The Dynamical Sine-Gordon Model
NASA Astrophysics Data System (ADS)
Hairer, Martin; Shen, Hao
2016-02-01
We introduce the dynamical sine-Gordon equation in two space dimensions with parameter {β}, which is the natural dynamic associated to the usual quantum sine-Gordon model. It is shown that when {β2 in (0, 16π/3)} the Wick renormalised equation is well-posed. In the regime {β2 in (0, 4π)}, the Da Prato-Debussche method [J Funct Anal 196(1):180-210, 2002; Ann Probab 31(4):1900-1916, 2003] applies, while for {β2 in [4π, 16π/3)}, the solution theory is provided via the theory of regularity structures [Hairer, Invent Math 198(2):269-504, 2014]. We also show that this model arises naturally from a class of {2 + 1} -dimensional equilibrium interface fluctuation models with periodic nonlinearities. The main mathematical difficulty arises in the construction of the model for the associated regularity structure where the role of the noise is played by a non-Gaussian random distribution similar to the complex multiplicative Gaussian chaos recently analysed in Lacoin et al. [Commun Math Phys 337(2):569-632, 2015].
Generalized universality in the massive sine-Gordon model
Nagy, S.; Sailer, K.; Nandori, I.; Polonyi, J.
2008-01-15
A nontrivial interplay of the UV and IR scaling laws, a generalization of the universality is demonstrated in the framework of the massive sine-Gordon model, as a result of a detailed study of the global behavior of the renormalization group flow and the phase structure.
The sine-Gordon model in the presence of defects
NASA Astrophysics Data System (ADS)
Avan, Jean; Doikou, Anastasia
2013-01-01
The sine-Gordon model in the presence of dynamical integrable defects is investigated. This is an application of the algebraic formulation introduced for integrable defects in earlier works. The quantities in involution as well as the associated Lax pairs are explicitly extracted. Integrability i also shown using certain sewing constraints, which emerge as suitable continuity conditions.
Breather-like structures in modified sine-Gordon models
NASA Astrophysics Data System (ADS)
Ferreira, L. A.; Zakrzewski, Wojtek J.
2016-05-01
We report analytical and numerical results on breather-like field configurations in a theory which is a deformation of the integrable sine-Gordon model in (1 + 1) dimensions. The main motivation of our study is to test the ideas behind the recently proposed concept of quasi-integrability, which emerged from the observation that some field theories possess an infinite number of quantities which are asymptotically conserved in the scattering of solitons, and periodic in time in the case of breather-like configurations. Even though the mechanism responsible for such phenomena is not well understood yet, it is clear that special properties of the solutions under a space-time parity transformation play a crucial role. The numerical results of the present paper give support for the ideas on quasi-integrability, as it is found that extremely long-lived breather configurations satisfy these parity properties. We also report on a mechanism, particular to the theory studied here, that favours the existence of long lived breathers even in cases of significant deformations of the sine-Gordon potential. We also find numerically that our breather-like configurations decay through the gradual increase of their frequency of oscillations.
Two-loop beta-functions of the sine-Gordon model
NASA Astrophysics Data System (ADS)
Balog, János; Hegedus, Árpád
2000-09-01
We recalculate the two-loop beta-functions in the two-dimensional sine-Gordon model in a two-parameter expansion around the asymptotically free point. Our results agree with those of Amit et al (Amit D J, Goldschmidt Y Y and Grinstein G 1980 J. Phys. A: Math. Gen. 13 585).
NASA Astrophysics Data System (ADS)
Baron, H. E.; Zakrzewski, W. J.
2016-06-01
We investigate the validity of collective coordinate approximations to the scattering of two solitons in several classes of (1+1) dimensional field theory models. We consider models which are deformations of the sine-Gordon (SG) or the nonlinear Schrödinger (NLS) model which posses soliton solutions (which are topological (SG) or non-topological (NLS)). Our deformations preserve their topology (SG), but change their integrability properties, either completely or partially (models become `quasi-integrable').
Critical dynamics of the sine-Gordon model in d=2-ɛ dimensions
NASA Astrophysics Data System (ADS)
Neudecker, Bernhard
1983-06-01
The renormalization scheme of Amit, Goldschmidt and Grinstein is extended to d=2-ɛ dimensions. The exponent ν of the correlation length v -1=2ɛ+ O(ɛ2) is in agreement with the result of Kosterlitz for the Coulomb gas. The exponent η of the correlation function of the sine-Gordon field is η=ɛ+ O(ɛ2). The scaling form of the dynamical structure factor S(q,ω) of the dynamic sine-Gordon Model A is studied in d=2-ɛ dimensions. The dynamic exponent z is found to be z=2+( b-1)ɛ+ O(ɛ2) for ɛ≧0. The constant b is given by the integral b = intlimits_0^infty {dss^{ - 2} exp } left( { - 2intlimits_s^infty {dxx^{ - 1} e^{ - x} } } right) = 2,371544...
Discrete translational invariance and mass-renormalization in the two-dimensional sine-Gordon model
NASA Astrophysics Data System (ADS)
Neudecker, Bernhard
1982-06-01
We consider the sine-Gordon model as a field-theory in which the interaction has a discrete translational invariance. It is shown that apart from a Gaussian contribution the Helmholtz free-energy exhibits this symmetry as well. Thus in an originally massless theory, the insertion of a mass term can be considered as a rather “weak” symmetry-breaking. Within the Amit-Goldschmidt-Grinstein renormalization-scheme we show that mass-renormalization is trivial.
Exact Mass-Coupling Relation for the Homogeneous Sine-Gordon Model
NASA Astrophysics Data System (ADS)
Bajnok, Zoltán; Balog, János; Ito, Katsushi; Satoh, Yuji; Tóth, Gábor Zsolt
2016-05-01
We derive the exact mass-coupling relation of the simplest multiscale quantum integrable model, i.e., the homogeneous sine-Gordon model with two mass scales. The relation is obtained by comparing the perturbed conformal field theory description of the model valid at short distances to the large distance bootstrap description based on the model's integrability. In particular, we find a differential equation for the relation by constructing conserved tensor currents, which satisfy a generalization of the Θ sum rule Ward identity. The mass-coupling relation is written in terms of hypergeometric functions.
Exact Mass-Coupling Relation for the Homogeneous Sine-Gordon Model.
Bajnok, Zoltán; Balog, János; Ito, Katsushi; Satoh, Yuji; Tóth, Gábor Zsolt
2016-05-01
We derive the exact mass-coupling relation of the simplest multiscale quantum integrable model, i.e., the homogeneous sine-Gordon model with two mass scales. The relation is obtained by comparing the perturbed conformal field theory description of the model valid at short distances to the large distance bootstrap description based on the model's integrability. In particular, we find a differential equation for the relation by constructing conserved tensor currents, which satisfy a generalization of the Θ sum rule Ward identity. The mass-coupling relation is written in terms of hypergeometric functions. PMID:27203313
Regularization of multi-soliton form factors in sine-Gordon model
NASA Astrophysics Data System (ADS)
Pálmai, T.
2012-08-01
A general and systematic regularization is developed for the exact solitonic form factors of exponential operators in the (1+1)-dimensional sine-Gordon model by analytical continuation of their integral representations. The procedure is implemented in Mathematica. Test results are shown for four- and six-soliton form factors. Catalogue identifier: AEMG_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEMG_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 1462 No. of bytes in distributed program, including test data, etc.: 15 488 Distribution format: tar.gz Programming language: Mathematica [1] Computer: PC Operating system: Cross-platform Classification: 7.7, 11.1, 23 Nature of problem: The multi-soliton form factors of the sine-Gordon model (relevant in two-dimensional physics) were given only by highly non-trivial integral representation with a limited domain of convergence. Practical applications of the form factors, e.g. calculation of correlation functions in two-dimensional condensed matter systems, were not possible in general. Solution method: Using analytic continuation techniques an efficient algorithm is found and implemented in Mathematica, which provides a general and systematic way to calculate multi-soliton form factors in the sine-Gordon model. The package contains routines to compute the two-, four- and six-soliton form factors. Running time: Strongly dependent on the desired accuracy and the number of solitons. For physical rapidities after an initialization of about 30 s, the calculation of the two-, four- and six-soliton form factors at a single point takes approximately 0.5 s, 2.5 s and 8 s, respectively. Wolfram Research, Inc., Mathematica Edition: Version 7.0, Wolfram Research, Inc., Champaign, Illinois, 2008.
Numerical and analytical tests of quasi-integrability in modified sine-Gordon models
NASA Astrophysics Data System (ADS)
Ferreira, L. A.; Zakrzewski, Wojtek J.
2014-01-01
Following our attempts to define quasi-integrability in which we related this concept to a particular symmetry of the two-soliton function we check this condition in three classes of modified sine-Gordon models in (1 + 1) dimensions. We find that the numerical results seen in various scatterings of two solitons and in the time evolution of breather-like structures support our ideas about the symmetry of the field configurations and its effects on the anomalies of the conservation laws of the charges.
Breaking integrability at the boundary: the sine-Gordon model with Robin boundary conditions
NASA Astrophysics Data System (ADS)
Arthur, Robert; Dorey, Patrick; Parini, Robert
2016-04-01
We explore boundary scattering in the sine-Gordon model with a non-integrable family of Robin boundary conditions. The soliton content of the field after collision is analysed using a numerical implementation of the direct scattering problem associated with the inverse scattering method. We find that an antikink may be reflected into various combinations of an antikink, a kink, and one or more breathers, depending on the values of the initial antikink velocity and a parameter associated with the boundary condition. In addition we observe regions with an intricate resonance structure arising from the creation of an intermediate breather whose recollision with the boundary is highly dependent on the breather phase.
Quench dynamics near a quantum critical point: Application to the sine-Gordon model
NASA Astrophysics Data System (ADS)
de Grandi, C.; Gritsev, V.; Polkovnikov, A.
2010-06-01
We discuss the quench dynamics near a quantum critical point focusing on the sine-Gordon model as a primary example. We suggest a unified approach to sudden and slow quenches, where the tuning parameter λ(t) changes in time as λ(t)˜υtr , based on the adiabatic expansion of the excitation probability in powers of υ . We show that the universal scaling of the excitation probability can be understood through the singularity of the generalized adiabatic susceptibility χ2r+2(λ) , which for sudden quenches (r=0) reduces to the fidelity susceptibility. In turn this class of susceptibilities is expressed through the moments of the connected correlation function of the quench operator. We analyze the excitations created after a sudden quench of the cosine potential using a combined approach of form-factors expansion and conformal perturbation theory for the low-energy and high-energy sector, respectively. We find the general scaling laws for the probability of exciting the system, the density of excited quasiparticles, the entropy and the heat generated after the quench. In the two limits where the sine-Gordon model maps to hard-core bosons and free massive fermions we provide the exact solutions for the quench dynamics and discuss the finite temperature generalizations.
Nonlinear waves in networks: model reduction for the sine-Gordon equation.
Caputo, Jean-Guy; Dutykh, Denys
2014-08-01
To study how nonlinear waves propagate across Y- and T-type junctions, we consider the two-dimensional (2D) sine-Gordon equation as a model and examine the crossing of kinks and breathers. Comparing energies for different geometries reveals that, for small widths, the angle of the fork plays no role. Motivated by this, we introduce a one-dimensional effective model whose solutions agree well with the 2D simulations for kink and breather solutions. These exhibit two different behaviors: a kink crosses if it has sufficient energy; conversely a breather crosses when v>1-ω, where v and ω are, respectively, its velocity and frequency. This methodology can be generalized to more complex nonlinear wave models. PMID:25215804
Quantum quenches in the sine-Gordon model: A semiclassical approach
NASA Astrophysics Data System (ADS)
Kormos, M.; Zaránd, G.
2016-06-01
We compute the time evolution of correlation functions after quantum quenches in the sine-Gordon model within the semiclassical approximation, which is expected to yield accurate results for small and slow quenches producing slow quasiparticles with low density. We demonstrate this by reproducing results of a recent form-factor calculation of the relaxation of expectation values [B. Bertini, D. Schuricht, and F. H. L. Essler, J. Stat. Mech. (2014) P10035, 10.1088/1742-5468/2014/10/P10035]. Extending these results, we find that—in the universal limit of vanishingly small quasiparticle velocities—the expectation values of most vertex operators do not decay to zero. We give analytic expressions for the relaxation of dynamic correlation functions and show that they have diffusive behavior for large timelike separation.
Quantum quenches in the sine-Gordon model: A semiclassical approach.
Kormos, M; Zaránd, G
2016-06-01
We compute the time evolution of correlation functions after quantum quenches in the sine-Gordon model within the semiclassical approximation, which is expected to yield accurate results for small and slow quenches producing slow quasiparticles with low density. We demonstrate this by reproducing results of a recent form-factor calculation of the relaxation of expectation values [B. Bertini, D. Schuricht, and F. H. L. Essler, J. Stat. Mech. (2014) P100351742-546810.1088/1742-5468/2014/10/P10035]. Extending these results, we find that-in the universal limit of vanishingly small quasiparticle velocities-the expectation values of most vertex operators do not decay to zero. We give analytic expressions for the relaxation of dynamic correlation functions and show that they have diffusive behavior for large timelike separation. PMID:27415202
Charge-varying sine-Gordon deformed defects
NASA Astrophysics Data System (ADS)
Bernardini, A. E.; Chinaglia, M.; da Rocha, Roldão
2015-05-01
Sine-Gordon deformed defects that exhibit unusual phenomenological features on the topological charge are investigated. The possibility of a smooth and continuous transition between topological (non-null charge) and non-topological (null charge) scenarios of deformed defects supported by sine-Gordon structures is evinced by the analytical calculation of topological charges and localized energy distributions. By describing cyclic deformation chains, we show that a triggering sine-Gordon model simultaneously supports kink- and lump-like defects, whose topological mass values are closed by trigonometric or hyperbolic successive deformations. In spite of preserving analytical closure relations constraining the topological masses of 3- and 4-cyclically deformed defects, the deformation chains produce kinks and lumps which exhibit non-monotonic behavior and extra inflection points. The outcome of our analysis suggests that cyclic deformations create novel scenarios of physical and mathematical applicability of defect structures supported by the sine-Gordon theory.
The noncommutative sine-Gordon breather
Fischer, Andre; Lechtenfeld, Olaf
2009-09-15
As shown by Lechtenfeld et al. [Nucl. Phys. B 705, 447 (2005)], there exists a noncommutative deformation of the sine-Gordon model which remains (classically) integrable but features a second scalar field. We employ the dressing method (adapted to the Moyal-deformed situation) for constructing the deformed kink-antikink and breather configurations. Explicit results and plots are presented for the leading noncommutativity correction to the breather. Its temporal periodicity is unchanged.
Breather boundary form factors in sine-Gordon theory
NASA Astrophysics Data System (ADS)
Lencsés, M.; Takács, G.
2011-11-01
A previously conjectured set of exact form factors of boundary exponential operators in the sinh-Gordon model is tested against numerical results from boundary truncated conformal space approach in boundary sine-Gordon theory, related by analytic continuation to sinh-Gordon model. We find that the numerical data strongly support the validity of the form factors themselves; however, we also report a discrepancy in the case of diagonal matrix elements, which remains unresolved for the time being.
Flux-flow mode in the sine-Gordon system
NASA Astrophysics Data System (ADS)
Jaworski, Marek
1998-07-01
An inverse transformation of the theta function is derived, making it possible to investigate a multiperiodic solution of the sine-Gordon equation in the limit of a dense sequence of overlapping solitons. A special case of a unidirectional soliton train interacting with small-amplitude quasi-linear oscillations is discussed as a simple model of the flux-flow state in a long one-dimensional Josephson junction. Approximate analytical solutions for the dispersion parameters are compared with numerical results.
Dynamical properties of the sine-Gordon quantum spin magnet Cu-PM at zero and finite temperature
NASA Astrophysics Data System (ADS)
Tiegel, Alexander C.; Honecker, Andreas; Pruschke, Thomas; Ponomaryov, Alexey; Zvyagin, Sergei A.; Feyerherm, Ralf; Manmana, Salvatore R.
2016-03-01
The material copper pyrimidine dinitrate (Cu-PM) is a quasi-one-dimensional spin system described by the spin-1/2 X X Z Heisenberg antiferromagnet with Dzyaloshinskii-Moriya interactions. Based on numerical results obtained by the density-matrix renormalization group, exact diagonalization, and accompanying electron spin resonance (ESR) experiments we revisit the spin dynamics of this compound in an applied magnetic field. Our calculations for momentum and frequency-resolved dynamical quantities give direct access to the intensity of the elementary excitations at both zero and finite temperature. This allows us to study the system beyond the low-energy description by the quantum sine-Gordon model. We find a deviation from the Lorentz invariant dispersion for the single-soliton resonance. Furthermore, our calculations only confirm the presence of the strongest boundary bound state previously derived from a boundary sine-Gordon field theory, while composite boundary-bulk excitations have too low intensities to be observable. Upon increasing the temperature, we find a temperature-induced crossover of the soliton and the emergence of new features, such as interbreather transitions. The latter observation is confirmed by our ESR experiments on Cu-PM over a wide range of the applied field.
A new explicit solution to the lattice sine-Gordon equation
NASA Astrophysics Data System (ADS)
Xu, Xiaoxue; Cao, Cewen
2016-03-01
Based on a new discrete Lax pair, an elementary explicit solution is found for the lattice sine-Gordon equation through Riemann surface method. It contains only exponential functions, quite different from the usual higher genus solutions, expressed with complicated theta functions. The solutions to the associated models, the lattice potential MKdV equation and a special H3 equation are also discussed.
NASA Astrophysics Data System (ADS)
Ge, Li; Shi, Yu
2012-10-01
Using the approach of low-energy effective field theory, the phase diagram is studied for a mixture of two species of pseudospin-\\frac{1}{2} Bose atoms with interspecies spin exchange. There are four mean-field regimes on the parameter plane of ge and gz, where ge is the interspecies spin-exchange interaction strength, while gz is the difference between the interaction strength of interspecies scattering without spin exchange of equal spins and that of unequal spins. Two regimes, with |gz| > |ge|, correspond to ground states with the total spins of the two species parallel or antiparallel along the z direction, and the low-energy excitations are equivalent to those of two-component spinless bosons. The other two regimes, with |ge| > |gz|, correspond to ground states with the total spins of the two species parallel or antiparallel on the xy plane, and the low-energy excitations are described by a sine-Gordon model coupled with a free scalar field, where the effective fields are combinations of the phases of the original four boson fields. In (1 + 1)-dimension, they are described by Kosterlitz-Thouless renormalization group (RG) equations, and there are three sectors in the phase plane of a scaling dimension and a dimensionless parameter proportional to the strength of the cosine interaction, both depending on the densities. The gaps of these elementary excitations are experimental probes of the underlying many-body ground states.
Control of antikinks of the Sine Gordon equation
NASA Astrophysics Data System (ADS)
Porubov, A. V.; Bondarenkov, R. S.; Fradkov, A. L.; Andrievsky, B. R.
2016-06-01
The control of the smoothness of an antikink profile of the Sine Gordon equation is considered. It is shown that variations in the initial conditions give rise to oscillations on the profile of the antikink. The control algorithm based on variation of one of the coefficient of the equation is developed to recover the smooth wave shape and the phase velocity of the antikink.
Perspective on classical strings from complex sine-Gordon solitons
Okamura, Keisuke; Suzuki, Ryo
2007-02-15
We study a family of classical string solutions with large spins on R{sub t}xS{sup 3} subspace of AdS{sub 5}xS{sup 5} background, which are related to Complex sine-Gordon solitons via Pohlmeyer's reduction. The equations of motion for the classical strings are cast into Lame equations and Complex sine-Gordon equations. We solve them under periodic boundary conditions, and obtain analytic profiles for the closed strings. They interpolate two kinds of known rigid configurations with two spins: on one hand, they reduce to folded or circular spinning/rotating strings in the limit where a soliton velocity goes to zero, while on the other hand, the dyonic giant magnons are reproduced in the limit where the period of a kink-array goes to infinity.
Quantum Creep and Quantum-Creep Transitions in 1D Sine-Gordon Chains.
Krajewski, Florian R; Müser, Martin H
2004-01-23
Discrete sine-Gordon (SG) chains are studied with path-integral molecular dynamics. Chains commensurate with the substrate show the transition from pinning to quantum creep at bead masses slightly larger than in the continuous SG model. Within the creep regime, a field-driven transition from creep to complete depinning is identified. The effects of disorder on the chain's dynamics depend on the potential's roughness exponent H. For example, quantum fluctuations are generally too small to depin the chain if H=1/2, while an H=0 chain can be pinned or unpinned depending on the bead masses. Thermal fluctuations always depin the chain. PMID:14753858
Generalized Sine-Gordon equation and dislocation dynamics of superlattice
NASA Astrophysics Data System (ADS)
Wu, Muying; Chen, Guihua; Luo, Shiyu
2013-07-01
By introducing a damping term, the Seeger equation describing the dislocations motion is reduced to the generalized Sine-Gordon equation, which is further reduced to the pendulum equation for the traveling wave solutions. The characteristics of the phase plane of the unperturbated system is analyzed and the chaotic behavior of the system is discussed with Melnikov method. It is shown that the energy of dislocation wave can efficiently transfer and release to the superlattice for appropriately chosen parameters, such that the stability of the superlattice can be improved.
Quantum sine-Gordon dynamics on analogue curved spacetime in a weakly imperfect scalar Bose gas
NASA Astrophysics Data System (ADS)
Volkoff, T. J.; Fischer, Uwe R.
2016-07-01
Using the coherent state functional integral expression of the partition function, we show that the sine-Gordon model on an analogue curved spacetime arises as the effective quantum field theory for phase fluctuations of a weakly imperfect Bose gas on an incompressible background superfluid flow when these fluctuations are restricted to a subspace of the single-particle Hilbert space. We consider bipartitions of the single-particle Hilbert space relevant to experiments on ultracold bosonic atomic or molecular gases, including, e.g., restriction to high- or low-energy sectors of the dynamics and spatial bipartition corresponding to tunnel-coupled planar Bose gases. By assuming full unitary quantum control in the low-energy subspace of a trapped gas, we show that (1) appropriately tuning the particle number statistics of the lowest-energy mode partially decouples the low- and high-energy sectors, allowing any low-energy single-particle wave function to define a background for sine-Gordon dynamics on curved spacetime and (2) macroscopic occupation of a quantum superposition of two states of the lowest two modes produces an analogue curved spacetime depending on two background flows, with respective weights continuously dependent on the corresponding weights of the superposed quantum states.
Conservation laws, Korteweg--de Vries and sine-Gordon systems, and the role of supersymmetry
Bagchi, B.; Lahiri, A.; Roy, P.K.
1989-02-15
It is shown that the eigenvalue problem of the L operator for the sine-Gordon equation can be put in a supersymmetric form. We comment on the connection between the conserved quantities of the Korteweg--de Vries and sine-Gordon systems.
Conservation laws and Hamiltonian structures of the generalized sine-Gordon hierarchy
NASA Astrophysics Data System (ADS)
Li, Fang; Xue, Bo; Li, Yan
2014-12-01
By introducing a 2 × 2 matrix spectral problem, a new hierarchy of nonlinear evolution equations is proposed. A typical equation in this hierarchy is the generalization of sine-Gordon equation. With the aid of trace identity, the Hamiltonian structures of the hierarchy are constructed. In addition, the infinite sequence of conserved quantities of the generalized sine-Gordon equation are obtained.
NASA Astrophysics Data System (ADS)
Misumi, Tatsuhiro; Nitta, Muneto; Sakai, Norisuke
2015-09-01
We compute multi-instanton amplitudes in the sine-Gordon quantum mechanics (periodic cosine potential) by integrating out quasi-moduli parameters corresponding to separations of instantons and anti-instantons. We propose an extension of Bogomolnyi-Zinn-Justin prescription for multi-instanton configurations and an appropriate subtraction scheme. We obtain the multi-instanton contributions to the energy eigenvalue of the lowest band at the zeroth order of the coupling constant. For the configurations with only instantons (anti-instantons), we obtain unambiguous results. For those with both instantons and anti-instantons, we obtain results with imaginary parts, which depend on the path of analytic continuation. We show that the imaginary parts of the multi-instanton amplitudes precisely cancel the imaginary parts of the Borel resummation of the perturbation series, and verify that our results completely agree with those based on the uniform-WKB calculations, thus confirming the resurgence structure: divergent perturbation series combined with the nonperturbative multi-instanton contributions conspire to give unambiguous results. We also study the neutral bion contributions in the {C}{P}^{N-1} model on {{R}}^1× {S}^1 with a small circumference, taking account of the relative phase moduli between the fractional instanton and anti-instanton. We find that the sign of the interaction potential depends on the relative phase moduli, and that both the real and imaginary parts resulting from quasi-moduli integral of the neutral bion get quantitative corrections compared to the sine-Gordon quantum mechanics.
Kovalyov, Mikhail
2010-06-15
In this article the sets of solutions of the sine-Gordon equation and its linearization the Klein-Gordon equation are discussed and compared. It is shown that the set of solutions of the sine-Gordon equation possesses a richer structure which partly disappears during linearization. Just like the solutions of the Klein-Gordon equation satisfy the linear superposition principle, the solutions of the sine-Gordon equation satisfy a nonlinear superposition principle.
Integrals of motion of the classical lattice sine-Gordon system
Enriquez, B.; Feigin, B.L. |
1995-12-01
We compute the local integrals of motions of the classical limit of the lattice sine-Gordon system, using a geometrical interpretation of the local sine-Gordon variables. Using an analogous description of the screened local variables, we show that these integrals are in involution. We present some remarks on relations with the situation at the roots of 1 and results on another latticization (linked to the principal subalgebra of s{ell}{sub 2} rather than the homogeneous one). Finally, we analyze a module of {open_quotes}screened semilocal variables, {close_quotes} on which the whole s{ell}{sub 2} acts.
Symmetries and soliton solutions of the Galilean complex Sine-Gordon equation
NASA Astrophysics Data System (ADS)
de Melo, G. R.; de Montigny, M.; Pinfold, J.; Tuszynski, J. A.
2016-03-01
We discuss a new equation, the Galilean version of the complex Sine-Gordon equation in 1 + 1 dimensions, Ψxx (1 -Ψ* Ψ) + 2 imΨt +Ψ* Ψx2- Ψ(1 -Ψ* Ψ) 2 = 0, derived from its relativistic counterpart via Galilean covariance. We determine its Lie point symmetries, discuss some group-invariant solutions, and examine some soliton solutions. The reduction under Galilean symmetry leads to an equation similar to the stationary Gross-Pitaevskii equation. This work is motivated in part by recent applications of the relativistic complex Sine-Gordon equation to the dynamics of Q-balls.
{pi} kinks in the parametrically driven sine-Gordon equation and applications
Zharnitsky, V.; Mitkov, I.
1997-07-08
Parametrically driven sine-Gordon equation with a mean-zero forcing is considered. It is shown that the system is well approximated by the double sine-Gordon equation using the normal form technique. The reduced equation possesses {pi}-kink solutions, which are also observed numerically in the original system. This result is applied to domain walls dynamics in one-dimensional easy-plane ferromagnets. For such system the existence of {pi}-kinks implies the true domain structure in the presence of high-frequency magnetic field.
Spectral averaging of small-amplitude sine-Gordon wave trains
NASA Astrophysics Data System (ADS)
Larson, J. W.; Tracy, E. R.
1988-11-01
It is well known that the nonlinear Schrödinger equation is the generic envelope description of nonlinear wave trains in the small-amplitude limit. V. E. Zakharov and E. A. Kuznetsov [Physica 18D, 455 (1986)] have shown that for many systems integrable via inverse-scattering techniques it is possible, through the use of multiscale techniques, to derive the nonlinear Schrödinger Lax pair from the Lax pair of the system that is being modulated. It will be shown that this technique of ``multiscale averaging'' can be applied to the sine-Gordon theory to obtain not only the nonlinear Schrödinger Lax pair from the sine-Gordon Lax pair, but also the nonlinear Schrödinger spectral data, conservation laws, Θ-function solutions, and reality constraint from their sine-Gordon counterparts. This allows a physical interpretation of the mathematical elements of the nonlinear Schrödinger envelope in terms of the physical characteristics of the sine-Gordon system that is being modulated.
NASA Astrophysics Data System (ADS)
Palmero, F.; Han, J.; English, L. Q.; Alexander, T. J.; Kevrekidis, P. G.
2016-01-01
We consider a chain of torsionally-coupled, planar pendula shaken horizontally by an external sinusoidal driver. It has been known that in such a system, theoretically modeled by the discrete sine-Gordon equation, intrinsic localized modes, also known as discrete breathers, can exist. Recently, the existence of multifrequency breathers via subharmonic driving has been theoretically proposed and numerically illustrated by Xu et al. (2014) [21]. In this paper, we verify this prediction experimentally. Comparison of the experimental results to numerical simulations with realistic system parameters (including a Floquet stability analysis), and wherever possible to analytical results (e.g. for the subharmonic response of the single driven-damped pendulum), yields good agreement. Finally, we report the period-1 and multifrequency edge breathers which are localized at the open boundaries of the chain, for which we have again found good agreement between experiments and numerical computations.
Darboux Transformation for the Vector Sine-Gordon Equation and Integrable Equations on a Sphere
NASA Astrophysics Data System (ADS)
Mikhailov, Alexander V.; Papamikos, Georgios; Wang, Jing Ping
2016-07-01
We propose a method for construction of Darboux transformations, which is a new development of the dressing method for Lax operators invariant under a reduction group. We apply the method to the vector sine-Gordon equation and derive its Bäcklund transformations. We show that there is a new Lax operator canonically associated with our Darboux transformation resulting an evolutionary differential-difference system on a sphere. The latter is a generalised symmetry for the chain of Bäcklund transformations. Using the re-factorisation approach and the Bianchi permutability of the Darboux transformations, we derive new vector Yang-Baxter map and integrable discrete vector sine-Gordon equation on a sphere.
Dressing method for the vector sine-Gordon equation and its soliton interactions
NASA Astrophysics Data System (ADS)
Mikhailov, Alexander V.; Papamikos, Georgios; Wang, Jing Ping
2016-06-01
In this paper, we develop the dressing method to study the exact solutions for the vector sine-Gordon equation. The explicit formulas for one kink and one breather are derived. The method can be used to construct multi-soliton solutions. Two soliton interactions are also studied. The formulas for position shift of the kink and position and phase shifts of the breather are given. These quantities only depend on the pole positions of the dressing matrices.
On the solution of the generalized wave and generalized sine-Gordon equations
NASA Technical Reports Server (NTRS)
Ablowitz, M. J.; Beals, R.; Tenenblat, K.
1986-01-01
The generalized wave equation and generalized sine-Gordon equations are known to be natural multidimensional differential geometric generalizations of the classical two-dimensional versions. In this paper, a system of linear differential equations is associated with these equations, and it is shown how the direct and inverse problems can be solved for appropriately decaying data on suitable lines. An initial-boundary value problem is solved for these equations.
Stochastic D-bifurcation for a damped sine-Gordon equation with noise
Huang, Qiongwei; Xue, Changfeng; Tang, Jiashi
2015-04-15
We investigate the stochastic bifurcation of a damped sine-Gordon equation with Dirichlet boundary conditions under the influence of multiplicative Gaussian white noise. Introducing a slow time scale, we derive the amplitude equations near the trivial solution by multiscale analysis. And the stationary probability density functions are formulated analytically using the stochastic averaging of energy envelope. The numerical calculations show that the system undergoes a stochastic D-bifurcation of energy envelope from a delta measure to new stationary measures when the control parameter crosses a critical point.
Nonlinear quantum-mechanical system associated with Sine-Gordon equation in (1 + 2) dimensions
Zarmi, Yair
2014-10-15
Despite the fact that it is not integrable, the (1 + 2)-dimensional Sine-Gordon equation has N-soliton solutions, whose velocities are lower than the speed of light (c = 1), for all N ≥ 1. Based on these solutions, a quantum-mechanical system is constructed over a Fock space of particles. The coordinate of each particle is an angle around the unit circle. U, a nonlinear functional of the particle number-operators, which obeys the Sine-Gordon equation in (1 + 2) dimensions, is constructed. Its eigenvalues on N-particle states in the Fock space are the slower-than-light, N-soliton solutions of the equation. A projection operator (a nonlinear functional of U), which vanishes on the single-particle subspace, is a mass-density generator. Its eigenvalues on multi-particle states play the role of the mass density of structures that emulate free, spatially extended, relativistic particles. The simplicity of the quantum-mechanical system allows for the incorporation of perturbations with particle interactions, which have the capacity to “annihilate” and “create” solitons – an effect that does not have an analog in perturbed classical nonlinear evolution equations.
NASA Astrophysics Data System (ADS)
Gershenzon, Naum; Bambakidis, Gust
2014-05-01
The Frenkel-Kontorova (FK) model and its continuum approximation, the sine-Gordon (SG) equation, are widely used for modeling various phenomena. In many practical applications the wave-train solution, which includes many solitons, is required. In such cases the system of Whitham's modulation equations, superimposed on the SG equation, provides such a solution. Here we consider several applications which use the SG modulation solutions [1-3]. Fault dynamics in the earth's crust, i.e. the nucleation and development of regular and slow earthquakes, is a complicated multidisciplinary problem which has been investigated using diverse approaches. Our approach, inspired by dislocation dynamics in crystals, is based on the FK model introduced to describe plasticity. In the model we propose, sliding occurs due to the movement of defects of a certain type (i.e. areas on the frictional surface with locally stressed material, known as a macroscopic dislocation or slip pulse) nucleated by shear stress in the presence of asperities. The spatial translation of a dislocation requires only a small fraction of the stress necessary for the uniform relative displacement of frictional surfaces. This is a fundamental distinction between our approach to macroscopic dry friction and those of others such as the Burridge-Knopoff and rate-and-state types of models. We show how this model can be applied to the qualitative and quantitative description of fault dynamics in general, and slow and regular earthquakes in particular. The three fundamental speeds of plate movement, earthquake migration, and seismic waves are shown to be connected in the FK model. The velocity of nonelastic stress propagation along faults is a function of accumulated stress. It changes from a few km/s during earthquakes to a few dozen km per day, month, or year during afterslip and inter-earthquake periods. The distribution of aftershocks in this model is consistent with both the Omori law for temporal distribution
Effects of Lévy noise on the dynamics of sine-Gordon solitons in long Josephson junctions
NASA Astrophysics Data System (ADS)
Guarcello, Claudio; Valenti, Davide; Carollo, Angelo; Spagnolo, Bernardo
2016-05-01
We numerically investigate the generation of solitons in current-biased long Josephson junctions in relation to the superconducting lifetime and the voltage drop across the device. The dynamics of the junction is modelled with a sine-Gordon equation driven by an oscillating field and subject to an external non-Gaussian noise. A wide range of $\\alpha$-stable L\\'evy distributions is considered as noise source, with varying stability index $\\alpha$ and asymmetry parameter $\\beta$. In junctions longer than a critical length, the mean switching time (MST) from superconductive to the resistive state assumes a values independent of the device length. Here, we demonstrate that such a value is directly related to the mean density of solitons which move into or from the washboard potential minimum corresponding to the initial superconductive state. Moreover, we observe: (i) a connection between the total mean soliton density and the mean potential difference across the junction; (ii) an inverse behavior of the mean voltage in comparison with the MST, with varying the junction length; (iii) evidences of non-monotonic behaviors, such as stochastic resonant activation and noise enhanced stability, of MST versus the driving frequency and noise intensity for different values of $\\alpha$ and $\\beta$; (iv) finally, these non-monotonic behaviors are found to be related to the mean density of solitons formed along the junction.
NASA Astrophysics Data System (ADS)
Pandir, Yusuf; Duzgun, Hasan Huseyin
2016-06-01
In this study, we investigate some new analytical solutions to the fractional Sine-Gordon equation by using the new version of generalized F-expansion method. The fractional derivatives are defined in the modified Riemann-Liouville context. As a result, new analytical solutions were obtained in terms Jacobi elliptic functions.
Zarmi, Yair
2016-01-01
Slower-than-light multi-front solutions of the Sine-Gordon in (1+2) dimensions, constructed through the Hirota algorithm, are mapped onto spatially localized structures, which emulate free, spatially extended, massive relativistic particles. A localized structure is an image of the junctions at which the fronts intersect. It propagates together with the multi-front solution at the velocity of the latter. The profile of the localized structure obeys the linear wave equation in (1+2) dimensions, to which a term that represents interaction with a slower-than-light, Sine-Gordon-multi-front solution has been added. This result can be also formulated in terms of a (1+2)-dimensional Lagrangian system, in which the Sine-Gordon and wave equations are coupled. Expanding the Euler-Lagrange equations in powers of the coupling constant, the zero-order part of the solution reproduces the (1+2)-dimensional Sine-Gordon fronts. The first-order part is the spatially localized structure. PACS: 02.30.Ik, 03.65.Pm, 05.45.Yv, 02.30.Ik. PMID:26930077
Koller, Andrew; Olshanii, Maxim
2011-12-15
We present a case demonstrating the connection between supersymmetric quantum mechanics (SUSYQM), reflectionless scattering, and soliton solutions of integrable partial differential equations. We show that the members of a class of reflectionless Hamiltonians, namely, Akulin's Hamiltonians, are connected via supersymmetric chains to a potential-free Hamiltonian, explaining their reflectionless nature. While the reflectionless property in question has been mentioned in the literature for over two decades, the enabling algebraic mechanism was previously unknown. Our results indicate that the multisoliton solutions of the sine-Gordon and nonlinear Schroedinger equations can be systematically generated via the supersymmetric chains connecting Akulin's Hamiltonians. Our findings also explain a well-known but little-understood effect in laser physics: when a two-level atom, initially in the ground state, is subjected to a laser pulse of the form V(t)=(n({h_bar}/2{pi})/{tau})/cosh(t/{tau}), with n being an integer and {tau} being the pulse duration, it remains in the ground state after the pulse has been applied, for any choice of the laser detuning.
Edge binding of sine-Gordon solitons in spin-orbit-coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Peotta, Sebastiano; Mireles, Francisco; Di Ventra, Massimiliano
2015-02-01
In recent experiments with ultracold gases a Raman coupling scheme is used to produce both spin-orbit (SO) and Zeeman-type couplings [Y.-J. Lin et al., Nature (London) 471, 83 (2011), 10.1038/nature09887]. Their competition drives a phase transition to a magnetized state with broken Z2 symmetry. Using a hydrodynamic approach we study a confined binary condensate subject to both SO and Zeeman-type couplings. We find that in the limit of small healing length and in the phase with unbroken symmetry, the boundary magnetization profile has an analytical solution in the form of a sine-Gordon soliton. The soliton is bound to the edge of the system by the nontrivial boundary condition resulting from the combined effect of the SO coupling and the drop in the particle density. The same boundary condition is important in the magnetized phase as well, where we characterize numerically the boundary spin structure. We further discuss how the nontrivial magnetization structure affects the density profile near the boundary, yet another prediction that can be tested in current experiments of spin-orbit-coupled condensates.
Specific sine-Gordon soliton dynamics in the presence of external driving forces
NASA Astrophysics Data System (ADS)
Reinisch, Gilbert; Fernandez, Jean Claude
1981-07-01
We consider the acceleration of a single sine-Gordon (SG) soliton kink wave by an external time-dependent force χ(t), first without any dissipation, and then in the presence of a weak damping effect. We use the method of Fogel, Trullinger, Bishop, and Krumhansl [FTBK,
NASA Astrophysics Data System (ADS)
Nguyen, Lu Trong Khiem
2016-07-01
A finite difference formula based on the predictor-corrector technique is presented to integrate the cylindrically and spherically symmetric sine-Gordon equations numerically. Based on various numerical observations, one property of the waves of kink type is conjectured and used to explain their returning effect. Several numerical experiments are carried out and they are in excellent agreement with the existing results. In addition, the corresponding modulation solution for the two-dimensional ring-shaped kink is extended to that in three-dimension. Both numerical and theoretical aspects are utilized to verify the reliability of the proposed numerical scheme and thus the analytical modulation solutions.
Koller, Andrew; Olshanii, Maxim
2011-12-01
We present a case demonstrating the connection between supersymmetric quantum mechanics (SUSYQM), reflectionless scattering, and soliton solutions of integrable partial differential equations. We show that the members of a class of reflectionless Hamiltonians, namely, Akulin's Hamiltonians, are connected via supersymmetric chains to a potential-free Hamiltonian, explaining their reflectionless nature. While the reflectionless property in question has been mentioned in the literature for over two decades, the enabling algebraic mechanism was previously unknown. Our results indicate that the multisoliton solutions of the sine-Gordon and nonlinear Schrödinger equations can be systematically generated via the supersymmetric chains connecting Akulin's Hamiltonians. Our findings also explain a well-known but little-understood effect in laser physics: when a two-level atom, initially in the ground state, is subjected to a laser pulse of the form V(t) = (nh/τ)/cosh(t/τ), with n being an integer and τ being the pulse duration, it remains in the ground state after the pulse has been applied, for any choice of the laser detuning. PMID:22304205
Dzhunushaliev, Vladimir; Folomeev, Vladimir; Singleton, Douglas; Myrzakulov, Ratbay
2010-08-15
In this paper we investigate wormhole and spherically symmetric solutions in four-dimensional gravity plus a matter source consisting of a ghost scalar field with a sine-Gordon potential. For the wormhole solutions we also include the possibility of electric and/or magnetic charges. For both types of solutions we perform a linear stability analysis and show that the wormhole solutions are stable and that when one turns on the electric and/or magnetic field the solution remains stable. The linear stability analysis of the spherically symmetric solutions indicates that they can be stable or unstable depending on one of the parameters of the system. This result for the spherically symmetric solution is nontrivial since a previous investigation of four-dimensional gravity plus a ghost scalar field with a {lambda}{phi}{sup 4} interaction found only unstable spherically symmetric solutions. Both the wormhole and spherically symmetric solutions presented here asymptotically go to anti-de Sitter space-time.
Studies of Kink-AntiKink Collisions in 1+1 D in φ^4 and Double Sine Gordon Nonlinear Wave Equations
NASA Astrophysics Data System (ADS)
Fasano, Christopher G.
1996-11-01
The manner in which kink and antikink solutions interact in nonlinear systems is strongly dependent upon the velocities in the collision. In certain velocity regions, the kink and antikink annihilate, while in other regions they bounce off of one another. We present studies of multiple bounce solutions for the collision of kinks and antikinks in a 1 + 1 dimensional φ^4 and Double Sine-Gordon systems. We confirm the existence of a repeated level structure for velocities at which 3, 4, 5, and 6 bounce solutions occur φ^4 as presented by previous authors ( Michael Peyrard and David K. Campbell, Physica 9D) (1983) 33, Peter Anninos, Samuel Oliveira, and Richard A. Matzner, Phys. Rev. D44 (1991) 1147 and we characterize the onset of each multiple bounce solution. The positions of these levels may be described by a simple extension of previous works, and imply that the system follows a specific ``route'' to ``chaotic'' annihilation. An analysis of kink-antinkink collisions in the Double-Sine Gordon equation will also be presented. This analysis reveals both interesting similarities and differences when compared to φ^4
Zarmi, Yair
2015-01-01
The (1+1)-dimensional Sine-Gordon equation passes integrability tests commonly applied to nonlinear evolution equations. Its kink solutions (one-dimensional fronts) are obtained by a Hirota algorithm. In higher space-dimensions, the equation does not pass these tests. Although it has been derived over the years for quite a few physical systems that have nothing to do with Special Relativity, the Sine-Gordon equation emerges as a non-linear relativistic wave equation. This opens the way for exploiting the tools of the Theory of Special Relativity. Using no more than the relativistic kinematics of tachyonic momentum vectors, from which the solutions are constructed through the Hirota algorithm, the existence and classification of N-moving-front solutions of the (1+2)- and (1+3)-dimensional equations for all N ≥ 1 are presented. In (1+2) dimensions, each multi-front solution propagates rigidly at one velocity. The solutions are divided into two subsets: Solutions whose velocities are lower than a limiting speed, c = 1, or are greater than or equal to c. To connect with concepts of the Theory of Special Relativity, c will be called “the speed of light.” In (1+3)-dimensions, multi-front solutions are characterized by spatial structure and by velocity composition. The spatial structure is either planar (rotated (1+2)-dimensional solutions), or genuinely three-dimensional – branes. Planar solutions, propagate rigidly at one velocity, which is lower than, equal to, or higher than c. Branes must contain clusters of fronts whose speed exceeds c = 1. Some branes are “hybrids”: different clusters of fronts propagate at different velocities. Some velocities may be lower than c but some must be equal to, or exceed, c. Finally, the speed of light cannot be approached from within the subset of slower-than-light solutions in both (1+2) and (1+3) dimensions. PMID:26020922
Zarmi, Yair
2015-01-01
The (1+1)-dimensional Sine-Gordon equation passes integrability tests commonly applied to nonlinear evolution equations. Its kink solutions (one-dimensional fronts) are obtained by a Hirota algorithm. In higher space-dimensions, the equation does not pass these tests. Although it has been derived over the years for quite a few physical systems that have nothing to do with Special Relativity, the Sine-Gordon equation emerges as a non-linear relativistic wave equation. This opens the way for exploiting the tools of the Theory of Special Relativity. Using no more than the relativistic kinematics of tachyonic momentum vectors, from which the solutions are constructed through the Hirota algorithm, the existence and classification of N-moving-front solutions of the (1+2)- and (1+3)-dimensional equations for all N ≥ 1 are presented. In (1+2) dimensions, each multi-front solution propagates rigidly at one velocity. The solutions are divided into two subsets: Solutions whose velocities are lower than a limiting speed, c = 1, or are greater than or equal to c. To connect with concepts of the Theory of Special Relativity, c will be called "the speed of light." In (1+3)-dimensions, multi-front solutions are characterized by spatial structure and by velocity composition. The spatial structure is either planar (rotated (1+2)-dimensional solutions), or genuinely three-dimensional--branes. Planar solutions, propagate rigidly at one velocity, which is lower than, equal to, or higher than c. Branes must contain clusters of fronts whose speed exceeds c = 1. Some branes are "hybrids": different clusters of fronts propagate at different velocities. Some velocities may be lower than c but some must be equal to, or exceed, c. Finally, the speed of light cannot be approached from within the subset of slower-than-light solutions in both (1+2) and (1+3) dimensions. PMID:26020922
Gulevich, D. R.; Savel'ev, Sergey; Kusmartsev, F. V.; Yampol'skii, V. A.; Nori, Franco
2009-09-01
We predict a class of excitations propagating along a Josephson vortex in two-dimensional Josephson junctions. These excitations are associated with the distortion of a Josephson vortex line of an arbitrary profile. We derive a universal analytical expression for the energy of arbitrary-shape excitations, investigate their influence on the dynamics of a vortex line, and discuss conditions where such excitations can be created. Finally, we show that such excitations play the role of a clock for a relativistically-moving Josephson vortex and suggest an experiment to measure a time-dilation effect analogous to that in special relativity. The position of the shape excitation on a Josephson vortex acts like a 'minute hand' showing the time in the rest frame associated with the vortex. Remarkably, at some conditions, the shape wave can carry negative energy: a vortex with the shape excitation can have less energy than the same vortex without it.
The abelian confinement mechanism revisited: New aspects of the Georgi-Glashow model
NASA Astrophysics Data System (ADS)
Anber, Mohamed M.
2014-02-01
The confinement problem remains one of the most difficult problems in theoretical physics. An important step toward the solution of this problem is Polyakov's work on abelian confinement. The Georgi-Glashow model is a natural testing ground for this mechanism which has been surprising us by its richness and wide applicability. In this work, we shed light on two new aspects of this model in 2+1 D. First, we develop a many-body description of the effective degrees of freedom. Namely, we consider a non-relativistic gas of W-bosons in the background of monopole-instanton plasma. Many-body treatment is a standard toolkit in condensed matter physics. However, we add a new twist by supplying the monopole-instantons as external background field. Using this construction along with a mean-field approximation, we calculate the form of the potential between two electric probes as a function of their separation. This potential is expressed in terms of the Meijer-G function which interpolates between logarithmic and linear behavior at small and large distances, respectively. Second, we develop a systematic approach to integrate out the effect of the W-bosons at finite temperature in the range 0≤T
Quantum mass shift of the soliton in the Skyrme model
Livne, H. )
1993-02-01
The quantum mass shift of the soliton in the Skyrme model has been calculated from all nonzero modes. The calculations were carried out using a method applied earlier to the sine-Gordon model. The mass shifts do not depend on the baryonic spin, therefore they are the same for the nucleon and the [Delta]. Our model parameters are the pion decay constant [ital F][sub [pi
Conceptual Foundations of Soliton Versus Particle Dualities Toward a Topological Model for Matter
NASA Astrophysics Data System (ADS)
Kouneiher, Joseph
2016-06-01
The idea that fermions could be solitons was actually confirmed in theoretical models in 1975 in the case when the space-time is two-dimensional and with the sine-Gordon model. More precisely S. Coleman showed that two different classical models end up describing the same fermions particle, when the quantum theory is constructed. But in one model the fermion is a quantum excitation of the field and in the other model the particle is a soliton. Hence both points of view can be reconciliated.The principal aim in this paper is to exhibit a solutions of topological type for the fermions in the wave zone, where the equations of motion are non-linear field equations, i.e. using a model generalizing sine- Gordon model to four dimensions, and describe the solutions for linear and circular polarized waves. In other words, the paper treat fermions as topological excitations of a bosonic field.
NASA Astrophysics Data System (ADS)
Cai, Yi; Schmidt, Michael A.
2016-05-01
Combining neutrino mass generation and a dark matter candidate in a unified model has always been intriguing. We revisit the class of R νMDM models, which incorporate minimal dark matter in radiative neutrino mass models based on the one-loop ultraviolet completions of the Weinberg operator. The possibility of an exact accidental Z 2 is completely ruled out in this scenario. We study the phenomenology of one of the models with an approximate Z 2 symmetry. In addition to the Standard Model particles, it contains two real scalar quintuplets, one vector-like quadruplet fermion and a fermionic quintuplet. The neutral component of the fermionic quintuplet serves as a good dark matter candidate which can be tested by the future direct and indirect detection experiments. The constraints from flavor physics and electroweak-scale naturalness are also discussed.
Long-range interactions and wave patterns in a DNA model.
Tabi, C B; Mohamadou, A; Kofané, T C
2010-07-01
We propose a spin-like model of DNA nonlinear dynamics with long-range interactions between adjacent base pairs. We show that the model equation is a modified sine-Gordon equation. We perform the linear stability analysis of a plane wave, which predicts high-amplitude and extended oscillating waves for high values of the long-range parameter. This is confirmed numerically and biological implications of the obtained patterns are suggested. PMID:20676723
The sausage sigma model revisited
NASA Astrophysics Data System (ADS)
Suneeta, Vardarajan
2015-06-01
Fateev’s sausage sigma models in two and three dimensions are known to be integrable. We study their stability under renormalization group (RG) flow in the target space by using results from the mathematics of Ricci flow. We show that the three-dimensional sausage is unstable, whereas the two-dimensional sausage appears to be stable at least at leading order as it approaches the sphere. We speculate that the stability results obtained are linked to the classification of ancient solutions to Ricci flow (i.e., sigma models that are nonperturbative in the infrared regime) in two and three dimensions. We also describe a class of perturbations of the three-dimensional sausage (with the same continuous symmetries) which remarkably decouple. This indicates that there could be a new solution to RG flow, which is described at least perturbatively as a deformation of the sausage.
Galeta, Leonardo; Pirjol, Dan; Schat, Carlos
2009-12-01
We show how to match the Isgur-Karl model to the spin-flavor quark operator expansion used in the 1/N{sub c} studies of the nonstrange negative parity L=1 excited baryons. Using the transformation properties of states and interactions under the permutation group S{sub 3} we are able to express the operator coefficients as overlap integrals, without making any assumption on the spatial dependence of the quark wave functions. The general mass operator leads to parameter free mass relations and constraints on the mixing angles that are valid beyond the usual harmonic oscillator approximation. The Isgur-Karl model with harmonic oscillator wave functions provides a simple counterexample that demonstrates explicitly that the alternative operator basis for the 1/N{sub c} expansion for excited baryons recently proposed by Matagne and Stancu is incomplete.
Q kink of the nonlinear O(3) {sigma} model involving an explicitly broken symmetry
Loginov, A. Yu.
2011-05-15
The (1 + 1)-dimensional nonlinear O(3) {sigma} model involving an explicitly broken symmetry is considered. Sphalerons are known to exist in this model. These sphalerons are of a topological origin and are embedded kinks of the sine-Gordon model. In the case of a compact spatial manifold S{sup 1}, sine-Gordon multikinks exist in the model. It is shown that the model admits a nonstatic generalization of the sine-Gordon kink/multikink, Q kink/multikink. Explicit expressions are obtained for the dependence of the Q kink energy and charge on the phase frequency of rotation. The Q kink is studied for stability, and expressions are obtained for the eigenfunctions and eigenfrequencies of the operator of quadratic fluctuations. It is shown that the Q kink is unstable over the entire admissible frequency range {omega} Element-Of [-1, 1]. The one-loop quantum correction to the static-kink mass is calculated, and the Q-kink zero mode is quantized. It is shown that, in a general static case, the field equations of the model are integrable in quadratures.
Lambert's multiple reflection model revisited
NASA Astrophysics Data System (ADS)
Hahlweg, Cornelius; Rothe, Hendrik
2011-10-01
In last years paper on the idea of Lambertian reflection we gave a partial translation of an almost lost chapter by Lambert on multiple reflection as a gimmick. The problem of multiple reflections is of special interest in scatterometric devices. The present paper is dedicated to a deeper discussion of the model proposed by J.H. Lambert or, better to say, a derivation using the matrix method of paraxial optics. Further some examples and special cases - especially the consequences for scatterometer design - are discussed. For easy handling it would be desirable to derive some simplified formulas describing the effective higher order refraction qualities of thick lenses, which might support the choice of lenses for certain applications.
The abelian confinement mechanism revisited: New aspects of the Georgi–Glashow model
Anber, Mohamed M.
2014-02-15
The confinement problem remains one of the most difficult problems in theoretical physics. An important step toward the solution of this problem is Polyakov’s work on abelian confinement. The Georgi–Glashow model is a natural testing ground for this mechanism which has been surprising us by its richness and wide applicability. In this work, we shed light on two new aspects of this model in 2+1 D. First, we develop a many-body description of the effective degrees of freedom. Namely, we consider a non-relativistic gas of W-bosons in the background of monopole–instanton plasma. Many-body treatment is a standard toolkit in condensed matter physics. However, we add a new twist by supplying the monopole–instantons as external background field. Using this construction along with a mean-field approximation, we calculate the form of the potential between two electric probes as a function of their separation. This potential is expressed in terms of the Meijer-G function which interpolates between logarithmic and linear behavior at small and large distances, respectively. Second, we develop a systematic approach to integrate out the effect of the W-bosons at finite temperature in the range 0≤T
A Multi-Level Model of Moral Functioning Revisited
ERIC Educational Resources Information Center
Reed, Don Collins
2009-01-01
The model of moral functioning scaffolded in the 2008 "JME" Special Issue is here revisited in response to three papers criticising that volume. As guest editor of that Special Issue I have formulated the main body of this response, concerning the dynamic systems approach to moral development, the problem of moral relativism and the role of…
Topological Twisted Sigma Model with H-flux Revisited
Chuang, Wu-yen
2006-08-18
In this paper we revisit the topological twisted sigma model with H-flux. We explicitly expand and then twist the worldsheet Lagrangian for bi-Hermitian geometry. we show that the resulting action consists of a BRST exact term and pullback terms, which only depend on one of the two generalized complex structures and the B-field. We then discuss the topological feature of the model.
Mathematical modeling of intrinsic Josephson junctions with capacitive and inductive couplings
NASA Astrophysics Data System (ADS)
Rahmonov, I. R.; Shukrinov, Yu M.; Zemlyanaya, E. V.; Sarhadov, I.; Andreeva, O.
2012-11-01
We investigate the current voltage characteristics (CVC) of intrinsic Josephson junctions (IJJ) with two types of couplings between junctions: capacitive and inductive. The IJJ model is described by a system of coupled sine-Gordon equations which is solved numerically by the 4th order Runge-Kutta method. The method of numerical simulation and numerical results are presented. The magnetic field distribution is calculated as the function of coordinate and time at different values of the bias current. The influence of model parameters on the CVC is studied. The behavior of the IJJ in dependence on coupling parameters is discussed.
Revisiting the minimal chaotic inflation model
NASA Astrophysics Data System (ADS)
Harigaya, Keisuke; Ibe, Masahiro; Kawasaki, Masahiro; Yanagida, Tsutomu T.
2016-05-01
We point out that the prediction of the minimal chaotic inflation model is altered if a scalar field takes a large field value close to the Planck scale during inflation due to a negative Hubble induced mass. In particular, we show that the inflaton potential is effectively flattened at a large inflaton field value in the presence of such a scalar field. The scalar field may be identified with the standard model Higgs field or super partners of standard model fermions. With such Hubble-induced flattening, we find that the minimal chaotic inflation model, especially the model with a quadratic potential, is consistent with recent observations of the cosmic microwave background fluctuation without modifying the inflation model itself.
The Bonn nuclear quark model revisited
Providencia, Constanca; Providencia, Joao da Cordeiro, Flavio; Yamamura, Masatoshi; Tsue, Yasuhiko; Nishiyama, Seiya
2009-08-15
We present the exact solutions to the equations of the lowest energy states of the colored and color-symmetric sectors of the Bonn quark model, which is SU(3) symmetric and is defined in terms of an effective pairing force with su(4) algebraic structure. We show that the groundstate of the model is not color symmetrical except for a narrow interval in the range of possible quark numbers. We also study the performance of the Glauber coherent state, as well as of superconducting states of the BCS type, with respect to the description, not only of the absolute (colored) groundstate, but also of the minimum energy state of the color-symmetrical sector, finding that it is remarkably good. We use the model to discuss, in a schematic context, some controversial aspects of the conventional treatment of color superconductivity.
Kuwaiti oil fires—Modeling revisited
NASA Astrophysics Data System (ADS)
Husain, Tahir
Just after the invasion of Kuwait, scientists began predictions on the environmental disaster due to threat by the Iraqi regime to blow out oil wells in the Kuwaiti oil fields. The findings with the speculations ranging from a nuclear winter to super-acid rain and global warming were presented in the World Climate Conference in Geneva in November 1990. Just before the war erupted in the middle of January 1991, a conference in London was called to discuss the potential risks to human life and ecological systems in case of blow out of oil fields. The scientists, using modeling techniques, raised the speculations about the global impact which, however, was discounted at a later stage. This paper presents an overview of the selected models used to assess the local, regional, and global impacts. The paper also highlights the model and data limitations and suggests future research directions to respond more effectively under emergency situations.
Potts-model critical manifolds revisited
NASA Astrophysics Data System (ADS)
Scullard, Christian R.; Lykke Jacobsen, Jesper
2016-03-01
We compute critical polynomials for the q-state Potts model on the Archimedean lattices, using a parallel implementation of the algorithm of Jacobsen (2014 J. Phys. A: Math. Theor 47 135001) that gives us access to larger sizes than previously possible. The exact polynomials are computed for bases of size 6 × 6 unit cells, and the root in the temperature variable v={{{e}}}K-1 is determined numerically at q = 1 for bases of size 8 × 8. This leads to improved results for bond percolation thresholds, and for the Potts-model critical manifolds in the real (q, v) plane. In the two most favourable cases, we find now the kagome-lattice threshold to eleven digits and that of the (3,{12}2) lattice to thirteen. Our critical manifolds reveal many interesting features in the antiferromagnetic region of the Potts model, and determine accurately the extent of the Berker-Kadanoff phase for the lattices studied.
The Hopfield model revisited: covariance and quantization
NASA Astrophysics Data System (ADS)
Belgiorno, F.; Cacciatori, S. L.; Dalla Piazza, F.
2016-01-01
There are several possible applications of quantum electrodynamics in dielectric media which require a quantum description for the electromagnetic field interacting with matter fields. The associated quantum models can refer to macroscopic electromagnetic fields or, alternatively, to mesoscopic fields (polarization fields) describing an effective interaction between electromagnetic field and matter fields. We adopt the latter approach, and focus on the Hopfield model for the electromagnetic field in a dielectric dispersive medium in a framework in which space-time dependent mesoscopic parameters occur, like susceptibility, matter resonance frequency, and also coupling between electromagnetic field and polarization field. Our most direct goal is to describe in a phenomenological way a space-time varying dielectric perturbation induced by means of the Kerr effect in nonlinear dielectric media. This extension of the model is implemented by means of a Lorentz-invariant Lagrangian which, for constant microscopic parameters, and in the rest frame, coincides with the standard one. Moreover, we deduce a covariant scalar product and provide a canonical quantization scheme which takes into account the constraints implicit in the model. Examples of viable applications are indicated.
The Motive--Strategy Congruence Model Revisited.
ERIC Educational Resources Information Center
Watkins, David; Hattie, John
1992-01-01
Research with 1,266 Australian secondary school students supports 2 propositions critical to the motive-strategy congruence model of J. B. Biggs (1985). Students tend to use learning strategies congruent with motivation for learning, and congruent motive-strategy combinations are associated with higher average school grades. (SLD)
Density waves in the Calogero model - revisited
Bardek, V. Feinberg, J. Meljanac, S.
2010-03-15
The Calogero model bears, in the continuum limit, collective excitations in the form of density waves and solitary modulations of the density of particles. This sector of the spectrum of the model was investigated, mostly within the framework of collective-field theory, by several authors, over the past 15 years or so. In this work we shall concentrate on periodic solutions of the collective BPS-equation (also known as 'finite amplitude density waves'), as well as on periodic solutions of the full static variational equations which vanish periodically (also known as 'large amplitude density waves'). While these solutions are not new, we feel that our analysis and presentation add to the existing literature, as we explain in the text. In addition, we show that these solutions also occur in a certain two-family generalization of the Calogero model, at special points in parameter space. A compendium of useful identities associated with Hilbert transforms, including our own proofs of these identities, appears in Appendix A. In Appendix B we also elucidate in the present paper some fine points having to do with manipulating Hilbert-transforms, which appear ubiquitously in the collective field formalism. Finally, in order to make this paper self-contained, we briefly summarize in Appendix C basic facts about the collective field formulation of the Calogero model.
Neural network modelling of CIMIS-ET0 (revisited)
NASA Astrophysics Data System (ADS)
Abrahart, R. J.; Ghani, N. Ab
2009-04-01
This paper will revisit the use of four independent hydrometeorological variables to predict 'reference crop evapotranspiration' in a neural network model - calculated as CIMIS-ET0 (Kisi, 2006; Aytek et al., 2008). The two earlier studies are coalesced and their published findings positioned in a broader environmental modelling context. Four models developed on similar datasets are compared and contrasted in the current exercise: a multiple linear regression model (MLIN: Pearson, 1896), a piecewise multiple linear regression model (M5 Model Tree; M5MT: Quinlan, 1992; Wang & Witten, 1997) and two neural network models developed on different optimisation algorithms - Conjugate Gradient (CGNN: Hestenes & Stiefel, 1952) and Levenberg-Marquet (LMNN: Levenberg, 1944; Marquardt, 1963). The results are presented using residual scatterplots so that the exact nature of the each individual modelling solution can be determined: permitting outputs to be interpreted in terms of structures, symmetries, orientations, local features and outliers. The reported inspection and interpretation of plots is matched against a selection of traditional numerical modelling statistics that were computed on HydroTest (http://www.hydrotest.org.uk; Dawson et al., 2007). The reported closeness of earlier neurocomputing outputs to predicted values estimated using a counterpart multiple linear regression model is explained in detail.
The maternal deprivation animal model revisited.
