived from Jupiter's atmospheric properties. The region that can potentially develop layered convection in Jupiter today is estimated to be limited to 10% of the mass. Movies associated to Figs. 1-3 are available at http://https://www.aanda.org

  1. Long-term Trends in Particulate Organic Carbon from a Low-Gradient Autotrophic Watershed

    Science.gov (United States)

    Fox, J.; Ford, W. I., III

    2014-12-01

    Recent insights from low-gradient streams dominated by fine surficial sediments have shown fluvial organic matter dynamics are governed by coupled hydrologic and biotic controls at event to seasonal timescales. Notwithstanding the importance of shorter timescales, quantity and quality of carbon in stream ecosystems at annual and decadal scales is of increased interest in order to understand if stream ecosystems are net stores or sinks of carbon and how stream carbon behaves under dynamic climate conditions. As part of an ongoing study in a low-gradient, agricultural watershed in the Bluegrass Region of Central Kentucky, an eight year dataset of transported particulate organic carbon (POC) was analyzed for the present study. The objective was to investigate if POC dynamics at multi-year timescales are governed by biotic or hydrologic processes. A statistical analysis using Empirical Mode Decomposition was performed on an 8 year dataset of transported sediment carbon, temperature, and log-transformed flowrates at the watershed outlet. Simulations from a previously validated, process-based, organic carbon model were utilized as further verification of drivers. Results from the analysis suggest that a 4 degree Celsius mean annual temperature shift corresponds to a 63% increase in organic carbon content at the main-stem, third order outlet and a 33% increase in organic carbon content at the main-stem inlet. Model and stable isotope results for the 8 year study support that long-term increases in organic carbon concentration are governed by biotic growth and humification of algal biomass in which increasing annual temperatures promote increased organic carbon production, relative to ecosystem respiration. This result contradicts conventional wisdom, suggesting projected warming trends will shift autotrophic freshwater systems to net heterotrophic, which has significant implications for the role of benthic stream ecosystems under changing climate conditions. Future work

  2. Vertical gradients in water chemistry and age in the Northern High Plains Aquifer, Nebraska, 2003

    Science.gov (United States)

    McMahon, P.B.; Böhlke, J.K.; Carney, C.P.

    2007-01-01

    The northern High Plains aquifer is the primary source of water used for domestic, industrial, and irrigation purposes in parts of Colorado, Kansas, Nebraska, South Dakota, and Wyoming. Despite the aquifer’s importance to the regional economy, fundamental ground-water characteristics, such as vertical gradients in water chemistry and age, remain poorly defined. As part of the U.S. Geological Survey’s National Water-Quality Assessment Program, water samples from nested, short-screen monitoring wells installed in the northern High Plains aquifer were analyzed for major ions, nutrients, trace elements, dissolved organic carbon, pesticides, stable and radioactive isotopes, dissolved gases, and other parameters to evaluate vertical gradients in water chemistry and age in the aquifer. Chemical data and tritium and radiocarbon ages show that water in the aquifer was chemically and temporally stratified in the study area, with a relatively thin zone of recently recharged water (less than 50 years) near the water table overlying a thicker zone of older water (1,800 to 15,600 radiocarbon years). In areas where irrigated agriculture was an important land use, the recently recharged ground water was characterized by elevated concentrations of major ions and nitrate and the detection of pesticide compounds. Below the zone of agricultural influence, major-ion concentrations exhibited small increases with depth and distance along flow paths because of rock/water interactions. The concentration increases were accounted for primarily by dissolved calcium, sodium, bicarbonate, sulfate, and silica. In general, the chemistry of ground water throughout the aquifer was of high quality. None of the approximately 90 chemical constituents analyzed in each sample exceeded primary drinking-water standards.Mass-balance models indicate that changes in groundwater chemistry along flow paths in the aquifer can be accounted for by small amounts of feldspar and calcite dissolution; goethite

  3. Classically Stable Nonsingular Cosmological Bounces

    Science.gov (United States)

    Ijjas, Anna; Steinhardt, Paul J.

    2016-09-01

    One of the fundamental questions of theoretical cosmology is whether the Universe can undergo a nonsingular bounce, i.e., smoothly transit from a period of contraction to a period of expansion through violation of the null energy condition (NEC) at energies well below the Planck scale and at finite values of the scale factor such that the entire evolution remains classical. A common claim has been that a nonsingular bounce either leads to ghost or gradient instabilities or a cosmological singularity. In this Letter, we consider a well-motivated class of theories based on the cubic Galileon action and present a procedure for explicitly constructing examples of a nonsingular cosmological bounce without encountering any pathologies and maintaining a subluminal sound speed for comoving curvature modes throughout the NEC violating phase. We also discuss the relation between our procedure and earlier work.

  4. Mercury contamination of the fish community of a semi-arid and arid river system: spatial variation and the influence of environmental gradients.

    Science.gov (United States)

    Smith, Alexandra; Abuzeineh, Alisa A; Chumchal, Matthew M; Bonner, Timothy H; Nowlin, Weston H

    2010-08-01

    Mercury (Hg) contamination of aquatic ecosystems is a global environmental problem. Data are abundant on Hg contamination and factors that affect its bioaccumulation in lake communities, but comparatively little information on riverine ecosystems exists. The present study examines fish Hg concentrations of the Lower Rio Grande/Rio Bravo del Norte drainage, Texas, USA and several of its major tributaries in order to assess whether spatial variation occurs in fish Hg concentrations in the drainage and if patterns of Hg contamination of fish are related to gradients in environmental factors thought to affect Hg concentrations in fish communities. Fish, invertebrates, sediments, and water quality parameters were sampled at 12 sites along the lower Rio Grande/Rio Bravo del Norte drainage multiple times over a one-year period. Spatial variation was significant in fish Hg concentrations when fish were grouped by literature-defined trophic guilds or as stable isotope-defined trophic levels, with highest concentrations found in the Big Bend region of the drainage. Mercury in fish in most trophic guilds and trophic levels were positively related to environmental factors thought to affect Hg in fish, including water column dissolved organic carbon (DOC) and sediment Hg concentrations. It is likely that fish Hg concentrations in the Big Bend region are relatively high because this section of the river has abundant geologic Hg sources and environmental conditions which may make it sensitive to Hg inputs (i.e., high DOC, variable water levels). Results from the present study indicate that Hg contamination of the Rio Grande/Rio Bravo del Norte has substantial implications for management and protection of native small-bodied obligate riverine fish, many of which are imperiled. Copyright 2010 SETAC

  5. Protein diffusion coefficients determined by macroscopic-gradient Rayleigh interferometry and dynamic light scattering.

    Science.gov (United States)

    Annunziata, Onofrio; Buzatu, Daniela; Albright, John G

    2005-12-20

    Dynamic light scattering (DLS) is extensively used for measuring macromolecule diffusion coefficients. Contrary to classical techniques based on macroscopic concentration gradients, DLS probes microscopic fluctuations in concentration. DLS accuracy and its concordance with macroscopic-gradient techniques remains an outstanding important issue. We measured lysozyme diffusion coefficients in aqueous salt using both DLS and Rayleigh interferometry, a highly accurate macroscopic-gradient technique. The precision of our results is unprecedented. We find that our DLS values were systematically 2% higher than interferometry values. We believe that our interferometric measurements have produced the most accurate diffusion data ever reported for a protein, providing a new standard for quality control of DLS measurements. Furthermore, by interferometry, we have determined the whole diffusion coefficient matrix required for rigorously describing lysozyme-salt coupled diffusion. For the first time, we experimentally demonstrate that DLS does not provide the protein diffusion coefficient but one eigenvalue of the diffusion coefficient matrix.

  6. Density-dependent adaptive resistance allows swimming bacteria to colonize an antibiotic gradient.

    Science.gov (United States)

    Hol, Felix J H; Hubert, Bert; Dekker, Cees; Keymer, Juan E

    2016-01-01

    During antibiotic treatment, antibiotic concentration gradients develop. Little is know regarding the effects of antibiotic gradients on populations of nonresistant bacteria. Using a microfluidic device, we show that high-density motile Escherichia coli populations composed of nonresistant bacteria can, unexpectedly, colonize environments where a lethal concentration of the antibiotic kanamycin is present. Colonizing bacteria establish an adaptively resistant population, which remains viable for over 24 h while exposed to the antibiotic. Quantitative analysis of multiple colonization events shows that collectively swimming bacteria need to exceed a critical population density in order to successfully colonize the antibiotic landscape. After colonization, bacteria are not dormant but show both growth and swimming motility under antibiotic stress. Our results highlight the importance of motility and population density in facilitating adaptive resistance, and indicate that adaptive resistance may be a first step to the emergence of genetically encoded resistance in landscapes of antibiotic gradients.

  7. Evidence of counter-gradient growth in western pond turtles (Actinemys marmorata) across thermal gradients

    Science.gov (United States)

    Snover, Melissa; Adams, Michael J.; Ashton, Donald T.; Bettaso, Jamie B.; Welsh, Hartwell H.

    2015-01-01

    Counter-gradient growth, where growth per unit temperature increases as temperature decreases, can reduce the variation in ectothermic growth rates across environmental gradients. Understanding how ectothermic species respond to changing temperatures is essential to their conservation and management due to human-altered habitats and changing climates.

  8. Using Spatial Gradients to Model Localization Phenomena

    Energy Technology Data Exchange (ETDEWEB)

    D.J.Bammann; D.Mosher; D.A.Hughes; N.R.Moody; P.R.Dawson

    1999-07-01

    We present the final report on a Laboratory-Directed Research and Development project, Using Spatial Gradients to Model Localization Phenomena, performed during the fiscal years 1996 through 1998. The project focused on including spatial gradients in the temporal evolution equations of the state variables that describe hardening in metal plasticity models. The motivation was to investigate the numerical aspects associated with post-bifurcation mesh dependent finite element solutions in problems involving damage or crack propagation as well as problems in which strain Localizations occur. The addition of the spatial gradients introduces a mathematical length scale that eliminates the mesh dependency of the solution. In addition, new experimental techniques were developed to identify the physical mechanism associated with the numerical length scale.

  9. Nonlinear conjugate gradient methods in micromagnetics

    Directory of Open Access Journals (Sweden)

    J. Fischbacher

    2017-04-01

    Full Text Available Conjugate gradient methods for energy minimization in micromagnetics are compared. The comparison of analytic results with numerical simulation shows that standard conjugate gradient method may fail to produce correct results. A method that restricts the step length in the line search is introduced, in order to avoid this problem. When the step length in the line search is controlled, conjugate gradient techniques are a fast and reliable way to compute the hysteresis properties of permanent magnets. The method is applied to investigate demagnetizing effects in NdFe12 based permanent magnets. The reduction of the coercive field by demagnetizing effects is μ0ΔH = 1.4 T at 450 K.

  10. Substrate curvature gradient drives rapid droplet motion.

    Science.gov (United States)

    Lv, Cunjing; Chen, Chao; Chuang, Yin-Chuan; Tseng, Fan-Gang; Yin, Yajun; Grey, Francois; Zheng, Quanshui

    2014-07-11

    Making small liquid droplets move spontaneously on solid surfaces is a key challenge in lab-on-chip and heat exchanger technologies. Here, we report that a substrate curvature gradient can accelerate micro- and nanodroplets to high speeds on both hydrophilic and hydrophobic substrates. Experiments for microscale water droplets on tapered surfaces show a maximum speed of 0.42  m/s, 2 orders of magnitude higher than with a wettability gradient. We show that the total free energy and driving force exerted on a droplet are determined by the substrate curvature and substrate curvature gradient, respectively. Using molecular dynamics simulations, we predict nanoscale droplets moving spontaneously at over 100  m/s on tapered surfaces.

  11. Conjugate gradient algorithms using multiple recursions

    Energy Technology Data Exchange (ETDEWEB)

    Barth, T.; Manteuffel, T.

    1996-12-31

    Much is already known about when a conjugate gradient method can be implemented with short recursions for the direction vectors. The work done in 1984 by Faber and Manteuffel gave necessary and sufficient conditions on the iteration matrix A, in order for a conjugate gradient method to be implemented with a single recursion of a certain form. However, this form does not take into account all possible recursions. This became evident when Jagels and Reichel used an algorithm of Gragg for unitary matrices to demonstrate that the class of matrices for which a practical conjugate gradient algorithm exists can be extended to include unitary and shifted unitary matrices. The implementation uses short double recursions for the direction vectors. This motivates the study of multiple recursion algorithms.

