Critical dynamics of the Potts model: short-time Monte Carlo simulations

International Nuclear Information System (INIS)

Silva, Roberto da; Drugowich de Felicio, J.R.

2004-01-01

We calculate the new dynamic exponent θ of the 4-state Potts model, using short-time simulations. Our estimates θ1=-0.0471(33) and θ2=-0.0429(11) obtained by following the behavior of the magnetization or measuring the evolution of the time correlation function of the magnetization corroborate the conjecture by Okano et al. [Nucl. Phys. B 485 (1997) 727]. In addition, these values agree with previous estimate of the same dynamic exponent for the two-dimensional Ising model with three-spin interactions in one direction, that is known to belong to the same universality class as the 4-state Potts model. The anomalous dimension of initial magnetization x0=zθ+β/ν is calculated by an alternative way that mixes two different initial conditions. We have also estimated the values of the static exponents β and ν. They are in complete agreement with the pertinent results of the literature

Random matrix theory and higher genus integrability: the quantum chiral Potts model

International Nuclear Information System (INIS)

Angles d'Auriac, J.Ch.; Maillard, J.M.; Viallet, C.M.

2002-01-01

We perform a random matrix theory (RMT) analysis of the quantum four-state chiral Potts chain for different sizes of the chain up to size L 8. Our analysis gives clear evidence of a Gaussian orthogonal ensemble (GOE) statistics, suggesting the existence of a generalized time-reversal invariance. Furthermore, a change from the (generic) GOE distribution to a Poisson distribution occurs when the integrability conditions are met. The chiral Potts model is known to correspond to a (star-triangle) integrability associated with curves of genus higher than zero or one. Therefore, the RMT analysis can also be seen as a detector of 'higher genus integrability'. (author)

Computerized tomography in atypical Pott's disease

International Nuclear Information System (INIS)

Cabrera, M.N.B.; Wang, E.H.M.

1993-01-01

Classical Pott's disease is described as a two-vertebrae disease with the destruction of the intervening invertebral disc. Computerized tomography has been used in the differential diagnosis of spine infections and neoplasms. We reviewed CT scans of patients seen at the Philippine General Hospital over a two-year period with atypical presentations of atypical tuberculous spondylitis. We used the computerized tomography findings described as characteristic of classical Pott's disease as criteria in evaluating the CT scans of patients diagnosed to have Atypical Pott's Disease. Although the number of patients prevented sensitivity and specificity studies to be done, our results strongly suggest that the same CT criteria used to diagnose Classical Pott's Disease may also be used to diagnose Pott's disease in its atypical form. (Author.). 13 refs

Self-duality for coupled Potts models on the triangular lattice

International Nuclear Information System (INIS)

Richard, Jean-Francois; Jacobsen, Jesper Lykke; Picco, Marco

2004-01-01

We present self-dual manifolds for coupled Potts models on the triangular lattice. We exploit two different techniques: duality followed by decimation, and mapping to a related loop model. The latter technique is found to be superior, and it allows us to include three-spin couplings. Starting from three coupled models, such couplings are necessary for generating self-dual solutions. A numerical study of the case of two coupled models leads to the identification of novel critical points

Potts Model with Invisible Colors : Random-Cluster Representation and Pirogov–Sinai Analysis

NARCIS (Netherlands)

Enter, Aernout C.D. van; Iacobelli, Giulio; Taati, Siamak

We study a recently introduced variant of the ferromagnetic Potts model consisting of a ferromagnetic interaction among q “visible” colors along with the presence of r non-interacting “invisible” colors. We introduce a random-cluster representation for the model, for which we prove the existence of

The Potts model and flows. 1. The pair correlation function

International Nuclear Information System (INIS)

Essam, J.W.; Tsallis, C.

1985-01-01

It is shown that the partition function for the lambda-state Potts model with pair-interactions is related to the expected number of integer mod-lambda flows in a percolation model. The relation is generalised to the pair correlation function. The resulting high temperature expansion coefficients are shown to be the flow polynomials of graph theory. An observation of Tsallis and Levy concerning the equivalent transmissivity of a cluster is also proved. (Author) [pt

Entropy-driven phase transition in low-temperature antiferromagnetic Potts models

Czech Academy of Sciences Publication Activity Database

Kotecký, R.; Sokal, A.D.; Swart, Jan M.

2014-01-01

Roč. 330, č. 3 (2014), s. 1339-1394 ISSN 0010-3616 R&D Projects: GA ČR GA201/09/1931; GA ČR GAP201/12/2613 Institutional support: RVO:67985556 Keywords : Antiferromagnetic Potts model * proper coloring * plane quadrangulation * phase transition * diced lattice Subject RIV: BA - General Mathematics Impact factor: 2.086, year: 2014 http://library.utia.cas.cz/separaty/2014/SI/swart-0429507.pdf

Nonlinear complexity behaviors of agent-based 3D Potts financial dynamics with random environments

Science.gov (United States)

Xing, Yani; Wang, Jun

2018-02-01

A new microscopic 3D Potts interaction financial price model is established in this work, to investigate the nonlinear complexity behaviors of stock markets. 3D Potts model, which extends the 2D Potts model to three-dimensional, is a cubic lattice model to explain the interaction behavior among the agents. In order to explore the complexity of real financial markets and the 3D Potts financial model, a new random coarse-grained Lempel-Ziv complexity is proposed to certain series, such as the price returns, the price volatilities, and the random time d-returns. Then the composite multiscale entropy (CMSE) method is applied to the intrinsic mode functions (IMFs) and the corresponding shuffled data to study the complexity behaviors. The empirical results indicate that the 3D financial model is feasible.

Multiscale multifractal DCCA and complexity behaviors of return intervals for Potts price model

Science.gov (United States)

Wang, Jie; Wang, Jun; Stanley, H. Eugene

2018-02-01

To investigate the characteristics of extreme events in financial markets and the corresponding return intervals among these events, we use a Potts dynamic system to construct a random financial time series model of the attitudes of market traders. We use multiscale multifractal detrended cross-correlation analysis (MM-DCCA) and Lempel-Ziv complexity (LZC) perform numerical research of the return intervals for two significant China's stock market indices and for the proposed model. The new MM-DCCA method is based on the Hurst surface and provides more interpretable cross-correlations of the dynamic mechanism between different return interval series. We scale the LZC method with different exponents to illustrate the complexity of return intervals in different scales. Empirical studies indicate that the proposed return intervals from the Potts system and the real stock market indices hold similar statistical properties.

Ferromagnetic Potts models with multisite interaction

Science.gov (United States)

Schreiber, Nir; Cohen, Reuven; Haber, Simi

2018-03-01

We study the q -state Potts model with four-site interaction on a square lattice. Based on the asymptotic behavior of lattice animals, it is argued that when q ≤4 the system exhibits a second-order phase transition and when q >4 the transition is first order. The q =4 model is borderline. We find 1 /lnq to be an upper bound on Tc, the exact critical temperature. Using a low-temperature expansion, we show that 1 /(θ lnq ) , where θ >1 is a q -dependent geometrical term, is an improved upper bound on Tc. In fact, our findings support Tc=1 /(θ lnq ) . This expression is used to estimate the finite correlation length in first-order transition systems. These results can be extended to other lattices. Our theoretical predictions are confirmed numerically by an extensive study of the four-site interaction model using the Wang-Landau entropic sampling method for q =3 ,4 ,5 . In particular, the q =4 model shows an ambiguous finite-size pseudocritical behavior.

On the critical frontiers of Potts ferromagnets

International Nuclear Information System (INIS)

Magalhaes, A.C.N. de; Tsallis, C.

1981-01-01

A conjecture concerning the critical frontiers of q- state Potts ferromagnets on d- dimensional lattices (d > 1) which generalize a recent one stated for planar lattices is formulated. The present conjecture is verified within satisfactory accuracy (exactly in some cases) for all the lattices or arrays whose critical points are known. Its use leads to the prediction of: a) a considerable amount of new approximate critical points (26 on non-planar regular lattices, some others on Husimi trees and cacti); b) approximate critical frontiers for some 3- dimensional lattices; c) the possibly asymptotically exact critical point on regular lattices in the limit d→infinite for all q>=1; d) the possibly exact critical frontier for the pure Potts model on fully anisotropic Bethe lattices; e) the possibly exact critical frontier for the general quenched random-bond Potts ferromagnet (any P(J)) on isotropic Bethe lattices. (Author) [pt

Variational approach for the N-state spin and gauge Potts model

International Nuclear Information System (INIS)

Masperi, L.; Omero, C.

1981-05-01

A hamiltonian variational treatment is applied both to the spin Potts model and to its gauge version for any number of states N and spatial dimensions d>=2. Regarding the former we reproduce correct critical coupling and latent heat for not too low N and d. For the latter, our approach turns the gauge theory into an equivalent d-dimensional classical spin model, which evaluated for d+1=4 gives results in agreement with 1/N expansions. (author)

Uniqueness of Gibbs measure for Potts model with countable set of spin values

International Nuclear Information System (INIS)

Ganikhodjaev, N.N.; Rozikov, U.A.

2004-11-01

We consider a nearest-neighbor Potts model with countable spin values 0,1,..., and non zero external field, on a Cayley tree of order k (with k+1 neighbors). We study translation-invariant 'splitting' Gibbs measures. We reduce the problem to the description of the solutions of some infinite system of equations. For any k≥1 and any fixed probability measure ν with ν(i)>0 on the set of all non negative integer numbers Φ={0,1,...} we show that the set of translation-invariant splitting Gibbs measures contains at most one point, independently on parameters of the Potts model with countable set of spin values on Cayley tree. Also we give a full description of the class of measures ν on Φ such that wit respect to each element of this class our infinite system of equations has unique solution {a i =1,2,...}, where a is an element of (0,1). (author)

Evaluation of the effective thermal conductivity of UO{sub 2} fuel by combining Potts model and finite difference method

Energy Technology Data Exchange (ETDEWEB)

Oh, Jae-Yong, E-mail: tylor@kaeri.re.kr [Korea Atomic Energy Research Institute, Daedeok-daero 1045, Yuseong, Daejeon 305-353 (Korea, Republic of); Koo, Yang-Hyun; Lee, Byung-Ho; Tahk, Young-Wook [Korea Atomic Energy Research Institute, Daedeok-daero 1045, Yuseong, Daejeon 305-353 (Korea, Republic of)

2011-07-15

This paper evaluated the effects of porosity on the effective thermal conductivity of UO{sub 2} fuel by combining the Potts model and the finite difference method (FDM). Two types of microstructures representing irradiated UO{sub 2} microstructures were simulated by the Potts model in the three dimensional cubic system. One represented very small intragranular bubbles and a few intergranular bubbles under a low temperature condition. The other represented large intergranular bubbles under a high temperature or annealing condition. For the simulated microstructures, the effective thermal conductivities were determined by FDM calculation of the temperature distributions under steady state condition. They were compared with an experimental equation and the effect of bubble morphology was investigated by fitting a porosity shape factor in the Maxwell-Eucken equation. The simulation results showed a good agreement with an experimental equation and demonstrated the capability of the Potts model to provide information on microstructure for calculating the effective thermal conductivity of UO{sub 2} fuel.

Mixing of the Glauber dynamics for the ferromagnetic Potts model

OpenAIRE

Bordewich, Magnus; Greenhill, Catherine; Patel, Viresh

2013-01-01

We present several results on the mixing time of the Glauber dynamics for sampling from the Gibbs distribution in the ferromagnetic Potts model. At a fixed temperature and interaction strength, we study the interplay between the maximum degree ($\\Delta$) of the underlying graph and the number of colours or spins ($q$) in determining whether the dynamics mixes rapidly or not. We find a lower bound $L$ on the number of colours such that Glauber dynamics is rapidly mixing if at least $L$ colours...

Simulation of High Burnup Structure in UO2 Using Potts Model

International Nuclear Information System (INIS)

Oh, Jae Yong; Koo, Yang Hyun; Lee, Byung Ho

2009-01-01

The evolution of a high burnup structure (HBS) in a light water reactor (LWR) UO 2 fuel was simulated using the Potts model. A simulation system for the Potts model was defined as a two-dimensional triangular lattice, for which the stored energy was calculated from both the irradiation damage of the UO 2 matrix and the formation of a grain boundary in the newly recrystallized small HBS grains. In the simulation, the evolution probability of the HBS is calculated by the system energy difference between before and after the Monte Carlo simulation step. The simulated local threshold burnup for the HBS formation was 62 MWd/kgU, consistent with the observed threshold burnup range of 60-80 MWd/kgU. The simulation revealed that the HBS was heterogeneously nucleated on the intergranular bubbles in the proximity of the threshold burnup and then additionally on the intragranular bubbles for a burnup above 86 MWd/kgU. In addition, the simulation carried out under a condition of no bubbles indicated that the bubbles played an important role in lowering the threshold burnup for the HBS formation, thereby enabling the HBS to be observed in the burnup range of conventional high burnup fuels

Pott's Spine with Bilateral Psoas Abscesses

OpenAIRE

Masavkar, Sanjeevani; Shanbag, Preeti; Inamdar, Prithi

2012-01-01

A high degree of suspicion and appropriate imaging studies are required for the early diagnosis of Pott's spine. We describe a 4-year-old boy with Pott's disease of the lumbar spine with bilateral psoas abscesses. The child responded to conservative treatment with antituberculous treatment and ultrasonographically guided percutaneous drainage of the abscesses.

Random-field Potts model for the polar domains of lead magnesium niobate and lead scandium tantalate

Energy Technology Data Exchange (ETDEWEB)

Qian, H.; Bursill, L.A

1997-06-01

A random filed Potts model is used to establish the spatial relationship between the nanoscale distribution of charges chemical defects and nanoscale polar domains for the perovskite-based relaxor materials lead magnesium niobate (PMN) and lead scandium tantalate (PST). The random fields are not set stochastically but are determined initially by the distribution of B-site cations (Mg, Nb) or (Sc, Ta) generated by Monte Carlo NNNI-model simulations for the chemical defects. An appropriate random field Potts model is derived and algorithms developed for a 2D lattice. It is shown that the local fields are strongly correlated with the chemical domain walls and that polar domains as a function of decreasing temperature is simulated for the two cases of PMN and PST. The dynamics of the polar clusters is also discussed. 33 refs., 9 figs.

Effects of Connectivity Disorder on the Potts Model

International Nuclear Information System (INIS)

Janke, W.; Weigel, M.

2003-01-01

The relevance of quenched, uncorrelated disorder coupling to the local energy density, its paradigm being the random-bond model, is judged by the Harris criterion. A generalization of the underlying argument to the case of spatially correlated disorder, exemplified by quasi-crystals, has been given by Luck. We address the question, whether a relevance criterion of this type is applicable to the case of spin models coupled to different kinds of random graphs. The geometrical fluctuation exponent appearing in Luck's criterion is precisely determined for the case of two-dimensional Poissonian Voronoi-Delaunay random lattices and planar, ''flat'' φ 3 Feynman diagrams. While previous work for the latter graphs is in accord with the determined relevance threshold, a preliminary analysis of the result of a Monte Carlo simulation of the three-states Pott model on Poissonian Voronoi Lattices presented here does not meet the expectation from the relevance criterion. (author)

'Duality twisted'boundary conditions in n-state Potts Models

International Nuclear Information System (INIS)

Schuetz, G.

1992-11-01

We discuss a new class of toroidal boundary conditions for one-dimensional quantum Hamiltonian with S n symmetry which are related to two-dimensional n-state Potts models in the extreme anisotropic Hamiltonian limit. At their self-dual point (a point were a second-order phase transition occurs for n=2,3,4) the duality transformation is shown to be an additional symmetry giving rise to a new class of 'duality twisted' toroidal boundary conditions. This corresponding Hamiltonians are given in terms of generators of the periodic Temprely-Lieb algebra with an odd number of generators. We discuss as an example the critical Ising model. Here the complete spectrum for the new boundary conditions can be obtained from a projection mechanism in the spin-1/2 XXZ Heisenberg chain. (author)

Renormalization group study of the one-dimensional quantum Potts model

International Nuclear Information System (INIS)

Solyom, J.; Pfeuty, P.

1981-01-01

The phase transition of the classical two-dimensional Potts model, in particular the order of the transition as the number of components q increases, is studied by constructing renormalization group transformations on the equivalent one-dimensional quatum problem. It is shown that the block transformation with two sites per cell indicates the existence of a critical qsub(c) separating the small q and large q regions with different critical behaviours. The physically accessible fixed point for q>qsub(c) is a discontinuity fixed point where the specific heat exponent α=1 and therefore the transition is of first order. (author)

Potts disease: Diagnosis with magnetic resonance imaging

Energy Technology Data Exchange (ETDEWEB)

Pursey, Jacqueline [MRI Department, Gartnavel General Hospitial, 1053 Great Western road, Glasgow G12 0YN (United Kingdom)], E-mail: Jacqueline.pursey@ggc.scot.nhs.uk; Stewart, Sharon [School of Health and Social Care, Caledonian University, Glasgow (United Kingdom)

2010-02-15

The eponymously named Potts disease is a relatively rare form of Tuberculosis (TB) which affects the spine. TB of the spine is one of the earliest diseases known to man and in the 20th century was thought to be a disease which had been defeated by the advent of antitubercular drugs. Over the last two decades there have been several reports which indicate a revival of TB in both the developing and developed world. Factors which may be contributing to this are the spread of the HIV virus, increased immigration and the emergence of drug resistant strains of the TB bacteria. Potts disease has an insidious onset and often the radiographic findings are far advanced when a diagnosis is finally reached. MRI is able to detect changes to the vertebrae in Potts disease earlier than radiographs. This case report outlines the clinical presentation of a young male with Potts disease who was HIV negative, and the important role that MRI plays in diagnosis and therefore in appropriate and timely intervention. The typical magnetic resonance (MR) imaging features and the radiographic hallmarks of the disease will also be discussed.

Potts disease: Diagnosis with magnetic resonance imaging

International Nuclear Information System (INIS)

Pursey, Jacqueline; Stewart, Sharon

2010-01-01

The eponymously named Potts disease is a relatively rare form of Tuberculosis (TB) which affects the spine. TB of the spine is one of the earliest diseases known to man and in the 20th century was thought to be a disease which had been defeated by the advent of antitubercular drugs. Over the last two decades there have been several reports which indicate a revival of TB in both the developing and developed world. Factors which may be contributing to this are the spread of the HIV virus, increased immigration and the emergence of drug resistant strains of the TB bacteria. Potts disease has an insidious onset and often the radiographic findings are far advanced when a diagnosis is finally reached. MRI is able to detect changes to the vertebrae in Potts disease earlier than radiographs. This case report outlines the clinical presentation of a young male with Potts disease who was HIV negative, and the important role that MRI plays in diagnosis and therefore in appropriate and timely intervention. The typical magnetic resonance (MR) imaging features and the radiographic hallmarks of the disease will also be discussed.

An explicit formula for the interface tension of the 2D Potts model

Science.gov (United States)

Borgs, Christian; Janke, Wolfhard

1992-11-01

We consider the exact correlation length calculations for the two-dimensional Potts model at the transition point β_t by Klümper, Schadschneider and Zittartz, and by Buffenoir and Wallon. We argue that the correlation length calculated by the latter authors is the correlation length in the disordered phase and then combine their result with duality and the assumption of complete wetting to give an explicit formula for the order-disorder interface tension σ_od of this model. The result is used to clarify a controversy stemming from different numerical simulations of σ_od.

C-periodicity and the physical mass in the 3-state Potts model

International Nuclear Information System (INIS)

Gavai, R.V.; Polley, L.

1993-07-01

The standard infinite-volume definition of connected correlation function and particle mass in the 3-state Potts model can be implemented in Monte Carlo simulations by using C-periodic spatial boundary conditions. This avoids both the breaking of translation invariance (cold wall b.c.) and the phase-dependent and thus possible biased evaluation of data (periodic b.c.). The numerical feasibility of the standard definitions is demonstrated by sample computations on a 24 x 24 x 48 lattice. (author). 11 refs, 5 figs, 1 tab

Cubic rare-earth compounds: variants of the three-state Potts model

International Nuclear Information System (INIS)

Kim, D.; Levy, P.M.; Uffer, L.F.

1975-01-01

In appropriate cubic fields, rare-earth ions have sixfold degenerate ground states. When the angular momentum of the rare earth is large, the six levels are characterized by states that are directed along the cube edges. Within these states the angular momentum operators J/sub x/, J/sub y/, and J/sub z/ have particularly simple matrix representations. The projection of an isotropic pair coupling between the rare earths onto these sixfold degenerate states leads to an interaction Hamiltonian H = -I Σ/sub (ij)/ sigma/sub i/sigma/sub j/delta/sub l/sub i/sub l/sub j//, where sigma takes on the values +-1 and l the values x, y, and z. This interaction is a variant of the three-state Potts model. Magnetic and quadrupolar anisotropy field terms are added to the Hamiltonian and the symmetry properties of the phase diagram associated with this model are determined. For nonzero quadrupolar anisotropy fields, the model is shown to have the thermodynamic behavior of an Ising model. However, for zero fields a new symmetry appears and in the mean-field approximation the model has tricritical-like exponents. This simple model is able to account for the large specific-heat critical exponent α' = 1 / 2 which has been observed for holmium antimonide in zero external fields. To the extent that the mean-field approximation is an accurate guide, we predict there are many cubic rare-earth compounds which exhibit tricritical-like behavior in zero field. In addition, for pure quadrupole coupling between rare earths in the sixfold degenerate states, the interaction Hamiltonian is exactly the three-state Potts model. In the mean-field approximation this system has a first-order phase transition. However, a small quadrupolar anisotropy field is sufficient to drive the system to a wing critical point. The specific heat has a critical exponent of α = 2 / 3 or 1 depending on the path taken to approach this critical point. (auth)

The Potts models and flows. III, standard and subgraph break-collapse methods

International Nuclear Information System (INIS)

Magalhaes, A.C.N. de; Essam, J.W.

1987-01-01

An algorithm is developed for the exact calculation of the many spin correlation functions of Potts model clusters which is more efficient than the standard break-collapse method traditionally used in real space renormalization group calculations. The improved performance is based on a relationship which, at any stage of the calculation, allows the replacement of certain subgraphs by single effective edges. Our method avoids, as in the standard one, the time consuming summation over spin states and can be very useful in series expansions and real space renormalisation group calculations on crystal lattices. (Author) [pt

Two-Dimensional Wetting Transition Modeling with the Potts Model

Science.gov (United States)

Lopes, Daisiane M.; Mombach, José C. M.

2017-12-01

A droplet of a liquid deposited on a surface structured in pillars may have two states of wetting: (1) Cassie-Baxter (CB), the liquid remains on top of the pillars, also known as heterogeneous wetting, or (2) Wenzel, the liquid fills completely the cavities of the surface, also known as homogeneous wetting. Studies show that between these two states, there is an energy barrier that, when overcome, results in the transition of states. The transition can be achieved by changes in geometry parameters of the surface, by vibrations of the surface or by evaporation of the liquid. In this paper, we present a comparison of two-dimensional simulations of the Cassie-Wenzel transition on pillar-structured surfaces using the cellular Potts model (CPM) with studies performed by Shahraz et al. In our work, we determine a transition diagram by varying the surface parameters such as the interpillar distance ( G) and the pillar height ( H). Our results were compared to those obtained by Shahraz et al. obtaining good agreement.

Influence of lattice defects on criticality of Potts ferromagnet

International Nuclear Information System (INIS)

Souza Costa, U.M. de.

1985-01-01

The critical properties of the q-state Potts ferromagnet and the anisotropic Heisenberg model on hypercubic lattices (d = 2,3); emphasis is given to the free surface and the interface effects, the Real Space Renormalization Group approach. The criticality of the quenched bond-mixed q-state Potts ferromagnet on square lattice is discussed. It is shown that, the crossover from the pure fixed point to the random one occurs, while q increases, through a pitchfork bifurcation; the relation-ship with the Harris criterion is analyzed. High precision numerical values for the critical temperatures corresponding to arbitrary concentrations of the coupling constants J sub(1) and J sub(2), and arbitrary ratios J sub(1)/J sub(2) are presented.(author)

Critical behaviour of the randomly stirred dynamical Potts model: novel universality class and effects of compressibility

International Nuclear Information System (INIS)

Antonov, N V; Kapustin, A S

2012-01-01

Critical behaviour of the dynamical Potts model, subjected to vivid turbulent mixing, is studied by means of the renormalization group. The advecting velocity field is modelled by Kraichnan’s rapid-change ensemble: Gaussian statistics with a given pair correlator 〈vv〉∝δ(t − t′) k −d−ξ , where k is the wave number, d is the dimension of space and 0 < ξ < 2 is an arbitrary exponent. The system exhibits different types of infrared scaling behaviour, associated with four infrared attractors of the renormalization group equations. In addition to the known asymptotic regimes (equilibrium Potts model and passive scalar field), the existence of a new, strongly non-equilibrium type of critical behaviour (universality class) is established, where the self-interaction of the order parameter and the turbulent mixing are equally important. The corresponding critical dimensions and the regions of stability for all the regimes are calculated in the leading order of the double expansion in ξ and ε = 6 − d. Special attention is paid to the effects of compressibility of the fluid, because they lead to interesting crossover phenomena. (paper)

Degenerate ground states and multiple bifurcations in a two-dimensional q-state quantum Potts model.

Science.gov (United States)

Dai, Yan-Wei; Cho, Sam Young; Batchelor, Murray T; Zhou, Huan-Qiang

2014-06-01

We numerically investigate the two-dimensional q-state quantum Potts model on the infinite square lattice by using the infinite projected entangled-pair state (iPEPS) algorithm. We show that the quantum fidelity, defined as an overlap measurement between an arbitrary reference state and the iPEPS ground state of the system, can detect q-fold degenerate ground states for the Z_{q} broken-symmetry phase. Accordingly, a multiple bifurcation of the quantum ground-state fidelity is shown to occur as the transverse magnetic field varies from the symmetry phase to the broken-symmetry phase, which means that a multiple-bifurcation point corresponds to a critical point. A (dis)continuous behavior of quantum fidelity at phase transition points characterizes a (dis)continuous phase transition. Similar to the characteristic behavior of the quantum fidelity, the magnetizations, as order parameters, obtained from the degenerate ground states exhibit multiple bifurcation at critical points. Each order parameter is also explicitly demonstrated to transform under the Z_{q} subgroup of the symmetry group of the Hamiltonian. We find that the q-state quantum Potts model on the square lattice undergoes a discontinuous (first-order) phase transition for q=3 and q=4 and a continuous phase transition for q=2 (the two-dimensional quantum transverse Ising model).

Evaporation-condensation transition of the two-dimensional Potts model in the microcanonical ensemble

KAUST Repository

Nogawa, Tomoaki

2011-12-05

The evaporation-condensation transition of the Potts model on a square lattice is numerically investigated by the Wang-Landau sampling method. An intrinsically system-size-dependent discrete transition between supersaturation state and phase-separation state is observed in the microcanonical ensemble by changing constrained internal energy. We calculate the microcanonical temperature, as a derivative of microcanonical entropy, and condensation ratio, and perform a finite-size scaling of them to indicate the clear tendency of numerical data to converge to the infinite-size limit predicted by phenomenological theory for the isotherm lattice gas model. © 2011 American Physical Society.

Excited state TBA and renormalized TCSA in the scaling Potts model

Science.gov (United States)

Lencsés, M.; Takács, G.

2014-09-01

We consider the field theory describing the scaling limit of the Potts quantum spin chain using a combination of two approaches. The first is the renormalized truncated conformal space approach (TCSA), while the second one is a new thermodynamic Bethe Ansatz (TBA) system for the excited state spectrum in finite volume. For the TCSA we investigate and clarify several aspects of the renormalization procedure and counter term construction. The TBA system is first verified by comparing its ultraviolet limit to conformal field theory and the infrared limit to exact S matrix predictions. We then show that the TBA and the renormalized TCSA match each other to a very high precision for a large range of the volume parameter, providing both a further verification of the TBA system and a demonstration of the efficiency of the TCSA renormalization procedure. We also discuss the lessons learned from our results concerning recent developments regarding the low-energy scattering of quasi-particles in the quantum Potts spin chain.

Pott's disease: a case of Mycobacterium xenopi infection of the spine.

Science.gov (United States)

Alfreijat, Majd; Ononiwu, Chiagozie; Sexton, Carlton

2012-01-01

Pott's disease is an infection of the spine with Mycobacterium tuberculosis that causes destruction of the spine elements resulting in progressive kyphosis. We are describing a rare case of Pott's disease where Mycobacterium xenopi was the inculpated organism.

Pott's disease: a case of Mycobacterium xenopi infection of the spine

Directory of Open Access Journals (Sweden)

Majd Alfreijat

2013-01-01

Full Text Available Pott's disease is an infection of the spine with Mycobacterium tuberculosis that causes destruction of the spine elements resulting in progressive kyphosis. We are describing a rare case of Pott's disease where Mycobacterium xenopi was the inculpated organism.

