WorldWideScience

Sample records for dispersion field study

  1. Urban Dispersion Program Overview and MID05 Field Study Summary

    Energy Technology Data Exchange (ETDEWEB)

    Allwine, K Jerry; Flaherty, Julia E.

    2007-07-31

    The Urban Dispersion Program (UDP) was a 4-year project (2004–2007) funded by the U.S. Department of Homeland Security with additional support from the Defense Threat Reduction Agency. The U.S. Environmental Protection Agency (EPA) also contributed to UDP through funding a human-exposure component of the New York City (NYC) field studies in addition to supporting an EPA scientist in conducting modeling studies of NYC. The primary goal of UDP was to improve the scientific understanding of the flow and diffusion of airborne contaminants through and around the deep street canyons of NYC. The overall UDP project manager and lead scientist was Dr. Jerry Allwine of Pacific Northwest National Laboratory. UDP had several accomplishments that included conducting two tracer and meteorological field studies in Midtown Manhattan.

  2. Study and verification on dispersion coefficient in wave field

    Institute of Scientific and Technical Information of China (English)

    SHEN LiangDuo; ZOU ZhiLi

    2012-01-01

    Transport and diffusion caused by coastal waves have different characteristics from those induced by flows.Through solving the vertical diffusion equation by an analytic method,this paper infers a theoretical formula of dispersion coefficient under the combined action of current and waves.It divides the general dispersion coefficient into six parts,including coefficients due to tidal current,Stokes drift,wave oscillation and interaction among them.It draws a conclusion that the contribution of dispersive effect induced by coastal waves is mainly produced by Stokes drift,while the contributions to time-averaged dispersion coefficient due to wave orbital motion and interaction between current and waves are very small.The results without tidal current are in agreement with the numerical and experimental results,which proves the correctness of the theoretical derivation.This paper introduces the variation characteristics of both the time-averaged and oscillating dispersion coefficients versus relative water depth,and demonstrates the physical implications of the oscillating mixing coefficient due to waves.We also apply the results to the costal vertical circulation and give its characteristics compared to Stokes drift.

  3. Study on the wind field and pollutant dispersion in street canyons using a stable numerical method

    Institute of Scientific and Technical Information of China (English)

    XIA Ji-yang; Dennis Y.C.LEUNG

    2005-01-01

    A stable finite element method for the time dependent Navier-Stokes equations was used for studying the wind flow and pollutant dispersion within street canyons. A three-step fractional method was used to solve the velocity field and the pressure field separately from the governing equations. The Streamline Upwind Petrov-Galerkin (SUPG) method was used to get stable numerical results. Numerical oscillation was minimized and satisfactory results can be obtained for flows at high Reynolds numbers. Simulating the flow over a square cylinder within a wide range of Reynolds numbers validates the wind field model. The Strouhal numbers obtained from the numerical simulation had a good agreement with those obtained from experiment. The wind field model developed in the present study is applied to simulate more complex flow phenomena in street canyons with two different building configurations. The results indicated that the flow at rooftop of buildings might not be assumed parallel to the ground as some numerical modelers did. A counter-clockwise rotating vortex may be found in street canyons with an inflow from the left to right. In addition, increasing building height can increase velocity fluctuations in the street canyon under certain circumstances, which facilitate pollutant dispersion. At high Reynolds numbers, the flow regimes in street canyons do not change with inflow velocity.

  4. Numerical study of turbulent diffusion. [Gaussian diffusion, velocity fields, small eddies, two-particle dispersion

    Energy Technology Data Exchange (ETDEWEB)

    McCoy, M.G.

    1975-11-01

    The problem of the numerical simulation of turbulent diffusion is studied. The two-dimensional velocity fields are assumed to be incompressible, homogeneous and stationary, and they are represented as stochastic processes. A technique is offered which creates velocity fields accurately representing the input statistics once a two point correlation function or an energy spectrum is given. Various complicated energy spectra may be represented utilizing this model. The program is then used to extract information concerning Gaussian diffusion processes. Various theories of other workers are tested including Taylor's classical representation of dispersion for times long compared with the Lagrangian correlation time. Also, a study is made of the relation between the Lagrangian and the Eulerian correlation function and a hypothesis is advanced and successfully tested. Questions concerning the relation between small eddies and the energy spectrum are considered. A criterion is advanced and successfully tested to decide whether small scale flow can be detected within the large eddies for any given spectrum. A method is developed to determine whether this small scale motion is in any sense periodic. Finally, the relation between two particle dispersion and the energy spectrum is studied anew and various theories are tested. (auth)

  5. Urban Dispersion Program MSG05 Field Study: Summary of Tracer and Meteorological Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Allwine, K Jerry; Flaherty, Julia E.

    2006-08-09

    The Urban Dispersion Program is a multi-year project, funded by the U.S. Department of Homeland Security, to better understand the flow and dispersion of airborne contaminants through and around the deep street canyons of New York City. The first tracer and meteorological field study was a limited study conducted during March 2005 near the Madison Square Garden in midtown Manhattan. Six safe, inert, gaseous perfluorocarbon tracers were released simultaneously at five street-level locations during two experimental days. In addition to collecting tracer data, meteorological data were also collected. Brookhaven National Laboratory conducted the bulk of the tracer and meteorological field efforts with Pacific Northwest National Laboratory and Stevens Institute of Technology assisting by measuring the vertical profile of winds. The Environmental Protection Agency worked with Brookhaven National Laboratory in accomplishing the personal exposure component of the study. This report presents some results from this analysis. In general, different release locations showed vastly different plume footprints for tracer materials, and the situation was made very complex with upwind and/or crosswind transport of tracer near street-level for the different release locations. Overall wind speeds and directions upwind and over the city were generally constant throughout each of the two experimental periods.

  6. Superradiant scattering of dispersive fields

    CERN Document Server

    Richartz, Maurício; Weinfurtner, Silke; Liberati, Stefano

    2013-01-01

    Motivated by analogue models of classical and quantum field theory in curved spacetimes and their recent experimental realizations, we consider wave scattering processes of dispersive fields exhibiting two extra degrees of freedom. In particular, we investigate how standard superradiant scattering processes are affected by subluminal or superluminal modifications of the dispersion relation. We analyze simple 1-dimensional toy-models based on fourth-order corrections to the standard second order wave equation and show that low-frequency waves impinging on generic scattering potentials can be amplified during the process. In specific cases, by assuming a simple step potential, we determine quantitatively the deviations in the amplification spectrum that arise due to dispersion, and demonstrate that the amplification can be further enhanced due to the presence of extra degrees of freedom. We also consider dispersive scattering processes in which the medium where the scattering takes place is moving with respect ...

  7. Dispersion Method Using Focused Ultrasonic Field

    Science.gov (United States)

    Kim, Jungsoon; Kim, Moojoon; Ha, Kanglyel; Chu, Minchul

    2010-07-01

    The dispersion of powders into liquids has become one of the most important techniques in high-tech industries and it is a common process in the formulation of various products, such as paint, ink, shampoo, beverages, and polishing media. In this study, an ultrasonic system with a cylindrical transducer is newly introduced for pure nanoparticle dispersion. The acoustics pressure field and the characteristics of the shock pulse caused by cavitation are investigated. The frequency spectrum of the pulse from the collapse of air bubbles in the cavitation is analyzed theoretically. It was confirmed that a TiO2 water suspension can be dispersed effectively using the suggested system.

  8. Field studies of transport and dispersion of atmospheric tracers in nocturnal drainage flows

    Energy Technology Data Exchange (ETDEWEB)

    Gudiksen, P.H.; Ferber, G.J.; Fowler, M.M.; Eberhard, W.L.; Fosberg, M.A.; Knuth, W.R.

    1984-01-01

    A series of tracer experiments were carried out as part of the Atmospheric Studies in Complex Terrain (ASCOT) program to evaluate pollutant transport and dispersion characteristics of nocturnal drainage flows within a valley in northern California. The results indicate that the degree of interaction of the drainage flows with the larger scale regional flows are strongly dependent on how well the shallow drainage flows are shielded by the surrounding topography from the external environment. For the valley under study, the drainage flows from about mid-slope elevations and below were generally decoupled from the externally generated flows; as evidenced by the similarity of the surface tracer distribution produced during widely varying regional flow conditions. However, tracers released immediately above the drainage flows near the ridge top did reveal considerable mixing between the transition layer flows and the underlying surface drainage flows. Likewise, the transport and dispersion of the tracers at elevated heights within the valley basin were extremely dependent on the influences of the regional scale flows on the valley circulation. The dispersion rates associated with the transition layer flows were dependent on topographic constraints but were appreciably higher than those reported for homogeneous flat terrain situations.

  9. Numerical study of near-field pollutant dispersion around a building complex emitted from a rooftop stack

    Science.gov (United States)

    Lateb, Mohamed

    The topic of environmental pollution is of special significance in the atmospheric boundary layer (ABL) especially in urban areas as it is one of the significant sources of poor indoor air quality due to contamination of fresh-air intakes. In city centres where external air pollution levels are relatively high, it is usually assumed that natural ventilation may not be able to provide adequate indoor air quality. Therefore mechanical ventilation and air-conditioning systems are thus being solicited to "clean" the incoming air (Kukadia and Palmer, 1998). There is evidence that such systems do not always provide clean fresh-air to the occupants of the building since several contaminants from nearby outside sources exist (e.g. vehicle exhaust, rooftop stack exhaust, wind-blown dust). Control of the pollutant sources and understanding the dispersion mechanisms, therefore, shall be considered as the first alternative to evaluate better these harmful phenomena. This thesis focuses on dispersion and transportation of pollutant emissions from a building rooftop stack situated in the wake of a neighbouring tower using numerical simulation approach. The main objective of this work is to contribute to the "best-practice" of numerical modelling for dispersion studies. For that, wind tunnel tests as well as full-scale experiments are numerically reproduced to shed light on the uncertainties related to the complex dispersion phenomenon when using CFD simulations. In the first study of this thesis, the behaviour of the flow and pollutant concentration fields around the two-building configuration are investigated by means of various k - epsilon turbulence models (i.e. standard, re-normalization group (RNG) and realizable k - epsilon models). The results show that the realizable k - epsilon model yields the best agreement with wind tunnel experimental data for lower stack height and smaller momentum ratio, while the RNG k - epsilon model performs best for taller stacks. Despite an

  10. Pollen dispersal in sugar beet production fields.

    Science.gov (United States)

    Darmency, Henri; Klein, Etienne K; De Garanbé, Thierry Gestat; Gouyon, Pierre-Henri; Richard-Molard, Marc; Muchembled, Claude

    2009-04-01

    Pollen-mediated gene flow has important implications for biodiversity conservation and for breeders and farmers' activities. In sugar beet production fields, a few sugar beet bolters can produce pollen as well as be fertilized by wild and weed beet. Since the crop, the wild beets, and the weed beets are the same species and intercross freely, the question of pollen flow is an important issue to determine the potential dispersal of transgenes from field to field and to wild habitats. We report here an experiment to describe pollen dispersal from a small herbicide-resistant sugar beet source towards male sterile target plants located along radiating lines up to 1,200 m away. Individual dispersal functions were inferred from statistical analyses and compared. Pollen limitation, as expected in root-production fields, was confirmed at all the distances from the pollen source. The number of resistant seeds produced by bait plants best fitted a fat-tailed probability distribution curve of pollen grains (power-law) dependent on the distance from the pollen source. A literature survey confirmed that power-law function could fit in most cases. The b coefficient was lower than 2. The number of fertilized flowers by background (herbicide-susceptible) pollen grains was uniform across the whole field. Airborne pollen had a fertilization impact equivalent to that of one adjacent bolter. The individual dispersal function from different pollen sources can be integrated to provide the pollen cloud composition for a given target plant, thus allowing modeling of gene flow in a field, inter-fields in a small region, and also in seed-production area. Long-distance pollen flow is not negligible and could play an important role in rapid transgene dispersal from crop to wild and weed beets in the landscape. The removing of any bolting, herbicide-resistant sugar beet should be compulsory to prevent the occurrence of herbicide-resistant weed beet, thus preventing gene flow to wild

  11. Dispersion of Magnetic Fields in Molecular Clouds

    CERN Document Server

    Hildebrand, Roger H; Dotson, Jessie L; Houde, Martin; Vaillancourt, John E

    2008-01-01

    We describe a method for determining the dispersion of magnetic field vectors about local mean fields in turbulent molecular clouds. The method is designed to avoid inaccurate estimates of MHD or turbulent dispersion - and hence to avoid inaccurate estimates of field strengths - due to large-scale, non-turbulent field structure when using the well-known method of Chandrasekhar and Fermi. Our method also provides accurate, independent estimates of the turbulent to mean magnetic field strength ratio. We discuss applications to the molecular clouds Orion, M17, and DR21.

  12. Overview of the Brooklyn traffic real-time ambient pollutant penetration and environmental dispersion (B-TRAPPED) study: theoretical background and model for design of field experiments.

    Science.gov (United States)

    Hahn, Intaek; Wiener, Russell W; Richmond-Bryant, Jennifer; Brixey, Laurie A; Henkle, Stacy W

    2009-12-01

    The Brooklyn traffic real-time ambient pollutant penetration and environmental dispersion (B-TRAPPED) study was a multidisciplinary field research project that investigated the transport, dispersion, and infiltration processes of traffic emission particulate matter (PM) pollutants in a near-highway urban residential area. The urban PM transport, dispersion, and infiltration processes were described mathematically in a theoretical model that was constructed to develop the experimental objectives of the B-TRAPPED study. In the study, simultaneous and continuous time-series PM concentration and meteorological data collected at multiple outdoor and indoor monitoring locations were used to characterize both temporal and spatial patterns of the PM concentration movements within microscale distances (dispersion of PM; (3) studying the influence of meteorological variables on the transport, dispersion, and infiltration processes; (4) characterizing the relationships between the building parameters and the infiltration mechanisms; (5) establishing a cause-and-effect relationship between outdoor-released PM and indoor PM concentrations and identifying the dominant mechanisms involved in the infiltration process; (6) evaluating the effectiveness of a shelter-in-place area for protection against outdoor-released PM pollutants; and (7) understanding the predominant airflow and pollutant dispersion patterns within the neighborhood using wind tunnel and CFD simulations. The 10 papers in this first set of papers presenting the results from the B-TRAPPED study address these objectives. This paper describes the theoretical background and models representing the interrelated processes of transport, dispersion, and infiltration. The theoretical solution for the relationship between the time-dependent indoor PM concentration and the initial PM concentration at the outdoor source was obtained. The theoretical models and solutions helped us to identify important parameters in the

  13. Dispersal behaviour of Trichogramma brassicae in maize fields

    NARCIS (Netherlands)

    Suverkropp, B.P.; Bigler, F.; Lenteren, van J.C.

    2009-01-01

    Glue-sprayed maize plants were used to study dispersal behaviour of the egg parasitoid Trichogramma brassicae Bezdenko (Hymenoptera Trichogrammatidae) in maize fields. To estimate the distance covered during an initial flight, T. brassicae were studied in a field cage with 73 glue-sprayed plants. Mo

  14. Dispersal

    Science.gov (United States)

    Clobert, J.; Danchin, E.; Dhondt, A.A.; Nichols, J.D.

    2001-01-01

    The ability of species to migrate and disperse is a trait that has interested ecologists for many years. Now that so many species and ecosystems face major environmental threats from habitat fragmentation and global climate change, the ability of species to adapt to these changes by dispersing, migrating, or moving between patches of habitat can be crucial to ensuring their survival. This book provides a timely and wide-ranging overview of the study of dispersal and incorporates much of the latest research. The causes, mechanisms, and consequences of dispersal at the individual, population, species and community levels are considered. The potential of new techniques and models for studying dispersal, drawn from molecular biology and demography, is also explored. Perspectives and insights are offered from the fields of evolution, conservation biology and genetics. Throughout the book, theoretical approaches are combined with empirical data, and care has been taken to include examples from as wide a range of species as possible.

  15. Progress in urban dispersion studies

    DEFF Research Database (Denmark)

    Batchvarova, E.; Gryning, Sven-Erik

    2006-01-01

    The present Study addresses recent achievements in better representation Of the urban area structure in meteorology and dispersion parameterisations. The setup and Main Outcome of several recent dispersion experiments in Urban areas and their use in model validation are discussed. The maximum...... BUBBLE Tracer Experiment) the horizontal spread of the plume corresponds to a Lagrangian time scale bigger than the value for ground Sources. Turbulence measurements LIP to 3-5 times the building height Lire needed for direct use in dispersion Calculations....

  16. Study of LPG Release & Dispersion Model

    Institute of Scientific and Technical Information of China (English)

    Mu Shanjun; Peng Xiangwei

    2003-01-01

    The current applicable release & dispersion models are reviewed. A typical model is developed on the basis of LPG storage conditions in China and the authors' research. The study is focused on the relationship between LPG composition and release rate, and on the influence of buildings or structures located in the surrounding area on the dispersion of gas plume. The established model is compared with existing models by the use of published field test data.

  17. Permeation Dispersal of Treatment Agents for In Situ Remediation in Low Permeability Media: 1. Field Studies in Unconfined Test Cells

    Energy Technology Data Exchange (ETDEWEB)

    Siegrist, R.L.; Smuin, D.R.; Korte, N.E.; Greene, D.W.; Pickering, D.A.; Lowe, K.S.; Strong-Gunderson, J.

    2000-08-01

    Chlorocarbons like trichloroethylene (TCE) are common contaminants of concern at US Department of Energy (DOE) facilities and industrial sites across the US and abroad. These contaminants of concern are present in source areas and in soil and ground water plumes as dissolved or sorbed phase constituents as well as dense nonaqueous-phase liquids (DNAPLs). These DNAPL compounds can be released to the environment through a variety of means including leaks in storage tanks and transfer lines, spills during transportation, and land treatment of wastes. When DNAPL compounds are present in low permeability media (LPM) like silt and clay layers or deposits, there are major challenges with assessment of their behavior and implementation of effective in situ remediation technologies. This report describes a field demonstration that was conducted at the Portsmouth Gaseous Diffusion Plant (PORTS) Clean Test Site (CTS) to evaluate the feasibility of permeation and dispersal of reagents into LPM. Various reagents and tracers were injected at seven test cells primarily to evaluate the feasibility of delivery, but also to evaluate the effects of the injected reagents on LPM. The various reagents and tracers were injected at the PORTS CTS using a multi-port injection system (MPIS) developed and provided by Hayward Baker Environmental, Inc.

  18. CFD simulation of near-field pollutant dispersion on a high-resolution grid: A case study by LES and RANS for a building group in downtown Montreal

    Science.gov (United States)

    Gousseau, P.; Blocken, B.; Stathopoulos, T.; van Heijst, G. J. F.

    2011-01-01

    Turbulence modeling and validation by experiments are key issues in the simulation of micro-scale atmospheric dispersion. This study evaluates the performance of two different modeling approaches (RANS standard k-ɛ and LES) applied to pollutant dispersion in an actual urban environment: downtown Montreal. The focus of the study is on near-field dispersion, i.e. both on the prediction of pollutant concentrations in the surrounding streets (for pedestrian outdoor air quality) and on building surfaces (for ventilation system inlets and indoor air quality). The high-resolution CFD simulations are performed for neutral atmospheric conditions and are validated by detailed wind-tunnel experiments. A suitable resolution of the computational grid is determined by grid-sensitivity analysis. It is shown that the performance of the standard k-ɛ model strongly depends on the turbulent Schmidt number, whose optimum value is case-dependent and a priori unknown. In contrast, LES with the dynamic subgrid-scale model shows a better performance without requiring any parameter input to solve the dispersion equation.

  19. Dispersion of Magnetic Fields in Molecular Clouds. II

    CERN Document Server

    Houde, Martin; Hildebrand, Roger H; Chitsazzadeh, Shadi; Kirby, Larry

    2009-01-01

    We expand our study on the dispersion of polarization angles in molecular clouds. We show how the effect of signal integration through the thickness of the cloud as well as across the area subtended by the telescope beam inherent to dust continuum measurements can be incorporated in our analysis to correctly account for its effect on the measured angular dispersion and inferred turbulent to large-scale magnetic field strength ratio. We further show how to evaluate the turbulent magnetic field correlation scale from polarization data of sufficient spatial resolution and high enough spatial sampling rate. We apply our results to the molecular cloud OMC-1, where we find a turbulent correlation length of approximately 16 mpc, a turbulent to large-scale magnetic field strength ratio of approximately 0.5, and a plane-of-the-sky large-scale magnetic field strength of approximately 0.76 mG.

  20. Pionic dispersion relations in presence of weak magnetic field

    CERN Document Server

    Adhya, Souvik Priyam; Biswas, Subhrajyoti; Roy, Pradip K

    2016-01-01

    In this work, dispersion relations of $\\pi^0$ and $\\pi^{\\pm}$ have been studied in vacuum in the limit of weak external magnetic field using a phenomenological pion-nucleon $(\\pi N)$ Lagrangian. For our purpose, we have calculated the results up to one loop order in self energy diagrams with the pseudoscalar $(PS)$ and pseudovector $(PV)$ pion-nucleon interactions. By assuming weak external magnetic field it is seen that the effective mass of pion gets explicit magnetic field dependence and it is modified significantly for the case of PS coupling. However, for the PV coupling, only a modest increase in the effective mass is observed. These modified dispersion relations due to the presence of the external field can have substantial influence in the phenomenological aspect of the mesons both in the context of neutron stars as well as relativistic heavy ion collisions.

  1. a New Stochastic Model of Turbulent Dispersion in the Convective Planetary Boundary Layer and the Results of the ATTERBURY-87 Field Study.

    Science.gov (United States)

    Liljegren, James Christian

    The development and validation of a new stochastic model for predicting the dispersion of a passive tracer in the convective boundary layer are presented. The methods and procedures employed and the results obtained from the Atterbury-87 field study of the dispersion of fog-oil smoke and hexachloroethane (HC) smoke are also described. The stochastic model represents a substantial improvement over previous modelling approaches in that it provides a more realistic treatment of the atmospheric turbulence, especially for the large-scale convective motions occurring in the daytime planetary boundary layer which are largely responsible for driving the dispersion process. Using the Langevin equation to model the Lagrangian velocities, the dispersion of a large number of passive tracer particles is computationally simulated. The shape of the resulting probability density function closely matches observations. The behavior of the autocorrelation of the modelled Lagrangian velocities also matches the non-exponential form computed from balloon-borne measurements by using the local integral time scale of the turbulence. The model was verified against data gathered from laboratory simulations of the boundary layer carried out in water tanks and wind tunnels as well as from actual field measurements. The predictions of the stochastic model were in agreement with the trends and magnitudes observed in the data, including the lift-off of the plume centerline from the ground due to the influence of the rising thermal updrafts. Comparisons of crosswind-integrated concentration and plume spread computed from the test data with the results of previous field studies of atmospheric dispersion indicated strong agreement. These comparisons revealed that the centerline of the smoke plume rose as the plume moved downwind due to the effects of thermal convection. Comparison of concentration data with the predictions of the stochastic model also showed good agreement and confirmed that the

  2. EDITORIAL: Colloidal dispersions in external fields Colloidal dispersions in external fields

    Science.gov (United States)

    Löwen, Hartmut

    2012-11-01

    third conference in a series that began in 2004 [2] and was continued in 2008 [3]. The CODEF meeting series is held in conjunction with the German Dutch Transregional Collaborative Research Centre SFB TR6 with the title Physics of Colloidal Dispersions in External Fields. Papers from scientists working within this network as well as those from further invited contributors are summarized in this issue. They are organized according to the type of field applied, namely: shear flow electric field laser-optical and magnetic field confinement other fields and active particles To summarize the highlights of this special issue as regards shear fields, the response of depletion-induced colloidal clusters to shear is explored in [4]. Soft particles deform under shear and their structural and dynamical behaviour is studied both by experiment [5] and theory [6]. Transient dynamics after switching on shear is described by a joint venture of theory, simulation and experiment in [7]. Colloids provide the fascinating possibility to drag single particles through the suspension, which gives access to microrheology (as opposed to macrorheology, where macroscopic boundaries are moved). Several theoretical aspects of microrheology are discussed in this issue [8-10]. Moreover, a microscopic theory for shear viscosity is presented [11]. Various aspects of colloids in electric fields are also included in this issue. Electrokinetic phenomena for charged suspensions couple flow and electric phenomena in an intricate way and are intensely discussed both by experiment and simulation in contributions [12-14]. Dielectric phenomena are also influenced by electric fields [15]. Electric fields can induce effective dipolar forces between colloids leading to string formation [16]. Finally, binary mixtures in an electric driving field exhibit laning [17]. Simulation [18] and theoretical [19] studies of this nonequilibrium phenomenon are also discussed in this issue. Laser-optical fields can be used to

  3. Study of Dispersion Coefficient Channel

    Science.gov (United States)

    Akiyama, K. R.; Bressan, C. K.; Pires, M. S. G.; Canno, L. M.; Ribeiro, L. C. L. J.

    2016-08-01

    The issue of water pollution has worsened in recent times due to releases, intentional or not, of pollutants in natural water bodies. This causes several studies about the distribution of pollutants are carried out. The water quality models have been developed and widely used today as a preventative tool, ie to try to predict what will be the concentration distribution of constituent along a body of water in spatial and temporal scale. To understand and use such models, it is necessary to know some concepts of hydraulic high on their application, including the longitudinal dispersion coefficient. This study aims to conduct a theoretical and experimental study of the channel dispersion coefficient, yielding more information about their direct determination in the literature.

  4. Gamma neutron method applied to field measurement of hydrodynamic dispersion

    Science.gov (United States)

    Brissaud, F.; Pappalardo, A.; Couchat, Ph.

    1983-06-01

    The gamma neutron method is applied to the study of solute movements during field irrigations under steady-state and transient hydrodynamic conditions. Two different types of behavior are discussed. In the first, the labeled water pulse velocity matches the conservation of the vertical rate of water and, when the deuterated water concentration profiles are mass-conservative, the experimental results are accurately described by the equation of dispersion. In the second, the pore water velocity differs considerably from that of strictly vertical displacements and the concentration profiles are not massconservative.

  5. Verification of HYDRASTAR: Analysis of hydraulic conductivity fields and dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Morris, S.T.; Cliffe, K.A. [AEA Technology, Harwell (United Kingdom)

    1994-10-01

    HYDRASTAR is a code for the stochastic simulation of groundwater flow. It can be used to simulate both time-dependent and steady-state groundwater flow at constant density. Realizations of the hydraulic conductivity field are generated using the Turning Bands algorithm. The realizations can be conditioned on measured values of the hydraulic conductivity using Kriging. This report describes a series of verification studies that have been carried out on the code. The first study concerns the accuracy of the implementation of the Turning Bands algorithm in HYDRASTAR. The implementation has been examined by evaluating the ensemble mean and covariance of the generated fields analytically and comparing them with their prescribed values. Three other studies were carried out in which HYDRASTAR was used to solve problems of uniform mean flow and to calculate the transport and dispersion of fluid particles. In all three cases the hydraulic conductivity fields were unconditioned. The first two were two-dimensional: one at small values of the variance of the logarithm of the hydraulic conductivity for which there exists analytical results that the code can be compared with, and one at moderate variance where the results can only be compared with those obtained by another code. The third problem was three dimensional with a small variance and again analytical results are available for comparison. 14 refs, 24 figs.

  6. Dispersal of solitary bees and bumblebees in a winter oilseed rape field

    DEFF Research Database (Denmark)

    Calabuig, Isabel

    2000-01-01

    Dispersal distributions of solitary bees and bumblebees were studied in a winter oilseed rape field. Window-traps were placed in the rape field along a line transect perpendicular to the field edge. 19 species of solitary bees were recorded and all but four species are polylectic, including...

  7. Field-scale variation in colloid dispersibility and transport

    DEFF Research Database (Denmark)

    Norgaard, Trine; Moldrup, P.; Ferre´, T. P A;

    2014-01-01

    risk of colloid-facilitated transport. Subsequently, using multiple linear regression (MLR) analyses, soil dispersibility was predicted at all three sample scales from the 24 measured, geo-referenced parameters to produce sets of only a few promising indicator parameters for evaluating soil stability...... and particle mobilization on field scale. The MLR analyses at each scale were separated in predictions using all, only north, and only south locations in the field. We found that different independent variables were included in the regression models when the sample scale increased from aggregate to column...... level. Generally, the predictive power of the regression models was better on the 1-2 mm aggregate scale than on the intact 100 cm3 and 20 cm × 20 cm scales. Overall, results suggested that different drivers controlled soil dispersibility 1 at the three scales and the two sub-areas of the field...

  8. A Case Study of the Weather Research and Forecasting Model Applied to the Joint Urban 2003 Tracer Field Experiment. Part 2: Gas Tracer Dispersion

    Science.gov (United States)

    Nelson, Matthew A.; Brown, Michael J.; Halverson, Scot A.; Bieringer, Paul E.; Annunzio, Andrew; Bieberbach, George; Meech, Scott

    2016-12-01

    The Quick Urban & Industrial Complex (QUIC) atmospheric transport, and dispersion modelling, system was evaluated against the Joint Urban 2003 tracer-gas measurements. This was done using the wind and turbulence fields computed by the Weather Research and Forecasting (WRF) model. We compare the simulated and observed plume transport when using WRF-model-simulated wind fields, and local on-site wind measurements. Degradation of the WRF-model-based plume simulations was cased by errors in the simulated wind direction, and limitations in reproducing the small-scale wind-field variability. We explore two methods for importing turbulence from the WRF model simulations into the QUIC system. The first method uses parametrized turbulence profiles computed from WRF-model-computed boundary-layer similarity parameters; and the second method directly imports turbulent kinetic energy from the WRF model. Using the WRF model's Mellor-Yamada-Janjic boundary-layer scheme, the parametrized turbulence profiles and the direct import of turbulent kinetic energy were found to overpredict and underpredict the observed turbulence quantities, respectively. Near-source building effects were found to propagate several km downwind. These building effects and the temporal/spatial variations in the observed wind field were often found to have a stronger influence over the lateral and vertical plume spread than the intensity of turbulence. Correcting the WRF model wind directions using a single observational location improved the performance of the WRF-model-based simulations, but using the spatially-varying flow fields generated from multiple observation profiles generally provided the best performance.

  9. National Atmospheric Release Advisory Center Dispersion Modeling of the Full-scale Radiological Dispersal Device (FSRDD) Field Trials.

    Science.gov (United States)

    Neuscamman, Stephanie; Yu, Kristen

    2016-05-01

    The results of the National Atmospheric Release Advisory Center (NARAC) model simulations are compared to measured data from the Full-Scale Radiological Dispersal Device (FSRDD) field trials. The series of explosive radiological dispersal device (RDD) experiments was conducted in 2012 by Defence Research and Development Canada (DRDC) and collaborating organizations. During the trials, a wealth of data was collected, including a variety of deposition and air concentration measurements. The experiments were conducted with one of the stated goals being to provide measurements to atmospheric dispersion modelers. These measurements can be used to facilitate important model validation studies. For this study, meteorological observations recorded during the tests are input to the diagnostic meteorological model, ADAPT, which provides 3-D, time-varying mean wind and turbulence fields to the LODI dispersion model. LODI concentration and deposition results are compared to the measured data, and the sensitivity of the model results to changes in input conditions (such as the particle activity size distribution of the source) and model physics (such as the rise of the buoyant cloud of explosive products) is explored. The NARAC simulations predicted the experimentally measured deposition results reasonably well considering the complexity of the release. Changes to the activity size distribution of the modeled particles can improve the agreement of the model results to measurement.

  10. Thermal fermionic dispersion relations in a magnetic field

    CERN Document Server

    Elmfors, P; Skagerstam, B S; Elmfors, Per; Persson, David; Skagerstam, Bo Sture

    1996-01-01

    The thermal self-energy of an electron in a static uniform magnetic field B is calculated to first order in the fine structure constant \\alpha and to all orders in eB. We use two methods, one based on the Furry picture and another based on Schwinger's proper-time method. As external states we consider relativistic Landau levels with special emphasis on the lowest Landau level. In the high-temperature limit we derive self-consistent dispersion relations for particle and hole excitations, showing the chiral asymmetry caused by the external field. For weak fields, earlier results on the ground- state energy and the anomalous magnetic moment are discussed and compared with the present analysis. In the strong-field limit the appearance of a field-independent imaginary part of the self-energy, related to Landau damping in the e^{+}e^{-} plasma, is pointed out.

  11. Powder diffraction studies using anomalous dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Cox, D.E. [Brookhaven National Lab., Upton, NY (United States); Wilkinson, A.P. [California Univ., Santa Barbara, CA (United States). Dept. of Materials

    1993-05-01

    With the increasing availability and accessibility of high resolution powder diffractometers at many synchrotron radiation sources throughout the world, there is rapidly-growing interest in the exploitation of anomalous dispersion techniques for structural studies of polycrystalline materials. In conjunction with the Rietveld profile method for structure refinement, such studies are especially useful for the determination of the site distributions of two or more atoms which are near neighbors in the periodic table, or atoms which are distributed among partially occupied sites. Additionally, it is possible to (1) determine the mean-square displacements associated with different kinds of atoms distributed over a single set of sites, (2) distinguish between different oxidation states and coordination geometries of a particular atom in a compound and (3) to determine f` for a wide range of atomic species as a function of energy in the vicinity of an absorption edge. Experimental methods for making anomalous dispersion measurements are described in some detail, including data collection strategies, data analysis and correlation problems, possible systematic errors, and the accuracy of the results. Recent work in the field is reviewed, including cation site-distribution studies (e.g. doped high {Tc} superconductors, ternary alloys, FeCo{sub 2}(PO{sub 4}){sub 3}, FeNi{sub 2}BO{sub 5}), oxidation-state contrast (e.g. YBa{sub 2}Cu{sub 3}O{sub 6+x}, Eu{sub 3}O{sub 4}, GaCl{sub 2}, Fe{sub 2}PO{sub 5}), and the effect of coordination geometry (e.g. Y{sub 3}Ga{sub 5}O{sub l2}).

  12. Powder diffraction studies using anomalous dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Cox, D.E. (Brookhaven National Lab., Upton, NY (United States)); Wilkinson, A.P. (California Univ., Santa Barbara, CA (United States). Dept. of Materials)

    1993-01-01

    With the increasing availability and accessibility of high resolution powder diffractometers at many synchrotron radiation sources throughout the world, there is rapidly-growing interest in the exploitation of anomalous dispersion techniques for structural studies of polycrystalline materials. In conjunction with the Rietveld profile method for structure refinement, such studies are especially useful for the determination of the site distributions of two or more atoms which are near neighbors in the periodic table, or atoms which are distributed among partially occupied sites. Additionally, it is possible to (1) determine the mean-square displacements associated with different kinds of atoms distributed over a single set of sites, (2) distinguish between different oxidation states and coordination geometries of a particular atom in a compound and (3) to determine f' for a wide range of atomic species as a function of energy in the vicinity of an absorption edge. Experimental methods for making anomalous dispersion measurements are described in some detail, including data collection strategies, data analysis and correlation problems, possible systematic errors, and the accuracy of the results. Recent work in the field is reviewed, including cation site-distribution studies (e.g. doped high [Tc] superconductors, ternary alloys, FeCo[sub 2](PO[sub 4])[sub 3], FeNi[sub 2]BO[sub 5]), oxidation-state contrast (e.g. YBa[sub 2]Cu[sub 3]O[sub 6+x], Eu[sub 3]O[sub 4], GaCl[sub 2], Fe[sub 2]PO[sub 5]), and the effect of coordination geometry (e.g. Y[sub 3]Ga[sub 5]O[sub l2]).

  13. Tracing river gravels: Insights into dispersion from a long-term field experiment

    Science.gov (United States)

    Haschenburger, J. K.

    2013-10-01

    Sediment dispersion is a fundamental component of the sediment transfer process in gravel-bed rivers. Modeling this process requires an understanding of the collective movement of mixed-size clasts. This study explores the temporal evolution of gravel dispersion to underscore the importance of field observation in informing modeling efforts. Magnetically tagged gravels deployed in Carnation Creek have been monitored repeatedly over 17 years. Four metrics used to describe the extent of dispersion document that the overall shape in the spatial distribution of grain location changes over time. The general trends mask the complexity of the dispersion process, expressed by channel sections where tracers are concentrated regardless of grain size. The distribution of total grain displacement responsible for dispersion evolves as tracers become well mixed. Results demonstrate that observations from the field are crucial to the understanding and modeling of sediment dispersion because they provide key insights into the dispersion process that must be known a priori for mathematical modeling and similar observations cannot be collected using laboratory flumes.

  14. Estimating adhesive seed-dispersal distances : field experiments and correlated random walks

    NARCIS (Netherlands)

    Mouissie, AM; Lengkeek, W; van Diggelen, R

    1. In this study we aimed to estimate distance distributions of adhesively dispersed seeds and the factors that determine them. 2. Seed attachment and detachment were studied using field experiments with a real sheep, a sheep dummy and a cattle dummy. Seed-retention data were used in correlated

  15. Correction of environmental magnetic fields for the acquisition of Nuclear magnetic relaxation dispersion profiles below Earth's field

    Science.gov (United States)

    Zampetoulas, Vasileios; Lurie, David J.; Broche, Lionel M.

    2017-09-01

    T1 relaxation times can be measured at a range of magnetic field strengths by Fast Field-Cycling (FFC) NMR relaxometry to provide T1-dispersion curves. These are valuable tools for the investigation of material properties as they provide information about molecular dynamics non-invasively. However, accessing information at fields below 230 μT (10 kHz proton Larmor frequency) requires careful correction of unwanted environmental magnetic fields. In this work a novel method is proposed that compensates for the environmental fields on a FFC-NMR relaxometer and extends the acquisition of Nuclear Magnetic Relaxation Dispersion profiles to 2.3 μT (extremely low field region), with direct application in the study of slow molecular motions. Our method is an improvement of an existing technique, reported by Anoardo and Ferrante in 2003, which exploits the non-adiabatic behaviour of the magnetisation in rapidly-varying magnetic fields and makes use of the oscillation of the signal amplitude to estimate the field strength. This increases the accuracy in measuring the environmental fields and allows predicting the optimal correction values by applying simple equations to fit the data acquired. Validation of the method is performed by comparisons with well-known dispersion curves obtained from polymers and benzene.

  16. The spin wave dispersion of NdCu 2 in strong magnetic fields

    Science.gov (United States)

    Kramp, S.; Loewenhaupt, M.; Rotter, M.

    2000-03-01

    The study of the spin wave excitation spectrum in NdCu 2 revealed a pronounced minimum which forms an energy gap. Previous experiments showed that the gap energy remains finite in external magnetic fields parallel to the b-axis. In this paper we report on measurements of the spin wave dispersion in strong magnetic fields applied parallel to the c-direction (hard magnetization axis). The spin wave gap changes its position and soft mode behavior at a magnetic phase transition is observed. The comparison with the dispersion at μ 0H ||b=3 T reveals the anisotropy between ( ac)-plane and b-axis.

  17. Noise-free scattering of the quantized electromagnetic field from a dispersive linear dielectric

    CERN Document Server

    Hillery, M; Hillery, Mark; Drummond, Peter D.

    2000-01-01

    We study the scattering of the quantized electromagnetic field from a linear, dispersive dielectric using the scattering formalism for quantum fields. The medium is modeled as a collection of harmonic oscillators with a number of distinct resonance frequencies. This model corresponds to the Sellmeir expansion, which is widely used to describe experimental data for real dispersive media. The integral equation for the interpolating field in terms of the in field is solved and the solution used to find the out field. The relation between the in and out creation and annihilation operators is found which allows one to calculate the S-matrix for this system. In this model, we find that there are absorption bands, but the input-output relations are completely unitary. No additional quantum noise terms are required.

  18. Quantifying dispersal from hydrothermal vent fields in the western Pacific Ocean.

    Science.gov (United States)

    Mitarai, Satoshi; Watanabe, Hiromi; Nakajima, Yuichi; Shchepetkin, Alexander F; McWilliams, James C

    2016-03-15

    Hydrothermal vent fields in the western Pacific Ocean are mostly distributed along spreading centers in submarine basins behind convergent plate boundaries. Larval dispersal resulting from deep-ocean circulations is one of the major factors influencing gene flow, diversity, and distributions of vent animals. By combining a biophysical model and deep-profiling float experiments, we quantify potential larval dispersal of vent species via ocean circulation in the western Pacific Ocean. We demonstrate that vent fields within back-arc basins could be well connected without particular directionality, whereas basin-to-basin dispersal is expected to occur infrequently, once in tens to hundreds of thousands of years, with clear dispersal barriers and directionality associated with ocean currents. The southwest Pacific vent complex, spanning more than 4,000 km, may be connected by the South Equatorial Current for species with a longer-than-average larval development time. Depending on larval dispersal depth, a strong western boundary current, the Kuroshio Current, could bridge vent fields from the Okinawa Trough to the Izu-Bonin Arc, which are 1,200 km apart. Outcomes of this study should help marine ecologists estimate gene flow among vent populations and design optimal marine conservation plans to protect one of the most unusual ecosystems on Earth.

  19. Simplified Atmospheric Dispersion Model andModel Based Real Field Estimation System ofAir Pollution

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    The atmospheric dispersion model has been well developed and applied in pollution emergency and prediction. Based on thesophisticated air diffusion model, this paper proposes a simplified model and some optimization about meteorological andgeological conditions. The model is suitable for what is proposed as Real Field Monitor and Estimation system. The principle ofsimplified diffusion model and its optimization is studied. The design of Real Field Monitor system based on this model and itsfundamental implementations are introduced.

  20. Early Student Support for Process Studies of Surface Freshwater Dispersal

    Science.gov (United States)

    2016-06-24

    light field is varied to decay exponentially with depth. The spectra of tracer variance are computed for different growth rates and related to the...To) 06/24/2016 FINAL 12/01 /2012-03/31 /2016 4. TITLE AND SUBTITLE sa. CONTRACT NUMBER Early Student Support for Process Studies of Surface...ONRREPORT Early Student Support Process Studies of Surface Freshwater Dispersal June 24, 2016 Amala Mahadevan Woods Hole Oceanographic Institution

  1. Entanglement of a quantum field with a dispersive medium.

    Science.gov (United States)

    Klich, Israel

    2012-08-10

    In this Letter we study the entanglement of a quantum radiation field interacting with a dielectric medium. In particular, we describe the quantum mixed state of a field interacting with a dielectric through plasma and Drude models and show that these generate very different entanglement behavior, as manifested in the entanglement entropy of the field. We also present a formula for a "Casimir" entanglement entropy, i.e., the distance dependence of the field entropy. Finally, we study a toy model of the interaction between two plates. In this model, the field entanglement entropy is divergent; however, as in the Casimir effect, its distance-dependent part is finite, and the field matter entanglement is reduced when the objects are far.

  2. Field Scale Variation in Water Dispersible Colloids from Aggregates and Intact Soil Samples

    DEFF Research Database (Denmark)

    Nørgaard, Trine; Møldrup, Per; Ferré, Ty P A

    Colloid-facilitated transport can play an important role in the transport of chemicals through the soil profile. The negative surface charge and large surface area makes colloids perfect carriers for strongly sorbing chemicals, like phosphorus and certain pesticides, in highly structured soils....... It is, however, difficult to quantify the amount of colloids ready available to participate in colloid-facilitated transport. In literature, the part of the colloidal fraction that readily disperses into suspension is referred to as water-dispersible clay (WDC). In this study we used two methods...... cm intact soil columns sampled from the same field grid also showed that the largest mass of particles and phosphorus leached from this part of the field. Thus, the presented WDC method comparison and results seem highly relevant in regard to field-scale mapping of leaching risk in regard to colloid...

  3. Field Scale Variation in Water Dispersible Colloids from Aggregates and Intact Soil Samples

    DEFF Research Database (Denmark)

    Nørgaard, Trine; Møldrup, Per; Ferré, Ty P A;

    Colloid-facilitated transport can play an important role in the transport of chemicals through the soil profile. The negative surface charge and large surface area makes colloids perfect carriers for strongly sorbing chemicals, like phosphorus and certain pesticides, in highly structured soils....... It is, however, difficult to quantify the amount of colloids ready available to participate in colloid-facilitated transport. In literature, the part of the colloidal fraction that readily disperses into suspension is referred to as water-dispersible clay (WDC). In this study we used two methods...... cm intact soil columns sampled from the same field grid also showed that the largest mass of particles and phosphorus leached from this part of the field. Thus, the presented WDC method comparison and results seem highly relevant in regard to field-scale mapping of leaching risk in regard to colloid...

  4. Dispersion of Magnetic Fields in Molecular Clouds. III

    CERN Document Server

    Houde, Martin; Vaillancourt, John E; Hildebrand, Roger H

    2011-01-01

    We apply our technique on the dispersion of magnetic fields in molecular clouds to high spatial resolution Submillimeter Array polarization data obtained for Orion KL in OMC-1, IRAS 16293, and NGC 1333 IRAS 4A. We show how one can take advantage of such high resolution data to characterize the magnetized turbulence power spectrum in the inertial and dissipation ranges. For Orion KL we determine that in the inertial range the spectrum can be approximately fitted with a power law k^-(2.9\\pm0.9) and we report a value of 9.9 mpc for {\\lambda}_AD, the high spatial frequency cutoff presumably due to turbulent ambipolar diffusion. For the same parameters we have \\sim k^-(1.4\\pm0.4) and a tentative value of {\\lambda}_AD \\simeq 2.2 mpc for NGC 1333 IRAS 4A, and \\sim k^-(1.8\\pm0.3) with an upper limit of {\\lambda}_AD < 1.8 mpc for IRAS 16293. We also discuss the application of the technique to interferometry measurements and the effects of the inherent spatial filtering process on the interpretation of the results.

  5. A Study on Physical Dispersion and Chemical Modification of Graphene

    Energy Technology Data Exchange (ETDEWEB)

    Yim, Eun-Chae; Kim, Seong-Jun [Chonnam National University, Gwangju (Korea, Republic of)

    2015-12-15

    Graphene has a wide spectrum on its application field due to various and excellent physical properties. However, it is very difficult to apply that graphene exists as lump or fold condition in general organic solvents. Besides, graphene was difficult to maintain as uniform condition due to chemical inert and distributions with various size and shapes. Therefore, this study was focused to study dispersion and modifying methods of aggregated graphene. The dispersion methods contain as follow: i) physical milling using glass bead, ii) co-treatment of glass bead and ultrasonic waves, iii) dispersion in organic solvents, iv) modifying with dry-ice. Milling using glass bead with size 2.5 mm was effective to be size decrease of 36.4% in comparison with control group. Mixed treatment of glass bead (size 2.5 mm) and ultrasonic waves (225W, 10 min) showed relative size decrease of 76%, suggesting that the size decrease depends on the size of glass bead, intensity of ultrasonic waves and treatment time. Solvents of Ethyl acetate (EA) and Isoprophyl alcohol (IPA) were used in order to improve dispersion by modifying surface of graphene. IPA of them showed a favorable dispersion with more -CO functional groups in the FT-IR analysis. On the other hand, the oxygen content of graphene surface modified by dry-ice was highly increased from 0.8 to 4.9%. From the results, it was decided that the favorable dispersion state for a long time was obtained under the condition of -CO functional group increase in IPA solvent.

  6. Seed dispersal in heterogeneous landscapes: linking field observations with spatially explicit models

    OpenAIRE

    Lavabre, Jessica E.; Stouffer, Daniel B.; SANZ, RUBÉN; Bascompte, Jordi

    2014-01-01

    Seed dispersal by animals drives persistence and colonization of the majority of fleshy-fruited plants. Different factors have been identified as important in shaping patterns of seed deposition. These factors include habitat heterogeneity, movement patterns of frugivore species, and their feeding behavior. Most studies, however, have analysed the effect of one factor at the time, either with a modelling approach or from field observations. Here, we combine empirical data with spatially-expli...

  7. Comparisons of Urban Transport and Dispersion Model Predictions to Field Trial Data

    Science.gov (United States)

    Heagy, J. F.; Warner, S.; Platt, N.; Urban, J.

    2007-12-01

    For the past 3 years our group at IDA has been involved in validation efforts associated with several Urban Transport and Dispersion (T&D) modeling systems. Models under study include MESO/RUSTIC, QUIC-URB/QUIC-PLUME, CT-Analyst, and four sub-models within HPAC, the Urban Canopy Model, Micro-Swift/Spray, the Urban Dispersion Model, and the Urban Windfield Module. Our main efforts have centered on supplying sponsors, and the T&D community as a whole, credible, protocol-driven comparisons of model predictions and field trial observations. I will review our most recent Urban T&D comparison work, with particular attention paid to comparisons of QUIC-URB/QUIC-PLUME predictions to the 29 continuous SF6 releases carried out during the Joint Urban 2003 (JU2003) field experiment in Oklahoma City.

  8. Dispersions of the resonance frequencies in an antidot system in a magnetic field

    CERN Document Server

    Lee, Y S

    2000-01-01

    An analytical and quantum-mechanical method is developed to study the collective excitation spectrum of an antidot system in a normal magnetic field. The problem is solved within the single-particle picture within the framework of an anisotropic quantum wire or dot, taking into account the classical phenomenon of edge magneto-plasmons (EMP's) through the renormalization of the effective strength of the antidot potential at a hole. The resulting dispersions with magnetic fields explain quantitatively the main spectrum of the antidot system observed in recent experiments.

  9. Control Effect of 80%Nicosulfuron·Atrazine Water-dispersible Granules on Weeds in Spring Maize Field

    Institute of Scientific and Technical Information of China (English)

    Yueqi SHEN; Rende Ql

    2014-01-01

    This study aimed to investigate the control effect of different concentrations of 80% nicosulfuron·atrazine water-dispersible granules on weeds in spring maize field. [Method] Maize field was sprayed with 300, 375, 450, 750 g/hm2 80% nicosulfuron·atrazine water-dispersible granules respectively, with 40 g/L nico-sulfuron suspending concentrate and 38% atrazine suspending concentrate as con-trol agents. Artificial weeding and control (CK) plots were set. [Result] Fresh weight control efficiency of 375-750 g/hm2 80% nicosulfuron ·atrazine water-dispersible granules was significantly higher than that of 40 g/L nicosulfuron suspending con-centrate and 38% atrazine suspending concentrate; no obvious phytotoxicity symp-toms were observed after application of 300-450 g/hm2 80% nicosulfuron·atrazine water-dispersible granules; 750 g/hm2 80% nicosulfuron·atrazine water-dispersible granules posed certain impact on the growth of maize seedlings. Compared with control plots, various doses of 80% nicosulfuron·atrazine water-dispersible granules signifi-cantly improved the yield of maize. [Conclusion] ln the present study, 375-450 g/hm2 80% nicosulfuron·atrazine water-dispersible granules exhibited high control effect on weeds in maize field and were safe for the growth of maize seedlings.

  10. Microbial Field Pilot Study

    Energy Technology Data Exchange (ETDEWEB)

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Chisholm, J.L.

    1990-11-01

    This report covers progress made during the first year of the Microbial Field Pilot Study project. Information on reservoir ecology and characterization, facility and treatment design, core experiments, bacterial mobility, and mathematical modeling are addressed. To facilitate an understanding of the ecology of the target reservoir analyses of the fluids which support bacteriological growth and the microbiology of the reservoir were performed. A preliminary design of facilities for the operation of the field pilot test was prepared. In addition, procedures for facilities installation and for injection treatments are described. The Southeast Vassar Vertz Sand Unit (SEVVSU), the site of the proposed field pilot study, is described physically, historically, and geologically. The fields current status is presented and the ongoing reservoir simulation is discussed. Core flood experiments conducted during the last year were used to help define possible mechanisms involved in microbial enhanced oil recovery. Two possible mechanisms, relative permeability effects and changes in the capillary number, are discussed and related to four Berea core experiments' results. The experiments were conducted at reservoir temperature using SEVVSU oil, brine, and bacteria. The movement and activity of bacteria in porous media were investigated by monitoring the growth of bacteria in sandpack cores under no flow conditions. The rate of bacteria advancement through the cores was determined. A mathematical model of the MEOR process has been developed. The model is a three phase, seven species, one dimensional model. Finite difference methods are used for solution. Advection terms in balance equations are represented with a third- order upwind differencing scheme to reduce numerical dispersion and oscillations. The model is applied to a batch fermentation example. 52 refs., 26 figs., 21 tabs.

  11. Cerium oxide dispersed multi walled carbon nanotubes as cathode material for flexible field emitters.

    Science.gov (United States)

    Baby, Tessy Theres; Rakhi, R B; Ravi, N; Ramaprabhu, S

    2012-08-01

    Nanomaterials based electron sources are omnipresent in modern flat panel displays. Multi walled carbon nanotubes (MWNT) are the well studied electron emitter among the carbon materials. Since the surface modification of MWNT with low work function materials would have a positive impact on the field emission property of MWNT, cerium oxide (CeO2) nanoparticles dispersed multi walled carbon nanotubes (CeO2/MWNT) were synthesized by catalytic chemical vapour deposition followed by chemical reduction and its field emission property was investigated. The high-purity MWNT as well as CeO2/MWNT showed crystalline structure conformed by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Further characterisation was done with Raman spectroscopy, UV-Visible absorption spectra and Fourier transform IR spectroscopy (FT-IR). The morphology and structural details of CeO2/MWNT composite was probed by field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray analysis (EDX). The direct evidence of the formation of CeO2/MWNT composites was given by transmission electron microscopy (TEM). The synthesized sample was coated over a flexible carbon paper using spin coating technique. The experiment was performed under a vacuum of 1 x 10(-6) Torr and Fowler-Nordheim equation was used to analyse the data. The turn-on voltage for the cerium oxide dispersed MWNT was found for a current density of 10 microA/cm2. The emission current density from the CeO2 nanoparticles dispersed MWNT reached 0.2 mA/cm2 at a reasonable bias field of 2.58 V/microm. The results were compared with those of pure MWNT and pure CeO2 nanoparticles with literature values.

  12. Duri Indonesia air emission inventory and dispersion modeling study

    Energy Technology Data Exchange (ETDEWEB)

    Soetjiptono, T.E.; Nugraha, S.; VanDerZanden, D.F. [and others

    1996-11-01

    The Caltex Pacific Indonesia production field located in Duri, Indonesia, is the world`s largest steam flood. Because of the large scale of these operations, there is an interest in understanding the emissions into the atmosphere from the various sources in the field as well as the possible impact on the air quality resulting from these emissions. To be proactive and to fulfill this need, a study was done to inventory emissions from the facilities in the field and to use air dispersion models to estimate impacts on the air quality using the inventory results. This paper will discuss methods and procedures used in & study to quantify the emissions from the following sources in the Duri field: process vents, production impoundments and wastewater canals, roads, fugitive emissions, storage links, and combustion sources. Emissions of the following pounds were addressed in the study: non-methane hydrocarbons (NMHC) and aromatic hydrocarbons (BTEX), hydrogen sulfide, nitrogen oxides, sulfur oxides, particulate matter (PM), and carbon monoxide. Because of the diverse nature of the sources in the field, a wide range of emission estimating procedures were used including direct measurement methods, empirical methods based on mass transfer principles, and standard emission factors or procedures available from the United States Environmental Protection Agency (U.S. EPA). To quantify and track the emissions data generated, a computerized emissions inventory was developed. This paper will also discuss the dispersion modeling methods that were used to estimate the ground level concentrations in the surrounding areas using the data developed in the emission inventory. These discussions are based upon the results of a preliminary study which is limited to a portion of the Duri production field.

  13. DNA fingerprinting validates seed dispersal curves from observational studies in the neotropical legume parkia.

    Science.gov (United States)

    Heymann, Eckhard W; Lüttmann, Kathrin; Michalczyk, Inga M; Saboya, Pedro Pablo Pinedo; Ziegenhagen, Birgit; Bialozyt, Ronald

    2012-01-01

    Determining the distances over which seeds are dispersed is a crucial component for examining spatial patterns of seed dispersal and their consequences for plant reproductive success and population structure. However, following the fate of individual seeds after removal from the source tree till deposition at a distant place is generally extremely difficult. Here we provide a comparison of observationally and genetically determined seed dispersal distances and dispersal curves in a Neotropical animal-plant system. In a field study on the dispersal of seeds of three Parkia (Fabaceae) species by two Neotropical primate species, Saguinus fuscicollis and Saguinus mystax, in Peruvian Amazonia, we observationally determined dispersal distances. These dispersal distances were then validated through DNA fingerprinting, by matching DNA from the maternally derived seed coat to DNA from potential source trees. We found that dispersal distances are strongly right-skewed, and that distributions obtained through observational and genetic methods and fitted distributions do not differ significantly from each other. Our study showed that seed dispersal distances can be reliably estimated through observational methods when a strict criterion for inclusion of seeds is observed. Furthermore, dispersal distances produced by the two primate species indicated that these primates fulfil one of the criteria for efficient seed dispersers. Finally, our study demonstrated that DNA extraction methods so far employed for temperate plant species can be successfully used for hard-seeded tropical plants.

  14. DNA fingerprinting validates seed dispersal curves from observational studies in the neotropical legume parkia.

    Directory of Open Access Journals (Sweden)

    Eckhard W Heymann

    Full Text Available BACKGROUND: Determining the distances over which seeds are dispersed is a crucial component for examining spatial patterns of seed dispersal and their consequences for plant reproductive success and population structure. However, following the fate of individual seeds after removal from the source tree till deposition at a distant place is generally extremely difficult. Here we provide a comparison of observationally and genetically determined seed dispersal distances and dispersal curves in a Neotropical animal-plant system. METHODOLOGY/PRINCIPAL FINDINGS: In a field study on the dispersal of seeds of three Parkia (Fabaceae species by two Neotropical primate species, Saguinus fuscicollis and Saguinus mystax, in Peruvian Amazonia, we observationally determined dispersal distances. These dispersal distances were then validated through DNA fingerprinting, by matching DNA from the maternally derived seed coat to DNA from potential source trees. We found that dispersal distances are strongly right-skewed, and that distributions obtained through observational and genetic methods and fitted distributions do not differ significantly from each other. CONCLUSIONS/SIGNIFICANCE: Our study showed that seed dispersal distances can be reliably estimated through observational methods when a strict criterion for inclusion of seeds is observed. Furthermore, dispersal distances produced by the two primate species indicated that these primates fulfil one of the criteria for efficient seed dispersers. Finally, our study demonstrated that DNA extraction methods so far employed for temperate plant species can be successfully used for hard-seeded tropical plants.

  15. Theoretical analysis of the electromagnetic field inside an anomalous-dispersion microresonator under synthetical pump

    Science.gov (United States)

    Xin, Xu; Xiaohong, Hu; Ye, Feng; Yuanshan, Liu; Wei, Zhang; Zhi, Yang; Wei, Zhao; Yishan, Wang

    2016-03-01

    We study the spatiotemporal evolution of the electromagnetic field inside a microresonator showing an anomalous dispersion at the pump wavelength by using the normalized Lugiato-Lefever equation. Unlike the traditional single continuous wave (CW) pumping, an additional pump source consisting of periodical pulse train with variable repetition rate is adopted. The influences of the microresonator properties and the pump parameters on the field evolution and the electromagnetic field profile are analyzed. The simulation results indicate that, in the anomalous dispersion regime, both increases of the input pulse amplitude and the repetition frequency can result in the field profiles consisting of multiple peaks. A series of equidistant pulses can also be obtained by increasing the CW pump power. In addition, we find that a large physical detuning between the pump laser carrier and the cavity resonance frequency also causes the splitting of the inside field. Project supported by the National Major Scientific Instrumentation Development Program of China (Grant No. 2011YQ120022), CAS/SAFEA International Partnership Program for Creative Research Teams, China, and the National Natural Science Foundation of China (Grant No. 61275164).

  16. Latitude-dependence and dispersion of the westward drift in the geomagnetic field

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The main geomagnetic field models of IGRF1900---2000 are used to study the latitude-dependence of the westward drift in the main field. The results show that the latitude-dependence exists in the magnetic components with different wavelengths (m=l-10). The globai-average westward drift rate of the component of m=l is 0.189°/a with the maximum of 0.295°/a at latitudes 40°-45°. The component of m=2 has an average drift rate of 0.411°/a with the maximum of 1.305°/a at latitude -60°. As for the components with further shorter wavelengths, the drift is generally restricted in a limited latitude range, and has many smaller drift rates. This latitude-dependence of westward drift can not be explained by rigid rotation of the earth's core. The results of this note also show that there is a negative dispersion in the westward drift, namely the components of long wavelengths drift faster than those of short wavelengths.This dispersion feature is not in agreement with Hide's MHD model. It is likely needed to find a new mechanism for explaining the observed feature of dispersion.

  17. Fusion processing of itraconazole solid dispersions by kinetisol dispersing: a comparative study to hot melt extrusion.

    Science.gov (United States)

    DiNunzio, James C; Brough, Chris; Miller, Dave A; Williams, Robert O; McGinity, James W

    2010-03-01

    KinetiSol Dispersing (KSD) is a novel high energy manufacturing process investigated here for the production of pharmaceutical solid dispersions. Solid dispersions of itraconazole (ITZ) and hypromellose were produced by KSD and compared to identical formulations produced by hot melt extrusion (HME). Materials were characterized for solid state properties by modulated differential scanning calorimetry and X-ray diffraction. Dissolution behavior was studied under supersaturated conditions. Oral bioavailability was determined using a Sprague-Dawley rat model. Results showed that KSD was able to produce amorphous solid dispersions in under 15 s while production by HME required over 300 s. Dispersions produced by KSD exhibited single phase solid state behavior indicated by a single glass transition temperature (T(g)) whereas compositions produced by HME exhibited two T(g)s. Increased dissolution rates for compositions manufactured by KSD were also observed compared to HME processed material. Near complete supersaturation was observed for solid dispersions produced by either manufacturing processes. Oral bioavailability from both processes showed enhanced AUC compared to crystalline ITZ. Based on the results presented from this study, KSD was shown to be a viable manufacturing process for the production of pharmaceutical solid dispersions, providing benefits over conventional techniques including: enhanced mixing for improved homogeneity and reduced processing times.

  18. CPMG relaxation rate dispersion in dipole fields around capillaries.

    Science.gov (United States)

    Kurz, F T; Kampf, T; Buschle, L R; Heiland, S; Schlemmer, H-P; Bendszus, M; Ziener, C H

    2016-09-01

    Transverse relaxation rates for Carr-Purcell-Meiboom-Gill (CPMG) sequences increase with inter-echo time in presence of microscopic magnetic field inhomogeneities due to nuclear spin diffusion. For a weak field approximation that includes diffusion effects, the CPMG relaxation rate shift for proton diffusion around capillaries in muscle tissue can be expressed in terms of a frequency correlation function and the inter-echo time. The present work provides an analytical expression for the local relaxation rate shift that is dependent on local blood volume fraction, diffusion coefficient, capillary radius, susceptibility difference and inter-echo time. Asymptotic regions of the model are in agreement with previous modeling results of Brooks et al., Luz et al. and Ziener et al. In comparison with simulation data, the model shows an equal or better accuracy than established approximations. Also, model behavior coincides with experimental data for rat heart and skeletal muscle. The present work provides analytical tools to extract sub-voxel information about uniform capillary networks that can be used to study capillary organization or micro-circulatory remodeling.

  19. Study of Dispersion Characteristics of Mercerized Pulp

    Directory of Open Access Journals (Sweden)

    Jingyi Hao

    2014-06-01

    Full Text Available Mercerized pulp is widely used in the filter paper industry. But the major challenge facing users of the pulp is its difficult dispersion in water. It was found that by applying a suitable degree of beating it was possible to achieve better dispersion than the original pulp. The beating degree before and after beating was almost the same. But the properties of filter paper were greatly improved after beating, especially for the formation index and burst index. The morphology of beaten fibers was analyzed by SEM with both the freeze-drying and air drying sample preparation process. The results showed that the primary cell wall of the beaten mercerized pulp fibers were swollen and partly peeled from the fiber main body after beating, as revealed by micrographs obtained after freeze-drying. The results suggest that the improvement of the fiber dispersion in water was caused by these changes on the fiber surface.

  20. The Spread of a Noise Field in a Dispersive Medium

    Directory of Open Access Journals (Sweden)

    Cohen Leon

    2010-01-01

    Full Text Available We discuss the production of induced noise by a pulse and the propagation of the noise in a dispersive medium. We present a simple model where the noise is the sum of pulses and where the mean of each pulse is random. We obtain explicit expressions for the standard deviation of the spatial noise as a function of time. We also formulate the problem in terms of a time-frequency phase space approach and in particular we use the Wigner distribution to define the spatial/spatial-frequency distribution.

  1. Preparation and study of properties of dispersed graphene oxide

    Directory of Open Access Journals (Sweden)

    Evgeniya Seliverstova

    2015-09-01

    Full Text Available Ability of graphene oxide to form stable dispersion in organic solvents was studied in this work. As it was shown, sonication of graphene leads to the decreas of the particle size. Stability of prepared graphene dispersions was studied upon measurements of distribution of number of the particles via size and change of optical density of the solutions with time. It was found that graphene oxide forms a more stable dispersion in tetrahydrofuran and dimethylformamide than in chloroform and acetone.

  2. On the renormalization procedure for quantum fields with modified dispersion relation in curved spacetimes

    CERN Document Server

    Nacir, Diana López

    2009-01-01

    We review our recent results on the renormalization procedure for a free quantum scalar field with modified dispersion relations in curved spacetimes. For dispersion relations containing up to $2s$ powers of the spatial momentum, the subtraction necessary to renormalize $$ and $$ depends on $s$. We first describe our previous analysis for spatially flat Friedman-Robertson-Walker and Bianchi type I metrics. Then we present a new power counting analysis for general background metrics in the weak field approximation.

  3. Combined effect of magnetic field and thermal dispersion on a non-darcy mixed convection

    KAUST Repository

    El-Amin, Mohamed

    2011-05-21

    This paper is devoted to investigate the influences of thermal dispersion and magnetic field on a hot semi-infinite vertical porous plate embedded in a saturated Darcy-Forchheimer-Brinkman porous medium. The coefficient of thermal diffusivity has been assumed to be the sum of the molecular diffusivity and the dynamic diffusivity due to mechanical dispersion. The effects of transverse magnetic field parameter (Hartmann number Ha), Reynolds number Re (different velocities), Prandtl number Pr (different types of fluids) and dispersion parameter on the wall shear stress and the heat transfer rate are discussed. © 2011 Science Press, Institute of Engineering Thermophysics, CAS and Springer-Verlag Berlin Heidelberg.

  4. Studies on effect of various surfactants on stable dispersion of graphene nano particles in simarouba biodiesel

    Science.gov (United States)

    Paramashivaiah, B. M.; Rajashekhar, C. R.

    2016-09-01

    Discovery of graphene has inspired researchers a range of potential applications. Conventional fluids with nanoparticle of size 1-100nm dispersed in them are called Nanofluids. Nanofluids are found to possess increased physical and thermal properties like thermal diffusivity, viscosity, thermal conductivity and convective heat transfer coefficient. These properties can be explored in the field of IC engines as additives in improving the engine performance and reducing the harmful emissions like NOx, CO, UBHC etc. In this work, a comparative study of two anionic dispersants Sodium Dodecyl Sulfate (SDS) and Sodium Dodecyl Benzene Sulfonate (SDBS) as dispersants for stable dispersion of graphene in Simarouba biodiesel with 20%blend in diesel (SME20) was made. Nanofluids samples of graphene at 20ppm and different mass fraction of SDBS & SDS were prepared. Dispersion of graphene was achieved by ultrasonication and magnetic stirring. Dispersion was characterized with Ultra Violet Visible (UV-Vis) spectroscopy. The UV-Vis absorption spectra revealed the presence of Graphene with characteristic λmax at around 250 nm. Experimental result showed that with increase in concentration of dispersant, the value of absorbance also increased. There is a linear relation between stability of dispersion and UV absorbency. An optimum graphene- to-surfactant ratio was determined. Surfactant concentration above or below this ratio was shown to decreases the stability of dispersion. For a mass fraction of 1:4, Graphene to SBDS ratio, the absolute value of UV absorbency was highest. Dispersion stability of SDBS was better than SDS at all concentration levels.

  5. Near-field investigation of the explosive dispersal of radioactive material based on a reconstructed spherical blast-wave flow.

    Science.gov (United States)

    Hummel, David; Ivan, Lucian

    2017-03-15

    A "dirty bomb" is a type of radiological dispersal device (RDD) that has been the subject of significant safety and security concerns given the disruption that would result from a postulated terrorist attack. Assessing the risks of radioactive dose in a hypothetical scenario requires models that can accurately predict dispersion in a realistic environment. Modelling a RDD is complicated by the fact that the most important phenomena occur over vastly disparate spatial and temporal length scales. Particulate dispersion in the air is generally considered on scales of hundreds to thousands of meters, and over periods of minutes and hours. Dispersion models are extremely sensitive, however, to the particle size and source characterization, which are determined in distances measured in micrometers to meters, over milliseconds or less. This study examines the extent to which the explosive blast determines the transport of contaminant particles relative to the atmospheric wind over distances relevant to "near-field" dispersion problems (i.e., hundreds of meters), which are relevant to urban environments. Our results indicate that whether or not the effect of the blast should be included in a near-field dispersion model is largely dependent on the size of the contaminant particle. Relatively large particles (i.e., >40 μm in diameter), which are most likely to be produced by a RDD, penetrate the leading shock front, thereby avoiding the reverse blast wind. Consequently, they travel much farther than suspended aerosols (<10 μm) before approaching the ambient wind velocity. This suggests that, for these "near-field" dispersion problems in urban environments, the transport of contaminants from the blast wave may be integral to accurately predicting their dispersion.

  6. Broadening our approaches to studying dispersal in raptors

    Science.gov (United States)

    Morrison, J.L.; Wood, P.B.

    2009-01-01

    Dispersal is a behavioral process having consequences for individual fitness and population dynamics. Recent advances in technology have spawned new theoretical examinations and empirical studies of the dispersal process in birds, providing opportunities for examining how this information may be applied to studies of the dispersal process in raptors. Many raptors are the focus of conservation efforts; thus, reliable data on all aspects of a species' population dynamics, including dispersal distances, movement rates, and mortality rates of dispersers, are required for population viability analyses that are increasingly used to inform management. Here, we address emerging issues and novel approaches used in the study of avian dispersal, and provide suggestions to consider when developing and implementing studies of dispersal in raptors. Clarifying study objectives is essential for selection of an appropriate methodology and sample size needed to obtain accurate estimates of movement distances and rates. Identifying an appropriate study-area size will allow investigators to avoid underestimating population connectivity and important population parameters. Because nomadic individuals of some species use temporary settling areas or home ranges before breeding, identification of these areas is critical for conservation efforts focusing on habitats other than breeding sites. Study designs for investigating raptor dispersal also should include analysis of environmental and social factors influencing dispersal, to improve our understanding of condition-dependent dispersal strategies. Finally, we propose a terminology for use in describing the variety of movements associated with dispersal behavior in raptors, and we suggest this terminology could be used consistently to facilitate comparisons among studies. ?? 2009 The Raptor Research Foundation, Inc.

