Yin, Deshun; Qu, Pengfei
2018-02-01
Protein lateral diffusion is considered anomalous in the plasma membrane. And this diffusion is related to membrane microstructure. In order to better describe the property of protein lateral diffusion and find out the inner relationship between protein lateral diffusion and membrane microstructure, this article applies variable-order fractional mean square displacement (f-MSD) function for characterizing the anomalous diffusion. It is found that the variable order can reflect the evolution of diffusion ability. The results of numerical simulation demonstrate variable-order f-MSD function can predict the tendency of anomalous diffusion during the process of confined diffusion. It is also noted that protein lateral diffusion ability during the processes of confined and hop diffusion can be split into three parts. In addition, the comparative analyses reveal that the variable order is related to the confinement-domain size and microstructure of compartment boundary too.
Xia, L.; Pont, S.C.; Heynderickx, I.E.J.
2017-01-01
We introduce a way to simultaneously measure the light density, light vector and diffuseness of the light field using a cubic illumination meter based on the spherical harmonics representation of the light field. This approach was applied to six light probe images of natural scenes and four real
From gas dynamics with large friction to gradient flows describing diffusion theories
Lattanzio, Corrado
2016-12-09
We study the emergence of gradient flows in Wasserstein distance as high friction limits of an abstract Euler flow generated by an energy functional. We develop a relative energy calculation that connects the Euler flow to the gradient flow in the diffusive limit regime. We apply this approach to prove convergence from the Euler-Poisson system with friction to the Keller-Segel system in the regime that the latter has smooth solutions. The same methodology is used to establish convergence from the Euler-Korteweg theory with monotone pressure laws to the Cahn-Hilliard equation.
From gas dynamics with large friction to gradient flows describing diffusion theories
Lattanzio, Corrado; Tzavaras, Athanasios
2016-01-01
We study the emergence of gradient flows in Wasserstein distance as high friction limits of an abstract Euler flow generated by an energy functional. We develop a relative energy calculation that connects the Euler flow to the gradient flow in the diffusive limit regime. We apply this approach to prove convergence from the Euler-Poisson system with friction to the Keller-Segel system in the regime that the latter has smooth solutions. The same methodology is used to establish convergence from the Euler-Korteweg theory with monotone pressure laws to the Cahn-Hilliard equation.
Fractional single-phase-lagging heat conduction model for describing anomalous diffusion
Directory of Open Access Journals (Sweden)
T.N. Mishra
2016-03-01
Full Text Available The fractional single-phase-lagging (FSPL heat conduction model is obtained by combining scalar time fractional conservation equation to the single-phase-lagging (SPL heat conduction model. Based on the FSPL heat conduction model, anomalous diffusion within a finite thin film is investigated. The effect of different parameters on solution has been observed and studied the asymptotic behavior of the FSPL model. The analytical solution is obtained using Laplace transform method. The whole analysis is presented in dimensionless form. Numerical examples of particular interest have been studied and discussed in details.
Queiros-Conde, D.; Foucher, F.; Mounaïm-Rousselle, C.; Kassem, H.; Feidt, M.
2008-12-01
Multi-scale features of turbulent flames near a wall display two kinds of scale-dependent fractal features. In scale-space, an unique fractal dimension cannot be defined and the fractal dimension of the front is scale-dependent. Moreover, when the front approaches the wall, this dependency changes: fractal dimension also depends on the wall-distance. Our aim here is to propose a general geometrical framework that provides the possibility to integrate these two cases, in order to describe the multi-scale structure of turbulent flames interacting with a wall. Based on the scale-entropy quantity, which is simply linked to the roughness of the front, we thus introduce a general scale-entropy diffusion equation. We define the notion of “scale-evolutivity” which characterises the deviation of a multi-scale system from the pure fractal behaviour. The specific case of a constant “scale-evolutivity” over the scale-range is studied. In this case, called “parabolic scaling”, the fractal dimension is a linear function of the logarithm of scale. The case of a constant scale-evolutivity in the wall-distance space implies that the fractal dimension depends linearly on the logarithm of the wall-distance. We then verified experimentally, that parabolic scaling represents a good approximation of the real multi-scale features of turbulent flames near a wall.
International Nuclear Information System (INIS)
Kubaschewski, O.
1983-01-01
The diffusion rate values of titanium, its compounds and alloys are summarized and tabulated. The individual chemical diffusion coefficients and self-diffusion coefficients of certain isotopes are given. Experimental methods are listed which were used for the determination of diffusion coefficients. Some values have been taken over from other studies. Also given are graphs showing the temperature dependences of diffusion and changes in the diffusion coefficient with concentration changes
Basilevsky, M V
2002-01-01
We develop an approach for derivation of quantum-classical relaxation equations for a two-channel problem. The treatment is based on the adiabatic channel wavefunctions and the system-bath coupling is modelled as a bilinear interaction in momentum representation. In the quantum-classical limit we obtain Liouville equations with the relaxation operator containing diffusion terms diagonal in Liouvillian space and the off-diagonal part which is responsible for thermal interlevel transitions. The high-frequency interlevel quantum beats are fully taken into account in this relaxation term. In the framework of the present formulation and as a consequence of the momentum-dependent interaction the Smoluchovsky diffusion limit can be reached without invoking Fokker-Planck equations as an intermediate step. The inherent property of equations so obtained is that the partial rates of interlevel transitions obey the principle of detailed balance. This result could not be gained in earlier treatments of the two-level diffu...
International Nuclear Information System (INIS)
Carlen, E.A.
1984-01-01
In Nelson's stochastic mechanics, quantum phenomena are described in terms of diffusions instead of wave functions. These diffusions are formally given by stochastic differential equations with extremely singular coefficients. Using PDE methods, we prove the existence of solutions. This reult provides a rigorous basis for stochastic mechanics. (orig.)
Pharmacobezoars described and demystified.
Simpson, Serge-Emile
2011-02-01
A bezoar is a concretion of foreign material that forms and persists in the gastrointestinal tract. Bezoars are classified by their material origins. Phytobezoars contain plant material, trichobezoars contain hair, lactobezoars contain milk proteins, and pharmacobezoars contain pharmaceutical products. Tablets, suspensions, and even insoluble drug delivery vehicles can, on rare occasions, and sometimes under specific circumstances, form pharmacobezoars. The goal of this review is to catalog and examine all of the available reports in the English language medical literature that convincingly describe the formation and management of pharmacobezoars. Articles included in this review were identified by performing searches using the terms "bezoar," "pharmacobezoar," and "concretion" in the following databases: OVID MEDLINE, PubMed, and JSTOR. The complete MEDLINE and JSTOR holdings were included in the search without date ranges. The results were limited to English language publications. Articles that described nonmedication bezoars were not included in the review. Articles describing phytobezoars, food bezoars, fecal impactions, illicit drug packet ingestions, enteral feeding material bezoars, and hygroscopic diet aid bezoars were excluded. The bibliographic references within the articles already accumulated were then examined in order to gather additional pharmacobezoar cases. The cases are grouped by pharmaceutical agent that formed the bezoar, and groupings are arranged in alphabetical order. Discussions and conclusions specific to each pharmaceutical agent are included in that agent's subheading. Patterns and themes that emerged in the review of the assembled case reports are reviewed and presented in a more concise format. Pharmacobezoars form under a wide variety of circumstances and in a wide variety of patients. They are difficult to diagnose reliably. Rules for suspecting, diagnosing, and properly managing a pharmacobezoar are highly dependent on the
[Deep mycoses rarely described].
Charles, D
1986-01-01
Beside deep mycoses very well known: histoplasmosis, candidosis, cryptococcosis, there are other mycoses less frequently described. Some of them are endemic in some countries: South American blastomycosis in Brazil, coccidioidomycosis in California; some others are cosmopolitan and may affect everyone: sporotrichosis, or may affect only immunodeficient persons: mucormycosis. They do not spare Africa, we may encounter basidiobolomycosis, rhinophycomycosis, dermatophytosis, sporotrichosis and, more recently reported, rhinosporidiosis. Important therapeutic progresses have been accomplished with amphotericin B and with antifungus imidazole compounds (miconazole and ketoconazole). Surgical intervention is sometime recommended in chromomycosis and rhinosporidiosis.
How Mathematics Describes Life
Teklu, Abraham
2017-01-01
The circle of life is something we have all heard of from somewhere, but we don't usually try to calculate it. For some time we have been working on analyzing a predator-prey model to better understand how mathematics can describe life, in particular the interaction between two different species. The model we are analyzing is called the Holling-Tanner model, and it cannot be solved analytically. The Holling-Tanner model is a very common model in population dynamics because it is a simple descriptor of how predators and prey interact. The model is a system of two differential equations. The model is not specific to any particular set of species and so it can describe predator-prey species ranging from lions and zebras to white blood cells and infections. One thing all these systems have in common are critical points. A critical point is a value for both populations that keeps both populations constant. It is important because at this point the differential equations are equal to zero. For this model there are two critical points, a predator free critical point and a coexistence critical point. Most of the analysis we did is on the coexistence critical point because the predator free critical point is always unstable and frankly less interesting than the coexistence critical point. What we did is consider two regimes for the differential equations, large B and small B. B, A, and C are parameters in the differential equations that control the system where B measures how responsive the predators are to change in the population, A represents predation of the prey, and C represents the satiation point of the prey population. For the large B case we were able to approximate the system of differential equations by a single scalar equation. For the small B case we were able to predict the limit cycle. The limit cycle is a process of the predator and prey populations growing and shrinking periodically. This model has a limit cycle in the regime of small B, that we solved for
New Described Dermatological Disorders
Directory of Open Access Journals (Sweden)
Müzeyyen Gönül
2014-01-01
Full Text Available Many advances in dermatology have been made in recent years. In the present review article, newly described disorders from the last six years are presented in detail. We divided these reports into different sections, including syndromes, autoinflammatory diseases, tumors, and unclassified disease. Syndromes included are “circumferential skin creases Kunze type” and “unusual type of pachyonychia congenita or a new syndrome”; autoinflammatory diseases include “chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature (CANDLE syndrome,” “pyoderma gangrenosum, acne, and hidradenitis suppurativa (PASH syndrome,” and “pyogenic arthritis, pyoderma gangrenosum, acne, and hidradenitis suppurativa (PAPASH syndrome”; tumors include “acquired reactive digital fibroma,” “onychocytic matricoma and onychocytic carcinoma,” “infundibulocystic nail bed squamous cell carcinoma,” and “acral histiocytic nodules”; unclassified disorders include “saurian papulosis,” “symmetrical acrokeratoderma,” “confetti-like macular atrophy,” and “skin spicules,” “erythema papulosa semicircularis recidivans.”
Analytical Solutions To Describe Juxtaposed Sands | Adeniji ...
African Journals Online (AJOL)
Mathematical (linear diffusion) equations are presented for two pseudoreservoir regions intersected by fault that describe the effects of partial communicating fault on pressure transient behaviour for each fault block. Green's and source function technique solve these equations. A two-well system is considered for the ...
International Nuclear Information System (INIS)
Tiwari, G.P.; Kale, G.B.; Patil, R.V.
1999-01-01
The article presents a brief survey of process of diffusion in solids. It is emphasised that the essence of diffusion is the mass transfer through the atomic jumps. To begin with formal equations for diffusion coefficient are presented. This is followed by discussions on mechanisms of diffusion. Except for solutes which form interstitial solid solution, diffusion in majority of cases is mediated through exchange of sites between an atom and its neighbouring vacancy. Various vacancy parameters such as activation volume, correlation factor, mass effect etc are discussed and their role in establishing the mode of diffusion is delineated. The contribution of dislocations and grain boundaries in diffusion process is brought out. The experimental determination of different types of diffusion coefficients are described. Finally, the pervasive nature of diffusion process in number of commercial processes is outlined to show the importance of diffusion studies in materials science and technology. (author)
International Nuclear Information System (INIS)
Anderson, R.C.
1976-01-01
A method is described for joining beryllium to beryllium by diffusion bonding. At least one surface portion of at least two beryllium pieces is coated with nickel. A coated surface portion is positioned in a contiguous relationship with another surface portion and subjected to an environment having an atmosphere at a pressure lower than ambient pressure. A force is applied on the beryllium pieces for causing the contiguous surface portions to abut against each other. The contiguous surface portions are heated to a maximum temperature less than the melting temperature of the beryllium, and the applied force is decreased while increasing the temperature after attaining a temperature substantially above room temperature. A portion of the applied force is maintained at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions
Five Describing Factors of Dyslexia
Tamboer, Peter; Vorst, Harrie C. M.; Oort, Frans J.
2016-01-01
Two subtypes of dyslexia (phonological, visual) have been under debate in various studies. However, the number of symptoms of dyslexia described in the literature exceeds the number of subtypes, and underlying relations remain unclear. We investigated underlying cognitive features of dyslexia with exploratory and confirmatory factor analyses. A…
Procedure to describe clavicular motion.
Gutierrez Delgado, Guivey; De Beule, Matthieu; Ortega Cardentey, Dolgis R; Segers, Patrick; Iznaga Benítez, Arsenio M; Rodríguez Moliner, Tania; Verhegghe, Benedict; Palmans, Tanneke; Van Hoof, Tom; Van Tongel, Alexander
2017-03-01
For many years, researchers have attempted to describe shoulder motions by using different mathematical methods. The aim of this study was to describe a procedure to quantify clavicular motion. The procedure proposed for the kinematic analysis consists of 4 main processes: 3 transcortical pins in the clavicle, motion capture, obtaining 3-dimensional bone models, and data processing. Clavicular motion by abduction (30° to 150°) and flexion (55° to 165°) were characterized by an increment of retraction of 27° to 33°, elevation of 25° to 28°, and posterior rotation of 14° to 15°, respectively. In circumduction, clavicular movement described an ellipse, which was reflected by retraction and elevation. Kinematic analysis shows that the articular surfaces move by simultaneously rolling and sliding on the convex surface of the sternum for the 3 movements of abduction, flexion, and circumduction. The use of 3 body landmarks in the clavicle and the direct measurement of bone allowed description of the osteokinematic and arthrokinematic movement of the clavicle. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.
International Nuclear Information System (INIS)
Garrett, G.A.; Shacter, J.
1978-01-01
A gaseous diffusion system is described comprising a plurality of diffusers connected in cascade to form a series of stages, each of the diffusers having a porous partition dividing it into a high pressure chamber and a low pressure chamber, and means for combining a portion of the enriched gas from a succeeding stage with a portion of the enriched gas from the low pressure chamber of each stage and feeding it into one extremity of the high pressure chamber thereof
Describing treatment effects to patients.
Moxey, Annette; O'Connell, Dianne; McGettigan, Patricia; Henry, David
2003-11-01
To examine the impact of different presentations of equivalent information (framing) on treatment decisions faced by patients. A systematic review of the published literature was conducted. English language publications allocating participants to different frames were retrieved using electronic and bibliographic searches. Two reviewers examined each article for inclusion, and assessed methodological quality. Study characteristics were tabulated and where possible, relative risks (RR; 95% confidence intervals) were calculated to estimate intervention effects. Thirty-seven articles, yielding 40 experimental studies, were included. Studies examined treatment (N = 24), immunization (N = 5), or health behavior scenarios (N = 11). Overall, active treatments were preferred when outcomes were described in terms of relative rather than absolute risk reductions or number needed to treat. Surgery was preferred to other treatments when treatment efficacy was presented in a positive frame (survival) rather than a negative frame (mortality) (relative risk [RR] = 1.51, 95% confidence interval [CI], 1.39 to 1.64). Framing effects were less obvious for immunization and health behavior scenarios. Those with little interest in the behavior at baseline were influenced by framing, particularly when information was presented as gains. In studies judged to be of good methodological quality and/or examining actual decisions, the framing effect, although still evident, was less convincing compared to the results of all included studies. Framing effects varied with the type of scenario, responder characteristics, scenario manipulations, and study quality. When describing treatment effects to patients, expressing the information in more than one way may present a balanced view to patients and enable them to make informed decisions.
Describing function theory as applied to thermal and neutronic problems
International Nuclear Information System (INIS)
Nassersharif, B.
1983-01-01
Describing functions have traditionally been used to obtain the solutions of systems of ordinary differential equations. In this work the describing function concept has been extended to include nonlinear, distributed parameter partial differential equations. A three-stage solution algorithm is presented which can be applied to any nonlinear partial differential equation. Two generalized integral transforms were developed as the T-transform for the time domain and the B-transform for the spatial domain. The thermal diffusion describing function (TDDF) is developed for conduction of heat in solids and a general iterative solution along with convergence criteria is presented. The proposed solution method is used to solve the problem of heat transfer in nuclear fuel rods with annular fuel pellets. As a special instance the solid cylindrical fuel pellet is examined. A computer program is written which uses the describing function concept for computing fuel pin temperatures in the radial direction during reactor transients. The second problem investigated was the neutron diffusion equation which is intrinsically different from the first case. Although, for most situations, it can be treated as a linear differential equation, the describing function method is still applicable. A describing function solution is derived for two possible cases: constant diffusion coefficient and variable diffusion coefficient. Two classes of describing functions are defined for each case which portray the leakage and absorption phenomena. For the specific case of a slab reactor criticality problem the comparison between analytical and describing function solutions revealed an excellent agreement
Modelling of Innovation Diffusion
Directory of Open Access Journals (Sweden)
Arkadiusz Kijek
2010-01-01
Full Text Available Since the publication of the Bass model in 1969, research on the modelling of the diffusion of innovation resulted in a vast body of scientific literature consisting of articles, books, and studies of real-world applications of this model. The main objective of the diffusion model is to describe a pattern of spread of innovation among potential adopters in terms of a mathematical function of time. This paper assesses the state-of-the-art in mathematical models of innovation diffusion and procedures for estimating their parameters. Moreover, theoretical issues related to the models presented are supplemented with empirical research. The purpose of the research is to explore the extent to which the diffusion of broadband Internet users in 29 OECD countries can be adequately described by three diffusion models, i.e. the Bass model, logistic model and dynamic model. The results of this research are ambiguous and do not indicate which model best describes the diffusion pattern of broadband Internet users but in terms of the results presented, in most cases the dynamic model is inappropriate for describing the diffusion pattern. Issues related to the further development of innovation diffusion models are discussed and some recommendations are given. (original abstract
Spin-diffusions and diffusive molecular dynamics
Farmer, Brittan; Luskin, Mitchell; Plecháč, Petr; Simpson, Gideon
2017-12-01
Metastable configurations in condensed matter typically fluctuate about local energy minima at the femtosecond time scale before transitioning between local minima after nanoseconds or microseconds. This vast scale separation limits the applicability of classical molecular dynamics (MD) methods and has spurned the development of a host of approximate algorithms. One recently proposed method is diffusive MD which aims at integrating a system of ordinary differential equations describing the likelihood of occupancy by one of two species, in the case of a binary alloy, while quasistatically evolving the locations of the atoms. While diffusive MD has shown itself to be efficient and provide agreement with observations, it is fundamentally a model, with unclear connections to classical MD. In this work, we formulate a spin-diffusion stochastic process and show how it can be connected to diffusive MD. The spin-diffusion model couples a classical overdamped Langevin equation to a kinetic Monte Carlo model for exchange amongst the species of a binary alloy. Under suitable assumptions and approximations, spin-diffusion can be shown to lead to diffusive MD type models. The key assumptions and approximations include a well-defined time scale separation, a choice of spin-exchange rates, a low temperature approximation, and a mean field type approximation. We derive several models from different assumptions and show their relationship to diffusive MD. Differences and similarities amongst the models are explored in a simple test problem.
Anisotropy in "isotropic diffusion" measurements due to nongaussian diffusion
DEFF Research Database (Denmark)
Jespersen, Sune Nørhøj; Olesen, Jonas Lynge; Ianuş, Andrada
2017-01-01
Designing novel diffusion-weighted NMR and MRI pulse sequences aiming to probe tissue microstructure with techniques extending beyond the conventional Stejskal-Tanner family is currently of broad interest. One such technique, multidimensional diffusion MRI, has been recently proposed to afford...... model-free decomposition of diffusion signal kurtosis into terms originating from either ensemble variance of isotropic diffusivity or microscopic diffusion anisotropy. This ability rests on the assumption that diffusion can be described as a sum of multiple Gaussian compartments, but this is often...
Diffusion in compacted betonite
International Nuclear Information System (INIS)
Muurinen, A.; Rantanen, J.
1985-01-01
The objective of this report is to collect the literature bearing on the diffusion in compacted betonite, which has been suggested as possible buffer material for the disposal of spent fuel. Diffusion in a porous, water-saturated material is usually described as diffusion in the pore-water where sorption on the solid matter can delay the migration in the instationary state. There are also models which take into consideration that the sorbed molecules can also move while being sorbed. Diffusion experiments in compacted bentonite have been reported by many authors. Gases, anions, cations and actinides have been used as diffusing molecules. The report collects the results and the information on the measurement methods. On the basis of the results can be concluded that different particles possibly follow different diffusion mechanisms. The parameters which affect the diffusion seem to be for example the size, the electric charge and the sorption properties of the diffusing molecule. The report also suggest the parameters to be used in the diffusion calculation of the safety analyses of spent fuel disposal. (author)
Michaud, Georges; Richer, Jacques
2015-01-01
This book gives an overview of atomic diffusion, a fundamental physical process, as applied to all types of stars, from the main sequence to neutron stars. The superficial abundances of stars as well as their evolution can be significantly affected. The authors show where atomic diffusion plays an essential role and how it can be implemented in modelling. In Part I, the authors describe the tools that are required to include atomic diffusion in models of stellar interiors and atmospheres. An important role is played by the gradient of partial radiative pressure, or radiative acceleration, which is usually neglected in stellar evolution. In Part II, the authors systematically review the contribution of atomic diffusion to each evolutionary step. The dominant effects of atomic diffusion are accompanied by more subtle effects on a large number of structural properties throughout evolution. One of the goals of this book is to provide the means for the astrophysicist or graduate student to evaluate the importanc...
Cherniak, D. J.; Zhang, X. Y.; Nakamura, M.; Watson, E. B.
2004-09-01
We report measurements of oxygen diffusion in natural monazites under both dry, 1-atm conditions and hydrothermal conditions. For dry experiments, 18O-enriched CePO4 powder and monazite crystals were sealed in Ag-Pd capsules with a solid buffer (to buffer at NNO) and annealed in 1-atm furnaces. Hydrothermal runs were conducted in cold-seal pressure vessels, where monazite grains were encapsulated with 18O-enriched water. Following the diffusion anneals, oxygen concentration profiles were measured with Nuclear Reaction Analysis (NRA) using the reaction 18O(p,α)15N. Over the temperature range 850-1100 °C, the Arrhenius relation determined for dry diffusion experiments on monazite is given by: Under wet conditions at 100 MPa water pressure, over the temperature range 700-880 °C, oxygen diffusion can be described by the Arrhenius relationship: Oxygen diffusion under hydrothermal conditions has a significantly lower activation energy for diffusion than under dry conditions, as has been found the case for many other minerals, both silicate and nonsilicate. Given these differences in activation energies, the differences between dry and wet diffusion rates increase with lower temperatures; for example, at 600 °C, dry diffusion will be more than 4 orders of magnitude slower than diffusion under hydrothermal conditions. These disparate diffusivities will result in pronounced differences in the degree of retentivity of oxygen isotope signatures. For instance, under dry conditions (presumably rare in the crust) and high lower-crustal temperatures (∼800 °C), monazite cores of 70-μm radii will preserve O isotope ratios for about 500,000 years; by comparison, they would be retained at this temperature under wet conditions for about 15,000 years.
International Nuclear Information System (INIS)
Brzoska, A.M.; Lenz, F.; Thies, M.; Negele, J.W.
2005-01-01
A phenomenological analysis of the distribution of Wilson loops in SU(2) Yang-Mills theory is presented in which Wilson loop distributions are described as the result of a diffusion process on the group manifold. It is shown that, in the absence of forces, diffusion implies Casimir scaling and, conversely, exact Casimir scaling implies free diffusion. Screening processes occur if diffusion takes place in a potential. The crucial distinction between screening of fundamental and adjoint loops is formulated as a symmetry property related to the center symmetry of the underlying gauge theory. The results are expressed in terms of an effective Wilson loop action and compared with various limits of SU(2) Yang-Mills theory
Detection of diffusible substances
Energy Technology Data Exchange (ETDEWEB)
Warembourg, M [Lille-1 Univ., 59 - Villeneuve-d' Ascq (France)
1976-12-01
The different steps of a radioautographic technique for the detection of diffusible substances are described. Using this radioautographic method, the topographic distribution of estradiol-concentrating neurons was studied in the nervous system and pituitary of the ovariectomized mouse and guinea-pig. A relatively good morphological preservation of structures can be ascertained on sections from unfixed, unembedded tissues prepared at low temperatures and kept-under relatively low humidity. The translocation or extraction of diffusible substances is avoided by directly mounting of frozen sections on dried photographic emulsion. Since no solvent is used, this technique excludes the major sources of diffusion artifacts and permits to be in favourable conditions for the localization of diffusible substances.
Shetty, Anil N; Chiang, Sharon; Maletic-Savatic, Mirjana; Kasprian, Gregor; Vannucci, Marina; Lee, Wesley
2014-01-01
In this article, we discuss the theoretical background for diffusion weighted imaging and diffusion tensor imaging. Molecular diffusion is a random process involving thermal Brownian motion. In biological tissues, the underlying microstructures restrict the diffusion of water molecules, making diffusion directionally dependent. Water diffusion in tissue is mathematically characterized by the diffusion tensor, the elements of which contain information about the magnitude and direction of diffusion and is a function of the coordinate system. Thus, it is possible to generate contrast in tissue based primarily on diffusion effects. Expressing diffusion in terms of the measured diffusion coefficient (eigenvalue) in any one direction can lead to errors. Nowhere is this more evident than in white matter, due to the preferential orientation of myelin fibers. The directional dependency is removed by diagonalization of the diffusion tensor, which then yields a set of three eigenvalues and eigenvectors, representing the magnitude and direction of the three orthogonal axes of the diffusion ellipsoid, respectively. For example, the eigenvalue corresponding to the eigenvector along the long axis of the fiber corresponds qualitatively to diffusion with least restriction. Determination of the principal values of the diffusion tensor and various anisotropic indices provides structural information. We review the use of diffusion measurements using the modified Stejskal-Tanner diffusion equation. The anisotropy is analyzed by decomposing the diffusion tensor based on symmetrical properties describing the geometry of diffusion tensor. We further describe diffusion tensor properties in visualizing fiber tract organization of the human brain.
Energy Technology Data Exchange (ETDEWEB)
Brogaard Kristensen, S.
2000-06-01
This report describes the work done on modelling and simulation of the complex diffusion of gas through the wall of a flexible pipe. The diffusion and thus the pressure in annulus depends strongly on the diffusion and solubility parameters of the gas-polymer system and on the degree of blocking of the outer surface of the inner liner due to pressure reinforcements. The report evaluates the basis modelling required to describe the complex geometries and flow patterns. Qualitatively results of temperature and concentration profiles are shown in the report. For the program to serve any modelling purpose in 'real life' the results need to be validated and possibly the model needs corrections. Hopefully, a full-scale test of a flexible pipe will provide the required temperatures and pressures in annulus to validate the models. (EHS)
Energy Technology Data Exchange (ETDEWEB)
Brogaard Kristensen, S
2000-06-01
This report describes the work done on modelling and simulation of the complex diffusion of gas through the wall of a flexible pipe. The diffusion and thus the pressure in annulus depends strongly on the diffusion and solubility parameters of the gas-polymer system and on the degree of blocking of the outer surface of the inner liner due to pressure reinforcements. The report evaluates the basis modelling required to describe the complex geometries and flow patterns. Qualitatively results of temperature and concentration profiles are shown in the report. For the program to serve any modelling purpose in 'real life' the results need to be validated and possibly the model needs corrections. Hopefully, a full-scale test of a flexible pipe will provide the required temperatures and pressures in annulus to validate the models. (EHS)
Fractional Diffusion Equations and Anomalous Diffusion
Evangelista, Luiz Roberto; Kaminski Lenzi, Ervin
2018-01-01
Preface; 1. Mathematical preliminaries; 2. A survey of the fractional calculus; 3. From normal to anomalous diffusion; 4. Fractional diffusion equations: elementary applications; 5. Fractional diffusion equations: surface effects; 6. Fractional nonlinear diffusion equation; 7. Anomalous diffusion: anisotropic case; 8. Fractional Schrödinger equations; 9. Anomalous diffusion and impedance spectroscopy; 10. The Poisson–Nernst–Planck anomalous (PNPA) models; References; Index.
International Nuclear Information System (INIS)
Silva, T.L. da.
1987-01-01
Is this thesis, a numerical method for the solution of the linear diffusion equation for a plasma containing two types of ions, with the possibility of charge exchange, has been developed. It has been shown that the decay time of the electron and ion densities is much smaller than that in a plasma containing only a single type of ion. A non-linear diffusion equation, which includes the effects of an external electric field varying linearly in time, to describe a slightly ionized plasma has also been developed. It has been verified that the decay of the electron density in the presence of such an electric field is very slow. (author)
Correlation Factors Describing Primary and Spatial Sensations of Sound Fields
ANDO, Y.
2002-11-01
The theory of subjective preference of the sound field in a concert hall is established based on the model of human auditory-brain system. The model consists of the autocorrelation function (ACF) mechanism and the interaural crosscorrelation function (IACF) mechanism for signals arriving at two ear entrances, and the specialization of human cerebral hemispheres. This theory can be developed to describe primary sensations such as pitch or missing fundamental, loudness, timbre and, in addition, duration sensation which is introduced here as a fourth. These four primary sensations may be formulated by the temporal factors extracted from the ACF associated with the left hemisphere and, spatial sensations such as localization in the horizontal plane, apparent source width and subjective diffuseness are described by the spatial factors extracted from the IACF associated with the right hemisphere. Any important subjective responses of sound fields may be described by both temporal and spatial factors.
Apparatus for diffusion separation
International Nuclear Information System (INIS)
Nierenberg, W.A.; Pontius, R.B.
1976-01-01
The method of testing the separation efficiency of porous permeable membranes is described which comprises causing a stream of a gaseous mixture to flow into contact with one face of a finely porous permeable membrane under such conditions that a major fraction of the mixture diffuses through the membrane, maintaining a rectangular cross section of the gaseous stream so flowing past said membrane, continuously recirculating the gas that diffuses through said membrane and continuously withdrawing the gas that does not diffuse through said membrane and maintaining the volume of said recirculating gas constant by continuously introducing into said continuously recirculating gas stream a mass of gas equivalent to that which is continuously withdrawn from said gas stream and comparing the concentrations of the light component in the entering gas, the withdrawn gas and the recirculated gas in order to determine the efficiency of said membrane
Bicarbonate diffusion through mucus.
Livingston, E H; Miller, J; Engel, E
1995-09-01
The mucus layer overlying duodenal epithelium maintains a pH gradient against high luminal acid concentrations. Despite these adverse conditions, epithelial surface pH remains close to neutrality. The exact nature of the gradient-forming barrier remains unknown. The barrier consists of mucus into which HCO3- is secreted. Quantification of the ability of HCO3- to establish and maintain the gradient depends on accurate measurement of this ion's diffusion coefficient through mucus. We describe new experimental and mathematical methods for diffusion measurement and report diffusion coefficients for HCO3- diffusion through saline, 5% mucin solutions, and rat duodenal mucus. The diffusion coefficients were 20.2 +/- 0.10, 3.02 +/- 0.31, and 1.81 +/- 0.12 x 10(-6) cm2/s, respectively. Modeling of the mucobicarbonate layer with this latter value suggests that for conditions of high luminal acid strength the neutralization of acid by HCO3- occurs just above the epithelial surface. Under these conditions the model predicts that fluid convection toward the lumen could be important in maintaining the pH gradient. In support of this hypothesis we were able to demonstrate a net luminal fluid flux of 5 microliters.min-1.cm-2 after perfusion of 0.15 N HCl in the rat duodenum.
International Nuclear Information System (INIS)
Ramsdell, J.V.
1988-03-01
Straight-line Gaussian models adequately describe atmospheric diffusion for many applications. They have been modified for use in estimating diffusion in building wakes by adding terms that include projected building area and by redefining the diffusion coefficients so that the coefficients have minimum values that are related to building dimensions. In a recent study, Ramsdell reviewed the building-wake dispersion models used by the Nuclear Regulatory Commission (NRC) in its control room habitability assessments. The review included comparison of model estimates of centerline concentrations with concentrations observed in experiments at seven nuclear reactors. In general, the models are conservative in that they tend to predict concentrations that are greater than those actually observed. However, the models show little skill in accounting for variations in the observed concentrations. Subsequently, the experimental data and multiples linear regression techniques have been used to develop a new building wake diffusion model. This paper describes the new building wake model and compares it with other models. 8 refs., 2 figs
International Nuclear Information System (INIS)
Lalis, A.; Rouviere, R.; Simon, G.
1976-01-01
A multipassage diffuser having 2p passages comprises a leak-tight cylindrical enclosure closed by a top cover and a bottom end-wall, parallel porous tubes which are rigidly assembled in sectors between tube plates and through which the gas mixture flows, the tube sectors being disposed at uniform intervals on the periphery of the enclosure. The top tube plates are rigidly fixed to an annular header having the shape of a half-torus and adapted to communicate with the tubes of the corresponding sector. Each passage is constituted by a plurality of juxtaposed sectors in which the mixture circulates in the same direction, the header being divided into p portions limited by radial partition-walls and each constituting two adjacent passages. The diffuser is provided beneath the bottom end-wall with p-1 leak-tight chambers each adapted to open into two different portions of the header, and with two collector-chambers each fitted with a nozzle for introducing the gas mixture and discharging the fraction of the undiffused mixture. By means of a central orifice formed in the bottom end-wall the enclosure communicates with a shaft for discharging the diffused fraction of the gas mixture
Oxygen diffusion in glasses and ceramic materials
International Nuclear Information System (INIS)
Kolitsch, A.; Richter, E.; Wolf, M.
1978-10-01
A survey is given on the published works to study oxygen diffusion in glasses and ceramic materials in the last years. In the first part methods are described for the measurement of oxygen diffusion coefficients and in the second part the published reports on oxygen diffusion in glasses, ceramic and other oxides are discussed. The most important results are summarized in different tables. (author)
Bayesian regularization of diffusion tensor images
DEFF Research Database (Denmark)
Frandsen, Jesper; Hobolth, Asger; Østergaard, Leif
2007-01-01
Diffusion tensor imaging (DTI) is a powerful tool in the study of the course of nerve fibre bundles in the human brain. Using DTI, the local fibre orientation in each image voxel can be described by a diffusion tensor which is constructed from local measurements of diffusion coefficients along...... several directions. The measured diffusion coefficients and thereby the diffusion tensors are subject to noise, leading to possibly flawed representations of the three dimensional fibre bundles. In this paper we develop a Bayesian procedure for regularizing the diffusion tensor field, fully utilizing...
Phenomenological approach to describe logistic growth and ...
Indian Academy of Sciences (India)
2016-10-18
Oct 18, 2016 ... Gompertz function, used to describe biological growth processes undergoing atrophy or a demographic and ... recognizing the characteristic feature of a system and .... demonstrated with the help of a thought experiment by.
describing a collaborative clothing design process between
African Journals Online (AJOL)
user
ISSN 0378-5254 Journal of Family Ecology and Consumer Sciences, Vol 43, 2015. Designing success: describing a ... PROCESS BETWEEN APPRENTICE DESIGNERS AND EXPERT DESIGN .... 5 Evaluation and decisions. (a) Outcomes.
International Nuclear Information System (INIS)
Cable, J.W.
1987-01-01
The diffuse scattering of neutrons from magnetic materials provides unique and important information regarding the spatial correlations of the atoms and the spins. Such measurements have been extensively applied to magnetically ordered systems, such as the ferromagnetic binary alloys, for which the observed correlations describe the magnetic moment fluctuations associated with local environment effects. With the advent of polarization analysis, these techniques are increasingly being applied to study disordered paramagnetic systems such as the spin-glasses and the diluted magnetic semiconductors. The spin-pair correlations obtained are essential in understanding the exchange interactions of such systems. In this paper, we describe recent neutron diffuse scattering results on the atom-pair and spin-pair correlations in some of these disordered magnetic systems. 56 refs
International Nuclear Information System (INIS)
Peters, R.D.
1978-01-01
The applications of diffusion bonding at the General Electric Neutron Devices Department are briefly discussed, with particular emphasis on the gold/gold or gold/indium joints made between metallized alumina ceramic parts in the vacuum switch tube and the crystal resonator programs. Fixtures which use the differential expansion of dissimilar metals are described and compared to one that uses hydraulic pressure to apply the necessary bonding force
Sensorimotor Interference When Reasoning About Described Environments
Avraamides, Marios N.; Kyranidou, Melina-Nicole
The influence of sensorimotor interference was examined in two experiments that compared pointing with iconic arrows and verbal responding in a task that entailed locating target-objects from imagined perspectives. Participants studied text narratives describing objects at locations around them in a remote environment and then responded to targets from memory. Results revealed only minor differences between the two response modes suggesting that bodily cues do not exert severe detrimental interference on spatial reasoning from imagined perspective when non-immediate described environments are used. The implications of the findings are discussed.
International Nuclear Information System (INIS)
Habib, S.
1994-01-01
We consider a simple quantum system subjected to a classical random force. Under certain conditions it is shown that the noise-averaged Wigner function of the system follows an integro-differential stochastic Liouville equation. In the simple case of polynomial noise-couplings this equation reduces to a generalized Fokker-Planck form. With nonlinear noise injection new ''quantum diffusion'' terms rise that have no counterpart in the classical case. Two special examples that are not of a Fokker-Planck form are discussed: the first with a localized noise source and the other with a spatially modulated noise source
Hereditary Diffuse Gastric Cancer
... Hereditary Diffuse Gastric Cancer Request Permissions Hereditary Diffuse Gastric Cancer Approved by the Cancer.Net Editorial Board , 10/2017 What is hereditary diffuse gastric cancer? Hereditary diffuse gastric cancer (HDGC) is a rare ...
Stochastic GARCH dynamics describing correlations between stocks
Prat-Ortega, G.; Savel'ev, S. E.
2014-09-01
The ARCH and GARCH processes have been successfully used for modelling price dynamics such as stock returns or foreign exchange rates. Analysing the long range correlations between stocks, we propose a model, based on the GARCH process, which is able to describe the main characteristics of the stock price correlations, including the mean, variance, probability density distribution and the noise spectrum.
How Digital Native Learners Describe Themselves
Thompson, Penny
2015-01-01
Eight university students from the "digital native" generation were interviewed about the connections they saw between technology use and learning, and also their reactions to the popular press claims about their generation. Themes that emerged from the interviews were coded to show patterns in how digital natives describe themselves.…
Using fundamental equations to describe basic phenomena
DEFF Research Database (Denmark)
Jakobsen, Arne; Rasmussen, Bjarne D.
1999-01-01
When the fundamental thermodynamic balance equations (mass, energy, and momentum) are used to describe the processes in a simple refrigeration system, then one finds that the resulting equation system will have a degree of freedom equal to one. Further investigations reveal that it is the equatio...
Did goethe describe attention deficit hyperactivity disorder?
Bonazza, Sara; Scaglione, Cesa; Poppi, Massimo; Rizzo, Giovanni
2011-01-01
As early as 1846, the typical symptoms of attention deficit hyperactivity disorder (ADHD) were described by Heinrich Hoffmann (1809-1894). However, in Goethe's masterpiece Faust (1832), the character of Euphorion strongly suggests ADHD diagnosis. Copyright © 2011 S. Karger AG, Basel.
Diffusive instabilities in hyperbolic reaction-diffusion equations
Zemskov, Evgeny P.; Horsthemke, Werner
2016-03-01
We investigate two-variable reaction-diffusion systems of the hyperbolic type. A linear stability analysis is performed, and the conditions for diffusion-driven instabilities are derived. Two basic types of eigenvalues, real and complex, are described. Dispersion curves for both types of eigenvalues are plotted and their behavior is analyzed. The real case is related to the Turing instability, and the complex one corresponds to the wave instability. We emphasize the interesting feature that the wave instability in the hyperbolic equations occurs in two-variable systems, whereas in the parabolic case one needs three reaction-diffusion equations.
A methodology to describe process control requirements
International Nuclear Information System (INIS)
Carcagno, R.; Ganni, V.
1994-01-01
This paper presents a methodology to describe process control requirements for helium refrigeration plants. The SSC requires a greater level of automation for its refrigeration plants than is common in the cryogenics industry, and traditional methods (e.g., written descriptions) used to describe process control requirements are not sufficient. The methodology presented in this paper employs tabular and graphic representations in addition to written descriptions. The resulting document constitutes a tool for efficient communication among the different people involved in the design, development, operation, and maintenance of the control system. The methodology is not limited to helium refrigeration plants, and can be applied to any process with similar requirements. The paper includes examples
Generating and Describing Affective Eye Behaviors
Mao, Xia; Li, Zheng
The manner of a person's eye movement conveys much about nonverbal information and emotional intent beyond speech. This paper describes work on expressing emotion through eye behaviors in virtual agents based on the parameters selected from the AU-Coded facial expression database and real-time eye movement data (pupil size, blink rate and saccade). A rule-based approach to generate primary (joyful, sad, angry, afraid, disgusted and surprise) and intermediate emotions (emotions that can be represented as the mixture of two primary emotions) utilized the MPEG4 FAPs (facial animation parameters) is introduced. Meanwhile, based on our research, a scripting tool, named EEMML (Emotional Eye Movement Markup Language) that enables authors to describe and generate emotional eye movement of virtual agents, is proposed.
How do consumers describe wine astringency?
Vidal, Leticia; Giménez, Ana; Medina, Karina; Boido, Eduardo; Ares, Gastón
2015-12-01
Astringency is one of the most important sensory characteristics of red wine. Although a hierarchically structured vocabulary to describe the mouthfeel sensations of red wine has been proposed, research on consumers' astringency vocabulary is lacking. In this context, the aim of this work was to gain an insight on the vocabulary used by wine consumers to describe the astringency of red wine and to evaluate the influence of wine involvement on consumers' vocabulary. One hundred and twenty-five wine consumers completed and on-line survey with five tasks: an open-ended question about the definition of wine astringency, free listing the sensations perceived when drinking an astringent wine, free listing the words they would use to describe the astringency of a red wine, a CATA question with 44 terms used in the literature to describe astringency, and a wine involvement questionnaire. When thinking about wine astringency consumers freely elicited terms included in the Mouth-feel Wheel, such as dryness and harsh. The majority of the specific sub-qualities of the Mouth-feel Wheel were not included in consumer responses. Also, terms not classified as astringency descriptors were elicited (e.g. acid and bitter). Only 17 out of the 31 terms from the Mouth-feel Wheel were used by more than 10% of participants when answering the CATA question. There were no large differences in the responses of consumer segments with different wine involvement. Results from the present work suggest that most of the terms of the Mouth-feel Wheel might not be adequate to communicate the astringency characteristics of red wine to consumers. Copyright © 2015 Elsevier Ltd. All rights reserved.
Anomalous diffusion in chaotic scattering
International Nuclear Information System (INIS)
Srokowski, T.; Ploszajczak, M.
1994-01-01
The anomalous diffusion is found for peripheral collision of atomic nuclei described in the framework of the molecular dynamics. Similarly as for chaotic billiards, the long free paths are the source of the long-time correlations and the anomalous diffusion. Consequences of this finding for the energy dissipation in deep-inelastic collisions and the dynamics of fission in hot nuclei are discussed (authors). 30 refs., 2 figs
A functional language for describing reversible logic
DEFF Research Database (Denmark)
Thomsen, Michael Kirkedal
2012-01-01
Reversible logic is a computational model where all gates are logically reversible and combined in circuits such that no values are lost or duplicated. This paper presents a novel functional language that is designed to describe only reversible logic circuits. The language includes high....... Reversibility of descriptions is guaranteed with a type system based on linear types. The language is applied to three examples of reversible computations (ALU, linear cosine transformation, and binary adder). The paper also outlines a design flow that ensures garbage- free translation to reversible logic...... circuits. The flow relies on a reversible combinator language as an intermediate language....
Using neural networks to describe tracer correlations
Directory of Open Access Journals (Sweden)
D. J. Lary
2004-01-01
Full Text Available Neural networks are ideally suited to describe the spatial and temporal dependence of tracer-tracer correlations. The neural network performs well even in regions where the correlations are less compact and normally a family of correlation curves would be required. For example, the CH4-N2O correlation can be well described using a neural network trained with the latitude, pressure, time of year, and methane volume mixing ratio (v.m.r.. In this study a neural network using Quickprop learning and one hidden layer with eight nodes was able to reproduce the CH4-N2O correlation with a correlation coefficient between simulated and training values of 0.9995. Such an accurate representation of tracer-tracer correlations allows more use to be made of long-term datasets to constrain chemical models. Such as the dataset from the Halogen Occultation Experiment (HALOE which has continuously observed CH4 (but not N2O from 1991 till the present. The neural network Fortran code used is available for download.
On Redundancy in Describing Linguistic Systems
Directory of Open Access Journals (Sweden)
Vladimir Borissov Pericliev
2015-12-01
Full Text Available On Redundancy in Describing Linguistic Systems The notion of system of linguistic elements figures prominently in most post-Saussurian linguistics up to the present. A “system” is the network of the contrastive (or, distinctive features each element in the system bears to the remaining elements. The meaning (valeur of each element in the system is the set of features that are necessary and jointly sufficient to distinguish this element from all others. The paper addresses the problems of “redundancy”, i.e. the occurrence of features that are not strictly necessary in describing an element in a system. Redundancy is shown to smuggle into the description of linguistic systems, this infelicitous practice illustrated with some examples from the literature (e.g. the classical phonemic analysis of Russian by Cherry, Halle, and Jakobson, 1953. The logic and psychology of the occurrence of redundancy are briefly sketched and it is shown that, in addition to some other problems, redundancy leads to a huge and unresolvable ambiguity of descriptions of linguistic systems (the Buridan’s ass problem.
Is an eclipse described in the Odyssey?
Baikouzis, Constantino; Magnasco, Marcelo O
2008-07-01
Plutarch and Heraclitus believed a certain passage in the 20th book of the Odyssey ("Theoclymenus's prophecy") to be a poetic description of a total solar eclipse. In the late 1920s, Schoch and Neugebauer computed that the solar eclipse of 16 April 1178 B.C.E. was total over the Ionian Islands and was the only suitable eclipse in more than a century to agree with classical estimates of the decade-earlier sack of Troy around 1192-1184 B.C.E. However, much skepticism remains about whether the verses refer to this, or any, eclipse. To contribute to the issue independently of the disputed eclipse reference, we analyze other astronomical references in the Epic, without assuming the existence of an eclipse, and search for dates matching the astronomical phenomena we believe they describe. We use three overt astronomical references in the epic: to Boötes and the Pleiades, Venus, and the New Moon; we supplement them with a conjectural identification of Hermes's trip to Ogygia as relating to the motion of planet Mercury. Performing an exhaustive search of all possible dates in the span 1250-1115 B.C., we looked to match these phenomena in the order and manner that the text describes. In that period, a single date closely matches our references: 16 April 1178 B.C.E. We speculate that these references, plus the disputed eclipse reference, may refer to that specific eclipse.
Watson, E. B.; Cherniak, D. J.
1997-05-01
Oxygen diffusion in natural, non-metamict zircon was characterized under both dry and water-present conditions at temperatures ranging from 765°C to 1500°C. Dry experiments were performed at atmospheric pressure by encapsulating polished zircon samples with a fine powder of 18O-enriched quartz and annealing the sealed capsules in air. Hydrothermal runs were conducted in cold-seal pressure vessels (7-70 MPa) or a piston cylinder apparatus (400-1000 MPa) on zircon samples encapsulated with both 18O-enriched quartz and 18O water. Diffusive-uptake profiles of 18O were measured in all samples with a particle accelerator, using the 18O(p, α) 15N reaction. For dry experimental conditions at 1100-1500°C, the resulting oxygen diffusivities (24 in all) are well described by: D dry (m 2/s) = 1.33 × 10 -4exp(-53920/T) There is no suggestion of diffusive anisotropy. Under wet conditions at 925°C, oxygen diffusion shows little or no dependence upon P H 2O in the range 7-1000 MPa, and is insensitive to total pressure as well. The results of 27 wet experiments at 767-1160°C and 7-1000 MPa can be described a single Arrhenius relationship: D wet (m 2/s) = 5.5 × 10 -12exp(-25280/T) The insensitivity of oxygen diffusion to P H 2O means that applications to geologic problems can be pursued knowing only whether the system of interest was 'wet' (i.e., P H 2O > 7MPa ) or 'dry'. Under dry conditions (presumably rare in the crust), zircons are extremely retentive of their oxygen isotopic signatures, to the extent that δ 18O would be perturbed at the center of a 200 μm zircon only during an extraordinarily hot and protracted event (e.g., 65 Ma at 900°C). Under wet conditions, δ 18O may or may not be retained in the central regions of individual crystals, cores or overgrowth rims, depending upon the specific thermal history of the system.
Frameworks for understanding and describing business models
DEFF Research Database (Denmark)
Nielsen, Christian; Roslender, Robin
2014-01-01
This chapter provides in a chronological fashion an introduction to six frameworks that one can apply to describing, understanding and also potentially innovating business models. These six frameworks have been chosen carefully as they represent six very different perspectives on business models...... and in this manner “complement” each other. There are a multitude of varying frameworks that could be chosen from and we urge the reader to search and trial these for themselves. The six chosen models (year of release in parenthesis) are: • Service-Profit Chain (1994) • Strategic Systems Auditing (1997) • Strategy...... Maps (2001) • Intellectual Capital Statements (2003) • Chesbrough’s framework for Open Business Models (2006) • Business Model Canvas (2008)...
Does Guru Granth Sahib describe depression?
Kalra, Gurvinder; Bhui, Kamaldeep; Bhugra, Dinesh
2013-01-01
Sikhism is a relatively young religion, with Guru Granth Sahib as its key religious text. This text describes emotions in everyday life, such as happiness, sadness, anger, hatred, and also more serious mental health issues such as depression and psychosis. There are references to the causation of these emotional disturbances and also ways to get out of them. We studied both the Gurumukhi version and the English translation of the Guru Granth Sahib to understand what it had to say about depression, its henomenology, and religious prescriptions for recovery. We discuss these descriptions in this paper and understand its meaning within the context of clinical depression. Such knowledge is important as explicit descriptions about depression and sadness can help encourage culturally appropriate assessment and treatment, as well as promote public health through education.
Describing chaotic attractors: Regular and perpetual points
Dudkowski, Dawid; Prasad, Awadhesh; Kapitaniak, Tomasz
2018-03-01
We study the concepts of regular and perpetual points for describing the behavior of chaotic attractors in dynamical systems. The idea of these points, which have been recently introduced to theoretical investigations, is thoroughly discussed and extended into new types of models. We analyze the correlation between regular and perpetual points, as well as their relation with phase space, showing the potential usefulness of both types of points in the qualitative description of co-existing states. The ability of perpetual points in finding attractors is indicated, along with its potential cause. The location of chaotic trajectories and sets of considered points is investigated and the study on the stability of systems is shown. The statistical analysis of the observing desired states is performed. We focus on various types of dynamical systems, i.e., chaotic flows with self-excited and hidden attractors, forced mechanical models, and semiconductor superlattices, exhibiting the universality of appearance of the observed patterns and relations.
Innovation diffusion in networks : the microeconomics of percolation
Zeppini, P.; Frenken, K.; Izquierdo, L.R.
2013-01-01
We implement a diffusion model for an innovative product in a market with a structure of social relationships. Diffusion is described with a percolation approach in the price space. Percolation shows a phase transition from a diffusion to a no-diffusion regime. This has strong implications for
Innovation diffusion in networks: the microeconomics of percolation
Zeppini, P.; Frenken, K.; Izquierdo, L.R.
2013-01-01
We implement a diffusion model for an innovative product in a market with a structure of social relationships. Diffusion is described with a percolation approach in the price space. Percolation shows a phase transition from a diffusion to a no-diffusion regime. This has strong implications for
Plans should abstractly describe intended behavior
Energy Technology Data Exchange (ETDEWEB)
Pfleger, K.; Hayes-Roth, B. [Stanford Univ., CA (United States)
1996-12-31
Planning is the process of formulating a potential course of action. How courses of action (plans) produced by a planning module are represented and how they are used by execution-oriented modules of a complex agent to influence or dictate behavior are critical architectural issues. In contrast to the traditional model of plans as executable programs that dictate precise behaviors, we claim that autonomous agents inhabiting dynamic, unpredictable environments can make better use of plans that only abstractly describe their intended behavior. Such plans only influence or constrain behavior, rather than dictating it. This idea has been discussed in a variety of contexts, but it is seldom incorporated into working complex agents. Experiments involving instantiations of our Adaptive Intelligent Systems architecture in a variety of domains have demonstrated the generality and usefulness of the approach, even with our currently simple plan representation and mechanisms for plan following. The behavioral benefits include (1) robust improvisation of goal-directed behavior in response to dynamic situations, (2) ready exploitation of dynamically acquired knowledge or behavioral capabilities, and (3) adaptation based on dynamic aspects of coordinating diverse behaviors to achieve multiple goals. In addition to these run-time advantages, the approach has useful implications for the design and configuration of agents. Indeed, the core ideas of the approach are natural extensions of fundamental ideas in software engineering.