Periodic p-adic Gibbs Measures of q-State Potts Model on Cayley Trees I: The Chaos Implies the Vastness of the Set of p-Adic Gibbs Measures

Science.gov (United States)

Ahmad, Mohd Ali Khameini; Liao, Lingmin; Saburov, Mansoor

2018-06-01

We study the set of p-adic Gibbs measures of the q-state Potts model on the Cayley tree of order three. We prove the vastness of the set of the periodic p-adic Gibbs measures for such model by showing the chaotic behavior of the corresponding Potts-Bethe mapping over Q_p for the prime numbers p≡1 (mod 3). In fact, for 0< |θ -1|_p< |q|_p^2 < 1 where θ =\\exp _p(J) and J is a coupling constant, there exists a subsystem that is isometrically conjugate to the full shift on three symbols. Meanwhile, for 0< |q|_p^2 ≤ |θ -1|_p< |q|_p < 1, there exists a subsystem that is isometrically conjugate to a subshift of finite type on r symbols where r ≥ 4. However, these subshifts on r symbols are all topologically conjugate to the full shift on three symbols. The p-adic Gibbs measures of the same model for the prime numbers p=2,3 and the corresponding Potts-Bethe mapping are also discussed. On the other hand, for 0< |θ -1|_p< |q|_p < 1, we remark that the Potts-Bethe mapping is not chaotic when p=3 and p≡ 2 (mod 3) and we could not conclude the vastness of the set of the periodic p-adic Gibbs measures. In a forthcoming paper with the same title, we will treat the case 0< |q|_p ≤ |θ -1|_p < 1 for all prime numbers p.

Potts glass reflection of the decoding threshold for qudit quantum error correcting codes

Science.gov (United States)

Jiang, Yi; Kovalev, Alexey A.; Pryadko, Leonid P.

We map the maximum likelihood decoding threshold for qudit quantum error correcting codes to the multicritical point in generalized Potts gauge glass models, extending the map constructed previously for qubit codes. An n-qudit quantum LDPC code, where a qudit can be involved in up to m stabilizer generators, corresponds to a ℤd Potts model with n interaction terms which can couple up to m spins each. We analyze general properties of the phase diagram of the constructed model, give several bounds on the location of the transitions, bounds on the energy density of extended defects (non-local analogs of domain walls), and discuss the correlation functions which can be used to distinguish different phases in the original and the dual models. This research was supported in part by the Grants: NSF PHY-1415600 (AAK), NSF PHY-1416578 (LPP), and ARO W911NF-14-1-0272 (LPP).

The potts chain in a random field: an exact solution

International Nuclear Information System (INIS)

Riera, R.; Chaves, C.M.G.F.; Santos, Raimundo R. dos.

1984-01-01

An exact solution is presented for the one-dimensional q-state Potts model in a quenched random field. The ferromagnetic phase is unstable against any small random field perturbation. The correlation function and the Edwards-Anderson order parameter Q are discussed. For finite q only the phase with Q ≠ 0 is present. (Author) [pt

Ising and Potts models: binding disorder-and dimension effects

International Nuclear Information System (INIS)

Curado, E.M.F.

1983-01-01

Within the real space renormalization group framework, some thermal equilibrium properties of pure and disordered insulating systems are calculated. In the pure hypercubic lattice system, the Ising model surface tension and the correlation length of the q-state Potts model, which generalizes the former are analyzed. Several asymptotic behaviors are obtained (for the first time as far as we know) for both functions and the influence of dimension over them can be observed. Accurate numerical proposals for the surface tension are made in several dimensions, and the effect of the number of states (q) on the correlation lenght is shown. In disordered systems, attention is focused essentiall on those which can be theoretically represented by pure sistem Hamiltonians where probability distributions are assumed for the coupling constants (disorder in the bonds). It is obtained with high precision several approximate critical surfaces for the quenched square-lattice Ising model, whose probability distribution can assume two positive values (hence there is no frustration). These aproximate surfaces contain all the exact known points. In the cases where the coupling constant probability distribution can also assume negative values (allowing disordered and frustrated systems), a theoretical treatment which distinguishes the frustration effect from the dilution one is proposed. This distinction can be seen by the different ways in which the bonds of any series-parallel topological array combine. (Author) [pt

Survival into seventh decade after a potts palliation for tetralogy of Fallot

NARCIS (Netherlands)

Oosterhof, Thomas; Jacobs, Monique; Cramer, Maarten-Jan; Mulder, Barbara J. M.

2007-01-01

In this case report we present a 62-year-old patient with unrepaired tetralogy of Fallot who underwent a Potts shunt for palliation. Survival into late adulthood of patients with unoperated tetralogy of Fallot is rare. This patient is currently in New York Heart Association (NYHA) class II. A Potts

Square-lattice random Potts model: criticality and pitchfork bifurcation

International Nuclear Information System (INIS)

Costa, U.M.S.; Tsallis, C.

1983-01-01

Within a real space renormalization group framework based on self-dual clusters, the criticality of the quenched bond-mixed q-state Potts ferromagnet on square lattice is discussed. On qualitative grounds it is exhibited that the crossover from the pure fixed point to the random one occurs, while q increases, through a pitchfork bifurcation; the relationship with Harris criterion is analyzed. On quantitative grounds high precision numerical values are presented for the critical temperatures corresponding to various concentrations of the coupling constants J 1 and J 2 , and various ratios J 1 /J 2 . The pure, random and crossover critical exponents are discussed as well. (Author) [pt

Multi-scale modeling in morphogenesis: a critical analysis of the cellular Potts model.

Directory of Open Access Journals (Sweden)

Anja Voss-Böhme

Full Text Available Cellular Potts models (CPMs are used as a modeling framework to elucidate mechanisms of biological development. They allow a spatial resolution below the cellular scale and are applied particularly when problems are studied where multiple spatial and temporal scales are involved. Despite the increasing usage of CPMs in theoretical biology, this model class has received little attention from mathematical theory. To narrow this gap, the CPMs are subjected to a theoretical study here. It is asked to which extent the updating rules establish an appropriate dynamical model of intercellular interactions and what the principal behavior at different time scales characterizes. It is shown that the longtime behavior of a CPM is degenerate in the sense that the cells consecutively die out, independent of the specific interdependence structure that characterizes the model. While CPMs are naturally defined on finite, spatially bounded lattices, possible extensions to spatially unbounded systems are explored to assess to which extent spatio-temporal limit procedures can be applied to describe the emergent behavior at the tissue scale. To elucidate the mechanistic structure of CPMs, the model class is integrated into a general multiscale framework. It is shown that the central role of the surface fluctuations, which subsume several cellular and intercellular factors, entails substantial limitations for a CPM's exploitation both as a mechanistic and as a phenomenological model.

q-state Potts-glass neural network based on pseudoinverse rule

International Nuclear Information System (INIS)

Xiong Daxing; Zhao Hong

2010-01-01

We study the q-state Potts-glass neural network with the pseudoinverse (PI) rule. Its performance is investigated and compared with that of the counterpart network with the Hebbian rule instead. We find that there exists a critical point of q, i.e., q cr =14, below which the storage capacity and the retrieval quality can be greatly improved by introducing the PI rule. We show that the dynamics of the neural networks constructed with the two learning rules respectively are quite different; but however, regardless of the learning rules, in the q-state Potts-glass neural networks with q≥3 there is a common novel dynamical phase in which the spurious memories are completely suppressed. This property has never been noticed in the symmetric feedback neural networks. Free from the spurious memories implies that the multistate Potts-glass neural networks would not be trapped in the metastable states, which is a favorable property for their applications.

Yang-Lee zeros for a Potts model of helix-coil transition with nontrivial topology

International Nuclear Information System (INIS)

Ananikian, N.; Ananikyan, L.; Artuso, R.; Sargsyan, K.

2007-07-01

The Yang-Lee partition function zeros of the Q-state Potts model on a zigzag ladder are studied by a transfer-matrix approach. This Q-state model has a non-trivial topology induced by three-site interactions on a zigzag ladder and is proposed as a description of helix-coil transition in homo-polymers. The Yang-Lee zeros are associated to complex values of the solvent-related coupling constant K (magnetic field) and they are exactly derived for arbitrary values of the system parameters: Q, J (coupling constant of hydrogen binding) and temperature. It is shown that there is only a quasi-phase transition for all temperatures. The densities of the Yang-Lee zeros are singular at the edge singularity points and the critical exponent σ = -1/2. (author)

Nature of phase transitions in Axelrod-like coupled Potts models in two dimensions

Science.gov (United States)

Gandica, Yerali; Chiacchiera, Silvia

2016-03-01

We study F coupled q -state Potts models in a two-dimensional square lattice. The interaction between the different layers is attractive to favor a simultaneous alignment in all of them, and its strength is fixed. The nature of the phase transition for zero field is numerically determined for F =2 ,3 . Using the Lee-Kosterlitz method, we find that it is continuous for F =2 and q =2 , whereas it is abrupt for higher values of q and/or F . When a continuous or a weakly first-order phase transition takes place, we also analyze the properties of the geometrical clusters. This allows us to determine the fractal dimension D of the incipient infinite cluster and to examine the finite-size scaling of the cluster number density via data collapse. A mean-field approximation of the model, from which some general trends can be determined, is presented too. Finally, since this lattice model has been recently considered as a thermodynamic counterpart of the Axelrod model of social dynamics, we discuss our results in connection with this one.

Two-dimensional Potts antiferromagnets with a phase transition at arbitrarily large q

Czech Academy of Sciences Publication Activity Database

Huang, Y.; Chen, K.; Deng, Y.; Jacobsen, J. L.; Kotecký, R.; Salas, J.; Sokal, Alan D.; Swart, Jan M.

2013-01-01

Roč. 87, Č. 1 (2013), 12136-1-12136-5 ISSN 1539-3755 R&D Projects: GA ČR GAP201/12/2613 Institutional support: RVO:67985556 Keywords : Monte Carlo simulation * two-dimensional lattices * q-state Potts Subject RIV: BE - Theoretical Physics Impact factor: 2.326, year: 2013 http://library.utia.cas.cz/separaty/2013/SI/swart-two-dimensional potts antiferromagnets with a phase transition at arbitrarily large q.pdf

Low-temperature expansions and correlation functions of the Z3-chiral Potts model

International Nuclear Information System (INIS)

Han, N.S.; Honecker, A.

1993-04-01

Using perturbative methods we derive new results for the spectrum and correlation functions of the general Z 3 -chiral Potts quantum chain in the massive low-temperature phase. Explicit calculations of the ground state energy and the first excitations in the zero momentum sector give excellent approximations and confirm the general statement that the spectrum in the low-temperature phase of general Z n -spin quantum chains is identical to one in the high-temperature phase where the role of charge and boundary conditions are interchanged. Using a perturbative expansion of the ground state for the Z 3 model we are able to gain some insight in correlation functions. We argue that they might be oscillating and give estimates for the oscillation length as well as the correlation length. (orig.)

Exact valence bond entanglement entropy and probability distribution in the XXX spin chain and the potts model.

Science.gov (United States)

Jacobsen, J L; Saleur, H

2008-02-29

We determine exactly the probability distribution of the number N_(c) of valence bonds connecting a subsystem of length L>1 to the rest of the system in the ground state of the XXX antiferromagnetic spin chain. This provides, in particular, the asymptotic behavior of the valence-bond entanglement entropy S_(VB)=N_(c)ln2=4ln2/pi(2)lnL disproving a recent conjecture that this should be related with the von Neumann entropy, and thus equal to 1/3lnL. Our results generalize to the Q-state Potts model.

Retropharyngeal cold abscess without Pott's spine | Singh | South ...

African Journals Online (AJOL)

Retropharyngeal cold abscess without Pott's spine. ... pyogenic osteomyelitis, tube‚rculosis of the spine, or external injuries caused by endoscopes ... in an adult woman without tuberculosis of the cervical spine who was managed surgically by ...

Simple method to calculate percolation, Ising and Potts clusters

International Nuclear Information System (INIS)

Tsallis, C.

1981-01-01

A procedure ('break-collapse method') is introduced which considerably simplifies the calculation of two - or multirooted clusters like those commonly appearing in real space renormalization group (RG) treatments of bond-percolation, and pure and random Ising and Potts problems. The method is illustrated through two applications for the q-state Potts ferromagnet. The first of them concerns a RG calculation of the critical exponent ν for the isotropic square lattice: numerical consistence is obtained (particularly for q→0) with den Nijs conjecture. The second application is a compact reformulation of the standard star-triangle and duality transformations which provide the exact critical temperature for the anisotropic triangular and honeycomb lattices. (Author) [pt

Applications of neural networks to the studies of phase transitions of two-dimensional Potts models

Science.gov (United States)

Li, C.-D.; Tan, D.-R.; Jiang, F.-J.

2018-04-01

We study the phase transitions of two-dimensional (2D) Q-states Potts models on the square lattice, using the first principles Monte Carlo (MC) simulations as well as the techniques of neural networks (NN). We demonstrate that the ideas from NN can be adopted to study these considered phase transitions efficiently. In particular, even with a simple NN constructed in this investigation, we are able to obtain the relevant information of the nature of these phase transitions, namely whether they are first order or second order. Our results strengthen the potential applicability of machine learning in studying various states of matters. Subtlety of applying NN techniques to investigate many-body systems is briefly discussed as well.

Using a method based on Potts Model to segment a micro-CT image stack of trabecular bones of femoral region

Energy Technology Data Exchange (ETDEWEB)

Andrade, Pedro H.A. de; Cabral, Manuela O.M., E-mail: andrade.pha@gmail.com [Universidade Federal de Pernambuco (DEN/UFPE), Recife, PE (Brazil). Departamento de Engenharia Nuclear; Vieira, Jose W.; Correia, Filipe L. de B., E-mail: jose.wilson59@uol.com.br [Instituto Federal de Educacao, Ciencia e Tecnologia de Pernambuco (IFPE), Recife, PE (Brazil); Lima, Fernando R. De A., E-mail: falima@cnen.gov.br [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (brazil)

2015-07-01

Exposure Computational Models are composed basically of an anthropomorphic phantom, a Monte Carlo (MC) code, and an algorithm simulator of the radioactive source. Tomographic phantoms are developed from medical images and must be pre-processed and segmented before being coupled to a MC code (which simulates the interaction of radiation with matter). This work presents a methodology used for treatment of micro-CT images stack of a femur, obtained from a 30 year old female skeleton provided by the Imaging Laboratory for Anthropology of the University of Bristol, UK. These images contain resolution of 60 micrometers and from these a block containing only 160 x 60 x 160 pixels of trabecular tissues and bone marrow was cut and saved as ⁎.sgi file (header + ⁎.raw file). The Grupo de Dosimetria Numerica (Recife-PE, Brazil) developed a software named Digital Image Processing (DIP), in which a method for segmentation based on a physical model for particle interaction known as Potts Model (or q-Ising) was implemented. This model analyzes the statistical dependence between sites in a network. In Potts Model, when the values of spin variables at neighboring sites are identical, it is assigned an 'energy of interaction' between them. Otherwise, it is said that the sites do not interact. Making an analogy between network sites and the pixels of a digital image and, moreover, between the spins variables and the intensity of the gray scale, it was possible to apply this model to obtain texture descriptors and segment the image. (author)

Using a method based on Potts Model to segment a micro-CT image stack of trabecular bones of femoral region

International Nuclear Information System (INIS)

Andrade, Pedro H.A. de; Cabral, Manuela O.M.; Lima, Fernando R. De A.

2015-01-01

Exposure Computational Models are composed basically of an anthropomorphic phantom, a Monte Carlo (MC) code, and an algorithm simulator of the radioactive source. Tomographic phantoms are developed from medical images and must be pre-processed and segmented before being coupled to a MC code (which simulates the interaction of radiation with matter). This work presents a methodology used for treatment of micro-CT images stack of a femur, obtained from a 30 year old female skeleton provided by the Imaging Laboratory for Anthropology of the University of Bristol, UK. These images contain resolution of 60 micrometers and from these a block containing only 160 x 60 x 160 pixels of trabecular tissues and bone marrow was cut and saved as ⁎.sgi file (header + ⁎.raw file). The Grupo de Dosimetria Numerica (Recife-PE, Brazil) developed a software named Digital Image Processing (DIP), in which a method for segmentation based on a physical model for particle interaction known as Potts Model (or q-Ising) was implemented. This model analyzes the statistical dependence between sites in a network. In Potts Model, when the values of spin variables at neighboring sites are identical, it is assigned an 'energy of interaction' between them. Otherwise, it is said that the sites do not interact. Making an analogy between network sites and the pixels of a digital image and, moreover, between the spins variables and the intensity of the gray scale, it was possible to apply this model to obtain texture descriptors and segment the image. (author)

Monte Carlo simulation of the three-state vector Potts model on a three-dimensional random lattice

International Nuclear Information System (INIS)

Jianbo Zhang; Heping Ying

1991-09-01

We have performed a numerical simulation of the three-state vector Potts model on a three-dimensional random lattice. The averages of energy density, magnetization, specific heat and susceptibility of the system in the N 3 (N=8,10,12) lattices were calculated. The results show that a first order nature of the Z(3) symmetry breaking transition appears, as characterized by a thermal hysterisis in the energy density as well as an abrupt drop of magnetization being sharper and discontinuous with increasing of volume in the cross-over region. The results obtained on the random lattice were consistent with those obtained on the three-dimensional cubic lattice. (author). 12 refs, 4 figs

On the τ(2)-model in the chiral Potts model and cyclic representation of the quantum group Uq(sl2)

International Nuclear Information System (INIS)

Roan Shishyr

2009-01-01

We identify the precise relationship between the five-parameter τ (2) -family in the N-state chiral Potts model and XXZ chains with U q (sl 2 )-cyclic representation. By studying the Yang-Baxter relation of the six-vertex model, we discover a one-parameter family of L-operators in terms of the quantum group U q (sl 2 ). When N is odd, the N-state τ (2) -model can be regarded as the XXZ chain of U q (sl 2 ) cyclic representations with q N =1. The symmetry algebra of the τ (2) -model is described by the quantum affine algebra U q (sl 2 -hat) via the canonical representation. In general, for an arbitrary N, we show that the XXZ chain with a U q (sl 2 )-cyclic representation for q 2N = 1 is equivalent to two copies of the same N-state τ (2) -model. (fast track communication)

Equilibrium state of the mean-field Potts glass

Czech Academy of Sciences Publication Activity Database

Janiš, Václav; Klíč, Antonín

2011-01-01

Roč. 23, č. 2 (2011), s. 1-5 ISSN 0953-8984 Institutional research plan: CEZ:AV0Z10100520 Keywords : Potts glass * replica-symmetry breaking * asymptotic expansion Subject RIV: BE - Theoretical Physics Impact factor: 2.546, year: 2011 http://iopscience.iop.org/0953-8984/23/2/022204/

Hierarchy of the low-lying excitations for the (2+1-dimensional q=3 Potts model in the ordered phase

Directory of Open Access Journals (Sweden)

Yoshihiro Nishiyama

2017-03-01

Full Text Available The (2+1-dimensional q=3 Potts model was simulated with the exact diagonalization method. In the ordered phase, the elementary excitations (magnons are attractive, forming a series of bound states in the low-energy spectrum. We investigate the low-lying spectrum through a dynamical susceptibility, which is readily tractable with the exact diagonalization method via the continued-fraction expansion. As a result, we estimate the series of (scaled mass gaps, m2,3,4/m1 (m1: single-magnon mass, in proximity to the transition point.

Weighted fractional permutation entropy and fractional sample entropy for nonlinear Potts financial dynamics

Energy Technology Data Exchange (ETDEWEB)

Xu, Kaixuan, E-mail: kaixuanxubjtu@yeah.net; Wang, Jun

2017-02-26

In this paper, recently introduced permutation entropy and sample entropy are further developed to the fractional cases, weighted fractional permutation entropy (WFPE) and fractional sample entropy (FSE). The fractional order generalization of information entropy is utilized in the above two complexity approaches, to detect the statistical characteristics of fractional order information in complex systems. The effectiveness analysis of proposed methods on the synthetic data and the real-world data reveals that tuning the fractional order allows a high sensitivity and more accurate characterization to the signal evolution, which is useful in describing the dynamics of complex systems. Moreover, the numerical research on nonlinear complexity behaviors is compared between the returns series of Potts financial model and the actual stock markets. And the empirical results confirm the feasibility of the proposed model. - Highlights: • Two new entropy approaches for estimation of nonlinear complexity are proposed for the financial market. • Effectiveness analysis of proposed methods is presented and their respective features are studied. • Empirical research of proposed analysis on seven world financial market indices. • Numerical simulation of Potts financial dynamics is preformed for nonlinear complexity behaviors.

Weighted fractional permutation entropy and fractional sample entropy for nonlinear Potts financial dynamics

International Nuclear Information System (INIS)

Xu, Kaixuan; Wang, Jun

2017-01-01

In this paper, recently introduced permutation entropy and sample entropy are further developed to the fractional cases, weighted fractional permutation entropy (WFPE) and fractional sample entropy (FSE). The fractional order generalization of information entropy is utilized in the above two complexity approaches, to detect the statistical characteristics of fractional order information in complex systems. The effectiveness analysis of proposed methods on the synthetic data and the real-world data reveals that tuning the fractional order allows a high sensitivity and more accurate characterization to the signal evolution, which is useful in describing the dynamics of complex systems. Moreover, the numerical research on nonlinear complexity behaviors is compared between the returns series of Potts financial model and the actual stock markets. And the empirical results confirm the feasibility of the proposed model. - Highlights: • Two new entropy approaches for estimation of nonlinear complexity are proposed for the financial market. • Effectiveness analysis of proposed methods is presented and their respective features are studied. • Empirical research of proposed analysis on seven world financial market indices. • Numerical simulation of Potts financial dynamics is preformed for nonlinear complexity behaviors.

Min-max Extrapolation Scheme for Fast Estimation of 3D Potts Field Partition Functions. Application to the Joint Detection-Estimation of Brain Activity in fMRI

International Nuclear Information System (INIS)

Risser, L.; Vincent, T.; Ciuciu, P.; Risser, L.; Idier, J.; Risser, L.; Forbes, F.

2011-01-01

In this paper, we propose a fast numerical scheme to estimate Partition Functions (PF) of symmetric Potts fields. Our strategy is first validated on 2D two-color Potts fields and then on 3D two- and three-color Potts fields. It is then applied to the joint detection-estimation of brain activity from functional Magnetic Resonance Imaging (fMRI) data, where the goal is to automatically recover activated, deactivated and inactivated brain regions and to estimate region dependent hemodynamic filters. For any brain region, a specific 3D Potts field indeed embodies the spatial correlation over the hidden states of the voxels by modeling whether they are activated, deactivated or inactive. To make spatial regularization adaptive, the PFs of the Potts fields over all brain regions are computed prior to the brain activity estimation. Our approach is first based upon a classical path-sampling method to approximate a small subset of reference PFs corresponding to pre-specified regions. Then, we propose an extrapolation method that allows us to approximate the PFs associated to the Potts fields defined over the remaining brain regions. In comparison with preexisting methods either based on a path sampling strategy or mean-field approximations, our contribution strongly alleviates the computational cost and makes spatially adaptive regularization of whole brain fMRI datasets feasible. It is also robust against grid inhomogeneities and efficient irrespective of the topological configurations of the brain regions. (authors)

Harvey Cushing, the spine surgeon: the surgical treatment of Pott disease.

Science.gov (United States)

Bydon, Ali; Dasenbrock, Hormuzdiyar H; Pendleton, Courtney; McGirt, Matthew J; Gokaslan, Ziya L; Quinones-Hinojosa, Alfredo

2011-08-01

Review of historical archival records. Describe Harvey Cushing's patients with spinal pathology. Harvey Cushing was a pioneer of modern surgery but his work on spine remains largely unknown. Review of the Chesney Medical Archives of the Johns Hopkins Hospital from 1896 to 1912. This is the first time that Cushing's spinal cases while he was at the Johns Hopkins Hospital, including those with Pott disease, have been described.Cushing treated three young men with psoas abscesses secondary to Pott disease during his residency: he drained the abscesses, debrided any accompanying necrotic vertebral bodies, irrigated the cavity with salt, and left the incision open to close by secondary intention. Although Cushing used Koch's "tuberculin therapy" (of intravenous administration of isolated tubercular bacilli) in one patient, he did not do so in the other two, likely because of the poor response of this first patient. Later in his tenure, Cushing performed a laminectomy on a patient with kyphosis and paraplegia secondary to Pott disease. These cases provide a view of Cushing early in his career, pointing to the extraordinary degree of independence that he had during his residency under William Steward Halsted; these cases may have been important in the surgical upbringing both of Cushing and his coresident, William Stevenson Baer, who became the first professor of Orthopedics at Johns Hopkins Hospital. At the turn of the last century, Pott disease was primarily treated by immobilization with bed rest, braces, and plaster-of-paris jackets; some surgeons also employed gradual correction of the deformity by hyperextension. Patients who failed a trial of conservative therapy (of months to years) were treated with a laminectomy. However, the limitations of these strategies led to the development of techniques that form the basis of contemporary spine surgery-instrumentation and fusion.

Operator content of the critical Potts model in d dimensions and logarithmic correlations

International Nuclear Information System (INIS)

Vasseur, Romain; Jacobsen, Jesper Lykke

2014-01-01

Using the symmetric group S Q symmetry of the Q-state Potts model, we classify the (scalar) operator content of its underlying field theory in arbitrary dimension. In addition to the usual identity, energy and magnetization operators, we find fields that generalize the N-cluster operators well-known in two dimensions, together with their subleading counterparts. We give the explicit form of all these operators – up to non-universal constants – both on the lattice and in the continuum limit for the Landau theory. We compute exactly their two- and three-point correlation functions on an arbitrary graph in terms of simple probabilities, and give the general form of these correlation functions in the continuum limit at the critical point. Specializing to integer values of the parameter Q, we argue that the analytic continuation of the S Q symmetry yields logarithmic correlations at the critical point in arbitrary dimension, thus implying a mixing of some scaling fields by the scale transformation generator. All these logarithmic correlation functions are given a clear geometrical meaning, which can be checked in numerical simulations. Several physical examples are discussed, including bond percolation, spanning trees and forests, resistor networks and the Ising model. We also briefly address the generalization of our approach to the O(n) model

Dynamical quantum phase transitions in the quantum Potts chain

NARCIS (Netherlands)

Karrasch, C.; Schuricht, D.|info:eu-repo/dai/nl/369284690

2017-01-01

We analyze the dynamics of the return amplitude following a sudden quench in the three-state quantum Potts chain. For quenches crossing the quantum critical point from the paramagnetic to the ferromagnetic phase, the corresponding rate function is non-analytic at critical times and behaves linearly

On P-Adic Quasi Gibbs Measures for Q + 1-State Potts Model on the Cayley Tree

International Nuclear Information System (INIS)

Mukhamedov, Farrukh

2010-06-01

In the present paper we introduce a new class of p-adic measures, associated with q +1-state Potts model, called p-adic quasi Gibbs measure, which is totally different from the p-adic Gibbs measure. We establish the existence p-adic quasi Gibbs measures for the model on a Cayley tree. If q is divisible by p, then we prove the occurrence of a strong phase transition. If q and p are relatively prime, then there is a quasi phase transition. These results are totally different from the results of [F.M.Mukhamedov, U.A. Rozikov, Indag. Math. N.S. 15(2005) 85-100], since q is divisible by p, which means that q + 1 is not divided by p, so according to a main result of the mentioned paper, there is a unique and bounded p-adic Gibbs measure (different from p-adic quasi Gibbs measure). (author)

[Pott's puffy tumor: a rare complication of frontal sinusitis].

Science.gov (United States)

Aínsa Laguna, D; Pons Morales, S; Muñoz Tormo-Figueres, A; Vega Senra, M I; Otero Reigada, M C

2014-05-01

Pott's puffy tumor is a rare complication of frontal sinusitis characterized by swelling and edema in the brow due to a subperiosteal abscess associated with frontal osteomyelitis. Added complications are cellulitis by extension to the orbit and intracranial infection by posterior extension, with high risk of meningitis, intracranial abscess, and venous sinus thrombosis. Early diagnosis and aggressive medical or surgical treatment are essential for optimal recovery of affected patients. In the antibiotic age it is extremely rare, with very few cases described in the recent literature. A case is presented of a Pott inflammatory tumor in a 7 year-old boy, as a complication of acute pansinusitis who presented with front preseptal swelling and intracranial involvement with thrombosis of ophthalmic and superior orbital veins and frontal epidural abscess extending to the subarachnoid space. Copyright © 2013 Asociación Española de Pediatría. Published by Elsevier Espana. All rights reserved.

Bond-diluted interface between semi-infinite Potts bulks: criticality

International Nuclear Information System (INIS)

Cavalcanti, S.B.; Tsallis, C.

1986-01-01

Within a real space renormalisation group framework, we discuss the criticality of a system constituted by two (not necessarily equal) semi-infinite ferromagnetic q-state Potts bulks separated by an interface. This interface is a bond-diluted Potts ferromagnet with a coupling constant which is in general different from those of both bulks. The phase diagram presents four physically different phases, namely the paramagnetic one, and the surface, single bulk and double bulk ferromagnetic ones. These various phases determine a multicritical surface which contains a higher order multicritical line. The critical concentration P c that is the concentration of the interface bonds which surface magnetic ordering is possible even if the bulks are disordered. An interesting feature comes out which is that P c varies continuously with J 1 /J s and J 2 /J s . The standard two-dimensional percolation concentration is recovered for J 1 =J 2 =0. (author) [pt

Exact results on the one-dimensional Potts lattice gas

International Nuclear Information System (INIS)

Riera, R.; Chaves, C.M.G.F.

1982-12-01

An exact calculation of the Potts Lattice Gas in one dimension is presented. Close to T=O 0 K, the uniform susceptibility presents an essencial singularity, when the excharge parameter is positive, and a power law behaviour with critical exponent γ=1, when this parameter is negative. (Author) [pt

Exact results on the one-dimensional Potts lattice gas

International Nuclear Information System (INIS)

Riera, R.; Chaves, C.M.G.F.

