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Sample records for black-winged stilts disperse

  1. Effects of Agricultural Management Policies on the Exposure of Black-Winged Stilts (Himantopus himantopus Chicks to Cholinesterase-Inhibiting Pesticides in Rice Fields.

    Directory of Open Access Journals (Sweden)

    Gregorio M Toral

    Full Text Available Levels of exposure to pesticides in rice fields can be significant depending on the environmental policies practiced. The aim of European Union integrated management policy is to reduce pesticide use and impact on environment. Rice fields provide an alternative breeding habitat for many waterbirds that are exposed to the pesticides used and therefore can be valuable indicators of their risk for wildlife. To evaluate integrated management success we examined exposure of Black-winged Stilts (Himantopus himantopus to cholinesterase-inhibiting pesticides in rice fields under different types of management by measuring plasma cholinesterase activity. Cholinesterase activity was lower in birds sampled in (a 2008 after a period of intense pesticide application, than in (b 2005-2007 and 2011 in rice fields subject to integrated management in Doñana (SW Spain and (c in control natural wetlands in Spain and Morocco. During 2009 and 2010, cholinesterase activity was lower in rice fields in Doñana than in rice fields in Larache and Sidi Allal Tazi (NW Morocco. Our results suggest that integrated management successfully reduced the exposure of Black-winged Stilts to pesticides in most of the years. Care should be taken to implement mosquito and pest crop controls on time and with environmentally friendly products in order to reduce its impact on wildlife.

  2. STILT: System design and performance

    Science.gov (United States)

    Mawson, N. R.; Steele, I. A.; Smith, R. J.

    2013-08-01

    The Small Telescopes Installed at the Liverpool Telescope (STILT) have been in operation since March 2009, collecting wide field data from their position, mounted to the Liverpool Telescope. The two instruments; SkycamT and SkycamZ have been used to create a variability search of the skies visible at La Palma with the limits of 12th and 18th R-band magnitude with fields of view of 21°× 21o and 1°× 1o. We provide here a description of the hardware and software setup and the performance of the system to date.

  3. Kinematics and kinetics of gait on stilts: identification of risk factors associated with construction stilt use.

    Science.gov (United States)

    Chiou, Sharon S; Pan, Christopher S; Bhattacharya, Amit

    2008-12-01

    This study investigated kinematics and kinetic strategies and identified risk factors associated with gait on stilts. A six-camera motion-analysis system and two force platforms were used to test 20 construction workers for straight walking or turning, with or without carrying tools while wearing safety shoes or stilts at different heights. The results indicated that gait on stilts is characterised by increases in stride length, step width and the percentage of double support period, decreases in cadence, minimum foot clearance and a weaker heel-strike and push-off. Stilts place greater joint loadings on lower extremities to compensate for the added weight and limitation in joint mobility. Smaller foot clearances found for gait on stilts constitute an increased risk for tripping over obstacles. Workers may need to avoid prolonged use of stilts to alleviate stresses on the joints. This study was conducted to determine to what extent stilts alter the gait strategies and to explain the compensatory movements. Prior to this study, there has been little substantive research to evaluate the stresses and potential injuries associated with stilts.

  4. Pododermatitis in captive-reared black stilts (Himantopus novaezelandiae).

    Science.gov (United States)

    Reissig, Elizabeth Chang; Tompkins, Daniel M; Maloney, Richard F; Sancha, Emily; Wharton, David A

    2011-09-01

    A potential cause of pododermatitis ("bumblefoot") was investigated in captive-reared juvenile black stilts at the Department of Conservation "Kaki Recovery Program" at Twizel, New Zealand. To address the importance of substrate, the development of clinical signs in individuals was compared among aviaries that contained rubber matting and/or salt footbaths, and controls. No effect of either experimental manipulation of the environment was apparent on pododermatitis development. With the substrate appearing not to be an initiating factor, and a previous study that indicated that the birds' diet fulfills the nutritional requirements for rearing black stilts in captivity, results of this study suggest that insufficient space for exercise may instead be the cause.

  5. Comparative reproductive biology of sympatric species: Nest and chick survival of American avocets and black-necked stilts

    Science.gov (United States)

    Ackerman, Joshua T.; Herzog, Mark P.; Takekawa, John Y.; Hartman, Christopher A.

    2014-01-01

    Identifying differences in reproductive success rates of closely related and sympatrically breeding species can be useful for understanding limitations to population growth. We simultaneously examined the reproductive ecology of American avocets Recurvirostra americana and black-necked stilts Himantopus mexicanus using 1274 monitored nests and 240 radio-marked chicks in San Francisco Bay, California. Although there were 1.8 times more avocet nests than stilt nests, stilts nonetheless fledged 3.3 times more chicks. Greater production by stilts than avocets was the result of greater chick survival from hatching to fledging (avocet: 6%; stilt: 40%), and not because of differences in clutch size (avocet: 3.84; stilt: 3.77), nest survival (avocet: 44%; stilt: 35%), or egg hatching success (avocet: 90%; stilt: 92%). We reviewed the literature and confirmed that nest survival and hatching success are generally similar when avocets and stilts breed sympatrically. In addition to species, chick survival was strongly influenced by age, site, and year. In particular, daily survival rates increased rapidly with chick age, with 70% of mortalities occurring ≤ 1 week after hatch. California gulls Larus californicus caused 55% of avocet, but only 15% of stilt, chick deaths. Differential use of micro-habitats likely reduced stilt chick’s vulnerability to gull predation, particularly during the first week after hatch, because stilts nested in vegetation 2.7 times more often than avocets and vegetation height was 65% taller at stilt nests compared with avocet nests. Our results demonstrate that two co-occurring and closely related species with similar life history strategies can differ markedly in reproductive success, and simultaneous studies of such species can identify differences that limit productivity.

  6. Baseline blood Pb levels of black-necked stilts on the upper Texas coast

    Science.gov (United States)

    Riecke, Thomas V.; Conway, Warren C.; Haukos, David A.; Moon, Jena A.; Comer, Christopher E.

    2015-01-01

    There are no known biological requirements for lead (Pb), and elevated Pb levels in birds can cause a variety of sub-lethal effects and mortality. Historic and current levels of Pb in mottled ducks (Anas fulvigula) suggest that environmental sources of Pb remain available on the upper Texas coast. Because of potential risks of Pb exposure among coexisting marsh birds, black-necked stilt (Himantopus mexicanus) blood Pb concentrations were measured during the breeding season. Almost 80 % (n = 120) of 152 sampled stilts exceeded the background threshold (>20 μg/dL) for Pb exposure. However, blood Pb concentrations did not vary by age or gender, and toxic or potentially lethal concentrations were rare (study suggest the presence of readily bioavailable sources of Pb, although potential impacts on local stilt populations remain unclear.

  7. THE CHARACTERISTICS OF THE SELF-SUPPORT STILT-HOUSES TOWARDS THE DISASTER POTENTIALITY AT THE CAMBAYA COASTAL AREA, MAKASSAR

    Directory of Open Access Journals (Sweden)

    Isfa Sastrawati

    2009-07-01

    Full Text Available Self-support stilt-houses at the coastal area have environment characteristics that are different from inland houses, and they have the disaster potentiality such as hurricanes, tidal waves, abrasion, earthquakes, and even tsunami. The stilt houses are very adaptable to climatic conditions and coastal disasters. The shape of the stilt houses at the coastal area must comply with aspects of safety, security, comfort, and health. This paper examines the characteristics of the stilt houses at the coastal area of Cambaya, Makassar, especially in terms of safety and security aspects. The aspects of safety and security include the resistance of the building construction towards disasters. Along with the development of the urban area, the demanding needs and limited financial-abilities, the owners of the houses at the Cambaya coastal area develop their houses by utilizing the empty space at the coastal area and the space under floor of the stilt house. The change of the building shape gives an effect on the poor quality of the building, building safety, and security. However, there are several stilt houses at Cambaya which could reduce the impacts of disasters on the safety of the residents through their local wisdom.

  8. Behavioural Study of Sanan and Jamnapari Cross Bred Goats Kept in a Stilted House

    Directory of Open Access Journals (Sweden)

    Ganiesha Jayamini De silva

    2014-07-01

    Full Text Available A sound understanding of the normal behaviour of an animal is important to assess its welfare standards. Behaviour of confined animals is useful in order to design proper housing systems. Objective of this study was to understand the behaviour of goats kept in a stilted house. Behaviour of 14 Sanan and Jamnapari goats (14Kg-37Kg kept in stilted house was observed using an ethograme for six one hour sessions in two days (rainy and hot. Each session lasted for five minutes. Frequency and times spent on seventeen mutually exhaustive behaviours were recorded. Goats spent significantly (P<0.05 more time on eating (31% than any of the other behaviours. Other important behaviours were resting (11%, licking (10%, ruminating (10% and walking (9.5%. Goats spent a substantial time on behaviours such as lying (7.3%, running (6.3%, freezing (6% and animal interaction (5.7%. The time budget on behaviours such as saltate (0.5%, sniffing (0.59%, chattering (0.59% and importantly on drinking (0.6% were very low. Behaviors such as freezing, head movement, animal interaction, saltate, running, rumination, chattering and chirping were affected by the climatic condition of the day. It was concluded that goats kept in stilted houses spend one third of their time budget on eating and but very little time on drinking.

  9. Black-necked stilts share nesting in the Merritt Island National Wildlife Refuge

    Science.gov (United States)

    1999-01-01

    A black-necked stilt waits near its nesting mate nest in the Merritt Island National Wildlife Refuge, which shares a boundary with Kennedy Space Center. Stilts usually produce three or four brown-spotted buff eggs in a shallow depression lined with grass or shell fragments. In the nesting season they are particularly agressive. Stilts are identified by a distinct head pattern of black and white, very long red legs, and straight, very thin bill. Their habitat is salt marshes and shallow coastal bays from Delaware and northern South America in the East, and freshwater marshes from Oregon and Saskatchewan to the Gulf Coast. The 92,000-acre wildlife refuge is a habitat for more than 310 species of birds, 25 mammals, 117 fishes and 65 amphibians and reptiles. The marshes and open water of the refuge also provide wintering areas for 23 species of migratory waterfowl, as well as a year-round home for great blue herons, great egrets, wood storks, cormorants, brown pelicans and other species of marsh and shore birds.

  10. ICT for smart evaluation of vernacular architecture in a stilt-house village

    Science.gov (United States)

    Almeida, Filipa; Virtudes, Ana Lídia

    2016-12-01

    Vernacular architecture typologies, such as wooden stilt-houses, have been threatened by the vulnerability to conservation status degradation. This problem is not an exception in Portugal, where the few remaining examples have been neglected, with the disappearance or abandonment of almost all buildings, damaging architectural and urban spatial features. This legacy is rapidly disappearing, weakening the European cultural map. This research presents the results from a smart evaluation method using an ICT (information and communication technology) platform designed for the smart evaluation of wooden stilt-houses, considering their conservation status. This platform was used in the five remaining stilthouse villages still existing in Portugal including about 90 buildings and 300 inhabitants, located along Tagus river banks. This article refers to one of these case studies, the village of Escaroupim, which was chosen because it is the most urban space in between all of them. On one hand, the results are an exhaustive survey of vernacular buildings, useful as guideline for spatial strategies and instruments to protect this legacy. On the other hand, it can be used in other similar wooden buildings, to check their conservation status and therefore to define best rehabilitation actions.

  11. The function of stilt roots in the growth strategy of Socratea exorrhiza (Arecaceae at two neotropical sites

    Directory of Open Access Journals (Sweden)

    Gregory R Goldsmith

    2007-12-01

    Full Text Available Arboreal palms have developed a variety of structural root modifications and systems to adapt to the harsh abiotic conditions of tropical rain forests. Stilt roots have been proposed to serve a number of functions including the facilitation of rapid vertical growth to the canopy and enhanced mechanical stability. To examine whether stilt roots provide these functions, we compared stilt root characteristics of the neotropical palm tree Socratea exorrhiza on sloped (>20º and flat locations at two lowland neotropical sites. S. exorrhiza (n=80 trees did not demonstrate differences in number of roots, vertical stilt root height, root cone circumference, root cone volume, or location of roots as related to slope. However, we found positive relationships between allocation to vertical growth and stilt root architecture including root cone circumference, number of roots, and root cone volume. Accordingly, stilt roots may allow S. exorrhiza to increase height and maintain mechanical stability without having to concurrently invest in increased stem diameter and underground root structure. This strategy likely increases the species ability to rapidly exploit light gaps as compared to non-stilt root palms and may also enhance survival as mature trees approach the theoretical limits of their mechanical stability. Rev. Biol. Trop. 55 (3-4: 787-793. Epub 2007 December, 28.Comparamos características físicas de raíces aéreas de la palmera Socratea exorrhiza en sitios inclinados (pendiente>20º y sitios planos, en dos lugares neotropicales. S. exorrhiza (n=80 árboles no muestra diferencias en el número de raíces, la altura vertical de las raíces, la circunferencia y la masa del cono de las raíces, o la posición de las raíces en los sitios con pendiente. Encontramos relaciones positivas entre el crecimiento vertical y la arquitectura de las raíces aéreas, incluso entre el número de raíces, la circunferencia del cono de las raíces, y la masa del

  12. Mercury contamination and effects on survival of American avocet and black-necked stilt chicks in San Francisco Bay.

    Science.gov (United States)

    Ackerman, Joshua T; Takekawa, John Y; Eagles-Smith, Collin A; Iverson, Samuel A

    2008-02-01

    We evaluated whether mercury influenced survival of free-ranging American avocet (Recurvirostra americana) and black-necked stilt (Himantopus mexicanus) chicks in San Francisco Bay, California. Using radio telemetry, we radio-marked 158 avocet and 79 stilt chicks at hatching and tracked them daily until their fate was determined. We did not find strong support for an influence of in ovo mercury exposure on chick survival, despite observing a wide range of mercury concentrations in chick down feathers at hatching (0.40-44.31 microg g(-1) fw). We estimated that chick survival rates were reduced by nest monitoring. In contrast to the telemetry results, we found that mercury concentrations in down feathers of dead chicks were higher than those in randomly-sampled live chicks of similar age. However, capture site was the most important variable influencing mercury concentrations, followed by year, species, and hatching date. Although laboratory studies have demonstrated negative effects of environmentally relevant mercury concentrations on chick survival, our results concur with the small number of previous field studies that have not been able to detect reduced survival in the wild.

  13. Fishermen and Little Fish: Migration and Hospitality in Maxine Beneba Clarke’s ‘The Stilt Fishermen of Kathaluwa’

    Directory of Open Access Journals (Sweden)

    Natalie Edwards

    2016-08-01

    Full Text Available In this article, we argue that Maxine Beneba Clarke’s tale ‘The Stilt Fishermen of Kathaluwa,’ in Foreign Soil (2014, is a provocative representation of migration in contemporary Australia. At a time in which the world is facing its largest migration since the Second World War and in which Australian border policy is making headlines around the world, Clarke’s tale is a powerful intervention in discourses of contemporary Australian identity and nationhood. We demonstrate that the tale is a subtle manipulation of what McCullough terms the ‘refugee narrative structure’ since it carefully undercuts the myth of a nation as a coherent narrative across time and space. By juxtaposing the tales of an illegal migrant and a volunteer case worker, and by setting the tale largely in a functioning detention centre, Clarke gives voice to the voiceless and draws parallels between individuals on different sides of the insider/outsider binary. The encounter that finally takes place between them implicates the reader very directly in discourses of contemporary migration and border policy.

  14. Hydrodynamic disperser

    Energy Technology Data Exchange (ETDEWEB)

    Bulatov, A.I.; Chernov, V.S.; Prokopov, L.I.; Proselkov, Yu.M.; Tikhonov, Yu.P.

    1980-01-15

    A hydrodynamic disperser is suggested which contains a housing, slit nozzles installed on a circular base arranged opposite from each other, resonators secured opposite the nozzle and outlet sleeve. In order to improve the effectiveness of dispersion by throttling the flow, each resonator is made in the form of a crimped plate with crimpings that decrease in height in a direction towards the nozzle.

  15. 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...

  16. 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

  17. Foraging ecology and habitat association of black-winged lovebird ...

    African Journals Online (AJOL)

    26.4% of the lovebirds in Bole Sub-City were observed foraging on Zea mays and 16.5 % on Ricinus communis while in Entoto Natural Park, 50% of these lovebirds used the berries of Juniperus procera. Among the identified foraging plant parts, fruit had 60% in Bole Sub-City and 66.6% in Entoto Natural Park. The threat ...

  18. Dispersion strengthening

    International Nuclear Information System (INIS)

    Scattergood, R.O.; Das, E.S.P.

    1976-01-01

    Using digital computer-based methods, models for dispersion strengthening can now be developed which take into account many of the important effects that have been neglected in the past. In particular, the self interaction of a dislocation can be treated, and a computer simulation method was developed to determine the flow stress of a random distribution of circular, impenetrable obstacles, taking into account all such interactions. The flow stress values depended on the obstacle sizes and spacings, over and above the usual 1/L dependence where L is the average obstacle spacing. From an analysis of the results, it was found that the main effects of the self interactions can be captured in a line tension analogue in which the obstacles appear to be penetrable

  19. Hydrodynamic dispersion

    International Nuclear Information System (INIS)

    Pryce, M.H.L.

    1985-01-01

    A dominant mechanism contributing to hydrodynamic dispersion in fluid flow through rocks is variation of travel speeds within the channels carrying the fluid, whether these be interstices between grains, in granular rocks, or cracks in fractured crystalline rocks. The complex interconnections of the channels ensure a mixing of those parts of the fluid which travel more slowly and those which travel faster. On a macroscopic scale this can be treated statistically in terms of the distribution of times taken by a particle of fluid to move from one surface of constant hydraulic potential to another, lower, potential. The distributions in the individual channels are such that very long travel times make a very important contribution. Indeed, while the mean travel time is related to distance by a well-defined transport speed, the mean square is effectively infinite. This results in an asymmetrical plume which differs markedly from a gaussian shape. The distribution of microscopic travel times is related to the distribution of apertures in the interstices, or in the microcracks, which in turn are affected in a complex way by the stresses acting on the rock matrix

  20. Seed dispersal in fens

    NARCIS (Netherlands)

    Middleton, Beth; van Diggelen, Rudy; Jensen, Kai

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and

  1. Clock synchronization and dispersion

    International Nuclear Information System (INIS)

    Giovannetti, Vittorio; Lloyd, Seth; Maccone, Lorenzo; Wong, Franco N C

    2002-01-01

    We present a method to defeat effects of dispersion of timing signals when synchronizing clocks. It is based on the recently proposed 'conveyor belt synchronization' scheme and on the quantum dispersion cancellation effect

  2. Dispersing powders in liquids

    CERN Document Server

    Nelson, RD

    1988-01-01

    This book provides powder technologists with laboratory procedures for selecting dispersing agents and preparing stable dispersions that can then be used in particle size characterization instruments. Its broader goal is to introduce industrial chemists and engineers to the phenomena, terminology, physical principles, and chemical considerations involved in preparing and handling dispersions on a commercial scale. The book introduces novices to: - industrial problems due to improper degree of dispersion; - the nomenclature used in describing particles; - the basic physica

  3. Theory of dispersive microlenses

    Science.gov (United States)

    Herman, B.; Gal, George

    1993-01-01

    A dispersive microlens is a miniature optical element which simultaneously focuses and disperses light. Arrays of dispersive mircolenses have potential applications in multicolor focal planes. They have a 100 percent optical fill factor and can focus light down to detectors of diffraction spot size, freeing up areas on the focal plane for on-chip analog signal processing. Use of dispersive microlenses allows inband color separation within a pixel and perfect scene registration. A dual-color separation has the potential for temperature discrimination. We discuss the design of dispersive microlenses and present sample results for efficient designs.

  4. Reviews Equipment: Chameleon Nano Flakes Book: Requiem for a Species Equipment: Laser Sound System Equipment: EasySense VISION Equipment: UV Flash Kit Book: The Demon-Haunted World Book: Nonsense on Stilts Book: How to Think about Weird Things Web Watch

    Science.gov (United States)

    2011-03-01

    WE RECOMMEND Requiem for a Species This book delivers a sober message about climate change Laser Sound System Sound kit is useful for laser demonstrations EasySense VISION Data Harvest produces another easy-to-use data logger UV Flash Kit Useful equipment captures shadows on film The Demon-Haunted World World-famous astronomer attacks pseudoscience in this book Nonsense on Stilts A thought-provoking analysis of hard and soft sciences How to Think about Weird Things This book explores the credibility of astrologers and their ilk WORTH A LOOK Chameleon Nano Flakes Product lacks good instructions and guidelines WEB WATCH Amateur scientists help out researchers with a variety of online projects

  5. Dispersal of forest insects

    Science.gov (United States)

    Mcmanus, M. L.

    1979-01-01

    Dispersal flights of selected species of forest insects which are associated with periodic outbreaks of pests that occur over large contiguous forested areas are discussed. Gypsy moths, spruce budworms, and forest tent caterpillars were studied for their massive migrations in forested areas. Results indicate that large dispersals into forested areas are due to the females, except in the case of the gypsy moth.

  6. Improved new generation dispersants

    International Nuclear Information System (INIS)

    Anon.

    1993-01-01

    The use of dispersants to combat oil spills has attracted controversy over the years, and there has been a number of accusations of the chemicals involved doing more harm than good. A new study by the International Petroleum Industry Environmental Conservation Association discusses the positive and the negatives of dispersant use to be considered when drawing up spill contingency plans. (author)

  7. Seed dispersal in fens

    Science.gov (United States)

    Middleton, B.; Van Diggelen, R.; Jensen, K.

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and reducing genetic exchange. Species in fragmented wetlands may have lower reproductive success, which can lead to biodiversity loss. While fens may have always been relatively isolated from each other, they have become increasingly fragmented in modern times within agricultural and urban landscapes in both Europe and North America. Dispersal by water, animals and wind has been hampered by changes related to development in landscapes surrounding fens. Because the seeds of certain species are long-lived in the seed bank, frequent episodes of dispersal are not always necessary to maintain the biodiversity of fens. However, of particular concern to restoration is that some dominant species, such as the tussock sedge Carex stricta, may not disperse readily between fens. Conclusions: Knowledge of seed dispersal can be used to maintain and restore the biodiversity of fens in fragmented landscapes. Given that development has fragmented landscapes and that this situation is not likely to change, the dispersal of seeds might be enhanced by moving hay or cattle from fens to damaged sites, or by reestablishing lost hydrological connections. ?? IAVS; Opulus Press.

  8. Dispersal and metapopulation stability

    Directory of Open Access Journals (Sweden)

    Shaopeng Wang

    2015-10-01

    Full Text Available Metapopulation dynamics are jointly regulated by local and spatial factors. These factors may affect the dynamics of local populations and of the entire metapopulation differently. Previous studies have shown that dispersal can stabilize local populations; however, as dispersal also tends to increase spatial synchrony, its net effect on metapopulation stability has been controversial. Here we present a simple metapopulation model to study how dispersal, in interaction with other spatial and local processes, affects the temporal variability of metapopulations in a stochastic environment. Our results show that in homogeneous metapopulations, the local stabilizing and spatial synchronizing effects of dispersal cancel each other out, such that dispersal has no effect on metapopulation variability. This result is robust to moderate heterogeneities in local and spatial parameters. When local and spatial dynamics exhibit high heterogeneities, however, dispersal can either stabilize or destabilize metapopulation dynamics through various mechanisms. Our findings have important theoretical and practical implications. We show that dispersal functions as a form of spatial intraspecific mutualism in metapopulation dynamics and that its effect on metapopulation stability is opposite to that of interspecific competition on local community stability. Our results also suggest that conservation corridors should be designed with appreciation of spatial heterogeneities in population dynamics in order to maximize metapopulation stability.

  9. A costal dispersion model

    International Nuclear Information System (INIS)

    Rahm, L.; Nyberg, L.; Gidhagen, L.

    1990-01-01

    A dispersion model to be used off costal waters has been developed. The model has been applied to describe the migration of radionuclides in the Baltic sea. A summary of the results is presented here. (K.A.E)

  10. Wave-equation dispersion inversion

    KAUST Repository

    Li, Jing; Feng, Zongcai; Schuster, Gerard T.

    2016-01-01

    We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained

  11. Reactimeter dispersion equation

    OpenAIRE

    A.G. Yuferov

    2016-01-01

    The aim of this work is to derive and analyze a reactimeter metrological model in the form of the dispersion equation which connects reactimeter input/output signal dispersions with superimposed random noise at the inlet. It is proposed to standardize the reactimeter equation form, presenting the main reactimeter computing unit by a convolution equation. Hence, the reactimeter metrological characteristics are completely determined by this unit hardware function which represents a transient re...

  12. Fickian dispersion is anomalous

    Science.gov (United States)

    Cushman, John H.; O'Malley, Dan

    2015-12-01

    The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion we illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.

  13. Coping with power dispersion?

    DEFF Research Database (Denmark)

    2014-01-01

    The last decades have witnessed a significant shift in policy competences away from central governments in Europe. The reallocation of competences spans over three dimensions: upwards; sideways; and downwards. This collection takes the dispersion of powers as a starting point and seeks to assess...... how the actors involved cope with the new configurations. In this introduction, we discuss the conceptualization of power dispersion and highlight the ways in which the contributions add to this research agenda. We then outline some general conclusions and end by indicating future avenues of research....... Taken together, the collection contributes some answers to the challenge of defining and measuring – in a comparative way – the control and co-ordination mechanisms which power dispersion generates. It also explores the tension between political actors' quest for autonomy and the acknowledgement...

  14. Interface, a dispersed architecture

    NARCIS (Netherlands)

    Vissers, C.A.

    1976-01-01

    Past and current specification techniques use timing diagrams and written text to describe the phenomenology of an interface. This paper treats an interface as the architecture of a number of processes, which are dispersed over the related system parts and the message path. This approach yields a

  15. Psychorheology of food dispersions

    Czech Academy of Sciences Publication Activity Database

    Štern, Petr; Panovská, Z.; Pokorný, J.

    2010-01-01

    Roč. 58, č. 1 (2010), s. 29-35 ISSN 0042-790X R&D Projects: GA AV ČR IAA2060404 Institutional research plan: CEZ:AV0Z20600510 Keywords : psychorheology * food dispersions * tomato ketchup * rheology * sensory analysis Subject RIV: BK - Fluid Dynamics Impact factor: 0.553, year: 2010

  16. Dispersal of sticky particles

    Science.gov (United States)

    Reddy, Ramana; Kumar, Sanjeev

    2007-12-01

    In this paper, we show through simulations that when sticky particles are broken continually, particles are dispersed into fine dust only if they are present in a narrow range of volume fractions. The upper limit of this range is 0.20 in the 2D and 0.10 in the 3D space. An increase in the dimensionality of space reduces the upper limit nearly by a factor of two. This scaling holds for dispersal of particles in hyperdimensional space of dimensions up to ten, the maximum dimension studied in this work. The maximum values of volume fractions obtained are significantly lower than those required for close packing and random packing of discs in 2D and spheres in 3D space. These values are also smaller than those required for critical phenomena of cluster percolation. The results obtained are attributed to merger cascades of sticky particles, triggered by breakup events. A simple theory that incorporates this cascade is developed to quantitatively explain the observed scaling of the upper limit with the dimensionality of space. The theory also captures the dynamics of the dispersal process in the corresponding range of particle volume fractions. The theory suggests that cascades of order one and two predominantly decide the upper limit for complete dispersal of particles.

  17. Dispersed flow film boiling

    International Nuclear Information System (INIS)

    Andreani, M.; Yadigaroglu, G.

    1989-12-01

    Dispersed flow film boiling is the heat transfer regime that occurs at high void fractions in a heated channel. The way this transfer mode is modelled in the NRC computer codes (RELAP5 and TRAC) and the validity of the assumption and empirical correlations used is discussed. An extensive review of the theoretical and experimental work related with heat transfer to highly dispersed mixtures reveals the basic deficiencies of these models: the investigation refers mostly to the typical conditions of low rate bottom reflooding, since the simulation of this physical situation by the computer codes has often showed poor results. The alternative models that are available in the literature are reviewed, and their merits and limits are highlighted. The modification that could improve the physics of the models implemented in the codes are identified. (author) 13 figs., 123 refs

  18. Working document dispersion models

    International Nuclear Information System (INIS)

    Dop, H. van

    1988-01-01

    This report is a summary of the most important results from June 1985 of the collaboration of the RIVM (Dutch National Institute for Public Health and Environment Hygiene) and KNMI (Royal Dutch Meteorologic Institute) on the domain of dispersion models. It contains a short description of the actual SO x /NO x -model. Furthermore it contains recommendations for modifications of some numerical-mathematical aspects and an impulse to a more complete description of chemical processes in the atmosphere and the (wet) deposition process. A separate chapter is devoted to the preparation of meteorologic data which are relevant for dispersion as well as atmospheric chemistry and deposition. This report serves as working document for the final formulation of a acidifying- and oxidant-model. (H.W.). 69 refs.; 51 figs.; 13 tabs.; 3 schemes

  19. Spatially Dispersed Employee Recovery

    DEFF Research Database (Denmark)

    Hvass, Kristian Anders; Torfadóttir, Embla

    2014-01-01

    Employee recovery addresses either employee well-being or management's practices in aiding employees in recovering themselves following a service failure. This paper surveys the cabin crew at a small, European, low-cost carrier and investigates employees' perceptions of management practices to aid...... personnel achieve service recovery. Employee recovery within service research often focuses on front-line employees that work in a fixed location, however a contribution to the field is made by investigating the recovery of spatially dispersed personnel, such as operational personnel in the transport sector......, who have a work place away from a fixed or central location and have minimal management contact. Results suggest that the support employees receive from management, such as recognition, information sharing, training, and strategic awareness are all important for spatially dispersed front...

  20. Heat dispersion in rivers

    International Nuclear Information System (INIS)

    Shaw, T.L.

    1974-01-01

    One of the tasks of the Sonderforschungsbereich 80 is to study the dispersion of heat discharged into rivers and other bodies of water and to develop methods which permit prediction of detrimental effects caused by the heated discharges. In order to help the SFB 80 to specify this task, Dr. Shaw, lecturer of Civil Engineering at the Bristol University, conducted a literature survey on heat-dispersion studies during the two months which he spent as a visiting research fellow with the SFB 80 at the University of Karlsruhe in the summer of 1973. The following report is the outcome of this survey. It gives Dr. Shaw's assessment of the present state of knowledge - based almost exclusively on literature in the English language - and compares this with the knowledge required by river planners. The apparent discrepancy leads to suggestions for future research. Selected references as well as a representative bibliography can be found at the end of the report. (orig.) [de

  1. Taylor dispersion of nanoparticles

    Science.gov (United States)

    Balog, Sandor; Urban, Dominic A.; Milosevic, Ana M.; Crippa, Federica; Rothen-Rutishauser, Barbara; Petri-Fink, Alke

    2017-08-01

    The ability to detect and accurately characterize particles is required by many fields of nanotechnology, including materials science, nanotoxicology, and nanomedicine. Among the most relevant physicochemical properties of nanoparticles, size and the related surface-to-volume ratio are fundamental ones. Taylor dispersion combines three independent phenomena to determine particle size: optical extinction, translational diffusion, and sheer-enhanced dispersion of nanoparticles subjected to a steady laminar flow. The interplay of these defines the apparent size. Considering that particles in fact are never truly uniform nor monodisperse, we rigorously address particle polydispersity and calculate the apparent particle size measured by Taylor dispersion analysis. We conducted case studies addressing aqueous suspensions of model particles and large-scale-produced "industrial" particles of both academic and commercial interest of various core materials and sizes, ranging from 15 to 100 nm. A comparison with particle sizes determined by transmission electron microscopy confirms that our approach is model-independent, non-parametric, and of general validity that provides an accurate account of size polydispersity—independently on the shape of the size distribution and without any assumption required a priori.

  2. Nozzle for electric dispersion reactor

    Science.gov (United States)

    Sisson, W.G.; Basaran, O.A.; Harris, M.T.

    1995-11-07

    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. 4 figs.

  3. Tracer dispersion - experiment and CFD

    International Nuclear Information System (INIS)

    Zitny, R.

    2004-01-01

    Description of tracer distribution by means of dispersion models is a method successfully used in process engineering for fifty years. Application of dispersion models in reactor engineering for characterization of flows in column apparatus, heat exchangers, etc. is summarized and experimental tracer techniques as well as CFD methods for dispersion coefficients evaluation are discussed. Possible extensions of thermal axial dispersion model (ADM) and a core-wall ADM model suitable for description of tracer dispersion in laminar flows are suggested as well as CFD implementation as 1D finite elements. (author)

  4. High density dispersion fuel

    International Nuclear Information System (INIS)

    Hofman, G.L.

    1996-01-01

    A fuel development campaign that results in an aluminum plate-type fuel of unlimited LEU burnup capability with an uranium loading of 9 grams per cm 3 of meat should be considered an unqualified success. The current worldwide approved and accepted highest loading is 4.8 g cm -3 with U 3 Si 2 as fuel. High-density uranium compounds offer no real density advantage over U 3 Si 2 and have less desirable fabrication and performance characteristics as well. Of the higher-density compounds, U 3 Si has approximately a 30% higher uranium density but the density of the U 6 X compounds would yield the factor 1.5 needed to achieve 9 g cm -3 uranium loading. Unfortunately, irradiation tests proved these peritectic compounds have poor swelling behavior. It is for this reason that the authors are turning to uranium alloys. The reason pure uranium was not seriously considered as a dispersion fuel is mainly due to its high rate of growth and swelling at low temperatures. This problem was solved at least for relatively low burnup application in non-dispersion fuel elements with small additions of Si, Fe, and Al. This so called adjusted uranium has nearly the same density as pure α-uranium and it seems prudent to reconsider this alloy as a dispersant. Further modifications of uranium metal to achieve higher burnup swelling stability involve stabilization of the cubic γ phase at low temperatures where normally α phase exists. Several low neutron capture cross section elements such as Zr, Nb, Ti and Mo accomplish this in various degrees. The challenge is to produce a suitable form of fuel powder and develop a plate fabrication procedure, as well as obtain high burnup capability through irradiation testing

  5. Spurious dispersion effects at FLASH

    International Nuclear Information System (INIS)

    Prat, Eduard

    2009-07-01

    The performance of the Free-Electron Laser (FEL) process imposes stringent demands on the transverse trajectory and size of the electron beam. Since transverse dispersion changes off-energy particle trajectories and increases the effective beam size, dispersion must be controlled. This thesis treats the concept of dispersion in linacs, and analyses the impact of dispersion on the electron beam and on the FEL process. It presents generation mechanisms for spurious dispersion, quantifying its importance for FLASH (Free-electron Laser in Hamburg) and the XFEL (European X-ray Free-Electron Laser). A method for measuring and correcting dispersion and its implementation in FLASH is described. Experiments of dispersion e ects on the transverse beam quality and on the FEL performance are presented. (orig.)

  6. Spurious dispersion effects at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Prat, Eduard

    2009-07-15

    The performance of the Free-Electron Laser (FEL) process imposes stringent demands on the transverse trajectory and size of the electron beam. Since transverse dispersion changes off-energy particle trajectories and increases the effective beam size, dispersion must be controlled. This thesis treats the concept of dispersion in linacs, and analyses the impact of dispersion on the electron beam and on the FEL process. It presents generation mechanisms for spurious dispersion, quantifying its importance for FLASH (Free-electron Laser in Hamburg) and the XFEL (European X-ray Free-Electron Laser). A method for measuring and correcting dispersion and its implementation in FLASH is described. Experiments of dispersion e ects on the transverse beam quality and on the FEL performance are presented. (orig.)

  7. Dispersion stability of thermal nanofluids

    Directory of Open Access Journals (Sweden)

    Fan Yu

    2017-10-01

    Full Text Available Thermal nanofluids, the engineered fluids with dispersed functional nanoparticles, have exhibited extraordinary thermophysical properties and added functionalities, and thus have enabled a broad range of important applications. The poor dispersion stability of thermal nanofluids, however, has been considered as a long-existing issue that limits their further development and practical application. This review overviews the recent efforts and progresses in improving the dispersion stability of thermal nanofluids such as mechanistic understanding of dispersion behavior of nanofluids, examples of both water-based and oil-based nanofluids, strategies to stabilize nanofluids, and characterization techniques for dispersion behavior of nanofluids. Finally, on-going research needs, and possible solutions to research challenges and future research directions in exploring stably dispersed thermal nanofluids are discussed. Keywords: Thermal nanofluids, Dispersion, Aggregation, Electrostatic stabilization, Steric stabilization

  8. Phonon dispersion in vanadium

    International Nuclear Information System (INIS)

    Ivanov, A.S.; Rumiantsev, A.Yu.

    1999-01-01

    Complete text of publication follows. Phonon dispersion curves in Vanadium metal are investigated by neutron inelastic scattering using three-axis spectrometers. Due to extremely low coherent scattering amplitude of neutrons in natural isotope mixture of vanadium the phonon frequencies could be determined in the energy range below about 15 meV. Several phonon groups were measured with the polarised neutron scattering set-up. It is demonstrated that the intensity of coherent inelastic scattering observed in the non-spin-flip channel vanishes in the spin-flip channel. The phonon density of states is measured on a single crystal keeping the momentum transfer equal to a vector of reciprocal lattice where the coherent inelastic scattering is suppressed. Phonon dispersion curves in vanadium, as measured by neutron and earlier by X-ray scattering, are described in frames of a charge-fluctuation model involving monopolar and dipolar degrees of freedom. The model parameters are compared for different transition metals with body-centred cubic-structure. (author)

  9. Dispersion and current measurements

    International Nuclear Information System (INIS)

    Boelskifte, S.

    1986-04-01

    A model for the simulation of particle movements in water should incorporate the mutual distance dependent correlation. As long as reliable data are given accessible a model can be created of the dispersion in a given area from a statistical description of turbulence. Current measurements have been performed in an area north of the Swedish nuclear power plant Barsebaeck, and statistical time series analysis have made it possible to estimate multivariate autoregressive moving-average (ARMA) models for these data using the Box-Jenkins method. The correlation structure for the area has been investigated in detail. Transport and dispersion models for the marine environment are used in estimating doses to the population from the aquatic food chain. Some of these models are described with special emphasis on the time and length scales they cover. Furthermore, to illustrate the background of the simulation model, short introductuions are given to health physics, time series analysis, and turbulence theory. Analysis of the simulation model shows the relative importance of the different parameters. The model can be expanded to conditional simulation, where the current measurements are used directly to simulate the movement of one of the particles. Results from the model are also compared to results from a sampling of bioindicators (Fucus vesiculosus) along the Danish coast. The reliability of bioindicators in this kind of experiment is discussed. (author)

  10. Quantum optical rotatory dispersion

    Science.gov (United States)

    Tischler, Nora; Krenn, Mario; Fickler, Robert; Vidal, Xavier; Zeilinger, Anton; Molina-Terriza, Gabriel

    2016-01-01

    The phenomenon of molecular optical activity manifests itself as the rotation of the plane of linear polarization when light passes through chiral media. Measurements of optical activity and its wavelength dependence, that is, optical rotatory dispersion, can reveal information about intricate properties of molecules, such as the three-dimensional arrangement of atoms comprising a molecule. Given a limited probe power, quantum metrology offers the possibility of outperforming classical measurements. This has particular appeal when samples may be damaged by high power, which is a potential concern for chiroptical studies. We present the first experiment in which multiwavelength polarization-entangled photon pairs are used to measure the optical activity and optical rotatory dispersion exhibited by a solution of chiral molecules. Our work paves the way for quantum-enhanced measurements of chirality, with potential applications in chemistry, biology, materials science, and the pharmaceutical industry. The scheme that we use for probing wavelength dependence not only allows one to surpass the information extracted per photon in a classical measurement but also can be used for more general differential measurements. PMID:27713928

  11. Metapopulation extinction risk: dispersal's duplicity.

    Science.gov (United States)

    Higgins, Kevin

    2009-09-01

    Metapopulation extinction risk is the probability that all local populations are simultaneously extinct during a fixed time frame. Dispersal may reduce a metapopulation's extinction risk by raising its average per-capita growth rate. By contrast, dispersal may raise a metapopulation's extinction risk by reducing its average population density. Which effect prevails is controlled by habitat fragmentation. Dispersal in mildly fragmented habitat reduces a metapopulation's extinction risk by raising its average per-capita growth rate without causing any appreciable drop in its average population density. By contrast, dispersal in severely fragmented habitat raises a metapopulation's extinction risk because the rise in its average per-capita growth rate is more than offset by the decline in its average population density. The metapopulation model used here shows several other interesting phenomena. Dispersal in sufficiently fragmented habitat reduces a metapopulation's extinction risk to that of a constant environment. Dispersal between habitat fragments reduces a metapopulation's extinction risk insofar as local environments are asynchronous. Grouped dispersal raises the effective habitat fragmentation level. Dispersal search barriers raise metapopulation extinction risk. Nonuniform dispersal may reduce the effective fraction of suitable habitat fragments below the extinction threshold. Nonuniform dispersal may make demographic stochasticity a more potent metapopulation extinction force than environmental stochasticity.

  12. Relativistic plasma dispersion functions

    International Nuclear Information System (INIS)

    Robinson, P.A.

    1986-01-01

    The known properties of plasma dispersion functions (PDF's) for waves in weakly relativistic, magnetized, thermal plasmas are reviewed and a large number of new results are presented. The PDF's required for the description of waves with small wave number perpendicular to the magnetic field (Dnestrovskii and Shkarofsky functions) are considered in detail; these functions also arise in certain quantum electrodynamical calculations involving strongly magnetized plasmas. Series, asymptotic series, recursion relations, integral forms, derivatives, differential equations, and approximations for these functions are discussed as are their analytic properties and connections with standard transcendental functions. In addition a more general class of PDF's relevant to waves of arbitrary perpendicular wave number is introduced and a range of properties of these functions are derived

  13. Statistical Thermodynamics of Disperse Systems

    DEFF Research Database (Denmark)

    Shapiro, Alexander

    1996-01-01

    Principles of statistical physics are applied for the description of thermodynamic equilibrium in disperse systems. The cells of disperse systems are shown to possess a number of non-standard thermodynamic parameters. A random distribution of these parameters in the system is determined....... On the basis of this distribution, it is established that the disperse system has an additional degree of freedom called the macro-entropy. A large set of bounded ideal disperse systems allows exact evaluation of thermodynamic characteristics. The theory developed is applied to the description of equilibrium...

  14. Geometry of physical dispersion relations

    International Nuclear Information System (INIS)

    Raetzel, Dennis; Rivera, Sergio; Schuller, Frederic P.

    2011-01-01

    To serve as a dispersion relation, a cotangent bundle function must satisfy three simple algebraic properties. These conditions are derived from the inescapable physical requirements that local matter field dynamics must be predictive and allow for an observer-independent notion of positive energy. Possible modifications of the standard relativistic dispersion relation are thereby severely restricted. For instance, the dispersion relations associated with popular deformations of Maxwell theory by Gambini-Pullin or Myers-Pospelov are not admissible. Dispersion relations passing the simple algebraic checks derived here correspond to physically admissible Finslerian refinements of Lorentzian geometry.

  15. Dispersion bias, dispersion effect, and the aerosol-cloud conundrum

    International Nuclear Information System (INIS)

    Liu Yangang; Daum, Peter H; Guo Huan; Peng Yiran

    2008-01-01

    This work examines the influences of relative dispersion (the ratio of the standard deviation to the mean radius of the cloud droplet size distribution) on cloud albedo and cloud radiative forcing, derives an analytical formulation that accounts explicitly for the contribution from droplet concentration and relative dispersion, and presents a new approach to parameterize relative dispersion in climate models. It is shown that inadequate representation of relative dispersion in climate models leads to an overestimation of cloud albedo, resulting in a negative bias of global mean shortwave cloud radiative forcing that can be comparable to the warming caused by doubling CO 2 in magnitude, and that this dispersion bias is likely near its maximum for ambient clouds. Relative dispersion is empirically expressed as a function of the quotient between cloud liquid water content and droplet concentration (i.e., water per droplet), yielding an analytical formulation for the first aerosol indirect effect. Further analysis of the new expression reveals that the dispersion effect not only offsets the cooling from the Twomey effect, but is also proportional to the Twomey effect in magnitude. These results suggest that unrealistic representation of relative dispersion in cloud parameterization in general, and evaluation of aerosol indirect effects in particular, is at least in part responsible for several outstanding puzzles of the aerosol-cloud conundrum: for example, overestimation of cloud radiative cooling by climate models compared to satellite observations; large uncertainty and discrepancy in estimates of the aerosol indirect effect; and the lack of interhemispheric difference in cloud albedo.

  16. Auroral electron time dispersion

    International Nuclear Information System (INIS)

    Kletzing, C.A.

    1989-01-01

    A sounding rocket flight was launched from Greenland in 1985 to study high latitude, early morning auroral physics. The payload was instrumented with electron and ion detectors, AC and DC electric field experiments, a plasma density experiment, and a magnetometer to measure the ambient field. The rocket was launched during disturbed conditions, when the polar cap was in a contracted state with visible aurora overhead. The electron data contained numerous signatures indicative of time-of-flight energy dispersion characterized by a coherent structure in which lower energy electrons arrived at the rocket after higher energy electrons. A model was constructed to explain this phenomena by the sudden application of a region of parallel electric field along a length of magnetic field line above the rocket. The model incorporates detector response and uses an altitudinal density profile based on auroral zone measurements. Three types of potential structures were tried: linear, quadratic and cubic. Of the three it was found that the cubic (electric field growing in a quadratic manner moving up the field line) produced the best fit to the data. The potential region was found to be approximately 1-2 R e in extent with the lower edge 3000-4000 km away from the rocket. The background electron temperature in the model which produced the best fit to the data was of the order of 15 eV

  17. Dispersal and migration

    Directory of Open Access Journals (Sweden)

    Schwarz, C.

    2004-06-01

    Full Text Available Ringing of birds unveiled many aspects of avian migration and dispersal movements. However, there is even much more to be explored by the use of ringing and other marks. Dispersal is crucial in understanding the initial phase of migration in migrating birds as it is to understand patterns and processes of distribution and gene flow. So far, the analysis of migration was largely based on analysing spatial and temporal patters of recoveries of ringed birds. However, there are considerable biases and pitfalls in using recoveries due to spatial and temporal variation in reporting probabilities. Novel methods are required for future studies separating the confounding effects of spatial and temporal heterogeneity of recovery data and heterogeneity of the landscape as well. These novel approaches should aim a more intensive and novel use of the existing recovery data by taking advantage of, for instance, dynamic and multistate modeling, should elaborate schemes for future studies, and should also include other marks that allow a more rapid data collection, like telemetry, geolocation and global positioning systems, and chemical and molecular markers. The latter appear to be very useful in the delineating origin of birds and connectivity between breeding and non–breeding grounds. Many studies of migration are purely descriptive. However, King and Brooks (King & Brooks, 2004 examine if movement patterns of dolphins change after the introduction of a gillnet ban. Bayesian methods are an interesting approach to this problem as they provide a meaningful measure of the probability that such a change occurred rather than simple yes/no response that is often the result of classical statistical methods. However, the key difficulty of a general implementation of Bayesian methods is the complexity of the modelling —there is no general userfriendly package that is easily accessible to most scientists. Drake and Alisauskas (Drake & Alisauskas, 2004 examine the

  18. 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 con...

  19. Nest-mediated seed dispersal

    Science.gov (United States)

    Robert J. Warren; Jason P. Love; Mark A. Bradford

    2017-01-01

    Many plant seeds travel on the wind and through animal ingestion or adhesion; however, an overlooked dispersal mode may lurk within those dispersal modes. Viable seeds may remain attached or embedded within materials birds gather for nest building. Our objective was to determine if birds inadvertently transport seeds when they forage for plant materials to...

  20. Definition of global dispersion coefficients

    International Nuclear Information System (INIS)

    Naff, R.L.

    1983-10-01

    For estimation of a global longitudinal dispersivity at the Gorleben site, data available primarily consist of suites of geophysical logs from wells penetrating the Quaternary aquifer. A length scale for the principle aquifer at Gorleben is to be found. Samples are to be taken separately to estimate the variance in hydraulic conductivity (Taylor Analysis, Fickian dispersion process). (DG)

  1. Wave-equation dispersion inversion

    KAUST Repository

    Li, Jing

    2016-12-08

    We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained from Rayleigh waves recorded by vertical-component geophones. Similar to wave-equation traveltime tomography, the complicated surface wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the phase-velocity and frequency domains. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2-D or 3-D S-wave velocity models. This procedure, denoted as wave-equation dispersion inversion (WD), does not require the assumption of a layered model and is significantly less prone to the cycle-skipping problems of full waveform inversion. The synthetic and field data examples demonstrate that WD can approximately reconstruct the S-wave velocity distributions in laterally heterogeneous media if the dispersion curves can be identified and picked. The WD method is easily extended to anisotropic data and the inversion of dispersion curves associated with Love waves.

  2. Dispersion Decay and Scattering Theory

    CERN Document Server

    Komech, Alexander

    2012-01-01

    A simplified, yet rigorous treatment of scattering theory methods and their applications Dispersion Decay and Scattering Theory provides thorough, easy-to-understand guidance on the application of scattering theory methods to modern problems in mathematics, quantum physics, and mathematical physics. Introducing spectral methods with applications to dispersion time-decay and scattering theory, this book presents, for the first time, the Agmon-Jensen-Kato spectral theory for the Schr?dinger equation, extending the theory to the Klein-Gordon equation. The dispersion decay plays a crucial role i

  3. Velocity Dispersions Across Bulge Types

    International Nuclear Information System (INIS)

    Fabricius, Maximilian; Bender, Ralf; Hopp, Ulrich; Saglia, Roberto; Drory, Niv; Fisher, David

    2010-01-01

    We present first results from a long-slit spectroscopic survey of bulge kinematics in local spiral galaxies. Our optical spectra were obtained at the Hobby-Eberly Telescope with the LRS spectrograph and have a velocity resolution of 45 km/s (σ*), which allows us to resolve the velocity dispersions in the bulge regions of most objects in our sample. We find that the velocity dispersion profiles in morphological classical bulge galaxies are always centrally peaked while the velocity dispersion of morphologically disk-like bulges stays relatively flat towards the center--once strongly barred galaxies are discarded.

  4. What Causes Animals to Disperse?

    Indian Academy of Sciences (India)

    research involving animal behaviour and ecology for a very long time. ... shall examine two different types of dispersals that occur, try to understand the ... finally look at some practical methods through which the phe- ..... further qualitative or.

  5. Birefringent dispersive FDTD subgridding scheme

    OpenAIRE

    De Deckere, B; Van Londersele, Arne; De Zutter, Daniël; Vande Ginste, Dries

    2016-01-01

    A novel 2D finite difference time domain (FDTD) subgridding method is proposed, only subject to the Courant limit of the coarse grid. By making mu or epsilon inside the subgrid dispersive, unconditional stability is induced at the cost of a sparse, implicit set of update equations. By only adding dispersion along preferential directions, it is possible to dramatically reduce the rank of the matrix equation that needs to be solved.

  6. Dispersion engineering for integrated nanophotonics

    CERN Document Server

    Vanbésien, Olivier

    2014-01-01

    This book shows how dispersion engineering in two dimensional dielectric photonic crystals can provide new effects for the precise control of light propagation for integrated nanophotonics.Dispersion engineering in regular and graded photonic crystals to promote anomalous refraction effects is studied from the concepts to experimental demonstration via nanofabrication considerations. Self collimation, ultra and negative refraction, second harmonic generation, mirage and invisibility effects which lead to an unprecedented control of light propagation at the (sub-)wavelength scale for the

  7. Dispersion coefficients for coastal regions

    International Nuclear Information System (INIS)

    MacRae, B.L.; Kaleel, R.J.; Shearer, D.L.

    1983-03-01

    The Nuclear Regulatory Commission (NRC) has undertaken an extensive atmospheric dispersion research and measurement program from which it is intended will emerge improved predictive techniques for employment in licensing decisions and for emergency planning and response. Through this program the NRC has conducted field measurement programs over a wide range of geographic and topographic locations, and are using the acquired tracer and meteorological measurements to evaluate existing dispersion models and prediction techniques, and to develop new techniques when necessary

  8. Atmospheric dispersion of radioactive materials

    International Nuclear Information System (INIS)

    Chino, Masamichi

    1988-01-01

    The report describes currently available techniques for predicting the dispersion of accidentally released radioactive materials and techniques for visualization using computer graphics. A simulation study is also made on the dispersion of radioactive materials released from the Chernobyl plant. The simplest models include the Gauss plume model and the puff model, which cannot serve to analyze the effects of the topography, vertical wind shear, temperature inversion layer, etc. Numerical analysis methods using advection and dispersion equations are widely adopted for detailed evaluation of dispersion in an emergency. An objective analysis model or a hydrodynamical model is often used to calculate the air currents which are required to determine the advection. A small system based on the puff model is widely adopted in Europe, where the topography is considered to have only simple effects. A more sophisticated large-sized system is required in nuclear facilities located in an area with more complex topographic features. An emergency system for dispersion calculation should be equipped with a graphic display to serve for quick understanding of the radioactivity distribution. (Nogami, K.)

  9. Micromixer based on Taylor dispersion

    International Nuclear Information System (INIS)

    Yang, H; Nguyen, N-T; Huang, X

    2006-01-01

    This paper reports an analytical model, the fabrication and the characterization of a polymeric micromixer based on Taylor dispersion. Due to the distributed velocity field over the channel cross section, the effective dispersion in axial direction in a microchannel is much stronger than the pure molecular diffusion. In our work, squential segmentation was used in the micromixer for improving mixing in a microchannel. The micromixer was designed and fabricated based on lamination of five 100-μm-thick polymer sheets. Rubber valve seats were embedded between the forth and the fifth layers. The polymer layers were machined using a CO 2 laser. The lamination of the five layers was carried out by a commercial hot laminator (Aurora LM-450HC). External solenoid actuators are used for closing the valves at the mixer inlets. The experimental results confirm the effect of Taylor dispersion. Mixing ratio can be adjusted by pulse width modulation of the control signal of the solenoids

  10. Improving IUE High Dispersion Extraction

    Science.gov (United States)

    Lawton, Patricia J.; VanSteenberg, M. E.; Massa, D.

    2007-01-01

    We present a different method to extract high dispersion International Ultraviolet Explorer (IUE) spectra from the New Spectral Image Processing System (NEWSIPS) geometrically and photometrically corrected (SI HI) images of the echellogram. The new algorithm corrects many of the deficiencies that exist in the NEWSIPS high dispersion (SIHI) spectra . Specifically, it does a much better job of accounting for the overlap of the higher echelle orders, it eliminates a significant time dependency in the extracted spectra (which can be traced to the background model used in the NEWSIPS extractions), and it can extract spectra from echellogram images that are more highly distorted than the NEWSIPS extraction routines can handle. Together, these improvements yield a set of IUE high dispersion spectra whose scientific integrity is sign ificantly better than the NEWSIPS products. This work has been supported by NASA ADP grants.

  11. STELLAR MASS DEPENDENT DISK DISPERSAL

    International Nuclear Information System (INIS)

    Kennedy, Grant M.; Kenyon, Scott J.

    2009-01-01

    We use published optical spectral and infrared (IR) excess data from nine young clusters and associations to study the stellar mass dependent dispersal of circumstellar disks. All clusters older than ∼3 Myr show a decrease in disk fraction with increasing stellar mass for solar to higher mass stars. This result is significant at about the 1σ level in each cluster. For the complete set of clusters we reject the null hypothesis-that solar and intermediate-mass stars lose their disks at the same rate-with 95%-99.9% confidence. To interpret this behavior, we investigate the impact of grain growth, binary companions, and photoevaporation on the evolution of disk signatures. Changes in grain growth timescales at fixed disk temperature may explain why early-type stars with IR excesses appear to evolve faster than their later-type counterparts. Little evidence that binary companions affect disk evolution suggests that photoevaporation is the more likely mechanism for disk dispersal. A simple photoevaporation model provides a good fit to the observed disk fractions for solar and intermediate-mass stars. Although the current mass-dependent disk dispersal signal is not strong, larger and more complete samples of clusters with ages of 3-5 Myr can improve the significance and provide better tests of theoretical models. In addition, the orbits of extra-solar planets can constrain models of disk dispersal and migration. We suggest that the signature of stellar mass dependent disk dispersal due to photoevaporation may be present in the orbits of observed extra-solar planets. Planets orbiting hosts more massive than ∼1.6 M sun may have larger orbits because the disks in which they formed were dispersed before they could migrate.

  12. Dispersion of multi-walled carbon nanotubes in biocompatible dispersants

    International Nuclear Information System (INIS)

    Piret, J.-P.; Detriche, S.; Vigneron, R.; Vankoningsloo, S.; Rolin, S.; Mejia Mendoza, J. H.; Masereel, B.; Lucas, S.; Delhalle, J.; Luizi, F.; Saout, C.; Toussaint, O.