Describing and Enhancing Collaboration at the Computer
Directory of Open Access Journals (Sweden)
Ken Beatty
2002-06-01
Full Text Available Computer-based learning materials differ from classroom practice in that they seldom explicitly offer opportunities for collaboration. Despite this, students do collaborate, helping one another through the content and affordances of computer materials. But, in doing so, students meet with challenges. Paradoxically, these challenges can either inspire or discourage learning and second-language acquisition. This paper, based on research with twenty Hong Kong university students in a controlled experiment, evaluates challenges to collaboration at the computer as evidenced by discourse. The students were videotaped and their discourse transcribed and evaluated both qualitatively and quantitatively, according to a set of discourse markers created to describe collaborative, non-collaborative and ambiguous strategies. The paper begins by exploring the differences between collaboration and similar terms such as teamwork and cooperative learning then goes on to define collaboration in the context of computer-assisted learning. It ends by presenting practical suggestions for software designers, teachers and students to enhance collaboration at the computer.
Oceanic diffusion in the coastal area
International Nuclear Information System (INIS)
Rukuda, Masaaki
1980-03-01
Described in this paper is the eddy diffusion in the area off Tokai Village investigated by means of dye diffusion experiment and of oceanic observation. In order to assess the oceanic diffusion in coastal areas, improved methods effective in complex field were developed. The oceanic diffusion was separated in two groups, horizontal and vertical diffusion respectively. Both these diffusions are combined and their analysis together is difficult. The oceanic diffusion is thus considered separately. Instantaneous point release is the basis of horizontal diffusion analysis. Continuous release is then the overlap of numerous instantaneous releases. It was shown that the diffusion parameters derived from the results of diffusion experiment or oceanic observation vary widely with time and place and with sea conditions. A simple diffusion equation was developed from the equation of continuity. The results were in good agreement with seasonal mean horizontal distribution of river water in the sea area. The vertical observation in diffusion experiment is difficult and the vertical structure of oceanic condition is complex, so that the research on vertical diffusion generally is not advanced yet. With river water as the tracer, a method of estimating vertical diffusion parameters with a Gaussian model or one-dimensional model was developed. The vertical diffusion near sea bottom was numerically analized with suspended particles in seawater as the tracer. Diffusion was computed for each particle size, and by summing up the vertical distribution of beam attenuation coefficient was estimated. By comparing the results of estimation and those of observation the vertical diffusivity and the particle size distribution at sea bottom could be estimated. (author)
Diffusion archeology for diffusion progression history reconstruction.
Sefer, Emre; Kingsford, Carl
2016-11-01
Diffusion through graphs can be used to model many real-world processes, such as the spread of diseases, social network memes, computer viruses, or water contaminants. Often, a real-world diffusion cannot be directly observed while it is occurring - perhaps it is not noticed until some time has passed, continuous monitoring is too costly, or privacy concerns limit data access. This leads to the need to reconstruct how the present state of the diffusion came to be from partial diffusion data. Here, we tackle the problem of reconstructing a diffusion history from one or more snapshots of the diffusion state. This ability can be invaluable to learn when certain computer nodes are infected or which people are the initial disease spreaders to control future diffusions. We formulate this problem over discrete-time SEIRS-type diffusion models in terms of maximum likelihood. We design methods that are based on submodularity and a novel prize-collecting dominating-set vertex cover (PCDSVC) relaxation that can identify likely diffusion steps with some provable performance guarantees. Our methods are the first to be able to reconstruct complete diffusion histories accurately in real and simulated situations. As a special case, they can also identify the initial spreaders better than the existing methods for that problem. Our results for both meme and contaminant diffusion show that the partial diffusion data problem can be overcome with proper modeling and methods, and that hidden temporal characteristics of diffusion can be predicted from limited data.
Describing pediatric dysphonia with nonlinear dynamic parameters
Meredith, Morgan L.; Theis, Shannon M.; McMurray, J. Scott; Zhang, Yu; Jiang, Jack J.
2008-01-01
Objective Nonlinear dynamic analysis has emerged as a reliable and objective tool for assessing voice disorders. However, it has only been tested on adult populations. In the present study, nonlinear dynamic analysis was applied to normal and dysphonic pediatric populations with the goal of collecting normative data. Jitter analysis was also applied in order to compare nonlinear dynamic and perturbation measures. This study’s findings will be useful in creating standards for the use of nonlinear dynamic analysis as a tool to describe dysphonia in the pediatric population. Methods The study included 38 pediatric subjects (23 children with dysphonia and 15 without). Recordings of sustained vowels were obtained from each subject and underwent nonlinear dynamic analysis and percent jitter analysis. The resulting correlation dimension (D2) and percent jitter values were compared across the two groups using t-tests set at a significance level of p = 0.05. Results It was shown that D2 values covary with the presence of pathology in children. D2 values were significantly higher in dysphonic children than in normal children (p = 0.002). Standard deviations indicated a higher level of variation in normal children’s D2 values than in dysphonic children’s D2 values. Jitter analysis showed markedly higher percent jitter in dysphonic children than in normal children (p = 0.025) and large standard deviations for both groups. Conclusion This study indicates that nonlinear dynamic analysis could be a viable tool for the detection and assessment of dysphonia in children. Further investigations and more normative data are needed to create standards for using nonlinear dynamic parameters for the clinical evaluation of pediatric dysphonia. PMID:18947887
Diffusion from cylindrical waste forms
International Nuclear Information System (INIS)
Thomas, G.F.
1985-05-01
The diffusion of a single component material from a finite cylindrical waste form, initially containing a uniform concentration of the material, is investigated. Under the condition that the cylinder is maintained in a well-stirred bath, expressions for the fractional inventory leached and the leach rate are derived with allowance for the possible permanent immobilization of the diffusant through its decay to a stable product and/or its irreversible reaction with the waste form matrix. The usefulness of the reported results in nuclear waste disposal applications is emphasized. The results reported herein are related to those previously derived at Oak Ridge National Laboratory by Bell and Nestor. A numerical scheme involving the partial decoupling of nested infinite summations and the use of rapidly converging rational approximants is recommended for the efficient implementation of the expressions derived to obtain reliable estimates of the bulk diffusion constant and the rate constant describing the diffusant-waste form interaction from laboratory data
Excess Entropy and Diffusivity
Indian Academy of Sciences (India)
First page Back Continue Last page Graphics. Excess Entropy and Diffusivity. Excess entropy scaling of diffusivity (Rosenfeld,1977). Analogous relationships also exist for viscosity and thermal conductivity.
On some applications of diffusion processes for image processing
International Nuclear Information System (INIS)
Morfu, S.
2009-01-01
We propose a new algorithm inspired by the properties of diffusion processes for image filtering. We show that purely nonlinear diffusion processes ruled by Fisher equation allows contrast enhancement and noise filtering, but involves a blurry image. By contrast, anisotropic diffusion, described by Perona and Malik algorithm, allows noise filtering and preserves the edges. We show that combining the properties of anisotropic diffusion with those of nonlinear diffusion provides a better processing tool which enables noise filtering, contrast enhancement and edge preserving.
Diffusion in a liquid alloy - theories and experiments
International Nuclear Information System (INIS)
Chastang, C.
1997-01-01
Different theories concerning the calculation of diffusion coefficients in liquid metals, as well for auto as for hetero-diffusion are presented and some experimental procedures using tracer techniques in shear cells and capillary tubes are described. Diffusion curves are calculated with the TRIO-EF code. Calculated and measured values of diffusion coefficients are compared and discussed with regard to various diffusion mechanisms. Copper gadolinium mixtures have been investigated in more detail. (C.B.)
International Nuclear Information System (INIS)
Uskov, V.A.; Kondrachenko, O.E.; Kondrachenko, L.A.
1977-01-01
A phenomenological theory of multicomponent diffusion involving interaction between the components is employed to analyze how the interaction between two admixtures affects their simultaneous or consequent diffusion into a semiconductor. The theory uses the equations of multicomponent dissusion under common conditions (constant diffusion coefficients and equilibrium distribution of vacancies). The experiments are described on In and Sb simultaneous diffusion into Ge. The diffusion is performed according to the routine gas phase technology with the use of radioactive isotopes In 114 and Sb 124 . It is shown that the introduction of an additional diffusion coefficient D 12 makes it possible to simply and precisely describe the distribution of interacting admixtures in complex diffusion alloying of semiconductors
Memory effects in turbulent diffusion
International Nuclear Information System (INIS)
Zagorodny, A.G.; Weiland, J.; Wilhelmsson, H.
1993-01-01
A non-Markovian approach is proposed for the derivation of the diffusion coefficient of saturated turbulence. A memory term accounting for nonlocal coherence effects is introduced in a new attempt to describe the transition between weak and strong turbulence. The result compares favourably with recent experiments as well as mode coupling simulations of fusion plasmas. (14 refs.)
The limitation and modification of flux-limited diffusion theory
International Nuclear Information System (INIS)
Liu Chengan; Huang Wenkai
1986-01-01
The limitation of various typical flux-limited diffusion theory and advantages of asymptotic diffusion theory with time absorption constant are analyzed and compared. The conclusions are as following: Though the flux-limited problem in neutron diffusion theory are theoretically solved by derived flux-limited diffusion equation, it's going too far to limit flux due to the inappropriate assumption in deriving flux-limited diffusion equation. The asymptotic diffusion theory with time absorption constant has eliminated the above-mentioned limitation, and it is more accurate than flux-limited diffusion theory in describing neutron transport problem
On the diffusion of innovations: A structural perspective
DEFF Research Database (Denmark)
Ostoic, Antonio Rivero
2010-01-01
Working paper describing structural models for the analysis of the diffusion of innovations and mechanisms for adoption. Additionally, some milestones in the study of innovation diffusion are given and a discussion of this matter.......Working paper describing structural models for the analysis of the diffusion of innovations and mechanisms for adoption. Additionally, some milestones in the study of innovation diffusion are given and a discussion of this matter....
Integrated Temperature Sensors based on Heat Diffusion
Van Vroonhoven, C.P.L.
2015-01-01
This thesis describes the theory, design and implementation of a new class of integrated temperature sensors, based on heat diffusion. In such sensors, temperature is sensed by measuring the time it takes for heat to diffuse through silicon. An on-chip thermal delay can be determined by geometry and
Conformational Diffusion and Helix Formation Kinetics
International Nuclear Information System (INIS)
Hummer, Gerhard; Garcia, Angel E.; Garde, Shekhar
2000-01-01
The time, temperature, and sequence dependences of helix formation kinetics of fully atomistic peptide models in explicit solvent are described quantitatively by a diffusive search within the coil state with barrierless transitions into the helical state. Conformational diffusion leads to nonexponential kinetics and jump-width dependences in temperature jump experiments. (c) 2000 The American Physical Society
Diffusion and scattering in multifractal clouds
Energy Technology Data Exchange (ETDEWEB)
Lovejoy, S. [McGill Univ., Montreal, Quebec (Canada); Schertzer, D. [Universite Pierre et Marie Curie, Paris (France); Waston, B. [St. Lawrence Univ., Canton, NY (United States)] [and others
1996-04-01
This paper describes investigations of radiative properties of multifractal clouds using two different approaches. In the first, diffusion is considered by examining the scaling properties of one dimensional random walks on media with multifractal diffusivities. The second approach considers the scattering statistics associated with radiative transport.
Molecular Diffusion Coefficients: Experimental Determination and Demonstration.
Fate, Gwendolyn; Lynn, David G.
1990-01-01
Presented are laboratory methods which allow the demonstration and determination of the diffusion coefficients of compounds ranging in size from water to small proteins. Included are the procedures involving the use of a spectrometer, UV cell, triterated agar, and oxygen diffusion. Results including quantification are described. (CW)
Gas phase thermal diffusion of stable isotopes
International Nuclear Information System (INIS)
Eck, C.F.
1979-01-01
The separation of stable isotopes at Mound Facility is reviewed from a historical perspective. The historical development of thermal diffusion from a laboratory process to a separation facility that handles all the noble gases is described. In addition, elementary thermal diffusion theory and elementary cascade theory are presented along with a brief review of the uses of stable isotopes
Conformational Diffusion and Helix Formation Kinetics
Energy Technology Data Exchange (ETDEWEB)
Hummer, Gerhard [Laboratory of Chemical Physics, Building 5, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States); Garcia, Angel E. [Theoretical Biology and Biophysics Group T-10, MS K710, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Garde, Shekhar [Department of Chemical Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180 (United States)
2000-09-18
The time, temperature, and sequence dependences of helix formation kinetics of fully atomistic peptide models in explicit solvent are described quantitatively by a diffusive search within the coil state with barrierless transitions into the helical state. Conformational diffusion leads to nonexponential kinetics and jump-width dependences in temperature jump experiments. (c) 2000 The American Physical Society.
Diffusing diffusivity: Rotational diffusion in two and three dimensions
Jain, Rohit; Sebastian, K. L.
2017-06-01
We consider the problem of calculating the probability distribution function (pdf) of angular displacement for rotational diffusion in a crowded, rearranging medium. We use the diffusing diffusivity model and following our previous work on translational diffusion [R. Jain and K. L. Sebastian, J. Phys. Chem. B 120, 3988 (2016)], we show that the problem can be reduced to that of calculating the survival probability of a particle undergoing Brownian motion, in the presence of a sink. We use the approach to calculate the pdf for the rotational motion in two and three dimensions. We also propose new dimensionless, time dependent parameters, αr o t ,2 D and αr o t ,3 D, which can be used to analyze the experimental/simulation data to find the extent of deviation from the normal behavior, i.e., constant diffusivity, and obtain explicit analytical expressions for them, within our model.
Diffusion archeology for diffusion progression history reconstruction
Sefer, Emre; Kingsford, Carl
2015-01-01
Diffusion through graphs can be used to model many real-world processes, such as the spread of diseases, social network memes, computer viruses, or water contaminants. Often, a real-world diffusion cannot be directly observed while it is occurring — perhaps it is not noticed until some time has passed, continuous monitoring is too costly, or privacy concerns limit data access. This leads to the need to reconstruct how the present state of the diffusion came to be from partial d...
Diffusion in condensed matter methods, materials, models
Kärger, Jörg
2005-01-01
Diffusion as the process of particle transport due to stochastic movement is a phenomenon of crucial relevance for a large variety of processes and materials. This comprehensive, handbook- style survey of diffusion in condensed matter gives detailed insight into diffusion as the process of particle transport due to stochastic movement. Leading experts in the field describe in 23 chapters the different aspects of diffusion, covering microscopic and macroscopic experimental techniques and exemplary results for various classes of solids, liquids and interfaces as well as several theoretical concepts and models. Students and scientists in physics, chemistry, materials science, and biology will benefit from this detailed compilation.
Pressure effect on grain boundary diffusion
International Nuclear Information System (INIS)
Smirnova, E.S.; Chuvil'deev, V.N.
1997-01-01
The influence of hydrostatic pressure on grain boundary diffusion and grain boundary migration in metallic materials is theoretically investigated. The model is suggested that permits describing changes in activation energy of grain boundary self-diffusion and diffusion permeability of grain boundaries under hydrostatic pressure. The model is based on the ideas about island-type structure of grain boundaries as well as linear relationship of variations in grain boundary free volume to hydrostatic pressure value. Comparison of theoretical data with experimental ones for a number of metals and alloys (α-Zr, Sn-Ge, Cu-In with Co, In, Al as diffusing elements) shows a qualitative agreement
On Describing Human White Matter Anatomy: The White Matter Query Language
Wassermann, Demian; Makris, Nikos; Rathi, Yogesh; Shenton, Martha; Kikinis, Ron; Kubicki, Marek; Westin, Carl-Fredrik
2013-01-01
The main contribution of this work is the careful syntactical definition of major white matter tracts in the human brain based on a neuroanatomist’s expert knowledge. We present a technique to formally describe white matter tracts and to automatically extract them from diffusion MRI data. The framework is based on a novel query language with a near-to-English textual syntax. This query language allows us to construct a dictionary of anatomical definitions describing white matter tracts. The d...
Drug diffusion across skin with diffusivity spatially modulated
Montoya Arroyave, Isabel
2014-05-01
A diffusion and delivery model of a drug across the skin with diffusivity spatially modulated is formulated and solved analytically using computer algebra. The model is developed using one-dimensional diffusion equation with a diffusivity which is a function of position in the skin; with an initial condition which is describing that the drug is initially contained inside a therapeutic patch; with a boundary condition according to which the change in concentration in the patch is minimal, such that assumption of zero flux at the patch-skin interface is valid; and with other boundary condition according to which the microcirculation in the capillaries just below the dermis carries the drug molecules away from the site at a very fast rate, maintaining the inner concentration at 0. The model is solved analytically by the method of the Laplace transform, with Bromwich integral and residue theorem. The concentration profile of the drug in the skin is expressed as an infinite series of Bessel functions. The corresponding total amount of delivered drug is expressed as an infinite series of decreasing exponentials. Also, the corresponding effective time for the therapeutic patch is determined. All computations were performed using computer algebra software, specifically Maple. The analytical results obtained are important for understanding and improving currentapplications of therapeutic patches. For future research it is interesting to consider more general models of spatial modulation of the diffusivity and the possible application of other computer algebra software such as Mathematica and Maxima.
Spin diffusion in disordered organic semiconductors
Li, Ling; Gao, Nan; Lu, Nianduan; Liu, Ming; Bässler, Heinz
2015-12-01
An analytical theory for spin diffusion in disordered organic semiconductors is derived. It is based on percolation theory and variable range hopping in a disordered energy landscape with a Gaussian density of states. It describes universally the dependence of the spin diffusion on temperature, carrier density, material disorder, magnetic field, and electric field at the arbitrary magnitude of the Hubbard energy of charge pairs. It is found that, compared to the spin transport carried by carriers hopping, the spin exchange will hinder the spin diffusion process at low carrier density, even under the condition of a weak electric field. Importantly, under the influence of a bias voltage, anomalous spreading of the spin packet will lead to an abnormal temperature dependence of the spin diffusion coefficient and diffusion length. This explains the recent experimental data for spin diffusion length observed in Alq3.
Apparatus for diffusion separation
International Nuclear Information System (INIS)
Nierenberg, W.A.
1976-01-01
A diffuser separator apparatus is described which comprises a plurality of flow channels in a single stage. Each of said channels has an inlet port and an outlet port and a constant cross sectional area between said ports. At least a portion of the defining surface of each of said channels is a diffusion separation membrane, and each of said channels is a different cross sectional area. Means are provided for connecting said channels in series so that each successive channel of said series has a smaller cross sectional area than the previous channel of said series. Also provided are a source of gaseous mixture, individual means for flowing said gaseous mixture to the inlet port of each of said channels, gas receiving and analyzing means, individual means for flowing gas passing from each of said outlet ports and means for flowing gas passing through said membranes to said receiving and analyzing means, and individual means for connecting the outlet port of each channel with the inlet port of the channel having the next smaller cross sectional area
Some basic mathematical methods of diffusion theory. [emphasis on atmospheric applications
Giere, A. C.
1977-01-01
An introductory treatment of the fundamentals of diffusion theory is presented, starting with molecular diffusion and leading up to the statistical methods of turbulent diffusion. A multilayer diffusion model, designed to permit concentration and dosage calculations downwind of toxic clouds from rocket vehicles, is described. The concepts and equations of diffusion are developed on an elementary level, with emphasis on atmospheric applications.
Diffusion welding; Soudage par diffusion
Energy Technology Data Exchange (ETDEWEB)
Daniault, J; Gillet, R [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires
1969-07-01
After a brief recall of the principle, and of the advantages of the method, we give some examples of metallic bonding in a first part where we describe preliminary trials: Ta-Mo, Zr-Zr, Zr-Nb, Nb-stainless steel, Mo-stainless steel, aluminium-aluminium (A5-A5). The second part of the note is devoted to trials on construction elements: on tubular elements for bonding between Mo or Nb on one hand, and stainless steel on the other hand (We indicate in what conditions the bonding are tight and what are their mechanical strength and their resistance to thermic cycles). We indicate, in this chapter, a method to obtain radiation windows in Be welded on an element made of stainless steel. (authors) [French] pres un bref rappel du principe, et des avantages de la methode, on donne quelques exemples de liaisons metalliques dans une premiere partie qui traite d'essais preliminaires: Ta - Mo, Zr - Zr, Zr - Nb, Nb - acier inoxydable, molybdene - acier inoxydable, aluminium - aluminium (A5-A5). La deuxieme partie de la note est consacree a des essais sur elements de construction: sur des elements tabulaires, pour des liaisons entre molybdene ou niobium d'une part, et acier inoxydable d'autre part. On indique dans quelles conditions les liaisons sont etanches et quelles sont leurs resistances mecaniques et aux chocs thermiques. On indique, dans ce meme chapitre, une methode pour l'obtention de fenetres en beryllium soudees sur un support en acier inoxydable. (auteurs)
Diffusion in inhomogeneous polymer membranes
Kasargod, Sameer S.; Adib, Farhad; Neogi, P.
1995-10-01
The dual mode sorption solubility isotherms assume, and in instances Zimm-Lundberg analysis of the solubilities show, that glassy polymers are heterogeneous and that the distribution of the solute in the polymer is also inhomogeneous. Under some conditions, the heterogeneities cannot be represented as holes. A mathematical model describing diffusion in inhomogeneous polymer membranes is presented using Cahn and Hilliard's gradient theory. The fractional mass uptake is found to be proportional to the fourth root of time rather than the square root, predicted by Fickian diffusion. This type of diffusion is classified as pseudo-Fickian. The model is compared with one experimental result available. A negative value of the persistence factor is obtained and the results are interpreted.
Voutilainen, M.; Sardini, P.; Togneri, L.; Siitari-Kauppi, M.; Timonen, J.
2010-12-01
In this work an effect of rock heterogeneity on diffusion was investigated. Time domain diffusion simulations were used to compare behavior of diffusion in homogeneous and heterogeneous 3D media. Tomographic images were used as heterogeneous rock media. One altered tonalite sample from Sievi, Finland, was chosen as test case for introduced analysis procedure. Effective diffusion coefficient of tonalite sample was determined with lab-scale experiments and the same coefficient was used also for homogeneous media. Somewhat technically complicated mathematical solution for analysis of through diffusion experiment is shortly described. Computed tomography (CT) is already quite widely used in many geological, petrological, and paleontological applications when the three-dimensional (3D) structure of the material is of interest, and is an excellent method for gaining information especially about its heterogeneity, grain size, or porosity. In addition to offering means for quantitative characterization, CT provides a lot of qualitative information [1]. A through -diffusion laboratory experiment using radioactive tracer was fitted using the Time Domain Diffusion (TDD) method. This rapid particle tracking method allows simulation of the heterogeneous diffusion based on pore-scale images and local values of diffusivities [2]. As a result we found out that heterogeneity has only a small effect to diffusion coefficient and in-diffusion profile for used geometry. Also direction dependency was tested and was found to be negligible. Whereas significant difference between generally accepted value and value obtained from simulations for constant m in Archie’s law was found. [1] Voutilainen, M., Siitari-Kauppi, M., Sardini, P., and Timonen, J., (2010). On pore-space characterization of an altered tonalite by X-ray µCT and the 14C-PMMA method (in progress). [2] Sardini, P., Robinet, J., Siitari-Kauppi, M., Delay, F., and Hellmuth, K-H, (2007). On direct simulation of heterogeneous
Statistical Inference for Partially Observed Diffusion Processes
DEFF Research Database (Denmark)
Jensen, Anders Christian
This thesis is concerned with parameter estimation for multivariate diffusion models. It gives a short introduction to diffusion models, and related mathematical concepts. we then introduce the method of prediction-based estimating functions and describe in detail the application for a two......-Uhlenbeck process, while chapter eight describes the detials of an R-package that was developed in relations to the application of the estimationprocedure of chapters five and six....
Diffuse scattering of neutrons
International Nuclear Information System (INIS)
Novion, C.H. de.
1981-02-01
The use of neutron scattering to study atomic disorder in metals and alloys is described. The diffuse elastic scattering of neutrons by a perfect crystal lattice leads to a diffraction spectrum with only Bragg spreads. the existence of disorder in the crystal results in intensity and position modifications to these spreads, and above all, to the appearance of a low intensity scatter between Bragg peaks. The elastic scattering of neutrons is treated in this text, i.e. by measuring the number of scattered neutrons having the same energy as the incident neutrons. Such measurements yield information on the static disorder in the crystal and time average fluctuations in composition and atomic displacements [fr
The diffuse interstellar medium
Cox, Donald P.
1990-01-01
The last 20 years of the efforts to understand the diffuse ISM are reviewed, with recent changes of fundamental aspects being highlighted. Attention is given to the interstellar pressure and its components, the weight of the ISM, the midplane pressure contributions, and pressure contributions at 1 kpc. What velocity dispersions, cosmic ray pressure, and magnetic field pressure that can be expected for a gas in a high magnetic field environment is addressed. The intercloud medium is described, with reference to the work of Cox and Slavin (1989). Various caveats are discussed and a number of areas for future investigation are identified. Steps that could be taken toward a successful phase segregation model are discussed.
A revised multi-Fickian moisture transport model to describe non-Fickian effects in wood
DEFF Research Database (Denmark)
Frandsen, Henrik Lund; Damkilde, Lars; Svensson, Staffan
2007-01-01
This paper presents a study and a refinement of the sorption rate model in a so-called multi-Fickian or multi-phase model. This type of model describes the complex moisture transport system in wood, which consists of separate water vapor and bound-water diffusion interacting through sorption...... sorption allow a simplification of the system to be modeled by a single Fickian diffusion equation. To determine the response of the system, the sorption rate model is essential. Here the function modeling the moisture-dependent adsorption rate is investigated based on existing experiments on thin wood...
Diffusion in reactor materials
International Nuclear Information System (INIS)
Fedorov, G.B.; Smirnov, E.A.
1984-01-01
The monograph contains a brief description of the principles underlying the theory of diffusion, as well as modern methods of studying diffusion. Data on self-diffusion and diffusion of impurities in a nuclear fuel and fissionable materials (uranium, plutonium, thorium, zirconium, titanium, hafnium, niobium, molybdenum, tungsten, beryllium, etc.) is presented. Anomalous diffusion, diffusion of components, and interdiffusion in binary and ternary alloys were examined. The monograph presents the most recent reference material on diffusion. It is intended for a wide range of researchers working in the field of diffusion in metals and alloys and attempting to discover new materials for application in nuclear engineering. It will also be useful for teachers, research scholars and students of physical metallurgy
International Nuclear Information System (INIS)
Reus, K.W.
1979-01-01
This thesis is concerned with the back-diffusion method of calculating the mutual diffusion coefficient of two gases. The applicability of this method for measuring diffusion coefficients at temperatures up to 1300 K is considered. A further aim of the work was to make a contribution to the description of the interatomic potential energy of noble gases at higher energies as a function of the internuclear distance. This was achieved with the measured diffusion coefficients, especially with those for high temperatures. (Auth.)
Diffusion Under Geometrical Constraint
Ogawa, Naohisa
2014-01-01
Here we discus the diffusion of particles in a curved tube. This kind of transport phenomenon is observed in biological cells and porous media. To solve such a problem, we discuss the three dimensional diffusion equation with a confining wall forming a thinner tube. We find that the curvature appears in a effective diffusion coefficient for such a quasi-one-dimensional system. As an application to higher dimensional case, we discuss the diffusion in a curved surface with ...
HERMES: A Model to Describe Deformation, Burning, Explosion, and Detonation
Energy Technology Data Exchange (ETDEWEB)
Reaugh, J E
2011-11-22
performance, whether as a result of accident, hazard, or a fault in the detonation train. These models describe the build-up of detonation from a shock stimulus. They are generally consistent with the mesoscale picture of ignition at many small defects in the plane of the shock front and the growth of the resulting hot-spots, leading to detonation in heterogeneous explosives such as plastic-bonded explosives (PBX). The models included terms for ignition, and also for the growth of reaction as tracked by the local mass fraction of product gas, {lambda}. The growth of reaction in such models incorporates a form factor that describes the change of surface area per unit volume (specific surface area) as the reaction progresses. For unimolecular crystalline-based explosives, the form factor is consistent with the mesoscale picture of a galaxy of hot spots burning outward and eventually interacting with each other. For composite explosives and propellants, where the fuel and oxidizer are segregated, the diffusion flame at the fuel-oxidizer interface can be interpreted with a different form factor that corresponds to grains burning inward from their surfaces. The form factor influences the energy release rate, and the amount of energy released in the reaction zone. Since the 19th century, gun and cannon propellants have used perforated geometric shapes that produce an increasing surface area as the propellant burns. This helps maintain the pressure as burning continues while the projectile travels down the barrel, which thereby increases the volume of the hot gas. Interior ballistics calculations use a geometric form factor to describe the changing surface area precisely. As a result, with a suitably modified form factor, detonation models can represent burning and explosion in damaged and broken reactant. The disadvantage of such models in application to accidents is that the ignition term does not distinguish between a value of pressure that results from a shock, and the same
DEFF Research Database (Denmark)
Zhang, Chen
Diffuse ceiling ventilation is an innovative ventilation concept where the suspended ceiling serves as air diffuser to supply fresh air into the room. Compared with conventional ventilation systems, diffuse ceiling ventilation can significantly reduce or even eliminate draught risk due to the low...
Fractional diffusion equation for heterogeneous medium
International Nuclear Information System (INIS)
Polo L, M. A.; Espinosa M, E. G.; Espinosa P, G.; Del Valle G, E.
2011-11-01
The asymptotic diffusion approximation for the Boltzmann (transport) equation was developed in 1950 decade in order to describe the diffusion of a particle in an isotropic medium, considers that the particles have a diffusion infinite velocity. In this work is developed a new approximation where is considered that the particles have a finite velocity, with this model is possible to describe the behavior in an anomalous medium. According with these ideas the model was obtained from the Fick law, where is considered that the temporal term of the current vector is not negligible. As a result the diffusion equation of fractional order which describes the dispersion of particles in a highly heterogeneous or disturbed medium is obtained, i.e., in a general medium. (Author)
A Systematic Procedure to Describe Shale Gas Permeability Evolution during the Production Process
Jia, B.; Tsau, J. S.; Barati, R.
2017-12-01
Gas flow behavior in shales is complex due to the multi-physics nature of the process. Pore size reduces as the in-situ stress increases during the production process, which will reduce intrinsic permeability of the porous media. Slip flow/pore diffusion enhances gas apparent permeability, especially under low reservoir pressures. Adsorption not only increases original gas in place but also influences gas flow behavior because of the adsorption layer. Surface diffusion between free gas and adsorption phase enhances gas permeability. Pore size reduction and the adsorption layer both have complex impacts on gas apparent permeability and non-Darcy flow might be a major component in nanopores. Previously published literature is generally incomplete in terms of coupling of all these four physics with fluid flow during gas production. This work proposes a methodology to simultaneously take them into account to describe a permeability evolution process. Our results show that to fully describe shale gas permeability evolution during gas production, three sets of experimental data are needed initially: 1) intrinsic permeability under different in-situ stress, 2) adsorption isotherm under reservoir conditions and 3) surface diffusivity measurement by the pulse-decay method. Geomechanical effects, slip flow/pore diffusion, adsorption layer and surface diffusion all play roles affecting gas permeability. Neglecting any of them might lead to misleading results. The increasing in-situ stress during shale gas production is unfavorable to shale gas flow process. Slip flow/pore diffusion is important for gas permeability under low pressures in the tight porous media. They might overwhelm the geomechanical effect and enhance gas permeability at low pressures. Adsorption layer reduces the gas permeability by reducing the effective pore size, but the effect is limited. Surface diffusion increases gas permeability more under lower pressures. The total gas apparent permeability might
Thermal diffusion (1963); Diffusion thermique (1963)
Energy Technology Data Exchange (ETDEWEB)
Lemarechal, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1963-07-01
This report brings together the essential principles of thermal diffusion in the liquid and gaseous phases. The macroscopic and molecular aspects of the thermal diffusion constant are reviewed, as well as the various measurement method; the most important developments however concern the operation of the CLUSIUS and DICKEL thermo-gravitational column and its applications. (author) [French] Ce rapport rassemble les principes essentiels de la diffusion thermique en phase liquide et en phase gazeuse. Les aspects macroscopique et moleculaire de la constante de diffusion thermique sont passes en revue ainsi que ses differentes methodes de mesure; mais les developpements les plus importants concernent le fonctionnement de ls colonne thermogravitationnelle de CLUSIUS et DICKEL et ses applications. (auteur)
Fractional diffusion equations and anomalous diffusion
Evangelista, Luiz Roberto
2018-01-01
Anomalous diffusion has been detected in a wide variety of scenarios, from fractal media, systems with memory, transport processes in porous media, to fluctuations of financial markets, tumour growth, and complex fluids. Providing a contemporary treatment of this process, this book examines the recent literature on anomalous diffusion and covers a rich class of problems in which surface effects are important, offering detailed mathematical tools of usual and fractional calculus for a wide audience of scientists and graduate students in physics, mathematics, chemistry and engineering. Including the basic mathematical tools needed to understand the rules for operating with the fractional derivatives and fractional differential equations, this self-contained text presents the possibility of using fractional diffusion equations with anomalous diffusion phenomena to propose powerful mathematical models for a large variety of fundamental and practical problems in a fast-growing field of research.
Composite interlayer for diffusion bonding
International Nuclear Information System (INIS)
1976-01-01
A ductile interlayer is described, which is useful for transient liquid phase diffusion bonding of metallic articles; the interlayer consisting of a melting point depressant and a plurality of ductile lamellae which are free from carbides, aluminides and borides. The composition and fabrication of the lamellae, and the process for bonding the metallic articles, depend on the composition of the metals to be bonded, and are exemplified in the specification. (U.K.)
Diffusion in molybdenum disilicide
International Nuclear Information System (INIS)
Salamon, M.; Mehrer, H.
2005-01-01
The diffusion behaviour of the high-temperature material molybdenum disilicide (MoSi 2 ) was completely unknown until recently. In this paper we present studies of Mo self-diffusion and compare our present results with our already published studies of Si and Ge diffusion in MoSi 2 . Self-diffusion of molybdenum in monocrystalline MoSi 2 was studied by the radiotracer technique using the radioisotope 99 Mo. Deposition of the radiotracer and serial sectioning after the diffusion anneals to determine the concentration-depth profiles was performed using a sputtering device. Diffusion of Mo is a very slow process. In the entire temperature region investigated (1437 to 2173 K), the 99 Mo diffusivities in both principal directions of the tetragonal MoSi 2 crystals obey Arrhenius laws, where the diffusion perpendicular to the tetragonal axis is faster by two to three orders of magnitude than parallel to it. The activation enthalpies for diffusion perpendicular and parallel to the tetragonal axis are Q perpendicular to = 468 kJ mol -1 (4.85 eV) and Q parallel = 586 kJ mol -1 (6.07 eV), respectively. Diffusion of Si and its homologous element Ge is fast and is mediated by thermal vacancies of the Si sublattice of MoSi 2 . The diffusion of Mo is by several orders of magnitude slower than the diffusion of Si and Ge. This large difference suggests that Si and Mo diffusion are decoupled and that the diffusion of Mo likely takes place via vacancies on the Mo sublattice. (orig.)
Diffuse Esophageal leiomyomatosis: a case report
Energy Technology Data Exchange (ETDEWEB)
Sung, Dong Wook; Chang, Suk Ki; Park, Seoung jin; Yoon, Yup; Kim, Youn hwa [Kyung Hee University Hospital, Suwon (Korea, Republic of)
2000-09-01
Leiomyomas are the most common benign tumors found in the esophagus. They are mostly solitary and multiple diffuse lesions are rare, occurring in only 2.4% of cases (1). We describe the case of a 13-year-old boy with a history of Alport syndrome who complained of progressive dysphagia and postprandial vomiting, and in whom diffuse leiomyomatosis of the esophagus was diagnosed. Chest PA showed mediastinal widening, and a barium study revealed diffuse esophageal wall thickening with dilatation, and obstruction at the level of the distal esophagus. Manometry showed increased pressure in the lower esophagus, and CT demonstrated diffuse thickening of the entire esophageal wall and an intraluminal mass in the distal esophagus, Follow-up CT three years later showed further esophageal wall thickening, as well as luminal narrowing. By means of distal esophagectomy, diffuse leiomyomatosis involving the entire esophageal wall and intraluminal mass was diagnosed. (author)
Carrier illumination measurement of dopant lateral diffusion
International Nuclear Information System (INIS)
Budiarto, E.; Segovia, M.; Borden, P.; Felch, S.
2005-01-01
This paper describes the application of the carrier illumination technique to non-destructively measure the lateral diffusion of implanted dopants after annealing. Experiments to validate the feasibility of this method employed test structures with a constant line width of 300 nm and varying undoped spaces of 100-5000 nm. The test patterns were implanted with a p-type dopant and annealed in a 3 x 3 matrix. For each implant condition, the measured lateral diffusion was found to increase with annealing temperature, as expected. More interestingly, the lateral diffusion was not observed to relate to the vertical diffusion by a fixed proportionality factor, as is usually assumed. The ratio of lateral to vertical diffusion varies with annealing temperature, with a trend that depends on the implant condition
Fractal diffusion equations: Microscopic models with anomalous diffusion and its generalizations
International Nuclear Information System (INIS)
Arkhincheev, V.E.
2001-04-01
To describe the ''anomalous'' diffusion the generalized diffusion equations of fractal order are deduced from microscopic models with anomalous diffusion as Comb model and Levy flights. It is shown that two types of equations are possible: with fractional temporal and fractional spatial derivatives. The solutions of these equations are obtained and the physical sense of these fractional equations is discussed. The relation between diffusion and conductivity is studied and the well-known Einstein relation is generalized for the anomalous diffusion case. It is shown that for Levy flight diffusion the Ohm's law is not applied and the current depends on electric field in a nonlinear way due to the anomalous character of Levy flights. The results of numerical simulations, which confirmed this conclusion, are also presented. (author)
Gorgolewski, Krzysztof J.; Auer, Tibor; Calhoun, Vince D.; Craddock, R. Cameron; Das, Samir; Duff, Eugene P.; Flandin, Guillaume; Ghosh, Satrajit S.; Glatard, Tristan; Halchenko, Yaroslav O.; Handwerker, Daniel A.; Hanke, Michael; Keator, David; Li, Xiangrui; Michael, Zachary
2016-01-01
International audience; The development of magnetic resonance imaging (MRI) techniques has defined modern neuroimaging. Since its inception, tens of thousands of studies using techniques such as functional MRI and diffusion weighted imaging have allowed for the non-invasive study of the brain. Despite the fact that MRI is routinely used to obtain data for neuroscience research, there has been no widely adopted standard for organizing and describing the data collected in an imaging experiment....
Metric diffusion along foliations
Walczak, Szymon M
2017-01-01
Up-to-date research in metric diffusion along compact foliations is presented in this book. Beginning with fundamentals from the optimal transportation theory and the theory of foliations; this book moves on to cover Wasserstein distance, Kantorovich Duality Theorem, and the metrization of the weak topology by the Wasserstein distance. Metric diffusion is defined, the topology of the metric space is studied and the limits of diffused metrics along compact foliations are discussed. Essentials on foliations, holonomy, heat diffusion, and compact foliations are detailed and vital technical lemmas are proved to aide understanding. Graduate students and researchers in geometry, topology and dynamics of foliations and laminations will find this supplement useful as it presents facts about the metric diffusion along non-compact foliation and provides a full description of the limit for metrics diffused along foliation with at least one compact leaf on the two dimensions.
Water diffusion in phosphate-containing hydrogels
International Nuclear Information System (INIS)
George, K.A.; Wentrup-Byrne, E.; Hill, D.J.T.; Whittaker, A.K.
2003-01-01
An understanding of the kinetics and diffusion of liquids through polymeric hydrogels is critical for the successful design and application of these materials in biomedical field, particularly as controlled drug delivery systems. In this study, the mechanisms of water transport and parameters that describe the diffusion process in crosslinked poly(2-hydroxyethylmethacrylate-co-methyloxyethylene phosphate), poly(HEMA-co-MOEP) polymers were investigated. The copolymerisation of HEMA with MOEP was initiated by γ radiolysis with full conversion of monomer to polymer. The sorption of water into the polymers with 0 - 30 mol% MOEP was monitored gravimetrically over a period of 2 - 3 weeks. This study provided an insight into the diffusion mechanism and showed that the PHEMA hydrogel displayed concentration-independent Fickian diffusion. As the concentration of MOEP in the network increased, the diffusion rate and the rigidity of the network also increased in a linear fashion. NMR imaging was used in conjunction with the gravimetric study to elucidate the transport mechanisms, diffusion coefficients and proportionality constants governing the water diffusion in the phosphate-containing polymers. The hydrogels with 3 - 20 mol% MOEP exhibited exponential concentration-dependent Fickian diffusion and the transport mechanism in the system with 30 mol% MOEP was shown to be anomalous. The systems with greater concentrations of MOEP displayed a high degree of fracturing during water sorption and resulted in the ultimate destruction of the cylindrical geometry
A3 Subscale Diffuser Test Article Design
Saunders, G. P.
2009-01-01
This paper gives a detailed description of the design of the A3 Subscale Diffuser Test (SDT) Article Design. The subscale diffuser is a geometrically accurate scale model of the A3 altitude rocket facility. It was designed and built to support the SDT risk mitigation project located at the E3 facility at Stennis Space Center, MS (SSC) supporting the design and construction of the A3 facility at SSC. The subscale test article is outfitted with a large array of instrumentation to support the design verification of the A3 facility. The mechanical design of the subscale diffuser and test instrumentation are described here
International Nuclear Information System (INIS)
Wong, Alexander; Glaister, Jeffrey; Cameron, Andrew; Haider, Masoom
2013-01-01
Prostate cancer is one of the leading causes of cancer death in the male population. Fortunately, the prognosis is excellent if detected at an early stage. Hence, the detection and localization of prostate cancer is crucial for diagnosis, as well as treatment via targeted focal therapy. New imaging techniques can potentially be invaluable tools for improving prostate cancer detection and localization. In this study, we introduce a new form of diffusion magnetic resonance imaging called correlated diffusion imaging, where the tissue being imaged is characterized by the joint correlation of diffusion signal attenuation across multiple gradient pulse strengths and timings. By taking into account signal attenuation at different water diffusion motion sensitivities, correlated diffusion imaging can provide improved delineation between cancerous tissue and healthy tissue when compared to existing diffusion imaging modalities. Quantitative evaluation using receiver operating characteristic (ROC) curve analysis, tissue class separability analysis, and visual assessment by an expert radiologist were performed to study correlated diffusion imaging for the task of prostate cancer diagnosis. These results are compared with that obtained using T2-weighted imaging and standard diffusion imaging (via the apparent diffusion coefficient (ADC)). Experimental results suggest that correlated diffusion imaging provide improved delineation between healthy and cancerous tissue and may have potential as a diagnostic tool for cancer detection and localization in the prostate gland. A new form of diffusion magnetic resonance imaging called correlated diffusion imaging (CDI) was developed for the purpose of aiding radiologists in cancer detection and localization in the prostate gland. Preliminary results show CDI shows considerable promise as a diagnostic aid for radiologists in the detection and localization of prostate cancer
Inpainting using airy diffusion
Lorduy Hernandez, Sara
2015-09-01
One inpainting procedure based on Airy diffusion is proposed, implemented via Maple and applied to some digital images. Airy diffusion is a partial differential equation with spatial derivatives of third order in contrast with the usual diffusion with spatial derivatives of second order. Airy diffusion generates the Airy semigroup in terms of the Airy functions which can be rewritten in terms of Bessel functions. The Airy diffusion can be used to smooth an image with the corresponding noise elimination via convolution. Also the Airy diffusion can be used to erase objects from an image. We build an algorithm using the Maple package ImageTools and such algorithm is tested using some images. Our results using Airy diffusion are compared with the similar results using standard diffusion. We observe that Airy diffusion generates powerful filters for image processing which could be incorporated in the usual packages for image processing such as ImageJ and Photoshop. Also is interesting to consider the possibility to incorporate the Airy filters as applications for smartphones and smart-glasses.
Determination of the diffusion coefficient of hydrogen ion in hydrogels.
Schuszter, Gábor; Gehér-Herczegh, Tünde; Szűcs, Árpád; Tóth, Ágota; Horváth, Dezső
2017-05-17
The role of diffusion in chemical pattern formation has been widely studied due to the great diversity of patterns emerging in reaction-diffusion systems, particularly in H + -autocatalytic reactions where hydrogels are applied to avoid convection. A custom-made conductometric cell is designed to measure the effective diffusion coefficient of a pair of strong electrolytes containing sodium ions or hydrogen ions with a common anion. This together with the individual diffusion coefficient for sodium ions, obtained from PFGSE-NMR spectroscopy, allows the determination of the diffusion coefficient of hydrogen ions in hydrogels. Numerical calculations are also performed to study the behavior of a diffusion-migration model describing ionic diffusion in our system. The method we present for one particular case may be extended for various hydrogels and diffusing ions (such as hydroxide) which are relevant e.g. for the development of pH-regulated self-healing mechanisms and hydrogels used for drug delivery.
Massively parallel diffuse optical tomography
Energy Technology Data Exchange (ETDEWEB)
Sandusky, John V.; Pitts, Todd A.
2017-09-05
Diffuse optical tomography systems and methods are described herein. In a general embodiment, the diffuse optical tomography system comprises a plurality of sensor heads, the plurality of sensor heads comprising respective optical emitter systems and respective sensor systems. A sensor head in the plurality of sensors heads is caused to act as an illuminator, such that its optical emitter system transmits a transillumination beam towards a portion of a sample. Other sensor heads in the plurality of sensor heads act as observers, detecting portions of the transillumination beam that radiate from the sample in the fields of view of the respective sensory systems of the other sensor heads. Thus, sensor heads in the plurality of sensors heads generate sensor data in parallel.
Morphological inversion of complex diffusion
Nguyen, V. A. T.; Vural, D. C.
2017-09-01
Epidemics, neural cascades, power failures, and many other phenomena can be described by a diffusion process on a network. To identify the causal origins of a spread, it is often necessary to identify the triggering initial node. Here, we define a new morphological operator and use it to detect the origin of a diffusive front, given the final state of a complex network. Our method performs better than algorithms based on distance (closeness) and Jordan centrality. More importantly, our method is applicable regardless of the specifics of the forward model, and therefore can be applied to a wide range of systems such as identifying the patient zero in an epidemic, pinpointing the neuron that triggers a cascade, identifying the original malfunction that causes a catastrophic infrastructure failure, and inferring the ancestral species from which a heterogeneous population evolves.
Discrimination of thermal diffusivity
Bergmann Tiest, W.M.; Kappers, A.M.L.
2009-01-01
Materials such as wood or metal which are at equal temperatures are perceived to be of different ‘coldness’ due to differences in thermal properties, such as the thermal diffusivity. The thermal diffusivity of a material is a parameter that controls the rate with which heat is extracted from the
Diffusion Based Photon Mapping
DEFF Research Database (Denmark)
Schjøth, Lars; Fogh Olsen, Ole; Sporring, Jon
2007-01-01
. To address this problem we introduce a novel photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way we preserve the important illumination features......, while eliminating noise. We call our method diffusion based photon mapping....
Diffusion Based Photon Mapping
DEFF Research Database (Denmark)
Schjøth, Lars; Olsen, Ole Fogh; Sporring, Jon
2006-01-01
. To address this problem we introduce a novel photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way we preserve the important illumination features......, while eliminating noise. We call our method diffusion based photon mapping....
Adaptation and Cultural Diffusion.
Ormrod, Richard K.
1992-01-01
Explores the role of adaptation in cultural diffusion. Explains that adaptation theory recognizes the lack of independence between innovations and their environmental settings. Discusses testing and selection, modification, motivation, and cognition. Suggests that adaptation effects are pervasive in cultural diffusion but require a broader, more…
International Nuclear Information System (INIS)
Lemarechal, A.
1963-01-01
This report brings together the essential principles of thermal diffusion in the liquid and gaseous phases. The macroscopic and molecular aspects of the thermal diffusion constant are reviewed, as well as the various measurement method; the most important developments however concern the operation of the CLUSIUS and DICKEL thermo-gravitational column and its applications. (author) [fr
Directory of Open Access Journals (Sweden)
Matthew A. Brodsky
2012-08-01
Full Text Available Background: It is generally agreed that diffusion of botulinum toxin occurs, but the extent of the spread and its clinical importance are disputed. Many factors have been suggested to play a role but which have the most clinical relevance is a subject of much discussion.Methods: This review discusses the variables affecting diffusion, including protein composition and molecular size as well as injection factors (e.g., volume, dose, injection method. It also discusses data on diffusion from comparative studies in animal models and human clinical trials that illustrate differences between the available botulinum toxin products (onabotulinumtoxinA, abobotulinumtoxinA, incobotulinumtoxinA, and rimabotulinumtoxinB.Results: Neither molecular weight nor the presence of complexing proteins appears to affect diffusion; however, injection volume, concentration, and dose all play roles and are modifiable. Both animal and human studies show that botulinum toxin products are not interchangeable, and that some products are associated with greater diffusion and higher rates of diffusion-related adverse events than others.Discussion: Each of the botulinum toxins is a unique pharmacologic entity. A working knowledge of the different serotypes is essential to avoid unwanted diffusion-related adverse events. In addition, clinicians should be aware that the factors influencing diffusion may range from properties intrinsic to the drug to accurate muscle selection as well as dilution, volume, and dose injected.
A new model of anomalous phosphorus diffusion in silicon
International Nuclear Information System (INIS)
Budil, M.; Poetzl, H.; Stingeder, G.; Grasserbauer, M.
1989-01-01
A model is presented to describe the 'kink and tail' diffusion of phosphorus. The diffusion behaviour of phosphorus is expplained by the motion of phosphorus-interstitial and phosphorus-vacancy pairs in different charge states. The model yields the enhancement of diffusion in the tail region depending on surface concentration. Furthermore it yields the same selfdiffusion coefficient for interstitials as the gold diffusion experiments. A transformation of the diffusion equation was found to reduce the number of simulation equations. (author) 7 refs., 5 figs
Method for manufacturing nuclear radiation detector with deep diffused junction
International Nuclear Information System (INIS)
Hall, R.N.
1977-01-01
Germanium radiation detectors are manufactured by diffusing lithium into high purity p-type germanium. The diffusion is most readily accomplished from a lithium-lead-bismuth alloy at approximately 430 0 C and is monitored by a quartz half cell containing a standard composition of this alloy. Detectors having n-type cores may be constructed by converting high purity p-type germanium to n-type by a lithium diffusion and subsequently diffusing some of the lithium back out through the surface to create a deep p-n junction. Production of coaxial germanium detectors comprising deep p-n junctions by the lithium diffusion process is described
Diffusion in Coulomb crystals.
Hughto, J; Schneider, A S; Horowitz, C J; Berry, D K
2011-07-01
Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions "hop" in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter Γ=175 to Coulomb parameters up to Γ=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.
Degenerate nonlinear diffusion equations
Favini, Angelo
2012-01-01
The aim of these notes is to include in a uniform presentation style several topics related to the theory of degenerate nonlinear diffusion equations, treated in the mathematical framework of evolution equations with multivalued m-accretive operators in Hilbert spaces. The problems concern nonlinear parabolic equations involving two cases of degeneracy. More precisely, one case is due to the vanishing of the time derivative coefficient and the other is provided by the vanishing of the diffusion coefficient on subsets of positive measure of the domain. From the mathematical point of view the results presented in these notes can be considered as general results in the theory of degenerate nonlinear diffusion equations. However, this work does not seek to present an exhaustive study of degenerate diffusion equations, but rather to emphasize some rigorous and efficient techniques for approaching various problems involving degenerate nonlinear diffusion equations, such as well-posedness, periodic solutions, asympt...
New diffusion mechanism for high temperature diffusion in solids
International Nuclear Information System (INIS)
Doan, N.V.; Adda, Y.
1986-09-01
A new atomic transport mechanism in solids at high temperatures has been discovered by Molecular Dynamics computer simulation. It can be described as a ring sequence of atomic replacements induced by unstable Frenkel pairs. This transport process takes place without stable defects, the atomic migration occurring indeed by simultaneous creation and migration of unstable defects. Starting from the analysis of this mechanism in different solids at high temperature (CaF 2 , Na, Ar) and in irradiated copper by subthreshold collisions, we discuss the role of this mechanism on various diffusion controlled phenomena and also on the atomic processes of defect creation
A model to describe potential effects of chemotherapy on critical radiobiological treatments
International Nuclear Information System (INIS)
Rodríguez-Pérez, D.; Desco, M.M.; Antoranz, J.C.
2016-01-01
Although chemo- and radiotherapy can annihilate tumors on their own. they are also used in coadjuvancy: improving local effects of radiotherapy using chemotherapy as a radiosensit.izer. The effects of radiotherapy are well described by current radiobiological models. The goal of this work is to describe a discrete radiotherapy model, that has been previously used describe high radiation dose response as well as unusual radio-responses of some types of tumors (e.g. prostate cancer), to obtain a model of chemo+radiotherapy that can describe how the outcome of their combination is a more efficient removal of the tumor. Our hypothesis is that, although both treatments haven different mechanisms, both affect similar key points of cell metabolism and regulation, that lead to cellular death. Hence, we will consider a discrete model where chemotherapy may affect a fraction of the same targets destroyed by radiotherapy. Although radiotherapy reaches all cells equally, chemotherapy diffuses through a tumor attaining lower concentration in its center and higher in its surface. With our simulations we study the enhanced effect of combined therapy treatment and how it depends on the tissue critical parameters (the parameters of the lion-extensive radiobiological model), the number of “targets” aimed at by chemotherapy, and the concentration and diffusion rate of the drug inside the tumor. The results show that an equivalent, cliemo-radio-dose can be computed that allows the prediction of the lower radiation dose that causes the same effect than a radio-only treatment. (paper)
A model to describe potential effects of chemotherapy on critical radiobiological treatments
Rodríguez-Pérez, D.; Desco, M. M.; Antoranz, J. C.