  12. Stable isotope customer list and summary of shipments - FY 1983

    International Nuclear Information System (INIS)

    Davis, W.C.

    1983-12-01

    This compilation is published as an aid to those concerned with the separation and sale of stable isotopes. The information is divided into four sections: (1) alphabetical list of domestic and foreign customers, showing the stable isotopes purchased during the fiscal year; (2) alphabetical list of isotopes, cross-referenced to customer numbers and divided into domestic and foreign categories; (3) alphabetical list of states and countries, cross-referenced to customer numbers and indicating geographical concentrations of isotope users; and (4) tabulation of the shipments, quantities, and dollars for domestic, foreign, and project categories for each isotope

  13. Stable isotope customer list and summary of shipments: FY 1984

    International Nuclear Information System (INIS)

    Tracy, J.G.

    1984-12-01

    This compilation is published as an aid to those concerned with the separation and sale of stable isotopes. The information is divided into four sections: (1) alphabetical list of domestic and foreign customers, showing the stable isotopes purchased during the fiscal year; (2) alphabetical list of isotopes, cross-referenced to customer numbers and divided into domestic and foreign categories; (3) alphabetical list of states and countries, cross-referenced to customer numbers and indicating geographical concentrations of isotope users; and (4) tabulation of the shipments, quantities, and dollars for domestic, foreign, and project categories for each isotope

  14. Two-Photon Fluorescence Microscopy for Determination of the Riboflavin Concentration in the Anterior Corneal Stroma When Using the Dresden Protocol.

    Science.gov (United States)

    Seiler, Theo G; Ehmke, Tobias; Fischinger, Isaak; Zapp, Daniel; Stachs, Oliver; Seiler, Theo; Heisterkamp, Alexander

    2015-10-01

    To determine the riboflavin concentration gradient in the anterior corneal stroma when using the Dresden protocol with different dextran solutions. Three different groups of porcine corneas, five each, were compared regarding the riboflavin concentration in the anterior stroma. Before all experiments, stable hydration conditions were established for the corresponding solution. All groups were treated with 0.1% riboflavin in different dextran solutions (15%, 16%, 20%). After imbibition, two-photon microscopy was used to determine fluorescence intensity. For signal attenuation and concentration determination corneas were saturated and measured a second time by two-photon microscopy. Additionally, the distribution was calculated mathematically and compared to the empiric results. Riboflavin concentration is decreasing with depth for all dextran solutions. A nearly constant concentration could be determined over the first 75 μm. Analysis of the fit functions leads to diffusion coefficients of D = 2.97 × 10-7 cm2/s for the 15% dextran solution, D = 2.34 × 10-7 cm2/s for the 16% dextran solution, and D = 1.28 × 10-7 cm2/s for the 20% dextran solution. The riboflavin gradients of the 20% dextran group were statistically significantly different from 15% dextran starting at a depth of 220 μm and deeper (P = 0.047). The 16% dextran group differed statistically at a depth of 250 μm and deeper (P = 0.047). These results show a significant difference to those published previously. With correct settings two-photon microscopy is a precise way to determine the concentration of riboflavin in cornea. The measured gradient is excellently fit by a Gaussian distribution, which comes out as a solution of Fick's second law.

  15. Review of new shapes for higher gradients

    International Nuclear Information System (INIS)

    Geng, R.L.

    2006-01-01

    High-gradient superconducting RF (SRF) cavities are needed for energy frontier superconducting accelerators. Progress has been made over the past decades and the accelerating gradient E acc has been increased from a few MV/m to ∼42 MV/m in SRF niobium cavities. The corresponding peak RF magnetic field H pk on the niobium cavity surface is approaching the intrinsic RF critical magnetic field H crit,RF , a hard physical limit at which superconductivity breaks down. Pushing the gradient envelope further by adopting new cavity shapes with a lower ratio of H pk /E acc has been recently proposed. For a reduced H pk /E acc , a higher ultimate E acc is sustained when H pk finally strikes H crit,RF . The new cavity geometry include the re-entrant shape conceived at Cornell University and the so-called 'Low-loss' shape proposed by a DESY/JLAB/KEK collaboration. Experimental work is being pursued at Cornell, KEK and JLAB. Results of single-cell cavities are encouraging. A record gradient of 47 MV/m was first demonstrated in a 1.3 GHz re-entrant niobium cavity at Cornell University. At the time of writing, a new record of 52 MV/m has been realized with another 1.3 GHz re-entrant cavity, designed and built at Cornell and processed and tested at KEK. Single-cell low-loss cavities have reached equally high gradients in the range of 45-51 MV/m at KEK and JLAB. Owing to their higher gradient potential and the encouraging single-cell cavity results, the new cavity shapes are becoming attractive for their possible use in the international linear collider (ILC). Experimental work on multi-cell niobium cavities of new shapes is currently under active exploration

  16. Frequency Analysis of Gradient Estimators in Volume Rendering

    NARCIS (Netherlands)

    Bentum, Marinus Jan; Lichtenbelt, Barthold B.A.; Malzbender, Tom

    1996-01-01

    Gradient information is used in volume rendering to classify and color samples along a ray. In this paper, we present an analysis of the theoretically ideal gradient estimator and compare it to some commonly used gradient estimators. A new method is presented to calculate the gradient at arbitrary

  17. Stable Hemiaminals: 2-Aminopyrimidine Derivatives

    Directory of Open Access Journals (Sweden)

    Anna Kwiecień

    2015-08-01

    Full Text Available Stable hemiaminals can be obtained in the one-pot reaction between 2-aminopyrimidine and nitrobenzaldehyde derivatives. Ten new hemiaminals have been obtained, six of them in crystal state. The molecular stability of these intermediates results from the presence of both electron-withdrawing nitro groups as substituents on the phenyl ring and pyrimidine ring, so no further stabilisation by intramolecular interaction is required. Hemiaminal molecules possess a tetrahedral carbon atom constituting a stereogenic centre. As the result of crystallisation in centrosymmetric space groups both enantiomers are present in the crystal structure.

  18. Organic synthesis with stable isotopes

    International Nuclear Information System (INIS)

    Daub, G.H.; Kerr, V.N.; Williams, D.L.; Whaley, T.W.

    1978-01-01

    Some general considerations concerning organic synthesis with stable isotopes are presented. Illustrative examples are described and discussed. The examples include DL-2-amino-3-methyl- 13 C-butanoic-3,4- 13 C 2 acid (DL-valine- 13 C 3 ); methyl oleate-1- 13 C; thymine-2,6- 13 C 2 ; 2-aminoethanesulfonic- 13 C acid (taurine- 13 C); D-glucose-6- 13 C; DL-2-amino-3-methylpentanoic-3,4- 13 C 2 acid (DL-isoleucine- 13 C 2 ); benzidine- 15 N 2 ; and 4-ethylsulfonyl-1-naphthalene-sulfonamide- 15 N

  19. Stable agents for imaging investigations

    International Nuclear Information System (INIS)

    Tofe, A.J.

    1976-01-01

    This invention concerns highly stable compounds useful in preparing technetium 99m based scintiscanning exploration agents. The compounds of this invention include a pertechnetate reducing agent or a solution of oxidized pertechnetate and an efficient proportion, sufficient to stabilize the compounds in the presence of oxygen and of radiolysis products, of ascorbic acid or a pharmaceutically acceptable salt or ester of this acid. The invention also concerns a perfected process for preparing a technetium based exploration agent, consisting in codissolving the ascorbic acid or a pharmaceutically acceptable salt or ester of such an acid and a pertechnetate reducing agent in a solution of oxidized pertechnetate [fr

  20. pH gradients in the diffusive boundary layer of subarctic macrophytes

    KAUST Repository

    Hendriks, Iris E.

    2017-06-20

    Highly productive macrophytes produce diurnal and seasonal cycles in CO concentrations modulated by metabolic activity, which cause discrepancies between pH in the bulk water and near seaweed blades, especially when entering the diffusion boundary layer (DBL). Calcifying epiphytic organisms living in this environment are therefore exposed to a different pH environment than that of the water column. To evaluate the actual pH environment on blade surfaces, we measured the thickness of the DBL and pH gradients within it for six subarctic macrophytes: Fucus vesiculosus, Ascophyllum nodosum, Ulva lactuca, Zostera marina, Saccharina longicruris, and Agarum clathratum. We measured pH under laboratory conditions at ambient temperatures (2–3 °C) and slow, stable flow over the blade surface at five light intensities (dark, 30, 50, 100 and 200 µmol photons m s). Boundary layer thickness ranged between 511 and 1632 µm, while the maximum difference in pH (∆pH) between the blade surface and the water column ranged between 0.4 ± 0.14 (average ± SE; Zostera) and 1.2 ± 0.13 (average ± SE; Ulva) pH units. These differences in pH are larger than predictions for pH changes in the bulk water by the end of the century. A simple quadratic model best described the relationship between light intensity and maximum ∆pH, pointing at relatively low optimum PAR of between 28 and 139 µmol photons m s to reach maximum ∆pH. Elevated pH at the blade surface may provide chemical “refugia” for calcifying epiphytic organisms, especially during summer at higher latitudes where photoperiods are long.

  1. Measurement of gradient magnetic field temporal characteristics

    International Nuclear Information System (INIS)

    Bartusek, K.; Jflek, B.

    1994-01-01

    We describe a technique of measuring the time dependence and field distortions of magnetic fields due to eddy currents (EC) produced by time-dependent magnetic field gradients. The EC measuring technique makes use of a large volume sample and selective RF excitation pulses and free induction decay (FID) (or a spin or gradient echo) to measure the out-of-phase component of the FID, which is proportional to γδB, i.e. the amount the signal is off resonance. The measuring technique is sensitive, easy to implement and interpret, and used for determining pre-emphasis compensation parameters

  2. Relativistic klystron research for high gradient accelerators

    International Nuclear Information System (INIS)

    Allen, M.A.; Callin, R.S.; Deruyter, H.

    1988-06-01

    Relativistic klystrons are being developed as a power source for high gradient accelerator applications which include large linear electron--positron colliders, compact accelerators, and FEL sources. We have attained 200MW peak power at 11.4 GHz from a relativistic klystron, and 140 MV/m longitudinal gradient in a short 11.4 GHz accelerator section. We report here on the design of our first klystrons, the results of our experiments so far, and some of our plans for the near future. 5 refs., 7 figs

  3. Crack Tip Mechanics in Distortion Gradient Plasticity

    DEFF Research Database (Denmark)

    Fuentes-Alonso, Sandra; Martínez Pañeda, Emilio

    2017-01-01

    The important role of geometrically necessary dislocations in structural integrity assessment has encouraged an extensive use of strain gradient plasticity theories to characterize the behavior at the small scales involved in crack tip deformation. However, despite the popularity of Distortion...... Gradient Plasticity (DGP), the influence on crack tip mechanics of DGP's distinguishing features that entail superior modelling capabilities has not been investigated yet. In this work crack tip fields are thoroughly examined by implementing the higher order theory of DGP in an implicit finite element...

  4. Gradient Learning Algorithms for Ontology Computing

    Science.gov (United States)

    Gao, Wei; Zhu, Linli

    2014-01-01

    The gradient learning model has been raising great attention in view of its promising perspectives for applications in statistics, data dimensionality reducing, and other specific fields. In this paper, we raise a new gradient learning model for ontology similarity measuring and ontology mapping in multidividing setting. The sample error in this setting is given by virtue of the hypothesis space and the trick of ontology dividing operator. Finally, two experiments presented on plant and humanoid robotics field verify the efficiency of the new computation model for ontology similarity measure and ontology mapping applications in multidividing setting. PMID:25530752

  5. Gradient Elasticity Formulations for Micro/Nanoshells

    Directory of Open Access Journals (Sweden)

    Bohua Sun

    2014-01-01

    Full Text Available The focus of this paper is on illustrating how to extend the second author’s gradient theory of elasticity to shells. Three formulations are presented based on the implicit gradient elasticity constitutive relation 1 -ld2∇2σij=Cijkl(1-ls2∇2εkl and its two approximations 1+ls2∇2-ld2∇2σij=Cijklεkl and σij=Cijkl(1+ld2∇2-ls2∇2εkl.

