Krishna, S.; Shukla, A.; Malik, R.P.
2014-12-15
Using the supersymmetric (SUSY) invariant restrictions on the (anti-)chiral supervariables, we derive the off-shell nilpotent symmetries of the general one (0+1)-dimensional N=2 SUSY quantum mechanical (QM) model which is considered on a (1, 2)-dimensional supermanifold (parametrized by a bosonic variable t and a pair of Grassmannian variables θ and θ-bar with θ{sup 2}=(θ-bar){sup 2}=0,θ(θ-bar)+(θ-bar)θ=0). We provide the geometrical meanings to the two SUSY transformations of our present theory which are valid for any arbitrary type of superpotential. We express the conserved charges and Lagrangian of the theory in terms of the supervariables (that are obtained after the application of SUSY invariant restrictions) and provide the geometrical interpretation for the nilpotency property and SUSY invariance of the Lagrangian for the general N=2 SUSY quantum theory. We also comment on the mathematical interpretation of the above symmetry transformations. - Highlights: • A novel method has been proposed for the derivation of N=2 SUSY transformations. • General N=2 SUSY quantum mechanical (QM) model with a general superpotential, is considered. • The above SUSY QM model is generalized onto a (1, 2)-dimensional supermanifold. • SUSY invariant restrictions are imposed on the (anti-)chiral supervariables. • Geometrical meaning of the nilpotency property is provided.
Off-shell kinematics in nuclear processes
NASA Astrophysics Data System (ADS)
Thakur, Jagannath
1983-11-01
A semirelativistic model based on an approximate solution of the Bethe-Salpeter equation used previously to construct a conserved electromagnetic current with arbitrary interaction is generalized to arbitrary processes and extended to many body targets. Although the technique appears valid and useful for introducing kinematic corrections in processes off few body targets, a paradoxical result emerges for large nuclei in that the relevant form factors, which must be evaluated far off-shell, can be dramatically different from that for free nucleons, contrary to the usual picture of the nucleus as composed of nearly free nucleons. NUCLEAR REACTIONS Bethe-Salpeter equation, off-shell kinematics, impulse approximation, paradox for large nuclei.
Deformations with maximal supersymmetries part 2: off-shell formulation
NASA Astrophysics Data System (ADS)
Chang, Chi-Ming; Lin, Ying-Hsuan; Wang, Yifan; Yin, Xi
2016-04-01
Continuing our exploration of maximally supersymmetric gauge theories (MSYM) deformed by higher dimensional operators, in this paper we consider an off-shell approach based on pure spinor superspace and focus on constructing supersymmetric deformations beyond the first order. In particular, we give a construction of the Batalin-Vilkovisky action of an all-order non-Abelian Born-Infeld deformation of MSYM in the non-minimal pure spinor formalism. We also discuss subtleties in the integration over the pure spinor superspace and the relevance of Berkovits-Nekrasov regularization.
Off-shell hydrodynamics from holography
Crossley, Michael; Glorioso, Paolo; Liu, Hong; Wang, Yifan
2016-02-18
In this article, we outline a program for obtaining an action principle for dissipative fluid dynamics by considering the holographic Wilsonian renormalization group applied to systems with a gravity dual. As a first step, in this paper we restrict to systems with a non-dissipative horizon. By integrating out gapped degrees of freedom in the bulk gravitational system between an asymptotic boundary and a horizon, we are led to a formulation of hydrodynamics where the dynamical variables are not standard velocity and temperature fields, but the relative embedding of the boundary and horizon hypersurfaces. At zeroth order, this action reduces tomore » that proposed by Dubovsky et al. as an off-shell formulation of ideal fluid dynamics.« less
Off-shell hydrodynamics from holography
NASA Astrophysics Data System (ADS)
Crossley, Michael; Glorioso, Paolo; Liu, Hong; Wang, Yifan
2016-02-01
We outline a program for obtaining an action principle for dissipative fluid dynamics by considering the holographic Wilsonian renormalization group applied to systems with a gravity dual. As a first step, in this paper we restrict to systems with a non-dissipative horizon. By integrating out gapped degrees of freedom in the bulk gravitational system between an asymptotic boundary and a horizon, we are led to a formulation of hydrodynamics where the dynamical variables are not standard velocity and temperature fields, but the relative embedding of the boundary and horizon hypersurfaces. At zeroth order, this action reduces to that proposed by Dubovsky et al. as an off-shell formulation of ideal fluid dynamics.
Taming the off-shell Higgs boson
NASA Astrophysics Data System (ADS)
Azatov, A.; Grojean, C.; Paul, A.; Salvioni, E.
2015-03-01
We study the off-shell Higgs data in the process pp → h (*) → Z (*) Z (*) → 4 l, to constrain deviations of the Higgs couplings. We point out that this channel can be used to resolve the long- and short-distance contributions to Higgs production by gluon fusion and can thus be complementary to in measuring the top Yukawa coupling. Our analysis, performed in the context of effective field theory, shows that current data do not allow drawing any model-independent conclusions. We study the prospects at future hadron colliders, including the high-luminosity LHC and accelerators with higher energy, up to 100 TeV. The available QCD calculations and the theoretical uncertainties affecting our analysis are also briefly discussed.
Compton scattering by a pion and off-shell effects
Scherer, S.; Fearing, H.W. )
1995-01-01
We consider Compton scattering by a pion in the framework of chiral perturbation theory. We investigate off-shell effects in the [ital s]- and [ital u]-channel pole diagrams. For that purpose we perform a field transformation which, in comparison with the standard Gasser and Leutwyler Lagrangian, generates additional terms at order [ital p][sup 4] proportional to the lowest-order equation of motion. As a result of the equivalence theorem the two Lagrangians predict the same Compton scattering [ital S]-matrix even though they generate different off-shell form factors. We conclude that off-shell effects are not only model dependent but also representation dependent.
Chiral perturbation theory and off-shell electromagnetic form factors
Rudy, T.E.; Fearing, H.W.; Scherer, S.
1995-05-10
The off-shell electromagnetic vertex of pions and kaons is calculated to {ital O}({ital p}{sup 4}) in the momentum expansion within the framework of chiral perturbation theory to one loop. The formalism of Gasser and Leutwyler is extended to accommodate the most general form for off-shell Green`s functions in the pseudoscalar meson sector. To that end we identify the structures at {ital O}({ital p}{sup 4}) which were initially removed by using the equation of motion of the lowest-order lagrangian. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
Higgs couplings: disentangling new physics with off-shell measurements.
Cacciapaglia, Giacomo; Deandrea, Aldo; La Rochelle, Guillaume Drieu; Flament, Jean-Baptiste
2014-11-14
After the discovery of a scalar resonance, resembling the Higgs boson, its couplings have been extensively studied via the measurement of various production and decay channels on the invariant mass peak. Recently, the possibility of using off-shell measurements has been suggested: in particular, the CMS Collaboration has published results based on the high-invariant mass cross section of the process gg→ZZ, which contains a contribution from the Higgs boson. While this measurement has been interpreted as a constraint on the Higgs width after very specific assumptions are taken on the Higgs couplings, in this Letter, we show that a much more model-independent interpretation is possible.
Bordered surfaces, off-shell amplitudes, sewing, and string field theory
Carlip, S.
1989-04-01
These lectures will deal with the current status of the sewing problem. The rationale for this approach is that any nonperturbative string theory must reproduce the Polyakov path integral as a perturbation series. If our experience in ordinary field theory is a guide --- and admittedly it may not be --- the terms in such a perturbation series, like Feynman diagrams, are likely to be built up from simple ''vertices'' and ''propagators,'' which can themselves be represented as (off-shell) Polyakov amplitudes. Hence an understanding of how to put together simple components into more complicated world sheet amplitudes is likely to give us much-needed information about the structure of nonperturbative string theory. To understand sewing, we must first understand the building blocks, off-shell Polyakov amplitudes. This is the subject of my first lecture. Next, we will explore the sewing of conformal field theories at a fixed conformal structure, that is, the reconstruction of correlation functions for a fixed surface /Sigma/ from those on a pair of surfaces /Sigma//sub 1/ and /Sigma//sub 2/ obtained by cutting /Sigma/ along a closed curve. We will then look at the problem of sewing amplitudes, integrals of correlation functions over moduli space. This will necessitate an understanding of how to build the moduli space of a complicated surface from simpler moduli spaces. Finally, we will briefly examine vertices and string field theories. 48 refs., 10 figs.
Off-shell single-top production at NLO matched to parton showers
NASA Astrophysics Data System (ADS)
Frederix, R.; Frixione, S.; Papanastasiou, A. S.; Prestel, S.; Torrielli, P.
2016-06-01
We study the hadroproduction of a W b pair in association with a light jet, focusing on the dominant t-channel contribution and including exactly at the matrix-element level all non-resonant and off-shell effects induced by the finite top-quark width. Our simulations are accurate to the next-to-leading order in QCD, and are matched to the Herwig6 and Pythia8 parton showers through the MC@NLO method. We present phenomenological results relevant to the 8 TeV LHC, and carry out a thorough comparison to the case of on-shell t-channel single-top production. We formulate our approach so that it can be applied to the general case of matrix elements that feature coloured intermediate resonances and are matched to parton showers.
Off-shell single-top production at NLO matched to parton showers
Frederix, R.; Frixione, S.; Papanastasiou, A. S.; Prestel, S.; Torrielli, P.
2016-06-06
We study the hadroproduction of a W b pair in association with a light jet, focusing on the dominant t -channel contribution and including exactly at the matrix-element level all non-resonant and off-shell effects induced by the finite top-quark width. Our simulations are accurate to the next-to-leading order in QCD, and are matched to the Herwig6 and Pythia8 parton showers through the MC@NLO method. We present phenomenological results relevant to the 8 TeV LHC, and carry out a thorough comparison to the case of on-shell t -channel single-top production. Furthermore, we formulate our approach so that it can be appliedmore » to the general case of matrix elements that feature coloured intermediate resonances and are matched to parton showers.« less
Off-shell electromagnetic form factors of pions and kaons in chiral perturbation theory
Rudy, T.E.; Fearing, H.W.; Scherer, S. )
1994-07-01
The off-shell electromagnetic vertex of a (pseudo)scalar particle contains, in general, two form factors [ital F] and [ital G] which depend, in addition to the squared momentum transfer, on the invariant masses associated with the initial and final legs of the vertex. Chiral perturbation theory to one loop is used to calculate the off-shell form factors of pions and kaons. The formalism of Gasser and Leutwyler, which was previously used to calculate the on-shell limit of the form factor [ital F], is extended to accommodate the most general form for off-shell Green's functions in the pseudoscalar meson sector. We find that chiral symmetry predicts that the form factors [ital F] of the charged pions and kaons go off-shell in the same way, i.e., the off-shell slope at the real photon point is given by the same new phenomenological constant [beta][sub 1]. Furthermore, it is shown that at order [ital p][sup 4] the form factor [ital F] of the [ital K][sup 0] does not show any off-shell dependence. The form factors [ital G] are all related to the form factors [ital F] in the correct fashion as required by the Ward-Takahashi identity. Numerical results for different off-shell kinematics are presented.
NLO QCD+EW predictions for V + jets including off-shell vector-boson decays and multijet merging
NASA Astrophysics Data System (ADS)
Kallweit, S.; Lindert, J. M.; Maierhöfer, P.; Pozzorini, S.; Schönherr, M.
2016-04-01
We present next-to-leading order (NLO) predictions including QCD and electroweak (EW) corrections for the production and decay of off-shell electroweak vector bosons in association with up to two jets at the 13 TeV LHC. All possible dilepton final states with zero, one or two charged leptons that can arise from off-shell W and Z bosons or photons are considered. All predictions are obtained using the automated implementation of NLO QCD+EW corrections in the O penLoops matrix-element generator combined with the Munich and Sherpa Monte Carlo frameworks. Electroweak corrections play an especially important role in the context of BSM searches, due to the presence of large EW Sudakov logarithms at the TeV scale. In this kinematic regime, important observables such as the jet transverse momentum or the total transverse energy are strongly sensitive to multijet emissions. As a result, fixed-order NLO QCD+EW predictions are plagued by huge QCD corrections and poor theoretical precision. To remedy this problem we present an approximate method that allows for a simple and reliable implementation of NLO EW corrections in the MePs@Nlo multijet merging framework. Using this general approach we present an inclusive simulation of vector-boson production in association with jets that guarantees NLO QCD+EW accuracy in all phase-space regions involving up to two resolved jets.
Novel method to deal with off-shell particles in cascade decays
NASA Astrophysics Data System (ADS)
Chakrabortty, Joydeep; Kundu, Anirban; Srivastava, Tripurari
2016-03-01
We propose a novel algorithm to compute the width of any generic n -body decay involving multiple off-shell particles having zero and nonzero spins. Starting from a toy example, we show the computations for three different processes that contain spin-0, -1/2 , and -1 off-shell particles. We check that our results match with the existing results at the analytical level. This proposal can be automatized and should be useful to compute the phase space for long cascade decays, without any Monte Carlo sampling.
Off-shell amplitudes as boundary integrals of analytically continued Wilson line slope
NASA Astrophysics Data System (ADS)
Kotko, P.; Serino, M.; Stasto, A. M.
2016-08-01
One of the methods to calculate tree-level multi-gluon scattering amplitudes is to use the Berends-Giele recursion relation involving off-shell currents or off-shell amplitudes, if working in the light cone gauge. As shown in recent works using the light-front perturbation theory, solutions to these recursions naturally collapse into gauge invariant and gauge-dependent components, at least for some helicity configurations. In this work, we show that such structure is helicity independent and emerges from analytic properties of matrix elements of Wilson line operators, where the slope of the straight gauge path is shifted in a certain complex direction. This is similar to the procedure leading to the Britto-Cachazo-Feng-Witten (BCFW) recursion, however we apply a complex shift to the Wilson line slope instead of the external momenta. While in the original BCFW procedure the boundary integrals over the complex shift vanish for certain deformations, here they are non-zero and are equal to the off-shell amplitudes. The main result can thus be summarized as follows: we derive a decomposition of a helicity-fixed off-shell current into gauge invariant component given by a matrix element of a straight Wilson line plus a reminder given by a sum of products of gauge invariant and gauge dependent quantities. We give several examples realizing this relation, including the five-point next-to-MHV helicity configuration.
NASA Astrophysics Data System (ADS)
Asaka, Keisuke; Kato, Junji; Kawamoto, Noboru; Miyake, Akiko
2013-11-01
We formulate N=2 twisted super Yang-Mills theory with a gauged central charge by superconnection formalism in two dimensions. We obtain off-shell invariant supermultiplets and actions with and without constraints, which is in contrast with the off-shell invariant D=N=4 super Yang-Mills formulation with unavoidable constraints.
One-Dimensional σ-MODELS with N = 5, 6, 7, 8 Off-Shell Supersymmetries
NASA Astrophysics Data System (ADS)
Gonzales, M.; Rojas, M.; Toppan, F.
We computed the actions for the one-dimensional (1D) N = 5 σ-models with respect to the two inequivalent (2, 8, 6) multiplets. Four supersymmetry generators are manifest, while the constraint originated by imposing the fifth supersymmetry automatically induces a full N = 8 off-shell invariance. The resulting action coincides in the two cases and corresponds to a conformally flat 2D target satisfying a special geometry of rigid type. To obtain these results we developed a computational method (for Maple 11) which does not require the notion of superfields and is instead based on the nowadays available list of the inequivalent representations of the 1D N-extended supersymmetry. Its application to systematically analyze the σ-models off-shell invariant actions for the remaining N = 5, 6, 7, 8 (k, 8, 8-k) multiplets, as well as for the N>8 representations, only requires more cumbersome computations.
Compton scattering from a pion: Off-shell effects and the equivalence theorem
Scherer, S.; Fearing, H.W.
1995-05-10
We consider Compton scattering from a pion in the framework of chiral perturbation theory ({chi}{ital PT}). We investigate off-shell effects in the s- and u-channel pole diagrams. For that purpose we perform a field transformation which, in comparison with the standard Gasser and Leutwyler lagrangian, generates additional terms at order {ital p}{sup 4} proportional to the lowest-order equation of motion. We demonstrate that the two lagrangians which generate different off-shell form factors predict the same Compton scattering S-matrix. This result is interpreted as an application of a generalized equivalence theorem. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
Off-shell superconformal nonlinear sigma-models in three dimensions
NASA Astrophysics Data System (ADS)
Kuzenko, Sergei M.; Park, Jeong-Hyuck; Tartaglino-Mazzucchelli, Gabriele; von Unge, Rikard
2011-01-01
We develop superspace techniques to construct general off-shell mathcal{N} ≤ 4 super-conformal sigma-models in three space-time dimensions. The most general mathcal{N} = 3 and mathcal{N} = 4 superconformal sigma-models are constructed in terms of mathcal{N} = 2 chiral superfields. Several superspace proofs of the folklore statement that mathcal{N} = 3 supersymmetry implies mathcal{N} = 4 are presented both in the on-shell and off-shell settings. We also elaborate on (super)twistor realisations for (super)manifolds on which the three-dimensional mathcal{N} -extended superconformal groups act transitively and which include Minkowski space as a subspace.
Holomorphic Chern-Simons theory coupled to off-shell Kodaira-Spencer gravity
NASA Astrophysics Data System (ADS)
Giusto, Stefano; Imbimbo, Camillo; Rosa, Dario
2012-10-01
We construct an action for holomorphic Chern-Simons theory that couples the gauge field to off-shell gravitational backgrounds, comprising the complex structure and the (3,0)-form of the target space. Gauge invariance of the off-shell action is achieved by enlarging the field space to include an appropriate system of Lagrange multipliers, ghost and ghost-for-ghost fields. Both the BRST transformations and the BV action are compactly and neatly written in terms of superfields which include fields, backgrounds and their antifields. We show that the anti-holomorphic target space derivative can be written as a BRST-commutator on a functional space containing the anti-fields of both the dynamical fields and the gravitational backgrounds. We derive from this result a Ward identity that determines the anti-holomorphic dependence of physical correlators.
Radiation-reaction in classical off-shell electrodynamics. I. The above mass-shell case
NASA Astrophysics Data System (ADS)
Aharonovich, I.; Horwitz, L. P.
2012-03-01
Offshell electrodynamics based on a manifestly covariant off-shell relativistic dynamics of Stueckelberg, Horwitz, and Piron, is five-dimensional. In this paper, we study the problem of radiation reaction of a particle in motion in this framework. In particular, the case of above-mass-shell is studied in detail, where the renormalization of the Lorentz force leads to a system of non-linear differential equations for 3 Lorentz scalars. The system is then solved numerically, where it is shown that the mass-shell deviation scalar ɛ either smoothly falls down to 0 (this result provides a mechanism for the mass stability of the off-shell theory), or strongly diverges under more extreme conditions. In both cases, no runaway motion is observed. Stability analysis indicates that the system seems to have chaotic behavior. It is also shown that, although a motion under which the mass-shell deviation ɛ is constant but not-zero, is indeed possible, but, it is unstable, and eventually it either decays to 0 or diverges.
Higher gauge theories from Lie n-algebras and off-shell covariantization
NASA Astrophysics Data System (ADS)
Carow-Watamura, Ursula; Heller, Marc Andre; Ikeda, Noriaki; Kaneko, Yukio; Watamura, Satoshi
2016-07-01
We analyze higher gauge theories in various dimensions using a supergeometric method based on a differential graded symplectic manifold, called a QP-manifold, which is closely related to the BRST-BV formalism in gauge theories. Extensions of the Lie 2-algebra gauge structure are formulated within the Lie n-algebra induced by the QP-structure. We find that in 5 and 6 dimensions there are special extensions of the gauge algebra. In these cases, a restriction of the gauge symmetry by imposing constraints on the auxiliary gauge fields leads to a covariantized theory. As an example we show that we can obtain an off-shell covariantized higher gauge theory in 5 dimensions, which is similar to the one proposed in [1].
Definitions of the off-shell relative momentum in relativistic theories
NASA Astrophysics Data System (ADS)
Giebink, David R.
1982-04-01
A variety of definitions of the relative momentum in off-shell systems are discussed and a set of basic requirements for these momenta are established. The off-mass-shell Wightman-Gårding four-momentum, which has been employed most recently by Morioka and Afnan, is shown to be ambiguously defined, and it is shown that the relative four-momentum that is suggested by the magic-vector prescription of Aaron, Amado, and Young should not be used in off-mass-shell systems because it and the total four-momentum do not constitute a complete set of variables for the two-body system. NUCLEAR REACTIONS Relativistic kinematics, relative momentum, Bethe-Salpeter equation, Blankenbecler-Sugar reductions.
Form factor of the B meson off-shell for the vertex B{sub s}*BK
Cerqueira, A. Jr.; Bracco, M. E.
2010-11-12
In this work we evaluate the coupling constant and the form factor for the vertex B{sub s}*BK using the QCD Sum Rules. In this case we consider the B meson off shell. The only theoretical evaluation for the coupling constant was made using the Heavy Hadron Chiral Perturbation Theory (HHChPT) and we made comparison with this result.
NASA Astrophysics Data System (ADS)
Cheng, Shi; Xu, Feng-Jun; Yang, Fu-Zhong
2014-04-01
According to the open-closed mirror symmetry and generalized Gel'fand-Kapranov-Zelerinski (GKZ) system, we calculate off-shell D-brane/F-theory effective superpotentials of four compact Calabi-Yau (CY) manifolds by integrating special periods of subsystem, and extracting the open Ooguri-Vafa invariants from the expansion of off-shell D-brane superpotentials.
Aad, G.
2015-07-17
The measurements of the ZZ and WW final states in the mass range above the \\(2m_Z\\) and \\(2m_W\\) thresholds provide a unique opportunity to measure the off-shell coupling strength of the Higgs boson. This paper presents constraints on the off-shell Higgs boson event yields normalised to the Standard Model prediction (signal strength) in the \\(ZZ \\rightarrow 4\\ell \\), \\(ZZ\\rightarrow 2\\ell 2\
Boos, E. E.; Keizerov, S. I.; Rahmetov, E. R.; Svirina, K. S.
2015-12-15
The radion is a scalar particle that occurs in brane world models and interacts with the trace of the energy–momentum tensor of the Standard Model (SM). The radion–SM fermion interaction Lagrangian differs from the Higgs boson–fermion interaction Lagrangian for off-shell fermions. It is shown that all additional, as compared to the Higgs boson, contributions to the amplitudes of radion production and decay processes involving off-shell fermions are canceled out for both massless and massive fermions. Thus, additional terms in the interaction Lagrangian do not change properties of these processes for the radion and the Higgs boson, except for the general normalization factors. This similarity is a consequence of gauge invariance for the processes with production of gauge bosons. When an additional scalar particle is produced, there are no apparent reasons for the above cancellation, as confirmed, for example, by the process with production of two scalar particles, which features an additional contribution of the radion in comparison with the Higgs boson.
NLO electroweak corrections to off-shell top-antitop production with leptonic decays at the LHC
NASA Astrophysics Data System (ADS)
Denner, Ansgar; Pellen, Mathieu
2016-08-01
For the first time the next-to-leading-order electroweak corrections to the full off-shell production of two top quarks that decay leptonically are presented. This calculation includes all off-shell, non-resonant, and interference effects for the 6-particle phase space. While the electroweak corrections are below one per cent for the integrated cross section, they reach up to 15% in the high-transverse-momentum region of distributions. To support the results of the complete one-loop calculation, we have in addition evaluated the electroweak corrections in two different pole approximations, one requiring two on-shell top quarks and one featuring two on-shell W bosons. While the former deviates by up to 10% from the full calculation for certain distributions, the latter provides a very good description for most observables. The increased centre-of-mass energy of the LHC makes the inclusion of electroweak corrections extremely relevant as they are particularly large in the Sudakov regime where new physics is expected to be probed.
Bevilacqua, G; Hartanto, H B; Kraus, M; Worek, M
2016-02-01
We present a complete description of top quark pair production in association with a jet in the dilepton channel. Our calculation is accurate to next-to-leading order (NLO) in QCD and includes all nonresonant diagrams, interferences, and off-shell effects of the top quark. Moreover, nonresonant and off-shell effects due to the finite W gauge boson width are taken into account. This calculation constitutes the first fully realistic NLO computation for top quark pair production with a final state jet in hadronic collisions. Numerical results for differential distributions as well as total cross sections are presented for the Large Hadron Collider at 8 TeV. With our inclusive cuts, NLO predictions reduce the unphysical scale dependence by more than a factor of 3 and lower the total rate by about 13% compared to leading-order QCD predictions. In addition, the size of the top quark off-shell effects is estimated to be below 2%.
Ford, William Paul; van Orden, Wally
2013-11-25
In this work, an off-shell extrapolation is proposed for the Regge-model NN amplitudes presented in a paper by Ford and Van Orden [ Phys. Rev. C 87 014004 (2013)] and in an eprint by Ford (arXiv:1310.0871 [nucl-th]). The prescriptions for extrapolating these amplitudes for one nucleon off-shell in the initial state are presented. Application of these amplitudes to calculations of deuteron electrodisintegration are presented and compared to the limited available precision data in the kinematical region covered by the Regge model.
Ford, William Paul; van Orden, Wally
2013-11-25
In this work, an off-shell extrapolation is proposed for the Regge-model NN amplitudes presented in a paper by Ford and Van Orden [ Phys. Rev. C 87 014004 (2013)] and in an eprint by Ford (arXiv:1310.0871 [nucl-th]). The prescriptions for extrapolating these amplitudes for one nucleon off-shell in the initial state are presented. Application of these amplitudes to calculations of deuteron electrodisintegration are presented and compared to the limited available precision data in the kinematical region covered by the Regge model.
Systemic Analysis Approaches for Air Transportation
NASA Technical Reports Server (NTRS)
Conway, Sheila
2005-01-01
Air transportation system designers have had only limited success using traditional operations research and parametric modeling approaches in their analyses of innovations. They need a systemic methodology for modeling of safety-critical infrastructure that is comprehensive, objective, and sufficiently concrete, yet simple enough to be used with reasonable investment. The methodology must also be amenable to quantitative analysis so issues of system safety and stability can be rigorously addressed. However, air transportation has proven itself an extensive, complex system whose behavior is difficult to describe, no less predict. There is a wide range of system analysis techniques available, but some are more appropriate for certain applications than others. Specifically in the area of complex system analysis, the literature suggests that both agent-based models and network analysis techniques may be useful. This paper discusses the theoretical basis for each approach in these applications, and explores their historic and potential further use for air transportation analysis.
NASA Astrophysics Data System (ADS)
Ivanov, M. V.; González-Jiménez, R.; Caballero, J. A.; Barbaro, M. B.; Donnelly, T. W.; Udías, J. M.
2013-11-01
The relativistic mean field (RMF) model is used to describe nucleons in the nucleus and thereby to evaluate the effects of having dynamically off-shell spinors. Compared with free, on-shell nucleons as employed in some other models, within the RMF nucleons are described by relativistic spinors with strongly enhanced lower components. In this work it is seen that for MiniBooNE kinematics, neutrino charged-current quasielastic cross sections show some sensitivity to these off-shell effects, while for the antineutrino-nucleus case the total cross sections are seen to be essentially independent of the enhancement of the lower components. As was found to be the case when comparing the RMF results with the neutrino-nucleus data, the present impulse approximation predictions within the RMF also fall short of the MiniBooNE antineutrino-nucleus data.
Bevilacqua, G; Hartanto, H B; Kraus, M; Worek, M
2016-02-01
We present a complete description of top quark pair production in association with a jet in the dilepton channel. Our calculation is accurate to next-to-leading order (NLO) in QCD and includes all nonresonant diagrams, interferences, and off-shell effects of the top quark. Moreover, nonresonant and off-shell effects due to the finite W gauge boson width are taken into account. This calculation constitutes the first fully realistic NLO computation for top quark pair production with a final state jet in hadronic collisions. Numerical results for differential distributions as well as total cross sections are presented for the Large Hadron Collider at 8 TeV. With our inclusive cuts, NLO predictions reduce the unphysical scale dependence by more than a factor of 3 and lower the total rate by about 13% compared to leading-order QCD predictions. In addition, the size of the top quark off-shell effects is estimated to be below 2%. PMID:26894704
Landauer Approach to Time-Dependent Transport
NASA Astrophysics Data System (ADS)
Chen, L. Y.; Nash, P. L.
Based upon the nonequilibrium Green's function formalism, we present a time-dependent Landauer approach to transport through a mesoscopic system under an ac bias voltage. The system is modeled as an elastic scatterer coupled to large electron reservoirs through perfect conducting wires (leads). The chemical potentials of the reservoirs are driven apart by the bias and, consequently, current flows through the leads from one reservoir to another. We examine the nonequilibrium statistical processes of electrons in the leads. The electronic waves are quantized on the basis of orthonormal wave packets moving along the leads, scattered by the scatterer, and coupled to the reservoirs. The time for an electron to traverse the leads between the source and the drain reservoirs plus the phase delay time caused by the scatterer is found to be the relevant time scale in the time-dependent transport. The frequency dependence of the admittance is fully investigated.
Aad, G.; Abbott, B.; Abdallah, J.; Abdinov, O.; Aben, R.; Abolins, M.; AbouZeid, O. S.; Abramowicz, H.; Abreu, H.; Abreu, R.; Abulaiti, Y.; Acharya, B. S.; Adamczyk, L.; Adams, D. L.; Adelman, J.; Adomeit, S.; Adye, T.; Affolder, A. A.; Agatonovic-Jovin, T.; Aguilar-Saavedra, J. A.; Agustoni, M.; Ahlen, S. P.; Ahmadov, F.; Aielli, G.; Akerstedt, H.; Åkesson, T. P. A.; Akimoto, G.; Akimov, A. V.; Alberghi, G. L.; Albert, J.; Albrand, S.; Alconada Verzini, M. J.; Aleksa, M.; Aleksandrov, I. N.; Alexa, C.; Alexander, G.; Alexopoulos, T.; Alhroob, M.; Alimonti, G.; Alio, L.; Alison, J.; Alkire, S. P.; Allbrooke, B. M. M.; Allport, P. P.; Aloisio, A.; Alonso, A.; Alonso, F.; Alpigiani, C.; Altheimer, A.; Alvarez Gonzalez, B.; Piqueras, D. Álvarez; Alviggi, M. G.; Amako, K.; Amaral Coutinho, Y.; Amelung, C.; Amidei, D.; Amor Dos Santos, S. P.; Amorim, A.; Amoroso, S.; Amram, N.; Amundsen, G.; Anastopoulos, C.; Ancu, L. S.; Andari, N.; Andeen, T.; Anders, C. F.; Anders, G.; Anderson, K. J.; Andreazza, A.; Andrei, V.; Angelidakis, S.; Angelozzi, I.; Anger, P.; Angerami, A.; Anghinolfi, F.; Anisenkov, A. V.; Anjos, N.; Annovi, A.; Antonelli, M.; Antonov, A.; Antos, J.; Anulli, F.; Aoki, M.; Aperio Bella, L.; Arabidze, G.; Arai, Y.; Araque, J. P.; Arce, A. T. H.; Arduh, F. A.; Arguin, J-F.; Argyropoulos, S.; Arik, M.; Armbruster, A. J.; Arnaez, O.; Arnal, V.; Arnold, H.; Arratia, M.; Arslan, O.; Artamonov, A.; Artoni, G.; Asai, S.; Asbah, N.; Ashkenazi, A.; Åsman, B.; Asquith, L.; Assamagan, K.; Astalos, R.; Atkinson, M.; Atlay, N. B.; Auerbach, B.; Augsten, K.; Aurousseau, M.; Avolio, G.; Axen, B.; Ayoub, M. K.; Azuelos, G.; Baak, M. A.; Baas, A. E.; Bacci, C.; Bachacou, H.; Bachas, K.; Backes, M.; Backhaus, M.; Badescu, E.; Bagiacchi, P.; Bagnaia, P.; Bai, Y.; Bain, T.; Baines, J. T.; Baker, O. K.; Balek, P.; Balestri, T.; Balli, F.; Banas, E.; Banerjee, Sw.; Bannoura, A. A. E.; Bansil, H. S.; Barak, L.; Baranov, S. P.; Barberio, E. L.; Barberis, D.; Barbero, M.; Barillari, T.; Barisonzi, M.; Barklow, T.; Barlow, N.; Barnes, S. L.; Barnett, B. M.; Barnett, R. M.; Barnovska, Z.; Baroncelli, A.; Barone, G.; Barr, A. J.; Barreiro, F.; Barreiro Guimarães da Costa, J.; Bartoldus, R.; Barton, A. E.; Bartos, P.; Bassalat, A.; Basye, A.; Bates, R. L.; Batista, S. J.; Batley, J. R.; Battaglia, M.; Bauce, M.; Bauer, F.; Bawa, H. S.; Beacham, J. B.; Beattie, M. D.; Beau, T.; Beauchemin, P. H.; Beccherle, R.; Bechtle, P.; Beck, H. P.; Becker, K.; Becker, M.; Becker, S.; Beckingham, M.; Becot, C.; Beddall, A. J.; Beddall, A.; Bednyakov, V. A.; Bee, C. P.; Beemster, L. J.; Beermann, T. A.; Begel, M.; Behr, J. K.; Belanger-Champagne, C.; Bell, W. H.; Bella, G.; Bellagamba, L.; Bellerive, A.; Bellomo, M.; Belotskiy, K.; Beltramello, O.; Benary, O.; Benchekroun, D.; Bender, M.; Bendtz, K.; Benekos, N.; Benhammou, Y.; Benhar Noccioli, E.; Benitez Garcia, J. A.; Benjamin, D. P.; Bensinger, J. R.; Bentvelsen, S.; Beresford, L.; Beretta, M.; Berge, D.; Bergeaas Kuutmann, E.; Berger, N.; Berghaus, F.; Beringer, J.; Bernard, C.; Bernard, N. R.; Bernius, C.; Bernlochner, F. U.; Berry, T.; Berta, P.; Bertella, C.; Bertoli, G.; Bertolucci, F.; Bertsche, C.; Bertsche, D.; Besana, M. I.; Besjes, G. J.; Bessidskaia Bylund, O.; Bessner, M.; Besson, N.; Betancourt, C.; Bethke, S.; Bevan, A. J.; Bhimji, W.; Bianchi, R. M.; Bianchini, L.; Bianco, M.; Biebel, O.; Bieniek, S. P.; Biglietti, M.; Bilbao De Mendizabal, J.; Bilokon, H.; Bindi, M.; Binet, S.; Bingul, A.; Bini, C.; Black, C. W.; Black, J. E.; Black, K. M.; Blackburn, D.; Blair, R. E.; Blanchard, J. -B.; Blanco, J. E.; Blazek, T.; Bloch, I.; Blocker, C.; Blum, W.; Blumenschein, U.; Bobbink, G. J.; Bobrovnikov, V. S.; Bocchetta, S. S.; Bocci, A.; Bock, C.; Boehler, M.; Bogaerts, J. A.; Bogdanchikov, A. G.; Bohm, C.; Boisvert, V.; Bold, T.; Boldea, V.; Boldyrev, A. S.; Bomben, M.; Bona, M.; Boonekamp, M.; Borisov, A.; Borissov, G.; Borroni, S.; Bortfeldt, J.; Bortolotto, V.; Bos, K.; Boscherini, D.; Bosman, M.; Boudreau, J.; Bouffard, J.; Bouhova-Thacker, E. V.; Boumediene, D.; Bourdarios, C.; Bousson, N.; Boutouil, S.; Boveia, A.; Boyd, J.; Boyko, I. R.; Bozic, I.; Bracinik, J.; Brandt, A.; Brandt, G.; Brandt, O.; Bratzler, U.; Brau, B.; Brau, J. E.; Braun, H. M.; Brazzale, S. F.; Brendlinger, K.; Brennan, A. J.; Brenner, L.; Brenner, R.; Bressler, S.; Bristow, K.; Bristow, T. M.; Britton, D.; Britzger, D.; Brochu, F. M.; Brock, I.; Brock, R.; Bronner, J.; Brooijmans, G.; Brooks, T.; Brooks, W. K.; Brosamer, J.; Brost, E.; Brown, J.; Bruckman de Renstrom, P. A.; Bruncko, D.; Bruneliere, R.; Bruni, A.; Bruni, G.; Bruschi, M.; Bryngemark, L.; Buanes, T.; Buat, Q.; Buchholz, P.; Buckley, A. G.; Buda, S. I.; Budagov, I. A.; Buehrer, F.; Bugge, L.; Bugge, M. K.
2015-07-01
Measurements of the ZZ and WW final states in the mass range above the 2m_{Z} and 2m_{W} thresholds provide a unique opportunity to measure the off-shell coupling strength of the Higgs boson. This paper presents constraints on the off-shell Higgs boson event yields normalised to the Standard Model prediction (signal strength) in the ZZ→4ℓ, ZZ→2ℓ2ν and WW→eνμν final states. The result is based on pp collision data collected by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 20.3 fb^{-1} at a collision energy of √s=8 TeV. Using the CL_{s} method, the observed 95 %% confidence level (CL) upper limit on the off-shell signal strength is in the range 5.1–8.6, with an expected range of 6.7–11.0. In each case the range is determined by varying the unknown gg→ZZ and gg→WW background K-factor from higher-order quantum chromodynamics corrections between half and twice the value of the known signal K-factor. Assuming the relevant Higgs boson couplings are independent of the energy scale of the Higgs boson production, a combination with the on-shell measurements yields an observed (expected) 95 % CL upper limit on ΓH/Γ^{SM}_{H} in the range 4.5–7.5 (6.5–11.2) using the same variations of the background K-factor. Assuming that the unknown gg→VV background K-factor is equal to the signal K-factor, this translates into an observed (expected) 95 % CL upper limit on the Higgs boson total width of 22.7 (33.0) MeV.
Hydrodynamical approach to transport in nanostructures
NASA Astrophysics Data System (ADS)
D'Agosta, Roberto; di Ventra, Massimiliano
2006-03-01
The electrical resistance induced by the viscous properties of the electron liquid has been recently derived.^1 In addition, it is known that the geometric constriction experienced by electrons flowing in a nanostructure gives rise to a fast ``collisional'' process.^2 These facts allow us to derive Navier-Stokes-type of equations, and therefore describe the electron flow on a par with a viscous and compressible liquid. By using this hydrodynamical approach we study electron transport in nanoscale systems and derive the conditions for the transition from laminar to turbulent flow in quantum point contacts. We also discuss possible experimental tests of these predictions. ^1 N. Sai, M. Zwolak, G. Vignale, and M. Di Ventra, Phys. Rev. Lett. 94, 186810 (2005).^2 M. Di Ventra and T.N. Todorov, J. Phys. Cond. Matt. 16, 8025 (2004); N. Bushong, N. Sai and, M. Di Ventra, Nano Lett. (in press).Work supported by the Department of Energy (DE-FG02-05ER46204)
NASA Astrophysics Data System (ADS)
Ozvenchuk, V.; Linnyk, O.; Gorenstein, M. I.; Bratkovskaya, E. L.; Cassing, W.
2013-06-01
We study the shear and bulk viscosities of partonic and hadronic matter as functions of temperature T within the parton-hadron-string dynamics (PHSD) off-shell transport approach. Dynamical hadronic and partonic systems in equilibrium are studied by the PHSD simulations in a finite box with periodic boundary conditions. The ratio of the shear viscosity to entropy density η(T)/s(T) from PHSD shows a minimum (with a value of about 0.1) close to the critical temperature Tc, while it approaches the perturbative QCD limit at higher temperatures in line with lattice QCD (lQCD) results. For T
Molecular approach to intracellular cargo transport
NASA Astrophysics Data System (ADS)
Yildiz, Ahmet
2010-03-01
Landmark discoveries in the study of cytoplasmic motors have been made through advances in single molecule biophysics and detailed mechanistic models exist for kinesin and dynein. However, the function of motors in physiological conditions has not been carefully tested. In cells, more than few dyneins can attach to the same cargo and interact with the opposite polarity motors of kinesin. To study the molecular crosstalk between the motors, we have used intraflagellar transport (IFT) in Chlamydomonas reinhardtii as a model system. Ultrahigh spatio-temporal tracking of single cargo movement showed that IFT particles move for long distances unidirectionally with 8 nm increments, agreeing with measured step sizes of kinesin and dynein. To measure how many motors transport each cargo, we have linked large polystyrene beads to internal IFT particles through a transmembrane protein. Force measurements indicated that, on average, 3-4 motors transport cargoes in each direction. The results showed that IFT motors are tightly coordinated and might be involved in recycling each other to the appropriate end of the flagellum.
2009-01-01
Background Membrane transporters play crucial roles in living cells. Experimental characterization of transporters is costly and time-consuming. Current computational methods for transporter characterization still require extensive curation efforts, especially for eukaryotic organisms. We developed a novel genome-scale transporter prediction and characterization system called TransportTP that combined homology-based and machine learning methods in a two-phase classification approach. First, traditional homology methods were employed to predict novel transporters based on sequence similarity to known classified proteins in the Transporter Classification Database (TCDB). Second, machine learning methods were used to integrate a variety of features to refine the initial predictions. A set of rules based on transporter features was developed by machine learning using well-curated proteomes as guides. Results In a cross-validation using the yeast proteome for training and the proteomes of ten other organisms for testing, TransportTP achieved an equivalent recall and precision of 81.8%, based on TransportDB, a manually annotated transporter database. In an independent test using the Arabidopsis proteome for training and four recently sequenced plant proteomes for testing, it achieved a recall of 74.6% and a precision of 73.4%, according to our manual curation. Conclusions TransportTP is the most effective tool for eukaryotic transporter characterization up to date. PMID:20003433
Comparison of approaches for predicting solute transport: sandbox experiments.
Illman, Walter A; Berg, Steven J; Yeh, Tian-Chyi Jim
2012-01-01
The main purpose of this paper was to compare three approaches for predicting solute transport. The approaches include: (1) an effective parameter/macrodispersion approach (Gelhar and Axness 1983); (2) a heterogeneous approach using ordinary kriging based on core samples; and (3) a heterogeneous approach based on hydraulic tomography. We conducted our comparison in a heterogeneous sandbox aquifer. The aquifer was first characterized by taking 48 core samples to obtain local-scale hydraulic conductivity (K). The spatial statistics of these K values were then used to calculate the effective parameters. These K values and their statistics were also used for kriging to obtain a heterogeneous K field. In parallel, we performed a hydraulic tomography survey using hydraulic tests conducted in a dipole fashion with the drawdown data analyzed using the sequential successive linear estimator code (Yeh and Liu 2000) to obtain a K distribution (or K tomogram). The effective parameters and the heterogeneous K fields from kriging and hydraulic tomography were used in forward simulations of a dipole conservative tracer test. The simulated and observed breakthrough curves and their temporal moments were compared. Results show an improvement in predictions of drawdown behavior and tracer transport when the K tomogram from hydraulic tomography was used. This suggests that the high-resolution prediction of solute transport is possible without collecting a large number of small-scale samples to estimate flow and transport properties that are costly to obtain at the field scale.
The off-shell axial anomaly via the {gamma}*{pi}{sup 0}{yields}{gamma} transition
Roberts, C.D.; Frank, M.R.; Mitchell, K.L.; Tandy, P.C.
1995-08-01
The {gamma}*{pi}{sup 0} {yields} {gamma} form factor, F{sup {pi}0{gamma}{gamma}}(s), including the extension off the pion mass-shell, is calculated in generalized impulse approximation within the Dyson-Schwinger Equation framework used to provide an excellent description of the pion charge form factor, described above. This anomalous process is a fundamentally important characteristic of the quantum field theoretical structure of QCD because it signals the breaking of the U{sub A}(1) symmetry by quantization. This form factor was measured by the CELLO collaboration at the PETRA storage ring using the process e{sup +}e{sup -} {yields} e{sup +}e{sup -} {pi}{sup 0}. There is a letter-of-intent at CEBAF to remeasure this form factor in virtual Compton scattering from a proton target. In this case a (virtual) pion is supplied by the target and a final real photon selected through the excellent missing mass spectrometry available at CEBAF. An extrapolation to the pion mass shell will be needed to deduce the physical transition form factor. Our calculation shows that the dependence on the virtual-pion momentum is smooth and well described by a simple suppression factor, which is qualitatively independent of the details of the pion interpolating field. The correct mass-shell value of this form factor is naturally generated in our approach and the q{sup 2} dependence is in accord with the available CELLO data. No parameters are adjusted to achieve this; the are fixed at the values derived in the study of F{sub {pi}}(q{sup 2}). A significant result of our study is that for this anomalous process, soft nonperturbative effects remain significant for Q{sup 2} < 20 GeV{sup 2}. A paper describing this work was submitted for publication.
NASA Astrophysics Data System (ADS)
Caola, Fabrizio; Dowling, Matthew; Melnikov, Kirill; Röntsch, Raoul; Tancredi, Lorenzo
2016-07-01
We compute next-to-leading order (NLO) QCD corrections to the production of two massive electroweak bosons in gluon fusion. We consider both the prompt production process gg → V V and the production mediated by an exchange of an s-channel Higgs boson, gg → H ∗ → V V . We include final states with both on- and off-shell vector bosons with leptonic decays. The gluonic production of vector bosons is a loop-induced process, including both massless and massive quarks in the loop. For gg → ZZ production, we obtain the NLO QCD corrections to the massive loops through an expansion around the heavy top limit. This approximation is valid below the top production threshold, giving a broad range of invariant masses between the Higgs production and the top production thresholds in which our results are valid. We explore the NLO QCD effects in gg → ZZ focusing, in particular, on the interference between prompt and Higgs-mediated processes. We find that the QCD corrections to the interference are large and similar in size to the corrections to both the signal and the background processes. At the same time, we observe that corrections to the interference change rapidly with the four-lepton invariant mass in the region around the ZZ production threshold. We also study the interference effects in gg → W + W - production where, due to technical limitations, we only consider contributions of massless loops. We find that the QCD corrections to the interference in this case are somewhat larger than those for either the signal or the background.
Synthesized voice approach callouts for air transport operations
NASA Technical Reports Server (NTRS)
Simpson, C. A.
1980-01-01
A flight simulation experiment was performed to determine the effectiveness of synthesized voice approach callouts for air transport operations. Flight deck data was first collected on scheduled air carrier operations to describe existing pilot-not-flying callout procedures in the flight context and to document the types and amounts of other auditory cockpit information during different types of air carrier operations. A flight simulation scenario for a wide-body jet transport airline training simulator was developed in collaboration with a major U.S. air carrier and flown by three-man crews of qualified line pilots as part of their normally scheduled recurrent training. Each crew flew half their approaches using the experimental synthesized voice approach callout system (SYNCALL) and the other half using the company pilot-not-flying approach callout procedures (PNF). Airspeed and sink rate performance was better with the SYNCALL system than with the PNF system for non-precision approaches. For the one-engine approach, for which SYNCALL made inappropriate deviation callouts, airspeed performance was worse with SYNCALL than with PNF. Reliability of normal altitude approach callouts was comparable for PNF on the line and in the simulator and for SYNCALL in the simulator.
Transport in molecular states language: Generalized quantum master equation approach
NASA Astrophysics Data System (ADS)
Esposito, Massimiliano; Galperin, Michael
2009-05-01
A simple scheme, capable of treating transport in molecular junctions in the language of many-body states, is presented. By introducing an ansatz in Liouville space, similar to the generalized Kadanoff-Baym approximation, a quantum master equation (QME)-like expression is derived starting from the exact equation of motion for Hubbard operators. Using an effective Liouville space propagation, a dressing similar to the standard diagrammatic one is proposed. The scheme is compared to the standard QME approach and its applicability to transport calculations is discussed.
Novel Approaches to Adaptive Angular Approximations in Computational Transport
Marvin L. Adams; Igor Carron; Paul Nelson
2006-06-04
The particle-transport equation is notoriously difficult to discretize accurately, largely because the solution can be discontinuous in every variable. At any given spatial position and energy E, for example, the transport solution can be discontinuous at an arbitrary number of arbitrary locations in the direction domain. Even if the solution is continuous it is often devoid of smoothness. This makes the direction variable extremely difficult to discretize accurately. We have attacked this problem with adaptive discretizations in the angle variables, using two distinctly different approaches. The first approach used wavelet function expansions directly and exploited their ability to capture sharp local variations. The second used discrete ordinates with a spatially varying quadrature set that adapts to the local solution. The first approach is very different from that in today’s transport codes, while the second could conceivably be implemented in such codes. Both approaches succeed in reducing angular discretization error to any desired level. The work described and results presented in this report add significantly to the understanding of angular discretization in transport problems and demonstrate that it is possible to solve this important long-standing problem in deterministic transport. Our results show that our adaptive discrete-ordinates (ADO) approach successfully: 1) Reduces angular discretization error to user-selected “tolerance” levels in a variety of difficult test problems; 2) Achieves a given error with significantly fewer unknowns than non-adaptive discrete ordinates methods; 3) Can be implemented within standard discrete-ordinates solution techniques, and thus could generate a significant impact on the field in a relatively short time. Our results show that our adaptive wavelet approach: 1) Successfully reduces the angular discretization error to arbitrarily small levels in a variety of difficult test problems, even when using the
Two-stream approach to electron transport and thermalization
Stamnes, K.
1981-04-01
An explicit solution to the electron transport and energy degradation problem is presented in the two-stream approximation. The validity of this simple approach is discussed, and it is shown that it can be extended to high electron energies (appropriate for applications to auroras) provided the coupling between the two streams, described by the backscatter ratio, is correctly estimated. A simple formula for the backscatter ratio which can be used at all energies is derived.
Global variational approach to elliptic transport barriers in three dimensions.
Oettinger, David; Blazevski, Daniel; Haller, George
2016-03-01
We introduce an approach to identify elliptic transport barriers in three-dimensional, time-aperiodic flows. Obtained as Lagrangian Coherent Structures (LCSs), the barriers are tubular non-filamenting surfaces that form and bound coherent material vortices. This extends a previous theory of elliptic LCSs as uniformly stretching material surfaces from two-dimensional to three-dimensional flows. Specifically, we obtain explicit expressions for the normals of pointwise (near-) uniformly stretching material surfaces over a finite time interval. We use this approach to visualize elliptic LCSs in steady and time-aperiodic ABC-type flows. PMID:27036192
Global variational approach to elliptic transport barriers in three dimensions
NASA Astrophysics Data System (ADS)
Oettinger, David; Blazevski, Daniel; Haller, George
2016-03-01
We introduce an approach to identify elliptic transport barriers in three-dimensional, time-aperiodic flows. Obtained as Lagrangian Coherent Structures (LCSs), the barriers are tubular non-filamenting surfaces that form and bound coherent material vortices. This extends a previous theory of elliptic LCSs as uniformly stretching material surfaces from two-dimensional to three-dimensional flows. Specifically, we obtain explicit expressions for the normals of pointwise (near-) uniformly stretching material surfaces over a finite time interval. We use this approach to visualize elliptic LCSs in steady and time-aperiodic ABC-type flows.
Applying electrical utility least-cost approach to transportation planning
McCoy, G.A.; Growdon, K.; Lagerberg, B.
1994-09-01
Members of the energy and environmental communities believe that parallels exist between electrical utility least-cost planning and transportation planning. In particular, the Washington State Energy Strategy Committee believes that an integrated and comprehensive transportation planning process should be developed to fairly evaluate the costs of both demand-side and supply-side transportation options, establish competition between different travel modes, and select the mix of options designed to meet system goals at the lowest cost to society. Comparisons between travel modes are also required under the Intermodal Surface Transportation Efficiency Act (ISTEA). ISTEA calls for the development of procedures to compare demand management against infrastructure investment solutions and requires the consideration of efficiency, socioeconomic and environmental factors in the evaluation process. Several of the techniques and approaches used in energy least-cost planning and utility peak demand management can be incorporated into a least-cost transportation planning methodology. The concepts of avoided plants, expressing avoidable costs in levelized nominal dollars to compare projects with different on-line dates and service lives, the supply curve, and the resource stack can be directly adapted from the energy sector.
Monte Carlo path sampling approach to modeling aeolian sediment transport
NASA Astrophysics Data System (ADS)
Hardin, E. J.; Mitasova, H.; Mitas, L.
2011-12-01
Coastal communities and vital infrastructure are subject to coastal hazards including storm surge and hurricanes. Coastal dunes offer protection by acting as natural barriers from waves and storm surge. During storms, these landforms and their protective function can erode; however, they can also erode even in the absence of storms due to daily wind and waves. Costly and often controversial beach nourishment and coastal construction projects are common erosion mitigation practices. With a more complete understanding of coastal morphology, the efficacy and consequences of anthropogenic activities could be better predicted. Currently, the research on coastal landscape evolution is focused on waves and storm surge, while only limited effort is devoted to understanding aeolian forces. Aeolian transport occurs when the wind supplies a shear stress that exceeds a critical value, consequently ejecting sand grains into the air. If the grains are too heavy to be suspended, they fall back to the grain bed where the collision ejects more grains. This is called saltation and is the salient process by which sand mass is transported. The shear stress required to dislodge grains is related to turbulent air speed. Subsequently, as sand mass is injected into the air, the wind loses speed along with its ability to eject more grains. In this way, the flux of saltating grains is itself influenced by the flux of saltating grains and aeolian transport becomes nonlinear. Aeolian sediment transport is difficult to study experimentally for reasons arising from the orders of magnitude difference between grain size and dune size. It is difficult to study theoretically because aeolian transport is highly nonlinear especially over complex landscapes. Current computational approaches have limitations as well; single grain models are mathematically simple but are computationally intractable even with modern computing power whereas cellular automota-based approaches are computationally efficient
Fluid-rock interaction: A reactive transport approach
Steefel, C.; Maher, K.
2009-04-01
Fluid-rock interaction (or water-rock interaction, as it was more commonly known) is a subject that has evolved considerably in its scope over the years. Initially its focus was primarily on interactions between subsurface fluids of various temperatures and mostly crystalline rocks, but the scope has broadened now to include fluid interaction with all forms of subsurface materials, whether they are unconsolidated or crystalline ('fluid-solid interaction' is perhaps less euphonious). Disciplines that previously carried their own distinct names, for example, basin diagenesis, early diagenesis, metamorphic petrology, reactive contaminant transport, chemical weathering, are now considered to fall under the broader rubric of fluid-rock interaction, although certainly some of the key research questions differ depending on the environment considered. Beyond the broadening of the environments considered in the study of fluid-rock interaction, the discipline has evolved in perhaps an even more important way. The study of water-rock interaction began by focusing on geochemical interactions in the absence of transport processes, although a few notable exceptions exist (Thompson 1959; Weare et al. 1976). Moreover, these analyses began by adopting a primarily thermodynamic approach, with the implicit or explicit assumption of equilibrium between the fluid and rock. As a result, these early models were fundamentally static rather than dynamic in nature. This all changed with the seminal papers by Helgeson and his co-workers (Helgeson 1968; Helgeson et al. 1969) wherein the concept of an irreversible reaction path was formally introduced into the geochemical literature. In addition to treating the reaction network as a dynamically evolving system, the Helgeson studies introduced an approach that allowed for the consideration of a multicomponent geochemical system, with multiple minerals and species appearing as both reactants and products, at least one of which could be
An alternative approach to charge transport in semiconducting electrodes
NASA Technical Reports Server (NTRS)
Thomchick, J.; Buoncristiani, A. M.
1980-01-01
The excess-carrier charge transport through the space-charge region of a semiconducting electrode is analyzed by a technique known as the flux method. In this approach reflection and transmission coefficients appropriate for a sheet of uniform semiconducting material describe its transport properties. A review is presented of the flux method showing that the results for a semiconductor electrode reduce in a limiting case to those previously found by Gaertner if the depletion layer is treated as a perfectly transmitting medium in which scattering and recombination are ignored. Then, in the framework of the flux method the depletion layer is considered more realistically by explicitly taking into account scattering and recombination processes which occur in this region.
Reactive Gas transport in soil: Kinetics versus Local Equilibrium Approach
NASA Astrophysics Data System (ADS)
Geistlinger, Helmut; Jia, Ruijan
2010-05-01
Gas transport through the unsaturated soil zone was studied using an analytical solution of the gas transport model that is mathematically equivalent to the Two-Region model. The gas transport model includes diffusive and convective gas fluxes, interphase mass transfer between the gas and water phase, and biodegradation. The influence of non-equilibrium phenomena, spatially variable initial conditions, and transient boundary conditions are studied. The objective of this paper is to compare the kinetic approach for interphase mass transfer with the standard local equilibrium approach and to find conditions and time-scales under which the local equilibrium approach is justified. The time-scale of investigation was limited to the day-scale, because this is the relevant scale for understanding gas emission from the soil zone with transient water saturation. For the first time a generalized mass transfer coefficient is proposed that justifies the often used steady-state Thin-Film mass transfer coefficient for small and medium water-saturated aggregates of about 10 mm. The main conclusion from this study is that non-equilibrium mass transfer depends strongly on the temporal and small-scale spatial distribution of water within the unsaturated soil zone. For regions with low water saturation and small water-saturated aggregates (radius about 1 mm) the local equilibrium approach can be used as a first approximation for diffusive gas transport. For higher water saturation and medium radii of water-saturated aggregates (radius about 10 mm) and for convective gas transport, the non-equilibrium effect becomes more and more important if the hydraulic residence time and the Damköhler number decrease. Relative errors can range up to 100% and more. While for medium radii the local equilibrium approach describes the main features both of the spatial concentration profile and the time-dependence of the emission rate, it fails completely for larger aggregates (radius about 100 mm
Approach to an Affordable and Sustainable Space Transportation System
NASA Technical Reports Server (NTRS)
McCleskey, Caey M.; Rhodes, R. E.; Robinson, J. W.; Henderson, E. M.
2012-01-01
This paper describes an approach and a general procedure for creating space transportation architectural concepts that are at once affordable and sustainable. Previous papers by the authors and other members of the Space Propulsion Synergy Team (SPST) focused on a functional system breakdown structure for an architecture and definition of high-payoff design techniques with a technology integration strategy. This paper follows up by using a structured process that derives architectural solutions focused on achieving life cycle affordability and sustainability. Further, the paper includes an example concept that integrates key design techniques discussed in previous papers. !
On the behavior of approaches to simulate reactive transport.
Saaltink, M W; Carrera, J; Ayora, C
2001-04-01
Two families of approaches exist to simulate reactive transport in groundwater: The Direct Substitution Approach (DSA), based on Newton-Raphson and the Picard or Sequential Iteration Approach (SIA). We applied basic versions of both methods to several test cases and compared both computational demands and quality of the solution for varying grid size. Results showed that the behavior of the two approaches is sensitive to both grid size and chemistry. As a general rule, the DSA is more robust than the SIA, in the sense that its convergence is less sensitive to time step size (any approach will converge given a sufficiently small time step). Moreover, the DSA leads to a better simulation of sharp fronts, which can only be reproduced with fine grids after many iterations when the SIA is used. As a consequence, the DSA runs faster than SIA in chemically difficult cases (i.e., highly non-linear and/or very retarded), because the SIA may require very small time steps to converge. On the other hand, the size of the system of equations is much larger for the DSA than for the SIA, so that its CPU time and memory requirements tend to be less favorable with increasing grid size. As a result, the SIA may become faster than the DSA for very large, chemically simple problems. The use of an iterative linear solver for the DSA makes its CPU time less sensitive to grid size. PMID:11285932
Approach to an Affordable and Productive Space Transportation System
NASA Technical Reports Server (NTRS)
McCleskey, Carey M.; Rhodes, Russel E.; Lepsch, Roger A.; Henderson, Edward M.; Robinson, John W.
2012-01-01
This paper describes an approach for creating space transportation architectures that are affordable, productive, and sustainable. The architectural scope includes both flight and ground system elements, and focuses on their compatibility to achieve a technical solution that is operationally productive, and also affordable throughout its life cycle. Previous papers by the authors and other members of the Space Propulsion Synergy Team (SPST) focused on space flight system engineering methods, along with operationally efficient propulsion system concepts and technologies. This paper follows up previous work by using a structured process to derive examples of conceptual architectures that integrate a number of advanced concepts and technologies. The examples are not intended to provide a near-term alternative architecture to displace current near-term design and development activity. Rather, the examples demonstrate an approach that promotes early investments in advanced system concept studies and trades (flight and ground), as well as in advanced technologies with the goal of enabling highly affordable, productive flight and ground space transportation systems.
Current approaches to enhance glutamate transporter function and expression.
Fontana, Andréia C K
2015-09-01
L-glutamate is the predominant excitatory neurotransmitter in the CNS and has a central role in a variety of brain functions. The termination of glutamate neurotransmission by excitatory amino acid transporters (EAATs) is essential to maintain glutamate concentration low in extracellular space and avoid excitotoxicity. EAAT2/GLT-1, being the most abundant subtype of glutamate transporter in the CNS, plays a key role in regulation of glutamate transmission. Dysfunction of EAAT2 has been correlated with various pathologies such as traumatic brain injury, stroke, amyotrophic lateral sclerosis, Alzheimer's disease, among others. Therefore, activators of the function or enhancers of the expression of EAAT2/GLT-1 could serve as a potential therapy for these conditions. Translational activators of EAAT2/GLT-1, such as ceftriaxone and LDN/OSU-0212320, have been described to have significant protective effects in animal models of amyotrophic lateral sclerosis and epilepsy. In addition, pharmacological activators of the activity of EAAT2/GLT-1 have been explored for decades and are currently emerging as promising tools for neuroprotection, having potential advantages over expression activators. This review describes the current status of the search for EAAT2/GLT-1 activators and addresses challenges and limitations that this approach might encounter. Termination of glutamate neurotransmission by glutamate transporter EAAT2 is essential to maintain homeostasis in the brain and to avoid excitotoxicity. Dysfunction of EAAT2 has been correlated with various neurological pathologies. Therefore, activators of the function or enhancers of the expression of EAAT2 (green arrows) could serve as a potential therapy for these conditions. This review describes the current status of the search for EAAT2 activators and addresses challenges and limitations of this approach. PMID:26096891
A Linear Systems Approach to Segmented Watershed Contaminant Transport
NASA Astrophysics Data System (ADS)
Carleton, J. N.
2013-12-01
The U.S. Environmental Protection Agency (USEPA) employs simulation models to estimate concentrations of pesticide residues in surface waters for risk assessment. These models have historically been used to simulate runoff loadings from homogeneous landscapes to isolated, well-mixed lentic systems that generically represent vulnerable waters. Recent efforts to refine this approach in terms of realism and geographic specificity have focused on enhancing the level of detail of the landscape representation, rather than that of receiving water hydrology. Linear systems theory and transfer function based approaches have been applied by various investigators to the representation of contaminant leaching through soils, and to surface water hydrology (e.g., unit hydrographs), but rarely to contaminant transport either within surface waters, or through multi-compartment systems such as stream networks. This poster describes a straightforward approach to simulating watersheds as segmented into collections of linked water bodies. The approach employs convolution integrals, impulse response functions, and the Discrete Fourier Transform to propagate concentration time series from upstream to downstream locations. Given knowledge only of estimated mean stream residence times, with appropriately-scaled segmentations of catchments, realistic representations of concentration dynamics are shown to be achievable. These representations are based upon high-frequency atrazine monitoring data sets collected over common time periods from upstream and downstream locations within the same small watersheds. Simulated concentrations are shown to match measured concentrations well in both the temporal and spectral domains without the need for calibration, and despite inherent simplifying assumptions such as steady flow. The approach may have utility for enhancing surface water hydrologic representation in contaminant modeling used for regulatory purposes.