2016-08-01
Although chemo- and radiotherapy can annihilate tumors on their own. they are also used in coadjuvancy: improving local effects of radiotherapy using chemotherapy as a radiosensit.izer. The effects of radiotherapy are well described by current radiobiological models. The goal of this work is to describe a discrete radiotherapy model, that has been previously used describe high radiation dose response as well as unusual radio-responses of some types of tumors (e.g. prostate cancer), to obtain a model of chemo+radiotherapy that can describe how the outcome of their combination is a more efficient removal of the tumor. Our hypothesis is that, although both treatments haven different mechanisms, both affect similar key points of cell metabolism and regulation, that lead to cellular death. Hence, we will consider a discrete model where chemotherapy may affect a fraction of the same targets destroyed by radiotherapy. Although radiotherapy reaches all cells equally, chemotherapy diffuses through a tumor attaining lower concentration in its center and higher in its surface. With our simulations we study the enhanced effect of combined therapy treatment and how it depends on the tissue critical parameters (the parameters of the lion-extensive radiobiological model), the number of “targets” aimed at by chemotherapy, and the concentration and diffusion rate of the drug inside the tumor. The results show that an equivalent, cliemo-radio-dose can be computed that allows the prediction of the lower radiation dose that causes the same effect than a radio-only treatment.
Diffuse-Interface Methods in Fluid Mechanics
Anderson, D. M.; McFadden, G. B.; Wheeler, A. A.
1997-01-01
The authors review the development of diffuse-interface models of hydrodynamics and their application to a wide variety of interfacial phenomena. The authors discuss the issues involved in formulating diffuse-interface models for single-component and binary fluids. Recent applications and computations using these models are discussed in each case. Further, the authors address issues including sharp-interface analyses that relate these models to the classical free-boundary problem, related computational approaches to describe interfacial phenomena, and related approaches describing fully-miscible fluids.
A tracer diffusion model derived from microstructure
International Nuclear Information System (INIS)
Lehikoinen, Jarmo; Muurinen, Arto; Olin, Markus
2012-01-01
Document available in extended abstract form only. Full text of publication follows: Numerous attempts have been made to explain the tracer diffusion of various solutes in compacted clays. These attempts have commonly suffered from an inability to describe the diffusion of uncharged and charged solutes with a single unified model. Here, an internally consistent approach to describing the diffusion of solutes in a heterogeneous porous medium, such as compacted bentonite, in terms of its microstructure is presented. The microstructure is taken to be represented by a succession of unit cells, which consist of two consecutive regions (Do, 1996). In the first region, the diffusion is viewed to occur in two parallel paths: one through microcrystalline units (micropores) and the other through meso-pores between the microcrystalline units. Solutes exiting these two paths are then joined together to continue diffusing through the second, disordered, region, connecting the two adjacent microcrystalline units. Adsorption (incl. co-ion exclusion) is thought to occur in the micropores, whereas meso-pores and the disordered region accommodate free species alone. Co-ions are also assumed to experience transfer resistance into and out of the micropores, which is characterized in the model by a transmission coefficient. Although the model is not new per se, its application to compacted clays has never been attempted before. It is shown that in the limit of strong adsorption, the effective diffusivity is limited from above only by the microstructural parameters of the model porous medium. As intuitive and logical as this result may appear, it has not been proven before. In the limit of vanishing disordered region, the effective diffusivity is no longer explicitly constrained by any of the model parameters. The tortuosity of the diffusion path, i.e. the quotient of the actual diffusion path length in the porous-medium coordinates and the characteristic length of the laboratory frame
Atmospheric diffusion wind tunnel with automatic measurement
Energy Technology Data Exchange (ETDEWEB)
Maki, S; Sakai, J; Murata, E
1974-01-01
A wind tunnel which permits estimates of atmospheric diffusion is described. Smoke from power plant smoke stacks, for example, can be simulated and traced to determine the manner of diffusion in the air as well as the grade of dilution. The wind tunnel is also capable of temperature controlled diffusion tests in which temperature distribution inside the wind tunnel is controlled. A minimum wind velocity of 10 cm can be obtained with accuracy within plus or minus 0.05 percent using a controlled direct current motor; diffusion tests are often made at low wind velocity. Fully automatic measurements can be obtained by using a minicomputer so that the operation and reading of the measuring instruments can be remotely controlled from the measuring chamber. (Air Pollut. Abstr.)
SNAP - a three dimensional neutron diffusion code
International Nuclear Information System (INIS)
McCallien, C.W.J.
1993-02-01
This report describes a one- two- three-dimensional multi-group diffusion code, SNAP, which is primarily intended for neutron diffusion calculations but can also carry out gamma calculations if the diffusion approximation is accurate enough. It is suitable for fast and thermal reactor core calculations and for shield calculations. SNAP can solve the multi-group neutron diffusion equations using finite difference methods. The one-dimensional slab, cylindrical and spherical geometries and the two-dimensional case are all treated as simple special cases of three-dimensional geometries. Numerous reflective and periodic symmetry options are available and may be used to reduce the number of mesh points necessary to represent the system. Extrapolation lengths can be specified at internal and external boundaries. (Author)
Theory of quantum diffusion in biased semiconductors
Bryksin, V V
2003-01-01
A general theory is developed to describe diffusion phenomena in biased semiconductors and semiconductor superlattices. It is shown that the Einstein relation is not applicable for all field strengths so that the calculation of the field-mediated diffusion coefficient represents a separate task. Two quite different diffusion contributions are identified. The first one disappears when the dipole operator commutes with the Hamiltonian. It plays an essential role in the theory of small polarons. The second contribution is obtained from a quantity that is the solution of a kinetic equation but that cannot be identified with the carrier distribution function. This is in contrast to the drift velocity, which is closely related to the distribution function. A general expression is derived for the quantum diffusion regime, which allows a clear physical interpretation within the hopping picture.
Diffusive limits for linear transport equations
International Nuclear Information System (INIS)
Pomraning, G.C.
1992-01-01
The authors show that the Hibert and Chapman-Enskog asymptotic treatments that reduce the nonlinear Boltzmann equation to the Euler and Navier-Stokes fluid equations have analogs in linear transport theory. In this linear setting, these fluid limits are described by diffusion equations, involving familiar and less familiar diffusion coefficients. Because of the linearity extant, one can carry out explicitly the initial and boundary layer analyses required to obtain asymptotically consistent initial and boundary conditions for the diffusion equations. In particular, the effects of boundary curvature and boundary condition variation along the surface can be included in the boundary layer analysis. A brief review of heuristic (nonasymptotic) diffusion description derivations is also included in our discussion
Diffusion in substitutionally disordered B2 intermetallics
International Nuclear Information System (INIS)
Belova, I.V.; Murch, G.E.
2002-01-01
In this paper, a comprehensive diffusion kinetics theory is formulated to describe seamlessly tracer and chemical diffusion in antistructurally disordered B2 intermetallics showing positive and negative deviations from stoichiometry. The theory is based around unit processes consisting of six-jump cycles that can be assisted by intrinsic and extrinsic antistructural atoms of either atomic species. The Ising alloy model is used to illustrate the formalism, but the formalism can be adapted to other models. Expressions are developed for the tracer diffusion coefficients, the phenomenological coefficients, the intrinsic diffusion coefficients, the interdiffusion coefficient and the various correlation factor components. Results for the tracer and collective correlation factors and the vacancy wind factor (in interdiffusion) are in excellent agreement with results from Monte Carlo computer simulations based around single vacancy jumps. (author)
Analysis of mercury diffusion pumps
International Nuclear Information System (INIS)
Dunn, K.A.
1991-01-01
Several mercury diffusion pump stages in the Tritium Purification process at the Savannah River Site (SRS) have been removed from service for scheduled preventive maintenance. These stages have been examined to determine if failure has occurred. Evidence of fatigue around the flange portion of the pump has been seen. In addition, erosion and cavitation inside the throat of the venturi tube and corrosion on the other surface of the venturi tube has been observed. Several measures are being examined in an attempt to improve the performance of these pumps. These measures, as well as the noted observations, are described. 4 refs
International Nuclear Information System (INIS)
Black, J.H.
1987-01-01
The author defines and discusses the nature of diffuse interstellar clouds. He discusses how they contribute to the general extinction of starlight. The atomic and molecular species that have been identified in the ultraviolet, visible, and near infrared regions of the spectrum of a diffuse cloud are presented. The author illustrates some of the practical considerations that affect absorption line observations of interstellar atoms and molecules. Various aspects of the theoretical description of diffuse clouds required for a full interpretation of the observations are discussed
Infrared diffuse interstellar bands
Galazutdinov, G. A.; Lee, Jae-Joon; Han, Inwoo; Lee, Byeong-Cheol; Valyavin, G.; Krełowski, J.
2017-05-01
We present high-resolution (R ˜ 45 000) profiles of 14 diffuse interstellar bands in the ˜1.45 to ˜2.45 μm range based on spectra obtained with the Immersion Grating INfrared Spectrograph at the McDonald Observatory. The revised list of diffuse bands with accurately estimated rest wavelengths includes six new features. The diffuse band at 15 268.2 Å demonstrates a very symmetric profile shape and thus can serve as a reference for finding the 'interstellar correction' to the rest wavelength frame in the H range, which suffers from a lack of known atomic/molecular lines.
International Nuclear Information System (INIS)
Mundy, J.N.; Rothman, S.J.; Lam, N.Q.; Nowicki, L.J.; Hoff, H.A.
1978-01-01
The lack of understanding of self-diffusion in Group VI metals together with the wide scatter in the measured values of tungsten self-diffusion has prompted the present measurements to be made over a wide temperature range (1/2Tsub(m) to Tsub(m)). The diffusion coefficients have been measured in the temperature range 1430-2630 0 C. The present measurements show non-linear Arrhenius behavior but a reliable two-exponential fit of the data should await further measurements. (Auth.)
Double diffusivity model under stochastic forcing
Chattopadhyay, Amit K.; Aifantis, Elias C.
2017-05-01
The "double diffusivity" model was proposed in the late 1970s, and reworked in the early 1980s, as a continuum counterpart to existing discrete models of diffusion corresponding to high diffusivity paths, such as grain boundaries and dislocation lines. It was later rejuvenated in the 1990s to interpret experimental results on diffusion in polycrystalline and nanocrystalline specimens where grain boundaries and triple grain boundary junctions act as high diffusivity paths. Technically, the model pans out as a system of coupled Fick-type diffusion equations to represent "regular" and "high" diffusivity paths with "source terms" accounting for the mass exchange between the two paths. The model remit was extended by analogy to describe flow in porous media with double porosity, as well as to model heat conduction in media with two nonequilibrium local temperature baths, e.g., ion and electron baths. Uncoupling of the two partial differential equations leads to a higher-ordered diffusion equation, solutions of which could be obtained in terms of classical diffusion equation solutions. Similar equations could also be derived within an "internal length" gradient (ILG) mechanics formulation applied to diffusion problems, i.e., by introducing nonlocal effects, together with inertia and viscosity, in a mechanics based formulation of diffusion theory. While being remarkably successful in studies related to various aspects of transport in inhomogeneous media with deterministic microstructures and nanostructures, its implications in the presence of stochasticity have not yet been considered. This issue becomes particularly important in the case of diffusion in nanopolycrystals whose deterministic ILG-based theoretical calculations predict a relaxation time that is only about one-tenth of the actual experimentally verified time scale. This article provides the "missing link" in this estimation by adding a vital element in the ILG structure, that of stochasticity, that takes into
Describing Earth system simulations with the Metafor CIM
Directory of Open Access Journals (Sweden)
B. N. Lawrence
2012-11-01
Full Text Available The Metafor project has developed a common information model (CIM using the ISO19100 series formalism to describe numerical experiments carried out by the Earth system modelling community, the models they use, and the simulations that result. Here we describe the mechanism by which the CIM was developed, and its key properties. We introduce the conceptual and application versions and the controlled vocabularies developed in the context of supporting the fifth Coupled Model Intercomparison Project (CMIP5. We describe how the CIM has been used in experiments to describe model coupling properties and describe the near term expected evolution of the CIM.
Diffusion between evolving interfaces
International Nuclear Information System (INIS)
Juntunen, Janne; Merikoski, Juha
2010-01-01
Diffusion in an evolving environment is studied by continuous-time Monte Carlo simulations. Diffusion is modeled by continuous-time random walkers on a lattice, in a dynamic environment provided by bubbles between two one-dimensional interfaces driven symmetrically towards each other. For one-dimensional random walkers constrained by the interfaces, the bubble size distribution dominates diffusion. For two-dimensional random walkers, it is also controlled by the topography and dynamics of the interfaces. The results of the one-dimensional case are recovered in the limit where the interfaces are strongly driven. Even with simple hard-core repulsion between the interfaces and the particles, diffusion is found to depend strongly on the details of the dynamical rules of particles close to the interfaces.
Peppin, Stephen S. L.
2009-01-01
concentrations they form a nearly rigid porous glass through which the fluid permeates. The theoretically determined pressure drop is nonlinear in the diffusion regime and linear in the permeation regime, in quantitative agreement with experimental measurements
DEFF Research Database (Denmark)
Pries-Heje, Jan; Baskerville, Richard
2014-01-01
approach. The study context is a design case in which an organization desires to diffuse its best practices across different groups. The design goal is embodied in organizational mechanisms to achieve this diffusion. The study used Theory of Planned Behavior (TPB) as a kernel theory. The artifacts...... resulting from the design were two-day training workshops conceptually anchored to TBP. The design theory was evaluated through execution of eight diffusion workshops involving three different groups in the same company. The findings indicate that the match between the practice and the context materialized...... that the behavior will be effective). These two factors were especially critical if the source context of the best practice is qualitatively different from the target context into which the organization is seeking to diffuse the best practice....
Peppin, Stephen S. L.
2009-01-01
Diffusion and permeation are discussed within the context of irreversible thermodynamics. A new expression for the generalized Stokes-Einstein equation is obtained which links the permeability to the diffusivity of a two-component solution and contains the poroelastic Biot-Willis coefficient. The theory is illustrated by predicting the concentration and pressure profiles during the filtration of a protein solution. At low concentrations the proteins diffuse independently while at higher concentrations they form a nearly rigid porous glass through which the fluid permeates. The theoretically determined pressure drop is nonlinear in the diffusion regime and linear in the permeation regime, in quantitative agreement with experimental measurements. © 2009 Walter de Gruyter, Berlin, New York.
Diffusion of hydrogen, deuterium, and tritium in niobium
International Nuclear Information System (INIS)
Matusiewicz, G.R.
1981-01-01
The diffusion of hydrogen in niobium was investigated over the temperature range 148 to 500 degrees Kelvin, using measurements of the elastic after effect caused by long range diffusion (the Gorsky Effect). Relaxation curves for pure annealed niobium were generally not of the single exponential form expected from the Gorsky Effect theory, but were described well by a sum of two exponential curves with different amplitudes and relaxation times. The effects of oxygen and nitrogen interstitials on the diffusion were studied and were not in agreement with conventional trapping models. Deuterium and tritium diffusion in niobium were also studied, and a non-classical isotope effect was observed. Hydrogen diffusion coefficients in several Nb-Ta alloys were measured, and the diffusivity in all these alloys exhibited a non-Arrhenius temperature dependence. Experimental results were compared to several models for diffusion and trapping. A model is presented which can account for the form of the relaxation curves observed in pure, annealed niobium
Directory of Open Access Journals (Sweden)
K. Banoo
1998-01-01
equation in the discrete momentum space. This is shown to be similar to the conventional drift-diffusion equation except that it is a more rigorous solution to the Boltzmann equation because the current and carrier densities are resolved into M×1 vectors, where M is the number of modes in the discrete momentum space. The mobility and diffusion coefficient become M×M matrices which connect the M momentum space modes. This approach is demonstrated by simulating electron transport in bulk silicon.
International Nuclear Information System (INIS)
Effenberger, F.; Fichtner, H.; Scherer, K.; Barra, S.; Kleimann, J.; Strauss, R. D.
2012-01-01
The spatial diffusion of cosmic rays in turbulent magnetic fields can, in the most general case, be fully anisotropic, i.e., one has to distinguish three diffusion axes in a local, field-aligned frame. We reexamine the transformation for the diffusion tensor from this local to a global frame, in which the Parker transport equation for energetic particles is usually formulated and solved. Particularly, we generalize the transformation formulae to allow for an explicit choice of two principal local perpendicular diffusion axes. This generalization includes the 'traditional' diffusion tensor in the special case of isotropic perpendicular diffusion. For the local frame, we describe the motivation for the choice of the Frenet-Serret trihedron, which is related to the intrinsic magnetic field geometry. We directly compare the old and the new tensor elements for two heliospheric magnetic field configurations, namely the hybrid Fisk and Parker fields. Subsequently, we examine the significance of the different formulations for the diffusion tensor in a standard three-dimensional model for the modulation of galactic protons. For this, we utilize a numerical code to evaluate a system of stochastic differential equations equivalent to the Parker transport equation and present the resulting modulated spectra. The computed differential fluxes based on the new tensor formulation deviate from those obtained with the 'traditional' one (only valid for isotropic perpendicular diffusion) by up to 60% for energies below a few hundred MeV depending on heliocentric distance.
Advanced manufacturing: Technology diffusion
Energy Technology Data Exchange (ETDEWEB)
Tesar, A.
1995-12-01
In this paper we examine how manufacturing technology diffuses rom the developers of technology across national borders to those who do not have the capability or resources to develop advanced technology on their own. None of the wide variety of technology diffusion mechanisms discussed in this paper are new, yet the opportunities to apply these mechanisms are growing. A dramatic increase in technology diffusion occurred over the last decade. The two major trends which probably drive this increase are a worldwide inclination towards ``freer`` markets and diminishing isolation. Technology is most rapidly diffusing from the US In fact, the US is supplying technology for the rest of the world. The value of the technology supplied by the US more than doubled from 1985 to 1992 (see the Introduction for details). History shows us that technology diffusion is inevitable. It is the rates at which technologies diffuse to other countries which can vary considerably. Manufacturers in these countries are increasingly able to absorb technology. Their manufacturing efficiency is expected to progress as technology becomes increasingly available and utilized.
International Nuclear Information System (INIS)
Dungey, J.W.
1984-01-01
The authors want to talk about future work, but first he will reply to Stan Cowley's comment on his naivety in believing in the whole story to 99% confidence in '65, when he knew about Fairfield's results. Does it matter whether you make the right judgment about theories? Yes, it does, particularly for experimentalists perhaps, but also for theorists. The work you do later depends on the judgment you've made on previous work. People have wasted a lot of time developing on insecure or even wrong foundations. Now for future work. One mild surprise the authors have had is that they haven't heard more about diffusion, in two contexts. Gordon Rostoker is yet to come and he may talk about particles getting into the magnetosphere by diffusion. Lots of noise is observed and so diffusion must happen. If time had not been short, the authors were planning to discuss in a handwaving way what sort of diffusion mechanisms one might consider. The other aspect of diffusion he was going to talk about is at the other end of things and is velocity diffusion, which is involved in anomalous resistivity
Multiphase Microfluidics The Diffuse Interface Model
2012-01-01
Multiphase flows are typically described assuming that the different phases are separated by a sharp interface, with appropriate boundary conditions. This approach breaks down whenever the lengthscale of the phenomenon that is being studied is comparable with the real interface thickness, as it happens, for example, in the coalescence and breakup of bubbles and drops, the wetting and dewetting of solid surfaces and, in general, im micro-devices. The diffuse interface model resolves these probems by assuming that all quantities can vary continuously, so that interfaces have a non-zero thickness, i.e. they are "diffuse". The contributions in this book review the theory and describe some relevant applications of the diffuse interface model for one-component, two-phase fluids and for liquid binary mixtures, to model multiphase flows in confined geometries.
Mesoscopic non-coherence as phase diffusion
International Nuclear Information System (INIS)
Milman, Perola; Davidovich, Luiz; Castin, Yvan
1997-01-01
In this work, we approach to the question whether it is possible to describe the process of non-coherence in terms of phase diffusion ψ. We will show that this can be done, for an electromagnetic field mode in a cavity interacting with a continuum of modes outside the cavity, for any value of α, where |α> is an eigenstate of the lowering operator for the harmonic oscillator. The description in terms of phase diffusion will occurs however in context of continuous observation of the field exiting the cavity. In this sense, the non-coherence process description as a quantum phase diffusion corresponds to an realization of the evolution described by the master equation, in terms of a stochastic Schroedinger equation. We will demonstrate that the average on many realizations corresponds exactly to the result obtained from the master equation
International Nuclear Information System (INIS)
Savovic, S.; Djordjevich, A.; Ristic, G.
2012-01-01
A theoretical evaluation of the properties and processes affecting the radon transport from subsurface soil into buildings is presented in this work. The solution of the relevant transport equation is obtained using the explicit finite difference method (EFDM). Results are compared with analytical steady-state solution reported in the literature. Good agreement is found. It is shown that EFDM is effective and accurate for solving the equation that describes radon diffusion, advection and decay during its transport from subsurface to buildings, which is especially important when arbitrary initial and boundary conditions are required. (authors)
Gas-induced friction and diffusion of rigid rotors
Martinetz, Lukas; Hornberger, Klaus; Stickler, Benjamin A.
2018-05-01
We derive the Boltzmann equation for the rotranslational dynamics of an arbitrary convex rigid body in a rarefied gas. It yields as a limiting case the Fokker-Planck equation accounting for friction, diffusion, and nonconservative drift forces and torques. We provide the rotranslational friction and diffusion tensors for specular and diffuse reflection off particles with spherical, cylindrical, and cuboidal shape, and show that the theory describes thermalization, photophoresis, and the inverse Magnus effect in the free molecular regime.
Aluminium and Alzheimer's disease: the science that describes the link
National Research Council Canada - National Science Library
Exley, Christopher
2001-01-01
... that has been encircled is the gene for the amyloid precursor protein. (Thanks to Walter Lukiw for supplying this information.) Aluminium and Alzheimer's Disease: The Science that Describes the LinkAluminium and Alzheimer's Disease The Science that Describes the Link Edited by Christopher Exley Birchall Centre for Inorganic Chemistry and Materials Scienc...
Type specimens of Pectinidae (Bivalvia) described by Ignaz von Born
Dijkstra, H.H.
2009-01-01
Born described in two publications (1778, 1780) the molluscs in the collection of Empress Maria Theresa (1717-1780), now in the Natural History Museum at Vienna. In this paper the Pectinidae type material is described. Ten new species were introduced of which Argopecten nucleus (Born, 1778) and
International Nuclear Information System (INIS)
Gardes, E.
2006-06-01
Proper knowledge of the diffusion rates of lead in monazite is necessary to understand the U-Th-Pb age anomalies of this mineral, which is one of the most used in geochronology after zircon. Diffusion experiments were performed in NdPO 4 monocrystals and in Nd 0.66 Ca 0.17 Th 0.17 PO 4 polycrystals from Nd 0.66 Pb 0.17 Th 0.17 PO 4 thin films to investigate Pb 2+ + Th 4+ ↔ 2 Nd 3+ and Pb 2+ ↔ Ca 2+ exchanges. Diffusion annealings were run between 1200 and 1500 Celsius degrees, at room pressure, for durations ranging from one hour to one month. The diffusion profiles were analysed using TEM (transmission electronic microscopy) and RBS (Rutherford backscattering spectroscopy). The diffusivities extracted for Pb 2+ + Th 4+ ↔ 2 Nd 3+ exchange follow an Arrhenius law with parameters E equals 509 ± 24 kJ mol -1 and log(D 0 (m 2 s -1 )) equals -3.41 ± 0.77. Preliminary data for Pb 2+ ↔ Ca 2+ exchange are in agreement with this result. The extrapolation of our data to crustal temperatures yields very slow diffusivities. For instance, the time necessary for a 50 μm grain to lose all of its lead at 800 Celsius degrees is greater than the age of the Earth. From these results and other evidence from the literature, we conclude that most of the perturbations in U-Th-Pb ages of monazite cannot be attributed to lead diffusion, but rather to interactions with fluids. (author)
Innovation and Diffusion--An Anthropological View.
du Toit, Brian M.
This chapter presents the anthropological theory of innovation and diffusion, and applies it to the problem of implementing planned change within the instructional development process. The work of Barnett and others on culture and planned culture change is described and applied to the educational system and the classroom environment. Barnett's…
Acetylene diffusion in Na-Y zeolite
Indian Academy of Sciences (India)
ideal guest molecule to start with. Here we ... In that case the incoherent scattering law, Sinc(Q, ω), alone describes the dynamics. Q(=k−k0) is the .... The results of QENS measurements to study the diffusion of acetylene gas in zeolite. Na-Y at ...
Histological characteristics of diffuse idiopathic skeletal hyperostosis
Kuperus, JS; Westerveld, L Anneloes; Rutges, Joost A; Alblas, Jacqueline; van Rijen, Mattie H; Bleys, Ronald L A W; Oner, F Cumhur; Verlaan, JJ
Diffuse idiopathic skeletal hyperostosis (DISH) is a predominantly radiographic diagnosis and histological knowledge of DISH is limited. The aim of this study was to describe the histological characteristics of DISH in the spinal column and to study the relation between DISH and intervertebral disc
Tracer diffusion study in binary alloys
International Nuclear Information System (INIS)
Bocquet, Jean-Louis
1973-01-01
The diffusional properties of dilute alloys are quite well described with 5 vacancy jump frequencies: the diffusion experiments allow as to determine only 3 jump frequency ratios. The first experiment set, found by Howard and Manning, was used in order to determine the 3 frequency ratios in the dilute Cu-Fe alloy. N.V. Doan has shown that the isotope effect measurements may be replaced by easier electromigration experiments: this new method was used with success for the dilute Ag-Zn and Ag-Cd alloys. Two effects which take place in less dilute alloys cannot be explained with the 5 frequency model, these are: the linear enhancement of solute diffusion and the departure from linear enhancement of solvent diffusion versus solute concentration. To explain these effects, we have had to take account of the influence of solute pairs on diffusion via 53 new vacancy jump frequencies. Diffusion in a concentrated alloy can be described with a quasi-chemical approach: we show that a description with 'surrounded atoms' allows the simultaneous explanation of the thermodynamical properties of the binary solid solution, the dependence of atomic jump frequencies with respect to the local concentration of the alloy. In this model, the two atomic species have a jump frequency spectrum at their disposal, which seems to greatly modify Manning's correlation analysis. (author) [fr
Diffusion Influenced Adsorption Kinetics.
Miura, Toshiaki; Seki, Kazuhiko
2015-08-27
When the kinetics of adsorption is influenced by the diffusive flow of solutes, the solute concentration at the surface is influenced by the surface coverage of solutes, which is given by the Langmuir-Hinshelwood adsorption equation. The diffusion equation with the boundary condition given by the Langmuir-Hinshelwood adsorption equation leads to the nonlinear integro-differential equation for the surface coverage. In this paper, we solved the nonlinear integro-differential equation using the Grünwald-Letnikov formula developed to solve fractional kinetics. Guided by the numerical results, analytical expressions for the upper and lower bounds of the exact numerical results were obtained. The upper and lower bounds were close to the exact numerical results in the diffusion- and reaction-controlled limits, respectively. We examined the validity of the two simple analytical expressions obtained in the diffusion-controlled limit. The results were generalized to include the effect of dispersive diffusion. We also investigated the effect of molecular rearrangement of anisotropic molecules on surface coverage.
Diffuse charge dynamics in ionic thermoelectrochemical systems
Stout, Robert F.; Khair, Aditya S.
2017-08-01
Thermoelectrics are increasingly being studied as promising electrical generators in the ongoing search for alternative energy sources. In particular, recent experimental work has examined thermoelectric materials containing ionic charge carriers; however, the majority of mathematical modeling has been focused on their steady-state behavior. Here, we determine the time scales over which the diffuse charge dynamics in ionic thermoelectrochemical systems occur by analyzing the simplest model thermoelectric cell: a binary electrolyte between two parallel, blocking electrodes. We consider the application of a temperature gradient across the device while the electrodes remain electrically isolated from each other. This results in a net voltage, called the thermovoltage, via the Seebeck effect. At the same time, the Soret effect results in migration of the ions toward the cold electrode. The charge dynamics are described mathematically by the Poisson-Nernst-Planck equations for dilute solutions, in which the ion flux is driven by electromigration, Brownian diffusion, and thermal diffusion under a temperature gradient. The temperature evolves according to the heat equation. This nonlinear set of equations is linearized in the (experimentally relevant) limit of a "weak" temperature gradient. From this, we show that the time scale on which the thermovoltage develops is the Debye time, 1 /D κ2 , where D is the Brownian diffusion coefficient of both ion species, and κ-1 is the Debye length. However, the concentration gradient due to the Soret effect develops on the bulk diffusion time, L2/D , where L is the distance between the electrodes. For thin diffuse layers, which is the condition under which most real devices operate, the Debye time is orders of magnitude less than the diffusion time. Therefore, rather surprisingly, the majority of ion motion occurs after the steady thermovoltage has developed. Moreover, the dynamics are independent of the thermal diffusion
Diffuse charge dynamics in ionic thermoelectrochemical systems.
Stout, Robert F; Khair, Aditya S
2017-08-01
Thermoelectrics are increasingly being studied as promising electrical generators in the ongoing search for alternative energy sources. In particular, recent experimental work has examined thermoelectric materials containing ionic charge carriers; however, the majority of mathematical modeling has been focused on their steady-state behavior. Here, we determine the time scales over which the diffuse charge dynamics in ionic thermoelectrochemical systems occur by analyzing the simplest model thermoelectric cell: a binary electrolyte between two parallel, blocking electrodes. We consider the application of a temperature gradient across the device while the electrodes remain electrically isolated from each other. This results in a net voltage, called the thermovoltage, via the Seebeck effect. At the same time, the Soret effect results in migration of the ions toward the cold electrode. The charge dynamics are described mathematically by the Poisson-Nernst-Planck equations for dilute solutions, in which the ion flux is driven by electromigration, Brownian diffusion, and thermal diffusion under a temperature gradient. The temperature evolves according to the heat equation. This nonlinear set of equations is linearized in the (experimentally relevant) limit of a "weak" temperature gradient. From this, we show that the time scale on which the thermovoltage develops is the Debye time, 1/Dκ^{2}, where D is the Brownian diffusion coefficient of both ion species, and κ^{-1} is the Debye length. However, the concentration gradient due to the Soret effect develops on the bulk diffusion time, L^{2}/D, where L is the distance between the electrodes. For thin diffuse layers, which is the condition under which most real devices operate, the Debye time is orders of magnitude less than the diffusion time. Therefore, rather surprisingly, the majority of ion motion occurs after the steady thermovoltage has developed. Moreover, the dynamics are independent of the thermal diffusion
Controlling chaos in dynamical systems described by maps
International Nuclear Information System (INIS)
Crispin, Y.; Marduel, C.
1994-01-01
The problem of suppressing chaotic behavior in dynamical systems is treated using a feedback control method with limited control effort. The proposed method is validated on archetypal systems described by maps, i.e. discrete-time difference equations. The method is also applicable to dynamical systems described by flows, i.e. by systems of ordinary differential equations. Results are presented for the one-dimensional logistic map and for a two-dimensional Lotka-Volterra map describing predator-prey population dynamics. It is shown that chaos can be suppressed and the system stabilized about a period-1 fixed point of the maps
Radiation induced diffusion as a method to protect surface
International Nuclear Information System (INIS)
Baumvol, I.J.R.
1980-01-01
Radiation induced diffusion forms a coating adeherent and without interface on the surface of metalic substrates. This coating improves the behaviour of metal to corrosion and abrasion. The effect of radiation induced diffusion of tin and calcium on pure iron surface is described and analyzed in this work. (author) [pt
Estimating the diffuseness of sound fields: A wavenumber analysis method
DEFF Research Database (Denmark)
Nolan, Melanie; Davy, John L.; Brunskog, Jonas
2017-01-01
The concept of a diffuse sound field is widely used in the analysis of sound in enclosures. The diffuse sound field is generally described as composed of plane waves with random phases, which wave number vectors are uniformly distributed over all angles of incidence. In this study, an interpretat...
A Simple Refraction Experiment for Probing Diffusion in Ternary Mixtures
Coutinho, Cecil A.; Mankidy, Bijith D.; Gupta, Vinay K.
2010-01-01
Diffusion is a fundamental phenomenon that is vital in many chemical processes such as mass transport in living cells, corrosion, and separations. We describe a simple undergraduate-level experiment based on Weiner's Method to probe diffusion in a ternary aqueous mixture of small molecular-weight molecules. As an illustration, the experiment…
Optimizing experimental parameters for tracking of diffusing particles
DEFF Research Database (Denmark)
Vestergaard, Christian L.
2016-01-01
We describe how a single-particle tracking experiment should be designed in order for its recorded trajectories to contain the most information about a tracked particle's diffusion coefficient. The precision of estimators for the diffusion coefficient is affected by motion blur, limited photon st...
Purulent meningitis with unusual diffusion-weighted MRI findings
International Nuclear Information System (INIS)
Abe, M.; Takayama, Y.; Yamashita, H.; Noguchi, M.; Sagoh, T.
2002-01-01
We describe unusual findings obtained by diffusion-weighted magnetic resonance imaging (MRI) in a patient with acute purulent meningitis caused by penicillin-resistant Streptococcus pneumoniae. Along cerebral convexities and the Sylvian fissure, multiple small intense lesions showed high signal intensity in these sequences. This may be the first report of diffusion-weighted in purulent meningitis
Storyboard GALILEO CRUISE SCIENCE OPPORTUNITIES describes asteroid encounters
1989-01-01
Storyboard with mosaicked image of an asteroid and entitled GALILEO CRUISE SCIENCE OPPORTUNITIES describes asteroid objectives. These objectives include: first asteroid encounter; surface geology, composition size, shape, mass; and relation of primitive bodies to meteorites.
Interculture: Some Concepts for Describing the Situation of Immigrants.
Ekstrand, Lars Henric; And Others
1981-01-01
Attempts to find new ways of describing and analyzing dynamic interactions in country of origin, host country, and immigrant community caused by migration. Analyzes linguistic models, concept of culture, emigration psychology, and identity formation. (Author/BK)
Performance of density functional theory methods to describe ...
Indian Academy of Sciences (India)
Unknown
Chemical compounds present different types of isomer- ism. When two isomers differ by ... of DFT methods to describe intramolecular hydrogen shifts. Three small ..... qualitative descriptions of intramolecular hydrogen shifts when large basis ...
International Nuclear Information System (INIS)
Evans, R.B. III; Davis, W. Jr.; Sutton, A.L. Jr.
1980-05-01
Experiments on diffusion of 137 Cs in five types of graphite were performed. The document provides a completion of the report that was started and includes a presentation of all of the diffusion data, previously unpublished. Except for data on mass transfer of 137 Cs in the Hawker-Siddeley graphite, analyses of experimental results were initiated but not completed. The mass transfer process of cesium in HS-1-1 graphite at 600 to 1000 0 C in a helium atmosphere is essentially pure diffusion wherein values of (E/epsilon) and ΔE of the equation D/epsilon = (D/epsilon) 0 exp [-ΔE/RT] are about 4 x 10 -2 cm 2 /s and 30 kcal/mole, respectively
DEFF Research Database (Denmark)
Schultz, Ulrik Pagh
2007-01-01
. Programming a modular, self-reconfigurable robot is however a complicated task: the robot is essentially a real-time, distributed embedded system, where control and communication paths often are tightly coupled to the current physical configuration of the robot. To facilitate the task of programming modular....... This approach allows the programmer to dynamically distribute behaviors throughout a robot and moreover provides a partial abstraction over the concrete physical shape of the robot. We have implemented a prototype of a distributed control diffusion system for the ATRON modular, self-reconfigurable robot......, self-reconfigurable robots, we present the concept of distributed control diffusion: distributed queries are used to identify modules that play a specific role in the robot, and behaviors that implement specific control strategies are diffused throughout the robot based on these role assignments...
DEFF Research Database (Denmark)
Zhang, Chen; Yu, Tao; Heiselberg, Per Kvols
cooling capacity, energy saving, low investment cost and low noise level; while the limitations include condensation risk and the limit on the room geometry. Furthermore, the crucial design parameters are summarized and their effects on the system performance are discussed. In addition to the stand...... is not well structured with this system. These become the motivations in developing the design guide. This design guide aims to establish a systematic understanding of diffuse ceiling ventilation and provide assistance in designing of such a system. The guide is targeted at design engineers, architects...... and manufacturers and the users of diffuse ceiling technology. The design guide introduces the principle and key characteristics of room air distribution with diffuse ceiling ventilation. It provides an overview of potential benefit and limitations of this technology. The benefits include high thermal comfort, high...
Vrentas, James S
2013-01-01
The book first covers the five elements necessary to formulate and solve mass transfer problems, that is, conservation laws and field equations, boundary conditions, constitutive equations, parameters in constitutive equations, and mathematical methods that can be used to solve the partial differential equations commonly encountered in mass transfer problems. Jump balances, Green’s function solution methods, and the free-volume theory for the prediction of self-diffusion coefficients for polymer–solvent systems are among the topics covered. The authors then use those elements to analyze a wide variety of mass transfer problems, including bubble dissolution, polymer sorption and desorption, dispersion, impurity migration in plastic containers, and utilization of polymers in drug delivery. The text offers detailed solutions, along with some theoretical aspects, for numerous processes including viscoelastic diffusion, moving boundary problems, diffusion and reaction, membrane transport, wave behavior, sedime...
Zulma Ageitos de Castellanos: Publications and status of described taxa.
Signorelli, Javier H; Urteaga, Diego; Teso, Valeria
2015-10-28
Zulma Ageitos de Castellanos was an Argentinian malacologist working in the "Facultad de Ciencias Naturales y Museo" at La Plata University where she taught invertebrate zoology between 1947 and 1990. Her scientific publications are listed in chronological order. Described genus-group and species-group taxa are listed. Information about the type locality and type material, and taxonomic remarks are also provided. Finally, type material of all described taxa was requested and, when located, illustrated.
Model checking biological systems described using ambient calculus
DEFF Research Database (Denmark)
Mardare, Radu Iulian; Priami, Corrado; Qualia, Paola
2005-01-01
Model checking biological systems described using ambient calculus. In Proc. of the second International Workshop on Computational Methods in Systems Biology (CMSB04), Lecture Notes in Bioinformatics 3082:85-103, Springer, 2005.......Model checking biological systems described using ambient calculus. In Proc. of the second International Workshop on Computational Methods in Systems Biology (CMSB04), Lecture Notes in Bioinformatics 3082:85-103, Springer, 2005....
Double porosity model to describe both permeability change and dissolution processes
International Nuclear Information System (INIS)
Niibori, Yuichi; Usui, Hideo; Chida, Taiji
2015-01-01
Cement is a practical material for constructing the geological disposal system of radioactive wastes. The dynamic behavior of both permeability change and dissolution process caused by a high pH groundwater was explained using a double porosity model assuming that each packed particle consists of the sphere-shaped aggregation of smaller particles. This model assumes two kinds of porosities between the particle clusters and between the particles, where the former porosity change mainly controls the permeability change of the bed, and the latter porosity change controls the diffusion of OH"- ions inducing the dissolution of silica. The fundamental equations consist of a diffusion equation of spherical coordinates of OH"- ions including the first-order reaction term and some equations describing the size changes of both the particles and the particle clusters with time. The change of over-all permeability of the packed bed is evaluated by Kozeny-Carman equation and the calculated radii of particle clusters. The calculated result well describes the experimental result of both permeability change and dissolution processes. (author)
Gorgolewski, Krzysztof J; Auer, Tibor; Calhoun, Vince D; Craddock, R Cameron; Das, Samir; Duff, Eugene P; Flandin, Guillaume; Ghosh, Satrajit S; Glatard, Tristan; Halchenko, Yaroslav O; Handwerker, Daniel A; Hanke, Michael; Keator, David; Li, Xiangrui; Michael, Zachary; Maumet, Camille; Nichols, B Nolan; Nichols, Thomas E; Pellman, John; Poline, Jean-Baptiste; Rokem, Ariel; Schaefer, Gunnar; Sochat, Vanessa; Triplett, William; Turner, Jessica A; Varoquaux, Gaël; Poldrack, Russell A
2016-06-21
The development of magnetic resonance imaging (MRI) techniques has defined modern neuroimaging. Since its inception, tens of thousands of studies using techniques such as functional MRI and diffusion weighted imaging have allowed for the non-invasive study of the brain. Despite the fact that MRI is routinely used to obtain data for neuroscience research, there has been no widely adopted standard for organizing and describing the data collected in an imaging experiment. This renders sharing and reusing data (within or between labs) difficult if not impossible and unnecessarily complicates the application of automatic pipelines and quality assurance protocols. To solve this problem, we have developed the Brain Imaging Data Structure (BIDS), a standard for organizing and describing MRI datasets. The BIDS standard uses file formats compatible with existing software, unifies the majority of practices already common in the field, and captures the metadata necessary for most common data processing operations.
Directory of Open Access Journals (Sweden)
R.T. DeHoff
2002-09-01
Full Text Available The phenomenological formalism, which yields Fick's Laws for diffusion in single phase multicomponent systems, is widely accepted as the basis for the mathematical description of diffusion. This paper focuses on problems associated with this formalism. This mode of description of the process is cumbersome, defining as it does matrices of interdiffusion coefficients (the central material properties that require a large experimental investment for their evaluation in three component systems, and, indeed cannot be evaluated for systems with more than three components. It is also argued that the physical meaning of the numerical values of these properties with respect to the atom motions in the system remains unknown. The attempt to understand the physical content of the diffusion coefficients in the phenomenological formalism has been the central fundamental problem in the theory of diffusion in crystalline alloys. The observation by Kirkendall that the crystal lattice moves during diffusion led Darken to develop the concept of intrinsic diffusion, i.e., atom motion relative to the crystal lattice. Darken and his successors sought to relate the diffusion coefficients computed for intrinsic fluxes to those obtained from the motion of radioactive tracers in chemically homogeneous samples which directly report the jump frequencies of the atoms as a function of composition and temperature. This theoretical connection between tracer, intrinsic and interdiffusion behavior would provide the basis for understanding the physical content of interdiffusion coefficients. Definitive tests of the resulting theoretical connection have been carried out for a number of binary systems for which all three kinds of observations are available. In a number of systems predictions of intrinsic coefficients from tracer data do not agree with measured values although predictions of interdiffusion coefficients appear to give reasonable agreement. Thus, the complete
Wu Zhuo Qun; Li Hui Lai; Zhao Jun Ning
2001-01-01
Nonlinear diffusion equations, an important class of parabolic equations, come from a variety of diffusion phenomena which appear widely in nature. They are suggested as mathematical models of physical problems in many fields, such as filtration, phase transition, biochemistry and dynamics of biological groups. In many cases, the equations possess degeneracy or singularity. The appearance of degeneracy or singularity makes the study more involved and challenging. Many new ideas and methods have been developed to overcome the special difficulties caused by the degeneracy and singularity, which
Phase transformation and diffusion
Kale, G B; Dey, G K
2008-01-01
Given that the basic purpose of all research in materials science and technology is to tailor the properties of materials to suit specific applications, phase transformations are the natural key to the fine-tuning of the structural, mechanical and corrosion properties. A basic understanding of the kinetics and mechanisms of phase transformation is therefore of vital importance. Apart from a few cases involving crystallographic martensitic transformations, all phase transformations are mediated by diffusion. Thus, proper control and understanding of the process of diffusion during nucleation, g
Diffusion equations and the time evolution of foreign exchange rates
Energy Technology Data Exchange (ETDEWEB)
Figueiredo, Annibal; Castro, Marcio T. de [Institute of Physics, Universidade de Brasília, Brasília DF 70910-900 (Brazil); Fonseca, Regina C.B. da [Department of Mathematics, Instituto Federal de Goiás, Goiânia GO 74055-110 (Brazil); Gleria, Iram, E-mail: iram@fis.ufal.br [Institute of Physics, Federal University of Alagoas, Brazil, Maceió AL 57072-900 (Brazil)
2013-10-01
We investigate which type of diffusion equation is most appropriate to describe the time evolution of foreign exchange rates. We modify the geometric diffusion model assuming a non-exponential time evolution and the stochastic term is the sum of a Wiener noise and a jump process. We find the resulting diffusion equation to obey the Kramers–Moyal equation. Analytical solutions are obtained using the characteristic function formalism and compared with empirical data. The analysis focus on the first four central moments considering the returns of foreign exchange rate. It is shown that the proposed model offers a good improvement over the classical geometric diffusion model.
Diffusion equations and the time evolution of foreign exchange rates
Figueiredo, Annibal; de Castro, Marcio T.; da Fonseca, Regina C. B.; Gleria, Iram
2013-10-01
We investigate which type of diffusion equation is most appropriate to describe the time evolution of foreign exchange rates. We modify the geometric diffusion model assuming a non-exponential time evolution and the stochastic term is the sum of a Wiener noise and a jump process. We find the resulting diffusion equation to obey the Kramers-Moyal equation. Analytical solutions are obtained using the characteristic function formalism and compared with empirical data. The analysis focus on the first four central moments considering the returns of foreign exchange rate. It is shown that the proposed model offers a good improvement over the classical geometric diffusion model.
The influence of the surface atomic structure on surface diffusion
International Nuclear Information System (INIS)
Ghaleb, Dominique
1984-03-01
This work represents the first quantitative study of the influence of the surface atomic structure on surface diffusion (in the range: 0.2 Tf up 0.5 Tf; Tf: melting temperature of the substrate). The analysis of our results on a microscopic scale shows low formation and migration energies for adatoms; we can describe the diffusion on surfaces with a very simple model. On (110) surfaces at low temperature the diffusion is controlled by the exchange mechanism; at higher temperature direct jumps of adatoms along the channels contribute also to the diffusion process. (author) [fr
Diffusion coefficient of three-dimensional Yukawa liquids
International Nuclear Information System (INIS)
Dzhumagulova, K. N.; Ramazanov, T. S.; Masheeva, R. U.
2013-01-01
The purpose of this work is an investigation of the diffusion coefficient of the dust component in complex plasma. The computer simulation of the Yukawa liquids was made on the basis of the Langevin equation, which takes into account the influence of buffer plasma on the dust particles dynamics. The Green–Kubo relation was used to calculate the diffusion coefficient. Calculations of the diffusion coefficient for a wide range of the system parameters were performed. Using obtained numerical data, we constructed the interpolation formula for the diffusion coefficient. We also show that the interpolation formula correctly describes experimental data obtained under microgravity conditions
Diffusion equations and the time evolution of foreign exchange rates
International Nuclear Information System (INIS)
Figueiredo, Annibal; Castro, Marcio T. de; Fonseca, Regina C.B. da; Gleria, Iram
2013-01-01
We investigate which type of diffusion equation is most appropriate to describe the time evolution of foreign exchange rates. We modify the geometric diffusion model assuming a non-exponential time evolution and the stochastic term is the sum of a Wiener noise and a jump process. We find the resulting diffusion equation to obey the Kramers–Moyal equation. Analytical solutions are obtained using the characteristic function formalism and compared with empirical data. The analysis focus on the first four central moments considering the returns of foreign exchange rate. It is shown that the proposed model offers a good improvement over the classical geometric diffusion model.
Diffuse uterine leiomyomatosis in a child
International Nuclear Information System (INIS)
Pai, Deepa; Coletti, Monette C.; Ladino-Torres, Maria; Caoili, Elaine; Elkins, Matthew
2012-01-01
Leiomyomas are the most common benign uterine tumor; however, this entity is relatively uncommon in the pediatric population. Although leiomyomas most commonly present as solitary uterine masses, unusual patterns of growth have been described including diffuse leiomyomatosis. In this condition, the myometrium of the uterus is symmetrically expanded by innumerable confluent leiomyomas; this pattern of growth is quite uncommon and has never been reported in a pediatric patient. This case report illustrates the imaging appearance of diffuse uterine leiomyomatosis in an otherwise healthy 16-year-old girl. (orig.)
Matrix diffusion user guide (release 2)
International Nuclear Information System (INIS)
Herbert, A.W.; Preece, T.E.
1989-04-01
This report presents an introduction to the use of the matrix diffusion option of the finite-element package NAMMU. The facilities available in the package are described; and the process of preparing the necessary input data is illustrated with an example. The matrix diffusion option of NAMMU models the transport of radionuclides in groundwater in a flow field governed by Darcy's Law. A detailed description of the mathematical model used for this option is given. The package uses the finite-element method. This allows the easy modelling of complex geological structures. (author)
Diffuse uterine leiomyomatosis in a child
Energy Technology Data Exchange (ETDEWEB)
Pai, Deepa; Coletti, Monette C.; Ladino-Torres, Maria; Caoili, Elaine [University of Michigan Health System, Department of Radiology, Section of Pediatric Radiology, Ann Arbor, MI (United States); Elkins, Matthew [University of Michigan Health System, Department of Pathology, Ann Arbor, MI (United States)
2012-01-15
Leiomyomas are the most common benign uterine tumor; however, this entity is relatively uncommon in the pediatric population. Although leiomyomas most commonly present as solitary uterine masses, unusual patterns of growth have been described including diffuse leiomyomatosis. In this condition, the myometrium of the uterus is symmetrically expanded by innumerable confluent leiomyomas; this pattern of growth is quite uncommon and has never been reported in a pediatric patient. This case report illustrates the imaging appearance of diffuse uterine leiomyomatosis in an otherwise healthy 16-year-old girl. (orig.)
International Nuclear Information System (INIS)
Chan, J.H.M.; Tsui, E.Y.K.; Yuen, M.K.; Peh, W.C.G.; Fong, D.; Fok, K.F.; Leung, K.M.; Fung, K.K.L.
2003-01-01
Myelinated axons of white matter demonstrate prominent directional differences in water diffusion. We performed diffusion-weighted imaging on ten patients with head injury to explore the feasibility of using water diffusion anisotropy for quantitating diffuse axonal injury. We showed significant decrease in diffusion anisotropy indices in areas with or without signal abnormality on T2 and T2*-weighted images. We conclude that the water diffusion anisotropy index a potentially useful, sensitive and quantitative way of diagnosing and assessing patients with diffuse axonal injury. (orig.)
Diffusion and sorption properties of radionuclides in compacted bentonite
Energy Technology Data Exchange (ETDEWEB)
Yu Ji-Wei; Neretnieks, I. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Chemical Engineering and Technology
1997-07-01
In this report, recent studies on sorption and diffusion of radionuclides in compacted bentonite have been reviewed. The sorption distribution coefficient and diffusion coefficient data obtained from experiments in the literature have been compiled. Based on these experimental data and the report SKB-TR--91-16 (Brandberg and Skagius, 1991), this report proposes a set of sorption distribution coefficient and diffusion coefficient values for modelling purpose for safety analysis of nuclear waste repositories. The variability and uncertainty of the diffusivity data span somewhat more than an order or magnitude up and down. Most of the nuclides have an effective diffusivity in around 10{sup -10} m{sup 2}/s. Ion exclusion effects are observed for C, Cl and for Tc in oxidizing waters. Effective diffusivities are nearly tow orders of magnitude lower for these elements and of the order of 10{sup -12} m{sup 2}/s. Surface diffusion effects are found for Cs, Ni, Pa, Pb, Ra, Sn, Sr and Zr. Effective diffusivities for these elements are of the order of 10{sup -8} m{sup 2}/s. The surface diffusion effect should decrease in saline waters which is seen for Cs and Sr where there are data available. It is also deemed that Ra will have this effect because of its similarity with Sr. The other nuclides should also show this decrease but no data is available. Sorption and diffusion mechanisms in compacted bentonite are discussed in the report. In highly compacted bentonite, sorption and hence its distribution coefficient is not well defined, and a pore diffusion coefficient or a surface diffusion coefficient is not well defined either. Therefore, an apparent diffusion coefficient and a total concentration gradient should be more relevant in describing the diffusion process in compacted bentonite. 99 refs.
Anomalous diffusion spreads its wings
Energy Technology Data Exchange (ETDEWEB)
Klafter, J. [School of Chemistry, Tel Aviv University, Tel-Aviv (Israel)]. E-mail: klafter@post.tau.ac.il; Sokolov, I.M. [Institute of Physics, Humboldt University, Berlin (Germany)]. E-mail: igor.sokolov@physik.hu-berlin.de
2005-08-01
An increasing number of natural phenomena do not fit into the relatively simple description of diffusion developed by Einstein a century ago. As all of us are no doubt aware, this year has been declared 'world year of physics' to celebrate the three remarkable breakthroughs made by Albert Einstein in 1905. However, it is not so well known that Einstein's work on Brownian motion - the random motion of tiny particles first observed and investigated by the botanist Robert Brown in 1827 - has been cited more times in the scientific literature than his more famous papers on special relativity and the quantum nature of light. In a series of publications that included his doctoral thesis, Einstein derived an equation for Brownian motion from microscopic principles - a feat that ultimately enabled Jean Perrin and others to prove the existence of atoms (see 'Einstein's random walk' Physics World January pp19-22). Einstein was not the only person thinking about this type of problem. The 27 July 1905 issue of Nature contained a letter with the title 'The problem of the random walk' by the British statistician Karl Pearson, who was interested in the way that mosquitoes spread malaria, which he showed was described by the well-known diffusion equation. As such, the displacement of a mosquito from its initial position is proportional to the square root of time, and the distribution of the positions of many such 'random walkers' starting from the same origin is Gaussian in form. The random walk has since turned out to be intimately linked to Einstein's work on Brownian motion, and has become a major tool for understanding diffusive processes in nature. (U.K.)