Marco, Eva M; Llorente, Ricardo; López-Gallardo, Meritxell; Mela, Virginia; Llorente-Berzal, Álvaro; Prada, Carmen; Viveros, María-Paz
2015-04-01
Early life stress, in the form of MD (24h at pnd 9), interferes with brain developmental trajectories modifying both behavioral and neurobiochemical parameters. MD has been reported to enhance neuroendocrine responses to stress, to affect emotional behavior and to impair cognitive function. More recently, changes in body weight gain, metabolic parameters and immunological responding have also been described. Present data give support to the fact that neuronal degeneration and/or astrocyte proliferation are present in specific brain regions, mainly hippocampus, prefrontal cortex and hypothalamus, which are particularly vulnerable to the effects of neonatal stress. The MD animal model arises as a valuable tool for the investigation of the brain processes occurring at the narrow time window comprised between pnd 9 and 10 that are critical for the establishment of brain circuitries critical for the regulation of behavior, metabolism and energy homeostasis. In the present review we will discuss three possible mechanisms that might be crucial for the effects of MD, namely, the rapid increase in glucocorticoids, the lack of the neonatal leptin surge, and the enhanced endocannabinoid signaling during the specific critical period of MD. A better understanding of the mechanisms underlying the detrimental consequences of MD is a concern for public health and may provide new insights into mental health prevention strategies and into novel therapeutic approaches in neuropsychiatry. PMID:25616179
The Mantel-Haenszel procedure revisited: models and generalizations.
Fidler, Vaclav; Nagelkerke, Nico
2013-01-01
Several statistical methods have been developed for adjusting the Odds Ratio of the relation between two dichotomous variables X and Y for some confounders Z. With the exception of the Mantel-Haenszel method, commonly used methods, notably binary logistic regression, are not symmetrical in X and Y. The classical Mantel-Haenszel method however only works for confounders with a limited number of discrete strata, which limits its utility, and appears to have no basis in statistical models. Here we revisit the Mantel-Haenszel method and propose an extension to continuous and vector valued Z. The idea is to replace the observed cell entries in strata of the Mantel-Haenszel procedure by subject specific classification probabilities for the four possible values of (X,Y) predicted by a suitable statistical model. For situations where X and Y can be treated symmetrically we propose and explore the multinomial logistic model. Under the homogeneity hypothesis, which states that the odds ratio does not depend on Z, the logarithm of the odds ratio estimator can be expressed as a simple linear combination of three parameters of this model. Methods for testing the homogeneity hypothesis are proposed. The relationship between this method and binary logistic regression is explored. A numerical example using survey data is presented. PMID:23516463
NASA Astrophysics Data System (ADS)
Delduc, F.; Magro, M.; Vicedo, B.
2012-08-01
The Faddeev-Reshetikhin procedure corresponds to a removal of the non-ultralocality of the classical SU(2) principal chiral model. It is realized by defining another field theory, which has the same Lax pair and equations of motion but a different Poisson structure and Hamiltonian. Following earlier work of M. Semenov-Tian-Shansky and A. Sevostyanov, we show how it is possible to alleviate in a similar way the non-ultralocality of symmetric space σ-models. The equivalence of the equations of motion holds only at the level of the Pohlmeyer reduction of these models, which corresponds to symmetric space sine-Gordon models. This work therefore shows indirectly that symmetric space sine-Gordon models, defined by a gauged Wess-Zumino-Witten action with an integrable potential, have a mild non-ultralocality. The first step needed to construct an integrable discretization of these models is performed by determining the discrete analogue of the Poisson algebra of their Lax matrices.
On a family of (1+1)-dimensional scalar field theory models: Kinks, stability, one-loop mass shifts
Alonso-Izquierdo, A.; Mateos Guilarte, J.
2012-09-15
In this paper we construct a one-parametric family of (1+1)-dimensional one-component scalar field theory models supporting kinks. Inspired by the sine-Gordon and {phi}{sup 4} models, we look at all possible extensions such that the kink second-order fluctuation operators are Schroedinger differential operators with Poeschl-Teller potential wells. In this situation, the associated spectral problem is solvable and therefore we shall succeed in analyzing the kink stability completely and in computing the one-loop quantum correction to the kink mass exactly. When the parameter is a natural number, the family becomes the hierarchy for which the potential wells are reflectionless, the two first levels of the hierarchy being the sine-Gordon and {phi}{sup 4} models. - Highlights: Black-Right-Pointing-Pointer We construct a family of scalar field theory models supporting kinks. Black-Right-Pointing-Pointer The second-order kink fluctuation operators involve Poeschl-Teller potential wells. Black-Right-Pointing-Pointer We compute the one-loop quantum correction to the kink mass with different methods.
Revisiting rodent models: Octodon degus as Alzheimer's disease model?
Steffen, Johannes; Krohn, Markus; Paarmann, Kristin; Schwitlick, Christina; Brüning, Thomas; Marreiros, Rita; Müller-Schiffmann, Andreas; Korth, Carsten; Braun, Katharina; Pahnke, Jens
2016-01-01
Alzheimer's disease primarily occurs as sporadic disease and is accompanied with vast socio-economic problems. The mandatory basic research relies on robust and reliable disease models to overcome increasing incidence and emerging social challenges. Rodent models are most efficient, versatile, and predominantly used in research. However, only highly artificial and mostly genetically modified models are available. As these 'engineered' models reproduce only isolated features, researchers demand more suitable models of sporadic neurodegenerative diseases. One very promising animal model was the South American rodent Octodon degus, which was repeatedly described as natural 'sporadic Alzheimer's disease model' with 'Alzheimer's disease-like neuropathology'. To unveil advantages over the 'artificial' mouse models, we re-evaluated the age-dependent, neurohistological changes in young and aged Octodon degus (1 to 5-years-old) bred in a wild-type colony in Germany. In our hands, extensive neuropathological analyses of young and aged animals revealed normal age-related cortical changes without obvious signs for extensive degeneration as seen in patients with dementia. Neither significant neuronal loss nor enhanced microglial activation were observed in aged animals. Silver impregnation methods, conventional, and immunohistological stains as well as biochemical fractionations revealed neither amyloid accumulation nor tangle formation. Phosphoepitope-specific antibodies against tau species displayed similar intraneuronal reactivity in both, young and aged Octodon degus.In contrast to previous results, our study suggests that Octodon degus born and bred in captivity do not inevitably develop cortical amyloidosis, tangle formation or neuronal loss as seen in Alzheimer's disease patients or transgenic disease models. PMID:27566602
Freight Network Equilibrium Model revisited: the Freight Network Modeling System
Tobin, R.L.
1984-01-01
The Freight Network Equilibrium Model (FNEM) was developed to study potential coal transportation impacts that could result from widespread conversion of boilers to use coal for fuel, as mandated under the Powerplant and Industrial Fuel Use Act of 1978. Continued improvement of FNEM and creation of auxiliary software and data during applications of the model in various transportation analyses led to the development of the Freight Network Modeling System, a general and flexible modeling system designed to have wide applicability to a variety of freight transportation analyses. It consists of compatible network data bases, data management software, models of freight transportation, report generators, and graphics output. The network data include US rail, water, highway, and pipeline systems. Data management software automates the task of setting up a study network of appropriate detail in appropriate regions of the country. The major analytical tools in the system are FNEM and Shortest Path Analysis and Display (SPAD); FNEM is predictive and simulates decisions of both shippers and carriers, taking into account the competition for transportation facilities; SPAD is a simpler model that optimizes routings of single shipments. Output for both FNEM and SPAD includes detailed routings, cost and delay estimates for all shipments, and data on total traffic levels. SPAD can be used interactively with routes displayed graphically. 13 references, 10 figures, 2 tables.
Statistical mechanics of nonlinear wave equations. 3. Metric transitivity for hyperbolic sine-gordon
NASA Astrophysics Data System (ADS)
McKean, H. P.
1995-05-01
McKean and Vaninsky proved that the canonical measure e - H d ∞ Q d ∞ P based upon the HamiltonianH = int [tfrac{1}{2}P^2 + tfrac{1}{2}(Q')^2 + F(Q)]dx of the wave equation ∂2 Q/∂ t 2 - ∂2 Q/∂ x 2 + f( Q) = 0 with restoring force f(Q)=F'(Q) is preserved by the associated flow of Q and P = Q ṡ, and they conjectured that metric transitivity prevails, always on the whole line, and likewise on the circle unless f(Q)=Q or f(Q)=sh Q. Here, the metric transitivity is proved for the whole line in the second case. The proof employs the beautiful "d'Alembert formula" of Krichever.
Lattice Boltzmann model for generalized nonlinear wave equations
NASA Astrophysics Data System (ADS)
Lai, Huilin; Ma, Changfeng
2011-10-01
In this paper, a lattice Boltzmann model is developed to solve a class of the nonlinear wave equations. Through selecting equilibrium distribution function and an amending function properly, the governing evolution equation can be recovered correctly according to our proposed scheme, in which the Chapman-Enskog expansion is employed. We validate the algorithm on some problems where analytic solutions are available, including the second-order telegraph equation, the nonlinear Klein-Gordon equation, and the damped, driven sine-Gordon equation. It is found that the numerical results agree well with the analytic solutions, which indicates that the present algorithm is very effective and can be used to solve more general nonlinear problems.
Ropero Peláez, Francisco Javier; Taniguchi, Shirley
2016-01-01
The gate control theory of pain proposed by Melzack and Wall in 1965 is revisited through two mechanisms of neuronal regulation: NMDA synaptic plasticity and intrinsic plasticity. The Melzack and Wall circuit was slightly modified by using strictly excitatory nociceptive afferents (in the original arrangement, nociceptive afferents were considered excitatory when they project to central transmission neurons and inhibitory when projecting to substantia gelatinosa). The results of our neurocomputational model are consistent with biological ones in that nociceptive signals are blocked on their way to the brain every time a tactile stimulus is given at the same locus where the pain was produced. In the computational model, the whole set of parameters, independently of their initialization, always converge to the correct values to allow the correct computation of the circuit. To test the model, other painful conditions were analyzed: phantom limb pain, wind-up and wind-down pain, breakthrough pain, and demyelinating syndromes like Guillain-Barré and multiple sclerosis. PMID:27088014
Ropero Peláez, Francisco Javier; Taniguchi, Shirley
2016-01-01
The gate control theory of pain proposed by Melzack and Wall in 1965 is revisited through two mechanisms of neuronal regulation: NMDA synaptic plasticity and intrinsic plasticity. The Melzack and Wall circuit was slightly modified by using strictly excitatory nociceptive afferents (in the original arrangement, nociceptive afferents were considered excitatory when they project to central transmission neurons and inhibitory when projecting to substantia gelatinosa). The results of our neurocomputational model are consistent with biological ones in that nociceptive signals are blocked on their way to the brain every time a tactile stimulus is given at the same locus where the pain was produced. In the computational model, the whole set of parameters, independently of their initialization, always converge to the correct values to allow the correct computation of the circuit. To test the model, other painful conditions were analyzed: phantom limb pain, wind-up and wind-down pain, breakthrough pain, and demyelinating syndromes like Guillain-Barré and multiple sclerosis. PMID:27088014
On the mass-coupling relation of multi-scale quantum integrable models
NASA Astrophysics Data System (ADS)
Bajnok, Zoltán; Balog, János; Ito, Katsushi; Satoh, Yuji; Tóth, Gábor Zsolt
2016-06-01
We determine exactly the mass-coupling relation for the simplest multi-scale quantum integrable model, the homogenous sine-Gordon model with two independent mass-scales. We first reformulate its perturbed coset CFT description in terms of the perturbation of a projected product of minimal models. This representation enables us to identify conserved tensor currents on the UV side. These UV operators are then mapped via form factor perturbation theory to operators on the IR side, which are characterized by their form factors. The relation between the UV and IR operators is given in terms of the sought-for mass-coupling relation. By generalizing the Θ sum rule Ward identity we are able to derive differential equations for the mass-coupling relation, which we solve in terms of hypergeometric functions. We check these results against the data obtained by numerically solving the thermodynamic Bethe Ansatz equations, and find a complete agreement.
LISREL Modeling: Genetic and Environmental Influences on IQ Revisited.
ERIC Educational Resources Information Center
Chipuer, Heather M.; And Others
1990-01-01
A model-fitting analysis of the covariance structure of an intelligence quotient (IQ) data set is reported using a model that considers additive and nonadditive genetic parameters and shared and nonshared environment parameters that permit different estimates for different types of relatives. The use of LISREL for such purposes is reviewed. (SLD)
Revisiting "Discrepancy Analysis in Continuing Medical Education: A Conceptual Model"
ERIC Educational Resources Information Center
Fox, Robert D.
2011-01-01
Based upon a review and analysis of selected literature, the author presents a conceptual model of discrepancy analysis evaluation for planning, implementing, and assessing the impact of continuing medical education (CME). The model is described in terms of its value as a means of diagnosing errors in the development and implementation of CME. The…
Terrestrial nitrogen cycling in Earth system models revisited
Stocker, Benjamin D; Prentice, I Colin; Cornell, Sarah; Davies-Barnard, T; Finzi, Adrien; Franklin, Oskar; Janssens, Ivan; Larmola, Tuula; Manzoni, Stefano; Näsholm, Torgny; Raven, John; Rebel, Karin; Reed, Sasha C.; Vicca, Sara; Wiltshire, Andy; Zaehle, Sönke
2016-01-01
Understanding the degree to which nitrogen (N) availability limits land carbon (C) uptake under global environmental change represents an unresolved challenge. First-generation ‘C-only’vegetation models, lacking explicit representations of N cycling,projected a substantial and increasing land C sink under rising atmospheric CO2 concentrations. This prediction was questioned for not taking into account the potentially limiting effect of N availability, which is necessary for plant growth (Hungate et al.,2003). More recent global models include coupled C and N cycles in land ecosystems (C–N models) and are widely assumed to be more realistic. However, inclusion of more processes has not consistently improved their performance in capturing observed responses of the global C cycle (e.g. Wenzel et al., 2014). With the advent of a new generation of global models, including coupled C, N, and phosphorus (P) cycling, model complexity is sure to increase; but model reliability may not, unless greater attention is paid to the correspondence of model process representations ande mpirical evidence. It was in this context that the ‘Nitrogen Cycle Workshop’ at Dartington Hall, Devon, UK was held on 1–5 February 2016. Organized by I. Colin Prentice and Benjamin D. Stocker (Imperial College London, UK), the workshop was funded by the European Research Council,project ‘Earth system Model Bias Reduction and assessing Abrupt Climate change’ (EMBRACE). We gathered empirical ecologists and ecosystem modellers to identify key uncertainties in terrestrial C–N cycling, and to discuss processes that are missing or poorly represented in current models.
Revisiting the mouse model of oxygen-induced retinopathy
Kim, Clifford B; D'Amore, Patricia A; Connor, Kip M
2016-01-01
Abnormal blood vessel growth in the retina is a hallmark of many retinal diseases, such as retinopathy of prematurity (ROP), proliferative diabetic retinopathy, and the wet form of age-related macular degeneration. In particular, ROP has been an important health concern for physicians since the advent of routine supplemental oxygen therapy for premature neonates more than 70 years ago. Since then, researchers have explored several animal models to better understand ROP and retinal vascular development. Of these models, the mouse model of oxygen-induced retinopathy (OIR) has become the most widely used, and has played a pivotal role in our understanding of retinal angiogenesis and ocular immunology, as well as in the development of groundbreaking therapeutics such as anti-vascular endothelial growth factor injections for wet age-related macular degeneration. Numerous refinements to the model have been made since its inception in the 1950s, and technological advancements have expanded the use of the model across multiple scientific fields. In this review, we explore the historical developments that have led to the mouse OIR model utilized today, essential concepts of OIR, limitations of the model, and a representative selection of key findings from OIR, with particular emphasis on current research progress. PMID:27499653
Revisiting the domain model for lithium intercalated graphite
Krishnan, Sridevi; Brenet, Gilles; Caliste, Damien; Genovese, Luigi; Deutsch, Thierry; Pochet, Pascal
2013-12-16
In this Letter, we study the stability of the domain model for lithium intercalated graphite in stages III and II by means of Density Functional Theory and Kinetic Lattice Monte Carlo simulations. We find that the domain model is either thermodynamically or kinetically stable when compared to the standard model in stages III and II. The existence of domains in the intercalation sequence is well supported by recent high resolution transmission electron microscope observations in lithiated graphite. Moreover, we predict that such domain staging sequences leads to a wide range of diffusivity as reported in experiments.
Electromagnetic braking revisited with a magnetic point dipole model
NASA Astrophysics Data System (ADS)
Land, Sara; McGuire, Patrick; Bumb, Nikhil; Mann, Brian P.; Yellen, Benjamin B.
2016-04-01
A theoretical model is developed to predict the trajectory of magnetized spheres falling through a copper pipe. The derive magnetic point dipole model agrees well with the experimental trajectories for NdFeB spherical magnets of varying diameter, which are embedded inside 3D printed shells with fixed outer dimensions. This demonstration of electrodynamic phenomena and Lenz's law serves as a good laboratory exercise for physics, electromagnetics, and dynamics classes at the undergraduate level.
Zwislocki's model of the middle ear re-visited
NASA Astrophysics Data System (ADS)
Withnell, Robert H.; Fields, Taylor N.
2015-12-01
Zwislocki's circuit model of the middle ear [11] has been used, in original or modified form, in subsequent studies modeling the ear [4, 6]. The model includes two eardrum modes of vibration, a shunt for flexible coupling between the incus and stapes, and a single tuned oscillator for ossicular vibration. The contribution of each of these mechanisms was examined by fitting a model of the ear to acoustic input impedance data from healthy human ears. The circuit elements for a non-ossicular eardrum vibration and a flexible coupling between the incus and stapes were found to be detrimental or non-essential for the model-fit-to-data. A single mode of eardrum vibration for sound transmission to the middle ear is consistent with the eardrum acting as an impedance-matching device, with pars-tensa eardrum vibration coupled to the ossicles [1]. A single-tuned oscillator was insufficient to account for the bandwidth of the ear. The frequency response of the ear suggests multiple resonant modes of ossicular vibration.
The hydrogeologic-geochemical model of Cerro Prieto revisited
Lippmann, M.J.; Halfman, S.E.; Truesdell, A.H.; Manon M., A.
1989-01-01
As the exploitation of the Cerro Prieto, Mexico, geothermal field continues, there is increasing evidence that the hydrogeologic model developed by Halfman et al. (1984, 1986) presents the basic features controlling the movement of geothermal fluids in the system. At the present time the total installed capacity at Cerro Prieto is 620 MWe requiring the production of more than 10,500 tonnes/hr of a brine-steam mixture. This significant rate of fluid production has resulted in changes in reservoir thermodynamic conditions and in the chemistry of the produced fluids. After reviewing the hydrogeologic-geochemical model of Cerro Prieto, some of the changes observed in the field due to its exploitation are discussed and interpreted on the basis of the model. 21 refs., 11 figs., 1 tab.
Energy-economy interactions revisited within a comprehensive sectoral model
Hanson, D. A.; Laitner, J. A.
2000-07-24
This paper describes a computable general equilibrium (CGE) model with considerable sector and technology detail, the ``All Modular Industry Growth Assessment'' Model (AMIGA). It is argued that a detailed model is important to capture and understand the several rolls that energy plays within the economy. Fundamental consumer and industrial demands are for the services from energy; hence, energy demand is a derived demand based on the need for heating, cooling mechanical, electrical, and transportation services. Technologies that provide energy-services more efficiently (on a life cycle basis), when adopted, result in increased future output of the economy and higher paths of household consumption. The AMIGA model can examine the effects on energy use and economic output of increases in energy prices (e.g., a carbon charge) and other incentive-based policies or energy-efficiency programs. Energy sectors and sub-sector activities included in the model involve energy extraction conversion and transportation. There are business opportunities to produce energy-efficient goods (i.e., appliances, control systems, buildings, automobiles, clean electricity). These activities are represented in the model by characterizing their likely production processes (e.g., lighter weight motor vehicles). Also, multiple industrial processes can produce the same output but with different technologies and inputs. Secondary recovery, i.e., recycling processes, are examples of these multiple processes. Combined heat and power (CHP) is also represented for energy-intensive industries. Other modules represent residential and commercial building technologies to supply energy services. All sectors of the economy command real resources (capital services and labor).
The Thirring-Wess model revisited: a functional integral approach
Belvedere, L.V. . E-mail: armflavio@if.uff.br
2005-06-01
We consider the Wess-Zumino-Witten theory to obtain the functional integral bosonization of the Thirring-Wess model with an arbitrary regularization parameter. Proceeding a systematic of decomposing the Bose field algebra into gauge-invariant- and gauge-non-invariant field subalgebras, we obtain the local decoupled quantum action. The generalized operator solutions for the equations of motion are reconstructed from the functional integral formalism. The isomorphism between the QED {sub 2} (QCD {sub 2}) with broken gauge symmetry by a regularization prescription and the Abelian (non-Abelian) Thirring-Wess model with a fixed bare mass for the meson field is established.
Re-visiting the trans insertion model for complexin clamping.
Krishnakumar, Shyam S; Li, Feng; Coleman, Jeff; Schauder, Curtis M; Kümmel, Daniel; Pincet, Frederic; Rothman, James E; Reinisch, Karin M
2015-01-01
We have previously proposed that complexin cross-links multiple pre-fusion SNARE complexes via a trans interaction to function as a clamp on SNARE-mediated neurotransmitter release. A recent NMR study was unable to detect the trans clamping interaction of complexin and therefore questioned the previous interpretation of the fluorescence resonance energy transfer and isothermal titration calorimetry data on which the trans clamping model was originally based. Here we present new biochemical data that underscore the validity of our previous interpretation and the continued relevancy of the trans insertion model for complexin clamping. PMID:25831964
NASA Astrophysics Data System (ADS)
Fowler, Keirnan J. A.; Peel, Murray C.; Western, Andrew W.; Zhang, Lu; Peterson, Tim J.
2016-03-01
Hydrologic models have potential to be useful tools in planning for future climate variability. However, recent literature suggests that the current generation of conceptual rainfall runoff models tend to underestimate the sensitivity of runoff to a given change in rainfall, leading to poor performance when evaluated over multiyear droughts. This research revisited this conclusion, investigating whether the observed poor performance could be due to insufficient model calibration and evaluation techniques. We applied an approach based on Pareto optimality to explore trade-offs between model performance in different climatic conditions. Five conceptual rainfall runoff model structures were tested in 86 catchments in Australia, for a total of 430 Pareto analyses. The Pareto results were then compared with results from a commonly used model calibration and evaluation method, the Differential Split Sample Test. We found that the latter often missed potentially promising parameter sets within a given model structure, giving a false negative impression of the capabilities of the model. This suggests that models may be more capable under changing climatic conditions than previously thought. Of the 282[347] cases of apparent model failure under the split sample test using the lower [higher] of two model performance criteria trialed, 155[120] were false negatives. We discuss potential causes of remaining model failures, including the role of data errors. Although the Pareto approach proved useful, our aim was not to suggest an alternative calibration strategy, but to critically assess existing methods of model calibration and evaluation. We recommend caution when interpreting split sample results.
What drives health care expenditure?--Baumol's model of 'unbalanced growth' revisited.
Hartwig, Jochen
2008-05-01
The share of health care expenditure in GDP rises rapidly in virtually all OECD countries, causing increasing concern among politicians and the general public. Yet, economists have to date failed to reach an agreement on what the main determinants of this development are. This paper revisits Baumol's [Baumol, W.J., 1967. Macroeconomics of unbalanced growth: the anatomy of urban crisis. American Economic Review 57 (3), 415-426] model of 'unbalanced growth', showing that the latter offers a ready explanation for the observed inexorable rise in health care expenditure. The main implication of Baumol's model in this context is that health care expenditure is driven by wage increases in excess of productivity growth. This hypothesis is tested empirically using data from a panel of 19 OECD countries. Our tests yield robust evidence in favor of Baumol's theory. PMID:18164773
Laws of reflection and Snell's law revisited by video modeling
NASA Astrophysics Data System (ADS)
Rodrigues, M.; Simeão Carvalho, P.
2014-07-01
Video modelling is being used, nowadays, as a tool for teaching and learning several topics in Physics. Most of these topics are related to kinematics. In this work we show how video modelling can be used for demonstrations and experimental teaching in optics, namely the laws of reflection and the well-known Snell's Law of light. Videos were recorded with a photo camera at 30 frames/s, and analysed with the open source software Tracker. Data collected from several frames was treated with the Data Tool module, and graphs were built to obtain relations between incident, reflected and refraction angles, as well as to determine the refractive index of Perspex. These videos can be freely distributed in the web and explored with students within the classroom, or as a homework assignment to improve student's understanding on specific contents. They present a large didactic potential for teaching basic optics in high school with an interactive methodology.
MRAC Revisited: Guaranteed Performance with Reference Model Modification
NASA Technical Reports Server (NTRS)
Stepanyan, Vahram; Krishnakumar, Kalmaje
2010-01-01
This paper presents modification of the conventional model reference adaptive control (MRAC) architecture in order to achieve guaranteed transient performance both in the output and input signals of an uncertain system. The proposed modification is based on the tracking error feedback to the reference model. It is shown that approach guarantees tracking of a given command and the ideal control signal (one that would be designed if the system were known) not only asymptotically but also in transient by a proper selection of the error feedback gain. The method prevents generation of high frequency oscillations that are unavoidable in conventional MRAC systems for large adaptation rates. The provided design guideline makes it possible to track a reference command of any magnitude form any initial position without re-tuning. The benefits of the method are demonstrated in simulations.
Stochastic resonance in neuron models: Endogenous stimulation revisited
NASA Astrophysics Data System (ADS)
Plesser, Hans E.; Geisel, Theo
2001-03-01
The paradigm of stochastic resonance (SR)-the idea that signal detection and transmission may benefit from noise-has met with great interest in both physics and the neurosciences. We investigate here the consequences of reducing the dynamics of a periodically driven neuron to a renewal process (stimulation with reset or endogenous stimulation). This greatly simplifies the mathematical analysis, but we show that stochastic resonance as reported earlier occurs in this model only as a consequence of the reduced dynamics.
The comfortable driving model revisited: traffic phases and phase transitions
NASA Astrophysics Data System (ADS)
Knorr, Florian; Schreckenberg, Michael
2013-07-01
We study the spatiotemporal patterns resulting from different boundary conditions for a microscopic traffic model and contrast them with empirical results. By evaluating the time series of local measurements, the local traffic states are assigned to the different traffic phases of Kerner’s three-phase traffic theory. For this classification we use the rule-based FOTO-method, which provides ‘hard’ rules for this assignment. Using this approach, our analysis shows that the model is indeed able to reproduce three qualitatively different traffic phases: free flow (F), synchronized traffic (S), and wide moving jams (J). In addition, we investigate the likelihood of transitions between the three traffic phases. We show that a transition from free flow to a wide moving jam often involves an intermediate transition: first from free flow to synchronized flow and then from synchronized flow to a wide moving jam. This is supported by the fact that the so-called F → S transition (from free flow to synchronized traffic) is much more likely than a direct F → J transition. The model under consideration has a functional relationship between traffic flow and traffic density. The fundamental hypothesis of the three-phase traffic theory, however, postulates that the steady states of synchronized flow occupy a two-dimensional region in the flow-density plane. Due to the obvious discrepancy between the model investigated here and the postulate of the three-phase traffic theory, the good agreement that we found could not be expected. For a more detailed analysis, we also studied vehicle dynamics at a microscopic level and provide a comparison of real detector data with simulated data of the identical highway segment.
Allele frequencies at microsatellite loci: The stepwise mutation model revisited
Valdes, A.M.; Slatkin, M. ); Freimer, N.B. )
1993-03-01
The authors summarize available data on the frequencies of alleles at microsatellite loci in human populations and compare observed distributions of allele frequencies to those generated by a simulation of the stepwise mutation model. They show that observed frequency distributions at 108 loci are consistent with the results of the model under the assumption that mutations cause an increase or decrease in repeat number by one and under the condition that the product Nu, where N is the effective population size and u is the mutation rate, is larger than one. It is also shown that the variance of the distribution of allele sizes is a useful estimator of Nu and performs much better than previously suggested estimators for the stepwise mutation model. In the data, there is no correlation between the mean and variance in allele size at a locus or between the number of alleles and mean allele size, which suggests that the mutation rate at these loci is independent of allele size. 39 refs., 6 figs., 4 tabs.
Revisiting absolute and relative judgments in the WITNESS model.
Fife, Dustin; Perry, Colton; Gronlund, Scott D
2014-04-01
The WITNESS model (Clark in Applied Cognitive Psychology 17:629-654, 2003) provides a theoretical framework with which to investigate the factors that contribute to eyewitness identification decisions. One key factor involves the contributions of absolute versus relative judgments. An absolute contribution is determined by the degree of match between an individual lineup member and memory for the perpetrator; a relative contribution involves the degree to which the best-matching lineup member is a better match to memory than the remaining lineup members. In WITNESS, the proportional contributions of relative versus absolute judgments are governed by the values of the decision weight parameters. We conducted an exploration of the WITNESS model's parameter space to determine the identifiability of these relative/absolute decision weight parameters, and compared the results to a restricted version of the model that does not vary the decision weight parameters. This exploration revealed that the decision weights in WITNESS are difficult to identify: Data often can be fit equally well by setting the decision weights to nearly any value and compensating with a criterion adjustment. Clark, Erickson, and Breneman (Law and Human Behavior 35:364-380, 2011) claimed to demonstrate a theoretical basis for the superiority of lineup decisions that are based on absolute contributions, but the relationship between the decision weights and the criterion weakens this claim. These findings necessitate reconsidering the role of the relative/absolute judgment distinction in eyewitness decision making. PMID:23943556
Animal models of neuropsychiatry revisited: a personal tribute to Teitelbaum.
Robbins, T W
2012-06-01
Several themes and principles of behavioural neuroscience are evident in the work of Phillip Teitelbaum. He has emphasised the importance of studying behaviour in simple preparations, of re-synthesising complex behavioural patterns from these elemental 'building-blocks' and understanding their often hierarchical organisation. He also more recently has become interested in the possible power of behavioural endophenotypes. His work has resulted in a new emphasis on animal neuropsychology which is highly relevant to human psychopathology. This article illustrates these themes from examples taken from animal models of sensory neglect, drug addiction and cognitive syndromes associated with schizophrenia and other neuropsychiatric disorders. PMID:22440232
Experimental model of myocardial infarction: Histopathology and reperfusion damage revisited.
Kren, Leos; Meluzin, Jaroslav; Pavlovsky, Zdenek; Mayer, Jiri; Kala, Petr; Groch, Ladislav; Hornacek, Ivan; Rauser, Petr; Vlasin, Michal
2010-09-15
The goal of this pilot study was to create an experimental model of myocardial infarction (for subsequent evaluation of the effectiveness of an alternative way of stem cell application - intracoronary cell infusion in the management of acute myocardial infarction). Four experimental animals, female pigs weighing between 30 and 40 kg, were used in the initial phase of this study to create an experimental model of acute myocardial infarction. An experimental myocardial infarction was performed via occlusion of the interventricular arm of the left coronary artery for 90 min. The hearts were examined 1 h, 3 days, 5 days, and 7 days after the procedure. Macroscopically, red infarction characteristic of reperfusion was found. Microscopically, the healing process with granulation tissue production/collagen deposition was remarkably accelerated compared to literature data. Repair processes in reperfused experimental myocardial infarction and/or reperfused autopsy specimens should not be evaluated on the basis of literature data only. Large collections of extracellular calcium were present. This phenomenon is not well described in the literature and probably has the potential for significantly interfering with the repair process. The histopathology of reperfused acute myoardial infarction deserves to be studied in further investigations. PMID:20451332
Tail Lobe Revisited: Magnetic Field Modeling Based on Plasma Data
NASA Technical Reports Server (NTRS)
Karlsson, S. B. P.; Tsyganenko, N. A.
1999-01-01
Plasma data from the ISEE-1 and -2 spacecraft during 1977-1980 have been used to determine the distribution of data points in the magnetotail in the range of distances -20 < XGSM < --15, i.e. which of the records that were located in the current sheet, in the tail lobe, in the magnetosheath and in the boundary layers respectively. The ISEE-1 and -2 magnetic field data for the records in the tail lobe were then used to model the tail lobe magnetic field dependence on the solar wind dynamic pressure, on the Interplanetary Magnetic Field (IMF) and on the Dst index. The tail lobe magnetic field was assumed to be dependent on the square root of the dynamic pressure based on the balance between the total magnetic pressure in the tail lobes and the dynamic pressure of the solar wind. The IMF dependent terms, added to the pressure term, were sought in many different forms while the Dst dependence of the tail lobe magnetic field was assumed to be linear. The field shows a strong dependence on the square root of the dynamic pressure and the different IMF dependent terms all constitute a significant contribution to the total field. However, the dependence on the Dst index turned out to be very weak at those down-tail distances. The results of this study are intended to be used for parameterizing future versions of the data-based models of the global magnetospheric magnetic field.
Critical rotation of general-relativistic polytropic models revisited
NASA Astrophysics Data System (ADS)
Geroyannis, V.; Karageorgopoulos, V.
2013-09-01
We develop a perturbation method for computing the critical rotational parameter as a function of the equatorial radius of a rigidly rotating polytropic model in the "post-Newtonia approximation" (PNA). We treat our models as "initial value problems" (IVP) of ordinary differential equations in the complex plane. The computations are carried out by the code dcrkf54.f95 (Geroyannis and Valvi 2012 [P1]; modified Runge-Kutta-Fehlberg code of fourth and fifth order for solving initial value problems in the complex plane). Such a complex-plane treatment removes the syndromes appearing in this particular family of IVPs (see e.g. P1, Sec. 3) and allows continuation of the numerical integrations beyond the surface of the star. Thus all the required values of the Lane-Emden function(s) in the post-Newtonian approximation are calculated by interpolation (so avoiding any extrapolation). An interesting point is that, in our computations, we take into account the complete correction due to the gravitational term, and this issue is a remarkable difference compared to the classical PNA. We solve the generalized density as a function of the equatorial radius and find the critical rotational parameter. Our computations are extended to certain other physical characteristics (like mass, angular momentum, rotational kinetic energy, etc). We find that our method yields results comparable with those of other reliable methods. REFERENCE: V.S. Geroyannis and F.N. Valvi 2012, International Journal of Modern Physics C, 23, No 5, 1250038:1-15.
The Zipf Law revisited: An evolutionary model of emerging classification
Levitin, L.B.; Schapiro, B.; Perlovsky, L.
1996-12-31
Zipf`s Law is a remarkable rank-frequency relationship observed in linguistics (the frequencies of the use of words are approximately inversely proportional to their ranks in the decreasing frequency order) as well as in the behavior of many complex systems of surprisingly different nature. We suggest an evolutionary model of emerging classification of objects into classes corresponding to concepts and denoted by words. The evolution of the system is derived from two basic assumptions: first, the probability to recognize an object as belonging to a known class is proportional to the number of objects in this class already recognized, and, second, there exists a small probability to observe an object that requires creation of a new class ({open_quotes}mutation{close_quotes} that gives birth to a new {open_quotes}species{close_quotes}). It is shown that the populations of classes in such a system obey the Zipf Law provided that the rate of emergence of new classes is small. The model leads also to the emergence of a second-tier structure of {open_quotes}super-classes{close_quotes} - groups of classes with almost equal populations.
Temperature Effect on Micelle Formation: Molecular Thermodynamic Model Revisited.
Khoshnood, Atefeh; Lukanov, Boris; Firoozabadi, Abbas
2016-03-01
Temperature affects the aggregation of macromolecules such as surfactants, polymers, and proteins in aqueous solutions. The effect on the critical micelle concentration (CMC) is often nonmonotonic. In this work, the effect of temperature on the micellization of ionic and nonionic surfactants in aqueous solutions is studied using a molecular thermodynamic model. Previous studies based on this technique have predicted monotonic behavior for ionic surfactants. Our investigation shows that the choice of tail transfer energy to describe the hydrophobic effect between the surfactant tails and the polar solvent molecules plays a key role in the predicted CMC. We modify the tail transfer energy by taking into account the effect of the surfactant head on the neighboring methylene group. The modification improves the description of the CMC and the predicted micellar size for aqueous solutions of sodium n-alkyl sulfate, dodecyl trimethylammonium bromide (DTAB), and n-alkyl polyoxyethylene. The new tail transfer energy describes the nonmonotonic behavior of CMC versus temperature. In the DTAB-water system, we redefine the head size by including the methylene group, next to the nitrogen, in the head. The change in the head size along with our modified tail transfer energy improves the CMC and aggregation size prediction significantly. Tail transfer is a dominant energy contribution in micellar and microemulsion systems. It also promotes the adsorption of surfactants at fluid-fluid interfaces and affects the formation of adsorbed layer at fluid-solid interfaces. Our proposed modifications have direct applications in the thermodynamic modeling of the effect of temperature on molecular aggregation, both in the bulk and at the interfaces. PMID:26854650
Paris basin petroleum systems revisited by two-dimensional modeling
Gaulier, J.M.; Burrus, J.; Poulet, M. ); Barlier, J. , Pau )
1991-03-01
The authors investigate the history of petroleum generation, expulsion, and migration along two E-W and N-W cross sections in the Paris basin. Source rocks, represented by Liassic marine shales (merely Hetangian-Sinemurian and Toarcian) reach the top of the oil window around 2,000 m and begin effective expulsion around 2,400 m. Reservoirs are essentially found in the subtle structures in the Dogger (carbonates) and Triassic (sandstones). These levels are normally separated from the source rocks by several hundred meters of impervious marls or shales. Regional faults are often viewed as major conduits that allow both expulsion and migration to the reservoirs. This petroleum system is seen by the use of two-dimensional modeling techniques: (1) The generation history is derived from an investigation of thermal history and kinetic modeling. They show that the present subsurface temperatures are influenced by regional convective discharge linked to the uplift of eastern and southeastern basin edges and that this cooling postdates the maturity. They also show that, in the eastern basin, the basement heat flow could have been increased since the Tertiary, at a time when Tertiary erosion had nearly frozen the maturity development. (2) The expulsion and migration are analyzed by coupling numerically the compaction history, the generation history, and the regional hydrodynamics. They show that expulsion efficiency is very much dependent on parameters not well constrained, but a sensitivity analysis confirms the prominent role of vertical faults as well as the influence of regional water flow on the distribution of accumulations.
Specificity in Transition State Binding: The Pauling Model Revisited
Amyes, Tina L.; Richard, John P.
2013-01-01
Linus Pauling proposed that the large rate accelerations for enzymes are due to the high specificity of the protein catalyst for binding the reaction transition state. The observation that stable analogs of the transition states for enzymatic reactions often act as tight-binding binding inhibitors provided early support for this simple and elegant proposal. We review experimental results which support the proposal that Pauling’s model provides a satisfactory explanation for the rate accelerations for many heterolytic enzymatic reactions through high energy reaction intermediates, such as proton transfer and decarboxylation. Specificity in transition state binding is obtained when the total intrinsic binding energy of the substrate is significantly larger than the binding energy observed at the Michaelis complex. The results of recent studies to characterize the specificity in binding of the enolate oxygen at the transition state for the 1,3-isomerization reaction catalyzed by ketosteroid isomerase are reviewed. Interactions between pig heart succinyl-CoA:3-oxoacid coenzyme A transferase (SCOT) and the nonreacting portions of CoA are responsible for a rate increase of 3 × 1012-fold, which is close to the estimated total 5 × 1013-fold enzymatic rate acceleration. Studies that partition the interactions between SCOT and CoA into their contributing parts are reviewed. Interactions of the protein with the substrate phosphodianion group provide a ca. 12 kcal/mol stabilization of the transition state for the reactions catalyzed by triosephosphate isomerase, orotidine 5′-monophosphate decarboxylase and α-glycerol phosphate dehydrogenase. The interactions of these enzymes with the substrate piece phosphite dianion provide a 6 – 8 kcal/mol stabilization of the transition state for reaction of the appropriate truncated substrate. Enzyme activation by phosphite dianion reflects the higher dianion affinity for binding to the enzyme-transition state complex compared
Yukawa Meson, Sakata Model and Baryon-Lepton Symmetry Revisited
NASA Astrophysics Data System (ADS)
Marshak, R. E.
It is difficult for me to grasp that this symposium is celebrating the jubilee of meson theory since I was a junior at Columbia College in 1935. I recall hearing a colloquium by Paul Dirac that year telling an enraptured audience about the infinite sea of negative energy states but I do not recall any special note being taken of the birth of an equally revolutionary concept, the Yukawa meson. Perhaps the reason was the publication of Hideki Yukawa's paper in an inaccessible Japanese journal, perhaps Dirac's electron theory was dealing with the well-known electromagnetic force whereas Yukawa' meson theory was put forth to understand the nature of two new forces - the nuclear and the weak. Whatever the reason, the situation changed drastically when I migrated to Cornell (to do my thesis under Hans Bethe during the years 1937sim39) and found a deep interest in meson theory. Thus, my own scientific career has almost spanned the period since the birth of meson theory but, what is more to the point, it has been strongly influenced by the work of Yukawa and his collaborators. It therefore gives me great pleasure to be able to talk at this MESON 50 symposium. As one of the oldest speakers, I shall respond in a loose way to Professor Maki's invitation to cover ``topics concerning the historical developments of hadron physics''. I shall select several major themes from the Japanese work that have had special interest for me. My remarks will fall under the four headings: (A) Yukawa Meson; (B) Sakata Model; (C) Baryon-Lepton Symmetry; and (D) Extensions of Baryon-Lepton Symmetry.
Microscopic theory of Brownian motion revisited: The Rayleigh model
NASA Astrophysics Data System (ADS)
Kim, Changho; Karniadakis, George Em
2013-03-01
We investigate three force autocorrelation functions
Revisiting food-based models of territoriality in solitary predators.
López-Bao, José V; Rodríguez, Alejandro; Delibes, Miguel; Fedriani, José M; Calzada, Javier; Ferreras, Pablo; Palomares, Francisco
2014-07-01
Food availability is considered a major factor determining spacing behaviour in territorial species, especially for females. Theoretically, spatial overlap (considered the opposite of territoriality) and food availability are related in a nonlinear manner (hypothesized inverted-U function), with high overlap levels at the extremes of a food availability gradient and low overlap at intermediate levels of this gradient. Similar patterns are expected for encounter frequencies owing to its expected correlation with spatial overlap. However, these predictions have rarely been tested in highly structured social systems on a broad gradient of food availability, which implicitly requires experimental manipulation. We test these predictions in a solitary, territorial and trophic specialist, the Iberian lynx Lynx pardinus, taking advantage of a three-decade data set of spatial behaviour in different scenarios of food availability (i.e. rabbit density). In contrast with expectations, home range overlap among resident females was low (median overlap index = 0.08, range 0-0.57) and core area overlap was nearly nil (median overlap index = 0, range 0-0.22) throughout the entire gradient of prey availability. Furthermore, spatial associations between pairs of females were negligible regardless marked variation in prey availability. Therefore, we did not find support for a model of flexible lynx territoriality driven by food availability. Our results suggest that the exclusive use of space in the Iberian lynx was not related to food. Lack of influence of prey availability on lynx territoriality may be adaptive to cope with the consequences of frequent drought-induced periods of prey scarcity or other disturbance typically affecting wild rabbit populations in Mediterranean environments. Thus, lynx would adopt an obstinate strategy of territoriality that consists in defending exclusive areas across a broad range of resource availability ensuring an exclusive access to the minimum
Mindless reading revisited: an analysis based on the SWIFT model of eye-movement control.
Nuthmann, Antje; Engbert, Ralf
2009-02-01
In this article, we revisit the mindless reading paradigm from the perspective of computational modeling. In the standard version of the paradigm, participants read sentences in both their normal version as well as the transformed (or mindless) version where each letter is replaced with a z. z-String scanning shares the oculomotor requirements with reading but none of the higher-level lexical and semantic processes. Here we use the z-string scanning task to validate the SWIFT model of saccade generation [Engbert, R., Nuthmann, A., Richter, E., & Kliegl, R. (2005). SWIFT: A dynamical model of saccade generation during reading. Psychological Review, 112(4), 777-813] as an example for an advanced theory of eye-movement control in reading. We test the central assumption of spatially distributed processing across an attentional gradient proposed by the SWIFT model. Key experimental results like prolonged average fixation durations in z-string scanning compared to normal reading and the existence of a string-length effect on fixation durations and probabilities were reproduced by the model, which lends support to the model's assumptions on visual processing. Moreover, simulation results for patterns of regressive saccades in z-string scanning confirm SWIFT's concept of activation field dynamics for the selection of saccade targets. PMID:19026673
A goodness-of-fit test for occupancy models with correlated within-season revisits
Wright, Wilson; Irvine, Kathryn M.; Rodhouse, Thomas J.
2016-01-01
Occupancy modeling is important for exploring species distribution patterns and for conservation monitoring. Within this framework, explicit attention is given to species detection probabilities estimated from replicate surveys to sample units. A central assumption is that replicate surveys are independent Bernoulli trials, but this assumption becomes untenable when ecologists serially deploy remote cameras and acoustic recording devices over days and weeks to survey rare and elusive animals. Proposed solutions involve modifying the detection-level component of the model (e.g., first-order Markov covariate). Evaluating whether a model sufficiently accounts for correlation is imperative, but clear guidance for practitioners is lacking. Currently, an omnibus goodnessof- fit test using a chi-square discrepancy measure on unique detection histories is available for occupancy models (MacKenzie and Bailey, Journal of Agricultural, Biological, and Environmental Statistics, 9, 2004, 300; hereafter, MacKenzie– Bailey test). We propose a join count summary measure adapted from spatial statistics to directly assess correlation after fitting a model. We motivate our work with a dataset of multinight bat call recordings from a pilot study for the North American Bat Monitoring Program. We found in simulations that our join count test was more reliable than the MacKenzie–Bailey test for detecting inadequacy of a model that assumed independence, particularly when serial correlation was low to moderate. A model that included a Markov-structured detection-level covariate produced unbiased occupancy estimates except in the presence of strong serial correlation and a revisit design consisting only of temporal replicates. When applied to two common bat species, our approach illustrates that sophisticated models do not guarantee adequate fit to real data, underscoring the importance of model assessment. Our join count test provides a widely applicable goodness-of-fit test and
NASA Astrophysics Data System (ADS)
Vattré, A.; Devincre, B.; Feyel, F.; Gatti, R.; Groh, S.; Jamond, O.; Roos, A.
2014-02-01
A unified model coupling 3D dislocation dynamics (DD) simulations with the finite element (FE) method is revisited. The so-called Discrete-Continuous Model (DCM) aims to predict plastic flow at the (sub-)micron length scale of materials with complex boundary conditions. The evolution of the dislocation microstructure and the short-range dislocation-dislocation interactions are calculated with a DD code. The long-range mechanical fields due to the dislocations are calculated by a FE code, taking into account the boundary conditions. The coupling procedure is based on eigenstrain theory, and the precise manner in which the plastic slip, i.e. the dislocation glide as calculated by the DD code, is transferred to the integration points of the FE mesh is described in full detail. Several test cases are presented, and the DCM is applied to plastic flow in a single-crystal Nickel-based superalloy.
Revisiting the Slichter mode of Mercury in the context of differentiated models
NASA Astrophysics Data System (ADS)
Escapa, A.; Fukushima, T.
2015-11-01
We revisit the Slichter mode of a set of differentiated Mercury models that were considered previously. We apply a different and independent formalism, based on variational principles of mechanics, to analytically model the internal translations of a body with a global internal perfect fluid layer limited by two differentiated rigid solid constituents that have a spherical symmetric mass distribution. The Slichter mode is specified by providing the time evolution of the barycenters of the solid constituents, the amplitude ratio of the mantle to the inner core, and the period of the oscillatory motion. All these parameters only depend on the mass of the body, the mass of the inner core, the density of the fluid, and the mean density of the inner core. For previously developed Mercury models we find, in contrast to other results, that there are no discontinuities in the Slichter period when passing from undifferentiated to differentiated inner cores. Hence, in a general situation, a potential detection of the Slichter mode cannot determine the differentiation of the inner core. We also find that the BepiColombo mission may be able to detect the Slichter mode caused by an impactor meteroid with a mass of about 1012 kg in the most favorable of circumstances. This shows that a measurable excitation of the mode by this mechanism is even more unlikely than was previously established, where a mass about 1010 kg was found. Appendices are available in electronic form at http://www.aanda.org
Ben-David, Avishai; Davidson, Charles E; Embury, Janon F
2008-11-01
We introduced a two-dimensional radiative transfer model for aerosols in the thermal infrared [Appl. Opt.45, 6860-6875 (2006)APOPAI0003-693510.1364/AO.45.006860]. In that paper we superimposed two orthogonal plane-parallel layers to compute the radiance due to a two-dimensional (2D) rectangular aerosol cloud. In this paper we revisit the model and correct an error in the interaction of the two layers. We derive new expressions relating to the signal content of the radiance from an aerosol cloud based on the concept of five directional thermal contrasts: four for the 2D diffuse radiance and one for direct radiance along the line of sight. The new expressions give additional insight on the radiative transfer processes within the cloud. Simulations for Bacillus subtilis var. niger (BG) bioaerosol and dustlike kaolin aerosol clouds are compared and contrasted for two geometries: an airborne sensor looking down and a ground-based sensor looking up. Simulation results suggest that aerosol cloud detection from an airborne platform may be more challenging than for a ground-based sensor and that the detection of an aerosol cloud in emission mode (negative direct thermal contrast) is not the same as the detection of an aerosol cloud in absorption mode (positive direct thermal contrast). PMID:19122735
NASA Astrophysics Data System (ADS)
Reina, Borja; Vera, Raül
2015-08-01
Hartle's model describes the equilibrium configuration of a rotating isolated compact body in perturbation theory up to second order in general relativity. The interior of the body is a perfect fluid with a barotropic equation of state, no convective motions and rigid rotation. That interior is matched across its surface to an asymptotically flat vacuum exterior. Perturbations are taken to second order around a static and spherically symmetric background configuration. Apart from the explicit assumptions, the perturbed configuration is constructed upon some implicit premises, in particular the continuity of the functions describing the perturbation in terms of some background radial coordinate. In this work we revisit the model within a modern general and consistent theory of perturbative matchings to second order, which is independent of the coordinates and gauges used to describe the two regions to be joined. We explore the matching conditions up to second order in full. The main particular result we present is that the radial function m0 (in the setting of the original work) of the second order perturbation tensor, contrary to the original assumption, presents a jump at the surface of the star, which is proportional to the value of the energy density of the background configuration there. As a consequence, the change in mass δ M needed by the perturbed configuration to keep the value of the central energy density unchanged must be amended. We also discuss some subtleties that arise when studying the deformation of the star.
Guterl, Jerome Smirnov, R. D.; Krasheninnikov, S. I.
2015-07-28
Desorption phase of thermal desorption spectroscopy (TDS) experiments performed on tungsten samples exposed to flux of hydrogen isotopes in fusion relevant conditions is analyzed using a reaction-diffusion model describing hydrogen retention in material bulk. Two regimes of hydrogen desorption are identified depending on whether hydrogen trapping rate is faster than hydrogen diffusion rate in material during TDS experiments. In both regimes, a majority of hydrogen released from material defects is immediately outgassed instead of diffusing deeply in material bulk when the evolution of hydrogen concentration in material is quasi-static, which is the case during TDS experiments performed with tungsten samples exposed to flux of hydrogen isotopes in fusion related conditions. In this context, analytical expressions of the hydrogen outgassing flux as a function of the material temperature are obtained with sufficient accuracy to describe main features of thermal desorption spectra (TDSP). These expressions are then used to highlight how characteristic temperatures of TDSP depend on hydrogen retention parameters, such as trap concentration or activation energy of detrapping processes. The use of Arrhenius plots to characterize retention processes is then revisited when hydrogen trapping takes place during TDS experiments. Retention processes are also characterized using the shape of desorption peaks in TDSP, and it is shown that diffusion of hydrogen in material during TDS experiment can induce long desorption tails visible aside desorption peaks at high temperature in TDSP. These desorption tails can be used to estimate activation energy of diffusion of hydrogen in material.
A goodness-of-fit test for occupancy models with correlated within-season revisits.
Wright, Wilson J; Irvine, Kathryn M; Rodhouse, Thomas J
2016-08-01
Occupancy modeling is important for exploring species distribution patterns and for conservation monitoring. Within this framework, explicit attention is given to species detection probabilities estimated from replicate surveys to sample units. A central assumption is that replicate surveys are independent Bernoulli trials, but this assumption becomes untenable when ecologists serially deploy remote cameras and acoustic recording devices over days and weeks to survey rare and elusive animals. Proposed solutions involve modifying the detection-level component of the model (e.g., first-order Markov covariate). Evaluating whether a model sufficiently accounts for correlation is imperative, but clear guidance for practitioners is lacking. Currently, an omnibus goodness-of-fit test using a chi-square discrepancy measure on unique detection histories is available for occupancy models (MacKenzie and Bailey, Journal of Agricultural, Biological, and Environmental Statistics, 9, 2004, 300; hereafter, MacKenzie-Bailey test). We propose a join count summary measure adapted from spatial statistics to directly assess correlation after fitting a model. We motivate our work with a dataset of multinight bat call recordings from a pilot study for the North American Bat Monitoring Program. We found in simulations that our join count test was more reliable than the MacKenzie-Bailey test for detecting inadequacy of a model that assumed independence, particularly when serial correlation was low to moderate. A model that included a Markov-structured detection-level covariate produced unbiased occupancy estimates except in the presence of strong serial correlation and a revisit design consisting only of temporal replicates. When applied to two common bat species, our approach illustrates that sophisticated models do not guarantee adequate fit to real data, underscoring the importance of model assessment. Our join count test provides a widely applicable goodness-of-fit test and
Revisiting the monopole components of effective interactions for the shell model
NASA Astrophysics Data System (ADS)
Wang, X. B.; Dong, G. X.
2015-12-01
In this paper, we revisit the monopole components of effective interactions for the shell model. Without going through specific nuclei or shell gaps, universal roles of central, tensor, and spin-orbit forces can be proved, reflecting the intrinsic features of shell model effective interactions. For monopole matrix elements, even and odd channels of central force often have a canceling effect. However, for the contributions to the shell evolution, its even and odd channels could have both positive or negative contributions, enhancing the role of central force on the shell structure. Tensor force is generally weaker than central force. However, for the effect on shell evolutions, tensor force can dominate or play a competitive role. A different systematics has been discovered between T = 1 and 0 channels. For example, tensor force, well established in the T = 0 channel, becomes uncertain in the T = 1 channel. We calculate the properties of neutron-rich oxygen and calcium isotopes in order to study T = 1 channel interactions further. It is learned that the main improvements of empirical interactions are traced to the central force. For non-central forces, antisymmetric spin-orbit (ALS) force, originated from many-body perturbations or three-body force, could also play an explicit role. T = 1 tensor forces are less constrained so their effect can differ in different empirical interactions. The influence of tensor force may sometimes be canceled by many-body effects. For T = 0 channels of effective interactions, which is the main source of neutron-proton correlations, central and tensor forces are the leading components. For T = 1 channels, which can act between like-particles, the request for many-body correlations could be more demanding, so that the monopole anomaly of the T = 1 channel might be more serious.
Making Productive Use of Four Models of School English: A Case Study Revisited
ERIC Educational Resources Information Center
Macken-Horarik, Mary
2014-01-01
At a time when political leaders and media pundits seek to narrow the English curriculum and reduce its knowledge structure to the "basics," it is helpful to revisit the potential of different approaches to learning in English that have evolved over time. In this paper I reflect on the semantic features of personal growth, cultural…
Casas, Laura; Szűcs, Réka; Vij, Shubha; Goh, Chin Heng; Kathiresan, Purushothaman; Németh, Sándor; Jeney, Zsigmond; Bercsényi, Miklós; Orbán, László
2013-01-01
The body of most fishes is fully covered by scales that typically form tight, partially overlapping rows. While some of the genes controlling the formation and growth of fish scales have been studied, very little is known about the genetic mechanisms regulating scale pattern formation. Although the existence of two genes with two pairs of alleles (S&s and N&n) regulating scale coverage in cyprinids has been predicted by Kirpichnikov and colleagues nearly eighty years ago, their identity was unknown until recently. In 2009, the 'S' gene was found to be a paralog of fibroblast growth factor receptor 1, fgfr1a1, while the second gene called 'N' has not yet been identified. We re-visited the original model of Kirpichnikov that proposed four major scale pattern types and observed a high degree of variation within the so-called scattered phenotype due to which this group was divided into two sub-types: classical mirror and irregular. We also analyzed the survival rates of offspring groups and found a distinct difference between Asian and European crosses. Whereas nude × nude crosses involving at least one parent of Asian origin or hybrid with Asian parent(s) showed the 25% early lethality predicted by Kirpichnikov (due to the lethality of the NN genotype), those with two Hungarian nude parents did not. We further extended Kirpichnikov's work by correlating changes in phenotype (scale-pattern) to the deformations of fins and losses of pharyngeal teeth. We observed phenotypic changes which were not restricted to nudes, as described by Kirpichnikov, but were also present in mirrors (and presumably in linears as well; not analyzed in detail here). We propose that the gradation of phenotypes observed within the scattered group is caused by a gradually decreasing level of signaling (a dose-dependent effect) probably due to a concerted action of multiple pathways involved in scale formation. PMID:24386179
Goh, Chin Heng; Kathiresan, Purushothaman; Németh, Sándor; Jeney, Zsigmond; Bercsényi, Miklós; Orbán, László
2013-01-01
The body of most fishes is fully covered by scales that typically form tight, partially overlapping rows. While some of the genes controlling the formation and growth of fish scales have been studied, very little is known about the genetic mechanisms regulating scale pattern formation. Although the existence of two genes with two pairs of alleles (S&s and N&n) regulating scale coverage in cyprinids has been predicted by Kirpichnikov and colleagues nearly eighty years ago, their identity was unknown until recently. In 2009, the ‘S’ gene was found to be a paralog of fibroblast growth factor receptor 1, fgfr1a1, while the second gene called ‘N’ has not yet been identified. We re-visited the original model of Kirpichnikov that proposed four major scale pattern types and observed a high degree of variation within the so-called scattered phenotype due to which this group was divided into two sub-types: classical mirror and irregular. We also analyzed the survival rates of offspring groups and found a distinct difference between Asian and European crosses. Whereas nude × nude crosses involving at least one parent of Asian origin or hybrid with Asian parent(s) showed the 25% early lethality predicted by Kirpichnikov (due to the lethality of the NN genotype), those with two Hungarian nude parents did not. We further extended Kirpichnikov's work by correlating changes in phenotype (scale-pattern) to the deformations of fins and losses of pharyngeal teeth. We observed phenotypic changes which were not restricted to nudes, as described by Kirpichnikov, but were also present in mirrors (and presumably in linears as well; not analyzed in detail here). We propose that the gradation of phenotypes observed within the scattered group is caused by a gradually decreasing level of signaling (a dose-dependent effect) probably due to a concerted action of multiple pathways involved in scale formation. PMID:24386179
Minimal Model of Plankton Systems Revisited with Spatial Diffusion and Maturation Delay.
Zhao, Jiantao; Tian, Jianjun Paul; Wei, Junjie
2016-03-01
This study revisits the minimal model for a plankton ecosystem proposed by Scheffer with spatial diffusion of plankton and the delay of the maturation period of herbivorous zooplankton. It deepens our understanding of effects of the nutrients and the predation of fish upon zooplankton on the dynamical patterns of the plankton system and also presents new phenomena induced by the delay with spatial diffusion. When the nutrient level is sufficient low, the zooplankton population collapses and the phytoplankton population reaches its carrying capacity. Mathematically, the global stability of the boundary equilibrium is proved. As the nutrient level increases, the system switches to coexistent equilibria or oscillations depending on the maturation period of zooplankton and the predation rate of fish on herbivorous zooplankton. Under an eutrophic condition, there is a unique coexistent homogeneous equilibrium, and the equilibrium density of phytoplankton increases, while the equilibrium density of herbivorous zooplankton decreases as the fish predation rate on herbivorous zooplankton is increasing. The study shows that the system will never collapses under the eutrophic condition unless the fish predation rate approaches infinite. The study also finds a functional bifurcation relation between the delay parameter of the maturation period of herbivorous zooplankton and the fish predation rate on herbivorous zooplankton that, above a critical value of the fish predation rate, the system stays at the coexistent equilibrium, and below that value, the system switches its dynamical patterns among stable and unstable equilibria and oscillations. The oscillations emerge from Hopf bifurcations, and a detailed mathematical analysis about the Hopf bifurcations is carried out to give relevant ecological predications. PMID:26934887
Solitons of electric polarization in multiferroics
NASA Astrophysics Data System (ADS)
Kiselev, V. V.; Raskovalov, A. A.
2016-03-01
Complete analysis of the properties of breathers in spiral multiferroic structures in the sine-Gordon model has been presented. The methods of the excitation and detection of the breathers in the external electric and magnetic fields have been discussed.
NASA Astrophysics Data System (ADS)
Seidl, Roman; Barthel, Roland
2016-04-01
Interdisciplinary scientific and societal knowledge plays an increasingly important role in global change research. Also, in the field of water resources interdisciplinarity as well as cooperation with stakeholders from outside academia have been recognized as important. In this contribution, we revisit an integrated regional modelling system (DANUBIA), which was developed by an interdisciplinary team of researchers and relied on stakeholder participation in the framework of the GLOWA-Danube project from 2001 to 2011 (Mauser and Prasch 2016). As the model was developed before the current increase in literature on participatory modelling and interdisciplinarity, we ask how a socio-hydrology approach would have helped and in what way it would have made the work different. The present contribution firstly presents the interdisciplinary concept of DANUBIA, mainly with focus on the integration of human behaviour in a spatially explicit, process-based numerical modelling system (Roland Barthel, Janisch, Schwarz, Trifkovic, Nickel, Schulz, and Mauser 2008; R. Barthel, Nickel, Meleg, Trifkovic, and Braun 2005). Secondly, we compare the approaches to interdisciplinarity in GLOWA-Danube with concepts and ideas presented by socio-hydrology. Thirdly, we frame DANUBIA and a review of key literature on socio-hydrology in the context of a survey among hydrologists (N = 184). This discussion is used to highlight gaps and opportunities of the socio-hydrology approach. We show that the interdisciplinary aspect of the project and the participatory process of stakeholder integration in DANUBIA were not entirely successful. However, important insights were gained and important lessons were learnt. Against the background of these experiences we feel that in its current state, socio-hydrology is still lacking a plan for knowledge integration. Moreover, we consider necessary that socio-hydrology takes into account the lessons learnt from these earlier examples of knowledge integration
Soliton models for thick branes
NASA Astrophysics Data System (ADS)
Peyravi, Marzieh; Riazi, Nematollah; Lobo, Francisco S. N.
2016-05-01
In this work, we present new soliton solutions for thick branes in 4+1 dimensions. In particular, we consider brane models based on the sine-Gordon (SG), φ 4 and φ 6 scalar fields, which have broken Z2 symmetry in some cases and are responsible for supporting and stabilizing the thick branes. The origin of the symmetry breaking in these models resides in the fact that the modified scalar field potential may have non-degenerate vacua. These vacua determine the cosmological constant on both sides of the brane. We also study the geodesic equations along the fifth dimension, in order to explore the particle motion in the neighborhood of the brane. Furthermore, we examine the stability of the thick branes, by determining the sign of the w^2 term in the expansion of the potential for the resulting Schrödinger-like equation, where w is the five-dimensional coordinate. It turns out that the φ ^4 brane is stable, while there are unstable modes for certain ranges of the model parameters in the SG and φ ^6 branes.