  7. Mean-field dispersion-induced spatial synchrony, oscillation and amplitude death, and temporal stability in an ecological model.

    Science.gov (United States)

    Banerjee, Tanmoy; Dutta, Partha Sharathi; Gupta, Anubhav

    2015-05-01

    One of the most important issues in spatial ecology is to understand how spatial synchrony and dispersal-induced stability interact. In the existing studies it is shown that dispersion among identical patches results in spatial synchrony; on the other hand, the combination of spatial heterogeneity and dispersion is necessary for dispersal-induced stability (or temporal stability). Population synchrony and temporal stability are thus often thought of as conflicting outcomes of dispersion. In contrast to the general belief, in this present study we show that mean-field dispersion is conducive to both spatial synchrony and dispersal-induced stability even in identical patches. This simultaneous occurrence of rather conflicting phenomena is governed by the suppression of oscillation states, namely amplitude death (AD) and oscillation death (OD). These states emerge through spatial synchrony of the oscillating patches in the strong-coupling strength. We present an interpretation of the mean-field diffusive coupling in the context of ecology and identify that, with increasing mean-field density, an open ecosystem transforms into a closed ecosystem. We report on the occurrence of OD in an ecological model and explain its significance. Using a detailed bifurcation analysis we show that, depending on the mortality rate and carrying capacity, the system shows either AD or both AD and OD. We also show that the results remain qualitatively the same for a network of oscillators. We identify a new transition scenario between the same type of oscillation suppression states whose geneses differ. In the parameter-mismatched case, we further report on the direct transition from OD to AD through a transcritical bifurcation. We believe that this study will lead to a proper interpretation of AD and OD in ecology, which may be important for the conservation and management of several communities in ecosystems.

  8. The radiative decay of a neutrino with a magnetic moment in a strong magnetic field with taking account of the positronium influence on the photon dispersion

    Science.gov (United States)

    Mosichkin, A. F.

    2016-02-01

    We study the process of the radiative decay of the neutrino with a magnetic moment in a strong magnetic field, with taking account of the influence of the positronium on the photon dispersion. The positronium contribution into the photon polarization operator leads to an essential modification of the photon dispersion law, and of the neutrino radiative decay amplitude. It has been shown that the probability of the neutrino radiative decay essentially increases under an influence of the positronium on the photon dispersion.

  9. Noise Studies of Externally Dispersed Interferometry for Doppler Velocimetry

    Energy Technology Data Exchange (ETDEWEB)

    Erskine, D J; Edelstein, J; Lloyd, J; Muirhead, P

    2006-05-04

    Externally Dispersed Interferometry (EDI) is the series combination of a fixed-delay field-widened Michelson interferometer with a dispersive spectrograph. This combination boosts the spectrograph performance for both Doppler velocimetry and high resolution spectroscopy. The interferometer creates a periodic comb that multiplies against the input spectrum to create moire fringes, which are recorded in combination with the regular spectrum. Both regular and high-frequency spectral components can be recovered from the data--the moire component carries additional information that increases the signal to noise for velocimetry and spectroscopy. Here we present simulations and theoretical studies of the photon limited Doppler velocity noise in an EDI. We used a model spectrum of a 1600K temperature star. For several rotational blurring velocities 0, 7.5, 15 and 25 km/s we calculated the dimensionless Doppler quality index (Q) versus wavenumber v. This is the normalized RMS of the derivative of the spectrum and is proportional to the photon-limited Doppler signal to noise ratio.

  10. Study on the Axial Dispersion of Liquid in Column Flotation

    Institute of Scientific and Technical Information of China (English)

    周鵾; 曾爱武; 高长宝; 余国琮

    2003-01-01

    An experimental study on the axial dispersion of liquid was carried out in a 0.382-m-ID flotation column packed with different structured packings or free of packings. The correlations of axial Peclet numbers with the liquid and gas superficial Reynolds numbers were developed for various packings. Among the packings tested, it is found that in the column packed with 250Y or 350Y packings the axial dispersion is the lowest. The addition of frother can decrease the axial dispersion. By the simulation analysis of the one-dimension dispersion model of packed flotation column, it is found that small axial dispersion, high collection rate constant and low axial liquid velocity can increase the collection zone recovery.

  11. Study on WC dispersion-strengthened copper

    Institute of Scientific and Technical Information of China (English)

    WANG Mengjun; ZHANG Liyong; LIU Xinyu

    2004-01-01

    Dispersion-strengthened copper (DSC) with WC as dispersoid was prepared by means of mechanical alloying (MA) following the traditional powder metallurgy (P/M) route. Influence of WC content on the properties of material was discussed in detail, and result shows that when the volume fraction of WC is 1.6%, the material achieves the best overall property, and a little more particle addition led to a less superior property owing to occurrence of particle agglomeration The as-sintered composite was designed to undergo a deformation of 75%. It is proved that appropriate deformation is helpful to attain a higher density and consequently better properties. Deformed material was then exposed to elevated temperature to test its effect on material. Annealing for 1 h at 1173K caused material to recover quite completely, but no obvious recrystallization was observed. It's supposed the particles handicaps motion of dislocations and material demonstrates good retention of strength with substantial improvement in elongation.

  12. Overview of the Full-scale Radiological Dispersal Device Field Trials.

    Science.gov (United States)

    Green, Anna Rae; Erhardt, Lorne; Lebel, Luke; Duke, M John M; Jones, Trevor; White, Dan; Quayle, Debora

    2016-05-01

    In 2012, Defence Research and Development Canada, in partnership with a number of other Canadian and International organizations, led a series of three field trials designed to simulate a Radiological Dispersal Device (RDD). These trials, known as the Full-Scale RDD (FSRDD) Field Trials, involved the explosive dispersal of a short-lived radioactive tracer ((140)La, t1/2 = 40.293 h). The FSRDD Field Trials required a significant effort in their planning, preparation, and execution to ensure that they were carried out in a safe, efficient manner and that the scientific goals of the trials were met. The discussion presented here details the planning and execution of the trials, outlines the relevant radiation safety aspects, provides a summary of the source term and atmospheric conditions for the three dispersal events, and provides an overview of the measurements that were made to track the plumes and deposition patterns.

  13. Far-field dispersal modeling for fuel-air-explosive devices

    Energy Technology Data Exchange (ETDEWEB)

    Glass, M.W.

    1990-05-01

    A computer model for simulating the explosive dispersal of a fuel agent in the far-field regime is described and is applied to a wide variety of initial conditions to judge their effect upon the resulting fuel/air cloud. This work was directed toward modeling the dispersal process associated with Fuel-Air-Explosives devices. The far-field dispersal regime is taken to be that time after the initial burster charge detonation in which the shock forces no longer dominate the flow field and initial canister and fuel mass breakup has occurred. The model was applied to a low vapor pressure fuel, a high vapor pressure fuel and a solid fuel. A strong dependence of the final cloud characteristics upon the initial droplet size distribution was demonstrated. The predicted fuel-air clouds were highly non-uniform in concentration. 18 refs., 86 figs., 4 tabs.

  14. Monodisperse granular flows in viscous dispersions in a centrifugal acceleration field

    Science.gov (United States)

    Cabrera, Miguel Angel; Wu, Wei

    2016-04-01

    Granular flows are encountered in geophysical flows and innumerable industrial applications with particulate materials. When mixed with a fluid, a complex network of interactions between the particle- and fluid-phase develops, resulting in a compound material with a yet unclear physical behaviour. In the study of granular suspensions mixed with a viscous dispersion, the scaling of the stress-strain characteristics of the fluid phase needs to account for the level of inertia developed in experiments. However, the required model dimensions and amount of material becomes a main limitation for their study. In recent years, centrifuge modelling has been presented as an alternative for the study of particle-fluid flows in a reduced scaled model in an augmented acceleration field. By formulating simple scaling principles proportional to the equivalent acceleration Ng in the model, the resultant flows share many similarities with field events. In this work we study the scaling principles of the fluid phase and its effects on the flow of granular suspensions. We focus on the dense flow of a monodisperse granular suspension mixed with a viscous fluid phase, flowing down an inclined plane and being driven by a centrifugal acceleration field. The scaled model allows the continuous monitoring of the flow heights, velocity fields, basal pressure and mass flow rates at different Ng levels. The experiments successfully identify the effects of scaling the plastic viscosity of the fluid phase, its relation with the deposition of particles over the inclined plane, and allows formulating a discussion on the suitability of simulating particle-fluid flows in a centrifugal acceleration field.

  15. Laboratory Study of Dispersion of Buoyant Surface Plumes

    DEFF Research Database (Denmark)

    Petersen, Ole; Larsen, Torben

    1990-01-01

    A laboratory a study on surface dispersion of buoyant plumes in open channel turbulence in made, where the buoyancy is due to both salinity and heat. The measured parameters are the downstream derivative of a plume width and height, which are integral-characteristics of the distributions of density......-differences. Other methods as infra-red sensing are used for visualizing purpose. The results are used to calibrate an integral model of the dispersion. Conclusions are that the dispersion of a buoyant surface plume can be treated the superposition of a buoyancy induced stretching and turbulent diffusion, reduced...

  16. Lorentz Dispersion Law from classical Hydrogen electron orbits in AC electric field via geometric algebra

    CERN Document Server

    Perez, Uzziel; Sugon, Quirino M; McNamara, Daniel J; Yoshikawa, Akimasa

    2015-01-01

    We studied the orbit of an electron revolving around an infinitely massive nucleus of a large classical Hydrogen atom subject to an AC electric field oscillating perpendicular to the electron's circular orbit. Using perturbation theory in geometric algebra, we show that the equation of motion of the electron perpendicular to the unperturbed orbital plane satisfies a forced simple harmonic oscillator equation found in Lorentz dispersion law in Optics. We show that even though we did not introduce a damping term, the initial orbital position and velocity of the electron results to a solution whose absorbed energies are finite at the dominant resonant frequency $\\omega=\\omega_0$; the electron slowly increases its amplitude of oscillation until it becomes ionized. We computed the average power absorbed by the electron both at the perturbing frequency and at the electron's orbital frequency. We graphed the trace of the angular momentum vector at different frequencies. We showed that at different perturbing frequen...

  17. Field induced spontaneous quasiparticle decay and renormalization of quasiparticle dispersion in a quantum antiferromagnet.

    Science.gov (United States)

    Hong, Tao; Qiu, Y; Matsumoto, M; Tennant, D A; Coester, K; Schmidt, K P; Awwadi, F F; Turnbull, M M; Agrawal, H; Chernyshev, A L

    2017-05-05

    The notion of a quasiparticle, such as a phonon, a roton or a magnon, is used in modern condensed matter physics to describe an elementary collective excitation. The intrinsic zero-temperature magnon damping in quantum spin systems can be driven by the interaction of the one-magnon states and multi-magnon continuum. However, detailed experimental studies on this quantum many-body effect induced by an applied magnetic field are rare. Here we present a high-resolution neutron scattering study in high fields on an S=1/2 antiferromagnet C9H18N2CuBr4. Compared with the non-interacting linear spin-wave theory, our results demonstrate a variety of phenomena including field-induced renormalization of one-magnon dispersion, spontaneous magnon decay observed via intrinsic linewidth broadening, unusual non-Lorentzian two-peak structure in the excitation spectra and a dramatic shift of spectral weight from one-magnon state to the two-magnon continuum.

  18. Lamb wave Shearwave dispersion ultrasound Vibrometry (SDUV) validation study.

    Science.gov (United States)

    Nenadic, Ivan; Urban, Matthew W; Mitchell, Scott A; Greenleaf, James F

    2010-01-01

    Our group has been investigating the use of Shearwave Dispersion Ultrasound Vibrometry (SDUV) for quantifying viscoelasticity of the myocardium. The primary aim of this study is the design and testing of viscoelastic materials suitable for validation of the Lamb wave model in the heart. The Lamb wave SDUV method was used to measure shear wave velocity dispersion of gelatin and urethane rubber plates in the range 40-500 Hz and estimate the material properties. A finite element model (FEM) of a viscoelastic plate submerged in water was used to study the appropriateness of the Lamb wave dispersion equations. An embedded sphere method was used as an independent measurement of viscoelasticity. The FEM wave velocity dispersion data were in excellent agreement with the theoretical predictions. Elasticity and viscosity of urethane and gelatin obtained using the Lamb wave SDUV and embedded sphere methods agree within one standard deviation.

  19. Dispersion of helically corrugated waveguides: Analytical, numerical, and experimental study

    Science.gov (United States)

    Burt, G.; Samsonov, S. V.; Ronald, K.; Denisov, G. G.; Young, A. R.; Bratman, V. L.; Phelps, A. D.; Cross, A. W.; Konoplev, I. V.; He, W.; Thomson, J.; Whyte, C. G.

    2004-10-01

    Helically corrugated waveguides have recently been studied for use in various applications such as interaction regions in gyrotron traveling-wave tubes and gyrotron backward-wave oscillators and as a dispersive medium for passive microwave pulse compression. The paper presents a summary of various methods that can be used for analysis of the wave dispersion of such waveguides. The results obtained from an analytical approach, simulations with the three-dimensional numerical code MAGIC, and cold microwave measurements are analyzed and compared.

  20. Wind dispersal of alien plant species into remnant natural vegetation from adjacent agricultural fields

    Directory of Open Access Journals (Sweden)

    Chika Egawa

    2017-07-01

    Full Text Available Knowledge regarding the seed dispersal of alien species is crucial to manage invasion risk in fragmented natural habitats. Focusing on wind dispersal, this study assessed the spatial and quantitative extents to which a remnant natural fen receives the seeds of alien species dispersed from adjacent hay meadows in Hokkaido, northern Japan. I established a total of 80 funnel seed traps in the fen at distances of 1, 2, 5, 10, 20, 30, 50, and 100 m from the meadows. The proportion of alien species in the seed rain at each distance was quantified, and the 99th-percentile dispersal distance from the meadows was estimated for each alien species by constructing dispersal kernels. Despite the presence of a marginal ditch and an elevational difference between the fen and the meadows, five alien species, including four grasses that do not have modified seed structures for wind dispersal, dispersed their seeds into the fen. These alien species accounted for up to 65.9% of the seed rain in terms of quantity. The 99th-percentile dispersal distances of the alien species ranged from 3.8 m to 309.3 m, and these distances were longer than the values predicted on the basis of their functional traits, such as terminal velocity. The results of this study demonstrated that numerous seeds of farmland-derived alien species were transported into the remnant vegetation via wind dispersal, and that simple predictions of dispersal distance based on functional traits could underestimate the potential area that alien species can reach. Continuous management both in farmland (to reduce seed escape and in remnant vegetation (to prevent the establishment of alien species is necessary to protect native vegetation from biological invasion in agricultural landscapes.

  1. "Cold" dispersion relation of corrugated waveguide filled with plasma immersed in a finite magnetic field

    Institute of Scientific and Technical Information of China (English)

    李伟; 魏彦玉; 谢鸿全; 刘盛纲; 巩马理

    2003-01-01

    A general dispersion equation of a partially filled plasma corrugated waveguide immersed in a finite magnetic field is presented. When the guiding magnet Bo →∞ or 0, this equation can be reduced to the results obtained in previous works.

  2. Carrier field shock formation of long wavelength femtosecond pulses in dispersive media

    CERN Document Server

    Panagiotopoulos, Paris; Kolesik, Miroslav; Moloney, Jerome V

    2015-01-01

    We numerically demonstrate the formation of carrier field shocks in various dispersive media for a wide variety of input conditions using two different electric field propagation models. In addition, an investigation of the impact of numerous physical effects on carrier wave shock is performed. It is shown that in many cases a field shock is essentially unavoidable and therefore extremely important in the propagation of intense long wavelength pulses in weakly dispersive nonlinear media such as noble gases, air, and single-crystal diamond. The results presented here are expected to have a significant impact in the field of ultrashort nonlinear optics, attosecond pulse generation, and wavepacket synthesis where the use of mid-IR wavelengths is becoming increasingly more important.

  3. Dispersion relations and entropy of scalar fields in Rindler and de Sitter spaces

    CERN Document Server

    Lenz, F; Yazaki, K

    2014-01-01

    Properties of scalar fields in Rindler and de Sitter spaces are the subject of this work. Using the "brick wall model'' the dispersion relations are determined and the remarkable properties common to both spaces as well as their differences are discussed. Equipped with these tools the horizon induced thermodynamics is revisited and shown to be dominated by a single mode propagating perpendicular to the horizon. Explicit expressions for the partition function, entropy and heat capacity for massless and massive fields are presented.

  4. Near-field heat transfer between graphene monolayers: Dispersion relation and parametric analysis

    Science.gov (United States)

    Yin, Ge; Yang, Jiang; Ma, Yungui

    2016-12-01

    Plasmon polaritons in graphene can enhance near-field heat transfer. In this work, we give a complete parametric analysis on the near-field heat transfer between two graphene monolayers that allows transfer efficiencies several orders-of-magnitude larger than blackbody radiation. Influences of major parameters are conclusively clarified from the changes of the interlayer supermode coupling and their dispersion relations. The method to maximize the near-field heat flux is discussed. The generalized Stefan-Boltzmann formula is proposed to describe the near-field heat transfer dominated by evanescent wave tunneling. Our results are of practical significance in guiding the design of thermal management systems.

  5. Influence of Complete Coriolis Force on the Dispersion Relation of Ocean Internal-wave in a Background Currents Field

    Directory of Open Access Journals (Sweden)

    Liu Yongjun

    2015-01-01

    Full Text Available In this thesis, the influence of complete Coriolis force (the model includes both the vertical and horizontal components of Coriolis force on the dispersion relation of ocean internal-wave under background currents field are studied, it is important to the study of ocean internal waves in density-stratified ocean. We start from the control equation of sea water movement in the background of the non-traditional approximation, and the vertical velocity solution is derived where buoyancy frequency N(z gradually varies with the ocean depth z. The results show that the influence of complete Coriolis force on the dispersion relation of ocean internal-wave under background currents field is obvious, and these results provide strong evidence for the understanding of dynamic process of density stratified ocean internal waves.

  6. Dispersion Forces

    CERN Document Server

    Buhmann, Stefan Yoshi

    2012-01-01

    In this book, a modern unified theory of dispersion forces on atoms and bodies is presented which covers a broad range of advanced aspects and scenarios. Macroscopic quantum electrodynamics is shown to provide a powerful framework for dispersion forces which allows for discussing general properties like their non-additivity and the relation between microscopic and macroscopic interactions. It is demonstrated how the general results can be used to obtain dispersion forces on atoms in the presence of bodies of various shapes and materials. Starting with a brief recapitulation of volume I, this volume II deals especially with bodies of irregular shapes, universal scaling laws, dynamical forces on excited atoms, enhanced forces in cavity quantum electrodynamics, non-equilibrium forces in thermal environments and quantum friction. The book gives both the specialist and those new to the field a thorough overview over recent results in the field. It provides a toolbox for studying dispersion forces in various contex...

  7. Prime focus wide-field corrector designs with lossless atmospheric dispersion correction

    Energy Technology Data Exchange (ETDEWEB)

    Saunders, Will [Australian Astron. Observ.; Gillingham, Peter [Australian Astron. Observ.; Smith, Greg [Australian Astron. Observ.; Kent, Steve [Fermilab; Doel, Peter [University Coll. London

    2014-07-18

    Wide-Field Corrector designs are presented for the Blanco and Mayall telescopes, the CFHT and the AAT. The designs are Terezibh-style, with 5 or 6 lenses, and modest negative optical power. They have 2.2-3 degree fields of view, with curved and telecentric focal surfaces suitable for fiber spectroscopy. Some variants also allow wide-field imaging, by changing the last WFC element. Apart from the adaptation of the Terebizh design for spectroscopy, the key feature is a new concept for a 'Compensating Lateral Atmospheric Dispersion Corrector', with two of the lenses being movable laterally by small amounts. This provides excellent atmospheric dispersion correction, without any additional surfaces or absorption. A novel and simple mechanism for providing the required lens motions is proposed, which requires just 3 linear actuators for each of the two moving lenses.

  8. Approach for fast numerical propagation of uniformly polarized random electromagnetic fields in dispersive linearly birefringent systems.

    Science.gov (United States)

    Makowski, Piotr L; Domanski, Andrzej W

    2013-09-01

    An efficient simulation technique is proposed for computing propagation of uniformly polarized statistically stationary fields in linear nonimage-forming systems that includes dispersion of linear birefringence to all orders. The method is based on the discrete-time Fourier transformation of modified frequency profiles of the spectral Stokes parameters. It works under the condition that all (linearly) birefringent sections present in the system are described by the same phase birefringence dispersion curve, being a monotonic function of the optical frequency within the bandwidth of the light. We demonstrate the technique as a supplement for the Mueller-Stokes matrix formalism extended to any uniformly polarized polychromatic illumination. Accuracy of its numerical implementation has been verified by using parameters of a Lyot depolarizer made of a highly birefringent and dispersive monomode photonic crystal fiber.

  9. Weight loss and P wave dispersion: a preliminary study.

    Science.gov (United States)

    Falchi, Anna Giulia; Grecchi, Ilaria; Muggia, Chiara; Tinelli, Carmine

    2014-01-01

    The aim of this study is to investigate if therapeutic weight loss reduces P wave dispersion. 20 obese patients (10 males and 10 females), part of a randomized clinical trial, were examined over a 6 month period. They were treated with a diet, aiming at 5% weight loss at the 6th month. After physical examination, they underwent laboratory tests, bioelectrical impedance analysis and a electrocardiogram (ECG). ECGs were transferred to a personal computer via a scanner and then magnified 400 times. We examined at baseline and at the 6th month, maximum and minimum P-wave duration, P-wave dispersion and heart rate. Comparing responders (patients who lost 5% of weight at t6) and not responders (who lost less than 5%), responders showed a significant reduction of P wave dispersion value (-0.38 [SD: 0.35] mm equal to -32.3 [SD: 11.3] % p=0.00001). All responders present a reduction of P wave dispersion, while for not-responders this is no longer evident. Finally, a good degree of correlation (r=0.54) between P wave dispersion difference and the decrease of weight was noticed. Females have a better response in P dispersion reduction strictly connected with their weight loss with a good correlation, (r=0.7, p=0.002), versus a moderate correlation evidenced in males (r=0.5, p=0.011). P wave duration and dispersion are significantly reduced in patients who lost more than 5% of weight and this decrease is highly related to the extent of weight loss. Copyright © 2014 Asian Oceanian Association for the Study of Obesity. Published by Elsevier Ltd. All rights reserved.

  10. [Lessons from Field Studies].

    Science.gov (United States)

    Yoshimura, Takesumi

    2015-01-01

    During my academic career for more than 40 years, I was involved in 18 epidemiological field studies, partially or fully. Among these field studies, four (1. Medical services in remote rural areas in Okinawa, 2. Yusho episode, 3. JICA Onchocerciasis Control Project in Guatemala, and 4. Miyako cohort study in Fukuoka) are introduced in this paper, including the latest situation after the presentation. Through these field works experienced by the author, the following lessons were gained. 1. Strong human reliance between researchers and the targeted population is essential in carrying out epidemiological surveys successfully in the field. 2. Data obtained from the survey should be carefully examined and analyzed so that those data may reflect the real situation.

  11. General motors sulfate dispersion experiment: an overview of the wind, temperature, and concentration fields

    Energy Technology Data Exchange (ETDEWEB)

    Chock, D.P.

    1977-01-01

    A major purpose of the General Motors Sulfate Dispersion Experiment was to study the influence of traffic on the dispersion of pollutants near the roadway. It was found that when the crossroad wind component was low there was upwind dispersion within a few meters of the road. This dispersion was further enhanced when a component of the wind was opposing the traffic in the upwind lanes. The vertical velocity fluctuation (sigma/sub w/) was generally higher in the downwind region than in the upwind region of the road, especially at low wind speeds. Thus, mechanical mixing due to the traffic contributed significantly to the vertical expansion of the plume. Waste heat generated from the traffic also resulted in plume rise near the roadway. Due to the relatively long time scale associated with the buoyancy effect, appreciable plume rise was observed mainly at very low crossroad winds. The implications of the experiment on the Gaussian model are discussed.

  12. Who dispersed the seeds? The use of DNA barcoding in frugivory and seed dispersal studies

    National Research Council Canada - National Science Library

    González‐Varo, Juan P; Arroyo, Juan M; Jordano, Pedro; Gilbert, M

    2014-01-01

    ... ‘which species dispersed the seeds’. This is essential for assessing how multiple frugivore species contribute distinctly to critical dispersal events such as seed delivery to safe sites, long...

  13. Stability studies of colloidal silica dispersions in binary solvent mixtures

    CERN Document Server

    Bean, K H

    1997-01-01

    A series of monodispersed colloidal silica dispersions, of varying radii, has been prepared. These particles are hydrophilic in nature due to the presence of surface silanol groups. Some of the particles have been rendered hydrophobic by terminally grafting n-alkyl (C sub 1 sub 8) chains to the surface. The stability of dispersions of these various particles has been studied in binary mixtures of liquids, namely (i) ethanol and cyclohexane, and (ii) benzene and n-heptane. The ethanol - cyclohexane systems have been studied using a variety of techniques. Adsorption excess isotherms have been established and electrophoretic mobility measurements have been made. The predicted stability of the dispersions from D.V.L.O. calculations is compared to the observed stability. The hydrophilic silica particles behave as predicted by the calculations, with the zeta potential decreasing and the van der Waals attraction increasing with increasing cyclohexane concentration. The hydrophobic particles behave differently than e...

  14. Who dispersed the seeds? The use of DNA barcoding in frugivory and seed dispersal studies

    OpenAIRE

    González-Varo, Juan P.; J.M. Arroyo; Jordano, Pedro

    2014-01-01

    Assessing dispersal events in plants faces important challenges and limitations. A methodological issue that limits advances in our understanding of seed dissemination by frugivorous animals is identifying 'which species dispersed the seeds'. This is essential for assessing how multiple frugivore species contribute distinctly to critical dispersal events such as seed delivery to safe sites, long-distance dispersal and the colonization of non-occupied habitats. Here, we describe DNA-barcoding ...

  15. Electro-optical determination of the constant electric dipole of disperse particles by the method of crossed electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Voitylov, V.V.; Spartakov, A.A.; Tolstoi, N.A.; Trusov, A.A.; Boitsova, I.N. [St. Petersburg State Univ. (Russian Federation)

    1995-04-01

    An electro-optical method of crossed electric fields is proposed for determining constant dipole colloidal particles moments of colloidal particles. Fields of this type make it possible to study the motion of colloidal particles determined exclusively by their constant moments, which substantially improves the measurement accuracy of these moments. This is of particular importance for the investigation of colloidal particles with constant dipole moments less than or comparable to induced dipole moments. For a number of disperse systems, the constant dipole moments per unit area of particles are determined. It is shown that the values of these specific moments are close to each other.

  16. Faraday rotation dispersion microscopy imaging of diamagnetic and chiral liquids with pulsed magnetic field.

    Science.gov (United States)

    Suwa, Masayori; Nakano, Yusuke; Tsukahara, Satoshi; Watarai, Hitoshi

    2013-05-21

    We have constructed an experimental setup for Faraday rotation dispersion imaging and demonstrated the performance of a novel imaging principle. By using a pulsed magnetic field and a polarized light synchronized to the magnetic field, quantitative Faraday rotation images of diamagnetic organic liquids in glass capillaries were observed. Nonaromatic hydrocarbons, benzene derivatives, and naphthalene derivatives were clearly distinguished by the Faraday rotation images due to the difference in Verdet constants. From the wavelength dispersion of the Faraday rotation images in the visible region, it was found that the resonance wavelength in the UV region, which was estimated based on the Faraday B-term, could be used as characteristic parameters for the imaging of the liquids. Furthermore, simultaneous acquisition of Faraday rotation image and natural optical rotation image was demonstrated for chiral organic liquids.

  17. Direct analysis of dispersive wave fields from near-field pressure measurements

    NARCIS (Netherlands)

    Horchens, L.

    2011-01-01

    Flexural waves play a significant role for the radiation of sound from plates. The analysis of flexural wave fields enables the detection of sources and transmission paths in plate-like structures. The measurement of these wave fields can be carried out indirectly by means of near-field acoustic hol

  18. Role of high-order dispersion on strong-field laser-molecule interactions

    Science.gov (United States)

    Dantus, Marcos; Nairat, Muath

    2016-05-01

    Strong-field (1012- 1016 W/ cm2) laser-matter interactions are characterized by the extent of fragmentation and charge of the resulting ions as a function of peak intensity and pulse duration. Interactions are influenced by high-order dispersion, which is difficult to characterize and compress. Fourth-order dispersion (FOD) causes a time-symmetric pedestal, while third-order dispersion (TOD) causes a leading (negative) or following (positive) pedestal. Here, we report on strong-field interactions with pentane and toluene molecules, tracking the molecular ion and the doubly charged carbon ion C2+ yields as a function of TOD and FOD for otherwise transform-limited (TL) 35fs pulses. We find TL pulses enhance molecular ion yield and suppress C2+ yield, while FOD reverses this trend. Interestingly, the leading pedestal in negative TOD enhances C2+ yield compared to positive TOD. Pulse pedestals are of particular importance in strong-field science because target ionization or alignment can be induced well before the main pulse arrives. A pedestal following an intense laser pulse can cause sequential ionization or accelerate electrons causing cascaded ionization. Control of high-order dispersion allows us to provide strong-field measurements that can help address the mechanisms responsible for different product ions in the presence and absence of pedestals. Financial support of this work comes from the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, DOE SISGR (DE-SC0002325)

  19. Theoretic Study on Dispersion Mechanism of Boron Nitride Nanotubes by Polynucleotides

    Science.gov (United States)

    Liang, Lijun; Hu, Wei; Zhang, Zhisen; Shen, Jia-Wei

    2016-12-01

    Due to the unique electrical and mechanical properties of boron nitride nanotubes (BNNT), BNNT has been a promising material for many potential applications, especially in biomedical field. Understanding the dispersion of BNNT in aqueous solution by biomolecules is essential for its use in biomedical applications. In this study, BNNT wrapped by polynucleotides in aqueous solution was investigated by molecular dynamics (MD) simulations. Our results demonstrated that the BNNT wrapped by polynucleotides could greatly hinder the aggregation of BNNTs and improve the dispersion of BNNTs in aqueous solution. Dispersion of BNNTs with the assistance of polynucleotides is greatly affected by the wrapping manner of polynucleotides on BNNT, which mainly depends on two factors: the type of polynucleotides and the radius of BNNT. The interaction between polynucleotides and BNNT(9, 9) is larger than that between polynucleotides and BNNT(5, 5), which leads to the fact that dispersion of BNNT(9, 9) is better than that of BNNT(5, 5) with the assistance of polynucleotides in aqueous solution. Our study revealed the molecular-level dispersion mechanism of BNNT with the assistance of polynucleotides in aqueous solution. It shades a light on the understanding of dispersion of single wall nanotubes by biomolecules.

  20. Dispersion equations for field-aligned cyclotron waves in axisymmetric magnetospheric plasmas

    Directory of Open Access Journals (Sweden)

    N. I. Grishanov

    2006-03-01

    Full Text Available In this paper, we derive the dispersion equations for field-aligned cyclotron waves in two-dimensional (2-D magnetospheric plasmas with anisotropic temperature. Two magnetic field configurations are considered with dipole and circular magnetic field lines. The main contribution of the trapped particles to the transverse dielectric permittivity is estimated by solving the linearized Vlasov equation for their perturbed distribution functions, accounting for the cyclotron and bounce resonances, neglecting the drift effects, and assuming the weak connection of the left-hand and right-hand polarized waves. Both the bi-Maxwellian and bi-Lorentzian distribution functions are considered to model the ring current ions and electrons in the dipole magnetosphere. A numerical code has been developed to analyze the dispersion characteristics of electromagnetic ion-cyclotron waves in an electron-proton magnetospheric plasma with circular magnetic field lines, assuming that the steady-state distribution function of the energetic protons is bi-Maxwellian. As in the uniform magnetic field case, the growth rate of the proton-cyclotron instability (PCI in the 2-D magnetospheric plasmas is defined by the contribution of the energetic ions/protons to the imaginary part of the transverse permittivity elements. We demonstrate that the PCI growth rate in the 2-D axisymmetric plasmasphere can be significantly smaller than that for the straight magnetic field case with the same macroscopic bulk parameters.

  1. Magnetic field effects on nonlocal wave dispersion characteristics of size-dependent nanobeams

    Science.gov (United States)

    Ebrahimi, Farzad; Barati, Mohammad Reza

    2017-01-01

    In this paper, wave propagation analysis of functionally graded size-dependent nanobeams embedded in elastic foundation exposed to a longitudinal magnetic field is conducted based on nonlocal elasticity theory. Material properties of nanobeam change gradually according to the sigmoid function. Applying an analytical solution, the acoustical and optical dispersion relations are explored for various wave number, nonlocality parameter, material composition, elastic foundation constants and magnetic field intensity. It is found that frequency and phase velocity of waves propagating in S-FGM nanobeam are significantly affected by these parameters. Also the presence of cutoff and escape frequencies in wave propagation analysis of embedded S-FGM nanobeams is investigated.

  2. Estimating urban roadside emissions with an atmospheric dispersion model based on in-field measurements.

    Science.gov (United States)

    Pu, Yichao; Yang, Chao

    2014-09-01

    Urban vehicle emission models have been utilized to calculate pollutant concentrations at both microscopic and macroscopic levels based on vehicle emission rates which few researches have been able to validate. The objective of our research is to estimate urban roadside emissions and calibrate it with in-field measurement data. We calculated the vehicle emissions based on localized emission rates, and used an atmospheric dispersion model to estimate roadside emissions. A non-linear regression model was applied to calibrate the localized emission rates using in-field measurement data. With the calibrated emission rates, emissions on urban roadside can be estimated with a high accuracy.

  3. Scattering matrix simulations of fields and dispersion relations in superconducting cavities for XFEL and ILC

    CERN Document Server

    Shinton, I

    2008-01-01

    The globalised cascaded scattering matrix technique is a well proven, practical method that can be used to simulate large accelerating RF structures in which realistic fabrication errors to be incorporated in an efficient manner without the necessity to re-mesh the entire geometry. The globalised scattering matrix (GMS) technique allows one to obtain the scattering matrix for a structure. The method allows rapid e.m. field calculations to be obtained. Results are presented on monopole mode fields and dispersion relations calculated from direct and analytical methods. Analytical approximate results are also presented for the equivalent shunt susceptance of an iris loaded structure.

  4. Study of dispersion forces with quantum Monte Carlo: toward a continuum model for solvation.

    Science.gov (United States)

    Amovilli, Claudio; Floris, Franca Maria

    2015-05-28

    We present a general method to compute dispersion interaction energy that, starting from London's interpretation, is based on the measure of the electronic electric field fluctuations, evaluated on electronic sampled configurations generated by quantum Monte Carlo. A damped electric field was considered in order to avoid divergence in the variance. Dispersion atom-atom C6 van der Waals coefficients were computed by coupling electric field fluctuations with static dipole polarizabilities. The dipole polarizability was evaluated at the diffusion Monte Carlo level by studying the response of the system to a constant external electric field. We extended the method to the calculation of the dispersion contribution to the free energy of solvation in the framework of the polarizable continuum model. We performed test calculations on pairs of some atomic systems. We considered He in ground and low lying excited states and Ne in the ground state and obtained a good agreement with literature data. We also made calculations on He, Ne, and F(-) in water as the solvent. Resulting dispersion contribution to the free energy of solvation shows the reliability of the method illustrated here.

  5. Are introduced species better dispersers than native species? A global comparative study of seed dispersal distance.

    Science.gov (United States)

    Flores-Moreno, Habacuc; Thomson, Fiona J; Warton, David I; Moles, Angela T

    2013-01-01

    We provide the first global test of the idea that introduced species have greater seed dispersal distances than do native species, using data for 51 introduced and 360 native species from the global literature. Counter to our expectations, there was no significant difference in mean or maximum dispersal distance between introduced and native species. Next, we asked whether differences in dispersal distance might have been obscured by differences in seed mass, plant height and dispersal syndrome, all traits that affect dispersal distance and which can differ between native and introduced species. When we included all three variables in the model, there was no clear difference in dispersal distance between introduced and native species. These results remained consistent when we performed analyses including a random effect for site. Analyses also showed that the lack of a significant difference in dispersal distance was not due to differences in biome, taxonomic composition, growth form, nitrogen fixation, our inclusion of non-invasive introduced species, or our exclusion of species with human-assisted dispersal. Thus, if introduced species do have higher spread rates, it seems likely that these are driven by differences in post-dispersal processes such as germination, seedling survival, and survival to reproduction.

  6. Effect of magnetic field on the wave dispersion relation in three-dimensional dusty plasma crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yang Xuefeng [School of Mathematical Sciences, Dalian University of Technology, Dalian 116024 (China); Wang Zhengxiong [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)

    2012-07-15

    Three-dimensional plasma crystals under microgravity condition are investigated by taking into account an external magnetic field. The wave dispersion relations of dust lattice modes in the body centered cubic (bcc) and the face centered cubic (fcc) plasma crystals are obtained explicitly when the magnetic field is perpendicular to the wave motion. The wave dispersion relations of dust lattice modes in the bcc and fcc plasma crystals are calculated numerically when the magnetic field is in an arbitrary direction. The numerical results show that one longitudinal mode and two transverse modes are coupled due to the Lorentz force in the magnetic field. Moreover, three wave modes, i.e., the high frequency phonon mode, the low frequency phonon mode, and the optical mode, are obtained. The optical mode and at least one phonon mode are hybrid modes. When the magnetic field is neither parallel nor perpendicular to the primitive wave motion, all the three wave modes are hybrid modes and do not have any intersection points. It is also found that with increasing the magnetic field strength, the frequency of the optical mode increases and has a cutoff at the cyclotron frequency of the dust particles in the limit of long wavelength, and the mode mixings for both the optical mode and the high frequency phonon mode increase. The acoustic velocity of the low frequency phonon mode is zero. In addition, the acoustic velocity of the high frequency phonon mode depends on the angle of the magnetic field and the wave motion but does not depend on the magnetic field strength.

  7. Simulation of plume dispersion of multiple releases in Fusion Field Trial-07 experiment

    Science.gov (United States)

    Pandey, Gavendra; Sharan, Maithili

    2015-12-01

    For an efficient source term estimation, it is important to use an accurate dispersion model with appropriate dispersion parameters. This is examined by simulating the dispersion of plumes resulted from the available multiple releases conducted at Fusion Field Trials, Dugway Proving Ground, Utah. The simulation is carried out with an earlier developed IIT (Indian Institute of Technology) dispersion model using the dispersion parameters in terms of measurements of turbulent velocity fluctuations. Simulation is discussed separately in both stable and unstable conditions in light of (i) plume behavior of observed and predicted concentrations in the form of isopleths, (ii) peak/maximum concentrations and (iii) overall concentration distribution. Simulated results from IIT model are compared with those obtained using AERMOD. Both, IIT model and AERMOD, predicted peak concentrations within a factor of two in all the releases and tracer transport is mostly along the mean wind direction. With IIT model, the higher concentrations are predicted close to observations in all the trials of stable conditions and with in a factor of two in the trials of unstable conditions. However, the relatively smaller concentrations are under-predicted severely in stable conditions and over-predicted in unstable conditions. The AERMOD exhibits the similar prediction of concentrations as in IIT model except slightly over-prediction in stable conditions and under-prediction in unstable conditions. The statistical measures for both the models are found good in agreement with the observations and a quantitative analysis based on F-test shows that the performance from both the models are found to be similar at 5% significance level.

  8. Reconsidering the effects of tannin on seed dispersal by rodents: evidence from enclosure and field experiments with artificial seeds.

    Science.gov (United States)

    Zhang, Mingming; Steele, Michael A; Yi, Xianfeng

    2013-11-01

    The question of how tannin affects feeding and hoarding preferences of rodents still remains poorly understood, in part, because it is difficult to control for other seed traits when considering the sole effect of tannin. Here, we constructed a series of artificial 'seeds' with different tannin levels, made from wheat flour, peanut powder and hydrolysable tannins, to determine the direct effects of tannin on both feeding and hoarding preferences. We first presented 'seeds' to individual rodents of two species (Tamias sibiricus and Apodemus peninsulae) confined in semi-natural enclosures and then monitored patterns of seed dispersal and consumption by free-ranging animals in a temperate forest in the Xiaoxing'an Mountains, Heilongjiang Province of China. Our results showed that small rodents displayed a significant preference for low-tannin 'seeds' for both consumption and caching in both captive and field experiments. Moreover, our two-year study consistently showed that tannin concentration was significantly and negatively correlated with the number of cached 'seeds' at both the individual and population levels. Seed size, compared with tannin concentrations, appeared to have little effect on dispersal distances and the number of 'seeds' cached. Low-tannin 'seeds' tended to be dispersed greater distances by rodents in the field than those with higher levels of tannin. These results failed to support those of previous reports indicating that acorns containing higher tannins are more likely to be cached by food hoarding animals.

  9. Microbial field pilot study

    Energy Technology Data Exchange (ETDEWEB)

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Coates, J.D.; Chisholm, J.L.

    1993-05-01

    A multi-well microbially enhanced oil recovery field pilot has been performed in the Southeast Vassar Vertz Sand Unit in Payne County, Oklahoma. The primary emphasis of the experiment was preferential plugging of high permeability zones for the purpose of improving waterflood sweep efficiency. Studies were performed to determine reservoir chemistry, ecology, and indigenous bacteria populations. Growth experiments were used to select a nutrient system compatible with the reservoir that encouraged growth of a group of indigenous nitrate-using bacteria and inhibit growth of sulfate-reducing bacteria. A specific field pilot area behind an active line drive waterflood was selected. Surface facilities were designed and installed. Injection protocols of bulk nutrient materials were prepared to facilitate uniform distribution of nutrients within the pilot area. By the end of December, 1991, 82.5 tons (75.0 tonnes) of nutrients had been injected in the field. A tracer test identified significant heterogeneity in the SEVVSU and made it necessary to monitor additional production wells in the field. The tracer tests and changes in production behavior indicate the additional production wells monitored during the field trial were also affected. Eighty two and one half barrels (13.1 m[sup 3]) of tertiary oil have been recovered. Microbial activity has increased CO[sub 2] content as indicated by increased alkalinity. A temporary rise in sulfide concentration was experienced. These indicate an active microbial community was generated in the field by the nutrient injection. Pilot area interwell pressure interference test results showed that significant permeability reduction occurred. The interwell permeabilities in the pilot area between the injector and the three pilot production wells were made more uniform which indicates a successful preferential plugging enhanced oil recovery project.

  10. Controlling dispersion forces between small particles with artificially created random light fields

    CERN Document Server

    Bruegger, Georges; Scheffold, Frank; Saenz, Juan Jose

    2015-01-01

    Appropriate combinations of laser beams can be used to trap and manipulate small particles with "optical tweezers" as well as to induce significant "optical binding" forces between particles. These interaction forces are usually strongly anisotropic depending on the interference landscape of the external fields. This is in contrast with the familiar isotropic, translationally invariant, van der Waals and, in general, Casimir-Lifshitz interactions between neutral bodies arising from random electromagnetic waves generated by equilibrium quantum and thermal fluctuations. Here we show, both theoretically and experimentally, that dispersion forces between small colloidal particles can also be induced and controlled using artificially created fluctuating light fields. Using optical tweezers as gauge, we present experimental evidence for the predicted isotropic attractive interactions between dielectric microspheres induced by laser-generated, random light fields. These light induced interactions open a path towards...

  11. Operational Generation of Urban Wind Fields to Support Transport and Dispersion Modeling

    Science.gov (United States)

    Copeland, J. H.; Sheu, R.; Brown, M. J.

    2007-12-01

    A realistic wind field is a key component to any transport and dispersion model simulation. In the urban environment observing the wind field accurately is complicated by the presence of the building structures themselves. In situ measurements are only representative over a limited area near the point of observation due to the influence of nearby buildings. Winds observed remotely, via radar or lidar, have good spatial resolution, but are limited to making measurements above rooftop. The Urban Shield project is an emergency response system for hazardous atmospheric releases in Arlington County Virginia. To provide building aware wind fields over a 100 square kilometer area for transport and dispersion modeling we use a combined approach of remotely sensed wind observations and very high resolution, ~10 meters, diagnostic wind modeling. In brief, the system uses 3-D wind analyses from Doppler radar and lidar as input to Los Alamos National Laboratory's QUIC-Urb empirical wind model. An overview of the system and results will be presented.

  12. Curcumin containing monoolein aqueous dispersions: A preformulative study

    Energy Technology Data Exchange (ETDEWEB)

    Esposito, Elisabetta, E-mail: ese@unife.it [Department of Life Sciences and Biotechnology, University of Ferrara, I-44121 Ferrara (Italy); Ravani, Laura [Department of Life Sciences and Biotechnology, University of Ferrara, I-44121 Ferrara (Italy); Mariani, Paolo [Department of Life and Environmental Sciences and CNISM, Università Politecnica delle Marche, I-60100 Ancona (Italy); Contado, Catia [Department of Chemistry, University of Ferrara, I-44121 Ferrara (Italy); Drechsler, Markus [Macromolecular Chemistry II, University of Bayreuth (Germany); Puglia, Carmelo [Department of Drug Sciences, University of Catania, I-95125 Catania (Italy); Cortesi, Rita [Department of Life Sciences and Biotechnology, University of Ferrara, I-44121 Ferrara (Italy)

    2013-12-01

    The present study describes the production and characterization of monoolein aqueous dispersions (MAD) as drug delivery systems for curcumin (CR). MAD based on monoolein and different emulsifiers have been produced and characterized. Morphology and dimensional distribution have been investigated by Cryogenic Transmission Electron Microscopy (cryo-TEM), X-ray and Photon Correlation Spectroscopy (PCS). Monoolein in different mixtures with sodium cholate, sodium caseinate, bentonite and poloxamer resulted in heterogeneous dispersions constituted of unilamellar vesicles, cubosomes and sponge type phases, depending on the employed components, as found by cryo-TEM and X-ray studies. CR was encapsulated with entrapment efficiencies depending on the MAD composition, particularly the highest was reached in the case of monoolein/poloxamer/sodium cholate mixture. The same mixture was able to maintain CR stability also after 6 months. CR release modalities were in vitro investigated in order to mimic a possible subcutaneous administration of MAD. It was found that MAD constituted of monoolein/poloxamer and monoolein/poloxamer/sodium cholate mixtures were able to sustain CR release. MAD viscous vehicles were produced by xanthan gum. CR percutaneous absorption has been studied in vitro using excised human skin membranes [stratum corneum epidermis (SCE)] mounted into Franz cells. It was found that fluxes (F{sub n}) of CR incorporated in MAD are influenced by the presence of monoolein based nanosystems. In particular xanthan gum based MAD better control CR diffusion from MAD. - Highlights: • Curcumin (CR) can be solubilized in monoolein aqueous dispersions (MAD). • Different emulsifiers result in different inner structures in the disperse phase. • Monoolein/poloxamer/sodium cholate mixture (MCP) results in the highest CR encapsulation. • MCP maintains CR stability for 6 months. • Xanthan gum based MAD better control CR fluxes with respect to plain gel and liquid MAD.

  13. Numerical simulations of LNG vapor dispersion in Brayton Fire Training Field tests with ANSYS CFX.

    Science.gov (United States)

    Qi, Ruifeng; Ng, Dedy; Cormier, Benjamin R; Mannan, M Sam

    2010-11-15

    Federal safety regulations require the use of validated consequence models to determine the vapor cloud dispersion exclusion zones for accidental liquefied natural gas (LNG) releases. One tool that is being developed in industry for exclusion zone determination and LNG vapor dispersion modeling is computational fluid dynamics (CFD). This paper uses the ANSYS CFX CFD code to model LNG vapor dispersion in the atmosphere. Discussed are important parameters that are essential inputs to the ANSYS CFX simulations, including the atmospheric conditions, LNG evaporation rate and pool area, turbulence in the source term, ground surface temperature and roughness height, and effects of obstacles. A sensitivity analysis was conducted to illustrate uncertainties in the simulation results arising from the mesh size and source term turbulence intensity. In addition, a set of medium-scale LNG spill tests were performed at the Brayton Fire Training Field to collect data for validating the ANSYS CFX prediction results. A comparison of test data with simulation results demonstrated that CFX was able to describe the dense gas behavior of LNG vapor cloud, and its prediction results of downwind gas concentrations close to ground level were in approximate agreement with the test data.

  14. Simulation of plume dispersion from single release in Fusion Field Trial-07 experiment

    Science.gov (United States)

    Singh, Sarvesh Kumar; Sharan, Maithili

    2013-12-01

    Accurate description of source-receptor relationship is required for an efficient source reconstruction. This is examined by simulating the dispersion of plumes resulted from the available ten trials of single releases conducted at Fusion Field Trials, Dugway Proving Ground, Utah. The simulation is addressed with an earlier developed IIT (Indian Institute of Technology) dispersion model using the dispersion parameters in terms of measurements of turbulent velocity fluctuations. Simulation is described separately in both stable and unstable conditions, characterizing the peak as well as overall observed concentration distribution. Simulated results are compared with those obtained using AERMOD. With IIT model, peak concentrations are predicted within a factor of two in all the trials. The higher concentrations (>5 × 10-4 g m-3) are well predicted in stable condition and under-predicted (within a factor of two) in unstable condition whereas relatively smaller concentrations (factor of six. The statistical measures for both the models are found well in agreement with the observations.

  15. Focus defect and dispersion mismatch in full-field optical coherence microscopy.

    Science.gov (United States)

    Dubois, Arnaud

    2017-03-20

    Full-field optical coherence microscopy (FFOCM) is an optical technique, based on low-coherence interference microscopy, for tomographic imaging of semi-transparent samples with micrometer-scale spatial resolution. The differences in refractive index between the sample and the immersion medium of the microscope objectives may degrade the FFOCM image quality because of focus defect and optical dispersion mismatch. These phenomena and their consequences are discussed in this theoretical paper. Experimental methods that have been implemented in FFOCM to minimize the adverse effects of these phenomena are summarized and compared.

  16. Microbial field pilot study

    Energy Technology Data Exchange (ETDEWEB)

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Chisholm, J.L.

    1992-03-01

    The objective of this project is to perform a microbial enhanced oil recovery field pilot in the Southeast Vassar Vertz Sand Unit (SEVVSU) in Payne County, Oklahoma. Indigenous, anaerobic, nitrate reducing bacteria will be stimulated to selectively plug flow paths which have been referentially swept by a prior waterflood. This will force future flood water to invade bypassed regions of the reservoir and increase sweep efficiency. This report covers progress made during the second year, January 1, 1990 to December 31, 1990, of the Microbial Field Pilot Study project. Information on reservoir ecology, surface facilities design, operation of the unit, core experiments, modeling of microbial processes, and reservoir characterization and simulation are presented in the report. To better understand the ecology of the target reservoir, additional analyses of the fluids which support bacteriological growth and the microbiology of the reservoir were performed. The results of the produced and injected water analysis show increasing sulfide concentrations with respect to time. In March of 1990 Mesa Limited Partnership sold their interest in the SEVVSU to Sullivan and Company. In April, Sullivan and Company assumed operation of the field. The facilities for the field operation of the pilot were refined and implementation was begun. Core flood experiments conducted during the last year were used to help define possible mechanisms involved in microbial enhanced oil recovery. The experiments were performed at SEVVSU temperature using fluids and inoculum from the unit. The model described in last year's report was further validated using results from a core flood experiment. The model was able to simulate the results of one of the core flood experiments with good quality.

  17. Microbial field pilot study

    Energy Technology Data Exchange (ETDEWEB)

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Chisholm, J.L.

    1992-03-01

    The objective of this project is to perform a microbial enhanced oil recovery field pilot in the Southeast Vassar Vertz Sand Unit (SEVVSU) in Payne County, Oklahoma. Indigenous, anaerobic, nitrate reducing bacteria will be stimulated to selectively plug flow paths which have been referentially swept by a prior waterflood. This will force future flood water to invade bypassed regions of the reservoir and increase sweep efficiency. This report covers progress made during the second year, January 1, 1990 to December 31, 1990, of the Microbial Field Pilot Study project. Information on reservoir ecology, surface facilities design, operation of the unit, core experiments, modeling of microbial processes, and reservoir characterization and simulation are presented in the report. To better understand the ecology of the target reservoir, additional analyses of the fluids which support bacteriological growth and the microbiology of the reservoir were performed. The results of the produced and injected water analysis show increasing sulfide concentrations with respect to time. In March of 1990 Mesa Limited Partnership sold their interest in the SEVVSU to Sullivan and Company. In April, Sullivan and Company assumed operation of the field. The facilities for the field operation of the pilot were refined and implementation was begun. Core flood experiments conducted during the last year were used to help define possible mechanisms involved in microbial enhanced oil recovery. The experiments were performed at SEVVSU temperature using fluids and inoculum from the unit. The model described in last year`s report was further validated using results from a core flood experiment. The model was able to simulate the results of one of the core flood experiments with good quality.

  18. STUDIES ON MELOXICAM SOLID DISPERSION INCORPORATED BUCCAL PATCHES

    Directory of Open Access Journals (Sweden)

    Mohammed Jafar

    2011-05-01

    Full Text Available Arthritis is one of the most common chronic diseases in the world. Life style effects of arthritis includes; Depression, Anxiety, Feelings of helplessness, Limitations on daily activities, Job limitations etc. Meloxicam, a non-steroidal anti-inflammatory drug is widely used in the treatment of rheumatoid arthritis, ankylosing spondulytis and osteoarthritis. It is also indicated for the management of dental pain, Post-traumatic and post-operative pain, inflammation and swelling. Recently it is considered as a potential drug for prevention and treatment of colorectal polyps. One of the major problems with this drug is its low solubility in biological fluids, which results into poor bioavailability and GI-Side effects after oral administration. The present work was aimed at overcoming these limitations of the drug. The first problem i.e. Poor solubility of meloxicam was overcome by solid dispersion technique and the same work was than published in a reputed online journal. The present study was the continuation of the published work, in this study buccal patches were prepared using varying percentage of carbopol 934p, HPMC (muco adhesive polymers and 50% W/W of propylene glycol (Plasticizer by solvent casting technique, using 32 factorial design. Prepared blank buccal patches were evaluated for various physical and mechanical parameters, patches which comply with reported results were selected for meloxicam and its solid dispersion incorporation. Meloxicam solid dispersion incorporated buccal patches were prepared and evaluated for drug content, in-vitro diffusion, in-vivo release of meloxicam in rabbits and stability study. All solid dispersion incorporated patches showed increased in-vitro drug release (i.e. between 94% to 99.98% over an extended period of 8hrs as compared to plain drug incorporated buccal patch. Whereas plain drug incorporated buccal patch showed only 31.22% in-vitro drug release in 8hrs. Release of meloxicam was slightly

  19. Relaxation dispersion NMR spectroscopy for the study of protein allostery.

    Science.gov (United States)

    Farber, Patrick J; Mittermaier, Anthony

    2015-06-01

    Allosteric transmission of information between distant sites in biological macromolecules often involves collective transitions between active and inactive conformations. Nuclear magnetic resonance (NMR) spectroscopy can yield detailed information on these dynamics. In particular, relaxation dispersion techniques provide structural, dynamic, and mechanistic information on conformational transitions occurring on the millisecond to microsecond timescales. In this review, we provide an overview of the theory and analysis of Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion NMR experiments and briefly describe their application to the study of allosteric dynamics in the homeodomain from the PBX transcription factor (PBX-HD). CPMG NMR data show that local folding (helix/coil) transitions in one part of PBX-HD help to communicate information between two distant binding sites. Furthermore, the combination of CPMG and other spin relaxation data show that this region can also undergo local misfolding, reminiscent of conformational ensemble models of allostery.

  20. Studies of Tracer Dispersion and Fluid Flow in Porous Media

    Energy Technology Data Exchange (ETDEWEB)

    Rage, T.

    1996-12-31

    This doctoral thesis explores the connection between the topology of a porous medium and its macroscopic transport properties and is based on computerized simulation. In porous media, both diffusion and convection contribute to the dispersion of a tracer and their combined effect is emphasized. The governing equations are solved numerically, using finite differences and Monte Carlo technique. The influence of finite Reynolds number on the outcome of echo-experiments is discussed. Comparing experiments and simulations it is found that nonlinear inertial forces lead to a visible deformation of a returned tracer at surprisingly small Reynolds numbers. In a study of tracer dispersion and fluid flow in periodic arrays of discs it is demonstrated that the mechanisms of mechanical dispersion in periodic media and in natural (non-periodic) porous media are essentially different. Measurements of the percolation probability distribution of a sandstone sample is presented. Local porosity theory predicts that this simple geometric function of a porous medium is of dominant importance for its macroscopic transport properties. It is demonstrated that many aspects of transport through fractures can be studied by using simple but realistic models and readily available computer resources. An example may be the transport of hydrocarbon fluids from the source rock to a reservoir. 165 refs., 44 figs., 1 table

  1. ELECTROHYDRODYNAMIC DISPERSION OF DEFORMABLE AERO-SOLS IN THE PRESENCE OF AN ELECTRIC FIELD AND CHEMICAL REACTION USING TAYLOR DISPERSION MODEL*

    Institute of Scientific and Technical Information of China (English)

    RUDRAIAH N.; DEVARAJU N.; NG Chiu-On

    2011-01-01

    Under the effects of electric field and chemical reaction, the problem of dispersion of aerosols in a poorly conducting fluid in a channel is solved analytically using the mixture theory together with a regular perturbation technique.It is shown that the aerosols are dispersed relative to a plane moving with the mean speed of atmospheric fluid as well as the mean speed of agglomeration of aerosol with a relative diffusion coefficient, called the Taylor dispersion coefficient.This coefficient is numerically computed and the results reveal that it increases with an increase in the electric number, but decreases with increasing porous parameter.The physical explanations for the phenomena are given in this article.

  2. Comparative Study on Atmospheric Dispersion Module of Level 3 PSA

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Dahye; Jang, Misuk; Kang, Hyun Sik; Kim, Seoung Rae [NESS, Daejeon (Korea, Republic of)

    2016-10-15

    Some regulation documents such as Regulatory Guides and NUREG publications from the U.S. Nuclear Regulatory Commission (NRC) have influences on domestic radiation environmental analyses. As renewal versions of NUREG-0800 and NUREG-1555 have issued lately, the assessment for Severe Accident (SA) with Probabilistic Safety Assessment (PSA) should be added to Safety Analysis Report (SAR) and Radiation Environmental Report (RER). Because these reports are the required documents for obtaining the construction permit and operating license, it is important to understand the PSA methodology and it needs to improve the site-specific input data of L3PSA codes for SA. First, our review focuses on the atmospheric dispersion and deposition related input data of L3PSA code in this paper. Then we will continue to review the improvements of other input data. Two atmospheric dispersion models, which are PAVAN developed for design basis accident and ATMOS of MACCS2 code developed for SA, were reviewed in this paper. L3PSA deals with the effects of severe accidents and basically includes the evaluation of both short- and long-term effects. Therefore, both the deposition effects and nuclide information(type, amount, and chemical characteristics of released radionuclide) would be considered as the input parameters of atmospheric dispersion model for L3PSA. Additionally, the meteorological data would be sampled randomly to meet the purpose of probabilistic method. However, the sampling method would be selected according to analysis purpose. After review, ATMOS module and its input data are suitably developed for the atmospheric dispersion analysis of L3PSA. However, ATMOS module was developed using the site-specific terrain and environment characteristics. For the domestic application, it needs to study the input data reflecting the Korean terrain and environment characteristics. It would be also continuously improved in response to the time- and site-specific changes of weather

  3. Long-Distance Wind-Dispersal of Spores in a Fungal Plant Pathogen: Estimation of Anisotropic Dispersal Kernels from an Extensive Field Experiment

    Science.gov (United States)

    Rieux, Adrien; Soubeyrand, Samuel; Bonnot, François; Klein, Etienne K.; Ngando, Josue E.; Mehl, Andreas; Ravigne, Virginie; Carlier, Jean; de Lapeyre de Bellaire, Luc

    2014-01-01

    Given its biological significance, determining the dispersal kernel (i.e., the distribution of dispersal distances) of spore-producing pathogens is essential. Here, we report two field experiments designed to measure disease gradients caused by sexually- and asexually-produced spores of the wind-dispersed banana plant fungus Mycosphaerella fijiensis. Gradients were measured during a single generation and over 272 traps installed up to 1000 m along eight directions radiating from a traceable source of inoculum composed of fungicide-resistant strains. We adjusted several kernels differing in the shape of their tail and tested for two types of anisotropy. Contrasting dispersal kernels were observed between the two types of spores. For sexual spores (ascospores), we characterized both a steep gradient in the first few metres in all directions and rare long-distance dispersal (LDD) events up to 1000 m from the source in two directions. A heavy-tailed kernel best fitted the disease gradient. Although ascospores distributed evenly in all directions, average dispersal distance was greater in two different directions without obvious correlation with wind patterns. For asexual spores (conidia), few dispersal events occurred outside of the source plot. A gradient up to 12.5 m from the source was observed in one direction only. Accordingly, a thin-tailed kernel best fitted the disease gradient, and anisotropy in both density and distance was correlated with averaged daily wind gust. We discuss the validity of our results as well as their implications in terms of disease diffusion and management strategy. PMID:25116080

  4. Long-distance wind-dispersal of spores in a fungal plant pathogen: estimation of anisotropic dispersal kernels from an extensive field experiment.

    Directory of Open Access Journals (Sweden)

    Adrien Rieux

    Full Text Available Given its biological significance, determining the dispersal kernel (i.e., the distribution of dispersal distances of spore-producing pathogens is essential. Here, we report two field experiments designed to measure disease gradients caused by sexually- and asexually-produced spores of the wind-dispersed banana plant fungus Mycosphaerella fijiensis. Gradients were measured during a single generation and over 272 traps installed up to 1000 m along eight directions radiating from a traceable source of inoculum composed of fungicide-resistant strains. We adjusted several kernels differing in the shape of their tail and tested for two types of anisotropy. Contrasting dispersal kernels were observed between the two types of spores. For sexual spores (ascospores, we characterized both a steep gradient in the first few metres in all directions and rare long-distance dispersal (LDD events up to 1000 m from the source in two directions. A heavy-tailed kernel best fitted the disease gradient. Although ascospores distributed evenly in all directions, average dispersal distance was greater in two different directions without obvious correlation with wind patterns. For asexual spores (conidia, few dispersal events occurred outside of the source plot. A gradient up to 12.5 m from the source was observed in one direction only. Accordingly, a thin-tailed kernel best fitted the disease gradient, and anisotropy in both density and distance was correlated with averaged daily wind gust. We discuss the validity of our results as well as their implications in terms of disease diffusion and management strategy.

  5. Alternating magnetic field energy absorption in the dispersion of iron oxide nanoparticles in a viscous medium

    Science.gov (United States)

    Smolkova, Ilona S.; Kazantseva, Natalia E.; Babayan, Vladimir; Smolka, Petr; Parmar, Harshida; Vilcakova, Jarmila; Schneeweiss, Oldrich; Pizurova, Nadezda

    2015-01-01

    Magnetic iron oxide nanoparticles were obtained by a coprecipitation method in a controlled growth process leading to the formation of uniform highly crystalline nanoparticles with average size of 13 nm, which corresponds to the superparamagnetic state. Nanoparticles obtained are a mixture of single-phase nanoparticles of magnetite and maghemite as well as nanoparticles of non-stoichiometric magnetite. The subsequent annealing of nanoparticles at 300 °C in air during 6 h leads to the full transformation to maghemite. It results in reduced value of the saturation magnetization (from 56 emu g-1 to 48 emu g-1) but does not affect the heating ability of nanoparticles. A 2-7 wt% dispersion of as-prepared and annealed nanoparticles in glycerol provides high heating rate in alternating magnetic fields allowed for application in magnetic hyperthermia; however the value of specific loss power does not exceed 30 W g-1. This feature of heat output is explained by the combined effect of magnetic interparticle interactions and the properties of the carrier medium. Nanoparticles coalesce during the synthesis and form aggregates showing ferromagnetic-like behavior with magnetization hysteresis, distinct sextets on Mössbauer spectrum, blocking temperature well about room temperature, which accounts for the higher energy barrier for magnetization reversal. At the same time, low specific heat capacity of glycerol intensifies heat transfer in the magnetic dispersion. However, high viscosity of glycerol limits the specific loss power value, since predominantly the Neel relaxation accounts for the absorption of AC magnetic field energy.

  6. Thermocamera studies of nitrous oxide dispersion in the dental surgery

    Energy Technology Data Exchange (ETDEWEB)

    Carlsson, P.; Hallen, B.; Hallonsten, A.L.; Ljungqvist, B.

    1983-06-01

    Nitrous oxide is used in dentistry for sedation and analgesia. Chronic occupational exposure of dental personnel to trace concentrations of nitrous oxide has been reported as a potential health hazard. A new application of the thermocamera technique was used to study the dispersion of nitrous oxide during dental analgesia. Four breathing systems with different evacuation systems were tested and found to vary in scavenging efficiency. A local exhaust system ensured minimal exposure when nitrous oxide leaks contaminating the air in the dentist's breathing zone occur.

  7. A larval dispersion study using lagrangian simulation of particles

    Directory of Open Access Journals (Sweden)

    Laura Rodríguez Díaz

    2014-06-01

    Full Text Available The continuous displacement of water allows stabilize the temperature and also distributes nutrients and plankton in the ocean and seas permitting the development of organisms and the transfers of larvae from the spawning areas to the habitat where adult fishes can be found. The area of study covers The North Atlantic Ocean so the principal aim of the study is analyze if released particles at the Florida Strait could cross the North Atlantic Ocean and reach the European shelf. To test this, it has simulated Lagrangian trajectories for different numbers of particles or "larvae" with a passive behavior (fixing at a depth of dispersion. It has analyzed the dispersion of those particles by using the data of the components U, V and W from the speed of currents provided by the database SODA which uses an ocean model based on Geophysical Fluid Dynamics Laboratory MOM2 and data profiles from World Ocean Atlas-94 and from Geosat, ERS-1 and TOPEX/Poseidon satellites. Considering the dispersive nature of the ocean, the simulations were performed by releasing many particles (typically of the order of several thousand and it was also necessary to perform an interpolation process in time and space so that the position of the particles could evolve. The simulations have been run with 5,000 particles and it has been considered a biological parameter (planktonic larval duration, PLD that represents the length of larval life. At this study it has been used PLD for a specific starfish larva (Sclerasterias tanneri larvae that can be found at the Gulf of Mexico at different locations. Particles were released in October at the most oceanward location of the Gulf of Mexico close to the Florida Strait where Sclerasterias tanneri larvae can be found. Those particles have been tracked for 660 days (660 days is the PLD of Sclerasterias tanneri larvae recording their position every 15 days. That it has done for a period of more than 100 years (1901-2010. The period (1901

  8. A Study on Fluid Dispersion after Liquid Filled Missile Impact

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Sang Shup; Hahm, Daegi; Choi, In-Kil [KAERI, Daejeon (Korea, Republic of)

    2015-05-15

    In order to fire damage evaluations by fuel included transportation crash, the fire duration should be analyzed that consider the fuel spread range, amount of leaked fuel, and various ignition sources. The water slug impact test performed in Sandia National Laboratory (SNL) in 2002 was representative. The cloud of mist dispersion range of the dyed red water and ejection velocity of water after impact were analyzed using Particle Image Velocimetry (PIV) method and numerical simulation. In this study, the included fluid was modeled by using smooth particle hydrodynamics (SPH) technique. The fluid dispersion range following impact was analyzed by considering the particle velocity and flying distance. The result values obtained through this study were compared to the water slug (WS) test results. And the applicability of an analysis method was verified by comparing the WS test results. The results and methodology obtained through this study can be utilized to damage assessment, fuel spread and fire risk for large infrastructures such as nuclear power plants following an aircraft impact. In this study, the included fluid was modeled by using smooth particle hydrodynamics (SPH) technique; the fluid spread range following an impact was analyzed. The radius of fluid spread on the numerical analysis became conservative than the WS test results. However, the shape of the cloud is similar to the WS test results.

  9. Application of asymmetric flow-field flow fractionation to the characterization of colloidal dispersions undergoing aggregation.

    Science.gov (United States)

    Lattuada, Marco; Olivo, Carlos; Gauer, Cornelius; Storti, Giuseppe; Morbidelli, Massimo

    2010-05-18

    The characterization of complex colloidal dispersions is a relevant and challenging problem in colloidal science. In this work, we show how asymmetric flow-field flow fractionation (AF4) coupled to static light scattering can be used for this purpose. As an example of complex colloidal dispersions, we have chosen two systems undergoing aggregation. The first one is a conventional polystyrene latex undergoing reaction-limited aggregation, which leads to the formation of fractal clusters with well-known structure. The second one is a dispersion of elastomeric colloidal particles made of a polymer with a low glass transition temperature, which undergoes coalescence upon aggregation. Samples are withdrawn during aggregation at fixed times, fractionated with AF4 using a two-angle static light scattering unit as a detector. We have shown that from the analysis of the ratio between the intensities of the scattered light at the two angles the cluster size distribution can be recovered, without any need for calibration based on standard elution times, provided that the geometry and scattering properties of particles and clusters are known. The nonfractionated samples have been characterized also by conventional static and dynamic light scattering to determine their average radius of gyration and hydrodynamic radius. The size distribution of coalescing particles has been investigated also through image analysis of cryo-scanning electron microscopy (SEM) pictures. The average radius of gyration and the average hydrodynamic radius of the nonfractionated samples have been calculated and successfully compared to the values obtained from the size distributions measured by AF4. In addition, the data obtained are also in good agreement with calculations made with population balance equations.

  10. Electromagnetic Field Penetration Studies

    Science.gov (United States)

    Deshpande, M.D.

    2000-01-01

    A numerical method is presented to determine electromagnetic shielding effectiveness of rectangular enclosure with apertures on its wall used for input and output connections, control panels, visual-access windows, ventilation panels, etc. Expressing EM fields in terms of cavity Green's function inside the enclosure and the free space Green's function outside the enclosure, integral equations with aperture tangential electric fields as unknown variables are obtained by enforcing the continuity of tangential electric and magnetic fields across the apertures. Using the Method of Moments, the integral equations are solved for unknown aperture fields. From these aperture fields, the EM field inside a rectangular enclosure due to external electromagnetic sources are determined. Numerical results on electric field shielding of a rectangular cavity with a thin rectangular slot obtained using the present method are compared with the results obtained using simple transmission line technique for code validation. The present technique is applied to determine field penetration inside a Boeing-757 by approximating its passenger cabin as a rectangular cavity filled with a homogeneous medium and its passenger windows by rectangular apertures. Preliminary results for, two windows, one on each side of fuselage were considered. Numerical results for Boeing-757 at frequencies 26 MHz, 171-175 MHz, and 428-432 MHz are presented.