Turbulent Evolution of a Plasma Described Through Classical Mechanics Only
International Nuclear Information System (INIS)
Escande, D.F.; Elskens, Y.
2003-01-01
For the first time an old dream of the XIXth century comes true: the non trivial evolution of a macroscopic many-body system is described through classical mechanics only. This is done for the relaxation of a warm electron beam in a plasma, which results in the generation of Langmuir turbulence and in the formation of a plateau in the velocity distribution function of the electrons. Our derivation starts from the hamiltonian describing the one-dimensional N-body system corresponding to the beam and plasma bulk electrons in electrostatic interaction. For such a system, the dynamics can be reduced to the resonant interaction of M Langmuir waves with N'( > 1 Langmuir waves with N' >> 1 beam particles. This yields the proof of the classical quasilinear equations describing the coupled evolution of the wave spectrum and of the beam velocity distribution function in the strongly nonlinear regime where their validity is the matter of a longstanding controversy
Quantum entropy of systems described by non-Hermitian Hamiltonians
International Nuclear Information System (INIS)
Sergi, Alessandro; Zloshchastiev, Konstantin G
2016-01-01
We study the quantum entropy of systems that are described by general non-Hermitian Hamiltonians, including those which can model the effects of sinks or sources. We generalize the von Neumann entropy to the non-Hermitian case and find that one needs both the normalized and non-normalized density operators in order to properly describe irreversible processes. It turns out that such a generalization monitors the onset of disorder in quantum dissipative systems. We give arguments for why one can consider the generalized entropy as the informational entropy describing the flow of information between the system and the bath. We illustrate the theory by explicitly studying few simple models, including tunneling systems with two energy levels and non-Hermitian detuning. (paper: quantum statistical physics, condensed matter, integrable systems)
Diffusion tensor and diffusion weighted imaging. Pictorial mathematics
Energy Technology Data Exchange (ETDEWEB)
Nakada, Tsutomu [California Univ., Davis, CA (United States)
1995-06-01
A new imaging algorithm for the treatment of a second order apparent diffusion tensor, D{sub app}{sup {xi}} is described. The method calls for only mathematics of images (pictorial mathematics) without necessity of eigenvalues/eigenvectors estimation. Nevertheless, it is capable of extracting properties of D{sub app}{sup {xi}} invariant to observation axes. While trace image is an example of images weighted by invariance of the tensor matrix, three dimensional anisotropy (3DAC) contrast represents the imaging method making use to anisotropic direction of tensor ellipsoid producing color coded contrast of exceptionally high anatomic resolution. Contrary to intuition, the processes require only a simple algorithm directly applicable to clinical magnetic resonance imaging (MRI). As a contrast method which precisely represents physical characteristics of a target tissue, invariant D{sub app}{sup {xi}} images produced by pictorial mathematics possess significant potential for a number of biological and clinical applications. (author).
Algorithm describing pressure distribution of non-contact TNT explosion
Directory of Open Access Journals (Sweden)
Radosław Kiciński
2014-12-01
Full Text Available [b]Abstract[/b]. The aim of this study is to develop a computational algorithm, describing the shock wave pressure distribution in the space induced by non-contact TNT explosion. The procedure describes pressure distribution on a damp surface of the hull. Simulations have been carried out using Abaqus/CAE. The study also shows the pressure waveform descriptions provided by various authors and presents them in charts. The formulated conclusions convince efficiency of the algorithm application.[b]Keywords:[/b] Underwater explosion, shock wave, CAE, TNT, Kobben class submarine
Use of conformal mapping to describe MHD wave propagation
International Nuclear Information System (INIS)
Bulanov, S.V.; Pegoraro, F.
1993-01-01
A method is proposed for finding explicit exact solutions of the magnetohydrodynamic equations describing the propagation of magnetoacoustic waves in a plasma in a magnetic potential that depends on two spatial coordinates. This method is based on the use of conformal mappings to transform the wave equation into an equation describing the propagation of waves in a uniform magnetic field. The basic properties of magnetoacoustic and Alfven waves near the critical points, magnetic separatrices, and in configuration with magnetic islands are discussed. Expressions are found for the dimensionless parameters which determine the relative roles of the plasma pressure, nonlinearity, and dissipation near the critical points. 30 refs
Sack, Jeff
2005-01-01
OsmoBeaker is a CD-ROM designed to enhance the learning of diffusion and osmosis by presenting interactive experimentation to the student. The software provides several computer simulations that take the student through different scenarios with cells, having different concentrations of solutes in them.
Diffusion Based Photon Mapping
DEFF Research Database (Denmark)
Schjøth, Lars; Sporring, Jon; Fogh Olsen, Ole
2008-01-01
. To address this problem, we introduce a photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way, we preserve important illumination features, while...
Bronnen van diffuse bodembelasting
Lijzen JPA; Ekelenkamp A; LBG; DGM/BO
1995-01-01
The aim of this study was to support the policy on preventive soil protection with information on the diffuse (non-local) emissions to soil and the influence on future soil quality. This study is related to inventories on (potential) sources of local soil pollution (e.g. industrial areas,
Energy Technology Data Exchange (ETDEWEB)
Mubarak, A S
1991-12-31
Rutherford backscattering spectromertry technique (RBS) was used to characterize and investigate the depth distribution profiles of Ca-impurities of Ca-doped soda-time glass. The purposely added Ca-impurities were introduced inti the glass matrix by a normal ion exchange diffusion process. The measurements and analysis were performed using 2 MeV {sup 2}He{sup +} ions supplied from the University of Jordan Van de Graff acceierator (JOVAG). The normalized concetration versus depth profile distributions for the Ca-imourities were determined, both theoretically and experimentally. The theoretical treatment was carried out by setting up and soiving the diffusion equation under the conditions of the experiment. The resulting profiles are characterized by a compiementary error function. the theoretical treeatment was extended to include the various methods of enhancing the diffusion process, e.g. using an electric field. The diffusion coefficient, assumed constant, of the Ca-impurities exchanged in the soda-lime glass was determined to be 1.23 x 10{sup 13} cm{sup 2}/s. A comparison between theoretically and experimentally determined profiles is made and commented at, where several conclusions are drawn and suggestions for future work are mentioned. (author). 38 refs., 21 figs., 10 Tabs.
DEFF Research Database (Denmark)
Schulz, Alexander
2015-01-01
is currently matter of discussion, called passive symplasmic loading. Based on the limited material available, this review compares the different loading modes and suggests that diffusion is the driving force in apoplasmic loaders, while bulk flow plays an increasing role in plants having a continuous...
Multienergy anomalous diffuse scattering
Czech Academy of Sciences Publication Activity Database
Kopecký, Miloš; Fábry, Jan; Kub, Jiří; Lausi, A.; Busetto, E.
2008-01-01
Roč. 100, č. 19 (2008), 195504/1-195504/4 ISSN 0031-9007 R&D Projects: GA AV ČR IAA100100529 Institutional research plan: CEZ:AV0Z10100523 Keywords : diffuse scattering * x-rays * structure determination Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.180, year: 2008
DEFF Research Database (Denmark)
Zhang, Chen; Yu, Tao; Heiselberg, Per Kvols
with conventional ventilation systems (mixing or displacement ventilation), diffuse ceiling ventilation can significantly reduce or even eliminate draught risk in the occupied zone. Moreover, this ventilation system presents a promising opportunity for energy saving, because of the low pressure loss, extended free...
DEFF Research Database (Denmark)
Zhang, Chen; Heiselberg, Per; Nielsen, Peter V.
2014-01-01
As a novel air distribution system, diffuse ceiling ventilation combines the suspended acoustic ceiling with ventilation supply. Due to the low-impulse supply from the large ceiling area, the system does not generate draught when supplying cold air. However, heat sources play an important role...
Pelleg, Joshua
2016-01-01
This textbook provides an introduction to changes that occur in solids such as ceramics, mainly at high temperatures, which are diffusion controlled, as well as presenting research data. Such changes are related to the kinetics of various reactions such as precipitation, oxidation and phase transformations, but are also related to some mechanical changes, such as creep. The book is composed of two parts, beginning with a look at the basics of diffusion according to Fick's Laws. Solutions of Fick’s second law for constant D, diffusion in grain boundaries and dislocations are presented along with a look at the atomistic approach for the random motion of atoms. In the second part, the author discusses diffusion in several technologically important ceramics. The ceramics selected are monolithic single phase ones, including: A12O3, SiC, MgO, ZrO2 and Si3N4. Of these, three refer to oxide ceramics (alumina, magnesia and zirconia). Carbide based ceramics are represented by the technologically very important Si-ca...
Final report [on solving the multigroup diffusion equations
International Nuclear Information System (INIS)
Birkhoff, G.
1975-01-01
Progress achieved in the development of variational methods for solving the multigroup neutron diffusion equations is described. An appraisal is made of the extent to which improved variational methods could advantageously replace difference methods currently used
Modeling dendrite density from magnetic resonance diffusion measurements
DEFF Research Database (Denmark)
Jespersen, Sune Nørhøj; Kroenke, CD; Østergaard, Leif
2007-01-01
in this model: (i) the dendrites and axons, which are modeled as long cylinders with two diffusion coefficients, parallel (DL) and perpendicular (DT) to the cylindrical axis, and (ii) an isotropic monoexponential diffusion component describing water diffusion within and across all other structures, i.......e., in extracellular space and glia cells. The model parameters are estimated from 153 diffusion-weighted images acquired from a formalin-fixed baboon brain. A close correspondence between the data and the signal model is found, with the model parameters consistent with literature values. The model provides......Diffusion-weighted imaging (DWI) provides a noninvasive tool to probe tissue microstructure. We propose a simplified model of neural cytoarchitecture intended to capture the essential features important for water diffusion as measured by NMR. Two components contribute to the NMR signal...
Diffusion Maps for Multimodal Registration
Directory of Open Access Journals (Sweden)
Gemma Piella
2014-06-01
Full Text Available Multimodal image registration is a difficult task, due to the significant intensity variations between the images. A common approach is to use sophisticated similarity measures, such as mutual information, that are robust to those intensity variations. However, these similarity measures are computationally expensive and, moreover, often fail to capture the geometry and the associated dynamics linked with the images. Another approach is the transformation of the images into a common space where modalities can be directly compared. Within this approach, we propose to register multimodal images by using diffusion maps to describe the geometric and spectral properties of the data. Through diffusion maps, the multimodal data is transformed into a new set of canonical coordinates that reflect its geometry uniformly across modalities, so that meaningful correspondences can be established between them. Images in this new representation can then be registered using a simple Euclidean distance as a similarity measure. Registration accuracy was evaluated on both real and simulated brain images with known ground-truth for both rigid and non-rigid registration. Results showed that the proposed approach achieved higher accuracy than the conventional approach using mutual information.
Polymer diffusion in the interphase between surface and solution.
Weger, Lukas; Weidmann, Monika; Ali, Wael; Hildebrandt, Marcus; Gutmann, Jochen Stefan; Hoffmann-Jacobsen, Kerstin
2018-05-22
Total internal reflection fluorescence correlation spectroscopy (TIR-FCS) is applied to study the self-diffusion of polyethylene glycol solutions in the presence of weakly attractive interfaces. Glass coverslips modified with aminopropyl- and propyl-terminated silanes are used to study the influence of solid surfaces on polymer diffusion. A model of three phases of polymer diffusion allows to describe the experimental fluorescence autocorrelation functions. Besides the two-dimensional diffusion of adsorbed polymer on the substrate and three-dimensional free diffusion in bulk solution, a third diffusion time scale is observed with intermediate diffusion times. This retarded three-dimensional diffusion in solution is assigned to long range effects of solid surfaces on diffusional dynamics of polymers. The respective diffusion constants show Rouse scaling (D~N -1 ) indicating a screening of hydrodynamic interactions by the presence of the surface. Hence, the presented TIR-FCS method proves to be a valuable tool to investigate the effect of surfaces on polymer diffusion beyond the first adsorbed polymer layer on the 100 nm length scale.
Real depletion in nodal diffusion codes
International Nuclear Information System (INIS)
Petkov, P.T.
2002-01-01
The fuel depletion is described by more than one hundred fuel isotopes in the advanced lattice codes like HELIOS, but only a few fuel isotopes are accounted for even in the advanced steady-state diffusion codes. The general assumption that the number densities of the majority of the fuel isotopes depend only on the fuel burnup is seriously in error if high burnup is considered. The real depletion conditions in the reactor core differ from the asymptotic ones at the stage of lattice depletion calculations. This study reveals which fuel isotopes should be explicitly accounted for in the diffusion codes in order to predict adequately the real depletion effects in the core. A somewhat strange conclusion is that if the real number densities of the main fissionable isotopes are not explicitly accounted for in the diffusion code, then Sm-149 should not be accounted for either, because the net error in k-inf is smaller (Authors)
Heavy water leak detection using diffusion sampler
International Nuclear Information System (INIS)
Joshi, M.L.; Hussain, S.A.
1990-01-01
In the Pressurrised Heavy Water Reactors (PHWRs) detection of the sources of heavy water leaks is importent both for the purpose of radiation hazard control as well as for the reduction of escape/loss of heavy water which, is an expensive nuclear material. This paper describes an application of tritium diffusion sampler for heavy water leak detection. The diffusion sampler comprises an usual tritium counting glass vial with a special orifice. The counting vial has water vapour, deficient in HTO concentration. The HTO present outside diffuses in the vial through the orifice, gets exchanged with water of the wet filter paper kept at the bottom and the moisture in the vial atmosphere which has HTO concentration lower than that outside. This results in continuation of net movement of HTO in the vial. The exchanged tritium is counted in liquid scintillation spectrometer. The method has a sensitivity of 10000 dpm/DAC-h. (author). 2 figs., 2 ta bs
Lithium diffusion in silver vanadium oxide
International Nuclear Information System (INIS)
Takeuchi, E.S.; Thiebolt, W.C. III
1989-01-01
Lithium/silver vanadium oxide (SVO) batteries have been developed to power implantable devices. The voltage of Li/SVO cells decreases with discharge allowing state of charge assessment by accurate determination of the cells' open circuit voltage. The open circuit voltage recovery of Li/SVO cells was monitored during intermittent high rate discharge. It was found that the voltage does not recover at the same rate or magnitude at all depths of discharge. The authors describe lithium diffusion in SVO studied by low scan rate voltammetry where utilization of SVO at various scan rates was used to determine the diffusion rate of lithium. A pulse technique was also used where the rate of lithium diffusion was measured at various depths of discharge
Water diffusion to assess meat microstructure.
Laghi, Luca; Venturi, Luca; Dellarosa, Nicolò; Petracci, Massimiliano
2017-12-01
In the quest for setting up rapid methods to evaluate water retention ability of meat microstructures, time domain nuclear magnetic resonance (TD-NMR) has gained a prominent role, due to the possibility to observe water located outside the myofibrils, easily lost upon storage or cooking. Diffusion weighted signals could be used to monitor the shape and dimension of the pores in which water is confined, thus boosting the information offered by TD-NMR. The work outlines a parsimonious model to describe relative abundance and diffusion coefficient of intra and extra myofibrillar water populations, exchange rate between them, diameter of the myofibrillar cells. To test our model, we registered diffusion and T 2 weighted NMR signals at 20MHz on fresh meat from pectoralis major muscle of 100days old female turkey. We then purposely altered water distribution and myofibrils shape by means of freezing. The model predicted nicely the consequences of the imposed modifications. Copyright © 2016. Published by Elsevier Ltd.
Maximal energy extraction under discrete diffusive exchange
Energy Technology Data Exchange (ETDEWEB)
Hay, M. J., E-mail: hay@princeton.edu [Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544 (United States); Schiff, J. [Department of Mathematics, Bar-Ilan University, Ramat Gan 52900 (Israel); Fisch, N. J. [Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544 (United States); Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
2015-10-15
Waves propagating through a bounded plasma can rearrange the densities of states in the six-dimensional velocity-configuration phase space. Depending on the rearrangement, the wave energy can either increase or decrease, with the difference taken up by the total plasma energy. In the case where the rearrangement is diffusive, only certain plasma states can be reached. It turns out that the set of reachable states through such diffusive rearrangements has been described in very different contexts. Building upon those descriptions, and making use of the fact that the plasma energy is a linear functional of the state densities, the maximal extractable energy under diffusive rearrangement can then be addressed through linear programming.
Superintendents Describe Their Leadership Styles: Implications for Practice
Bird, James J.; Wang, Chuang
2013-01-01
Superintendents from eight southeastern United States school districts self-described their leadership styles across the choices of autocratic, laissez-faire, democratic, situational, servant, or transformational. When faced with this array of choices, the superintendents chose with arguable equitableness, indicating that successful leaders can…
Linear Plasma Oscillation Described by Superposition of Normal Modes
DEFF Research Database (Denmark)
Pécseli, Hans
1974-01-01
The existence of steady‐state solutions to the linearized ion and electron Vlasov equation is demonstrated for longitudinal waves in an initially stable plasma. The evolution of an arbitrary initial perturbation can be described by superposition of these solutions. Some common approximations...
Tentative purely geometrical Machian framework for describing gravity and inertia
Energy Technology Data Exchange (ETDEWEB)
Goldoni, R [Pisa Univ. (Italy). Ist. di Matematica
1979-03-03
The purely geometrical Machian approach to gravitation presented in this letter improves an already published one. In any non vacuum cosmos the gravitational equations in gravitational units are identical to Einstein's equations, while the equations describing the gravitational field in local atomic units are integrodifferential equations in agreement with the available experimental data.
Describing the Corneal Shape after Wavefront-Optimized Photorefractive Keratectomy
de Jong, Tim; Wijdh, Robert H. J.; Koopmans, Steven A.; Jansonius, Nomdo M.
2014-01-01
PURPOSE: To develop a procedure for describing wavefront-optimized photorefractive keratectomy (PRK) corneas and to characterize PRK-induced changes in shape. METHODS: We analyzed preoperative and postoperative corneal elevation data of 41 eyes of 41 patients (mean [±SD] age, 38 [±11] years) who
Describing Soils: Calibration Tool for Teaching Soil Rupture Resistance
Seybold, C. A.; Harms, D. S.; Grossman, R. B.
2009-01-01
Rupture resistance is a measure of the strength of a soil to withstand an applied stress or resist deformation. In soil survey, during routine soil descriptions, rupture resistance is described for each horizon or layer in the soil profile. The lower portion of the rupture resistance classes are assigned based on rupture between thumb and…
Describing, Instantiating and Evaluating a Reference Architecture : A Case Study
Avgeriou, Paris
2003-01-01
The result of a domain maturing is the emergence of reference architectures that offer numerous advantages to software architects and other stakeholders. However there is no straightforward way to describe a reference architecture and in sequence to design instances for specific systems, while at
Deaf Autism: Common Instructional Practices Described by Deaf Educators
Rutledge, Felicia
2017-01-01
The purpose of this research study was to identify common instructional practices described by teachers of the deaf with students who are deaf with autism that increase both student engagement and instructional outcomes. As the diversity of students increase within deaf/hard of hearing programs, research is emerging in the area of deaf autism.…
Nomenclature proposal to describe vocal fold motion impairment
Rosen, Clark A.; Mau, Ted; Remacle, Marc; Hess, Markus; Eckel, Hans E.; Young, VyVy N.; Hantzakos, Anastasios; Yung, Katherine C.; Dikkers, Frederik G.
2016-01-01
The terms used to describe vocal fold motion impairment are confusing and not standardized. This results in a failure to communicate accurately and to major limitations of interpreting research studies involving vocal fold impairment. We propose standard nomenclature for reporting vocal fold
Nomenclature proposal to describe vocal fold motion impairment
Rosen, Clark A.; Mau, Ted; Remacle, Marc; Hess, Markus; Eckel, Hans E.; Young, VyVy N.; Hantzakos, Anastasios; Yung, Katherine C.; Dikkers, Frederik G.
The terms used to describe vocal fold motion impairment are confusing and not standardized. This results in a failure to communicate accurately and to major limitations of interpreting research studies involving vocal fold impairment. We propose standard nomenclature for reporting vocal fold
First described case of prosthetic joint infection with Clostridium disporicum.
McBride, Joseph A; Sterkel, Alana K; Rehrauer, William M; Smith, Jeannina A
2017-12-01
An orthopedic hardware infection with Clostridium disporicum is described. C. disporicum is a gram positive anaerobic bacillus which can contain two subterminal spores. C. disporicum had not previously been reported in musculoskeletal infections. Gram stains demonstrating gram positive bacilli with two subterminal spores should alert practitioners to the possibility of C. disporicum infection. Published by Elsevier Ltd.
Performance of density functional theory methods to describe ...
Indian Academy of Sciences (India)
Fukui function shows a small dependence with both the exchange and correlation functional and the basis set. Evolution of the Fukui function along the reaction path describes important changes in the basic sites of the corresponding molecules. These results are in agreement with the chemical behavior of those species.
Mechanisms underlying anomalous diffusion in the plasma membrane.
Krapf, Diego
2015-01-01
The plasma membrane is a complex fluid where lipids and proteins undergo diffusive motion critical to biochemical reactions. Through quantitative imaging analyses such as single-particle tracking, it is observed that diffusion in the cell membrane is usually anomalous in the sense that the mean squared displacement is not linear with time. This chapter describes the different models that are employed to describe anomalous diffusion, paying special attention to the experimental evidence that supports these models in the plasma membrane. We review models based on anticorrelated displacements, such as fractional Brownian motion and obstructed diffusion, and nonstationary models such as continuous time random walks. We also emphasize evidence for the formation of distinct compartments that transiently form on the cell surface. Finally, we overview heterogeneous diffusion processes in the plasma membrane, which have recently attracted considerable interest. Copyright © 2015. Published by Elsevier Inc.
A statistical approach to strange diffusion phenomena
International Nuclear Information System (INIS)
Milligen, B.Ph. van; Carreras, B.A.; Sanchez, R.
2005-01-01
The study of particle (and heat) transport in fusion plasmas has revealed the existence of what might be called 'unusual' transport phenomena. Such phenomena are: unexpected scaling of the confinement time with system size, power degradation (i.e. sub-linear scaling of energy content with power input), profile stiffness (also known as profile consistency), rapid transient transport phenomena such as cold and heat pulses (travelling much faster than the diffusive timescale would allow), non-local behaviour and central profile peaking during off-axis heating, associated with unexplained inward pinches. The standard modelling framework, essentially equal to Fick's Law plus extensions, has great difficulty in providing an all-encompassing and satisfactory explanation of all these phenomena. This difficulty has motivated us to reconsider the basics of the modelling of diffusive phenomena. Diffusion is based on the well-known random walk. The random walk is captured in all its generality in the Continuous Time Random Walk (CTRW) formalism. The CTRW formalism is directly related to the well-known Generalized Master Equation, which describes the behaviour of tracer particle diffusion on a very fundamental level, and from which the phenomenological Fick's Law can be derived under some specific assumptions. We show that these assumptions are not necessarily satisfied under fusion plasma conditions, in which case other equations (such as the Fokker-Planck diffusion law or the Master Equation itself) provide a better description of the phenomena. This fact may explain part of the observed 'strange' phenomena (namely, the inward pinch). To show how the remaining phenomena mentioned above may perhaps find an explanation in the proposed alternative modelling framework, we have designed a toy model that incorporates a critical gradient mechanism, switching between rapid (super-diffusive) and normal diffusive transport as a function of the local gradient. It is then demonstrated
Measurement of diffusive properties of intact rock
Energy Technology Data Exchange (ETDEWEB)
Harvey, K B
1996-12-01
In the Postclosure Assessment of a Reference System for the Disposal of Canada`s Nuclear Fuel Waste (Goodwin et al. 1994) the disposal vault is assumed to be surrounded by a zone of intact rock, referred to as the `exclusion zone.` A sensitivity analysis of the relative effectiveness of the several engineered and natural barriers that contribute to the safety of the reference disposal system has shown that this zone of intact rock is the most effective of these barriers to the movement of radionuclides through the reference system. Peer review of the geosphere model used in the case study for the EIS (Environmental Impact Statement) of the Canadian Nuclear Fuel Waste Management Program has identified the need to quantify the properties of the intact rock surrounding the disposal vault that would control the transport of radionuclides by diffusion. The Postclosure Assessment also identified the need for appropriate values of the free water diffusion coefficient (D{sub o}) for {sup 129}1 and {sup 14}C. The measurement of rock resistivity allows the calculation of the Formation Factor for a rock This review describes the Formation Factor, diffusivity, permeability, and porosity, and how these properties might be measured or inferred for insitu rock under the conditions that apply to the intact rock surrounding a potential disposal vault. The importance of measuring the intrinsic diffusion coefficient (D{sup i}) of diffusing species under solution salinities simulating those of groundwaters is emphasised, and a method of measurement is described that is independent of the diffusing medium, and which would be appropriate for measurements made in chemically complex media such as groundwaters. (author). 95 refs., 4 tabs., 39 figs.
Measurement of diffusive properties of intact rock
International Nuclear Information System (INIS)
Harvey, K.B.
1996-12-01
In the Postclosure Assessment of a Reference System for the Disposal of Canada's Nuclear Fuel Waste (Goodwin et al. 1994) the disposal vault is assumed to be surrounded by a zone of intact rock, referred to as the 'exclusion zone.' A sensitivity analysis of the relative effectiveness of the several engineered and natural barriers that contribute to the safety of the reference disposal system has shown that this zone of intact rock is the most effective of these barriers to the movement of radionuclides through the reference system. Peer review of the geosphere model used in the case study for the EIS (Environmental Impact Statement) of the Canadian Nuclear Fuel Waste Management Program has identified the need to quantify the properties of the intact rock surrounding the disposal vault that would control the transport of radionuclides by diffusion. The Postclosure Assessment also identified the need for appropriate values of the free water diffusion coefficient (D o ) for 129 1 and 14 C. The measurement of rock resistivity allows the calculation of the Formation Factor for a rock This review describes the Formation Factor, diffusivity, permeability, and porosity, and how these properties might be measured or inferred for insitu rock under the conditions that apply to the intact rock surrounding a potential disposal vault. The importance of measuring the intrinsic diffusion coefficient (D i ) of diffusing species under solution salinities simulating those of groundwaters is emphasised, and a method of measurement is described that is independent of the diffusing medium, and which would be appropriate for measurements made in chemically complex media such as groundwaters. (author). 95 refs., 4 tabs., 39 figs
Polyphase diffusion of fission products in graphite
International Nuclear Information System (INIS)
Dannert, V.
1989-05-01
The report attempts to give an introduction into the subject of fission product transport in nuclear graphite and results in an extended proposal of a transport-model. Beginning with a rough description of the graphite in question, an idea about the physical transport-phenomena in graphite is developed. Some of the basic experimental methods, especially techniques of porosimetry, determination of sorption-isotherms and of course several transport-experiments, are briefly described and their results are discussed. Some of the most frequent transport models are introduced and assessed with the criteria emphasized in this report. An extended model is proposed including the following main ideas: The transport of the fission-products is regarded as a two-phase-diffusion process through the open pores of the graphite. The two phases are: surface-diffusion and gas-diffusion. A time-dependent coupling of the two diffusion-phases by sorption-isotherms and a concentration-dependence of the surface diffusion coefficient, also related to the physical behaviour of the sorption-isotherms, are the basic properties of the proposed model. (orig./HP) [de
Diffusive epidemic process: theory and simulation
International Nuclear Information System (INIS)
Maia, Daniel Souza; Dickman, Ronald
2007-01-01
We study the continuous absorbing-state phase transition in the one-dimensional diffusive epidemic process via mean-field theory and Monte Carlo simulation. In this model, particles of two species (A and B) hop on a lattice and undergo reactions B → A and A+B → 2B; the total particle number is conserved. We formulate the model as a continuous-time Markov process described by a master equation. A phase transition between the (absorbing) B-free state and an active state is observed as the parameters (reaction and diffusion rates, and total particle density) are varied. Mean-field theory reveals a surprising, nonmonotonic dependence of the critical recovery rate on the diffusion rate of B particles. A computational realization of the process that is faithful to the transition rates defining the model is devised, allowing for direct comparison with theory. Using the quasi-stationary simulation method we determine the order parameter and the survival time in systems of up to 4000 sites. Due to strong finite-size effects, the results converge only for large system sizes. We find no evidence for a discontinuous transition. Our results are consistent with the existence of three distinct universality classes, depending on whether A particles diffusive more rapidly, less rapidly or at the same rate as B particles. We also perform quasi-stationary simulations of the triplet creation model, which yield results consistent with a discontinuous transition at high diffusion rates
Flux-limited diffusion models in radiation hydrodynamics
International Nuclear Information System (INIS)
Pomraning, G.C.; Szilard, R.H.
1993-01-01
The authors discuss certain flux-limited diffusion theories which approximately describe radiative transfer in the presence of steep spatial gradients. A new formulation is presented which generalizes a flux-limited description currently in widespread use for large radiation hydrodynamic calculations. This new formation allows more than one Case discrete mode to be described by a flux-limited diffusion equation. Such behavior is not extant in existing formulations. Numerical results predicted by these flux-limited diffusion models are presented for radiation penetration into an initially cold halfspace. 37 refs., 5 figs
New constitutive equations to describe infinitesimal elastic-plastic deformations
International Nuclear Information System (INIS)
Boecke, B.; Link, F.; Schneider, G.; Bruhns, O.T.
1983-01-01
A set of constitutive equations is presented to describe infinitesimal elastic-plastic deformations of austenitic steel in the range up to 600 deg C. This model can describe the hardening behaviour in the case of mechanical loading and hardening, and softening behaviour in the case of thermal loading. The loading path can be either monotonic or cyclic. For this purpose, the well-known isotropic hardening model is continually transferred into the kinematic model according to Prager, whereby suitable internal variables are chosen. The occurring process-dependent material functions are to be determined by uniaxial experiments. The hardening function g and the translation function c are determined by means of a linearized stress-strain behaviour in the plastic range, whereby a coupling condition must be taken into account. As a linear hardening process is considered to be too unrealistic, nonlinearity is achieved by introducing a small function w, the determination procedure of which is given. (author)
National survey describing and quantifying students with communication needs.
Andzik, Natalie R; Schaefer, John M; Nichols, Robert T; Chung, Yun-Ching
2018-01-01
Research literature has yet to quantify and describe how students with complex communication needs are supported in the classroom and how special educators are being prepared to offer support. This study sought out special educators to complete a survey about their students with complex communication needs. Over 4,000 teachers representing 50 states reported on the communicative and behavioral characteristics of 15,643 students. Teachers described the training they have received and instructional approaches they used. The majority of students were reported to use speech as their primary communication mode. Over half of students utilizing alternative and augmentative communication (AAC) were reported to have non-proficient communication. Teacher training varied across respondents as well as the supports they used to support these students in the classroom. The majority of students with disabilities using AAC when communicating across the nation are not proficiently communicating. Implications and recommendations will be discussed.
Statistical models describing the energy signature of buildings
DEFF Research Database (Denmark)
Bacher, Peder; Madsen, Henrik; Thavlov, Anders
2010-01-01
Approximately one third of the primary energy production in Denmark is used for heating in buildings. Therefore efforts to accurately describe and improve energy performance of the building mass are very important. For this purpose statistical models describing the energy signature of a building, i...... or varying energy prices. The paper will give an overview of statistical methods and applied models based on experiments carried out in FlexHouse, which is an experimental building in SYSLAB, Risø DTU. The models are of different complexity and can provide estimates of physical quantities such as UA......-values, time constants of the building, and other parameters related to the heat dynamics. A method for selecting the most appropriate model for a given building is outlined and finally a perspective of the applications is given. Aknowledgements to the Danish Energy Saving Trust and the Interreg IV ``Vind i...
Recently described clinically important anaerobic bacteria: medical aspects.
Finegold, S M; Jousimies-Somer, H
1997-09-01
There is still inadequate information on the role of certain newly described or reclassified anaerobes in disease processes, on their normal sites of carriage, and on their antimicrobial susceptibilities. Herein, we summarize this information (most of the literature reviewed is from the past 5 years, but a few of the articles are approximately 10 years old). Porphyromonas species had seemed to be relatively nonpathogenic, but recent work indicates that this belief is incorrect. P. gingivalis, P levii-like organisms, and P. endodontalis-like organisms have been recovered from a variety of oral and extraoral infections. P. macacae has been recovered from infected cat bite wounds. Sutterella wadsworthensis, recently differentiated from Campylobacter gracilis, has been found in a variety of infections. Bilophila wadsworthia has also been recovered from a wide variety of infections. Newly described anaerobic cocci, gram-positive nonsporeforming rods, and clostridia have also been isolated from various infections.
The Pearson diffusions: A class of statistically tractable diffusion processes
DEFF Research Database (Denmark)
Forman, Julie Lyng; Sørensen, Michael
The Pearson diffusions is a flexible class of diffusions defined by having linear drift and quadratic squared diffusion coefficient. It is demonstrated that for this class explicit statistical inference is feasible. Explicit optimal martingale estimating func- tions are found, and the corresponding...
The scentscape: An integrative framework describing scents in servicescapes
Girard, Marc; Girard, Anna; Suppin, Anna-Caroline; Bartsch, Silke
2016-01-01
The systematic use of ambient scents is a trend in service companies that is accompanied by increasing research attention. However, we lack a theoretical framework that ad-dresses ambient scents' specific role in physical surroundings of services. Thus, this article develops the 'scentscape', a model that describes the process of olfactory stimulation and its impacts on customers and employees in service environments. The paper extends Bitner's servicescape model (1992) and combines it with G...
A relation to describe rate-dependent material failure.
Voight, B
1989-01-13
The simple relation OmegaOmega-alpha = 0, where Omega is a measurable quantity such as strain and A and alpha are empirical constants, describes the behavior of materials in terminal stages of failure under conditions of approximately constant stress and temperature. Applicable to metals and alloys, ice, concrete, polymers, rock, and soil, the relation may be extended to conditions of variable and multiaxial stress and may be used to predict time to failure.
Lattice cell diffusion coefficients. Definitions and comparisons
International Nuclear Information System (INIS)
Hughes, R.P.
1980-01-01
Definitions of equivalent diffusion coefficients for regular lattices of heterogeneous cells have been given by several authors. The paper begins by reviewing these different definitions and the unification of their derivation. This unification makes clear how accurately each definition (together with appropriate cross-section definitions to preserve the eigenvalue) represents the individual reaction rates within the cell. The approach can be extended to include asymmetric cells and whereas before, the buckling describing the macroscopic flux shape was real, here it is found to be complex. A neutron ''drift'' coefficient as well as a diffusion coefficient is necessary to produce the macroscopic flux shape. The numerical calculation of the various different diffusion coefficients requires the solutions of equations similar to the ordinary transport equation for an infinite lattice. Traditional reactor physics codes are not sufficiently flexible to solve these equations in general. However, calculations in certain simple cases are presented and the theoretical results quantified. In difficult geometries, Monte Carlo techniques can be used to calculate an effective diffusion coefficient. These methods relate to those already described provided that correlation effects between different generations of neutrons are included. Again, these effects are quantified in certain simple cases. (author)
International Nuclear Information System (INIS)
Hanna, S.R.
1976-01-01
It is hoped that urban diffusion models of air pollutants can eventually confidently be used to make major decisions, such as in planning the layout of a new industrial park, determining the effects of a new highway on air quality, or estimating the results of a new automobile emissions exhaust system. The urban diffusion model itself should be able to account for point, line, and area sources, and the local aerodynamic effects of street canyons and building wakes. Removal or transformations due to dry or wet deposition and chemical reactions are often important. It would be best if the model included meteorological parameters such as wind speed and temperature as dependent variables, since these parameters vary significantly when air passes from rural surfaces over urban surfaces
Directory of Open Access Journals (Sweden)
Roberto Cipriani
2011-06-01
Full Text Available It is quite likely that the origins of prayer are to be found in ancient mourning and bereavement rites. Primeval ritual prayer was codified and handed down socially to become a deep-rooted feature of people’s cultural behavior, so much so, that it may surface again several years later, in the face of death, danger, need, even in the case of relapse from faith and religious practice. Modes of prayer depend on religious experience, on relations between personal prayer and political action, between prayer and forgiveness, and between prayer and approaches to religions. Various forms of prayer exist, from the covert-hidden to the overt-manifest kind. How can they be investigated? How can one, for instance, explore mental prayer? These issues regard the canon of diffused religion and, therefore, of diffused prayer.
Diffusion in heterogeneous lattices
Czech Academy of Sciences Publication Activity Database
Tarasenko, Alexander; Jastrabík, Lubomír
2010-01-01
Roč. 256, č. 17 (2010), s. 5137-5144 ISSN 0169-4332 R&D Projects: GA AV ČR KAN301370701; GA MŠk(CZ) 1M06002 Institutional research plan: CEZ:AV0Z10100522 Keywords : lattice- gas systems * diffusion * Monte Carlo simulations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.795, year: 2010
International Nuclear Information System (INIS)
Mezin, M.
1976-01-01
The report presents an introduction to general basic principles of the gaseous diffusion process for the separation of uranium isotopes. Dealt with are: a) theoretical background and basic considerations of separation work and production costs, b) construction of a single separation stage and a multistage plant, c) the components of a plant and the optimization factors, d) cost factors. The text is illustrated by instructive diagrammes and flow charts. (RB) [de
Surface diffusion of sorbed radionuclides
International Nuclear Information System (INIS)
Berry, J.A.; Bond, K.A.
1991-01-01
Surface diffusion has in the past been invoked to explain rates of radionuclide migration which were greater than those predicted. Results were generally open to interpretation but the possible existence of surface diffusion, whereby sorbed radionuclides could potentially migrate at much enhanced rates, necessitated investigation. In this work through-diffusion experiments have shown that although surface diffusion does exist for some nuclides, the magnitude of the phenomenon is not sufficient to affect repository safety assessment modelling. (author)
Diffusion in cladding materials
International Nuclear Information System (INIS)
Anand, M.S.; Pande, B.M.; Agarwala, R.P.
1992-01-01
Aluminium has been used as a cladding material in most research reactors because its low neutron absorption cross section and ease of fabrication. However, it is not suitable for cladding in power reactors and as such zircaloy-2 is normally used as a clad because it can withstand high temperature. It has low neutron absorption cross section, good oxidation, corrosion, creep properties and possesses good mechanical strength. With the passage of time, further development in this branch of science took place and designers started looking for better neutron economy and less hydrogen pickup in PHW reactors. The motion of fission products in the cladding material could pose a problem after long operation. In order to understand their behaviour under reactor environment, it is essential to study first the diffusion under normal conditions. These studies will throw light on the interaction of defects with impurities which would in turn help in understanding the mechanism of diffusion. In this article, it is intended to discuss the diffusion behaviour of impurities in cladding materials.(i.e. aluminium, zircaloy-2, zirconium-niobium alloy etc.). (author). 94 refs., 4 figs., 3 tabs
Analytical simulation platform describing projections in computed tomography systems
International Nuclear Information System (INIS)
Youn, Hanbean; Kim, Ho Kyung
2013-01-01
To reduce the patient dose, several approaches such as spectral imaging using photon counting detectors and statistical image reconstruction, are being considered. Although image-reconstruction algorithms may significantly enhance image quality in reconstructed images with low dose, true signal-to-noise properties are mainly determined by image quality in projections. We are developing an analytical simulation platform describing projections to investigate how quantum-interaction physics in each component configuring CT systems affect image quality in projections. This simulator will be very useful for an improved design or optimization of CT systems in economy as well as the development of novel image-reconstruction algorithms. In this study, we present the progress of development of the simulation platform with an emphasis on the theoretical framework describing the generation of projection data. We have prepared the analytical simulation platform describing projections in computed tomography systems. The remained further study before the meeting includes the following: Each stage in the cascaded signal-transfer model for obtaining projections will be validated by the Monte Carlo simulations. We will build up energy-dependent scatter and pixel-crosstalk kernels, and show their effects on image quality in projections and reconstructed images. We will investigate the effects of projections obtained from various imaging conditions and system (or detector) operation parameters on reconstructed images. It is challenging to include the interaction physics due to photon-counting detectors into the simulation platform. Detailed descriptions of the simulator will be presented with discussions on its performance and limitation as well as Monte Carlo validations. Computational cost will also be addressed in detail. The proposed method in this study is simple and can be used conveniently in lab environment
A model to describe the performance of the UASB reactor.
Rodríguez-Gómez, Raúl; Renman, Gunno; Moreno, Luis; Liu, Longcheng
2014-04-01
A dynamic model to describe the performance of the Upflow Anaerobic Sludge Blanket (UASB) reactor was developed. It includes dispersion, advection, and reaction terms, as well as the resistances through which the substrate passes before its biotransformation. The UASB reactor is viewed as several continuous stirred tank reactors connected in series. The good agreement between experimental and simulated results shows that the model is able to predict the performance of the UASB reactor (i.e. substrate concentration, biomass concentration, granule size, and height of the sludge bed).
Icosahedral symmetry described by an incommensurately modulated crystal structure model
DEFF Research Database (Denmark)
Wolny, Janusz; Lebech, Bente
1986-01-01
A crystal structure model of an incommensurately modulated structure is presented. Although six different reciprocal vectors are used to describe the model, all calculations are done in three dimensions making calculation of the real-space structure trivial. Using this model, it is shown that both...... the positions of the bragg reflections and information about the relative intensities of these reflections are in full accordance with the diffraction patterns reported for microcrystals of the rapidly quenched Al86Mn14 alloy. It is also shown that at least the local structure possesses full icosahedral...
[Health consequences of smoking electronic cigarettes are poorly described].
Tøttenborg, Sandra Søgaard; Holm, Astrid Ledgaard; Wibholm, Niels Christoffer; Lange, Peter
2014-09-01
Despite increasing popularity, health consequences of vaping (smoking electronic cigarettes, e-cigarettes) are poorly described. Few studies suggest that vaping has less deleterious effects on lung function than smoking conventional cigarettes. One large study found that e-cigarettes were as efficient as nicotine patches in smoking cessation. The long-term consequences of vaping are however unknown and while some experts are open towards e-cigarettes as a safer way of satisfying nicotine addiction, others worry that vaping in addition to presenting a health hazard may lead to an increased number of smokers of conventional cigarettes.
Two heuristic approaches to describe periodicities in genomic microarrays
Directory of Open Access Journals (Sweden)
Jörg Aßmus
2009-09-01
Full Text Available In the first part we discuss the filtering of panels of time series based on singular value decomposition. The discussion is based on an approach where this filtering is used to normalize microarray data. We point out effects on the periodicity and phases for time series panels. In the second part we investigate time dependent periodic panels with different phases. We align the time series in the panel and discuss the periodogram of the aligned time series with the purpose of describing the periodic structure of the panel. The method is quite powerful assuming known phases in the model, but it deteriorates rapidly for noisy data.
A Model Describing Stable Coherent Synchrotron Radiation in Storage Rings
International Nuclear Information System (INIS)
Sannibale, F.
2004-01-01
We present a model describing high power stable broadband coherent synchrotron radiation (CSR) in the terahertz frequency region in an electron storage ring. The model includes distortion of bunch shape from the synchrotron radiation (SR), which enhances higher frequency coherent emission, and limits to stable emission due to an instability excited by the SR wakefield. It gives a quantitative explanation of several features of the recent observations of CSR at the BESSY II storage ring. We also use this model to optimize the performance of a source for stable CSR emission
A model describing stable coherent synchrotron radiation in storage rings
International Nuclear Information System (INIS)
Sannibale, F.; Byrd, J.M.; Loftsdottir, A.; Venturini, M.; Abo-Bakr, M.; Feikes, J.; Holldack, K.; Kuske, P.; Wuestefeld, G.; Huebers, H.-W.; Warnock, R.
2004-01-01
We present a model describing high power stable broadband coherent synchrotron radiation (CSR) in the terahertz frequency region in an electron storage ring. The model includes distortion of bunch shape from the synchrotron radiation (SR), which enhances higher frequency coherent emission, and limits to stable emission due to an instability excited by the SR wakefield. It gives a quantitative explanation of several features of the recent observations of CSR at the BESSY II storage ring. We also use this model to optimize the performance of a source for stable CSR emission
Numerical solution of multigroup diffuse equations of one-dimensional geometry
International Nuclear Information System (INIS)
Pavelesku, M.; Adam, S.
1975-01-01
The one-dimensional diffuse theory is used for reactor physics calculations of fast reactors. Computer program based on the one-dimensional diffuse theory is speedy and not memory consuming. The algorithm is described for the three-zone fast reactor criticality computation in one-dimensional diffusion approximation. This algorithm is realised on IBM 370/135 computer. (I.T.)
Diagram of collisional regimes for particle diffusion in a stochastic magnetic field
International Nuclear Information System (INIS)
Misguich, J.H.; Balescu, R.
1995-01-01
This document deals with static stochastic fields, where magnetic lines experience exponential separation and magnetic diffusion. It more particularly focuses on the diffusivity of collisional particles in such a fields and presents a general graph which describes most regimes of collisional and weakly collisional diffusion for guiding centers in a time-independent magnetic field. (TEC). 9 refs., 1 fig., 2 tabs
Rodrigues, P.R.
2011-01-01
In diffusion magnetic resonance imaging (DMRI) the Brownian motion of the water molecules, within biological tissue, is measured through a series of images. In diffusion tensor imaging (DTI) this diffusion is represented using tensors. DTI describes, in a non-invasive way, the local anisotropy
Solute diffusivity in undisturbed soil
DEFF Research Database (Denmark)
Lægdsmand, Mette; Møldrup, Per; Schjønning, Per
2012-01-01
Solute diffusivity in soil plays a major role in many important processes with relation to plant growth and environmental issues. Soil solute diffusivity is affected by the volumetric water content as well as the morphological characteristics of water-filled pores. The solute diffusivity in intact...
Colour in flux: describing and printing colour in art
Parraman, Carinna
2008-01-01
This presentation will describe artists, practitioners and scientists, who were interested in developing a deeper psychological, emotional and practical understanding of the human visual system who were working with wavelength, paint and other materials. From a selection of prints at The Prints and Drawings Department at Tate London, the presentation will refer to artists who were motivated by issues relating to how colour pigment was mixed and printed, to interrogate and explain colour perception and colour science, and in art, how artists have used colour to challenge the viewer and how a viewer might describe their experience of colour. The title Colour in Flux refers, not only to the perceptual effect of the juxtaposition of one colour pigment with another, but also to the changes and challenges for the print industry. In the light of screenprinted examples from the 60s and 70s, the presentation will discuss 21 st century ideas on colour and how these notions have informed the Centre for Fine Print Research's (CFPR) practical research in colour printing. The latter part of this presentation will discuss the implications for the need to change methods in mixing inks that moves away from existing colour spaces, from non intuitive colour mixing to bespoke ink sets, colour mixing approaches and colour mixing methods that are not reliant on RGB or CMYK.
A Kinetic Model Describing Injury-Burden in Team Sports.
Fuller, Colin W
2017-12-01
Injuries in team sports are normally characterised by the incidence, severity, and location and type of injuries sustained: these measures, however, do not provide an insight into the variable injury-burden experienced during a season. Injury burden varies according to the team's match and training loads, the rate at which injuries are sustained and the time taken for these injuries to resolve. At the present time, this time-based variation of injury burden has not been modelled. To develop a kinetic model describing the time-based injury burden experienced by teams in elite team sports and to demonstrate the model's utility. Rates of injury were quantified using a large eight-season database of rugby injuries (5253) and exposure (60,085 player-match-hours) in English professional rugby. Rates of recovery from injury were quantified using time-to-recovery analysis of the injuries. The kinetic model proposed for predicting a team's time-based injury burden is based on a composite rate equation developed from the incidence of injury, a first-order rate of recovery from injury and the team's playing load. The utility of the model was demonstrated by examining common scenarios encountered in elite rugby. The kinetic model developed describes and predicts the variable injury-burden arising from match play during a season of rugby union based on the incidence of match injuries, the rate of recovery from injury and the playing load. The model is equally applicable to other team sports and other scenarios.
Limitations of Poisson statistics in describing radioactive decay.
Sitek, Arkadiusz; Celler, Anna M
2015-12-01
The assumption that nuclear decays are governed by Poisson statistics is an approximation. This approximation becomes unjustified when data acquisition times longer than or even comparable with the half-lives of the radioisotope in the sample are considered. In this work, the limits of the Poisson-statistics approximation are investigated. The formalism for the statistics of radioactive decay based on binomial distribution is derived. The theoretical factor describing the deviation of variance of the number of decays predicated by the Poisson distribution from the true variance is defined and investigated for several commonly used radiotracers such as (18)F, (15)O, (82)Rb, (13)N, (99m)Tc, (123)I, and (201)Tl. The variance of the number of decays estimated using the Poisson distribution is significantly different than the true variance for a 5-minute observation time of (11)C, (15)O, (13)N, and (82)Rb. Durations of nuclear medicine studies often are relatively long; they may be even a few times longer than the half-lives of some short-lived radiotracers. Our study shows that in such situations the Poisson statistics is unsuitable and should not be applied to describe the statistics of the number of decays in radioactive samples. However, the above statement does not directly apply to counting statistics at the level of event detection. Low sensitivities of detectors which are used in imaging studies make the Poisson approximation near perfect. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
Experimental investigation of statistical models describing distribution of counts
International Nuclear Information System (INIS)
Salma, I.; Zemplen-Papp, E.
1992-01-01
The binomial, Poisson and modified Poisson models which are used for describing the statistical nature of the distribution of counts are compared theoretically, and conclusions for application are considered. The validity of the Poisson and the modified Poisson statistical distribution for observing k events in a short time interval is investigated experimentally for various measuring times. The experiments to measure the influence of the significant radioactive decay were performed with 89 Y m (T 1/2 =16.06 s), using a multichannel analyser (4096 channels) in the multiscaling mode. According to the results, Poisson statistics describe the counting experiment for short measuring times (up to T=0.5T 1/2 ) and its application is recommended. However, analysis of the data demonstrated, with confidence, that for long measurements (T≥T 1/2 ) Poisson distribution is not valid and the modified Poisson function is preferable. The practical implications in calculating uncertainties and in optimizing the measuring time are discussed. Differences between the standard deviations evaluated on the basis of the Poisson and binomial models are especially significant for experiments with long measuring time (T/T 1/2 ≥2) and/or large detection efficiency (ε>0.30). Optimization of the measuring time for paired observations yields the same solution for either the binomial or the Poisson distribution. (orig.)
Workplace culture in psychiatric nursing described by nurses.
Kurjenluoma, K; Rantanen, A; McCormack, B; Slater, P; Hahtela, N; Suominen, T
2017-12-01
This study looks to describe the workplace culture from the viewpoints of stress, job satisfaction and practice environment. Data were collected from nurses (n = 109) using a web-based survey, The Person-Centred Nursing Index, from two purposefully selected hospital districts in Finland. Data were statistically analysed. Nurses described their workplace culture in slightly positive terms. Nurses only occasionally experienced stress (mean = 2.56, SD = 0.55) and were fairly satisfied with their job (mean = 4.75, SD = 0.66) and their practice environment (mean = 4.42, SD = 0.81). Demographic variables such as the nurses' age, length of time in nursing, time at their present hospital, working shifts and their use of patient restriction were more frequently associated with their perceived workplace culture. Older nurses and those with a longer work history in the nursing profession tended to be more satisfied with their workplace culture in psychiatric nursing. Young and/or newly graduated nurses felt more negatively on their workplace culture; this issue should be recognised and addressed with appropriate support and mentoring. Nurses who used restrictive measures were more often less satisfied with their workplace culture. Continuous efforts are needed to reduce the use of coercive measures, which challenge also the managers to support nursing practice to be more person-centred. © 2017 Nordic College of Caring Science.
In their own words: describing Canadian physician leadership.
Snell, Anita J; Dickson, Graham; Wirtzfeld, Debrah; Van Aerde, John
2016-07-04
Purpose This is the first study to compile statistical data to describe the functions and responsibilities of physicians in formal and informal leadership roles in the Canadian health system. This mixed-methods research study offers baseline data relative to this purpose, and also describes physician leaders' views on fundamental aspects of their leadership responsibility. Design/methodology/approach A survey with both quantitative and qualitative fields yielded 689 valid responses from physician leaders. Data from the survey were utilized in the development of a semi-structured interview guide; 15 physician leaders were interviewed. Findings A profile of Canadian physician leadership has been compiled, including demographics; an outline of roles, responsibilities, time commitments and related compensation; and personal factors that support, engage and deter physicians when considering taking on leadership roles. The role of health-care organizations in encouraging and supporting physician leadership is explicated. Practical implications The baseline data on Canadian physician leaders create the opportunity to determine potential steps for improving the state of physician leadership in Canada; and health-care organizations are provided with a wealth of information on how to encourage and support physician leaders. Using the data as a benchmark, comparisons can also be made with physician leadership as practiced in other nations. Originality/value There are no other research studies available that provide the depth and breadth of detail on Canadian physician leadership, and the embedded recommendations to health-care organizations are informed by this in-depth knowledge.
Diffusion of Zonal Variables Using Node-Centered Diffusion Solver
Energy Technology Data Exchange (ETDEWEB)
Yang, T B
2007-08-06
Tom Kaiser [1] has done some preliminary work to use the node-centered diffusion solver (originally developed by T. Palmer [2]) in Kull for diffusion of zonal variables such as electron temperature. To avoid numerical diffusion, Tom used a scheme developed by Shestakov et al. [3] and found their scheme could, in the vicinity of steep gradients, decouple nearest-neighbor zonal sub-meshes leading to 'alternating-zone' (red-black mode) errors. Tom extended their scheme to couple the sub-meshes with appropriate chosen artificial diffusion and thereby solved the 'alternating-zone' problem. Because the choice of the artificial diffusion coefficient could be very delicate, it is desirable to use a scheme that does not require the artificial diffusion but still able to avoid both numerical diffusion and the 'alternating-zone' problem. In this document we present such a scheme.