  6. Gradient learning algorithms for ontology computing.

    Science.gov (United States)

    Gao, Wei; Zhu, Linli

    2014-01-01

    The gradient learning model has been raising great attention in view of its promising perspectives for applications in statistics, data dimensionality reducing, and other specific fields. In this paper, we raise a new gradient learning model for ontology similarity measuring and ontology mapping in multidividing setting. The sample error in this setting is given by virtue of the hypothesis space and the trick of ontology dividing operator. Finally, two experiments presented on plant and humanoid robotics field verify the efficiency of the new computation model for ontology similarity measure and ontology mapping applications in multidividing setting.

  7. Improving dimensionality reduction with spectral gradient descent.

    Science.gov (United States)

    Memisevic, Roland; Hinton, Geoffrey

    2005-01-01

    We introduce spectral gradient descent, a way of improving iterative dimensionality reduction techniques. The method uses information contained in the leading eigenvalues of a data affinity matrix to modify the steps taken during a gradient-based optimization procedure. We show that the approach is able to speed up the optimization and to help dimensionality reduction methods find better local minima of their objective functions. We also provide an interpretation of our approach in terms of the power method for finding the leading eigenvalues of a symmetric matrix and verify the usefulness of the approach in some simple experiments.

  8. On lower order strain gradient plasticity theories

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Hutchinson, J. W.

    2002-01-01

    By way of numerical examples, this paper explores the nature of solutions to a class of strain gradient plasticity theories that employ conventional stresses, equilibrium equations and boundary conditions. Strain gradients come into play in these modified conventional theories only to alter...... the tangential moduli governing increments of stress and strain. It is shown that the modification is far from benign from a mathematical standpoint, changing the qualitative character of solutions and leading to a new type of localization that appears to be unphysical....

  9. Gradient Learning Algorithms for Ontology Computing

    Directory of Open Access Journals (Sweden)

    Wei Gao

    2014-01-01

    Full Text Available The gradient learning model has been raising great attention in view of its promising perspectives for applications in statistics, data dimensionality reducing, and other specific fields. In this paper, we raise a new gradient learning model for ontology similarity measuring and ontology mapping in multidividing setting. The sample error in this setting is given by virtue of the hypothesis space and the trick of ontology dividing operator. Finally, two experiments presented on plant and humanoid robotics field verify the efficiency of the new computation model for ontology similarity measure and ontology mapping applications in multidividing setting.

  10. Self-Generated Chemoattractant Gradients: Attractant Depletion Extends the Range and Robustness of Chemotaxis.

    Directory of Open Access Journals (Sweden)

    Luke Tweedy

    2016-03-01

    Full Text Available Chemotaxis is fundamentally important, but the sources of gradients in vivo are rarely well understood. Here, we analyse self-generated chemotaxis, in which cells respond to gradients they have made themselves by breaking down globally available attractants, using both computational simulations and experiments. We show that chemoattractant degradation creates steep local gradients. This leads to surprising results, in particular the existence of a leading population of cells that moves highly directionally, while cells behind this group are undirected. This leading cell population is denser than those following, especially at high attractant concentrations. The local gradient moves with the leading cells as they interact with their surroundings, giving directed movement that is unusually robust and can operate over long distances. Even when gradients are applied from external sources, attractant breakdown greatly changes cells' responses and increases robustness. We also consider alternative mechanisms for directional decision-making and show that they do not predict the features of population migration we observe experimentally. Our findings provide useful diagnostics to allow identification of self-generated gradients and suggest that self-generated chemotaxis is unexpectedly universal in biology and medicine.

  11. Self-Generated Chemoattractant Gradients: Attractant Depletion Extends the Range and Robustness of Chemotaxis.

    Science.gov (United States)

    Tweedy, Luke; Knecht, David A; Mackay, Gillian M; Insall, Robert H

    2016-03-01

    Chemotaxis is fundamentally important, but the sources of gradients in vivo are rarely well understood. Here, we analyse self-generated chemotaxis, in which cells respond to gradients they have made themselves by breaking down globally available attractants, using both computational simulations and experiments. We show that chemoattractant degradation creates steep local gradients. This leads to surprising results, in particular the existence of a leading population of cells that moves highly directionally, while cells behind this group are undirected. This leading cell population is denser than those following, especially at high attractant concentrations. The local gradient moves with the leading cells as they interact with their surroundings, giving directed movement that is unusually robust and can operate over long distances. Even when gradients are applied from external sources, attractant breakdown greatly changes cells' responses and increases robustness. We also consider alternative mechanisms for directional decision-making and show that they do not predict the features of population migration we observe experimentally. Our findings provide useful diagnostics to allow identification of self-generated gradients and suggest that self-generated chemotaxis is unexpectedly universal in biology and medicine.

  12. BACTERIOPHAGE AND MICROSPHERE TRANSPORT IN SATURATED POROUS MEDIA: FORCED-GRADIENT EXPERIMENT AT BORDEN, ONTARIO

    Science.gov (United States)

    A two-well forced-gradient experiment involving virus and microsphere transport was carried out in a sandy aquifer in Borden, Ontario, Canada. Virus traveled at least a few meters in the experiment, but virus concentrations at observation points 1 and 2.54 m away from the injecti...

  13. Proteomic investigations of the ventriculo-lumbar gradient in human CSF

    DEFF Research Database (Denmark)

    Simonsen, Anja Hviid; Bech, Sara Brynhild Winther; Laursen, Inga

    2010-01-01

    Cerebrospinal fluid (CSF) is an ideal biological material in which to search for new biomarkers for improved diagnosis of neurological diseases. During a lumbar puncture between 5 and 15 mL of CSF are obtained. Previous studies have assessed the ventriculo-lumbar concentration gradient of a numbe...

  14. HNO3 fluxes to a deciduous forest derived using gradient and REA methods

    DEFF Research Database (Denmark)

    Pryor, S.C.; Barthelmie, R.J.; Jensen, B.

    2002-01-01

    Summertime nitric acid concentrations over a deciduous forest in the midwestern United States are reported, which range between 0.36 and 3.3 mug m(-3). Fluxes to the forest are computed using the relaxed eddy accumulation technique and gradient methods. In accord with previous studies, the result...

  15. Stable cosmology in chameleon bigravity

    Science.gov (United States)

    De Felice, Antonio; Mukohyama, Shinji; Oliosi, Michele; Watanabe, Yota

    2018-02-01

    The recently proposed chameleonic extension of bigravity theory, by including a scalar field dependence in the graviton potential, avoids several fine-tunings found to be necessary in usual massive bigravity. In particular it ensures that the Higuchi bound is satisfied at all scales, that no Vainshtein mechanism is needed to satisfy Solar System experiments, and that the strong coupling scale is always above the scale of cosmological interest all the way up to the early Universe. This paper extends the previous work by presenting a stable example of cosmology in the chameleon bigravity model. We find a set of initial conditions and parameters such that the derived stability conditions on general flat Friedmann background are satisfied at all times. The evolution goes through radiation-dominated, matter-dominated, and de Sitter eras. We argue that the parameter space allowing for such a stable evolution may be large enough to encompass an observationally viable evolution. We also argue that our model satisfies all known constraints due to gravitational wave observations so far and thus can be considered as a unique testing ground of gravitational wave phenomenologies in bimetric theories of gravity.

  16. Characterization of stable fly (Diptera: Muscidae) larval developmental habitat at round hay bale feeding sites.

    Science.gov (United States)

    Talley, Justin; Broce, Alberto; Zurek, Ludek

    2009-11-01

    In this study, we examined the stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), larval developmental habitat within the round hay bale feeding sites on cattle pastures, and we identified three zones with distinct characteristics around two types of hay feeders (ring and cone). The parameters monitored in each zone included stable fly emergence, substrate temperature, moisture, pH, thickness of hay-manure layer, and concentration of fecal coliform bacteria (Escherichia coli and Klebsiella oxytoca) as indicators of fecal material. All measurements were conducted during the period of high stable fly prevalence (HSF) in May-June and low stable fly prevalence (LSF) in July-August to better understand the environmental factors influencing stable fly seasonality. Substrate temperature and fecal coliform concentration were the only two significantly different factors between HSF and LSF. Temperatures ranged from 21 to 25 degrees C during HSF versus 25-30 degrees C in LSF but all were within the range for successful stable fly development. Fecal coliform concentrations ranged from 4.2 x 10(3) to 4.1 x 10(4) colony-forming units (CFU)/g of the substrate during HSF and from undetectable (stable fly development (egg to adult). Temperature was significantly higher and stable fly developmental time significantly shorter in all substrates containing hay when compared with that of manure alone, but no significant differences were detected in stable fly emergence among the substrates. These results strongly indicate that the fecal microbial community plays an important role in stable fly larval development in hay feeding sites and that it is the main factor behind stable fly developmental seasonality on pastures. Our results also demonstrate that animal manure mixed with hay provides conditions for faster stable fly development than manure alone; however, hay does not significantly affect overall stable fly emergence.

  17. Measurements of the horizontal gradient of ammonia over a conifer forest in Denmark

    DEFF Research Database (Denmark)

    Hovmand, M.F.; Andersen, H.V.; Løfstrøm, P.

    1998-01-01

    Horizontal gradients of ammonia have been measured in order to determine the spatial variation of the concentration above a forest as a function of distance from ammonia emitting areas. Measurements were carried out in June 1994 during conditions with winds from north and west. Concentration leve...... concentration gradients, although calculated concentration levels may be higher than measured due to the use of yearly average emissions as input to the model calculations. (C) 1998 Elsevier Science Ltd. All rights reserved....... in the forest; in general the percentage decreases were lower during northerly winds (16%) than those obtained during westerly winds (67%). This is probably due to the larger extension of emitting areas towards north than towards the west. Model calculations are comparable with the measured ammonia...

  18. Adaptive evolution of Escherichia coli to Ciprofloxacin in controlled stress environments: emergence of tolerance in spatial and temporal gradients

    Science.gov (United States)

    Deng, J.; Sanford, R. A.; Dong, Y.; Shechtman, L. A.; Zhou, L.; Alcalde, R.; Werth, C. J.; Fouke, B. W.

    2016-12-01

    Microorganisms in nature have evolved in response to a variety of environmental stresses, including gradients of temperature, pH, substrate availability and aqueous chemistry. While environmental stresses are considered to be the driving forces of adaptive evolution, the impact and extent of any specific stress needed to drive such changes has not been well characterized. In this study, the antibiotic Ciprofloxacin was used as a stressor and systematically applied to E. coli st. 307 cells via a spatial gradient in a microfluidic pore network and a temporal gradient in batch cultures. The microfluidic device facilitated in vitro real-time tracking of bacterial abundances and dynamic spatial distributions in response to the gradients of both the antibiotic and nutrients. Cells collected from the microfluidic device showed growth on plates containing up to 10-times the original minimum inhibition concentration (MIC). In batch systems, Ciprofloxacin was used to evaluate adaptive responses via temporal gradients, in which the stressor concentration was incrementally increased over time with each transfer of the culture after 24 hours of growth. Responses of E. coli 307 to these stress patterns were measured by quantifying changes in the MIC for Ciprofloxacin. Over a period of 18 days of step-wise concentration increments, bacterial cells were observed to acquire tolerance gradually and eventually adapt to a 28-fold increase in the original MIC. Samples at different stages within the temporal Ciprofloxacin gradient treatment show different extents of resistance. All samples exhibited resistance exceeding the highest exposure stress concentration. In combination with the spatial and temporal gradient systems, this work provides the first comprehensive measure of the dynamic resistance of E. coli in response to Ciprofloxacin concentration gradients. These will provide invaluable insights to understand the effects of antibiotic stresses on bacterial adaptive evolution in

  19. Migration of liquid phase from the primary/peritectic interface in a temperature gradient

    Science.gov (United States)

    Peng, Peng; Li, XinZhong; Su, YanQing; Guo, JingJie

    2016-07-01

    The migration of the liquid droplets from the primary α/peritectic β interface at the peritectic temperature TP has been observed and analyzed in a Sn-Ni peritectic alloy. During the isothermal annealing stage of the interrupted directional solidification, a concentration gradient is established across the liquid droplets along the direction of the temperature gradient due to the temperature gradient zone melting. Simultaneous remelting/resolidification at the top/bottom of the liquid droplets by this concentration gradient have been confirmed to lead to migration of these droplets towards higher temperatures. The dependence of the migration distance of the liquid droplets on isothermal annealing time has been well predicted. Furthermore, since the lengths of the liquid droplet are not uniform along the direction of the temperature gradient, the remelting/resolidification rates which are dependent on the local morphology of liquid droplet are different at different local positions of the liquid droplets. It has been demonstrated that the morphology of the liquid droplet was also influenced by the morphologies of the liquid phase themselves. Therefore, the morphology of the liquid droplet itself changes from spherical to some kinds of irregular shapes during its migration.