1983-01-01

An exact calculation of the Potts Lattice Gas in one dimension is presented. Close to T=O 0 K, the uniform susceptibility presents an essential singularity, when the exchange parameter is positive, and a power law behaviour with critical exponent γ=1, when this parameter is negative. (Author) [pt

Strange attractor in the Potts spin glass on hierarchical lattices

Energy Technology Data Exchange (ETDEWEB)

Lima, Washington de [Universidade Federal de Pernambuco, Centro Acadêmico do Agreste, Pernambuco (Brazil); Camelo-Neto, G. [Universidade Federal de Alagoas, Núcleo de Ciências Exatas, Laboratório de Física Teórica e Computacional, CEP 57309-005 Arapiraca, Alagoas (Brazil); Coutinho, S., E-mail: sergio@ufpe.br [Universidade Federal de Pernambuco, Departamento de Física, Laboratório de Física Teórica e Computacional, Cidade Universitária, CEP 50670-901 Recife, Pernambuco (Brazil)

2013-11-29

The spin-glass q-state Potts model on d-dimensional diamond hierarchical lattices is investigated by an exact real space renormalization group scheme. Above a critical dimension d{sub l}(q) for q>2, the coupling constants probability distribution flows to a low-temperature strange attractor or to the high-temperature paramagnetic fixed point, according to the temperature is below or above the critical temperature T{sub c}(q,d). The strange attractor was investigated considering four initial different distributions for q=3 and d=5 presenting strong robustness in shape and temperature interval suggesting a condensed phase with algebraic decay.

Improved contact prediction in proteins: Using pseudolikelihoods to infer Potts models

Science.gov (United States)

Ekeberg, Magnus; Lövkvist, Cecilia; Lan, Yueheng; Weigt, Martin; Aurell, Erik

2013-01-01

Spatially proximate amino acids in a protein tend to coevolve. A protein's three-dimensional (3D) structure hence leaves an echo of correlations in the evolutionary record. Reverse engineering 3D structures from such correlations is an open problem in structural biology, pursued with increasing vigor as more and more protein sequences continue to fill the data banks. Within this task lies a statistical inference problem, rooted in the following: correlation between two sites in a protein sequence can arise from firsthand interaction but can also be network-propagated via intermediate sites; observed correlation is not enough to guarantee proximity. To separate direct from indirect interactions is an instance of the general problem of inverse statistical mechanics, where the task is to learn model parameters (fields, couplings) from observables (magnetizations, correlations, samples) in large systems. In the context of protein sequences, the approach has been referred to as direct-coupling analysis. Here we show that the pseudolikelihood method, applied to 21-state Potts models describing the statistical properties of families of evolutionarily related proteins, significantly outperforms existing approaches to the direct-coupling analysis, the latter being based on standard mean-field techniques. This improved performance also relies on a modified score for the coupling strength. The results are verified using known crystal structures of specific sequence instances of various protein families. Code implementing the new method can be found at http://plmdca.csc.kth.se/.

The spectrum of massive excitations of 3d 3-state Potts model and universality

International Nuclear Information System (INIS)

Falcone, R.; Fiore, R.; Gravina, M.; Papa, A.

2007-01-01

We consider the mass spectrum of the 3d 3-state Potts model in the broken phase (a) near the second order Ising critical point in the temperature-magnetic field plane and (b) near the weakly first order transition point at zero magnetic field. In the case (a), we compare the mass spectrum with the prediction from universality of mass ratios in the 3d Ising class; in the case (b), we determine a mass ratio to be compared with the corresponding one in the spectrum of screening masses of the (3+1)d SU(3) pure gauge theory at finite temperature in the deconfined phase near the transition. The agreement in the comparison in the case (a) would represent a non-trivial test of validity of the conjecture of spectrum universality. A positive answer to the comparison in the case (b) would suggest the possibility to extend this conjecture to weakly first order phase transitions

Anisotropic square lattice Potts ferromagnet: renormalization group treatment

International Nuclear Information System (INIS)

Oliveira, P.M.C. de; Tsallis, C.

1981-01-01

The choice of a convenient self-dual cell within a real space renormalization group framework enables a satisfactory treatment of the anisotropic square lattice q-state Potts ferromagnet criticality. The exact critical frontier and dimensionality crossover exponent PHI as well as the expected universality behaviour (renormalization flow sense) are recovered for any linear scaling factor b and all values of q(q - [pt

Dilute Potts chain in a magnetic field

International Nuclear Information System (INIS)

Chaves, C.M.; Riera, R.

1983-03-01

The Potts lattice gas in presence of a uniform magnetic field is solved exactly in one dimension. For negative values of the exchange parameter, the magnetization curve exhibits two or three steps, depending on the concentration of vacancies. These steps arise as a result of the competition between the exchange interaction and the magnetic field, being associated to different structural distribution of vacancies and to the magnetic ordering of one or both sublattices. (Author) [pt

Finite-size behaviour of generalized susceptibilities in the whole phase plane of the Potts model

Science.gov (United States)

Pan, Xue; Zhang, Yanhua; Chen, Lizhu; Xu, Mingmei; Wu, Yuanfang

2018-01-01

We study the sign distribution of generalized magnetic susceptibilities in the temperature-external magnetic field plane using the three-dimensional three-state Potts model. We find that the sign of odd-order susceptibility is opposite in the symmetric (disorder) and broken (order) phases, but that of the even-order one remains positive when it is far away from the phase boundary. When the critical point is approached from the crossover side, negative fourth-order magnetic susceptibility is observable. It is also demonstrated that non-monotonic behavior occurs in the temperature dependence of the generalized susceptibilities of the energy. The finite-size scaling behavior of the specific heat in this model is mainly controlled by the critical exponent of the magnetic susceptibility in the three-dimensional Ising universality class. Supported by Fund Project of National Natural Science Foundation of China (11647093, 11405088, 11521064), Fund Project of Sichuan Provincial Department of Education (16ZB0339), Fund Project of Chengdu Technological University (2016RC004) and the Major State Basic Research Development Program of China (2014CB845402)

Multi-particle structure in the Zn-chiral Potts models

International Nuclear Information System (INIS)

Gehlen, G. von; Honecker, A.

1992-10-01

We calculate the lowest translationally invariant levels of the Z 3 - and Z 4 -symmetrical chiral Potts quantum chains, using numerical diagonalization of the hamiltonian for N≤12 and N≤10 sites, respectively, and extrapolating N→∞. In the high-temperature massive phase we find that the pattern of the low-lying zero momentum levels can be explained assuming the existence of n-1 particles carrying Z n -charges Q=1, ..., n-1 (mass m Q ), and their scattering states. In the superintegrable case the masses of the n-1 particles become proportional to their respective charges: m Q =Qm 1 . Exponential convergence in N is observed for the single particle gaps, while power convergence is seen for the scattering levels. We also verify that qualitatively the same pattern appears for the self-dual and integrable cases. For general Z n we show that the energy-momentum relations of the particles show a parity non-conservation asymmetry which for very high temperatures is exclusive due to the presence of a macroscopic momentum P m =(1-2Q/n)Φ, where Φ is the chiral angle and Q is the Z n -charge of the respective particle. (orig.)

The covariance matrix of the Potts model: A random cluster analysis

International Nuclear Information System (INIS)

Borgs, C.; Chayes, J.T.

1996-01-01

We consider the covariance matrix, G mn = q 2 x ,m); δ(σ y ,n)>, of the d-dimensional q-states Potts model, rewriting it in the random cluster representation of Fortuin and Kasteleyn. In many of the q ordered phases, we identify the eigenvalues of this matrix both in terms of representations of the unbroken symmetry group of the model and in terms of random cluster connectivities and covariances, thereby attributing algebraic significance to these stochastic geometric quantities. We also show that the correlation length and the correlation length corresponding to the decay rate of one on the eigenvalues in the same as the inverse decay rate of the diameter of finite clusters. For dimension of d=2, we show that this correlation length and the correlation length of two-point function with free boundary conditions at the corresponding dual temperature are equal up to a factor of two. For systems with first-order transitions, this relation helps to resolve certain inconsistencies between recent exact and numerical work on correlation lengths at the self-dual point β o . For systems with second order transitions, this relation implies the equality of the correlation length exponents from above below threshold, as well as an amplitude ratio of two. In the course of proving the above results, we establish several properties of independent interest, including left continuity of the inverse correlation length with free boundary conditions and upper semicontinuity of the decay rate for finite clusters in all dimensions, and left continuity of the two-dimensional free boundary condition percolation probability at β o . We also introduce DLR equations for the random cluster model and use them to establish ergodicity of the free measure. In order to prove these results, we introduce a new class of events which we call decoupling events and two inequalities for these events

Pott's Puffy Tumor Arising from Frontal Sinusitis

Energy Technology Data Exchange (ETDEWEB)

Lim, Ji Yeon; Kang, Hyun Koo [Seoul Veterans Hospital, Seoul (Korea, Republic of)

2010-02-15

Pott's puffy tumor is an extremely rare and potentially life-threatening complication of frontal sinusitis. We report a case of a 64-year-old man who presented at our emergency department with mild tenderness on the glabellar area and diplopia. Computed Tomography (CT) revealed frontal sinusitis and osteomyelitis of the frontal bone. Following sinus trephination and long-term antibiotic therapy, the patient achieved a complete recovery.

Duality and the universality class of the three-state Potts antiferromagnet on plane quadrangulations

Science.gov (United States)

Lv, Jian-Ping; Deng, Youjin; Jacobsen, Jesper Lykke; Salas, Jesús; Sokal, Alan D.

2018-04-01

We provide a criterion based on graph duality to predict whether the three-state Potts antiferromagnet on a plane quadrangulation has a zero- or finite-temperature critical point, and its universality class. The former case occurs for quadrangulations of self-dual type, and the zero-temperature critical point has central charge c =1 . The latter case occurs for quadrangulations of non-self-dual type, and the critical point belongs to the universality class of the three-state Potts ferromagnet. We have tested this criterion against high-precision computations on four lattices of each type, with very good agreement. We have also found that the Wang-Swendsen-Kotecký algorithm has no critical slowing-down in the former case, and critical slowing-down in the latter.

A tree-decomposed transfer matrix for computing exact Potts model partition functions for arbitrary graphs, with applications to planar graph colourings

International Nuclear Information System (INIS)

Bedini, Andrea; Jacobsen, Jesper Lykke

2010-01-01

Combining tree decomposition and transfer matrix techniques provides a very general algorithm for computing exact partition functions of statistical models defined on arbitrary graphs. The algorithm is particularly efficient in the case of planar graphs. We illustrate it by computing the Potts model partition functions and chromatic polynomials (the number of proper vertex colourings using Q colours) for large samples of random planar graphs with up to N = 100 vertices. In the latter case, our algorithm yields a sub-exponential average running time of ∼ exp(1.516√N), a substantial improvement over the exponential running time ∼exp (0.245N) provided by the hitherto best-known algorithm. We study the statistics of chromatic roots of random planar graphs in some detail, comparing the findings with results for finite pieces of a regular lattice.

Criticality of the Potts ferromagnet in Midgal-Kadanoff - like hierarchical lattices

International Nuclear Information System (INIS)

Silva, L.R. da; Tsallis, C.

1987-01-01

Within the real space renormalisation group framework, we discuss the critical point and exponent υ of the Potts ferromagnet in b-sized Migdal-Kadanoff-like hierarchical lattices. Both b → ∞ and b → 1 limits are exhibited. The important discrepancies that might exist between the exact results for d-dimensional hierarchical lattices and d-dimensional Bravais lattices are illustrated. (Author) [pt

Une localisation exceptionnelle de la tuberculose vertébrale Mal de Pott sous-occipital

Science.gov (United States)

Yahyaoui, Sana; Majdoub, Senda; Zaghouani, Houneida; Fradj, Hosni Ben; Bakir, Dejla; Bouajina, Elyes; Kraiem, Chakib

2013-01-01

Le mal de Pott est la forme la plus commune de la tuberculose osseuse touchant essentiellement le rachis dorso-lombaire. La localisation sous-occipitale reste exceptionnelle. Le diagnostic de cette entité est le plus souvent tardif ce qui expose à des complications graves. Les radiographies standard ne sont parlantes qu’à un stade tardif de la maladie, d'où l'intérêt de l'imagerie moderne notamment la tomodensitométrie (TDM) et l'imagerie par résonance magnétique (IRM) qui permettent un diagnostic précoce. Nous rapportons un nouveau cas de tuberculose sous-occipitale. Le diagnostic était posé sur l'imagerie en coupe et confirmé histologiquement à la biopsie transorale. Sont rappelés les aspects en imagerie de cette localisation particulière du mal de Pott. PMID:23819005

Inflection points of microcanonical entropy: Monte Carlo simulation of q state Potts model on a finite square lattice

Energy Technology Data Exchange (ETDEWEB)

Praveen, E., E-mail: svmstaya@gmail.com; Satyanarayana, S. V. M., E-mail: svmstaya@gmail.com [Department of Physics, Pondicherry University, Puducherry-605014 (India)

2014-04-24

Traditional definition of phase transition involves an infinitely large system in thermodynamic limit. Finite systems such as biological proteins exhibit cooperative behavior similar to phase transitions. We employ recently discovered analysis of inflection points of microcanonical entropy to estimate the transition temperature of the phase transition in q state Potts model on a finite two dimensional square lattice for q=3 (second order) and q=8 (first order). The difference of energy density of states (DOS) Δ ln g(E) = ln g(E+ ΔE) −ln g(E) exhibits a point of inflexion at a value corresponding to inverse transition temperature. This feature is common to systems exhibiting both first as well as second order transitions. While the difference of DOS registers a monotonic variation around the point of inflexion for systems exhibiting second order transition, it has an S-shape with a minimum and maximum around the point of inflexion for the case of first order transition.

Inflection points of microcanonical entropy: Monte Carlo simulation of q state Potts model on a finite square lattice

International Nuclear Information System (INIS)

Praveen, E.; Satyanarayana, S. V. M.

2014-01-01

Traditional definition of phase transition involves an infinitely large system in thermodynamic limit. Finite systems such as biological proteins exhibit cooperative behavior similar to phase transitions. We employ recently discovered analysis of inflection points of microcanonical entropy to estimate the transition temperature of the phase transition in q state Potts model on a finite two dimensional square lattice for q=3 (second order) and q=8 (first order). The difference of energy density of states (DOS) Δ ln g(E) = ln g(E+ ΔE) −ln g(E) exhibits a point of inflexion at a value corresponding to inverse transition temperature. This feature is common to systems exhibiting both first as well as second order transitions. While the difference of DOS registers a monotonic variation around the point of inflexion for systems exhibiting second order transition, it has an S-shape with a minimum and maximum around the point of inflexion for the case of first order transition

Renormalisation-group specific heat of the square lattice Potts ferromagnet

International Nuclear Information System (INIS)

Martin, H.O.; Tsallis, C.

1982-01-01

The free and internal energies and specific heat of the q-state Potts ferromagnet are discussed. A real space renormalisation group approach is presented which recovers a considerable amount of exact particular results for all dimensionalities (hypercubic lattices). The square lattice case is calculated in detail by using self-dual clusters (which provide the exact critical point for all q). Comparison with Onsager results (q=2) is satisfactory; the general tendencies for q different 2 (1 [pt

Radiative corrections to the quark masses in the ferromagnetic Ising and Potts field theories

Directory of Open Access Journals (Sweden)

Sergei B. Rutkevich

2017-10-01

Full Text Available We consider the Ising Field Theory (IFT, and the 3-state Potts Field Theory (PFT, which describe the scaling limits of the two-dimensional lattice q-state Potts model with q=2, and q=3, respectively. At zero magnetic field h=0, both field theories are integrable away from the critical point, have q degenerate vacua in the ferromagnetic phase, and q(q−1 particles of the same mass – the kinks interpolating between two different vacua. Application of a weak magnetic field induces confinement of kinks into bound states – the “mesons” (for q=2,3 consisting predominantly of two kinks, and “baryons” (for q=3, which are essentially the three-kink excitations. The kinks in the confinement regime are also called “the quarks”. We review and refine the Form Factor Perturbation Theory (FFPT, adapting it to the analysis of the confinement problem in the limit of small h, and apply it to calculate the corrections to the kink (quark masses induced by the multi-kink fluctuations caused by the weak magnetic field. It is shown that the subleading third-order ∼h3 correction to the kink mass vanishes in the IFT. The leading second order ∼h2 correction to the kink mass in the 3-state PFT is estimated by truncation the infinite form factor expansion at the first term representing contribution of the two-kink fluctuations into the kink self-energy.

Radiative corrections to the quark masses in the ferromagnetic Ising and Potts field theories

Science.gov (United States)

Rutkevich, Sergei B.

2017-10-01

We consider the Ising Field Theory (IFT), and the 3-state Potts Field Theory (PFT), which describe the scaling limits of the two-dimensional lattice q-state Potts model with q = 2, and q = 3, respectively. At zero magnetic field h = 0, both field theories are integrable away from the critical point, have q degenerate vacua in the ferromagnetic phase, and q (q - 1) particles of the same mass - the kinks interpolating between two different vacua. Application of a weak magnetic field induces confinement of kinks into bound states - the "mesons" (for q = 2 , 3) consisting predominantly of two kinks, and "baryons" (for q = 3), which are essentially the three-kink excitations. The kinks in the confinement regime are also called "the quarks". We review and refine the Form Factor Perturbation Theory (FFPT), adapting it to the analysis of the confinement problem in the limit of small h, and apply it to calculate the corrections to the kink (quark) masses induced by the multi-kink fluctuations caused by the weak magnetic field. It is shown that the subleading third-order ∼h3 correction to the kink mass vanishes in the IFT. The leading second order ∼h2 correction to the kink mass in the 3-state PFT is estimated by truncation the infinite form factor expansion at the first term representing contribution of the two-kink fluctuations into the kink self-energy.

Surface effects in the Potts ferromagnet

International Nuclear Information System (INIS)

Tsallis, C.; Sarmento, E.F.

1984-01-01

Within a real space renormalisation group framework, the phase diagram of a semi-infinite cubic-lattice q-state Potts ferromagnet is studied, in which the free surface coupling constant J sub(S) = (1+Δ)J sub(B) might be different from the bulk one J sub(B). The starting value Δ sub(c) (q) is calculated above which surface order is possible even if bulk order is absent. Our results can be alternatively seen as approximate for the simple cubic lattice (as a matter of fact, the Ising value Δ sub(c) (2) obtained approaches the series result better than any other theory known consequently Δ sub(c) (q) is expected to be quite satisfactory even for q not= 2) or as exact for a well defined diamond-like hierarchical lattice. In the q →0 limit, Δ sub(c) diverges as 1/√q. (Author) [pt

Mean-field solution of the Potts glass near the transition temperature to the ordered phase

Czech Academy of Sciences Publication Activity Database

Janiš, Václav; Klíč, Antonín

2011-01-01

Roč. 84, č. 6 (2011), "064446-1"-"064446-10" ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100520 Keywords : Potts glass * hierarchic solutions with replicated spins * continuous replica-symmetry breaking Subject RIV: BE - Theoretical Physics Impact factor: 3.691, year: 2011

Potts ferromagnet correlation length in hypercubic lattices: Renormalization - group approach

International Nuclear Information System (INIS)

Curado, E.M.F.; Hauser, P.R.

1984-01-01

Through a real space renormalization group approach, the q-state Potts ferromagnet correlation length on hierarchical lattices is calculated. These hierarchical lattices are build in order to simulate hypercubic lattices. The high-and-low temperature correlation length asymptotic behaviours tend (in the Ising case) to the Bravais lattice correlation length ones when the size of the hierarchical lattice cells tends to infinity. It is conjectured that the asymptotic behaviours several values of q and d (dimensionality) so obtained are correct. Numerical results are obtained for the full temperature range of the correlation length. (Author) [pt

Long-range inverse two-spin correlations in one-dimensional Potts lattices

International Nuclear Information System (INIS)

Tejero, C.F.; Cuesta, J.A.; Brito, R.

1989-01-01

The inverse two-spin correlation function of a one-dimensional three-state Potts lattice with constant nearest-neighbor interactions in a uniform external field is derived exactly. It is shown that the external field induces long-range correlations. The inverse two-spin correlation function decays in a monotonic exponential fashion for a ferromagnetic lattice, while it decays in an oscillatory exponential fashion for an antiferromagnetic lattice. With no external field the inverse two-spin correlation function has a finite range equal to that of the interactions

Vertebral column decancellation in Pott's deformity: use of Surgimap Spine for preoperative surgical planning, retrospective review of 18 patients.

Science.gov (United States)

Hu, Wenhao; Zhang, Xuesong; Yu, Jiayi; Hu, Fanqi; Zhang, Hao; Wang, Yan

2018-01-15

In the late stage of Spinal tuberculosis, the bony destruction and vertebral collapse often leads to significant kyphosis, presenting clinically as a painful gibbus deformity, with increased instability, vertebral body translations and increased risk of neurologic involvement. Vertebral column decancellation is thought to be suitable for most patients with severe rigid kyphosis. Surgimap Spine, could offer a pragmatic graphical method for the surgical planning of osteotomies. The aim of this study was to evaluate the efficacy of Vertebral column decancellation planned preoperatively with the computer software-assistance in the patients with Pott's kyphosis. Between May 2012 and May 2015, 18 patients with Pott's kyphosis underwent the Vertebral column decancellation using Surgimap Spine for preoperative surgical planning. Preoperative and postoperative Konstam's angle, sagittal vertical angle, lumbar lordosis, thoracic kyphosis, pelvic tilt and pelvic incidence were measured. Visual analog scale and American Spinal Injury Association were documented. The Konstam's angles decreased from 88.1° (range, 70-105°) preoperatively to 18.5° (range, 7-31°) (P column decancellation is an effective treatment option for severe Pott's kyphosis. The surgical planning software Surgimap Spine can be a reliable and helpful tool that provides a simplified method to evaluate and analyze the spino-pelvic parameters and simulate the osteotomy procedure. According to individual character, the appropriate surgery strategy should be selected.

Parallel family trees for transfer matrices in the Potts model

Science.gov (United States)

Navarro, Cristobal A.; Canfora, Fabrizio; Hitschfeld, Nancy; Navarro, Gonzalo

2015-02-01

The computational cost of transfer matrix methods for the Potts model is related to the question in how many ways can two layers of a lattice be connected? Answering the question leads to the generation of a combinatorial set of lattice configurations. This set defines the configuration space of the problem, and the smaller it is, the faster the transfer matrix can be computed. The configuration space of generic (q , v) transfer matrix methods for strips is in the order of the Catalan numbers, which grows asymptotically as O(4m) where m is the width of the strip. Other transfer matrix methods with a smaller configuration space indeed exist but they make assumptions on the temperature, number of spin states, or restrict the structure of the lattice. In this paper we propose a parallel algorithm that uses a sub-Catalan configuration space of O(3m) to build the generic (q , v) transfer matrix in a compressed form. The improvement is achieved by grouping the original set of Catalan configurations into a forest of family trees, in such a way that the solution to the problem is now computed by solving the root node of each family. As a result, the algorithm becomes exponentially faster than the Catalan approach while still highly parallel. The resulting matrix is stored in a compressed form using O(3m ×4m) of space, making numerical evaluation and decompression to be faster than evaluating the matrix in its O(4m ×4m) uncompressed form. Experimental results for different sizes of strip lattices show that the parallel family trees (PFT) strategy indeed runs exponentially faster than the Catalan Parallel Method (CPM), especially when dealing with dense transfer matrices. In terms of parallel performance, we report strong-scaling speedups of up to 5.7 × when running on an 8-core shared memory machine and 28 × for a 32-core cluster. The best balance of speedup and efficiency for the multi-core machine was achieved when using p = 4 processors, while for the cluster

Short-time dynamics of random-bond Potts ferromagnet with continuous self-dual quenched disorders

OpenAIRE

Pan, Z. Q.; Ying, H. P.; Gu, D. W.

2001-01-01

We present Monte Carlo simulation results of random-bond Potts ferromagnet with the Olson-Young self-dual distribution of quenched disorders in two-dimensions. By exploring the short-time scaling dynamics, we find universal power-law critical behavior of the magnetization and Binder cumulant at the critical point, and thus obtain estimates of the dynamic exponent $z$ and magnetic exponent $\\eta$, as well as the exponent $\\theta$. Our special attention is paid to the dynamic process for the $q...

Transcatheter Potts shunt creation in patients with severe pulmonary arterial hypertension: initial clinical experience.

Science.gov (United States)

Esch, Jesse J; Shah, Pinak B; Cockrill, Barbara A; Farber, Harrison W; Landzberg, Michael J; Mehra, Mandeep R; Mullen, Mary P; Opotowsky, Alexander R; Waxman, Aaron B; Lock, James E; Marshall, Audrey C

2013-04-01

Patients with severe pulmonary arterial hypertension (PAH) face significant morbidity and death as a consequence of progressive right heart failure. Surgical shunt placement between the left PA and descending aorta (Potts shunt) appears promising for PAH palliation in children; however, surgical mortality is likely to be unacceptably high in adults with PAH. We describe a technique for transcatheter Potts shunt (TPS) creation by fluoroscopically guided retrograde needle perforation of the descending aorta at the site of apposition to the left PA to create a tract for deployment of a covered stent between these vessels. This covered stent-anchored by the vessel walls and surrounding tissue-serves as the shunt. TPS creation was considered in 7 patients and performed in 4. The procedure was technically successful in 3 patients; 1 patient died during the procedure as a result of uncontrolled hemothorax. One acute survivor, critically ill at the time of TPS creation, later died of comorbidities. The 2 mid-term survivors (follow-up of 10 and 4 months) are well at home, with symptomatic improvement and no late complications. The 3 candidate patients in whom the procedure was not performed died within 1 month of consideration, underscoring the tenuous nature of this population. TPS creation is feasible and may offer symptomatic relief to select patients with refractory PAH. Further study of this innovative approach is warranted. Copyright © 2013 International Society for Heart and Lung Transplantation. Published by Elsevier Inc. All rights reserved.

Anisotropic cubic lattice potts ferromagnet: renormalisation group treatment

International Nuclear Information System (INIS)

Tsallis, C.; Schwaccheim, G.; Silva, L.R. da; Rio Grande do Norte Univ., Natal

1983-01-01

Within a real space renormalisation group framework, the criticality of the fully anisotropic (arbitrary J sub(x), J sub(y) and J sub(z)) q-state Potts ferromagnet in simple cubic lattice is discussed. Several already known exact results for the d=1 and d=2 particular cases are recovered. Furthermore it is obtained: (i) the q-dependence of the d=3 correlation length critical exponent ν 3 (in particular, if q→0, ν 3 (q) approximatelly ν 3 (0)+ν 3 '(0)q) where the present approximate values are ν 3 (0) or approx.= 1.105 and ν 3 '(0) or approx.=-0.66; (ii) the q-dependence d=2 d=3 crossover critical exponent phi 23 (in particular, phi 23 varies as 1/√q if q Q→0); (iii) through a convenient numerical extrapolation, a quite accurate proposal for the critical temperatures corresponding to arbitrary ratios J sub(y)/ J sub(x) and J sub(z) / J sub(x) and values of q. (Author) [pt

Optimized broad-histogram simulations for strong first-order phase transitions: droplet transitions in the large-Q Potts model

International Nuclear Information System (INIS)

Bauer, Bela; Troyer, Matthias; Gull, Emanuel; Trebst, Simon; Huse, David A

2010-01-01

The numerical simulation of strongly first-order phase transitions has remained a notoriously difficult problem even for classical systems due to the exponentially suppressed (thermal) equilibration in the vicinity of such a transition. In the absence of efficient update techniques, a common approach for improving equilibration in Monte Carlo simulations is broadening the sampled statistical ensemble beyond the bimodal distribution of the canonical ensemble. Here we show how a recently developed feedback algorithm can systematically optimize such broad-histogram ensembles and significantly speed up equilibration in comparison with other extended ensemble techniques such as flat-histogram, multicanonical and Wang–Landau sampling. We simulate, as a prototypical example of a strong first-order transition, the two-dimensional Potts model with up to Q = 250 different states in large systems. The optimized histogram develops a distinct multi-peak structure, thereby resolving entropic barriers and their associated phase transitions in the phase coexistence region—such as droplet nucleation and annihilation, and droplet–strip transitions for systems with periodic boundary conditions. We characterize the efficiency of the optimized histogram sampling by measuring round-trip times τ(N, Q) across the phase transition for samples comprised of N spins. While we find power-law scaling of τ versus N for small Q∼ 2 , we observe a crossover to exponential scaling for larger Q. These results demonstrate that despite the ensemble optimization, broad-histogram simulations cannot fully eliminate the supercritical slowing down at strongly first-order transitions

Optimized broad-histogram simulations for strong first-order phase transitions: droplet transitions in the large-Q Potts model

Science.gov (United States)

Bauer, Bela; Gull, Emanuel; Trebst, Simon; Troyer, Matthias; Huse, David A.