Fractional diffusion models of transport in magnetically confined plasmas
International Nuclear Information System (INIS)
Castillo-Negrete, D. del; Carreras, B. A.; Lynch, V. E.
2005-01-01
Experimental and theoretical evidence suggests that transport in magnetically confined fusion plasmas deviates from the standard diffusion paradigm. Some examples include the confinement time scaling in L-mode plasmas, rapid pulse propagation phenomena, and inward transport in off-axis fueling experiments. The limitations of the diffusion paradigm can be traced back to the restrictive assumptions in which it is based. In particular, Fick's law, one of the cornerstones of diffusive transport, assumes that the fluxes only depend on local quantities, i. e. the spatial gradient of the field (s). another key issue is the Markovian assumption that neglects memory effects. Also, at a microscopic level, standard diffusion assumes and underlying Gaussian, uncorrelated stochastic process (i. e. a Brownian random walk) with well defined characteristic spatio-temporal scales. Motivated by the need to develop models of non-diffusive transport, we discuss here a class of transport models base on the use of fractional derivative operators. The models incorporates in a unified way non-Fickian transport, non-Markovian processes or memory effects, and non-diffusive scaling. At a microscopic level, the models describe an underlying stochastic process without characteristic spatio-temporal scales that generalizes the Brownian random walk. As a concrete case study to motivate and test the model, we consider transport of tracers in three-dimensional, pressure-gradient-driven turbulence. We show that in this system transport is non-diffusive and cannot be described in the context of the standard diffusion parading. In particular, the probability density function (pdf) of the radial displacements of tracers is strongly non-Gaussian with algebraic decaying tails, and the moments of the tracer displacements exhibit super-diffusive scaling. there is quantitative agreement between the turbulence transport calculations and the proposed fractional diffusion model. In particular, the model
Xiang-Guo, Meng; Ji-Suo, Wang; Hong-Yi, Fan; Cheng-Wei, Xia
2016-04-01
We solve the fermionic master equation for a thermal bath to obtain its explicit Kraus operator solutions via the fermionic state approach. The normalization condition of the Kraus operators is proved. The matrix representation for these solutions is obtained, which is incongruous with the result in the book completed by Nielsen and Chuang [Quantum Computation and Quantum Information, Cambridge University Press, 2000]. As especial cases, we also present the Kraus operator solutions to master equations for describing the amplitude-decay model and the diffusion process at finite temperature. Project supported by the National Natural Science Foundation of China (Grant No. 11347026), the Natural Science Foundation of Shandong Province, China (Grant Nos. ZR2013AM012 and ZR2012AM004), and the Research Fund for the Doctoral Program and Scientific Research Project of Liaocheng University, Shandong Province, China.
Semi-empirical master curve concept describing the rate capability of lithium insertion electrodes
Heubner, C.; Seeba, J.; Liebmann, T.; Nickol, A.; Börner, S.; Fritsch, M.; Nikolowski, K.; Wolter, M.; Schneider, M.; Michaelis, A.
2018-03-01
A simple semi-empirical master curve concept, describing the rate capability of porous insertion electrodes for lithium-ion batteries, is proposed. The model is based on the evaluation of the time constants of lithium diffusion in the liquid electrolyte and the solid active material. This theoretical approach is successfully verified by comprehensive experimental investigations of the rate capability of a large number of porous insertion electrodes with various active materials and design parameters. It turns out, that the rate capability of all investigated electrodes follows a simple master curve governed by the time constant of the rate limiting process. We demonstrate that the master curve concept can be used to determine optimum design criteria meeting specific requirements in terms of maximum gravimetric capacity for a desired rate capability. The model further reveals practical limits of the electrode design, attesting the empirically well-known and inevitable tradeoff between energy and power density.
Diffusion coefficient calculations for cylindrical cells
International Nuclear Information System (INIS)
Lam-Hime, M.
1983-03-01
An accurate and general diffusion coefficient calculation for cylindrical cells is described using isotropic scattering integral transport theory. This method has been particularly applied to large regular lattices of graphite-moderated reactors with annular coolant channels. The cells are divided into homogeneous zones, and a zone-wise flux expansion is used to formulate a collision probability problem. The reflection of neutrons at the cell boundary is accounted for by the conservation of the neutron momentum. The uncorrected diffusion coefficient Benoist's definition is used, and the described formulation does not neglect any effect. Angular correlation terms, energy coupling non-uniformity and anisotropy of the classical flux are exactly taken into account. Results for gas-graphite typical cells are given showing the importance of these approximations
Contribution to the study of diffusion in rare earth metals and actinides
International Nuclear Information System (INIS)
Marbach, Gabriel.
1978-07-01
This work describes several experiments carried out in order to understand the process of self diffusion in rare earth and actinides (self diffusion of body centered cubic γ neptunium, diffusion of gadolinium in body centered delta cerium, measurement of the activation volume of face centered cubic γ cerium). The unstable electronic structure of some elements cannot be correlate with anomalous diffusion properties. In fact the diffusion parameters of neptunium and plutonium are similar (high diffusivity and low activation energy) whereas the electronic structure of neptunium is stable and that of plutonium is temperature dependent. The negative activation volume of the body centered cubic phases of plutonium and cerium does not indicate a particular diffusion mechanism since self diffusion is faster under pressure in face centered cubic γ cerium where a vacancy mechanism is assumed according to earlier results. The vacancy mechanism is the most probable diffusion process in the body centered cubic and compact phases of rare earths and actinides [fr
Describing the Peptide Binding Specificity of HLA-C
DEFF Research Database (Denmark)
Rasmussen, Michael; Harndahl, Mikkel Nors; Nielsen, Morten
for 5 HLA-C molecules and for all, but one, molecule we find a high frequency of binders, >70%, among these peptides. To extend the examined peptide space, we use bioinformatic prediction tools to search for additional binders. Finally, we update our prediction tool, NetMHCpan, with the HLA-C affinity......Human leukocyte antigen (HLA) presents peptides to T-cells for immune scrutiny. Whereas HLA-A and -B have been described in great detail, HLA-C has received much less attention. Here, to increase the coverage of HLA-C and the accuracy of the corresponding tools, we have generated HLA-C molecules...... data and show that the predictive performance for HLA-C molecules now is increased to a level comparable withthat of HLA-A and -B. These novel HLA-C molecules and predictors are successfully used to generate HLA-C tetramers and validate HLA-C-restricted T cell responses....
Describing Quadratic Cremer Point Polynomials by Parabolic Perturbations
DEFF Research Database (Denmark)
Sørensen, Dan Erik Krarup
1996-01-01
We describe two infinite order parabolic perturbation proceduresyielding quadratic polynomials having a Cremer fixed point. The main ideais to obtain the polynomial as the limit of repeated parabolic perturbations.The basic tool at each step is to control the behaviour of certain externalrays.......Polynomials of the Cremer type correspond to parameters at the boundary of ahyperbolic component of the Mandelbrot set. In this paper we concentrate onthe main cardioid component. We investigate the differences between two-sided(i.e. alternating) and one-sided parabolic perturbations.In the two-sided case, we prove...... the existence of polynomials having an explicitlygiven external ray accumulating both at the Cremer point and at its non-periodicpreimage. We think of the Julia set as containing a "topologists double comb".In the one-sided case we prove a weaker result: the existence of polynomials havingan explicitly given...
Models for describing the thermal characteristics of building components
DEFF Research Database (Denmark)
Jimenez, M.J.; Madsen, Henrik
2008-01-01
, for example. For the analysis of these tests, dynamic analysis models and methods are required. However, a wide variety of models and methods exists, and the problem of choosing the most appropriate approach for each particular case is a non-trivial and interdisciplinary task. Knowledge of a large family....... The characteristics of each type of model are highlighted. Some available software tools for each of the methods described will be mentioned. A case study also demonstrating the difference between linear and nonlinear models is considered....... of these approaches may therefore be very useful for selecting a suitable approach for each particular case. This paper presents an overview of models that can be applied for modelling the thermal characteristics of buildings and building components using data from outdoor testing. The choice of approach depends...
Can the "standard" unitarized Regge models describe the TOTEM data?
Alkin, A; Martynov, E
2013-01-01
The standard Regge poles are considered as inputs for two unitarization methods: eikonal and U-matrix. It is shown that only models with three input pomerons and two input odderons can describe the high energy data on $pp$ and $\\bar pp$ elastic scattering including the new data from Tevatron and LHC. However, it seems that the both considered models require a further modification (e.g. nonlinear reggeon trajectories and/or nonexponential vertex functions) for a more satisfactory description of the data at 19.0 GeV$\\leq \\sqrt{s}\\leq$ 7 TeV and 0.01 $\\leq |t|\\leq $14.2 GeV$^{2}$.
Describing linguistic information in a behavioural framework: Possible or not?
Energy Technology Data Exchange (ETDEWEB)
De Cooman, G. [Universiteit Gent, Zwijnaarde (Belgium)
1996-12-31
The paper discusses important aspects of the representation of linguistic information, using imprecise probabilities with a behavioural interpretation. We define linguistic information as the information conveyed by statements in natural language, but restrict ourselves to simple affirmative statements of the type {open_quote}subject-is-predicate{close_quote}. Taking the behavioural stance, as it is described in detail, we investigate whether it is possible to give a mathematical model for this kind of information. In particular, we evaluate Zadeli`s suggestion that we should use possibility measures to this end. We come to tile conclusion that, generally speaking, possibility measures are possibility models for linguistic information, but that more work should be done in order to evaluate the suggestion that they may be the only ones.
International Nuclear Information System (INIS)
Li Pengfei; Hu Gang; Chen Runsheng
2008-01-01
Gene transcriptional regulation (TR) processes are often described by coupled nonlinear ordinary differential equations (ODEs). When the dimension of TR circuits is high (e.g. n ≥ 3) the motions of the corresponding ODEs may, very probably, show self-sustained oscillations and chaos. On the other hand, chaoticity may be harmful for the normal biological functions of TR processes. In this letter we numerically study the dynamics of 3-gene TR ODEs in great detail, and investigate many 4-, 5-, and 10-gene TR systems by randomly choosing figures and parameters in the conventionally accepted ranges. And we find that oscillations are very seldom and no chaotic motion is observed, even if the dimension of systems is sufficiently high (n ≥ 3). It is argued that the observation of nonchaoticity of these ODEs agrees with normal functions of actual TR processes
Principal spectra describing magnetooptic permittivity tensor in cubic crystals
Energy Technology Data Exchange (ETDEWEB)
Hamrlová, Jana [Nanotechnology Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); IT4Innovations Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Legut, Dominik [IT4Innovations Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Veis, Martin [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague, 121 16 Czech Republic (Czech Republic); Pištora, Jaromír [Nanotechnology Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Hamrle, Jaroslav, E-mail: jaroslav.hamrle@vsb.cz [IT4Innovations Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague, 121 16 Czech Republic (Czech Republic); Department of Physics, VSB – Technical University of Ostrava, 17. listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic)
2016-12-15
We provide unified phenomenological description of magnetooptic effects being linear and quadratic in magnetization. The description is based on few principal spectra, describing elements of permittivity tensor up to the second order in magnetization. Each permittivity tensor element for any magnetization direction and any sample surface orientation is simply determined by weighted summation of the principal spectra, where weights are given by crystallographic and magnetization orientations. The number of principal spectra depends on the symmetry of the crystal. In cubic crystals owning point symmetry we need only four principal spectra. Here, the principal spectra are expressed by ab initio calculations for bcc Fe, fcc Co and fcc Ni in optical range as well as in hard and soft x-ray energy range, i.e. at the 2p- and 3p-edges. We also express principal spectra analytically using modified Kubo formula.
Chapter 35: Describing Data and Data Collections in the VO
Kent, B. R.; Hanisch, R. J.; Williams, R. D.
The list of numbers: 19.22, 17.23, 18.11, 16.98, and 15.11, is of little intrinsic interest without information about the context in which they appear. For instance, are these daily closing stock prices for your favorite investment, or are they hourly photometric measurements of an increasingly bright quasar? The information needed to define this context is called metadata. Metadata are data about data. Astronomers are familiar with metadata through the headers of FITS files and the names and units associated with columns in a table or database. In the VO, metadata describe the contents of tables, images, and spectra, as well as aggregate collections of data (archives, surveys) and computational services. Moreover, VO metadata are constructed according to rules that avoid ambiguity and make it clear whether, in the example above, the stock prices are in dollars or euros, or the photometry is Johnson V or Sloan g. Organization of data is important in any scientific discipline. Equally crucial are the descriptions of that data: the organization publishing the data, its creator or the person making it available, what instruments were used, units assigned to measurement, calibration status, and data quality assessment. The Virtual Observatory metadata scheme not only applies to datasets, but to resources as well, including data archive facilities, searchable web forms, and online analysis and display tools. Since the scientific output flowing from large datasets depends greatly on how well the data are described, it is important for users to understand the basics of the metadata scheme in order to locate the data that they want and use it correctly. Metadata are the key to data discovery and data and service interoperability in the Virtual Observatory.
Angular momentum and torque described with the complex octonion
International Nuclear Information System (INIS)
Weng, Zi-Hua
2014-01-01
The paper aims to adopt the complex octonion to formulate the angular momentum, torque, and force etc in the electromagnetic and gravitational fields. Applying the octonionic representation enables one single definition of angular momentum (or torque, force) to combine some physics contents, which were considered to be independent of each other in the past. J. C. Maxwell used simultaneously two methods, the vector terminology and quaternion analysis, to depict the electromagnetic theory. It motivates the paper to introduce the quaternion space into the field theory, describing the physical feature of electromagnetic and gravitational fields. The spaces of electromagnetic field and of gravitational field can be chosen as the quaternion spaces, while the coordinate component of quaternion space is able to be the complex number. The quaternion space of electromagnetic field is independent of that of gravitational field. These two quaternion spaces may compose one octonion space. Contrarily, one octonion space can be separated into two subspaces, the quaternion space and S-quaternion space. In the quaternion space, it is able to infer the field potential, field strength, field source, angular momentum, torque, and force etc in the gravitational field. In the S-quaternion space, it is capable of deducing the field potential, field strength, field source, current continuity equation, and electric (or magnetic) dipolar moment etc in the electromagnetic field. The results reveal that the quaternion space is appropriate to describe the gravitational features, including the torque, force, and mass continuity equation etc. The S-quaternion space is proper to depict the electromagnetic features, including the dipolar moment and current continuity equation etc. In case the field strength is weak enough, the force and the continuity equation etc can be respectively reduced to that in the classical field theory
Particle diffusion in a spheromak
International Nuclear Information System (INIS)
Meyerhofer, D.D.; Levinton, F.M.; Yamada, M.
1988-01-01
The local carbon particle diffusion coefficient was measured in the Proto S-1/C spheromak using a test particle injection scheme. When the plasma was not in a force-free Taylor state, and when there were pressure gradients in the plasma, the particle diffusion was five times that predicted by Bohm and was consistent with collisional drift wave diffusion. The diffusion appears to be driven by correlations of the fluctuating electric field and density. During the decay phase of the discharge when the plasma was in the Taylor state, the diffusion coefficient of the carbon was classical. 23 refs., 4 figs
Advanced diffusion processes and phenomena
Öchsner, Andreas; Belova, Irina
2014-01-01
This topical volume on Advanced Diffusion Processes and Phenomena addresses diffusion in a wider sense of not only mass diffusion but also heat diffusion in fluids and solids. Both diffusion phenomena play an important role in the characterization of engineering materials and corresponding structures. Understanding these different transport phenomena at many levels, from atomistic to macro, has therefore long attracted the attention of many researchers in materials science and engineering and related disciplines. The present topical volume captures a representative cross-section of some of the
Measuring methods of matrix diffusion
International Nuclear Information System (INIS)
Muurinen, A.; Valkiainen, M.
1988-03-01
In Finland the spent nuclear fuel is planned to be disposed of at large depths in crystalline bedrock. The radionuclides which are dissolved in the groundwater may be able to diffuse into the micropores of the porous rock matrix and thus be withdrawn from the flowing water in the fractures. This phenomenon is called matrix diffusion. A review over matrix diffusion is presented in the study. The main interest is directed to the diffusion of non-sorbing species. The review covers diffusion experiments and measurements of porosity, pore size, specific surface area and water permeability
Galerkin method for solving diffusion equations
International Nuclear Information System (INIS)
Tsapelkin, E.S.
1975-01-01
A programme for the solution of the three-dimensional two-group multizone neutron diffusion problem in (x, y, z)-geometry is described. The programme XYZ-5 gives the currents of both groups, the effective neutron multiplication coefficient and several integral properties of the reactor. The solution was found with the Galerkin method using speciallly constructed and chosen coordinate functions. The programme is written in ALGOL-60 and consists of 5 parts. Its text is given
Classical diffusion: theory and simulation codes
International Nuclear Information System (INIS)
Grad, H.; Hu, P.N.
1978-03-01
A survey is given of the development of classical diffusion theory which arose from the observation of Grad and Hogan that the Pfirsch-Schluter and Neoclassical theories are very special and frequently inapplicable because they require that plasma mass flow be treated as transport rather than as a state variable of the plasma. The subsequent theory, efficient numerical algorithms, and results of various operating codes are described
Some notes on experiments measuring diffusion of sorbed nuclides through porous media
International Nuclear Information System (INIS)
Lever, D.A.
1986-11-01
Various experimental techniques for measuring the important parameters governing diffusion of sorbed nuclides through water-saturated porous media are described, and the particular parameters obtained from each technique are discussed. Recent experiments in which diffusive transport takes place more rapidly than expected are reviewed. The author recommends that through-transport diffusion experiments are the most satisfactory method of determining whether this arises from surface diffusion of sorbed nuclides. (author)
A multigroup flux-limited asymptotic diffusion Fokker-Planck equation
International Nuclear Information System (INIS)
Liu Chengan
1987-01-01
A more perfrect flux-limited method is applied to combine with asymptotic diffusion theory of the radiation transpore, and the high peaked component in the scattering angle is treated with Fokker-Planck methods, thus the flux-limited asymptotic diffusion Fokker-Planck equation has been founded. Since the equation is of diffusion form, it retains the simplity and the convenience of the classical diffusion theory, and improves precision in describing radiation transport problems
International Nuclear Information System (INIS)
Kwiotek, A.; Grzywna, Z.J.
2005-01-01
Diffusion in a bounded region (or diffusive mass transport) can be seen from at least three platforms: - chemistry of he Fick's equation; - chemical engineering. To pose a particular problem we have to provide some additional conditions (initial conditions, boundary conditions and further). As we understood it in all cases diffusion is considered in an open region (in other words in one phase). Chemical engineering however brings an idea of 'diffusion' between phases. We claim that there isn't diffusion between phases. One can only consider mass transport between phases. Mass transport (or transfer in chemical engineering jargon) from one phase to another composes of: diffusion in first phase partition at an interface diffusion in second phase. (author)
Modeling of Reaction Processes Controlled by Diffusion
International Nuclear Information System (INIS)
Revelli, Jorge
2003-01-01
Stochastic modeling is quite powerful in science and technology.The technics derived from this process have been used with great success in laser theory, biological systems and chemical reactions.Besides, they provide a theoretical framework for the analysis of experimental results on the field of particle's diffusion in ordered and disordered materials.In this work we analyze transport processes in one-dimensional fluctuating media, which are media that change their state in time.This fact induces changes in the movements of the particles giving rise to different phenomena and dynamics that will be described and analyzed in this work.We present some random walk models to describe these fluctuating media.These models include state transitions governed by different dynamical processes.We also analyze the trapping problem in a lattice by means of a simple model which predicts a resonance-like phenomenon.Also we study effective diffusion processes over surfaces due to random walks in the bulk.We consider different boundary conditions and transitions movements.We derive expressions that describe diffusion behaviors constrained to bulk restrictions and the dynamic of the particles.Finally it is important to mention that the theoretical results obtained from the models proposed in this work are compared with Monte Carlo simulations.We find, in general, excellent agreements between the theory and the simulations
Diffusion Driven Combustion Waves in Porous Media
Aldushin, A. P.; Matkowsky, B. J.
2000-01-01
Filtration of gas containing oxidizer, to the reaction zone in a porous medium, due, e.g., to a buoyancy force or to an external pressure gradient, leads to the propagation of Filtration combustion (FC) waves. The exothermic reaction occurs between the fuel component of the solid matrix and the oxidizer. In this paper, we analyze the ability of a reaction wave to propagate in a porous medium without the aid of filtration. We find that one possible mechanism of propagation is that the wave is driven by diffusion of oxidizer from the environment. The solution of the combustion problem describing diffusion driven waves is similar to the solution of the Stefan problem describing the propagation of phase transition waves, in that the temperature on the interface between the burned and unburned regions is constant, the combustion wave is described by a similarity solution which is a function of the similarity variable x/square root of(t) and the wave velocity decays as 1/square root of(t). The difference between the two problems is that in the combustion problem the temperature is not prescribed, but rather, is determined as part of the solution. We will show that the length of samples in which such self-sustained combustion waves can occur, must exceed a critical value which strongly depends on the combustion temperature T(sub b). Smaller values of T(sub b) require longer sample lengths for diffusion driven combustion waves to exist. Because of their relatively small velocity, diffusion driven waves are considered to be relevant for the case of low heat losses, which occur for large diameter samples or in microgravity conditions, Another possible mechanism of porous medium combustion describes waves which propagate by consuming the oxidizer initially stored in the pores of the sample. This occurs for abnormally high pressure and gas density. In this case, uniformly propagating planar waves, which are kinetically controlled, can propagate, Diffusion of oxidizer decreases
Iotov, Mihail S.
The goals of this research are twofold: First, to develop methods and tools for studying problems in chemistry, material science and biology, as well as accurate prediction of the properties of structures and materials of importance to those fields. Second, use those tools to apply the methods to practical problems. In terms of methodology development this thesis focuses on two topics: One: Development of a massively parallel computer program to perform electronic, atomic, molecular levels simulations of problems in chemistry, material science and biology. This computer program uses existing and emerging hardware platforms and parallel tools and is based on decades long research in computer modeling and algorithms. We report on that development in Chapter 3. Two: Development of tools for Molecular Dynamics simulation and methods and tools for course-grained meso-scale modeling of transport properties and especially diffusion of gas penetrants in polymers. We have formulated a new method for extracting coarse-grained information from short (0.2-0.5 nanoseconds [ns]) MD simulations and use this in a meso-scale simulation to calculate diffusion constants in polymer matrices. This is a grid-based method, which calculates the average probability of each grid point of being a void and performs constrained and biased Monte Carlo (MC) dynamics to reach much longer time regimes than possible in MD. The MC method mimics the three regimes of mean square deviation (MSD) behavior seen in MD, thus accounting for the proper mobility of the voids and the compressibility of the polymer matrix. Theoretical discussions and justification for the method is presented in chapter 6. Initial results on He diffusion in a low-density polyethylene (PE) matrix are presented in chapter 7. The behavior at different temperatures follows closely the trend observed from calibrating long term MD for this particular system.
Diffusion in silicon isotope heterostructures
Energy Technology Data Exchange (ETDEWEB)
Silvestri, Hughes Howland [Univ. of California, Berkeley, CA (United States)
2004-01-01
The simultaneous diffusion of Si and the dopants B, P, and As has been studied by the use of a multilayer structure of isotopically enriched Si. This structure, consisting of 5 pairs of 120 nm thick natural Si and ^{28}Si enriched layers, enables the observation of ^{30}Si self-diffusion from the natural layers into the ^{28}Si enriched layers, as well as dopant diffusion from an implanted source in an amorphous Si cap layer, via Secondary Ion Mass Spectrometry (SIMS). The dopant diffusion created regions of the multilayer structure that were extrinsic at the diffusion temperatures. In these regions, the Fermi level shift due to the extrinsic condition altered the concentration and charge state of the native defects involved in the diffusion process, which affected the dopant and self-diffusion. The simultaneously recorded diffusion profiles enabled the modeling of the coupled dopant and self-diffusion. From the modeling of the simultaneous diffusion, the dopant diffusion mechanisms, the native defect charge states, and the self- and dopant diffusion coefficients can be determined. This information is necessary to enhance the physical modeling of dopant diffusion in Si. It is of particular interest to the modeling of future electronic Si devices, where the nanometer-scale features have created the need for precise physical models of atomic diffusion in Si. The modeling of the experimental profiles of simultaneous diffusion of B and Si under p-type extrinsic conditions revealed that both species are mediated by neutral and singly, positively charged Si self-interstitials. The diffusion of As and Si under extrinsic n-type conditions yielded a model consisting of the interstitialcy and vacancy mechanisms of diffusion via singly negatively charged self-interstitials and neutral vacancies. The simultaneous diffusion of P and Si has been modeled on the basis of neutral and singly negatively charged self-interstitials and neutral and singly
International Nuclear Information System (INIS)
Leo, Stefano de; Rotelli, Pietro
2009-01-01
We present the results of the planar diffusion of a Dirac particle by step and barrier potentials, when the incoming wave impinges at an arbitrary angle with the potential. Except for right-angle incidence this process is characterized by the appearance of spin flip terms. For the step potential, spin flip occurs for both transmitted and reflected waves. However, we find no spin flip in the transmitted barrier result. This is surprising because the barrier result may be derived directly from a two-step calculation. We demonstrate that the spin flip cancellation indeed occurs for each ''particle'' (wave packet) contribution. (orig.)
International Nuclear Information System (INIS)
Pretzsch, G.; Boerner, E.; Lehmann, R.; Sarenio, O.
1986-01-01
The invention relates to the detection of radioactive gases emitting alpha particles like radon, thoron and their alpha-decaying daughters by means of a diffusion chamber with a passive detector, preferably with a solid state track detector. In the chamber above and towards the detector there is a single metallized electret with negative polarity. The distance between electret and detector corresponds to the range of the alpha particles of radon daughters in air at the most. The electret collects the positively charged daughters and functions as surface source. The electret increases the sensitivity by the factor 4
International Nuclear Information System (INIS)
Ott, D.J.; Chen, Y.M.; Hewson, E.G.; Richter, J.E.; Wu, W.C.; Gelfand, D.W.; Castell, D.O.
1988-01-01
Radiologic and manometric findings were correlated in 17 patients with diffuse esophageal spasm (DES). All patients initially had chest pain and/or dysphagia and had a manometric diagnosis of DES. Mean percentage of normal peristalsis manometrically was 46% (range, 20%-80%). Based on radiologic examination, an esophageal motor disorder consistent with DES was diagnosed in 12 of 17 patients, and there was one misinterpretation of achalasia. Radiologic detection was not related significantly to the percentage of peristalsis seen on manometric examination. Mean esophageal wall thickness as measured radiographically in patients with DES was 2.6 mm, compared with 2.5 mm in 17 individuals with normal results of manometry
International Nuclear Information System (INIS)
Michaud, Georges; Montmerle, Thierry
1977-01-01
This paper is dealing with the origin of the elements in the universe. The scheme of nucleosynthesis is kept to explain the stellar generation of helium, carbon, etc... from the initial hydrogen; but a nonlinear theory is then elaborated to account for the anomalous abundances which were observed. The chemical elements would diffuse throughout the outer layers of a star under the action of the opposite forces of gravitation and radiation. This theory, with completing the nucleosynthesis, would contribute to give a consistent scheme of the elemental origin and abundances [fr
Communication skills training: describing a new conceptual model.
Brown, Richard F; Bylund, Carma L
2008-01-01
Current research in communication in physician-patient consultations is multidisciplinary and multimethodological. As this research has progressed, a considerable body of evidence on the best practices in physician-patient communication has been amassed. This evidence provides a foundation for communication skills training (CST) at all levels of medical education. Although the CST literature has demonstrated that communication skills can be taught, one critique of this literature is that it is not always clear which skills are being taught and whether those skills are matched with those being assessed. The Memorial Sloan-Kettering Cancer Center Comskil Model for CST seeks to answer those critiques by explicitly defining the important components of a consultation, based on Goals, Plans, and Actions theories and sociolinguistic theory. Sequenced guidelines as a mechanism for teaching about particular communication challenges are adapted from these other methods. The authors propose that consultation communication can be guided by an overarching goal, which is achieved through the use of a set of predetermined strategies. Strategies are common in CST; however, strategies often contain embedded communication skills. These skills can exist across strategies, and the Comskil Model seeks to make them explicit in these contexts. Separate from the skills are process tasks and cognitive appraisals that need to be addressed in teaching. The authors also describe how assessment practices foster concordance between skills taught and those assessed through careful coding of trainees' communication encounters and direct feedback.
Terms for describing new, advanced nuclear power plants
International Nuclear Information System (INIS)
1997-04-01
The IAEA's Division of Nuclear Power and the Fuel Cycle (then the Division of Nuclear Power) took an initiative in this field some years ago when work was initiated in the area of ''safety related terms'' by its International Working Group on Advanced Technologies for Water Cooled Reactors. This activity drew on advice from reactor design organizations, research institutes and government organizations, and aimed at helping eliminate confusion and misuse of safety related terms in widespread use, clarifying technical thinking regarding these terms, and improving nuclear power acceptability by providing precisely described technical meanings to them. After discussion also in the International Working Groups for Gas Cooled Reactors and Fast Reactors, the work resulted in the publication in September 1991 of IAEA-TECDOC-626, entitled ''Safety Related Terms for Advanced Nuclear Plants'', which has become a widely used publication. The present TECDOC has been prepared using the same approach to obtain advice from involved parties. Drafts of this report have been reviewed by the International Working Groups on Water Cooled Reactors, Fast Reactors and Gas Cooled Reactors, as well as by the IAEA's International Fusion Research Council (IFRC). The comments and suggestions received have been evaluated and utilized for producing the present TECDOC. 3 figs
INCAS: an analytical model to describe displacement cascades
Energy Technology Data Exchange (ETDEWEB)
Jumel, Stephanie E-mail: stephanie.jumel@edf.fr; Claude Van-Duysen, Jean E-mail: jean-claude.van-duysen@edf.fr
2004-07-01
REVE (REactor for Virtual Experiments) is an international project aimed at developing tools to simulate neutron irradiation effects in Light Water Reactor materials (Fe, Ni or Zr-based alloys). One of the important steps of the project is to characterise the displacement cascades induced by neutrons. Accordingly, the Department of Material Studies of Electricite de France developed an analytical model based on the binary collision approximation. This model, called INCAS (INtegration of CAScades), was devised to be applied on pure elements; however, it can also be used on diluted alloys (reactor pressure vessel steels, etc.) or alloys composed of atoms with close atomic numbers (stainless steels, etc.). INCAS describes displacement cascades by taking into account the nuclear collisions and electronic interactions undergone by the moving atoms. In particular, it enables to determine the mean number of sub-cascades induced by a PKA (depending on its energy) as well as the mean energy dissipated in each of them. The experimental validation of INCAS requires a large effort and could not be carried out in the framework of the study. However, it was verified that INCAS results are in conformity with those obtained from other approaches. As a first application, INCAS was applied to determine the sub-cascade spectrum induced in iron by the neutron spectrum corresponding to the central channel of the High Flux Irradiation Reactor of Oak Ridge National Laboratory.
INCAS: an analytical model to describe displacement cascades
Jumel, Stéphanie; Claude Van-Duysen, Jean
2004-07-01
REVE (REactor for Virtual Experiments) is an international project aimed at developing tools to simulate neutron irradiation effects in Light Water Reactor materials (Fe, Ni or Zr-based alloys). One of the important steps of the project is to characterise the displacement cascades induced by neutrons. Accordingly, the Department of Material Studies of Electricité de France developed an analytical model based on the binary collision approximation. This model, called INCAS (INtegration of CAScades), was devised to be applied on pure elements; however, it can also be used on diluted alloys (reactor pressure vessel steels, etc.) or alloys composed of atoms with close atomic numbers (stainless steels, etc.). INCAS describes displacement cascades by taking into account the nuclear collisions and electronic interactions undergone by the moving atoms. In particular, it enables to determine the mean number of sub-cascades induced by a PKA (depending on its energy) as well as the mean energy dissipated in each of them. The experimental validation of INCAS requires a large effort and could not be carried out in the framework of the study. However, it was verified that INCAS results are in conformity with those obtained from other approaches. As a first application, INCAS was applied to determine the sub-cascade spectrum induced in iron by the neutron spectrum corresponding to the central channel of the High Flux Irradiation Reactor of Oak Ridge National Laboratory.
INCAS: an analytical model to describe displacement cascades
International Nuclear Information System (INIS)
Jumel, Stephanie; Claude Van-Duysen, Jean
2004-01-01
REVE (REactor for Virtual Experiments) is an international project aimed at developing tools to simulate neutron irradiation effects in Light Water Reactor materials (Fe, Ni or Zr-based alloys). One of the important steps of the project is to characterise the displacement cascades induced by neutrons. Accordingly, the Department of Material Studies of Electricite de France developed an analytical model based on the binary collision approximation. This model, called INCAS (INtegration of CAScades), was devised to be applied on pure elements; however, it can also be used on diluted alloys (reactor pressure vessel steels, etc.) or alloys composed of atoms with close atomic numbers (stainless steels, etc.). INCAS describes displacement cascades by taking into account the nuclear collisions and electronic interactions undergone by the moving atoms. In particular, it enables to determine the mean number of sub-cascades induced by a PKA (depending on its energy) as well as the mean energy dissipated in each of them. The experimental validation of INCAS requires a large effort and could not be carried out in the framework of the study. However, it was verified that INCAS results are in conformity with those obtained from other approaches. As a first application, INCAS was applied to determine the sub-cascade spectrum induced in iron by the neutron spectrum corresponding to the central channel of the High Flux Irradiation Reactor of Oak Ridge National Laboratory
Computer modeling describes gravity-related adaptation in cell cultures.
Alexandrov, Ludmil B; Alexandrova, Stoyana; Usheva, Anny
2009-12-16
Questions about the changes of biological systems in response to hostile environmental factors are important but not easy to answer. Often, the traditional description with differential equations is difficult due to the overwhelming complexity of the living systems. Another way to describe complex systems is by simulating them with phenomenological models such as the well-known evolutionary agent-based model (EABM). Here we developed an EABM to simulate cell colonies as a multi-agent system that adapts to hyper-gravity in starvation conditions. In the model, the cell's heritable characteristics are generated and transferred randomly to offspring cells. After a qualitative validation of the model at normal gravity, we simulate cellular growth in hyper-gravity conditions. The obtained data are consistent with previously confirmed theoretical and experimental findings for bacterial behavior in environmental changes, including the experimental data from the microgravity Atlantis and the Hypergravity 3000 experiments. Our results demonstrate that it is possible to utilize an EABM with realistic qualitative description to examine the effects of hypergravity and starvation on complex cellular entities.
[Nursing between ethic and aesthetic. Profession described by media].
Gradellini, Cinzia; Idamou, Sara; Lusetti, Simona
2013-01-01
Nurse's role, according to the media, does not fit the role and evolution that nursing had in these last years: nursing remains unknown to public. Objective of research is to define how nurse's image is described by media. analysis of two newspapers, at national and local level with respect to articles about nurses, taking into account numbers of articles, position, topic (malpractice, frauds/crimes, job/economical cuts, praise). A second part of research has been focused on online newspapers, by using key words. Analysis of television medical dramas about presence of nurse, competences, relationship with physician/patient, social elements, context of work (acute or chronic), impact on patients welfare, and eventually ethical-deontological aspects has been carried out. on three hundred articles related health context, thirty-nine talk about nurse; five of those are in first page. 39% of articles regards frauds/crimes, 19% job/economical cuts, 15% malpractice. With respect to online articles, 66% concerns frauds/crimes. In medical dramas there is small attention to nurse who has generic competence as well as other health professional but doctor. The nurse character is played only by women. a low level of professionalism comes out both from newspaper and television. A specific professional identity is often absent furthermore nurses are relegated to a role of weakness in work and private circumstance.
An ontological approach to describing neurons and their relationships
Directory of Open Access Journals (Sweden)
David J. Hamilton
2012-04-01
Full Text Available The advancement of neuroscience, perhaps the most information rich discipline of all the life sciences, requires basic frameworks for organizing the vast amounts of data generated by the research community to promote novel insights and integrated understanding. Since Cajal, the neuron remains a fundamental unit of the nervous system, yet even with the explosion of information technology, we still have few comprehensive or systematic strategies for aggregating cell-level knowledge. Progress toward this goal is hampered by the multiplicity of names for cells and by lack of a consensus on the criteria for defining neuron types. However, through umbrella projects like the Neuroscience Information Framework and the International Neuroinformatics Coordinating Facility, we have the opportunity to propose and implement an informatics infrastructure for establishing common tools and approaches to describe neurons through a standard terminology for nerve cells and a database (a Neuron Registry where these descriptions can be deposited and compared. This article provides an overview of the problem and outlines a solution approach utilizing ontological characterizations.
DBH Prediction Using Allometry Described by Bivariate Copula Distribution
Xu, Q.; Hou, Z.; Li, B.; Greenberg, J. A.
2017-12-01
Forest biomass mapping based on single tree detection from the airborne laser scanning (ALS) usually depends on an allometric equation that relates diameter at breast height (DBH) with per-tree aboveground biomass. The incapability of the ALS technology in directly measuring DBH leads to the need to predict DBH with other ALS-measured tree-level structural parameters. A copula-based method is proposed in the study to predict DBH with the ALS-measured tree height and crown diameter using a dataset measured in the Lassen National Forest in California. Instead of exploring an explicit mathematical equation that explains the underlying relationship between DBH and other structural parameters, the copula-based prediction method utilizes the dependency between cumulative distributions of these variables, and solves the DBH based on an assumption that for a single tree, the cumulative probability of each structural parameter is identical. Results show that compared with the bench-marking least-square linear regression and the k-MSN imputation, the copula-based method obtains better accuracy in the DBH for the Lassen National Forest. To assess the generalization of the proposed method, prediction uncertainty is quantified using bootstrapping techniques that examine the variability of the RMSE of the predicted DBH. We find that the copula distribution is reliable in describing the allometric relationship between tree-level structural parameters, and it contributes to the reduction of prediction uncertainty.
Problems of describing the cumulative effect in relativistic nuclear physics
International Nuclear Information System (INIS)
Baldin, A.M.
1979-01-01
The problem of describing the cumulative effect i.e., the particle production on nuclei in the range kinematically forbidden for one-nucleon collisions, is studied. Discrimination of events containing cumulative particles fixes configurations in the wave function of a nucleus, when several nucleons are closely spaced and their quark-parton components are collectivized. For the cumulative processes under consideration large distances between quarks are very important. The fundamental facts and theoretical interpretation of the quantum field theory and of the condensed media theory in the relativistic nuclear physics are presented in brief. The collisions of the relativistic nuclei with low momentum transfers is considered in a fast moving coordinate system. The basic parameter determining this type of collisions is the energy of nucleon binding in nuclei. It has been shown that the short-range correlation model provides a good presentation of many characteristics of the multiple particle production and it may be regarded as an approximate universal property of hadron interactions
The self-describing data sets file protocol and Toolkit
International Nuclear Information System (INIS)
Borland, M.; Emery, L.
1995-01-01
The Self-Describing Data Sets (SDDS) file protocol continues to be used extensively in commissioning the Advanced Photon Source (APS) accelerator complex. SDDS protocol has proved useful primarily due to the existence of the SDDS Toolkit, a growing set of about 60 generic commandline programs that read and/or write SDDS files. The SDDS Toolkit is also used extensively for simulation postprocessing, giving physicists a single environment for experiment and simulation. With the Toolkit, new SDDS data is displayed and subjected to complex processing without developing new programs. Data from EPICS, lab instruments, simulation, and other sources are easily integrated. Because the SDDS tools are commandline-based, data processing scripts are readily written using the user's preferred shell language. Since users work within a UNIX shell rather than an application-specific shell or GUI, they may add SDDS-compliant programs and scripts to their personal toolkits without restriction or complication. The SDDS Toolkit has been run under UNIX on SUN OS4, HP-UX, and LINUX. Application of SDDS to accelerator operation is being pursued using Tcl/Tk to provide a GUI
Conceptual hierarchical modeling to describe wetland plant community organization
Little, A.M.; Guntenspergen, G.R.; Allen, T.F.H.
2010-01-01
Using multivariate analysis, we created a hierarchical modeling process that describes how differently-scaled environmental factors interact to affect wetland-scale plant community organization in a system of small, isolated wetlands on Mount Desert Island, Maine. We followed the procedure: 1) delineate wetland groups using cluster analysis, 2) identify differently scaled environmental gradients using non-metric multidimensional scaling, 3) order gradient hierarchical levels according to spatiotem-poral scale of fluctuation, and 4) assemble hierarchical model using group relationships with ordination axes and post-hoc tests of environmental differences. Using this process, we determined 1) large wetland size and poor surface water chemistry led to the development of shrub fen wetland vegetation, 2) Sphagnum and water chemistry differences affected fen vs. marsh / sedge meadows status within small wetlands, and 3) small-scale hydrologic differences explained transitions between forested vs. non-forested and marsh vs. sedge meadow vegetation. This hierarchical modeling process can help explain how upper level contextual processes constrain biotic community response to lower-level environmental changes. It creates models with more nuanced spatiotemporal complexity than classification and regression tree procedures. Using this process, wetland scientists will be able to generate more generalizable theories of plant community organization, and useful management models. ?? Society of Wetland Scientists 2009.
The complexity of organizational change: describing communication during organizational turbulence.
Salem, Philip
2013-01-01
Organizational researchers and practitioners have been interested in organizational change for some time. Historically, they have directed most of their efforts at improving the efficiency of planned top-down change. These efforts were strategic attempts at altering parameters leading to transformational change. Most efforts failed to meet their intended purposes. Transformational organizational change has not been likely. The legitimate systems have been robust. There has been little systematic investigation of the communication occurring during these efforts. The purpose of this essay is to describe results of a mixed methods research project answering two research questions. (a) How do organizational members communicate during a time of turbulence? (b) What features of this communication suggest the potential for or resistance to transformative change? Comparing the results at the beginning of the period to other periods, gives insight into how social actors communicate and enact the organization during a threshold period where transformational change was possible. Results reveal identifiable patterns of communication as communication strategies, parameters, or basins of attraction. The overall pattern explains how micro communication patterns intersect and how the accumulation of these patterns may resist or accomplish change at a macro level.
Kinetic isotope effects and how to describe them
Directory of Open Access Journals (Sweden)
Konstantin Karandashev
2017-11-01
Full Text Available We review several methods for computing kinetic isotope effects in chemical reactions including semiclassical and quantum instanton theory. These methods describe both the quantization of vibrational modes as well as tunneling and are applied to the ⋅H + H2 and ⋅H + CH4 reactions. The absolute rate constants computed with the semiclassical instanton method both using on-the-fly electronic structure calculations and fitted potential-energy surfaces are also compared directly with exact quantum dynamics results. The error inherent in the instanton approximation is found to be relatively small and similar in magnitude to that introduced by using fitted surfaces. The kinetic isotope effect computed by the quantum instanton is even more accurate, and although it is computationally more expensive, the efficiency can be improved by path-integral acceleration techniques. We also test a simple approach for designing potential-energy surfaces for the example of proton transfer in malonaldehyde. The tunneling splittings are computed, and although they are found to deviate from experimental results, the ratio of the splitting to that of an isotopically substituted form is in much better agreement. We discuss the strengths and limitations of the potential-energy surface and based on our findings suggest ways in which it can be improved.
Using the MWC model to describe heterotropic interactions in hemoglobin
Rapp, Olga
2017-01-01
Hemoglobin is a classical model allosteric protein. Research on hemoglobin parallels the development of key cooperativity and allostery concepts, such as the ‘all-or-none’ Hill formalism, the stepwise Adair binding formulation and the concerted Monod-Wymann-Changuex (MWC) allosteric model. While it is clear that the MWC model adequately describes the cooperative binding of oxygen to hemoglobin, rationalizing the effects of H+, CO2 or organophosphate ligands on hemoglobin-oxygen saturation using the same model remains controversial. According to the MWC model, allosteric ligands exert their effect on protein function by modulating the quaternary conformational transition of the protein. However, data fitting analysis of hemoglobin oxygen saturation curves in the presence or absence of inhibitory ligands persistently revealed effects on both relative oxygen affinity (c) and conformational changes (L), elementary MWC parameters. The recent realization that data fitting analysis using the traditional MWC model equation may not provide reliable estimates for L and c thus calls for a re-examination of previous data using alternative fitting strategies. In the current manuscript, we present two simple strategies for obtaining reliable estimates for MWC mechanistic parameters of hemoglobin steady-state saturation curves in cases of both evolutionary and physiological variations. Our results suggest that the simple MWC model provides a reasonable description that can also account for heterotropic interactions in hemoglobin. The results, moreover, offer a general roadmap for successful data fitting analysis using the MWC model. PMID:28793329
International Nuclear Information System (INIS)
Smirnova, E.S.; Chuvil'deev, V.N.
1998-01-01
The model is suggested which describes the influence of large-angle grain boundary migration on a diffusion controlled creep rate in polycrystalline materials (Coble creep). The model is based on the concept about changing the value of migrating boundary free volume when introducing dislocations distributed over the grain bulk into this boundary. Expressions are obtained to calculate the grain boundary diffusion coefficient under conditions of boundary migration and the parameter, which characterized the value of Coble creep acceleration. A comparison is made between calculated and experimental data for Cd, Co and Fe
Development of lithium diffused radiation resistant solar cells, part 2
Payne, P. R.; Somberg, H.
1971-01-01
The work performed to investigate the effect of various process parameters on the performance of lithium doped P/N solar cells is described. Effort was concentrated in four main areas: (1) the starting material, (2) the boron diffusion, (3) the lithium diffusion, and (4) the contact system. Investigation of starting material primarily involved comparison of crucible grown silicon (high oxygen content) and Lopex silicon (low oxygen content). In addition, the effect of varying growing parameters of crucible grown silicon on lithium cell output was also examined. The objective of the boron diffusion studies was to obtain a diffusion process which produced high efficiency cells with minimal silicon stressing and could be scaled up to process 100 or more cells per diffusion. Contact studies included investigating sintering of the TiAg contacts and evaluation of the contact integrity.
Describing of elements IO field in a testing computer program
Directory of Open Access Journals (Sweden)
Igor V. Loshkov
2017-01-01
Full Text Available A standard of describing the process of displaying interactive windows on a computer monitor, through which an output of questions and input of answers are implemented during computer testing, is presented in the article [11]. According to the proposed standard, the description of the process mentioned above is performed with a format line, containing element names, their parameters as well as grouping and auxiliary symbols. Program objects are described using elements of standard. The majority of objects create input and output windows on a computer monitor. The aim of our research was to develop a minimum possible set of elements of standard to perform mathematical and computer science testing.The choice of elements of the standard was conducted in parallel with the development and testing of the program that uses them. This approach made it possible to choose a sufficiently complete set of elements for testing in fields of study mentioned above. For the proposed elements, names were selected in such a way: firstly, they indicate their function and secondly, they coincide with the names of elements in other programming languages that are similar by function. Parameters, their names, their assignments and accepted values are proposed for the elements. The principle of name selection for the parameters was the same as for elements of the standard: the names should correspond to their assignments or coincide with names of similar parameters in other programming languages. The parameters define properties of objects. Particularly, while the elements of standard create windows, the parameters define object properties (location, size, appearance and the sequence in which windows are created. All elements of standard, proposed in this article are composed in a table, the columns of which have names and functions of these elements. Inside the table, the elements of standard are grouped row by row into four sets: input elements, output elements, input
Directory of Open Access Journals (Sweden)
Mafalda Costa Neves
2015-01-01
Conclusion: We describe a diffuse form of sporadic ICC hyperplasia harbouring multifocal GISTs, mimicking diffuse ICC hyperplasia in hereditary GIST syndromes. Detection of somatic c-KIT exon 11 mutation ruled out a hereditary disorder.
Autopathography and depression: describing the 'despair beyond despair'.
Moran, Stephen T
2006-01-01
The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, emphasizes diagnosis and statistically significant commonalities in mental disorders. As stated in the Introduction, "[i]t must be admitted that no definition adequately specifies precise boundaries for the concept of 'mental disorder' " (DSM-IV, 1994, xxi). Further, "[t]he clinician using DSM-IV should ... consider that individuals sharing a diagnosis are likely to be heterogeneous, even in regard to the defining features of the diagnosis, and that boundary cases will be difficult to diagnose in any but a probabilistic fashion" (DSM-IV, 1994, xxii). This article proposes that it may be helpful for clinicians to study narratives of illness which emphasize this heterogeneity over statistically significant symptoms. This paper examines the recorded experiences of unusually articulate sufferers of the disorder classified as Major Depression. Although sharing a diagnosis, Hemingway, Fitzgerald, and Styron demonstrated different understandings of their illness and its symptoms and experienced different resolutions, which may have had something to do with the differing meanings they made of it. I have proposed a word, autopathography, to describe a type of literature in which the author's illness is the primary lens through which the narrative is filtered. This word is an augmentation of an existing word, pathography, which The Oxford English Dictionary, Second Edition, defines as "a) [t]he, or a, description of a disease," and "b) [t]he, or a, study of the life and character of an individual or community as influenced by a disease." The second definition is the one that I find relevant and which I feel may be helpful to clinicians in broadening their understanding of the patient's experience.
Describing phase coexistence in systems with small phases
International Nuclear Information System (INIS)
Lovett, R
2007-01-01
Clusters of atoms can be studied in molecular beams and by computer simulation; 'liquid drops' provide elementary models for atomic nuclei and for the critical nuclei of nucleation theory. These clusters are often described in thermodynamic terms, but the behaviour of small clusters near a phase boundary is qualitatively different from the behaviour at a first order phase transition in idealized thermodynamics. In the idealized case the density and entropy show mathematically sharp discontinuities when the phase boundary is crossed. In large, but finite, systems, the phase boundaries become regions of state space wherein these properties vary rapidly but continuously. In small clusters with a large surface/volume ratio, however, the positive interfacial free energy makes it unlikely, even in states on phase boundaries, that a cluster will have a heterogeneous structure. What is actually seen in these states is a structure that fluctuates in time between homogeneous structures characteristic of the two sides of the phase boundary. That is, structural fluctuations are observed. Thermodynamics only predicts average properties; statistical mechanics is required to understand these fluctuations. Failure to distinguish thermodynamic properties and characterizations of fluctuations, particularly in the context of first order phase transitions, has led to suggestions that the classical rules for thermodynamic stability are violated in small systems and that classical thermodynamics provides an inconsistent description of these systems. Much of the confusion stems from taking statistical mechanical identifications of thermodynamic properties, explicitly developed for large systems, and applying them uncritically to small systems. There are no inconsistencies if thermodynamic properties are correctly identified and the distinction between thermodynamic properties and fluctuations is made clear
Diffusion in Solids Fundamentals, Methods, Materials, Diffusion-Controlled Processes
Mehrer, Helmut
2007-01-01
Diffusion is a vital topic in solid-state physics and chemistry, physical metallurgy and materials science. Diffusion processes are ubiquitous in solids at elevated temperatures. A thorough understanding of diffusion in materials is crucial for materials development and engineering. This book first gives an account of the central aspects of diffusion in solids, for which the necessary background is a course in solid state physics. It then provides easy access to important information about diffuson in metals, alloys, semiconductors, ion-conducting materials, glasses and nanomaterials. Several diffusion-controlled phenomena, including ionic conduction, grain-boundary and dislocation pipe diffusion, are considered as well. Graduate students in solid-state physics, physical metallurgy, materials science, physical and inorganic chemistry or geophysics will benefit from this book as will physicists, chemists, metallurgists, materials engineers in academic and industrial research laboratories.
The diffusion of microfinance.
Banerjee, Abhijit; Chandrasekhar, Arun G; Duflo, Esther; Jackson, Matthew O
2013-07-26
To study the impact of the choice of injection points in the diffusion of a new product in a society, we developed a model of word-of-mouth diffusion and then applied it to data on social networks and participation in a newly available microfinance loan program in 43 Indian villages. Our model allows us to distinguish information passing among neighbors from direct influence of neighbors' participation decisions, as well as information passing by participants versus nonparticipants. The model estimates suggest that participants are seven times as likely to pass information compared to informed nonparticipants, but information passed by nonparticipants still accounts for roughly one-third of eventual participation. An informed household is not more likely to participate if its informed friends participate. We then propose two new measures of how effective a given household would be as an injection point. We show that the centrality of the injection points according to these measures constitutes a strong and significant predictor of eventual village-level participation.
Diffuse infiltrative lung disease
International Nuclear Information System (INIS)
Niden, A.H.; Mishkin, F.S.
1984-01-01
The authors discuss their approach to the diagnosis and management of patients with DILD. Gallium scans play a central role in this process. Not only do they help them decide whom to biopsy, but also where to biopsy. The scans can be used for the early detection of disease in a high-risk population, for following the progression and regression of disease, for the regulation of medication, and for the evaluation of therapy. Bronchoalveolar lung lavage appears to be equally sensitive. However, patients are less willing to undergo repeated fiberoptic bronchoscopies than lung scans. Both tests may prove useful, one complementing the other. Gallium imaging has also been utilized by the authors in select patients with questionable diffuse lung infiltrates roentgenographically or with a normal chest roentgenogram, chronic respiratory symptoms, and abnormal pulmonary function studies. An abnormal gallium lung scan in these clinical situations helps them select which patients have a diffuse active pulmonary process meriting transbronchial biopsies. This has proven to be of particular value in the management of older patients
The diffusion bonding of advanced material
International Nuclear Information System (INIS)
Khan, T.I.