NASA Astrophysics Data System (ADS)
Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Brondolin, E.; Dragicevic, M.; Erö, J.; Flechl, M.; Friedl, M.; Frühwirth, R.; Ghete, V. M.; Hartl, C.; Hörmann, N.; Hrubec, J.; Jeitler, M.; König, A.; Krammer, M.; Krätschmer, I.; Liko, D.; Matsushita, T.; Mikulec, I.; Rabady, D.; Rad, N.; Rahbaran, B.; Rohringer, H.; Schieck, J.; Schöfbeck, R.; Strauss, J.; Treberer-Treberspurg, W.; Waltenberger, W.; Wulz, C.-E.; Mossolov, V.; Shumeiko, N.; Suarez Gonzalez, J.; Alderweireldt, S.; Cornelis, T.; de Wolf, E. 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M.; Antunovic, Z.; Kovac, M.; Brigljevic, V.; Kadija, K.; Luetic, J.; Micanovic, S.; Sudic, L.; Attikis, A.; Mavromanolakis, G.; Mousa, J.; Nicolaou, C.; Ptochos, F.; Razis, P. A.; Rykaczewski, H.; Finger, M.; Finger, M.; Carrera Jarrin, E.; Assran, Y.; Ellithi Kamel, A.; Mahrous, A.; Radi, A.; Calpas, B.; Kadastik, M.; Murumaa, M.; Perrini, L.; Raidal, M.; Tiko, A.; Veelken, C.; Eerola, P.; Pekkanen, J.; Voutilainen, M.; Härkönen, J.; Karimäki, V.; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Lehti, S.; Lindén, T.; Luukka, P.; Peltola, T.; Tuominiemi, J.; Tuovinen, E.; Wendland, L.; Talvitie, J.; Tuuva, T.; Besancon, M.; Couderc, F.; Dejardin, M.; Denegri, D.; Fabbro, B.; Faure, J. 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A.; Chierici, R.; Contardo, D.; Courbon, B.; Depasse, P.; El Mamouni, H.; Fan, J.; Fay, J.; Gascon, S.; Gouzevitch, M.; Ille, B.; Lagarde, F.; Laktineh, I. B.; Lethuillier, M.; Mirabito, L.; Pequegnot, A. L.; Perries, S.; Popov, A.; Ruiz Alvarez, J. D.; Sabes, D.; Sordini, V.; Vander Donckt, M.; Verdier, P.; Viret, S.; Toriashvili, T.; Tsamalaidze, Z.; Autermann, C.; Beranek, S.; Feld, L.; Heister, A.; Kiesel, M. K.; Klein, K.; Lipinski, M.; Ostapchuk, A.; Preuten, M.; Raupach, F.; Schael, S.; Schulte, J. F.; Verlage, T.; Weber, H.; Zhukov, V.; Ata, M.; Brodski, M.; Dietz-Laursonn, E.; Duchardt, D.; Endres, M.; Erdmann, M.; Erdweg, S.; Esch, T.; Fischer, R.; Güth, A.; Hebbeker, T.; Heidemann, C.; Hoepfner, K.; Knutzen, S.; Merschmeyer, M.; Meyer, A.; Millet, P.; Mukherjee, S.; Olschewski, M.; Padeken, K.; Papacz, P.; Pook, T.; Radziej, M.; Reithler, H.; Rieger, M.; Scheuch, F.; Sonnenschein, L.; Teyssier, D.; Thüer, S.; Cherepanov, V.; Erdogan, Y.; Flügge, G.; Geenen, H.; Geisler, M.; Hoehle, F.; Kargoll, B.; Kress, T.; Künsken, A.; Lingemann, J.; Nehrkorn, A.; Nowack, A.; Nugent, I. M.; Pistone, C.; Pooth, O.; Stahl, A.; Aldaya Martin, M.; Asin, I.; Beernaert, K.; Behnke, O.; Behrens, U.; Borras, K.; Burgmeier, A.; Campbell, A.; Contreras-Campana, C.; Costanza, F.; Diez Pardos, C.; Dolinska, G.; Dooling, S.; Eckerlin, G.; Eckstein, D.; Eichhorn, T.; Gallo, E.; Garay Garcia, J.; Geiser, A.; Gizhko, A.; Gunnellini, P.; Harb, A.; Hauk, J.; Hempel, M.; Jung, H.; Kalogeropoulos, A.; Karacheban, O.; Kasemann, M.; Katsas, P.; Kieseler, J.; Kleinwort, C.; Korol, I.; Lange, W.; Leonard, J.; Lipka, K.; Lobanov, A.; Lohmann, W.; Mankel, R.; Melzer-Pellmann, I.-A.; Meyer, A. B.; Mittag, G.; Mnich, J.; Mussgiller, A.; Ntomari, E.; Pitzl, D.; Placakyte, R.; Raspereza, A.; Roland, B.; Sahin, M. Ö.; Saxena, P.; Schoerner-Sadenius, T.; Seitz, C.; Spannagel, S.; Stefaniuk, N.; Trippkewitz, K. D.; van Onsem, G. P.; Walsh, R.; Wissing, C.; Blobel, V.; Centis Vignali, M.; Draeger, A. R.; Dreyer, T.; Erfle, J.; Garutti, E.; Goebel, K.; Gonzalez, D.; Görner, M.; Haller, J.; Hoffmann, M.; Höing, R. S.; Junkes, A.; Klanner, R.; Kogler, R.; Kovalchuk, N.; Lapsien, T.; Lenz, T.; Marchesini, I.; Marconi, D.; Meyer, M.; Niedziela, M.; Nowatschin, D.; Ott, J.; Pantaleo, F.; Peiffer, T.; Perieanu, A.; Pietsch, N.; Poehlsen, J.; Sander, C.; Scharf, C.; Schleper, P.; Schlieckau, E.; Schmidt, A.; Schumann, S.; Schwandt, J.; Stadie, H.; Steinbrück, G.; Stober, F. M.; Tholen, H.; Troendle, D.; Usai, E.; Vanelderen, L.; Vanhoefer, A.; Vormwald, B.; Barth, C.; Baus, C.; Berger, J.; Böser, C.; Butz, E.; Chwalek, T.; Colombo, F.; de Boer, W.; Descroix, A.; Dierlamm, A.; Fink, S.; Frensch, F.; Friese, R.; Giffels, M.; Gilbert, A.; Haitz, D.; Hartmann, F.; Heindl, S. M.; Husemann, U.; Katkov, I.; Kornmayer, A.; Lobelle Pardo, P.; Maier, B.; Mildner, H.; Mozer, M. U.; Müller, T.; Müller, Th.; Plagge, M.; Quast, G.; Rabbertz, K.; Röcker, S.; Roscher, F.; Schröder, M.; Sieber, G.; Simonis, H. J.; Ulrich, R.; Wagner-Kuhr, J.; Wayand, S.; Weber, M.; Weiler, T.; Williamson, S.; Wöhrmann, C.; Wolf, R.; Anagnostou, G.; Daskalakis, G.; Geralis, T.; Giakoumopoulou, V. A.; Kyriakis, A.; Loukas, D.; Psallidas, A.; Topsis-Giotis, I.; Agapitos, A.; Kesisoglou, S.; Panagiotou, A.; Saoulidou, N.; Tziaferi, E.; Evangelou, I.; Flouris, G.; Foudas, C.; Kokkas, P.; Loukas, N.; Manthos, N.; Papadopoulos, I.; Paradas, E.; Strologas, J.; Filipovic, N.; Bencze, G.; Hajdu, C.; Hidas, P.; Horvath, D.; Sikler, F.; Veszpremi, V.; Vesztergombi, G.; Zsigmond, A. J.; Beni, N.; Czellar, S.; Karancsi, J.; Molnar, J.; Szillasi, Z.; Bartók, M.; Makovec, A.; Raics, P.; Trocsanyi, Z. L.; Ujvari, B.; Choudhury, S.; Mal, P.; Mandal, K.; Nayak, A.; Sahoo, D. K.; Sahoo, N.; Swain, S. K.; Bansal, S.; Beri, S. B.; Bhatnagar, V.; Chawla, R.; Dhingra, N.; Gupta, R.; Bhawandeep, U.; Kalsi, A. K.; Kaur, A.; Kaur, M.; Kumar, R.; Mehta, A.; Mittal, M.; Singh, J. B.; Walia, G.; Kumar, Ashok; Bhardwaj, A.; Choudhary, B. C.; Garg, R. B.; Keshri, S.; Kumar, A.; Malhotra, S.; Naimuddin, M.; Nishu, N.; Ranjan, K.; Sharma, R.; Sharma, V.; Bhattacharya, R.; Bhattacharya, S.; Chatterjee, K.; Dey, S.; Dutta, S.; Ghosh, S.; Majumdar, N.; Modak, A.; Mondal, K.; Mukhopadhyay, S.; Nandan, S.; Purohit, A.; Roy, A.; Roy, D.; Roy Chowdhury, S.; Sarkar, S.; Sharan, M.; Chudasama, R.; Dutta, D.; Jha, V.; Kumar, V.; Mohanty, A. K.; Pant, L. M.; Shukla, P.; Topkar, A.; Aziz, T.; Banerjee, S.; Bhowmik, S.; Chatterjee, R. M.; Dewanjee, R. K.; Dugad, S.; Ganguly, S.; Ghosh, S.; Guchait, M.; Gurtu, A.; Jain, Sa.; Kole, G.; Kumar, S.; Mahakud, B.; Maity, M.; Majumder, G.; Mazumdar, K.; Mitra, S.; Mohanty, G. B.; Parida, B.; Sarkar, T.; Sur, N.; Sutar, B.; Wickramage, N.; Chauhan, S.; Dube, S.; Kapoor, A.; Kothekar, K.; Rane, A.; Sharma, S.; Bakhshiansohi, H.; Behnamian, H.; Etesami, S. M.; Fahim, A.; Khakzad, M.; Mohammadi Najafabadi, M.; Naseri, M.; Paktinat Mehdiabadi, S.; Rezaei Hosseinabadi, F.; Safarzadeh, B.; Zeinali, M.; Felcini, M.; Grunewald, M.; Abbrescia, M.; Calabria, C.; Caputo, C.; Colaleo, A.; Creanza, D.; Cristella, L.; de Filippis, N.; de Palma, M.; Fiore, L.; Iaselli, G.; Maggi, G.; Maggi, M.; Miniello, G.; My, S.; Nuzzo, S.; Pompili, A.; Pugliese, G.; Radogna, R.; Ranieri, A.; Selvaggi, G.; Silvestris, L.; Venditti, R.; Abbiendi, G.; Battilana, C.; Bonacorsi, D.; Braibant-Giacomelli, S.; Brigliadori, L.; Campanini, R.; Capiluppi, P.; Castro, A.; Cavallo, F. R.; Chhibra, S. S.; Codispoti, G.; Cuffiani, M.; Dallavalle, G. M.; Fabbri, F.; Fanfani, A.; Fasanella, D.; Giacomelli, P.; Grandi, C.; Guiducci, L.; Marcellini, S.; Masetti, G.; Montanari, A.; Navarria, F. L.; Perrotta, A.; Rossi, A. M.; Rovelli, T.; Siroli, G. P.; Tosi, N.; Cappello, G.; Chiorboli, M.; Costa, S.; di Mattia, A.; Giordano, F.; Potenza, R.; Tricomi, A.; Tuve, C.; Barbagli, G.; Ciulli, V.; Civinini, C.; D'Alessandro, R.; Focardi, E.; Gori, V.; Lenzi, P.; Meschini, M.; Paoletti, S.; Sguazzoni, G.; Viliani, L.; Benussi, L.; Bianco, S.; Fabbri, F.; Piccolo, D.; Primavera, F.; Calvelli, V.; Ferro, F.; Lo Vetere, M.; Monge, M. R.; Robutti, E.; Tosi, S.; Brianza, L.; Dinardo, M. E.; Fiorendi, S.; Gennai, S.; Gerosa, R.; Ghezzi, A.; Govoni, P.; Malvezzi, S.; Manzoni, R. A.; Marzocchi, B.; Menasce, D.; Moroni, L.; Paganoni, M.; Pedrini, D.; Pigazzini, S.; Ragazzi, S.; Redaelli, N.; Tabarelli de Fatis, T.; Buontempo, S.; Cavallo, N.; di Guida, S.; Esposito, M.; Fabozzi, F.; Iorio, A. O. M.; Lanza, G.; Lista, L.; Meola, S.; Merola, M.; Paolucci, P.; Sciacca, C.; Thyssen, F.; Azzi, P.; Bacchetta, N.; Benato, L.; Bisello, D.; Boletti, A.; Carlin, R.; Checchia, P.; Dall'Osso, M.; Dorigo, T.; Dosselli, U.; Gasparini, F.; Gasparini, U.; Gozzelino, A.; Lacaprara, S.; Margoni, M.; Meneguzzo, A. T.; Montecassiano, F.; Passaseo, M.; Pazzini, J.; Pegoraro, M.; Pozzobon, N.; Ronchese, P.; Simonetto, F.; Torassa, E.; Tosi, M.; Zanetti, M.; Zotto, P.; Zucchetta, A.; Zumerle, G.; Braghieri, A.; Magnani, A.; Montagna, P.; Ratti, S. P.; Re, V.; Riccardi, C.; Salvini, P.; Vai, I.; Vitulo, P.; Alunni Solestizi, L.; Bilei, G. M.; Ciangottini, D.; Fanò, L.; Lariccia, P.; Leonardi, R.; Mantovani, G.; Menichelli, M.; Saha, A.; Santocchia, A.; Androsov, K.; Azzurri, P.; Bagliesi, G.; Bernardini, J.; Boccali, T.; Castaldi, R.; Ciocci, M. A.; Dell'Orso, R.; Donato, S.; Fedi, G.; Foà, L.; Giassi, A.; Grippo, M. T.; Ligabue, F.; Lomtadze, T.; Martini, L.; Messineo, A.; Palla, F.; Rizzi, A.; Savoy-Navarro, A.; Spagnolo, P.; Tenchini, R.; Tonelli, G.; Venturi, A.; Verdini, P. G.; Barone, L.; Cavallari, F.; D'Imperio, G.; Del Re, D.; Diemoz, M.; Gelli, S.; Jorda, C.; Longo, E.; Margaroli, F.; Meridiani, P.; Organtini, G.; Paramatti, R.; Preiato, F.; Rahatlou, S.; Rovelli, C.; Santanastasio, F.; Amapane, N.; Arcidiacono, R.; Argiro, S.; Arneodo, M.; Bartosik, N.; Bellan, R.; Biino, C.; Cartiglia, N.; Costa, M.; Covarelli, R.; Degano, A.; Demaria, N.; Finco, L.; Kiani, B.; Mariotti, C.; Maselli, S.; Migliore, E.; Monaco, V.; Monteil, E.; Obertino, M. M.; Pacher, L.; Pastrone, N.; Pelliccioni, M.; Pinna Angioni, G. L.; Ravera, F.; Romero, A.; Ruspa, M.; Sacchi, R.; Sola, V.; Solano, A.; Staiano, A.; Belforte, S.; Candelise, V.; Casarsa, M.; Cossutti, F.; Della Ricca, G.; Gobbo, B.; La Licata, C.; Schizzi, A.; Zanetti, A.; Nam, S. K.; Butanov, K.; Kim, D. H.; Kim, G. N.; Kim, M. S.; Kong, D. 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2016-09-01
A search is presented for the Higgs boson off-shell production in gluon fusion and vector boson fusion processes with the Higgs boson decaying into a W+W- pair and the W bosons decaying leptonically. The data observed in this analysis are used to constrain the Higgs boson total decay width. The analysis is based on the data collected by the CMS experiment at the LHC, corresponding to integrated luminosities of 4.9 fb-1 at a centre-of-mass energy of 7 TeV and 19.4 fb-1 at 8 TeV, respectively. An observed (expected) upper limit on the off-shell Higgs boson event yield normalised to the standard model prediction of 2.4 (6.2) is obtained at the 95% CL for the gluon fusion process and of 19.3 (34.4) for the vector boson fusion process. Observed and expected limits on the total width of 26 and 66 MeV are found, respectively, at the 95% confidence level (CL). These limits are combined with the previous result in the ZZ channel leading to observed and expected 95% CL upper limits on the width of 13 and 26 MeV, respectively. [Figure not available: see fulltext.
Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Brondolin, E.; Dragicevic, M.; Erö, J.; et al
2016-09-09
A search is presented for the Higgs boson off-shell production in gluon fusion and vector boson fusion processes with the Higgs boson decaying into a WW pair and the W bosons decaying leptonically. The data observed in this analysis are used to constrain the Higgs boson total decay width. The analysis is based on the data collected by the CMS experiment at the LHC, corresponding to integrated luminosities of 4.9 inverse femtobarns at a centre-of-mass energy of 7 TeV and 19.4 inverse femtobarns at 8 TeV, respectively. An observed (expected) upper limit on the off-shell Higgs boson event yield normalisedmore » to the standard model prediction of 2.4 (6.2) is obtained at the 95% CL for the gluon fusion process and of 19.3 (34.4) for the vector boson fusion process. Observed and expected limits on the total width of 26 and 66 MeV are found, respectively, at the 95% confidence level (CL). These limits are combined with the previous result in the ZZ channel leading to observed and expected 95% CL upper limits on the width of 13 and 26 MeV, respectively.« less
Filtered density function approach for reactive transport in groundwater
NASA Astrophysics Data System (ADS)
Suciu, Nicolae; Schüler, Lennart; Attinger, Sabine; Knabner, Peter
2016-04-01
Spatial filtering may be used in coarse-grained simulations (CGS) of reactive transport in groundwater, similar to the large eddy simulations (LES) in turbulence. The filtered density function (FDF), stochastically equivalent to a probability density function (PDF), provides a statistical description of the sub-grid, unresolved, variability of the concentration field. Besides closing the chemical source terms in the transport equation for the mean concentration, like in LES-FDF methods, the CGS-FDF approach aims at quantifying the uncertainty over the whole hierarchy of heterogeneity scales exhibited by natural porous media. Practically, that means estimating concentration PDFs on coarse grids, at affordable computational costs. To cope with the high dimensionality of the problem in case of multi-component reactive transport and to reduce the numerical diffusion, FDF equations are solved by particle methods. But, while trajectories of computational particles are modeled as stochastic processes indexed by time, the concentration's heterogeneity is modeled as a random field, with multi-dimensional, spatio-temporal sets of indices. To overcome this conceptual inconsistency, we consider FDFs/PDFs of random species concentrations weighted by conserved scalars and we show that their evolution equations can be formulated as Fokker-Planck equations describing stochastically equivalent processes in concentration-position spaces. Numerical solutions can then be approximated by the density in the concentration-position space of an ensemble of computational particles governed by the associated Itô equations. Instead of sequential particle methods we use a global random walk (GRW) algorithm, which is stable, free of numerical diffusion, and practically insensitive to the increase of the number of particles. We illustrate the general FDF approach and the GRW numerical solution for a reduced complexity problem consisting of the transport of a single scalar in groundwater
Meng, Jianxin; Mei, Deqing Yang, Keji; Fan, Zongwei
2014-08-14
In existing ultrasonic transportation methods, the long-range transportation of micro-particles is always realized in step-by-step way. Due to the substantial decrease of the driving force in each step, the transportation is lower-speed and stair-stepping. To improve the transporting velocity, a non-stepping ultrasonic transportation approach is proposed. By quantitatively analyzing the acoustic potential well, an optimal region is defined as the position, where the largest driving force is provided under the condition that the driving force is simultaneously the major component of an acoustic radiation force. To keep the micro-particle trapped in the optimal region during the whole transportation process, an approach of optimizing the phase-shifting velocity and phase-shifting step is adopted. Due to the stable and large driving force, the displacement of the micro-particle is an approximately linear function of time, instead of a stair-stepping function of time as in the existing step-by-step methods. An experimental setup is also developed to validate this approach. Long-range ultrasonic transportations of zirconium beads with high transporting velocity were realized. The experimental results demonstrated that this approach is an effective way to improve transporting velocity in the long-range ultrasonic transportation of micro-particles.
Vertical transport by convective clouds: Comparisons of three modeling approaches
NASA Technical Reports Server (NTRS)
Pickering, Kenneth E.; Thompson, Anne M.; Tao, Wei-Kuo; Rood, Richard B.; Mcnamara, Donna P.; Molod, Andrea M.
1995-01-01
A preliminary comparison of the GEOS-1 (Goddard Earth Observing System) data assimilation system convective cloud mass fluxes with fluxes from a cloud-resolving model (the Goddard Cumulus Ensemble Model, GCE) is reported. A squall line case study (10-11 June 1985 Oklahoma PRESTORM episode) is the basis of the comparison. Regional (central U. S.) monthly total convective mass flux for June 1985 from GEOS-1 compares favorably with estimates from a statistical/dynamical approach using GCE simulations and satellite-derived cloud observations. The GEOS-1 convective mass fluxes produce reasonable estimates of monthly-averaged regional convective venting of CO from the boundary layer at least in an urban-influenced continental region, suggesting that they can be used in tracer transport simulations.
Reconciling perturbative approaches in phonon-assisted transport junctions.
Agarwalla, Bijay Kumar; Segal, Dvira
2016-02-21
We present consistent results for molecular conduction using two central-complementary approaches: the non-equilibrium Green's function technique and the quantum master equation method. Our model describes electronic conduction in a donor-acceptor junction in which electron transfer is coupled to nuclear motion, modeled by a harmonic vibrational mode. This primary mode is further coupled to secondary phonon modes, a thermal bath. Assuming weak electron-phonon coupling but an arbitrary large molecule-metal hybridization, we compute several non-equilibrium transport quantities: the mean phonon number of the primary mode, charge current statistics. We further present scaling relations for the cumulants valid in the large voltage regime. Our analysis illustrates that the non-equilibrium Green's function technique and the quantum master equation method can be worked out consistently, when taking into account corresponding scattering processes. PMID:26896971
An approach for economic analysis of intermodal transportation.
Sahin, Bahri; Yilmaz, Huseyin; Ust, Yasin; Guneri, Ali Fuat; Gulsun, Bahadir; Turan, Eda
2014-01-01
A different intermodal transportation model based on cost analysis considering technical, economical, and operational parameters is presented. The model consists of such intermodal modes as sea-road, sea-railway, road-railway, and multimode of sea-road-railway. A case study of cargo transportation has been carried out by using the suggested model. Then, the single road transportation mode has been compared to intermodal modes in terms of transportation costs. This comparison takes into account the external costs of intermodal transportation. The research reveals that, in the short distance transportation, single transportation modes always tend to be advantageous. As the transportation distance gets longer, intermodal transportation advantages begin to be effective on the costs. In addition, the proposed method in this study leads to determining the fleet size and capacity for transportation and the appropriate transportation mode.
An Approach for Economic Analysis of Intermodal Transportation
Sahin, Bahri; Ust, Yasin; Guneri, Ali Fuat; Gulsun, Bahadir; Turan, Eda
2014-01-01
A different intermodal transportation model based on cost analysis considering technical, economical, and operational parameters is presented. The model consists of such intermodal modes as sea-road, sea-railway, road-railway, and multimode of sea-road-railway. A case study of cargo transportation has been carried out by using the suggested model. Then, the single road transportation mode has been compared to intermodal modes in terms of transportation costs. This comparison takes into account the external costs of intermodal transportation. The research reveals that, in the short distance transportation, single transportation modes always tend to be advantageous. As the transportation distance gets longer, intermodal transportation advantages begin to be effective on the costs. In addition, the proposed method in this study leads to determining the fleet size and capacity for transportation and the appropriate transportation mode. PMID:25152919
Theoretical approaches to turbulent transport near marginal stability
Krommes, J.A.; Boldyrev, S.
1996-12-31
The presence of large microturbulent transport, such as caused by ion-temperature-gradient-driven (ITG) fluctuations, tends to drive temperature profiles toward marginal (linear) stability over much of the minor cross-section. The possibility that some profiles may be submarginal (linearly stable) yet carry substantial turbulent flux is of particular interest: it affects the interpretation of experimental data, and may imply that linear analysis is inadequate for the accurate determination of stable (e.g., enhanced-reversed-shear) operating regimes. Submarginal profiles are intimately related to nonlinear instability mechanisms for the self-sustainment of turbulence even in the presence of eigenmodes that axe linearly stable. Such self-sustainment has been observed in a variety of computer simulations. In the present work, the following approaches to the analysis of submarginal transport and nonlinear self-sustainment are conceptually linked and exploited: exactly solvable statistical model problems; discrete {open_quotes}sand-pile{close_quotes} dynamics and self-organized criticality (SOC); bifurcation theory; and {open_quotes}nonlinear instability{close_quotes} mechanisms. A nontrivial yet solvable statistical advection model is constructed that emphasizes the importance of subcritical bifurcations to submarginal turbulent profiles. The SOC of discrete lattice automata is interpreted as a consequence of a kind of subcritical bifurcation, and the submarginal profiles of certain SOC models axe related to the subcritical dynamics of the solvable model. Drake`s recent reduced model for the nonlinear instability of collisional drift waves is shown to exhibit a subcritical Hopf bifurcation, lending support to the interpretation of the mechanism as a driver for self-sustained turbulence. An analogous bifurcation is sought for a simple model of ITG turbulence, and the universality of the nonlinear instability is addressed.
Random walk approach for dispersive transport in pipe networks
NASA Astrophysics Data System (ADS)
Sämann, Robert; Graf, Thomas; Neuweiler, Insa
2016-04-01
Keywords: particle transport, random walk, pipe, network, HYSTEM-EXTAN, OpenGeoSys After heavy pluvial events in urban areas the available drainage system may be undersized at peak flows (Fuchs, 2013). Consequently, rainwater in the pipe network is likely to spill out through manholes. The presence of hazardous contaminants in the pipe drainage system represents a potential risk to humans especially when the contaminated drainage water reaches the land surface. Real-time forecasting of contaminants in the drainage system needs a quick calculation. Numerical models to predict the fate of contaminants are usually based on finite volume methods. Those are not applicable here because of their volume averaging elements. Thus, a more efficient method is preferable, which is independent from spatial discretization. In the present study, a particle-based method is chosen to calculate transport paths and spatial distribution of contaminants within a pipe network. A random walk method for particles in turbulent flow in partially filled pipes has been developed. Different approaches for in-pipe-mixing and node-mixing with respect to the geometry in a drainage network are shown. A comparison of dispersive behavior and calculation time is given to find the fastest model. The HYSTEM-EXTRAN (itwh, 2002) model is used to provide hydrodynamic conditions in the pipe network according to surface runoff scenarios in order to real-time predict contaminant transport in an urban pipe network system. The newly developed particle-based model will later be coupled to the subsurface flow model OpenGeoSys (Kolditz et al., 2012). References: Fuchs, L. (2013). Gefährdungsanalyse zur Überflutungsvorsorge kommunaler Entwässerungssysteme. Sanierung und Anpassung von Entwässerungssystemen-Alternde Infrastruktur und Klimawandel, Österreichischer Wasser-und Abfallwirtschaftsverband, Wien, ISBN, 978-3. itwh (2002). Modellbeschreibung, Institut für technisch-wissenschaftliche Hydrologie Gmb
Supramolecular Approaches to Combining Membrane Transport with Adhesion
2013-01-01
Cells carefully control the transit of compounds through their membranes using “gated” protein channels that respond to chemical stimuli. Connexin gap junctions, which are high conductance cell-to-cell channels, are a remarkable class of “gated” channel with multiple levels of assembly. A gap junction between adhering cells comprises two half-channels in each cell membrane that adhere to each other to form a continuous cell-to-cell channel. Each half-channel is a hexameric assembly of six protein transmembrane subunits. These gap junctions display both intramembrane assembly and intermembrane assembly, making them an attractive target for biomimetic studies. Although many examples of self-assembled channels have been developed, few can also mediate intermembrane adhesion. Developing systems that combine membrane adhesion with controlled transit across the membrane would not only provide a better understanding of self-assembly in and around the membrane, but would also provide a route towards smart biomaterials, targeted drug delivery and an interface with nanotechnology. This Account describes our biomimetic approaches to combining membrane adhesion with membrane transport, using both self-assembled “sticky” pores and “sticky” nanoparticles to trigger transit across membranes. This combination links both fundamental and applied research, acting as a bridge between molecular level assembly and the formation of functional biomaterials. The ultimate goal is to create complex self-assembled systems in biological or biomimetic environments that can both interface with cells and transport compounds across bilayers in response to remote chemical or electromagnetic signals. Our research in this area started with fundamental studies of intramembrane and intermembrane self-assembly, building upon previously known channel-forming compounds to create self-assembled channels that were switchable or able to mediate vesicle–vesicle adhesion. Subsequently
A Systems Approach to Scalable Transportation Network Modeling
Perumalla, Kalyan S
2006-01-01
Emerging needs in transportation network modeling and simulation are raising new challenges with respect to scal-ability of network size and vehicular traffic intensity, speed of simulation for simulation-based optimization, and fidel-ity of vehicular behavior for accurate capture of event phe-nomena. Parallel execution is warranted to sustain the re-quired detail, size and speed. However, few parallel simulators exist for such applications, partly due to the challenges underlying their development. Moreover, many simulators are based on time-stepped models, which can be computationally inefficient for the purposes of modeling evacuation traffic. Here an approach is presented to de-signing a simulator with memory and speed efficiency as the goals from the outset, and, specifically, scalability via parallel execution. The design makes use of discrete event modeling techniques as well as parallel simulation meth-ods. Our simulator, called SCATTER, is being developed, incorporating such design considerations. Preliminary per-formance results are presented on benchmark road net-works, showing scalability to one million vehicles simu-lated on one processor.
Scattering approach to quantum transport and many body effects
NASA Astrophysics Data System (ADS)
Pichard, Jean-Louis; Freyn, Axel
2010-12-01
We review a series of works discussing how the scattering approach to quantum transport developed by Landauer and Buttiker for one body elastic scatterers can be extended to the case where electron-electron interactions act inside the scattering region and give rise to many body scattering. Firstly, we give an exact numerical result showing that at zero temperature a many body scatterer behaves as an effective one body scatterer, with an interaction dependent transmission. Secondly, we underline that this effective scatterer depends on the presence of external scatterers put in its vicinity. The implications of this non local scattering are illustrated studying the conductance of a quantum point contact where electrons interact with a scanning gate microscope. Thirdly, using the numerical renormalization group developed by Wilson for the Kondo problem, we study a double dot spinless model with an inter-dot interaction U and inter-dot hopping td, coupled to leads by hopping terms tc. We show that the quantum conductance as a function of td is given by a universal function, independently of the values of U and tc, if one measures td in units of a characteristic scale τ(U,tc). Mapping the double dot system without spin onto a single dot Anderson model with spin and magnetic field, we show that τ(U,tc) = 2TK, where TK is the Kondo temperature of the Anderson model.
NASA Technical Reports Server (NTRS)
Garcia, Jerry L.; McCleskey, Carey M.; Bollo, Timothy R.; Rhodes, Russel E.; Robinson, John W.
2012-01-01
This paper presents a structured approach for achieving a compatible Ground System (GS) and Flight System (FS) architecture that is affordable, productive and sustainable. This paper is an extension of the paper titled "Approach to an Affordable and Productive Space Transportation System" by McCleskey et al. This paper integrates systems engineering concepts and operationally efficient propulsion system concepts into a structured framework for achieving GS and FS compatibility in the mid-term and long-term time frames. It also presents a functional and quantitative relationship for assessing system compatibility called the Architecture Complexity Index (ACI). This paper: (1) focuses on systems engineering fundamentals as it applies to improving GS and FS compatibility; (2) establishes mid-term and long-term spaceport goals; (3) presents an overview of transitioning a spaceport to an airport model; (4) establishes a framework for defining a ground system architecture; (5) presents the ACI concept; (6) demonstrates the approach by presenting a comparison of different GS architectures; and (7) presents a discussion on the benefits of using this approach with a focus on commonality.
A new continuum approach for nonlinear kinetic simulation and transport analysis
Dai, Zongliang Wang, Shaojie; Xu, Yingfeng; Ye, Lei; Xiao, Xiaotao
2015-02-15
A numerical code based on the I-transform approach is developed to solve the nonlinear Vlasov equation and carry out the transport analysis. The numerical results given by the I-transform approach agree with the conservative semi-Lagrangian approach in the Landau damping case and the bump-on-tail instability case. The diffusivities induced by the random fields and the quasilinear transport are also successfully demonstrated by using the new approach. It is found that the nonlinear transport in the one-dimensional Langmuir turbulence cannot be well-described by a simple diffusion model, due to the strong particle trapping at the nonlinear stage.
Complex membrane transport systems. A non-Markovian approach.
Stephan, W
1985-01-01
This paper suggests a method of how to deal with complex membrane transport systems such as ion channels or ion pumps formed by proteins. The complexity of these systems results from the fact that proteins may undergo an internal dynamics of conformational changes and may thereby affect the transmembrane transport. Usually, complex transport systems are mapped into multi-state graphs and couched in terms of Markovian master equations. It is shown in this paper how the dimensionality of such multi-state systems can be reduced. The resulting description may be expressed in the form of a generalized master equation with a memory function as integral kernel. The memory function reflects the protein's own dynamics and its overall effect on the transport. This formalism, non-Markovian in nature, is applied to describe the time-dependent action of ion pumps. A general model is constructed on the basis of the rate theory which contains all the essential parts of ion pumps such as a catalytic unit and a channel-like conduit for ion translocation and which is still analytically tractable. The short-time behaviour of the pumping process turns out to be of particular interest, since it reveals the dynamics of the catalytic unit itself. A strong correlation of the particle's motion over times less than a certain correlation time has been found. This result is compared with experimental findings on the proton pump of Halobacterium halobium. It is concluded that such a perfect short-time memory could be a generic property of active transport systems.
A Data-Driven Approach for Upscaling Solute Transport Models
NASA Astrophysics Data System (ADS)
Hill, D. J.
2004-12-01
The goal of this study is to use a machine learning tool, genetic programming (GP), a domain independent model generator, to search for an upscaled hydrologic model. The development of upscaled models of hydrologic processes has long been a concern of researchers, because computational limitations prevent the use of high-resolution models capable of resolving all of the spatial variability of model domains. In particular, researchers have struggled for decades to develop upscaled numerical models for solute transport in porous media, where the scale of variability can range from the order of a few meters in the horizontal direction but only ten to twenty centimeters in the vertical direction. A wide variety of methods have been employed to develop upscaled solute transport models, including stochastic analysis, spatial filtering, and homogenization. However, these methods all rely upon various simplifying assumptions (e.g. small conductivity variance, a grid-scale significantly larger than the largest scale of heterogeneity). Moreover, these methods usually make additional assumptions about the physics of the sub-grid processes. This study examines the use of GP to search for an upscaled model of transport of a solute pulse by horizontal flow in a perfectly stratified aquifer. GP was chosen because it creates mathematical models of input data from which information about the underlying physical processes can be extracted. This type of transport system was selected as the first application of the proposed upscaling method, because it has been extensively studied in the literature, and thus will allow for a direct comparison that will demonstrate the efficacy of the data-driven upscaling method. It has been suggested that if the upscaled model domain of this type of system is a depth averaged representation of the aquifer, the plume evolution can be modeled in a Lagrangian coordinate system as a Fickian dispersive process with a time dependent dispersion coefficient
Mobile transporter path planning using a genetic algorithm approach
NASA Technical Reports Server (NTRS)
Baffes, Paul; Wang, Lui
1988-01-01
The use of an optimization technique known as a genetic algorithm for solving the mobile transporter path planning problem is investigated. The mobile transporter is a traveling robotic vehicle proposed for the Space Station which must be able to reach any point of the structure autonomously. Specific elements of the genetic algorithm are explored in both a theoretical and experimental sense. Recent developments in genetic algorithm theory are shown to be particularly effective in a path planning problem domain, though problem areas can be cited which require more research. However, trajectory planning problems are common in space systems and the genetic algorithm provides an attractive alternative to the classical techniques used to solve these problems.
Mobile Transporter Path Planning Using A Genetic Algorithm Approach
NASA Astrophysics Data System (ADS)
Baffes, Paul; Wang, Lui
1988-10-01
The use of an optimization technique known as a genetic algorithm for solving the mobile transporter path planning problem is investigated. The mobile transporter is a traveling robotic vehicle proposed for the space station which must be able to reach any point of the structure autonomously. Specific elements of the genetic algorithm are explored in both a theoretical and experimental sense. Recent developments in genetic algorithm theory are shown to be particularly effective in a path planning problem domain, though problem areas can be cited which require more research. However, trajectory planning problems are common in space systems and the genetic algorithm provides an attractive alternative to the classical techniques used to solve these problems.
Gray, William G.
2008-01-01
This work is the fourth in a series of papers on the thermodynamically constrained averaging theory (TCAT) approach for modeling flow and transport phenomena in multiscale porous medium systems. The general TCAT framework and the mathematical foundation presented in previous works are built upon by formulating macroscale models for conservation of mass, momentum, and energy, and the balance of entropy for a species in a phase volume, interface, and common curve. In addition, classical irreversible thermodynamic relations for species in entities are averaged from the microscale to the macroscale. Finally, we comment on alternative approaches that can be used to connect species and entity conservation equations to a constrained system entropy inequality, which is a key component of the TCAT approach. The formulations detailed in this work can be built upon to develop models for species transport and reactions in a variety of multiphase systems. PMID:19255613
Modeling flow and transport in unsaturated fractured rock: An evaluation of the continuum approach
Liu, Hui-Hai; Haukwa, Charles B.; Ahlers, C. Fredrik; Bodvarsson, Gudmundur S.; Flint, Alan L.; Guertal, William B.
2002-09-01
Because the continuum approach is relatively simple and straightforward to implement, it has been commonly used in modeling flow and transport in unsaturated fractured rock. However, the usefulness of this approach can be questioned in terms of its adequacy for representing fingering flow and transport in unsaturated fractured rock. The continuum approach thus needs to be evaluated carefully by comparing simulation results with field observations directly related to unsaturated flow and transport processes. This paper reports on such an evaluation, based on a combination of model calibration and prediction, using data from an infiltration test carried out in a densely fractured rock within the unsaturated zone of Yucca Mountain, Nevada. Comparisons between experimental and modeling results show that the continuum approach may be able to capture important features of flow and transport processes observed from the test. The modeling results also show that matrix diffusion may have a significant effect on the overall transport behavior in unsaturated fractured rocks, which can be used to estimate effective fracture-matrix interface areas based on tracer transport data. While more theoretical, numerical, and experimental studies are needed to provide a conclusive evaluation, this study suggests that the continuum approach is useful for modeling flow and transport in unsaturated, densely fractured rock.
Modeling flow and transport in unsaturated fractured rock: an evaluation of the continuum approach.
Liu, Hui-Hai; Haukwa, Charles B; Ahlers, C Fredrik; Bodvarsson, Gudmundur S; Flint, Alan L; Guertal, William B
2003-01-01
Because the continuum approach is relatively simple and straightforward to implement, it has been commonly used in modeling flow and transport in unsaturated fractured rock. However, the usefulness of this approach can be questioned in terms of its adequacy for representing fingering flow and transport in unsaturated fractured rock. The continuum approach thus needs to be evaluated carefully by comparing simulation results with field observations directly related to unsaturated flow and transport processes. This paper reports on such an evaluation, based on a combination of model calibration and prediction, using data from an infiltration test carried out in a densely fractured rock within the unsaturated zone of Yucca Mountain, Nevada. Comparisons between experimental and modeling results show that the continuum approach may be able to capture important features of flow and transport processes observed from the test. The modeling results also show that matrix diffusion may have a significant effect on the overall transport behavior in unsaturated fractured rocks, which can be used to estimate effective fracture-matrix interface areas based on tracer transport data. While more theoretical, numerical, and experimental studies are needed to provide a conclusive evaluation, this study suggests that the continuum approach is useful for modeling flow and transport in unsaturated, densely fractured rock. PMID:12714290
Modeling flow and transport in unsaturated fractured rock: An evaluation of the continuum approach
Liu, H.-H.; Haukwa, C.B.; Ahlers, C.F.; Bodvarsson, G.S.; Flint, A.L.; Guertal, W.B.
2003-01-01
Because the continuum approach is relatively simple and straightforward to implement, it has been commonly used in modeling flow and transport in unsaturated fractured rock. However, the usefulness of this approach can be questioned in terms of its adequacy for representing fingering flow and transport in unsaturated fractured rock. The continuum approach thus needs to be evaluated carefully by comparing simulation results with field observations directly related to unsaturated flow and transport processes. This paper reports on such an evaluation, based on a combination of model calibration and prediction, using data from an infiltration test carried out in a densely fractured rock within the unsaturated zone of Yucca Mountain, Nevada. Comparisons between experimental and modeling results show that the continuum approach may be able to capture important features of flow and transport processes observed from the test. The modeling results also show that matrix diffusion may have a significant effect on the overall transport behavior in unsaturated fractured rocks, which can be used to estimate effective fracture-matrix interface areas based on tracer transport data. While more theoretical, numerical, and experimental studies are needed to provide a conclusive evaluation, this study suggests that the continuum approach is useful for modeling flow and transport in unsaturated, densely fractured rock. ?? 2002 Elsevier Science B.V. All rights reserved.
Quasilinear transport approach to equilibration of quark-gluon plasmas
Mrowczynski, Stanislaw; Mueller, Berndt
2010-03-15
We derive the transport equations of quark-gluon plasma in the quasilinear approximation. The equations are either of the Balescu-Lenard or Fokker-Planck form. The plasma's dynamics is assumed to be governed by longitudinal chromoelectric fields. The isotropic plasma, which is stable, and the two-stream system, which is unstable, are considered in detail. A process of equilibration is briefly discussed in both cases. The peaks of the two-stream distribution are shown to rapidly dissolve in time.
A Dynamic Tree Approach to Environmental Transport on Hillslopes
NASA Astrophysics Data System (ADS)
Passalacqua, P.; Zaliapin, I.; Foufoula-Georgiou, E.; Ghil, M.; Dietrich, W. E.
2010-12-01
The concept of dynamic tree was introduced in Zaliapin et al. (2010) as the basis of an extended conceptual framework to study the transport of spatially heterogeneous fluxes as they propagate down a network of a given topology. Here we are interested in extending this framework over the whole basin by incorporating the hillslope paths and their geometry, which are known to differ from those of the river network. Focusing on the fluxes that start at a source, propagate downstream and have constant velocity, we first capture the static structure of the hillslope network by representing it by a tree (static tree). We then describe the transport down the hillslope tree as a particular case of nearest-neighbor hierarchical aggregation and thus obtaining the so-called dynamic tree. The properties of both the dynamic and static trees are analyzed by applying Horton-Strahler and Tokunaga taxonomies. The results obtained in three hillslope areas of different characteristics, two located in California and one in Oregon, show that both the static and the dynamic tree can be well approximated by Tokunaga self-similar trees (SSTs), in agreement with what previously obtained for the channelized paths of the river network but with different parameters. The degree of side branching is larger for the static tree than for the dynamic. We also observed a phase transition in the dynamics of the three systems which reflects an abrupt emergence of a giant cluster of connected streams.
Transport in fractal media: an effective scale-invariant approach.
Hernandez-Coronado, H; Coronado, M; Herrera-Hernandez, E C
2012-06-01
In this paper an advective-dispersion equation with scale-dependent coefficients is proposed for describing transport through fractals. This equation is obtained by imposing scale invariance and assuming that the porosity, the dispersion coefficient, and the velocity follow fractional power laws on the scale. The model incorporates the empirically found trends in highly heterogeneous media, regarding the dependence of the dispersivity on the scale and the dispersion coefficient on the velocity. We conclude that the presence of nontrivial fractal parameters produces anomalous dispersion, as expected, and that the presence of convective processes induces a reescalation in the concentration and shifts the tracer velocity to different values with respect to the nonfractal case.
Air pollution exposure: An activity pattern approach for active transportation
NASA Astrophysics Data System (ADS)
Adams, Matthew D.; Yiannakoulias, Nikolaos; Kanaroglou, Pavlos S.
2016-09-01
In this paper, we demonstrate the calculation of personal air pollution exposure during trips made by active transportation using activity patterns without personal monitors. We calculate exposure as the inhaled dose of particulate matter 2.5 μg or smaller. Two modes of active transportation are compared, and they include cycling and walking. Ambient conditions are calculated by combining mobile and stationary monitoring data in an artificial neural network space-time model. The model uses a land use regression framework and has a prediction accuracy of R2 = 0.78. Exposure is calculated at 10 m or shorter intervals during the trips using inhalation rates associated with both modes. The trips are children's routes between home and school. The average dose during morning cycling trips was 2.17 μg, during morning walking trips was 3.19 μg, during afternoon cycling trips was 2.19 μg and during afternoon walking trips was 3.23 μg. The cycling trip dose was significantly lower than the walking trip dose. The air pollution exposure during walking or cycling trips could not be strongly predicted by either the school or household ambient conditions, either individually or in combination. Multiple linear regression models regressing both the household and school ambient conditions against the dose were only able to account for, at most, six percent of the variance in the exposure. This paper demonstrates that incorporating activity patterns when calculating exposure can improve the estimate of exposure compared to its calculation from ambient conditions.
Solute transport in sand and chalk: a probabilistic approach
NASA Astrophysics Data System (ADS)
Carlier, E.; El Khattabi, J.; Potdevin, J. L.
2006-03-01
A probabilistic approach is used to simulate particle tracking for two types of porous medium. The first is sand grains with a single intergranular porosity. Particle tracking is carried out by advection and dispersion. The second is chalk granulates with intergranular and matrix porosities. Sorption can occur with advection and dispersion during particle tracking.Particle tracking is modelled as the sum of elementary steps with independent random variables in the sand medium. An exponential distribution is obtained for each elementary step and shows that the whole process is Markovian. A Gamma distribution or probability density function is then deduced. The relationships between dispersivity and the elementary step are given using the central limit theorem.Particle tracking in the chalky medium is a non-Markovian process. The probability density function depends on a power of the distance. Experimental simulations by dye tracer tests on a column have been performed for different distances and discharges.The probabilistic approach computations are in good agreement with the experimental data. The probabilistic computation seems an interesting and complementary approach to simulate transfer phenomena in porous media with respect to the traditional numerical methods.
Transport through a correlated interface: Auxiliary master equation approach
NASA Astrophysics Data System (ADS)
Titvinidze, Irakli; Dorda, Antonius; von der Linden, Wolfgang; Arrigoni, Enrico
2015-12-01
We present improvements of a recently introduced numerical method [E. Arrigoni et al., Phys. Rev. Lett. 110, 086403 (2013), 10.1103/PhysRevLett.110.086403] to compute steady-state properties of strongly correlated electronic systems out of equilibrium. The method can be considered as a nonequilibrium generalization of exact diagonalization based dynamical mean-field theory (DMFT). The key modification for the nonequilibrium situation consists in addressing the DMFT impurity problem within an auxiliary system consisting of the correlated impurity, Nb uncorrelated bath sites, and two Markovian environments (sink and reservoir). Algorithmic improvements in the impurity solver allow to treat efficiently larger values of Nb than previously in DMFT. This increases the accuracy of the results and is crucial for a correct description of the physical behavior of the system in the relevant parameter range including a semiquantitative description of the Kondo regime. To illustrate the approach, we consider a monoatomic layer of correlated orbitals, described by the single-band Hubbard model, attached to two metallic leads. The nonequilibrium situation is driven by a bias voltage applied to the leads. For this system, we investigate the spectral function and the steady-state current-voltage characteristics in the weakly as well as in the strongly interacting limit. In particular, we investigate the nonequilibrium behavior of quasiparticle excitations within the Mott gap of the correlated layer. We find for low-bias voltage Kondo-type behavior in the vicinity of the insulating phase. In particular, we observe a splitting of the Kondo resonance as a function of the bias voltage.
Poveschenko, T.; Poveschenko, O.
2012-07-01
This paper presents the new approach to creation of geometrical module for nuclear reactor neutron transport computer simulation analysis so called the differential cross method. It is elaborated for detecting boards between physical zones. It is proposed to use GMSH open source mesh editor extended by some features: a special option and a special kind of mesh (cubic background mesh).This method is aimed into Monte Carlo Method as well as for deterministic neutron transport methods. Special attention is attended for reactor core composed of a set of material zones with complicate geometrical boundaries. The idea of this approach is described. In general case method works for 3-D space. Algorithm of creation of the geometrical module is given. 2-D neutron transport benchmark-test for RBMK reactor cluster cell is described. It demonstrates the ability of this approach to provide flexible definition of geometrical meshing with preservation of curved surface or any level of heterogeneity. (authors)
Number-resolved master equation approach to quantum measurement and quantum transport
NASA Astrophysics Data System (ADS)
Li, Xin-Qi
2016-08-01
In addition to the well-known Landauer-Büttiker scattering theory and the nonequilibrium Green's function technique for mesoscopic transports, an alternative (and very useful) scheme is quantum master equation approach. In this article, we review the particle-number ( n)-resolved master equation ( n-ME) approach and its systematic applications in quantum measurement and quantum transport problems. The n-ME contains rich dynamical information, allowing efficient study of topics such as shot noise and full counting statistics analysis. Moreover, we also review a newly developed master equation approach (and its n-resolved version) under self-consistent Born approximation. The application potential of this new approach is critically examined via its ability to recover the exact results for noninteracting systems under arbitrary voltage and in presence of strong quantum interference, and the challenging non-equilibrium Kondo effect.
Comparing approaches for simulating the reactive transport of U(VI) in ground water
Curtis, G.P.; Kohler, M.; Davis, J.A.
2009-01-01
The reactive transport of U(VI) in a well-characterized shallow alluvial aquifer at a former U(VI) mill located near Naturita, CO, was predicted for comparative purposes using a surface complexation model (SCM) and a constant K d approach to simulate U(VI) adsorption. The ground water at the site had U(VI) concentrations that ranged from 0.01 to 20 ??M, alkalinities that ranged from 2.5 to 18 meq/L, and a nearly constant pH of 7.1. The SCM used to simulate U(VI) adsorption was previously determined independently using laboratory batch adsorption experiments. Simulations obtained using the SCM approach were compared with simulations that used a constant K d approach to simulate adsorption using previously determined site-specific K d values. In both cases, the ground water flow and transport models used a conceptual model that was previously calibrated to a chloride plume present at the site. Simulations with the SCM approach demonstrated that the retardation factor varied temporally and spatially because of the differential transport of alkalinity and dissolved U(VI) and the nonlinearity of the U(VI) adsorption. The SCM model also simulated a prolonged slow decline in U(VI) concentration, which was not simulated using a constant K d model. Simulations using the SCM approach and the constant K d approach were similar after 20 years of transport but diverged significantly after 60 years. The simulations demonstrate the need for site-specific geochemical information on U(VI) adsorption to produce credible simulations of future transport. ?? 2009 Springer-Verlag.
NASA Astrophysics Data System (ADS)
Chiloyan, Vazrik; Zeng, Lingping; Huberman, Samuel; Maznev, Alexei A.; Nelson, Keith A.; Chen, Gang
2016-07-01
The phonon Boltzmann transport equation (BTE) is widely utilized to study non-diffusive thermal transport. We find a solution of the BTE in the thin film transient thermal grating (TTG) experimental geometry by using a recently developed variational approach with a trial solution supplied by the Fourier heat conduction equation. We obtain an analytical expression for the thermal decay rate that shows excellent agreement with Monte Carlo simulations. We also obtain a closed form expression for the effective thermal conductivity that demonstrates the full material property and heat transfer geometry dependence, and recovers the limits of the one-dimensional TTG expression for very thick films and the Fuchs-Sondheimer expression for very large grating spacings. The results demonstrate the utility of the variational technique for analyzing non-diffusive phonon-mediated heat transport for nanostructures in multi-dimensional transport geometries, and will assist the probing of the mean free path distribution of materials via transient grating experiments.
NASA Technical Reports Server (NTRS)
Grantham, W. D.; Smith, P. M.; Deal, P. L.; Neely, W. R., Jr.
1984-01-01
A six-degree-of-freedom, ground based simulator study is conducted to evaluate the low-speed flight characteristics of four dissimilar cargo transport airplanes. These characteristics are compared with those of a large, present-day (reference) transport configuration similar to the Lockheed C-5A airplane. The four very large transport concepts evaluated consist of single-fuselage, twin-fuselage, triple-fuselage, and span-loader configurations. The primary piloting task is the approach and landing operation. The results of his study indicate that all four concepts evaluated have unsatisfactory longitudinal and lateral directional low speed flight characteristics and that considerable stability and control augmentation would be required to improve these characteristics (handling qualities) to a satisfactory level. Through the use of rate command/attitude hold augmentation in the pitch and roll axes, and the use of several turn-coordination features, the handling qualities of all four large transports simulated are improved appreciably.
Quantum thermal transport through anharmonic systems: A self-consistent approach
NASA Astrophysics Data System (ADS)
He, Dahai; Thingna, Juzar; Wang, Jian-Sheng; Li, Baowen
2016-10-01
We propose a feasible and effective approach to study quantum thermal transport through anharmonic systems. The main idea is to obtain an effective harmonic Hamiltonian for the anharmonic system by applying the self-consistent phonon theory. By using the effective harmonic Hamiltonian, we study thermal transport within the framework of the nonequilibrium Green's function method using the celebrated Caroli formula. We corroborate our quantum self-consistent approach by using the quantum master equation that can deal with anharmonicity exactly, but is limited to the weak system-bath coupling regime. Finally, in order to demonstrate its strength, we apply the quantum self-consistent approach to study thermal rectification in a weakly coupled two-segment anharmonic system.
A new approach to calculate the transport matrix in RF cavities
Eidelman, Yu.; Mokhov, N.; Nagaitsev, S.; Solyak, N.; /Fermilab
2011-03-01
A realistic approach to calculate the transport matrix in RF cavities is developed. It is based on joint solution of equations of longitudinal and transverse motion of a charged particle in an electromagnetic field of the linac. This field is a given by distribution (measured or calculated) of the component of the longitudinal electric field on the axis of the linac. New approach is compared with other matrix methods to solve the same problem. The comparison with code ASTRA has been carried out. Complete agreement for tracking results for a TESLA-type cavity is achieved. A corresponding algorithm will be implemented into the MARS15 code. A realistic approach to calculate the transport matrix in RF cavities is developed. Complete agreement for tracking results with existed code ASTRA is achieved. New algorithm will be implemented into MARS15 code.
Shafii, Mohammad Ali Meidianti, Rahma Wildian, Fitriyani, Dian; Tongkukut, Seni H. J.; Arkundato, Artoto
2014-09-30
Theoretical analysis of integral neutron transport equation using collision probability (CP) method with quadratic flux approach has been carried out. In general, the solution of the neutron transport using the CP method is performed with the flat flux approach. In this research, the CP method is implemented in the cylindrical nuclear fuel cell with the spatial of mesh being conducted into non flat flux approach. It means that the neutron flux at any point in the nuclear fuel cell are considered different each other followed the distribution pattern of quadratic flux. The result is presented here in the form of quadratic flux that is better understanding of the real condition in the cell calculation and as a starting point to be applied in computational calculation.
Xu, Tianfu; Pruess, Karsten
2000-08-08
Reactive fluid flow and geochemical transport in unsaturated fractured rocks has received increasing attention for studies of contaminant transport, groundwater quality, waste disposal, acid mine drainage remediation, mineral deposits, sedimentary diagenesis, and fluid-rock interactions in hydrothermal systems. This paper presents methods for modeling geochemical systems that emphasize: (1) involvement of the gas phase in addition to liquid and solid phases in fluid flow, mass transport and chemical reactions, (2) treatment of physically and chemically heterogeneous and fractured rocks, (3) the effect of heat on fluid flow and reaction properties and processes, and (4) the kinetics of fluid-rock interaction. The physical and chemical process model is embodied in a system of partial differential equations for flow and transport, coupled to algebraic equations and ordinary differential equations for chemical interactions. For numerical solution, the continuum equations are discretized in space and time. Space discretization is based on a flexible integral finite difference approach that can use irregular gridding to model geologic structure; time is discretized fully implicitly as a first-order finite difference. Heterogeneous and fractured media are treated with a general multiple interacting continua method that includes double-porosity, dual-permeability, and multi-region models as special cases. A sequential iteration approach is used to treat the coupling between fluid flow and mass transport on the one hand, chemical reactions on the other. Applications of the methods developed here to variably saturated geochemical systems are presented in a companion paper (part 2, this issue).
An exact approach for studying cargo transport by an ensemble of molecular motors
2013-01-01
Background Intracellular transport is crucial for many cellular processes where a large fraction of the cargo is transferred by motor-proteins over a network of microtubules. Malfunctions in the transport mechanism underlie a number of medical maladies. Existing methods for studying how motor-proteins coordinate the transfer of a shared cargo over a microtubule are either analytical or are based on Monte-Carlo simulations. Approaches that yield analytical results, while providing unique insights into transport mechanism, make simplifying assumptions, where a detailed characterization of important transport modalities is difficult to reach. On the other hand, Monte-Carlo based simulations can incorporate detailed characteristics of the transport mechanism; however, the quality of the results depend on the number and quality of simulation runs used in arriving at results. Here, for example, it is difficult to simulate and study rare-events that can trigger abnormalities in transport. Results In this article, a semi-analytical methodology that determines the probability distribution function of motor-protein behavior in an exact manner is developed. The method utilizes a finite-dimensional projection of the underlying infinite-dimensional Markov model, which retains the Markov property, and enables the detailed and exact determination of motor configurations, from which meaningful inferences on transport characteristics of the original model can be derived. Conclusions Under this novel probabilistic approach new insights about the mechanisms of action of these proteins are found, suggesting hypothesis about their behavior and driving the design and realization of new experiments. The advantages provided in accuracy and efficiency make it possible to detect rare events in the motor protein dynamics, that could otherwise pass undetected using standard simulation methods. In this respect, the model has allowed to provide a possible explanation for possible mechanisms
A sequential partly iterative approach for multicomponent reactive transport with CORE2D
Samper, J.; Xu, T.; Yang, C.
2008-11-01
CORE{sup 2D} V4 is a finite element code for modeling partly or fully saturated water flow, heat transport and multicomponent reactive solute transport under both local chemical equilibrium and kinetic conditions. It can handle coupled microbial processes and geochemical reactions such as acid-base, aqueous complexation, redox, mineral dissolution/precipitation, gas dissolution/exsolution, ion exchange, sorption via linear and nonlinear isotherms, sorption via surface complexation. Hydraulic parameters may change due to mineral precipitation/dissolution reactions. Coupled transport and chemical equations are solved by using sequential iterative approaches. A sequential partly-iterative approach (SPIA) is presented which improves the accuracy of the traditional sequential noniterative approach (SNIA) and is more efficient than the general sequential iterative approach (SIA). While SNIA leads to a substantial saving of computing time, it introduces numerical errors which are especially large for cation exchange reactions. SPIA improves the efficiency of SIA because the iteration between transport and chemical equations is only performed in nodes with a large mass transfer between solid and liquid phases. The efficiency and accuracy of SPIA are compared to those of SIA and SNIA using synthetic examples and a case study of reactive transport through the Llobregat Delta aquitard in Spain. SPIA is found to be as accurate as SIA while requiring significantly less CPU time. In addition, SPIA is much more accurate than SNIA with only a minor increase in computing time. A further enhancement of the efficiency of SPIA is achieved by improving the efficiency of the Newton-Raphson method used for solving chemical equations. Such an improvement is obtained by working with increments of log-concentrations and ignoring the terms of the Jacobian matrix containing derivatives of activity coefficients. A proof is given for the symmetry and non-singularity of the Jacobian matrix
Noaman, B. A.; Korman, C. E.
2009-04-23
In this paper, we present a deterministic approach to calculate terminal current noise characteristics in semiconductor devices in the framework of semiclassical transport based on the spherical harmonics of the Boltzmann Transport Equation. The model relies on the solution of the Boltzmann equation in the frequency domain with special initial and boundary conditions. The terminal current fluctuation is directly related to scattering without the additional Langevin noise term added to the calculation. Simulation results are presented for the terminal current spectral density for a 1-D n{sup +}nn{sup +} structure due to elastic-acoustic and intervally scattering.
An Inverse Analysis Approach to the Characterization of Chemical Transport in Paints
Willis, Matthew P.; Stevenson, Shawn M.; Pearl, Thomas P.; Mantooth, Brent A.
2014-01-01
The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in understanding contaminant mass transport and the ability to decontaminate materials. If a material is contaminated, over time, the transport of highly toxic chemicals (such as chemical warfare agent species) out of the material can result in vapor exposure or transfer to the skin, which can result in percutaneous exposure to personnel who interact with the material. Due to the high toxicity of chemical warfare agents, the release of trace chemical quantities is of significant concern. Mapping subsurface concentration distribution and transport characteristics of absorbed agents enables exposure hazards to be assessed in untested conditions. Furthermore, these tools can be used to characterize subsurface reaction dynamics to ultimately design improved decontaminants or decontamination procedures. To achieve this goal, an inverse analysis mass transport modeling approach was developed that utilizes time-resolved mass spectroscopy measurements of vapor emission from contaminated paint coatings as the input parameter for calculation of subsurface concentration profiles. Details are provided on sample preparation, including contaminant and material handling, the application of mass spectrometry for the measurement of emitted contaminant vapor, and the implementation of inverse analysis using a physics-based diffusion model to determine transport properties of live chemical warfare agents including distilled mustard (HD) and the nerve agent VX. PMID:25226346
An inverse analysis approach to the characterization of chemical transport in paints.
Willis, Matthew P; Stevenson, Shawn M; Pearl, Thomas P; Mantooth, Brent A
2014-08-29
The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in understanding contaminant mass transport and the ability to decontaminate materials. If a material is contaminated, over time, the transport of highly toxic chemicals (such as chemical warfare agent species) out of the material can result in vapor exposure or transfer to the skin, which can result in percutaneous exposure to personnel who interact with the material. Due to the high toxicity of chemical warfare agents, the release of trace chemical quantities is of significant concern. Mapping subsurface concentration distribution and transport characteristics of absorbed agents enables exposure hazards to be assessed in untested conditions. Furthermore, these tools can be used to characterize subsurface reaction dynamics to ultimately design improved decontaminants or decontamination procedures. To achieve this goal, an inverse analysis mass transport modeling approach was developed that utilizes time-resolved mass spectroscopy measurements of vapor emission from contaminated paint coatings as the input parameter for calculation of subsurface concentration profiles. Details are provided on sample preparation, including contaminant and material handling, the application of mass spectrometry for the measurement of emitted contaminant vapor, and the implementation of inverse analysis using a physics-based diffusion model to determine transport properties of live chemical warfare agents including distilled mustard (HD) and the nerve agent VX.
Natural Organic Matter Transport Modeling with a Continuous Time Random Walk Approach
McInnis, Daniel P.; Bolster, Diogo; Maurice, Patricia A.
2014-01-01
Abstract In transport experiments through columns packed with naturally Fe/Al oxide-coated quartz sand, breakthrough curves (BTCs) of natural organic matter (NOM) displayed strong and persistent power law tailing that could not be described by the classical advection–dispersion equation. Tailing was not observed in BTCs for a nonreactive tracer (sulforhodamine B); therefore, the anomalous transport is attributed to diverse adsorptive behavior of the polydisperse NOM sample rather than to physical heterogeneity of the porous medium. NOM BTC tailing became more pronounced with decreases in pH and increases in ionic strength, conditions previously shown to be associated with enhanced preferential adsorption of intermediate to high molecular weight NOM components. Drawing from previous work on anomalous solute transport, we develop an approach to model NOM transport within the framework of a continuous time random walk (CTRW) and show that under all conditions examined, the CTRW model is able to capture tailing of NOM BTCs by accounting for differences in transport rates of NOM fractions through a distribution of effective retardation factors. These results demonstrate the importance of considering effects of adsorptive fractionation on NOM mobility, and illustrate the ability of the CTRW model to describe transport of a multicomponent solute. PMID:24596449
Evaluation of microwave landing system approaches in a wide-body transport simulator
NASA Technical Reports Server (NTRS)
Summers, L. G.; Feather, J. B.
1992-01-01
The objective of this study was to determine the suitability of flying complex curved approaches using the microwave landing system (MLS) with a wide-body transport aircraft. Fifty pilots in crews of two participated in the evaluation using a fixed-base simulator that emulated an MD-11 aircraft. Five approaches, consisting of one straight-in approach and four curved approaches, were flown by the pilots using a flight director. The test variables include the following: (1) manual and autothrottles; (2) wind direction; and (3) type of navigation display. The navigation display was either a map or a horizontal situation indicator (HSI). A complex wind that changed direction and speed with altitude, and included moderate turbulence, was used. Visibility conditions were Cat 1 or better. Subjective test data included pilot responses to questionnaires and pilot comments. Objective performance data included tracking accuracy, position error at decision height, and control activity. Results of the evaluation indicate that flying curved MLS approaches with a wide-body transport aircraft is operationally acceptable, depending upon the length of the final straight segment and the complexity of the approach.
A PERFECT MATCH CONDITION FOR POINT-SET MATCHING PROBLEMS USING THE OPTIMAL MASS TRANSPORT APPROACH
CHEN, PENGWEN; LIN, CHING-LONG; CHERN, I-LIANG
2013-01-01
We study the performance of optimal mass transport-based methods applied to point-set matching problems. The present study, which is based on the L2 mass transport cost, states that perfect matches always occur when the product of the point-set cardinality and the norm of the curl of the non-rigid deformation field does not exceed some constant. This analytic result is justified by a numerical study of matching two sets of pulmonary vascular tree branch points whose displacement is caused by the lung volume changes in the same human subject. The nearly perfect match performance verifies the effectiveness of this mass transport-based approach. PMID:23687536
NASA Astrophysics Data System (ADS)
McNab, W. W.; Narasimhan, T. N.
1994-09-01
The chemical transformation of organic contaminants in natural groundwater systems is clearly dependent upon local geochemistry which determines the thermodynamically favorable degradation reactions and the nature of local microbial populations. Conversely, groundwater geochemistry may be impacted significantly in terms of pH and redox couple speciation by the chemical transformation of sufficient quantities of organic compounds. Therefore an understanding of the coupling between degradation reactions, local geochemistry, and chemical transport is essential in predicting the chemical evolution of contaminated aquifers. Equilibrium-based reactive chemical transport models are usually not utilized for problems involving the transport of degradable organic compounds due to slow reaction kinetics and the persistence of intermediate degradation products. In this study we propose a reactive geochemical transport model which considers these types of degradation reactions. An expert system approach is used to postulate a set of sequential, first-order degradation reactions for the organic compounds based upon thermodynamic considerations and user-defined rules. Redox disequilibrium provides the driving force for the abiotic or microbially mediated transformation of the organic compounds as well as the associated response of groundwater geochemistry. Coupling between local inorganic geochemistry and reacting organic compounds is achieved by assuring conservation of operational valence and mass balance. The composite geochemical model is in turn coupled with an integral finite difference transport algorithm using a two-step sequential solution approach. The transport equation is solved separately for each inorganic aqueous species, complex, and dissolved organic species, allowing a high degree of flexibility in problem definition. We apply the model to an illustrative example problem concerning the introduction of aromatic hydrocarbons and chlorinated ethenes into an
McNab, W.W. Jr.; Narasimhan, T.N. )
1994-09-01
The chemical transformation of organic contaminants in natural groundwater systems is clearly dependent upon local geochemistry which determines the thermodynamically favorable degradation reactions and the nature of local microbial populations. Conversely, groundwater geochemistry may be impacted significantly in terms of pH and redox couple speciation by the chemical transformation of sufficient quantities of organic compounds. Therefore an understanding of the coupling between degradation reactions, local geochemistry, and chemical transport is essential in predicting the chemical evolution of contaminated aquifers. Equilibrium-based reactive chemical transport models are usually not utilized for problems involving the transport of degradable organic compounds due to slow reaction kinetics and the persistence of intermediate degradation products. In this study we propose a reactive geochemical transport model which considers these types of degradation reactions. An expert system approach is used to postulate a set of sequential, first-order degradation reactions for the organic compounds based upon thermodynamic considerations and user-defined rules. Redox disequilibrium provides the driving force for the abiotic or microbially mediated transformation of the organic compounds as well as the associated response of groundwater geochemistry. Coupling between local inorganic geochemistry and reacting organic compounds is achieved by assuring conservation of operation valence and mass balance. The composite geochemical model is in turn coupled with an integral finite difference transport algorithm using a two-step sequential solution approach. The transport equation is solved separately for each inorganic aqueous species, complex, and dissolved organic species, allowing degree of flexibility in problem definition. 58 refs., 18 figs., 2 tabs.
Jin, Jinshuang; Li, Jun; Liu, Yu; Li, Xin-Qi; Yan, YiJing
2014-06-28
Beyond the second-order Born approximation, we propose an improved master equation approach to quantum transport under self-consistent Born approximation. The basic idea is to replace the free Green's function in the tunneling self-energy diagram by an effective reduced propagator under the Born approximation. This simple modification has remarkable consequences. It not only recovers the exact results for quantum transport through noninteracting systems under arbitrary voltages, but also predicts the challenging nonequilibrium Kondo effect. Compared to the nonequilibrium Green's function technique that formulates the calculation of specific correlation functions, the master equation approach contains richer dynamical information to allow more efficient studies for such as the shot noise and full counting statistics.
NASA Astrophysics Data System (ADS)
Ercan, Ilke; Anderson, Neal G.
2010-06-01
Bushong, Sai, and Di Ventra (BSD) recently demonstrated that steady-state transport can emerge solely from quantum dynamics in a globally closed system consisting of a nanoscale conductor bridging two electrodes by Bushong et al. [Nano Lett. 5, 2569 (2005)]. They reported calculations, based on a simple tight-binding implementation of the "microcanonical" approach (TBIMCA) by Di Ventra and Todorov [J. Phys.: Condens. Matter 16, 8025 (2004)], in which a steady-state conductor current consistent in magnitude with the quantum conductance G0=2e2/h is established after an initial bias-induced imbalance in electrode populations begins to equalize. In this work, BSD's TBIMCA is generalized, and their expressions for the time-dependent current and local occupation functions are shown to apply only to a restricted class of structures. Calculations of the current dynamics and local occupation functions, based on the generalized formalism, are then presented for a wide variety of electrode-conductor-electrode geometries. These calculations provide a more comprehensive characterization of the TBIMCA, enable identification of the conditions under which signature features of nanoscale transport emerge, and show that the emergence of these features hinges critically on details of the structure geometry. This structure dependence represents an important consideration for application of the TBIMCA to the modeling of transport through nanostructures and should be recognized in any attempt to identify and explain signature features of nanoscale transport within this approach.
NASA Technical Reports Server (NTRS)
Zee, Stacey; Murray, D.
2009-01-01
The Federal Aviation Administration (FAA), Office of Commercial Space Transportation (AST) licenses and permits U.S. commercial space launch and reentry activities, and licenses the operation of non-federal launch and reentry sites. ASTs mission is to ensure the protection of the public, property, and the national security and foreign policy interests of the United States during commercial space transportation activities and to encourage, facilitate, and promote U.S. commercial space transportation. AST faces unique challenges of ensuring the protection of public health and safety while facilitating and promoting U.S. commercial space transportation. AST has developed an Environmental Management System (EMS) and a Safety Management System (SMS) to help meet its mission. Although the EMS and SMS were developed independently, the systems share similar elements. Both systems follow a Plan-Do-Act-Check model in identifying potential environmental aspects or public safety hazards, assessing significance in terms of severity and likelihood of occurrence, developing approaches to reduce risk, and verifying that the risk is reduced. This paper will describe the similarities between ASTs EMS and SMS elements and how AST is building a collaborative approach in environmental and safety management to reduce impacts to the environment and risks to the public.
Diagrammatic and asymptotic approaches to the origins of radiative transport theory: tutorial.
Cazé, A; Schotland, John C
2015-08-01
The radiative transport equation (RTE) is used widely to describe the propagation of multiply scattered light in disordered media. In this tutorial, we present two derivations of the RTE for scalar wave fields. The first derivation is based on diagrammatic perturbation theory, while the second stems from an asymptotic multiscale expansion. Although the two approaches are quite distinct mathematically, some common ground can be found and is discussed. PMID:26367292
An approach to market analysis for lighter than air transportation of freight
NASA Technical Reports Server (NTRS)
Roberts, P. O.; Marcus, H. S.; Pollock, J. H.
1975-01-01
An approach is presented to marketing analysis for lighter than air vehicles in a commercial freight market. After a discussion of key characteristics of supply and demand factors, a three-phase approach to marketing analysis is described. The existing transportation systems are quantitatively defined and possible roles for lighter than air vehicles within this framework are postulated. The marketing analysis views the situation from the perspective of both the shipper and the carrier. A demand for freight service is assumed and the resulting supply characteristics are determined. Then, these supply characteristics are used to establish the demand for competing modes. The process is then iterated to arrive at the market solution.
Danby, G.T.; Powell, J.R.
1988-01-01
Mechanically levitated transport system approaches are assessed with regard to thrust power needs, track cost, suspension stability, and safety. The null flux suspension appears as the favored approach, having the least thrust power requirements, highest stability, and lowest amount of track material. Various null flux configurations are described together with their operating parameters. The Linear Synchronous Motor (LSM) propulsion system is also described for propelling the suspended vehicles. Cryogenics and superconductivity aspects are discussed and the effect of high T/sub c/ superconductors evaluated. 13 refs., 16 figs., 2 tabs.
Kouri, Donald J.; Vijay, Amrendra; Zhang, Haiyan; Zhang, Jingfeng; Hoffman, David K.
2007-05-01
A method and system for solving the inverse acoustic scattering problem using an iterative approach with consideration of half-off-shell transition matrix elements (near-field) information, where the Volterra inverse series correctly predicts the first two moments of the interaction, while the Fredholm inverse series is correct only for the first moment and that the Volterra approach provides a method for exactly obtaining interactions which can be written as a sum of delta functions.
Clark, Renee M; Besterfield-Sacre, Mary E
2009-03-01
We take a novel approach to analyzing hazardous materials transportation risk in this research. Previous studies analyzed this risk from an operations research (OR) or quantitative risk assessment (QRA) perspective by minimizing or calculating risk along a transport route. Further, even though the majority of incidents occur when containers are unloaded, the research has not focused on transportation-related activities, including container loading and unloading. In this work, we developed a decision model of a hazardous materials release during unloading using actual data and an exploratory data modeling approach. Previous studies have had a theoretical perspective in terms of identifying and advancing the key variables related to this risk, and there has not been a focus on probability and statistics-based approaches for doing this. Our decision model empirically identifies the critical variables using an exploratory methodology for a large, highly categorical database involving latent class analysis (LCA), loglinear modeling, and Bayesian networking. Our model identified the most influential variables and countermeasures for two consequences of a hazmat incident, dollar loss and release quantity, and is one of the first models to do this. The most influential variables were found to be related to the failure of the container. In addition to analyzing hazmat risk, our methodology can be used to develop data-driven models for strategic decision making in other domains involving risk.