2010-01-01

The numerical simulation of strongly first-order phase transitions has remained a notoriously difficult problem even for classical systems due to the exponentially suppressed (thermal) equilibration in the vicinity of such a transition. In the absence of efficient update techniques, a common approach for improving equilibration in Monte Carlo simulations is broadening the sampled statistical ensemble beyond the bimodal distribution of the canonical ensemble. Here we show how a recently developed feedback algorithm can systematically optimize such broad-histogram ensembles and significantly speed up equilibration in comparison with other extended ensemble techniques such as flat-histogram, multicanonical and Wang-Landau sampling. We simulate, as a prototypical example of a strong first-order transition, the two-dimensional Potts model with up to Q = 250 different states in large systems. The optimized histogram develops a distinct multi-peak structure, thereby resolving entropic barriers and their associated phase transitions in the phase coexistence region—such as droplet nucleation and annihilation, and droplet-strip transitions for systems with periodic boundary conditions. We characterize the efficiency of the optimized histogram sampling by measuring round-trip times τ(N, Q) across the phase transition for samples comprised of N spins. While we find power-law scaling of τ versus N for small Q \\lesssim 50 and N \\lesssim 40^2 , we observe a crossover to exponential scaling for larger Q. These results demonstrate that despite the ensemble optimization, broad-histogram simulations cannot fully eliminate the supercritical slowing down at strongly first-order transitions.

Le mal de pott sous occipital révélé par un abcès rétro pharyngien a ...

African Journals Online (AJOL)

Introduction : Pott's disease is the most frequent localisation of osteo-articular tuberculosis. The suboccipital localisation remains rare. Case report : A 12-years old boy, admitted for cervicalgy and dysphagia. His clinical exam revealed a swelling of posterior pharyngeal wall associated with a basicervical tumefaction ...

A cellular Potts model for the MMP-dependent and -independent cancer cell migration in matrix microtracks of different dimensions

Science.gov (United States)

Scianna, Marco; Preziosi, Luigi

2014-03-01

Cell migration is fundamental in a wide variety of physiological and pathological phenomena, among other in cancer invasion and development. In particular, the migratory/invasive capability of single metastatic cells is fundamental in determining the malignancy of a solid tumor. Specific cell migration phenotypes result for instance from the reciprocal interplay between the biophysical and biochemical properties of both the malignant cells themselves and of the surrounding environment. In particular, the extracellular matrices (ECMs) forming connective tissues can provide both loosely organized zones and densely packed barriers, which may impact cell invasion mode and efficiency. The critical processes involved in cell movement within confined spaces are (i) the proteolytic activity of matrix metalloproteinases (MMPs) and (ii) the deformation of the entire cell body, and in particular of the nucleus. We here present an extended cellular Potts model (CPM) to simulate a bio-engineered matrix system, which tests the active motile behavior of a single cancer cell into narrow channels of different widths. As distinct features of our approach, the cell is modeled as a compartmentalized discrete element, differentiated in the nucleus and in the cytosolic region, while a directional shape-dependent movement is explicitly driven by the evolution of its polarity vector. As outcomes, we find that, in a large track, the tumor cell is not able to maintain a directional movement. On the contrary, a structure of subcellular width behaves as a contact guidance sustaining cell persistent locomotion. In particular, a MMP-deprived cell is able to repolarize and follow the micropattern geometry, while a full MMP activity leads to a secondary track expansion by degrading the matrix structure. Finally, we confirm that cell movement within a subnuclear structure can be achieved either by pericellular proteolysis or by a significant deformation of cell nucleus.

On the critical point of the fully-anisotropic quenched bond-random Potts ferromagnet in triangular and honeycomb lattices

International Nuclear Information System (INIS)

Tsallis, C.; Santos, R.J.V. dos

1983-01-01

On conjectural grounds an equation that provides a very good approximation for the critical temperature of the fully-anisotropic homogeneous quenched bond-random q-state Potts ferromagnet in triangular and honeycomb lattices is presented. Almost all the exact particular results presently known for the square, triangular and honeycomb lattices are recovered; the numerical discrepancy is quite small for the few exceptions. Some predictions that we believe to be exact are made explicite as well. (Author) [pt

Conjecture on the critical frontier of the fully anisotropic homogeneous quenched bond-mixed potts ferromagnet in square lattice

International Nuclear Information System (INIS)

Tsallis, C.

1980-01-01

It is conjectured that a logarithmic provides a very accurate approximation of the yet unknown critical frontier of a fully anisotropic homogeneous quenched bond-mixed q-state Potts ferromagnet in square lattice, where the random coupling constant J is distributed according to the laws P(J) and P'(J) for 'horizontal' and 'vertical' bonds respectively. Such an equation contains as particular cases a great number of exact results as well as a few recent conjectures (which are definitively only approximate). (Author) [pt

How self-reliance is understood: viewpoints from one local ...

African Journals Online (AJOL)

How self-reliance is understood: viewpoints from one local community in Malawi. ... model that resists dependence on external aid, empowers community development, and provides opportunities to sustain development activity through local initiative, can be employed to increase social capital leading to sustainable growth.

Clinical pattern of Pott's disease of the spine, outcome of treatment and prognosis in adult Sudanese patients

Energy Technology Data Exchange (ETDEWEB)

Mbbs, El Bashir Gusm Elbari Ahmed [Clinical Medicine, University of Khartoum, Khartoum (Sudan)

1997-04-01

Fifty patients admitted to Khartoum Teaching Hospital and Shaab Teaching Hospital in the period from October 1994- October 1996 and diagnosed as Pott's disease of spine were included in the study. Patients below the age of 15 years were excluded. Full history and physical examination were performed in each patients. Haemoglobin concentration, Packed cell volume . (PCV) Erythrocyte Sedimentation Rate (ESR), White Blood Cell Count total and differential were done for all patients together with chest X-Ray, spinal X-Ray A. P. and lateral views. Myelogram, CT Scan, Mantoux and CSF examinations were done when needed.The main age of the study group was 41.3{+-}17.6 years, with male to female ratio of 30-20 (3:2). Tuberculoses spondylitis affect the cervical spines in 2 cases (3.45%), the upper thoracic in 10 cases (17.24%), mid thoracic 20 times (34.48%), lower thoracic 20 cases (34>48%), lumber spines 6 cases (10.35%) and no lesion in the sacral spines. Pulmonary tuberculosis was found in 18 patients (36%) together with Pott's disease of the spine.All patients came with back pain, lower limbs weakness and the course of the disease was progressive, 35 patients (70%) were unable to walk, and the sphincters were affected in 37 patients (74%) of the cases.On medical treatment 37 patients (74%) showed progressive improvement, 5 patients (10%) remained static or deteriorated and 8 patients (16%) died. 2 of those who died had developed severe bed sores and anemia before death, 3 of them developed deep vein thrombosis (DVT) and died even though they started anticoagulant therapy, two patients developed drug induced hepatitis and died in spite of stopping the drugs, and one patient had got militry tuberculosis showed no adverse effect on outcome of treatment. Surgery done on two patients showed good outcome.(Author)

Clinical pattern of Pott's disease of the spine, outcome of treatment and prognosis in adult Sudanese patients

International Nuclear Information System (INIS)

Mbbs, El Bashir Gusm Elbari Ahmed

1997-04-01

Fifty patients admitted to Khartoum Teaching Hospital and Shaab Teaching Hospital in the period from October 1994- October 1996 and diagnosed as Pott's disease of spine were included in the study. Patients below the age of 15 years were excluded. Full history and physical examination were performed in each patients. Haemoglobin concentration, Packed cell volume . (PCV) Erythrocyte Sedimentation Rate (ESR), White Blood Cell Count total and differential were done for all patients together with chest X-Ray, spinal X-Ray A. P. and lateral views. Myelogram, CT Scan, Mantoux and CSF examinations were done when needed.The main age of the study group was 41.3±17.6 years, with male to female ratio of 30-20 (3:2). Tuberculoses spondylitis affect the cervical spines in 2 cases (3.45%), the upper thoracic in 10 cases (17.24%), mid thoracic 20 times (34.48%), lower thoracic 20 cases (34>48%), lumber spines 6 cases (10.35%) and no lesion in the sacral spines. Pulmonary tuberculosis was found in 18 patients (36%) together with Pott's disease of the spine.All patients came with back pain, lower limbs weakness and the course of the disease was progressive, 35 patients (70%) were unable to walk, and the sphincters were affected in 37 patients (74%) of the cases.On medical treatment 37 patients (74%) showed progressive improvement, 5 patients (10%) remained static or deteriorated and 8 patients (16%) died. 2 of those who died had developed severe bed sores and anemia before death, 3 of them developed deep vein thrombosis (DVT) and died even though they started anticoagulant therapy, two patients developed drug induced hepatitis and died in spite of stopping the drugs, and one patient had got militry tuberculosis showed no adverse effect on outcome of treatment. Surgery done on two patients showed good outcome.(Author)

Frontiers and critical expoents in percolation and Ising and Potts ferromagnets: renormalization group and others techniques

International Nuclear Information System (INIS)

Magalhaes, A.C.N. de.

1982-01-01

By using real space renormalization group methods, bond percolation on d-dimensional hypercubic (d = 2, 3, 4), first - and second - neighbour isotropic square, anisotropic square and 'inhomogeneous' 4-8 lattices is studied. Through some extrapolation methods, critical points and/or frontiers are obtained (as well as the critical exponent ν sub(p) in the isotropic cases) for these lattices that, or agree well with other available results, or are new as far as it is know (first - and second - neighbour isotropic square and 'inhomogeneous' 4-8 lattices). A conjecture concerning approximate (eventually exact) critical points and, in certain situations, critical frontiers of q-state Potts ferromagnets on d-dimensional lattices (d > 1) is formulated. This conjecture is verified within good accuracy for all the lattices whose critical points are known, and it allows the prediction of a great number of new results, some of them it is believed to be exact. Within a real space renomalization group framework, accurate approximations for the critical frontiers associated with the quenched bond-diluted first-neighbour spin-1/2 Ising ferromagnet on triangular and honeycomb lattices are calculated. The best numerical proposals lead, in both pure bond percolation (p = p sub(c)) and pure Ising (p = 1) limits, to the exact critical points and (dt 0 /dp) sub(p = p sub(c)) (where t 0 identical to tanh J/K sub(B) T), and to a 0.15% (0.96%) error in (dt 0 /dp) sub(p = 1) for the triangular (honeycomb) lattice; for p sub(c) 0 (for fixed p) of 0.27% (0.14%) is estimated for the triangular (honeycomb) lattice. It is exhibited, for many star-triangle graph pairs with any number of terminals and different sizes, that the exact q = 1, 2, 3, 4 critical points of Potts ferromagnets can aZZ of them, be obtained from any one of such graph pairs. (Author) [pt

Single-cluster dynamics for the random-cluster model

NARCIS (Netherlands)

Deng, Y.; Qian, X.; Blöte, H.W.J.

2009-01-01

We formulate a single-cluster Monte Carlo algorithm for the simulation of the random-cluster model. This algorithm is a generalization of the Wolff single-cluster method for the q-state Potts model to noninteger values q>1. Its results for static quantities are in a satisfactory agreement with those

The fitness landscape of HIV-1 gag: advanced modeling approaches and validation of model predictions by in vitro testing.

Directory of Open Access Journals (Sweden)

Jaclyn K Mann

2014-08-01

Full Text Available Viral immune evasion by sequence variation is a major hindrance to HIV-1 vaccine design. To address this challenge, our group has developed a computational model, rooted in physics, that aims to predict the fitness landscape of HIV-1 proteins in order to design vaccine immunogens that lead to impaired viral fitness, thus blocking viable escape routes. Here, we advance the computational models to address previous limitations, and directly test model predictions against in vitro fitness measurements of HIV-1 strains containing multiple Gag mutations. We incorporated regularization into the model fitting procedure to address finite sampling. Further, we developed a model that accounts for the specific identity of mutant amino acids (Potts model, generalizing our previous approach (Ising model that is unable to distinguish between different mutant amino acids. Gag mutation combinations (17 pairs, 1 triple and 25 single mutations within these predicted to be either harmful to HIV-1 viability or fitness-neutral were introduced into HIV-1 NL4-3 by site-directed mutagenesis and replication capacities of these mutants were assayed in vitro. The predicted and measured fitness of the corresponding mutants for the original Ising model (r = -0.74, p = 3.6×10-6 are strongly correlated, and this was further strengthened in the regularized Ising model (r = -0.83, p = 3.7×10-12. Performance of the Potts model (r = -0.73, p = 9.7×10-9 was similar to that of the Ising model, indicating that the binary approximation is sufficient for capturing fitness effects of common mutants at sites of low amino acid diversity. However, we show that the Potts model is expected to improve predictive power for more variable proteins. Overall, our results support the ability of the computational models to robustly predict the relative fitness of mutant viral strains, and indicate the potential value of this approach for understanding viral immune evasion

A thermodynamic counterpart of the Axelrod model of social influence: The one-dimensional case

Science.gov (United States)

Gandica, Y.; Medina, E.; Bonalde, I.

2013-12-01

We propose a thermodynamic version of the Axelrod model of social influence. In one-dimensional (1D) lattices, the thermodynamic model becomes a coupled Potts model with a bonding interaction that increases with the site matching traits. We analytically calculate thermodynamic and critical properties for a 1D system and show that an order-disorder phase transition only occurs at T=0 independent of the number of cultural traits q and features F. The 1D thermodynamic Axelrod model belongs to the same universality class of the Ising and Potts models, notwithstanding the increase of the internal dimension of the local degree of freedom and the state-dependent bonding interaction. We suggest a unifying proposal to compare exponents across different discrete 1D models. The comparison with our Hamiltonian description reveals that in the thermodynamic limit the original out-of-equilibrium 1D Axelrod model with noise behaves like an ordinary thermodynamic 1D interacting particle system.

Feeling (Mis)Understood and Intergroup Friendships in Interracial Interactions.

Science.gov (United States)

Shelton, Nicole; Douglass, Sara; Garcia, Randi L; Yip, Tiffany; Trail, Thomas E

2014-09-01

The present research investigated whether having out-group friends serves as a buffer for feeling misunderstood in interracial interactions. Across three experience sampling studies, we found that among ethnic minorities who have few White friends or are not interacting with White friends, daily interracial interactions are associated with feeling less understood. By contrast, we found that among ethnic minorities who have more White friends or are interacting with White friends, the relationship between daily interracial interactions and feeling understood is not significant. We did not find similar results for Whites; that is, having ethnic minority friends did not play a role in the relationship between daily interracial interactions and feeling understood. Together, these studies demonstrate the beneficial effects of intergroup friendships for ethnic minorities. © 2014 by the Society for Personality and Social Psychology, Inc.

Ground state entropy of the Potts antiferromagnet on triangular lattice strips

International Nuclear Information System (INIS)

Chang Shuchiuan; Shrock, Robert

2001-01-01

We present exact calculations of the zero-temperature partition function (chromatic polynomial) P for the q-state Potts antiferromagnet on triangular lattice strips of arbitrarily great length L x vertices and of width L y vertices and, in the L x →∞ limit, the exponent of the ground state entropy, W=e S 0 /k B . The strips considered, with their boundary conditions (BC), are (a) (FBC y , PBC x ) = cyclic for L y =3, 4, (b) (FBC y , TPBC x ) = Moebius, L y =3, (c) (PBC y , PBC x ) = toroidal, L y =3, (d) (PBC y , TPBC x ) = Klein bottle, L y =3, (e) (PBC y , FBC x ) = cylindrical, L y =5, 6, and (f) (FBC y , FBC x ) = free, L y =5, where F, P, and TP denote free, periodic, and twisted periodic. Several interesting features are found, including the presence of terms in P proportional to cos(2πL x /3) for case (c). The continuous locus of points B where W is nonanalytic in the q plane is discussed for each case and a comparative discussion is given of the respective loci B for families with different boundary conditions. Numerical values of W are given for infinite-length strips of various widths and are shown to approach values for the 2D lattice rapidly. A remark is also made concerning a zero-free region for chromatic zeros. Some results are given for strips of other lattices

Poorly Understood Aspects of Striated Muscle Contraction

Directory of Open Access Journals (Sweden)

Alf Månsson

2015-01-01

Full Text Available Muscle contraction results from cyclic interactions between the contractile proteins myosin and actin, driven by the turnover of adenosine triphosphate (ATP. Despite intense studies, several molecular events in the contraction process are poorly understood, including the relationship between force-generation and phosphate-release in the ATP-turnover. Different aspects of the force-generating transition are reflected in the changes in tension development by muscle cells, myofibrils and single molecules upon changes in temperature, altered phosphate concentration, or length perturbations. It has been notoriously difficult to explain all these events within a given theoretical framework and to unequivocally correlate observed events with the atomic structures of the myosin motor. Other incompletely understood issues include the role of the two heads of myosin II and structural changes in the actin filaments as well as the importance of the three-dimensional order. We here review these issues in relation to controversies regarding basic physiological properties of striated muscle. We also briefly consider actomyosin mutation effects in cardiac and skeletal muscle function and the possibility to treat these defects by drugs.

Instrumentação anterior da coluna em espondilite tuberculosa mal de pott: Relato de caso

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Farage Luciano

2002-01-01

Full Text Available Relatamos caso de tratamento cirúrgico com instrumentação anterior em espondilite tuberculosa (mal de Pott, em mulher de 71 anos, que se encontrava em tratamento para tuberculose na forma pulmonar e evoluiu com dor lombar, dificuldade progressiva para deambular, cifose e disfunção vesical. A ressonância magnética revelou lesão nos corpos vertebrais de T12 e L1 com abcesso paravertebral. A paciente foi tratada cirurgicamente por acesso tóraco-abdominal lateral. Os corpos vertebrais foram ressecados, foi instalado uma gaiola vertical (mesh cage e a coluna foi estabilizada com placa lateral (Z plate e parafusos fixados em T11 e L2. Essa técnica permite boa artrodese dos corpos vertebrais remanescentes e boa estabilidade da coluna, sem comprometer a eficácia dos tuberculostáticos. A paciente foi avaliada um ano após a operação e não apresentava déficit motor, dor residual e a cifose foi desfeita.

A fatal case of spinal tuberculosis mistaken for metastatic lung cancer: recalling ancient Pott's disease

Directory of Open Access Journals (Sweden)

Duchna Hans-Werner

2009-11-01

Full Text Available Abstract Background Tuberculous spondylitis (Pott's disease is an ancient human disease. Because it is rare in high-income, tuberculosis (TB low incidence countries, misdiagnoses occur as sufficient clinical experience is lacking. Case presentation We describe a fatal case of a patient with spinal TB, who was mistakenly irradiated for suspected metastatic lung cancer of the spine in the presence of a solitary pulmonary nodule of the left upper lobe. Subsequently, the patient progressed to central nervous system TB, and finally, disseminated TB before the accurate diagnosis was established. Isolation and antimycobacterial chemotherapy were initiated after an in-hospital course of approximately three months including numerous health care related contacts and procedures. Conclusion The rapid diagnosis of spinal TB demands a high index of suspicion and expertise regarding the appropriate diagnostic procedures. Due to the devastating consequences of a missed diagnosis, Mycobacterium tuberculosis should be considered early in every case of spondylitis, intraspinal or paravertebral abscess. The presence of certain alarm signals like a prolonged history of progressive back pain, constitutional symptoms or pulmonary nodules on a chest radiograph, particularly in the upper lobes, may guide the clinical suspicion.

Bethe ansatz study for ground state of Fateev Zamolodchikov model

International Nuclear Information System (INIS)

Ray, S.

1997-01-01

A Bethe ansatz study of a self-dual Z N spin lattice model, originally proposed by V. A. Fateev and A. B. Zamolodchikov, is undertaken. The connection of this model to the Chiral Potts model is established. Transcendental equations connecting the zeros of Fateev endash Zamolodchikov transfer matrix are derived. The free energies for the ferromagnetic and the anti-ferromagnetic ground states are found for both even and odd spins. copyright 1997 American Institute of Physics

A Literature Review of Empowerment With a Suggested Empowerment Model for the BDF

Science.gov (United States)

2003-12-01

rights movement, feminism , and others. Potterfield (1999) indicates that through personal conversation with management and employee empowerment...corporate culture and the style of management. Potts and Sykes (1993, p.63) state: In the traditional corporate culture, policy manuals often...Connecticut, 1999. 19. Potts, T. and Sykes , A., Executive Talent, 1st ed., Irwin, Illinois, 1993. 20. Quinn, R.E. and Spreitzer, G.M., “The Road

Random defect lines in conformal minimal models

International Nuclear Information System (INIS)

Jeng, M.; Ludwig, A.W.W.

2001-01-01

We analyze the effect of adding quenched disorder along a defect line in the 2D conformal minimal models using replicas. The disorder is realized by a random applied magnetic field in the Ising model, by fluctuations in the ferromagnetic bond coupling in the tricritical Ising model and tricritical three-state Potts model (the phi 12 operator), etc. We find that for the Ising model, the defect renormalizes to two decoupled half-planes without disorder, but that for all other models, the defect renormalizes to a disorder-dominated fixed point. Its critical properties are studied with an expansion in ε∝1/m for the mth Virasoro minimal model. The decay exponents X N =((N)/(2))1-((9(3N-4))/(4(m+1) 2 ))+O((3)/(m+1)) 3 of the Nth moment of the two-point function of phi 12 along the defect are obtained to 2-loop order, exhibiting multifractal behavior. This leads to a typical decay exponent X typ =((1)/(2))1+((9)/((m+1) 2 ))+O((3)/(m+1)) 3 . One-point functions are seen to have a non-self-averaging amplitude. The boundary entropy is larger than that of the pure system by order 1/m 3 . As a byproduct of our calculations, we also obtain to 2-loop order the exponent X-tilde N =N1-((2)/(9π 2 ))(3N-4)(q-2) 2 +O(q-2) 3 of the Nth moment of the energy operator in the q-state Potts model with bulk bond disorder

3D-Ising model as a string theory in three-dimensional euclidean space

International Nuclear Information System (INIS)

Sedrakyan, A.

1992-11-01

A three-dimensional string model is analyzed in the strong coupling regime. The contribution of surfaces with different topology to the partition function is essential. A set of corresponding models is discovered. Their critical indices, which depend on two integers (m,n) are calculated analytically. The critical indices of the three-dimensional Ising model should belong to this set. A possible connection with the chain of three dimensional lattice Pott's models is pointed out. (author) 22 refs.; 2 figs

Urachal tumour: case report of a poorly understood carcinoma

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Vallarino Luigi

2009-11-01

Full Text Available Abstract Background Urachal carcinoma is an uncommon neoplasm associated with poor prognosis. Case presentation A 45-year-old man was admitted with complaints of abdominal pain and pollakisuria. A soft mass was palpable under his navel. TC-scan revealed a 11 × 6 cm tumor, which was composed of a cystic lesion arising from the urachus and a solid mass component at the urinary bladder dome. The tumor was removed surgically. Histological examination detected poor-differentiated adenocarcinoma, which had invaded the urinary bladder. The patient has been followed up without recurrence for 6 months. Conclusion The urachus is the embryological remnant of urogenital sinus and allantois. Involution usually happens before birth and urachus is present as a median umbilical ligament. The pathogenesis of urachal tumours is not fully understood. Surgery is the treatment of choice and role of adjuvant treatment is not clearly understood.

Modelling microstructural evolution under irradiation

International Nuclear Information System (INIS)

Tikare, V.

2015-01-01

Microstructural evolution of materials under irradiation is characterised by some unique features that are not typically present in other application environments. While much understanding has been achieved by experimental studies, the ability to model this microstructural evolution for complex materials states and environmental conditions not only enhances understanding, it also enables prediction of materials behaviour under conditions that are difficult to duplicate experimentally. Furthermore, reliable models enable designing materials for improved engineering performance for their respective applications. Thus, development and application of mesoscale microstructural model are important for advancing nuclear materials technologies. In this chapter, the application of the Potts model to nuclear materials will be reviewed and demonstrated, as an example of microstructural evolution processes. (author)

On exotic supersymmetries of the φ1,3 deformation of minimal models

International Nuclear Information System (INIS)

Kadiri, A.; Saidi, E.H.; Zerouaoui, S.J.; Sedra, M.B.

1994-07-01

Using algebraic and field theoretical methods, we study the fractional spin symmetries of the φ 1,3 deformation of minimal models. The particular example of the D=2 three state tricritical Potts model is examined in detail. Various models based on subalgebras and appropriate discrete automorphism groups of the two dimensional fractional spin algebra are obtained. General features such as superspace and superfield representations, the U q (sl 2 ) symmetry, the spontaneous exotic supersymmetry breaking, relations with the N=2 Landau Ginzburg models as well as other things are discussed. (author). 24 refs

Mal de Pott en pediatría: presentación de 5 casos y revisión de la literatura

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Gladys Abreu Suárez

2002-09-01

Full Text Available Se presentan 5 de los 6 niños afectados de mal de Pott en el período de 1995 a 2001, para una incidencia del 4,5 % del total de casos de tuberculosis infantil en Cuba. La mayoría de los niños tenía alrededor de 2 años de edad, con un predominio de la afectación lumbar en 4 pacientes. El cuadro clínico fue insidioso, y fueron más frecuentes el dolor de espalda y los trastornos a la marcha. El diagnóstico fue clinicorradiológico, y la tuberculina positiva en 4 niños. Sólo se aisló Micobacterium tuberculosis en un paciente, en el que concomitaban lesiones pulmonares. En 3 enfermos se hallaron abscesos paravertebrales (2 en la región dorsal, y el otro en el psoas. Aún se encuentran 3 pacientes en tratamiento; de los 2 curados, uno tiene pérdida de la lordosis fisiológica lumbar, y otro perdió un cuerpo vertebral con una giba residual ligera. Se concluye que, aunque la tuberculosis infantil no es un problema de salud en Cuba, y el mal de Pott no es frecuente, debe tenerse en cuenta ante un niño pequeño que se consulte con manifestaciones insidiosas de trastornos de la marcha y dolor de espalda.5 of the 6 children affected by Pott’s disease from 1995 to 2001 are presented in this paper for an incidence of 4.5 % of the total of cases of infantile tuberculosis in Cuba. Most of the children were about 2 years old. A predominance of lumbar affection was observed in 4 patients. The clinical picture was insidious and back pain and walking disorders were more frequent. The diagnosis was clinicoradiological and tuberculin was positive in 4 children. Micobacterium tuberculosis was only isolated from a patient with concomitant pulmonary injuries. Paravertebral abscesses (2 in the dorsal region and the other in the psoas were found in 3 patients. There are still 3 patients under treatment: one of the two that were cured suffers from loss of the physiological lumbar lordosis and the other lost a vertebral body and presents a mild residual

The n-component cubic model and flows: subgraph break-collapse method

International Nuclear Information System (INIS)

Essam, J.W.; Magalhaes, A.C.N. de.

1988-01-01

We generalise to the n-component cubic model the subgraph break-collapse method which we previously developed for the Potts model. The relations used are based on expressions which we recently derived for the Z(λ) model in terms of mod-λ flows. Our recursive algorithm is similar, for n = 2, to the break-collapse method for the Z(4) model proposed by Mariz and coworkers. It allows the exact calculation for the partition function and correlation functions for n-component cubic clusters with n as a variable, without the need to examine all of the spin configurations. (author) [pt

Le mal de Pott: à propos de 82 cas

Directory of Open Access Journals (Sweden)

Badr Fedoul

2011-03-01

Full Text Available Nous rapportant dans cette étude, les résultats de l’expérience du service de neurochirurgie du CHU Hassan II de Fès dans la prise en charge du mal de pott dans la région de Fès. Il s’agit d’une étude rétrospective de quatre-vingt-deux cas; étalée sur une période de cinq ans (janvier 2002 au décembre 2006. L’objectif de ce travail était d’illustrer les différents aspects épidémiologiques, diagnostiques et thérapeutiques de la localisation vertébrale de la tuberculose dans notre pratique. L'âge moyen de nos patients était de 43,1 ans, avec une légère prédominance féminine (53,82%. La durée d'évolution de la maladie était longue (dix mois en moyenne; ceci est expliquée par la symptomatologie initiale insidieuse faite de rachialgies (98,78% et une admission des patients au stade de complications neurologiques (41,46%. La radiographie standard était réalisée chez tous nos patients, et complétée par la TDM dans 86.58% des cas ce qui a permis de déceler la prédominance de l'atteinte dorsale et lombaire. L'IRM est l'examen de choix, elle était demandée chez tous les malades déficitaires (37,8%.Tous nos patients ont bénéficié d'un traitement antibacillaire associé à une immobilisation du foyer pottique. Une décompression par voie antérieure était réalisée chez 29 patients (35,36 %; alors que la laminectomie n'était pratiquée que chez 5 patients (6.09 %, tandis que l'évacuation de l'abcès de psoas était réalisée chez 25 patients (30,48 %. Le diagnostic de certitude histologique était posé dans 51 cas (62,19%. Les meilleurs résultats étaient obtenus chez les malades opérés par voie antérieure, 26 cas (89,65% de récupération totale et 3 cas (10,34% partielle. L'évolution vers la consolidation et la fusion vertébrale était la règle chez tous nos malades et ceci au bout de 4 à 18 mois après le traitement.