2001-01-01
As a joining process diffusion bonding has been used since early periods, and artifacts have been found which date back to 3000 years. However, over the last 20 years this joining process has been rediscovered and research has been carried out to understand the mechanisms of the process, and the application of the technique to advanced materials. This paper will review some of the reasons to why diffusion bonding may be preferred over other more conventional welding processes to join advanced alloy systems. It also describes in brief the different types of bonding processes, namely, solid-state and liquid phase bonding techniques. The paper demonstrates the application of diffusion bonding processes to join a range of dissimilar materials for instance: oxide dispersion strengthened superalloys, titanium to duplex stainless steels and engineering ceramics such as Si/sub 3/N/sub 4/ to metal alloys. The research work highlights the success and limitations of the diffusion bonding process and is based on the experience of the author and his colleagues. (author)
Effective diffusion in laminar convective flows
International Nuclear Information System (INIS)
Rosenbluth, M.N.; Berk, H.L.; Doxas, I.; Horton, W.
1987-03-01
The effective diffusion coefficient D* of a passive component, such as test particles, dye, temperature, magnetic flux, etc., is derived for motion in periodic two-dimensional incompressible convective flow with characteristic velocity v and size d in the presence of an intrinsic local diffusivity D. Asymptotic solutions for effective diffusivity D*(P) in the large P limit, with P ∼ vd/D, is shown to be of the form D* = cDP/sup 1/2/ with c being a coefficient that is determined analytically. The constant c depends on the geometry of the convective cell and on an average of the flow speed along the separatrix. The asymptotic method of evaluation applies to both free boundary and rough boundary flow patterns and it is shown that the method can be extended to more complicated patterns such as the flows generated by rotating cylinders, as in the problem considered by Nadim, Cox, and Brenner [J. Fluid Mech., 164: 185 (1986)]. The diffusivity D* is readily calculated for small P, but the evaluation for arbitrary P requires numerical methods. Monte Carlo particle simulation codes are used to evaluate D* at arbitrary P, and thereby describe the transition for D* between the large and small P limits
Diffusion with Varying Drag; the Runaway Problem.
Rollins, David Kenneth
We study the motion of electrons in an ionized plasma of electrons and ions in an external electric field. A probability distribution function describes the electron motion and is a solution of a Fokker-Planck equation. In zero field, the solution approaches an equilibrium Maxwellian. For arbitrarily small field, electrons overcome the diffusive effects and are freely accelerated by the field. This is the electron runaway phenomenon. We treat the electric field as a small perturbation. We consider various diffusion coefficients for the one dimensional problem and determine the runaway current as a function of the field strength. Diffusion coefficients, non-zero on a finite interval are examined. Some non-trivial cases of these can be solved exactly in terms of known special functions. The more realistic case where the diffusion coefficient decays with velocity are then considered. To determine the runaway current, the equivalent Schrodinger eigenvalue problem is analysed. The smallest eigenvalue is shown to be equal to the runaway current. Using asymptotic matching a solution can be constructed which is then used to evaluate the runaway current. The runaway current is exponentially small as a function of field strength. This method is used to extract results from the three dimensional problem.
Diffusion with varying drag; the runaway problem
International Nuclear Information System (INIS)
Rollins, D.K.
1986-01-01
The motion of electrons in an ionized plasma of electrons and ions in an external electric field is studied. A probability distribution function describes the electron motion and is a solution of a Fokker-Planck equation. In zero field, the solution approaches an equilibrium Maxwellian. For arbitrarily small field, electrons overcome the diffusive effects and are freely accelerated by the field. This is the electron-runaway phenomenon. The electric field is treated as a small perturbation. Various diffusion coefficients are considered for the one dimensional problem, and the runaway current is determined as a function of the field strength. Diffusion coefficients, non-zero on a finite interval are examined. Some non-trivial cases of these can be solved exactly in terms of known special functions. The more realistic case where the diffusion coeffient decays with velocity are then considered. To determine the runaway current, the equivalent Schroedinger eigenvalue problem is analyzed. The smallest eigenvalue is shown to be equal to the runaway current. Using asymptotic matching, a solution can be constructed which is then used to evaluate the runaway current. The runaway current is exponentially small as a function of field strength. This method is used to extract results from the three dimensional problem
Observation of diffusion phenomena of liquid phase with multiple components
International Nuclear Information System (INIS)
Eguchi, Wataru
1979-01-01
The diffusion phenomena of liquid phase with multiple components was directly observed, and the factors contributing to complex material transfer were investigated, comparing to the former experimental results. The most excellent method of observing the diffusion behavior of liquid phase used heretofore is to trace the time history of concentration distribution for each component in unsteady diffusion process. The method of directly observing the concentration distribution is usually classified into the analysis of diffused samples, the checking of radioactive isotope tracers, and the measurement of light refraction and transmission. The most suitable method among these is to trace this time history by utilizing the spectrophotometer of position scanning type. An improved spectrophotometer was manufactured for trial. The outline of the measuring system and the detail of the optical system of this new type spectrophotometer are explained. The resolving power for position measurement is described with the numerical calculation. As for the observation examples of the diffusion phenomena of liquid phase with multiple components, the diffusion of multiple electrolytes in aqueous solution, the observation of the material transfer phenomena accompanied by heterogeneous and single phase chemical reaction, and the observation of concentration distribution in the liquid diaphragm in a reaction absorption system are described. For each experimental item, the test apparatus, the sample material, the test process, the test results and the evaluation are explained in detail, and the diffusion phenomena of liquid phase with multiple components were pretty well elucidated. (Nakai, Y.)
Gaseous diffusion flames: simple structures and their interaction
Energy Technology Data Exchange (ETDEWEB)
Cavaliere, A. [Universita degli Studi Federico II, Naples (Italy). Dip. di Ingegneria Chimica; Ragucci, R. [Istituto di Ricerche sulla Combustione C,N.R., Naples (Italy)
2001-07-01
This is a synoptic overview of a selection of works dealing with single diffusive structures, with their mutual interaction in simple flows and their statistical modeling in complex flows. The focus is on reacting conditions pertaining to gaseous diffusion flames, but isothermal structures are also described when they are of some conceptual interest. This paper considers only few representative works for each subject, which are functional in explaining the key characteristics of the diffusive structures. The extension, given to single subjects, is not weighed according to the number of related publications but on the relevance to the basic understanding of the general framework concerning diffusion flames. One-dimensional structures are first discussed. They are ordered according to the number of balance equation terms needed for their description. Two-dimensional (2D) structures are then introduced following an order based on their convolution level. Some pioneering work on three-dimensional structures is further quoted. The temporal evolution of simple structures in quiescent or simple flowing 2D systems is considered. The latter case is exploited to present classification of diffusion-controlled mixing regimes. Modeling characterization approach of turbulent diffusion flames is also described in order to yield a self-sufficient didactic presentation. The approach based on the flame surface density model is specifically discussed because of its potential use in the determination of qualitative and quantitative features of simple diffusion flames. (author)
Neutron diffusion: connection with the theory of browniam motion
International Nuclear Information System (INIS)
Dellagi, Mohamed
1977-01-01
The displacement of the neutron projection on an axis Ox and its density of probability are introduced instead of describing the diffusion theory with neutron density, as is usual. If the point source O is isotropic and neutron monoenergetic, the brownian particle described by Langevin's equation and neutron have the same time correlation of velocity [fr
International Nuclear Information System (INIS)
Till, Bernie C; Driessen, Peter F
2014-01-01
Starting from first principles, we derive the telegraph equation to describe the propagation of sound waves in rigid tubes by using a simple approach that yields a lossy transmission line model with frequency-independent parameters. The approach is novel in the sense that it has not been found in the literature or textbooks. To derive the lossy acoustic telegraph equation from the lossless wave equation, we need only to relax the assumption that the dynamical variables are constant over the entire cross-sectional area of the tube. In this paper, we do this by introducing a relatively narrow boundary layer at the wall of the tube, over which the dynamical variables decrease linearly from the constant value to zero. This allows us to make very simple corrections to the lossless case, and to express them in terms of two parameters, namely the viscous diffusion time constant and the thermal diffusion time constant. The coefficients of the resulting telegraph equation are frequency-independent. A comparison with the telegraph equation for the electrical transmission line establishes precise relationships between the electrical circuit elements and the physical properties of the fluid. These relationships are thus proven a posteriori rather than asserted a priori. In this way, we arrive at an instructive and useful derivation of the acoustic telegraph equation, which takes viscous damping and thermal dissipation into account, and is accessible to students at the undergraduate level. This derivation does not resort to the combined heavy machinery of fluid dynamics and thermodynamics, does not assume that the waveforms are sinusoidal, and does not assume any particular cross-sectional shape of the tube. Surprisingly, we have been unable to find a comparable treatment in the standard introductory physics and acoustics texts, or in the literature. (paper)
Oxide film assisted dopant diffusion in silicon carbide
Energy Technology Data Exchange (ETDEWEB)
Tin, Chin-Che, E-mail: cctin@physics.auburn.ed [Department of Physics, Auburn University, Alabama 36849 (United States); Mendis, Suwan [Department of Physics, Auburn University, Alabama 36849 (United States); Chew, Kerlit [Department of Electrical and Electronic Engineering, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Kuala Lumpur (Malaysia); Atabaev, Ilkham; Saliev, Tojiddin; Bakhranov, Erkin [Physical Technical Institute, Uzbek Academy of Sciences, 700084 Tashkent (Uzbekistan); Atabaev, Bakhtiyar [Institute of Electronics, Uzbek Academy of Sciences, 700125 Tashkent (Uzbekistan); Adedeji, Victor [Department of Chemistry, Geology and Physics, Elizabeth City State University, North Carolina 27909 (United States); Rusli [School of Electrical and Electronic Engineering, Nanyang Technological University (Singapore)
2010-10-01
A process is described to enhance the diffusion rate of impurities in silicon carbide so that doping by thermal diffusion can be done at lower temperatures. This process involves depositing a thin film consisting of an oxide of the impurity followed by annealing in an oxidizing ambient. The process uses the lower formation energy of silicon dioxide relative to that of the impurity-oxide to create vacancies in silicon carbide and to promote dissociation of the impurity-oxide. The impurity atoms then diffuse from the thin film into the near-surface region of silicon carbide.
Oxide film assisted dopant diffusion in silicon carbide
International Nuclear Information System (INIS)
Tin, Chin-Che; Mendis, Suwan; Chew, Kerlit; Atabaev, Ilkham; Saliev, Tojiddin; Bakhranov, Erkin; Atabaev, Bakhtiyar; Adedeji, Victor; Rusli
2010-01-01
A process is described to enhance the diffusion rate of impurities in silicon carbide so that doping by thermal diffusion can be done at lower temperatures. This process involves depositing a thin film consisting of an oxide of the impurity followed by annealing in an oxidizing ambient. The process uses the lower formation energy of silicon dioxide relative to that of the impurity-oxide to create vacancies in silicon carbide and to promote dissociation of the impurity-oxide. The impurity atoms then diffuse from the thin film into the near-surface region of silicon carbide.
Explosive instabilities of reaction-diffusion equations including pinch effects
International Nuclear Information System (INIS)
Wilhelmsson, H.
1992-01-01
Particular solutions of reaction-diffusion equations for temperature are obtained for explosively unstable situations. As a result of the interplay between inertial, diffusion, pinch and source processes certain 'bell-shaped' distributions may grow explosively in time with preserved shape of the spatial distribution. The effect of the pinch, which requires a density inhomogeneity, is found to diminish the effect of diffusion, or inversely to support the inertial and source processes in creating the explosion. The results may be described in terms of elliptic integrals or. more simply, by means of expansions in the spatial coordinate. An application is the temperature evolution of a burning fusion plasma. (au) (18 refs.)
Confinement and diffusion in tokamaks
International Nuclear Information System (INIS)
McWilliams, R.
1988-01-01
The effect of electric field fluctuations on confinement and diffusion in tokamak is discussed. Based on the experimentally determined cross-field turbolent diffusion coefficient, D∼3.7*cT e /eB(δn i /n i ) rms which is also derived by a simple theory, the cross-field diffusion time, tp=a 2 /D, is calculated and compared to experimental results from 51 tokamak for standard Ohmic operation
Statistical model of a gas diffusion electrode. III. Photomicrograph study
Energy Technology Data Exchange (ETDEWEB)
Winsel, A W
1965-12-01
A linear section through a gas diffusion electrode produces a certain distribution function of sinews with the pores. From this distribution function some qualities of the pore structure are derived, and an automatic device to determine the distribution function is described. With a statistical model of a gas diffusion electrode the behavior of a DSK electrode is discussed and compared with earlier measurements of the flow resistance of this material.
Diffusion of zinc into an unpassivated surface of indium phosphide
International Nuclear Information System (INIS)
Budko, T.O.; Gushchinskaya, E.V.; Emelyanenko, Yu.S.; Malyshev, S.A.
1989-01-01
Peculiarities are studied of the diffusion of Zn into an unpassivated surface of InP in an open gasflow system. In the region where the carrier concentration profile is described by an erfc (error function compliment), the diffusion coefficient and activation energy are determined. It is shown that thermal processes cause changes in the charge state of Zn in InP which result in a variation of the carrier profile in the semiconductor. (author)
International Nuclear Information System (INIS)
Cherstvy, Andrey G; Metzler, Ralf
2015-01-01
We study generalized anomalous diffusion processes whose diffusion coefficient D(x, t) ∼ D 0 |x| α t β depends on both the position x of the test particle and the process time t. This process thus combines the features of scaled Brownian motion and heterogeneous diffusion parent processes. We compute the ensemble and time averaged mean squared displacements of this generalized diffusion process. The scaling exponent of the ensemble averaged mean squared displacement is shown to be the product of the critical exponents of the parent processes, and describes both subdiffusive and superdiffusive systems. We quantify the amplitude fluctuations of the time averaged mean squared displacement as function of the length of the time series and the lag time. In particular, we observe a weak ergodicity breaking of this generalized diffusion process: even in the long time limit the ensemble and time averaged mean squared displacements are strictly disparate. When we start to observe this process some time after its initiation we observe distinct features of ageing. We derive a universal ageing factor for the time averaged mean squared displacement containing all information on the ageing time and the measurement time. External confinement is shown to alter the magnitudes and statistics of the ensemble and time averaged mean squared displacements. (paper)
Diffuse lung disease: Pneumoconioses
International Nuclear Information System (INIS)
McLoud, T.C.
1987-01-01
This paper begins with a discussion of the 1980 International Labour Organization classification of the pneumoconioses. Emphasis is on the common pneumoconioses, that is, silicosis, coalworker's pneumoconiosis, and asbestos-related pleural and parenchymal disease. Examples of the five radiographic forms of silicosis-simple and complicated silicosis, Caplan syndrome, silicotuberculosis, and acute silicosis- are presented, and the differential diagnoses are discussed. Discussion of asbestos-related disease included pleural manifestations such as plaques, diffuse pleural thickening, and asbestos pleural effusion as well as asbestosis and malignancies associated with asbestos exposure, such as bronchogenic carcinoma and malignant mesothelioma. Although the standard radiographic findings are stressed, the use of CT in the diagnosis of pneumoconiosis and the staging of dust-related malignancies is also discussed
On Diffusive Climatological Models.
Griffel, D. H.; Drazin, P. G.
1981-11-01
A simple, zonally and annually averaged, energy-balance climatological model with diffusive heat transport and nonlinear albedo feedback is solved numerically. Some parameters of the model are varied, one by one, to find the resultant effects on the steady solution representing the climate. In particular, the outward radiation flux, the insulation distribution and the albedo parameterization are varied. We have found an accurate yet simple analytic expression for the mean annual insolation as a function of latitude and the obliquity of the Earth's rotation axis; this has enabled us to consider the effects of the oscillation of the obliquity. We have used a continuous albedo function which fits the observed values; it considerably reduces the sensitivity of the model. Climatic cycles, calculated by solving the time-dependent equation when parameters change slowly and periodically, are compared qualitatively with paleoclimatic records.
Diffuse parenchymal lung disease
Directory of Open Access Journals (Sweden)
Sara Tomassetti
2017-04-01
Full Text Available Between September 2015 and August 2016 there were >1500 publications in the field of diffuse parenchymal lung diseases (DPLDs. For the Clinical Year in Review session at the European Respiratory Society Congress that was held in London, UK, in September 2016, we selected only five articles. This selection, made from the enormous number of published papers, does not include all the relevant studies that will significantly impact our knowledge in the field of DPLDs in the near future. This review article provides our personal view on the following topics: early diagnosis of idiopathic pulmonary fibrosis, current knowledge on the multidisciplinary team diagnosis of DPLDs and the diagnostic role of transbronchial cryobiopsy in this diagnostic setting, insights on the new entity of interstitial pneumonia with autoimmune features, and new therapeutic approaches for scleroderma-related interstitial lung disease.
Convergence of Nelson diffusions
International Nuclear Information System (INIS)
Dell'Antonio, G.; Posilicano, A.
1991-01-01
Let ψ t , ψ t n , n≥1, be solutions of Schroedinger equations with potentials form-bounded by -1/2 Δ and initial data in H 1 (R d ). Let P, P n , n≥1, be the probability measures on the path space Ω=C(R + , R d ) given by the corresponding Nelson diffusions. We show that if {ψ t n } n≥1 converges to ψ t in H 2 (R d ), uniformly in t over compact intervals, then {P n } n≥1 converges to P in total variation. Moreover, if the potentials are in the Kato class K d , we show that the above result follows from H 1 -convergence of initial data, and K d -convergence of potentials. (orig.)
Hereditary diffuse gastric cancer
DEFF Research Database (Denmark)
van der Post, Rachel S; Vogelaar, Ingrid P; Carneiro, Fátima
2015-01-01
Germline CDH1 mutations confer a high lifetime risk of developing diffuse gastric (DGC) and lobular breast cancer (LBC). A multidisciplinary workshop was organised to discuss genetic testing, surgery, surveillance strategies, pathology reporting and the patient's perspective on multiple aspects......, including diet post gastrectomy. The updated guidelines include revised CDH1 testing criteria (taking into account first-degree and second-degree relatives): (1) families with two or more patients with gastric cancer at any age, one confirmed DGC; (2) individuals with DGC before the age of 40 and (3...... the high mortality associated with invasive disease, prophylactic total gastrectomy at a centre of expertise is advised for individuals with pathogenic CDH1 mutations. Breast cancer surveillance with annual breast MRI starting at age 30 for women with a CDH1 mutation is recommended. Standardised endoscopic...
Nonlocal diffusion and applications
Bucur, Claudia
2016-01-01
Working in the fractional Laplace framework, this book provides models and theorems related to nonlocal diffusion phenomena. In addition to a simple probabilistic interpretation, some applications to water waves, crystal dislocations, nonlocal phase transitions, nonlocal minimal surfaces and Schrödinger equations are given. Furthermore, an example of an s-harmonic function, its harmonic extension and some insight into a fractional version of a classical conjecture due to De Giorgi are presented. Although the aim is primarily to gather some introductory material concerning applications of the fractional Laplacian, some of the proofs and results are new. The work is entirely self-contained, and readers who wish to pursue related subjects of interest are invited to consult the rich bibliography for guidance.
MHD diffuser model test program
Energy Technology Data Exchange (ETDEWEB)
Idzorek, J J
1976-07-01
Experimental results of the aerodynamic performance of seven candidate diffusers are presented to assist in determining their suitability for joining an MHD channel to a steam generator at minimum spacing. The three dimensional diffusers varied in area ratio from 2 to 3.8 and wall half angle from 2 to 5 degrees. The program consisted of five phases: (1) tailoring a diffuser inlet nozzle to a 15 percent blockage; (2) comparison of isolated diffusers at enthalpy ratios 0.5 to 1.0 with respect to separation characteristics and pressure recovery coefficients; (3) recording the optimum diffuser exit flow distribution; (4) recording the internal flow distribution within the steam generator when attached to the diffuser; and (5) observing isolated diffuser exhaust dynamic characteristics. The 2 and 2-1/3 degree half angle rectangular diffusers showed recovery coefficients equal to 0.48 with no evidence of flow separation or instability. Diffusion at angles greater than these produced flow instabilities and with angles greater than 3 degrees random flow separation and reattachment.
MHD diffuser model test program
International Nuclear Information System (INIS)
Idzorek, J.J.
1976-07-01
Experimental results of the aerodynamic performance of seven candidate diffusers are presented to assist in determining their suitability for joining an MHD channel to a steam generator at minimum spacing. The three dimensional diffusers varied in area ratio from 2 to 3.8 and wall half angle from 2 to 5 degrees. The program consisted of five phases: (1) tailoring a diffuser inlet nozzle to a 15 percent blockage; (2) comparison of isolated diffusers at enthalpy ratios 0.5 to 1.0 with respect to separation characteristics and pressure recovery coefficients; (3) recording the optimum diffuser exit flow distribution; (4) recording the internal flow distribution within the steam generator when attached to the diffuser; and (5) observing isolated diffuser exhaust dynamic characteristics. The 2 and 2-1/3 degree half angle rectangular diffusers showed recovery coefficients equal to 0.48 with no evidence of flow separation or instability. Diffusion at angles greater than these produced flow instabilities and with angles greater than 3 degrees random flow separation and reattachment
Diffusion rates for elevated releases
International Nuclear Information System (INIS)
Ramsdell, J.V.
1983-11-01
A search of the literature related to diffusion from elevated sources has determined that an adequate data base exists for use in developing parameterizations for estimating diffusion rates for material released from free standing stacks at nuclear power plants. A review of published data analyses indicates that a new parameterization of horizontal diffusion rates specifically for elevated releases is not likely to significantly change the magnitudes of horizontal diffusion coefficients on the average. However, the uncertainties associated with horizontal diffusion coefficient estimates under any given set of atmospheric conditions could be reduced by a new parameterization. Similarly, a new parameterization of vertical diffusion rates would be unlikely to significantly alter the magnitudes of diffusion coefficients for unstable atmospheric conditons. However, for neutral and stable atmospheric conditions, a new parameterization of vertical diffusion rates might increase vertical diffusion coefficients significantly. The increase would move ground-level time-integrated concentration maxima closer to the plant and would increase the maxima. 55 references, 2 figures, 4 tables
International Nuclear Information System (INIS)
Wehinger, Björn; Krisch, Michael; Bosak, Alexeï; Chernyshov, Dmitry; Bulat, Sergey; Ezhov, Victor
2014-01-01
Single crystals of ice Ih, extracted from the subglacial Lake Vostok accretion ice layer (3621 m depth) were investigated by means of diffuse x-ray scattering and inelastic x-ray scattering. The diffuse scattering was identified as mainly inelastic and rationalized in the frame of ab initio calculations for the ordered ice XI approximant. Together with Monte-Carlo modelling, our data allowed reconsidering previously available neutron diffuse scattering data of heavy ice as the sum of thermal diffuse scattering and static disorder contribution. (paper)
Diffusion of condenser water discharge
International Nuclear Information System (INIS)
Iwakiri, Toshio
1977-01-01
Thermal and nuclear power stations in Japan are mostly located in coastal area, and the cooling water is discharged into sea as warm water. Recently, large interest is taken in this matter, and it is desirable to predict the diffusion of warm discharge accurately and to take effective measures for lowering the temperature. As for the methods of predicting the diffusion of warm discharge, simplified estimation, mathematical analysis and hydrographical model experiment are used corresponding to objects and conditions. As for the measures to lower temperature, the method of discharging warm water into deep sea bottom was confirmed to be very effective. In this paper, the phenomena of diffusion of warm discharge in sea, the methods of predicting the diffusion of warm discharge, and the deep sea discharge as the measure for lowering temperature are outlined. The factors concerning the diffusion of warm discharge in sea are the conditions of discharge, topography and sea state, and the diffusion is roughly divided into mixing diffusion in the vicinity of warm water outlet and eddy diffusion in distant region. It is difficult to change artificially the conditions of diffusion in distant region, and the measures of raising the rate of dilution in near region are effective, therefore the deep sea discharge is adopted. (Kako, I.)
Diffusion effects in undulator radiation
Directory of Open Access Journals (Sweden)
Ilya Agapov
2014-11-01
Full Text Available Quantum diffusion effects in undulator radiation in semiclassical approximation are considered. Short-term effects on the electron beam motion are discussed and it is shown that approaches based on diffusion approximation with drift-diffusion coefficients derived from undulator or bending magnet radiation spectrum, and on Poisson statistics with radiation spectrum defined by the local beding field, all lead to similar results in terms of electron energy spread for cases of practical interest. An analytical estimate of the influence of quantum diffusion on the undulator radiation spectrum is derived.
Sodium diffusion in boroaluminosilicate glasses
DEFF Research Database (Denmark)
Smedskjaer, Morten M.; Zheng, Qiuju; Mauro, John C.
2011-01-01
of isothermal sodium diffusion in BAS glasses by ion exchange, inward diffusion, and tracer diffusion experiments. By varying the [SiO2]/[Al2O3] ratio of the glasses, different structural regimes of sodium behavior are accessed. We show that the mobility of the sodium ions decreases with increasing [SiO2]/[Al2O......Understanding the fundamentals of alkali diffusion in boroaluminosilicate (BAS) glasses is of critical importance for advanced glass applications, e.g., the production of chemically strengthened glass covers for personal electronic devices. Here, we investigate the composition dependence...
Diffusion of fluoride in bovine enamel
International Nuclear Information System (INIS)
Flim, G.J.; Arends, J.; Kolar, Z.
1976-01-01
The uptake of 18 F and the penetration of both F and 18 F in bovine enamel was investigated. Sodium fluoride solutions buffered at pH 7 were employed. The uptake of 18 F was measured by a method described by R. Duckworth and M. Braden, Archs. Oral. Biol., 12(1967), pp. 217-230. The penetration concentration profiles of fluoride (F, 18 F) in the enamel were measured by a sectioning technique. The 18 F uptake in enamel was proportional to approximately tsup(3/4); t being the uptake time. The 18 F concentration as a function of the position in the enamel can be described by: c*(x,t) = c 0 *(t)exp[-α*(t)x]. After correction for the initial fluoride concentration in enamel, for unlabelled fluoride the same dependency is obtained. A model based on simultaneous diffusion and chemical reaction in the pores and diffusion into the hydroxyapatite crystallites will be presented. The results show that diffusion coefficients of the pores are approximately equal to 10 -10 cm 2 s -1 and in the apatite crystallites approximately equal to 10 -17 cm 2 s -1 . The limitations and the approximations of the model are discussed
International Nuclear Information System (INIS)
Juranyi, Fanni; Gonzalez Sanchez, Fatima; Gimmi, Thomas; Bestel, Martina; Van Loon, Luc; Diamond, Larryn W.
2013-01-01
Observable water diffusion processes in clays and their parameters depend on the spatial- and time-scale of the measurement. Comparing the diffusion coefficients of quasielastic neutron scattering and tracer through-diffusion, 'chemical' and 'geometrical' effects can be distinguished and quantified. Results for montmorillonite and illite in the Na- and Ca- form illustrate this very well. Swelling clays such as montmorillonite are especially interesting because of the interlayer water. This water is confined in form of few layers such that the diffusion occurs essentially in 2D. Furthermore the ratio of interlayer- and external- (macro-pore) water changes as a function of bulk dry density and degree of water saturation. Therefore it is of interest to describe the diffusion process using these parameters. Finally, the activation energy of the diffusion should be equal for both methods assuming that the geometrical factor does not depend on temperature. For the montmorillonites this was not the case, which might also indicate that the main processes on the two scales are different. We conclude that the geometrical factor and the electrostatic constraint can be determined from a comparison of the diffusion coefficients measured by the two different techniques: quasielastic neutron scattering and tracer through diffusion. Furthermore, activation energies obtained at the two scales are similar for clays having no interlayer water. For montmorillonite the activation energy values are different. Further investigations are required to clarify the reason. (authors)
International Nuclear Information System (INIS)
Sato, Haruo
2001-01-01
A program (TDROCK1. FOR) for simulation and analysis of through-diffusion experiments for a single layer of diffusion media was developed. This program was made by Pro-Fortran language, which was suitable for scientific and technical calculations, and relatively easy explicit difference method was adopted for an analysis. In the analysis, solute concentration in the tracer cell as a function of time that we could not treat to date can be input and the decrease in the solute concentration as a function of time by diffusion from the tracer cell to the measurement cell, the solute concentration distribution in the porewater of diffusion media and the solute concentration in the measurement cell as a function of time can be calculated. In addition, solution volume in both cells and diameter and thickness of the diffusion media are also variable as an input condition. This simulation program could well explain measured result by simulating solute concentration in the measurement cell as a function of time for case which apparent and effective diffusion coefficients were already known. Based on this, the availability and applicability of this program to actual analysis and simulation were confirmed. This report describes the theoretical treatment for the through-diffusion experiments for a single layer of diffusion media, analytical model, an example of source program and the manual. (author)
Turing instability in reaction-diffusion systems with nonlinear diffusion
Energy Technology Data Exchange (ETDEWEB)
Zemskov, E. P., E-mail: zemskov@ccas.ru [Russian Academy of Sciences, Dorodnicyn Computing Center (Russian Federation)
2013-10-15
The Turing instability is studied in two-component reaction-diffusion systems with nonlinear diffusion terms, and the regions in parametric space where Turing patterns can form are determined. The boundaries between super- and subcritical bifurcations are found. Calculations are performed for one-dimensional brusselator and oregonator models.
Uranium enrichment by the gaseous diffusion process
International Nuclear Information System (INIS)
Petit, J.F.
1977-01-01
After a brief description of the process and technology (principle, stage constitution, cascade constitution, and description of a plant), the author gives the history of gaseous diffusion and describes the existing facilities. Among the different enrichment processes contemplated in the USA during and after the last world war, gaseous diffusion has been the only one to be developed industrially on a wide scale in the USA, then in the UK, in the USSR and in France. The large existing capacities in the USA provided the country with a good starting base for the development of a light-water nuclear power plant programme, the success of which led to a shortfall in production means. France and the USA, possessing the necessary know-how, have been able to undertake the realization of two industrial programmes: the CIP-CUP programme in the USA and the Eurodif project in France. Current plans still call for the construction of several plants by 1990. Can the gaseous diffusion process meet this challenge. Technically, there is no doubt about it. Economically, this process is mainly characterized by large energy consumption and the necessity to build large plants. This leads to a large investment, at least for the first plant. Other processes have been developed with a view to reducing both energy and capital needs. However, in spite of continuous studies and technological progress, no process has yet proved competitive. Large increments in capacities are still expected to come from gaseous diffusion, and several projects taking into account the improvements in flexibility, automatization, reliability and reduced investment, are analysed in the paper. Combining new facilities with existing plants has already proved to be of great interest. This situation explains why gaseous diffusion is being further investigated and new processes are being studied. (author)
Fractional diffusion models of nonlocal transport
International Nuclear Information System (INIS)
Castillo-Negrete, D. del
2006-01-01
A class of nonlocal models based on the use of fractional derivatives (FDs) is proposed to describe nondiffusive transport in magnetically confined plasmas. FDs are integro-differential operators that incorporate in a unified framework asymmetric non-Fickian transport, non-Markovian ('memory') effects, and nondiffusive scaling. To overcome the limitations of fractional models in unbounded domains, we use regularized FDs that allow the incorporation of finite-size domain effects, boundary conditions, and variable diffusivities. We present an α-weighted explicit/implicit numerical integration scheme based on the Grunwald-Letnikov representation of the regularized fractional diffusion operator in flux conserving form. In sharp contrast with the standard diffusive model, the strong nonlocality of fractional diffusion leads to a linear in time response for a decaying pulse at short times. In addition, an anomalous fractional pinch is observed, accompanied by the development of an uphill transport region where the 'effective' diffusivity becomes negative. The fractional flux is in general asymmetric and, for steady states, it has a negative (toward the core) component that enhances confinement and a positive component that increases toward the edge and leads to poor confinement. The model exhibits the characteristic anomalous scaling of the confinement time, τ, with the system's size, L, τ∼L α , of low-confinement mode plasma where 1<α<2 is the order of the FD operator. Numerical solutions of the model with an off-axis source show that the fractional inward transport gives rise to profile peaking reminiscent of what is observed in tokamak discharges with auxiliary off-axis heating. Also, cold-pulse perturbations to steady sates in the model exhibit fast, nondiffusive propagation phenomena that resemble perturbative experiments
Derivation of a volume-averaged neutron diffusion equation; Atomos para el desarrollo de Mexico
Energy Technology Data Exchange (ETDEWEB)
Vazquez R, R.; Espinosa P, G. [UAM-Iztapalapa, Av. San Rafael Atlixco 186, Col. Vicentina, Mexico D.F. 09340 (Mexico); Morales S, Jaime B. [UNAM, Laboratorio de Analisis en Ingenieria de Reactores Nucleares, Paseo Cuauhnahuac 8532, Jiutepec, Morelos 62550 (Mexico)]. e-mail: rvr@xanum.uam.mx
2008-07-01
This paper presents a general theoretical analysis of the problem of neutron motion in a nuclear reactor, where large variations on neutron cross sections normally preclude the use of the classical neutron diffusion equation. A volume-averaged neutron diffusion equation is derived which includes correction terms to diffusion and nuclear reaction effects. A method is presented to determine closure-relationships for the volume-averaged neutron diffusion equation (e.g., effective neutron diffusivity). In order to describe the distribution of neutrons in a highly heterogeneous configuration, it was necessary to extend the classical neutron diffusion equation. Thus, the volume averaged diffusion equation include two corrections factor: the first correction is related with the absorption process of the neutron and the second correction is a contribution to the neutron diffusion, both parameters are related to neutron effects on the interface of a heterogeneous configuration. (Author)
Anion and cation diffusion in barium titanate and strontium titanate
International Nuclear Information System (INIS)
Kessel, Markus Franz
2012-01-01
data suggests that oxygen vacancies and electron holes play the key role in the formation of the equilibrium surface space-charge layers. The oxygen vacancy diffusivities and the oxygen vacancy migration enthalpy are compared to other experimentally and theoretically derived data for barium titanate and a global expression for the temperature dependence of the oxygen vacancy diffusivity is determined. The latter was used for a comparison of the oxygen vacancy diffusivity and the oxygen vacancy migration enthalpy for BaTiO 3 to other perovskite oxides. Furthermore, this work shows results from cation interdiffusion experiments between BaZrO 3 and SrTiO 3 . Thin films of barium zirconate were deposited on strontium titanate single crystals and the cation interdiffusion investigated as a function of temperature. All four cations show a main diffusion profile and an additional fast diffusion profile. Each main diffusion profile can be described independently by the thick-film solution of the diffusion equation suggesting the diffusion coefficients to be concentration independent. The fast diffusion profiles are attributed to fast diffusion of Ba and Zr along dislocations of the SrTiO 3 single crystals and fast diffusion of Sr and Ti along the grain boundaries of the polycrystalline thin-film BaZrO 3 . The migration enthalpies of the bulk profiles for all four cations are very similar. The results suggest a complex diffusion mechanism with coupled diffusion of the cation vacancies on the A and B sites of the perovskite lattice.
WWER radial reflector modeling by diffusion codes
International Nuclear Information System (INIS)
Petkov, P. T.; Mittag, S.
2005-01-01
The two commonly used approaches to describe the WWER radial reflectors in diffusion codes, by albedo on the core-reflector boundary and by a ring of diffusive assembly size nodes, are discussed. The advantages and disadvantages of the first approach are presented first, then the Koebke's equivalence theory is outlined and its implementation for the WWER radial reflectors is discussed. Results for the WWER-1000 reactor are presented. Then the boundary conditions on the outer reflector boundary are discussed. The possibility to divide the library into fuel assembly and reflector parts and to generate each library by a separate code package is discussed. Finally, the homogenization errors for rodded assemblies are presented and discussed (Author)
Communication: Memory effects and active Brownian diffusion
Energy Technology Data Exchange (ETDEWEB)
Ghosh, Pulak K. [Department of Chemistry, Presidency University, Kolkata 700073 (India); Li, Yunyun, E-mail: yunyunli@tongji.edu.cn [Center for Phononics and Thermal Energy Science, Tongji University, Shanghai 200092 (China); Marchegiani, Giampiero [Dipartimento di Fisica, Università di Camerino, I-62032 Camerino (Italy); Marchesoni, Fabio [Center for Phononics and Thermal Energy Science, Tongji University, Shanghai 200092 (China); Dipartimento di Fisica, Università di Camerino, I-62032 Camerino (Italy)
2015-12-07
A self-propelled artificial microswimmer is often modeled as a ballistic Brownian particle moving with constant speed aligned along one of its axis, but changing direction due to random collisions with the environment. Similarly to thermal noise, its angular randomization is described as a memoryless stochastic process. Here, we speculate that finite-time correlations in the orientational dynamics can affect the swimmer’s diffusivity. To this purpose, we propose and solve two alternative models. In the first one, we simply assume that the environmental fluctuations governing the swimmer’s propulsion are exponentially correlated in time, whereas in the second one, we account for possible damped fluctuations of the propulsion velocity around the swimmer’s axis. The corresponding swimmer’s diffusion constants are predicted to get, respectively, enhanced or suppressed upon increasing the model memory time. Possible consequences of this effect on the interpretation of the experimental data are discussed.
Holistic BIM Adoption and Diffusion in Malaysia
Directory of Open Access Journals (Sweden)
Mamter Shahela
2016-01-01
Full Text Available Building Information Modeling is modeling technology and associated set of processes to produce, communicate and analyze digital information models for construction life cycle. Although many benefits can gain by the implementation of BIM, the pace adoption of BIM in Malaysia is still slow. There is an abundance of theories and models purporting to describe the drivers and mechanisms of how new technologies are adopted or diffused into a particular section of society or by individuals or stake players. In addition, many acceptance theories, which imply the adoption of new technologies and can be applied in every sector. This paper aims to present a review of the existing literature of BIM adoption and diffusion theory/model/framework in Malaysia. Researcher revealed the list of driven factors of Holistic BIM Adoption. In addition, it will deal with how to work effectively with groups that initially are relatively
Anomalous diffusion in a symbolic model
International Nuclear Information System (INIS)
Ribeiro, H V; Lenzi, E K; Mendes, R S; Santoro, P A
2011-01-01
In this work, we investigate some statistical properties of symbolic sequences generated by a numerical procedure in which the symbols are repeated following the power-law probability density. In this analysis, we consider that the sum of n symbols represents the position of a particle in erratic movement. This approach reveals a rich diffusive scenario characterized by non-Gaussian distribution and, depending on the power-law exponent or the procedure used to build the walker, we may have superdiffusion, subdiffusion or usual diffusion. Additionally, we use the continuous-time random walk framework to compare the analytic results with the numerical data, thereby finding good agreement. Because of its simplicity and flexibility, this model can be a candidate for describing real systems governed by power-law probability densities.
Photovoltaic technology diffusion. Contact and interact
International Nuclear Information System (INIS)
Kruijsen, J.
1999-09-01
How can the diffusion of photovoltaic technologies be advanced? Photovoltaics convert light into electrical energy. They are environmentally friendly, reliable and have minimal maintenance requirements. Up to now, their introduction into the electricity market has been dominated by a technology push perspective. However, this has not yet resulted in a large-scale implementation. This thesis describes a network approach to advance photovoltaic diffusion and presents four guiding principles intended for the parties concerned: those who supply the photovoltaic technologies (e.g., developers of photovoltaic cells); those who integrate photovoltaic technologies into (new) product systems (e.g., engineering firms); the users of photovoltaic systems (e.g., housing corporations); and those who stimulate the use of photovoltaics (e.g., policymakers, subsidisers, branch organisations, financial institutes, and NGOs). refs
Triplet exciton diffusion in organic semiconductors
Energy Technology Data Exchange (ETDEWEB)
Koehler, Anna [Department of Physics, University of Bayreuth (Germany)
2010-07-01
Efficient triplet exciton emission has allowed improved operation of organic light-emitting diodes (LEDs). To enhance the device performance, it is necessary to understand what governs the motion of triplet excitons through the organic semiconductor. We use a series of poly(p-phenylene)-type conjugated polymers and oligomers of variable degree of molecular distortion (i.e. polaron formation) and energetic disorder as model systems to study the Dexter-type triplet exciton diffusion in thin films. We show that triplet diffusion can be quantitatively described in the framework of a Holstein small polaron model (Marcus theory) that is extended to include contributions from energetic disorder. The model predicts a tunnelling process at low temperatures followed by a thermally activated hopping process above a transition temperature. In contrast to charge transfer, the activation energy required for triplet exciton transfer can be deduced from the optical spectra. We discuss the implications for device architecture.
Effects of Impeller-Diffuser Interaction on Centrifugal Compressor Performance
Tan, Choon S.
2003-01-01
This research program focuses on characterizing the effect of impeller-diffuser interactions in a centrifugal compressor stage on its performance using unsteady threedimensional Reynolds-averaged Navier-Stokes simulations. The computed results show that the interaction between the downstream diffuser pressure field and the impeller tip clearance flow can account for performance changes in the impeller. The magnitude of performance change due to this interaction was examined for an impeller with varying tip clearance followed by a vaned or vaneless diffuser. The impact of unsteady impeller-diffuser interaction, primarily through the impeller tip clearance flow, is reflected through a time-averaged change in impeller loss, blockage and slip. The results show that there exists a tip clearance where the beneficial effect of the impeller-diffuser interaction on the impeller performance is at a maximum. A flow feature that consists of tip flow back leakage was shown to occur at design speed for the centrifugal compressor stage. This flow phenomenon is described as tip flow that originates in one passage, flows downstream of the impeller trailing edge and then returns to upstream of the impeller trailing edge of a neighboring passage. Such a flow feature is a source of loss in the impeller. A hypothesis is put forth to show that changing the diffuser vane count and changing impeller-diffuser gap has an analogous effect on the impeller performance. The centrifugal compressor stage was analyzed using diffusers of different vane counts, producing an impeller performance trend similar to that when the impeller-diffuser gap was varied, thus supporting the hypothesis made. This has the implication that the effect impeller performance associated with changing the impeller-diffuser gap and changing diffuser vane count can be described by the non-dimensional ratio of impeller-diffuser gap to diffuser vane pitch. A procedure is proposed and developed for isolating impeller passage
Kinetic Monte Carlo Simulation of Oxygen and Cation Diffusion in Yttria-Stabilized Zirconia
Good, Brian
2011-01-01
Yttria-stabilized zirconia (YSZ) is of interest to the aerospace community, notably for its application as a thermal barrier coating for turbine engine components. In such an application, diffusion of both oxygen ions and cations is of concern. Oxygen diffusion can lead to deterioration of a coated part, and often necessitates an environmental barrier coating. Cation diffusion in YSZ is much slower than oxygen diffusion. However, such diffusion is a mechanism by which creep takes place, potentially affecting the mechanical integrity and phase stability of the coating. In other applications, the high oxygen diffusivity of YSZ is useful, and makes the material of interest for use as a solid-state electrolyte in fuel cells. The kinetic Monte Carlo (kMC) method offers a number of advantages compared with the more widely known molecular dynamics simulation method. In particular, kMC is much more efficient for the study of processes, such as diffusion, that involve infrequent events. We describe the results of kinetic Monte Carlo computer simulations of oxygen and cation diffusion in YSZ. Using diffusive energy barriers from ab initio calculations and from the literature, we present results on the temperature dependence of oxygen and cation diffusivity, and on the dependence of the diffusivities on yttria concentration and oxygen sublattice vacancy concentration. We also present results of the effect on diffusivity of oxygen vacancies in the vicinity of the barrier cations that determine the oxygen diffusion energy barriers.
Models of diffuse solar radiation
Energy Technology Data Exchange (ETDEWEB)
Boland, John; Ridley, Barbara [Centre for Industrial and Applied Mathematics, University of South Australia, Mawson Lakes Boulevard, Mawson Lakes, SA 5095 (Australia); Brown, Bruce [Department of Statistics and Applied Probability, National University of Singapore, Singapore 117546 (Singapore)
2008-04-15
For some locations both global and diffuse solar radiation are measured. However, for many locations, only global is measured, or inferred from satellite data. For modelling solar energy applications, the amount of radiation on a tilted surface is needed. Since only the direct component on a tilted surface can be calculated from trigonometry, we need to have diffuse on the horizontal available. There are regression relationships for estimating the diffuse on a tilted surface from diffuse on the horizontal. Models for estimating the diffuse radiation on the horizontal from horizontal global that have been developed in Europe or North America have proved to be inadequate for Australia [Spencer JW. A comparison of methods for estimating hourly diffuse solar radiation from global solar radiation. Sol Energy 1982; 29(1): 19-32]. Boland et al. [Modelling the diffuse fraction of global solar radiation on a horizontal surface. Environmetrics 2001; 12: 103-16] developed a validated model for Australian conditions. We detail our recent advances in developing the theoretical framework for the approach reported therein, particularly the use of the logistic function instead of piecewise linear or simple nonlinear functions. Additionally, we have also constructed a method, using quadratic programming, for identifying values that are likely to be erroneous. This allows us to eliminate outliers in diffuse radiation values, the data most prone to errors in measurement. (author)
Osmosis and Diffusion Conceptual Assessment
Fisher, Kathleen M.; Williams, Kathy S.; Lineback, Jennifer Evarts
2011-01-01
Biology student mastery regarding the mechanisms of diffusion and osmosis is difficult to achieve. To monitor comprehension of these processes among students at a large public university, we developed and validated an 18-item Osmosis and Diffusion Conceptual Assessment (ODCA). This assessment includes two-tiered items, some adopted or modified…
The diffusion of constitutional rights
Goderis, B.V.G.; Versteeg, M.
Constitutions are commonly regarded as uniquely national products, shaped by domestic ideals and politics. This paper develops and empirically investigates a novel hypothesis, which is that constitutions are also shaped by transnational influence, or “diffusion.” Constitutional rights can diffuse
Diffusion measurements by Raman spectroscopy
DEFF Research Database (Denmark)
Hansen, Susanne Brunsgaard; Shapiro, Alexander; Berg, Rolf W.
Poster "Diffusion measurements by Raman spectroscopy", See poster at http://www.kemi.dtu.dk/~ajo/rolf/petroday2004.ppt......Poster "Diffusion measurements by Raman spectroscopy", See poster at http://www.kemi.dtu.dk/~ajo/rolf/petroday2004.ppt...
Consequences of Diffusion of Innovations.
Goss, Kevin F.
1979-01-01
The article traces evolution of diffusion theory; illustrates undesirable consequences in a cross-cultural setting, reviews criticisms of several scholars; considers distributional effects and unanticipated consequences for potential ameliorative impact on diffusion theory; and codifies these factors into a framework for research into consequences…
Enhancement of diffusers BRDF accuracy
Otter, Gerard; Bazalgette Courrèges-Lacoste, Gregory; van Brug, Hedser; Schaarsberg, Jos Groote; Delwart, Steven; del Bello, Umberto
2017-11-01
This paper reports the result of an ESA study conducted at TNO to investigate properties of various diffusers. Diffusers are widely used in space instruments as part of the on-board absolute calibration. Knowledge of the behaviour of the diffuser is therefore most important. From measurements of launched instruments in-orbit it has been discovered that when a diffuser is used in the vacuum of space the BRDF can change with respect to the one in ambient conditions. This is called the air/vacuum effect and has been simulated in this study by measuring the BRDF in a laboratory in ambient as well as vacuum conditions. Another studied effect is related to the design parameters of the optical system and the scattering properties of the diffuser. The effect is called Spectral Features and is a noise like structure superimposed on the diffuser BRDF. Modern space spectrometers, which have high spectral resolution and/or a small field of view (high spatial resolution) are suffering from this effect. The choice of diffuser can be very critical with respect to the required absolute radiometric calibration of an instrument. Even if the Spectral Features are small it can influence the error budget of the retrieval algorithms for the level 2 products. in this presentation diffuser trade-off results are presented and the Spectral Features model applied to the optical configuration of the MERIS instrument is compared to in-flight measurements of MERIS.
Thermal diffusivity of felsic to mafic granulites at elevated temperatures
Ray, Labani; Förster, H.-J.; Schilling, F. R.; Förster, A.
2006-11-01
The thermal diffusivity of felsic and intermediate granulites (charnockites, enderbites), mafic granulites, and amphibolite-facies gneisses has been measured up to temperatures of 550 °C using a transient technique. The rock samples are from the Archean and Pan-African terranes of the Southern Indian Granulite Province. Thermal diffusivity at room temperature ( DRT) for different rock types ranges between 1.2 and 2.2 mm 2 s - 1 . For most of the rocks, the effect of radiative heat transfer is observed at temperatures above 450 °C. However, for few enderbites and mafic granulites, radiative heat transfer is negligible up to 550 °C. In the temperature range of conductive heat transfer, i.e., between 20 ° and 450 °C, thermal diffusivity decreases between 35% and 45% with increasing temperature. The temperature dependence of the thermal diffusivity is directly correlated with the thermal diffusivity at room temperature, i.e., the higher the thermal diffusivity at room temperature, DRT, the greater is its temperature dependence. In this temperature range i.e., between 20 and 450 °C, thermal diffusivity can be expressed as D = 0.7 mm 2 s -1 + 144 K ( DRT - 0.7 mm 2 s -1 ) / ( T - 150 K), where T is the absolute temperature in Kelvin. At higher temperatures, an additional radiative contribution is observed according to CT3, where C varies from 10 - 9 to 10 - 10 depending on intrinsic rock properties (opacity, absorption behavior, grain size, grain boundary, etc). An equation is presented that describes the temperature and pressure dependence thermal diffusivity of rocks based only on the room-temperature thermal diffusivity. Room-temperature thermal diffusivity and its temperature dependence are mainly dependent on the major mineralogy of the rock. Because granulites are important components of the middle and lower continental crust, the results of this study provide important constraints in quantifying more accurately the thermal state of the deeper continental
Self-diffusion in dense granular shear flows.
Utter, Brian; Behringer, R P
2004-03-01
Diffusivity is a key quantity in describing velocity fluctuations in granular materials. These fluctuations are the basis of many thermodynamic and hydrodynamic models which aim to provide a statistical description of granular systems. We present experimental results on diffusivity in dense, granular shear flows in a two-dimensional Couette geometry. We find that self-diffusivities D are proportional to the local shear rate gamma; with diffusivities along the direction of the mean flow approximately twice as large as those in the perpendicular direction. The magnitude of the diffusivity is D approximately gamma;a(2), where a is the particle radius. However, the gradient in shear rate, coupling to the mean flow, and strong drag at the moving boundary lead to particle displacements that can appear subdiffusive or superdiffusive. In particular, diffusion appears to be superdiffusive along the mean flow direction due to Taylor dispersion effects and subdiffusive along the perpendicular direction due to the gradient in shear rate. The anisotropic force network leads to an additional anisotropy in the diffusivity that is a property of dense systems and has no obvious analog in rapid flows. Specifically, the diffusivity is suppressed along the direction of the strong force network. A simple random walk simulation reproduces the key features of the data, such as the apparent superdiffusive and subdiffusive behavior arising from the mean velocity field, confirming the underlying diffusive motion. The additional anisotropy is not observed in the simulation since the strong force network is not included. Examples of correlated motion, such as transient vortices, and Lévy flights are also observed. Although correlated motion creates velocity fields which are qualitatively different from collisional Brownian motion and can introduce nondiffusive effects, on average the system appears simply diffusive.
Hydrogen diffusion in the anode of Ni/MH secondary batteries
Feng, F.; Northwood, D. O.
Hydrogen diffusion coefficients ( D) were evaluated in a LaNi 4.7Al 0.3 metal hydride electrode as a function of depth of discharge (DoD) using a newly developed electrochemical method which describes more precisely the practical diffusion behavior. It was found that the hydrogen diffusion coefficient in this electrode increases with increasing DoD at ambient temperature, and for this electrode at 50% DoD, the hydrogen diffusion coefficient increases with increase in temperature, and the activation energy for hydrogen diffusion is 37.3 kJ mol -1.
Determination of activation energy of hydrogen diffusion in Zr-2.5%Nb alloy
International Nuclear Information System (INIS)
Chandra, Komal; Kulkarni, A.S.; Ramanjaneyulu, P.S.; Yadav, C.S.; Saxena, M.K.; Tomar, B.S.; Ramakumar, K.L.; Sunil, Sourav; Singh, R.N.
2013-01-01
The present paper describes the study on the determination of diffusion coefficient of hydrogen in Zr-2.5%Nb alloy. Hydrogen was charged on Zr-2.5% Nb alloy electrolytically. After annealing at required temperature, hydrogen concentration at various depths from the charged end was determined employing hot vacuum extraction-quadrupole mass spectrometer (HVE-QMS). The depth profile was used to obtain the diffusion coefficient employing Fick's second law of diffusion. From the Arrhenius relation between diffusion coefficient and temperature, activation energy of hydrogen diffusion was calculated. (author)
International Nuclear Information System (INIS)
Fouet, J.M.; Starynkevitch, B.
1987-01-01
Incremental development and maintenance of large systems imply that control be clearly separated from knowledge. Finding efficient control for a given class of knowledge is itself a matter of expertise, to which knowledge-based methods may and should be applied. We present here two attempts at building root systems that may later be tuned by knowledge engineers, using the semantics of each particular application. These systems are given heuristics in a declarative manner, which they use to control the application of heuristics. Eventually, some heuristics may be used to compile others (or themselves) into efficient pieces of programmed code
International Nuclear Information System (INIS)
Lee, Gun Do; Wang, C. Z.; Lu, Z. Y.; Ho, K. M.