  20. Quantifying dynamic changes in plantar pressure gradient in diabetics with peripheral neuropathy

    Directory of Open Access Journals (Sweden)

    Chi-Wen Lung

    2016-07-01

    Full Text Available Diabetic foot ulcers remain one of the most serious complications of diabetes. Peak plantar pressure (PPP and peak pressure gradient (PPG during walking have been shown to be associated with the development of diabetic foot ulcers. To gain further insight into the mechanical etiology of diabetic foot ulcers, examination of the pressure gradient angle (PGA has been recently proposed. The PGA quantifies directional variation or orientation of the pressure gradient during walking, and provides a measure of whether pressure gradient patterns are concentrated or dispersed along the plantar surface. We hypothesized that diabetics at risk of foot ulceration would have smaller PGA in key plantar regions, suggesting less movement of the pressure gradient over time. A total of 27 participants were studied, including 19 diabetics with peripheral neuropathy and 8 non-diabetic control subjects. A foot pressure measurement system was used to measure plantar pressures during walking. PPP, PPG and PGA were calculated for four foot regions - 1st toe (T1, 1st metatarsal head (M1, 2nd metatarsal head (M2, and heel (HL. Consistent with prior studies, PPP and PPG were significantly larger in the diabetic group compared to non-diabetic controls in the T1 and M1 regions, but not M2 or HL. For example, PPP was 165% (P=0.02 and PPG was 214% (P<0.001 larger in T1. PGA was found to be significantly smaller in the diabetic group in T1 (46%, P=0.04, suggesting a more concentrated pressure gradient pattern under the toe. The proposed PGA may improve our understanding of the role of pressure gradient on the risk of diabetic foot ulcers.

  1. Decomposing the land-use specific response of plant functional traits along environmental gradients.

    Science.gov (United States)

    Fontana, Veronika; Kohler, Marina; Niedrist, Georg; Bahn, Michael; Tappeiner, Ulrike; Frenck, Georg

    2017-12-01

    Environmental conditions affect functional trait variability within communities and thus shape ecosystem properties. With the ability of plants to adapt morphologically and physiologically to changing abiotic conditions, gradient analysis was shown to be a suitable tool to identify the drivers which determine trait values. Apart from direct environmental drivers and indirect gradients such as elevation, also anthropogenic effects (e.g. irrigation, grazing) can influence trait variability. Our aim was to assess the interactive effects of different environmental drivers on major plant traits and to investigate how these are modulated within two different land-use types (hay meadow vs. pasture). An elevational gradient spanning 1000m was decomposed into its underlying direct components (temperature, water input, length of growing season) for the investigation of gradual responses of five prominent functional traits (aboveground dry weight (AGDW), vegetative height (VegHt), specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen concentration (LNC)) for key species from two functional groups (grasses, forbs) in the two land-use/management regimes. The present study revealed that the detailed analysis of single direct gradients provides substantial additional information on trait response which remains hidden or is even reversed if only indirect gradients such as elevation are analysed. However, trait response to the combination of the three direct gradients aligned surprisingly well with trait response to the indirect gradient underpinning the adequate representation of temperature, water input and length of growing season by elevation. The response of traits significantly depended on the management regime and corresponding intensity which was shown to play an overriding role and constrained and attenuated response ranges of traits to climatic gradients. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Climatic effects on decomposing litter and substrate chemistry along climatological gradients.

    Science.gov (United States)

    Berg, B.

    2009-04-01

    Climatic effects on decomposing litter and substrate chemistry along climatological gradients. B. Berg, Dipartimento Biologia Strutturale e Funzionale, Complesso Universitario, Monte San Angelo, via Cintia, I-80126 Napoli, Italy and Department of Forest Ecology, P.O. Box 27, University of Helsinki, FIN-00014, Helsinki, Finland. Studies of several processes, using climatic gradients do provide new information as compared with studies at e.g. a single site. Decomposition of plant litter in such gradients give response in decomposition rates to natural climate conditions. Thus Scots pine needle litter incubated in a climate gradient with annual average temperature (AVGT) ranging from -0.5 to 6.8oC had a highly significant increase in initial mass-loss rate with R2 = 0.591 (p<0.001) and a 5o increase in temperature doubled the mass-loss rate. As a contrast - needle litter of Norway spruce incubated in the same transect had no significant response to climate and for initial litter a 5o increase increased mass-loss rate c. 6%. For more decomposed Scots pine litter we could see that the effect of temperature on mass-loss rate gradually decreased until it disappeared. Long-term decomposition studies revealed differences in litter decomposition patterns along a gradient, even for the same type of litter. This could be followed by using an asymptotic function that gave, (i) a measure a maximum level of decomposition, (ii) the initial decomposition rate. Over a gradient the calculated maximum level of decomposition decreased with increasing AVGT. Other gradient studies revealed an effect of AVGT on litter chemical composition. Pine needle litter from stands under different climate conditions had nutrient concentrations related to AVGT. Thus N, P, K, and S were positively related to AVGT and Mn negatively, all of them significantly. This information may be used to explain the changing pattern in decomposition over the gradient.

  3. Large Airborne Full Tensor Gradient Data Inversion Based on a Non-Monotone Gradient Method

    Science.gov (United States)

    Sun, Yong; Meng, Zhaohai; Li, Fengting

    2018-03-01

    Following the development of gravity gradiometer instrument technology, the full tensor gravity (FTG) data can be acquired on airborne and marine platforms. Large-scale geophysical data can be obtained using these methods, making such data sets a number of the "big data" category. Therefore, a fast and effective inversion method is developed to solve the large-scale FTG data inversion problem. Many algorithms are available to accelerate the FTG data inversion, such as conjugate gradient method. However, the conventional conjugate gradient method takes a long time to complete data processing. Thus, a fast and effective iterative algorithm is necessary to improve the utilization of FTG data. Generally, inversion processing is formulated by incorporating regularizing constraints, followed by the introduction of a non-monotone gradient-descent method to accelerate the convergence rate of FTG data inversion. Compared with the conventional gradient method, the steepest descent gradient algorithm, and the conjugate gradient algorithm, there are clear advantages of the non-monotone iterative gradient-descent algorithm. Simulated and field FTG data were applied to show the application value of this new fast inversion method.

  4. Annular beam with segmented phase gradients

    Directory of Open Access Journals (Sweden)

    Shubo Cheng

    2016-08-01

    Full Text Available An annular beam with a single uniform-intensity ring and multiple segments of phase gradients is proposed in this paper. Different from the conventional superposed vortices, such as the modulated optical vortices and the collinear superposition of multiple orbital angular momentum modes, the designed annular beam has a doughnut intensity distribution whose radius is independent of the phase distribution of the beam in the imaging plane. The phase distribution along the circumference of the doughnut beam can be segmented with different phase gradients. Similar to a vortex beam, the annular beam can also exert torques and rotate a trapped particle owing to the orbital angular momentum of the beam. As the beam possesses different phase gradients, the rotation velocity of the trapped particle can be varied along the circumference. The simulation and experimental results show that an annular beam with three segments of different phase gradients can rotate particles with controlled velocities. The beam has potential applications in optical trapping and optical information processing.

  5. Subspace learning from image gradient orientations

    NARCIS (Netherlands)

    Tzimiropoulos, Georgios; Zafeiriou, Stefanos; Pantic, Maja

    2012-01-01

    We introduce the notion of subspace learning from image gradient orientations for appearance-based object recognition. As image data is typically noisy and noise is substantially different from Gaussian, traditional subspace learning from pixel intensities fails very often to estimate reliably the

  6. Considerations of ion temperature gradient driven turbulence

    International Nuclear Information System (INIS)

    Cowley, S.C.; Kulsrud, R.M.

    1991-02-01

    The ion temperature gradient driven instability is considered in this paper. Physical pictures are presented to clarify the nature of the instability. The saturation of a single eddy is modeled by a simple nonlinear equation. We show that eddies which are elongated in the direction of the temperature gradient are the most unstable and have the highest saturation amplitudes. In a sheared magnetic field, such elongated eddies twist with the field lines. This structure is shown to be alternative to the usual Fourier mode picture in which the mode is localized around the surface where k parallel = 0. We show how these elongated twisting eddies, which are an integral part of the ''ballooning mode'' structure, could survive in a torus. The elongated eddies are shown to be unstable to secondary instabilities that are driven by the large gradients in the long eddy. We argue that this mechanism isotropizes ion temperature gradient turbulence. We further argue that the ''mixing length'' is set by this nonlinear process, not by a linear eigenmode width. 17 refs., 6 figs

  7. Gradient realization of nonlinear control systems

    NARCIS (Netherlands)

    Cortes monforte, J.; Cortés, J.; Crouch, P.E.; Astolfi, A.; van der Schaft, Arjan; Gordillo, F.

    2003-01-01

    We investigate necessary and su?cient conditions under which a nonlinear afine control system with outputs can be written as a gradient control system corresponding to some pseudo-Riemannian metric defined on the state space. The results rely on a suitable notion of compatibility of the system with

  8. Joining of Tungsten Armor Using Functional Gradients

    International Nuclear Information System (INIS)

    John Scott O'Dell

    2006-01-01

    The joining of low thermal expansion armor materials such as tungsten to high thermal expansion heat sink materials has been a major problem in plasma facing component (PFC) development. Conventional planar bonding techniques have been unable to withstand the high thermal induced stresses resulting from fabrication and high heat flux testing. During this investigation, innovative functional gradient joints produced using vacuum plasma spray forming techniques have been developed for joining tungsten armor to copper alloy heat sinks. A model was developed to select the optimum gradient architecture. Based on the modeling effort, a 2mm copper rich gradient was selected. Vacuum plasma pray parameters and procedures were then developed to produce the functional gradient joint. Using these techniques, dual cooling channel, medium scale mockups (32mm wide x 400mm length) were produced with vacuum plasma spray formed tungsten armor. The thickness of the tungsten armor was up to 5mm thick. No evidence of debonding at the interface between the heat sink and the vacuum plasma sprayed material was observed.

  9. Joining of Tungsten Armor Using Functional Gradients

    Energy Technology Data Exchange (ETDEWEB)

    John Scott O' Dell

    2006-12-31

    The joining of low thermal expansion armor materials such as tungsten to high thermal expansion heat sink materials has been a major problem in plasma facing component (PFC) development. Conventional planar bonding techniques have been unable to withstand the high thermal induced stresses resulting from fabrication and high heat flux testing. During this investigation, innovative functional gradient joints produced using vacuum plasma spray forming techniques have been developed for joining tungsten armor to copper alloy heat sinks. A model was developed to select the optimum gradient architecture. Based on the modeling effort, a 2mm copper rich gradient was selected. Vacuum plasma pray parameters and procedures were then developed to produce the functional gradient joint. Using these techniques, dual cooling channel, medium scale mockups (32mm wide x 400mm length) were produced with vacuum plasma spray formed tungsten armor. The thickness of the tungsten armor was up to 5mm thick. No evidence of debonding at the interface between the heat sink and the vacuum plasma sprayed material was observed.

  10. Instabilities in power law gradient hardening materials

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    2005-01-01

    Tension and compression instabilities are investigated for specimens with dimensions in the micron range. A finite strain generalization of a higher order strain gradient plasticity theory is implemented in a finite element scheme capable of modeling power law hardening materials. Effects...

  11. Gradient based filtering of digital elevation models

    DEFF Research Database (Denmark)

    Knudsen, Thomas; Andersen, Rune Carbuhn

    We present a filtering method for digital terrain models (DTMs). The method is based on mathematical morphological filtering within gradient (slope) defined domains. The intention with the filtering procedure is to improbé the cartographic quality of height contours generated from a DTM based on ...

  12. Stochastic gradient versus recursive least squares learning

    Czech Academy of Sciences Publication Activity Database

    Slobodyan, Sergey; Bogomolova, Anna; Kolyuzhnov, Dmitri

    -, č. 309 (2006), s. 1-21 ISSN 1211-3298 Institutional research plan: CEZ:AV0Z70850503 Keywords : constant gain adaptive learning * stochastic gradient learning * recursive least squares Subject RIV: AH - Economics http://www.cerge-ei.cz/pdf/wp/Wp309.pdf

  13. Stable isotope mass spectrometry in petroleum exploration

    International Nuclear Information System (INIS)

    Mathur, Manju

    1997-01-01

    The stable isotope mass spectrometry plays an important role to evaluate the stable isotopic composition of hydrocarbons. The isotopic ratios of certain elements in petroleum samples reflect certain characteristics which are useful for petroleum exploration

  14. Vertical Gradients in Water Chemistry and Age in the Southern High Plains Aquifer, Texas, 2002

    Science.gov (United States)

    McMahon, P.B.; Böhlke, J.K.; Lehman, T.M.