  11. Peripheral transverse densities of the baryon octet from chiral effective field theory and dispersion analysis

    Science.gov (United States)

    Alarcón, J. M.; Hiller Blin, A. N.; Vicente Vacas, M. J.; Weiss, C.

    2017-08-01

    The baryon electromagnetic form factors are expressed in terms of two-dimensional densities describing the distribution of charge and magnetization in transverse space at fixed light-front time. We calculate the transverse densities of the spin-1/2 flavor-octet baryons at peripheral distances b = O (Mπ-1) using methods of relativistic chiral effective field theory (χEFT) and dispersion analysis. The densities are represented as dispersive integrals over the imaginary parts of the form factors in the timelike region (spectral functions). The isovector spectral functions on the two-pion cut t > 4 Mπ2 are calculated using relativistic χEFT including octet and decuplet baryons. The χEFT calculations are extended into the ρ meson mass region using an N / D method that incorporates the pion electromagnetic form factor data. The isoscalar spectral functions are modeled by vector meson poles. We compute the peripheral charge and magnetization densities in the octet baryon states, estimate the uncertainties, and determine the quark flavor decomposition. The approach can be extended to baryon form factors of other operators and the moments of generalized parton distributions.

  12. Heat diffusion characteristics of magnetite nanoparticles dispersed hydro-gel in alternating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Suto, Makoto [Graduate School of Environmental Studies, Tohoku University, Sendai (Japan); Kosukegawa, Hiroyuki; Maruta, Kaoru; Ohta, Makoto [Institute of Fluid Science, Tohoku University, Sendai (Japan); Tohji, Kazuyuki [Graduate School of Environmental Studies, Tohoku University, Sendai (Japan); Jeyadevan, Balachandran [Graduate School of Environmental Studies, Tohoku University, Sendai (Japan)], E-mail: jeya@mail.kankyo.tohoku.ac.jp

    2009-10-15

    Heat diffusion characteristics of a spherical heat source dispersing magnetite nanoparticles (MNPs) in hydro-gel were investigated numerically and experimentally to evaluate the conditions required for magnetic fluid hyperthermia (MFH). Numerical estimation assumed one-dimensional spherical model and constant heat evolution. Experimental observation was carried out by exposing the magnetite-dispersed hydro-gel in an AC magnetic field with strength and frequency of 3.2 kA/m and 600 kHz, respectively. The temperature distribution observed along the radial axis of the spherical heat source agreed well with the theoretical estimation quantitatively and qualitatively. However, the minor difference existed between the theory and experiment was due to the variation in experimentally determined and actual particle size distributions. Thus, we could conclude that the proposed algorithm could be extended to be used in the estimation of the temperature distribution in intravital conditions with blood flow, metabolism etc., to arrive at biologically significant conclusions helpful for MFH cancer treatment.

  13. Phytophthora capsici Epidemic Dispersion on Commercial Pepper Fields in Aguascalientes, Mexico

    Directory of Open Access Journals (Sweden)

    Adrián Zapata-Vázquez

    2012-01-01

    Full Text Available Chili pepper blight observed on pepper farms from north Aguascalientes was monitored for the presence of Phytophthora capsici during 2008–2010. Initially, ELISA tests were directed to plant samples from greenhouses and rustic nurseries, showing an 86% of positive samples. Later, samples of wilted plants from the farms during the first survey were tested with ELISA. The subsequent survey on soil samples included mycelia isolation and PCR amplification of a 560 bp fragment of ITS-specific DNA sequence of P. capsici. Data was analyzed according to four geographical areas defined by coordinates to ease the dispersal assessment. In general, one-third of the samples from surveyed fields contained P. capsici, inferring that this may be the pathogen responsible of the observed wilt. Nevertheless, only five sites from a total of 92 were consistently negative to P. capsici. The presence of this pathogen was detected through ELISA and confirmed through PCR. The other two-thirds of the negative samples may be attributable to Fusarium and Rhizoctonia, both isolated instead of Phytophthora in these areas. Due to these striking results, this information would be of interest for local plant protection committees and farmers to avoid further dispersal of pathogens to new lands.

  14. Phytophthora capsici epidemic dispersion on commercial pepper fields in Aguascalientes, Mexico.

    Science.gov (United States)

    Zapata-Vázquez, Adrián; Sánchez-Sánchez, Mario; del-Río-Robledo, Alicia; Silos-Espino, Héctor; Perales-Segovia, Catarino; Flores-Benítez, Silvia; González-Chavira, Mario Martín; Valera-Montero, Luis Lorenzo

    2012-01-01

    Chili pepper blight observed on pepper farms from north Aguascalientes was monitored for the presence of Phytophthora capsici during 2008-2010. Initially, ELISA tests were directed to plant samples from greenhouses and rustic nurseries, showing an 86% of positive samples. Later, samples of wilted plants from the farms during the first survey were tested with ELISA. The subsequent survey on soil samples included mycelia isolation and PCR amplification of a 560 bp fragment of ITS-specific DNA sequence of P. capsici. Data was analyzed according to four geographical areas defined by coordinates to ease the dispersal assessment. In general, one-third of the samples from surveyed fields contained P. capsici, inferring that this may be the pathogen responsible of the observed wilt. Nevertheless, only five sites from a total of 92 were consistently negative to P. capsici. The presence of this pathogen was detected through ELISA and confirmed through PCR. The other two-thirds of the negative samples may be attributable to Fusarium and Rhizoctonia, both isolated instead of Phytophthora in these areas. Due to these striking results, this information would be of interest for local plant protection committees and farmers to avoid further dispersal of pathogens to new lands.

  15. Electromagnetic Field Behavior in Dispersive Isotropic Negative Phase Velocity/Negative Refractive Index Guided Wave Structures Compatible with Millimeter-Wave Monolithic Integrated Circuits

    Directory of Open Access Journals (Sweden)

    Clifford M. Krowne

    2007-01-01

    Full Text Available A microstrip configuration has been loaded with a dispersive isotropic left-handed medium (LHM substrate and studied regarding its high frequency millimeter-wave behavior near 100 GHz. This has been accomplished using a full-wave integral-equation anisotropic Green's function code configured to run for isotropy. Never before seen electromagnetic field distributions are produced, unlike anything found in normal media devices, using this ab initio solver. These distributions are made in the cross-sectional dimension, with the field propagating in the perpendicular direction. It is discovered that the LHM distributions are so radically different from ordinary media used as a substrate that completely new electronic devices based upon the new physics become a real possibility. The distinctive dispersion diagram for the dispersive medium, consisting of unit cells with split ring resonator-rod combinations, is provided over the upper millimeter-wave frequency regime.

  16. A scheme for teleporting Schrdinger-cat states via the dispersive atom-cavity-field interaction

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A proposal is presented for teleporting Schrding-cat states. The process of the teleportation is achieved through the dispersive atom-cavity-field interaction. In this proposal, only measurement on the cavity field and on the singlet atomic states are used.

  17. A study of dispersion in complex terrain under winter conditions using high-resolution mesoscale and Lagrangian particle models

    Directory of Open Access Journals (Sweden)

    J. L. Palau

    2005-11-01

    Full Text Available A mesoscale model (MM5, a dispersive Langrangian particle model (FLEXPART, and intensive meteorological and COrrelation SPECtrometer (COSPEC measurements from a field campaign are used to examine the advection and turbulent diffusion patterns associated with interactions and forcings between topography, synoptic atmospheric flows and thermally-driven circulations. This study describes the atmospheric dispersion of emissions from a power plant with a 343-meter-tall chimney, situated on very complex terrain in the North-East of Spain, under winter conditions. During the field campaign, the plume was transported with low transversal dispersion and deformed essentially due to the effect of mechanical turbulence. The main surface impacts appeared at long distances from the emission source (more than 30 km. The results show that the coupled models (MM5 and FLEXPART are able to predict the plume integral advection from the power plant on very complex terrain. Integral advection and turbulent dispersion are derived from the dispersive Lagrangian model output for three consecutive days so that a direct quantitative comparison has been made between the temporal evolution of the predicted three-dimensional dispersive conditions and the COSPEC measurements. Comparison between experimental and simulated transversal dispersion shows an index of agreement between 80% and 90%, within distance ranges from 6 to 33 km from the stack. Linked to the orographic features, the simulated plume impacts on the ground more than 30 km away from the stack, because of the lee waves simulated by MM5.

  18. In vitro dissolution study of atorvastatin binary solid dispersion

    Science.gov (United States)

    Jahan, Rahat; Islam, Md. Saiful; Tanwir, Ahmad; Chowdhury, Jakir Ahmed

    2013-01-01

    The aim of the present study was to improve the solubility and dissolution rate of atorvastatin (ATV), a slight water-soluble drug, by solid dispersion (SD) technique using a hydrophilic carrier Poloxamer 188 (POL188). Physical mixing (PM) and solvent evaporation (SE) method were used to prepare ATV-SD where different drug-carrier ratios were used. Prepared formulations were characterized in their solid state by solubility study; differential scanning calorimetry, scanning electron microscopy, and Fourier transform infrared spectroscopy which demonstrated changes in the formulations supporting the improved solubility. Percent content of POL188 in the SD matrix was found to play the pivotal role in the improvement of dissolution property of ATV. In case of PM, highest enhancement in drug release was found for 1:3 ratio (P < 0.05, ANOVA Single factor) whereas in case of SE, 3:0.5 ratio of ATV-POL188 resulted the maximum enhancement in ATV release (P < 0.05, ANOVA Single factor). Analysis of dissolution data of optimized formula indicated the best fitting with Peppas-Korsmeyer model and the drug release kinetics was fickian diffusion. In conclusion, binary SD prepared by both PM and SE technique using POL188 could be considered as a simple, efficient method to prepare ATV solid dispersions with significant improvement in the dissolution rate. PMID:23662278

  19. In vitro dissolution study of atorvastatin binary solid dispersion

    Directory of Open Access Journals (Sweden)

    Rahat Jahan

    2013-01-01

    Full Text Available The aim of the present study was to improve the solubility and dissolution rate of atorvastatin (ATV, a slight water-soluble drug, by solid dispersion (SD technique using a hydrophilic carrier Poloxamer 188 (POL188. Physical mixing (PM and solvent evaporation (SE method were used to prepare ATV-SD where different drug-carrier ratios were used. Prepared formulations were characterized in their solid state by solubility study; differential scanning calorimetry, scanning electron microscopy, and Fourier transform infrared spectroscopy which demonstrated changes in the formulations supporting the improved solubility. Percent content of POL188 in the SD matrix was found to play the pivotal role in the improvement of dissolution property of ATV. In case of PM, highest enhancement in drug release was found for 1:3 ratio (P < 0.05, ANOVA Single factor whereas in case of SE, 3:0.5 ratio of ATV-POL188 resulted the maximum enhancement in ATV release (P < 0.05, ANOVA Single factor. Analysis of dissolution data of optimized formula indicated the best fitting with Peppas-Korsmeyer model and the drug release kinetics was fickian diffusion. In conclusion, binary SD prepared by both PM and SE technique using POL188 could be considered as a simple, efficient method to prepare ATV solid dispersions with significant improvement in the dissolution rate.

  20. Large Eddy Simulation of the Wind Field and Pollution Dispersion in Building Array

    Science.gov (United States)

    Shi, R. F.; Cui, G. X.; Xu, C. X.; Zhang, Z. S.; Wang, Z. S.

    The air quality is one of the significant issues in sustainable development of modern city. In the paperthe Large Eddy Simulation (LES) is used to predict the wind field and pollution dispersion in residence district. The flow in residence district is characterized by the complicated geometry, vortex patterns, unsteadiness etc.; hence the LES is the suitable method for the flow. The finite volume method with fourth order accuracy is utilized for numerical simulation and immerse boundary method (IBM) is applied to the solid boundary condition. The numerical scheme has been validated for a number of complex flows (Xu et al. 2006). A number of testing cases have been performed and the results are compared with experimental data in good agreement. One of the testing cases is an array of cubic buildings with height H, length B and width W of 0.12m. The flow Reynolds number based on the free stream velocity and the height of the building is equal to 4 x 106. A point concentration source is located at 4W in front of the building array. The dynamic Smagorinsky model is used for the subgrid stress. The predicted results are compared with the wind tunnel measurements by Davidson et al. (1996). Figure 1 and 2 shows the typical wind speed distributions and the mean concentration at H/2 and L ay /2, They are in good agreement with experimental data. The results indicate that the proposed numerical scheme of LES is capable of predicting wind field and pollution dispersion in residence district. Moreover numerical simulation can provide more information about the flow pattern and concentration distribution for better understanding the phenomena.

  1. A terahertz study of taurine: Dispersion correction and mode couplings

    Science.gov (United States)

    Dai, Zelin; Xu, Xiangdong; Gu, Yu; Li, Xinrong; Wang, Fu; Lian, Yuxiang; Fan, Kai; Cheng, Xiaomeng; Chen, Zhegeng; Sun, Minghui; Jiang, Yadong; Yang, Chun; Xu, Jimmy

    2017-03-01

    The low-frequency characteristics of polycrystalline taurine were studied experimentally by terahertz (THz) absorption spectroscopy and theoretically by ab initio density-functional simulations. Full optimizations with semi-empirical dispersion correction were performed in spectral computations and vibrational mode assignments. For comparison, partial optimizations with pure density functional theory were conducted in parallel. Results indicate that adding long-range dispersion correction to the standard DFT better reproduces the measured THz spectra than the popular partial optimizations. The main origins of the observed absorption features were also identified. Moreover, a coupled-oscillators model was proposed to explain the experimental observation of the unusual spectral blue-shift with the increase of temperature. Such coupled-oscillators model not only provides insights into the temperature dynamics of non-bonded interactions but also offers an opportunity to better understand the physical mechanisms behind the unusual THz spectral behaviors in taurine. Particularly, the simulation approach and novel coupled-oscillators model presented in this work are applicable to analyze the THz spectra of other molecular systems.

  2. A dispersion study of CO2 in a closed area

    Science.gov (United States)

    Korinek, Tomas; Frana, Karel

    2016-06-01

    Predictions of air pollution dispersion in an indoor environment are important outputs to control a fresh air ventilation or energy building efficiency. This study deals with numerical simulations of a formation and dispersion of carbon dioxide (CO2) in a closed area. Numerical simulations were carried out by the Reynolds Averaged Navier-Stokes (RANS) approach. A simple domain with one pollution source was used for a validation of the mathematical model, in which values of the CO2 concentration were calculated using CFD and measured. The CO2 was created as a combustion product of the ethanol. There were used two different methods for the calculation of the CO2 formation. The first method adopted the species transport model with reactions and the second method was the non-premix combustion model based on the mixture fraction theory. The third method used in numerical simulations was a constant mass flow inlet of CO2. All computational methods provided a sufficient agreement of the CO2 concentration with the experimental data.

  3. Study on Dispersion Properties of Photonic Crystal Fiber by Effective-Index Model

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The group-velocity-dispersion properties of photonic crystal fiber (PCF) were investigated by effective-index model. The relationship between waveguide dispersion and structure parameters: the pitch A and the relative hole size/was studied.

  4. Study on Dispersion Properties of Photonic Crystal Fiber by Effective-Index Model

    Institute of Scientific and Technical Information of China (English)

    Ren Guobin; Wang Zhi; Lou Shuqin; Jian Shuisheng

    2003-01-01

    The group-velocity-dispersion properties of photonic crystal fiber (PCF) were investigated by effective-index model. The relationship between waveguide dispersion and structure parameters: the pitch and the relative hole size f was studied.

  5. Validation of the DIFFAL, HPAC and HotSpot Dispersion Models Using the Full-Scale Radiological Dispersal Device (FSRDD) Field Trials Witness Plate Deposition Dataset.

    Science.gov (United States)

    Purves, Murray; Parkes, David

    2016-05-01

    Three atmospheric dispersion models--DIFFAL, HPAC, and HotSpot--of differing complexities have been validated against the witness plate deposition dataset taken during the Full-Scale Radiological Dispersal Device (FSRDD) Field Trials. The small-scale nature of these trials in comparison to many other historical radiological dispersion trials provides a unique opportunity to evaluate the near-field performance of the models considered. This paper performs validation of these models using two graphical methods of comparison: deposition contour plots and hotline profile graphs. All of the models tested are assessed to perform well, especially considering that previous model developments and validations have been focused on larger-scale scenarios. Of the models, HPAC generally produced the most accurate results, especially at locations within ∼100 m of GZ. Features present within the observed data, such as hot spots, were not well modeled by any of the codes considered. Additionally, it was found that an increase in the complexity of the meteorological data input to the models did not necessarily lead to an improvement in model accuracy; this is potentially due to the small-scale nature of the trials.

  6. Wind tunnel studies of gas dispersion from ground level source

    Directory of Open Access Journals (Sweden)

    Michálek Petr

    2015-01-01

    Full Text Available Measurements of gas dispersion from ground source were performed in a boundary layer wind tunnel in VZLU Prague. The measurements include non-buoyant gas dispersion behind a ground level source on a flat plane, on a simple rectangular building model and behind a model hill and rectangular barrier. These measurements will serve for verification of a new gas dispersion software being developed in VZLU. The dispersion model is intended for use by firemen and ambulance services in the case of an accident for immediate estimation of the area with dangerous gas concentration. The dispersion model will use precalculated results for chosen areas in the Czech Republic with industrial plants and residential building in the neighborhood. The size of contaminated area will be estimated using actual meteorological situation, i.e. wind speed and direction etc. and precalculated data of flow and dispersion in the chosen location.

  7. Wind tunnel studies of gas dispersion from ground level source

    Science.gov (United States)

    Michálek, Petr; Zacho, David

    2015-05-01

    Measurements of gas dispersion from ground source were performed in a boundary layer wind tunnel in VZLU Prague. The measurements include non-buoyant gas dispersion behind a ground level source on a flat plane, on a simple rectangular building model and behind a model hill and rectangular barrier. These measurements will serve for verification of a new gas dispersion software being developed in VZLU. The dispersion model is intended for use by firemen and ambulance services in the case of an accident for immediate estimation of the area with dangerous gas concentration. The dispersion model will use precalculated results for chosen areas in the Czech Republic with industrial plants and residential building in the neighborhood. The size of contaminated area will be estimated using actual meteorological situation, i.e. wind speed and direction etc. and precalculated data of flow and dispersion in the chosen location.

  8. [Progress in study of oral biofilm dispersal-inducing agents].

    Science.gov (United States)

    Yan, Zhu; Jingmei, Yang; Dingyu, Duan; Yi, Xu

    2014-12-01

    Communities of bacteria wrapped in self-generated extracellular polymeric matrix and attached to a solid surface are known as biofilm. Biofilm formation and development can be divided into three stages: adhesion of cells to a surface, reproduction of the cells, and dispersion of cells. The procedure, which surface-attached biofilm disperses bacterial cells into the environment to colonize new sites, is defined as biofilm dispersal. Biofilm dispersal is an essential stage of biofilm life cycle. It plays an important role in the transmission of bacteria. For many pathogenic bacteria, biofilm dispersal can transform bacteria in biofilm into planktonic state and promote the spread of infection. The formation of biofilm may increase the resistance of bacteria to antimicrobial agent and host defence response compared with planktonic cells. In the oral cavity, oral microorganism can attach to the surface of oral tissue and prosthesis to form biofilm. Dental caries and periodontal disease are oral chronic infections diseases of the oral tissue. The occurrence of them has a close relationship with biofilm. The mechanism of dispersal is a hot topic in recent years. Some agents which promote dispersal might be a therapeutic potential against biofilm infections. The clinical implication of dispersal agents and potential application are promising. This article reviews the dispersal-inducing agents of oral biofilms.

  9. Ultrafast dark-field surface inspection with hybrid-dispersion laser scanning

    Science.gov (United States)

    Yazaki, Akio; Kim, Chanju; Chan, Jacky; Mahjoubfar, Ata; Goda, Keisuke; Watanabe, Masahiro; Jalali, Bahram

    2014-06-01

    High-speed surface inspection plays an important role in industrial manufacturing, safety monitoring, and quality control. It is desirable to go beyond the speed limitation of current technologies for reducing manufacturing costs and opening a new window onto a class of applications that require high-throughput sensing. Here, we report a high-speed dark-field surface inspector for detection of micrometer-sized surface defects that can travel at a record high speed as high as a few kilometers per second. This method is based on a modified time-stretch microscope that illuminates temporally and spatially dispersed laser pulses on the surface of a fast-moving object and detects scattered light from defects on the surface with a sensitive photodetector in a dark-field configuration. The inspector's ability to perform ultrafast dark-field surface inspection enables real-time identification of difficult-to-detect features on weakly reflecting surfaces and hence renders the method much more practical than in the previously demonstrated bright-field configuration. Consequently, our inspector provides nearly 1000 times higher scanning speed than conventional inspectors. To show our method's broad utility, we demonstrate real-time inspection of the surface of various objects (a non-reflective black film, transparent flexible film, and reflective hard disk) for detection of 10 μm or smaller defects on a moving target at 20 m/s within a scan width of 25 mm at a scan rate of 90.9 MHz. Our method holds promise for improving the cost and performance of organic light-emitting diode displays for next-generation smart phones, lithium-ion batteries for green electronics, and high-efficiency solar cells.

  10. Characteristic Features of Stone-Wales Defects in Single-Walled Carbon Nanotube; Adsorption, Dispersion, and Field Emission

    Directory of Open Access Journals (Sweden)

    Seungkwang Roh

    2010-01-01

    Full Text Available Adsorption behaviors of dodecanethiol (C12H25SH molecules are investigated on the surface of single-walled carbon nanotubes (SWCNTs with vibrational and X-ray photoelectron spectrometers. The active adsorption sites are proved as Stone-Wales (SW defects (5–7 ring defects. The SW defect-removed SWCNTs formed by reacting nanotubes with allyl acrylate molecules are compared with pristine SWCNTs in dispersion and field emission. The former shows higher dispersion and field emission than the latter.

  11. Dispersion of Magnetic Fields in Molecular Clouds. IV - Analysis of Interferometry Data

    CERN Document Server

    Houde, Martin; Plambeck, Richard L; Vaillancourt, John E; Hildebrand, Roger H

    2016-01-01

    We expand on the dispersion analysis of polarimetry maps toward applications to interferometry data. We show how the filtering of low-spatial frequencies can be accounted for within the idealized Gaussian turbulence model, initially introduced for single-dish data analysis, to recover reliable estimates for correlation lengths of magnetized turbulence, as well as magnetic field strengths (plane-of-the-sky component) using the Davis-Chandrasekhar-Fermi method. We apply our updated technique to TADPOL/CARMA data obtained on W3(OH), W3 Main, and DR21(OH). For W3(OH) our analysis yields a turbulence correlation length $\\delta\\simeq19$ mpc, a ratio of turbulent-to-total magnetic energy $\\left\\langle B_{\\mathrm{t}}^{2}\\right\\rangle /\\left\\langle B^{2}\\right\\rangle \\simeq0.58$, and a magnetic field strength $B_{0}\\sim1.1\\:\\mathrm{mG}$; for W3 Main $\\delta\\simeq22$ mpc, $\\left\\langle B_{\\mathrm{t}}^{2}\\right\\rangle /\\left\\langle B^{2}\\right\\rangle \\simeq0.74$, and $B_{0}\\sim0.7\\:\\mathrm{mG}$; while for DR21(OH) $\\del...

  12. Spontaneous dispersion of PdO onto acid sites of zeolites studied by in situ DXAFS

    CERN Document Server

    Okumura, K; Niwa, M; Yokota, S; Kato, K; Tanida, H; Uruga, T

    2003-01-01

    The generation of highly dispersed PdO over zeolite supports was studied using in situ energy-dispersive XAFS (DXAFS) technique. From the comparison with the Na-ZSM-5, it was found that the oxidation as well as the spontaneous dispersion of Pd was promoted through the interaction between PdO and acid sites of H-form zeolites. (author)

  13. Numerical Study of Traffic Pollutant Dispersion within Different Street Canyon Configurations

    Directory of Open Access Journals (Sweden)

    Yucong Miao

    2014-01-01

    Full Text Available The objective of this study is to numerically study flow and traffic exhaust dispersion in urban street canyons with different configurations to find out the urban-planning strategies to ease the air pollution. The Computational Fluid Dynamics (CFD model used in this study—Open Source Field Operation and Manipulation (OpenFOAM software package—was firstly validated against the wind-tunnel experiment data by using three different k-ε turbulence models. And then the patterns of flow and dispersion within three different kinds of street canyon configuration under the perpendicular approaching flow were numerically studied. The result showed that the width and height of building can dramatically affect the pollution level inside the street canyon. As the width or height of building increases, the pollution at the pedestrian level increases. And the asymmetric configuration (step-up or step-down street canyon could provide better ventilation. It is recommended to design a street canyon with nonuniform configurations. And the OpenFOAM software package can be used as a reliable tool to study flows and dispersions around buildings.

  14. Colloidal dispersions in external fields: from equilibrium to non-equilibrium

    Science.gov (United States)

    Lowen, Hartmut

    2010-03-01

    Dispersions of colloidal particles are excellent model systems of classical statistical mechanics in order to understand the principles of self-organization processes. Using an external field (e.g. electric or magnetic field) the effective interaction between the colloidal particles can be tailored and the system can be brought into non-equilibrium in a controlled way. Glass formation after an ultrafast quench in a two-dimensional superparamagnetic binary colloidal mixture [1,2] will be discussed as well as lane [3,4,5,6,7] and band [8] formation in mixtures of charged suspensions and dusty plasmas driven by an electric field. [4pt] References:[0pt] [1] L. Assoud, F. Ebert, P. Keim, R. Messina, G. Maret, H. Lowen, Phys. Rev. Letters 102, 238301 (2009). [0pt] [2] L. Assoud, F. Ebert, P. Keim, R. Messina, G. Maret, H. Lowen, J. Phys.: Condensed Matter 21, 464114 (2009). [0pt] [3] J. Dzubiella, G. P. Hoffmann, H. Lowen, Phys. Rev. E 65, 021402 (1-8) (2002). [0pt] [4] M. E. Leunissen, C. G. Christova, A. P. Hynninen, C. P. Royall, A. I. Campbell, A. Imhof, M. Dijkstra, R. van Roij, A. van Blaaderen, Nature 437, 235 (2005). [0pt] [5] M. Rex, H. Lowen, Phys. Rev. E 75, 051402 (2007). [0pt] [6] M. Rex, C. P. Royall, A. van Blaaderen, H. Lowen, Lane formation in driven colloidal mixtures: is it continuous or discontinuous?, http://arxiv.org/abs/0812.0908 [0pt] [7] K. R. Sutterlin, A. Wysocki, A. V. Ivlev, C. Rath, H. M. Thomas, M. Rubin-Zuzic, W. J. Goedheer, V. E. Fortov, A. M. Lipaev, V. I. Molotkov, O. F. Petrov, G. E. Morfill, H. Lowen, Phys. Rev. Letters 102, 085003 (2009). [0pt] [8] A. Wysocki, H. Lowen, Phys. Rev. E 79, 041408 (2009).

  15. A Study of Dispersion Compensation of Polarization Multiplexing-Based OFDM-OCDMA for Radio-over-Fiber Transmissions

    Directory of Open Access Journals (Sweden)

    Chih-Ta Yen

    2016-09-01

    Full Text Available Chromatic dispersion from optical fiber is the most important problem that produces temporal skews and destroys the rectangular structure of code patterns in the spectra-amplitude-coding-based optical code-division multiple-access (SAC-OCDMA system. Thus, the balance detection scheme does not work perfectly to cancel multiple access interference (MAI and the system performance will be degraded. Orthogonal frequency-division multiplexing (OFDM is the fastest developing technology in the academic and industrial fields of wireless transmission. In this study, the radio-over-fiber system is realized by integrating OFDM and OCDMA via polarization multiplexing scheme. The electronic dispersion compensation (EDC equalizer element of OFDM integrated with the dispersion compensation fiber (DCF is used in the proposed radio-over-fiber (RoF system, which can efficiently suppress the chromatic dispersion influence in long-haul transmitted distance. A set of length differences for 10 km-long single-mode fiber (SMF and 4 km-long DCF is to verify the compensation scheme by relative equalizer algorithms and constellation diagrams. In the simulation result, the proposed dispersion mechanism successfully compensates the dispersion from SMF and the system performance with dispersion equalizer is highly improved.

  16. A Study of Dispersion Compensation of Polarization Multiplexing-Based OFDM-OCDMA for Radio-over-Fiber Transmissions.

    Science.gov (United States)

    Yen, Chih-Ta; Chen, Wen-Bin

    2016-09-07

    Chromatic dispersion from optical fiber is the most important problem that produces temporal skews and destroys the rectangular structure of code patterns in the spectra-amplitude-coding-based optical code-division multiple-access (SAC-OCDMA) system. Thus, the balance detection scheme does not work perfectly to cancel multiple access interference (MAI) and the system performance will be degraded. Orthogonal frequency-division multiplexing (OFDM) is the fastest developing technology in the academic and industrial fields of wireless transmission. In this study, the radio-over-fiber system is realized by integrating OFDM and OCDMA via polarization multiplexing scheme. The electronic dispersion compensation (EDC) equalizer element of OFDM integrated with the dispersion compensation fiber (DCF) is used in the proposed radio-over-fiber (RoF) system, which can efficiently suppress the chromatic dispersion influence in long-haul transmitted distance. A set of length differences for 10 km-long single-mode fiber (SMF) and 4 km-long DCF is to verify the compensation scheme by relative equalizer algorithms and constellation diagrams. In the simulation result, the proposed dispersion mechanism successfully compensates the dispersion from SMF and the system performance with dispersion equalizer is highly improved.

  17. THE MADISON SQUARE GARDEN DISPERSION STUDY (MSG05) METEOROLOGICAL DATA DESCRIPTION.

    Energy Technology Data Exchange (ETDEWEB)

    REYNOLDS, R.M.

    2006-10-01

    MSG05 was a study of atmospheric transport and dispersion in the deep urban canyons of Midtown New York City, in the area of Madison Square Garden. This downtown area is considered to be a prime target for terrorist activities, and has one of the largest commuter populations in the world. Little is known about air flow and hazardous gas dispersion in such scenarios, since previous urban field experiments have focused on small to medium sized cities with much smaller street canyons. On March 10 and 14, 2005, a series of Perfluorocarbon Tracer (PFT) tracers were released and tracked with about 30 sampling stations at radial distances of about 0.2 and 0.4 km, with vertical profiles near a 250 m tall building (One Penn Plaza). Meteorological stations collected wind data in the MSG vicinity, at street level and rooftop level. MSG05 is expected to provide useful information on rapid vertical dispersion will assist in planning for more extensive studies. This data release is being made available to a restricted group of key scientists who have worked on the project. Part of the QA program involves feedback from scientists and modelers who are working on this study. This document describes the meteorological component of the project. The file organization and metadata are detailed so that a researcher can work with the data sets.

  18. Evaluation of the ERP dispersion model using Darlington tracer-study data. Report No. 90-200-K

    Energy Technology Data Exchange (ETDEWEB)

    Wright, S.C.

    1990-01-01

    In this study, site-boundary atmospheric dilution factors calculated by the atmospheric dispersion model used in the ERP (Emergency Response Planning) computer code were compared to data collected during the Darlington tracer study. The purpose of this comparison was to obtain estimates of model uncertainty under a variety of conditions. This report provides background on ERP, the ERP dispersion model and the Darlington tracer study. Model evaluation techniques are discussed briefly, and the results of the comparison of model calculations with the field data are presented and reviewed.

  19. Temporal coupled mode theory linking to surface-wave dispersion relations in near-field electromagnetic heat transfer

    Science.gov (United States)

    Iizuka, Hideo; Fan, Shanhui

    2016-11-01

    We provide a detailed discussion of the use of coupled mode theory to describe near-field heat transfer. We consider a simple physical model system of coupled harmonic oscillators with each oscillator maintaining at a different temperature, where heat transfer between the oscillators can be analytically treated from first-principles using the Newton's equation and the fluctuation dissipation theorem. Applying a slowly varying envelope approximation to the Newton's equation, we derive a coupled mode theory formalism. We then apply this coupled mode theory formalism in the study of the near-field heat transfer between either silicon carbide plates or between two graphene sheets. The coupled mode theory provides a quantitative link between the dispersion relation of the coupled system and the heat transfer, and agrees with exact numerical results over all range of wavevectors. To obtain such complete agreement, the key observation here is that one should include the frequency shift, that is, the frequency of the individual mode used in the coupled mode theory should be different from the frequency of the mode of an isolated structure. Finally, we show that the coupled mode theory can be applied even when more than two modes are involved in the heat transfer. As an example, we extend our formalism to the near-field heat transfer in a four-layer graphene structure.

  20. Atmospheric dispersion of argon-41 from anuclear research reactor: measurement and modeling of plume geometry and gamma radiation field

    DEFF Research Database (Denmark)

    Lauritzen, Bent; Astrup, Poul; Drews, Martin

    2003-01-01

    An atmospheric dispersion experiment was conducted using a visible tracer along with the routine release of argon-41 from the BR1 research reactor in Mol, Belgium. Simultaneous measurements of plume geometry and radiation fields for argon-41 decay were performed as well as measurements of the argon...

  1. “Cold” dispersion relation of corrugated waveguide filled with plasma immersed in a finite magnetic field

    Institute of Scientific and Technical Information of China (English)

    LiWei; WeiYan-Yu; XieHong-Quan; LiuSheng-Gang; GongMa-Li

    2003-01-01

    A general dispersion equation of a partially filled plasma corrugated waveguide immersed in a finite magnetic field is presented.When the guiding magnet B0→∞ or 0, this equation can be reduced to the results obtained in previous works.

  2. Atmospheric dispersion of argon-41 from anuclear research reactor: measurement and modeling of plume geometry and gamma radiation field

    DEFF Research Database (Denmark)

    Lauritzen, Bent; Astrup, Poul; Drews, Martin

    2003-01-01

    An atmospheric dispersion experiment was conducted using a visible tracer along with the routine release of argon-41 from the BR1 research reactor in Mol, Belgium. Simultaneous measurements of plume geometry and radiation fields for argon-41 decay were performed as well as measurements of the argon...

  3. On the entanglement of a quantum field with a dispersive medium

    CERN Document Server

    Klich, Israel

    2011-01-01

    The modification of the quantum state of electromagnetic fields in the presence of matter yields fascinating effects such as the Casimir effect and the Lamb shift. Here we consider another aspect of such interaction: the entanglement of the matter and radiation as measured by the von-Neumann entropy of field. Indeed, in the presence of a dissipative medium, the electromagnetic field cannot be described as a pure state anymore. In particular, we find that the plasma and Drude models of dielectrics correspond to very different entanglement behavior. We present a formula for the "Casimir" entanglement entropy, i.e. the distance dependence of the field entropy. Finally, we study a toy model of the interaction between two plates. In this model the field entanglement entropy is divergent, however, as in the Casimir effect, its distance dependent part is finite.

  4. Physicochemical characterization and solubility enhancement studies of allopurinol solid dispersions

    Directory of Open Access Journals (Sweden)

    Jagdale Swati Changdeo

    2011-09-01

    Full Text Available Allopurinol is a commonly used drug in the treatment of chronic gout or hyperuricaemia associated with treatment of diuretic conditions. One of the major problems with the drug is that it is practically insoluble in water, which results in poor bioavailability after oral administration. In the present study, solid dispersions of allopurinol were prepared by solvent evaporation, kneading method, co-precipitation method, co-grinding method and closed melting methods to increase its water solubility. Hydrophilic carriers such as polyvinylpyrrolidone, polyethylene glycol 6000 were used in the ratio of 1:1, 1:2 and 1:4 (drug to carrier ratio. The aqueous solubility of allopurinol was favored by the presence of both polymers. These new formulations were characterized in the liquid state by phase solubility studies and in the solid state by differential scanning calorimetry, powder X-ray diffraction, UV and Fourier Transform Infrared spectroscopy. Solid state characterizations indicated that allopurinol was present as an amorphous material and entrapped in polymer matrix. In contrast to the very slow dissolution rate of pure allopurinol, the dispersion of the drug in the polymers considerably enhanced the dissolution rate. Solid dispersion prepared with polyvinylpyrrolidone showed highest improvement in wettability and dissolution rate of allopurinol. Mathematical modeling of in vitro dissolution data indicated the best fitting with Korsemeyer-Peppas model and the drug release kinetics primarily as Non-Fickian diffusion. Therefore, the present study showed that polyvinylpyrrolidone and polyethylene glycol 6000 have a significant solubilizing effect on allopurinol.Alopurinol é fármaco comumente utilizado no tratamento de gota crônica ou hiperuricemia associada com o tratamento em condições diuréticas. Um dos maiores problemas com o fármaco é que este é praticamente insolúvel em água, o que resulta em baixa biodisponibilidade na administra

  5. The SLcam: A full-field energy dispersive X-ray camera

    CERN Document Server

    Bjeoumikhov, A; Langhoff, N; Ordavo, I; Radtke, M; Reinholz, U; Riesemeier, H; Scharf, O; Soltau, H; Wedell, R

    2012-01-01

    The color X-ray camera (SLcam) is a full-field single photon imager. As stand-alone camera, it is applicable for energy and space-resolved X-ray detection measurements. The exchangeable poly-capillary optics in front of a beryllium entrance window conducts X-ray photons from the probe to distinguished energy dispersive pixels on a pnCCD. The dedicated software enables the acquisition and the online processing of the spectral data for all 69696 pixels, leading to a real-time visualization of the element distribution in a sample. No scanning system is employed. A first elemental composition image of the sample is visible within minutes while statistics is improving in the course of time. Straight poly-capillary optics allows for 1:1 imaging with a space resolution of 50 um and no limited depth of sharpness, ideal to map uneven objects. Using conically shaped optics, a magnification of 6 times was achieved with a space resolution of 10 um. We present a measurement with a laboratory source showing the camera capa...

  6. Dynamic polarization of the LiH molecule in strong light field in anomalous-dispersion domain

    CERN Document Server

    Shtoff, A V; Gusarov, S I; Dmitriev, Yu

    1995-01-01

    A new method is proposed to calculate the polarization vector of a molecule in a monochromatic external field in the anomalous-despersion domain. The method takes into account the instantaneous switching of the field. A simple modification of the method allows one to consider a more general switching procedure. As an illustration of the method Fourier components of the polarization vector of the LiH molecule in the anomalous -dispersion domain is calculated.

  7. Carbon nanotubes filled polymer composites: A comprehensive study on improving dispersion, network formation and electrical conductivity

    Science.gov (United States)

    Chakravarthi, Divya Kannan

    In this dissertation, we determine how the dispersion, network formation and alignment of carbon nanotubes in polymer nanocomposites affect the electrical properties of two different polymer composite systems: high temperature bismaleimide (BMI) and polyethylene. The knowledge gained from this study will facilitate optimization of the above mentioned parameters, which would further enhance the electrical properties of polymer nanocomposites. BMI carbon fiber composites filled with nickel-coated single walled carbon nanotubes (Ni-SWNTs) were processed using high temperature vacuum assisted resin transfer molding (VARTM) to study the effect of lightning strike mitigation. Coating the SWNTs with nickel resulted in enhanced dispersions confirmed by atomic force microscopy (AFM) and dynamic light scattering (DLS). An improved interface between the carbon fiber and Ni-SWNTs resulted in better surface coverage on the carbon plies. These hybrid composites were tested for Zone 2A lightning strike mitigation. The electrical resistivity of the composite system was reduced by ten orders of magnitude with the addition of 4 weight percent Ni-SWNTs (calculated with respect to the weight of a single carbon ply). The Ni-SWNTs - filled composites showed a reduced amount of damage to simulated lightning strike compared to their unfilled counterparts indicated by the minimal carbon fiber pull out. Methods to reduce the electrical resistivity of 10 weight percent SWNTs --- medium density polyethylene (MDPE) composites were studied. The composites processed by hot coagulation method were subjected to low DC electric fields (10 V) at polymer melt temperatures to study the effect of viscosity, nanotube welding, dispersion and, resultant changes in electrical resistivity. The electrical resistivity of the composites was reduced by two orders of magnitude compared to 10 wt% CNT-MDPE baseline. For effective alignment of SWNTs, a new process called Electric field Vacuum Spray was devised to

  8. Dispersive and dissipative effects in quantum field theory in curved space-time to model condensed matter systems

    CERN Document Server

    Busch, Xavier

    2014-01-01

    The two main predictions of quantum field theory in curved space-time, namely Hawking radiation and cosmological pair production, have not been directly tested and involve ultra high energy configurations. As a consequence, they should be considered with caution. Using the analogy with condensed matter systems, their analogue versions could be tested in the lab. Moreover, the high energy behavior of these systems is known and involves dispersion and dissipation, which regulate the theory at short distances. When considering experiments which aim to test the above predictions, there will also be a competition between the stimulated emission from thermal noise and the spontaneous emission out of vacuum. In order to measure these effects, one should thus compute the consequences of UV dispersion and dissipation, and identify observables able to establish that the spontaneous emission took place. In this thesis, we first analyze the effects of dispersion and dissipation on both Hawking radiation and pair particle...

  9. Host-Seeking Behavior and Dispersal of Triatoma infestans, a Vector of Chagas Disease, under Semi-field Conditions

    Science.gov (United States)

    Castillo-Neyra, Ricardo; Barbu, Corentin M.; Salazar, Renzo; Borrini, Katty; Naquira, Cesar; Levy, Michael Z.

    2015-01-01

    Chagas disease affects millions of people in Latin America. The control of this vector-borne disease focuses on halting transmission by reducing or eliminating insect vector populations. Most transmission of Trypanosoma cruzi, the causative agent of Chagas disease, involves insects living within or very close to households and feeding mostly on domestic animals. As animal hosts can be intermittently present it is important to understand how host availability can modify transmission risk to humans and to characterize the host-seeking dispersal of triatomine vectors on a very fine scale. We used a semi-field system with motion-detection cameras to characterize the dispersal of Triatoma infestans, and compare the behavior of vector populations in the constant presence of hosts (guinea pigs), and after the removal of the hosts. The emigration rate – net insect population decline in original refuge – following host removal was on average 19.7% of insects per 10 days compared to 10.2% in constant host populations (p = 0.029). However, dispersal of T. infestans occurred in both directions, towards and away from the initial location of the hosts. The majority of insects that moved towards the original location of guinea pigs remained there for 4 weeks. Oviposition and mortality were observed and analyzed in the context of insect dispersal, but only mortality was higher in the group where animal hosts were removed (p-value vector control. Removing domestic animals in infested areas increases vector dispersal from the first day of host removal. The implications of these patterns of vector dispersal in a field setting are not yet known but could result in movement towards human rooms. PMID:25569228

  10. Characterization and Pharmacokinetic Study of Aprepitant Solid Dispersions with Soluplus®

    OpenAIRE

    Jinwen Liu; Meijuan Zou; Hongyu Piao; Yi Liu; Bo Tang; Ying Gao; Ning Ma; Gang Cheng

    2015-01-01

    Solid dispersions are a useful approach to improve the dissolution rate and bioavailability of poorly water-soluble active pharmaceutical ingredients (APIs). The aim of this study was to improve the physicochemical properties and bioavailability of a poorly water-soluble aprepitant by preparation of solid dispersions. The solid dispersions were characterized by dissolution, FTIR, XRPD, DSC, SEM and pharmacokinetic studies in rats. The dissolution rate of the aprepitant was significantly incre...

  11. Studies on dispersive stabilization of porous media flows

    Energy Technology Data Exchange (ETDEWEB)

    Daripa, Prabir, E-mail: prabir.daripa@math.tamu.edu; Gin, Craig [Department of Mathematics, Texas A& M University, College Station, Texas 77843 (United States)

    2016-08-15

    Motivated by a need to improve the performance of chemical enhanced oil recovery (EOR) processes, we investigate dispersive effects on the linear stability of three-layer porous media flow models of EOR for two different types of interfaces: permeable and impermeable interfaces. Results presented are relevant for the design of smarter interfaces in the available parameter space of capillary number, Peclet number, longitudinal and transverse dispersion, and the viscous profile of the middle layer. The stabilization capacity of each of these two interfaces is explored numerically and conditions for complete dispersive stabilization are identified for each of these two types of interfaces. Key results obtained are (i) three-layer porous media flows with permeable interfaces can be almost completely stabilized by diffusion if the optimal viscous profile is chosen, (ii) flows with impermeable interfaces can also be almost completely stabilized for short time, but become more unstable at later times because diffusion flattens out the basic viscous profile, (iii) diffusion stabilizes short waves more than long waves which leads to a “turning point” Peclet number at which short and long waves have the same growth rate, and (iv) mechanical dispersion further stabilizes flows with permeable interfaces but in some cases has a destabilizing effect for flows with impermeable interfaces, which is a surprising result. These results are then used to give a comparison of the two types of interfaces. It is found that for most values of the flow parameters, permeable interfaces suppress flow instability more than impermeable interfaces.

  12. Atmospheric-dispersion experiments in the near and medium field (Fourth European Community Compaign, Turbigo, Italy, September 1979)

    Energy Technology Data Exchange (ETDEWEB)

    Longhetto, A.: Guillot, P; Anfossi, D.; Bacci, P.; Elisei, G.; Frego, G.; Sandroni, S.

    1982-05-01

    The results of the fourth European experiment on the remote sensing of atmospheric dispersion and boundary layer structure, sponsored by the Commission of the European Communities, are presented. The field experiment was carried out at the Turbigo, Italy, power plant in September 1979 and involved the collection of complete and simultaneous information on atmospheric and pollutant parameters over an extended area. The primary objectives of the experiments were to measure the meteorological conditions under low-wind unstable conditions and apply the results to plume trajectory models, comparing the calculated trajectories with those actually measured in the field, and to measure trajectories and dispersion when plumes from stacks of different height and emission characteristics merge to form a single plume. In addition, the atmospheric-stability categories from different types of measurement were derived and compared, and their applicability to models of dispersion was investigated. The dispersion parameters obtained from measurements with different instruments were compared, and the effectiveness of changing the sulfur content of the power station fuel on reducing ground-level concentrations of SO/sub 2/ were measured.

  13. Optimized dispersion of nanoparticles for biological in vitro and in vivo studies

    Directory of Open Access Journals (Sweden)

    Coester Conrad

    2008-11-01

    Full Text Available Abstract Background The aim of this study was to establish and validate a practical method to disperse nanoparticles in physiological solutions for biological in vitro and in vivo studies. Results TiO2 (rutile dispersions were prepared in distilled water, PBS, or RPMI 1640 cell culture medium. Different ultrasound energies, various dispersion stabilizers (human, bovine, and mouse serum albumin, Tween 80, and mouse serum, various concentrations of stabilizers, and different sequences of preparation steps were applied. The size distribution of dispersed nanoparticles was analyzed by dynamic light scattering and zeta potential was measured using phase analysis light scattering. Nanoparticle size was also verified by transmission electron microscopy. A specific ultrasound energy of 4.2 × 105 kJ/m3 was sufficient to disaggregate TiO2 (rutile nanoparticles, whereas higher energy input did not further improve size reduction. The optimal sequence was first to sonicate the nanoparticles in water, then to add dispersion stabilizers, and finally to add buffered salt solution to the dispersion. The formation of coarse TiO2 (rutile agglomerates in PBS or RPMI was prevented by addition of 1.5 mg/ml of human, bovine or mouse serum albumin, or mouse serum. The required concentration of albumin to stabilize the nanoparticle dispersion depended on the concentration of the nanoparticles in the dispersion. TiO2 (rutile particle dispersions at a concentration lower than 0.2 mg/ml could be stabilized by the addition of 1.5 mg/ml albumin. TiO2 (rutile particle dispersions prepared by this method were stable for up to at least 1 week. This method was suitable for preparing dispersions without coarse agglomerates (average diameter 2 (rutile, ZnO, Ag, SiOx, SWNT, MWNT, and diesel SRM2975 particulate matter. Conclusion The optimized dispersion method presented here appears to be effective and practicable for preparing dispersions of nanoparticles in physiological

  14. Prisoners in their habitat? Generalist dispersal by habitat specialists: a case study in southern water vole (Arvicola sapidus.

    Directory of Open Access Journals (Sweden)

    Alejandro Centeno-Cuadros

    Full Text Available Habitat specialists inhabiting scarce and scattered habitat patches pose interesting questions related to dispersal such as how specialized terrestrial mammals do to colonize distant patches crossing hostile matrices. We assess dispersal patterns of the southern water vole (Arvicola sapidus, a habitat specialist whose habitat patches are distributed through less than 2% of the study area (overall 600 km² and whose populations form a dynamic metapopulational network. We predict that individuals will require a high ability to move through the inhospitable matrix in order to avoid genetic and demographic isolations. Genotypes (N = 142 for 10 microsatellites and sequences of the whole mitochondrial Control Region (N = 47 from seven localities revealed a weak but significant genetic structure partially explained by geographic distance. None of the landscape models had a significant effect on genetic structure over that of the Euclidean distance alone and no evidence for efficient barriers to dispersal was found. Contemporary gene flow was not severely limited for A. sapidus as shown by high migration rates estimates (>10% between non-neighbouring areas. Sex-biased dispersal tests did not support differences in dispersal rates, as shown by similar average axial parent-offspring distances, in close agreement with capture-mark-recapture estimates. As predicted, our results do not support any preferences of the species for specific landscape attributes on their dispersal pathways. Here, we combine field and molecular data to illustrate how a habitat specialist mammal might disperse like a habitat generalist, acquiring specific long-distance dispersal strategies as an adaptation to patchy, naturally fragmented, heterogeneous and unstable habitats.

  15. Methods for studying seed dispersal and its importance for colonization of new sites

    OpenAIRE

    Vlasta, Tomáš

    2015-01-01

    Study of seed dispersal is crucial for understanding of several processes in life of plants and landscape. Seed dispesal is very important for persistence of local populations in fragmented landscape, it plays an important role in succession, it helps to protect plant populations againts loss of genetic variability. We usually recognize several types of seed dispersal depending on vector (dispersal by wind, animals and water.) In nature, it is very common that seed can be independently disper...

  16. A Study of the Effects of Different Urban Wind Models on Dispersion Patterns Using Joint Urban 2003 Data

    Energy Technology Data Exchange (ETDEWEB)

    Gowardhan, A A; Brown, M J

    2012-02-21

    The Quick Urban & Industrial Complex (QUIC) Dispersion Modeling System has been developed to rapidly compute the transport and dispersion of toxic agent releases in the vicinity of buildings. It is composed of a wind solver, an 'urbanized' Lagrangian random-walk model, and a graphical user interface. QUIC has two different wind models: (a) The QUIC-URB wind solver, an empirically-based diagnostic wind model and (b) The QUIC-CFD (RANS) solver, based on the 3D Reynolds-Averaged Navier-Stokes (RANS) equations. In this paper, we discuss the effect of different wind models on dispersion patterns in dense built-up areas. The model-computed wind from the two urban wind models- QUIC-URB and QUIC-CFD are used to drive the dispersion model. The concentration fields are then compared to measurements from the Oklahoma City Joint Urban 2003 field experiment. QUIC produces high-resolution 3-D mean wind and concentration fields around buildings, in addition to deposition on the ground and building surfaces. It has options for different release types, including point, moving point, line, area, and volumetric sources, as well as dense gas, explosive buoyant rise, multi-particle size, bioslurry, and two-phase releases. Other features include indoor infiltration, a pressure solver, outer grid simulations, vegetative canopies, and population exposure calculations. It has been used for biological agent sensor siting in cities, vulnerability assessments for heavier-than-air chemical releases at industrial facilities, and clean-up assessments for radiological dispersal device (RDD) releases in cities (e.g., see Linger et al., 2005; Brown, 2006a, b). QUIC has also been used for dust transport studies (Bowker et al., 2007a) and for the impact of highway sound barriers on the transport and dispersion of vehicle emissions (Bowker et al., 2007b).

  17. Frequency dispersion of the magnetic anisotropy field in metallic magnetic films with the plane anisotropy of electrical conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Zimin, A.B.; Kornev, Y.V.; Sementsova, T.M.; Sidorenkov, V.V.

    1986-07-01

    Presence of the frequency dispersion of the field of induced single axis magnetic anisotropy and the angular position of the axis of easy magnetization in the film plane has been determined in metallic magnetic films with plane anisotropy of electrical conductivity. Theoretical dependences have been obtained which given satisfactory agreement with experimental data for cobalt and permalloy films prepared by sputtering on glass substrates and using the incident molecular beam under an angle with the substrate.

  18. FEM numerical model study of electrosurgical dispersive electrode design parameters.

    Science.gov (United States)

    Pearce, John A

    2015-01-01

    Electrosurgical dispersive electrodes must safely carry the surgical current in monopolar procedures, such as those used in cutting, coagulation and radio frequency ablation (RFA). Of these, RFA represents the most stringent design constraint since ablation currents are often more than 1 to 2 Arms (continuous) for several minutes depending on the size of the lesion desired and local heat transfer conditions at the applicator electrode. This stands in contrast to standard surgical activations, which are intermittent, and usually less than 1 Arms, but for several seconds at a time. Dispersive electrode temperature rise is also critically determined by the sub-surface skin anatomy, thicknesses of the subcutaneous and supra-muscular fat, etc. Currently, we lack fundamental engineering design criteria that provide an estimating framework for preliminary designs of these electrodes. The lack of a fundamental design framework means that a large number of experiments must be conducted in order to establish a reasonable design. Previously, an attempt to correlate maximum temperatures in experimental work with the average current density-time product failed to yield a good match. This paper develops and applies a new measure of an electrode stress parameter that correlates well with both the previous experimental data and with numerical models of other electrode shapes. The finite element method (FEM) model work was calibrated against experimental RF lesions in porcine skin to establish the fundamental principle underlying dispersive electrode performance. The results can be used in preliminary electrode design calculations, experiment series design and performance evaluation.

  19. Preliminary study of a dispersed fringe type sensing system

    Institute of Scientific and Technical Information of China (English)

    Yong Zhang; Gen-Rong Liu; Yue-Fei Wang; Ye-Ping Li; Ya-Jun Zhang; Liang Zhang

    2009-01-01

    Telescopes with large aspherical primary mirrors collect more light and are therefore sought after by astronomers. Instead of using a single large one-piece mirror, smaller segments can be assembled into a useable telescopic primary. Because the seg-ments must fit together to create the effect of a single mirror, segmented optics present unique challenges to the fabrication and testing that are absent in monolithic optics. A dispersed fringe sensor (DFS) using a broadband point source is an efficient method for cophasing and is also highly automated and robust. Unlike the widely adopted Shack-Hartmann Wavefront sensor and curvature wavefront sensor with edge sensors for cali-bration of relative pistons, DFS can estimate the piston between segments by only using the spectrum formed by the transmissive grating's dispersion, and therefore can replace the edge sensors, which are difficult to calibrate. We introduce the theory of the DFS and Dispersed Hartmann Sensor (DHS) for further utilization of the coarse phasing method of DFS. According to the theory, we bring out the preliminary system design of the cophas-ing experimental system based on DFS and DHS which is now established in our institute. Finally, a summary is reached.

  20. General Motors sulfate dispersion experiment - An analysis of the wind field near a road

    Energy Technology Data Exchange (ETDEWEB)

    Chock, D.P.

    1980-06-01

    An investigation of the mean wind field fluctuations observed near a controlled, heavily traveled level roadway is presented. The mean wind field was studied in terms of velocity defects relative to the ambient mean wind the wind fluctuations were analyzed in terms of energy spectra, velocity cross-spectra, excesses of velocity variances, and cross-covariances over their ambient values. The influence of traffic on the ambient wind field extended vertically up to at least 4.5 m above ground, and horizontally to at least 30 m downwind of the road the wind tended to move up as it approached the road and down as it left the road except when the cross-road wind was low. When intense traffic shear existed between the local wind field and an opposing traffic direction, large turbulent energy productions generated large eddies. The large eddies also increased the mixing volume, so that when the ambient wind opposed the traffic generation on the upwind lanes, the pollutant concentration upwind of the road could be higher than that of downwind.

  1. THE NEW YORK MIDTOWN DISPERSION STUDY (MID-05) METEOROLOGICAL DATA REPORT.

    Energy Technology Data Exchange (ETDEWEB)

    REYNOLDS,R.M.; SULLIVAN, T.M.; SMITH, S.; CASSELLA, V.

    2007-01-01

    The New York City midtown dispersion program, MID05, examined atmospheric transport in the deep urban canyons near Rockefeller Center. Little is known about air flow and hazardous gas dispersion under such conditions, since previous urban field experiments have focused on small to medium sized cities with much smaller street canyons and examined response over a much larger area. During August, 2005, a series of six gas tracer tests were conducted and sampling was conducted over a 2 km grid. A critical component of understanding gas movement in these studies is detailed wind and meteorological information in the study zone. To support data interpretation and modeling, several meteorological stations were installed at street level and on roof tops in Manhattan. In addition, meteorological data from airports and other weather instrumentation around New York City were collected. This document describes the meteorological component of the project and provides an outline of data file formats for the different instruments. These data provide enough detail to support highly-resolved computational simulations of gas transport in the study zone.

  2. THE NEW YORK MIDTOWN DISPERSION STUDY (MID-05) METEOROLOGICAL DATA REPORT.

    Energy Technology Data Exchange (ETDEWEB)

    REYNOLDS,R.M.; SULLIVAN, T.M.; SMITH, S.; CASSELLA, V.

    2007-01-01

    The New York City midtown dispersion program, MID05, examined atmospheric transport in the deep urban canyons near Rockefeller Center. Little is known about air flow and hazardous gas dispersion under such conditions, since previous urban field experiments have focused on small to medium sized cities with much smaller street canyons and examined response over a much larger area. During August, 2005, a series of six gas tracer tests were conducted and sampling was conducted over a 2 km grid. A critical component of understanding gas movement in these studies is detailed wind and meteorological information in the study zone. To support data interpretation and modeling, several meteorological stations were installed at street level and on roof tops in Manhattan. In addition, meteorological data from airports and other weather instrumentation around New York City were collected. This document describes the meteorological component of the project and provides an outline of data file formats for the different instruments. These data provide enough detail to support highly-resolved computational simulations of gas transport in the study zone.

  3. Probing the dispersion properties of 1D nanophotonic waveguides with far-field Fourier optics

    DEFF Research Database (Denmark)

    Le Thomas, N.; Jágerská, J.; Houdré, R.

    2008-01-01

    We present an advanced Fourier space imaging technique to probe guided light in nanophotonic structures with an effective numerical aperture of 2.5. This superresolution technique allows us to successfully investigate the dispersive properties of 1D nanowaveguides such as photonic crystal W1...

  4. Contaminant dispersion with personal displacement ventilation, Part I: Base case study

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yue [Department of Civil, Architectural, Environmental Engineering, University of Miami, Coral Gables (United States); Yang, Xudong; Yang, Caiqing [Department of Building Science, Tsinghua University, School of Architecture, Beijing 100084 (China); Srebric, Jelena [Department of Architectural Engineering, The Pennsylvania State University, University Park (United States)

    2009-10-15

    Personal displacement ventilation (PDV) is a new ventilation concept that combines the positive features of displacement ventilation with those of task conditioning or personalized ventilation. PDV is expected to create a micro-environment around an occupant to control the environment individually. In this study, a base PDV case with a contaminant source at different locations was modeled for contaminant dispersion in a full-scale chamber. Computational fluid dynamics (CFD) was used to simulate the indoor airflow and pollutant transport, and the simulation results were validated against the experimental data. The contaminant concentration field for three different contaminant source locations was analyzed. Based on our results, it seems that this kind of PDV system cannot create the expected ''micro-environment'' to avoid the disturbance of the outside airflow. Further studies on how to improve the PDV performance are given in the companion paper. (author)

  5. Study of the stability of polarization mode dispersion in fibre

    Institute of Scientific and Technical Information of China (English)

    付松年; 吴重庆; 刘海涛; 沈平; 董晖

    2003-01-01

    Polarization mode dispersion (PMD) is the ultimate limitation to high bit-rate fibre communication system. The stability of PMD is very important to its measurement and compensation. This paper puts forward a method to measure the stability of PMD by measuring the stability of the state of polarization (SOP) and introduces the conception of time evolution vector (TEV) of SOP. We observe the fact that the regularity of the principal state of polarization changing with time is the same as other SOPs', if we neglect the dependence of TEV on wavelength. We also measure the SOP's stability of some fibres with different lengths, and obtain results of PMD changing with time.

  6. Linear entropy dynamics of the field in the Jaynes-Cummings model with an intensity-dependent coupling in the dispersive approximation

    Institute of Scientific and Technical Information of China (English)

    李春先; 方卯发

    2003-01-01

    We present the linear entropy dynarmics of the field state in the dispersive cavity in the Jaynes-Cummings model with an intensity-dependent coupling in the dispersive approximation, and investigate the influence of dissipation on entanglement between the field and the atoms. We show that the coherence properties of the field are also affected by the cavity when the nonlinear process of the field interacting with the atoms with an intensity-dependent coupling is involved, and find that the dissipation constant, the intensity of the field and the atomic distribution angle have different influence on the coherence properties of the field.

  7. Spectroscopic Studies on Graphenes Dispersed Within Polymeric Matrices

    Science.gov (United States)

    Ferreira, Filipe; Brito, Felipe; Chipara, Dorina; Ajayan, Pullickel; Francisco, Wesley; Chipara, Cristian; Simonetti, Evelyn; Cartwright, Charles; Cividanes, Luciana; Hinthorne, James; Thim, Gilmar; Vajtai, Robert; Chipara, Mircea; Instituto Tecnológico de Aeronáutica Collaboration; University of Texas Pan American Collaboration; Rice University Collaboration

    Graphenes have been dispersed within various polymeric matrices (polyethylene, polyethylene oxide, polystyrene, and epoxy resins). Some have been used as purchased (pristine and functionalized graphene platelets from Cheap Tubes). Pristine and functionalized graphene oxides have been obtained in laboratory according to W. Hummers, R. Offeman, (''Preparation of Graphitic Oxide''. J Am Chem Soc 80, 6, 1339, 1958) and by original functionalization processes. All these samples were investigated by Raman spectroscopy using a Renishaw InVia spectrometer operating at 532 and 785 nm. Additional information has been obtained by Wide Angle X-Ray Scattering using a Bruker Discover 8 spectrometer. Raman spectra have been fitted by a convolution of modified Breit-Wigner-Fano line shapes and the main parameters (position, intensity, width, asymmetry factor) of each line are discussed. The research aims to a better identification of graphene related nanostructures isolated or dispersed within polymeric matrices by Raman spectroscopy. FAPESP (Grant 2013/20218-0) and CNPq (Grant 141197/2014 5) for financial support, LAS/INPE and LEFE/UNESP for collaboration.

  8. Sensitivity model study of regional mercury dispersion in the atmosphere

    Science.gov (United States)

    Gencarelli, Christian N.; Bieser, Johannes; Carbone, Francesco; De Simone, Francesco; Hedgecock, Ian M.; Matthias, Volker; Travnikov, Oleg; Yang, Xin; Pirrone, Nicola

    2017-01-01

    Atmospheric deposition is the most important pathway by which Hg reaches marine ecosystems, where it can be methylated and enter the base of food chain. The deposition, transport and chemical interactions of atmospheric Hg have been simulated over Europe for the year 2013 in the framework of the Global Mercury Observation System (GMOS) project, performing 14 different model sensitivity tests using two high-resolution three-dimensional chemical transport models (CTMs), varying the anthropogenic emission datasets, atmospheric Br input fields, Hg oxidation schemes and modelling domain boundary condition input. Sensitivity simulation results were compared with observations from 28 monitoring sites in Europe to assess model performance and particularly to analyse the influence of anthropogenic emission speciation and the Hg0(g) atmospheric oxidation mechanism. The contribution of anthropogenic Hg emissions, their speciation and vertical distribution are crucial to the simulated concentration and deposition fields, as is also the choice of Hg0(g) oxidation pathway. The areas most sensitive to changes in Hg emission speciation and the emission vertical distribution are those near major sources, but also the Aegean and the Black seas, the English Channel, the Skagerrak Strait and the northern German coast. Considerable influence was found also evident over the Mediterranean, the North Sea and Baltic Sea and some influence is seen over continental Europe, while this difference is least over the north-western part of the modelling domain, which includes the Norwegian Sea and Iceland. The Br oxidation pathway produces more HgII(g) in the lower model levels, but overall wet deposition is lower in comparison to the simulations which employ an O3 / OH oxidation mechanism. The necessity to perform continuous measurements of speciated Hg and to investigate the local impacts of Hg emissions and deposition, as well as interactions dependent on land use and vegetation, forests, peat

  9. Transmission Experiment of 80-Gbit/s-Based WDM Signals Using an OPGW in the Field and In-service Chromatic Dispersion Monitering through Envelope Modulated WDM Signals

    Science.gov (United States)

    Yamashita, Ikuo; Oro, Kyoichi; Seikai, Shigeyuki

    A field experiment on transmission of 80-Gbit/s-based wavelength division multiplexing (WDM) signals is successfully carried out. In order to keep good transmission quality, technique of an in-service dispersion monitoring and an adaptive control of the chromatic dispersion are proposed. Difference of the propagation delay between channels caused by the chromatic dispersion of the transmission line is detected using signals superimposed on the envelope of the WDM pulses. Dispersion alteration of the transmission line is estimated from the measured delay in real-time. Accuracy of the method is clarified through a transmission experiment using wound fibers in an oven changing their temperature. The field experiment on 80Gbit/s × 8WDM transmission using an OPGW with 60km × 2spans is carried out and fine BER performances are obtained in all channels. Transmission properties are found to be stable owing to the dispersion control techniques throughout the field trial.

  10. Long-distance aerial dispersal modelling of Culicoides biting midges: case studies of incursions into Australia.

    Science.gov (United States)

    Eagles, Debbie; Melville, Lorna; Weir, Richard; Davis, Steven; Bellis, Glenn; Zalucki, Myron P; Walker, Peter J; Durr, Peter A

    2014-06-19

    Previous studies investigating long-distance, wind-borne dispersal of Culicoides have utilised outbreaks of clinical disease (passive surveillance) to assess the relationship between incursion and dispersal event. In this study, species of exotic Culicoides and isolates of novel bluetongue viruses, collected as part of an active arbovirus surveillance program, were used for the first time to assess dispersal into an endemic region. A plausible dispersal event was determined for five of the six cases examined. These include exotic Culicoides specimens for which a possible dispersal event was identified within the range of two days--three weeks prior to their collection and novel bluetongue viruses for which a dispersal event was identified between one week and two months prior to their detection in cattle. The source location varied, but ranged from Lombok, in eastern Indonesia, to Timor-Leste and southern Papua New Guinea. Where bluetongue virus is endemic, the concurrent use of an atmospheric dispersal model alongside existing arbovirus and Culicoides surveillance may help guide the strategic use of limited surveillance resources as well as contribute to continued model validation and refinement. Further, the value of active surveillance systems in evaluating models for long-distance dispersal is highlighted, particularly in endemic regions where knowledge of background virus and vector status is beneficial.

  11. Fourth field experiment on atmospheric dispersion around the isolated hill Sophienhoehe in September 1989. Methods - experiments - data bank

    Energy Technology Data Exchange (ETDEWEB)

    Zeuner, G. [ed.; Heinemann, K. [ed.

    1993-05-01

    In order to establish a data bank for the validation of advanced dispersion models, comprehensive meteorological measurements and dispersion experiments in a complex terrain with a well measured topography were carried out. These investigations became possible in cooperation with several external groups and with the financial support of the `Bundesminister fuer Umwelt, Naturschutz und Reaktorsicherheit`. In this report the methods, experiments and results (data bank) of the fourth field experiment are described. (orig.) [Deutsch] Um eine Datenbasis fuer die Validierung von fortgeschrittenen Ausbreitungsmodellen zur Verfuegung zu stellen, wurden umfangreiche meteorologische Messungen und Ausbreitungsexperimente in einem gut vermessenen nicht ebenem Gelaende durchgefuehrt. Diese Untersuchungen wurden durch die Zusammenarbeit mit verschiedenen externen Gruppen und die finanzielle Unterstuetzung des Bundesministers fuer Umwelt, Naturschutz und Reaktorsicherheit ermoeglicht. In diesem Bericht sind die Methoden, die Experimente und die Ergebnisse der vierten Messkampagne zusammengestellt. (orig.)

  12. Effects of confinement and external fields on structure and transport in colloidal dispersions in reduced dimensionality.

    Science.gov (United States)

    Wilms, D; Deutschländer, S; Siems, U; Franzrahe, K; Henseler, P; Keim, P; Schwierz, N; Virnau, P; Binder, K; Maret, G; Nielaba, P

    2012-11-21

    In this work, we focus on low-dimensional colloidal model systems, via simulation studies and also some complementary experiments, in order to elucidate the interplay between phase behavior, geometric structures and transport properties. In particular, we try to investigate the (nonlinear!) response of these very soft colloidal systems to various perturbations: uniform and uniaxial pressure, laser fields, shear due to moving boundaries and randomly quenched disorder. We study ordering phenomena on surfaces or in monolayers by Monte Carlo computer simulations of binary hard-disk mixtures, the influence of a substrate being modeled by an external potential. Weak external fields allow a controlled tuning of the miscibility of the mixture. We discuss the laser induced de-mixing for the three different possible couplings to the external potential. The structural behavior of hard spheres interacting with repulsive screened Coulomb or dipolar interaction in 2D and 3D narrow constrictions is investigated using Brownian dynamics simulations. Due to misfits between multiples of the lattice parameter and the channel widths, a variety of ordered and disordered lattice structures have been observed. The resulting local lattice structures and defect probabilities are studied for various cross sections. The influence of a self-organized order within the system is reflected in the velocity of the particles and their diffusive behavior. Additionally, in an experimental system of dipolar colloidal particles confined by gravity on a solid substrate we investigate the effect of pinning on the dynamics of a two-dimensional colloidal liquid. This work contains sections reviewing previous work by the authors as well as new, unpublished results. Among the latter are detailed studies of the phase boundaries of the de-mixing regime in binary systems in external light fields, configurations for shear induced effects at structured walls, studies on the effect of confinement on the structures

  13. Studies of the developmental toxicity of polycarboxylate dispersing agents.

    Science.gov (United States)

    Nolen, G A; Monroe, A; Hassall, C D; Iavicoli, J; Jamieson, R A; Daston, G P

    1989-06-01

    Three linear polycarboxylate compounds, two linear polyacrylates (90,000 MW and 4,500 MW) and one linear polyacrylate-maleate copolymer (12,000 MW), were tested for their teratogenic potential in female Sprague Dawley rats. These polymers, which were tested as sodium salts, are used as dispersing agents in detergent formulations at levels of 1-5%. All compounds were administered by gavage during organogenesis (days 6-15 of pregnancy). No adverse effects on development were seen with any of the three compounds at any of the doses tested. The highest dose, and therefore the minimum no-effect dose, for the three linear polymers was 1125 mg/kg/day for the 90,000 MW polyacrylate, 3000 mg/kg/day for the 4,500 MW polyacrylate, and 6670 mg/kg/day for the polyacrylate-maleate copolymer. Based on these data, these compounds are not developmentally toxic, even at very high dose levels.