1999-01-01
The diffusion pathways along the trough and between the trough and the dimer row on the Si(100) surface are investigated by tight-binding molecular dynamics calculations using the environment dependent tight-binding silicon potential and by ab initio calculations using the Car-Parrinello method. The studies discover new diffusion pathways consisting of rotation of addimer. The calculated energy barrier are in excellent agreement with experiment. The rotational diffusion pathway between the trough and the dimer row is much more energetically favorable than other diffusion pathways by parallel and perpendicular addimer. The new pathway along the trough is nearly same as the energy barrier of the diffusion pathway by dissociation of the addimer
Application of polycrystalline diffusion barriers
International Nuclear Information System (INIS)
Tsymbal, V.A.; Kolupaev, I.N.
2010-01-01
Degradation of contacts of the electronic equipment at the raised temperatures is connected with active diffusion redistribution of components contact - metalized systems (CMS) and phase production on interphase borders. One of systems diffusion barriers (DB) are polycrystalline silicide a film, in particular silicides of the titan. Reception disilicide the titan (TiSi 2 ) which on the parameters is demanded for conditions of microelectronics from known silicides of system Ti-Si, is possible as a result of direct reaction of a film of the titan and a substrate of silicon, and at sedimentation of layer Ti-Si demanded stoichiometric structure. Simultaneously there is specific problem polycrystalline diffusion a barrier (PDB): the polycrystalline provides structural balance and metastability film disilicide, but leaves in it borders of grains - easy local ways of diffusion. In clause the analysis diffusion permeability polycrystalline and polyphase DB is made and recommendations for practical methods of increase of blocking properties PDB are made.
Diffusion in membranes: Toward a two-dimensional diffusion map
Directory of Open Access Journals (Sweden)
Toppozini Laura
2015-01-01
Full Text Available For decades, quasi-elastic neutron scattering has been the prime tool for studying molecular diffusion in membranes over relevant nanometer distances. These experiments are essential to our current understanding of molecular dynamics of lipids, proteins and membrane-active molecules. Recently, we presented experimental evidence from X-ray diffraction and quasi-elastic neutron scattering demonstrating that ethanol enhances the permeability of membranes. At the QENS 2014/WINS 2014 conference we presented a novel technique to measure diffusion across membranes employing 2-dimensional quasi-elastic neutron scattering. We present results from our preliminary analysis of an experiment on the cold neutron multi-chopper spectrometer LET at ISIS, where we studied the self-diffusion of water molecules along lipid membranes and have the possibility of studying the diffusion in membranes. By preparing highly oriented membrane stacks and aligning them horizontally in the spectrometer, our aim is to distinguish between lateral and transmembrane diffusion. Diffusion may also be measured at different locations in the membranes, such as the water layer and the hydrocarbon membrane core. With a complete analysis of the data, 2-dimensional mapping will enable us to determine diffusion channels of water and ethanol molecules to quantitatively determine nanoscale membrane permeability.
The magnetic diffusion of neutrons; La diffusion magnetique des neutrons
Energy Technology Data Exchange (ETDEWEB)
Koehler, W C [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires
1959-07-01
The purpose of this report is to examine briefly the diffusion of neutrons by substances, particularly by crystals containing permanent atomic or ionic magnetic moments. In other words we shall deal with ferromagnetic, antiferromagnetic, ferrimagnetic or paramagnetic crystals, but first it is necessary to touch on nuclear diffusion of neutrons. We shall start with the interaction of the neutron with a single diffusion centre; the results will then be applied to the magnetic interactions of the neutron with the satellite electrons of the atom; finally we shall discuss the diffusion of neutrons by crystals. (author) [French] Le but de ce rapport est d'examiner, brievement, la diffusion des neutrons par les substances, et surtout, par des cristaux qui contiennent des moments magnetiques atomiques ou ioniques permanents. C'est-a-dire que nous nous interesserons aux cristaux ferromagnetiques, antiferromagnetiques, ferrimagnetiques ou paramagnetiques; il nous faut cependant rappeler d'abord la diffusion nucleaire des neutrons. Nous commencerons par l'interaction du neutron avec un seul centre diffuseur; puis les resultats seront appliques aux interactions magnetiques du neutron avec les electrons satellites de l'atome; enfin nous discuterons la diffusion des neutrons par les cristaux. (auteur)
Multidimensional diffusion processes
Stroock, Daniel W
1997-01-01
From the reviews: "… Both the Markov-process approach and the Itô approach … have been immensely successful in diffusion theory. The Stroock-Varadhan book, developed from the historic 1969 papers by its authors, presents the martingale-problem approach as a more powerful - and, in certain regards, more intrinsic-means of studying the foundations of the subject. […] … the authors make the uncompromising decision not "to proselytise by intimidating the reader with myriad examples demonstrating the full scope of the techniques", but rather to persuade the reader "with a careful treatment of just one problem to which they apply". […] Most of the main tools of stochastic-processes theory are used, ..but it is the formidable combination of probability theory with analysis … which is the core of the work. […] I have emphasized the great importance of the Stroock-Varadhan book. It contains a lot more than I have indicated; in particular, its many exercises conain much interesting material. For immediat...
Diffusion of aqueous solutions of ionic, zwitterionic, and polar solutes
Teng, Xiaojing; Huang, Qi; Dharmawardhana, Chamila Chathuranga; Ichiye, Toshiko
2018-06-01
The properties of aqueous solutions of ionic, zwitterionic, and polar solutes are of interest to many fields. For instance, one of the many anomalous properties of aqueous solutions is the behavior of water diffusion in different monovalent salt solutions. In addition, solutes can affect the stabilities of macromolecules such as proteins in aqueous solution. Here, the diffusivities of aqueous solutions of sodium chloride, potassium chloride, tri-methylamine oxide (TMAO), urea, and TMAO-urea are examined in molecular dynamics simulations. The decrease in the diffusivity of water with the concentration of simple ions and urea can be described by a simple model in which the water molecules hydrogen bonded to the solutes are considered to diffuse at the same rate as the solutes, while the remainder of the water molecules are considered to be bulk and diffuse at almost the same rate as pure water. On the other hand, the decrease in the diffusivity of water with the concentration of TMAO is apparently affected by a decrease in the diffusion rate of the bulk water molecules in addition to the decrease due to the water molecules hydrogen bonded to TMAO. In other words, TMAO enhances the viscosity of water, while urea barely affects it. Overall, this separation of water molecules into those that are hydrogen bonded to solute and those that are bulk can provide a useful means of understanding the short- and long-range effects of solutes on water.
Innovation diffusion equations on correlated scale-free networks
Energy Technology Data Exchange (ETDEWEB)
Bertotti, M.L., E-mail: marialetizia.bertotti@unibz.it [Free University of Bozen–Bolzano, Faculty of Science and Technology, Bolzano (Italy); Brunner, J., E-mail: johannes.brunner@tis.bz.it [TIS Innovation Park, Bolzano (Italy); Modanese, G., E-mail: giovanni.modanese@unibz.it [Free University of Bozen–Bolzano, Faculty of Science and Technology, Bolzano (Italy)
2016-07-29
Highlights: • The Bass diffusion model can be formulated on scale-free networks. • In the trickle-down version, the hubs adopt earlier and act as monitors. • We improve the equations in order to describe trickle-up diffusion. • Innovation is generated at the network periphery, and hubs can act as stiflers. • We compare diffusion times, in dependence on the scale-free exponent. - Abstract: We introduce a heterogeneous network structure into the Bass diffusion model, in order to study the diffusion times of innovation or information in networks with a scale-free structure, typical of regions where diffusion is sensitive to geographic and logistic influences (like for instance Alpine regions). We consider both the diffusion peak times of the total population and of the link classes. In the familiar trickle-down processes the adoption curve of the hubs is found to anticipate the total adoption in a predictable way. In a major departure from the standard model, we model a trickle-up process by introducing heterogeneous publicity coefficients (which can also be negative for the hubs, thus turning them into stiflers) and a stochastic term which represents the erratic generation of innovation at the periphery of the network. The results confirm the robustness of the Bass model and expand considerably its range of applicability.
Oxygen diffusion through soil covers on sulphidic mine tailings
International Nuclear Information System (INIS)
Yanful, E.K.
1993-01-01
Engineered soil covers are being evaluated under Canada's Mine Environment Neutral Drainage (MEND) program for their effectiveness in preventing and controlling acid generation in sulfidic mill tailings. A critical parameter for predicting the performance of these covers is the diffusion coefficient of gaseous oxygen in the cover materials. Laboratory experiments conducted to determine the effective diffusion coefficient of a candidate cover material, a glacial till from an active mine site, are described. The diffusion coefficient is determined by fitting a semianalytic solution of the one-dimensional, transient diffusion equation to experimental gaseous oxygen concentration versus time graphs. Effective diffusion coefficients determined at high water saturations (85%--95%) were of the order of 8 x 10 -8 m 2 /s. The diffusion coefficients decreased with increase in water saturation as a result of the low diffusivity of gaseous oxygen in water relative to that in air and the low solubility of oxygen in water. Placement of soil covers in high saturation conditions would ensure that the flux of oxygen into tailings underneath such covers is low, resulting in low acid flux. This is confirmed by combined laboratory, field, and modeling studies
Self-diffusion in single crystalline silicon nanowires
Südkamp, T.; Hamdana, G.; Descoins, M.; Mangelinck, D.; Wasisto, H. S.; Peiner, E.; Bracht, H.
2018-04-01
Self-diffusion experiments in single crystalline isotopically controlled silicon nanowires with diameters of 70 and 400 nm at 850 and 1000 °C are reported. The isotope structures were first epitaxially grown on top of silicon substrate wafers. Nanowires were subsequently fabricated using a nanosphere lithography process in combination with inductively coupled plasma dry reactive ion etching. Three-dimensional profiling of the nanosized structure before and after diffusion annealing was performed by means of atom probe tomography (APT). Self-diffusion profiles obtained from APT analyses are accurately described by Fick's law for self-diffusion. Data obtained for silicon self-diffusion in nanowires are equal to the results reported for bulk silicon crystals, i.e., finite size effects and high surface-to-volume ratios do not significantly affect silicon self-diffusion. This shows that the properties of native point defects determined from self-diffusion in bulk crystals also hold for nanosized silicon structures with diameters down to 70 nm.
Bulk diffusion in a kinetically constrained lattice gas
Arita, Chikashi; Krapivsky, P. L.; Mallick, Kirone
2018-03-01
In the hydrodynamic regime, the evolution of a stochastic lattice gas with symmetric hopping rules is described by a diffusion equation with density-dependent diffusion coefficient encapsulating all microscopic details of the dynamics. This diffusion coefficient is, in principle, determined by a Green-Kubo formula. In practice, even when the equilibrium properties of a lattice gas are analytically known, the diffusion coefficient cannot be computed except when a lattice gas additionally satisfies the gradient condition. We develop a procedure to systematically obtain analytical approximations for the diffusion coefficient for non-gradient lattice gases with known equilibrium. The method relies on a variational formula found by Varadhan and Spohn which is a version of the Green-Kubo formula particularly suitable for diffusive lattice gases. Restricting the variational formula to finite-dimensional sub-spaces allows one to perform the minimization and gives upper bounds for the diffusion coefficient. We apply this approach to a kinetically constrained non-gradient lattice gas in two dimensions, viz. to the Kob-Andersen model on the square lattice.
Innovation diffusion equations on correlated scale-free networks
International Nuclear Information System (INIS)
Bertotti, M.L.; Brunner, J.; Modanese, G.
2016-01-01
Highlights: • The Bass diffusion model can be formulated on scale-free networks. • In the trickle-down version, the hubs adopt earlier and act as monitors. • We improve the equations in order to describe trickle-up diffusion. • Innovation is generated at the network periphery, and hubs can act as stiflers. • We compare diffusion times, in dependence on the scale-free exponent. - Abstract: We introduce a heterogeneous network structure into the Bass diffusion model, in order to study the diffusion times of innovation or information in networks with a scale-free structure, typical of regions where diffusion is sensitive to geographic and logistic influences (like for instance Alpine regions). We consider both the diffusion peak times of the total population and of the link classes. In the familiar trickle-down processes the adoption curve of the hubs is found to anticipate the total adoption in a predictable way. In a major departure from the standard model, we model a trickle-up process by introducing heterogeneous publicity coefficients (which can also be negative for the hubs, thus turning them into stiflers) and a stochastic term which represents the erratic generation of innovation at the periphery of the network. The results confirm the robustness of the Bass model and expand considerably its range of applicability.
A free boundary problem describing the saturated-unsaturated flow in a porous medium
Directory of Open Access Journals (Sweden)
Gabriela Marinoschi
2004-01-01
Full Text Available This paper presents a functional approach to a nonlinear model describing the complete physical process of water infiltration into an unsaturated soil, including the saturation occurrence and the advance of the wetting front. The model introduced in this paper involves a multivalued operator covering the simultaneous saturated and unsaturated flow behaviors and enhances the study of the displacement of the free boundary between these two flow regimes. The model resides in Richards' equation written in pressure form with an initial condition and boundary conditions which in this work express the inflow due to the rain on the soil surface on the one hand, and characterize a certain permeability corresponding to the underground boundary, on the other hand. Existence, uniqueness, and regularity results for the transformed model in diffusive form, that is, for the moisture of the soil, and the existence of the weak solution for the pressure form are proved in the 3D case. The main part of the paper focuses on the existence of the free boundary between the saturated and unsaturated parts of the soil, and this is proved, in the 1D case, for certain stronger assumptions on the initial data and boundary conditions.
A flowing plasma model to describe drift waves in a cylindrical helicon discharge
International Nuclear Information System (INIS)
Chang, L.; Hole, M. J.; Corr, C. S.
2011-01-01
A two-fluid model developed originally to describe wave oscillations in the vacuum arc centrifuge, a cylindrical, rapidly rotating, low temperature, and confined plasma column, is applied to interpret plasma oscillations in a RF generated linear magnetized plasma [WOMBAT (waves on magnetized beams and turbulence)], with similar density and field strength. Compared to typical centrifuge plasmas, WOMBAT plasmas have slower normalized rotation frequency, lower temperature, and lower axial velocity. Despite these differences, the two-fluid model provides a consistent description of the WOMBAT plasma configuration and yields qualitative agreement between measured and predicted wave oscillation frequencies with axial field strength. In addition, the radial profile of the density perturbation predicted by this model is consistent with the data. Parameter scans show that the dispersion curve is sensitive to the axial field strength and the electron temperature, and the dependence of oscillation frequency with electron temperature matches the experiment. These results consolidate earlier claims that the density and floating potential oscillations are a resistive drift mode, driven by the density gradient. To our knowledge, this is the first detailed physics model of flowing plasmas in the diffusion region away from the RF source. Possible extensions to the model, including temperature nonuniformity and magnetic field oscillations, are also discussed.
A model describing intra-granular fission gas behaviour in oxide fuel for advanced engineering tools
Pizzocri, D.; Pastore, G.; Barani, T.; Magni, A.; Luzzi, L.; Van Uffelen, P.; Pitts, S. A.; Alfonsi, A.; Hales, J. D.
2018-04-01
The description of intra-granular fission gas behaviour is a fundamental part of any model for the prediction of fission gas release and swelling in nuclear fuel. In this work we present a model describing the evolution of intra-granular fission gas bubbles in terms of bubble number density and average size, coupled to gas release to grain boundaries. The model considers the fundamental processes of single gas atom diffusion, gas bubble nucleation, re-solution and gas atom trapping at bubbles. The model is derived from a detailed cluster dynamics formulation, yet it consists of only three differential equations in its final form; hence, it can be efficiently applied in engineering fuel performance codes while retaining a physical basis. We discuss improvements relative to previous single-size models for intra-granular bubble evolution. We validate the model against experimental data, both in terms of bubble number density and average bubble radius. Lastly, we perform an uncertainty and sensitivity analysis by propagating the uncertainties in the parameters to model results.
Directory of Open Access Journals (Sweden)
Yusuke Kishita
2016-01-01
Full Text Available Due to the rapid expansion of information and communication technology (ICT usage, the telecommunications industry is faced with a challenge to promote green ICT toward achieving a low-carbon society. One critical obstacle in planning long-term strategies for green ICT is the uncertainty of various external factors, such as consumers’ lifestyle and technological advancement. To tackle this issue, this paper employs a scenario planning method to analyze electricity consumption in the telecommunications industry, where both changes in various external factors and energy-saving measures are assumed. We propose a model to estimate future electricity consumption of the telecommunications industry using a statistical approach. In a case study, we describe four scenarios that differ in the diffusion of ICT and the technological advancement of ICT equipment in order to analyze the electricity consumption in Japan’s telecommunications industry to 2030. The results reveal that the electricity consumption in 2030 becomes 0.7–1.6-times larger than the 2012 level (10.7 TWh/year. It is also shown that the most effective measures to reduce the electricity consumption include improving the energy efficiency of IP (Internet Protocol communication equipment and mobile communication equipment.
Diffusion of multiple species with excluded-volume effects
Bruna, Maria; Chapman, S. Jonathan
2012-01-01
Stochastic models of diffusion with excluded-volume effects are used to model many biological and physical systems at a discrete level. The average properties of the population may be described by a continuum model based on partial differential equations. In this paper we consider multiple interacting subpopulations/species and study how the inter-species competition emerges at the population level. Each individual is described as a finite-size hard core interacting particle undergoing Brownian motion. The link between the discrete stochastic equations of motion and the continuum model is considered systematically using the method of matched asymptotic expansions. The system for two species leads to a nonlinear cross-diffusion system for each subpopulation, which captures the enhancement of the effective diffusion rate due to excluded-volume interactions between particles of the same species, and the diminishment due to particles of the other species. This model can explain two alternative notions of the diffusion coefficient that are often confounded, namely collective diffusion and self-diffusion. Simulations of the discrete system show good agreement with the analytic results. © 2012 American Institute of Physics.
Conservative diffusions: a constructive approach to Nelson's stochastic mechanics
International Nuclear Information System (INIS)
Carlen, E.A.
1984-01-01
In Nelson's stochastic mechanics, quantum phenomena are described in terms of diffusions instead of wave functions; this thesis is a study of that description. Concern here is with the possibility of describing, as opposed to explaining, quantum phenomena in terms of diffusions. In this direction, the following questions arise: ''Do the diffusion of stochastic mechanics - which are formally given by stochastic differential equations with extremely singular coefficients - really exist.'' Given that they exist, one can ask, ''Do these diffusions have physically reasonable paths to study the behavior of physical systems.'' These are the questions treated in this thesis. In Chapter 1, stochastic mechanics and diffusion theory are reviewed, using the Guerra-Morato variational principle to establish the connection with the Schroedinger equation. Chapter II settles the first of the questions raised above. Using PDE methods, the diffusions of stochastic mechanics are constructed. The result is sufficiently general to be of independent mathematical interest. In Chapter III, potential scattering in stochastic mechanics is treated and direct probabilistic methods of studying quantum scattering problems are discussed. The results provide a solid YES in answer to the second question raised above
Diffusion tensor optical coherence tomography
Marks, Daniel L.; Blackmon, Richard L.; Oldenburg, Amy L.
2018-01-01
In situ measurements of diffusive particle transport provide insight into tissue architecture, drug delivery, and cellular function. Analogous to diffusion-tensor magnetic resonance imaging (DT-MRI), where the anisotropic diffusion of water molecules is mapped on the millimeter scale to elucidate the fibrous structure of tissue, here we propose diffusion-tensor optical coherence tomography (DT-OCT) for measuring directional diffusivity and flow of optically scattering particles within tissue. Because DT-OCT is sensitive to the sub-resolution motion of Brownian particles as they are constrained by tissue macromolecules, it has the potential to quantify nanoporous anisotropic tissue structure at micrometer resolution as relevant to extracellular matrices, neurons, and capillaries. Here we derive the principles of DT-OCT, relating the detected optical signal from a minimum of six probe beams with the six unique diffusion tensor and three flow vector components. The optimal geometry of the probe beams is determined given a finite numerical aperture, and a high-speed hardware implementation is proposed. Finally, Monte Carlo simulations are employed to assess the ability of the proposed DT-OCT system to quantify anisotropic diffusion of nanoparticles in a collagen matrix, an extracellular constituent that is known to become highly aligned during tumor development.
Macrolides for diffuse panbronchiolitis.
Lin, Xiufang; Lu, Jing; Yang, Ming; Dong, Bi Rong; Wu, Hong Mei
2015-01-25
Diffuse panbronchiolitis (DPB) is a chronic airways disease predominantly affecting East Asians. Macrolides, a class of antibiotics, have been used as the main treatment for DPB, based on evidence from retrospective and non-randomised studies. To assess the efficacy and safety of macrolides for DPB. We searched CENTRAL (2014, Issue 6), MEDLINE (1966 to July week 1, 2014), EMBASE (1974 to July 2014), Chinese Biomedical Literature Database (CBM) (1978 to July 2014), China National Knowledge Infrastructure (CNKI) (1974 to July 2014), KoreaMed (1997 to July 2014) and Database of Japana Centra Revuo Medicina (1983 to July 2014). Randomised controlled trials (RCTs) or quasi-RCTs assessing the effect of macrolides for DPB. Two review authors independently assessed study quality and subsequent risk of bias according to The Cochrane Collaboration's tool for assessing risk of bias. The primary outcomes were five-year survival rate, lung function and clinical response. We used risk ratios (RR) for individual trial results in the data analysis and measured all outcomes with 95% confidence intervals (CI). Only one RCT (19 participants) with significant methodological limitations was included in this review. It found that the computerised tomography images of all participants treated with a long-term, low-dose macrolide (erythromycin) improved from baseline, while the images of 71.4% of participants in the control group (with no treatment) worsened and 28.6% remained unchanged. Adverse effects were not reported. This review was previously published in 2010 and 2013. For this 2014 update, we identified no new trials for inclusion or exclusion. There is little evidence for macrolides in the treatment of DPB. We are therefore unable to make any new recommendations. It may be reasonable to use low-dose macrolides soon after diagnosis is made and to continue this treatment for at least six months, according to current guidelines.
Oxygen and nitrogen diffusion in coal-molecular sieve
International Nuclear Information System (INIS)
Stefanescu, Doina Maria
1996-01-01
Recently, the air separation process based on selective adsorption of carbon-molecular sieves has been developed strongly. The separation is based on the system kinematics and depends on the oxygen diffusion in adsorber micropores. The oxygen is preferentially adsorbed and in given conditions it is possible to obtain nitrogen of high purity. Recent theoretical and experimental studies concerning the production of nitrogen by PSA process have shown that the obtained performances can not be described by a constant diffusion model. The paper present the 'dual' model assumed for O 2 and N 2 diffusion through molecular sieve as well as the experimental data obtained in the adsorption study on carbon material produced at ICIS to determine the diffusivity values in micropores
Small-polaron model of light atom diffusion
International Nuclear Information System (INIS)
Emin, D.
1977-01-01
A number of researchers have treated the diffusion of light interstitials in metals in strict analogy with the theory for the hopping diffusion of electrons in low-mobility insulators. In other words, these authors view the diffusion of light atoms as simply being an example of small-polaron hopping motion. In this paper the motion of a small polaron is introduced, and the mechanism of its motion is described. The experimental results are then succinctly presented. Next the physical assumptions implicit in the theory are compared with the situation which is believed to characterize the existence and motion of light interstitial atoms in metals. Concomitantly, the modifications of the small-polaron theory required in applying it to light atom diffusion are ennumerated
Effective diffusion in time-periodic linear planar flow
International Nuclear Information System (INIS)
Indeikina, A.; Chang, H.
1993-01-01
It is shown that when a point source of solute is inserted into a time-periodic, unbounded linear planar flow, the large-time, time-average transport of the solute can be described by classical anisotropic diffusion with constant effective diffusion tensors. For a given vorticity and forcing period, elongational flow is shown to be the most dispersive followed by simple shear and rotational flow. Large-time diffusivity along the major axis of the time-average concentration ellipse, whose alignment is predicted from the theory, is shown to increase with vorticity for all flows and decrease with increasing forcing frequency for elongational flow and simple shear. For the interesting case of rotational flow, there exist discrete resonant frequencies where the time-average major diffusivity reaches local maxima equal to the time-average steady flow case with zero forcing frequency
NMR diffusion simulation based on conditional random walk.
Gudbjartsson, H; Patz, S
1995-01-01
The authors introduce here a new, very fast, simulation method for free diffusion in a linear magnetic field gradient, which is an extension of the conventional Monte Carlo (MC) method or the convolution method described by Wong et al. (in 12th SMRM, New York, 1993, p.10). In earlier NMR-diffusion simulation methods, such as the finite difference method (FD), the Monte Carlo method, and the deterministic convolution method, the outcome of the calculations depends on the simulation time step. In the authors' method, however, the results are independent of the time step, although, in the convolution method the step size has to be adequate for spins to diffuse to adjacent grid points. By always selecting the largest possible time step the computation time can therefore be reduced. Finally the authors point out that in simple geometric configurations their simulation algorithm can be used to reduce computation time in the simulation of restricted diffusion.
Tracer gas diffusion sampling test plan
International Nuclear Information System (INIS)
Rohay, V.J.
1993-01-01
Efforts are under way to employ active and passive vapor extraction to remove carbon tetrachloride from the soil in the 200 West Area an the Hanford Site as part of the 200 West Area Carbon Tetrachloride Expedited Response Action. In the active approach, a vacuum is applied to a well, which causes soil gas surrounding the well to be drawn up to the surface. The contaminated air is cleaned by passage through a granular activated carbon bed. There are questions concerning the radius of influence associated with application of the vacuum system and related uncertainties about the soil-gas diffusion rates with and without the vacuum system present. To address these questions, a series of tracer gas diffusion sampling tests is proposed in which an inert, nontoxic tracer gas, sulfur hexafluoride (SF 6 ), will be injected into a well, and the rates of SF 6 diffusion through the surrounding soil horizon will be measured by sampling in nearby wells. Tracer gas tests will be conducted at sites very near the active vacuum extraction system and also at sites beyond the radius of influence of the active vacuum system. In the passive vapor extraction approach, barometric pressure fluctuations cause soil gas to be drawn to the surface through the well. At the passive sites, the effects of barometric ''pumping'' due to changes in atmospheric pressure will be investigated. Application of tracer gas testing to both the active and passive vapor extraction methods is described in the wellfield enhancement work plan (Rohay and Cameron 1993)
Local diffusion coefficient determination: Mediterranean Sea experiments
International Nuclear Information System (INIS)
Bacciola, D.; Borghini, M.; Cannarsa, S.
1993-10-01
The Mediterranean is a semi/enclosed basin characterized by the presence of channels and straits influencing the circulation, temperature and salinity fields. The tides generally have amplitudes of the order of 10 cm and velocities of few cm/s. Conversely, the wind forced circulation is very strong and can assume velocity values of 1 m/s at the sea surface. The temperature and salinity fields have a high temporal and spatial variability, because of many mixing processes existing in the sea. For example, the waters coming from the Provencal basin meet those waters coming from the Tyrrhenian Sea in the eastern Ligurian Sea, creating meanders and eddies. Local runoff influences significantly the coastal circulation. This paper describes diffusion experiments carried out in this complex environment. The experimental apparatus for the detection of the fluorescine released at sea was composed by two Turner mod. 450 fluorometres. During the experiments, temperature and salinity vertical profiles were measured by using a CTD; meteorological data were acquired on a dinghy. The positioning was obtained by means of a Motorola system, having a precision of about 1 meter. The experiments were carried out under different stratification and wind conditions. From data analysis it was found that the horizontal diffusion coefficient does not depend on time or boundary conditions. The role of stratification is important with regard to vertical displacement of the dye. However, its role with regard to vertical diffusion cannot be assessed with the actual experimental apparatus
Diffusion and perfusion imaging of bone marrow
International Nuclear Information System (INIS)
Biffar, Andreas; Dietrich, Olaf; Sourbron, Steven; Duerr, Hans-Roland; Reiser, Maximilian F.; Baur-Melnyk, Andrea
2010-01-01
In diffusion-weighted magnetic resonance imaging (DWI), the observed MRI signal intensity is attenuated by the self-diffusion of water molecules. DWI provides information about the microscopic structure and organization of a biological tissue, since the extent and orientation of molecular motion is influenced by these tissue properties. The most common method to measure perfusion in the body using MRI is T1-weighted dynamic contrast enhancement (DCE-MRI). The analysis of DCE-MRI data allows determining the perfusion and permeability of a biological tissue. DWI as well as DCE-MRI are established techniques in MRI of the brain, while significantly fewer studies have been published in body imaging. In recent years, both techniques have been applied successfully in healthy bone marrow as well as for the characterization of bone marrow alterations or lesions; e.g., DWI has been used in particular for the differentiation of benign and malignant vertebral compression fractures. In this review article, firstly a short introduction to diffusion-weighted and dynamic contrast-enhanced MRI is given. Non-quantitative and quantitative approaches for the analysis of DWI and semiquantitative and quantitative approaches for the analysis of DCE-MRI are introduced. Afterwards a detailed overview of the results of both techniques in healthy bone marrow and their applications for the diagnosis of various bone-marrow pathologies, like osteoporosis, bone tumors, and vertebral compression fractures are described.
Thermal neutron diffusion parameters in homogeneous mixtures
Energy Technology Data Exchange (ETDEWEB)
Drozdowicz, K.; Krynicka, E. [Institute of Nuclear Physics, Cracow (Poland)
1995-12-31
A physical background is presented for a computer program which calculates the thermal neutron diffusion parameters for homogeneous mixtures of any compounds. The macroscopic absorption, scattering and transport cross section of the mixture are defined which are generally function of the incident neutron energy. The energy-averaged neutron parameters are available when these energy dependences and the thermal neutron energy distribution are assumed. Then the averaged diffusion coefficient and the pulsed thermal neutron parameters (the absorption rare and the diffusion constant) are also defined. The absorption cross section is described by the 1/v law and deviations from this behaviour are considered. The scattering cross section can be assumed as being almost constant in the thermal neutron region (which results from the free gas model). Serious deviations are observed for hydrogen atoms bound in molecules and a special study in the paper is devoted to this problem. A certain effective scattering cross section is found in this case on a base of individual exact data for a few hydrogenous media. Approximations assumed for the average cosine of the scattering angle are also discussed. The macroscopic parameters calculated are averaged over the Maxwellian energy distribution for the thermal neutron flux. An information on the input data for the computer program is included. (author). 10 refs, 4 figs, 5 tabs.
Thermal neutron diffusion parameters in homogeneous mixtures
International Nuclear Information System (INIS)
Drozdowicz, K.; Krynicka, E.
1995-01-01
A physical background is presented for a computer program which calculates the thermal neutron diffusion parameters for homogeneous mixtures of any compounds. The macroscopic absorption, scattering and transport cross section of the mixture are defined which are generally function of the incident neutron energy. The energy-averaged neutron parameters are available when these energy dependences and the thermal neutron energy distribution are assumed. Then the averaged diffusion coefficient and the pulsed thermal neutron parameters (the absorption rare and the diffusion constant) are also defined. The absorption cross section is described by the 1/v law and deviations from this behaviour are considered. The scattering cross section can be assumed as being almost constant in the thermal neutron region (which results from the free gas model). Serious deviations are observed for hydrogen atoms bound in molecules and a special study in the paper is devoted to this problem. A certain effective scattering cross section is found in this case on a base of individual exact data for a few hydrogenous media. Approximations assumed for the average cosine of the scattering angle are also discussed. The macroscopic parameters calculated are averaged over the Maxwellian energy distribution for the thermal neutron flux. An information on the input data for the computer program is included. (author). 10 refs, 4 figs, 5 tabs
Diffusion transport of nanoparticles at nanochannel boundaries
International Nuclear Information System (INIS)
Mahadevan, T. S.; Milosevic, M.; Kojic, M.; Hussain, F.; Kojic, N.; Serda, R.; Ferrari, M.; Ziemys, A.
2013-01-01
The manipulation of matter at the nanoscale has unleashed a great potential for engineering biomedical drug carriers, but the transport of nanoparticles (NPs) under nanoscale confinement is still poorly understood. Using colloidal physics to describe NP interactions, we have computationally studied the passive transport of NPs using experimentally relevant conditions from bulk into a nanochannel of 60–90 nm height. NP size, channel height, and the Debye length are comparable so that changes in nanoscale dimensions may induce substantial changes in NP transport kinetics. We show that subtle changes in nanochannel dimensions may alter the energy barrier by about six orders of magnitude resulting in different NP penetration depths and diffusion mechanisms: ballistic, first-order and quasi zero-order transport regimes. The analysis of NP diffusion by continuum methods reveals that apparent diffusivity is reduced by decreasing channel size. The continuum finite element (FE) numerical method reproduced the colloidal model results only when surface interactions were accounted for. These results give a new insight into NP passive transport at the boundaries of nanoconfined domains, and have implications on the design of nanoscale fluidics and NP systems for biomedical and engineering applications.
FINELM: a multigroup finite element diffusion code
International Nuclear Information System (INIS)
Higgs, C.E.; Davierwalla, D.M.
1981-06-01
FINELM is a FORTRAN IV program to solve the Neutron Diffusion Equation in X-Y, R-Z, R-theta, X-Y-Z and R-theta-Z geometries using the method of Finite Elements. Lagrangian elements of linear or higher degree to approximate the spacial flux distribution have been provided. The method of dissections, coarse mesh rebalancing and Chebyshev acceleration techniques are available. Simple user defined input is achieved through extensive input subroutines. The input preparation is described followed by a program structure description. Sample test cases are provided. (Auth.)
Orientational diffusion of n-alkyl cyanides
International Nuclear Information System (INIS)
Zhu Xiang; Farrer, Richard A; Zhong Qin; Fourkas, John T
2005-01-01
Ultrafast optical Kerr effect spectroscopy has been used to study the temperature-dependent orientational dynamics of a series of nitriles with n-alkyl chains ranging from one to 11 carbons in length. In all cases the orientational diffusion is found to be described by a single-exponential decay. Analysis of the orientational correlation times using the Debye-Stokes-Einstein equation suggests that the molecules adopt extended configurations and reorient as rigid rods. The liquids with shorter alkyl chains undergo an apparent ordering transition as they are cooled
Johnson-Matthey diffuser characterization testing
International Nuclear Information System (INIS)
Foster, P. J.; Klein, J. E.; Sessions, H. T.; Morgan, G. A.
2008-01-01
A diffuser/permeator commercially fabricated by Johnson-Matthey was purchased for characterization testing at the Savannah River National Laboratory (SRNL). A test system was fabricated to test not only feed and bleed flows and pressures, but also permeate pressure for flows up to 20 sLPM. The tests described in this paper consider the effect of various inert gas types, feed gas compositions, methods for temperature control, and varying tube pressure on permeation of H 2 through the Pd/Ag tubes. (authors)
Shape Analysis Using the Auto Diffusion Function
DEFF Research Database (Denmark)
Gebal, Katarzyna; Bærentzen, Jakob Andreas; Aanæs, Henrik
2009-01-01
Scalar functions defined on manifold triangle meshes is a starting point for many geometry processing algorithms such as mesh parametrization, skeletonization, and segmentation. In this paper, we propose the Auto Diffusion Function (ADF) which is a linear combination of the eigenfunctions......, it is controlled by a single parameter which can be interpreted as feature scale, and, finally, the ADF is invariant to rigid and isometric deformations. We describe the ADF and its properties in detail and compare it to other choices of scalar functions on manifolds. As an example of an application, we present...
Conception of a target diffusible Pt. 3
International Nuclear Information System (INIS)
Peters, J.M.
1980-01-01
A new manufacturing self-replenishing target has been tested for the regeneration of deuteride titanium (γ) phase followed by the study of its behaviour under deuteron beam in the production of neutrons by the D(d,n) 3 He reaction. An interpretation of the self-replenishing mechanism is attempted here, based on diffusion and flow rate measurements through the target (Pd-Ag) (70%-30%), 0.5 mm of thickness, - Ti layer (522 μg cm -2 ). A general formula is proposed to describe the flow rate variations during the regeneration experiences. (author)
Moessbauer effect and vacancy diffusion
International Nuclear Information System (INIS)
Gunther, L.
1976-01-01
A dynamical theory of vacancy diffusion which was motivated by the need to explain recent experimental results for the Moessbauer spectra of Fe in Cu, Fe in Au and Fe in Al is presented. Diffusion in these systems is dominated by the vacancy mechanism, which involves strong correlations between successive jumps. The theory developed by Singwi and Sjoelander for the Moessbauer spectrum of a diffusing nucleus is therefore not applicable. The inverse of the normalized Moessbauer spectrum evaluated at zero frequency is introduced as a useful means of comparing experimental with theoretical spectral widths
Simulation of multivariate diffusion bridges
DEFF Research Database (Denmark)
Bladt, Mogens; Finch, Samuel; Sørensen, Michael
We propose simple methods for multivariate diffusion bridge simulation, which plays a fundamental role in simulation-based likelihood and Bayesian inference for stochastic differential equations. By a novel application of classical coupling methods, the new approach generalizes a previously...... proposed simulation method for one-dimensional bridges to the mulit-variate setting. First a method of simulating approzimate, but often very accurate, diffusion bridges is proposed. These approximate bridges are used as proposal for easily implementable MCMC algorithms that produce exact diffusion bridges...
Self diffusion in isotopic fluid
International Nuclear Information System (INIS)
Tankeshwar, K.
1991-01-01
Expressions for the second and fourth frequency sum rules of the velocity auto-correlation function have been obtained for an isotopic fluid. These expressions and Mori memory function formalism have been used to study the influence of the particle mass and mole fraction on the self diffusion coefficient. Our results confirm the weak mass dependence of the self diffusion. The influence of the mole fraction of the light particles on the self diffusion constant has been found to increase for the larger particle mass. (author). 17 refs, 1 fig., 2 tabs
Muon diffusion in noble metals
International Nuclear Information System (INIS)
Schillaci, M.E.; Bokema, C.; Heffner, R.H.; Hutson, R.L.; Leon, M.; Olsen, C.E.; Dodds, S.A.; MacLaughlin, D.E.; Richards, P.M.
1983-01-01
Diffusion-induced muon depolarization in dilute AgGd and AgEr were measured in the temperature range 200-700 K and have thereby determined the muon diffusion parameters in Ag. The diffusion parameters for μ + in Cu, Ag, and Au are compared with those of hydrogen. For Ag and Au, the μ + parameters are similar to those of hydrogen, whereas for Cu, the μ + parameters are much smaller. Lattice-activated tunneling and over-barrier hopping are investigated with computational models. 15 references, 1 figure, 2 tables
Muon diffusion in noble metals
International Nuclear Information System (INIS)
Schillaci, M.E.; Boekema, C.; Heffner, R.H.; Hutson, R.L.; Leon, M.; Olsen, C.E.; Dodds, S.A.; MacLaughlin, D.E.; Richards, P.M.
1982-01-01
Diffusion-induced muon depolarization was measured in dilute AgGd and AgEr in the temperature range 200 to 700 0 K and have thereby determined the muon diffusion parameters in Ag. The diffusion parameters for μ + in Cu, Ag, and Au are compared with those of hydrogen. For Ag and Au, the μ + parameters are similar to those of hydrogen, whereas for Cu, the μ + parameters are much smaller. Lattice-activated tunneling and over-barrier hopping are investigated with computational models
Genetics Home Reference: hereditary diffuse gastric cancer
... Health Conditions Hereditary diffuse gastric cancer Hereditary diffuse gastric cancer Printable PDF Open All Close All Enable Javascript ... Diffuse Gastric Cancer MedlinePlus Encyclopedia: Gastric Cancer National Cancer ... Option Overview General Information from MedlinePlus ( ...
Improved diffuser for augmenting a wind turbine
Foreman, K.M.; Gilbert, B.L.
A diffuser for augmenting a wind turbine having means for energizing the boundary layer at several locations along the diffuser walls is improved by the addition of a short collar extending radially outward from the outlet of the diffuser.
Study of uranium-titanium diffusion; Etude de la diffusion uranium-titane
Energy Technology Data Exchange (ETDEWEB)
Adda, Y; Philibert, J [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires; Institut de Recherches de la Siderurgie Francaise (IRSID), 78 - Saint-Germain-en-Laye (France)
1959-07-01
In the overall scheme of research on the chemical diffusion of uranium and the transition metals we have studied the uranium-titanium system. The diffusion couples are prepared by welding together small plates of uranium and titanium under pressure, using a technique already described by us. After diffusion under vacuum, polished sections of the samples were micro-graphically examined. This inspection showed that intergranular diffusion occurred at temperatures below 650 deg. C. At higher temperatures, the diffusion occurred uniquely throughout the volume of the metal, and the diffusion zone appeared as a succession of micro-graphically distinguishable bands. Study of the rate of increase of these corresponding 'penetration coefficients'. In addition, we have observed important variations in microhardness within the diffusion zone, we have tried to relate these variations to the variation of concentration. This is measured with the Castaing microprobe. We have thus accurately established the concentration-penetration curves for temperatures between 950 and 1075 deg. C. From these curves, we have calculated the diffusion coefficient D as a function of the concentration using Matano's method. At all temperatures, D(c) curve has a U form as for the U-Zr system. The activation energy has a maximum value of 42 kcal/g atom at an atomic concentration of 0,5. Even though we have rarely seen pores in the diffusion zone, we have nevertheless observed an important Kirkendall-effect by studying the displacements x{sub i} of the interface using tungsten wires as markers. These displacements can be expressed as a function of time and temperature by the equation: x{sub i} = 0,9 t {sup 1/2} exp ( - 14600/(RT)). Finally, using Darken's equations we calculated the intrinsic diffusion coefficients Du and Dti as well as the corresponding activation energies. These energies are similar (QU = 38,5 and QTi = 40 kcal/at. g) and also almost the same as those found for the U-Zr system
Can slow-diffusing solute atoms reduce vacancy diffusion in advanced high-temperature alloys?
International Nuclear Information System (INIS)
Goswami, Kamal Nayan; Mottura, Alessandro
2014-01-01
The high-temperature mechanical properties of precipitate-strengthened advanced alloys can be heavily influenced by adjusting chemical composition. The widely-accepted argument within the community is that, under certain temperature and loading conditions, plasticity occurs only in the matrix, and dislocations have to rely on thermally-activated climb mechanisms to overcome the barriers to glide posed by the hard precipitates. This is the case for γ′-strengthened Ni-based superalloys. The presence of dilute amounts of slow-diffusing solute atoms, such as Re and W, in the softer matrix phase is thought to reduce plasticity by retarding the climb of dislocations at the interface with the hard precipitate phase. One hypothesis is that the presence of these solutes must hinder the flow of vacancies, which are essential to the climb process. In this work, density functional theory calculations are used to inform two analytical models to describe the effect of solute atoms on the diffusion of vacancies. Results suggest that slow-diffusing solute atoms are not effective at reducing the diffusion of vacancies in these systems
Rapid-relocation model for describing high-fluence retention of rare gases implanted in solids
Wittmaack, K.
2009-09-01
to be due to bombardment induced relocation and reemission, only the remaining 10% (or less) can be attributed to sputter erosion. The relocation efficiency is interpreted as the 'speed' of radiation enhanced diffusion towards the surface. The directionality of diffusion is attributed to the gradient of the defect density on the large-depth side of the damage distribution where most of the implanted rare gas atoms come to rest. Based on SRIM calculations, two representative parameters are defined, the peak number of lattice displacements, Nd,m, and the spacing, △ zr,d, between the peaks of the range and the damage distributions. Support in favour of rapid rare gas relocation by radiation enhanced diffusion is provided by the finding that the relocation efficiencies for Ar and Xe, which vary by up to one order of magnitude, scale as Ψ=kN/Δz, independent to the implantation energy (10-80 keV Ar, 10-500 keV Xe), within an error margin of only ± 15%. The parameter k contains the properties of the implanted rare gas atoms. A recently described computer simulation model, which assumed that the pressure established by the implanted gas drives reemission, is shown to reproduce measured Xe profiles quite well, but only at that energy at which the fitting parameter of the model was determined (140 keV). Using the same parameter at other energies, deviations by up to a factor of four are observed.
Atmospheric turbulence and diffusion research
International Nuclear Information System (INIS)
Hosker, R.P. Jr.
1993-01-01
The Atmospheric Turbulence and Diffusion Division (well known in the atmospheric dispersion community as the Atmospheric Turbulence and Diffusion Laboratory, ATDL) is one of several field facilities of NOAAs Air Resources Laboratory, headquartered in Silver Spring, Maryland. The laboratory conducts research on matters of atmospheric diffusion and turbulent exchange, concerning air quality. ATDD focuses attention on the physics of the lower atmosphere, with special emphasis on the processes contributing to atmospheric transport, dispersion, deposition, and air-surface exchange, and on the development of predictive capabilities using the results of this research. Research is directed toward issues of national and global importance related to the missions of DOE, to DOE's Oak Ridge Field Office, and to NOAA. The program is divided into four major projects: plume transport and diffusion in the planetary boundary layer, complex topography, canopy micrometeorology, and air-surface exchange
Diffusion mechanisms in intermetallic compounds
Energy Technology Data Exchange (ETDEWEB)
Larikov, L N [ANU, Inst. Metallofiziki, Kiev (Ukraine)
1992-08-01
Recent research aimed at the identification of the principal mechanisms of diffusion in intermetallics is reviewed. In particular, attention is given to the effect of the type of interatomic bond on the contribution of different mechanisms to diffusion in ordered metallic compounds. Results of an analysis of experimental determinations of diffusion coefficients D(A) and D(B) in binary intermetallics (CuZn, Cu3Sn, AuCd, AgZn, AgMg, InSb, GaSb, AlSb, Fe3Al, FeAl, FeAl3, Ni3Al, Ni3Nb, FeSn, FeSn2, Ni3Sn2, Ni3Sn4, Co3Sn2, CoSn, CoSn2, and CoGa) are presented, and it is shown that the D(A)/D(B) ratio differs substantially for different diffusion mechanisms. 60 refs.
Diffusion of single oxidation pond
Directory of Open Access Journals (Sweden)
Song Ruo-Yuan
2016-01-01
Full Text Available The hydraulic characteristic of an oxidation pond was studied by the tracer experiment, and an empirical formula of Peclet number was obtained, which can be well applied to the model of plug flow reactor with longitudinal diffusion.
Computational Diffusion MRI : MICCAI Workshop
Grussu, Francesco; Ning, Lipeng; Tax, Chantal; Veraart, Jelle
2018-01-01
This volume presents the latest developments in the highly active and rapidly growing field of diffusion MRI. The reader will find numerous contributions covering a broad range of topics, from the mathematical foundations of the diffusion process and signal generation, to new computational methods and estimation techniques for the in-vivo recovery of microstructural and connectivity features, as well as frontline applications in neuroscience research and clinical practice. These proceedings contain the papers presented at the 2017 MICCAI Workshop on Computational Diffusion MRI (CDMRI’17) held in Québec, Canada on September 10, 2017, sharing new perspectives on the most recent research challenges for those currently working in the field, but also offering a valuable starting point for anyone interested in learning computational techniques in diffusion MRI. This book includes rigorous mathematical derivations, a large number of rich, full-colour visualisations and clinically relevant results. As such, it wil...
Diffusion coefficient for anomalous transport
International Nuclear Information System (INIS)
1986-01-01
A report on the progress towards the goal of estimating the diffusion coefficient for anomalous transport is given. The gyrokinetic theory is used to identify different time and length scale inherent to the characteristics of plasmas which exhibit anomalous transport
Diffusion formation and psychiatric diseases
International Nuclear Information System (INIS)
Reith, W.; Kulikovski, J.
2015-01-01
The basic principle behind diffusion is Brownian motion. The diffusion parameters obtained in a clinical association provide information on the spatial distribution of water molecule mobility and, therefore, evidence of the morphological integrity of the white and grey matters of the brain. In recent years functional magnetic resonance imaging (fMRI) could contribute to obtaining a detailed understanding of the cortical and subcortical cerebral networks. Diffusion tensor imaging (DTI) investigations can demonstrate the extent of anisotropy and the fiber pathways in so-called parametric images. For example, in Alzheimer's disease DTI reveals a reduced structural connectivity between the posterior cingulum and the hippocampus. This article shows examples of the application of diffusion-weighted imaging (DWI) in psychiatric disorders. (orig.) [de
Atomistic simulations of diffusion mechanisms in off-stoichiometric Al-rich Ni3Al
International Nuclear Information System (INIS)
Duan, Jinsong
2007-01-01
This paper presents dynamics simulation results of diffusion in off-stoichiometric Al-rich Ni 3 Al (Ni 73 Al 27 ) at temperature ranging from 1300 to 1550 K. The interatomic forces are described by the Finnis-Sinclair type N-body potentials. Particular attention is devoted to the effect of the extra 2% of Al atoms sitting on the Ni sublattice as antisite point defects (Al Ni ) on diffusion. Simulation results show that Ni atoms mainly diffuse through the Ni sublattice at the temperatures investigated. Al atoms diffuse via both the intrasublattice and antistructure bridge (ASB) mechanisms. The contribution to Al diffusion from the ASB mechanism decreases at the lower temperature (T Ni ) enhances both Al and Ni diffusion in Ni 73 Al 27 . The Ni-Al coupled diffusion effect is observed and understood at the atomic level for the first time
Diffusion processes and memory effects
International Nuclear Information System (INIS)
Mokshin, Anatolii V; Yulmetyev, Renat M; Haenggi, Peter
2005-01-01
We report the results of the numerical estimation of statistical memory effects in diffusion for two various systems: Lennard-Jones fluids and the model of the Brownian particle in a one-dimensional harmonic lattice. We have found the relation between the diffusion coefficient and the non-Markovity parameter, which is linear for the Lennard-Jones systems in liquid state. The relation between the memory measure and the excess entropy is also discussed here
Diffusion through statically compacted clay
International Nuclear Information System (INIS)
Ho, C.L.; Shebl, M.A.A.
1994-01-01
This paper presents experimental work on the effect of compaction on contaminant flow through clay liners. The experimental program included evaluation of soil properties, compaction, permeability and solute diffusion. A permeameter was built of non reactive materials to test samples compacted at different water contents and compactive efforts. The flow of a permeating solute, LiCl, was monitored. Effluent samples were collected for solute concentration measurements. The concentrations were measured by performing atomic adsorption tests. The analyzed results showed different diffusion characteristics when compaction conditions changed. At each compactive effort, permeability decreased as molding water content increased. Consequently, transit time (measured at relative concentration 50%) increased and diffusivity decreased. As compactive effort increased for soils compacted dry of optimum, permeability and diffusion decreased. On the other hand, as compactive effort increased for soils compacted wet of optimum, permeability and diffusivity increased. Tortuosity factor was indirectly measured from the diffusion and retardation rate. Tortuosity factor also decreased as placement water content was increased from dry of optimum to wet of optimum. Then decreases were more pronounced for low compactive effort tests. 27 refs., 7 figs., 5 tabs
Diffusion MRI findings in phenylketonuria
Energy Technology Data Exchange (ETDEWEB)
Sener, R.N. [Dept. of Radiology, Ege Univ. Hospital, Izmir (Turkey)
2003-12-01
Two patients with phenylketonuria were studied who were under dietary control since infancy, and who were mentally normal. Diffusion MRI was obtained using a spin-echo, echo-planar sequence with a gradient strength of 30 mT/m at 1.5 T. A trace sequence (TR=5700 ms, and TE=139 ms) was used, acquired in 22 s. Heavily diffusion-weighted (b=1000 mm{sup 2}/s) images, and the apparent diffusion coefficient (ADC) values from automatically generated ADC maps were studied. There were two different patterns in these two patients, restricted and increased diffusion patterns. Restricted diffusion pattern consisted of high-signal on b=1000 s/mm{sup 2} images with low ADC values ranging from 0.46 to 0.57 x 10{sup -3} mm{sup 2}/s. Increased diffusion pattern consisted of normal b=1000 s/mm{sup 2} images with high ADC values ranging from 1.37 to 1.63 x 10{sup -3} mm{sup 2}/s. It is likely that these values reflected presence of two different histopathological changes in phenylketonuria or reflected different stages of the same disease. (orig.)
Diffusion MRI findings in phenylketonuria
International Nuclear Information System (INIS)
Sener, R.N.
2003-01-01
Two patients with phenylketonuria were studied who were under dietary control since infancy, and who were mentally normal. Diffusion MRI was obtained using a spin-echo, echo-planar sequence with a gradient strength of 30 mT/m at 1.5 T. A trace sequence (TR=5700 ms, and TE=139 ms) was used, acquired in 22 s. Heavily diffusion-weighted (b=1000 mm 2 /s) images, and the apparent diffusion coefficient (ADC) values from automatically generated ADC maps were studied. There were two different patterns in these two patients, restricted and increased diffusion patterns. Restricted diffusion pattern consisted of high-signal on b=1000 s/mm 2 images with low ADC values ranging from 0.46 to 0.57 x 10 -3 mm 2 /s. Increased diffusion pattern consisted of normal b=1000 s/mm 2 images with high ADC values ranging from 1.37 to 1.63 x 10 -3 mm 2 /s. It is likely that these values reflected presence of two different histopathological changes in phenylketonuria or reflected different stages of the same disease. (orig.)