Graph Based Models for Unsupervised High Dimensional Data Clustering and Network Analysis

Science.gov (United States)

2015-01-01

A. Porter and my advisor. The text is primarily written by me. Chapter 5 is a version of [46] where my contribution is all of the analytical ...inn Euclidean space, a variational method refers to using calculus of variation techniques to find the minimizer (or maximizer) of a functional (energy... geometric inter- pretation of modularity optimization contrasts with existing interpretations (e.g., probabilistic ones or in terms of the Potts model

Statistical Shape Modelling and Markov Random Field Restoration (invited tutorial and exercise)

DEFF Research Database (Denmark)

Hilger, Klaus Baggesen

This tutorial focuses on statistical shape analysis using point distribution models (PDM) which is widely used in modelling biological shape variability over a set of annotated training data. Furthermore, Active Shape Models (ASM) and Active Appearance Models (AAM) are based on PDMs and have proven...... deformation field between shapes. The tutorial demonstrates both generative active shape and appearance models, and MRF restoration on 3D polygonized surfaces. ''Exercise: Spectral-Spatial classification of multivariate images'' From annotated training data this exercise applies spatial image restoration...... using Markov random field relaxation of a spectral classifier. Keywords: the Ising model, the Potts model, stochastic sampling, discriminant analysis, expectation maximization....

Multiscale modeling of large deformations in 3-D polycrystals

International Nuclear Information System (INIS)

Lu Jing; Maniatty, Antoinette; Misiolek, Wojciech; Bandar, Alexander

2004-01-01

An approach for modeling 3-D polycrystals, linking to the macroscale, is presented. A Potts type model is used to generate a statistically representative grain structures with periodicity to allow scale-linking. The grain structures are compared to experimentally observed grain structures to validate that they are representative. A macroscale model of a compression test is compared against an experimental compression test for an Al-Mg-Si alloy to determine various deformation paths at different locations in the samples. These deformation paths are then applied to the experimental grain structure using a scale-bridging technique. Preliminary results from this work will be presented and discussed

The storage capacity of Potts models for semantic memory retrieval

Science.gov (United States)

Kropff, Emilio; Treves, Alessandro

2005-08-01

We introduce and analyse a minimal network model of semantic memory in the human brain. The model is a global associative memory structured as a collection of N local modules, each coding a feature, which can take S possible values, with a global sparseness a (the average fraction of features describing a concept). We show that, under optimal conditions, the number cM of modules connected on average to a module can range widely between very sparse connectivity (high dilution, c_{M}/N\\to 0 ) and full connectivity (c_{M}\\to N ), maintaining a global network storage capacity (the maximum number pc of stored and retrievable concepts) that scales like pc~cMS2/a, with logarithmic corrections consistent with the constraint that each synapse may store up to a fraction of a bit.

Bubbly vertex dynamics: A dynamical and geometrical model for epithelial tissues with curved cell shapes

Science.gov (United States)

Ishimoto, Yukitaka; Morishita, Yoshihiro

2014-11-01

In order to describe two-dimensionally packed cells in epithelial tissues both mathematically and physically, there have been developed several sorts of geometrical models, such as the vertex model, the finite element model, the cell-centered model, and the cellular Potts model. So far, in any case, pressures have not neatly been dealt with and the curvatures of the cell boundaries have been even omitted through their approximations. We focus on these quantities and formulate them in the vertex model. Thus, a model with the curvatures is constructed, and its algorithm for simulation is provided. The possible extensions and applications of this model are also discussed.

Statistical mechanics of human resource allocation

Science.gov (United States)

Inoue, Jun-Ichi; Chen, He

2014-03-01

We provide a mathematical platform to investigate the network topology of agents, say, university graduates who are looking for their positions in labor markets. The basic model is described by the so-called Potts spin glass which is well-known in the research field of statistical physics. In the model, each Potts spin (a tiny magnet in atomic scale length) represents the action of each student, and it takes a discrete variable corresponding to the company he/she applies for. We construct the energy to include three distinct effects on the students' behavior, namely, collective effect, market history and international ranking of companies. In this model system, the correlations (the adjacent matrix) between students are taken into account through the pairwise spin-spin interactions. We carry out computer simulations to examine the efficiency of the model. We also show that some chiral representation of the Potts spin enables us to obtain some analytical insights into our labor markets. This work was financially supported by Grant-in-Aid for Scientific Research (C) of Japan Society for the Promotion of Science No. 25330278.

A Rare Case of Pott's Disease (Spinal Tuberculosis) Mimicking Metastatic Disease in the Southern Region of Denmark.

Science.gov (United States)

Osmanagic, Azra; Emamifar, Amir; Christian Bang, Jacob; Jensen Hansen, Inger Marie

2016-06-07

Pott's disease (PD) or spinal tuberculosis is a rare condition which accounts for less than 1% of total tuberculosis (TB) cases. The incidence of PD has recently increased in Europe and the United States, mainly due to immigration; however, it is still a rare diagnosis in Scandinavian countries, and if overlooked it might lead to significant neurologic complications. A 78-year-old woman, originally from Eastern Europe, presented to the emergency department with a complaint of nausea, vomiting, weight loss, and severe back pain. On admission she was febrile and had leukocytosis and increased C-reactive protein. Initial spinal x-ray was performed and revealed osteolytic changes in the vertebral body of T11 and T12. Magnetic resonance imaging (MRI) of the spine illustrated spondylitis of T10, T11, and T12, with multiple paravertebral and epidural abscesses, which was suggestive of PD. Polymerase chain reaction (PCR) of the patient's gastric fluid was positive for Mycobacterium tuberculosis (MT). Based on MRI and PCR findings, standard treatment for TB was initiated. Results of the spine biopsy and culture showed colonies of MT and confirmed the diagnosis afterwards. Due to the instability of the spine and severe and continuous pain, spine-stabilizing surgery was performed. Her TB was cured after nine months of treatment. PD is an important differential diagnosis of malignancy that should be diagnosed instantly. History of exposure to TB and classic radiologic finding can help make the diagnosis.

Z(λ) model and flows: subgraph break-collapse method

International Nuclear Information System (INIS)

Essam, J.W.; Magalhaes, A.C.N. de.

1988-01-01

A recursive algorithm previously developed for the λ-state Potts model is generalised to the Z(λ) model. The relations used are based on an expression we derive for the pair correlation function in terms of mod-λ flows, which represents an extension of a similar result for the partition function previously obtained by Biggs. The use of flows enables us to prove and extend the formulae which appear in the break-collapse method of Mariz and coworkers. It is argued that the use of of fixed-flow bonds rather than the precollapsed bonds used by the latter authors leads to a more efficient algorithm. (author) [pt

Donors in Semiconductors - are they Understood in Electronic Era?

International Nuclear Information System (INIS)

Dmochowski, Janusz E

2007-01-01

The physics of semiconductors and contemporary electronics cannot be understood without impurities. The hydrogen-like shallow donor (and acceptor) state of electron (hole) bound by Coulomb electrostatic force of excess charge of impurity is used to control conductivity of semiconductors and construct semiconductor diodes, transistors and numerous types of semiconductor electronic and optoelectronic devices, including lasers. Recently, surprisingly, the physics of impurity donors appeared to be much reacher. Experimental evidence has been provided for universal existence of other types of electronic states of the same donor impurity: i) mysterious, deep, DX-type state resulting in metastability - slow hysteresis phenomena - understood as two-electron, acceptor-like state of donor impurity, formed upon large lattice distortion or rearrangement around impurity and accompanying capture of second electron, resulting in negative electron correlation energy U; ii) deep, localized, fully symmetric, A1, one-electron donor state of substitutional impurity. The latter state can be formed from the 'ordinary' shallow hydrogen-like state in the process of strong localization of electron by short range, local potential of impurity core, preserving full (A 1 ) symmetry of the substitutional impurity in the host lattice. The 'anticrossing' of the two A 1 (shallow hydrogenic and deep localized) energy levels upon transformation is observed. All types of electronic states of impurity can be universally observed for the same donor impurity and mutual transformation between different states occur upon changing experimental conditions. The knowledge about existence and properties of these n ew , molecular type, donor states in semiconductors seems still await general recognition and positive application in contemporary material and device science and engineering

Draft of M2 Report on Integration of the Hybrid Hydride Model into INL's MBM Framework for Review

Energy Technology Data Exchange (ETDEWEB)

Tikare, Veena; Weck, Philippe F.; Schultz, Peter Andrew; Clark, Blythe; Glazoff, Michael V.; Homer, Eric R.

2014-07-01

This report documents the development, demonstration and validation of a mesoscale, microstructural evolution model for simulation of zirconium hydride {delta}-ZrH{sub 1.5} precipitation in the cladding of used nuclear fuels that may occur during long-term dry storage. While the Zr-based claddings are manufactured free of any hydrogen, they absorb hydrogen during service, in the reactor by a process commonly termed ‘hydrogen pick-up’. The precipitation and growth of zirconium hydrides during dry storage is one of the most likely fuel rod integrity failure mechanisms either by embrittlement or delayed hydride cracking of the cladding. While the phenomenon is well documented and identified as a potential key failure mechanism during long-term dry storage (NUREG/CR-7116), the ability to actually predict the formation of hydrides is poor. The model being documented in this work is a computational capability for the prediction of hydride formation in different claddings of used nuclear fuels. This work supports the Used Fuel Disposition Research and Development Campaign in assessing the structural engineering performance of the cladding during and after long-term dry storage. This document demonstrates a basic hydride precipitation model that is built on a recently developed hybrid Potts-phase field model that combines elements of Potts-Monte Carlo and the phase-field models. The model capabilities are demonstrated along with the incorporation of the starting microstructure, thermodynamics of the Zr-H system and the hydride formation mechanism.

On Models with Uncountable Set of Spin Values on a Cayley Tree: Integral Equations

International Nuclear Information System (INIS)

Rozikov, Utkir A.; Eshkobilov, Yusup Kh.

2010-01-01

We consider models with nearest-neighbor interactions and with the set [0, 1] of spin values, on a Cayley tree of order k ≥ 1. We reduce the problem of describing the 'splitting Gibbs measures' of the model to the description of the solutions of some nonlinear integral equation. For k = 1 we show that the integral equation has a unique solution. In case k ≥ 2 some models (with the set [0, 1] of spin values) which have a unique splitting Gibbs measure are constructed. Also for the Potts model with uncountable set of spin values it is proven that there is unique splitting Gibbs measure.

Self-Organized Societies: On the Sakoda Model of Social Interactions

Directory of Open Access Journals (Sweden)

Pablo Medina

2017-01-01

Full Text Available We characterize the behavior and the social structures appearing from a model of general social interaction proposed by Sakoda. The model consists of two interacting populations in a two-dimensional periodic lattice with empty sites. It contemplates a set of simple rules that combine attitudes, ranges of interactions, and movement decisions. We analyze the evolution of the 45 different interaction rules via a Potts-like energy function which drives the system irreversibly to an equilibrium or a steady state. We discuss the robustness of the social structures, dynamical behaviors, and the existence of spatial long range order in terms of the social interactions and the equilibrium energy.

Antiferromagnetic Ising model with transverse and longitudinal field

International Nuclear Information System (INIS)

Kischinhevsky, M.

1985-01-01

We study the quantum hamiltonian version of the Ising Model in one spacial dimension under an external longitudinal (uniform) field at zero temperature. A phenomenological renormalization group procedure is used to obtain the phase diagram; the transverse and longitudinal zero field limits are studied and we verify the validity of universality at non zero transverse fields, where two-dimensional critical behaviour is obtained. To perform the numerical calculations we use the Lanczos scheme, which gives highly precise results with rather short processing times. We also analyse the possibility of using these techniques to extend the present work to the quantum hamiltonian version of the q-state Potts Model (q>2) in larger system. (author) [pt

High-throughput detection of prostate cancer in histological sections using probabilistic pairwise Markov models.

Science.gov (United States)

Monaco, James P; Tomaszewski, John E; Feldman, Michael D; Hagemann, Ian; Moradi, Mehdi; Mousavi, Parvin; Boag, Alexander; Davidson, Chris; Abolmaesumi, Purang; Madabhushi, Anant

2010-08-01

In this paper we present a high-throughput system for detecting regions of carcinoma of the prostate (CaP) in HSs from radical prostatectomies (RPs) using probabilistic pairwise Markov models (PPMMs), a novel type of Markov random field (MRF). At diagnostic resolution a digitized HS can contain 80Kx70K pixels - far too many for current automated Gleason grading algorithms to process. However, grading can be separated into two distinct steps: (1) detecting cancerous regions and (2) then grading these regions. The detection step does not require diagnostic resolution and can be performed much more quickly. Thus, we introduce a CaP detection system capable of analyzing an entire digitized whole-mount HS (2x1.75cm(2)) in under three minutes (on a desktop computer) while achieving a CaP detection sensitivity and specificity of 0.87 and 0.90, respectively. We obtain this high-throughput by tailoring the system to analyze the HSs at low resolution (8microm per pixel). This motivates the following algorithm: (Step 1) glands are segmented, (Step 2) the segmented glands are classified as malignant or benign, and (Step 3) the malignant glands are consolidated into continuous regions. The classification of individual glands leverages two features: gland size and the tendency for proximate glands to share the same class. The latter feature describes a spatial dependency which we model using a Markov prior. Typically, Markov priors are expressed as the product of potential functions. Unfortunately, potential functions are mathematical abstractions, and constructing priors through their selection becomes an ad hoc procedure, resulting in simplistic models such as the Potts. Addressing this problem, we introduce PPMMs which formulate priors in terms of probability density functions, allowing the creation of more sophisticated models. To demonstrate the efficacy of our CaP detection system and assess the advantages of using a PPMM prior instead of the Potts, we alternately

Collective cell motion in endothelial monolayers

International Nuclear Information System (INIS)

Szabó, A; Ünnep, R; Méhes, E; Czirók, A; Twal, W O; Argraves, W S; Cao, Y

2010-01-01

Collective cell motility is an important aspect of several developmental and pathophysiological processes. Despite its importance, the mechanisms that allow cells to be both motile and adhere to one another are poorly understood. In this study we establish statistical properties of the random streaming behavior of endothelial monolayer cultures. To understand the reported empirical findings, we expand the widely used cellular Potts model to include active cell motility. For spontaneous directed motility we assume a positive feedback between cell displacements and cell polarity. The resulting model is studied with computer simulations and is shown to exhibit behavior compatible with experimental findings. In particular, in monolayer cultures both the speed and persistence of cell motion decreases, transient cell chains move together as groups and velocity correlations extend over several cell diameters. As active cell motility is ubiquitous both in vitro and in vivo, our model is expected to be a generally applicable representation of cellular behavior

Integral hierarchies and percolation

International Nuclear Information System (INIS)

Klein, W.; Stell, G.

1985-01-01

For a variation of the Potts model which has been shown to describe continuum percolation, we derive a hierarchy of integral equations of Kirkwood-Salsburg type. The distribution functions which are the solutions of this hierarchy can be simply related to the connectedness functions in continuum percolation. From this hierarchy a second set of equations is derived from which the connectedness functions can be obtained directly. This approach is extremely useful when investigating properties of systems far from the percolation transition. These hierarchies are solved exactly in the mean-field (Kac-Baker) limit and possible implications for cluster growth are discussed. The relation between the Potts model for continuum percolation and the Widom-Rowlinson model is also noted

Markov random fields simulation: an introduction to the stochastic modelling of petroleum reservoirs; Simulacao de campos aleatorios markovianos: uma introducao voltada a modelagem estocastica de reservatorios de petroleo

Energy Technology Data Exchange (ETDEWEB)

Saldanha Filho, Paulo Carlos

1998-02-01

Stochastic simulation has been employed in petroleum reservoir characterization as a modeling tool able to reconcile information from several different sources. It has the ability to preserve the variability of the modeled phenomena and permits transference of geological knowledge to numerical models of flux, whose predictions on reservoir constitute the main basis for reservoir management decisions. Several stochastic models have been used and/or suggested, depending on the nature of the phenomena to be described. Markov Random Fields (MRFs) appear as an alternative for the modeling of discrete variables, mainly reservoirs with mosaic architecture of facies. In this dissertation, the reader is introduced to the stochastic modeling by MRFs in a generic sense. The main aspects of the technique are reviewed. MRF Conceptual Background is described: its characterization through the Markovian property and the equivalence to Gibbs distributions. The framework for generic modeling of MRFs is described. The classical models of Ising and Potts-Strauss are specific in this context and are related to models of Ising and Potts-Strauss are specific in this context and are related to models used in petroleum reservoir characterization. The problem of parameter estimation is discussed. The maximum pseudolikelihood estimators for some models are presented. Estimators for two models useful for reservoir characterization are developed, and represent a new contribution to the subject. Five algorithms for the Conditional Simulation of MRFs are described: the Metropolis algorithm, the algorithm of German and German (Gibbs sampler), the algorithm of Swendsen-Wang, the algorithm of Wolff, and the algorithm of Flinn. Finally, examples of simulation for some of the models discussed are presented, along with their implications on the modelling of petroleum reservoirs. (author)

Socialization understood in a dynamic way

Directory of Open Access Journals (Sweden)

Todorović Milorad R.

2017-01-01

Full Text Available In psychology, the process of socialization often gets the meaning it does not actually have and it also gets attached to things that are related to other processes. Here, socialization is understood only as the entering of a subject into a socio-symbolic order where he acquires his own identity. This entering into a separating order places the good on one side, and the bad on the other, and it is essentially a process that strongly designates the world by giving a man's instinctive nature the social contours obtained through imposed standards. Every form of anti-social behaviour, as well as every great psychological deviation, shows the lack of proper integration into the symbolic. Psychology, as a general theory of the psyche, and social psychology especially, indicates the social and cultural conditions that influence the mental construction. Without the dynamics of psychology, which depicts the psychological life through mental dynamics, psychological etiologies especially of those forms of behaviour that have no social verification would be neglected. Starting from the social and cultural conditions that build the 'psychological', it explains how the motives for suppression of all impulsive tendencies, aggression and libido are built. Mastering the impulses involves the construction of a moral instance (super-ego that differentiates and exists as a constant threat to the ego who tries to smuggle certain instinctive tendencies. Given that it is known, ever since Freud, that - from the standpoint of limiting the impulses, from the standpoint of morality - a man has a completely immoral part (instinctive, id; a part that is struggling to be moral (ego; and a super-ego that can be hyper-moral, and then become utterly cruel (Freud 2006a: 120, it can be observed that socialization is involved in the good part and in the bad part of a man. Success in a man's defense from Eros and Thanatos, on the one hand, and in his defense from the impulses of

Off-critical W∞ and Virasoro algebras as dynamical symmetries of the integrable models

International Nuclear Information System (INIS)

Sotkov, G.; Stanishkov, M.

1993-01-01

An infinite set of new non commuting conserved charges in a specific class of perturbed CFT's is founded and a criterion for their existence is presented. They appear to be higher momenta of the already known commuting conserved currents. The algebra they close consists of two non commuting W ∞ algebras. Various Virasoro subalgebras of the full symmetry algebra are founded. It is shown on the examples of the perturbed Ising and Potts models that one of them plays an essential role in the computation of the correlation functions of the fields of the theory. (author)

Multilevel discretized random field models with 'spin' correlations for the simulation of environmental spatial data

Science.gov (United States)

Žukovič, Milan; Hristopulos, Dionissios T.

2009-02-01

A current problem of practical significance is how to analyze large, spatially distributed, environmental data sets. The problem is more challenging for variables that follow non-Gaussian distributions. We show by means of numerical simulations that the spatial correlations between variables can be captured by interactions between 'spins'. The spins represent multilevel discretizations of environmental variables with respect to a number of pre-defined thresholds. The spatial dependence between the 'spins' is imposed by means of short-range interactions. We present two approaches, inspired by the Ising and Potts models, that generate conditional simulations of spatially distributed variables from samples with missing data. Currently, the sampling and simulation points are assumed to be at the nodes of a regular grid. The conditional simulations of the 'spin system' are forced to respect locally the sample values and the system statistics globally. The second constraint is enforced by minimizing a cost function representing the deviation between normalized correlation energies of the simulated and the sample distributions. In the approach based on the Nc-state Potts model, each point is assigned to one of Nc classes. The interactions involve all the points simultaneously. In the Ising model approach, a sequential simulation scheme is used: the discretization at each simulation level is binomial (i.e., ± 1). Information propagates from lower to higher levels as the simulation proceeds. We compare the two approaches in terms of their ability to reproduce the target statistics (e.g., the histogram and the variogram of the sample distribution), to predict data at unsampled locations, as well as in terms of their computational complexity. The comparison is based on a non-Gaussian data set (derived from a digital elevation model of the Walker Lake area, Nevada, USA). We discuss the impact of relevant simulation parameters, such as the domain size, the number of

Dual protection: more needed than practised or understood.

Science.gov (United States)

Berer, Marge

2006-11-01

Although non-barrier contraceptive use has become a global norm, unprotected sex in relation to sexually transmitted infections remains the norm almost everywhere. Dual protection is protection from unwanted pregnancy, HIV and other sexually transmitted infections, and is a form of safer sex for heterosexual couples that is more needed than practised or understood. This paper draws on a review of the literature in family planning, obstetrics and gynaecology, and AIDS-related journals from 1998 to early 2005. Definitions of dual protection, found mainly in family planning literature, are very narrow. Condoms remain the mainstay of dual protection, but the aim of this paper is to provide an expanded list of dual protection methods to show that there is a range of options. These include non-penetrative sex and the increasing use of condoms with the back-up of emergency contraception on the part of young people. The fact that people may fail to use dual protection consistently and correctly is not a valid reason not to promote it. It is never too late for those providing family planning and STI/HIV prevention services to start promoting condoms and dual protection. In the long-term, the development of highly efficacious and highly acceptable methods of dual protection is an urgent research priority, starting with a wider range of condoms that will appeal to more people.

arXiv Spin models in complex magnetic fields: a hard sign problem

CERN Document Server

de Forcrand, Philippe

2018-01-01

Coupling spin models to complex external fields can give rise to interesting phenomena like zeroes of the partition function (Lee-Yang zeroes, edge singularities) or oscillating propagators. Unfortunately, it usually also leads to a severe sign problem that can be overcome only in special cases; if the partition function has zeroes, the sign problem is even representation-independent at these points. In this study, we couple the N-state Potts model in different ways to a complex external magnetic field and discuss the above mentioned phenomena and their relations based on analytic calculations (1D) and results obtained using a modified cluster algorithm (general D) that in many cases either cures or at least drastically reduces the sign-problem induced by the complex external field.

Modeling of 3D Aluminum Polycrystals during Large Deformations

International Nuclear Information System (INIS)

Maniatty, Antoinette M.; Littlewood, David J.; Lu Jing; Pyle, Devin

2007-01-01

An approach for generating, meshing, and modeling 3D polycrystals, with a focus on aluminum alloys, subjected to large deformation processes is presented. A Potts type model is used to generate statistically representative grain structures with periodicity to allow scale-linking. The grain structures are compared to experimentally observed grain structures to validate that they are representative. A procedure for generating a geometric model from the voxel data is developed allowing for adaptive meshing of the generated grain structure. Material behavior is governed by an appropriate crystal, elasto-viscoplastic constitutive model. The elastic-viscoplastic model is implemented in a three-dimensional, finite deformation, mixed, finite element program. In order to handle the large-scale problems of interest, a parallel implementation is utilized. A multiscale procedure is used to link larger scale models of deformation processes to the polycrystal model, where periodic boundary conditions on the fluctuation field are enforced. Finite-element models, of 3D polycrystal grain structures will be presented along with observations made from these simulations

Universality of ordering dynamics in conserved multicomponent systems

DEFF Research Database (Denmark)

Jeppesen, Claus; Mouritsen, Ole G.

1993-01-01

A comparative study is performed of the ordering dynamics and spinodal decomposition processes in two-dimensional two-state and three-state ferromagnetic Potts models with conserved order parameter. The models are investigated by Monte Carlo quenching simulations on both square and triangular...

Effects of mobile vacancies on the dynamics of ordering and phase separation in nonconserved multicomponent systems

DEFF Research Database (Denmark)

Gilhøj, Henriette; Jeppesen, Claus; Mouritsen, Ole G.

1995-01-01

The effects of mobile vacancies on the dynamics of ordering processes and phase separation in multicomponent systems are studied via Monte Carlo simulations of a two-dimensional seven-state ferromagnetic Potts model with varying degrees of site dilution. The model displays phase equilibria...

Free association transitions in models of cortical latching dynamics

International Nuclear Information System (INIS)

Russo, Eleonora; Treves, Alessandro; Kropff, Emilio; Namboodiri, Vijay M K

2008-01-01

Potts networks, in certain conditions, hop spontaneously from one discrete attractor state to another, a process we have called latching dynamics. When continuing indefinitely, latching can serve as a model of infinite recursion, which is nontrivial if the matrix of transition probabilities presents a structure, i.e. a rudimentary grammar. We show here, with computer simulations, that latching transitions cluster in a number of distinct classes: effectively random transitions between weakly correlated attractors; structured, history-dependent transitions between attractors with intermediate correlations; and oscillations between pairs of closely overlapping attractors. Each type can be described by a reduced set of equations of motion, which, once numerically integrated, matches simulations results. We propose that the analysis of such equations may offer clues on how to embed meaningful grammatical structures into more realistic models of specific recursive processes

Free association transitions in models of cortical latching dynamics

Energy Technology Data Exchange (ETDEWEB)

Russo, Eleonora; Treves, Alessandro; Kropff, Emilio [SISSA, Cognitive Neuroscience, via Beirut 4, 34014 Trieste (Italy); Namboodiri, Vijay M K [Department of Physics, IIT Bombay, Powai, Mumbai, India 400076 (India)], E-mail: russo@sissa.it, E-mail: vijay_mkn@iitb.ac.in, E-mail: ale@sissa.it, E-mail: kropff@sissa.it

2008-01-15

Potts networks, in certain conditions, hop spontaneously from one discrete attractor state to another, a process we have called latching dynamics. When continuing indefinitely, latching can serve as a model of infinite recursion, which is nontrivial if the matrix of transition probabilities presents a structure, i.e. a rudimentary grammar. We show here, with computer simulations, that latching transitions cluster in a number of distinct classes: effectively random transitions between weakly correlated attractors; structured, history-dependent transitions between attractors with intermediate correlations; and oscillations between pairs of closely overlapping attractors. Each type can be described by a reduced set of equations of motion, which, once numerically integrated, matches simulations results. We propose that the analysis of such equations may offer clues on how to embed meaningful grammatical structures into more realistic models of specific recursive processes.

Mesoscopic simulation of recrystallization and grain growth

International Nuclear Information System (INIS)

Rollett, A.D.

2000-01-01

A brief summary of simulation techniques for recrystallization and grain growth is given. The available methods include surface evolver, front tracking (including finite element methods and vertex methods), networks of curves, phase field, cellular automata, and Monte Carlo. Two of the models that use a regular lattice, the Potts model and the Cellular Automaton (CA) model, have proved to be very useful. Microstructure is represented on a discrete lattice where the value of the field at each point represents the local orientation of the material and boundaries exist between points of unlike orientation. Two issues are discussed: one is a hybrid approach to combining the standard Monte Carlo and cellular automata algorithms for recrystallization modeling. The second is adaptation of the MC method for modeling grain growth (and recrystallization) with physically based boundary properties. Both models have significant limitations in their standard forms. The CA model is very useful and efficient for simulating recrystallization with deterministic motion of the recrystallization fronts. It can be adapted to simulate curvature driven migration provided that multiple sub-lattices are used with a probabilistic switching rule. The Potts model is very successful in modeling curvature driven boundary migration and grain growth. It does not simulate the proportionality between boundary velocity and a stored energy driving force, however, unless rather restricted conditions of stored energy (in relation to the grain boundary energy) and lattice temperature are satisfied. A new approach based on a hybrid of the Potts model (MC) and the Cellular Automaton (CA) model has been developed to obtain the desired limiting behavior for both curvature-driven and stored energy-driven grain boundary migration. The combination of methods is achieved by interleaving the two different types of reorientation event in time. The results show that the hybrid algorithm models the Gibbs

Hybrid models for the simulation of microstructural evolution influenced by coupled, multiple physical processes

Energy Technology Data Exchange (ETDEWEB)

Tikare, Veena [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hernandez-Rivera, Efrain [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Madison, Jonathan D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Holm, Elizabeth Ann [Carnegie Mellon Univ., Pittsburgh, PA (United States); Patterson, Burton R. [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Homer, Eric R. [Brigham Young Univ., Provo, UT (United States). Dept. of Mechanical Engineering

2013-09-01

Most materials microstructural evolution processes progress with multiple processes occurring simultaneously. In this work, we have concentrated on the processes that are active in nuclear materials, in particular, nuclear fuels. These processes are coarsening, nucleation, differential diffusion, phase transformation, radiation-induced defect formation and swelling, often with temperature gradients present. All these couple and contribute to evolution that is unique to nuclear fuels and materials. Hybrid model that combines elements from the Potts Monte Carlo, phase-field models and others have been developed to address these multiple physical processes. These models are described and applied to several processes in this report. An important feature of the models developed are that they are coded as applications within SPPARKS, a Sandiadeveloped framework for simulation at the mesoscale of microstructural evolution processes by kinetic Monte Carlo methods. This makes these codes readily accessible and adaptable for future applications.

Feeling Heard & Understood in the Hospital Environment: Benchmarking Communication Quality Among Patients with Advanced Cancer Before and After Palliative Care Consultation.