    2010-01-01

    Owing to their phenomenal electrical and mechanical properties, carbon nanotubes (CNT) have been an area of intense research since their discovery in 1991. Different applications for these nanoparticles have been proposed, among others, in electronics and optics but also in the medical field. In parallel, emerging studies have suggested potential toxic effects of CNT while others did not, generating some conflicting outcomes. These discrepancies could be, in part, due to different suspension approaches used and to the agglomeration state of CNT in solution. In this study, we described a standardized protocol to obtain stable CNT suspensions, using two biocompatible dispersants (Pluronic F108 and hydroxypropylcellulose) and to estimate the concentration of CNT in solution. CNT appear to be greatly individualized in these two dispersants with no detection of remaining bundles or agglomerates after sonication and centrifugation. Moreover, CNT remained perfectly dispersed when added to culture medium used for in vitro cell experiments. We also showed that Pluronic F108 is a better dispersant than hydroxypropylcellulose. In conclusion, we have developed a standardized protocol using biocompatible surfactants to obtain reproducible and stable multi-walled carbon nanotubes suspensions which can be used for in vitro or in vivo toxicological studies.

  13. DIMO, a plant dispersal model

    NARCIS (Netherlands)

    Wamelink, G.W.W.; Jochem, R.; Greft, van der J.G.M.; Franke, J.; Malinowska, A.H.; Geertsema, W.; Prins, A.H.; Ozinga, W.A.; Hoek, van der D.C.J.; Grashof-Bokdam, C.J.

    2014-01-01

    Due to human activities many natural habitats have become isolated. As a result the dispersal of many plant species is hampered. Isolated populations may become extinct and have a lower probability to become reestablished in a natural way. Moreover, plant species may be forced to migrate to new

  14. A generalized advection dispersion equation

    Indian Academy of Sciences (India)

    This paper examines a possible effect of uncertainties, variability or heterogeneity of any dynamic system when being included in its evolution rule; the notion is illustrated with the advection dispersion equation, which describes the groundwater pollution model. An uncertain derivative is defined; some properties of.

  15. Ability Dispersion and Team Performance

    DEFF Research Database (Denmark)

    Hoogendoorn, Sander; Parker, Simon C.; Van Praag, Mirjam

    What is the effect of dispersed levels of cognitive ability of members of a (business) team on their team's performance? This paper reports the results of a field experiment in which 573 students in 49 teams start up and manage real companies under identical circumstances. We ensured exogenous va...

  16. Statistical description of turbulent dispersion

    NARCIS (Netherlands)

    Brouwers, J.J.H.

    2012-01-01

    We derive a comprehensive statistical model for dispersion of passive or almost passive admixture particles such as fine particulate matter, aerosols, smoke and fumes, in turbulent flow. The model rests on the Markov limit for particle velocity. It is in accordance with the asymptotic structure of

  17. Magnetic exciton dispersion in praseodymium

    DEFF Research Database (Denmark)

    Rainford, B. D.; Houmann, Jens Christian Gylden

    1971-01-01

    Measurements of the dispersion of magnetic excitons have been made in a single crystal of praseodymium metal using inelastic neutron scattering. A preliminary analysis of the data yields the first detailed information about the exchange interactions and the crystal field splittings in the light...... rare-earth metals....

  18. On Dispersion in Visual Photoreceptors

    NARCIS (Netherlands)

    Stavenga, D.G.; Barneveld, H.H. van

    1975-01-01

    An idealized visual pigment absorbance spectrum is used together with a Kramers-Kronig dispersion relation to calculate the contribution of the visual pigment to the refractive index of the fly photoreceptor. It appears that an absorption coefficient of 0.010 µm-1 results in a refractive index

  19. Dispersal in Mastomys natalensis mice

    DEFF Research Database (Denmark)

    Van Hooft, Pim; Cosson, J F; Vibe-Petersen, Solveig

    2008-01-01

    Mastomys natalensis is the major pest rodent in sub-Saharan Africa. In this study, population genetic techniques were used to gain new insights into its dispersal behaviour, a critical parameter in pest management. Using 11 microsatellites, 272 individuals from a 300 ha area in Tanzania were geno...

  20. Dispersion modeling by kinematic simulation: Cloud dispersion model

    International Nuclear Information System (INIS)

    Fung, J C H; Perkins, R J

    2008-01-01

    A new technique has been developed to compute mean and fluctuating concentrations in complex turbulent flows (tidal current near a coast and deep ocean). An initial distribution of material is discretized into any small clouds which are advected by a combination of the mean flow and large scale turbulence. The turbulence can be simulated either by kinematic simulation (KS) or direct numerical simulation. The clouds also diffuse relative to their centroids; the statistics for this are obtained from a separate calculation of the growth of individual clouds in small scale turbulence, generated by KS. The ensemble of discrete clouds is periodically re-discretized, to limit the size of the small clouds and prevent overlapping. The model is illustrated with simulations of dispersion in uniform flow, and the results are compared with analytic, steady state solutions. The aim of this study is to understand how pollutants disperses in a turbulent flow through a numerical simulation of fluid particle motion in a random flow field generated by Fourier modes. Although this homogeneous turbulent is rather a 'simple' flow, it represents a building block toward understanding pollutant dispersion in more complex flow. The results presented here are preliminary in nature, but we expect that similar qualitative results should be observed in a genuine turbulent flow.

  1. UV curable aqueous dispersions for wood coatings

    International Nuclear Information System (INIS)

    Peeters, S.; Bleus, J.P.; Wang, Z.J.; Arceneaux, J. A.; Hall, J.

    1999-01-01

    In this paper the characterisation of aqueous dispersions of UV curable resins is described. Two types of dispersions were used: dispersions that are tacky after water evaporation and tack - free before cure dispersions. The physical and rheological properties of these products have been determined and the performance of these dispersions in various formulations, especially for wood applications has been studied. With these dispersions, it is possible to produce coatings having a good cure speed, good surface hardness and good solvent -, chemical - and water resistance

  2. Laser control of natural disperse systems

    Science.gov (United States)

    Vlasova, Olga L.; Bezrukova, Alexandra G.

    2003-10-01

    Different water disperse systems were studied by integral (spectroturbidemetry) and differential light scattering method with a laser as a source of light. The investigation done concerns the state of kaolin dispersions at storage and under dilution as an example of mineral dispersion systems such as natural water. The role of some light scattering parameters for an optical analysis of water dispersions, like the dispersion of erythrocytes and bacterial cells -Escherichia coli is discussed. The results obtained can help to elaborate the methods for on-line optical control fo natural disperse systems (water, air) with mineral and biological particles.

  3. Nanocomposites from Stable Dispersions of Carbon Nanotubes in Polymeric Matrices Using Dispersion Interaction

    Science.gov (United States)

    Wise, Kristopher Eric (Inventor); Park, Cheol (Inventor); Kang, Jin Ho (Inventor); Siochi, Emilie J. (Inventor); Harrison, Joycelyn S. (Inventor)

    2016-01-01

    Stable dispersions of carbon nanotubes (CNTs) in polymeric matrices include CNTs dispersed in a host polymer or copolymer whose monomers have delocalized electron orbitals, so that a dispersion interaction results between the host polymer or copolymer and the CNTs dispersed therein. Nanocomposite products, which are presented in bulk, or when fabricated as a film, fiber, foam, coating, adhesive, paste, or molding, are prepared by standard means from the present stable dispersions of CNTs in polymeric matrices, employing dispersion interactions, as presented hereinabove.

  4. Transverse dispersion in heterogeneous fractures

    International Nuclear Information System (INIS)

    Dershowitz, Bill; Shuttle, Dawn; Klise, Kate; Outters, Nils; Hermanson, Jan

    2004-12-01

    This report evaluates the significance of transverse dispersion processes for solute transport in a single fracture. Transverse dispersion is a potentially significant process because it increases the fracture surface area available for sorptive and diffusive properties, and has the potential to transport solute between what would otherwise be distinctive, streamline pathways. Transverse dispersion processes are generally ignored in one-dimensional repository performance assessment approaches. This report provides an initial assessment of the magnitude of transverse dispersion effect in a single heterogeneous fracture on repository safety assessment. This study builds on a previous report which considered the network effects on transport dispersion including streamline routing and mixing at fracture intersections. The project uses FracMan software. This platform has been extensively used by SKB in other projects. FracMan software is designed to generate and analyze DFN's as well as to compute fluid flow in DFN's with the MAFIC Finite element method (FEM) code. Solute transport was modeled using the particle tracking inside MAFIC, the 2-D Laplace Transform Galerkin inside PAWorks/LTG, and the 1-D Laplace Transform approach designed to replicate FARF31 inside GoldSim.The study reported here focuses on a single, 20-meter scale discrete fracture, with simplified boundary conditions intended to represent the position of this fracture within a fracture network. The range of assumptions made regarding fracture heterogeneity were as follows: Base case, Heterogeneous fracture, geostatistical field, correlation length 0.01 m. Case 1a, Homogeneous fracture, transmissivity = 10 -7 m 2 /s. Case 1b, Heterogeneous fracture, non-channeled geostatistical field correlation length 5 m. Case 1c, Heterogeneous fracture, channeled, anisotropic geostatistical field. Case 1d, Heterogeneous fracture, fracture intersection zone (FIZ) permeability enhanced. Case 5, Simple channelized

  5. Procedure for preparation of dispersions

    International Nuclear Information System (INIS)

    1978-01-01

    Procedure for the preparation of a water based dispersion of cerium oxide, characterised in that a suspension of cerium (IV) hydroxide is formed with an acid, where the acid is in the state of a disaggregation of aggregated crystalline cerium hydroxide, the suspension being preheated for a specified time and to a specified temperature, so that the pH value becomes constant, and whereby the quantity of acid in the suspension is such that the constant pH value is lower than 5.4, so that a conditioned suspension may be obtained, and water may be mixed with the conditioned suspension for making a water based dispersion of cerium oxide. (G.C.)

  6. Stochastic models for atmospheric dispersion

    DEFF Research Database (Denmark)

    Ditlevsen, Ove Dalager

    2003-01-01

    Simple stochastic differential equation models have been applied by several researchers to describe the dispersion of tracer particles in the planetary atmospheric boundary layer and to form the basis for computer simulations of particle paths. To obtain the drift coefficient, empirical vertical...... positions close to the boundaries. Different rules have been suggested in the literature with justifications based on simulation studies. Herein the relevant stochastic differential equation model is formulated in a particular way. The formulation is based on the marginal transformation of the position...... velocity distributions that depend on height above the ground both with respect to standard deviation and skewness are substituted into the stationary Fokker/Planck equation. The particle position distribution is taken to be uniform *the well/mixed condition( and also a given dispersion coefficient...

  7. Ability Dispersion and Team Performance

    DEFF Research Database (Denmark)

    Hoogendoorn, Sander; Parker, Simon C.; Van Praag, Mirjam

    What is the effect of dispersed levels of cognitive ability of members of a (business) team on their team's performance? This paper reports the results of a field experiment in which 573 students in 49 (student) teams start up and manage real companies under identical circumstances for one year. We...... ensured exogenous variation in otherwise random team composition by assigning students to teams based on their measured cognitive abilities. Each team performs a variety of tasks, often involving complex decision making. The key result of the experiment is that the performance of business teams first...... increases and then decreases with ability dispersion. We seek to understand this finding by developing a model in which team members of different ability levels form sub- teams with other team members with similar ability levels to specialize in different productive tasks. Diversity spreads production over...

  8. Magnetic effects in anomalous dispersion

    International Nuclear Information System (INIS)

    Blume, M.

    1992-01-01

    Spectacular enhancements of magnetic x-ray scattering have been predicted and observed experimentally. These effects are the result of resonant phenomena closely related to anomalous dispersion, and they are strongest at near-edge resonances. The theory of these resonances will be developed with particular attention to the symmetry properties of the scatterer. While the phenomena to be discussed concern magnetic properties the transitions are electric dipole or electric quadrupole in character and represent a subset of the usual anomalous dispersion phenomena. The polarization dependence of the scattering is also considered, and the polarization dependence for magnetic effects is related to that for charge scattering and to Templeton type anisotropic polarization phenomena. It has been found that the strongest effects occur in rare-earths and in actinides for M shell edges. In addition to the scattering properties the theory is applicable to ''forward scattering'' properties such as the Faraday effect and circular dichroism

  9. Faraday anomalous dispersion optical tuners

    Science.gov (United States)

    Wanninger, P.; Valdez, E. C.; Shay, T. M.

    1992-01-01

    Common methods for frequency stabilizing diode lasers systems employ gratings, etalons, optical electric double feedback, atomic resonance, and a Faraday cell with low magnetic field. Our method, the Faraday Anomalous Dispersion Optical Transmitter (FADOT) laser locking, is much simpler than other schemes. The FADOT uses commercial laser diodes with no antireflection coatings, an atomic Faraday cell with a single polarizer, and an output coupler to form a compound cavity. This method is vibration insensitive, thermal expansion effects are minimal, and the system has a frequency pull in range of 443.2 GHz (9A). Our technique is based on the Faraday anomalous dispersion optical filter. This method has potential applications in optical communication, remote sensing, and pumping laser excited optical filters. We present the first theoretical model for the FADOT and compare the calculations to our experimental results.

  10. Dispersed Fringe Sensing Analysis - DFSA

    Science.gov (United States)

    Sigrist, Norbert; Shi, Fang; Redding, David C.; Basinger, Scott A.; Ohara, Catherine M.; Seo, Byoung-Joon; Bikkannavar, Siddarayappa A.; Spechler, Joshua A.

    2012-01-01

    Dispersed Fringe Sensing (DFS) is a technique for measuring and phasing segmented telescope mirrors using a dispersed broadband light image. DFS is capable of breaking the monochromatic light ambiguity, measuring absolute piston errors between segments of large segmented primary mirrors to tens of nanometers accuracy over a range of 100 micrometers or more. The DFSA software tool analyzes DFS images to extract DFS encoded segment piston errors, which can be used to measure piston distances between primary mirror segments of ground and space telescopes. This information is necessary to control mirror segments to establish a smooth, continuous primary figure needed to achieve high optical quality. The DFSA tool is versatile, allowing precise piston measurements from a variety of different optical configurations. DFSA technology may be used for measuring wavefront pistons from sub-apertures defined by adjacent segments (such as Keck Telescope), or from separated sub-apertures used for testing large optical systems (such as sub-aperture wavefront testing for large primary mirrors using auto-collimating flats). An experimental demonstration of the coarse-phasing technology with verification of DFSA was performed at the Keck Telescope. DFSA includes image processing, wavelength and source spectral calibration, fringe extraction line determination, dispersed fringe analysis, and wavefront piston sign determination. The code is robust against internal optical system aberrations and against spectral variations of the source. In addition to the DFSA tool, the software package contains a simple but sophisticated MATLAB model to generate dispersed fringe images of optical system configurations in order to quickly estimate the coarse phasing performance given the optical and operational design requirements. Combining MATLAB (a high-level language and interactive environment developed by MathWorks), MACOS (JPL s software package for Modeling and Analysis for Controlled Optical

  11. Hydrodynamic dispersion within porous biofilms

    KAUST Repository

    Davit, Y.

    2013-01-23

    Many microorganisms live within surface-associated consortia, termed biofilms, that can form intricate porous structures interspersed with a network of fluid channels. In such systems, transport phenomena, including flow and advection, regulate various aspects of cell behavior by controlling nutrient supply, evacuation of waste products, and permeation of antimicrobial agents. This study presents multiscale analysis of solute transport in these porous biofilms. We start our analysis with a channel-scale description of mass transport and use the method of volume averaging to derive a set of homogenized equations at the biofilm-scale in the case where the width of the channels is significantly smaller than the thickness of the biofilm. We show that solute transport may be described via two coupled partial differential equations or telegrapher\\'s equations for the averaged concentrations. These models are particularly relevant for chemicals, such as some antimicrobial agents, that penetrate cell clusters very slowly. In most cases, especially for nutrients, solute penetration is faster, and transport can be described via an advection-dispersion equation. In this simpler case, the effective diffusion is characterized by a second-order tensor whose components depend on (1) the topology of the channels\\' network; (2) the solute\\'s diffusion coefficients in the fluid and the cell clusters; (3) hydrodynamic dispersion effects; and (4) an additional dispersion term intrinsic to the two-phase configuration. Although solute transport in biofilms is commonly thought to be diffusion dominated, this analysis shows that hydrodynamic dispersion effects may significantly contribute to transport. © 2013 American Physical Society.

  12. Dispersion of Bed Load Particles

    OpenAIRE

    SAWAI, Kenji

    1987-01-01

    The motion of bed load particles is so irregular that they disperse remarkably with time.In this study, some flume tests using painted tracer particles were carried out, in which thedispersive property of tracers changed variously with sediment feed rate.In analysing this process, a stochastic simulation model is proposed where it is discussedabout the degree of exposure of individual particle near the bed surface and about the variationof its pick up rate. The exponential distribution of ste...

  13. Faraday anomalous dispersion optical filters

    Science.gov (United States)

    Shay, T. M.; Yin, B.; Alvarez, L. S.

    1993-01-01

    The effect of Faraday anomalous dispersion optical filters on infrared and blue transitions of some alkali atoms is calculated. A composite system is designed to further increase the background noise rejection. The measured results of the solar background rejection and image quality through the filter are presented. The results show that the filter may provide high transmission and high background noise rejection with excellent image quality.

  14. Dispersive stresses in wind farms

    Science.gov (United States)

    Segalini, Antonio; Braunbehrens, Robert; Hyvarinen, Ann

    2017-11-01

    One of the most famous models of wind farms is provided by the assumption that the farm can be approximated as a horizontally-homogeneous forest canopy with vertically-varying force intensity. By means of this approximation, the flow-motion equations become drastically simpler, as many of the three-dimensional effects are gone. However, the application of the horizontal average operator to the RANS equations leads to the appearance of new transport terms (called dispersive stresses) originating from the horizontal (small-scale) variation of the mean velocity field. Since these terms are related to the individual turbine signature, they are expected to vanish outside the roughness sublayer, providing a definition for the latter. In the present work, an assessment of the dispersive stresses is performed by means of a wake-model approach and through the linearised code ORFEUS developed at KTH. Both approaches are very fast and enable the characterization of a large number of wind-farm layouts. The dispersive stress tensor and its effect on the turbulence closure models are investigated, providing guidelines for those simulations where it is impossible to resolve the farm at a turbine scale due to grid requirements (as, for instance, mesoscale simulations).

  15. Improving practical atmospheric dispersion models

    International Nuclear Information System (INIS)

    Hunt, J.C.R.; Hudson, B.; Thomson, D.J.

    1992-01-01

    The new generation of practical atmospheric dispersion model (for short range ≤ 30 km) are based on dispersion science and boundary layer meteorology which have widespread international acceptance. In addition, recent improvements in computer skills and the widespread availability of small powerful computers make it possible to have new regulatory models which are more complex than the previous generation which were based on charts and simple formulae. This paper describes the basis of these models and how they have developed. Such models are needed to satisfy the urgent public demand for sound, justifiable and consistent environmental decisions. For example, it is preferable that the same models are used to simulate dispersion in different industries; in many countries at present different models are used for emissions from nuclear and fossil fuel power stations. The models should not be so simple as to be suspect but neither should they be too complex for widespread use; for example, at public inquiries in Germany, where simple models are mandatory, it is becoming usual to cite the results from highly complex computational models because the simple models are not credible. This paper is written in a schematic style with an emphasis on tables and diagrams. (au) (22 refs.)

  16. Dispersion relations in loop calculations

    International Nuclear Information System (INIS)

    Kniehl, B.A.

    1996-01-01

    These lecture notes give a pedagogical introduction to the use of dispersion relations in loop calculations. We first derive dispersion relations which allow us to recover the real part of a physical amplitude from the knowledge of its absorptive part along the branch cut. In perturbative calculations, the latter may be constructed by means of Cutkosky's rule, which is briefly discussed. For illustration, we apply this procedure at one loop to the photon vacuum-polarization function induced by leptons as well as to the γf anti-f vertex form factor generated by the exchange of a massive vector boson between the two fermion legs. We also show how the hadronic contribution to the photon vacuum polarization may be extracted from the total cross section of hadron production in e + e - annihilation measured as a function of energy. Finally, we outline the application of dispersive techniques at the two-loop level, considering as an example the bosonic decay width of a high-mass Higgs boson. (author)

  17. Chromatic Dispersion Estimation in Digital Coherent Receivers

    DEFF Research Database (Denmark)

    Soriano, Ruben Andres; Hauske, Fabian N.; Guerrero Gonzalez, Neil

    2011-01-01

    Polarization-diverse coherent demodulation allows to compensate large values of accumulated linear distortion by digital signal processing. In particular, in uncompensated links without optical dispersion compensation, the parameter of the residual chromatic dispersion (CD) is vital to set...

  18. Statistical Physics of Colloidal Dispersions.

    Science.gov (United States)

    Canessa, E.

    Available from UMI in association with The British Library. Requires signed TDF. This thesis is concerned with the equilibrium statistical mechanics of colloidal dispersions which represent useful model systems for the study of condensed matter physics; namely, charge stabilized colloidal dispersions and polymer stabilized colloidal dispersions. A one-component macroparticle approach is adopted in order to treat the macroscopic and microscopic properties of these systems in a simple and comprehensive manner. The thesis opens with the description of the nature of the colloidal state before reviewing some basic definitions and theory in Chapter II. In Chapter III a variational theory of phase equilibria based on the Gibbs-Bogolyobov inequality is applied to sterically stabilized colloidal dispersions. Hard spheres are chosen as the reference system for the disordered phases while an Einstein model is used for the ordered phases. The new choice of pair potential, taken for mathematical convenience, is a superposition of two Yukawa functions. By matching a double Yukawa potential to the van der Waals attractive potential at different temperatures and introducing a purely temperature dependent coefficient to the repulsive part, a rich variety of observed phase separation phenomena is qualitatively described. The behaviour of the potential is found to be consistent with a small decrease of the polymer layer thickness with increasing temperature. Using the same concept of a collapse transition the non-monotonic second virial coefficient is also explained and quantified. It is shown that a reduction of the effective macroparticle diameter with increasing temperature can only be partially examined from the point of view of a (binary-) polymer solution theory. This chapter concludes with the description of the observed, reversible, depletion flocculation behaviour. This is accomplished by using the variational formalism and by invoking the double Yukawa potential to allow

  19. Dispersion properties of photonic crystal fibres

    DEFF Research Database (Denmark)

    Bjarklev, Anders Overgaard; Broeng, Jes; Dridi, Kim

    1998-01-01

    Approximate dispersion and bending properties of all-silica two-dimensional photonic crystal fibres are characterised by the combination of an effective-index model and classical analysis tools for optical fibres. We believe for the first time to have predicted the dispersion properties of photonic...... crystal fibres. The results strongly indicate that these fibres have potential applications as dispersion managing components...

  20. Catchment Dispersion Mechanisms in an Urban Context

    Science.gov (United States)

    Gironas, J. A.; Mejia, A.; Rossel, F.; Rinaldo, A.; Rodriguez, F.

    2014-12-01

    Dispersion mechanisms have been examined in-depth in natural catchments in previous studies. However, these dispersion mechanisms have been studied little in urban catchments, where artificial transport elements and morphological arrangements are expected to modify travel times and mobilize excess rainfall from spatially distributed impervious sites. Thus, these features can modify the variance of the catchment's travel times and hence the total dispersion. This work quantifies the dispersion mechanisms in an urban catchment using the theory of transport by travel times as represented by the Urban Morpho-climatic Instantaneous Unit Hydrograph (U-McIUH) model. This model computes travel times based on kinematic wave theory and accounts explicitly for the path heterogeneities and altered connectivity patterns characteristic of an urban drainage network. The analysis is illustrated using the Aubinière urban catchment (France) as a case study. We found that kinematic dispersion is dominant for small rainfall intensities, whereas geomorphologic dispersion becomes more dominant for larger intensities. The total dispersion scales with the drainage area in a power law fashion. The kinematic dispersion is dominant across spatial scales up to a threshold of approximately 2-3 km2, after which the geomorphologic dispersion becomes more dominant. Overall, overland flow is responsible for most of the dispersion, while conduits tend to counteract the increase of the geomorphologic dispersion with a negative kinematic dispersion. Further studies with other catchments are needed to assess whether the latter is a general feature of urban drainage networks.

  1. Dispersion of coupled mode-gap cavities

    NARCIS (Netherlands)

    Lian, Jin; Sokolov, Sergei; Yuce, E.; Combrie, S.; de Rossi, A.; Mosk, Allard

    2015-01-01

    The dispersion of a coupled resonator optical waveguide made of photonic crystal mode-gap cavities is pronouncedly asymmetric. This asymmetry cannot be explained by the standard tight binding model. We show that the fundamental cause of the asymmetric dispersion is the inherent dispersive cavity

  2. Characterization of finite spaces having dispersion points

    International Nuclear Information System (INIS)

    Al-Bsoul, A. T

    1997-01-01

    In this paper we shall characterize the finite spaces having dispersion points. Also, we prove that the dispersion point of a finite space with a dispersion points fixed under all non constant continuous functions which answers the question raised by J. C obb and W. Voxman in 1980 affirmatively for finite space. Some open problems are given. (author). 16 refs

  3. Normal-dispersion microresonator Kerr frequency combs

    Directory of Open Access Journals (Sweden)

    Xue Xiaoxiao

    2016-06-01

    Full Text Available Optical microresonator-based Kerr frequency comb generation has developed into a hot research area in the past decade. Microresonator combs are promising for portable applications due to their potential for chip-level integration and low power consumption. According to the group velocity dispersion of the microresonator employed, research in this field may be classified into two categories: the anomalous dispersion regime and the normal dispersion regime. In this paper, we discuss the physics of Kerr comb generation in the normal dispersion regime and review recent experimental advances. The potential advantages and future directions of normal dispersion combs are also discussed.

  4. Dispersed publication of editorial research

    DEFF Research Database (Denmark)

    Rosenberg, Jacob; Pommergaard, Hans-Christian; Vinther, Siri

    2015-01-01

    INTRODUCTION: There seems to be no dedicated journals available for publication of editorial research in the biomedical sciences; that is research into editorial or publication process issues involving the scientific approach to writing, reviewing, editing and publishing. It is unknown where papers...... journals with a median of one article per journal (range: 1-17). CONCLUSION: The publication of papers on editorial research seems to be dispersed. In order to increase the visibility of this research field, it may be reasonable to establish well-defined platforms such as dedicated journals or journal...

  5. A nonlocal inhomogeneous dispersal process

    Science.gov (United States)

    Cortázar, C.; Coville, J.; Elgueta, M.; Martínez, S.

    This article in devoted to the study of the nonlocal dispersal equation u(x,t)=∫R J({x-y}/{g(y)}){u(y,t)}/{g(y)} dy-u(x,t) in R×[0,∞), and its stationary counterpart. We prove global existence for the initial value problem, and under suitable hypothesis on g and J, we prove that positive bounded stationary solutions exist. We also analyze the asymptotic behavior of the finite mass solutions as t→∞, showing that they converge locally to zero.

  6. Taylor dispersion on a fractal

    International Nuclear Information System (INIS)

    Mazo, R.M.

    1998-01-01

    Taylor dispersion is the greatly enhanced diffusion in the direction of a fluid flow caused by ordinary diffusion in directions orthogonal to the flow. It is essential that the system be bounded in space in the directions orthogonal to the flow. We investigate the situation where the medium through which the flow occurs has fractal properties so that diffusion in the orthogonal directions is anomalous and non-Fickian. The effective diffusion in the flow direction remains normal; its width grows proportionally with the time. However, the proportionality constant depends on the fractal dimension of the medium as well as its walk dimension. (author)

  7. Extragalactic dispersion measures of fast radio bursts

    International Nuclear Information System (INIS)

    Xu, Jun; Han, J. L.

    2015-01-01

    Fast radio bursts show large dispersion measures, much larger than the Galactic dispersion measure foreground. Therefore, they evidently have an extragalactic origin. We investigate possible contributions to the dispersion measure from host galaxies. We simulate the spatial distribution of fast radio bursts and calculate the dispersion measures along the sightlines from fast radio bursts to the edge of host galaxies by using the scaled NE2001 model for thermal electron density distributions. We find that contributions to the dispersion measure of fast radio bursts from the host galaxy follow a skew Gaussian distribution. The peak and the width at half maximum of the dispersion measure distribution increase with the inclination angle of a spiral galaxy, to large values when the inclination angle is over 70°. The largest dispersion measure produced by an edge-on spiral galaxy can reach a few thousand pc cm −3 , while the dispersion measures from dwarf galaxies and elliptical galaxies have a maximum of only a few tens of pc cm −3 . Notice, however, that additional dispersion measures of tens to hundreds of pc cm −3 can be produced by high density clumps in host galaxies. Simulations that include dispersion measure contributions from the Large Magellanic Cloud and the Andromeda Galaxy are shown as examples to demonstrate how to extract the dispersion measure from the intergalactic medium. (paper)

  8. Introduction to nonlinear dispersive equations

    CERN Document Server

    Linares, Felipe

    2015-01-01

    This textbook introduces the well-posedness theory for initial-value problems of nonlinear, dispersive partial differential equations, with special focus on two key models, the Korteweg–de Vries equation and the nonlinear Schrödinger equation. A concise and self-contained treatment of background material (the Fourier transform, interpolation theory, Sobolev spaces, and the linear Schrödinger equation) prepares the reader to understand the main topics covered: the initial-value problem for the nonlinear Schrödinger equation and the generalized Korteweg–de Vries equation, properties of their solutions, and a survey of general classes of nonlinear dispersive equations of physical and mathematical significance. Each chapter ends with an expert account of recent developments and open problems, as well as exercises. The final chapter gives a detailed exposition of local well-posedness for the nonlinear Schrödinger equation, taking the reader to the forefront of recent research. The second edition of Introdu...

  9. Dispersivity in heterogeneous permeable media

    International Nuclear Information System (INIS)

    Chesnut, D.A.

    1994-01-01

    When one fluid displaces another through a one-dimensional porous medium, the composition changes from pure displacing fluid at the inlet to pure displaced fluid some distance downstream. The distance over which an arbitrary percentage of this change occurs is defined as the mixing zone length, which increases with increasing average distance traveled by the displacement front. For continuous injection, the mixing zone size can be determined from a breakthrough curve as the time required for the effluent displacing fluid concentration to change from, say, 10% to 90%. In classical dispersion theory, the mixing zone grows in proportion to the square root of the mean distance traveled, or, equivalently, to the square root of the mean breakthrough time. In a multi-dimensional heterogeneous medium, especially at field scales, the size of the mixing zone grows almost linearly with mean distance or travel time. If an observed breakthrough curve is forced to fit the, clinical theory, the resulting effective dispersivity, instead of being constant, also increases almost linearly with the spatial or temporal scale of the problem. This occurs because the heterogeneity in flow properties creates a corresponding velocity distribution along the different flow pathways from the inlet to the outlet of the system. Mixing occurs mostly at the outlet, or wherever the fluid is sampled, rather than within the medium. In this paper, we consider the effects. of this behavior on radionuclide or other contaminant migration

  10. Dispersivity in heterogeneous permeable media

    International Nuclear Information System (INIS)

    Chesnut, D.A.

    1994-01-01

    When one fluid displaces another through a one-dimensional porous medium, the composition changes from pure displacing fluid at the inlet to pure displaced fluid some distance downstream. The distance over which an arbitrary percentage (typically 80%) of this change occurs is defined as the mixing zone length, which increases with increasing average distance traveled by the displacement front. Alternatively, for continuous injection, the mixing zone size can be determined from a breakthrough curve as the time required for the effluent displacing fluid concentration to change from, say, 10% to 90%. In classical dispersion theory, the mixing zone grows in proportion to the square root of the mean distance traveled, or, equivalently, to the square root of the mean breakthrough time. In a multi-dimensional heterogeneous medium, especially at field scales, the size of the mixing zone grows almost linearly with mean distance or travel time. If an observed breakthrough curve is forced to fit the classical theory, the resulting effective dispersivity, instead of being constant, also increases almost linearly with the spatial or temporal scale of the problem. This occurs because the heterogeneity in flow properties creates a corresponding velocity distribution along the different flow pathways from the inlet to the outlet of the system. Mixing occurs mostly at the outlet, or wherever the fluid is sampled, rather than within the medium. In this paper, we consider the effects of this behavior on radionuclide or other contaminant migration

  11. A laboratory dispersant effectiveness test which reflects dispersant efficiency in the field

    International Nuclear Information System (INIS)

    Lunel, T.; Wood, P.

    1996-01-01

    Oil dispersion efficiencies of surfactants, from laboratory dispersion tests and field data were compared and calibrated. Data from an oil spill, where dispersants were used as a major part of the response, was analysed. The data was accumulated through the monitoring of the dispersant operation of the Sea Empress spill incident, in which Forties Blend oil was spilled at sea. This detailed data set was used to calibrate existing laboratory dispersant tests, and to devise a new International Dispersant Effectiveness Test. The objective was to create a comprehensive guide to decision making on whether and when to start a dispersant spraying operation. The dispersion efficiencies obtained from the laboratory dispersant tests were compared with field data. Flume tests produced the highest percentage of dispersed oil for all the dispersal tests. However, it was emphasised that the total percentage of oil dispersed should not be the only measure of dispersant effectiveness, since it does not distinguish between the contribution of natural and chemically enhanced dispersion. 9 refs., 1 tab., 9 figs

  12. Pollen Forecast and Dispersion Modelling

    Science.gov (United States)

    Costantini, Monica; Di Giuseppe, Fabio; Medaglia, Carlo Maria; Travaglini, Alessandro; Tocci, Raffaella; Brighetti, M. Antonia; Petitta, Marcello

    2014-05-01

    The aim of this study is monitoring, mapping and forecast of pollen distribution for the city of Rome using in-situ measurements of 10 species of common allergenic pollens and measurements of PM10. The production of daily concentration maps, associated to a mobile phone app, are innovative compared to existing dedicated services to people who suffer from respiratory allergies. The dispersal pollen is one of the most well-known causes of allergic disease that is manifested by disorders of the respiratory functions. Allergies are the third leading cause of chronic disease and it is estimated that tens millions of people in Italy suffer from it. Recent works reveal that during the last few years there was a progressive increase of affected subjects, especially in urban areas. This situation may depend: on the ability to transport of pollutants, on the ability to react between pollutants and pollen and from a combination of other irritants, existing in densely populated and polluted urban areas. The methodology used to produce maps is based on in-situ measurements time series relative to 2012, obtained from networks of air quality and pollen stations in the metropolitan area of Rome. The monitoring station aerobiological of University of Rome "Tor Vergata" is located at the Department of Biology. The instrument used to pollen monitoring is a volumetric sampler type Hirst (Hirst 1952), Model 2000 VPPS Lanzoni; the data acquisition is carried out as reported in Standard UNI 11008:2004 - "Qualità dell'aria - Metodo di campionamento e conteggio dei granuli pollinici e delle spore fungine aerodisperse" - the protocol that describes the procedure for measuring of the concentration of pollen grains and fungal spores dispersed into the atmosphere, and reported in the "Manuale di gestione e qualità della R.I.M.A" (Travaglini et. al. 2009). All 10 allergenic pollen are monitored since 1996. At Tor Vergata university is also operating a meteorological station (SP2000, CAE

  13. Tomography with energy dispersive diffraction

    Science.gov (United States)

    Stock, S. R.; Okasinski, J. S.; Woods, R.; Baldwin, J.; Madden, T.; Quaranta, O.; Rumaiz, A.; Kuczewski, T.; Mead, J.; Krings, T.; Siddons, P.; Miceli, A.; Almer, J. D.

    2017-09-01

    X-ray diffraction can be used as the signal for tomographic reconstruction and provides a cross-sectional map of the crystallographic phases and related quantities. Diffraction tomography has been developed over the last decade using monochromatic x-radiation and an area detector. This paper reports tomographic reconstruction with polychromatic radiation and an energy sensitive detector array. The energy dispersive diffraction (EDD) geometry, the instrumentation and the reconstruction process are described and related to the expected resolution. Results of EDD tomography are presented for two samples containing hydroxyapatite (hAp). The first is a 3D-printed sample with an elliptical crosssection and contains synthetic hAp. The second is a human second metacarpal bone from the Roman-era cemetery at Ancaster, UK and contains bio-hAp which may have been altered by diagenesis. Reconstructions with different diffraction peaks are compared. Prospects for future EDD tomography are also discussed.

  14. Determination of dispersity of crushed granite

    International Nuclear Information System (INIS)

    Liu Dejun; Fan Xianhua; Zhang Yingjie; Yao Jun; Zhou Duo; Wang Yong

    2004-01-01

    The experimental crushed granite column breakthrough curves, using 99 Tc as spike tracer and 3 H as invariant tracer, are analyzed by different linear regression techniques. Dispersity of crushed granite and retardation factor of 99 TcO 4 - on the crushed granite are determined simultaneously by one linear regression technique. Dispersity of crushed granite is also obtained with 3 H as invariant tracer by the other linear regression technique. The dispersities found by spike source and invariant source methods are compared. The experimental results show that the dispersity found by spike source method is close to that found by invariant source method. It indicates that dispersity is only the characteristic of dispersion medium

  15. Determination of dispersity of crushed granite

    International Nuclear Information System (INIS)

    Liu, D.J.; Fan, X.H.

    2005-01-01

    Experimental crushed granite column breakthrough curves, using 99 Tc as spike tracer and 3 H as invariant tracer, were analyzed by different linear regression techniques. Dispersity of crushed granite and the retardation factor of 99 TcO 4 - on the crushed granite were determined simultaneously by one linear regression. Dispersity of crushed granite was also obtained with 3 H as invariant tracer by the other linear regression. The dispersities found by spike source and invariant source methods are compared. Experimental results show that the dispersity found by the spike source method is close to that found by the invariant source method. This indicates that dispersity is only a characteristic of the dispersion medium. (author)

  16. Integrating individual movement behaviour into dispersal functions.

    Science.gov (United States)

    Heinz, Simone K; Wissel, Christian; Conradt, Larissa; Frank, Karin

    2007-04-21

    Dispersal functions are an important tool for integrating dispersal into complex models of population and metapopulation dynamics. Most approaches in the literature are very simple, with the dispersal functions containing only one or two parameters which summarise all the effects of movement behaviour as for example different movement patterns or different perceptual abilities. The summarising nature of these parameters makes assessing the effect of one particular behavioural aspect difficult. We present a way of integrating movement behavioural parameters into a particular dispersal function in a simple way. Using a spatial individual-based simulation model for simulating different movement behaviours, we derive fitting functions for the functional relationship between the parameters of the dispersal function and several details of movement behaviour. This is done for three different movement patterns (loops, Archimedean spirals, random walk). Additionally, we provide measures which characterise the shape of the dispersal function and are interpretable in terms of landscape connectivity. This allows an ecological interpretation of the relationships found.

  17. Single-particle dispersion in compressible turbulence

    Science.gov (United States)

    Zhang, Qingqing; Xiao, Zuoli

    2018-04-01

    Single-particle dispersion statistics in compressible box turbulence are studied using direct numerical simulation. Focus is placed on the detailed discussion of effects of the particle Stokes number and turbulent Mach number, as well as the forcing type. When solenoidal forcing is adopted, it is found that the single-particle dispersion undergoes a transition from the ballistic regime at short times to the diffusive regime at long times, in agreement with Taylor's particle dispersion argument. The strongest dispersion of heavy particles is announced when the Stokes number is of order 1, which is similar to the scenario in incompressible turbulence. The dispersion tends to be suppressed as the Mach number increases. When hybrid solenoidal and compressive forcing at a ratio of 1/2 is employed, the flow field shows apparent anisotropic property, characterized by the appearance of large shock wave structures. Accordingly, the single-particle dispersion shows extremely different behavior from the solenoidal forcing case.

  18. Membranes as separators of dispersed emulsion phases

    OpenAIRE

    Lefferts, A.G.

    1997-01-01

    The reuse or discharge of industrial waste waters, containing small fractions of dispersed oil, requires a purification treatment for which membranes can be used. If only little oil is present, removal of the dispersed phase might be preferable to the more commonly applied removal of the continuous phase. For this purpose dispersed phase separators can be applied, which combine the features of conventional coalescers and membrane filtration. The membrane surface promotes coalescence ...

  19. Formulation of disperse systems science and technology

    CERN Document Server

    Tadros, Tharwat F

    2014-01-01

    This book presents comprehensively the science and technology behind the formulation of disperse systems like emulsions, suspensions, foams and others. Starting with a general introduction, the book covers a broad range of topics like the role of different classes of surfactants, stability of disperse systems, formulation of different dispersions, evaluation of formulations and many more. Many examples are included, too. Written by the experienced author and editor Tharwart Tadros, this book is indispensable for every scientist working in the field.

  20. Key factors for UV curable pigment dispersions

    International Nuclear Information System (INIS)

    Magny, B.; Pezron, E.; Ciceron, P.H.; Askienazy, A.

    1999-01-01

    UV oligomers with good pigment dispersion are needed to allow good formulation flexibility and possibility to apply thinner films. Pigment dispersion mainly depends on three phenomena: the wetting of agglomerates, the breakage of agglomerates by mechanical stress and the stabilization of smaller agglomerates and primary particles against flocculation. It has been shown that oligomers with low viscosity and low surface tension induce a good pigment wetting. Examples of monomers and oligomers for good pigment dispersion are given

  1. Liquid agents for dispersion of hard alloys

    International Nuclear Information System (INIS)

    Putintseva, M.N.

    2006-01-01

    Effects of dispersant properties on granulometric, chemical, and phase composition of the products of WC hard alloy electroerosion are considered. It is established that an increase of liquid dispersant permittivity results in enhanced powder dispersity, and an increase of boiling temperature and kinematic viscosity of a hydrocarbon liquid promotes a carbon loss from WC and intensifies pyrolysis of the liquid.On electroerosion of WC base hard alloy in oil a powder particle consists of b-WC+W 2 C phases, in kerosine - of a-WC+b-WC, in distilled water - of W+W 2 C. The viscosity of liquid dispersants practically has no effect on powder particle size [ru

  2. 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.

  3. Effectiveness of dispersants on thick oil slicks

    International Nuclear Information System (INIS)

    Ross, S.; Belore, R.

    1993-01-01

    Experiments were conducted to determine the relationship between dispersant effectiveness and oil slick thickness, and thereby determine the optimum time for applying dispersant onto spilled oil at sea. Tests were completed at a lab-scale level by varying the three parameters of oil type, dispersant application, and oil thickness. The tests were intended to be comparative only. The primary oils used were Alberta sweet mix blend and Hibernia B-27 crude. The dispersant, Corexit 9527, was applied either premixed with the oil, dropwise in one application, or dropwise in multiple applications to simulate a multi-hit aircraft operation. The apparatus used in the experiment was an oscillating hoop tank, with oil-containing rings used to obtain and maintain uniform slick thickness. The results indicate that the effectiveness potential of a chemical dispersant does not decrease as slick thickness increases. In fact, results of the tests involving Hibernia oil suggest that oils that tend to herd easily would be treated more effectively if dispersant were applied when the oil was relatively thick (1 mm or greater) to avoid herding problems. The oil slicks premixed with dispersant did not disperse well in the thick oil tests, not because of dispersant-oil interaction problems but because of reduced mixing energy. 6 refs., 4 figs., 1 tab

  4. Modelling airborne dispersion of coarse particulate material

    International Nuclear Information System (INIS)

    Apsley, D.D.

    1989-03-01

    Methods of modelling the airborne dispersion and deposition of coarse particulates are presented, with the emphasis on the heavy particles identified as possible constituents of releases from damaged AGR fuel. The first part of this report establishes the physical characteristics of the irradiated particulate in airborne emissions from AGR stations. The second part is less specific and describes procedures for extending current dispersion/deposition models to incorporate a coarse particulate component: the adjustment to plume spread parameters, dispersion from elevated sources and dispersion in conjunction with building effects and plume rise. (author)

  5. Does an ant-dispersed plant, Viola reichenbachiana, suffer from reduced seed dispersal under inundation disturbances?

    NARCIS (Netherlands)

    Prinzing, A.; Dauber, J.; Hammer, E.; Hammouti, N.; Bohning-Gaese, K.

    2008-01-01

    Many plant species use ants as seed dispersers. This dispersal mode is considered to be susceptible to disturbances, but the effect of natural, small-scale disturbances is still unknown. We investigated how small-scale disturbances due to inundation affect seed dispersal in Viola reichenbachiana, a

  6. Dispersed and decentralised settlement system

    Directory of Open Access Journals (Sweden)

    Andrej Černe

    2004-01-01

    Full Text Available In the process of reintegration of the urban system new settlements are emerging on theurban rim, transitional zones are reurbanised, derelict areas within the cities are being developedand degraded urban areas of derelict industrial complexes are being renaturalised. Inthe periphery combined research and production parks are being set up, in the open landscapeintegrated business, trade and recreational centres are springing up. Decentralisationand recentralisation of focal points of development accompany the contemporary processesof reurbanisation and suburbanisation – they are simultaneous and move in two-direction i.e. to and from the city. We understand them as manifestation of a dynamic balance amongcontradiction existing between the centre and the rim. Deindustrialisation and relocation ofproduction and distribution from the centres of gravity to the periphery generate extensivedegraded urban areas within cities and between the city and suburbs. The periphery is beingurbanised with the creation of new, dispersed and nonhierachical poles of development, andthe city and inner city is undergoing reurbanization. The general environmental conditionsin the city and in the countryside are being equalised, the potentials of development arebeing sought in the comparative advantages of local conditions: be it attractive urban districts,be it suburban entities or countryside areas.

  7. Databases of surface wave dispersion

    Directory of Open Access Journals (Sweden)

    L. Boschi

    2005-06-01

    Full Text Available Observations of seismic surface waves provide the most important constraint on the elastic properties of the Earth’s lithosphere and upper mantle. Two databases of fundamental mode surface wave dispersion were recently compiled and published by groups at Harvard (Ekström et al., 1997 and Utrecht/Oxford (Trampert and Woodhouse, 1995, 2001, and later employed in 3-d global tomographic studies. Although based on similar sets of seismic records, the two databases show some significant discrepancies. We derive phase velocity maps from both, and compare them to quantify the discrepancies and assess the relative quality of the data; in this endeavour, we take careful account of the effects of regularization and parametrization. At short periods, where Love waves are mostly sensitive to crustal structure and thickness, we refer our comparison to a map of the Earth’s crust derived from independent data. On the assumption that second-order effects like seismic anisotropy and scattering can be neglected, we find the measurements of Ekström et al. (1997 of better quality; those of Trampert and Woodhouse (2001 result in phase velocity maps of much higher spatial frequency and, accordingly, more difficult to explain and justify geophysically. The discrepancy is partly explained by the more conservative a priori selection of data implemented by Ekström et al. (1997. Nevertheless, it becomes more significant with decreasing period, which indicates that it could also be traced to the different measurement techniques employed by the authors.

  8. Pay Dispersion and Performance in Teams

    DEFF Research Database (Denmark)

    Bucciol, Alessandro; Foss, Nicolai J; Piovesan, Marco

    2014-01-01

    Extant research offers conflicting predictions about the effect of pay dispersion on team performance. We collected a unique dataset from the Italian soccer league to study the effect of intra-firm pay dispersion on team performance, under different definitions of what constitutes a "team". This ...

  9. A new optical rotation dispersion formula

    International Nuclear Information System (INIS)

    Kimel, I.

    1981-12-01

    A new dispersion formula for the rotatory power is obtained in the framework of Kubo forlalism for transport coefficients. Unlike the well known Rosenfeld-Condon dispersion law, this formula is consistent with the free electron gas asymptotic behavior. (Author) [pt

  10. Discrete dispersion models and their Tweedie asymptotics

    DEFF Research Database (Denmark)

    Jørgensen, Bent; Kokonendji, Célestin C.

    2016-01-01

    The paper introduce a class of two-parameter discrete dispersion models, obtained by combining convolution with a factorial tilting operation, similar to exponential dispersion models which combine convolution and exponential tilting. The equidispersed Poisson model has a special place in this ap......The paper introduce a class of two-parameter discrete dispersion models, obtained by combining convolution with a factorial tilting operation, similar to exponential dispersion models which combine convolution and exponential tilting. The equidispersed Poisson model has a special place...... in this approach, whereas several overdispersed discrete distributions, such as the Neyman Type A, Pólya-Aeppli, negative binomial and Poisson-inverse Gaussian, turn out to be Poisson-Tweedie factorial dispersion models with power dispersion functions, analogous to ordinary Tweedie exponential dispersion models...... with power variance functions. Using the factorial cumulant generating function as tool, we introduce a dilation operation as a discrete analogue of scaling, generalizing binomial thinning. The Poisson-Tweedie factorial dispersion models are closed under dilation, which in turn leads to a Poisson...

  11. Seed Dispersal Potential of Asian Elephants

    DEFF Research Database (Denmark)

    Harich, Franziska K.; Treydte, Anna Christina; Ogutu, Joseph Ochieng

    2016-01-01

    Elephants, the largest terrestrial mega-herbivores, play an important ecological role in maintaining forest ecosystem diversity. While several plant species strongly rely on African elephants (Loxodonta africana; L. cyclotis) as seed dispersers, little is known about the dispersal potential of As...

  12. Interspecific nematode signals regulate dispersal behavior.

    Directory of Open Access Journals (Sweden)

    Fatma Kaplan

    Full Text Available Dispersal is an important nematode behavior. Upon crowding or food depletion, the free living bacteriovorus nematode Caenorhabditis elegans produces stress resistant dispersal larvae, called dauer, which are analogous to second stage juveniles (J2 of plant parasitic Meloidogyne spp. and infective juveniles (IJs of entomopathogenic nematodes (EPN, e.g., Steinernema feltiae. Regulation of dispersal behavior has not been thoroughly investigated for C. elegans or any other nematode species. Based on the fact that ascarosides regulate entry in dauer stage as well as multiple behaviors in C. elegans adults including mating, avoidance and aggregation, we hypothesized that ascarosides might also be involved in regulation of dispersal behavior in C. elegans and for other nematodes such as IJ of phylogenetically related EPNs.Liquid chromatography-mass spectrometry analysis of C. elegans dauer conditioned media, which shows strong dispersing activity, revealed four known ascarosides (ascr#2, ascr#3, ascr#8, icas#9. A synthetic blend of these ascarosides at physiologically relevant concentrations dispersed C. elegans dauer in the presence of food and also caused dispersion of IJs of S. feltiae and J2s of plant parasitic Meloidogyne spp. Assay guided fractionation revealed structural analogs as major active components of the S. feltiae (ascr#9 and C. elegans (ascr#2 dispersal blends. Further analysis revealed ascr#9 in all Steinernema spp. and Heterorhabditis spp. infected insect host cadavers.Ascaroside blends represent evolutionarily conserved, fundamentally important communication systems for nematodes from diverse habitats, and thus may provide sustainable means for control of parasitic nematodes.

  13. 21 CFR 178.3725 - Pigment dispersants.

    Science.gov (United States)

    2010-04-01

    ... HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: ADJUVANTS, PRODUCTION AIDS, AND SANITIZERS Certain Adjuvants and Production Aids § 178.3725 Pigment dispersants. Subject to the provisions of this... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Pigment dispersants. 178.3725 Section 178.3725 Food...

  14. Dispersions of Carbon nanotubes in Polymer Matrices

    Science.gov (United States)

    Wise, Kristopher Eric (Inventor); Park, Cheol (Inventor); Siochi, Emilie J. (Inventor); Harrison, Joycelyn S. (Inventor); Lillehei, Peter T. (Inventor); Lowther, Sharon E. (Inventor)

    2010-01-01

    Dispersions of carbon nanotubes exhibiting long term stability are based on a polymer matrix having moieties therein which are capable of a donor-acceptor complexation with carbon nanotubes. The carbon nanotubes are introduced into the polymer matrix and separated therein by standard means. Nanocomposites produced from these dispersions are useful in the fabrication of structures, e.g., lightweight aerospace structures.

  15. Membranes as separators of dispersed emulsion phases

    NARCIS (Netherlands)

    Lefferts, A.G.

    1997-01-01

    The reuse or discharge of industrial waste waters, containing small fractions of dispersed oil, requires a purification treatment for which membranes can be used. If only little oil is present, removal of the dispersed phase might be preferable to the more commonly applied removal of the

  16. A synthesis of empirical plant dispersal kernels

    Czech Academy of Sciences Publication Activity Database

    Bullock, J. M.; González, L. M.; Tamme, R.; Götzenberger, Lars; White, S. M.; Pärtel, M.; Hooftman, D. A. P.

    2017-01-01

    Roč. 105, č. 1 (2017), s. 6-19 ISSN 0022-0477 Institutional support: RVO:67985939 Keywords : dispersal kernel * dispersal mode * probability density function Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 5.813, year: 2016

  17. Interaction between molecular complexes in dispersive media

    International Nuclear Information System (INIS)

    Banagas, E.A.; Manykin, E.A.

    1987-01-01

    The interaction between molecular complexes in different dispersive media with local and nonlocal screening is investigated theoretically. On the basis of results of numerical analysis on a computer, the dependence of the coupled-system spectrum and the interaction energy of the polarized modes on the characteristic parameters of the dispersive media is considered

  18. Modeling of atmospheric dispersion of radionuclides

    International Nuclear Information System (INIS)

    Baklouti, Nada

    2010-01-01

    This work is a prediction of atmospheric dispersion of radionuclide from a chronic rejection of the nuclear power generating plant that can be located in one of the Tunisian sites: Skhira or Bizerte. Also it contains a study of acute rejection 'Chernobyl accident' which was the reference for the validation of GENII the code of modeling of atmospheric dispersion.

  19. Dispersion-induced nonlinearities in semiconductors

    DEFF Research Database (Denmark)

    Mørk, Jesper; Mecozzi, A.

    2002-01-01

    A dispersive and saturable medium is shown, under very general conditions, to possess ultrafast dynamic behaviour due to non-adiabatic polarisation dynamics. Simple analytical expressions relating the effect to the refractive index dispersion of a semiconductor ire derived and the magnitude...... of the equivalent Kerr coefficient is shown to be in qualitative agreement with measurements on active semiconductor waveguides....

  20. Modeling the dispersal of spiny lobster (

    NARCIS (Netherlands)

    Whomersley, P.; van der Molen, J.; Holt, D.; Trundle, C.; Clark, S.; Fletcher, D.

    2018-01-01

    Knowledge of larval dispersal, population dynamics and connectivity in relation to the management and conservation of commercially important species is vital if existing fisheries are to remain sustainable into the future. Larval dispersal of the commercially exploited spiny lobster, Palinurus

  1. Employment Effects of Spatial Dispersal of Refugees

    DEFF Research Database (Denmark)

    Damm, Anna Piil; Rosholm, Michael

    We argue that spatial dispersal influences labour market assimilation of refugees through two mechanisms: first, the local job offer arrival rate and, second, place utility. Our partial search model with simultaneous job and residential location search predicts that the reservation wage for local...... by evaluating the employment effects of the Danish spatial dispersal policy carried out 1986-1998....

  2. An atmospheric dispersion index for prescribed burning

    Science.gov (United States)

    Leonidas G. Lavdas

    1986-01-01

    A numerical index that estimates the atmosphere's capacity to disperse smoke from prescribed burning is described. The physical assumptions and mathematical development of the index are given in detail. A preliminary interpretation of dispersion index values is offered. A FORTRAN subroutine package for computing the index is included.

  3. Dispersive and erodible soils - fundamental differences

    CSIR Research Space (South Africa)

    Paige-Green, P

    2008-11-01

    Full Text Available Dispersive, erodible and slaking soils are prevalent over wide areas of South Africa. Each of these materials increases the cost of construction, but dispersive soils are likely to lead to far more serious problems, particularly in dam construction...

  4. Spectral dispersion and fringe detection in IOTA

    Science.gov (United States)

    Traub, W. A.; Lacasse, M. G.; Carleton, N. P.

    1990-01-01

    Pupil plane beam combination, spectral dispersion, detection, and fringe tracking are discussed for the IOTA interferometer. A new spectrometer design is presented in which the angular dispersion with respect to wavenumber is nearly constant. The dispersing element is a type of grism, a series combination of grating and prism, in which the constant parts of the dispersion add, but the slopes cancel. This grism is optimized for the display of channelled spectra. The dispersed fringes can be tracked by a matched-filter photon-counting correlator algorithm. This algorithm requires very few arithmetic operations per detected photon, making it well-suited for real-time fringe tracking. The algorithm is able to adapt to different stellar spectral types, intensity levels, and atmospheric time constants. The results of numerical experiments are reported.

  5. Pay Dispersion and Performance in Teams

    Science.gov (United States)

    Bucciol, Alessandro; Foss, Nicolai J.; Piovesan, Marco

    2014-01-01

    Extant research offers conflicting predictions about the effect of pay dispersion on team performance. We collected a unique dataset from the Italian soccer league to study the effect of intra-firm pay dispersion on team performance, under different definitions of what constitutes a “team”. This peculiarity of our dataset can explain the conflicting evidence. Indeed, we also find positive, null, and negative effects of pay dispersion on team performance, using the same data but different definitions of team. Our results show that when the team is considered to consist of only the members who directly contribute to the outcome, high pay dispersion has a detrimental impact on team performance. Enlarging the definition of the team causes this effect to disappear or even change direction. Finally, we find that the detrimental effect of pay dispersion is due to worse individual performance, rather than a reduction of team cooperation. PMID:25397615

  6. Analysis of site-specific dispersion conditions

    International Nuclear Information System (INIS)

    Paesler-Sauer, J.