ERIC Educational Resources Information Center
Court, Deborah
1999-01-01
Revisits and reviews Imre Lakatos' ideas on "Falsification and the Methodology of Scientific Research Programmes." Suggests that Lakatos' framework offers an insightful way of looking at the relationship between theory and research that is relevant not only for evaluating research programs in theoretical physics, but in the social sciences as…
Basic, Ivan; Nadramija, Damir; Flajslik, Mario; Amic, Dragan; Lucic, Bono
2007-12-26
Several quantitative structure-activity studies for this data set containing 107 HEPT derivatives have been performed since 1997, using the same set of molecules by (more or less) different classes of molecular descriptors. Multivariate Regression (MR) and Artificial Neural Network (ANN) models were developed and in each study the authors concluded that ANN models are superior to MR ones. We re-calculated multivariate regression models for this set of molecules using the same set of descriptors, and compared our results with the previous ones. Two main reasons for overestimation of the quality of the ANN models in previous studies comparing with MR models are: (1) wrong calculation of leave-one-out (LOO) cross-validated (CV) correlation coefficient for MR models in Luco et al., J. Chem. Inf. Comput. Sci. 37 392-401 (1997), and (2) incorrect estimation/interpretation of leave-one-out (LOO) cross-validated and predictive performance and power of ANN models. More precise and fairer comparison of fit and LOO CV statistical parameters shows that MR models are more stable. In addition, MR models are much simpler than ANN ones. For real testing the predictive performance of both classes of models we need more HEPT derivatives, because all ANN models that presented results for external set of molecules used experimental values in optimization of modeling procedure and model parameters.
NASA Astrophysics Data System (ADS)
Bašic, Ivan; Nadramija, Damir; Flajšlik, Mario; Amić, Dragan; Lučić, Bono
2007-12-01
Several quantitative structure-activity studies for this data set containing 107 HEPT derivatives have been performed since 1997, using the same set of molecules by (more or less) different classes of molecular descriptors. Multivariate Regression (MR) and Artificial Neural Network (ANN) models were developed and in each study the authors concluded that ANN models are superior to MR ones. We re-calculated multivariate regression models for this set of molecules using the same set of descriptors, and compared our results with the previous ones. Two main reasons for overestimation of the quality of the ANN models in previous studies comparing with MR models are: (1) wrong calculation of leave-one-out (LOO) cross-validated (CV) correlation coefficient for MR models in Luco et al., J. Chem. Inf. Comput. Sci. 37 392-401 (1997), and (2) incorrect estimation/interpretation of leave-one-out (LOO) cross-validated and predictive performance and power of ANN models. More precise and fairer comparison of fit and LOO CV statistical parameters shows that MR models are more stable. In addition, MR models are much simpler than ANN ones. For real testing the predictive performance of both classes of models we need more HEPT derivatives, because all ANN models that presented results for external set of molecules used experimental values in optimization of modeling procedure and model parameters.
Borza, Liana Rada; Gavrilovici, Cristina; Stockman, René
2015-01-01
The present paper revisits the ethical models of patient--physician relationship from the perspective of patient autonomy and values. It seems that the four traditional models of physician--patient relationship proposed by Emanuel & Emanuel in 1992 closely link patient values and patient autonomy. On the other hand, their reinterpretation provided by Agarwal & Murinson twenty years later emphasizes the independent expression of values and autonomy in individual patients. Additionally, patient education has been assumed to join patient values and patient autonomy. Moreover, several authors have noted that, over the past few decades, patient autonomy has gradually replaced the paternalistic approach based on the premise that the physician knows what is best for the patient. Neither the paternalistic model of physician-patient relationship, nor the informative model is considered to be satisfactory, as the paternalistic model excludes patient values from decision making, while the informative model excludes physician values from decision making. However, the deliberative model of patient-physician interaction represents an adequate alternative to the two unsatisfactory approaches by promoting shared decision making between the physician and the patient. It has also been suggested that the deliberative model would be ideal for exercising patient autonomy in chronic care and that the ethical role of patient education would be to make the deliberative model applicable to chronic care. In this regard, studies have indicated that the use of decision support interventions might increase the deliberative capacity of chronic patients. PMID:26204658
NASA Astrophysics Data System (ADS)
McGurk, B. J.; Painter, T. H.
2014-12-01
Deterministic snow accumulation and ablation simulation models are widely used by runoff managers throughout the world to predict runoff quantities and timing. Model fitting is typically based on matching modeled runoff volumes and timing with observed flow time series at a few points in the basin. In recent decades, sparse networks of point measurements of the mountain snowpacks have been available to compare with modeled snowpack, but the comparability of results from a snow sensor or course to model polygons of 5 to 50 sq. km is suspect. However, snowpack extent, depth, and derived snow water equivalent have been produced by the NASA/JPL Airborne Snow Observatory (ASO) mission for spring of 20013 and 2014 in the Tuolumne River basin above Hetch Hetchy Reservoir. These high-resolution snowpack data have exposed the weakness in a model calibration based on runoff alone. The U.S. Geological Survey's Precipitation Runoff Modeling System (PRMS) calibration that was based on 30-years of inflow to Hetch Hetchy produces reasonable inflow results, but modeled spatial snowpack location and water quantity diverged significantly from the weekly measurements made by ASO during the two ablation seasons. The reason is that the PRMS model has many flow paths, storages, and water transfer equations, and a calibrated outflow time series can be right for many wrong reasons. The addition of a detailed knowledge of snow extent and water content constrains the model so that it is a better representation of the actual watershed hydrology. The mechanics of recalibrating PRMS to the ASO measurements will be described, and comparisons in observed versus modeled flow for both a small subbasin and the entire Hetch Hetchy basin will be shown. The recalibrated model provided a bitter fit to the snowmelt recession, a key factor for water managers as they balance declining inflows with demand for power generation and ecosystem releases during the final months of snow melt runoff.
NASA Astrophysics Data System (ADS)
Saito, F.; Abe-Ouchi, A.; Takahashi, K.; Blatter, H.
2016-01-01
The present paper revisits the future surface-climate experiments on the Greenland ice sheet proposed by the Sea-level Response to Ice Sheet Evolution (SeaRISE; Bindschadler et al., 2013) study. The projections of the different SeaRISE participants show dispersion, which has not been examined in detail to date. A series of sensitivity experiments are conducted and analyzed using the ice-sheet model for integrated Earth-system studies (IcIES) by replacing one or more formulations of the model parameters with those adopted in other model(s). The results show that large potential sources of the dispersion among the projections of the different SeaRISE participants are differences in the initialization methods and in the surface mass balance methods, and both aspects have almost equal impact on the results. The treatment of ice-sheet margins in the simulation has a secondary impact on the dispersion. We conclude that spinning up the model using fixed topography through the spin-up period while the temperature is allowed to evolve according to the surface temperature history is the preferred representation, at least for the experiment configuration examined in the present paper. A benchmark model experimental setup that most of the numerical models can perform is proposed for future intercomparison projects, in order to evaluate the uncertainties relating to pure ice-sheet model flow characteristics.
Shao, Mingyu; Zhou, Shuigeng; Guan, Jihong
2015-08-01
Protein-protein interaction (PPI) networks are crucial for organisms. Many research efforts have thus been devoted to the study on the topological properties and models of PPI networks. However, existing studies did not always report consistent results on the topological properties of PPI networks. Although a number of PPI network models have been introduced, yet in the literature there is no convincing conclusion on which model is best for describing PPI networks. This situation is primarily caused by the incompleteness of current PPI datasets. To solve this problem, in this study, the authors propose to revisit the topological properties and models of PPI networks from the perspective of PPI dataset evolution. Concretely, they used 12 PPI datasets of Arabidopsis thaliana and 10 PPI datasets of Saccharomyces cerevisiae from different Biological General Repository for Interaction Datasets (BioGRID) database versions, and compared the topological properties of these datasets and the fitting capabilities of five typical PPI network models over these datasets. PMID:26243826
Benzophenone Ultrafast Triplet Population: Revisiting the Kinetic Model by Surface-Hopping Dynamics
2016-01-01
The photochemistry of benzophenone, a paradigmatic organic molecule for photosensitization, was investigated by means of surface-hopping ab initio molecular dynamics. Different mechanisms were found to be relevant within the first 600 fs after excitation; the long-debated direct (S1 → T1) and indirect (S1 → T2 → T1) mechanisms for population of the low-lying triplet state are both possible, with the latter being prevalent. Moreover, we established the existence of a kinetic equilibrium between the two triplet states, never observed before. This fact implies that a significant fraction of the overall population resides in T2, eventually allowing one to revisit the usual spectroscopic assignment proposed by transient absorption spectroscopy. This finding is of particular interest for photocatalysis as well as for DNA damages studies because both T1 and T2 channels are, in principle, available for benzophenone-mediated photoinduced energy transfer toward DNA. PMID:26821061
Benzophenone Ultrafast Triplet Population: Revisiting the Kinetic Model by Surface-Hopping Dynamics.
Marazzi, Marco; Mai, Sebastian; Roca-Sanjuán, Daniel; Delcey, Mickaël G; Lindh, Roland; González, Leticia; Monari, Antonio
2016-02-18
The photochemistry of benzophenone, a paradigmatic organic molecule for photosensitization, was investigated by means of surface-hopping ab initio molecular dynamics. Different mechanisms were found to be relevant within the first 600 fs after excitation; the long-debated direct (S1 → T1) and indirect (S1 → T2 → T1) mechanisms for population of the low-lying triplet state are both possible, with the latter being prevalent. Moreover, we established the existence of a kinetic equilibrium between the two triplet states, never observed before. This fact implies that a significant fraction of the overall population resides in T2, eventually allowing one to revisit the usual spectroscopic assignment proposed by transient absorption spectroscopy. This finding is of particular interest for photocatalysis as well as for DNA damages studies because both T1 and T2 channels are, in principle, available for benzophenone-mediated photoinduced energy transfer toward DNA. PMID:26821061
Local conformational perturbations of the DNA molecule in the SG-model
NASA Astrophysics Data System (ADS)
Krasnobaeva, L. A.; Shapovalov, A. V.
2015-11-01
Within the formalism of the Fokker-Planck equation, the influence of nonstationary external force, random force, and dissipation effects on dynamics local conformational perturbations (kink) propagating along the DNA molecule is investigated. Such waves have an important role in the regulation of important biological processes in living systems at the molecular level. As a dynamic model of DNA was used a modified sine-Gordon equation, simulating the rotational oscillations of bases in one of the chains DNA. The equation of evolution of the kink momentum is obtained in the form of the stochastic differential equation in the Stratonovich sense within the framework of the well-known McLaughlin and Scott energy approach. The corresponding Fokker-Planck equation for the momentum distribution function coincides with the equation describing the Ornstein-Uhlenbek process with a regular nonstationary external force. The influence of the nonlinear stochastic effects on the kink dynamics is considered with the help of the Fokker- Planck nonlinear equation with the shift coefficient dependent on the first moment of the kink momentum distribution function. Expressions are derived for average value and variance of the momentum. Examples are considered which demonstrate the influence of the external regular and random forces on the evolution of the average value and variance of the kink momentum. Within the formalism of the Fokker-Planck equation, the influence of nonstationary external force, random force, and dissipation effects on the kink dynamics is investigated in the sine-Gordon model. The equation of evolution of the kink momentum is obtained in the form of the stochastic differential equation in the Stratonovich sense within the framework of the well-known McLaughlin and Scott energy approach. The corresponding Fokker-Planck equation for the momentum distribution function coincides with the equation describing the Ornstein-Uhlenbek process with a regular nonstationary
Quantum mass shift of the soliton in the Skyrme model
NASA Astrophysics Data System (ADS)
Livne, Hillel
1993-02-01
The quantum mass shift of the soliton in the Skyrme model has been calculated from all nonzero modes. The calculations were carried out using a method applied earlier to the sine-Gordon model. The mass shifts do not depend on the baryonic spin, therefore they are the same for the nucleon and the Δ. Our model parameters are the pion decay constant Fπ, with its experimental value, and the pionic mass mπ, once in the chiral limit mπ=0 and also with the experimental value. We justify taking for the Skyrme parameter e the experimental value of gρππ, the mesonic ρ-pion coupling constant. The results depend on the vibrational energy. In this case an energy cutoff must be introduced. Using renormalization considerations as in the nonlinear σ model, we have chosen this cutoff to be eFπ=1136 MeV. Our results (for e=gρππ=6.11 and Fπ=186 MeV) are MN=996 MeV, MΔ=1593 MeV for mπ=0 MN=857 MeV, MΔ=1641 MeV for mπ=138 MeV. The spin dependence and the energy contribution of the coupling term between vibrations and rotations are being considered here only in a qualitative way.
Ising tricriticality in the extended Hubbard model with bond dimerization
NASA Astrophysics Data System (ADS)
Ejima, Satoshi; Essler, Fabian H. L.; Lange, Florian; Fehske, Holger
2016-06-01
We explore the quantum phase transition between Peierls and charge-density-wave insulating states in the one-dimensional, half-filled, extended Hubbard model with explicit bond dimerization. We show that the critical line of the continuous Ising transition terminates at a tricritical point, belonging to the universality class of the tricritical Ising model with central charge c =7 /10 . Above this point, the quantum phase transition becomes first order. Employing a numerical matrix-product-state based (infinite) density-matrix renormalization group method we determine the ground-state phase diagram, the spin and two-particle charge excitations gaps, and the entanglement properties of the model with high precision. Performing a bosonization analysis we can derive a field description of the transition region in terms of a triple sine-Gordon model. This allows us to derive field theory predictions for the power-law (exponential) decay of the density-density (spin-spin) and bond-order-wave correlation functions, which are found to be in excellent agreement with our numerical results.
Revisiting a model of ontogenetic growth: estimating model parameters from theory and data.
Moses, Melanie E; Hou, Chen; Woodruff, William H; West, Geoffrey B; Nekola, Jeffery C; Zuo, Wenyun; Brown, James H
2008-05-01
The ontogenetic growth model (OGM) of West et al. provides a general description of how metabolic energy is allocated between production of new biomass and maintenance of existing biomass during ontogeny. Here, we reexamine the OGM, make some minor modifications and corrections, and further evaluate its ability to account for empirical variation on rates of metabolism and biomass in vertebrates both during ontogeny and across species of varying adult body size. We show that the updated version of the model is internally consistent and is consistent with other predictions of metabolic scaling theory and empirical data. The OGM predicts not only the near universal sigmoidal form of growth curves but also the M(1/4) scaling of the characteristic times of ontogenetic stages in addition to the curvilinear decline in growth efficiency described by Brody. Additionally, the OGM relates the M(3/4) scaling across adults of different species to the scaling of metabolic rate across ontogeny within species. In providing a simple, quantitative description of how energy is allocated to growth, the OGM calls attention to unexplained variation, unanswered questions, and opportunities for future research. PMID:18419571
Bottomonium spectrum revisited
NASA Astrophysics Data System (ADS)
Segovia, Jorge; Ortega, Pablo G.; Entem, David R.; Fernández, Francisco
2016-04-01
We revisit the bottomonium spectrum motivated by the recently exciting experimental progress in the observation of new bottomonium states, both conventional and unconventional. Our framework is a nonrelativistic constituent quark model which has been applied to a wide range of hadronic observables from the light to the heavy quark sector, and thus the model parameters are completely constrained. Beyond the spectrum, we provide a large number of electromagnetic, strong and hadronic decays in order to discuss the quark content of the bottomonium states and give more insights about a better way to determine their properties experimentally.
Benedek, Mathias; Neubauer, Aljoscha C
2013-12-01
Fifty years ago, Mednick [Psychological Review, 69 (1962) 220] proposed an elaborate model that aimed to explain how creative ideas are generated and why creative people are more likely to have creative ideas. The model assumes that creative people have flatter associative hierarchies and as a consequence can more fluently retrieve remote associative elements, which can be combined to form creative ideas. This study aimed at revisiting Mednick's model and providing an extensive test of its hypotheses. A continuous free association task was employed and association performance was compared between groups high and low in creativity, as defined by divergent thinking ability and self-report measures. We found that associative hierarchies do not differ between low and high creative people, but creative people showed higher associative fluency and more uncommon responses. This suggests that creativity may not be related to a special organization of associative memory, but rather to a more effective way of accessing its contents. The findings add to the evidence associating creativity with highly adaptive executive functioning. PMID:24532853
The concept of quasi-integrability for modified non-linear Schrödinger models
NASA Astrophysics Data System (ADS)
Ferreira, L. A.; Luchini, G.; Zakrzewski, Wojtek J.
2012-09-01
We consider modifications of the nonlinear Schrödinger model (NLS) to look at the recently introduced concept of quasi-integrability. We show that such models possess an infinite number of quasi-conserved charges which present intriguing properties in relation to very specific space-time parity transformations. For the case of two-soliton solutions where the fields are eigenstates of this parity, those charges are asymptotically conserved in the scattering process of the solitons. Even though the charges vary in time their values in the far past and the far future are the same. Such results are obtained through analytical and numerical methods, and employ adaptations of algebraic techniques used in integrable field theories. Our findings may have important consequences on the applications of these models in several areas of non-linear science. We make a detailed numerical study of the modified NLS potential of the form V ~ (| ψ|2)2+ ɛ , with ɛ being a perturbation parameter. We perform numerical simulations of the scattering of solitons for this model and find a good agreement with the results predicted by the analytical considerations. Our paper shows that the quasi-integrability concepts recently proposed in the context of modifications of the sine-Gordon model remain valid for perturbations of the NLS model.
NASA Astrophysics Data System (ADS)
Bourdin, P. A.; Nakamura, T.; Narita, Y.
2015-12-01
Electromagnetic Parcile-In-Cell (PIC) simulations are widely used to study plasma phenomena where kinetic scales are coupled to fluid scales. One of these phenomena is the evolution of magnetic reconnection. Switch-on effects have been described earlier for magneto-/hydrodynamic (MHD and HD) simulations, where oscillations are ignited by the initial condition and the usual instantaneous way of starting a simulation run. Here we revisit the GEM setup (a Harris current sheet) and demonstrate the immediate generation of oscillations propagating perpendicular to the magnetic shear layer (in Bz). Also we show how these oscillations do not dissipate quickly and will later be mode-converted to generate wave power, first in By, much later also in Bx (pointing along the shear direction). One needs to take care not to interpret these oscillations as physical wave modes associated with the nature of reconnection. We propose a method to prevent such switch-on effects from the beginning, that should be considered for implementation in other PIC simulation codes as well.
Tibayrenc, Michel; Ayala, Francisco J
2015-11-01
Comparing the population structure of Trypanosoma cruzi with that of other pathogens, including parasitic protozoa, fungi, bacteria and viruses, shows that the agent of Chagas disease shares typical traits with many other species, related to a predominant clonal evolution (PCE) pattern: statistically significant linkage disequilibrium, overrepresented multilocus genotypes, near-clades (genetic subdivisions somewhat blurred by occasional genetic exchange/hybridization) and "Russian doll" patterns (PCE is observed, not only at the level of the whole species, but also, within the near-clades). Moreover, T. cruzi population structure exhibits linkage with the diversity of several strongly selected genes, with gene expression profiles, and with some major phenotypic traits. We discuss the evolutionary significance of these results, and their implications in terms of applied research (molecular epidemiology/strain typing, analysis of genes of interest, vaccine and drug design, immunological diagnosis) and of experimental evolution. Lastly, we revisit the long-term debate of describing new species within the T. cruzi taxon. PMID:26188332
Revisiting B_s rightarrow μ ^+μ ^- in the two-Higgs doublet models with Z_2 symmetry
NASA Astrophysics Data System (ADS)
Cheng, Xiao-Dong; Yang, Ya-Dong; Yuan, Xing-Bo
2016-03-01
We revisit the rare leptonic decay B_s rightarrow μ ^+ μ ^- in the two-Higgs doublet models (2HDMs) with a softly broken Z_2 symmetry, namely type-I, type-II, type-X and type-Y 2HDMs. We have derived the relevant full one-loop Wilson coefficients of the four 2HDMs from the recent calculation in the aligned 2HDM by Li, Lu and Pich, which could be mapped to all the four 2HDMs for both large and small tan β . It is found that a new term associated with the soft Z_2 symmetry breaking parameter M can be enhanced by tan ^2β in the type-II 2HDM, which has not been considered in the literature. Imposing both theoretical and experimental constraints, we have renewed the bounds on the parameter spaces of the four 2HDMs. Different from our previous paper, however, we find that all the four 2HDMs give sizable and similar contributions to overline{B}(B_s rightarrow μ ^+ μ ^-) within the stringently restricted parameter spaces, but very tiny as regards the mass-eigenstate rate asymmetry A_{Δ Γ }; this makes it unfeasible to discriminate the four types of 2HDM with the correlations between the observables in B_s rightarrow μ ^+ μ ^- decay.
NASA Astrophysics Data System (ADS)
Guterl, Jerome; Smirnov, Roman; Krasheninnikov, Sergei
2015-11-01
Plasma-material interactions may strongly influence plasma performance and life-time of future magnetic fusion devices. Understanding the multifaceted physics of hydrogen retention in plasma-facing components (PFC) is thus crucial, but remains challenging due to the wide spectrum of retention processes on PFC surface and in PFC bulk induced by long-time exposure of PFC to high flux of energy and particles. We revisit here some aspects of reaction-diffusion models used to investigate hydrogen retention in material. We focus on analysis of thermal desorption spectroscopy (TDS) experiment considering only one type of traps in material and first neglecting surface effects. We show that solute hydrogen concentration in retention region usually remains in equilibrium during TDS experiments. In this regime, analytic description of thermal desorption spectra indicates that trapping of solute hydrogen during TDS cannot be ignored. Main features of thermal desorption are then analytically described and refined interpretation of Arrhenius plots is proposed. Effects of surface processes on hydrogen outgassing during TDS experiments are then introduced and surface-limited outgassing regimes are discussed.
Revisiting a Statistical Shortcoming When Fitting the Langmuir Model to Sorption Data
Technology Transfer Automated Retrieval System (TEKTRAN)
The Langmuir model is commonly used for describing sorption behavior of reactive solutes to surfaces. Fitting the Langmuir model to sorption data requires either the use of nonlinear regression or, alternatively, linear regression using one of the linearized versions of the model. Statistical limit...
Revisiting single photon avalanche diode current-voltage modeling and transient characteristics
Javitt, M.; Savuskan, V. Merhav, T.; Nemirovsky, Y.
2014-05-28
A model for the current-voltage and transient behavior of Single Photon Avalanche Diodes (SPADs) based on device physics is presented. The results of the model are compared to actual measurements and a reasonable fit is seen. Additionally, the model provides a useful tool for designing quenching circuitry and determining optimal operation conditions of the SPAD.
ERIC Educational Resources Information Center
Clarke, Paul; Crawford, Claire; Steele, Fiona; Vignoles, Anna
2015-01-01
The use of fixed (FE) and random effects (RE) in two-level hierarchical linear regression is discussed in the context of education research. We compare the robustness of FE models with the modelling flexibility and potential efficiency of those from RE models. We argue that the two should be seen as complementary approaches. We then compare both…
Perfect plastic approximation revisited: a flowline network model for calving glaciers
NASA Astrophysics Data System (ADS)
Ultee, E.; Bassis, J. N.
2015-12-01
Accurate modeling of outlet glacier dynamics requires knowledge of many factors—ice thickness, bed topography, air/ocean temperature, precipitation rate—specific to individual glaciers, and for which only limited data exists. Furthermore, key processes such as iceberg calving remain poorly understood and difficult to include in models. In light of these challenges to even the most sophisticated models, there is great value in simple, computationally efficient models that can capture first-order effects. Many of the simplest models currently in use produce glacier profiles along a central flowline, either ignoring the contribution of tributaries or relying on a measure of "equivalent width" to handle those contributions. Here, we present a simple model that generalizes Nye's 1953 perfect plastic approximation so that it also predicts the position of the glacier terminus based on the yield strength. Moreover, our model simulates not only a central flowline, but the interactions of a network of tributaries. The model requires only minimal information: glacier geometry (network structure and bed topography, available from observation for select glaciers) and basal shear strength (a reasonably-constrained parameter). We apply the model to Columbia Glacier, Alaska and show that, despite its simplicity, the model is able to reproduce observed centerline profiles and terminus retreat for the main branch as well as selected tributaries. Finally, we illustrate how our model can be applied to constrain the calving contribution of individual glaciers to 21st century sea level rise.
Revisiting Aerosol Effects in Global Climate Models Using an Aerosol Lidar Simulator
NASA Astrophysics Data System (ADS)
Ma, P. L.; Chepfer, H.; Winker, D. M.; Ghan, S.; Rasch, P. J.
2015-12-01
Aerosol effects are considered a major source of uncertainty in global climate models and the direct and indirect radiative forcings have strong model dependency. These forcings are routinely evaluated (and calibrated) against observations, among them satellite retrievals are greatly used for their near-global coverage. However, the forcings calculated from model output are not directly comparable with those computed from satellite retrievals since sampling and algorithmic differences (such as cloud screening, noise reduction, and retrieval) between models and observations are not accounted for. It is our hypothesis that the conventional model validation procedures for comparing satellite observations and model simulations can mislead model development and introduce biases. Hence, we have developed an aerosol lidar simulator for global climate models that simulates the CALIOP lidar signal at 532nm. The simulator uses the same algorithms as those used to produce the "GCM-oriented CALIPSO Aerosol Product" to (1) objectively sample lidar signal profiles; and (2) derive aerosol fields (e.g., extinction profile, aerosol type, etc) from lidar signals. This allows us to sample and derive aerosol fields in the model and real atmosphere in identical ways. Using the Department of Energy's ACME model simulations, we found that the simulator-retrieved aerosol distribution and aerosol-cloud interactions are significantly different from those computed from conventional approaches, and that the model is much closer to satellite estimates than previously believed.
Re-visiting projections of PCBs in Lower Hudson River fish using model emulation.
Field, L Jay; Kern, John W; Rosman, Lisa B
2016-07-01
Remedial decision making at large contaminated sediment sites with bioaccumulative contaminants often relies on complex mechanistic models to forecast future concentrations and compare remedial alternatives. Remedial decision-making for the Hudson River PCBs Superfund site involved predictions of future levels of PCBs in Upper Hudson River (UHR) and Lower Hudson River (LHR) fish. This study applied model emulation to evaluate the impact of updated sediment concentrations on the original mechanistic model projections of time to reach risk-based target thresholds in fish in the LHR under Monitored Natural Attenuation (MNA) and the selected dredging remedy. The model emulation approach used a combination of nonlinear and linear regression models to estimate UHR water PCBs as a function of UHR sediment PCBs and to estimate fish concentrations in the LHR as a function of UHR water PCBs, respectively. Model emulation captured temporal changes in sediment, water, and fish PCBs predicted by the mechanistic model over the emulation period. The emulated model, using updated sediment concentrations and a revised estimate of recovery rate, matched the trend in annual monitoring data for white perch and largemouth bass in the LHR between 1997 and 2014. Our best predictions based on the emulated model indicate that the projected time to reach fish tissue risk-based thresholds in the LHR will take decades longer than the original mechanistic model projections. PMID:27017079
Revisiting Gaussian Process Regression Modeling for Localization in Wireless Sensor Networks.
Richter, Philipp; Toledano-Ayala, Manuel
2015-01-01
Signal strength-based positioning in wireless sensor networks is a key technology for seamless, ubiquitous localization, especially in areas where Global Navigation Satellite System (GNSS) signals propagate poorly. To enable wireless local area network (WLAN) location fingerprinting in larger areas while maintaining accuracy, methods to reduce the effort of radio map creation must be consolidated and automatized. Gaussian process regression has been applied to overcome this issue, also with auspicious results, but the fit of the model was never thoroughly assessed. Instead, most studies trained a readily available model, relying on the zero mean and squared exponential covariance function, without further scrutinization. This paper studies the Gaussian process regression model selection for WLAN fingerprinting in indoor and outdoor environments. We train several models for indoor/outdoor- and combined areas; we evaluate them quantitatively and compare them by means of adequate model measures, hence assessing the fit of these models directly. To illuminate the quality of the model fit, the residuals of the proposed model are investigated, as well. Comparative experiments on the positioning performance verify and conclude the model selection. In this way, we show that the standard model is not the most appropriate, discuss alternatives and present our best candidate. PMID:26370996
Revisiting Gaussian Process Regression Modeling for Localization in Wireless Sensor Networks
Richter, Philipp; Toledano-Ayala, Manuel
2015-01-01
Signal strength-based positioning in wireless sensor networks is a key technology for seamless, ubiquitous localization, especially in areas where Global Navigation Satellite System (GNSS) signals propagate poorly. To enable wireless local area network (WLAN) location fingerprinting in larger areas while maintaining accuracy, methods to reduce the effort of radio map creation must be consolidated and automatized. Gaussian process regression has been applied to overcome this issue, also with auspicious results, but the fit of the model was never thoroughly assessed. Instead, most studies trained a readily available model, relying on the zero mean and squared exponential covariance function, without further scrutinization. This paper studies the Gaussian process regression model selection for WLAN fingerprinting in indoor and outdoor environments. We train several models for indoor/outdoor- and combined areas; we evaluate them quantitatively and compare them by means of adequate model measures, hence assessing the fit of these models directly. To illuminate the quality of the model fit, the residuals of the proposed model are investigated, as well. Comparative experiments on the positioning performance verify and conclude the model selection. In this way, we show that the standard model is not the most appropriate, discuss alternatives and present our best candidate. PMID:26370996
NASA Astrophysics Data System (ADS)
Schmidt, Alexandre G. M.; Paiva, Milena M.
2012-03-01
We revisit the quantum two-person duel. In this problem, both Alice and Bob each possess a spin-1/2 particle which models dead and alive states for each player. We review the Abbott and Flitney result—now considering non-zero α1 and α2 in order to decide if it is better for Alice to shoot or not the second time—and we also consider a duel where players do not necessarily start alive. This simple assumption allows us to explore several interesting special cases, namely how a dead player can win the duel shooting just once, or how can Bob revive Alice after one shot, and the better strategy for Alice—being either alive or in a superposition of alive and dead states—fighting a dead opponent.
Myong, R. S.; Nagdewe, S. P.
2011-05-20
The Grad's closure for the high-order moment equation is revisited and, by extending his theory, a physically motivated closure is developed for the one-dimensional velocity shear gas flow. The closure is based on the physical argument of the relative importance of various terms appearing in the moment equation. Also, the closure is derived such that the resulting theory may be inclusive of the well established linear theory (Navier-Stokes-Fourier) as limiting case near local thermal equilibrium.
Modeling the Information-Seeking Behavior of Social Scientists: Ellis's Study Revisited.
ERIC Educational Resources Information Center
Meho, Lokman I.; Tibbo, Helen R.
2003-01-01
Revises David Ellis's information-seeking behavior model of social scientists which includes six generic features: starting, chaining, browsing, differentiating, monitoring, and extracting. Suggests four new features be added: accessing, networking, verifying, and information managing; and describes a new model that includes searching, accessing,…
Revisiting the Model of Creative Destruction: St. Jacobs, Ontario, a Decade Later
ERIC Educational Resources Information Center
Mitchell, Clare J. A.; de Waal, Sarah B.
2009-01-01
Ten years ago, the model of creative destruction was developed to predict the fate of communities that base their development on the commodification of rural heritage (Mitchell, C.J.A., 1998. Entrepreneurialism, commodification and creative destruction: a model of post-modern community development. Journal of Rural Studies 14, 273-286). Its…
The Two-Capacitor Problem Revisited: A Mechanical Harmonic Oscillator Model Approach
ERIC Educational Resources Information Center
Lee, Keeyung
2009-01-01
The well-known two-capacitor problem, in which exactly half the stored energy disappears when a charged capacitor is connected to an identical capacitor, is discussed based on the mechanical harmonic oscillator model approach. In the mechanical harmonic oscillator model, it is shown first that "exactly half" the work done by a constant applied…
NASA Astrophysics Data System (ADS)
Marshall, David P.; Munday, David R.; Allison, Lesley C.; Hay, Russell J.; Johnson, Helen L.
2016-01-01
Gill's (1968) model of the Antarctic Circumpolar Current (ACC) is reinterpreted for a stratified, reduced-gravity ocean, where the barotropic streamfunction is replaced by the pycnocline depth, and the bottom drag coefficient by the Gent and McWilliams eddy diffusivity. The resultant model gives a simple description of the lateral structure of the ACC that is consistent with contemporary descriptions of ACC dynamics. The model is used to investigate and interpret the sensitivity of the ACC to the latitudinal profile of the surface wind stress. A substantial ACC remains when the wind jet is shifted north of the model Drake Passage, even by several thousand kilometers. The integral of the wind stress over the circumpolar streamlines is found to be a useful predictor of the magnitude of the volume transport through the model Drake Passage, although it is necessary to correct for basin-wide zonal pressure gradients in order to obtain good quantitative agreement.
Revisiting node-based SIR models in complex networks with degree correlations
NASA Astrophysics Data System (ADS)
Wang, Yi; Cao, Jinde; Alofi, Abdulaziz; AL-Mazrooei, Abdullah; Elaiw, Ahmed
2015-11-01
In this paper, we consider two growing networks which will lead to the degree-degree correlations between two nearest neighbors in the network. When the network grows to some certain size, we introduce an SIR-like disease such as pandemic influenza H1N1/09 to the population. Due to its rapid spread, the population size changes slowly, and thus the disease spreads on correlated networks with approximately fixed size. To predict the disease evolution on correlated networks, we first review two node-based SIR models incorporating degree correlations and an edge-based SIR model without considering degree correlation, and then compare the predictions of these models with stochastic SIR simulations, respectively. We find that the edge-based model, even without considering degree correlations, agrees much better than the node-based models incorporating degree correlations with stochastic SIR simulations in many respects. Moreover, simulation results show that for networks with positive correlation, the edge-based model provides a better upper bound of the cumulative incidence than the node-based SIR models, whereas for networks with negative correlation, it provides a lower bound of the cumulative incidence.
CALPUFF and AERMOD model validation study in the near field: Martins Creek revisited.
Dresser, Alan L; Huizer, Robert D
2011-06-01
This paper describes a near-field validation study involving the steady-state, U.S. Environmental Protection Agency (EPA) guideline model AERMOD and the nonsteady-state puff model CALPUFF. Relative model performance is compared with field measurements collected near Martins Creek, PA-a rural, hilly area along the Pennsylvania-New Jersey border. The principal emission sources in the study were two coal-fired power plants with tall stacks and buoyant plumes. Over 1 yr of sulfur dioxide measurements were collected at eight monitors located at or above the two power plants' stack tops. Concurrent meteorological data were available at two sites. Both sites collected data 10 m above the ground. One of the sites also collected sonic detection and ranging measurements up to 420 m above ground. The ability of the two models to predict monitored sulfur dioxide concentrations was assessed in a four-part model validation. Each part of the validation applied different criteria and statistics to provide a comprehensive evaluation of model performance. Because of their importance in regulatory applications, an emphasis was placed on statistics that demonstrate the model's ability to reproduce the upper end of the concentration distribution. On the basis of the combined results of the four-part validation (i.e., weight of evidence), the performance of CALPUFF was judged to be superior to that of AERMOD. PMID:21751581
Revisiting the Cape Cod Bacteria Injection Experiment Using a Stochastic Modeling Approach
Maxwell, R M; Welty, C; Harvey, R W
2006-11-22
Bromide and resting-cell bacteria tracer tests carried out in a sand and gravel aquifer at the USGS Cape Cod site in 1987 were reinterpreted using a three-dimensional stochastic approach and Lagrangian particle tracking numerical methods. Bacteria transport was strongly coupled to colloid filtration through functional dependence of local-scale colloid transport parameters on hydraulic conductivity and seepage velocity in a stochastic advection-dispersion/attachment-detachment model. Information on geostatistical characterization of the hydraulic conductivity (K) field from a nearby plot was utilized as input that was unavailable when the original analysis was carried out. A finite difference model for groundwater flow and a particle-tracking model of conservative solute transport was calibrated to the bromide-tracer breakthrough data using the aforementioned geostatistical parameters. An optimization routine was utilized to adjust the mean and variance of the lnK field over 100 realizations such that a best fit of a simulated, average bromide breakthrough curve is achieved. Once the optimal bromide fit was accomplished (based on adjusting the lnK statistical parameters in unconditional simulations), a stochastic particle-tracking model for the bacteria was run without adjustments to the local-scale colloid transport parameters. Good predictions of the mean bacteria breakthrough data were achieved using several approaches for modeling components of the system. Simulations incorporating the recent Tufenkji and Elimelech [1] equation for estimating single collector efficiency were compared to those using the Rajagopalan and Tien [2] model. Both appeared to work equally well at predicting mean bacteria breakthrough using a constant mean bacteria diameter for this set of field conditions, with the Rajagopalan and Tien model yielding approximately a 30% lower peak concentration and less tailing than the Tufenkji and Elimelech formulation. Simulations using a distribution
The Goodwin model revisited: Hopf bifurcation, limit-cycle, and periodic entrainment
NASA Astrophysics Data System (ADS)
Woller, Aurore; Gonze, Didier; Erneux, Thomas
2014-08-01
The three-variable Goodwin oscillator is a minimal model demonstrating the emergence of oscillations in simple biochemical feedback systems. As a prototypical oscillator, this model was extensively studied from a theoretical point of view and applied to various biological systems, including circadian clocks. Here, we reexamine this model, derive analytically the amplitude equation near the Hopf bifurcation and investigate the effect of a periodic modulation of the oscillator. In particular, we compare the entrainment performance when the free oscillator displays either self-sustained or damped oscillations. We discuss the results in the context of circadian oscillators.
The consensus in the two-feature two-state one-dimensional Axelrod model revisited
NASA Astrophysics Data System (ADS)
Biral, Elias J. P.; Tilles, Paulo F. C.; Fontanari, José F.
2015-04-01
The Axelrod model for the dissemination of culture exhibits a rich spatial distribution of cultural domains, which depends on the values of the two model parameters: F, the number of cultural features and q, the common number of states each feature can assume. In the one-dimensional model with F = q = 2, which is closely related to the constrained voter model, Monte Carlo simulations indicate the existence of multicultural absorbing configurations in which at least one macroscopic domain coexist with a multitude of microscopic ones in the thermodynamic limit. However, rigorous analytical results for the infinite system starting from the configuration where all cultures are equally likely show convergence to only monocultural or consensus configurations. Here we show that this disagreement is due simply to the order that the time-asymptotic limit and the thermodynamic limit are taken in the simulations. In addition, we show how the consensus-only result can be derived using Monte Carlo simulations of finite chains.
A NEW APPROACH TO HYDROLOGIC MODELING: DERIVED DISTRIBUTIONS REVISITED. (R824780)
A fractal geometric procedure to model hydrologic (geophysical) phenomena is introduced. The method consists of using derived distributions, obtained by transforming arbitrary multinomial multifractal measures via fractal interpolating functions, to represent observed hydrologic ...
The mouse gut microbiome revisited: From complex diversity to model ecosystems.
Clavel, Thomas; Lagkouvardos, Ilias; Blaut, Michael; Stecher, Bärbel
2016-08-01
Laboratory mice are the most commonly used animal model in translational medical research. In recent years, the impact of the gut microbiota (i.e. communities of microorganisms in the intestine) on host physiology and the onset of diseases, including metabolic and neuronal disorders, cancers, gastrointestinal infections and chronic inflammation, became a focal point of interest. There is abundant evidence that mouse phenotypes in disease models vary greatly between animal facilities or commercial providers, and that this variation is associated with differences in the microbiota. Hence, there is a clear discrepancy between the widespread use of mouse models in research and the patchwork knowledge on the mouse gut microbiome. In the present manuscript, we summarize data pertaining to the diversity and functions of the mouse gut microbiota, review existing work on gnotobiotic mouse models, and discuss challenges and opportunities for current and future research in the field. PMID:26995267
Revisiting low-fidelity two-fluid models for gas-solids transport
NASA Astrophysics Data System (ADS)
Adeleke, Najeem; Adewumi, Michael; Ityokumbul, Thaddeus
2016-08-01
Two-phase gas-solids transport models are widely utilized for process design and automation in a broad range of industrial applications. Some of these applications include proppant transport in gaseous fracking fluids, air/gas drilling hydraulics, coal-gasification reactors and food processing units. Systems automation and real time process optimization stand to benefit a great deal from availability of efficient and accurate theoretical models for operations data processing. However, modeling two-phase pneumatic transport systems accurately requires a comprehensive understanding of gas-solids flow behavior. In this study we discuss the prevailing flow conditions and present a low-fidelity two-fluid model equation for particulate transport. The model equations are formulated in a manner that ensures the physical flux term remains conservative despite the inclusion of solids normal stress through the empirical formula for modulus of elasticity. A new set of Roe-Pike averages are presented for the resulting strictly hyperbolic flux term in the system of equations, which was used to develop a Roe-type approximate Riemann solver. The resulting scheme is stable regardless of the choice of flux-limiter. The model is evaluated by the prediction of experimental results from both pneumatic riser and air-drilling hydraulics systems. We demonstrate the effect and impact of numerical formulation and choice of numerical scheme on model predictions. We illustrate the capability of a low-fidelity one-dimensional two-fluid model in predicting relevant flow parameters in two-phase particulate systems accurately even under flow regimes involving counter-current flow.
Revisiting the homology modeling of G-protein coupled receptors: β1-adrenoceptor as an example.
Zhu, Mengyuan; Li, Minyong
2012-06-01
G-protein coupled receptors (GPCRs) are recognized to constitute the largest family of membrane proteins. Due to the disproportion in the quantity of crystal structures and their amino acid sequences, homology modeling contributes a reasonable and feasible approach to GPCR theoretical coordinates. With the brand new crystal structures resolved recently, herein we deliberated how to designate them as templates to carry out homology modeling in four aspects: (1) various sequence alignment methods; (2) protein weight matrix; (3) different sets of multiple templates; (4) active and inactive state of templates. The accuracy of models was evaluated by comparing the similarity of stereo conformation and molecular docking results between models and the experimental structure of Meleagris gallopavo β(1)-adrenergic receptor (Mg_Adrb1) that we desired to develop as an example. Our results proposed that: (1) Cobalt and MAFFT, two algorithms of sequence alignment, were suitable for single- and multiple-template modeling, respectively; (2) Blosum30 is applicable to align sequences in the case of low sequence identity; (3) multiple-template modeling is not always better than single-template one; (4) the state of template is an influential factor in simulating the GPCR structures as well. PMID:22454032
Revisiting Turbulence Model Validation for High-Mach Number Axisymmetric Compression Corner Flows
NASA Technical Reports Server (NTRS)
Georgiadis, Nicholas J.; Rumsey, Christopher L.; Huang, George P.
2015-01-01
Two axisymmetric shock-wave/boundary-layer interaction (SWBLI) cases are used to benchmark one- and two-equation Reynolds-averaged Navier-Stokes (RANS) turbulence models. This validation exercise was executed in the philosophy of the NASA Turbulence Modeling Resource and the AIAA Turbulence Model Benchmarking Working Group. Both SWBLI cases are from the experiments of Kussoy and Horstman for axisymmetric compression corner geometries with SWBLI inducing flares of 20 and 30 degrees, respectively. The freestream Mach number was approximately 7. The RANS closures examined are the Spalart-Allmaras one-equation model and the Menter family of kappa - omega two equation models including the Baseline and Shear Stress Transport formulations. The Wind-US and CFL3D RANS solvers are employed to simulate the SWBLI cases. Comparisons of RANS solutions to experimental data are made for a boundary layer survey plane just upstream of the SWBLI region. In the SWBLI region, comparisons of surface pressure and heat transfer are made. The effects of inflow modeling strategy, grid resolution, grid orthogonality, turbulent Prandtl number, and code-to-code variations are also addressed.
Revisit of the interacting holographic dark energy model after Planck 2015
NASA Astrophysics Data System (ADS)
Feng, Lu; Zhang, Xin
2016-08-01
We investigate the observational constraints on the interacting holographic dark energy model. We consider five typical interacting models with the interaction terms Q = 3βHρde, Q = 3βHρc, Q = 3βH(ρde+ρc), Q = 3βH√ρdeρc, and Q = 3βHρdeρc/ρde+ρc, respectively, where β is a dimensionless coupling constant. The observational data we use in this paper include the JLA compilation of type Ia supernovae data, the Planck 2015 distance priors data of cosmic microwave background observation, the baryon acoustic oscillations measurements, and the Hubble constant direct measurement. We make a comparison for these five interacting holographic dark energy models by employing the information criteria, and we find that, within the framework of holographic dark energy, the Q = 3βHρdeρc/ρde+ρc model is most favored by current data, and the Q = 3βHρc model is relatively not favored by current data. For the Q = 3βHρde and Q = 3βHρdeρc/ρde+ρc models, a positive coupling β can be detected at more than 2σ significance.
NASA Astrophysics Data System (ADS)
Liu, C.; Wen, H.; Liu, J.; Ko, M.; Yan, H.; Chang, L.
2012-12-01
translative offset between two similar images to be rapidly estimated. To meet the requirements in remote sensing and biomedical imaging, the technology of phase correlation has been extended to the sub-pixel level. Liu and Yan (2008) developed a robust phase correlation model using the based feature matching for image co-registration and DEM generation. Considering the fact that the Formosat-2 consecutive images are intrinsically stereo pairs with very narrow baselines, this innovative stereo-matching algorithm based on SPPC technique is employed to process Formosat-2 daily revisit stereo pairs with very narrow baselines. The detailed accuracy and efficiency analysis is investigated for the study area, Namasha, Kaohsiung, using the 50cm resolution aerial photo and the 2m resolution DEM derived from airborne LiDAR data. The archive of Formosat-2 images in Taiwan area collected from 2005 to 2012 was screened out, with the intention to select the consecutive pairs of those areas where major slope disasters occurred in the past eight years. This research encourages the repeated topography surveys of geomorphic changes using digital surface models deriving from Formosat-2 daily revisit stereo pair with very narrow baseline.
18 Years Later: Revisiting a Groundwater Model of the Cambric Site at NTS
NASA Astrophysics Data System (ADS)
Considine, E. J.; Wheatcraft, S. W.; Meerschaert, M. M.
2004-12-01
Since its advent in 1974, the Radionuclide Migration Project at the Nevada Test Site has spawned several interesting groundwater modeling ventures. Of interest to this research is the Cambric detonation site, where a tracer test was conducted from 1975 to 1991. Burbey and Wheatcraft (1986) built a groundwater/transport model of the Cambric site and at the time of calibration had achieved a good match to the measured data. Since then the predicted concentrations have diverged from the measured concentrations, which exhibit classic heavy-tailed behavior. It has been hypothesized that the Fractional Advection Dispersion Equation (FADE) will better predict these late-time high concentrations; this research will apply the FADE to the Cambric problem and aims to reach a more complete understanding of the physical significance of the coefficients contained in the FADE. We first built a preliminary groundwater model, employing the traditional Advection Dispersion Equation, in the hopes of duplicating Burbey's predicted concentrations. Burbey used the Deep Well Disposal Model, whereas this investigation used MODFLOW and MT3D. While the new model has produced a breakthrough curve fitting the peak concentration, it too fails to produce the heavy tail seen in the measured data. Also of concern is the nonuniqueness of the new model's solution; the best-fit breakthrough curve can be produced by changing either one of at least two parameters. We believe that both of these shortcomings (under predicted late-time concentrations and non-uniqueness) may be resolved by using the FADE. Not only does fractional theory permit heavy tails, but also it effectively replaces aquifer heterogeneity with fractional derivatives, thereby reducing the probability of a nonunique solution. Future work includes modeling the Cambric problem with Tadjeran and Meerschaert's numerical, fractional, radial-flow transport code (2003) and evaluating the code's applicability to varied flow and transport
NASA Astrophysics Data System (ADS)
Fischer, Lukas P.; Peter, Toni; Holm, Christian; de Graaf, Joost
2015-08-01
The so-called "raspberry" model refers to the hybrid lattice-Boltzmann and Langevin molecular dynamics scheme for simulating the dynamics of suspensions of colloidal particles, originally developed by Lobaskin and Dünweg [New J. Phys. 6, 54 (2004)], wherein discrete surface points are used to achieve fluid-particle coupling. This technique has been used in many simulation studies on the behavior of colloids. However, there are fundamental questions with regards to the use of this model. In this paper, we examine the accuracy with which the raspberry method is able to reproduce Stokes-level hydrodynamic interactions when compared to analytic expressions for solid spheres in simple-cubic crystals. To this end, we consider the quality of numerical experiments that are traditionally used to establish these properties and we discuss their shortcomings. We show that there is a discrepancy between the translational and rotational mobility reproduced by the simple raspberry model and present a way to numerically remedy this problem by adding internal coupling points. Finally, we examine a non-convex shape, namely, a colloidal dumbbell, and show that the filled raspberry model replicates the desired hydrodynamic behavior in bulk for this more complicated shape. Our investigation is continued in de Graaf et al. [J. Chem. Phys. 143, 084108 (2015)], wherein we consider the raspberry model in the confining geometry of two parallel plates.
Two-ball problem revisited: Limitations of event-driven modeling
NASA Astrophysics Data System (ADS)
Müller, Patric; Pöschel, Thorsten
2011-04-01
The main precondition of simulating systems of hard particles by means of event-driven modeling is the assumption of instantaneous collisions. The aim of this paper is to quantify the deviation of event-driven modeling from the solution of Newton’s equation of motion using a paradigmatic example: If a tennis ball is held above a basketball with their centers vertically aligned, and the balls are released to collide with the floor, the tennis ball may rebound at a surprisingly high speed. We show in this article that the simple textbook explanation of this effect is an oversimplification, even for the limit of perfectly elastic particles. Instead, there may occur a rather complex scenario including multiple collisions which may lead to a very different final velocity as compared with the velocity resulting from the oversimplified model.
NASA Astrophysics Data System (ADS)
Barakos, G.; Mitsoulis, E.; Assimacopoulos, D.
1994-04-01
Numerical simulations have been undertaken for the benchmark problem of natural convection flow in a square cavity. The control volume method is used to solve the conservation equations for laminar and turbulent flows for a series of Rayleigh numbers (Ra) reaching values up to 10(exp 10). The k-epsilon model has been used for turbulence modelling with and without logarithmic wall functions. Uniform and non-uniform (stretched) grids have been employed with increasing density to guarantee accurate solutions, especially near the walls for high Ra-values. ADI and SIP solvers are implemented to accelerate convergence. Excellent agreement is obtained with previous numerical solutions, while some discrepancies with others for high Ra-values may be due to a possibly different implementation of the wall functions. Comparisons with experimental data for heat transfer (Nusselt number) clearly demonstrates the limitations of the standard k-epsilon model with logarithmic wall functions, which gives significant overpredictions.
Revisiting the Concept of Level of Detail in 3d City Modelling
NASA Astrophysics Data System (ADS)
Biljecki, F.; Zhao, J.; Stoter, J.; Ledoux, H.
2013-09-01
This review paper discusses the concept of level of detail in 3D city modelling, and is a first step towards a foundation for a standardised definition. As an introduction, a few level of detail specifications, outlooks and approaches are given from the industry. The paper analyses the general uncertainties and shortcomings around the concept of level of detail in 3D city modelling such as ordinality and inconsistencies, and identifies factors that constitute a specific level of detail. The paper proposes a framework for a new consistent LoD definition which would consolidate present and future LoD paradigms, gives an example of an LoD specification, discusses open questions such as the contexts for which 3D city models are used in practice, and gives prospects for a future quantification and sorting of levels of detail.
Revisiting the cape cod bacteria injection experiment using a stochastic modeling approach
Maxwell, R.M.; Welty, C.; Harvey, R.W.
2007-01-01
Bromide and resting-cell bacteria tracer tests conducted in a sandy aquifer at the U.S. Geological Survey Cape Cod site in 1987 were reinterpreted using a three-dimensional stochastic approach. Bacteria transport was coupled to colloid filtration theory through functional dependence of local-scale colloid transport parameters upon hydraulic conductivity and seepage velocity in a stochastic advection - dispersion/attachment - detachment model. Geostatistical information on the hydraulic conductivity (K) field that was unavailable at the time of the original test was utilized as input. Using geostatistical parameters, a groundwater flow and particle-tracking model of conservative solute transport was calibrated to the bromide-tracer breakthrough data. An optimization routine was employed over 100 realizations to adjust the mean and variance ofthe natural-logarithm of hydraulic conductivity (InK) field to achieve best fit of a simulated, average bromide breakthrough curve. A stochastic particle-tracking model for the bacteria was run without adjustments to the local-scale colloid transport parameters. Good predictions of mean bacteria breakthrough were achieved using several approaches for modeling components of the system. Simulations incorporating the recent Tufenkji and Elimelech (Environ. Sci. Technol. 2004, 38, 529-536) correlation equation for estimating single collector efficiency were compared to those using the older Rajagopalan and Tien (AIChE J. 1976, 22, 523-533) model. Both appeared to work equally well at predicting mean bacteria breakthrough using a constant mean bacteria diameter for this set of field conditions. Simulations using a distribution of bacterial cell diameters available from original field notes yielded a slight improvement in the model and data agreement compared to simulations using an average bacterial diameter. The stochastic approach based on estimates of local-scale parameters for the bacteria-transport process reasonably captured
NASA Astrophysics Data System (ADS)
Roustan, Yelva; Duhanyan, Nora; Bocquet, Marc; Winiarek, Victor
2013-04-01
A sensitivity study of the numerical model, as well as, an inverse modelling approach applied to the atmospheric dispersion issues after the Chernobyl disaster are both presented in this paper. On the one hand, the robustness of the source term reconstruction through advanced data assimilation techniques was tested. On the other hand, the classical approaches for sensitivity analysis were enhanced by the use of an optimised forcing field which otherwise is known to be strongly uncertain. The POLYPHEMUS air quality system was used to perform the simulations of radionuclide dispersion. Activity concentrations in air and deposited to the ground of iodine-131, caesium-137 and caesium-134 were considered. The impact of the implemented parameterizations of the physical processes (dry and wet depositions, vertical turbulent diffusion), of the forcing fields (meteorology and source terms) and of the numerical configuration (horizontal resolution) were investigated for the sensitivity study of the model. A four dimensional variational scheme (4D-Var) based on the approximate adjoint of the chemistry transport model was used to invert the source term. The data assimilation is performed with measurements of activity concentrations in air extracted from the Radioactivity Environmental Monitoring (REM) database. For most of the investigated configurations (sensitivity study), the statistics to compare the model results to the field measurements as regards the concentrations in air are clearly improved while using a reconstructed source term. As regards the ground deposited concentrations, an improvement can only be seen in case of satisfactorily modelled episode. Through these studies, the source term and the meteorological fields are proved to have a major impact on the activity concentrations in air. These studies also reinforce the use of reconstructed source term instead of the usual estimated one. A more detailed parameterization of the deposition process seems also to be
NASA Astrophysics Data System (ADS)
Robock, Alan; Oman, Luke; Stenchikov, Georgiy L.
2007-07-01
Twenty years ago, the results of climate model simulations of the response to smoke and dust from a massive nuclear exchange between the superpowers could be summarized as "nuclear winter," with rapid temperature, precipitation, and insolation drops at the surface that would threaten global agriculture for at least a year. The global nuclear arsenal has fallen by a factor of three since then, but there has been an expansion of the number of nuclear weapons states, with additional states trying to develop nuclear arsenals. We use a modern climate model to reexamine the climate response to a range of nuclear wars, producing 50 and 150 Tg of smoke, using moderate and large portions of the current global arsenal, and find that there would be significant climatic responses to all the scenarios. This is the first time that an atmosphere-ocean general circulation model has been used for such a simulation and the first time that 10-year simulations have been conducted. The response to the 150 Tg scenario can still be characterized as "nuclear winter," but both produce global catastrophic consequences. The changes are more long-lasting than previously thought, however, because the new model, National Aeronautics and Space Administration Goddard Institute for Space Studies ModelE, is able to represent the atmosphere up to 80 km, and simulates plume rise to the middle and upper stratosphere, producing a long aerosol lifetime. The indirect effects of nuclear weapons would have devastating consequences for the planet, and continued nuclear arsenal reductions will be needed before the threat of nuclear winter is removed from the Earth.
ERIC Educational Resources Information Center
Bell, Cathy K.; Guerrero, Anthony; Matsu, Courtenay; Takeshita, Junji; Haning, William; Schultz, Karen
2010-01-01
Objective: The authors describe curricular modifications created in response to the changing culture of medical education, health care systems, academic medicine, and generational differences. The authors propose a model child psychiatry inpatient curriculum that is sustainable within a community teaching hospital in the 21st century. Methods: The…
Localization-Delocalization in Bridged Mixed-Valence Metal Clusters: Vibronic PKS Model Revisited.
Palii, A; Tsukerblat, B; Clemente-Juan, J M; Aldoshin, S M
2015-09-24
Here we describe a new vibronic model of mixed valence (MV) dimer inspired by the conventional Piepho, Krausz, and Schatz (PKS) approach. We attempted to partially lift the main restriction of the PKS model dealing with the vibronically independent moieties of a MV molecule. The refined version of the PKS model in which the bridging ligands are included deals with the three main interactions: electron transfer (integral t0) related to the high-symmetric ligand configuration, on-site vibronic coupling (parameter υ) arising from the modulation of the crystal field on the metal sites by the breathing displacements of their nearest ligand surroundings, and intercenter vibronic coupling (parameter ζ) describing the dependence of the electron transfer on ligand positions in the course of their breathing movement. We apply the modified model to the analysis of the adiabatic potentials and electronic density distributions in the minima of their lower sheets for the cases of one-electron MV dimer with long and short bridges and for the two-electron MV dimer exhibiting a valence disproportionation effect. The inclusion of the intercenter interaction in addition to the conventional PKS coupling is shown to produce a strong effect on the degree of localization in MV dimers and, in particular, on the assignments to the Robin and Day classes and on the conditions of stabilization of valence disproportionated states in bielectron transfer systems. PMID:26305153
The Raspberry model for hydrodynamic interactions revisited. II. The effect of confinement
NASA Astrophysics Data System (ADS)
de Graaf, Joost; Peter, Toni; Fischer, Lukas P.; Holm, Christian
2015-08-01
The so-called "raspberry" model refers to the hybrid lattice-Boltzmann (LB) and Langevin molecular dynamics schemes for simulating the dynamics of suspensions of colloidal particles, originally developed by Lobaskin and Dünweg [New J. Phys. 6, 54 (2004)], wherein discrete surface points are used to achieve fluid-particle coupling. In this paper, we present a follow up to our study of the effectiveness of the raspberry model in reproducing hydrodynamic interactions in the Stokes regime for spheres arranged in a simple-cubic crystal [Fischer et al., J. Chem. Phys. 143, 084107 (2015)]. Here, we consider the accuracy with which the raspberry model is able to reproduce such interactions for particles confined between two parallel plates. To this end, we compare our LB simulation results to established theoretical expressions and finite-element calculations. We show that there is a discrepancy between the translational and rotational mobilities when only surface coupling points are used, as also found in Part I of our joint publication. We demonstrate that adding internal coupling points to the raspberry can be used to correct said discrepancy in confining geometries as well. Finally, we show that the raspberry model accurately reproduces hydrodynamic interactions between a spherical colloid and planar walls up to roughly one LB lattice spacing.
Holland in Iceland revisited: an emic approach to evaluating U.S. vocational interest models.
Einarsdóttir, Sif; Rounds, James; Su, Rong
2010-07-01
An emic approach was used to test the structural validity and applicability of Holland's (1997) RIASEC (Realistic, Investigative, Artistic, Social, Enterprising, Conventional) model in Iceland. Archival data from the development of the Icelandic Interest Inventory (Einarsdóttir & Rounds, 2007) were used in the present investigation. The data included an indigenous pool of occupations and work-task items representing Iceland's world of work that had been administered to a sample of 597 upper secondary school students. Multidimensional scaling analysis and property vector fitting using Prediger's (1981) work-task dimensions were applied to the item responses to test if the RIASEC model could be identified. The results indicated that a 4-dimensional solution better explains the interest space in Iceland than Holland's 2-dimensional RIASEC representation. The work-task dimension of People-Things and the Sex-Type and Prestige dimensions were located in the 1st and 2nd dimensions of the multidimensional scaling solution, but Data-Ideas, a dimension critical to the RIASEC model, was not. The 3rd and 4th dimensions did not correspond to any dimensions previously detected in structural studies in the United States and seem to be related to specific ecological, cultural, and political forces in Iceland. These results demonstrate the importance of selecting representative indigenous occupations and work tasks when evaluating the RIASEC model. The present study is an example of the next step in a comprehensive cross-cultural research program on vocational interests, an emic investigation. PMID:21133585
Sulfur in the early martian atmosphere revisited: Experiments with a 3-D Global Climate Model
NASA Astrophysics Data System (ADS)
Kerber, Laura; Forget, François; Wordsworth, Robin
2015-11-01
Volcanic SO2 in the martian atmosphere has been invoked as a way to create a sustained or transient greenhouse during early martian history. Many modeling studies have been performed to test the feasibility of this hypothesis, resulting in a range of conclusions, from highly feasible to highly improbable. In this study we perform a wide range of simulations using the 3-D Laboratoire de Météorologie Dynamique Generic Global Climate Model (GCM) in order to place earlier results into context and to explore the sensitivity of model outcomes to parameters such as SO2 mixing ratio, atmospheric H2O content, background atmospheric pressure, and aerosol size, abundance, and composition. We conclude that SO2 is incapable of creating a sustained greenhouse on early Mars, and that even in the absence of aerosols, local and daily temperatures rise above 273 K for only for limited periods with favorable background CO2 pressures. In the presence of even small amounts of aerosols, the surface is dramatically cooled for realistic aerosol sizes. Brief, mildly warm conditions require the co-occurrence of many improbable factors, while cooling is achieved for a wide range of model parameters. Instead of causing warming, sulfur in the martian atmosphere may have caused substantial cooling, leading to the end of clement climate conditions on early Mars.
ERIC Educational Resources Information Center
Seaton, Marjorie; Marsh, Herbert W.; Parker, Philip D.; Craven, Rhonda G.; Yeung, Alexander S.
2015-01-01
The reciprocal effects model (REM) predicts a reciprocal relation between academic self-concept and academic achievement, whereby prior academic self-concept is associated with future gains in achievement, and prior achievement is related to subsequent academic self-concept. Although research in this area has been extensive, there has been a…
Meille, Christophe; Barbolosi, Dominique; Ciccolini, Joseph; Freyer, Gilles; Iliadis, Athanassios
2016-08-01
Controlling effects of drugs administered in combination is particularly challenging with a densified regimen because of life-threatening hematological toxicities. We have developed a mathematical model to optimize drug dosing regimens and to redesign the dose intensification-dose escalation process, using densified cycles of combined anticancer drugs. A generic mathematical model was developed to describe the main components of the real process, including pharmacokinetics, safety and efficacy pharmacodynamics, and non-hematological toxicity risk. This model allowed for computing the distribution of the total drug amount of each drug in combination, for each escalation dose level, in order to minimize the average tumor mass for each cycle. This was achieved while complying with absolute neutrophil count clinical constraints and without exceeding a fixed risk of non-hematological dose-limiting toxicity. The innovative part of this work was the development of densifying and intensifying designs in a unified procedure. This model enabled us to determine the appropriate regimen in a pilot phase I/II study in metastatic breast patients for a 2-week-cycle treatment of docetaxel plus epirubicin doublet, and to propose a new dose-ranging process. In addition to the present application, this method can be further used to achieve optimization of any combination therapy, thus improving the efficacy versus toxicity balance of such a regimen. PMID:26946136
The PANAS Structure Revisited: On the Validity of a Bifactor Model in Community and Forensic Samples
ERIC Educational Resources Information Center
Leue, Anja; Beauducel, Andre
2011-01-01
The Positive and Negative Affect Schedule (PANAS) is a widely used inventory for the assessment of affect in psychology and other applied sciences. Despite its popularity, the structure of the PANAS is still under debate. On the one hand, there is evidence of the traditional 2-factor model with Positive Affect (PA) and Negative Affect (NA) as…
Revisiting the Home Literacy Model of Reading Development in an Orthographically Consistent Language
ERIC Educational Resources Information Center
Manolitsis, George; Georgiou, George K.; Parrila, Rauno
2011-01-01
We examined the applicability of the Home Literacy Model in an orthographically transparent language (Greek). Seventy Greek children were followed from kindergarten until grade 4. In kindergarten they were tested in non-verbal intelligence, vocabulary, phonological sensitivity, rapid naming, and letter knowledge. The parents of the children also…
The Structure of Academic Self-Concepts Revisited: The Nested Marsh/Shavelson Model
ERIC Educational Resources Information Center
Brunner, Martin; Keller, Ulrich; Dierendonck, Christophe; Reichert, Monique; Ugen, Sonja; Fischbach, Antoine; Martin, Romain
2010-01-01
The nested Marsh/Shavelson (NMS) model integrates structural characteristics of academic self-concepts that have proved empirically incompatible in previous studies. Specifically, it conceives of academic self-concepts to be subject specific, strongly separated across domains, and hierarchically organized, with general academic self-concept at the…
Social Mobility and Post-Compulsory Education: Revisiting Boudon's Model of Social Opportunity
ERIC Educational Resources Information Center
Thompson, Ron; Simmons, Robin
2013-01-01
This paper uses Raymond Boudon's model of educational expansion to examine the relationship between education and social mobility, paying particular attention to post-compulsory education--an important site of social differentiation in England. The paper shows how Boudon focuses explicitly on the consequences of educational expansion, and…
Restructuring a Teacher Education Unit with P-12 Partner Schools. A Collaborative Model Revisited.