    2004-01-01

    The southern High Plains aquifer is the primary source of water used for domestic, industrial, and irrigation purposes in parts of New Mexico and Texas. Despite the aquifer's importance to the overall economy of the southern High Plains, fundamental ground-water characteristics, such as vertical gradients in water chemistry and age, remain poorly defined. As part of the U.S. Geological Survey's National Water-Quality Assessment Program, water samples from nested, short-screen monitoring wells installed in the southern High Plains aquifer at two locations (Castro and Hale Counties, Texas) were analyzed for field parameters, major ions, nutrients, trace elements, dissolved organic carbon, pesticides, stable and radioactive isotopes, and dissolved gases to evaluate vertical gradients in water chemistry and age in the aquifer. Tritium measurements indicate that recent (post-1953) recharge was present near the water table and that deeper water was recharged before 1953. Concentrations of dissolved oxygen were largest (2.6 to 5.6 milligrams per liter) at the water table and decreased with depth below the water table. The smallest concentrations were less than 0.5 milligram per liter. The largest major-ion concentrations generally were detected at the water table because of the effects of overlying agricultural activities, as indicated by postbomb tritium concentrations and elevated nitrate and pesticide concentrations at the water table. Below the zone of agricultural influence, major-ion concentrations exhibited small increases with depth and distance along flow paths because of rock/water interactions and mixing with water from the underlying aquifer in rocks of Cretaceous age. The concentration increases primarily were accounted for by dissolved sodium, bicarbonate, chloride, and sulfate. Nitrite plus nitrate concentrations at the water table were 2.0 to 6.1 milligrams per liter as nitrogen, and concentrations substantially decreased with depth in the aquifer to a

  15. Measures of ozone concentrations using passive sampling in forests of South Western Europe

    International Nuclear Information System (INIS)

    Sanz, M.J.; Calatayud, V.; Sanchez-Pena, G.

    2007-01-01

    Ambient ozone concentrations were measured with passive samplers in the framework of the EU and UN/ECE Level II forest monitoring programme. Data from France, Italy, Luxembourg, Spain and Switzerland are reported for 2000-2002, covering the period from April to September. The number of plots increased from 67 in 2000 to 83 in 2002. The year 2001 experienced the highest ozone concentrations, reflecting more stable summer meteorological conditions. Average 6-month ozone concentrations above 45 ppb were measured this year in 40.3% of the plots, in contrast with the less than 21% measured in the other 2 years. Gradients of increasing ozone levels were observed from North to South and with altitude. Comments are made on the regional trends and on the time frame of the higher ozone episodes. Also, some recommendations enabling a better comparison between plots are provided. - Ozone concentrations in forested areas of SW Europe during the period 2000-2002 showed highest values in 2001, as well as a tendency to increase towards the South and with altitude

  16. Measures of ozone concentrations using passive sampling in forests of South Western Europe

    Energy Technology Data Exchange (ETDEWEB)

    Sanz, M.J. [Fundacion CEAM, Charles R. Darwin 14, Parc Tecnologic, E-46980 Paterna, Valencia (Spain)]. E-mail: mjose@ceam.es; Calatayud, V. [Fundacion CEAM, Charles R. Darwin 14, Parc Tecnologic, E-46980 Paterna, Valencia (Spain); Sanchez-Pena, G. [Servicio de Proteccion de los Montes contra Agentes Nocivos, Direccion General para la Biodiversidad, Ministerio de Medio Ambiente, Gran Via de San Francisco, 4, E-28005, Madrid (Spain)

    2007-02-15

    Ambient ozone concentrations were measured with passive samplers in the framework of the EU and UN/ECE Level II forest monitoring programme. Data from France, Italy, Luxembourg, Spain and Switzerland are reported for 2000-2002, covering the period from April to September. The number of plots increased from 67 in 2000 to 83 in 2002. The year 2001 experienced the highest ozone concentrations, reflecting more stable summer meteorological conditions. Average 6-month ozone concentrations above 45 ppb were measured this year in 40.3% of the plots, in contrast with the less than 21% measured in the other 2 years. Gradients of increasing ozone levels were observed from North to South and with altitude. Comments are made on the regional trends and on the time frame of the higher ozone episodes. Also, some recommendations enabling a better comparison between plots are provided. - Ozone concentrations in forested areas of SW Europe during the period 2000-2002 showed highest values in 2001, as well as a tendency to increase towards the South and with altitude.

  17. A sandwich-designed temperature-gradient incubator for studies of microbial temperature responses.

    Science.gov (United States)

    Elsgaard, Lars; Jørgensen, Leif Wagner

    2002-03-01

    A temperature-gradient incubator (TGI) is described, which produces a thermal gradient over 34 aluminium modules (15x30x5 cm) intersected by 2-mm layers of partly insulating graphite foil (SigraFlex Universal). The new, sandwich-designed TGI has 30 rows of six replicate sample wells for incubation of 28-ml test tubes. An electric plate heats one end of the TGI, and the other end is cooled by thermoelectric Peltier elements in combination with a liquid cooling system. The TGI is equipped with 24 calibrated Pt-100 temperature sensors and insulated by polyurethane plates. A PC-operated SCADA (Supervisory Control And Data Acquisition) software (Genesis 4.20) is applied for temperature control using three advanced control loops. The precision of the TGI temperature measurements was better than +/-0.12 degrees C, and for a 0-40 degrees C gradient, the temperature at the six replicate sample wells varied less than +/-0.04 degrees C. Temperatures measured in incubated water samples closely matched the TGI temperatures, which showed a linear relationship to the sample row number. During operation for 8 days with a gradient of 0-40 degrees C, the temperature at the cold end was stable within +/-0.02 degrees C, while the temperatures at the middle and the warm end were stable within +/-0.08 degrees C (n=2370). Using the new TGI, it was shown that the fine-scale (1 degrees C) temperature dependence of S(o) oxidation rates in agricultural soil (0-29 degrees C) could be described by the Arrhenius relationship. The apparent activation energy (E(a)) for S(o) oxidation was 79 kJ mol(-1), which corresponded to a temperature coefficient (Q(10)) of 3.1. These data demonstrated that oxidation of S(o) in soil is strongly temperature-dependent. In conclusion, the new TGI allowed a detailed study of microbial temperature responses as it produced a precise, stable, and certifiable temperature gradient by the new and combined use of sandwich-design, thermoelectric cooling, and advanced

  18. Stable rotating dipole solitons in nonlocal media

    DEFF Research Database (Denmark)

    Lopez-Aguayo, Servando; Skupin, Stefan; Desyatnikov, Anton S.

    2006-01-01

    We present the first example of stable rotating two-soliton bound states in nonlinear optical media with nonlocal response. We show that, in contrast to media with local response, nonlocality opens possibilities to generate stable azimuthons.......We present the first example of stable rotating two-soliton bound states in nonlinear optical media with nonlocal response. We show that, in contrast to media with local response, nonlocality opens possibilities to generate stable azimuthons....

  19. Phase gradient metasurface with broadband anomalous reflection based on cross-shaped units

    Science.gov (United States)

    Chen, Zhaobin; Deng, Hui; Xiong, Qingxu; Liu, Chen

    2018-03-01

    It has been pointed out by many documents that a phase gradient metasurface with wideband characteristics can be designed by the unit with a low-quality factor ( Q value). In this paper, a cross-shaped unit with a low-quality factor Q is proposed. By changing the variable parameters of the unit, it is found that the reflection phase of the unit can achieve a stable distribution of phase gradient in the frequency range of 8.0-20.0 GHz. we analyze variation of the electromagnetic field distribution on the unit with frequency and find that the size along electrical field polarization of electromagnetic field distribution area changes with frequency. Based on our design, effective size of electromagnetic field distribution area keeps meeting the subwavelength condition, thus stable phase distribution is gained across broadened bandwidth. It is found by the analysis of the phase gradient metasurface composed of seven units that the metasurface can exhibit anomalous reflection in the wide frequency band of 8.0-20.0 GHz, and the efficiency of abnormal reflection is higher in the range of 10.0-18.0 GHz. The error between the simulation results of abnormal reflection angle and the theoretical result is only - 1.5° to 0.5° after the work of comparison. Therefore, the metasurface designed by the new cross-shaped unit has a good control on the deflection direction of the reflected wave, and shows obvious advantages in widening the bandwidth.

  20. Uses of stable isotopes in fish ecology

    Science.gov (United States)

    Analyses of fish tissues (other than otoliths) for stable isotope ratios can provide substantial information on fish ecology, including physiological ecology. Stable isotopes of nitrogen and carbon frequently are used to determine the mix of diet sources for consumers. Stable i...

  1. Periodicity of the stable isotopes

    CERN Document Server

    Boeyens, J C A

    2003-01-01

    It is demonstrated that all stable (non-radioactive) isotopes are formally interrelated as the products of systematically adding alpha particles to four elementary units. The region of stability against radioactive decay is shown to obey a general trend based on number theory and contains the periodic law of the elements as a special case. This general law restricts the number of what may be considered as natural elements to 100 and is based on a proton:neutron ratio that matches the golden ratio, characteristic of biological and crystal growth structures. Different forms of the periodic table inferred at other proton:neutron ratios indicate that the electronic configuration of atoms is variable and may be a function of environmental pressure. Cosmic consequences of this postulate are examined. (author)

  2. Stable States of Biological Organisms

    Science.gov (United States)

    Yukalov, V. I.; Sornette, D.; Yukalova, E. P.; Henry, J.-Y.; Cobb, J. P.

    2009-04-01

    A novel model of biological organisms is advanced, treating an organism as a self-consistent system subject to a pathogen flux. The principal novelty of the model is that it describes not some parts, but a biological organism as a whole. The organism is modeled by a five-dimensional dynamical system. The organism homeostasis is described by the evolution equations for five interacting components: healthy cells, ill cells, innate immune cells, specific immune cells, and pathogens. The stability analysis demonstrates that, in a wide domain of the parameter space, the system exhibits robust structural stability. There always exist four stable stationary solutions characterizing four qualitatively differing states of the organism: alive state, boundary state, critical state, and dead state.

  3. Theory of stable allocations II

    Directory of Open Access Journals (Sweden)

    Pantelić Svetlana

    2015-01-01

    Full Text Available The Swedish Royal Academy awarded the 2012 Nobel Prize in Economics to Lloyd Shapley and Alvin Roth, for the theory of stable allocations and the practice of market design. These two American researchers worked independently from each other, combining basic theory and empirical investigations. Through their experiments and practical design they generated a flourishing field of research and improved the performance of many markets. Shapley provided the fundamental theoretical contribution to this field of research, whereas Roth, a professor at the Harvard University in Boston, developed and upgraded these theoretical investigations by applying them to the American market of medical doctors. Namely, their research helps explain the market processes at work, for instance, when doctors are assigned to hospitals, students to schools and human organs for transplant to recipients.

  4. Stable massive particles at colliders

    Energy Technology Data Exchange (ETDEWEB)

    Fairbairn, M.; /Stockholm U.; Kraan, A.C.; /Pennsylvania U.; Milstead, D.A.; /Stockholm U.; Sjostrand, T.; /Lund U.; Skands, P.; /Fermilab; Sloan, T.; /Lancaster U.

    2006-11-01

    We review the theoretical motivations and experimental status of searches for stable massive particles (SMPs) which could be sufficiently long-lived as to be directly detected at collider experiments. The discovery of such particles would address a number of important questions in modern physics including the origin and composition of dark matter in the universe and the unification of the fundamental forces. This review describes the techniques used in SMP-searches at collider experiments and the limits so far obtained on the production of SMPs which possess various colour, electric and magnetic charge quantum numbers. We also describe theoretical scenarios which predict SMPs, the phenomenology needed to model their production at colliders and interactions with matter. In addition, the interplay between collider searches and open questions in cosmology such as dark matter composition are addressed.

  5. Tubing-Electrospinning: A One-Step Process for Fabricating Fibrous Matrices with Spatial, Chemical, and Mechanical Gradients.