  14. [Study on solid dispersion of precipitated calcium carbonate-based oleanolic acid].

    Science.gov (United States)

    Yan, Hong-mei; Zhang, Zhen-hai; Jia, Xiao-bin; Jiang, Yan-rong; Sun, E

    2015-05-01

    Oleanolic acid-precipitated calcium carbonate solid dispersion was prepared by using solvent evaporation method. The microscopic structure and physicochemical properties of solid dispersion were analyzed using differential scanning calorimetry and scanning electron microscopy (SEM). And its in vitro release also was investigated. The properties of the precipitated calcium carbonate was studied which was as a carrier of oleanolic acid solid dispersion. Differential scanning calorimetry analysis suggested that oleanolic acid may be present in solid dispersion as amorphous substance. The in vitro release determination results of oleanolic acid-precipitated calcium carbonate (1: 5) solid dispersion showed accumulated dissolution rate of.oleanolic acid was up to 90% at 45 min. Accelerating experiment showed that content and in vitro dissolution of oleanolic acid solid dispersion did not change after storing over 6 months. The results indicated that in vitro dissolution of oleanolic acid was improved greatly by the solid dispersion with precipitated calcium carbonate as a carrier. The solid dispersion is a stabilizing system which has actual applied value.

  15. Characterization and Pharmacokinetic Study of Aprepitant Solid Dispersions with Soluplus®

    Directory of Open Access Journals (Sweden)

    Jinwen Liu

    2015-06-01

    Full Text Available Solid dispersions are a useful approach to improve the dissolution rate and bioavailability of poorly water-soluble active pharmaceutical ingredients (APIs. The aim of this study was to improve the physicochemical properties and bioavailability of a poorly water-soluble aprepitant by preparation of solid dispersions. The solid dispersions were characterized by dissolution, FTIR, XRPD, DSC, SEM and pharmacokinetic studies in rats. The dissolution rate of the aprepitant was significantly increased by solid dispersions, and XRD, DSC, and SEM analysis indicated that the aprepitant existed in an amorphous form within the solid dispersions. The result of dissolution study showed that the dissolution rate of SDs was nearly five-fold faster than aprepitant. FTIR spectrometry suggested the presence of intermolecular hydrogen bonds between the aprepitant and polymer. Pharmacokinetic studies in rats indicated that the degree drug absorption was comparable with that of Emend®. Aprepitant exists in an amorphous state in solid dispersions and the solid dispersions can markedly improve the dissolution and oral bioavailability of the aprepitant. The AUC0–t of the SDs was 2.4-fold that of the aprepitant. In addition, the method and its associated techniques are very easy to carry out.

  16. Characterization and Pharmacokinetic Study of Aprepitant Solid Dispersions with Soluplus®.

    Science.gov (United States)

    Liu, Jinwen; Zou, Meijuan; Piao, Hongyu; Liu, Yi; Tang, Bo; Gao, Ying; Ma, Ning; Cheng, Gang

    2015-06-19

    Solid dispersions are a useful approach to improve the dissolution rate and bioavailability of poorly water-soluble active pharmaceutical ingredients (APIs). The aim of this study was to improve the physicochemical properties and bioavailability of a poorly water-soluble aprepitant by preparation of solid dispersions. The solid dispersions were characterized by dissolution, FTIR, XRPD, DSC, SEM and pharmacokinetic studies in rats. The dissolution rate of the aprepitant was significantly increased by solid dispersions, and XRD, DSC, and SEM analysis indicated that the aprepitant existed in an amorphous form within the solid dispersions. The result of dissolution study showed that the dissolution rate of SDs was nearly five-fold faster than aprepitant. FTIR spectrometry suggested the presence of intermolecular hydrogen bonds between the aprepitant and polymer. Pharmacokinetic studies in rats indicated that the degree drug absorption was comparable with that of Emend®. Aprepitant exists in an amorphous state in solid dispersions and the solid dispersions can markedly improve the dissolution and oral bioavailability of the aprepitant. The AUC0-t of the SDs was 2.4-fold that of the aprepitant. In addition, the method and its associated techniques are very easy to carry out.

  17. Influence of the gravitational field on the quantum-nondemolition measurement of atomic momentum in the dispersive Jaynes-Cummings model

    Energy Technology Data Exchange (ETDEWEB)

    Mohammadi, M [Physics Department, Science and Research Campus Azad University of Tehran, Tehran (Iran, Islamic Republic of); Naderi, M H [Quantum Optics Group, University of Isfahan, Isfahan (Iran, Islamic Republic of); Soltanolkotabi, M [Quantum Optics Group, University of Isfahan, Isfahan (Iran, Islamic Republic of)

    2006-09-01

    We present a theoretical scheme based on an su(2) dynamical algebraic structure to investigate the influence of a homogeneous gravitational field on the quantum-nondemolition measurement of atomic momentum in the dispersive Jaynes-Cummings model. In the dispersive Jaynes-Cummings model, when detuning is large and the atomic motion is in a propagating light wave, we consider a two-level atom interacting with the quantized cavity field in the presence of a homogeneous gravitational field. We derive an effective Hamiltonian describing the dispersive atom-field interaction in the presence of the gravitational field. We investigate the influence of the gravitational field on both the momentum filter and momentum distribution. Particularly, we find that the gravitational field decreases both the tooth spacing of momentum and the tooth width of momentum.

  18. Synthesis, characterization and studies on magneto-viscous properties of magnetite dispersed water based nanofluids

    Science.gov (United States)

    Paul, Gayatri; Kumar Das, Prasanta; Manna, Indranil

    2016-04-01

    Magnetic nanofluids, commonly known as ferrofluids, containing surfactant coated magnetite nanoparticles (having mean size ∼11 nm) uniformly dispersed in water are synthesized by chemical co-precipitation method. The rheological properties of magnetic nanofluid at different concentrations of nanoparticle loading have been investigated by varying different parameters including the magnetic field strength. Shear thinning is observed in the non-Newtonian magnetic nanofluids under the application of magnetic field. The observed increase in yield stress (calculated by fitting the Herschel and Bulkley model) with the applied magnetic field and concentration of dispersed nanoparticles confirm the formation of large aggregates that restrict or prohibit the flow characteristics of the otherwise Newtonian magnetic nanofluid. The hysteresis observed during the application and withdrawal of magnetic field suggests that the chain or column like structures fail to relax within the allowed measurement time interval.

  19. Characterization and solubility study of norfloxacin-polyethylene glycol, polyvinylpyrrolidone and carbopol 974p solid dispersions.

    Science.gov (United States)

    Gorajana, Adinarayana; Kit, Wong W; Dua, Kamal

    2015-01-01

    Norfloxacin has a low aqueous solubility which leads to poor dissolution. Keeping this fact in mind the purpose of the present study is to formulate and evaluate norfloxacin solid dispersion. Solid dispersions were prepared using hydrophilic carriers like polyethylene glycol (PEG) 4000, polyvinylpyrrolidone (PVP) k30 and carbopol 974pNF (CP) in various ratios using solvent evaporation technique. These formulations were evaluated using solubility studies, dissolution studies; Fourier transmitted infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetery (DSC). The influence of polymer type and drug to polymer ratio on the solubility and dissolution rate of norfloxacin was also evaluated. FTIR analysis showed no interaction of all three polymers with norfloxacin. The results from XRD and DSC analyses of the solid dispersion preparations showed that norfloxacin existsin its amorphous form. Among the Norfloxacin: PEG solid dispersions, Norfloxacin: PEG 1:14 ratio showed the highest dissolution rate at pH 6.8. For norfloxacin: PVP solid dispersions, norfloxacin: PVP 1:10 ratio showed the highest dissolution rate at pH 6.8. For Norfloxacin: CP solid dispersions, norfloxacin: P 1:2 ratio showed the highest dissolution rate at pH 6.8. The solid dispersion of norfloxacin with polyethylene glycol (PEG) 4000, polyvinylpyrrolidone (PVP) k30 and carbopol 974p NF (CP), lends an ample credence for better therapeutic efficacy.

  20. Effects of spatial dispersion in near-field radiative heat transfer between two parallel metallic surfaces

    CERN Document Server

    Chapuis, Pierre-Olivier; Henkel, Carsten; Joulain, Karl; Greffet, Jean-Jacques

    2008-01-01

    We study the heat transfer between two parallel metallic semi-infinite media with a gap in the nanometer-scale range. We show that the near-field radiative heat flux saturates at distances smaller than the metal skin depth when using a local dielectric constant and investigate the origin of this effect. The effect of non-local corrections is analysed using the Lindhard-Mermin and Boltzmann-Mermin models. We find that local and non-local models yield the same heat fluxes for gaps larger than 2 nm. Finally, we explain the saturation observed in a recent experiment as a manifestation of the skin depth and show that heat is mainly dissipated by eddy currents in metallic bodies.

  1. Dispersion of rotation of polarization plane and circular dichroism for alkaline atoms in intense radiation fields

    Science.gov (United States)

    Karagodova, Tamara Y.; Kuptsova, Anna V.

    1998-10-01

    The method of computer simulations on nonlinear resonant magneto-optical effects developed for real multi-level atoms in the two laser fields of arbitrary intensity and external magnetic field is applied for the polarization effects of different types calculations and investigations of the dependence of the characteristics of these effects on magnetic field strength, intensities, polarizations and detunings of laser fields for alkaline atoms. The essence of the method consists in simulations and analysis of the plots of dependence of quasienergies on parameters (detunings and intensities of radiation fields, magnetic field strength), which are obtained with the help of sorting subprogram, and selection of suitable algorithms for calculations of characteristics of nonlinear resonant magneto-optical effects. One-photon and two photon resonant effects are investigated for wide range of magnetic field strength from Zeeman to Paschen Back effects. Some new features in the spectra of rotation of plane of polarization and circular dicohroizm of different types are predicted. The results show the agreement with known experiments. Such calculations of nonlinear resonant magneto-optical effects in the intense laser fields resonant to adjacent transitions and magnetic field show the opportunity of investigation the modifications of electronic structure due to intense radiation fields and strong external magnetic field in atomic gases and also may be used for the treatment of new methods of phase-polarization selection of modes of tunable lasers.

  2. How does the functional diversity of frugivorous birds shape the spatial pattern of seed dispersal? A case study in a relict plant species.

    Science.gov (United States)

    Lavabre, Jessica E; Gilarranz, Luis J; Fortuna, Miguel A; Bascompte, Jordi

    2016-05-19

    Genetic markers used in combination with network analysis can characterize the fine spatial pattern of seed dispersal and assess the differential contribution of dispersers. As a case study, we focus on the seed dispersal service provided by a small guild of frugivorous birds to the common yew, Taxus baccata L., in southern Spain. We build the spatial networks of seed dispersal events between trees and seed-plots within the studied population-local network-and the spatial network that includes all dispersal events-regional network. Such networks are structured in well-defined modules, i.e. groups of tightly connected mother trees and seed-plots. Neither geographical distance, nor microhabitat type explained this modular structure, but when long-distance dispersal events are incorporated in the network it shows a relative increase in overall modularity. Independent field observations suggested the co-occurrence of two complementary groups, short- and long-distance dispersers, mostly contributing to the local and regional seed rain, respectively. The main long-distance disperser at our site, Turdus viscivorus, preferentially visits the most productive trees, thus shaping the seed rain at the landscape scale and affecting the local modular organization. We end by discussing how DNA barcoding could serve to better quantify the role of functional diversity. © 2016 The Authors.

  3. How does the functional diversity of frugivorous birds shape the spatial pattern of seed dispersal? A case study in a relict plant species

    Science.gov (United States)

    Gilarranz, Luis J.; Fortuna, Miguel A.; Bascompte, Jordi

    2016-01-01

    Genetic markers used in combination with network analysis can characterize the fine spatial pattern of seed dispersal and assess the differential contribution of dispersers. As a case study, we focus on the seed dispersal service provided by a small guild of frugivorous birds to the common yew, Taxus baccata L., in southern Spain. We build the spatial networks of seed dispersal events between trees and seed-plots within the studied population—local network—and the spatial network that includes all dispersal events—regional network. Such networks are structured in well-defined modules, i.e. groups of tightly connected mother trees and seed-plots. Neither geographical distance, nor microhabitat type explained this modular structure, but when long-distance dispersal events are incorporated in the network it shows a relative increase in overall modularity. Independent field observations suggested the co-occurrence of two complementary groups, short- and long-distance dispersers, mostly contributing to the local and regional seed rain, respectively. The main long-distance disperser at our site, Turdus viscivorus, preferentially visits the most productive trees, thus shaping the seed rain at the landscape scale and affecting the local modular organization. We end by discussing how DNA barcoding could serve to better quantify the role of functional diversity. PMID:27114581

  4. Sensitive determination of sertraline by capillary electrophoresis with dispersive liquid-liquid microextraction and field-amplified sample stacking.

    Science.gov (United States)

    Huang, Shiou-Wen; Hsieh, Ming-Mu; Chang, Sarah Y

    2012-11-15

    A novel method for the determination of sertraline using dispersive liquid-liquid microextraction (DLLME) coupled with capillary electrophoresis (CE) was developed. Acetone and dichloromethane were used as the disperser solvent and extraction solvent, respectively. A mixture of the extraction and disperser solvents was rapidly injected into a 1.0 mL aqueous sample to form a cloudy solution. After the extraction, sertraline was analyzed using CE that was equipped with UV detection. A 74-fold improvement in the sensitivity was observed when DLLME was used to extract sertraline. Since the DLLME extract residue was redissolved with 5 μL of water that contained 20% methanol, the detection sensitivity was further enhanced through the use of field-amplified sample stacking (FASS). A 11-fold improvement in the sensitivity was obtained when FASS was used to on-line concentrate sertraline. Under optimal extraction and stacking conditions, the calibration curve, which ranged from 0.01 to 1 μM was observed to be linear. The limit of detection (LOD) at a signal-to-noise ratio of 3 was 2.5 nM for sertraline. An approximately 814-fold improvement in the sensitivity was observed for sertraline compare with injection of standard solution without the DLLME and FASS procedures. This developed method was successfully applied to the determination of sertraline in human urine samples.

  5. Aspects of the competition between atom-field and field-environment couplings under the influence of an external source in dispersive Jaynes-Cummings model

    CERN Document Server

    De Faria, J G P

    2002-01-01

    We give a fully description of the dynamics of an atom dispersively coupled to a field mode in a dissipative environment fed by an external source. The competition between the unitary atom-field (which leads to entanglement) and the dissipative field-environment couplings are investigated in detail. We find the time evolution of the global atom-field system for any initial state and we show that atom-field steady state is at most classically correlated. For an initial state chosen, we evaluate the purity loss of the global system and of atomic and field subsystems as a function of time. We find that the source will tend to compensate for the dissipation of the field intensity and to accelerate decoherence of the global and atomic states. Moreover, we show that the degree of entanglement of the atom-field state, for the particular initial state chosen, can be completely quantified by concurrence. Analytical expression for time evolution of the concurrence is given.

  6. Comparative Study Between Dispersive and Non-Dispersive Dielectric Permittivity in Spectral Remittances of Chiral Sculptured Zirconia Thin Films

    CERN Document Server

    Babaei, Ferydon; 10.1016/j.optcom.2008.02.012

    2010-01-01

    The transmission and reflection spectra from a right-handed chiral sculptured zirconia thin film are calculated using the piecewise homogeneity approximation method and the Bruggeman homogenization formalism by considering that the propagation of both dispersive and non-dispersive dielectric function occurs for axial and non-axial states. The comparison of spectral results shows that the dispersion of the dielectric function has a considerable effect on the results. In axial excitation of cross-polarized reflectances and co-polarized transmittances the dispersion effect becomes more pronounced at wavelengths further away from the homogenization wavelength. This is also true in case of non-axial excitation of circular transmittances, while there are considerable differences for cross-polarized reflectances where (wavelength) the first Bragg peak occurs. At wavelengths in the vicinity of the homogenization wavelength the dispersion effect of the dielectric function in becomes more significant.

  7. Synthesis, characterization and studies on magneto-viscous properties of magnetite dispersed water based nanofluids

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Gayatri [Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, West Bengal (India); Kumar Das, Prasanta, E-mail: pkd@mech.iitkgp.ernet.in [Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, West Bengal (India); Manna, Indranil [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Kharagpur, West Bengal (India); Department of Materials Science and Engineering, Indian Institute of Technology Kanpur, Uttar Pradesh (India)

    2016-04-15

    Magnetic nanofluids, commonly known as ferrofluids, containing surfactant coated magnetite nanoparticles (having mean size ∼11 nm) uniformly dispersed in water are synthesized by chemical co-precipitation method. The rheological properties of magnetic nanofluid at different concentrations of nanoparticle loading have been investigated by varying different parameters including the magnetic field strength. Shear thinning is observed in the non-Newtonian magnetic nanofluids under the application of magnetic field. The observed increase in yield stress (calculated by fitting the Herschel and Bulkley model) with the applied magnetic field and concentration of dispersed nanoparticles confirm the formation of large aggregates that restrict or prohibit the flow characteristics of the otherwise Newtonian magnetic nanofluid. The hysteresis observed during the application and withdrawal of magnetic field suggests that the chain or column like structures fail to relax within the allowed measurement time interval. - Highlights: • Magnetite dispersed water nanofluids are prepared by chemical precipitation method. • Effect of shear and magnetic field on the viscosity of nanofluids are investigated. • Applied field enhances the viscosity by several times and causes shear thinning. • Chain-like or columnar aggregates of nanoparticles formed increases the viscosity.

  8. Studies on Dissolution Enhancement of Prednisolone, a Poorly Water-Soluble Drug by Solid Dispersion Technique

    Directory of Open Access Journals (Sweden)

    Parvin Zakeri-Milani

    2011-06-01

    Full Text Available Introduction: Prednisolone is a class II substance according to the Biopharmaceutics Classification System. It is a poorly water soluble agent. The aim of the present study was to improve dissolution rate of a poorly water-soluble drug, prednisolone, by a solid dispersion technique. Methods: Solid dispersion of prednisolone was prepared with PEG 6000 or different carbohydrates such as lactose and dextrin with various ratios of the drug to carrier i.e., 1:10, 1:20 and 1:40. Solid dispersions were prepared by coevaporation method. The evaluation of the properties of the dispersions was performed using dissolution studies, Fourier-transform infrared spectroscopy and x-ray powder diffractometery. Results: The results indicated that lactose is suitable carriers to enhance the in vitro dissolution rate of prednisolone. The data from the x-ray diffraction showed that the drug was still detectable in its solid state in all solid dispersions except solid dispersions prepared by dextrin as carrier. The results from infrared spectroscopy showed no well-defined drug–carrier interactions for coevaporates. Conclusion: Solid dispersion of a poorly water-soluble drug, prednisolone may alleviate the problems of delayed and inconsistent rate of dissolution of the drug.

  9. An SPH Study of Molten Matte-Slag Dispersion

    Science.gov (United States)

    Natsui, Shungo; Nashimoto, Ryota; Kumagai, Takehiko; Kikuchi, Tatsuya; Suzuki, Ryosuke O.

    2017-02-01

    The transient behaviors of two immiscible liquids, namely, molten matte and molten slag, with a high interfacial tension were investigated using the smoothed particle hydrodynamics model. Numerical simulations were performed using a discrete-element-type method that could track the movement of both the continuous liquid phase and the dispersed one directly. Numerical simulations were also performed for conditions corresponding to different interfacial tension and density values. Further, the predicted topological changes as well as the relationship between the physical properties and the droplet size distribution were investigated. It was found that, with an increase in the interfacial tension, the large droplets formed aggregate quickly with the bulk phase, owing to the buoyancy force. It was also found that the absolute value of the interfacial tension determines the interfacial area, suggesting that it also affects the droplet settling time. As such, we can conclude that the nonlinearly changed interface shape can easily become unstable as a result of only a slight change in the curvature.

  10. An SPH Study of Molten Matte-Slag Dispersion

    Science.gov (United States)

    Natsui, Shungo; Nashimoto, Ryota; Kumagai, Takehiko; Kikuchi, Tatsuya; Suzuki, Ryosuke O.

    2017-06-01

    The transient behaviors of two immiscible liquids, namely, molten matte and molten slag, with a high interfacial tension were investigated using the smoothed particle hydrodynamics model. Numerical simulations were performed using a discrete-element-type method that could track the movement of both the continuous liquid phase and the dispersed one directly. Numerical simulations were also performed for conditions corresponding to different interfacial tension and density values. Further, the predicted topological changes as well as the relationship between the physical properties and the droplet size distribution were investigated. It was found that, with an increase in the interfacial tension, the large droplets formed aggregate quickly with the bulk phase, owing to the buoyancy force. It was also found that the absolute value of the interfacial tension determines the interfacial area, suggesting that it also affects the droplet settling time. As such, we can conclude that the nonlinearly changed interface shape can easily become unstable as a result of only a slight change in the curvature.

  11. Gellan gum capped silver nanoparticle dispersions and hydrogels: cytotoxicity and in vitro diffusion studies

    Science.gov (United States)

    Dhar, S.; Murawala, P.; Shiras, A.; Pokharkar, V.; Prasad, B. L. V.

    2012-01-01

    The preparation of highly stable water dispersions of silver nanoparticles using the naturally available gellan gum as a reducing and capping agent is reported. Further, exploiting the gel formation characteristic of gellan gum silver nanoparticle incorporated gels have also been prepared. The optical properties, morphology, zeta potential and long-term stability of the synthesized silver nanoparticles were investigated. The superior stability of the gellan gum-silver nanoparticle dispersions against pH variation and electrolyte addition is revealed. Finally, we studied the cytotoxicity of AgNP dispersions in mouse embryonic fibroblast cells (NIH3T3) and also evaluated the in vitro diffusion of AgNP dispersions/gels across rat skin.The preparation of highly stable water dispersions of silver nanoparticles using the naturally available gellan gum as a reducing and capping agent is reported. Further, exploiting the gel formation characteristic of gellan gum silver nanoparticle incorporated gels have also been prepared. The optical properties, morphology, zeta potential and long-term stability of the synthesized silver nanoparticles were investigated. The superior stability of the gellan gum-silver nanoparticle dispersions against pH variation and electrolyte addition is revealed. Finally, we studied the cytotoxicity of AgNP dispersions in mouse embryonic fibroblast cells (NIH3T3) and also evaluated the in vitro diffusion of AgNP dispersions/gels across rat skin. Electronic supplementary information (ESI) available: Time dependent UV-Vis spectral studies revealing the stability of AgNP dispersions and agar plate images displaying the antibacterial activity of AgNPs. See DOI: 10.1039/c1nr10957j

  12. Faraday rotation dispersion measurements of diamagnetic organic liquids and simultaneous determination of natural optical rotatory dispersion using a pulsed magnetic field.

    Science.gov (United States)

    Suwa, Masayori; Miyamoto, Kayoko; Watarai, Hitoshi

    2013-01-01

    We constructed an apparatus to measure the wavelength dispersion of the Faraday rotation in the visible region, and determined the Verdet constants of diamagnetic organic liquids, including aliphatic compounds, benzene derivatives, and naphthalene derivatives. These three groups were easily distinguished by the magnitudes of their Verdet constants. Based on the theory developed by Serber, we determined the enhancing effect of π*←π transitions on the visible-light Faraday rotation angles observed for aromatic compounds. Furthermore, we propose a novel approach for simultaneously observing Faraday rotation dispersion and natural optical rotatory dispersion.

  13. NO to NO2 conversion rate analysis and implications for dispersion model chemistry methods using Las Vegas, Nevada near-road field measurements

    Science.gov (United States)

    Kimbrough, Sue; Chris Owen, R.; Snyder, Michelle; Richmond-Bryant, Jennifer

    2017-09-01

    The nitrogen dioxide/oxides of nitrogen (NO2/NOX) ratio is an important surrogate for NO to NO2 chemistry in dispersion models when estimating NOX impacts in a near-road environment. Existing dispersion models use different techniques and assumptions to represent NO to NO2 conversion and do not fully characterize all of the important atmospheric chemical and mechanical processes. Thus, ;real-world; ambient measurements must be analyzed to assess the behavior of NO2/NOX ratios near roadways. An examination of NO2/NOX ratio data from a field study conducted in Las Vegas, Nevada (NV), from mid-December, 2008 through mid-December, 2009 provides insights into the appropriateness of assumptions about the NO2/NOX ratio included in dispersion models. Data analysis indicates multiple factors affect the downwind NO2/NOX ratio. These include spatial gradient, background ozone (O3), source emissions of NO and NO2, and background NO2/NOX ratio. Analysis of the NO2/NOX ratio spatial gradient indicates that under high O3 conditions, the change in the ratio is fairly constant once a certain O3 threshold (≥30 ppb) is reached. However, under low O3 conditions (chemistry is driving the NO2/NOX ratios whereas under low O3 conditions, atmospheric mixing is the driving factor.

  14. Mathematical approximations for the amplitude of the fundamental mode field (LP01) of a dispersion shifted fiber at six wavelengths

    Science.gov (United States)

    Lamarche, Louis

    2009-06-01

    Hydro-Quebec optical network includes more than 5,000 km of optical ground wires [1] (OPGW) using dispersion shifted fibers (SMF-DSTM) [2]-[3]. This paper provides a model of the index profile for a typical reference fiber and the mathematical approximations of the amplitude of the LP01 mode at six important wavelengths (1.31, 1.41, 1.45, 1.48, 1.55, 1.625 μm). The fiber model has a triangular core and a quadratic ring shape. The weakly guided mode is obtained using the variational principle [4] implemented using an algorithm based on a Laguerre-Gauss-Bessel approximation of the field [5]. We modeled the wavelength dependence of the index of refraction of germanium doped silica using an experimental formula [6]. A comprehensive algorithm was developed to compute the normalized damping factor W and the normalized propagation constant U in the variational algorithm. The mode field diameter, group velocity and chromatic dispersion were also computed at the above wavelengths.

  15. Sediment transport and dispersal pathways in the Lower Cretaceous sands of the Britannia Field, derived from magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Hailwood, E.; Ding, F. [Core Magnetics, Sedbergh (United Kingdom)

    2000-11-01

    Sediment transport directions and dispersal patterns in the Lower Cretaceous sands of the Britannia Field have been investigated, using magnetic anisotropy and palaeomagnetic core re-orientation methods, to aid understanding of the geometry and architecture of the reservoir sand units. The results indicate that sands were sourced mainly from the north. This applies both to the massive sand bodies with lobate geometry in the lower reservoir zones in the western part of the field and to the laminated slurried beds with tabular geometry in the upper zones in the eastern part. Thus, sediment in this part of the Outer Moray Firth play appears to have been derived largely from a discrete point source to the north rather than from axial flow along the Witch Ground Graben. (Author)

  16. Optimized method for preparation of TiO2 nanoparticles dispersion for biological study.

    Science.gov (United States)

    Zhang, Xiaoqiang; Yin, Lihong; Tang, Meng; Pu, Yuepu

    2010-08-01

    The objective of the present study was to develop a practical method to prepare a stable dispersion of TiO2 nanoparticles for biological studies. To address this matter a variety of different approaches for suspension of nanoparticles were conducted. TiO2 (rutile/anatase) dispersions were prepared in distilled water following by treated with different ultrasound energies and various dispersion stabilizers (1.0% carboxymethyl cellulose, 0.5% hydroxypropyl methyl cellulose K4M, 100% fetal bovine serum, and 2.5% bovine serum albumin). The average size of dispersed TiO2 (rutile/anatase) nanoparticles was measured by dynamic light scattering device. Agglomerate sizes of TiO2 in distilled water and 100% FBS were estimated using TEM analysis. Sedimentation rate of TiO2 (rutile/anatase) nanoparticles in dispersion was monitored by optical absorbance detection. In vitro cytotoxicity of various stabilizers in 16-HBE cells was measured using MTT assay. The optimized process for preparation of TiO2 (rutile/anatase) nanoparticles dispersion was first to vibrate the nanoparticles by vortex and disperse particles by ultrasonic vibration in distilled water, then to add dispersion stabilizers to the dispersion, and finally to sonicate the nanoparticles in dispersion. TiO2 (rutile/anatase) nanoparticles were disaggregated sufficiently with an ultrasound energy of 33 W for 10 min. The formation of TiO2 (rutile/anatase) agglomerates in distilled water was decreased obviously by addition of 1.0% CMC, 0.5% HPMC K4M, 100% FBS and 2.5% BSA. For the benefit of cell growth, FBS is the most suitable stabilizer for preparation of TiO2 (rutile/anatase) particle dispersions and subsequent investigation of the in vivo and in vitro behavior of TiO2 (rutile/anatase) nanoparticles. This method is practicable to prepare a stable dispersion of TiO2 (rutile/anatase) nanoparticles for at least 120 h.

  17. Flow and dispersion in anisotropic porous media: a Lattice-Boltzmann study

    CERN Document Server

    Maggiolo, Dario; Guarnieri, Massimo

    2016-01-01

    Given their capability of spreading active chemical species and collecting electricity, porous media made of carbon fibers are extensively used as diffusion layers in energy storage systems, such as redox flow batteries. In spite of this, the dispersion dynamics of species inside porous media is still not well understood and often lends itself to different interpretations. Actually, the microscopic design of efficient porous media which can potentially and effectively improve the performances of flow batteries, is a still open challenge. The present study aims to investigate the effect of fibrous media micro-structure on dispersion, in particular the effect of fiber orientation on drag and dispersion dynamics. Several Lattice-Boltzmann simulations of {flows through} differently-oriented fibrous media coupled with Lagrangian simulations of particle tracers have been performed. Results show that orienting fibers preferentially along the streamwise direction minimizes the drag and maximizes the dispersion, which...

  18. Dispersal of G-band bright points at different longitudinal magnetic field strengths

    CERN Document Server

    Yunfei, Yang; Song, Feng; Hui, Deng; Feng, Wang; Jiaben, Lin

    2015-01-01

    G-band bright points (GBPs) are thought to be the foot-points of magnetic flux tubes. The aim of this paper is to investigate the relation between the diffusion regimes of GBPs and the associated longitudinal magnetic field strengths. Two high resolution observations of different magnetized environments were acquired with the Hinode/Solar Optical Telescope. Each observation was recorded simultaneously with G-band filtergrams and Narrow-band Filter Imager (NFI) Stokes I and V images. GBPs are identified and tracked automatically, and then categorized into several groups by their longitudinal magnetic field strengths, which are extracted from the calibrated NFI magnetograms using a point-by-point method. The Lagrangian approach and the distribution of diffusion indices approach are adopted separately to explore the diffusion regime of GBPs for each group. It is found that the values of diffusion index and diffusion coefficient both decrease exponentially with the increasing longitudinal magnetic field strengths...

  19. Long-term resource variation and group size: A large-sample field test of the Resource Dispersion Hypothesis

    Directory of Open Access Journals (Sweden)

    Morecroft Michael D

    2001-07-01

    Full Text Available Abstract Background The Resource Dispersion Hypothesis (RDH proposes a mechanism for the passive formation of social groups where resources are dispersed, even in the absence of any benefits of group living per se. Despite supportive modelling, it lacks empirical testing. The RDH predicts that, rather than Territory Size (TS increasing monotonically with Group Size (GS to account for increasing metabolic needs, TS is constrained by the dispersion of resource patches, whereas GS is independently limited by their richness. We conducted multiple-year tests of these predictions using data from the long-term study of badgers Meles meles in Wytham Woods, England. The study has long failed to identify direct benefits from group living and, consequently, alternative explanations for their large group sizes have been sought. Results TS was not consistently related to resource dispersion, nor was GS consistently related to resource richness. Results differed according to data groupings and whether territories were mapped using minimum convex polygons or traditional methods. Habitats differed significantly in resource availability, but there was also evidence that food resources may be spatially aggregated within habitat types as well as between them. Conclusions This is, we believe, the largest ever test of the RDH and builds on the long-term project that initiated part of the thinking behind the hypothesis. Support for predictions were mixed and depended on year and the method used to map territory borders. We suggest that within-habitat patchiness, as well as model assumptions, should be further investigated for improved tests of the RDH in the future.

  20. Dispersion Modeling.

    Science.gov (United States)

    Budiansky, Stephen

    1980-01-01

    This article discusses the need for more accurate and complete input data and field verification of the various models of air pollutant dispension. Consideration should be given to changing the form of air quality standards based on enhanced dispersion modeling techniques. (Author/RE)

  1. Some Observational and Modeling Studies of the Atmospheric Boundary Layer at Mississippi Gulf Coast for Air Pollution Dispersion Assessment

    Directory of Open Access Journals (Sweden)

    Anjaneyulu Yerramilli

    2008-12-01

    Full Text Available Coastal atmospheric conditions widely vary from those over inland due to the land-sea interface, temperature contrast and the consequent development of local circulations. In this study a field meteorological experiment was conducted to measure vertical structure of boundary layer during the period 25-29 June, 2007 at three locations Seabee base, Harrison and Wiggins sites in the Mississippi coast. A GPS Sonde along with slow ascent helium balloon and automated weather stations equipped with slow and fast response sensors were used in the experiment. GPS sonde were launched at three specific times (0700 LT, 1300 LT and 1800 LT during the experiment days. The observations indicate shallow boundary layer near the coast which gradually develops inland. The weather research and forecasting (WRF meso-scale atmospheric model and a Lagrangian particle dispersion model (HYSPLIT are used to simulate the lower atmospheric flow and dispersion in a range of 100 km from the coast for 28-30 June, 2007. The simulated meteorological parameters were compared with the experimental observations. The meso-scale model results show significant temporal and spatial variations in the meteorological fields as a result of development of sea breeze flow, its coupling with the large scale flow field and the ensuing alteration in the mixing depth across the coast. Simulated ground-level concentrations of SO2 from four elevated point sources located along the coast indicate diurnal variation and impact of the local sea-land breeze on the direction of the plume. Model concentration levels were highest during the stable morning condition and during the sea-breeze time in the afternoon. The highest concentrations were found up to 40 km inland during sea breeze time. The study illustrates the application of field meteorological observations for the validation of WRF which is coupled to HYSPLIT for dispersion assessment in the coastal region.

  2. One-loop omega-potential of quantum fields with ellipsoid constant-energy surface dispersion law

    Science.gov (United States)

    Kazinski, P. O.; Shipulya, M. A.

    2011-10-01

    Rapidly convergent expansions of a one-loop contribution to the partition function of quantum fields with ellipsoid constant-energy surface dispersion law are derived. The omega-potential is naturally decomposed into three parts: the quasiclassical contribution, the contribution from the branch cut of the dispersion law, and the oscillating part. The low- and high-temperature expansions of the quasiclassical part are obtained. An explicit expression and a relation of the contribution from the cut with the Casimir term and vacuum energy are established. The oscillating part is represented in the form of the Chowla-Selberg expansion of the Epstein zeta function. Various resummations of this expansion are considered. The general procedure developed is then applied to two models: massless particles in a box both at zero and nonzero chemical potential, and electrons in a thin metal film. Rapidly convergent expansions of the partition function and average particle number are obtained for these models. In particular, the oscillations of the chemical potential of conduction electrons in graphene and a thin metal film due to a variation of size of the crystal are described.

  3. Dispersion of Electric-Field-Induced Faraday Effect in Magnetoelectric Cr2O3

    Science.gov (United States)

    Wang, Junlei; Binek, Christian

    2016-03-01

    The frequency dependence of the electric-field-induced magneto-optical Faraday effect is investigated in the magnetoelectric antiferromagnet chromia. Two electrically induced Faraday signals superimpose in proportion to the linear magnetoelectric susceptibility α and the antiferromagnetic order parameter η . The relative strength of these contributions is determined by the frequency of the probing light and can be tuned between extreme characteristics following the temperature dependence of α or η . The frequency dependence is analyzed in terms of electric dipole transitions of perturbed Cr3 + crystal-field states. The results allow us to measure voltage-controlled selection, isothermal switching, and temperature dependence of η in a tabletop setup. The voltage-specific Faraday rotation is independent of the sample thickness, making the method scalable and versatile down to the limit of dielectric breakdown.

  4. Can dispersion corrections annihilate the dispersion-driven nano-aggregation of non-polar groups? An ab initio molecular dynamics study of ionic liquid systems.

    Science.gov (United States)

    Firaha, Dzmitry S; Thomas, Martin; Hollóczki, Oldamur; Korth, Martin; Kirchner, Barbara

    2016-11-28

    In this study, we aim at understanding the influence of dispersion correction on the ab initio molecular dynamics simulations of ionic liquid (IL) systems. We investigated a large bulk system of the 1-butyl-3-methylimidazolium triflate IL and a small cluster system of ethylamine in ethylammonium nitrate both under periodic boundary conditions. The large system displays several changes upon neglect of dispersion correction, the most striking one is the surprising decrease of the well-known microheterogeneity which is accompanied by an increase of side chain hydrogen atom-anion interplay. For the diffusion coefficient, we observe a correction towards experimental behavior in terms of the cation becoming faster than the anion with dispersion correction. Changes in the electronic structure upon dispersion correction are reflected in larger/smaller dipole moments for anions/cations also seen in the calculated IR spectrum. The energetics of different ion pair dimer subsystems (polar and non-polar) are in accordance with the analysis of the trajectories: A detailed balance in the ionic liquid system determines its particular behavior. While the overall interaction terms for dispersion-corrected calculations are higher, the decrease in microheterogeneity upon inclusion of dispersion interaction becomes obvious due to the relation between all contributions to polar-polar terms. For the small system, we clearly observe the well known behavior that the hybrid functionals show higher reaction barriers than the pure generalized gradient approximation (GGA) functionals. The correction of dispersion reduces the discrepancies in some cases. Accounting for the number of jumps, we observe that dispersion correction reduces the discrepancies from 50% to less than 10%.

  5. Can dispersion corrections annihilate the dispersion-driven nano-aggregation of non-polar groups? An ab initio molecular dynamics study of ionic liquid systems

    Science.gov (United States)

    Firaha, Dzmitry S.; Thomas, Martin; Hollóczki, Oldamur; Korth, Martin; Kirchner, Barbara

    2016-11-01

    In this study, we aim at understanding the influence of dispersion correction on the ab initio molecular dynamics simulations of ionic liquid (IL) systems. We investigated a large bulk system of the 1-butyl-3-methylimidazolium triflate IL and a small cluster system of ethylamine in ethylammonium nitrate both under periodic boundary conditions. The large system displays several changes upon neglect of dispersion correction, the most striking one is the surprising decrease of the well-known microheterogeneity which is accompanied by an increase of side chain hydrogen atom-anion interplay. For the diffusion coefficient, we observe a correction towards experimental behavior in terms of the cation becoming faster than the anion with dispersion correction. Changes in the electronic structure upon dispersion correction are reflected in larger/smaller dipole moments for anions/cations also seen in the calculated IR spectrum. The energetics of different ion pair dimer subsystems (polar and non-polar) are in accordance with the analysis of the trajectories: A detailed balance in the ionic liquid system determines its particular behavior. While the overall interaction terms for dispersion-corrected calculations are higher, the decrease in microheterogeneity upon inclusion of dispersion interaction becomes obvious due to the relation between all contributions to polar-polar terms. For the small system, we clearly observe the well known behavior that the hybrid functionals show higher reaction barriers than the pure generalized gradient approximation (GGA) functionals. The correction of dispersion reduces the discrepancies in some cases. Accounting for the number of jumps, we observe that dispersion correction reduces the discrepancies from 50% to less than 10%.

  6. Dispersion model studies for Space Shuttle environmental effects activities

    Science.gov (United States)

    1981-01-01

    The NASA/MSFC REED computer code was developed for predicting concentrations, dosage, and deposition downwind from rocket vehicle launches. The calculation procedures and results of nine studies using the code are presented. Topics include plume expansion, hydrazine concentrations, and hazard calculations for postulated fuel spills.

  7. Improved dispersion method of multi-wall carbon nanotube for inhalation toxicity studies of experimental animals.

    Science.gov (United States)

    Taquahashi, Yuhji; Ogawa, Yukio; Takagi, Atsuya; Tsuji, Masaki; Morita, Koichi; Kanno, Jun

    2013-01-01

    A multi-wall carbon nanotube (MWCNT) product Mitsui MWNT-7 is a mixture of dispersed single fibers and their agglomerates/aggregates. In rodents, installation of such mixture induces inflammatory lesions triggered predominantly by the aggregates/agglomerates at the level of terminal bronchiole of the lungs. In human, however, pulmonary toxicity induced by dispersed single fibers that reached the lung alveoli is most important to assess. Therefore, a method to generate aerosol predominantly consisting of dispersed single fibers without changing their length and width is needed for inhalation studies. Here, we report a method (designated as Taquann method) to effectively remove the aggregate/agglomerates and enrich the well-dispersed singler fibers in dry state without dispersant and without changing the length and width distribution of the single fibers. This method is base on two major concept; liquid-phase fine filtration and critical point drying to avoid re-aggregation by surface tension. MWNT-7 was suspended in Tert-butyl alcohol, freeze-and-thawed, filtered by a vibrating 25 µm mesh Metallic Sieve, snap-frozen by liquid nitrogen, and vacuum-sublimated (an alternative method to carbon dioxide critical point drying). A newly designed direct injection system generated well-dispersed aerosol in an inhalation chamber. The lung of mice exposed to the aerosol contained single fibers with a length distribution similar to the original and the Taquann-treated sample. Taquann method utilizes inexpensive materials and equipments mostly found in common biological laboratories, and prepares dry powder ready to make well-dispersed aerosol. This method and the chamber with direct injection system would facilitate the inhalation toxicity studies more relevant to human exposure.

  8. Guidance and dispersion studies of National Launch System ascent trajectories

    Science.gov (United States)

    Hanson, John M.; Shrader, M. W.; Chang, Hopen; Freeman, Scott E.

    1992-01-01

    The National Launch System (NLS) is a joint concept, between DoD and NASA, for building a family of new launch vehicles. Two of the many choices to be made are the trajectory shaping methods and the onboard guidance scheme. This paper presents results from some ongoing studies to address these issues. First, potential gains from new guidance concepts are listed. Next the paper gives a list of possible discriminators between different guidance schemes, lists a number of potential guidance schemes, and explains two in some detail. A reference scheme is tested to determine its performance versus the discriminators. Finally, results from some special studies using the reference guidance scheme are given, including the effects of closed-loop guidance initiation time, time of enforcement of sideslip, vehicle roll for engine out, time and location of an engine out, use of load relief control, and use of day of launch wind biasing.

  9. Field-structured composite studies.

    Energy Technology Data Exchange (ETDEWEB)

    Martin, James Ellis; Williamson, Rodney L.

    2004-04-01

    Field-structured composites (FSCs) were produced by hosting micron-sized gold-coated nickel particles in a pre-polymer and allowing the mixture to cure in a magnetic field environment. The feasibility of controlling a composite's electrical conductivity using feedback control applied to the field coils was investigated. It was discovered that conductivity in FSCs is primarily determined by stresses in the polymer host matrix due to cure shrinkage. Thus, in cases where the structuring field was uniform and unidirectional so as to produce chainlike structures in the composite, no electrical conductivity was measured until well after the structuring field was turned off at the gel point. In situations where complex, rotating fields were used to generate complex, three-dimensional structures in a composite, very small, but measurable, conductivity was observed prior to the gel point. Responsive, sensitive prototype chemical sensors were developed based on this technology with initial tests showing very promising results.

  10. Tracer Studies to Characterize the Effects of Roadside Noise Barriers on Near-Road Pollutant Dispersion under Varying Atmospheric Stability Conditions

    Science.gov (United States)

    A roadway toxics dispersion study was conducted by the Field Research Division (FRD) of NOAA at the Idaho National Laboratory (INL) near Idaho Falls, ID to document the effects on concentrations of roadway emissions behind a roadside sound barrier in various conditions of atmosph...

  11. A Sensitivity Study of the Validation of Three Regulatory Dispersion Models

    Directory of Open Access Journals (Sweden)

    Keith D.   Harsham

    2008-01-01

    Full Text Available Lidar measurements were made of the dispersion of the plume from a coastal industrial plant over three weeks between September 1996 and May 1998. 67 experimental runs were obtained, mostly of 30 min duration, and these were analysed to provide plume parameters (i.e. height, vertical and lateral spreads. These measurements were supplemented by local meteorological measurements at two portable meteorological stations and also by radiosonde measurements of wind, temperature and pressure profiles. The dispersion was modelled using three commercial regulatory models: ISC3 (EPA, Trinity Consultants and Lakes Environmental, UK-ADMS (CERC and AERMOD (EPA, Lakes Environmental. Where possible, each model was run applying all choices as between urban or rural surface characteristics; wind speed measured at 10 m or 100 m; and surface corrected for topography or topography plus buildings. We have compared the range of output from each model with the Lidar measurements. In the main, the models underestimated dispersion in the near field and overestimated it beyond a few hundred m. ISC tended to show the smallest dispersion, while AERMOD gave the largest values for the lateral spread and ADMS gave the largest values of the vertical spread. Buoyant plume rise was modelled well in neutral conditions but rather erratically in unstable conditions. The models are quite sensitive to the reasonable input choices listed above: the full range of sensitivity is comparable to the difference between the median modelled value and the measured value.

  12. A structure study of copper oxide for monolayer dispersion of anatase supported

    Institute of Scientific and Technical Information of China (English)

    Fen-LanZi; Xiao-haiCai; 等

    2001-01-01

    The monolayer dispersion of copper oxide on the surface of anatase and its effect on the properties have been studied by X-ray photoelectron spectroscopy(XPS) and X-ray extended absorption fine structure(EXAFS).XPS results give an utmost dispersion capacity of 7.2mg/gTiO2.Strong interactions between copper oxide and anatase can be seen from EXAFS results.The structure of the supported CuO species is strongly dependent on the amount of CuO loading.When the content of CuO loading is below the utmost dispersion capacity,the surface of CuO/TiO2 is dominated by the highly dispersed CuO species having no-Cu-O-Cu-chains,The copper ion is located in an octahedral coordination environment,and the Cu-O-coordination distance is much longer than that in pure crystalline CuO,when CuO loading is exceeds the utmost dispersion capacity,crystalline CuO is formed on the surface of CuO/TiO2,From the result of the sturcture study,it is Cu-O octahedral Coordination and coordination distance change in comparation with pure crystalline Cuo on the surface CuO/TiO2 that have catalytic activity.

  13. Studies on mechanism of enhanced dissolution of albendazole solid dispersions with crystalline carriers

    Directory of Open Access Journals (Sweden)

    Kalaiselvan R

    2006-01-01

    Full Text Available The main purpose of this research was to study the mechanism of drug release from solid dispersions of albendazole, giving special emphasis to particle size of the drug in solid dispersions. Solid dispersions were prepared using three different carriers, mixing ratios and methods in an attempt to improve the solubility and dissolution rate of albendazole. The mechanism of enhanced dissolution was investigated by a novel dissolution technique as an adjunct to phase solubility study, wettability test, differential scanning calorimetry, X-ray diffractometry, infrared spectroscopy and scanning electron microscopy. The solubility of albendazole was greater with albendazole-poloxamer 407 system, while polyethylene glycol dispersions showed predominant wettability. Physical mixtures showed enhanced dissolution compared with the pure drug, due to improved wetting and solubilization of drug in the diffusion layer offering carrier-rich microenvironment. Preparation of solid dispersion further improved the dissolution compared to the physical mixture, owing to increased surface area for mass transfer, thermodynamically enhanced dissolution of a higher energy amorphous form from the carrier, in addition to improved wetting and solubilization. All carriers showed comparable degree of drug particle size reduction, whereas mixing ratio and method of preparation substantially affected the particle size. Intermolecular association of drug with the carrier led to inhibition of drug recrystallization.

  14. Does spore ultrastructure mirror different dispersal strategies in mosses? A study of seven iberian orthotrichum species.

    Directory of Open Access Journals (Sweden)

    Nagore G Medina

    Full Text Available Most mosses have xerochastic dispersal (i.e., they open their capsules when conditions are dry, which is thought to favor long-distance dispersal. However, there are several species that use a hygrochastic strategy: spores are dispersed when conditions are wet. The significance of this strategy in the Mediterranean region is unknown. In this study, we explored whether ultrastructural features related to differences in spore resistance may explain these different strategies of spore dispersal. To this end, we examined the ultrastructural features of the spores of seven closely related species in the moss genus Orthotrichum. These species all grow as epiphytes in sub-Mediterranean forests, and the group includes both xerochastic and hygrochastic members. First, we found that the spore wall layers exhibit several features previously undescribed in mosses. Second, we discovered that there are only subtle differences in spore ultrastructure with regards to spore wall thickness, the degree of plastid development, or the storage substances used. We suggest that the hygrochastic dispersal in mosses from Mediterranean environments might be related to a safe-site strategy, rather than to drought avoidance, and we underscore the necessity of conducting spore ultrastructural studies on a greater number of bryophyte species.

  15. In-medium dispersion relations of charmonia studied by the maximum entropy method

    Science.gov (United States)

    Ikeda, Atsuro; Asakawa, Masayuki; Kitazawa, Masakiyo

    2017-01-01

    We study in-medium spectral properties of charmonia in the vector and pseudoscalar channels at nonzero momenta on quenched lattices, especially focusing on their dispersion relation and the weight of the peak. We measure the lattice Euclidean correlation functions with nonzero momenta on the anisotropic quenched lattices and study the spectral functions with the maximum entropy method. The dispersion relations of charmonia and the momentum dependence of the weight of the peak are analyzed with the maximum entropy method together with the errors estimated probabilistically in this method. We find a significant increase of the masses of charmonia in medium. We also find that the functional form of the charmonium dispersion relations is not changed from that in the vacuum within the error even at T ≃1.6 Tc for all the channels we analyze.

  16. In-medium dispersion relations of charmonia studied by maximum entropy method

    CERN Document Server

    Ikeda, Atsuro; Kitazawa, Masakiyo

    2016-01-01

    We study in-medium spectral properties of charmonia in the vector and pseudoscalar channels at nonzero momenta on quenched lattices, especially focusing on their dispersion relation and weight of the peak. We measure the lattice Euclidean correlation functions with nonzero momenta on the anisotropic quenched lattices and study the spectral functions with the maximum entropy method. The dispersion relations of charmonia and the momentum dependence of the weight of the peak are analyzed with the maximum entropy method together with the errors estimated probabilistically in this method. We find significant increase of the masses of charmonia in medium. It is also found that the functional form of the charmonium dispersion relations is not changed from that in the vacuum within the error even at $T\\simeq1.6T_c$ for all the channels we analyzed.

  17. Study of the dispersion of natural gas issuing from compressor stations through silencers with upper cover.

    Science.gov (United States)

    García, J; Migoya, E; Lana, J A; Crespo, A

    2008-04-15

    The aim of the present study is the simulation of the dispersion of natural gas issuing from the silencer of compressor stations during vent operations. The objective is to analyze the dispersion of the gas emitted under different conditions of mass flow rate at the exit and ambient cross-flow velocity. We have considered a silencer with an upper cover to protect it from the rain and the fall of objects. The influence of the upper cover of the silencer on the dispersion of natural gas has also been studied, and non-dimensional approaches of the model have been proposed to simplify the problem. Seven different cases have been solved, using two models: a 3D model based on the commercial code FLUENT, and a simplified quasi-one-dimensional model. The results obtained in both cases have been compared, and the range of validity of the one-dimensional model in non-dimensional form has been discussed.

  18. Discrete element method study of fuel relocation and dispersal during loss-of-coolant accidents

    Science.gov (United States)

    Govers, K.; Verwerft, M.

    2016-09-01

    The fuel fragmentation, relocation and dispersal (FFRD) during LOCA transients today retain the attention of the nuclear safety community. The fine fragmentation observed at high burnup may, indeed, affect the Emergency Core Cooling System performance: accumulation of fuel debris in the cladding ballooned zone leads to a redistribution of the temperature profile, while dispersal of debris might lead to coolant blockage or to debris circulation through the primary circuit. This work presents a contribution, by discrete element method, towards a mechanistic description of the various stages of FFRD. The fuel fragments are described as a set of interacting particles, behaving as a granular medium. The model shows qualitative and quantitative agreement with experimental observations, such as the packing efficiency in the balloon, which is shown to stabilize at about 55%. The model is then applied to study fuel dispersal, for which experimental parametric studies are both difficult and expensive.

  19. Colloidal dispersions for the delivery of acyclovir: A comparative study

    Directory of Open Access Journals (Sweden)

    Rita Cortesi

    2011-01-01

    Full Text Available This paper describes a comparative study on the performances of ethosomes and solid lipid nanoparticle as delivery systems for acyclovir. Ethosomes were spontaneously produced by dissolution of phosphatidylcholine and acyclovir in ethanol followed by addition of an aqueous buffer while solid lipid nanoparticle were produced by homogenization and ultrasonication. Both colloidal systems were morphologically characterized by cryo-transmission electron microscopy. The encapsulation efficiency was 94.2±2.8% for ethosomes and 53.2±0.2% for solid lipid nanoparticle. Concerning Z potential, both formulations are close to neutrality. The diffusion coefficients of the drug from ethosomes and solid lipid nanoparticle, determined by a Franz cell method, were 9.4 and 1.2-fold lower as compared to the free acyclovir in solution, thus evidencing the ability of both colloidal systems in enhancing the diffusion of the drug. The antiviral activity against HSV-1 of both systems was tested by plaque reduction assay in monolayer cultures of Vero cells. Data showed that no significant differences in the antiviral activity were observed by acyclovir in the free or loaded forms. Taken together these results, colloidal systems could be interesting to mediate the penetration of acyclovir within Vero cells.

  20. Physical model studies of dispersion in fracture systems

    Energy Technology Data Exchange (ETDEWEB)

    Hull, L.C.

    1985-04-01

    The purposes of the laboratory-scale fracture network experiments are to study mechanisms controlling solute transport under conditions of known fracture parameters, to evaluate injection-backflow test procedures under conditions of known reservoir parameters, and to acquire data for validation of numerical models. Validation of computer codes against laboratory data collected under controlled conditions provides reassurance that the codes deal with important processes in a realistic manner. Preliminary simulations of the dual-permeability physical model have been made using the FRACSL reservoir code. These simulations permit locating electrodes and piezometers in the most advantageous positions to record tracer migration and pressure response. Much of the physical modeling effort this year was oriented towards validating the particle tracking algorithm used in FRACSL, and developing a better theoretical understanding of transport processes in fractures. Experiments were conducted in single fractures and single fracture junctions, and data on tracer migration collected. The Prickett, Naymik, and Lonnquist Random Walk aquifer simulation program has been modfied to simulate flow in single fractures. The particle tracking algorithm was also used to simulate infinite parallel plates under conditions where analytical solutions to the transport equation could be derived. The first case is for zero diffusion in the fracture, and transport based on a parabolic velocity profile. The second case is for diffusion homogenizing the tracer solution across the fracture. The particle tracking algorithm matched both analytical solutions quite well, with the same grid for both simulations. 48 refs., 41 figs., 2 tabs.

  1. Colloidal Dispersions for the Delivery of Acyclovir: A Comparative Study

    Science.gov (United States)

    Cortesi, Rita; Ravani, Laura; Menegatti, Enea; Drechsler, M.; Esposito, Elisabetta

    2011-01-01

    This paper describes a comparative study on the performances of ethosomes and solid lipid nanoparticle as delivery systems for acyclovir. Ethosomes were spontaneously produced by dissolution of phosphatidylcholine and acyclovir in ethanol followed by addition of an aqueous buffer while solid lipid nanoparticle were produced by homogenization and ultrasonication. Both colloidal systems were morphologically characterized by cryo-transmission electron microscopy. The encapsulation efficiency was 94.2±2.8% for ethosomes and 53.2±0.2% for solid lipid nanoparticle. Concerning Z potential, both formulations are close to neutrality. The diffusion coefficients of the drug from ethosomes and solid lipid nanoparticle, determined by a Franz cell method, were 9.4 and 1.2-fold lower as compared to the free acyclovir in solution, thus evidencing the ability of both colloidal systems in enhancing the diffusion of the drug. The antiviral activity against HSV-1 of both systems was tested by plaque reduction assay in monolayer cultures of Vero cells. Data showed that no significant differences in the antiviral activity were observed by acyclovir in the free or loaded forms. Taken together these results, colloidal systems could be interesting to mediate the penetration of acyclovir within Vero cells. PMID:23112407

  2. Colloidal dispersions for the delivery of acyclovir: a comparative study.

    Science.gov (United States)

    Cortesi, Rita; Ravani, Laura; Menegatti, Enea; Drechsler, M; Esposito, Elisabetta

    2011-11-01

    This paper describes a comparative study on the performances of ethosomes and solid lipid nanoparticle as delivery systems for acyclovir. Ethosomes were spontaneously produced by dissolution of phosphatidylcholine and acyclovir in ethanol followed by addition of an aqueous buffer while solid lipid nanoparticle were produced by homogenization and ultrasonication. Both colloidal systems were morphologically characterized by cryo-transmission electron microscopy. The encapsulation efficiency was 94.2±2.8% for ethosomes and 53.2±0.2% for solid lipid nanoparticle. Concerning Z potential, both formulations are close to neutrality. The diffusion coefficients of the drug from ethosomes and solid lipid nanoparticle, determined by a Franz cell method, were 9.4 and 1.2-fold lower as compared to the free acyclovir in solution, thus evidencing the ability of both colloidal systems in enhancing the diffusion of the drug. The antiviral activity against HSV-1 of both systems was tested by plaque reduction assay in monolayer cultures of Vero cells. Data showed that no significant differences in the antiviral activity were observed by acyclovir in the free or loaded forms. Taken together these results, colloidal systems could be interesting to mediate the penetration of acyclovir within Vero cells.

  3. A smoothed particle hydrodynamics (SPH) study of sediment dispersion on the seafloor

    Science.gov (United States)

    Tran-Duc, Thien; Phan-Thien, Nhan; Khoo, Boo Cheong

    2017-08-01

    Ocean-scale sediment dispersion and sedimentation problems are studied using the Smoothed Particle Hydrodynamics (SPH). A SPH formulation based on a mixture model for two-phase flows is developed to investigate the problem. The sediment mass transport via the settling advection and the turbulent diffusion of the suspended sediment are fully accounted for in the current SPH model. The simulations are carried out in an opened boundary domain with a unidirectional underlined current, with relevant deposition/re-suspension boundary conditions on the seafloor. The factors influencing the sedimentation process, such as the hindering and the bottom shear stress effects, are also considered. The simulation results reveal that the sediment convection near the sediment source location is caused by both the ocean current and secondary density driven flows that are created by the concurrent settling motion of suspended sediment particles, while the downstream sediment transport in the far field is only driven by the ocean current. The peak sediment concentration in the ambient ocean water is found to correlate with the sediment release rate, and the settlement rate is inversely proportional to the initial height of the disturbed sediment.

  4. Dispersion stabilization of silver nanoparticles in synthetic lung fluid studied under in situ conditions

    Energy Technology Data Exchange (ETDEWEB)

    MacCuspie, R.I.; Allen, A.J.; Hackley, V.A. (NIST)

    2014-09-24

    The dispersion stabilization of silver nanoparticles (AgNPs) in synthetic lung fluid was studied to interrogate the effects on colloidal stability due to the principal constituents of the fluid. The colloidal stability of 20 nm citrate-AgNPs dispersed in the presence of each constituent of the synthetic lung fluid (individually, the complete fluid, and without additives) was observed during titration of increasing sodium chloride concentration. A variety of complementary in situ measurement techniques were utilized, including dynamic light scattering, ultraviolet-visible absorption spectroscopy, atomic force microscopy, and small-angle X-ray scattering, which provided a collective set of information that enabled far better understanding of the dispersion behavior in the fluid than any one technique alone. It was observed that AgNPs continued to adsorb bovine serum albumin (BSA) protein from the synthetic lung fluid solution as the sodium chloride concentration increased, until a maximum BSA coating was achieved prior to reaching the physiological sodium chloride concentration of 154 mmol L{sup -1}. BSA was determined to be the constituent of the synthetic lung fluid that is required to provide colloidal stability at high salt loadings, though the phospholipid constituent exerts a subtle effect. Additionally, as AgNPs are a distinctly different class of nanoparticles apart from the carbon nanotubes and titanium dioxide nanoparticles initially reported to be dispersible using this fluid, this work also demonstrates the broad applicability of synthetic lung fluid in providing stable dispersions for engineered nanoparticles for use in biological assays.

  5. Analysis of dispersion of heated effluent from power plant: a case study

    Indian Academy of Sciences (India)

    VIKRAM SHAH; ANKIT DEKHATWALA; JYOTIRMAY BANERJEE; A K PATRA

    2017-04-01

    Thermal dispersion of heated effluent in a lake near nuclear power plant is analysed. Lake Bathymetry is established by data collection at a pre-planned matrix of sample points in the lake. Threedimensional geometric model of the lake is developed based on the geometric data collected, using a high accuracy GPS and a dead weight based depth meter at respective sample points of the lake matrix. A turbine type digital flow meter is used to measure the velocities at the intake and blow down points of the lake. Numerical analysis of flow and thermal dispersion is carried out using PLIC-VOF two-phase model with the two-equationk-epsilon model for turbulence closure. Numerical results for varying flow and blow down temperature conditions and wind speed are studied. It is observed that the thermal gradients are steeper in the curved area near the blowdown point. Small increase in main inlet (inlet II) velocity suppresses the dispersion of high-temperature contours significantly. Thermal discharge and dispersed temperature is monitored using temperature sensor mounted floating buoy at various locations in the lake. It is established that the thermal dispersion is influenced by wind velocity and the presence of water hyacinth in the lake.

  6. STUDY ON THE EFFECTS OF VARIOUS DISINTEGRANTS ON AMOXICILLIN TRIHYDRATE DISPERSIBLE TABLETS

    Directory of Open Access Journals (Sweden)

    Jayaprakash S

    2012-05-01

    Full Text Available The objective of this work was to develop a formulation of amoxicillin trihydrate dispersible tablets of 320mg in a low production value, using cheap amoxicillin trihydrate raw materials available in the market, with direct compression or wet granulation method. Amoxicillin trihydrate is a semisynthetic antibiotic, an analogue of ampicillin with a broad spectrum of bactericidal activity against gram +ve and gram –ve organism. Dispersible tablets are uncoated or film coated tablets intended to be dispersed in water before administration giving a homogeneous dispersion. The WHO prefers dispersible dosage form for the elderly and paediatric patients due to its ease in the administration. Amoxicillin trihydrate dispersible tablet was manufactured with the different disintegrants such as maize starch, crospovidone, croscarmellose, sodium starch glycolate, croscarmellose. The powder blend was evaluated for angle of repose, bulk density, tapped density, compressibility index and hausner’s ratio. After compression the tablets were subjected to weight variation, %drug content, buoyancy studies and in-vitro release studies. The wet granulation was excluded from the formulation due to its high cost if production, direct compression was selected due to its low cost and ease of production. The optimized formulation F10 had showed 99.11% of drug release in 40 min and disintegration of tablet was 25 seconds. The result of FTIR analysis of pure drug alone and drug with excipients there was not showed any physical and chemical interaction. F10 had undergone DTA, which shows the thermal stability of the formulation. The stability studies of optimized formulation F10 at 30◦C / 65%RH, 40◦C / 75%RH did not show any change in tested parameters and release.

  7. Preparation, characterization and in vivo studies of amorphous solid dispersion of berberine with hydrogenated phosphatidylcholine.

    Science.gov (United States)

    Shi, Chunyang; Tong, Qing; Fang, Jianguo; Wang, Chenguang; Wu, Jizhou; Wang, Wenqing

    2015-07-10

    Berberine, a pure crystalline quaternary ammonium salt with the basic structure of isoquinoline alkaloid, has multiple pharmacological bioactivities. But the poor bioavailability of berberine limited its wide clinical applications. In the present study, we aimed to develop an amorphous solid dispersion of berberine with hydrogenated phosphatidylcholine (HPC) in order to improve its bioavailability. The physical characterization studies such as differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), Fourier transform infrared spectrophotometry (FT-IR) and scanning electron microscopy (SEM) were conducted to characterize the formation of amorphous berberine HPC solid dispersion (BHPC-SD). The everted intestinal sac and single-pass intestinal perfusion study proved that permeability and intestinal absorption of amorphous BHPC-SD was improved compared with that of pure crystalline berberine, and the pharmacokinetic study results demonstrated that the extent of bioavailability was significantly increased as well. However, the dissolution study indicated that the aqueous cumulative dissolution percentages of berberine remained unchanged or even lower by means of preparation into solid dispersion with HPC. Therefore, according to the previous mechanistic studies, the present results supported that it is the enhanced molecularly dissolved concentration (supersaturation) of berberine by transformation from crystalline structure into amorphous solid dispersions that triggers the enhanced permeability, and consequently results in the improved intestinal absorption and bioavailability.

  8. Air quality assessment based on road traffic pollutants dispersion modelling: Giurgiu – Ruse Bridge Case study

    Directory of Open Access Journals (Sweden)

    Dragos MIHAI

    2012-12-01

    Full Text Available The paper presents a case study related to air quality assessment along an important high traffic bridge (Giurgiu - Ruse, by dispersion modelling of the main pollutants. In order to estimate the level of pollution caused by bridge road traffic in the closest urban areas, Giurgiu and Ruse and based on the traffic data, four scenarios for the air quality assessment have been carried out according to different meteorological conditions. The dispersion modeling was realized on specialized environmental pollution software, which features a fully operational Gauss model in its base module. There are presented dispersion maps for the main road traffic pollutants (NOx, CO, SO2, THC, aiming to evaluate their impact on the urban areas vicinity, in four different wind directions scenarios, at a constant temperature. Conclusions are presented according to available European Legislation and future scenarios are proposed, for other different meteorological conditions.

  9. Study Pulse Parameters versus Cavity Length for Both Dispersion Regimes in FM Mode Locked

    Directory of Open Access Journals (Sweden)

    Bushra Razooky Mhdi

    2015-03-01

    Full Text Available To demonstrate the effect of changing cavity length for  FM mode locked on pulse parameters and make comparison for both dispersion regime , a plot for each pulse parameter as Lr function are presented for normal and anomalous dispersion regimes. The analysis is based on the theoretical study and the results of numerical simulation using MATLAB. The effect of both normal and anomalous dispersion regimes on output pulses is investigate Fiber length effects on pulse parameters are investigated by driving the modulator into different values. A numerical solution for model equations using fourth-fifth order, Runge-Kutta method is performed through MATLAB 7.0 program. Fiber length effect on pulse parameters is investigated by driving the modulator into different values of lengths. Result shows that, the output pulse width from the FM mode locked equals to τ= 501ns anomalous regime and τ=518ns in normal regime.

  10. Studying dispersions of ferroelectric nanopowders in dioctyl phthalate as dielectric media for capacitive electronic components

    Science.gov (United States)

    Gorokhovskii, A. V.; Gorshkov, N. V.; Burmistrov, I. N.; Goffman, V. G.; Tret'yachenko, E. V.; Sevryugin, A. V.; Fedorov, F. S.; Kovyneva, N. N.

    2016-06-01

    The electrical properties of dispersions of a powdered ferroelectric nanocomposite based on ilmenite (FeTiO3) and hollandite (K1.46Ti7.2Fe0.8O16) in dioctyl phthalate have been studied by impedance spectroscopy techniques in a frequency range of 10-1-106 Hz. The influence of stabilizing additives of cationic and anionic surfactants and iron acetylacetonate on the permittivity, conductivity, and dielectric losses was determined for dispersions containing 40 mass % of the solid composite. The influence of composition on the mechanisms of relaxation processes in the system is discussed.

  11. Experimental Study of Relationships between Ultrasonic Attenuation and Dispersion for Ceramic Matrix Composite

    Science.gov (United States)

    Naumenko, A. A.; Shcherbinin, S. A.; Makariev, D. I.; Rybyanets, A. N.

    In this paper an experimental study of different ceramic matrix composites with high elastic losses and dispersion (porous piezoceramics, composites ceramics/crystals) were carried out. Complex sets of elastic, dielectric, and piezoelectric parameters of the porous piezoceramics and ceramic matrix piezocomposites were determined by the impedance spectroscopy method using Piezoelectric Resonance Analysis software. Microstructure of polished and chipped surfaces of composite samples was observed with the optical and scanning electron microcopies. Experimental frequency dependencies of attenuation coefficients and ultrasonic velocities for different ceramic matrix composites were compared with the theoretical results obtained using general Kramers-Kronig relations between the ultrasonic attenuation and dispersion.

  12. Numerical Study of Spray dispersion in premixing Chamber for Low-NOx Engines

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The present work describes a numerical study of a confined two-phase flow under high-pressure conditions,typical of gas turbine combustors.An Eulerian frame was used for the gas phase together with a Lagrangian approach to describe the dispersed phase.The computational method was extended to high-pressure environments.which are ore representative of the practical gas turbine operating conditions.The results are compared with experimental data,and revealed the ability of the model to increase the knowledge of the turbulent dispersion phenomena for this type of practical conditions(high pressure and cofined flows).

  13. Complex plasmas and colloidal dispersions particle-resolved studies of classical liquids and solids

    CERN Document Server

    Ivlev, Alexei; Morfill, Gregor; Royall, C. Patrick

    2012-01-01

    Complex plasmas and colloidal dispersions represent different states of soft matter. They are complementary in many ways, with the most important being that complex plasmas are virtually undamped at the particle timescales, whereas colloidal dispersions are overdamped and therefore can be brought into equilibrium in a very controlled manner. Otherwise, both fields have similar advantages: fully resolved 3D particle trajectories can easily be visualized, the pair interactions are tunable, and particles can be manipulated individually or collectively. These unique properties allow us to investigate generic processes occurring in liquids or solids at the most fundamental individual particle level. The principal research topics to be addressed in the book include: particle dynamics in liquids, with the emphasis on mesoscopic processes in the supercooled (glassy) state, e.g. dynamical heterogeneity, phase transitions in solids, with particular attention to the evolutionary paths of crystal structure development an...