    1989-03-01

    This report presents an analysis of atmospheric dispersion conditions in the environs of nuclear power stations in the Federal Republic of Germany. The analysis is based on meteorological data measured on the power station sites (KFUe = nuclear reactor remote control records) and by neighbouring stations operated by the German Weather Service. The data are series of hourly mean values of wind and temperature gradient or stability class over the period of one or more years. The aim of the data analysis is to find types of dispersion conditions characterized by the flow field and stratification, and to assess the feasibility of calculating these quantities in the case of an emergency. Influences of terrain structures in the environs of the site are considered. The annual frequencies of types of dispersion situations are assessed, the capability to recognize the dispersion situation from meteorological data measured on the site and the applicability of dispersion models are discussed. (orig.) [de

  7. Solitonic Dispersive Hydrodynamics: Theory and Observation

    Science.gov (United States)

    Maiden, Michelle D.; Anderson, Dalton V.; Franco, Nevil A.; El, Gennady A.; Hoefer, Mark A.

    2018-04-01

    Ubiquitous nonlinear waves in dispersive media include localized solitons and extended hydrodynamic states such as dispersive shock waves. Despite their physical prominence and the development of thorough theoretical and experimental investigations of each separately, experiments and a unified theory of solitons and dispersive hydrodynamics are lacking. Here, a general soliton-mean field theory is introduced and used to describe the propagation of solitons in macroscopic hydrodynamic flows. Two universal adiabatic invariants of motion are identified that predict trapping or transmission of solitons by hydrodynamic states. The result of solitons incident upon smooth expansion waves or compressive, rapidly oscillating dispersive shock waves is the same, an effect termed hydrodynamic reciprocity. Experiments on viscous fluid conduits quantitatively confirm the soliton-mean field theory with broader implications for nonlinear optics, superfluids, geophysical fluids, and other dispersive hydrodynamic media.

  8. UFOMOD - atmospheric dispersion and deposition

    International Nuclear Information System (INIS)

    Panitz, H.J.; Matzerath, C.; Paesler-Sauer, J.

    1989-10-01

    The report gives an introduction into the modelling of atmospheric dispersion and deposition which has been implemented in the new program system UFOMOD for assessing the consequences after nuclear accidents. According to the new structure of UFOMOD, different trajectory models with ranges of validity near to the site and at far distances are applied. Emphasis is laid on the description of the segmented plume model MUSEMET and its affilated submodels, being the removal of activity from the cloud by dry and wet deposition, and special effects like plume rise and the behaviour of plumes released into building wakes. In addition, the evaluation of γ-dose correction factors to take account of the finite extent of the radioactive plume in the near range (up to about 20 km) are described. Only brief introductions are given into the principles of the other models available: the puff model RIMPUFF, the long-range puff model MESOS, and the special straight-line Gaussian model ISOLA which are used if low-level long-duration releases are considered. To define starting times of weather sequences and the probabilities of occurrence of these sequences, it is convenient to perform stratified sampling. Therefore, the preprocessing program package METSAM has been developed to perform for generic ACAs a random sampling of weather sequences out off a population of classified weather conditions. The sampling procedure and a detailed input/output (I/O) description is presented and an additional appendix, respectively. A general overview on the I/O structure of MUSEMET as well as a brief user guide to run the KfK version of the MESOS code are also given in the appendix. (orig.) [de

  9. The Braer incident: Dispersion in action

    International Nuclear Information System (INIS)

    Thomas, D.

    1993-01-01

    In January 1993, the tanker Braer foundered in the Shetland Islands and pollution from the cargo of 85,000 tonnes of Gullfaks crude oil was reported almost immediately. The tanker was battered by storm winds and finally broke up, spilling the remainder of its cargo into the bay at Garth's Ness. Dispersants were applied to the oil plumes, assisting the significant natural dispersion. Shoreline protection and cleanup activities included construction of spade dams and sorbent barriers. Oil concentrations in water, air, sediment, and fish were monitored. The sampling program undertaken during the spill period is described. Measured hydrocarbon concentrations in salmon farm areas were not observed to rise above 4 ppM. The high rates of dispersion make the Braer incident worthy of detailed study both in terms of understanding the mechanism of the dispersion process and also in assessing the environmental effects following high dispersed oil concentrations. Estimates of the spill's mass balance are provided for the bay at Garth's Ness, where the highest oil concentrations were observed, and along the 26 km of coastline which received the most significant concentrations of dispersed oil. Contrary to laboratory experiments which showed that the Gullfaks crude would emulsify at the high sea states prevailing at the time, the Braer spill did not emulsify and most of the oil released was dispersed naturally into the water column. It appears that it is most appropriate to model the Braer spill as a spillage of floating or dissolved chemical. 4 refs., 4 figs., 6 tabs

  10. Dispersion cancellation in a triple Laue interferometer

    International Nuclear Information System (INIS)

    Lemmel, Hartmut

    2014-01-01

    The concept of dispersion cancellation has been established in light optics to improve the resolution of interferometric measurements on dispersive media. Odd order dispersion cancellation allows to measure phase shifts without defocusing the interferometer due to wave packet displacements, while even order dispersion cancellation allows to measure time lags without losing resolution due to wave packet spreading. We report that either type of dispersion cancellation can be realized very easily in a triple Laue interferometer. Such interferometers are Mach–Zehnder interferometers based on Bragg diffraction, and are commonly used for neutrons and x-rays. Although the first x-ray interferometer was built nearly five decades ago, the feature of dispersion cancellation hasn't been recognized so far because the concept was hardly known in the neutron and x-ray community. However, it explains right away the surprising decoupling of phase shift and spatial displacement that we have discovered recently in neutron interferometry (Lemmel and Wagh 2010 Phys. Rev. A 82 033626). Furthermore, this article might inspire the light optics community to consider whether a triple Laue interferometer for laser light would be useful and feasible. We explain how dispersion cancellation works in neutron interferometry, and we describe the setup rigorously by solving the Schrödinger equation and by calculating the path integral. We point out, that the latter has to be evaluated with special care since in our setup the beam trajectory moves with respect to the crystal lattice of the interferometer. (paper)

  11. Generalized dispersive wave emission in nonlinear fiber optics.

    Science.gov (United States)

    Webb, K E; Xu, Y Q; Erkintalo, M; Murdoch, S G

    2013-01-15

    We show that the emission of dispersive waves in nonlinear fiber optics is not limited to soliton-like pulses propagating in the anomalous dispersion regime. We demonstrate, both numerically and experimentally, that pulses propagating in the normal dispersion regime can excite resonant dispersive radiation across the zero-dispersion wavelength into the anomalous regime.

  12. Anomalous dispersion enhanced Cerenkov phase-matching

    Energy Technology Data Exchange (ETDEWEB)

    Kowalczyk, T.C.; Singer, K.D. [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Physics; Cahill, P.A. [Sandia National Labs., Albuquerque, NM (United States)

    1993-11-01

    The authors report on a scheme for phase-matching second harmonic generation in polymer waveguides based on the use of anomalous dispersion to optimize Cerenkov phase matching. They have used the theoretical results of Hashizume et al. and Onda and Ito to design an optimum structure for phase-matched conversion. They have found that the use of anomalous dispersion in the design results in a 100-fold enhancement in the calculated conversion efficiency. This technique also overcomes the limitation of anomalous dispersion phase-matching which results from absorption at the second harmonic. Experiments are in progress to demonstrate these results.

  13. Noise figure of amplified dispersive Fourier transformation

    International Nuclear Information System (INIS)

    Goda, Keisuke; Jalali, Bahram

    2010-01-01

    Amplified dispersive Fourier transformation (ADFT) is a powerful tool for fast real-time spectroscopy as it overcomes the limitations of traditional optical spectrometers. ADFT maps the spectrum of an optical pulse into a temporal waveform using group-velocity dispersion and simultaneously amplifies it in the optical domain. It greatly simplifies spectroscopy by replacing the diffraction grating and detector array in the conventional spectrometer with a dispersive fiber and single-pixel photodetector, enabling ultrafast real-time spectroscopic measurements. Following our earlier work on the theory of ADFT, here we study the effect of noise on ADFT. We derive the noise figure of ADFT and discuss its dependence on various parameters.

  14. Phase noise of dispersion-managed solitons

    International Nuclear Information System (INIS)

    Spiller, Elaine T.; Biondini, Gino

    2009-01-01

    We quantify noise-induced phase deviations of dispersion-managed solitons (DMS) in optical fiber communications and femtosecond lasers. We first develop a perturbation theory for the dispersion-managed nonlinear Schroedinger equation (DMNLSE) in order to compute the noise-induced mean and variance of the soliton parameters. We then use the analytical results to guide importance-sampled Monte Carlo simulations of the noise-driven DMNLSE. Comparison of these results with those from the original unaveraged governing equations confirms the validity of the DMNLSE as a model for many dispersion-managed systems and quantify the increased robustness of DMS with respect to noise-induced phase jitter.

  15. An expert system for dispersion model interpretation

    International Nuclear Information System (INIS)

    Skyllingstad, E.D.; Ramsdell, J.V.

    1988-10-01

    A prototype expert system designed to diagnose dispersion model uncertainty is described in this paper with application to a puff transport model. The system obtains qualitative information from the model user and through an expert-derived knowledge base, performs a rating of the current simulation. These results can then be used in combination with dispersion model output for deciding appropriate evacuation measures. Ultimately, the goal of this work is to develop an expert system that may be operated accurately by an individual uneducated in meteorology or dispersion modeling. 5 refs., 3 figs

  16. Removal of Disperse Blue 56 and Disperse Red 135 dyes from aqueous dispersions by modified montmorillonite nanoclay

    Directory of Open Access Journals (Sweden)

    Ahmadishoar Javad

    2017-01-01

    Full Text Available In this study modified montmorillonite was used as an adsorbent for the removal of two selected disperse dyes i.e., Disperse Blue 56 (DB and Disperse Red 135 (DR from dye dispersions. The adsorption equilibrium data of dyes adsorption were investigated by using Nernst, Freundlich and Langmuir isotherm models. The adsorption kinetics was analyzed by using different models including pseudo-first-order, pseudo-second-order, Elovich and Intraparticle diffusion model. The Freundlich isotherm was found to be the most appropriate model for describing the sorption of the dyes on modified nanoclay. The best fit to the experimental results was obtained by using the pseudo-second-order kinetic equation, which satisfactorily described the process of dye adsorption. Although different kinetic models may control the rate of the adsorption process, the results indicated that the main rate limiting step was the intraparticle diffusion. The results showed that the proposed modified montmorillonite could be used as an effective adsorbent for the removal of disperse dyes even from highly concentrated dispersions.

  17. Dispersion, sorption and photodegradation of petroleum hydrocarbons in dispersant-seawater-sediment systems.

    Science.gov (United States)

    Zhao, Xiao; Liu, Wen; Fu, Jie; Cai, Zhengqing; O'Reilly, S E; Zhao, Dongye

    2016-08-15

    This work examined effects of model oil dispersants on dispersion, sorption and photodegradation of petroleum hydrocarbons in simulated marine systems. Three dispersants (Corexit 9500A, Corexit 9527A and SPC 1000) were used to prepare dispersed water accommodated oil (DWAO). While higher doses of dispersants dispersed more n-alkanes and PAHs, Corexit 9500A preferentially dispersed C11-C20 n-alkanes, whereas Corexit 9527A was more favorable for smaller alkanes (C10-C16), and SPC 1000 for C12-C28 n-alkanes. Sorption of petroleum hydrocarbons on sediment was proportional to TPH types/fractions in the DWAOs. Addition of 18mg/L of Corexit 9500A increased sediment uptake of 2-3 ring PAHs, while higher dispersant doses reduced the uptake, due to micelle-enhanced solubilization effects. Both dispersed n-alkanes and PAHs were susceptible to photodegradation under simulated sunlight. For PAHs, both photodegradation and photo-facilitated alkylation were concurrently taking place. The information can facilitate sounder assessment of fate and distribution of dispersed oil hydrocarbons in marine systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Effects of chemical dispersants on oil physical properties and dispersion. Volume 1

    International Nuclear Information System (INIS)

    Khelifa, A.; Fingas, M.; Hollebone, B.P.; Brown, C.E.; Pjontek, D.

    2007-01-01

    Laboratory and field testing have shown that the dispersion of oil spilled in water is influenced by chemical dispersants via the modification of the interfacial properties of the oil, such as oil-brine interfacial tension (IFT). This study focused on new laboratory experiments that measured the effects on the physical properties and dispersion of oil, with particular reference to the effects of chemical dispersants on IFT and oil viscosity and the subsequent effects on oil droplet formation. Experiments were conducted at 15 degrees C using Arabian Medium, Alaska North Slope and South Louisiana crude and Corexit 9500 and Corexit 9527 chemical dispersants. The dispersants were denser than the 3 oils. The effect of IFT reduction on oil dispersion was measured and showed substantial reduction in the size and enhancement of the concentration of oil droplets in the water column. It was shown that the brine-oil IFT associated with the 3 crudes reduced to less than 3.6 mN/m with the application of the chemical dispersants, even at a low dispersant-to-oil ratio (DOR) value of 1:200. The use of chemical dispersants increased the viscosity of the dispersant-oil mixture up to 40 per cent over the neat crude oil. It was shown that for each mixing condition, an optimum value of DOR exists that provides for maximal dispersant effectiveness. The IFT reaches maximum reduction at optimum DOR. It was suggested that oil spill modelling can be improved with further study of IFT reduction with DOR and variations of critical micelle concentration with the type and solubility of chemical dispersant, oil type and oil to water ratio. 13 refs., 3 tabs., 7 figs

  19. Dispersal Timing: Emigration of Insects Living in Patchy Environments.

    Directory of Open Access Journals (Sweden)

    Milica Lakovic

    Full Text Available Dispersal is a life-history trait affecting dynamics and persistence of populations; it evolves under various known selective pressures. Theoretical studies on dispersal typically assume 'natal dispersal', where individuals emigrate right after birth. But emigration may also occur during a later moment within a reproductive season ('breeding dispersal'. For example, some female butterflies first deposit eggs in their natal patch before migrating to other site(s to continue egg-laying there. How breeding compared to natal dispersal influences the evolution of dispersal has not been explored. To close this gap we used an individual-based simulation approach to analyze (i the evolution of timing of breeding dispersal in annual organisms, (ii its influence on dispersal (compared to natal dispersal. Furthermore, we tested (iii its performance in direct evolutionary contest with individuals following a natal dispersal strategy. Our results show that evolution should typically result in lower dispersal under breeding dispersal, especially when costs of dispersal are low and population size is small. By distributing offspring evenly across two patches, breeding dispersal allows reducing direct sibling competition in the next generation whereas natal dispersal can only reduce trans-generational kin competition by producing highly dispersive offspring in each generation. The added benefit of breeding dispersal is most prominent in patches with small population sizes. Finally, the evolutionary contests show that a breeding dispersal strategy would universally out-compete natal dispersal.

  20. The Dangers of Dispersal of Responsibilities

    Directory of Open Access Journals (Sweden)

    Adriana Schiopoiu Burlea

    2017-05-01

    Full Text Available Taking into account that it is in the nature of the modern corporation that risks are distributed over several agents, we discuss in this paper the organisational behaviour as it results from such dispersal of responsibilities for both the principal and the agent. We explore the hypothesis that dispersal of responsibilities could be the result or a cause of a lack of consensus between the principal and the agent. Our findings suggest that a dispersal of responsibilities has a negative impact on the principal-agent relationship and that it represents a foundation for theoretical and empirical approaches to organisational behaviour. We find that agent perceptions of a dispersal of responsibilities are linked to his/her resistance to the principal’s interests, but this relationship is deeper than was suggested by previous research. However, if the sharing of responsibilities does not run parallel to that, we may have as a result what we call an agency problem.

  1. Adsorption of an anionic dispersant on lignite

    Energy Technology Data Exchange (ETDEWEB)

    Yavuz, R.; Kucukbayrak, S. [Istanbul Technical University, Istanbul (Turkey). Dept. of Chemical Engineering, Chemical & Metallurgical Engineering Faculty

    2001-12-01

    Since coal is not a homogeneous substance but a mixture of carbonaceous materials and mineral matter, it has a variety of surface properties. Therefore, it is not easy to control the properties of coal suspensions by simply adjusting variables, such as pH and/or electrolyte. A chemical agent needs to be added to control the properties of the coal suspensions. The adsorption behavior of an anionic dispersant in the presence of a wetting agent using some Turkish lignite samples was investigated. The effects of dispersant concentration, temperature and pH on the dispersant adsorption were studied systematically, and the experimental results are presented. Pellupur B69 as a dispersant, commercial mixture of formaldehyde condensate sodium salt of naphthalene sulphonic acid, and Texapon N{sub 2}5 as a wetting agent, a sodium lauryl ether sulfate, have been used.

  2. Dispersion engineering in metamaterials and metasurfaces

    Science.gov (United States)

    Li, Xiong; Pu, Mingbo; Ma, Xiaoliang; Guo, Yinghui; Gao, Ping; Luo, Xiangang

    2018-02-01

    Dispersion engineering is essential for spectral utilization in electromagnetic systems. However, it is difficult to manage the dispersions in both natural materials and traditional electromagnetic waveguides since they are tightly related to fine structures of atoms, molecules and causality. The emergence of metamaterials and metasurfaces, which are made of subwavelength inclusions offers tremendous freedom to manipulate the electromagnetic parameters of materials and modes. Here, we review the basic principles, practical applications and recent advancements of the dispersion engineering in metadevices. The contributions of dispersion management in metadevice-based super-resolution imaging/nanolithography systems, planar functional devices, as well as the broadband perfect absorbers/polarization converters are discussed in depth. The challenges faced by this field as well as future developing trends are also presented in the conclusions.

  3. PETROLEUM-COLLECTING AND DISPERSING CHEMICALS FOR ...

    African Journals Online (AJOL)

    Preferred Customer

    Films of petroleum origin reflecting sunlight rays hinder absorption of energy by water necessary for life ... Dispersing chemicals like mechanical clean-up methods have their own place in fighting oil spills. They are ... yellow color, and filtered.

  4. Resuspension parameters for TRAC dispersion model

    International Nuclear Information System (INIS)

    Langer, G.

    1987-01-01

    Resuspension factors for the wind erosion of soil contaminated with plutonium are necessary to run the Rocky Flats Plant Terrain Responsive Atmospheric Code (TRAC). The model predicts the dispersion and resulting population dose due to accidental plutonium releases

  5. Modeling electrical dispersion phenomena in Earth materials

    Directory of Open Access Journals (Sweden)

    D. Patella

    2008-06-01

    Full Text Available It is illustrated that IP phenomena in rocks can be described using conductivity dispersion models deduced as solutions to a 2nd-order linear differential equation describing the motion of a charged particle immersed in an external electrical field. Five dispersion laws are discussed, namely: the non-resonant positive IP model, which leads to the classical Debye-type dispersion law and by extension to the Cole-Cole model, largely used in current practice; the non-resonant negative IP model, which allows negative chargeability values, known in metals at high frequencies, to be explained as an intrinsic physical property of earth materials in specific field cases; the resonant flat, positive or negative IP models, which can explain the presence of peak effects at specific frequencies superimposed on flat, positive or negative dispersion spectra.

  6. Long anterior zonules and pigment dispersion.

    Science.gov (United States)

    Moroi, Sayoko E; Lark, Kurt K; Sieving, Paul A; Nouri-Mahdavi, Kouros; Schlötzer-Schrehardt, Ursula; Katz, Gregory J; Ritch, Robert

    2003-12-01

    To describe pigment dispersion associated with long anterior zonules. Multicenter observational case series. Fifteen patients, seven of whom were treated for glaucoma or ocular hypertension, were identified with long anterior zonules and pigment dispersion. Transmission electron microscopy was performed on one anterior capsule specimen. All patients had anterior zonules that inserted centrally on the lens capsule. Signs of pigment dispersion included corneal endothelial pigmentation, loss of the pupillary ruff, and variable trabecular meshwork pigmentation. Ultrasound biomicroscopy verified the lack of posterior iris insertion and concavity. There was no exfoliation material. Transmission electron microscopy showed zonular lamellae with adherent pigment granules, and no exfoliation material. Long anterior zonules inserted onto the central lens capsule may cause mechanical disruption of the pigment epithelium at the pupillary ruff and central iris leading to pigment dispersion.

  7. Analytic properties of the whistler dispersion function

    International Nuclear Information System (INIS)

    Daniell, G.J.

    1986-01-01

    The analytic properties of the dispersion function of a whistler are investigated in the complex frequency plane. It possesses a pole and a branch point at a frequency equal to the minimum value of the electron gyrofrequency along the path of propagation. An integral equation relates the dispersion function to the distribution of magnetospheric electrons along the path and the solution of this equation is obtained. It is found that the electron density in the equatorial plane is very simply related to the dispersion function. A discussion of approximate formulae to represent the dispersion shows how particular terms can be related to attributes of the electron density distribution, and a new approximate formula is proposed. (author)

  8. SANS observations on weakly flocculated dispersions

    DEFF Research Database (Denmark)

    Mischenko, N.; Ourieva, G.; Mortensen, K.

    1997-01-01

    Structural changes occurring in colloidal dispersions of poly-(methyl metacrylate) (PMMA) particles, sterically stabilized with poly-(12-hydroxystearic acid) (PHSA), while varying the solvent quality, temperature and shear rate, are investigated by small-angle neutron scattering (SANS......). For a moderately concentrated dispersion in a marginal solvent the transition on cooling from the effective stability to a weak attraction is monitored, The degree of attraction is determined in the framework of the sticky spheres model (SSM), SANS and rheological results are correlated....

  9. Phonon dispersion relations for caesium thiocyanate

    International Nuclear Information System (INIS)

    Irving, M.A.; Smith, T.F.; Elcombe, M.M.

    1984-01-01

    Room temperature phonon dispersion relations for frequencies below 2 THz have been measured, along the three orthorhombic axes and selected diagonal directions by neutron inelastic scattering, for caesium thiocyanate. These curves, which represent 13 acoustic modes and 11 optic modes of vibration, do not agree with the dispersion behaviour calculated from the rigid-ion model developed by Ti and Ra to describe their Raman scattering observations

  10. Modelling of pollution dispersion in atmosphere

    International Nuclear Information System (INIS)

    Borysiewicz, M.; Stankiewicz, R.

    1994-01-01

    The paper contains the review of the mathematical foundation of atmospheric dispersion models. The atmospheric phenomena relevant to atmospheric dispersion model are discussed. In particular the parametrization of processes with time and space scales smaller than numerical grid size, limited by available computer power, is presented. The special attention was devoted to similarity theory and parametrization of boundary layer. The numerical methods are analysed and the drawbacks of the method are presented. (author). 99 refs, 15 figs, 3 tabs

  11. Employment Effects of Spatial Dispersal of Refugees

    DEFF Research Database (Denmark)

    Damm, Anna Piil; Rosholm, Michael

    Spatial dispersal policies may influence labour market integration of refugees through two mechanisms. First, it may affect the local job offer arrival rate, and second, it may affect place utility. We investigate the second mechanism theoretically by formulating a partial search model in which a...... due to large local reservation wage effects. We investigate both mechanisms empirically and test the predictions of the theoretical model by evaluating the employment effects of the Danish spatial dispersal policy carried out 1986-1998....

  12. Employment Effects of Spatial Dispersal of Refugees

    OpenAIRE

    Damm, Anna Piil; Rosholm, Michael

    2005-01-01

    We argue that spatial dispersal influences labour market assimilation of refugees through two mechanisms: first, the local job offer arrival rate and, second, place utility. Our partial search model with simultaneous job and residential location search predicts that the reservation wage for local jobs decreases with place utility. We argue that spatial dispersal decreases average place utility of refugees which decreases the transition rate into first job due to large local reservation wages....

  13. URANIUM BISMUTHIDE DISPERSION IN MOLTEN METAL

    Science.gov (United States)

    Teitel, R.J.

    1959-10-27

    The formation of intermetallic bismuth compounds of thorium or uranium dispersed in a liquid media containing bismuth and lead is described. A bismuthide of uranium dispersed in a liquid metal medium is formed by dissolving uranium in composition of lead and bismuth containing less than 80% lead and lowering the temperature of the composition to a temperature below the point at which the solubility of uranium is exceeded and above the melting point of the composition.

  14. Dispersed-phase catalysis in coal liquefaction

    International Nuclear Information System (INIS)

    Utz, B.R.; Cugini, A.V.; Frommell, E.A.

    1990-01-01

    This paper reports that the specific reaction (activation) conditions for the conversion of catalyst precursors to unsupported catalyst have a direct effect on the catalytic activity and dispersion. The importance of reaction intermediates in decomposition of ammonium heptamolybdate and ammonium tetrathiomolybdate, and the sensitivity of these intermediates to reaction conditions, were studied in coal liquefaction systems. Recent results indicate that optimization of activation conditions facilitates the formation of a highly dispersed and active form of molybdenum disulfide for coal liquefaction. The use of the catalyst precursors ammonium heptamolybdate, ammonium tetrathiomolybdate, and molybdenum trisulfide for the conversion of coal to soluble products will be discussed. The use of an unsupported dispersed-phase catalyst for direct coal liquefaction is not a novel concept and has been employed in may studies with varying success. Dispersed-phase catalysts soluble and oil-soluble salts, and as finely divided powders. While some methods of catalyst introduction give higher dispersion of the catalyst and greater activity for the liquefaction of coal, all of the techniques allow the formation of a finely dispersed inorganic phase

  15. Estimate of dispersion in an unsaturated aquifer

    Science.gov (United States)

    Stephenson, D.; De Jesus, A. S. M.

    1985-10-01

    The Nuclear Development Corporation of South Africa (Pty) Ltd. (NUCOR) is constructing a low-level radioactive waste disposal site near Springbok in Namaqualand, an arid region to the west of South Africa. A groundwater model was developed which required site-specific data and this work describes procedures developed to assess the dispersivity of the soil in the vicinity of the proposed site. Preliminary laboratory tests, carried out using a sodium chloride solution, indicated the order of magnitude of the dispersivity for saturated soil at various levels. This enabled site tests to be designed. The site tests were done by injecting a pulse of scandium-46 into a hole and monitoring the displacement of the radioactive cloud as it moved down under gravity and spread laterally. A mathematical model was developed to predict the behaviour of the cloud and calibration of the model yielded vertical and horizontal dispersivities. The dispersion of radioactivity at the cloud front was assumed to occur in unsaturated medium while the continuously injected water behind the radioactivity was assumed to disperse in a saturated medium. Thus monitoring the concentration of both yielded approximate values for the effective dispersivities in unsaturated and saturated media.

  16. Spatially varying dispersion to model breakthrough curves.

    Science.gov (United States)

    Li, Guangquan

    2011-01-01

    Often the water flowing in a karst conduit is a combination of contaminated water entering at a sinkhole and cleaner water released from the limestone matrix. Transport processes in the conduit are controlled by advection, mixing (dilution and dispersion), and retention-release. In this article, a karst transport model considering advection, spatially varying dispersion, and dilution (from matrix seepage) is developed. Two approximate Green's functions are obtained using transformation of variables, respectively, for the initial-value problem and for the boundary-value problem. A numerical example illustrates that mixing associated with strong spatially varying conduit dispersion can cause strong skewness and long tailing in spring breakthrough curves. Comparison of the predicted breakthrough curve against that measured from a dye-tracing experiment between Ames Sink and Indian Spring, Northwest Florida, shows that the conduit dispersivity can be as large as 400 m. Such a large number is believed to imply strong solute interaction between the conduit and the matrix and/or multiple flow paths in a conduit network. It is concluded that Taylor dispersion is not dominant in transport in a karst conduit, and the complicated retention-release process between mobile- and immobile waters may be described by strong spatially varying conduit dispersion. Copyright © 2010 The Author(s). Journal compilation © 2010 National Ground Water Association.

  17. Juvenile dispersal in Calomys venustus (Muridae: Sigmodontinae)

    Science.gov (United States)

    Priotto, José; Steinmann, Andrea; Provensal, Cecilia; Polop, Jaime

    2004-05-01

    Both spacing behaviour and dispersal movement are viewed as hierarchical processes in which the effects may be expressed at spatial scale. This research was carried out to examine the hypothesis that the presence of parents promotes the dispersal of juveniles from their natal nest and their father or mother home-range, in Calomys venustus.The study was carried out in four 0.25 ha fences (two controls and two experimentals), in a natural pasture. This study had two periods: Father Removal (FR) (August and December 1997; year one) and Mother Removal (MR) (August 1998 and January 1999; year two). For the FR treatment fathers were removed after juveniles were born, but in the MR treatment mothers were removed after the juveniles were weaned. The effect of parents on the dispersal distance of juveniles was analysed with respect to their natal nest and their mother and father home-range. Dispersal distance from the nest of C. venustus was independent of either male or female parent. Juveniles were more dispersing in relation to the centre of activity of their mothers than to that of their fathers, and females were more dispersing than males. Female juveniles overlap their home-range with their parents less than male juveniles do. The differences observed between female and male juveniles would be related to their different sexual maturation times, as well as to the female territoriality.

  18. Magnon dispersion in thin magnetic films

    International Nuclear Information System (INIS)

    Balashov, T; Wulfhekel, W; Buczek, P; Sandratskii, L; Ernst, A

    2014-01-01

    Although the dispersion of magnons has been measured in many bulk materials, few studies deal with the changes in the dispersion when the material is in the form of a thin film, a system that is of interest for applications. Here we review inelastic tunneling spectroscopy studies of magnon dispersion in Mn/Cu 3 Au(1 0 0) and present new studies on Co and Ni thin films on Cu(1 0 0). The dispersion in Mn and Co films closely follows the dispersion of bulk samples with negligible dependence on thickness. The lifetime of magnons depends slightly on film thickness, and decreases considerably as the magnon energy increases. In Ni/Cu(1 0 0) films the thickness dependence of dispersion is much more pronounced. The measurements indicate a considerable mode softening for thinner films. Magnon lifetimes decrease dramatically near the edge of the Brillouin zone due to a close proximity of the Stoner continuum. The experimental study is supported by first-principles calculations. (paper)

  19. Magnon dispersion in thin magnetic films.

    Science.gov (United States)

    Balashov, T; Buczek, P; Sandratskii, L; Ernst, A; Wulfhekel, W

    2014-10-01

    Although the dispersion of magnons has been measured in many bulk materials, few studies deal with the changes in the dispersion when the material is in the form of a thin film, a system that is of interest for applications. Here we review inelastic tunneling spectroscopy studies of magnon dispersion in Mn/Cu3Au(1 0 0) and present new studies on Co and Ni thin films on Cu(1 0 0). The dispersion in Mn and Co films closely follows the dispersion of bulk samples with negligible dependence on thickness. The lifetime of magnons depends slightly on film thickness, and decreases considerably as the magnon energy increases. In Ni/Cu(1 0 0) films the thickness dependence of dispersion is much more pronounced. The measurements indicate a considerable mode softening for thinner films. Magnon lifetimes decrease dramatically near the edge of the Brillouin zone due to a close proximity of the Stoner continuum. The experimental study is supported by first-principles calculations.

  20. Surgical Management of Iatrogenic Pigment Dispersion Glaucoma.

    Science.gov (United States)

    Mierlo, Camille Van; Pinto, Luis Abegão; Stalmans, Ingeborg

    2015-01-01

    Iatrogenic pigment dispersion syndrome generally originates from a repetitive, mechanical trauma to the pigmented posterior epithelium of the iris. This trauma can arise after intraocular surgery, most commonly due to an abnormal contact between the intraocular lens (IOL) and the iris. Whether surgical removal of this primary insult can lead to a successful intraocular pressure (IOP) control remains unclear. Case-series. Patients with IOP elevation and clinical signs of pigment dispersion were screened for a diagnosis of iatrogenic IOL-related pigment dispersion. Three patients in which the IOL or the IOL-bag complex caused a pigment dispersion through a repetitive iris chafing were selected. In two cases, replacement of a sulcus-based single-piece IOL (patient 1) or a sub-luxated in-the-bag IOL (patient 2) by an anterior-chamber (AC) iris-fixed IOL led to a sustained decrease in IOP. In the third case, extensive iris atrophy and poor anatomical AC parameters for IOL implantation precluded further surgical intervention. IOL-exchange appears to be a useful tool in the management of iatrogenic pigment dispersion glaucoma due to inappropriate IOL implantation. This cause-oriented approach seems to be effective in controlling IOP, but should be offered only if safety criteria are met. How to cite this article: Van Mierlo C, Abegao Pinto L, Stalmans I. Surgical Management of Iatrogenic Pigment Dispersion Glaucoma. J Curr Glaucoma Pract 2015;9(1):28-32.

  1. Rheological Behavior of Bentonite-Polyester Dispersions

    Science.gov (United States)

    Abu-Jdayil, Basim; Al-Omari, Salah Addin

    2013-07-01

    The rheological behavior of a bentonite clay dispersed in unsaturated polyester was investigated. The effects of the solid content and particle size on the steady and transient rheological properties of the dispersions were studied. In addition, two types of bentonite with different Na+/Ca+2 ratio were used in this study. The Herschel-Bulkley and the Weltman models were used to describe the apparent viscosity of the bentonite-polyester composite in relation to the shear rate and shearing time. The bentonite-polyester dispersions were found to exhibit both Newtonian and non-Newtonian behavior. The transition from a Newtonian to a Bingham plastic and then to a shear-thinning material with a yield stress was found to depend on the solid concentration, the particle size, and the type of bentonite. At a low solid content, the apparent viscosity of the bentonite dispersion increased linearly with solid concentration. But a dramatic increase in the apparent viscosity beyond a solid content of 20 wt.% was observed. On the other hand, a thixotropic behavior was detected in bentonite-polyester dispersions with a high solid content and a low particle size. However, this behavior was more pronounced in dispersions with a high Na+/Ca+2 ratio.

  2. Cefuroxime axetil solid dispersions prepared using solution enhanced dispersion by supercritical fluids.

    Science.gov (United States)

    Jun, Seoung Wook; Kim, Min-Soo; Jo, Guk Hyun; Lee, Sibeum; Woo, Jong Soo; Park, Jeong-Sook; Hwang, Sung-Joo

    2005-12-01

    Cefuroxime axetil (CA) solid dispersions with HPMC 2910/PVP K-30 were prepared using solution enhanced dispersion by supercritical fluids (SEDS) in an effort to increase the dissolution rate of poorly water-soluble drugs. Their physicochemical properties in solid state were characterized by differential scanning calorimeter (DSC), powder X-ray diffraction (PXRD), Fourier transform infrared spectrometry (FT-IR) and scanning electron microscopy. No endothermic and characteristic diffraction peaks corresponding to CA were observed for the solid dispersions in DSC and PXRD. FTIR analysis demonstrated the presence of intermolecular hydrogen bonds between CA and HPMC 2910/PVP K-30 in solid dispersions, resulting in the formation of amorphous or non-crystalline CA. Dissolution studies indicated that the dissolution rates were remarkably increased in solid dispersions compared with those in the physical mixture and drug alone. In conclusion, an amorphous or non-crystalline CA solid dispersion prepared using SEDS could be very useful for the formulation of solid dosage forms.

  3. Dispersal kernel estimation: A comparison of empirical and modelled particle dispersion in a coastal marine system

    Science.gov (United States)

    Hrycik, Janelle M.; Chassé, Joël; Ruddick, Barry R.; Taggart, Christopher T.

    2013-11-01

    Early life-stage dispersal influences recruitment and is of significance in explaining the distribution and connectivity of marine species. Motivations for quantifying dispersal range from biodiversity conservation to the design of marine reserves and the mitigation of species invasions. Here we compare estimates of real particle dispersion in a coastal marine environment with similar estimates provided by hydrodynamic modelling. We do so by using a system of magnetically attractive particles (MAPs) and a magnetic-collector array that provides measures of Lagrangian dispersion based on the time-integration of MAPs dispersing through the array. MAPs released as a point source in a coastal marine location dispersed through the collector array over a 5-7 d period. A virtual release and observed (real-time) environmental conditions were used in a high-resolution three-dimensional hydrodynamic model to estimate the dispersal of virtual particles (VPs). The number of MAPs captured throughout the collector array and the number of VPs that passed through each corresponding model location were enumerated and compared. Although VP dispersal reflected several aspects of the observed MAP dispersal, the comparisons demonstrated model sensitivity to the small-scale (random-walk) particle diffusivity parameter (Kp). The one-dimensional dispersal kernel for the MAPs had an e-folding scale estimate in the range of 5.19-11.44 km, while those from the model simulations were comparable at 1.89-6.52 km, and also demonstrated sensitivity to Kp. Variations among comparisons are related to the value of Kp used in modelling and are postulated to be related to MAP losses from the water column and (or) shear dispersion acting on the MAPs; a process that is constrained in the model. Our demonstration indicates a promising new way of 1) quantitatively and empirically estimating the dispersal kernel in aquatic systems, and 2) quantitatively assessing and (or) improving regional hydrodynamic

  4. Design and development of a dust dispersion chamber to quantify the dispersibility of rock dust.

    Science.gov (United States)

    Perera, Inoka E; Sapko, Michael J; Harris, Marcia L; Zlochower, Isaac A; Weiss, Eric S

    2016-01-01

    Dispersible rock dust must be applied to the surfaces of entries in underground coal mines in order to inert the coal dust entrained or made airborne during an explosion and prevent propagating explosions. 30 CFR. 75.2 states that "… [rock dust particles] when wetted and dried will not cohere to form a cake which will not be dispersed into separate particles by a light blast of air …" However, a proper definition or quantification of "light blast of air" is not provided. The National Institute for Occupational Safety and Health (NIOSH) has, consequently, designed a dust dispersion chamber to conduct quantitative laboratory-scale dispersibility experiments as a screening tool for candidate rock dusts. A reproducible pulse of air is injected into the chamber and across a shallow tray of rock dust. The dust dispersed and carried downwind is monitored. The mass loss of the dust tray and the airborne dust measurements determine the relative dispersibility of the dust with respect to a Reference rock dust. This report describes the design and the methodology to evaluate the relative dispersibility of rock dusts with and without anti-caking agents. Further, the results of this study indicate that the dispersibility of rock dusts varies with particle size, type of anti-caking agent used, and with the untapped bulk density. Untreated rock dusts, when wetted and dried forming a cake that was much less dispersible than the reference rock dust used in supporting the 80% total incombustible content rule.

  5. The dispersion of SWCNTs treated by coupling and dispersing agents in fiber reinforced polymer composities

    Science.gov (United States)

    Duan, Yuexin; Yuan, Lu; Zhao, Yan; Guan, Fengxia

    2007-07-01

    It is an obstacle issue for Carbon nanotubes (CNTs) applied in fiber reinforced polymer composites that CNTs is dispersed in nano-level, particularly for single-wall Carbon nanotubes (SWCNTs). In this paper, SWCNTs were treated by the coupling agent like volan and dispersing agent as BYK to improve the dispersion in the Glass Fiber/Epoxy composites. The result of dispersion of SWCNTs in composites was observed by Scanning electron microscopy (SEM). Then the Glass Transition Temperature (Tg) of these kinds of composites with treated and untreated SWCNTs were obtained by Dynamic Mechanical Thermal Analysis (DMTA). Moreover, the bending properties of these composites were tested.

  6. Modeling of corium dispersion in DCH accidents

    International Nuclear Information System (INIS)

    Wu, Q.

    1996-01-01

    A model that governs the dispersion process in the direct containment heating (DCH) reactor accident scenario is developed by a stepwise approach. In this model, the whole transient is subdivided into four phases with an isothermal assumption. These are the liquid and gas discharge, the liquid film flow in the cavity before gas blowdown, the liquid and gas flow in the cavity with droplet entrainment, and the liquid transport and re-entrainment in the subcompartment. In each step, the dominant driving mechanisms are identified to construct the governing equations. By combining all the steps together, the corium dispersion information is obtained in detail. The key parameters are predicted quantitatively. These include the fraction of liquid that flows out of the cavity before gas blowdown, the dispersion fraction and the mean droplet diameter in the cavity, the cavity pressure rise due to the liquid friction force, and the dispersion fractions in the containment via different paths. Compared with the data of the 1:10 scale experiments carried out at Purdue University, fairly good agreement is obtained. A stand-alone prediction of the corium dispersion under prototypic Zion reactor conditions is carried out by assuming an isothermal process without chemical reactions. (orig.)

  7. Atmospheric dispersion models of radioactivity releases

    International Nuclear Information System (INIS)

    Oza, R.B.

    2016-01-01

    In view of the rapid industrialization in recent time, atmospheric dispersion models have become indispensible 'tools' to ensure that the effects of releases are well within the acceptable limits set by the regulatory authority. In the case of radioactive releases from the nuclear facility, though negligible in quantity and many a times not even measurable, it is required to demonstrate the compliance of these releases to the regulatory limits set by the regulatory authority by carrying out radiological impact assessment. During routine operations of nuclear facility, the releases are so low that environmental impact is usually assessed with the help of atmospheric dispersion models as it is difficult to distinguish negligible contribution of nuclear facility to relatively high natural background radiation. The accidental releases from nuclear facility, though with negligible probability of occurrence, cannot be ruled out. In such cases, the atmospheric dispersion models are of great help to emergency planners for deciding the intervention actions to minimize the consequences in public domain and also to workout strategies for the management of situation. In case of accidental conditions, the atmospheric dispersion models are also utilized for the estimation of probable quantities of radionuclides which might have got released to the atmosphere. Thus, atmospheric dispersion models are an essential tool for nuclear facility during routine operation as well as in the case of accidental conditions

  8. Does Environmental Knowledge Inhibit Hominin Dispersal?

    Science.gov (United States)

    Wren, Colin D; Costopoulos, Andre

    2015-07-01

    We investigated the relationship between the dispersal potential of a hominin population, its local-scale foraging strategies, and the characteristics of the resource environment using an agent-based modeling approach. In previous work we demonstrated that natural selection can favor a relatively low capacity for assessing and predicting the quality of the resource environment, especially when the distribution of resources is highly clustered. That work also suggested that the more knowledge foraging populations had about their environment, the less likely they were to abandon the landscape they know and disperse into novel territory. The present study gives agents new individual and social strategies for learning about their environment. For both individual and social learning, natural selection favors decreased levels of environmental knowledge, particularly in low-heterogeneity environments. Social acquisition of detailed environmental knowledge results in crowding of agents, which reduces available reproductive space and relative fitness. Agents with less environmental knowledge move away from resource clusters and into areas with more space available for reproduction. These results suggest that, rather than being a requirement for successful dispersal, environmental knowledge strengthens the ties to particular locations and significantly reduces the dispersal potential as a result. The evolved level of environmental knowledge in a population depends on the characteristics of the resource environment and affects the dispersal capacity of the population.

  9. Oak Dispersal Syndromes: Do Red and White Oaks Exhibit Different Dispersal Srategies?

    Science.gov (United States)

    Michael Steele; Peter Smallwood; William B. Terzaghi; John E. Carlson; Thomas conteras; Amy McEuen

    2004-01-01

    We provide an overview of the ecological and evolutionary interactions between oaks and several of their dispersal agents, and review a series of studies that demonstrate how various acorn characteristics affect feeding and caching decisions of these animals, which in turn may influence oak dispersal and establishment. We demonstrate that acorns of red oak species show...

  10. Tailoring Dispersion properties of photonic crystal waveguides by topology optimization

    DEFF Research Database (Denmark)

    Stainko, Roman; Sigmund, Ole

    2007-01-01

    based design updates. The goal of the optimization process is to come up with slow light, zero group velocity dispersion photonic waveguides or photonic waveguides with tailored dispersion properties for dispersion compensation purposes. Two examples concerning reproduction of a specific dispersion...

  11. Measurement of small dispersion values in optical components

    DEFF Research Database (Denmark)

    Peucheret, Christophe; Liu, Fenghai; Pedersen, Rune Johan Skullerud

    1999-01-01

    It is reported that small dispersion values in optical components can be measured using the RF modulation method originally restricted to large dispersions. Using a constant dispersion offset, arbitrarily small dispersion values can be measured with a resolution as good as 1.2 ps/nm....

  12. Natal dispersal and personalities in great tits (Parus major)

    NARCIS (Netherlands)

    Dingemanse, NJ; Both, C; van Noordwijk, AJ; Rutten, AL; Drent, PJ; Noordwijk, Arie J. van; Drent, Piet J.

    2003-01-01

    Dispersal is a major determinant of the dynamics and genetic structure of populations, and its consequences depend not only on average dispersal rates and distances, but also on the characteristics of dispersing and philopatric individuals. We investigated whether natal dispersal correlated with a

  13. Dynamics of Dispersive Wave Generation in Gas-Filled Photonic Crystal Fiber with the Normal Dispersion

    Directory of Open Access Journals (Sweden)

    Zhixiang Deng

    2017-01-01

    Full Text Available The absence of Raman and unique pressure-tunable dispersion is the characteristic feature of gas-filled photonic crystal fiber (PCF, and its zero dispersion points can be extended to the near-infrared by increasing gas pressure. The generation of dispersive wave (DW in the normal group velocity dispersion (GVD region of PCF is investigated. It is demonstrated that considering the self-steepening (SS and introducing the chirp of the initial input pulse are two suitable means to control the DW generation. The SS enhances the relative average intensity of blue-shift DW while weakening that of red-shift DW. The required propagation distance of DW emission is markedly varied by introducing the frequency chirp. Manipulating DW generation in gas-filled PCF by the combined effects of either SS or chirp and three-order dispersion (TOD provides a method for a concentrated transfer of energy into the targeted wavelengths.

  14. Employment effects of spatial dispersal of refugees

    DEFF Research Database (Denmark)

    Damm, Anna Piil; Rosholm, Michael

    2010-01-01

    Refugees subjected to a spatial dispersal tend to be assigned to a location outside the immigrant-dense cities. We argue that such locations are associated with low place utility. Our partial equilibrium search model with simultaneous job and residential location search predicts that the reservat......Refugees subjected to a spatial dispersal tend to be assigned to a location outside the immigrant-dense cities. We argue that such locations are associated with low place utility. Our partial equilibrium search model with simultaneous job and residential location search predicts...... that the reservation wage for local jobs decreases with place utility. We test the theoretical prediction by estimating the effects of characteristics of the location of assignment on the transition rate into the first job. Our sample is male refugees aged 30-59 who were subjected to the Danish spatial dispersal...

  15. Sphagnum moss disperses spores with vortex rings.

    Science.gov (United States)

    Whitaker, Dwight L; Edwards, Joan

    2010-07-23

    Sphagnum spores, which have low terminal velocities, are carried by turbulent wind currents to establish colonies many kilometers away. However, spores that are easily kept aloft are also rapidly decelerated in still air; thus, dispersal range depends strongly on release height. Vascular plants grow tall to lift spores into sufficient wind currents for dispersal, but nonvascular plants such as Sphagnum cannot grow sufficiently high. High-speed videos show that exploding capsules of Sphagnum generate vortex rings to efficiently carry spores high enough to be dispersed by turbulent air currents. Spores launched ballistically at similar speeds through still air would travel a few millimeters and not easily reach turbulent air. Vortex rings are used by animals; here, we report vortex rings generated by plants.

  16. Mechanical dispersion in fractured crystalline rock systems

    International Nuclear Information System (INIS)

    Lafleur, D.W.; Raven, K.G.

    1986-12-01

    This report compiles and evaluates the hydrogeologic parameters describing the flow of groundwater and transport of solutes in fractured crystalline rocks. This report describes the processes of mechanical dispersion in fractured crystalline rocks, and compiles and evaluates the dispersion parameters determined from both laboratory and field tracer experiments. The compiled data show that extrapolation of the reliable test results performed over intermediate scales (10's of m and 10's to 100's of hours) to larger spatial and temporal scales required for performance assessment of a nuclear waste repository in crystalline rock is not justified. The reliable measures of longitudinal dispersivity of fractured crystalline rock are found to range between 0.4 and 7.8 m

  17. Taylor dispersion in wind-driven current

    Science.gov (United States)

    Li, Gang; Wang, Ping; Jiang, Wei-Quan; Zeng, Li; Li, Zhi; Chen, G. Q.

    2017-12-01

    Taylor dispersion associated with wind-driven currents in channels, shallow lakes and estuaries is essential to hydrological environmental management. For solute dispersion in a wind-driven current, presented in this paper is an analytical study of the evolution of concentration distribution. The concentration moments are intensively derived for an accurate presentation of the mean concentration distribution, up to the effect of kurtosis. The vertical divergence of concentration is then deduced by Gill's method of series expansion up to the fourth order. Based on the temporal evolution of the vertical concentration distribution, the dispersion process in the wind-driven current is concretely characterized. The uniform shear leads to a special symmetrical distribution of mean concentration free of skewness. The non-uniformity of vertical concentration is caused by convection and smeared out gradually by the effect of diffusion, but fails to disappear even at large times.

  18. Dispersion self-energy of the electron

    International Nuclear Information System (INIS)

    Hawton, M.

    1991-01-01

    Electron mass renormalization and the Lamb shift have been investigated using the dispersion self-energy formalism. If shifts of both the electromagnetic field and quantum-mechanical transitions frequencies are considered, absorption from the electromagnetic field is canceled by emission due to atomic fluctuations. The frequencies of all modes are obtained from the self-consistency condition that the field seen by the electron is the same as the field produced by the expectation value of current. The radiation present can thus be viewed as arising from emission and subsequent reabsorption by matter. As developed here, the numerical predictions of dispersion theory are identical to those of quantum electrodynamics. The physical picture implied by dispersion theory is discussed in the context of semiclassical theories and quantum electrodynamics

  19. Glass transition in soft-sphere dispersions

    International Nuclear Information System (INIS)

    RamIrez-Gonzalez, P E; Medina-Noyola, M

    2009-01-01

    The concept of dynamic equivalence among mono-disperse soft-sphere fluids is employed in the framework of the self-consistent generalized Langevin equation (SCGLE) theory of colloid dynamics to calculate the ideal glass transition phase diagram of model soft-sphere colloidal dispersions in the softness-concentration state space. The slow dynamics predicted by this theory near the glass transition is compared with available experimental data for the decay of the intermediate scattering function of colloidal dispersions of soft-microgel particles. Increasing deviations from this simple scheme occur for increasingly softer potentials, and this is studied here using the Rogers-Young static structure factor of the soft-sphere systems as the input of the SCGLE theory, without assuming a priori the validity of the equivalence principle above.

  20. Training for Internationalization through Domestic Geographical Dispersion

    DEFF Research Database (Denmark)

    Santangelo, Grazia D.; Stucchi, Tamara

    Traditionally created to deal with the unfriendly domestic environment, business groups (BGs) are increasingly internationalizing. However, how BGs can reconcile their strictly domestic orientation with an international dimension still remains an open question. Drawing on arguments from...... organizational learning, we seek to solve this puzzle in relation to the internationalization of Indian BGs. In particular, we argue that in heterogeneous domestic emerging markets BG’s geographical dispersion across sub-national states provides training for internationalization. To internationalize successfully......, BGs need to develop the capability of managing geographically dispersed units in institutional heterogeneous contexts. Domestic geographical dispersion would indeed help the BG dealing with different regulations, customers and infrastructures. However, there is less scope for such training as BGs...

  1. Dispersal behavior of yellowjacket (Vespula germanica) queens.

    Science.gov (United States)

    Masciocchi, Maité; Martinez, Andrés S; Pereira, Ana J; Villacide, José M; Corley, Juan C

    2018-02-01

    Understanding the factors that affect animal dispersal behavior is important from both fundamental and applied perspectives. Dispersal can have clear evolutionary and ecological consequences, but for nonnative insect pests, dispersal capacity can also help to explain invasion success. Vespula germanica is a social wasp that, in the last century, has successfully invaded several regions of the world, showing one of the highest spread rates reported for a nonnative insect. In contrast with nonsocial wasps, in social species, queens are responsible for population redistribution and spread, as workers are sterile. For V. germanica, it has been observed that queen flight is limited to 2 distinct periods: early autumn, when new queens leave the nest to mate and find sheltered places in which to hibernate, and spring when new colonies are founded. Our aim was to study the flight behavior of V. germanica queens by focusing on the different periods in which dispersal occurs, characterizing as well the potential contribution of queen flight (i.e., distance) to the observed geographical spread. Our results suggest that the distances flown by nonoverwintered queens is greater than that flown by overwintered individuals, suggesting that the main queen dispersal events would occur before queens enter hibernation. This could relate to a behavioral trait of the queens to avoid the inbreeding with related drones. Additionally, given the short distances flown and remarkable geographical spread observed, we provide evidence showing that queen dispersal by flight is likely to contribute proportionately less to population spread than human-aided factors. © 2016 Institute of Zoology, Chinese Academy of Sciences.

  2. Familial occurrence of pigment dispersion syndrome.

    Science.gov (United States)

    Bovell, A M; Damji, K F; Dohadwala, A A; Hodge, W G; Allingham, R R

    2001-02-01

    Pigment dispersion syndrome affects up to 4% of the white population. It is characterized by the presence of transillumination defects, Krukenberg's spindle and dense trabecular meshwork pigmentation. Open-angle glaucoma will develop in as many as 50% of affected patients. In this study we describe the familial occurrence of pigment dispersion syndrome in six North American pedigrees and the phenotypic characteristics with respect to pigment dispersion syndrome and glaucoma. Probands with pigment dispersion syndrome were identified in glaucoma clinics at university eye centres in Ottawa and Durham, NC. Families with two or more affected members were evaluated. All willing members in each family underwent a thorough clinical examination and were classified as affected with pigment dispersion syndrome, suspect or unaffected. The previous medical records were reviewed to obtain the past medical and ocular history, including risk factors for glaucoma. All six families are white. Three families show at least two generations of affected members. Of the 43 subjects examined 58% were women. All 14 affected members showed moderate to heavy trabecular meshwork pigmentation and either Krukenberg's spindle or transillumination defects. The affected members were also considerably more myopic (mean spherical equivalent for the right eye -4.72 dioptres) than the suspect group or the unaffected group (mean spherical equivalent -0.79 D and +1.19 D respectively) (p pigment dispersion syndrome. Our ultimate goal is to identify the gene(s) that causes this disorder in order to clarify its molecular etiology and pathophysiology. This may give rise to a molecular classification of the disease as well as provide the foundation for genetic testing and new treatment approaches.

  3. Thermophysical properties of dispersed metal materials

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Hyun; Kim, Jong Chul [KRISS, Taejeon (Korea)

    2002-04-01

    Thermal conductivities of the preliminarily fabricated U-Mo dispersion fuel meats have been measured to estimate the center temperature of the irradiation fuels. Thermal conductivities at temperatures ranging from room temperature to 500 .deg. C were calculated by measuring diffusivities, specific heat capacities and densities of dispersion fuel meats. The molybdenum content of fuel meats was varied to be 6wt%, 8wt%, and 10wt% and the volume fraction of U-Mo fuel powders were changed to be 10 vol%, 30vol%, 40 vol%, and 50 vol%. 13 refs., 39 figs., 13 tabs. (Author)

  4. Dispersion and transport of atmospheric pollutants

    International Nuclear Information System (INIS)

    Cieslik, S.

    1991-01-01

    This paper presents the physical mechanisms that govern the dispersion and transport of air pollutant; the influence of the state of the 'carrying fluid', i.e. the role of meteorology; and finally, outlines the different techniques of assessing the process. Aspects of physical mechanisms and meteorology covered include: fate of an air pollutant; turbulence and dispersion; transport; wind speed and direction; atmospheric stability; and the role of atmospheric water. Assessment techniques covered are: concentrations measurements; modelling meteorological observations; and tracer releases. It is concluded that the only way to reduce air pollution is to pollute less. 10 refs., 12 figs., 2 tabs

  5. Phonon dispersion curves for CsCN

    International Nuclear Information System (INIS)

    Gaur, N.K.; Singh, Preeti; Rini, E.G.; Galgale, Jyostna; Singh, R.K.

    2004-01-01

    The motivation for the present work was gained from the recent publication on phonon dispersion curves (PDCs) of CsCN from the neutron scattering technique. We have applied the extended three-body force shell model (ETSM) by incorporating the effect of coupling between the translation modes and the orientation of cyanide molecules for the description of phonon dispersion curves of CsCN between the temperatures 195 and 295 K. Our results on PDCs in symmetric direction are in good agreement with the experimental data measured with inelastic neutron scattering technique. (author)

  6. Relativistic energy loss in a dispersive medium

    DEFF Research Database (Denmark)

    Houlrik, Jens Madsen

    2002-01-01

    The electron energy loss in a dispersive medium is obtained using macroscopic electrodynamics taking advantage of a static frame of reference. Relativistic corrections are described in terms of a dispersive Lorentz factor obtained by replacing the vacuum velocity c by the characteristic phase...... velocity c/n, where n is the complex index of refraction. The angle-resolved energy-loss spectrum of a Drude conductor is analyzed in detail and it is shown that the low-energy peak due to Ohmic losses is enhanced compared to the classical approximation....