Science.gov (United States)

Ingersoll, Luke T; Saeed, Fahad; Ladwig, Susan; Norton, Sally A; Anderson, Wendy; Alexander, Stewart C; Gramling, Robert

2018-05-02

Maximizing value in palliative care requires continued development and standardization of communication quality indicators. To describe the basic epidemiology of a newly-adopted patient-centered communication quality indicator for hospitalized palliative care patie9nts with advanced cancer. Cross-sectional analysis of 207 advanced cancer patients who received palliative care consultation at two medical centers in the United States. Participants completed the Heard & Understood quality indicator immediately before and the day following the initial palliative care consultation: "Over the past two days ["24 hours" for the post-consultation version], how much have you felt heard and understood by the doctors, nurses and hospital staff? Completely/Quite a Bit/Moderately/Slightly/Not at All". We categorized "Completely" as indicating ideal quality. Approximately one-third indicated ideal Heard & Understood quality before palliative care consultation. Age, financial security, emotional distress, preferences for comfort-longevity tradeoffs at end-of-life, and prognosis expectations were associated with pre-consultation quality. Among those with less-than-ideal quality at baseline, 56% rated feeling more Heard & Understood the day following palliative care consultation. The greatest pre-post improvement was among people who had unformed end-of-life treatment preferences or who reported having "no idea" about their prognosis at baseline. Most patients felt incompletely heard and understood at the time of referral to palliative care consultation and more than half improved following consultation. Feeling heard and understood is an important quality indicator sensitive to interventions to improve care and key variations in the patient experience. Copyright © 2018. Published by Elsevier Inc.

On grain growth kinetics in two-phase polycrystalline materials ...

Indian Academy of Sciences (India)

Abstract. Monte Carlo Potts model simulation was carried out on a 2D square lattice for various surface fractions ... The observations are in good agreement with known theoretical ... conceptual basis of the Monte Carlo method as a simulation.

Multilevel discretized random field models with 'spin' correlations for the simulation of environmental spatial data

International Nuclear Information System (INIS)

Žukovič, Milan; Hristopulos, Dionissios T

2009-01-01

A current problem of practical significance is how to analyze large, spatially distributed, environmental data sets. The problem is more challenging for variables that follow non-Gaussian distributions. We show by means of numerical simulations that the spatial correlations between variables can be captured by interactions between 'spins'. The spins represent multilevel discretizations of environmental variables with respect to a number of pre-defined thresholds. The spatial dependence between the 'spins' is imposed by means of short-range interactions. We present two approaches, inspired by the Ising and Potts models, that generate conditional simulations of spatially distributed variables from samples with missing data. Currently, the sampling and simulation points are assumed to be at the nodes of a regular grid. The conditional simulations of the 'spin system' are forced to respect locally the sample values and the system statistics globally. The second constraint is enforced by minimizing a cost function representing the deviation between normalized correlation energies of the simulated and the sample distributions. In the approach based on the N c -state Potts model, each point is assigned to one of N c classes. The interactions involve all the points simultaneously. In the Ising model approach, a sequential simulation scheme is used: the discretization at each simulation level is binomial (i.e., ± 1). Information propagates from lower to higher levels as the simulation proceeds. We compare the two approaches in terms of their ability to reproduce the target statistics (e.g., the histogram and the variogram of the sample distribution), to predict data at unsampled locations, as well as in terms of their computational complexity. The comparison is based on a non-Gaussian data set (derived from a digital elevation model of the Walker Lake area, Nevada, USA). We discuss the impact of relevant simulation parameters, such as the domain size, the number of

Simple model for multiple-choice collective decision making.

Science.gov (United States)

Lee, Ching Hua; Lucas, Andrew

2014-11-01

We describe a simple model of heterogeneous, interacting agents making decisions between n≥2 discrete choices. For a special class of interactions, our model is the mean field description of random field Potts-like models and is effectively solved by finding the extrema of the average energy E per agent. In these cases, by studying the propagation of decision changes via avalanches, we argue that macroscopic dynamics is well captured by a gradient flow along E. We focus on the permutation symmetric case, where all n choices are (on average) the same, and spontaneous symmetry breaking (SSB) arises purely from cooperative social interactions. As examples, we show that bimodal heterogeneity naturally provides a mechanism for the spontaneous formation of hierarchies between decisions and that SSB is a preferred instability to discontinuous phase transitions between two symmetric points. Beyond the mean field limit, exponentially many stable equilibria emerge when we place this model on a graph of finite mean degree. We conclude with speculation on decision making with persistent collective oscillations. Throughout the paper, we emphasize analogies between methods of solution to our model and common intuition from diverse areas of physics, including statistical physics and electromagnetism.

Can yeast glycolysis be understood in terms of in vitro kinetics of the constituent enxymes? Testing biochemistry.

NARCIS (Netherlands)

Teusink, B.; Passarge, J.R.; Reijenga, C.A.; Esgalhado, M.E.L.M.; van der Weijden, C.C.; Schepper, M.; Walsh, M.C.; Bakker, B.M.; van Dam, K.; Westerhoff, H.V.; Snoep, J.L.

2000-01-01

This paper examines whether the in vivo behavior of yeast glycolysis can be understood in terms of the in vitro kinetic properties of the constituent enzymes. In nongrowing, anaerobic, compressed Saccharomyces cerevisiae the values of the kinetic parameters of most glycolytic enzymes were

Connectivity: a primer in phase transitions and critical phenomena for students of particle physics

International Nuclear Information System (INIS)

Stanley, H.E.

1983-01-01

This introduction to the phase transitions and critical phenomena focuses on the theme of connectivity, and illustrates concepts with a paradigm of connectivity, such as the percolation problem. The phenomenon of bond percolation, where a finite section of ''fence'' has both conducting and insulating links, is described. Three approaches to the study of connectivity phenomena are described: exact enumeration procedures, Monte Carlo simulation, and renormalization groups. Exact enumeration probabilities are calculated. Lattice animals are discussed. Computer simulation is described as simple: assign random numbers, then design algorithms that recognize clusters. The Monte Carlo simulations have not lead to higher accuracy in predicting critical exponents, but have given a graphic illustration of what a million-site cluster looks like. The incipient infinite cluster can also be described. In this case, the magnetic correlations of a dilute magnetic system will spread along the ''backbone bonds'' rather than by ''dangling ends.'' Renormalization group approaches are also treated. Finally, relations between connectivity and models of critical thermal phenomena such as the Ising Model, the Potts model, and polychromatic generalization of the Potts Model, are discussed

3D microstructural evolution of primary recrystallization and grain growth in cold rolled single-phase aluminum alloys

Science.gov (United States)

Adam, Khaled; Zöllner, Dana; Field, David P.

2018-04-01

Modeling the microstructural evolution during recrystallization is a powerful tool for the profound understanding of alloy behavior and for use in optimizing engineering properties through annealing. In particular, the mechanical properties of metallic alloys are highly dependent upon evolved microstructure and texture from the softening process. In the present work, a Monte Carlo (MC) Potts model was used to model the primary recrystallization and grain growth in cold rolled single-phase Al alloy. The microstructural representation of two kinds of dislocation densities, statistically stored dislocations and geometrically necessary dislocations were quantified based on the ViscoPlastic Fast Fourier transform method. This representation was then introduced into the MC Potts model to identify the favorable sites for nucleation where orientation gradients and entanglements of dislocations are high. Additionally, in situ observations of non-isothermal microstructure evolution for single-phase aluminum alloy 1100 were made to validate the simulation. The influence of the texture inhomogeneity is analyzed from a theoretical point of view using an orientation distribution function for deformed and evolved texture.

Dynamics of ordering in highly degenerate models with anisotropic grain-boundary potential: Effects of temperature and vortex formation

DEFF Research Database (Denmark)

Jeppesen, Claus; Flyvbjerg, Henrik; Mouritsen, Ole G.

1989-01-01

-temperature Potts-ordered phase to an intermediate phase which lacks conventional long-range order, and another transition which takes the system to the high-temperature disordered phase. The linear nature of the sine potential used makes it a marginal case in the sense that it favors neither hard domain boundaries...

Phenomenological approach to the statistics and dynamics of model systems

International Nuclear Information System (INIS)

Choi, M.Y.

1985-01-01

This thesis investigates the equilibrium and nonequilibrium properties of some model systems, and consists of two parts. Part 1 deals with phase transitions in frustrated xy models, which can serve as a model for the coupled Josephson junction arrays. The Hubbard-Stratanovich transform is developed to construct the Landau-Ginzburg-Wilson Hamiltonians for uniformly frustrated xy models both on a square lattice and on a triangular lattice, which reflect the formation of various superlattices according to the frustration f. Near the critical point, the system with f equal to 1/4 on a triangular lattice is shown to belong to the same universality class as the fully frustrated system on a square lattice. By decomposing two mode systems into two coupled xy models and by applying the Migdal-Kadanoff approximation, the possibilities of Ising-like or three-state Potts-like transition are shown in addition to the Kosterlitz-Thouless-like ones. Part 2 considers the time evaluation of model systems with retarded interactions. For such systems, a master equation is derived with non-Markovian character. It is shown that in higher dimensions, the interplay between interaction strength and delay can lead to complicated behavior

Is restlessness best understood as a process? Reflecting on four boys’ restlessness during music therapy in kindergarten

Science.gov (United States)

Helle-Valle, Anna; Binder, Per-Einar; Anderssen, Norman; Stige, Brynjulf

2017-01-01

ABSTRACT ADHD can be considered an internationally recognized framework for understanding children’s restlessness. In this context, children’s restlessness is understood as a symptom of neurodevelopmental disorder. However, there are other possible understandings of children’s restlessness. In this article, we explore four boys’ collaborative and creative process as it is described and understood by three adults. The process is framed by a community music therapy project in a Norwegian kindergarten, and we describe four interrelated phases of this process: Exploring musical vitality and cooperation, Consolidating positions, Performing together, and Discovering ripple effects. We discuss these results in relation to seven qualities central to a community music therapy approach: participation, resource orientation, ecology, performance, activism, reflexivity and ethics. We argue that in contrast to a diagnostic approach that entails a focus on individual problems, a community music therapy approach can shed light on adult and systemic contributions to children’s restlessness. PMID:28532331

Mesoscale Benchmark Demonstration Problem 1: Mesoscale Simulations of Intra-granular Fission Gas Bubbles in UO2 under Post-irradiation Thermal Annealing

Energy Technology Data Exchange (ETDEWEB)

Li, Yulan; Hu, Shenyang Y.; Montgomery, Robert; Gao, Fei; Sun, Xin; Tonks, Michael; Biner, Bullent; Millet, Paul; Tikare, Veena; Radhakrishnan, Balasubramaniam; Andersson , David

2012-04-11

A study was conducted to evaluate the capabilities of different numerical methods used to represent microstructure behavior at the mesoscale for irradiated material using an idealized benchmark problem. The purpose of the mesoscale benchmark problem was to provide a common basis to assess several mesoscale methods with the objective of identifying the strengths and areas of improvement in the predictive modeling of microstructure evolution. In this work, mesoscale models (phase-field, Potts, and kinetic Monte Carlo) developed by PNNL, INL, SNL, and ORNL were used to calculate the evolution kinetics of intra-granular fission gas bubbles in UO2 fuel under post-irradiation thermal annealing conditions. The benchmark problem was constructed to include important microstructural evolution mechanisms on the kinetics of intra-granular fission gas bubble behavior such as the atomic diffusion of Xe atoms, U vacancies, and O vacancies, the effect of vacancy capture and emission from defects, and the elastic interaction of non-equilibrium gas bubbles. An idealized set of assumptions was imposed on the benchmark problem to simplify the mechanisms considered. The capability and numerical efficiency of different models are compared against selected experimental and simulation results. These comparisons find that the phase-field methods, by the nature of the free energy formulation, are able to represent a larger subset of the mechanisms influencing the intra-granular bubble growth and coarsening mechanisms in the idealized benchmark problem as compared to the Potts and kinetic Monte Carlo methods. It is recognized that the mesoscale benchmark problem as formulated does not specifically highlight the strengths of the discrete particle modeling used in the Potts and kinetic Monte Carlo methods. Future efforts are recommended to construct increasingly more complex mesoscale benchmark problems to further verify and validate the predictive capabilities of the mesoscale modeling

Fast Segmentation From Blurred Data in 3D Fluorescence Microscopy.

Science.gov (United States)

Storath, Martin; Rickert, Dennis; Unser, Michael; Weinmann, Andreas

2017-10-01

We develop a fast algorithm for segmenting 3D images from linear measurements based on the Potts model (or piecewise constant Mumford-Shah model). To that end, we first derive suitable space discretizations of the 3D Potts model, which are capable of dealing with 3D images defined on non-cubic grids. Our discretization allows us to utilize a specific splitting approach, which results in decoupled subproblems of moderate size. The crucial point in the 3D setup is that the number of independent subproblems is so large that we can reasonably exploit the parallel processing capabilities of the graphics processing units (GPUs). Our GPU implementation is up to 18 times faster than the sequential CPU version. This allows to process even large volumes in acceptable runtimes. As a further contribution, we extend the algorithm in order to deal with non-negativity constraints. We demonstrate the efficiency of our method for combined image deconvolution and segmentation on simulated data and on real 3D wide field fluorescence microscopy data.

Maximum Entropy Estimation of Transition Probabilities of Reversible Markov Chains

Directory of Open Access Journals (Sweden)

Erik Van der Straeten

2009-11-01

Full Text Available In this paper, we develop a general theory for the estimation of the transition probabilities of reversible Markov chains using the maximum entropy principle. A broad range of physical models can be studied within this approach. We use one-dimensional classical spin systems to illustrate the theoretical ideas. The examples studied in this paper are: the Ising model, the Potts model and the Blume-Emery-Griffiths model.

Mise au point

African Journals Online (AJOL)

Le diagnostic de mal de Pott sous occipital associé à une localisation tuberculeuse pulmonaire a été retenu. Le traite- ment anti-tuberculeux a ... The follow-up was 6 years. Discussion : The sub occipital pain Pott localisation was rare. ... 6), associée à une opacité fibreuse rétractile du lobe pulmonaire supérieure gauche.

Modeling and complexity of stochastic interacting Lévy type financial price dynamics

Science.gov (United States)

Wang, Yiduan; Zheng, Shenzhou; Zhang, Wei; Wang, Jun; Wang, Guochao

2018-06-01

In attempt to reproduce and investigate nonlinear dynamics of security markets, a novel nonlinear random interacting price dynamics, which is considered as a Lévy type process, is developed and investigated by the combination of lattice oriented percolation and Potts dynamics, which concerns with the instinctive random fluctuation and the fluctuation caused by the spread of the investors' trading attitudes, respectively. To better understand the fluctuation complexity properties of the proposed model, the complexity analyses of random logarithmic price return and corresponding volatility series are preformed, including power-law distribution, Lempel-Ziv complexity and fractional sample entropy. In order to verify the rationality of the proposed model, the corresponding studies of actual security market datasets are also implemented for comparison. The empirical results reveal that this financial price model can reproduce some important complexity features of actual security markets to some extent. The complexity of returns decreases with the increase of parameters γ1 and β respectively, furthermore, the volatility series exhibit lower complexity than the return series

Conformal field theory and 2D critical phenomena. Part 1

International Nuclear Information System (INIS)

Zamolodchikov, A.B.; Zamolodchikov, Al.B.

1989-01-01

Review of the recent developments in the two-dimensional conformal field theory and especially its applications to the physics of 2D critical phenomena is given. It includes the Ising model, the Potts model. Minimal models, corresponding to theories invariant under higher symmetries, such as superconformal theories, parafermionic theories and theories with current and W-algebras are also discussed. Non-hamiltonian approach to two-dimensional field theory is formulated. 126 refs

Improving contact prediction along three dimensions.

Directory of Open Access Journals (Sweden)

Christoph Feinauer

2014-10-01

Full Text Available Correlation patterns in multiple sequence alignments of homologous proteins can be exploited to infer information on the three-dimensional structure of their members. The typical pipeline to address this task, which we in this paper refer to as the three dimensions of contact prediction, is to (i filter and align the raw sequence data representing the evolutionarily related proteins; (ii choose a predictive model to describe a sequence alignment; (iii infer the model parameters and interpret them in terms of structural properties, such as an accurate contact map. We show here that all three dimensions are important for overall prediction success. In particular, we show that it is possible to improve significantly along the second dimension by going beyond the pair-wise Potts models from statistical physics, which have hitherto been the focus of the field. These (simple extensions are motivated by multiple sequence alignments often containing long stretches of gaps which, as a data feature, would be rather untypical for independent samples drawn from a Potts model. Using a large test set of proteins we show that the combined improvements along the three dimensions are as large as any reported to date.

SLE in self-dual critical Z(N) spin systems: CFT predictions

International Nuclear Information System (INIS)

Santachiara, Raoul

2008-01-01

The Schramm-Loewner evolution (SLE) describes the continuum limit of domain walls at phase transitions in two-dimensional statistical systems. We consider here the SLE in Z(N) spin models at their self-dual critical point. For N=2 and N=3 these models correspond to the Ising and three-state Potts model. For N≥4 the critical self-dual Z(N) spin models are described in the continuum limit by non-minimal conformal field theories with central charge c≥1. By studying the representations of the corresponding chiral algebra, we show that two particular operators satisfy a two level null vector condition which, for N≥4, presents an additional term coming from the extra symmetry currents action. For N=2,3 these operators correspond to the boundary conditions changing operators associated to the SLE 16/3 (Ising model) and to the SLE 24/5 and SLE 10/3 (three-state Potts model). We suggest a definition of the interfaces within the Z(N) lattice models. The scaling limit of these interfaces is expected to be described at the self-dual critical point and for N≥4 by the SLE 4(N+1)/(N+2) and SLE 4(N+2)/(N+1) processes

A Monte Carlo model for 3D grain evolution during welding

Science.gov (United States)

Rodgers, Theron M.; Mitchell, John A.; Tikare, Veena

2017-09-01

Welding is one of the most wide-spread processes used in metal joining. However, there are currently no open-source software implementations for the simulation of microstructural evolution during a weld pass. Here we describe a Potts Monte Carlo based model implemented in the SPPARKS kinetic Monte Carlo computational framework. The model simulates melting, solidification and solid-state microstructural evolution of material in the fusion and heat-affected zones of a weld. The model does not simulate thermal behavior, but rather utilizes user input parameters to specify weld pool and heat-affect zone properties. Weld pool shapes are specified by Bézier curves, which allow for the specification of a wide range of pool shapes. Pool shapes can range from narrow and deep to wide and shallow representing different fluid flow conditions within the pool. Surrounding temperature gradients are calculated with the aide of a closest point projection algorithm. The model also allows simulation of pulsed power welding through time-dependent variation of the weld pool size. Example simulation results and comparisons with laboratory weld observations demonstrate microstructural variation with weld speed, pool shape, and pulsed-power.

In silico modeling for tumor growth visualization.

Science.gov (United States)

Jeanquartier, Fleur; Jean-Quartier, Claire; Cemernek, David; Holzinger, Andreas

2016-08-08

Cancer is a complex disease. Fundamental cellular based studies as well as modeling provides insight into cancer biology and strategies to treatment of the disease. In silico models complement in vivo models. Research on tumor growth involves a plethora of models each emphasizing isolated aspects of benign and malignant neoplasms. Biologists and clinical scientists are often overwhelmed by the mathematical background knowledge necessary to grasp and to apply a model to their own research. We aim to provide a comprehensive and expandable simulation tool to visualizing tumor growth. This novel Web-based application offers the advantage of a user-friendly graphical interface with several manipulable input variables to correlate different aspects of tumor growth. By refining model parameters we highlight the significance of heterogeneous intercellular interactions on tumor progression. Within this paper we present the implementation of the Cellular Potts Model graphically presented through Cytoscape.js within a Web application. The tool is available under the MIT license at https://github.com/davcem/cpm-cytoscape and http://styx.cgv.tugraz.at:8080/cpm-cytoscape/ . In-silico methods overcome the lack of wet experimental possibilities and as dry method succeed in terms of reduction, refinement and replacement of animal experimentation, also known as the 3R principles. Our visualization approach to simulation allows for more flexible usage and easy extension to facilitate understanding and gain novel insight. We believe that biomedical research in general and research on tumor growth in particular will benefit from the systems biology perspective.

Three-body interactions in sociophysics and their role in coalition forming

Science.gov (United States)

Naumis, Gerardo G.; Samaniego-Steta, F.; del Castillo-Mussot, M.; Vázquez, G. J.

2007-06-01

An study of the effects of three-body interactions in the process of coalition formation is presented. In particular, we modify a spin glass model of bimodal propensities and also a Potts model in order to include a particular three-body Hamiltonian that reproduces the main features of the required interactions. The model can be used to study conflicts, political struggles, political parties, social networks, wars and organizational structures. As an application, we analyze a simplified model of the Iraq war.

Study of the attractor structure of an agent-based sociological model

Energy Technology Data Exchange (ETDEWEB)

Timpanaro, Andre M; Prado, Carmen P C, E-mail: timpa@if.usp.br, E-mail: prado@if.usp.br [Instituto de Fisica da Universidade de Sao Paulo, Sao Paulo (Brazil)

2011-03-01

The Sznajd model is a sociophysics model that is based in the Potts model, and used for describing opinion propagation in a society. It employs an agent-based approach and interaction rules favouring pairs of agreeing agents. It has been successfully employed in modeling some properties and scale features of both proportional and majority elections (see for instance the works of A. T. Bernardes and R. N. Costa Filho), but its stationary states are always consensus states. In order to explain more complicated behaviours, we have modified the bounded confidence idea (introduced before in other opinion models, like the Deffuant model), with the introduction of prejudices and biases (we called this modification confidence rules), and have adapted it to the discrete Sznajd model. This generalized Sznajd model is able to reproduce almost all of the previous versions of the Sznajd model, by using appropriate choices of parameters. We solved the attractor structure of the resulting model in a mean-field approach and made Monte Carlo simulations in a Barabasi-Albert network. These simulations show great similarities with the mean-field, for the tested cases of 3 and 4 opinions. The dynamical systems approach that we devised allows for a deeper understanding of the potential of the Sznajd model as an opinion propagation model and can be easily extended to other models, like the voter model. Our modification of the bounded confidence rule can also be readily applied to other opinion propagation models.

Universal critical wrapping probabilities in the canonical ensemble

Directory of Open Access Journals (Sweden)

Hao Hu

2015-09-01

Full Text Available Universal dimensionless quantities, such as Binder ratios and wrapping probabilities, play an important role in the study of critical phenomena. We study the finite-size scaling behavior of the wrapping probability for the Potts model in the random-cluster representation, under the constraint that the total number of occupied bonds is fixed, so that the canonical ensemble applies. We derive that, in the limit L→∞, the critical values of the wrapping probability are different from those of the unconstrained model, i.e. the model in the grand-canonical ensemble, but still universal, for systems with 2yt−d>0 where yt=1/ν is the thermal renormalization exponent and d is the spatial dimension. Similar modifications apply to other dimensionless quantities, such as Binder ratios. For systems with 2yt−d≤0, these quantities share same critical universal values in the two ensembles. It is also derived that new finite-size corrections are induced. These findings apply more generally to systems in the canonical ensemble, e.g. the dilute Potts model with a fixed total number of vacancies. Finally, we formulate an efficient cluster-type algorithm for the canonical ensemble, and confirm these predictions by extensive simulations.

Imagen: absceso retrofaríngeo tuberculoso

OpenAIRE

Díaz de Cerio Canduela, Pedro

2011-01-01

[ES]Se presenta el caso de un paciente diagnosticado de tuberculosis pulmonar que presenta un gran absceso retrofaringeo secundario a un mal de Pott cervical. Las imágenes demuestran la gran afectación del plano retrofaringeo, así como el desgaste de los cuerpos vertebrales cervicales. [EN] The case of a patient diagnosed with pulmonary tuberculosis has a large retropharyngeal abscess secondary to cervical Pott's disease. The images show the high level involvement of the retropharyngeal a...

Multiscale Modeling of the Early CD8 T-Cell Immune Response in Lymph Nodes: An Integrative Study

Directory of Open Access Journals (Sweden)

Sotiris A. Prokopiou

2014-09-01

Full Text Available CD8 T-cells are critical  in controlling infection by intracellular  pathogens. Upon encountering antigen presenting cells, T-cell receptor activation promotes the differentiation of naïve CD8 T-cells into strongly proliferating  activated and effector stages. We propose a 2D-multiscale computational model to study the maturation of CD8 T-cells in a lymph node controlled by their molecular profile. A novel molecular pathway is presented and converted into an ordinary differential  equation model, coupled with a cellular Potts model to describe cell-cell interactions. Key molecular  players such as activated IL2 receptor and Tbet levels  control the differentiation  from naïve into activated and effector stages, respectively,  while caspases and Fas-Fas ligand interactions control cell apoptosis.  Coupling  this molecular model to the cellular scale successfully  reproduces  qualitatively the evolution of total CD8 T-cell counts observed in mice lymph node, between Day 3 and 5.5 post-infection. Furthermore, this model allows us to make testable predictions  of the evolution of the different CD8 T-cell stages.

Phase transition in a spatial Lotka-Volterra model

International Nuclear Information System (INIS)

Szabo, Gyorgy; Czaran, Tamas

2001-01-01

Spatial evolution is investigated in a simulated system of nine competing and mutating bacterium strains, which mimics the biochemical war among bacteria capable of producing two different bacteriocins (toxins) at most. Random sequential dynamics on a square lattice is governed by very symmetrical transition rules for neighborhood invasions of sensitive strains by killers, killers by resistants, and resistants by sensitives. The community of the nine possible toxicity/resistance types undergoes a critical phase transition as the uniform transmutation rates between the types decreases below a critical value P c above that all the nine types of strains coexist with equal frequencies. Passing the critical mutation rate from above, the system collapses into one of three topologically identical (degenerated) states, each consisting of three strain types. Of the three possible final states each accrues with equal probability and all three maintain themselves in a self-organizing polydomain structure via cyclic invasions. Our Monte Carlo simulations support that this symmetry-breaking transition belongs to the universality class of the three-state Potts model

Synergy of cell-cell repulsion and vacuolation in a computational model of lumen formation.

Science.gov (United States)

Boas, Sonja E M; Merks, Roeland M H

2014-03-06

A key step in blood vessel development (angiogenesis) is lumen formation: the hollowing of vessels for blood perfusion. Two alternative lumen formation mechanisms are suggested to function in different types of blood vessels. The vacuolation mechanism is suggested for lumen formation in small vessels by coalescence of intracellular vacuoles, a view that was extended to extracellular lumen formation by exocytosis of vacuoles. The cell-cell repulsion mechanism is suggested to initiate extracellular lumen formation in large vessels by active repulsion of adjacent cells, and active cell shape changes extend the lumen. We used an agent-based computer model, based on the cellular Potts model, to compare and study both mechanisms separately and combined. An extensive sensitivity analysis shows that each of the mechanisms on its own can produce lumens in a narrow region of parameter space. However, combining both mechanisms makes lumen formation much more robust to the values of the parameters, suggesting that the mechanisms may work synergistically and operate in parallel, rather than in different vessel types.

Synergy of cell–cell repulsion and vacuolation in a computational model of lumen formation

Science.gov (United States)

Boas, Sonja E. M.; Merks, Roeland M. H.

2014-01-01

A key step in blood vessel development (angiogenesis) is lumen formation: the hollowing of vessels for blood perfusion. Two alternative lumen formation mechanisms are suggested to function in different types of blood vessels. The vacuolation mechanism is suggested for lumen formation in small vessels by coalescence of intracellular vacuoles, a view that was extended to extracellular lumen formation by exocytosis of vacuoles. The cell–cell repulsion mechanism is suggested to initiate extracellular lumen formation in large vessels by active repulsion of adjacent cells, and active cell shape changes extend the lumen. We used an agent-based computer model, based on the cellular Potts model, to compare and study both mechanisms separately and combined. An extensive sensitivity analysis shows that each of the mechanisms on its own can produce lumens in a narrow region of parameter space. However, combining both mechanisms makes lumen formation much more robust to the values of the parameters, suggesting that the mechanisms may work synergistically and operate in parallel, rather than in different vessel types. PMID:24430123

Yes Virginia, quantum mechanics can be understood

CERN Document Server

Wallace, John P

2017-01-01

Virginia, B. W. Wooster, and Jeeves take up physics with the hope of understanding quantum mechanics. In the process they take a rather grand tour on an old sailing ship and aid a sow in distress. On their journey they discover that physics is not as difficult a subject as they imagined. When they dismantled physics and reassembled it in a form where gravity, strong, electromagnetic and the weak forces all stem from understanding the gaming strategy known as the fair-game. That great cultural divide first expounded by the novelist C.P.Snow was found to be a mere ditch that can be stepped over. The sins of the past were violations of energy conservation and strange notions about what mass actually represents. Now mass is defined without the assistance of the Standard Model. Things will not be the same. Singularities have been banished. The electron now has a scale and is no longer captive in a point. The gluon is no longer essential along with the single virtual photon.

Off-critical statistical models: factorized scattering theories and bootstrap program

International Nuclear Information System (INIS)

Mussardo, G.

1992-01-01

We analyze those integrable statistical systems which originate from some relevant perturbations of the minimal models of conformal field theories. When only massive excitations are present, the systems can be efficiently characterized in terms of the relativistic scattering data. We review the general properties of the factorizable S-matrix in two dimensions with particular emphasis on the bootstrap principle. The classification program of the allowed spins of conserved currents and of the non-degenerate S-matrices is discussed and illustrated by means of some significant examples. The scattering theories of several massive perturbations of the minimal models are fully discussed. Among them are the Ising model, the tricritical Ising model, the Potts models, the series of the non-unitary minimal models M 2,2n+3 , the non-unitary model M 3,5 and the scaling limit of the polymer system. The ultraviolet limit of these massive integrable theories can be exploited by the thermodynamics Bethe ansatz, in particular the central charge of the original conformal theories can be recovered from the scattering data. We also consider the numerical method based on the so-called conformal space truncated approach which confirms the theoretical results and allows a direct measurement of the scattering data, i.e. the masses and the S-matrix of the particles in bootstrap interaction. The problem of computing the off-critical correlation functions is discussed in terms of the form-factor approach

Criticality of the discrete N-vector ferromagnet in planar self-dual lattices

International Nuclear Information System (INIS)

Mariz, A.M.; Silva, L.R. da; Stella, A.; Tsallis, C.