  14. Microscale anthropogenic pollution modelling in a small tropical island during weak trade winds: Lagrangian particle dispersion simulations using real nested LES meteorological fields

    Science.gov (United States)

    Cécé, Raphaël; Bernard, Didier; Brioude, Jérome; Zahibo, Narcisse

    2016-08-01

    Tropical islands are characterized by thermal and orographical forcings which may generate microscale air mass circulations. The Lesser Antilles Arc includes small tropical islands (width lower than 50 km) where a total of one-and-a-half million people live. Air quality over this region is affected by anthropogenic and volcanic emissions, or saharan dust. To reduce risks for the population health, the atmospheric dispersion of emitted pollutants must be predicted. In this study, the dispersion of anthropogenic nitrogen oxides (NOx) is numerically modelled over the densely populated area of the Guadeloupe archipelago under weak trade winds, during a typical case of severe pollution. The main goal is to analyze how microscale resolutions affect air pollution in a small tropical island. Three resolutions of domain grid are selected: 1 km, 333 m and 111 m. The Weather Research and Forecasting model (WRF) is used to produce real nested microscale meteorological fields. Then the weather outputs initialize the Lagrangian Particle Dispersion Model (FLEXPART). The forward simulations of a power plant plume showed good ability to reproduce nocturnal peaks recorded by an urban air quality station. The increase in resolution resulted in an improvement of model sensitivity. The nesting to subkilometer grids helped to reduce an overestimation bias mainly because the LES domains better simulate the turbulent motions governing nocturnal flows. For peaks observed at two air quality stations, the backward sensitivity outputs identified realistic sources of NOx in the area. The increase in resolution produced a sharper inverse plume with a more accurate source area. This study showed the first application of the FLEXPART-WRF model to microscale resolutions. Overall, the coupling model WRF-LES-FLEXPART is useful to simulate the pollutant dispersion during a real case of calm wind regime over a complex terrain area. The forward and backward simulation results showed clearly that the

  15. Dispersion Studies on Multimode Polymer Spiral Waveguides for Board-Level Optical Interconnects

    CERN Document Server

    Chen, Jian; Edwards, Tom J; Brown, Christian T A; Penty, Richard V; White, Ian H

    2016-01-01

    Dispersion studies are conducted on 1m long multimode polymer spiral waveguides with different refractive index profiles. Bandwidth-length products >40GHzxm are obtained from such waveguides under a 50/125 um MMF, indicating the potential of this technology.

  16. Evaluation of tag entanglement as a factor in harmonic radar studies of insect dispersal

    Science.gov (United States)

    The observation of insects and other small organisms entangled in the habitat after the addition of vertical or trailing electronic tags to their body has generated concerns on the suitability of harmonic radars to track the dispersal of insects. This study compared the walking behavior of adult Co...

  17. Aggregation dynamics and magnetic properties of magnetic micrometer-sized particles dispersed in a fluid under the action of rotating magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Llera, María [Instituto de Ciencias, Universidad Nacional de General Sarmiento, Buenos Aires (Argentina); Codnia, Jorge [Instituto de Ciencias, Universidad Nacional de General Sarmiento, Buenos Aires (Argentina); Centro de Investigaciones en Láseres y Aplicaciones, CITEDEF-CONICET, Buenos Aires (Argentina); Jorge, Guillermo A., E-mail: gjorge@ungs.edu.ar [Instituto de Ciencias, Universidad Nacional de General Sarmiento, Buenos Aires (Argentina)

    2015-06-15

    We present a dynamic study of soft magnetic, commercial Fe and Ni micrometer-sized particles dispersed in oleic acid and subjected to a variable (rotating) magnetic field in the horizontal plane. A very complex structure is formed after the particles decant towards the bottom liquid–solid interface and the magnetic field is applied for several minutes. The dynamics of structure formation was studied by means of the registration and analysis of microscopic video images, through a Matlab image analysis script. Several parameters, such as the number of clusters, the perimeter-based fractal dimension and circularity, were calculated as a function of time. The time evolution of the number of clusters was found to follow a power-law behavior, with an exponent consistent with that found in other studies for magnetic systems, whereas the typical formation time depends on the particle diameter and field configuration. Complementarily, the magnetic properties of the formed structure were studied, reproducing the experiment with liquid paraffin as the containing fluid, and then letting it solidify. The sample obtained was studied by vibrating sample magnetometry. The magnetization curves show that the material obtained is a planar magnetically anisotropic material, which could eventually be used as an anisotropic magnetic sensor or actuator. - Highlights: • Dynamic study of Fe and Ni particles in oleic acid under rotating fields. • A very complex system of interconnected clusters was observed. • Larger particles had a smaller aggregation time. • A power law behavior of the number of clusters vs. time. • A Fe-paraffin sample with planar anisotropy characterized.

  18. Experimental Study of the Effect of Graphite Dispersion on the Heat Transfer Phenomena in a Reactor Cavity Cooling System

    Energy Technology Data Exchange (ETDEWEB)

    Vaghetto, Rodolfo; Capone, Luigi; Hassan, Yassin A

    2011-05-31

    An experimental activity was performed to observe and study the effects of graphite dispersion and deposition on thermal-hydraulic phenomena in a reactor cavity cooling system (RCCS). The small-scale RCCS experimental facility (16.5 x 16.5 x 30.4 cm) used for this activity represents half of the reactor cavity with an electrically heated vessel. Water flowing through five vertical pipes removes the heat produced in the vessel and releases it into the environment by mixing with cold water in a large tank. The particle image velocimetry technique was used to study the velocity field of the air inside the cavity. A set of 52 thermocouples was installed in the facility to monitor the temperature profiles of the vessel, pipe walls, and air. Ten grams of a fine graphite powder (average particle size 2 m) was injected into the cavity through a spraying nozzle placed at the bottom of the vessel. The temperatures and air velocity field were recorded and compared with the measurements obtained before the graphite dispersion, showing a decrease of the temperature surfaces that was related to an increase in their emissivity. The results contribute to the understanding of RCCS capability in an accident scenario.

  19. Coalescence of dispersed phase for immiscible polymer blends in quiescent flow field

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Y.H.; Choi, G.Y.; Kim, H.G.; Seo, C.W.; Choi, J.H.; Min, K.E. [Kyungpook National University, Taegu (Korea)

    2002-05-01

    The deformation and coalescence behaviors of immiscible LDPE/PS blends (86.5/13.5 vol%) prepared by internal mixer were studied using rheometer and scanning electron microscope. The fine droplets coagulated at initial stage of mixing, and deformed fiber at large strain. The critical capillary number was calculated according to the empirical equation of De Bruijn and it was 0.96, the local capillary number was 3.867. The polymer blends were annealed at 200 deg. C for carious time to investigate morphological change of polymer blends. The maximum size of droplet after annealing at 200 deg. C was found at {gamma}=1798, and there was destruction of the morphology at 15 minutes of annealing time. The viscosity of matrix was critical to determine a coalescence of droplet. (author). 34 refs., 3 tabs., 6 figs.

  20. Phonon dispersion and heat capacity in polyfuran

    Science.gov (United States)

    Ali, Parvej; Srivastava, Seema; Ali Khan, Irfan; Gupta, V. D.; Ansari, Saif-ul-Islam

    A study of the normal modes of vibration and their dispersion in polyfuran (Pfu) based on the Urey-Bradley force field is reported. It provides a detailed interpretation of IR and Raman spectra. Characteristic features of dispersion curves such as regions of high density-of-states, repulsion and character mixing of dispersive modes are discussed. Predictive values of heat capacity as a function of temperature are calculated.

  1. Dispersants in an organic medium: synthesis and physicochemical study of dispersants for fuels and lubricants; Dispersants en milieu organique: synthese et etude physicochimique de dispersants pour carburants et lubrifiants

    Energy Technology Data Exchange (ETDEWEB)

    Dubois-Clochard, M.C.

    1998-11-19

    Carbonaceous deposits coming from the fuel and the lubricant are known to form over time at critical locations in an engine. In general, the deposits have an adverse effect on four functional areas which are the fuel metering system, the intake system, the lubrication system and the combustion chambers. These deposits can degrade vehicle performance and drive-ability, reduce fuel economy, increase fuel consumption and pollutant emissions and may lead to the destruction of the engine. In order to remedy these problems, detergent-dispersant additives are used in fuels and lubricants to avoid or decrease deposit adhesion on metallic surfaces and prevent from deposit aggregation. These products are mainly polymer surfactants and in this work, poly-iso-butenyl-succinimide of different structures have been studied. Firstly, 'comb like' polymers have been synthesized. Then they have been compared to classical di-bloc additives in terms of performance and action mechanism. These additives are adsorbed from their hydrophilic polyamine part on the acidic functions of the carbon black surface chosen as an engine deposit model and on the aluminium oxide function of an aluminium powder chosen as an engine wall model. The adsorption increases with temperature on the two solids. Their affinity with the solid surface increases with the length of the hydrophilic part. In the same way, changing the di-bloc structure for a comb like one lead to a better adsorption. At low concentration, it has been shown that the adsorption phenomenon was irreversible, due to the polymer structure of the polar part. Depending on the space required by the hydrophilic part on the solid surface, a more of less dense monolayer is formed. At higher concentrations, an important increase of the adsorbed amount appears. This phenomenon is totally reversible showing that the interactions additive / additive are weak. The dispersing efficiency of a comb like structure is better than a di-bloc one as

  2. Field Evaluation of the Explosive Deposition of Cesium on Concrete Surfaces Following the Detonation of a Mock Radiological Dispersal Device (RDD)

    Energy Technology Data Exchange (ETDEWEB)

    Gates-Anderson, D D; Fisher, R; Sutton, M; Rasmussen, C; Viani, B; McNab, W; Gray, J; Hu, Q

    2006-11-10

    Researchers at Lawrence Livermore National Laboratory conducted a field study to evaluate the deposition of an explosively dispersed radionuclide surrogate (CsCl) on grime and non-grime containing urban surfaces. An additional objective of this study was to evaluate several laboratory surface contamination techniques for the preparation of mock urban surfaces in order to determine the method that most closely mimics surface contamination following an RDD event. The field study was conducted at the LLNL Site 300 Contained Firing Facility (CFF). For our study, we detonated a mock RDD made using C4 and non-radioactive CsCl. Lab prepared concrete samples (3.8 cm x 7.6 cm cylinders) were made using 4 different conditioning regimes to mimic a range of conditions that may be encountered during an RDD event. This sample set included dry, wet, carbonated and non-carbonated cores with and without the application of urban grime. In addition, concreted samples (13 cm x 13 cm x 5 cm) removed from an urban surface were placed inside the CFF chamber. The samples were placed inside the firing chamber at 3 different distances from the mock RDD device. Following the detonation of the mock RDD, the samples were removed from the firing chamber and selected cores were characterized by laser ablation and scanning electron microscopy. Preliminary results suggest that Cs migrates into the concrete samples and the presence of a grime layer does not appear to impede this migration.

  3. Dispersion pattern and fixed precision sequential sampling of Sitobion avenae (Fabricus (Hemiptera: Aphididae in wheat fields of Badjgah (Fars province in Iran

    Directory of Open Access Journals (Sweden)

    V. Soltani Ghasemloo

    2013-12-01

    Full Text Available Understanding the dispersion pattern of a species is an important pre-requisite for developing an effective pest management program. In this study, four hundred wheat plants were surveyed for Sitobion avenae twice a week during 2010 and 2011 growing seasons in two fields of Badjgah (Fars province in Iran. In each field only one of the two cultivers of Bahar or Shiraz was planted. Analysis of spatial distribution pattern using Taylor’s power law and Iwao’s regression model showed that S. avenae exhibited an aggregated distribution on wheat. Taylor’s power law was estimated from 84 data sets and fitted the data better than Iwao’s regression model. The optimal sample sizes needed for fixed precision levels of 0.25 and 0.30 were estimated using Taylor’s regression coefficients, and the required sample sizes increased dramatically with increased levels of precision. Therefore, the samplingplan we presented here should be used as a tool for an efficient estimation of S. avenae population density in wheat fields for pest management decision.

  4. Transverse Field Dispersion in the Generalized Nonlinear Schrödinger Equation: Four Wave Mixing in a Higher Order Mode Fiber

    DEFF Research Database (Denmark)

    Pedersen, Martin Erland Vestergaard; Cheng, Ji; Xu, Chris

    2013-01-01

    An improved version of the generalized nonlinear Schrödinger equation is derived, which takes into account the correct dispersion of the transverse field distribution. The new improved version of the generalized nonlinear Schrödinger equation is verified to give the same results as the standard...

  5. Numerical simulations of barnacle larval dispersion coupled with field observations on larval abundance, settlement and recruitment in a tropical monsoon influenced coastal marine environment

    Science.gov (United States)

    Gaonkar, Chetan A.; Samiksha, S. V.; George, Grinson; Aboobacker, V. M.; Vethamony, P.; Anil, Arga Chandrashekar

    2012-06-01

    Larval abundance in an area depends on various factors which operate over different spatial and temporal scales. Identifying the factors responsible for variations in larval supply and abundance is important to understand the settlement and recruitment variability of their population in a particular area. In view of this, observations were carried out to monitor the larval abundance, settlement and recruitment of barnacles on a regular basis for a period of two years. The results were then compared with the numerical modelling studies carried out along the west coast of India. Field observations of larval abundance showed temporal variations. The least abundance of larvae was mostly observed during the monsoon season and the peak in abundance was mostly observed during the pre-monsoon season. Numerical simulations also showed a seasonal change in larval dispersion and retention patterns. During pre-monsoon season the larval movement was mostly found towards south and the larvae released from the northern release sites contributed to larval abundance within the estuaries, whereas during the monsoon season the larval movement was mostly found towards north and the larvae released from southern release sites contributed to larval abundance within the estuary. During post-monsoon season, the larval movement was found towards the north in the beginning of the season and is shifted towards the south at the end of the season, but the movement was mostly restricted near to the release sites. Larval supply from the adjacent rocky sites to the estuaries was higher during the pre-monsoon season and the retention of larvae released from different sites within the estuaries was found to be highest during the late post-monsoon and early pre-monsoon season. Maximum larval supply and retention during the pre-monsoon season coincided with maximum larval abundance, settlement and recruitment of barnacles observed in the field studies. These observations showed that the pattern of

  6. Stability and generalization in seed dispersal networks: a case study of frugivorous fish in Neotropical wetlands.

    Science.gov (United States)

    Correa, Sandra Bibiana; Arujo, Joisiane K; Penha, Jerry; Nunes da Cunha, Catia; Bobier, Karen E; Anderson, Jill T

    2016-08-31

    When species within guilds perform similar ecological roles, functional redundancy can buffer ecosystems against species loss. Using data on the frequency of interactions between fish and fruit, we assessed whether co-occurring frugivores provide redundant seed dispersal services in three species-rich Neotropical wetlands. Our study revealed that frugivorous fishes have generalized diets; however, large-bodied fishes had greater seed dispersal breadth than small species, in some cases, providing seed dispersal services not achieved by smaller fish species. As overfishing disproportionately affects big fishes, the extirpation of these species could cause larger secondary extinctions of plant species than the loss of small specialist frugivores. To evaluate the consequences of frugivore specialization for network stability, we extracted data from 39 published seed dispersal networks of frugivorous birds, mammals and fish (our networks) across ecosystems. Our analysis of interaction frequencies revealed low frugivore specialization and lower nestedness than analyses based on binary data (presence-absence of interactions). In that case, ecosystems may be resilient to loss of any given frugivore. However, robustness to frugivore extinction declines with specialization, such that networks composed primarily of specialist frugivores are highly susceptible to the loss of generalists. In contrast with analyses of binary data, recently developed algorithms capable of modelling interaction strengths provide opportunities to enhance our understanding of complex ecological networks by accounting for heterogeneity of frugivore-fruit interactions.

  7. Field-scale dispersal of Aphodius dung beetles (Coleoptera: Scarabaeidae) in response to avermectin treatments on pastured cattle.

    Science.gov (United States)

    Webb, L; Beaumont, D J; Nager, R G; McCracken, D I

    2010-04-01

    Very few studies have examined, at the field scale, the potential for faecal residues in the dung of avermectin-treated cattle to affect dung-breeding insects. The current study examined populations of dung beetles (Scarabaeidae: Aphodius) using pitfall traps baited with dung from untreated cattle on 26 fields across eight farms in southwest Scotland. The fields were grazed either by untreated cattle or by cattle treated with an avermectin product, i.e. doramectin or ivermectin. During the two-year study, significantly more beetles were trapped in fields grazed by treated cattle (n=9377 beetles) than in fields where cattle remained untreated (n=2483 beetles). Additional trials showed that beetles preferentially colonised dung of untreated versus doramectin-treated cattle. This may explain the higher captures of beetles in traps baited with dung of untreated cattle, which were located in fields of treated cattle. Given that Aphodius beetles avoided dung of treated cattle in the current study, the potential harmful effects of avermectin residues in cattle dung could be reduced through livestock management practices that maximise the availability of dung from untreated livestock in areas where avermectins are being used.

  8. Chemical dispersants

    NARCIS (Netherlands)

    Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.

    2016-01-01

    Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil biodeg

  9. Chemical dispersants

    NARCIS (Netherlands)

    Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.

    2016-01-01

    Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil

  10. Preparation, Characterization and Stability Studies of Glassy Solid Dispersions of Indomethacin using PVP and Isomalt as carriers

    OpenAIRE

    2012-01-01

    Objective(s) The purpose of the present study was to use the solid dispersion (SD) technique to improve the dissolution rates of indomethacin (IMC). Materials and Methods IMC solid dispersions in PVP K30 and isomalt (GALEN IQ 990) were prepared using the solvent evaporation technique and a hot melt method in weight ratios of 2, 10 and 30% (IMC:PVP). Solid dispersions and physical mixtures were characterized by X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC) and dissol...

  11. Numerical and Experimental Studies on Flow and Pollutant Dispersion in Urban Street Canyons

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this study numerical simulations and water tank experiments were used to investigate the flow and pollutant dispersion in an urban street canyon. Two types of canyon geometry were tested. The studies indicate that in a step-up notch canyon (higher buildings on the downstream side of the canyon), the height and shape of the upstream lower buildings plays an important role in flow pattern and pollutant dispersion,while in a step-down notch canyon (lower buildings on the downstream side), the downstream lower buildings have little influence. The studies also show that the substitution of tall towers for parallelepiped buildings on one side of the canyon may enhance the street ventilation and decrease the pollutant concentration emitted by motor vehicles.

  12. Field Guides in Academe: A Citation Study

    Science.gov (United States)

    Schmidt, Dianne

    2006-01-01

    Field guides are common in libraries but are generally not considered scholarly. This study examines citations to fifty field guides to determine how they were used in scholarly publications, finding that field guides are frequently cited as a source of data on the ranges, habits, and descriptions of plants and animals.

  13. Investigations on atmospheric dispersion of air pollutants after short-time releases in complex terrain. Third field experiment on atmospheric dispersion around the isolated hill Sophienhoehe in August/September 1988. Methods - experiments - data bank

    Energy Technology Data Exchange (ETDEWEB)

    Zeuner, G.; Heinemann, K. [eds.; Bahmann, W.; Becker, K.; Frank, J.; Gryning, S.E.; Lyck, E.; Mextorf, O.; Moellmann-Coers, M.; Moenig, C.; Narres, H.D.; Oetz, C.; Oetz, W.; Polster, G.; Veroustraete, F.; Voss, W.

    1990-09-01

    In order to set up a data bank for the validation of advanced dispersion models, comprehensive meteorological measurements and dispersion experiments in a complex terrain with a well measured topography are being carried out. These investigations have become possible in cooperation with several external groups and with the financial support of the `Bundesminister fuer Umwelt, Naturschutz und Reaktorsicherheit`. In this report the methods, experiments and results (data bank) of the third field experiment are described. (orig.). [Deutsch] Um eine Datenbasis fuer die Validierung von fortgeschrittenen Ausbreitungsmodellen zur Verfuegung zu stellen, werden umfangreiche meteorologische Messungen und Ausbreitungsexperimente in einem gut vermessenen nicht ebenem Gelaende durchgefuehrt. Diese Untersuchungen werden durch die Zusammenarbeit mit verschiedenen externen Gruppen und die finanzielle Unterstuetzung des Bundesministers fuer Umwelt, Naturschutz und Reaktorsicherheit ermoeglicht. In diesem Beriicht sind die Methoden, doe Experimente und die Ergebnisse der dritten Messkampagne zusammengestellt. (orig.).

  14. Dispersion modeling of accidental releases of toxic gases - Sensitivity study and optimization of the meteorological input

    Science.gov (United States)

    Baumann-Stanzer, K.; Stenzel, S.

    2009-04-01

    Several air dispersion models are available for prediction and simulation of the hazard areas associated with accidental releases of toxic gases. The most model packages (commercial or free of charge) include a chemical database, an intuitive graphical user interface (GUI) and automated graphical output for effective presentation of results. The models are designed especially for analyzing different accidental toxic release scenarios ("worst-case scenarios"), preparing emergency response plans and optimal countermeasures as well as for real-time risk assessment and management. Uncertainties in the meteorological input together with incorrect estimates of the source play a critical role for the model results. The research project RETOMOD (reference scenarios calculations for toxic gas releases - model systems and their utility for the fire brigade) was conducted by the Central Institute for Meteorology and Geodynamics (ZAMG) in cooperation with the Vienna fire brigade, OMV Refining & Marketing GmbH and Synex Ries & Greßlehner GmbH. RETOMOD was funded by the KIRAS safety research program at the Austrian Ministry of Transport, Innovation and Technology (www.kiras.at). The main tasks of this project were 1. Sensitivity study and optimization of the meteorological input for modeling of the hazard areas (human exposure) during the accidental toxic releases. 2. Comparison of several model packages (based on reference scenarios) in order to estimate the utility for the fire brigades. This presentation gives a short introduction to the project and presents the results of task 1 (meteorological input). The results of task 2 are presented by Stenzel and Baumann-Stanzer in this session. For the aim of this project, the observation-based analysis and forecasting system INCA, developed in the Central Institute for Meteorology and Geodynamics (ZAMG) was used. INCA (Integrated Nowcasting through Comprehensive Analysis) data were calculated with 1 km horizontal resolution and

  15. Preface: Proceedings of the Colloidal Dispersions in External Fields II Conference (Bonn-Bad Godesberg, 31 March 2 April 2008)

    Science.gov (United States)

    Löwen, H.

    2008-10-01

    This special issue reflects the scientific programme of the International Colloidal Dispersions in External Fields Conference (CODEF II) that took place in Bonn-Bad Godesberg from 31 March-2 April 2008. This is the second conference in a series that started in 2004 when the first CODEF meeting was held. The proceedings of the first CODEF meeting were summarized in a previous special issue (Journal of Physics: Condensed Matter 16 (issue 38)). The present issue represents recent progress in this rapidly developing field. The CODEF meeting series is held in conjunction with the German-Dutch Transregional Collaborative Research Centre SFB TR6 with the title Physics of Colloidal Dispersions in External Fields. Scientists working within this network as well as international invited guest speakers contributed to these meetings. The contributions in this issue are organized according to the type of different fields applied namely: bulk (no external field) shear flow electric field magnetic and laser-optical field confinement We would like to thank the CODEF II sponsors (Deutsche Forschungsgemeinschaft and MWFZ Mainz) for their financial support. Furthermore, we thank IOP Publishing for their willingness to publish the proceedings of this conference as a special issue. Participants O Alarcón-Waess (Puebla), M Allen (Coventry), J L Arauz-Lara (San Luis Potosi), L Assoud (Düsseldorf), G K Auernhammer (Mainz), R Backofen (Dresden), M Balbás-Gambra (Munich), J Bammert (Bayreuth), M Baptista (Mainz), J-L Barrat (Lyon), M Bier (Utrecht), K Binder (Mainz), R Blaak (Düsseldorf), V Blickle (Stuttgart), D Block (Kiel), S Böhm (Düsseldorf), V Botan (Mainz), J P Bouchaud (Paris), J Brader (Konstanz), G Brambilla (Montpellier), W J Briels (Enschede), M Brinkmann (Göttingen), C Brunet (Paris), H-J Butt (Mainz), M A Camargo Chaparro (Düsseldorf), R Castañeda Priego (Guanajuato), J J Cerdà Pino (Frankfurt), A Chatterji (Jülich), M Chavez Paez (San Luis Potosi), A Chremos

  16. Modelling of radionuclides dispersion in coastal waters. A study case on the dispersion of radionuclides released with the liquid effluents of Angra dos Reis NPP - Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, H.M.; Veiga, L.; Rochedo, E.; Vetere, M.I. [Instituto de Radioprotecao e Dosimetria (IRD), Rio de Janeiro, RJ (Brazil); Osvath, I. [International Atomic Energy Agency, Monaco (Monaco). Marine Environment Lab

    1997-12-31

    The problem of the dispersion of radionuclides at coastal areas is discussed. The study focused on the dispersion of {sup 3}H and {sup 137}Cs released at Ribeira Bay, Rio de Janeiro, Brazil, with the liquid effluents of the Angra dos Reis nuclear power plant. It has been demonstrated that due to the site specific hydrodynamics the exportation of radionuclides to the open ocean would be a rather fast process. The study also examined the best strategy for accidental releases. It could be evaluated that in terms of the radionuclide inventory in the boxes the release at Itaorna Inlet would be a better option than the release at Piraquara de Fora Inlet. However, this option should be examined after a detailed dose assessment study. (author) 6 refs.

  17. Theoretical study of the adsorption of aromatic units on carbon allotropes including explicit (empirical) DFT dispersion corrections and implicitly dispersion-corrected functionals: the pyridine case.

    Science.gov (United States)

    Ramos-Berdullas, Nicolás; Pérez-Juste, Ignacio; Van Alsenoy, Christian; Mandado, Marcos

    2015-01-01

    The suitability of implicitly dispersion-corrected functionals, namely the M06-2X, for the determination of interaction energies and electron polarization densities in adsorption studies of aromatic molecules on carbon allotropes surfaces is analysed by comparing the results with those obtained using explicit dispersion through Grimme's empirical corrections. Several models of increasing size for the graphene sheet together with one-dimensional curved carbon structures, (5,5), (6,6) and (7,7) armchair single-walled nanotubes, and two-dimensional curved carbon structures, C60 fullerene, have been considered as substrates in this work, whereas pyridine has been chosen as an example for the adsorbed aromatic molecule. Comparison with recent experimental estimations of the adsorption energy and calculations using periodic boundary conditions on a supercell of 72 carbon atoms indicates that a finite model containing ninety six carbon atoms (C96) approaches quite well the adsorption on a graphene sheet. Analysis of the interaction energy components reveals that the M06-2X functional accounts for most of the dispersion energy implicitly, followed far by wB97X and B3LYP, whereas B97 and BLYP do not differ too much from HF. It has been found that M06-2X corrects only the energy component associated to dispersion and leaves the rest, electrostatic, Pauli and induction "unaltered" with respect to the other DFT functionals investigated. Moreover, only the M06-2X functional reflects the effect of dispersion on the electron polarization density, whereas for the remaining functionals the polarization density does not differ too much from the HF density. This makes the former functional more suitable a priori for the calculation of electron density related properties in these adsorption complexes.

  18. VDTs: Field levels, epidemiology, and laboratory studies

    Energy Technology Data Exchange (ETDEWEB)

    Kavet, R.; Tell, R.A. (Richard Tell Associates, Inc., Las Vegas, NV (USA))

    1991-07-01

    As the use of video display terminals (VDTs) has expanded, questions have been raised as to whether working at a VDT affects the risk of adverse pregnancy outcome. A particular focus for these questions has been the very low frequency (VLF) magnetic field produced by a VDT's horizontal deflection coil. VDTs also produce VLF electric fields, extremely low frequency (ELF) electric and magnetic fields, and static electric fields, Ten studies of pregnancy outcome in VDT operators have been conducted in six countries, and with one exception, none has concluded that magnetic fields from VDTs may predispose pregnant operators to spontaneous abortion or congenital malformation. The epidemiologic studies conducted thus far do not provide a basis for concluding that VDT work and adverse pregnancy outcome are associated. Studies of fetal resorptions and malformations in rodents exposed to VLF magnetic fields have produced inconsistent findings. Two laboratories in Sweden that studied mice have reported positive results, one laboratory showing field-related malformations (but not resorptions) and the other showing field-related resorptions (but not malformations). Two Canadian laboratories have reported negative results in rats and mice. Studies of avian embryos have also yielded inconsistent results, but lacking a maternal-fetal placental interface, avian embryos are a questionable model for evaluating human reproductive risks. Finally, VLF electric and magnetic fields measured at the operator position are in compliance with field strength standards and guidelines that have been established around the world. 55 refs.

  19. Study of marine magnetic field

    Digital Repository Service at National Institute of Oceanography (India)

    Bhattacharya, G.C.

    (COB) is again both a basic scientific requirement as well at some places is a requirement under the UNCLOS related Legal Continental Shelf demarcation purpose. In the oceanic areas, the marine magnetic studies are one of the essential tools... oceans increased, more and more deviations from this simplified model, such as propagating ridges and overlapping spreading centers were discovered. These observations enabled the study of new aspects of seafloor spreading process beyond the initial...

  20. A Study On Dispersion Stability Of Nickel Nanoparticles Synthesized By Wire Explosion In Liquid Media

    Directory of Open Access Journals (Sweden)

    Kim C.K.

    2015-06-01

    Full Text Available In this study, nickel nanoparticles were synthesized in ethanol using portable pulsed wire evaporation, which is a one-step physical method. From transmission electron microscopy images, it was found that the Ni nanoparticles exhibited a spherical shape with an average diameter of 7.3 nm. To prevent aggregation of the nickel nanoparticles, a polymer surfactant was added into the ethanol before the synthesis of nickel nanoparticles, and adsorbed on the freshly synthesized nickel nanoparticles during the wire explosion. The dispersion stability of the prepared nickel nanofluids was investigated by zeta-potential analyzer and Turbiscan optical analyzer. As a result, the optimum concentration of polymer surfactant to be added was suggested for the maximized dispersion stability of the nickel nanofluids.

  1. Integral Field Spectroscopy of High-Redshift Star Forming Galaxies with Laser Guided Adaptive Optics: Evidence for Dispersion-Dominated Kinematics

    CERN Document Server

    Law, David R; Erb, Dawn K; Larkin, James E; Pettini, Max; Shapley, Alice E; Wright, Shelley A

    2007-01-01

    We present early results from an ongoing study of the kinematic structure of star-forming galaxies at redshift z ~ 2 - 3 using integral-field spectroscopy of rest-frame optical nebular emission lines in combination with Keck laser guide star adaptive optics (LGSAO). We show kinematic maps of 3 target galaxies Q1623-BX453, Q0449-BX93, and DSF2237a-C2 located at redshifts z = 2.1820, 2.0067, and 3.3172 respectively, each of which is well-resolved with a PSF measuring approximately 0.11 - 0.15 arcsec (~ 900 - 1200 pc at z ~ 2-3) after cosmetic smoothing. Neither galaxy at z ~ 2 exhibits substantial kinematic structure on scales >~ 30 km/s; both are instead consistent with largely dispersion-dominated velocity fields with sigma ~ 80 km/s along any given line of sight into the galaxy. In contrast, DSF2237a-C2 presents a well-resolved gradient in velocity over a distance of ~ 4 kpc with peak-to-peak amplitude of 140 km/s. It is unlikely that DSF2237a-C2 represents a dynamically cold rotating disk of ionized gas as ...

  2. Quality by design approach for formulation development: a case study of dispersible tablets.

    Science.gov (United States)

    Charoo, Naseem A; Shamsher, Areeg A A; Zidan, Ahmed S; Rahman, Ziyaur

    2012-02-28

    The focus of the current investigations was to apply quality by design (QbD) approach to the development of dispersible tablets. Critical material and process parameters are linked to the critical quality attributes of the product. Variability is reduced by product and process understanding which translates into quality improvement, risk reduction and productivity enhancement. The risk management approach further leads to better understanding of the risks, ways to mitigate them and control strategy is proposed commensurate with the level of the risk. Design space in combination with pharmaceutical quality management system provide for flexible regulatory approaches with opportunity for continuous improvement that benefit patient and manufacturer alike. The development of dispersible tablet was proposed in the current study through a QbD paradigm for a better patient compliance and product quality. The quality target product profile of a model biopharmaceutical class II drug was identified. Initial risk analysis led to the identification of the critical quality attributes. Physicochemical characterization and compatibility studies of the drug with commonly used excipients were performed. Experiments were designed with focus on critical material and process attributes. Design space was identified and risk factors for all the possible failure modes were below critical levels after the implementation of control strategy. Compliance to the design space provides an opportunity to release batches in a real time. In conclusion, QbD tools together with risk and quality management tools provided an effective and efficient paradigm to build the quality into dispersible tablet.

  3. Physicochemical studies on solid dispersions of poorly water-soluble drugs

    Energy Technology Data Exchange (ETDEWEB)

    Bikiaris, Dimitrios [Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, 541 24 Thessaloniki (Greece); Papageorgiou, George Z. [Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, 541 24 Thessaloniki (Greece); Stergiou, Anagnostis [Department of Physics, Aristotle University of Thessaloniki, 541 24, Thessaloniki (Greece); Pavlidou, Eleni [Department of Physics, Aristotle University of Thessaloniki, 541 24, Thessaloniki (Greece); Karavas, Evangelos [Pharmathen S.A., Pharmaceutical Industry, Dervenakion Str. 6, Pallini Attikis, 153 51 Attiki (Greece); Kanaze, Ferras [Section of Pharmaceutics and Drug Control, Department of Pharmacy, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Macedonia (Greece); Georgarakis, Manolis [Section of Pharmaceutics and Drug Control, Department of Pharmacy, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Macedonia (Greece)]. E-mail: georgara@pharm.auth.gr

    2005-12-01

    Polyvinylpyrrolidone (PVP) and poly(ethylene glycol) (PEG) solid dispersions with Felodipine or Hesperetin having up to 20 wt% drug were prepared using solvent evaporation method. Solid dispersions in comparison with their physical mixtures were studied using differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM) and hot stage polarizing light microscopy (HSM). PVP formulations with low drug load proved to be amorphous, since no crystalline Felodipine or Hesperetin drugs were detected using DSC and WAXD. Low and fast heating rates were applied for DSC study, to prevent changes in the samples caused during heating. Similarity between results of WAXD and DSC was also found in the case of physical mixtures, where the drug was in the crystalline state. However, though specific tests showed the high sensitivity of the DSC technique, it was difficult to arrive to reliable results for PEG solid dispersions or physical mixtures with low drug content by DSC, even by high heating rates. Crystalline drug could not be detected by DSC, leading to erroneous conclusions about the physical state of the drug, in contrast to WAXD. On the other hand, HSM proved the presence of small drug particles in the solid dispersions with PEG and the dissolution of the drug in the melt of PEG on heating. In such systems, in which a polymer with low melting point is used as drug carrier, DSC is inappropriate technique and must be used always in combination with HSM. The coupling of WAXD with thermal analysis, allowed complete physicochemical characterization and better understanding which is essential for a first prediction of dissolution characteristics of such formulations.

  4. Study on transport of Dy(Ⅲ) by dispersion supported liquid membrane

    Institute of Scientific and Technical Information of China (English)

    PEI Liang; YAO Binghua; FU Xinglong

    2009-01-01

    The transport of Dy(Ⅲ) through a dispersion supported liquid membrane (DSLM) consisting of polyvinylidene fluoride mem-brane (PVDF) as the liquid membrane support and dispersion solution including HC1 solution as the stripping solution and 2-ethyl hexyl phosphonic aeid-mono-2-ethyl hexyl ester (PC-88A) dissolved in kerosene as the membrane solution, was studied. The effects of pH value, initial concentration of Dy(Ⅲ) and different ionic strength in the feed phase, volume ratio of membrane solution and stripping solution, con-centration of HC1 solution, concentration of carder, different stripping agents in the dispersion phase on transport of Dy(Ⅲ) were also inves-tigated, respectively. As a result, when the concentration of HCI solution was 4.0 mol/L, concentration of PC-88A was 0.10 mol/L, and vol-ume ratio of membrane solution and stripping solution was 40:20 in the dispersion phase, and pH value was 5.0 in the feed phase, the trans-port effect of Dy(Ⅲ) was the best. Ionic strength had no obvious effect on transport of Dy(Ⅲ). Under the optimum condition studied, when initial concentration of Dy(Ⅲ) was 0.8×10-4 mol/L, the transport rate of Dy(Ⅲ) was up to 96.2% during the transport time of 95 min. The kinetic equation was developed in terms of the law of mass diffusion and the theory of interface chemistry. The diffusion coefficient of Dy(Ⅲ) in the membrane and the thickness of diffusion layer between feed phase and membrane phase were obtained and the values were 1.99×10-7 m2/s and 15.97 μm, respectively. The results were in good agreement with experimental results.

  5. The influence of the directional energy distribution on the nonlinear dispersion relation in a random gravity wave field

    Science.gov (United States)

    Huang, N. E.; Tung, C.-C.

    1977-01-01

    The influence of the directional distribution of wave energy on the dispersion relation is calculated numerically using various directional wave spectrum models. The results indicate that the dispersion relation varies both as a function of the directional energy distribution and the direction of propagation of the wave component under consideration. Furthermore, both the mean deviation and the random scatter from the linear approximation increase as the energy spreading decreases. Limited observational data are compared with the theoretical results. The agreement is favorable.

  6. Ion-dispersion and rapid electron fluctuations in the cusp: a case study

    Directory of Open Access Journals (Sweden)

    J. Lunde

    2008-08-01

    Full Text Available We present results from co-ordinated measurements with the low altitude REIMEI satellite and the ESR (EISCAT Svalbard Radar, together with other ground-based instruments carried out in February 2006. The results mainly relate to the dayside cusp where clear signatures of so-called ion-dispersion are seen in the satellite data. The cusp ion-dispersion is important for helping to understand the temporal and spatial structure of magnetopause reconnection. Whenever a satellite crosses boundaries of flux tubes or convection cells, cusp structures such as ion-dispersion will always be encountered. In our case we observed 3 distinct steps in the ion energy, but it includes at least 2 more steps as well, which we interpret as temporal features in relation to pulsed reconnection at the magnetopause. In addition, fast variations of the electron flux and energy occurring during these events have been studied in detail. The variations of the electron population, if interpreted as structures crossed by the REIMEI satellite, would map near the magnetopause to similar features as observed previously with the Cluster satellites. These were explained as Alfvén waves originating from an X-line of magnetic reconnection.

  7. Microcrystalline cellulose-carboxymethyl cellulose sodium as an effective dispersant for drug nanocrystals: A case study.

    Science.gov (United States)

    Dan, JiXiu; Ma, YueQin; Yue, PengFei; Xie, YuanBiao; Zheng, Qin; Hu, PengYi; Zhu, WeiFeng; Yang, Ming

    2016-01-20

    This study is aimed at seeking an alternative dispersant for spray drying of drug nanosuspensions. The ideal dispersant is not only able to prevent the agglomeration of drug nanocrystals in the suspension state, but also it is able to preserve redispersibility of drug nanocrystals after drying. An active pharmaceutical ingredient (API) was used as a model drug. API nanosuspensions were prepared by homogenization and converted into nanocrystals powder (API-NP) with microcrystalline cellulose-carboxymethyl cellulose sodium (MCCS) via spray drying. It was found that MCCS was able to prevent the aggregation of API-NP in the suspension state and the agglomeration during spray-drying process, possibility due to its high Zeta potential and steric barrier from network structure, and reduction of API size at nanoscale and incorporation into MCCS network structure did not affect the solid state of API as evidenced by DSC and XRD analysis. The spray-dried API-NP/MCCS powders exhibited excellent sphere-shape performance, and could easily redispersed to API-NC suspensions state. Dissolution of the spray-dried API-NP was distinctly superior to those of the crude powder and physical mixture, respectively. Within 30 min, approximate 85.87% of API was dissolved from the API-NP/MCCS. MCCS was demonstrated to be an effective dispersant for spray-dried drug nanocrystals and preservation of the nanocrystals associated with excellent redispersibility.

  8. [Study on Spatial Dispersal and Migration Events of Japanese Encephalitis Virus].

    Science.gov (United States)

    Gao, Xiaoyan; Zhou, Haiwei; Liu, Hong; Fu, Shihong; Wang, Huanyu; Guo, Zhenyang; Li, Xiaolong; Liang, Guodong

    2015-05-01

    To explore the spatial distribution mechanism of Japanese encephalitis virus (JEV), PhyML v3.0 was used to build phylogenetic tree using JEV sequences in the dataset. PAUP v4.0 and Migrapyhla softz ware were then used to analyze the migration events. The results showed that a total of 95 migration events were observed during the dispersal of JEV throughout Asia. Further analysis revealed that Thailand, and several Chinese provinces (including Shandong, Shanghai, Sichuan and Yunnan), were the main migration sources of JEV. JEV spread from these migration sources as follows: from Thailand to Australia, Cambodia, Tibet and India; from Shanghai to eastern coastal Asian regions and Yunnan; from Shandong to Korea, Zhejiang, Hubei, Shanxi and Liaoning; from Sichuan mainly to inland regions of China, as well as Vietnam and Japan; and from Yunnan to Zhejiang. This study indicated that frequent migration events occurred during the dispersal of JEV in the Asia and Pacific regions, and that Thailand, Shandong, Shanghai, Sichuan and Yunnan were the sources of JEV dispersal.

  9. A Statistical Study of Injection/Dispersion Events in Saturn's Inner Magnetosphere

    Science.gov (United States)

    Chen, Y.; Hill, T. W.

    2007-12-01

    In the inner magnetosphere of a rapidly rotating planet like Jupiter or Saturn, radial transport of plasma is mainly composed of hot, tenuous plasma moving inward and cold, denser plasma moving outward. The drift dispersion of injecting hot plasma provides direct evidence for this convective process. The Cassini Plasma Spectrometer (CAPS) has frequently reported observations of such injection/dispersion events [e.g., Burch et al., 2005 GRL L14S02; Hill et al., 2005 GRL L14S10]. Based on the study of Hill et al., the analysis of the properties of such signatures is continued in this paper, with a much larger data set of 26 Cassini orbits of Saturn, extending from July 2004 to August 2006. A statistical picture of the injection/dispersion characteristics is developed, indicating the distributions of ages, time scales and length scales. Moreover, an interesting rotational modulation of occurrence frequency is present in the Voyager-era Saturn Longitude System (SLS), but not in the Cassini-era Saturn Kilometric Radiation (SKR) system. A periodogram analysis using the Lomb-Scargle algorithm is underway to provide the accurate information of the recurrence period. Preliminary results show multiple-peaks in the period window near 11 hours.

  10. Conservation psychology as a field of study

    Directory of Open Access Journals (Sweden)

    Polona Kalc

    2016-01-01

    Full Text Available During the past decades the importance of psychology has become more prominent when addressing environmental issues. At the turn of the millennium a new field of psychological research was introduced to scientific community. The so-called conservation psychology strives to merge and spur basic and applied psychological research from the field of (proenvironmental behaviour and sustainable development. Together with environmental and population psychology, it forms Division 34 of American Psychological Association. However, conservation psychology is not a broadly known and renowned field of study in Slovenia. Therefore, the main purpose of the present article is to introduce conservation psychology as a possible field of study to Slovenian psychologists.

  11. Video Field Studies with your Cell Phone

    DEFF Research Database (Denmark)

    Buur, Jacob; Fraser, Euan

    2010-01-01

    Many researchers and practitioners in HCI, Interaction Design, Design Anthropology swear to video when dung field studies of potential users. This is due to the power of the media for capturing practices and contexts, conveying empathy, and engaging audiences. Newcomers to the field, and in parti......Many researchers and practitioners in HCI, Interaction Design, Design Anthropology swear to video when dung field studies of potential users. This is due to the power of the media for capturing practices and contexts, conveying empathy, and engaging audiences. Newcomers to the field...

  12. Dielectric Dispersion Studies Indicate Change in Structure of Water by Potentised Homeopathic Medicines

    Science.gov (United States)

    Mahata, C. R.

    2012-12-01

    Response of living bodies to different vastly `diluted' homeopathic medicines are different (rejecting the sceptic's view of `placebo' effect), though they are chemically same. Till now there is no satisfactory answer to how one such medicine differs from another in terms of scientifically measurable parameters. This paper tries to address this basic issue by taking two medicines of the same potency and two different potencies of the same medicine, namely, Arnica Mont 30c, 200c and Anacardium Orient 30c, 200c. These potencies are well above the Avogadro limit. The investigation reported here proceeds with the concept of `induced molecular structure' advanced by a number of scientists. Dielectric dispersion is used as the tool for experimental verification. It is based on the fact that when the exciting frequency of applied electric field equals the characteristic frequency, then macromolecules resonate leading to anomalous dielectric dispersion associated with sharp increase in dielectric loss, the resonance frequencies being different for macromolecules of different structures or dimensions. The results suggest that medicine- and potency-specific attributes are acquired by the vehicle (i.e. water) in the form of macromolecules generated by the potentization process of homeopathy making one medicine structurally different from another.

  13. Final Report for the Joint Urban 2003 Atmospheric Dispersion Study in Oklahoma City: Lawrence Livermore National Laboratory participation

    Energy Technology Data Exchange (ETDEWEB)

    Leach, M J

    2005-10-12

    The Joint Urban 2003 (JU2003) field study was designed to collect meteorological and tracer data resolving atmospheric dispersion at scales-of-motion ranging from flows in and around a single city block, in and around several blocks in the downtown Central Business District (CBD), and into the suburban Oklahoma City area a few km from the CBD. Indoor tracer and flow measurements within four downtown study buildings were also made in conjunction with detailed outdoor measurements investigating the outdoor-indoor exchange rates and mechanisms. The movement of tracer within the study buildings was also studied. The data from the field experiment is being used to evaluate models that are being developed for predicting dispersion of contaminants in urban areas. These models may be fast-response models based on semi-empirical algorithms that are used in real-time emergencies, or highly sophisticated computational fluid dynamics models that resolve individual building faces and crevices. The data from the field experiment, together with the models, can then be used to develop other advanced tools that are especially valuable in the efforts to thwart terrorists. These include tools for finding location and characteristics of a contaminant source; tools that can be used for real-time response or for forensic investigation. The tools will make use of monitoring networks for biological agents that are being established in several sensitive cities throughout the nation. This major urban study was conducted beginning June 28 and ending July 31, 2003. It included several integrated scientific components necessary to describe and understand the physical processes governing dispersion within and surrounding an urban area and into and within building environments. The components included characterizing: (1) the urban boundary layer and the development of the urban boundary layer within the atmospheric boundary layer, (2) the flows within and downwind of the tall-building core, (3

  14. Dispersal of Engineered Male Aedes aegypti Mosquitoes.

    Science.gov (United States)

    Winskill, Peter; Carvalho, Danilo O; Capurro, Margareth L; Alphey, Luke; Donnelly, Christl A; McKemey, Andrew R

    2015-11-01

    Aedes aegypti, the principal vector of dengue fever, have been genetically engineered for use in a sterile insect control programme. To improve our understanding of the dispersal ecology of mosquitoes and to inform appropriate release strategies of 'genetically sterile' male Aedes aegypti detailed knowledge of the dispersal ability of the released insects is needed. The dispersal ability of released 'genetically sterile' male Aedes aegypti at a field site in Brazil has been estimated. Dispersal kernels embedded within a generalized linear model framework were used to analyse data collected from three large scale mark release recapture studies. The methodology has been applied to previously published dispersal data to compare the dispersal ability of 'genetically sterile' male Aedes aegypti in contrasting environments. We parameterised dispersal kernels and estimated the mean distance travelled for insects in Brazil: 52.8 m (95% CI: 49.9 m, 56.8 m) and Malaysia: 58.0 m (95% CI: 51.1 m, 71.0 m). Our results provide specific, detailed estimates of the dispersal characteristics of released 'genetically sterile' male Aedes aegypti in the field. The comparative analysis indicates that despite differing environments and recapture rates, key features of the insects' dispersal kernels are conserved across the two studies. The results can be used to inform both risk assessments and release programmes using 'genetically sterile' male Aedes aegypti.

  15. Exfoliation and dispersion of LDH modified with N-tetrabromophthaloyl-glutamic in poly(vinyl alcohol): Morphological and thermal studies

    Indian Academy of Sciences (India)

    Shadpour Mallakpour; Mohammad Dinari; Meysam Talebi

    2015-03-01

    In this study, modified LDH (M-LDH) was synthesized by the co-precipitation reaction of Al(NO3)3.9H2O, Mg(NO3)2.6H2O and N-tetrabromophthaloyl-glutamic (Br-Gl) in short time. M-LDH nanofillers were embedded into poly(vinyl alcohol) (PVA) matrix via ultrasonic irradiation technique which provided PVA/M-LDH NCs. The morphology and structure of the prepared samples were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), field emission scanning electron microscopy and X-ray diffraction techniques TGA of the PVA/M-LDH NCs showed that the thermal stability was improved. The enhancement of thermal properties was ascribed to the homogeneous and good dispersion of M-LDH sheets in the PVA matrix by hydrogen bonding between O–H groups of PVA and the M-LDH.

  16. Self-organization of polyurethane pre-polymers as studied by self-consistent field theory

    NARCIS (Netherlands)

    Li, Feng; Tuinier, Remco; Casteren, Van Ilse; Tennebroek, Ronald; Overbeek, Ad; Leermakers, F.A.M.

    2016-01-01

    Using self-consistent field (SCF) theory, we studied the self-assembly characteristics of polyurethane pre-polymer dispersions in aqueous solutions. With a molecularly detailed model implementing the Scheutjens-Fleer discretization scheme, it is shown how the stability, equilibrium size, and inte

  17. Optimization study on the formulation of roxithromycin dispersible tablet using experimental design.

    Science.gov (United States)

    Weon, K Y; Lee, K T; Seo, S H

    2000-10-01

    This study set out to improve the physical and pharmaceutical characteristics of the present formulation using an appropriate experimental design. The work described here concerns the formulation of the dispersible tablet applying direct compression method containing roxithromycin in the form of coated granules. In this study 2(3) factorial design was used as screening test model and Central Composite Design (CCC) associated with response surface methodology was used as optimization study model to develop and to optimize the proper formulation of roxithromycin dispersible tablet. The three independent variables investigated were functional excipients like binder (X1), disintegrant (X2) and lubricant (X3). The effects of these variables were investigated on the following responses: hardness (Y1), friability (Y2) and disintegration time (Y3) of tablet. Three replicates at the center levels of the each design were used to independently calculate the experimental error and to detect any curvature in the response surface. This enabled the best formulations to be selected objectively. The effect order of each term to all response variable was X3> X2> X1> X1*X2> X2*X2> X2*X3> X3*X3> X1*X3> X1*X1 and model equations on each response variables were generated. Optimized compositions of formula were accordingly computed using those model equations and confirmed by following demonstration study. As a result, this study has demonstrated the efficiency and effectiveness of using a systematic formulation optimization process to develop the tablet formulation of roxithromycin dispersible tablet with limited experiment.

  18. A Variable-resolution Surface Wave Dispersion Study of Eurasia, North Africa, and Surrounding Regions

    Energy Technology Data Exchange (ETDEWEB)

    Pasyanos, M E

    2005-03-21

    This paper presents the results of a large-scale study of surface wave dispersion performed across Eurasia and North Africa. Improvements were made to previous surface wave work by enlarging the study region, increasing path density, improving spatial resolution, and expanding the period range. This study expands the coverage area northwards and eastwards relative to a previous dispersion analysis, which covered only North Africa and the Middle East. We have significantly increased the number of seismograms examined and group velocity measurements made. We have now made good quality dispersion measurements for about 30,000 Rayleigh wave and 20,000 Love wave paths, and have incorporated measurements from several other researchers into the study. A conjugate gradient method was employed for the group velocity tomography, which improved the inversion from the previous study by adopting a variable smoothness. This technique allows us to go to higher resolution where the data allow without producing artifacts. The current results include both Love and Rayleigh wave inversions across the region for periods from 7 to 100 seconds at 1{sup o} resolution. Short period group velocities are sensitive to slow velocities associated with large sedimentary features such as the Caspian Sea, West Siberian Platform, Mediterranean Sea, Bay of Bengal, Tarim Basin, and Persian Gulf. Intermediate periods are sensitive to differences in crustal thickness, such as those between oceanic and continental crust or along orogenic zones and continental plateaus. At longer periods, fast velocities are consistently found beneath cratons while slow upper mantle velocities occur along rift systems, subduction zones, and collision zones such as the Tethys Belt. We have compared the group velocities at various periods with features such as sediment thickness, topographic height, crustal thickness, proximity to plate boundaries, lithospheric age and lithospheric thickness, and find significant

  19. Accurate numerical simulation of the far-field tsunami caused by the 2011 Tohoku earthquake, including the effects of Boussinesq dispersion, seawater density stratification, elastic loading, and gravitational potential change

    Science.gov (United States)

    Baba, Toshitaka; Allgeyer, Sebastien; Hossen, Jakir; Cummins, Phil R.; Tsushima, Hiroaki; Imai, Kentaro; Yamashita, Kei; Kato, Toshihiro

    2017-03-01

    In this study, we considered the accurate calculation of far-field tsunami waveforms by using the shallow water equations and accounting for the effects of Boussinesq dispersion, seawater density stratification, elastic loading, and gravitational potential change in a finite difference scheme. By comparing numerical simulations that included and excluded each of these effects with the observed waveforms of the 2011 Tohoku tsunami, we found that all of these effects are significant and resolvable in the far field by the current generation of deep ocean-bottom pressure gauges. Our calculations using previously published, high-resolution models of the 2011 Tohoku tsunami source exhibited excellent agreement with the observed waveforms to a degree that has previously been possible only with near-field or regional observations. We suggest that the ability to model far-field tsunamis with high accuracy has important implications for tsunami source and hazard studies.

  20. Comparative study on dispersion and interfacial properties of single walled carbon nanotube/polymer composites using Hansen solubility parameters.

    Science.gov (United States)

    Ma, Jing; Larsen, Raino Mikael

    2013-02-01

    Dispersion and interfacial strain transfer of single walled carbon nanotubes (SWNTs) are two major challenges for the utilization of SWNTs as reinforcements in polymer composites. Surface modifications could help change the dispersion and interfacial properties. In this study, nanocomposites were fabricated by solution blending 1 wt % SWNTs with various modification (nonmodified, nitric acid functionalized, and amine functionalized SWNTs) and three kinds of polymeric materials (polycarbonate, polyvinylidene fluoride, and epoxy). Chemical compatibilities between SWNTs and solvents or polymers are calculated by the Hansen solubility parameters (HSP) method. The dispersion of the SWNTs in solvents is evaluated by dynamic light scattering. The dispersion of SWNTs in polymers evaluated by a light optical microscope (LOM) generally agrees with the HSP prediction. The strain transfer from the matrix to SWNTs is mainly related to the dispersion, the bundle size, the residual thermal stresses on the sample, and, to lesser degree, the HSP.

  1. The hydraulics of a straight bedrock channel: Insights from solute dispersion studies

    Science.gov (United States)

    Richardson, Keith; Carling, Paul Anthony

    2006-12-01

    temporary storage zones for solute. The changes in bulk flow parameters observed at discharges in excess of Q2 indicate that a significant portion of the channel cross section is acting only as storage and is not contributing to the discharge of the channel. This can be explained by the presence of a central core flow decoupled from marginal slack water and from dead zones in the margins. The results show that the study reach behaves differently from channels from which dispersive fraction values have previously been reported for a range of discharges.

  2. The influence of an electric field on photodegradation and self healing in disperse orange 11 dye-doped PMMA thin films

    CERN Document Server

    Anderson, Benjamin; Kuzyk, Mark G

    2013-01-01

    The influence of an applied electric field on reversible photodegradation of disperse orange 11 (DO11) doped into PMMA is measured using digital imaging and conductivity measurements. Correlations between optical imaging, which measures photodegradation and recovery, and photoconductivity enables an association to be made between the damaged fragments and their contribution to current, thus establishing that damaged fragments are charged species, or polarizable. Hence, the decay and recovery process should be controllable with the applications of an electric field. Indeed, we find that the dye polymer system is highly sensitive to an applied electric field, which drastically affects the decay and recovery dynamics. We demonstrate accelerated recovery when one field polarity is applied during burning, and the opposite polarity is applied during recovery. This work suggests that the damage threshold can be increased through electric field conditioning; and, the results are qualitatively consistent with the doma...

  3. A Study on the Impact of Vegetation and Green Roof on Increasing the Wind Speed and Pollutants Dispersion in the Urban Canyons Based on Computational Fluid Dynamics Model

    Directory of Open Access Journals (Sweden)

    SH Hosseini

    2016-12-01

    Full Text Available Background and Objective: Increasing population growth and construction of high-rise buildings have doubled the amount of environmental pollution in the cities. Moreover, people use the open urban spaces more than before in order to meet their ecological needs. Accordingly, some parameters such as various vegetation and continuous winds streams can be considerably influential in transmittance of the particle pollution.  Therefore, the aim of this research was to study the impacts of different green roofs on the dispersion of pollutants in the standpoint of height and density for urban airflow condition of Shiraz City, Iran. Materials and Methods: In this study, a literature review in the field computer simulation with the help of computational fluid dynamics (CFD model in Envi-met software environment was used. Results: Regarding the importance of using vegetation in the urban spaces, vertical dispersion of the particles in presence of vegetation was explored. By comparing the basic model (without vegetation results with models including vegetation with short, medium and high crowns, it was revealed that vegetation with medium crowns is the closest model to the basic model with a difference of 7.65 m2/s in terms of vertical dispersion of particles; in fact, it was the most optimized condition for maximizing the dispersion of environmental pollutants. Conclusion: The results showed that the green roofs in the buildings increase the horizontal dispersion of the particulate pollution and decrease this term in the vertical dispersion. Finally, by an expansion of green roof usage in the buildings the sustainability in architecture and urbanism can be achieved.

  4. Dry powder inhalers: study of the parameters influencing adhesion and dispersion of fluticasone propionate.

    Science.gov (United States)

    Le, V N P; Hoang Thi, T H; Robins, E; Flament, M P

    2012-06-01

    Interactions between particles are dependent on the physicochemical characteristics of the interacting particles but it is also important to consider the manufacturing process. Blending active pharmaceutical ingredient (API) with carrier is a critical stage that determines the blend homogeneity and is the first step towards obtaining the final quality of the powder blend. The aim of this work was to study parameters that influence the interactions between API and carrier in adhesive mixtures used in DPI and their effect on API dispersion. The study was done with fluticasone propionate blended with lactose 'Lactohale 200'. The study was based on the influence of the operating conditions (speed, mixing time, resting steps during mixing), the size of the carrier and the storage conditions on the blend properties and on the API dispersion. The quality of the blends was examined by analysing the API content uniformity. Adhesion characteristics were evaluated by submitting mixtures to a sieving action by air depression with the Alpine air-jet sieve. Aerodynamic evaluation of fine particle fraction (FPF) was obtained using a Twin Stage Impinger; the FPF being defined as the mass percentage of API below 6.4 μm. For good dispersion and therefore good homogeneity of the API in the carrier particles, speed and powder blending time have to be sufficient, but not too long to prevent the appearance of static electricity, which is not favourable to homogeneity and stability. The FPF increases with the decrease in the carrier size. The storage conditions have also to be taken into consideration. Higher humidity favours the adhesion of API on the carrier and decreases the FPF.

  5. Determination of hydraulic conductivity in three dimensions and its relation to dispersivity: Chapter D in Ground-water contamination by crude oil at the Bemidji, Minnesota, research site; US Geological Survey Toxic Waste--ground-water contamination study

    Science.gov (United States)

    1984-01-01

    Recent investigations suggest that dispersion in aquifers is scale dependent and a function of the heterogeneity of aquifer materials. Theoretical stochastic studies indicate that determining hydraulic-conductivity variability in three dimensions is important in analyzing the dispersion process. Even though field methods are available to approximate hydraulic conductivity in three dimensions, the methods are not generally used because of high cost of field equipment and because measurement and analysis techniques are cumbersome and time consuming. The hypothesis of this study is that field-determined values of dispersivity are scale dependent and that they may be described as a function of hydraulic conductivity in three dimensions. The objectives of the study at the Bemidji research site are to (1) determine hydraulic conductivity of the porous media in three dimensions, (2) determine field values of dispersivity and its scale dependence on hydraulic conductivity, and (3) develop and apply a computerized data-collection, storage, and analysis system for field use in comprehensive determination of hydraulic conductivity and dispersivity. Plans for this investigation involve a variety of methods of analysis. Hydraulic conductivity will be determined separately in the horizontal and vertical planes of the hydraulic-conductivity ellipsoid. Field values of dispersivity will be determined by single-well and doublet-well injection or withdrawal tests with tracers. A computerized data-collection, storage, and analysis system to measure pressure, flow rate, tracer concentrations, and temperature will be designed for field testing. Real-time computer programs will be used to analyze field data. The initial methods of analysis will be utilized to meet the objectives of the study. Preliminary field data indicate the aquifer underlying the Bemidji site is vertically heterogeneous, cross-bedded outwash. Preliminary analysis of the flow field around a hypothetical doublet

  6. Experimental Study of Dispersion and Deposition of Expiratory Aerosols in Aircraft Cabins and Impact on Infectious Disease Transmission

    DEFF Research Database (Denmark)

    To, G.N.S.; Wan, M.P.; Chao, C.Y.H.

    2009-01-01

    The dispersion and deposition characteristics of polydispersed expiratory aerosols were investigated in an aircraft cabin mockup to study the transmission of infectious diseases. The airflow was characterized by particle image velocimetry (PIV) measurements. Aerosol dispersionwas measured...

  7. Rheology and orientational distributions of rodlike particles with magnetic moment normal to the particle axis for semi-dense dispersions (analysis by means of mean field approximation).

    Science.gov (United States)

    Satoh, Akira; Sakuda, Yasuhiro

    2007-04-15

    We have considered a semi-dense dispersion composed of ferromagnetic rodlike particles with a magnetic moment normal to the particle axis to investigate the rheological properties and particle orientational distribution in a simple shear flow as well as an external magnetic field. We have adopted the mean field approximation to take into account magnetic particle-particle interactions. The basic equation of the orientational distribution function has been derived from the balance of the torques and solved numerically. The results obtained here are summarized as follows. For a very strong magnetic field, the magnetic moment of the rodlike particle is strongly restricted in the field direction, so that the particle points to directions normal to the flow direction (and also to the magnetic field direction). This characteristic of the particle orientational distribution is also valid for the case of a strong particle-particle interaction, as in the strong magnetic field case. To the contrary, for a weak interaction among particles, the particle orientational distribution is governed by a shear flow as well as an applied magnetic field. When the magnetic particle-particle interaction is strong under circumstances of an applied magnetic field, the magnetic moment has a tendency to incline to the magnetic field direction more strongly. This leads to the characteristic that the viscosity decreases with decreasing the distance between particles, and this tendency becomes more significant for a stronger particle-particle interaction. These characteristics concerning the viscosity are quite different from those for a semi-dense dispersion composed of rodlike particles with a magnetic moment along the particle direction.

  8. Rheological properties and orientational distributions of dilute ferromagnetic spherocylinder particle dispersions. Part II. Analysis for the two typical magnetic field directions.

    Science.gov (United States)

    Aoshima, Masayuki; Satoh, Akira; Chantrell, Roy W; Coverdale, Geoff N

    2002-09-15

    We have investigated the orientational distributions and rheological properties of dilute colloidal dispersions, which consist of ferromagnetic spherocylinder particles. First, the governing equation of the orientational distribution function has been derived for the typical two cases of magnetic field directions: the direction parallel to the shear flow and the direction parallel to the angular velocity vector of the shear flow. The equation has been solved approximately by Galerkin's method. With these numerical solutions we have obtained the results of the orientational distribution and viscosity. The results obtained for the magnetic field in the shear flow direction are summarized as follows. In the case of a weak magnetic field, the particle tends to orient nearly toward the shear flow direction and its opposite direction. As the magnetic field increases, the orientation of the particle is restricted and the viscosity increases significantly. As the influence of the magnetic field becomes dominant, an overshoot in the viscosity curve appears. This is due to the fact that there is a maximum deviation of the averaged particle direction from the magnetic field direction. When the strength of the magnetic field increases significantly, the particle inclines close to the magnetic field direction and the viscosity converges to a constant value. Particles with a larger aspect ratio give rise to a larger increment in the viscosity since such elongated particles induce larger resistance in a flow field. We also have obtained results for the case of the magnetic field in the direction parallel to the angular velocity vector of the shear flow. When the flow field is dominant over both the rotational Brownian motion and the magnetic interaction, the particle rotates in the plane nearly perpendicular to the magnetic field direction. As the magnetic field increases, the particle inclines toward the magnetic direction. For this direction of field, the viscosity is

  9. Ultra-sensitive speciation analysis of mercury by CE-ICP-MS together with field-amplified sample stacking injection and dispersive solid-phase extraction.

    Science.gov (United States)

    Chen, YiQuan; Cheng, Xian; Mo, Fan; Huang, LiMei; Wu, Zujian; Wu, Yongning; Xu, LiangJun; Fu, FengFu

    2016-04-01

    A simple dispersive solid-phase extraction (DSPE) used to extract and preconcentrate ultra-trace MeHg, EtHg and Hg(2+) from water sample, and a sensitive method for the simultaneous analysis of MeHg, EtHg and Hg(2+) by using capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS) with field-amplified sample stacking injection (FASI) were first reported in this study. The DSPE used thiol cotton particles as adsorbent, and is simple and effective. It can be used to extract and preconcentrate ultra-trace mercury compounds in water samples within 30 min with a satisfied recovery and no mercury species alteration during the process. The FASI enhanced the sensitivity of CE-ICP-MS with 25-fold, 29-fold and 27-fold for MeHg, EtHg and Hg(2+) , respectively. Using FASI-CE-ICP-MS together with DSPE, we have successfully determined ultra-trace MeHg, EtHg and Hg(2+) in tap water with a limits of quantification (LOQs) of 0.26-0.45 pg/mL, an RSD (n = 3) mercury.

  10. In vivo field dependence of proton relaxation times in human brain, liver and skeletal muscle: a multicenter study

    DEFF Research Database (Denmark)

    Henriksen, O; de Certaines, J D; Spisni, A;

    1993-01-01

    T1 and T2 relaxation times are fundamental parameters for signal contrast behaviour in MRI. A number of ex vivo relaxometry studies have dealt with the magnetic field dispersion of T1. By means of multicenter study within the frame of the COMAC BME Concerted Action on Tissue Characterization by MRI...... and MRS, the in vivo field dispersion of T1 and T2 has been measured in order to evaluate whether ex vivo data are representative for the in vivo situation. Brain, skeletal muscle, and liver of healthy human volunteers were studied. Fifteen MR units with a field strength ranging from 0.08 T to 1.5 T took...... part in the trial, which comprised 218 volunteers. All the MR systems were tested for measurement accuracy using the Eurospin TO5 test object. The measured relaxation data were subsequently corrected according to the obtained calibration curves. The results showed a clear field dispersion of T1...

  11. Simple field-based automated dispersive liquid-liquid microextraction of trace level phthalate esters in natural waters with gas chromatography and mass spectrometric analysis.

    Science.gov (United States)

    Leng, Geng; Chen, Wenjin; Wang, Yong

    2016-09-01

    A small, simple, and field-based automated dispersive liquid-liquid microextraction method followed by gas chromatography mass spectrometric analysis was developed for trace level phthalate esters analysis in natural waters. With a single syringe pump that is coupled with a multiposition valve, the whole extraction procedure including cleaning, sampling, mixing of extractant and disperser solvents, extraction, phase separation, and analytes collection was carried out in a totally automated way with a sample throughput of 21 h(-1) . Key factors, such as type and ratio of the extractant and disperser solvent, aspiration flow rate, extraction time, and matrix effect, were thoroughly investigated. Under the optimum conditions, linearity was found in the range from 0.03 to 60 μg/L. Limits of detection ranged from 0.0015 to 0.003 μg/L. Enrichment factors were in a range of 106-141. Reproducibility and recoveries were assessed by testing a series of three natural water samples that were spiked with different concentration levels. Finally, the proposed method was successfully applied in analysis of real surface waters. The developed system is inexpensive, light (2.6 kg), simple to use, applicable in the field, with high sample throughput, and sensitive enough for trace level phthalate esters analysis in natural waters.

  12. Substituted corannulenes and sumanenes as fullerene receptors. A dispersion-corrected density functional theory study.

    Science.gov (United States)

    Josa, Daniela; Rodríguez-Otero, Jesús; Cabaleiro-Lago, Enrique M; Santos, Lucas A; Ramalho, Teodorico C

    2014-10-09

    Stacking interactions between substituted buckybowls (corannulene and sumanene) with fullerenes (C60 and C70) were studied at the B97-D2/TZVP level of theory. Corannulene and sumanene monomers were substituted with five and six Br, Cl, CH3, C2H, or CN units, respectively. A comprehensive study was conducted, analyzing the interaction of corannulenes and sumanenes with several faces of both fullerenes. According to our results, in all cases substitution gave rise to larger interaction energies if compared with those of unsubstituted buckybowls. The increase of dispersion seems to be the main source of the enhanced binding, so an excellent correlation between the increase of interaction energy and the increase of dispersion contribution takes place. One of the noteworthy phenomena that appears is the so-called CH···π interaction, which is responsible for the strong interaction of sumanene complexes (if compared with that of corannulene complexes). This interaction also causes the substitution with CH3 groups (in which one of the H atoms points directly to the π cloud of fullerene) to be the most favorable case. This fact can be easily visualized by noncovalent interaction plots.

  13. Dispersion/Aggregation of polymer grafted nanorods in a polymer matrix studied by Dissipative Particle Dynamics

    Science.gov (United States)

    Maia, Joao; Khani, Shaghayegh

    2015-03-01

    Nanorods are incorporated into polymer matrices for fabricating composite materials with enhanced physical and mechanical properties.The final macroscopic properties of the composites are directly related to the dispersion and organization of the nanoparticles in the matrix. For instance, a significant improvement in the mechanical properties of the nanorod-polymer composites is observed upon formation of a percolating network. One way of controlling the assembly of nanorods in the polymer medium is adjusting the chemical interactions which is done through grafting polymer chains on the surface of the rods. The recent developments in the computational techniques have paved the road for further understanding of the controlled dispersion and aggregation of nanorods in polymer matrices. In this study, Dissipative Particle Dynamics (DPD) is employed in order to investigate the effect of enthalpic and entopic variables on the phase behavior of the abovementioned nanocomposites. In DPD, the interaction parameter between the components of the systems can be mapped onto the Flory-Huggins χ-parameter via well-known Groot-Warren expression. This works studies the effect of the enthalpic and entropic variables on phase transitions. The main goal is to provide a phase diagram than can be used to guide the experiments in designing new materials.

  14. Quantification of myocardial blood flow and blood flow reserve in the presence of arterial dispersion: a simulation study.

    Science.gov (United States)

    Schmitt, Melanie; Viallon, Magalie; Thelen, Manfred; Schreiber, Wolfgang G

    2002-04-01

    Myocardial blood flow (MBF) can be quantified using dynamic T1-weighted MRI of diffusible tracers and a mathematical model of underlying vasculature. Quantification of MBF by means of T1- weighted MRI requires knowledge of the arterial input function (AIF). The AIF can be estimated from the left ventricular (LV) cavity. However, dispersion may occur between the LV and the tissue of interest because of the laminar blood flow profiles, branching of venules, and because of stenosis. To evaluate the influence of dispersion on the results of MBF quantification, a simulation study was performed. The dispersion was described as a convolution of the AIF with an exponential residue function. Synthetic tissue and AIF curves were analyzed and the derived parameters fit to the simulated parameters. The results show that an unaccounted dispersion may result in a systematic underestimation of MBF up to approximately 50%. Underestimation increases with increasing dispersion and with increasing MBF. Assuming equal dispersion at rest and during hyperemia, myocardial perfusion reserve (MPR) estimates are also susceptible to underestimation of approximately 20%. An unaccounted dispersion therefore can lead to systematic underestimation of both blood flow and perfusion reserve.