  7. Improvements in or relating to dispersions

    International Nuclear Information System (INIS)

    Woodhead, J.L.

    1981-01-01

    A process is described for the preparation of an aqueous dispersion of ceria which comprises forming a slurry of cerium IV hydroxide with water and an acid, the acid being capable of causing deaggregation of aggregated crystallites in the cerium IV hydroxide, heating the slurry for such a time and at such a temperature that the pH reaches a steady value, the quantity of acid in the slurry being such that the steady value of pH is below 5.4, thereby to produce a conditioned slurry, and admixing water with the conditioned slurry to produce an aqueous dispersion of ceria. (author)

  8. Dispersion - does it degrade a pulse envelope

    International Nuclear Information System (INIS)

    Deighton, M.O.

    1985-01-01

    In hostile environments, transmitting information as ultrasonic Lamb wave pulses has advantages, since the stainless steel strip serving as a waveguide is very durable. Besides attenuation, velocity dispersion (inherent in Lamb waves) can be important even in fairly short guides. Theory shows that unlimited propagation of a pulsed r.f. envelope is possible, even with dispersion present. The constant group velocity needed would favour asub(o)-mode pulses over other modes, provided ordinary attenuation is small. An approximate formula indicates the useful range of a pulse, when group velocity does vary. (author)

  9. Wage Dispersion and Decentralization of Wage Bargaining

    DEFF Research Database (Denmark)

    Dahl, Christian M.; Le Maire, Christian Daniel; Munch, Jakob Roland

    in the individual worker's wage-setting system that facilitates identification of the effects of decentralization. Consistent with predictions we find that wages are more dispersed under firm-level bargaining compared to more centralized wage-setting systems. However, the differences across wage-setting systems......This paper studies how decentralization of wage bargaining from sector to firm level influences wage levels and wage dispersion. We use a detailed panel data set covering a period of decentralization in the Danish labor market. The decentralization process provides exogenous variation...

  10. Saturable absorption in detonation nanodiamond dispersions

    Science.gov (United States)

    Vanyukov, Viatcheslav; Mikheev, Gennady; Mogileva, Tatyana; Puzyr, Alexey; Bondar, Vladimir; Lyashenko, Dmitry; Chuvilin, Andrey

    2017-07-01

    We report on a saturable absorption in aqueous dispersions of nanodiamonds with femtosecond laser pulse excitation at a wavelength of 795 nm. The open aperture Z-scan experiments reveal that in a wide range of nanodiamond particle sizes and concentrations, a light-induced increase of transmittance occurs. The transmittance increase originates from the saturation of light absorption and is associated with a light absorption at 1.5 eV by graphite and dimer chains (Pandey dimer chains). The obtained key nonlinear parameters of nanodiamond dispersions are compared with those of graphene and carbon nanotubes, which are widely used for the mode-locking.

  11. Seed Dispersal Anachronisms: Rethinking the Fruits Extinct Megafauna Ate

    OpenAIRE

    Guimarães, Paulo R.; Galetti, Mauro; Jordano, Pedro

    2008-01-01

    Background: Some neotropical, fleshy-fruited plants have fruits structurally similar to paleotropical fruits dispersed by megafauna (mammals .103 kg), yet these dispersers were extinct in South America 10–15 Kyr BP. Anachronic dispersal systems are best explained by interactions with extinct animals and show impaired dispersal resulting in altered seed dispersal dynamics. Methodology/Principal Findings: We introduce an operational definition of megafaunal fruits and perform a comparativ...

  12. Effects of Earthworms on the Dispersal of Steinernema spp.

    OpenAIRE

    Shapiro, D. I.; Tylka, G. L.; Berry, E. C.; Lewis, L. C.

    1995-01-01

    Previous studies indicated that dispersal of S. carpocapsae may be enhanced in soil with earthworms. The objective of this research was to determine and compare the effects of earthworms on dispersal of other Steinernema spp. Vertical dispersal of Steinernema carpocapsae, S. feltiae, and S. glaseri was tested in soil columns in the presence and absence of earthworms (Lumbricus terrestris). Dispersal was evaluated by a bioassay and by direct extraction of nematodes from soil. Upward dispersal ...

  13. Spectral phase shift and residual angular dispersion of an accousto-optic programme dispersive filter

    International Nuclear Information System (INIS)

    Boerzsoenyi, A.; Meroe, M.

    2010-01-01

    Complete text of publication follows. There is an increasing demand for active and precise dispersion control of ultrashort laser pulses. In chirped pulse amplification (CPA) laser systems, the dispersion of the optical elements of the laser has to be compensated at least to the fourth order to obtain high temporal contrast compressed pulses. Nowadays the most convenient device for active and programmable control of spectral phase and amplitude of broadband laser pulses is the acousto-optic programmable dispersive filter (AOPDF), claimed to be able to adjust the spectral phase up to the fourth order. Although it has been widely used, surprisingly enough there has been only a single, low resolution measurement reported on the accuracy of the induced spectral phase shift of the device. In our paper we report on the first systematic experiment aiming at the precise characterization of an AOPDF device. In the experiment the spectral phase shift of the AOPDF device was measured by spectrally and spatially resolved interferometry, which is especially powerful tool to determine small dispersion values with high accuracy. Besides the spectral phase dispersion, we measured both the propagation direction angular dispersion (PDAD) and the phase front angular dispersion (PhFAD). Although the two quantities are equal for plane waves, there may be noticeable difference for Gaussian pulses. PDAD was determined simply by focusing the beam on the slit of an imaging spectrograph, while PhFAD was measured by the use of an inverted Mach-Zehnder interferometer and an imaging spectrograph. In the measurements, the spectral phase shift and both types of angular dispersion have been recorded upon the systematic change of all the accessible functions of the acousto-optic programmable dispersive filter. The measured values of group delay dispersion (GDD) and third order dispersion (TOD) have been found to agree with the preset values within the error of the measurement (1 fs 2 and 10 fs 3

  14. Dispersant effectiveness: Studies into the causes of effectiveness variations

    International Nuclear Information System (INIS)

    Fingas, M.F.; Kyle, D.; Tennyson, E.

    1995-01-01

    Effectiveness, a key issue of using dispersants, is affected by many interrelated factors. The principal factors involved are the oil composition, dispersant formulation, sea surface turbulence and dispersant quantity. Oil composition is a very strong determinant. Current dispersant formulation effectiveness correlates strongly with the amount of saturate component in the oil. The other components of the oil, the asphaltenes, resins or polars and aromatic fractions show a negative correlation with the dispersant effectiveness. Viscosity is also a predictor of dispersant effectiveness and may have an effect because it is in turn determined by oil composition. Dispersant composition is significant and interacts with oil composition. Dispersants show high effectiveness at HLB values near 10. Sea turbulence strongly affects dispersant effectiveness.Effectiveness rises with increasing turbulence to a maximum value. Effectiveness for current commercial dispersants is gaussian around a peak salinity value. Peak effectiveness is achieved at very high dispersant quantities--at a ratio of 1:5, dispersant-to-oil volume. Dispersant effectiveness for those oils tested and under the conditions measured, is approximately logarithmic with dispersant quantity and will reach about 50% of its peak value at a dispersant to oil ratio of about 1:20 and near zero at a ratio of about 1:50

  15. Analytical simulation of two dimensional advection dispersion ...

    African Journals Online (AJOL)

    The study was designed to investigate the analytical simulation of two dimensional advection dispersion equation of contaminant transport. The steady state flow condition of the contaminant transport where inorganic contaminants in aqueous waste solutions are disposed of at the land surface where it would migrate ...

  16. Advection models of longitudinal dispersion in rivers

    NARCIS (Netherlands)

    Kranenburg, C.

    1996-01-01

    A derivation is presented of a general cross-section averaged model of longitudinal dispersion, which is based on the notion of the advection of tracer particles. Particle displacement length and particle travel time are conceived as stochastic variables, and a joint probability density function is

  17. Analytical Simulation of Two Dimensional Advection Dispersion ...

    African Journals Online (AJOL)

    ADOWIE PERE

    ABSTRACT: The study was designed to investigate the analytical simulation of two dimensional advection dispersion equation of contaminant transport. The steady state flow condition of the contaminant transport where inorganic contaminants in aqueous waste solutions are disposed of at the land surface where it would ...

  18. Dispersion of Chernobyl radioactive plume over Europe

    International Nuclear Information System (INIS)

    Albergel, A.

    1988-01-01

    A long-range pollutant transport and removal model, is used to analyse the Chernobyl radioactive plume dispersion over the Europe Continent. Model predictions are compared to field measurements of Cs-137 activity in the air from April 26th, to May 5th 1986 [fr

  19. Characterising refractive index dispersion in chalcogenide glasses

    DEFF Research Database (Denmark)

    Fang, Y.; Sojka, L.; Jayasuriya, D.

    2016-01-01

    Much effort has been devoted to the study of glasses that contain the chalcogen elements (sulfur, selenium and tellurium) for photonics' applications out to MIR wavelengths. In this paper we describe some techniques for determining the refractive index dispersion characteristics of these glasses...

  20. Dispersions in Semi-Classical Dynamics

    International Nuclear Information System (INIS)

    Zielinska-Pfabe, M.; Gregoire, C.

    1987-01-01

    Dispersions around mean values of one-body observables are obtained by restoring classical many-body correlations in Vlasov and Landau-Vlasov dynamics. The method is applied to the calculation of fluctuations in mass, charge and linear momentum in heavy-ion collisions. Results are compared to those obtained by the Balian-Veneroni variational principle in semi-classical approximation

  1. Influence of waste solid on nuclide dispersal

    International Nuclear Information System (INIS)

    Seitz, M.G.; Steindler, M.J.

    1981-01-01

    The method most often considered for permanent disposal of radioactive waste is to incorporate the waste into a solid, which is then placed in a geologic formation. The solid is made of waste and nonradioactive additives, with the formulation selected to produce a durable solid that will minimize the potential for dispersal of the radionuclides. Leach rates of radionuclides incorporated in the solid waste indicate the quantity of radioactivity available for dispersal at any time; but leach rates of stable constituents can be just as important to radionuclide dispersal by groundwater. The constituents of the solid will perturb the chemical character of the groundwater and, thereby, profoundly affect the interaction of radionuclides with the geologic medium. An explicit example of how the solid waste can affect radionuclide dispersal is illustrated by the results of experiments that measure cesium adsorption in the presence of rubidium. The experiments were performed with granulated oolitic limestone that absorbed cesium from groundwater solutions to which various concentrations of stable rubidium chloride had been added. The results are expressed as partition coefficients. Large coefficients indicate strong adsorption by the rock and, hence, slow migration. The partition coefficient for cesium decreases as the rubidium concentration in solution is increased. Because the coeficient for cesium depends on the amount of rubidium in solution, it will depend on the leach rate of rubidium from the solid. Rubidium has no radionuclides of concern for long-term isolation of nuclear waste, so its leach rate from a waste solid is rarely ever reported

  2. Fractional vector calculus for fractional advection dispersion

    Science.gov (United States)

    Meerschaert, Mark M.; Mortensen, Jeff; Wheatcraft, Stephen W.

    2006-07-01

    We develop the basic tools of fractional vector calculus including a fractional derivative version of the gradient, divergence, and curl, and a fractional divergence theorem and Stokes theorem. These basic tools are then applied to provide a physical explanation for the fractional advection-dispersion equation for flow in heterogeneous porous media.

  3. Laterally and longitudinally dispersive recoil mass separators

    International Nuclear Information System (INIS)

    Wollnik, H.

    1987-01-01

    Principles of laterally dispersive and time-of-flight mass separators are outlined. Special emphasis is given to separators for very energetic recoils for which electrostatic fields would be technologically impossible. The principle of energy isochronous time-of-flight mass separators is shown to be applicable to storage rings. (orig.)

  4. Problems with Discontinuous Diffusion/Dispersion Coefficients

    Directory of Open Access Journals (Sweden)

    Stefano Ferraris

    2012-01-01

    accurate on smooth solutions and based on a special numerical treatment of the diffusion/dispersion coefficients that makes its application possible also when such coefficients are discontinuous. Numerical experiments confirm the convergence of the numerical approximation and show a good behavior on a set of benchmark problems in two space dimensions.

  5. Fused deposition modelling of sodium caseinate dispersions

    NARCIS (Netherlands)

    Schutyser, M.A.I.; Houlder, S.; Wit, de Martin; Buijsse, C.A.P.; Alting, A.C.

    2018-01-01

    Only recently, researchers have started experimenting with 3D printing of foods. The aim of this study was to investigate 3D printed objects from sodium caseinate dispersions, exhibiting reversible gelation behaviour. Gelation and dispensing behaviour were explored and structures of different

  6. New Information Dispersal Techniques for Trustworthy Computing

    Science.gov (United States)

    Parakh, Abhishek

    2011-01-01

    Information dispersal algorithms (IDA) are used for distributed data storage because they simultaneously provide security, reliability and space efficiency, constituting a trustworthy computing framework for many critical applications, such as cloud computing, in the information society. In the most general sense, this is achieved by dividing data…

  7. Accelerated Physical Stability Testing of Amorphous Dispersions.

    Science.gov (United States)

    Mehta, Mehak; Suryanarayanan, Raj

    2016-08-01

    The goal was to develop an accelerated physical stability testing method of amorphous dispersions. Water sorption is known to cause plasticization and may accelerate drug crystallization. In an earlier investigation, it was observed that both the increase in mobility and decrease in stability in amorphous dispersions was explained by the "plasticization" effect of water (Mehta et al. Mol. Pharmaceutics 2016, 13 (4), 1339-1346). In this work, the influence of water concentration (up to 1.8% w/w) on the correlation between mobility and crystallization in felodipine dispersions was investigated. With an increase in water content, the α-relaxation time as well as the time for 1% w/w felodipine crystallization decreased. The relaxation times of the systems, obtained with different water concentration, overlapped when the temperature was scaled (Tg/T). The temperature dependencies of the α-relaxation time as well as the crystallization time were unaffected by the water concentration. Thus, the value of the coupling coefficient, up to a water concentration of 1.8% w/w, was approximately constant. Based on these findings, the use of "water sorption" is proposed to build predictive models for crystallization in slow crystallizing dispersions.

  8. Mars Exploration Rovers Landing Dispersion Analysis

    Science.gov (United States)

    Knocke, Philip C.; Wawrzyniak, Geoffrey G.; Kennedy, Brian M.; Desai, Prasun N.; Parker, TImothy J.; Golombek, Matthew P.; Duxbury, Thomas C.; Kass, David M.

    2004-01-01

    Landing dispersion estimates for the Mars Exploration Rover missions were key elements in the site targeting process and in the evaluation of landing risk. This paper addresses the process and results of the landing dispersion analyses performed for both Spirit and Opportunity. The several contributors to landing dispersions (navigation and atmospheric uncertainties, spacecraft modeling, winds, and margins) are discussed, as are the analysis tools used. JPL's MarsLS program, a MATLAB-based landing dispersion visualization and statistical analysis tool, was used to calculate the probability of landing within hazardous areas. By convolving this with the probability of landing within flight system limits (in-spec landing) for each hazard area, a single overall measure of landing risk was calculated for each landing ellipse. In-spec probability contours were also generated, allowing a more synoptic view of site risks, illustrating the sensitivity to changes in landing location, and quantifying the possible consequences of anomalies such as incomplete maneuvers. Data and products required to support these analyses are described, including the landing footprints calculated by NASA Langley's POST program and JPL's AEPL program, cartographically registered base maps and hazard maps, and flight system estimates of in-spec landing probabilities for each hazard terrain type. Various factors encountered during operations, including evolving navigation estimates and changing atmospheric models, are discussed and final landing points are compared with approach estimates.

  9. Theoretical Magnon Dispersion Curves for Gd

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker; Harmon, B. N.; Freeman, A. J.

    1975-01-01

    The magnon dispersion curve of Gd metal has been determined from first principles by use of augmented-plane-wave energy bands and wave functions. The exchange matrix elements I(k⃗, k⃗′) between the 4f electrons and the conduction electrons from the first six energy bands were calculated under...

  10. Dispersion analysis of spaced antenna scintillation measurement

    Directory of Open Access Journals (Sweden)

    M. Grzesiak

    2009-07-01

    Full Text Available We present a dispersion analysis of the phase of GPS signals received at high latitude. Basic theoretical aspects for spectral analysis of two-point measurement are given. To account for nonstationarity and statistical robustness a power distribution of the windowed Fourier transform cross-spectra as a function of frequency and phase is analysed using the Radon transform.

  11. FEATURES OF RESTORATION OF DISPERSE POROUS MATERIALS

    Directory of Open Access Journals (Sweden)

    S. L. Rovin

    2016-01-01

    Full Text Available The article presents the results of research recycling of dispersed materials in rotary furnaces. Has been received new data on the of heat and mass transfer processes and carry out intensive and continuous process of solid- liquid-phase reduction of oxides in a single unit.

  12. Polymer Inclusion Membranes with Strip Dispersion

    Directory of Open Access Journals (Sweden)

    Yueh-Hsien Li

    2017-06-01

    Full Text Available The present work investigated the permeation of indium ions through a polymer inclusion membrane (PIM, prepared with cellulose triacetate (CTA as the base polymer, tris(2-butoxyethyl phosphate (TBEP as the plasticizer and di-(2-ethylhexylphosphoric acid (D2EHPA as the extractant. With 5 M HCl aqueous solution as the strip solution, we observed an initial indium permeability of 2.4 × 10−4 m/min. However, the permeability decreases with time, dropping to about 3.4 × 10−5 m/min after 200 min of operation. Evidence was obtained showing that hydrolysis of CTA occurred, causing a dramatic decrease in the feed pH (protons transported from strip to feed solutions and a loss of extractant and plasticizer from the membrane, and then leading to the loss of indium permeability. To alleviate the problem of hydrolysis, we proposed an operation scheme called polymer inclusion membranes with strip dispersion: dispersing the strip solution in extractant-containing oil and then bringing the dispersion to contact with the polymer membrane. Since the strong acid was dispersed in oil, the membrane did not directly contact the strong acid at all times, and membrane hydrolysis was thus alleviated and the loss of indium permeability was effectively prevented. With the proposed scheme, a stable indium permeability of 2.5 × 10−4 m/min was obtained during the whole time period of the permeation experiment.

  13. Overseas seed dispersal by migratory birds

    NARCIS (Netherlands)

    Viana, D.S.; Gangoso, L.; Bouten, W.; Figuerola, J.

    2016-01-01

    Long-distance dispersal (LDD) promotes the colonization of isolated and remote habitats, and thus it has been proposed as a mechanism for explaining the distributions of many species. Birds are key LDD vectors for many sessile organisms such as plants, yet LDD beyond local and regional scales has

  14. Dispersion of breakdown voltage of liquid helium

    International Nuclear Information System (INIS)

    Ishii, Itaru; Noguchi, Takuya

    1978-01-01

    As for the electrical insulation characteristics of liquid helium, the discrepancy among the measured values by each person is very large even in the fundamental DC breakdown voltage in uniform electric field. The dispersion of experimental values obtained in the experiments by the same person is also large. Hereafter, the difference among the mean values obtained by each experimenter will be referred to as ''deviation of mean values'', and the dispersion of measured values around the mean value obtained by the same person as ''deviation around the man value''. The authors have mainly investigated on the latter experimentally. The cryostat was made of stainless steel, and the innermost helium chamber was of 500 mm I.D. and approximately 1200 mm deep. The high voltage electrode was of brass sphere of 25 mm diameter, and the low voltage electrode was of brass plate. The experiment was conducted for liquid helium boiling at 4.2 K and 1 atm, and the breakdown voltage and time lag were measured by applying the approximately square wave impulses of fast rise and long tail, ramp and DC voltages. The cause of the deviation of mean values may be the presence of impurity particles or the effect of electrode shape. As for the deviation around the mean value, the dispersion is large, and its standard deviation may amount to 10 to 20% of the man value. The dispersion is not due to the statistical time lag, but is due to parameters that vary with breakdown. (Wakatsuki, Y.)

  15. Computing modal dispersion characteristics of radially Asymmetric ...

    African Journals Online (AJOL)

    We developed a matrix theory that applies to with non-circular/circular but concentric layers fibers. And we compute the dispersion characteristics of radially unconventional fiber, known as Asymmetric Bragg fiber. An attempt has been made to determine how the modal characteristics change as circular Bragg fiber is ...

  16. Chemical countermeasures: Dispersants overview of dispersant use (including application) and research issues

    International Nuclear Information System (INIS)

    Butler, J.N.

    1992-01-01

    I will attempt in twenty minutes to summarize the state of research on oil spill dispersants as I perceive it. The expertise I bring to this task includes 20 years of experience with the fate and effects of petroleum in the marine environment, including participation in the 1973 and 1981 NRC studies and three years as chairman of the NRC committee on oil spill dispersants. I More recently I served on a committee of the International Maritime Organization which reviewed the open-quotes Impact of oil and related chemicals and wastes on the marine environment.close quotes That report will be published this year. However, my statements in this paper are not made as a representative of either NRC or IMO. They are my own interpretation of scientific literature cited in the above reviews. Dispersants are chemical formulations, which include surface active agents, designed to decrease the interfacial tension between oil and water. Because the first attempts to disperse oil on a large scale, at the Torrey Canyon spill of 1967, used highly toxic degreasing agents, dispersants have an undeserved reputation for toxicity. In fact, for twenty years dispersant formulations have been developed with an emphasis on reducing their toxicity to marine life. The dispersal of oil in water has been documented in the laboratory by dozens of papers (see references in NRC 1989, pp 70-79), and in the field by dozens of studies (NRC 1989, pp 165- 193). The toxicity of commercial dispersant formulations (NRC 1989, pp 81-123) and dispersed oil (NRC 1989, pp 123-147) has been tested on a wide variety of marine organisms ranging from algae to salmonid fishes. The NRC review has been updated by the IMO/GESAMP (1992) study, but the conclusions remain unchanged

  17. Reliability benefits of dispersed wind resource development

    International Nuclear Information System (INIS)

    Milligan, M.; Artig, R.

    1998-05-01

    Generating capacity that is available during the utility peak period is worth more than off-peak capacity. Wind power from a single location might not be available during enough of the peak period to provide sufficient value. However, if the wind power plant is developed over geographically disperse locations, the timing and availability of wind power from these multiple sources could provide a better match with the utility's peak load than a single site. There are other issues that arise when considering disperse wind plant development. Singular development can result in economies of scale and might reduce the costs of obtaining multiple permits and multiple interconnections. However, disperse development can result in cost efficiencies if interconnection can be accomplished at lower voltages or at locations closer to load centers. Several wind plants are in various stages of planning or development in the US. Although some of these are small-scale demonstration projects, significant wind capacity has been developed in Minnesota, with additional developments planned in Wyoming, Iowa and Texas. As these and other projects are planned and developed, there is a need to perform analysis of the value of geographically disperse sites on the reliability of the overall wind plant.This paper uses a production-cost/reliability model to analyze the reliability of several wind sites in the state of Minnesota. The analysis finds that the use of a model with traditional reliability measures does not produce consistent, robust results. An approach based on fuzzy set theory is applied in this paper, with improved results. Using such a model, the authors find that system reliability can be optimized with a mix of disperse wind sites

  18. The concave iris in pigment dispersion syndrome.

    Science.gov (United States)

    Liu, Lance; Ong, Ee Lin; Crowston, Jonathan

    2011-01-01

    To visualize the changes of the iris contour in patients with pigment dispersion syndrome after blinking, accommodation, and pharmacologic miosis using anterior segment optical coherence tomography. Observational case series. A total of 33 eyes of 20 patients with pigment dispersion syndrome. Each eye was imaged along the horizontal 0- to 180-degree meridian using the Visante Anterior Segment Imaging System (Carl Zeiss Meditec, Dublin, CA). Scans were performed at baseline and after focusing on an internal fixation target for 5 minutes, forced blinking, accommodation, and pharmacologic miosis with pilocarpine 2%. Quantitative analysis of the changes in the iris configuration. After 5 minutes of continual fixation, the iris became planar with the mean ± standard deviation curvature decreasing from 214 ± 74 μm to 67 ± 76 μm (P pigment dispersion syndrome after forced blinking, but the iris concavity recovered to 227 ± 113 μm (P = 0.34) and 238 ± 119 μm (P = 0.19) with the -3.0 and -6.0 diopter lenses, respectively. Pilocarpine-induced miosis caused the iris to assume a planar configuration in all subjects. This study shows that the iris in pigment dispersion syndrome assumes a planar configuration when fixating and that the concavity of the iris surface is not restored by blinking. Accommodation restored the iris concavity, suggesting that the posterior curvature of the iris in pigment dispersion syndrome is induced and probably maintained, at least in part, by accommodation. Copyright © 2011 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

  19. The trajectory of dispersal research in conservation biology. Systematic review.

    Directory of Open Access Journals (Sweden)

    Don A Driscoll

    Full Text Available Dispersal knowledge is essential for conservation management, and demand is growing. But are we accumulating dispersal knowledge at a pace that can meet the demand? To answer this question we tested for changes in dispersal data collection and use over time. Our systematic review of 655 conservation-related publications compared five topics: climate change, habitat restoration, population viability analysis, land planning (systematic conservation planning and invasive species. We analysed temporal changes in the: (i questions asked by dispersal-related research; (ii methods used to study dispersal; (iii the quality of dispersal data; (iv extent that dispersal knowledge is lacking, and; (v likely consequences of limited dispersal knowledge. Research questions have changed little over time; the same problems examined in the 1990s are still being addressed. The most common methods used to study dispersal were occupancy data, expert opinion and modelling, which often provided indirect, low quality information about dispersal. Although use of genetics for estimating dispersal has increased, new ecological and genetic methods for measuring dispersal are not yet widely adopted. Almost half of the papers identified knowledge gaps related to dispersal. Limited dispersal knowledge often made it impossible to discover ecological processes or compromised conservation outcomes. The quality of dispersal data used in climate change research has increased since the 1990s. In comparison, restoration ecology inadequately addresses large-scale process, whilst the gap between knowledge accumulation and growth in applications may be increasing in land planning. To overcome apparent stagnation in collection and use of dispersal knowledge, researchers need to: (i improve the quality of available data using new approaches; (ii understand the complementarities of different methods and; (iii define the value of different kinds of dispersal information for supporting

  20. The trajectory of dispersal research in conservation biology. Systematic review.

    Science.gov (United States)

    Driscoll, Don A; Banks, Sam C; Barton, Philip S; Ikin, Karen; Lentini, Pia; Lindenmayer, David B; Smith, Annabel L; Berry, Laurence E; Burns, Emma L; Edworthy, Amanda; Evans, Maldwyn J; Gibson, Rebecca; Heinsohn, Rob; Howland, Brett; Kay, Geoff; Munro, Nicola; Scheele, Ben C; Stirnemann, Ingrid; Stojanovic, Dejan; Sweaney, Nici; Villaseñor, Nélida R; Westgate, Martin J

    2014-01-01

    Dispersal knowledge is essential for conservation management, and demand is growing. But are we accumulating dispersal knowledge at a pace that can meet the demand? To answer this question we tested for changes in dispersal data collection and use over time. Our systematic review of 655 conservation-related publications compared five topics: climate change, habitat restoration, population viability analysis, land planning (systematic conservation planning) and invasive species. We analysed temporal changes in the: (i) questions asked by dispersal-related research; (ii) methods used to study dispersal; (iii) the quality of dispersal data; (iv) extent that dispersal knowledge is lacking, and; (v) likely consequences of limited dispersal knowledge. Research questions have changed little over time; the same problems examined in the 1990s are still being addressed. The most common methods used to study dispersal were occupancy data, expert opinion and modelling, which often provided indirect, low quality information about dispersal. Although use of genetics for estimating dispersal has increased, new ecological and genetic methods for measuring dispersal are not yet widely adopted. Almost half of the papers identified knowledge gaps related to dispersal. Limited dispersal knowledge often made it impossible to discover ecological processes or compromised conservation outcomes. The quality of dispersal data used in climate change research has increased since the 1990s. In comparison, restoration ecology inadequately addresses large-scale process, whilst the gap between knowledge accumulation and growth in applications may be increasing in land planning. To overcome apparent stagnation in collection and use of dispersal knowledge, researchers need to: (i) improve the quality of available data using new approaches; (ii) understand the complementarities of different methods and; (iii) define the value of different kinds of dispersal information for supporting management

  1. Design of self-dispersible charged-polymer building blocks for waterborne polyurethane dispersions

    NARCIS (Netherlands)

    Jiménez-Pardo, I.; Sun, P.; van Benthem, R.A.T.M.; Esteves, A.C.C.

    2018-01-01

    Waterborne polyurethane dispersions (PUDs) currently have a wide spectrum of applications as coating resins for biomedical products, food packaging, cosmetics and traditional coatings. At present, PUDs are commonly prepared by the “prepolymer extension” method in which isocyanate terminated

  2. Aqueous solubility, dispersibility and toxicity of biodiesels

    International Nuclear Information System (INIS)

    Hollebone, B.P.; Fieldhouse, B.; Lumley, T.C.; Landriault, M.; Doe, K.; Jackman, P.

    2007-01-01

    The renewed interest in the use of biological fuels can be attributed to that fact that feedstocks for fatty-acid ester biodiesels are renewable and can be reclaimed from waste. Although there are significant benefits to using biodiesels, their increased use leaves potential for accidental release to the environment. Therefore, their environmental behaviours and impacts must be evaluated along with the risk associated with their use. Biodiesel fuels may be made from soy oil, canola oil, reclaimed restaurant grease, fish oil and animal fat. The toxicological fate of biofuel depends on the variability of its chemical composition. This study provided an initial assessment of the aqueous fate and effects of biodiesel from a broad range of commonly available feedstocks and their blends with petroleum diesels. The study focused primarily on the fate and impact of these fuels in fresh-water. The use of chemical dispersion as a countermeasure for saltwater was also investigated. The exposure of aquatic ecosystems to biodiesels and petroleum diesel occurs via the transfer of material from the non-aqueous phase liquid (NAPL) into the aqueous phase, as both soluble and dispersed components. The aqueous solubilities of the fuels were determined from the equilibrium water-accommodated fraction concentrations. The acute toxicities of many biodiesels were reported for 3 test species used by Environment Canada for toxicological evaluation, namely rainbow trout, the water flea and a luminescent bacterium. This study also evaluated the natural potential for dispersion of the fuels in the water column in both low and high-energy wave conditions. Chemical dispersion as a potential countermeasure for biodiesel spills was also evaluated using solubility testing, acute toxicity testing, and dispersibility testing. It was shown that biodiesels have much different fates and impacts from petroleum diesels. The compounds partitioning into the water column are also very different for each

  3. Modifying Silicates for Better Dispersion in Nanocomposites

    Science.gov (United States)

    Campbell, Sandi

    2005-01-01

    An improved chemical modification has been developed to enhance the dispersion of layered silicate particles in the formulation of a polymer/silicate nanocomposite material. The modification involves, among other things, the co-exchange of an alkyl ammonium ion and a monoprotonated diamine with interlayer cations of the silicate. The net overall effects of the improved chemical modification are to improve processability of the nanocomposite and maximize the benefits of dispersing the silicate particles into the polymer. Some background discussion is necessary to give meaning to a description of this development. Polymer/silicate nanocomposites are also denoted polymer/clay composites because the silicate particles in them are typically derived from clay particles. Particles of clay comprise layers of silicate platelets separated by gaps called "galleries." The platelet thickness is 1 nm. The length varies from 30 nm to 1 m, depending on the silicate. In order to fully realize the benefits of polymer/silicate nanocomposites, it is necessary to ensure that the platelets become dispersed in the polymer matrices. Proper dispersion can impart physical and chemical properties that make nanocomposites attractive for a variety of applications. In order to achieve nanometer-level dispersion of a layered silicate into a polymer matrix, it is typically necessary to modify the interlayer silicate surfaces by attaching organic functional groups. This modification can be achieved easily by ion exchange between the interlayer metal cations found naturally in the silicate and protonated organic cations - typically protonated amines. Long-chain alkyl ammonium ions are commonly chosen as the ion-exchange materials because they effectively lower the surface energies of the silicates and ease the incorporation of organic monomers or polymers into the silicate galleries. This completes the background discussion. In the present improved modification of the interlayer silicate surfaces

  4. Wage Dispersion and Decentralization of Wage Bargaining

    DEFF Research Database (Denmark)

    Dahl, Christian Møller; le Maire, Christian Daniel; Munch, Jakob R.

    2013-01-01

    This article studies how decentralization of wage bargaining from sector to firm level influences wage levels and wage dispersion. We use detailed panel data covering a period of decentralization in the Danish labor market. The decentralization process provides variation in the individual worker......'s wage-setting system that facilitates identification of the effects of decentralization. We find a wage premium associated with firm-level bargaining relative to sector-level bargaining and that the return to skills is higher under the more decentralized wage-setting systems. Using quantile regression......, we also find that wages are more dispersed under firm-level bargaining compared to more centralized wage-setting systems....

  5. Anomalous acoustic dispersion in architected microlattice metamaterials

    Science.gov (United States)

    KröDel, Sebastian; Palermo, Antonio; Daraio, Chiara

    The ability to control dispersion in acoustic metamaterials is crucial to realize acoustic filtering and rectification devices as well as perfect imaging using negative refractive index materials. Architected microlattice metamaterials immersed in fluid constitute a versatile platform for achieving such control. We investigate architected microlattice materials able to exploit locally resonant modes of their fundamental building blocks that couple with propagating acoustic waves. Using analytical, numerical and experimental methods we find that such lattice materials show a hybrid dispersion behavior governed by Biot's theory for long wavelengths and multiple scattering theory when wave frequency is close to the resonances of the building block. We identify the relevant geometric parameters to alter and control the group and phase velocities in this class of acoustic metamaterials. Furthermore, we fabricate small-scale acoustic metamaterial samples using high precision SLA additive manufacturing and test the resulting materials experimentally using a customized ultrasonic setup. This work paves the way for new acoustic devices based on microlattice metamaterials.

  6. Radiological Dispersion Devices: are we prepared?

    Energy Technology Data Exchange (ETDEWEB)

    Sohier, Alain [Decision Strategy Research Department (Radiation Protection Division), Belgian Nuclear Research Centre (SCK-CEN), Boeretang 200, B-2400 Mol (Belgium)]. E-mail: asohier@sckcen.be; Hardeman, Frank [Decision Strategy Research Department (Radiation Protection Division), Belgian Nuclear Research Centre (SCK-CEN), Boeretang 200, B-2400 Mol (Belgium)

    2006-07-01

    Already before the events of September 11th 2001 concern was raised about the spread of orphan sources and their potential use in Radiological Dispersion Devices by terrorist groups. Although most of the simulated scenarios foresee a rather limited direct health impact on the population, the affected region would suffer from the indirect consequences such as social disruption, cleanup requirements and economic costs. The nature of such a radiological attack would anyway be different compared to conventional radiological accidents, basically because it can happen anywhere at any time. Part of the response resides in a general preparedness scheme incorporating attacks with Radiological Dispersion Devices. Training of different potential intervention teams is essential. The response would consist of a prioritised list of actions adapted to the circumstances. As the psychosocial dimension of the crisis could be worse than the purely radiological one, an adapted communication strategy with the public aspect would be a key issue.

  7. Gold Nanospheres Dispersed Light Responsive Epoxy Vitrimers

    Directory of Open Access Journals (Sweden)

    Zhenhua Wang

    2018-01-01

    Full Text Available Vitrimers represent a new class of smart materials. They are covalently crosslinked like thermosets, yet they can be reprocessed like thermoplastics. The underlying mechanism is the rapid exchange reactions which form new bonds while breaking the old ones. So far, heating is the most widely used stimulus to activate the exchange reaction. Compared to heating, light not only is much more convenient to achieve remote and regional control, but can also offer fast healing. Gold nanospheres are excellent photothermal agents, but they are difficult to disperse into vitrimers as they easily aggregate. In this paper, we use polydopamine to prepare gold nanospheres. The resultant polydopamine-coated gold nanospheres (GNS can be well dispersed into epoxy vitrimers, endowing epoxy vitrimers with light responsivity. The composites can be reshaped permanently and temporarily with light at different intensity. Efficient surface patterning and healing are also demonstrated.

  8. A THEOREM ON CENTRAL VELOCITY DISPERSIONS

    International Nuclear Information System (INIS)

    An, Jin H.; Evans, N. Wyn

    2009-01-01

    It is shown that, if the tracer population is supported by a spherical dark halo with a core or a cusp diverging more slowly than that of a singular isothermal sphere (SIS), the logarithmic cusp slope γ of the tracers must be given exactly by γ = 2β, where β is their velocity anisotropy parameter at the center unless the same tracers are dynamically cold at the center. If the halo cusp diverges faster than that of the SIS, the velocity dispersion of the tracers must diverge at the center too. In particular, if the logarithmic halo cusp slope is larger than two, the diverging velocity dispersion also traces the behavior of the potential. The implication of our theorem on projected quantities is also discussed. We argue that our theorem should be understood as a warning against interpreting results based on simplifying assumptions such as isotropy and spherical symmetry.

  9. Round beams generated by vertical dispersion

    International Nuclear Information System (INIS)

    Bagley, P.

    1990-01-01

    Simulations suggest that in e + e - storage rings collisions of round beams (equal emittances and equal β*) can produce very large tune shifts and luminosities. We understand how to make equal β*s, but generating equal emittances is more difficult. We describe an equal emittance scheme that uses several skew quads to couple horizontal dispersion into vertical dispersion. These skew quads also produce a coupling bump. At the interaction point and at other points outside the coupling bump, the motion is not coupled, so that the 'A' normal mode corresponds to horizontal motion and the 'B' normal mode corresponds to vertical motion. We present a round beam lattice for CESR that incorporates this scheme

  10. New developments in dispersion theory. I

    International Nuclear Information System (INIS)

    Hamilton, J.; Petersen, J.L.

    1975-01-01

    The notes arose out of a series of lectures given in Copenhagen in 1973/74. The principal aim of the course was to give a reasonably comprehensive account of the considerable number of new ideas and techniques in dispersion theory which have been developed over the past few years. General background material is also given but is treated in less detail. Modern dispersion theory is seen to have two principal types of application in high energy strong interaction physics. Although not sharply seperated they can be characterized roughly as (1) use of dynamical singularities in the amplitude analysis of experimental data, and (2) dynamical interpretation of hadronic amplitudes. In the first volume the authors have concentrated on applications of the first class. A companion volume is planned in which some of the important dominantly dynamical areas of application will be described. (Auth.)

  11. Dispersion and stabilization of cochleate nanoparticles.

    Science.gov (United States)

    Bozó, Tamás; Wacha, András; Mihály, Judith; Bóta, Attila; Kellermayer, Miklós S Z

    2017-08-01

    Cochleates, calcium-stabilized membrane rolls of nanoscale diameter, promise a unique and efficient way of delivering lipid-soluble drugs, proteins or nucleic acids into biological systems because they protect the encapsulated material against enzymatic or chemical degradation. Self-aggregation, which typically arises during production and storage is a major obstacle that has so far precluded the development of an efficient cochleate-based drug-delivery system. Here we show that citric acid, added transiently in a narrow concentration range, effectively disperses cochleate aggregates, stabilizes the disperse state for long-term storage and preserves the canonical ultrastructure and topological characteristics of cochleate nanoparticles. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Atmospheric tracer experiments for regional dispersion studies

    International Nuclear Information System (INIS)

    Heffter, J.L.; Ferber, G.J.

    1980-01-01

    Tracer experiments are being conducted to verify atmospheric transport and dispersion calculations at distances from tens to hundreds of km from pollutant sources. In one study, a 2 1/2 year sampling program has been carried out at 13 sites located 30 to 140 km from a source of 85 Kr at the Savannah River Plant in South Carolina. Average weekly concentrations as well as twice-daily concentrations were obtained. Sampling data and meteorological data, including surface, tower, and rawinsonde observations are available on magnetic tape for model verification studies. Some verification results for the Air Resources Laboratories Atmospheric Transort and Dispersion Model (ARL-ATAD) are shown for averaging periods from one week to two years

  13. Corneal collagen crosslinking and pigment dispersion syndrome.

    Science.gov (United States)

    LaHood, Benjamin R; Moore, Sacha

    2017-03-01

    We describe the case of a keratoconus patient with pigment dispersion syndrome (PDS) who was treated for progressive corneal ectasia with corneal collagen crosslinking (CXL). Pigment dispersion syndrome has been shown to have associated morphologic changes of the corneal endothelium. Corneal CXL has the potential to cause toxicity to the corneal endothelium, and adjacent pigment might increase the likelihood of damage. In this case, the presence of PDS had no detrimental effect on the outcome of treatment, and no complications were observed at 12 months follow-up, indicating that it may be safe to perform corneal CXL in the setting of PDS. This is an important observation as the number of indications for corneal CXL grows. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  14. Uncertainty in dispersion forecasts using meteorological ensembles

    International Nuclear Information System (INIS)

    Chin, H N; Leach, M J

    1999-01-01

    The usefulness of dispersion forecasts depends on proper interpretation of results. Understanding the uncertainty in model predictions and the range of possible outcomes is critical for determining the optimal course of action in response to terrorist attacks. One of the objectives for the Modeling and Prediction initiative is creating tools for emergency planning for special events such as the upcoming the Olympics. Meteorological forecasts hours to days in advance are used to estimate the dispersion at the time of the event. However, there is uncertainty in any meteorological forecast, arising from both errors in the data (both initial conditions and boundary conditions) and from errors in the model. We use ensemble forecasts to estimate the uncertainty in the forecasts and the range of possible outcomes

  15. Highly dispersive transparency in coupled metamaterials

    International Nuclear Information System (INIS)

    Thuy, V T T; Park, J W; Lee, Y P; Tung, N T; Lam, V D; Rhee, J Y

    2010-01-01

    We investigate the coupling between bright and quasi-dark eigenmodes in a planar metamaterial supporting highly dispersive transparency. The specific design of such a metamaterial consists of a cut wire (CW) and a single-gap split-ring resonator (SRR). Through the numerical simulation and the equivalent-circuit analysis, we demonstrate that the response of the SRR, which is weakly excited by external electric field, plays the role of a quasi-dark eigenmode in the presence of a strongly radiative CW. Furthermore, by extending and relating our study to the trapped mode resonances and the coupling between dark and bright modes, a more comprehensive perspective for the metamaterial realization of highly dispersive transmission and slow-light applications is provided

  16. Debris Dispersion Model Using Java 3D

    Science.gov (United States)

    Thirumalainambi, Rajkumar; Bardina, Jorge

    2004-01-01

    This paper describes web based simulation of Shuttle launch operations and debris dispersion. Java 3D graphics provides geometric and visual content with suitable mathematical model and behaviors of Shuttle launch. Because the model is so heterogeneous and interrelated with various factors, 3D graphics combined with physical models provides mechanisms to understand the complexity of launch and range operations. The main focus in the modeling and simulation covers orbital dynamics and range safety. Range safety areas include destruct limit lines, telemetry and tracking and population risk near range. If there is an explosion of Shuttle during launch, debris dispersion is explained. The shuttle launch and range operations in this paper are discussed based on the operations from Kennedy Space Center, Florida, USA.

  17. Dispersion relations in three-particle systems

    International Nuclear Information System (INIS)

    Grach, I.L.; Harodetskij, I.M.; Shmatikov, M.Zh.

    1979-01-01

    Positions of all dynamical singularities of the triangular nonrelativistic diagram are calculated including the form factors. The jumps of the amplitude are written in an analitical form. The dispersion method predictions for bound states in the three-particle system are compared with the results of the Amado exactly solvable model. It is shown that the one-channel N/D method is equivalent to the pole approximation in the Amado model, and that the three-particle s channel unitarity should be taken into account calculating (in the dispersion method) the ground and excited states of the three-particle system. The relation of the three-particle unitary contribution to the Thomas theorem and Efimov effect is briefly discussed

  18. Modified dispersion relations, inflation, and scale invariance

    Science.gov (United States)

    Bianco, Stefano; Friedhoff, Victor Nicolai; Wilson-Ewing, Edward

    2018-02-01

    For a certain type of modified dispersion relations, the vacuum quantum state for very short wavelength cosmological perturbations is scale-invariant and it has been suggested that this may be the source of the scale-invariance observed in the temperature anisotropies in the cosmic microwave background. We point out that for this scenario to be possible, it is necessary to redshift these short wavelength modes to cosmological scales in such a way that the scale-invariance is not lost. This requires nontrivial background dynamics before the onset of standard radiation-dominated cosmology; we demonstrate that one possible solution is inflation with a sufficiently large Hubble rate, for this slow roll is not necessary. In addition, we also show that if the slow-roll condition is added to inflation with a large Hubble rate, then for any power law modified dispersion relation quantum vacuum fluctuations become nearly scale-invariant when they exit the Hubble radius.

  19. Radiological Dispersion Devices: are we prepared?

    International Nuclear Information System (INIS)

    Sohier, Alain; Hardeman, Frank

    2006-01-01

    Already before the events of September 11th 2001 concern was raised about the spread of orphan sources and their potential use in Radiological Dispersion Devices by terrorist groups. Although most of the simulated scenarios foresee a rather limited direct health impact on the population, the affected region would suffer from the indirect consequences such as social disruption, cleanup requirements and economic costs. The nature of such a radiological attack would anyway be different compared to conventional radiological accidents, basically because it can happen anywhere at any time. Part of the response resides in a general preparedness scheme incorporating attacks with Radiological Dispersion Devices. Training of different potential intervention teams is essential. The response would consist of a prioritised list of actions adapted to the circumstances. As the psychosocial dimension of the crisis could be worse than the purely radiological one, an adapted communication strategy with the public aspect would be a key issue

  20. Dispersed generation: impact on the electricity system

    International Nuclear Information System (INIS)

    Delfanti, M.; Merlo, M.; Silvestri, A.

    2009-01-01

    The paper deals with the impact of Dispersed Generation (D G) on the national electricity system, by proposing a practical approach for determining the current capacity of the networks to accepts this form of generation (hosting capacity). With the prospect of an increasing intake of D G, we finally draft a possible evolution of distribution networks based on the integration of energy and information networks. [it

  1. [Disperse endocrine system and APUD concept].

    Science.gov (United States)

    Mil'to, I V; Sukhodolo, I V; Gereng, E A; Shamardina, L A

    2011-01-01

    This review describes the problems of disperse endocrine system and APUD-system morphology, summarizes some debatable issues of single endocrine cell biology. The data presented refer to the history of both systems discovery, morphological methods of their study, developmental sources, their structural organization and physiological roles of their cells. The significance of single endocrine cells in the regulation of the organism functions is discussed.

  2. Titanium oxide dispersion-strengthened ferritic alloys

    International Nuclear Information System (INIS)

    Hendrix, W.; Vandermeulen, W.

    1980-04-01

    The available data on the DT02 and DT3911 ferritic dispersion strengthened alloys, developed at SCK/CEN, Mol, Belgium, are presented. Both alloys consist of Fe - 13% Cr - 1.5% Mo to which 2% TiO 2 and about 3.5% Ti are added (wt.%). Their main use is for the fabrication of fast breeder reactor cladding tubes but their application as turbine blade material is also envisaged for cases where high damping is important. (auth.)

  3. NMR dispersion measurement of dynamic nuclear polarization

    International Nuclear Information System (INIS)

    Davies, K.; Cox, S.F.J.

    1978-01-01

    The feasibility of monitoring dynamic nuclear polarization from the NMR dispersive susceptibility is examined. Two prototype instruments are tested in a polarized proton target using organic target material. The more promising employs a tunnel diode oscillator, inside the target cavity, and should provide a precise polarization measurement working at a frequency far enough from the main resonance for the disturbance of the measured polarization to be negligible. Other existing methods for measuring target polarization are briefly reviewed. (author)

  4. REVIEW ON SPRAY DRIED SOLID DISPERSION

    OpenAIRE

    Zambre Radhika Ashok, Dr. Shendge R.S, Narode Pravin Ravindra, Sonawane Swapnil Prakash

    2018-01-01

    The drug solubility is the most challenging aspect for the formulation development. The poorly soluble drug has poor dissolution and absorption of drug. The low aqueous solubility of drug is required to formulate the drug into more soluble and hence bioavailable drug product. The different technique is being used to enhance the solubility of poorly water soluble drugs. Spray dried solid dispersion of drug is one of the most widely used technology to enhance the solubility of the poorly water ...

  5. Effective spectral dispersion of refractive index modulation

    Czech Academy of Sciences Publication Activity Database

    Vojtíšek, Petr; Květoň, M.; Richter, I.

    2017-01-01

    Roč. 19, č. 4 (2017), č. článku 045603. ISSN 2040-8978 R&D Projects: GA MŠk(CZ) LO1206 Institutional support: RVO:61389021 Keywords : volume gratings * holography * dispersion * refractive index modulation Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 1.741, year: 2016 http://iopscience.iop.org/article/10.1088/2040-8986/aa6092/meta

  6. Photon Dispersion in a Supernova Core

    OpenAIRE

    Kopf, A.; Raffelt, G.

    1997-01-01

    While the photon forward-scattering amplitude on free magnetic dipoles (e.g. free neutrons) vanishes, the nucleon magnetic moments still contribute significantly to the photon dispersion relation in a supernova (SN) core where the nucleon spins are not free due to their interaction. We study the frequency dependence of the relevant spin susceptibility in a toy model with only neutrons which interact by one-pion exchange. Our approach amounts to calculating the photon absorption rate from the ...

  7. Structural investigation of biogenic ferrihydrite nanoparticles dispersion

    International Nuclear Information System (INIS)

    Balasoiu, M.; Ishchenko, L.A.; Stolyar, S.V.; Iskhakov, R.S.; Rajkher, Yu.L.; Kuklin, A.I.; Solov'ev, D.V.; Arzumanyan, G.M.; Kurkin, T.S.; Aranghel, D.

    2010-01-01

    Structural properties of biogenic ferrihydrite nanoparticles produced by bacteria Klebsiella oxytoca are investigated. Investigations of morphology and size of particles dispersed in water by means of high-resolution transmission electron microscopy and small angle X-ray scattering measurements were performed. By model calculations followed by fitting procedure the structural parameters of a cylinder of radius R = (4.87 ± 0.02) nm and height L = (2.12 ± 0.04) nm are obtained

  8. Aqueous solution dispersement of carbon nanotubes

    Science.gov (United States)

    Kim, Jae-Woo (Inventor); Park, Cheol (Inventor); Choi, Sang H. (Inventor); Lillehei, Peter T. (Inventor); Harrison, Joycelyn S. (Inventor)

    2011-01-01

    Carbon nanotubes (CNTs) are dispersed in an aqueous buffer solution consisting of at least 50 weight percent water and a remainder weight percent that includes a buffer material. The buffer material has a molecular structure defined by a first end, a second end, and a middle disposed between the first and second ends. The first end is a cyclic ring with nitrogen and oxygen heteroatomes, the middle is a hydrophobic alkyl chain, and the second end is a charged group.

  9. Fluff-thieving birds sabotage seed dispersal

    OpenAIRE

    Rohwer, Vanya G.; Pauw, Anton; Martin, Paul R.

    2017-01-01

    Characterizing many species interactions as mutualisms can be misleading because some members of the interaction derive greater fitness benefits at the expense of other members. We provide detailed natural history data on a suspected bird?plant mutualism in South Africa where many species of birds use fluffy Eriocephalus seed material to construct their nests, potentially dispersing seeds for the plant. We focus on a common bird, Prinia maculosa, which invests heavily in gathering Eriocephalu...

  10. Dispersion of contaminants in saturated porous media

    International Nuclear Information System (INIS)

    Moltyaner, G.L.; Poisson, J.M.

    1987-10-01

    The main objective of this paper is to outline the experimental and theoretical investigations performed in an attempt to validate the applicability of finite element based numerical models for the prediction of the behaviour of a conservative tracer at the Twin Lake aquifer, Chalk River Nuclear Laboratories, Chalk River, Ontario. The essential point is that the 3/4 of a million data points obtained at the Twin Lake site from a 40 m natural gradient tracer test provide a unique opportunity for quantifying the system variability and for testing finite element models of the dispersion process. The subject of this discussion is the advection-dispersion model of contaminant transport - its equation and solution by the Galerkin finite element method. The report gives a brief description of the experimental data and the methods for the estimation of transport parameters. Scales of averaging associated with the conceptual formulation of the dispersion process, measurement of process variables, parameter estimation and the numerical models are discussed. The compatibility between the scales is emphasized as a major requirement for predictive modelling. The developed finite element model of the radioiodine transport describes the overall behaviour of the tracer plume but lacks the capability to simulate the fingerlike spreading of the plume due to the fact that the grid does not have an adequately fine space discretization. Unfortunately, a refinement of the grid spacing is limited by the size of the site computer memory. For the advection-dominated transport, as that encountered at the Twin Lake aquifer, the failure to satisfy fine mesh requirement causes numerical dispersion. In general, it was concluded that the conventional finite element model may produce accurate simulation of the tracer cloud provided that the adequately fine space discretization of the grid compatible with the support scale of measurements and the adequately fine time discretization are made. This

  11. CONCRETE BASED ON MODIFIED DISPERSE CEMENT SYSTEM

    Directory of Open Access Journals (Sweden)

    D. V. Rudenko

    2016-08-01

    Full Text Available Purpose. The article considers definition of the bond types occurring in a modified cement concrete matrix, and the evaluation of the quality of these links in a non-uniform material to determine the geometrical and physical relationships between the structure and the cement matrix modifiers. Methodology. To achieve this purpose the studies covered the microstructure of dispersed modified concrete cement matrix, the structure formation mechanism of the modified cement concrete system of natural hardening; as well as identification of the methods of sound concrete strength assessment. Findings. The author proposed a model of the spatial structure of the concrete cement matrix, modified by particulate reinforcement crystal hydrates. The initial object of study is a set of volume elements (cells of the cement matrix and the system of the spatial distribution of reinforcing crystallohydrates in these volume elements. It is found that the most dangerous defects such as cracks in the concrete volume during hardening are formed as a result of internal stresses, mainly in the zone of cement matrix-filler contact or in the area bordering with the largest pores of the concrete. Originality. The result of the study is the defined mechanism of the process of formation of the initial strength and stiffness of the modified cement matrix due to the rapid growth of crystallohydrates in the space among the dispersed reinforcing modifier particles. Since the lack of space prevents from the free growth of crystals, the latter cross-penetrate, forming a dense structure, which contributes to the growth of strength. Practical value. Dispersed modifying cement matrix provides a durable concrete for special purposes with the design performance characteristics. The developed technology of dispersed cement system modification, the defined features of its structure formation mechanism and the use of congruence principle for the complex of technological impacts of physical

  12. Evaluation of hovercraft for dispersant application

    Energy Technology Data Exchange (ETDEWEB)

    Dickens, D; Belore, R; Buist, I; Humphrey, B

    1988-01-01

    A series of field trials were carried out in Vancouver, Canada in July and August 1986 to determine whether or not hovercraft should be considered for dispersant application. Questions are: the ability of the hovercraft to ''fly'' over an oil slick at high speed without displacing the oil out of the path, the potential for using the hovercraft to impart vertical mixing energy into the water column to aid in the dispersant process and, the ability to mount a suitable spray boom and obtain a uniform spray pattern across the swath width. The field trials and subsequent interpretation of results provide positive answers to the first and second question. The question of mixing energy requires some qualification. The hovercraft contributes considerable mixing energy to the immediate water surface through air entrainment but this effect is short lived and there does not appear to be significant long term vertical mixing in the hovercraft wake. Recommendations are made for operating procedures and boom mounting which should ensure a uniform drop size and dose rate across a swath up to 18 m. The cushion air escaping from around the craft perimeter is not an important factor in adversly affecting the dispersant spray pattern. Depending on the type of machine available, hovcercraft have the capability of treating up to a 1km/sup 2/ slick between loads, at average speeds in the 15 to 25 knot range. The inherent advantages of high transit speed to the site (up to 45 Knots), amphibious operation (i.e. not draft limited) and lack of ceiling or visibility restrictions provide hovercarft with unique capabilities in the dispersant application role. Two patents relating to the process have been abstracted. Appendix B gives the sprecifications of two different models of hovercrafts. 14 refs., 29 figs., 6 tabs.

  13. Plasma Dispersion Functions for Complex Frequencies

    International Nuclear Information System (INIS)

    Pavlov, S. S.; Castejon, F.

    2005-01-01

    Plasma dispersion functions for complex wave propagation frequency in the weak relativistic regime for arbitrary longitudinal refractive index are estimated and presented in this work. These functions, that are know as Shkarofsky functions in the case of real frequency, are estimated using a new method that avoids the singularities that appear in previous calculations shown in the preceding literature. These results can be used to obtain the properties of plasma instabilities in the weakly relativistic regime. (Author) 14 refs

  14. Employment Effects of Spatial Dispersal of Refugees

    OpenAIRE

    Anna Piil Damm; Michael Rosholm

    2006-01-01

    Spatial dispersal policies may influence labour market integration of refugees through two mechanisms. First, it may affect the local job offer arrival rate, and second, it may affect place utility. We investigate the second mechanism theoretically by formulating a partial search model in which an individual searches simultaneously for a job and for a new residential location. The model predicts that the reservation wage for local jobs is decreasing in place utility. We argue that spatial dis...