ERIC Educational Resources Information Center
Hegler, Kay L.; Forester, Lyn C.
This paper explores some of the many reasons to restructure, suggests the participants in restructuring, responds to Goodlad's (1990) postulates and essentials of restructuring and describes a model for restructuring between a teacher preparation program and P-12 schools. Reasons for restructuring can be classified into three categories: changes…
ERIC Educational Resources Information Center
Elander, Kelly; Cronje, Johannes C.
2016-01-01
While learning interventions were traditionally classified as either objectivist or constructivist there has been an increasing tendency for practitioners to use elements of both paradigms in a consolidated fashion. This has meant a re-think of the two perspectives as diametrically opposite. A four-quadrant model, first proposed in this journal…
Holland in Iceland Revisited: An Emic Approach to Evaluating U.S. Vocational Interest Models
ERIC Educational Resources Information Center
Einarsdottir, Sif; Rounds, James; Su, Rong
2010-01-01
An emic approach was used to test the structural validity and applicability of Holland's (1997) RIASEC (Realistic, Investigative, Artistic, Social, Enterprising, Conventional) model in Iceland. Archival data from the development of the Icelandic Interest Inventory (Einarsdottir & Rounds, 2007) were used in the present investigation. The data…
Re-visiting crash-speed relationships: A new perspective in crash modelling.
Imprialou, Maria-Ioanna M; Quddus, Mohammed; Pitfield, David E; Lord, Dominique
2016-01-01
Although speed is considered to be one of the main crash contributory factors, research findings are inconsistent. Independent of the robustness of their statistical approaches, crash frequency models typically employ crash data that are aggregated using spatial criteria (e.g., crash counts by link termed as a link-based approach). In this approach, the variability in crashes between links is explained by highly aggregated average measures that may be inappropriate, especially for time-varying variables such as speed and volume. This paper re-examines crash-speed relationships by creating a new crash data aggregation approach that enables improved representation of the road conditions just before crash occurrences. Crashes are aggregated according to the similarity of their pre-crash traffic and geometric conditions, forming an alternative crash count dataset termed as a condition-based approach. Crash-speed relationships are separately developed and compared for both approaches by employing the annual crashes that occurred on the Strategic Road Network of England in 2012. The datasets are modelled by injury severity using multivariate Poisson lognormal regression, with multivariate spatial effects for the link-based model, using a full Bayesian inference approach. The results of the condition-based approach show that high speeds trigger crash frequency. The outcome of the link-based model is the opposite; suggesting that the speed-crash relationship is negative regardless of crash severity. The differences between the results imply that data aggregation is a crucial, yet so far overlooked, methodological element of crash data analyses that may have direct impact on the modelling outcomes. PMID:26571206
The chemistry of C3 and C2 in cometary comae. I. Current models revisited
NASA Astrophysics Data System (ADS)
Weiler, M.
2012-02-01
Context. It is widely accepted that C3 and in particular C2 play an important role in the compositional classification of comets, and the most well-established classification scheme to date is indeed based on the Haser production rates of these two radicals. A link between both C3 and C2 and their actual parent molecules would therefore be desirable to allow both a physical and chemical interpretation of the compositional classification of comets. A first detailed study was performed by Helbert and collaborators for comet C/1995 O1 (Hale-Bopp), which suggested a link between these two radicals and the parent species C2H2, C2H6, and C3H4. Aims: We extend previous studies of the formation of C3 and C2 to other comets at smaller heliocentric distances. The proposed model for the formation of these two radicals is tested for these comets. Methods: We compare the observed radial column densities of C3 and C2 in the comae of the comets C/2001 Q4 (NEAT), C/2002 T7 (LINEAR), and 9P/Tempel 1 with the results of a one-dimensional multi-fluid coma chemistry model. The shape of the modelled radial column density profiles are compared with the observed profiles, and the production rates of the parent species are computed by fitting the observational data with the model. Results: We do not find that C2H6 is a significant parent species of the observed cometary C2. Furthermore, electron impact reactions do not play an important role in the formation of C3. The model for the formation of C3 and C2 derived from comet Hale-Bopp is inconsistent with observations of these radicals in other comets. Based on observations collected at the European Southern Observatory, Chile (ESO programmes 073.C-0571 and 075.C-0355).
One-dimensional Bose gas in optical lattices of arbitrary strength
NASA Astrophysics Data System (ADS)
Astrakharchik, Grigory E.; Krutitsky, Konstantin V.; Lewenstein, Maciej; Mazzanti, Ferran
2016-02-01
One-dimensional Bose gas with contact interaction in optical lattices at zero temperature is investigated by means of the exact diffusion Monte Carlo algorithm. The results obtained from the fundamental continuous model are compared with those obtained from the lattice (discrete) Bose-Hubbard model, using exact diagonalization, and from the quantum sine-Gordon model. We map out the complete phase diagram of the continuous model and determine the regions of applicability of the Bose-Hubbard model. Various physical quantities characterizing the systems are calculated, and it is demonstrated that the sine-Gordon model used for shallow lattices is inaccurate.
The Rotating Morse-Pekeris Oscillator Revisited
ERIC Educational Resources Information Center
Zuniga, Jose; Bastida, Adolfo; Requena, Alberto
2008-01-01
The Morse-Pekeris oscillator model for the calculation of the vibration-rotation energy levels of diatomic molecules is revisited. This model is based on the realization of a second-order exponential expansion of the centrifugal term about the minimum of the vibrational Morse oscillator and the subsequent analytical resolution of the resulting…
The Zee-Babu model revisited in the light of new data
NASA Astrophysics Data System (ADS)
Herrero-Garcia, Juan; Nebot, Miguel; Rius, Nuria; Santamaria, Arcadi
2014-08-01
We update previous analyses of the Zee-Babu model in the light of new data, e.g., the mixing angle θ13, the rare decay μ→eγ and the LHC results. We also analyze the possibility of accommodating the deviations in Γ(H→γγ) hinted by the LHC experiments, and the stability of the scalar potential. We find that neutrino oscillation data and low energy constraints are still compatible with masses of the extra charged scalars accessible to LHC. Moreover, if any of them is discovered, the model can be falsified by combining the information on the singly and doubly charged scalar decay modes with neutrino data. Conversely, if the neutrino spectrum is found to be inverted and the CP phase δ is quite different from π, the masses of the charged scalars will be well outside the LHC reach.
Microscopic Car-Following Models Revisited: From Road Works to Fundamental Diagrams
NASA Astrophysics Data System (ADS)
Seidel, T.; Gasser, I.; Werner, B.
2009-01-01
We analyze the dynamics of the classical optimal velocity model for the case of road works. We introduce a new viewpoint, the so-called rotation solutions, which in case of an additional symmetry leads to Ponies-on-a-Merry-Go-Round-solutions (POMs) [D. G. Aronson, M. Golubitsky, and J. Mallet-Paret, Nonlinearity, 4 (1991), p. 903]. This approach, which is also useful for the case without road works, opens the possibility of analytical and numerical bifurcation studies, which show a wide variety in the possible dynamics of this very simple model. In addition, we mimic different measurement approaches and recover the famous inverse Greek lambda structure in the fundamental diagram.
NASA Astrophysics Data System (ADS)
Crifo, J.-F.; Loukianov, G. A.; Rodionov, A. V.; Zakharov, V. V.
2005-07-01
This paper describes the first computations of dust distributions in the vicinity of an active cometary nucleus, using a multidimensional Direct Simulation Monte Carlo Method (DSMC). The physical model is simplistic: spherical grains of a broad range of sizes are liberated by H 2O sublimation from a selection of nonrotating sunlit spherical nuclei, and submitted to the nucleus gravity, the gas drag, and the solar radiation pressure. The results are compared to those obtained by the previously described Dust Multi-Fluid Method (DMF) and demonstrate an excellent agreement in the regions where the DMF is usable. Most importantly, the DSMC allows the discovery of hitherto unsuspected dust coma properties in those cases which cannot be treated by the DMF. This leads to a thorough reconsideration of the properties of the near-nucleus dust dynamics. In particular, the results show that (1) none of the three forces considered here can be neglected a priori, in particular not the radiation pressure; (2) hitherto unsuspected new families of grain trajectories exist, for instance trajectories leading from the nightside surface to the dayside coma; (3) a wealth of balistic-like trajectories leading from one point of the surface to another point exist; on the dayside, such trajectories lead to the formation of "mini-volcanoes." The present model and results are discussed carefully. It is shown that (1) the neglected forces (inertia associated with a nucleus rotation, solar tidal force) are, in general, not negligible everywhere, and (2) when allowing for these additional forces, a time-dependent model will, in general, have to be used. The future steps of development of the model are outlined.
Huxley's Model for Muscle Contraction Revisited: The Importance of Microscopic Reversibility.
Astumian, R Dean
2015-01-01
Andrew Huxley's model for muscle contraction is the first mechanistic description of how an energy-providing chemical reaction, ATP hydrolysis, can be coupled by a molecule (myosin) to do work in the environment in a cyclic process. The model was originally used to fit experimentally obtained force vs velocity curves, and has served as a paradigm for understanding mechanochemical coupling ever since. Despite the remarkable success in fitting kinetic data, Huxley's model is thermodynamically inconsistent in several regards, most notably in its failure to include thermal noise in the description of the mechanical transitions by which motion occurs. This inconsistency has led subsequent workers to incorrect conclusions regarding the importance of mechanical transitions for determining the direction of motion, the efficiency of energy conversion, the ratio of forward to backward steps, and the applied force necessary to stop the motion of chemically driven molecular motors. In this chapter an extension of Huxley's model is described where the principle of microscopic reversibility provides a framework for developing a thermodynamically consistent description of a molecular machine. The results show clearly that mechanical strain and the so-called "power stroke" are irrelevant for determining the directionality and thermodynamic properties of any chemically driven molecular motor. Instead these properties are controlled entirely by the chemical specificity that describes how the relative rates of the ATP hydrolysis reaction depend, by allosteric interactions, on the mechanical state of the molecule. This mechanism has been termed an "information ratchet" in the literature. In contrast to the results for chemical driving, a power stroke can be a key component for the operation of an optically driven motor, the transitions of which do not obey microscopic reversibility. PMID:26122749
The faint young Sun problem revisited with a 3-D climate-carbon model - Part 1
NASA Astrophysics Data System (ADS)
Le Hir, G.; Teitler, Y.; Fluteau, F.; Donnadieu, Y.; Philippot, P.
2014-04-01
During the Archaean, the Sun's luminosity was 18 to 25% lower than the present day. One-dimensional radiative convective models (RCM) generally infer that high concentrations of greenhouse gases (CO2, CH4) are required to prevent the early Earth's surface temperature from dropping below the freezing point of liquid water and satisfying the faint young Sun paradox (FYSP, an Earth temperature at least as warm as today). Using a one-dimensional (1-D) model, it was proposed in 2010 that the association of a reduced albedo and less reflective clouds may have been responsible for the maintenance of a warm climate during the Archaean without requiring high concentrations of atmospheric CO2 (pCO2). More recently, 3-D climate simulations have been performed using atmospheric general circulation models (AGCM) and Earth system models of intermediate complexity (EMIC). These studies were able to solve the FYSP through a large range of carbon dioxide concentrations, from 0.6 bar with an EMIC to several millibars with AGCMs. To better understand this wide range in pCO2, we investigated the early Earth climate using an atmospheric GCM coupled to a slab ocean. Our simulations include the ice-albedo feedback and specific Archaean climatic factors such as a faster Earth rotation rate, high atmospheric concentrations of CO2 and/or CH4, a reduced continental surface, a saltier ocean, and different cloudiness. We estimated full glaciation thresholds for the early Archaean and quantified positive radiative forcing required to solve the FYSP. We also demonstrated why RCM and EMIC tend to overestimate greenhouse gas concentrations required to avoid full glaciations or solve the FYSP. Carbon cycle-climate interplays and conditions for sustaining pCO2 will be discussed in a companion paper.
The Educational Model of Private Colleges of Osteopathic Medicine: Revisited for 2003-2013.
Cummings, Mark
2015-12-01
Trends in the development of new private colleges of osteopathic medicine (COMs) described by the author in 2003 have accelerated in the ensuing decade. During 2003 to 2013, 10 new COMs as well as 2 remote teaching sites and 4 new branch campuses at private institutions were accredited, leading to a 98% increase in the number of students enrolled in private COMs. The key features of the private COM educational model during this period were a reliance on student tuition, the establishment of health professions education programs around the medical school, the expansion of class size, the creation of branch campuses and remote teaching sites, an environment that emphasizes teaching over research, and limited involvement in facilities providing clinical services to patients. There is institutional ownership of preclinical instruction, but clinical instruction occurs in affiliated hospitals and medical institutions where students are typically taught by volunteer and/or adjunct faculty.Between 2003 and 2013, this model attracted smaller universities and organizations, which implemented the strategies of established private COMs in initiating new private COMs, branch campuses, and remote teaching sites. The new COMs have introduced changes to the osteopathic profession and private COM model by expanding to new parts of the country and establishing the first for-profit medical school accredited in the United States in modern times. They have also increased pressure on the system of osteopathic graduate medical education, as the number of funded GME positions available to their graduates is less than the need. PMID:26039139
Revisiting the thermodynamic modelling of type I gas-hydroquinone clathrates.
Conde, M M; Torré, J P; Miqueu, C
2016-04-21
Under specific pressure and temperature conditions, certain gaseous species can be engaged in a host lattice of hydroquinone molecules, forming a supramolecular entity called a gas hydroquinone clathrate. This study is devoted to the thermodynamic modelling of type I hydroquinone clathrates. The gases considered in this work are argon, krypton, xenon, methane, nitrogen, oxygen and hydrogen sulphide. The basic van der Waals and Platteeuw model, which is, for example, not able to predict well the phase equilibrium properties of such clathrates at high temperature, is modified and extended by considering first the solubility of the guest in solid HQ and then the mutual interactions between the gaseous molecules inside the clathrate structure (i.e. guest-guest interactions). Other improvements of the basic theory, such as the choice of the reference state, are proposed, and a unique set of thermodynamic parameters valid for all the studied guests are finally calculated. Very good agreement is obtained between the model predictions and the experimental data available in the literature. Our results clearly demonstrate that the highest level of theory is necessary to describe well both the triphasic equilibrium line (where the HQ clathrate, the native hydroquinone HQα and the gas coexist), the occupancy of the guest in the clathrate, and the intercalation enthalpy. PMID:27004460
Zhang, Xuesong; Srinivasan, Ragahvan; Arnold, J. G.; Izaurralde, Roberto C.; Bosch, David
2011-04-21
Accurate analysis of water flow pathways from rainfall to streams is critical for simulating water use, climate change impact, and contaminants transport. In this study, we developed a new scheme to simultaneously calibrate surface flow (SF) and baseflow (BF) simulations of soil and water assessment tool (SWAT) by combing evolutionary multi-objective optimization (EMO) and BF separation techniques. The application of this scheme demonstrated pronounced trade-off of SWAT’s performance on SF and BF simulations. The simulated major water fluxes and storages variables (e.g. soil moisture, evapotranspiration, and groundwater) using the multiple parameters from EMO span wide ranges. Uncertainty analysis was conducted by Bayesian model averaging of the Pareto optimal solutions. The 90% confidence interval (CI) estimated using all streamflows substantially overestimate the uncertainty of low flows on BF days while underestimating the uncertainty of high flows on SF days. Despite using statistical criteria calculated based on streamflow for model selection, it is important to conduct diagnostic analysis of the agreement of SWAT behaviour and actual watershed dynamics. The new calibration technique can serve as a useful tool to explore the tradeoff between SF and BF simulations and provide candidates for further diagnostic assessment and model identification.
Lithospheric Flexure and Sedimentary Basin Evolution: the Steer's Head Model Re-visited
NASA Astrophysics Data System (ADS)
Moore, J. D. P.; Watts, A. B.
2015-12-01
Backstripping studies of biostratigraphic data from deep wells show that sediment loading is one of the main factors controlling the subsidence and uplift history of sedimentary basins. Previous studies based on single layer models of elastic and viscoelastic plates overlying an inviscid fluid have shown that sediment loading, together with a tectonic subsidence that decreases exponentially with time, can explain the large-scale 'architecture' of rift-type basins and, in some cases, details of their internal stratigraphy such as onlap and offlap patterns. One problem with these so-called 'steer's head' models is that they were based on a simple rheological model in which the long-term strength of the lithosphere increased with thermal age. Recent oceanic flexure studies, however, reveal that the long-term strength of the lithosphere depends not only on thermal age, but also load age. We have used the thermal structure based on plate cooling models, together with recent experimentally-derived flow laws, to compute the viscosity structure of the lithosphere and a new analytical model to compute the flexure of a multilayer viscoelastic plate by a trapezoid-shaped sediment load at different times since basin initiation. If we define the nondimensional number Dw = τm/τt, where τm is the Maxwell time constant and τt is the thermal time constant, we find that for Dw << 1 the flexure approximates that of an elastic plate and an onlap pattern forms at the edge of basin (Fig. 1), whereas for Dw >> 1 the flexure approximates that of a viscoelastic plate and an offlap pattern develops (Fig. 2). Interestingly Dw ~ 1 produces a basin in which onlap dominates its early evolution while offlap dominates its later evolution and an unconformity separates the two different stratal patterns (Fig. 3). Therefore, when consideration is given to the fact that the long-term strength of the lithosphere depends on both thermal and load age we are able to produce stratal geometries that
NASA Astrophysics Data System (ADS)
Joetzjer, E.; Poulter, B.; Ciais, P.; Sala, A.; Sack, L.; Bartlett, M.
2015-12-01
In the past decade, two extreme droughts experienced by the Amazon rainforest led to a perturbation of carbon cycle dynamics and forest structure, partly through an increase in tree mortality. While there is a relatively strong consensus in CMIP5 projections for an increase in both frequency and intensity of droughts across the Amazon, the potential for forest die-off constitutes a large uncertainty in projections of climate impacts on terrestrial ecosystems and carbon cycle feedbacks. Two long-term through fall exclusion experiments (TFE) provided novel observations of Amazonian ecosystem responses under drought. These experiments also provided a great opportunity to evaluate and improve models' behavior under drought by comparing simulations and observations. While current DGVM use a wide array of algorithms to represent mortality, most are associated with large uncertainty for representing drought-induced mortality, and require updating to include current information of physiological processes. During very strong droughts, the leaves desiccate and stems may undergo catastrophic embolism. However, even before that point, stomata close, to minimize excessive water loss and risk of hydraulic failure, which reduces carbon assimilation. To maintain respiration and other functions, plants may eventually deplete stored non-structural carbon compounds (NSC), which may have negative impacts on plant and eventually increase the probability of mortality.Here, we describe a new parameterization of the mortality process induced by drought using the ORCHIDEE-CAN dynamic vegetation model and test it using the two TFE results. We first updated and evaluated both the representation of hydraulic architecture and the NSC pool dynamics using in situ data. We implemented a direct climate effect on mortality through catastrophic stem embolism, based on hydraulic vulnerability curves. In addition, we explored the role of NSC on hydraulic failure and mortality by coupling in the model
Revisiting ENSO Coupled Instability Theory and SST Error Growth in a Fully Coupled Model
NASA Astrophysics Data System (ADS)
Larson, S.; Kirtman, B. P.
2015-12-01
In an effort to untangle certain mechanisms contributing to the initiation of ENSO events, a coupled model framework is presented to isolate coupled instability induced SST error (or anomaly) growth in the ENSO region. The modeling framework using CCSM4 allows for seasonal ensembles of initialized simulations that are utilized to quantify the spatial and temporal behavior of coupled instabilities and the associated implications for ENSO predictability. The experimental design allows for unstable growth of initial perturbations that are not prescribed and several cases exhibit sufficiently rapid growth to produce ENSO events that do not require a previous ENSO event, large-scale wind trigger, or subsurface heat content precursor. Without these precursors, however, ENSO amplitude is reduced, suggesting that a combination of processes is essential to achieving peak amplitude in CCSM4. The results imply that even without classical precursors, including western Pacific "preconditioning," ENSO events can be excited via coupled instabilities in fully coupled models. By removing the subsurface heat content precursor, however, essentially a lower bounds for ENSO predictability in CCSM4 is established, although seasonal ensembles initialized later in the calendar year retain some predictability. The initial error growth exhibits strong seasonality with fastest growth during spring and summer and also dependence on the initialization month with fastest growth occurring in the July ensemble. The error growth displays a well-defined seasonal limit with ensembles initialized in the winter or spring exhibiting a clear seasonal halt in error growth around September, consistent with increased background stability typical during fall. Overall, dynamically driven error growth in CCSM4 is deemed best characterized by strong seasonality, dependence on the initialization month, and nonlinearity. The results pose real implications for predictability because the final error structure is
Revisiting the infrared spectra of active galactic nuclei with a new torus emission model
NASA Astrophysics Data System (ADS)
Fritz, J.; Franceschini, A.; Hatziminaoglou, E.
2006-03-01
We describe improved modelling of the emission by dust in a toroidal-like structure heated by a central illuminating source within active galactic nuclei (AGNs). We have chosen a simple but realistic torus geometry, a flared disc, and a dust grain distribution function including a full range of grain sizes. The optical depth within the torus is computed in detail taking into account the different sublimation temperatures of the silicate and graphite grains, which solves previously reported inconsistencies in the silicate emission feature in type 1 AGNs. We exploit this model to study the spectral energy distributions (SEDs) of 58 extragalactic (both type 1 and type 2) sources using archival optical and infrared data. We find that both AGN and starburst contributions are often required to reproduce the observed SEDs, although in a few cases they are very well fitted by a pure AGN component. The AGN contribution to the far-infrared luminosity is found to be higher in type 1 sources, with all the type 2 requiring a substantial contribution from a circumnuclear starburst. Our results appear in agreement with the AGN unified scheme, because the distributions of key parameters of the torus models turn out to be compatible for type 1 and type 2 AGNs. Further support to the unification concept comes from comparison with medium-resolution infrared spectra of type 1 AGNs by the Spitzer observatory, showing evidence for a moderate silicate emission around 10 μm, which our code reproduces. From our analysis we infer accretion flows in the inner nucleus of local AGNs characterized by high equatorial optical depths (AV~= 100), moderate sizes (Rmax < 100 pc) and very high covering factors (f~= 80 per cent) on average.
Chayanov revisited: A model for the economics of complex kin units
Hammel, E. A.
2005-01-01
Chayanov's model of the peasant economy is based on autarkic nuclear family households. Expansion to the more complex households and kin groups common in peasant societies shows that the sharp changes Chayanov observed in the consumer/producer ratio over the domestic cycle are smoothed by the intergenerational structure of complex households and extended kin groups. This amelioration may be retarded by competition between constituent units. Understanding the dynamics of the developmental cycle and micropolitics of domestic groups is a useful correction to Chayanov's widely used formulation, especially in developing countries where complex kin structures are common. PMID:15867158
Revisiting models of crustal growth; the role of preservation and destruction
NASA Astrophysics Data System (ADS)
Roberts, Nick; Spencer, Christopher
2015-04-01
The rate of growth of the continental crust remains a topic of much debate. Individual continents and cratons show apparent episodic magmatic activity and associated continental growth. Because our archive of Earth's history is locked up in the continental crust, most records of Earth history similarly have an episodic nature to them. One long-standing model has been that these episodes of continental growth are related to both large mantle upwelling and mantle overturn events. Another model that has been in and out of favour, is that continental growth was rapid in the early Earth history, and that net growth has been near-zero since at least the Mesoarchaean. Crustal growth rates based on modelling of isotopic systems tend to feature an increasing volume through time, with a faster rate up to the Meso- to Neoarchaean. As well as being derived from the mantle, continental crust can also be returned to the mantle. The net continental growth rate is a balance between this addition and loss. A problem with many crustal growth models is that they are based on the record preserved today. Although attempts have been made to account for intra-continental recycling, continental loss back into the mantle is generally unaccounted for. For this reason, many crustal growth curves can be considered a minimum. With an approach using Hf and O isotopes in zircon, it can be shown that at least 50% of the current volume of continental crust was formed by 3 Ga, and that of this current volume, at least 45% has been recycled intra-crustally. Current estimates of crustal mass-balance suggest that continental addition is similar to rates of continental loss. But how far back in time has this been the case? If plate tectonics and deep subduction have been around since the late Archaean, then it is likely that rates of reworking have been high since this time also. The hotly debated question: what style of plate tectonics and continental growth mechanisms existed throughout the Archaean
Revisiting the nonequilibrium phase transition of the triplet-creation model
NASA Astrophysics Data System (ADS)
Cardozo, G. O.; Fontanari, J. F.
2006-06-01
The nonequilibrium phase transition in the triplet-creation model is investigated using critical spreading and the conservative diffusive contact process. The results support the claim that at high enough diffusion the phase transition becomes discontinuous. As the diffusion probability increases the critical exponents change continuously from the ordinary directed percolation (DP) class to the compact directed percolation (CDP). The fractal dimension of the critical cluster, however, switches abruptly between those two universality classes. Strong crossover effects in both methods make it difficult, if not impossible, to establish the exact location of the tricritical point.
Cats protecting birds revisited.
Fan, Meng; Kuang, Yang; Feng, Zhilan
2005-09-01
In this paper, we revisit the dynamical interaction among prey (bird), mesopredator (rat), and superpredator (cat) discussed in [Courchamp, F., Langlais, M., Sugihara, G., 1999. Cats protecting birds: modelling the mesopredator release effect. Journal of Animal Ecology 68, 282-292]. First, we develop a prey-mesopredator-superpredator (i.e., bird-rat-cat, briefly, BRC) model, where the predator's functional responses are derived based on the classical Holling's time budget arguments. Our BRC model overcomes several model construction problems in Courchamp et al. (1999), and admits richer, reasonable and realistic dynamics. We explore the possible control strategies to save or restore the bird by controlling or eliminating the rat or the cat when the bird is endangered. We establish the existence of two types of mesopredator release phenomena: severe mesopredator release, where once superpredators are suppressed, a burst of mesopredators follows which leads their shared prey to extinction; and mild mesopredator release, where the mesopredator release could assert more negative impact on the endemic prey but does not lead the endemic prey to extinction. A sharp sufficient criterion is established for the occurrence of severe mesopredator release. We also show that, in a prey-mesopredator-superpredator trophic food web, eradication of introduced superpredators such as feral domestic cats in the BRC model, is not always the best solution to protect endemic insular prey. The presence of a superpredator may have a beneficial effect in such systems. PMID:15998496
Spectral function of the Tomonaga-Luttinger model revisited: Power laws and universality
NASA Astrophysics Data System (ADS)
Markhof, L.; Meden, V.
2016-02-01
We reinvestigate the momentum-resolved single-particle spectral function of the Tomonaga-Luttinger model. In particular, we focus on the role of the momentum dependence of the two-particle interaction V (q ) . Usually, V (q ) is assumed to be a constant and integrals are regularized in the ultraviolet "by hand" employing an ad hoc procedure. As the momentum dependence of the interaction is irrelevant in the renormalization group sense, this does not affect the universal low-energy properties of the model, e.g., exponents of power laws, if all energy scales are sent to zero. If, however, the momentum k is fixed away from the Fermi momentum kF, with |k - kF| setting a nonvanishing energy scale, the details of V (q ) start to matter. We provide strong evidence that any curvature of the two-particle interaction at small transferred momentum q destroys power-law scaling of the momentum-resolved spectral function as a function of energy. Even for |k - kF| much smaller than the momentum-space range of the interaction the spectral line shape depends on the details of V (q ) . The significance of our results for universality in the Luttinger liquid sense, for experiments on quasi-one-dimensional metals, and for recent results on the spectral function of one-dimensional correlated systems taking effects of the curvature of the single-particle dispersion into account ("nonlinear LL phenomenology") is discussed.
Urban Morphology Influence on Urban Albedo: A Revisit with the S olene Model
NASA Astrophysics Data System (ADS)
Groleau, Dominique; Mestayer, Patrice G.
2013-05-01
This heuristic study of the urban morphology influence on urban albedo is based on some 3,500 simulations with the S olene model. The studied configurations include square blocks in regular and staggered rows, rectangular blocks with different street widths, cross-shaped blocks, infinite street canyons and several actual districts in Marseilles, Toulouse and Nantes, France. The scanned variables are plan density, facade density, building height, layout orientation, latitude, date and time of the day. The sky-view factors of the ground and canopy surfaces are also considered. This study demonstrates the significance of the facade density, in addition to the built plan density, as the explanatory geometrical factor to characterize the urban morphology, rather than building height. On the basis of these albedo calculations the puzzling results of Kondo et al. (Boundary-Layer Meteorol 100:225-242, 2001) for the influence of building height are explained, and the plan density influence is quantitatively assessed. It is shown that the albedo relationship with plan and facade densities obtained with the regular square plot configuration may be considered as a reference for all other configurations, with the exception of the infinite street canyon that shows systematic differences for the lower plan densities. The curves representing this empirical relationship may be used as a sort of abacus for all other geometries while an approximate simple mathematical model is proposed, as well as relationships between the albedo and sky-view factors.
Limited fetch revisited: Comparison of wind input terms, in surface wave modeling
NASA Astrophysics Data System (ADS)
Pushkarev, Andrei; Zakharov, Vladimir
2016-07-01
Results pertaining to numerical solutions of the Hasselmann kinetic equation (HE), for wind driven sea spectra, in the fetch limited geometry, are presented. Five versions of source functions, including the recently introduced ZRP model (Zakharov et al., 2012), have been studied, for the exact expression of Snl and high-frequency implicit dissipation, due to wave-breaking. Four of the five experiments were done in the absence of spectral peak dissipation for various Sin terms. They demonstrated the dominance of quadruplet wave-wave interaction, in the energy balance, and the formation of self-similar regimes, of unlimited wave energy growth, along the fetch. Between them was the ZRP model, which strongly agreed with dozens of field observations performed in the seas and lakes, since 1947. The fifth, the WAM3 wind input term experiment, used additional spectral peak dissipation and reproduced the results of a previous, similar, numerical simulation described in Komen et al. (1994), but only supported the field experiments for moderate fetches, demonstrating a total energy saturation at half of that of the Pierson-Moscowits limit. The alternative framework for HE numerical simulation is proposed, along with a set of tests, allowing one to select physically-justified source terms.
Columella cells revisited: novel structures, novel properties, and a novel gravisensing model
NASA Technical Reports Server (NTRS)
Staehelin, L. A.; Zheng, H. Q.; Yoder, T. L.; Smith, J. D.; Todd, P.
2000-01-01
A hundred years of research has not produced a clear understanding of the mechanism that transduces the energy associated with the sedimentation of starch-filled amyloplast statoliths in root cap columella cells into a growth response. Most models postulate that the statoliths interact with microfilaments (MF) to transmit signals to the plasma membrane (or ER), or that sedimentation onto these organelles produces the signals. However, no direct evidence for statolith-MF links has been reported, and no asymmetric structures of columella cells have been identified that might explain how a root turned by 90 degrees knows which side is up. To address these and other questions, we have (1) quantitatively examined the effects of microgravity on the size, number, and spatial distribution of statoliths; (2) re-evaluated the ultrastructure of columella cells in high-pressure frozen/freeze-substituted roots; and (3) followed the sedimentation dynamics of statolith movements in reoriented root tips. The findings have led to the formulation of a new model for the gravity-sensing apparatus of roots, which envisages the cytoplasm pervaded by an actin-based cytoskeletal network. This network is denser in the ER-devoid central region of the cell than in the ER-rich cell cortex and is coupled to receptors in the plasma membrane. Statolith sedimentation is postulated to disrupt the network and its links to receptors in some regions of the cell cortex, while allowing them to reform in other regions and thereby produce a directional signal.
NASA Astrophysics Data System (ADS)
Ota, Kazutaka; Kohda, Masanori; Hori, Michio; Sato, Tetsu
2011-10-01
Alternative reproductive tactics are widespread in males and may cause intraspecific differences in testes investment. Parker's sneak-guard model predicts that sneaker males, who mate under sperm competition risk, invest in testes relatively more than bourgeois conspecifics that have lower risk. Given that sneakers are much smaller than bourgeois males, sneakers may increase testes investment to overcome their limited sperm productivity because of their small body sizes. In this study, we examined the mechanism that mediates differential testes investment across tactics in the Lake Tanganyika cichlid fish Lamprologus callipterus. In the Rumonge population of Burundi, bourgeois males are small compared with those in other populations and have a body size close to sneaky dwarf males. Therefore, if differences in relative testis investment depend on sperm competition, the rank order of relative testis investment should be dwarf males > bourgeois males in Rumonge = bourgeois males in the other populations. If differences in relative testis investment depend on body size, the rank order of relative testes investment should be dwarf males > bourgeois males in Rumonge > bourgeois males in the other populations. Comparisons of relative testis investment among the three male groups supported the role of sperm competition, as predicted by the sneak-guard model. Nevertheless, the effects of absolute body size on testes investment should be considered to understand the mechanisms underlying intraspecific variation in testes investment caused by alternative reproductive tactics.
Quesenberry, Peter J.; Dooner, Mark S.; Aliotta, Jason M.
2010-01-01
The phenotype of marrow hematopoietic stem cells is determined by cell cycle state and microvesicle entry into the stem cells. The stem cell population is continually changing based on cell cycle transit and thus can only be defined on a population basis. Purification of marrow stem cells only addresses the heterogeneity of these populations. When whole marrow is studied, the long-term repopulating stem cells are in active cell cycle. However, with some variability, when highly purified stem cells are studied, the cells appear to be dormant. Thus, the study of purified stem cells is intrinsically misleading. Tissue-derived microvesicles enhanced by injury effect the phenotype of different cell classes. We propose that previously described stem cell plasticity is due to microvesicle modulation. We further propose a stem cell population model in which the individual cell phenotypes continually changes, but the population phenotype is relatively stable. This, in turn, is modulated by microvesicle and microenvironmental influences. PMID:20382199
Revisiting the capture velocity of a cesium magneto-optical trap: model, simulation and experiment
NASA Astrophysics Data System (ADS)
Anwar, Muhammad; Magalhães, Daniel V.; Müller, Stella T.; Faisal, Muhammad; Nawaz, Muhammad; Ahmed, Mushtaq
2014-12-01
In this work, we have explored ab initio the capture process in a magneto-optical trap by theory, simulation and experiment. We measured the capture velocity vc of a cesium vapor cell magneto-optical trap (VCMOT) from its capture rate R and developed an exact model for the capture rate of a VCMOT in terms of its capture velocity, background density and trap laser beam diameter. We measured the capture velocity of a cesium VCMOT for various trap laser intensities and magnetic field gradients. We observed that the capture velocity is a damping force as well as a restoring force phenomenon. We supported our findings by performing simulations for single atom trajectories in a 1D cesium MOT. Finally, we concluded that two MOTs can have the same capture velocities but very different capture rates, thereby revealing that these are two fundamentally different characteristics of the MOT.
Ehrenfest urn revisited: Playing the game on a realistic fluid model
NASA Astrophysics Data System (ADS)
Scalas, Enrico; Martin, Edgar; Germano, Guido
2007-07-01
The Ehrenfest urn process, also known as the dogs and fleas model, is realistically simulated by molecular dynamics of the Lennard-Jones fluid. The key variable is Δz —i.e., the absolute value of the difference between the number of particles in one half of the simulation box and in the other half. This is a pure-jump stochastic process induced, under coarse graining, by the deterministic time evolution of the atomic coordinates. We discuss the Markov hypothesis by analyzing the statistical properties of the jumps and the waiting times between the jumps. In the limit of a vanishing integration time step, the distribution of waiting times becomes closer to an exponential and, therefore, the continuous-time jump stochastic process is Markovian. The random variable Δz behaves as a Markov chain and, in the gas phase, the observed transition probabilities follow the predictions of the Ehrenfest theory.
Intuitive Logic Revisited: New Data and a Bayesian Mixed Model Meta-Analysis
Singmann, Henrik; Klauer, Karl Christoph; Kellen, David
2014-01-01
Recent research on syllogistic reasoning suggests that the logical status (valid vs. invalid) of even difficult syllogisms can be intuitively detected via differences in conceptual fluency between logically valid and invalid syllogisms when participants are asked to rate how much they like a conclusion following from a syllogism (Morsanyi & Handley, 2012). These claims of an intuitive logic are at odds with most theories on syllogistic reasoning which posit that detecting the logical status of difficult syllogisms requires effortful and deliberate cognitive processes. We present new data replicating the effects reported by Morsanyi and Handley, but show that this effect is eliminated when controlling for a possible confound in terms of conclusion content. Additionally, we reanalyze three studies () without this confound with a Bayesian mixed model meta-analysis (i.e., controlling for participant and item effects) which provides evidence for the null-hypothesis and against Morsanyi and Handley's claim. PMID:24755777
Revisiting classic water erosion models in drylands: The strong impact of biological soil crusts
Bowker, M.A.; Belnap, J.; Bala, Chaudhary V.; Johnson, N.C.
2008-01-01
Soil erosion and subsequent degradation has been a contributor to societal collapse in the past and is one of the major expressions of desertification in arid regions. The revised universal soil loss equation (RUSLE) models soil lost to water erosion as a function of climate erosivity (the degree to which rainfall can result in erosion), topography, soil erodibility, and land use/management. The soil erodibility factor (K) is primarily based upon inherent soil properties (those which change slowly or not at all) such as soil texture and organic matter content, while the cover/management factor (C) is based on several parameters including biological soil crust (BSC) cover. We examined the effect of two more precise indicators of BSC development, chlorophyll a and exopolysaccharides (EPS), upon soil stability, which is closely inversely related to soil loss in an erosion event. To examine the relative influence of these elements of the C factor to the K factor, we conducted our investigation across eight strongly differing soils in the 0.8 million ha Grand Staircase-Escalante National Monument. We found that within every soil group, chlorophyll a was a moderate to excellent predictor of soil stability (R2 = 0.21-0.75), and consistently better than EPS. Using a simple structural equation model, we explained over half of the variance in soil stability and determined that the direct effect of chlorophyll a was 3?? more important than soil group in determining soil stability. Our results suggest that, holding the intensity of erosive forces constant, the acceleration or reduction of soil erosion in arid landscapes will primarily be an outcome of management practices. This is because the factor which is most influential to soil erosion, BSC development, is also among the most manageable, implying that water erosion in drylands has a solution. ?? 2008 Elsevier Ltd.
Pathways from adult education to well-being: The Tuijnman model revisited
NASA Astrophysics Data System (ADS)
Jenkins, Andrew; Wiggins, Richard D.
2015-02-01
There is a growing interest among researchers and policy-makers in the influence of adult learning on a range of outcomes, notably health and well-being. Much of the research to date has tended to focus on younger adults and the immediate benefits of course participation. The longer-term outcomes, such as the potential of accumulated learning experience for enriching later life, have been neglected. The study presented in this article adopts a lifecourse approach to participation in learning and the potential benefits of learning. The authors concentrate on adult education in mid-life, that is between the ages of 33 and 50, as the measure of learning participation. Their research draws upon previous work conducted by Albert Tuijnman which used Swedish data and which was published a quarter of a century ago in the pages of the International Review of Education. The authors of this paper seek to replicate and extend his pioneering work, using data from the National Child Development Study (NCDS), a large-scale survey containing information on all those born in Britain in one week in 1958. Follow-up data were collected at various points in childhood and adulthood, most recently when the cohort reached the age of 50, thus enabling insights into long-term developments. The authors analyse well-being at age 50 as an outcome in structural equation models (SEM). This approach helps to understand the pathways through which adult education has an impact on well-being. The estimated models show how adult education in mid-life has an influence on the type and quality of jobs which are accessible to individuals, and how this in turn can contribute to higher well-being at age 50.
Revisiting the Climate Impacts of Cool Roofs around the Globe Using an Earth System Model
NASA Astrophysics Data System (ADS)
Zhang, J.; Zhang, K.; Ban-Weiss, G. A.
2015-12-01
In this study, we use the Community Earth System Model to investigate the effects of employing cool roofs (i.e. increasing roof albedo from 0.15 to 0.9) on urban, regional, and global climates. After increasing the roof albedo, urban heat islands are reduced significantly over the globe during summer, and those at low latitudes during winter; the annual- and global-mean urban minus rural air temperature decreases from 1.6 K to 1.2 K. We mainly focus on changes in energy fluxes and climates in four regions: the United States, China, India, and Europe. For each region, solar radiation reflected by surface increases proportionally to the estimated albedo increase induced by roof albedo change. Without considering clouds, the increase in reflected solar radiation at surface leads to proportional increase in outgoing shortwave radiation at top of the atmosphere, suggesting a radiative cooling effect of cool roofs. On the other hand, the variations of cloud forcing in the model are more significant than the influence of cool roofs on energy balance at top of the atmosphere in some areas. Aerosols are known to partially offset the effects of cool roofs by absorbing solar radiation, and also reflecting radiation back to surface. However, we find that additional aerosol forcing is only 5-10% of the increase in reflected solar radiation at surface. Previous studies disagree in cool roof's influence on global climate. We find that its influence on global mean temperature is negligible; the temperature decreases by 0.0015 K, with a high uncertainty of 0.026 K.
Sulfur in the Early Martian Atmosphere Revisited: Experiments with a 3-D Global Climate Model
NASA Astrophysics Data System (ADS)
Kerber, L.; Forget, F.; Wordsworth, R.
2013-09-01
Data returned from the surface of Mars during the 1970s revealed intriguing geological evidence for a warmer and wetter early martian climate. Dendritic valley networks were discovered by Mariner 9 on ancient Noachian terrain [1], indicating that liquid water had flowed across the surface in the distant past. Since this time, geological investigations into early Martian history have attempted to ascertain the nature and level of activity of the early Martian hydrological cycle [e.g. 2-5] while atmospheric modeling efforts have focused on how the atmosphere could be warmed to temperatures great enough to sustain such activity [see 6-7 for reviews]. Geological and spectroscopic investigations have refined the history and chronology of Noachian Mars over time, and circulation of liquid water has been invoked to explain several spatially and temporally distinct morphological and chemical signatures found in the geological record. Detections of iron and magnesium-rich clays are widespread in the oldest Martian terrains, suggesting a period of pH-neutral aqueous alteration [e.g., 8]. Valley network incision also took place during the Noachian period [9]. Some chains of river valleys and craters lakes extend for thousands of kilometers, suggesting temperatures at least clement enough for sustained ice-covered flow [3,10]. The commencement of valley network incision is not well constrained, but the period of Mg/Fe clay formation appears to have ended before the termination of valley network formation, as the visible fluvial systems appear to have remobilized existing clays rather than forming them [5,8]. There is also evidence that the cessation of valley network formation was abrupt [11]. Towards the end of the Noachian, erosion rates appear to have been significantly higher than during subsequent periods, a process that has also been attributed to aqueous processes [12]. A period of sulfate formation followed, likely characterized by acidic, evaporitic playa environments
Blankenbach 3 revisited: intricate time-dependent patterns in a simple model of mantle convection
NASA Astrophysics Data System (ADS)
Hu, Z.; van Keken, P. E.
2010-12-01
We evaluate time-dependent nature of mantle convection using a simple 2D Cartesian model with internal heating based on the benchmark case 3 in Blankenbach et al. (Geophysical Journal International, 1989). We are particularly interested in the bifurcation patterns of the Vrms-Nu phase plot for Rayleigh numbers (Ra) around the benchmark value (Ra = 2.16×105), but more information is disclosed when we go to higher Ra (up to 8×105). We also investigate the role of the boundary conditions, for which we change to periodic boundary conditions for a second bifurcation study. We find an intricate pattern in the behavior of the heat flow (as measured by the Nusselt number Nu(t)) and the kinetic energy (as measured by Vrms(t)) which include period doubling, break down of periodic into episodic flow and reorganization into periodic flow at higher Ra. Two patterns of bifurcation are found. One is the period doubling pattern, described in Blankenbach et al. 1989 and referred to as P2-P4 bifurcation. The period doubling results from the differentiation of existing limit points of the time series of Nu or Vrms. The other pattern is period-preserving, which is found at higher Ra number in this study. In the period-preserving bifurcation, the new limit points (peak and valley) of the Nu and Vrms time series showed up as a twist in the monotonic intervals between a peak and valley. In this case the period doesn’t change. Both of the two patterns are observed in the models with the two types of boundary conditions (reflective and periodic). At a given Ra, different solutions can be obtained with different initial conditions. The initial condition is usually a solution with its Ra in the neighborhood, and with this neighborhood searching method, we were able to span the bifurcation plot (Ra-limit points of Nu(t) or Vrms(t)) to the range of Ra = 1×105~8×105 with both two boundary conditions. In this process, hysteresis is observed as expected in dynamic system, and the overlap of
NASA Astrophysics Data System (ADS)
WöLfler, Andreas; Kurz, Walter; Fritz, Harald; Stüwe, Kurt
2011-08-01
This study comprises a reassessment of the classical model of lateral extrusion in the Eastern Alps by using recently published geochronological data, sedimentary ages from intramontane basins, ages and distribution of magmatic rocks, and information from seismic profiles. Extrusion-related faulting continuously propagated from the western toward the central eastern part of the Eastern Alps during Oligocene to Middle Miocene times. This is confined by oblique convergence between the Adriatic and European plates. During Middle Miocene times, extrusion became not only lateral in terms of parallel to the trend of the Eastern Alps, but was characterized by a displacement vector at a high angle to the strike of the orogen. This resulted in the exhumation of the Schladming and Pohorje blocks that were exhumed within extensional bridges at the northern and southern terminations of the Pöls-Lavanttal fault system, respectively. From Middle Miocene to recent times, extrusion was controlled by overall extension between the Dinaric and Carpathian subduction zones. The influence of north directed compression triggered by the northward moving Adriatic plate diminished, and the influence of the retreating Carpathian subduction zone increased. This gave rise to Miocene volcanism that is exclusively found east of the Dinaric subduction zone. We therefore consider that lateral extrusion in the Eastern Alps can be subdivided into distinct tectonic phases, with less pronounced eastward extension-related displacement between Late Oligocene and Middle Miocene times. As soon as the Eastern Alps passed the Dinaric subduction zone, the entire domain became highly extensive.
Chatterjee, Ankita; Kundu, Sudip
2015-01-01
Chlorophyll is one of the most important pigments present in green plants and rice is one of the major food crops consumed worldwide. We curated the existing genome scale metabolic model (GSM) of rice leaf by incorporating new compartment, reactions and transporters. We used this modified GSM to elucidate how the chlorophyll is synthesized in a leaf through a series of bio-chemical reactions spanned over different organelles using inorganic macronutrients and light energy. We predicted the essential reactions and the associated genes of chlorophyll synthesis and validated against the existing experimental evidences. Further, ammonia is known to be the preferred source of nitrogen in rice paddy fields. The ammonia entering into the plant is assimilated in the root and leaf. The focus of the present work is centered on rice leaf metabolism. We studied the relative importance of ammonia transporters through the chloroplast and the cytosol and their interlink with other intracellular transporters. Ammonia assimilation in the leaves takes place by the enzyme glutamine synthetase (GS) which is present in the cytosol (GS1) and chloroplast (GS2). Our results provided possible explanation why GS2 mutants show normal growth under minimum photorespiration and appear chlorotic when exposed to air. PMID:26443104
THERMAL NON-EQUILIBRIUM REVISITED: A HEATING MODEL FOR CORONAL LOOPS
Lionello, Roberto; Linker, Jon A.; Mikic, Zoran; Winebarger, Amy R.; Mok, Yung E-mail: linkerj@predsci.com E-mail: amy.r.winebarger@nasa.gov
2013-08-20
The location and frequency of events that heat the million-degree corona are still a matter of debate. One potential heating scenario is that the energy release is effectively steady and highly localized at the footpoints of coronal structures. Such an energy deposition drives thermal non-equilibrium solutions in the hydrodynamic equations in longer loops. This heating scenario was considered and discarded by Klimchuk et al. on the basis of their one-dimensional simulations as incapable of reproducing observational characteristics of loops. In this paper, we use three-dimensional simulations to generate synthetic emission images, from which we select and analyze six loops. The main differences between our model and that of Klimchuk et al. concern (1) dimensionality, (2) resolution, (3) geometrical properties of the loops, (4) heating function, and (5) radiative function. We find evidence, in this small set of simulated loops, that the evolution of the light curves, the variation of temperature along the loops, the density profile, and the absence of small-scale structures are compatible with the characteristics of observed loops. We conclude that quasi-steady footpoint heating that drives thermal non-equilibrium solutions cannot yet be ruled out as a viable heating scenario for EUV loops.
EQUATION OF STATE AND HUGONIOT LOCUS FOR POROUS MATERIALS: P-ALPHA MODEL REVISITED
R. MENIKOFF; ET AL
1999-08-01
Foams, porous solids and granular materials have a characteristic Hugoniot locus that for weak shocks is concave in the (particle velocity, shock velocity)-plane. An equation of state (EOS) that has this property can be constructed implicitly from a Helmholtz free energy of the form {Psi}{sub s}(V,T,{phi}) = {Psi}{sub s}(V,T)+B({phi}) where the equilibrium volume fraction {phi}{sub eq} is determined by minimizing {Psi}, i.e., the condition {partial_derivative}{sub {psi}} {Psi} = 0. For many cases, a Hayes EOS for the pure solid {Psi}{sub s}(V,T) is adequate. This provides a thermodynamically consistent framework for the P-{alpha} model. For this form of EOS the volume fraction has a similar effect to an endothermic reaction in that the partial Hugoniot loci with fixed {psi} are shifted to the left in the (V,P)-plane with increasing f. The equilibrium volume fraction can then be chosen to match the concavity of the principal Hugoniot locus. An example is presented for the polymer estane. A small porosity of only 1.4 percent is required to match the experimental concavity in the Hugoniot data. This type of EOS can also be used to obtain the so-called ''universal'' Hugoniot for liquids.
Chatterjee, Ankita; Kundu, Sudip
2015-01-01
Chlorophyll is one of the most important pigments present in green plants and rice is one of the major food crops consumed worldwide. We curated the existing genome scale metabolic model (GSM) of rice leaf by incorporating new compartment, reactions and transporters. We used this modified GSM to elucidate how the chlorophyll is synthesized in a leaf through a series of bio-chemical reactions spanned over different organelles using inorganic macronutrients and light energy. We predicted the essential reactions and the associated genes of chlorophyll synthesis and validated against the existing experimental evidences. Further, ammonia is known to be the preferred source of nitrogen in rice paddy fields. The ammonia entering into the plant is assimilated in the root and leaf. The focus of the present work is centered on rice leaf metabolism. We studied the relative importance of ammonia transporters through the chloroplast and the cytosol and their interlink with other intracellular transporters. Ammonia assimilation in the leaves takes place by the enzyme glutamine synthetase (GS) which is present in the cytosol (GS1) and chloroplast (GS2). Our results provided possible explanation why GS2 mutants show normal growth under minimum photorespiration and appear chlorotic when exposed to air. PMID:26443104
A New Model of Weak Acid Permeation through Membranes Revisited: Does Overton Still Rule?
Saparov, Sapar M.; Antonenko, Yuri N.; Pohl, Peter
2006-01-01
According to a recent publication by Thomae, A. V., H. Wunderli-Allenspach, and S. D. Krämer (2005. Biophys. J. 89:1802–1811), membrane bilayers are well-permeable to the charged species of aromatic carboxylic acids. At physiological pH, the anions were claimed to be the major diffusing species. In contrast, calculation of the Born energy barrier predicts a 105-fold higher permeability for the uncharged (protonated) form. To test the new model, we now have measured both the current carried by the salicylate anion through solvent-free planar membranes and the amount of protons transported by the neutral species. The corresponding membrane permeabilities of the charged and protonated forms were 4 × 10−7 cm/s and 1.2 cm/s. These data are in perfect agreement with literature data gathered in the last three decades (compare, e.g., Gutknecht, J., and D. C. Tosteson. 1973. Science. 182:1258–1261). They indicate that the report by Thomae at al. represents an experimental artifact. The well-documented role of neutral species in the permeation process of weak acids and bases across artificial and natural membranes is not in question. Overton still rules. PMID:16603491
Equation of State and Hugoniot locus for porous materials: P--α model revisited
NASA Astrophysics Data System (ADS)
Menikoff, Ralph; Kober, Edward
1999-06-01
Foams, porous solids and granular materials have a characteristic Hugoniot locus that for weak shocks is concave in the (particle velocity, shock velocity)-plane. An equation of state (EOS) that has this property can be constructed implicitly from a Helmholtz free energy of the form F(V,T,φ) = F_s(V,T) + B(φ) where the equilibrium volume fraction φ_eq is determined by minimizing F, phi.e., the condition partial_φ F = 0. For many cases, a Hayes EOS for the pure solid F_s(V,T) is adequate. This provides a thermodynamically consistent framework for the P--α model. For this form of EOS, we show that the volume fraction has a similar effect to an endothermic reaction in that the partial Hugoniot loci with fixed φ are shifted to the left in the (V,P)-plane with increasing φ. The equilibrium volume fraction can then be chosen to match the concavity of the principal Hugoniot locus. An example is presented for the polymer estane. A small porosity of only 1.4 per cent is required to match the experimental concavity in the Hugoniot data. This type of EOS can also be used to obtain the so-called ``universal'' Hugoniot for liquids.
NASA Astrophysics Data System (ADS)
Hunana, P.; Zank, G. P.; Goldstein, M. L.; Webb, G. M.; Adhikari, L.
2016-03-01
Solar wind observational studies have emphasized that the solar wind plasma data is bounded by the mirror and firehose instabilities, and it is often believed that these instabilities are of a purely kinetic nature. The simplest fluid model that generalizes magnetohydrodynamics with anisotropic temperatures is the Chew-Goldberger-Low model (CGL). Here we briefly revisit the CGL description and discuss its (otherwise well-documented) linear firehose and mirror instability thresholds; namely that the firehose instability threshold is identical to the one found from linear kinetic theory and that the mirror threshold contains a factor of 6 error. We consider a simple higher-order fluid model with time dependent heat flux equations and show that the mirror instability threshold is correctly reproduced. We also present fully nonlinear three-dimensional simulations of freely decaying turbulence for the Hall-CGL model with isothermal electrons. The spatial resolution of these simulations is 5123 and the formation of a spectral break in magnetic and velocity field spectra around the proton inertial length is found.
Meta-Analytic Connectivity Modelling Revisited: Controlling for Activation Base Rates
Langner, Robert; Rottschy, Claudia; Laird, Angela R.; Fox, Peter T.; Eickhoff, Simon B.
2014-01-01
Co-activation of distinct brain regions is a measure of functional interaction, or connectivity, between those regions. The co-activation pattern of a given region can be investigated using seed-based activation likelihood estimation meta-analysis of functional neuroimaging data stored in databases such as BrainMap. This method reveals inter-regional functional connectivity by determining brain regions that are consistently co-activated with a given region of interest (the “seed”) across a broad range of experiments. In current implementations of this meta-analytic connectivity modelling (MACM), significant spatial convergence (i.e. consistent co-activation) is distinguished from noise by comparing it against an unbiased null-distribution of random spatial associations between experiments according to which all grey-matter voxels have the same chance of convergence. As the a priori probability of finding activation in different voxels markedly differs across the brain, computing such a quasi-rectangular null-distribution renders the detection of significant convergence more likely in those voxels that are frequently activated. Here, we propose and test a modified MACM approach that takes this activation frequency bias into account. In this new specific co-activation likelihood estimation (SCALE) algorithm, a null-distribution is generated that reflects the base rate of reporting activation in any given voxel and thus equalizes the a priori chance of finding across-study convergence in each voxel of the brain. Using four exemplary seed regions (right visual area V4, left anterior insula, right intraparietal sulcus, and subgenual cingulum), our tests corroborated the enhanced specificity of the modified algorithm, indicating that SCALE may be especially useful for delineating distinct core networks of co-activation. PMID:24945668
Revisiting 2D numerical models for the 19th century outbursts of η Carinae
NASA Astrophysics Data System (ADS)
González, R. F.; Villa, A. M.; Gómez, G. C.; de Gouveia Dal Pino, E. M.; Raga, A. C.; Cantó, J.; Velázquez, P. F.; de La Fuente, E.
2010-02-01
We present here new results of two-dimensional hydrodynamical simulations of the eruptive events of the 1840s (the great) and the 1890s (the minor) eruptions suffered by the massive star η Carinae (Car). The two bipolar nebulae commonly known as the Homunculus and the little Homunculus (LH) were formed from the interaction of these eruptive events with the underlying stellar wind. We assume here an interacting, non-spherical multiple-phase wind scenario to explain the shape and the kinematics of both Homunculi, but adopt a more realistic parametrization of the phases of the wind. During the 1890s eruptive event, the outflow speed decreased for a short period of time. This fact suggests that the LH is formed when the eruption ends, from the impact of the post-outburst η Car wind (that follows the 1890s event) with the eruptive flow (rather than by the collision of the eruptive flow with the pre-outburst wind, as claimed in previous models; González et al.). Our simulations reproduce quite well the shape and the observed expansion speed of the large Homunculus. The LH (which is embedded within the large Homunculus) becomes Rayleigh-Taylor unstable and develop filamentary structures that resemble the spatial features observed in the polar caps. In addition, we find that the interior cavity between the two Homunculi is partially filled by material that is expelled during the decades following the great eruption. This result may be connected with the observed double-shell structure in the polar lobes of the η Car nebula. Finally, as in previous work, we find the formation of tenuous, equatorial, high-speed features that seem to be related to the observed equatorial skirt of η Car.
NASA Astrophysics Data System (ADS)
Batic, Matej; Begalli, Marcia; Han, Min Cheol; Hauf, Steffen; Hoff, Gabriela; Kim, Chan Hyeong; Kim, Han Sung; Grazia Pia, Maria; Saracco, Paolo; Weidenspointner, Georg
2014-06-01
A systematic review of methods and data for the Monte Carlo simulation of photon interactions is in progress: it concerns a wide set of theoretical modeling approaches and data libraries available for this purpose. Models and data libraries are assessed quantitatively with respect to an extensive collection of experimental measurements documented in the literature to determine their accuracy; this evaluation exploits rigorous statistical analysis methods. The computational performance of the associated modeling algorithms is evaluated as well. An overview of the assessment of photon interaction models and results of the experimental validation are presented.
The Ti-Mn system revisited: experimental investigation and thermodynamic modelling.
Khan, A U; Brož, P; Premović, M; Pavlů, J; Vřeštál, J; Yan, X; Maccio, D; Saccone, A; Giester, G; Rogl, P
2016-08-17
As the Ti-Mn phase diagram is part of numerous ternary and higher order systems of technological importance, the present paper defines phase relations which have been experimentally established throughout this work from 800 °C to the melting range based on Differential Thermal Analyses (DTA), X-ray powder diffraction, metallography and Electron Probe Micro Analysis (EPMA) techniques on ∼50 alloys, which were prepared by arc melting or high frequency melting under high purity argon starting from freshly cleaned metal ingots. Novel compounds were identified and reaction isotherms were redefined accordingly. In the Ti-rich region a novel compound TiMn was detected, sandwiched between the known phases: TiMn1-x (∼45 at% Mn) and TiMn1+x (∼55 at% Mn). In the Mn-rich region the hitherto unknown crystal structure of TiMn∼3 was solved from X-ray single crystal diffraction data and found to be of a unique structure type Ti6(Ti1-xMnx)6Mn25 (x = 0.462; space group Pbam (#55); a = 0.79081(3) nm, b = 2.58557(9) nm, c = 0.47931(2) nm), which consists of two consecutive layers of the hexagonal MgZn2-type Laves phase (TiMn2) and a combined layer of alternate structure blocks of MgZn2 type and Zr4Al3 type. Whereas TiMn can be considered as a line compound (solubility range <∼1 at%), the homogeneity regions of the Ti-Mn compounds are significant (determined by EPMA): TiMn1-x (44.0 to 46.6 at% Mn), TiMn1+x (54.6 to 56.3 at% Mn), Ti1+xMn2-x (MgZn2-type, 59 to 69 at% Mn at 1000 °C: -0.08 < x < 0.23), TiMn∼3 (unique type; 74 to 76.5 at% Mn) and TiMn∼4 (R-phase: Ti8(TixMn1-x)6Mn39, 80 to 84 at% Ti). Supported by ab initio calculations of the ground state energy for the Laves phase, the new experimental results enabled thermodynamic modelling of the entire Ti-Mn phase diagram providing a complete and novel set of thermodynamic data thus providing a sound basis for future thermodynamic predictions of higher order Ti-Mn-X-Y systems. PMID:27498605
Spin-bowling in cricket re-visited: model trajectories for various spin-vector angles
NASA Astrophysics Data System (ADS)
Robinson, Garry; Robinson, Ian
2016-08-01
In this paper we investigate, via the calculation of model trajectories appropriate to slow bowling in cricket, the effects on the flight path of the ball before pitching due to changes in the angle of the spin-vector. This was accomplished by allowing the spin-vector to vary in three ways. Firstly, from off-spin, where the spin-vector points horizontally and directly down the pitch, to top-spin where it points horizontally towards the off-side of the pitch. Secondly, from off-spin to side-spin where, for side-spin, the spin-vector points vertically upwards. Thirdly, where the spin-vector points horizontally and at 45° to the pitch (in the general direction of ‘point’, as viewed by the bowler), and is varied towards the vertical, while maintaining the 45° angle in the horizontal plane. It is found that, as is well known, top-spin causes the ball to dip in flight, side-spin causes the ball to move side-ways in flight and, perhaps most importantly, off-spin can cause the ball to drift to the off-side of the pitch late in its flight as it begins to fall. At a more subtle level it is found that, if the total spin is kept constant and a small amount of top-spin is added to the ball at the expense of some off-spin, there is little change in the side-ways drift. However, a considerable reduction in the length at which the ball pitches occurs, ∼25 cm, an amount that batsmen can ignore at their peril. On the other hand, a small amount of side-spin introduced to a top-spin delivery does not alter the point of pitching significantly, but produces a considerable amount of side-ways drift, ∼10 cm or more. For pure side-spin the side-ways drift is up to ∼30 cm. When a side-spin component is added to the spin of a ball bowled with a mixture of off-spin and top-spin in equal proportions, significant movement occurs in both the side-ways direction and in the point of pitching, of the order of a few tens of centimetres.
Zwanzig model of multi-component mixtures of biaxial particles: y3 theory re-visited
NASA Astrophysics Data System (ADS)
Sokolova, E. P.; Tumanyan, N. P.; Vlasov, A. Yu.; Masters, A. J.