  15. Predicting dispersal of auto-gyrating fruit in tropical trees: a case study from the Dipterocarpaceae.

    Science.gov (United States)

    Smith, James R; Bagchi, Robert; Ellens, Judith; Kettle, Chris J; Burslem, David F R P; Maycock, Colin R; Khoo, Eyen; Ghazoul, Jaboury

    2015-05-01

    Seed dispersal governs the distribution of plant propagules in the landscape and hence forms the template on which density-dependent processes act. Dispersal is therefore a vital component of many species coexistence and forest dynamics models and is of applied value in understanding forest regeneration. Research on the processes that facilitate forest regeneration and restoration is given further weight in the context of widespread loss and degradation of tropical forests, and provides impetus to improve estimates of seed dispersal for tropical forest trees. South-East Asian lowland rainforests, which have been subject to severe degradation, are dominated by trees of the Dipterocarpaceae family which constitute over 40% of forest biomass. Dipterocarp dispersal is generally considered to be poor given their large, gyration-dispersed fruits. However, there is wide variability in fruit size and morphology which we hypothesize mechanistically underpins dispersal potential through the lift provided to seeds mediated by the wings. We explored experimentally how the ratio of fruit wing area to mass ("inverse wing loading," IWL) explains variation in seed dispersal kernels among 13 dipterocarp species by releasing fruit from a canopy tower. Horizontal seed dispersal distances increased with IWL, especially at high wind speeds. Seed dispersal of all species was predominantly local, with 90% of seed dispersing <10 m, although maximum dispersal distances varied widely among species. We present a generic seed dispersal model for dipterocarps based on attributes of seed morphology and provide modeled seed dispersal kernels for all dipterocarp species with IWLs of 1-50, representing 75% of species in Borneo.

  16. Simulation study of dispersion and removal of particulate matter from traffic by road-side vegetation barrier.

    Science.gov (United States)

    Morakinyo, Tobi Eniolu; Lam, Yun Fat

    2016-04-01

    Well-positioned and configured vegetation barriers (VBs) have been suggested as one of the green infrastructures that could improve near-road (local) air quality. This is because of their influence on the underlying mechanisms: dispersion and mass removal (by deposition). Some studies have investigated air quality improvement by near-road vegetation barrier using the dispersion-related method while few studies have done the same using the deposition-related method. However, decision making on vegetation barrier's configuration and placement for need-based maximum benefit requires a combined assessment with both methods which are not commonly found in a single study. In the present study, we employed a computational fluid dynamics model, ENVI-met, to evaluate the air quality benefit of near-road vegetation barrier using an integrated dispersion-deposition approach. A technique based on distance between source (road) and point of peak concentration before dwindling concentration downwind begins referred to as "distance to maximum concentration (DMC)" has been proposed to determine optimum position from source and thickness of vegetation barrier for improved dispersion and deposition-based benefit, respectively. Generally, a higher volume of vegetation barrier increases the overall mass removal while it weakens dispersion of pollutant within the same domain. Hence, the benefit of roadside vegetation barrier is need-based and can be expressed as either higher mass deposition or higher mass dispersion. Finally, recommendations on applications of our findings were presented.

  17. Evaluating Wind Fields from a Diagnostic Model Over Complex Terrain in the Phoenix Region and Implications to Dispersion Calculations for Regional Emergency Response

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Weiguo; Shaw, William J.

    2009-12-01

    This paper compares the wind field from a diagnostic model (CALMET) over complex terrain in the Phoenix region in the USA with observations that are gridded by a state-of-the-art Four-Dimensional Data Assimilation (FDDA) system. The wind difference between the CALMET and FDDA wind fields is larger at night than in the day. The magnitude of the wind difference can be smaller than 5% of the mean wind speed at low levels in areas with dense observational stations, while it can be larger than 80% in areas without observational stations or at high altitudes. The vector-mean wind direction difference over the domain is 15 deg on the surface level and 25 deg between 10 and 1500 m. To evaluate the effects of the wind difference on dispersion calculations, dispersion of a hypothetical passive tracer released from surface point sources is simulated by the second-order closure integrated puff (SCIPUFF) model driven by the CALMET and FDDA wind fields, respectively. Differences in the two simulated tracer concentration fields increase with time due to accumulation of effects of the wind differences both near the surface and at higher altitudes. Even for the release in the area with the densest distribution of surface stations, the relative difference in the peak surface concentration from CALMET-SCIPUFF and from FDDA-SCIPUFF is less than 10% only within 0.5 hr after the release in the afternoon, and increases to 70% at 1.5 hr; this is because of large differences in wind above the surface. For the release in the area with few stations, the difference can be larger than 100% or even larger after 1.5 hr from the release. To improve dispersion simulations driven by the CALMET wind in the region, observations at upper-air stations are needed and the current surface observation network needs to be reorganized or more stations are needed to account for the influence of terrain.

  18. Nonperturbative studies of quantum field theories on noncommutative spaces

    Energy Technology Data Exchange (ETDEWEB)

    Volkholz, J.

    2007-11-16

    This work deals with three quantum field theories on spaces with noncommuting position operators. Noncommutative models occur in the study of string theories and quantum gravity. They usually elude treatment beyond the perturbative level. Due to the technique of dimensional reduction, however, we are able to investigate these theories nonperturbatively. This entails translating the action functionals into a matrix language, which is suitable for numerical simulations. First we explore the {lambda}{phi}{sup 4} model on a noncommutative plane. We investigate the continuum limit at fixed noncommutativity, which is known as the double scaling limit. Here we focus especially on the fate of the striped phase, a phase peculiar to the noncommutative version of the regularized {lambda}{phi}{sup 4} model. We find no evidence for its existence in the double scaling limit. Next we examine the U(1) gauge theory on a four-dimensional spacetime, where two spatial directions are noncommutative. We examine the phase structure and find a new phase with a spontaneously broken translation symmetry. In addition we demonstrate the existence of a finite double scaling limit which confirms the renormalizability of the theory. Furthermore we investigate the dispersion relation of the photon. In the weak coupling phase our results are consistent with an infrared instability predicted by perturbation theory. If the translational symmetry is broken, however, we find a dispersion relation corresponding to a massless particle. Finally, we investigate a supersymmetric theory on the fuzzy sphere, which features scalar neutral bosons and Majorana fermions. The supersymmetry is exact in the limit of infinitely large matrices. We investigate the phase structure of the model and find three distinct phases. Summarizing, we study noncommutative field theories beyond perturbation theory. Moreover, we simulate a supersymmetric theory on the fuzzy sphere, which might provide an alternative to attempted

  19. Thermal compatibility studies of unirradiated UMo alloys dispersed in aluminum

    Science.gov (United States)

    Lee, Don Bae; Kim, Ki Hwan; Kim, Chang Kyu

    1997-11-01

    The thermal compatibility of centrifugally atomized UMo alloys with aluminium has been studied. The results of the investigations show that the U-2 wt% Mo/aluminum dispersions increase in volume by 26% at 400°C after 2000 h. This large volume change is mainly due to the formation of voids and cracks resulting from nearly complete interdiffusion of UMo and aluminum. No significant dimensional changes occur in the U-10 wt% Mo/aluminum dispersions. Interdiffusion between U-10 wt% Mo and aluminum is found to be minimal. The different diffusion behavior is primarily due to the fact that U-10 wt% Mo particles are much more supersaturated with substitutional molybdenum than U-2 wt% Mo particles. The aluminum diffuses into the U-2 wt% Mo particles relatively rapidly along grain boundary with nearly pure uranium, forming UAl 3 almost fully throughout the 2000 h anneal, whereas the molybdenum supersaturated in the U-10 wt% Mo particles inhibits the diffusion of aluminum atoms. U-10 wt% Mo displays superior thermal compatibility with aluminum compared to U-2 wt% Mo.

  20. Using ancient DNA to study the origins and dispersal of ancestral Polynesian chickens across the Pacific.

    Science.gov (United States)

    Thomson, Vicki A; Lebrasseur, Ophélie; Austin, Jeremy J; Hunt, Terry L; Burney, David A; Denham, Tim; Rawlence, Nicolas J; Wood, Jamie R; Gongora, Jaime; Girdland Flink, Linus; Linderholm, Anna; Dobney, Keith; Larson, Greger; Cooper, Alan

    2014-04-01

    The human colonization of Remote Oceania remains one of the great feats of exploration in history, proceeding east from Asia across the vast expanse of the Pacific Ocean. Human commensal and domesticated species were widely transported as part of this diaspora, possibly as far as South America. We sequenced mitochondrial control region DNA from 122 modern and 22 ancient chicken specimens from Polynesia and Island Southeast Asia and used these together with Bayesian modeling methods to examine the human dispersal of chickens across this area. We show that specific techniques are essential to remove contaminating modern DNA from experiments, which appear to have impacted previous studies of Pacific chickens. In contrast to previous reports, we find that all ancient specimens and a high proportion of the modern chickens possess a group of unique, closely related haplotypes found only in the Pacific. This group of haplotypes appears to represent the authentic founding mitochondrial DNA chicken lineages transported across the Pacific, and allows the early dispersal of chickens across Micronesia and Polynesia to be modeled. Importantly, chickens carrying this genetic signature persist on several Pacific islands at high frequencies, suggesting that the original Polynesian chicken lineages may still survive. No early South American chicken samples have been detected with the diagnostic Polynesian mtDNA haplotypes, arguing against reports that chickens provide evidence of Polynesian contact with pre-European South America. Two modern specimens from the Philippines carry haplotypes similar to the ancient Pacific samples, providing clues about a potential homeland for the Polynesian chicken.

  1. Assessing nanomaterial exposures in aquatic ecotoxicological testing: Framework and case studies based on dispersion and dissolution.

    Science.gov (United States)

    Kennedy, Alan J; Coleman, Jessica G; Diamond, Stephen A; Melby, Nicolas L; Bednar, Anthony J; Harmon, Ashley; Collier, Zachary A; Moser, Robert

    2017-05-01

    The unique behavior of engineered nanomaterials (ENM) in aqueous media and dynamic changes in particle settling, agglomeration and dissolution rates is a challenge to the consistency, reliability and interpretation of standard aquatic hazard bioassay results. While the toxicological endpoints (e.g., survival, growth, reproduction, etc.) in ecotoxicity bioassays are largely applicable to ENMs, the standard methods as written for dissolved substances are confounded by the dynamic settling, agglomeration and dissolution of particulate ENMs during the bioassay. A testing framework was designed to serve as a starting point to identify approaches for the consistent conduct of aquatic hazard tests that account for the behavior of ENMs in test media and suitable data collection to support representative exposure metrology. The framework was demonstrated by conducting three case studies testing ENMs with functionally distinct characteristics and behaviors. Pretests with a temporal sampling of particle concentration, agglomeration and dissolution were conducted on each ENM in test media. Results indicated that a silver nanoparticle (AgNP) powder was not dispersible, a nano-TiO2 powder was dispersible but unstable, and a polyvinylpyrrolidinone-coated AgNP was relatively stable in test media. Based on these functional results, Ceriodaphnia dubia bioassays were conducted to compare different exposure summary methods (nominal, arithmetic average, geometric average, time-weighted average) for calculating and expressing toxicity endpoints. Results indicated that while arithmetic means were effective for expressing the toxicity of more stable materials, time-weighted averaged concentrations were appropriate for the unstable nano-TiO2.

  2. An experimental study of dielectric dispersion in porous media and its dependence on pore geometry

    Energy Technology Data Exchange (ETDEWEB)

    Haslund, E.

    1996-12-31

    Understanding water saturated composite media are important in the study of oil reservoirs. This doctoral thesis discusses measurements of the frequency dependent permittivity and conductivity of water saturated porous glass specimens. The experiments are designed to investigate the dispersion resulting from the geometrical properties of the pore space. Measurements are presented of the effective complex dielectric constant of water saturated porous glass specimens for frequencies below 13 MHz. The specimens are made from sintered glass spheres, and in some specimens thin plates are mixed in with the spheres. Low-conductivity water is used to saturate the pore space in order to scale the frequency range of the Maxwell-Wagner dispersion into the measurement range. The experiments are compared with two different effective medium approaches. One approach is the Mendelson and Cohen theory with randomly oriented spheroidal grains in addition to spherical grains, the other the Local porosity theory due to Hilfer. Both theories were found to be in good agreement with the experimental observations. 175 refs., 59 figs., 1 table

  3. Kinetic modeling and half life study on bioremediation of crude oil dispersed by Corexit 9500

    Energy Technology Data Exchange (ETDEWEB)

    Zahed, Mohammad Ali [School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang (Malaysia); Aziz, Hamidi Abdul, E-mail: cehamidi@eng.usm.my [School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang (Malaysia); Isa, Mohamed Hasnain [Civil Engineering Department, Universiti Teknologi PETRONAS, 31750 Tronoh, Perak (Malaysia); Mohajeri, Leila; Mohajeri, Soraya [School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang (Malaysia); Kutty, Shamsul Rahman Mohamed [Civil Engineering Department, Universiti Teknologi PETRONAS, 31750 Tronoh, Perak (Malaysia)

    2011-01-30

    Hydrocarbon pollution in marine ecosystems occurs mainly by accidental oil spills, deliberate discharge of ballast waters from oil tankers and bilge waste discharges; causing site pollution and serious adverse effects on aquatic environments as well as human health. A large number of petroleum hydrocarbons are biodegradable, thus bioremediation has become an important method for the restoration of oil polluted areas. In this research, a series of natural attenuation, crude oil (CO) and dispersed crude oil (DCO) bioremediation experiments of artificially crude oil contaminated seawater was carried out. Bacterial consortiums were identified as Acinetobacter, Alcaligenes, Bacillus, Pseudomonas and Vibrio. First order kinetics described the biodegradation of crude oil. Under abiotic conditions, oil removal was 19.9% while a maximum of 31.8% total petroleum hydrocarbons (TPH) removal was obtained in natural attenuation experiment. All DCO bioreactors demonstrated higher and faster removal than CO bioreactors. Half life times were 28, 32, 38 and 58 days for DCO and 31, 40, 50 and 75 days for CO with oil concentrations of 100, 500, 1000 and 2000 mg/L, respectively. The effectiveness of Corexit 9500 dispersant was monitored in the 45 day study; the results indicated that it improved the crude oil biodegradation rate.

  4. How does the functional diversity of frugivorous birds shape the spatial pattern of seed dispersal? A case study in a relict plant species

    OpenAIRE

    Lavabre, Jessica E.; Gilarranz, Luis J.; Fortuna, Miguel A.; Bascompte, Jordi

    2016-01-01

    Genetic markers used in combination with network analysis can characterize the fine spatial pattern of seed dispersal and assess the differential contribution of dispersers. As a case study, we focus on the seed dispersal service provided by a small guild of frugivorous birds to the common yew, Taxus baccata L., in southern Spain. We build the spatial networks of seed dispersal events between trees and seed-plots within the studied population— local network—and the spatial n...

  5. Interaction Between Flames and Electric Fields Studied

    Science.gov (United States)

    Yuan, Zeng-Guang; Hegde, Uday

    2003-01-01

    The interaction between flames and electric fields has long been an interesting research subject that has theoretical importance as well as practical significance. Many of the reactions in a flame follow an ionic pathway: that is, positive and negative ions are formed during the intermediate steps of the reaction. When an external electric field is applied, the ions move according to the electric force (the Coulomb force) exerted on them. The motion of the ions modifies the chemistry because the reacting species are altered, it changes the velocity field of the flame, and it alters the electric field distribution. As a result, the flame will change its shape and location to meet all thermal, chemical, and electrical constraints. In normal gravity, the strong buoyant effect often makes the flame multidimensional and, thus, hinders the detailed study of the problem.

  6. A study of the oxide dispersion and recrystallization in NiCrAl prepared from preoxidized powder

    Science.gov (United States)

    Glasgow, T. K.

    1975-01-01

    The SAP technique of dispersion strengthening (formation of an oxide dispersion by preoxidation of metal powders) was applied to atomized powder of the alloy Ni-17Cr-5Al-0.2 Y. SAP-NiCrAl was worked by extrusion and rod rolling at 1205 C and by swaging at 760 C. A variety of annealing treatments were applied after working to determine the recrystallization response. NiCrAlY, similarly prepared from atomized powder, but without a preoxidation treatment, was examined for comparison. The SAP-NiCrAl of this study exhibited oxide particle size and spacing much larger than that usually observed in oxide dispersion strengthened alloys; nonetheless, it was possible to achieve abnormal (secondary) recrystallization in the SAP-NiCrAl as has been reported for other oxide dispersion strengthened alloys. In contrast, unoxidized NiCrAlY exhibited only primary recrystallization.

  7. Comparative Study on Dispersion and Interfacial Properties of Single Walled Carbon Nanotube/Polymer Composites Using Hansen Solubility Parameters

    DEFF Research Database (Denmark)

    Ma, Jing; Larsen, Mikael

    2013-01-01

    Dispersion and interfacial strain transfer of single walled carbon nanotubes (SWNTs) are two major challenges for the utilization of SWNTs as reinforcements in polymer composites. Surface modifications could help change the dispersion and interfacial properties. In this study, nanocomposites were...... fabricated by solution blending 1 wt % SWNTs with various modification (nonmodified, nitric acid functionalized, and amine functionalized SWNTs) and three kinds of polymeric materials (polycarbonate, polyvinylidene fluoride, and epoxy). Chemical compatibilities between SWNTs and solvents or polymers...... are calculated by the Hansen solubility parameters (HSP) method. The dispersion of the SWNTs in solvents is evaluated by dynamic light scattering. The dispersion of SWNTs in polymers evaluated by a light optical microscope (LOM) generally agrees with the HSP prediction. The strain transfer from the matrix...

  8. Atmospheric dispersion of an elevated release in a rural environment: Comparison between field SF 6 tracer measurements and computations of Briggs and ADMS models

    Science.gov (United States)

    Connan, O.; Leroy, C.; Derkx, F.; Maro, D.; Hébert, D.; Roupsard, P.; Rozet, M.

    2011-12-01

    The French Institute for Radiological Protection and Nuclear Safety (IRSN), in collaboration with VEOLIA (French environmental services company), conducted experimental campaigns to study atmospheric dispersion around an Energy Recycling Unit (EUR). The objectives were to study dispersion for an elevated release in a rural environment and to compare results with those of models. The atmospheric dispersion was studied by SF 6 tracer injection into a 40 m high stack. Maximum values of experimental Atmospheric Transfer Coefficients (ATC max) and horizontal dispersion standard deviations ( σh) were compared to predictions from a first generation Briggs gaussian model as well as results from the latest generation ADMS 4.1 gaussian model. In neutral atmospheric conditions, the Briggs and ADMS models are in good agreement with experimental data in terms of ATC and σh. In unstable condition, for σh, both ADMS and Briggs models slightly overestimate the data for winter and summer conditions. In unstable conditions, ADMS and Briggs models overestimated ATC max. The statistical evaluation of the models versus experimental data shows neither models ever meets all of the criteria for good performance. However, statistical evaluation indicates that the ADMS model is more suitable for neutral condition, and that the Briggs model is more reliable for summer unstable conditions.

  9. Refining Climate Change Projections for Organisms with Low Dispersal Abilities: A Case Study of the Caspian Whip Snake

    Science.gov (United States)

    Sahlean, Tiberiu C.; Gherghel, Iulian; Papeş, Monica; Strugariu, Alexandru; Zamfirescu, Ştefan R.

    2014-01-01

    Climate warming is one of the most important threats to biodiversity. Ectothermic organisms such as amphibians and reptiles are especially vulnerable as climatic conditions affect them directly. Ecological niche models (ENMs) are increasingly popular in ecological studies, but several drawbacks exist, including the limited ability to account for the dispersal potential of the species. In this study, we use ENMs to explore the impact of global climate change on the Caspian whip snake (Dolichophis caspius) as model for organisms with low dispersal abilities and to quantify dispersal to novel areas using GIS techniques. Models generated using Maxent 3.3.3 k and GARP for current distribution were projected on future climatic scenarios. A cost-distance analysis was run in ArcGIS 10 using geomorphological features, ecological conditions, and human footprint as “costs” to dispersal of the species to obtain a Maximum Dispersal Range (MDR) estimate. All models developed were statistically significant (PMaxent predicted a doubling of suitable climatic area, while GARP predicted a more conservative expansion. Both models agreed on an expansion of suitable area northwards, with minor decreases at the southern distribution limit. The MDR area calculated using the Maxent model represented a third of the total area of the projected model. The MDR based on GARP models recovered only about 20% of the total area of the projected model. Thus, incorporating measures of species’ dispersal abilities greatly reduced estimated area of potential future distributions. PMID:24670422

  10. Dung longevity influences the fate of endozoochorically dispersed seeds in forest ecosystems

    National Research Council Canada - National Science Library

    Jaroszewicz, Bogdan; Piroznikow, Ewa

    2011-01-01

    ... (studied in the field) effects of endozoochory. The influence of environmental conditions on the fate of endozoochorically dispersed seeds and subsequent plant establishment is still not well understood...

  11. Numerical Study of Electric Field Enhanced Combustion

    KAUST Repository

    Han, Jie

    2016-12-26

    Electric fields can be used to change and control flame properties, for example changing flame speed, enhancing flame stability, or reducing pollutant emission. The ions generated in flames are believed to play the primary role. Although experiments have been carried out to study electric field enhanced combustion, they are not sufficient to explain how the ions in a flame are affected by an electric field. It is therefore necessary to investigate the problem through numerical simulations. In the present work, the electric structure of stabilized CH4/air premixed flames at atmospheric pressure within a direct current field is studied using numerical simulations. This study consists of three parts. First, the transport equations are derived from the Boltzmann kinetic equation for each individual species. Second, a general method for computing the diffusivity and mobility of ions in a gas mixture is introduced. Third, the mechanisms for neutral and charged species are improved to give better predictions of the concentrations of charged species, based on experimental data. Following from this, comprehensive numerical results are presented, including the concentrations and fluxes of charged species, the distributions of the electric field and electric potential, and the electric current-voltage relation. Two new concepts introduced with the numerical results are the plasma sheath and dead zone in the premixed flame. A reactive plasma sheath and a Boltzmann relation sheath are discovered in the region near the electrodes. The plasma sheath penetrates into the flame gas when a voltage is applied, and penetrating further if the voltage is higher. The zone outside the region of sheath penetration is defined as the dead zone. With the two concepts, analytical solutions for the electric field, electric potential and current-voltage curve are derived. The solutions directly describe the electric structure of a premixed flame subject to a DC field. These analytical solutions

  12. Characterization, Molecular Docking, and In Vitro Dissolution Studies of Solid Dispersions of 20(S-Protopanaxadiol

    Directory of Open Access Journals (Sweden)

    Qi Zhang

    2017-02-01

    Full Text Available In this study, we prepared solid dispersions (SDs of 20(S-protopanaxadiol (PPD using a melting-solvent method with different polymers, in order to improve the solubility and dissolution performance of drugs with poor water solubility. The SDs were characterized via differential scanning calorimetry (DSC, powder X-ray diffraction (PXRD, Fourier transform infrared spectroscopy (FTIR, nuclear magnetic resonance (NMR, and molecular docking and dynamics study. DSC and PXRD results indicated that PPD crystallinity in SDs was significantly reduced, and that the majority of PPD is amorphous. No interaction was observed between PPD and polymers on FTIR and NMR spectra. Molecular docking and dynamic calculations indicated that the PPD molecule localized to the interpolated charged surface, rather than within the amorphous polymer chain network, which might help prevent PPD crystallization, consequently enhancing the PPD dispersion in polymers. An in vitro dissolution study revealed that the SDs considerably improved the PPD dissolution performance in distilled water containing 0.35% Tween-80 (T-80. Furthermore, among three PPD-SDs formulations, Poloxamer188 (F68 was the most effective in improving the PPD solubility and was even superior to the mixed polymers. Therefore, the SD prepared with F68 as a hydrophilic polymer carrier might be a promising strategy for improving solubility and in vitro dissolution performance. F68-based SD, containing PPD with a melting-solvent preparation method, can be used as a promising, nontoxic, quick-release, and effective intermediate for other pharmaceutical formulations, in order to achieve a more effective drug delivery.

  13. Dispersive hydrodynamics: Preface

    Science.gov (United States)

    Biondini, G.; El, G. A.; Hoefer, M. A.; Miller, P. D.

    2016-10-01

    This Special Issue on Dispersive Hydrodynamics is dedicated to the memory and work of G.B. Whitham who was one of the pioneers in this field of physical applied mathematics. Some of the papers appearing here are related to work reported on at the workshop "Dispersive Hydrodynamics: The Mathematics of Dispersive Shock Waves and Applications" held in May 2015 at the Banff International Research Station. This Preface provides a broad overview of the field and summaries of the various contributions to the Special Issue, placing them in a unified context.

  14. Kinematic study of the effect of dispersion in quantum vacuum emission from strong laser pulses

    CERN Document Server

    Finazzi, Stefano

    2012-01-01

    A strong light pulse propagating in a nonlinear medium causes an effective change in the local refractive index. With a suitable tuning of the pulse velocity, the leading and trailing edge of the pulse were predicted to behave as analogue black and white horizons in the limit of a dispersionless medium. In this paper, we study a more realistic situation where the frequency dispersion of the medium is fully taken into account. As soon as negative frequency modes are present in the comoving frame, spontaneous emission of quantum vacuum radiation is expected to arise independently of the presence of horizons. We finally investigate the kinematic constraints put on the emission and we show that the optimal directions to observe Hawking-like emission form a narrow angle with the direction of propagation of the pulse.

  15. Energy-dispersive study of the interactions of fast neutrons with matter

    CERN Document Server

    Altstadt, E; Eckert, S; Freiesleben, H; Galindo, V; Grosse, E; Naumann, B; Weiss, F P

    2003-01-01

    The construction and the first use of a compact time-of-flight system for the energy-dispersive study of the interaction of fast neutrons with materials are content of a network project of the Research Center Rossendorf, to which also the Technical University Dresden contributes in the framework of a common DFG project. The planned time-of-flight experiments with pulsed neutrons will be performed at the radiation source ELBE. First results on the development of a neutron-production target are presented. By means of radiation-transport and finite-element programs the distributions of the energy deposition of the used pulsed electron beam of the radiation source ELBE and the temperature in the neutron radiator as well as the expected particle spectra and fluxes at the measurement place were calculated. Considerations on the development of a beam catcher are discussed.

  16. Kinetics study of crystallization with the disorder-bcc-fcc phase transition of charged colloidal dispersions.

    Science.gov (United States)

    Zhou, Hongwei; Xu, Shenghua; Sun, Zhiwei; Du, Xuan; Liu, Lixia

    2011-06-21

    Structure transformation (disorder-bcc-fcc) in charged colloidal dispersions, as a manifestation of the Ostwald's step rule, was confirmed by means of reflection spectrum (RS) measurements in our previous study. By taking advantage of a reflection spectrum containing plenty of information about the crystallization behaviors, time-dependent changes of parameters associated with the crystal structure and composition during the disorder-bcc-fcc transition are reported by treating the data from RS in this article. In addition, Avrami's model is adopted to analyze the transition process and investigate the transition rate. On the basis of the above investigations, associated kinetic features of crystallization with the disorder-bcc-fcc transition are described.

  17. Nuclear magnetic resonance study of epoxy- based polymer-dispersed liquid crystal droplets

    CERN Document Server

    Han, J W

    1998-01-01

    In this work, polymer-dispersed liquid crystals (PDLC) samples were prepared and studied by nuclear magnetic resonance. Proton NMR spectra and spin-lattice relaxations of 4-cyano-4'-pentylbiphenyl(5CB) and p-methoxybenzylidene-p-n-butylaniline (MBBA) liquid crystals confined in microdroplets were measured. The experimental results were compared with those of the liquid crystals in the pores of silica-gels and with those of the mixing components. The experimental results indicated that the nematic ordering in the microdroplets differed markedly from that observed in bulk nematic crystals. In addition, we examined spin-lattice relaxation mechanisms. The proton spin-lattice relaxation mechanisms in bulk nematic liquid crystals are well established. However, when nematic liquid crystals are confined in microdroplets, the relaxation mechanisms are expected to be affected. We examined possible relaxation mechanisms to explain the observed increase in the spin-lattice relaxation rate of liquid crystals confined in m...

  18. Imaging Studies of photodamage and self-healing in disperse orange 11 dye-doped PMMA

    CERN Document Server

    Anderson, Benjamin; Kuzyk, Mark G

    2011-01-01

    We report on optical imaging studies of self-healing after laser-induced photodamage in disperse orange 11 dye doped into poly(methyl methacrylate) (PMMA) polymer. In particular, the high spatial-contrast image of the damage track made by a line focus pump laser allows the recovery rates to be measured as a function of burn dose using the relationship between transverse distance and pump intensity profile. The time evolution of the damaged population results in an intensity-independent time constant of {\\tau} = 490\\pm23 min, in agreement with independent measurements of the time evolution of amplified spontaneous emission. Also observed is a damage threshold above which the material does not fully recover.

  19. Luminescence study of nanosized Al2O3:Tb3+ obtained by gas-dispersed synthesis

    Science.gov (United States)

    Berezovskaya, I. V.; Poletaev, N. I.; Khlebnikova, M. E.; Zatovsky, I. V.; Bychkov, K. L.; Efryushina, N. P.; Khomenko, O. V.; Dotsenko, V. P.

    2016-09-01

    Terbium-doped Al2O3 samples were obtained by gas-dispersed synthesis. It was shown that the resulting powders, with particle sizes of 10-70 nm, consist of a mixture of transition aluminas, among which the δ *-polymorph is dominant. The luminescence properties of Al2O3:Tb3+ have been studied upon excitation in the UV-visible range of the spectrum. It was found that Tb3+ ions cause several groups of inhomogeneously broadened emission bands in the range of 470-640 nm, which are characteristic for disordered materials. In addition, the emission spectra contain a broad band at about 450 nm and several narrower ones in the 680-720 nm region. These features are attributed to surface defects and impurity Cr3+ ions occupying Al3+ octahedral positions, respectively.

  20. Study on microwave photonic filters based on lasers and dispersive fiber

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A general theoretical model for microwave photonic filters based on multi-wavelength light source and dispersive media is summarized and presented, and is applied to the analysis of double-laser-based microwave photonic notch filters' performance.The different influences of the double-sideband(DSB) modulation and the single-sideband(SSB) modulation are demonstrated and explained theoretically. Furthermore, the impact of different factors, such as frequency spacing, 3dB bandwidth and the spectrum amplitude mismatch on the performance of the microwave photonic notch filters are also studied. The numerical simulation results are in good agreement with predictions, and could be beneficial for future optimization of microwave photonic filters.

  1. Broadband Microwave Spectroscopy as a Tool to Study Dispersion Interactions in Camphor-Alcohol Systems

    Science.gov (United States)

    Fatima, Mariyam; Perez, Cristobal; Schnell, Melanie

    2016-06-01

    Many biological processes such as chemical recognition and protein folding are mainly controlled by the interplay between hydrogen bonds and dispersive forces. Broadband rotational spectroscopy studies of weakly bound complexes are able to accurately reveal the structures and internal dynamics of molecular clusters isolated in the gas phase. To investigate the influence of the interplay between different types of weak intermolecular interactions and how it controls the preferred active sites of an amphiphilic molecule, we are using camphor (C10H16O, 1,7,7-trimethylbicyclo[2.2.1]hepta-2-one) with different aliphatic alcohol systems. Camphor is a conformationally rigid bicyclic molecule endowed with considerable steric hindrance and has a single polar group (-C=O). The rotational spectrum of camphor and its structure has been previously reported [1] as well as multiple clusters with water [2]. In order to determine the structure of the camphor-alcohol complexes, we targeted low energy rotational transitions in the 2-8 GHz range under the isolated conditions of a molecular jet in the gas phase. The data obtained suggests that camphor forms one complex with methanol and two with ethanol, with differences in the intermolecular interaction in both complexes. With these results, we aim to study the shift in intermolecular interaction from hydrogen bonding to dispersion with the increase in the size of the aliphatic alcohol. [1] Z. Kisiel, et al., Phys. Chem. Chem. Phys., 5 (2003), 820-826. [2] C. Pérez, et al, J. Phys. Chem. Lett., 7 (2016), 154-160.

  2. Fast drying and film formation of latex dispersions studied with FTIR spectroscopic imaging.

    Science.gov (United States)

    Kimber, James A; Gerst, Matthias; Kazarian, Sergei G

    2014-11-18

    Drying of thin latex films (∼20 μm) at high drying speeds (of the order of seconds) has been studied by fast chemical imaging. ATR-FTIR spectroscopic imaging combined with a fast "kinetic" mode was used to acquire spectral images without coaddition, enabling the amount of water and homogeneity of the drying film to be studied over time. Drying profiles, constructed from analyzing the water content in each image, show two stages of drying, a fast and a slow region. The formulation of latex dispersions affects the onset of slow drying and the volume fraction of water remaining at the onset of slow drying. In this work, the effect of physical properties, film thickness and glass transition temperature (Tg), were investigated, as well as the effect of monomer composition where two monomoers, 2-ethylhexyl acrylate and n-butyl acrylate, and the amount of hydrophilic comonomer, methyl methacrylate (MMA), were varied. It was found that thicker films produced slower overall drying and that the formulation with a Tg above the minimum film formation temperature did not dry evenly, exhibiting cracking. However, the drying kinetics of high and low Tg films were similar, highlighting the advantage of using a spatially-resolved spectroscopic approach. Formulations containing more MMA dried faster than those with less. This was due to the hydrophilicity of MMA and the increase in Tg of the dispersion from the addition of MMA. Overall, FTIR spectroscopic imaging was shown to be a suitable approach in measuring film drying at high speeds as both chemical changes and chemical distribution could be analyzed over time.

  3. Spectroscopy of clusters in the ESO distant cluster survey (EDisCS). II.. Redshifts, velocity dispersions, and substructure for clusters in the last 15 fields

    Science.gov (United States)

    Milvang-Jensen, B.; Noll, S.; Halliday, C.; Poggianti, B. M.; Jablonka, P.; Aragón-Salamanca, A.; Saglia, R. P.; Nowak, N.; von der Linden, A.; De Lucia, G.; Pelló, R.; Moustakas, J.; Poirier, S.; Bamford, S. P.; Clowe, D. I.; Dalcanton, J. J.; Rudnick, G. H.; Simard, L.; White, S. D. M.; Zaritsky, D.

    2008-05-01

    Aims: We present spectroscopic observations of galaxies in 15 survey fields as part of the ESO Distant Cluster Survey (EDisCS). We determine the redshifts and velocity dispersions of the galaxy clusters located in these fields, and we test for possible substructure in the clusters. Methods: We obtained multi-object mask spectroscopy using the FORS2 instrument at the VLT. We reduced the data with particular attention to the sky subtraction. We implemented the method of Kelson for performing sky subtraction prior to any rebinning/interpolation of the data. From the measured galaxy redshifts, we determine cluster velocity dispersions using the biweight estimator and test for possible substructure in the clusters using the Dressler-Shectman test. Results: The method of subtracting the sky prior to any rebinning/interpolation of the data delivers photon-noise-limited results, whereas the traditional method of subtracting the sky after the data have been rebinned/interpolated results in substantially larger noise for spectra from tilted slits. Redshifts for individual galaxies are presented and redshifts and velocity dispersions are presented for 21 galaxy clusters. For the 9 clusters with at least 20 spectroscopically confirmed members, we present the statistical significance of the presence of substructure obtained from the Dressler-Shectman test, and substructure is detected in two of the clusters. Conclusions: Together with data from our previous paper, spectroscopy and spectroscopic velocity dispersions are now available for 26 EDisCS clusters with redshifts in the range 0.40-0.96 and velocity dispersions in the range 166 km s-1-1080 km s-1. Based on observations collected at the European Southern Observatory, Chile, as part of large programme 166.A-0162 (the ESO Distant Cluster Survey). Full Table 4 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/482/419

  4. Strategies of offspring investment and dispersal in a spatially structured environment: a theoretical study using ants.

    Science.gov (United States)

    Cronin, Adam L; Loeuille, Nicolas; Monnin, Thibaud

    2016-02-05

    Offspring investment strategies vary markedly between and within taxa, and much of this variation is thought to stem from the trade-off between offspring size and number. While producing larger offspring can increase their competitive ability, this often comes at a cost to their colonization ability. This competition-colonization trade-off (CCTO) is thought to be an important mechanism supporting coexistence of alternative strategies in a wide range of taxa. However, the relative importance of an alternative and possibly synergistic mechanism-spatial structuring of the environment-remains the topic of some debate. In this study, we explore the influence of these mechanisms on metacommunity structure using an agent-based model built around variable life-history traits. Our model combines explicit resource competition and spatial dynamics, allowing us to tease-apart the influence of, and explore the interaction between, the CCTO and the spatial structure of the environment. We test our model using two reproductive strategies which represent extremes of the CCTO and are common in ants. Our simulations show that colonisers outperform competitors in environments subject to higher temporal and spatial heterogeneity and are favoured when agents mature late and invest heavily in reproduction, whereas competitors dominate in low-disturbance, high resource environments and when maintenance costs are low. Varying life-history parameters has a marked influence on coexistence conditions and yields evolutionary stable strategies for both modes of reproduction. Nonetheless, we show that these strategies can coexist over a wide range of life-history and environmental parameter values, and that coexistence can in most cases be explained by a CCTO. By explicitly considering space, we are also able to demonstrate the importance of the interaction between dispersal and landscape structure. The CCTO permits species employing different reproductive strategies to coexist over a wide

  5. Ophthalmic effects of petroleum dispersant exposure on common murres (Uria aalge): An experimental study.

    Science.gov (United States)

    Fiorello, Christine V; Freeman, Kate; Elias, Becky A; Whitmer, Emily; Ziccardi, Michael H

    2016-12-15

    The safety of chemical dispersants used during oil spill responses is largely unknown in birds. We captured common murres in Monterey Bay, CA and exposed them to Corexit EC9500a, crude oil, or a combination in artificial seawater. We performed ophthalmic examinations and measured intraocular pressures and tear production before and after exposure. Loglinear analysis found that exposure to oil or dispersant was related to the development of conjunctivitis and corneal ulcers. Odds ratios for birds exposed to oil or dispersant were positive and significant for the development of conjunctivitis, while odds ratios for the development of corneal ulcers were positive and significant only for birds exposed to a high concentration of oil. Ocular exposure to dispersants and petroleum in seabirds may cause conjunctivitis and may play a role in the development of corneal ulcers. These results have implications for policymakers who develop protocols for the use of dispersants during marine oil spills. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Enhanced Field Emission Studies on Niobium Surfaces Relevant to High Field Superconducting Radio-Frequency Devices

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Tong [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)

    2002-09-18

    Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radiofrequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling. The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish an optimized process to minimize or eliminate EFE. To achieve these goals, a scanning field emission microscope (SFEM) was designed and built as an extension to an existing commercial scanning electron microscope (SEM). In the SFEM chamber of ultra high vacuum, a sample is moved laterally in a raster pattern under a high voltage anode tip for EFE detection and localization. The sample is then transferred under vacuum to the SEM chamber equipped with an energy-dispersive x-ray spectrometer for individual emitting site characterization. Compared to other systems built for similar purposes, this apparatus has low cost and maintenance, high operational flexibility, considerably bigger scan area, as well as reliable performance. EFE sources from planar Nb have been studied after various surface preparation, including chemical etching and electropolishing, combined with ultrasonic or high-pressure water rinse. Emitters have been identified, analyzed and the preparation process has been examined and improved based on EFE results. As a result, field-emission-free or near field-emission-free surfaces at ~140 MV/m have been consistently achieved with the above techniques. Characterization on the remaining emitters leads to the conclusion that no evidence of intrinsic emitters, i.e., no fundamental electric field limit induced by EFE, has been observed up to ~140 MV/m. Chemically etched and electropolished Nb are compared and no significant difference is observed up to ~140 MV/m. To

  7. Analysis of high allergenicity airborne pollen dispersion: common ragweed study case in Lithuania.

    Science.gov (United States)

    Šaulienė, Ingrida; Veriankaitė, Laura

    2012-01-01

    The appearance of ragweed pollen in the air became more frequent in northerly countries. Attention of allergologists and aerobiologists in these countries is focused on the phenomenon that Ambrosia plants found relatively sporadic but the amount of pollen is high in particular days. Over the latter decade, a matter of particular concern has been Ambrosia pollen, whose appearance in the air is determined by the plants dispersing it and meteorological processes that alter pollen release, dissemination, transport or deposition on surfaces. Pollen data used in this study were collected in three pollen-trapping sites in Lithuania. The data corresponding to 2006-2011 years of pollen monitoring were documented graphically and evaluated statistically. Analysis of the pollen data suggests that although the number of ragweed plants identified has not increased over the latter decade, the total pollen count has been on the increase during the recent period. The highest atmospheric pollen load is established on the last days of August and first days of September. The estimated effect of meteorological parameters on pollen dispersal in the air showed that in Lithuania ragweed pollen is recorded when the relative air humidity is about 70%, and the minimal air temperature is not less than 12°C. Analysis of wind change effect on pollen count indicates that pollen is most often recorded in the air when the changes in wind speed are low (1-2 m/s). We have established a regularity exhibiting an increase in ragweed pollen count conditioned by south-eastern winds in Lithuania.

  8. Surface structural, morphological, and catalytic studies of homogeneously dispersed anisotropic Ag nanostructures within mesoporous silica

    Science.gov (United States)

    Sareen, Shweta; Mutreja, Vishal; Pal, Bonamali; Singh, Satnam

    2016-11-01

    Highly dispersed anisotropic Ag nanostructures were synthesized within the channels of 3-aminopropyltrimethoxysilane (APTMS)-modified mesoporous SBA-15 for catalyzing the reduction of p-dinitrobenzene, p-nitrophenol, and p-nitroacetophenone, respectively. A green templating process without involving any reducing agent, by varying the amount (1-10 wt.%) of Ag loading followed by calcination at 350 °C under H2 led to change in the morphology of Ag nanoparticles from nanospheres ( 7-8 nm) to nanorods (aspect ratio 12-30 nm) without any deformation in mesoporous sieves. In comparison to white bare SBA-15, gray-colored samples were formed with Ag impregnation exhibiting absorption bands at 484 and 840 nm indicating the formation of anisotropic Ag nanostructures within mesoporous matrix. TEM and FE-SEM micrographs confirmed the presence of evenly dispersed Ag nanostructures within as well as on the surface of mesoporous matrix. AFM studies indicated a small decrease in the average roughness of SBA-15 from 20.59 to 19.21 nm for 4 wt.% Ag/m-SBA-15, illustrating the encapsulation of majority of Ag nanoparticles in the siliceous matrix and presence of small amount of Ag nanoparticles on the mesoporous support. Moreover, due to plugging of mesopores with Ag, a significant decrease in surface area from 680 m2/g of SBA-15 to 385 m2/g was observed. The Ag-impregnated SBA-15 catalyst displayed superior catalytic activity than did bare SBA-15 with 4 wt.% Ag-loaded catalyst exhibiting optimum activity for selective reduction of p-nitrophenol to p-aminophenol (100 %), p-nitroacetophenone to p-aminoacetophenone (100 %), and p-dinitrobenzene to p-nitroaniline (87 %), with a small amount of p-phenylenediamine formation.

  9. Stability and magnetic interactions between magnetite nanoparticles dispersed in zeolite as studied using Mössbauer spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Herojit singh, L. [Materials Science Group Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Govindaraj, R., E-mail: govind@igcar.gov.in [Materials Science Group Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Mythili, R. [Physical Metallurgy Group Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Amarendra, G. [Materials Science Group Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)

    2016-11-15

    Stability of superparamagnetic magnetite nanoparticles as formed in Zeolite has been addressed in a detailed manner based on isochronal annealing studies using Mössbauer spectroscopy. A strong binding of these nanoparticles in Zeolite has been deduced as the coarsening of the nanoparticles is observed following annealing treatments beyond 825 K. In addition, the magnetic interactions between these superparamagnetic magnetite nanoparticles in the as dispersed condition in Zeolite have been elucidated by means of low temperature Mössbauer studies. A strong dependence of the dipole–dipole interactions between superparamagnetic particles of cubic iron oxides is deduced based on this study. - Highlights: • Dispersion of superparamagnetic magnetite particles in zeolite. • A strong binding of magnetite particles in zeolite deduced using Mössbauer studies. • Difference in spin relaxation behavior of bare and zeolite dispersed magnetite particles. • A strong dipole–dipole interactions between magnetite particles.

  10. An LES study of pollen dispersal from isolated populations: Effects of source size and boundary-layer scaling

    Science.gov (United States)

    Chamecki, Marcelo; Meneveau, Charles; Parlange, Marc B.

    2008-11-01

    A framework to simulate pollen dispersal in the atmospheric boundary layer based on the large eddy simulation technique is developed. Pollen is represented by a continuum concentration field and is evolved following an advection-diffusion equation including a gravitational settling term. The approach is validated against classical data on point-source releases and our own field data for a natural ragweed field. The LES is further used as a tool to investigate the effect of source size on the patterns of pollen ground deposition, an issue of fundamental importance in the development of policies for genetically modified crops. The cross-wind integrated deposition is shown to scale with the pollen boundary-layer height at the trailing edge of the field and a simple practical expression based on the development of the pollen boundary layer is proposed to scale results from small test fields to realistic agricultural conditions.

  11. High-resolution study of nuclear magnetic relaxation dispersion of purine nucleotides: effects of spin-spin coupling.

    Science.gov (United States)

    Kiryutin, Alexey; Ivanov, Konstantin; Yurkovskaya, Alexandra; Vieth, Hans-Martin

    2008-01-01

    By combining magnetic field cycling in the range from 0.1mT to 7T with high-resolution NMR detection the T(1) relaxation dispersion (nuclear magnetic relaxation dispersion (NMRD)) of protons in the nucleotides adenosine mono-phosphate and guanosine mono-phosphate was measured in a site-specific way. While at high field the individual spins have distinctly different T(1) times, their scalar spin-spin interaction fulfills at low field the condition of strong coupling and leads to convergence of their T(1) dispersion curves. In addition, the spin-spin coupling can lead to oscillatory components in the relaxation kinetics traceable to a coupling between spin polarization and coherence in the relaxation process. As a consequence the NMRD curves do not directly reflect the spectral density function of the motional processes, but the effects of motion and spin coupling must be separated for a reliable evaluation. A theoretical approach is described allowing such an analysis.

  12. Nozzle for electric dispersion reactor

    Science.gov (United States)

    Sisson, Warren G.; Basaran, Osman A.; Harris, Michael T.

    1995-01-01

    A nozzle for an electric dispersion reactor includes two concentric electrodes, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode.

  13. Comparative study of sustained-release lipid microparticles and solid dispersions containing ibuprofen

    Directory of Open Access Journals (Sweden)

    Hugo Almeida

    2012-09-01

    Full Text Available Ibuprofen is one of the most important non-steroidal anti-inflammatory drugs used in the treatment of inflammatory diseases. In its pure state, ibuprofen presents poor physical and mechanical characteristics and its use in solid dosage forms needs the addition of excipients that improve these properties. The selection of the best excipients and the most suitable pharmaceutical dosage form to carry ibuprofen is very important for the industrial success of this drug. Given these factors, lipid microparticles and solid dispersions of ibuprofen with cetyl alcohol, stearic acid, and hydrogenated castor oil were prepared. These formulations were intended to improve the physical and mechanical characteristics and to sustain the release of this drug. Physical mixtures were also prepared with the same ingredients in similar proportions. The solid dispersions of ibuprofen/stearic acid and ibuprofen/hydrogenated castor oil showed the best flow characteristics compared with pure ibuprofen. Further, gelatin capsules filled with lipid microparticles and solid dispersions were submitted to dissolution tests in order to study the influence of the prepared systems in the release profiles of ibuprofen. Prolonged release of ibuprofen was achieved with the lipid microparticles and solid dispersions prepared with the different types of excipients.O ibuprofeno é um dos antiinflamatórios não esteróides mais utilizados no tratamento de patologias associadas a processos inflamatórios. Este fármaco, quando no seu estado puro, apresenta características físicas e mecânicas pouco satisfatórias e a sua utilização em formas sólidas só é possível se forem adicionados excipientes que permitam melhorar estas propriedades. A seleção dos excipientes ideais e da forma farmacêutica mais adequada para veicular o ibuprofeno é fundamental para o sucesso industrial deste fármaco. Tendo em conta estes fatores, prepararam-se micropartículas lipídicas e dispersões s

  14. A computational study of tandem dual wheel aerodynamics and the effect of fenders and fairings on spray dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Paschkewitz, J S

    2006-01-13

    With the goal of understanding how to mitigate the safety hazard of splash and spray around heavy vehicles, a computational study of the aerodynamics and spray dispersion about a simplified trailer wheel assembly has been completed. A tandem dual slick (TDS) wheel model that neglects complex geometric features such as brakes, wheel bolts and wheel cutouts but with the same dimensions as an actual trailer wheel assembly was used . A detailed simulation of the wheels alone demonstrated that the flow field is both unsteady and complex, containing a number of vortical structures that interact strongly with spray. Preliminary simulations with fenders and fairings demonstrated that these devices prevent the ballistic transport of drops larger than approximately 0.1 mm, but the fine mist speculated to be responsible for visibility reduction is unaffected. This work suggests that to use computational fluid dynamics (CFD) to design and evaluate spray mitigation strategies the jet or sheet breakup processes can be modeled using an array of injectors of small (< 0.01 mm) water droplets; however the choice of size distribution, injection locations, directions and velocities is largely unknown and requires further study. Possible containment strategies would include using flow structures to 'focus' particles into regions away from passing cars or surface treatments to capture small drops.

  15. Surface Modification of Alumina Nanoparticles: A Dispersion Study in Organic Media.

    Science.gov (United States)

    Soleimani, Esmaiel; Zamani, Narges

    2017-09-01

    The alumina nanoparticles (NPs) have been synthesized from reaction between alum with ammonia and then calcined the precipitate at 1200 °C for 4 h. Its surface was modified by oleic acid (OA) and trimethoxyvinylsilane (TMVS) in o-xylene at 50 °C. The alumina NPs and its modified were characterized by XRD, FT-IR, SEM, EDX and TGA. The TGA analysis indicated that the grafting amount of OA and TMVS were 10.5 and 8.0% respectively. The dispersion of modified NPs was determined in monomers such as methyl methacrylate (MMA), butyl acrylate (BuA) and styrene (St) and in solvents such as ethanol, hexane and acetone. The experimental results showed that the highest dispersion was happened NPs modified by oleic acid in n-hexane, while the highest dispersion was observed NPs modified by TMVS in acetone. The results indicate that NPs modified by oleic acid formed a stable dispersion in MMA and BuA. The highest amount of dispersion happened NPs modified by oleic acid in MMA and BuA in initial weight of 5 and 2.5% respectively, while stable dispersion is formed in styrene when TMVS is used as modifier. The highest amount of dispersion was happened NPs modified by TMVS in styrene in initial weight of 2.5%.

  16. Study on water-dispersible colloids in saline-alkali soils by atomic force microscopy and spectrometric methods.

    Science.gov (United States)

    Liu, Zhiguo; Xu, Fengjie; Zu, Yuangang; Meng, Ronghua; Wang, Wenjie

    2016-06-01

    Recent studies have revealed that water-dispersible colloids play an important role in the transport of nutrients and contaminants in soils. In this study, water-dispersible colloids extracted from saline-alkali soils have been characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV absorption spectra. AFM observation indicated that the water-dispersible colloids contain some large plates and many small spherical particles. XRD, XPS, and UV absorption measurement revealed that the water-dispersible colloids are composed of kaolinite, illite, calcite, quartz and humic acid. In addition, UV absorption measurement demonstrated that the humic acids are associated with clay minerals. Water-dispersible colloids in the saline-alkali soils after hydrolyzed polymaleic anhydride treatment and an agricultural soil (nonsaline-alkali soil) were also investigated for comparison. The obtained results implied that the saline-alkali condition facilitates the formation of a large quantity of colloids. The use of AFM combined with spectrometric methods in the present study provides new knowledge on the colloid characteristics of saline-alkali soils. Microsc. Res. Tech. 79:525-531, 2016. © 2016 Wiley Periodicals, Inc.

  17. Spectroscopy of clusters in the ESO distant cluster survey (EDisCS).II. Redshifts, velocity dispersions, and substructure for clusters in the last 15 fields

    CERN Document Server

    Milvang-Jensen, Bo; Halliday, Claire; Poggianti, Bianca M; Jablonka, Pascale; Aragon-Salamanca, Alfonso; Saglia, Roberto P; Nowak, Nina; von der Linden, Anja; De Lucia, Gabriella; Pello, Roser; Moustakas, John; Poirier, Sebastien; Bamford, Steven P; Clowe, Douglas I; Dalcanton, Julianne J; Rudnick, Gregory H; Simard, Luc; White, Simon D M; Zaritsky, Dennis

    2008-01-01

    AIMS. We present spectroscopic observations of galaxies in 15 survey fields as part of the ESO Distant Cluster Survey (EDisCS). We determine the redshifts and velocity dispersions of the galaxy clusters located in these fields, and we test for possible substructure in the clusters. METHODS. We obtained multi-object mask spectroscopy using the FORS2 instrument at the VLT. We reduced the data with particular attention to the sky subtraction. We implemented the method of Kelson for performing sky subtraction prior to any rebinning/interpolation of the data. From the measured galaxy redshifts, we determine cluster velocity dispersions using the biweight estimator and test for possible substructure in the clusters using the Dressler-Shectman test. RESULTS. The method of subtracting the sky prior to any rebinning/interpolation of the data delivers photon-noise-limited results, whereas the traditional method of subtracting the sky after the data have been rebinned/interpolated results in substantially larger noise f...

  18. Climatic variability, plasticity, and dispersal: A case study from Lake Tana, Ethiopia.

    Science.gov (United States)

    Grove, Matt; Lamb, Henry; Roberts, Helen; Davies, Sarah; Marshall, Mike; Bates, Richard; Huws, Dei

    2015-10-01

    The numerous dispersal events that have occurred during the prehistory of hominin lineages are the subject of longstanding and increasingly active debate in evolutionary anthropology. As well as research into the dating and geographic extent of such dispersals, there is an increasing focus on the factors that may have been responsible for dispersal. The growing body of detailed regional palaeoclimatic data is invaluable in demonstrating the often close relationship between changes in prehistoric environments and the movements of hominin populations. The scenarios constructed from such data are often overly simplistic, however, concentrating on the dynamics of cyclical contraction and expansion during severe and ameliorated conditions respectively. This contribution proposes a two-stage hypothesis of hominin dispersal in which populations (1) accumulate high levels of climatic tolerance during highly variable climatic phases, and (2) express such heightened tolerance via dispersal in subsequent low-variability phases. Likely dispersal phases are thus proposed to occur during stable climatic phases that immediately follow phases of high climatic variability. Employing high resolution palaeoclimatic data from Lake Tana, Ethiopia, the hypothesis is examined in relation to the early dispersal of Homo sapiens out of East Africa and into the Levant. A dispersal phase is identified in the Lake Tana record between c. 112,550 and c. 96,975 years ago, a date bracket that accords well with the dating evidence for H. sapiens occupation at the sites of Qafzeh and Skhul. Results are discussed in relation to the complex pattern of H. sapiens dispersal out of East Africa, with particular attention paid to the implications of recent genetic chronologies for the origin of non-African modern humans. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Microbial field pilot study. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Coates, J.D.; Chisholm, J.L.

    1993-05-01

    A multi-well microbially enhanced oil recovery field pilot has been performed in the Southeast Vassar Vertz Sand Unit in Payne County, Oklahoma. The primary emphasis of the experiment was preferential plugging of high permeability zones for the purpose of improving waterflood sweep efficiency. Studies were performed to determine reservoir chemistry, ecology, and indigenous bacteria populations. Growth experiments were used to select a nutrient system compatible with the reservoir that encouraged growth of a group of indigenous nitrate-using bacteria and inhibit growth of sulfate-reducing bacteria. A specific field pilot area behind an active line drive waterflood was selected. Surface facilities were designed and installed. Injection protocols of bulk nutrient materials were prepared to facilitate uniform distribution of nutrients within the pilot area. By the end of December, 1991, 82.5 tons (75.0 tonnes) of nutrients had been injected in the field. A tracer test identified significant heterogeneity in the SEVVSU and made it necessary to monitor additional production wells in the field. The tracer tests and changes in production behavior indicate the additional production wells monitored during the field trial were also affected. Eighty two and one half barrels (13.1 m{sup 3}) of tertiary oil have been recovered. Microbial activity has increased CO{sub 2} content as indicated by increased alkalinity. A temporary rise in sulfide concentration was experienced. These indicate an active microbial community was generated in the field by the nutrient injection. Pilot area interwell pressure interference test results showed that significant permeability reduction occurred. The interwell permeabilities in the pilot area between the injector and the three pilot production wells were made more uniform which indicates a successful preferential plugging enhanced oil recovery project.

  20. NUMERICAL STUDIES ON AIRFLOW AND POLLUTANT DISPERSION IN URBAN STREET CANYONS FORMED BY SLANTED ROOF BUILDINGS

    Institute of Scientific and Technical Information of China (English)

    HUANG Yuan-dong; JIN Ming-xia; SUN Ya-nan

    2007-01-01

    Based on the CFD technique, fifteen cases were evaluated for the airflows and pollutant dispersions inside urban street canyons formed by slanted roof buildings. The simulated wind fields and concentration contours show that W/H, W/h and h/H (where W is the street width, and H and h are the heights of buildings at the leeward and windward sides of the street, respectively) are the crucial factors in determining the vortex structure and pollutant distribution within a canyon. It is concluded that (1) in a symmetrical canyon, at W/H =0.5 two vortices (an upper clockwise vortex between the slanted roofs and a lower counter-clockwise one) are developed and pollutants accumulate on the windward side of the street, whereas at W/H=2.0 only one clockwise vortex is generated and thus pollution piles up on the leeward side, (2) in a step-up canyon with W/H =0.5 to 2.0 (at h/H =1.5 to 2.0)and a step-down canyon with W/h=1.0 (at h/H =0.5 to 0.667), the pollution level close to the lower building is higher than that close to the taller building since a clockwise vortex is generated in the step-up canyon and a counter-clockwise one in the step-down canyon, (3) in a narrow step-down canyon with W/h=0.5 (at h/H =0.667) very poor ventilation properties is detected, and inside a wider step-down canyon with W/h=2.0 the vortex structure and consequently pollutant distribution varies greatly with h/H.

  1. Study on Enhanced Dissolution of Azilsartan-Loaded Solid Dispersion, Prepared by Combining Wet Milling and Spray-Drying Technologies.

    Science.gov (United States)

    Lu, Tianshu; Sun, Yinghua; Ding, Dawei; Zhang, Qi; Fan, Rui; He, Zhonggui; Wang, Jing

    2017-02-01

    The purpose of this study was to develop a combination method of wet milling and spray-drying technologies to prepare the solid dispersion and improve the dissolution rate of poorly water-soluble drug candidates. Azilsartan (AZL) was selected as the model drug for its poor water solubility. In the study, AZL-loaded solid dispersion was prepared with polyethylene glycol 6000 (PEG6000) and hydroxypropyl cellulose with super low viscosity (HPC-SL) as stabilizers by using combination of wet grinding and spray-drying methods. The high AZL loading solid dispersion was then characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and Fourier transform infrared spectroscopy (FTIR). Besides, dissolution test was carried out by the paddle method and stability investigation was also conducted. As a result, the dissolution rate of the solid dispersion tablets was found to be greater than conventional tablets, but in close agreement with market tablets. Furthermore, the formulation was shown to be stable at 40 ± 2°C and 75 ± 5% for at least 6 months, owing to its decreased particle size, morphology, and its crystal form. It was concluded that the combination of wet milling and spray-drying approaches to prepare solid dispersion would be a prospective method to improve the dissolution rate of poorly water-soluble drugs.

  2. How important is the dispersion interaction for cyclobis(paraquat-p-phenylene)-based molecular "shuttles"? A theoretical study

    Science.gov (United States)

    Romero, Carlos; Fomina, Lioudmila; Fomine, Serguei

    Inclusion complexes of cyclobis(paraquat-p-phenylene) and various aromatic molecules in their neutral and oxidized form were studied at the LMP2/6-311+G**//BHandHLYP/6-31G* level of theory, which represents the highest level theoretical study to date for these complexes. The results show that it is dispersion interaction that contributes most to the binding energy. One electron oxidation of a guest molecule leads to complete dissociation of inclusion complex generating strong repulsion potential between guest and host molecules. Electrostatic interactions also can play an important role, provided the guest molecule has a dipole moment; however, dispersion interactions always dominate in binding energy.

  3. Using a test solution of NaCl in water for studying the finely dispersed spraying of liquids

    Science.gov (United States)

    Ishmatov, A. N.; Vorozhtsov, B. I.; Arkhipov, V. A.

    2013-12-01

    Both theoretically and experimentally, the suitability of a technique for studying the finely dispersed spraying of liquids based on an analysis of salt residue particles formed as a result of evaporation of test solutions of NaCl in water was evaluated. Data gained in studying the dispersion of droplets in the droplet clouds produced by pulsed and ultrasonic atomizers are reported. During pulsed atomization, salt residue particles of various morphologies were found to form, this finding pointing to realization of unsteady conditions for particle evolution.

  4. A study of the formation of magnetically active solid dispersions of phenacetin using atomic and magnetic force microscopy

    Directory of Open Access Journals (Sweden)

    Liana Stanislavovna Usmanova

    2017-01-01

    Full Text Available A lot of pharmaceutical substances have a poor solubility that limits their absorption and distribution to the targeted sites to elicit the desired action without causing untoward effects on healthy cells or tissues. For such drugs, new modes of delivery have to be developed for efficient and effective delivery of the drug to the target site. Formation of magnetically active solid dispersion of such drugs could be a useful approach to addressing this problem because they combine targeted delivery and good solubility. In this work, the distribution of superparamagnetic nanoparticles in the solid dispersion of polyethylene glycol with average molecular weight 950-1050 g/mol and phenacetin was studied using atomic force and magnetic force microscopy. The distribution of nanoparticles was found to be uniform in studied composites. Magnetically active solid dispersions may find application in the production of the capsulated drug delivery systems with enhanced solubility parameters.

  5. Pollutant dispersion studies - An update on the problems in Indian coastal waters

    Digital Repository Service at National Institute of Oceanography (India)

    Swamy, G.N.

    Pollutant dispersion problems along the Indian coastal waters are characterisEd. by site-specificity, as a result of seasonal and physiographic variabilities. Presence of large rivers, estuaries and backwaters add to the problems of waste disposal...

  6. Dispersion and rheological studies of Y–PSZ tape casting slurry

    Indian Academy of Sciences (India)

    K G Vasantha Kumari; K Sasidharan; M Sapna; Raghu Natarajan

    2005-04-01

    Different solvent systems in combination with three different dispersants were tried to find out the suitable solvent–dispersant combination, which give optimum dispersion of PSZ. Based on sedimentation, viscosity and rheology characteristics, zeotropic ethanol : xylene with a ratio of 50 : 50 along with 0.5 wt% phosphate ester was found to be the best solvent and dispersant combination. Optimized tape casting slurry was prepared using PEG 600 and BBP as plasticizers and PVB as the binder. Cyclohexanone was used as the homogenizer. The optimized slurry composition with 58% solid loading exhibited shear-thinning pseudoplastic rheological behaviour. Y–PSZ tapes of ∼ 50 m thickness free from visible defects were cast with a green tape density of 55%.

  7. Studies of Solar Vector Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    WANG Jingxiu

    2011-01-01

    In this article, we report a few advances in the studies based on the solar vector magnetic field observations which were carried out mainly with the Solar Magnetic Field Telescope at the Huairou Solar Observing Station in the 1990s. (1) We developed necessary methodology and concepts in vector magnetogram analysis (Wang et al. 1996). For the first time, we proposed to use the photospheric free magnetic energy to quantify the major flare productivity of solar active regions (ARs), and it had been proved to be the best parameter in representing the major flare activity. (2) We revealed that there was always a dominant sense of magnetic shear in a given AR (Wang 1994), which was taken as the premise of the helicity calculation in ARs; we made the first quantitative estimation of magnetic helicity evolution in ARs (Wang 1996). (3) We identified the first group of evidence of magnetic reconnection in the lower solar atmosphere with vector magnetic field observations and proposed a two-step reconnection flare model to interpret the observed association of flux cancellation and flares (Wang and Shi 1993). Efforts to quantify the major flare productivity of super active regions with vector magnetic field observations have been also taken.

  8. Energy tourism: An emerging field of study

    OpenAIRE

    2014-01-01

    After conceptualizing the interrelationships between energy and tourism, the authors provide a definition of energy tourism as a new niche of industrial tourism, theorize on how it overlaps with other types of special interest tourism, and discuss specifics concerning its forms, locales, and possible societal impacts. Potential directions, along with research questions, for future research in the field of energy tourism are proposed. Then, the results of an explorative pilot study of energy t...

  9. A Comparative Study of Dispersion Techniques for Nanocomposite Made with Nanoclays and an Unsaturated Polyester Resin

    OpenAIRE

    Farida Bensadoun; Nadir Kchit; Catherine Billotte; François Trochu; Edu Ruiz

    2011-01-01

    Over the last few years, polymer/clay nanocomposites have been an area of intensive research due to their capacity to improve the properties of the polymer resin. These nanocharged polymers exhibit a complex rheological behavior due to their dispersed structure in the matrix. Thus, to gain fundamental understanding of nanocomposite dispersion, characterization of their internal structure and their rheological behavior is crucial. Such understanding is also key to determine the manufacturing c...

  10. Dispersal of aquatic organisms by waterbirds: a review of past research and priorities for future studies

    OpenAIRE

    Figuerola, Jordi; Green, Andy J.

    2002-01-01

    1. Inland wetlands constitute ecological islands of aquatic habitat often isolated by huge areas of non-suitable terrestrial habitats. Although most aquatic organisms lack the capacity to disperse by themselves to neighbouring catchments, many species present widespread distributions consistent with frequent dispersal by migratory waterbirds. 2. A literature review indicates that bird-mediated passive transport of propagules of aquatic invertebrates and plants is a frequent pr...

  11. Dispersion and Structure Studies of Molybdenum Oxide on Anatase TiO2

    Institute of Scientific and Technical Information of China (English)

    ZI Feng-lan; GUO Hong-you; WU Nian-zu; XIE Ya-ning; HU Tian-dou

    2004-01-01

    X-ray photoelectron spectroscopy(XPS) and extended X-ray absorption fine structure(EXAFS) were used to characterize the structure of the mixture of molybdenum oxide and anatase calcined at 723 K. The results indicate that molybdenum oxide can disperse onto the surface of anatase(TiO2) and the dispersion threshold is 11.2 mg in per gram of MoO3 or 4.8 Mo atoms/nm2 TiO2. When the content of MoO3 is below the dispersion threshold, MoO3 species is in highly dispersed state interacting strongly with TiO2 support and in discrete tetrahedral coordination, [MoO4], on the surface of TiO2. When the MoO3 loading is above this value, MoO3 exists in both dispersed phase and crystalline phase. MoO3 in dispersed phase is still a discrete [MoO4] tetrahedron; MoO3 in crystal phase is in octahedral coordination.

  12. Thermodynamic and kinetic study of volatile compounds in biopolymer based dispersions.

    Science.gov (United States)

    Samavati, Vahid; Emam-Djomeh, Zahra; Mehdinia, Ali

    2014-01-01

    Partitioning and release of ethyl acetate and diacetyl from two matrices with a different composition was studied by applying static head space gas chromatography. Two matrices with a different composition have been developed: one containing carbohydrates (Tragacanth gum) and in the second one, called complex matrix, a lipid (oleic acid) was added. The roles of carbohydrate (Tragacanth gum) and lipid (oleic acid) on the retention of all the aroma compounds were pointed out. Changes in the composition of matrices exhibited a considerable effect on the thermodynamic component as expressed by the air/liquid partition coefficient (Ka/l) values at equilibrium (20 °C). The kinetic study of the release from these matrices had shown a decrease of the initial rate of release (Ri) by reference with water. The rheological properties of all matrices were investigated and the flow behaviour of all matrices was successfully modelled with power law and Ellis models and power law model was found as the better model to describe the flow behaviour of dispersions.

  13. Environmental instability as a motor for dispersal: a case study from a growing population of glossy ibis.

    Directory of Open Access Journals (Sweden)

    Simone Santoro

    Full Text Available Dispersal is a life-history trait directly affecting population dynamics and species range shifts and thus playing a prominent role in the response to climate change. Nonetheless, the relationship between extreme climatic events and dispersal has received little attention in birds. Here we focused on climatic, demographic and individual factors affecting the dispersal propensity of a major glossy ibis population. We performed a capture-resighting analysis on individuals born and observed at Doñana (South-West Spain over fourteen years. We applied a multiple analytical approach to show that single-site capture-resighting estimates were a reliable index of dispersal propensity from the area. We focused on the emigration of Doñana-born individuals sporadically (transients and regularly (residents frequenting their natal area. Droughts during two out of 14 study years caused higher apparent dispersal rates, explaining most of the annual variation in these rates. The age structure of Doñana-born individuals resighted simultaneously locally and in Morocco in one week over the 2010 autumn confirmed that the 2005 drought boosted permanent emigration. As numbers increased steadily during non-drought years since the formation of the colony in 1996 to several thousand pairs, philopatry increased gradually, while transients probability appeared to be related to average breeding success. Age, sex, density, quality of foraging habitat and breeding success in the previous season were not found to directly affect apparent dispersal. Nonetheless, autumn sex ratio gradually switched from male (≈0.68 to female-skewed (≈0.44 by the end of the study period, suggesting that males and females respond differently to high densities reached in recent years. This study demonstrates the importance of extreme climatic events as a powerful motor for spread of species in expansion. Also, it suggests different factors drive emigration of individuals according to their

  14. Study on a new nano-dispersing agent and its effect for increasing suspension ability of alcohol-based coatings

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    A study for further improving the suspension rate of alcohol-based coatings using a new nano-dispersing agent has been presented in this paper. The results of experiments show that the new nano-dispersing agent should be used in combination with organic auxiliary agent which significantly increases the suspension effect of alcohol-based coatings. By the methods, the suspension rates of 99%, 98%, 96% and 94% can be achieved at 2h, 2h, 48h and 72h, respectively. These alcohol-based coatings have characters of higher strength, lower gas evolution, better brush ability and no blister after ignition.

  15. ReaxFF-lg: correction of the ReaxFF reactive force field for London dispersion, with applications to the equations of state for energetic materials.