Atmospheric diffusion of large clouds
Energy Technology Data Exchange (ETDEWEB)
Crawford, T. V. [Univ. of California, Lawrence Radiation Lab., Livermore, California (United States)
1967-07-01
Clouds of pollutants travel within a coordinate system that is fixed to the earth's surface, and they diffuse and grow within a coordinate system fixed to the cloud's center. This paper discusses an approach to predicting the cloud's properties, within the latter coordinate system, on space scales of a few hundred meters to a few hundred kilometers and for time periods of a few days. A numerical cloud diffusion model is presented which starts with a cloud placed arbitrarily within the troposphere. Similarity theories of atmospheric turbulence are used to predict the horizontal diffusivity as a function of initial cloud size, turbulent atmospheric dissipation, and time. Vertical diffusivity is input as a function of time and height. Therefore, diurnal variations of turbulent diffusion in the boundary layer and effects of temperature inversions, etc. can be modeled. Nondiffusive cloud depletion mechanisms, such as dry deposition, washout, and radioactive decay, are also a part of this numerical model. An effluent cloud, produced by a reactor run at the Nuclear Rocket Development Station, Nevada, is discussed in this paper. Measurements on this cloud, for a period of two days, are compared to calculations with the above numerical cloud diffusion model. In general, there is agreement. within a factor of two, for airborne concentrations, cloud horizontal area, surface air concentrations, and dry deposition as airborne concentration decreased by seven orders of magnitude during the two-day period. (author)
Diffusion, confusion and functional MRI
International Nuclear Information System (INIS)
Le Bihan, Denis
2012-01-01
Diffusion MRI has been introduced in 1985 and has had a very successful life on its own. While it has become a standard for imaging stroke and white matter disorders, the borders between diffusion MRI and the general field of fMRI have always remained fuzzy. First, diffusion MRI has been used to obtain images of brain function, based on the idea that diffusion MRI could also be made sensitive to blood flow, through the intra-voxel incoherent motion (IVIM) concept. Second, the IVIM concept helped better understand the contribution from different vasculature components to the BOLD fMRI signal. Third, it has been shown recently that a genuine fMRI signal can be obtained with diffusion MRI. This 'DfMRI' signal is notably different from the BOLD fMRI signal, especially for its much faster response to brain activation both at onset and offset, which points out to structural changes in the neural tissues, perhaps such as cell swelling, occurring in activated neural tissue. This short article reviews the major steps which have paved the way for this exciting development, underlying how technical progress with MRI equipment has each time been instrumental to expand the horizon of diffusion MRI toward the field of fMRI. (authors)
Multi-Shell Hybrid Diffusion Imaging (HYDI) at 7 Tesla in TgF344-AD Transgenic Alzheimer Rats
Daianu, Madelaine; Jacobs, Russell E.; Weitz, Tara M.; Town, Terrence C.; Thompson, Paul M.
2015-01-01
Diffusion weighted imaging (DWI) is widely used to study microstructural characteristics of the brain. Diffusion tensor imaging (DTI) and high-angular resolution imaging (HARDI) are frequently used in radiology and neuroscience research but can be limited in describing the signal behavior in composite nerve fiber structures. Here, we developed and assessed the benefit of a comprehensive diffusion encoding scheme, known as hybrid diffusion imaging (HYDI), composed of 300 DWI volumes acquired a...
Lead diffusion in monazite; Diffusion du plomb dans la monazite
Energy Technology Data Exchange (ETDEWEB)
Gardes, E
2006-06-15
Proper knowledge of the diffusion rates of lead in monazite is necessary to understand the U-Th-Pb age anomalies of this mineral, which is one of the most used in geochronology after zircon. Diffusion experiments were performed in NdPO{sub 4} monocrystals and in Nd{sub 0.66}Ca{sub 0.17}Th{sub 0.17}PO{sub 4} polycrystals from Nd{sub 0.66}Pb{sub 0.17}Th{sub 0.17}PO{sub 4} thin films to investigate Pb{sup 2+} + Th{sup 4+} {r_reversible} 2 Nd{sup 3+} and Pb{sup 2+} {r_reversible} Ca{sup 2+} exchanges. Diffusion annealings were run between 1200 and 1500 Celsius degrees, at room pressure, for durations ranging from one hour to one month. The diffusion profiles were analysed using TEM (transmission electronic microscopy) and RBS (Rutherford backscattering spectroscopy). The diffusivities extracted for Pb{sup 2+} + Th{sup 4+} {r_reversible} 2 Nd{sup 3+} exchange follow an Arrhenius law with parameters E equals 509 {+-} 24 kJ mol{sup -1} and log(D{sub 0} (m{sup 2}s{sup -1})) equals -3.41 {+-} 0.77. Preliminary data for Pb{sup 2+} {r_reversible} Ca{sup 2+} exchange are in agreement with this result. The extrapolation of our data to crustal temperatures yields very slow diffusivities. For instance, the time necessary for a 50 {mu}m grain to lose all of its lead at 800 Celsius degrees is greater than the age of the Earth. From these results and other evidence from the literature, we conclude that most of the perturbations in U-Th-Pb ages of monazite cannot be attributed to lead diffusion, but rather to interactions with fluids. (author)
Diffusion theory model for optimization calculations of cold neutron sources
International Nuclear Information System (INIS)
Azmy, Y.Y.
1987-01-01
Cold neutron sources are becoming increasingly important and common experimental facilities made available at many research reactors around the world due to the high utility of cold neutrons in scattering experiments. The authors describe a simple two-group diffusion model of an infinite slab LD 2 cold source. The simplicity of the model permits to obtain an analytical solution from which one can deduce the reason for the optimum thickness based solely on diffusion-type phenomena. Also, a second more sophisticated model is described and the results compared to a deterministic transport calculation. The good (particularly qualitative) agreement between the results suggests that diffusion theory methods can be used in parametric and optimization studies to avoid the generally more expensive transport calculations
Diffusion of charged particles in a stochastic magnetic field
International Nuclear Information System (INIS)
Balescu, R.; Misguich, J.H.; Nakach, R.
1992-07-01
The diffusive motion of charged particles in a stochastic magnetic field is investigated systematically in a model in which the statistics of both the collisions and the magnetic field are described by coloured noises characterized, respectively, by a finite correlation time and finite correlation lengths. An analytic solution is obtained for the basic nonlinear differential equation of the model..It describes asymptotically a pure diffusion process, in which the mean square displacement in the perpendicular direction, Γ(t), grows proportionally to time (after a sufficiently long time). The corresponding diffusion coefficient scales like the fourth power of the magnetic fluctuation intensity. The values obtained are in very good agreement with experimental data in reverse-field pinch experiments. The present result contradicts earlier results predicting subdiffusive behaviour: Γ(t) ∼ t 1/2 or Γ(t) ∼ t 1/4 . The relation of these results to ours is discussed in detail
Neutron transport equation - indications on homogenization and neutron diffusion
International Nuclear Information System (INIS)
Argaud, J.P.
1992-06-01
In PWR nuclear reactor, the practical study of the neutrons in the core uses diffusion equation to describe the problem. On the other hand, the most correct method to describe these neutrons is to use the Boltzmann equation, or neutron transport equation. In this paper, we give some theoretical indications to obtain a diffusion equation from the general transport equation, with some simplifying hypothesis. The work is organised as follows: (a) the most general formulations of the transport equation are presented: integro-differential equation and integral equation; (b) the theoretical approximation of this Boltzmann equation by a diffusion equation is introduced, by the way of asymptotic developments; (c) practical homogenization methods of transport equation is then presented. In particular, the relationships with some general and useful methods in neutronic are shown, and some homogenization methods in energy and space are indicated. A lot of other points of view or complements are detailed in the text or the remarks
SNAP-3D: a three-dimensional neutron diffusion code
International Nuclear Information System (INIS)
McCallien, C.W.J.
1975-10-01
A preliminary report is presented describing the data requirements of a one- two- or three-dimensional multi-group diffusion code, SNAP-3D. This code is primarily intended for neutron diffusion calculations but it can also carry out gamma calculations if the diffuse approximation is accurate enough. It is suitable for fast and thermal reactor core calculations and for shield calculations. It is assumed the reader is familiar with the older, two-dimensional code SNAP and can refer to the report [TRG-Report-1990], describing it. The present report concentrates on the enhancements to SNAP that have been made to produce the three-dimensional version, SNAP-3D, and is intended to act a a guide on data preparation until a single, comprehensive report can be published. (author)
Energy Technology Data Exchange (ETDEWEB)
Mori, H.; Abe, O.; Aoki, S.; Masumoto, T.; Yoshikawa, T.; Kunimatsu, A; Hayashi, N.; Ohtomo, K. [Graduate School of Medicine, Univ. of Tokyo (Japan). Dept. of Radiology
2002-11-01
Diffusion-weighted MR imaging has been applicable to the differential diagnosis of abscesses and necrotic or cystic brain tumors. However, restricted water diffusion is not necessarily specific for brain abscess. We describe ring-enhancing metastases of lung carcinoma characterized by high signal intensity on diffusion-weighted MR images. The signal pattern probably reflected intralesional hemorrhage. The present report adds to the growing literature regarding the differential diagnosis of ring-enhancing brain lesions.
Rodrigues, P.R.
2011-01-01
In diffusion magnetic resonance imaging (DMRI) the Brownian motion of the water molecules, within biological tissue, is measured through a series of images. In diffusion tensor imaging (DTI) this diffusion is represented using tensors. DTI describes, in a non-invasive way, the local anisotropy pattern enabling the reconstruction of the nervous fibers - dubbed tractography. DMRI constitutes a powerful tool to analyse the structure of the white matter within a voxel, but also to investigate the...
Study of mechanisms of hydrogen diffusion in separation devices. Third annual report, 1979-1980
International Nuclear Information System (INIS)
Lee, M.H.
1980-01-01
The main results are in the following three areas: (1) examination of a diffusion model for PdH system, (2) connection between the diffusion model and other physical models, (3) related problems. Advances made during the third year of this project, particularly in understanding the physical model for hydrogen diffusion, make it possible to begin to meet some of the long-range objectives described in the initial proposals of 1977-1978
The behavior of diffusion and permeation of tritium through 316L stainless steel
International Nuclear Information System (INIS)
Changqi Shan; Aiju Wu; Qingwang Chen
1991-01-01
Results on diffusivity, solubility coefficient and permeability of tritium through palladium-plated 316 L stainless steel are described. An empirical formula for the diffusivity, the solubility coefficient and the permeability of tritium through palladium-plated 316 L stainless steel at various temperatures is presented. The influence of tritium pressure on the permeability, and the isotope effect of diffusivity of hydrogen and tritium in 316 L stainless steel is discussed. (orig.)
Helzel, Christiane; Tzavaras, Athanasios
2016-01-01
We consider a kinetic model, which describes the sedimentation of rod-like particles in dilute suspensions under the influence of gravity, presented in Helzel and Tzavaras (submitted for publication). Here we restrict our considerations to shear flow and consider a simplified situation, where the particle orientation is restricted to the plane spanned by the direction of shear and the direction of gravity. For this simplified kinetic model we carry out a linear stability analysis and we derive two different nonlinear macroscopic models which describe the formation of clusters of higher particle density. One of these macroscopic models is based on a diffusive scaling, the other one is based on a so-called quasi-dynamic approximation. Numerical computations, which compare the predictions of the macroscopic models with the kinetic model, complete our presentation.
The emission of heavy clusters described in the mean-field HFB theory: the case of 242Cm
International Nuclear Information System (INIS)
Robledo, L.M.; Warda, M.
2008-01-01
The emission of a nucleus of 34 Si by the parent 96 242 Cm is a process in the diffuse borderline between cluster emission and standard mass asymmetric fission. In this paper we analyze in a microscopic framework such process using the standard mean field techniques used to describe cluster emission. They include Hartree-Fock-Bogoliubov constrained calculations with the Gogny D1S interaction and the octupole moment operator as the collective coordinate to describe the process. Collective masses and all kind of zero point energy corrections are considered which allows for a parameter free estimation of the process' half-life. The agreement with experiment is quite satisfactory. (author)
Helzel, Christiane
2016-07-22
We consider a kinetic model, which describes the sedimentation of rod-like particles in dilute suspensions under the influence of gravity, presented in Helzel and Tzavaras (submitted for publication). Here we restrict our considerations to shear flow and consider a simplified situation, where the particle orientation is restricted to the plane spanned by the direction of shear and the direction of gravity. For this simplified kinetic model we carry out a linear stability analysis and we derive two different nonlinear macroscopic models which describe the formation of clusters of higher particle density. One of these macroscopic models is based on a diffusive scaling, the other one is based on a so-called quasi-dynamic approximation. Numerical computations, which compare the predictions of the macroscopic models with the kinetic model, complete our presentation.
Experimental Investigation of Radio-Turbulence Induced Diffusion -- Final Report
Energy Technology Data Exchange (ETDEWEB)
Spitz, H. B.; Usman, S.
2005-07-07
includes effects of molecular diffusion and convection to describe the transport of radon in water. The effective diffusion coefficients measured in these experiments are 6.8 x 10{sup -4} {+-} 28% and 3.5 x 10{sup -4} {+-} 34% cm{sup 2} sec{sup -1} for the steady-state and transient diffusion conditions, respectively. Water barriers ranging in thickness from 30-50 cm reduce the amount of radon released from the radium-bearing source material by a factor of 0.3-0.1, respectively.
Ion diffusion in compacted bentonite
Energy Technology Data Exchange (ETDEWEB)
Lehikoinen, J. [VTT Chemical Technology, Espoo (Finland)
1999-03-01
In the study, a two-dimensional molecular-level diffusion model, based on a modified form of the Gouy-Chapman (GC) theory of the electrical double layers, for hydrated ionic species in compacted bentonite was developed. The modifications to the GC theory, which forms the very kernel of the diffusion model, stem from various non-conventional features: ionic hydration, dielectric saturation, finite ion-sizes and specific adsorption. The principal objectives of the study were met. With the aid of the consistent diffusion model, it is a relatively simple matter to explain the experimentally observed macroscopic exclusion for anions as well as the postulated, but greatly controversial, surface diffusion for cations. From purely theoretical grounds, it was possible to show that the apparent diffusivities of cations, anions and neutral molecules (i) do not exhibit order-or-magnitude differences, and (ii) are practically independent of the solution ionic strength used and, consequently, of the distribution coefficient, K{sub d}, unless they experience specific binding onto the substrate surface. It was also of interest to investigate the equilibrium anionic concentration distribution in the pore geometry of the GMM model as a function of the solution ionic strength, and to briefly speculate its consequences to diffusion. An explicit account of the filter-plate effect was taken by developing a computerised macroscopic diffusion model, which is based upon the very robust and efficient Laplace Transform Finite-Difference technique. Finally, the inherent limitations as well as the potential fields of applications of the models were addressed. (orig.) 45 refs.
Ion diffusion in compacted bentonite
International Nuclear Information System (INIS)
Lehikoinen, J.
1999-03-01
In the study, a two-dimensional molecular-level diffusion model, based on a modified form of the Gouy-Chapman (GC) theory of the electrical double layers, for hydrated ionic species in compacted bentonite was developed. The modifications to the GC theory, which forms the very kernel of the diffusion model, stem from various non-conventional features: ionic hydration, dielectric saturation, finite ion-sizes and specific adsorption. The principal objectives of the study were met. With the aid of the consistent diffusion model, it is a relatively simple matter to explain the experimentally observed macroscopic exclusion for anions as well as the postulated, but greatly controversial, surface diffusion for cations. From purely theoretical grounds, it was possible to show that the apparent diffusivities of cations, anions and neutral molecules (i) do not exhibit order-or-magnitude differences, and (ii) are practically independent of the solution ionic strength used and, consequently, of the distribution coefficient, K d , unless they experience specific binding onto the substrate surface. It was also of interest to investigate the equilibrium anionic concentration distribution in the pore geometry of the GMM model as a function of the solution ionic strength, and to briefly speculate its consequences to diffusion. An explicit account of the filter-plate effect was taken by developing a computerised macroscopic diffusion model, which is based upon the very robust and efficient Laplace Transform Finite-Difference technique. Finally, the inherent limitations as well as the potential fields of applications of the models were addressed. (orig.)
A mathematical study of the influence of pore geometry on diffusion
International Nuclear Information System (INIS)
Melnyk, T.W.; Skeet, A.M.M.
1987-01-01
Diffusion into the pore space of plutonic rock matrices is an important phenomenon that can affect the migration of radionuclides and other contaminants in groundwater systems. The effects of irregular pore geometry on rates of diffusive transport are examined in this report. Approximate equations describing steady-state diffusive transport in pores of variable geometry are presented and indicate a strong dependence of the diffusion rates on the geometry of the pore space. Finite-element diffusion calculations were carried out for a series of pores containing storage spaces with rectangular cross-sections. The calculations showed the time taken to reach steady-state is affected by the pore geometry. The results of these calculations were used to simulate typical laboratory diffusion experiments and to evaluate the interpretation of effective diffusion parameters obtained from analysis of the simulated experiments using both capillary and dead-end pore models of the pore space. A capillary model of the pore space requires two independent parameters to characterize the pore space, and is shown, in general, to be inadequate to describe the pre-steady-state regime. The diffusion of radionuclides in groundwater systems lies in this non-steady-state regime. More complex mathematical descriptions of the pore space, using more variables and parameters, can accurately describe the non-steady-state transport. The capillary model, with effective parameter values, gives reasonable results when the size of the dead-end pore space is small relative to the overall diffusion distance under consideration
Package characterization by laboratory leaching and diffusion experiments using radionuclides
International Nuclear Information System (INIS)
Das, H.A.
1989-01-01
The leaching of solid inorganic waste from loaded concrete or cement by incoming water can be described in terms of a steady-state outward diffusion of the saturated solution, formed inside the pores. In this paper, the derived equations permit the prediction of long-term leaching behavior. Radiotracer experiments enable the determination of the parameters involved
Diffusion of fish from a single release point
DEFF Research Database (Denmark)
Sparrevohn, Claus Reedtz; Nielsen, Anders; Støttrup, Josianne
2002-01-01
In a field experiment, 3529 turbot (Psetta maxima) were released in order to estimate and describe the movements of hatchery-reared fish by applying diffusion theory. After liberation, the development of the population density was estimated during the following 9 days, and from that, the rate of ...
Homogenization of a thermo-diffusion system with Smoluchowski interactions
Krehel, O.; Aiki, T.; Muntean, A.
2014-01-01
We study the solvability and homogenization of a thermal-diffusion reaction problem posed in a periodically perforated domain. The system describes the motion of populations of hot colloidal particles interacting together via Smoluchowski production terms. The upscaled system, obtained via two-scale
Reaction Diffusion and Chemotaxis for Decentralized Gathering on FPGAs
Directory of Open Access Journals (Sweden)
Bernard Girau
2009-01-01
and rapid simulations of the complex dynamics of this reaction-diffusion model. Then we describe the FPGA implementation of the environment together with the agents, to study the major challenges that must be solved when designing a fast embedded implementation of the decentralized gathering model. We analyze the results according to the different goals of these hardware implementations.
Plateau diffusion coefficient for arbitrary flux surface geometry
International Nuclear Information System (INIS)
Meier, H.K.; Hirshman, S.P.; Sigmar, D.J.; Lao, L.L.
1981-03-01
A relatively simple but accurate representation has been developed for magnetic flux surfaces; it is valid for finite β and it describes configurations with both ellipticity and D-shape. This representation has been applied to the computation of the diffusion coefficient in the plateau regime
Diffuse Ceiling Inlet Systems and the Room Air Distribution
DEFF Research Database (Denmark)
Nielsen, Peter V.; Jensen, Rasmus Lund; Rong, Li
2010-01-01
A diffuse ceiling inlet system is an air distribution system which is supplying the air through the whole ceiling. The system can remove a large heat load without creating draught in the room. The paper describes measurements in the case of both cooling and heating, and CFD predictions are given...
Diffuse eosinophilic gastroenteritis with antral obstruction: a case report
International Nuclear Information System (INIS)
Moon, Sung Hee; Kim, Young Bok; Lee, Koung Hee
2000-01-01
Eosinophilic gastroenteritis is a rare disease characterized by tissue eosinophilia that can involve different layers of the gut wall and cause various gastrointestinal symptoms. We describe the UGI and CT findings of a case of diffuse eosinophilic gastroenteritis with tumor-like antral obstruction due to thickening of the submucosa and muscle layer in a 21-year-old male. (author)
Diffuse eosinophilic gastroenteritis with antral obstruction: a case report
Energy Technology Data Exchange (ETDEWEB)
Moon, Sung Hee; Kim, Young Bok; Lee, Koung Hee [National Police Hospital, Seoul (Korea, Republic of)
2000-02-01
Eosinophilic gastroenteritis is a rare disease characterized by tissue eosinophilia that can involve different layers of the gut wall and cause various gastrointestinal symptoms. We describe the UGI and CT findings of a case of diffuse eosinophilic gastroenteritis with tumor-like antral obstruction due to thickening of the submucosa and muscle layer in a 21-year-old male. (author)
Post-processing interstitialcy diffusion from molecular dynamics simulations
International Nuclear Information System (INIS)
Bhardwaj, U.; Bukkuru, S.; Warrier, M.
2016-01-01
An algorithm to rigorously trace the interstitialcy diffusion trajectory in crystals is developed. The algorithm incorporates unsupervised learning and graph optimization which obviate the need to input extra domain specific information depending on crystal or temperature of the simulation. The algorithm is implemented in a flexible framework as a post-processor to molecular dynamics (MD) simulations. We describe in detail the reduction of interstitialcy diffusion into known computational problems of unsupervised clustering and graph optimization. We also discuss the steps, computational efficiency and key components of the algorithm. Using the algorithm, thermal interstitialcy diffusion from low to near-melting point temperatures is studied. We encapsulate the algorithms in a modular framework with functionality to calculate diffusion coefficients, migration energies and other trajectory properties. The study validates the algorithm by establishing the conformity of output parameters with experimental values and provides detailed insights for the interstitialcy diffusion mechanism. The algorithm along with the help of supporting visualizations and analysis gives convincing details and a new approach to quantifying diffusion jumps, jump-lengths, time between jumps and to identify interstitials from lattice atoms. -- Graphical abstract:
Post-processing interstitialcy diffusion from molecular dynamics simulations
Energy Technology Data Exchange (ETDEWEB)
Bhardwaj, U., E-mail: haptork@gmail.com [Computational Analysis Division, BARC, Visakhapatnam, Andhra Pradesh, 530012 (India); Bukkuru, S. [Nuclear Physics Dept., Andhra University, Visakhapatnam, 530003 (India); Warrier, M. [Computational Analysis Division, BARC, Visakhapatnam, Andhra Pradesh, 530012 (India)
2016-01-15
An algorithm to rigorously trace the interstitialcy diffusion trajectory in crystals is developed. The algorithm incorporates unsupervised learning and graph optimization which obviate the need to input extra domain specific information depending on crystal or temperature of the simulation. The algorithm is implemented in a flexible framework as a post-processor to molecular dynamics (MD) simulations. We describe in detail the reduction of interstitialcy diffusion into known computational problems of unsupervised clustering and graph optimization. We also discuss the steps, computational efficiency and key components of the algorithm. Using the algorithm, thermal interstitialcy diffusion from low to near-melting point temperatures is studied. We encapsulate the algorithms in a modular framework with functionality to calculate diffusion coefficients, migration energies and other trajectory properties. The study validates the algorithm by establishing the conformity of output parameters with experimental values and provides detailed insights for the interstitialcy diffusion mechanism. The algorithm along with the help of supporting visualizations and analysis gives convincing details and a new approach to quantifying diffusion jumps, jump-lengths, time between jumps and to identify interstitials from lattice atoms. -- Graphical abstract:.
Diffusion-weighted imaging in acute demyelinating myelopathy
International Nuclear Information System (INIS)
Zecca, Chiara; Cereda, Carlo; Tschuor, Silvia; Staedler, Claudio; Nadarajah, Navarajah; Bassetti, Claudio L.; Gobbi, Claudio; Wetzel, Stephan; Santini, Francesco
2012-01-01
Diffusion-weighted imaging (DWI) has become a reference MRI technique for the evaluation of neurological disorders. Few publications have investigated the application of DWI for inflammatory demyelinating lesions. The purpose of the study was to describe diffusion-weighted imaging characteristics of acute, spinal demyelinating lesions. Six consecutive patients (two males, four females; aged 28-64 years) with acute spinal cord demyelinating lesions were studied in a prospective case series design from June 2009 to October 2010. We performed magnetic resonance imaging studies from 2 to 14 days from symptom onset on the patients with relapsing remitting multiple sclerosis (n = 3) or clinically isolated syndrome (n = 3). Main outcome measures were diffusion-weighted imaging and apparent diffusion coefficient pattern (ADC) of acute spinal cord demyelinating lesions. All spinal lesions showed a restricted diffusion pattern (DWI+/ADC-) with a 24% median ADC signal decrease. A good correlation between clinical presentation and lesion site was observed. Acute demyelinating spinal cord lesions show a uniform restricted diffusion pattern. Clinicians and neuro-radiologists should be aware that this pattern is not necessarily confirmatory for an ischaemic aetiology. (orig.)
Diffusion-weighted imaging in acute demyelinating myelopathy
Energy Technology Data Exchange (ETDEWEB)
Zecca, Chiara; Cereda, Carlo; Tschuor, Silvia; Staedler, Claudio; Nadarajah, Navarajah; Bassetti, Claudio L.; Gobbi, Claudio [Ospedale Regionale di Lugano, Servizio di Neurologia e Neuroradiologia, Neurocenter of Southern Switzerland, Lugano (Switzerland); Wetzel, Stephan [Swiss Neuro Institute (SNI), Abteilung fuer Neuroradiologie, Hirslanden Klinik Zuerich, Zuerich (Switzerland); Santini, Francesco [University of Basel Hospital, Division of Radiological Physics, Basel (Switzerland)
2012-06-15
Diffusion-weighted imaging (DWI) has become a reference MRI technique for the evaluation of neurological disorders. Few publications have investigated the application of DWI for inflammatory demyelinating lesions. The purpose of the study was to describe diffusion-weighted imaging characteristics of acute, spinal demyelinating lesions. Six consecutive patients (two males, four females; aged 28-64 years) with acute spinal cord demyelinating lesions were studied in a prospective case series design from June 2009 to October 2010. We performed magnetic resonance imaging studies from 2 to 14 days from symptom onset on the patients with relapsing remitting multiple sclerosis (n = 3) or clinically isolated syndrome (n = 3). Main outcome measures were diffusion-weighted imaging and apparent diffusion coefficient pattern (ADC) of acute spinal cord demyelinating lesions. All spinal lesions showed a restricted diffusion pattern (DWI+/ADC-) with a 24% median ADC signal decrease. A good correlation between clinical presentation and lesion site was observed. Acute demyelinating spinal cord lesions show a uniform restricted diffusion pattern. Clinicians and neuro-radiologists should be aware that this pattern is not necessarily confirmatory for an ischaemic aetiology. (orig.)
Identification of the Diffusion Parameter in Nonlocal Steady Diffusion Problems
Energy Technology Data Exchange (ETDEWEB)
D’Elia, M., E-mail: mdelia@fsu.edu, E-mail: mdelia@sandia.gov [Sandia National Laboratories (United States); Gunzburger, M. [Florida State University (United States)
2016-04-15
The problem of identifying the diffusion parameter appearing in a nonlocal steady diffusion equation is considered. The identification problem is formulated as an optimal control problem having a matching functional as the objective of the control and the parameter function as the control variable. The analysis makes use of a nonlocal vector calculus that allows one to define a variational formulation of the nonlocal problem. In a manner analogous to the local partial differential equations counterpart, we demonstrate, for certain kernel functions, the existence of at least one optimal solution in the space of admissible parameters. We introduce a Galerkin finite element discretization of the optimal control problem and derive a priori error estimates for the approximate state and control variables. Using one-dimensional numerical experiments, we illustrate the theoretical results and show that by using nonlocal models it is possible to estimate non-smooth and discontinuous diffusion parameters.
Radiologic findings of diffuse Pulmonary hemorrhage
Energy Technology Data Exchange (ETDEWEB)
Seo, Mi Ra; Song, Koun Sik; Lee, Jin Seong; Lim, Tae Hwan [Ulsan Univ. College of Medicine, Seoul (Korea, Republic of)
1998-12-01
To describe the chest radiographic and CT findings of diffuse pulmonary hemorrhage. Two radiologists retrospectively analysed the chest radiographic and CT findings of six patients with diffuse pulmonary hemorrhage. Using open lung biopsy(n=3D2) and transbronchial lung biopsy or bronchoalveolar lavage(n=3D4), diagnosis was based on the presence of hemosiderin-laden macrophage or intra-alveolar hemorrhage. Underlying diseases were Wegener's granulomatosis(n=3D2), antiphospholipid antibody syndrome(n=3D2), Henoch-Schonlein purpura(n=3D1), and idopathic pulmonary hemosiderosis(n=3D1). In all patients, sequential chest radiographs, obtained during a one to six-month period, were available. HRCT scans were obtained in five patinets, and conventional CT scans in one. Follow-up HRCT scans were obtained in two. We also analyzed the patterns of involvement, distribution and sequential changes in the pulmonary abnormalities seen on chest radiographs and CT scans. Chest radiographs showed multifocal patchy consolidation(n=3D6), ground-glass opacity(n=3D3), and multiple granular or nodular opacity(n=3D3). These lesions were intermingled in five patients, while in one there was consolidation only. Sequential chest radiographs demonstrated the improvement of initial pulmonary abnormalities and appearance of new lesions elsewhere within 5-6 days, though within 7-25 (average, 13) days, these had almost normalized. HRCT scans showed patchy consolidation(n=3D5), multiple patchy ground-glass opacity(n=3D5), or ill-defined air space nodules(n=3D4). These lesions were intermingled in five patients, and in one, ground-glass opacity only was noted. In two patients there were interlobular septal thickening and intalobular reticular opacity. The distribution of these abnormalities was almost always bilateral, diffuse with no zonal predominancy, and spared the apex of the lung and subpleural region were less affected. Although chest radiographic and CT findings of diffuse pulmonary
Radiologic findings of diffuse Pulmonary hemorrhage
International Nuclear Information System (INIS)
Seo, Mi Ra; Song, Koun Sik; Lee, Jin Seong; Lim, Tae Hwan
1998-01-01
To describe the chest radiographic and CT findings of diffuse pulmonary hemorrhage. Two radiologists retrospectively analysed the chest radiographic and CT findings of six patients with diffuse pulmonary hemorrhage. Using open lung biopsy(n=3D2) and transbronchial lung biopsy or bronchoalveolar lavage(n=3D4), diagnosis was based on the presence of hemosiderin-laden macrophage or intra-alveolar hemorrhage. Underlying diseases were Wegener's granulomatosis(n=3D2), antiphospholipid antibody syndrome(n=3D2), Henoch-Schonlein purpura(n=3D1), and idopathic pulmonary hemosiderosis(n=3D1). In all patients, sequential chest radiographs, obtained during a one to six-month period, were available. HRCT scans were obtained in five patinets, and conventional CT scans in one. Follow-up HRCT scans were obtained in two. We also analyzed the patterns of involvement, distribution and sequential changes in the pulmonary abnormalities seen on chest radiographs and CT scans. Chest radiographs showed multifocal patchy consolidation(n=3D6), ground-glass opacity(n=3D3), and multiple granular or nodular opacity(n=3D3). These lesions were intermingled in five patients, while in one there was consolidation only. Sequential chest radiographs demonstrated the improvement of initial pulmonary abnormalities and appearance of new lesions elsewhere within 5-6 days, though within 7-25 (average, 13) days, these had almost normalized. HRCT scans showed patchy consolidation(n=3D5), multiple patchy ground-glass opacity(n=3D5), or ill-defined air space nodules(n=3D4). These lesions were intermingled in five patients, and in one, ground-glass opacity only was noted. In two patients there were interlobular septal thickening and intalobular reticular opacity. The distribution of these abnormalities was almost always bilateral, diffuse with no zonal predominancy, and spared the apex of the lung and subpleural region were less affected. Although chest radiographic and CT findings of diffuse pulmonary
Liang, Yingjie; Chen, Wen
2018-03-01
Ultraslow diffusion has been observed in numerous complicated systems. Its mean squared displacement (MSD) is not a power law function of time, but instead a logarithmic function, and in some cases grows even more slowly than the logarithmic rate. The distributed-order fractional diffusion equation model simply does not work for the general ultraslow diffusion. Recent study has used the local structural derivative to describe ultraslow diffusion dynamics by using the inverse Mittag-Leffler function as the structural function, in which the MSD is a function of inverse Mittag-Leffler function. In this study, a new stretched logarithmic diffusion law and its underlying non-local structural derivative diffusion model are proposed to characterize the ultraslow diffusion in aging dense colloidal glass at both the short and long waiting times. It is observed that the aging dynamics of dense colloids is a class of the stretched logarithmic ultraslow diffusion processes. Compared with the power, the logarithmic, and the inverse Mittag-Leffler diffusion laws, the stretched logarithmic diffusion law has better precision in fitting the MSD of the colloidal particles at high densities. The corresponding non-local structural derivative diffusion equation manifests clear physical mechanism, and its structural function is equivalent to the first-order derivative of the MSD.
Passive Rocket Diffuser Testing: Reacting Flow Performance of Four Second-Throat Geometries
Jones, Daniel R.; Allgood, Daniel C.; Saunders, Grady P.
2016-01-01
Second-throat diffusers serve to isolate rocket engines from the effects of ambient back pressure. As one of the nation's largest rocket testing facilities, the performance and design limitations of diffusers are of great interest to NASA's Stennis Space Center. This paper describes a series of tests conducted on four diffuser configurations to better understand the effects of inlet geometry and throat area on starting behavior and boundary layer separation. The diffusers were tested for a duration of five seconds with a 1455-pound thrust, LO2/GH2 thruster to ensure they each reached aerodynamic steady state. The effects of a water spray ring at the diffuser exits and a water-cooled deflector plate were also evaluated. Static pressure and temperature measurements were taken at multiple axial locations along the diffusers, and Computational Fluid Dynamics (CFD) simulations were used as a tool to aid in the interpretation of data. The hot combustion products were confirmed to enable the diffuser start condition with tighter second throats than predicted by historical cold-flow data or the theoretical normal shock method. Both aerodynamic performance and heat transfer were found to increase with smaller diffuser throats. Spray ring and deflector cooling water had negligible impacts on diffuser boundary layer separation. CFD was found to accurately capture diffuser shock structures and full-flowing diffuser wall pressures, and the qualitative behavior of heat transfer. However, the ability to predict boundary layer separated flows was not consistent.
Diffuse and vascular hepatic diseases; Diffuse und vaskulaere Lebererkrankungen
Energy Technology Data Exchange (ETDEWEB)
Kreimeyer, S.; Grenacher, L. [Universitaetsklinikum Heidelberg, Abteilung Diagnostische und Interventionelle Radiologie, Heidelberg (Germany)
2011-08-15
In addition to focal liver lesions, diffuse and vascular disorders of the liver represent a wide spectrum of liver diseases which are from the radiological point of view often difficult or nearly impossible to diagnose. Classical diagnostic methods are computed tomography and magnetic resonance imaging in addition to ultrasound. Diffuse parenchymal damage caused by diseases of various etiologies is therefore difficult to evaluate because it often lacks characteristic morphological features. For hepatic steatosis, hemochromatosis/siderosis as an example of a diffuse storage disease and sarcoidosis and candidiasis as infectious/inflammatory diseases, an image-based diagnosis is appropriate in some cases. For most diffuse liver diseases, however only nonspecific changes are visualized. Vascular pathologies of the liver, such as the Budd-Chiari syndrome and portal vein thrombosis, however, can usually be diagnosed very clearly using radiology and there is also a very effective interventional radiological treatment. Chronic diseases very often culminate in liver cirrhosis which is highly associated with an increased risk of liver cancer. (orig.) [German] Neben den fokalen Leberlaesionen stellen diffuse und vaskulaere Lebererkrankungen ein weites Spektrum an Erkrankungen der Leber dar, die radiologisch oft schwer oder gar nicht diagnostizierbar sind. Klassische diagnostische Verfahren sind dabei neben dem Ultraschall die Computertomographie und die Magnetresonanztomographie. Diffuse Parenchymschaeden, bedingt durch Erkrankungen unterschiedlichster Aetiologie, sind deshalb schwierig evaluierbar, weil haeufig charakteristische bildmorphologische Merkmale fehlen. Die Steatosis hepatis, die Haemochromatose/Siderose als Beispiel der Speicherkrankheiten sowie die Sarkoidose und die Candidose als infektioes-entzuendliche Erkrankungen sind einer bildbasierten Diagnosestellung z. T. zugaenglich, bei den meisten diffusen Lebererkrankungen jedoch zeigen sich lediglich unspezifische
Hydrogen diffusion and trapping in bcc and fcc metals
International Nuclear Information System (INIS)
Richter, D.
1979-01-01
The fundamental aspects of the metal--hydrogen systems are described. The large number of anomalous properties are the reason for continuous scientific effort. The time scale of hydrogen motion is extremely short. The characteristic frequencies of the localized modes of hydrogen in Ta, Nb, or V are in the order of 10 -14 sec (energies between 0.1 to 0.2 eV); the jump frequencies for H-diffusion at elevated temperatures in those systems are between 10 +12 to 10 +13 sec -1 . They are comparable with the correlation times for diffusion in liquids and more than ten orders of magnitude larger than the jump times for nitrogen in Nb. Out of the large number of experimental data this paper will survey only some recent results on representative fcc and bcc metals for dilute H solutions. The nature of the elementary step in H-diffusion is described. Here the temperature and isotope dependence of the H-diffusion coefficient gives hints to the mechanism involved. The experimental results are discussed in terms of semiclassical and quantum mechanical diffusion theories
THE DETERMINATION OF DIFFUSION COEFFICIENT OF INVERT MATERIALS
International Nuclear Information System (INIS)
P. Heller and J. Wright
2000-01-01
The Engineered Barrier System (EBS) Testing Department is performing tests in the Department of Energy's Atlas Facility to evaluate the performance of various means for increasing the time for breakthrough of radionuclides from the waste package to the base of the invert. This includes testing various barriers in the invert as a means of increasing breakthrough time through the process of diffusion. A diffusion barrier may serve as an invert material for the emplacement drifts. The invert material may consist of crushed tuff from the repository excavation at Yucca Mountain or silica sand. The objective of this report is to determine the diffusion coefficient of the crushed tuff and silica sand invert materials specified by the EBS Testing Department. The laboratory derived information from the testing was used in the Nernst-Einstein equation (Jurinak et al. 1987, p. 626) to determine the diffusion coefficient of the invert material. This report transmits the results and describes the methodology and interpretation. The scope of this report is to determine the diffusion coefficients of the invert materials mentioned above using the centrifuge at UFA Ventures. Standard laboratory procedures, described in Section 2 of this report, were used. The diffusion coefficients are to be determined over a range of moisture contents. The report contains the diffusion coefficients calculated by the Nernst-Einstein equation (Jurinak et al. 1987, p. 626) that become a part of the Technical Database. Raw data is also included in the report, however this data does not become part of the Technical Database as per Section 3.23 of AP-SIII.3Q ''Submittal and Incorporation of Data to the Technical Data Management System''. A sieve analysis of the samples was not conducted as part of this report, but sieve analysis may be accomplished as part of other reports. Two samples of crushed tuff and two samples of silica sand were tested
Gaseous diffusion -- the enrichment workhorse
International Nuclear Information System (INIS)
Shoemaker, J.E. Jr.
1984-01-01
Construction of the first large-scale gaseous diffusion facility was started as part of the Manhattan Project in Oak Ridge, Tennessee, in 1943. This facility, code named ''K-25,'' began operation in January 1945 and was fully on stream by September 1945. Four additional process buildings were later added in Oak Ridge as the demand for enriched uranium escalated. New gaseous diffusion plants were constructed at Paducah, Kentucky, and Portsmouth, Ohio, during this period. The three gaseous diffusion plants were the ''workhorses'' which provided the entire enriched uranium demand for the United States during the 1950s and 1960s. As the demand for enriched uranium for military purposes decreased during the early 1960s, power to the diffusion plants was curtailed to reduce production. During the 1960s, as plans for the nuclear power industry were formulated, the role of the diffusion plants gradually changed from providing highly-enriched uranium for the military to providing low-enriched uranium for power reactors
Radionuclide diffusion in soils. III
International Nuclear Information System (INIS)
Cipakova, A.; Szabova, T.
1988-01-01
Samples were taken of five soil types for determining diffusion coefficients, namely chernozem, illimerized brown soil, degraded chernozem, gleizated brown soil and heavy loamy brown soil. 5 layers of soil having a thickness of 1 cm each were placed in diffusion columns. 20 ml of water with 0.45 MBq 85 Sr of distilled water was poured over the columns. 10 ml of distilled water was poured over the columns every 5 days for monitoring the effect of the amount of precipitation and its distribution - a similarity with rainfall in the driest month, 41 ml of distilled water was then poured over the column every 5 days or 82 ml of distilled water every 10 days - imitating the month with the highest rainfall level. The effect of salts and various concentrations of salt mixtures on the value of the diffusion coefficient were monitored in solutions of NaNO 3 , KNO 3 and Ca(NO 3 ) 2 with added activity 0.45 MGq of 85 SrCl 2 . Diffusion was monitored for 101 days. All measured values are tabulated. The smallest diffusion coefficient was found in chernozem in the presence of H 2 O and the highest value was found in illimerized brown soil in the presence of 0.15 M of KNO 3 . (E.S.). 2 tabs., 10 refs
Diffusion of graphite. The effect of cylindrical canals
International Nuclear Information System (INIS)
Carle, R.; Clouet d'Orval, C.; Martelly, J.; Mazancourt, T. de; Sagot, M.; Lattes, R.; Teste du Bailler, A.
1957-01-01
Experiments on thermal neutron diffusion in the graphite used as moderator in the pile G1 have been carried out. The object of these experiments is to determine: - the intrinsic quality of this graphite, characterised by its diffusion length L or its Laplacian 1/L 2 - the effect of the canals, which modifies anisotropically the macroscopic diffusion equation and is characterized by two principal diffusion regions (or two principal Laplacian), valid respectively for the diffusion in the direction of the canals and in a perpendicular direction. In order to determine them two experiments are necessary, in which the second derivatives of the flux in relation to the space coordinates are very different. These experiments form the object of the first two parts. Part 1: Diffusion along the axis of a flux coming from the pile source, and limited radially by a quasi cylindrical screen of cadmium bars. This screen, or Faraday cage is designed to give to the thermal flux produced the same radius of extrapolation to zero as that of the pile source. The determination of L (with the graphite full) has been made under the same conditions. The measurements have been interpreted in two ways. The influence of the brackets holding the detectors is discussed. Part 2: Radial diffusion in the graphite surrounding the 'long' cylindrical pile. This is well described by a sum of Bessel functions. Part 3: Results (valid for d = 1.61 t = 17 deg. C). For the graphite without cavity L = 52.7 ± 0.4 cm. The effect of the canals on the diffusion area and its anisotropy are in excellent agreement with the theory of Behrens: L(parallel) = 64.6 cm and L(perpendicular) 62.2 cm. Appendix: Theory of the Faraday cage. (author) [fr
International Nuclear Information System (INIS)
Ni Jianming; Chen Shuang; Liu Jianjun; Huang Gang; Shen Tianzhen; Chen Xingrong
2010-01-01
Background and purpose: Although diffusion characteristics of white matter (WM) and its aging effects have been well described in the literature, diffusion characteristics of grey matter (GM), especially the cortical GM, have not been fully evaluated. In the present study, we used the fluid-inversion prepared diffusion imaging (FLIPD) technique to determine if there are age-related water diffusivity changes in GM. Materials and methods: 120 healthy volunteers were recruited for our study. They were divided into three age groups: group one (20-39 years old), group two (40-59 years old) and group three (60 years or older). All patients were evaluated with MRI using FLIPD at 3.0 T. Apparent diffusion coefficient (ADC) values of the frontal GM, cingulate cortex and thalami were determined bilaterally by region-of-interest analysis. Results: Group three had significantly higher ADC values in both thalami and the left frontal GM compared to group two or group one. No ADC value difference was found among the three groups in the right frontal GM and bilateral cingulate cortex. There was a significant positive correlation between individual ADC values and age in both thalami and left frontal GM. For the cingulate cortex and the right frontal GM, ADC values did not correlate significantly with advancing age. Conclusion: Statistically significant age-related diffusion changes were observed in both thalami and the left frontal cortex. The data reported here may serve as a reference for future studies.
International Nuclear Information System (INIS)
Tardiveau, P; Moreau, N; Bentaleb, S; Postel, C; Pasquiers, S
2009-01-01
The dynamics of a point-to-plane corona discharge induced in high pressure air under nanosecond scale high overvoltage is investigated. The electrical and optical properties of the discharge can be described in space and time with fast and precise current measurements coupled to gated and intensified imaging. Under atmospheric pressure, the discharge exhibits a diffuse pattern like a multielectron avalanche propagating through a direct field ionization mechanism. The diffuse regime can exist since the voltage rise time is much shorter than the characteristic time of the field screening effects, and as long as the local field is higher than the critical ionization field in air. As one of these conditions is not fulfilled, the discharge turns into a multi-channel regime and the diffuse-to-filamentary transition strongly depends on the overvoltage, the point-to-plane gap length and the pressure. When pressure is increased above atmospheric pressure, the diffuse stage and its transition to streamers seem to satisfy similarity rules as the key parameter is the reduced critical ionization field only. However, above 3 bar, neither diffuse avalanche nor streamer filaments are observed but a kind of streamer-leader regime, due to the fact that mechanisms such as photoionization and heat diffusion are not similar to pressure.
A mathematical model in charactering chloride diffusivity in unsaturated cementitious material
Zhang, Y.; Ye, G.; Pecur, I.B.; Baricevic, A.; Stirmer, N; Bjegovic, D.
2017-01-01
In this paper, a new analytic model for predicting chloride diffusivity in unsaturated cementitious materials is developed based on conductivity theory and Nernst-Einstein equation. The model specifies that chloride diffusivity in unsaturated cementitious materials can be mathematically described as
Computation of short-time diffusion using the particle simulation method
International Nuclear Information System (INIS)
Janicke, L.
1983-01-01
The method of particle simulation allows a correct description of turbulent diffusion even in areas near the source and the computation of overall average values (anticipated values). The model is suitable for dealing with complex situation. It is derived from the K-model which describes the dispersion of noxious matter using the diffusion formula. (DG) [de
van Stroe, A.J.; Janssen, L.J.J.
1993-01-01
An accurate and rapid method for detg. the diffusion coeffs. of electrochem. active gases in electrolytes is described. The technique is based on chronoamperometry where transient currents are measured and interpreted with a Cottrell-related equation. The diffusion coeffs. of oxygen were detd. for
Fabrication and research of high purity germanium detectors with abrupt and thin diffusion layer
International Nuclear Information System (INIS)
Rodriguez Cabal, A. E.; Diaz Garcia, A.
1997-01-01
A different high purity germanium detector's fabrication method is described. A very thin diffusion film with an abrupt change of the type of conductivity is obtained. The fine diffusion layer thickness makes possibly their utilization in experimental systems in which all the data are elaborated directly on the computer. (author) [es
Inward Cationic Diffusion and Formation of Silica-Rich Surface Nanolayer of Glass
DEFF Research Database (Denmark)
Smedskjær, Morten Mattrup; Deubener, Joachim; Yue, Yuanzheng
2009-01-01
form and are incorporated into the glass structure. Both the V4+ and the hydroxyl contents increase with increasing ta and hydrogen partial pressure. The inward diffusion enhances the hardness of the glass surface. The mechanism of the inward diffusion is suggested on the basis of a model describing...
Diffusion of Innovation Theory: A Bridge for the Research-Practice Gap in Counseling
Murray, Christine E.
2009-01-01
This article presents a diffusion of innovation theory-based framework for addressing the gap between research and practice in the counseling profession. The author describes the nature of the research-practice gap and presents an overview of diffusion of innovation theory. On the basis of the application of several major postulates of diffusion…
A point-centered diffusion differencing for unstructured meshes in 3-D
International Nuclear Information System (INIS)
Palmer, T.S.
1994-01-01
We describe a point-centered diffusion discretization for 3-D unstructured meshes of polyhedra. The method has several attractive qualities, including second-order accuracy and preservation of linear solutions. A potential drawback to the scheme is that the diffusion matrix is asymmetric, in general. Results of numerical test problems illustrate the behavior of the scheme
International Nuclear Information System (INIS)
Arun, Sasikumar; Mittal, Bhagwant Rai; Shukla, Jaya; Bhattacharya, Anish; Kumar, Praveen
2013-01-01
The authors describe a 50 days old pre-term infant with persistent hyperinsulinemic hypoglycemia of infancy in whom 68 Ga DOTATATE positron emission tomography/computerized tomography scan showed diffusely increased tracer uptake in the entire pancreas with no abnormal tracer uptake anywhere else in the body, suggestive of a diffuse variant of nesidioblastosis. (author)
Diffuse sound field: challenges and misconceptions
DEFF Research Database (Denmark)
Jeong, Cheol-Ho
2016-01-01
Diffuse sound field is a popular, yet widely misused concept. Although its definition is relatively well established, acousticians use this term for different meanings. The diffuse sound field is defined by a uniform sound pressure distribution (spatial diffusion or homogeneity) and uniform...... tremendously in different chambers because the chambers are non-diffuse in variously different ways. Therefore, good objective measures that can quantify the degree of diffusion and potentially indicate how to fix such problems in reverberation chambers are needed. Acousticians often blend the concept...... of mixing and diffuse sound field. Acousticians often refer diffuse reflections from surfaces to diffuseness in rooms, and vice versa. Subjective aspects of diffuseness have not been much investigated. Finally, ways to realize a diffuse sound field in a finite space are discussed....
Nonlinear Diffusion and Transient Osmosis
International Nuclear Information System (INIS)
Igarashi, Akira; Rondoni, Lamberto; Botrugno, Antonio; Pizzi, Marco
2011-01-01
We investigate both analytically and numerically the concentration dynamics of a solution in two containers connected by a narrow and short channel, in which diffusion obeys a porous medium equation. We also consider the variation of the pressure in the containers due to the flow of matter in the channel. In particular, we identify a phenomenon, which depends on the transport of matter across nano-porous membranes, which we call ''transient osmosis . We find that nonlinear diffusion of the porous medium equation type allows numerous different osmotic-like phenomena, which are not present in the case of ordinary Fickian diffusion. Experimental results suggest one possible candidate for transiently osmotic processes. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)
Nitrogen diffusion in zirconium nitride
International Nuclear Information System (INIS)
Desmaison, J.G.; Smeltzer, W.W.
1977-01-01
Nitrogen diffusion in polycrystalline ZrN/sub 0.71-0.79/ spheres, 60 and 90 μm diameter, was studied by the gas-solid exchange technique using 15 N as a tracer at a nitrogen pressure of 220 torr and 1000 to 1200 0 C. These specimens were characterized by chemical analyses, density, lattice parameter, and structural measurements. The tracer diffusion coefficient can be expressed as D* (cm 2 /S) = 3.0 x 10 -10 exp (-23,000/RT). This result, when compared to a previous determination obtained in the same conditions with 254 μm thick plates, confirms that nitrogen transport in this polycrystalline solid at temperatures less than 1200 0 C is associated with a short-circuit diffusion mechanism
Tracer diffusion in ternary alloys
International Nuclear Information System (INIS)
Tahir-Kheli, R.A.
1985-07-01
An intuitive extension of the theory for diffusion in dynamic binary alloys given in the preceding paper is presented. This theory has also received an independent derivation, based on more formal procedures, by Holdsworth and Elliott. We present Monte Carlo estimates for diffusion correlation factors, fsup(A), fsup(B), and fsup(C) and compare them with the theory. The agreement between the theoretical results and the Monte Carlo estimates for the correlation factors of the slow particles, i.e., fsup(C) and fsup(B), is found to be generally good. In contrast, for the correlation factor, fsup(A), referring to the diffusion coefficient of fast particles in the system, the theoretical results are found to be systematically lower by a small but resolvable margin. It is suggested that this is occasioned by the neglect of spatial constraints on the scattering of coupled tracer-background particle field pairs. (author)
Emissivity of discretized diffusion problems
International Nuclear Information System (INIS)
Densmore, Jeffery D.; Davidson, Gregory; Carrington, David B.
2006-01-01
The numerical modeling of radiative transfer by the diffusion approximation can produce artificially damped radiation propagation if spatial cells are too optically thick. In this paper, we investigate this nonphysical behavior at external problem boundaries by examining the emissivity of the discretized diffusion approximation. We demonstrate that the standard cell-centered discretization produces an emissivity that is too low for optically thick cells, a situation that leads to the lack of radiation propagation. We then present a modified boundary condition that yields an accurate emissivity regardless of cell size. This modified boundary condition can be used with a deterministic calculation or as part of a hybrid transport-diffusion method for increasing the efficiency of Monte Carlo simulations. We also discuss the range of applicability, as a function of cell size and material properties, when this modified boundary condition is employed in a hybrid technique. With a set of numerical calculations, we demonstrate the accuracy and usefulness of this modified boundary condition
Single Crystal Diffuse Neutron Scattering
Directory of Open Access Journals (Sweden)
Richard Welberry
2018-01-01
Full Text Available Diffuse neutron scattering has become a valuable tool for investigating local structure in materials ranging from organic molecular crystals containing only light atoms to piezo-ceramics that frequently contain heavy elements. Although neutron sources will never be able to compete with X-rays in terms of the available flux the special properties of neutrons, viz. the ability to explore inelastic scattering events, the fact that scattering lengths do not vary systematically with atomic number and their ability to scatter from magnetic moments, provides strong motivation for developing neutron diffuse scattering methods. In this paper, we compare three different instruments that have been used by us to collect neutron diffuse scattering data. Two of these are on a spallation source and one on a reactor source.