The paper considers the thermodynamic and phase ordering properties of a multi-component Zwanzig mixture of hard rectangular biaxial parallelepipeds. An equation of state (EOS) is derived based on an estimate of the number of arrangements of the particles on a three- dimensional cubic lattice. The methodology is a generalization of the Flory-DiMarzio counting scheme, but, unlike previous work, this treatment is thermodynamically consistent. The results are independent of the order in which particles are placed on the lattice. By taking the limit of zero lattice spacing, a translationally continuous variant of the model (the off-lattice variant) is obtained. The EOS is identical to that obtained previously by a wide variety of different approaches. In the off-lattice limit, it corresponds to a third-level y-expansion and, in the case of a binary mixture of square platelets, it also corresponds to the EOS obtained from fundamental measure theory. On the lattice it is identical to the EOS obtained by retaining only complete stars in the virial expansion. The off-lattice theory is used to study binary mixtures of rods (R1 - R2) and binary mixtures of platelets (P1 - P2). The particles were uniaxial, of length (thickness) L and width D. The aspect ratios Γi = Li/Di of the components were kept constant (Γ1R = 15, Γ1P = 1/15 and Γ2R = 150, Γ2P = 1/150), so the second virial coefficient of R1 was identical to P1 and similarly for R2 and P2. The volume ratio of particles 1 and 2, v1/v2, was then varied, with the constraints that viR = viP and ILM0001. Results on nematic-isotropic (N - I) phase coexistence at an infinite dilution of component 2, are qualitatively similar for rods and platelets. At small values of the ratio v1/v2, the addition of component 2 (i.e. a thin rod (e.g. a polymer) or a thin plate) results in the stabilization of the nematic phase. For larger values of v1/v2, however, this effect is reversed and the addition of component 2 destabilizes the
NASA Astrophysics Data System (ADS)
Schulthess, Thomas C.
2015-05-01
Writing efficient scientific software that makes best use of the increasing complexity of computer architectures requires bringing together modelling, applied mathematics and computer engineering. Physics may help unite these approaches.
NASA Astrophysics Data System (ADS)
Steinbach, Ingo; Plapp, Mathis
2012-11-01
Zener's model of pearlite transformation in steels can be viewed as the prototype of many microstructure evolution models in materials science. It links principles of thermodynamics and kinetics to the scale of the microstructure. In addition it solves a very practical problem: How the hardness of steel is correlated to the conditions of processing. Although the model is well established since the 1950s, quantitative explanation of growth kinetics was missing until very recently. The present paper will shortly review the classical model of pearlite transformation. Zener's conjecture of maximum entropy production will be annotated by modern theoretical and experimental considerations of a band of stable (sometimes oscillating) states around the state of maximum entropy production. Finally, an explanation of the growth kinetics observed in experiments is proposed based on diffusion fluxes driven by stress gradients due to large transformation strain.
Two-dimensional thermofield bosonization II: Massive fermions
Amaral, R.L.P.G.
2008-11-15
We consider the perturbative computation of the N-point function of chiral densities of massive free fermions at finite temperature within the thermofield dynamics approach. The infinite series in the mass parameter for the N-point functions are computed in the fermionic formulation and compared with the corresponding perturbative series in the interaction parameter in the bosonized thermofield formulation. Thereby we establish in thermofield dynamics the formal equivalence of the massive free fermion theory with the sine-Gordon thermofield model for a particular value of the sine-Gordon parameter. We extend the thermofield bosonization to include the massive Thirring model.
ERIC Educational Resources Information Center
Richert, Alex; Binder, P. -M.
2011-01-01
The siphon is a very useful example of early technology, the operation of which has long been well understood. A recent article makes the claim that established beliefs regarding this device are incorrect and proposes a "chain model" in which intermolecular forces within the fluid play a large role while atmospheric pressure does not. We have…
Lorentz violation naturalness revisited
NASA Astrophysics Data System (ADS)
Belenchia, Alessio; Gambassi, Andrea; Liberati, Stefano
2016-06-01
We revisit here the naturalness problem of Lorentz invariance violations on a simple toy model of a scalar field coupled to a fermion field via a Yukawa interaction. We first review some well-known results concerning the low-energy percolation of Lorentz violation from high energies, presenting some details of the analysis not explicitly discussed in the literature and discussing some previously unnoticed subtleties. We then show how a separation between the scale of validity of the effective field theory and that one of Lorentz invariance violations can hinder this low-energy percolation. While such protection mechanism was previously considered in the literature, we provide here a simple illustration of how it works and of its general features. Finally, we consider a case in which dissipation is present, showing that the dissipative behaviour does not percolate generically to lower mass dimension operators albeit dispersion does. Moreover, we show that a scale separation can protect from unsuppressed low-energy percolation also in this case.
Multinomial pattern matching revisited
NASA Astrophysics Data System (ADS)
Horvath, Matthew S.; Rigling, Brian D.
2015-05-01
Multinomial pattern matching (MPM) is an automatic target recognition algorithm developed for specifically radar data at Sandia National Laboratories. The algorithm is in a family of algorithms that first quantizes pixel value into Nq bins based on pixel amplitude before training and classification. This quantization step reduces the sensitivity of algorithm performance to absolute intensity variation in the data, typical of radar data where signatures exhibit high variation for even small changes in aspect angle. Our previous work has focused on performance analysis of peaky template matching, a special case of MPM where binary quantization is used (Nq = 2). Unfortunately references on these algorithms are generally difficult to locate and here we revisit the MPM algorithm and illustrate the underlying statistical model and decision rules for two algorithm interpretations: the 1-of-K vector form and the scalar. MPM can also be used as a detector and specific attention is given to algorithm tuning where "peak pixels" are chosen based on their underlying empirical probabilities according to a reward minimization strategy aimed at reducing false alarms in the detection scenario and false positives in a classification capacity. The algorithms are demonstrated using Monte Carlo simulations on the AFRL civilian vehicle dataset for variety of choices of Nq.
P., Henry
2008-11-20
A recent article in which John Searle claims to refute dualism is examined from a scientific perspective. John Searle begins his recent article 'Dualism Revisited' by stating his belief that the philosophical problem of consciousness has a scientific solution. He then claims to refute dualism. It is therefore appropriate to examine his arguments against dualism from a scientific perspective. Scientific physical theories contain two kinds of descriptions: (1) Descriptions of our empirical findings, expressed in an every-day language that allows us communicate to each other our sensory experiences pertaining to what we have done and what we have learned; and (2) Descriptions of a theoretical model, expressed in a mathematical language that allows us to communicate to each other certain ideas that exist in our mathematical imaginations, and that are believed to represent, within our streams of consciousness, certain aspects of reality that we deem to exist independently of their being perceived by any human observer. These two parts of our scientific description correspond to the two aspects of our general contemporary dualistic understanding of the total reality in which we are imbedded, namely the empirical-mental aspect and the theoretical-physical aspect. The duality question is whether this general dualistic understanding of ourselves should be regarded as false in some important philosophical or scientific sense.
Cui, Wei; Lansac, Yves; Lee, Hochun; Hong, Seung-Tae; Jang, Yun Hee
2016-09-14
Complex formation between lithium (Li(+)) ions and electrolyte molecules would affect the ionic conductivity through the electrolyte in lithium-ion batteries (LIBs). We hence revisit the solvation number of Li(+) in the most commonly used ethylene carbonate (EC) electrolyte. The solvation number n of Li(+)(EC)n in the first solvation shell of Li(+) is estimated on the basis of the free energy calculated by the density functional theory combined with a hybrid solvation model where the explicit solvation shell of Li(+) is immersed in a free volume of an implicit bulk solvent. This new hybrid solvation (implicit and explicit) model predicts the most probable solvation number (n = 4) and solvation free energy (-91.3 kcal mol(-1)) of Li(+) in a good agreement with those predicted by calculations employing simpler solvation models (either implicit or explicit). The desolvation (n = 2) of Li(0)(EC)n upon reduction near anodes is also well described with this new hybrid model. PMID:27506245
Benedek, Mathias; Neubauer, Aljoscha C
2013-01-01
Fifty years ago, Mednick [Psychological Review, 69 (1962) 220] proposed an elaborate model that aimed to explain how creative ideas are generated and why creative people are more likely to have creative ideas. The model assumes that creative people have flatter associative hierarchies and as a consequence can more fluently retrieve remote associative elements, which can be combined to form creative ideas. This study aimed at revisiting Mednick’s model and providing an extensive test of its hypotheses. A continuous free association task was employed and association performance was compared between groups high and low in creativity, as defined by divergent thinking ability and self-report measures. We found that associative hierarchies do not differ between low and high creative people, but creative people showed higher associative fluency and more uncommon responses. This suggests that creativity may not be related to a special organization of associative memory, but rather to a more effective way of accessing its contents. The findings add to the evidence associating creativity with highly adaptive executive functioning. PMID:24532853
NASA Astrophysics Data System (ADS)
Gromov, S. S.; Joeckel, P.; Brenninkmeijer, C. A.
2012-12-01
We present the results of global modeling of the stable carbon isotope composition of atmospheric tracers, with a focus on the isotopic composition of CO and its sensitivity to key atmospheric processes. We revisit the results of earlier simplified bottom-up model approaches consistently lacking tropospheric 13CO compared to observed isotope ratios. In this study we employ a more elaborate modeling framework including the comprehensive isotopic chemistry mechanism in the ECHAM/MESSy Atmospheric Chemistry (EMAC) general circulation model. The Modular Earth Submodel System (MESSy) framework incorporated in EMAC allows an explicit, more realistic treatment of the isotope effects (e.g., fractionation due to chemistry, diffusion, dry deposition) on a per species basis. In addition, our review of the isotope-inclusive emissions of CO and its precursors suggests more 13C-enriched surface sources compared to previous estimates. We further revise the parameterization of the kinetic isotope effect (KIE) in the reaction of CO with OH, the principal atmospheric sink of CO crucially influencing its airborne isotope composition. In contrast to the conventional (pressure-only dependent) assumption, the new complex rate coefficient parameterization for CO+OH suggests a slight (~0.5‰ per 10K) inverse temperature dependence of the 13C KIE, owing to the change in partitioning between the different reaction exit channels. Our results with EMAC do not support the inferences of the studies suggesting lower input of highly 13C-depleted carbon from methane to CO. In particular, we estimate high (0.94) average yield of CO per reacted CH4 molecule in the troposphere, which is a diagnosed variable in EMAC, rather than an assumed parameter. It is also shown that due to the preferential removal of the lighter isotopologues of the CH4→CO chain intermediates (e.g. formaldehyde and methanol), the photochemically produced CO becomes supplementary enriched in 13C; nonetheless, this effect for
Model of Deep Non-Volcanic Tremor in Episodic Tremor and Slip Events
NASA Astrophysics Data System (ADS)
Gershenzon, N. I.; Bambakidis, G.
2014-12-01
Bursts of tremor accompany a moving slip pulse in Episodic Tremor and Slip (ETS) events. The sources of this non-volcanic tremor (NVT) are largely unknown. We have developed a model describing the mechanism of NTV generation. According to this model, NTV is a reflection of resonant-type oscillations excited in a fault at certain depth ranges. From a mathematical viewpoint, tremor (phonons) and slip pulses (solitons) are two different solutions of the sine-Gordon equation describing frictional processes inside a fault. In an ETS event, a moving slip pulse generates tremor due to interaction with structural heterogeneities in a fault and to failures of small asperities (see Figure). Observed tremor parameters, such as central frequency and frequency attenuation curve, are associated with fault parameters and conditions, such as elastic modulus, effective normal stress, penetration hardness and friction. Model prediction of NTV frequency content is consistent with observations. In the framework of this model it is possible to explain the complicated pattern of tremor migration, including rapid tremor propagation and reverse tremor migration. Migration along the strike direction is associated with movement of the slip pulse. Rapid tremor propagation in the slip-parallel direction is associated with movement of kinks along a 2D slip pulse. A slip pulse, pinned in some places, can fragment into several pulses, causing tremor associated with some of these pulse fragments to move opposite to the main propagation direction. The model predicts that the frequency content of tremor during an ETS event is slightly different from the frequency content of ambient tremor and tremor triggered by earthquakes. Figure 1. The slip velocity w of a slip pulse in time-space (x-t) coordinates moving in (a) ideal substrate and (b) substrate with a structural heterogeneity. Pulse is driven by constant external shear stress. Figure 1(b) shows that the pulse oscillates about an obstacle
Measuring Hospital Quality Using Pediatric Readmission and Revisit Rates
Vittinghoff, Eric; Asteria-Peñaloza, Renée; Edwards, Jeffrey D.; Yazdany, Jinoos; Lee, Henry C.; Boscardin, W. John; Cabana, Michael D.; Dudley, R. Adams
2013-01-01
OBJECTIVE: To assess variation among hospitals on pediatric readmission and revisit rates and to determine the number of high- and low-performing hospitals. METHODS: In a retrospective analysis using the State Inpatient and Emergency Department Databases from the Healthcare Cost and Utilization Project with revisit linkages available, we identified pediatric (ages 1–20 years) visits with 1 of 7 common inpatient pediatric conditions (asthma, dehydration, pneumonia, appendicitis, skin infections, mood disorders, and epilepsy). For each condition, we calculated rates of all-cause readmissions and rates of revisits (readmission or presentation to the emergency department) within 30 and 60 days of discharge. We used mixed logistic models to estimate hospital-level risk-standardized 30-day revisit rates and to identify hospitals that had performance statistically different from the group mean. RESULTS: Thirty-day readmission rates were low (<10.0%) for all conditions. Thirty-day rates of revisit to the inpatient or emergency department setting ranged from 6.2% (appendicitis) to 11.0% (mood disorders). Study hospitals (n = 958) had low condition-specific visit volumes (37.0%–82.8% of hospitals had <25 visits). The only condition with >1% of hospitals labeled as different from the mean on 30-day risk-standardized revisit rates was mood disorders (4.2% of hospitals [n = 15], range of hospital performance 6.3%–15.9%). CONCLUSIONS: We found that when comparing hospitals’ performances to the average, few hospitals that care for children are identified as high- or low-performers for revisits, even for common pediatric diagnoses, likely due to low hospital volumes. This limits the usefulness of condition-specific readmission or revisit measures in pediatric quality measurement. PMID:23979094
A Hydrostatic Paradox Revisited
ERIC Educational Resources Information Center
Ganci, Salvatore
2012-01-01
This paper revisits a well-known hydrostatic paradox, observed when turning upside down a glass partially filled with water and covered with a sheet of light material. The phenomenon is studied in its most general form by including the mass of the cover. A historical survey of this experiment shows that a common misunderstanding of the phenomenon…
Revisiting Bioaccumulation Criteria
The objective of workgroup 5 was to revisit the B(ioaccumulation) criteria that are currently being used to identify POPs under the Stockholm Convention and PBTs under CEPA, TSCA, REACh and other programs. Despite the lack of a recognized definition for a B substance, we defined ...
Colloquial Hebrew Imperatives Revisited
ERIC Educational Resources Information Center
Bolozky, Shmuel
2009-01-01
In revisiting Bolozky's [Bolozky, Shmuel, 1979. "On the new imperative in colloquial Hebrew." "Hebrew Annual Review" 3, 17-24] and Bat-El's [Bat-El, Outi, 2002. "True truncation in colloquial Hebrew imperatives." "Language" 78(4), 651-683] analyses of colloquial Hebrew imperatives, the article argues for restricting Imperative Truncation to the…
Swedish Successful Schools Revisited
ERIC Educational Resources Information Center
Hoog, Jonas; Johansson, Olof; Olofsson, Anders
2009-01-01
Purpose: The purpose of this paper is to describe the results of a follow-up study of two Swedish schools in which, five years previously, the principals had been successful leaders. Had this success been maintained? Design/methodology/approach: Two schools were revisited to enable the authors to interview principals and teachers as well as…
Revisiting the Rhetorical Curriculum
ERIC Educational Resources Information Center
Rutten, Kris; Soetaert, Ronald
2012-01-01
The aim of the special strand on "Revisiting the rhetorical curriculum" is to explore the educational potential of a new rhetorical perspective, specifically in relation to different traditions within educational and rhetorical studies. This implies that we do not only look at education "in" rhetoric, but that we position education also "as" a…
Revisiting Curriculum Potential
ERIC Educational Resources Information Center
Deng, Zongyi
2011-01-01
This article analyzes the notion of curriculum potential by revisiting the ideas of Miriam Ben-Peretz and Joseph Schwab. Invoking the German "Didaktik" tradition and by way of a curriculum-making framework, the paper argues that interpreting curriculum materials for curriculum potential requires a careful analysis and unpacking of the meanings and…
Anodic Polarization Curves Revisited
ERIC Educational Resources Information Center
Liu, Yue; Drew, Michael G. B.; Liu, Ying; Liu, Lin
2013-01-01
An experiment published in this "Journal" has been revisited and it is found that the curve pattern of the anodic polarization curve for iron repeats itself successively when the potential scan is repeated. It is surprising that this observation has not been reported previously in the literature because it immediately brings into…
The Linguistic Repertoire Revisited
ERIC Educational Resources Information Center
Busch, Brigitta
2012-01-01
This article argues for the relevance of poststructuralist approaches to the notion of a linguistic repertoire and introduces the notion of language portraits as a basis for empirical study of the way in which speakers conceive and represent their heteroglossic repertoires. The first part of the article revisits Gumperz's notion of a linguistic…
NASA Astrophysics Data System (ADS)
Ezer, Tal
2016-08-01
The difficulty of simulating a realistic Gulf Stream (GS) that separates from the coast at Cape Hatteras has troubled numerical ocean modelers for a long time, and the problem is evident in different models, from the early models of the 1980s to the modern models of today. The source of the problem is not completely understood yet, since GS simulations are sensitive to many different factors, such as numerical parameterization, model grid, treatment of topography and forcing fields. A curious result of early models is that models with terrain-following vertical grids (e.g., "sigma" or "s" coordinates) seem to achieve a better GS separation than z-level models of similar resolution, so the impact of the vertical grid type on GS simulations is revisited here. An idealized generalized coordinate numerical model is used to compare between a sigma-coordinate grid and a z-level grid while maintaining the same numerical code and model parameters. Short-term diagnostic-prognostic calculations focus on the initial dynamic adjustment of the GS from a given initial condition and imposed boundary conditions. In diagnostic calculations, wherein the three-dimensional flow field is adjusted to time-invariant temperature and salinity data, the GS is quite realistic independent of the grid type. However, when switching to prognostic calculations, the GS in the z-level model tends to immediately develop an unrealistic GS branch that continues along the continental slope instead of separating from the coast at Cape Hatteras. The GS is more realistic in either a sigma-coordinate model or in a z-level model with a vertical wall replacing the continental slope. Increasing the vertical resolution in the z-level model reduces numerical noise, but it does not solve the GS separation problem. Vorticity balance analysis shows that the Joint Effect of Baroclinicity and bottom Relief (JEBAR) and its associated bottom pressure torque are very sensitive to the choice of vertical grid. A stepped
One-loop kink mass shifts: A computational approach
NASA Astrophysics Data System (ADS)
Alonso Izquierdo, A.; Guilarte, J. Mateos
2011-11-01
In this paper we develop a procedure to compute the one-loop quantum correction to the kink masses in generic (1+1)-dimensional one-component scalar field theoretical models. The procedure uses the generalized zeta function regularization method helped by the Gilkey-de Witt asymptotic expansion of the heat function via Mellin's transform. We find a formula for the one-loop kink mass shift that depends only on the part of the energy density with no field derivatives, evaluated by means of a symbolic software algorithm that automates the computation. The improved algorithm with respect to earlier work in this subject has been tested in the sine-Gordon and λ(ϕ)24 models. The quantum corrections of the sG-soliton and λ(-kink masses have been estimated with a relative error of 0.00006% and 0.00007% respectively. Thereafter, the algorithm is applied to other models. In particular, an interesting one-parametric family of double sine-Gordon models interpolating between the ordinary sine-Gordon and a re-scaled sine-Gordon model is addressed. Another one-parametric family, in this case of ϕ models, is analyzed. The main virtue of our procedure is its versatility: it can be applied to practically any type of relativistic scalar field models supporting kinks.
Quasi-integrability in the modified defocusing non-linear Schrödinger model and dark solitons
NASA Astrophysics Data System (ADS)
Blas, H.; Zambrano, M.
2016-03-01
The concept of quasi-integrability has been examined in the context of deformations of the defocusing non-linear Schrödinger model (NLS). Our results show that the quasi-integrability concept, recently discussed in the context of deformations of the sine-Gordon, Bullough-Dodd and focusing NLS models, holds for the modified defocusing NLS model with dark soliton solutions and it exhibits the new feature of an infinite sequence of alternating conserved and asymptotically conserved charges. For the special case of two dark soliton solutions, where the field components are eigenstates of a space-reflection symmetry, the first four and the sequence of even order charges are exactly conserved in the scattering process of the solitons. Such results are obtained through analytical and numerical methods, and employ adaptations of algebraic techniques used in integrable field theories. We perform extensive numerical simulations and consider the scattering of dark solitons for the cubic-quintic NLS model with potential V=η {I}^2-in /6{I}^3 and the saturable type potential satisfying [InlineEquation not available: see fulltext.], with a deformation parameter ɛ ∈ [InlineMediaObject not available: see fulltext.] and I = | ψ|2. The issue of the renormalization of the charges and anomalies, and their (quasi)conservation laws are properly addressed. The saturable NLS supports elastic scattering of two soliton solutions for a wide range of values of { η, ɛ, q}. Our results may find potential applications in several areas of non-linear science, such as the Bose-Einstein condensation.
Asymptotic behavior of dispersive waves in a spiral structure at large times
NASA Astrophysics Data System (ADS)
Kiselev, V. V.
2016-04-01
In the framework of the sine-Gordon integrable model for spiral magnetic structures, we investigate the behavior at large times of a weakly nonlinear dispersive wave field generated by a spatially local initial excitation of the structure. The method used is based on a direct asymptotic analysis of the corresponding matrix of the Riemann problem on the torus.
Twokink excitation in a spiral magnetic structure
NASA Astrophysics Data System (ADS)
Kiselev, V. V.; Raskovalov, A. A.
2016-01-01
Twokink excitations in the spiral structures of magnets and multiferroics are found and analyzed within the framework for the sine-Gordon model. It is shown that the movement and interaction of the kinks is accompanied by macroscopic translations of the spiral structure. The ways of observing and exciting kinks in the external magnetic field are discussed.
NASA Astrophysics Data System (ADS)
Fathi, Albert
2015-07-01
In this paper we revisit our joint work with Antonio Siconolfi on time functions. We will give a brief introduction to the subject. We will then show how to construct a Lipschitz time function in a simplified setting. We will end with a new result showing that the Aubry set is not an artifact of our proof of existence of time functions for stably causal manifolds.
Revisiting Dialogues and Monologues
ERIC Educational Resources Information Center
Kvernbekk, Tone
2012-01-01
In educational discourse dialogue tends to be viewed as being (morally) superior to monologue. When we look at them as basic forms of communication, we find that dialogue is a two-way, one-to-one form and monologue is a one-way, one-to-many form. In this paper I revisit the alleged (moral) superiority of dialogue. First, I problematize certain…
NASA Astrophysics Data System (ADS)
Moresi, Louis
2015-04-01
Dynamic Topography Revisited Dynamic topography is usually considered to be one of the trinity of contributing causes to the Earth's non-hydrostatic topography along with the long-term elastic strength of the lithosphere and isostatic responses to density anomalies within the lithosphere. Dynamic topography, thought of this way, is what is left over when other sources of support have been eliminated. An alternate and explicit definition of dynamic topography is that deflection of the surface which is attributable to creeping viscous flow. The problem with the first definition of dynamic topography is 1) that the lithosphere is almost certainly a visco-elastic / brittle layer with no absolute boundary between flowing and static regions, and 2) the lithosphere is, a thermal / compositional boundary layer in which some buoyancy is attributable to immutable, intrinsic density variations and some is due to thermal anomalies which are coupled to the flow. In each case, it is difficult to draw a sharp line between each contribution to the overall topography. The second definition of dynamic topography does seem cleaner / more precise but it suffers from the problem that it is not measurable in practice. On the other hand, this approach has resulted in a rich literature concerning the analysis of large scale geoid and topography and the relation to buoyancy and mechanical properties of the Earth [e.g. refs 1,2,3] In convection models with viscous, elastic, brittle rheology and compositional buoyancy, however, it is possible to examine how the surface topography (and geoid) are supported and how different ways of interpreting the "observable" fields introduce different biases. This is what we will do. References (a.k.a. homework) [1] Hager, B. H., R. W. Clayton, M. A. Richards, R. P. Comer, and A. M. Dziewonski (1985), Lower mantle heterogeneity, dynamic topography and the geoid, Nature, 313(6003), 541-545, doi:10.1038/313541a0. [2] Parsons, B., and S. Daly (1983), The
Revisiting the Continua of Biliteracy: International and Critical Perspectives.
ERIC Educational Resources Information Center
Hornberger, Nancy H.; Skilton-Sylvester, Ellen
2000-01-01
The continua model of biliteracy offers a framework to situate research, teaching, and language planning in linguistically diverse settings. The continua model is revisited from the perspective of international cases of educational policy and practice in linguistically diverse settings, and from a critical perspective that seeks to make explicit…
Radiolytic Cryovolcanism Revisited
NASA Astrophysics Data System (ADS)
Cooper, J. F.; Cooper, P. D.; Sittler, E. C.; Wesenberg, R. P.
2013-12-01
Active geysers of water vapor and ice grains from the south pole of Enceladus are not yet definitively explained in terms of energy sources and processes. Other instances of hot (Io) and cold (Mars, Triton) volcanism beyond Earth are known if not fully understood. We revisit, in comparison to other models, the 'Old Faithful' theory of radiolytic gas-driven cryovolcanism first proposed by Cooper et al. [Plan. Sp. Sci. 2009]. In the energetic electron irradiation environment of Enceladus within Saturn's magnetosphere, a 10-percent duty cycle could be maintained for current geyser activity driven by gases from oxidation of ammonia to N2 and methane to CO2 in the thermal margins of a south polar sea. Much shorter duty cycles down to 0.01 percent would be required to account for thermal power output up to 16 GW, Steady accumulation of oxidant energy over four billion years could have powered all Enceladus emissions over the past four hundred thousand to four hundred million years. There could be separate energy sources driving mass flow and thermal emission over vastly different time scales. Since episodic tidal dissipation on 10 Myr time scales at 0.1 - 1 Gyr intervals [O'Neill and Nimmo, Nature 2010], and thus duty cycles 1 - 10 percent, could heat the polar sea to the current level, the radiolytic energy source could easily power and modulate the geyser mass flow on million-year time scales. Maximum thermal emission temperature 223 K [Abramov and Spencer, Icarus 2009] hints at thermal buffering in the basal and vent wall layers by a 1:1 H2O:H2O2 radiolytic eutectic, assuming deep ice crust saturation with H2O2 from long cumulative surface irradiation and downward ice convection. Due to density stratification the peroxide eutectic and salt water layers could separate, so that the denser peroxide layer (1.2 g/cc) descends to the polar sea while the lighter salt water (1.05 g/cc) rises along separate channels. Methane reservoirs could be found dissolved into the polar
Reframing in dentistry: revisited.
Nuvvula, Sivakumar; Kamatham, Rekalakshmi; Challa, Ramasubbareddy; Asokan, Sharath
2013-01-01
The successful practice of dentistry involves a good combination of technical skills and soft skills. Soft skills or communication skills are not taught extensively in dental schools and it can be challenging to learn and at times in treating dental patients. Guiding the child's behavior in the dental operatory is one of the preliminary steps to be taken by the pediatric dentist and one who can successfully modify the behavior can definitely pave the way for a life time comprehensive oral care. This article is an attempt to revisit a simple behavior guidance technique, reframing and explain the possible psychological perspectives behind it for better use in the clinical practice. PMID:24021326
Daly, Aidan C.; Holmes, Chris
2015-01-01
As cardiac cell models become increasingly complex, a correspondingly complex ‘genealogy’ of inherited parameter values has also emerged. The result has been the loss of a direct link between model parameters and experimental data, limiting both reproducibility and the ability to re-fit to new data. We examine the ability of approximate Bayesian computation (ABC) to infer parameter distributions in the seminal action potential model of Hodgkin and Huxley, for which an immediate and documented connection to experimental results exists. The ability of ABC to produce tight posteriors around the reported values for the gating rates of sodium and potassium ion channels validates the precision of this early work, while the highly variable posteriors around certain voltage dependency parameters suggests that voltage clamp experiments alone are insufficient to constrain the full model. Despite this, Hodgkin and Huxley's estimates are shown to be competitive with those produced by ABC, and the variable behaviour of posterior parametrized models under complex voltage protocols suggests that with additional data the model could be fully constrained. This work will provide the starting point for a full identifiability analysis of commonly used cardiac models, as well as a template for informative, data-driven parametrization of newly proposed models. PMID:27019736
Daly, Aidan C; Gavaghan, David J; Holmes, Chris; Cooper, Jonathan
2015-12-01
As cardiac cell models become increasingly complex, a correspondingly complex 'genealogy' of inherited parameter values has also emerged. The result has been the loss of a direct link between model parameters and experimental data, limiting both reproducibility and the ability to re-fit to new data. We examine the ability of approximate Bayesian computation (ABC) to infer parameter distributions in the seminal action potential model of Hodgkin and Huxley, for which an immediate and documented connection to experimental results exists. The ability of ABC to produce tight posteriors around the reported values for the gating rates of sodium and potassium ion channels validates the precision of this early work, while the highly variable posteriors around certain voltage dependency parameters suggests that voltage clamp experiments alone are insufficient to constrain the full model. Despite this, Hodgkin and Huxley's estimates are shown to be competitive with those produced by ABC, and the variable behaviour of posterior parametrized models under complex voltage protocols suggests that with additional data the model could be fully constrained. This work will provide the starting point for a full identifiability analysis of commonly used cardiac models, as well as a template for informative, data-driven parametrization of newly proposed models. PMID:27019736
NASA Astrophysics Data System (ADS)
Favis-Mortlock, David
2010-05-01
One finding from the GCTE evaluation of soil erosion models (Jetten et al., 1999) is that the models tested were, in general, weak regarding the spatial aspects of erosion. A perfectly adequate simulation of runoff and soil loss at the catchment outlet could be produced even if the model did a poor job of identifying the location of erosion hotspots within that catchment. Spatially, the models could give "the right answer for the wrong reason". As well as casting doubt on the validity of process representations within such a model, this kind of result is clearly unacceptable when using it to plan or evaluate soil conservation measures within the catchment. With this as a background, the RillGrow series of soil erosion models were developed. These represent an eroding hillslope area as a self-organizing system (e.g. Favis-Mortlock, 1998; Favis-Mortlock et al., 2000). Microtopography is considered to determine the spatial pattern of overland flow and hence of surface lowering; such lowering modifies the path of subsequent flow. This simple iterative relationship generates rill networks emergently, i.e. as a collective whole-system response to many local interactions. The approach removes a requirement of many erosion models: the need to ‘pre-specify' rill characteristics even for an unrilled surface. However, computational constraints currently confine RillGrow to simulation of small, plot-sized, areas. Even on such small areas however, model validation is not straightforward. In a series of validation studies, DEMs of the microtopography of real soil surfaces (from both laboratory flumes and hillslope plots) were used as inputs to the RillGrow model. Model-simulated rill networks were then compared with those which developed on the real soil surfaces. Other model outputs (e.g. hydrographs and sedigraphs at the outlet; water depths and velocities at points on the surface) were similarly compared. While conceptually simple, problems with this approach include: * The
NASA Astrophysics Data System (ADS)
Hourdin, Frédéric; Grandpeix, Jean-Yves; Rio, Catherine; Bony, Sandrine; Jam, Arnaud; Cheruy, Frédérique; Rochetin, Nicolas; Fairhead, Laurent; Idelkadi, Abderrahmane; Musat, Ionela; Dufresne, Jean-Louis; Lahellec, Alain; Lefebvre, Marie-Pierre; Roehrig, Romain
2013-05-01
Based on a decade of research on cloud processes, a new version of the LMDZ atmospheric general circulation model has been developed that corresponds to a complete recasting of the parameterization of turbulence, convection and clouds. This LMDZ5B version includes a mass-flux representation of the thermal plumes or rolls of the convective boundary layer, coupled to a bi-Gaussian statistical cloud scheme, as well as a parameterization of the cold pools generated below cumulonimbus by re-evaporation of convective precipitation. The triggering and closure of deep convection are now controlled by lifting processes in the sub-cloud layer. An available lifting energy and lifting power are provided both by the thermal plumes and by the spread of cold pools. The individual parameterizations were carefully validated against the results of explicit high resolution simulations. Here we present the work done to go from those new concepts and developments to a full 3D atmospheric model, used in particular for climate change projections with the IPSL-CM5B coupled model. Based on a series of sensitivity experiments, we document the differences with the previous LMDZ5A version distinguishing the role of parameterization changes from that of model tuning. Improvements found previously in single-column simulations of case studies are confirmed in the 3D model: (1) the convective boundary layer and cumulus clouds are better represented and (2) the diurnal cycle of convective rainfall over continents is delayed by several hours, solving a longstanding problem in climate modeling. The variability of tropical rainfall is also larger in LMDZ5B at intraseasonal time-scales. Significant biases of the LMDZ5A model however remain, or are even sometimes amplified. The paper emphasizes the importance of parameterization improvements and model tuning in the frame of climate change studies as well as the new paradigm that represents the improvement of 3D climate models under the control of
NASA Astrophysics Data System (ADS)
Goutorbe, Bruno
2010-05-01
There are presently several candidate models for the thermal structure and evolution of the oceanic lithosphere, which essentially differ by the imposed basal condition. The latter condition represents the additional heat brought at the base of lithosphere (should it exist), and it can take the form of a fixed basal temperature or a fixed basal heat flow. I investigate this problem with the help of a shear velocity model of the upper mantle. Velocities of the lithospheric mantle are converted to temperatures using up-to-date constraints related to the velocity-temperature relationship (namely, constraints on thermoelastic parameters, mantle composition and attenuation factor), and an averaging by age interval is then applied. A particular care is dedicated to the estimation of final uncertainties on temperature, to allow for a quantitative interpretation. This work reconfirms that heat is brought by some mean at the base of the lithosphere, as a half-space cooling thermal evolution falls well below the seismically derived temperatures and their uncertainties. However, I do not observe within the age range (0-160 My) an asymptotic thickness for the lithosphere, which is at odds with the widely used plate model, whereby the additional heat supply is represented by a fixed temperature at some depth. Adding bathymetry and surface heat flow as joint constraints, I find that a model which prescribes a constant heat flow at some isotherm (the so-called Chablis model) provides a better fit to the data than the plate model. Only a strongly reduced thermal expansivity (reduction by at least 30 per cent with respect to the experimental value) allows the latter model achieving a joint-fitting comparable to the former model, and then with a fit to temperature that remains poor. The good fit of the plate model thus relies on a thermal expansivity reduced down to the lowest limit and on ocean depth, whose behaviour at old ages is considerably obscured by anomalous crust. The
Mancuso, Katherine; Mauck, Matthew C; Kuchenbecker, James A; Neitz, Maureen; Neitz, Jay
2010-01-01
In 1993, DeValois and DeValois proposed a 'multi-stage color model' to explain how the cortex is ultimately able to deconfound the responses of neurons receiving input from three cone types in order to produce separate red-green and blue-yellow systems, as well as segregate luminance percepts (black-white) from color. This model extended the biological implementation of Hurvich and Jameson's Opponent-Process Theory of color vision, a two-stage model encompassing the three cone types combined in a later opponent organization, which has been the accepted dogma in color vision. DeValois' model attempts to satisfy the long-remaining question of how the visual system separates luminance information from color, but what are the cellular mechanisms that establish the complicated neural wiring and higher-order operations required by the Multi-stage Model? During the last decade and a half, results from molecular biology have shed new light on the evolution of primate color vision, thus constraining the possibilities for the visual circuits. The evolutionary constraints allow for an extension of DeValois' model that is more explicit about the biology of color vision circuitry, and it predicts that human red-green colorblindness can be cured using a retinal gene therapy approach to add the missing photopigment, without any additional changes to the post-synaptic circuitry. PMID:20238067
A practical method of predicting client revisit intention in a hospital setting.
Lee, Kyun Jick
2005-01-01
Data mining (DM) models are an alternative to traditional statistical methods for examining whether higher customer satisfaction leads to higher revisit intention. This study used a total of 906 outpatients' satisfaction data collected from a nationwide survey interviews conducted by professional interviewers on a face-to-face basis in South Korea, 1998. Analyses showed that the relationship between overall satisfaction with hospital services and outpatients' revisit intention, along with word-of-mouth recommendation as intermediate variables, developed into a nonlinear relationship. The five strongest predictors of revisit intention were overall satisfaction, intention to recommend to others, awareness of hospital promotion, satisfaction with physician's kindness, and satisfaction with treatment level. PMID:15923917
Revisiting Constructivist Teaching Methods in Ontario Colleges Preparing for Accreditation
ERIC Educational Resources Information Center
Schultz, Rachel A.
2015-01-01
At the time of writing, the first community colleges in Ontario were preparing for transition to an accreditation model from an audit system. This paper revisits constructivist literature, arguing that a more pragmatic definition of constructivism effectively blends positivist and interactionist philosophies to achieve both student centred…
Mancuso, Katherine; Mauck, Matthew C.; Kuchenbecker, James A.; Neitz, Maureen; Neitz, Jay
2011-01-01
In 1993, DeValois and DeValois proposed a “multi-stage color model” to explain how the cortex is ultimately able to deconfound the responses of neurons receiving input from three cone types in order to produce separate red-green and blue-yellow systems, as well as segregate luminance percepts (black-white) from color. This model extended the biological implementation of Hurvich and Jameson’s Opponent-Process Theory of color vision, a two-stage model encompassing the three cone types combined in a later opponent organization, which has been the accepted dogma in color vision. DeValois’ model attempts to satisfy the long-remaining question of how the visual system separates luminance information from color, but what are the cellular mechanisms that establish the complicated neural wiring and higher-order operations required by the Multi-stage Model? During the last decade and a half, results from molecular biology have shed new light on the evolution of primate color vision, thus constraining the possibilities for the visual circuits. The evolutionary constraints allow for an extension of DeValois' model that is more explicit about the biology of color vision circuitry, and it predicts that human red-green colorblindness can be cured using a retinal gene therapy approach to add the missing photopigment, without any additional changes to the post-synaptic circuitry. PMID:20238067
ERIC Educational Resources Information Center
Pike, Gary R.
The relationship between job performance and job satisfaction was evaluated using a longitudinal model. During the winter quarter of 1987, approximately 2,000 students at the University of Tennessee (Knoxville) received a student satisfaction survey designed to measure student opinions about programs and services at the university and department…
ERIC Educational Resources Information Center
Haedt-Matt, Alissa A.; Keel, Pamela K.
2011-01-01
The affect regulation model of binge eating, which posits that patients binge eat to reduce negative affect (NA), has received support from cross-sectional and laboratory-based studies. Ecological momentary assessment (EMA) involves momentary ratings and repeated assessments over time and is ideally suited to identify temporal antecedents and…
Can an Opportunity to Learn at Work Reduce Stress?: A Revisitation of the Job Demand-Control Model
ERIC Educational Resources Information Center
Panari, Chiara; Guglielmi, Dina; Simbula, Silvia; Depolo, Marco
2010-01-01
Purpose: This paper aims to extend the stress-buffering hypothesis of the demand-control model. In addition to the control variable, it seeks to analyse the role of an opportunity for learning and development (L&D) in the workplace as a moderator variable between increased demands and need for recovery. Design/methodology/approach: A questionnaire…
NASA Astrophysics Data System (ADS)
Nazem, Mohsen; Trépanier, Martin; Morency, Catherine
2015-01-01
An Enhanced Intervening Opportunities Model (EIOM) is developed for Public Transit (PT). This is a distribution supply dependent model, with single constraints on trip production for work trips during morning peak hours (6:00 a.m.-9:00 a.m.) within the Island of Montreal, Canada. Different data sets, including the 2008 Origin-Destination (OD) survey of the Greater Montreal Area, the 2006 Census of Canada, GTFS network data, along with the geographical data of the study area, are used. EIOM is a nonlinear model composed of socio-demographics, PT supply data and work location attributes. An enhanced destination ranking procedure is used to calculate the number of spatially cumulative opportunities, the basic variable of EIOM. For comparison, a Basic Intervening Opportunities Model (BIOM) is developed by using the basic destination ranking procedure. The main difference between EIOM and BIOM is in the destination ranking procedure: EIOM considers the maximization of a utility function composed of PT Level Of Service and number of opportunities at the destination, along with the OD trip duration, whereas BIOM is based on a destination ranking derived only from OD trip durations. Analysis confirmed that EIOM is more accurate than BIOM. This study presents a new tool for PT analysts, planners and policy makers to study the potential changes in PT trip patterns due to changes in socio-demographic characteristics, PT supply, and other factors. Also it opens new opportunities for the development of more accurate PT demand models with new emergent data such as smart card validations.
Ballou, David P.; Zhao, Yunde; Brandish, Philip E.; Marletta, Michael A.
2002-01-01
Soluble guanylate cyclase (sGC) is a ferrous iron hemoprotein receptor for nitric oxide (NO). NO binding to the heme activates the enzyme 300-fold. sGC as isolated is five-coordinate, ferrous with histidine as the axial ligand. The NO-activated enzyme is a five-coordinate nitrosyl complex where the axial histidine bond is broken. Past studies using rapid-reaction kinetics demonstrated that both the formation of a six-coordinate intermediate and the conversion of the intermediate to the activated five-coordinate nitrosyl complex depended on the concentration of NO. A model invoking a second NO molecule as a catalyst for the conversion of the six-coordinate intermediate to the five-coordinate sGC–NO complex was proposed to explain the observed kinetic data. A recent study [Bellamy, T. C., Wood, J. & Garthwaite, J. (2002) Proc. Natl. Acad. Sci. USA 99, 507–510] concluded that a simple two-step binding model explains the results. Here we show through further analysis and simulations of previous data that the simple two-step binding model cannot be used to describe our results. Instead we show that a slightly more complex two-step binding model, where NO is used as a ligand in the first step and a catalyst in the second step, can describe our results quite satisfactorily. These new simulations combined with the previous activation data lead to the conclusion that the intermediate six-coordinate sGC–NO complex has substantial activity. The model derived from our simulations also can account for the slow deactivation of sGC that has been observed in vitro. PMID:12209005
NASA Technical Reports Server (NTRS)
Bielawa, Richard L.
1988-01-01
In response to a systematic methodology assessment program directed to the aeroelastic stability of hingeless helicopter rotor blades, improved basic aeroelastic reformulations and new formulations relating to structural sweep were achieved. Correlational results are presented showing the substantially improved performance of the G400 aeroelastic analysis incorporating these new formulations. The formulations pertain partly to sundry solutions to classic problem areas, relating to dynamic inflow with vortex-ring state operation and basic blade kinematics, but mostly to improved physical modeling of elastic axis offset (structural sweep) in the presence of nonlinear structural twist. Specific issues addressed are an alternate modeling of the delta EI torsional excitation due to compound bending using a force integration approach, and the detailed kinematic representation of an elastically deflected point mass of a beam with both structural sweep and nonlinear twist.
Theodorakis, Panagiotis E; Dellago, Christoph; Kahl, Gerhard
2013-01-14
We discuss a coarse-grained model recently proposed by Starr and Sciortino [J. Phys.: Condens. Matter 18, L347 (2006)] for spherical particles functionalized with short single DNA strands. The model incorporates two key aspects of DNA hybridization, i.e., the specificity of binding between DNA bases and the strong directionality of hydrogen bonds. Here, we calculate the effective potential between two DNA-functionalized particles of equal size using a parallel replica protocol. We find that the transition from bonded to unbonded configurations takes place at considerably lower temperatures compared to those that were originally predicted using standard simulations in the canonical ensemble. We put particular focus on DNA-decorations of tetrahedral and octahedral symmetry, as they are promising candidates for the self-assembly into a single-component diamond structure. Increasing colloid size hinders hybridization of the DNA strands, in agreement with experimental findings. PMID:23320725
NASA Astrophysics Data System (ADS)
Oksala, M. E.; Kochukhov, O.; Krtička, J.; Townsend, R. H. D.; Wade, G. A.; Prvák, M.; Mikulášek, Z.; Silvester, J.; Owocki, S. P.
2015-08-01
The initial success of the Rigidly Rotating Magnetosphere (RRM) model application to the B2Vp star σ Ori E by Townsend, Owocki & Groote triggered a renewed era of observational monitoring of this archetypal object. We utilize high-resolution spectropolarimetry and the magnetic Doppler imaging (MDI) technique to simultaneously determine the magnetic configuration, which is predominately dipolar, with a polar strength Bd = 7.3-7.8 kG and a smaller non-axisymmetric quadrupolar contribution, as well as the surface distribution of abundance of He, Fe, C, and Si. We describe a revised RRM model that now accepts an arbitrary surface magnetic field configuration, with the field topology from the MDI models used as input. The resulting synthetic H α emission and broad-band photometric observations generally agree with observations, however, several features are poorly fit. To explore the possibility of a photospheric contribution to the observed photometric variability, the MDI abundance maps were used to compute a synthetic photospheric light curve to determine the effect of the surface inhomogeneities. Including the computed photospheric brightness modulation fails to improve the agreement between the observed and computed photometry. We conclude that the discrepancies cannot be explained as an effect of inhomogeneous surface abundance. Analysis of the UV light variability shows good agreement between observed variability and computed light curves, supporting the accuracy of the photospheric light variation calculation. We thus conclude that significant additional physics is necessary for the RRM model to acceptably reproduce observations of not only σ Ori E, but also other similar stars with significant stellar wind-magnetic field interactions.
Dang, Nhan C; Zazubovich, Valter; Reppert, Mike; Neupane, Bhanu; Picorel, Rafael; Seibert, Michael; Jankowiak, Ryszard
2008-08-14
The CP43 core antenna complex of photosystem II is known to possess two quasi-degenerate "red"-trap states (Jankowiak, R. et al. J. Phys. Chem. B 2000, 104, 11805). It has been suggested recently (Zazubovich, V.; Jankowiak, R. J. Lumin. 2007, 127, 245) that the site distribution functions of the red states (A and B) are uncorrelated and that narrow holes are burned in the subpopulations of chlorophylls (Chls) from states A and B that are the lowest-energy Chl in their complex and previously thought not to transfer energy. This model of uncorrelated excitation energy transfer (EET) between the quasidegenerate bands is expanded by taking into account both electron-phonon and vibrational coupling. The model is applied to fit simultaneously absorption, emission, zero-phonon action, and transient hole burned (HB) spectra obtained for the CP43 complex with minimized contribution from aggregation. It is demonstrated that the above listed spectra can be well-fitted using the uncorrelated EET model, providing strong evidence for the existence of efficient energy transfer between the two lowest energy states, A and B (either from A to B or from B to A), in CP43. Possible candidate Chls for the low-energy A and B states are discussed, providing a link between CP43 structure and spectroscopy. Finally, we propose that persistent holes originate from regular NPHB accompanied by the redistribution of oscillator strength due to excitonic interactions, rather than photoconversion involving Chl-protein hydrogen bonding, as suggested before ( Hughes J. L. et al. Biochemistry 2006, 45, 12345 ). In the accompanying paper (Reppert, M.; Zazubovich, V.; Dang, N. C.; Seibert, M.; Jankowiak, R. J. Phys. Chem. B 2008, 9934), it is demonstrated that the model discussed in this manuscript is consistent with excitonic calculations, which also provide very good fits to both transient and persistent HB spectra obtained under non-line-narrowing conditions. PMID:18642949
NASA Astrophysics Data System (ADS)
Kartalev, M.; Keremidarska, V.; Dryer, M.
2016-04-01
Earlier developed single fluid gas-dynamic model of solar wind-comet ionosphere interaction is applied to reveal some specifics in the morphology of the shocked "contaminated" solar wind region (cometosheath). The model is based on the Euler equations with added mass-loading, mass-loss and frictional force terms. Numerous reactions are taken into account in these terms including photoionization, charge transfer, dissociative recombination and ion-neutral frictional force. The electromagnetic terms are omitted, thus reducing the MHD single-fluid system of equations to gas-dynamic one. The used shock-fitting numerical scheme allows the separation of distinct areas formed by the considered interaction and exploration of their properties in detail. Attention is focused on the region between the shock wave and the contact surface as well as on the positions of these boundaries. Accurate examination of the distribution of density, temperature and velocity reveals spatial variations that resemble the variations registered by a number of spacecraft in the vicinity of comets. No specific comparisons with data are made at this stage. Two very first events of the Rosetta spacecraft's crossing of the magnetic cavity boundary around Comet 67P/Churyumov-Gerasimenko are discussed using a "faux-transient" application of our steady-state model.
Fee, Michale S.
2012-01-01
In its simplest formulation, reinforcement learning is based on the idea that if an action taken in a particular context is followed by a favorable outcome, then, in the same context, the tendency to produce that action should be strengthened, or reinforced. While reinforcement learning forms the basis of many current theories of basal ganglia (BG) function, these models do not incorporate distinct computational roles for signals that convey context, and those that convey what action an animal takes. Recent experiments in the songbird suggest that vocal-related BG circuitry receives two functionally distinct excitatory inputs. One input is from a cortical region that carries context information about the current “time” in the motor sequence. The other is an efference copy of motor commands from a separate cortical brain region that generates vocal variability during learning. Based on these findings, I propose here a general model of vertebrate BG function that combines context information with a distinct motor efference copy signal. The signals are integrated by a learning rule in which efference copy inputs gate the potentiation of context inputs (but not efference copy inputs) onto medium spiny neurons in response to a rewarded action. The hypothesis is described in terms of a circuit that implements the learning of visually guided saccades. The model makes testable predictions about the anatomical and functional properties of hypothesized context and efference copy inputs to the striatum from both thalamic and cortical sources. PMID:22754501
NASA Astrophysics Data System (ADS)
Loeb, N. G.; Wang, H.; Cheng, A.; Kato, S.; Fasullo, J.; Xu, K. M.; Allan, R. P.
2015-12-01
Recent studies have shown strong linkages between hemispheric asymmetries in atmospheric and oceanic energy budgets, tropical precipitation and the mean position of the Intertropical Convergence Zone (ITCZ). The energetics framework has been used to explain why the mean position of the ITCZ is in the Northern Hemisphere and to study large-scale circulation and precipitation responses to changes in the hemispheric distribution of heating. Here, we expand upon these earlier studies by also considering estimates of hemispheric asymmetry in surface and atmospheric radiation budget derived from satellite observations, which enables a decomposition of cross-equatorial heat transport in terms of radiative and non-radiative (i.e., combined latent and sensible heat) components. Satellite observations of top-of-atmosphere (TOA) and surface radiation budget from the Clouds and the Earth's Radiation Budget (CERES) are combined with mass corrected vertically integrated atmospheric energy divergence from reanalysis to infer the regional distribution of the TOA, atmospheric and surface energy budget terms over the globe. Observed radiative and combined sensible and latent heat contributions to atmospheric and oceanic cross-equatorial heat transports are compared with simulations from 30 models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Results show that most CMIP5 models that overestimate tropical precipitation in the SH have too much net downward surface radiation and combined latent and sensible heat flux in the SH relative to the NH. In addition, many of the models also underestimate atmospheric radiative cooling in the SH compared to the NH. Consequently, the models have excessive heating of the SH atmosphere and anomalous SH to NH cross-equatorial heat transport. The anomalous northward heat transport occurs via the upper branch of the northern Hadley Cell, while anomalous NH to SH moisture transport occurs in the lower branch of the northern
Gregory, Sonia M.; Pokorny, Antje; Almeida, Paulo F.F.
2009-01-01
Abstract The all-or-none kinetic model that we recently proposed for the antimicrobial peptide cecropin A is tested here for magainin 2. In mixtures of phosphatidylcholine (PC)/phosphatidylglycerol (PG) 50:50 and 70:30, release of contents from lipid vesicles occurs in an all-or-none fashion and the differences between PC/PG 50:50 and 70:30 can be ascribed mainly to differences in binding, which was determined independently and is ∼20 times greater to PC/PG 50:50 than to 70:30. Only one variable parameter, β, corresponding to the ratio of the rates of pore opening to pore closing, is used to fit dye release kinetics from these two mixtures, for several peptide/lipid ratios ranging from 1:25 to 1:200. However, unlike for cecropin A where it stays almost constant, β increases five times as the PG content of the vesicles increases from 30 to 50%. Thus, magainin 2 is more sensitive to anionic lipid content than cecropin A. But overall, magainin follows the same all-or-none kinetic model as cecropin A in these lipid mixtures, with slightly different parameter values. When the PG content is reduced to 20 mol %, dye release becomes very low; the mechanism appears to change, and is consistent with a graded kinetic model. We suggest that the peptide may be inducing formation of PG domains. In either mechanism, no peptide oligomerization occurs and magainin catalyzes dye release in proportion to its concentration on the membrane in a peptide state that we call a pore. We envision this structure as a chaotic or stochastic type of pore, involving both lipids and peptides, not a well-defined, peptide-lined channel. PMID:19134472
NASA Astrophysics Data System (ADS)
Braithwaite, C. J. R.; Montaggioni, L. F.; Camoin, G. F.; Dalmasso, H.; Dullo, W. C.; Mangini, A.
Until recently, concepts of coral reef growth and accumulation have been predominantly based on a Darwinian model. In this, the upwards and outwards growth of a reef core (a coral framework) takes place over a foreslope consisting of reef talus, with the simultaneous filling of the back-reef lagoon by reef-derived debris. The principal adaptations of this pattern relate to the influence of relative changes in sea level and commonly ignore oceanographic factors such as storm frequency and severity. Boreholes through the outer edge of a fringing reef in the Seychelles, western Indian Ocean, reveal a record of Holocene sediment accumulation first established approximately 8ka ago. Faunal and floral associations show that growth of this body began in relatively deep water but that this shallowed to <5m within 1ka. Subsequent accumulation was of ``keep-up'' style but, as the rate of sea-level rise slowed, shoaling became more frequent and aggradation was limited by reducing accommodation space. Constructional facies are characterised either by massive corals, including Leptastrea, Porites and faviids, or by branching corals, typically Acropora of the danai-robusta group. Coral surfaces may be encrusted by red algae, foraminifera and vermetids, and are commonly bored by filamentous algae, clionids and molluscs. However, detrital facies are volumetrically dominant, and the paucity of a constructional framework requires a re-evaluation of models of reef accretion. New models relate the geometry of accretion to the interplay between extreme storm events and fairweather hydrodynamic conditions. These suggest that a contiguous framework forms in areas of moderate fairweather energy without extreme storm events. Severe storms destroy the continuity of reef structures and generate increasing volumes of coarse detritus. Low storm severity, coupled with low fairweather hydrodynamic energy, may promote the accumulation of fine-grained reef-derived sediments that inhibit framework
NASA Astrophysics Data System (ADS)
Loeb, Norman G.; Wang, Hailan; Cheng, Anning; Kato, Seiji; Fasullo, John T.; Xu, Kuan-Man; Allan, Richard P.
2016-05-01
Satellite based top-of-atmosphere (TOA) and surface radiation budget observations are combined with mass corrected vertically integrated atmospheric energy divergence and tendency from reanalysis to infer the regional distribution of the TOA, atmospheric and surface energy budget terms over the globe. Hemispheric contrasts in the energy budget terms are used to determine the radiative and combined sensible and latent heat contributions to the cross-equatorial heat transports in the atmosphere (AHTEQ) and ocean (OHTEQ). The contrast in net atmospheric radiation implies an AHTEQ from the northern hemisphere (NH) to the southern hemisphere (SH) (0.75 PW), while the hemispheric difference in sensible and latent heat implies an AHTEQ in the opposite direction (0.51 PW), resulting in a net NH to SH AHTEQ (0.24 PW). At the surface, the hemispheric contrast in the radiative component (0.95 PW) dominates, implying a 0.44 PW SH to NH OHTEQ. Coupled model intercomparison project phase 5 (CMIP5) models with excessive net downward surface radiation and surface-to-atmosphere sensible and latent heat transport in the SH relative to the NH exhibit anomalous northward AHTEQ and overestimate SH tropical precipitation. The hemispheric bias in net surface radiative flux is due to too much longwave surface radiative cooling in the NH tropics in both clear and all-sky conditions and excessive shortwave surface radiation in the SH subtropics and extratropics due to an underestimation in reflection by clouds.
NASA Astrophysics Data System (ADS)
Bakış, H.; Bakış, V.; Eker, Z.; Demircan, O.
2016-05-01
The spectral lines of the secondary component of the active binary system R Ara were uncovered for the first time, which allowed directly to determine the parameters of the spectroscopic orbit. The mass ratio of the system is updated to a new observational value of M2/M1 = 0.305 ± 0.005 which is ˜20 per cent smaller than the literature value (M2/M1 = 0.39). Modelling the reconstructed component spectra yielded the equatorial rotational velocities of the components as vrot1 = 202 km s-1 and vrot2 = 73 km s-1 indicating a very fast rotation (˜5 times faster than the synchronous rotation velocity) for the primary and synchronous rotation for the secondary component. The circumstellar material in the system was investigated using the Hipparcossatellite data and the high-resolution (R ˜ 41 000) spectral data. According to our model, there is always material transferring from the secondary component on to the primary causing a hot region on its surface. The structural difference between the spectra taken at the same orbital phase but at different epochs proved that the density and the velocity of the transferring material are variable. There are three main trends in the light curve and spectral line variations suggesting the activity cycles for the system, namely quiescent, moderate and, active cycles. It was estimated that the circumstellar material around could be extended to large distances up to 40 R⊙ from the system.
NASA Astrophysics Data System (ADS)
Bunzel, Felix; Notz, Dirk; Toudal Pedersen, Leif
2016-04-01
The thickness of snow covering sea ice is a crucial parameter in any algorithm deriving sea-ice thickness from satellite-measured sea-ice freeboard. Here we investigate whether such snow thickness can robustly be estimated by assuming a simple correlation between snow thickness and sea-ice thickness. Such correlation is sometimes applied in schemes that aim at correcting the multi-year Warren snow climatology for the more recent past. In order to quantify the relationship between sea-ice thickness and snow depth, we analyse the correlation of ice thickness and snow depth in a multi-century pre-industrial model simulation and in a transient historical simulation performed with the Max Planck Institute Earth System Model (MPI-ESM). We find correlation coefficients to be low in the central Arctic, while they show substantial regional and temporal variations in the vicinity of the ice edge. Our results point towards possibly substantial errors in algorithms that assume too simplistic a relationship between sea-ice thickness and snow depth.
Saint-Cyr, Manuel Jimmy; Perrin-Guyomard, Agnès; Manceau, Jacqueline; Houée, Paméla; Delmas, Jean-Michel; Rolland, Jean-Guy; Laurentie, Michel
2015-12-01
Due to its toxic properties, high stability, and prevalence, the presence of deoxynivalenol (DON) in the food chain is a major threat to food safety and therefore a health risk for both humans and animals. In this study, experiments were carried out with sows and female rats to examine the kinetics of DON after intravenous and oral administration at 100 µg/kg of body weight. After intravenous administration of DON in pigs, a two-compartment model with rapid initial distribution (0.030 ± 0.019 h) followed by a slower terminal elimination phase (1.53 ± 0.54 h) was fitted to the concentration profile of DON in pig plasma. In rats, a short elimination half-life (0.46 h) and a clearance of 2.59 L/h/kg were estimated by sparse sampling non-compartmental analysis. Following oral exposure, DON was rapidly absorbed and reached maximal plasma concentrations (Cmax) of 42.07 ± 8.48 and 10.44 ± 5.87 µg/L plasma after (t(max)) 1.44 ± 0.52 and 0.17 h in pigs and rats, respectively. The mean bioavailability of DON was 70.5% ± 25.6% for pigs and 47.3% for rats. In the framework of DON risk assessment, these two animal models could be useful in an exposure scenario in two different ways because of their different bioavailability. PMID:26633505
Saint-Cyr, Manuel Jimmy; Perrin-Guyomard, Agnès; Manceau, Jacqueline; Houée, Paméla; Delmas, Jean-Michel; Rolland, Jean-Guy; Laurentie, Michel
2015-01-01
Due to its toxic properties, high stability, and prevalence, the presence of deoxynivalenol (DON) in the food chain is a major threat to food safety and therefore a health risk for both humans and animals. In this study, experiments were carried out with sows and female rats to examine the kinetics of DON after intravenous and oral administration at 100 µg/kg of body weight. After intravenous administration of DON in pigs, a two-compartment model with rapid initial distribution (0.030 ± 0.019 h) followed by a slower terminal elimination phase (1.53 ± 0.54 h) was fitted to the concentration profile of DON in pig plasma. In rats, a short elimination half-life (0.46 h) and a clearance of 2.59 L/h/kg were estimated by sparse sampling non-compartmental analysis. Following oral exposure, DON was rapidly absorbed and reached maximal plasma concentrations (Cmax) of 42.07 ± 8.48 and 10.44 ± 5.87 µg/L plasma after (tmax) 1.44 ± 0.52 and 0.17 h in pigs and rats, respectively. The mean bioavailability of DON was 70.5% ± 25.6% for pigs and 47.3% for rats. In the framework of DON risk assessment, these two animal models could be useful in an exposure scenario in two different ways because of their different bioavailability. PMID:26633505
NASA Astrophysics Data System (ADS)
Izzo, Dario
2015-01-01
The orbital boundary value problem, also known as Lambert problem, is revisited. Building upon Lancaster and Blanchard approach, new relations are revealed and a new variable representing all problem classes, under L-similarity, is used to express the time of flight equation. In the new variable, the time of flight curves have two oblique asymptotes and they mostly appear to be conveniently approximated by piecewise continuous lines. We use and invert such a simple approximation to provide an efficient initial guess to an Householder iterative method that is then able to converge, for the single revolution case, in only two iterations. The resulting algorithm is compared, for single and multiple revolutions, to Gooding's procedure revealing to be numerically as accurate, while having a significantly smaller computational complexity.
Anonymous Signatures Revisited
NASA Astrophysics Data System (ADS)
Saraswat, Vishal; Yun, Aaram
We revisit the notion of the anonymous signature, first formalized by Yang, Wong, Deng and Wang [10], and then further developed by Fischlin [4] and Zhang and Imai [11]. We present a new formalism of anonymous signature, where instead of the message, a part of the signature is withheld to maintain anonymity. We introduce the notion unpretendability to guarantee infeasibility for someone other than the correct signer to pretend authorship of the message and signature. Our definition retains applicability for all previous applications of the anonymous signature, provides stronger security, and is conceptually simpler. We give a generic construction from any ordinary signature scheme, and also show that the short signature scheme by Boneh and Boyen [2] can be naturally regarded as such a secure anonymous signature scheme according to our formalism.
NASA Astrophysics Data System (ADS)
Balcerak, Ernie
2012-12-01
In January 1994, the two geostationary satellites known as Anik-E1 and Anik-E2, operated by Telesat Canada, failed one after the other within 9 hours, leaving many northern Canadian communities without television and data services. The outage, which shut down much of the country's broadcast television for hours and cost Telesat Canada more than $15 million, generated significant media attention. Lam et al. used publicly available records to revisit the event; they looked at failure details, media coverage, recovery effort, and cost. They also used satellite and ground data to determine the precise causes of those satellite failures. The researchers traced the entire space weather event from conditions on the Sun through the interplanetary medium to the particle environment in geostationary orbit.