    Science.gov (United States)

    Liu, Lianchi; Liu, Yi; Zybin, Sergey V; Sun, Huai; Goddard, William A

    2011-10-13

    The practical levels of density functional theory (DFT) for solids (LDA, PBE, PW91, B3LYP) are well-known not to account adequately for the London dispersion (van der Waals attraction) so important in molecular solids, leading to equilibrium volumes for molecular crystals ~10-15% too high. The ReaxFF reactive force field is based on fitting such DFT calculations and suffers from the same problem. In the paper we extend ReaxFF by adding a London dispersion term with a form such that it has low gradients (lg) at valence distances leaving the already optimized valence interactions intact but behaves as 1/R(6) for large distances. We derive here these lg corrections to ReaxFF based on the experimental crystal structure data for graphite, polyethylene (PE), carbon dioxide, and nitrogen and for energetic materials: hexahydro-1,3,5-trinitro-1,3,5-s-triazine (RDX), pentaerythritol tetranitrate (PETN), 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), and nitromethane (NM). After this dispersion correction the average error of predicted equilibrium volumes decreases from 18.5 to 4.2% for the above systems. We find that the calculated crystal structures and equation of state with ReaxFF-lg are in good agreement with experimental results. In particular, we examined the phase transition between α-RDX and γ-RDX, finding that ReaxFF-lg leads to excellent agreement for both the pressure and volume of this transition occurring at ~4.8 GPa and ~2.18 g/cm(3) density from ReaxFF-lg vs 3.9 GPa and ~2.21 g/cm(3) from experiment. We expect ReaxFF-lg to improve the descriptions of the phase diagrams for other energetic materials.

  16. Vowel dispersion in Truku

    OpenAIRE

    Chiang, Wen-yu; Chiang, Fang-mei

    2013-01-01

    This study investigates the dispersion of vowel space in Truku, an endangered Austronesian language in Taiwan. Adaptive Dispersion (Liljencrants and Lindblom, 1972; Lindblom, 1986, 1990) proposes that the distinctive sounds of a language tend to be positioned in phonetic space in a way that maximizes perceptual contrast. For example, languages with large vowel inventories tend to expand the overall acoustic vowel space. Adaptive Dispersion predicts that the distance between the point vowels w...

  17. Field study of heavy oil viscosity reduction for production transport

    Energy Technology Data Exchange (ETDEWEB)

    Pinto, J.; Annichiariccom, G.; Montanez, M. [Ecopetrol S.A. (Venezuela); Faust, M.; Weathers, T. [Nalco Energy Services (Colombia); Parra, R. [Nalco de Colombia Ltda. (Colombia)

    2011-07-01

    In the heavy oil industry, production and transportation are expensive processes requiring complex equipment and procedures. The main issue with heavy crude oil is its high viscosity. A method using naphtha injection was developed to dilute the fluids and aid in water separation, but this method is expensive and raises safety issues. To reduce naphtha consumption, Ecopetrol and Nalco Energy Services developed a new dispersion technology. This paper presents this technology and the results of its field trial in the Chichimene oil field. Key production indicators were monitored to determine how effective the emulsion method was in enhancing production. Results showed no negative effect on the separation facility or oil and water quality while reducing by 75% the injection of diluent. This paper presents a dispersion technology which successfully reduced the need for naphtha and thus reduced production costs.

  18. "Dispersion modeling approaches for near road | Science ...

    Science.gov (United States)

    Roadway design and roadside barriers can have significant effects on the dispersion of traffic-generated pollutants, especially in the near-road environment. Dispersion models that can accurately simulate these effects are needed to fully assess these impacts for a variety of applications. For example, such models can be useful for evaluating the mitigation potential of roadside barriers in reducing near-road exposures and their associated adverse health effects. Two databases, a tracer field study and a wind tunnel study, provide measurements used in the development and/or validation of algorithms to simulate dispersion in the presence of noise barriers. The tracer field study was performed in Idaho Falls, ID, USA with a 6-m noise barrier and a finite line source in a variety of atmospheric conditions. The second study was performed in the meteorological wind tunnel at the US EPA and simulated line sources at different distances from a model noise barrier to capture the effect on emissions from individual lanes of traffic. In both cases, velocity and concentration measurements characterized the effect of the barrier on dispersion.This paper presents comparisons with the two datasets of the barrier algorithms implemented in two different dispersion models: US EPA’s R-LINE (a research dispersion modelling tool under development by the US EPA’s Office of Research and Development) and CERC’s ADMS model (ADMS-Urban). In R-LINE the physical features reveal

  19. Molecular interaction between glimepiride and Soluplus®-PEG 4000 hybrid based solid dispersions: Characterisation and anti-diabetic studies.

    Science.gov (United States)

    Reginald-Opara, Joy Nneji; Attama, Anthony; Ofokansi, Kenneth; Umeyor, Chukwuebuka; Kenechukwu, Frankline

    2015-12-30

    The objective of this study was to evaluate a novel blend of polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol 6000 grafted copolymer (Soluplus®) and polyethylene glycol (PEG) 4000 for solubility enhancement, physicochemical stability and anti-diabetic efficacy of the produced solid dispersions containing glimepiride, a biopharmaceutics classification system (BCS) class II sulphonylurea. Different batches of glimepiride solid dispersions (SD) were prepared by the solvent evaporation method using the individual polymers and blends of the polymers at different ratios. The Soluplus®-PEG 4000 (sol-PEG) hybrid polymer based glimepiride solid dispersions were characterized by differential scanning calorimetry (DSC), fourier transform infrared (FTIR) spectroscopy, micromeritics and dissolution studies. In vivo anti-diabetic activity was determined by measuring the changes in blood glucose concentrations in albino rats. The solid dispersions showed good flow properties and excellent practical yield. Drug content and release from the different formulations increased when Soluplus® was used as the main matrix polymer. The kinetics of drug release from all the solid dispersions followed first order. Solid state characterization confirmed the formation of amorphous glimepiride solid dispersions in the Sol-PEG hybrid polymer and no strong drug-polymer interaction was observed. The blood glucose reduction in albino rats by the Sol-PEG-Glim SDs was significantly (p<0.05) higher and more sustained when compared with the plain drug sample and commercially available product. Optimized SD batches (SP1 and SP3) showed a reduction in blood glucose level from 100% to 9.81% and 8.97%, respectively, at Tmax of 3h. The Sol-PEG-Glim SD was found to be stable over a period of 6 months (at 40°C, 70% RH) with no significant changes in the drug content. Thus, the Sol-PEG polymeric hybrids represent a promising tool for enhanced delivery of glimepiride.

  20. Synthesis, spectroscopic, thermal and electrochemical studies on thiazolyl azo based disperse dyes bearing coumarin

    Science.gov (United States)

    Özkütük, Müjgan; İpek, Ezgi; Aydıner, Burcu; Mamaş, Serhat; Seferoğlu, Zeynel

    2016-03-01

    In this study, seven novel thiazolyl azo disperse dyes (6a-g) were synthesized and fully characterized by FT-IR, 1H NMR, 13C NMR, and mass spectral techniques. The electronic absorption spectra of the dyes in solvents of different polarities cover a λmax range of 404-512 nm. The absorption properties of the dyes changed drastically upon acidification. This was due to the protonation of the nitrogen in the thiazole ring, which in turn increased the donor-acceptor interplay of the π system in the dyes, and therefore increased the absorption properties of the prepared dyes. Thermal analysis showed that these dyes are thermal stable up to 269 °C. Additionally, the electrochemical behavior of the dyes (6a-g) were investigated using cyclic voltammetric and chronoamperometric techniques, in the presence of 0.10 M tetrabutylammonium tetrafluoroborate, in dimethylsulfoxide, at a glassy carbon electrode. The number of transferred electrons, and the diffusion coefficient were determined by electrochemical methods. The results showed that, for all the dyes, one oxidation peak and two reduction peaks were observed.

  1. Phonon dispersion on Ag (100) surface: A modified analytic embedded atom method study

    Science.gov (United States)

    Xiao-Jun, Zhang; Chang-Le, Chen

    2016-01-01

    Within the harmonic approximation, the analytic expression of the dynamical matrix is derived based on the modified analytic embedded atom method (MAEAM) and the dynamics theory of surface lattice. The surface phonon dispersions along three major symmetry directions , and X¯M¯ are calculated for the clean Ag (100) surface by using our derived formulas. We then discuss the polarization and localization of surface modes at points X¯ and M¯ by plotting the squared polarization vectors as a function of the layer index. The phonon frequencies of the surface modes calculated by MAEAM are compared with the available experimental and other theoretical data. It is found that the present results are generally in agreement with the referenced experimental or theoretical results, with a maximum deviation of 10.4%. The agreement shows that the modified analytic embedded atom method is a reasonable many-body potential model to quickly describe the surface lattice vibration. It also lays a significant foundation for studying the surface lattice vibration in other metals. Project supported by the National Natural Science Foundation of China (Grant Nos. 61471301 and 61078057), the Scientific Research Program Funded by Shaanxi Provincial Education Department, China (Grant No. 14JK1301), and the Specialized Research Fund for the Doctoral Program of Higher Education, China (Grant No. 20126102110045).

  2. A model study of Fuego volcanic aerosol dispersion in the lower stratosphere

    Science.gov (United States)

    Remsberg, E. E.; Turner, R. E.; Butler, C. F.

    1982-01-01

    A zonally averaged time-dependent primitive equation model is used to simulate the dispersion of both a carbon 14 injection and the volcanic aerosol from the 1974 Fuego eruption. It is noted that both injections occurred at low latitudes to midlatitudes in the Northern Hemisphere. The eddy flux terms, which account for the major portion of the transport in the lower stratosphere of this model, are specified in a manner similar to that of Harwood and Pyle (1975). Comparisons with data underline the ability of the model to simulate the vertical character of the tracer while maintaining reasonable meridional transport times. For the aerosol study, the simulated 1/e decay time at 37 deg N and for the 16- to 21-km altitude region is 9 months, whereas lidar measurements at the same latitude give a decay time of 8 months. The simulated vertical width at half-maximum for the aerosol tracer at 37 deg N and 19 deg N and for 6 months after the event possesses values of 5.0 km and 3.6 km, respectively, whereas the observed lidar values are 4.4 km and 3.0 km, respectively. The tracer transport to the Southern Hemisphere also is in qualitative agreement with the limited data that are available.

  3. Numerical Study of Ammonia Leak and Dispersion in the International Space Station

    Science.gov (United States)

    Son, Chang H.

    2012-01-01

    Release of ammonia into the International Space Station (ISS) cabin atmosphere can occur if the water/ammonia barrier breach of the active thermal control system (ATCS) interface heat exchanger (IFHX) happens. After IFHX breach liquid ammonia is introduced into the water-filled internal thermal control system (ITCS) and then to the cabin environment through a ruptured gas trap. Once the liquid water/ammonia mixture exits ITCS, it instantly vaporizes and mixes with the U.S. Laboratory cabin air that results in rapid deterioration of the cabin conditions. The goal of the study is to assess ammonia propagation in the Station after IFHX breach to plan the operation procedure. A Computational Fluid Dynamics (CFD) model for accurate prediction of airflow and ammonia transport within each of the modules in the ISS cabin was developed. CFD data on ammonia content in the cabin aisle way of the ISS and, in particular, in the Russian On- Orbit Segment during the period of 15 minutes after gas trap rupture are presented for four scenarios of rupture response. Localized effects of ammonia dispersion and risk mitigation are discussed.

  4. Intraurban-scale dispersion modelling of particulate matter concentrations: Applications for exposure estimates in cohort studies

    Science.gov (United States)

    Gaines Wilson, J.; Zawar-Reza, Peyman

    Epidemiological studies relating air pollution to health effects often estimate personal exposure to particulate matter using values from a central ambient monitoring site as a proxy. However, when there is a significant amount of variation in particulate concentrations across an urban area, the use of central sites may result in exposure misclassification that induces error in long-term cohort epidemiological study designs. When spatially dense monitoring data are not available, advanced dispersion models may offer one solution to the problem of accurately characterising intraurban particulate concentrations across an area. This study presents results from an intraurban assessment of The Air Pollution Model (TAPM)—an Integrated Meteorological-Emission (IME) Model. Particles less than 10 μm in aerodynamic diameter (PM 10) were modelled and compared with a dense intraurban monitoring network in Christchurch, New Zealand, a city with high winter levels of particulate air pollution. Despite the area's high intraurban concentration variability, and meteorological and topographical complexity, the model performed satisfactorily overall, with mean observed and modelled concentrations of 42.9 and 43.4 μg m -3, respectively, while the mean Index of Agreement (IOA) between individual sites was 0.60 and the mean systematic RMSE was 16.9 μg m -3. Most of the systematic error in the model was due to coarse spatial resolution of the local emission inventory and complex meteorology attributed to localised convergence of drainage flows, especially on the western and southern fringes of the urban area. Given further improvements in site-specific estimates within urban areas, IME models such as TAPM may be a viable alternative to central sites for estimating personal exposure in longer-term (monthly or annual) cohort epidemiological studies.

  5. Field study plan for alternate barriers

    Energy Technology Data Exchange (ETDEWEB)

    Freeman, H.D.; Gee, G.W.; Relyea, J.F.

    1989-05-01

    Pacific Northwest Laboratory (PNL) is providing technical assistance in selecting, designing, evaluating, and demonstrating protective barriers. As part of this technical assistance effort, asphalt, clay, and chemical grout will be evaluated for use as alternate barriers. The purpose of the subsurface layer is to reduce the likelihood that extreme events (i.e., 100-year maximum storms, etc.) will cause significant drainage through the barrier. The tests on alternate barriers will include laboratory and field analysis of the subsurface layer performance. This field test plan outlines the activities required to test and design subsurface moisture barriers. The test plan covers activities completed in FY 1988 and planned through FY 1992 and includes a field-scale test of one or more of the alternate barriers to demonstrate full-scale application techniques and to provide performance data on a larger scale. Tests on asphalt, clay, and chemical grout were initiated in FY 1988 in small (30.5 cm diameter) tube-layer lysimeters. The parameters used for testing the materials were different for each one. The tests had to take into account the differences in material characteristics and response to change in conditions, as well as information provided by previous studies. 33 refs., 8 figs., 1 tab.

  6. Effects of threading dislocations on drain current dispersion and slow transients in unpassivated AlGaN/GaN/Si heterostructure field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Saptarsi, E-mail: saptarsi123@gmail.com; Dinara, Syed Mukulika; Mukhopadhyay, Partha; Jana, Sanjay K.; Bag, Ankush; Kabi, Sanjib [Advanced Technology Development Centre, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India); Chakraborty, Apurba [Department of E and E C E, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India); Chang, Edward Yi [Department of Material Science and Engineering, National Chiao Tung University, Hsinchu 30050, Taiwan (China); Biswas, Dhrubes [Advanced Technology Development Centre, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India); Department of E and E C E, Indian Institute of Technology Kharagpur, Kharagpur 721302 (India)

    2014-08-18

    Current transient analysis combined with response to pulsed bias drives have been used to explore the possibilities of threading dislocations affecting the current dispersion characteristics of AlGaN/GaN heterostructure field-effect transistors (HFETs). A growth strategy is developed to modulate the dislocation density among the heterostructures grown on silicon by plasma-assisted molecular-beam epitaxy. Slow pulsed I-V measurements show severe compressions and appear to be significantly dependent on the threading dislocation density. By analyzing the corresponding slow detrapping process, a deep-level trap with emission time constant in the order of seconds was identified as the cause. Among the specimens, both in the epilayers and at the surface, the number of dislocations was found to have a notable influence on the spatial distribution of deep-level trap density. The observations confirm that the commonly observed degraded frequency performance among AlGaN/GaN HFETs in the form of DC-radio frequency dispersions can at least partly be correlated with threading dislocation density.

  7. Energy-Dispersive X-Ray Diffraction Studies of the Texture in Cold-Rolled Alpha-Beta Brass

    DEFF Research Database (Denmark)

    Szpunar, J.; Gerward, L.

    1980-01-01

    It is shown that energy-dispersive X-ray diffraction can be used for simultaneous measurement of several pole figures and that the accuracy is sufficient for the determination of the crystallite orientation distribution. The method is applied to the study of the texture in Cu-43 wt % Zn duplex...... alpha-beta brass rolled to 80% reduction....

  8. Vadose Zone Transport Field Study: Summary Report

    Energy Technology Data Exchange (ETDEWEB)

    Ward, Andy L.; Conrad, Mark E.; Daily, William D.; Fink, James B.; Freedman, Vicky L.; Gee, Glendon W.; Hoversten, Gary M.; Keller, Jason M.; Majer, Ernest L.; Murray, Christopher J.; White, Mark D.; Yabusaki, Steven B.; Zhang, Z. F.

    2006-07-31

    From FY 2000 through FY 2003, a series of vadose zone transport field experiments were conducted as part of the U.S. Department of Energy’s Groundwater/Vadose Zone Integration Project Science and Technology Project, now known as the Remediation and Closure Science Project, and managed by the Pacific Northwest National Laboratory (PNNL). The series of experiments included two major field campaigns, one at a 299-E24-11 injection test site near PUREX and a second at a clastic dike site off Army Loop Road. The goals of these experiments were to improve our understanding of vadose zone transport processes; to develop data sets to validate and calibrate vadose zone flow and transport models; and to identify advanced monitoring techniques useful for evaluating flow-and-transport mechanisms and delineating contaminant plumes in the vadose zone at the Hanford Site. This report summarizes the key findings from the field studies and demonstrates how data collected from these studies are being used to improve conceptual models and develop numerical models of flow and transport in Hanford’s vadose zone. Results of these tests have led to a better understanding of the vadose zone. Fine-scale geologic heterogeneities, including grain fabric and lamination, were observed to have a strong effect on the large-scale behavior of contaminant plumes, primarily through increased lateral spreading resulting from anisotropy. Conceptual models have been updated to include lateral spreading and numerical models of unsaturated flow and transport have revised accordingly. A new robust model based on the concept of a connectivity tensor was developed to describe saturation-dependent anisotropy in strongly heterogeneous soils and has been incorporated into PNNL’s Subsurface Transport Over Multiple Phases (STOMP) simulator. Application to field-scale transport problems have led to a better understanding plume behavior at a number of sites where lateral spreading may have dominated waste

  9. Pulp-seed attachment is a dominant variable explaining legitimate seed dispersal: a case study on woolly monkeys.

    Science.gov (United States)

    Stevenson, Pablo R

    2011-07-01

    Seed dispersal is a mutualistic interaction in which frugivores gain nutrients and plants gain when seeds are transported to adequate places for establishment. However, this relationship is prone to deceit, for example, when frugivores spit-out seeds in the proximity of parental trees. Still, few hypotheses have offered explanations on why deceiving strategies are not widespread. In this study, I explore the importance of how difficult it is to mechanically separate the nutritious pulp from the seeds, as a factor that can explain the chance a seed has of being dispersed by woolly monkeys (Lagothrix lagothricha). I completed 1,440 h of focal animal follows during 2 years in order to quantify the chances plant species have of being dispersed. To do so, I evaluated the residuals from the relationship between the number of seeds manipulated and seeds dispersed by a population of woolly monkeys in Tinigua Park (Colombia). For 74 fruit species, I estimated how difficult it is to separate pulp from seeds as the time needed to separate the parts. An exponential model showed that this variable was able to predict 38% of the variation on dispersal probability, demonstrating that, when it is difficult to separate the pulp from the seeds, the probability of legitimate dispersal increases. However, when fruit parts were easy to separate, there was more variation in the outcome. My results suggest that many plants have evolved mechanisms (e.g., small seeds embedded in pulp, strong attachment, irregular seed surface, and thin pulp layer) that preclude deceit by frugivores.

  10. Carcinogenic effects of oil dispersants: A KEGG pathway-based RNA-seq study of human airway epithelial cells.

    Science.gov (United States)

    Liu, Yao-Zhong; Zhang, Lei; Roy-Engel, Astrid M; Saito, Shigeki; Lasky, Joseph A; Wang, Guangdi; Wang, He

    2017-02-20

    The health impacts of the BP oil spill are yet to be further revealed as the toxicological effects of oil products and dispersants on human respiratory system may be latent and complex, and hence difficult to study and follow up. Here we performed RNA-seq analyses of a system of human airway epithelial cells treated with the BP crude oil and/or dispersants Corexit 9500 and Corexit 9527 that were used to help break up the oil spill. Based on the RNA-seq data, we then systemically analyzed the transcriptomic perturbations of the cells at the KEGG pathway level using two pathway-based analysis tools, GAGE (generally applicable gene set enrichment) and GSNCA (Gene Sets Net Correlations Analysis). Our results suggested a pattern of change towards carcinogenesis for the treated cells marked by upregulation of ribosomal biosynthesis (hsa03008) (p=1.97E-13), protein processing (hsa04141) (p=4.09E-7), Wnt signaling (hsa04310) (p=6.76E-3), neurotrophin signaling (hsa04722) (p=7.73E-3) and insulin signaling (hsa04910) (p=1.16E-2) pathways under the dispersant Corexit 9527 treatment, as identified by GAGE analysis. Furthermore, through GSNCA analysis, we identified gene co-expression changes for several KEGG cancer pathways, including small cell lung cancer pathway (hsa05222, p=9.99E-5), under various treatments of oil/dispersant, especially the mixture of oil and Corexit 9527. Overall, our results suggested carcinogenic effects of dispersants (in particular Corexit 9527) and their mixtures with the BP crude oil, and provided further support for more stringent safety precautions and regulations for operations involving long-term respiratory exposure to oil and dispersants.

  11. DISPERSION ANALYSIS OF CYLINDRICALLOVE WAVES AND NUMERICALCALCULATION OF SH WAVES FIELD%柱面Love波频散分析与SH波场的数值计算

    Institute of Scientific and Technical Information of China (English)

    姚桂锦; 王克协; 马俊; 伍先运

    2001-01-01

    SH wave field excited by circumferential shear source incylindrically double-layered media is theoretically analysed.Dispersion equation of cylindrical Love waves(guide waves)has been derived.Both existence condition and existence range of cylindrical Love waves are discussed.Dispersion and excitation of cylindrical Love waves are investigated by numerical calculation.It is discovered that the lowest order cylindrical Love waves have cut-off frequency,which differs from Love waves in half-space with horizontally double-layered elastic media.The asymptotic expression of dispersion equation of cylindrical Love waves as well radius r1→∞ consistently tends to the dispersion equation in the horizontal half-space case,and cut-off frequency tends to zero.The transient full waveform calculation is also calculated and illustrated,showing that realizing direct shear wave logs through exciting SH wave would be a more forthright way.%对贴井壁环型剪切源在柱状双层弹性介质中激发的SH波场进行了理论求解,导出了柱面Love波频散方程,讨论了柱面Love波存在的条件及其区域.通过数值计算考察了柱面Love波的频散特性和激发强度,发现最低阶柱面Love波具有截止频率,这与平面半空间双层弹性介质模型下的Love波无截止频率的特征不同.渐近分析与数值考察都表明,井径r1→∞时,柱面Love波频散方程趋向平面双层半空间的Love波方程,柱面Love波的截止频率趋于零.全波计算还显示用激发SH波来探测侵入带外原状地层的横波信息是一个十分简洁的途径.

  12. Naturalistic Field Studies of Sleep and Performance

    Science.gov (United States)

    2009-04-01

    sleep  opportunity and creating acute and chronic  sleep  loss   Mathematical models combined with quantitative cognitive  architecture  are  useful for...Violanti, Cecil Burchfiel, Bryan  Vila, and Michael E. Andrew. (2008) “Waiting Time Distributions of  Actigraphy   Measured  Sleep .” Open  Sleep  Journal 2...AD_________________ Award Number: W81XWH-05-1-0099 TITLE: Naturalistic Field Studies of Sleep and

  13. Test of the rem-counter WENDI-II from Eberline in different energy-dispersed neutron fields

    Energy Technology Data Exchange (ETDEWEB)

    Gutermuth, F.; Radon, T.; Fehrenbacher, G.; Siekmann, R.

    2004-03-01

    The neutron rem-counter WENDI-II from Eberline was tested in high-energy particle accelerator produced neutron fields. A radioactive {sup 241}Am-Be({alpha}n) source was used as a reference. The experimentally determined responses are compared to Monte-Carlo simulations of the response function done by R. H. Olsher et al. (2000). The energy spectra of the accelerator produced neutron fields were determined employing Monte-Carlo simulations, too. According to the simulations done by C. Birattari et al. (1998) and in this work these neutron fields exhibit large contributions to the ambient dose equivalent resulting from neutrons with kinetic energy of more than 20 MeV up to a few 100 MeV. The WENDI-II detector proved to show a response of approximately 3.10{sup 9} pulses per Sievert ambient dose equivalent. Considering the experimental and statistical uncertainties the results are consistent with the assumption that the dose response of the WENDI-II reproduces quite accurately the function for the ambient dose equivalent of the ICRP 74.

  14. Dispersal, individual movement and spatial ecology a mathematical perspective

    CERN Document Server

    Maini, Philip; Petrovskii, Sergei

    2013-01-01

    Dispersal of plants and animals is one of the most fascinating subjects in ecology. It has long been recognized as an important factor affecting ecosystem dynamics. Dispersal is apparently a phenomenon of biological origin; however, because of its complexity, it cannot be studied comprehensively by biological methods alone. Deeper insights into dispersal properties and implications require interdisciplinary approaches involving biologists, ecologists and mathematicians. The purpose of this book is to provide a forum for researches with different backgrounds and expertise and to ensure further advances in the study of dispersal and spatial ecology. This book is unique in its attempt to give an overview of dispersal studies across different spatial scales, such as the scale of individual movement, the population scale and the scale of communities and ecosystems. It is written by top-level experts in the field of dispersal modeling and covers a wide range of problems ranging from the identification of Levy walks...

  15. Dispersion effects in SiO2 polymorphs: An ab initio study

    Science.gov (United States)

    Hay, Henri; Ferlat, Guillaume; Casula, Michele; Seitsonen, Ari Paavo; Mauri, Francesco

    2015-10-01

    The effect of electronic dispersion over a wide variety of SiO2 polymorphs (faujasite, ferrierite, α -cristobalite, α -quartz, coesite, and stishovite) is investigated using state-of-the-art density functional theory. Different functionals and dispersion correction schemes are compared, ranging from the local density approximation to fully nonlocal exchange-correlation functionals. It is shown that both empirical dispersion corrections and fully nonlocal functionals improve the energetics and give correct volumetric data. However, the correct volume results come from error cancellation between an overestimation of the Si-O distance and an underestimation of the Si-O-Si angle. Quantum Monte Carlo is used to compute the quartz-cristobalite energy difference within an accuracy of 0.2 kCal/mol per SiO2 unit. This demonstrates the feasability of achieving subchemical accuracy on extended systems, and confirms the validity of the Slater-Jastrow ansatz for describing SiO2 polymorphs.

  16. Experimental and numerical study of the dispersion of carbon dioxide plume.

    Science.gov (United States)

    Xing, Ji; Liu, Zhenyi; Huang, Ping; Feng, Changgen; Zhou, Yi; Zhang, Deping; Wang, Feng

    2013-07-15

    Carbon Capture and Storage (CCS) and Enhanced Oil Recovery (EOR) technologies have been widely applied in the environmental protection and petroleum production fields. However, accidental release of carbon dioxide may cause damage and losses during oil and gas production. This paper presents a reduced-scale field experiment designed to imitate a CO2 blowout for the purpose of acquiring concentration the distribution in the flow field. Additionally, computational fluid dynamics (CFD) code was used to perform numerical simulations of the field experiment using the k-ε, RNG k-ε and SST k-ω models. The results of these models were compared with the experimental data for validation, and statistical performance indicators were introduced to verify the simulated values. According to experimental and numerical results, the interior flow structure of a CO2 plume was analyzed together with consideration of negative buoyancy effects. The concentration as a function of time was studied by comparing the observed values and simulation results. We conclude that the CFD simulation results from the k-ε and SST k-ω models are in acceptable agreement with the experimental data according to the Chang's criteria, and predicted values from the RNG k-ε model are unsatisfactory. Therefore, the CFD techniques can be satisfactorily applied in industrial risk analysis procedures with acceptable accuracy according to the Chang's criteria. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Uncovering dispersion properties in semiconductor waveguides to study photon-pair generation

    Science.gov (United States)

    Laiho, K.; Pressl, B.; Schlager, A.; Suchomel, H.; Kamp, M.; Höfling, S.; Schneider, C.; Weihs, G.

    2016-10-01

    We investigate the dispersion properties of ridge Bragg-reflection waveguides to deduce their phasematching characteristics. These are crucial for exploiting them as sources of parametric down-conversion (PDC). In order to estimate the phasematching bandwidth we first determine the group refractive indices of the interacting modes via Fabry-Perot experiments in two distant wavelength regions. Second, by measuring the spectra of the emitted PDC photons, we gain access to their group index dispersion. Our results offer a simple approach for determining the PDC process parameters in the spectral domain, and provide important feedback for designing such sources, especially in the broadband case.

  18. Uncovering dispersion properties in semiconductor waveguides to study photon-pair generation

    CERN Document Server

    Laiho, K; Schlager, A; Suchomel, H; Höfling, S; Kamp, M; Schneider, C; Weihs, G

    2016-01-01

    We investigate the dispersion properties of ridge Bragg-reflection waveguides to deduce their phasematching characteristics. These are crucial for exploiting them as sources of parametric down-conversion (PDC). In order to estimate the phasematching bandwidth we first determine the group refractive indices of the interacting modes via Fabry-Perot experiments in two distant wavelength regions. Second, by measuring the spectra of the emitted PDC photons we gain access to their group index dispersion. Our results offer a simple approach for determining the PDC process parameters in the spectral domain and provide an important feedback for designing such sources, especially in the broadband case.

  19. Study of the low-frequency dispersion of permittivity and resistivity in tight rocks

    Science.gov (United States)

    Liu, Hongqi; Jie, Tian; Li, Bo; Youming, Deng; Chunning, Qiu

    2017-08-01

    The road to understanding the frequency dispersion (relaxation) of permittivity and resistivity in tight rocks remains relatively uncharted. Our team from Da'anzhai Group, Jurassic formation, Sichuan Basin carried out practical research to explore this phenomenon. The research was conducted under laboratory conditions for a selection of low frequencies, with ranges between 0.1 Hz to 1 kHz. Our research has shown that, although both the permittivity and resistivity decrease as the frequency increases, the two individual metrics display different behaviours when compared with each other. While the degree of resistivity variation is minimal, to the point that it is redundant, the permittivity, on the other hand, demonstrates something that is scientifically noteworthy. Permittivity has a distinctive dispersion degree across the entire sample of frequencies and the difference between the minimum and maximum frequencies is several orders of magnitude. An additional, and unexpected, learning from our research is that the level of frequency dispersion increases as the water saturation and concentration increases. In this paper, a collection of equations has been formulated to describe this relationship. These equations particularly shed light on the areas of rock porosity and saturation. They also show that the degree of frequency dispersion of permittivity or resistivity can be used as a function of water saturation and concentration. Two new variables are introduced here, DR and DC, to demonstrate the relaxation law quantitatively. In our practical research, we have characterised the relationship between the saturation and concentration with dielectric relaxation, using three different concentrations of DR and DC and five different saturations of NaCl solution. In difference to conventional Archie's multiple experimental parameters, we have established a new formula to derive the saturation from Rp and Cp, or from DR and DC directly. Two important frequencies were also

  20. Using the Wasserstein distance to compare fields of pollutants: application to the radionuclide atmospheric dispersion of the Fukushima-Daiichi accident

    Directory of Open Access Journals (Sweden)

    Alban Farchi

    2016-09-01

    Full Text Available The verification of simulations against data and the comparison of model simulation of pollutant fields rely on the critical choice of statistical indicators. Most of the scores are based on point-wise, that is, local, value comparison. Such indicators are impacted by the so-called double penalty effect. Typically, a misplaced blob of pollutants will doubly penalise such a score because it is predicted where it should not be and is not predicted where it should be. The effect is acute in plume simulations where the concentrations gradient can be sharp. A non-local metric that would match concentration fields by displacement would avoid such double penalty. Here, we experiment on such a metric known as the Wasserstein distance, which tells how penalising moving the pollutants is. We give a mathematical introduction to this distance and discuss how it should be adapted to handle fields of pollutants. We develop and optimise an open Python code to compute this distance. The metric is applied to the dispersion of cesium-137 of the Fukushima-Daiichi nuclear power plant accident. We discuss of its application in model-to-model comparison but also in the verification of model simulation against a map of observed deposited cesium-137 over Japan. As hoped for, the Wasserstein distance is less penalising, and yet retains some of the key discriminating properties of the root mean square error indicator.

  1. A fuzzy-theory-based method for studying the effect of information transmission on nonlinear crowd dispersion dynamics

    Science.gov (United States)

    Fu, Libi; Song, Weiguo; Lo, Siuming

    2017-01-01

    Emergencies involved in mass events are related to a variety of factors and processes. An important factor is the transmission of information on danger that has an influence on nonlinear crowd dynamics during the process of crowd dispersion. Due to much uncertainty in this process, there is an urgent need to propose a method to investigate the influence. In this paper, a novel fuzzy-theory-based method is presented to study crowd dynamics under the influence of information transmission. Fuzzy functions and rules are designed for the ambiguous description of human states. Reasonable inference is employed to decide the output values of decision making such as pedestrian movement speed and directions. Through simulation under four-way pedestrian situations, good crowd dispersion phenomena are achieved. Simulation results under different conditions demonstrate that information transmission cannot always induce successful crowd dispersion in all situations. This depends on whether decision strategies in response to information on danger are unified and effective, especially in dense crowds. Results also suggest that an increase in drift strength at low density and the percentage of pedestrians, who choose one of the furthest unoccupied Von Neumann neighbors from the dangerous source as the drift direction at high density, is helpful in crowd dispersion. Compared with previous work, our comprehensive study improves an in-depth understanding of nonlinear crowd dynamics under the effect of information on danger.

  2. Magnetic orientation of nontronite clay in aqueous dispersions and its effect on water diffusion.

    Science.gov (United States)

    Abrahamsson, Christoffer; Nordstierna, Lars; Nordin, Matias; Dvinskikh, Sergey V; Nydén, Magnus

    2015-01-01

    The diffusion rate of water in dilute clay dispersions depends on particle concentration, size, shape, aggregation and water-particle interactions. As nontronite clay particles magnetically align parallel to the magnetic field, directional self-diffusion anisotropy can be created within such dispersion. Here we study water diffusion in exfoliated nontronite clay dispersions by diffusion NMR and time-dependant 1H-NMR-imaging profiles. The dispersion clay concentration was varied between 0.3 and 0.7 vol%. After magnetic alignment of the clay particles in these dispersions a maximum difference of 20% was measured between the parallel and perpendicular self-diffusion coefficients in the dispersion with 0.7 vol% clay. A method was developed to measure water diffusion within the dispersion in the absence of a magnetic field (random clay orientation) as this is not possible with standard diffusion NMR. However, no significant difference in self-diffusion coefficient between random and aligned dispersions could be observed.

  3. A parametric study of dispersion processes in semi-enclosed basins

    Energy Technology Data Exchange (ETDEWEB)

    Buffoni, G. [ENEA, Centro Ricerche S. Teresa, La Spezia (Italy). Dipt. di Innovazione; Bellucci, A.; Zambianchi, E. [Istituto Universitario Navale, Neapel (Italy); Griffa, A. [Consiglio Nazionale delle Ricerche, La Spezia (Italy)

    1999-07-01

    The dispersion processes in semi-enclosed basins with stationary flows have been studied by means of an Eulerian advection-diffusion model. Special interest have been given to quantities which characterize the macroscopic state of the system: the normalized total quantity C(t) (C (0) = 1) of a tracer inside the basin, and its residence time T. Also the principal eigenvalue {tau}{sub 0} of the advection-diffusion problem has been considered, since for stationery flows C (t) attains, for time t long enough, an exponential decay shape C{sub 0}exp (-t/{tau}{sub 0} ). The focus is one the comparison between cases where the flow is rotational with re circulations, represented by a flow with a gyre at the outflow. The sensitivity of the results to a number of parameters, including initial and boundary conditions and the eddy diffusivity coefficient, have been studied. It is found that for small Peclet numbers, when the flow is highly diffusive, the results do not depend strongly on the flow structure. {tau}{sub 0} tends to a constant limit (dependent on the boundary conditions) at decreasing Peclet number, and T is approximated by T asymptotically equal to {tau}{sub 0}. For high Peclet numbers, instead, the rotational and irrotational cases are qualitatively different. For rotational flows, {tau}{sub 0}, tends to zero at increasing Peclet number, and T tends toward the advective time scale. For flows with re circulations, in which the tracer tends to be trapped inside the gyre, {tau}{sub 0} increases at increasing Peclet numbers and T asymptotically equal to {tau}{sub 0}, for all initial and boundary conditions. The values of T and {tau}{sub 0} do not change significantly in the range of realistic Peclet numbers considered. This suggests that, for flows with re circulations, the macroscopic dispersion properties depend only weakly on the eddy diffusion coefficient. [Italian] Processi di dispersione in bacini semi-chiusi caratterizzati da flussi stazionari sono stati

  4. A parametric study of dispersion processes in semi-enclosed basins

    Energy Technology Data Exchange (ETDEWEB)

    Buffoni, G. [ENEA, Centro Ricerche S. Teresa, La Spezia (Italy). Dipt. di Innovazione; Bellucci, A.; Zambianchi, E. [Istituto Universitario Navale, Neapel (Italy); Griffa, A. [Consiglio Nazionale delle Ricerche, La Spezia (Italy)

    1999-07-01

    The dispersion processes in semi-enclosed basins with stationary flows have been studied by means of an Eulerian advection-diffusion model. Special interest have been given to quantities which characterize the macroscopic state of the system: the normalized total quantity C(t) (C (0) = 1) of a tracer inside the basin, and its residence time T. Also the principal eigenvalue {tau}{sub 0} of the advection-diffusion problem has been considered, since for stationery flows C (t) attains, for time t long enough, an exponential decay shape C{sub 0}exp (-t/{tau}{sub 0} ). The focus is one the comparison between cases where the flow is rotational with re circulations, represented by a flow with a gyre at the outflow. The sensitivity of the results to a number of parameters, including initial and boundary conditions and the eddy diffusivity coefficient, have been studied. It is found that for small Peclet numbers, when the flow is highly diffusive, the results do not depend strongly on the flow structure. {tau}{sub 0} tends to a constant limit (dependent on the boundary conditions) at decreasing Peclet number, and T is approximated by T asymptotically equal to {tau}{sub 0}. For high Peclet numbers, instead, the rotational and irrotational cases are qualitatively different. For rotational flows, {tau}{sub 0}, tends to zero at increasing Peclet number, and T tends toward the advective time scale. For flows with re circulations, in which the tracer tends to be trapped inside the gyre, {tau}{sub 0} increases at increasing Peclet numbers and T asymptotically equal to {tau}{sub 0}, for all initial and boundary conditions. The values of T and {tau}{sub 0} do not change significantly in the range of realistic Peclet numbers considered. This suggests that, for flows with re circulations, the macroscopic dispersion properties depend only weakly on the eddy diffusion coefficient. [Italian] Processi di dispersione in bacini semi-chiusi caratterizzati da flussi stazionari sono stati

  5. Incorporating ecology and social system into formal hypotheses to guide field studies of color vision in primates.

    Science.gov (United States)

    Bunce, John A

    2015-05-01

    The X-linked gene polymorphism responsible for the variable color vision of most Neotropical monkeys and some lemurs is thought to be maintained by balancing selection, such that trichromats have an advantage over dichromats for some ecologically important task(s). However, evidence for such an advantage in wild primate populations is equivocal. The purpose of this study is to refine a hypothesis for a trichromat advantage by tailoring it to the ecology of territorial primates with female natal dispersal, such that dispersing trichromatic females have a foraging and, by extension, survival advantage over dichromats. I then examine the most practical way to test this hypothesis using field data. Indirect evidence in support of the hypothesis may take the form of differences in genotype frequencies among life stages and differences in disperser food item encounter rates. A deterministic evolutionary matrix population model and a stochastic model of food patch encounter rates are constructed to investigate the magnitude of such differences and the likelihood of statistical detection using field data. Results suggest that, although the sampling effort required to detect the hypothesized genotype frequency differences is impractical, a field study of reasonable scope may be able to detect differences in disperser foraging rates. This study demonstrates the utility of incorporating socioecological details into formal hypotheses during the planning stages of field studies of primate color vision. © 2015 Wiley Periodicals, Inc.

  6. Pharmacokinetics and bioequivalence studies of galantamine hydrobromide dispersible tablet in healthy male Chinese volunteers.

    Science.gov (United States)

    Zhang, Li-jun; Fang, Xiao-ling; Li, Xue-ning; Wang, Qing-song; Han, Li-mei; Zhang, Zhi-wen; Sha, Xian-yi

    2007-03-01

    A randomized, two-way, crossover study was conducted in 18 healthy male Chinese volunteers to compare pharmacokinetics profiles of galantamine hydrobromide dispersible tablet with that of conventional tablet. A single oral dose of 10 mg galantamine was administrated to each volunteer. Plasma concentrations of galantamine were determined by a validated high-performance liquid chromatography (HPLC) method with fluorescence detection, which allowed 1 ng/mL to be assayed as the lowest quantifiable concentration. From plasma concentrations, AUC(0-->t) (the area under the plasma concentration-time curve from time 0 to the last sampling time, 32 hr), AUC(0-->infinity) (the area under the plasma concentration-time curve from time 0 to infinity), t((1/2)) (elimination of half-life of the terminal log linear phase), C(max) (maximum plasma drug concentration) and T(max) (time to reach C(max)) were evaluated through noncompartmental pharmacokinetic analysis. AUC(0-->t) and AUC(0-->infinity) were calculated by the linear-log trapezoidal rule method. C(max) and T(max) were obtained directly from the plasma concentration-time curve. Analysis of variance was carried out using logarithmically transformed AUC(0-->t), AUC(0-->infinity) and C(max). As far as AUC(0-->t), AUC(0-->infinity) and C(max) were concerned, there was no statistically significant difference between the test and reference formulations. Ninety percent confidence intervals (90% CI) for the ratio of AUC(0-->t), AUC(0-->infinity) and C(max) values for the test and reference formulations were 100.4-107.8%, 99.0-107.2% and 87.5-111.3%, respectively. As the 90% CIs of AUC(0-->t), AUC(0-->infinity) and C(max) were entirely within 80-125%, two formulations were considered bioequivalent.

  7. Geochemistry of the Phlegraean Fields (Italy) proximal sources for major Mediterranean tephras: Implications for the dispersal of Plinian and co-ignimbritic components of explosive eruptions

    Science.gov (United States)

    Tomlinson, Emma L.; Arienzo, Ilenia; Civetta, Lucia; Wulf, Sabine; Smith, Victoria C.; Hardiman, Mark; Lane, Christine S.; Carandente, Antonio; Orsi, Giovanni; Rosi, Mauro; Müller, Wolfgang; Menzies, Martin A.

    2012-09-01

    Volcanic activity at Phlegraean Fields, Italy, produced several major marker tephras over a 50 ka period. The caldera forming eruptions of the Campanian Ignimbrite (CI) and Neapolitan Yellow Tuff (NYT) are of particular importance for tephrostratigraphy in Europe. Other key eruptions from this source include the Pomici Principali (PP) and the Tufi Biancastri eruptions. We combine analyses of fresh glasses from proximal locations (i.e., juvenile clasts in proximal flow and fall deposits) with data for key tephra layers from Lago Grande di Monticchio, 120 km to the east. The micron-beam major (EMPA) and trace (LA-ICP-MS) element glass dataset allows us to: (a) distinguish between tephra units produced from the Phlegraean Fields before and during the CI eruption (CI-series), and before and during the NYT and PP eruptions (NYT-series/PP); (b) discriminate between the CI and the geochemically similar Pre-CI pyroclastic deposits; (c) separate the NYT from Pre-NYT tephra units, although both major and trace elements do show significant overlap. The complex compositional overlap between Pre-NYT tephras may present a problem for tephra correlations in the 14-39 ka time window and may have resulted in incorrect proximal-distal and distal-distal correlations. The diagnostic chemical criteria detailed herein permits more accurate matching of distal tephras with their proximal equivalents and hence will improve chronostratigraphy of distal settings and give insight into tephra dispersal. We show that the dispersal of PP tephra was more limited than previously thought. The surge/fall (Lower Member) and subsequent pyroclastic density current (Upper Member) phases of the NYT eruption can be recognised in distal settings. Both the NYT Lower and Upper Members are found in distal localities to the east of the Phlegraean Fields, however the Lower Member is found in the absence of the Upper Member in locations to the far north of Phlegraean Fields. Chemical compositions of the Plinian

  8. Preliminary studies on seed dispersal of swallow-wort (Vincetoxicum spp.)

    Science.gov (United States)

    Vincetoxicum rossicum (pale swallow-wort) and V. nigrum (black swallow-wort) are invasive, perennial vines that have become problematic in natural areas in the northeastern United States and neighboring southeastern Canada. Both species reproduce primarily via wind-dispersed seeds in the form of ac...

  9. SANS study to probe nanoparticle dispersion in nanocomposite membranes of aromatic polyamide and functionalized silica nanoparticles.

    Science.gov (United States)

    Jadav, Ghanshyam L; Aswal, Vinod K; Singh, Puyam S

    2010-11-01

    Silica nanoparticles produced from organically functionalized silicon alkoxide precursors were incorporated into polyamide film to produce a silica-polyamide nanocomposite membrane with enhanced properties. The dispersion of the silica nanoparticles in the nanocomposite membrane was characterized by performing small-angle neutron scattering (SANS) measurements on dilute reactant systems and dilute solution suspensions of the final product. Clear scattering of monodisperse spherical particles of 10-18 A R(g) were observed from dilute solutions of the initial reactant system. These silica nanoparticles initially reacted with diamine monomers of polyamide and subsequently were transformed into polyamide-coated silica nanoparticles; finally nanoparticle aggregates of 27-45 A R(g) were formed. The nanoparticle dispersion of the membrane as the nanosized aggregates is in corroboration with ring- or chain-like assemblies of the nanoparticles dispersed in the bulk polyamide phase as observed by transmission electron microscopy. It is demonstrated that dispersions of silica nanoparticles as the nanosized aggregates in the polyamide phase could be achieved in the nanocomposite membrane with a silica content up to about 2 wt.%. Nanocomposite membranes with higher silica loading approximately 10 wt.% lead to the formation of large aggregates of sizes over 100 A R(g) in addition to the nanosized aggregates.

  10. Seed dispersal by ants and its consequences for the phenology of plants : a study system for mutualistic animal plant interactions

    OpenAIRE

    Oberrath, Reik

    2000-01-01

    The hypothesis was tested that ant dispersed plant species are adapted to the seasonal variation in ant activity, i.e. that ant dispersed plant species produce ripe fruits when the activity of their seed dispersers is especially high. Two testable predictions of this hypothesis exist: 1. Ant dispersed and differently dispersed plant species differ in their seasonal development, i.e. ant dispersed plant species fruit (flower) earlier or later in the year than other plant species. Floristic inv...

  11. Estudo das dispersões aquosas de nanotubos de carbono utilizando diferentes surfactantes Study of aqueous dispersions of carbon nanotubes using different surfactants

    Directory of Open Access Journals (Sweden)

    Isabella R. da Silva

    2013-01-01

    Full Text Available The dispersion of carbon nanotubes in water for their utilization in nanoscale devices is a challenging task. Comparative studies on interaction and dispersion of multi-wall carbon nanotubes (MWNT using two different surfactants (sodium dodecyl sulfate, SDS, and polyoxyethylenesorbitanmonooleate, Tween 80 are presented. The interaction between carbon nanotubes and surfactants was studied by tensiometry, conductivimetry, and fluorimetry. The dispersions of MWNT in surfactants were characterized using a UV-vis spectrophotometer. For effective dispersion, the minimum weight ratio of MWNT to surfactant was 1:41 and 1:3 for SDS and Tween 80, respectively.

  12. Numerical study of the small dispersion limit of the Korteweg-de Vries equation and asymptotic solutions

    CERN Document Server

    Grava, T

    2012-01-01

    We study numerically the small dispersion limit for the Korteweg-de Vries (KdV) equation $u_t+6uu_x+\\epsilon^{2}u_{xxx}=0$ for $\\epsilon\\ll1$ and give a quantitative comparison of the numerical solution with various asymptotic formulae for small $\\epsilon$ in the whole $(x,t)$-plane. The matching of the asymptotic solutions is studied numerically.

  13. Video Field Studies with your Cell Phone

    DEFF Research Database (Denmark)

    Buur, Jacob; Fraser, Euan

    2010-01-01

    is monumental, that equipment is difficult to handle etc. This tutorial presents a lightweight entry into video field studies, using cheap devices like cell phones and portable webcams for informal shooting and simple computer handling for editing. E.g. how far can you get with an iPhone or a video capable i......, and in particular practitioners from smaller organizations are understandably nervous about embarking on video projects out of fear that it is difficult to get consent in the first place, that the ethics is difficult to handle, that video shooting makes the social relations awkward, that the editing task......Pod? Or with the GoPRO sports camera? Our approach has a strong focus on how to use video in design, rather than on the technical side. The goal is to engage design teams in meaningful discussions based on user empathy, rather than to produce beautiful videos. Basically it is a search for a minimalist way...

  14. Expatriate Compound Living: An Ethnographic Field Study

    DEFF Research Database (Denmark)

    Lauring, Jakob; Selmer, Jan

    2009-01-01

    ethnographic field-work methodology, including interviews and participant observation during a period of three months, this exploratory study investigated 16 Danish business expatriates of a large Danish corporation and their families living in the same compound in Saudi Arabia. They shared their spare time...... and the expatriates had the same working hours in the same subsidiary. Results show that a Danish national group was established and maintained. This in-group dominated life in the compound and at work it may have contributed to the perceptual bias and discriminatory behaviour demonstrated by the Danish expatriates......In certain countries, closed expatriate compounds have developed.  They serve to provide resident expatriates and accompanying family members with a comfortable and safe environment. Unfortunately, not much is known about compound life since associated empirical research is scarce. Through...

  15. High resolution NMR study of T{sub 1} magnetic relaxation dispersion. IV. Proton relaxation in amino acids and Met-enkephalin pentapeptide

    Energy Technology Data Exchange (ETDEWEB)

    Pravdivtsev, Andrey N.; Yurkovskaya, Alexandra V.; Ivanov, Konstantin L., E-mail: ivanov@tomo.nsc.ru [International Tomography Center, Institutskaya 3a, Novosibirsk 630090 (Russian Federation); Department of Physics, Novosibirsk State University, Pirogova 2, Novosibirsk 630090 (Russian Federation); Vieth, Hans-Martin [Institut für Experimentalphysik, Freie Universität Berlin Arnimallee 14, 14195 Berlin (Germany)

    2014-10-21

    Nuclear Magnetic Relaxation Dispersion (NMRD) of protons was studied in the pentapeptide Met-enkephalin and the amino acids, which constitute it. Experiments were run by using high-resolution Nuclear Magnetic Resonance (NMR) in combination with fast field-cycling, thus enabling measuring NMRD curves for all individual protons. As in earlier works, Papers I–III, pronounced effects of intramolecular scalar spin-spin interactions, J-couplings, on spin relaxation were found. Notably, at low fields J-couplings tend to equalize the apparent relaxation rates within networks of coupled protons. In Met-enkephalin, in contrast to the free amino acids, there is a sharp increase in the proton T{sub 1}-relaxation times at high fields due to the changes in the regime of molecular motion. The experimental data are in good agreement with theory. From modelling the relaxation experiments we were able to determine motional correlation times of different residues in Met-enkephalin with atomic resolution. This allows us to draw conclusions about preferential conformation of the pentapeptide in solution, which is also in agreement with data from two-dimensional NMR experiments (rotating frame Overhauser effect spectroscopy). Altogether, our study demonstrates that high-resolution NMR studies of magnetic field-dependent relaxation allow one to probe molecular mobility in biomolecules with atomic resolution.

  16. A comparative simulation study on three lattice systems for the phase separation of polymer-dispersed liquid crystals

    Indian Academy of Sciences (India)

    Y J Jeon; M Jamil; Hyo-Dong Lee; J T Rhee

    2008-09-01

    This article reports a comparative study of the phase separation process in a polymer-dispersed liquid crystal, based on a Metropolis Monte Carlo simulation study of three lattice systems. We propose a model for the different processes occurring in the formation of polymer-dispersed liquid crystals (PDLCs). The mechanism of PDLC is studied as a function of quench temperature, concentration and degree of polymerization of liquid crystals and polymers. The obtained resultant phase diagrams of the three systems are approximated and compared with the Flory–Huggins theory, and show a good agreement. It has been observed in the simulation results that among all the three systems, the 40 × 40 × 40 lattice showed the most accurate, reliable and stable results.

  17. Spatial and temporal seed dispersal of squarrose knapweed (Centaurea virgata Lam. ssp. squarrosa (Willd.) Gugler) in west central Utah, a case study

    Science.gov (United States)

    Scott L. Jensen; Stephen B. Monsen; Pat Fosse

    2008-01-01

    This case study documents temporal and spatial squarrose knapweed (Centaurea virgata Lam. spp. squarrosa (Willd.) Gugler) seed dispersal from study sites in central Utah. Felt seed traps were placed along transects extending from sites occupied by squarrose knapweed into adjacent plant communities. Seed dispersal from knapweed...

  18. Joint DOE/NRC field study of tracer migration in the unsaturated zone

    Energy Technology Data Exchange (ETDEWEB)

    Nyhan, J.; Polzer, W.; Essington, E.; Cokal, E.; Lane, L.; Lopez, E.; Stallings, E.; Walker, R.

    1986-03-01

    The results of a joint DOE/NRC field experiment to evaluate leaching and transport of solutes in a sandy silt backfill used for shallow land burial operations at Los Alamos are presented for steady-state and unsteady-state flow conditions. The migration of iodide, bromide, and lithium through the backfill material is studied as functions of depth and time and they are compared with one another. The bromide and iodide tracer data are used to estimate the diffusion coefficient, the tortuosity factor, and dispersivity. These values are used to calculate effective dispersion coefficients for subsequent analyses of the retardation factor and the distribution coefficient for lithium using least squares procedures. The results of the tracer migration study are discussed relative to challenges facing the waste management community, and chemical transport modeling opportunities are presented for a modeling workshop to be held in FY86.

  19. Studies on the Surface Interaction and Dispersity of Silver Nanoparticles in Organic Solvents

    Institute of Scientific and Technical Information of China (English)

    ZENG Rong; RONG Min-Zhi; ZHANG Ming-Qiu; ZENG Han-Min

    2000-01-01

    Silver nanoparticles with different sizes have been prepared by microemulsion and have been surface-modified with C12H25SH. Electron spin resonance results indicate that there exist some kinds of surface local paramagnetic sites in capped Ag nanoparticles, which leads to the relation between electron spin resonance parameters and particle size deviating from Kawabata's description. Thereis a strong interaction between nanosilver and chloroform. The smaller the particles, the stronger the interaction. Transmission electron microscopy and ultravilolet-visible absorption spectra confirmed that Ag nanoparticles are well dispersed in chloroform, implying that a good dispersity of Ag nanoparticles in polymers could be obtained by means of solution mixing by using chloroform as the solvent.

  20. The variability of processes involved in transgene dispersal - case studies from Brassica and related genera

    DEFF Research Database (Denmark)

    Bagger Jørgensen, Rikke; Hauser, Thure Pavlo; D'Hertefeldt, T.

    2009-01-01

    Background, aim, and scope We strive to predict consequences of genetically modified plants (GMPs) being cultivated openly in the environment, as human and animal health, biodiversity, agricultural practise and farmers’ economy could be affected. Therefore, it is unfortunate that the risk...... of fitness parameters. Monitoring of the extent of spontaneous introgression in natural populations was also performed. Modelling was used as an additional tool to identify key parameters in gene flow. Results The GM plant may affect the environment directly or indirectly by dispersal of the transgene....... In the present review, this is illustrated through a bunch of examples mostly from our own research on oilseed rape, Brassica napus. In the Brassica cases, the variability affected all five main steps in the process of gene dispersal. The modelling performed suggests that in Brassica, differences in fitness...

  1. A Lagrangian Approach to Studying Instantaneous Plume Dispersion and Concentration Fluctations

    Science.gov (United States)

    2007-11-02

    liquid PMCH from a reservoir (a medical IV bag), through a hypodermic needle , and onto a hotplate located within the duct. The temperature of the...plume theory in which time-averaged dispersion is the result of plume meander and relative plume diffusion (Gifford 1959). Wind data near release height...Science Degree will be completed in Environmental Engineering, 1998). Note: Mark only assisted in fieldwork and data analysis during one month of the

  2. Experiment study of wavelength conversion in a dispersion-flattened photonic crystal fiber

    Institute of Scientific and Technical Information of China (English)

    Qiuguo Wang; Bojun Yang; Lan Zhang; Hu Zhang; Li He

    2007-01-01

    @@ Wavelength conversion based on four-wave mixing (FWM) has been demonstrated using a 40-m dispersion flattened highly nonlinear photonic crystal fiber (HNL-PCF). A conversion efficiency of -26 dB for a pump power of 19.5 dBm and a conversion bandwidth of 28 nm have been obtained, which are limited by the continuous wave (CW) laser wavelength range and tunability of optical band pass filters (OBPFs).

  3. Internal Gravity Waves in the Strait of Luzon: Dispersion Studies Using Fourier and Continuous Wavelet Transforms

    Science.gov (United States)

    2009-10-09

    are compared to results from Korteweg D’Vries theory. Good agreement is obtained for dispersion estimates using wavelet analysis and those from KdV ...analysis and those from KdV theory. 1 Background Internal waves (IWs) occur throughout the world’s oceans and seas. Well known examples in- clude IWs...recognize that KdV theory describes a two-layer model and the IWs under Understanding the Earth as a Complex System 235 investigation occur in a

  4. A Comparative Study of Dispersion Techniques for Nanocomposite Made with Nanoclays and an Unsaturated Polyester Resin

    Directory of Open Access Journals (Sweden)

    Farida Bensadoun

    2011-01-01

    Full Text Available Over the last few years, polymer/clay nanocomposites have been an area of intensive research due to their capacity to improve the properties of the polymer resin. These nanocharged polymers exhibit a complex rheological behavior due to their dispersed structure in the matrix. Thus, to gain fundamental understanding of nanocomposite dispersion, characterization of their internal structure and their rheological behavior is crucial. Such understanding is also key to determine the manufacturing conditions to produce these nanomaterials by liquid composite molding (LCM process. This paper investigates the mix of nanoclays particles in an unsaturated polyester resin using three different dispersion techniques: manual mixing, sonication, and high shear mixing (HSM. This paper shows that the mixing method has a significant effect on the sample morphology. Rheology, scanning electron microscopy (SEM, and differential scanning calorimetry (DSC characterization techniques were used to analyze the blends morphology and evaluate the nanoclays stacks/polymer matrix interaction. Several phenomena, such as shear thinning and premature polymer gelification, were notably observed.

  5. Oxide dispersion strengthened Fe–12Cr steel in three dimensions: An electron tomography study

    Energy Technology Data Exchange (ETDEWEB)

    Castro, V. de, E-mail: vanessa.decastro@uc3m.es [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Departamento de Física, Universidad Carlos III de Madrid, Avenida de la Universidad 30, 28911 Leganés, Madrid (Spain); Rodrigo, P. [Departamento de Ciencia e Ingeniería de Materiales, Universidad Rey Juan Carlos, c/Tulipán s.n., 28933 Móstoles, Madrid (Spain); Marquis, E.A. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI (United States); Lozano-Perez, S. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom)

    2014-01-15

    Highlights: • An ODS Fe–12Cr steel was reconstructed in 3D using electron tomography. • Electron tomography allowed reconstruction of nanoparticles down to 5 nm. • Reconstruction showed that some particles are found within Cr-rich precipitates. -- Abstract: In this work, scanning-transmission electron microscope tomography and atom-probe tomography were successfully applied to characterize the Y- and Cr-rich secondary phases present in an oxide dispersion strengthened reduced activation Fe–12Cr alloy in three dimensions. Electron energy loss spectroscopy, energy dispersive spectroscopy and energy filtered transmission electron microscopy were used to obtain analytical information about the region used for electron tomography reconstruction. The results obtained with these techniques provided accurate information regarding the Y-rich nanoparticle dispersion and chemistry and their association with the Cr-rich precipitates present in the alloy. Reconstructions show that Y-rich nanoparticles are frequently found to be embedded within the larger Cr-rich carbides and oxides, which would decrease the amount of nanoparticles capable of strengthening the matrix.

  6. Laboratory study of fluid viscosity induced ultrasonic velocity dispersion in reservoir sandstones

    Science.gov (United States)

    He, Tao; Zou, Chang-Chun; Pei, Fa-Gen; Ren, Ke-Ying; Kong, Fan-Da; Shi, Ge

    2010-06-01

    Ultrasonic velocities of a set of saturated sandstone samples were measured at simulated in-situ pressures in the laboratory. The samples were obtained from the W formation of the WXS Depression and covered low to nearly high porosity and permeability ranges. The brine and four different density oils were used as pore fluids, which provided a good chance to investigate fluid viscosity-induced velocity dispersion. The analysis of experimental observations of velocity dispersion indicates that (1) the Biot model can explain most of the small discrepancy (about 2-3%) between ultrasonic measurements and zero frequency Gassmann predictions for high porosity and permeability samples saturated by all the fluids used in this experiment and is also valid for medium porosity and permeability samples saturated with low viscosity fluids (less than approximately 3 mP·S) and (2) the squirt flow mechanism dominates the low to medium porosity and permeability samples when fluid viscosity increases and produces large velocity dispersions as high as about 8%. The microfracture aspect ratios were also estimated for the reservoir sandstones and applied to calculate the characteristic frequency of the squirt flow model, above which the Gassmann’ s assumptions are violated and the measured high frequency velocities cannot be directly used for Gassmann’s fluid replacement at the exploration seismic frequency band for W formation sandstones.

  7. Spatially dispersive dynamical response of hot carriers in doped graphene

    OpenAIRE

    Kukhtaruk, S. M.; V. A. Kochelap; Sokolov, V. N.; Kim, K. W.

    2015-01-01

    We study theoretically wave-vector and frequency dispersion of the complex dynamic conductivity tensor (DCT), $\\sigma_{lm}(\\mathbf{k}, \\omega)$, of doped monolayer graphene under a strong dc electric field. For a general analysis, we consider the weak ac field of arbitrary configuration given by two independent vectors, the ac field polarization and the wave vector $\\mathbf{k}$. The high-field transport and linear response to the ac field are described on the base of the Boltzmann kinetic equ...

  8. ERP Systems Created to Support Academic Management in Contexts of Geographic Dispersion: A Case Study in Regional Higher Education

    Directory of Open Access Journals (Sweden)

    Gabriel Moreno

    2017-01-01

    Full Text Available In response to extension of coverage goals in higher education, academic programs offering has been growing in regions geographically dispersed which management requires solid information systems able to adapt to the context needs and particularities. This paper presents a descriptive case study conducted in one of the head offices of Corporación Universitaria Minuto de Dios operating in 34 municipalities of cundinamarca department in colombia, highlighting challenges evidenced in the process of design and implementation of a custom ERP system. The case of study provides wide contextual details about selection and design of components, customization, integration and evaluation of the ERP system. Through this analysis are documented (a the challenges in integration, escalability and interoperability of ERP systems in higher education that are evidenced in a context of regionalization with geographic dispersion variables; and (b the differential features provided by a custom ERP system respect to the currently used systems in higher education.

  9. Estimation of dispersion curves by combining Effective Elastic Constants and SAFE Method: A case study in a plate under stress

    Science.gov (United States)

    Quiroga, J. E.; Mujica, L.; Villamizar, R.; Ruiz, M.; Camacho, J.

    2017-05-01

    This paper presents an approach to calculate dispersion curves for homogeneous and isotropic plates subject to stress, via Semi-Analytical Finite Element and the Effective Elastic Constants, since stresses in the waveguide modify the phase and group velocities of the lamb waves. In the proposed methodology an isotropic specimen subjected to anisotropic loading is emulated by proposing an equivalent stress-free anisotropic specimen. This approximation facilitates determining the dispersion curves by using the well-studied numerical solution for the stress-free cases. The lamb wave in anisotropic materials can be studied by means of the Effective Elastic Constants, which reduces the complexity of the numerical implementation. Finally, numerical data available in literature were used to validate the proposed methodology, where it could be demonstrated its effectiveness as approximated method.

  10. Numerical study on mixing performance of glass fiber dispersion in a twin-screw extruder with backward-mixing elements

    Science.gov (United States)

    Hirata, Kunihiro; Ishida, Hiroshi; Hiragori, Motohiro; Nakayama, Yasuya; Kajiwara, Toshihisa

    2015-05-01

    In the kneading of glass-fiber-reinforced plastics by twin-screw extrusion, the use of a backward-mixing screw (BMS) element for melt mixing has been found to be effective in dispersing glass-fiber bundles. In this study, we use the computational fluid dynamics (CFD) to study the mechanism of dispersion by a BMS element for glass fiber bundles. The result of CFD for a BMS and a forward kneading disk (FKD) reveals that the melt mixing by a BMS is highly effective to act the required stress on overall resin. In addition, there is a good correlation between the incidence of undispersed glass-fiber bundles measured experimentally and the minimum value of distribution of the time-integrated stress calculated numerically. On the basis of the above results, we propose a method to predict the operating conditions in which the incident probability of undispersed glass-fiber bundles and thermal degradation are controlled.

  11. Evolution of dispersal distance.

    Science.gov (United States)

    Durrett, Rick; Remenik, Daniel

    2012-03-01

    The problem of how often to disperse in a randomly fluctuating environment has long been investigated, primarily using patch models with uniform dispersal. Here, we consider the problem of choice of seed size for plants in a stable environment when there is a trade off between survivability and dispersal range. Ezoe (J Theor Biol 190:287-293, 1998) and Levin and Muller-Landau (Evol Ecol Res 2:409-435, 2000) approached this problem using models that were essentially deterministic, and used calculus to find optimal dispersal parameters. Here we follow Hiebeler (Theor Pop Biol 66:205-218, 2004) and use a stochastic spatial model to study the competition of different dispersal strategies. Most work on such systems is done by simulation or nonrigorous methods such as pair approximation. Here, we use machinery developed by Cox et al. (Voter model perturbations and reaction diffusion equations 2011) to rigorously and explicitly compute evolutionarily stable strategies.

  12. Formulation, Pharmacokinetic, and Efficacy Studies of Mannosylated Self-Emulsifying Solid Dispersions of Noscapine.

    Directory of Open Access Journals (Sweden)

    Terrick Andey

    Full Text Available To formulate hydroxypropyl methylcellulose-stabilized self-emulsifying solid dispersible carriers of noscapine to enhance oral bioavailability.Formulation of noscapine (Nos self-emulsifying solid dispersible microparticles (SESDs was afforded by emulsification using an optimized formula of Labrafil M1944, Tween-80, and Labrasol followed by spray-drying with hydroxypropyl methylcellulose (HPMC, with and without mannosamine (Mann-Nos_SESDs and Nos_SESDs respectively; self-microemulsifying liquid dispersions (SMEDDs with and without mannosamine (Mann-Nos_SMEDDs and Nos_SMEDDs respectively were also prepared. SMEDDs and SESDs were characterized for size, polydispersity, surface charge, entrapment efficiency, in vitro permeability, in vitro release kinetics, and oral pharmacokinetics in Sprague-Dawley rats (10 mg/kg p.o. The antitumor efficacy of Mann-Nos_SESDs on the basis of chemosensitization to cisplatin (2.0 mg/kg, i.v. was investigated in a chemorefractory lung tumor Nu/Nu mouse model up to a maximal oral dose of 300 mg/kg.The oil/surfactant/co-surfactant mixture of Labrafil M1944, Tween-80, and Labrasol optimized at weight ratios of 62.8:9.30:27.90% produced stable self-microemulsifying dispersions (SMEDDs at a SMEDD to water ratio of 1-3:7-9 parts by weight. SMEDDs had hydrodynamic diameters between 231 and 246 nm; surface charges ranged from -16.50 to -18.7 mV; and entrapment efficiencies were between 32 and 35%. SESDs ranged in size between 5.84 and 6.60 μm with surface charges from -10.62 to -12.40 mV and entrapment efficiencies of 30.96±4.66 and 32.05±3.72% (Nos_SESDs and Mann-Nos_SESDs respectively. Mann-Nos_SESDs exhibited saturating uptake across Caco-2 monolayers (Papp = 4.94±0.18 × 10(-6 cm/s, with controlled release of 50% of Nos in 6 hr at pH 6.8 following Higuchi kinetics. Mann-Nos_ SESDs was 40% more bioavailable compared to Nos_SESDs; and was effective in sensitizing H1650 SP cells to Cisplatin in vitro and in an orthotopic

  13. Formulation, Pharmacokinetic, and Efficacy Studies of Mannosylated Self-Emulsifying Solid Dispersions of Noscapine

    Science.gov (United States)

    Andey, Terrick; Patel, Apurva; Marepally, Srujan; Chougule, Mahavir; Spencer, Shawn D.; Rishi, Arun K.; Singh, Mandip

    2016-01-01

    Purpose To formulate hydroxypropyl methylcellulose-stabilized self-emulsifying solid dispersible carriers of noscapine to enhance oral bioavailability. Methods Formulation of noscapine (Nos) self-emulsifying solid dispersible microparticles (SESDs) was afforded by emulsification using an optimized formula of Labrafil M1944, Tween-80, and Labrasol followed by spray-drying with hydroxypropyl methylcellulose (HPMC), with and without mannosamine (Mann-Nos_SESDs and Nos_SESDs respectively); self-microemulsifying liquid dispersions (SMEDDs) with and without mannosamine (Mann-Nos_SMEDDs and Nos_SMEDDs respectively) were also prepared. SMEDDs and SESDs were characterized for size, polydispersity, surface charge, entrapment efficiency, in vitro permeability, in vitro release kinetics, and oral pharmacokinetics in Sprague-Dawley rats (10 mg/kg p.o). The antitumor efficacy of Mann-Nos_SESDs on the basis of chemosensitization to cisplatin (2.0 mg/kg, IV) was investigated in a chemorefractory lung tumor Nu/Nu mouse model up to a maximal oral dose of 300 mg/kg. Results The oil/surfactant/co-surfactant mixture of Labrafil M1944, Tween-80, and Labrasol optimized at weight ratios of 62.8:9.30:27.90% produced stable self-microemulsifying dispersions (SMEDDs) at a SMEDD to water ratio of 1–3:7–9 parts by weight. SMEDDs had hydrodynamic diameters between 231 and 246 nm; surface charges ranged from -16.50 to -18.7 mV; and entrapment efficiencies were between 32 and 35%. SESDs ranged in size between 5.84 and 6.60 μm with surface charges from -10.62 to -12.40 mV and entrapment efficiencies of 30.96±4.66 and 32.05±3.72% (Nos_SESDs and Mann-Nos_SESDs respectively). Mann-Nos_SESDs exhibited saturating uptake across Caco-2 monolayers (Papp = 4.94±0.18 × 10−6 cm/s), with controlled release of 50% of Nos in 6 hr at pH 6.8 following Higuchi kinetics. Mann-Nos_ SESDs was 40% more bioavailable compared to Nos_SESDs; and was effective in sensitizing H1650 SP cells to Cisplatin in vitro

  14. History of Resistance Welding Oxide Dispersion Strengthened Cladding and other High Temperature Materials at Center for Advanced Energy Studies

    Energy Technology Data Exchange (ETDEWEB)

    Larry Zirker; Nathan Jerred; Dr. Indrajit Charit; James Cole

    2012-03-01

    Research proposal 08-1079, 'A Comparative Study of Welded ODS Cladding Materials for AFCI/GNEP,' was funded in 2008 under an Advanced Fuel Cycle Initiative (AFCI) Research and Development Funding Opportunity, number DE-PS07-08ID14906. Th proposal sought to conduct research on joining oxide dispersion strengthen (ODS) tubing material to a solid end plug. This document summarizes the scientific and technical progress achieved during the project, which ran from 2008 to 2011.