Clark, Renee M; Besterfield-Sacre, Mary E
2009-03-01
We take a novel approach to analyzing hazardous materials transportation risk in this research. Previous studies analyzed this risk from an operations research (OR) or quantitative risk assessment (QRA) perspective by minimizing or calculating risk along a transport route. Further, even though the majority of incidents occur when containers are unloaded, the research has not focused on transportation-related activities, including container loading and unloading. In this work, we developed a decision model of a hazardous materials release during unloading using actual data and an exploratory data modeling approach. Previous studies have had a theoretical perspective in terms of identifying and advancing the key variables related to this risk, and there has not been a focus on probability and statistics-based approaches for doing this. Our decision model empirically identifies the critical variables using an exploratory methodology for a large, highly categorical database involving latent class analysis (LCA), loglinear modeling, and Bayesian networking. Our model identified the most influential variables and countermeasures for two consequences of a hazmat incident, dollar loss and release quantity, and is one of the first models to do this. The most influential variables were found to be related to the failure of the container. In addition to analyzing hazmat risk, our methodology can be used to develop data-driven models for strategic decision making in other domains involving risk. PMID:19087232
Surrogate model approach for improving the performance of reactive transport simulations
NASA Astrophysics Data System (ADS)
Jatnieks, Janis; De Lucia, Marco; Sips, Mike; Dransch, Doris
2016-04-01
Reactive transport models can serve a large number of important geoscientific applications involving underground resources in industry and scientific research. It is common for simulation of reactive transport to consist of at least two coupled simulation models. First is a hydrodynamics simulator that is responsible for simulating the flow of groundwaters and transport of solutes. Hydrodynamics simulators are well established technology and can be very efficient. When hydrodynamics simulations are performed without coupled geochemistry, their spatial geometries can span millions of elements even when running on desktop workstations. Second is a geochemical simulation model that is coupled to the hydrodynamics simulator. Geochemical simulation models are much more computationally costly. This is a problem that makes reactive transport simulations spanning millions of spatial elements very difficult to achieve. To address this problem we propose to replace the coupled geochemical simulation model with a surrogate model. A surrogate is a statistical model created to include only the necessary subset of simulator complexity for a particular scenario. To demonstrate the viability of such an approach we tested it on a popular reactive transport benchmark problem that involves 1D Calcite transport. This is a published benchmark problem (Kolditz, 2012) for simulation models and for this reason we use it to test the surrogate model approach. To do this we tried a number of statistical models available through the caret and DiceEval packages for R, to be used as surrogate models. These were trained on randomly sampled subset of the input-output data from the geochemical simulation model used in the original reactive transport simulation. For validation we use the surrogate model to predict the simulator output using the part of sampled input data that was not used for training the statistical model. For this scenario we find that the multivariate adaptive regression splines
NASA Astrophysics Data System (ADS)
Gao, Zhe
As the dimensions of commonly used semiconductor devices have shrunk into nanometer regime, it is recognized that the influence of quantum effects on their electrostatic and transport properties cannot be ignored. In the past few decades, various computational models and approaches have been developed to analyze these properties in nanostructures and devices. Among these computational models, the Schrodinger-Poisson model has been widely adopted for quantum mechanical electrostatic and transport analysis of nanostructures and devices such as quantum wires, metal--oxide--semiconductor field effect transistors (MOSFETs) and nanoelectromechanical systems (NEMS). The numerical results allow for evaluations of the electrical properties such as charge concentration and potential profile in these structures. The emergence of MOSFETs with multiple gates, such as Trigates, FinFETs and Pi-gates, offers a superior electrostatic control of devices by the gates, which can be therefore used to reduce the short channel effects within those devices. Full 2-D electrostatic and transport analysis enables a better understanding of the scalability of devices, geometric effects on the potential and charge distribution, and transport characteristics of the transistors. The Schrodinger-Poisson model is attractive due to its simplicity and straightforward implementation by using standard numerical methods. However, as it is required to solve a generalized eigenvalue problem generated from the discretization of the Schrodinger equation, the computational cost of the analysis increases quickly when the system's degrees of freedom (DOFs) increase. For this reason, techniques that enable an efficient solution of discretized Schrodinger equation in multidimensional domains are desirable. In this work, we seek to accelerate the numerical solution of the Schrodinger equation by using a component mode synthesis (CMS) approach. In the CMS approach, a nanostructure is divided into a set of
Modeling nitrogen transport and transformation in aquifers using a particle-tracking approach
NASA Astrophysics Data System (ADS)
Cui, Zhengtao; Welty, Claire; Maxwell, Reed M.
2014-09-01
We have integrated multispecies biodegradation and geochemical reactions into an existing particle-tracking code to simulate reactive transport in three-dimensional variably saturated media, with a focus on nitrification and denitrification processes. This new numerical model includes reactive air-phase transport so that gases such as N2 and CO2 can be tracked. Although nitrogen biodegradation is the primary problem addressed here, the method presented is also applicable to other reactive multispecies transport problems. We verified the model by comparison with (1) analytical solutions for saturated one- and two-dimensional cases; (2) a finite element model for a one-dimensional unsaturated case; and (3) laboratory observations for a one-dimensional saturated case. Good agreement between the new code and the verification problems is demonstrated. The new model can simulate nitrogen transport and transformation in a heterogeneous permeability field where sharp concentration gradients are present. An example application to nitrogen species biodegradation and transport of a plume emanating from a leaking sewer in a heterogeneous, variably saturated aquifer is presented to illustrate this capability. This example is a novel application of coupling unsaturated/saturated zone transport with nitrogen species biodegradation. The code has the computational advantages of particle-tracking algorithms, including local and global mass conservation and minimal numerical dispersion. We also present new methods for improving particle code efficiency by implementing the concept of tracking surplus/deficit particles and particle recycling in order to control the growth of particle numbers. The new model retains the advantages of the particle tracking approach such as allowing relatively low spatial and temporal resolutions to be used, while incorporating the robustness of grid-based Monod kinetics to simulate biogeochemical reactions.
A non-equilibrium equation-of-motion approach to quantum transport utilizing projection operators
NASA Astrophysics Data System (ADS)
Ochoa, Maicol A.; Galperin, Michael; Ratner, Mark A.
2014-11-01
We consider a projection operator approach to the non-equilbrium Green function equation-of-motion (PO-NEGF EOM) method. The technique resolves problems of arbitrariness in truncation of an infinite chain of EOMs and prevents violation of symmetry relations resulting from the truncation (equivalence of left- and right-sided EOMs is shown and symmetry with respect to interchange of Fermi or Bose operators before truncation is preserved). The approach, originally developed by Tserkovnikov (1999 Theor. Math. Phys. 118 85) for equilibrium systems, is reformulated to be applicable to time-dependent non-equilibrium situations. We derive a canonical form of EOMs, thus explicitly demonstrating a proper result for the non-equilibrium atomic limit in junction problems. A simple practical scheme applicable to quantum transport simulations is formulated. We perform numerical simulations within simple models and compare results of the approach to other techniques and (where available) also to exact results.
Two-scale approach for the coupled heat and moisture transport
NASA Astrophysics Data System (ADS)
Kruis, Jaroslav; Krejčí, Tomáš
2016-06-01
This paper describes two-level approach for coupled heat and moisture transport in masonry structures. Motivation for two-level description comes from two major difficulties connected with masonry. First, the size of stone blocks is much larger than the size of mortar layers and very fine mesh has to be used. Second, the masonry composition is always random and therefore the concept of representative volume is reasonable. In two-level approach, the macro-scale level deals with a structure while the meso-scale level is concentrated on detailed composition of the masonry. Connection between the macro and meso level will be described. This two-level approach is suitable for parallel computers.
NASA Astrophysics Data System (ADS)
Mosthaf, K.; Rosenberg, L.; Balbarini, N.; Broholm, M. M.; Bjerg, P. L.; Binning, P. J.
2014-12-01
It is important to understand the fate and transport of contaminants in limestone aquifers because they are a major drinking water resource. This is challenging because they are highly heterogeneous; with micro-porous grains, flint inclusions, and being heavily fractured. Several modeling approaches have been developed to describe contaminant transport in fractured media, such as the discrete fracture (with various fracture geometries), equivalent porous media (with and without anisotropy), and dual porosity models. However, these modeling concepts are not well tested for limestone geologies. Given available field data and model purpose, this paper therefore aims to develop, examine and compare modeling approaches for transport of contaminants in fractured limestone aquifers. The model comparison was conducted for a contaminated site in Denmark, where a plume of a dissolved contaminant (PCE) has migrated through a fractured limestone aquifer. Multilevel monitoring wells have been installed at the site and available data includes information on spill history, extent of contamination, geology and hydrogeology. To describe the geology and fracture network, data from borehole logs was combined with an analysis of heterogeneities and fractures from a nearby excavation (analog site). Methods for translating the geological information and fracture mapping into each of the model concepts were examined. Each model was compared with available field data, considering both model fit and measures of model suitability. An analysis of model parameter identifiability and sensitivity is presented. Results show that there is considerable difference between modeling approaches, and that it is important to identify the right one for the actual scale and model purpose. A challenge in the use of field data is the determination of relevant hydraulic properties and interpretation of aqueous and solid phase contaminant concentration sampling data. Traditional water sampling has a bias
A simple approach to fabricate the rose petal-like hierarchical surfaces for droplet transportation
NASA Astrophysics Data System (ADS)
Yuan, Chao; Huang, Mengyu; Yu, Xingjian; Ma, Yupu; Luo, Xiaobing
2016-11-01
Precise transportation of liquid microdroplets is a great challenge in the microfluidic field. A sticky superhydrophobic surface with a high static contact angle (CA) and a large contact angle hysteresis (CAH) is recognized as the favorable tool to deal with the challenging job. Some approaches have been proposed to fabricate such surface, such as mimicing the dual-scale hierarchical structure of a natural material, like rose petal. However, the available approaches normally require multiple processing steps or are carried out with great expense. In this study, we report a straightforward and inexpensive method for fabricating the sticky superhydrophobic surfaces. The fabrication relies on electroless galvanic deposition to coat the copper substrates with a textured layer of silver. The whole fabrication process is carried out under ambient conditions by using conventional laboratory materials and equipments, and generally take less than 15 min. Despite the simplicity of this fabrication method, the rose petal-like hierarchical structures and the corresponding sticky superhydrophobic wetting properties were well achieved on the artificial surfaces. For instance, the surface with a deposition time of 10 s exhibits the superhydrophobity with a CA of 151.5°, and the effective stickiness with a CAH of 56.5°. The prepared sticky superhydrophobic surfaces are finally shown in the application of droplet transportation, in which the surface acts as a mechanical hand to grasp and transport the water droplet.
A Fuzzy Approach of the Competition on the Air Transport Market
NASA Technical Reports Server (NTRS)
Charfeddine, Souhir; DeColigny, Marc; Camino, Felix Mora; Cosenza, Carlos Alberto Nunes
2003-01-01
The aim of this communication is to study with a new scope the conditions of the equilibrium in an air transport market where two competitive airlines are operating. Each airline is supposed to adopt a strategy maximizing its profit while its estimation of the demand has a fuzzy nature. This leads each company to optimize a program of its proposed services (frequency of the flights and ticket prices) characterized by some fuzzy parameters. The case of monopoly is being taken as a benchmark. Classical convex optimization can be used to solve this decision problem. This approach provides the airline with a new decision tool where uncertainty can be taken into account explicitly. The confrontation of the strategies of the companies, in the ease of duopoly, leads to the definition of a fuzzy equilibrium. This concept of fuzzy equilibrium is more general and can be applied to several other domains. The formulation of the optimization problem and the methodological consideration adopted for its resolution are presented in their general theoretical aspect. In the case of air transportation, where the conditions of management of operations are critical, this approach should offer to the manager elements needed to the consolidation of its decisions depending on the circumstances (ordinary, exceptional events,..) and to be prepared to face all possibilities. Keywords: air transportation, competition equilibrium, convex optimization , fuzzy modeling,
NASA Astrophysics Data System (ADS)
Leal, Allan M. M.; Kulik, Dmitrii A.; Kosakowski, Georg
2016-02-01
We present a numerical method for multiphase chemical equilibrium calculations based on a Gibbs energy minimization approach. The method can accurately and efficiently determine the stable phase assemblage at equilibrium independently of the type of phases and species that constitute the chemical system. We have successfully applied our chemical equilibrium algorithm in reactive transport simulations to demonstrate its effective use in computationally intensive applications. We used FEniCS to solve the governing partial differential equations of mass transport in porous media using finite element methods in unstructured meshes. Our equilibrium calculations were benchmarked with GEMS3K, the numerical kernel of the geochemical package GEMS. This allowed us to compare our results with a well-established Gibbs energy minimization algorithm, as well as their performance on every mesh node, at every time step of the transport simulation. The benchmark shows that our novel chemical equilibrium algorithm is accurate, robust, and efficient for reactive transport applications, and it is an improvement over the Gibbs energy minimization algorithm used in GEMS3K. The proposed chemical equilibrium method has been implemented in Reaktoro, a unified framework for modeling chemically reactive systems, which is now used as an alternative numerical kernel of GEMS.
A lithofacies approach for modeling non-Fickian solute transport in a heterogeneous alluvial aquifer
NASA Astrophysics Data System (ADS)
Bianchi, Marco; Zheng, Chunmiao
2016-01-01
Stochastic realizations of lithofacies assemblage based on lithological data from a relatively small number of boreholes were used to simulate solute transport at the well-known Macrodispersion Experiment (MADE) site in Mississippi (USA). With sharp vertical contrasts and lateral connectivity explicitly accounted for in the corresponding hydraulic conductivity fields, experimental results from a large-scale tracer experiment were adequately reproduced with a relatively simple model based on advection and local dispersion. The geologically based model of physical heterogeneity shows that one well-interconnected lithofacies, with a significantly higher hydraulic conductivity and accounting for 12% of the total aquifer volume, may be responsible for the observed non-Fickian transport behavior indicated by the asymmetric shape of the plumes and by variations of the dispersion rate in both space and time. This analysis provides a lithological basis to the hypothesis that transport at MADE site is controlled by a network of high-conductivity sediments embedded in a less permeable matrix. It also explains the calibrated value of the ratio of mobile to total porosities used in previous modeling studies based on the dual-domain mass transfer approach. The results of this study underscore the importance of geologically plausible conceptualizations of the subsurface for making accurate predictions of the fate and transport of contaminants in highly heterogeneous aquifers. These conceptualizations may be developed through integration of raw geological data with expert knowledge, interpretation, and appropriate geostatistical methods.
An expected consequence approach to route choice in the maritime transportation of crude oil.
Siddiqui, Atiq; Verma, Manish
2013-11-01
Maritime transportation is the major conduit of international trade, and the primary link for global crude oil movement. Given the volume of oil transported on international maritime links, it is not surprising that oil spills of both minor and major types result, although most of the risk-related work has been confined to the local settings. We propose an expected consequence approach for assessing oil-spill risk from intercontinental transportation of crude oil that not only adheres to the safety guidelines specified by the International Maritime Organization but also outlines a novel technique that makes use of coarse global data to estimate accident probabilities. The proposed estimation technique, together with four of the most popular cost-of-spill models from the literature, were applied to study and analyze a realistic size problem instance. Numerical analyses showed that: a shorter route may not necessarily be less risky; an understanding of the inherent oil-spill risk of different routes could potentially facilitate tanker routing decisions; and the associated negotiations over insurance premium between the transport company and the not-for-profit prevention and indemnity clubs. Finally, we note that only the linear model should be used with one of the three nonlinear cost-of-spill models for evaluating tanker routes.
ERIC Educational Resources Information Center
Crank, Ron
This instructional unit is one of 10 developed by students on various energy-related areas that deals specifically with transportation and energy use. Its objective is for the student to be able to discuss the implication of energy usage as it applies to the area of transportation. Some topics covered are efficiencies of various transportation…
NASA Astrophysics Data System (ADS)
Lamprecht, C.; Plochberger, B.; Ruprecht, V.; Wieser, S.; Rankl, C.; Heister, E.; Unterauer, B.; Brameshuber, M.; Danzberger, J.; Lukanov, P.; Flahaut, E.; Schütz, G.; Hinterdorfer, P.; Ebner, A.
2014-03-01
In the past decade carbon nanotubes (CNTs) have been widely studied as a potential drug-delivery system, especially with functionality for cellular targeting. Yet, little is known about the actual process of docking to cell receptors and transport dynamics after internalization. Here we performed single-particle studies of folic acid (FA) mediated CNT binding to human carcinoma cells and their transport inside the cytosol. In particular, we employed molecular recognition force spectroscopy, an atomic force microscopy based method, to visualize and quantify docking of FA functionalized CNTs to FA binding receptors in terms of binding probability and binding force. We then traced individual fluorescently labeled, FA functionalized CNTs after specific uptake, and created a dynamic ‘roadmap’ that clearly showed trajectories of directed diffusion and areas of nanotube confinement in the cytosol. Our results demonstrate the potential of a single-molecule approach for investigation of drug-delivery vehicles and their targeting capacity.
Unified semiclassical approach to electronic transport from diffusive to ballistic regimes
NASA Astrophysics Data System (ADS)
Geng, Hao; Deng, Wei-Yin; Ren, Yue-Jiao; Sheng, Li; Xing, Ding-Yu
2016-09-01
We show that by integrating out the electric field and incorporating proper boundary conditions, a Boltzmann equation can describe electron transport properties, continuously from the diffusive to ballistic regimes. General analytical formulas of the conductance in D = 1,2,3 dimensions are obtained, which recover the Boltzmann–Drude formula and Landauer–Büttiker formula in the diffusive and ballistic limits, respectively. This intuitive and efficient approach can be applied to investigate the interplay of system size and impurity scattering in various charge and spin transport phenomena, when the quantum interference effect is not important. Project supported by the National Basic Research Program of China (Grant Nos. 2015CB921202 and 2014CB921103) and the National Natural Science Foundation of China (Grant No. 11225420).
NASA Technical Reports Server (NTRS)
Parrish, R. V.; Bowles, R. L.
1983-01-01
This paper addresses the issues of motion/visual cueing fidelity requirements for vortex encounters during simulated transport visual approaches and landings. Four simulator configurations were utilized to provide objective performance measures during simulated vortex penetrations, and subjective comments from pilots were collected. The configurations used were as follows: fixed base with visual degradation (delay), fixed base with no visual degradation, moving base with visual degradation (delay), and moving base with no visual degradation. The statistical comparisons of the objective measures and the subjective pilot opinions indicated that although both minimum visual delay and motion cueing are recommended for the vortex penetration task, the visual-scene delay characteristics were not as significant a fidelity factor as was the presence of motion cues. However, this indication was applicable to a restricted task, and to transport aircraft. Although they were statistically significant, the effects of visual delay and motion cueing on the touchdown-related measures were considered to be of no practical consequence.
Comparison of Flamelet Models with the Transported Mass Fraction Approach for Supersonic Combustion
NASA Astrophysics Data System (ADS)
Li, Wenhai; Alabi, Ken; Ladeinde, Foluso
2015-11-01
In this study, two fully compressible RANS, LES, and combined RANS/LES flow solvers - AEROFLO and VULCAN, both of which were originally developed by the United States Department of Defense but have since been significantly enhanced and commercialized by our organization, are used to investigate the accuracy of flamelet-based approach when employed to model supersonic combustion. The flamelet results from both codes are assessed relative to solutions obtained by solving the transport equations for the mass fractions - which is also supported by one of the codes, and making familiar assumptions about the closure of the reaction rate. The studies are carried out in the flamelet regime, and the numerical procedures are based on high-order schemes, which are also used to solve the level-set and mixture fraction transport equations used to study, respectively, premixed and non-premixed combustion. The effects of supersonic Mach numbers on the results are discussed.
Unified semiclassical approach to electronic transport from diffusive to ballistic regimes
NASA Astrophysics Data System (ADS)
Geng, Hao; Deng, Wei-Yin; Ren, Yue-Jiao; Sheng, Li; Xing, Ding-Yu
2016-09-01
We show that by integrating out the electric field and incorporating proper boundary conditions, a Boltzmann equation can describe electron transport properties, continuously from the diffusive to ballistic regimes. General analytical formulas of the conductance in D = 1,2,3 dimensions are obtained, which recover the Boltzmann-Drude formula and Landauer-Büttiker formula in the diffusive and ballistic limits, respectively. This intuitive and efficient approach can be applied to investigate the interplay of system size and impurity scattering in various charge and spin transport phenomena, when the quantum interference effect is not important. Project supported by the National Basic Research Program of China (Grant Nos. 2015CB921202 and 2014CB921103) and the National Natural Science Foundation of China (Grant No. 11225420).
de Nazelle, Audrey; Nieuwenhuijsen, Mark; Panis, Luc Int; Anaya, Esther; Avila-Palencia, Ione; Boschetti, Florinda; Brand, Christian; Cole-Hunter, Tom; Dons, Evi; Eriksson, Ulf; Gaupp-Berghausen, Mailin; Kahlmeier, Sonja; Laeremans, Michelle; Mueller, Natalie; Orjuela, Juan Pablo; Racioppi, Francesca; Raser, Elisabeth; Rojas-Rueda, David; Schweizer, Christian; Standaert, Arnout; Uhlmann, Tina; Wegener, Sandra; Götschi, Thomas
2016-01-01
Introduction Only one-third of the European population meets the minimum recommended levels of physical activity (PA). Physical inactivity is a major risk factor for non-communicable diseases. Walking and cycling for transport (active mobility, AM) are well suited to provide regular PA. The European research project Physical Activity through Sustainable Transport Approaches (PASTA) pursues the following aims: (1) to investigate correlates and interrelations of AM, PA, air pollution and crash risk; (2) to evaluate the effectiveness of selected interventions to promote AM; (3) to improve health impact assessment (HIA) of AM; (4) to foster the exchange between the disciplines of public health and transport planning, and between research and practice. Methods and analysis PASTA pursues a mixed-method and multilevel approach that is consistently applied in seven case study cities. Determinants of AM and the evaluation of measures to increase AM are investigated through a large scale longitudinal survey, with overall 14 000 respondents participating in Antwerp, Barcelona, London, Örebro, Rome, Vienna and Zurich. Contextual factors are systematically gathered in each city. PASTA generates empirical findings to improve HIA for AM, for example, with estimates of crash risks, factors on AM-PA substitution and carbon emissions savings from mode shifts. Findings from PASTA will inform WHO's online Health Economic Assessment Tool on the health benefits from cycling and/or walking. The study's wide scope, the combination of qualitative and quantitative methods and health and transport methods, the innovative survey design, the general and city-specific analyses, and the transdisciplinary composition of the consortium and the wider network of partners promise highly relevant insights for research and practice. Ethics and dissemination Ethics approval has been obtained by the local ethics committees in the countries where the work is being conducted, and sent to the European
Goodarz Ahmadi
2002-07-01
In this project, a computational modeling approach for analyzing flow and ash transport and deposition in filter vessels was developed. An Eulerian-Lagrangian formulation for studying hot-gas filtration process was established. The approach uses an Eulerian analysis of gas flows in the filter vessel, and makes use of the Lagrangian trajectory analysis for the particle transport and deposition. Particular attention was given to the Siemens-Westinghouse filter vessel at Power System Development Facility in Wilsonville in Alabama. Details of hot-gas flow in this tangential flow filter vessel are evaluated. The simulation results show that the rapidly rotation flow in the spacing between the shroud and the vessel refractory acts as cyclone that leads to the removal of a large fraction of the larger particles from the gas stream. Several alternate designs for the filter vessel are considered. These include a vessel with a short shroud, a filter vessel with no shroud and a vessel with a deflector plate. The hot-gas flow and particle transport and deposition in various vessels are evaluated. The deposition patterns in various vessels are compared. It is shown that certain filter vessel designs allow for the large particles to remain suspended in the gas stream and to deposit on the filters. The presence of the larger particles in the filter cake leads to lower mechanical strength thus allowing for the back-pulse process to more easily remove the filter cake. A laboratory-scale filter vessel for testing the cold flow condition was designed and fabricated. A laser-based flow visualization technique is used and the gas flow condition in the laboratory-scale vessel was experimental studied. A computer model for the experimental vessel was also developed and the gas flow and particle transport patterns are evaluated.
Fienen, M.; Hunt, R.; Krabbenhoft, D.; Clemo, T.
2009-01-01
Flow path delineation is a valuable tool for interpreting the subsurface hydrogeochemical environment. Different types of data, such as groundwater flow and transport, inform different aspects of hydrogeologie parameter values (hydraulic conductivity in this case) which, in turn, determine flow paths. This work combines flow and transport information to estimate a unified set of hydrogeologic parameters using the Bayesian geostatistical inverse approach. Parameter flexibility is allowed by using a highly parameterized approach with the level of complexity informed by the data. Despite the effort to adhere to the ideal of minimal a priori structure imposed on the problem, extreme contrasts in parameters can result in the need to censor correlation across hydrostratigraphic bounding surfaces. These partitions segregate parameters into faci??s associations. With an iterative approach in which partitions are based on inspection of initial estimates, flow path interpretation is progressively refined through the inclusion of more types of data. Head observations, stable oxygen isotopes (18O/16O) ratios), and tritium are all used to progressively refine flow path delineation on an isthmus between two lakes in the Trout Lake watershed, northern Wisconsin, United States. Despite allowing significant parameter freedom by estimating many distributed parameter values, a smooth field is obtained. Copyright 2009 by the American Geophysical Union.
NASA Astrophysics Data System (ADS)
Fienen, M.; Hunt, R.; Krabbenhoft, D.; Clemo, T.
2009-08-01
Flow path delineation is a valuable tool for interpreting the subsurface hydrogeochemical environment. Different types of data, such as groundwater flow and transport, inform different aspects of hydrogeologic parameter values (hydraulic conductivity in this case) which, in turn, determine flow paths. This work combines flow and transport information to estimate a unified set of hydrogeologic parameters using the Bayesian geostatistical inverse approach. Parameter flexibility is allowed by using a highly parameterized approach with the level of complexity informed by the data. Despite the effort to adhere to the ideal of minimal a priori structure imposed on the problem, extreme contrasts in parameters can result in the need to censor correlation across hydrostratigraphic bounding surfaces. These partitions segregate parameters into facies associations. With an iterative approach in which partitions are based on inspection of initial estimates, flow path interpretation is progressively refined through the inclusion of more types of data. Head observations, stable oxygen isotopes (18O/16O ratios), and tritium are all used to progressively refine flow path delineation on an isthmus between two lakes in the Trout Lake watershed, northern Wisconsin, United States. Despite allowing significant parameter freedom by estimating many distributed parameter values, a smooth field is obtained.
Reactive solute transport in streams: A surface complexation approach for trace metal sorption
Runkel, R.L.; Kimball, B.A.; McKnight, Diane M.; Bencala, K.E.
1999-01-01
A model for trace metals that considers in-stream transport, metal oxide precipitation-dissolution, and pH-dependent sorption is presented. Linkage between a surface complexation submodel and the stream transport equations provides a framework for modeling sorption onto static and/or dynamic surfaces. A static surface (e.g., an iron-oxide-coated streambed) is defined as a surface with a temporally constant solid concentration. Limited contact between solutes in the water column and the static surface is considered using a pseudokinetic approach. A dynamic surface (e.g., freshly precipitated metal oxides) has a temporally variable solid concentration and is in equilibrium with the water column. Transport and deposition of solute mass sorbed to the dynamic surface is represented in the stream transport equations that include precipitate settling. The model is applied to a pH-modification experiment in an acid mine drainage stream. Dissolved copper concentrations were depressed for a 3 hour period in response to the experimentally elevated pH. After passage of the pH front, copper was desorbed, and dissolved concentrations returned to ambient levels. Copper sorption is modeled by considering sorption to aged hydrous ferric oxide (HFO) on the streambed (static surface) and freshly precipitated HFO in the water column (dynamic surface). Comparison of parameter estimates with reported values suggests that naturally formed iron oxides may be more effective in removing trace metals than synthetic oxides used in laboratory studies. The model's ability to simulate pH, metal oxide precipitation-dissolution, and pH-dependent sorption provides a means of evaluating the complex interactions between trace metal chemistry and hydrologic transport at the field scale.
Lattice hydrodynamic model based traffic control: A transportation cyber-physical system approach
NASA Astrophysics Data System (ADS)
Liu, Hui; Sun, Dihua; Liu, Weining
2016-11-01
Lattice hydrodynamic model is a typical continuum traffic flow model, which describes the jamming transition of traffic flow properly. Previous studies in lattice hydrodynamic model have shown that the use of control method has the potential to improve traffic conditions. In this paper, a new control method is applied in lattice hydrodynamic model from a transportation cyber-physical system approach, in which only one lattice site needs to be controlled in this control scheme. The simulation verifies the feasibility and validity of this method, which can ensure the efficient and smooth operation of the traffic flow.
Automatic guidance and control of a transport aircraft during a helical landing approach
NASA Technical Reports Server (NTRS)
Crawford, D. J.
1975-01-01
A linear optimal regulator theory was applied to a nonlinear simulation of a transport aircraft performing a helical landing approach. A closed-form expression for the quasi-steady nominal flight path is presented along with the method for determining the corresponding constant nominal control inputs. The Jacobian matrices and the weighting matrices in the cost functional were time varying. A method of solving for the optimal feedback gains is reviewed. The control system was tested on several alternative landing approaches using both 3 deg and 6 deg flight path angles. On each landing approach, the aircraft was subjected to large random initial-state errors and to randomly directed crosswinds. The system was also tested for sensitivity to changes in the parameters of the aircraft and of the atmosphere. Results indicate that performance of the optimal controller on all the 3 deg approaches is very good. The control system proved to be reasonably insensitive to parametric uncertainties. Performance is not as good on the 6 deg approaches. A modification to the 6 deg flight path was proposed for the purpose of improving performance.
Flight evaluation of two segment approaches for jet transport noise abatement
NASA Technical Reports Server (NTRS)
Rogers, R. A.; Wohl, B.; Gale, C. M.
1973-01-01
A 75 flight-hour operational evaluation was conducted with a representative four-engine fan-jet transport in a representative airport environment. The flight instrument systems were modified to automatically provide pilots with smooth and continuous pitch steering command information during two-segment approaches. Considering adverse weather, minimum ceiling and flight crew experience criteria, a transition initiation altitude of approximately 800 feet AFL would have broadest acceptance for initiating two-segment approach procedures in scheduled service. The profile defined by the system gave an upper glidepath of approximately 6 1/2 degrees. This was 1/2 degree greater than inserted into the area navigation system. The glidepath error is apparently due to an erroneous along-track, distance-to-altitude profile.
ANFIS-based approach for predicting sediment transport in clean sewer
Azamathulla, H. Md.; Ab. Ghani, Aminuddin; Fei, Seow Yen
2012-01-01
The necessity of sewers to carry sediment has been recognized for many years. Typically, old sewage systems were designated based on self-cleansing concept where there is no deposition in sewer. These codes were applicable to non-cohesive sediments (typically storm sewers). This study presents adaptive neuro-fuzzy inference system (ANFIS), which is a combination of neural network and fuzzy logic, as an alternative approach to predict the functional relationships of sediment transport in sewer pipe systems. The proposed relationship can be applied to different boundaries with partially full flow. The present ANFIS approach gives satisfactory results (r2 = 0.98 and RMSE = 0.002431) compared to the existing predictor. PMID:22389640
N3LO NN interaction adjusted to light nuclei in ab exitu approach
NASA Astrophysics Data System (ADS)
Shirokov, A. M.; Shin, I. J.; Kim, Y.; Sosonkina, M.; Maris, P.; Vary, J. P.
2016-10-01
We use phase-equivalent transformations to adjust off-shell properties of similarity renormalization group evolved chiral effective field theory NN interaction (Idaho N3LO) to fit selected binding energies and spectra of light nuclei in an ab exitu approach. We then test the transformed interaction on a set of additional observables in light nuclei to verify that it provides reasonable descriptions of these observables with an apparent reduced need for three- and many-nucleon interactions.
NASA Astrophysics Data System (ADS)
Weiss, Lee; Thé, Jesse; Gharabaghi, Bahram; Stainsby, Eleanor A.; Winter, Jennifer G.
2014-10-01
Windblown dust simulations are one of the most uncertain types of atmospheric transport models. This study presents an integrated PM10 emission, transport and deposition model which has been validated using monitored data. This model characterizes the atmospheric phosphorus load focusing on the major local sources within the Lake Simcoe airshed including paved and unpaved roads, agricultural sources, construction sites and aggregate mining sources. This new approach substantially reduces uncertainty by providing improved estimates of the friction velocities than those developed previously. Modeling improvements were also made by generating and validating an hourly windfield using detailed meteorology, topography and land use data for the study area. The model was used to estimate dust emissions generated in the airshed and to simulate the long-range transport and deposition of PM10 to Lake Simcoe. The deposition results from the model were verified against observed bulk collector phosphorus concentration data for both wet and dry deposition. Bulk collector data from stations situated outside the airshed in a remote, undeveloped area were also compared to determine the background contribution from distant sources.
Identification of transport processes in column experiments using a frequency domain approach
NASA Astrophysics Data System (ADS)
Shuai, Xiufu; Yost, Russell S.
2007-10-01
When a solute transport process is viewed as a dynamic system with input and output, a system identification technique can be used to study it from input-output data. According to the design of excitation signals in the system identification approach, the commonly used rectangular pulse as input signal for column experiments is not optimum because it does not simultaneously meet the requirements for exciting the studied transport process, i.e., possessing frequency components with high enough amplitude and wide enough passband. In this article, stepped sine signals were proposed to replace the rectangular pulse because their amplitude and passband can be independently chosen. The stepped sine signals of concentration were generated by a High Performance Liquid Chromatography (HPLC) and used as the input for the column experiments to identify parameters of the convection-dispersion equation (CDE) and mobile-immobile model (MIM). In order to test the effect of noise on the identification of transport process, numerical experiments were carried out to identify the CDE under white noise when the input was designed as stepped sine functions and rectangular pulse. The results of the numerical experiments showed that the input signal of a sine function was more robust and accurate in process identification than that of a rectangular pulse.
Approaching disorder-free transport in high-mobility conjugated polymers.
Venkateshvaran, Deepak; Nikolka, Mark; Sadhanala, Aditya; Lemaur, Vincent; Zelazny, Mateusz; Kepa, Michal; Hurhangee, Michael; Kronemeijer, Auke Jisk; Pecunia, Vincenzo; Nasrallah, Iyad; Romanov, Igor; Broch, Katharina; McCulloch, Iain; Emin, David; Olivier, Yoann; Cornil, Jerome; Beljonne, David; Sirringhaus, Henning
2014-11-20
Conjugated polymers enable the production of flexible semiconductor devices that can be processed from solution at low temperatures. Over the past 25 years, device performance has improved greatly as a wide variety of molecular structures have been studied. However, one major limitation has not been overcome; transport properties in polymer films are still limited by pervasive conformational and energetic disorder. This not only limits the rational design of materials with higher performance, but also prevents the study of physical phenomena associated with an extended π-electron delocalization along the polymer backbone. Here we report a comparative transport study of several high-mobility conjugated polymers by field-effect-modulated Seebeck, transistor and sub-bandgap optical absorption measurements. We show that in several of these polymers, most notably in a recently reported, indacenodithiophene-based donor-acceptor copolymer with a near-amorphous microstructure, the charge transport properties approach intrinsic disorder-free limits at which all molecular sites are thermally accessible. Molecular dynamics simulations identify the origin of this long sought-after regime as a planar, torsion-free backbone conformation that is surprisingly resilient to side-chain disorder. Our results provide molecular-design guidelines for 'disorder-free' conjugated polymers.
Berkolaiko, G.; Kuipers, J.
2013-11-15
To study electronic transport through chaotic quantum dots, there are two main theoretical approaches. One involves substituting the quantum system with a random scattering matrix and performing appropriate ensemble averaging. The other treats the transport in the semiclassical approximation and studies correlations among sets of classical trajectories. There are established evaluation procedures within the semiclassical evaluation that, for several linear and nonlinear transport moments to which they were applied, have always resulted in the agreement with random matrix predictions. We prove that this agreement is universal: any semiclassical evaluation within the accepted procedures is equivalent to the evaluation within random matrix theory. The equivalence is shown by developing a combinatorial interpretation of the trajectory sets as ribbon graphs (maps) with certain properties and exhibiting systematic cancellations among their contributions. Remaining trajectory sets can be identified with primitive (palindromic) factorisations whose number gives the coefficients in the corresponding expansion of the moments of random matrices. The equivalence is proved for systems with and without time reversal symmetry.
Approaching disorder-free transport in high-mobility conjugated polymers.
Venkateshvaran, Deepak; Nikolka, Mark; Sadhanala, Aditya; Lemaur, Vincent; Zelazny, Mateusz; Kepa, Michal; Hurhangee, Michael; Kronemeijer, Auke Jisk; Pecunia, Vincenzo; Nasrallah, Iyad; Romanov, Igor; Broch, Katharina; McCulloch, Iain; Emin, David; Olivier, Yoann; Cornil, Jerome; Beljonne, David; Sirringhaus, Henning
2014-11-20
Conjugated polymers enable the production of flexible semiconductor devices that can be processed from solution at low temperatures. Over the past 25 years, device performance has improved greatly as a wide variety of molecular structures have been studied. However, one major limitation has not been overcome; transport properties in polymer films are still limited by pervasive conformational and energetic disorder. This not only limits the rational design of materials with higher performance, but also prevents the study of physical phenomena associated with an extended π-electron delocalization along the polymer backbone. Here we report a comparative transport study of several high-mobility conjugated polymers by field-effect-modulated Seebeck, transistor and sub-bandgap optical absorption measurements. We show that in several of these polymers, most notably in a recently reported, indacenodithiophene-based donor-acceptor copolymer with a near-amorphous microstructure, the charge transport properties approach intrinsic disorder-free limits at which all molecular sites are thermally accessible. Molecular dynamics simulations identify the origin of this long sought-after regime as a planar, torsion-free backbone conformation that is surprisingly resilient to side-chain disorder. Our results provide molecular-design guidelines for 'disorder-free' conjugated polymers. PMID:25383522
Approaching disorder-free transport in high-mobility conjugated polymers
NASA Astrophysics Data System (ADS)
Venkateshvaran, Deepak; Nikolka, Mark; Sadhanala, Aditya; Lemaur, Vincent; Zelazny, Mateusz; Kepa, Michal; Hurhangee, Michael; Kronemeijer, Auke Jisk; Pecunia, Vincenzo; Nasrallah, Iyad; Romanov, Igor; Broch, Katharina; McCulloch, Iain; Emin, David; Olivier, Yoann; Cornil, Jerome; Beljonne, David; Sirringhaus, Henning
2014-11-01
Conjugated polymers enable the production of flexible semiconductor devices that can be processed from solution at low temperatures. Over the past 25 years, device performance has improved greatly as a wide variety of molecular structures have been studied. However, one major limitation has not been overcome; transport properties in polymer films are still limited by pervasive conformational and energetic disorder. This not only limits the rational design of materials with higher performance, but also prevents the study of physical phenomena associated with an extended π-electron delocalization along the polymer backbone. Here we report a comparative transport study of several high-mobility conjugated polymers by field-effect-modulated Seebeck, transistor and sub-bandgap optical absorption measurements. We show that in several of these polymers, most notably in a recently reported, indacenodithiophene-based donor-acceptor copolymer with a near-amorphous microstructure, the charge transport properties approach intrinsic disorder-free limits at which all molecular sites are thermally accessible. Molecular dynamics simulations identify the origin of this long sought-after regime as a planar, torsion-free backbone conformation that is surprisingly resilient to side-chain disorder. Our results provide molecular-design guidelines for `disorder-free' conjugated polymers.
Designing optimal transportation networks: a knowledge-based computer-aided multicriteria approach
Tung, S.I.
1986-01-01
The dissertation investigates the applicability of using knowledge-based expert systems (KBES) approach to solve the single-mode (automobile), fixed-demand, discrete, multicriteria, equilibrium transportation-network-design problem. Previous works on this problem has found that mathematical programming method perform well on small networks with only one objective. Needed is a solution technique that can be used on large networks having multiple, conflicting criteria with different relative importance weights. The KBES approach developed in this dissertation represents a new way to solve network design problems. The development of an expert system involves three major tasks: knowledge acquisition, knowledge representation, and testing. For knowledge acquisition, a computer aided network design/evaluation model (UFOS) was developed to explore the design space. This study is limited to the problem of designing an optimal transportation network by adding and deleting capacity increments to/from any link in the network. Three weighted criteria were adopted for use in evaluating each design alternative: cost, average V/C ratio, and average travel time.
Quantifying Vadose Zone Flow and Transport Uncertainties Using a Unified, Hierarchical Approach
Meyer, Philip D.; Murray, Christopher J.; Rockhold, Mark L.; Schaap, Marcel
2002-06-01
The objective of this research is to develop and demonstrate a general approach for modeling flow and transport in the heterogeneous vadose zone. The approach uses similar media scaling, geostatistics, and conditional simulation methods to estimate soil hydraulic parameters at unsampled locations from field-measured water content data and scale-mean hydraulic parameters determined from available site characterization data. Neural network methods are being developed to estimate soil hydraulic parameters from more easily measured physical property data such as bulk density, organic matter content, and percentages of sand, silt, and clay (or particle-size distributions). Field water content distributions are being estimated using various geophysical methods including neutron moderation, ground-penetrating radar, and electrical resistance tomography. One of the primary goals of this research is to determine relationships between the type of data used in model parameterization, the quantity of data available, the scale of the measurement, and the uncertainty in predictions of flow and transport using these methods. Evaluation of the relationships between available data, scale, and uncertainty are using data from a large-scale, controlled field experiment.
Quantifying Vadose Zone Flow and Transport Uncertainties Using a Unified, Hierarchical Approach
Meyer, Philip D.; Murray, Chris J.; Rockhold, Mark L.
2001-06-01
The objective of this research is to develop and demonstrate a general approach for modeling flow and transport in the heterogeneous vadose zone. The approach uses similar media scaling, geostatistics, and conditional simulation methods to estimate soil hydraulic parameters at unsampled locations from field-measured water content data and scale-mean hydraulic parameters determined from available site characterization data. Neural network methods are being developed to estimate soil hydraulic parameters from more easily measured physical property data such as bulk density, organic matter content, and percentages of sand, silt, and clay (or particle-size distributions). Field water content distributions are being estimated using various geophysical methods including neutron moderation, ground-penetrating radar, and electrical resistance tomography. One of the primary goals of this research is to determine relationships between the type of data used in model parameterization, th e quantity of data available, the scale of the measurement, and the uncertainty in predictions of flow and transport using these methods. Evaluation of the relationships between available data, scale, and uncertainty will use primarily existing data from large-scale, controlled experiments.
A numerical spectral approach to solve the dislocation density transport equation
NASA Astrophysics Data System (ADS)
Djaka, K. S.; Taupin, V.; Berbenni, S.; Fressengeas, C.
2015-09-01
A numerical spectral approach is developed to solve in a fast, stable and accurate fashion, the quasi-linear hyperbolic transport equation governing the spatio-temporal evolution of the dislocation density tensor in the mechanics of dislocation fields. The approach relies on using the Fast Fourier Transform algorithm. Low-pass spectral filters are employed to control both the high frequency Gibbs oscillations inherent to the Fourier method and the fast-growing numerical instabilities resulting from the hyperbolic nature of the transport equation. The numerical scheme is validated by comparison with an exact solution in the 1D case corresponding to dislocation dipole annihilation. The expansion and annihilation of dislocation loops in 2D and 3D settings are also produced and compared with finite element approximations. The spectral solutions are shown to be stable, more accurate for low Courant numbers and much less computation time-consuming than the finite element technique based on an explicit Galerkin-least squares scheme.
Selim, H M; Zhang, Hua
2013-01-01
Competition among various heavy metal species for available adsorption sites on soil matrix surfaces can enhance the mobility of contaminants in the soil environment. Accurate predictions of the fate and behavior of heavy metals in soils and geologic media requires the understanding of the underlying competitive-sorption and transport processes. In this review, we present equilibrium and kinetic models for competitive heavy metal sorption and transport in soils. Several examples are summarized to illustrate the impact of competing ions on the reactivities and mobility of heavy metals in the soil-water environment. We demonstrate that equilibrium Freundlich approaches can be extended to account for competitive sorption of cations and anions with the incorporation of competition coefficients associated with each reaction. Furthermore, retention models of the multiple-reaction type including the two-site nonlinear equilibrium-kinetic models and the concurrent- and consecutive-multireaction models were modified to describe commonly observed time-dependent behaviors of heavy metals in soils. We also show that equilibrium Langmuir and kinetic second-order models can be extended to simulate the competitive sorption and transport in soils, although the use of such models is limited due to their simplifying assumptions. A major drawback of the empirically based Freundlich and Langmuir approaches is that their associated parameters are specific for each soil. Alternatively, geochemical models that are based on ion-exchange and surface-complexation concepts are capable of quantifying the competitive behavior of several chemical species under a wide range of environmental conditions. Such geochemical models, however, are incapable of describing the time-dependent sorption behavior of heavy metal ions in competitive systems. Further research is needed to develop a general-purpose model based on physical and chemical mechanisms governing competitive sorption in soils.
A systems approach to energy management and policy in commuter rail transportation
NASA Astrophysics Data System (ADS)
Owan, Ransome Egimine
1998-12-01
This research is motivated by a recognition of energy as a significant part of the transportation problem. Energy is a long-term variable cost that is controllable. The problem is comprised of: the limited supply of energy, chronic energy deficits and oil imports, energy cost, poor fuel substitution, and the undesirable environmental effects of transportation fuels (Green House Gases and global warming). Mass transit systems are energy intensive networks and energy is a direct constraint to the supply of affordable transportation. Commuter railroads are also relatively unresponsive to energy price changes due to travel demand patterns, firm power needs and slow adoption of efficient train technologies. However, the long term energy demand is lacking in existing transportation planning philosophy. In spite of the apparent oversight, energy is as important as urban land use, funding and congestion, all of which merit explicit treatment. This research was conducted in the form of a case study of New Jersey Transit in an attempt to broaden the understanding of the long-term effects of energy in a transportation environment. The systems approach method that is driven by heuristic models was utilized to investigate energy usage, transit peer group efficiency, energy management regimes, and the tradeoffs between energy and transportation, a seldom discussed topic in the field. Implicit in systems thinking is the methodological hunt for solutions. The energy problem was divided into thinking is the methodological hunt for solutions. The energy problem was divided into smaller parts that in turn were simpler to solve. The research presented five heuristic models: Transit Energy Aggregation Model, Structural Energy Consumption Model, Traction Power Consumption Model, Conjunctive Demand Model, and a Managerial Action Module. A putative relationship was established between traction energy, car-miles, seasonal and ambient factors, without inference of direct causality. The co
Towards a filtered density function approach for reactive transport in groundwater
NASA Astrophysics Data System (ADS)
Suciu, N.; Schüler, L.; Attinger, S.; Knabner, P.
2016-04-01
Evolution equations for probability density functions (PDFs) and filtered density functions (FDFs) of random species concentrations weighted by conserved scalars are formulated as Fokker-Planck equations describing stochastically equivalent processes in concentration-position spaces. This approach provides consistent numerical PDF/FDF solutions, given by the density in the concentration-position space of an ensemble of computational particles governed by the associated Itô equations. The solutions are obtained by a global random walk (GRW) algorithm, which is stable, free of numerical diffusion, and practically insensitive to the increase of the number of particles. The general FDF approach and the GRW numerical solution are illustrated for a reduced complexity problem consisting of the transport of a single scalar in groundwater. Randomness is induced by the stochastic parameterization of the hydraulic conductivity, characterized by short range correlations and small variance. The objective is to infer the statistics of the random concentration sampled at the plume center of mass, integrated over the transverse dimension of a two-dimensional spatial domain. The PDF/FDF problem can therefore be formulated in a two-dimensional domain as well, a spatial dimension and one in the concentration space. The upscaled drift and diffusion coefficients describing the PDF transport in the physical space are estimated on single-trajectories of diffusion in velocity fields with short-range correlations, owing to their self-averaging property. The mixing coefficients describing the PDF transport in concentration spaces are parameterized by the trend and the noise inferred from the statistical analysis of an ensemble of simulated concentration time series, as well as by classical mixing models. A Gaussian spatial filter applied to a Kraichnan velocity field generator is used to construct coarse-grained simulations (CGS) for FDF problems. The purposes of the CGS simulations are
A dual-permeability approach to preferential water flow and solute transport in shrinking soils
NASA Astrophysics Data System (ADS)
Coppola, Antonio; dragonetti, giovanna; Comegna, Alessandro; Gerke, Horst H.; Basile, Angelo
2016-04-01
The pore systems in most natural soils is dynamically changing due to alternating swelling and shrinkage processes, which induces changes in pore volume and pore size distribution including deformations in pore geometry. This is a serious difficulty for modeling flow and transport in dual permeability approaches, as it will also require that the geometrical deformation of both the soil matrix and the fracture porous systems be taken into account, as well as the dynamics of soil hydraulic properties in response to the domain deformations. This study follows up a previous work by the same authors extending the classical rigid (RGD) approach formerly proposed by Gerke and van Genuchten, to account for shrinking effects (SHR) in modeling water flow and solute transport in dual-permeability porous media. In this study we considered three SHR scenarios, assuming that aggregate shrinkage may change either: (i) the hydraulic properties of the two pore domains, (ii) their relative fractions, and (iii) both, hydraulic properties and fractions of the two domains. The objective was to compare simulation results obtained under the RGD and the SHR assumptions to illustrate the impact of matrix volume changes on water storage, water fluxes and solute concentrations during: 1) An infiltration process bringing an initially dry soil to saturation, 2) A drainage process starting from an initially saturated soil. For an infiltration process, the simulated wetting front and the solute concentration propagation velocity, as well as the water fluxes, water and solute exchange rates, for the three SHR scenarios significantly deviated from the RGD. By contrast, relatively similar water content profiles evolved under all scenarios during drying. Overall, compared to the RGD approach, the effect of changing the hydraulic properties and the weight of the two domains according to the shrinkage behavior of the soil aggregates induced a much more rapid response in terms of water fluxes and
Alvarez, P. E.; Vallejo, A. E.
2008-01-01
Kinetics of facilitated ion transport through planar bilayer membranes are normally analyzed by electrical conductance methods. The additional use of electrical relaxation techniques, such as voltage jump, is necessary to evaluate individual rate constants. Although electrochemical impedance spectroscopy is recognized as the most powerful of the available electric relaxation techniques, it has rarely been used in connection with these kinetic studies. According to the new approach presented in this work, three steps were followed. First, a kinetic model was proposed that has the distinct quality of being general, i.e., it properly describes both carrier and channel mechanisms of ion transport. Second, the state equations for steady-state and for impedance experiments were derived, exhibiting the input–output representation pertaining to the model’s structure. With the application of a method based on the similarity transformation approach, it was possible to check that the proposed mechanism is distinguishable, i.e., no other model with a different structure exhibits the same input–output behavior for any input as the original. Additionally, the method allowed us to check whether the proposed model is globally identifiable (i.e., whether there is a single set of fit parameters for the model) when analyzed in terms of its impedance response. Thus, our model does not represent a theoretical interpretation of the experimental impedance but rather constitutes the prerequisite to select this type of experiment in order to obtain optimal kinetic identification of the system. Finally, impedance measurements were performed and the results were fitted to the proposed theoretical model in order to obtain the kinetic parameters of the system. The successful application of this approach is exemplified with results obtained for valinomycin–K+ in lipid bilayers supported onto gold substrates, i.e., an arrangement capable of emulating biological membranes. PMID:19669528
NASA Astrophysics Data System (ADS)
Ozbek, M. M.; Pinder, G. F.
2006-12-01
There is a growing need in hydrologic and environmental modeling and management to segregate uncertainty, whether it occurs in input parameters or in possible alternative models, into aleatory uncertainty (i.e., irreducible or stochastic) and epistemic uncertainty (i.e., reducible or due to lack of knowledge). While aleatory uncertainty has been known and used as the only source of uncertainty in the hydrologic community for a long time, the notion of epistemic uncertainty is relatively new and it can be due several reasons including 1) field and laboratory methods used in the measurement of parameters, 2) techniques used to interpolate measured values at selected locations, and more importantly, 3) subjective expert opinion interpreting data available to augment existing prior parametric information. A natural framework to quantify epistemic uncertainty has been fuzzy set theory. In this paper, we use the extension principle of fuzzy set theory to simulate groundwater flow and transport with fuzzy model parameters. Our novel implementation of the principle involves two major steps: 1) a tessellation of the parameter space that results in simplexes over which the state variable is approximated by means of trial functions, followed by 2) the optimization of degrees of membership for the state variable in each simplex where the trial functions and the fuzzy parameter membership functions are used as the constraints of the optimization algorithm. We compare our approach to other known approaches to using the extension principle to address groundwater flow and transport in the saturated zone, and highlight features of our approach that apply to any physically based model with fuzzy parameter input.
Numerical and experimental approaches to study soil transport and clogging in granular filters
NASA Astrophysics Data System (ADS)
Kanarska, Y.; Smith, J. J.; Ezzedine, S. M.; Lomov, I.; Glascoe, L. G.
2012-12-01
Failure of a dam by erosion ranks among the most serious accidents in civil engineering. The best way to prevent internal erosion is using adequate granular filters in the transition areas where important hydraulic gradients can appear. In case of cracking and erosion, if the filter is capable of retaining the eroded particles, the crack will seal and the dam safety will be ensured. Numerical modeling has proved to be a cost-effective tool for improving our understanding of physical processes. Traditionally, the consideration of flow and particle transport in porous media has focused on treating the media as continuum. Practical models typically address flow and transport based on the Darcy's law as a function of a pressure gradient and a medium-dependent permeability parameter. Additional macroscopic constitutes describe porosity, and permeability changes during the migration of a suspension through porous media. However, most of them rely on empirical correlations, which often need to be recalibrated for each application. Grain-scale modeling can be used to gain insight into scale dependence of continuum macroscale parameters. A finite element numerical solution of the Navier-Stokes equations for fluid flow together with Lagrange multiplier technique for solid particles was applied to the simulation of soil filtration in the filter layers of gravity dam. The numerical approach was validated through comparison of numerical simulations with the experimental results of base soil particle clogging in the filter layers performed at ERDC. The numerical simulation correctly predicted flow and pressure decay due to particle clogging. The base soil particle distribution was almost identical to those measured in the laboratory experiment. It is believed that the agreement between simulations and experimental data demonstrates the applicability of the proposed approach for prediction of the soil transport and clogging in embankment dams. To get more precise understanding of
Aggarwal, Preeti; Jain, Suresh
2015-10-01
This study adopted an integrated 'source-to-receptor' assessment paradigm in order to determine the effects of emissions from passenger transport on urban air quality and human health in the megacity, Delhi. The emission modeling was carried out for the base year 2007 and three alternate (ALT) policy scenarios along with a business as usual (BAU) scenario for the year 2021. An Activity-Structure-Emission Factor (ASF) framework was adapted for emission modeling, followed by a grid-wise air quality assessment using AERMOD and a health impact assessment using an epidemiological approach. It was observed that a 2021-ALT-III scenario resulted in a maximum concentration reduction of ~24%, ~42% and ~58% for carbon monoxide (CO), nitrogen dioxide (NO2) and particulate matter (PM), respectively, compared to a 2021-BAU scenario. Further, it results in significant reductions in respiratory and cardiovascular mortality, morbidity and Disability Adjusted Life Years (DALY) by 41% and 58% on exposure to PM2.5 and NO2 concentrations when compared to the 2021-BAU scenario, respectively. In other words, a mix of proposed policy interventions namely the full-phased introduction of the Integrated Mass Transit System, fixed bus speed, stringent vehicle emission norms and a hike in parking fees for private vehicles would help in strengthening the capability of passenger transport to cater to a growing transport demand with a minimum health burden in the Delhi region. Further, the study estimated that the transport of goods would be responsible for ~5.5% additional VKT in the 2021-BAU scenario; however, it will contribute ~49% and ~55% additional NO2 and PM2.5 concentrations, respectively, in the Delhi region. Implementation of diesel particulate filters for goods vehicles in the 2021-ALT-IV-O scenario would help in the reduction of ~87% of PM2.5 concentration, compared to the 2021-BAU scenario; translating into a gain of 1267 and 505 DALY per million people from exposure to PM2.5 and NO
Takahashi, Kou; Kong, Qiongman; Lin, Yuchen; Stouffer, Nathan; Schulte, Delanie A; Lai, Liching; Liu, Qibing; Chang, Ling-Chu; Dominguez, Sky; Xing, Xuechao; Cuny, Gregory D; Hodgetts, Kevin J; Glicksman, Marcie A; Lin, Chien-Liang Glenn
2015-03-01
Glutamatergic systems play a critical role in cognitive functions and are known to be defective in Alzheimer's disease (AD) patients. Previous literature has indicated that glial glutamate transporter EAAT2 plays an essential role in cognitive functions and that loss of EAAT2 protein is a common phenomenon observed in AD patients and animal models. In the current study, we investigated whether restored EAAT2 protein and function could benefit cognitive functions and pathology in APPSw,Ind mice, an animal model of AD. A transgenic mouse approach via crossing EAAT2 transgenic mice with APPSw,Ind. mice and a pharmacological approach using a novel EAAT2 translational activator, LDN/OSU-0212320, were conducted. Findings from both approaches demonstrated that restored EAAT2 protein function significantly improved cognitive functions, restored synaptic integrity, and reduced amyloid plaques. Importantly, the observed benefits were sustained one month after compound treatment cessation, suggesting that EAAT2 is a potential disease modifier with therapeutic potential for AD. PMID:25711212
NASA Astrophysics Data System (ADS)
Nicolaides, C.; Cueto-Felgueroso, L.; Juanes, R.
2011-12-01
The study of networks as complex systems has revolutionized many disciplines in physics and the social and natural sciences. Recently, the focus of network science has shifted from the analysis of the network topology to the study of the dynamics of processes that take place on them. Here, we adopt a bosonic (metapopulation) network approach to characterize transport and reaction on fracture networks. In a bosonic network, nodes contain populations of particles, which may undertake contact processes within them. This coarse-grained conceptualization permits modeling of nonequilibrium phenomena such as incomplete mixing and kinetic reactions. Particles then move between connected nodes along links, with a rate that reflects the traffic patterns through the network. We generate fracture networks from realistic statistical properties of fracture density, orientation and aperture, and solve potential flow on the network for simple flow configurations. It is well known that the transport of passive particles with complete mixing at the nodes on a fracture network or a scale-free network is anomalous [1,2]. Here, we extend this analysis to account for incomplete mixing at the nodes by considering two types of particles, A and B, which come in contact at the nodes at a rate α (the mixing rate) to produce type-C particles: A+B-> 2C. In the limit of α -> ∞ we recover the instantaneous mixing case. Further, type-C particles decay into stable type-D particles at a rate λ : C→ D. As a result, we capture the interplay among the transport, mixing and reaction time scales on a fracture network. Our analysis demonstrates the strong dependence of global mixing and spreading on incomplete local mixing, and allows us to obtain robust scalings for the spatio-temporal distributions of particles.
Ding, Mengning; He, Qiyuan; Wang, Gongming; Cheng, Hung-Chieh; Huang, Yu; Duan, Xiangfeng
2015-01-01
In situ monitoring electrochemical interfaces is crucial for fundamental understanding and continued optimization of electrocatalysts. Conventional spectroscopic techniques are generally difficult to implement for in situ electrochemical studies. Here we report an on-chip electrical transport spectroscopy approach for directly probing the electrochemical surfaces of metallic nanocatalysts in action. With a four-electrode device configuration, we demonstrate that the electrical properties of ultrafine platinum nanowires are highly sensitive and selective to the electrochemical surface states, enabling a nanoelectronic signalling pathway that reveals electrochemical interface information during in-device cyclic voltammetry. Our results not only show a high degree of consistency with generally accepted conclusions in platinum electrochemistry but also offer important insights on various practically important electrochemical reactions. This study defines a nanoelectronic strategy for in situ electrochemical surface studies with high surface sensitivity and surface specificity. PMID:26245937
Ding, Mengning; He, Qiyuan; Wang, Gongming; Cheng, Hung-Chieh; Huang, Yu; Duan, Xiangfeng
2015-08-06
In situ monitoring electrochemical interfaces is crucial for fundamental understanding and continued optimization of electrocatalysts. Conventional spectroscopic techniques are generally difficult to implement for in situ electrochemical studies. Here we report an on-chip electrical transport spectroscopy approach for directly probing the electrochemical surfaces of metallic nanocatalysts in action. With a four-electrode device configuration, we demonstrate that the electrical properties of ultrafine platinum nanowires are highly sensitive and selective to the electrochemical surface states, enabling a nanoelectronic signalling pathway that reveals electrochemical interface information during in-device cyclic voltammetry. Our results not only show a high degree of consistency with generally accepted conclusions in platinum electrochemistry but also offer important insights on various practically important electrochemical reactions. This study defines a nanoelectronic strategy for in situ electrochemical surface studies with high surface sensitivity and surface specificity.
Simulation of decelerating landing approaches on an externally blown flap STOL transport airplane
NASA Technical Reports Server (NTRS)
Grantham, W. D.; Nguyen, L. T.; Deal, P. L.
1974-01-01
A fixed-base simulator program was conducted to define the problems and methods for solution associated with performing decelerating landing approaches on a representative STOL transport having a high wing and equipped with an external-flow jet flap in combination with four high-bypass-ratio fan-jet engines. Real-time digital simulation techniques were used. The computer was programed with equations of motion for six degrees of freedom and the aerodynamic inputs were based on measured wind-tunnel data. The pilot's task was to capture the localizer and the glide slope and to maintain them as closely as possible while decelerating from an initial airspeed of 140 knots to a final airspeed of 75 knots, while under IFR conditions.
NASA Astrophysics Data System (ADS)
Cartoixà, Xavier; Dettori, Riccardo; Melis, Claudio; Colombo, Luciano; Rurali, Riccardo
2016-07-01
We study thermal transport in porous Si nanowires (SiNWs) by means of approach-to-equilibrium molecular dynamics simulations. We show that the presence of pores greatly reduces the thermal conductivity, κ, of the SiNWs as long mean free path phonons are suppressed. We address explicitly the dependence of κ on different features of the pore topology—such as the porosity and the pore diameter—and on the nanowire (NW) geometry—diameter and length. We use the results of the molecular dynamics calculations to tune an effective model, which is capable of capturing the dependence of κ on porosity and NW diameter. The model illustrates the failure of Matthiessen's rule to describe the coupling between boundary and pore scattering, which we account for by the inclusion of an additional empirical term.
High-Payoff Space Transportation Design Approach with a Technology Integration Strategy
NASA Technical Reports Server (NTRS)
McCleskey, C. M.; Rhodes, R. E.; Chen, T.; Robinson, J.
2011-01-01
A general architectural design sequence is described to create a highly efficient, operable, and supportable design that achieves an affordable, repeatable, and sustainable transportation function. The paper covers the following aspects of this approach in more detail: (1) vehicle architectural concept considerations (including important strategies for greater reusability); (2) vehicle element propulsion system packaging considerations; (3) vehicle element functional definition; (4) external ground servicing and access considerations; and, (5) simplified guidance, navigation, flight control and avionics communications considerations. Additionally, a technology integration strategy is forwarded that includes: (a) ground and flight test prior to production commitments; (b) parallel stage propellant storage, such as concentric-nested tanks; (c) high thrust, LOX-rich, LOX-cooled first stage earth-to-orbit main engine; (d) non-toxic, day-of-launch-loaded propellants for upper stages and in-space propulsion; (e) electric propulsion and aero stage control.
Spatially-resolved investigation of transport in semiconductors: a photothermal deflection approach
Skumanich, A.; Fournier, D.; Boccara, A.C.; Amer, N.M.
1985-06-01
The unique ability of photothermal deflection spectroscopy to probe the local index of refraction of matter is exploited to investigate, in a spatially-resolved manner, thermal and electronic transport in semiconductors. An added advantage of this approach is that it is contactless; hence, it obviates the classical problems associated with electrodes and contacts. The basic premise of the technique is the use of the heat associated with non-radiative processes (e.g., recombination of carriers) to deflect a focussed laser probe beam (sub-gap energy) propagating through the semiconductor. The deflection of the probe beam is caused by a change in the refractive index of the sample which is in turn governed by carrier diffusion and recombination.
New Approaches to Overcome Transport Related Drug Resistance in Trypanosomatid Parasites
Garcia-Salcedo, Jose A.; Unciti-Broceta, Juan D.; Valverde-Pozo, Javier; Soriano, Miguel
2016-01-01
Leishmania and Trypanosoma are members of the Trypanosomatidae family that cause severe human infections such as leishmaniasis, Chagas disease, and sleeping sickness affecting millions of people worldwide. Despite efforts to eradicate them, migrations are expanding these infections to developing countries. There are no vaccines available and current treatments depend only on chemotherapy. Drug resistance is a major obstacle for the treatment of these diseases given that existing drugs are old and limited, with some having severe side effects. Most resistance mechanisms developed by these parasites are related with a decreased uptake or increased efflux of the drug due to mutations or altered expression of membrane transporters. Different new approaches have been elaborated that can overcome these mechanisms of resistance including the use of inhibitors of efflux pumps and drug carriers for both active and passive targeting. Here we review new formulations that have been successfully applied to circumvent resistance related to drug transporters, opening alternative ways to solve drug resistance in protozoan parasitic diseases. PMID:27733833
A second order residual based predictor-corrector approach for time dependent pollutant transport
NASA Astrophysics Data System (ADS)
Pavan, S.; Hervouet, J.-M.; Ricchiuto, M.; Ata, R.
2016-08-01
We present a second order residual distribution scheme for scalar transport problems in shallow water flows. The scheme, suitable for the unsteady cases, is obtained adapting to the shallow water context the explicit Runge-Kutta schemes for scalar equations [1]. The resulting scheme is decoupled from the hydrodynamics yet the continuity equation has to be considered in order to respect some important numerical properties at discrete level. Beyond the classical characteristics of the residual formulation presented in [1,2], we introduce the possibility to iterate the corrector step in order to improve the accuracy of the scheme. Another novelty is that the scheme is based on a precise monotonicity condition which guarantees the respect of the maximum principle. We thus end up with a scheme which is mass conservative, second order accurate and monotone. These properties are checked in the numerical tests, where the proposed approach is also compared to some finite volume schemes on unstructured grids. The results obtained show the interest in adopting the predictor-corrector scheme for pollutant transport applications, where conservation of the mass, monotonicity and accuracy are the most relevant concerns.
NASA Astrophysics Data System (ADS)
Majdalani, Samer; Michel, Eric; di Pietro, Liliana; Angulo-Jaramillo, Rafael; Rousseau, Marine
2007-05-01
Understanding particle movement in soils is a major concern for both geotechnics and soil physics with regard to environmental protection and water resources management. This paper describes a model for mobilization and preferential transport of soil particles through structured soils. The approach combines a kinematic-dispersive wave model for preferential water flow with a convective-dispersive equation subject to a source/sink term for particle transport and mobilization. Particle detachment from macropore walls is considered during both the steady and transient water flow regimes. It is assumed to follow first-order kinetics with a varying detachment efficiency, which depends on the history of the detachment process. Estimates of model parameters are obtained by comparing simulations with experimental particle breakthrough curves obtained during infiltrations through undisturbed soil columns. Both water flux and particle concentrations are satisfactorily simulated by the model. Particle mobilization parameters favoring both attachment and detachment of particles are related to the incoming solution ionic strength by a Fermi-type function.
Modeling PSA Problems - II: A Cell-to-Cell Transport Theory Approach
Labeau, P.E.; Izquierdo, J.M.
2005-06-15
In the first paper of this series, we presented an extension of the classical theory of dynamic reliability in which the actual occurrence of an event causing a change in the system dynamics is possibly delayed. The concept of stimulus activation, which triggers the realization of an event after a distributed time delay, was introduced. This gives a new understanding of competing events in the sequence delineation process.In the context of the level-2 probabilistic safety analysis (PSA), the information on stimulus activation mainly consists of regions of the process variables space where the activation can occur with a given probability. The evolution equations of the extended theory of probabilistic dynamics are therefore particularized to a transport process between discrete cells defined in phase-space on this basis. Doing so, an integrated and coherent approach to level-2 PSA problems is propounded. This amounts to including the stimulus concept and the associated stochastic delays discussed in the first paper in the frame of a cell-to-cell transport process.In addition, this discrete model provides a theoretical basis for the definition of appropriate numerical schemes for integrated level-2 PSA applications.
NASA Astrophysics Data System (ADS)
Barreto, Lucas; Perkins, Edward; Johannsen, Jens; Ulstrup, Søren; Fromm, Felix; Raidel, Christian; Seyller, Thomas; Hofmann, Philip
2013-01-01
The electronic transport properties of epitaxial monolayer graphene (MLG) and hydrogen-intercalated quasi free-standing bilayer graphene (QFBLG) on SiC(0001) are investigated by micro multi-point probes. Using a probe with 12 contacts, we perform four-point probe measurements with the possibility to effectively vary the contact spacing over more than one order of magnitude, allowing us to establish that the transport is purely two-dimensional. Combined with the carrier density obtained by angle-resolved photoemission spectroscopy, we find the room temperature mobility of MLG to be (870±120) cm2/V s. The transport in QFBLG is also found to be two-dimensional with a mobility of (1600±160) cm2/V s.
Inference of reactive transport model parameters using a Bayesian multivariate approach
NASA Astrophysics Data System (ADS)
Carniato, Luca; Schoups, Gerrit; van de Giesen, Nick
2014-08-01
Parameter estimation of subsurface transport models from multispecies data requires the definition of an objective function that includes different types of measurements. Common approaches are weighted least squares (WLS), where weights are specified a priori for each measurement, and weighted least squares with weight estimation (WLS(we)) where weights are estimated from the data together with the parameters. In this study, we formulate the parameter estimation task as a multivariate Bayesian inference problem. The WLS and WLS(we) methods are special cases in this framework, corresponding to specific prior assumptions about the residual covariance matrix. The Bayesian perspective allows for generalizations to cases where residual correlation is important and for efficient inference by analytically integrating out the variances (weights) and selected covariances from the joint posterior. Specifically, the WLS and WLS(we) methods are compared to a multivariate (MV) approach that accounts for specific residual correlations without the need for explicit estimation of the error parameters. When applied to inference of reactive transport model parameters from column-scale data on dissolved species concentrations, the following results were obtained: (1) accounting for residual correlation between species provides more accurate parameter estimation for high residual correlation levels whereas its influence for predictive uncertainty is negligible, (2) integrating out the (co)variances leads to an efficient estimation of the full joint posterior with a reduced computational effort compared to the WLS(we) method, and (3) in the presence of model structural errors, none of the methods is able to identify the correct parameter values.
NASA Astrophysics Data System (ADS)
Hendrickson, Heidi Phillips
A fundamental understanding of charge separation in organic materials is necessary for the rational design of optoelectronic devices suited for renewable energy applications and requires a combination of theoretical, computational, and experimental methods. Density functional theory (DFT) and time-dependent (TD)DFT are cost effective ab-initio approaches for calculating fundamental properties of large molecular systems, however conventional DFT methods have been known to fail in accurately characterizing frontier orbital gaps and charge transfer states in molecular systems. In this dissertation, these shortcomings are addressed by implementing an optimally-tuned range-separated hybrid (OT-RSH) functional approach within DFT and TDDFT. The first part of this thesis presents the way in which RSH-DFT addresses the shortcomings in conventional DFT. Environmentally-corrected RSH-DFT frontier orbital energies are shown to correspond to thin film measurements for a set of organic semiconducting molecules. Likewise, the improved RSH-TDDFT description of charge transfer excitations is benchmarked using a model ethene dimer and silsesquioxane molecules. In the second part of this thesis, RSH-DFT is applied to chromophore-functionalized silsesquioxanes, which are currently investigated as candidates for building blocks in optoelectronic applications. RSH-DFT provides insight into the nature of absorptive and emissive states in silsesquioxanes. While absorption primarily involves transitions localized on one chromophore, charge transfer between chromophores and between chromophore and silsesquioxane cage have been identified. The RSH-DFT approach, including a protocol accounting for complex environmental effects on charge transfer energies, was tested and validated against experimental measurements. The third part of this thesis addresses quantum transport through nano-scale junctions. The ability to quantify a molecular junction via spectroscopic methods is crucial to their
NASA Astrophysics Data System (ADS)
Kou, Wenjun; Griffith, Boyce E.; Pandolfino, John E.; Kahrilas, Peter J.; Patankar, Neelesh A.