  15. Dispersion fuel for nuclear research facilities

    International Nuclear Information System (INIS)

    Kushtym, A.V.; Belash, M.M.; Zigunov, V.V.; Slabospitska, O.O.; Zuyok, V.A.

    2017-01-01

    Designs and process flow sheets for production of nuclear fuel rod elements and assemblies TVS-XD with dispersion composition UO_2+Al are presented. The results of fuel rod thermal calculation applied to Kharkiv subcritical assembly and Kyiv research reactor VVR-M, comparative characteristics of these fuel elements, the results of metallographic analyses and corrosion tests of fuel pellets are given in this paper

  16. Longitudinal ultrasonic waves dispersion in bars

    International Nuclear Information System (INIS)

    Suarez Antola, R.

    2001-01-01

    The exhibition intends to review some aspects of the propagation of the longitudinal ultrasonic pulses shortly in bars of traverse section uniform.Aspects they are part of the denominated geometric dispersion of the pulses.This phenomenon It can present like an additional complication in the ultrasonic essay of low frequency of thin pieces in structures and machines but takes place former ex professed in some applications of the wave guides been accustomed to in the prosecution of signs

  17. Oxide dispersion-strengthened ferritic alloys

    International Nuclear Information System (INIS)

    Asbroeck, P. van.

    1976-10-01

    The publication gives the available data on the DTO2 dispersion-strengthened ferritic alloy developed at C.E.N./S.C.K. Mol, Belgium. DTO2 is a Fe-Cr-Mo ferritic alloy, strengthened by addition of titanium oxide and of titanium leading to the formation of Chi phase. It was developed for use as canning material for fast breeder reactors. (author)

  18. Wave modulation in a nonlinear dispersive medium

    International Nuclear Information System (INIS)

    Kim, Y.C.; Khadra, L.; Powers, E.J.

    1980-01-01

    A model describing the simultaneous amplitude and phase modulation of a carrier wave propagating in a nonlinear dispersive medium is developed in terms of nonlinear wave-wave interactions between the sidebands and a low frequency wave. It is also shown that the asymmetric distribution of sidebands is determined by the wavenumber dependence of the coupling coefficient. Digital complex demodulation techniques are used to study modulated waves in a weakly ionized plasma and the experimental results support the analytical model

  19. Manufacturing Experience for Oxide Dispersion Strengthened Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, Wendy D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Doherty, Ann L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Henager, Charles H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lavender, Curt A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Montgomery, Robert O. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Omberg, Ronald P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Smith, Mark T. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Webster, Ryan A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-09-22

    This report documents the results of the development and the manufacturing experience gained at the Pacific Northwest National Laboratories (PNNL) while working with the oxide dispersion strengthened (ODS) materials MA 956, 14YWT, and 9YWT. The Fuel Cycle Research and Development program of the Office of Nuclear Energy has implemented a program to develop a Uranium-Molybdenum metal fuel for light water reactors. ODS materials have the potential to provide improved performance for the U-Mo concept.

  20. Modeling of Rayleigh wave dispersion in Iberia

    Directory of Open Access Journals (Sweden)

    José Badal

    2011-01-01

    Full Text Available Phase and group velocities of 15–70 s Rayleigh waves propagating across the Iberian Peninsula have been transformed into local dispersion curves by linear inversion of travel times. The procedure permits that the waveform dispersion to be obtained as a continuous period-dependent velocity function at grid points belonging to the area probed by the waves, thus providing phase- and group-velocity contour maps for several periods within the interval of interest. The regionalization process rests on a homogeneous initial data set in which the number of observations remains almost constant for all periods of reference. Damped least-squares inversion of the local dispersion curves for shear-wave velocity structure is performed to obtain depth-dependent S-wave velocity profiles at the grid points covering the model region. The reliability of the results should improve significantly owing to the use of phase and group velocities simultaneously. On this basis, we have built horizontal depth sections that give an updated view of the seismic velocity structure of the peninsula at lithospheric and upper mantle depths (20–200 km. After averaging all the pure-path S-wave velocities previously determined at each grid point, the velocity-depth models so obtained for major tectonic units allow the comparison between the Hercynian basement and other areas of Mesozoic folding and Tertiary basins.

  1. Uranium Dispersion and Dosimetry (UDAD) Code

    International Nuclear Information System (INIS)

    Momeni, M.H.; Yuan, Y.; Zielen, A.J.

    1979-05-01

    The Uranium Dispersion and Dosimetry (UDAD) Code provides estimates of potential radiation exposure to individuals and to the general population in the vicinity of a uranium processing facility. The UDAD Code incorporates the radiation dose from the airborne release of radioactive materials, and includes dosimetry of inhalation, ingestion, and external exposures. The removal of raioactive particles from a contaminated area by wind action is estimated, atmospheric concentrations of radioactivity from specific sources are calculated, and source depletion as a result of deposition, fallout, and ingrowth of radon daughters are included in a sector-averaged Gaussian plume dispersion model. The average air concentration at any given receptor location is assumed to be constant during each annual release period, but to increase from year to year because of resuspension. Surface contamination and deposition velocity are estimated. Calculation of the inhalation dose and dose rate to an individual is based on the ICRP Task Group Lung Model. Estimates of the dose to the bronchial epithelium of the lung from inhalation of radon and its short-lived daughters are calculated based on a dose conversion factor from the BEIR report. External radiation exposure includes radiation from airborne radionuclides and exposure to radiation from contaminated ground. Terrestrial food pathways include vegetation, meat, milk, poultry, and eggs. Internal dosimetry is based on ICRP recommendations. In addition, individual dose commitments, population dose commitments, and environmental dose commitments are computed. This code also may be applied to dispersion of any other pollutant

  2. Casein Micelle Dispersions under Osmotic Stress

    Science.gov (United States)

    Bouchoux, Antoine; Cayemitte, Pierre-Emerson; Jardin, Julien; Gésan-Guiziou, Geneviève; Cabane, Bernard

    2009-01-01

    Abstract Casein micelles dispersions have been concentrated and equilibrated at different osmotic pressures using equilibrium dialysis. This technique measured an equation of state of the dispersions over a wide range of pressures and concentrations and at different ionic strengths. Three regimes were found. i), A dilute regime in which the osmotic pressure is proportional to the casein concentration. In this regime, the casein micelles are well separated and rarely interact, whereas the osmotic pressure is dominated by the contribution from small residual peptides that are dissolved in the aqueous phase. ii), A transition range that starts when the casein micelles begin to interact through their κ-casein brushes and ends when the micelles are forced to get into contact with each other. At the end of this regime, the dispersions behave as coherent solids that do not fully redisperse when osmotic stress is released. iii), A concentrated regime in which compression removes water from within the micelles, and increases the fraction of micelles that are irreversibly linked to each other. In this regime the osmotic pressure profile is a power law of the residual free volume. It is well described by a simple model that considers the micelle to be made of dense regions separated by a continuous phase. The amount of water in the dense regions matches the usual hydration of proteins. PMID:19167314

  3. Axial Dispersion during Hanford Saltcake Washing

    International Nuclear Information System (INIS)

    Josephson, Gary B.; Geeting, John GH; Lessor, Delbert L.; Barton, William B.

    2006-01-01

    Clean up of Hanford salt cake wastes begins with dissolution retrieval of the sodium rich salts that make up the dominant majority of mass in the tanks. Water moving through the porous salt cake dissolves the soluble components and also displaces the soluble radionuclides (e.g. 137Cs and 99TcO4- ). The separation that occurs from this displacement, known as Selective dissolution, is an important component in Hanford?s pretreatment of low activity wastes for subsequent Supplemental treatment. This paper describes lab scale testing conducted to evaluate Selective dissolution of cesium from non-radioactive Hanford tank 241-S-112 salt cake simulant containing the primary chemicals found the actual tank. An modified axial dispersion model with increasing axial dispersion was developed to predict cesium removal. The model recognizes that water dissolves the salt cake during washing, which causes an increase in the axial dispersion during the wash. This model was subsequently compared with on-line cesium measurements from the retrieval of tank 241-S-112. The model had remarkably good agreement with both the lab scale and full scale data

  4. Platoon Dispersion Analysis Based on Diffusion Theory

    Directory of Open Access Journals (Sweden)

    Badhrudeen Mohamed

    2017-01-01

    Full Text Available Urbanization and gro wing demand for travel, causes the traffic system to work ineffectively in most urban areas leadin g to traffic congestion. Many approaches have been adopted to address this problem, one among them being the signal co-ordination. This can be achieved if the platoon of vehicles that gets discharged at one signal gets green at consecutive signals with minimal delay. However, platoons tend to get dispersed as they travel and this dispersion phenomenon should be taken into account for effective signal coordination. Reported studies in this area are from the homogeneous and lane disciplined traffic conditions. This paper analyse the platoon dispersion characteristics under heterogeneous and lane-less traffic conditions. Out of the various modeling techniques reported, the approach based on diffusion theory is used in this study. The diffusion theory based models so far assumed thedata to follow normal distribution. However, in the present study, the data was found to follow lognormal distribution and hence the implementation was carried out using lognormal distribution. The parameters of lognormal distribution were calibrated for the study condition. For comparison purpose, normal distribution was also calibrated and the results were evaluated. It was foun d that model with log normal distribution performed better in all cases than the o ne with normal distribution.

  5. Delayed shear enhancement in mesoscale atmospheric dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Moran, M.D. [Atmospheric Environment Service, Ontario (Canada); Pielke, R.A. [Colorado State Univ., Fort Collins, CO (United States)

    1994-12-31

    Mesoscale atmospheric dispersion (MAD) is more complicated than smaller-scale dispersion because the mean wind field can no longer be considered steady or horizontally homogeneous over mesoscale time and space scales. Wind shear also plays a much more important role on the mesoscale: horizontal dispersion can be enhanced and often dominated by vertical wind shear on these scales through the interaction of horizontal differential advection and vertical mixing. Just over 30 years ago, Pasquill suggested that this interaction need not be simultaneous and that the combination of differential horizontal advection with delayed or subsequent vertical mixing could maintain effective horizontal diffusion in spite of temporal or spatial reductions in boundary-layer turbulence intensity. This two-step mechanism has not received much attention since then, but a recent analysis of observations from and numerical simulations of two mesoscale tracer experiments suggests that delayed shear enhancement can play an important role in MAD. This paper presents an overview of this analysis, with particular emphasis on the influence of resolvable vertical shear on MAD in these two case studies and the contributions made by delayed shear enhancement.

  6. Contractility Dispersion in Long QT Syndrome

    Directory of Open Access Journals (Sweden)

    MH Nikoo

    2009-09-01

    Full Text Available Background: Previous studies, using M mode echocardiography, provided unexpected evidence of a mechanical alteration in patients with long QT syndrome. The aim of this study was to evaluate entire left ventricular (LV wall motion characteristics in patients with long QT syndrome using tissue Doppler imaging. Methods: We enrolled 17 patients with congenital long QT syndrome [11 female and 6 male], aged 21 to 45 years. 10 subjects without cardiac disease were also selected as a control group. Two-dimensional tissue Doppler imaging (TDI recording of the LV was obtained from the basal and mid-segments from apical four-chamber, two-chamber, and long-axis views. ‘Myocardial Contraction Duration’ [MCD] was defined as the time from start of R wave on ECG to end of S wave on TDI. MCD was measured in the six LV wall positions: septal, anteroseptal, lateral, inferior, posterior and anterior positions.Results: LV contractility dispersion was significantly greater in long QT syndrome patients compared to control group [0.051 ± 0.011 vs. 0.016 ± 0.06; P < 0.001]. Conclusion: Our study evaluated left ventricular dispersion of contractility duration in patients with long QT syndrome. This mechanical dispersion may be a reflection of the inhomogeneity of repolarisation in the long QT syndrome.

  7. Jet noise reduction via dispersed phase injection

    Science.gov (United States)

    Greska, Brent; Krothapalli, Anjaneyulu; Arakeri, Vijay

    2001-11-01

    A recently developed hot jet aeroacoustics facility at FMRL,FAMU-FSU College of Engineering has been used to study the far field noise characteristics of hot supersonic jets as influenced by the injection of a dispersed phase with low mass loading.The measured SPL from a fully expanded Mach 1.36 hot jet shows a peak value of about 139 dB at 40 deg from the jet axis.By injecting atomized water,the SPL are reduced in the angular region of about 30 deg to 50 deg with the maximum reduction being about 2 dB at 40 deg.However,with the use of non atomized aqueous polymer solution as a dispersed phase the noise levels are reduced over all angular positions by at least 1 dB with the maximum reduction being about 3 dB at 40 deg.The injection of a dispersed phase readily kills the screech; the initial results show promise and optimization studies are underway to find methods of further noise reduction.

  8. Temporal variations in atmospheric dispersion at Hanford

    International Nuclear Information System (INIS)

    Ramsdell, J.V.; Burk, K.W.

    1990-01-01

    Climatological data are frequently used to estimate atmospheric dispersion factors for historical periods and for future releases for which adequate meteorological data are unavailable. This practice routinely leads to questions concerning the representativeness of data used. The work described here was performed to provide a basis for answering these questions at the U.S. Department of Energy's Hanford Site in eastern Washington. Atmospheric transport and diffusion near Hanford have been examined using a Lagrangian puff dispersion model and hourly meteorological data from the Hanford Meteorological Station and a network of 24 surface wind stations for a 5-yr period. Average normalized monthly concentrations were computed at 2.5-km intervals on a 31 by 31 grid from January 1983 through 1987, assuming an elevated release in the 200-East Area. Monthly average concentrations were used to determine 5-yr mean pattern and monthly mean patterns and the interannual variability about each pattern. Intra-annual and diurnal variations in dispersion factors are examined for six locations near Hanford

  9. Chaotic Lagrangian models for turbulent relative dispersion.

    Science.gov (United States)

    Lacorata, Guglielmo; Vulpiani, Angelo

    2017-04-01

    A deterministic multiscale dynamical system is introduced and discussed as a prototype model for relative dispersion in stationary, homogeneous, and isotropic turbulence. Unlike stochastic diffusion models, here trajectory transport and mixing properties are entirely controlled by Lagrangian chaos. The anomalous "sweeping effect," a known drawback common to kinematic simulations, is removed through the use of quasi-Lagrangian coordinates. Lagrangian dispersion statistics of the model are accurately analyzed by computing the finite-scale Lyapunov exponent (FSLE), which is the optimal measure of the scaling properties of dispersion. FSLE scaling exponents provide a severe test to decide whether model simulations are in agreement with theoretical expectations and/or observation. The results of our numerical experiments cover a wide range of "Reynolds numbers" and show that chaotic deterministic flows can be very efficient, and numerically low-cost, models of turbulent trajectories in stationary, homogeneous, and isotropic conditions. The mathematics of the model is relatively simple, and, in a geophysical context, potential applications may regard small-scale parametrization issues in general circulation models, mixed layer, and/or boundary layer turbulence models as well as Lagrangian predictability studies.

  10. Meteorological Uncertainty of atmospheric Dispersion model results (MUD)

    DEFF Research Database (Denmark)

    Havskov Sørensen, Jens; Amstrup, Bjarne; Feddersen, Henrik

    The MUD project addresses assessment of uncertainties of atmospheric dispersion model predictions, as well as optimum presentation to decision makers. Previously, it has not been possible to estimate such uncertainties quantitatively, but merely to calculate the 'most likely' dispersion scenario....

  11. The role of individual variation in marine larval dispersal

    KAUST Repository

    Nanninga, Gerrit B.; Berumen, Michael L.

    2014-01-01

    individuals may shape heterogeneity in patterns of connectivity. The concept of context- and condition-dependent dispersal describes the balance between the costs and benefits of dispersal that arises from the interaction of temporal and spatial landscape

  12. Marine Dispersal Scales Are Congruent over Evolutionary and Ecological Time

    KAUST Repository

    Pinsky, Malin L.; Saenz-Agudelo, Pablo; Salles, Océ ane C.; Almany, Glenn R.; Bode, Michael; Berumen, Michael L.; André fouë t, Serge; Thorrold, Simon R.; Jones, Geoffrey P.; Planes, Serge

    2016-01-01

    -distance dispersal are based on direct ecological observations of dispersing individuals, while indirect evolutionary estimates often suggest substantially greater homogeneity among populations. Reconciling these two approaches and their seemingly competing

  13. Dispersal and biogeography of silica-scaled chrysophytes

    DEFF Research Database (Denmark)

    Kristiansen, Jørgen

    2008-01-01

    The silica-scaled chrysophytes—here mainly represented by the freshwater genera Mallomonas and Synura—have special problems in dispersal from one habitat to another because they cannot tolerate desiccation. Their dispersal is limited by the fragile construction and aquatic habit. Dispersal from one...... water body to another involves dangerous changes of the environment, and the ability to avoid desiccation during transport is crucial. So, air-borne and ectozoic dispersal by birds or mammals can only work at short distances. This danger may be avoided by endozoic dispersal of thick-walled cysts; as far....... The distribution of a species at a given time depends on several factors: dispersal capacity—available vectors—suitable available habitats—and most important: sufficient time for dispersal. It is remarkable that the chrysophytes—in spite of their fragile cell construction and apparently low dispersal capacity...

  14. Dispersant effectiveness in the field on fresh oils and emulsions

    International Nuclear Information System (INIS)

    Lunel, T.; Davies, L.

    1996-01-01

    A detailed data set on the effectiveness of dispersants on fresh oils and emulsions, was presented. The data set could be used to calibrate laboratory dispersant tests and dispersion models so that oil spill response teams would have accurate information to make decisions regarding remediation processes. AEA Technology developed steady state continuous release experiments to provide a data set with quantitative measures of dispersant effectiveness in the field. The Sea Empress incident was closely monitored in order to compare the quantification obtained through field trials. It was noted that the prediction of the percentage of oil dispersed chemically is not the only indication of whether or not to use a dispersant. The important determinant to consider should be the extent to which the natural dispersion process would be enhanced by dispersant application. 17 refs., 5 tabs., 18 figs

  15. Skeletonized wave equation of surface wave dispersion inversion

    KAUST Repository

    Li, Jing; Schuster, Gerard T.

    2016-01-01

    We present the theory for wave equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. Similar to wave-equation travel

  16. Studying the factors affecting urban dispersion in mashhad metropolis

    African Journals Online (AJOL)

    economic, social, and physical aspects including increased air pollution, potential deterioration within ... solutions to control this problem. The tools used in ... Key words: urban dispersion, technology, roots of Mashhad dispersion, the price of

  17. Dispersion Engineering of Bose-Einstein Condensates

    Science.gov (United States)

    Khamehchi, Mohammad Amin

    The subject of this dissertation is engineering the dispersion relation for dilute Bose-Einstein condensates (BECs). When a BEC is immersed into suitably tailored laser fields its dispersion can be strongly modified. Prominent examples for such laser fields include optical lattice geometries and Raman dressing fields. The ability to engineer the dispersion of a BEC allows for the investigation of a range of phenomena related to quantum hydrodynamics and condensed matter. In the first context, this dissertation studies the excitation spectrum of a spin-orbit coupled (SOC) BEC. The spin-orbit coupling is generated by " dressing" the atoms with two Raman laser fields. The excitation spectrum has a Roton-like feature that can be altered by tuning the Raman laser parameters. It is demonstrated that the Roton mode can be softened, but it does not reach the ground state energy for the experimental conditions we had. Furthermore, the expansion of SOC BECs in 1D is studied by relaxing the trap allowing the BEC to expand in the SOC direction. Contrary to the findings for optical lattices, it is observed that the condensate partially occupies quasimomentum states with negative effective mass, and therefore an abrupt deceleration is observed although the mean field force is along the direction of expansion. In condensed-matter systems, a periodic lattice structure often plays an important role. In this context, an alternative to the Raman dressing scheme can be realized by coupling the s- and p- bands of a static optical lattice via a weak moving lattice. The bands can be treated as pseudo-spin states. It is shown that similar to the dispersion relation of a Raman dressed SOC, the quasimomentum of the ground state is different from zero. Coherent coupling of the SOC dispersion minima can lead to the realization of the stripe phase even though it is not the thermodynamic ground state of the system. Along the lines of studying the hydrodynamics of BECs, three novel

  18. Control of Dispersion in Hollow Core Photonic Crystal Fibers

    DEFF Research Database (Denmark)

    Roberts, John

    2007-01-01

    The dispersion of hollow core photonic crystal fibers can be tailored by modifying a single ring of holes in the cladding. The dispersion can be lowered and flattened, or alternatively greatly increased, in a controlled manner.......The dispersion of hollow core photonic crystal fibers can be tailored by modifying a single ring of holes in the cladding. The dispersion can be lowered and flattened, or alternatively greatly increased, in a controlled manner....

  19. Analytical solutions of advection-dispersion equation for varying ...

    African Journals Online (AJOL)

    Analytical solutions are obtained for a one-dimensional advection–dispersion equation with variable coefficients in a longitudinal domain. Two cases are considered. In the first one the solute dispersion is time dependent along a uniform flow in a semi-infinite domain while in the second case the dispersion and the velocity ...

  20. Behavioral tradeoffs when dispersing across a patchy landscape.

    Science.gov (United States)

    Patrick A. Zollner; Steven L. Lima

    2005-01-01

    A better understanding of the behavior of dispersing animals will assist in determining the factors that limit their success and ultimately help improve the way dispersal is incorporated into population models. To that end, we used a simulation model to investigate three questions about behavioral tradeoffs that dispersing animals might face: (i) speed of movement...

  1. Melt dispersion of thermoplastic polystyrene in polymer polyols

    NARCIS (Netherlands)

    2009-01-01

    Polystyrene is dispersed into a polyol via a mechanical dispersion process. A stabilizer is present to stabilize the dispersed polymer particles. The stabilizer includes a copolymer of (1) from 10 to 70% by weight of a branched polyol which has a molecular weight of from 4000 to 20,000, from 0.2 to

  2. Spatial characterization of catchment dispersion mechanisms in an urban context

    Science.gov (United States)

    Rossel, Florian; Gironás, Jorge; Mejía, Alfonso; Rinaldo, Andrea; Rodriguez, Fabrice

    2014-12-01

    Previous studies have examined in-depth the dispersion mechanisms in natural catchments. In contrast, these dispersion mechanisms have been studied little in urban catchments, where artificial transport elements and morphological arrangements are expected to modify travel times and mobilize excess rainfall from spatially distributed impervious sites. This has the ability to modify the variance of the catchment's travel times and hence the total dispersion. This work quantifies the dispersion mechanisms in an urban catchment using the theory of transport by travel times as represented by the Urban Morpho-climatic Instantaneous Unit Hydrograph (U-McIUH) model. The U-McIUH computes travel times based on kinematic wave theory and accounts explicitly for the path heterogeneities and altered connectivity patterns characteristic of an urban drainage network. The analysis is illustrated using the Aubinière urban catchment in France as a case study. We found that kinematic dispersion is dominant for small rainfall intensities, whereas geomorphologic dispersion becomes more dominant for larger intensities. The total dispersion scales with the drainage area in a power law fashion. The kinematic dispersion is dominant across spatial scales up to a threshold of approximately 2-3 km2, after which the geomorphologic dispersion becomes more dominant. Overall, overland flow is responsible for most of the dispersion in the catchment, while conduits tend to counteract the increase of the geomorphologic dispersion with a negative kinematic dispersion. Further study with other catchments is needed to asses if the latter is a general feature of urban drainage networks.

  3. Patterns and mechanisms of dispersal in a keystone seagrass species

    DEFF Research Database (Denmark)

    Jahnke, M.; Christensen, Asbjørn; Micu, D.

    2016-01-01

    •Z. noltei shows low genetic connectivity (from 10 s to 100 s of km) in the Black Sea.•Physical modelling of dispersal well agree with estimates of genetic connectivity.•Physical and genetic connectivity show possible but rare long distance dispersal.•Seeds get dispersed locally while shoots have...

  4. Dispersion of radioactive materials in air and water

    International Nuclear Information System (INIS)

    Tolksdorf, P.; Meurin, G.

    1976-01-01

    A review of current analytical methods for treating the dispersion of radioactive material in air and water is given. It is shown that suitable calculational models, based on experiments, exist for the dispersion in air. By contrast, the analysis of the dispersion of radioactive material in water still depends on the evaluation of experiments with site-specific models. (orig.) [de

  5. Evaluating Chemical Dispersant Efficacy In An Experimental Wave Tank: 1, Dispersant Effectiveness As A Function Of Energy Dissipation Rate

    Science.gov (United States)

    Numerous laboratory test systems have been developed for the comparison of efficacy between various chemical oil dispersant formulations. However, for the assessment of chemical dispersant effectiveness under realistic sea state, test protocols are required to produce hydrodynam...

  6. Fast Running Urban Dispersion Model for Radiological Dispersal Device (RDD) Releases: Model Description and Validation

    Energy Technology Data Exchange (ETDEWEB)

    Gowardhan, Akshay [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Neuscamman, Stephanie [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Donetti, John [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Walker, Hoyt [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Belles, Rich [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Eme, Bill [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Homann, Steven [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Simpson, Matthew [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC); Nasstrom, John [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). National Atmospheric Release Advisory Center (NARAC)

    2017-05-24

    Aeolus is an efficient three-dimensional computational fluid dynamics code based on finite volume method developed for predicting transport and dispersion of contaminants in a complex urban area. It solves the time dependent incompressible Navier-Stokes equation on a regular Cartesian staggered grid using a fractional step method. It also solves a scalar transport equation for temperature and using the Boussinesq approximation. The model also includes a Lagrangian dispersion model for predicting the transport and dispersion of atmospheric contaminants. The model can be run in an efficient Reynolds Average Navier-Stokes (RANS) mode with a run time of several minutes, or a more detailed Large Eddy Simulation (LES) mode with run time of hours for a typical simulation. This report describes the model components, including details on the physics models used in the code, as well as several model validation efforts. Aeolus wind and dispersion predictions are compared to field data from the Joint Urban Field Trials 2003 conducted in Oklahoma City (Allwine et al 2004) including both continuous and instantaneous releases. Newly implemented Aeolus capabilities include a decay chain model and an explosive Radiological Dispersal Device (RDD) source term; these capabilities are described. Aeolus predictions using the buoyant explosive RDD source are validated against two experimental data sets: the Green Field explosive cloud rise experiments conducted in Israel (Sharon et al 2012) and the Full-Scale RDD Field Trials conducted in Canada (Green et al 2016).

  7. Dispersion Distance and the Matter Distribution of the Universe in Dispersion Space.

    Science.gov (United States)

    Masui, Kiyoshi Wesley; Sigurdson, Kris

    2015-09-18

    We propose that "standard pings," brief broadband radio impulses, can be used to study the three-dimensional clustering of matter in the Universe even in the absence of redshift information. The dispersion of radio waves as they travel through the intervening plasma can, like redshift, be used as a cosmological distance measure. Because of inhomogeneities in the electron density along the line of sight, dispersion is an imperfect proxy for radial distance and we show that this leads to calculable dispersion-space distortions in the apparent clustering of sources. Fast radio bursts (FRBs) are a new class of radio transients that are the prototypical standard ping and, due to their high observed dispersion, have been interpreted as originating at cosmological distances. The rate of fast radio bursts has been estimated to be several thousand over the whole sky per day and, if cosmological, the sources of these events should trace the large-scale structure of the Universe. We calculate the dispersion-space power spectra for a simple model where electrons and FRBs are biased tracers of the large-scale structure of the Universe, and we show that the clustering signal could be measured using as few as 10 000 events. Such a survey is in line with what may be achieved with upcoming wide-field radio telescopes.

  8. NOISY DISPERSION CURVE PICKING (NDCP): a Matlab friendly suite package for fully control dispersion curve picking

    Science.gov (United States)

    Granados, I.; Calo, M.; Ramos, V.

    2017-12-01

    We developed a Matlab suite package (NDCP, Noisy Dispersion Curve Picking) that allows a full control over parameters to identify correctly group velocity dispersion curves in two types of datasets: correlograms between two stations or surface wave records from earthquakes. Using the frequency-time analysis (FTAN), the procedure to obtain the dispersion curves from records with a high noise level becomes difficult, and sometimes, the picked curve result in a misinterpreted character. For correlogram functions, obtained with cross-correlation of noise records or earthquake's coda, a non-homogeneous noise sources distribution yield to a non-symmetric Green's function (GF); to retrieve the complete information contained in there, NDCP allows to pick the dispersion curve in the time domain both in the causal and non-causal part of the GF. Then the picked dispersion curve is displayed on the FTAN diagram to in order to check if it matches with the maximum of the signal energy avoiding confusion with overtones or spike of noise. To illustrate how NDCP performs, we show exemple using: i) local correlograms functions obtained from sensors deployed into a volcanic caldera (Los Humeros, in Puebla, Mexico), ii) regional correlograms functions between two stations of the National Seismological Service (SSN, Servicio Sismológico Nacional in Spanish), and iii) surface wave seismic record for an earthquake located in the Pacific Ocean coast of Mexico and recorded by the SSN. This work is supported by the GEMEX project (Geothermal Europe-Mexico consortium).

  9. Partitioning of fresh crude oil between floating, dispersed and sediment phases: Effect of exposure order to dispersant and granular materials.

    Science.gov (United States)

    Boglaienko, Daria; Tansel, Berrin

    2016-06-15

    When three or more high and low energy substrates are mixed, wetting order can significantly affect the behavior of the mixture. We analyzed the phase distribution of fresh floating Louisiana crude oil into dispersed, settled and floating phases depending on the exposure sequence to Corexit 9500A (dispersant) and granular materials. In the experiments artificial sea water at salinity 34‰ was used. Limestone (2.00-0.300 mm) and quartz sand (0.300-0.075 mm) were used as the natural granular materials. Dispersant Corexit 9500A increased the amount of dispersed oil up to 33.76 ± 7.04%. Addition of granular materials after the dispersant increased dispersion of oil to 47.96 ± 1.96%. When solid particles were applied on the floating oil before the dispersant, oil was captured as oil-particle aggregates and removed from the floating layer. However, dispersant addition led to partial release of the captured oil, removing it from the aggregated form to the dispersed and floating phases. There was no visible oil aggregation with the granular materials when quartz or limestone was at the bottom of the flask before the addition of oil and dispersant. The results show that granular materials can be effective when applied from the surface for aggregating or dispersing oil. However, the granular materials in the sediments are not effective neither for aggregating nor dispersing floating oil. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Wave equation dispersion inversion using a difference approximation to the dispersion-curve misfit gradient

    KAUST Repository

    Zhang, Zhendong

    2016-07-26

    We present a surface-wave inversion method that inverts for the S-wave velocity from the Rayleigh wave dispersion curve using a difference approximation to the gradient of the misfit function. We call this wave equation inversion of skeletonized surface waves because the skeletonized dispersion curve for the fundamental-mode Rayleigh wave is inverted using finite-difference solutions to the multi-dimensional elastic wave equation. The best match between the predicted and observed dispersion curves provides the optimal S-wave velocity model. Our method can invert for lateral velocity variations and also can mitigate the local minimum problem in full waveform inversion with a reasonable computation cost for simple models. Results with synthetic and field data illustrate the benefits and limitations of this method. © 2016 Elsevier B.V.

  11. Pulse Propagation in Presence of Polarization Mode Dispersion and Chromatic Dispersion in Single Mode Fibers

    Directory of Open Access Journals (Sweden)

    Hassan Abid Yasser

    2013-01-01

    Full Text Available The presence of (first and second orders polarization mode dispersion (PMD, chromatic dispersion, and initial chirp makes effects on the propagated pulses in single mode fiber. Nowadays, there is not an accurate mathematical formula that describes the pulse shape in the presence of these effects. In this work, a theoretical study is introduced to derive a generalized formula. This formula is exactly approached to mathematical relations used in their special cases. The presence of second-order PMD (SOPMD will not affect the orthogonality property between the principal states of polarization. The simulation results explain that the interaction of the SOPMD components with the conventional effects (chromatic dispersion and chirp will cause a broadening/narrowing and shape distortion. This changes depend on the specified values of SOPMD components as well as the present conventional parameters.

  12. The Dispersion of Employees' Wage Increase and Firm Performance

    DEFF Research Database (Denmark)

    Grund, Christian; Westergård-Nielsen, Niels Chr.

    2008-01-01

    than the dispersion of wage levels. It is reasonable to expect greater dispersion of wage increases to be associated with higher monetary incentives, but also with increased perceptions of unfairness. The authors' analysis of linked employer-employee data from Denmark for the years 1992-97 shows......Previous studies examining intra-firm wage dispersion and firm performance have focused on wage levels. The authors of this study argue that for purposes of comparing wage dispersion's positive incentive effects with its adverse morale effects, the dispersion of wage increases is more revealing...

  13. Fundamentals of energy dispersive X-ray analysis

    CERN Document Server

    Russ, John C; Kiessling, R; Charles, J

    1984-01-01

    Fundamentals of Energy Dispersive X-ray Analysis provides an introduction to the fundamental principles of dispersive X-ray analysis. It presents descriptions, equations, and graphs to enable the users of these techniques to develop an intuitive and conceptual image of the physical processes involved in the generation and detection of X-rays. The book begins with a discussion of X-ray detection and measurement, which is accomplished by one of two types of X-ray spectrometer: energy dispersive or wavelength dispersive. The emphasis is on energy dispersive spectrometers, given their rather wid

  14. Dispersion factors - tables and diagrams for the Karlsruhe site

    International Nuclear Information System (INIS)

    Papadopoulos, D.; Baer, M.; Honcu, S.

    1984-02-01

    Dispersion experiments were performed at the Nuclear Research Center for the Karlsruhe site. The evaluation of these experiments allowed to determine the parameters of lateral or vertical atmospheric dispersions. This report is a compilation of tables and diagrams showing the dispersion factors calculated with the help of the dispersion parameters. These dispersion factors are valid for the Karlsruhe site. They have been normalized to 1 m/s wind speed and to 1 g/s (or 1 Bq/s) source strength. (orig.) [de

  15. Modelling Pollutant Dispersion in a Street Network

    Science.gov (United States)

    Salem, N. Ben; Garbero, V.; Salizzoni, P.; Lamaison, G.; Soulhac, L.

    2015-04-01

    This study constitutes a further step in the analysis of the performances of a street network model to simulate atmospheric pollutant dispersion in urban areas. The model, named SIRANE, is based on the decomposition of the urban atmosphere into two sub-domains: the urban boundary layer, whose dynamics is assumed to be well established, and the urban canopy, represented as a series of interconnected boxes. Parametric laws govern the mass exchanges between the boxes under the assumption that the pollutant dispersion within the canopy can be fully simulated by modelling three main bulk transfer phenomena: channelling along street axes, transfers at street intersections, and vertical exchange between street canyons and the overlying atmosphere. Here, we aim to evaluate the reliability of the parametrizations adopted to simulate these phenomena, by focusing on their possible dependence on the external wind direction. To this end, we test the model against concentration measurements within an idealized urban district whose geometrical layout closely matches the street network represented in SIRANE. The analysis is performed for an urban array with a fixed geometry and a varying wind incidence angle. The results show that the model provides generally good results with the reference parametrizations adopted in SIRANE and that its performances are quite robust for a wide range of the model parameters. This proves the reliability of the street network approach in simulating pollutant dispersion in densely built city districts. The results also show that the model performances may be improved by considering a dependence of the wind fluctuations at street intersections and of the vertical exchange velocity on the direction of the incident wind. This opens the way for further investigations to clarify the dependence of these parameters on wind direction and street aspect ratios.

  16. EDF plan for a dispersant injection trial

    International Nuclear Information System (INIS)

    Mercier, Stephane; Corredera, Geraldine; Alves-Vieira, Maria; Mansour, Carine; You, Dominique

    2012-09-01

    In its strategy for SG fouling control, EDF is considering the use of dispersant as a preventive remedy. A trial on Golfech 2 started in May 2012. The dispersant selected for the trial is Polyacrylic Acid (PAA). The main goals of the test are to check and quantify the gain on iron transport to blowdown, to evaluate the possible effects on secondary side chemistry and the operational costs of the injection - reactant, ion exchange resins and filters. The results of the test, if satisfying, will be used to set EDF strategy for dispersant long term use on its fleet. So, one concern about the trial is to make sure that the conclusions of this test will be applicable to a wide range of EDF plants. For that purpose, several criteria have been examined for the choice of the candidate plant such as fouling level, secondary circuit materials (presence or absence of copper alloys,...), SG tube material, thermal power margin, secondary side chemistry (amine used and pH applied). Before starting the trial, EDF had to take into account the international feedback and to adapt it to its specific requirements: the neutralization amine was switched from ETA to morpholine, additional work had been completed to validate the innocuousness of PAA injection for EDF plants... This work especially includes laboratory testing of secondary side corrosion cracking in the presence of PAA and water chemistries used in EdF plants. Moreover, investigation on the thermal stability of PAA and degradation products was completed and further evaluation of environmental impact was performed. A dedicated skid for the injection of PAA was implemented in Golfech Chemicals injection room. The installation and the process were notably designed to take into account the high viscosity of the commercial product, and the need to proceed to a good rinsing of the pipes without increasing the discharged effluents. The first available data from Golfech 2 trial are also provided and discussed. (authors)

  17. Modelling airborne dispersion for disaster management

    Science.gov (United States)

    Musliman, I. A.; Yohnny, L.

    2017-05-01

    Industrial disasters, like any other disasters, can happen anytime, anywhere and in any form. Airborne industrial disaster is a kind of catastrophic event involving the release of particles such as chemicals and industrial wastes into environment in gaseous form, for instance gas leakages. Unlike solid and liquid materials, gases are often colourless and odourless, the particles are too tiny to be visible to the naked eyes; hence it is difficult to identify the presence of the gases and to tell the dispersion and location of the substance. This study is to develop an application prototype to perform simulation modelling on the gas particles to determine the dispersion of the gas particles and to identify the coverage of the affected area. The prototype adopted Lagrangian Particle Dispersion (LPD) model to calculate the position of the gas particles under the influence of wind and turbulent velocity components, which are the induced wind due to the rotation of the Earth, and Convex Hull algorithm to identify the convex points of the gas cloud to form the polygon of the coverage area. The application performs intersection and overlay analysis over a set of landuse data at Pasir Gudang, Johor industrial and residential area. Results from the analysis would be useful to tell the percentage and extent of the affected area, and are useful for the disaster management to evacuate people from the affected area. The developed application can significantly increase efficiency of emergency handling during a crisis. For example, by using a simulation model, the emergency handling can predict what is going to happen next, so people can be well informed and preparations works can be done earlier and better. Subsequently, this application helps a lot in the decision making process.

  18. Modelling airborne dispersion for disaster management

    International Nuclear Information System (INIS)

    Musliman, I A; Yohnny, L

    2017-01-01

    Industrial disasters, like any other disasters, can happen anytime, anywhere and in any form. Airborne industrial disaster is a kind of catastrophic event involving the release of particles such as chemicals and industrial wastes into environment in gaseous form, for instance gas leakages. Unlike solid and liquid materials, gases are often colourless and odourless, the particles are too tiny to be visible to the naked eyes; hence it is difficult to identify the presence of the gases and to tell the dispersion and location of the substance. This study is to develop an application prototype to perform simulation modelling on the gas particles to determine the dispersion of the gas particles and to identify the coverage of the affected area. The prototype adopted Lagrangian Particle Dispersion (LPD) model to calculate the position of the gas particles under the influence of wind and turbulent velocity components, which are the induced wind due to the rotation of the Earth, and Convex Hull algorithm to identify the convex points of the gas cloud to form the polygon of the coverage area. The application performs intersection and overlay analysis over a set of landuse data at Pasir Gudang, Johor industrial and residential area. Results from the analysis would be useful to tell the percentage and extent of the affected area, and are useful for the disaster management to evacuate people from the affected area. The developed application can significantly increase efficiency of emergency handling during a crisis. For example, by using a simulation model, the emergency handling can predict what is going to happen next, so people can be well informed and preparations works can be done earlier and better. Subsequently, this application helps a lot in the decision making process. (paper)

  19. Utilities for high performance dispersion model PHYSIC

    International Nuclear Information System (INIS)

    Yamazawa, Hiromi

    1992-09-01

    The description and usage of the utilities for the dispersion calculation model PHYSIC were summarized. The model was developed in the study of developing high performance SPEEDI with the purpose of introducing meteorological forecast function into the environmental emergency response system. The procedure of PHYSIC calculation consists of three steps; preparation of relevant files, creation and submission of JCL, and graphic output of results. A user can carry out the above procedure with the help of the Geographical Data Processing Utility, the Model Control Utility, and the Graphic Output Utility. (author)

  20. Modified dispersion relations and black hole physics

    International Nuclear Information System (INIS)

    Ling Yi; Li Xiang; Hu Bo

    2006-01-01

    A modified formulation of the energy-momentum relation is proposed in the context of doubly special relativity. We investigate its impact on black hole physics. It turns out that such a modification will give corrections to both the temperature and the entropy of black holes. In particular, this modified dispersion relation also changes the picture of Hawking radiation greatly when the size of black holes approaches the Planck scale. It can prevent black holes from total evaporation, as a result providing a plausible mechanism to treat the remnant of black holes as a candidate for dark matter

  1. Forging Oxide-Dispersion-Strengthened Superalloys

    Science.gov (United States)

    Harf, F. H.; Glasgow, T. K.; Moracz, D. J.; Austin, C. M.

    1986-01-01

    Cladding of mild steel prevents surface cracking when alloy contacts die. Continual need for improvements in properties of alloys capable of withstanding elevated temperatures. Accomplished by using oxide-dispersion-strengthed superalloys such as Inconel Alloy MA 6000. Elevated tensile properties of forged alloy equal those of hot-rolled MA 6000 bar. Stress-rupture properties somewhat lower than those of bar stock but, at 1,100 degrees C, exceed those of strongest commercial single crystal, directionally solidified and conventionally cast superalloys.

  2. On dispersive derivation of triangle anomaly

    International Nuclear Information System (INIS)

    Horejsi, J.

    1985-01-01

    A straightforward generalization of the results of some previous treatments, in which the Adler-Bell-Jachiw triangle anomaly has been recovered with the help of dispersion relation is presented. The absorptive part of the VVA triangle diagram with the external momenta k, p at vector vertices such as K 2 =p 2 =0 is considered. An integral of the imaginary part of the relevant invariant amplitude is calculated explicitly. It is shown that the anomalous contribution to the axial Ward identity is reproduced. This also enables one to demonstrate the delta-like behaviour of sich an imaginary part in k 2 → 0, m → 0 limit

  3. Modeling pollutant dispersion within a tornadic thunderstorm

    Energy Technology Data Exchange (ETDEWEB)

    Pepper, D W

    1982-01-01

    A three-dimensional numerical model has been developed to calculate ground-level air concentration and deposition of particles entrained in a tornadic thunderstorm. The rotational characteristics of the tornadic storm are within the larger mesoscale flow of the storm system and transported with the vortex. Turbulence exchange coefficients are based on empirical values. The quasi-Lagrangian method of moments is used to model the transport of concentration within a grid cell volume. Results indicate that updrafts and downdrafts, coupled with scavenging of particles by precipitation, account for most of the material being deposited closer to the site than anticipated. Approximately 5% of the pollutant is dispersed into the stratosphere.

  4. Absorption and dispersion of ultrasonic waves

    CERN Document Server

    Herzfeld, Karl F; Massey, H S W; Brueckner, Keith A

    1959-01-01

    Absorption and Dispersion of Ultrasonic Waves focuses on the influence of ultrasonics on molecular processes in liquids and gases, including hydrodynamics, energy exchange, and chemical reactions. The book first offers information on the Stokes-Navier equations of hydrodynamics, as well as equations of motion, viscosity, formal introduction of volume viscosity, and linearized wave equation for a nonviscous fluid. The manuscript then ponders on energy exchange between internal and external degrees of freedom as relaxation phenomenon; effect of slow energy exchange on sound propagation; differe

  5. Laboratory Tests for Dispersive Soil Viscosity Determining

    Science.gov (United States)

    Ter-Martirosyan, Z. G.; Ter-Martirosyan, A. Z.; Sobolev, E. S.

    2017-11-01

    There are several widespread methods for soil viscosity determining now. The standard shear test device and torsion test apparatus are the most commonly used installations to do that. However, the application of them has a number of disadvantages. Therefore, the specialists of Moscow State University of Civil Engineering proposed a new device to determine the disperse soil viscosity on the basis of a stabilometer with the B-type camera (viscosimeter). The paper considers the construction of a viscosimeter and the technique for determining soil viscosity inside this tool as well as some experimental verification results of its work.

  6. Energy flow in angularly dispersive optical systems

    International Nuclear Information System (INIS)

    Ware, M.; Dibble, W. E.; Glasgow, S. A.; Peatross, J.

    2001-01-01

    Light-pulse propagation in angularly dispersive systems is explored in the context of a center-of-mass definition of energy arrival time. In this context the time of travel is given by a superposition of group delays weighted by the spectral content of the pulse. With this description the time of travel from one point to the next for a pulse is found to be completely determined by the spectral content, independent of the state of chirp. The effect of sensor orientation on arrival time is also considered. [copyright] 2001 Optical Society of America

  7. Photon gas with hyperbolic dispersion relations

    International Nuclear Information System (INIS)

    Mohseni, Morteza

    2013-01-01

    We investigate the density of states for a photon gas confined in a nonmagnetic metamaterial medium in which some components of the permittivity tensor are negative. We study the effect of the resulting hyperbolic dispersion relations on the black body spectral density. We show that for both of the possible wavevector space topologies, the spectral density vanishes at a certain frequency. We obtain the partition function and derive some thermodynamical quantities of the system. To leading order, the results resemble those of a one- or two-dimensional photon gas with an enhanced density of states. (paper)

  8. Requirements for materials of dispersion fuel elements

    International Nuclear Information System (INIS)

    Samojlov, A.G.; Kashtanov, A.I.; Volkov, V.S.

    1982-01-01

    Requirements for materials of dispersion fuel elements are considered. The necessity of structural and fissile materials compatibility at maximum permissible operation temperatures and temperatures arising in a fuel element during manufacture is pointed out. The fuel element structural material must be ductile, possess high mechanical strength minimum neutron absorption cross section, sufficient heat conductivity, good corrosion resistance in a coolant and radiation resistance. The fissile material must have high fissile isotope concentration, radiation resistance, high thermal conductivity, certain porosity high melting temperature must not change the composition under irradiation

  9. Experimental investigation of smoothing by spectral dispersion

    International Nuclear Information System (INIS)

    Regan, Sean P.; Marozas, John A.; Kelly, John H.; Boehly, Thomas R.; Donaldson, William R.; Jaanimagi, Paul A.; Keck, Robert L.; Kessler, Terrance J.; Meyerhofer, David D.; Seka, Wolf

    2000-01-01

    Measurements of smoothing rates for smoothing by spectral dispersion (SSD) of high-power, solid-state laser beams used for inertial confinement fusion (ICF) research are reported. Smoothing rates were obtained from the intensity distributions of equivalent target plane images for laser pulses of varying duration. Simulations of the experimental data with the known properties of the phase plates and the frequency modulators are in good agreement with the experimental data. These results inspire confidence in extrapolating to higher bandwidths and other SSD configurations that may be suitable for ICF experiments and ultimately for direct-drive laser-fusion ignition. (c) 2000 Optical Society of America

  10. Plasticity of oxide dispersion strengthened ferritic alloys

    International Nuclear Information System (INIS)

    Zakine, C.; Prioul, C.; Alamo, A.; Francois, D.

    1993-01-01

    Two 13%Cr oxide dispersion strengthened (ODS) ferritic alloys, DT and DY, exhibiting different oxide particle size distribution and a χ phase precipitation were studied. Their tensile properties have been tested from 20 to 700 C. Experimental observations during room temperature tensile tests performed in a scanning electronic microscope have shown that the main damage mechanism consists in microcracking of the χ phase precipitates on grain boundaries. These alloys are high tensile and creep resistant between 500 and 700 C. Their strongly stress-sensitive creep behaviour can be described by usual creep laws and incorporating a threshold stress below which the creep rate is negligible. (orig.)

  11. A novel method for combating dispersion induced power fading in dispersion compensating fiber

    DEFF Research Database (Denmark)

    Lebedev, Alexander; Vegas Olmos, Juan José; Iglesias Olmedo, Miguel

    2013-01-01

    We experimentally investigate the performance of 60 GHz double sideband (DSB) radio over fiber (RoF) links that employ dispersion compensating fiber (DCF). Error free transmission of 3 Gbps signals over 1 m of wireless distance is reported. In order to overcome experimentally observed chromatic...... dispersion (CD) induced power fading of radio frequency (RF) signal, we propose a method for improvement of RF carrier-to-noise (C/N) ratio through introduction of a degree of RF frequency tunability. Overall results improve important aspects of directly modulated RoF systems and demonstrate the feasibility...

  12. Seed-dispersal distributions by trumpeter hornbills in fragmented landscapes

    Science.gov (United States)

    Lenz, Johanna; Fiedler, Wolfgang; Caprano, Tanja; Friedrichs, Wolfgang; Gaese, Bernhard H.; Wikelski, Martin; Böhning-Gaese, Katrin

    2011-01-01

    Frugivorous birds provide important ecosystem services by transporting seeds of fleshy fruited plants. It has been assumed that seed-dispersal kernels generated by these animals are generally leptokurtic, resulting in little dispersal among habitat fragments. However, little is known about the seed-dispersal distribution generated by large frugivorous birds in fragmented landscapes. We investigated movement and seed-dispersal patterns of trumpeter hornbills (Bycanistes bucinator) in a fragmented landscape in South Africa. Novel GPS loggers provide high-quality location data without bias against recording long-distance movements. We found a very weakly bimodal seed-dispersal distribution with potential dispersal distances up to 14.5 km. Within forest, the seed-dispersal distribution was unimodal with an expected dispersal distance of 86 m. In the fragmented agricultural landscape, the distribution was strongly bimodal with peaks at 18 and 512 m. Our results demonstrate that seed-dispersal distributions differed when birds moved in different habitat types. Seed-dispersal distances in fragmented landscapes show that transport among habitat patches is more frequent than previously assumed, allowing plants to disperse among habitat patches and to track the changing climatic conditions. PMID:21177686

  13. The role of individual variation in marine larval dispersal

    KAUST Repository

    Nanninga, Gerrit B.

    2014-12-08

    The exchange of individuals among patchy habitats plays a central role in spatial ecology and metapopulation dynamics. Dispersal is frequently observed to vary non-randomly within populations (e.g., short vs. long), indicating that variability among individuals may shape heterogeneity in patterns of connectivity. The concept of context- and condition-dependent dispersal describes the balance between the costs and benefits of dispersal that arises from the interaction of temporal and spatial landscape heterogeneity (the context) with phenotypic variability among individuals (the condition). While this hypothesis is widely accepted in terrestrial theory, it remains questionable to what extent the concept of adaptive dispersal strategies may apply to marine larval dispersal, a process that is largely determined by stochastic forces. Yet, larvae of many taxa exhibit strong navigational capabilities and there is mounting evidence of widespread intra-specific variability in biological traits that are potentially correlated with dispersal potential. While so far there are few known examples of real larval dispersal polymorphisms, intra-specifically variable dispersal strategies may be common in marine systems. Whether adaptive or not, it is becoming apparent that inter-individual heterogeneity in morphology, behavior, condition, and life history traits may have critical effects on population-level heterogeneity in dispersal. Here, we explore the eco-evolutionary causes and consequences of intrinsic and extrinsic variability on larval dispersal by synthesizing the existing literature and drawing conceptual parallels from terrestrial theory. We emphasize the potential importance of larval dispersal polymorphisms in marine population dynamics.

  14. Dispersion Compensation of Fiber Optic Systems for KSC Applications

    Science.gov (United States)

    Kozaitis, Samuel P.; Hand, Larry

    1996-01-01

    Installed fibers such as those at the Kennedy Space Center (KSC) are optimized for use at 1310 nm because they have zero dispersion at that wavelength. An installed fiber system designed to operate at 1310 nm will operate at a much lower data rate when operated at 1550 nm because the dispersion is not zero at 1550 nm. Using dispersion measurements of both installed and dispersion compensating fibers, we compensated a 21.04 km length of installed fiber with 4.25 km of dispersion compensating fiber. Using the compensated fiber-optic link, we reduced the dispersion to 0.494 ps/nm-km, from an uncompensated dispersion of 16.8 ps/nm-km. The main disadvantage of the compensated link using DC fiber was an increase in attenuation. Although the increase was not necessarily severe, it could be significant when insertion losses, connector losses, and fiber attenuation are taken into account.

  15. mc1r Pathway regulation of zebrafish melanosome dispersion

    DEFF Research Database (Denmark)

    Richardson, Jennifer; Lundegaard, Pia Rengtved; Reynolds, Natalie L

    2008-01-01

    Zebrafish rapidly alter their pigmentation in response to environmental changes. For black melanocytes, this change is due to aggregation or dispersion of melanin in the cell. Dispersion and aggregation are controlled by intracellular cyclic adenosine monophosphate (cAMP) levels, which increase...... in mammals, and melanosome dispersal in cold-blood vertebrates, the pathway components are highly conserved. However, it has only been assumed that mc1r mediates melanosome dispersal in fish. Here, using morpholino oligonucleotides designed to knockdown mc1r expression, we find that mc1r morphants are unable...... to disperse melanosomes when grown in dark conditions. We also use chemical modifiers of the cAMP pathway, and find an unexpected response to the specific phosphodiesterase 4 (PDE4) inhibitor, rolipram, in melanosome dispersal. When treated with the drug, melanosomes fail to fully disperse in dark conditions...

  16. Measuring short distance dispersal of Alliaria petiolata and determining potential long distance dispersal mechanisms

    Directory of Open Access Journals (Sweden)

    Christopher A. Loebach

    2018-03-01

    Full Text Available Introduction Alliaria petiolata, an herbaceous plant, has invaded woodlands in North America. Its ecology has been thoroughly studied, but an overlooked aspect of its biology is seed dispersal distances and mechanisms. We measured seed dispersal distances in the field and tested if epizoochory is a potential mechanism for long-distance seed dispersal. Methods Dispersal distances were measured by placing seed traps in a sector design around three seed point sources, which consisted of 15 second-year plants transplanted within a 0.25 m radius circle. Traps were placed at intervals ranging from 0.25–3.25 m from the point source. Traps remained in the field until a majority of seeds were dispersed. Eight probability density functions were fitted to seed trap counts via maximum likelihood. Epizoochory was tested as a potential seed dispersal mechanism for A. petiolata through a combination of field and laboratory experiments. To test if small mammals transport A. petiolata seeds in their fur, experimental blocks were placed around dense A. petiolata patches. Each block contained a mammal inclusion treatment (MIT and control. The MIT consisted of a wood-frame (31 × 61× 31 cm covered in wire mesh, except for the two 31 × 31 cm ends, placed over a germination tray filled with potting soil. A pan filled with bait was placed in the center of the tray. The control frame (11 × 31 × 61 cm was placed over a germination tray and completely covered in wire mesh to exclude animal activity. Treatments were in the field for peak seed dispersal. In March, trays were moved to a greenhouse and A. petiolata seedlings were counted and then compared between treatments. To determine if A. petiolata seeds attach to raccoon (Procyon lotor and white-tailed deer (Odocoileus virginianus fur, wet and dry seeds were dropped onto wet and dry fur. Furs were rotated 180 degrees and the seeds that remained attached were counted. To measure seed retention, seeds

  17. Feasibility of using Ohmsett for dispersant testing and research

    International Nuclear Information System (INIS)

    Ross, S.L.; Buist, I.A.; Potter, S.G.; Belore, R.C.