  15. Development of amorphous dispersions of artemether with hydrophilic polymers via spray drying: Physicochemical and in silico studies

    Directory of Open Access Journals (Sweden)

    Jaywant N. Pawar

    2016-06-01

    Full Text Available Artemether (ARM is a poorly water soluble and poorly permeable drug effective against acute and severe falciparum malaria, hence there is a strong need to improve its solubility. The objective of the study was to enhance the solubility and dissolution rate of ARM by preparation of solid dispersions using spray-drying technique. Solid dispersions of ARM were prepared with Soluplus, Kollidon VA 64, HPMC and Eudragit EPO at weight ratios of 1:1, 1:2, 1:3 using spray drying technology, and characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC, and X-ray powder diffraction (XRD to identify the physicochemical interaction between drug and carrier, as well as effect on dissolution. The prepared solid dispersion of ARM with polymers showed reduced crystallinity as compared to neat ARM, which was confirmed by DSC and XRD. Drug/polymer interactions were studied in-silico by docking and molecular dynamics which indicated formation of van der Waals type of interactions of ARM with the polymers. Based on solubility studies, the optimum drug/Soluplus ratio was found to be 1:3. The dissolution studies of formulation SD3 showed highest drug release up to 82% compared to neat ARM giving only 20% at 60 minutes. The spray-dried products were free of crystalline ARM; possessed higher dissolution rates, and were stable over a period according to ICH guidelines. These findings suggest that an amorphous solid dispersion of ARM could be a viable option for enhancing the dissolution rate of ARM.

  16. Study of dispersive and nonlinear effects of coastal wave dynamics with a fully nonlinear potential flow model

    Science.gov (United States)

    Benoit, Michel; Yates, Marissa L.; Raoult, Cécile

    2017-04-01

    Efficient and accurate numerical models simulating wave propagation are required for a variety of engineering projects including the evaluation of coastal risks, the design of protective coastal structures, and the estimation of the potential for marine renewable energy devices. Nonlinear and dispersive effects are particularly significant in the coastal zone where waves interact with the bottom, the shoreline, and coastal structures. The main challenge in developing a numerical models is finding a compromise between computational efficiency and the required accuracy of the simulated wave field. Here, a potential approach is selected and the (fully nonlinear) water wave problem is formulated using the Euler-Zakharov equations (Zakharov, 1968) describing the temporal evolution of the free surface elevation and velocity potential. The proposed model (Yates and Benoit, 2015) uses a spectral approach in the vertical (i.e. the vertical variation of the potential is approximated by a linear combination of the first NT+1 Chebyshev polynomials, following the work of Tian and Sato (2008)). The Zakharov equations are integrated in time using a fourth-order Runge-Kutta scheme with a constant time step. At each sub-timestep, the Laplace Boundary Value Problem (BVP) is solved to estimate the free surface vertical velocity using the spectral approach, with typical values of NT between 5 to 8 for practical applications. The 1DH version of the code is validated with comparisons to the experimental data set of Becq-Girard et al. (1999), which studied the propagation of irregular waves over a beach profile with a submerged bar. The nonlinear and dispersive capacities of the model are verified with the correct representation of wave-wave interactions, in particular the transfer of energy between different harmonic components during wave propagation (analysis of the transformation of the variance spectrum along the channel). Evolution of wave skewness, asymmetry and kurtosis along the

  17. TSUNAMI PROPAGATION OVER THE NORTH PACIFIC: DISPERSIVE AND NONDISPERSIVE MODELS

    Directory of Open Access Journals (Sweden)

    Juan Horrillo

    2012-01-01

    Full Text Available Hydrostatic (HY and non-hydrostatic (NHY tsunami physics is compared by application to the Kuril Island Tsunami (KIT of November 2006 and the Japan Tsunami (JT of March 2011. Our purpose is to study the significance of dispersive vs. non-dispersive long waves on global tsunami propagation. A tool which is well suited to revealing tsunami wave transformations is the energy flux. Expressions for dispersive and non-dispersive fluxes have been formulated. This provides an understanding of the role of dispersion in tsunami propagation and dissipation. Separating the pressure field into two parts i.e., HY and NHY shows that dispersive waves extract energy from the main wave, directing the dispersive energy flux away from the wave front. The major result of the application of the energy flux to non-dispersive waves is an enhanced understanding of later tsunami wave train arrivals at distant points – with arrivals sometimes occurring several hours after an initial forerunner wave. Computations show that strong differences between non-dispersive and dispersive waves develop along the length of the main energy beam. This has important consequences for accurate tsunami prediction and warnings.

  18. Management of winter weeds affects Frankliniella fusca (Thysanoptera: Thripidae) dispersal.

    Science.gov (United States)

    Beaudoin, A L P; Kennedy, G G

    2012-04-01

    Frankliniella fusca (Hinds) naturally disperses from winter weeds to crops in spring, causing direct and indirect damage. Field preparation before planting includes use of herbicides or cultivation to kill unwanted vegetation, which adversely affects F. fusca host plants and potentially influences F. fusca dispersal. Common chickweed, Stellaria media (L.), infested with F. fusca, was used as a model to study effects of timing and type of vegetation management on adult dispersal. Infested weeds were caged and F. fusca weekly dispersal was monitored using sticky traps. Weed management treatments performed at an early (14 April-11 May) or late (2 wk after early treatment) date consisted of glyphosate, paraquat, disking, hoeing, or untreated control. Late glyphosate and hoeing treatments resulted in cumulative dispersal statistically similar to or greater than from control plots. Compared with the control, significantly more F. fusca dispersed from the glyphosate and hoeing plots during the 3 wk after treatment. More thrips dispersed from the late paraquat treatment 1 wk post-application than from the control. Dispersal from the disked treatment and early paraquat treatment was similar to that of the control 1- to 3-wk post-treatment. Early treatments resulted in significantly smaller cumulative dispersal than the control in all but one instance. Late disking and paraquat treatments resulted in cumulative F. fusca captures that were statistically similar or less than that in the control. Winter weed management type and timing affect F. fusca dispersal magnitude and duration.

  19. PM10 source measurement methodology: Field studies

    Energy Technology Data Exchange (ETDEWEB)

    Farthing, W.E.; Martin, R.S.; Dawes, S.S.; Williamson, A.D.

    1989-05-01

    Two candidate measurement methods, Constant Sampling Rate (CSR) and Exhaust Gas Recycle (EGR), have been developed to measure emissions of in-stack PM-10 particulate matter with aerodynamic diameter less than 10 micrometers. Two field tests were performed at the clinker cooler exhaust of a Portland cement plant to quantify precision and comparability of these techniques. In addition, accuracy was determined for total particulate measurement by comparison to Method 17. Collocated sampling trains were operated parallel with two Method 17 trains. In the second test, two CSR and one EGR trains were operated parallel to two Method 17 trains. The operating procedures used for the CSR and EGR trains are described in detail. In measurement of PM-10 and total particulate matter, the precision of both the CSR and EGR techniques was found to be of the same magnitude as Method 17 (approximately 5%). A small bias was found between CSR and EGR PM-10 results (15%) and between EGR and Method 17 total particulate matter (10%). Although small, these observed differences, combined with the results of laboratory studies reported elsewhere, led to a recommendation for an increase in the length of sampling nozzles. This modification improved cyclone performance and is incorporated into the nozzle geometries described in the application guides for CSR and EGR.

  20. Dispersion phenomena in helical flow in a concentric annulus.

    Science.gov (United States)

    Song, Young Seok; Brenner, Howard

    2009-12-14

    We examined dispersion phenomena of solutes in helical flow in a concentric annulus through a multiscale approach. The helical flow was developed by the combination of the Poiseuille flow and Couette flow. Here, we present an analytic model that can address the multidimensional Taylor dispersion in the helical flow under a lateral field of thermophoresis (or thermal diffusion) in the gapwise direction. Macroscopic parameters including the average solute velocity and dispersivity were analyzed using relevant microscopic physicochemical properties. The mathematically obtained results were validated by the numerical simulation carried out in this study. The findings show that macrotransport processes are robust and straightforward to handle multidimensional dispersion phenomena of solutes in helical flow. This study is expected to provide a theoretical platform for applications of helical flow such as tube exchangers, oil drilling, and multidimensional field flow fractionations (e.g., helical flow field flow fractionation).

  1. Relativistic Mean Field Study on Halo Structures of Mirror Nuclei

    Institute of Scientific and Technical Information of China (English)

    LIANG Yu-Jie; LI Yan-Song; LIU Zu-Hua; ZHOU Hong-Yu

    2009-01-01

    Halo structures of some light mirror nuclei are investigated with the relativistic mean field (RMF) theory.The calculations show that the dispersion of the valence proton is larger than that of the valence neutron in its mirror nucleus,the difference between the root-mean-square (rms) radius of the valence nucleon in each pair of mirror nuclei becomes smailer with the increase of the mass number A,and all the ratios of the rms radius of the valence nucleon to that of the matter in each pair o~ mirror nuclei decrease almost linearly with the increase of the mass number A.

  2. The Milky Way: paediatric milk-based dispersible tablets prepared by direct compression - a proof-of-concept study.

    Science.gov (United States)

    Orubu, Samuel E F; Hobson, Nicholas J; Basit, Abdul W; Tuleu, Catherine

    2017-04-01

    Dispersible tablets are proposed by the World Health Organization as the preferred paediatric formulation. It was hypothesised that tablets made from a powdered milk-base that disperse in water to form suspensions resembling milk might be a useful platform to improve acceptability in children. Milk-based dispersible tablets containing various types of powdered milk and infant formulae were formulated. The influence of milk type and content on placebo tablet properties was investigated using a design-of-experiments approach. Responses measured included friability, crushing strength and disintegration time. Additionally, the influence of compression force on the tablet properties of a model formulation was studied by compaction simulation. Disintegration times increased as milk content increased. Compaction simulation studies showed that compression force influenced disintegration time. These results suggest that the milk content, rather than type, and compression force were the most important determinants of disintegration. Up to 30% milk could be incorporated to produce 200 mg 10-mm flat-faced placebo tablets by direct compression disintegrating within 3 min in 5-10 ml of water, which is a realistic administration volume in children. The platform could accommodate 30% of a model active pharmaceutical ingredient (caffeine citrate). © 2016 Royal Pharmaceutical Society.

  3. A study on amphiphilic fluorinated block copolymer in graphite exfoliation using supercritical CO2 for stable graphene dispersion.

    Science.gov (United States)

    Kim, Young Hyun; Lee, Hyang Moo; Choi, Sung Wook; Cheong, In Woo

    2017-09-18

    In this study, poly(2,2,2-trifluoroethyl methacrylate)-block-poly(4-vinylpyridine) (PTFEMA-b-PVP) was synthesized by stepwise reversible addition-fragmentation chain transfer (RAFT) polymerization for the preparation of graphene by the exfoliation of graphite nanoplatelets (GPs) in supercritical CO2 (SCCO2). Two different block copolymers (low and high molecular weights) were prepared with the same block ratio and used at different concentrations in the SCCO2 process. The amount of PTFEMA-b-PVP adsorbed on the GPs and the electrical conductivity of the SCCO2-treated GP samples were evaluated using thermogravimetric analysis (TGA) and four-point probe method, respectively. All GP samples treated with SCCO2 were then dispersed in methanol and the dispersion stability was investigated using online turbidity measurements. The concentration and morphology of few-layer graphene stabilized with PTFEMA-b-PVP in the supernatant solution were investigated by gravimetry, scanning electron microscopy, and Raman spectroscopy. Destabilization study of the graphene dispersions revealed that the longer block copolymer exhibited better affinity for graphene, resulting in a higher yield of stable graphene with minimal defects. Copyright © 2017. Published by Elsevier Inc.

  4. Combustion Safety Simplified Test Protocol Field Study

    Energy Technology Data Exchange (ETDEWEB)

    Brand, L. [Gas Technology Inst., Des Plaines, IL (United States); Cautley, D. [Gas Technology Inst., Des Plaines, IL (United States); Bohac, D. [Gas Technology Inst., Des Plaines, IL (United States); Francisco, P. [Gas Technology Inst., Des Plaines, IL (United States); Shen, L. [Gas Technology Inst., Des Plaines, IL (United States); Gloss, S. [Gas Technology Inst., Des Plaines, IL (United States)

    2015-11-01

    Combustions safety is an important step in the process of upgrading homes for energy efficiency. There are several approaches used by field practitioners, but researchers have indicated that the test procedures in use are complex to implement and provide too many false positives. Field failures often mean that the house is not upgraded until after remediation or not at all, if not include in the program. In this report the PARR and NorthernSTAR DOE Building America Teams provide a simplified test procedure that is easier to implement and should produce fewer false positives. A survey of state weatherization agencies on combustion safety issues, details of a field data collection instrumentation package, summary of data collected over seven months, data analysis and results are included. The project team collected field data on 11 houses in 2015.

  5. Study on phase retardation characteristic of LCVR using dispersion analysis and SVM

    Institute of Scientific and Technical Information of China (English)

    HU; Dongmei; LIU; Quan; NIU; Guocheng; ZHU; Yifeng; YU; Lintao

    2015-01-01

    To calibrate the phase retardance of a Liquid crystal variable retarder(LCVR),its birefringence dispersion characteristic was analyzed,and the Support vector machines(SVM) algorithm was adopted to establish the prediction model.The obtained SVM decision function was used as a part of LCVR phase retardance,which was generated by the driving voltage.The experimental verification was carried out with a 568 nm laser.The results show that the deviation of the experimental value and the theoretical value is about 0.0061λ.SVM method could be used as an effective method for LCVR phase retardance characteristic calibration.

  6. Determining the group velocity dispersion by field analysis for the LP0X, LP1X, and LP2X mode groups independently of the fiber length: applications to step-index fibers

    DEFF Research Database (Denmark)

    Israelsen, Stine Møller; Usuga Castaneda, Mario A.; Rottwitt, Karsten

    2017-01-01

    By knowing the electric field distribution of a guided mode in an optical fiber, we are able to evaluate the group velocity dispersion in a weakly guiding step-index fiber for a pure mode in the LP0X, LP1X, and LP2X mode groups independently of the fiber length. We demonstrate the method...

  7. Stability and magnetic interactions between magnetite nanoparticles dispersed in zeolite as studied using Mössbauer spectroscopy

    Science.gov (United States)

    Herojit singh, L.; Govindaraj, R.; Mythili, R.; Amarendra, G.

    2016-11-01

    Stability of superparamagnetic magnetite nanoparticles as formed in Zeolite has been addressed in a detailed manner based on isochronal annealing studies using Mössbauer spectroscopy. A strong binding of these nanoparticles in Zeolite has been deduced as the coarsening of the nanoparticles is observed following annealing treatments beyond 825 K. In addition, the magnetic interactions between these superparamagnetic magnetite nanoparticles in the as dispersed condition in Zeolite have been elucidated by means of low temperature Mössbauer studies. A strong dependence of the dipole-dipole interactions between superparamagnetic particles of cubic iron oxides is deduced based on this study.

  8. Computer-aided screening system for cervical precancerous cells based on field emission scanning electron microscopy and energy dispersive x-ray images and spectra

    Science.gov (United States)

    Jusman, Yessi; Ng, Siew-Cheok; Hasikin, Khairunnisa; Kurnia, Rahmadi; Osman, Noor Azuan Bin Abu; Teoh, Kean Hooi

    2016-10-01

    The capability of field emission scanning electron microscopy and energy dispersive x-ray spectroscopy (FE-SEM/EDX) to scan material structures at the microlevel and characterize the material with its elemental properties has inspired this research, which has developed an FE-SEM/EDX-based cervical cancer screening system. The developed computer-aided screening system consisted of two parts, which were the automatic features of extraction and classification. For the automatic features extraction algorithm, the image and spectra of cervical cells features extraction algorithm for extracting the discriminant features of FE-SEM/EDX data was introduced. The system automatically extracted two types of features based on FE-SEM/EDX images and FE-SEM/EDX spectra. Textural features were extracted from the FE-SEM/EDX image using a gray level co-occurrence matrix technique, while the FE-SEM/EDX spectra features were calculated based on peak heights and corrected area under the peaks using an algorithm. A discriminant analysis technique was employed to predict the cervical precancerous stage into three classes: normal, low-grade intraepithelial squamous lesion (LSIL), and high-grade intraepithelial squamous lesion (HSIL). The capability of the developed screening system was tested using 700 FE-SEM/EDX spectra (300 normal, 200 LSIL, and 200 HSIL cases). The accuracy, sensitivity, and specificity performances were 98.2%, 99.0%, and 98.0%, respectively.

  9. Analytical Studies of the Cloud Droplet Spectral Dispersion Influence on the First Indirect Aerosol Effect

    Institute of Scientific and Technical Information of China (English)

    XIE Xiaoning; LIU Xiaodong

    2013-01-01

    Atmospheric aerosols (acting as cloud condensation nuclei) can enhance the cloud droplet number concentration and reduce the cloud droplet size,and in turn affect the cloud optical depth,as well as the cloud albedo,and thereby exert a radiative influence on climate (the first indirect aerosol effect).In this paper,based on various relationships between cloud droplet spectral dispersion (ε) and cloud droplet number concentration (Nc),we analytically derive the corresponding expressions of the cloud radiative forcing induced by changes in the cloud droplet number concentration.Further quantitative evaluation indicates that the cloud radiative forcing induced by aerosols for the different ε-Nc relationships varies from-29.1% to 25.2%,compared to the case without considering spectral dispersion (ε =0).Our results suggest that an accurate description of ε-Nc relationships helps to reduce the uncertainty of the first indirect aerosol effect and advances our scientific understanding of aerosol-cloud-radiation interactions.

  10. XAFS studies on highly dispersed Ni 2P/SiO 2 catalysts for hydrodesulfurization of 4,6-dimethyldibenzothiophene

    Science.gov (United States)

    Cho, Kye-Sung; Lee, Yong-Kul

    2010-09-01

    The Ni 2P catalysts were prepared by a new synthetic method with the use of less oxidic phosphorus precursor in order to achieve high dispersion on silica support, and their structural properties and catalytic activity in HDS of 4,6-DMDBT were studied. Comparison was made with a conventionally prepared sample which was obtained by temperature programmed reduction method. Various characterizations were conducted by BET, CO uptake, TPR, XRD and X-ray absorption spectroscopy. The amounts of CO chemisorption uptake were 64 and 20 μmol g -1 for Ni 2P/SiO 2-LT and Ni 2P/SiO 2-HT, respectively, indicating that the low temperature reduction technique led to better dispersion of Ni 2P particles on SiO 2 support. The catalytic activity in the HDS of 4,6-DMDBT followed the order, Ni 2P/SiO 2-HT(54%)dispersion of the Ni 2P phase.

  11. Germination Ecology and Seed Dispersal of a Critically Endangered Plant: A Case Study of Pomaderris vacciniifolia (Round-Leaf Pomaderris).

    Science.gov (United States)

    Patykowski, John; Dell, Matthew; Gibson, Maria

    2016-01-01

    Change in ecosystem disturbance regimes from human land-use poses a worldwide problem for management of rare species. Two important types of disturbance influencing the persistence of species in Australian ecosystems are habitat fragmentation and fire. In this study, seed dispersal and the germination ecology of Pomaderris vacciniifolia-a critically endangered, rare endemic Australian shrub-were examined to identify likely influences of fire and fragmentation on the decline of populations. The response of seed germination to simulated effects of wildfire and canopy openings was investigated, as was the unaided dispersal capability of seeds from parent plants. A significant increase in germination rate was observed following 100°C heat treatment to seeds, while smoke and light exposure had little influence. Seed imbibition was strongly influenced by heat treatment. The findings indicate a likely positive post-fire germination response, with implications for recruitment success determined by moisture availability following fire. Unaided seed dispersal was limited, which partly explains the apparent decline of populations. Understanding disturbance requirements for threatened species, and subsequent management of landscapes for disturbance, will aid conservation of rare species throughout the world.

  12. Solid dispersions of the penta-ethyl ester prodrug of diethylenetriaminepentaacetic acid (DTPA): formulation design and optimization studies.

    Science.gov (United States)

    Yang, Yu-Tsai; Di Pasqua, Anthony J; Zhang, Yong; Sueda, Katsuhiko; Jay, Michael

    2014-11-01

    The penta-ethyl ester prodrug of diethylenetriaminepentaacetic acid (DTPA), which exists as an oily liquid, was incorporated into a solid dispersion for oral administration by the solvent evaporation method using blends of polyvinylpyrrolidone (PVP), Eudragit® RL PO and α-tocopherol. D-optimal mixture design was used to optimize the formulation. Formulations that had a high concentration of both Eudragit® RL PO and α-tocopherol exhibited low water absorption and enhanced stability of the DTPA prodrug. Physicochemical properties of the optimal formulation were evaluated using Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). In vitro release of the prodrug was evaluated using the USP Type II apparatus dissolution method. DSC studies indicated that the matrix had an amorphous structure, while FTIR spectrometry showed that DTPA penta-ethyl ester and excipients did not react with each other during formation of the solid dispersion. Dissolution testing showed that the optimized solid dispersion exhibited a prolonged release profile, which could potentially result in a sustained delivery of DTPA penta-ethyl to enhance bioavailability. In conclusion, DTPA penta-ethyl ester was successfully incorporated into a solid matrix with high drug loading and improved stability compared to prodrug alone.

  13. Dispersion of sulphur in the northern hemisphere. A study with a 3-dimensional time-resolved model

    Energy Technology Data Exchange (ETDEWEB)

    Tarrason, L.

    1995-12-31

    This thesis on atmospheric dispersion of sulphur presents a calculation of intercontinental transport of oxidized sulphur and allocates different contributions to sulphur background levels over Europe. It is found that a significant fraction of anthropogenic sulphur (AS) is transported out of continental boundaries thus affecting the background levels over major parts of the northern hemisphere. Over Europe, the contribution of AS from North America is similar in amount to that of Asian AS and natural sources from the North Atlantic Ocean. Although the yearly contribution of intercontinental transport to deposition of sulphur over Europe is quite small, it can be much more important over certain areas and seasons and is comparable to the contributions from individual European countries. The calculations are based on a three-dimensional Eulerian time-resolved model that describes sulphur dispersion in the atmosphere in connection with large-scale synoptic flows and agree well with observations. The thesis emphasizes the role of synoptic scale atmospheric motions in determining intercontinental transport of sulphur. It indicates the need to resolve individual cyclones and anticyclones in order to describe the dispersion and distribution of atmospheric sulphur in the northern hemisphere and stresses the value of comparing model calculations with observations, both in atmospheric chemistry studies and in climate applications. 260 refs., 50 figs., 17 tabs.

  14. A comparative study of thermo-sensitive hydrogels with water-insoluble paclitaxel in molecule, nanocrystal and microcrystal dispersions.

    Science.gov (United States)

    Lin, Zhiqiang; Mei, Dong; Chen, Meiwan; Wang, Yitao; Chen, Xianhui; Wang, Zhaoyang; He, Bing; Zhang, Hua; Wang, Xueqing; Dai, Wenbing; Yin, Yuxin; Zhang, Qiang

    2015-09-28

    In situ thermo-sensitive hydrogels have attracted increasing attention for alternative cancer therapies due to their long-term and effective drug levels at local sites. Besides synthesizing new thermo-sensitive polymers, we can also fabricate this delivery system by combining a hydrogel with a thermo-response and drug in a different dispersion state, such as drug nanocrystals. However, the impact of the drug dispersion state or dimension on the quality of such a local injectable system is still unknown. So, here we developed and compared three types of F127 hydrogel systems with either paclitaxel or the near infra-red probe DiR in molecules (MOs), nanocrystals (NCs) and microcrystals (MCs), respectively. With 120 nm rod-shape nanocrystals, the NCs-Gel achieved a high drug loading, moderate drug release rate and gel erosion in vitro and in vivo, medium intratumoral drug residue but the best anti-tumor efficacy in 4T1 tumor bearing BALB/c mice. With the free drug solubilized in 20 nm micelles of the gel, the MOs-Gel system demonstrated the least drug loading and the fastest drug release and gel erosion, leading to the least intratumoral residue as well as the lowest anti-tumor effect. Finally, when dispersed in micron-grade rod-shape drug crystals, the MCs-Gel exhibited a high drug loading but poor stability, precipitating in vitro and in vivo, the highest intratumoral residue but the least drug release, resulting in moderate tumor inhibition. In conclusion, this study clarifies the effect of the drug dispersion state and scale on the behavior of a thermo-sensitive hydrogel, indicating the advantage of the NCs-Gel system, and it provides a basis for the future design of the local delivery of hydrophobic anti-cancer agents.

  15. A comparative study of thermo-sensitive hydrogels with water-insoluble paclitaxel in molecule, nanocrystal and microcrystal dispersions

    Science.gov (United States)

    Lin, Zhiqiang; Mei, Dong; Chen, Meiwan; Wang, Yitao; Chen, Xianhui; Wang, Zhaoyang; He, Bing; Zhang, Hua; Wang, Xueqing; Dai, Wenbing; Yin, Yuxin; Zhang, Qiang

    2015-09-01

    In situ thermo-sensitive hydrogels have attracted increasing attention for alternative cancer therapies due to their long-term and effective drug levels at local sites. Besides synthesizing new thermo-sensitive polymers, we can also fabricate this delivery system by combining a hydrogel with a thermo-response and drug in a different dispersion state, such as drug nanocrystals. However, the impact of the drug dispersion state or dimension on the quality of such a local injectable system is still unknown. So, here we developed and compared three types of F127 hydrogel systems with either paclitaxel or the near infra-red probe DiR in molecules (MOs), nanocrystals (NCs) and microcrystals (MCs), respectively. With 120 nm rod-shape nanocrystals, the NCs-Gel achieved a high drug loading, moderate drug release rate and gel erosion in vitro and in vivo, medium intratumoral drug residue but the best anti-tumor efficacy in 4T1 tumor bearing BALB/c mice. With the free drug solubilized in 20 nm micelles of the gel, the MOs-Gel system demonstrated the least drug loading and the fastest drug release and gel erosion, leading to the least intratumoral residue as well as the lowest anti-tumor effect. Finally, when dispersed in micron-grade rod-shape drug crystals, the MCs-Gel exhibited a high drug loading but poor stability, precipitating in vitro and in vivo, the highest intratumoral residue but the least drug release, resulting in moderate tumor inhibition. In conclusion, this study clarifies the effect of the drug dispersion state and scale on the behavior of a thermo-sensitive hydrogel, indicating the advantage of the NCs-Gel system, and it provides a basis for the future design of the local delivery of hydrophobic anti-cancer agents.

  16. Primate seed dispersers as umbrella species: a case study from Kibale National Park, Uganda, with implications for Afrotropical forest conservation.

    Science.gov (United States)

    Lambert, Joanna E

    2011-01-01

    Almost half of the world's extant primate species are of conservation concern [IUCN, International Union for the Conservation of Nature Red List of Threatened Species, 2008]. Primates are also effective seed dispersers. The implications of and interactions between these two facts are increasingly understood, and data demonstrating the consequences of losing primates for forest ecology are now available from throughout the tropics. However, a reality is that not all species-and the mutualisms among them-can be protected. Conservation managers must make difficult decisions and use shortcuts in the implementation of conservation tactics. Using taxa as "umbrellas" is one such shortcut, although a lack of an operational definition of what an umbrella species is and how to choose one has made implementing this tactic difficult. In this study, I discuss primates as umbrellas by defining a selection index in terms of richness/co-occurrence, rarity, and sensitivity to anthropogenic disturbance. I evaluate the anthropoid assemblage of Kibale National Park, Uganda, in light of the selection index and determine that Cercopithecus is the genus best fitting the criteria for umbrella status. I then evaluate the functional significance-in terms of seed dispersal-of using Cercopithecus monkeys (guenons) as umbrellas. Results from 1,047 hr of observation of focal fruiting trees in Kibale indicate that Cercopithecus ascanius was the most commonly observed frugivore visitor (July 2001-June 2002). These data corroborate earlier data collected in Kibale demonstrating that guenons are highly effective seed dispersers. Patterns of richness/co-occurrence, rarity, and sensitivity observed in Kibale are reflected in Afrotropical forests more generally, with the genus Cercopithecus tending to exhibit greatest richness/co-occurrence with taxonomically similar species, to be neither extremely rare nor ubiquitous, and also to be moderately sensitive to human disturbance. Moreover, in all

  17. Geomagnetic Observations for Main Field Studies

    DEFF Research Database (Denmark)

    Matzka, Jürgen; Chulliat, A.; Mandea, M.

    2010-01-01

    Direct measurements of the geomagnetic field have been made for more than 400 years, beginning with individual determinations of the angle between geographic and magnetic North. This was followed by the start of continuous time series of full vector measurements at geomagnetic observatories and t...... for magnetic field measurements on ground and in space and covers geomagnetic observatories, repeat stations, automatic observatories, satellites and historic observations. Special emphasis is laid on the global network of geomagnetic observatories....... and the beginning of geomagnetic repeat stations surveys in the 19th century. In the second half of the 20th century, true global coverage with geomagnetic field measurements was accomplished by magnetometer payloads on low-Earth-orbiting satellites. This article describes the procedures and instruments...

  18. Local study of pollutants dispersion by a real time tracer method; Etude locale de la dispersion de polluants par une methode de tracage en temps reel

    Energy Technology Data Exchange (ETDEWEB)

    Faivre-Pierret, R.X.; Sestier-Carlin, R.; Berne, P.

    1992-12-31

    It is possible to use a Gaussian mathematical model of atmospheric dispersion for calculating atmospheric transfer coefficient (ATC) in long range model, but for proximity models, an experimental model using a tracer technic has to take in account ground effects and natural or artificial obstacles. SF{sub 6} tracer method gives the true plume ground trace in real time. The measured ATC shows a larger ground trace, lower concentration in the axis, and a displacement of the maximum concentration with regard to wind axis in comparison with the calculated ATC. (A.B.). 14 refs., 4 figs., 1 tab.

  19. INFLUENCE OF CHROMATIC DISPERSION, DISPERSION SLOPE, DISPERSION CURVATURE ON MICROWAVE GENERATION USING TWO CASCADE MODULATORS

    OpenAIRE

    Mandeep Singh; S.K. Raghuwanshi

    2013-01-01

    This work presents a theoretical study of harmonic generation of microwave signals after detection of a modulated optical carrier in cascaded two electro-optic modulators. Dispersion is one of the major limiting factors for microwave generation in microwave photonics. In this paper, we analyze influence of chromatic dispersion, dispersion slope, dispersion curvature on microwave generation using two cascaded MZMs and it has been found that output intensity of photodetector reduces when disper...

  20. Current trends in studies on reverse-mode polymer dispersed liquid-crystal films — A review

    Science.gov (United States)

    Ahmad, Farzana; Jamil, M.; Jeon, Y. J.

    2014-07-01

    Reverse-mode polymer dispersed liquid crystals (PDLCs) comprise an important new class of materials for optical device applications. Generally reverse-mode PDLCs are transparent and opaque in the absence and presence of an external field, respectively. Display devices based on reverse-mode PDLC technology are useful for large-area displays; because their fabrication for manufacturing shutters is considered to be easier and faster, they are also employed for automotive technology and smart windows. These devices can be operated at a low voltage, which conserves energy in intelligent-device applications. This work presents a comprehensive review of past research regarding reverse-mode PDLCs and includes the advantageous features, applications, and various fabrication methods of reverse-mode PDLCs and photo-chromic reverse-mode PDLCs. In addition, some new features of this technology that have recently been reported and future investigations by a variety of research groups are presented.

  1. STUDY OF TOPOLOGY OPTIMIZATION FOR THERMO-STRUCTURAL COUPLING FIELD

    Institute of Scientific and Technical Information of China (English)

    Zuo Kongtian; Qian Qin; Zhao Yudong; Chen Liping

    2005-01-01

    A number of critical problems of topology optimization concerning the thermostructural coupling field are studied at length. The governing equations and topology optimization model for the thermal-structural coupling field are derived, with an adjoint method for sensitivity analysis of the thermo-structural coupling field proposed. The optimization algorithm for coupling field topology optimization is investigated and a flowchart of coupling field topology optimization presented. The theory and algorithms are implemented and verified by two numerical examples.

  2. A Study of Coaxial Rotor Performance and Flow Field Characteristics

    Science.gov (United States)

    2016-01-22

    A Study of Coaxial Rotor Performance and Flow Field Characteristics Natasha L. Barbely Aerospace Engineer NASA Ames Research Center Moffett Field...The pressure field generated by the two airfoils aided our interpretation of the more complex coaxial rotor system flow field. The pressure fields...velocity (ft/sec) Z vertical distance between rotors (ft) αS pitch angle (deg), negative pitch down κint coaxial rotor induced power interference

  3. TSUNAMI DISPERSION SENSITIVITY TO SEISMIC SOURCE PARAMETERS

    Directory of Open Access Journals (Sweden)

    Oleg Igorevich Gusev

    2016-05-01

    Full Text Available The study focuses on the sensitivity of frequency dispersion effects to the form of initial surface elevation of seismic tsunami source. We vary such parameters of the source as rupture depth, dip-angle and rake-angle. Some variations in magnitude and strike angle are considered. The fully nonlinear dispersive model on a rotating sphere is used for wave propagation simulations. The main feature of the algorithm is the splitting of initial system on two subproblems of elliptic and hyperbolic type, which allows implementation of well-suitable numerical methods for them. The dispersive effects are estimated through differences between computations with the dispersive and nondispersive models. We consider an idealized test with a constant depth, a model basin for near-field tsunami simulations and a realistic scenario. Our computations show that the dispersion effects are strongly sensitive to the rupture depth and the dip-angle variations. Waves generated by sources with lager magnitude may be even more affected by dispersion.

  4. Dispersive shock waves and modulation theory

    Science.gov (United States)

    El, G. A.; Hoefer, M. A.

    2016-10-01

    There is growing physical and mathematical interest in the hydrodynamics of dissipationless/dispersive media. Since G.B. Whitham's seminal publication fifty years ago that ushered in the mathematical study of dispersive hydrodynamics, there has been a significant body of work in this area. However, there has been no comprehensive survey of the field of dispersive hydrodynamics. Utilizing Whitham's averaging theory as the primary mathematical tool, we review the rich mathematical developments over the past fifty years with an emphasis on physical applications. The fundamental, large scale, coherent excitation in dispersive hydrodynamic systems is an expanding, oscillatory dispersive shock wave or DSW. Both the macroscopic and microscopic properties of DSWs are analyzed in detail within the context of the universal, integrable, and foundational models for uni-directional (Korteweg-de Vries equation) and bi-directional (Nonlinear Schrödinger equation) dispersive hydrodynamics. A DSW fitting procedure that does not rely upon integrable structure yet reveals important macroscopic DSW properties is described. DSW theory is then applied to a number of physical applications: superfluids, nonlinear optics, geophysics, and fluid dynamics. Finally, we survey some of the more recent developments including non-classical DSWs, DSW interactions, DSWs in perturbed and inhomogeneous environments, and two-dimensional, oblique DSWs.

  5. Toward a Field of Interfaith Studies

    Science.gov (United States)

    Patel, Eboo

    2013-01-01

    Scholars from a range of fields have long taken an interest in how people who orient around religion differently interact with one another. Indeed, this phenomenon has been the subject of important works in political science ("The Clash of Civilizations" by Samuel Huntington), sociology ("American Grace" by Robert Putnam and…

  6. Combustion Safety Simplified Test Protocol Field Study

    Energy Technology Data Exchange (ETDEWEB)

    Brand, L [Gas Technology Inst., Des Plaines, IL (United States); Cautley, D. [Gas Technology Inst., Des Plaines, IL (United States); Bohac, D. [Gas Technology Inst., Des Plaines, IL (United States); Francisco, P. [Gas Technology Inst., Des Plaines, IL (United States); Shen, L. [Gas Technology Inst., Des Plaines, IL (United States); Gloss, S. [Gas Technology Inst., Des Plaines, IL (United States)

    2015-11-05

    "9Combustions safety is an important step in the process of upgrading homes for energy efficiency. There are several approaches used by field practitioners, but researchers have indicated that the test procedures in use are complex to implement and provide too many false positives. Field failures often mean that the house is not upgraded until after remediation or not at all, if not include in the program. In this report the PARR and NorthernSTAR DOE Building America Teams provide a simplified test procedure that is easier to implement and should produce fewer false positives. A survey of state weatherization agencies on combustion safety issues, details of a field data collection instrumentation package, summary of data collected over seven months, data analysis and results are included. The project provides several key results. State weatherization agencies do not generally track combustion safety failures, the data from those that do suggest that there is little actual evidence that combustion safety failures due to spillage from non-dryer exhaust are common and that only a very small number of homes are subject to the failures. The project team collected field data on 11 houses in 2015. Of these homes, two houses that demonstrated prolonged and excessive spillage were also the only two with venting systems out of compliance with the National Fuel Gas Code. The remaining homes experienced spillage that only occasionally extended beyond the first minute of operation. Combustion zone depressurization, outdoor temperature, and operation of individual fans all provide statistically significant predictors of spillage.

  7. Toward a Field of Interfaith Studies

    Science.gov (United States)

    Patel, Eboo

    2013-01-01

    Scholars from a range of fields have long taken an interest in how people who orient around religion differently interact with one another. Indeed, this phenomenon has been the subject of important works in political science ("The Clash of Civilizations" by Samuel Huntington), sociology ("American Grace" by Robert Putnam and…

  8. Comparing land use regression and dispersion modelling to assess residential exposure to ambient air pollution for epidemiological studies.

    Science.gov (United States)

    de Hoogh, Kees; Korek, Michal; Vienneau, Danielle; Keuken, Menno; Kukkonen, Jaakko; Nieuwenhuijsen, Mark J; Badaloni, Chiara; Beelen, Rob; Bolignano, Andrea; Cesaroni, Giulia; Pradas, Marta Cirach; Cyrys, Josef; Douros, John; Eeftens, Marloes; Forastiere, Francesco; Forsberg, Bertil; Fuks, Kateryna; Gehring, Ulrike; Gryparis, Alexandros; Gulliver, John; Hansell, Anna L; Hoffmann, Barbara; Johansson, Christer; Jonkers, Sander; Kangas, Leena; Katsouyanni, Klea; Künzli, Nino; Lanki, Timo; Memmesheimer, Michael; Moussiopoulos, Nicolas; Modig, Lars; Pershagen, Göran; Probst-Hensch, Nicole; Schindler, Christian; Schikowski, Tamara; Sugiri, Dorothee; Teixidó, Oriol; Tsai, Ming-Yi; Yli-Tuomi, Tarja; Brunekreef, Bert; Hoek, Gerard; Bellander, Tom

    2014-12-01

    Land-use regression (LUR) and dispersion models (DM) are commonly used for estimating individual air pollution exposure in population studies. Few comparisons have however been made of the performance of these methods. Within the European Study of Cohorts for Air Pollution Effects (ESCAPE) we explored the differences between LUR and DM estimates for NO2, PM10 and PM2.5. The ESCAPE study developed LUR models for outdoor air pollution levels based on a harmonised monitoring campaign. In thirteen ESCAPE study areas we further applied dispersion models. We compared LUR and DM estimates at the residential addresses of participants in 13 cohorts for NO2; 7 for PM10 and 4 for PM2.5. Additionally, we compared the DM estimates with measured concentrations at the 20-40 ESCAPE monitoring sites in each area. The median Pearson R (range) correlation coefficients between LUR and DM estimates for the annual average concentrations of NO2, PM10 and PM2.5 were 0.75 (0.19-0.89), 0.39 (0.23-0.66) and 0.29 (0.22-0.81) for 112,971 (13 study areas), 69,591 (7) and 28,519 (4) addresses respectively. The median Pearson R correlation coefficients (range) between DM estimates and ESCAPE measurements were of 0.74 (0.09-0.86) for NO2; 0.58 (0.36-0.88) for PM10 and 0.58 (0.39-0.66) for PM2.5. LUR and dispersion model estimates correlated on average well for NO2 but only moderately for PM10 and PM2.5, with large variability across areas. DM predicted a moderate to large proportion of the measured variation for NO2 but less for PM10 and PM2.5. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Dispersive transport across interfaces

    Science.gov (United States)

    Berkowitz, Brian; Adler, Pierre

    2015-04-01

    Experiments demonstrating asymmetrical dispersive transport of a conservative tracer across interfaces between different porous materials have recently been performed. Here, this phenomenon is studied numerically on the pore scale. The flow field is derived by solving the Stokes equation. The dispersive transport is simulated by a large number of particles undergoing random walks under the simultaneous action of convection and diffusion. Two main two-dimensional configurations are studied; each consists of two segments (called coarse and fine) with the same structure, porosity, and length along the main flow, but different characteristic solid/pore sizes. One structure consists of two channels containing cavities of different sizes, and the second of square "grains" of different sizes. At time t=0, a large number of particles is injected (as a pulse) around a given cross-section. The corresponding breakthrough curves (BTCs) are registered as functions of time at six different cross sections. Calculations are made twice; in the first case (CtoF), particles are injected in the coarse side and are transported towards the fine one; in the second one (FtoC), the opposite case is studied. These calculations are performed for various Péclet numbers (Pe). Comparison of the resulting BTCs shows features that are similar to experimental observations, but with qualitative and quantitative differences. The influences of the medium, of the injection and observation planes, and of Pe are detailed and discussed. A BTC for pulse injection can be characterized by its maximum M(t_M) and the time tM at which it occurs. The observed differences for channels bounded by cavities are very small. However for the granular structures, M(t_M) is always larger for FtoC than for CtoF ; tM depends on all the parameters, namely Pe, the size ratio between the large and small grains, the injection and the observation planes. The numerical results are systematically compared with solutions of one

  10. 浮选柱中液相轴向返混的研究%Study on the Axial Dispersion of Liquid in Column Flotation

    Institute of Scientific and Technical Information of China (English)

    周鹍; 曾爱武; 高长宝; 余国琮

    2003-01-01

    An experimental study on the axial dispersion of liquid was carried out in a 0.382-m-ID flotation columnpacked with different structured packings or free of packings. The correlations of axial Peclet numbers with theliquid and gas superficial Reynolds numbers were developed for various packings. Among the packings tested, itis found that in the column packed with 250Y or 350Y packings the axial dispersion is the lowest. The additionof frother can decrease the axial dispersion. By the simulation analysis of the one-dimension dispersion model ofpacked flotation column, it is found that small axial dispersion, high collection rate constant and low axial liquidvelocity can increase the collection zone recovery.

  11. Rates of Gravel Dispersion

    Science.gov (United States)

    Haschenburger, J. K.

    2010-12-01

    Sediment transfers in gravel-bed rivers involve the three-dimensional dispersion of mixed size sediment. From a kinematics standpoint, few studies are available to inform on the streamwise and vertical rates of sediment dispersion in natural channels. This research uses a gravel tracing program to quantify dispersion rates over 19 flood seasons. Empirical observations come from Carnation Creek, a small gravel-bed river with large woody debris located on the west coast of Vancouver Island, Canada. Frequent floods and the relatively limited armor layer facilitate streambed activity and relatively high bedload transport rates, typically under partial sediment transport conditions. Over 2500 magnetically tagged stones, ranging in size from 16 to 180 mm, were deployed on the bed surface between 1989 and 1992 in four generations. To quantify gravel dispersion over distances up to 2.6 km, observations are taken from 11 recoveries. Over 280 floods capable of moving bedload occurred during this period, with five exceeding the estimated bankfull discharge. Streamwise dispersion is quantified by virtual velocity, while dispersion into the streambed is quantified by a vertical burial rate. The temporal trend in streamwise dispersion rates is described by a power function. Initial virtual velocities decline rapidly from around 1.4 m/hr to approach an asymptote value of about 0.2 m/hr. The rapid change corresponds to a significant increase in the proportion of buried tracers due to vertical mixing. Initial burial rates reflect the magnitude of the first flood after tracer deployment and range from 0.07 to 0.46 cm/hr depending on tracer generation. Burial rates converge to about 0.06 cm/hr after the fourth flood season and then gradually decline to about 0.01 cm/hr. Thus, the rate of streamwise dispersion exceeds that of vertical dispersion by three orders of magnitude when the movement of sediment routinely activated by floods is considered.

  12. Dispersion of single-walled carbon nanotubes by a natural lung surfactant for pulmonary in vitro and in vivo toxicity studies

    Directory of Open Access Journals (Sweden)

    Mercer Robert R

    2010-10-01

    Full Text Available Abstract Background Accumulating evidence indicate that the degree of dispersion of nanoparticles has a strong influence on their biological activities. The aims of this study were to develop a simple and rapid method of nanoparticle dispersion using a natural lung surfactant and to evaluate the effect of dispersion status of SWCNT on cytotoxicity and fibrogenicity in vitro and in vivo. Results The natural lung surfactant Survanta® was used to disperse single-walled carbon nanotubes (SWCNT in a biological medium. At physiologically relevant concentrations, Survanta® produced well dispersed SWCNT without causing a cytotoxic or fibrogenic effect. In vitro studies show that Survanta®-dispersed SWCNT (SD-SWCNT stimulated proliferation of lung epithelial cells at low doses (0.04-0.12 μg/ml or 0.02-0.06 μg/cm2 exposed surface area but had a suppressive effect at high doses. Non-dispersed SWCNT (ND-SWCNT did not exhibit these effects, suggesting the importance of dispersion status of SWCNT on bioactivities. Studies using cultured human lung fibroblasts show that SD-SWCNT stimulated collagen production of the cells. This result is supported by a similar observation using Acetone/sonication dispersed SWCNT (AD-SWCNT, suggesting that Survanta® did not mask the bioactivity of SWCNT. Likewise, in vivo studies show that both SD-SWCNT and AD-SWCNT induced lung fibrosis in mice, whereas the dispersing agent Survanta® alone or Survanta®-dispersed control ultrafine carbon black had no effect. Conclusions The results indicate that Survanta® was effective in dispersing SWCNT in biological media without causing cytotoxic effects at the test concentrations used in this study. SD-SWCNT stimulated collagen production of lung fibroblasts in vitro and induced lung fibrosis in vivo. Similar results were observed with AD-SWCNT, supporting the conclusion that Survanta® did not mask the bioactivities of SWCNT and thus can be used as an effective dispersing agent

  13. Studies on relative catalytic efficiencies of zinc and aluminium on nucleation of dispersed bismuth droplets

    Indian Academy of Sciences (India)

    Sanjay Chaubey

    2007-04-01

    In Zn–Bi and Al–Bi systems, both of which belong to monotectic class, dispersion of second phase particles within the matrix have been produced through rapid solidification processing (RSP) route. In order to understand relative catalytic efficiencies of Zn and Al matrices in catalyzing nucleation of Bi particles entrapped in the respective metal matrices, thermal analysis in constant program mode was performed. Thermal analyses revealed that Bi undercools by 132° in Zn matrix and by 157° in Al matrix. Thermodynamic barrier to nucleation (*) for Bi has also been calculated, which is 39.8 kcal/mole and 47.085 kcal/mole, in Zn and Al matrices, respectively at the maximum recorded undercoolings.

  14. Experimental study on stimulated scattering of ZnO nanospheres dispersed in water

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Jiulin, E-mail: hyq1304@126.com; Wu, Haopeng [Nanchang Hangkong University, Jiangxi Engineering Laboratory for Optoelectronics Testing Technology (China); Yan, Feng; Yang, Junjie [Nanchang Hangkong University, School of Measuring and Optical Engineering (China); He, Xingdao, E-mail: xingdaohe@126.com [Nanchang Hangkong University, Jiangxi Engineering Laboratory for Optoelectronics Testing Technology (China)

    2016-01-15

    The backward stimulated scattering (BSS) from ZnO nanospheres dispersed in water has been investigated experimentally by employing a Nd:YAG pulse laser with ∼532 nm wavelength and ∼8 ns pulse width as the pump laser source. The present results show that the BSS effect is uniquely and unequivocally different compared to other known stimulated scattering, such as stimulated Rayleigh scattering, stimulated Brillouin scattering, and stimulated Raman scattering, and it displays the characteristics of no frequency shift and threshold dependence on initial spontaneous Mie scattering seed source. These can be understood by means of the Mie scattering theory and a laser-induced stationary Bragg grating model.

  15. Aloha - Optics studies by combined kick-response and dispersion fits.

    CERN Document Server

    Fuchsberger, K

    2009-01-01

    The Aloha software is based on a JAVA reimplementation of the former LOCO response fitting code [1]. The project was initiated in order to have a tool that is available online in the control room to quickly analyze kick response data during the LHC injection tests and startup. Later it was extended to handle dispersion data as another source for fit-constraints and to import other input data as for example alignment and trim-values. It was already successfully used to determine monitor- an corrector-gains as well as identifying various error sources during the LHC injection tests. This note describes the principles used by Aloha as well as some implementation details of this software package.

  16. CFD Study of Gas Dispersion and Jet Fires in Complex Geometries

    DEFF Research Database (Denmark)

    Osenbroch, Jørgen

    been performed. The results have been compared to large scale experimental findings (Savvides et al. 1999, BG Technology & Shell Global Solutions April 1999). The pre-release ventilation rates are in good quantitative agreement with experiments and well within the criteria for acceptable performance......An implementation and validation of a gas dispersion model and a radiation model in the Computational Fluid Dynamics (CFD) code EXSIM (Sæter 1998, Hjertager et al. 1992) have been performed. The extended code is named FLEXSIM (Fire Leak Explosion Simulator). The computational simulations have been....... The predicted flammable gas volumes show an acceptable quantitative agreement with the majority of the measurements within a factor of two. The flammable gas volumes inside the module are in general over predicted but show an acceptable overall quantitative statistical performance. Two simulations with decaying...

  17. Dynamic simulation of dispersed, grid-connected photovoltaic power systems: System studies

    Science.gov (United States)

    Wasynczuk, O.; Carroll, D. P.; Gareis, G. E.; Krause, P. C.; Ong, C. M.; Schwartz, R. J.

    1985-03-01

    To investigate the operating characteristics and dynamic behavior of photovoltaic (PV) power systems, four PV system configurations were selected as representative of those currently being used in PV applications. These included single and three phase, line and self commutated power conditioners with a flat plate PV array as the dc source. Detailed computer models of each of these systems were developed and incorporated into dynamic representations of typical primary and secondary distribution feeders. The dynamic electrical behavior of the PV and distribution systems following common network disturbances such as large load changes, PV system startup, and cloud cover transients are characterized. The dynamic behavior was also investigated during abnormal operating conditions following line faults, PV system malfunctions, and islanding or distribution systems containing significant levels of dispersed PV generation. Results of verification tests involving two of the single phase PV system configurations, in which the simulated response characteristics are compared with actual measurements, are also provided.

  18. Distributions of Personalities Within Occupations and Fields of Study

    Science.gov (United States)

    Holland, John L.; Holland, Joan E.

    1977-01-01

    Self Directed Search (SDS) and Vocational Preference Inventory (VPI) results occupations and fields of study were organized to show the distributions of personalities within an occupation or field of study. The results show that single fields tolerate several types, but some types occur only infrequently. (Author)

  19. A critical review on the scaling theory of dispersion

    Science.gov (United States)

    Zech, Alraune; Mai, Juliane; Attinger, Sabine; Dietrich, Peter; Teutsch, Georg; Fiori, Aldo; Rubin, Yoram

    2014-05-01

    The phenomenon of dispersive mixing of solutes in aquifers is subject of research since decades. The characterization of dispersivity at a particular field site is a prerequisite to predict the movement and spreading of a contaminant plume. Experimental investigations have shown, that field-scale dispersivities vary over orders of magnitude, which apparently depends on the scale of measurement. Gelhar et al. [1992] and Schulze-Makuch [2005] have reviewed a large number of transport experiments reported in the literature. Based on that data Schulze-Makuch [2005] performed a trend analysis of longitudinal dispersivity, fostering the empirical relationship of a power law between dispersivities and the scale of measurement without an upper bound. The goal of our study is to critically revisit not only the data used for the trend analysis but the power-law scale dependence of longitudinal dispersivity (e.g. Neuman [1990], Xu and Eckstein [1995]). Our particular focus is on the reported dispersivities of large amount (larger than 100m) and large measurement scales (in the order of kilometers). We aim to evaluate current theories of transport against a critical "mass" of field experiments and to bracket the conditions of their applicability. We further aim to evaluate the adequacy of the field sampling techniques that were employed from the perspective of more than 30 years development in modeling and field characterization. Given the tremendous progress in field data acquisition techniques and new insights gained, it is reasonable to expect that interpretations of past experiments may be flawed due to the limitations or inadequacy of field sampling techniques. Gelhar, L.W., C. Welty, and K.R. Rehfeldt, 1992, A critical review of data on field-scale dispersion in aquifers, Water Resources Research 28, No. 7: 1955-1974. Schulze-Makuch, D., 2005, Longitudinal dispersivity data and implications for scaling behavior, Ground Water, Vol. 43, No. 3, 443-456. Neuman, S.P., 1990

  20. A Study on Solute Dispersion in a Three Layer Blood-like Liquid Flowing through a Rigid Artery

    National Research Council Canada - National Science Library

    Sudip Debnath; Apu Kumar Saha; Ashis Kumar Roy

    2017-01-01

    The unsteady dispersion of a solute has been discussed by the method of generalized dispersion technique in a blood-like liquid flowing through a pipe under the combined effects of finite yield stress...

  1. Hydrogeological Study Report, Lajes Field, Azores, Portugal

    Science.gov (United States)

    2005-02-01

    seismic hazards in the Azorean Archipelago is due to its location near the plate boundary between Africa, Eurasia, and North America . Terceira Island...Açores como Recurso Natural, especialmente em Agricultura e Industria do Turismo. O clima de Portuga. Fasc. XVIII, INMG. Lisboa. CH2M HILL (2004) Data...Praia da Vitória. Relatório Preliminar. Universidade dos Açores. MWH Americas Inc, 2003, Water System Evaluation Report, Lajes Field, Terceira Island

  2. Deformation study of Kamojang geothermal field

    Science.gov (United States)

    Ramdhani, B. D.; Meilano, I.; Sarsito, D. A.

    2017-07-01

    GPS has proven to be an indispensable tool in the effort to understand crust deformation before, during, and after the big earthquake events through data analysis and numerical simulation. The development of GPS technology has been able to prove as a method for the detection of geothermal activity that related to deformation. Furthermore, the correlation of deformation and geothermal activity are related to the analysis of potential hazards in the geothermal field itself. But unfortunately, only few GPS observations established to see the relationship of tectonic and geothermal activity around geothermal energy area in Indonesia. This research will observe the interaction between deformation and geothermal sources around the geothermal field Kamojang using geodetic GPS. There are 4 campaign observed points displacement direction to north-east, and 2 others heading to south-east. The displacement of the observed points may have not able proven cause by deformation of geothermal activity due to duration of observation. Since our research considered as pioneer for such investigation in Indonesia, we expect our methodology and our findings could become a starter for other geothermal field cases in Indonesia.

  3. A CFD study on the effectiveness of trees to disperse road traffic emissions at a city scale

    Science.gov (United States)

    Jeanjean, A. P. R.; Hinchliffe, G.; McMullan, W. A.; Monks, P. S.; Leigh, R. J.

    2015-11-01

    This paper focuses on the effectiveness of trees at dispersing road traffic emissions on a city scale. CFD simulations of air-pollutant concentrations were performed using the OpenFOAM software platform using the k-ε model. Results were validated against the CODASC wind tunnel database before being applied to a LIDAR database of buildings and trees representing the City of Leicester (UK). Most other CFD models in the literature typically use idealised buildings to model wind flow and pollution dispersion. However, the methodology used in this study uses real buildings and trees data from LIDAR to reconstruct a 3D representation of Leicester City Centre. It focuses on a 2 × 2 km area which is on a scale larger than those usually used in other CFD studies. Furthermore, the primary focus of this study is on the interaction of trees with wind flow dynamics. It was found that in effect, trees have a regionally beneficial impact on road traffic emissions by increasing turbulence and reducing ambient concentrations of road traffic emissions by 7% at pedestrian height on average. This was an important result given that previous studies generally concluded that trees trapped pollution by obstructing wind flow in street canyons. Therefore, this study is novel both in its methodology and subsequent results, highlighting the importance of combining local and regional scale models for assessing the impact of trees in urban planning.

  4. Measurement of the factor of dispersion in air for a field of 0,8{sup *} 8,0 CM {sup 2}; Medida del factor de dispersion en aire para un campo de 0,8{sup *} 8,0 CM{sup 2}

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-Tejedor Alonso, S.; Huertas Martinez, C.; Penedo Cobos, J. M.; Garcia Castejon, M. A.; Rincon Perezx, M.

    2013-07-01

    The measures of this factor of dispersion in air is usually performed with an ionization chamber cover a cap of balance of such thickness that is achieved the electronic balance, and must be covered completely the CAP by the radiation field. This procedure is not applicable for small fields. The need to measure the Sc of a field of 0.8{sup *} 0.8 cm{sup 2} for a new system of planning led us to try another measure procedure proposed in the literature, using detectors of semiconductor with a sheet of cerrobend by way of balance Cap. (Author)

  5. A second order Rosenbrock method applied to photochemical dispersion problems

    NARCIS (Netherlands)

    Verwer, J.G.; Spee, E.J.; Blom, J.G.; Hundsdorfer, W.

    1997-01-01

    A 2nd-order, L-stable Rosenbrock method from the field of stiff ordinary differential equations is studied for application to atmospheric dispersion problems describing photochemistry, advective and turbulent diffusive transport. Partial differential equation problems of this type occur in the field

  6. Geosynthetic clay liners - slope stability field study

    Energy Technology Data Exchange (ETDEWEB)

    Carson, D.A. [Environmental Protection Agency, Cincinnati, OH (United States); Daniel, D.E. [Univ. of Illinois, Urbana, IL (United States); Koerner, R.M. [Geosynthetic Research Institute, Philadelphia, PA (United States); Bonaparte, R. [GeoSyntec Consultants, Atlanta, GA (United States)

    1997-12-31

    A field research project was developed to examine the internal shear performance of geosynthetic clay liners (GCLs). Several combinations of cross sections were assembled using GCL materials that were available at the time of project initiation. The cross sections utilized were intended to simulate landfill cover applications. Thirteen (13) resulting test plots were constructed on two different slope angles, and each plot is instrumented for physical displacement and soil moisture characteristics. Test plots were constructed in a manner that dictated the shear plane in the clay portion of the GCL product. The project purpose is to assess field performance and to verify design parameters associated with the application of GCLs in waste containment applications. Interim research data shows that test slopes on 2H:1V show global deformation, but little internal shear evidence, and the 3H:1V slopes show little deformation at approximately 650 days. The research is ongoing, and this paper presents the most recent information available from the project.

  7. Studies of GRACE Gravity Field Inversion Techniques

    Science.gov (United States)

    Wang, L.; Shum, C.; Duan, J.; Schmidt, M.; Yuan, D.; Watkins, M. M.

    2008-12-01

    The geophysical inverse problem using satellite observations, such as GRACE, to estimate gravity change and mass variations at the Earth's surface is a well-known ill-posed problem. Different methods using different basis function (representing the gravity field) for different purposes (global or regional inversion) have been employed to obtain a stable solution, such as Bayesian estimation with prior information, the repro-BIQUUE of variance components and iterative least-squares estimation with simultaneous updating of a prior covariance, and to achieve enhanced spatial resolutions. The gravity field representation methods include spherical harmonics, regional gridded data (including mascons), and various wavelet representations (Poisson wavelets, Blackman band-limited regional wavelets with global representation). Finally, the use of data types (KBR range, range-rate, range-rate-rate) and data-generation methods (e.g., nonlinear orbit determination and geophysical inverse approach, energy conservation principle, etc) could also reflect relative inversion accuracy and the content of signal spectra in the resulting solution. In this contribution, we present results of a simulation experiment, which used various solution techniques and data types to attempt to quantify the relative advantage and disadvantage of each of the techniques.

  8. Simulation study for the monitoring of industrial exhaust dispersion using a DIAL system

    Science.gov (United States)

    Veerabuthiran, S.; Jindal, Mukesh Kumar; Dudeja, Jai Paul; Dubey, Deepak Kumar; Kumar, Anil

    2006-12-01

    Computer simulations have been carried out to optimize the IR Differential Absorption Lidar (DIAL) system in order to measure the gaseous pollutants released by the industries. The concentration of the gaseous pollutants due to elevated sources is computed using the Gaussian dispersion model. For given atmospheric conditions and stack physical parameters, the downwind distance (x) at which the SO II reaches the safe limit of its toxicity has been computed at given other two coordinates (y, z) with respect to chimney. The gaseous pollutants released by the industries will be effectively monitored by the proposed DIAL system, which will be placed at New Delhi (28.35 degrees N, 77.12 degrees E), India. The performance of the Lidar has been optimized based on the various system parameters incorporating the atmospheric conditions and stack physical parameters. Further, the backscattered return powers at on- & -off line wavelengths, the required energy to be transmitted and the position at which the lidar system should be posted have been computed in order to monitor SO II.

  9. Thermal compatibility studies of U 3Si 2 dispersion fuels prepared with centrifugally atomized powder

    Science.gov (United States)

    Kim, Ki-Hwan; Park, Jong-Man; Kim, Chang-Kyu; Hofman, Gerard L.; Paik, Kyung-Wook

    The interaction between atomized U 3Si 2 and aluminum in dispersion fuel samples has been characterized and compared with that of comminuted U 3Si 2. Fuel samples with atomized powder showed a smaller volume increase compared to those with the comminuted powder, irrespective of heat treatment, and volume fraction of U 3Si 2 powder. The possible reasons for this seem to be as follows: (1) the smaller specific surface area of the atomized spherical powder compared to the irregular comminuted powder translating in a smaller U 3Si 2-Al interface area for the former affecting what appears to be a diffusion-controlled interaction process, (2) the atomized fuel samples also contain lower fraction of as-fabricated porosity than the comminuted fuel samples, which may enhance the restraint force in the swelling fuel meat, (3) the comminuted powder particles have distinctive aluminum penetration paths in the form of deformation zones that originated from the comminution process. There appear to be two pronounced penetration paths of aluminum into atomized U 3Si 2 powder; (1) through the phase interface, leaving a central unreacted island, (2) along grain boundaries, leaving several unreacted islands.

  10. Re-dispersible Li+ and Eu3+ co-doped CdS nanoparticles: Luminescence studies

    Indian Academy of Sciences (India)

    N S Gajbhiye; Raghumani Singh Ninghoujam; Asar Ahmed; D K Panda; S S Umare; S J Sharma

    2008-02-01

    Re-dispersible CdS, 5 at.% Eu3+-doped CdS, 2 at.% Li+ and 5 at.% Eu3+ co-doped CdS nanoparticles in organic solvent are prepared by urea hydrolysis in ethylene glycol medium at a low temperature of 170°C. CdS nanoparticles have spherical shape with a diameter of ∼ 80 nm. The asymmetric ratio (21) of the integrated intensities of the electrical dipole transition to the magnetic dipole transition for 5 at.% Eu3+-doped CdS is found to be 3.8 and this ratio is significantly decreased for 2 at.% Li+ and 5 at.% Eu3+ co-doped CdS (21 = 2.6). It establishes that the symmetry environment of Eu3+ ion is more favored by Li-doping. Extra peak at 550 nm (green emission) could be seen for 2 and 5 at.% Eu3+ co-doped CdS. Also, the significant energy transfer from host CdS to Eu3+ is found for 5 at.% Eu3+-doped CdS compared to that for 2 at.% Li+ and 5 at.% Eu3+ co-doped CdS.

  11. A Dispersion Model Evaluation Study for Real-Time Application in Complex Terrain.

    Science.gov (United States)

    Desiato, F.

    1991-08-01

    A few tracer experiments were carried out in autumn 1984 and summer 1985 at the Lago Brasimone site, on the Appennini Mountains approximately 50 km south of Bologna with the purpose assessing the atmospheric dispersion of pollutants under drainage flow conditions. The three-dimensional transport and diffusion model MATHEW/ADPIC (M/A) has been applied to selected tracer and meteorological data with the aim of assessing the model performance under complex terrain and meteorological conditions, and its sensitivity to input data available in real-time applications. Boundary layer input parameters were derived through standard algorithms based on tethersonde and pilot balloon measurements. Model simulations of the most significant tracer experiments have been assessed by means of several evaluation criteria, and the sensitivity to some input data has been investigated. The results show that if a limited spatial uncertainty in the computed concentration pattern is taken into account, M/A provides a good agreement with observed concentrations. The quality of the results is very sensitive to the presence of wind measurements where the deviation of the flow due to the shape of the valley is observed.

  12. Analytical study of dispersion relations for shear horizontal wave propagation in plates with periodic stubs

    KAUST Repository

    Xu, Yanlong

    2015-08-01

    The coupled mode theory with coupling of diffraction modes and waveguide modes is usually used on the calculations of transmission and reflection coefficients for electromagnetic waves traveling through periodic sub-wavelength structures. In this paper, I extend this method to derive analytical solutions of high-order dispersion relations for shear horizontal (SH) wave propagation in elastic plates with periodic stubs. In the long wavelength regime, the explicit expression is obtained by this theory and derived specially by employing an effective medium. This indicates that the periodical stubs are equivalent to an effective homogenous layer in the long wavelength. Notably, in the short wavelength regime, high-order diffraction modes in the plate and high-order waveguide modes in the stubs are considered with modes coupling to compute the band structures. Numerical results of the coupled mode theory fit pretty well with the results of the finite element method (FEM). In addition, the band structures\\' evolution with the height of the stubs and the thickness of the plate shows clearly that the method can predict well the Bragg band gaps, locally resonant band gaps and high-order symmetric and anti-symmetric thickness-twist modes for the periodically structured plates. © 2015 Elsevier B.V.

  13. Numerical simulations of barnacle larval dispersion coupled with field observations on larval abundance, settlement and recruitment in a tropical monsoon influenced coastal marine environment

    Digital Repository Service at National Institute of Oceanography (India)

    Gaonkar, C.A.; Samiksha S.V.; George, G.; Aboobacker V.M.; Vethamony, P.; Anil, A.C.

    different circumstances. Environmental variability is the main cause for such differences. Larvae are likely to disperse or retain more without settling behavior or mortality factors. Factors such as food availability and predation can also influence... both feeding as well as non-feeding stages, success of larval populations depends on its dispersal/retention to habitats with sufficient food. The non-feeding larval stage (cyprids) can last for several days depending on the stored energy content...

  14. Magnetic field studies of massive main sequence stars

    CERN Document Server

    Schoeller, M; Ilyin, I; Kharchenko, N V; Briquet, M; Langer, N; Oskinova, L M

    2011-01-01

    We report on the status of our spectropolarimetric observations of massive stars. During the last years, we have discovered magnetic fields in many objects of the upper main sequence, including Be stars, beta Cephei and Slowly Pulsating B stars, and a dozen O stars. Since the effects of those magnetic fields have been found to be substantial by recent models, we are looking into their impact on stellar rotation, pulsation, stellar winds, and chemical abundances. Accurate studies of the age, environment, and kinematic characteristics of the magnetic stars are also promising to give us new insight into the origin of the magnetic fields. Furthermore, longer time series of magnetic field measurements allow us to observe the temporal variability of the magnetic field and to deduce the stellar rotation period and the magnetic field geometry. Studies of the magnetic field in massive stars are indispensable to understand the conditions controlling the presence of those fields and their implications on the stellar phy...

  15. Dispersion Interactions in Water Clusters.

    Science.gov (United States)

    Guidez, Emilie B; Gordon, Mark S

    2017-05-18

    The importance of dispersion forces in water clusters is examined using the effective fragment potential (EFP) method. Since the original EFP1 water potential does not include dispersion, a dispersion correction to the EFP1 potential (EFP1-D) was derived and implemented. The addition of dispersion to the EFP1 potential yields improved geometries for water clusters that contain 2-6 molecules. The importance of the odd E7 contribution to the dispersion energy is investigated. The E7 dispersion term is repulsive for all of the water clusters studied here and can have a magnitude that is as large as half of the E6 value. The E7 term therefore contributes to larger intermolecular distances for the optimized geometries. Inclusion of many-body effects and/or higher order terms may be necessary to further improve dispersion energies and optimized geometries.

  16. Impact of trees on pollutant dispersion in street canyons: A numerical study of the annual average effects in Antwerp, Belgium.

    Science.gov (United States)

    Vranckx, Stijn; Vos, Peter; Maiheu, Bino; Janssen, Stijn

    2015-11-01

    Effects of vegetation on pollutant dispersion receive increased attention in attempts to reduce air pollutant concentration levels in the urban environment. In this study, we examine the influence of vegetation on the concentrations of traffic pollutants in urban street canyons using numerical simulations with the CFD code OpenFOAM. This CFD approach is validated against literature wind tunnel data of traffic pollutant dispersion in street canyons. The impact of trees is simulated for a variety of vegetation types and the full range of approaching wind directions at 15° interval. All these results are combined using meteo statistics, including effects of seasonal leaf loss, to determine the annual average effect of trees in street canyons. This analysis is performed for two pollutants, elemental carbon (EC) and PM10, using background concentrations and emission strengths for the city of Antwerp, Belgium. The results show that due to the presence of trees the annual average pollutant concentrations increase with about 8% (range of 1% to 13%) for EC and with about 1.4% (range of 0.2 to 2.6%) for PM10. The study indicates that this annual effect is considerably smaller than earlier estimates which are generally based on a specific set of governing conditions (1 wind direction, full leafed trees and peak hour traffic emissions).

  17. Enhancement of dissolution rate of class II drugs (Hydrochlorothiazide); a comparative study of the two novel approaches; solid dispersion and liqui-solid techniques

    Science.gov (United States)

    Khan, Amjad; Iqbal, Zafar; Shah, Yasar; Ahmad, Lateef; Ismail; Ullah, Zia; Ullah, Aman

    2015-01-01

    Liqui-solid technique and solid dispersion formation are two novel approaches for enhancement of dissolution rate of BCS class II drugs. Liqui-solid compact converts a liquid drug or drug solution into a free flowing powder with enhanced dissolution rate. In case of solid dispersion drug is molecularly dispersed in a hydrophilic polymer in solid state. In the present study