2015-11-01
This work extends a fiber-based immersed boundary (IB) model of esophageal transport by incorporating a continuum model of the deformable esophageal wall. The continuum-based esophagus model adopts finite element approach that is capable of describing more complex and realistic material properties and geometries. The leakage from mismatch between Lagrangian and Eulerian meshes resulting from large deformations of the esophageal wall is avoided by careful choice of interaction points. The esophagus model, which is described as a multi-layered, fiber-reinforced nonlinear elastic material, is coupled to bolus and muscle-activation models using the IB approach to form the esophageal transport model. Cases of esophageal transport with different esophagus models are studied. Results on the transport characteristics, including pressure field and esophageal wall kinematics and stress, are analyzed and compared. Support from NIH grant R01 DK56033 and R01 DK079902 is gratefully acknowledged. BEG is supported by NSF award ACI 1460334.
Kópházi, József Lathouwers, Danny
2015-09-15
In this paper a new method for the discretization of the radiation transport equation is presented, based on a discontinuous Galerkin method in space and angle that allows for local refinement in angle where any spatial element can support its own angular discretization. To cope with the discontinuous spatial nature of the solution, a generalized Riemann procedure is required to distinguish between incoming and outgoing contributions of the numerical fluxes. A new consistent framework is introduced that is based on the solution of a generalized eigenvalue problem. The resulting numerical fluxes for the various possible cases where neighboring elements have an equal, higher or lower level of refinement in angle are derived based on tensor algebra and the resulting expressions have a very clear physical interpretation. The choice of discontinuous trial functions not only has the advantage of easing local refinement, it also facilitates the use of efficient sweep-based solvers due to decoupling of unknowns on a large scale thereby approaching the efficiency of discrete ordinates methods with local angular resolution. The approach is illustrated by a series of numerical experiments. Results show high orders of convergence for the scalar flux on angular refinement. The generalized Riemann upwinding procedure leads to stable and consistent solutions. Further the sweep-based solver performs well when used as a preconditioner for a Krylov method.
Li, H.; Li, G.
2014-08-28
An accelerated Finite Element Contact Block Reduction (FECBR) approach is presented for computational analysis of ballistic transport in nanoscale electronic devices with arbitrary geometry and unstructured mesh. Finite element formulation is developed for the theoretical CBR/Poisson model. The FECBR approach is accelerated through eigen-pair reduction, lead mode space projection, and component mode synthesis techniques. The accelerated FECBR is applied to perform quantum mechanical ballistic transport analysis of a DG-MOSFET with taper-shaped extensions and a DG-MOSFET with Si/SiO{sub 2} interface roughness. The computed electrical transport properties of the devices obtained from the accelerated FECBR approach and associated computational cost as a function of system degrees of freedom are compared with those obtained from the original CBR and direct inversion methods. The performance of the accelerated FECBR in both its accuracy and efficiency is demonstrated.
Lubatsch, Andreas; Frank, Regine
2014-08-20
We report a quantum field theoretical description of light transport and random lasing. The Bethe-Salpeter equation is solved including maximally crossed diagrams and non-elastic scattering. This is the first theoretical framework that combines so called off-shell scattering and lasing in random media. We present results for the self-consistent scattering mean free path that varies over the width of the sample. Further we discuss the density dependent correlation length of self-consistent transport in disordered media composed of semi-conductor Mie scatterers.
Miller, Cass T.
2009-01-01
This work is the fifth in a series of papers on the thermodynamically constrained averaging theory (TCAT) approach for modeling flow and transport phenomena in multiscale porous medium systems. The general TCAT framework and the mathematical foundation presented in previous works are used to develop models that describe species transport and single-fluid-phase flow through a porous medium system in varying physical regimes. Classical irreversible thermodynamics formulations for species in fluids, solids, and interfaces are developed. Two different approaches are presented, one that makes use of a momentum equation for each entity along with constitutive relations for species diffusion and dispersion, and a second approach that makes use of a momentum equation for each species in an entity. The alternative models are developed by relying upon different approaches to constrain an entropy inequality using mass, momentum, and energy conservation equations. The resultant constrained entropy inequality is simplified and used to guide the development of closed models. Specific instances of dilute and non-dilute systems are examined and compared to alternative formulation approaches. PMID:22563137
NASA Astrophysics Data System (ADS)
Bullen, T. D.; Bailey, S. W.; McGuire, K. J.; Brousseau, P.; Ross, D. S.; Bourgault, R.; Zimmer, M. A.
2010-12-01
Understanding the origin of metals in watersheds, as well as the transport and cycling processes that affect them is of critical importance to watershed science. Metals can be derived both from weathering of minerals in the watershed soils and bedrock and from atmospheric deposition, and can have highly variable residence times in the watershed due to cycling through plant communities and retention in secondary mineral phases prior to release to drainage waters. Although much has been learned about metal cycling and transport through watersheds using simple “box model” approaches that define unique input, output and processing terms, the fact remains that watersheds are inherently complex and variable in terms of substrate structure, hydrologic flowpaths and the influence of plants, all of which affect the chemical composition of water that ultimately passes through the watershed outlet. In an effort to unravel some of this complexity at a watershed scale, we have initiated an interdisciplinary, hydropedology-focused study of the hydrologic reference watershed (Watershed 3) at the Hubbard Brook Experimental Forest in New Hampshire, USA. This 41 hectare headwater catchment consists of a beech-birch-maple-spruce forest growing on soils developed on granitoid glacial till that mantles Paleozoic metamorphic bedrock. Soils vary from lateral spodosols downslope from bedrock exposures near the watershed crest to vertical and bi-modal spodosols along hillslopes to umbrepts at toe-slope positions and inferred hydrologic pinch points created by bedrock and till structure. Using a variety of chemical and isotope tracers (e.g., K/Na, Ca/Sr, Sr/Ba, Fe/Mn, 87Sr/86Sr, Ca-Sr-Fe stable isotopes) on water, soil and plant samples in an end-member mixing analysis approach, we are attempting to discretize the watershed according to soil types encountered along determined hydrologic flowpaths in order better constrain the various biogeochemical processes that control the delivery of
Evidence-based approach to assess passive diffusion and carrier-mediated drug transport.
Di, Li; Artursson, Per; Avdeef, Alex; Ecker, Gerhard F; Faller, Bernard; Fischer, Holger; Houston, J Brian; Kansy, Manfred; Kerns, Edward H; Krämer, Stefanie D; Lennernäs, Hans; Sugano, Kiyohiko
2012-08-01
Evidence supporting the action of passive diffusion and carrier-mediated (CM) transport in drug bioavailability and disposition is discussed to refute the recently proposed theory that drug transport is CM-only and that new transporters will be discovered that possess transport characteristics ascribed to passive diffusion. Misconceptions and faulty speculations are addressed to provide reliable guidance on choosing appropriate tools for drug design and optimization.
Regional CO2 flux estimates from estuarine environments: a reactive-transport modeling approach
NASA Astrophysics Data System (ADS)
Goossens, Nicolas; Laruelle, Goulven G.; Arndt, Sandra; Regnier, Pierre
2013-04-01
Estuaries are key components of the land-ocean continuum and play an important role in the global carbon cycle. Large amounts of terrestrial carbon are channelled through estuaries before reaching the ocean. During estuarine transit, numerous biogeochemical processes transform the carbon flux, resulting in a significant CO2 evasion flux to the atmosphere. The global estuarine CO2 outgassing is evaluated at 0.25±0.25 PgC yr-1. Yet, these estimates rely on the extrapolation of local measurements and the scarcity of such measurements conducts to large uncertainties. Furthermore, the global quantification is biased towards anthropogenically impacted estuarine systems located in industrialized countries. Here we provide a first assessment of the estuarine carbon budget and, in particular, CO2 evasion fluxes using a generic and effective reactive-transport model (RTM) approach that is applicable at the regional scale. The new approach is based on the mutual dependency between estuarine geometry and hydrodynamics and uses idealized estuarine geometries. Global river databases (GLORICH) and watershed model outputs (GlobalNEWS) are used to quantify input fluxes for the generic estuarine model. The new modeling approach provides not only a quantification of the estuarine carbon budget, but also allows disentangling the relative contributions of biogeochemical and physical processes to estuarine CO2 emissions. Preliminary results are presented for the North Eastern coast of the US. Model results are consistent with observations and indicate that the net heterotrophy of these systems is the major contributor to estuarine CO2 fluxes (>50%), followed by outgassing of supersaturated riverine waters and nitrification. Results also highlight the strong seasonality in the biogeochemical dynamics. In addition, significant heterogeneity is observed across different estuaries due to spatial heterogeneities in climate forcing, estuarine geometry or riverine input fluxes. The proposed
An approach to selecting routes over which to transport excess salt from the Deaf Smith County Site
Not Available
1987-09-01
This report presents an approach to be utilized in the identification of rail and/or highway routes for the disposal of waste salt and other salt contaminated material from repository construction. Relevant issues regarding salt transport also are identified. The report identifies a sequence of activities that precede actual route selection, i.e., final selection of a salt disposal method and its location, refined estimates of salt shipment volume and schedule, followed by selection of rail or truck or a combination thereof, as the preferred transport mode. After these factors are known, the route selection process can proceed. Chapter 2.0 of this report identifies directives and requirements that potentially could affect salt transport from the Deaf Smith site. A summary of salt disposal alternatives and reference cases is contained in Chapter 3.0. Chapter 4.0 identifies and discusses current methods of salt handling and transport in the United States, and also provides some perspective as to the volume of excess salt to be transported from the Deaf Smith site relative to current industry practices. Chapter 5.0 identifies an approach to the salt transportation issue, and suggests one system for evaluating alternative highway routes for truck shipments.
A Many-Task Parallel Approach for Multiscale Simulations of Subsurface Flow and Reactive Transport
Scheibe, Timothy D.; Yang, Xiaofan; Schuchardt, Karen L.; Agarwal, Khushbu; Chase, Jared M.; Palmer, Bruce J.; Tartakovsky, Alexandre M.
2014-12-16
Continuum-scale models have long been used to study subsurface flow, transport, and reactions but lack the ability to resolve processes that are governed by pore-scale mixing. Recently, pore-scale models, which explicitly resolve individual pores and soil grains, have been developed to more accurately model pore-scale phenomena, particularly reaction processes that are controlled by local mixing. However, pore-scale models are prohibitively expensive for modeling application-scale domains. This motivates the use of a hybrid multiscale approach in which continuum- and pore-scale codes are coupled either hierarchically or concurrently within an overall simulation domain (time and space). This approach is naturally suited to an adaptive, loosely-coupled many-task methodology with three potential levels of concurrency. Each individual code (pore- and continuum-scale) can be implemented in parallel; multiple semi-independent instances of the pore-scale code are required at each time step providing a second level of concurrency; and Monte Carlo simulations of the overall system to represent uncertainty in material property distributions provide a third level of concurrency. We have developed a hybrid multiscale model of a mixing-controlled reaction in a porous medium wherein the reaction occurs only over a limited portion of the domain. Loose, minimally-invasive coupling of pre-existing parallel continuum- and pore-scale codes has been accomplished by an adaptive script-based workflow implemented in the Swift workflow system. We describe here the methods used to create the model system, adaptively control multiple coupled instances of pore- and continuum-scale simulations, and maximize the scalability of the overall system. We present results of numerical experiments conducted on NERSC supercomputing systems; our results demonstrate that loose many-task coupling provides a scalable solution for multiscale subsurface simulations with minimal overhead.
NASA Astrophysics Data System (ADS)
Reyes, J.; Vizuete, W.; Serre, M. L.; Xu, Y.
2015-12-01
The EPA employs a vast monitoring network to measure ambient PM2.5 concentrations across the United States with one of its goals being to quantify exposure within the population. However, there are several areas of the country with sparse monitoring spatially and temporally. One means to fill in these monitoring gaps is to use PM2.5 modeled estimates from Chemical Transport Models (CTMs) specifically the Community Multi-scale Air Quality (CMAQ) model. CMAQ is able to provide complete spatial coverage but is subject to systematic and random error due to model uncertainty. Due to the deterministic nature of CMAQ, often these uncertainties are not quantified. Much effort is employed to quantify the efficacy of these models through different metrics of model performance. Currently evaluation is specific to only locations with observed data. Multiyear studies across the United States are challenging because the error and model performance of CMAQ are not uniform over such large space/time domains. Error changes regionally and temporally. Because of the complex mix of species that constitute PM2.5, CMAQ error is also a function of increasing PM2.5 concentration. To address this issue we introduce a model performance evaluation for PM2.5 CMAQ that is regionalized and non-linear. This model performance evaluation leads to error quantification for each CMAQ grid. Areas and time periods of error being better qualified. The regionalized error correction approach is non-linear and is therefore more flexible at characterizing model performance than approaches that rely on linearity assumptions and assume homoscedasticity of CMAQ predictions errors. Corrected CMAQ data are then incorporated into the modern geostatistical framework of Bayesian Maximum Entropy (BME). Through cross validation it is shown that incorporating error-corrected CMAQ data leads to more accurate estimates than just using observed data by themselves.
NASA Astrophysics Data System (ADS)
Tejedor, A.; Foufoula-Georgiou, E.; Longjas, A.; Zaliapin, I. V.
2014-12-01
River deltas are intricate landscapes with complex channel networks that self-organize to deliver water, sediment, and nutrients from the apex to the delta top and eventually to the coastal zone. The natural balance of material and energy fluxes which maintains a stable hydrologic, geomorphologic, and ecological state of a river delta, is often disrupted by external factors causing topological and dynamical changes in the delta structure and function. A formal quantitative framework for studying river delta topology and transport dynamics and their response to change is lacking. Here we present such a framework based on spectral graph theory and demonstrate its value in quantifying the complexity of the delta network topology, computing its steady state fluxes, and identifying upstream (contributing) and downstream (nourishment) areas from any point in the network. We use this framework to construct vulnerability maps that quantify the relative change of sediment and water delivery to the shoreline outlets in response to possible perturbations in hundreds of upstream links. This enables us to evaluate which links (hotspots) and what management scenarios would most influence flux delivery to the outlets, paving the way of systematically examining how local or spatially distributed delta interventions can be studied within a systems approach for delta sustainability.
Projectile fragmentation of 40,48Ca and isotopic scaling in a transport approach
NASA Astrophysics Data System (ADS)
Mikhailova, T. I.; Erdemchimeg, B.; Artukh, A. G.; Di Toro, M.; Wolter, H. H.
2016-07-01
We investigate theoretically projectile fragmentation in reactions of 40,48Ca on 9Be and 181Ta targets using a Boltzmann-type transport approach, which is supplemented by a statistical decay code to describe the de-excitation of the hot primary fragments. We determine the thermodynamical properties of the primary fragments and calculate the isotope distributions of the cold final fragments. These describe the data reasonably well. For the pairs of projectiles with different isotopic content we analyze the isotopic scaling (or isoscaling) of the final fragment distributions, which has been used to extract the symmetry energy of the primary source. The calculation exhibits isoscaling behavior for the total yields as do the experiments. We also perform an impact-parameter-dependent isoscaling analysis in view of the fact that the primary systems at different impact parameters have very different properties. Then the isoscaling behavior is less stringent, which we can attribute to specific structure effects of the 40,48Ca pair. The symmetry energy determined in this way depends on these structure effects.
Forward-backward transport theories of ion-solid interactions: Variational approach
NASA Astrophysics Data System (ADS)
Prinja, Anil K.
1989-05-01
The relationship between the popular so-called backward or Lindhard-type transport equations for linear energetic cascades and the direct or forward Boltzmann equation description is rigorously examined for an arbitrary atomic species mix. A variational principle is systematically derived that characterizes the forward model with generalized boundary conditions (internal reflection at a free surface) and is extremized to yield self-consistently the adjoint equations and boundary conditions as components of the corresponding Euler-Lagrange system. The adjoint function is treated purely as a mathematical artifact, which follows naturally from the variational principle. Dubious physical arguments to assign adjoint boundary conditions are thereby avoided. A truly backward description is derived from the adjoint formalism, which under the assumption of space and time homogeneity, reduces to the familiar Lindhard form. The Lindhard-type equations are seen to be neither backward nor forward equations but assume a hybrid form. In contrast, the forward and truly backward (or adjoint) models are exact and of general validity. They are complementary approaches and thus describe a duality that is mediated by the variational principle.
Ganeshkumar, P; Gokulakrishnan, P
2015-01-01
In Indian four-lane express highway, millions of vehicles are travelling every day. Accidents are unfortunate and frequently occurring in these highways causing deaths, increase in death toll, and damage to infrastructure. A mechanism is required to avoid such road accidents at the maximum to reduce the death toll. An Emergency Situation Prediction Mechanism, a novel and proactive approach, is proposed in this paper for achieving the best of Intelligent Transportation System using Vehicular Ad Hoc Network. ESPM intends to predict the possibility of occurrence of an accident in an Indian four-lane express highway. In ESPM, the emergency situation prediction is done by the Road Side Unit based on (i) the Status Report sent by the vehicles in the range of RSU and (ii) the road traffic flow analysis done by the RSU. Once the emergency situation or accident is predicted in advance, an Emergency Warning Message is constructed and disseminated to all vehicles in the area of RSU to alert and prevent the vehicles from accidents. ESPM performs well in emergency situation prediction in advance to the occurrence of an accident. ESPM predicts the emergency situation within 0.20 seconds which is comparatively less than the statistical value. The prediction accuracy of ESPM against vehicle density is found better in different traffic scenarios.
Description of sorbing tracers transport in fractured media using the lattice model approach.
Jiménez-Hornero, Francisco J; Giráldez, Juan V; Laguna, Ana
2005-12-01
The transport of contaminants in fractured media is a complex phenomenon with a great environmental impact. It has been described with several models, most of them based on complex partial differential equations, that are difficult to apply when equilibrium and nonequilibrium dynamics are considered in complex boundaries. With the aim of overcoming this limitation, a combination of two lattice Bathnagar, Gross and Krook (BGK) models, derived from the lattice Boltzmann model, is proposed in this paper. The fractured medium is assumed to be a single fissure in a porous rock matrix. The proposed approach permits us to deal with two processes with different length scales: advection-dispersion in the fissure and diffusion within the rock matrix. In addition to the mentioned phenomena, sorption reactions are also considered. The combined model has been tested using the experimental breakthrough curves obtained by Garnier et al. (Garnier, J.M., Crampon, N., Préaux, C., Porel, G., Vreulx, M., 1985. Traçage par 13C, 2H, I- et uranine dans la nappe de la craie sénonienne en écoulement radial convergent (Béthune, France). J. Hidrol. 78, 379-392.) giving acceptable results. A study on the influence of the lattice BGK models parameters controlling sorption and matrix diffusion on the breakthrough curves shape is included. PMID:16183166
Gokulakrishnan, P.
2015-01-01
In Indian four-lane express highway, millions of vehicles are travelling every day. Accidents are unfortunate and frequently occurring in these highways causing deaths, increase in death toll, and damage to infrastructure. A mechanism is required to avoid such road accidents at the maximum to reduce the death toll. An Emergency Situation Prediction Mechanism, a novel and proactive approach, is proposed in this paper for achieving the best of Intelligent Transportation System using Vehicular Ad Hoc Network. ESPM intends to predict the possibility of occurrence of an accident in an Indian four-lane express highway. In ESPM, the emergency situation prediction is done by the Road Side Unit based on (i) the Status Report sent by the vehicles in the range of RSU and (ii) the road traffic flow analysis done by the RSU. Once the emergency situation or accident is predicted in advance, an Emergency Warning Message is constructed and disseminated to all vehicles in the area of RSU to alert and prevent the vehicles from accidents. ESPM performs well in emergency situation prediction in advance to the occurrence of an accident. ESPM predicts the emergency situation within 0.20 seconds which is comparatively less than the statistical value. The prediction accuracy of ESPM against vehicle density is found better in different traffic scenarios. PMID:26065014
Bettaney, Kim E; Sukumar, Preethi; Hussain, Rohanah; Siligardi, Giuliano; Henderson, Peter J F; Patching, Simon G
2013-02-01
Abstract A systematic approach was used for the cloning and amplified expression in Escherichia coli of the genes for each of three inositol transport proteins (IolF, IolT, YfiG) from Bacillus subtilis that are evolutionarily-related to human transporters. Inducible amplified expression of each was achieved to levels of ∼ 10-15% of total protein in E. coli inner membrane preparations. The functional integrity of each heterologously-expressed protein was demonstrated by measuring the kinetics of (3)H-myo-inositol transport into energized whole cells; this confirmed that IolT is the major inositol transporter, IolF is an inefficient transporter of this substrate and demonstrated that YfiG is an inositol transport protein for the first time. Competition for (3)H-myo-inositol transport by 17 unlabelled compounds revealed all three proteins to be highly specific in recognizing inositols over sugars. IolT was confirmed to be highly specific for both myo- and D-chiro-inositol and IolF was confirmed to prefer D-chiro-inositol over myo-inositol. YfiG selectively recognized myo-inositol, D-chiro-inositol and, uniquely, L-chiro-inositol. All three proteins were successfully solubilized and purified in milligram quantities from inner membrane preparations and their suitability for inclusion in crystallization trials was assessed by analysis of structural integrity and thermal stability using circular dichroism spectroscopy followed by examination for monodispersity using gel filtration chromatography.
Modelling nitrogen transport and turnover at the hillslope scale - a process oriented approach
NASA Astrophysics Data System (ADS)
Klatt, S.; Haas, E.; Kiese, R.; Butterbach-Bahl, K.; Wlotzka, M.; Heuveline, V.; Kraft, P.; Breuer, L.
2012-12-01
Biogeochemical models used for simulating greenhouse gas (GHG) emissions are mainly designed for the plot scale. Lateral fluxes of nutrients such as nitrate, which may be important drivers for soil GHG emissions, are not or only scarcely considered and explored in such models. This is due to the complexity of microbiological, physic-chemical and plant processes which need to be investigated and simulated along one spatial dimension, the depth, so that the introduction of a second (a hillslope) or third (entire landscapes) spatial dimension is likely to introduce additional complexity which can hardly be handled by most models. However, plot scale models, validated with data obtained at plot scale studies, will systematically under- or overestimate key GHG production and consumption processes if lateral in- or efflux of nutrients to or from a given site is of significant importance. E.g. in laterally connected environments, such as riparian zones denitrification will be fuelled by lateral influx of nitrate from uphill positioned fertilized land. Thus, landscape approaches are needed to identify and realistically simulate GHG emissions. The poster will present a coupled modeling system consisting of the fully distributed hydrology model CMF coupled to the regional ecosystem model LandscapeDNDC. The model coupling was preformed using the OpenPALM coupler from Cerfacs, France which is based on parallel computer technology. The coupler synchronizes the two models with respect to simulation time and performs the exchange of data (water fluxes, nutrient concentrations, etc.) from and to the models. The resulting coupled hydrology-ecosystem model was applied to simulate carbon and nitrogen cycling along a three dimensional virtual hillslope. In the experiment the uphill section of the domain consists of intensive arable land (maize - wheat rotation with up to 300 kg N fertilization) whereas the lowland section and riparian zone consists of extensive grassland. The
Transport properties of long straight nano-channels in electrolyte solutions: a systematic approach.
Yaroshchuk, Andriy E
2011-10-14
The principle of local thermodynamic equilibrium is systematically employed for obtaining various transport properties of long straight nano-channels. The concept of virtual solution is used to describe situations of non-negligible overlap of diffuse parts of electric double layers (EDLs) in nano-channels. Generic expressions for a variety of transport properties of long straight nano-channels are obtained in terms of quasi-equilibrium distribution coefficients of ions and functionals of quasi-equilibrium distribution of electrostatic potential. Further, the Poisson-Boltzmann approach is used to specify these expressions for long straight slit-like nano-channels. In the approximation of non-overlapped diffuse parts of double electric layers in nano-channels, simple analytical expressions are obtained for the apparent electrophoretic mobilities of (trace) analytes of arbitrary charge as well as for the salt reflection coefficient (osmotic pressure), salt diffusion permeability and electro-viscosity (electrokinetic energy conversion). The approximate solutions are compared with the results of rigorous solution of non-linearized Poisson-Boltzmann equation, and the accuracy of approximation is shown to be typically excellent when the nano-channel half-height exceeds ca.3 Debye screening lengths. Due to non-negligible electrostatic adsorption of ions by nano-channels, the apparent electrophoretic mobilities of counter-ionic analytes in nano-channels are smaller than in micro-channels whereas those of co-ionic analytes are larger. This dependence on the charge is useful for the separation of analytes of close electrophoretic mobilities. The osmotic pressure is shown to be positive, negative or pass through maxima as a function of applied salt-concentration difference within a fairly narrow range of ratios of nano-channel height to the Debye screening length. The diffusion permeability of charged nano-channels to single salts is demonstrated (for the first time) to be
Woody debris transport modelling by a coupled DE-SW approach
NASA Astrophysics Data System (ADS)
Persi, Elisabetta; Petaccia, Gabriella; Sibilla, Stefano
2016-04-01
The presence of wood in rivers is gaining more and more attention: on one side, the inclusion of woody debris in streams is emphasized for its ecological benefits; on the other hand, particular attention must be paid to its management, not to affect hydraulic safety. Recent events have shown that wood can be mobilized during floodings (Comiti et al. 2008, Lange and Bezzola 2006), aggravating inundations, in particular near urban areas. For this reason, the inclusion of woody debris influence on the prediction of flooded areas is an important step toward the reduction of hydraulic risk. Numerical modelling plays an important role to this purpose. Ruiz-Villanueva et al. (2014) use a two-dimensional numerical model to calculate the kinetics of cylindrical woody debris transport, taking into account also the hydrodynamic effects of wood. The model here presented couples a Discrete Element approach (DE) for the calculation of motion of a cylindrical log with the solution of the Shallow Water Equations (SW), in order to simulate woody debris transport in a two-dimensional stream. In a first step, drag force, added mass force and side force are calculated from flow and log velocities, assuming a reference area and hydrodynamic coefficients taken from literature. Then, the equations of dynamics are solved to model the planar roto-translation of the wooden cylinder. Model results and its physical reliability are clearly affected by the values of the drag and side coefficients, which in turn depend upon log submergence and angle towards the flow direction. Experimental studies to evaluate drag and side coefficients can be found for a submerged cylinder, with various orientations (Gippel et al. 1996; Hoang et al. 2015). To extend such results to the case of a floating (non-totally submerged) cylinder, the authors performed a series of laboratory tests whose outcomes are implemented in the proposed DE-SW model, to assess the effects of these values on the dynamic of woody
NASA Astrophysics Data System (ADS)
Santoro, Francesco; Bellomo, Alessandro; Bolle, Andrea; Vittori, Roberto
2014-08-01
This paper summarizes the results of the pre-feasibility studies carried out in 2012 on the concept of sub orbital and hypersonic, high altitude flight in support of future generation transportation. Currently, while the High Altitude Flight is mostly instrumental to touristic purposes and emphasizes the so called Spaceports as futuristic, customers-luring airports featured with all the support services, the “Spacegate” concept deals with scheduled traveling in the upper part of the atmosphere between two points over the Earth surface, with significant reduction of the transfer time. The first part of the paper provides a theoretical approach to the matter, by proposing an “operational” mapping of the atmosphere as well as of the different kinds of flight occurring at High Altitude. The second part of the paper addresses the problem of the limited human capability of maintaining an active control of the vehicle during the re-entry phase and introduces the “Spacegate” concept as the conical portion of the atmosphere above the landing site, whose surface delimits the spiral-descending trajectories that the pilot can travel for a safe re-entry. This paper further outlines the results of the preliminary definition of top level operational requirements and derived architecture functional modules in support to the “Spacegate” implementation. Special attention was given to the favorable geographic and climatic conditions of Italy that make this Country suitable enough for future experimental sub orbital flights and related operations. An initial analysis was performed on the regulatory backbone that has to be built to properly operate High Altitude Flight vehicles in Italy according to the concept of an Italian “Spacegate”. A Preliminary Master Plan/Road Map for the “Spacegate” has been laid out, with special emphasis to selected near term activities and support infrastructures necessary to be carried out to better refine the study in preparation
A dynamical quasiparticle approach for the QGP bulk and transport properties
NASA Astrophysics Data System (ADS)
Berrehrah, Hamza; Bratkovskaya, Elena; Steinert, Thorsten; Cassing, Wolfgang
2016-05-01
The properties of quantum chromodynamics (QCD) nowadays are accessible by lattice QCD calculations at vanishing quark chemical potential μq = 0, but often lack a transparent physical interpretation. In this review, we report about results from an extended dynamical quasiparticle model (DQPM∗) in which the effective parton propagators have a complex self-energy that depends on the temperature T of the medium as well as on the chemical potential μq and the parton three-momentum p with respect to the medium at rest. It is demonstrated that this approach allows for a good description of QCD thermodynamics with respect to the entropy density, pressure, etc. above the critical temperature Tc ≈ 158 MeV. Furthermore, the quark susceptibility χq and the quark number density nq are found to be reproduced simultaneously at zero and finite quark chemical potential. The shear and bulk viscosities η,ζ, and the electric conductivity σe from the DQPM∗ also turn out in close agreement with lattice results for μq =0. The DQPM∗, furthermore, allows to evaluate the momentum p, T and μq dependencies of the partonic degrees of freedom also for larger μq which are mandatory for transport studies of heavy-ion collisions in the regime 5GeV < sNN < 10GeV. We finally calculate the charm quark diffusion coefficient Ds - evaluated from the differential cross-sections of partons in the medium for light and heavy quarks by employing the propagators and couplings from the DQPM - and compare it to the available lattice data. It is argued that the complete set of observables allows for a transparent interpretation of the properties of hot QCD.
Modeling of Coastal Effluent Transport: an Approach to Linking of Far-field and Near-field Models
Yang, Zhaoqing; Khangaonkar, Tarang P.
2008-09-01
One of the challenges in effluent transport modeling in coastal tidal environments is the proper calculation of initial dilution in connection with the far-field transport model. In this study, an approach of external linkage of far-field and near-field effluent transport models is presented, and applied to simulate the effluent transport in the Port Angeles Harbor, Washington in the Strait of Juan de Fuca. A near-field plume model was used to calculate the effluent initial dilution and a three-dimensional (3-D) hydrodynamic model was developed to simulate the tidal circulation and far-field effluent transport in the Port Angeles Harbor. In the present study, the hydrodynamic model was driven by tides and surface winds. Observed water surface elevation and velocity data were used to calibrate the model over a period covering the neap-spring tidal cycle. The model was also validated with observed surface drogue trajectory data. The model successfully reproduced the tidal dynamics in the study area and good agreements between model results and observed data were obtained. This study demonstrated that the linkage between the near-field and far-field models in effluent transport modeling can be achieved through iteratively adjusting the model grid sizes such that the far-field modeled dilution ratio and effluent concentration in the effluent discharge model grid cell match the concentration calculated by the near-field plume model.
Dharmala, Kiran; Yoo, Jin Wook; Lee, Chi H
2008-11-12
Drug efflux-transporters serve as a major barrier to anticancer drugs at the target site. One strategy to enhance the therapeutic efficacy of drugs against cancer is to increase their available concentrations at the target site by suppressing or modulating efflux-transporters. This manuscript deals with the development and evaluation of the particle type drug delivery system made of stearic acid (Solid Lipid Nanoparticle - SLN) and chitosan for the delivery of Phenethyl Isothiocyanate (PEITC), a tumor-suppressive agent, through the pulmonary route. The rationale behind the particle type drug delivery system involves a prior release of the efflux-transporter inhibitors, such as tamoxifen, verapamil HCl or nifedipine, to suppress or modulate the efflux activity of ABC transporters followed by the release of the efflux-transporter substrate, PEITC. The efficacy of Chitosan-SLN Microparticles (CSM) as a carrier for PEITC was evaluated by investigating the release profiles of PEITC loaded in CSM and its cytotoxicity in the presence or absence of the efflux-transporter inhibitors. An initial burst release of the inhibitors, followed by gradual, sustained release of PEITC and subsequent increase in cytotoxicity was observed. This finding indicated that the efflux transporter inhibitors significantly affected the PEITC uptake rate by Calu-3 cells. Judging from these results, CSM can be an efficient drug delivery system for the substrates susceptible to the efflux-transporters. PMID:18723057
Flight-test measurement of the noise reduction of a jet transport delayed flap approach procedure
NASA Technical Reports Server (NTRS)
Foster, J. D.; Lasagna, P. L.
1976-01-01
A delayed flap approach procedure was flight tested using the NASA CV-990 airplane to measure and analyze the noise produced beneath the flight path. Three other types of landing approaches were also flight tested to provide a comparison of the noise reduction benefits to the delayed flap approach. The conventional type of approach was used as a baseline to compare the effectiveness of the other approaches. The decelerating approach is a variation of the delayed flap approach. A detailed comparison of the ground perceived noise generated during the approaches is presented. For this comparison, the measured noise data were normalized to compensate for variations in aircraft weight and winds that occurred during the flight tests. The data show that the reduced flap approach offers some noise reduction, while the delayed flap and decelerating approaches offer significant noise reductions over the conventional approach.
Zhang, G. P.; Liu, Xiaojie; Wang, C. Z.; Yao, Y. X.; Zhang, Jian; Ho, K. M.
2013-02-12
Structural and electronic properties, including deformation, magnetic moment, Mulliken population, bond order, as well as electronic transport properties, of zigzag graphene nanoribbon (ZGNR) with Co adatoms on hollow sites are investigated by quasi-atomic minimal basis orbits (QUAMBOs), a first-principles tight binding (TB) scheme based on density functional theory (DFT), combined with a non-equilibrium Green's function. For electronic transport, below the Fermi level the transmission is strongly suppressed and spin dependent as a result of magnetism by Co adatom adsorption, while above the Fermi level the transmission is slightly distorted and spin independent. Due to the local environment dependence of QUAMBOs–TB parameters, we construct QUAMBOs–TB parameters of ZGNR leads and ZGNR with Co adatoms on hollow center sites by a divide-and-conquer approach, and accurately reproduce the electronic transmission behavior. Our QUAMBO–NEGF method is a new and promising way of examining electronic transport in large-scale systems.
Berkolaiko, G.; Kuipers, J.
2013-12-15
Electronic transport through chaotic quantum dots exhibits universal behaviour which can be understood through the semiclassical approximation. Within the approximation, calculation of transport moments reduces to codifying classical correlations between scattering trajectories. These can be represented as ribbon graphs and we develop an algorithmic combinatorial method to generate all such graphs with a given genus. This provides an expansion of the linear transport moments for systems both with and without time reversal symmetry. The computational implementation is then able to progress several orders further than previous semiclassical formulae as well as those derived from an asymptotic expansion of random matrix results. The patterns observed also suggest a general form for the higher orders.
Mehmani, Yashar; Oostrom, Martinus; Balhoff, Matthew
2014-03-20
Several approaches have been developed in the literature for solving flow and transport at the pore-scale. Some authors use a direct modeling approach where the fundamental flow and transport equations are solved on the actual pore-space geometry. Such direct modeling, while very accurate, comes at a great computational cost. Network models are computationally more efficient because the pore-space morphology is approximated. Typically, a mixed cell method (MCM) is employed for solving the flow and transport system which assumes pore-level perfect mixing. This assumption is invalid at moderate to high Peclet regimes. In this work, a novel Eulerian perspective on modeling flow and transport at the pore-scale is developed. The new streamline splitting method (SSM) allows for circumventing the pore-level perfect mixing assumption, while maintaining the computational efficiency of pore-network models. SSM was verified with direct simulations and excellent matches were obtained against micromodel experiments across a wide range of pore-structure and fluid-flow parameters. The increase in the computational cost from MCM to SSM is shown to be minimal, while the accuracy of SSM is much higher than that of MCM and comparable to direct modeling approaches. Therefore, SSM can be regarded as an appropriate balance between incorporating detailed physics and controlling computational cost. The truly predictive capability of the model allows for the study of pore-level interactions of fluid flow and transport in different porous materials. In this paper, we apply SSM and MCM to study the effects of pore-level mixing on transverse dispersion in 3D disordered granular media.
Tosco, Tiziana; Sethi, Rajandrea
2010-12-01
The use of zerovalent iron micro- and nanoparticles (MZVI and NZVI) for groundwater remediation is hindered by colloidal instability, causing aggregation (for NZVI) and sedimentation (for MZVI) of the particles. Transportability of MZVI and NZVI in porous media was previously shown to be significantly increased if viscous shear-thinning fluids (xanthan gum solutions) are used as carrier fluids. In this work, a novel modeling approach is proposed and applied for the simulation of 1D flow and transport of highly concentrated (20 g/L) non-newtonian suspensions of MZVI and NZVI, amended with xanthan gum (3 g/L). The coupled model is able to simulate the flow of a shear thinning fluid including the variable apparent viscosity arising from changes in xanthan and suspended iron particle concentrations. The transport of iron particles is modeled using a dual-site approach accounting for straining and physicochemical deposition/release phenomena. A general formulation for reversible deposition is herein proposed, that includes all commonly applied dynamics (linear attachment, blocking, ripening). Clogging of the porous medium due to deposition of iron particles is modeled by tying porosity and permeability to deposited iron particles. The numerical model proved to adequately fit the transport tests conducted using both MZVI and NZVI and can develop into a powerful tool for the design and the implementation of full scale zerovalent iron applications.
A variational approach for dissipative quantum transport in a wide parameter space.
Zhang, Yu; Yam, ChiYung; Chen, GuanHua
2015-09-14
Recent development of theoretical method for dissipative quantum transport has achieved notable progresses in the weak or strong electron-phonon coupling regime. However, a generalized theory for dissipative quantum transport in a wide parameter space had not been established. In this work, a variational polaron theory for dissipative quantum transport in a wide range of electron-phonon coupling is developed. The optimal polaron transformation is determined by the optimization of the Feynman-Bogoliubov upper bound of free energy. The free energy minimization ends up with an optimal mean-field Hamiltonian and a minimal interaction Hamiltonian. Hence, second-order perturbation can be applied to the transformed system, resulting in an accurate and efficient method for the treatment of dissipative quantum transport with different electron-phonon coupling strength. Numerical benchmark calculation on a single site model coupled to one phonon mode is presented. PMID:26619516
SELECTION AND CALIBRATION OF SUBSURFACE REACTIVE TRANSPORT MODELS USING A SURROGATE-MODEL APPROACH
While standard techniques for uncertainty analysis have been successfully applied to groundwater flow models, extension to reactive transport is frustrated by numerous difficulties, including excessive computational burden and parameter non-uniqueness. This research introduces a...
A variational approach for dissipative quantum transport in a wide parameter space
Zhang, Yu Kwok, YanHo; Chen, GuanHua; Yam, ChiYung
2015-09-14
Recent development of theoretical method for dissipative quantum transport has achieved notable progresses in the weak or strong electron-phonon coupling regime. However, a generalized theory for dissipative quantum transport in a wide parameter space had not been established. In this work, a variational polaron theory for dissipative quantum transport in a wide range of electron-phonon coupling is developed. The optimal polaron transformation is determined by the optimization of the Feynman-Bogoliubov upper bound of free energy. The free energy minimization ends up with an optimal mean-field Hamiltonian and a minimal interaction Hamiltonian. Hence, second-order perturbation can be applied to the transformed system, resulting in an accurate and efficient method for the treatment of dissipative quantum transport with different electron-phonon coupling strength. Numerical benchmark calculation on a single site model coupled to one phonon mode is presented.
Devés, R; Krupka, R M
1978-06-16
Kinetic equations are derived for reversible inhibition of both active and facilitated transport systems for seven common experimental arrangements. It is shown that the unique features of transport kinetics may be exploited to give new kinds of information. It is also shown that that the familiar rules of enzyme kinetics, though often applied to transport, can be seriously misleading. The analysis leads to the following general conclusions: (1) A competitive mechanism frequently gives rise to non-competitive kinetics, depending on the experimental design, but a non-competitive mechanism never produces competitive kinetics. (2) Inhibition studies on exchange diffusion at equilibrium in non-active systems or in the final steady state in active systems are the only unambiguous kinetic tests to distinguish competitive from non-competitive mechanisms. (3) Substrate analogs that are bound to the carrier and transported are readily distinguished by inhibition kinetics from those not transported, even though both may rapidly enter the cell by another route. (4) Even in non-active systems competitive inhibitors commonly have far different affinities for the substrate sites on the two membranes faces: where sufficient non-polarity allows their penetration into the cell, inhibition kinetics readily establish such sideness in their action. (5) Inhibition kinetics of the mixed competitive and non-competitive type result from moderately asymmetrical binding of inhibitor at the substrate site. (6) Asymmetry is a necessary feature of active transport: hence studies of inhibition kinetics should provide important insights into its mechanism.
NASA Astrophysics Data System (ADS)
Bobik, P.; Boschini, M. J.; Della Torre, S.; Gervasi, M.; Grandi, D.; La Vacca, G.; Pensotti, S.; Putis, M.; Rancoita, P. G.; Rozza, D.; Tacconi, M.; Zannoni, M.
2016-05-01
The cosmic rays propagation inside the heliosphere is well described by a transport equation introduced by Parker in 1965. To solve this equation, several approaches were followed in the past. Recently, a Monte Carlo approach became widely used in force of its advantages with respect to other numerical methods. In this approach the transport equation is associated to a fully equivalent set of stochastic differential equations (SDE). This set is used to describe the stochastic path of quasi-particle from a source, e.g., the interstellar space, to a specific target, e.g., a detector at Earth. We present a comparison of forward-in-time and backward-in-time methods to solve the cosmic rays transport equation in the heliosphere. The Parker equation and the related set of SDE in the several formulations are treated in this paper. For the sake of clarity, this work is focused on the one-dimensional solutions. Results were compared with an alternative numerical solution, namely, Crank-Nicolson method, specifically developed for the case under study. The methods presented are fully consistent each others for energy greater than 400 MeV. The comparison between stochastic integrations and Crank-Nicolson allows us to estimate the systematic uncertainties of Monte Carlo methods. The forward-in-time stochastic integrations method showed a systematic uncertainty <5%, while backward-in-time stochastic integrations method showed a systematic uncertainty <1% in the studied energy range.
NASA Astrophysics Data System (ADS)
Guo, L.; Huang, H.; Gaston, D.; Redden, G. D.; Fox, D. T.; Fujita, Y.
2010-12-01
Inducing mineral precipitation in the subsurface is one potential strategy for immobilizing trace metal and radionuclide contaminants. Generating mineral precipitates in situ can be achieved by manipulating chemical conditions, typically through injection or in situ generation of reactants. How these reactants transport, mix and react within the medium controls the spatial distribution and composition of the resulting mineral phases. Multiple processes, including fluid flow, dispersive/diffusive transport of reactants, biogeochemical reactions and changes in porosity-permeability, are tightly coupled over a number of scales. Numerical modeling can be used to investigate the nonlinear coupling effects of these processes which are quite challenging to explore experimentally. Many subsurface reactive transport simulators employ a de-coupled or operator-splitting approach where transport equations and batch chemistry reactions are solved sequentially. However, such an approach has limited applicability for biogeochemical systems with fast kinetics and strong coupling between chemical reactions and medium properties. A massively parallel, fully coupled, fully implicit Reactive Transport simulator (referred to as “RAT”) based on a parallel multi-physics object-oriented simulation framework (MOOSE) has been developed at the Idaho National Laboratory. Within this simulator, systems of transport and reaction equations can be solved simultaneously in a fully coupled, fully implicit manner using the Jacobian Free Newton-Krylov (JFNK) method with additional advanced computing capabilities such as (1) physics-based preconditioning for solution convergence acceleration, (2) massively parallel computing and scalability, and (3) adaptive mesh refinements for 2D and 3D structured and unstructured mesh. The simulator was first tested against analytical solutions, then applied to simulating induced calcium carbonate mineral precipitation in 1D columns and 2D flow cells as analogs
NASA Technical Reports Server (NTRS)
Gasso, S.; Stein, A.; Marino, F.; Castellano, E.; Udisti, R.; Ceratto, J.
2010-01-01
The understanding of present atmospheric transport processes from Southern Hemisphere (SH) landmasses to Antarctica can improve the interpretation of stratigraphic data in Antarctic ice cores. In addition, long range transport can deliver key nutrients normally not available to marine ecosystems in the Southern Ocean and may trigger or enhance primary productivity. However, there is a dearth of observational based studies of dust transport in the SH. This work aims to improve current understanding of dust transport in the SH by showing a characterization of two dust events originating in the Patagonia desert (south end of South America). The approach is based on a combined and complementary use of satellite retrievals (detectors MISR, MODIS, GLAS ,POLDER, OMI,), transport model simulation (HYSPLIT) and surface observations near the sources and aerosol measurements in Antarctica (Neumayer and Concordia sites). Satellite imagery and visibility observations confirm dust emission in a stretch of dry lakes along the coast of the Tierra del Fuego (TdF) island (approx.54deg S) and from the shores of the Colihue Huapi lake in Central Patagonia (approx.46deg S) in February 2005. Model simulations initialized by these observations reproduce the timing of an observed increase in dust concentration at the Concordia Station and some of the observed increases in atmospheric aerosol absorption (here used as a dust proxy) in the Neumayer station. The TdF sources were the largest contributors of dust at both sites. The transit times from TdF to the Neumayer and Concordia sites are 6-7 and 9-10 days respectively. Lidar observations and model outputs coincide in placing most of the dust cloud in the boundary layer and suggest significant de- position over the ocean immediately downwind. Boundary layer dust was detected as far as 1800 km from the source and approx.800 km north of the South Georgia Island over the central sub-Antarctic Atlantic Ocean. Although the analysis suggests the
NASA Astrophysics Data System (ADS)
Ramanujam, Padma
1999-08-01
Public concern over the state of the environment has grown over the past decade. All indications are that this concern will continue to influence policy making into the foreseeable future. Road transport is seen as the major contributor to environmental degradation. Transportation planners around the world face the question: cleaner air and/or faster commutes? While individual vehicles can be made more environmentally friendly, the sheer scale of growth in world-wide vehicle numbers is projected to cause significant environmental degradation in the longer run, and in the absence of newer and stricter polices. It is a challenge for governments to find policies that ensure congestion-free metropolitan areas while guaranteeing both critical environmental quality levels and a sufficient infrastructure access to all groups involved. The objective of the dissertation is to provide a mathematical framework to study transportation policy models for the purpose of controlling congestion and pollution. Towards this objective. a series of transportation policy models are developed to study travel behavior and to quantity the reductions in congestion and automobile emissions. The dissertation begins with a brief historical overview of some of the pioneering works in urban transportation economics and later presents the theoretical foundation for the transportation policy models developed. The dissertation introduces single modal and multimodal transportation network policy models that accomplish road pricing with the imposition of goal targets on link loads. as well as, integrated traffic equilibrium models with marketable mobile emission permits. Furthermore, equilibrium conditions are derived for each model, and both qualitative analysis and computational procedures are studied. Finally, the dissertation concludes with a comparative study of the relationship between regulatory pricing models and marketable emission permit transportation models and a discussion on key factors
Reactive Transport Modeling: An Essential Tool and a New ResearchApproach for the Earth Sciences
Steefel, Carl I.; DePaolo, Donald J.; Lichtner, Peter C.
2005-08-25
Reactive transport modeling is an essential tool for the analysis of coupled physical, chemical, and biological processes in Earth systems, and has additional potential to better integrate the results from focused fundamental research on Earth materials. Appropriately designed models can describe the interactions of competing processes at a range of spatial and time scales, and hence are critical for connecting the advancing capabilities for materials characterization at the atomic scale with the macroscopic behavior of complex Earth systems. Reactive transport modeling has had a significant impact on the treatment of contaminant retardation in the subsurface, the description of elemental and nutrient fluxes between major Earth reservoirs, and in the treatment of deep Earth processes such as metamorphism and magma transport. Active topics of research include the development of pore scale and hybrid, or multiple continua, models to capture the scale dependence of coupled reactive transport processes. Frontier research questions, that are only now being addressed, include the effects of chemical microenvironments, coupled thermal mechanical chemical processes, controls on mineral fluid reaction rates in natural media, and scaling of reactive transport processes from the microscopic to pore to field scale.
Drummond, Jennifer D; Davies-Colley, Robert J; Stott, Rebecca; Sukias, James P; Nagels, John W; Sharp, Alice; Packman, Aaron I
2015-07-01
Long-term survival of pathogenic microorganisms in streams enables long-distance disease transmission. In order to manage water-borne diseases more effectively we need to better predict how microbes behave in freshwater systems, particularly how they are transported downstream in rivers. Microbes continuously immobilize and resuspend during downstream transport owing to a variety of processes including gravitational settling, attachment to in-stream structures such as submerged macrophytes, and hyporheic exchange and filtration within underlying sediments. We developed a stochastic model to describe these microbial transport and retention processes in rivers that also accounts for microbial inactivation. We used the model to assess the transport, retention, and inactivation of Escherichia coli in a small stream and the underlying streambed sediments as measured from multitracer injection experiments. The results demonstrate that the combination of laboratory experiments on sediment cores, stream reach-scale tracer experiments, and multiscale stochastic modeling improves assessment of microbial transport in streams. This study (1) demonstrates new observations of microbial dynamics in streams with improved data quality than prior studies, (2) advances a stochastic modeling framework to include microbial inactivation processes that we observed to be important in these streams, and (3) synthesizes new and existing data to evaluate seasonal dynamics.
Makedonska, Nataliia; Painter, Scott L.; Bui, Quan M.; Gable, Carl W.; Karra, Satish
2015-09-16
The discrete fracture network (DFN) model is a method to mimic discrete pathways for fluid flow through a fractured low-permeable rock mass, and may be combined with particle tracking simulations to address solute transport. However, experience has shown that it is challenging to obtain accurate transport results in three-dimensional DFNs because of the high computational burden and difficulty in constructing a high-quality unstructured computational mesh on simulated fractures. We present a new particle tracking capability, which is adapted to control volume (Voronoi polygons) flow solutions on unstructured grids (Delaunay triangulations) on three-dimensional DFNs. The locally mass-conserving finite-volume approach eliminates mass balance-related problems during particle tracking. The scalar fluxes calculated for each control volume face by the flow solver are used to reconstruct a Darcy velocity at each control volume centroid. The groundwater velocities can then be continuously interpolated to any point in the domain of interest. The control volumes at fracture intersections are split into four pieces, and the velocity is reconstructed independently on each piece, which results in multiple groundwater velocities at the intersection, one for each fracture on each side of the intersection line. This technique enables detailed particle transport representation through a complex DFN structure. Verified for small DFNs, the new simulation capability enables numerical experiments on advective transport in large DFNs to be performed. As a result, we demonstrate this particle transport approach on a DFN model using parameters similar to those of crystalline rock at a proposed geologic repository for spent nuclear fuel in Forsmark, Sweden.
Makedonska, Nataliia; Painter, Scott L.; Bui, Quan M.; Gable, Carl W.; Karra, Satish
2015-09-16
The discrete fracture network (DFN) model is a method to mimic discrete pathways for fluid flow through a fractured low-permeable rock mass, and may be combined with particle tracking simulations to address solute transport. However, experience has shown that it is challenging to obtain accurate transport results in three-dimensional DFNs because of the high computational burden and difficulty in constructing a high-quality unstructured computational mesh on simulated fractures. We present a new particle tracking capability, which is adapted to control volume (Voronoi polygons) flow solutions on unstructured grids (Delaunay triangulations) on three-dimensional DFNs. The locally mass-conserving finite-volume approach eliminates massmore » balance-related problems during particle tracking. The scalar fluxes calculated for each control volume face by the flow solver are used to reconstruct a Darcy velocity at each control volume centroid. The groundwater velocities can then be continuously interpolated to any point in the domain of interest. The control volumes at fracture intersections are split into four pieces, and the velocity is reconstructed independently on each piece, which results in multiple groundwater velocities at the intersection, one for each fracture on each side of the intersection line. This technique enables detailed particle transport representation through a complex DFN structure. Verified for small DFNs, the new simulation capability enables numerical experiments on advective transport in large DFNs to be performed. As a result, we demonstrate this particle transport approach on a DFN model using parameters similar to those of crystalline rock at a proposed geologic repository for spent nuclear fuel in Forsmark, Sweden.« less
A hybrid (Monte Carlo/deterministic) approach for multi-dimensional radiation transport
Bal, Guillaume; Davis, Anthony B.; Langmore, Ian
2011-08-20
Highlights: {yields} We introduce a variance reduction scheme for Monte Carlo (MC) transport. {yields} The primary application is atmospheric remote sensing. {yields} The technique first solves the adjoint problem using a deterministic solver. {yields} Next, the adjoint solution is used as an importance function for the MC solver. {yields} The adjoint problem is solved quickly since it ignores the volume. - Abstract: A novel hybrid Monte Carlo transport scheme is demonstrated in a scene with solar illumination, scattering and absorbing 2D atmosphere, a textured reflecting mountain, and a small detector located in the sky (mounted on a satellite or a airplane). It uses a deterministic approximation of an adjoint transport solution to reduce variance, computed quickly by ignoring atmospheric interactions. This allows significant variance and computational cost reductions when the atmospheric scattering and absorption coefficient are small. When combined with an atmospheric photon-redirection scheme, significant variance reduction (equivalently acceleration) is achieved in the presence of atmospheric interactions.
Murray, Chris; Allen-King, Richelle; Weissmann, Gary
2006-06-01
This project is testing the hypothesis that sedimentary lithofacies determine the geochemical and physical hydrologic properties that control reactive solute transport (Figure 1). We are testing that hypothesis for one site, a portion of the saturated zone at the Hanford Site (Ringold Formation), and for a model solute, carbon tetrachloride (CT). The representative geochemical and physical aquifer properties selected for quantification in the proposed project are the properties that control CT transport: hydraulic conductivity (K) and reactivity (sorption distribution coefficient, Kd, and anaerobic transformation rate constant, kn). We are combining observations at outcrop analog sites (to measure lithofacies dimensions and statistical relations) with measurements from archived and fresh core samples (for geochemical experiments and to provide additional constraint to the stratigraphic model) from the Ringold Formation to place local-scale lithofacies successions, and their distinct hydrologic property distributions, into the basinal context, thus allowing us to estimate the spatial distributions of properties that control reactive solute transport in the subsurface.
An optimal transport approach for seismic tomography: application to 3D full waveform inversion
NASA Astrophysics Data System (ADS)
Métivier, L.; Brossier, R.; Mérigot, Q.; Oudet, E.; Virieux, J.
2016-11-01
The use of optimal transport distance has recently yielded significant progress in image processing for pattern recognition, shape identification, and histograms matching. In this study, the use of this distance is investigated for a seismic tomography problem exploiting the complete waveform; the full waveform inversion. In its conventional formulation, this high resolution seismic imaging method is based on the minimization of the L 2 distance between predicted and observed data. Application of this method is generally hampered by the local minima of the associated L 2 misfit function, which correspond to velocity models matching the data up to one or several phase shifts. Conversely, the optimal transport distance appears as a more suitable tool to compare the misfit between oscillatory signals, for its ability to detect shifted patterns. However, its application to the full waveform inversion is not straightforward, as the mass conservation between the compared data cannot be guaranteed, a crucial assumption for optimal transport. In this study, the use of a distance based on the Kantorovich-Rubinstein norm is introduced to overcome this difficulty. Its mathematical link with the optimal transport distance is made clear. An efficient numerical strategy for its computation, based on a proximal splitting technique, is introduced. We demonstrate that each iteration of the corresponding algorithm requires solving the Poisson equation, for which fast solvers can be used, relying either on the fast Fourier transform or on multigrid techniques. The development of this numerical method make possible applications to industrial scale data, involving tenths of millions of discrete unknowns. The results we obtain on such large scale synthetic data illustrate the potentialities of the optimal transport for seismic imaging. Starting from crude initial velocity models, optimal transport based inversion yields significantly better velocity reconstructions than those based on
NASA Astrophysics Data System (ADS)
Grado-Caffaro, Maria Angeles; Grado-Caffaro, Martin
2014-05-01
In this paper, we propose a diffusive-transport-based analytical formulation to calculate the linear electrical conductance through a multiwalled carbon nanotube with defects. In fact, on the one hand, by considerations on diffusive transport and, on the other hand, using the Drude model, we find out that the conductance (at Fermi energy) of an imperfect multiwalled carbon nanotube is approximately equal to the fundamental conductance quantum multiplied by the number of layers (or shells) of the tube. Our result agrees with experimental data.
Hybrid method of deterministic and probabilistic approaches for multigroup neutron transport problem
Lee, D.
2012-07-01
A hybrid method of deterministic and probabilistic methods is proposed to solve Boltzmann transport equation. The new method uses a deterministic method, Method of Characteristics (MOC), for the fast and thermal neutron energy ranges and a probabilistic method, Monte Carlo (MC), for the intermediate resonance energy range. The hybrid method, in case of continuous energy problem, will be able to take advantage of fast MOC calculation and accurate resonance self shielding treatment of MC method. As a proof of principle, this paper presents the hybrid methodology applied to a multigroup form of Boltzmann transport equation and confirms that the hybrid method can produce consistent results with MC and MOC methods. (authors)
NASA Astrophysics Data System (ADS)
Çeçen, A.; Fast, T.; Kumbur, E. C.; Kalidindi, S. R.
2014-01-01
The diffusion media (DM) has been shown to be a vital component for performance of polymer electrolyte fuel cells (PEFCs). The DM has a dual-layer structure composed of a macro-substrate referred to as the gas diffusion layer (GDL) coated with a micro-porous layer (MPL). Efficient prediction of the effective transport properties of the DM from its internal structure is essential to optimizing the multifunctional characteristics of this critical component. In this work, a unique data-driven approach to establishing structure-property correlations is introduced and applied to the case of gas diffusion in the GDL and MPL. This new approach provides an automated process to produce unbiased estimators to microstructural variance, in contrast to many process-related (hence biased) parameters employed by prominent correlations in the field. The present approach starts with a rigorous quantification of microstructure in the form of n-point statistics. It is followed by the identification of the key aspects of the internal structure through the use of principle component analysis. A data-driven correlation is established when the principal components are related to effective diffusivity by multivariate linear regression. This data-driven approach is compared to the conventional correlations and shown to achieve a very high accuracy for capturing the diffusive transport in the tested PEFC components.
Volkov, Vadim
2015-01-01
Ion transport is the fundamental factor determining salinity tolerance in plants. The Review starts from differences in ion transport between salt tolerant halophytes and salt-sensitive plants with an emphasis on transport of potassium and sodium via plasma membranes. The comparison provides introductory information for increasing salinity tolerance. Effects of salt stress on ion transport properties of membranes show huge opportunities for manipulating ion fluxes. Further steps require knowledge about mechanisms of ion transport and individual genes of ion transport proteins. Initially, the Review describes methods to measure ion fluxes, the independent set of techniques ensures robust and reliable basement for quantitative approach. The Review briefly summarizes current data concerning Na+ and K+ concentrations in cells, refers to primary thermodynamics of ion transport and gives special attention to individual ion channels and transporters. Simplified scheme of a plant cell with known transport systems at the plasma membrane and tonoplast helps to imagine the complexity of ion transport and allows choosing specific transporters for modulating ion transport. The complexity is enhanced by the influence of cell size and cell wall on ion transport. Special attention is given to ion transporters and to potassium and sodium transport by HKT, HAK, NHX, and SOS1 proteins. Comparison between non-selective cation channels and ion transporters reveals potential importance of ion transporters and the balance between the two pathways of ion transport. Further on the Review describes in detail several successful attempts to overexpress or knockout ion transporters for changing salinity tolerance. Future perspectives are questioned with more attention given to promising candidate ion channels and transporters for altered expression. Potential direction of increasing salinity tolerance by modifying ion channels and transporters using single point mutations is discussed and
Ikeda, Kenji; Utoguchi, Naoki; Tsutsui, Hidenobu; Yamaue, Satoko; Homemoto, Manami; Nakao, Erina; Hukunaga, Yumi; Yamasaki, Kyohei; Myotoku, Michiaki; Hirotani, Yoshihiko
2011-02-01
Human choriocarcinoma cells have been used as models for studying transcellular drug transport through placental trophoblasts. However, these models allow the transport of low-molecular-weight drugs through intercellular gap junctions. This study aimed at investigating the differentiation patterns of JEG-3 choriocarcinoma cells under different culture conditions and establishing the appropriate model of in vitro syncytiotrophoblast drug transport. Paracellular permeability was estimated by measuring the transepithelial electrical resistance (TEER) across JEG-3 cell layers. The mRNA expression levels of non-expressed in choriocarcinoma clone 1 (NECC1) and breast cancer resistance protein (BCRP), and those of E-cadherin (ECAD) and cadherin-11 (CDH11), which are adherens junction-associated proteins related to fusogenic ability of syncytiotrophoblasts differentiated from cytotrophoblasts, protein expression levels were considered as the differentiation signals. The highest TEER values were obtained in the JEG-3 cells cultured in the Dulbecco's modified Eagle's medium (DMEM)/Ham's F-12 (1:1) mixed medium (CS-C(®) ; Dainippon Sumitomo Pharma Co. Ltd., Osaka, Japan). By comparing the TEER values and the differentiation signals, the authors identified at least five JEG-3 cell-differentiation patterns. The differentiation pattern of JEG-3 cultured in CS-C resembled the syncytiotrophoblast-like differentiation signal characterizations in vivo. In conclusion, the syncytiotrophoblast-like models of differentiating JEG-3 cells cultured in CS-C might be appropriate for evaluating drug transport across the placental trophoblast.
Forecasting long-range atmospheric pollutant transport and dispersion: Approaches and issues
Griggs, D.P.; Addis, R.P.
1996-01-11
The ability to forecast the transport and diffusion of airborne contaminants over long distances is vital when responding to nuclear emergencies. Increases in computing capabilities and ready access to large-scale model output make it possible to employ advanced three-dimensional prognostic models to forecast the long-range transport of toxic or radioactive gases for emergency response. The Savannah River Technology Center (SRTC) of the U.S. Department of Energy`s Savannah River Site demonstrated this during the European Tracer EXperiment (ETEX). ETEX, conducted in the Fall of 1994, is designed to evaluate the performance of models for long-range atmospheric pollutant transport and dispersion. ETEX involved two tracer experiments as well as a multinational real-time modeling exercise. The real-time modeling component tested the ability of participants to provide timely long-range forecasts of the tracer plume transport and diffusion. Notification of the time, location and amount of tracer occurred after the start of the release. Participants provided 60-hour forecasts of tracer surface concentration within 6 hours of being notified, and updated forecasts every 12 hours thereafter. The two tracer experiments were conducted near Rennes, France on October 23, 1994 and November 14, 1994.
New Approaches to Quantifying Transport Model Error in Atmospheric CO2 Simulations
NASA Technical Reports Server (NTRS)
Ott, L.; Pawson, S.; Zhu, Z.; Nielsen, J. E.; Collatz, G. J.; Gregg, W. W.
2012-01-01
In recent years, much progress has been made in observing CO2 distributions from space. However, the use of these observations to infer source/sink distributions in inversion studies continues to be complicated by difficulty in quantifying atmospheric transport model errors. We will present results from several different experiments designed to quantify different aspects of transport error using the Goddard Earth Observing System, Version 5 (GEOS-5) Atmospheric General Circulation Model (AGCM). In the first set of experiments, an ensemble of simulations is constructed using perturbations to parameters in the model s moist physics and turbulence parameterizations that control sub-grid scale transport of trace gases. Analysis of the ensemble spread and scales of temporal and spatial variability among the simulations allows insight into how parameterized, small-scale transport processes influence simulated CO2 distributions. In the second set of experiments, atmospheric tracers representing model error are constructed using observation minus analysis statistics from NASA's Modern-Era Retrospective Analysis for Research and Applications (MERRA). The goal of these simulations is to understand how errors in large scale dynamics are distributed, and how they propagate in space and time, affecting trace gas distributions. These simulations will also be compared to results from NASA's Carbon Monitoring System Flux Pilot Project that quantified the impact of uncertainty in satellite constrained CO2 flux estimates on atmospheric mixing ratios to assess the major factors governing uncertainty in global and regional trace gas distributions.
Final Report: Transport and its regulation in Marine Microorganisms: A Genomic Based Approach
Brian Palenik; Bianca Brahamsha; Ian Paulsen
2009-09-03
This grant funded the analysis and annotation of the genomes of Synechococcus and Ostreococcus, major marine primary producers. Particular attention was paid to the analysis of transporters using state of the art bioinformatics analyses. During the analysis of the Synechococcus genome, some of the components of the unique bacterial swimming apparatus of one species of Synechococcus (Clade III, strain WH8102) were determined and these included transporters, novel giant proteins and glycosyltransferases. This grant funded the analysis of gene expression in Synechococcus using whole genome microarrays. These analyses revealed the strategies by which marine cyanobacteria respond to environmental conditions such as the absence of phosphorus, a common limiting nutrient, and the interaction of Synechococcus with other microbes. These analyses will help develop models of gene regulation in cyanobacteria and thus help predict their responses to changes in environmental conditions.
A novel approach to hydrogen recovery, storage and transport: Final technical report
Fowler, M.C.; Sangiovanni, J.J.
1988-12-01
The obtaining of high purity hydrogen from the coal gasification process is a series of chemical reactions, several of which require preparation/purification. At any point in the process, it would be useful to have a chemical separation system which can purify the product hydrogen and store it in convenient form. The purpose of this research program is to evaluate one such candidate system, the catalytically reversible hydrogenation of an aromatic hydrocarbon, toluene, to its corresponding cyclical paraffin, methylcyclohexane. In this reaction scheme, the hydrogen present in the product flow from, in principle, any reaction in the coal gasification process is extracted from the flow by reaction with toluene, a readily transportable liquid at ambient temperatures, to form methylcyclohexane, MCH, which is also a liquid at ambient conditions. The hydrogen stored in the organic hydride could therefore be transported and released when desired in the reverse reaction to give recoverable toluene and the desired hydrogen. 13 refs., 30 figs., 22 tabs.
Soft-Stowed Approach: Safe Transportation to ISS for Experiments, Spares & New Hardware
NASA Astrophysics Data System (ADS)
Itta, Antonietta; Quagliotti, Francesco
2012-07-01
The ISS operational and logistic scenario relies on the regular upload of new experiments and maintenance hardware. The extension of the ISS lifetime places even more emphasis on a resupply policy based on safe, cheap and flexible transportation solutions to ISS. A transportation method suitable for all available carriers is represented by foam packaged items put inside bags or containers. This flight condition can now be analyzed thanks to the results derived from an extensive test campaign performed by Boeing in 2009 under NASA sponsorship. Data and guidelines are provided for the calculation of the attenuated flight environments due to the soft packaging conditions. The paper also reports a real life application: the uploading to ISS of the Columbus PDU (some 90 kg) inside ATV II Johannes Kepler, wrapped in 1” of zotek and put inside a M01 bag. The mission was successful: PDU is today safely stored inside a Columbus Rack.
Furukawa, Akira; Tanaka, Hajime
2009-09-25
Using molecular dynamics simulations, we show clear evidence for the nonlocal mesoscopic nature of the anomalous viscous transport in a supercooled liquid and its direct link to dynamic heterogeneity: (i) a distinct crossover from the microscopic to macroscopic viscosity at a mesoscopic length scale, which is comparable to the correlation length of dynamic heterogeneity and grows with an increase in the degree of supercooling; (ii) a strong anisotropic decay of the shear-stress autocorrelation at a finite wave number, which indicates intrinsic decoupling between the longitudinal and transverse dynamics. Our findings suggest the fundamental importance of the growing dynamic correlation in anomalous transport and shed new light on the nature of slow dynamics.
POWELL, KIMBERLYR.
2004-05-25
Implementation of monitored natural attenuation (MNA) as a remediation method requires a mechanistic understanding of the natural attenuation processes occurring at a given site. For inorganic contaminants, natural attenuation typically involves a decrease in metal toxicity and/or mobility. These natural processes include dilution, dispersion, sorption (including adsorption, absorption, and precipitation), and redox processes. In order to better quantify these processes in terms of metal availability, sequential extraction experiments were carried out on subsurface soil samples impacted by a low pH, high sulfate, metals (Be, Ni, U, As) plume associated with the long-term operation of a coal plant at the Savannah River Site. These laboratory scale studies provide mechanistic information regarding the solid phases in the soils associated with natural attenuation of the contaminant metals. This data provides input to be evaluated in the definition of the contaminant source term as well as transport of contaminants for site transport models.
Bergvall, Martin; Grip, Harald; Sjöström, Jan; Laudon, Hjalmar
2007-09-01
Contaminant transport is generally considered to be a key factor when assessing and classifying the environmental risk of polluted areas. In the study presented here, a steady-state approach was applied to obtain estimates of the transit time and concentration of the pesticide metabolite BAM (2,6-dichlorobenzoamide) at a site where it is contaminating a municipal drinking water supply. A Monte Carlo simulation technique was used to quantify the uncertainty of the results and to evaluate the sensitivity of the used parameters. The adopted approach yielded an estimated median transit time of 10 y for the BAM transport from the polluted site to the water supply. Soil organic carbon content in the unsaturated zone and the hydraulic conductivity in the saturated zone explained 44% and 23% of the uncertainty in the transit time estimate, respectively. The sensitivity analysis showed that the dilution factor due to regional groundwater flow and the soil organic carbon content at the polluted site explained 53% and 31% of the uncertainty of concentration estimates, respectively. In conclusion, the adopted steady-state approach can be used to obtain reliable first estimates of transit time and concentration, but to improve concentration predictions of degrading contaminants, a dynamic model is probably required.