    2000-01-01

    Laboratory dispersant testing proved to be of limited value for the prediction of actual dispersant effectiveness in spill situations. Variables such as oil type, weathered state, dispersant type, dispersant-to-oil ratio application method etc. were difficult to reproduce. A feasibility study was conducted at the Ohmsett facility in Leonardo, New Jersey to determine if the site was suitable for dispersant effectiveness testing. The study consisted of four phases: (1) interfacial tension laboratory tests, (2) turbidity tests, (3) the determination of the efficiency of filtering materials at the facility and alternative filtering materials, and (3) full-scale testing. Results indicated that dispersant in the water after the tests affected the interfacial tension of oils used in other tests following this one. Noticeable dispersion of floating oil occurred only after the concentration of dispersant in the water reached 400 ppm, making it possible to conduct consecutive experiments without having to worry about residual dispersant in the tank. The filtering of water to remove the dispersed oil was only required after several experiments had taken place on a given day. Evidently, it was only possible to have an underwater view of the dispersant testing during the first test of a series. The use of cellulose to aid the filtering at the facility removed most of the dispersed oil. The use of activated carbon resulted in a high degree of efficiency for the removal of dissolved dispersant. The testing of dispersant at Ohmsett proved possible as long as the design and implementation phases of the testing program respected the limitations stipulated above. 3 refs., 3 tabs., 3 figs

  18. Humans as long-distance dispersers of rural plant communities.

    Directory of Open Access Journals (Sweden)

    Alistair G Auffret

    Full Text Available Humans are known for their capacity to disperse organisms long distances. Long-distance dispersal can be important for species threatened by habitat destruction, but research into human-mediated dispersal is often focused upon few and/or invasive species. Here we use citizen science to identify the capacity for humans to disperse seeds on their clothes and footwear from a known species pool in a valuable habitat, allowing for an assessment of the fraction and types of species dispersed by humans in an alternative context. We collected material from volunteers cutting 48 species-rich meadows throughout Sweden. We counted 24,354 seeds of 197 species, representing 34% of the available species pool, including several rare and protected species. However, 71 species (36% are considered invasive elsewhere in the world. Trait analysis showed that seeds with hooks or other appendages were more likely to be dispersed by humans, as well as those with a persistent seed bank. More activity in a meadow resulted in more dispersal, both in terms of species and representation of the source communities. Average potential dispersal distances were measured at 13 km. We consider humans capable seed dispersers, transporting a significant proportion of the plant communities in which they are active, just like more traditional vectors such as livestock. When rural populations were larger, people might have been regular and effective seed dispersers, and the net rural-urban migration resulting in a reduction in humans in the landscape may have exacerbated the dispersal failure evident in declining plant populations today. With the fragmentation of habitat and changes in land use resulting from agricultural change, and the increased mobility of humans worldwide, the dispersal role of humans may have shifted from providers of regular local and landscape dispersal to providers of much rarer long-distance and regional dispersal, and international invasion.

  19. Dispersion and shape engineered plasmonic nanosensors

    Science.gov (United States)

    Jeong, Hyeon-Ho; Mark, Andrew G.; Alarcón-Correa, Mariana; Kim, Insook; Oswald, Peter; Lee, Tung-Chun; Fischer, Peer

    2016-04-01

    Biosensors based on the localized surface plasmon resonance (LSPR) of individual metallic nanoparticles promise to deliver modular, low-cost sensing with high-detection thresholds. However, they continue to suffer from relatively low sensitivity and figures of merit (FOMs). Herein we introduce the idea of sensitivity enhancement of LSPR sensors through engineering of the material dispersion function. Employing dispersion and shape engineering of chiral nanoparticles leads to remarkable refractive index sensitivities (1,091 nm RIU-1 at λ=921 nm) and FOMs (>2,800 RIU-1). A key feature is that the polarization-dependent extinction of the nanoparticles is now characterized by rich spectral features, including bipolar peaks and nulls, suitable for tracking refractive index changes. This sensing modality offers strong optical contrast even in the presence of highly absorbing media, an important consideration for use in complex biological media with limited transmission. The technique is sensitive to surface-specific binding events which we demonstrate through biotin-avidin surface coupling.

  20. Dispersion and betatron matching into the linac

    International Nuclear Information System (INIS)

    Decker, F.J.; Adolphsen, C.; Corbett, W.J.; Emma, P.; Hsu, I.; Moshammer, H.; Seeman, J.T.; Spence, W.L.

    1991-05-01

    In high energy linear colliders, the low emittance beam from a damping ring has to be preserved all the way to the linac, in the linac and to the interaction point. In particular, the Ring-To-Linac (RTL) section of the SLAC Linear Collider (SLC) should provide an exact betatron and dispersion match from the damping ring to the linac. A beam with a non-zero dispersion shows up immediately as an increased emittance, while with a betatron mismatch the beam filaments in the linac. Experimental tests and tuning procedures have shown that the linearized beta matching algorithms are insufficient if the actual transport line has some unknown errors not included in the model. Also, adjusting quadrupole strengths steers the beam if it is offset in the quadrupole magnets. These and other effects have lead to a lengthy tuning process, which in the end improves the matching, but is not optimal. Different ideas will be discussed which should improve this matching procedure and make it a more reliable, faster and simpler process. 5 refs., 2 figs

  1. Wastewater effluent dispersal in Southern California Bays

    KAUST Repository

    Uchiyama, Yusuke; Idica, Eileen Y.; McWilliams, James C.; Stolzenbach, Keith D.

    2014-01-01

    The dispersal and dilution of urban wastewater effluents from offshore, subsurface outfalls is simulated with a comprehensive circulation model with downscaling in nested grid configurations for San Pedro and Santa Monica Bays in Southern California during Fall of 2006. The circulation is comprised of mean persistent currents, mesoscale and submesoscale eddies, and tides. Effluent volume inflow rates at Huntington Beach and Hyperion are specified, and both their present outfall locations and alternative nearshore diversion sites are assessed. The effluent tracer concentration fields are highly intermittent mainly due to eddy currents, and their probability distribution functions have long tails of high concentration. The dilution rate is controlled by submesoscale stirring and straining in tracer filaments. The dominant dispersal pattern is alongshore in both directions, approximately along isobaths, over distances of more than 10. km before dilution takes over. The current outfall locations mostly keep the effluent below the surface and away from the shore, as intended, but the nearshore diversions do not. © 2014 Elsevier Ltd.

  2. Powder diffraction studies using anomalous dispersion

    International Nuclear Information System (INIS)

    Cox, D.E.; Wilkinson, A.P.

    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 T c superconductors, ternary alloys, FeCo 2 (PO 4 ) 3 , FeNi 2 BO 5 ), oxidation-state contrast (e.g. YBa 2 Cu 3 O 6+x , Eu 3 O 4 , GaCl 2 , Fe 2 PO 5 ), and the effect of coordination geometry (e.g. Y 3 Ga 5 O l2 )

  3. Oil Dispersion with Abamectin as Active Ingredient

    Directory of Open Access Journals (Sweden)

    Slavica Gašić

    2011-01-01

    Full Text Available Abamectin was developed as an insecticide, nematocide and acaricide for use on a varietyof agricultural and horticultural crops. The products with this active ingredient can befound on the market mostly formulated as emulsifiable concentrate (EC. Usually producersrecommend using the EC formulation of abamectin together with some kind of adjuvants(natural oils to improve efficacy of the active ingredient. To overcome the efficacy problemwe tried to formulate the active ingredient abamectin as oil dispersion (OD. Oil dispersion,preferably based on naturally derived oils could improve pesticide efficacy. This type of pesticideformulation contains oil instead of water as in classical suspension concentrate andtypically has better retention and coverage. In the case of abamectin, in this investigationsoybean oil was used with the mixture of different nonionic emulsifiers. Content of abamecetinin formulation was 1.8 %. The developed formulation was tested for few importantparameters. The obtained physicochemical properties for the above mentioned formulationhave shown that it is stable and could be used in plant protection.

  4. Overseas seed dispersal by migratory birds.

    Science.gov (United States)

    Viana, Duarte S; Gangoso, Laura; Bouten, Willem; Figuerola, Jordi

    2016-01-13

    Long-distance dispersal (LDD) promotes the colonization of isolated and remote habitats, and thus it has been proposed as a mechanism for explaining the distributions of many species. Birds are key LDD vectors for many sessile organisms such as plants, yet LDD beyond local and regional scales has never been directly observed nor quantified. By sampling birds caught while in migratory flight by GPS-tracked wild falcons, we show that migratory birds transport seeds over hundreds of kilometres and mediate dispersal from mainland to oceanic islands. Up to 1.2% of birds that reached a small island of the Canary Archipelago (Alegranza) during their migration from Europe to Sub-Saharan Africa carried seeds in their guts. The billions of birds making seasonal migrations each year may then transport millions of seeds. None of the plant species transported by the birds occurs in Alegranza and most do not occur on nearby Canary Islands, providing a direct example of the importance of environmental filters in hampering successful colonization by immigrant species. The constant propagule pressure generated by these LDD events might, nevertheless, explain the colonization of some islands. Hence, migratory birds can mediate rapid range expansion or shifts of many plant taxa and determine their distribution. © 2016 The Author(s).

  5. mathematical modelling of atmospheric dispersion of pollutants

    International Nuclear Information System (INIS)

    Mohamed, M.E.

    2002-01-01

    the main objectives of this thesis are dealing with environmental problems adopting mathematical techniques. in this respect, atmospheric dispersion processes have been investigated by improving the analytical models to realize the realistic physical phenomena. to achieve these aims, the skeleton of this work contained both mathematical and environmental topics,performed in six chapters. in chapter one we presented a comprehensive review study of most important informations related to our work such as thermal stability , plume rise, inversion, advection , dispersion of pollutants, gaussian plume models dealing with both radioactive and industrial contaminants. chapter two deals with estimating the decay distance as well as the decay time of either industrial or radioactive airborne pollutant. further, highly turbulent atmosphere has been investigated as a special case in the three main thermal stability classes namely, neutral, stable, and unstable atmosphere. chapter three is concerned with obtaining maximum ground level concentration of air pollutant. the variable effective height of pollutants has been considered throughout the mathematical treatment. as a special case the constancy of effective height has been derived mathematically and the maximum ground level concentration as well as its location have been established

  6. Fluff-thieving birds sabotage seed dispersal.

    Science.gov (United States)

    Rohwer, Vanya G; Pauw, Anton; Martin, Paul R

    2017-01-01

    Characterizing many species interactions as mutualisms can be misleading because some members of the interaction derive greater fitness benefits at the expense of other members. We provide detailed natural history data on a suspected bird-plant mutualism in South Africa where many species of birds use fluffy Eriocephalus seed material to construct their nests, potentially dispersing seeds for the plant. We focus on a common bird, Prinia maculosa , which invests heavily in gathering Eriocephalus material. Prinias spent 5 of their median 6-day nest construction period adding seed material to their nests and frequently travelled outside their territory boundary to gather Eriocephalus material. Yet, prinias gathered primarily Eriocephalus fluff and actively avoided gathering seeds. The average prinia nest contained only 6.6 seeds, but contained fluff from 579 seeds. These data suggest that prinias provide limited dispersal benefits to Eriocephalus plants. By contrast, the large amounts of Eriocephalus fluff in prinia nests, and the effort that prinias invest in gathering it, suggest that prinias benefit from constructing their nests with Eriocephalus material. We end by outlining hypotheses for possible fitness benefits that Eriocephalus material could provide prinias and other birds.

  7. Wastewater effluent dispersal in Southern California Bays

    KAUST Repository

    Uchiyama, Yusuke

    2014-03-01

    The dispersal and dilution of urban wastewater effluents from offshore, subsurface outfalls is simulated with a comprehensive circulation model with downscaling in nested grid configurations for San Pedro and Santa Monica Bays in Southern California during Fall of 2006. The circulation is comprised of mean persistent currents, mesoscale and submesoscale eddies, and tides. Effluent volume inflow rates at Huntington Beach and Hyperion are specified, and both their present outfall locations and alternative nearshore diversion sites are assessed. The effluent tracer concentration fields are highly intermittent mainly due to eddy currents, and their probability distribution functions have long tails of high concentration. The dilution rate is controlled by submesoscale stirring and straining in tracer filaments. The dominant dispersal pattern is alongshore in both directions, approximately along isobaths, over distances of more than 10. km before dilution takes over. The current outfall locations mostly keep the effluent below the surface and away from the shore, as intended, but the nearshore diversions do not. © 2014 Elsevier Ltd.

  8. Fluff-thieving birds sabotage seed dispersal

    Science.gov (United States)

    2017-01-01

    Characterizing many species interactions as mutualisms can be misleading because some members of the interaction derive greater fitness benefits at the expense of other members. We provide detailed natural history data on a suspected bird–plant mutualism in South Africa where many species of birds use fluffy Eriocephalus seed material to construct their nests, potentially dispersing seeds for the plant. We focus on a common bird, Prinia maculosa, which invests heavily in gathering Eriocephalus material. Prinias spent 5 of their median 6-day nest construction period adding seed material to their nests and frequently travelled outside their territory boundary to gather Eriocephalus material. Yet, prinias gathered primarily Eriocephalus fluff and actively avoided gathering seeds. The average prinia nest contained only 6.6 seeds, but contained fluff from 579 seeds. These data suggest that prinias provide limited dispersal benefits to Eriocephalus plants. By contrast, the large amounts of Eriocephalus fluff in prinia nests, and the effort that prinias invest in gathering it, suggest that prinias benefit from constructing their nests with Eriocephalus material. We end by outlining hypotheses for possible fitness benefits that Eriocephalus material could provide prinias and other birds. PMID:28280552

  9. Mechanisms of dispersion during liquid hydrogen leakage

    International Nuclear Information System (INIS)

    Proust, C.; Gaston, D.

    2000-01-01

    INERIS conducts research programs with a mission of assessing and preventing accidental and chronic risks to people and the environment due to industrial plants, chemical substances and underground operation. This paper is a study of the dispersion mechanism of cryogenic hydrogen and the mechanisms of flame propagation in clouds of hydrogen. The objective is to contribute to the industrial control implementation of significant storage of hydrogen liquid that has pressure close to the atmospheric pressure. Within the framework of this program, the only interest is with the risk presented by escape of significant flow. This corresponds to accidental ruptures in tanks. The following four phases are looked at: the escape incident and the determination of the leak flow; the formation of the liquid layer and the vaporization of the hydrogen; the formation of the Hydrogen cloud in air; and the explosive ignition in the atmosphere, propagation of the explosive flame and evaluation of the pressure wave. This situation has been limited to dispersion in free air and does not consider the impact of containment

  10. Hydrodynamic dispersion of microswimmers in suspension

    Science.gov (United States)

    Martin, Matthieu; Rafaï, Salima; Peyla, Philippe

    2014-11-01

    In our laboratory, we study hydrodynamics of suspensions of micro-swimmers. These micro-organisms are unicellular algae Chlamydomonas Rheinhardii which are able to swim by using their flagella. The swimming dynamics of these micro-swimmers can be seen as a random walk, in absence of any kind of interaction. In addition, these algae have the property of being phototactic, i.e. they swim towards the light. Combining this property with a hydrodynamic flow, we were able to reversibly separate algae from the rest of the fluid. But for sufficiently high volume fraction, these active particles interact with each other. We are now interested in how the coupling of hydrodynamic interactions between swimmers and phototaxis can modify the swimming dynamics at the scale of the suspension. To this aim, we conduct experiments in microfluidic devices to study the dispersion of the micro-organisms in a the liquid phase as a function of the volume fraction. We show that the dispersion of an assembly of puller type microswimmers is quantitatively affected by hydrodynamics interactions. Phd student.

  11. Phonon dispersion curves of fcc La

    International Nuclear Information System (INIS)

    Stassis, C.; Loong, C.; Zarestky, J.

    1982-01-01

    Large single crystals of fcc La were grown in situ and were used to study the lattice dynamics of this phase of La by coherent inelastic neutron scattering. The phonon dispersion curves have been measured along the [xi00], [xixi0], [xixixi], and [0xi1] symmetry directions at 660 and 1100 K. The T[xixixi] branch exhibits anomalous dispersion for xi>0.25 and, in addition, close to the zone boundary, the phonon frequencies of this branch decrease with decreasing temperature. This soft-mode behavior may be related to the #betta→α# transformation in La, an assumption supported by recent band-theoretical calculations of the generalized susceptibility of fcc La. At X the frequencies of the L[xi00] branch are considerably lower than those of the corresponding branch of #betta#-Ce; a similar but not as pronounced effect is observed for the frequencies of the L[xixixi] branch close to the point L. Since the calculated generalized susceptibility of fcc La exhibits strong peaks at X and L, these anomalies may be due to the renormalization of the phonon frequencies by virtual fbold-arrow-left-rightd transitions to the unoccupied 4f level in La. The data were used to evaluate the elastic constants, the phonon density of states, and the lattice specific heat at constant pressure C/sub P//sup

  12. Pigment dispersion syndrome: a clinical study.

    Science.gov (United States)

    Scheie, H G; Cameron, J D

    1981-01-01

    This study involved a group of 407 patients (799 eyes) with pigment dispersion syndrome gathered from a glaucoma population of 9200 patients. The sex distribution was equal. The majority (65%) of patients were myopic. The incidence of retinal detachment was 6.4%. No patients were black, but 5 were mulatto. Approximately one-quarter of the patients wih pigment dispersion syndrome (31% of the men, 19% of the women) had glaucoma. The average age of onset of glaucoma was 15 years less than in control patients with chronic simple glaucoma. When both eyes were affected by glaucoma, the glaucoma was consistently more severe in the eye with the more heavily pigmented angle. The degree of iris transillumination was found to be of no importance in predicting the presence of glaucoma or the severity of trabecular pigmentation. The pressure in 66% of the eyes with pigmentary glaucoma was controlled medically. A higher percentage of patients with pigmentary glaucoma required surgery than patients in the control group with chronic simple glaucoma. Men with pigmentary glaucoma required surgery at a much earlier age than women with pigmentary glaucoma. PMID:7236571

  13. Dispersion analysis of biotoxins using HPAC software

    International Nuclear Information System (INIS)

    Wu, A.; Nurthen, N.; Horstman, A.; Watson, R.; Phillips, M.

    2009-01-01

    Biotoxins are emerging threat agents produced by living organisms: bacteria, plants, or animals. Biotoxins are generally classified as cyanotoxins, hemotoxins, necrotoxins, neurotoxins, and cytotoxins. The application of classical biotoxins as weapons of terror has been realized because of extreme potency and lethality; ease of production, transport, and misuse; and the need for prolonged intensive care among affected persons. Recently, emerging biotoxins, such as ricin and T2 micotoxin have been clandestinely used by either terrorist groups or military combat operations. It is thus highly desirable to have a modeling system to simulate dispersions of biotoxins in a terrorist attack scenario in order to provide prompt technical support and casualty estimation to the first responders and military rescuers. The Hazard Prediction and Assessment Capability (HPAC) automated software system provides the means to accurately predict the effects of hazardous material released into the atmosphere and its impact on civilian and military populations. The system uses integrated source terms, high-resolution weather forecasts and atmospheric transport and dispersion analyses to model hazard areas produced by military or terrorist incidents and industrial accidents. We have successfully incorporated physical, chemical, epidemiological and biological characteristics of a variety of biotoxins into the HPAC system and have conducted numerous analyses for our emergency responders. The health effects caused by these hazards are closely reflected in HPAC output results.(author)

  14. Bioavailability of chemically-dispersed crude oil

    International Nuclear Information System (INIS)

    Harris, B.C.; Bonner, J.S.; McDonald, T.J.; Fuller, C.B.; Page, C.A.; Dimitriou-Christidis, P.; Sterling, M.C.; Autenrieth, R.L.

    2002-01-01

    Oil spills can be treated with surfactant compounds to disperse them. This method enables the hydrophobic compounds to overcome their repulsion for water, enter the water phase and be diluted. Once in the water, the biodegradation fraction of the oil biodegrades over time and the residual fraction is deposited over a large area. One major issue which is not fully understood is whether oil compounds pass through the water phase to free floating cells or directly enter oil-attached microbial cells from the oil particle. In this study, crude oil was placed in a swirling flask with Corpus Christi Bay water and was then chemically dispersed with Corexit 9500. The biodegradation was then monitored and assessed. First order rate coefficients were determined based on the disappearance of specific compounds. The rate coefficients for total target PAHs were consistent for all tests. Napthalene, phenanthrene, dibenzothiophene and their alkylated homologs were among the target compounds. The trend was also observed for total target analytes and for total target saturates. The results indicate that the biodegradation rate coefficient was not dependent on the bulk concentration of oil in the water column. It was concluded that biodegradation rates was controlled by partitioning of the compounds between the two phases, and other factors such as particle size distribution and the capability of the microbial culture, temperature and nutrients. 13 refs., 1 tab., 6 figs

  15. Proto-planetary disc evolution and dispersal

    Science.gov (United States)

    Rosotti, Giovanni Pietro

    2015-05-01

    Planets form from gas and dust discs in orbit around young stars. The timescale for planet formation is constrained by the lifetime of these discs. The properties of the formed planetary systems depend thus on the evolution and final dispersal of the discs, which is the main topic of this thesis. Observations reveal the existence of a class of discs called "transitional", which lack dust in their inner regions. They are thought to be the last stage before the complete disc dispersal, and hence they may provide the key to understanding the mechanisms behind disc evolution. X-ray photoevaporation and planet formation have been studied as possible physical mechanisms responsible for the final dispersal of discs. However up to now, these two phenomena have been studied separately, neglecting any possible feedback or interaction. In this thesis we have investigated what is the interplay between these two processes. We show that the presence of a giant planet in a photo-evaporating disc can significantly shorten its lifetime, by cutting the inner regions from the mass reservoir in the exterior of the disc. This mechanism produces transition discs that for a given mass accretion rate have larger holes than in models considering only X-ray photo-evaporation, constituting a possible route to the formation of accreting transition discs with large holes. These discs are found in observations and still constitute a puzzle for the theory. Inclusion of the phenomenon called "thermal sweeping", a violent instability that can destroy a whole disc in as little as 10 4 years, shows that the outer disc left can be very short-lived (depending on the X-ray luminosity of the star), possibly explaining why very few non accreting transition discs are observed. However the mechanism does not seem to be efficient enough to reconcile with observations. In this thesis we also show that X-ray photo-evaporation naturally explains the observed correlation between stellar masses and accretion

  16. Nanostructured hybrid materials from aqueous polymer dispersions.

    Science.gov (United States)

    Castelvetro, Valter; De Vita, Cinzia

    2004-05-20

    Organic-inorganic (O-I) hybrids with well-defined morphology and structure controlled at the nanometric scale represent a very interesting class of materials both for their use as biomimetic composites and because of their potential use in a wide range of technologically advanced as well as more conventional application fields. Their unique features can be exploited or their role envisaged as components of electronic and optoelectronic devices, in controlled release and bioencapsulation, as active substrates for chromatographic separation and catalysis, as nanofillers for composite films in packaging and coating, in nanowriting and nanolithography, etc. A synergistic combination or totally new properties with respect to the two components of the hybrid can arise from nanostructuration, achieved by surface modification of nanostructures, self-assembling or simply heterophase dispersion. In fact, owing to the extremely large total surface area associated with the resulting morphologies, the interfacial interactions can deeply modify the bulk properties of each component. A wide range of starting materials and of production processes have been studied in recent years for the controlled synthesis and characterization of hybrid nanostructures, from nanoparticle or lamellar dispersions to mesoporous materials obtained from templating nanoparticle dispersions in a continuous, e.g. ceramic precursor, matrix. This review is aimed at giving some basic definitions of what is intended as a hybrid (O-I) material and what are the main synthetic routes available. The various methods for preparing hybrid nanostructures and, among them, inorganic-organic or O-I core-shell nanoparticles, are critically analyzed and classified based on the reaction medium (aqueous, non-aqueous), and on the role it plays in directing the final morphology. Particular attention is devoted to aqueous systems and water-borne dispersions which, in addition to being environmentally more acceptable or even a

  17. Generalization of the dispersion relations demonstration; Generalisation de la demonstration des relations de dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Omnes, Roland [Commissariat a l' energie atomique et aux energies alternatives - CEA (France)

    1960-07-01

    A modification of the dispersion relations demonstration for two-particle collisions in field theory is indicated. The direct study of the holomorphy domain of the reaction amplitude, without any reference to a particular coordinate system, allows to demonstrate the dispersion relations with fixed pulse transfer for any input and output particle mass. Reprint of a paper published in Comptes rendus des seances de l'Academie des Sciences, t. 250, p. 1203-1205, sitting of 15 February 1960 [French] On indique une modification de la demonstration des relations de dispersion pour les collisions a deux particules en theorie des champs. En etudiant directement le domaine d'holomorphie de l'amplitude de reaction sans se referer a un systeme de coordonnees particulier, on demontre les relations de dispersion a transfert d'impulsion fixe dans le cas ou les masses des particules entrantes et sortantes sont quelconques. Reproduction d'un article publie dans les Comptes rendus des seances de l'Academie des Sciences, t. 250, p. 1203-1205, seance du 15 fevrier 1960.

  18. Dispersive shock waves in systems with nonlocal dispersion of Benjamin-Ono type

    Science.gov (United States)

    El, G. A.; Nguyen, L. T. K.; Smyth, N. F.

    2018-04-01

    We develop a general approach to the description of dispersive shock waves (DSWs) for a class of nonlinear wave equations with a nonlocal Benjamin-Ono type dispersion term involving the Hilbert transform. Integrability of the governing equation is not a pre-requisite for the application of this method which represents a modification of the DSW fitting method previously developed for dispersive-hydrodynamic systems of Korteweg-de Vries (KdV) type (i.e. reducible to the KdV equation in the weakly nonlinear, long wave, unidirectional approximation). The developed method is applied to the Calogero-Sutherland dispersive hydrodynamics for which the classification of all solution types arising from the Riemann step problem is constructed and the key physical parameters (DSW edge speeds, lead soliton amplitude, intermediate shelf level) of all but one solution type are obtained in terms of the initial step data. The analytical results are shown to be in excellent agreement with results of direct numerical simulations.

  19. Wave equation dispersion inversion using a difference approximation to the dispersion-curve misfit gradient

    KAUST Repository

    Zhang, Zhendong; Schuster, Gerard T.; Liu, Yike; Hanafy, Sherif M.; Li, Jing

    2016-01-01

    We present a surface-wave inversion method that inverts for the S-wave velocity from the Rayleigh wave dispersion curve using a difference approximation to the gradient of the misfit function. We call this wave equation inversion of skeletonized

  20. Do oil dispersants make spilled oil more toxic to fish?

    International Nuclear Information System (INIS)

    Hodson, P.

    2010-01-01

    The Deepwater Horizon blowout in the Gulf of Mexico was the world's largest oil spill in terms of duration and volume spilled. Clean-up operations, which involved the continuous and wide-spread use of oil dispersant at the surface and at the seabed discharge point at 1500 metres depth, gave rise to public concern about dispersant toxicity. Reports from the United States Environmental Protection Agency (EPA) claimed little difference in acute toxicity to marine fish and invertebrate species among commonly available dispersants and between dispersed and non-dispersed Louisiana Sweet Crude. Technically, the toxicity of waterborne hydrocarbons does not vary with chemical dispersion. However, the EPA omitted any consideration of loading, and misled the public about the risks of dispersant use in oil clean-up. This study examined the chronic toxicity of dispersed oil to fish embryos. The study revealed that toxicity expressed as oil loading increases by a factor of 10 to 1000 times with dispersion, largely because 10 to 1000 times more oil enters the water column. Since the action of dispersant is on the exposure component of the risk equation, not on the potency of the toxic components of oil, then the risk of oil toxicity to fish increases an equivalent amount.

  1. Thieving rodents as substitute dispersers of megafaunal seeds

    Science.gov (United States)

    Jansen, Patrick A.; Hirsch, Ben T.; Emsens, Willem-Jan; Zamora-Gutierrez, Veronica; Wikelski, Martin; Kays, Roland

    2012-01-01

    The Neotropics have many plant species that seem to be adapted for seed dispersal by megafauna that went extinct in the late Pleistocene. Given the crucial importance of seed dispersal for plant persistence, it remains a mystery how these plants have survived more than 10,000 y without their mutualist dispersers. Here we present support for the hypothesis that secondary seed dispersal by scatter-hoarding rodents has facilitated the persistence of these large-seeded species. We used miniature radio transmitters to track the dispersal of reputedly megafaunal seeds by Central American agoutis, which scatter-hoard seeds in shallow caches in the soil throughout the forest. We found that seeds were initially cached at mostly short distances and then quickly dug up again. However, rather than eating the recovered seeds, agoutis continued to move and recache the seeds, up to 36 times. Agoutis dispersed an estimated 35% of seeds for >100 m. An estimated 14% of the cached seeds survived to the next year, when a new fruit crop became available to the rodents. Serial video-monitoring of cached seeds revealed that the stepwise dispersal was caused by agoutis repeatedly stealing and recaching each other’s buried seeds. Although previous studies suggest that rodents are poor dispersers, we demonstrate that communities of rodents can in fact provide highly effective long-distance seed dispersal. Our findings suggest that thieving scatter-hoarding rodents could substitute for extinct megafaunal seed dispersers of tropical large-seeded trees. PMID:22802644

  2. Marine Dispersal Scales Are Congruent over Evolutionary and Ecological Time

    KAUST Repository

    Pinsky, Malin L.

    2016-12-15

    The degree to which offspring remain near their parents or disperse widely is critical for understanding population dynamics, evolution, and biogeography, and for designing conservation actions. In the ocean, most estimates suggesting short-distance dispersal are based on direct ecological observations of dispersing individuals, while indirect evolutionary estimates often suggest substantially greater homogeneity among populations. Reconciling these two approaches and their seemingly competing perspectives on dispersal has been a major challenge. Here we show for the first time that evolutionary and ecological measures of larval dispersal can closely agree by using both to estimate the distribution of dispersal distances. In orange clownfish (Amphiprion percula) populations in Kimbe Bay, Papua New Guinea, we found that evolutionary dispersal kernels were 17 km (95% confidence interval: 12–24 km) wide, while an exhaustive set of direct larval dispersal observations suggested kernel widths of 27 km (19–36 km) or 19 km (15–27 km) across two years. The similarity between these two approaches suggests that ecological and evolutionary dispersal kernels can be equivalent, and that the apparent disagreement between direct and indirect measurements can be overcome. Our results suggest that carefully applied evolutionary methods, which are often less expensive, can be broadly relevant for understanding ecological dispersal across the tree of life.

  3. Estimating plume dispersion: a comparison of several sigma schemes

    International Nuclear Information System (INIS)

    Irwin, J.S.

    1983-01-01

    The lateral and vertical Gaussian plume dispersion parameters are estimated and compared with field tracer data collected at 11 sites. The dispersion parameter schemes used in this analysis include Cramer's scheme, suggested for tall stack dispersion estimates, Draxler's scheme, suggested for elevated and surface releases, Pasquill's scheme, suggested for interim use in dispersion estimates, and the Pasquill--Gifford scheme using Turner's technique for assigning stability categories. The schemes suggested by Cramer, Draxler and Pasquill estimate the dispersion parameters using onsite measurements of the vertical and lateral wind-velocity variances at the effective release height. The performances of these schemes in estimating the dispersion parameters are compared with that of the Pasquill--Gifford scheme, using the Prairie Grass and Karlsruhe data. For these two experiments, the estimates of the dispersion parameters using Draxler's scheme correlate better with the measurements than did estimates using the Pasquill--Gifford scheme. Comparison of the dispersion parameter estimates with the measurement suggests that Draxler's scheme for characterizing the dispersion results in the smallest mean fractional error in the estimated dispersion parameters and the smallest variance of the fractional errors

  4. Dispersal patterns of red foxes relative to population density

    Science.gov (United States)

    Allen, Stephen H.; Sargeant, Alan B.

    1993-01-01

    Factors affecting red fox (Vulpes vulpes) dispersal patterns are poorly understood but warranted investigation because of the role of dispersal in rebuilding depleted populations and transmission of diseases. We examined dispersal patterns of red foxes in North Dakota based on recoveries of 363 of 854 foxes tagged as pups and relative to fox density. Foxes were recovered up to 8.6 years after tagging; 79% were trapped or shot. Straight-line distances between tagging and recovery locations ranged from 0 to 302 km. Mean recovery distances increased with age and were greater for males than females, but longest individual recovery distances were by females. Dispersal distances were not related to population density for males (P = 0.36) or females (P = 0.96). The proportion of males recovered that dispersed was inversely related to population density (r = -0.94; n = 5; P = 0.02), but not the proportion of females (r = -0.49; n = 5; P = 0.40). Dispersal directions were not uniform for either males (P = 0.003) or females (P = 0.006); littermates tended to disperse in similar directions (P = 0.09). A 4-lane interstate highway altered dispersal directions (P = 0.001). Dispersal is a strong innate behavior of red foxes (especially males) that results in many individuals of both sexes traveling far from natal areas. Because dispersal distance was unaffected by fox density, populations can be rebuilt and diseases transmitted long distances regardless of fox abundance.

  5. Regulatory policies for using oil dispersants in the Barents Sea

    Directory of Open Access Journals (Sweden)

    Natalia Belkina

    2015-04-01

    Full Text Available Use of dispersants requires assessment of which environmental values are at stake. In the Barents Sea this issue is of high concern as large oil spills can cause transboundary pollution, affecting the interests of two neighbouring countries. The Joint Contingency Plan in the Barents Sea does not set any specific requirements for use of dispersants and lets Norway and Russia follow their national procedures. The Plan emphasizes that in case of transboundary pollution the decision to use dispersants shall only be undertaken upon common agreement. The paper presents a comparison of the national regulatory approaches of Norway and Russia to using dispersants. The research is based on the analysis of legislative documents and interviews with oil companies, oil spill responders and relevant national authorities. The research reveals that in both countries use of dispersants requires preliminary authorization of the national agencies. In Norway the pre-approval procedure and the algorithm of dispersants involvement in response to a real accident are clearly documented and are regularly tested. This has made the process of approval for using dispersants more efficient. In Russia the lack of practical experience in using dispersants and well-established approval procedures can result in a long and unclear permitting process for each oil spill case. This could seriously hinder the use of dispersants to combat transboundary pollution in the Barents Sea, even if it is considered to be beneficial. We conclude that the development of a harmonized approach for dispersants use in the Barents Sea should be thoroughly assessed.

  6. Dispersion Theory of Direct Nuclear Reactions

    International Nuclear Information System (INIS)

    Shapiro, I.S.

    1963-01-01

    applicability. The method referred to is known as dispersion theory or dispersion method. In the form used for the description of direct processes, the dispersion theory originated and developed in the physics of the strong interactions of elementary particles. The theory has replaced the Hamiltonian formalism of quantum field thecry and contributed to a substantial advance in the solution of some problems. The possibility of applying dispersion theory to the auantitative description of direct processes stems from the very structure of this theory in which any ''compound'' particle (a nucleus, for example) which actually exists in a free state is treated exactly as an ''elementary'' particle. It is significant that certain sequences of dispersion theory are manifested in the properties of direct reactions no doubt more saliently than in the physics of the strong interactions of elementary particles. The ''dispersion nature'' of direct processes ''sticks out'' of experimental data so obviously that to grasp the essence of the dispersion approach it is worthwhile enumerating briefly the basic facts of direct nuclear reactions. (author)

  7. Dispersion Theory of Direct Nuclear Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Shapiro, I. S. [Institute Of Theoretical And Experimental Physics, Moscow, USSR (Russian Federation)

    1963-01-15

    applicability. The method referred to is known as dispersion theory or dispersion method. In the form used for the description of direct processes, the dispersion theory originated and developed in the physics of the strong interactions of elementary particles. The theory has replaced the Hamiltonian formalism of quantum field thecry and contributed to a substantial advance in the solution of some problems. The possibility of applying dispersion theory to the auantitative description of direct processes stems from the very structure of this theory in which any ''compound'' particle (a nucleus, for example) which actually exists in a free state is treated exactly as an ''elementary'' particle. It is significant that certain sequences of dispersion theory are manifested in the properties of direct reactions no doubt more saliently than in the physics of the strong interactions of elementary particles. The ''dispersion nature'' of direct processes ''sticks out'' of experimental data so obviously that to grasp the essence of the dispersion approach it is worthwhile enumerating briefly the basic facts of direct nuclear reactions. (author)

  8. Seed dispersal anachronisms: rethinking the fruits extinct megafauna ate.

    Directory of Open Access Journals (Sweden)

    Paulo R Guimarães

    Full Text Available BACKGROUND: Some neotropical, fleshy-fruited plants have fruits structurally similar to paleotropical fruits dispersed by megafauna (mammals > 10(3 kg, yet these dispersers were extinct in South America 10-15 Kyr BP. Anachronic dispersal systems are best explained by interactions with extinct animals and show impaired dispersal resulting in altered seed dispersal dynamics. METHODOLOGY/PRINCIPAL FINDINGS: We introduce an operational definition of megafaunal fruits and perform a comparative analysis of 103 Neotropical fruit species fitting this dispersal mode. We define two megafaunal fruit types based on previous analyses of elephant fruits: fruits 4-10 cm in diameter with up to five large seeds, and fruits > 10 cm diameter with numerous small seeds. Megafaunal fruits are well represented in unrelated families such as Sapotaceae, Fabaceae, Solanaceae, Apocynaceae, Malvaceae, Caryocaraceae, and Arecaceae and combine an overbuilt design (large fruit mass and size with either a single or few ( 100 seeds. Within-family and within-genus contrasts between megafaunal and non-megafaunal groups of species indicate a marked difference in fruit diameter and fruit mass but less so for individual seed mass, with a significant trend for megafaunal fruits to have larger seeds and seediness. CONCLUSIONS/SIGNIFICANCE: Megafaunal fruits allow plants to circumvent the trade-off between seed size and dispersal by relying on frugivores able to disperse enormous seed loads over long-distances. Present-day seed dispersal by scatter-hoarding rodents, introduced livestock, runoff, flooding, gravity, and human-mediated dispersal allowed survival of megafauna-dependent fruit species after extinction of the major seed dispersers. Megafauna extinction had several potential consequences, such as a scale shift reducing the seed dispersal distances, increasingly clumped spatial patterns, reduced geographic ranges and limited genetic variation and increased among

  9. Evaluation of three oil spill laboratory dispersant effectiveness tests

    International Nuclear Information System (INIS)

    Sullivan, D.; Farlow, J.; Sahatjian, K.A.

    1993-01-01

    Chemical dispersants can be used to reduce the interfacial tension of floating oil slicks so that the oils disperse more rapidly into the water column and thus pose less of a threat to shorelines, birds, and marine mammals. The laboratory test currently specified in federal regulations to measure dispersant effectiveness is not especially easy or inexpensive, and generates a rather large quantity of oily waste water. This paper describes the results of an effort by the EPA to identify a more suitable laboratory dispersant effectiveness test. EPA evaluated three laboratory methods: the Revised Standard Dispersant Effectiveness Test currently used (and required by regulation) in the United States, the swirling flask test (developed by Environment Canada), and the IFP-dilution test (used in france and other European countries). Six test oils and three dispersants were evaluated; dispersants were applied to the oil at an average 1:10 ratio (dispersant to oil) for each of the three laboratory methods. Screening efforts were used to focus on the most appropriate oil/dispersant combination for detailed study. A screening criterion was established that required a combination that gave at least 20% effectiveness results. The selected combination turned out to be Prudhoe Bay crude oil and the dispersant Corexit 9527. This combination was also most likely to be encountered in US coastal waters. The EPA evaluation concluded that the three tests gave similar precision results, but that the swirling flask test was fastest, cheapest, simplest, and required least operator skill. Further, EPA is considering conducting the dispersant effectiveness test itself, rather than having data submitted by a dispersant manufacturer, and establishing an acceptability criterion (45% efficiency) which would have to be met before a dispersant could be placed on the Product Schedule of the National Contingency Plan (NCP)

  10. Scaling of Natal Dispersal Distances in Terrestrial Birds and Mammals

    Directory of Open Access Journals (Sweden)

    Glenn D. Sutherland

    2000-07-01

    Full Text Available Natal dispersal is a process that is critical in the spatial dynamics of populations, including population spread, recolonization, and gene flow. It is a central focus of conservation issues for many vertebrate species. Using data for 77 bird and 68 mammal species, we tested whether median and maximum natal dispersal distances were correlated with body mass, diet type, social system, taxonomic family, and migratory status. Body mass and diet type were found to predict both median and maximum natal dispersal distances in mammals: large species dispersed farther than small ones, and carnivorous species dispersed farther than herbivores and omnivores. Similar relationships occurred for carnivorous bird species, but not for herbivorous or omnivorous ones. Natal dispersal distances in birds or mammals were not significantly related to broad categories of social systems. Only in birds were factors such as taxonomic relatedness and migratory status correlated with natal dispersal, and then only for maximum distances. Summary properties of dispersal processes appeared to be derived from interactions among behavioral and morphological characteristics of species and from their linkages to the dynamics of resource availability in landscapes. In all the species we examined, most dispersers moved relatively short distances, and long-distance dispersal was uncommon. On the basis of these findings, we fit an empirical model based on the negative exponential distribution for calculating minimum probabilities that animals disperse particular distances from their natal areas. This model, coupled with knowledge of a species' body mass and diet type, can be used to conservatively predict dispersal distances for different species and examine possible consequences of large-scale habitat alterations on connectedness between populations. Taken together, our results can provide managers with the means to identify species vulnerable to landscape-level habitat changes

  11. Origin and Dispersal of Domesticated Peach Palm

    Directory of Open Access Journals (Sweden)

    Charles R. Clement

    2017-11-01

    Full Text Available Peach palm (Bactris gasipaes Kunth is a Neotropical palm domesticated by Native Americans. Its domestication resulted in a set of landraces (var. gasipaes, some with very starchy fruit used for fermentation, others with an equilibrium of starch and oil used as snacks. Which of the three wild types (var. chichagui was involved and where the domestication process began are unclear, with three hypotheses under discussion: an origin in southwestern Amazonia; or in northwestern South America; or multiple origins. We reevaluate one of the wild types, defining it as the incipient domesticate, and then evaluate these hypotheses using the Brazilian peach palm Core Collection and selected herbaria samples to: (1 model the potential distributions of wild and domesticated populations; (2 identify the probable origin of domestication with a phylogeographic analysis of chloroplast DNA sequences; and (3 determine the dispersal routes after domestication using spatial analysis of genetic diversity based on 17 nuclear microsatellite loci. The two very small-fruited wild types have distinct distributions in the northern Andes region and across southern Amazonia, both under moderately humid climates, while the incipient domesticate, partly sympatric with the southern wild type, is also found along the Equatorial Andes, in a more humid climatic envelope, more similar to that of the domesticated landraces. Two distribution models for Last Glacial Maximum conditions (CCSM4, MIROC also suggest distinct distributions for the two wild populations. The chloroplast DNA phylogeographic network confirms the area of sympatry of the incipient domesticate and the southern wild type in southwestern Amazonia as the origin of domestication. The spatial patterns of genetic diversity confirm the proposal of two dispersals, one along the Ucayali River, into western Amazonia, northwestern South America and finally Central America; the other along the Madeira River into central and

  12. Diffusive dynamics of nanoparticles in aqueous dispersions

    KAUST Repository

    He, Kai; Spannuth, Melissa; Conrad, Jacinta C.; Krishnamoorti, Ramanan

    2012-01-01

    The diffusive dynamics of 100 nm to 400 nm diameter polystyrene nanoparticles dispersed in water were studied using brightfield and fluorescence based differential dynamic microscopy (DDM) and compared to those obtained from dynamic light scattering. The relaxation times measured with brightfield and fluorescence DDM over a broad range of concentration of nanoparticles (10 -6 ≤ φ ≤ 10-3) and scattering vectors (0.5 μm-1 < q < 10 μm-1) are in excellent agreement with each other and extrapolate quantitatively to those obtained from DLS measurements. The diffusion coefficients extracted from the q-dependent relaxation times using all three methods are independent of the nanoparticle concentration. © 2012 The Royal Society of Chemistry.

  13. Meteorological perspective on intermediate range atmospheric dispersion

    International Nuclear Information System (INIS)

    Van der Hoven, I.

    1981-01-01

    The intermediate range of atmospheric transport and diffusion is defined as those dispersion processes which take place at downwind distances of 10 to 100 kilometers from pollutant sources. Meteorologists often define this range as the mesoscale. It is the range of distances where certain environmental assessments are of concern such as the determination of significant deterioration of visibility, the effect of effluent releases from tall stacks, and the effect of pollutant sources in rural settings upon the more distant urban centers. Atmospheric diffusion theory is based on steady state conditions and spatial homogeniety. Techniques must be developed to measure the inhomogenieties, models must be devised to account for the complexities, and a data base consisting of appropriate measured meteorological parameters concurrent with tracer gas concentrations should be collected

  14. Hydrodynamics of annular-dispersed flow

    International Nuclear Information System (INIS)

    Ishii, M.; Kataoka, I.

    1982-01-01

    The interfacial drag, droplet entrainment, and droplet size distributions are important for detailed mechanistic modeling of annular dispersed two-phase flow. In view of this, recently developed correlations for these parameters are presented and discussed in this paper. The drag correlations for multiple fluid particle systems have been developed from a similarity hypothesis based on the mixture viscosity model. The results show that the drag coefficient depends on the particle Reynolds number and droplet concentration. The onset on droplet entrainment significantly alters the mechanisms of mass, momentum, and energy transfer between the film and gas core flow as well as the transfer between the two-phase mixture and the wall. By assuming the roll wave entrainment mechanism, the correlations for the amount of entrained droplet as well as for the droplet size distribution have been obtained from a simple model in collaboration with a large number of data

  15. Catalysis on singly dispersed bimetallic sites

    Science.gov (United States)

    Zhang, Shiran; Nguyen, Luan; Liang, Jin-Xia; Shan, Junjun; Liu, Jingyue; Frenkel, Anatoly I.; Patlolla, Anitha; Huang, Weixin; Li, Jun; Tao, Franklin

    2015-08-01

    A catalytic site typically consists of one or more atoms of a catalyst surface that arrange into a configuration offering a specific electronic structure for adsorbing or dissociating reactant molecules. The catalytic activity of adjacent bimetallic sites of metallic nanoparticles has been studied previously. An isolated bimetallic site supported on a non-metallic surface could exhibit a distinctly different catalytic performance owing to the cationic state of the singly dispersed bimetallic site and the minimized choices of binding configurations of a reactant molecule compared with continuously packed bimetallic sites. Here we report that isolated Rh1Co3 bimetallic sites exhibit a distinctly different catalytic performance in reduction of nitric oxide with carbon monoxide at low temperature, resulting from strong adsorption of two nitric oxide molecules and a nitrous oxide intermediate on Rh1Co3 sites and following a low-barrier pathway dissociation to dinitrogen and an oxygen atom. This observation suggests a method to develop catalysts with high selectivity.

  16. Air quality dispersion models from energy sources

    International Nuclear Information System (INIS)

    Lazarevska, Ana

    1996-01-01

    Along with the continuing development of new air quality models that cover more complex problems, in the Clean Air Act, legislated by the US Congress, a consistency and standardization of air quality model applications were encouraged. As a result, the Guidelines on Air Quality Models were published, which are regularly reviewed by the Office of Air Quality Planning and Standards, EPA. These guidelines provide a basis for estimating the air quality concentrations used in accessing control strategies as well as defining emission limits. This paper presents a review and analysis of the recent versions of the models: Simple Terrain Stationary Source Model; Complex Terrain Dispersion Model; Ozone,Carbon Monoxide and Nitrogen Dioxide Models; Long Range Transport Model; Other phenomenon Models:Fugitive Dust/Fugitive Emissions, Particulate Matter, Lead, Air Pathway Analyses - Air Toxic as well as Hazardous Waste. 8 refs., 4 tabs., 2 ills

  17. Study on niobium carbide dispersed superconducting tapes

    Energy Technology Data Exchange (ETDEWEB)

    Wada, H; Tachikawa, K [National Research Inst. for Metals, Tokyo (Japan); Oh' asa, M [Science Univ. of Tokyo (Japan)

    1977-11-01

    Niobium carbide (NbC) dispersed superconducting tapes have been fabricated by two metallurgical processes. In the first process, Ni-Nb-C alloys are directly arc melted and hot worked in air and the NbC phase is distributed in the form of fine discrete particles. In the second process, Ni-Nb and Ni-Nb-Cu alloys are arc melted, hot worked and subjected to solid-state carburization. NbC then precipitates along the grain boundaries, forming a network. The highest superconducting transition temperature attained is about 11 K. Taken together with the lattice parameter measurement, this indicates that NbC with a nearly perfect NaCl structure is formed in both processes. Measured values of the upper critical field, the critical current density and the volume fraction of the NbC phase are also discussed.

  18. Normal dispersion femtosecond fiber optical parametric oscillator.

    Science.gov (United States)

    Nguyen, T N; Kieu, K; Maslov, A V; Miyawaki, M; Peyghambarian, N

    2013-09-15

    We propose and demonstrate a synchronously pumped fiber optical parametric oscillator (FOPO) operating in the normal dispersion regime. The FOPO generates chirped pulses at the output, allowing significant pulse energy scaling potential without pulse breaking. The output average power of the FOPO at 1600 nm was ∼60  mW (corresponding to 1.45 nJ pulse energy and ∼55% slope power conversion efficiency). The output pulses directly from the FOPO were highly chirped (∼3  ps duration), and they could be compressed outside of the cavity to 180 fs by using a standard optical fiber compressor. Detailed numerical simulation was also performed to understand the pulse evolution dynamics around the laser cavity. We believe that the proposed design concept is useful for scaling up the pulse energy in the FOPO using different pumping wavelengths.

  19. Spray drying formulation of amorphous solid dispersions.

    Science.gov (United States)

    Singh, Abhishek; Van den Mooter, Guy

    2016-05-01

    Spray drying is a well-established manufacturing technique which can be used to formulate amorphous solid dispersions (ASDs) which is an effective strategy to deliver poorly water soluble drugs (PWSDs). However, the inherently complex nature of the spray drying process coupled with specific characteristics of ASDs makes it an interesting area to explore. Numerous diverse factors interact in an inter-dependent manner to determine the final product properties. This review discusses the basic background of ASDs, various formulation and process variables influencing the critical quality attributes (CQAs) of the ASDs and aspects of downstream processing. Also various aspects of spray drying such as instrumentation, thermodynamics, drying kinetics, particle formation process and scale-up challenges are included. Recent advances in the spray-based drying techniques are mentioned along with some future avenues where major research thrust is needed. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Dispersion characteristics of negative refraction sonic crystals

    International Nuclear Information System (INIS)

    Wu, L.-Y.; Chen, L.-W.; Wang, R.C.-C.

    2008-01-01

    Dispersion characteristics of negative refraction sonic crystals are investigated. The plane wave expansion method is used to calculate the equifrequency surface; the dependences of refractive direction on frequencies and incident angles for triangular lattices are shown. There exist the positive and negative refractive waves which include k.V g ≥0 and k.V g ≤0 in the second band for the triangular system. We also use the finite element method to demonstrate that the relative intensity of the transmitted acoustic waves is dependent on incident frequencies and angles. The positions of the partial band gaps obtained by the plane wave expansion method are in good agreement with those obtained by the finite element method. The sonic crystals with negative effective index are shown to have higher transmission intensities. By using the negative refraction behavior, we can design a sonic crystal plane lens to focus a sonic wave

  1. Velocity dispersion profiles of clusters of galaxies

    International Nuclear Information System (INIS)

    Struble, M.F.

    1979-01-01

    Velocity dispersion as a function of radius, called sigma/sub ls/ profiles, is presented for 13 clusters of galaxies having > or =30 radial velocities from both published and unpublished lists. A list of probable new members and possible outlying members for these clusters is also given. chi 2 and Kolmogoroff--Smirnoff one-sample tests for the goodness of fit of power laws to portions of the profiles indicate two significant structures in some profiles: (1) a local minimum corresponding to the local minimum noted in surface density or surface brightness profiles, and (2) a decrease in sigma/sub ls/ toward the cores. Both of these features are discussed in terms of a comparison with Wielen's N-body simulations. The sigma/sub ls/ profiles are placed in a new classification scheme which lends itself to interpreting clusters in a dynamical age sequence. The velocity field of galaxies at large distances from cluster centers is also discussed

  2. Dispersive force between dissimilar materials: Geometrical effects

    International Nuclear Information System (INIS)

    Noguez, Cecilia; Roman-Velazquez, C.E.

    2004-01-01

    We calculate the Casimir force or dispersive van der Waals force between a spherical nanoparticle and a planar substrate, both with arbitrary dielectric properties. We show that the force between the sphere and half-space can be calculated through the interacting surface plasmons of the bodies. Using a Spectral Representation formalism, we show that the force of a sphere made of a material A and a half-space made of a material B differs from the case when the sphere is made of B, and the half-space is made of A. We find that the difference depends on the plasma frequency of the materials, the geometry, and the distance of separation between the sphere and half-space. The differences show the importance of the geometry, and make evident the necessity of realistic descriptions of the system beyond the Derjaguin Approximation or Proximity Theorem Approximation

  3. Excitation methods for energy dispersive analysis

    International Nuclear Information System (INIS)

    Jaklevic, J.M.

    1976-01-01

    The rapid development in recent years of energy dispersive x-ray fluorescence analysis has been based primarily on improvements in semiconductor detector x-ray spectrometers. However, the whole analysis system performance is critically dependent on the availability of optimum methods of excitation for the characteristic x rays in specimens. A number of analysis facilities based on various methods of excitation have been developed over the past few years. A discussion is given of the features of various excitation methods including charged particles, monochromatic photons, and broad-energy band photons. The effects of the excitation method on background and sensitivity are discussed from both theoretical and experimental viewpoints. Recent developments such as pulsed excitation and polarized photons are also discussed

  4. Reliability analysis of dispersion nuclear fuel elements

    Science.gov (United States)

    Ding, Shurong; Jiang, Xin; Huo, Yongzhong; Li, Lin an

    2008-03-01

    Taking a dispersion fuel element as a special particle composite, the representative volume element is chosen to act as the research object. The fuel swelling is simulated through temperature increase. The large strain elastoplastic analysis is carried out for the mechanical behaviors using FEM. The results indicate that the fission swelling is simulated successfully; the thickness increments grow linearly with burnup; with increasing of burnup: (1) the first principal stresses at fuel particles change from tensile ones to compression ones, (2) the maximum Mises stresses at the particles transfer from the centers of fuel particles to the location close to the interfaces between the matrix and the particles, their values increase with burnup; the maximum Mises stresses at the matrix exist in the middle location between the two particles near the mid-plane along the length (or width) direction, and the maximum plastic strains are also at the above region.

  5. Reliability analysis of dispersion nuclear fuel elements

    Energy Technology Data Exchange (ETDEWEB)

    Ding Shurong [Department of Mechanics and Engineering Science, Fudan University, Shanghai 200433 (China)], E-mail: dsr1971@163.com; Jiang Xin [Department of Mechanics and Engineering Science, Fudan University, Shanghai 200433 (China); Huo Yongzhong [Department of Mechanics and Engineering Science, Fudan University, Shanghai 200433 (China)], E-mail: yzhuo@fudan.edu.cn; Li Linan [Department of Mechanics, Tianjin University, Tianjin 300072 (China)

    2008-03-15

    Taking a dispersion fuel element as a special particle composite, the representative volume element is chosen to act as the research object. The fuel swelling is simulated through temperature increase. The large strain elastoplastic analysis is carried out for the mechanical behaviors using FEM. The results indicate that the fission swelling is simulated successfully; the thickness increments grow linearly with burnup; with increasing of burnup: (1) the first principal stresses at fuel particles change from tensile ones to compression ones, (2) the maximum Mises stresses at the particles transfer from the centers of fuel particles to the location close to the interfaces between the matrix and the particles, their values increase with burnup; the maximum Mises stresses at the matrix exist in the middle location between the two particles near the mid-plane along the length (or width) direction, and the maximum plastic strains are also at the above region.

  6. Strongly coupled dispersed two-phase flows; Ecoulements diphasiques disperses fortement couples

    Energy Technology Data Exchange (ETDEWEB)

    Zun, I.; Lance, M.; Ekiel-Jezewska, M.L.; Petrosyan, A.; Lecoq, N.; Anthore, R.; Bostel, F.; Feuillebois, F.; Nott, P.; Zenit, R.; Hunt, M.L.; Brennen, C.E.; Campbell, C.S.; Tong, P.; Lei, X.; Ackerson, B.J.; Asmolov, E.S.; Abade, G.; da Cunha, F.R.; Lhuillier, D.; Cartellier, A.; Ruzicka, M.C.; Drahos, J.; Thomas, N.H.; Talini, L.; Leblond, J.; Leshansky, A.M.; Lavrenteva, O.M.; Nir, A.; Teshukov, V.; Risso, F.; Ellinsen, K.; Crispel, S.; Dahlkild, A.; Vynnycky, M.; Davila, J.; Matas, J.P.; Guazelli, L.; Morris, J.; Ooms, G.; Poelma, C.; van Wijngaarden, L.; de Vries, A.; Elghobashi, S.; Huilier, D.; Peirano, E.; Minier, J.P.; Gavrilyuk, S.; Saurel, R.; Kashinsky, O.; Randin, V.; Colin, C.; Larue de Tournemine, A.; Roig, V.; Suzanne, C.; Bounhoure, C.; Brunet, Y.; Tanaka, A.T.; Noma, K.; Tsuji, Y.; Pascal-Ribot, S.; Le Gall, F.; Aliseda, A.; Hainaux, F.; Lasheras, J.; Didwania, A.; Costa, A.; Vallerin, W.; Mudde, R.F.; Van Den Akker, H.E.A.; Jaumouillie, P.; Larrarte, F.; Burgisser, A.; Bergantz, G.; Necker, F.; Hartel, C.; Kleiser, L.; Meiburg, E.; Michallet, H.; Mory, M.; Hutter, M.; Markov, A.A.; Dumoulin, F.X.; Suard, S.; Borghi, R.; Hong, M.; Hopfinger, E.; Laforgia, A.; Lawrence, C.J.; Hewitt, G.F.; Osiptsov, A.N.; Tsirkunov, Yu. M.; Volkov, A.N.