1989-01-01

An extended version of the discrete N-vector (or cubic) ferromagnetic model withon a real space renormalization group approach which preserves the two-spin correlation function is studied. The N-evolution (for real values of N) of the Wheatstone-bridge hierarchical lattice phase diagram, which presents paramagnetic, intermediate (nematic-like) and ferromagnetic phases, as well as of the thermal υ and crossover φ critical exponents, is presented. The self-avoiding walk problem is recovered in the N → O limit, and the so called ''corner-rule'' is reobtained in a larger context. The Ising, N- and 2N-state Potts ferromagnets are recovered as particular cases. An interchange of stability occurs at N=N* ≅ 6.9 in such a way that the 2N-state Potts special point (were all three existing phases join) is a multicritical one if N N* (consistently φ(N*)=O). For the cubic model, υ(N) presents a maximum at N=N max ≅1.5. The results are exact, for all N, for the Wheatstone-bridge hierarchical lattice, and approximate, for N≤ 2, for the square lattice. The connection between the present approach and the phenomenological renormalization group, is discussed. (author) [pt

Series expansions without diagrams

International Nuclear Information System (INIS)

Bhanot, G.; Creutz, M.; Horvath, I.; Lacki, J.; Weckel, J.

1994-01-01

We discuss the use of recursive enumeration schemes to obtain low- and high-temperature series expansions for discrete statistical systems. Using linear combinations of generalized helical lattices, the method is competitive with diagrammatic approaches and is easily generalizable. We illustrate the approach using Ising and Potts models. We present low-temperature series results in up to five dimensions and high-temperature series in three dimensions. The method is general and can be applied to any discrete model

The Late Ordovician Extinction: How it became the best understood of the five major extinctions.

Science.gov (United States)

Sheehan, P.

2003-04-01

The end Ordovician extinction has become arguably the best-understood major extinction event in Earth History. A plethora of workers have established the pattern of faunal change and causes of the extinction with remarkably little disagreement. The first indication of increased extinction at the end of the Ordovician was a graph of global diversity patterns by Norman Newell in 1967, although he did not recognize it as a major event. The presence of a major extinction event became clear as William Berry and Art Boucot assembled data for Silurian correlation charts in the late 1960s. The first reports of North African glaciation in the late 1960s provided a cause for the extinction and study of the event snowballed. It was no accident that recognition of the extinction began in North America, because it was there that the extinction completely overturned faunas in the epicontinental seas. Glacio-eustatic regression of shallow seaway coincided with the disappearance of endemic Laurentian faunas and replacement by a highly cosmopolitan fauna in the Silurian. Once the event was established in North America, paleontologists soon found evidence of the event around the globe. The well-documented Hirnantia Fauna was found to correspond to the glacial interval, and Pat Brenchley soon recognized that there were two pulses of extinction, at the beginning and end of the glaciation. At the same time that the faunal changes were being documented geologic studies of the glaciation provided information on the environmental changes associated with the extinction. The timing of the glacial maximum was established in Africa and by the presence of dropstones in high latitude marine rocks. The 1990s saw geochemical techniques employed that allowed examination of atmospheric CO2 and temperature changes. In many places carbonate deposition declined. Glacio-eustatic regression was obvious in many areas, and a sea-level decline in the range of 50-100 m was established. Shallow

Neoliberal policies and urban reconfigurations. Victoria, San Fernando, province of Buenos Aires, a city understood from theory

Directory of Open Access Journals (Sweden)

Laura Ester Donadío

2016-07-01

Full Text Available This article aims to explain from a theoretical conceptual approach the particularities that exist in Victoria, San Fernando, Buenos Aires, from its urban production. Through a series of field works, semi-structured interviews and observations, it was possible to perceive that in this locality, there are three logics of city production, market, state and necessity, according to Abramo, P. (2002. The post-development cities of Latin America, a space in which constant tensions are generated that alter the harmonious development of daily life and the interaction of those who inhabit the area. On the other hand, it is also perceived that the inhabitants naturalize that way of life, their spatial disposition, the progressive privatization of public areas and the proliferation of closed housing estates. Here is a quote that we have heard repeatedly in interviews with the neighbors: "No one in Victoria gives a ball to anyone." At the moment of understanding Victoria from the theory, we take into account such concepts as the "heterotopy" of Foucault M. (1967 - understood as the juxtaposition of spaces that would be incompatible -the term "com-fusa city" (Abramo P. - as an urban structure that interweaves two traditional models (the Mediterranean compact and the Anglo-Saxon diffused, the notion of "privatopia" by I.Rodriguez Chumillas (2005 and E. Mckenzie (1994 as private spatial consolidation, and finally the concepts: informative and dual cities of R Castells (1995 terms that emerge from the process of globalization, which may be useful to think about the reality of Victoria .

Extending canonical Monte Carlo methods

International Nuclear Information System (INIS)

Velazquez, L; Curilef, S

2010-01-01

In this paper, we discuss the implications of a recently obtained equilibrium fluctuation-dissipation relation for the extension of the available Monte Carlo methods on the basis of the consideration of the Gibbs canonical ensemble to account for the existence of an anomalous regime with negative heat capacities C α with α≈0.2 for the particular case of the 2D ten-state Potts model

Poorly understood and often miscategorized congenital umbilical cord hernia: an alternative repair method.

Science.gov (United States)

İnce, E; Temiz, A; Ezer, S S; Gezer, H Ö; Hiçsönmez, A

2017-06-01

Umbilical cord hernia is poorly understood and often miscategorized as "omphalocele minor". Careless clamping of the cord leads to iatrogenic gut injury in the situation of umbilical cord hernia. This study aimed to determine the characteristics and outcomes of umbilical cord hernias. We also highlight an alternative repair method for umbilical cord hernias. We recorded 15 cases of umbilical cord hernias over 10 years. The patients' data were retrospectively reviewed, and preoperative preparation of the newborn, gestational age, birth weight, other associated malformations, surgical technique used, enteral nutrition, and length of hospitalization were recorded. This study included 15 neonates with umbilical cord hernias. The mean gestational age at the time of referral was 38.2 ± 2.1

Factorizable S-matrix and symmetry operator with toroidal rapidity values

International Nuclear Information System (INIS)

Hu Zhanning; Hou Boyu

1992-01-01

The factorizable S-matrix was constructed and the symmetry operator which commutes with the S-metric and has a new form of 'co-product', the elements of which depend on the parameters defining the toroidal rapidity surface. By defining a new operator which commutes with the symmetry operator the Yang-Baxter equation can be obtained. Finally, the relation between the broken Z N -symmetric model and the chiral Potts model was expressed explicitly in the self-dual genus zero limit

Lattice models and integrability: a special issue in honour of F Y Wu

Science.gov (United States)

Guttmann, A. J.; Jacobsen, J. L.

2012-12-01

published in the April issue of Physical Review Letters (PRL) of the same year [4], and in September 1967, Wu moved to Northeastern University to join Lieb's group. Wu taught at Northeastern for 39 years until his retirement in 2006 as the Matthews Distinguished University Professor of Physics. Over the years, Wu has published more than 230 papers and monographs, and he continues to publish after retirement. Most of his research since 1967 is in exact and rigorous analyses of lattice models and integrable systems, which is the theme of this special issue. In 1968, after Wu's arrival at Northeastern, Lieb and Wu obtained the exact solution of the ground state of the one-dimensional Hubbard model and published the result in PRL [5], a work which has since become highly important after the advent of high-temperature superconductivity. This Lieb-Wu paper and Wu's 1982 review of the Potts model in Reviews of Modern Physics [37] are among the most cited papers in condensed matter physics. Later in 1968 Lieb departed Northeastern for MIT. As a result, the full version of the solution was not published until 34 years later [38] when Lieb and Wu collaborated to work on the manuscript on the occasion of Wu's 70th birthday. Wu spent the summer of 1968 at Stony Brook as the guest of C N Yang. Working with Yang's student, C Fan, he extended the Pfaffian solution of the Ising model to general lattices and termed such models 'free-fermion', a term now in common use [6]. In 1972, Wu visited R J Baxter, whom he had met earlier in 1968 at MIT, in Canberra, Australia, with the support of a Fulbright grant. They solved the triangular-lattice Ising model with 3-spin interactions [7], a model now known as the Baxter-Wu model. It was an ideal collaboration. While Baxter derived the solution algebraically, Wu used graphical methods to reduce the problem to an Ashkin-Teller model, which greatly simplifies the presentation. While in Canberra, Wu also studied the 8-vertex model on the honeycomb

Nucleation barrier reconstruction via the seeding method in a lattice model with competing nucleation pathways.

Science.gov (United States)

Lifanov, Yuri; Vorselaars, Bart; Quigley, David

2016-12-07

We study a three-species analogue of the Potts lattice gas model of nucleation from solution in a regime where partially disordered solute is a viable thermodynamic phase. Using a multicanonical sampling protocol, we compute phase diagrams for the system, from which we determine a parameter regime where the partially disordered phase is metastable almost everywhere in the temperature-fugacity plane. The resulting model shows non-trivial nucleation and growth behaviour, which we examine via multidimensional free energy calculations. We consider the applicability of the model in capturing the multi-stage nucleation mechanisms of polymorphic biominerals (e.g., CaCO 3 ). We then quantitatively explore the kinetics of nucleation in our model using the increasingly popular "seeding" method. We compare the resulting free energy barrier heights to those obtained via explicit free energy calculations over a wide range of temperatures and fugacities, carefully considering the propagation of statistical error. We find that the ability of the "seeding" method to reproduce accurate free energy barriers is dependent on the degree of supersaturation, and severely limited by the use of a nucleation driving force Δμ computed for bulk phases. We discuss possible reasons for this in terms of underlying kinetic assumptions, and those of classical nucleation theory.

Influence of dilution and nature of the interaction on surface and interface magnetism

International Nuclear Information System (INIS)

Tsallis, C.

1986-01-01

The recent theoretical effort of the Rio de Janeiro/CBPF group on surface magnetism is tutorially reviewed. Within a real space renormalization group framework, we analyse the influence of factors such as the number of states per spin (q-state Potts model), the signs of the coupling constants (mixed ferro and antiferromagnetic interactions), the presence of a second semi-infinite bulk (interface case), the symmetry of the interaction (anisotropic Heisenberg model), and surface and/or bulk dilution (bond quenched model). A variety of interesting physical effects emerges. (Autor) [pt

The Opium Must Go Thru The Opium Must Go Thru

Directory of Open Access Journals (Sweden)

Anita Flanders Rebello

2008-04-01

Full Text Available In The Opium Must Go Thru, Charles Potts' "potty" poetic prose puns away in an irreverential anti-civilization protest against everything that is new-old to sublime the old-new - but the dark and light of Yin and Yang are the same that bothered Shakespeare in his day. This book, as the drawings by Robert McNealy illustrate, is a mad socio-economic philosophic chess game. . . an intel lectual whooped up hippy riddle. You ask yourself if Potts is a brain or a bum. The words and the thought behind the words are an exasperating jumble, until you get the "beat" - the mood - maybe a couple of beers, a little "pot". . . No,that won't help because it's too haphardly logical "The water buffalo who bailed out the hot green house once turned to an underfucked cow and murmured "Nobody here understands what I say". And Potts can jump from this hurly-burly into crystal clear statements such as, "But the children can think circles around them. Children have always been the redeemers."

The market of human organs: a window into a poorly understood global business.

Science.gov (United States)

Surman, O S; Saidi, R; Purtilo, R; Simmerling, M; Ko, D; Burke, T F

2008-03-01

The global demand for human organs has set the stage for an exploding and poorly understood global business in human organs. Whenever there is demand for a product, the opportunity for business arises. The form that a business takes is dependent on a complex network of inputs and outputs, each affecting the others. Historically, the details of any specific market are drastically underestimated. Nowhere is this truer than in the market of human organs. The drivers, which propel the "goods" of human organs, form a flourishing business. Critical analysis is essential to understanding of the supply and demand sides and to determine the role of government in regulating the industry. Governmental groups have dismissed formation of a regulated market for organ sales. The concept is nonetheless a topic of active discussion, motivated by the suffering of patients in need of organs and exploitation of the victims of human trafficking. Ethical principles have been invoked on each side of the ensuing debate. Theory in the absence of sufficient data is shaky ground for enactment of new policy. The Aristotelian concept of "practical wisdom" and the pragmatism of William James illuminate the importance of scientific investigation as guide to policy formation. How will stakeholders benefit or lose? What impact might be anticipated in regard to organized medicine's social contract? What can we learn about cross-cultural differences and their effect on the global landscape?

A global sensitivity analysis approach for morphogenesis models

KAUST Repository

Boas, Sonja E. M.

2015-11-21

Background Morphogenesis is a developmental process in which cells organize into shapes and patterns. Complex, non-linear and multi-factorial models with images as output are commonly used to study morphogenesis. It is difficult to understand the relation between the uncertainty in the input and the output of such ‘black-box’ models, giving rise to the need for sensitivity analysis tools. In this paper, we introduce a workflow for a global sensitivity analysis approach to study the impact of single parameters and the interactions between them on the output of morphogenesis models. Results To demonstrate the workflow, we used a published, well-studied model of vascular morphogenesis. The parameters of this cellular Potts model (CPM) represent cell properties and behaviors that drive the mechanisms of angiogenic sprouting. The global sensitivity analysis correctly identified the dominant parameters in the model, consistent with previous studies. Additionally, the analysis provided information on the relative impact of single parameters and of interactions between them. This is very relevant because interactions of parameters impede the experimental verification of the predicted effect of single parameters. The parameter interactions, although of low impact, provided also new insights in the mechanisms of in silico sprouting. Finally, the analysis indicated that the model could be reduced by one parameter. Conclusions We propose global sensitivity analysis as an alternative approach to study the mechanisms of morphogenesis. Comparison of the ranking of the impact of the model parameters to knowledge derived from experimental data and from manipulation experiments can help to falsify models and to find the operand mechanisms in morphogenesis. The workflow is applicable to all ‘black-box’ models, including high-throughput in vitro models in which output measures are affected by a set of experimental perturbations.

A global sensitivity analysis approach for morphogenesis models.

Science.gov (United States)

Boas, Sonja E M; Navarro Jimenez, Maria I; Merks, Roeland M H; Blom, Joke G

2015-11-21

Morphogenesis is a developmental process in which cells organize into shapes and patterns. Complex, non-linear and multi-factorial models with images as output are commonly used to study morphogenesis. It is difficult to understand the relation between the uncertainty in the input and the output of such 'black-box' models, giving rise to the need for sensitivity analysis tools. In this paper, we introduce a workflow for a global sensitivity analysis approach to study the impact of single parameters and the interactions between them on the output of morphogenesis models. To demonstrate the workflow, we used a published, well-studied model of vascular morphogenesis. The parameters of this cellular Potts model (CPM) represent cell properties and behaviors that drive the mechanisms of angiogenic sprouting. The global sensitivity analysis correctly identified the dominant parameters in the model, consistent with previous studies. Additionally, the analysis provided information on the relative impact of single parameters and of interactions between them. This is very relevant because interactions of parameters impede the experimental verification of the predicted effect of single parameters. The parameter interactions, although of low impact, provided also new insights in the mechanisms of in silico sprouting. Finally, the analysis indicated that the model could be reduced by one parameter. We propose global sensitivity analysis as an alternative approach to study the mechanisms of morphogenesis. Comparison of the ranking of the impact of the model parameters to knowledge derived from experimental data and from manipulation experiments can help to falsify models and to find the operand mechanisms in morphogenesis. The workflow is applicable to all 'black-box' models, including high-throughput in vitro models in which output measures are affected by a set of experimental perturbations.

Content-Based Instruction Understood in Terms of Connectionism and Constructivism

Science.gov (United States)

Lain, Stephanie

2016-01-01

Despite the number of articles devoted to the topic of content-based instruction (CBI), little attempt has been made to link the claims for CBI to research in cognitive science. In this article, I review the CBI model of foreign language (FL) instruction in the context of its close alignment with two emergent frameworks in cognitive science:…

Deep neural networks for direct, featureless learning through observation: The case of two-dimensional spin models

Science.gov (United States)

Mills, Kyle; Tamblyn, Isaac

2018-03-01

We demonstrate the capability of a convolutional deep neural network in predicting the nearest-neighbor energy of the 4 ×4 Ising model. Using its success at this task, we motivate the study of the larger 8 ×8 Ising model, showing that the deep neural network can learn the nearest-neighbor Ising Hamiltonian after only seeing a vanishingly small fraction of configuration space. Additionally, we show that the neural network has learned both the energy and magnetization operators with sufficient accuracy to replicate the low-temperature Ising phase transition. We then demonstrate the ability of the neural network to learn other spin models, teaching the convolutional deep neural network to accurately predict the long-range interaction of a screened Coulomb Hamiltonian, a sinusoidally attenuated screened Coulomb Hamiltonian, and a modified Potts model Hamiltonian. In the case of the long-range interaction, we demonstrate the ability of the neural network to recover the phase transition with equivalent accuracy to the numerically exact method. Furthermore, in the case of the long-range interaction, the benefits of the neural network become apparent; it is able to make predictions with a high degree of accuracy, and do so 1600 times faster than a CUDA-optimized exact calculation. Additionally, we demonstrate how the neural network succeeds at these tasks by looking at the weights learned in a simplified demonstration.

Random-fractal Ansatz for the configurations of two-dimensional critical systems.

Science.gov (United States)

Lee, Ching Hua; Ozaki, Dai; Matsueda, Hiroaki

2016-12-01

Critical systems have always intrigued physicists and precipitated the development of new techniques. Recently, there has been renewed interest in the information contained in the configurations of classical critical systems, whose computation do not require full knowledge of the wave function. Inspired by holographic duality, we investigated the entanglement properties of the classical configurations (snapshots) of the Potts model by introducing an Ansatz ensemble of random fractal images. By virtue of the central limit theorem, our Ansatz accurately reproduces the entanglement spectra of actual Potts snapshots without any fine tuning of parameters or artificial restrictions on ensemble choice. It provides a microscopic interpretation of the results of previous studies, which established a relation between the scaling behavior of snapshot entropy and the critical exponent. More importantly, it elucidates the role of ensemble disorder in restoring conformal invariance, an aspect previously ignored. Away from criticality, the breakdown of scale invariance leads to a renormalization of the parameter Σ in the random fractal Ansatz, whose variation can be used as an alternative determination of the critical exponent. We conclude by providing a recipe for the explicit construction of fractal unit cells consistent with a given scaling exponent.

Supplementary Material for: A global sensitivity analysis approach for morphogenesis models

KAUST Repository

Boas, Sonja

2015-01-01

Abstract Background Morphogenesis is a developmental process in which cells organize into shapes and patterns. Complex, non-linear and multi-factorial models with images as output are commonly used to study morphogenesis. It is difficult to understand the relation between the uncertainty in the input and the output of such ‘black-box’ models, giving rise to the need for sensitivity analysis tools. In this paper, we introduce a workflow for a global sensitivity analysis approach to study the impact of single parameters and the interactions between them on the output of morphogenesis models. Results To demonstrate the workflow, we used a published, well-studied model of vascular morphogenesis. The parameters of this cellular Potts model (CPM) represent cell properties and behaviors that drive the mechanisms of angiogenic sprouting. The global sensitivity analysis correctly identified the dominant parameters in the model, consistent with previous studies. Additionally, the analysis provided information on the relative impact of single parameters and of interactions between them. This is very relevant because interactions of parameters impede the experimental verification of the predicted effect of single parameters. The parameter interactions, although of low impact, provided also new insights in the mechanisms of in silico sprouting. Finally, the analysis indicated that the model could be reduced by one parameter. Conclusions We propose global sensitivity analysis as an alternative approach to study the mechanisms of morphogenesis. Comparison of the ranking of the impact of the model parameters to knowledge derived from experimental data and from manipulation experiments can help to falsify models and to find the operand mechanisms in morphogenesis. The workflow is applicable to all ‘black-box’ models, including high-throughput in vitro models in which output measures are affected by a set of experimental perturbations.

Can delusions be understood linguistically?

Science.gov (United States)

Hinzen, Wolfram; Rosselló, Joana; McKenna, Peter

2016-07-01

Delusions are widely believed to reflect disturbed cognitive function, but the nature of this remains elusive. The "un-Cartesian" cognitive-linguistic hypothesis maintains (a) that there is no thought separate from language, that is, there is no distinct mental space removed from language where "thinking" takes place; and (b) that a somewhat broadened concept of grammar is responsible for bestowing meaning on propositions, and this among other things gives them their quality of being true or false. It is argued that a loss of propositional meaning explains why delusions are false, impossible and sometimes fantastic. A closely related abnormality, failure of linguistic embedding, can additionally account for why delusions are held with fixed conviction and are not adequately justified by the patient. The un-Cartesian linguistic approach to delusions has points of contact with Frith's theory that inability to form meta-representations underlies a range of schizophrenic symptoms. It may also be relevant to the nature of the "second factor" in monothematic delusions in neurological disease. Finally, it can inform the current debate about whether or not delusions really are beliefs.

Home is to be understood

DEFF Research Database (Denmark)

Buhl, Mie; Werner Hansen, Siv

2018-01-01

, and involved artists with refugee status (mainly from Syria), a group of local volunteers, and members of the museum staff. The project derived from the annual theme “ON THE MOVE” and culminated in an art exhibition and event on June 4th 2016. Up until then the museum had invited the artists to create artworks...... for the exhibition, while including the volunteers in the process, facilitating the meeting of those who are at home and those who are on the run. In this sense, the MFSK situates themselves as a social-political activist; a contemporary institution dealing with contemporary societal issues. The migrant and refugee...... of engaging with themes of refuge, home and exile? What are the implications of volunteering in such project? The paper’s discussions are framed by the theories of gallery education (Bishop, 2006; Mörsch, 2009), co-creation in museums (Simon, 2010), community arts (Kester, 2013), and draws on fieldwork...

Can delusions be understood linguistically?

Science.gov (United States)

Hinzen, Wolfram; Rosselló, Joana; McKenna, Peter

2016-01-01

ABSTRACT Delusions are widely believed to reflect disturbed cognitive function, but the nature of this remains elusive. The “un-Cartesian” cognitive-linguistic hypothesis maintains (a) that there is no thought separate from language, that is, there is no distinct mental space removed from language where “thinking” takes place; and (b) that a somewhat broadened concept of grammar is responsible for bestowing meaning on propositions, and this among other things gives them their quality of being true or false. It is argued that a loss of propositional meaning explains why delusions are false, impossible and sometimes fantastic. A closely related abnormality, failure of linguistic embedding, can additionally account for why delusions are held with fixed conviction and are not adequately justified by the patient. The un-Cartesian linguistic approach to delusions has points of contact with Frith’s theory that inability to form meta-representations underlies a range of schizophrenic symptoms. It may also be relevant to the nature of the “second factor” in monothematic delusions in neurological disease. Finally, it can inform the current debate about whether or not delusions really are beliefs. PMID:27322493

How flares can be understood

International Nuclear Information System (INIS)

Severny, A.B.

1977-01-01

Specific features of the flare phenomenon which are important for understanding of flares are the following: (1) Fine structure of visible emission of flares, especially at the very beginning and in the pre-flare active region. This structure can be seen also in later stages of development as bright points, some of which exist from the flare beginning (Babin's observations at Crimea, 1972-1976). (2) Turbulent motion with velocities up to 250-300 km s -1 as can be estimated from broadening of emission lines. (3) Predominantly red asymmetry of emission lines in the explosive phase and during further development of flares. (4) 'Supersonic' velocities and supergravitational accelerations of separate moving masses of the flare plasma. (5) The appearance of flares in areas with high grad H, exceeding 0.1 G km -1 which is equivalent to regions of electric currents > approximately 10 11 A. (6) Strong variations of net magnetic flux through the active region, as it follows from Meudon, Crimean, and Sacramento Peak (Rust's) observations. (Auth.)

We Have Not Understood Descartes.

Science.gov (United States)

Vallias, Andras

1996-01-01

Describes a personal involvement with digital media and the origins of the conception of the "diagrammatic" poem. Reflects on what is considered to be a poem in tune with today's computerized society. (PA)

Building crop models within different crop modelling frameworks

NARCIS (Netherlands)

Adam, M.Y.O.; Corbeels, M.; Leffelaar, P.A.; Keulen, van H.; Wery, J.; Ewert, F.

2012-01-01

Modular frameworks for crop modelling have evolved through simultaneous progress in crop science and software development but differences among these frameworks exist which are not well understood, resulting in potential misuse for crop modelling. In this paper we review differences and similarities

Adsorption on metal surfaces: Final report

International Nuclear Information System (INIS)

Einstein, T.L.; Glover, R.E. III; Park, R.L.

1987-01-01

This report discusses the progress at the University of Maryland Department of Physics on the adsorption of atoms or molecules on the surfaces of metals. Also discussed are: Phase transformation studies; the use of transfer matrices to study the 2-d, 3-state chiral Potts model; electron-induced ionization of core electrons of atoms; the reflected electron energy loss fine structure above the M/sub 2,3/ core excitation edge of Cu; and other research in atomic and solid state physics

Break-collapse method for resistor networks-renormalization group applications

International Nuclear Information System (INIS)

Tsallis, C.; Coniglio, A.; Redner, S.

1982-01-01

The break-collapse method recently introduced for the q-state Potts model is adapted for resistor networks. This method greatly simplifies the calculation of the conductance of an arbitrary two-terminal d-dimensional array of conductances, obviating the use of either Kirchhoff's laws or the star-triangle or similiar transformations. Related properties are discussed as well. An illustrative real-space renormalization-group treatment of the random resistor problem on the square lattice is presented; satisfactory results are obtained. (Author) [pt

The Prior Can Often Only Be Understood in the Context of the Likelihood

Directory of Open Access Journals (Sweden)

Andrew Gelman

2017-10-01

Full Text Available A key sticking point of Bayesian analysis is the choice of prior distribution, and there is a vast literature on potential defaults including uniform priors, Jeffreys’ priors, reference priors, maximum entropy priors, and weakly informative priors. These methods, however, often manifest a key conceptual tension in prior modeling: a model encoding true prior information should be chosen without reference to the model of the measurement process, but almost all common prior modeling techniques are implicitly motivated by a reference likelihood. In this paper we resolve this apparent paradox by placing the choice of prior into the context of the entire Bayesian analysis, from inference to prediction to model evaluation.

Recent progress in the theory of random surfaces and simplicial quantum gravity

International Nuclear Information System (INIS)

Ambjoern, J.

1995-01-01

Some of the recent developments in the theory of random surfaces and simplicial quantum gravity is reviewed. For 2d quantum gravity this includes the failure of Regge calculus, our improved understanding of the c>1 regime, some surprises for q-state Potts models with q>4, attempts to use renormalization group techniques, new critical behavior of random surface models with extrinsic curvature and improved algorithms. For simplicial quantum gravity in higher dimensions it includes a discussion of the exponential entropy bound needed for the models to be well defined, the question of ''computational ergodicity'' and the question of how to extract continuum behavior from the lattice simulations. ((orig.))

La structure de Jordan des matrices de transfert des modeles de boucles et la relation avec les hamiltoniens XXZ

Science.gov (United States)

Morin-Duchesne, Alexi

Lattice models such as percolation, the Ising model and the Potts model are useful for the description of phase transitions in two dimensions. Finding analytical solutions is done by calculating the partition function, which in turn requires finding eigenvalues of transfer matrices. At the critical point, the two dimensional statistical models are invariant under conformal transformations and the construction of rational conformal field theories, as the continuum limit of these lattice models, allows one to compute the partition function at the critical point. Many researchers think however that the paradigm of rational conformal conformal field theories can be extended to include models with non diagonalizable transfer matrices. These models would then be described, in the scaling limit, by logarithmic conformal field theories and the representations of the Virasoro algebra coming into play would be indecomposable. We recall the construction of the double-row transfer matrix DN (λ, u) of the Fortuin-Kasteleyn model, seen as an element of the Temperley-Lieb algebra. This transfer matrix comes into play in physical theories through its representation in link modules (or standard modules). The vector space on which this representation acts decomposes into sectors labelled by a physical parameter d, the number of defects, which remains constant or decreases in the link representations. This thesis is devoted to the identification of the Jordan structure of DN(λ, u) in the link representations. The parameter β = 2 cos λ = -(q + q-1) fixes the theory : for instance β = 1 for percolation and 2 for the Ising model. On the geometry of the strip with open boundary conditions, we show that DN(λ, u) has the same Jordan blocks as its highest Fourier coefficient, FN. We study the non-diagonalizability of FN through the divergences of some of the eigenstates of ρ(F N) that appear at the critical values of λ. The Jordan cells we find in ρ(DN(λ, u)) have rank 2 and

Modeling evolutionary dynamics of epigenetic mutations in hierarchically organized tumors.