    Science.gov (United States)

    Kim, Jung-Suk; Im, Byung Gee; Jin, Gyuhyung; Jang, Jae-Hyung

    2016-08-31

    Guiding newly generated tissues in a gradient pattern, thereby precisely mimicking inherent tissue morphology and subsequently arranging the intimate networks between adjacent tissues, is essential to raise the technical levels of tissue engineering and facilitate its transition into the clinic. In this study, a straightforward electrospinning method (the tubing-electrospinning technique) was developed to create fibrous matrices readily with diverse gradient patterns and to induce patterned cellular responses. Gradient fibrous matrices can be produced simply by installing a series of polymer-containing lengths of tubing into an electrospinning circuit and sequentially processing polymers without a time lag. The loading of polymer samples with different characteristics, including concentration, wettability, and mechanical properties, into the tubing system enabled unique features in fibrous matrices, such as longitudinal gradients in fiber density, surface properties, and mechanical stiffness. The resulting fibrous gradients were shown to arrange cellular migration and residence in a gradient manner, thereby offering efficient cues to mediate patterned tissue formation. The one-step process using tubing-electrospinning apparatus can be used without significant modifications regardless of the type of fibrous gradient. Hence, the tubing-electrospinning system can serve as a platform that can be readily used by a wide-range of users to induce patterned tissue formation in a gradient manner, which will ultimately improve the functionality of tissue engineering scaffolds.

  6. The stable K0 giant star β Gem

    Energy Technology Data Exchange (ETDEWEB)

    Gray, David F., E-mail: dfgray@uwo.ca [Department of Physics and Astronomy, University of Western Ontario, 1151 Richmond Street, London, Ontario, N6A 3K7 (Canada)

    2014-12-01

    A nine-season spectroscopic study of the photosphere of β Gem (K0 III) shows this low-luminosity giant to be stable, with no effective temperature variations above ∼2 K, and no secular temperature variations over the 2002-2010 time span above 0.2 K per year. The radial-velocity variations are consistent with an orbital variation of ∼40 m s{sup –1}. The projected rotation rate is found to be 1.70 ± 0.20 km s{sup –1} with a macroturbulence dispersion of 4.53 ± 0.10 km s{sup –1}. The third-signature plot is also invariant and shows a granulation velocity gradient 20% smaller than the solar gradient. The absolute shift of the third-signature plot gives a blueshift-corrected radial velocity of 3385 ± 70 m s{sup –1}. Bisector mapping of the Fe I λ6253 line yields a flux deficit of 12% ± 1% in area, somewhat smaller than for other giants, but the shape and the position of the peak at 4.8 km s{sup –1} is consistent with other giants. All of the investigated photospheric parameters are consistent with β Gem being a low-luminosity giant in agreement with its absolute magnitude.

  7. NMR and NQR study of the thermodynamically stable quasicrystals

    Energy Technology Data Exchange (ETDEWEB)

    Shastri, Ananda [Iowa State Univ., Ames, IA (United States)

    1995-02-10

    27Al and 61,65Cu NMR measurements are reported for powder samples of stable AlCuFe and AlCuRu icosahedral quasicrystals and their crystalline approximants, and for a AlPdMn single grain quasicrystal. Furthermore, 27Al NQR spectra at 4.2 K have been observed in the AlCuFe and AlCuRu samples. From the quadrupole perturbed NMR spectra at different magnetic fields, and from the zero field NQR spectra, a wide distribution of local electric field gradient (EFG) tensor components and principal axis system orientations was found at the Al site. A model EFG calculation based on a 1/1 AlCuFe approximant was successful in explaining the observed NQR spectra. It is concluded that the average local gradient is largely determined by the p-electron wave function at the Al site, while the width of the distribution is due to the lattice contribution to the EFG. Comparison of 63Cu NMR with 27Al NMR shows that the EFG distribution at the two sites is similar, but that the electronic contribution to the EFG is considerably smaller at the Cu site, in agreement with a more s-type wave function of the conduction electrons.

  8. Development of the CARS method for measurement of pressure and temperature gradients in centrifuges

    International Nuclear Information System (INIS)

    Zeltmann, A.H.; Valentini, J.J.

    1983-12-01

    These experiments evaluated the feasibility of applying the CARS technique to the measurement of UF 6 concentrations and pressure gradients in a gas centrifuge. The resultant CARS signals were properly related to system parameters as suggested by theory. The results have been used to guide design of an apparatus for making CARS measurements in a UF 6 gas centrifuge. Ease of measurement is expected for pressures as low as 0.1 torr. Temperature gradients can be measured by this technique with changes in the data acquisition method. 16 references, 8 figures, 2 tables

  9. Energy approach to brittle fracture in strain-gradient modelling

    Science.gov (United States)

    Placidi, Luca; Barchiesi, Emilio

    2018-02-01

    In this paper, we exploit some results in the theory of irreversible phenomena to address the study of quasi-static brittle fracture propagation in a two-dimensional isotropic continuum. The elastic strain energy density of the body has been assumed to be geometrically nonlinear and to depend on the strain gradient. Such generalized continua often arise in the description of microstructured media. These materials possess an intrinsic length scale, which determines the size of internal boundary layers. In particular, the non-locality conferred by this internal length scale avoids the concentration of deformations, which is usually observed when dealing with local models and which leads to mesh dependency. A scalar Lagrangian damage field, ranging from zero to one, is introduced to describe the internal state of structural degradation of the material. Standard Lamé and second-gradient elastic coefficients are all assumed to decrease as damage increases and to be locally zero if the value attained by damage is one. This last situation is associated with crack formation and/or propagation. Numerical solutions of the model are provided in the case of an obliquely notched rectangular specimen subjected to monotonous tensile and shear loading tests, and brittle fracture propagation is discussed.

  10. Simulation of Paramecium Chemotaxis Exposed to Calcium Gradients.

    Science.gov (United States)

    Sarvestani, Ali N; Shamloo, Amir; Ahmadian, Mohammad Taghi

    2016-06-01

    Paramecium or other ciliates have the potential to be utilized for minimally invasive surgery systems, making internal body organs accessible. Paramecium shows interesting responses to changes in the concentration of specific ions such as K(+), Mg(2+), and Ca(2+) in the ambient fluid. Some specific responses are observed as, changes in beat pattern of cilia and swimming toward or apart from the ion source. Therefore developing a model for chemotactic motility of small organisms is necessary in order to control the directional movements of these microorganisms before testing them. In this article, we have developed a numerical model, investigating the effects of Ca(2+) on swimming trajectory of Paramecium. Results for Ca(2+)-dependent chemotactic motility show that calcium gradients are efficient actuators for controlling the Paramecium swimming trajectory. After applying a very low Ca(2+) gradient, a directional chemotaxis of swimming Paramecium is observable in this model. As a result, chemotaxis is shown to be an efficient method for controlling the propulsion of these small organisms.

  11. Development of O-18 stable isotope separation technology using membrane

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae Woo; Kim, Taek Soo; Choi, Hwa Rim; Park, Sung Hee; Lee, Ki Tae; Chang, Dae Shik

    2006-06-15

    The ultimate goal of this investigation is to develop the separation technology for O-18 oxygen stable isotope used in a cyclotron as a target for production of radioisotope F-18. F-18 is a base material for synthesis of [F-18]FDG radio-pharmaceutical, which is one of the most important tumor diagnostic agent used in PET (Positron Emission Tomography). More specifically, this investigation is focused on three categories as follow, 1) development of the membrane distillation isotope separation process to re-enrich O-18 stable isotope whose isotopic concentration is reduced after used in a cyclotron, 2) development of organic impurity purification technology to remove acetone, methanol, ethanol, and acetonitrile contained in a used cyclotron O-18 enriched target water, and 3) development of a laser absorption spectroscopic system for analyzing oxygen isotopic concentration in water.

  12. Unstable ion-temperature-gradient modes in the Wendelstein 7-X stellarator configuration

    Science.gov (United States)

    Rafiq, T.; Kleiber, R.; Nadeem, M.; Persson, M.

    2002-12-01

    The linear stability of the ion-temperature-gradient modes (ITG) in the electrostatic limit is examined in the short wavelength region by using a two fluid reactive model in fully three-dimensional Wendelstein 7-X (W7-X) stellarator [G. Grieger et al., Plasma Physics and Controlled Nuclear Fusion Research, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 3, p. 525] geometry. The spectrum of stable and unstable modes and their real frequencies and eigenfunctions are calculated. The effects of density gradients, temperature gradients, temperature ratios, wavevector, ballooning angle, curvature and local magnetic shear on the ITG mode are also investigated. The frequency and growth rate of the most unstable ITG mode is calculated and visualized for a specific magnetic flux surface. For the equilibrium under investigation both localized and extended eigenmodes are found. The effect of small and large temperature ratios, small and large density gradients as well as large local magnetic shear are all found to be stabilizing. The highest growth rates are found at the outer part of the surface where the local magnetic shear is small and normal curvature is unfavorable.

  13. Concentration of trace elements in marine organisms

    International Nuclear Information System (INIS)

    Ishii, Takaaki; Suzuki, Hamaji; Iimura, Mitsue; Koyanagi, Taku

    1976-01-01

    Information on the quality and quantity of stable trace elements in marine environments is frequently required to analyze the radioecological behavior of radionuclides released from nuclear facilities into the sea. In the present work, special attention was concentrated in determination of stable Mn, Fe, Co, Zn, Rb and Cs in marine organisms to estimate the concentration factors for these elements and corresponding radionuclides. Marine organisms (fishes, marine invertebrates and seaweeds) were collected at the seashore of Ibaragi prefecture and provided for chemical analysis after dry-ashing and wet-ashing. Atomic absorption spectrophotometry and neutron activation analysis were applied to determine the concentration of elements. The concentration of stable elements in fish muscle was independent on species of the fishes though slightly higher trends were observed in ''Usumebaru'', Sebastes nivosus for Cs, ''Ishimochi'', Nibea mitsukurii for Zn and Fe compared with other species. The concentration of Co, Zn and Fe in muscle of marine invertebrates was one order of magnitude higher than fish muscles especially in shellfishes for Co. Seaweeds showed peculiar species specificity for the concentration of stable trace elements and remarkable differences was observed between the species even among the same genus. (auth.)

  14. Tungsten Stable Isotope Compositions of Ferromanganese Crusts

    Science.gov (United States)

    Abraham, K.; Barling, J.; Hein, J. R.; Schauble, E. A.; Halliday, A. N.

    2014-12-01

    We report the first accurate and precise data for mass-dependent fractionation of tungsten (W) stable isotopes, using a double spike technique and MC-ICPMS. Results are expressed relative to the NIST 3136 W isotope standard as per mil deviations in 186W/184W (δ186W). Although heavy element mass-dependent fractionations are expected to be small, Tl and U both display significant low temperature isotopic fractionations. Theoretical calculations indicate that W nuclear volume isotopic effects should be smaller than mass-dependent fractionations at low temperatures. Hydrogenetic ferromanganese (Fe-Mn) crusts precipitate directly from seawater and have been used as paleoceanographic recorders of temporal changes in seawater chemistry. Crusts are strongly enriched in W and other metals, and are a promising medium for exploring W isotopic variability. Tungsten has a relatively long residence time in seawater of ~61,000 years, mainly as the tungstate ion (WO42-). Water depth profiles show conservative behaviour. During adsorption on Fe-Mn crusts, W species form inner-sphere complexes in the hexavalent (W6+) state. The major host phase is thought to be Mn oxides and the lighter W isotope is expected to be absorbed preferentially. Surface scrapings of 13 globally distributed hydrogenetic Fe-Mn crusts display δ186W from -0.08 to -0.22‰ (±0.03‰, 2sd). A trend toward lighter W isotope composition exists with increasing water depth (~1500 to ~5200m) and W concentration. One hydrothermal Mn-oxide sample is anomalously light and Mn nodules are both heavy and light relative to Fe-Mn crusts. Tungsten speciation depends on concentration, pH, and time in solution and is not well understood because of the extremely slow kinetics of the reactions. In addition, speciation of aqueous and/or adsorbed species might be sensitive to pressure, showing similar thermodynamic stability but different effective volumes. Thus, W stable isotopes might be used as a water-depth barometer in

  15. Spatial and Temporal Variation in Methane Concentrations, Fluxes, and Sources in Lakes in Arctic Alaska

    Science.gov (United States)

    Townsend-Small, Amy; Škerström, Frida; Arp, Christopher D.; Hinkel, Kenneth M.