Do anthropogenic transports facilitate stored-product pest moth dispersal? A molecular approach
NASA Astrophysics Data System (ADS)
Ryne, Camilla; Bensch, Staffan
2008-02-01
Stored-product moths cause large economic damage in food processing industries and storage facilities. Control of indoor pests is currently dealt with locally, and control strategies seldom include different mills or cooperative industries in joint efforts to reduce infestations. In colder climates where conditions hinder flight dispersal of stored-product moths, we hypothesize that human transport between mills will facilitate dispersal. Albeit considered intuitive, this hypothesis has so far never been tested. Male moths from three mills (populations) in southern Sweden and Denmark were collected and by using amplified fragment length polymorphism (AFLP) pair-wise F st values were calculated. Cluster (population) origins of the genotypes were computed by using a model-based method, structure. The results suggest that known transportation of flour between two mills generate genetically more similar populations of the economically important stored-product moth, Ephestia kuehniella (Zell.) (Lepidoptera; Pyralidae), compared to the third mill, with another distribution area, but situated geographically in between the other mills. The structure model placed the sampled genotypes to belong to either two or five original populations, with a higher probability of two original populations. The third mill was consistently different from the other two mills independent of the models’ calculated number of populations. Although the study was restricted to three mills and one transportation route, it highlights the possibility that transportation of food products promotes genetic mixing (i.e. dispersal) of insect pest populations. Including cooperating mills in control (or monitor) strategy schemes against stored-product pest insects would therefore be a more effective action, rather than to treat each mill separately.
Transport of sulfadiazine in soil columns — Experiments and modelling approaches
NASA Astrophysics Data System (ADS)
Wehrhan, Anne; Kasteel, Roy; Simunek, Jirka; Groeneweg, Joost; Vereecken, Harry
2007-01-01
Antibiotics, such as sulfadiazine, reach agricultural soils directly through manure of grazing livestock or indirectly through the spreading of manure or sewage sludge on the field. Knowledge about the fate of antibiotics in soils is crucial for assessing the environmental risk of these compounds, including possible transport to the groundwater. Transport of 14C-labelled sulfadiazine was investigated in disturbed soil columns at a constant flow rate of 0.26 cm h - 1 near saturation. Sulfadiazine was applied in different concentrations for either a short or a long pulse duration. Breakthrough curves of sulfadiazine and the non-reactive tracer chloride were measured. At the end of the leaching period the soil concentration profiles were determined. The peak maxima of the breakthrough curves were delayed by a factor of 2 to 5 compared to chloride and the decreasing limbs are characterized by an extended tailing. However, the maximum relative concentrations differed as well as the eluted mass fractions, ranging from 18 to 83% after 500 h of leaching. To identify relevant sorption processes, breakthrough curves of sulfadiazine were fitted with a convective-dispersive transport model, considering different sorption concepts with one, two and three sorption sites. Breakthrough curves can be fitted best with a three-site sorption model, which includes two reversible kinetic and one irreversible sorption site. However, the simulated soil concentration profiles did not match the observations for all of the used models. Despite this incomplete process description, the obtained results have implications for the transport behavior of sulfadiazine in the field. Its leaching may be enhanced if it is frequently applied at higher concentrations.
Liddelow, Shane A.; Temple, Sally; Møllgård, Kjeld; Gehwolf, Renate; Wagner, Andrea; Bauer, Hannelore; Bauer, Hans-Christian; Phoenix, Timothy N.; Dziegielewska, Katarzyna M.; Saunders, Norman R.
2012-01-01
Exchange mechanisms across the blood–cerebrospinal fluid (CSF) barrier in the choroid plexuses within the cerebral ventricles control access of molecules to the central nervous system, especially in early development when the brain is poorly vascularised. However, little is known about their molecular or developmental characteristics. We examined the transcriptome of lateral ventricular choroid plexus in embryonic day 15 (E15) and adult mice. Numerous genes identified in the adult were expressed at similar levels at E15, indicating substantial plexus maturity early in development. Some genes coding for key functions (intercellular/tight junctions, influx/efflux transporters) changed expression during development and their expression patterns are discussed in the context of available physiological/permeability results in the developing brain. Three genes: Secreted protein acidic and rich in cysteine (Sparc), Glycophorin A (Gypa) and C (Gypc), were identified as those whose gene products are candidates to target plasma proteins to choroid plexus cells. These were investigated using quantitative- and single-cell-PCR on plexus epithelial cells that were albumin- or total plasma protein-immunopositive. Results showed a significant degree of concordance between plasma protein/albumin immunoreactivity and expression of the putative transporters. Immunohistochemistry identified SPARC and GYPA in choroid plexus epithelial cells in the embryo with a subcellular distribution that was consistent with transport of albumin from blood to cerebrospinal fluid. In adult plexus this pattern of immunostaining was absent. We propose a model of the cellular mechanism in which SPARC and GYPA, together with identified vesicle-associated membrane proteins (VAMPs) may act as receptors/transporters in developmentally regulated transfer of plasma proteins at the blood–CSF interface. PMID:22457777
An Integrated Hydrologic Modeling Approach to Cesium-137 Transport in Forested Fukushima Watersheds
NASA Astrophysics Data System (ADS)
Siirila-Woodburn, E. R.; Steefel, C. I.; Williams, K. H.; Birkholzer, J. T.
2015-12-01
The 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in Japan resulted in a significant dissemination of cesium-137 (Cs-137) over a wide area west of the plant, including the contamination of many watersheds and the subsequent evacuation of many communities. Today approximately 90% of on-land Cs-137 fallout following the accident resides in the upper 5 cm of forest soils. While this can be partially attributed to the forested composition of the prefecture (70%), there is also difficulty in cleanup efforts in these regions due to a lack of understanding and predictive capability of radioisotopes transport at the catchment to watershed scale. Subsequently, there is an uncertain, but likely long-term impact on local communities with implications for the use of nuclear energy use worldwide. Due to the complex nature of forest eco-hydrology, sophisticated modeling tools to accurately predict Cs-137 fluxes across different spatial and temporal scales are required. High fidelity, high resolution numerical modeling techniques in conjunction with parallel high performance computing is required to accurately determine transport and feedbacks in these complex systems. To better understand the fundamental transport of Cs-137, a watershed near the FDNPP is modeled with an integrated hydrologic model that includes variably saturated groundwater and overland flow in addition to atmospheric and vegetative processes via a coupled land surface model. Of specific interest is the impact of land cover type on hydrologic flow in the area, which will likely play an important role in erosion patterns and the consequent transport of Cs-137 strongly sorbed to surface soils. Risk management practices (for example, passive remediation versus active remediation such as targeted logging) for two principal tree types (evergreen and deciduous) are informed given the simulated responses to flow patterns assuming different quantities and spatial distribution patterns of each tree type.
Modeling coupled nanoparticle aggregation and transport in porous media: A Lagrangian approach
NASA Astrophysics Data System (ADS)
Taghavy, Amir; Pennell, Kurt D.; Abriola, Linda M.
2015-01-01
Changes in nanoparticle size and shape due to particle-particle interactions (i.e., aggregation or agglomeration) may significantly alter particle mobility and retention in porous media. To date, however, few modeling studies have considered the coupling of transport and particle aggregation processes. The majority of particle transport models employ an Eulerian modeling framework and are, consequently, limited in the types of collisions and aggregate sizes that can be considered. In this work, a more general Lagrangian modeling framework is developed and implemented to explore coupled nanoparticle aggregation and transport processes. The model was verified through comparison of model simulations to published results of an experimental and Eulerian modeling study (Raychoudhury et al., 2012) of carboxymethyl cellulose (CMC)-modified nano-sized zero-valent iron particle (nZVI) transport and retention in water-saturated sand columns. A model sensitivity analysis reveals the influence of influent particle concentration (ca. 70 to 700 mg/L), primary particle size (10-100 nm) and pore water velocity (ca. 1-6 m/day) on particle-particle, and, consequently, particle-collector interactions. Model simulations demonstrate that, when environmental conditions promote particle-particle interactions, neglecting aggregation effects can lead to under- or over-estimation of nanoparticle mobility. Results also suggest that the extent to which higher order particle-particle collisions influence aggregation kinetics will increase with the fraction of primary particles. This work demonstrates the potential importance of time-dependent aggregation processes on nanoparticle mobility and provides a numerical model capable of capturing/describing these interactions in water-saturated porous media.
A head-up display format for transport aircraft approach and landing
NASA Technical Reports Server (NTRS)
Bray, R. S.; Scott, B. C.
1981-01-01
An electronic flight-guidance display format was designed for use in evaluations of the collimated head-up display concept applied to transport aircraft landing. In the design process of iterative evaluation and modification, some general principles, or guidelines, applicable to electronic flight displays were suggested. The usefulness of an indication of instantaneous inertial flightpath was clearly demonstrated. Evaluator pilot acceptance of the unfamiliar display concepts was very positive when careful attention was given to indoctrination and training.
A head-up display format for application to transport aircraft approach and landing
NASA Technical Reports Server (NTRS)
Bray, R. S.
1980-01-01
A head up display (HUD) format used in simulator studies of the application of HUD to the landing of civil transport aircraft is described in detail. The display features an indication of the aircraft's instantaneous flightpath that constitutes the primary controlled element. Discrete ILS error and altitude signals are scaled and positioned to provide precise guidance modes when tracked with the flightpath symbol. Consideration is given to both the availability and nonavailability of inertial velocity information in the aircraft.
Two-dimensional boltzmann transport equation approach to simulation of local ion implantation
NASA Astrophysics Data System (ADS)
Komarov, F. F.; Mozolevski, I. E.; Rogach, V. P.
1995-05-01
A new theoretical model and software tool is proposed for simulation of two-dimensional local ion implantation in a target of arbitrary geometry. The program uses an algorithm of numerical solution of the boundary value problem for Boltzmann transport equation in two dimensions and permits to calculate the angular and energy distribution function of the particles moving in a multilayered multicomponent target. The program is essentially time saving and can be implemented on an IBM PC AT standard configuration computer.
A neural network approach for the determination of interhospital transport mode.
Hosseini-Nezhad, S M; Yamashita, T S; Bielefeld, R A; Krug, S E; Pao, Y H
1995-08-01
We report on the construction of neural networks for determining whether pediatric patients requiring transport to a tertiary care center should be moved by air or by ground. The networks were based on the functional-link net architecture. In two experiments, feedforward supervised-learning neural nets were trained with examples of an expert's decisions and then were used in a consulting mode to provide advice on cases not previously encountered. Training and validation were performed by a combination of the k-fold cross-validation and leaving-one-out sampling methods. Use of the functional-link net rather than the customary backpropagation net enabled us to carry out the training with fairly large amounts of data in realistically short time periods. In the first experiment, capillary refill, skin color, and stridor were consistently the input variables that were most strongly associated with the decision output. In both experiments, the networks were validated by comparing their performance retrospectively against the determination of an expert pediatric transport physician. The network was trained based on the expert's opinion about the correct mode of transport for each case with error rates of less than 10(-5).
Transport coefficients of Quark-Gluon Plasma in a Kinetic Theory approach
NASA Astrophysics Data System (ADS)
Puglisi, A.; Plumari, S.; Scardina, F.; Greco, V.
2014-07-01
One of the main results of heavy ions collision at relativistic energy experiments is the very small shear viscosity to entropy density ratio of the Quark-Gluon Plasma, close to the conjectured lower bound η/s = 1/4π for systems in the infinite coupling limit. Transport coefficients like shear viscosity are responsible of non-equilibrium properties of a system: Green- Kubo relations give us an exact expression to compute these coefficients. We computed shear viscosity numerically using Green-Kubo relation in the framework of Kinetic Theory solving the relativistic transport Boltzmann equation in a finite box with periodic boundary conditions. We investigated different cases of particles, for one component system (gluon matter), interacting via isotropic or anisotropic cross-section in the range of temperature of interest for HIC. Green-Kubo results are in agreement with Chapman-Enskog approximation while Relaxation Time approximation can underestimates the viscosity of a factor 2. Another transport coefficient of interest is the electric conductivity σel which determines the response of QGP to the electromagnetic fields present in the early stage of the collision. We study the σel dependence on microscopic details of interaction and we find also in this case that Relaxation Time Approximation is a good approximation only for isotropic cross-section.
Effects of self-organization on transport in granular matter: A network-based approach
NASA Astrophysics Data System (ADS)
Smart, A.; Umbanhowar, P.; Ottino, J.
2007-07-01
Granular matter may be one of the simplest prototypes of what have come to be regarded as complex systems —systems where simple interactions can lead to rich, often surprising, global behavior. For example, interparticle contacts in a granular system give rise to networks that are 1) heterogeneous, i.e., a few particles support high compressive force, while many others support relatively little, and 2) self-organized, i.e., spatially correlated strong forces tend to form a sub-network of interconnecting "force chains". Using numerical simulations, we investigate the influence of heterogeneity and self-organization on the transport properties of granular matter, with particular attention to heat conduction —a phenomenon of ubiquitous importance in engineering and nature. We find that self-organization in the granular network promotes efficient transport. Furthermore, a network-attack experiment suggests that contacts with high betweenness centrality, not necessarily those with highest local heat transfer coefficient, most significantly influence transport behavior. We find that concepts of network theory yield valuable insight —both qualitative and quantitative— into the observed behavior.
NASA Astrophysics Data System (ADS)
Hansen, Scott K.; Scher, Harvey; Berkowitz, Brian
2014-07-01
Both Eulerian and Lagrangian reactive transport simulations in natural media require selection of a parameter that controls the “promiscuity” of the reacting particles. In Eulerian models, measurement of this parameter may be difficult because its value will generally differ between natural (diffusion-limited) systems and batch experiments, even though both are modeled by reaction terms of the same form. And in Lagrangian models, there previously has been no a priori way to compute this parameter. In both cases, then, selection is typically done by calibration, or ad hoc. This paper addresses the parameter selection problem for Fickian transport by deriving, from first principles and D (the diffusion constant) the reaction-rate-controlling parameters for particle tracking (PT) codes and for the diffusion-reaction equation (DRE). Using continuous time random walk analysis, exact reaction probabilities are derived for pairs of potentially reactive particles based on D and their probability of reaction provided that they collocate. Simultaneously, a second PT scheme directly employing collocation probabilities is derived. One-to-one correspondence between each of D, the reaction radius specified for a PT scheme, and the DRE decay constant are then developed. These results serve to ground reactive transport simulations in their underlying thermodynamics, and are confirmed by simulations.
Sustainable transport planning using GIS and remote sensing: an integrated approach
NASA Astrophysics Data System (ADS)
Giorgoudis, Marios D.; Hadjimitsis, Diofantos G.; Shiftan, Yoram
2014-08-01
The main advantage of using GIS is its ability to access and analyze spatially distributed data. The applications of GIS to transportation can be viewed as involving either on data retrieval; data integrator; or data analysis. The use of remote sensing can assist the retrieval of land use changes. Indeed, the integration of GIS and remote sensing will be used to fill the gap in the smart transport planning. A four step research is going to be done in order to try to integrate the usage of GIS and remote sensing to sustainable transport planning. The proposed research will be held in the city of Limassol, Cyprus. The data that are going to be used are data that are going to be collected through questionnaires, and other available data from the Cyprus Public Works Department and from the Remote Sensing Laboratory and Geo-Environment Research Lab of the Cyprus University of Technology. Overall, statistical analysis and market segmentation of data will be done, the land usage will be examined, and a scenario building on mode choice will be held. This paper presents an overview of the methodology that will be adopted.
NASA Astrophysics Data System (ADS)
Zhang, J.; Nguyen Viet, T.; Wang, X.; Chen, H.; Gin, K. Y. H.
2014-12-01
The fate and transport processes of emerging contaminants in aquatic ecosystems are complex, which are not only determined by their own properties but also influenced by the environmental setting, physical, chemical and biological processes. A 3D-emerging contaminant model has been developed based on Delft3D water quality model and coupled with a hydrodynamic model and a catchment-scale 1D- hydrological and hydraulic model to study the possible fate and transport mechanisms of perfluorinated compounds (PFCs) in Marina Reservoir in Singapore. The main processes in the contaminant model include partitioning (among detritus, dissolved organic matter and phytoplankton), settling, resuspension and degradation. We used the integrated model to quantify the distribution of the total PFCs and two major components, namely perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) in the water, sediments and organisms in the reservoir. The model yielded good agreement with the field measurements when evaluated based on the datasets in 2009 and 2010 as well as recent observations in 2013 and 2014. Our results elucidate that the model can be a useful tool to characterize the occurrence, sources, sinks and trends of PFCs both in the water column and in the sediments in the reservoir. Thisapproach provides a better understanding of mechanisms that influence the fate and transport of emerging contaminants and lays down a framework for future experiments to further explore how the dominant environmental factors change towards mitigation of emerging contaminants in the reservoirs.
Stalker, Timothy J; Welsh, John D; Tomaiuolo, Maurizio; Wu, Jie; Colace, Thomas V; Diamond, Scott L; Brass, Lawrence F
2014-09-11
Hemostatic thrombi formed after a penetrating injury have a distinctive structure in which a core of highly activated, closely packed platelets is covered by a shell of less-activated, loosely packed platelets. We have shown that differences in intrathrombus molecular transport emerge in parallel with regional differences in platelet packing density and predicted that these differences affect thrombus growth and stability. Here we test that prediction in a mouse vascular injury model. The studies use a novel method for measuring thrombus contraction in vivo and a previously characterized mouse line with a defect in integrin αIIbβ3 outside-in signaling that affects clot retraction ex vivo. The results show that the mutant mice have a defect in thrombus consolidation following vascular injury, resulting in an increase in intrathrombus transport rates and, as predicted by computational modeling, a decrease in thrombin activity and platelet activation in the thrombus core. Collectively, these data (1) demonstrate that in addition to the activation state of individual platelets, the physical properties of the accumulated mass of adherent platelets is critical in determining intrathrombus agonist distribution and platelet activation and (2) define a novel role for integrin signaling in the regulation of intrathrombus transport rates and localization of thrombin activity. PMID:24951426
NASA Astrophysics Data System (ADS)
Stanko, Z.; Boyce, S. E.; Yeh, W. W. G.
2015-12-01
Model reduction techniques using proper orthogonal decomposition (POD) have been very effective in applications to confined groundwater flow models. These techniques consist of performing a projection of the solution of the full model onto a reduced basis. POD combined with the snapshot approach has been successfully applied to highly discretized linear models. In many cases, the reduced model is orders of magnitude smaller than the full model and runs 1,000 times faster. For nonlinear models, such as the unconfined groundwater flow, direct application of POD requires additional calls to the full model to generate additional snapshots. This is time consuming and increases the dimension of the reduced model. The discrete empirical interpolation method (DEIM) is a technique that avoids the additional full model calls and captures the dynamics of the nonlinear term while reducing the dimensions. Here, POD and DEIM are combined to reduce both the nonlinear unconfined groundwater flow and solute transport equations. To prove the concept, simple one-dimensional models are created for MODFLOW and MT3DMS separately. The dual approach is then tested on a density-dependent flow and transport simulation using the LMT package developed for MODFLOW. For each iteration of the nonlinear flow solver and the transport solver, the respective reduced models are solved instead. Numerical experiments show that significant reduction is obtainable before errors become too large. This method is well suited for a coastal aquifer seawater intrusion scenario, where nonlinearities only exist in small subregions of the model domain. A fine discretization can be utilized and POD will effectively eliminate unnecessary parameterization by projecting the full model system matrix onto a subspace with fewer column dimensions. DEIM can then reduce the row dimension of the original system by using only those state variable nodes with the most influence. This combined approach allows for full
Two-loop off-shell QCD amplitudes in FDR
NASA Astrophysics Data System (ADS)
Page, Ben; Pittau, Roberto
2015-11-01
We link the FDR treatment of ultraviolet (UV) divergences to dimensional regularization up to two loops in QCD. This allows us to derive the one-loop and two-loop coupling constant and quark mass shifts necessary to translate infrared finite quantities computed in FDR to the overline{MS} renormalization scheme. As a by-product of our analysis, we solve a problem analogous to the historical difficulties of the Four Dimensional Helicity (FDH) method beyond one loop. An alternative formulation of FDH is then presented that preserves the renormalizability properties of QCD without introducing evanescent quantities.
Pudlak, M; Pichugin, K N; Nazmitdinov, R G; Pincak, R
2011-11-01
Creation of electrons or excitons by external fields in a system with initially statistically independent unrelaxed vibrational modes leads to an initial condition term. The contribution of this term in the time convolution generalized master-equation approach is studied in the second order of the perturbation theory in path-integral formalism. The developed approach, applied for the analysis of dynamics in the photosynthetic reaction center, exhibits the key role of the initial condition terms at the primary stage of electron transfer.
Song, Linze; Shi, Qiang
2015-05-07
We present a new non-perturbative method to calculate the charge carrier mobility using the imaginary time path integral approach, which is based on the Kubo formula for the conductivity, and a saddle point approximation to perform the analytic continuation. The new method is first tested using a benchmark calculation from the numerical exact hierarchical equations of motion method. Imaginary time path integral Monte Carlo simulations are then performed to explore the temperature dependence of charge carrier delocalization and mobility in organic molecular crystals (OMCs) within the Holstein and Holstein-Peierls models. The effects of nonlocal electron-phonon interaction on mobility in different charge transport regimes are also investigated.
Stieglitz, M.; Shaman, J.; McNamara, J.; Engel, V.; Shanley, J.; Kling, G.W.
2003-01-01
Hydrologic processes control much of the export of organic matter and nutrients from the land surface. It is the variability of these hydrologic processes that produces variable patterns of nutrient transport in both space and time. In this paper, we explore how hydrologic "connectivity" potentially affects nutrient transport. Hydrologic connectivity is defined as the condition by which disparate regions on the hillslope are linked via subsurface water flow. We present simulations that suggest that for much of the year, water draining through a catchment is spatially isolated. Only rarely, during storm and snowmelt events when antecedent soil moisture is high, do our simulations suggest that mid-slope saturation (or near saturation) occurs and that a catchment connects from ridge to valley. Observations during snowmelt at a small headwater catchment in Idaho are consistent with these model simulations. During early season discharge episodes, in which the mid-slope soil column is not saturated, the electrical conductivity in the stream remains low, reflecting a restricted, local (lower slope) source of stream water and the continued isolation of upper and mid-slope soil water and nutrients from the stream system. Increased streamflow and higher stream water electrical conductivity, presumably reflecting the release of water from the upper reaches of the catchment, are simultaneously observed when the mid-slope becomes sufficiently wet. This study provides preliminary evidence that the seasonal timing of hydrologic connectivity may affect a range of ecological processes, including downslope nutrient transport, C/N cycling, and biological productivity along the toposequence. A better elucidation of hydrologic connectivity will be necessary for understanding local processes as well as material export from land to water at regional and global scales. Copyright 2003 by the American Geophysical Union.
NASA Astrophysics Data System (ADS)
Ezzedine, S. M.
2009-12-01
Fractures and fracture networks are the principal pathways for transport of water and contaminants in groundwater systems, enhanced geothermal system fluids, migration of oil and gas, carbon dioxide leakage from carbon sequestration sites, and of radioactive and toxic industrial wastes from underground storage repositories. A major issue to overcome when characterizing a fractured reservoir is that of data limitation due to accessibility and affordability. Moreover, the ability to map discontinuities in the rock with available geological and geophysical tools tends to decrease particularly as the scale of the discontinuity goes down. Geological characterization data include measurements of fracture density, orientation, extent, and aperture, and are based on analysis of outcrops, borehole optical and acoustic televiewer logs, aerial photographs, and core samples, among other techniques. All of these measurements are taken at the field scale through a very sparse limited number of deep boreholes. These types of data are often reduced to probability distribution functions for predictive modeling and simulation in a stochastic framework such as a stochastic discrete fracture network. Stochastic discrete fracture network models enable, through Monte Carlo realizations and simulations, probabilistic assessment of flow and transport phenomena that are not adequately captured using continuum models. Despite the fundamental uncertainties inherited within the probabilistic reduction of the sparse data collected, very little work has been conducted on quantifying uncertainty on the reduced probabilistic distribution functions. In the current study, using nested Monte Carlo simulations, we present the impact of parameter uncertainties of the distribution functions of fracture density, orientation, aperture and size on the flow and transport using topological measures such as fracture connectivity, physical characteristics such as effective hydraulic conductivity tensors, and
Study of Transport Properties in Armchair Graphyne Nanoribbons: A Density Functional Approach
NASA Astrophysics Data System (ADS)
Golafrooz Shahri, S.; Roknabadi, M. R.; Shahtahmasebi, N.; Behdani, M.
2016-07-01
In present paper, the non-equilibrium Green function (NEGF) method along with the density functional theory (DFT) are used to investigate the effect of width on transport and electronic properties of armchair graphyne (γ-graphyne) nanoribbons. The results show that all the studied nanoribbons are semiconductor and their band gaps decrease as the widths of nanoribbons increase, which will result in increasing current at a certain voltage. Also our results show the promising application of armchair graphyne nanoribbons in nano-electrical devices.
Lee, H.; Lee, D.
2013-07-01
This paper presents a new hybrid method of continuous energy Monte Carlo (MC) and multi-group Method of Characteristics (MOC). For a continuous energy neutron transport analysis, the hybrid method employs a continuous energy MC for resonance energy range to treat the resonances accurately and a multi-group MOC for high and low energy ranges for efficiency. Numerical test with a model problem confirms that the hybrid method can produce consistent results with the reference continuous energy MC-only calculation as well as multi-group MOC-only calculation. (authors)
NASA Astrophysics Data System (ADS)
Xu, Dong; Wu, Heng; Liu, Huiming; Gong, Linghui; Xu, Xiangdong; Li, L. F.
2012-06-01
The thermal conductivity of three foamed pipes has been tested for the development of liquid nitrogen transmission pipelines. By establishing a function between evaporation rate and thermal conductivity, we obtain effective thermal conductivity without destroying pipes. The comparison between our test and test coupons shows that this test device is reliable and could be a standard test for checking insulation properties of in situ foamed pipes transporting liquid nitrogen. The scientific principles, system design, experimental results and effect factors of the test are presented in this paper.
Liu, Shuanglong; Feng, Yuan Ping; Zhang, Chun
2013-11-21
We show that when a molecular junction is under an external bias, its properties cannot be uniquely determined by the total electron density in the same manner as the density functional theory for ground state properties. In order to correctly incorporate bias-induced nonequilibrium effects, we present a dual mean field (DMF) approach. The key idea is that the total electron density together with the density of current-carrying electrons are sufficient to determine the properties of the system. Two mean fields, one for current-carrying electrons and the other one for equilibrium electrons can then be derived. Calculations for a graphene nanoribbon junction show that compared with the commonly used ab initio transport theory, the DMF approach could significantly reduce the electric current at low biases due to the non-equilibrium corrections to the mean field potential in the scattering region.
NASA Astrophysics Data System (ADS)
Xu, Dazhi; Cao, Jianshu
2016-08-01
The concept of polaron, emerged from condense matter physics, describes the dynamical interaction of moving particle with its surrounding bosonic modes. This concept has been developed into a useful method to treat open quantum systems with a complete range of system-bath coupling strength. Especially, the polaron transformation approach shows its validity in the intermediate coupling regime, in which the Redfield equation or Fermi's golden rule will fail. In the polaron frame, the equilibrium distribution carried out by perturbative expansion presents a deviation from the canonical distribution, which is beyond the usual weak coupling assumption in thermodynamics. A polaron transformed Redfield equation (PTRE) not only reproduces the dissipative quantum dynamics but also provides an accurate and efficient way to calculate the non-equilibrium steady states. Applications of the PTRE approach to problems such as exciton diffusion, heat transport and light-harvesting energy transfer are presented.
NASA Astrophysics Data System (ADS)
Douglas, E. M.; Kirshen, P. H.; Bosma, K.; Watson, C.; Miller, S.; McArthur, K.
2015-12-01
There now exists a plethora of information attesting to the reality of our changing climate and its impacts on both human and natural systems. There also exists a growing literature linking climate change impacts and transportation infrastructure (highways, bridges, tunnels, railway, shipping ports, etc.) which largely agrees that the nation's transportation systems are vulnerable. To assess this vulnerability along the coast, flooding due to sea level rise and storm surge has most commonly been evaluated by simply increasing the water surface elevation and then estimating flood depth by comparing the new water surface elevation with the topographic elevations of the land surface. While this rudimentary "bathtub" approach may provide a first order identification of potential areas of vulnerability, accurate assessment requires a high resolution, physically-based hydrodynamic model that can simulate inundation due to the combined effects of sea level rise, storm surge, tides and wave action for site-specific locations. Furthermore, neither the "bathtub" approach nor other scenario-based approaches can quantify the probability of flooding due to these impacts. We developed a high resolution coupled ocean circulation-wave model (ADCIRC/SWAN) that utilizes a Monte Carlo approach for predicting the depths and associated exceedance probabilities of flooding due to both tropical (hurricanes) and extra-tropical storms under current and future climate conditions. This required the development of an entirely new database of meteorological forcing (e.g. pressure, wind speed, etc.) for historical Nor'easters in the North Atlantic basin. Flooding due to hurricanes and Nor'easters was simulated separately and then composite flood probability distributions were developed. Model results were used to assess the vulnerability of the Central Artery/Tunnel system in Boston, Massachusetts to coastal flooding now and in the future. Local and regional adaptation strategies were
Namazi-Rad, Mohammad-Reza; Dunbar, Michelle; Ghaderi, Hadi; Mokhtarian, Payam
2015-01-01
To achieve greater transit-time reduction and improvement in reliability of transport services, there is an increasing need to assist transport planners in understanding the value of punctuality; i.e. the potential improvements, not only to service quality and the consumer but also to the actual profitability of the service. In order for this to be achieved, it is important to understand the network-specific aspects that affect both the ability to decrease transit-time, and the associated cost-benefit of doing so. In this paper, we outline a framework for evaluating the effectiveness of proposed changes to average transit-time, so as to determine the optimal choice of average arrival time subject to desired punctuality levels whilst simultaneously minimizing operational costs. We model the service transit-time variability using a truncated probability density function, and simultaneously compare the trade-off between potential gains and increased service costs, for several commonly employed cost-benefit functions of general form. We formulate this problem as a constrained optimization problem to determine the optimal choice of average transit time, so as to increase the level of service punctuality, whilst simultaneously ensuring a minimum level of cost-benefit to the service operator. PMID:25992902
OLSON,CRAIG L.
2000-05-17
Heavy ion beam transport through the containment chamber plays a crucial role in all heavy ion fusion (HIF) scenarios. Here, several parameters are used to characterize the operating space for HIF beams; transport modes are assessed in relation to evolving target/accelerator requirements; results of recent relevant experiments and simulations of HIF transport are summarized; and relevant instabilities are reviewed. All transport options still exist, including (1) vacuum ballistic transport, (2) neutralized ballistic transport, and (3) channel-like transport. Presently, the European HIF program favors vacuum ballistic transport, while the US HIF program favors neutralized ballistic transport with channel-like transport as an alternate approach. Further transport research is needed to clearly guide selection of the most attractive, integrated HIF system.
NASA Astrophysics Data System (ADS)
Yin, P.; Mitchell, C. N.; Spencer, P.; McCrea, I.; Pedersen, T.
2008-09-01
During the Halloween 2003 storm event, significant electron density enhancements at elevated F-layer altitudes were recorded by the EISCAT and ESR radars in northern Europe between 20:00 and 24:00 UT on 30 October. At the same time, a sequence of optical images from Qaanaaq in northern Greenland captured a series of eastward-propagating polar cap patches. In this paper, an advanced 4-D tomographic method based on the assimilation of global GPS data, coupled to a predictive Kalman filtering technique, has been used to reveal the linkage between these ionospheric structures. The combination of the various data sources has clearly established the time history of this extreme event, in which high-density plasma was uplifted in the dayside ionosphere and convected anti-sunward across the polar cap to European high latitudes at an elevated F-layer. Using this multi instrument approach, we can differentiate between those density structures observed at the ESR which occurred as a result of cross-polar transport and those more likely to have been produced by in-situ soft particle precipitation, a distinction which is supported by the ESR and EISCAT data. The multi-diagnostic approach reported here has the potential significantly to extend our current understanding of high latitude plasma transport and the origin of electron density enhancements.
Atchley, Adam L; Maxwell, Reed M; Navarre-Sitchler, Alexis K
2013-06-01
Increased human health risk associated with groundwater contamination from potential carbon dioxide (CO2) leakage into a potable aquifer is predicted by conducting a joint uncertainty and variability (JUV) risk assessment. The approach presented here explicitly incorporates heterogeneous flow and geochemical reactive transport in an efficient manner and is used to evaluate how differences in representation of subsurface physical heterogeneity and geochemical reactions change the calculated risk for the same hypothetical aquifer scenario where a CO2 leak induces increased lead (Pb(2+)) concentrations through dissolution of galena (PbS). A nested Monte Carlo approach was used to take Pb(2+) concentrations at a well from an ensemble of numerical reactive transport simulations (uncertainty) and sample within a population of potentially exposed individuals (variability) to calculate risk as a function of both uncertainty and variability. Pb(2+) concentrations at the well were determined with numerical reactive transport simulation ensembles using a streamline technique in a heterogeneous 3D aquifer. Three ensembles with variances of log hydraulic conductivity (σ(2)lnK) of 1, 3.61, and 16 were simulated. Under the conditions simulated, calculated risk is shown to be a function of the strength of subsurface heterogeneity, σ(2)lnK and the choice between calculating Pb(2+) concentrations in groundwater using equilibrium with galena and kinetic mineral reaction rates. Calculated risk increased with an increase in σ(2)lnK of 1 to 3.61, but decreased when σ(2)lnK was increased from 3.61 to 16 for all but the highest percentiles of uncertainty. Using a Pb(2+) concentration in equilibrium with galena under CO2 leakage conditions (PCO2 = 30 bar) resulted in lower estimated risk than the simulations where Pb(2+) concentrations were calculated using kinetic mass transfer reaction rates for galena dissolution and precipitation. This study highlights the importance of
NASA Astrophysics Data System (ADS)
Regnier, P.; Aguilera, D.; Jourabchi, P.; Meile, C.; van Cappellen, P.; Vanderborght, J.-P.
2003-04-01
Reactive-transport models (RTMs) are traditionally developed and used to investigate the fate and transport of a selected set of chemical constituents within a given compartment of the earth, mainly at the local or subregional scale. As a result, existing RTMs tend to be environment and application specific. For instance, at the continent-ocean interface, RTMs have been used to simulate, among others, biogeochemical dynamics in rivers, estuaries, coastal areas, aquifers, and sediments. The development of upscaling protocols, where RTMs of interconnected environments are progressively aggregated into larger system units is critical for merging marine and continental approaches to biogeochemical cycles. However, one of the major challenges to achieve this goal is in the realistic and consistent representation of highly complex reaction networks that characterize the chemical dynamics of the natural environments present along the continent-ocean continuum (rivers, estuaries, coastal areas, sediments). The expanding knowledge about (bio)geochemical transformation processes achieved via field- and laboratory-based experiments needs also to be made available and integrated consistently (i.e. with comparable level of complexities) across traditional disciplinary barriers, by utilizing the unifying conceptual and mathematical principles underlying all RTMs. Our modeling approach, based on a modular concept, offers the necessary flexibility for the implementation of new theoretical and experimental information on the rates and pathways of biogeochemical reactions. A key component of our reaction network simulator is the "Knowledge Base", which acts as a single evolving repository of up-to-date information on biogeochemical processes. The development of self-consistent, "Knowledge-Based" biogeochemical reaction network modules, which can be merged with existing transport models of the various compartments of the hydrosphere along the continent-ocean continuum, creates a
Atchley, Adam L; Maxwell, Reed M; Navarre-Sitchler, Alexis K
2013-06-01
Increased human health risk associated with groundwater contamination from potential carbon dioxide (CO2) leakage into a potable aquifer is predicted by conducting a joint uncertainty and variability (JUV) risk assessment. The approach presented here explicitly incorporates heterogeneous flow and geochemical reactive transport in an efficient manner and is used to evaluate how differences in representation of subsurface physical heterogeneity and geochemical reactions change the calculated risk for the same hypothetical aquifer scenario where a CO2 leak induces increased lead (Pb(2+)) concentrations through dissolution of galena (PbS). A nested Monte Carlo approach was used to take Pb(2+) concentrations at a well from an ensemble of numerical reactive transport simulations (uncertainty) and sample within a population of potentially exposed individuals (variability) to calculate risk as a function of both uncertainty and variability. Pb(2+) concentrations at the well were determined with numerical reactive transport simulation ensembles using a streamline technique in a heterogeneous 3D aquifer. Three ensembles with variances of log hydraulic conductivity (σ(2)lnK) of 1, 3.61, and 16 were simulated. Under the conditions simulated, calculated risk is shown to be a function of the strength of subsurface heterogeneity, σ(2)lnK and the choice between calculating Pb(2+) concentrations in groundwater using equilibrium with galena and kinetic mineral reaction rates. Calculated risk increased with an increase in σ(2)lnK of 1 to 3.61, but decreased when σ(2)lnK was increased from 3.61 to 16 for all but the highest percentiles of uncertainty. Using a Pb(2+) concentration in equilibrium with galena under CO2 leakage conditions (PCO2 = 30 bar) resulted in lower estimated risk than the simulations where Pb(2+) concentrations were calculated using kinetic mass transfer reaction rates for galena dissolution and precipitation. This study highlights the importance of
NASA Astrophysics Data System (ADS)
Trinchero, Paolo; Painter, Scott; Ebrahimi, Hedieh; Koskinen, Lasse; Molinero, jorge; Selroos, Jan-Olof
2015-04-01
Due to the high heterogeneity of fractured media and the ubiquitous lack of a complete site characterization, deterministic simulations of radionuclide transport in fractured rocks are notoriously highly uncertain. This uncertainty is usually addressed using stochastic methods; e.g. the connectivity structure of the medium is described using multiple realizations of Discrete Fracture Networks (DFN), which are then combined to particle tracking simulations. In these formulations, many complex geochemical retention processes are typically lumped into a single parameter: the distribution coefficient (Kd). This approach relies on an important assumption: the Kd values are constant in time. This hypothesis is critical under long-term geochemical changes as it is known that the distribution coefficient depends on the pH, redox conditions and major chemistry of the system. In this work, we present a novel methodology that combines the robustness of stochastic methods with an explicit description of water-solute-rock interaction processes. The reconciliation of all these is achieved by using a dynamic Kd approach. The hydrogeochemical evolution of the site of study is first computed using long-term and large-scale mechanistic reactive transport simulations. The simulated hydrochemical conditions are then used to generate a complete database of Kd values, which represent the hydrochemical conditions in every position and time of the model domain. Then, MARFA (Painter and Mancillas, 2009) is used to carry out Time Domain Random Walk (TDRW) simulations of radionuclide transport. In these simulations, Kd values are dynamically updated using the afore-mentioned database. The results (i.e. radionuclide breakthrough curves) bring the signature of the underlying changes in the background geochemistry.
NASA Astrophysics Data System (ADS)
Esser, B. K.; Moran, J. E.; Hudson, G. B.; Carle, S. F.; McNab, W.; Tompson, A. F.; Moore, K.; Beller, H.; Kane, S.; Eaton, G.
2003-12-01
More than 1/3 of active public drinking water supply wells in California produce water with nitrate-N levels indicative of anthropogenic inputs (> 4 mg/L). Understanding how the distribution of nitrate in California groundwater basins will evolve is vital to water supply and infrastructure planning. To address this need, we are studying the basin-scale reactive transport of nitrate in the Livermore and Llagas basins of Northern California. Both basins have increasingly urban populations heavily reliant on groundwater. A distinct nitrate "plume" exists in the Livermore Basin (Alameda County) whereas pervasive nitrate contamination exists in shallow groundwaters of the Llagas Basin (Santa Clara County). The sources and timing of nitrate contamination in these basins are not definitively known; septic systems, irrigated agriculture and livestock operations exist or have existed in both areas. The role of denitrification in controlling nitrate distribution is also unknown; dissolved oxygen levels are sufficiently low in portions of each basin as to indicate the potential for denitrification. We have collected water from 60 wells, and are determining both groundwater age (by the 3H/3He method) and the extent of denitrification (by the excess N2 method). Excess nitrogen is being determined by both membrane-inlet and noble gas mass spectrometry, using Ar and Ne content to account for atmospheric N2. We are also analyzing for stable istotopes of nitrate and water, nitrate co-contaminants, and general water quality parameters. Preliminary analysis of archival water district data from both basins suggests positive correlations of nitrate with Ca+2, Mg+2 and bicarbonate and negative correlation with pH. In the Llagas Basin, a negative correlation also exists between nitrate and temperature. Flow path-oriented reactive transport modeling is being explored as a tool to aid in the identification of both the sources of nitrate and evidence for denitrification in both basins
21st century space transportation system design approach - HL-20 personnel launch system
NASA Astrophysics Data System (ADS)
Stone, Howard W.; Piland, William M.
1993-10-01
This article provides an introduction to and overview of the research that was conducted on the HL-20 lifting body. The concept has been defined as an option for a personnel launch system (PLS) that is intended to carry six to eight Space Station Freedom crew persons. In this role the HL-20 will complement the Space Shuttle operation and ensure the ability to transport people to and from Earth orbit after the year 2000. The research covers a broad range of disciplines, including aerodynamics, aerodynamic heating and thermal protection systems, structural design, subsystem definition, trajectory and guidance system development for entry and abort, production and operations, and human factors. This article also presents the lifting-body heritage, design features of the concept, and HL-20/PLS mission requirements.
Gas transport and bubble collapse in rhyolitic magma: an experimental approach
NASA Astrophysics Data System (ADS)
Westrich, Henry R.; Eichelberger, John C.
1994-12-01
A series of experiments was conducted to test concepts of porous flow degassing of rhyolitic magma during ascent and of the subsequent collapse of vesicles in degassed magma to form obsidian. Dense, synthetically hydrated, natural glasses were pressurized under water-saturated conditions and then decompressed to achieve a range of porosities in the presence of a tracer vapor, D2O. Rapid isotopic exchange indicative of vapor transport rather than of simple diffusion occurred at a porosity >60 vol.%, in accord with earlier gas permeability measurements on cold natural samples. In another series of experiments, natural and synthetic pumices, vesiculated by degassing to atmospheric pressure, rapidly collapsed to dense glass on repressurization to the modest pressures prevailing in lava flows. No relict bubble textures remained. These results support the hypothesis that effusive eruptions result from the syneruptive escape of gas from permeable magmatic foam, and that a process analogous to welding yields dense lavas when such foams are extruded.
Capel, P.D.; McCarthy, K.A.; Barbash, J.E.
2008-01-01
This paper is an introduction to the following series of papers that report on in-depth investigations that have been conducted at five agricultural study areas across the United States in order to gain insights into how environmental processes and agricultural practices interact to determine the transport and fate of agricultural chemicals in the environment. These are the first study areas in an ongoing national study. The study areas were selected, based on the combination of cropping patterns and hydrologic setting, as representative of nationally important agricultural settings to form a basis for extrapolation to unstudied areas. The holistic, watershed-scale study design that involves multiple environmental compartments and that employs both field observations and simulation modeling is presented. This paper introduces the overall study design and presents an overview of the hydrology of the five study areas. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.
Song, Shuai; Su, Chao; Lu, Yonglong; Wang, Tieyu; Zhang, Yueqing; Liu, Shijie
2016-01-01
Urban areas are generally regarded as major sources of some semivolatile organic compounds and other persistent organic pollutants (POPs) to the surrounding regions. Huge differences in contaminant emissions between urban and rural areas directly affect their fate in environmental media. Little is known about POPs behavior between urban and rural areas at a regional scale. A spatially resolved Berkeley-Trent-Urban-Rural Fate Model (BETR-UR) was designed by coupling land cover information to simulate the transport of POPs between urban and rural areas, and the Bohai Rim was used as a case study to estimate Polycyclic Aromatic Hydrocarbon (PAH) fate. The processes of contaminant fate including emission, inter-compartmental transfer, advection and degradation in urban and rural areas were simulated in the model. Simulated PAH concentrations in environmental media of urban and rural areas were very close to measured values. The model accuracy was highly improved, with the average absolute relative error for PAH concentrations reduced from 37% to 3% compared with unimproved model results. PAH concentrations in urban soil and air were considerably higher than those in rural areas. Sensitivity analysis showed temperature was the most influential parameter for Phen rather than for Bap, whose fate was more influenced by emission rate, compartment dimension, transport velocity and chemical persistence. Uncertainty analysis indicated modeled results in urban media had higher uncertainty than those in rural areas due to larger variations of emissions in urban areas. The differences in urban and rural areas provided us with valuable guidance on policy setting for urban-rural POP control.
Master equation approach to charge injection and transport in organic insulators
NASA Astrophysics Data System (ADS)
Freire, José A.; Voss, Grasiela
2005-03-01
We develop a master equation model of a disordered organic insulator sandwiched between metallic electrodes by treating as rate processes both the injection and the internal transport. We show how the master equation model allows for the inclusion of crucial correlation effects in the charge transport, particularly of the Pauli exclusion principle and of space-charge effects, besides, being dependent on just the microscopic form of the transfer rate between the localized electronic states, it allows for the investigation of different microscopic scenarios in the organic, such as polaronic hopping, correlated energy levels, interaction with image charge, etc. The model allows for a separate analysis of the injection and the recombination currents. We find that the disorder, besides increasing the injection current, eliminates the possibility of observation of a Fowler-Nordheim injection current at zero temperature, and that it does not alter the Schottky barrier size of the zero-field thermionic injection current from the value based on the energy difference between the electrode Fermi level and the highest occupied molecular orbital/lowest unoccupied molecular orbital levels in the organic, but it makes the Arrhenius temperature dependence appear at larger temperatures. We investigate how the I(V ) characteristics of a device is affected by the presence of correlations in the site energy distribution and by the form of the internal hopping rate, specifically the Miller-Abrahams rate and the Marcus or small-polaron rate. We show that the disorder does not modify significantly the eβ√E field dependence of the net current due to the Schottky barrier lowering caused by the attraction between the charge and its image in the electrode.
NASA Astrophysics Data System (ADS)
Khaska, Mahmoud; Le Gal La Salle, Corinne; Verdoux, Patrick
2015-04-01
Arsenic contamination represents a major risk to human health as one of the most prominent environmental causes of cancer mortality. Mining activities, particularly those involving arsenic rich ores have an impact on the environment and on human health that may persist for many decades after mine closure. The relationships between As released from alluvial aquifer in the vicinity of the sulfide-rich mine dumps was demonstrated with geochemical and isotopic tracers (major and traces elements, 87Sr/86Sr, 18O, 2H). Strontium isotopes were used to trace the transport of As downstream from a As rich tailing dam. Increasing As and Fe concentrations in surface water are explained by As release associated with alluvial groundwater discharge to the stream. This process occurs in a moderately reduced section of the stream downgradient from the sulfide-rich tailing dam. High As, total Fe and low Eh in groundwater confirm the discharge of alluvial groundwater and explain its impact on surface water. Transport of As between surface and groundwater can be described as follows: 1- Subsurface moderately reducing conditions prevail in groundwater downgradient from the tailing dams. This suggests a flux of reduced water from sulfide-rich tailing dams which is characterized by its high As and Fe content resulting from the reduction of Fe-sulfides. 2- Upon mixing with surface water, oxidizing conditions prevails and precipitate as Fe hydroxide on the stream bed. As and Sr subsequently adsorbed on the Fe -oxyhydroxide surface. This process contributes to the immobilization of As in surface water. Remaining dissolved As in surface water can be re-introduced in alluvial groundwater downstream of the reducing zone.
Environmental transport and human exposure: A multimedia approach in health-risk policy
McKone, T.E.
1992-05-01
In his treatise Air, Water, and Places, the ancient-Greek physician Hippocrates demonstrated that the appearance of disease in human populations is influenced by the quality of air, water, and food; the topography of the land; and general living habits. This approach is still relevant and, indeed, the conerstone of modem efforts to relate public health to environmental factors. What has changed is the precision with which we can measure and model these long-held relationships. Environmental scientists recognize that plants, animals, and humans encounter environmental contaminants via complex transfers through air, water, and food and use multimedia models to evaluate these transfers. In this report, I explore the use of multimedia models both to examine pollution trends and as a basis for characterizing human health risks and ecological risks. The strengths and weaknesses of the approach are discussed.
Non-equilibrium STLS approach to transport properties of single impurity Anderson model
Rezai, Raheleh Ebrahimi, Farshad
2014-04-15
In this work, using the non-equilibrium Keldysh formalism, we study the effects of the electron–electron interaction and the electron-spin correlation on the non-equilibrium Kondo effect and the transport properties of the symmetric single impurity Anderson model (SIAM) at zero temperature by generalizing the self-consistent method of Singwi, Tosi, Land, and Sjolander (STLS) for a single-band tight-binding model with Hubbard type interaction to out of equilibrium steady-states. We at first determine in a self-consistent manner the non-equilibrium spin correlation function, the effective Hubbard interaction, and the double-occupancy at the impurity site. Then, using the non-equilibrium STLS spin polarization function in the non-equilibrium formalism of the iterative perturbation theory (IPT) of Yosida and Yamada, and Horvatic and Zlatic, we compute the spectral density, the current–voltage characteristics and the differential conductance as functions of the applied bias and the strength of on-site Hubbard interaction. We compare our spectral densities at zero bias with the results of numerical renormalization group (NRG) and depict the effects of the electron–electron interaction and electron-spin correlation at the impurity site on the aforementioned properties by comparing our numerical result with the order U{sup 2} IPT. Finally, we show that the obtained numerical results on the differential conductance have a quadratic universal scaling behavior and the resulting Kondo temperature shows an exponential behavior. -- Highlights: •We introduce for the first time the non-equilibrium method of STLS for Hubbard type models. •We determine the transport properties of SIAM using the non-equilibrium STLS method. •We compare our results with order-U2 IPT and NRG. •We show that non-equilibrium STLS, contrary to the GW and self-consistent RPA, produces the two Hubbard peaks in DOS. •We show that the method keeps the universal scaling behavior and correct
A probabilistic approach to emissions from transportation sector in the coming decades
NASA Astrophysics Data System (ADS)
Yan, F.; Winijkul, E.; Bond, T. C.; Streets, D. G.
2010-12-01
Future emission estimates are necessary for understanding climate change, designing national and international strategies for air quality control and evaluating mitigation policies. Emission inventories are uncertain and future projections even more so. Most current emission projection models are deterministic; in other words, there is only single answer for each scenario. As a result, uncertainties have not been included in the estimation of climate forcing or other environmental effects, but it is important to quantify the uncertainty inherent in emission projections. We explore uncertainties of emission projections from transportation sector in the coming decades by sensitivity analysis and Monte Carlo simulations. These projections are based on a technology driven model: the Speciated Pollutants Emission Wizard (SPEW)-Trend, which responds to socioeconomic conditions in different economic and mitigation scenarios. The model contains detail about technology stock, including consumption growth rates, retirement rates, timing of emission standards, deterioration rates and transition rates from normal vehicles to vehicles with extremely high emission factors (termed “superemitters”). However, understanding of these parameters, as well as relationships with socioeconomic conditions, is uncertain. We project emissions from transportation sectors under four different IPCC scenarios (A1B, A2, B1, and B2). Due to the later implementation of advanced emission standards, Africa has the highest annual growth rate (1.2-3.1%) from 2010 to 2050. Superemitters begin producing more than 50% of global emissions around year 2020. We estimate uncertainties from the relationships between technological change and socioeconomic conditions and examine their impact on future emissions. Sensitivities to parameters governing retirement rates are highest, causing changes in global emissions from-26% to +55% on average from 2010 to 2050. We perform Monte Carlo simulations to examine
DeSimone, L.A.; Howes, B.L.
1998-01-01
Nitrogen transport and transformations were followed over the initial 3 years of development of a plume of wastewater-contaminated groundwater in Cape Cod, Massachusetts. Ammonification and nitrification in the unsaturated zone and ammonium sorption in the saturated zone were predominant, while loss of fixed nitrogen through denitrification was minor. The major effect of transport was the oxidation of discharged organic and inorganic forms to nitrate, which was the dominant nitrogen form in transit to receiving systems. Ammonification and nitrification in the unsaturated zone transformed 16-19% and 50-70%, respectively, of the total nitrogen mass discharged to the land surface during the study but did not attenuate the nitrogen loading. Nitrification in the unsaturated zone also contributed to a pH decrease of 2 standard units and to an N2O increase (46-660 ??g N/L in the plume). Other processes in the unsaturated zone had little net effect: Ammonium sorption removed <1% of the total discharged nitrogen mass; filtering of particulate organic nitrogen was less than 3%; ammonium and nitrate assimilation was less than 6%; and ammonia volatilization was less than 0.25%. In the saturated zone a central zone of anoxic groundwater (DO ??? 0.05 mg/L) was first detected 17 months after effluent discharge to the aquifer began, which expanded at about the groundwater-flow velocity. Although nitrate was dominant at the water table, the low, carbon-limited rates of denitrification in the anoxic zone (3.0-9.6 (ng N/cm3)/d) reduced only about 2% of the recharged nitrogen mass to N2. In contrast, ammonium sorption in the saturated zone removed about 16% of the recharged nitrogen mass from the groundwater. Ammonium sorption was primarily limited to anoxic zone, where nitrification was prevented, and was best described by a Langmuir isotherm in which effluent ionic concentrations were simulated. The initial nitrogen load discharged from the groundwater system may depend largely on
Different modelling approaches to evaluate nitrogen transport and turnover at the watershed scale
NASA Astrophysics Data System (ADS)
Epelde, Ane Miren; Antiguedad, Iñaki; Brito, David; Jauch, Eduardo; Neves, Ramiro; Garneau, Cyril; Sauvage, Sabine; Sánchez-Pérez, José Miguel
2016-08-01
This study presents the simulation of hydrological processes and nutrient transport and turnover processes using two integrated numerical models: Soil and Water Assessment Tool (SWAT) (Arnold et al., 1998), an empirical and semi-distributed numerical model; and Modelo Hidrodinâmico (MOHID) (Neves, 1985), a physics-based and fully distributed numerical model. This work shows that both models reproduce satisfactorily water and nitrate exportation at the watershed scale at annual and daily basis, MOHID providing slightly better results. At the watershed scale, both SWAT and MOHID simulated similarly and satisfactorily the denitrification amount. However, as MOHID numerical model was the only one able to reproduce adequately the spatial variation of the soil hydrological conditions and water table level fluctuation, it proved to be the only model able of reproducing the spatial variation of the nutrient cycling processes that are dependent to the soil hydrological conditions such as the denitrification process. This evidences the strength of the fully distributed and physics-based models to simulate the spatial variability of nutrient cycling processes that are dependent to the hydrological conditions of the soils.
NASA Astrophysics Data System (ADS)
Langel, Christopher Michael
A computational investigation has been performed to better understand the impact of surface roughness on the flow over a contaminated surface. This thesis highlights the implementation and development of the roughness amplification model in the flow solver OVERFLOW-2. The model, originally proposed by Dassler, Kozulovic, and Fiala, introduces an additional scalar field roughness amplification quantity. This value is explicitly set at rough wall boundaries using surface roughness parameters and local flow quantities. This additional transport equation allows non-local effects of surface roughness to be accounted for downstream of rough sections. This roughness amplification variable is coupled with the Langtry-Menter model and used to modify the criteria for transition. Results from flat plate test cases show good agreement with experimental transition behavior on the flow over varying sand grain roughness heights. Additional validation studies were performed on a NACA 0012 airfoil with leading edge roughness. The computationally predicted boundary layer development demonstrates good agreement with experimental results. New tests using varying roughness configurations are being carried out at the Texas A&M Oran W. Nicks Low Speed Wind Tunnel to provide further calibration of the roughness amplification method. An overview and preliminary results are provided of this concurrent experimental investigation.
A multilevel cost-space approach to solving the balanced long transportation problem
NASA Technical Reports Server (NTRS)
Cavanaugh, Kevin J.; Henson, Van Emden
1993-01-01
We develop a multilevel scheme for solving the balanced long transportation problem, that is, given a set (c(sub kj)) of shipping costs from a set of M supply nodes S(sub k) to a set of N demand nodes D(sub j), we seek to find a set of flows, (x(sub kj)), that minimizes the total cost Sigma(sub k=1)(exp M) Sigma(sub j=1)(exp N) x(sub kj)c(sub kj). We require that the problem be balanced, that is, the total demand must equal the total supply. Solution techniques for this problem are well known from optimization and linear programming. We examine this problem, however, in order to develop principles that can then be applied to more intractible problems of optimization. We develop a multigrid scheme for solving the problem, defining the grids, relaxation, and intergrid operators. Numerical experimentation shows that this line of research may prove fruitful. Further research directions are suggested.
Crapse, Kimberly P.; Serkiz, Steven M.; Pishko, Adrian L.; Kaplan, Daniel L.; Lee, Cindy M.; Schank, Anja
2005-08-18
To quantify metal natural attenuation processes in terms of environmental availability, sequential extraction experiments were carried out on subsurface soil samples impacted by a low pH, high sulfate, metals (Be, Ni, U, As) plume associated with the long-term operation of a coal plant at the Savannah River Site in South Carolina. Despite significant heterogeneity resulting both from natural and anthropogenic factors, sequential extraction results demonstrate that pH is a controlling factor in the prediction of the distribution of metal contaminants within the solid phases in soils at the site as well as the contaminant partitioning between the soil and the soil solution. Results for beryllium, the most mobile metal evaluated, exhibit increasing attenuation along the plume flow path which corresponds to an increasing plume pH. These laboratory- and field-scale studies provide mechanistic information regarding partitioning of metals to soils at the site (one of the major attenuation mechanisms for the metals at the field site). Subsequently, these data have been used in the definition of the contaminant source terms and contaminant transport factors in risk modeling for the site.
Non-equilibrium STLS approach to transport properties of single impurity Anderson model
NASA Astrophysics Data System (ADS)
Rezai, Raheleh; Ebrahimi, Farshad
2014-04-01
In this work, using the non-equilibrium Keldysh formalism, we study the effects of the electron-electron interaction and the electron-spin correlation on the non-equilibrium Kondo effect and the transport properties of the symmetric single impurity Anderson model (SIAM) at zero temperature by generalizing the self-consistent method of Singwi, Tosi, Land, and Sjolander (STLS) for a single-band tight-binding model with Hubbard type interaction to out of equilibrium steady-states. We at first determine in a self-consistent manner the non-equilibrium spin correlation function, the effective Hubbard interaction, and the double-occupancy at the impurity site. Then, using the non-equilibrium STLS spin polarization function in the non-equilibrium formalism of the iterative perturbation theory (IPT) of Yosida and Yamada, and Horvatic and Zlatic, we compute the spectral density, the current-voltage characteristics and the differential conductance as functions of the applied bias and the strength of on-site Hubbard interaction. We compare our spectral densities at zero bias with the results of numerical renormalization group (NRG) and depict the effects of the electron-electron interaction and electron-spin correlation at the impurity site on the aforementioned properties by comparing our numerical result with the order U2 IPT. Finally, we show that the obtained numerical results on the differential conductance have a quadratic universal scaling behavior and the resulting Kondo temperature shows an exponential behavior.
Time-dependent and steady-state Gutzwiller approach for nonequilibrium transport in nanostructures
NASA Astrophysics Data System (ADS)
Lanatà, Nicola; Strand, Hugo U. R.
2012-09-01
We extend the time-dependent Gutzwiller variational approach, recently introduced by Schirò and Fabrizio [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.076401 105, 076401 (2010)], to impurity problems. Furthermore, we derive a consistent theory for the steady state, and show its equivalence with the previously introduced nonequilibrium steady-state extension of the Gutzwiller approach. The method is shown to be able to capture dissipation in the leads, so that a steady state is reached after a sufficiently long relaxation time. The time-dependent method is applied to the single-orbital Anderson impurity model at half filling, modeling a quantum dot coupled to two leads. In these exploratory calculations, the Gutzwiller projector is limited to act only on the impurity. The strengths and the limitations of this approximation are assessed via comparison with state-of-the-art continuous-time quantum Monte Carlo results. Finally, we discuss how the method can be systematically improved by extending the region of action of the Gutzwiller projector.
A Systematic Approach for Developing Conceptual Models of Contaminant Transport at the Hanford Site
NASA Astrophysics Data System (ADS)
Murray, C. J.; Last, G. V.; Rohay, V. J.; Schelling, F. J.; Hildebrand, R. D.; Morse, J. G.
2004-12-01
The U.S. Department of Energy (DOE) faces many decisions regarding future remedial actions and waste disposal at the Hanford Site in southeast Washington State. To support these decisions, DOE recognized the need for a comprehensive and systematic approach to developing and documenting complete, consistent, and defensible conceptual models of contaminant release and migration. After reviewing existing conceptual model development methodologies that might be applicable to environmental assessments at the Hanford Site, DOE initiated efforts to adapt and implement the Features, Events, and Processes (FEP) methodology developed for use in performance assessments of nuclear waste disposal systems by NIREX. In adapting this methodology for use in the environmental assessments at Hanford, the international list of FEPs, compiled from nuclear waste disposal programs, was evaluated to develop a list of potentially relevant Hanford-specific FEPs. The international nuclear waste programs focus on deep geologic disposal while waste disposal at the Hanford Site involves burial in shallow unconsolidated geologic deposits. Thus, a graphical tool called the Process Relationship Diagram (PRD) was created to assist in identifying the international FEPs and additional factors that are relevant to Hanford, and to illustrate the relationships among these factors. The PRD is similar in form and function to the Master Directed Diagram used by NIREX to provide a visual and systematic structure for the FEP methodology. Adaptation of this approach is showing promise in facilitating the development of conceptual models and selection of relevant factors to be incorporated into environmental uncertainty assessments for the Hanford Site.
Dixon, Kenneth L; Lee, Patricia L; Flach, Gregory P
2008-05-01
A graded approach to flow and transport modeling has been used as a cost effective solution to evaluating potential groundwater risk in support of Deactivation and Decommissioning activities at the United States Department of Energy's Savannah River Site (SRS) in Aiken, South Carolina. This approach balances modeling complexity with potential risk and has been successfully used at SRS to reduce costs and accelerate schedule without compromising human health or the environment. The approach incorporates both simple spreadsheet calculations (i.e., screening models) and complex numerical modeling to evaluate the threat to human health posed by contaminants leaching from decommissioned concrete building slabs. Simple spreadsheet calculations were used to produce generic slab concentration limits for a suite of radiological and non-radiological contaminants for a chemical separations area at SRS. These limits, which are based upon the United States Environmental Protection Agency Soil Screening Guidance, were used to eliminate most building slabs from further risk assessment, thereby limiting the time and associated cost of the more rigorous assessment to higher risk facilities. Of the more than 58 facilities located in the area, to date only one slab has been found to have a contaminant concentration in excess of the area specific slab limit. For this slab, a more rigorous numerical modeling effort was undertaken which eliminated some of the simplifying and conservative assumptions inherent in the spreadsheet calculations. Results from the more sophisticated numerical model show that the remaining contaminant of concern would not likely impact groundwater above drinking water standards. PMID:18403957
Important issues facing model-based approaches to tunneling transport in molecular junctions
NASA Astrophysics Data System (ADS)
Bâldea, Ioan
Extensive studies on thin films indicated a generic cubic current-voltage $I-V$ dependence as a salient feature of charge transport by tunneling. A quick glance at $I-V$ data for molecular junctions suggests a qualitatively similar behavior. This would render model-based studies almost irrelevant, since, whatever the model, its parameters can always be adjusted to fit symmetric (asymmetric) $I-V$ curves characterized by two (three) expansion coefficients. Here, we systematically examine popular models based on tunneling barrier or tight-binding pictures and demonstrate that, for a quantitative description at biases of interest ($V$ slightly higher than the transition voltage $V_t$), cubic expansions do not suffice. A detailed collection of analytical formulae as well as their conditions of applicability are presented to facilitate experimentalists colleagues to process and interpret their experimental data by obtained by measuring currents in molecular junctions. We discuss in detail the limits of applicability of the various models and emphasize that uncritically adjusting model parameters to experiment may be unjustified because the values deduced in this way may fall in ranges rendering a specific model invalid or incompatible to ab initio estimates. We exemplify with the benchmark case of oligophenylene-based junctions, for which results of ab initio quantum chemical calculations are also reported. As a specific issue, we address the impact of the spatial potential profile and show that it is not notable up to biases V somewhat larger than V_t, unlike at higher biases, where it may be responsible for negative differential resistance effects.
Transport-theoretical description of nuclear reactions
NASA Astrophysics Data System (ADS)
Buss, O.; Gaitanos, T.; Gallmeister, K.; van Hees, H.; Kaskulov, M.; Lalakulich, O.; Larionov, A. B.; Leitner, T.; Weil, J.; Mosel, U.
2012-03-01
In this review we first outline the basics of transport theory and its recent generalization to off-shell transport. We then present in some detail the main ingredients of any transport method using in particular the Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) implementation of this theory as an example. We discuss the potentials used, the ground state initialization and the collision term, including the in-medium modifications of the latter. The central part of this review covers applications of GiBUU to a wide class of reactions, starting from pion-induced reactions over proton and antiproton reactions on nuclei to heavy-ion collisions (up to about 30 AGeV). A major part concerns also the description of photon-, electron- and neutrino-induced reactions (in the energy range from a few 100 MeV to a few 100 GeV). For this wide class of reactions GiBUU gives an excellent description with the same physics input and the same code being used. We argue that GiBUU is an indispensable tool for any investigation of nuclear reactions in which final-state interactions play a role. Studies of pion-nucleus interactions, nuclear fragmentation, heavy-ion reactions, hypernucleus formation, hadronization, color transparency, electron-nucleus collisions and neutrino-nucleus interactions are all possible applications of GiBUU and are discussed in this article.
NASA Astrophysics Data System (ADS)
Lachhvani, Lavkesh; Pahari, Sambaran; Goswami, Rajiv; Bajpai, Manu; Yeole, Yogesh; Chattopadhyay, P. K.
2016-06-01
A long confinement time of electron plasma, approaching magnetic pumping transport limit, has been observed in SMARTEX-C (a small aspect ratio partial torus with R o / a ˜ 1.59 ). Investigations of the growth rate reveal that they are governed by instabilities like resistive wall destabilization, ion driven instabilities, and electron-neutral collisions. Successful confinement of electron plasmas exceeding > 1 × 10 5 poloidal E → × B → rotations lasting for nearly 2.1 ± 0.1 s is achieved by suppressing these instabilities. The confinement time has been estimated in two ways: (a) from the frequency scaling of the linear diocotron mode launched from sections of the wall that are also used as capacitive probes and (b) by dumping the plasma onto a charge collector at different hold times.
NASA Astrophysics Data System (ADS)
Fazio, Peppino; Santamaria, Amilcare Francesco; De Rango, Floriano; Tropea, Mauro; Serianni, Abdon
2016-05-01
In the last years the physical security in transportation systems is becoming a critical issue due to the high number of accidents and emergency situations. With the increasing availability of technological applications in vehicular environments researchers aimed at minimizing the probability of road accidents. In this paper, we propose a new platform able to discover dangerous driving behaviors. We based our application on the on-board diagnosis standard, able to provide all the needed information directly from the electronic vehicle control unit . We integrated the received data with a fuzzy logic approach, obtaining a description of the driver behavior. The overall system can take several initiatives (alarms, rpm corrections, etc.), in order to notify the driver bad behavior. The performance of the proposed scheme has been validated through a deep campaign of driving simulations.
Song, Linze; Shi, Qiang
2015-05-01
We present a new non-perturbative method to calculate the charge carrier mobility using the imaginary time path integral approach, which is based on the Kubo formula for the conductivity, and a saddle point approximation to perform the analytic continuation. The new method is first tested using a benchmark calculation from the numerical exact hierarchical equations of motion method. Imaginary time path integral Monte Carlo simulations are then performed to explore the temperature dependence of charge carrier delocalization and mobility in organic molecular crystals (OMCs) within the Holstein and Holstein-Peierls models. The effects of nonlocal electron-phonon interaction on mobility in different charge transport regimes are also investigated. PMID:25956086
NASA Astrophysics Data System (ADS)
Yoshizawa, Akira; Abe, Hiroyuki; Matsuo, Yuichi; Fujiwara, Hitoshi; Mizobuchi, Yasuhiro
2012-07-01
A Reynolds-averaged approach to turbulent shear flows is sought with resort to a three-equation method. Its novelty is the introduction of a turbulent-viscosity transport equation through the transport equation for the Reynolds stress in addition to those for the turbulent kinetic energy and the dissipation rate. The latter two equations are used for evaluating the dimensional coefficients in the former. The aim of this model is to enhance the capability to cope with nonstationary and advection effects in various turbulent flows. The adaptability to them is confirmed through the application to homogeneous-shear and supersonic free-shear flows. In particular, the reasonable prediction is obtained in the latter where the growth rate of the shear layer is suppressed with the increase in the convective Mach number. The present model is also applied to a three-dimensional flow past a wing tip as an instance of complex aeronautical flows, and the excessive diffusion of the trailing vortices is shown to be suppressed. The turbulent-viscosity representation for the Reynolds stress is systematically supplemented with nonlinear effects of mean-velocity gradient tensors, and its adequacy is verified in a channel flow.
NASA Astrophysics Data System (ADS)
Bulgakova, Nadezhda M.; Stoian, Razvan; Rosenfeld, Arkadi; Marine, Wladimir; Campbell, Eleanor E.
2004-09-01
We present a continuum model, based on a drift-diffusion approach, aimed to describe the dynamics of electronic excitation, heating and charge-carrier transport in different materials (metals, semiconductors, and dielectrics) under femtosecond and nanosecond pulsed laser irradiation. The laser-induced charging of the targets is investigated at laser intensities above the material removal threshold. It is demonstrated that, under near-infrared femtosecond irradiation regimes, charging of dielectric surfaces causes a sub-picosecond electrostatic rupture of the superficial layers, alternatively called Coulomb explosion (CE), while this effect is strongly inhibited for metals and semiconductors as a consequence of superior carrier transport properties. On the other hand, simulations of UV nanosecond pulsed laser interaction with bulk silicon have pointed out the possibility of Coulomb explosion in semiconductors. For such regimes a simple analytical theory for the threshold laser fluence of CE has been developed, showing results in agreement with the experimental observations. Various related aspects concerning the possibility of CE depending on different irradiation parameters (fluence, wavelength and pulse duration) are discussed. This includes the temporal and spatial dynamics of charge-carrier generation in non-metallic targets and evolution of the reflection and absorption characteristics.