Chibani, Omar; Moftah, Belal; Ma, C.-M. Charlie
2011-01-15
Purpose: To commission Monte Carlo beam models for five Varian megavoltage photon beams (4, 6, 10, 15, and 18 MV). The goal is to closely match measured dose distributions in water for a wide range of field sizes (from 2x2 to 35x35 cm{sup 2}). The second objective is to reinvestigate the sensitivity of the calculated dose distributions to variations in the primary electron beam parameters. Methods: The GEPTS Monte Carlo code is used for photon beam simulations and dose calculations. The linear accelerator geometric models are based on (i) manufacturer specifications, (ii) corrections made by Chibani and Ma [''On the discrepancies between Monte Carlo dose calculations and measurements for the 18 MV Varian photon beam,'' Med. Phys. 34, 1206-1216 (2007)], and (iii) more recent drawings. Measurements were performed using pinpoint and Farmer ionization chambers, depending on the field size. Phase space calculations for small fields were performed with and without angle-based photon splitting. In addition to the three commonly used primary electron beam parameters (E{sub AV} is the mean energy, FWHM is the energy spectrum broadening, and R is the beam radius), the angular divergence ({theta}) of primary electrons is also considered. Results: The calculated and measured dose distributions agreed to within 1% local difference at any depth beyond 1 cm for different energies and for field sizes varying from 2x2 to 35x35 cm{sup 2}. In the penumbra regions, the distance to agreement is better than 0.5 mm, except for 15 MV (0.4-1 mm). The measured and calculated output factors agreed to within 1.2%. The 6, 10, and 18 MV beam models use {theta}=0 deg., while the 4 and 15 MV beam models require {theta}=0.5 deg. and 0.6 deg., respectively. The parameter sensitivity study shows that varying the beam parameters around the solution can lead to 5% differences with measurements for small (e.g., 2x2 cm{sup 2}) and large (e.g., 35x35 cm{sup 2}) fields, while a perfect agreement is
Toffano-Nioche, Claire; Gautheret, Daniel; Leclerc, Fabrice
2015-01-01
A structural and functional classification of H/ACA and H/ACA-like motifs is obtained from the analysis of the H/ACA guide RNAs which have been identified previously in the genomes of Euryarchaea (Pyrococcus) and Crenarchaea (Pyrobaculum). A unified structure/function model is proposed based on the common structural determinants shared by H/ACA and H/ACA-like motifs in both Euryarchaea and Crenarchaea. Using a computational approach, structural and energetic rules for the guide:target RNA-RNA interactions are derived from structural and functional data on the H/ACA RNP particles. H/ACA(-like) motifs found in Pyrococcus are evaluated through the classification and their biological relevance is discussed. Extra-ribosomal targets found in both Pyrococcus and Pyrobaculum might support the hypothesis of a gene regulation mediated by H/ACA(-like) guide RNAs in archaea. PMID:26240384
NASA Astrophysics Data System (ADS)
Mielikainen, Jarno; Huang, Bormin; Huang, Allen
2015-10-01
The Thompson cloud microphysics scheme is a sophisticated cloud microphysics scheme in the Weather Research and Forecasting (WRF) model. The scheme is very suitable for massively parallel computation as there are no interactions among horizontal grid points. Compared to the earlier microphysics schemes, the Thompson scheme incorporates a large number of improvements. Thus, we have optimized the speed of this important part of WRF. Intel Many Integrated Core (MIC) ushers in a new era of supercomputing speed, performance, and compatibility. It allows the developers to run code at trillions of calculations per second using the familiar programming model. In this paper, we present our results of optimizing the Thompson microphysics scheme on Intel Many Integrated Core Architecture (MIC) hardware. The Intel Xeon Phi coprocessor is the first product based on Intel MIC architecture, and it consists of up to 61 cores connected by a high performance on-die bidirectional interconnect. The coprocessor supports all important Intel development tools. Thus, the development environment is familiar one to a vast number of CPU developers. Although, getting a maximum performance out of MICs will require using some novel optimization techniques. New optimizations for an updated Thompson scheme are discusses in this paper. The optimizations improved the performance of the original Thompson code on Xeon Phi 7120P by a factor of 1.8x. Furthermore, the same optimizations improved the performance of the Thompson on a dual socket configuration of eight core Intel Xeon E5-2670 CPUs by a factor of 1.8x compared to the original Thompson code.
NASA Astrophysics Data System (ADS)
Gibbs, Jeremy A.; Fedorovich, Evgeni; Shapiro, Alan
2015-02-01
Two formulations of the surface thermal boundary condition commonly employed in numerical modelling of atmospheric stably stratified surface-layer flows are evaluated using analytical considerations and observational data from the Cabauw site in the Netherlands. The first condition is stated in terms of the surface heat flux and the second is stated in terms of the vertical potential temperature difference. The similarity relationships used to relate the flux and the difference are based on conventional log-linear expressions for vertical profiles of wind velocity and potential temperature. The heat-flux formulation results in two physically meaningful values for the friction velocity with no obvious criteria available to choose between solutions. Both solutions can be obtained numerically, which casts doubt on discarding one of the solutions as was previously suggested based on stability arguments. This solution ambiguity problem is identified as the key issue of the heat-flux condition formulation. In addition, the agreement between the temperature difference evaluated from similarity solutions and their measurement-derived counterparts from the Cabauw dataset appears to be very poor. Extra caution should be paid to the iterative procedures used in the model algorithms realizing the heat-flux condition as they could often provide only partial solutions for the friction velocity and associated temperature difference. Using temperature difference as the lower boundary condition bypasses the ambiguity problem and provides physically meaningful values of heat flux for a broader range of stability condition in terms of the flux Richardson number. However, the agreement between solutions and observations of the heat flux is again rather poor. In general, there is a great need for practicable similarity relationships capable of treating the vertical turbulent transport of momentum and heat under conditions of strong stratification in the surface layer.
NASA Astrophysics Data System (ADS)
Li, Maolin; Chen, Guofang
2013-11-01
The early reported pseudo-first-order reaction kinetics of the polymer-supported metallic nanocatalysts for the model reaction of p-nitrophenol (p-NP)/NaBH4 were probably oversimplified. Here a detailed study of p-NP reduction by NaBH4 in the presence of the raspberry-like poly(allylamine hydrochloride)-modified polymer poly(glycidyl methacrylate) composite sub-microspheres with tunable gold nanoparticles (PGMA@PAH@AuNPs) was presented. Effects of polyelectrolyte concentration, the ratio of polymer spheres to gold nanoparticles, and the solution pH value for composite synthesis on the induction period, reaction time, average reaction rate and average turnover frequency were systematically investigated. Experimental results in all cases of our study revealed an nth order (n > 1) of the p-NP/NaBH4 catalytic reaction by the prepared polymer composite particles. The apparent order of reaction, n, is dependent on the total surface area of the coated gold nanoparticles on the polymer spheres, which can be closely correlated with the tunable gold nanoparticle surface coverage. The mechanism of the observed catalytic activity enhancement was proposed based on active epoxy groups of the polymer spheres and a large adsorption of p-nitrophenolate anions onto the positively-charged spheres.
Bohr's 1913 molecular model revisited
Svidzinsky, Anatoly A.; Scully, Marlan O.; Herschbach, Dudley R.
2005-01-01
It is generally believed that the old quantum theory, as presented by Niels Bohr in 1913, fails when applied to few electron systems, such as the H2 molecule. Here, we find previously undescribed solutions within the Bohr theory that describe the potential energy curve for the lowest singlet and triplet states of H2 about as well as the early wave mechanical treatment of Heitler and London. We also develop an interpolation scheme that substantially improves the agreement with the exact ground-state potential curve of H2 and provides a good description of more complicated molecules such as LiH, Li2, BeH, and He2. PMID:16103360
Bohr's 1913 molecular model revisited.
Svidzinsky, Anatoly A; Scully, Marlan O; Herschbach, Dudley R
2005-08-23
It is generally believed that the old quantum theory, as presented by Niels Bohr in 1913, fails when applied to few electron systems, such as the H(2) molecule. Here, we find previously undescribed solutions within the Bohr theory that describe the potential energy curve for the lowest singlet and triplet states of H(2) about as well as the early wave mechanical treatment of Heitler and London. We also develop an interpolation scheme that substantially improves the agreement with the exact ground-state potential curve of H(2) and provides a good description of more complicated molecules such as LiH, Li(2), BeH, and He(2). PMID:16103360
Stacking Global Seismograms Revisited
NASA Astrophysics Data System (ADS)
Shearer, P. M.; Buehler, J. S.; Denolle, M.; Fan, W.; Ma, Z.; Mancinelli, N. J.; Matoza, R. S.; Wang, W.; Wang, Y.; Zhan, Z.
2014-12-01
Over 20 years ago, stacks of global seismograms produced direct images of the global seismic wavefield highlighting the visibility, frequency content, and polarity of known seismic phases, and also identified a host of new phases associated with reflections and phase conversions from upper-mantle discontinuities. Two different stacking methods proved particularly useful: (1) STA/LTA-filtered stacks that describe the local signal-to-noise characteristics of the major seismic phases. These serve to image the entire wavefield in a uniform way for educational purposes and to show which phases are observed most clearly as a guide to future research. These stacks also resolve SH versus SV timing differences consistent with radial anisotropy. (2) Reference-phase stacks that preserve the polarity, amplitude, and timing of traces with respect to a specified target phase. These show a large number of top-side and bottom-side reflections and phase conversions from the 410- and 660-km discontinuities that create weak phases with a characteristic "railroad track" appearance both preceding and following many of the main seismic phases. Reference-phase stacking can also be used to produce coherent surface-wave stacks at very long periods, which directly show the dispersive character of the surface waves. Here we revisit and update these stacks by exploiting the vastly increased data now available from the IRIS DMC to produce greatly improved wavefield images. We present several examples of the different stacking approaches and point out their various features, including promising targets for future research.
Aziz, M; Jacob, A; Wang, P
2014-01-01
Sepsis is a life-threatening illness that occurs due to an abnormal host immune network which extends through the initial widespread and overwhelming inflammation, and culminates at the late stage of immunosupression. Recently, interest has been shifted toward therapies aimed at reversing the accompanying periods of immune suppression. Studies in experimental animals and critically ill patients have demonstrated that increased apoptosis of lymphoid organs and some parenchymal tissues contributes to this immune suppression, anergy and organ dysfunction. Immediate to the discoveries of the intracellular proteases, caspases for the induction of apoptosis and inflammation, and their striking roles in sepsis have been focused elaborately in a number of original and review articles. Here we revisited the different aspects of caspases in terms of apoptosis, pyroptosis, necroptosis and inflammation and focused their links in sepsis by reviewing several recent findings. In addition, we have documented striking perspectives which not only rewrite the pathophysiology, but also modernize our understanding for developing novel therapeutics against sepsis. PMID:25412304
42 CFR 488.30 - Revisit user fee for revisit surveys.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 42 Public Health 5 2012-10-01 2012-10-01 false Revisit user fee for revisit surveys. 488.30 Section 488.30 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) STANDARDS AND CERTIFICATION SURVEY, CERTIFICATION, AND ENFORCEMENT PROCEDURES General Provisions § 488.30 Revisit user fee...
Revisiting a magneto-elastic strange attractor
NASA Astrophysics Data System (ADS)
Tam, Jee Ian; Holmes, Philip
2014-03-01
We revisit an early example of a nonlinear oscillator that exhibits chaotic motions when subjected to periodic excitation: the magneto-elastically buckled beam. In the paper of Moons and Holmes (1980) [1] magnetic field calculations were outlined but not carried through; instead the nonlinear forces responsible for creation of a two-well potential and buckling were fitted to a polynomial function after reduction to a single mode model. In the present paper we compute the full magnetic field and use it to approximate the forces acting on the beam, also using a single mode reduction. This provides a complete model that accurately predicts equilibria, bifurcations, and free oscillation frequencies of an experimental device. We also compare some periodic, transient and chaotic motions with those obtained by numerical simulations of the single mode model, further illustrating the rich dynamical behavior of this simple electromechanical system.
Cultural Warping of Childbirth, Revisited
Budin, Wendy C.
2007-01-01
In this column, the editor of The Journal of Perinatal Education revisits Doris Haire's classic 1972 article, “The Cultural Warping of Childbirth,” and describes the birth culture of today. The editor also describes the contents of this issue, which offer a broad range of resources, research, and inspiration for childbirth educators in their efforts to promote normal birth.
Erratum: Interstellar Abundance Standards Revisited
NASA Astrophysics Data System (ADS)
Sofia, U. J.; Meyer, D. M.
2001-09-01
In the Letter ``Interstellar Abundance Standards Revisited'' by U. J. Sofia and D. M. Meyer (ApJ, 554, L221 [2001]), Table 2 and its footnotes contain several typographical errors. The corrected table is shown below. We note that the solar reference standard now implies a positive abundance of nitrogen in halo dust.
The "Mushroom Cloud" Demonstration Revisited
ERIC Educational Resources Information Center
Panzarasa, Guido; Sparnacci, Katia
2013-01-01
A revisitation of the classical "mushroom cloud" demonstration is described. Instead of aniline and benzoyl peroxide, the proposed reaction involves household chemicals such as alpha-pinene (turpentine oil) and trichloroisocyanuric acid ("Trichlor") giving an impressive demonstration of oxidation and combustion reactions that…
Revisiting the 1761 Transatlantic Tsunami
NASA Astrophysics Data System (ADS)
Baptista, Maria Ana; Wronna, Martin; Miranda, Jorge Miguel
2016-04-01
The tsunami catalogs of the Atlantic include two transatlantic tsunamis in the 18th century the well known 1st November 1755 and the 31st March 1761. The 31st March 1761 earthquake struck Portugal, Spain, and Morocco. The earthquake occurred around noontime in Lisbon alarming the inhabitants and throwing down ruins of the past 1st November 1755 earthquake. According to several sources, the earthquake was followed by a tsunami observed as far as Cornwall (United Kingdom), Cork (Ireland) and Barbados (Caribbean). The analysis of macroseismic information and its compatibility with tsunami travel time information led to a source area close to the Ampere Seamount with an estimated epicenter circa 34.5°N 13°W. The estimated magnitude of the earthquake was 8.5. In this study, we revisit the tsunami observations, and we include a report from Cadiz not used before. We use the results of the compilation of the multi-beam bathymetric data, that covers the area between 34°N - 38°N and 12.5°W - 5.5°W and use the recent tectonic map published for the Southwest Iberian Margin to select among possible source scenarios. Finally, we use a non-linear shallow water model that includes the discretization and explicit leap-frog finite difference scheme to solve the shallow water equations in the spherical or Cartesian coordinate to compute tsunami waveforms and tsunami inundation and check the results against the historical descriptions to infer the source of the event. This study received funding from project ASTARTE- Assessment Strategy and Risk Reduction for Tsunamis in Europe a collaborative project Grant 603839, FP7-ENV2013 6.4-3
Dynamical spin structure factor of one-dimensional interacting fermions
NASA Astrophysics Data System (ADS)
Zyuzin, Vladimir A.; Maslov, Dmitrii L.
2015-02-01
We revisit the dynamic spin susceptibility χ (q ,ω ) of one-dimensional interacting fermions. To second order in the interaction, backscattering results in a logarithmic correction to χ (q ,ω ) at q ≪kF , even if the single-particle spectrum is linearized near the Fermi points. Consequently, the dynamic spin structure factor Im χ (q ,ω ) is nonzero at frequencies above the single-particle continuum. In the boson language, this effect results from the marginally irrelevant backscattering operator of the sine-Gordon model. Away from the threshold, the high-frequency tail of Im χ (q ,ω ) due to backscattering is larger than that due to finite mass by a factor of kF/q . We derive the renormalization group equations for the coupling constants of the g -ology model at finite ω and q and find the corresponding expression for χ (q ,ω ) , valid to all orders in the interaction but not in the immediate vicinity of the continuum boundary, where the finite-mass effects become dominant.
Electron heating in capacitively coupled plasmas revisited
NASA Astrophysics Data System (ADS)
Lafleur, T.; Chabert, P.; Booth, J. P.
2014-06-01
We revisit the problem of electron heating in capacitively coupled plasmas (CCPs), and propose a method for quantifying the level of collisionless and collisional heating in plasma simulations. The proposed procedure, based on the electron mechanical energy conservation equation, is demonstrated with particle-in-cell simulations of a number of single and multi-frequency CCPs operated in regimes of research and industrial interest. In almost all cases tested, the total electron heating is comprised of collisional (ohmic) and pressure heating parts. This latter collisionless component is in qualitative agreement with the mechanism of electron heating predicted from the recent re-evaluation of theoretical models. Finally, in very electrically asymmetric plasmas produced in multi-frequency discharges, we observe an additional collisionless heating mechanism associated with electron inertia.
Complexity and Control in Solitary Conductive PDEs
NASA Astrophysics Data System (ADS)
Ivancevic, Vladimir G.; Reid, Darryn J.
2015-11-01
In this Chapter, we review and analyze models of controlled complexity in nonlinear pulse conduction, ranging from the Hodgkin-Huxley action potentials propagating along neural fibers to rogue waves in optical fibers. The novel model proposed is an alternative to the Hodgkin-Huxley neural model in the form of the sine-Gordon wave equation. This new alternative explains pulse conduction in terms of general wave phenomena (such as kinks, solitons and breathers).
Hénin, Emilie; Meille, Christophe; Barbolosi, Dominique; You, Benoit; Guitton, Jérôme; Iliadis, Athanassios; Freyer, Gilles
2016-04-01
The MODEL1 trial is the first model-driven phase I/II dose-escalation study of densified docetaxel plus epirubicin administration in metastatic breast cancer patients, a regimen previously known to induce unacceptable life-threatening toxicities. The primary objective was to determine the maximum tolerated dose of this densified regimen. Study of the efficacy was a secondary objective. Her2-negative, hormone-resistant metastatic breast cancer patients were treated with escalating doses of docetaxel plus epirubicin every 2 weeks for six cycles with granulocyte colony stimulating factor support. A total of 16 patients were treated with total doses ranging from 85 to 110 mg of docetaxel plus epirubicin per cycle. Dose escalation was controlled by a non-hematological toxicity model. Dose densification was guided by a model of neutrophil kinetics, able to optimize docetaxel plus epirubicin dosing with respect to pre-defined acceptable levels of hematological toxicity while ensuring maximal efficacy. The densified treatment was safe since hematological toxicity was much lower compared to previous findings, and other adverse events were consistent with those observed with this regimen. The maximal tolerated dose was 100 mg given every 2 weeks. The response rate was 45 %; median progression-free survival was 10.4 months, whereas 54.6 months of median overall survival was achieved. The optimized docetaxel plus epirubicin dosing regimen led to fewer toxicities associated with higher efficacy as compared with standard or empirical densified dosing. This study suggests that model-driven dosage adjustment can lead to improved efficacy-toxicity balance in patients with cancer when several anticancer drugs are combined. PMID:27002506
First Grade Writers Revisit Their Work
ERIC Educational Resources Information Center
Hansen, Jane A.
2007-01-01
In this article, the author focuses on first grade readers and writers who revisit their work and describes what first-graders do when they revisit their writing about science and literature and review collections of their work. The first-graders discussed here are in Elaine O'Connor's classroom at Clark Elementary School in Charlottesville. In a…
Benjamin Franklin and Mesmerism, revisited.
McConkey, Kevin M; Perry, Campbell
2002-10-01
The authors revisit and update their previous historiographical note (McConkey & Perry, 1985) on Benjamin Franklin's involvement with and investigation of animal magnetism or mesmerism. They incorporate more recent literature and offer additional comment about Franklin's role in and views about mesmerism. Franklin had a higher degree of personal involvement with and a more detailed opinion of mesmerism than has been previously appreciated. PMID:12362950
Interpolating function and Stokes phenomena
NASA Astrophysics Data System (ADS)
Honda, Masazumi; Jatkar, Dileep P.
2015-11-01
When we have two expansions of physical quantity around two different points in parameter space, we can usually construct a family of functions, which interpolates the both expansions. In this paper we study analytic structures of such interpolating functions and discuss their physical implications. We propose that the analytic structures of the interpolating functions provide information on analytic property and Stokes phenomena of the physical quantity, which we approximate by the interpolating functions. We explicitly check our proposal for partition functions of zero-dimensional φ4 theory and Sine-Gordon model. In the zero dimensional Sine-Gordon model, we compare our result with a recent result from resurgence analysis. We also comment on construction of interpolating function in Borel plane.
Vortex operator and BKT transition in Abelian duality
NASA Astrophysics Data System (ADS)
Chern, Tong
2016-04-01
We give a new simple derivation for the sine-Gordon description of Berezinskii-Kosterlitz-Thouless (BKT) phase transition. Our derivation is simpler than traditional derivations. Besides, our derivation is a continuous field theoretic derivation by using path integration, different from the traditional derivations which are based on lattice theory or based on Coulomb gas model. Our new derivation relies on Abelian duality of two dimensional quantum field theory. By utilizing this duality in path integration, we find that the vortex configurations are naturally mapped to exponential operators in dual description. Since these operators are the vortex operators that can create vortices, the sine-Gordon description then naturally follows. Our method may be useful for the investigation to the BKT physics of superconductors.
Hormuzdiar, J.N.; Hsu, S.D.
1999-02-01
We describe a class of pionic breather solutions (PBS) which appear in the chiral Lagrangian description of low-energy QCD. These configurations are long lived, with lifetimes greater than 10{sup 3} fm/c, and could arise as remnants of disoriented chiral condensate (DCC) formation at RHIC. We show that the chiral Lagrangian equations of motion for a uniformly isospin-polarized domain reduce to those of the sine-Gordon model. Consequently, our solutions are directly related to the breather solutions of sine-Gordon theory in 3+1 dimensions. We investigate the possibility of PBS formation from multiple domains of DCC, and show that the probability of formation is non-negligible. {copyright} {ital 1999} {ital The American Physical Society}
Local conformational perturbations of the DNA molecule in the SG-model
Krasnobaeva, L. A.; Shapovalov, A. V.
2015-11-17
Within the formalism of the Fokker–Planck equation, the influence of nonstationary external force, random force, and dissipation effects on dynamics local conformational perturbations (kink) propagating along the DNA molecule is investigated. Such waves have an important role in the regulation of important biological processes in living systems at the molecular level. As a dynamic model of DNA was used a modified sine-Gordon equation, simulating the rotational oscillations of bases in one of the chains DNA. The equation of evolution of the kink momentum is obtained in the form of the stochastic differential equation in the Stratonovich sense within the framework of the well-known McLaughlin and Scott energy approach. The corresponding Fokker–Planck equation for the momentum distribution function coincides with the equation describing the Ornstein–Uhlenbek process with a regular nonstationary external force. The influence of the nonlinear stochastic effects on the kink dynamics is considered with the help of the Fokker– Planck nonlinear equation with the shift coefficient dependent on the first moment of the kink momentum distribution function. Expressions are derived for average value and variance of the momentum. Examples are considered which demonstrate the influence of the external regular and random forces on the evolution of the average value and variance of the kink momentum. Within the formalism of the Fokker–Planck equation, the influence of nonstationary external force, random force, and dissipation effects on the kink dynamics is investigated in the sine–Gordon model. The equation of evolution of the kink momentum is obtained in the form of the stochastic differential equation in the Stratonovich sense within the framework of the well-known McLaughlin and Scott energy approach. The corresponding Fokker–Planck equation for the momentum distribution function coincides with the equation describing the Ornstein–Uhlenbek process with a regular
The Discipline Controversy Revisited.
ERIC Educational Resources Information Center
Baumrind, Diana
1996-01-01
Found that neither the authoritative model nor the liberal (permissive) model offers parents an efficacious model of childrearing. Each polarized model contains an element of truth, but each demonizes the other. Argues that within a responsive and supportive parent-child relationship, prudent use of punishment is a necessary tool in discipline.…
Nonlinear dynamics of breathers in the spiral structures of magnets
NASA Astrophysics Data System (ADS)
Kiselev, V. V.; Raskovalov, A. A.
2016-06-01
The structure and properties of pulsating solitons (breathers) in the spiral structures of magnets are analyzed within the sine-Gordon model. The breather core pulsations are shown to be accompanied by local shifts and oscillations of the spiral structure with the formation of "precursors" and "tails" in the moving soliton. The possibilities for the observation and excitation of breathers in the spiral structures of magnets and multiferroics are discussed.
Topological defects with long-range interactions
NASA Astrophysics Data System (ADS)
Mello, B. A.; González, J. A.; Guerrero, L. E.; López-Atencio, E.
1998-07-01
We investigate a modified sine-Gordon equation which possesses soliton solutions with long-range interaction. We introduce a generalized version of the Ginzburg-Landau equation which supports long-range topological defects in D = 1 and D > 1. The interaction force between the defects decays so slowly that it is possible to enter the non-extensivity regime. These results can be applied to non-equilibrium systems, pattern formation and growth models.
The concept of quasi-integrability: a concrete example
NASA Astrophysics Data System (ADS)
Ferreira, L. A.; Zakrzewski, Wojtek J.
2011-05-01
We use the deformed sine-Gordon models recently presented by Bazeia et al [1] to take the first steps towards defining the concept of quasi-integrability. We consider one such definition and use it to calculate an infinite number of quasi-conserved quantities through a modification of the usual techniques of integrable field theories. Performing an expansion around the sine-Gordon theory we are able to evaluate the charges and the anomalies of their conservation laws in a perturbative power series in a small parameter which describes the "closeness" to the integrable sine-Gordon model. We show that in the case of the two-soliton scattering the charges, up to first order of perturbation, are conserved asymptotically, i.e. their values are the same in the distant past and future, when the solitons are well separated. We indicate that this property may hold or not to higher orders depending on the behavior of the two-soliton solution under a special parity transformation. For closely bound systems, such as breather-like field configurations, the situation however is more complex and perhaps the anomalies have a different structure implying that the concept of quasi-integrability does not apply in the same way as in the scattering of solitons. We back up our results with the data of many numerical simulations which also demonstrate the existence of long lived breather-like and wobble-like states in these models.
Doppler ultrasound--basics revisited.
Eagle, Mary
Palpation of pedal pulses alone is known to be an unreliable indicator for the presence of arterial disease. Using portable Doppler ultrasound to measure the resting ankle brachial pressure index is superior to palpation of peripheral pulses as an assessment of the adequacy pf the arterial supply in the lower limb. Revisiting basics, this article aims to aid the clinician to understand and perform hand-held Doppler ultrasound effectively while involving the client or patient in the process. The author describes the basics of Doppler ultrasound, how to select correct equipment for the process, and interpretation of results to further enhance clinicians' knowledge. PMID:16835512
MOPEX Workshop Results Revisited
NASA Astrophysics Data System (ADS)
Leavesley, G. H.
2003-12-01
A complementary program to the Prediction in Ungauged Basins (PUB) program is the Model Parameter Estimation Experiment (MOPEX). The primary goal of MOPEX is to develop techniques for the a priori estimation of parameters in land surface parameterization schemes in atmospheric models and in hydrologic models. A recent MOPEX workshop evaluated the use of a priori estimated parameters in eight hydrologic models. A data set of mean areal precipitation, temperature, and potential evapotranspiration was provided for each of 12 basins located predominantly in the southeastern United States. While workshop results provided valuable insight to some problems in a priori parameter estimation within and among models, additional questions remain. Using additional data sets for the 12 basins, alternative parameter estimation techniques are being evaluated to compare the use of distributed values of precipitation and temperature to the use of mean areal values in the original study. Also, the magnitudes of the uncertainty in streamflow prediction resulting from errors in the meteorological variables and their distribution are being compared with the magnitudes of uncertainty associated with errors in parameter estimates of basin physical characteristics. The U.S Geological Survey's distributed-parameter watershed model PRMS was one of the eight models used in the MOPEX workshop and is the model being used to conduct these further studies. Results of this investigation are presented.
Chao, Alex; /SLAC
2008-07-25
An early, but at the time illuminating, piece of work on how to deal with a general, linearly coupled accelerator lattice is revisited. This work is based on the SLIM formalism developed in 1979-1981.
Johansen, Øistein; Reed, Mark; Bodsberg, Nils Rune
2015-04-15
This paper presents a new semi-empirical model for oil droplet size distributions generated by single breaking wave events. Empirical data was obtained from laboratory experiments with different crude oils at different stages of weathering. The paper starts with a review of the most commonly used model for natural dispersion, which is followed by a presentation of the laboratory study on oil droplet size distributions formed by breaking waves conducted by SINTEF on behalf of the NOAA/UNH Coastal Response Research Center. The next section presents the theoretical and empirical foundation for the new model. The model is based on dimensional analysis and contains two non-dimensional groups; the Weber and Reynolds number. The model was validated with data from a full scale experimental oil spill conducted in the Haltenbanken area offshore Norway in July 1982, as described in the last section of the paper. PMID:25752537
Rabbits killing birds revisited.
Zhang, Jimin; Fan, Meng; Kuang, Yang
2006-09-01
We formulate and study a three-species population model consisting of an endemic prey (bird), an alien prey (rabbit) and an alien predator (cat). Our model overcomes several model construction problems in existing models. Moreover, our model generates richer, more reasonable and realistic dynamics. We explore the possible control strategies to save or restore the bird by controlling or eliminating the rabbit or the cat when the bird is endangered. We confirm the existence of the hyperpredation phenomenon, which is a big potential threat to most endemic prey. Specifically, we show that, in an endemic prey-alien prey-alien predator system, eradication of introduced predators such as the cat alone is not always the best solution to protect endemic insular prey since predator control may fail to protect the indigenous prey when the control of the introduced prey is not carried out simultaneously. PMID:16529776
Scaling Relationships for Spherical Polymer Brushes Revisited.
Chen, Guang; Li, Hao; Das, Siddhartha
2016-06-16
In this short paper, we revisit the scaling relationships for spherical polymer brushes (SPBs), i.e., polymer brushes grafted to rigid, spherical particles. Considering that the brushes can be described to be encased in a series of hypothetical spherical blobs, we identify significant physical discrepancies in the model of Daoud and Cotton (Journal of Physics, 1982), which is considered to be the state of the art in scaling modeling of SPBs. We establish that the "brush" configuration of the polymer molecules forming the SPBs is possible only if the swelling ratio (which is the ratio of the end-to-end length of the blob-encased polymer segment to the corresponding coil-like polymer segment) is always less than unity-a notion that has been erroneously overlooked in the model of Daoud and Cotton. We also provide new scaling arguments that (a) establish this swelling (or more appropriately shrinking) ratio as a constant (less than unity) for the case of "good" solvent, (b) recover the scaling predictions for blob dimension and monomer number and monomer concentration distributions within the blob, and PMID:27232497
The Sakharov Experiment Revisited for Granular Materials
NASA Astrophysics Data System (ADS)
Vogler, Tracy
2013-06-01
Sakharov and co-workers in 1965 proposed an experiment in which a sinusoidal perturbation in a planar wave evolves as it travels through a material. More recent, Liu and co-workers utilized gas gun techniques rather than explosives to drive the shock wave, resulting in a better defined input. The technique has been applied to liquids such as water and mercury as well as solids such as aluminum. All analyses of the experiments conducted to date have utilized a viscous fluid approach, even for the solids. Here, the concept of the decay of a perturbation in a shock wave is revisited and applied to granular materials. Simulations utilizing continuum models for the granular materials as well as mesoscale models in which individual particles are resolved are utilized. It is found that the perturbation decay is influenced by the strength (deviatoric behavior) used in the continuum model. In the mesocale calculations, the simulation parameters as well as the computational approach influence the results. Finally, initial experimental results for the technique using granular tungsten carbide are presented. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin company, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Sunday School Revisited: An Alternative to Christian Education of the Church Today?
ERIC Educational Resources Information Center
Song, Nam Soon
2013-01-01
This article attempts to demonstrate similarities between the socioeconomic, cultural, and religious contexts of 18th-century England and 21st-century Canada. Revisiting the Sunday School movement in 18th-century England provides insights for the development of renewed Sunday School models in the current Canadian context of transnational…
Atmospheric Entry Heating of Micrometeorites Revisited: Higher Temperatures and Potential Biases
NASA Technical Reports Server (NTRS)
Love, S.; Alexander, C. M. OD.
2001-01-01
The atmospheric entry heating model of Love and Brownlee appears to have overestimated evaporation rates by as much as two orders of magnitude. Here we revisit the issue of atmospheric entry heating, using a revised prescription for evaporation rates. Additional information is contained in the original extended abstract.
Framing the Future: Revisiting the Place of Educational Expectations in Status Attainment
ERIC Educational Resources Information Center
Bozick, Robert; Alexander, Karl; Entwisle, Doris; Dauber, Susan; Kerr, Kerri
2010-01-01
This study revisits the Wisconsin model of status attainment from a life course developmental perspective. Fixed-effects regression analyses lend strong support to the Wisconsin framework's core proposition that academic performance and significant others' influence shape educational expectations. However, investigating the process of expectation…
Greenberg, J. M.
2003-07-16
In a previous paper the author and Demay advanced a model to explain the melt fracture instability observed when molten linear polymer melts are extruded in a capillary rheometer operating under the controlled condition that the inlet flow rate was held constant. The model postulated that the melts were a slightly compressible viscous fluid and allowed for slipping of the melt at the wall. The novel feature of that model was the use of an empirical switch law which governed the amount of wall slip. The model successfully accounted for the oscillatory behavior of the exit flow rate, typically referred to as the melt fracture instability, but did not simultaneously yield the fine scale spatial oscillations in the melt typically referred to as shark skin. In this note a new model is advanced which simultaneously explains the melt fracture instability and shark skin phenomena. The model postulates that the polymer is a slightly compressible linearly viscous fluid but assumes no slip boundary conditions at the capillary wall. In simple shear the shear stress {tau}and strain rate d are assumed to be related by d = F{tau} where F ranges between F{sub 2} and F{sub 1} > F{sub 2}. A strain rate dependent yield function is introduced and this function governs whether F evolves towards F{sub 2} or F{sub 1}. This model accounts for the empirical observation that at high shears polymers align and slide more easily than at low shears and explains both the melt fracture and shark skin phenomena.
Friston, Karl J.; Bastos, André M.; Oswal, Ashwini; van Wijk, Bernadette; Richter, Craig; Litvak, Vladimir
2014-01-01
This technical paper offers a critical re-evaluation of (spectral) Granger causality measures in the analysis of biological timeseries. Using realistic (neural mass) models of coupled neuronal dynamics, we evaluate the robustness of parametric and nonparametric Granger causality. Starting from a broad class of generative (state-space) models of neuronal dynamics, we show how their Volterra kernels prescribe the second-order statistics of their response to random fluctuations; characterised in terms of cross-spectral density, cross-covariance, autoregressive coefficients and directed transfer functions. These quantities in turn specify Granger causality — providing a direct (analytic) link between the parameters of a generative model and the expected Granger causality. We use this link to show that Granger causality measures based upon autoregressive models can become unreliable when the underlying dynamics is dominated by slow (unstable) modes — as quantified by the principal Lyapunov exponent. However, nonparametric measures based on causal spectral factors are robust to dynamical instability. We then demonstrate how both parametric and nonparametric spectral causality measures can become unreliable in the presence of measurement noise. Finally, we show that this problem can be finessed by deriving spectral causality measures from Volterra kernels, estimated using dynamic causal modelling. PMID:25003817
NASA Technical Reports Server (NTRS)
Kaufman, F.
1972-01-01
The air afterglow, 0 + NO2 chemiluminescence, is discussed in terms of fluorescence, photodissociation, and quantum theoretical calculations of NO2. The experimental results presented include pressure dependence, M-dependence, spectral dependence of P and M, temperature dependence, and infrared measurements. The NO2 energy transfer model is also discussed.
Revisiting "Beyond Instructional Design"
ERIC Educational Resources Information Center
Sims, Rod
2015-01-01
Since the article "Beyond Instructional Design: Making Learning Design a Reality" (Sims, 2006) was published, much has changed in the opportunities we have for learning, and Professor Rod Sims's thinking has evolved. In this article, Professor Rod Sims reflects upon his original article, and he offers an evolved model of learning design,…
ERIC Educational Resources Information Center
Price, William J.
2001-01-01
An administrator trainer/former superintendent's experience suggests that corporate governance models don't fit the reality of school governance in many districts. Elected board members define their roles differently than their business counterparts and derive little or no monetary benefit from public service. The "new breed" resemble political…
ERIC Educational Resources Information Center
Papademetri-Kachrimani, Chrystalla
2012-01-01
In this paper I argue my opposition to the consensus which has dominated the literature that young children view shapes as a whole and pay no attention to shape structure and that geometrical thinking can be described through a hierarchical model formed by levels. This consensus is linked to van Hiele's weok by van Hiele-based research. In the…
Bag, Satadru; Sahni, Varun; Shtanov, Yuri; Unnikrishnan, Sanil E-mail: varun@iucaa.ernet.in E-mail: sanil@lnmiit.ac.in
2014-07-01
We explore the possibility of emergent cosmology using the effective potential formalism. We discover new models of emergent cosmology which satisfy the constraints posed by the cosmic microwave background (CMB). We demonstrate that, within the framework of modified gravity, the emergent scenario can arise in a universe which is spatially open/closed. By contrast, in general relativity (GR) emergent cosmology arises from a spatially closed past-eternal Einstein Static Universe (ESU). In GR the ESU is unstable, which creates fine tuning problems for emergent cosmology. However, modified gravity models including Braneworld models, Loop Quantum Cosmology (LQC) and Asymptotically Free Gravity result in a stable ESU. Consequently, in these models emergent cosmology arises from a larger class of initial conditions including those in which the universe eternally oscillates about the ESU fixed point. We demonstrate that such an oscillating universe is necessarily accompanied by graviton production. For a large region in parameter space graviton production is enhanced through a parametric resonance, casting serious doubts as to whether this emergent scenario can be past-eternal.
No-scale ripple inflation revisited
Li, Tianjun; Li, Zhijin; Nanopoulos, Dimitri V. E-mail: lizhijin@physics.tamu.edu
2014-04-01
We revisit the no-scale ripple inflation model, where no-scale supergravity is modified by an additional term for the inflaton field in the Kähler potential. This term not only breaks one SU(N,1) symmetry explicitly, but also plays an important role for inflation. We generalize the superpotential in the no-scale ripple inflation model slightly. There exists a discrete Z{sub 2} symmetry/parity in the scalar potential in general, which can be preserved or violated by the non-canonical nomalized inflaton kinetic term. Thus, there are three inflation paths: one parity invariant path, and the left and right paths for parity violating scenario. We show that the inflations along the parity invariant path and right path are consistent with the Planck results. However, the gavitino mass for the parity invariant path is so large that the inflation results will be invalid if we consider the inflaton supersymmetry breaking soft mass term. Thus, only the inflation along the right path gives the correct and consistent results. Notably, the tensor-to-scalar ratio in such case can be large, with a value around 0.05, which may be probed by the future Planck experiment.
Charge symmetry breaking in Λ hypernuclei revisited
NASA Astrophysics Data System (ADS)
Gal, Avraham
2015-05-01
The large charge symmetry breaking (CSB) implied by the Λ binding energy difference Δ BΛ4 (0g.s.+) ≡BΛ (He4Λ) -BΛ (H4Λ) = 0.35 ± 0.06 MeV of the A = 4 mirror hypernuclei ground states, determined from emulsion studies, has defied theoretical attempts to reproduce it in terms of CSB in hyperon masses and in hyperon-nucleon interactions, including one pion exchange arising from Λ-Σ0 mixing. Using a schematic strong-interaction ΛN ↔ ΣN coupling model developed by Akaishi and collaborators for s-shell Λ hypernuclei, we revisit the evaluation of CSB in the A = 4 Λ hypernuclei and extend it to p-shell mirror Λ hypernuclei. The model yields values of Δ BΛ4 (0g.s.+) ∼ 0.25 MeV. Smaller size and mostly negative p-shell binding energy differences are calculated for the A = 7- 10 mirror hypernuclei, in rough agreement with the few available data. CSB is found to reduce by almost 30 keV the 110 keV B10Λ g.s. doublet splitting anticipated from the hyperon-nucleon strong-interaction spin dependence, thereby explaining the persistent experimental failure to observe the 2exc- → 1g.s.- γ-ray transition.
Allostery and cooperativity revisited
Cui, Qiang; Karplus, Martin
2008-01-01
Although phenomenlogical models that account for cooperativity in allosteric systems date back to the early and mid-60's (e.g., the KNF and MWC models), there is resurgent interest in the topic due to the recent experimental and computational studies that attempted to reveal, at an atomistic level, how allostery actually works. In this review, using systems for which atomistic simulations have been carried out in our groups as examples, we describe the current understanding of allostery, how the mechanisms go beyond the classical MWC/Pauling-KNF descriptions, and point out that the “new view” of allostery, emphasizing “population shifts,” is, in fact, an “old view.” The presentation offers not only an up-to-date description of allostery from a theoretical/computational perspective, but also helps to resolve several outstanding issues concerning allostery. PMID:18560010
Lunar thermal history revisited.
NASA Technical Reports Server (NTRS)
Mcconnell, R. K., Jr.; Gast, P. W.
1972-01-01
New information is used to demonstrate that better models for the thermal history of the moon are required. As a first step, account is taken of (1) a nonuniform initial composition in terms of fraction of low melting to high melting phase present, and for variation in the uranium, potassium, and thorium contents as a function of depth, (2) partitioning of the radioactive elements between the melt and the solid phases, and (3) a cutoff value of melt which must be exceeded before magma can move to the surface. The results of several attempts to determine whether reasonable conditions, composition, and thermal properties can be expected to give rise to two separate periods of volcanism are discussed. Two models with somewhat different distributions of radioactive heat sources and different conductivities are examined.
Which String Breaks? Revisited
NASA Astrophysics Data System (ADS)
Frye, Christopher
2011-03-01
Many have seen the common introductory physics demonstration in which a heavy ball hangs from a string, with another identical string hanging freely from the ball. When the instructor pulls the bottom string slowly, the top string breaks. However, when the instructor pulls the bottom string very rapidly, the bottom string breaks. This simple experiment is used to demonstrate inertia and Newton's laws. In The Physics Teacher of November 1996, there is an article in which the authors create a model of this problem in an attempt to explain the outcomes quantitatively. However, their analysis gave strange results. Using an improved model, I will show that the results of this demonstration can be obtained using only simple calculations. This work was funded by a RAMP grant from the University of Central Florida.
Parental overprotection revisited.
Thomasgard, M; Metz, W P
1993-01-01
Dimensions of parental overprotection are clarified in a critical review of the research and clinical literature. An indulgent style of parenting is distinguished from an overprotective parent-child relationship. Differential antecedents and outcomes are proposed for each of these forms of parent-child interaction. Measures of protection are reviewed. A new conceptual model of parental overprotection is presented which takes into account child, parent, family, socio-cultural, environmental and resiliency factors. Directions for future research are suggested. PMID:8287694
Geometrical deuteron stripping revisited
Neoh, Y. S.; Yap, S. L.
2014-03-05
We investigate the reality of the idea of geometrical deuteron stripping originally envisioned by Serber. By taking into account of realistic deuteron wavefunction, nuclear density, and nucleon stopping mean free path, we are able to estimate inclusive deuteron stripping cross section for deuteron energy up to before pion production. Our semiclassical model contains only one global parameter constant for all nuclei which can be approximated by Woods-Saxon or any other spherically symmetric density distribution.
NASA Technical Reports Server (NTRS)
Linnell, Albert P.; Kallrath, Josef
1986-01-01
New analysis tools and additional unanalyzed observations justify a reanalysis of MR Cygni. The reanalysis applied successively more restrictive physical models, each with an optimization program. The final model assigned separate first and second order limb darkening coefficients, from model atmospheres, to individual grid points. Proper operation of the optimization procedure was tested on simulated observational data, produced by light synthesis with assigned system parameters, and modulated by simulated observational error. The iterative solution converged to a weakly-determined mass ratio of 0.75. Assuming the B3 primary component is on the main sequence, the HR diagram location of the secondary from the light ratio (ordinate) and adjusted T sub eff (abscissa) was calculated. The derived mass ratio, together with a main-sequence mass for the B3 component, implies a main-sequence secondary spectral type of B4. The photometrically-determined secondary radii agree with this spectral type, in marginal disagreement with the B7 type from the HR diagram analysis. The individual masses, derived from the radial velocity curve of the primary component, the photometrically-determined i, and alternative values of derived mass ratio are seriously discrepant with main sequence objects. The imputed physical status of the system is in disagreement with representations that have appeared in the literature.
Zhang, Xuetao; Huang, Jie; Yigit-Elliott, Serap; Rosenholtz, Ruth
2015-01-01
Observers can quickly search among shaded cubes for one lit from a unique direction. However, replace the cubes with similar 2-D patterns that do not appear to have a 3-D shape, and search difficulty increases. These results have challenged models of visual search and attention. We demonstrate that cube search displays differ from those with "equivalent" 2-D search items in terms of the informativeness of fairly low-level image statistics. This informativeness predicts peripheral discriminability of target-present from target-absent patches, which in turn predicts visual search performance, across a wide range of conditions. Comparing model performance on a number of classic search tasks, cube search does not appear unexpectedly easy. Easy cube search, per se, does not provide evidence for preattentive computation of 3-D scene properties. However, search asymmetries derived from rotating and/or flipping the cube search displays cannot be explained by the information in our current set of image statistics. This may merely suggest a need to modify the model's set of 2-D image statistics. Alternatively, it may be difficult cube search that provides evidence for preattentive computation of 3-D scene properties. By attributing 2-D luminance variations to a shaded 3-D shape, 3-D scene understanding may slow search for 2-D features of the target. PMID:25780063
Mores, Robert
2016-08-01
Schelleng [J. Acoust. Soc. Am. 53, 26-41 (1973)], Askenfelt [J. Acoust. Soc. Am. 86, 503-516 (1989)], Schumacher [J. Acoust. Soc. Am. 96, 1985-1998 (1994)], and Schoonderwaldt, Guettler, and Askenfelt [Acta Acust. Acust. 94, 604-622 (2008)] formulated-in different ways-how the maximum bow force relates to bow velocity, bow-bridge distance, string impedance, and friction coefficients. Issues of uncertainty are how to account for friction or for the rotational admittance of the strings. Related measurements at the respective transitions between regimes of Helmholtz motion and non-Helmholtz motion employ a variety of bowing machines and stringed instruments. The related findings include all necessary parameters except the friction coefficients, leaving the underlying models unconfirmed. Here, a bowing pendulum has been constructed which allows precise measurement of relevant bowing parameters, including the friction coefficients. Two cellos are measured across all strings for three different bow-bridge distances. The empirical data suggest that-taking the diverse elements of existing models as options-Schelleng's model combined with Schumacher's velocity term yields the best fit. Furthermore, the pendulum employs a bow driving mechanism with adaptive impedance which discloses that mentioned regimes are stable and transitions between them sometimes require a hysteresis on related parameters. PMID:27586745
Zhang, Xuetao; Huang, Jie; Yigit-Elliott, Serap; Rosenholtz, Ruth
2015-01-01
Observers can quickly search among shaded cubes for one lit from a unique direction. However, replace the cubes with similar 2-D patterns that do not appear to have a 3-D shape, and search difficulty increases. These results have challenged models of visual search and attention. We demonstrate that cube search displays differ from those with “equivalent” 2-D search items in terms of the informativeness of fairly low-level image statistics. This informativeness predicts peripheral discriminability of target-present from target-absent patches, which in turn predicts visual search performance, across a wide range of conditions. Comparing model performance on a number of classic search tasks, cube search does not appear unexpectedly easy. Easy cube search, per se, does not provide evidence for preattentive computation of 3-D scene properties. However, search asymmetries derived from rotating and/or flipping the cube search displays cannot be explained by the information in our current set of image statistics. This may merely suggest a need to modify the model's set of 2-D image statistics. Alternatively, it may be difficult cube search that provides evidence for preattentive computation of 3-D scene properties. By attributing 2-D luminance variations to a shaded 3-D shape, 3-D scene understanding may slow search for 2-D features of the target. PMID:25780063
Revisiting Antarctic Ozone Depletion
NASA Astrophysics Data System (ADS)
Grooß, Jens-Uwe; Tritscher, Ines; Müller, Rolf
2015-04-01
Antarctic ozone depletion is known for almost three decades and it has been well settled that it is caused by chlorine catalysed ozone depletion inside the polar vortex. However, there are still some details, which need to be clarified. In particular, there is a current debate on the relative importance of liquid aerosol and crystalline NAT and ice particles for chlorine activation. Particles have a threefold impact on polar chlorine chemistry, temporary removal of HNO3 from the gas-phase (uptake), permanent removal of HNO3 from the atmosphere (denitrification), and chlorine activation through heterogeneous reactions. We have performed simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS) employing a recently developed algorithm for saturation-dependent NAT nucleation for the Antarctic winters 2011 and 2012. The simulation results are compared with different satellite observations. With the help of these simulations, we investigate the role of the different processes responsible for chlorine activation and ozone depletion. Especially the sensitivity with respect to the particle type has been investigated. If temperatures are artificially forced to only allow cold binary liquid aerosol, the simulation still shows significant chlorine activation and ozone depletion. The results of the 3-D Chemical Transport Model CLaMS simulations differ from purely Lagrangian longtime trajectory box model simulations which indicates the importance of mixing processes.
Revisiting Tversky's diagnosticity principle.
Evers, Ellen R K; Lakens, Daniël
2014-01-01
Similarity is a fundamental concept in cognition. In 1977, Amos Tversky published a highly influential feature-based model of how people judge the similarity between objects. The model highlights the context-dependence of similarity judgments, and challenged geometric models of similarity. One of the context-dependent effects Tversky describes is the diagnosticity principle. The diagnosticity principle determines which features are used to cluster multiple objects into subgroups. Perceived similarity between items within clusters is expected to increase, while similarity between items in different clusters decreases. Here, we present two pre-registered replications of the studies on the diagnosticity effect reported in Tversky (1977). Additionally, one alternative mechanism that has been proposed to play a role in the original studies, an increase in the choice for distractor items (a substitution effect, see Medin et al., 1995), is examined. Our results replicate those found by Tversky (1977), revealing an average diagnosticity-effect of 4.75%. However, when we eliminate the possibility of substitution effects confounding the results, a meta-analysis of the data provides no indication of any remaining effect of diagnosticity. PMID:25161638
Revisiting Tversky's diagnosticity principle
Evers, Ellen R. K.; Lakens, Daniël
2013-01-01
Similarity is a fundamental concept in cognition. In 1977, Amos Tversky published a highly influential feature-based model of how people judge the similarity between objects. The model highlights the context-dependence of similarity judgments, and challenged geometric models of similarity. One of the context-dependent effects Tversky describes is the diagnosticity principle. The diagnosticity principle determines which features are used to cluster multiple objects into subgroups. Perceived similarity between items within clusters is expected to increase, while similarity between items in different clusters decreases. Here, we present two pre-registered replications of the studies on the diagnosticity effect reported in Tversky (1977). Additionally, one alternative mechanism that has been proposed to play a role in the original studies, an increase in the choice for distractor items (a substitution effect, see Medin et al., 1995), is examined. Our results replicate those found by Tversky (1977), revealing an average diagnosticity-effect of 4.75%. However, when we eliminate the possibility of substitution effects confounding the results, a meta-analysis of the data provides no indication of any remaining effect of diagnosticity. PMID:25161638
Axisymmetric multiwormholes revisited
NASA Astrophysics Data System (ADS)
Clément, Gérard
2016-06-01
The construction of stationary axisymmetric multiwormhole solutions to gravitating field theories admitting toroidal reductions to three-dimensional gravitating sigma models is reviewed. We show that, as in the multi-black hole case, strut singularities always appear in this construction, except for very special configurations with an odd number of centers. We also review the analytical continuation of the multicenter solution across the n cuts associated with the wormhole mouths. The resulting Riemann manifold has 2^n sheets interconnected by 2^{n-1}n wormholes. We find that the maximally extended multicenter solution can never be asymptotically locally flat in all the Riemann sheets.
Multiscale Fluctuation Analysis Revisited
NASA Astrophysics Data System (ADS)
Struzik, Zbigniew R.; Kiyono, Ken; Yamamoto, Yoshiharu
2007-07-01
Ubiquitous non-Gaussianity of the probability density of (time-series) fluctuations in many real world phenomena has been known and modelled extensively in recent years. Similarly, the analysis of (multi)scaling properties of (fluctuations in) complex systems has become a standard way of addressing unknown complexity. Yet the combined analysis and modelling of multiscale behaviour of probability density — multiscale PDF analysis — has only recently been proposed for the analysis of time series arising in complex systems, such as the cardiac neuro-regulatory system, financial markets or hydrodynamic turbulence. This relatively new technique has helped significantly to expand the previously obtained insights into the phenomena addressed. In particular, it has helped to identify a novel class of scale invariant behaviour of the multiscale PDF in healthy heart rate regulation during daily activity and in a market system undergoing crash dynamics. This kind of invariance reflects invariance of the system under renormalisation and resembles behaviour at criticality of a system undergoing continuous phase transition — indeed in both phenomena, such phase transition behaviour has been revealed. While the precise mechanism underlying invariance of the PDF under system renormalisation of both systems discussed is not to date understood, there is an intimate link between the non-Gaussian PDF characteristics and the persistent invariant correlation structure emerging between fluctuations across scale and time.
Secret Public Key Protocols Revisited
NASA Astrophysics Data System (ADS)
Lim, Hoon Wei; Paterson, Kenneth G.
Password-based protocols are important and popular means of providing human-to-machine authentication. The concept of secret public keys was proposed more than a decade ago as a means of securing password-based authentication protocols against off-line password guessing attacks, but was later found vulnerable to various attacks. In this paper, we revisit the concept and introduce the notion of identity-based secret public keys. Our new identity-based approach allows secret public keys to be constructed in a very natural way using arbitrary random strings, eliminating the structure found in, for example, RSA or ElGamal keys. We examine identity-based secret public key protocols and give informal security analyses, indicating that they are secure against off-line password guessing and other attacks.
Extended equal area criterion revisited
Xue, X.; Wehenkel, L.; Belhomme, R.; Rousseaux, P.; Pavella, M. ); Euxibie, E.; Heilbronn, B.; Lesigne, J.F. )
1992-08-01
This paper reports on a case study conducted on the EHV French power system in order to revisit the extended equal area criterion and test its suitability as a fast transient stability indicator. The assumptions underlying the method are reexamined, causes liable to invalidate them are identified, and indices are devised to automatically circumvent them. The selection of candidate critical machines is also reconsidered and an augmented criterion is proposed. The various improvements are developed and tested on about 1000 stability scenarios, covering the entire 400-kV system; the severity of the scenarios, resulting from the combination of weakened both pre- and post-fault configurations, subjects the method to particularly stringent conditions. The obtained results show that the devised tools contribute to significantly reinforce its robustness and reliability.
The climate continuum revisited
NASA Astrophysics Data System (ADS)
Emile-Geay, J.; Wang, J.; Partin, J. W.
2015-12-01
A grand challenge of climate science is to quantify the extent of natural variability on adaptation-relevant timescales (10-100y). Since the instrumental record is too short to adequately estimate the spectra of climate measures, this information must be derived from paleoclimate proxies, which may harbor a many-to-one, non-linear (e.g. thresholded) and non-stationary relationship to climate. In this talk, I will touch upon the estimation of climate scaling behavior from climate proxies. Two case studies will be presented: an investigation of scaling behavior in a reconstruction of global surface temperature using state-of- the-art data [PAGES2K Consortium, in prep] and methods [Guillot et al., 2015]. Estimating the scaling exponent β in spectra derived from this reconstruction, we find that 0 < β < 1 in most regions, suggesting long-term memory. Overall, the reconstruction-based spectra are steeper than the ones based on an instrumental dataset [HadCRUT4.2, Morice et al., 2012], and those estimated from PMIP3/CMIP5 models, suggesting the climate system is more energetic at multidecadal to centennial timescales than can be inferred from the short instrumental record or from the models developed to reproduce it [Laepple and Huybers, 2014]. an investigation of scaling behavior in speleothems records of tropical hydroclimate. We will make use of recent advances in proxy system modeling [Dee et al., 2015] and investigate how various aspects of the speleothem system (karst dynamics, age uncertainties) may conspire to bias the estimate of scaling behavior from speleothem timeseries. The results suggest that ignoring such complications leads to erroneous inferences about hydroclimate scaling. References Dee, S. G., J. Emile-Geay, M. N. Evans, Allam, A., D. M. Thompson, and E. J. Steig (2015), J. Adv. Mod. Earth Sys., 07, doi:10.1002/2015MS000447. Guillot, D., B. Rajaratnam, and J. Emile-Geay (2015), Ann. Applied. Statist., pp. 324-352, doi:10.1214/14-AOAS794. Laepple, T
NASA Astrophysics Data System (ADS)
Henderson, Robert K.
1999-12-01
It is widely accepted in the electronics industry that measurement gauge error variation should be no larger than 10% of the related specification window. In a previous paper, 'What Amount of Measurement Error is Too Much?', the author used a framework from the process industries to evaluate the impact of measurement error variation in terms of both customer and supplier risk (i.e., Non-conformance and Yield Loss). Application of this framework in its simplest form suggested that in many circumstances the 10% criterion might be more stringent than is reasonably necessary. This paper reviews the framework and results of the earlier work, then examines some of the possible extensions to this framework suggested in that paper, including variance component models and sampling plans applicable in the photomask and semiconductor businesses. The potential impact of imperfect process control practices will be examined as well.
Partial quantum logics revisited
NASA Astrophysics Data System (ADS)
Vetterlein, Thomas
2011-01-01
Partial Boolean algebras (PBAs) were introduced by Kochen and Specker as an algebraic model reflecting the mutual relationships among quantum-physical yes-no tests. The fact that not all pairs of tests are compatible was taken into special account. In this paper, we review PBAs from two sides. First, we generalise the concept, taking into account also those yes-no tests which are based on unsharp measurements. Namely, we introduce partial MV-algebras, and we define a corresponding logic. Second, we turn to the representation theory of PBAs. In analogy to the case of orthomodular lattices, we give conditions for a PBA to be isomorphic to the PBA of closed subspaces of a complex Hilbert space. Hereby, we do not restrict ourselves to purely algebraic statements; we rather give preference to conditions involving automorphisms of a PBA. We conclude by outlining a critical view on the logico-algebraic approach to the foundational problem of quantum physics.
NASA Astrophysics Data System (ADS)
Santos, Mauro; Zintzaras, Elias; Szathmáry, Eörs
2003-10-01
Why did sex ever arise in the first place? Why it does not disappear in view of the greater efficiency of asexuals? These are clearly two different questions, and we suggest here that the solution for the origin of sex does not necessarily come from theoretical considerations based on currently existing genetic systems. Thus, while we agree with a number of authors in that the emergence of sex (understood as the exchange of genetic material between genomes) is deeply rooted in the origin of life and happened during the very early stages in the transition from individual genes (`replicators') to bacteria-like cells (`reproducers'), we challenge the idea that recombinational repair was the major selective force for the emergence of sex. Taking the stochastic corrector model as a starting point, we provide arguments that question the putative costs of redundancy in primitive protocells. In addition, if genes that cause intragenomic conflict (i.e., parasites) are taken into account, it is certainly wrong to suggest that cellular fusion would be beneficial at the population level (although this strong claim needs some qualifications). However, when a continuous input of deleterious mutations that impair the fitness of the protocell as a whole is considered in the model (in the realistic range in which stable mutant distributions of quasi-species within compartments are established), there are circumstances when sex could be beneficial as a side effect of the dynamic equilibrium between cellular fusion-mutation-selection. The scenario we have explored numerically is fully consistent with the idea that the universal ancestor was not a discrete entity but an ensemble of proto-organisms that exchanged much genetic information.
GLOBAL STAR FORMATION REVISITED
Silk, Joseph; Norman, Colin E-mail: norman@stsci.edu
2009-07-20
A general treatment of disk star formation is developed from a dissipative multiphase model, with the dominant dissipation due to cloud collisions. The Schmidt-Kennicutt (SK) law emerges naturally for star-forming disks and starbursts. We predict that there should be an inverse correlation between Tully-Fisher law and SK law residuals. The model is extended to include a multiphase treatment of supernova feedback that leads to a turbulent pressure-regulated generalization of the star formation law and is applicable to gas-rich starbursts. Enhanced pressure, as expected in merger-induced star formation, enhances star formation efficiency. An upper limit is derived for the disk star formation rate in starbursts that depends on the ratio of global ISM to cloud pressures. We extend these considerations to the case where the interstellar gas pressure in the inner galaxy is dominated by outflows from a central active galactic nucleus (AGN). During massive spheroid formation, AGN-driven winds trigger star formation, resulting in enhanced supernova feedback and outflows. The outflows are comparable to the AGN-boosted star formation rate and saturate in the super-Eddington limit. Downsizing of both SMBH and spheroids is a consequence of AGN-driven positive feedback. Bondi accretion feeds the central black hole with a specific accretion rate that is proportional to the black hole mass. AGN-enhanced star formation is mediated by turbulent pressure and relates spheroid star formation rate to black hole accretion rate. The relation between black hole mass and spheroid velocity dispersion has a coefficient (Salpeter time to gas consumption time ratio) that provides an arrow of time. Highly efficient, AGN-boosted star formation can occur at high redshift.
Revisiting Twomey's approximation for peak supersaturation
NASA Astrophysics Data System (ADS)
Shipway, B. J.
2015-04-01
Twomey's seminal 1959 paper provided lower and upper bound approximations to the estimation of peak supersaturation within an updraft and thus provides the first closed expression for the number of nucleated cloud droplets. The form of this approximation is simple, but provides a surprisingly good estimate and has subsequently been employed in more sophisticated treatments of nucleation parametrization. In the current paper, we revisit the lower bound approximation of Twomey and make a small adjustment that can be used to obtain a more accurate calculation of peak supersaturation under all potential aerosol loadings and thermodynamic conditions. In order to make full use of this improved approximation, the underlying integro-differential equation for supersaturation evolution and the condition for calculating peak supersaturation are examined. A simple rearrangement of the algebra allows for an expression to be written down that can then be solved with a single lookup table with only one independent variable for an underlying lognormal aerosol population. While multimodal aerosol with N different dispersion characteristics requires 2N+1 inputs to calculate the activation fraction, only N of these one-dimensional lookup tables are needed. No additional information is required in the lookup table to deal with additional chemical, physical or thermodynamic properties. The resulting implementation provides a relatively simple, yet computationally cheap, physically based parametrization of droplet nucleation for use in climate and Numerical Weather Prediction models.
Targeting Cancer Metabolism - Revisiting the Warburg Effects
Tran, Quangdon; Lee, Hyunji; Park, Jisoo; Kim, Seon-Hwan; Park, Jongsun
2016-01-01
After more than half of century since the Warburg effect was described, this atypical metabolism has been standing true for almost every type of cancer, exhibiting higher glycolysis and lactate metabolism and defective mitochondrial ATP production. This phenomenon had attracted many scientists to the problem of elucidating the mechanism of, and reason for, this effect. Several models based on oncogenic studies have been proposed, such as the accumulation of mitochondrial gene mutations, the switch from oxidative phosphorylation respiration to glycolysis, the enhancement of lactate metabolism, and the alteration of glycolytic genes. Whether the Warburg phenomenon is the consequence of genetic dysregulation in cancer or the cause of cancer remains unknown. Moreover, the exact reasons and physiological values of this peculiar metabolism in cancer remain unclear. Although there are some pharmacological compounds, such as 2-deoxy-D-glucose, dichloroacetic acid, and 3-bromopyruvate, therapeutic strategies, including diet, have been developed based on targeting the Warburg effect. In this review, we will revisit the Warburg effect to determine how much scientists currently understand about this phenomenon and how we can treat the cancer based on targeting metabolism. PMID:27437085
Targeting Cancer Metabolism - Revisiting the Warburg Effects.
Tran, Quangdon; Lee, Hyunji; Park, Jisoo; Kim, Seon-Hwan; Park, Jongsun
2016-07-01
After more than half of century since the Warburg effect was described, this atypical metabolism has been standing true for almost every type of cancer, exhibiting higher glycolysis and lactate metabolism and defective mitochondrial ATP production. This phenomenon had attracted many scientists to the problem of elucidating the mechanism of, and reason for, this effect. Several models based on oncogenic studies have been proposed, such as the accumulation of mitochondrial gene mutations, the switch from oxidative phosphorylation respiration to glycolysis, the enhancement of lactate metabolism, and the alteration of glycolytic genes. Whether the Warburg phenomenon is the consequence of genetic dysregulation in cancer or the cause of cancer remains unknown. Moreover, the exact reasons and physiological values of this peculiar metabolism in cancer remain unclear. Although there are some pharmacological compounds, such as 2-deoxy-D-glucose, dichloroacetic acid, and 3-bromopyruvate, therapeutic strategies, including diet, have been developed based on targeting the Warburg effect. In this review, we will revisit the Warburg effect to determine how much scientists currently understand about this phenomenon and how we can treat the cancer based on targeting metabolism. PMID:27437085
Erskine, M.C.