    2003-07-01

    This document gathers the abstracts of the Euromech 421 colloquium about strongly coupled dispersed two-phase flows. Behaviors specifically due to the two-phase character of the flow have been categorized as: suspensions, particle-induced agitation, microstructure and screening mechanisms; hydrodynamic interactions, dispersion and phase distribution; turbulence modulation by particles, droplets or bubbles in dense systems; collective effects in dispersed two-phase flows, clustering and phase distribution; large-scale instabilities and gravity driven dispersed flows; strongly coupled two-phase flows involving reacting flows or phase change. Topic l: suspensions particle-induced agitation microstructure and screening mechanisms hydrodynamic interactions between two very close spheres; normal stresses in sheared suspensions; a critical look at the rheological experiments of R.A. Bagnold; non-equilibrium particle configuration in sedimentation; unsteady screening of the long-range hydrodynamic interactions of settling particles; computer simulations of hydrodynamic interactions among a large collection of sedimenting poly-disperse particles; velocity fluctuations in a dilute suspension of rigid spheres sedimenting between vertical plates: the role of boundaries; screening and induced-agitation in dilute uniform bubbly flows at small and moderate particle Reynolds numbers: some experimental results. Topic 2: hydrodynamic interactions, dispersion and phase distribution: hydrodynamic interactions in a bubble array; A 'NMR scattering technique' for the determination of the structure in a dispersion of non-brownian settling particles; segregation and clustering during thermo-capillary migration of bubbles; kinetic modelling of bubbly flows; velocity fluctuations in a homogeneous dilute dispersion of high-Reynolds-number rising bubbles; an attempt to simulate screening effects at moderate particle Reynolds numbers using an hybrid formulation; modelling the two

  7. Dispersion, deposition and resuspension of atmospheric contaminants

    International Nuclear Information System (INIS)

    Anon.

    1985-01-01

    The following topics are discussed: dry deposition, oil shale fugitive air emissions, particle resuspension and translocation, theoretical studies and applications, and processing of emissions by clouds and precipitation. The concentration of contaminant species in air is governed by the rate of input from sources, the rate of dilution or dispersion as a result of air turbulence, and the rate of removal to the surface by wet and dry deposition processes. Once on the surface, contaminants also may be resuspended, depending on meteorological and surface conditions. An understanding of these processes is necessary for accurate prediction of exposures of hazardous or harmful contaminants to humans, animals, and crops. In the field, plume dispersion and plume depletion by dry deposition were studied by the use of tracers. Dry deposition was investigated for particles of both respiration and inhalation interest. Complementary dry deposition studies of particles to rock canopies were conducted under controlled conditions in a wind tunnel. Because of increasing concern about hazardous, organic gases in the atmosphere some limited investigations of the dry deposition of nitrobenzene to a lichen mat were conducted in a stirred chamber. Resuspension was also studied using tracers and contaminated surfaces and in the wind tunnel. The objective of the resuspension studies was to develop and verify models for predicting the airborne concentrations of contaminants over areas with surface contamination, develop resuspension rate predictors for downwind transport, and develop predictors for resuspension input to the food chain. These models will be of particular relevance to the evaluation of deposition and resuspension of both radionuclides and chemical contaminants

  8. Irradiation creep of dispersion strengthened copper alloy

    International Nuclear Information System (INIS)

    Pokrovsky, A.S.; Barabash, V.R.; Fabritsiev, S.A.

    1997-01-01

    Dispersion strengthened copper alloys are under consideration as reference materials for the ITER plasma facing components. Irradiation creep is one of the parameters which must be assessed because of its importance for the lifetime prediction of these components. In this study the irradiation creep of a dispersion strengthened copper (DS) alloy has been investigated. The alloy selected for evaluation, MAGT-0.2, which contains 0.2 wt.% Al 2 O 3 , is very similar to the GlidCop trademark alloy referred to as Al20. Irradiation creep was investigated using HE pressurized tubes. The tubes were machined from rod stock, then stainless steel caps were brazed onto the end of each tube. The creep specimens were pressurized by use of ultra-pure He and the stainless steel caps subsequently sealed by laser welding. These specimens were irradiated in reactor water in the core position of the SM-2 reactors to a fluence level of 4.5-7.1 x 10 21 n/cm 2 (E>0.1 MeV), which corresponds to ∼3-5 dpa. The irradiation temperature ranged from 60-90 degrees C, which yielded calculated hoop stresses from 39-117 MPa. A mechanical micrometer system was used to measure the outer diameter of the specimens before and after irradiation, with an accuracy of ±0.001 mm. The irradiation creep was calculated based on the change in the diameter. Comparison of pre- and post-irradiation diameter measurements indicates that irradiation induced creep is indeed observed in this alloy at low temperatures, with a creep rate as high as ∼2 x 10 -9 s -1 . These results are compared with available data for irradiation creep for stainless steels, pure copper, and for thermal creep of copper alloys

  9. Irradiation creep of dispersion strengthened copper alloy

    Energy Technology Data Exchange (ETDEWEB)

    Pokrovsky, A.S.; Barabash, V.R.; Fabritsiev, S.A. [and others

    1997-04-01

    Dispersion strengthened copper alloys are under consideration as reference materials for the ITER plasma facing components. Irradiation creep is one of the parameters which must be assessed because of its importance for the lifetime prediction of these components. In this study the irradiation creep of a dispersion strengthened copper (DS) alloy has been investigated. The alloy selected for evaluation, MAGT-0.2, which contains 0.2 wt.% Al{sub 2}O{sub 3}, is very similar to the GlidCop{trademark} alloy referred to as Al20. Irradiation creep was investigated using HE pressurized tubes. The tubes were machined from rod stock, then stainless steel caps were brazed onto the end of each tube. The creep specimens were pressurized by use of ultra-pure He and the stainless steel caps subsequently sealed by laser welding. These specimens were irradiated in reactor water in the core position of the SM-2 reactors to a fluence level of 4.5-7.1 x 10{sup 21} n/cm{sup 2} (E>0.1 MeV), which corresponds to {approx}3-5 dpa. The irradiation temperature ranged from 60-90{degrees}C, which yielded calculated hoop stresses from 39-117 MPa. A mechanical micrometer system was used to measure the outer diameter of the specimens before and after irradiation, with an accuracy of {+-}0.001 mm. The irradiation creep was calculated based on the change in the diameter. Comparison of pre- and post-irradiation diameter measurements indicates that irradiation induced creep is indeed observed in this alloy at low temperatures, with a creep rate as high as {approx}2 x 10{sup {minus}9}s{sup {minus}1}. These results are compared with available data for irradiation creep for stainless steels, pure copper, and for thermal creep of copper alloys.

  10. Suspended sediment drift and dispersion at Hibernia

    International Nuclear Information System (INIS)

    Tedford, T.; Drozdowski, A.; Hannah, C.G.

    2003-01-01

    Surface water waves and near-bottom currents around the Hibernia oil production platform on the Grand Banks of Newfoundland were examined to determine how the different seasons affect changes in wave magnitude and directions of water currents. Wave observations revealed a strong correlation with seasons, with the larger waves occurring in fall and early winter. There was no obvious seasonality in the size or direction of currents. The benthic boundary layer transport (BBLT) model was used to predict the drift and dispersion pathways of suspended drilling muds discharged from the Hibernia platform. The 2-year study from March 1998 to May 2000 involved 5-day BBLT model simulations covering the complete period of current meter deployment. The study focused on the sensitivity of the drift and dispersion to variability in the physical environment and uncertainty in the bottom stress calculation and particle settling velocity. The BBLT model incorporates a stress dependent particle settling velocity that includes the main features of the flocculations of drill mud fines under marine conditions. The study provides a better understanding of how drill mud concentration levels can change with variations in waves, currents, and bottom stress. It was determined that drift is generally oriented along the northwest/southeast axis, with a typical magnitude of 0.8 cm/sec for the fast settling velocity and 3.1 cm/sec for the slow settling velocity. It was concluded that near-surface or mid-depth discharges of drilling mud in the summer may not reach the sea floor. 17 refs., 13 tabs., 36 figs

  11. Pollen Dispersion Forecast At Regional Scale

    Science.gov (United States)

    Mangin, A.; Asthma Forecast System Team

    The forecast of the pollen concentration is generally based on an identification of sim- ilar coincidence of measured pollen at given points and meteorological data that is searched in an archive and which, with the help of experts, allows building a predicted value. This may be classified under the family of statistical approaches for forecast- ing. While palynologists make these methods more and more accurate with the help of innovative techniques of regression against empirical rules and/or evolving mathe- matical structures (e.g. neural networks), the spatial dispersion of the pollen is not or poorly considered, mainly because it requires a lot of means and technique that are not familiar to this scientific discipline. The research on pollen forecasts are presently mainly focused on the problematic of modeling the behavior of pollen trends and sea- sons at one location regardless of the topography, the locations of emitters, the relative strengths of emitter, in one word the Sspatial backgroundT. This research work was a & cedil;successful attempt to go a step further combining this SlocalT approach with a trans- & cedil;port/dispersion modeling allowing the access to mapping of concentration. The areas of interest that were selected for the demonstration of feasibility were 200x200km zones centered on Cordoba, Barcelona and Bologna and four pollen types were ex- amined, namely: Cupressaceae, Olea europaea, Poaceae and Parietaria. At the end of this three-year European project in December 2001, the system was fully deployed and validated. The multidisciplinary team will present the original methodologies that were derived for modeling the numerous aspects of this problem and also some con- clusions regarding potential extent to other areas and taxa.

  12. Dispersion and Cluster Scales in the Ocean

    Science.gov (United States)

    Kirwan, A. D., Jr.; Chang, H.; Huntley, H.; Carlson, D. F.; Mensa, J. A.; Poje, A. C.; Fox-Kemper, B.

    2017-12-01

    Ocean flow space scales range from centimeters to thousands of kilometers. Because of their large Reynolds number these flows are considered turbulent. However, because of rotation and stratification constraints they do not conform to classical turbulence scaling theory. Mesoscale and large-scale motions are well described by geostrophic or "2D turbulence" theory, however extending this theory to submesoscales has proved to be problematic. One obvious reason is the difficulty in obtaining reliable data over many orders of magnitude of spatial scales in an ocean environment. The goal of this presentation is to provide a preliminary synopsis of two recent experiments that overcame these obstacles. The first experiment, the Grand LAgrangian Deployment (GLAD) was conducted during July 2012 in the eastern half of the Gulf of Mexico. Here approximately 300 GPS-tracked drifters were deployed with the primary goal to determine whether the relative dispersion of an initially densely clustered array was driven by processes acting at local pair separation scales or by straining imposed by mesoscale motions. The second experiment was a component of the LAgrangian Submesoscale Experiment (LASER) conducted during the winter of 2016. Here thousands of bamboo plates were tracked optically from an Aerostat. Together these two deployments provided an unprecedented data set on dispersion and clustering processes from 1 to 106 meter scales. Calculations of statistics such as two point separations, structure functions, and scale dependent relative diffusivities showed: inverse energy cascade as expected for scales above 10 km, a forward energy cascade at scales below 10 km with a possible energy input at Langmuir circulation scales. We also find evidence from structure function calculations for surface flow convergence at scales less than 10 km that account for material clustering at the ocean surface.

  13. Dense gas dispersion in the atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Nielsen, Morten

    1998-09-01

    Dense gas dispersion is characterized by buoyancy induced gravity currents and reduction of the vertical mixing. Liquefied gas releases from industrial accidents are cold because of the heat of evaporation which determines the density for a given concentration and physical properties. The temperature deficit is moderated by the heat flux from the ground, and this convection is an additional source of turbulence which affects the mixing. A simple model as the soil heat flux is used to estimate the ability of the ground to sustain the heat flux during release. The initial enthalpy, release rate, initial entrainment and momentum are discussed for generic source types and the interaction with obstacles is considered. In the MTH project BA experiments source with and without momentum were applied. The continuously released propane gas passed a two-dimensional removable obstacle perpendicular to the wind direction. Ground-level gas concentrations and vertical profiles of concentration, temperature, wind speed and turbulence were measured in front of and behind the obstacle. Ultrasonic anemometers providing fast velocity and concentration signals were mounted at three levels on the masts. The observed turbulence was influenced by the stability and the initial momentum of the jet releases. Additional information were taken from the `Dessert tortoise` ammonia jet releases, from the `Fladis` experiment with transition from dense to passive dispersion, and from the `Thorney Island` continuous releases of isothermal freon mixtures. The heat flux was found to moderate the negative buoyancy in both the propane and ammonia experiments. The heat flux measurements are compared to an estimate by analogy with surface layer theory. (au) 41 tabs., 146 ills., 189 refs.

  14. Dispersal from deep ocean sources: physical and related scientific processes

    International Nuclear Information System (INIS)

    Robinson, A.R.; Kupferman, S.L.

    1985-02-01

    This report presents the results of the workshop ''Dispersal from Deep Ocean Sources: Physical and Related Scientific Processes,'' together with subsequent developments and syntheses of the material discussed there. The project was undertaken to develop usable predictive descriptions of dispersal from deep oceanic sources. Relatively simple theoretical models embodying modern ocean physics were applied, and observational and experimental data bases were exploited. All known physical processes relevant to the dispersal of passive, conservative tracers were discussed, and contact points for inclusion of nonconservative processes (biological and chemical) were identified. Numerical estimates of the amplitude, space, and time scales of dispersion were made for various mechanisms that control the evolution of the dispersal as the material spreads from a bottom point source to small-, meso-, and world-ocean scales. Recommendations for additional work are given. The volume is presented as a handbook of dispersion processes. It is intended to be updated as new results become available

  15. In vitro Dissolution Studies on Solid Dispersions of Mefenamic Acid.

    Science.gov (United States)

    Rao, K R S Sambasiva; Nagabhushanam, M V; Chowdary, K P R

    2011-03-01

    Solid dispersions of mefanamic acid with a water-soluble polymer polyvinyl pyrrolidine and a super disintegrant, primojel were prepared by common solvent and solvent evaporation methods employing methanol as the solvent. The dissolution rate and dissolution efficiency of the prepared solid dispersions were evaluated in comparison to the corresponding pure drug. Solid dispersions of mefenamic acid showed a marked enhancement in dissolution rate and dissolution efficiency. At 1:4 ratio of mefenamic acid-primojel a 2.61 fold increase in the dissolution rate of mefenamic acid was observed with solid dispersion. The solid dispersions in combined carriers gave much higher rates of dissolution than super disintegrants alone. Mefanamic acid-primojel-polyvinyl pyrrolidine (1:3.2:0.8) solid dispersion gave a 4.11 fold increase in the dissolution rate of mefenamic acid. Super disintegrants alone or in combination with polyvinyl pyrrolidine could be used to enhance the dissolution rate of mefenamic acid.

  16. 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...

  17. The Electrochemical Behavior of Dispersions of Spherical Ultramicroelectrodes.

    Science.gov (United States)

    1986-07-30

    means of bipolar electrolyses with dispersions. Polarization equations are predicted for highly simplified models based on the concept of the mixture...three-dimensional electrodes. Bipolar electrolyses on dispersions of spherical particles have been proposed and the behavior of such electrodes in the...photodecomposition of water (e.g. see (32-41)). It should be noted that the size range of the particles which will be most frequently used in dispersion

  18. Acoustic phonon dispersion of CoSi2

    International Nuclear Information System (INIS)

    Weiss, L.; Rumyantsev, A.Yu.; Ivanov, A.S.

    1985-01-01

    The acoustical phonon dispersion curves of CoSi 2 are measured at room temperature along the main symmetry directions by means of coherent one-phonon scattering of thermal neutrons. The dispersion curves are compared with those of Ge, Si, and the fluorite structure types as CaF 2 and UO 2 . From the slope of the phonon dispersion curves at the GAMMA-point the elastic constants have been obtained

  19. Hyper dispersion pulse compressor for chirped pulse amplification systems

    Science.gov (United States)

    Barty, Christopher P. J.

    2011-11-29

    A grating pulse compressor configuration is introduced for increasing the optical dispersion for a given footprint and to make practical the application for chirped pulse amplification (CPA) to quasi-narrow bandwidth materials, such as Nd:YAG. The grating configurations often use cascaded pairs of gratings to increase angular dispersion an order of magnitude or more. Increased angular dispersion allows for decreased grating separation and a smaller compressor footprint.

  20. Limited dispersal in mobile hunter–gatherer Baka Pygmies

    Science.gov (United States)

    Verdu, Paul; Leblois, Raphaël; Froment, Alain; Théry, Sylvain; Bahuchet, Serge; Rousset, François; Heyer, Evelyne; Vitalis, Renaud

    2010-01-01

    Hunter–gatherer Pygmies from Central Africa are described as being extremely mobile. Using neutral genetic markers and population genetics theory, we explored the dispersal behaviour of the Baka Pygmies from Cameroon, one of the largest Pygmy populations in Central Africa. We found a strong correlation between genetic and geographical distances: a pattern of isolation by distance arising from limited parent–offspring dispersal. Our study suggests that mobile hunter–gatherers do not necessarily disperse over wide geographical areas. PMID:20427330

  1. Dynamics of platicons due to third-order dispersion

    Science.gov (United States)

    Lobanov, Valery E.; Cherenkov, Artem V.; Shitikov, Artem E.; Bilenko, Igor A.; Gorodetsky, Michael L.

    2017-07-01

    Dynamics of platicons caused by the third-order dispersion is studied. It is shown that under the influence of the third-order dispersion platicons obtain angular velocity depending both on dispersion and on detuning value. A method of tuning of platicon associated optical frequency comb repetition rate is proposed. Contribution to the Topical Issue "Theory and Applications of the Lugiato-Lefever Equation", edited by Yanne K. Chembo, Damia Gomila, Mustapha Tlidi, Curtis R. Menyuk.

  2. 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.

  3. Fundamental aspects of solid dispersion technology for poorly soluble drugs

    Directory of Open Access Journals (Sweden)

    Yanbin Huang

    2014-02-01

    Full Text Available The solid dispersion has become an established solubilization technology for poorly water soluble drugs. Since a solid dispersion is basically a drug–polymer two-component system, the drug–polymer interaction is the determining factor in its design and performance. In this review, we summarize our current understanding of solid dispersions both in the solid state and in dissolution, emphasizing the fundamental aspects of this important technology.

  4. ENSEMBLE methods to reconcile disparate national long range dispersion forecasts

    OpenAIRE

    Mikkelsen, Torben; Galmarini, S.; Bianconi, R.; French, S.

    2003-01-01

    ENSEMBLE is a web-based decision support system for real-time exchange and evaluation of national long-range dispersion forecasts of nuclear releases with cross-boundary consequences. The system is developed with the purpose to reconcile among disparatenational forecasts for long-range dispersion. ENSEMBLE addresses the problem of achieving a common coherent strategy across European national emergency management when national long-range dispersion forecasts differ from one another during an a...

  5. Optically controlled tunable dispersion compensators based on pumped fiber gratings.

    Science.gov (United States)

    Shu, Xuewen; Sugden, Kate; Bennion, Ian

    2011-08-01

    We demonstrate optically tunable dispersion compensators based on pumping fiber Bragg gratings made in Er/Yb codoped fiber. The tunable dispersion for a chirped grating and also a uniform-period grating was successfully demonstrated in the experiment. The dispersion of the chirped grating was tuned from 900 to 1990 ps/nm and also from -600 to -950 ps/nm in the experiment. © 2011 Optical Society of America

  6. Dispersion relations and sum rules for natural optical activity

    International Nuclear Information System (INIS)

    Thomaz, M.T.; Nussenzveig, H.M.

    1981-06-01

    Dispersion relations and sum rules are derived for the complex rotatory power of an arbitrary linear (nonmagnetic) isotropic medium showing natural optical activity. Both previously known dispersion relations and sum rules as well as new ones are obtained. It is shown that the Rosenfeld-Condon dispersion formula is inconsistent with the expected asymptotic behavior at high frequencies. A new dispersion formula based on quantum eletro-dynamics removes this inconsistency; however, it still requires modification in the low-frequency limit. (Author) [pt

  7. Larval fish dispersal in a coral-reef seascape

    KAUST Repository

    Almany, Glenn R.

    2017-05-23

    Larval dispersal is a critical yet enigmatic process in the persistence and productivity of marine metapopulations. Empirical data on larval dispersal remain scarce, hindering the use of spatial management tools in efforts to sustain ocean biodiversity and fisheries. Here we document dispersal among subpopulations of clownfish (Amphiprion percula) and butterflyfish (Chaetodon vagabundus) from eight sites across a large seascape (10,000 km2) in Papua New Guinea across 2 years. Dispersal of clownfish was consistent between years, with mean observed dispersal distances of 15 km and 10 km in 2009 and 2011, respectively. A Laplacian statistical distribution (the dispersal kernel) predicted a mean dispersal distance of 13–19 km, with 90% of settlement occurring within 31–43 km. Mean dispersal distances were considerably greater (43–64 km) for butterflyfish, with kernels declining only gradually from spawning locations. We demonstrate that dispersal can be measured on spatial scales sufficient to inform the design of and test the performance of marine reserve networks.

  8. Monolithic Approach to Oxide Dispersion Strengthened Aluminum, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Nassau Stern Company is investigating an approach for manufacturing oxide dispersion strengthened (ODS) aluminum in bulk rather than powder form. The approach...

  9. Minimizing Dispersion in FDTD Methods with CFL Limit Extension

    Science.gov (United States)

    Sun, Chen

    The CFL extension in FDTD methods is receiving considerable attention in order to reduce the computational effort and save the simulation time. One of the major issues in the CFL extension methods is the increased dispersion. We formulate a decomposition of FDTD equations to study the behaviour of the dispersion. A compensation scheme to reduce the dispersion in CFL extension is constructed and proposed. We further study the CFL extension in a FDTD subgridding case, where we improve the accuracy by acting only on the FDTD equations of the fine grid. Numerical results confirm the efficiency of the proposed method for minimising dispersion.

  10. Larval fish dispersal in a coral-reef seascape

    KAUST Repository

    Almany, Glenn R.; Planes, Serge; Thorrold, Simon R.; Berumen, Michael L.; Bode, Michael; Saenz Agudelo, Pablo; Bonin, Mary C.; Frisch, Ashley J.; Harrison, Hugo B.; Messmer, Vanessa; Nanninga, Gerrit B.; Priest, Mark; Srinivasan, Maya; Sinclair-Taylor, Tane; Williamson, David H.; Jones, Geoffrey P.

    2017-01-01

    Larval dispersal is a critical yet enigmatic process in the persistence and productivity of marine metapopulations. Empirical data on larval dispersal remain scarce, hindering the use of spatial management tools in efforts to sustain ocean biodiversity and fisheries. Here we document dispersal among subpopulations of clownfish (Amphiprion percula) and butterflyfish (Chaetodon vagabundus) from eight sites across a large seascape (10,000 km2) in Papua New Guinea across 2 years. Dispersal of clownfish was consistent between years, with mean observed dispersal distances of 15 km and 10 km in 2009 and 2011, respectively. A Laplacian statistical distribution (the dispersal kernel) predicted a mean dispersal distance of 13–19 km, with 90% of settlement occurring within 31–43 km. Mean dispersal distances were considerably greater (43–64 km) for butterflyfish, with kernels declining only gradually from spawning locations. We demonstrate that dispersal can be measured on spatial scales sufficient to inform the design of and test the performance of marine reserve networks.

  11. Dispersant field testing : a review of procedures and considerations

    International Nuclear Information System (INIS)

    Fingas, M.F.

    2004-01-01

    The effectiveness of a dispersant is defined by the amount of oil that the dispersant puts into the water column compared to the amount of oil that was initially spilled. Effectiveness is generally determined visually in plumes of dispersed oil that are visible from ships and aircraft. This paper describes 25 specific issues and technical concerns regarding field testing of dispersant effectiveness. Recent field tests were reviewed and literature that relates to testing procedures was sited. The 25 factors that are important for the appropriate outcome of dispersant field experiments include: mass balance; proper controls; analytical method; differential plume movement; time lag and length of time followed; mathematics of calculation and integration; lower and upper limits of analytical methods; use of remote sensing; thickness measurement; behaviour of oil with surfactant content; surfactant stripping; tracking surface oil and dispersed oil; recovering surface oil; visibility of oil from the surface; background levels of hydrocarbons; fluorescence of dispersant; herding; emulsion breaking; application success; heterogeneity of slick and plume; deposition measurements; true analytical standards; effect of wind on dispersant and slick; dispersant run-off; and weathering of the oil. It was concluded that the most important factors are the ability to determine mass balance, use proper controls, analytical methods and to avoid procedures that give incorrect results. 34 refs., 4 tabs., 1 fig

  12. Chromatic Dispersion Compensation Using Photonic Crystal Fibers with Hexagonal Distribution

    Directory of Open Access Journals (Sweden)

    Erick E. Reyes-Vera

    2013-11-01

    Full Text Available In this paper we show various configurations of photonic crystal fiber with hexagonal holes distribution for compensation of chromatic dispersion in optical communications links. The vectorial finite element method with scattering boundary condition was used for the analysis of the fibers. From these results it was estimated variation of the dispersion and the dispersion slope with respect to change in the diameter of the holes in the microstructure. With the above was possible to obtain values of dispersion in the C and L bands of telecommunications close to -850 ps / nm * km, with confinement losses 10-3 dB / km

  13. Axial dispersion via shear-enhanced diffusion in colloidal suspensions

    KAUST Repository

    Griffiths, I. M.

    2012-03-01

    The familiar example of Taylor dispersion of molecular solutes is extended to describe colloidal suspensions, where the fluctuations that contribute to dispersion arise from hydrodynamic interactions. The generic scheme is illustrated for a suspension of particles in a pressure-driven pipe flow, with a concentration-dependent diffusivity that captures both the shear-induced and Brownian contributions. The effect of the cross-stream migration via shear-induced diffusion is shown to dramatically reduce the axial dispersion predicted by classical Taylor dispersion for a molecular solute. Analytic and numerical solutions are presented that illustrate the effect of the concentration dependence of this nonlinear hydrodynamic mechanism. Copyright © EPLA, 2012.

  14. An invasive slug exploits an ant-seed dispersal mutualism.

    Science.gov (United States)

    Meadley Dunphy, Shannon A; Prior, Kirsten M; Frederickson, Megan E

    2016-05-01

    Plant-animal mutualisms, such as seed dispersal, are often vulnerable to disruption by invasive species. Here, we show for the first time how a non-ant invasive species negatively affects seed dispersal by ants. We examined the effects of several animal species that co-occur in a temperate deciduous forest-including native and invasive seed-dispersing ants (Aphaenogaster rudis and Myrmica rubra, respectively), an invasive slug (Arion subfuscus), and native rodents-on a native myrmecochorous plant, Asarum canadense. We experimentally manipulated ant, slug, and rodent access to seed depots and measured seed removal. We also video-recorded depots to determine which other taxa interact with seeds. We found that A. rudis was the main disperser of seeds and that A. subfuscus consumed elaiosomes without dispersing seeds. Rodent visitation was rare, and rodent exclusion had no significant effect on seed or elaiosome removal. We then used data obtained from laboratory and field mesocosm experiments to determine how elaiosome robbing by A. subfuscus affects seed dispersal by A. rudis and M. rubra. We found that elaiosome robbing by slugs reduced seed dispersal by ants, especially in mesocosms with A. rudis, which picks up seeds more slowly than M. rubra. Taken together, our results show that elaiosome robbing by an invasive slug reduces seed dispersal by ants, suggesting that invasive slugs can have profound negative effects on seed dispersal mutualisms.

  15. High Resilience of Seed Dispersal Webs Highlighted by the Experimental Removal of the Dominant Disperser.

    Science.gov (United States)

    Timóteo, Sérgio; Ramos, Jaime Albino; Vaughan, Ian Phillip; Memmott, Jane

    2016-04-04

    The pressing need to conserve and restore habitats in the face of ongoing species loss [1, 2] requires a better understanding of what happens to communities when species are lost or reinstated [3, 4]. Theoretical models show that communities are relatively insensitive to species loss [5, 6]; however, they disagree with field manipulations showing a cascade of extinctions [7, 8] and have seldom been tested under field conditions (e.g., [9]). We experimentally removed the most abundant seed-dispersing ant species from seed dispersal networks in a Mediterranean landscape, replicating the experiment in three types of habitat, and then compared these communities to un-manipulated control communities. Removal did not result in large-scale changes in network structure. It revealed extensive structural plasticity of the remaining community, which rearranged itself through rewiring, while maintaining its functionality. The remaining ant species widened their diet breadth in a way that maintained seed dispersal, despite the identity of many interactions changing. The species interaction strength decreased; thus, the importance of each ant species for seed dispersal became more homogeneous, thereby reducing the dependence of seed species on one dominant ant species. Compared to the experimental results, a simulation model that included rewiring considerably overestimated the effect of species loss on network robustness. If community-level species loss models are to be of practical use in ecology or conservation, they need to include behavioral and population responses, and they need to be routinely tested under field conditions; doing this would be to the advantage of both empiricists and theoreticians. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Plume dispersion in four pine thinning scenarios: development of a simple pheromone dispersion model

    Science.gov (United States)

    Holly Peterson; Harold Thistle; Brian Lamb; Gene Allwine; Steve Edburg; Brian Strom

    2010-01-01

    A unique field campaign was conducted in 2004 to examine how changes in stand density may affect dispersion of insect pheromones in forest canopies. Over a l4-day period, 126 tracer tests were performed, and conditions ranged from an unthinned loblolly pine (Pinus taeda) canopy through a series of thinning scenarios with basal areas of32.l, 23.0, and 16.1 m2ha-l.ln...

  17. Two-patch population models with adaptive dispersal: the effects of varying dispersal speeds

    Czech Academy of Sciences Publication Activity Database

    Cressman, R.; Křivan, Vlastimil

    2013-01-01

    Roč. 67, č. 2 (2013), s. 329-358 ISSN 0303-6812 Grant - others:The University of Tennessee(US) EF-0832858; National Science Foundation(US) DMS 0931642 Institutional support: RVO:60077344 Keywords : competition * dispersal * evolution Subject RIV: EH - Ecology, Behaviour Impact factor: 2.388, year: 2013 http://link.springer.com/content/pdf/10.1007%2Fs00285-012-0548-3.pdf

  18. Surface Solid Dispersion and Solid Dispersion of Meloxicam: Comparison and Product Development.

    Science.gov (United States)

    Chaturvedi, Mayank; Kumar, Manish; Pathak, Kamla; Bhatt, Shailendra; Saini, Vipin

    2017-12-01

    Purpose: A comparative study was carried out between surface solid dispersion (SSD) and solid dispersion (SD) of meloxicam (MLX) to assess the solubility and dissolution enhancement approach and thereafter develop as patient friendly orodispersible tablet. Methods: Crospovidone (CPV), a hydrophilic carrier was selected for SSD preparation on the basis of 89% in- vitro MLX adsorption, 19% hydration capacity and high swelling index. SD on the other hand was made with PEG4000. Both were prepared by co-grinding and solvent evaporation method using drug: carrier ratios of 1:1, 1:4, and 1:8. Formulation SSDS3 (MLX: CPV in 1:8 ratio) made by solvent evaporation method showed t 50% of 28 min and 80.9% DE 50min which was higher in comparison to the corresponding solid dispersion, SDS3 (t 50% of 35min and 76.4% DE 50min ). Both SSDS3 and SDS3 were developed as orodispersible tablets and evaluated. Results: Tablet formulation F3 made with SSD3 with a disintegration time of 11 secs, by wetting time= 6 sec, high water absorption of 78%by wt and cumulative drug release of 97% proved to be superior than the tablet made with SD3. Conclusion: Conclusively, the SSD of meloxicam has the potential to be developed as fast acing formulation that can ensure almost complete release of drug.

  19. Surface Solid Dispersion and Solid Dispersion of Meloxicam: Comparison and Product Development

    Directory of Open Access Journals (Sweden)

    Mayank Chaturvedi

    2017-12-01

    Full Text Available Purpose: A comparative study was carried out between surface solid dispersion (SSD and solid dispersion (SD of meloxicam (MLX to assess the solubility and dissolution enhancement approach and thereafter develop as patient friendly orodispersible tablet. Methods: Crospovidone (CPV, a hydrophilic carrier was selected for SSD preparation on the basis of 89% in- vitro MLX adsorption, 19% hydration capacity and high swelling index. SD on the other hand was made with PEG4000. Both were prepared by co-grinding and solvent evaporation method using drug: carrier ratios of 1:1, 1:4, and 1:8. Formulation SSDS3 (MLX: CPV in 1:8 ratio made by solvent evaporation method showed t50% of 28 min and 80.9% DE50min which was higher in comparison to the corresponding solid dispersion, SDS3 (t50% of 35min and 76.4% DE50min. Both SSDS3 and SDS3 were developed as orodispersible tablets and evaluated. Results: Tablet formulation F3 made with SSD3 with a disintegration time of 11 secs, by wetting time= 6 sec, high water absorption of 78%by wt and cumulative drug release of 97% proved to be superior than the tablet made with SD3. Conclusion: Conclusively, the SSD of meloxicam has the potential to be developed as fast acing formulation that can ensure almost complete release of drug.

  20. Dispersion of effluents in the atmosphere; Dispersion des effluents dans l`atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-12-31

    This conference day was organized by the `convection` section of the French association of thermal engineers with the support of the environment and energy mastery agency (ADEME). This book of proceedings contains 10 papers entitled: `physical modeling of atmospheric dispersion in wind tunnels. Some industrial examples`; `modeling of the noxious effects of a fire on the environment of an industrial site: importance of thermal engineering related hypotheses`; `atmospheric diffusion of a noxious cloud: fast evaluation method of safety areas around refrigerating installations that use ammonia`; `modeling of atmospheric flows in urban areas in order to study the dispersion of pollutants`; `use of a dispersion parameter to characterize the evolution of a diffusion process downstream of a linear source of passive contaminant placed inside a turbulent boundary layer`; `elements of reflexion around the development of an analytical methodology applied to the elaboration of measurement strategies of air quality in ambient and outdoor atmospheres around industrial sites`; `state-of-the-art about treatment techniques for VOC-rich gaseous effluents`; `characteristics of the time variation of the atmospheric pollution in the Paris region and visualization of its space distribution`; `mass-spectrometry for the measurement of atmospheric pollutants`; `volume variations in natural convection turbulence`. (J.S.)

  1. Dispersion of effluents in the atmosphere; Dispersion des effluents dans l`atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-12-31

    This conference day was organized by the `convection` section of the French association of thermal engineers with the support of the environment and energy mastery agency (ADEME). This book of proceedings contains 10 papers entitled: `physical modeling of atmospheric dispersion in wind tunnels. Some industrial examples`; `modeling of the noxious effects of a fire on the environment of an industrial site: importance of thermal engineering related hypotheses`; `atmospheric diffusion of a noxious cloud: fast evaluation method of safety areas around refrigerating installations that use ammonia`; `modeling of atmospheric flows in urban areas in order to study the dispersion of pollutants`; `use of a dispersion parameter to characterize the evolution of a diffusion process downstream of a linear source of passive contaminant placed inside a turbulent boundary layer`; `elements of reflexion around the development of an analytical methodology applied to the elaboration of measurement strategies of air quality in ambient and outdoor atmospheres around industrial sites`; `state-of-the-art about treatment techniques for VOC-rich gaseous effluents`; `characteristics of the time variation of the atmospheric pollution in the Paris region and visualization of its space distribution`; `mass-spectrometry for the measurement of atmospheric pollutants`; `volume variations in natural convection turbulence`. (J.S.)

  2. Novel applications of the dispersive optical model

    Science.gov (United States)

    Dickhoff, W. H.; Charity, R. J.; Mahzoon, M. H.

    2017-03-01

    A review of recent developments of the dispersive optical model (DOM) is presented. Starting from the original work of Mahaux and Sartor, several necessary steps are developed and illustrated which increase the scope of the DOM allowing its interpretation as generating an experimentally constrained functional form of the nucleon self-energy. The method could therefore be renamed as the dispersive self-energy method. The aforementioned steps include the introduction of simultaneous fits of data for chains of isotopes or isotones allowing a data-driven extrapolation for the prediction of scattering cross sections and level properties in the direction of the respective drip lines. In addition, the energy domain for data was enlarged to include results up to 200 MeV where available. An important application of this work was implemented by employing these DOM potentials to the analysis of the (d, p) transfer reaction using the adiabatic distorted wave approximation. We review these calculations which suggest that physically meaningful results are easier to obtain by employing DOM ingredients as compared to the traditional approach which relies on a phenomenologically-adjusted bound-state wave function combined with a global (nondispersive) optical-model potential. Application to the exotic 132Sn nucleus also shows great promise for the extrapolation of DOM potentials towards the drip line with attendant relevance for the physics of FRIB. We note that the DOM method combines structure and reaction information on the same footing providing a unique approach to the analysis of exotic nuclei. We illustrate the importance of abandoning the custom of representing the non-local Hartree-Fock (HF) potential in the DOM by an energy-dependent local potential as it impedes the proper normalization of the solution of the Dyson equation. This important step allows for the interpretation of the DOM potential as representing the nucleon self-energy permitting the calculations of

  3. The physiological effects of oil, dispersant and dispersed oil on the bay mussel, Mytilus trossulus, in Arctic/Subarctic conditions.

    Science.gov (United States)

    Counihan, Katrina L

    2018-06-01

    Increasing oil development around Alaska and other Arctic regions elevates the risk for another oil spill. Dispersants are used to mitigate the impact of an oil spill by accelerating natural degradation processes, but the reduced hydrophobicity of dispersed oil may increase its bioavailability to marine organisms. There is limited research on the effect of dispersed oil on cold water species and ecosystems. Therefore, spiked exposure tests were conducted with bay mussels (Mytilus trossulus) in seawater with non-dispersed oil, Corexit 9500 and oil dispersed with different concentrations of Corexit 9500. After three weeks of exposure, acute and chronic physiological impacts were determined. The majority of physiological responses occurred during the first seven days of exposure, with mussels exhibiting significant cytochrome P450 activity, superoxide dismutase activity and heat shock protein levels. Mussels exposed to non-dispersed oil also experienced immune suppression, reduced transcription and higher levels of mortality. After 21 days, mussels in all treatments exhibited evidence of genetic damage, tissue loss and a continued stress response. Bay mussels are useful as indicators of ecosystem health and recovery, and this study was an important step in understanding how non-dispersed oil, dispersant and dispersed oil affect the physiology of this sentinel species in Arctic/subarctic conditions. Copyright © 2018 Elsevier B.V. All rights reserved.

  4. Dispersant affects the cellular influences of single-wall carbon nanotube: the role of CNT as carrier of dispersants.

    Science.gov (United States)

    Horie, Masanori; Stowe, Mayumi; Tabei, Miki; Kato, Haruhisa; Nakamura, Ayako; Endoh, Shigehisa; Morimoto, Yasuo; Fujita, Katsuhide

    2013-06-01

    The application of carbon nanotube (CNT) as a functional material to engineering and life sciences is advanced. In order to evaluate the cytotoxicity of CNT in vitro, some chemical and biological reagents are used for dispersants. In the present study, the cellular influences of six kinds of chemical or biological reagents used as dispersants were examined. Pluronic F-127, Pluronic F-68, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), pulmonary surfactant preparation Surfacten®, bovine serum albumin (BSA) and Tween 80 were used in the preparation of CNT-medium dispersants. The influences of each reagent on cell viability in human lung carcinoma A549 cells were small. However, Pluronic F-127, DPPC, Surfacten® and Tween 80 induced an increase of intracellular reactive oxygen species (ROS) level. Next, CNT-medium dispersions were prepared, using each reagent as a dispersant and applied to A549 cells. The cellular influences depended on the kind of dispersant. Cells exposed to CNT dispersion including Pluronic® F-127, Surfacten®, DPPC and Tween 80 showed LDH release to the culture supernatant. Induction of intracellular ROS level was observed in cells exposed to CNT dispersion including each reagent except BSA. These results suggest that the adsorbed dispersant reagents on the surface of the CNT affect its cellular influences, particularly the induction of oxidative stress.

  5. Aquatic dispersion modelling of a tritium plume in Lake Ontario

    International Nuclear Information System (INIS)

    Klukas, M.H.; Moltyaner, G.L.

    1996-05-01

    Approximately 2900 kg of tritiated water, containing 2.3E+15 Bq of tritium, were released to Lake Ontario via the cooling water discharge when a leak developed in a moderator heat exchanger in Unit 1 at the Pickering Nuclear Generating Station (PNGS) on 1992 August 2. The release provided the opportunity to study the dispersion of a tritium plume in the coastal zone of Lake Ontario. Current direction over the two-week period following the release was predominantly parallel to the shore, and elevated tritium concentrations were observed up to 20 km east and 85 km west of the PNGS. Predictions of the tritium plume movement were made using current velocity measurements taken at 8-m depth, 2.5 km offshore from Darlington and using a empirical relationship where alongshore current speed is assumed to be proportional to the alongshore component of the wind speed. The tritium migration was best described using current velocity measurements. The tritium plume dispersion is modelled using the one-dimensional advection-dispersion equation. Transport parameters are the alongshore current speed and longitudinal dispersion coefficient. Longitudinal dispersion coefficients, estimated by fitting the solution of the advection-dispersion equation to measured concentration distance profiles ranged from 3.75 to 10.57 m 2 s -1 . Simulations using the fitted values of the dispersion coefficient were able to describe maximum tritium concentrations measured at water supply plants located within 25 km of Pickering to within a factor of 3. The dispersion coefficient is a function of spatial and temporal variability in current velocity and the fitted dispersion coefficients estimated here may not be suitable for predicting tritium plume dispersion under different current conditions. The sensitivity of the dispersion coefficient to variability in current conditions should be evaluated in further field experiments. (author). 13 refs., 7 tabs., 12 figs

  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. Extensible automated dispersive liquid–liquid microextraction

    Energy Technology Data Exchange (ETDEWEB)

    Li, Songqing; Hu, Lu; Chen, Ketao; Gao, Haixiang, E-mail: hxgao@cau.edu.cn

    2015-05-04

    Highlights: • An extensible automated dispersive liquid–liquid microextraction was developed. • A fully automatic SPE workstation with a modified operation program was used. • Ionic liquid-based in situ DLLME was used as model method. • SPE columns packed with nonwoven polypropylene fiber was used for phase separation. • The approach was applied to the determination of benzoylurea insecticides in water. - Abstract: In this study, a convenient and extensible automated ionic liquid-based in situ dispersive liquid–liquid microextraction (automated IL-based in situ DLLME) was developed. 1-Octyl-3-methylimidazolium bis[(trifluoromethane)sulfonyl]imide ([C{sub 8}MIM]NTf{sub 2}) is formed through the reaction between [C{sub 8}MIM]Cl and lithium bis[(trifluoromethane)sulfonyl]imide (LiNTf{sub 2}) to extract the analytes. Using a fully automatic SPE workstation, special SPE columns packed with nonwoven polypropylene (NWPP) fiber, and a modified operation program, the procedures of the IL-based in situ DLLME, including the collection of a water sample, injection of an ion exchange solvent, phase separation of the emulsified solution, elution of the retained extraction phase, and collection of the eluent into vials, can be performed automatically. The developed approach, coupled with high-performance liquid chromatography–diode array detection (HPLC–DAD), was successfully applied to the detection and concentration determination of benzoylurea (BU) insecticides in water samples. Parameters affecting the extraction performance were investigated and optimized. Under the optimized conditions, the proposed method achieved extraction recoveries of 80% to 89% for water samples. The limits of detection (LODs) of the method were in the range of 0.16–0.45 ng mL{sup −1}. The intra-column and inter-column relative standard deviations (RSDs) were <8.6%. Good linearity (r > 0.9986) was obtained over the calibration range from 2 to 500 ng mL{sup −1}. The proposed

  8. Extensible automated dispersive liquid–liquid microextraction

    International Nuclear Information System (INIS)

    Li, Songqing; Hu, Lu; Chen, Ketao; Gao, Haixiang

    2015-01-01

    Highlights: • An extensible automated dispersive liquid–liquid microextraction was developed. • A fully automatic SPE workstation with a modified operation program was used. • Ionic liquid-based in situ DLLME was used as model method. • SPE columns packed with nonwoven polypropylene fiber was used for phase separation. • The approach was applied to the determination of benzoylurea insecticides in water. - Abstract: In this study, a convenient and extensible automated ionic liquid-based in situ dispersive liquid–liquid microextraction (automated IL-based in situ DLLME) was developed. 1-Octyl-3-methylimidazolium bis[(trifluoromethane)sulfonyl]imide ([C 8 MIM]NTf 2 ) is formed through the reaction between [C 8 MIM]Cl and lithium bis[(trifluoromethane)sulfonyl]imide (LiNTf 2 ) to extract the analytes. Using a fully automatic SPE workstation, special SPE columns packed with nonwoven polypropylene (NWPP) fiber, and a modified operation program, the procedures of the IL-based in situ DLLME, including the collection of a water sample, injection of an ion exchange solvent, phase separation of the emulsified solution, elution of the retained extraction phase, and collection of the eluent into vials, can be performed automatically. The developed approach, coupled with high-performance liquid chromatography–diode array detection (HPLC–DAD), was successfully applied to the detection and concentration determination of benzoylurea (BU) insecticides in water samples. Parameters affecting the extraction performance were investigated and optimized. Under the optimized conditions, the proposed method achieved extraction recoveries of 80% to 89% for water samples. The limits of detection (LODs) of the method were in the range of 0.16–0.45 ng mL −1 . The intra-column and inter-column relative standard deviations (RSDs) were <8.6%. Good linearity (r > 0.9986) was obtained over the calibration range from 2 to 500 ng mL −1 . The proposed method opens a new avenue

  9. Study of nonequilibrium dispersed two phase flow

    International Nuclear Information System (INIS)

    Reyes, J.N. Jr.

    1986-01-01

    Understanding the behavior of liquid droplets in a superheated steam environment is essential to the accurate prediction of nuclear fuel rod surface temperatures during the blowdown and reflood phase of a loss-of-coolant-accident (LOCA). In response to this need, this treatise presents several original and significant contributions to the field of thermofluid physics. The research contained herein presents a statistical derivation of the two-phase mass, momentum, and energy-conservation equations using a droplet continuity equation analogous to that used in the Kinetic Theory of Gases. Unlike the Eulerian volume and time-averaged conservation equations generally used to describe dispersed two-phase flow behavior, this statistical averaging approach results in an additional mass momentum or energy term in each of the respective conservation equations. Further, this study demonstrates that current definitions of the volumetric vapor generation rate used in the mass conservation equation are inappropriate results under certain circumstances. The mass conservation equation derived herein is used to obtain a new definition for the volumetric vapor-generation rate. Last, a simple two phase phenomenological model, based on the statistically averaged conservation equations, is presented and solved analytically. It is shown that the actual quality and vapor temperature, under these circumstances, depend on a single dimensionless group

  10. Dispersion interferometer for controlled fusion devices

    International Nuclear Information System (INIS)

    Drachev, V.P.; Krasnikov, Yu.I.; Bagryansky, P.A.

    1992-01-01

    A common feature in interferometry is the presence of two independent optical channels. Since wave phase in a medium depends on the geometrical path, polarization and radiation frequency, respectively, one can distinguish three types of interferometric schemes when the channels are geometrically separated, or separation occurs in polarizations or radiation frequencies. We have developed a measurement scheme based on a dispersion interferometer (DI) for plasma diagnostics in the experiments on controlled fusion. DI optical channels have the same geometrical path and are separated in radiation frequency. Use of a common optical path causes the main advantage of the DI technique - low sensitivity to vibrations of optical elements. The use of the DI technique for diagnostics of a laser spark in air and of arc discharges has shown its essential advantages as compared to classical interferometers. Interest in the DI technique from the viewpoint of its application in controlled fusion devices is determined also generated by the possibility of developing a compact multichannel interferometer not requiring a vibration isolation structure. (author) 14 refs., 3 figs

  11. Dispersive Wave Analysis Using the Chirplet Transform

    International Nuclear Information System (INIS)

    Kerber, Florian; Luangvilai, Kritsakorn; Kuttig, Helge; Niethammer, Marc; Jacobs, Laurence J.

    2007-01-01

    Time-frequency representations (TFR) are a widely used tool to analyze signals of guided waves such as Lamb waves. As a consequence of the uncertainty principle, however, the resolution in time and frequency is limited for all existing TFR methods. Due to the multi-modal and dispersive character of Lamb waves, displacement or energy related quantities can only be allocated to individual modes when they are well-separated in the time-frequency plane.The chirplet transform (CT) has been introduced as a generalization of both the wavelet and Short-time Fourier transform (STFT). It offers additional degrees of freedom to adjust time-frequency atoms which can be exploited in a model-based approach to match the group delay of individual modes. Thus, more exact allocation of quantities of interest is possible.The objective of this research is to use a previously developed adaptive algorithm based on the CT for nondestructive evaluation. Both numerically and experimentally generated data for a single aluminum plate is analyzed to determine the accuracy and robustness of the new method in comparison the classical STFT

  12. Radiocarbon dispersion around Canadian nuclear facilities

    International Nuclear Information System (INIS)

    Milton, G.M.; Kramer, S.J.; Brown, R.M.; Repta, C.J.W.; King, K.J.; Rao, R.R.

    1995-01-01

    Canadian deuterium uranium (CANDU) pressurized heavy-water reactors produce 14 C by neutron activation of trace quantities of nitrogen in annular gas and reactor components ( 14 N(n,p) 14 C), and from 17 O in the heavy water moderator by ( 17 O(n,α) 14 C). The radiocarbon produced in the moderator is removed on ion exchange resins incorporated in the water purification systems; however, a much smaller gaseous portion is vented from reactor stacks at activity levels considerably below 1% of permissible derived emission limits. Early measurements of the carbon speciation indicated that >90% of the 14 C emitted was in the form of CO 2 .We conducted surveys of the atmospheric dispersion of 14 CO 2 at the Chalk River Laboratories and at the Pickering Nuclear Generating Station. We analyzed air, vegetation, soils and tree rings to add to the historical record of 14 C emissions at these sites, and to gain an understanding of the relative importance of the various carbon pools that act as sources/sinks within the total 14 C budget. Better model parameters than those currently available for calculating the dose to the critical group can be obtained in this manner. Global dose estimates may require the development of techniques for estimating emissions occurring outside the growing season. (author)

  13. Brazing copper to dispersion-strengthened copper

    Science.gov (United States)

    Ryding, David G.; Allen, Douglas; Lee, Richard H.

    1996-11-01

    The advanced photon source is a state-of-the-art synchrotron light source that will produce intense x-ray beams, which will allow the study of smaller samples and faster reactions and processes at a greater level of detail than has ben possible to date. The beam is produced by using third- generation insertion devices in a 7-GeV electron/positron storage ring that is 1,104 meters in circumference. The heat load from these intense high-power devices is very high, and certain components must sustain total heat loads of 3 to 15 kW and heat fluxes of 30 W/mm$_2). Because the beams will cycle on and off many times, thermal shock and fatigue will be a problem. High heat flux impinging on a small area causes a large thermal gradient that results in high stress. GlidCop, a dispersion-strengthened copper, is the desired design material because of its high thermal conductivity and superior mechanical properties as compared to copper and its alloys. GlidCop is not amenable to joining by fusion welding, and brazing requires diligence because of high diffusivity. Brazing procedures were developed using optical and scanning electron microscopy.

  14. Microtribology of aqueous carbon nanotube dispersions

    KAUST Repository

    Kristiansen, Kai De Lange; Zeng, Hongbo; Wang, Peng; Israelachvili, Jacob N.

    2011-01-01

    The tribological behavior of carbon nanotubes (CNTs) in aqueous humic acid (HA) solutions was studied using a surface forces apparatus (SFA) and shows promising lubricant additive properties. Adding CNTs to the solution changes the friction forces between two mica surfaces from "adhesion controlled" to "load controlled" friction. The coefficient of friction with either single-walled (SW) or multi-walled (MW) CNT dispersions is in the range 0.30-0.55 and is independent of the load and sliding velocity. More importantly, lateral sliding promotes a redistribution or accumulation, rather than squeezing out, of nanotubes between the surfaces. This accumulation reduced the adhesion between the surfaces (which generally causes wear/damage of the surfaces), and no wear or damage was observed during continuous shearing experiments that lasted several hours even under high loads (pressures â∼10 MPa). The frictional properties can be understood in terms of the Cobblestone Model where the friction force is related to the fraction of the adhesion energy dissipated during impacts of the nanoparticles. We also develop a simple generic model based on the van der Waals interactions between particles and surfaces to determine the relation between the dimensions of nanoparticles and their tribological properties when used as additives in oil- or water-based lubricants. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Development of a tritium dispersion code

    International Nuclear Information System (INIS)

    Bell, R.P.; Davis, M.W.; Joseph, S.; Wong, K.Y.

    1985-01-01

    This paper describes the development and verification of a computer code designed to calculate the radiation dose to man following acute or chronic atmospheric releases of tritium gas and oxide from a point source. The Ontario Hydro Tritium Dispersion Code calculates tritium concentrations in air, soil, and vegetation and doses to man resulting from inhalation/immersion and ingestion of food, milk meat and water. The deposition of HT to soil, conversion of HT to HTO by soil enzymes and resuspension of HTO to air have been incorporated into the terrestrial compartment model and are unique features of the code. Sensitivity analysis has identified the HT deposition velocity and the equivalent water depth of the vegetation compartment as two parameters which have a strong influence on dose calculations. Tritium concentrations in vegetation and soil calculated by the code were in reasonable agreement with experimental results. The radiological significance of including the mechanisms of HT to HTO conversion and resuspension of HTO to air is illustrated

  16. Solitons in plasma and other dispersive media

    International Nuclear Information System (INIS)

    Ichikawa, Y.H.; Wadati, Miki.

    1977-03-01

    A review is given to recent development of extensive studies of nonlinear waves with purpose of showing methods of systematic analysis of nonlinear phenomena has been now established on the basis of new concept ''soliton''. Firstly, characteristic properties of various kinds of solitons are discussed with illustration of typical nonlinear evolution equations. Brief discussions are also given to basic mechanisms which ensure the remarkable stability and individuality of solitons. The reductive perturbation theory is a key method to reduce a given nonlinear system to a soliton system. Introductory survey is presented for an example of ionic mode in plasmas, although the method can be applied to any dispersive medium. Central subject of the present review is the analytical methods of solving nonlinear evolution equations. The inverse method, the Beacklund transformation and the conservation laws are discussed to emphasize that very firm analytical basis is now available to disentangle the nonlinear problems. Finally, a notion of ''dressed'' solitons is introduced on basis of the higher order analysis of the reductive perturbation theory. In spite of the fact that success is restricted so far only for the one dimensional system, the achievement of soliton physics encourages us to face dawn of nonlinear physics with a confident expectation for forthcoming break through in the field. (auth.)

  17. RHEOLOGY OF CHICKPEA PROTEIN CONCENTRATE DISPERSIONS

    Directory of Open Access Journals (Sweden)

    Aurelia Ionescu

    2011-12-01

    Full Text Available Chickpea proteins are used as ingredients in comminuted sausage products and many oriental textured foods. Rheological behaviour of chickpea protein concentrate was studied using a controlled stress rheometer. The protein dispersion prepared with phosphate buffer at pH 7.0 presented non-Newtonian shear thinning behaviour and rheological data well fitted to the Sisko, Carreau and Cross models. The viscoelastic properties of the chickpea protein suspensions were estimated by measuring the storage and loss moduli in oscillatory frequency conditions (0.1-10 Hz at 20°C. Moreover, thermally induced gelation of the chickpea proteins (16, 24 and 36% was studied at pH 7.0 and 4.5 in the temperature range 50 to 100oC and salt concentration ranging from 0 to 1 M. Gelling behaviour was quantified by means of dynamic rheological measurements. Gels formation was preceded by the decrease of storage modulus and loss moduli, coupled with the increase of the phase angle (delta. The beginning of thermal gelation was influenced by protein concentration, pH and salt level. In all studied cases, storage modulus increased rapidly in the temperature range 70-90°C. All rheological parameters measured at 90°C were significantly higher at pH 4.5 compared to pH 7.0.

  18. Ecological succession as an energy dispersal process.

    Science.gov (United States)

    Würtz, Peter; Annila, Arto

    2010-04-01

    Ecological succession is described by the 2nd law of thermodynamics. According to the universal law of the maximal energy dispersal, an ecosystem evolves toward a stationary state in its surroundings by consuming free energy via diverse mechanisms. Species are the mechanisms that conduct energy down along gradients between repositories of energy which consist of populations at various thermodynamic levels. The salient characteristics of succession, growing biomass production, increasing species richness and shifting distributions of species are found as consequences of the universal quest to diminish energy density differences in least time. The analysis reveals that during succession the ecosystem's energy transduction network, i.e., the food web organizes increasingly more effective in the free energy reduction by acquiring new, more effective and abandoning old, less effective species of energy transduction. The number of species does not necessarily peak at the climax state that corresponds to the maximum-entropy partition of species maximizing consumption of free energy. According to the theory of evolution by natural selection founded on statistical physics of open systems, ecological succession is one among many other evolutionary processes. Copyright (c) 2010 Elsevier Ireland Ltd. All rights reserved.