NASA Astrophysics Data System (ADS)
Bulgakova, N. M.; Stoian, R.; Rosenfeld, A.; Hertel, I. V.; Marine, W.; Campbell, E. E. B.
2005-07-01
We present a continuum model, based on a drift-diffusion approach, aimed at describing the dynamics of electronic excitation, heating, and charge-carrier transport in different materials (metals, semiconductors, and dielectrics) under femtosecond and nanosecond pulsed laser irradiation. The laser-induced charging of the targets is investigated at laser intensities above the material removal threshold. It is demonstrated that, for near-infrared femtosecond irradiation, charging of dielectric surfaces causes a sub-picosecond electrostatic rupture of the superficial layers, alternatively called Coulomb explosion (CE), while this effect is strongly inhibited for metals and semiconductors as a consequence of superior carrier transport properties. On the other hand, application of the model to UV nanosecond pulsed laser interaction with bulk silicon has pointed out the possibility of Coulomb explosion in semiconductors. For such regimes a simple analytical theory for the threshold laser fluence of CE has been developed, showing results in agreement with the experimental observations. Various related aspects concerning the possibility of CE depending on different irradiation parameters (fluence, wavelength and pulse duration) and material properties are discussed. This includes the temporal and spatial dynamics of charge-carrier generation in non-metallic targets and evolution of the reflection and absorption characteristics.
NASA Astrophysics Data System (ADS)
Trinchero, P.; Painter, S. L.; Ebrahimi, H.; Koskinen, L.; Molinero, J.; Selroos, J. O.
2014-12-01
Due to the high heterogeneity of fractured media and the ubiquitous lack of a complete site characterization, deterministic simulations of radionuclide transport in fractured rocks are notoriously highly uncertain. This epistemic uncertainty is typically addressed using stochastic methods; e.g. the connectivity structure of the medium is described using one or multiple realizations of Discrete Fracture Networks (DFN), which are then combined to Time Domain Random Walk (TDRW) simulations (e.g. Painter and Cvetkovic, 2005). In these formulations, many complex geochemical retention processes are usually lumped into a single parameter: the distribution coefficient (Kd). Although this approach is mathematically robust and numerically efficient, it relies on an important assumption: the Kd value of each radionuclide is constant in time. This assumption could be critical under long-term geochemical changes as it is demonstrated that the distribution coefficient depends on the pH, redox conditions and major chemistry of the system. In this work, we present a novel methodology that combines the robustness of stochastic methods with a sound and explicit description of water-solute-rock interaction processes. The reconciliation of all these is achieved by using an "intelligent Kd" approach. The hydrogeochemical evolution of the site of study is first computed using long-term and large-scale mechanistic reactive transport simulations. The simulated hydrochemical conditions are then used to generate a complete database of Kd values, which represent the hydrochemical conditions in every position and time of the model domain. Then, TDRW simulations, based on one or multiple DFN realizations, are fed with these data and the results (e.g. radionuclide breakthrough curves) implicitly bring the signature of the underlying changes in the background geochemistry.
Kourgialas, Nektarios N; Karatzas, George P
2015-07-01
The water flow and the mass transport of agrochemicals in the unsaturated and saturated zone were simulated in the extended alluvial basin of Keritis river in Crete, Greece (a predominantly flat and most productive citrus growing area) using the hydrological model MIKE SHE. This model was set up based on information on land use, geology, soil structure, meteorological data, as well as groundwater level data from pumping wells. Additionally, field measurements of the soil moisture at six different locations from three soil depths (0.1, 0.2, and 0.3 m) were used as targets to calibrate and validate the unsaturated flow model while for saturated condition, groundwater level data from three well locations were used. Following the modeling approach, the agrochemical mass transport simulation was performed as well, based on different application doses. After the successful calibration processes, the obtained 1D modeling results of soil moisture-pressure related to soil depth at different locations were used to design a proper and cost-effective irrigation programme (irrigation timing, frequency, application rates, etc.) for citrus orchards. The results of the present simulation showed a very good correlation with the field measurements. Based on these results, a proper irrigation plan can be designed at every site of the model domain reducing the water consumption up to 38% with respect to the common irrigation practices and ensuring the citrus water productivity. In addition, the effect of the proposed irrigation scheduling on citrus yield was investigated. Regarding the agrochemical concentration in the groundwater for all dose cases was below the maximum permissible limit. The only exception was for the highest dose in areas where the water table is high. Thus, this modeling approach could be used as a tool for appropriate water management in an agricultural area estimating at each time and location the availability of soil water, contributing to a cost
Curtis, G.P.
2003-01-01
Reactive solute transport models are useful tools for analyzing complex geochemical behavior resulting from biodegradation of organic compounds by multiple terminal electron acceptors (TEAPs). The usual approach of simulating the reactions of multiple TEAPs by an irreversible Monod rate law was compared with simulations that assumed a partial local equilibrium or kinetically controlled reactions subject to the requirement that the Gibbs free energy of reaction (?? G) was either less than zero or less than a threshold value. Simulations were performed using a single organic substrate and O2, FeOOH, SO4-2 and CO2 as the terminal electron acceptors. It was assumed that the organic substrate was slowly and completely fermented to CO2 and H2 and the H2 was oxidized by the TEAPs. Simulations using the Monod approach showed that this irreversible rate law forced the reduction of both FeOOH and CO2 to proceed even when ?? G was positive. This resulted in an over prediction in amount of FeOOH reduced to Fe(II) in parts of the domain and it resulted in large errors in pH. Simulations using mass action kinetics agreed with equilibrium simulations for the case of large rate constants. The extent of reductive dissolution of FeOOH was strongly dependent on the thermodynamic stability of the FeOOH phase. Transport simulations performed assuming that the reactions of the TEAPs stopped when ?? G exceeded a threshold value showed that only simulated H2 concentrations were affected if the threshold value was the same for each TEAP. Simulated H2 concentrations were controlled by the fastest reaction of the TEAP, but it was common for reactions to occur concomitantly rather than sequentially. ?? 2003. Published by Elsevier Science Ltd.
Chen, DI-WEN
2001-11-21
Airborne hazardous plumes inadvertently released during nuclear/chemical/biological incidents are mostly of unknown composition and concentration until measurements are taken of post-accident ground concentrations from plume-ground deposition of constituents. Unfortunately, measurements often are days post-incident and rely on hazardous manned air-vehicle measurements. Before this happens, computational plume migration models are the only source of information on the plume characteristics, constituents, concentrations, directions of travel, ground deposition, etc. A mobile ''lighter than air'' (LTA) system is being developed at Oak Ridge National Laboratory that will be part of the first response in emergency conditions. These interactive and remote unmanned air vehicles will carry light-weight detectors and weather instrumentation to measure the conditions during and after plume release. This requires a cooperative computationally organized, GPS-controlled set of LTA's that self-coordinate around the objectives in an emergency situation in restricted time frames. A critical step before an optimum and cost-effective field sampling and monitoring program proceeds is the collection of data that provides statistically significant information, collected in a reliable and expeditious manner. Efficient aerial arrangements of the detectors taking the data (for active airborne release conditions) are necessary for plume identification, computational 3-dimensional reconstruction, and source distribution functions. This report describes the application of stochastic or geostatistical simulations to delineate the plume for guiding subsequent sampling and monitoring designs. A case study is presented of building digital plume images, based on existing ''hard'' experimental data and ''soft'' preliminary transport modeling results of Prairie Grass Trials Site. Markov Bayes Simulation, a coupled Bayesian/geostatistical methodology, quantitatively combines soft information
Transport and deposition of carbon at catchment scale: stabilization mechanisms approach
NASA Astrophysics Data System (ADS)
Martínez-Mena, María; Almagro, María; Díaz-Pereira, Elvira; García-Franco, Noelia; Boix-Fayos, Carolina
2016-04-01
Terrestrial sedimentation buries large amounts of organic carbon (OC) annually, contributing to the terrestrial carbon sink. The temporal significance of this sink will strongly depend on the attributes of the depositional environment, but also on the characteristics of the OC reaching these sites and its stability upon deposition. The fate of the redistributed OC will ultimately depend on the mechanisms of its physical and chemical protection against decomposition, its turnover rates and the conditions under which the OC is stored in sedimentary settings. This framework is more complex in Mediterranean river basins where sediments are often redistributed under a range of environmental conditions in ephemeral, intermittent and perennial fluvial courses, sometimes within the same catchment. The OC stabilization mechanisms and their relations with aggregation at different transport and sedimentary deposits is under those conditions highly uncertain. The main objective of this work was to characterize the stabilization and mineralization of OC in sediments in transit (suspended load), at a range of depositional settings (alluvial bars, reservoir sediments) and soils from the source areas in a sub-catchment (111 km2) at the headwaters of the Segura catchment in South East Spain. In order to obtain a deeper knowledge on the predominant stabilization mechanism corresponding to each erosional phase, the following organic carbon fractionation method was carried out: Four aggregate size classes were distinguished by sieving (large and small macroaggregates, free microaggregates, and free silt plus clay fraction), and the microaggregates occluded within macroaggregates (SMm) were isolated. As a further step, an oxidation of the OC occluded in silt plus clay fraction and that of the free silt plus clay fraction was performed to estimate the oxidant resistant OC pool. Measured OC in these fractions can be related to three functional pools: active (free particulate organic
Lucia, Umberto; Ponzetto, Antonio; Deisboeck, Thomas S.
2016-01-01
To investigate biosystems, we propose a new thermodynamic concept that analyses ion, mass and energy flows across the cell membrane. This paradigm-shifting approach has a wide applicability to medically relevant topics including advancing cancer treatment. To support this claim, we revisit ‘Norton-Simon’ and evolving it from an already important anti-cancer hypothesis to a thermodynamic theorem in medicine. We confirm that an increase in proliferation and a reduction in apoptosis trigger a maximum of ATP consumption by the tumor cell. Moreover, we find that positive, membrane-crossing ions lead to a decrease in the energy used by the tumor, supporting the notion of their growth inhibitory effect while negative ions apparently increase the cancer’s consumption of energy hence reflecting a growth promoting impact. Our results not only represent a thermodynamic proof of the original Norton-Simon hypothesis but, more concretely, they also advance the clinically intriguing and experimentally testable, diagnostic hypothesis that observing an increase in negative ions inside a cell in vitro, and inside a diseased tissue in vivo, may indicate growth or recurrence of a tumor. We conclude with providing theoretical evidence that applying electromagnetic field therapy early on in the treatment cycle may maximize its anti-cancer efficacy. PMID:26822208
NASA Technical Reports Server (NTRS)
Mitra, Debasis; Thomas, Ajai; Hemminger, Joseph; Sakowski, Barbara
2001-01-01
In this research we have developed an algorithm for the purpose of constraint processing by utilizing relational algebraic operators. Van Beek and others have investigated in the past this type of constraint processing from within a relational algebraic framework, producing some unique results. Apart from providing new theoretical angles, this approach also gives the opportunity to use the existing efficient implementations of relational database management systems as the underlying data structures for any relevant algorithm. Our algorithm here enhances that framework. The algorithm is quite general in its current form. Weak heuristics (like forward checking) developed within the Constraint-satisfaction problem (CSP) area could be also plugged easily within this algorithm for further enhancements of efficiency. The algorithm as developed here is targeted toward a component-oriented modeling problem that we are currently working on, namely, the problem of interactive modeling for batch-simulation of engineering systems (IMBSES). However, it could be adopted for many other CSP problems as well. The research addresses the algorithm and many aspects of the problem IMBSES that we are currently handling.
NASA Astrophysics Data System (ADS)
Popp, Andrea; Moeck, Christian; Radny, Dirk; Borer, Paul; Affolter, Annette; Epting, Jannis; Huggenberger, Peter; Auckenthaler, Adrian; Schirmer, Mario
2015-04-01
Drinking water supply in urban areas is challenging due to different kinds of water use and potential groundwater contamination. We investigate an area where drinking water production is close to different contaminated sites. The study site is characterized by a high complexity of the tectonic and geological setting with a gravel and a karstic aquifer. The two aquifers are partly connected, partly disconnected by an aquitard. To avoid drinking water contamination, artificial groundwater recharge with surface water into the gravel aquifer is used to create a hydraulic barrier between the contaminated sites and the water abstraction wells. Trace compounds, that were found in former times in the surface water but not nowadays, are still detected in the extracted drinking water. Different studies have been performed such as numerical modeling, intensive groundwater monitoring and investigation of drilling cores to get a differentiated overview of the distribution of the contaminants. Back-diffusion from the matrix due to changing hydraulic boundary was stated to be the reason for the actual distribution of the contaminants. In a first approach due to the lack of experimental data or evidence from field measurements, the permeabilities of the karstic aquifer were assumed as homogeneous. In our study, we seek to identify the flow and transport processes within the system including the fracture network in a combined approach of field work and 3D modeling with FEFLOW. During a field campaign we acquired water samples for the analysis of stable water isotopes as well as organic and inorganic compounds. Furthermore, tritium and helium samples were taken to estimate water ages and to determine the flow through the fracture networks. A combination of existing and recently obtained data was used to build and validate a 3D flow and transport model. The simulation of different scenarios such as the water flow for varying injection and extraction rates as well as particle
Use of ADCPs for suspended sediment transport monitoring: An empirical approach
NASA Astrophysics Data System (ADS)
Venditti, J. G.; Church, M.; Attard, M. E.; Haught, D.
2016-04-01
A horizontally mounted 300 kHz acoustic Doppler current profiler was deployed in Fraser River at Mission, British Columbia, to test its capability to detect size-classified concentration of suspended sediment. Bottle samples in-beam provide a direct calibration of the hADCP signals. We also deployed a 600 kHz vertically mounted ADCP from a boat in combination with bottle samples. Fraser River at Mission is 525 m wide with moderate suspended sediment concentration (up to 350 mg L-1 in our measurements, mostly silt), and a modest sand load only at high flows. We use an entirely empirical approach to calculate the sediment load using ADCPs to test the reliability of acoustic methods when assumptions embedded in the sonar equation about the relation between suspended sediment size and concentration, and acoustic signals are violated. vADCP calibration using matched individual bottle samples and acoustic backscatter departed from the expected theoretical relation. Calibration using depth-averaged sediment concentration and acoustic backscatter more closely matched theoretical expectations, but varied through the season. hADCP calibrations conformed with theoretical expectations and did not exhibit seasonal variation. Silt and sand were successfully discriminated; however, silt dominates the correlations. We found no coherent relation between acoustic attenuation and silt concentration. In-beam results are extended by correlation to estimate mean sediment concentration and total suspended flux in the entire channel: this auxiliary correlation cancels any calibration bias and permits monitoring of size-classified suspended sediment in absence of detailed information of sediment grain-size distribution.
Dixon, K; Patricia Lee, P; Gregory Flach, G
2007-06-07
A graded approach to flow and transport modeling has been used as a cost effective solution to evaluating potential groundwater risk in support of Deactivation and Decommissioning activities at the United States Department of Energy's Savannah River Site. This approach incorporates both simple spreadsheet calculations and complex numerical modeling to evaluate the threat to human health posed by contaminants leaching from decommissioned concrete building slabs. Simple spread sheet calculations were used to produce generic slab concentration limits for a suite of radiological and non-radiological contaminants for a chemical separations area at Savannah River Site. These limits, which are based upon the United States Environmental Protection Agency Soil Screening guidance, were used to eliminate most building slabs from further risk assessment. Of the more than 58 facilities located in the area, to date only one slab has been found to have a contaminant concentration in excess of the area specific slab limit. For this slab, a more rigorous numerical modeling effort was undertaken reducing the conservatisms inherent in the spreadsheet calculations. Using the more sophisticated numerical model, it was possible to show that the remaining contaminant of concern would not likely impact groundwater above drinking water standards.
NASA Astrophysics Data System (ADS)
Porporato, A. M.; Parolari, A.
2015-12-01
Ecohydrological processes in the root zone act as a dynamic interface between the atmosphere and the deeper soil layers, modulating the conditions that drive chemical weathering along the soil profile. Among these processes, soil moisture dynamics respond to intermittent rainfall pulses and to runoff and evapotranspiration losses. In addition, carbon dioxide (CO2) and its associated acidity are introduced into the soil moisture via root and microbial respiration. The coupling of soil moisture and CO2 dynamics in the root zone acts as an important controller of the critical zone development through the chemical weathering and water chemistry exported through runoff and percolation. Due to spatial and temporal variability and non-linearity, modeling these coupled root zone soil moisture and CO2 dynamics presents a number of challenges. In this talk, a lumped, macroscopic approach to modeling soil moisture, CO2 transport, and chemical weathering in the critical zone is introduced. The model considers a homogeneous soil column, therefore simplifying known spatial heterogeneities, and focuses on temporal variability resulting from non-linear processes and stochastic rainfall forcing. First, at short time-scales, the deterministic temporal evolution of soil moisture, dissolved inorganic carbon, pH, and alkalinity is analyzed using a dynamical system approach. Second, at longer inter-annual time-scales where rainfall stochasticity becomes an important driver of the system behavior, the system is analyzed probabilistically and its average behavior described using a novel macroscopic approach. This averaging of the nonlinear stochastic dynamics results in a closure problem that is addressed through a first-order approximation of non-linear fluxes, including the correlation between soil moisture and solutes. The model provides a method to assess how changes in external forcing or system properties propagate into and alter critical zone structure and function, and to isolate
Evaporation-driven transport and precipitation of salt in porous-media: A multi-domain approach
NASA Astrophysics Data System (ADS)
Jambhekar, Vishal Arun; Schmid, Karen Sophie; Helmig, Rainer
2014-05-01
Introduction: Evaporative salinization a major concern worldwide is observed across many environmental, agricultural and engineering applications. In the context of agriculture, salinization caused due to excess irrigation and use of artificial fertilizers in last few decades deteriorated productive land to a large extent. Many scientists have conducted experimental and numerical studies related to evaporative salinization [1, 2]. However, to our knowledge most of the performed numerical studies neglect the influence of atmospheric processes and free-flow pours-media interaction, which could play a significant role for salinization in a natural system. With our model concept we attempt to study and analyze the influence of atmospheric processes on dissolved salt transport, evaporation dynamics and salt-precipitation. Evaporation is mainly driven by diffusion, related to the vapor pressure gradient across liquid-air interface and advection, related to the tangential wind velocity at the soil surface. Moreover, it is also affected by the complex interactions between the flow and transport processes in the atmosphere and the porous-medium. On the atmosphere side, it is influenced by wind velocity, air temperature, humidity, radiation etc. On the porous-medium side, it is strongly related to the advective and diffusive fluxes, heterogeneity in salinity distribution (causes osmosis) and salt precipitation (causes pore clogging). As discussed in [1] evaporation of saline solutions can be explained into three different stages. Model: Our model is capable to handle coupled single-phase-compositional free and three-phase-compositional porous-media flow and transport. It is based on a two-domain approach, where non-isothermal sub-models are used for free-flow and porous-media sub-domains [3]. The sub-models are coupled using interface conditions ensuring continuity of mass, momentum and energy. This facilitates to describe evaporation independent of any boundary condition at
Navarro, Amparo; Fernández-Liencres, M Paz; Peña-Ruiz, Tomás; García, Gregorio; Granadino-Roldán, José M; Fernández-Gómez, Manuel
2016-08-01
Density functional theory calculations were carried out to investigate the evolvement of charge transport properties of a set of new discotic systems as a function of ring and heteroatom (B, Si, S, and Se) substitution on the basic structure of perylene. The replacement of six-membered rings by five-membered rings in the reference compound has shown a prominent effect on the electron reorganization energy that decreases ∼0.2 eV from perylene to the new carbon five-membered ring derivative. Heteroatom substitution with boron also revealed to lower the LUMO energy level and increase the electron affinity, therefore lowering the electron injection barrier compared to perylene. Since the rate of the charge transfer between two molecules in columnar discotic systems is strongly dependent on the orientation of the stacked cores, the total energy and transfer integral of a dimer as a disc is rotated with respect to the other along the stacking axis have been predicted. Aimed at obtaining a more realistic approach to the bulk structure, the molecular geometry of clusters made up of five discs was fully optimized, and charge transfer rate and mobilities were estimated for charge transport along a one dimensional pathway. Heteroatom substitution with selenium yields electron transfer integral values ∼0.3 eV with a relative disc orientation of 25°, which is the preferred angle according to the dimer energy profile. All the results indicate that the tetraselenium-substituted derivative, not synthetized so far, could be a promising candidate among those studied in this work for the fabrication of n-type semiconductors based on columnar discotic liquid crystals materials. PMID:27497578
NASA Astrophysics Data System (ADS)
Navarro, Amparo; Fernández-Liencres, M. Paz; Peña-Ruiz, Tomás; García, Gregorio; Granadino-Roldán, José M.; Fernández-Gómez, Manuel
2016-08-01
Density functional theory calculations were carried out to investigate the evolvement of charge transport properties of a set of new discotic systems as a function of ring and heteroatom (B, Si, S, and Se) substitution on the basic structure of perylene. The replacement of six-membered rings by five-membered rings in the reference compound has shown a prominent effect on the electron reorganization energy that decreases ˜0.2 eV from perylene to the new carbon five-membered ring derivative. Heteroatom substitution with boron also revealed to lower the LUMO energy level and increase the electron affinity, therefore lowering the electron injection barrier compared to perylene. Since the rate of the charge transfer between two molecules in columnar discotic systems is strongly dependent on the orientation of the stacked cores, the total energy and transfer integral of a dimer as a disc is rotated with respect to the other along the stacking axis have been predicted. Aimed at obtaining a more realistic approach to the bulk structure, the molecular geometry of clusters made up of five discs was fully optimized, and charge transfer rate and mobilities were estimated for charge transport along a one dimensional pathway. Heteroatom substitution with selenium yields electron transfer integral values ˜0.3 eV with a relative disc orientation of 25°, which is the preferred angle according to the dimer energy profile. All the results indicate that the tetraselenium-substituted derivative, not synthetized so far, could be a promising candidate among those studied in this work for the fabrication of n-type semiconductors based on columnar discotic liquid crystals materials.
Chaudhury, Sanhita; Bhattacharyya, Arunasis; Goswami, Asok
2014-11-01
The work describes a novel and cleaner approach of electrodriven selective transport of Cs from simulated nuclear waste solutions through cellulose tri acetate (CTA)/poly vinyl chloride (PVC) based polymer inclusion membrane. The electrodriven cation transport together with the use of highly Cs+ selective hexachlorinated derivative of cobalt bis dicarbollide, allows to achieve selective separation of Cs+ from high concentration of Na+ and other fission products in nuclear waste solutions. The transport selectivity has been studied using radiotracer technique as well as atomic emission spectroscopic technique. Transport studies using CTA based membrane have been carried out from neutral solution as well as 0.4 M HNO3, while that with PVC based membrane has been carried out from 3 M HNO3. High decontamination factor for Cs+ over Na+ has been obtained in all the cases. Experiment with simulated high level waste solution shows selective transport of Cs+ from most of other fission products also. Significantly fast Cs+ transport rate along with high selectivity is an interesting feature observed in this membrane. The current efficiency for Cs+ transport has been found to be ∼100%. The promising results show the possibility of using this kind of electrodriven membrane transport methods for nuclear waste treatment.
NASA Astrophysics Data System (ADS)
Smith, H. G.; Blake, W. H.
2012-04-01
Fine sediment and associated contaminants transported through river networks can have important impacts on water quality, aquatic habitat and ecosystem function long after catchment remediation measures have been implemented. In this context, the potential role of fine sediment as a secondary source of pollution requires attention. Knowledge of fine sediment transfer and storage in river basins is essential for predicting recovery times of rivers affected by historic or contemporary industrial pollution e.g. mining. It is also vital for determining the effectiveness of management actions in reducing the supply of contaminated sediment to coastal ecosystems. Against this background, we aim to determine the residence/travel times of fine sediment through a river network in south-west England. The approach utilises fallout radionuclides (Cs-137, excess Pb-210, Be-7) to (i) infer diffuse sources of sediment and associated contaminants transported in suspension over event and seasonal timescales and (ii) estimate fine sediment residence times based on differences in radioactive decay rates. Information on downstream changes in sediment sources within basins is critical for interpreting residence times using fallout radionuclide data since changes in source type (e.g. surface versus subsurface) may influence residence time signals. Consequently, analysis of sediment sources for a set of nested monitoring sites is coupled with methods for estimating residence time e.g. comparison of Be-7/excess Pb-210 ratios and a two-compartment radionuclide mass balance model comprising slow and rapid transport components. The present study focuses on the River Tamar (917 km2), an agricultural basin with an extensive history of metal mining and legacy of fine sediment contamination. Sampling of land use and channel bank source material across the basin has been undertaken for the sediment source analysis in conjunction with integrated suspended sediment sampling over monthly intervals
NASA Astrophysics Data System (ADS)
Albert, Christopher G.; Heyn, Martin F.; Kapper, Gernot; Kasilov, Sergei V.; Kernbichler, Winfried; Martitsch, Andreas F.
2016-08-01
Toroidal torque generated by neoclassical viscosity caused by external non-resonant, non-axisymmetric perturbations has a significant influence on toroidal plasma rotation in tokamaks. In this article, a derivation for the expressions of toroidal torque and radial transport in resonant regimes is provided within quasilinear theory in canonical action-angle variables. The proposed approach treats all low-collisional quasilinear resonant neoclassical toroidal viscosity regimes including superbanana-plateau and drift-orbit resonances in a unified way and allows for magnetic drift in all regimes. It is valid for perturbations on toroidally symmetric flux surfaces of the unperturbed equilibrium without specific assumptions on geometry or aspect ratio. The resulting expressions are shown to match the existing analytical results in the large aspect ratio limit. Numerical results from the newly developed code NEO-RT are compared to calculations by the quasilinear version of the code NEO-2 at low collisionalities. The importance of the magnetic shear term in the magnetic drift frequency and a significant effect of the magnetic drift on drift-orbit resonances are demonstrated.
NASA Astrophysics Data System (ADS)
Endres, Stephan; van Hees, Hendrik; Bleicher, Marcus
2016-08-01
Dilepton production in heavy-ion collisions at collider energies—i.e., for the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC)—is studied within an approach that uses coarse-grained transport simulations to calculate thermal dilepton emission applying in-medium spectral functions from hadronic many-body theory and partonic production rates based on lattice calculations. The microscopic output from the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) model is hereby put on a grid of space-time cells, which makes it possible to extract the local temperature and chemical potential in each cell via an equation of state. The resulting dilepton spectra are in good agreement with the experimental results for the range of energies available at RHIC, √{sN N}=19.6 -200 GeV . The comparison of the data with the outcome from the coarse-grained UrQMD simulations shows that the newest measurements by the PHENIX and STAR Collaborations are consistent and that the low-mass spectra can be described by a cocktail of hadronic decay contributions together with thermal emission from broadened vector-meson spectral functions and from the quark-gluon plasma phase. Predictions for dilepton results at LHC energies show no significant change of the spectra as compared to RHIC, but a higher fraction of thermal contribution and harder slopes of the transverse-momentum distributions owing to the higher temperatures and flow obtained.
NASA Astrophysics Data System (ADS)
Khandelwal, Manish; Mench, M. M.
The concept of using controlled temperature gradients to non-parasitically remove excess water from porous media during PEFC stack shutdown has been numerically investigated. An integrated modeling approach focusing both at stack and single cell level is presented. The stack thermal model is developed to obtain detailed temperature distribution across the PEFC stack. The two-phase unit fuel cell model is developed to investigate the detailed water and thermal transport in the PEFC components after shutdown, which for the first time includes thermo-osmotic flow in the membrane. The model accounts for capillary and phase-change induced flow in the porous media, and thermo-osmotic and diffusive flow in the polymer membrane. The single cell model is used to estimate the local water distribution with land or channel boundary condition, and the experimentally validated stack thermal model provided the transient temperature boundary conditions. Two different stack designs are compared to quantify the residual water in the stack. Model results indicate that a favorable temperature gradient can be formed in the stack to enhance the water drainage rate, esp. at anode end cell locations, where freeze/thaw damage has been observed to occur.
Muñoz Rojo, Miguel; Martín, Jaime; Grauby, Stéphane; Borca-Tasciuc, Theodorian; Dilhaire, Stefan; Martin-Gonzalez, Marisol
2015-03-01
Correction for 'Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials' by Miguel Muñoz Rojo et al., Nanoscale, 2014, 6, 7858-7865. PMID:25668105
Muñoz Rojo, Miguel; Martín, Jaime; Grauby, Stéphane; Borca-Tasciuc, Theodorian; Dilhaire, Stefan; Martin-Gonzalez, Marisol
2015-03-01
Correction for 'Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials' by Miguel Muñoz Rojo et al., Nanoscale, 2014, 6, 7858-7865.
NASA Astrophysics Data System (ADS)
Park, D. K.; Bae, G. O.; Joun, W.; Park, B. H.; Park, J.; Park, I.; Lee, K. K.
2015-12-01
The GWHP system uses a stable temperature of groundwater for cooling and heating in buildings and thus has been known as one of the most energy-saving and cost-efficient renewable energy techniques. A GWHP facility was installed at an island located at the confluence of North Han and South Han rivers, Korea. Because of well-developed alluvium, the aquifer is suitable for application of this system, extracting and injecting a large amount of groundwater. However, the numerical experiments under various operational conditions showed that it could be vulnerable to thermal interference due to the highly permeable gravel layer, as a preferential path of thermal plume migration, and limited space for well installation. Thus, regional groundwater flow must be an important factor of consideration for the efficient operation under these conditions but was found to be not simple in this site. While the groundwater level in this site totally depends on the river stage control of Paldang dam, the direction and velocity of the regional groundwater flow, observed using the colloidal borescope, have been changed hour by hour with the combined flows of both the rivers. During the pumping and injection tests, the water discharges in Cheongpyeong dam affected their respective results. Moreover, the measured NO3-N concentrations might imply the effect of agricultural activities around the facility on the groundwater quality along the regional flow. It is obvious that the extraction and injection of groundwater during the facility operation will affect the fate of the agricultural contaminants. Particularly, the gravel layer must also be a main path for contaminant migration. The simulations for contaminant transport during the facility operation showed that the operation strategy for only thermal efficiency could be unsafe and unstable in respect of groundwater quality. All these results concluded that the integrated approach on groundwater flow and heat/solute transport is necessary
Bagdadi, Andrea; Orona, Nadia; Fernández, Eugenio; Altamirano, Anibal; Amorena, Carlos
2010-09-01
We have realized that our Biology undergraduate students learn biological concepts as established truths without awareness of the body of experimental evidence supporting the emerging models as usually presented in handbooks and texts in general. Therefore, we have implemented a laboratory practice in our course of Physiology and Biophysics, aimed to introduce the students in the way the scientific models and theories are built, through the measurement of Na(+) transport in frog skin. Transepithelial Na(+) transport was assessed in the frog skin, with measurements of short circuit currents. The mucosal Na(+) and serosal K(+) concentrations were modified and the effects were recorded. These effects were reversible. Addition of a drug that blocks epithelial Na(+) channels (amiloride) to the mucosal side solution abolished the short circuit current. Sodium fluxes were calculated, and the results were adjusted to Michaelis-Menten kinetics. The impact of the proposed practice on the students is discussed.
Bagdadi, Andrea; Orona, Nadia; Fernández, Eugenio; Altamirano, Anibal; Amorena, Carlos
2010-09-01
We have realized that our Biology undergraduate students learn biological concepts as established truths without awareness of the body of experimental evidence supporting the emerging models as usually presented in handbooks and texts in general. Therefore, we have implemented a laboratory practice in our course of Physiology and Biophysics, aimed to introduce the students in the way the scientific models and theories are built, through the measurement of Na(+) transport in frog skin. Transepithelial Na(+) transport was assessed in the frog skin, with measurements of short circuit currents. The mucosal Na(+) and serosal K(+) concentrations were modified and the effects were recorded. These effects were reversible. Addition of a drug that blocks epithelial Na(+) channels (amiloride) to the mucosal side solution abolished the short circuit current. Sodium fluxes were calculated, and the results were adjusted to Michaelis-Menten kinetics. The impact of the proposed practice on the students is discussed. PMID:21567849
Martins, S A; Daily, W D; Ramirez, A L
2002-01-31
Subsurface imaging technology, such as electric resistance tomography (ERT), is rapidly improving as a means for characterizing some soil properties of the near-surface hydrologic regime. While this information can be potentially useful in developing hydrologic models of the subsurface that are required for contaminant transport investigations, an image alone of the subsurface soil regime gives little or no information about how the site will respond to groundwater flow or contaminant transport. In fact, there is some question that tomographic imaging of soils alone can even provide meaningful values of hydraulic properties, such as the permeability structure, which is critical to estimates of contaminant transport at a site. The main objective of this feasibility study was to initiate research on electrical imaging not just as a way to characterize the soil structure by mapping different soil types at a site but as a means of obtaining quantitative information about how a site will respond hydrologically to an infiltration event. To this end, a scaled system of electrode arrays was constructed that simulates the subsurface electrode distribution used at the LLNL Vadose Zone Observatory (VZO) where subsurface imaging of infiltration events has been investigated for several years. The electrode system was immersed in a 10,000-gallon tank to evaluate the fundamental relationship between ERT images and targets of a given volume that approximate infiltration-induced conductivity anomalies. With LDRD funds we have explored what can be initially learned about porous flow and transport using two important electrical imaging methods--electric resistance tomography (ERT) and electric impedance tomography (EIT). These tomographic methods involve passing currents (DC or AC) between two electrodes within or between electrode arrays while measuring the electric potential at the remaining electrodes. With the aid of a computer-based numerical inversion scheme, the potentials are
Peng, Kuan-wei; Bacon, James; Zheng, Ming; Guo, Yingying; Wang, Michael Zhuo
2015-07-01
Hepatic OATPs 1B1, 1B3 and 2B1, as well as P-gp, play important roles in regulating liver uptake and biliary excretion of drugs. The intrinsic ethnic variability in OATP1B1-mediated hepatic uptake of statins has been proposed to underlie the ethnic variability in plasma exposures of statins between Caucasians and Asians. Using a targeted quantitative proteomic approach, we determined hepatic protein concentrations of OATP1B1, OATP1B3, OATP2B1, P-gp, and PMCA4 (a housekeeping protein) in a panel of human livers (n = 141) and compared protein expression across Caucasian, Asian, African-American, and unidentified donors. Using an optimized protocol that included sodium deoxycholate as a membrane protein solubilizer, the hepatic protein expression levels (mean ± S.D.) of these transporters across all livers were determined to be 15.0 ± 6.0, 16.1 ± 8.1, 4.1 ± 1.3, 0.6 ± 0.2, and 2.4 ± 1.0 fmol/μg of total membrane protein, respectively. The scaling factor was 3.5 mg of total membrane protein in 100 mg of wet liver tissue. OATP1B1 protein expression was significantly associated with the c.388A>G (rs2306283, N130D) single nucleotide polymorphism. When compared across ethnicity, the hepatic expression levels of OATP1B1 and OATP1B3 were unexpectedly higher in Asians relative to Caucasians, suggesting that hepatic OATP expression alone does not explain the increased systemic statin levels in Asians compared with Caucasians. These findings may help improve physiologically based pharmacokinetic modeling to predict statin pharmacokinetic profiles and enable extrapolation of pharmacokinetic data of OATP substrates across ethnic groups.
NASA Astrophysics Data System (ADS)
Tutolo, B. M.; Luhmann, A. J.; Kong, X.; Seyfried, W. E.; Saar, M. O.
2012-12-01
the experimental system. Significantly, the application of these rate laws to feldspathic systems requires accurate thermodynamic data for primary and secondary aluminum-bearing minerals and aqueous species, particularly when modeling the transition from far-from-equilibrium to near-equilibrium rates as the experiment progresses. Overall, the reactive transport modeling approach presented here strengthens predictions of subsurface response to CO2 injection by integrating advanced characterization methods, accurate thermodynamic and kinetic data, and properly scaled geochemical and physical flow models.
NASA Technical Reports Server (NTRS)
Grantham, W. D.; Smith, P. M.; Neely, W. R., Jr.; Deal, P. L.; Yenni, K. R.
1985-01-01
Six-degree-of-freedom ground-based and in-flight simulator studies were conducted to evaluate the low-speed flight characteristics of a twin-fuselage passenger transport airplane and to compare these characteristics with those of a large, single-fuselage (reference) transport configuration similar to the Lockheed C-5A airplane. The primary piloting task was the approach and landing task. The results of this study indicated that the twin-fuselage transport concept had acceptable but unsatisfactory longitudinal and lateral-directional low-speed flight characteristics, and that stability and control augmentation would be required in order to improve the handling qualities. Through the use of rate-command/attitude-hold augmentation in the pitch and roll axes, and the use of several turn coordination features, the handling qualities of the simulated transport were improved appreciably. The in-flight test results showed excellent agreement with those of the six-degree-of-freedom ground-based simulator handling qualities tests. As a result of the in-flight simulation study, a roll-control-induced normal-acceleration criterion was developed. The handling qualities of the augmented twin-fuselage passenger transport airplane exhibited an improvement over the handling characteristics of the reference (single-fuselage) transport.
NASA Astrophysics Data System (ADS)
Harris, Courtney K.; Wiberg, Patricia L.
1997-09-01
Modeling shelf sediment transport rates and bed reworking depths is problematic when the wave and current forcing conditions are not precisely known, as is usually the case when long-term sedimentation patterns are of interest. Two approaches to modeling sediment transport under such circumstances are considered. The first relies on measured or simulated time series of flow conditions to drive model calculations. The second approach uses as model input probability distribution functions of bottom boundary layer flow conditions developed from wave and current measurements. Sediment transport rates, frequency of bed resuspension by waves and currents, and bed reworking calculated using the two methods are compared at the mid-shelf STRESS (Sediment TRansport on Shelves and Slopes) site on the northern California continental shelf. Current, wave and resuspension measurements at the site are used to generate model inputs and test model results. An 11-year record of bottom wave orbital velocity, calculated from surface wave spectra measured by the National Data Buoy Center (NDBC) Buoy 46013 and verified against bottom tripod measurements, is used to characterize the frequency and duration of wave-driven transport events and to estimate the joint probability distribution of wave orbital velocity and period. A 109-day record of hourly current measurements 10 m above bottom is used to estimate the probability distribution of bottom boundary layer current velocity at this site and to develop an auto-regressive model to simulate current velocities for times when direct measurements of currents are not available. Frequency of transport, the maximum volume of suspended sediment, and average flux calculated using measured wave and simulated current time series agree well with values calculated using measured time series. A probabilistic approach is more amenable to calculations over time scales longer than existing wave records, but it tends to underestimate net transport
Liu, Gaisheng; Lu, Zhiming; Zhang, Dongxiao
2007-01-01
A new approach has been developed for solving solute transport problems in randomly heterogeneous media using the Karhunen-Loève-based moment equation (KLME) technique proposed by Zhang and Lu (2004). The KLME approach combines the Karhunen-Loève decomposition of the underlying random conductivity field and the perturbative and polynomial expansions of dependent variables including the hydraulic head, flow velocity, dispersion coefficient, and solute concentration. The equations obtained in this approach are sequential, and their structure is formulated in the same form as the original governing equations such that any existing simulator, such as Modular Three-Dimensional Multispecies Transport Model for Simulation of Advection, Dispersion, and Chemical Reactions of Contaminants in Groundwater Systems (MT3DMS), can be directly applied as the solver. Through a series of two-dimensional examples, the validity of the KLME approach is evaluated against the classical Monte Carlo simulations. Results indicate that under the flow and transport conditions examined in this work, the KLME approach provides an accurate representation of the mean concentration. For the concentration variance, the accuracy of the KLME approach is good when the conductivity variance is 0.5. As the conductivity variance increases up to 1.0, the mismatch on the concentration variance becomes large, although the mean concentration can still be accurately reproduced by the KLME approach. Our results also indicate that when the conductivity variance is relatively large, neglecting the effects of the cross terms between velocity fluctuations and local dispersivities, as done in some previous studies, can produce noticeable errors, and a rigorous treatment of the dispersion terms becomes more appropriate.
NASA Astrophysics Data System (ADS)
Wang, Yu-hai
2016-10-01
Wave shapes that induce velocity skewness and acceleration asymmetry are usually responsible for onshore sediment transport, whereas undertow and bottom slope effect normally contribute to offshore sediment transport. By incorporating these counteracting driving forces in a phase-averaged manner, the theoretically-based quasi-steady formula of Wang (2007) is modified to predict the magnitude and direction of net cross-shore total load transport under the coaction of wave and current. The predictions show an excellent agreement with the measurement data on medium and fine sand collected by Dohmen-Janssen and Hanes (2002) and Schretlen (2012) in a full-scale wave flume at the Coastal Research Centre in Hannover, Germany. The modified formula can predict the net onshore transport of fine sand in sheet flows. In particular, it can predict the net offshore transport of medium sand in rippled beds through enlarged bed roughness, as well as the net offshore transport of fine-to-coarse sand in sheet flows with the aid of a new criterion to judge the occurrence of net offshore transport.
Papaluca, Arturo; Ramotar, Dindial
2016-01-01
Organic cation transporter (OCT) function is critical for cellular homeostasis. C. elegans lacking OCT-1 displays a shortened lifespan and increased susceptibility to oxidative stress. We show that these phenotypes can be rescued by downregulating the OCT-1 paralogue, OCT-2. Herein, we delineate a biochemical pathway in C. elegans where uptake of genotoxic chemotherapeutics such as doxorubicin and cisplatin, and subsequent DNA damage-induced apoptosis of germ cells, are dependent exclusively upon OCT-2. We characterized OCT-2 as the main uptake transporter for doxorubicin, as well as a number of other therapeutic agents and chemical compounds, some identified through ligand-protein docking analyses. We provide insights into the conserved features of the structure and function and gene regulation of oct-1 and oct-2 in distinct tissues of C. elegans. Importantly, our innovative approach of exploiting C. elegans uptake transporters in combination with defective DNA repair pathways will have broad applications in medicinal chemistry. PMID:27786254
Fricke, Wieland
2015-02-01
In a recent Opinion paper, Wegner (Journal of Experimental Botany 65, 381-392, 2014) adapts a concept developed for water flow in animal tissues to propose a model, which can explain the loading of water into the root xylem against a difference in water potential (Ψ) between the xylem parenchyma cell (more negative Ψ) and the xylem vessel (less negative Ψ). In this model, the transport of water is energized through the co-transport of ions such as K(+) and Cl(-) through plasma membrane-located transporters. The emphasis of the model is on the thermodynamic feasibility of the co-transport mechanism per se. However, what is lacking is a quantitative evaluation of the energy input required at the organismal level to sustain such a co-transport mechanism in the face of considerable net (transpirational) flows of water through the system. Here, we use a ratio of 500 water molecules being co-transported for every pair of K(+) and Cl(-) ions, as proposed for the animal system, to calculate the energy required to sustain daytime and night-time transpirational water flow in barley plants through a water co-transport mechanism. We compare this energy with the total daily net input of energy through photosynthetic carbon assimilation. Water co-transport can facilitate the filling of xylem against a difference in Ψ of 1.0MPa and puts a minor drain on the energy budget of the plant. Based on these findings it cannot be excluded that water co-transport in plants contributes significantly to xylem filling during night-time and possibly also daytime transpiration.
Valente, Nina Leão Marques; Vallada, Homero; Cordeiro, Quirino; Miguita, Karen; Bressan, Rodrigo Affonseca; Andreoli, Sergio Baxter; Mari, Jair Jesus; Mello, Marcelo Feijó
2011-05-01
Posttraumatic stress disorder (PTSD) is a prevalent, disabling anxiety disorder marked by behavioral and physiologic alterations which commonly follows a chronic course. Exposure to a traumatic event constitutes a necessary, but not sufficient, factor. There is evidence from twin studies supporting a significant genetic predisposition to PTSD. However, the precise genetic loci still remain unclear. The objective of the present study was to identify, in a case-control study, whether the brain-derived neurotrophic factor (BDNF) val66met polymorphism (rs6265), the dopamine transporter (DAT1) three prime untranslated region (3'UTR) variable number of tandem repeats (VNTR), and the serotonin transporter (5-HTTPRL) short/long variants are associated with the development of PTSD in a group of victims of urban violence. All polymorphisms were genotyped in 65 PTSD patients as well as in 34 victims of violence without PTSD and in a community control group (n = 335). We did not find a statistical significant difference between the BDNF val66met and 5-HTTPRL polymorphism and the traumatic phenotype. However, a statistical association was found between DAT1 3'UTR VNTR nine repeats and PTSD (OR = 1.82; 95% CI, 1.20-2.76). This preliminary result confirms previous reports supporting a susceptibility role for allele 9 and PTSD.
Quek, Su Ying; Khoo, Khoong Hong
2014-11-18
CONSPECTUS: The emerging field of flexible electronics based on organics and two-dimensional (2D) materials relies on a fundamental understanding of charge and spin transport at the molecular and nanoscale. It is desirable to make predictions and shine light on unexplained experimental phenomena independently of experimentally derived parameters. Indeed, density functional theory (DFT), the workhorse of first-principles approaches, has been used extensively to model charge/spin transport at the nanoscale. However, DFT is essentially a ground state theory that simply guarantees correct total energies given the correct charge density, while charge/spin transport is a nonequilibrium phenomenon involving the scattering of quasiparticles. In this Account, we critically assess the validity and applicability of DFT to predict charge/spin transport at the nanoscale. We also describe a DFT-based approach, DFT+Σ, which incorporates corrections to Kohn-Sham energy levels based on many-electron calculations. We focus on single-molecule junctions and then discuss how the important considerations for DFT descriptions of transport can differ in 2D materials. We conclude that when used appropriately, DFT and DFT-based approaches can play an important role in making predictions and gaining insight into transport in these materials. Specifically, we shall focus on the low-bias quasi-equilibrium regime, which is also experimentally most relevant for single-molecule junctions. The next question is how well can the scattering of DFT Kohn-Sham particles approximate the scattering of true quasiparticles in the junction? Quasiparticles are electrons (holes) that are surrounded by a constantly changing cloud of holes (electrons), but Kohn-Sham particles have no physical significance. However, Kohn-Sham particles can often be used as a qualitative approximation to quasiparticles. The errors in standard DFT descriptions of transport arise primarily from errors in the Kohn-Sham energy levels
NASA Technical Reports Server (NTRS)
Olds, John R.
1995-01-01
The Commercial Space Transportation Study (CSTS) suggests that considerable market expansion in earth-to-orbit transportation would take place if current launch prices could be reduced to around $400 per pound of payload. If these low prices can be achieved, annual payload delivered to low earth orbit (LEO) is predicted to reach 6.7 million pounds. The primary market growth will occur in communications, government missions, and civil transportation. By establishing a cost target of $100-$200 per pound of payload for a new launch system, the Highly Reusable Space Transportation (HRST) program has clearly set its sights on removing the current restriction on market growth imposed by today's high launch costs. In particular, achieving the goal of $100-$200 per pound of payload will require significant coordinated efforts in (1) marketing strategy development, (2) business planning, (3) system operational strategy, (4) vehicle technical design, and (5) vehicle maintenance strategy.
NASA Technical Reports Server (NTRS)
Mansour, Nagi N.; Wray, Alan A.; Mehrotra, Piyush; Henney, Carl; Arge, Nick; Godinez, H.; Manchester, Ward; Koller, J.; Kosovichev, A.; Scherrer, P.; Zhao, J.; Stein, R.; Duvall, T.; Fan, Y.
2013-01-01
The Sun lies at the center of space weather and is the source of its variability. The primary input to coronal and solar wind models is the activity of the magnetic field in the solar photosphere. Recent advancements in solar observations and numerical simulations provide a basis for developing physics-based models for the dynamics of the magnetic field from the deep convection zone of the Sun to the corona with the goal of providing robust near real-time boundary conditions at the base of space weather forecast models. The goal is to develop new strategic capabilities that enable characterization and prediction of the magnetic field structure and flow dynamics of the Sun by assimilating data from helioseismology and magnetic field observations into physics-based realistic magnetohydrodynamics (MHD) simulations. The integration of first-principle modeling of solar magnetism and flow dynamics with real-time observational data via advanced data assimilation methods is a new, transformative step in space weather research and prediction. This approach will substantially enhance an existing model of magnetic flux distribution and transport developed by the Air Force Research Lab. The development plan is to use the Space Weather Modeling Framework (SWMF) to develop Coupled Models for Emerging flux Simulations (CMES) that couples three existing models: (1) an MHD formulation with the anelastic approximation to simulate the deep convection zone (FSAM code), (2) an MHD formulation with full compressible Navier-Stokes equations and a detailed description of radiative transfer and thermodynamics to simulate near-surface convection and the photosphere (Stagger code), and (3) an MHD formulation with full, compressible Navier-Stokes equations and an approximate description of radiative transfer and heating to simulate the corona (Module in BATS-R-US). CMES will enable simulations of the emergence of magnetic structures from the deep convection zone to the corona. Finally, a plan
NASA Technical Reports Server (NTRS)
Borowski, S.; Clark, J.; Sefcik, R.; Corban, R.; Alexander, S.
1995-01-01
The results of integrated systems and mission studies are presented which quantify the benefits and rationale for developing a common, modular lunar/Mars space transportation system (STS) based on nuclear thermal rocket (NTR) technology. At present NASA's Exploration Program Office (ExPO) is considering chemical propulsion for an 'early return to the Moon' and NTR propulsion for the more demanding Mars missions to follow. The time and cost to develop these multiple systems are expected to be significant. The Nuclear Propulsion Office (NPO) has examined a variety of lunar and Mars missions and heavy lift launch vehicle (HLLV) options in an effort to determine a 'standardized' set of engine and stage components capable of satisfying a wide range of Space Exploration Initiative (SEI) missions. By using these components in a 'building block' fashion, a variety of single and multi-engine lunar and Mars vehicles can be configured. For NASA's 'First Lunar Outpost' (FLO) mission, an expendable NTR stage powered by two 50 klbf engines can deliver approximately 96 metric tons (t) to translunar injection (TLI) conditions for an initial mass in low earth orbit (IMLEO) of approximately 198 t compared to 250 t for a cryogenic chemical TLI stage. The NTR stage liquid hydrogen (LH2) tank has a 10 m diameter, 14.5 m length, and 66 t LH2 capacity. The NTR utilizes a UC-ZrC-graphite 'composite' fuel with a specific impulse (Isp) capability of approximately 900 s and an engine thrust-to-weight ratio of approximately 4.3. By extending the size and LH2 capacity of the lunar NTR stage to approximately 20 m and 96 t, respectively, a single launch Mars cargo vehicle capable of delivering approximately 50 t of surface payload is possible. Three 50 klbf NTR engines and the two standardized LH2 tank sizes developed for lunar and Mars cargo vehicle applications would be used to configure the Mars piloted vehicle for a mission as early as 2010. The paper describes the features of the 'common
Nishimura, Takeshi; Matano, Naoyuki; Morishima, Taichi; Kakinuma, Chieko; Hayashi, Ken-Ichiro; Komano, Teruya; Kubo, Minoru; Hasebe, Mitsuyasu; Kasahara, Hiroyuki; Kamiya, Yuji; Koshiba, Tomokazu
2012-10-01
The monocot coleoptile tip region has been generally supposed to be the source of IAA to supply IAA to basal parts by the polar IAA transport system, which results in gravi- and phototropic curvature of coleoptiles. Based on this IAA transport system and gravitropism of maize coleoptiles, we have developed two screening methods to identify small molecules from a large chemical library that inhibit IAA transport. The methods detect molecules that affect (i) gravitropic curvature of coleoptiles; and (ii) the amount of IAA transported from the tip. From 10,000 chemicals, eight compounds were identified and categorized into two groups. Four chemicals in group A decreased IAA transport from the tip, and increased endogenous IAA levels in the tip. The structures of two compounds resembled that of 1-N-naphthylphthalamic acid (NPA), but those of the other two differed from structures of known IAA transport inhibitors. Four chemicals in group B strongly inhibited IAA transport from the tip, but IAA levels at the tip were only slightly affected. At higher concentrations, group B compounds inhibited germination of Arabidopsis, similarly to brefeldin A (BFA). Analysis of the cellular distribution of PIN2-green fluorescent protein (GFP) and PIN1-GFP in Arabidopsis revealed that one of the four chemicals in group B induced internalization of PIN1 and PIN2 proteins into vesicles smaller than BFA bodies, suggesting that this compound affects cellular vesicle trafficking systems related to PIN trafficking. The eight chemicals identified here will be a useful tool for understanding the mechanisms of IAA transport in plants. PMID:22875609
NASA Astrophysics Data System (ADS)
Yeghiazarian, L. L.; Walker, M. J.; Binning, P.; Parlange, J.-Y.; Montemagno, C. D.
2006-09-01
Recent outbreaks of cryptosporidiosis raise serious concerns about the effectiveness of watershed management in controlling the risk of contamination by pathogens. A modeling strategy that takes into account the inherent randomness of the occurrence and transport of pathogens in surface water is important for accurate risk assessment and prediction of water contamination events. This paper presents a stochastic Markov model of microorganism transport, with distinct states of microorganism behavior capturing the microbial partitioning between solid and aqueous phases in runoff and soil surface, including the partitioning among soil particles of various sizes. A connection between the soil sediment and microbial transport is established through the incorporation of an erosion model (WEPP) into the microorganism transport model. Probability distribution functions of microorganism occurrence in time and space are constructed, and their properties are analyzed. A deterministic mathematical model of coupled pathogen and sediment transport is developed in parallel to parameterize the Markov process. The numerical values for the Markov model parameters were derived from two sets of experimental data. Model results show that areas with clay soils are more likely than sandy soils to contribute to contamination events and that the most influential transport parameters are the saturated hydraulic conductivity, rainfall intensity, and topographic slope.
Kishimoto, Wataru; Ishiguro, Naoki; Ludwig-Schwellinger, Eva; Ebner, Thomas; Maeda, Kazuya; Sugiyama, Yuichi
2016-02-01
In vitro half-maximal inhibitory concentration (IC50) is a key parameter for accurately predicting the potential risk for P-glycoprotein (P-gp)--mediated drug--drug interactions. We aimed to compare the IC50 values estimated by different approaches and determine the usefulness of model-based approaches. Transcellular transport of digoxin across Caco-2 monolayer was investigated using various concentrations of P-gp inhibitors, quinidine, verapamil, and zosuquidar. To calculate IC50 values, 3 traditional parameters were used: apical-to-basal (AtoB) and basal-to-apical (BtoA) clearance (CL) with inhibitors (CLAtoB,i and CLBtoA,i) and the difference between the efflux ratios (ERs) with P-gp inhibitors (ERi) and those under complete P-gp inhibition [ER(-P-gp)]. Furthermore, a new model-based approach was applied that uses the difference between the reciprocals of CLAtoB with P-gp inhibitors (1/CLAtoB,i) and those under complete P-gp inhibition [1/CLAtoB(-P-gp)] as parameters. IC50 values obtained from 2 model-based approaches [ERi - ER(-P-gp) and 1/CLAtoB,i - 1/CLAtoB(-P-gp)] were comparable, whereas 2.6- to 6.6-fold larger IC50 values were estimated from empirical approaches (CLAtoB,i and CLBtoA,i). The reason for such difference in IC50 values is that indicators for model-based approaches, but not empirical approaches, directly reflect the P-gp function. Our new approach [1/CLAtoB,i - 1/CLAtoB(-P-gp)] based on only AtoB transcellular transport could substitute for current estimation methods using ER.
Iqbal, Asif; Allan, Andrew; Zito, Rocco
2016-03-01
The study aims to develop an emission inventory (EI) approach and conduct an inventory for vehicular sources in Dhaka City, Bangladesh. A meso-scale modelling approach was adopted for the inventory; the factors that influence the emissions and the magnitude of emission variation were identified and reported on, which was an innovative approach to account emissions unlike the conventional inventory approaches. Two techniques for the emission inventory were applied, viz. (i) a combined top-down and bottom-up approach that considered the total vehicle population and the average diurnal on-road vehicle speed profile in the city and (ii) a bottom-up approach that accounted for road link-specific emissions of the city considering diurnal traffic volume and speed profiles of the respective roads. For the bottom-up approach, road link-specific detailed data were obtained through field survey in 2012, where mid-block traffic count of the day, vehicle speed profile, road network and congestion data were collected principally. The emission variances for the change in transport system characteristics (like change in fuel type, AC usage pattern, increased speed and reduced congestion/stopping) were predicted and analysed in this study; congestion influenced average speed of the vehicles, and fuel types in the vehicles were identified as the major stressors. The study performance was considered reasonable when comparing with the limited number of similar studies conducted earlier. Given the increasing trend of private vehicles each year coupled with increasing traffic congestion, the city is under threat of increased vehicular emissions unless a good management strategy is implemented. Although the inventory is conducted for Dhaka and the result may be important locally, the approach adopted in this research is innovative in nature to be followed for conducting research on other urban transport systems.
Iqbal, Asif; Allan, Andrew; Zito, Rocco
2016-03-01
The study aims to develop an emission inventory (EI) approach and conduct an inventory for vehicular sources in Dhaka City, Bangladesh. A meso-scale modelling approach was adopted for the inventory; the factors that influence the emissions and the magnitude of emission variation were identified and reported on, which was an innovative approach to account emissions unlike the conventional inventory approaches. Two techniques for the emission inventory were applied, viz. (i) a combined top-down and bottom-up approach that considered the total vehicle population and the average diurnal on-road vehicle speed profile in the city and (ii) a bottom-up approach that accounted for road link-specific emissions of the city considering diurnal traffic volume and speed profiles of the respective roads. For the bottom-up approach, road link-specific detailed data were obtained through field survey in 2012, where mid-block traffic count of the day, vehicle speed profile, road network and congestion data were collected principally. The emission variances for the change in transport system characteristics (like change in fuel type, AC usage pattern, increased speed and reduced congestion/stopping) were predicted and analysed in this study; congestion influenced average speed of the vehicles, and fuel types in the vehicles were identified as the major stressors. The study performance was considered reasonable when comparing with the limited number of similar studies conducted earlier. Given the increasing trend of private vehicles each year coupled with increasing traffic congestion, the city is under threat of increased vehicular emissions unless a good management strategy is implemented. Although the inventory is conducted for Dhaka and the result may be important locally, the approach adopted in this research is innovative in nature to be followed for conducting research on other urban transport systems. PMID:26857254
Zhou, Nan; McNeil, Michael A.
2009-05-01
Transportation mobility in India has increased significantly in the past decades. From 1970 to 2000, motorized mobility (passenger-km) has risen by 888%, compared with an 88% population growth (Singh,2006). This contributed to many energy and environmental issues, and an energy strategy incorporates efficiency improvement and other measures needs to be designed. Unfortunately, existing energy data do not provide information on driving forces behind energy use and sometime show large inconsistencies. Many previous studies address only a single transportation mode such as passenger road travel; did not include comprehensive data collection or analysis has yet been done, or lack detail on energy demand by each mode and fuel mix. The current study will fill a considerable gap in current efforts, develop a data base on all transport modes including passenger air and water, and freight in order to facilitate the development of energy scenarios and assess significance of technology potential in a global climate change model. An extensive literature review and data collection has been done to establish the database with breakdown of mobility, intensity, distance, and fuel mix of all transportation modes. Energy consumption was estimated and compared with aggregated transport consumption reported in IEA India transportation energy data. Different scenarios were estimated based on different assumptions on freight road mobility. Based on the bottom-up analysis, we estimated that the energy consumption from 1990 to 2000 increased at an annual growth rate of 7% for the mid-range road freight growth case and 12% for the high road freight growth case corresponding to the scenarios in mobility, while the IEA data only shows a 1.7% growth rate in those years.
NASA Astrophysics Data System (ADS)
Paugam, R.; Wooster, M.; Freitas, S. R.; Martin, M. Val
2015-03-01
Landscape fires produce smoke containing a very wide variety of chemical species, both gases and aerosols. For larger, more intense fires that produce the greatest amounts of emissions per unit time, the smoke tends initially to be transported vertically or semi-vertically close by the source region, driven by the intense heat and convective energy released by the burning vegetation. The column of hot smoke rapidly entrains cooler ambient air, forming a rising plume within which the fire emissions are transported. This characteristics of this plume, and in particular the height to which it rises before releasing the majority of the smoke burden into the wider atmosphere, are important in terms of how the fire emissions are ultimately transported, since for example winds at different altitudes maybe quite different. This difference in atmospheric transport then may also affect the longevity, chemical conversion and fate of the plumes chemical consituents, with for example very high plume injection heights being associated with extreme long-range atmospheric transport. Here we review how such landscape-scale fire smoke plume injection heights are represented in larger scale atmospheric transport models aiming to represent the impacts of wildfire emissions on component of the Earth system. The use of satellite Earth observation (EO) data is commonly used for this, and detail the EO datasets capable of being used to remotely assess wildfire plume height distributions and the driving characteristics of the causal fires. We also discus both the physical mechanisms and dynamics taking place in fire plumes, and investigate the efficiency and limitations of currently available injection height parameterizations. Finally, we conclude by suggestion some future parameterization developments and ideas on EO data selection that maybe relevant to the instigation of enhanced methodologies aimed at injection height representation.
NASA Astrophysics Data System (ADS)
Paugam, R.; Wooster, M.; Freitas, S.; Martin, M. Val
2016-01-01
Landscape fires produce smoke containing a very wide variety of chemical species, both gases and aerosols. For larger, more intense fires that produce the greatest amounts of emissions per unit time, the smoke tends initially to be transported vertically or semi-vertically close by the source region, driven by the intense heat and convective energy released by the burning vegetation. The column of hot smoke rapidly entrains cooler ambient air, forming a rising plume within which the fire emissions are transported. The characteristics of this plume, and in particular the height to which it rises before releasing the majority of the smoke burden into the wider atmosphere, are important in terms of how the fire emissions are ultimately transported, since for example winds at different altitudes may be quite different. This difference in atmospheric transport then may also affect the longevity, chemical conversion, and fate of the plumes chemical constituents, with for example very high plume injection heights being associated with extreme long-range atmospheric transport. Here we review how such landscape-scale fire smoke plume injection heights are represented in larger-scale atmospheric transport models aiming to represent the impacts of wildfire emissions on component of the Earth system. In particular we detail (i) satellite Earth observation data sets capable of being used to remotely assess wildfire plume height distributions and (ii) the driving characteristics of the causal fires. We also discuss both the physical mechanisms and dynamics taking place in fire plumes and investigate the efficiency and limitations of currently available injection height parameterizations. Finally, we conclude by suggesting some future parameterization developments and ideas on Earth observation data selection that may be relevant to the instigation of enhanced methodologies aimed at injection height representation.
Bostick, Kent; Daniel, Anamary; Tachiev, Georgio; Malek-Mohammadi, Siamak
2013-07-01
In this case study, groundwater/surface water modeling was used to determine efficacy of stabilization in place with hydrologic isolation for remediation of mercury contaminated areas in the Upper East Fork Poplar Creek (UEFPC) Watershed in Oak Ridge, TN. The modeling simulates the potential for mercury in soil to contaminate groundwater above industrial use risk standards and to contribute to surface water contamination. The modeling approach is unique in that it couples watershed hydrology with the total mercury transport and provides a tool for analysis of changes in mercury load related to daily precipitation, evaporation, and runoff from storms. The model also allows for simulation of colloidal transport of total mercury in surface water. Previous models for the watershed only simulated average yearly conditions and dissolved concentrations that are not sufficient for predicting mercury flux under variable flow conditions that control colloidal transport of mercury in the watershed. The transport of mercury from groundwater to surface water from mercury sources identified from information in the Oak Ridge Environmental Information System was simulated using a watershed scale model calibrated to match observed daily creek flow, total suspended solids and mercury fluxes. Mercury sources at the former Building 81-10 area, where mercury was previously retorted, were modeled using a telescopic refined mesh with boundary conditions extracted from the watershed model. Modeling on a watershed scale indicated that only source excavation for soils/sediment in the vicinity of UEFPC had any effect on mercury flux in surface water. The simulations showed that colloidal transport contributed 85 percent of the total mercury flux leaving the UEFPC watershed under high flow conditions. Simulation of dissolved mercury transport from liquid elemental mercury and adsorbed sources in soil at former Building 81-10 indicated that dissolved concentrations are orders of magnitude
Liu, Henry C; Goldenberg, Anne; Chen, Yuchen; Lun, Christina; Wu, Wei; Bush, Kevin T; Balac, Natasha; Rodriguez, Paul; Abagyan, Ruben; Nigam, Sanjay K
2016-10-01
Statistical analysis was performed on physicochemical descriptors of ∼250 drugs known to interact with one or more SLC22 "drug" transporters (i.e., SLC22A6 or OAT1, SLC22A8 or OAT3, SLC22A1 or OCT1, and SLC22A2 or OCT2), followed by application of machine-learning methods and wet laboratory testing of novel predictions. In addition to molecular charge, organic anion transporters (OATs) were found to prefer interacting with planar structures, whereas organic cation transporters (OCTs) interact with more three-dimensional structures (i.e., greater SP3 character). Moreover, compared with OAT1 ligands, OAT3 ligands possess more acyclic tetravalent bonds and have a more zwitterionic/cationic character. In contrast, OCT1 and OCT2 ligands were not clearly distinquishable form one another by the methods employed. Multiple pharmacophore models were generated on the basis of the drugs and, consistent with the machine-learning analyses, one unique pharmacophore created from ligands of OAT3 possessed cationic properties similar to OCT ligands; this was confirmed by quantitative atomic property field analysis. Virtual screening with this pharmacophore, followed by transport assays, identified several cationic drugs that selectively interact with OAT3 but not OAT1. Although the present analysis may be somewhat limited by the need to rely largely on inhibition data for modeling, wet laboratory/in vitro transport studies, as well as analysis of drug/metabolite handling in Oat and Oct knockout animals, support the general validity of the approach-which can also be applied to other SLC and ATP binding cassette drug transporters. This may make it possible to predict the molecular properties of a drug or metabolite necessary for interaction with the transporter(s), thereby enabling better prediction of drug-drug interactions and drug-metabolite interactions. Furthermore, understanding the overlapping specificities of OATs and OCTs in the context of dynamic transporter tissue
ERIC Educational Resources Information Center
Li, James J.; Lee, Steve S.
2013-01-01
Emerging evidence suggests that some individuals may be simultaneously more responsive to the effects from environmental adversity "and" enrichment (i.e., differential susceptibility). Given that parenting behavior and a variable number tandem repeat polymorphism in the 3'untranslated region of the dopamine transporter (DAT1) gene…
NASA Astrophysics Data System (ADS)
Dhont, Blaise; Rousseau, Gauthier; Ancey, Christophe
2016-04-01
Experimental and field studies have shown how intermittent bedload transport can be at low flow rates. The development and validation of bedload-transport equations require high-resolution records over long periods of time. Two technologies are considered in the present investigation: image processing and accelerometers mounted on impact plates. The former has been successfully applied to monitor bedload transport in many flume experiments, and the latter has shown encouraging results at different field sites. Calibration is a major issue in both cases, and it is often difficult to assess the precision of the data collected. In our talk, we show how to calibrate and compare the performances of accelerometer and image-processing based techniques in laboratory conditions. The accelerometer is fixed on a perforated steel plate, which is placed vertically at the lower end of the flume. The vibrations due to the particles impacting the plate are recorded with a sampling frequency of 10 kHz. The proxy for bedload transport rate is chosen as the number of peaks above a fixed threshold of the recorded signal. Note that impact plates are usually set in flush with the bed, and to our knowledge, the vertical configuration presented here has not yet been documented. The experimental setup for image processing involves a video-camera that takes top-view images of the particles moving over a white board mounted at the outlet of the flume. Data storage poses an issue, which can be got round by pre-processing the images in real time. The bedload transport rate is estimated based on the number of particles that are identified on the images. The two technologies have the advantages of being cost-effective and demanding limited effort for implementation. They provide high-resolution bedload transport rates over several hours. Estimates of bedload discharge were found to be robust and accurate for low sediment transport rates. At higher rates, the sensors may saturate due the arrival
NASA Astrophysics Data System (ADS)
Comolli, Alessandro; Moussey, Charlie; Dentz, Marco
2016-04-01
Transport processes in groundwater systems are strongly affected by the presence of heterogeneity. The heterogeneity leads to non-Fickian features, that manifest themselves in the heavy-tailed breakthrough curves, as well as in the non-linear growth of the mean squared displacement and in the non-Gaussian plumes of solute particles. The causes of non-Fickian transport can be the heterogeneity in the flow fields and the processes of mass exchange between mobile and immobile phases, such as sorption/desorption reactions and diffusive mass transfer. Here, we present a Continuous Time Random Walk (CTRW) model that describes the transport of solutes in d-dimensional systems by taking into account both heterogeneous advection and mobile-immobile mass transfer. In order to account for these processes in the CTRW, the heterogeneities are mapped onto a distribution of transition times, which can be decomposed into advective transition times and trapping times, the latter being treated as a compound Poisson process. While advective transition times are related to the Eulerian flow velocities and, thus, to the conductivity distribution, trapping times depend on the sorption/desorption time scale, in case of reactive problems, or on the distribution of diffusion times in the immobile zones. Since the trapping time scale is typically much larger than the advective time scale, we observe the existence of two temporal regimes. The pre-asymptotic regime is defined by a characteristic time scale at which the properties of transport are fully determined by the heterogeneity of the advective field. On the other hand, in the asymptotic regime both the heterogeneity and the mass exchange processes play a role in conditioning the behaviour of transport. We consider different scenarios to discuss the relative importance of the advective heterogeneity and the mass transfer for the occurrence of non-Fickian transport. For each case we calculate analytically the scalings of the breakthrough
NASA Technical Reports Server (NTRS)
Snyder, C. T.; Fry, E. B.; Drinkwater, F. J., III; Forrest, R. D.; Scott, B. C.; Benefield, T. D.