    2017-11-01

    Climate warming may lead to a positive feedback of increased emissions of CH4 from sediments beneath Arctic lakes, but the contribution of these lakes to the global CH4 budget is poorly quantified. Here we present results of a study of CH4 concentrations and sources from a series of 50 lakes in Arctic Alaska across an 80,000 km2 spatial gradient and a 2 year time period. We measured dissolved CH4 concentrations and stable isotopes of CH4 in lakes in the North Slope of Alaska in August 2014 and 2015 and April 2015 (under ice). Stable isotopes indicated that biogenic CH4 dominated versus thermogenic sources, with both acetate fermentation and carbonate reduction sources. Dissolved CH4 was about 100 times higher under the ice than during the summer, indicating that the spring ice off period is a large source of atmospheric CH4. Open-water dissolved CH4 concentrations had a negative relationship with latitude in both years of our study, although CH4 fluxes were consistent among a subset of lakes measured along a 150 km north to south transect in both years (14 lakes in 2014 and 12 in 2015). Dissolved CH4 concentrations and fluxes were significantly higher in August 2015 versus August 2014, concurrent with a 3°C higher mean water temperature in 2015 versus 2014. Much longer-term monitoring is needed, however, to conclude that CH4 emissions from Arctic lakes mirror observed warming trends. This study provides valuable baseline data and can inform methods for future studies investigating carbon cycle-climate change feedbacks in Alaskan Arctic lakes.

  16. Seasonal variations of stable carbon isotopic composition and biogenic tracer compounds of water-soluble organic aerosols in a deciduous forest

    Directory of Open Access Journals (Sweden)

    Y. Miyazaki

    2012-02-01

    Full Text Available To investigate the seasonal changes in biogenic water-soluble organic carbon (WSOC aerosols in a boreal forest, aerosol samples were collected continuously in the canopy of a deciduous forest in northern Japan during 2009–2010. Stable carbon isotopic composition of WSOC (δ13CWSOC in total suspended particulate matter (TSP exhibited a distinct seasonal cycle, with lower values from June through September (−25.5±0.5 ‰. This cycle follows the net CO2 exchange between the forest ecosystem and the atmosphere, indicating that δ13CWSOC likely reflects the biological activity at the forest site. WSOC concentrations showed the highest values in early summer and autumn. Positive matrix factorization (PMF analysis indicated that the factor in which biogenic secondary organic aerosols (BSOAs dominated accounted for ~40 % of the highest concentrations of WSOC, where BSOAs mostly consisted of α-/β-pinene SOA. In addition, primary biological aerosol particles (PBAPs made similar contributions (~57 % to the WSOC near the forest floor in early summer. This finding indicates that the production of both primary and secondary WSOC aerosols is important during the growing season in a deciduous forest. The methanesulfonic acid (MSA maximum was also found in early summer and had a distinct vertical gradient with larger concentrations near the forest floor. Together with the similar vertical gradients found for WSOC and δ13CWSOC as well as the α-/β-pinene SOA tracers, our results indicate that the forest floor, including ground vegetation and soil, acts as a significant source of WSOC in TSP within a forest canopy at the study site.

  17. Gradient fiber electrospinning of layered scaffolds using controlled transitions in fiber diameter.

    Science.gov (United States)

    Grey, Casey P; Newton, Scott T; Bowlin, Gary L; Haas, Thomas W; Simpson, David G

    2013-07-01

    We characterize layered, delamination resistant, tissue engineering scaffolds produced by gradient electrospinning using computational fluid dynamics, measurements of fiber diameter with respect to dynamic changes in polymer concentration, SEM analysis, and materials testing. Gradient electrospinning delivers a continuously variable concentration of polymer to the electrospinning jet, resulting in scaffolds that exhibit controlled transitions in fiber diameter across the Z-axis. This makes it possible to produce scaffolds that exhibit very different fiber sizes and material properties on opposing surfaces while eliminating the boundary layers that lead to delamination failures. In materials testing bi-layered laminated electrospun scaffolds (layer 1 = electrospinning fabricated with fibers of this type on opposing surfaces fracture and fail as unified, and mechanically integrated, structures. Gradient electrospinning also eliminates the anisotropic strain properties observed in scaffolds composed of highly aligned fibers. In burst testing, scaffolds composed of aligned fibers produced using gradient electrospinning exhibit superior material properties with respect to scaffolds composed of random or aligned fibers produced from a single polymer concentration or as bi-layered, laminated structures. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Gradient waveform pre-emphasis based on the gradient system transfer function.

    Science.gov (United States)

    Stich, Manuel; Wech, Tobias; Slawig, Anne; Ringler, Ralf; Dewdney, Andrew; Greiser, Andreas; Ruyters, Gudrun; Bley, Thorsten A; Köstler, Herbert

    2018-02-25

    The gradient system transfer function (GSTF) has been used to describe the distorted k-space trajectory for image reconstruction. The purpose of this work was to use the GSTF to determine the pre-emphasis for an undistorted gradient output and intended k-space trajectory. The GSTF of the MR system was determined using only standard MR hardware without special equipment such as field probes or a field camera. The GSTF was used for trajectory prediction in image reconstruction and for a gradient waveform pre-emphasis. As test sequences, a gradient-echo sequence with phase-encoding gradient modulation and a gradient-echo sequence with a spiral read-out trajectory were implemented and subsequently applied on a structural phantom and in vivo head measurements. Image artifacts were successfully suppressed by applying the GSTF-based pre-emphasis. Equivalent results are achieved with images acquired using GSTF-based post-correction of the trajectory as a part of image reconstruction. In contrast, the pre-emphasis approach allows reconstruction using the initially intended trajectory. The artifact suppression shown for two sequences demonstrates that the GSTF can serve for a novel pre-emphasis. A pre-emphasis based on the GSTF information can be applied to any arbitrary sequence type. © 2018 International Society for Magnetic Resonance in Medicine.

  19. Magnetoelectric Transverse Gradient Sensor with High Detection Sensitivity and Low Gradient Noise.

    Science.gov (United States)

    Zhang, Mingji; Or, Siu Wing

    2017-10-25

    We report, theoretically and experimentally, the realization of a high detection performance in a novel magnetoelectric (ME) transverse gradient sensor based on the large ME effect and the magnetic field gradient (MFG) technique in a pair of magnetically-biased, electrically-shielded, and mechanically-enclosed ME composites having a transverse orientation and an axial separation. The output voltage of the gradient sensor is directly obtained from the transverse MFG-induced difference in ME voltage between the two ME composites and is calibrated against transverse MFGs to give a high detection sensitivity of 0.4-30.6 V/(T/m), a strong common-mode magnetic field noise rejection rate of 35 mm. An analysis of experimental gradient noise spectra obtained in a magnetically-unshielded laboratory environment reveals the domination of the pink (1/ f ) noise, dielectric loss noise, and power-frequency noise below 3 kHz, in addition to the circuit noise above 3 kHz, in the gradient sensor. The high detection performance, together with the added merit of passive and direct ME conversion by the large ME effect in the ME composites, makes the gradient sensor suitable for the passive, direct, and broadband detection of transverse MFGs.

  20. Proposed gravity-gradient dynamics experiments in lunar orbit using the RAE-B spacecraft

    Science.gov (United States)

    Blanchard, D. L.; Walden, H.

    1973-01-01

    A series of seven gravity-gradient dynamics experiments is proposed utilizing the Radio Astronomy Explorer (RAE-B) spacecraft in lunar orbit. It is believed that none of the experiments will impair the spacecraft structure or adversely affect the continuation of the scientific mission of the satellite. The first experiment is designed to investigate the spacecraft dynamical behavior in the absence of libration damper action and inertia. It requires stable gravity-gradient capture of the spacecraft in lunar orbit with small amplitude attitude librations as a prerequisite. Four subsequent experiments involve partial retraction, ultimately followed by full redeployment, of one or two of the 230-meter booms forming the lunar-directed Vee-antenna. These boom length change operations will induce moderate amplitude angular librations of the spacecraft.

  1. DOUBLE-DIFFUSIVE MIXING IN STELLAR INTERIORS IN THE PRESENCE OF HORIZONTAL GRADIENTS

    Energy Technology Data Exchange (ETDEWEB)

    Medrano, M.; Garaud, P. [Department of Applied Mathematics and Statistics, Baskin School of Engineering, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95060 (United States); Stellmach, S. [Institut für Geophysik, Westfälische Wilhelms-Universität Münster, Münster D-48149 (Germany)

    2014-09-10

    We have identified a potentially important source of mixing in stellar radiation zones which would arise whenever two conditions are satisfied: (1) the presence of an inverse vertical compositional gradient, and (2) the presence of density-compensating horizontal gradients of temperature and composition. The former can be caused by off-center nuclear burning, atomic diffusion, or surface accretion. The latter could be caused by rotation, tides, meridional flows, etc. The linear instability and its nonlinear development have been studied in an oceanographic context. It is known to drive the formation of stacks of fingering layers separated by diffusive interfaces, called intrusions. Using three-dimensional numerical simulations of the process in the astrophysically relevant region of parameter space, we find similar results and demonstrate that the material transport in the intrusive regime can be highly enhanced compared with pure diffusion, even in systems which would otherwise be stable to fingering (thermohaline) convection.

  2. Research on n-γ discrimination method based on spectrum gradient analysis of signals

    International Nuclear Information System (INIS)

    Luo Xiaoliang; Liu Guofu; Yang Jun; Wang Yueke

    2013-01-01

    Having discovered that there are distinct differences between the spectrum gradient of the output neutron and γ-ray signal from liquid scintillator detectors, this paper presented a n-γ discrimination method called spectrum gradient analysis (SGA) based on frequency-domain features of the pulse signals. The basic principle and feasibility of SGA method were discussed and the validity of n-γ discrimination results of SGA was verified by the associated particle neutron flight experiment. The discrimination performance of SGA was evaluated under different conditions of sampling rates ranging from 5 G/s to 250 M/s. The results show that SGA method exhibits insensitivity to noise, strong anti-interference ability, stable discrimination performance and lower amount of calculation in contrast with time-domain n-γ discrimination methods. (authors)

  3. Effect of price elasticity of demand in monopolies with gradient adjustment

    International Nuclear Information System (INIS)

    Cavalli, Fausto; Naimzada, Ahmad

    2015-01-01

    Highlights: •A monopoly with isoelastic demand function is studied. •Reduced rationality monopolist uses gradient adjustment. •If marginal cost is small, increasing elasticity leads to stable dynamics. •For large marginal cost, dynamic can be unstable for both small and large elasticity. -- Abstract: We study a monopolistic market characterized by a constant elasticity demand function, in which the firm technology is described by a linear total cost function. The firm is assumed to be boundedly rational and to follow a gradient rule to adjust the production level in order to optimize its profit. We focus on what happens on varying the price elasticity of demand, studying the effect on the equilibrium stability. We prove that, depending on the relation between the market size and the marginal cost, two different scenarios are possible, in which elasticity has either a stabilizing or a mixed stabilizing/destabilizing effect

  4. Model predictive control for wind power gradients

    DEFF Research Database (Denmark)

    Hovgaard, Tobias Gybel; Boyd, Stephen; Jørgensen, John Bagterp

    2015-01-01

    We consider the operation of a wind turbine and a connected local battery or other electrical storage device, taking into account varying wind speed, with the goal of maximizing the total energy generated while respecting limits on the time derivative (gradient) of power delivered to the grid. We...... wind data and modern wind forecasting methods. The simulation results using real wind data demonstrate the ability to reject the disturbances from fast changes in wind speed, ensuring certain power gradients, with an insignificant loss in energy production....... ranges. The system dynamics are quite non-linear, and the constraints and objectives are not convex functions of the control inputs, so the resulting optimal control problem is difficult to solve globally. In this paper, we show that by a novel change of variables, which focuses on power flows, we can...

  5. Structures and Strength of Gradient Nanostructures

    DEFF Research Database (Denmark)

    Hansen, Niels; Zhang, Xiaodan; Huang, Xiaoxu

    distance from the surface forming a gradient structure. In this study [2], by shot peening of a low carbon steel a gradient structure has been produced extending to about 1 mm below the surface. A number of strengthening mechanisms have been analyzed as a basis for a calculation of the stress and strain......A recent study [1] has shown that a microstructure can be refined to a record low of 5 nm and that dislocation glide is still a controlling mechanism at this length scale. The nanostructure was produced in Cu by applying a very high strain in friction. The stress and strain decrease with increasing...... as a function of the distance from the surface. The results are evaluated by a finite element investigation of shot peening....