1997-04-01
The upper Paleozoic succession in the Oquirrh basin in unusually thick, up to 9300 m, and consists mainly of a Pennsylvanian-middle Permian miogeocline of northwestern Utah. Previous workers have suggested a tectonic origin for the Oquirrh basin that is incompatible with the basin location in both time and space. There is no evidence for Pennsylvanian and Lower Permian tectonism in the middle of the miogeocline. Thermal evidence from the Mississippian Mission Canyon shale does no support the implied deep burial of the crustal sag models of basin formation. Stratigraphic and facies evidence indicates a growth fault origin for the basin. Regional isopach maps and facies maps are powerful tools in interpreting depositional environments and in reconstructing fold-and-thrust belts. However, the location of measured sections relative to the location of the growth fault basin. The Charleston-Nebo thrust may have essentially reversed the movement on a growth fault. Thick Oquirrh basin sedimentary rocks may not be required to balance structural sections across this thrust fault. A thin-skinned, extensional growth fault origin for the Oquirrh basin implies that the Cordilleran miogeocline did not participate in the Pennsylvanian north-vergent uplifts of the Ancestral Rocky Mountains.
Fechner's aesthetics revisited.
Phillips, Flip; Norman, J Farley; Beers, Amanda M
2010-01-01
Gustav Fechner is widely respected as a founding father of experimental psychology and psychophysics but fewer know of his interests and work in empirical aesthetics. In the later 1800s, toward the end of his career, Fechner performed experiments to empirically evaluate the beauty of rectangles, hypothesizing that the preferred shape would closely match that of the so-called 'golden rectangle'. His findings confirmed his suspicions, but in the intervening decades there has been significant evidence pointing away from that finding. Regardless of the results of this one study, Fechner ushered in the notion of using a metric to evaluate beauty in a psychophysical way. In this paper, we recreate the experiment using more naturalistic stimuli. We evaluate subjects' preferences against models that use various types of object complexity as metrics. Our findings that subjects prefer either very simple or very complex objects runs contrary to the hypothesized results, but are systematic none the less. We conclude that there are likely to be useful measures of aesthetic preference but they are likely to be complicated by the difficulty in defining some of their constituent parts. PMID:20819476
Configurational Entropy Revisited
NASA Astrophysics Data System (ADS)
Lambert, Frank L.
2007-09-01
Entropy change is categorized in some prominent general chemistry textbooks as being either positional (configurational) or thermal. In those texts, the accompanying emphasis on the dispersal of matter—independent of energy considerations and thus in discord with kinetic molecular theory—is most troubling. This article shows that the variants of entropy can be treated from a unified viewpoint and argues that to decrease students' confusion about the nature of entropy change these variants of entropy should be merged. Molecular energy dispersal in space is implicit but unfortunately tacit in the cell models of statistical mechanics that develop the configurational entropy change in gas expansion, fluids mixing, or the addition of a non-volatile solute to a solvent. Two factors are necessary for entropy change in chemistry. An increase in thermodynamic entropy is enabled in a process by the motional energy of molecules (that, in chemical reactions, can arise from the energy released from a bond energy change). However, entropy increase is only actualized if the process results in a larger number of arrangements for the system's energy, that is, a final state that involves the most probable distribution for that energy under the new constraints. Positional entropy should be eliminated from general chemistry instruction and, especially benefiting "concrete minded" students, it should be replaced by emphasis on the motional energy of molecules as enabling entropy change.
NASA Technical Reports Server (NTRS)
Maynard, N. C.; Gebowsky, J. M.
1976-01-01
Saturation of the dc double probe instrument on Explorer 45 was used to identify the plasmapause. A data base was developed to statistically study the average position of the plasmapause over 14.5 hours of magnetic local time under differing magnetic conditions. The afternoon-evening bulge in the L coordinate of the plasmapause versus local time was found centered between 20 and 21 hours MLT during magnetically quiet periods and shifted toward dusk as activity increased, but always post dusk. During quiet periods a bulge in the L coordinate near noon was also seen, which disappeared as activity increased. The average local time distribution plasmapause position during high magnetic activity was irregular in the afternoon region where large scale convection models predict the creation of plasmatails or detached plasma regions from increases in the solar wind induced convection. The results suggest that solar wind induced convection is partially shielded from the dayside. As the intensity of the convection is increased, it more effectively penetrates the dayside, which shifts the post dusk bulge nearer to dusk and eliminates the quiet-time bulge near noon.
NASA Astrophysics Data System (ADS)
Sahni, Varun
2016-07-01
The Phantom brane is based on the normal branch of the DGP braneworld. It possesses a phantom-like equation of state at late times, but no big-rip future singularity. In this braneworld, the cosmological constant is dynamically screened at late times. Consequently it provides a good fit to SDSS DR11 measurements of H(z) at high redshifts. We obtain a closed system of equations for scalar perturbations on the brane. Perturbations of radiation, matter and the Weyl fluid are self-consistently evolved until the present epoch. We find that the late time growth of density perturbations on the brane proceeds at a faster rate than in ΛCDM. Additionally, the gravitational potentials φ, Ψ evolve differently on the brane than in ΛCDM, for which φ = Ψ. On the Brane, by contrast, the ratio φ/Ψ exceeds unity during the late matter dominated epoch (z ≤ 50). These features emerge as smoking gun tests of phantom brane cosmology and allow predictions of this scenario to be tested against observations of galaxy clustering and large scale structure. The phantom brane also displays a pole in its equation of state, which provides a key test of this dark energy model.
Ancient deforestation revisited.
Hughes, J Donald
2011-01-01
The image of the classical Mediterranean environment of the Greeks and Romans had a formative influence on the art, literature, and historical perception of modern Europe and America. How closely does is this image congruent with the ancient environment as it in reality existed? In particular, how forested was the ancient Mediterranean world, was there deforestation, and if so, what were its effects? The consensus of historians, geographers, and other scholars from the mid-nineteenth century through the first three quarters of the twentieth century was that human activities had depleted the forests to a major extent and caused severe erosion. My research confirmed this general picture. Since then, revisionist historians have questioned these conclusions, maintaining instead that little environmental damage was done to forests and soils in ancient Greco-Roman times. In a reconsideration of the question, this paper looks at recent scientific work providing proxy evidence for the condition of forests at various times in ancient history. I look at three scientific methodologies, namely anthracology, palynology, and computer modeling. Each of these avenues of research offers support for the concept of forest change, both in abundance and species composition, and episodes of deforestation and erosion, and confirms my earlier work. PMID:20669043
NASA Astrophysics Data System (ADS)
Douglas, A.
2007-01-01
contrast simple, comprising one or two cycles of large amplitude followed by a low-amplitude coda. Earthquake signals on the other hand were often complex with numerous arrivals of similar amplitude spread over 35 s or more. It therefore appeared that earthquakes could be recognised on complexity. Later however, complex explosion signals were observed which reduced the apparent effectiveness of complexity as a criterion for identifying earthquakes. Nevertheless, the AWE Group concluded that for many paths to teleseismic distances, Earth is transparent for P signals and this provides a window through which source differences will be most clearly seen. Much of the research by the Group has focused on understanding the influence of source type on P seismograms recorded at teleseismic distances. Consequently the paper concentrates on teleseismic methods of distinguishing between explosions and earthquakes. One of the most robust criteria for discriminating between earthquakes and explosions is the m b : M s criterion which compares the amplitudes of the SP P waves as measured by the body-wave magnitude m b, and the long-period (LP: ˜0.05 Hz) Rayleigh-wave amplitude as measured by the surface-wave magnitude M s; the P and Rayleigh waves being the main wave types used in forensic seismology. For a given M s, the m b for explosions is larger than for most earthquakes. The criterion is difficult to apply however, at low magnitude (say m b < 4.5) and there are exceptions—earthquakes that look like explosions. A difficulty with identification criteria developed in the early days of forensic seismology was that they were in the main empirical—it was not known why they appeared to work and if there were test sites or earthquakes where they would fail. Consequently the AWE Group in cooperation with the University of Cambridge used seismogram modelling to try and understand what controls complexity of SP P seismograms, and to put the m b : M s criterion on a theoretical basis. The
The Baroreflex Mechanism Revisited.
Rabinovitch, A; Friedman, M; Braunstein, D; Biton, Y; Aviram, I
2015-08-01
We state that the autonomic part of the brain controls the blood pressure (BP) and the heart rate (HR) via the baroreflex mechanism in all situations of human activity (at sleep, at rest, during exercise, fright etc.), in a way which is not, as was hitherto assumed, a mere homeostatic tool or even a resetting device, designed to bring these variables on the road to preset values. The baroreflex is rather a continuous feedback mechanism commanded by the autonomic part of the brain, leading to values appropriate to the situation at hand. Feasibility of this assertion is demonstrated here by using the Seidel-Herzel feedback system outside of its regular practice. Results show indeed that the brain can, and we claim that it does, control the HR and BP throughout life. New responses are demonstrated, e.g., to a sudden fear or apnea. In this event, large BP and HR overshoots are expected before the variables can relax to a new level. Response to abrupt downward change in the controlling parameter shows an undershoot in HR and just a gradual resetting in the BP. The relaxation from sudden external changes to various expected states are calculated and discussed and properties of the Rheos test are explained. Experimental findings for orthostatic tests and for babies under translations and rotations reveal complete qualitative agreement with our model and show no need to invoke the operation of additional body systems. Our method should be the preferred one by the Occam Razor approach. The outcomes may lead to beneficial clinical implication. PMID:26394627
Texture synthesis: textons revisited.
Charalampidis, Dimitrios
2006-03-01
This paper introduces a technique for synthesizing natural textures, with emphasis on quasiperiodic and structural textures. Textures are assumed to be composed of three components, namely illumination, structure, and stochastic. The contribution of this work is that, in contrast to previous techniques, it proposes a joint approach for handling the texture's global illumination, irregular structure, and stochastic component which may be correlated to the other two components. Furthermore, the proposed technique does not produce verbatim copies in the synthesized texture. More specifically, a top-down approach is used for extraction of texture elements (textons) in which, in contrast to previous texton-based approaches, no assumptions regarding perfect periodicity are made. The structure itself can be modeled as a stochastic process. Consequently, textons are allowed to have irregular and nonidentical shapes. In the synthesis stage, a new nonregular textural structure is designed from the original one that defines the place holders for textons. We call such place holders empty textons (e-textons). The e-textons are filled in by a representative texton. Since e-textons do not have identical shapes, a texton shape-matching procedure is required. After adding the illumination to the structural component, a strictly localized version of a block sampling technique is applied to add the stochastic component. The block sampling technique combined with the addition of the illumination component provides a significant improvement in the appearance of synthesized textures. Results show that the proposed method is successful in synthesizing structural textures visually indistinguishable to the original. Moreover, the method is successful in synthesizing a variety of stochastic textures. PMID:16519362
The Lanthanide Contraction Revisited
Seitz, Michael; Oliver, Allen G.; Raymond, Kenneth N.
2007-04-19
A complete, isostructural series of lanthanide complexes (except Pm) with the ligand TREN-1,2-HOIQO has been synthesized and structurally characterized by means of single-crystal X-ray analysis. All complexes are 1D-polymeric species in the solid state, with the lanthanide being in an eight-coordinate, distorted trigonal-dodecahedral environment with a donor set of eight unique oxygen atoms. This series constitutes the first complete set of isostructural lanthanide complexes with a ligand of denticity greater than two. The geometric arrangement of the chelating moieties slightly deviates across the lanthanide series, as analyzed by a shape parameter metric based on the comparison of the dihedral angles along all edges of the coordination polyhedron. The apparent lanthanide contraction in the individual Ln-O bond lengths deviates considerably from the expected quadratic decrease that was found previously in a number of complexes with ligands of low denticity. The sum of all bond lengths around the trivalent metal cation, however, is more regular, showing an almost ideal quadratic behavior across the entire series. The quadratic nature of the lanthanide contraction is derived theoretically from Slater's model for the calculation of ionic radii. In addition, the sum of all distances along the edges of the coordination polyhedron show exactly the same quadratic dependency as the Ln-X bond lengths. The universal validity of this coordination sphere contraction, concomitant with the quadratic decrease in Ln-X bond lengths, was confirmed by reexamination of four other, previously published, almost complete series of lanthanide complexes. Due to the importance of multidentate ligands for the chelation of rare-earth metals, this result provides a significant advance for the prediction and rationalization of the geometric features of the corresponding lanthanide complexes, with great potential impact for all aspects of lanthanide coordination.
NASA Astrophysics Data System (ADS)
Brenner, Howard
2006-10-01
Öttinger's recent nontraditional incorporation of fluctuations into the formulation of the friction matrix appearing in the phenomenological GENERIC theory of nonequilibrium irreversible processes is shown to furnish transport equations for single-component gases and liquids undergoing heat transfer which support the view that revisions to the Navier-Stokes-Fourier (N-S-F) momentum/energy equation set are necessary, as empirically proposed by the author on the basis of an experimentally supported theory of diffuse volume transport. The hypothesis that the conventional N-S-F equations prevail without modification only in the case of “incompressible” fluids, where the density ρ of the fluid is uniform throughout, serves to determine the new phenomenological parameter α‧ appearing in the GENERIC friction matrix. In the case of ideal gases the consequences of this constitutive hypothesis are shown to yield results identical to those derived theoretically by Öttinger on the basis of a “proper” coarse-graining of Boltzmann's kinetic equation. A major consequence of the present work is that the fluid's specific momentum density v is equal to its volume velocity vv, rather than to its mass velocity vm, contrary to current views dating back 250 years to Euler. In the case of rarefied gases the proposed modifications are also observed to agree with those resulting from Klimontovich's molecularly based, albeit ad hoc, self-diffusion addendum to Boltzmann's collision integral. Despite the differences in their respective physical models-molecular vs. phenomenological-the role played by Klimontovich's collisional addition to Boltzmann's equation in modifying the N-S-F equations is noted to constitute a molecular counterpart of Öttinger's phenomenological fluctuation addition to the GENERIC friction matrix. Together, these two theories collectively recognize the need to address multiple- rather than single- encounter collisions between a test molecule and its
ACL Roof Impingement Revisited
Tanksley, John Anthony; Conte, Evan J.; Werner, Brian C.; Gwathmey, Frank Winston; Brockmeier, Stephen F.; Miller, Mark D.
2015-01-01
Objectives: Anatomic femoral tunnel placement for single-bundle ACL reconstruction is now well accepted. The ideal location for the tibial tunnel, however, has not been studied extensively. A wide range of anterior to posterior (A-P) tibial tunnel locations are considered acceptable. Biomechanical data suggests that the anterior fibers of the native ACL are more functional. Similarly, ACL grafts placed more anteriorly in the footprint have resulted in improved clinical results in at least one study. However, the concern for intercondylar roof impingement has tempered enthusiasm for a more anterior tibial tunnel placement. Investigations by Howell and others on roof impingement have focused only on the transtibial technique. Our study seeks to characterize intercondylar roof impingement in a 3-D cadaveric model with both transtibial and independent femoral tunnel drilling techniques in the setting of an anteriorly positioned tibial tunnel. Methods: Twelve fresh frozen cadaver knees (six matched pairs) were randomized to either a transtibial or an independent femoral (IF) drilling technique. Tibial guide pins were placed in the anterior half of the ACL tibial footprint following arthroscopic debridement of the native ACL. A fluoroscopic calculation of the tibial guide pin location using the technique described by Staubli was used to ensure a relatively anterior position of the tibial tunnel (Staubli < 35). All efforts were made to place the femoral tunnel anatomically in the center of the footprint. An 8 mm Gore-Tex smoother was passed into the knee to function as a radiopaque surrogate graft, and the knees then underwent computed tomography in maximal extension. Graft-visualized 3D-CT reformatting was used to evaluate for roof impingement by analyzing the Impingement Review Index (IRI) as described by Iriuchishima. Tunnel morphology, knee flexion, and intra-articular graft angles were also recorded. Results: Two grafts (2/6, 33.3 %) in the TT group impinged upon the
NASA Astrophysics Data System (ADS)
Haq, Bilal U.
2014-02-01
Eustatic sea-level changes of the Cretaceous are reevaluated based on a synthesis of global stratigraphic data. A new terminology for local/regional or relative sea-level changes (eurybatic shifts) is proposed to distinguish them from global (eustatic) sea-level changes, with the observation that all measures of sea-level change in any given location are eurybatic, even when they include a strong global signal. Solid-earth factors that influence inherited regional topography and thus modify physical measures of amplitude of the sea-level rises and falls locally are reviewed. One of these factors, dynamic topography (surface expression of mass flow in the upper mantle on land- and seascapes), is considered most pertinent in altering local measures of amplitude of sea-level events on third-order time scales (0.5-3.0 Myr). Insights gained from these models have led to the reconciliation of variance between amplitude estimates of eurybatic shifts in any given region and global measures of eustatic changes. Global estimates of third-order events can only be guesstimated at best by averaging the eurybatic data from widely distributed time-synchronous events. Revised curves for both long-term and short-term sea-level variations are presented for the Cretaceous Period. The curve representing the long-term envelope shows that average sea levels throughout the Cretaceous remained higher than the present day mean sea level (75-250 m above PDMSL). Sea level reached a trough in mid Valanginian (~ 75 m above PDMSL), followed by two high points, the first in early Barremian (~ 160-170 m above PDMSL) and the second, the highest peak of the Cretaceous, in earliest Turonian (~ 240-250 m above PDMSL). The curve also displays two ~ 20 Myr-long periods of relatively high and stable sea levels (Aptian through early Albian and Coniacian through Campanian). The short-term curve identifies 58 third-order eustatic events in the Cretaceous, most have been documented in several basins, while
ERIC Educational Resources Information Center
Benedek, Mathias; Neubauer, Aljoscha C.
2013-01-01
Fifty years ago, Mednick ["Psychological Review", 69 (1962) 220] proposed an elaborate model that aimed to explain how creative ideas are generated and why creative people are more likely to have creative ideas. The model assumes that creative people have flatter associative hierarchies and as a consequence can more fluently retrieve…
NASA Astrophysics Data System (ADS)
Douglas, A.
2007-01-01
contrast simple, comprising one or two cycles of large amplitude followed by a low-amplitude coda. Earthquake signals on the other hand were often complex with numerous arrivals of similar amplitude spread over 35 s or more. It therefore appeared that earthquakes could be recognised on complexity. Later however, complex explosion signals were observed which reduced the apparent effectiveness of complexity as a criterion for identifying earthquakes. Nevertheless, the AWE Group concluded that for many paths to teleseismic distances, Earth is transparent for P signals and this provides a window through which source differences will be most clearly seen. Much of the research by the Group has focused on understanding the influence of source type on P seismograms recorded at teleseismic distances. Consequently the paper concentrates on teleseismic methods of distinguishing between explosions and earthquakes. One of the most robust criteria for discriminating between earthquakes and explosions is the m b : M s criterion which compares the amplitudes of the SP P waves as measured by the body-wave magnitude m b, and the long-period (LP: ˜0.05 Hz) Rayleigh-wave amplitude as measured by the surface-wave magnitude M s; the P and Rayleigh waves being the main wave types used in forensic seismology. For a given M s, the m b for explosions is larger than for most earthquakes. The criterion is difficult to apply however, at low magnitude (say m b < 4.5) and there are exceptions—earthquakes that look like explosions. A difficulty with identification criteria developed in the early days of forensic seismology was that they were in the main empirical—it was not known why they appeared to work and if there were test sites or earthquakes where they would fail. Consequently the AWE Group in cooperation with the University of Cambridge used seismogram modelling to try and understand what controls complexity of SP P seismograms, and to put the m b : M s criterion on a theoretical basis. The
Marko, Nicholas F.; Weil, Robert J.; Schroeder, Jason L.; Lang, Frederick F.; Suki, Dima; Sawaya, Raymond E.
2014-01-01
Purpose Approximately 12,000 glioblastomas are diagnosed annually in the United States. The median survival rate for this disease is 12 months, but individual survival rates can vary with patient-specific factors, including extent of surgical resection (EOR). The goal of our investigation is to develop a reliable strategy for personalized survival prediction and for quantifying the relationship between survival, EOR, and adjuvant chemoradiotherapy. Patients and Methods We used accelerated failure time (AFT) modeling using data from 721 newly diagnosed patients with glioblastoma (from 1993 to 2010) to model the factors affecting individualized survival after surgical resection, and we used the model to construct probabilistic, patient-specific tools for survival prediction. We validated this model with independent data from 109 patients from a second institution. Results AFT modeling using age, Karnofsky performance score, EOR, and adjuvant chemoradiotherapy produced a continuous, nonlinear, multivariable survival model for glioblastoma. The median personalized predictive error was 4.37 months, representing a more than 20% improvement over current methods. Subsequent model-based calculations yield patient-specific predictions of the incremental effects of EOR and adjuvant therapy on survival. Conclusion Nonlinear, multivariable AFT modeling outperforms current methods for estimating individual survival after glioblastoma resection. The model produces personalized survival curves and quantifies the relationship between variables modulating patient-specific survival. This approach provides comprehensive, personalized, probabilistic, and clinically relevant information regarding the anticipated course of disease, the overall prognosis, and the patient-specific influence of EOR and adjuvant chemoradiotherapy. The continuous, nonlinear relationship identified between expected median survival and EOR argues against a surgical management strategy based on rigid EOR
Nakagome, Shigeki; Sato, Takehiro; Ishida, Hajime; Hanihara, Tsunehiko; Yamaguchi, Tetsutaro; Kimura, Ryosuke; Mano, Shuhei; Oota, Hiroki
2015-06-01
Various hypotheses for the peopling of the Japanese archipelago have been proposed, which can be classified into three models: transformation, replacement, and hybridization. In recent years, one of the hybridization models ("dual-structure model") has been widely accepted. According to this model, Neolithic hunter-gatherers known as Jomon, who are assumed to have originated in southeast Asia and lived in the Japanese archipelago greater than 10,000 years ago, admixed with an agricultural people known as Yayoi, whom were migrants from the East Asian continent 2,000-3,000 years ago. Meanwhile, some anthropologists propose that rather, morphological differences between the Jomon and Yayoi people can be explained by microevolution following the lifestyle change. To resolve this controversy, we compared three demographic models by approximate Bayesian computation using genome-wide single nucleotide polymorphism (gwSNP) data from the Ainu people who are thought to be direct descendants of indigenous Jomon. If we assume Chinese people sampled in Beijing from HapMap have the same ancestry as Yayoi, then the hybridization model is predicted to be between 29 and 63 times more likely than the replacement and transformation models, respectively. Furthermore, our data provide strong support for a model in which the Jomon lineages had population structure diversified in local areas before the admixture event. Initial divergence between the Jomon and Yayoi ancestries was dated to late Pleistocene, followed by the divergence of Jomon lineages at early Holocene. These results suggest gwSNP data provides a detailed picture of the complex hybridization model for Japanese population history. PMID:25758010
Ryan, James; Hendler, James; Bennett, Kristin P
2015-12-01
Electronic Healthcare Records (EHRs) have the potential to improve healthcare quality and to decrease costs by providing quality metrics, discovering actionable insights, and supporting decision-making to improve future outcomes. Within the United States Medicaid Program, rates of recidivism among emergency department (ED) patients serve as metrics of hospital performance that help ensure efficient and effective treatment within the ED. We analyze ED Medicaid patient data from 1,149,738 EHRs provided by a hospital over a 2-year period to understand the characteristics of the ED return visits within a 72-hour time frame. Frequent flyer patients with multiple revisits account for 47% of Medicaid patient revisits over this period. ED encounters by frequent flyer patients with prior 72-hour revisits in the last 6 months are thrice more likely to result in a readmit than those of infrequent patients. Statistical L1-logistic regression and random forest analyses reveal distinct patterns of ED usage and patient diagnoses between frequent and infrequent patient encounters, suggesting distinct opportunities for interventions to improve efficacy of care and streamline ED workflow. This work forms a foundation for future development of predictive models, which could flag patients at high risk of revisiting. PMID:27441405
2013-01-01
Aim To describe the evidence base relating to the Cognitive-Interpersonal Maintenance Model for anorexia nervosa (AN). Background A Cognitive-Interpersonal Maintenance Model maintenance model for anorexia nervosa was described in 2006. This model proposed that cognitive, socio-emotional and interpersonal elements acted together to both cause and maintain eating disorders. Method A review of the empirical literature relating to the key constructs of the model (cognitive, socio-emotional, interpersonal) risk and maintaining factors for anorexia nervosa was conducted. Results Set shifting and weak central coherence (associated with obsessive compulsive traits) have been widely studied. There is some evidence to suggest that a strong eye for detail and weak set shifting are inherited vulnerabilities to AN. Set shifting and global integration are impaired in the ill state and contribute to weak central coherence. In addition, there are wide-ranging impairments in socio-emotional processing including: an automatic bias in attention towards critical and domineering faces and away from compassionate faces; impaired signalling of, interpretation and regulation of emotions. Difficulties in social cognition may in part be a consequence of starvation but inherited vulnerabilities may also contribute to these traits. The shared familial traits may accentuate family members’ tendency to react to the frustrating and frightening symptoms of AN with high expressed emotion (criticism, hostility, overprotection), and inadvertently perpetuate the problem. Conclusion The cognitive interpersonal model is supported by accumulating evidence. The model is complex in that cognitive and socio-emotional factors both predispose to the illness and are exaggerated in the ill state. Furthermore, some of the traits are inherited vulnerabilities and are present in family members. The clinical formulations from the model are described as are new possibilities for targeted treatment. PMID:24999394
Hofman, Abe D.; Visser, Ingmar; Jansen, Brenda R. J.; van der Maas, Han L. J.
2015-01-01
We propose and test three statistical models for the analysis of children’s responses to the balance scale task, a seminal task to study proportional reasoning. We use a latent class modelling approach to formulate a rule-based latent class model (RB LCM) following from a rule-based perspective on proportional reasoning and a new statistical model, the Weighted Sum Model, following from an information-integration approach. Moreover, a hybrid LCM using item covariates is proposed, combining aspects of both a rule-based and information-integration perspective. These models are applied to two different datasets, a standard paper-and-pencil test dataset (N = 779), and a dataset collected within an online learning environment that included direct feedback, time-pressure, and a reward system (N = 808). For the paper-and-pencil dataset the RB LCM resulted in the best fit, whereas for the online dataset the hybrid LCM provided the best fit. The standard paper-and-pencil dataset yielded more evidence for distinct solution rules than the online data set in which quantitative item characteristics are more prominent in determining responses. These results shed new light on the discussion on sequential rule-based and information-integration perspectives of cognitive development. PMID:26505905
42 CFR 488.30 - Revisit user fee for revisit surveys.
Code of Federal Regulations, 2013 CFR
2013-10-01
... SERVICES (CONTINUED) STANDARDS AND CERTIFICATION SURVEY, CERTIFICATION, AND ENFORCEMENT PROCEDURES General... be subject to user fees unless otherwise exempted. Revisit survey means a survey performed with..., or substantiated complaint survey and that is designed to evaluate the extent to which...
42 CFR 488.30 - Revisit user fee for revisit surveys.
Code of Federal Regulations, 2011 CFR
2011-10-01
... SERVICES (CONTINUED) STANDARDS AND CERTIFICATION SURVEY, CERTIFICATION, AND ENFORCEMENT PROCEDURES General... be subject to user fees unless otherwise exempted. Revisit survey means a survey performed with..., or substantiated complaint survey and that is designed to evaluate the extent to which...
42 CFR 488.30 - Revisit user fee for revisit surveys.
Code of Federal Regulations, 2010 CFR
2010-10-01
... SERVICES (CONTINUED) STANDARDS AND CERTIFICATION SURVEY, CERTIFICATION, AND ENFORCEMENT PROCEDURES General... be subject to user fees unless otherwise exempted. Revisit survey means a survey performed with..., or substantiated complaint survey and that is designed to evaluate the extent to which...
NASA Astrophysics Data System (ADS)
Réal, Florent; Vallet, Valérie; Flament, Jean-Pierre; Masella, Michel
2013-09-01
We present a revised version of the water many-body model TCPE [M. Masella and J.-P. Flament, J. Chem. Phys. 107, 9105 (1997)], which is based on a static three charge sites and a single polarizable site to model the molecular electrostatic properties of water, and on an anisotropic short range many-body energy term specially designed to accurately model hydrogen bonding in water. The parameters of the revised model, denoted TCPE/2013, are here developed to reproduce the ab initio energetic and geometrical properties of small water clusters (up to hexamers) and the repulsive water interactions occurring in cation first hydration shells. The model parameters have also been refined to reproduce two liquid water properties at ambient conditions, the density and the vaporization enthalpy. Thanks to its computational efficiency, the new model range of applicability was validated by performing simulations of liquid water over a wide range of temperatures and pressures, as well as by investigating water liquid/vapor interfaces over a large range of temperatures. It is shown to reproduce several important water properties at an accurate enough level of precision, such as the existence liquid water density maxima up to a pressure of 1000 atm, the water boiling temperature, the properties of the water critical point (temperature, pressure, and density), and the existence of a "singularity" temperature at about 225 K in the supercooled regime. This model appears thus to be particularly well-suited for characterizing ion hydration properties under different temperature and pressure conditions, as well as in different phases and interfaces.
Réal, Florent; Vallet, Valérie; Flament, Jean-Pierre; Masella, Michel
2013-09-21
We present a revised version of the water many-body model TCPE [M. Masella and J.-P. Flament, J. Chem. Phys. 107, 9105 (1997)], which is based on a static three charge sites and a single polarizable site to model the molecular electrostatic properties of water, and on an anisotropic short range many-body energy term specially designed to accurately model hydrogen bonding in water. The parameters of the revised model, denoted TCPE/2013, are here developed to reproduce the ab initio energetic and geometrical properties of small water clusters (up to hexamers) and the repulsive water interactions occurring in cation first hydration shells. The model parameters have also been refined to reproduce two liquid water properties at ambient conditions, the density and the vaporization enthalpy. Thanks to its computational efficiency, the new model range of applicability was validated by performing simulations of liquid water over a wide range of temperatures and pressures, as well as by investigating water liquid/vapor interfaces over a large range of temperatures. It is shown to reproduce several important water properties at an accurate enough level of precision, such as the existence liquid water density maxima up to a pressure of 1000 atm, the water boiling temperature, the properties of the water critical point (temperature, pressure, and density), and the existence of a "singularity" temperature at about 225 K in the supercooled regime. This model appears thus to be particularly well-suited for characterizing ion hydration properties under different temperature and pressure conditions, as well as in different phases and interfaces. PMID:24070292
Cheng, Feng; Chen, Zhao-Xu
2016-02-01
Pd/ZnO is a promising catalyst studied for methanol steam reforming (MSR) and the 1 : 1 PdZn alloy is demonstrated to be the active component. It is believed that MSR starts from methanol dehydrogenation to methoxy. Previous studies of methanol dehydrogenation on the ideal PdZn(111) surface show that methanol adsorbs weakly on the PdZn(111) surface and it is hard for methanol to transform into methoxy because of the high dehydrogenation barrier, indicating that the catalyst model is not appropriate for investigating the first step of MSR. Using the model derived from our recent kinetic Monte Carlo simulations, we examined the process CH3OH → CH3O → CH2O → CHO → CO. Compared with the ideal model, methanol adsorbs much more strongly and the barrier from CH3OH → CH3O is much lower on the kMC model. On the other hand, the C-H bond breaking of CH3O, CH2O and CHO becomes harder. We show that co-adsorbed water is important for refreshing the active sites. The present study shows that the first MSR step most likely takes place on three-fold hollow sites formed by Zn atoms, and the inhomogeneity of the PdZn alloy may exert significant influences on reactions. PMID:26771029
ERIC Educational Resources Information Center
Mason, W. Alex
2001-01-01
Studied the relationship between self-esteem and delinquency using latent growth curve modeling. Analyses of panel data for 2,213 adolescent boys from the Youth in Transition Study supported Kaplan's self-derogation theory of delinquency (H. Kaplan, 1978) by showing that delinquency was positively associated with growth in self-esteem among…
Hiatt, JR; Rivard, MJ
2014-06-01
Purpose: The model S700 Axxent electronic brachytherapy source by Xoft was characterized in 2006 by Rivard et al. The source design was modified in 2006 to include a plastic centering insert at the source tip to more accurately position the anode. The objectives of the current study were to establish an accurate Monte Carlo source model for simulation purposes, to dosimetrically characterize the new source and obtain its TG-43 brachytherapy dosimetry parameters, and to determine dose differences between the source with and without the centering insert. Methods: Design information from dissected sources and vendor-supplied CAD drawings were used to devise the source model for radiation transport simulations of dose distributions in a water phantom. Collision kerma was estimated as a function of radial distance, r, and polar angle, θ, for determination of reference TG-43 dosimetry parameters. Simulations were run for 10{sup 10} histories, resulting in statistical uncertainties on the transverse plane of 0.03% at r=1 cm and 0.08% at r=10 cm. Results: The dose rate distribution the transverse plane did not change beyond 2% between the 2006 model and the current study. While differences exceeding 15% were observed near the source distal tip, these diminished to within 2% for r>1.5 cm. Differences exceeding a factor of two were observed near θ=150° and in contact with the source, but diminished to within 20% at r=10 cm. Conclusions: Changes in source design influenced the overall dose rate and distribution by more than 2% over a third of the available solid angle external from the source. For clinical applications using balloons or applicators with tissue located within 5 cm from the source, dose differences exceeding 2% were observed only for θ>110°. This study carefully examined the current source geometry and presents a modern reference TG-43 dosimetry dataset for the model S700 source.
Revisiting Bohr's semiclassical quantum theory.
Ben-Amotz, Dor
2006-10-12
Bohr's atomic theory is widely viewed as remarkable, both for its accuracy in predicting the observed optical transitions of one-electron atoms and for its failure to fully correspond with current electronic structure theory. What is not generally appreciated is that Bohr's original semiclassical conception differed significantly from the Bohr-Sommerfeld theory and offers an alternative semiclassical approximation scheme with remarkable attributes. More specifically, Bohr's original method did not impose action quantization constraints but rather obtained these as predictions by simply matching photon and classical orbital frequencies. In other words, the hydrogen atom was treated entirely classically and orbital quantized emerged directly from the Planck-Einstein photon quantization condition, E = h nu. Here, we revisit this early history of quantum theory and demonstrate the application of Bohr's original strategy to the three quintessential quantum systems: an electron in a box, an electron in a ring, and a dipolar harmonic oscillator. The usual energy-level spectra, and optical selection rules, emerge by solving an algebraic (quadratic) equation, rather than a Bohr-Sommerfeld integral (or Schroedinger) equation. However, the new predictions include a frozen (zero-kinetic-energy) state which in some (but not all) cases lies below the usual zero-point energy. In addition to raising provocative questions concerning the origin of quantum-chemical phenomena, the results may prove to be of pedagogical value in introducing students to quantum mechanics. PMID:17020371
Li, Xia; Cheng, Jin; Zhou, Zhiguang
2016-07-01
Type 1 diabetes (T1D) results from a chronic autoimmune process that leads to β-cell destruction and exogenous insulin dependence. The natural history of T1D proposed by Eisenbarth suggested six relatively independent stages over the course of the entire disease process, which was considered to be linear and chronic. Based on this classical theory, immunotherapies aim to prevent or reverse all these periods of β-cell loss. Over the past 30 years, much novel information about the pathogenesis of T1D proved that there are complex metabolic changes occurring throughout the entire disease process. Therefore, new possible models for the natural history of the disease have been proposed; these models, in turn, may help facilitate fresh avenues for the prevention and cure of T1D. Herein, we briefly review recent findings in this field of research, with the aim of providing a better theoretical basis for clinical practice. PMID:26754489
Revisiting the Regenerative Possibilities of Ortiz
ERIC Educational Resources Information Center
Duques, Matthew
2004-01-01
The author of this article revisits Simon Ortiz's poem, "From Sand Creek," in which the latter can in so few words convey both the horrific tragedy of conquest and colonization, while at the same time find a space for possibility, a means for recovery that is never about forgetting but always occurs as a kind of recuperative remembering. Ortiz…
Phenomenology of n - n ¯ oscillations revisited
Gardner, S.; Jafari, E.
2015-05-22
We revisit the phenomenology of n-n¯ oscillations in the presence of external magnetic fields, highlighting the role of spin. We show, contrary to long-held belief, that the n-n¯ transition rate need not be suppressed, opening new opportunities for its empirical study.
The Evil of Banality: Arendt Revisited
ERIC Educational Resources Information Center
Minnich, Elizabeth
2014-01-01
"The banality of evil" (Arendt) remains controversial and useful. Ironically, the concept is now itself a banality. To revisit and extend it, we consider the "evil of banality", the profound dangers of cliched thoughtlessness. A distinction is proposed: "intensive" versus "extensive evils". The former takes…
Revisiting separation properties of convex fuzzy sets
Technology Transfer Automated Retrieval System (TEKTRAN)
Separation of convex sets by hyperplanes has been extensively studied on crisp sets. In a seminal paper separability and convexity are investigated, however there is a flaw on the definition of degree of separation. We revisited separation on convex fuzzy sets that have level-wise (crisp) disjointne...
Revisiting and Rethinking the Reading Process.
ERIC Educational Resources Information Center
Kucer, Stephen B.; Tuten, Jenny
2003-01-01
Reports on the authors' revisiting of the reading process using proficient adult readers (advanced graduate students in a school of education) as their informants. Begins with a brief overview of the current debate concerning the nature of reading and explains how they went about investigating the issue. Discusses what they learned from their…
Fine structure of the butterfly diagram revisited
NASA Astrophysics Data System (ADS)
Major, Balázs
The latitudinal time distribution of sunspots (butterfly diagram) was studied by Becker (1959) and Antalová & Gnevyshev (1985). Our goal is to revisit these studies. In the first case we check whether there is a poleward migration in sunspot activity. In the second case we confirm the results, and make more quantitative statements concerning their significance and the position of the activity peaks.
Benay, G; Wipff, G
2014-03-20
We report a molecular dynamics (MD) study of biphasic systems involved in the liquid-liquid extraction of uranyl nitrate by tri-n-butylphosphate (TBP) to hexane, from "pH neutral" or acidic (3 M nitric acid) aqueous solutions, to assess the model dependence of the surface activity and partitioning of TBP alone, of its UO2(NO3)2(TBP)2 complex, and of UO2(NO3)2 or UO2(2+) uncomplexed. For this purpose, we first compare several electrostatic representations of TBP with regards to its polarity and conformational properties, its interactions with H2O, HNO3, and UO2(NO3)2 species, its relative free energies of solvation in water or oil environments, the properties of the pure TBP liquid and of the pure-TBP/water interface. The free energies of transfer of TBP, UO2(NO3)2, UO2(2+), and the UO2(NO3)2(TBP)2 complex across the water/oil interface are then investigated by potential of mean force (PMF) calculations, comparing different TBP models and two charge models of uranyl nitrate. Describing uranyl and nitrate ions with integer charges (+2 and -1, respectively) is shown to exaggerate the hydrophilicity and surface activity of the UO2(NO3)2(TBP)2 complex. With more appropriate ESP charges, mimicking charge transfer and polarization effects in the UO2(NO3)2 moiety or in the whole complex, the latter is no more surface active. This feature is confirmed by MD, PMF, and mixing-demixing simulations with or without polarization. Furthermore, with ESP charges, pulling the UO2(NO3)2 species to the TBP phase affords the formation of UO2(NO3)2(TBP)2 at the interface, followed by its energetically favorable extraction. The neutral complexes should therefore not accumulate at the interface during the extraction process, but diffuse to the oil phase. A similar feature is found for an UO2(NO3)2(Amide)2 neutral complex with fatty amide extracting ligands, calling for further simulations and experimental studies (e.g., time evolution of the nonlinear spectroscopic signature and of surface
Roumelioti, Maria Eleni; Nolin, Thomas; Unruh, Mark L.; Argyropoulos, Christos
2016-01-01
Background Beta-2 Microglobulin (β2M) is a prototypical “middle molecule” uremic toxin that has been associated with a higher risk of death in hemodialysis patients. A quantitative description of the relative importance of factors determining β2M concentrations among patients with impaired kidney function is currently lacking. Methods Herein we undertook a systematic review of existing studies reporting patient level data concerning generation, elimination and distribution of β2M in order to develop a population model of β2M kinetics. We used this model and previously determined relationships between predialysis β2M concentration and survival, to simulate the population distribution of predialysis β2M and the associated relative risk (RR) of death in patients receiving conventional thrice-weekly hemodialysis with low flux (LF) and high flux (HF) dialyzers, short (SD) and long daily (LD) HF hemodialysis sessions and on-line hemodiafiltration at different levels of residual renal function (RRF). Results We identified 9 studies of 106 individuals and 156 evaluations of or more compartmental kinetic parameters of β2M. These studies used a variety of experimental methods to determine β2M kinetics ranging from isotopic dilution to profiling of intra/inter dialytic concentration changes. Most of the patients (74/106) were on dialysis with minimal RRF, thus facilitating the estimation of non-renal elimination kinetics of β2M. In large scale (N = 10000) simulations of individuals drawn from the population of β2M kinetic parameters, we found that, higher dialytic removal materially affects β2M exposures only when RRF (renal clearance of β2M) was below 2 ml/min. In patients initiating conventional HF hemodialysis, total loss of RRF was predicted to be associated with a RR of death of more than 20%. Hemodiafiltration and daily dialysis may decrease the high risk of death of anuric patients by 10% relative to conventional, thrice weekly HF dialysis. Only daily
Machining as a mechanical property test revisited
NASA Astrophysics Data System (ADS)
Smith, David L.
There is much need for data on mechanical behavior of metals at high strains and strain rates. This need is dictated by modeling of processes like forming and machining, wherein the material in the deformation zone is subjected to severe deformation conditions atypical of conventional material property tests such as tension and torsion. Accurate flow stress data is an essential input for robust prediction of process outputs. Similar requirements arise from applications in high speed ballistic penetration and design of materials for armor. Since the deformation zone in cutting of metals is characterized by unique and extreme combinations of strain, strain rate and temperature, an opportunity exists for using plane-strain cutting as a mechanical property test for measuring flow properties of metals. The feasibility of using plane-strain cutting to measure flow properties of metals is revisited in the light of recent data showing controllability of the deformation conditions in chip formation by systematic variation of process input parameters. A method is outlined as to how the deformation conditions can be varied by changing the process parameters. The method is applied to cutting of commercially pure copper (FCC), iron (BCC) and zinc (HCP). Forces and chip geometries are measured, in conjunction with particle image velocimetry characterization of the deformation using high speed image sequences. The flow stresses are estimated from these measurements. The measured flow stress and its dependence on strain are shown to agree well with prior measurements of these parameters using conventional tests, and flow stress inferred from hardness characterization. The method is also demonstrated to be able to measure properties of metals that recrystallize at room temperature (zinc), wherein quasi-static tests predict much lower strength. Sources of variability and uncertainty in the application of this measurement technique are discussed. Future work in the context of further
NASA Astrophysics Data System (ADS)
Aydin, Murat G.; Engelder, Terry
2014-12-01
Both bedding-parallel slickensides and cleavage duplexes are forms of mesoscopic-scale detachment faulting populating black (Marcellus and Geneseo/Burket) and intervening gray (Mahantango) shales of the Middle Devonian, a section known for abnormal pore pressure below the Appalachian Plateau. The abundance and the orientation of slickensides and cleavage duplexes in the more organic-rich black shale relative to gray shale suggests that maturation-related abnormal pore pressure facilitates detachment, a mesoscopic manifestation of the Hubbert-Rubey pore pressure model for overthrust faulting. The former are discrete slip surfaces whereas the latter consists of nested, anastomosing slip surfaces, either cutting through bedding or on disrupted bedding surfaces stacked as mesoscopic versions of thrust duplexes. Cleavage duplexes are between a few cm and over 1 m thick with their hanging walls commonly transported toward the Appalachian foreland, regardless of local limb dip. Cleavage duplexes are most common near the stratigraphic maximum flooding surface, the organic-rich section most prone to develop maturation-related pore pressure in the Middle Devonian gas shales. Bedding-parallel slickensides are somewhat more evenly distributed in the black shale but also found in overlying gray shale. In both black and gray shales, slickensides are more abundant on the limbs of folds, an indication of pore-pressure-related flexural-slip folding. On the macroscopic scale, the Pine Mountain Block of the Southern Appalachian Mountains was enabled by a basal detachment cutting along the Upper Devonian Chattanooga black shale which has a thermal maturity sufficient for the generation of abnormal pore pressure. The Pine Mountain block is a large-scale overthrust showing little evidence of collapse of the hinterland side, a credible example of a pore-pressure-aided overthrust fault block of the type envisioned by the Hubbert-Rubey model.
NASA Astrophysics Data System (ADS)
Bea, F.; Montero, P.; Anbar, M. Abu; Molina, J. F.; Scarrow, J. H.
2011-08-01
Bir Safsaf is one of the four Precambrian inliers of the southern Egyptian Western Desert; it is located midway between the juvenile crust of the Arabian-Nubian Shield and the Archean terranes of Gebel Kamil, near the Libyan border. Contrary to previous belief, Bir Safsaf is exclusively composed of late Pan-African granitoids, with U/Pb SHRIMP ages between 627 Ma and 595 Ma. The presence of pre-Pan-African materials is limited to scarce inherited zircons with ~ 2.1 Ga and ~ 2.7 Ga, ages that are well-represented in the pre-Pan-African terranes of the neighboring Gebel Kamil inlier. Early Pan-African inherited zircons with ages of ~ 640-650 Ma and ~ 750 Ma are also found. The granitoids of Bir Safsaf show a large geochemical variability, with an overall composition similar to subduction-related granites, but they lack the inter-elemental correlations characteristic of magmatic differentiation, magma mixing or hybridization. This chemically heterogeneous set of granitoids has, nonetheless, nearly uniform initial 87Sr/ 86Sr and 143Nd/ 144Nd, and a ~ 1.5 Ga Nd model age (T DM) despite no new crust being formed at that time in northeast Africa. To reconcile the large chemical variability, the isotopic homogeneity, and the "mixed" Nd model age, we propose that these granitoids were derived from a lithologically heterogeneous pre-Pan African source that, prior to melting, was thoroughly homogenized with respect to Sr and Nd isotopes by convective metasomatism caused by juvenile hydrothermal fluids probably released from a subduction zone.
Finite frequency tomography: the checkerboard test revisited
NASA Astrophysics Data System (ADS)
Mercerat, E. D.; Zaroli, C.; Nolet, G.
2011-12-01
We address some consequences of the application of finite frequency theory for seismic tomography by revisiting the classical checkerboard test. We use a simple borehole-to-borehole experiment set-up in order to have complete control of the situation and to avoid complicating factors such as crustal corrections that still hamper global tomography. We are particularly interested in the feasibility of using ray-based finite frequency kernels in the inversion of travel time perturbations measured by crosscorrelation, in the cross-dependence between S wave velocity perturbations and the measured P travel times, and in the benefits of using finite-frequency theory on one or multiple frequency bands. We have done a 3D checkerboard test to assess the influence of these issues. Full-waveform synthetic seismograms are calculated using the spectral elements method up to 2 kHz maximum frequency. The computational domain extends 200 m x 120 m x 120 m and the target velocity model is a checkerboard with 12 m x 12 m x 12 m blocks of velocities 5% slower and faster than the background (homogeneous, Vp=6 km/s) model. First, we make a comparison between finite-frequency kernels calculated by ray theory with those based on the spectral elements method (adjoint technique), in terms of resolution, accuracy, but also computational cost. From synthetic seismograms calculated for the 3D checkerboard model as well as for the homogeneous model, we measure crosscorrelation travel times at different frequency bands and invert them with classical ray theory as well as with finite frequency theory. Several interesting features are highlighted in our multi-band data set, such as the wavefront healing effect. For instance, we observe that the delay times, in absolute value, are usually larger at short (0.5 ms) than long (4 ms) periods. This can be explained by the presence of the "doughnut hole" along the geometrical ray path in the sensitivity kernels, whose diameter is proportional to the
NASA Astrophysics Data System (ADS)
Martínez-Loriente, Sara; Sallarès, Valentí; Gràcia, Eulàlia; Bartolome, Rafael; Ranero, César
2015-04-01
We present a new classification of geological (basement) domains at the Africa-Eurasia plate boundary offshore SW Iberia, together with a regional geodynamic reconstruction spanning from the Mesozoic extension to the Neogene-to-present-day convergence. It is based on seismic velocity and density models along two regional wide-angle seismic transects, one running NW-SE from the Tagus to the Seine abyssal plains, and the other running N-S from S Portugal to the Seine Abyssal Plain, combined with previously available information. The seismic velocity and density structure at the Seine Abyssal Plain and the internal Gulf of Cadiz indicates the presence of a highly heterogeneous oceanic crust, similar to that described in ultra-slow spreading centers, whereas in the Horseshoe and Tagus abyssal plains, the basement structure resembles that of exhumed mantle sections identified in the Northern Atlantic margin. The integration of all this new information allows defining the presence of three oceanic domains off SW Iberia: (1) the Seine Abyssal Plain domain, generated during the first stages of slow seafloor spreading in the NE segment of the Central Atlantic (Early Jurassic); (2) the Gulf of Cadiz domain, made of oceanic crust generated in the Alpine-Tethys spreading system between Iberia and Africa, which was coeval with the formation of the Seine Abyssal Plain domain and lasted up to the North Atlantic continental break-up (Late Jurassic); and (3) the Gorringe Bank domain, mainly made of rocks exhumed from the mantle with little synchronous magmatism, which formed during the first stages of North Atlantic opening (Early Cretaceous). Our models suggest that the Seine Abyssal Plain and Gulf of Cadiz domains are separated by the Lineament South strike-slip fault, whereas the Gulf of Cadiz and Gorringe Bank domains appear to be limited by a deep thrust fault located at the center of the Horseshoe Abyssal Plain, which coincides with the seismicity cluster nucleated in the
Simon, Raphael; Tennant, Sharon M.; Galen, James E.; Levine, Myron M.
2011-01-01
Non-typhoidal Salmonella enterica (NTS) serovars Typhimurium and Enteritidis are important causes of bacterial gastroenteritis in the USA and worldwide. In sub-Saharan Africa these two serovars are emerging as agents associated with lethal invasive disease (e.g., bacteremia, meningitis). The development of NTS vaccines, based on mucosally-administered live attenuated strains and parenteral non-living antigens, could diminish the NTS disease burden globally. Mouse models of S. Typhimurium and S. Enteritidis invasive disease can accelerate the development of NTS vaccines. Live attenuated NTS vaccines elicit both cellular and humoral immunity in mice and their efficacy is well established. In contrast, non-living vaccines that primarily elicit humoral immunity have demonstrated variable efficacy. An analysis of the reported studies with non-living vaccines against S. Typhimurium and S. Enteritidis reveals that efficacy is influenced by two important independent variables: 1) the innate susceptibility to NTS infection that differs dramatically between commonly used mouse strains and, 2) the virulence of the NTS strain used for challenge. Protection by non-living vaccines has generally been seen only in host-pathogen interactions where a sub-lethal infection results, such as challenging resistant mice with either highly virulent or weakly virulent strains or susceptible mice with weakly virulent strains. The immunologic basis of this discrepancy and the implications for human NTS vaccine development are reviewed herein. PMID:21616112
Pauluhn, J; Carson, A; Costa, D L; Gordon, T; Kodavanti, U; Last, J A; Matthay, M A; Pinkerton, K E; Sciuto, A M
2007-08-01
A workshop was held February 14, 2007, in Arlington, VA, under the auspices of the Phosgene Panel of the American Chemistry Council. The objective of this workshop was to convene inhalation toxicologists and medical experts from academia, industry and regulatory authorities to critically discuss past and recent inhalation studies of phosgene in controlled animal models. This included presentations addressing the benefits and limitations of rodent (mice, rats) and nonrodent (dogs) species to study concentration x time (C x t) relationships of acute and chronic types of pulmonary changes. Toxicological endpoints focused on the primary pulmonary effects associated with the acute inhalation exposure to phosgene gas and responses secondary to injury. A consensus was reached that the phosgene-induced increased pulmonary extravasation of fluid and protein can suitably be probed by bronchoalveolar lavage (BAL) techniques. BAL fluid analyses rank among the most sensitive methods to detect phosgene-induced noncardiogenic, pulmonary high-permeability edema following acute inhalation exposure. Maximum protein concentrations in BAL fluid occurred within 1 day after exposure, typically followed by a latency period up to about 15 h, which is reciprocal to the C x t exposure relationship. The C x t relationship was constant over a wide range of concentrations and single exposure durations. Following intermittent, repeated exposures of fixed duration, increased tolerance to recurrent exposures occurred. For such exposure regimens, chronic effects appear to be clearly dependent on the concentration rather than the cumulative concentration x time relationship. The threshold C x t product based on an increased BAL fluid protein following single exposure was essentially identical to the respective C x t product following subchronic exposure of rats based on increased pulmonary collagen and influx of inflammatory cells. Thus, the chronic outcome appears to be contingent upon the acute
NASA Astrophysics Data System (ADS)
Seif, Stefanie; Mignan, Arnaud; Wiemer, Stefan
2013-04-01
Numerous studies have suggested that short-term foreshocks observed prior to large earthquakes are undistinguishable from the normal behaviour of seismicity, which is well described for example by the Epidemic-Type Aftershock Sequence (ETAS) model. Here we show that these studies fail to extract abnormal foreshock behaviour due to the much more frequent occurrence of aftershocks in comparison to potential foreshocks, which results in undervaluing the role of foreshocks. We first define mainshocks as earthquakes of magnitude M6+ and use a space-time-magnitude window method with a maximum distance of 10 km to the mainshock, a maximum time range of 3 days before the mainshock and a minimum magnitude M4+ to define foreshocks in Southern California and in Italy. We then compare the observed rate of foreshock-mainshock pairs to the rate expected by ETAS simulations. Similar to previous studies, these results indicate that the foreshock activity observed in real catalogues is compatible with the ETAS model. Definition of foreshocks with a window method is, however, simplistic, since any individual event may be considered a foreshock although it is impossible to distinguish a foreshock from background or aftershock activity at a one-to-one event basis. We extend our foreshock analysis based on the predictions of the Non-Critical Precursory Accelerating Seismicity Theory (NC PAST), which are: (1) foreshocks are due to overloading on the main fault and occur in clusters, the activity of which is significantly higher than background activity, (2) microseismicity (M<3) must be included for the emergence of a reliable signal and (3) foreshocks are not systematic before large earthquakes due to aleatoric uncertainty on the rupture process. Following these guidelines, we systematically investigate foreshock sequences before large earthquakes (M6+) in Southern California and Italy. Using different approaches, we finally show that significant anomalies are observed before some
NASA Astrophysics Data System (ADS)
Yasui, Kyuichi; Kozuka, Teruyuki; Yasuoka, Masaki; Kato, Kazumi
2015-11-01
There are two major categories in a thermoacoustic prime-mover. One is the traveling-wave type and the other is the standing-wave type. A simple analytical model of a standing-wave thermoacoustic prime-mover is proposed at relatively low heat-flux for a stack much shorter than the acoustic wavelength, which approximately describes the Brayton cycle. Numerical simulations of Rott's equations have revealed that the work flow (acoustic power) increases by increasing of the amplitude of the particle velocity (| U|) for the traveling-wave type and by increasing cosΦ for the standing-wave type, where Φ is the phase difference between the particle velocity and the acoustic pressure. In other words, the standing-wave type is a phase-dominant type while the traveling-wave type is an amplitude-dominant one. The ratio of the absolute value of the traveling-wave component (| U|cosΦ) to that of the standing-wave component (| U|sinΦ) of any thermoacoustic engine roughly equals the ratio of the absolute value of the increasing rate of | U| to that of cosΦ. The different mechanism between the traveling-wave and the standing-wave type is discussed regarding the dependence of the energy efficiency on the acoustic impedance of a stack as well as that on ωτα, where ω is the angular frequency of an acoustic wave and τα is the thermal relaxation time. While the energy efficiency of the traveling-wave type at the optimal ωτα is much higher than that of the standing-wave type, the energy efficiency of the standing-wave type is higher than that of the traveling-wave type at much higher ωτα under a fixed temperature difference between the cold and the hot ends of the stack.
NASA Astrophysics Data System (ADS)
Hinrichsen, H.-H.; Lehmann, A.; Petereit, C.; Nissling, A.; Ustups, D.; Bergström, U.; Hüssy, K.
2016-04-01
In the highly variable environment of the Baltic Sea two genetically distinct cod stocks exist, one west of the island of Bornholm, which is referred to as the western stock, and one to the east of Bornholm, the eastern stock. A hydrodynamic model combined with a Lagrangian particle tracking technique was utilised to provide spatially and temporally resolved long-term information on environmentally-related (i) spawning habitat size, (ii) egg/yolk-sac larval survival, (iii) separation of causes of mortality, and (iv) connectivity between spawning areas of eastern Baltic cod. Simulations were performed to quantify processes generating heterogeneity in spatial distribution of cod eggs and yolk sac larvae up to the first-feeding stage. The spatial extent of cod eggs represented as virtual drifters is primarily determined by oxygen and salinity conditions at spawning, which define the habitat requirement to which cod's physiology is suited for egg development. The highest habitat suitability occurred in the Bornholm Basin, followed by the Gdansk Deep, while relatively low habitat suitability was obtained for the Arkona and the Gotland Basin. During drift egg and yolk sac larval survival is to a large extent affected by sedimentation. Eggs initially released in the western spawning grounds (Arkona and Bornholm Basin) were more affected by sedimentation than those released in the eastern spawning grounds (Gdansk Deep and Gotland Basin). Highest relative survival of eastern Baltic cod eggs occurred in the Bornholm Basin, with a pronounced decrease towards the Gdansk Deep and the Gotland Basin. Relatively low survival rates in the Gdansk Deep and in the Gotland Basin were attributable to oxygen-dependent mortality. Low oxygen content had almost no impact on survival in the Arkona Basin. For all spawning areas temperature dependent mortality was only evident after severe winters. Egg buoyancy in relation to topographic features like bottom sills and strong bottom slopes
Revisiting the Scattering Greenhouse Effect of CO2 Ice Clouds
NASA Astrophysics Data System (ADS)
Kitzmann, D.
2016-02-01
Carbon dioxide ice clouds are thought to play an important role for cold terrestrial planets with thick CO2 dominated atmospheres. Various previous studies showed that a scattering greenhouse effect by carbon dioxide ice clouds could result in a massive warming of the planetary surface. However, all of these studies only employed simplified two-stream radiative transfer schemes to describe the anisotropic scattering. Using accurate radiative transfer models with a general discrete ordinate method, this study revisits this important effect and shows that the positive climatic impact of carbon dioxide clouds was strongly overestimated in the past. The revised scattering greenhouse effect can have important implications for the early Mars, but also for planets like the early Earth or the position of the outer boundary of the habitable zone.
Revisiting Johnson and Jackson boundary conditions for granular flows
Li, Tingwen; Benyahia, Sofiane
2012-07-01
In this article, we revisit Johnson and Jackson boundary conditions for granular flows. The oblique collision between a particle and a flat wall is analyzed by adopting the classic rigid-body theory and a more realistic semianalytical model. Based on the kinetic granular theory, the input parameter for the partial-slip boundary conditions, specularity coefficient, which is not measurable in experiments, is then interpreted as a function of the particle-wall restitution coefficient, the frictional coefficient, and the normalized slip velocity at the wall. An analytical expression for the specularity coefficient is suggested for a flat, frictional surface with a low frictional coefficient. The procedure for determining the specularity coefficient for a more general problem is outlined, and a working approximation is provided.
The flow along an external corner revisited
NASA Astrophysics Data System (ADS)
Denier, Jim; Jewell, Nathaniel
2013-11-01
We revisit the problem of the flow of an almost inviscid fluid along an external corner made from the junction of two quarter infinite plates joined at an angle 0 < α < π / 2 . The structure of the boundary layer which develops along the corner is explored using a computational approach based upon a spectral element discretisation of the steady two-dimensional boundary-layer equations. We pay particular attention to the case when the angle α is small, thus approximating the semi-infinte quarter plate problem considered by Stewartson (1961) and recently revisited by Duck & Hewitt (2012). Our results, which demonstrate a thickening of the boundary-layer near the sharp corner, will be discussed in the context of the asymptotic theory developed in the aforementioned papers.
Quasar X-Ray Spectra Revisited: Erratum
NASA Astrophysics Data System (ADS)
Shastri, P.; Wilkes, B. J.; Elvis, M.; McDowell, J.
1994-08-01
In the paper "Quasar X-Ray Spectra Revisited " by P. Shastri, B. J. Wilkes, M. Elvis, and J. McDowell (ApJ, 410,29 [1993]), there is an error in the flux density levels in Figures 4a and 4b. As a result of an error during rebinning of the optical spectrophotometry data, the flux density levels in those two figures are a factor of 5 lower then their actual value.
NASA Astrophysics Data System (ADS)
Ge, M. L.; et al.
1996-09-01
The Table of Contents for the full book PDF is as follows: * Preface * Part I: Satellite Meeting of STATPHYS-19 * Boundary Yang-Baxter in the RSOS/SOS Representation * Quantum Domains in Ferromagnetic Anisotropic Heisenberg Chains * The Generalized Chiral Clock Model and its Phase Diagram * Algebraic Solution of the Coincidence Problem for Crystals and Quasicrystals * Reflection Equations and Surface Critical Phenomena * Fully Packed Loop Models * Quantum Field Theories in terms of Group-Valued Local Fields: An Overview * C-Statiscal Transition Transforms of the Heisenberg Spin Chain and Braided Symmetry * U(1)-Invariant Local and Integrable Lattice Formulation of the Massive Thirring Model * Corner Transfer Matrices and Novel Polynomials * Rigorous and Numerical Results on Two-Dimensional Oriented Self-Avoiding Walks * The Price for Quantum Group Symmetry: Chiral Versus 2D WZNW Model * Integrable Zn-Chiral Potts Model : The Missing Rapidity-Momentum Relation * Dilute Algebras and Solvable Lattice Models * Falicov-Kimball Model: Ground States and Flux Phase Problem * Mutual Exclusion Statistics in the Exactly Solvable Model of the Mott Metal-Insulator Transition * Quantum Group and the Hofstadter Problem * Domain Walls in the Spin-S Quantum Ising Chain * Quantization of Nonultralocal Models - Generalization of the Theorem for the Multiple Coproduct * Multipoint Functions(Form-factors) of Quantum sine-Gordon Field with Boundary * Three-Dimensional Vertex Model * Probability of Phase Separation and Two Point Temperature Correlation Functions for the Bose Gas with Delta Interaction * On the Fundamental Invariant of the Hecke Algebra Hn(q) * Ternary Z3-Graded Algebras and New Gauge Theories * Thermodynamics of Integrable Quantum Chains : Free Energy and Correlation Lengths * Quantum Integrable Systems and Classical Discrete Nonlinear Dynamics * Quantum Jacobi-Trudi Formula and Analytic Bethe Ansatz * On Boundary Condition of Single Particle and the Spectrum of Many
BHQ revisited (2): Texture development
NASA Astrophysics Data System (ADS)
Kilian, Rüdiger; Heilbronner, Renée
2016-04-01
appears that grains can be unfavourably oriented for glide despite their c-axis direction falling in those positions which were used in the "classical" interpretation. Additionally, it turns out that grain-scale dispersion axes can be used to describe the kinematic behaviour in a more consistent way compared to the rotations axes obtained from intragranular misorientations in the range of 2-10°. The implications derived from the experimental data set will be compared to data obtained from natural quartz mylonites which formed in a comparable recrystallization regime. This is the companion poster to "BHQ revisited (I) looking at grain size" where the development of the dynamically recrystallized grain size is addressed. Reference cited: Heilbronner, R., and J. Tullis (2006), Evolution of c axis pole figures and grain size during dynamic recrystallization: Results from experimentally sheared quartzite, J. Geophys. Res., 111, B10202, doi:10.1029/2005JB004194.