1972-01-01
A ground-based simulator investigation was conducted in preparation for and correlation with an-flight simulator program. The objective of these studies was to define minimum acceptable levels of static longitudinal stability for landing approach following stability augmentation systems failures. The airworthiness authorities are presently attempting to establish the requirements for civil transports with only the backup flight control system operating. Using a baseline configuration representative of a large delta wing transport, 20 different configurations, many representing negative static margins, were assessed by three research test pilots in 33 hours of piloted operation. Verification of the baseline model to be used in the TIFS experiment was provided by computed and piloted comparisons with a well-validated reference airplane simulation. Pilot comments and ratings are included, as well as preliminary tracking performance and workload data.
NASA Astrophysics Data System (ADS)
Grant, S. A.; Mansell, R. S.; Bloom, S. A.; Rhue, R. D.
1995-01-01
Batch cation exchange and column experiments were conducted to evaluate selectivity coefficients which have been suggested for describing cation exchange reactions in solute transport models. Vanselow selectivity coefficients were calculated for cation exchange equilibria with a cation resin and for equilibria reported in the literature with a Yolo loam soil. Experimental column data were compared with data from simulations generated by a numerical solute transport model to evaluate Vanselow, Gaines-Thomas, and statistical thermodynamic selectivity coefficients. With the cation resin, the statistical thermodynamic selectivity coefficient gave the most reliable estimate of column effluent cation concentrations. In a column packed with the Yolo loam soil, the Vanselow selectivity coefficient gave the most accurate prediction of column response. Use of variable (as opposed to fixed) Vanselow selectivity coefficients gave more accurate predictions of column experiments. The use of ternary cation exchange data did not improve predictions of column response.
NASA Astrophysics Data System (ADS)
Rasa, E.; Foglia, L.; Mackay, D. M.; Ginn, T. R.; Scow, K. M.
2009-12-01
A numerical groundwater fate and transport model was developed for analyses of data from field experiments evaluating the impacts of ethanol on the natural attenuation of benzene, toluene, ethylbenzene, and xylenes (BTEX) and methyl tert-butyl ether (MTBE) at Vandenberg Air Force Base, Site 60. We used the U.S. Geological Survey (USGS) groundwater flow (MODFLOW2000) and transport (MT3DMS) models in conjunction with the USGS universal inverse modeling code (UCODE) to jointly determine flow and transport parameters using bromide tracer data from multiple experiments in the same location. The key flow and transport parameters include hydraulic conductivity of aquifer and aquitard layers, porosity, and transverse and longitudinal dispersivity. Aquifer and aquitard layers were assumed homogenous in this study. Therefore, the calibration parameters were not spatially variable within each layer. A total of 162 monitoring wells in seven transects perpendicular to the mean flow direction were monitored over the course of ten months, resulting in 1,766 bromide concentration data points and 149 head values used as observations for the inverse modeling. The results showed the significance of the concentration observation data in predicting the flow model parameters and indicated the sensitivity of the hydraulic conductivity of different zones in the aquifer including the excavated former contaminant zone. The model has already been used to evaluate alternative designs for further experiments on in situ bioremediation of the tert-butyl alcohol (TBA) plume remaining at the site. We describe the recent applications of the model and future work, including adding reaction submodels to the calibrated flow model.
NASA Astrophysics Data System (ADS)
Chen, X.; Motew, M.; Booth, E.; Carpenter, S. R.; Steven, L. I.; Kucharik, C. J.
2015-12-01
The Yahara River basin located in southern Wisconsin is a watershed with long-term eutrophication issues due largely to a thriving dairy industry upstream of the Madison chain of lakes. Steady phosphorus loading from manure production and other sources has contributed directly to blue-green algae blooms and poor water quality in the lakes and river system, and is often viewed as the most important environmental problem to solve in the region. In this study, the daily streamflow and monthly nitrogen (N), sediment and phosphorus (P) transport, as well as the lake levels in the Yahara River basin are simulated using a physically-based hydrologic routing model: the Terrestrial Hydrology Model with Biogeochemistry (THMB). The original model includes representation of water and nitrogen transport but as part of this work, P transport and lake regulation are added into the model. The modified THMB model is coupled with the AgroIBIS-VSF agroecosystem model to represent dynamic coupling between agricultural management in the watershed, and N, P, and sediment transport to lakes and streams. We will present model calibration and validation results that demonstrate the hydrologic routing capability of THMB for a spatial resolution of 220m, several orders of magnitude finer than attempted previously with THMB. The calibrated modeling system is being used to simulate the impacts of climate change and land management on biogeochemistry in the Yahara watershed under four different pathways of change to the year 2070 (Yahara 2070). These scenarios are Abandonment and Renewal, Accelerated Innovation, Connected Communities and Nested Watersheds, which are used to better understand how future decision-making influences the provisioning and trade-offs of ecosystem services.
Guo, Cen; Yang, Kyunghee; Brouwer, Kenneth R; St Claire, Robert L; Brouwer, Kim L R
2016-08-01
Transporter-mediated alterations in bile acid disposition may have significant toxicological implications. Current methods to predict interactions are limited by the interplay of multiple transporters, absence of protein in the experimental system, and inaccurate estimates of inhibitor concentrations. An integrated approach was developed to predict altered bile acid disposition due to inhibition of multiple transporters using the model bile acid taurocholate (TCA). TCA pharmacokinetic parameters were estimated by mechanistic modeling using sandwich-cultured human hepatocyte data with protein in the medium. Uptake, basolateral efflux, and biliary clearance estimates were 0.63, 0.034, and 0.074 mL/min/g liver, respectively. Cellular total TCA concentrations (Ct,Cells) were selected as the model output based on sensitivity analysis. Monte Carlo simulations of TCA Ct,Cells in the presence of model inhibitors (telmisartan and bosentan) were performed using inhibition constants for TCA transporters and inhibitor concentrations, including cellular total inhibitor concentrations ([I]t,cell) or unbound concentrations, and cytosolic total or unbound concentrations. For telmisartan, the model prediction was accurate with an average fold error (AFE) of 0.99-1.0 when unbound inhibitor concentration ([I]u) was used; accuracy dropped when total inhibitor concentration ([I]t) was used. For bosentan, AFE was 1.2-1.3 using either [I]u or [I]t This difference was evaluated by sensitivity analysis of the cellular unbound fraction of inhibitor (fu,cell,inhibitor), which revealed higher sensitivity of fu,cell,inhibitor for predicting TCA Ct,Cells when inhibitors exhibited larger ([I]t,cell/IC50) values. In conclusion, this study demonstrated the applicability of a framework to predict hepatocellular bile acid concentrations due to drug-mediated inhibition of transporters using mechanistic modeling and cytosolic or cellular unbound concentrations. PMID:27233294
Adkins, Harold; Geelhood, Ken; Koeppel, Brian; Coleman, Justin; Bignell, John; Flores, Gregg; Wang, Jy-An; Sanborn, Scott; Spears, Robert; Klymyshyn, Nick
2013-09-30
This document addresses Oak Ridge National Laboratory milestone M2FT-13OR0822015 Demonstration of Approach and Results on Used Nuclear Fuel Performance Characterization. This report provides results of the initial demonstration of the modeling capability developed to perform preliminary deterministic evaluations of moderate-to-high burnup used nuclear fuel (UNF) mechanical performance under normal conditions of storage (NCS) and normal conditions of transport (NCT) conditions. This report also provides results from the sensitivity studies that have been performed. Finally, discussion on the long-term goals and objectives of this initiative are provided.
Saâdi, Zakaria; Guillevic, Jérôme
2016-01-01
Uncertainties on the mathematical modelling of radon ((222)Rn) transport in an unsaturated covered uranium mill tailings (UMT) soil at field scale can have a great impact on the estimation of the average measured radon exhalation rate to the atmosphere at the landfill cover. These uncertainties are usually attributed to the numerical errors from numerical schemes dealing with soil layering, and to inadequate modelling of physical processes at the soil/plant/atmosphere interface and of the soil hydraulic and transport properties, as well as their parameterization. In this work, we demonstrate how to quantify these uncertainties by comparing simulation results from two different numerical models to experimental data of radon exhalation rate and activity concentration in the soil-gas measured in a covered UMT-soil near the landfill site Lavaugrasse (France). The first approach is based on the finite volume compositional (i.e., water, radon, air) transport model TOUGH2/EOS7Rn (Transport Of Unsaturated Groundwater and Heat version 2/Equation Of State 7 for Radon; Saâdi et al., 2014), while the second one is based on the finite difference one-component (i.e., radon) transport model TRACI (Transport de RAdon dans la Couche Insaturée; Ferry et al., 2001). Transient simulations during six months of variable rainfall and atmospheric air pressure showed that the model TRACI usually overestimates both measured radon exhalation rate and concentration. However, setting effective unsaturated pore diffusivities of water, radon and air components in soil-liquid and gas to their physical values in the model EOS7Rn, allowed us to enhance significantly the modelling of these experimental data. Since soil evaporation has been neglected, none of these two models was able to simulate the high radon peaks observed during the dry periods of summer. However, on average, the radon exhalation rate calculated by EOS7Rn was 34% less than that was calculated by TRACI, and much closer to the
Saâdi, Zakaria; Guillevic, Jérôme
2016-01-01
Uncertainties on the mathematical modelling of radon ((222)Rn) transport in an unsaturated covered uranium mill tailings (UMT) soil at field scale can have a great impact on the estimation of the average measured radon exhalation rate to the atmosphere at the landfill cover. These uncertainties are usually attributed to the numerical errors from numerical schemes dealing with soil layering, and to inadequate modelling of physical processes at the soil/plant/atmosphere interface and of the soil hydraulic and transport properties, as well as their parameterization. In this work, we demonstrate how to quantify these uncertainties by comparing simulation results from two different numerical models to experimental data of radon exhalation rate and activity concentration in the soil-gas measured in a covered UMT-soil near the landfill site Lavaugrasse (France). The first approach is based on the finite volume compositional (i.e., water, radon, air) transport model TOUGH2/EOS7Rn (Transport Of Unsaturated Groundwater and Heat version 2/Equation Of State 7 for Radon; Saâdi et al., 2014), while the second one is based on the finite difference one-component (i.e., radon) transport model TRACI (Transport de RAdon dans la Couche Insaturée; Ferry et al., 2001). Transient simulations during six months of variable rainfall and atmospheric air pressure showed that the model TRACI usually overestimates both measured radon exhalation rate and concentration. However, setting effective unsaturated pore diffusivities of water, radon and air components in soil-liquid and gas to their physical values in the model EOS7Rn, allowed us to enhance significantly the modelling of these experimental data. Since soil evaporation has been neglected, none of these two models was able to simulate the high radon peaks observed during the dry periods of summer. However, on average, the radon exhalation rate calculated by EOS7Rn was 34% less than that was calculated by TRACI, and much closer to the
Heitmuller, Franklin T; Raphelt, Nolan
2012-07-15
Instream-flow scientists embrace streamflow as the master variable driving aquatic and riparian ecosystems, and that natural flow variability is imperative for river conservation and restoration efforts. Sediment transport, which is critical for maintenance of physical habitats in rivers and floodplains, has received less direct attention from instream-flow practitioners. This article serves to highlight the roles of sediment-transport evaluations in modifying or verifying instream-flow prescriptions based on hydrology alone. Two examples of sediment-transport evaluations are discussed in relation to the Texas Senate Bill 3 Environmental Flows allocation process, a mandate to "develop environmental flow analyses and a recommended flow regime" that "maintain(s) the viability of the state's streams, rivers, and bay and estuary systems" using "reasonably available science". The first example provides an evaluation of effective discharge of suspended-sediment load of the lower Brazos River. The magnitude and frequency of effective discharge occurs between typical high-flow pulses and overbank flows, indicating that hydrologic and physical processes are not optimally coupled in some flow-regime models. The second example utilizes the Hydrology-Based Environmental Flow Regime (HEFR) model to prescribe instream flows for the lower Sabine River, and compares modeled bed-material loads for observed and HEFR-prescribed flow regimes. Results indicate that annual water and sediment yields are greatly reduced for the modeled flow regime. It should be noted, however, that different input variables to the HEFR model would have resulted in different computations of water and sediment yields, reinforcing that instream-flow practitioners should exercise great caution when applying rule-of-thumb procedures to generate flow prescriptions. PMID:22425877
Heitmuller, Franklin T; Raphelt, Nolan
2012-07-15
Instream-flow scientists embrace streamflow as the master variable driving aquatic and riparian ecosystems, and that natural flow variability is imperative for river conservation and restoration efforts. Sediment transport, which is critical for maintenance of physical habitats in rivers and floodplains, has received less direct attention from instream-flow practitioners. This article serves to highlight the roles of sediment-transport evaluations in modifying or verifying instream-flow prescriptions based on hydrology alone. Two examples of sediment-transport evaluations are discussed in relation to the Texas Senate Bill 3 Environmental Flows allocation process, a mandate to "develop environmental flow analyses and a recommended flow regime" that "maintain(s) the viability of the state's streams, rivers, and bay and estuary systems" using "reasonably available science". The first example provides an evaluation of effective discharge of suspended-sediment load of the lower Brazos River. The magnitude and frequency of effective discharge occurs between typical high-flow pulses and overbank flows, indicating that hydrologic and physical processes are not optimally coupled in some flow-regime models. The second example utilizes the Hydrology-Based Environmental Flow Regime (HEFR) model to prescribe instream flows for the lower Sabine River, and compares modeled bed-material loads for observed and HEFR-prescribed flow regimes. Results indicate that annual water and sediment yields are greatly reduced for the modeled flow regime. It should be noted, however, that different input variables to the HEFR model would have resulted in different computations of water and sediment yields, reinforcing that instream-flow practitioners should exercise great caution when applying rule-of-thumb procedures to generate flow prescriptions.
Schamfuß, Susan; Neu, Thomas R; Harms, Hauke; Wick, Lukas Y
2014-01-01
Bioavailability of contaminants is a prerequisite for their effective biodegradation in soil. The average bulk concentration of a contaminant, however, is not an appropriate measure for its availability; bioavailability rather depends on the dynamic interplay of potential mass transfer (flux) of a compound to a microbial cell and the capacity of the latter to degrade the compound. In water-unsaturated parts of the soil, mycelia have been shown to overcome bioavailability limitations by actively transporting and mobilizing organic compounds over the range of centimeters. Whereas the extent of mycelia-based transport can be quantified easily by chemical means, verification of the contaminant-bioavailability to bacterial cells requires a biological method. Addressing this constraint, we chose the PAH fluorene (FLU) as a model compound and developed a water unsaturated model microcosm linking a spatially separated FLU point source and the FLU degrading bioreporter bacterium Burkholderia sartisoli RP037-mChe by a mycelial network of Pythium ultimum. Since the bioreporter expresses eGFP in response of the PAH flux to the cell, bacterial FLU exposure and degradation could be monitored directly in the microcosms via confocal laser scanning microscopy (CLSM). CLSM and image analyses revealed a significant increase of the eGFP expression in the presence of P. ultimum compared to controls without mycelia or FLU thus indicating FLU bioavailability to bacteria after mycelia-mediated transport. CLSM results were supported by chemical analyses in identical microcosms. The developed microcosm proved suitable to investigate contaminant bioavailability and to concomitantly visualize the involved bacteria-mycelial interactions. PMID:25590867
NASA Technical Reports Server (NTRS)
Frost, Chad R.; Franklin, James A.; Hardy, Gordon H.
2002-01-01
A piloted simulation was performed on the Vertical Motion Simulator at NASA Ames Research Center to evaluate flying qualities of a tilt-wing Short Take-Off and Landing (STOL) transport aircraft during final approach and landing. The experiment was conducted to assess the design s handling qualities, and to evaluate the use of flightpath-centered guidance for the precision approach and landing tasks required to perform STOL operations in instrument meteorological conditions, turbulence, and wind. Pilots rated the handling qualities to be satisfactory for all operations evaluated except those encountering extreme crosswinds and severe windshear; even in these difficult meteorological conditions, adequate handling qualities were maintained. The advanced flight control laws and guidance displays provided consistent performance and precision landings.
NASA Technical Reports Server (NTRS)
Miller, G. K., Jr.
1979-01-01
The use of decoupled longitudinal controls during the approach and landing of a typical twin-engine jet transport in the presence of wind shear was studied. The simulation included use of a localizer and flight director to capture and maintain a 3 deg glide slope. The pilot then completed the landing by using visual cues provided below an altitude of 200 m by closed-circuit television and a terrain model. The decoupled controls used constant prefilter and feedback gains to provide steady state decoupling of flight path angle, pitch angle, and forward velocity. The use of the decoupled control system improved pilot performance during the approach and at touchdown in the presence of wind shears. The pilots preferred the decoupled controls and rated the task 1 to 3 increments better on a pilot rating scale, depending on wind conditions, than was the case when conventional controls were used.
Gustafson, William I.; Berg, Larry K.; Easter, Richard C.; Ghan, Steven J.
2008-05-30
All estimates of aerosol indirect effects on the global energy balance have either completely neglected the influence of aerosol on convective clouds or treated the influence in a highly parameterized manner. Embedding cloud-resolving models (CRMs) within each grid cell of a global model provides a multiscale modelling framework for treating both the influence of aerosols on convective as well as stratiform clouds and the influence of all clouds on the aerosol, but treating the interactions explicitly by simulating all aerosol processes in the CRM would be computationally prohibitive. An alternate approach is to use horizontal statistics (e.g., cloud mass flux, cloud fraction, and precipitation) from the CRM simulation to drive a single-column parameterization of cloud effects on the aerosol and then use the aerosol profile to simulate aerosol effects on clouds within the CRM. Here we test this concept for vertical transport by clouds, using a CRM with tracer transport simulated explicitly to serve as a benchmark. We show that this parameterization, driven by the CRM’s cloud mass fluxes, reproduces the tracer transport by the CRM significantly better than a single column model that uses a conventional convective cloud parameterization.
Hu, Wensi S. Lin, Y.-H.; Shih, C.-C.
2007-09-28
Mutant 6B7 of Salmonella enterica serovar Typhimurium has a transposon inserted in the putative transporter gene yjeH and shows a more-than-fourfold reduction in resistance to ceftriaxone. In this report we have used proteomic analysis to compare outer membrane protein profiles between this mutant and its parental strain R200. Five identified proteins were found to be altered. Of these proteins, the level of expression of the porin OmpD was increased and those of the putative outer membrane proteins STM1530 and STM3031, a subunit of the proton-pumping oxidoreductase NuoB and the heat shock protein MopA were decreased in 6B7 strain. Although the function of the yjeH gene remains unknown, a complementation assay suggested that the OmpD, STM1530, STM3031, NuoB, and MopA proteins are associated with ceftriaxone resistance and the expression of these proteins is influenced by the putative transporter gene yjeH in S. enterica serovar Typhimurium.
Yun, Jeonghun; Lee, Geunsik; Kim, Kwang S
2016-07-01
Zigzag graphene nanoribbon (zGNR) of narrow width has a moderate energy gap in its antiferromagnetic ground state. So far, first-principles electron transport calculations have been performed using nonequilibrium Green function (NEGF) method combined with density functional theory (DFT). However, the commonly practiced bottom-gate control has not been studied computationally due to the need to simulate an electron reservoir that fixes the chemical potential of electrons in the zGNR and electrodes. Here, we present the isochemical potential scheme to describe the top/back-gate effect using external potential. Then, we examine the change in electronic state under the modulation of chemical potential and the subsequent electron transport phenomena in zGNR transistor under substantial top-/back-gate and bias voltages. The gate potential can activate the device states resulting in a boosted current. This gate-controlled current-boosting could be utilized for designing novel zGNR field effect transistors (FETs). PMID:27299184
NASA Astrophysics Data System (ADS)
Beisman, J. J., III; Maxwell, R. M.; Navarre-Sitchler, A.; Steefel, C. I.
2014-12-01
Understanding the interactions between physical, geochemical, and biological processes in the shallow subsurface is prerequisite to the development of effective contamination remediation techniques, or the accurate quantification of nutrient fluxes and biogeochemical cycling. Here we present recent developments to the massively parallel reactive transport code ParCrunchFlow. This model, previously applicable only to steady-state, saturated subsurface flows, has been extended to transient, surface-subsurface systems. Proof-of-concept simulations detailing reactive transport processes in hillslope and floodplain settings will be presented. In order to reduce the numerical dispersion inherent in grid based advection schemes, which can lead to an over prediction of reaction rates, a weighted, essentially non-oscillatory (WENO) advection scheme has been implemented, providing formal fifth-order spatial and third-order temporal accuracy. We use a mass-conservative, positivity-preserving flux limiter while advecting solute concentrations to prevent non-physical solutions. The effects of advection schemes and their associated numerical dispersion on reaction rates are evaluated by comparing our scheme to a monotonic lower order scheme in a transverse mixing scenario. The work presented here allows a better understanding of nutrient cycling dynamics in watershed systems.
Wang, Lichun; Cardenas, M Bayani
2015-08-01
The quantitative study of transport through fractured media has continued for many decades, but has often been constrained by observational and computational challenges. Here, we developed an efficient quasi-3D random walk particle tracking (RWPT) algorithm to simulate solute transport through natural fractures based on a 2D flow field generated from the modified local cubic law (MLCL). As a reference, we also modeled the actual breakthrough curves (BTCs) through direct simulations with the 3D advection-diffusion equation (ADE) and Navier-Stokes equations. The RWPT algorithm along with the MLCL accurately reproduced the actual BTCs calculated with the 3D ADE. The BTCs exhibited non-Fickian behavior, including early arrival and long tails. Using the spatial information of particle trajectories, we further analyzed the dynamic dispersion process through moment analysis. From this, asymptotic time scales were determined for solute dispersion to distinguish non-Fickian from Fickian regimes. This analysis illustrates the advantage and benefit of using an efficient combination of flow modeling and RWPT. PMID:26042625
NASA Technical Reports Server (NTRS)
White, K. C.; Bourquin, K. R.
1974-01-01
Centerline noise measured during standard ILS and two-segment approaches in DC-8-61 aircraft were compared with noise predicted for these procedures using an existing noise prediction technique. Measured data is considered to be in good agreement with predicted data. Ninety EPNdB sideline locations were calculated from flight data obtained during two-segment approaches and were compared with predicted 90 EPNdB contours that were computed using three different models for excess ground attenuation and a contour with no correction for ground attenuation. The contour not corrected for ground attenuation was in better agreement with the measured data.
NASA Astrophysics Data System (ADS)
Selle, Benny; Schwientek, Marc; Osenbrück, Karsten
2013-04-01
The understanding of flow paths and travel times of water and solutes in catchments can be substantially improved by a combination of bottom-up and top-down modelling approaches. This hypothesis was tested for the 180 km² Ammer catchment in south-western Germany in which the landuse is dominated by agricultural and urban areas. The Ammer River with a mean discharge of 1 m³/s is mainly fed by springs from karstified and fractured aquifers. A limestone aquifer is extensively used for groundwater production. As a first step, we analysed measured concentrations of major ions, selected organic micro-pollutants and environmental tracers for surface water, springs and deep groundwater from wells using typical top-down approaches such as principal component analysis and lumped parameter models. From these approaches, we gained an initial understanding of water and solute fluxes in the catchment. The initial hypotheses on subsurface flow paths and travel times were subsequently tested using a numerical, 3-D groundwater model as a typical bottom-up approach. Our synthesis of top-down and bottom-up approaches provided us with a reliable picture of the dominant processes governing water and solute fluxes in the Ammer catchment. Several spring waters indicated mixing with wastewater. These contaminations were indentified to be caused by either recharge of surface water or leaky sewer systems. Deep percolation below the plant root zone polluted with agrochemicals was found to affect most springs and surface waters resulting in nitrate concentrations of approximately 30 mg/l. This process also influenced some of the drinking-water wells, although water quality for most of these wells is still relatively high due to some attenuation of pollutants but - above all - due to a significant proportion of groundwater with ages > 50 years. However, water quality will likely decrease if contaminants break through and/or conditions for microbiological attenuation process will deteriorate
2012-01-01
The electroluminescence (EL) and photoluminescence of Si nanocrystals (Si-nc) from multilayered samples of Si/SiO are investigated. Si-nc are formed within Si and SiO layers after furnace annealing. It is found that the presence of Si interlayers creates extra carrier paths for EL emission. A comparative study is further performed on a multilayered Si/SiO sample and a single-layered one with Si and SiO homogeneously mixed. Both samples have the same ratio of Si to O and the same contents of Si and O. The multilayered sample is found to have higher EL intensity, less turn-on voltage, lower resistance, and higher current efficiency than the single-layered one. The results indicate that Si interlayers in Si/SiO may act as carrier channels, which promote carrier transport and enhance the EL emission of Si-nc. PMID:22448989
NASA Astrophysics Data System (ADS)
Ye, Junye; le Roux, Jakobus A.; Arthur, Aaron D.
2016-08-01
We study the physics of locally born interstellar pickup proton acceleration at the nearly perpendicular solar wind termination shock (SWTS) in the presence of a random magnetic field spiral angle using a focused transport model. Guided by Voyager 2 observations, the spiral angle is modeled with a q-Gaussian distribution. The spiral angle fluctuations, which are used to generate the perpendicular diffusion of pickup protons across the SWTS, play a key role in enabling efficient injection and rapid diffusive shock acceleration (DSA) when these particles follow field lines. Our simulations suggest that variation of both the shape (q-value) and the standard deviation (σ-value) of the q-Gaussian distribution significantly affect the injection speed, pitch-angle anisotropy, radial distribution, and the efficiency of the DSA of pickup protons at the SWTS. For example, increasing q and especially reducing σ enhances the DSA rate.
Simmons, C T; Fenstemaker, T R; Sharp, J M
2001-11-01
In certain hydrogeological situations, fluid density variations occur because of changes in the solute or colloidal concentration, temperature, and pressure of the groundwater. These include seawater intrusion, high-level radioactive waste disposal, groundwater contamination, and geothermal energy production. When the density of the invading fluid is greater than that of the ambient one, density-driven free convection can lead to transport of heat and solutes over larger spatial scales and significantly shorter time scales than compared with diffusion alone. Beginning with the work of Lord Rayleigh in 1916, thermal and solute instabilities in homogeneous media have been studied in detail for almost a century. Recently, these theoretical and experimental studies have been applied in the study of groundwater phenomena, where the assumptions of homogeneity and isotropy rarely, if ever, apply. The critical role that heterogeneity plays in the onset as well as the growth and/or decay of convective motion is discussed by way of a review of pertinent literature and numerical simulations performed using a variable-density flow and solute transport numerical code. Different styles of heterogeneity are considered and range from continuously "trending" heterogeneity (sinusoidal and stochastic permeability distributions) to discretely fractured geologic media. Results indicate that both the onset of instabilities and their subsequent growth and decay are intimately related to the structure and variance of the permeability field. While disordered heterogeneity tends to dissipate convection through dispersive mixing, an ordered heterogeneity (e.g., sets of vertical fractures) allows instabilities to propagate at modest combinations of fracture aperture and separation distances. Despite a clearer understanding of the processes that control the onset and propagation of instabilities, resultant plume patterns and their migration rates and pathways do not appear amenable to
Vaupel, P; Kallinowski, F; Dave, S; Gabbert, H; Bastert, G
1985-01-01
A new model is presented for the study of oxygen supply and substrate utilization in human tumor tissue. In this approach human tumor material thrives in immune-deficient nude rats. The host chosen allows the continuous evaluation of all relevant parameters. From the data obtained so far it is concluded that this model is a valid tool in investigation of the metabolic status of human tumors.
NASA Astrophysics Data System (ADS)
Majumdar, Arnab
The mammalian lung consists of an asymmetric binary tree through which air is transported to the gas exchange units, called alveoli. In this thesis; we study the asymmetric bifurcation of the airway tree and develop models of the transport processes and relations describing the connection between lung inflation and branching structure. We examine the branching pattern of the airway tree of four mammalian species and demonstrate that the bifurcations are self-similar. We derive closed form expressions for the distribution of airway diameters as a function of generation number utilizing an asymmetric flow-division model. Our findings suggest that the empirically observed structural heterogeneity of the airway tree can be explained by simple deterministic rules of the branching pattern. In lung diseases, airways can close during expiration. During inspiration, these closures reopen in avalanches, leading to a series of discrete increments in lung volume with increasing pressure. To reproduce the experimental pressure-volume (P-V) relations of the lungs, we develop a model consisting of an asymmetric bifurcating structure with random blockages that can be removed by the pressure of the fluid. We show that the P-V relations can be decomposed into a linear superposition of paths connecting the root of the tree to the alveoli. We solve the inverse problem to estimate the underlying path length distribution of the tree by analyzing experimental P-V curves. This distribution agrees well with available morphometric data on airway structure. When some airways collapse during expiration, the downstream sub-tree becomes isolated from the root trapping air behind the closure. Consequently, the P-V curve develops hysteresis. We obtain analytical solutions for this hysteretic behavior and the amount of trapped gas during deflation. The opening of collapsed airways is an explosive process generating an audible sound, called crackle. We derive a relationship between the amplitude of
NASA Astrophysics Data System (ADS)
Perez, Pedro; Miranda, Regina
2013-04-01
emission inventory, together with the mobile source's parameters and the disaggregated transport activity data. The paper will also identify emission and concentration differences and gradients of certain magnitude/factor (e.g. comparison between estimated ATPs hourly concentrations in Madrid City Center and in the peripheries). Furthermore, because of the higher contribution of road mobile sources to GHGs and ATPs emissions in Madrid, small gradients between urban highways and residential areas will be expected. Second, the paper objectives are to develop valid methods and approaches to measure air quality and to develop valid road transport emission inventories to assess correlations between external costs, epidemiology and emissions in order to reveal how traffic pollution affects people exposure to key contaminants and disease development, and identify susceptible emission scenarios and health impacts. We have conducted general emission inventory studies providing preliminary evidence of regional road transport air pollution impacts on external cost growth and disease development. Third, we also aim to demonstrate short and long-term impacts of road transport emissions on external costs development using innovative multi-methodological methods interfaced with environmental chemistry and meteorology following meteorological and chemical fields with contrasting high/low traffic emissions in several linked components involving: air pollutant assessment using local measurements, height of the boundary layer, meteorological environment interactions on external costs and epidemiology, mapping of Madrid (identifying gradients of emissions), integrative causal modeling using statistical models, and trend and scenario analyses on external costs and impacts on human health. Meteorological and chemical fields will be obtained from local records collected by surface meteorological and air quality stations. These two sets of fields define the horizontal and vertical profiles of
NASA Astrophysics Data System (ADS)
Tejedor, Alejandro; Longjas, Anthony; Zaliapin, Ilya; Foufoula-Georgiou, Efi
2015-06-01
River deltas are intricate landscapes with complex channel networks that self-organize to deliver water, sediment, and nutrients from the apex to the delta top and eventually to the coastal zone. The natural balance of material and energy fluxes, which maintains a stable hydrologic, geomorphologic, and ecological state of a river delta, is often disrupted by external perturbations causing topological and dynamical changes in the delta structure and function. A formal quantitative framework for studying delta channel network connectivity and transport dynamics and their response to change is lacking. Here we present such a framework based on spectral graph theory and demonstrate its value in computing delta's steady state fluxes and identifying upstream (contributing) and downstream (nourishment) areas and fluxes from any point in the network. We use this framework to construct vulnerability maps that quantify the relative change of sediment and water delivery to the shoreline outlets in response to possible perturbations in hundreds of upstream links. The framework is applied to the Wax Lake delta in the Louisiana coast of the U.S. and the Niger delta in West Africa. In a companion paper, we present a comprehensive suite of metrics that quantify topologic and dynamic complexity of delta channel networks and, via application to seven deltas in diverse environments, demonstrate their potential to reveal delta morphodynamics and relate to notions of vulnerability and robustness.
Schmidts, Miriam; Frank, Valeska; Eisenberger, Tobias; al Turki, Saeed; Bizet, Albane A.; Antony, Dinu; Rix, Suzanne; Decker, Christian; Bachmann, Nadine; Bald, Martin; Vinke, Tobias; Toenshoff, Burkhard; Donato, Natalia Di; Neuhann, Theresa; Hartley, Jane L.; Maher, Eamonn R.; Bogdanović, Radovan; Peco-Antić, Amira; Mache, Christoph; Hurles, Matthew E.; Joksić, Ivana; Guć-Šćekić, Marija; Dobricic, Jelena; Brankovic-Magic, Mirjana; Bolz, Hanno J.; Pazour, Gregory J.; Beales, Philip L.; Scambler, Peter J.; Saunier, Sophie; Mitchison, Hannah M.; Bergmann, Carsten
2014-01-01
Ciliopathies are genetically heterogeneous disorders characterized by variable expressivity and overlaps between different disease entities. This is exemplified by the short rib-polydactyly syndromes, Jeune, Sensenbrenner, and Mainzer-Saldino chondrodysplasia syndromes. These three syndromes are frequently caused by mutations in intraflagellar transport (IFT) genes affecting the primary cilia, which play a crucial role in skeletal and chondral development. Here, we identified mutations in IFT140, an IFT complex A gene, in five Jeune asphyxiating thoracic dystrophy (JATD) and two Mainzer-Saldino syndrome (MSS) families, by screening a cohort of 66 JATD/MSS patients using whole exome sequencing and targeted resequencing of a customized ciliopathy gene panel. We also found an enrichment of rare IFT140 alleles in JATD compared with nonciliopathy diseases, implying putative modifier effects for certain alleles. IFT140 patients presented with mild chest narrowing, but all had end-stage renal failure under 13 years of age and retinal dystrophy when examined for ocular dysfunction. This is consistent with the severe cystic phenotype of Ift140 conditional knockout mice, and the higher level of Ift140 expression in kidney and retina compared with the skeleton at E15.5 in the mouse. IFT140 is therefore a major cause of cono-renal syndromes (JATD and MSS). The present study strengthens the rationale for IFT140 screening in skeletal ciliopathy spectrum patients that have kidney disease and/or retinal dystrophy. PMID:23418020
NASA Astrophysics Data System (ADS)
Triska, F. J.; Pringle, C. M.; Duff, J. H.; Avanzino, R. J.; Ardon, M.
2005-05-01
Soluble reactive phosphorus (SRP) transport retention was determined since 1988 at 4 sites in three rain forest streams draining La Selva Biological Station, Costa Rica. SRP levels can be naturally high there due to regional geothermal groundwater discharge at ambient temperature. Mean SRP was 89±53ug/L for the Salto (1988-1996) compared to 21±39ug/L for a tributary Pantano (1988-1998) and 26±35ug/L in the nearby Sabalo. After 1997 Salto SRP was determined separately in upland (Upper Salto) and lowland forest (Lower Salto) reaches. Upper Salto SRP is low until enriched at the slope transition. There high SRP springs contribute approximately 36% of long term discharge and 85% of SRP load leaving the watershed. TP is negatively correlated to discharge in all streams. SRP is not correlated to discharge at low SRP sites, but negatively correlated to discharge in Lower Salto when data from 2 ENSO events (EL Nino Southern Oscillation) are removed. Short-term SPR conservative tracer addition experiments indicate high retention at all sites. Retention is dominated by sediment, as indicated by subsequent adsorption-desorption studies. Enhanced input to high SRP streams can affect biotic metabolism, litter decomposition and secondary production in these tropical environments.
Nejand, Bahram Abdollahi; Ahmadi, Vahid; Shahverdi, Hamid Reza
2015-10-01
In this work we reported sputter deposited NiOx/Ni double layer as an HTM/contact couple in normal architecture of perovskite solar cell. A perovskite solar cell that is durable for more than 60 days was achieved, with increasing efficiency from 1.3% to 7.28% within 6 days. Moreover, low temperature direct deposition of NiOx layer on perovskite layer was introduced as a potential hole transport material for an efficient cost-effective solar cell applicable for various morphologies of perovskite layers, even for perovskite layers containing pinholes, which is a notable challenge in perovskite solar cells. The angular deposition of NiOx layers by dc reactive magnetron sputtering showed uniform and crack-free coverage of the perovskite layer with no negative impact on perovskite structure that is suitable for nickel back contact layer, surface shielding against moisture, and mechanical damages. Replacing the expensive complex materials in previous perovskite solar cells with low cost available materials introduces cost-effective scalable perovskite solar cells.
NASA Technical Reports Server (NTRS)
Denery, D. G.; White, K. C.; Drinkwater, F. J., III
1974-01-01
NASA, in cooperation with the FAA, is evaluating the two-segment approach as a routine procedure for reducing aircraft noise. The program calls for separate flight evaluations using a 727 and a DC-8, and an extrapolation of these results to determine the adaptability of the technique to the rest of the fleet. The total program is reviewed. The profile and procedures developed and the noise reduction achievable are presented. The vortex characteristics behind an aircraft on a two-segment path is covered. Finally, cost estimates for retrofitting aircraft with two-segment avionics are presented.
Haire, Melissa A.; Vargo, David D.
2007-01-30
The selected configuration for the Project Prometheus Space Nuclear Power Plant was a direct coupling of Brayton energy conversion loop(s) to a single reactor heat source through the gas coolant/working fluid. A mixture of helium (He) and xenon (Xe) gas was assumed as the coolant/working fluid. Helium has superior thermal conductivity while xenon is added to increase the gas atomic weight to benefit turbomachinery design. Both elements have the advantage of being non-reactive. HeXe transport properties (viscosity and thermal conductivity) were needed to calculate pressure drops and heat transfer rates. HeXe mixture data are limited, necessitating the use of semi-empirical correlations to calculate mixture properties. Several approaches are available. Pure component properties are generally required in the mixture calculations. While analytical methods are available to estimate pure component properties, adequate helium and xenon pure component data are available. This paper compares the sources of pure component data and the approaches to calculate mixture properties. Calculated mixture properties are compared to the limited mixture data and approaches are recommended to calculate both pure component and mixture properties. Given the limited quantity of HeXe mixture data (all at one atmosphere), additional testing may have been required for Project Prometheus to augment the existing data and confirm the selection of mixture property calculation methods.
Grebe, Mechthild; Pröfrock, Daniel; Kakuschke, Antje; Broekaert, Jose A C; Prange, Andreas
2010-10-01
The health status of marine mammals such as harbour seals (Phoca vitulina) represents an indirect but powerful way for the assessment of environmental changes. The present work illustrates the first investigation and characterisation of Tf isolated from blood samples of North Sea harbour seals with a view to using changes in Tf isoform patterns as an additional parameter in extended studies of their health status. Therefore, an HPLC-ICP-MS approach has been developed which allows the highly resolved separation and fractionation of up to eight different Tf isoforms, as well as their sensitive and specific detection on the basis of their characteristic iron content. Molecule-specific detection techniques such as nanoLC-ESI-QTRAP-MS or MALDI-TOF-MS were used as complementary techniques to unambiguously identify the isolated proteins as Tf via cross species protein identification and to further characterise the molecular weight as well as the sialic acid content, which is responsible for the elution behaviour of the different isoforms during their ion exchange separation. A molecular mass above 80 kDa has been measured for the different seal Tf isoforms, which is in good agreement with the known molecular mass in other mammalian species, while the estimated pI of the different isoforms indicates some differences in comparison to other species. A number of homologies to known Tf sequences have been observed, which finally allows the cross species protein identification. The combined metallomics orientated analytical approach, which includes the complementary application of element and molecule-specific detection techniques, opens up interesting possibilities for the fast and targeted isolation and identification of a diagnostically relevant metal containing protein from an un-sequenced mammalian species prior to its utilisation in extended studies.
Simmons, C.S.; Cole, C.R.
1985-05-01
This document was written for the National Low-Level Waste Management Program to provide guidance for managers and site operators who need to select ground-water transport codes for assessing shallow-land burial site performance. The guidance given in this report also serves the needs of applications-oriented users who work under the direction of a manager or site operator. The guidelines are published in two volumes designed to support the needs of users having different technical backgrounds. An executive summary, published separately, gives managers and site operators an overview of the main guideline report. This volume includes specific recommendations for decision-making managers and site operators on how to use these guidelines. The more detailed discussions about the code selection approach are provided. 242 refs., 6 figs.
Keith Rule; Erik Perry; Jim Chrzanowski; Mike Viola; Ron Strykowsky
2003-09-15
Original estimates stated that the amount of radioactive waste that will be generated during the dismantling of the Tokamak Fusion Test Reactor will approach two million kilograms with an associated volume of 2,500 cubic meters. The materials were activated by 14 MeV neutrons and were highly contaminated with tritium, which present unique challenges to maintain integrity during packaging and transportation. In addition, the majority of this material is stainless steel and copper structural metal that were specifically designed and manufactured for this one-of-a-kind fusion research reactor. This provided further complexity in planning and managing the waste. We will discuss the engineering concepts, innovative practices, and technologies that were utilized to size reduce, stabilize, and package the many unique and complex components of this reactor. This waste was packaged and shipped in many different configurations and methods according to the transportation regulations and disposal facility requirements. For this particular project, we were able to utilize two separate disposal facilities for burial. This paper will conclude with a complete summary of the actual results of the waste management costs, volumes, and best practices that were developed from this groundbreaking and successful project.
Kamaraj, Balu; Purohit, Rituraj
2016-11-01
Oculocutaneous albinism type IV (OCA4) is an autosomal recessive inherited disorder which is characterized by reduced biosynthesis of melanin pigmentation in skin, hair, and eyes and caused by the genetic mutations in the membrane-associated transporter protein (MATP) encoded by SLC45A2 gene. The MATP protein consists of 530 amino acids which contains 12 putative transmembrane domains and plays an important role in pigmentation and probably functions as a membrane transporter in melanosomes. We scrutinized the most OCA4 disease-associated mutation and their structural consequences on SLC45A2 gene. To understand the atomic arrangement in 3D space, the native and mutant structures were modeled. Further the structural behavior of native and mutant MATP protein was investigated by molecular dynamics simulation (MDS) approach in explicit lipid and water background. We found Y317C as the most deleterious and disease-associated SNP on SLC45A2 gene. In MDS, mutations in MATP protein showed loss of stability and became more flexible, which alter its structural conformation and function. This phenomenon has indicated a significant role in inducing OCA4. Our study explored the understanding of molecular mechanism of MATP protein upon mutation at atomic level and further helps in the field of pharmacogenomics to develop a personalized medicine for OCA4 disorder. J. Cell. Biochem. 117: 2608-2619, 2016. © 2016 Wiley Periodicals, Inc. PMID:27019209
Theory of contributon transport
Painter, J.W.; Gerstl, S.A.W.; Pomraning, G.C.
1980-10-01
A general discussion of the physics of contributon transport is presented. To facilitate this discussion, a Boltzmann-like transport equation for contributons is obtained, and special contributon cross sections are defined. However, the main goal of this study is to identify contributon transport equations and investigate possible deterministic solution techniques. Four approaches to the deterministic solution of the contributon transport problem are investigated. These approaches are an attempt to exploit certain attractive properties of the contributon flux, psi = phi phi/sup +/, where phi and phi/sup +/ are the solutions to the forward and adjoint Boltzmann transport equations.
Narasimhan, T.N.; Wang, J.S.Y.
1992-07-01
The authors of this report have been participating in the Sandia National Laboratory`s hydrologic performance assessment of the Yucca Mountain, Nevada, since 1983. The scope of this work is restricted to the unsaturated zone at Yucca Mountain and to technical questions about hydrology and chemical transport. The issues defined here are not to be confused with the elaborate hierarchy of issues that forms the framework of the US Department of Energy plans for characterizing the site (DOE, 1989). The overall task of hydrologic performance assessment involves issues related to hydrology, geochemistry, and energy transport in a highly heterogeneous natural geologic system which will be perturbed in a major way by the disposal activity. Therefore, a rational evaluation of the performance assessment issues must be based on an integrated appreciation of the aforesaid interacting processes. Accordingly, a hierarchical approach is taken in this report, proceeding from the statement of the broad features of the site that make it the site for intensive studies and the rationale for disposal strategy, through the statement of the fundamental questions that need to be answered, to the identification of the issues that need resolution. Having identified the questions and issues, the report then outlines the tasks to be undertaken to resolve the issues. The report consists essentially of two parts. The first part deals with the definition of issues summarized above. The second part summarizes the findings of the authors between 1983 and 1989 under the activities of the former Nevada Nuclear Waste Storage Investigations (NNWSI) and the current YMP.
Thrower, Alex W.; Janairo, Lisa
2013-07-01
related to the selection of a consolidated storage site. The approach would be characterized by informed discussion and deliberation, bringing together stakeholders from government, the non-governmental (NGO) community, industry, and other sectors. Because site selection would result in regional transportation impacts, the development of the transportation system (e.g., route identification, infrastructure improvements) would be integrated into the issue-resolution process. In addition to laying out the necessary steps and associated timeline, the authors address the challenges of building public trust and confidence in the new waste management program, as well as the difficulty of reaching and sustaining broad-based consensus on a decision to host a consolidated storage facility. (authors)
NASA Technical Reports Server (NTRS)
Grantham, William D.
1989-01-01
The primary objective was to provide information to the flight controls/flying qualities engineer that will assist him in determining the incremental flying qualities and/or pilot-performance differences that may be expected between results obtained via ground-based simulation (and, in particular, the six-degree-of-freedom Langley Visual/Motion Simulator (VMS)) and flight tests. Pilot opinion and performance parameters derived from a ground-based simulator and an in-flight simulator are compared for a jet-transport airplane having 32 different longitudinal dynamic response characteristics. The primary pilot tasks were the approach and landing tasks with emphasis on the landing-flare task. The results indicate that, in general, flying qualities results obtained from the ground-based simulator may be considered conservative-especially when the pilot task requires tight pilot control as during the landing flare. The one exception to this, according to the present study, was that the pilots were more tolerant of large time delays in the airplane response on the ground-based simulator. The results also indicated that the ground-based simulator (particularly the Langley VMS) is not adequate for assessing pilot/vehicle performance capabilities (i.e., the sink rate performance for the landing-flare task when the pilot has little depth/height perception from the outside scene presentation).
Rogers, S.W.; Ong, S.K.; Stenback, G.A.; Golchin, J.; Kjartanson, B.H.
2007-01-15
Expedited site characterization and groundwater monitoring using direct-push technology and conventional monitoring wells were conducted at a former manufactured gas plant site. Biogeochemical data and heterotrophic plate counts support the presence of microbially mediated remediation. By superimposing solutions of a two-dimensional reactive transport analytical model, first-order degradation rate coefficients (day{sup -1}) of various compounds for the dissolved-phase plume were estimated (i.e., benzene (0.0084), naphthalene (0.0058), and acenaphthene (0.0011)). The total mass transformed by aerobic respiration, nitrate reduction, and sulfate reduction around the free-phase coal-tar dense-nonaqueous-phase-liquid region and in the plume was estimated to be approximately 4.5 kg/y using a biogeochemical mass-balance approach. The total mass transformed using the degradation rate coefficients was estimated to be approximately 3.6 kg/y. Results showed that a simple two-dimensional analytical model and a biochemical mass balance with geochemical data from expedited site characterization can be useful for rapid estimation of mass-transformation rates.
Rogers, Shane W; Ong, Say Kee; Stenback, Greg A; Golchin, Johanshir; Kjartanson, Bruce H
2007-01-01
Expedited site characterization and groundwater monitoring using direct-push technology and conventional monitoring wells were conducted at a former manufactured gas plant site. Biogeochemical data and heterotrophic plate counts support the presence of microbially mediated remediation. By superimposing solutions of a two-dimensional reactive transport analytical model, first-order degradation rate coefficients ((day-1) ) of various compounds for the dissolved-phase plume were estimated (i.e., benzene [0.0084], naphthalene [0.0058], and acenaphthene [0.0011]). The total mass transformed by aerobic respiration, nitrate reduction, and sulfate reduction around the free-phase coal-tar dense-nonaqueous-phase-liquid region and in the plume was estimated to be approximately 4.5 kg/y using a biogeochemical mass-balance approach. The total mass transformed using the degradation rate coefficients was estimated to be approximately 3.6 kg/y. Results showed that a simple two-dimensional analytical model and a biochemical mass balance with geochemical data from expedited site characterization can be useful for rapid estimation of mass-transformation rates.
Srivastava, Anshika; Mishra, Avshesh; Singh, Rajan; Rai, Rajani; Srivastava, Neena; Mittal, Balraj
2013-01-01
Objective Cholesterol gallstone disease (CGD) is a multifactorial and multistep disease. Apart from female gender and increasing age being the documented non-modifiable risk factor for gallstones the pathobiological mechanisms underlying the phenotypic expression of CGD appear to be rather complex, and one or more variations in genes could play critical roles in the diverse pathways further progressing to cholesterol crystal formation. In the present study we performed genotyping score, Multifactor dimensionality reduction (MDR) and Classification and Regression Tree analysis (CART) to identify combinations of alleles among the hormonal, hepatocanalicular transporter and adipogenesis differentiation pathway genes in modifying the risk for CGD. Design The present case-control study recruited total of 450 subjects, including 230 CGD patients and 220 controls. We analyzed common ESR1, ESR2, PGR, ADRB3, ADRA2A, ABCG8, SLCO1B1, PPARγ2, and SREBP2 gene polymorphisms to find out combinations of genetic variants contributing to CGD risk, using multi-analytical approaches (G-score, MDR, and CART). Results Single locus analysis by logistic regression showed association of ESR1 IVS1-397C>T (rs2234693), IVS1-351A>G (rs9340799) PGR ins/del (rs1042838) ADRB3-190 T>C (rs4994) ABCG8 D19H (rs11887534), SLCO1B1 Exon4 C>A (rs11045819) and SREBP2 1784G>C (rs2228314) with CGD risk. However, the MDR and CART analysis revealed ESR1 IVS1-397C>T (rs2234693) ADRB3-190 T>C (rs4994) and ABCG8 D19H (rs11887534) polymorphisms as the best polymorphic signature for discriminating between cases and controls. The overall odds ratio for the applied multi-analytical approaches ranged from 4.33 to 10.05 showing an incremental risk for cholesterol crystal formation. In conclusion, our muti-analytical approach suggests that, ESR1, ADRB3, in addition to ABCG8 genetic variants confer significant risk for cholesterol gallstone disease. PMID:23577061
NASA Astrophysics Data System (ADS)
Mahfouzi, Farzad
Current and future technological needs increasingly motivate the intensive scientific research of the properties of materials at the nano-scale. One of the most important domains in this respect at present concerns nano-electronics and its diverse applications. The great interest in this domain arises from the potential reduction of the size of the circuit components, maintaining their quality and functionality, and aiming at greater efficiency, economy, and storage characteristics for the corresponding physical devices. The aim of this thesis is to present a contribution to the analysis of the electronic charge and spin transport phenomena that occur at the quantum level in nano-structures. This thesis spans the areas of quantum transport theory through time-dependent systems, electron-boson interacting systems and systems of interest to spintronics. A common thread in the thesis is to develop the theoretical foundations and computational algorithms to numerically simulate such systems. In order to optimize the numerical calculations I resort to different techniques (such as graph theory in finding inverse of a sparse matrix, adaptive grids for integrations and programming languages (e.g., MATLAB and C++) and distributed computing tools (MPI, CUDA). Outline of the Thesis: After giving an introduction to the topics covered in this thesis in Chapter 1, I present the theoretical foundations to the field of non-equilibrium quantum statistics in Chapter 2. The applications of this formalism and the results are covered in the subsequent chapters as follows: Spin and charge quantum pumping in time-dependent systems: Covered in Chapters 3, 4 and 5, this topics was initially motivated by experiments on measuring voltage signal from a magnetic tunnel junction (MTJ) exposed to a microwave radiation in ferromagnetic resonance (FMR) condition. In Chapter 3 we found a possible explanation for the finite voltage signal measured from a tunnel junction consisting of only a single
Trajectory structures and transport
Vlad, Madalina; Spineanu, Florin
2004-11-01
The special problem of transport in two-dimensional divergence-free stochastic velocity fields is studied by developing a statistical approach, the nested subensemble method. The nonlinear process of trapping determined by such fields generates trajectory structures whose statistical characteristics are determined. These structures strongly influence the transport.
NASA Astrophysics Data System (ADS)
Mahfouzi, Farzad
Current and future technological needs increasingly motivate the intensive scientific research of the properties of materials at the nano-scale. One of the most important domains in this respect at present concerns nano-electronics and its diverse applications. The great interest in this domain arises from the potential reduction of the size of the circuit components, maintaining their quality and functionality, and aiming at greater efficiency, economy, and storage characteristics for the corresponding physical devices. The aim of this thesis is to present a contribution to the analysis of the electronic charge and spin transport phenomena that occur at the quantum level in nano-structures. This thesis spans the areas of quantum transport theory through time-dependent systems, electron-boson interacting systems and systems of interest to spintronics. A common thread in the thesis is to develop the theoretical foundations and computational algorithms to numerically simulate such systems. In order to optimize the numerical calculations I resort to different techniques (such as graph theory in finding inverse of a sparse matrix, adaptive grids for integrations and programming languages (e.g., MATLAB and C++) and distributed computing tools (MPI, CUDA). Outline of the Thesis: After giving an introduction to the topics covered in this thesis in Chapter 1, I present the theoretical foundations to the field of non-equilibrium quantum statistics in Chapter 2. The applications of this formalism and the results are covered in the subsequent chapters as follows: Spin and charge quantum pumping in time-dependent systems: Covered in Chapters 3, 4 and 5, this topics was initially motivated by experiments on measuring voltage signal from a magnetic tunnel junction (MTJ) exposed to a microwave radiation in ferromagnetic resonance (FMR) condition. In Chapter 3 we found a possible explanation for the finite voltage signal measured from a tunnel junction consisting of only a single
Off-shell effects for the reaction pp{yields}{pi}d at high energies
Lee, T.S.H.; Locher, M.P.; Lu, Y.
1995-08-01
The reaction pp {yields} {pi}d is studied in a relativistic meson rescattering model. For 1.3 < T{sub p} < 2.4 GeV, the differential cross section and the asymmetry are calculated and compared to experiment. The model introduces simple form factors for the leading {pi}N partial waves, which depend on the virtuality of the exchanged {pi} and {rho} mesons. All remaining input is derived from experimental constraints. The data can be described by energy-independent form factors. The asymmetries are sensitive to pp distortion factors and further details of the model. A paper describing our results was published.
Dilaton and off-shell (non-critical string) effects in Boltzmann equation for species abundances
NASA Astrophysics Data System (ADS)
Lahanas, Ab; Mavromatos, Ne; Nanopoulos, Dv
In this work we derive the modifications to the Boltzmann equation governing the cosmic evolution of relic abundances induced by dilaton dissipative-source and non-critical-string terms in dilaton-driven non-equilibrium string Cosmologies. We also discuss briefly the most important phenomenological consequences, including modifications of the constraints on the available parameter space of cosmologically appealing particle physics models, imposed by recent precision data of astrophysical measurements.
Addendum to ``Off-shell structure of the anomalous Z and γ self-couplings''
NASA Astrophysics Data System (ADS)
Gounaris, G. J.; Layssac, J.; Renard, F. M.
2002-01-01
We point out that the lowest dimension operators that preserve SU(2)×U(1) gauge invariance and induce gauge boson self-interactions affecting only the neutral gauge bosons are just two dim=8 operators. If these operators constitute the only new physics source, there will then exist only two independent anomalous couplings affecting Z and γ: i.e., one CP conserving and one CP violating. On this basis, we give the corresponding relations among the ZZZ, ZZγ, and γγZ couplings used up to now in the analyses of experimental data. A reanalysis taking these relations into account should produce much more stringent constraints on the anomalous couplings.
Sewing relations and duality for BRST off-shell string tadpole amplitudes
Ordonez, C.R. ); Rey, S.; Rubin, M.A.; Zucchini, R.
1989-09-15
Using a Becchi-Rouet-Stora-Tyutin- (BRST-)invariant first-quantized formalism for closed-bosonic-string theory, we construct amplitudes for closed-string tadpoles in the conformal gauge and discuss the connection with covariant string field theory in the Siegel gauge. We also show that the application of the sewing rules, previously found for propagators, to pairs of these tadpole amplitudes yields the Klein-bottle and annulus one-loop vacuum amplitudes as required by duality and factorization.
dos Santos, Sandra C.; Teixeira, Miguel C.; Dias, Paulo J.; Sá-Correia, Isabel
2014-01-01
Multidrug/Multixenobiotic resistance (MDR/MXR) is a widespread phenomenon with clinical, agricultural and biotechnological implications, where MDR/MXR transporters that are presumably able to catalyze the efflux of multiple cytotoxic compounds play a key role in the acquisition of resistance. However, although these proteins have been traditionally considered drug exporters, the physiological function of MDR/MXR transporters and the exact mechanism of their involvement in resistance to cytotoxic compounds are still open to debate. In fact, the wide range of structurally and functionally unrelated substrates that these transporters are presumably able to export has puzzled researchers for years. The discussion has now shifted toward the possibility of at least some MDR/MXR transporters exerting their effect as the result of a natural physiological role in the cell, rather than through the direct export of cytotoxic compounds, while the hypothesis that MDR/MXR transporters may have evolved in nature for other purposes than conferring chemoprotection has been gaining momentum in recent years. This review focuses on the drug transporters of the Major Facilitator Superfamily (MFS; drug:H+ antiporters) in the model yeast Saccharomyces cerevisiae. New insights into the natural roles of these transporters are described and discussed, focusing on the knowledge obtained or suggested by post-genomic research. The new information reviewed here provides clues into the unexpectedly complex roles of these transporters, including a proposed indirect regulation of the stress response machinery and control of membrane potential and/or internal pH, with a special emphasis on a genome-wide view of the regulation and evolution of MDR/MXR-MFS transporters. PMID:24847282
Urbatsch, Todd James
2015-06-15
We present an overview of radiation transport, covering terminology, blackbody raditation, opacities, Boltzmann transport theory, approximations to the transport equation. Next we introduce several transport methods. We present a section on Caseology, observing transport boundary layers. We briefly broach topics of software development, including verification and validation, and we close with a section on high energy-density experiments that highlight and support radiation transport.
Sasaki, Takayuki; Tsuchiya, Yoshiyuki; Ariyoshi, Michiyo; Ryan, Peter R; Furuichi, Takuya; Yamamoto, Yoko
2014-12-01
Wheat and Arabidopsis plants respond to aluminum (Al) ions by releasing malate from their root apices via Al-activated malate transporter. Malate anions bind with the toxic Al ions and contribute to the Al tolerance of these species. The genes encoding the transporters in wheat and Arabidopsis, TaALMT1 and AtALMT1, respectively, were expressed in Xenopus laevis oocytes and characterized electrophysiologically using the two-electrode voltage clamp system. The Al-activated currents generated by malate efflux were detected for TaALMT1 but not for AtALMT1. Chimeric proteins were generated by swapping the N- and C-terminal halves of TaALMT1 and AtALMT1 (Ta::At and At::Ta). When these chimeras were characterized in oocytes, Al-activated malate efflux was detected for the Ta::At chimera but not for At::Ta, suggesting that the N-terminal half of TaALMT1 is necessary for function in oocytes. An additional chimera, Ta(48)::At, generated by swapping 17 residues from the N-terminus of AtALMT1 with the equivalent 48 residues from TaALMT1, was sufficient to support transport activity. This 48 residue region includes a helical region with a putative transmembrane domain which is absent in AtALMT1. The deletion of this domain from Ta(48)::At led to the complete loss of transport activity. Furthermore, truncations and a deletion at the C-terminal end of TaALMT1 indicated that a putative helical structure in this region was also required for transport function. This study provides insights into the structure-function relationships of Al-activated ALMT proteins by identifying specific domains on the N- and C-termini of TaALMT1 that are critical for basal transport function and Al responsiveness in oocytes.
Andrews, Robert W.; Birdie, Tiraz; Wilborn, Bill; Mukhopadhyay, Bimal
2012-07-01
Quantitative modeling of the potential for contaminant transport from sources associated with underground nuclear testing at Yucca Flat is an important part of the strategy to develop closure plans for the residual contamination. At Yucca Flat, the most significant groundwater resource that could potentially be impacted is the Lower Carbonate Aquifer (LCA), a regionally extensive aquifer that supplies a significant portion of the water demand at the Nevada National Security Site, formerly the Nevada Test Site. Developing and testing reasonable models of groundwater flow in this aquifer is an important precursor to performing subsequent contaminant transport modeling used to forecast contaminant boundaries at Yucca Flat that are used to identify potential use restriction and regulatory boundaries. A model of groundwater flow in the LCA at Yucca Flat has been developed. Uncertainty in this model, as well as other transport and source uncertainties, is being evaluated as part of the Underground Testing Area closure process. Several alternative flow models of the LCA in the Yucca Flat/Climax Mine CAU have been developed. These flow models are used in conjunction with contaminant transport models and source term models and models of contaminant transport from underground nuclear tests conducted in the overlying unsaturated and saturated alluvial and volcanic tuff rocks to evaluate possible contaminant migration in the LCA for the next 1,000 years. Assuming the flow and transport models are found adequate by NNSA/NSO and NDEP, the models will undergo a peer review. If the model is approved by NNSA/NSO and NDEP, it will be used to identify use restriction and regulatory boundaries at the start of the Corrective Action Decision Document Corrective Action Plan (CADD/CAP) phase of the Corrective Action Strategy. These initial boundaries may be revised at the time of the Closure Report phase of the Corrective Action Strategy. (authors)
NASA Astrophysics Data System (ADS)
Chen, B.; Xu, X. D.; Yang, S.; Zhao, T. L.
2012-02-01
The Asian Summer Monsoon (ASM) region has been recognized as a key region that plays a vital role in troposphere-to-stratosphere transport (TST), which can significantly impact the budget of global atmospheric constituents and climate change. However, the details of transport from the boundary layer (BL) to tropopause layer (TL) over this region, particularly from a climatological perspective, remains an issue of uncertainty. In this study, we present the climatological properties of BL-to-TL transport over the ASM region during boreal summer season (June-July-August) from 2001 to 2009. A comprehensive tracking analysis is conducted based on a large ensemble of TST-trajectories departing from the atmospheric BL and arriving at TL. Driven by the winds fields from the NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) Global Forecast System, all TST-trajectories are selected from the high resolution datasets generated by the Lagrangian particle transport model FLEXPART using a domain-filling technique. Three key atmospheric boundary layer sources for BL-to-TL transport are identified with their contributions: (i) 38% from the region between tropical Western Pacific region and South China Seas (WP), (ii) 21% from Bay of Bengal and South Asian subcontinent (BOB), and (iii) 12% from the Tibetan Plateau, which includes the South Slope of the Himalayas (TIB). Controlled by the different patterns of atmospheric circulation, the air masses originating from these three source regions are transported along the different tracks into the TL. The spatial distributions of these three source regions remain similarly from year to year. The timescales of transport from BL to TL by the large-scale ascents range from 1 to 7 weeks, contributing up to 60-70% of the overall TST; whereas the transport governed by the deep convection overshooting becomes faster, with timescales of 1-2 days and contributions of 20-30%. These results provide
Thatcher, Jack D
2013-04-16
This Teaching Resource provides and describes two animated lessons that illustrate general properties of transport proteins. The lesson called "transport protein classes" depicts major classes and subclasses of transport proteins. The "transporters, mechanism of action" lesson explains how transporters and P class ATPase (adenosine triphosphatase) pumps function. These animations serve as valuable resources for any collegiate-level course that describes these important factors. Courses that might use them include introductory biology, biochemistry, cell biology, physiology, and biophysics.
Smith, A.M.; Rice, P.; Hyde, R.; Peterson, R.
1995-02-01
Between 1952 and 1970, over two million cubic feet of transuranic mixed waste was buried in shallow pits and trenches in the Subsurface Disposal Area at the Idaho National Engineering Laboratory Radioactive Waste Management Complex. Commingled with this two million cubic feet of waste is up to 10 million cubic feet of fill soil. The pits and trenches were constructed similarly to municipal landfills with both stacked and random dump waste forms such as barrels and boxes. The main contaminants are micron-sized particles of plutonium and americium oxides, chlorides, and hydroxides. Retrieval, treatment, and disposal is one of the options being considered for the waste. This report describes the results of a field demonstration conducted to evaluate technologies for excavating, and transporting buried transuranic wastes at the INEL, and other hazardous or radioactive waste sites throughout the US Department of Energy complex. The full-scale demonstration, conduced at RAHCO Internationals facilities in Spokane, Washington, in the summer of 1994, evaluated equipment performance and techniques for digging, dumping, and transporting buried waste. Three technologies were evaluated in the demonstration: an Innovative End Effector for dust free dumping, a Telerobotic Transport Vehicle to convey retrieved waste from the digface, and a Remote Operated Excavator to deploy the Innovative End Effector and perform waste retrieval operations. Data were gathered and analyzed to evaluate retrieval performance parameters such as retrieval rates, transportation rates, human factors, and the equipment`s capability to control contamination spread.
NASA Astrophysics Data System (ADS)
Wikiniyadhanee, Rakkreat; Chotpantarat, Srilert; Ong, Say Kee
2015-11-01
Column experiments were performed under various ionic strengths (0.0-0.9 mM) using 10 mg L- 1 of Cd2 + without kaolinite colloids and 10 mg L- 1 Cd2 + mixed with 100 mg L- 1 kaolinite colloids. The nonequilibrium two-site model (TSM) described the behavior of both Cd2 + transport and Cd2 + co-transported with kaolinite colloids better than the equilibrium model (CDeq) (R2 = 0.978-0.996). The results showed that an increase in ionic strength negatively impacted the retardation factors (R) of both Cd2 + and Cd2 + mixed with kaolinite colloids. The presence of kaolinite colloids increased the retardation factors of Cd2 + from 7.23 to 7.89, 6.76 to 6.61 and 3.79 to 6.99 for ionic strengths of 0.225, 0.45 and 0.9 mM, respectively. On the other hand, the presence of kaolinite colloids decreased the retardation factor of Cd2 + from 8.13 to 7.83 for ionic strength of 0.0 mM. The fraction of instantaneous sorption sites (f) parameters, kinetic constant for sorption sites (α) and Freundlich constant (Kf) were estimated from HYDRUS-1D of TSM for Cd2 + transport. The fraction of instantaneous sorption sites was found to increase for an increase in ionic strength. Kf values of Cd2 + transport without kaolinite colloids for 0.0, 0.225 and 0.45 mM were found to be higher than those of Cd2 + transport with kaolinite colloids, except for ionic strength of 0.9 mM. Hence, the presence of kaolinite colloids probably retarded the mobility of Cd2 + in porous media for higher ionic strengths. Furthermore, retardation factors and Kf values of both Cd2 + transport and Cd2 + co-transport were shown to decrease when ionic strength increased. Interestingly, according to TSM, the fraction of instantaneous sorption sites tends to increase for an increase in ionic strength, which imply that the mechanism of Cd2 + sorption onto quartz sand can be better described using equilibrium sorption rather than nonequilibrium sorption for an increase in ionic strength.
Wikiniyadhanee, Rakkreat; Chotpantarat, Srilert; Ong, Say Kee
2015-11-01
Column experiments were performed under various ionic strengths (0.0-0.9 mM) using 10 mg L(-1) of Cd(2+) without kaolinite colloids and 10 mg L(-1) Cd(2+) mixed with 100 mg L(-1) kaolinite colloids. The nonequilibrium two-site model (TSM) described the behavior of both Cd(2+) transport and Cd(2+) co-transported with kaolinite colloids better than the equilibrium model (CD(eq)) (R(2)=0.978-0.996). The results showed that an increase in ionic strength negatively impacted the retardation factors (R) of both Cd(2+) and Cd(2+) mixed with kaolinite colloids. The presence of kaolinite colloids increased the retardation factors of Cd(2+) from 7.23 to 7.89, 6.76 to 6.61 and 3.79 to 6.99 for ionic strengths of 0.225, 0.45 and 0.9 mM, respectively. On the other hand, the presence of kaolinite colloids decreased the retardation factor of Cd(2+) from 8.13 to 7.83 for ionic strength of 0.0 mM. The fraction of instantaneous sorption sites (f) parameters, kinetic constant for sorption sites (α) and Freundlich constant (K(f)) were estimated from HYDRUS-1D of TSM for Cd(2+) transport. The fraction of instantaneous sorption sites was found to increase for an increase in ionic strength. K(f) values of Cd(2+) transport without kaolinite colloids for 0.0, 0.225 and 0.45 mM were found to be higher than those of Cd(2+) transport with kaolinite colloids, except for ionic strength of 0.9 mM. Hence, the presence of kaolinite colloids probably retarded the mobility of Cd(2+) in porous media for higher ionic strengths. Furthermore, retardation factors and K(f) values of both Cd(2+) transport and Cd(2+) co-transport were shown to decrease when ionic strength increased. Interestingly, according to TSM, the fraction of instantaneous sorption sites tends to increase for an increase in ionic strength, which imply that the mechanism of Cd(2+) sorption onto quartz sand can be better described using equilibrium sorption rather than nonequilibrium sorption for an increase in ionic strength.