  19. Microtribology of aqueous carbon nanotube dispersions

    KAUST Repository

    Kristiansen, Kai De Lange

    2011-09-23

    The tribological behavior of carbon nanotubes (CNTs) in aqueous humic acid (HA) solutions was studied using a surface forces apparatus (SFA) and shows promising lubricant additive properties. Adding CNTs to the solution changes the friction forces between two mica surfaces from "adhesion controlled" to "load controlled" friction. The coefficient of friction with either single-walled (SW) or multi-walled (MW) CNT dispersions is in the range 0.30-0.55 and is independent of the load and sliding velocity. More importantly, lateral sliding promotes a redistribution or accumulation, rather than squeezing out, of nanotubes between the surfaces. This accumulation reduced the adhesion between the surfaces (which generally causes wear/damage of the surfaces), and no wear or damage was observed during continuous shearing experiments that lasted several hours even under high loads (pressures â∼10 MPa). The frictional properties can be understood in terms of the Cobblestone Model where the friction force is related to the fraction of the adhesion energy dissipated during impacts of the nanoparticles. We also develop a simple generic model based on the van der Waals interactions between particles and surfaces to determine the relation between the dimensions of nanoparticles and their tribological properties when used as additives in oil- or water-based lubricants. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Helium in inert matrix dispersion fuels

    International Nuclear Information System (INIS)

    Veen, A. van; Konings, R.J.M.; Fedorov, A.V.

    2003-01-01

    The behaviour of helium, an important decay product in the transmutation chains of actinides, in dispersion-type inert matrix fuels is discussed. A phenomenological description of its accumulation and release in CERCER and CERMET fuel is given. A summary of recent He-implantation studies with inert matrix metal oxides (ZrO 2 , MgAl 2 O 4 , MgO and Al 2 O 3 ) is presented. A general picture is that for high helium concentrations helium and vacancy defects form helium clusters which convert into over-pressurized bubbles. At elevated temperature helium is released from the bubbles. On some occasions thermal stable nano-cavities or nano-pores remain. On the basis of these results the consequences for helium induced swelling and helium storage in oxide matrices kept at 800-1000 deg. C will be discussed. In addition, results of He-implantation studies for metal matrices (W, Mo, Nb and V alloys) will be presented. Introduction of helium in metals at elevated temperatures leads to clustering of helium to bubbles. When operational temperatures are higher than 0.5 melting temperature, swelling and helium embrittlement might occur

  1. Dispersion parameters: impact on calculated reactor accident consequences

    Energy Technology Data Exchange (ETDEWEB)

    Aldrich, D.C.

    1979-01-01

    Much attention has been given in recent years to the modeling of the atmospheric dispersion of pollutants released from a point source. Numerous recommendations have been made concerning the choice of appropriate dispersion parameters. A series of calculations has been performed to determine the impact of these recommendations on the calculated consequences of large reactor accidents. Results are presented and compared in this paper.

  2. Pulse splitting in nonlinear media with anisotropic dispersion properties

    DEFF Research Database (Denmark)

    Bergé, L.; Juul Rasmussen, J.; Schmidt, M.R.

    1998-01-01

    The nonlinear self-focusing of beams in media with anisotropic (mix-signed) dispersion is investigated. Theoretical predictions employing virial-type arguments and self-similar techniques suggest that a pulse propagating in a nonlinear medium with anisotropic dispersion will not collapse...

  3. Biophysical models of larval dispersal in the Benguela Current ...

    African Journals Online (AJOL)

    We synthesise and update results from the suite of biophysical, larval-dispersal models developed in the Benguela Current ecosystem. Biophysical models of larval dispersal use outputs of physical hydrodynamic models as inputs to individual-based models in which biological processes acting during the larval life are ...

  4. DEVELOPMENT OF SUSTAINED RELEASE TABLETS CONTAINING SOLID DISPERSIONS OF BACLOFEN

    Directory of Open Access Journals (Sweden)

    K. H. Janardhana

    2015-07-01

    Full Text Available Sustained release tablets containing solid dispersions granules of a poorly water soluble drug were prepared to investigate the controlled release of the drug. Baclofen was chosen because of its poor water solubility and short elimination half-life. Poloxamer 188 and PEG 6000 were used as solid dispersion carrier. Free flowing solid dispersion granules were prepared by adsorbing the melt of the drug and carriers onto the surface of an adsorbent, Carbopol 934P followed by direct compression with HPMC K4M and HPMC K100 to obtain an solid dispersion loaded sustained release tablets. FTIR studies confirmed that the compatibility of drug and carriers. Differential scanning calorimetry (DSC and X-ray diffraction (XRD revealed partially amorphous structures of the drug in solid dispersion granules. The solid dispersion granules dissolved completely within 30 min, which was much faster than that of pure drug baclofen. The sustained release of baclofen from the solid dispersion containing tablet was achieved for 2 h in gastric fluid (pH 1.2 and for up to 10 h in intestinal fluid (pH 6.8. A combination of solid dispersion techniques using adsorption and sustained release concepts is a promising approach to control the release rate of poorly water-soluble drugs.

  5. DEVELOPMENT OF SUSTAINED RELEASE TABLETS CONTAINING SOLID DISPERSIONS OF BACLOFEN

    Directory of Open Access Journals (Sweden)

    K. H. Janardhana

    2013-12-01

    Full Text Available Sustained release tablets containing solid dispersions granules of a poorly water soluble drug were prepared to investigate the controlled release of the drug. Baclofen was chosen because of its poor water solubility and short elimination half-life. Poloxamer 188 and PEG 6000 were used as solid dispersion carrier. Free flowing solid dispersion granules were prepared by adsorbing the melt of the drug and carriers onto the surface of an adsorbent, Carbopol 934P followed by direct compression with HPMC K4M and HPMC K100 to obtain an solid dispersion loaded sustained release tablets. FTIR studies confirmed that the compatibility of drug and carriers. Differential scanning calorimetry (DSC and X-ray diffraction (XRD revealed partially amorphous structures of the drug in solid dispersion granules. The solid dispersion granules dissolved completely within 30 min, which was much faster than that of pure drug baclofen. The sustained release of baclofen from the solid dispersion containing tablet was achieved for 2 h in gastric fluid (pH 1.2 and for up to 10 h in intestinal fluid (pH 6.8. A combination of solid dispersion techniques using adsorption and sustained release concepts is a promising approach to control the release rate of poorly water-soluble drugs.

  6. Laboratory Study of Dispersion of Buoyant Surface Plumes

    DEFF Research Database (Denmark)

    Petersen, Ole; Larsen, Torben

    1990-01-01

    -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...

  7. Plant functional connectivity – integrating landscape structure and effective dispersal

    NARCIS (Netherlands)

    Auffret, Alistair G.; Rico, Yessica; Bullock, James M.; Hooftman, Danny A.P.; Pakeman, Robin J.; Soons, Merel B.; Suárez-Esteban, Alberto; Traveset, Anna; Wagner, Helene H.; Cousins, Sara A.O.

    2017-01-01

    Dispersal is essential for species to survive the threats of habitat destruction and climate change. Combining descriptions of dispersal ability with those of landscape structure, the concept of functional connectivity has been popular for understanding and predicting species’ spatial responses to

  8. Milkweed Seed Dispersal: A Means for Integrating Biology and Physics.

    Science.gov (United States)

    Bisbee, Gregory D.; Kaiser, Cheryl A.

    1997-01-01

    Describes an activity that integrates biology and physics concepts by experimenting with the seed dispersal of common milkweed or similar wind-dispersed seeds. Student teams collect seeds and measure several parameters, review principles of trajectory motion, perform experiments, and graph data. Students examine the ideas of…

  9. Investigation of Solid Dispersion of Atorvastatin Calcium in ...

    African Journals Online (AJOL)

    ATC), a poorly watersoluble 3-hydroxy 3-methyl glutaryl CoA (HMG-CoA) reductase inhibitor, by a solid dispersion technique using polyethylene glycol 6000 (PEG 6000) or polyvinylpyrrolidone k30 (PVP K30). Methods: The solid dispersions were ...

  10. Fused silica thermal conductivity dispersion at high temperature

    International Nuclear Information System (INIS)

    Bouchut, P.; Decruppe, D.; Delrive, L.

    2004-01-01

    A continuous CO 2 laser is focused to locally anneal small fused silica spots. A noncontact radiometry diagnostic enables us to follow surface temperature variation that occurs from site to site. A 'steady state' dispersion of surface temperature is observed across our sample. We show that nonhomogeneous silica thermal conductivity, above 1000 K is responsible for this temperature dispersion

  11. Dispersal behavior correlates with personality of a North American fish

    Institute of Scientific and Technical Information of China (English)

    Josh E.RASMUSSEN; Mark C.BELK

    2012-01-01

    The process of dispersal is determined by the interaction of individual (intrinsic) traits and environmental (extrinsic) factors.Although many studies address and quantify dispersal,few evaluate both intrinsic and extrinsic factors jointly.We test the relative importance of intrinsic traits (exploration tendency and size) and extrinsic factors (population density and habitat quality) on dispersal of a medium-sized western United States minnow,southern lcatherside chub Lepidomeda aliciae.A generalized linear model with a binomial response was used to determine the probability of individuals dispersing one year after tagging.Medium-sized individuals that were more prone to explore novel environments were 10.7 times more likely to be recaptured outside of their original capture area after a year (dispersal) compared to non-explorer individuals of the same size class.Differences between explorer classifications within the small and large size classes were negligible.Open habitat within 50 m upstream also increased the probability of dispersal relative to controls.Relative location within the study reach,and population density were not significantly related to dispersal probabilities of individuals.Our results indicate that understanding ofpersonality may illuminate patterns of dispersal within and among populations [Current Zoology 58 (2):260-270,2012].

  12. Dispersion correction through movement of the closed orbit

    International Nuclear Information System (INIS)

    Parzen, G.

    1980-01-01

    The closed orbit correction system can be used to correct the vertical dispersion by displacing the orbit at the quadrupoles and sextupoles. The accuracy of the results have been verified by comparison with exact calculations. Results for correcting the horizontal dispersion are also given

  13. Dispersion relations for 1D high-gain FELs

    International Nuclear Information System (INIS)

    Webb, S.D.; Litvinenko, V.N.

    2010-01-01

    We present analytical results for the one-dimensional dispersion relation for high-gain FELs. Using kappa-n distributions, we obtain analytical relations between the dispersion relations for various order kappa distributions. Since an exact solution exists for the kappa-1 (Lorentzian) distribution, this provides some insight into the number of modes on the way to the Gaussian distribution.

  14. Seed dispersal by vertebrates in Madagascar's forests: review and ...

    African Journals Online (AJOL)

    seeds. Thus, understanding plant - frugivore interactions is of critical importance for the conservation and ... ance of many plant species on frugivores for their dispersal. Understanding this ecosystem service can provide us ... edge of this ecosystem service in Madagascar. Understanding seed dispersal is important because ...

  15. Effective viscosity of dispersions approached by a statistical continuum method

    NARCIS (Netherlands)

    Mellema, J.; Willemse, M.W.M.

    1983-01-01

    The problem of the determination of the effective viscosity of disperse systems (emulsions, suspensions) is considered. On the basis of the formal solution of the equations governing creeping flow in a statistically homogeneous dispersion, the effective viscosity is expressed in a series expansion

  16. Vertical dispersion produced by random closed orbit distortions and sextupoles

    International Nuclear Information System (INIS)

    Suzuki, Toshio.

    1977-01-01

    Vertical dispersion appears even in a machine designed with plane symmetry because of vertical closed orbit distortions, linear coupling and coupling due to sextupoles. This gives rise to several undesirable effects in an electron-positron storage ring such as PEP. Vertical dispersion at the interaction point will increase beam height and reduce luminosity. Vertical dispersion around the ring will modify vertical emittance and partition numbers for synchrotron radiation damping. It will also induce betatron-synchrotron resonance and affect chromaticity correction. Vertical dispersion due to random closed orbit distortions and sextupoles has been studied by Piwinski, and he has indicated that correction of chromaticity and chromatic change of β-function is important. However, he has assumed one error element and evaluated the dispersion at the position of the element. We generalize his argument to a more realistic case and derive more precise criteria for the correction of vertical dispersion. Horizontal dispersion due to perturbations is also studied. Vertical dispersion due to linear coupling is neglected in this note, since it has been studied by other authors. 7 refs

  17. National and International Income Dispersion and Aggregate Expenditures

    NARCIS (Netherlands)

    C. Fillat; J.F. François (Joseph)

    2004-01-01

    textabstractWe examine linkages between aggregate household income, distribution of that income, and aggregate cross-country expenditure patterns. We are able to decompose income effects into international income dispersion effects (from variations in average income) and national income dispersion

  18. Dispersive shock mediated resonant radiations in defocused nonlinear medium

    Science.gov (United States)

    Bose, Surajit; Chattopadhyay, Rik; Bhadra, Shyamal Kumar

    2018-04-01

    We report the evolution of resonant radiation (RR) in a self-defocused nonlinear medium with two zero dispersion wavelengths. RR is generated from dispersive shock wave (DSW) front when the pump pulse is in non-solitonic regime close to first zero dispersion wavelength (ZDW). DSW is responsible for pulse splitting resulting in the generation of blue solitons when leading edge of the pump pulse hits the first ZDW. DSW also generates a red shifted dispersive wave (DW) in the presence of higher order dispersion coefficients. Further, DSW through cross-phase modulation with red shifted dispersive wave (DW) excites a localized radiation. The presence of zero nonlinearity point in the system restricts red-shift of RR and enhances the red shifting of DW. It also helps in the formation of DSW at shorter distance and squeezes the solitonic region beyond second zero dispersion point. Predicted results indicate that the spectral evolution depends on the product of Kerr nonlinearity and group velocity dispersion.

  19. FDTD scattered field formulation for scatterers in stratified dispersive media.

    Science.gov (United States)

    Olkkonen, Juuso

    2010-03-01

    We introduce a simple scattered field (SF) technique that enables finite difference time domain (FDTD) modeling of light scattering from dispersive objects residing in stratified dispersive media. The introduced SF technique is verified against the total field scattered field (TFSF) technique. As an application example, we study surface plasmon polariton enhanced light transmission through a 100 nm wide slit in a silver film.

  20. Dispersion relation and relative intensity for double-plasmon satellites

    International Nuclear Information System (INIS)

    Srivastava, K.S.; Shiv Singh; Harsh, O.K.

    1981-01-01

    An expression for the dispersion relation and the relative intensity of double-plasmon oscillations and satellites has been derived by extending the dispersion relation and the extended Bohm and Pines Hamiltonian to second order. The calculated value of the relative intensity of the double-plasmon satellite for Be agrees fairly well with the value observed experimentally by other workers. (orig.)

  1. A Riemann problem with small viscosity and dispersion

    Directory of Open Access Journals (Sweden)

    Kayyunnapara Thomas Joseph

    2006-09-01

    Full Text Available In this paper we prove existence of global solutions to a hyperbolic system in elastodynamics, with small viscosity and dispersion terms and derive estimates uniform in the viscosity-dispersion parameters. By passing to the limit, we prove the existence of solution the Riemann problem for the hyperbolic system with arbitrary Riemann data.

  2. In-town dispersion calculations with RIMPUFF and UDM

    DEFF Research Database (Denmark)

    Astrup, P.; Thykier-Nielsen, Søren; Mikkelsen, Torben

    2005-01-01

    and in depositions obtained with a code designed for dispersion of a release from a nuclear power plant, typically situated at a distance from densely inhabited areas, and a code specifically designed forpredicting dispersion from sources inside urban areas. The codes applied are the RIMPUFF code, RIsø Mesoscale...

  3. Regional zooplankton dispersal provides spatial insurance for ecosystem function.

    Science.gov (United States)

    Symons, Celia C; Arnott, Shelley E

    2013-05-01

    Changing environmental conditions are affecting diversity and ecosystem function globally. Theory suggests that dispersal from a regional species pool may buffer against changes in local community diversity and ecosystem function after a disturbance through the establishment of functionally redundant tolerant species. The spatial insurance provided by dispersal may decrease through time after environmental change as the local community monopolizes resources and reduces community invasibility. To test for evidence of the spatial insurance hypothesis and to determine the role dispersal timing plays in this response we conducted a field experiment using crustacean zooplankton communities in a subarctic region that is expected to be highly impacted by climate change - Churchill, Canada. Three experiments were conducted where nutrients, salt, and dispersal were manipulated. The three experiments differed in time-since-disturbance that the dispersers were added. We found that coarse measures of diversity (i.e. species richness, evenness, and Shannon-Weiner diversity) were generally resistant to large magnitude disturbances, and that dispersal had the most impact on diversity when dispersers were added shortly after disturbance. Ecosystem functioning (chl-a) was degraded in disturbed communities, but dispersal recovered ecosystem function to undisturbed levels. This spatial insurance for ecosystem function was mediated through changes in community composition and the relative abundance of functional groups. Results suggest that regional diversity and habitat connectivity will be important in the future to maintain ecosystem function by introducing functionally redundant species to promote compensatory dynamics. © 2012 Blackwell Publishing Ltd.

  4. Advances and Problems in Mathematical Modelling of Dispersion of ...

    African Journals Online (AJOL)

    Most expressions for dispersion of pollutants have failed to give accurate predictions in both channel and natural stream flows. This paper outlines the basic concepts on which the fundamental dispersion equations have been derived. Some of the advances on these equations are examined and their deficiencies pointed ...

  5. Axon density and axon orientation dispersion in children born preterm

    NARCIS (Netherlands)

    Kelly, Claire E.; Thompson, Deanne K.; Chen, Jian; Leemans, Alexander; Adamson, Christopher L.; Inder, Terrie E.; Cheong, Jeanie L Y; Doyle, Lex W.; Anderson, Peter J.

    2016-01-01

    Background Very preterm birth (VPT, <32 weeks' gestation) is associated with altered white matter fractional anisotropy (FA), the biological basis of which is uncertain but may relate to changes in axon density and/or dispersion, which can be measured using Neurite Orientation Dispersion and Density

  6. Dispersion for the preparation of an injectable radiopharmaceutical scanning agent

    International Nuclear Information System (INIS)

    Wolfangel, R.G.

    1976-01-01

    The invention deals with the preparation of a dispersion of a tin (II) sulphur colloid in an aqueous solution with additions of a stabilizing agent. Labelled with sup(99m)Tc, the dispersion can be used as an injectable radiopharmaceutical scanning agent. (VJ) [de

  7. A model for evaluating dispersed outdoor recreation use estimation

    Science.gov (United States)

    Stanley J. Zarnoch; Donald B. K. English; Susan M. Kocis

    2004-01-01

    An outdoor recreation use simulator (ORUS) has been developed to simulate dispersed recreation survey data similar to that collected by the National Visitor Use Monitoring (NVUM) Project's survey of the national forests of the U.S.A. Statistical distributions are used to represent the various behaviors of recreationists during their visit to a dispersed area. The...

  8. Dispersion effect and auto-reconditioning performance of nanometer ...

    Indian Academy of Sciences (India)

    This paper reported on dispersion effect and dispersing techniques of nanometer WS2 particles in the green lubricant concocted by us. And it also researched on auto-reconditioning performance of nanometer WS2 particles to the abrasive surfaces of steel ball from four-ball tribology test and piston ring from engine ...

  9. An Orbit And Dispersion Correction Scheme for the PEP II

    International Nuclear Information System (INIS)

    Cai, Y.; Donald, M.; Shoaee, H.; White, G.; Yasukawa, L.A.

    2011-01-01

    To achieve optimum luminosity in a storage ring it is vital to control the residual vertical dispersion. In the original PEP storage ring, a scheme to control the residual dispersion function was implemented using the ring orbit as the controlling element. The 'best' orbit not necessarily giving the lowest vertical dispersion. A similar scheme has been implemented in both the on-line control code and in the simulation code LEGO. The method involves finding the response matrices (sensitivity of orbit/dispersion at each Beam-Position-Monitor (BPM) to each orbit corrector) and solving in a least squares sense for minimum orbit, dispersion function or both. The optimum solution is usually a subset of the full least squares solution. A scheme of simultaneously correcting the orbits and dispersion has been implemented in the simulation code and on-line control system for PEP-II. The scheme is based on the eigenvector decomposition method. An important ingredient of the scheme is to choose the optimum eigenvectors that minimize the orbit, dispersion and corrector strength. Simulations indicate this to be a very effective way to control the vertical residual dispersion.

  10. Quantitative energy-dispersive electron probe X-ray microanalysis ...

    Indian Academy of Sciences (India)

    Abstract. An energy-dispersive electron probe X-ray microanalysis (ED-EPMA) technique us- ing an energy-dispersive X-ray detector with an ultra-thin window, designated as low-Z particle. EPMA, has been developed. The low-Z particle EPMA allows the quantitative determination of concentrations of low-Z elements such ...

  11. Parasite dispersal risk tolerance is mediated by its reproductive value.

    Science.gov (United States)

    Nolan, Maxcy P; Delaplane, Keith S

    2017-10-01

    Parasite dispersal theory draws heavily upon epidemiological SIR models in which host status (susceptible (S), infected (I), or recovered (R)) is used to study parasite dispersal evolution. In contrast to these extrinsically host-centric drivers, in this study we focus on an intrinsic driver, the parasite's reproductive value (predicted future offspring) as a regulator of the extent to which the individual will engage in risky dispersal behaviour. As a model system we use the honeybee Apis mellifera and its ectoparasite, the mite Varroa destructor . Mite reproduction happens exclusively inside cells of bee brood, and newly emerged fecund mites may parasitize either a homocolonial brood cell (low risk dispersal) or emigrate to a new bee colony via phoretic attachment to mature forager bees (high risk dispersal). In an empirical bioassay, prepartum mites (high reproductive value) and postpartum mites (low reproductive value) were offered a choice of newly emerged homocolonial worker bees (low risk), homocolonial pollen forager bees (high risk), or heterocolonial pollen foragers (high risk). A preference for newly emerged bees was earlier and more strongly sustained among prepartum mites. This suggests comparatively greater dispersal risk tolerance among postpartum mites with lower reproductive value. A dangerous bid for dispersal may be adaptive if the individual has already successfully reproduced and the rewards for successful dispersal are sufficiently large.

  12. Dispersal ability determines the scaling properties of species abundance distributions

    DEFF Research Database (Denmark)

    Borda-De-Água, Luís; Whittaker, Robert James; Cardoso, Pedro

    2017-01-01

    with computer simulations, low dispersal ability species generate a hump for intermediate abundance classes earlier than the distributions of high dispersal ability species. Importantly, when plotted as function of sample size, the raw moments of the SADs of arthropods have a power law pattern similar...

  13. A general evaluation of the irradiation behaviour of dispersion fuels

    International Nuclear Information System (INIS)

    Hofman, G.L.

    1995-01-01

    The irradiation behaviour of aluminum-based dispersion fuels is evaluated with emphasis on metallurgical processes that control the dispersion behaviour. Phase transformations and microstructural changes resulting from fuel-matrix interactions and the effect of fissioning in fuel are discussed. (author)

  14. Small-angle neutron scattering from colloidal dispersions

    International Nuclear Information System (INIS)

    Ottewill, R.H.

    1991-01-01

    A survey is given of recent work on the use of small-angle neutron scattering to examine colloidal dispersions. Particular attention is given to the determination of particle size and polydispersity, the determination of particle morphology and the behaviour of concentrated colloidal dispersions, both at rest and under the influence of an applied shear field. (orig.)

  15. Evolution of velocity dispersion along cold collisionless flows

    International Nuclear Information System (INIS)

    Banik, Nilanjan; Sikivie, Pierre

    2016-01-01

    We found that the infall of cold dark matter onto a galaxy produces cold collisionless flows and caustics in its halo. If a signal is found in the cavity detector of dark matter axions, the flows will be readily apparent as peaks in the energy spectrum of photons from axion conversion, allowing the densities, velocity vectors and velocity dispersions of the flows to be determined. We also discuss the evolution of velocity dispersion along cold collisionless flows in one and two dimensions. A technique is presented for obtaining the leading behaviour of the velocity dispersion near caustics. The results are used to derive an upper limit on the energy dispersion of the Big Flow from the sharpness of its nearby caustic, and a prediction for the dispersions in its velocity components

  16. Clay squirt: Local flow dispersion in shale-bearing sandstones

    DEFF Research Database (Denmark)

    Sørensen, Morten Kanne; Fabricius, Ida Lykke

    2017-01-01

    Dispersion of elastic-wave velocity is common in sandstone and larger in shaly sandstone than in clean sandstone. Dispersion in fluid-saturated shaly sandstone often exceeds the level expected from the stress-dependent elastic moduli of dry sandstone. The large dispersion has been coined clay...... squirt and is proposed to originate from a pressure gradient between the clay microporosity and the effective porosity. We have formulated a simple model that quantifies the clay-squirt effect on bulk moduli of sandstone with homogeneously distributed shale laminae or dispersed shale. The model...... predictions were compared with the literature data. For sandstones with dispersed shale, agreement was found, whereas other sandstones have larger fluid-saturated bulk modulus, possibly due to partially load-bearing shales or heterogeneous shale distribution. The data that agree with the clay-squirt model...

  17. Chemical dispersibility testing of fresh and weathered oils

    International Nuclear Information System (INIS)

    Brandvik, P.J.; Daling, P.S.; Aareskjold, K.

    1991-05-01

    This activity in the DIspersants on Weathered Oils-project (DIWO) is a continuation and an extended study of the dispersibility study described in DIWO report No. 3. The main objective has been to study the chemical dispersibility of fresh and weathered oils produced or transported in Norwegian waters. Other important aims of this study have been: To correlate the effectiveness results obtained by three different laboratory methods; to determine the relationship between the dispersant effectiveness and the change in the oils' physico-chemical properties due to weathering (topping, photo-oxidation and w/o-emulsification). This study has been performed with 8 different oil types and 12 different weathering degrees of each oil type. The work performed clearly demonstrates that the oil type and especially the weathering properties are essential for the performance of dispersants at sea. 41 figs., 5 tabs., 16 refs

  18. Velocity Dispersion of Ionized Gas and Multiple Supernova Explosions

    Directory of Open Access Journals (Sweden)

    Vasiliev E. O.

    2015-06-01

    Full Text Available We use 3D numerical simulations to study the evolution of the Hα intensity and velocity dispersion for single and multiple supernova (SN explosions. We find that the IHα– σ diagram obtained for simulated gas flows is similar in shape to that observed in dwarf galaxies. We conclude that colliding SN shells with significant difference in age are responsible for high velocity dispersion that reaches up to ≳ 100 km s−1. Such a high velocity dispersion could be hardly obtained for a single SN remnant. Peaks of velocity dispersion in the IHα– σ diagram may correspond to several isolated or merged SN remnants with moderately different ages. Degrading the spatial resolution in the Hα intensity and velocity dispersion maps makes the simulated IHα– σ diagrams close to those observed in dwarf galaxies not only in shape, but also quantitatively.

  19. Nuclear risk from atmospheric dispersion in Northern Europe - Summary Report

    DEFF Research Database (Denmark)

    Lauritzen, Bent

    The objective of the NordRisk II project has been to derive practical means for assessing the risks from long-range atmospheric dispersion of radioac-tive materials. An atlas over different atmospheric dispersion and deposi-tion scenarios has been developed using historical numerical weather pre......-diction (NWP) model data. The NWP model data covers three years span-ning the climate variability associated with the North Atlantic Oscillation, and the atlas considers radioactive releases from 16 release sites in and near the Nordic countries. A statistical analysis of the long-range disper......-sion and deposition patterns is undertaken to quantify the mean dispersion and deposition as well as the variability. Preliminary analyses show that the large-scale atmospheric dispersion and deposition is near-isotropic, irrespective of the release site and detailed climatology, and allows for a simple...

  20. Coalescence kinetics of dispersed crude oil in a laboratory reactor

    International Nuclear Information System (INIS)

    Sterling, M.C. Jr.; Ojo, T.; Autenrieth, R.L.; Bonner, J.S.; Page, C.A.; Ernst, A.N.S.

    2002-01-01

    A study was conducted to examine the effects of salinity and mixing energy on the resurfacing and coalescence rates of chemically dispersed crude oil droplets. This kinetic study involved the use of mean shear rates to characterize the mixing energy in a laboratory reactor. Coagulation kinetics of dispersed crude oil were determined within a range of mean shear rates of 5, 10, 15, and 20 per second, and with salinity values of 10 and 30 per cent. Observed droplet distributions were fit to a transport-reaction model to estimate collision efficiency values and their dependence on salinity and mixing energy. Dispersant efficiencies were compared with those derived from other laboratory testing methods. Experimentally determined dispersant efficiencies were found to be 10 to 50 per cent lower than predicted using a non-interacting droplet model, but dispersant efficiencies were higher than those predicted using other testing methods. 24 refs., 1 tab., 3 figs

  1. Dispersal of Beauveria bassiana by the activity of nettle insects.

    Science.gov (United States)

    Meyling, Nicolai V; Pell, Judith K; Eilenberg, Jørgen

    2006-10-01

    Recent studies have shown that the entomopathogenic fungus Beauveria bassiana occurs naturally on the phylloplanes of several plants, including nettles. Insects could, by their activity, be contributing to this inoculum by dispersing it from other sites. The potential of nettle aphids Microlophium carnosum and their predator Anthocoris nemorum to disperse conidia of B. bassiana from soil to nettles and from sporulating cadavers in the nettle canopy was investigated in laboratory experiments. In petri dish assays, aphids showed potential to distribute B. bassiana from soil to nettle leaves. Predators dispersed inoculum from both soil and cadavers to nettle leaves in petri dishes. In microcosms, aphids did not disperse B. bassiana from the soil or from cadavers confined in the canopy, but A. nemorum were able to transfer inoculum from soil into the nettle canopy and to distribute conidia from cryptic cadavers. In some instances, infections were initiated in aphids and predators as a consequence of dispersal.

  2. Pigment dispersion syndrome masquerading as acute anterior uveitis.

    Science.gov (United States)

    Gonzalez-Gonzalez, Luis Alonso; Rodríguez-García, Alejandro; Foster, C Stephen

    2011-06-01

    Signs and symptoms of pigment dispersion may be confused with those of acute anterior uveitis. This case series is intended to aid the ophthalmologist in the clinical differentiation between these two disorders. The authors present a series of 6 patients with pigment dispersion who were initially diagnosed as having acute anterior uveitis and treated with anti-inflammatory medication, including corticosteroids. The patients were referred for a second opinion due to poor or no response to therapy and were found to have pigment dispersion instead of uveitis. Symptoms of pigment dispersion may consist of blurred vision, redness, ocular pain, and photophobia, all of which are also symptoms of acute anterior uveitis. These symptoms, plus the fact that pigment floating in the aqueous humor can be mistaken for inflammation, make diagnosis challenging. Moreover, the possible co-existence of true anterior uveitis and pigment dispersion makes the diagnosis and treatment more difficult.

  3. Investigation on dispersion in the active optical waveguide resonator

    Science.gov (United States)

    Qiu, Zihan; Gao, Yining; Xie, Wei

    2018-03-01

    Introducing active gain in the optical waveguide resonator not only compensates the loss, but also can change the dispersion relationship in the ring resonator. It is demonstrated that the group delay time is negative when the resonator is in the undercoupled condition, which also means the resonator exhibits the fast light effect. Theoretical analysis indicates that fast light effect due to anomalous dispersion, would be manipulated by the gain coefficient controlled by the input pump light power and that fast light would enhance scale factor of the optical resonant gyroscope. Resonance optical gyroscope (ROG)'s scale factor for measuring rotation rate is enhanced by anomalous dispersion with superluminal light propagation. The sensitivity of ROG could be enhanced by anomalous dispersion by coupled resonators even considering the effect of anomalous dispersion and propagation gain on broadened linewidth, and this could result in at least two orders of magnitude enhancement in sensitivity.

  4. Attenuation and Dispersion in Earth's Materials

    Science.gov (United States)

    Gueguen, Y.

    2012-04-01

    One of the last challenges of Pr. Luigi Burlini has been to set up an experimental apparatus that would measure elastic wave attenuation under high pressure conditions. This project has since been developed by his colleagues and students at ETH. As a tribute to Luigi Burlini, this presentation aims at recalling why such measurements are important , how challenging such a project is, and what the main issues ahead are. Most of our knowledge about either crustal layers (seismic exploration) or deeper layers (seismology) results from data related to elastic wave propagation inside the Earth. The large amount of available data as well as the huge capability of computers are such that descriptions in terms of isotropic homogeneous layers appear to be very crude today. Anisotropic, heterogeneous models are reported at various scales. In addition, accounting for wave attenuation (the Q factor) is potentially of great interest. The Q factor is highly sensitive to processes that involve some departure from perfect elasticity. Its knowledge may provide information on possible fluid content, temperature, etc. This is because various processes may dissipate energy (and thus lower Q value) as a result of fluid flow, solid flow, etc., depending on the precise P-T conditions at depth. This points immediately to the theoretical challenge of Q investigations: there are many possible ways for a rock to not behave as a perfect elastic body. To model these various mechanisms and identify in which conditions they can take place is a first major challenge. The second challenge is on the experimental ground. What is looked for is to get low frequencies (f close to seismic frequencies) Q data on crustal (or mantle) rocks at high pressure P-high temperature T. Experiments in such highT-high P-low f conditions are extremely difficult to perform. Only in Canberra (I. Jackson) and now in Zurich such conditions have been achieved. Attenuation and dispersion (frequency dependence) of elastic

  5. Coalescence in dense water/oil dispersions

    Energy Technology Data Exchange (ETDEWEB)

    Thunem, H

    1993-06-01

    This project has been divided into three parts. The first part has been to review a large amount of literature to obtain models describing separate stages of the coalescence of a single drop at an interface. These stages include the drop deformation, the film thinning, the critical film thickness, and the drop breakup. The second part has been to evaluate the different models and select which to use in the development of the OneDrop program. The models describing drop deformation and film thinning were supplied by Charles and Mason, however the film thinning model has been slightly enhanced in this project. The models and the enhancements made have been compared to experimental data from the literature and from work done by undergraduate students at our department. The third part of the project has been to implement the models to drop-drop coalescence, and to write the SIM program to simulate the coalescence in a system of many drops. We use the same equations as in the OneDrop case, except for the film thinning. But by using a similar derivation as for the OneDrop case, an equation for the SIM case has been developed. We have made the assumption that the physical phenomena regarding drop deformation, film thinning and critical film thickness are the same in the OneDrop and SIM cases, so the experimental validation of OneDrop also apply to SIM. By using the results from the SIM program, we can obtain some information about how different physical parameters will affect the collision frequency and collision efficiency. We may use this information to derive empirical equations describing these parameters effect on the coalescence probability in a dispersion. 207 refs., 83 figs., 21 tabs.

  6. Modelling long-distance seed dispersal in heterogeneous landscapes.

    Energy Technology Data Exchange (ETDEWEB)

    Levey, Douglas, J.; Tewlsbury, Joshua, J.; Bolker, Benjamin, M.

    2008-01-01

    1. Long-distance seed dispersal is difficult to measure, yet key to understanding plant population dynamics and community composition. 2. We used a spatially explicit model to predict the distribution of seeds dispersed long distances by birds into habitat patches of different shapes. All patches were the same type of habitat and size, but varied in shape. They occurred in eight experimental landscapes, each with five patches of four different shapes, 150 m apart in a matrix of mature forest. The model was parameterized with smallscale movement data collected from field observations of birds. In a previous study we validated the model by testing its predictions against observed patterns of seed dispersal in real landscapes with the same types and spatial configuration of patches as in the model. 3. Here we apply the model more broadly, examining how patch shape influences the probability of seed deposition by birds into patches, how dispersal kernels (distributions of dispersal distances) vary with patch shape and starting location, and how movement of seeds between patches is affected by patch shape. 4. The model predicts that patches with corridors or other narrow extensions receive higher numbers of seeds than patches without corridors or extensions. This pattern is explained by edgefollowing behaviour of birds. Dispersal distances are generally shorter in heterogeneous landscapes (containing patchy habitat) than in homogeneous landscapes, suggesting that patches divert the movement of seed dispersers, ‘holding’ them long enough to increase the probability of seed defecation in the patches. Dispersal kernels for seeds in homogeneous landscapes were smooth, whereas those in heterogenous landscapes were irregular. In both cases, long-distance (> 150 m) dispersal was surprisingly common, usually comprising approximately 50% of all dispersal events. 5. Synthesis . Landscape heterogeneity has a large influence on patterns of long-distance seed dispersal. Our

  7. Attenuation and velocity dispersion in the exploration seismic frequency band

    Science.gov (United States)

    Sun, Langqiu

    In an anelastic medium, seismic waves are distorted by attenuation and velocity dispersion, which depend on petrophysical properties of reservoir rocks. The effective attenuation and velocity dispersion is a combination of intrinsic attenuation and apparent attenuation due to scattering, transmission response, and data acquisition system. Velocity dispersion is usually neglected in seismic data processing partly because of insufficient observations in the exploration seismic frequency band. This thesis investigates the methods of measuring velocity dispersion in the exploration seismic frequency band and interprets the velocity dispersion data in terms of petrophysical properties. Broadband, uncorrelated vibrator data are suitable for measuring velocity dispersion in the exploration seismic frequency band, and a broad bandwidth optimizes the observability of velocity dispersion. Four methods of measuring velocity dispersion in uncorrelated vibrator VSP data are investigated, which are the sliding window crosscorrelation (SWCC) method, the instantaneous phase method, the spectral decomposition method, and the cross spectrum method. Among them, the SWCC method is a new method and has satisfactory robustness, accuracy, and efficiency. Using the SWCC method, velocity dispersion is measured in the uncorrelated vibrator VSP data from three areas with different geological settings, i.e., Mallik gas hydrate zone, McArthur River uranium mines, and Outokumpu crystalline rocks. The observed velocity dispersion is fitted to a straight line with respect to log frequency for a constant (frequency-independent) Q value. This provides an alternative method for calculating Q. A constant Q value does not directly link to petrophysical properties. A modeling study is implemented for the Mallik and McArthur River data to interpret the velocity dispersion observations in terms of petrophysical properties. The detailed multi-parameter petrophysical reservoir models are built according to

  8. Optimizing optical pre-dispersion using transmit DSP for mitigation of Kerr nonlinearities in dispersion managed cables

    Science.gov (United States)

    Hopkins, James; Gaudette, Jamie; Mehta, Priyanth

    2013-10-01

    With the advent of digital signal processing (DSP) in optical transmitters and receivers, the ability to finely tune the ratio of pre and post dispersion compensation can be exploited to best mitigate the nonlinear penalties caused by the Kerr effect. A portion of the nonlinear penalty in optical communication channels has been explained by an increase in peak to average power ratio (PAPR) inherent in highly dispersed signals. The standard approach for minimizing these impairments applies 50% pre dispersion compensation and 50% post dispersion compensation, thereby decreasing average PAPR along the length of the cable, as compared with either 100% pre or post dispersion compensation. In this paper we demonstrate that simply considering the net accumulated dispersion, and applying 50/50 pre/post dispersion is not necessarily the best way to minimize PAPR and subsequent Kerr nonlinearities. Instead, we consider the cumulative dispersion along the entire length of the cable, and, taking into account this additional information, derive an analytic formula for the minimization of PAPR. Alignment with simulation and experimental measurements is presented using a commercially available 100Gb/s dual-polarization binary phase-shift-keying (DP-BPSK) coherent modem, with transmitter and receiver DSP. Measurements are provided from two different 5000km dispersion managed Submarine test-beds, as well as a 3800km terrestrial test-bed with a mixture of SMF-28 and TWRS optical fiber. This method is shown to deviate significantly from the conventional 50/50 method described above, in dispersion managed communications systems, and more closely aligns with results obtained from simulation and data collected from laboratory test-beds.

  9. Dispersal networks for enhancing bacterial degradation in heterogeneous environments

    International Nuclear Information System (INIS)

    Banitz, Thomas; Wick, Lukas Y.; Fetzer, Ingo; Frank, Karin; Harms, Hauke; Johst, Karin

    2011-01-01

    Successful biodegradation of organic soil pollutants depends on their bioavailability to catabolically active microorganisms. In particular, environmental heterogeneities often limit bacterial access to pollutants. Experimental and modelling studies revealed that fungal networks can facilitate bacterial dispersal and may thereby improve pollutant bioavailability. Here, we investigate the influence of such bacterial dispersal networks on biodegradation performance under spatially heterogeneous abiotic conditions using a process-based simulation model. To match typical situations in polluted soils, two types of abiotic conditions are studied: heterogeneous bacterial dispersal conditions and heterogeneous initial resource distributions. The model predicts that networks facilitating bacterial dispersal can enhance biodegradation performance for a wide range of these conditions. Additionally, the time horizon over which this performance is assessed and the network's spatial configuration are key factors determining the degree of biodegradation improvement. Our results support the idea of stimulating the establishment of fungal mycelia for enhanced bioremediation of polluted soils. - Highlights: → Bacterial dispersal networks can considerably improve biodegradation performance. → They facilitate bacterial access to dispersal-limited areas and remote resources. → Abiotic conditions, time horizon and network structure govern the improvements. → Stimulating the establishment of fungal mycelia promises enhanced soil remediation. - Simulation modelling demonstrates that fungus-mediated bacterial dispersal can considerably improve the bioavailability of organic pollutants under spatially heterogeneous abiotic conditions typical for water-unsaturated soils.

  10. Dispersal networks for enhancing bacterial degradation in heterogeneous environments

    Energy Technology Data Exchange (ETDEWEB)

    Banitz, Thomas, E-mail: thomas.banitz@ufz.de [Department of Ecological Modelling, UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig (Germany); Wick, Lukas Y.; Fetzer, Ingo [Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig (Germany); Frank, Karin [Department of Ecological Modelling, UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig (Germany); Harms, Hauke [Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig (Germany); Johst, Karin [Department of Ecological Modelling, UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig (Germany)

    2011-10-15

    Successful biodegradation of organic soil pollutants depends on their bioavailability to catabolically active microorganisms. In particular, environmental heterogeneities often limit bacterial access to pollutants. Experimental and modelling studies revealed that fungal networks can facilitate bacterial dispersal and may thereby improve pollutant bioavailability. Here, we investigate the influence of such bacterial dispersal networks on biodegradation performance under spatially heterogeneous abiotic conditions using a process-based simulation model. To match typical situations in polluted soils, two types of abiotic conditions are studied: heterogeneous bacterial dispersal conditions and heterogeneous initial resource distributions. The model predicts that networks facilitating bacterial dispersal can enhance biodegradation performance for a wide range of these conditions. Additionally, the time horizon over which this performance is assessed and the network's spatial configuration are key factors determining the degree of biodegradation improvement. Our results support the idea of stimulating the establishment of fungal mycelia for enhanced bioremediation of polluted soils. - Highlights: > Bacterial dispersal networks can considerably improve biodegradation performance. > They facilitate bacterial access to dispersal-limited areas and remote resources. > Abiotic conditions, time horizon and network structure govern the improvements. > Stimulating the establishment of fungal mycelia promises enhanced soil remediation. - Simulation modelling demonstrates that fungus-mediated bacterial dispersal can considerably improve the bioavailability of organic pollutants under spatially heterogeneous abiotic conditions typical for water-unsaturated soils.

  11. Dispersion of Nanomaterials in Aqueous Media: Towards Protocol Optimization.

    Science.gov (United States)

    Kaur, Inder; Ellis, Laura-Jayne; Romer, Isabella; Tantra, Ratna; Carriere, Marie; Allard, Soline; Mayne-L'Hermite, Martine; Minelli, Caterina; Unger, Wolfgang; Potthoff, Annegret; Rades, Steffi; Valsami-Jones, Eugenia

    2017-12-25

    The sonication process is commonly used for de-agglomerating and dispersing nanomaterials in aqueous based media, necessary to improve homogeneity and stability of the suspension. In this study, a systematic step-wise approach is carried out to identify optimal sonication conditions in order to achieve a stable dispersion. This approach has been adopted and shown to be suitable for several nanomaterials (cerium oxide, zinc oxide, and carbon nanotubes) dispersed in deionized (DI) water. However, with any change in either the nanomaterial type or dispersing medium, there needs to be optimization of the basic protocol by adjusting various factors such as sonication time, power, and sonicator type as well as temperature rise during the process. The approach records the dispersion process in detail. This is necessary to identify the time points as well as other above-mentioned conditions during the sonication process in which there may be undesirable changes, such as damage to the particle surface thus affecting surface properties. Our goal is to offer a harmonized approach that can control the quality of the final, produced dispersion. Such a guideline is instrumental in ensuring dispersion quality repeatability in the nanoscience community, particularly in the field of nanotoxicology.

  12. Asymmetry in species regional dispersal ability and the neutral theory.

    Directory of Open Access Journals (Sweden)

    Jiajia Liu

    Full Text Available The neutral assumption that individuals of either the same or different species share exactly the same birth, death, migration, and speciation probabilities is fundamental yet controversial to the neutral theory. Several theoretical studies have demonstrated that a slight difference in species per capita birth or death rates can have a profound consequence on species coexistence and community structure. Whether asymmetry in migration, a vital demographic parameter in the neutral model, plays an important role in community assembly still remains unknown. In this paper, we relaxed the ecological equivalence assumption of the neutral model by introducing differences into species regional dispersal ability. We investigated the effect of asymmetric dispersal on the neutral local community structure. We found that per capita asymmetric dispersal among species could reduce species richness of the local community and result in deviations of species abundance distributions from those predicted by the neutral model. But the effect was moderate compared with that of asymmetries in birth or death rates, unless very large asymmetries in dispersal were assumed. A large difference in species dispersal ability, if there is, can overwhelm the role of random drift and make local community dynamics deterministic. In this case, species with higher regional dispersal abilities tended to dominate in the local community. However, the species abundance distribution of the local community under asymmetric dispersal could be well fitted by the neutral model, but the neutral model generally underestimated the fundamental biodiversity number but overestimated the migration rate in such communities.

  13. Characterization of Nanoreinforcement Dispersion in Inorganic Nanocomposites: A Review

    Directory of Open Access Journals (Sweden)

    Nouari Saheb

    2014-05-01

    Full Text Available Metal and ceramic matrix composites have been developed to enhance the stiffness and strength of metals and alloys, and improve the toughness of monolithic ceramics, respectively. It is possible to further improve their properties by using nanoreinforcement, which led to the development of metal and ceramic matrix nanocomposites, in which case, the dimension of the reinforcement is on the order of nanometer, typically less than 100 nm. However, in many cases, the properties measured experimentally remain far from those estimated theoretically. This is mainly due to the fact that the properties of nanocomposites depend not only on the properties of the individual constituents, i.e., the matrix and reinforcement as well as the interface between them, but also on the extent of nanoreinforcement dispersion. Therefore, obtaining a uniform dispersion of the nanoreinforcement in the matrix remains a key issue in the development of nanocomposites with the desired properties. The issue of nanoreinforcement dispersion was not fully addressed in review papers dedicated to processing, characterization, and properties of inorganic nanocomposites. In addition, characterization of nanoparticles dispersion, reported in literature, remains largely qualitative. The objective of this review is to provide a comprehensive description of characterization techniques used to evaluate the extent of nanoreinforcement dispersion in inorganic nanocomposites and critically review published work. Moreover, methodologies and techniques used to characterize reinforcement dispersion in conventional composites, which may be used for quantitative characterization of nanoreinforcement dispersion in nanocomposites, is also presented.

  14. Biodegradation of dispersants used in the treatment of oil spills

    International Nuclear Information System (INIS)

    Bergueiro Lopez, J.R.; Lalucat Jo, J.; Marti Moreno, A.; Morales Correas, N.

    1993-01-01

    The biodegradation of one of the most commonly used commercially available dispersants in the treatment of hydrocarbon out-flow was studied. The culture mediums employed were sea water, sterile sea water, and medium M19 (Merck). The latter two were inoculated with two kinds of microorganisms of the Pseudomona genus isolated from sludge from a waste treatment plant. The dispersants used is a commercial product made of anionic sulphated dispersants (1.710% by weight); anionic sulphonated dispersants (0.144%) and non-ionic dispersants (8.146%), both accompained by hidrocarbonated solvent (90%). The degradation processes occurred at differents temperatures (20, 30 and 37). The greatest degradation was obtained at 30 degree centigree. The degradation percentages obtained with the miscroorganisms were 40% of the anionic total and 70% of the non-ionic total after 56 hours for the 5:2 strain and 40% of the anionic total and 9.3% of the non-ionic total after 186 hours for the 1:3 strain. The sulphonated anionic dispersant fraction showed practically no degradation under these experimental conditions. The DBO, for a simple containing (Sterile) sea water and dispersant and inoculated with Pseudomonas was also determined. The value obtained was 595 mg. of O 2 /l. Sea water and medium M9 were used as a control. (Author)

  15. Dispersed oil disrupts microbial pathways in pelagic food webs.

    Directory of Open Access Journals (Sweden)

    Alice C Ortmann

    Full Text Available Most of the studies of microbial processes in response to the Deepwater Horizon oil spill focused on the deep water plume, and not on the surface communities. The effects of the crude oil and the application of dispersants on the coastal microbial food web in the northern Gulf of Mexico have not been well characterized even though these regions support much of the fisheries production in the Gulf. A mesocosm experiment was carried out to determine how the microbial community off the coast of Alabama may have responded to the influx of surface oil and dispersants. While the addition of glucose or oil alone resulted in an increase in the biomass of ciliates, suggesting transfer of carbon to higher trophic levels was likely; a different effect was seen in the presence of dispersant. The addition of dispersant or dispersed oil resulted in an increase in the biomass of heterotrophic prokaryotes, but a significant inhibition of ciliates, suggesting a reduction in grazing and decrease in transfer of carbon to higher trophic levels. Similar patterns were observed in two separate experiments with different starting nutrient regimes and microbial communities suggesting that the addition of dispersant and dispersed oil to the northern Gulf of Mexico waters in 2010 may have reduced the flow of carbon to higher trophic levels, leading to a decrease in the production of zooplankton and fish on the Alabama shelf.

  16. Dispersed oil disrupts microbial pathways in pelagic food webs.

    Science.gov (United States)

    Ortmann, Alice C; Anders, Jennifer; Shelton, Naomi; Gong, Limin; Moss, Anthony G; Condon, Robert H

    2012-01-01

    Most of the studies of microbial processes in response to the Deepwater Horizon oil spill focused on the deep water plume, and not on the surface communities. The effects of the crude oil and the application of dispersants on the coastal microbial food web in the northern Gulf of Mexico have not been well characterized even though these regions support much of the fisheries production in the Gulf. A mesocosm experiment was carried out to determine how the microbial community off the coast of Alabama may have responded to the influx of surface oil and dispersants. While the addition of glucose or oil alone resulted in an increase in the biomass of ciliates, suggesting transfer of carbon to higher trophic levels was likely; a different effect was seen in the presence of dispersant. The addition of dispersant or dispersed oil resulted in an increase in the biomass of heterotrophic prokaryotes, but a significant inhibition of ciliates, suggesting a reduction in grazing and decrease in transfer of carbon to higher trophic levels. Similar patterns were observed in two separate experiments with different starting nutrient regimes and microbial communities suggesting that the addition of dispersant and dispersed oil to the northern Gulf of Mexico waters in 2010 may have reduced the flow of carbon to higher trophic levels, leading to a decrease in the production of zooplankton and fish on the Alabama shelf.

  17. Enhancement of dissolution of Telmisartan through use of solid dispersion technique surface solid dispersion

    Directory of Open Access Journals (Sweden)

    Bhumika Patel

    2012-01-01

    Full Text Available The present study was aimed to increase the solubility of the poorly water soluble drug Telmisartan by using Surface solid dispersion (SSD made of polymers like Poloxamer 407, PEG 6000 by Solvent evaporation method. The drug was solubilized by surfactants and/or polymers then adsorbed onto the surface of extremely fine carriers to increase its surface area and to form the SSD which give the more Surface area for absorption of the drug. A 2 2 full factorial design was used to investigate for each carrier the joint influence of formulation variables: Amount of carrier and adsorbent. Saturation solubility studies shows the improvement in solubility of drug batch SSD 8 give more solubility improvement than the other batch, in-vitro dissolution of pure drug, physical mixtures and SSDs were carried out in that SSDs were found to be effective in increasing the dissolution rate of Telmisartan in form of SSD when compared to pure drug. Also FT-IR spectroscopy, differential scanning calorimetry and X-ray diffractometry studies were carried out in order to characterize the drug and Surface solid dispersion. Furthermore, both DSC and X-ray diffraction showed a decrease in the melting enthalpy and reduced drug crystallinity consequently in SSDs. However, infrared spectroscopy revealed no drug interactions with the carriers.

  18. Increases of QT dispersion, corrected QT dispersion and QT interval in young healthy individuals during Ramadan fasting

    Directory of Open Access Journals (Sweden)

    Moradmand S

    2003-06-01

    Full Text Available Ramadan fasting is one of the most important religious duties of Muslims, that its effect on the heart has not been determined yet. Our objective was to evaluate the effect of Ramadan fasting on ventricular repolarization as assessed by QT interval, corrected QT interval, QT dispersion or corrected QT dispersion. Sixthy healthy subjects aged 20 to 35 years were dispersion included in this study. QT interval, corrected QT interval (QTc QT dispersion QTc dispersion, RR interval and QRS axis were measured in 12-lead surface electrocardiogram, once during fasting (10 to 11.5 hours of absolute fasting from food and liquid and another time, 15 tp 60 minutes after eating food at sunset, All of the subjects had been fasting 11 to 12 hours each day at least for 25 days during Ramadan. The study was performed at Amir Alam hospital in the year 2000. Maximal QT interval, mean QT interval and RR-interval, were longer during fasting (P<0.05, and both QT dispersion and QTc dispersion were increased (P<0.05. (QT dispersion: mean ±SD= 57.2±20.1 ms during fasting Vs 41.6±15.1 ms after meal, QTc dispersion=75.4±24.6 ms during fasting Vs 64.1±22.8 ms after meal. But mean QTc interval maximal QTc interval and QRS axis showed no significant difference. Prolongation of QT interval and RR interval during fasting, instead of no significant changes in corrected QT interval may primarily suggest that prolongation of RR-interval causes QTc interval not to have significant difference. But increases of QT dispersion and corrected QT dispersion (QTc dispersion during fasting -that are more reliable indicators of ventricular repolarization-support the idea that ventricular repolarization may be changed during Ramadan fasting. QT dispersion in cardiac patients is showed to increase from normal values of 30-40 to 64-138 ms, but in our study their increases did not reach critical value.

  19. The QT dispersion and QTc dispersion in patients presenting with acute neurological events and its impact on early prognosis

    Directory of Open Access Journals (Sweden)

    Kailash Kumar Rahar

    2016-01-01

    Full Text Available Aims: To find out and investigate whether the QT dispersion and QTc dispersion is related to type and prognosis of the acute stroke in patients presenting within 24 h of the onset of stroke. Settings and Design: This was a observational study conducted at Mahatma Gandhi Hospital, Dr. SN. Medical College, Jodhpur, during January 2014 to January 2015. Subjects and Methods: The patients presented within 24 h of onset of acute stroke (hemorrhagic, infarction, or transient ischemic event were included in the study. The stroke was confirmed by computed tomography scan and magnetic resonance imaging. Patients with (i altered sensorium because of metabolic, infective, seizures, trauma, or tumor; (ii prior history of cardiovascular disease, electrocardiographic abnormalities' because of dyselectrolytemia; and (iii and patients who were on drugs (antiarrhythmic drugs, antipsychotic drugs, erythromycin, theophylline, etc., which known to cause electrocardiogram changes, were excluded from the study. National Institute of Health Stroke Score (NIHSS was calculated at the time of admission and Modified Rankin Scale (MRS at the time of discharge. Fifty age- and sex-matched healthy controls included. Statistical Analysis Used: Student's t-test, ANOVA, and area under curve for sensitivity and specificity for the test. Results: We included 52 patients (male/female: 27/25 and 50 controls (26/24. The mean age of patients was 63.17 ± 08.90 years. Of total patients, infarct was found in 32 (61.53%, hemorrhage in 18 (34.61%, transient ischemic attack (TIA in 1 (1.9%, and subarachnoid hemorrhage in 1 (1.9% patient. The QT dispersion and QTc dispersion were significantly higher in cases as compare to controls. (87.30 ± 24.42 vs. 49.60 ± 08.79 ms; P < 0.001 and (97.53 ± 27.36 vs. 56.28 ± 09.86 ms; P < 0.001. Among various types of stroke, the mean QT dispersion and QTc dispersion were maximum and significantly higher in hemorrhagic stroke as compared to infarct and

  20. Genetic insights into dispersal distance and disperser fitness of African lions (Panthera leo) from the latitudinal extremes of the Kruger National Park, South Africa

    NARCIS (Netherlands)

    Hooft, van Pim; Keet, Dewald F.; Brebner, Diana K.; Bastos, Armanda D.S.

    2018-01-01

    Background: Female lions generally do not disperse far beyond their natal range, while males can disperse distances of over 200 km. However, in bush-like ecosystems dispersal distances less than 25 km are reported. Here, we investigate dispersal in lions sampled from the northern and southern