42 CFR 488.30 - Revisit user fee for revisit surveys.
Code of Federal Regulations, 2014 CFR
2014-10-01
... SERVICES (CONTINUED) STANDARDS AND CERTIFICATION SURVEY, CERTIFICATION, AND ENFORCEMENT PROCEDURES General... subject to user fees unless otherwise exempted. Revisit survey means a survey performed with respect to a... substantiated complaint survey and that is designed to evaluate the extent to which...
Revisiting cosmic no-hair theorem for inflationary settings
NASA Astrophysics Data System (ADS)
Maleknejad, A.; Sheikh-Jabbari, M. M.
2012-06-01
In this work we revisit Wald’s cosmic no-hair theorem [R. M. Wald, Phys. Rev. DPRVDAQ0556-2821 28, 2118 (1983).10.1103/PhysRevD.28.2118] in the context of accelerating Bianchi cosmologies for a generic cosmic fluid with nonvanishing anisotropic stress tensor and when the fluid energy-momentum tensor is of the form of a cosmological constant term plus a piece which does not respect strong or dominant energy conditions. Such a fluid is the one appearing in inflationary models. We show that for such a system anisotropy may grow, in contrast to the cosmic no-hair conjecture. In particular, for a generic inflationary model we show that there is an upper bound on the growth of anisotropy. For slow-roll inflationary models, our analysis can be refined further and the upper bound is found to be of the order of slow-roll parameters. We examine our general discussions and our extension of Wald’s theorem for three classes of slow-roll inflationary models, generic multiscalar field driven models, anisotropic models involving U(1) gauge fields and the gauge-flation scenario.
On deformations of AdS n × S n supercosets
NASA Astrophysics Data System (ADS)
Hoare, B.; Roiban, R.; Tseytlin, A. A.
2014-06-01
We study the deformed AdS 5 × S 5 supercoset model of arXiv:1309.5850 which depends on one parameter κ and has classical quantum group symmetry. We confirm the conjecture that in the "maximal" deformation limit, κ → ∞, this model is T-dual to "flipped" double Wick rotation of the target space AdS 5 × S 5, i.e. dS 5 × H 5 space supported by an imaginary 5-form flux. In the imaginary deformation limit, κ → i, the corresponding target space metric is of a pp-wave type and thus the resulting light-cone gauge S-matrix becomes relativistically invariant. Omitting non-unitary contributions of imaginary WZ terms, we find that this tree-level S-matrix is equivalent to that of the generalized sine-Gordon model representing the Pohlmeyer reduction of the undeformed AdS 5 × S 5 superstring model. We also study in some detail similar deformations of the AdS 3 × S 3 and AdS 2 × S 2 supercosets. The bosonic part of the deformed AdS 3 × S 3 model happens to be equivalent to the symmetric case of the sum of the Fateev integrable deformation of the SL(2) and SU(2) principal chiral models, while in the AdS 2 × S 2 case the role of the Fateev model is played by the 2d "sausage" model. The κ = i limits are again directly related to the Pohlmeyer reductions of the corresponding AdS n × S n supercosets: (2,2) super sine-Gordon model and its complex sine-Gordon analog. We also discuss possible deformations of AdS 3 × S 3 with more than one parameter.
The pollen tube paradigm revisited.
Kroeger, Jens; Geitmann, Anja
2012-12-01
The polar growth process characterizing pollen tube elongation has attracted numerous modeling attempts over the past years. While initial models focused on recreating the correct cellular geometry, recent models are increasingly based on experimentally assessed cellular parameters such as the dynamics of signaling processes and the mechanical properties of the cell wall. Recent modeling attempts have therefore substantially gained in biological relevance and predictive power. Different modeling methods are explained and the power and limitations of individual models are compared. Focus is on several recent models that use closed feedback loops in order to generate limit cycles representing the oscillatory behavior observed in growing tubes. PMID:23000432
Some comments on quasi-integrability
NASA Astrophysics Data System (ADS)
Ferreira, L. A.; Zakrzewski, Wojtek J.
2011-04-01
In this paper we present our preliminary results which suggest that some field theory models are 'almost' integrable; i.e. they possess a large number of 'almost' conserved quantities. First we demonstrate this, in some detail, on a class of models which generalise sine-Gordon model in (1+1) dimensions. Then, we point out that many field configurations of these models look like those of the integrable systems and others are very close to being integrable. Finally we attempt to quantify these claims looking in particular, both analytically and numerically, at some long lived field configurations which resemble breathers.
Storage coefficient revisited: is purely vertical strain a good assumption?
Burbey, T J
2001-01-01
The storage coefficient that is used ubiquitously today was first defined by the analytical work of Theis and Jacob over a half-century ago. Inherent within this definition is the restriction of purely vertical compression of the aquifer during a reduction in pressure. The assumption is revisited and quantitatively evaluated by comparing numerical results using both one- and three-dimensional strain models in the presence of three-dimensional flow. Results indicate that (1) calculated hydraulic head values are nearly identical for both models; (2) the release of water from storage in terms of volume strain is nearly identical for both models and that the location of maximum production moves outward from the well as a function of time; (3) the vertical strain components are markedly different with at least 50% of the total volume of water pumped originating from horizontal strain (and increasing to as much as 70%); and (4) for the one-dimensional strain model to yield the necessary quantity of water to the pumped well, the resulting vertical compaction (land subsidence) is as much as four times greater and vertical strain is as much as 60% greater than the three-dimensional strain model. Results indicate that small changes in porosity resulting from horizontal strain can yield extremely large quantities of water to the pumping well. This study suggests that the assumption of purely vertical strain used in the definition of the storage coefficient is not valid. PMID:11341012
Revisiting the Source Process of the 2007 Tocopilla, Chile Earthquake
NASA Astrophysics Data System (ADS)
Simons, M.; Minson, S. E.; Jolivet, R.; Jiang, J.; Beck, J. L.
2013-12-01
We revisit the 2007 Mw 7.7 Tocopilla, Chile earthquake to create a finite fault kinematic source model based on the current best practices in data analysis and inversion methods. The data used to constrain the source model include both static GPS offsets and 1 Hz kinematic GPS time series, as well as interferograms which have been reanalyzed to remove tropospheric effects which can be quite significant in this region. Our inversion methodology is a Bayesian approach that uses only physics-based constraints on the rupture evolution, and which utilizes models of both the observational noise and the errors in our forward model to obtain the ensemble of all plausible rupture models which satisfy both the data and our a priori assumptions. This approach allows us to better understand which parts of the rupture process are well-constrained and which are not, and thus to better understand how the 2007 Tocopilla, Chile earthquake rupture fits into the sequence of large earthquakes which have been mosaicking the northern Chile subduction zone.
Sloan Digital Sky Survey Photometric Calibration Revisited
Marriner, John; /Fermilab
2012-06-29
The Sloan Digital Sky Survey calibration is revisited to obtain the most accurate photometric calibration. A small but significant error is found in the flat-fielding of the Photometric telescope used for calibration. Two SDSS star catalogs are compared and the average difference in magnitude as a function of right ascension and declination exhibits small systematic errors in relative calibration. The photometric transformation from the SDSS Photometric Telescope to the 2.5 m telescope is recomputed and compared to synthetic magnitudes computed from measured filter bandpasses.
Orthorhombic Zr2Co11 phase revisited
Li, X. -Z.; Zhang, W. Y.; Sellmyer, D. J.; Zhao, X.; Nguyen, M. C.; Wang, C. Z.; Ho, K. M.
2014-10-01
The structure of the orthorhombic Zr2Co11 phase was revisited in the present work. Selected-area electron diffraction (SAED) and high-resolution electron microscopy (HREM) techniques were used to investigate the structure. They show the orthorhombic Zr2Co11 phase has a 1-D incommensurate modulated structure. The structure can be approximately described as a B-centered orthorhombic lattice. The lattice parameters of the orthorhombic Zr2Co11 phase have been determined by a tilt series of SAED patterns. A hexagonal network with a modulation wave has been observed in the HREM image and the hexagonal motif is considered as the basic structural unit.
Sloan Digital Sky Survey Photometric Calibration Revisited
NASA Astrophysics Data System (ADS)
Marriner, J.
2016-05-01
The Sloan Digital Sky Survey calibration is revisited to obtain the most accurate photometric calibration. A small but significant error is found in the flat-fielding of the Photometric telescope used for calibration. Two SDSS star catalogs are compared and the average difference in magnitude as a function of right ascension and declination exhibits small systematic errors in relative calibration. The photometric transformation from the SDSS Photometric Telescope to the 2.5 m telescope is recomputed and compared to synthetic magnitudes computed from measured filter bandpasses.
Lorthois, Sylvie; Duru, Paul; Billanou, Ian; Quintard, Michel; Celsis, Pierre
2014-07-21
One the one hand, capillary permeability to water is a well-defined concept in microvascular physiology, and linearly relates the net convective or diffusive mass fluxes (by unit area) to the differences in pressure or concentration, respectively, that drive them through the vessel wall. On the other hand, the permeability coefficient is a central parameter introduced when modeling diffusible tracers transfer from blood vessels to tissue in the framework of compartmental models, in such a way that it is implicitly considered as being identical to the capillary permeability. Despite their simplifying assumptions, such models are at the basis of blood flow quantification by H2(15)O Positron Emission Tomgraphy. In the present paper, we use fluid dynamic modeling to compute the transfers of H2(15)O between the blood and brain parenchyma at capillary scale. The analysis of the so-obtained kinetic data by the Renkin-Crone model, the archetypal compartmental model, demonstrates that, in this framework, the permeability coefficient is highly dependent on both flow rate and capillary radius, contrarily to the central hypothesis of the model which states that it is a physiological constant. Thus, the permeability coefficient in Renkin-Crone׳s model is not conceptually identical to the physiologic permeability as implicitly stated in the model. If a permeability coefficient is nevertheless arbitrarily chosen in the computed range, the flow rate determined by the Renkin-Crone model can take highly inaccurate quantitative values. The reasons for this failure of compartmental approaches in the framework of brain blood flow quantification are discussed, highlighting the need for a novel approach enabling to fully exploit the wealth of information available from PET data. PMID:24637002
Ikuta, Tetsuro; Saiga, Hidetoshi
2007-12-15
Comparative studies on expression patterns of developmental genes along the anterior-posterior axis of the embryonic central nervous system (CNS) between vertebrates and ascidians led to the notion of "tripartite organization," a common ground plan of the CNS, consisting of the anterior, central and posterior regions expressing Otx, Pax2/5/8 and Hox genes, respectively. In ascidians, however, descriptions and interpretations about expression of the developmental genes regarded as region specific have become not necessarily consistent. To address this issue, we examined detailed expression of key developmental genes for the ascidian CNS, including Otx, Pax2/5/8a, En, Fgf8/17/18, Dmbx, Lhx3 and Hox genes, in the CNS around the junction of the trunk and tail of three different tailbud-stage embryos of Ciona intestinalis, employing double-fluorescence in situ hybridization, followed by staining with DAPI to precisely locate expressing cells for each gene. Based on these observations, we have constructed detailed gene expression maps of the region at the tailbud stages. Our analysis shows that expression of several genes regarded as markers for specific domains in the ascidian CNS changes dynamically within a relatively short period. This motivates us to revisit to the tripartite ground plan and the origin of the midbrain-hindbrain boundary (MHB) region. PMID:17996862
Increased 30-Day Emergency Department Revisits Among Homeless Patients with Mental Health Conditions
Lam, Chun Nok; Arora, Sanjay; Menchine, Michael
2016-01-01
Introduction Patients with mental health conditions frequently use emergency medical services. Many suffer from substance use and homelessness. If they use the emergency department (ED) as their primary source of care, potentially preventable frequent ED revisits and hospital readmissions can worsen an already crowded healthcare system. However, the magnitude to which homelessness affects health service utilization among patients with mental health conditions remains unclear in the medical community. This study assessed the impact of homelessness on 30-day ED revisits and hospital readmissions among patients presenting with mental health conditions in an urban, safety-net hospital. Methods We conducted a secondary analysis of administrative data on all adult ED visits in 2012 in an urban safety-net hospital. Patient demographics, mental health status, homelessness, insurance coverage, level of acuity, and ED disposition per ED visit were analyzed using multilevel modeling to control for multiple visits nested within patients. We performed multivariate logistic regressions to evaluate if homelessness moderated the likelihood of mental health patients’ 30-day ED revisits and hospital readmissions. Results Study included 139,414 adult ED visits from 92,307 unique patients (43.5±15.1 years, 51.3% male, 68.2% Hispanic/Latino). Nearly 8% of patients presented with mental health conditions, while 4.6% were homeless at any time during the study period. Among patients with mental health conditions, being homeless contributed to an additional 28.0% increase in likelihood (4.28 to 5.48 odds) of 30-day ED revisits and 38.2% increase in likelihood (2.04 to 2.82 odds) of hospital readmission, compared to non-homeless, non-mental health (NHNM) patients as the base category. Adjusted predicted probabilities showed that homeless patients presenting with mental health conditions have a 31.1% chance of returning to the ED within 30-day post discharge and a 3.7% chance of hospital
NLTE in a Hot Hydrogen Star: Auer & Mihalas Revisited
NASA Astrophysics Data System (ADS)
Wiersma, J.; Rutten, R. J.; Lanz, T.
2003-01-01
We pay tribute to two landmark papers published by Auer & Mihalas in 1969. They modeled hot-star NLTE-RE hydrogen-only atmospheres, using two simplified hydrogen atoms: ApJ 156, 157: H I levels 1, 2 and c, Lyman α the only line ApJ 156, 681: H I levels 1, 2, 3 and c, Balmer α the only line and computed LTE and NLTE models with the single line turned on and off. The results were extensively analyzed in the two papers. Any student of stellar line formation should take these beautiful papers to heart. The final exercise in Rutten's lecture notes ``Radiative Transfer in Stellar Atmospheres'' asks the student to work through five pages of questions concerning diagrams from the first paper alone! That exercise led to the present work in which we recompute the Auer-Mihalas hot-hydrogen-star models with TLUSTY, adding results from a complete hydrogen atom for comparison. Our motivation for this Auer-Mihalas re-visitation is twofold: 1. to add diagnostic diagrams to the ones published by Auer & Mihalas, in particular Bν, Jν, Sν graphs to illustrate the role of the radiation field, and radiative heating & cooling graphs to illustrate the radiative energy budget, 2. to see the effect of adding the rest of the hydrogen atom.
Quantization table design revisited for image/video coding.
Yang, En-Hui; Sun, Chang; Meng, Jin
2014-11-01
Quantization table design is revisited for image/video coding where soft decision quantization (SDQ) is considered. Unlike conventional approaches, where quantization table design is bundled with a specific encoding method, we assume optimal SDQ encoding and design a quantization table for the purpose of reconstruction. Under this assumption, we model transform coefficients across different frequencies as independently distributed random sources and apply the Shannon lower bound to approximate the rate distortion function of each source. We then show that a quantization table can be optimized in a way that the resulting distortion complies with certain behavior. Guided by this new design principle, we propose an efficient statistical-model-based algorithm using the Laplacian model to design quantization tables for DCT-based image coding. When applied to standard JPEG encoding, it provides more than 1.5-dB performance gain in PSNR, with almost no extra burden on complexity. Compared with the state-of-the-art JPEG quantization table optimizer, the proposed algorithm offers an average 0.5-dB gain in PSNR with computational complexity reduced by a factor of more than 2000 when SDQ is OFF, and a 0.2-dB performance gain or more with 85% of the complexity reduced when SDQ is ON. Significant compression performance improvement is also seen when the algorithm is applied to other image coding systems proposed in the literature. PMID:25248184
Supersymmetry at Finite Temperature Revisited
NASA Astrophysics Data System (ADS)
Paranjape, M. B.; Taormina, A.; Wijewardhana, L. C. R.
1983-05-01
The authors have formulated supersymmetry at finite temperature, generalizing the recent observations by Van Hove. They find that in a two-dimensional model broken supersymmetry is not restored at high temperature.
Revisiting the Cosmological Mass Function
NASA Astrophysics Data System (ADS)
Lim, Seunghwan; Lee, J.
2013-01-01
A non-stochastic scale-independent multi-dimensional barrier model of ellipsoidal collapse for the excursion set halo mass function is presented. The key concept of our model is that a bound halo forms at the moment when the initial shear eigenvalues hit a multi-dimensional absorbing barrier of constant height in their random walking process. The multi-dimensional barrier height that characterizes the analytic halo mass function is empirically determined by fitting the numerical results from the high-resolution N-body simulation to our model. It is found that the best-fit value of the barrier height is independent of redshift and key cosmological parameters. Our analytic model with empirically determined barrier-height is shown to work excellently in the wide mass-range at various redshifts: The ratio of the model to the N-body results departs from unity by up to 5% over 1011 1015M⊙/h at z=0, 0.5 and 1 for both of the FoF-halo and SO-halo cases. It is also shown that our analytic model naturally explains the stochastic behaviors of the density threshold value and its log-normal distribution.
The concept of quasi-integrability
NASA Astrophysics Data System (ADS)
Ferreira, Luiz. A.; Luchini, G.; Zakrzewski, Wojtek J.
2013-10-01
We show that certain field theory models, although non-integrable according to the usual definition of integrability, share some of the features of integrable theories for certain configurations. Here we discuss our attempt to define a "quasi-integrable theory", through a concrete example: a deformation of the (integrable) sine-Gordon potential. The techniques used to describe and define this concept are both analytical and numerical. The zero-curvature representation and the abelianisation procedure commonly used in integrable field theories are adapted to this new case and we show that they produce asymptotically conserved charges that can then be observed in the simulations of scattering of solitons.
Standing spin waves and solitons in a quasi-one-dimensional spiral structure
Kiselev, V. V. Raskovalov, A. A.
2013-02-15
On the basis of the sine-Gordon model, we calculated the absorption spectrum for the external pump power in a quasi-one-dimensional spiral structure of easy-plane magnets without the inversion center in the presence of a static magnetic field perpendicular to the magnetic spiral axis. It is shown that these data can be used for determining the material constants of the magnet and diagnostics of spin waves and solitons in its spiral structure. The possibility of using magnetooptical methods to observe local translations of the spiral structure during formation and motion of solitons in it is discussed.
NASA Astrophysics Data System (ADS)
Gudnason, Sven Bjarke; Nitta, Muneto
2014-10-01
Skyrmions can be transformed into lumps or baby Skyrmions by being trapped inside a domain wall. Here we find that they can also be transformed into sine-Gordon kinks when confined by vortices, resulting in confined Skyrmions. We show this both by an effective field theory approach and by direct numerical calculations. The existence of these trapped and confined Skyrmions does not rely on higher-derivative terms when the host solitons are flat or straight. We also construct a Skyrmion as a twisted vortex ring in a model with a sixth-order derivative term.
Silicate Glass Corrosion Mechanism revisited
NASA Astrophysics Data System (ADS)
Geisler, Thorsten; Lenting, Christoph; Dohmen, Lars
2015-04-01
Understanding the mechanism(s) of aqueous corrosion of nuclear waste borosilicate glasses is essential to predict their long-term aqueous durability in a geologic repository. Several observations have been made with compositionally different silicate glasses that cannot be explained by any of the established glass corrosion models. These models are based on diffusion-controlled ion exchange and subsequent structural reorganisation of a leached, hydrated residual glass, leaving behind a so-called gel layer. In fact, the common observation of lamellar to more complex pattern formation observed in experiment and nature, the porous structure of the corrosion layer, an atomically sharp boundary between the corrosion zone and the underlying pristine glass, as well as results of novel isotope tracer and in situ, real time experiments rather support an interface-coupled glass dissolution-silica reprecipitation model. In this model, the congruent dissolution of the glass is coupled in space and time to the precipitation and growth of amorphous silica at an inwardly moving reaction front. We suggest that these coupled processes have to be considered to realistically model the long-term performance of silicate glasses in aqueous environments.
Kaolin polytypes revisited ab initio.
Mercier, Patrick H J; Le Page, Yvon
2008-04-01
The well known 36 distinguishable transformations between adjacent kaolin layers are split into 20 energetically distinguishable transformations (EDT) and 16 enantiomorphic transformations, hereafter denoted EDT*. For infinitesimal energy contribution of interactions between non-adjacent layers, the lowest-energy models must result from either (a) repeated application of an EDT or (b) alternate application of an EDT and its EDT*. All modeling, quantum input preparation and interpretation was performed with Materials Toolkit, and quantum optimizations with VASP. Kaolinite and dickite are the lowest-energy models at zero temperature and pressure, whereas nacrite and HP-dickite are the lowest-enthalpy models under moderate pressures based on a rough enthalpy/pressure graph built from numbers given in the supplementary tables. Minor temperature dependence of this calculated 0 K graph would explain the bulk of the current observations regarding synthesis, diagenesis and transformation of kaolin minerals. Other stackings that we list have energies so competitive that they might crystallize at ambient pressure. A homometric pair of energetically distinguishable ideal models, one of them for nacrite, is exposed. The printed experimental structure of nacrite correctly corresponds to the stable member of the pair. In our opinion, all recent literature measurements of the free energy of bulk kaolinite are too negative by approximately 15 kJ mol(-1) for some unknown reason. PMID:18369284
NASA Astrophysics Data System (ADS)
Land, Kate; Magueijo, João
2007-06-01
In light of the three-year data release from the Wilkinson Microwave Anisotropy Probe, we re-examine the evidence for the `Axis of Evil' (AoE). We discover that previous statistics are not robust with respect to the data sets available and different treatments of the Galactic plane. We identify the cause of the instability and implement an alternative `model selection' approach. A comparison to Gaussian isotropic simulations finds the features significant at the 94-98 per cent level, depending on the particular AoE model. The Bayesian evidence finds lower significance, ranging from `substantial' at Δ(lnE) ~ 1.4 to no evidence for the most general AoE model.
Revisiting interaction in knowledge translation
Ginsburg, Liane R; Lewis, Steven; Zackheim, Lisa; Casebeer, Ann
2007-01-01
Background Although the study of research utilization is not new, there has been increased emphasis on the topic over the recent past. Science push models that are researcher driven and controlled and demand pull models emphasizing users/decision-maker interests have largely been abandoned in favour of more interactive models that emphasize linkages between researchers and decisionmakers. However, despite these and other theoretical and empirical advances in the area of research utilization, there remains a fundamental gap between the generation of research findings and the application of those findings in practice. Methods Using a case approach, the current study looks at the impact of one particular interaction approach to research translation used by a Canadian funding agency. Results Results suggest there may be certain conditions under which different levels of decisionmaker involvement in research will be more or less effective. Four attributes are illuminated by the current case study: stakeholder diversity, addressability/actionability of results, finality of study design and methodology, and politicization of results. Future research could test whether these or other variables can be used to specify some of the conditions under which different approaches to interaction in knowledge translation are likely to facilitate research utilization. Conclusion This work suggests that the efficacy of interaction approaches to research translation may be more limited than current theory proposes and underscores the need for more completely specified models of research utilization that can help address the slow pace of change in this area. PMID:17971208
The Medical Excuse Game Revisited
ERIC Educational Resources Information Center
Corson-Rikert, Janet; Christmas, William A.
2009-01-01
Academic policies that require medical excuses are based on mistrust of students and conflict with institutional honor codes. Such policies undermine the philosophical and educational foundations of higher education; namely, to model and nurture honesty, integrity, and citizenship in emerging adults. Instead, they encourage hypocrisy and…
Photonic dark matter portal revisited
NASA Astrophysics Data System (ADS)
Alavi, S. A.; Kazemian, F. S.
2016-05-01
In our previous paper, we studied a model of dark matter (DM) in which the hidden sector interacts with standard model particles via a hidden photonic portal (HP). We investigated the effects of this new interaction on the hydrogen atom and obtained an upper bound for the coupling of the model as f ≤ 10-12. In this work, we study the effects of HP on two interesting exotic atoms namely muonium and positronium. We obtain a tighter upper limit on the coupling as f ≤ 10-13. We also calculate the change (shift) in the Aharonov-Bohm phase due to HP and find that the phase shift is negligibly small (for DM particles mass in the GeV range). Recently a 3.5 keV X-ray line signal observed in the spectrum of 73 galaxy clusters, reported by the XXM-Newton X-ray observatory. Since in HP model the DM particles can decay directly into photons, so we finally calculate the value of the coupling constant f using the condition ΔEDM = 3.5 keV.
Changes in Sea Levels around the British Isles Revisited (Invited)
NASA Astrophysics Data System (ADS)
Teferle, F. N.; Hansen, D. N.; Bingley, R. M.; Williams, S. D.; Woodworth, P. L.; Gehrels, W. R.; Bradley, S. L.; Stocchi, P.
2009-12-01
Recently a number of new and/or updated sources for estimates of vertical land movements for the British Isles have become available allowing the relative and average changes in sea levels for this region to be revisited. The geodetic data set stems from a combination of re-processed continuous Global Positioning System (GPS) measurements from stations in the British Isles and from a global reference frame network, and absolute gravity (AG) measurements from two stations in the British Isles. The geologic data set of late Holocene sea level indicators has recently been updated, now applying corrections for the 20th century sea level rise, syphoning effect and late Holocene global ice melt, and expanded to Northern Ireland and Ireland. Several new model predictions of the glacial isostatic adjustment (GIA) process active in this region form the modelling data set of vertical land movements for the British Isles. Correcting the updated revised local reference (RLR) trends from the Permanent Service for Mean Sea Level (PSMSL) with these vertical land movement data sets, regional and averaged changes in sea levels around the British Isles have been investigated. Special focus is thereby also given to the coastal areas that have recently been identified within the UK Climate Projections 2009.
Slowly rotating homogeneous masses revisited
NASA Astrophysics Data System (ADS)
Reina, Borja
2016-02-01
Hartle's model for slowly rotating stars has been extensively used to compute equilibrium configurations of slowly rotating stars to second order in perturbation theory in general relativity, given a barotropic equation of state. A recent study based on the modern theory of perturbed matchings concludes that the functions in the (first and second order) perturbation tensors can always be taken as continuous at the surface of the star, except for the second-order function m0. This function presents a jump at the surface of the star proportional to the discontinuity of the energy density there. This concerns only a particular outcome of the model: the change in mass δM. In this paper, the amended change in mass is calculated for the case of constant density stars.
The deep planetary magnetotail revisited
NASA Technical Reports Server (NTRS)
Macek, Wieslaw M.
1989-01-01
The magnetotail model of Grzedzielski and Macek (1988) is extended to great distances in the antisolar direction. For typical solar wind parameters at 1 AU and the most probable set of parameters of the model as determined for the ISEE-3 region of 200 earth radii, R(E), the open geotail extends to at least 3000 - 4000 R(E) downstream from earth, where it forms a cavity filled with a dense hot plasma and low magnetic field strengths. The cross section of this cavity in the plane perpendicular to the earth-sun line has dimensions of 300 - 400 R(E) parallel to the ecliptic plane, but only 5 R(E) in the direction normal to the ecliptic. It seems likely that the magnetotail would become filamentary at such distances.
Silent cries, dancing tears: the metapsychology of art revisited/revised.
Aragno, Anna
2011-04-01
Against the backdrop of a broad survey of the literature on applied psychoanalysis, a number of concepts underpinning the metapsychology of art are revisited and revised: sublimation; interrelationships between primary and secondary processes; symbolization; "fantasy"; and "cathexis." Concepts embedded in dichotomous or drive/energic contexts are examined and reformulated in terms of a continuum of semiotic processes. Freudian dream structure is viewed as a biological/natural template for nonrepressive artistic forms of sublimation. The synthesis presented proposes a model of continuous rather than discontinuous processes, in a nonenergic, biosemiotic metatheoretical framework. PMID:21653915
Revisiting the Saffman-Taylor Experiment: Imbibition Patterns and Liquid-Entrainment Transitions
NASA Astrophysics Data System (ADS)
Levaché, Bertrand; Bartolo, Denis
2014-07-01
We revisit the Saffman-Taylor experiment focusing on the forced-imbibition regime where the displacing fluid wets the confining walls. We demonstrate a new class of invasion patterns that do not display the canonical fingering shapes. We evidence that these unanticipated patterns stem from the entrainment of thin liquid films from the moving meniscus. We then theoretically explain how the interplay between the fluid flow at the contact line and the interface deformations results in the destabilization of liquid interfaces. In addition, this minimal model conveys a unified framework which consistently accounts for all the liquid-entrainment scenarios that have been hitherto reported.
Long, cold, early r process? Neutrino-induced nucleosynthesis in He shells revisited.
Banerjee, Projjwal; Haxton, W C; Qian, Yong-Zhong
2011-05-20
We revisit a ν-driven r-process mechanism in the He shell of a core-collapse supernova, finding that it could succeed in early stars of metallicity Z ≲ 10⁻³ Z(⊙), at relatively low temperatures and neutron densities, producing A ~ 130 and 195 abundance peaks over ~10-20 s. The mechanism is sensitive to the ν emission model and to ν oscillations. We discuss the implications of an r process that could alter interpretations of abundance data from metal-poor stars, and point out the need for further calculations that include effects of the supernova shock. PMID:21668217
Wang Shuang; Li Xiaodong; Li Miao
2010-11-15
We investigate the cosmic age problem associated with 9 extremely old globular clusters in M31 galaxy and 1 very old high-z quasar automatic plate-measuring machine 08279+5255 at z=3.91. These 9 globular clusters have not been used to study the cosmic age problem in the previous literature. By evaluating the age of the Universe in the {Lambda} cold dark matter model with the observational constraints from the Type Ia supernovae, the baryon acoustic oscillations, the cosmic microwave background, and the independent H{sub 0} measurements, we find that the existence of 5 globular clusters and 1 high-z quasar are in tension (over 2{sigma} confidence level) with the current cosmological observations. So if the age estimates of these objects are correct, the cosmic age puzzle still remains in the standard cosmology. Moreover, we extend our investigations to the cases of the interacting dark energy models. It is found that although the introduction of the interaction between dark sectors can give a larger cosmic age, the interacting dark energy models still have difficulty to pass the cosmic age test.
Influenza A virus recycling revisited.
Dowdle, W. R.
1999-01-01
Current textbooks link influenza pandemics to influenza A virus subtypes H2 (1889-91), H3 (1990), H1 (1918-20), H2 (1957-58) and H3 (1968), a pattern suggesting subtype recycling in humans. Since H1 reappeared in 1977, whatever its origin, some workers feel that H2 is the next pandemic candidate. This report reviews the publications on which the concept of influenza A virus subtype recycling is based and concludes that the data are inconsistent with the purported sequence of events. The three influenza pandemics prior to 1957-58 were linked with subtypes through retrospective studies of sera from the elderly, or through seroarchaeology. The pandemic seroarchaeological model for subtype H1 has been validated by the recent recovery of swine virus RNA fragments from persons who died from influenza in 1918. Application of the model to pre-existing H3 antibody among the elderly links the H3 subtype to the pandemic of 1889-91, not that of 1900 as popularly quoted. Application of the model to pre-existing H2 antibody among the elderly fails to confirm that this subtype caused a pandemic in the late 1800's, a finding which is consistent with age-related excess mortality patterns during the pandemics of 1957 (H2) and 1968 (H3). H2 variants should be included in pandemic planning for a number of reasons, but not because of evidence of recycling. It is not known when the next pandemic will occur or which of the 15 (or more) haemagglutinin subtypes will be involved. Effective global surveillance remains the key to influenza preparedness. PMID:10593030
Revisits within 48 Hours to a Thai Emergency Department
Nithimathachoke, Adisak; Tirrell, Gregory Philip; Surawongwattana, Sataporn; Liu, Shan Woo
2016-01-01
Objective. Emergency department (ED) revisits are a common ED quality measure. This study was undertaken to ascertain the contributing factors of revisits within 48 hours to a Thai ED and to explore physician-related, illness-related, and patient-related factors behind those revisits. Methods. This study was a chart review from one tertiary care, urban Thai hospital from October 1, 2009, to September 31, 2010. We identified patients who returned to the ED within 48 hours for the same or related complaints after their initial discharge. Three physicians classified revisit as physician-related, illness-related, and patient-related factors. Results. Our study included 172 ED patients' charts. 86/172 (50%) were male and the mean age was 38 ± 5.6 (SD) years. The ED revisits contributing factors were physician-related factors [86/172 (50.0%)], illness-related factors [61/172 (35.5%)], and patient-related factor [25/172 (14.5%)], respectively. Among revisits classified as physician-related factors, 40/86 (46.5%) revisits were due to misdiagnosis and 36/86 (41.9%) were due to suboptimal management. Abdominal pain [27/86 (31.4%)] was the majority of physician-related chief complaints, followed by fever [16/86 (18.6%)] and dyspnea [15/86 (17.4%)]. Conclusion. Misdiagnosis and suboptimal management contributed to half of the 48-hour repeat ED visits in this Thai hospital. PMID:27478642
Risk Prediction of Emergency Department Revisit 30 Days Post Discharge: A Prospective Study
Hao, Shiying; Jin, Bo; Shin, Andrew Young; Zhao, Yifan; Zhu, Chunqing; Li, Zhen; Hu, Zhongkai; Fu, Changlin; Ji, Jun; Wang, Yong; Zhao, Yingzhen; Dai, Dorothy; Culver, Devore S.; Alfreds, Shaun T.; Rogow, Todd; Stearns, Frank; Sylvester, Karl G.; Widen, Eric; Ling, Xuefeng B.
2014-01-01
Background Among patients who are discharged from the Emergency Department (ED), about 3% return within 30 days. Revisits can be related to the nature of the disease, medical errors, and/or inadequate diagnoses and treatment during their initial ED visit. Identification of high-risk patient population can help device new strategies for improved ED care with reduced ED utilization. Methods and Findings A decision tree based model with discriminant Electronic Medical Record (EMR) features was developed and validated, estimating patient ED 30 day revisit risk. A retrospective cohort of 293,461 ED encounters from HealthInfoNet (HIN), Maine's Health Information Exchange (HIE), between January 1, 2012 and December 31, 2012, was assembled with the associated patients' demographic information and one-year clinical histories before the discharge date as the inputs. To validate, a prospective cohort of 193,886 encounters between January 1, 2013 and June 30, 2013 was constructed. The c-statistics for the retrospective and prospective predictions were 0.710 and 0.704 respectively. Clinical resource utilization, including ED use, was analyzed as a function of the ED risk score. Cluster analysis of high-risk patients identified discrete sub-populations with distinctive demographic, clinical and resource utilization patterns. Conclusions Our ED 30-day revisit model was prospectively validated on the Maine State HIN secure statewide data system. Future integration of our ED predictive analytics into the ED care work flow may lead to increased opportunities for targeted care intervention to reduce ED resource burden and overall healthcare expense, and improve outcomes. PMID:25393305
Revisiting the Simplified Bernoulli Equation
Heys, Jeffrey J; Holyoak, Nicole; Calleja, Anna M; Belohlavek, Marek; Chaliki, Hari P
2010-01-01
Background: The assessment of the severity of aortic valve stenosis is done by either invasive catheterization or non-invasive Doppler Echocardiography in conjunction with the simplified Bernoulli equation. The catheter measurement is generally considered more accurate, but the procedure is also more likely to have dangerous complications. Objective: The focus here is on examining computational fluid dynamics as an alternative method for analyzing the echo data and determining whether it can provide results similar to the catheter measurement. Methods: An in vitro heart model with a rigid orifice is used as a first step in comparing echocardiographic data, which uses the simplified Bernoulli equation, catheterization, and echocardiographic data, which uses computational fluid dynamics (i.e., the Navier-Stokes equations). Results: For a 0.93cm2 orifice, the maximum pressure gradient predicted by either the simplified Bernoulli equation or computational fluid dynamics was not significantly different from the experimental catheter measurement (p > 0.01). For a smaller 0.52cm2 orifice, there was a small but significant difference (p < 0.01) between the simplified Bernoulli equation and the computational fluid dynamics simulation, with the computational fluid dynamics simulation giving better agreement with experimental data for some turbulence models. Conclusion: For this simplified, in vitro system, the use of computational fluid dynamics provides an improvement over the simplified Bernoulli equation with the biggest improvement being seen at higher valvular stenosis levels. PMID:21625471
The Foundations of Diffusion Revisited
van Milligen, B. Ph.; Carreras, Benjamin A; Sanchez, Raul
2005-12-01
Diffusion is essentially the macroscopic manifestation of random (Brownian) microscopic motion. This idea has been generalized in the continuous time random walk formalism, which under quite general conditions leads to a generalized master equation (GME) that provides a useful modelling framework for transport. Here we review some of the basic ideas underlying this formalism from the perspective of transport in (magnetic confinement) plasmas. Under some specific conditions, the fluid limit of the GME corresponds to the Fokker-Planck (FP) diffusion equation in inhomogeneous systems, which reduces to Fick's law when the system is homogeneous. It is suggested that the FP equation may be preferable in fusion plasmas due to the inhomogeneity of the system, which would imply that part of the observed inward convection ('pinch') can be ascribed to this inhomogeneity. The GME also permits a mathematically sound approach to more complex transport issues, such as the incorporation of critical gradients and non-local transport mechanisms. A toy model incorporating these ingredients was shown to possess behaviour that bears a striking similarity to certain unusual phenomena observed in fusion plasmas.
Seasonal dating of Sappho's 'Midnight Poem' revisited
NASA Astrophysics Data System (ADS)
Cuntz, Manfred; Gurdemir, Levent; George, Martin
2016-04-01
Sappho was a Greek lyric poet who composed a significant array of pristine poetry. Although much of it has been lost, her reputation has endured thanks to numerous surviving fragments. One of her contributions includes the so-called 'Midnight Poem', which contains a line about the Pleiades, setting sometime before midnight, and supposedly observed from the island of Lesbos. This poem also refers to the setting of the Moon. Sappho's Midnight Poem thus represents a prime example of where ancient poetry and astronomy merge, and it also offers the possibility of seasonal dating. Previously, Herschberg and Mebius (1990) estimated that the poem was composed in late winter/early spring, a time frame that is not unusual for lyrics of an amorous nature. The aim of our paper is to revisit this earlier finding by using modern-day software. Our study confirms Herschberg and Mebius' result, but also conveys further information.
Linear stability of a vortex ring revisited
NASA Astrophysics Data System (ADS)
Fukumoto, Yasuhide; Hattori, Yuji
We revisit the stability of an elliptically strained vortex and a thin axisymmetric vortex ring, embedded in an inviscid incompressible fluid, to three-dimensional disturbances of infinitesimal amplitude. The results of Tsai & Widnall (1976) for an elliptically strained vortex are simplified by providing an explicit expression for the disturbance flow field. A direct relation is established with the elliptical instability. For Kelvin's vortex ring, the primary perturbation to the Rankine vortex is a dipole field. We show that the dipole field causes a parametric resonance instability between axisymmetric and bending waves at intersection points of the dispersion curves. It is found that the dipole effect predominates over the straining effect for a very thin core. The mechanism is attributable to stretching of the disturbance vortex lines in the toroidal direction.
The Doppler spread theory and parameterization revisited
NASA Astrophysics Data System (ADS)
Hines, Colin O.
2004-07-01
The author's earlier Doppler Spread Theory (DST) and Doppler Spread Parameterization (DSP) are revisited with a new understanding of the dichotomous roles played by nonlinearity in Eulerian and Lagrangian coordinates, respectively. An embryo Lagrangian DST is introduced and employed to assess the original DST. Earlier results near the Eulerian spectral peak are found to be reasonably valid, whereas those at greater vertical wavenumber are confirmed to have produced too much spreading. The earlier DSP is found to need little if any change, though specific values are suggested for its two most important ``fudge factors''. In a more general context, the continuing identity of a wave undergoing certain nonlinear interactions with other waves is discussed.
The Species Problem in Myxomycetes Revisited.
Walker, Laura M; Stephenson, Steven L
2016-08-01
Species identification in the myxomycetes (plasmodial slime molds or myxogastrids) poses particular challenges to researchers as a result of their morphological plasticity and frequent alteration between sexual and asexual life strategies. Traditionally, myxomycete morphology has been used as the primary method of species delimitation. However, with the increasing availability of genetic information, traditional myxomycete taxonomy is being increasingly challenged, and new hypotheses continue to emerge. Due to conflicts that sometimes occur between traditional and more modern species concepts that are based largely on molecular data, there is a pressing need to revisit the discussion surrounding the species concept used for myxomycetes. Biological diversity is being increasingly studied with molecular methods and data accumulates at ever-faster rates, making resolution of this matter urgent. In this review, currently used and potentially useful species concepts (biological, morphological, phylogenetic and ecological) are reviewed, and an integrated approach to resolve the myxomycete species problem is discussed. PMID:27351595
Visser's massive graviton bimetric theory revisited
Roany, Alain de; Chauvineau, Bertrand; Freitas Pacheco, Jose A. de
2011-10-15
A massive gravity theory was proposed by Visser in the late 1990s. This theory, based on a background metric b{sub {alpha}{beta}} and on an usual dynamical metric g{sub {alpha}{beta}} has the advantage of being free of ghosts as well as discontinuities present in other massive theories proposed in the past. In the present investigation, the equations of Visser's theory are revisited with particular care on the related conservation laws. It will be shown that a multiplicative factor is missing in the graviton tensor originally derived by Visser, which has no incidence on the weak field approach but becomes important in the strong field regime when, for instance, cosmological applications are considered. In this case, contrary to some previous claims found in the literature, we conclude that a nonstatic background metric is required in order to obtain a solution able to mimic the {Lambda}CDM cosmology.
Biofluiddynamics of balistiform and gymnotiform locomotion: Revisited
NASA Astrophysics Data System (ADS)
Sprinkle, Brennan; Bale, Rahul; Singh, Amneet; Chen, Nelson; Maciver, Malcom; Patankar, Neelesh
2015-11-01
Gymnotiform and balistiform swimmers are those which have an undulatory fin affixed to a rigid body unlike anguilliforms who undulate their entire body. Is there a mechanical advantage to gymnotiform and balistiform swimming? This question was investigated by Lighthill & Blake in a four paper series Biofluiddynamics of balistiform and gymnotiform locomotion. We revisit this work using fully resolved numerical simulations of the types of swimmers considered by Lighthill & Blake to interrogate the issue of mechanical advantage for rigid body swimmers. In doing so, we find that while there is advantage to rigid body swimming, the mechanism of `momentum enhancement,' proposed by Lighthill and Blake, is not the cause. Further, we use our results and simulations to explain why some gymnotiform and balistiform swimmers have their propulsor attached to their bodies at an angle. This work was supported in part by NSF grants CBET-0828749, CMMI-0941674 and CBET-1066575. Computational resources were provided by Northwestern University High Performance Computing System-Quest.
Gilead revisited: faith and recovery.
Bussema, Evelyn F; Bussema, Kenneth E
2007-01-01
The role of spirituality in recovery from mental illness has gained increased attention in recent years. In this article, the authors present an update on previous work exploring the role and function of religion/spirituality in the lives of people participating in a psychiatric rehabilitation program (Bussema & Bussema, 2000). Fifty-eight (58) participants age 18 to 64 completed a spirituality survey based on Pargament's five coping functions of religion. Chi-square tests for independence and independent groups t-tests were performed. Seventy-one percent of the respondents reported that their spiritual life has played a significant role in their recovery. Reported religious coping strategies are discussed within the framework of a recovery model of service delivery. PMID:17458454
Regulatory T cells: stability revisited
Bailey-Bucktrout, Samantha L.; Bluestone, Jeffrey A.
2011-01-01
Breakdown in self-tolerance is due, in part, to a loss of regulatory T (Treg) cells. Recently, a controversy has surfaced about whether Treg cells are overwhelmingly stable, or if they can be reprogrammed in inflammatory and autoimmune environments. Those in the instability “camp” have shown that a fraction of Treg cells lose Foxp3 and acquire effector arm activities. Instability is coupled with IL-2 insufficiency and the inflammatory milieu that promote reprogramming. Here, we highlight the basic tenets of each viewpoint and discuss technical, biological and environmental differences in the models that may help yield a unifying hypothesis. Also considered is how Treg cell instability could link to development of autoimmune disease and the implications for Treg cell-based cellular therapy trials. PMID:21620768
Baruch Plan revisited. Master's thesis
Johnson, R.M.
1993-09-15
The primary concern in world politics is the proliferation of nuclear weapons. With the end of the Cold War, and dramatic democratic changes in Eastern Europe, many experts believe that international control of nuclear weapons is possible. This thesis examines the Baruch Plan as a model for international control of nuclear weapons. In doing so, this thesis outlines the original plan and details the initial criticism. The International Atomic Energy Agency is examined for its capability in the areas of inspections and verification. The enforcement capability of the United Nations is also discussed. This thesis concludes that the political climate is favorable for such dramatic changes however, the organizations which would be responsible for the maintenance of the system, namely the IAEA and the United Nations are not yet ready to assume their role.
The rhizosphere revisited: root microbiomics
Bakker, Peter A. H. M.; Berendsen, Roeland L.; Doornbos, Rogier F.; Wintermans, Paul C. A.; Pieterse, Corné M. J.
2013-01-01
The rhizosphere was defined over 100 years ago as the zone around the root where microorganisms and processes important for plant growth and health are located. Recent studies show that the diversity of microorganisms associated with the root system is enormous. This rhizosphere microbiome extends the functional repertoire of the plant beyond imagination. The rhizosphere microbiome of Arabidopsis thaliana is currently being studied for the obvious reason that it allows the use of the extensive toolbox that comes with this model plant. Deciphering plant traits that drive selection and activities of the microbiome is now a major challenge in which Arabidopsis will undoubtedly be a major research object. Here we review recent microbiome studies and discuss future research directions and applicability of the generated knowledge. PMID:23755059
Budded baculovirus particle structure revisited.
Wang, Qiushi; Bosch, Berend-Jan; Vlak, Just M; van Oers, Monique M; Rottier, Peter J; van Lent, Jan W M
2016-02-01
Baculoviruses are a group of enveloped, double-stranded DNA insect viruses with budded (BV) and occlusion-derived (ODV) virions produced during their infection cycle. BVs are commonly described as rod shaped particles with a high apical density of protein extensions (spikes) on the lipid envelope surface. However, due to the fragility of BVs the conventional purification and electron microscopy (EM) staining methods considerably distort the native viral structure. Here, we use cryo-EM analysis to reveal the near-native morphology of two intensively studied baculoviruses, Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) and Spodoptera exigua MNPV (SeMNPV), as models for BVs carrying GP64 and F as envelope fusion protein on the surface. The now well-preserved AcMNPV and SeMNPV BV particles have a remarkable elongated, ovoid shape leaving a large, lateral space between nucleocapsid (NC) and envelope. Consistent with previous findings the NC has a distinctive cap and base structure interacting tightly with the envelope. This tight interaction may explain the partial retaining of the envelope on both ends of the NC and the disappearance of the remainder of the BV envelope in the negative-staining EM images. Cryo-EM also reveals that the viral envelope contains two layers with a total thickness of ≈ 6-7 nm, which is significantly thicker than a usual biological membrane (<4 nm) as measured by X-ray scanning. Most spikes are densely clustered at the two apical ends of the virion although some envelope proteins are also found more sparsely on the lateral regions. The spikes on the surface of AcMNPV BVs appear distinctly different from those of SeMNPV. Based on our observations we propose a new near-native structural model of baculovirus BVs. PMID:26743500
Norton, Larry
2014-01-01
At the root of science lie basic rules, if we can discover or deduce them. This is not an abstract project but practical; if we can understand the why then perhaps we can rationally intervene. One of the unifying unsolved problems in physics is the hypothetical "Theory of Everything." In a similar vein, we can ask whether our own field contains such hidden fundamental truths and, if so, how we can use them to develop better therapies and outcomes for our patients. Modern oncology has developed as drugs and translational science have matured over the 50 years since ASCO's founding, but almost from that beginning tumor modeling has been a key tool. Through this general approach Norton and Simon changed our understanding of cancer biology and response to therapy when they described the fit of Gompertzian curves to both clinical and animal observations of tumor growth. The practical relevance of these insights has only grown with the development of DNA sequencing promising a raft of new targets (and drugs). In that regard, Larry Norton's contribution to this year's Educational Book reminds us to always think creatively about the fundamental problems of tumor growth and metastases as well as therapeutic response. Demonstrating the creativity and thoughtfulness that have marked his remarkable career, he now incorporates a newer concept of self-seeding to further explain why Gompertzian growth occurs and, in the process, provides a novel potential therapeutic target. As you read his elegantly presented discussion, consider how this understanding, wisely applied to the modern era of targeted therapies, might speed the availability of better treatments. But even more instructive is his personal model-not only the Norton-Simon Hypothesis-of how to live and approach science, biology, patients and their families, as well as the broader community. He shows that with energy, enthusiasm, optimism, intellect, and hard work we can make the world better. Clifford A. Hudis, MD, FACP
Groundwater and river water interaction on Cikapundung River: Revisited
NASA Astrophysics Data System (ADS)
Darul, A.; Irawan, D. E.; Trilaksono, N. J.
2015-09-01
The interaction between groundwater and Cikapundung river water has not changed significantly in 16 years of period. This paper revisit the similar research based on 43 measurement points: 13 dug wells, 2 springs, and 24 river, distributed along the riverbank at Curug Dago to Batununggal segment. The field measurements were taken in rainy season of April to May 2014 using portable instruments. Six parameters were measured: water level, temperature, total dissolved solids (TDS), dissolved-oxygen (DO), and pH. The new model is unable to detect significant change in water flow, however it finds two local anomalies in Dago Pojok and Cikapayang area. Both locations show local drawdown circle which can induce influent stream in overal effluent environment. Moreover, water quality parameters indicate mixing processes between groundwater and river water, with erratic pattern both in effluent and influent stream. Also some DO and TDS readings exceed the permissible limit. These values suggest a lifted groundwater mineralization from organic and non-organic sources and change of chemical stability. The source of contamination is still under further examination.
Psychological Well-Being Revisited: Advances in Science and Practice
Ryff, Carol D.
2014-01-01
This article reviews the research and interventions that have grown up around a model of psychological well-being (Ryff, 1989) generated more than two decades ago to address neglected aspects of positive functioning, such as purposeful engagement in life, realization of personal talents and capacities, and enlightened self-knowledge. The conceptual origins of this formulation are revisited and scientific products emerging from six thematic areas are examined: (1) how well-being changes across adult development and later life, (2) what are the personality correlates of well-being, (3) how well-being is linked with experiences in family life, (4) how well-being relates to work and other community activities, (5) what are the connections between well-being and health, including biological risk factors, (6) and via clinical and intervention studies, how psychological well-being can be promoted for ever greater segments of society. Together, these topics illustrate flourishing interest across diverse scientific disciplines in understanding adults as striving, meaning-making, proactive organisms who are actively negotiating the challenges of life. A take-home message is that increasing evidence supports the health protective features of psychological well-being in reducing risk for disease and promoting length of life. A recurrent and increasingly important theme is resilience – the capacity to maintain or regain well-being in the face of adversity. Implications for future research and practice are considered. PMID:24281296
Fever tree revisited: From malaria to autoinflammatory diseases.
Pastore, Serena; Vuch, Josef; Bianco, Anna Monica; Taddio, Andrea; Tommasini, Alberto
2015-11-01
Over the centuries the idea of recurrent fevers has mainly been associated with malaria, but many other fevers, such as typhoid and diphtheria were cause for concern. It is only in recent times, with the more severe forms of fever from infectious origin becoming less frequent or a cause for worry that we started noticing recurrent fevers without any clear infectious cause, being described as having a pathogenesis of autoinflammatory nature. The use of molecular examinations in many cases can allow a diagnosis where the cause is monogenic. In other cases, however the pathogenesis is likely to be multifactorial and the diagnostic-therapeutic approach is strictly clinical. The old fever tree paradigm developed to describe fevers caused by malaria has been revisited here to describe today's periodic fevers from the periodic fever adenitis pharyngitis aphthae syndrome to the more rare autoinflammatory diseases. This model may allow us to place cases that are yet to be identified which are likely to be of multifactorial origin. PMID:26566482
Fever tree revisited: From malaria to autoinflammatory diseases
Pastore, Serena; Vuch, Josef; Bianco, Anna Monica; Taddio, Andrea; Tommasini, Alberto
2015-01-01
Over the centuries the idea of recurrent fevers has mainly been associated with malaria, but many other fevers, such as typhoid and diphtheria were cause for concern. It is only in recent times, with the more severe forms of fever from infectious origin becoming less frequent or a cause for worry that we started noticing recurrent fevers without any clear infectious cause, being described as having a pathogenesis of autoinflammatory nature. The use of molecular examinations in many cases can allow a diagnosis where the cause is monogenic. In other cases, however the pathogenesis is likely to be multifactorial and the diagnostic-therapeutic approach is strictly clinical. The old fever tree paradigm developed to describe fevers caused by malaria has been revisited here to describe today’s periodic fevers from the periodic fever adenitis pharyngitis aphthae syndrome to the more rare autoinflammatory diseases. This model may allow us to place cases that are yet to be identified which are likely to be of multifactorial origin. PMID:26566482
The Sinai triple junction revisited
NASA Astrophysics Data System (ADS)
Courtillot, Vincent; Armijo, Rolando; Tapponnier, Paul
1987-09-01
This paper is a summary of a more detailed analysis of the kinematics of the Sinai triple junction (Courtillot et al., 1987). Accurate kinematic data are lacking along the Red Sea and they can be supplemented by bathymetric, topographic and geological data pertaining to the three arms of the entirely continental Sinai triple junction. Motions across the northern Red Sea and along the Gulf of Elat are an order of magnitude larger than across the Gulf of Suez. The direction of motion there remains a major uncertainty. A possible kinematic model is highlighted, in which right-lateral strike-slip motion and small pull-apart basins occur along the Gulf of Suez, in agreement with recent field observations in Egypt. Early Miocene is marked by major geodynamical changes all along the northern boundaries of the African and Indian plates. We suggest that rifting in the Arabian Sea, Gulf of Aden, Red Sea and Gulf of Suez was initiated at the end of the first phase of continental extrusion of Indochina, when the Tibetan plateau began to rise and spreading in the South China Sea came to a halt.
Software package SIMPRE--revisited.
Karbowiak, Mirosław; Rudowicz, Czesław
2014-10-01
This article elucidates the pitfalls identified in the software package SIMPRE recently developed by Baldoví et al. (J. Comput. Chem. 2013, 34, 1961) for modeling the spectroscopic and magnetic properties of single ion magnets as well as single-molecule magnets. Analysis of the methodology used therein reveals that the crystal field parameters (CFPs), expressed nominally in the Stevens formalism, exhibit features characteristic for the CFPs expressed in the Wybourne notation. The resemblance of the two types of CFPs introduces a serious confusion that may lead to wrong comparisons of the CFPs taken from various sources. To clarify this confusion, the properties of the CFPs Bkq ( Akq, Ckq) associated with the Stevens operators Okq(X = S, J, or L), which belong to the class of the tesseral-tensor operators, are contrasted with those of the CFPs Bkq associated with the Wybourne operators Cq(k), which belong to the class of the spherical-tensor operators. Importantly, the confused properties of Stevens and Wybourne operators may bear on reliability of SIMPRE calculations. To consider this question independent calculations are carried out using the complete approach and compared with those of the restricted approach utilized earlier. It appears that the numerical results of the package SIMPRE are formally acceptable, however, the meaning of the CFPs must be properly reformulated. Several other conceptual problems arising from misinterpretations of the crucial notions and the CFP notations identified therein are also discussed and clarified. PMID:25082729
The Holstein polaron problem revisited
NASA Astrophysics Data System (ADS)
Tayebi, Amin; Zelevinsky, Vladimir
2016-06-01
The Holstein Hamiltonian was proposed half a century ago; since then, decades of research have come up empty handed in the pursuit of a closed-form solution. An exact solution to the two-site Holstein model is presented in this paper. The obtained results provide a clear image of the Hamiltonian structure and allow for the investigation of the symmetry, energy level crossings and polaronic characteristics of the system. The main mathematical tool is a three-term recurrence relation between the wave function amplitudes, which was obtained using the properties of a family of orthogonal functions, namely the Poisson–Charlier polynomials. It is shown that, with the appropriate choice of basis, the eigenfunctions of the problem naturally fall into two families (parities) associated with the discrete {{{Z}}}2 symmetry of the Hamiltonian. The asymptotic solution to the recurrence relation is found by using the Birkhoff expansion. The asymptotic sets the truncation criterion for the wave function, which ensures the accurate calculation of the energy levels for any strength of electron–phonon interaction. The level crossing of states with different parities is discussed and the exact points of broken symmetry are found analytically. The results are used as the building blocks for studying a four-site system. The inherited symmetries lead to the formation of a sparse matrix that is convenient for numerical calculations.
Deuterated polycyclic aromatic hydrocarbons: Revisited
NASA Astrophysics Data System (ADS)
Doney, K. D.; Candian, A.; Mori, T.; Onaka, T.; Tielens, A. G. G. M.
2016-02-01
Aims: The amount of deuterium locked up in polycyclic aromatic hydrocarbons (PAHs) has to date been an uncertain value. We present a near-infrared (NIR) spectroscopic survey of Hii regions in the Milky Way, Large Magellanic Cloud, and Small Magellanic Cloud obtained with AKARI, which aims to search for features indicative of deuterated PAHs (PAD or Dn-PAH) to better constrain the D/H ratio of PAHs. Methods: Fifty-three Hii regions were observed in the NIR (2.5-5 μm), using the Infrared Camera (IRC) on board the AKARI satellite. Through comparison of the observed spectra with a theoretical model of deuterated PAH vibrational modes, the aromatic and (a)symmetric aliphatic C-D stretch modes were identified. Results: We see emission features between 4.4-4.8 μm, which could be unambiguously attributed to deuterated PAHs in only six of the observed sources, all of which are located in the Milky Way. In all cases, the aromatic C-D stretching feature is weaker than the aliphatic C-D stretching feature, and, in the case of M17b, this feature is not observed at all. Based on the weak or absent PAD features in most of the observed spectra, it is suggested that the mechanism for PAH deuteration in the ISM is uncommon.
Mantle plumes on Venus revisited
NASA Technical Reports Server (NTRS)
Kiefer, Walter S.
1992-01-01
The Equatorial Highlands of Venus consist of a series of quasicircular regions of high topography, rising up to about 5 km above the mean planetary radius. These highlands are strongly correlated with positive geoid anomalies, with a peak amplitude of 120 m at Atla Regio. Shield volcanism is observed at Beta, Eistla, Bell, and Atla Regiones and in the Hathor Mons-Innini Mons-Ushas Mons region of the southern hemisphere. Volcanos have also been mapped in Phoebe Regio and flood volcanism is observed in Ovda and Thetis Regiones. Extensional tectonism is also observed in Ovda and Thetis Regiones. Extensional tectonism is also observed in many of these regions. It is now widely accepted that at least Beta, Atla, Eistla, and Bell Regiones are the surface expressions of hot, rising mantel plumes. Upwelling plumes are consistent with both the volcanism and the extensional tectonism observed in these regions. The geoid anomalies and topography of these four regions show considerable variation. Peak geoid anomalies exceed 90 m at Beta and Atla, but are only 40 m at Eistla and 24 m at Bell. Similarly, the peak topography is greater at Beta and Atla than at Eistla and Bell. Such a range of values is not surprising because terrestrial hotspot swells also have a side range of geoid anomalies and topographic uplifts. Kiefer and Hager used cylindrical axisymmetric, steady-state convection calculations to show that mantle plumes can quantitatively account for both the amplitude and the shape of the long-wavelength geoid and topography at Beta and Atla. In these models, most of the topography of these highlands is due to uplift by the vertical normal stress associated with the rising plume. Additional topography may also be present due to crustal thickening by volcanism and crustal thinning by rifting. Smrekar and Phillips have also considered the geoid and topography of plumes on Venus, but they restricted themselves to considering only the geoid-topography ratio and did not
Zircon Saturation Re-Revisited
NASA Astrophysics Data System (ADS)
Boehnke, P.; Trail, D.; Schmitt, A. K.; Watson, E. B.; Harrison, M.
2011-12-01
Zircon saturation in silicate melts has been utilized for magma thermometry and predicting the survival of zircon xenocrysts in crustal melts for nearly 30 years. The original calibration, which assumed only compositional (M = [2Ca+Na+K]/[AlxSi]) and temperature controls, was bolstered by subsequent experimental investigations and thermometry of volcanic rocks and glasses. These latter studies, while confirming the general predictions of the model, suggested that other environmental parameters (e.g., pressure, H 2O, halogens, [Fe], oxygen fugacity, etc.) might have second-order effects. Given the tremendous advances in micro-analytical capabilities over the intervening three decades, we have returned to this question with a view to obtaining a refined zircon solubility calibration as a function of P, T, [H2O] and FM (= [Na+K+2(Ca+Mg+Fe)]/[AlxSi]). Detailed SEM imaging of the original low-temperature crystallization experiments (1.2-2.1 kbar) revealed limitations of this approach and we chose instead to use a new experimental design in which shattered Mud Tank zircon is infiltrated by melts of selected composition and water contents. 10 kbar hydrothermal experiments (925o and 850oC) were run for sufficiently long durations (2 to 3 days) to ensure microscale diffusive equilibration of Zr released by zircon dissolution into the intercrystalline melt pools. Sectioned run products were analyzed by SIMS ion imaging of selected areas where glass is exposed in close proximity to or surrounded by Mud Tank zircon fragments. Ion imaging has the advantage of permitting high spatial resolution (3 μm) analysis of the glasses allowing assessment of Zr equilibration. Using synthetic glass standards, we found [Zr] in anhydrous glasses to be enhanced by ca. 20% relative to hydrous (at 6 wt.% H2O). Our new experiments and re-analysis of the earlier glasses broadly reproduce the original calibration, albeit with substantially enhanced (factor of five) precision compared to the
Dynamics of dolphin porpoising revisited.
Weihs, D
2002-11-01
Porpoising is the popular name for the high-speed surface piercing motion of dolphins and other species, in which long, ballistic jumps are alternated with sections of swimming close to the surface. The first analysis of this behavior (Au and Weihs, 1980) showed that above a certain "crossover" speed this behavior is energetically advantageous, as the reduction in drag due to movement in the air becomes greater than the added cost of leaping.Since that publication several studies documented porpoising behavior at high speeds. The observations indicated that the behavior was more complex than previously assumed. The leaps were interspersed with relatively long swimming bouts, of about twice the leap length. In the present paper, the possibility of dolphins using a combination of leaping and burst and coast swimming is examined. A three-phase model is proposed, in which the dolphin leaps out of the water at a speed U(f), which is the final speed obtained at the end of the burst phase of burst and coast swimming. The leap is at constant speed and so the animal returns to the water at U(f), goes to a shallow depth and starts horizontal coasting while losing speed, till it reaches U(i). At that point it starts active swimming, accelerating to U(f). It then starts the next leap. Ranges of speeds for which this three-stage swimming is advantageous are calculated as a function of animal and physical parameters.NotationC-Constant defined in equation (12)C(D)-Coasting drag coefficientD-Dragg-Gravitational accelerationH-Height of jumpJ-Energy required for jumpk-Ratio of swim length to jump lengthl-DistanceL-Total distance (eq. 28)m-Added massM-Animal massM(1)-Total massr-Coefficient defined in eq. (22)R-Ratio of energies, for three-phase swimmingR(2)-Ratio of energies, for burst and coast swimmingt-TimeT-ThrustU-SpeedV-Body volumeW-Weightα-Emergence (=return) angleβ-Swim / coast drag penalty ratioγ-Surface effects drag ratioρ-Density of seawater and cetacean