Renken, R.A.; Patterson, R.D.; Orzol, L.L.; Dixon, Joann
2001-01-01
Rapid urban development and population growth in Palm Beach County, Florida, have been accompanied with the need for additional freshwater withdrawals from the surficial aquifer system. To maintain water quality, County officials protect capture areas and determine zones of transport of municipal supply wells. A multistep process was used to help automate the delineation of wellhead protection areas. A modular ground-water flow model (MODFLOW) Telescopic Mesh Refinement program (MODTMR) was used to construct an embedded flow model and combined with particle tracking to delineate zones of transport to supply wells; model output was coupled with a geographic information system. An embedded flow MODFLOW model was constructed using input and output file data from a preexisting three-dimensional, calibrated model of the surficial aquifer system. Three graphical user interfaces for use with the geographic information software, ArcView, were developed to enhance the telescopic mesh refinement process. These interfaces include AvMODTMR for use with MODTMR; AvHDRD to build MODFLOW river and drain input files from dynamically segmented linear (canals) data sets; and AvWELL Refiner, an interface designed to examine and convert well coverage spatial data layers to a MODFLOW Well package input file. MODPATH (the U.S. Geological Survey particle-tracking postprocessing program) and MODTOOLS (the set of U.S. Geological Survey computer programs to translate MODFLOW and MODPATH output to a geographic information system) were used to map zones of transport. A steady-state, five-layer model of the Boca Raton area was created using the telescopic mesh refinement process and calibrated to average conditions during January 1989 to June 1990. A sensitivity analysis of various model parameters indicates that the model is most sensitive to changes in recharge rates, hydraulic conductivity for layer 1, and leakance for layers 3 and 4 (Biscayne aquifer). Recharge (58 percent); river (canal
Yang, Qing; Easter, Richard C.; Campuzano-Jost, Pedro; Jimenez, Jose L.; Fast, Jerome D.; Ghan, Steven J.; Wang, Hailong; Berg, Larry K.; Barth, Mary; Liu, Ying; Shrivastava, ManishKumar B.; Singh, Balwinder; Morrison, H.; Fan, Jiwen; Ziegler, Conrad L.; Bela, Megan; Apel, Eric; Diskin, G. S.; Mikoviny, Tomas; Wisthaler, Armin
2015-08-20
The effect of wet scavenging on ambient aerosols in deep, continental convective clouds in the mid-latitudes is studied for a severe storm case in Oklahoma during the Deep Convective Clouds and Chemistry (DC3) field campaign. A new passive-tracer based transport analysis framework is developed to characterize the convective transport based on the vertical distribution of several slowly reacting and nearly insoluble trace gases. The passive gas concentration in the upper troposphere convective outflow results from a mixture of 47% from the lower level (0-3 km), 21% entrained from the upper troposphere, and 32% from mid-atmosphere based on observations. The transport analysis framework is applied to aerosols to estimate aerosol transport and wet-scavenging efficiency. Observations yield high overall scavenging efficiencies of 81% and 68% for aerosol mass (Dp < 1μm) and aerosol number (0.03< Dp < 2.5μm), respectively. Little chemical selectivity to wet scavenging is seen among observed submicron sulfate (84%), organic (82%), and ammonium (80%) aerosols, while nitrate has a much lower scavenging efficiency of 57% likely due to the uptake of nitric acid. Observed larger size particles (0.15 - 2.5μm) are scavenged more efficiently (84%) than smaller particles (64%; 0.03 - 0.15μm). The storm is simulated using the chemistry version of the WRF model. Compared to the observation based analysis, the standard model underestimates the wet scavenging efficiency for both mass and number concentrations with low biases of 31% and 40%, respectively. Adding a new treatment of secondary activation significantly improves simulation results, so that the bias in scavenging efficiency in mass and number concentrations is reduced to <10%. This supports the hypothesis that secondary activation is an important process for wet removal of aerosols in deep convective storms.
Gray, William G.; Miller, Cass T.
2010-01-01
This work is the eighth in a series that develops the fundamental aspects of the thermodynamically constrained averaging theory (TCAT) that allows for a systematic increase in the scale at which multiphase transport phenomena is modeled in porous medium systems. In these systems, the explicit locations of interfaces between phases and common curves, where three or more interfaces meet, are not considered at scales above the microscale. Rather, the densities of these quantities arise as areas per volume or length per volume. Modeling of the dynamics of these measures is an important challenge for robust models of flow and transport phenomena in porous medium systems, as the extent of these regions can have important implications for mass, momentum, and energy transport between and among phases, and formulation of a capillary pressure relation with minimal hysteresis. These densities do not exist at the microscale, where the interfaces and common curves correspond to particular locations. Therefore, it is necessary for a well-developed macroscale theory to provide evolution equations that describe the dynamics of interface and common curve densities. Here we point out the challenges and pitfalls in producing such evolution equations, develop a set of such equations based on averaging theorems, and identify the terms that require particular attention in experimental and computational efforts to parameterize the equations. We use the evolution equations developed to specify a closed two-fluid-phase flow model. PMID:21197134
NASA Astrophysics Data System (ADS)
Paradis, Hedvig; Andersson, Martin; Sundén, Bengt
2016-08-01
A 3D model at microscale by the lattice Boltzmann method (LBM) is proposed for part of an anode of a solid oxide fuel cell (SOFC) to analyze the interaction between the transport and reaction processes and structural parameters. The equations of charge, momentum, heat and mass transport are simulated in the model. The modeling geometry is created with randomly placed spheres to resemble the part of the anode structure close to the electrolyte. The electrochemical reaction processes are captured at specific sites where spheres representing Ni and YSZ materials are present with void space. This work focuses on analyzing the effect of structural parameters such as porosity, and percentage of active reaction sites on the ionic current density and concentration of H2 using LBM. It is shown that LBM can be used to simulate an SOFC anode at microscale and evaluate the effect of structural parameters on the transport processes to improve the performance of the SOFC anode. It was found that increasing the porosity from 30 to 50 % decreased the ionic current density due to a reduction in the number of reaction sites. Also the consumption of H2 decreased with increasing porosity. When the percentage of active reaction sites was increased while the porosity was kept constant, the ionic current density increased. However, the H2 concentration was slightly reduced when the percentage of active reaction sites was increased. The gas flow tortuosity decreased with increasing porosity.
Fredholm, Bertil B; Nordén, Bengt
2010-01-01
There is a need to reduce the amount of fossil energy used for transport, both because of the easily available fossil fuel is becoming sparser and because of climate concerns. In this article, the concept of "peak oil" is briefly presented. Second, a practical approach to reduction of fossil fuel use for transport elaborated by two British commissions is presented. A key feature is the introduction of electric cars. This raises the third issue covered in this article: namely, how battery technology is going to meet the increasing needs posed by the transport sector. PMID:20873684
Strongly interacting parton matter equilibration
Ozvenchuk, V.; Linnyk, O.; Bratkovskaya, E.; Gorenstein, M.; Cassing, W.
2012-07-15
We study the kinetic and chemical equilibration in 'infinite' parton matter within the Parton-Hadron-String Dynamics transport approach. The 'infinite' matter is simulated within a cubic box with periodic boundary conditions initialized at different energy densities. Particle abundances, kinetic energy distributions, and the detailed balance of the off-shell quarks and gluons in the strongly-interacting quarkgluon plasma are addressed and discussed.
ERIC Educational Resources Information Center
Executive Educator, 1990
1990-01-01
This special section on student transportation offers a case study of a school system that recycles buses for safety drills; articles on fuel-saving strategies, the pros and cons of contracting for transportation services or operating a publicly owned bus fleet, and advice on full cost accounting for transportation costs; and a transportation…
NASA Technical Reports Server (NTRS)
Hall, Timothy M.; Wuebbles, Donald J.; Boering, Kristie A.; Eckman, Richard S.; Lerner, Jean; Plumb, R. Alan; Rind, David H.; Rinsland, Curtis P.; Waugh, Darryn W.; Wei, Chu-Feng
1999-01-01
MM II defined a series of experiments to better understand and characterize model transport and to assess the realism of this transport by comparison to observations. Measurements from aircraft, balloon, and satellite, not yet available at the time of MM I [Prather and Remsberg, 1993], provide new and stringent constraints on model transport, and address the limits of our transport modeling abilities. Simulations of the idealized tracers the age spectrum, and propagating boundary conditions, and conserved HSCT-like emissions probe the relative roles of different model transport mechanisms, while simulations of SF6 and C02 make the connection to observations. Some of the tracers are related, and transport diagnostics such as the mean age can be derived from more than one of the experiments for comparison to observations. The goals of the transport experiments are: (1) To isolate the effects of transport in models from other processes; (2) To assess model transport for realistic tracers (such as SF6 and C02) for comparison to observations; (3) To use certain idealized tracers to isolate model mechanisms and relationships to atmospheric chemical perturbations; (4) To identify strengths and weaknesses of the treatment of transport processes in the models; (5) To relate evaluated shortcomings to aspects of model formulation. The following section are included:Executive Summary, Introduction, Age Spectrum, Observation, Tropical Transport in Models, Global Mean Age in Models, Source-Transport Covariance, HSCT "ANOY" Tracer Distributions, and Summary and Conclusions.
Transporter taxonomy - a comparison of different transport protein classification schemes.
Viereck, Michael; Gaulton, Anna; Digles, Daniela; Ecker, Gerhard F
2014-06-01
Currently, there are more than 800 well characterized human membrane transport proteins (including channels and transporters) and there are estimates that about 10% (approx. 2000) of all human genes are related to transport. Membrane transport proteins are of interest as potential drug targets, for drug delivery, and as a cause of side effects and drug–drug interactions. In light of the development of Open PHACTS, which provides an open pharmacological space, we analyzed selected membrane transport protein classification schemes (Transporter Classification Database, ChEMBL, IUPHAR/BPS Guide to Pharmacology, and Gene Ontology) for their ability to serve as a basis for pharmacology driven protein classification. A comparison of these membrane transport protein classification schemes by using a set of clinically relevant transporters as use-case reveals the strengths and weaknesses of the different taxonomy approaches.
Gray, William G.; Miller, Cass T.
2009-01-01
This work is the seventh in a series that introduces and employs the thermodynamically constrained averaging theory (TCAT) for modeling flow and transport in multiscale porous medium systems. This paper expands the previous analyses in the series by developing models at a scale where spatial variations within the system are not considered. Thus the time variation of variables averaged over the entire system is modeled in relation to fluxes at the boundary of the system. This implementation of TCAT makes use of conservation equations for mass, momentum, and energy as well as an entropy balance. Additionally, classical irreversible thermodynamics is assumed to hold at the microscale and is averaged to the megascale, or system scale. The fact that the local equilibrium assumption does not apply at the megascale points to the importance of obtaining closure relations that account for the large-scale manifestation of small-scale variations. Example applications built on this foundation are suggested to stimulate future work. PMID:20436941
Rojo, Miguel Muñoz; Martín, Jaime; Grauby, Stéphane; Borca-Tasciuc, Theodorian; Dilhaire, Stefan; Martin-Gonzalez, Marisol
2014-07-21
To date, there is no experimental characterization of thermal conductivity of semiconductor polymeric individual nanowires embedded in a matrix. This work reports on scanning thermal microscopy measurements in a 3ω configuration to determine how the thermal conductivity of individual nanowires made of a model conjugated polymer (P3HT) is modified when decreasing their diameters. We observe a reduction of thermal conductivity, from λNW = 2.29 ± 0.15 W K(-1) m(-1) to λNW = 0.5 ± 0.24 W K(-1) m(-1), when the diameter of nanowires is reduced from 350 nm to 120 nm, which correlates with the polymer crystal orientation measured by WAXS. Through this work, the foundations for future polymer thermal transport engineering are presented. PMID:24933655
Petrov, A.V.; Samsonova, L.M.; Vasil`kova, N.A.; Zinin, A.I.; Zinina, G.A. |
1994-06-01
Methodological aspects of the numerical modeling of the groundwater contaminant transport for the Lake Karachay area are discussed. Main features of conditions of the task are the high grade of non-uniformity of the aquifer in the fractured rock massif and the high density of the waste solutions, and also the high volume of the input data: both on the part of parameters of the aquifer (number of pump tests) and on the part of observations of functions of processes (long-time observations by the monitoring well grid). The modeling process for constructing the two dimensional regional model is described, and this model is presented as the basic model for subsequent full three-dimensional modeling in sub-areas of interest. Original powerful mathematical apparatus and computer codes for finite-difference numerical modeling are used.
NASA Astrophysics Data System (ADS)
Chen, Quan; Liu, Zhifei; Kissel, Catherine
2015-04-01
Terrigenous detrital materials buried at sea is a book documenting their whole life, including the continental environment where they originated from and the transport process they experienced. In order to reconstruct the East Asian monsoon evolution in late Quaternary, we need to read this book correctly. The key problem is to well understand the proxies and pick the right ones, because most of them are affected by several factors. In this study, clay and magnetic mineralogical measurements and geochemical XRF analyses were conducted on Core MD12-3432 taken from the northern South China Sea at 2125 m water depth during the CIRCEA cruise organized within Franco-Chinese LIA-MONOCL framework on board the R.V. Marion Dufresne. The age model is derived from both carbonate and magnetic stratigraphy. The clearly identified Laschamp and Iceland Basin geomagnetic excursions are used as tie points. Coupled earth magnetic field paleointensity and carbonate content record calibrated from XRF core scanned calcium intensity, we established a robust age model, indicating that Core MD12-3432 covers the last 410 kyr with an average sedimentation rate of 12.4 cm/kyr. The calibrated XRF-scan data provide high-resolution Ti/Ca, Al/Si and K/Al ratios. Ti/Ca and Al/Si ratios vary in phase, indicating strong clastic flux and short transport distances during glacials. Variations in K/Al ratio show an independent pattern, suggesting that temperature-driven chemical weathering is not the main control factor. Special attention needs therefore to be paid to the transport process. For that purpose, anisotropy of magnetic susceptibility was measured on discrete samples at 50 cm intervals. Orientations of the principal anisotropy axes could be reconstructed, using the NRM declination to orient the core in the horizontal plane. The maximum axis is relatively well oriented in the stratigraphic plane of the sedimentary magnetic fabric. A 90° shift is observed at the MIS 5-6 boundary, suggesting a
NASA Astrophysics Data System (ADS)
Schröder, D.; Bender, C. L.; Arlt, T.; Osenberg, M.; Hilger, A.; Risse, S.; Ballauff, M.; Manke, I.; Janek, J.
2016-10-01
Computed tomography with x-rays is a powerful tool to analyze the complex reaction and transport processes that occur inside electrochemical storage devices. To this day, a better insight into the occurring processes is needed and will yield improvements in energy density and cycling stability of next-generation batteries. Herein we present general considerations for the use of x-ray tomography of batteries to gain a detailed insight during operation. Furthermore, we present examples for the tomography of zinc-oxygen batteries, sodium-oxygen batteries and metal-sulfur batteries, elucidating performance limiting degradation processes such as dendrite formation and loss of liquid electrolyte. With the method applied, we aim to establish an effective link between the battery and x-ray community by offering a guideline on how to apply x-ray tomography to propel research on battery materials and entire batteries.
Rojo, Miguel Muñoz; Martín, Jaime; Grauby, Stéphane; Borca-Tasciuc, Theodorian; Dilhaire, Stefan; Martin-Gonzalez, Marisol
2014-07-21
To date, there is no experimental characterization of thermal conductivity of semiconductor polymeric individual nanowires embedded in a matrix. This work reports on scanning thermal microscopy measurements in a 3ω configuration to determine how the thermal conductivity of individual nanowires made of a model conjugated polymer (P3HT) is modified when decreasing their diameters. We observe a reduction of thermal conductivity, from λNW = 2.29 ± 0.15 W K(-1) m(-1) to λNW = 0.5 ± 0.24 W K(-1) m(-1), when the diameter of nanowires is reduced from 350 nm to 120 nm, which correlates with the polymer crystal orientation measured by WAXS. Through this work, the foundations for future polymer thermal transport engineering are presented.
NASA Astrophysics Data System (ADS)
Rahbaralam, Maryam; Fernàndez-Garcia, Daniel; Sanchez-Vila, Xavier
2015-12-01
Random walk particle tracking methods are a computationally efficient family of methods to solve reactive transport problems. While the number of particles in most realistic applications is in the order of 106-109, the number of reactive molecules even in diluted systems might be in the order of fractions of the Avogadro number. Thus, each particle actually represents a group of potentially reactive molecules. The use of a low number of particles may result not only in loss of accuracy, but also may lead to an improper reproduction of the mixing process, limited by diffusion. Recent works have used this effect as a proxy to model incomplete mixing in porous media. In this work, we propose using a Kernel Density Estimation (KDE) of the concentrations that allows getting the expected results for a well-mixed solution with a limited number of particles. The idea consists of treating each particle as a sample drawn from the pool of molecules that it represents; this way, the actual location of a tracked particle is seen as a sample drawn from the density function of the location of molecules represented by that given particle, rigorously represented by a kernel density function. The probability of reaction can be obtained by combining the kernels associated to two potentially reactive particles. We demonstrate that the observed deviation in the reaction vs time curves in numerical experiments reported in the literature could be attributed to the statistical method used to reconstruct concentrations (fixed particle support) from discrete particle distributions, and not to the occurrence of true incomplete mixing. We further explore the evolution of the kernel size with time, linking it to the diffusion process. Our results show that KDEs are powerful tools to improve computational efficiency and robustness in reactive transport simulations, and indicates that incomplete mixing in diluted systems should be modeled based on alternative mechanistic models and not on a
NASA Astrophysics Data System (ADS)
le Roux, J. A.
2012-12-01
It has been argued that the acceleration of SEPS at a quasi-parallel CME-driven shock to GeV energies in the corona only occurs if strong wave-excitation by SEPs ahead of the shock reduces the parallel mean free path upstream, thus boosting the rate of diffusive shock acceleration. To investigate this issue, we modeled SEP acceleration at a fast parallel traveling shock in the corona with an existing time-dependent focused transport model. The model has been expanded recently to also feature time-dependent self-excitation and damping of Alfvén waves by SEP anisotropies ahead of the shock based on standard quasi-linear theory. Alfvén wave propagation near the traveling shock is modeled based on standard theory for wave transport in a slowly varying non-uniform plasma medium. Preliminary results will be shown to illustrate the increase in wave power driven by SEP anisotropies upstream, the effect of the shock wave in shortening the wave length and increasing the wave amplitude of Alfvén waves, and the associated acceleration of SEPs by 1st order Fermi acceleration to high energies. The role of the acceleration of the cross-shock solar wind flow, which was found to create a downstream population of shock pre-heated particles which forms an additional source for injection into 1st order Fermi acceleration, will be discussed in terms of how it affects self-excitation of Alfvén waves and the formation of high-energy SEPs by 1st order Fermi acceleration.
NASA Astrophysics Data System (ADS)
Kim, Jung Jin; Stockhausen, William; Kim, Suam; Cho, Yang-Ki; Seo, Gwang-Ho; Lee, Joon-Soo
2015-11-01
To understand interannual variability in the distribution of the early life stages of Todarodes pacificus summer spawning population, and to identify the key transport processes influencing this variability, we used a coupled bio-physical model that combines an individual-based model (IBM) incorporating ontogenetic vertical migration for paralarval behavior and temperature-dependent survival process with a ROMS oceanographic model. Using the distribution of paralarvae observed in the northern East China Sea (ECS) during several field cruises as an end point, the spawning ground for the summer-spawning population was estimated to extend from southeast Jeju Island to the central ECS near 29°N by running the model backwards in time. Running the model forward, interannual variability in the distribution of paralarvae predicted by the model was consistent with that observed in several field surveys; surviving individuals in the northern ECS were substantially more abundant in late July 2006 than in 2007, in agreement with observed paralarval distributions. The total number of surviving individuals at 60 days after release based on the simulation throughout summer spawning period (June-August) was 20,329 for 2006, compared with 13,816 for 2007. The surviving individuals were mainly distributed in the East/Japan Sea (EJS), corresponding to a pathway following the nearshore branch of the Tsushima Warm Current flowing along the Japanese coast during both years. In contrast, the abundance of surviving individuals was extremely low in 2007 compared to 2006 on the Pacific side of Japan. Interannual variability in transport and survival processes made a substantial impact on not only the abundance of surviving paralarvae, but also on the flux of paralarvae to adjacent waters. Our simulation results for between-year variation in paralarval abundance coincide with recruitment (year n + 1) variability of T. pacificus in the field. The agreement between the simulation and field
Commercial jet transport crashworthiness
NASA Technical Reports Server (NTRS)
Widmayer, E.; Brende, O. B.
1982-01-01
The results of a study to identify areas of research and approaches that may result in improved occupant survivability and crashworthiness of transport aircraft are given. The study defines areas of structural crashworthiness for transport aircraft which might form the basis for a research program. A 10-year research and development program to improve the structural impact resistance of general aviation and commercial jet transport aircraft is planned. As part of this program parallel studies were conducted to review the accident experience of commercial transport aircraft, assess the accident performance of structural components and the status of impact resistance technology, and recommend areas of research and development for that 10-year plan. The results of that study are also given.
Nucleocytoplasmic transport of macromolecules.
Corbett, A H; Silver, P A
1997-01-01
Nucleocytoplasmic transport is a complex process that consists of the movement of numerous macromolecules back and forth across the nuclear envelope. All macromolecules that move in and out of the nucleus do so via nuclear pore complexes that form large proteinaceous channels in the nuclear envelope. In addition to nuclear pores, nuclear transport of macromolecules requires a number of soluble factors that are found both in the cytoplasm and in the nucleus. A combination of biochemical, genetic, and cell biological approaches have been used to identify and characterize the various components of the nuclear transport machinery. Recent studies have shown that both import to and export from the nucleus are mediated by signals found within the transport substrates. Several studies have demonstrated that these signals are recognized by soluble factors that target these substrates to the nuclear pore. Once substrates have been directed to the pore, most transport events depend on a cycle of GTP hydrolysis mediated by the small Ras-like GTPase, Ran, as well as other proteins that regulate the guanine nucleotide-bound state of Ran. Many of the essential factors have been identified, and the challenge that remains is to determine the exact mechanism by which transport occurs. This review attempts to present an integrated view of our current understanding of nuclear transport while highlighting the contributions that have been made through studies with genetic organisms such as the budding yeast, Saccharomyces cerevisiae. PMID:9184010
NASA Astrophysics Data System (ADS)
Rixhon, Gilles; May, Simon Matthias; Engel, Max; Mechernich, Silke; Keulertz, Rebecca; Schroeder-Ritzrau, Andrea; Fohlmeister, Jens; Frank, Norbert; Dunai, Tibor; Brueckner, Helmut
2016-04-01
Coastal hazard assessment depends on reliable information on the magnitude and frequency of past high-energy wave events (EWE: tsunamis, storms). For this purpose onshore sedimentary records represent promising geo-archives for the mid- and late-Holocene EWE history. In comparison to fine-grained sediments which have been extensively studied in the recent past, supralittoral megaclasts are less investigated, essentially due to the difficulties related to the dating of corresponding depositional events, and thus their limited value for inferring the timing of major events. On Bonaire (Leeward Antilles, Caribbean), supratidal coarse-clast deposits form prominent landforms all around the island. Fields of large boulders (up to 150 t) are among the best-studied reef-top megaclasts worldwide. Transport by Holocene tsunamis is assumed at least for the largest boulders (Engel and May, 2012). Although a large dataset of 14C and electron spin resonance (ESR) ages is available for major coral rubble ridges and ramparts, showing some age clusters during the Late Holocene, it is still debated whether these data reflect the timing of major depositional/transport event(s), and how these data sets are biased by reworking of coral fragments. In addition, different processes may be responsible for the deposition of the coral rubble ridges and ramparts (storm) and the solitary megaclasts (tsunami). As an attempt to overcome the current challenges for dating the dislocation of the megaclasts, three distinct dating methods were implemented: (i) 14C dating of boring bivalves (Lithophaga) attached to the boulders; (ii) uranium-series (U/Th) dating of post-depositional, secondary calcitic flowstone at the underside of the boulders; and (iii) surface exposure dating of overturned boulders via 36Cl concentration measurements in corals. The three 14C datings yield age estimates >37 ka, i.e. most probably beyond the applicability of the method, which sheds doubt on the usefulness of this
NASA Astrophysics Data System (ADS)
Ichino, Matteo C.; Clark, Malcolm R.; Drazen, Jeffrey C.; Jamieson, Alan; Jones, Daniel O. B.; Martin, Adrian P.; Rowden, Ashley A.; Shank, Timothy M.; Yancey, Paul H.; Ruhl, Henry A.
2015-06-01
Most of our knowledge about deep-sea habitats is limited to bathyal (200-3000 m) and abyssal depths (3000-6000 m), while relatively little is known about the hadal zone (6000-11,000 m). The basic paradigm for the distribution of deep seafloor biomass suggests that the reduction in biomass and average body size of benthic animals along depth gradients is mainly related to surface productivity and remineralisation of sinking particulate organic carbon with depth. However, there is evidence that this pattern is somewhat reversed in hadal trenches by the funnelling of organic sediments, which would result in increased food availability along the axis of the trenches and towards their deeper regions. Therefore, despite the extreme hydrostatic pressure and remoteness from the pelagic food supply, it is hypothesized that biomass can increase with depth in hadal trenches. We developed a numerical model of gravitational lateral sediment transport along the seafloor as a function of slope, using the Kermadec Trench, near New Zealand, as a test environment. We propose that local topography (at a scale of tens of kilometres) and trench shape can be used to provide useful estimates of local accumulation of food and, therefore, patterns of benthic biomass. Orientation and steepness of local slopes are the drivers of organic sediment accumulation in the model, which result in higher biomass along the axis of the trench, especially in the deepest spots, and lower biomass on the slopes, from which most sediment is removed. The model outputs for the Kermadec Trench are in agreement with observations suggesting the occurrence of a funnelling effect and substantial spatial variability in biomass inside a trench. Further trench surveys will be needed to determine the degree to which seafloor currents are important compared with the gravity-driven transport modelled here. These outputs can also benefit future hadal investigations by highlighting areas of potential biological interest
NASA Technical Reports Server (NTRS)
Kurkowski, R. L.; Barber, M. R.; Garodz, L. J.
1976-01-01
A series of flight tests was conducted to evaluate the vortex wake characteristics of a Boeing 727 (B727-200) aircraft during conventional and two-segment ILS approaches. Twelve flights of the B727, which was equipped with smoke generators for vortex marking, were flown and its vortex wake was intentionally encountered by a Lear Jet model 23 (LR-23) and a Piper Twin Comanche (PA-30). Location of the B727 vortex during landing approach was measured using a system of photo-theodolites. The tests showed that at a given separation distance there were no readily apparent differences in the upsets resulting from deliberate vortex encounters during the two types of approaches. Timed mappings of the position of the landing configuration vortices showed that they tended to descend approximately 91 m(300 ft) below the flight path of the B727. The flaps of the B727 have a dominant effect on the character of the trailed wake vortex. The clean wing produces a strong, concentrated vortex but as the flaps are lowered, the vortex system becomes more diffuse. Pilot opinion and roll acceleration data indicate that 4.5 n.mi. would be a minimum separation distance at which roll control of light aircraft (less than 5,670 kg (12,500 lb) could be maintained during parallel encounters of the B727's landing configuration wake. This minimum separation distance is generally in scale with results determined from previous tests of other aircraft using the small roll control criteria.
Basile, Jan
2011-07-01
Hyperglycemia is a defining characteristic of type 2 diabetes mellitus and is a major risk factor associated with the development of many microvascular complications. There are numerous therapies currently available to treat hyperglycemia, but glycemic control rates remain poor. One potential reason is the decline in ß-cell function over time, which decreases the effectiveness of therapies that rely on insulin action. The kidney occupies a central position in the control of glucose homeostasis by its role in gluconeogenesis and by regulating glucose excretion. Under normal conditions, glucose filtered by the kidney is virtually totally reabsorbed in the proximal tubule by the sodium-glucose co-transporter 2 (SGLT2). Inhibition of SGLT2 is an attractive, insulin-independent target for increasing glucose excretion in the setting of hyperglycemia. A number of SGLT2 inhibitors have been synthesized, and results from preclinical studies have shown that they increase glucose excretion and normalize plasma glucose in diabetic models. Initial clinical data are promising and suggest that SGLT2 inhibitors may be a new therapeutic option for treating type 2 diabetes mellitus.
ERIC Educational Resources Information Center
McCready, Mark J.; Leighton, David T.
1987-01-01
Discusses the problems created in graduate chemical engineering programs when students enter with a wide diversity of understandings of transport phenomena. Describes a two-semester graduate transport course sequence at the University of Notre Dame which focuses on fluid mechanics and heat and mass transfer. (TW)
Transportation Sector Module - NEMS Documentation
2014-01-01
Documents the objectives, analytical approach and development of the National Energy Modeling System (NEMS) Transportation Model (TRAN). The report catalogues and describes the model assumptions, computational methodology, parameter estimation techniques, model source code, and forecast results generated by the model.
NASA Technical Reports Server (NTRS)
Middleton, D. B.; Hurt, G. J., Jr.; Bergeron, H. P.; Patton, J. M., Jr.; Deal, P. L.; Champine, R. A.
1975-01-01
A moving-base simulator investigation of the problems of recovery and landing of a STOL aircraft after failure of an outboard engine during final approach was made. The approaches were made at 75 knots along a 6 deg glide slope. The engine was failed at low altitude and the option to go around was not allowed. The aircraft was simulated with each of three control systems, and it had four high-bypass-ratio fan-jet engines exhausting against large triple-slotted wing flaps to produce additional lift. A virtual-image out-the-window television display of a simulated STOL airport was operating during part of the investigation. Also, a simple heads-up flight director display superimposed on the airport landing scene was used by the pilots to make some of the recoveries following an engine failure. The results of the study indicated that the variation in visual cues and/or motion cues had little effect on the outcome of a recovery, but they did have some effect on the pilot's response and control patterns.
NASA Astrophysics Data System (ADS)
Mendoza, D. L.; Gurney, K. R.
2011-12-01
The transportation sector is the second largest CO2 emitting economic sector in the United States, accounting for 32.3% of the total U.S. emissions in 2002. Within the transportation sector, the largest component (80%) is made up of onroad emissions. In order to accurately quantify future emissions and evaluate emissions regulation strategies, analysis must account for spatially-explicit fleet distribution, driving patterns, and mitigation strategies. Studies to date, however, have either focused on one of these three components, have been only completed at the national scale, or have not explicitly represented CO2 emissions instead relying on the use of vehicle miles traveled (VMT) as an emissions proxy. We compare a high resolution onroad emissions data product (Vulcan) to a national averaging of the Vulcan result. This comparison is performed in four groupings: light duty (LD) and heavy duty (HD) vehicle classes, and rural and urban road classes. Two different bias metrics are studied: 1) the state-specific, group-specific bias and 2) the same bias when weighted by the state share of the national group-specific emissions. In the first metric, we find a spread of positive and negative biases for the LD and HD vehicle groupings and these biases are driven by states having a greater/lesser proportion of LD/HD vehicles within their total state fleet than found from a national average. The standard deviation of these biases is 2.01% and 0.75% for the LD and HD groupings, respectively. These biases correlate with the road type present in a state, so that biases found in the urban and LD groups are both positive or both negative, with a similar relationship found between biases of the rural and HD groups. Additionally, the road group bias is driven by the distribution of VMT on individual road classes within the road groupings. When normalized by national totals, the state-level group-specific biases reflect states with large amounts of onroad travel that deviate
NASA Astrophysics Data System (ADS)
Casola, J.; Johanson, E.; Groth, P.; Snow, C.; Choate, A.
2012-12-01
Southeastern Pennsylvania Transportation Authority (SEPTA), with support from the Federal Transit Administration, has been investigating its agency's vulnerability to weather-related disruption and damages as a way to inform an overall adaptation strategy for climate variability and change. Exploiting daily rail service records maintained by SEPTA and observations from nearby weather stations, we have developed a methodology for quantifying the sensitivity of SEPTA's Manayunk/Norristown rail line to various weather events (e.g., snow storms, heat waves, heavy rainfall and flooding, tropical storms). For each type of event, sensitivity is equated to the frequency and extent of service disruptions associated with the event, and includes the identification of thresholds beyond which impacts are observed. In addition, we have estimated the monetary costs associated with repair and replacement of infrastructure following these events. Our results have facilitated discussions with SEPTA operational staff, who have outlined the institutional aspects of their preparation and response processes for these weather events. We envision the methodology as being useful for resource and infrastructure managers across the public and private sector, and potentially scalable to smaller or larger operations. There are several advantageous aspects of the method: 1) the quantification of sensitivity, and the coupling of that sensitivity to cost information, provides credible input to SEPTA decision-makers as they establish the priorities and level of investment associated with their adaptation actions for addressing extreme weather; 2) the method provides a conceptual foundation for estimating the magnitude, frequency, and costs of potential future impacts at a local scale, especially with regard to heat waves; 3) the sensitivity information serves as an excellent discussion tool, enabling further research and information gathering about institutional relationships and procedures. These
Rassu, Giovanna; Soddu, Elena; Cossu, Massimo; Brundu, Antonio; Cerri, Guido; Marchetti, Nicola; Ferraro, Luca; Regan, Raymond F; Giunchedi, Paolo; Gavini, Elisabetta; Dalpiaz, Alessandro
2015-03-10
We propose the formulation and characterization of solid microparticles as nasal drug delivery systems able to increase the nose-to-brain transport of deferoxamine mesylate (DFO), a neuroprotector unable to cross the blood brain barrier and inducing negative peripheral impacts. Spherical chitosan chloride and methyl-β-cyclodextrin microparticles loaded with DFO (DCH and MCD, respectively) were obtained by spray drying. Their volume-surface diameters ranged from 1.77 ± 0.06 μm (DCH) to 3.47 ± 0.05 μm (MCD); the aerodynamic diameters were about 1.1 μm and their drug content was about 30%. In comparison with DCH, MCD enhanced the in vitro DFO permeation across lipophilic membranes, similarly as shown by ex vivo permeation studies across porcine nasal mucosa. Moreover, MCD were able to promote the DFO permeation across monolayers of PC 12 cells (neuron-like), but like DCH, it did not modify the DFO permeation pattern across Caco-2 monolayers (epithelial-like). Nasal administration to rats of 200 μg DFO encapsulated in the microparticles resulted in its uptake into the cerebrospinal fluid (CSF) with peak values ranging from 3.83 ± 0.68 μg/mL (DCH) to 14.37 ± 1.69 μg/mL (MCD) 30 min after insufflation of microparticles. No drug CSF uptake was detected after nasal administration of a DFO water solution. The DFO systemic absolute bioavailabilities obtained by DCH and MCD nasal administration were 6% and 15%, respectively. Chitosan chloride and methyl-β-cyclodextrins appear therefore suitable to formulate solid microparticles able to promote the nose to brain uptake of DFO and to limit its systemic exposure. PMID:25620068
NASA Astrophysics Data System (ADS)
Mamula Tartalja, Danica; Srećković, Milesa
2014-09-01
Nanoparticles’ structure, size, morphology, and surface conditions have significant influence on their performance and considerable impact on their application in biosystems. In this study some methods of nanoparticle analysis including structural x-ray diffraction, scanning electron and transmission electron microscopy size distribution and morphology characterization, superconducting quantum interference device and Faraday method magnetic and temperature dependence of specific resistance measurements, infrared spectroscopy, and laser light scattering based estimation of particle size distribution are surveyed. These methods illustrate the importance of a versatile approach to nanoparticle characterization, as the basis for their selection for particular applications. Since the methods of synthesis crucially affect the nanoparticle characteristics, the presented characterization techniques could also help to choose the most appropriate one.
NASA Astrophysics Data System (ADS)
Poudel, Kumud Raj
proteins. This deliberate contrast was created in order to provide a complete outlook into the transport properties and energetics of these crucial biological components in planar, heterogeneous bio-mimetic assemblies.
Patra, Malay; Awuah, Samuel G.; Lippard, Stephen J.
2016-01-01
Glycoconjugation is a promising strategy for specific targeting of cancer. In this study, we investigated the effect of D-glucose substitution position on the biological activity of glucose-platinum conjugates (Glc-Pts). We synthesized and characterized all possible positional isomers (C1α, C1β, C2, C3, C4 and C6) of a Glc-Pt. The synthetic routes presented here could in principle be extended to prepare glucose-conjugates with different active ingredients than platinum. The biological activities of the compounds were evaluated both in vitro and in vivo. We discovered that variation in position of substitution of D-glucose not only alters the cellular uptake and cytotoxicity profile but also the GLUT1 specificity of resulting glycoconjugates, where GLUT1 is glucose transporter 1. The C1α- and C2-substituted Glc-Pts (1α and 2) accumulate in cancer cells most efficiently compared to the others, whereas the C3-Glc-Pt (3) is taken up least efficiently. Compounds 1α and 2 are more potent compared to 3 in DU145 cells. The α- and β-anomer of the C1-Glc-Pt also differ significantly in their cellular uptake and activity profiles. No significant differences in uptake of the Glc-Pts were observed in noncancerous RWPE2 cells. The GLUT1 specificity of the Glc-Pts was evaluated by determining the cellular uptake in the absence and presence of the GLUT1 inhibitor cytochalasin B, and by comparing their anticancer activity in DU145 cells and a GLUT1 knockdown cell line. The results reveal that C2-substituted Glc-Pt 2 has the highest GLUT1 specific internalization, which also reflects the best cancer targeting ability. In a syngeneic breast cancer mouse model overexpressing GLUT1, compound 2 showed antitumor efficacy and selective uptake in tumors with no observable toxicity. This study thus reveals the synthesis of all positional isomers of D-glucose substitution for platinum warhead with detailed glycotargeting characterization in cancer. PMID:27570149
Design objectives - Air transportation
NASA Technical Reports Server (NTRS)
Beheim, M. A.
1974-01-01
The mainline of air transportation is expected to continue to be based on the medium to long haul turbine powered subsonic aircraft. With greater emphasis on energy conservation, there will be considerable interest in making additional progress in propulsion system efficiency. Continued improvement in turbofan engines is expected to occur, but there may be a less conventional approach in the background. Opportunities for expanding short haul air services will certainly materialize. The outlook for supersonic air transport is less clear because of complex political and economic factors.
Smart vehicular transportation systems
Little, C.Q.; Wilson, C.W.
1997-05-01
This work builds upon established Sandia intelligent systems technology to develop a unique approach for the integration of intelligent system control into the US Highway and urban transportation systems. The Sandia developed concept of the COPILOT controller integrates a human driver with computer control to increase human performance while reducing reliance on detailed driver attention. This research extends Sandia expertise in sensor based, real-time control of robotics systems to high speed transportation systems. Knowledge in the form of maps and performance characteristics of vehicles provides the automatic decision making intelligence needed to plan optimum routes, maintain safe driving speeds and distances, avoid collisions, and conserve fuel.
Szalárdy, Levente; Zádori, Dénes; Klivényi, Péter; Toldi, József; Vécsei, László
2015-01-01
Impaired function of certain mitochondrial respiratory complexes has long been linked to the pathogenesis of chronic neurodegenerative disorders such as Parkinson's and Huntington's diseases. Furthermore, genetic alterations of mitochondrial genome or nuclear genes encoding proteins playing essential roles in maintaining proper mitochondrial function can lead to the development of severe systemic diseases associated with neurodegeneration and vacuolar myelinopathy. At present, all of these diseases lack effective disease modifying therapy. Following a brief commemoration of Professor Albert Szent-Györgyi, a Nobel Prize laureate who pioneered in the field of cellular respiration, antioxidant processes, and the roles of free radicals in health and disease, the present paper overviews the current knowledge on the involvement of mitochondrial dysfunction in central nervous system diseases associated with neurodegeneration including Parkinson's and Huntington's disease as well as mitochondrial encephalopathies. The review puts special focus on the involvement and the potential therapeutic relevance of peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC-1α), a nuclear-encoded master regulator of mitochondrial biogenesis and antioxidant responses in these disorders, the transcriptional activation of which may hold novel therapeutic value as a more system-based approach aiming to restore mitochondrial functions in neurodegenerative processes. PMID:26301042
Development of transportation operations requirements
Grady, S.T.; Best, R.E.; Danese, F.L.; Peterson, R.W. ); Pope, R.B. )
1990-01-01
Transport conditions at various utility sties vary dramatically in terms of characteristics at and near the site, requirements, administrative procedures, and other factors. Continuation of design efforts for the OCRWM transportation operations system requires that the operating requirements for the transportation system -- quantity of fuel per unit time per site -- be identified so that the effect the variations have on the system can be accommodated. The approach outlined in this paper provides for an identification of specific sites, evaluation of shipment capabilities at each site, and integration of the sites into multi-site shipping campaigns to scope the logistics management problem for the transportation operations system. 1 fig., 1 tab.
Thatcher, Jack D
2013-04-16
These animations depict generalities of intercellular transport. The animation called "permeability and transport" demonstrates the permeability of four classes of molecules. The "gap junctions" animation shows how these intercellular complexes exclude large factors while they allow small factors to diffuse between cells. These animations serve as useful resources for any collegiate-level course that describes these processes. Courses that might use them include biochemistry, biophysics, cell biology, introductory biology, and physiology.
Reexamining charmless B{yields}PV decays in the QCD factorization approach
Li Xinqiang; Yang Yadong
2006-06-01
Using the QCD factorization approach, we reexamine the two-body hadronic charmless B-meson decays to final states involving a pseudoscalar (P) and a vector (V) meson, with inclusion of the penguin contractions of spectator-scattering amplitudes induced by the b{yields}Dg*g* (where D=d or s, and g* denotes an off-shell gluon) transitions, which are of order {alpha}{sub s}{sup 2}. Their impacts on the CP-averaged branching ratios and CP-violating asymmetries are examined. We find that these higher order penguin contraction contributions have significant impacts on some specific decay modes. Since B{yields}{pi}K*, K{rho} decays involve the same electroweak physics as B{yields}{pi}K puzzles, we present a detailed analysis of these decays and find that the five R-ratios for the B{yields}{pi}K*, K{rho} system are in agreement with experimental data except for R({pi}K*). Generally, these new contributions are found to be important for penguin-dominated B{yields}PV decays.
Bedload transport in alluvial channels
Bravo-Espinosa, M.; Osterkamp, W.R.; Lopes, V.L.
2003-01-01
Hydraulic, sediment, land-use, and rock-erosivity data of 22 alluvial streams were used to evaluate conditions of bedload transport and the performance of selected bedload-transport equations. Transport categories of transport-limited (TL), partially transport-limited (PTL), and supply-limited (SL) were identified by a semiquantitative approach that considers hydraulic constraints on sediment movement and the processes that control sediment availability at the basin scale. Equations by Parker et al. in 1982, Schoklitsch in 1962, and Meyer-Peter and Muller in 1948 adequately predicted sediment transport in channels with TL condition, whereas the equations of Bagnold in 1980, and Schoklitsch, in 1962, performed well for PTL and SL conditions. Overall, the equation of Schoklitsch predicted well the measured bedload data for eight of 22 streams, and the Bagnold equation predicted the measured data in seven streams.
Ambipolar acoustic transport in silicon
NASA Astrophysics Data System (ADS)
Barros, A. D.; Batista, P. D.; Tahraoui, A.; Diniz, J. A.; Santos, P. V.
2012-07-01
We have investigated the ambipolar transport of electrons and holes by electrically generated surface acoustic waves (SAWs) on silicon wafers coated with a piezoelectric ZnO film. The transport experiments were carried out by using a focused laser beam to optically excite carriers. The carriers are then captured by the moving SAW piezoelectric field and then transported towards a lateral p-i-n junction, where they are electrically detected. The piezoelectric modulation modifies the current vs. voltage characteristics of the lateral p-i-n junction. This behavior is accounted for by a simple model for the change of the junction potential by the SAW fields. We demonstrate that electrons and holes can be acoustically transported over distances approaching 100 μm, the transport efficiency being limited by the low mobility of holes in the material. These results open the way for silicon-based acousto-electric devices using ambipolar transport such as photo-detectors and solar cells.
Heat transport in nonuniform superconductors
NASA Astrophysics Data System (ADS)
Richard, Caroline; Vorontsov, Anton B.
2016-08-01
We calculate electronic energy transport in inhomogeneous superconductors using a fully self-consistent nonequilibrium quasiclassical Keldysh approach. We develop a general theory and apply it to a superconductor with an order parameter that forms domain walls of the type encountered in the Fulde-Ferrell-Larkin-Ovchinnikov state. The heat transport in the presence of a domain wall is inherently anisotropic and nonlocal. The bound states in the nonuniform region play a crucial role and control heat transport in several ways: (i) they modify the spectrum of quasiparticle states and result in Andreev reflection processes and (ii) they hybridize with the impurity band and produce a local transport environment with properties very different from those in a uniform superconductor. As a result of this interplay, heat transport becomes highly sensitive to temperature, magnetic field, and disorder. For strongly scattering impurities, we find that the transport across domain walls at low temperatures is considerably more efficient than in the uniform superconducting state.
ERIC Educational Resources Information Center
Bete, Tim, Ed.
1998-01-01
Presents the opinions of four transportation experts on issues related to school buses. The experts respond to the following questions: will advertisements placed on buses be used to generate district revenue; will compressed natural gas or liquefied natural gas become standard fuel for school buses; and will school bus seat belts be mandatory and…
Technology Transfer Automated Retrieval System (TEKTRAN)
The selective movement and redistribution of ions and small organic molecules is essential for plant growth and cellular homeostasis. Because of this, plants have evolved numerous proteins that facilitate the transport of minerals, sugars, metabolites, and other compounds through the limiting membra...
Manned transportation system study - Evaluation of candidate transportation architectures
NASA Technical Reports Server (NTRS)
Lance, Nicholas; Klemer, R.; Sooter, C.
1992-01-01
The overall evaluation process, the tool developed to perform the evaluation, and the evaluation results in determining the right approach to meet the nation's mannned transportation needs are presented. To address the various considerations, architecture sets consisting of the candidate transportation systems are constructed. As this methodology results in multiple architectures to examine, an architecture evaluation tool was developed to facilitate the evaluation of the architecture attribute values from the system values of the attributes.
Antistrange meson-baryon interaction in hot and dense nuclear matter
NASA Astrophysics Data System (ADS)
Cabrera, D.; Tolós, L.; Aichelin, J.; Bratkovskaya, E.
2014-11-01
We present a study of in-medium cross sections and (off-shell) transition rates for the most relevant binary reactions for strange pseudoscalar meson production close to threshold in heavy-ion collisions at energies available at the Facility for Antiproton and Ion Research. Our results rely on a chiral unitary approach in coupled channels which incorporates the s and p waves of the kaon-nucleon interaction. The formalism, which is modified in the hot and dense medium to account for Pauli blocking effects, mean-field binding on baryons, and pion and kaon self-energies, has been improved to implement unitarization and self-consistency for both the s - and the p -wave interactions at finite temperature and density. This gives access to in-medium amplitudes in several elastic and inelastic coupled channels with strangeness content S =-1 . The obtained total cross sections mostly reflect the fate of the Λ (1405 ) resonance, which melts in the nuclear environment, whereas the off-shell transition probabilities are also sensitive to the in-medium properties of the hyperons excited in the p -wave amplitudes [Λ ,Σ , and Σ*(1385 ) ]. The single-particle potentials of these hyperons at finite momentum, density, and temperature are also discussed in connection with the pertinent scattering amplitudes. Our results are the basis for future implementations in microscopic transport approaches accounting for off-shell dynamics of strangeness production in nucleus-nucleus collisions.
Gasificaton Transport: A Multiphase CFD Approach & Measurements
Dimitri Gidaspow; Veeraya Jiradilok; Mayank Kashyap; Benjapon Chalermsinsuwan
2009-02-14
The objective of this project was to develop predictive theories for the dispersion and mass transfer coefficients and to measure them in the turbulent fluidization regime, using existing facilities. A second objective was to use our multiphase CFD tools to suggest optimized gasifier designs consistent with aims of Future Gen. We have shown that the kinetic theory based CFD codes correctly compute: (1) Dispersion coefficients; and (2) Mass transfer coefficients. Hence, the kinetic theory based CFD codes can be used for fluidized bed reactor design without any such inputs. We have also suggested a new energy efficient method of gasifying coal and producing electricity using a molten carbonate fuel cell. The principal product of this new scheme is carbon dioxide which can be converted into useful products such as marble, as is done very slowly in nature. We believe this scheme is a lot better than the canceled FutureGen, since the carbon dioxide is safely sequestered.
Transportation Anslysis Simulation System
2004-08-23
TRANSIMS version 3.1 is an integrated set of analytical and simulation models and supporting databases. The system is designed to create a virtual metropolitan region with representation of each of the regions individuals, their activities and the transportation infrastructure they use. TRANSIMS puts into practice a new, disaggregate approach to travel demand modeling using agent-based micro-simulation technology. TRANSIMS methodology creates a virtual metropolitan region with representation of the transportation infrastructure and the population, at the level of households and individual travelers. Trips a planned to satisfy the populations activity pattems at the individual traveler level. TRANSIMS then simulates the movement of travelers and vehicles across the transportation network using multiple modes, including car, transit, bike and walk, on a second-by-second basis. Metropolitan planners must plan growth of their cities according to the stringent transportation system planning requirements of the Interniodal Surface Transportation Efficiency Act of 1991, the Clean Air Act Amendments of 1990 and other similar laws and regulations. These require each state and its metropotitan regions to work together to develop short and long term transportation improvement plans. The plans must (1) estimate the future transportation needs for travelers and goods movements, (2) evaluate ways to manage and reduce congestion, (3) examine the effectiveness of building new roads and transit systems, and (4) limit the environmental impact of the various strategies. The needed consistent and accurate transportation improvement plans require an analytical capability that properly accounts for travel demand, human behavior, traffic and transit operations, major investments, and environmental effects. Other existing planning tools use aggregated information and representative behavior to predict average response and average use of transportation facilities. They do not account
Transportation Anslysis Simulation System
2004-08-23
TRANSIMS version 3.1 is an integrated set of analytical and simulation models and supporting databases. The system is designed to create a virtual metropolitan region with representation of each of the regions individuals, their activities and the transportation infrastructure they use. TRANSIMS puts into practice a new, disaggregate approach to travel demand modeling using agent-based micro-simulation technology. TRANSIMS methodology creates a virtual metropolitan region with representation of the transportation infrastructure and the population, at themore » level of households and individual travelers. Trips a planned to satisfy the populations activity pattems at the individual traveler level. TRANSIMS then simulates the movement of travelers and vehicles across the transportation network using multiple modes, including car, transit, bike and walk, on a second-by-second basis. Metropolitan planners must plan growth of their cities according to the stringent transportation system planning requirements of the Interniodal Surface Transportation Efficiency Act of 1991, the Clean Air Act Amendments of 1990 and other similar laws and regulations. These require each state and its metropotitan regions to work together to develop short and long term transportation improvement plans. The plans must (1) estimate the future transportation needs for travelers and goods movements, (2) evaluate ways to manage and reduce congestion, (3) examine the effectiveness of building new roads and transit systems, and (4) limit the environmental impact of the various strategies. The needed consistent and accurate transportation improvement plans require an analytical capability that properly accounts for travel demand, human behavior, traffic and transit operations, major investments, and environmental effects. Other existing planning tools use aggregated information and representative behavior to predict average response and average use of transportation facilities. They do not
Panel 4 - applications to transportation
Nichols, F.; Au, J.; Bhattacharya, R.; Bhushan, B.; Blunier, D.; Boardman, B.; Brombolich, L.; Davidson, J.; Graham, M.; Hakim, N.; Harris, K.; Hay, R.; Herk, L.; Hojnacki, H.; Rourk, D.; Kamo, R.; Nieman, B.; O`Neill, D.; Peterson, M.B.; Pfaffenberger, G.; Pryor, R.W.; Russell, J.; Syniuta, W.; Tamor, M.; Vojnovich, T.; Yarbrough, W.; Yust, C.S.
1993-01-01
The aim of this group was to compile a listing of current and anticipated future problem areas in the transportation industry where the properties of diamond and DLC films make them especially attractive and where the panel could strongly endorse the establishment of DOE/Transportation Industry cooperative research efforts. This section identifies the problem areas for possible applications of diamond/DLC technology and presents indications of current approaches to these problems.
Forage Harvest and Transport Costs
Butler, J.; Downing, M.; Turhollow, A.
1998-12-01
An engineering-economic approach is used to calculate harvest, in-field transport, and over-the-road transport costs for hay as bales and modules, silage, and crop residues as bales and modules. Costs included are equipment depreciation interest; fuel, lube, and oil; repairs; insurance, housing, and taxes; and labor. Field preparation, pest control, fertilizer, land, and overhead are excluded from the costs calculated Equipment is constrained by power available, throughput or carrying capacity, and field speed.
Picard, J.
1988-01-01
In the beginning of 1965, the participants to the starting up of first French LNG transportation system between ARZEW and LE HAVRE were indeed pioneers when they started the cool-down of the three tanks of LE HAVRE, with a LNG freight delivered by old liberty-ship ''BEAUVAIS''. Could they forecast the development of LNG industry in FRANCE and in the world and imagine that modest 'JULES VERNE' and his two english brothers would have, 25 years later, 80 successors - more than five times as big, for the main part of them, that 12 liquefaction plants would be running in the world, supplying about twenty LNG terminals. For the first time, a country - FRANCE - can draw the lessons from the exploitation of the 3 LNG transportation systems during a long period. That is the subject of the present paper.
Linder, M C; Wooten, L; Cerveza, P; Cotton, S; Shulze, R; Lomeli, N
1998-05-01
In adult humans, the net absorption of dietary copper is approximately 1 mg/d. Dietary copper joins some 4-5 mg of endogenous copper flowing into the gastrointestinal tract through various digestive juices. Most of this copper returns to the circulation and to the tissues (including liver) that formed them. Much lower amounts of copper flow into and out of other major parts of the body (including heart, skeletal muscle, and brain). Newly absorbed copper is transported to body tissues in two phases, borne primarily by plasma protein carriers (albumin, transcuprein, and ceruloplasmin). In the first phase, copper goes from the intestine to the liver and kidney; in the second phase, copper usually goes from the liver (and perhaps also the kidney) to other organs. Ceruloplasmin plays a role in this second phase. Alternatively, liver copper can also exit via the bile, and in a form that is less easily reabsorbed. Copper is also present in and transported by other body fluids, including those bathing the brain and central nervous system and surrounding the fetus in the amniotic sac. Ceruloplasmin is present in these fluids and may also be involved in copper transport there. The concentrations of copper and ceruloplasmin in milk vary with lactational stage. Parallel changes occur in ceruloplasmin messenger RNA expression in the mammary gland (as determined in pigs). Copper in milk ceruloplasmin appears to be particularly available for absorption, at least in rats. PMID:9587137
Linder, M C; Wooten, L; Cerveza, P; Cotton, S; Shulze, R; Lomeli, N
1998-05-01
In adult humans, the net absorption of dietary copper is approximately 1 mg/d. Dietary copper joins some 4-5 mg of endogenous copper flowing into the gastrointestinal tract through various digestive juices. Most of this copper returns to the circulation and to the tissues (including liver) that formed them. Much lower amounts of copper flow into and out of other major parts of the body (including heart, skeletal muscle, and brain). Newly absorbed copper is transported to body tissues in two phases, borne primarily by plasma protein carriers (albumin, transcuprein, and ceruloplasmin). In the first phase, copper goes from the intestine to the liver and kidney; in the second phase, copper usually goes from the liver (and perhaps also the kidney) to other organs. Ceruloplasmin plays a role in this second phase. Alternatively, liver copper can also exit via the bile, and in a form that is less easily reabsorbed. Copper is also present in and transported by other body fluids, including those bathing the brain and central nervous system and surrounding the fetus in the amniotic sac. Ceruloplasmin is present in these fluids and may also be involved in copper transport there. The concentrations of copper and ceruloplasmin in milk vary with lactational stage. Parallel changes occur in ceruloplasmin messenger RNA expression in the mammary gland (as determined in pigs). Copper in milk ceruloplasmin appears to be particularly available for absorption, at least in rats.
Quantum transport through aromatic molecules
Ojeda, J. H.; Rey-González, R. R.; Laroze, D.
2013-12-07
In this paper, we study the electronic transport properties through aromatic molecules connected to two semi-infinite leads. The molecules are in different geometrical configurations including arrays. Using a nearest neighbor tight-binding approach, the transport properties are analyzed into a Green's function technique within a real-space renormalization scheme. We calculate the transmission probability and the Current-Voltage characteristics as a function of a molecule-leads coupling parameter. Our results show different transport regimes for these systems, exhibiting metal-semiconductor-insulator transitions and the possibility to employ them in molecular devices.
Charm production in Pb + Pb collisions at energies available at the CERN Large Hadron Collider
NASA Astrophysics Data System (ADS)
Song, Taesoo; Berrehrah, Hamza; Cabrera, Daniel; Cassing, Wolfgang; Bratkovskaya, Elena
2016-03-01
We study charm production in Pb +Pb collisions at √{sN N}=2.76 TeV in the parton-hadron-string-dynamics (PHSD) transport approach and the charm dynamics in the partonic and hadronic medium. The charm quarks are produced through initial binary nucleon-nucleon collisions by using the pythia event generator, taking into account the (anti-)shadowing incorporated in the eps09 package. The produced charm quarks interact with off-shell massive partons in the quark-gluon plasma and are hadronized into D mesons through coalescence or fragmentation close to the critical energy density, and then interact with hadrons in the final hadronic stage with scattering cross sections calculated in an effective Lagrangian approach with heavy-quark spin symmetry. The PHSD results show a reasonable RAA and elliptic flow of D mesons in comparison to the experimental data for Pb +Pb collisions at √{sN N}=2.76 TeV from the ALICE Collaboration. We also study the effect of temperature-dependent off-shell charm quarks in relativistic heavy-ion collisions. We find that the scattering cross sections are only moderately affected by off-shell charm degrees of freedom. However, the position of the peak of RAA for D mesons depends on the strength of the scalar partonic forces which also have an impact on the D meson elliptic flow. The comparison with experimental data on the RAA suggests that the repulsive force is weaker for off-shell charm quarks as compared to that for light quarks. Furthermore, the effects from radiative charm energy loss appear to be low compared to the collisional energy loss up to transverse momenta of ˜15 GeV/c .
Saturated Zone Colloid Transport
H. Viswanathan; P. Reimus
2003-09-05
Colloid retardation is influenced by the attachment and detachment of colloids from immobile surfaces. This analysis demonstrates the development of parameters necessary to estimate attachment and detachment of colloids and, hence, retardation in both fractured tuff and porous alluvium. Field and experimental data specific to fractured tuff are used for the analysis of colloid retardation in fractured tuff. Experimental data specific to colloid transport in alluvial material from Yucca Mountain as well as bacteriophage field studies in alluvial material, which are thought to be good analogs for colloid transport, are used to estimate attachment and detachment of colloids in the alluvial material. There are no alternative scientific approaches or technical methods for calculating these retardation factors.
Preface: Nonclassical Transport
Bolshov, L.; Kondratenko, P.; Pruess, K.
2008-09-01
Transport phenomena in highly heterogeneous media can be dramatically different from those in homogeneous media and therefore are of great fundamental and practical interest. Anomalous transport occurs in semiconductor physics, plasma physics, astrophysics, biology, and other areas. It plays an especially important role in hydrogeology because it may govern the rate of migration and degree of dispersion of groundwater contaminants from hazardous waste sites. The series of four articles in this special section of Vadose Zone Journal is devoted to transport phenomena in heterogeneous media in the context of geologic disposal of radioactive waste. It contains the results of joint investigations performed at the Nuclear Safety Institute of the Russian Academy of Sciences and Lawrence Berkeley National Laboratory in California. The work was supported by the U.S. DOE (under Contract No. DEAC02-05CH11231). The problems addressed in this research involve a broad range of space and time scales and were approached using modern methods of theoretical and computational physics, such as scaling analysis and diagrammatic techniques used before in critical phenomena theory. Special attention is paid to the asymptotics of concentration behavior (concentration tails). This issue is exceptionally important for the reliability assessments of radioactive waste disposal because, depending on the structure of the tails, concentrations at large distances from the source can differ by many orders of magnitude. In the first paper of this special section, Bolshov et al. (2008b) present an overview of field and laboratory observations that demonstrate nonclassical flow and transport behavior in geologic media. It is recognized that natural fracture networks as a rule have fractal geometry and can be classified as percolation systems. This is one of the main factors giving rise to anomalous transport in geologic media. Another important factor is the presence of contaminant traps provided by
NASA Technical Reports Server (NTRS)
2001-01-01
The Space Shuttle Atlantis, STS-110 mission, deployed this railcar, called the Mobile Transporter, and an initial 43-foot section of track, the S0 (S-zero) truss, preparing the International Space Station (ISS) for future spacewalks. The first railroad in space, the Mobile Transporter will allow the Station's robotic arm to travel up and down the finished truss for future assembly and maintenance. The 27,000-pound S0 truss is the first of 9 segments that will make up the Station's external framework that will eventually stretch 356 feet (109 meters), or approximately the length of a football field. The completed truss structure will hold solar arrays and radiators to provide power and cooling for additional international research laboratories from Japan and Europe that will be attached to the Station. The Space Shuttle Orbiter Atlantis, STS-110 mission, was launched April 8, 2002 and returned to Earth April 19, 2002. STS-110's Extravehicular Activity (EVA) marked the first use of the Station's robotic arm to maneuver spacewalkers around the Station.
NASA Technical Reports Server (NTRS)
Pohorille, Andrew; DeVincenzi, Donald L. (Technical Monitor)
2001-01-01
The transport of protons across membranes is an essential process for both bioenergetics of modern cells and the origins of cellular life. All living systems make use of proton gradients across cell walls to convert environmental energy into a high-energy chemical compound, adenosine triphosphate (ATP), synthesized from adenosine diphosphate. ATP, in turn, is used as a source of energy to drive many cellular reactions. The ubiquity of this process in biology suggests that even the earliest cellular systems were relying on proton gradient for harvesting environmental energy needed to support their survival and growth. In contemporary cells, proton transfer is assisted by large, complex proteins embedded in membranes. The issue addressed in this Study was: how the same process can be accomplished with the aid of similar but much simpler molecules that could have existed in the protobiological milieu? The model system used in the study contained a bilayer membrane made of phospholipid, dimyristoylphosphatidylcholine (DMPC) which is a good model of the biological membranes forming cellular boundaries. Both sides of the bilayer were surrounded by water which simulated the environment inside and outside the cell. Embedded in the membrane was a fragment of the Influenza-A M$_2$ protein and enough sodium counterions to maintain system neutrality. This protein has been shown to exhibit remarkably high rates of proton transport and, therefore, is an excellent model to study the formation of proton gradients across membranes. The Influenza M$_2$ protein is 97 amino acids in length, but a fragment 25 amino acids long. which contains a transmembrane domain of 19 amino acids flanked by three amino acids on each side. is sufficient to transport protons. Four identical protein fragments, each folded into a helix, aggregate to form small channels spanning the membrane. Protons are conducted through a narrow pore in the middle of the channel in response to applied voltage. This
RAETRAD MODEL OF RADON GAS GENERATION, TRANSPORT, AND INDOOR ENTRY
The report describes the theoretical basis, implementation, and validation of the Radon Emanation and Transport into Dwellings (RAETRAD) model, a conceptual and mathematical approach for simulating radon (222Rn) gas generation and transport from soils and building foundations to ...
Redirecting treatment during neonatal transport.
Dulkerian, Susan J; Douglas, Webra Price; Taylor, Renee McCraine
2011-01-01
Neonatal transport teams comprise multidisciplinary health care providers who are skilled in patient care, communication and customer service, and equipment mechanics. They are extensively trained in resuscitation and stabilization, preparing for accelerating care, and their focus is preservation of life. In any situation focused on caring for critically ill patients, ethical issues and questions may arise. For instance, is it compassionate and/or cost-effective to separate mothers and infants when continuing/accelerating care is futile, and when and how should care be redirected from acute and lifesaving care to comfort care and bereavement support for the family? The knowledge and skills required to address such situations and communicate and participate in a redirection of care may not be adequately emphasized in the preparation of the professionals responsible for stabilizing and transporting critically ill newborns. This article raises issues relating to transport and redirecting care such as eligibility for transport, parental request and consent, separation of mothers and infants, palliative and bereavement care, ethical considerations, competitive transport environment, and customer service. A shared mental model is essential. The focus of this article is not to provide answers to all of these issues, but to highlight the complexity of the topic of redirecting treatment during neonatal transport. Redirecting treatment needs to be discussed, and health care professionals should be prepared during their transport team training. Each family and situation must be approached individually, with the acceptance that there will always be more questions than answers. PMID:21540683
Stereoselectivity of chiral drug transport: a focus on enantiomer-transporter interaction.
Zhou, Quan; Yu, Lu-Shan; Zeng, Su
2014-08-01
Drug transporters and drug metabolism enzymes govern drug absorption, distribution, metabolism and elimination. Many literature works presenting important aspects related to stereochemistry of drug metabolism are available. However, there is very little literature on stereoselectivity of chiral drug transport and enantiomer-transporter interaction. In recent years, the experimental research within this field showed good momentum. Herein, an up-to-date review on this topic was presented. Breast Cancer Resistance Protein (BCRP), Multidrug Resistance Proteins (MRP), P-glycoprotein (P-gp), Organic Anion Transporters (OATs), Organic Anion Transporting Polypeptides (OATPs), Organic Cation Transporters (OCTs), Peptide Transport Proteins (PepTs), Human Proton-Coupled Folate Transporter (PCFT) and Multidrug and Toxic Extrusion Proteins (MATEs), have been reported to exhibit either positive or negative enantio-selective substrate recognition. The approaches utilized to study chirality in enantiomer-transporter interaction include inhibition experiments of specific transporters in cell models (e.g. Caco-2 cells), transport study using drug resistance cell lines or transgenic cell lines expressing transporters in wild type or variant, the use of transporter knockout mice, pharmacokinetics association of single nucleotide polymorphism in transporters, pharmacokinetic interaction study of racemate in the presence of specific transporter inhibitor or inducer, molecule cellular membrane affinity chromatography and pharmacophore modeling. Enantiomer-enantiomer interactions exist in chiral transport. The strength and/or enantiomeric preference of stereoselectivity may be species or tissue-specific, concentration-dependent and transporter family member-dependent. Modulation of specific drug transporter by pure enantiomers might exhibit opposite stereoselectivity. Further studies with integrated approaches will open up new horizons in stereochemistry of pharmacokinetics. PMID:24796860
Toward Optimal Transport Networks
NASA Technical Reports Server (NTRS)
Alexandrov, Natalia; Kincaid, Rex K.; Vargo, Erik P.
2008-01-01
Strictly evolutionary approaches to improving the air transport system a highly complex network of interacting systems no longer suffice in the face of demand that is projected to double or triple in the near future. Thus evolutionary approaches should be augmented with active design methods. The ability to actively design, optimize and control a system presupposes the existence of predictive modeling and reasonably well-defined functional dependences between the controllable variables of the system and objective and constraint functions for optimization. Following recent advances in the studies of the effects of network topology structure on dynamics, we investigate the performance of dynamic processes on transport networks as a function of the first nontrivial eigenvalue of the network's Laplacian, which, in turn, is a function of the network s connectivity and modularity. The last two characteristics can be controlled and tuned via optimization. We consider design optimization problem formulations. We have developed a flexible simulation of network topology coupled with flows on the network for use as a platform for computational experiments.
Lob, W S
1990-09-01
Mobile robots perform fetch-and-carry tasks autonomously. An intelligent, sensor-equipped mobile robot does not require dedicated pathways or extensive facility modification. In the hospital, mobile robots can be used to carry specimens, pharmaceuticals, meals, etc. between supply centers, patient areas, and laboratories. The HelpMate (Transitions Research Corp.) mobile robot was developed specifically for hospital environments. To reach a desired destination, Help-Mate navigates with an on-board computer that continuously polls a suite of sensors, matches the sensor data against a pre-programmed map of the environment, and issues drive commands and path corrections. A sender operates the robot with a user-friendly menu that prompts for payload insertion and desired destination(s). Upon arrival at its selected destination, the robot prompts the recipient for a security code or physical key and awaits acknowledgement of payload removal. In the future, the integration of HelpMate with robot manipulators, test equipment, and central institutional information systems will open new applications in more localized areas and should help overcome difficulties in filling transport staff positions.
Lob, W S
1990-09-01
Mobile robots perform fetch-and-carry tasks autonomously. An intelligent, sensor-equipped mobile robot does not require dedicated pathways or extensive facility modification. In the hospital, mobile robots can be used to carry specimens, pharmaceuticals, meals, etc. between supply centers, patient areas, and laboratories. The HelpMate (Transitions Research Corp.) mobile robot was developed specifically for hospital environments. To reach a desired destination, Help-Mate navigates with an on-board computer that continuously polls a suite of sensors, matches the sensor data against a pre-programmed map of the environment, and issues drive commands and path corrections. A sender operates the robot with a user-friendly menu that prompts for payload insertion and desired destination(s). Upon arrival at its selected destination, the robot prompts the recipient for a security code or physical key and awaits acknowledgement of payload removal. In the future, the integration of HelpMate with robot manipulators, test equipment, and central institutional information systems will open new applications in more localized areas and should help overcome difficulties in filling transport staff positions. PMID:2208684
Russian federal program on transportation development
NASA Astrophysics Data System (ADS)
Inozemtsev, Vladimir G.
2002-04-01
The transportation infrastructure of the Russia is a vast network of automotive ways, railroads, waterways, pipelines and supporting transportation infrastructures. All kinds of modern transportation use high-level technology. It is necessary to apply last scientific achievements for transportation safety and service feature improvements. Scientific and engineering developments of the Russian transportation have been decreased during the last ten years due to economical problems in our country. Russian government, Federal Ministries, and scientific organizations understand inadmissibility of the transportation lag. Therefore, the Federal Program named 'Updating of the Russian transportation system' has been accepted. To provide a modern stage of the transportation system development based on last science achievement it will spend many scientific and industrial resources. Therefore, it is difficult to overestimate development and using of photonic systems for all kinds of the transportation. The First Conference on Photonics for Transportation (1999) was devoted to the state of the art of photonic system application for on ground and aerospace vehicles, navigation, inspection, observation and monitoring equipments for transportation, and novel photonic elements. After that novel approaches on photonics and its applications for transportation have been in Russia.
McKone, Thomas E.
2009-03-01
on (1) the composition of the soil and physical state of the soil, (2) the chemical and physical properties of the substance of interest, and (3) transformation rates in soil. Our particular focus is on approaches for constructing soil-transport algorithms and soil-transport parameters for incorporation within multimedia fate models. We show how MTC's can be developed to construct a simple two-compartment air-soil system. We then demonstrate how a multi-layer-box-model approach for soil-mass balance converges to the exact analytical solution for concentration and mass balance. Finally, we demonstrate and evaluate the performance of the algorithms in a model with applications to the specimen chemicals benzene, hexachlorobenzene, lindane gammahexachlorocyclohexane, benzo(a)pyrene, nickel, and copper.
Auxin transport during root gravitropism: transporters and techniq