  6. Temperature Gradient Driven Lasing and Stimulated Cooling

    Science.gov (United States)

    Sandner, K.; Ritsch, H.

    2012-11-01

    A laser can be understood as a thermodynamic engine converting heat to a coherent single mode field close to Carnot efficiency. To achieve lasing, spectral shaping of the excitation light is used to generate a higher effective temperature on the pump than on the gain transition. Here, using a toy model of a quantum well structure with two suitably designed tunnel-coupled wells kept at different temperatures, we predict that lasing can also occur on an actual spatial temperature gradient between the pump and gain regions. Gain and narrow band laser emission require a sufficiently large temperature gradient and resonator quality. Lasing appears concurrent with amplified heat flow between the reservoirs and points to a new form of stimulated solid state cooling. In addition, such a mechanism could reduce intrinsic heating and thus extend the operating regime of quantum cascade lasers by substituting phonon emission driven injection by a phonon absorption step.

  7. Optimizing sampling approaches along ecological gradients

    DEFF Research Database (Denmark)

    Schweiger, Andreas; Irl, Severin D. H.; Steinbauer, Manuel

    2016-01-01

    1. Natural scientists and especially ecologists use manipulative experiments or field observations along gradients to differentiate patterns driven by processes from those caused by random noise. A well-conceived sampling design is essential for identifying, analysing and reporting underlying...... patterns in a statistically solid and reproducible manner, given the normal restrictions in labour, time and money. However, a technical guideline about an adequate sampling design to maximize prediction success under restricted resources is lacking. This study aims at developing such a solid...... and reproducible guideline for sampling along gradients in all fields of ecology and science in general. 2. We conducted simulations with artificial data for five common response types known in ecology, each represented by a simple function (no response, linear, exponential, symmetric unimodal and asymmetric...

  8. Velocity Gradient Power Functional for Brownian Dynamics

    Science.gov (United States)

    de las Heras, Daniel; Schmidt, Matthias

    2018-01-01

    We present an explicit and simple approximation for the superadiabatic excess (over ideal gas) free power functional, admitting the study of the nonequilibrium dynamics of overdamped Brownian many-body systems. The functional depends on the local velocity gradient and is systematically obtained from treating the microscopic stress distribution as a conjugate field. The resulting superadiabatic forces are beyond dynamical density functional theory and are of a viscous nature. Their high accuracy is demonstrated by comparison to simulation results.

  9. CERN/KEK: Very high accelerating gradients

    International Nuclear Information System (INIS)

    Anon.

    1993-01-01

    Full text: A world-wide effort is under way to develop linear electron-positron colliders so that physics experiments can be extended into a range of energies where circular machines (necessarily much larger than CERN's 27-kilometre LEP machine) would be crippled by synchrotron radiation. CERN is studying the feasibility of building a 2 TeV machine called CLIC powered not by individual klystrons, but by a high intensity electron 'drive' linac running parallel to the main linac (November 1990, page 7). This drive linac will itself be powered by similar superconducting cavities to those developed for LEP. A high gradient is an obvious design aim for any future high energy linear collider because it makes it shorter and therefore cheaper - the design figure for the CLIC machine is 80 MV/m. The CLIC study group has taken a significant step forward in demonstrating the technical feasibility of their machine by achieving peak and average accelerating gradients of 137 MV/m and 84 MV/m respectively in a short section of accelerating structure during high gradient tests at the Japanese KEK Laboratory last year. This result obtained within the framework of a CERN/KEK collaboration on linear colliders was obtained using a 20-cell accelerating section built at CERN using state-of the- art technology which served both as a model for CLIC studies as well as a prototype for the Japanese Linear Collider studies. The operating frequency of the model accelerating section is 2.6 times lower than the CLIC frequency but was chosen because a high power r.f. source and pulse compression scheme has been developed for this frequency at KEK. Testing CLIC models at 11.4 GHz is however more stringent than at 30 GHz because the chance of electrical breakdown increases as the frequency is lowered. This recent result clearly demonstrates that a gradient of 80 MV/m is feasible

  10. Advanced concepts for high-gradient acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Whittum, D.H.

    1998-08-01

    The promise of high-gradient accelerator research is a future for physics beyond the 5-TeV energy scale. Looking beyond what can be engineered today, the authors examine basic research directions for colliders of the future, from mm-waves to lasers, and from solid-state to plasmas, with attention to material damage, beam-dynamics, a workable collision scheme, and energetics.

  11. Designing optimal nanofocusing with a gradient hyperlens

    Science.gov (United States)

    Shen, Lian; Prokopeva, Ludmila J.; Chen, Hongsheng; Kildishev, Alexander V.

    2017-11-01

    We report the design of a high-throughput gradient hyperbolic lenslet built with real-life materials and capable of focusing a beam into a deep sub-wavelength spot of λ/23. This efficient design is achieved through high-order transformation optics and circular effective-medium theory (CEMT), which are used to engineer the radially varying anisotropic artificial material based on the thin alternating cylindrical metal and dielectric layers. The radial gradient of the effective anisotropic optical constants allows for matching the impedances at the input and output interfaces, drastically improving the throughput of the lenslet. However, it is the use of the zeroth-order CEMT that enables the practical realization of a gradient hyperlens with realistic materials. To illustrate the importance of using the CEMT versus the conventional planar effective-medium theory (PEMT) for cylindrical anisotropic systems, such as our hyperlens, both the CEMT and PEMT are adopted to design gradient hyperlenses with the same materials and order of elemental layers. The CEMT- and PEMT-based designs show similar performance if the number of metal-dielectric binary layers is sufficiently large (9+ pairs) and if the layers are sufficiently thin. However, for the manufacturable lenses with realistic numbers of layers (e.g. five pairs) and thicknesses, the performance of the CEMT design continues to be practical, whereas the PEMT-based design stops working altogether. The accurate design of transformation optics-based layered cylindrical devices enabled by CEMT allow for a new class of robustly manufacturable nanophotonic systems, even with relatively thick layers of real-life materials.

  12. Magnetoresponsive Photonic Microspheres with Structural Color Gradient.

    Science.gov (United States)

    Lee, Seung Yeol; Choi, Jongkook; Jeong, Jong-Ryul; Shin, Jung H; Kim, Shin-Hyun

    2017-04-01

    Photonic Janus particles are created by alternately sputtering silica and titania on microspheres in order to obtain a structural color gradient. In addition, the microspheres are rendered magnetoresponsive. The Janus microspheres with optical and magnetic anisotropy enable on-demand control over orientation and structural color through manipulation of an external magnetic field, thereby being useful as active color pigments for reflection-mode displays. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Radial oxygen gradients over rat cortex arterioles

    OpenAIRE

    Galler, Michael

    2011-01-01

    Purpose: We present the results of the visualisation of radial oxygen gradients in rats’ cortices and their use in neurocritical management. Methods: PO2 maps of the cortex of 10 wistar rats were obtained with a camera (SensiMOD, PCO, Kehlheim, Germany). Those pictures were analyzed and edited by a custom-made software. We chose a vessel for examination. A matrix, designed to evaluate the cortical O2 partial pressure, was placed vertically to the artery and afterwards multiple regio...

  14. High gradient accelerators for linear light sources

    Energy Technology Data Exchange (ETDEWEB)

    Barletta, W.A.

    1988-09-26

    Ultra-high gradient radio frequency linacs powered by relativistic klystrons appear to be able to provide compact sources of radiation at XUV and soft x-ray wavelengths with a duration of 1 picosecond or less. This paper provides a tutorial review of the physics applicable to scaling the present experience of the accelerator community to the regime applicable to compact linear light sources. 22 refs., 11 figs., 21 tabs.

  15. Stable Treemaps via Local Moves.

    Science.gov (United States)

    Sondag, Max; Speckmann, Bettina; Verbeek, Kevin

    2018-01-01

    Treemaps are a popular tool to visualize hierarchical data: items are represented by nested rectangles and the area of each rectangle corresponds to the data being visualized for this item. The visual quality of a treemap is commonly measured via the aspect ratio of the rectangles. If the data changes, then a second important quality criterion is the stability of the treemap: how much does the treemap change as the data changes. We present a novel stable treemapping algorithm that has very high visual quality. Whereas existing treemapping algorithms generally recompute the treemap every time the input changes, our algorithm changes the layout of the treemap using only local modifications. This approach not only gives us direct control over stability, but it also allows us to use a larger set of possible layouts, thus provably resulting in treemaps of higher visual quality compared to existing algorithms. We further prove that we can reach all possible treemap layouts using only our local modifications. Furthermore, we introduce a new measure for stability that better captures the relative positions of rectangles. We finally show via experiments on real-world data that our algorithm outperforms existing treemapping algorithms also in practice on either visual quality and/or stability. Our algorithm scores high on stability regardless of whether we use an existing stability measure or our new measure.

  16. Preparation of counterion stabilized concentrated silver sols.

    Science.gov (United States)

    LaPlante, Sylas; Halaciuga, Ionel; Goia, Dan V

    2011-07-01

    A strategy for obtaining stable concentrated silver dispersions without dedicated stabilizing agents is presented. This approach consists of rapidly mixing aqueous solutions of silver salicylate and ascorbic acid. By using salicylate as Ag(+) counterion, it is possible to prepare stable sols with metal concentrations up to two orders of magnitude higher than with silver nitrate. The stabilizing effect of the counterion is the result of a decreased ionic strength due to salicylate protonation and its adsorption on the surface of silver. Both effects increase the range of the electrostatic repulsive forces by expanding the electrical double layer. Copyright © 2011 Elsevier Inc. All rights reserved.

  17. Air temperature gradient in large industrial hall

    Science.gov (United States)

    Karpuk, Michał; Pełech, Aleksander; Przydróżny, Edward; Walaszczyk, Juliusz; Szczęśniak, Sylwia

    2017-11-01

    In the rooms with dominant sensible heat load, volume airflow depends on many factors incl. pre-established temperature difference between exhaust and supply airflow. As the temperature difference is getting higher, airflow volume drops down, consequently, the cost of AHU is reduced. In high industrial halls with air exhaust grids located under the ceiling additional temperature gradient above working zone should be taken into consideration. In this regard, experimental research of the vertical air temperature gradient in high industrial halls were carried out for the case of mixing ventilation system The paper presents the results of air temperature distribution measurements in high technological hall (mechanically ventilated) under significant sensible heat load conditions. The supply airflow was delivered to the hall with the help of the swirl diffusers while exhaust grids were located under the hall ceiling. Basing on the air temperature distribution measurements performed on the seven pre-established levels, air temperature gradient in the area between 2.0 and 7.0 m above the floor was calculated and analysed.

  18. Gradient field microscopy of unstained specimens.

    Science.gov (United States)

    Kim, Taewoo; Sridharan, Shamira; Popescu, Gabriel

    2012-03-12

    We present a phase derivative microscopy technique referred to as gradient field microscopy (GFM), which provides the first-order derivatives of the phase associated with an optical field passing through a transparent specimen. GFM utilizes spatial light modulation at the Fourier plane of a bright field microscope to optically obtain the derivatives of the phase and increase the contrast of the final image. The controllable spatial modulation pattern allows us to obtain both one component of the field gradient (derivative along one direction) and the gradient intensity, which offers some advantages over the regular differential interference contrast (DIC) microscopy. Most importantly, unlike DIC, GFM does not use polarizing optics and, thus, it is applicable to birefringent samples. We demonstrate these features of GFM with studies of static and dynamic biological cells (HeLa cells and red blood cells). We show that GFM is capable of qualitatively providing information about cell membrane fluctuations. Specifically, we captured the disappearance of the bending mode of fluctuations in osmotically swollen red blood cells.

  19. Learnability of e–stable equilibria

    Czech Academy of Sciences Publication Activity Database

    Christev, A.; Slobodyan, Sergey

    2014-01-01

    Roč. 18, č. 5 (2014), s. 959-984 ISSN 1365-1005 Institutional support: RVO:67985998 Keywords : adaptive learning * expectational stability * stochastic gradient Subject RIV: AH - Economics Impact factor: 0.667, year: 2014

  20. Learnability of e–stable equilibria

    Czech Academy of Sciences Publication Activity Database

    Christev, A.; Slobodyan, Sergey

    2014-01-01

    Roč. 18, č. 5 (2014), s. 959-984 ISSN 1365-1005 Institutional support: PRVOUK-P23 Keywords : adaptive learning * expectational stability * stochastic gradient Subject RIV: AH - Economics Impact factor: 0.667, year: 2014