Directory of Open Access Journals (Sweden)

Andrea Sottoriva

2011-05-01

Full Text Available The cancer stem cell (CSC concept is a highly debated topic in cancer research. While experimental evidence in favor of the cancer stem cell theory is apparently abundant, the results are often criticized as being difficult to interpret. An important reason for this is that most experimental data that support this model rely on transplantation studies. In this study we use a novel cellular Potts model to elucidate the dynamics of established malignancies that are driven by a small subset of CSCs. Our results demonstrate that epigenetic mutations that occur during mitosis display highly altered dynamics in CSC-driven malignancies compared to a classical, non-hierarchical model of growth. In particular, the heterogeneity observed in CSC-driven tumors is considerably higher. We speculate that this feature could be used in combination with epigenetic (methylation sequencing studies of human malignancies to prove or refute the CSC hypothesis in established tumors without the need for transplantation. Moreover our tumor growth simulations indicate that CSC-driven tumors display evolutionary features that can be considered beneficial during tumor progression. Besides an increased heterogeneity they also exhibit properties that allow the escape of clones from local fitness peaks. This leads to more aggressive phenotypes in the long run and makes the neoplasm more adaptable to stringent selective forces such as cancer treatment. Indeed when therapy is applied the clone landscape of the regrown tumor is more aggressive with respect to the primary tumor, whereas the classical model demonstrated similar patterns before and after therapy. Understanding these often counter-intuitive fundamental properties of (non-hierarchically organized malignancies is a crucial step in validating the CSC concept as well as providing insight into the therapeutical consequences of this model.

A model for simulation of coupled microstructural and compositional evolution

International Nuclear Information System (INIS)

Tikare, Veena; Homer, Eric R.; Holm, Elizabeth A.

2011-01-01

The formation, transport and segregation of components in nuclear fuels fundamentally control their behavior, performance, longevity and safety. Most nuclear fuels enter service with a uniform composition consisting of a single phase with two or three components. Fission products form, introducing more components. The segregation and transport of the components is complicated by the underlying microstructure consisting of grains, pores, bubbles and more, which is evolving under temperature gradients during service. As they evolve, components and microstructural features interact such that composition affects microstructure and vice versa. The ability to predict the interdependent compositional and microstructural evolution in 3D as a function of burn-up would greatly improve the ability to design safe, high burn-up nuclear fuels. We present a model that combines elements of Potts Monte Carlo, MC, and the phase-field model to treat coupled microstructural-compositional evolution. This hybrid model uses an equation of state, EOS, based on the microstructural state and the composition. The microstructural portion uses the traditional MC EOS and the compositional portion uses the phase-field EOS: E hyb = N Σ i=1 (E v (q i ,C)+1/2 n Σ j=1 J(q i ,q j )) + ∫κ c (∇C) 2 dV. E v is the bulk free energy of each site i and J is the bond energy between neighboring sites i and j; thus, this term defines the microstructural interfacial energy. The last term is the compositional interfacial energy as defined in the traditional phase-field model. Evolution of coupled microstructure-composition is simulated by minimizing free energy in a path dependent manner. This model will be presented and will be demonstrated by applying it to evolution of nuclear fuels during service. (author)

Critical excitation spectrum of a quantum chain with a local three-spin coupling.

Science.gov (United States)

McCabe, John F; Wydro, Tomasz

2011-09-01

Using the phenomenological renormalization group (PRG), we evaluate the low-energy excitation spectrum along the critical line of a quantum spin chain having a local interaction between three Ising spins and longitudinal and transverse magnetic fields, i.e., a Turban model. The low-energy excitation spectrum found with the PRG agrees with the spectrum predicted for the (D(4),A(4)) conformal minimal model under a nontrivial correspondence between translations at the critical line and discrete lattice translations. Under this correspondence, the measurements confirm a prediction that the critical line of this quantum spin chain and the critical point of the two-dimensional three-state Potts model are in the same universality class.

Critical excitation spectrum of a quantum chain with a local three-spin coupling

International Nuclear Information System (INIS)

McCabe, John F.; Wydro, Tomasz

2011-01-01

Using the phenomenological renormalization group (PRG), we evaluate the low-energy excitation spectrum along the critical line of a quantum spin chain having a local interaction between three Ising spins and longitudinal and transverse magnetic fields, i.e., a Turban model. The low-energy excitation spectrum found with the PRG agrees with the spectrum predicted for the (D 4 ,A 4 ) conformal minimal model under a nontrivial correspondence between translations at the critical line and discrete lattice translations. Under this correspondence, the measurements confirm a prediction that the critical line of this quantum spin chain and the critical point of the two-dimensional three-state Potts model are in the same universality class.

Modeling containment of large wildfires using generalized linear mixed-model analysis

Science.gov (United States)

Mark Finney; Isaac C. Grenfell; Charles W. McHugh

2009-01-01

Billions of dollars are spent annually in the United States to contain large wildland fires, but the factors contributing to suppression success remain poorly understood. We used a regression model (generalized linear mixed-model) to model containment probability of individual fires, assuming that containment was a repeated-measures problem (fixed effect) and...

Screening masses in the SU(3) pure gauge theory and universality

International Nuclear Information System (INIS)

Falcone, R.; Fiore, R.; Gravina, M.; Papa, A.

2007-01-01

We determine from Polyakov loop correlators the screening masses in the deconfined phase of the (3+1)d SU(3) pure gauge theory at finite temperature near the transition, for two different channels of angular momentum and parity. Their ratio is compared with that of the massive excitations with the same quantum numbers in the 3d 3-state Potts model in the broken phase near the transition point at zero magnetic field. Moreover we study the inverse decay length of the correlation between the real parts and between the imaginary parts of the Polyakov loop and compare the results with expectations from perturbation theory and mean-field Polyakov loop models

Chiral phase from three-spin interactions in an optical lattice

International Nuclear Information System (INIS)

D'Cruz, Christian; Pachos, Jiannis K.

2005-01-01

A spin-1/2 chain model that includes three-spin interactions can effectively describe the dynamics of two species of bosons trapped in an optical lattice with a triangular-ladder configuration. A perturbative theoretical approach and numerical study of its ground state is performed that reveals a rich variety of phases and criticalities. We identify phases with periodicity one, two, or three, as well as critical points that belong in the same universality class as the Ising or the three-state Potts model. We establish a range of parameters, corresponding to a large degeneracy present between phases with period 2 and 3, that nests a gapless incommensurate chiral phase

A power law of order 1/4 for critical mean field Swendsen-Wang dynamics

CERN Document Server

Long, Yun; Ning, Weiyang; Peres, Yuval

2014-01-01

The Swendsen-Wang dynamics is a Markov chain widely used by physicists to sample from the Boltzmann-Gibbs distribution of the Ising model. Cooper, Dyer, Frieze and Rue proved that on the complete graph K_n the mixing time of the chain is at most O(\\sqrt{n}) for all non-critical temperatures. In this paper the authors show that the mixing time is \\Theta(1) in high temperatures, \\Theta(\\log n) in low temperatures and \\Theta(n^{1/4}) at criticality. They also provide an upper bound of O(\\log n) for Swendsen-Wang dynamics for the q-state ferromagnetic Potts model on any tree of n vertices.

A test of conformal invariance: Correlation functions on a disk

International Nuclear Information System (INIS)

Badke, R.; Rittenberg, V.; Ruegg, H.

1985-06-01

Using conformal invariance one can derive the correlation functions of a disk from those in the half-plane. The correlation function in the half-plane is determined by the 'small' conformal invariance up to an unknown function of one variable. By measuring through the Monte Carlo method the correlation function for two different configurations, the unknown function can be eliminated and one obtains a test of conformal invariance. It is shown that the Ising and the three state Potts model pass the test for very small lattices. (orig.)

New numerical method to study phase transitions and its applications

International Nuclear Information System (INIS)

Lee, Jooyoung; Kosterlitz, J.M.

1991-11-01

We present a powerful method of identifying the nature of transitions by numerical simulation of finite systems. By studying the finite size scaling properties of free energy barrier between competing states, we can identify unambiguously a weak first order transition even when accessible system sizes are L/ξ < 0.05 as in the five state Potts model in two dimensions. When studying a continuous phase transition we obtain quite accurate estimates of critical exponents by treating it as a field driven first order transition. The method has been successfully applied to various systems

Linear Models

CERN Document Server

Searle, Shayle R

2012-01-01

This 1971 classic on linear models is once again available--as a Wiley Classics Library Edition. It features material that can be understood by any statistician who understands matrix algebra and basic statistical methods.

African Journal of Marine Science - Vol 33, No 1 (2011)

African Journals Online (AJOL)

... area between western and eastern Mediterranean basins (Siculo-Tunisian Strait) ... Cross-shelf observations of diet and diel feeding behaviour of the bearded goby ... WHH Sauer, W Potts, D Raberinary, J Anderson, MJ Sylvio Perrine.

Genetic demixing and evolution in linear stepping stone models

Science.gov (United States)

Korolev, K. S.; Avlund, Mikkel; Hallatschek, Oskar; Nelson, David R.

2010-04-01

Results for mutation, selection, genetic drift, and migration in a one-dimensional continuous population are reviewed and extended. The population is described by a continuous limit of the stepping stone model, which leads to the stochastic Fisher-Kolmogorov-Petrovsky-Piscounov equation with additional terms describing mutations. Although the stepping stone model was first proposed for population genetics, it is closely related to “voter models” of interest in nonequilibrium statistical mechanics. The stepping stone model can also be regarded as an approximation to the dynamics of a thin layer of actively growing pioneers at the frontier of a colony of micro-organisms undergoing a range expansion on a Petri dish. The population tends to segregate into monoallelic domains. This segregation slows down genetic drift and selection because these two evolutionary forces can only act at the boundaries between the domains; the effects of mutation, however, are not significantly affected by the segregation. Although fixation in the neutral well-mixed (or “zero-dimensional”) model occurs exponentially in time, it occurs only algebraically fast in the one-dimensional model. An unusual sublinear increase is also found in the variance of the spatially averaged allele frequency with time. If selection is weak, selective sweeps occur exponentially fast in both well-mixed and one-dimensional populations, but the time constants are different. The relatively unexplored problem of evolutionary dynamics at the edge of an expanding circular colony is studied as well. Also reviewed are how the observed patterns of genetic diversity can be used for statistical inference and the differences are highlighted between the well-mixed and one-dimensional models. Although the focus is on two alleles or variants, q -allele Potts-like models of gene segregation are considered as well. Most of the analytical results are checked with simulations and could be tested against recent spatial

The Center of Gravity, Systemically Understood

Science.gov (United States)

2013-05-23

manner that gave him the time to pursue and destroy the retreating army. Centuries later, another great captain – Napoléon Bonaparte – employed...Jena-Auerstadt 1806 In 1806, Napoléon Bonaparte became the first operational artist in the history of modern war when he defeated the Prussian... Napoleon , Operational Art, and the Jena Campaign,” in Historical Perspectives of the Operational Art, ed. Michael D. Krause and R. Cody Phillips

The lucid interval associated with epidural bleeding: evolving understanding.

Science.gov (United States)

Ganz, Jeremy C

2013-04-01

, which in turn would delay the development of symptoms. The lucid interval as previously conceived was not properly understood by the French school or by Percival Pott and Benjamin Bell, who all described a symptom-free period prior to the development of infection. The first to have a proper understanding of the interval in relation to an EDH was John Abernethy. The modern description and definition of the lucid interval was the work of Hutchinson and Jacobson in the latter half of the 19th century. Understanding of the pathophysiology of the lucid interval has been advanced by the work of Ford and McLaurin in Cincinnati and a group in Oslo, with the demonstration of what it takes to loosen dura and how an arteriovenous shunt slows down for a while the accumulation of an EDH.

76 FR 75942 - Qualification of Drivers; Exemption Applications; Vision

Science.gov (United States)

2011-12-05

... renewable two-year period. They are: Anthony Brandano (MA) William R. Braun (NM) Stanley E. Elliott (UT.... Mallory (OK) Eldon Miles (IN) Norman V. Myers (WA) Jack E. Potts, Jr. (PA) Neal A. Richard (LA) John E...

The physics of magnetic resonance imaging: how well understood is it?

International Nuclear Information System (INIS)

Reynolds, S.E.

2000-01-01

Full text: Part of my work involves tutoring trainee radiologists on the physics of magnetic resonance imaging (MRI). I have observed that a full understanding of the physics involved with MRI, or nuclear magnetic resonance (NMR) to be more specific, seems to be beyond the hopes of many people working in the field. All diagnostic radiology textbooks that I have read touch very superficially on the physics of NMR and sometimes the explanations and models used are quite inaccurate and misleading. After further investigation, I found some very good coverage on the subject in chemistry texts. The physics of NMR is based on some very difficult quantum mechanical concepts. What I have managed to understand has been tremendously satisfying and has shed light on several conceptual difficulties which I initially struggled with. The physics of MRI is based on the motion of the hydrogen proton when subjected to an external magnetic field. Protons, which are positively charged particles, have an intrinsic spin and as a result, a magnetic field. A proton, when placed in an external magnetic field, undergoes several changes in its motion. The laws of quantum mechanics govern these changes. Diagnostic radiology textbook models describing the motion of a proton tend to be poor and inaccurate leading to confusion. For example, subatomic particles are subject to laws of quantum mechanics and are forbidden to align exactly with an applied magnetic field thus creating precession. Some textbooks make no attempt to explain this phenomenon whereas others attempt a superficial but inadequate quantum mechanical explanation. I am interested to canvas opinions from others involved in MRI as to difficulties they have encountered with the understanding of the physics of MRI and how they have been overcome. Copyright (2000) Australasian College of Physical Scientists and Engineers in Medicine

78 FR 67452 - Qualification of Drivers; Exemption Applications; Vision

Science.gov (United States)

2013-11-12

... exemption for a renewable two-year period. They are: Anthony Brandano (MA) Stanley E. Elliott (UT) Elmer E...) Raymond P. Madron (MD) Ronald S. Mallory (OK) Eldon Miles (IN) Norman V. Myers (WA) Jack E. Potts, Jr. (PA...

Exact critical properties of two-dimensional polymer networks from conformal invariance

International Nuclear Information System (INIS)

Duplantier, B.

1988-03-01

An infinity of exact critical exponents for two-dimensional self-avoiding walks can be derived from conformal invariance and Coulomb gas techniques applied to the O(n) model and to the Potts model. They apply to polymer networks of any topology, for which a general scaling theory is given, valid in any dimension d. The infinite set of exponents has also been calculated to O(ε 2 ), for d=4-ε. The 2D study also includes other universality classes like the dense polymers, the Hamiltonian walks, the polymers at their θ-point. Exact correlation functions can be further given for Hamiltonian walks, and exact winding angle probability distributions for the self-avoiding walks

Computational Modeling of Large Wildfires: A Roadmap

KAUST Repository

Coen, Janice L.; Douglas, Craig C.

2010-01-01

Wildland fire behavior, particularly that of large, uncontrolled wildfires, has not been well understood or predicted. Our methodology to simulate this phenomenon uses high-resolution dynamic models made of numerical weather prediction (NWP) models

Download this PDF file

African Journals Online (AJOL)

Proff.Adewunmi

greatest failures in the history of public health” (Potts and Walsh, 2003, p. ... outdoors (Autier et al., 1998). ... benefits of promoting condoms and other risk reduction tools could thus be “attenuated at the population level and could even be offset ...

Retropharyngeal cold abscess without Pott's spine

African Journals Online (AJOL)

tube≠rculosisof the spine, or external injuries caused by endoscopes or foreignbodies (e.g. fish bones). Tuberculosis of ... drainage of the abscess to achieve optimal results. ... well-defined hypodense necrotic lesion from C1 to C4 measuring.

Conflict Prevalence in Primary School and How It Is Understood to Affect Teaching and Learning in Ghana

Directory of Open Access Journals (Sweden)

Nana Afia Amponsaa Opoku-Asare

2015-07-01

Full Text Available Verbal and non-verbal interactions that occur daily between teachers and headteachers, teachers and pupils, and among pupils can generate conflict that may adversely affect teaching, learning, and schooling effectiveness. Little attention is, however, paid to the quality of relationships that exists between teachers and pupils, among teachers, among pupils, between teachers and their school heads, and between schools and their local communities. This study sought to investigate conflict prevalence in Ghana’s primary schools, and how relationship conflict is understood to affect teaching and learning at the level of headteachers as administrators, teachers as classroom managers, and pupils as learners, and direct beneficiaries of primary education. Using data gathered via interview, questionnaire administration, and observation in 30 public primary schools in 10 circuits of one district of Ashanti Region, the findings revealed a high prevalence of fighting, heckling, bullying, and other forms of relationship conflict among pupils; strained teacher–pupil relations due to insolence, indiscipline, and use of offensive language; and teacher–parent arguments and quarrels due to harsh punishment and verbal assault of pupils. Teacher–pupil conflicts may extend to teachers excluding the affected pupils from teaching and learning activities, denying them the rights to ask and answer questions, and have their class exercises marked, leading to lowered pupil self-esteem, reduced concentration during lessons, and passive involvement in learning activities, which could result in truancy and school dropout. Strengthening guidance mechanisms and encouraging peer mediation could significantly curb conflict in school environments and thereby raise educational standards in the district.

Small vessel disease, neurovascular regulation and cognitive impairment: post-mortem studies reveal a complex relationship, still poorly understood.

Science.gov (United States)

Love, Seth; Miners, J Scott

2017-07-15

The contribution of vascular disease to cognitive impairment is under-recognized and the pathogenesis is poorly understood. This information gap has multiple causes, including a lack of post-mortem validation of clinical diagnoses of vascular cognitive impairment (VCI) or vascular dementia (VaD), the exclusion of cases with concomitant neurodegenerative disease when diagnosing VCI/VaD, and a lack of standardization of neuropathological assessment protocols for vascular disease. Other contributors include a focus on end-stage destructive lesions to the exclusion of more subtle types of diffuse brain injury, on structural abnormalities of arteries and arterioles to the exclusion of non-structural abnormalities and capillary damage, and the use of post-mortem sampling strategies that are biased towards the identification of neurodegenerative pathologies. Recent studies have demonstrated the value of detailed neuropathology in characterizing vascular contributions to cognitive impairment (e.g. in diabetes), and highlight the importance of diffuse white matter changes, capillary damage and vasoregulatory abnormalities in VCI/VaD. The use of standardized, evidence-based post-mortem assessment protocols and the inclusion of biochemical as well as morphological methods in neuropathological studies should improve the accuracy of determination of the contribution of vascular disease to cognitive impairment and clarify the relative contribution of different pathogenic processes to the tissue damage. © 2017 The Author(s). published by Portland Press Limited on behalf of the Biochemical Society.

Inference of epistatic effects in a key mitochondrial protein

Science.gov (United States)

Nelson, Erik D.; Grishin, Nick V.

2018-06-01

We use Potts model inference to predict pair epistatic effects in a key mitochondrial protein—cytochrome c oxidase subunit 2—for ray-finned fishes. We examine the effect of phylogenetic correlations on our predictions using a simple exact fitness model, and we find that, although epistatic effects are underpredicted, they maintain a roughly linear relationship to their true (model) values. After accounting for this correction, epistatic effects in the protein are still relatively weak, leading to fitness valleys of depth 2 N s ≃-5 in compensatory double mutants. Interestingly, positive epistasis is more pronounced than negative epistasis, and the strongest positive effects capture nearly all sites subject to positive selection in fishes, similar to virus proteins evolving under selection pressure in the context of drug therapy.

An analytical model for beaconing in VANETs

NARCIS (Netherlands)

van Eenennaam, Martijn; Remke, Anne Katharina Ingrid; Heijenk, Geert

2012-01-01

IEEE 802.11 CSMA/CA is generally considered to be well-understood, and many detailed models are available. However, most models focus on Unicast in small-scale W-LAN scenarios. When modelling beaconing in VANETs, the Broadcast nature and the (potentially) large number of nodes cause phenomena

Johnson-Laird's mental models theory and its principles: an application with cell mental models of high school students

OpenAIRE

Mª Luz Rodríguez Palmero; Javier Marrero Acosta; Marco Antonio Moreira

2001-01-01

Following a discussion of Johnson-Laird's mental models theory, we report a study regarding high school students mental representations of cell, understood as mental models. Research findings suggest the appropriatedness of such a theory as a framework to interpret students' representations.

tion of tuberculous lymphadenopathy, paraspinal masses

African Journals Online (AJOL)

Enrique

of tuberculous infection, and his name continues in use to describe the spondylitis associated with this infec- tion (Pott's disease). Tuberculous spondylitis is defined as an infection caused by Mycobac-. An unusual presenta- tion of tuberculous lymphadenopathy, paraspinal masses with spondylitis in a young boy.

On D=2 (1/3,1/3) supersymmetric theories 2

International Nuclear Information System (INIS)

Saidi, E.H.; Zerouaoui, J.; Sedra, M.B.

1994-06-01

Denoting by D=2 (1/3,1/3) superalgebra; the off critical symmetry of the Φ 5/7,5/7 perturbation of the C=6/7 conformal theory, we build a new superspace solution of the (1/3,1/3) - subalgebra generated by spin ±1/3 charge operators extending the usual (1/2,1/2) supersymmetry generated by spin ±1/2 charges. This solution is based on the use of two Grassmann variables instead of one parafermionic variable θ ±1/3 satisfying the cubic nilpotency condition (θ ±1/3 ) 3 =0. Known results on the C=6/7 tricritical Potts model are recovered as special features. A relation with N=2 Landau-Ginzburg models is also discussed. (author). 17 refs, 1 tab

Collective cell streams in epithelial monolayers depend on cell adhesion

International Nuclear Information System (INIS)

Czirók, András; Varga, Katalin; Méhes, Előd; Szabó, András

2013-01-01

We report spontaneously emerging, randomly oriented, collective streaming behavior within a monolayer culture of a human keratinocyte cell line, and explore the effect of modulating cell adhesions by perturbing the function of calcium-dependent cell adhesion molecules. We demonstrate that decreasing cell adhesion induces narrower and more anisotropic cell streams, reminiscent of decreasing the Taylor scale of turbulent liquids. To explain our empirical findings, we propose a cell-based model that represents the dual nature of cell–cell adhesions. Spring-like connections provide mechanical stability, while a cellular Potts model formalism represents surface-tension driven attachment. By changing the relevance and persistence of mechanical links between cells, we are able to explain the experimentally observed changes in emergent flow patterns. (paper)

Ashkin-Teller criticality and weak first-order behavior of the phase transition to a fourfold degenerate state in two-dimensional frustrated Ising antiferromagnets

Science.gov (United States)

Liu, R. M.; Zhuo, W. Z.; Chen, J.; Qin, M. H.; Zeng, M.; Lu, X. B.; Gao, X. S.; Liu, J.-M.

2017-07-01

We study the thermal phase transition of the fourfold degenerate phases (the plaquette and single-stripe states) in the two-dimensional frustrated Ising model on the Shastry-Sutherland lattice using Monte Carlo simulations. The critical Ashkin-Teller-like behavior is identified both in the plaquette phase region and the single-stripe phase region. The four-state Potts critical end points differentiating the continuous transitions from the first-order ones are estimated based on finite-size-scaling analyses. Furthermore, a similar behavior of the transition to the fourfold single-stripe phase is also observed in the anisotropic triangular Ising model. Thus, this work clearly demonstrates that the transitions to the fourfold degenerate states of two-dimensional Ising antiferromagnets exhibit similar transition behavior.

How visual cognition influences process model comprehension

NARCIS (Netherlands)

Petrusel, Razvan; Mendling, Jan; Reijers, Hajo A.

2017-01-01

Process analysts and other professionals extensively use process models to analyze business processes and identify performance improvement opportunities. Therefore, it is important that such models can be easily and properly understood. Previous research has mainly focused on two types of factors

Breaking quotations

NARCIS (Netherlands)

Maier, E.

2008-01-01

Quotation exhibits characteristics of both use and mention. I argue against the recently popular pragmatic reductions of quotation to mere language use (Recanati 1), and in favor of a truly hybrid account synthesizing and extending Potts (2) and Geurts & Maier (3), using a mention logic and a

Evil Understood as the Absence of Freedom

DEFF Research Database (Denmark)

Rabjerg, Bjørn

2017-01-01

Self-development is closely related to the idea of formation (or what is referred to as Bildung in German). But when speaking of formation, we have to address the question, ‘what are we formed by?’ Is the human being formed by him- or herself, or by resources originating from outside the self? Fr...

Integrating intracellular dynamics using CompuCell3D and Bionetsolver: applications to multiscale modelling of cancer cell growth and invasion.

Directory of Open Access Journals (Sweden)

Vivi Andasari

Full Text Available In this paper we present a multiscale, individual-based simulation environment that integrates CompuCell3D for lattice-based modelling on the cellular level and Bionetsolver for intracellular modelling. CompuCell3D or CC3D provides an implementation of the lattice-based Cellular Potts Model or CPM (also known as the Glazier-Graner-Hogeweg or GGH model and a Monte Carlo method based on the metropolis algorithm for system evolution. The integration of CC3D for cellular systems with Bionetsolver for subcellular systems enables us to develop a multiscale mathematical model and to study the evolution of cell behaviour due to the dynamics inside of the cells, capturing aspects of cell behaviour and interaction that is not possible using continuum approaches. We then apply this multiscale modelling technique to a model of cancer growth and invasion, based on a previously published model of Ramis-Conde et al. (2008 where individual cell behaviour is driven by a molecular network describing the dynamics of E-cadherin and β-catenin. In this model, which we refer to as the centre-based model, an alternative individual-based modelling technique was used, namely, a lattice-free approach. In many respects, the GGH or CPM methodology and the approach of the centre-based model have the same overall goal, that is to mimic behaviours and interactions of biological cells. Although the mathematical foundations and computational implementations of the two approaches are very different, the results of the presented simulations are compatible with each other, suggesting that by using individual-based approaches we can formulate a natural way of describing complex multi-cell, multiscale models. The ability to easily reproduce results of one modelling approach using an alternative approach is also essential from a model cross-validation standpoint and also helps to identify any modelling artefacts specific to a given computational approach.

Firm efficiency and returns-to-scale in the honey bee pollination services industry

Science.gov (United States)

Honeybees are well-known for producing honey, but they also provide critical ecosystem services through pollination (Goulson, 2003; Potts et al., 2010; Ványi et al., 2012). This pollination service is vital to the production of many cash crops, on which the U.S. agricultural sector depends (Aizen an...

African Journal of Marine Science - Vol 30, No 1 (2008)

African Journals Online (AJOL)

Estuarine use by spotted grunter Pomadasys commersonnii in a South African estuary, as determined by acoustic telemetry · EMAIL FULL TEXT EMAIL FULL TEXT DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. A-R Childs, PD Cowley, TF Næsje, AJ Booth, WM Potts, EB Thorstad, F Økland, 123-132.

Probability on graphs random processes on graphs and lattices

CERN Document Server

Grimmett, Geoffrey

2018-01-01

This introduction to some of the principal models in the theory of disordered systems leads the reader through the basics, to the very edge of contemporary research, with the minimum of technical fuss. Topics covered include random walk, percolation, self-avoiding walk, interacting particle systems, uniform spanning tree, random graphs, as well as the Ising, Potts, and random-cluster models for ferromagnetism, and the Lorentz model for motion in a random medium. This new edition features accounts of major recent progress, including the exact value of the connective constant of the hexagonal lattice, and the critical point of the random-cluster model on the square lattice. The choice of topics is strongly motivated by modern applications, and focuses on areas that merit further research. Accessible to a wide audience of mathematicians and physicists, this book can be used as a graduate course text. Each chapter ends with a range of exercises.

Review of Parton Recombination Models

International Nuclear Information System (INIS)

Bass, Steffen A

2006-01-01

Parton recombination models have been very successful in explaining data taken at RHIC on hadron spectra and emission patterns in Au+Au collisions at transverse momenta above 2 GeV/c, which have exhibited features which could not be understood in the framework of basic perturbative QCD. In this article I will review the current status on recombination models and outline which future challenges need to be addressed by this class of models

Surgeon-level reporting presented by funnel plot is understood by doctors but inaccurately interpreted by members of the public.

Science.gov (United States)

Bhalla, Ashish; Mehrotra, Prerna; Amawi, Falah; Lund, Jonathan N

2015-01-01

Risk-adjusted outcome data for general surgeons practicing in the United Kingdom were published for the first time in 2013 with the aim of increasing transparency, improving standards, and providing the public with information to aid decision making. Most specialties used funnel plots to present their data. We assess the ability of members of the public (MoP), medical students, nonsurgical doctors (NSD), and surgeons to understand risk-adjusted surgical outcome data. A fictitious outcome dataset was created and presented in the form of a funnel plot to 10 participants from each of the aforementioned group. Standard explanatory text was provided. Each participant was given 5 minutes to review the funnel plot and complete a questionnaire. For each question, there was only 1 correct answer. Completion rate was 100% (n = 40). No difference existed between NSD and surgeons. A significant difference for identification of the "worst performing surgeon" was noted between surgeons and MoP (p plot significantly "more difficult" to interpret than surgeons did (p < 0.01) and NSD (p < 0.01). MoP found these data significantly more "difficult to understand" and were less likely to both spot "outliers" and use this data to inform decisions than doctors. Surgeons should be aware that outcome data may require an alternative method of presentation to be understood by MoP. Copyright © 2015 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.

Ovarian tumor attachment, invasion and vascularization reflect unique microenvironments in the peritoneum:Insights from xenograft and mathematical models

Directory of Open Access Journals (Sweden)

Mara P. Steinkamp

2013-05-01

Full Text Available Ovarian cancer relapse is often characterized by metastatic spread throughout the peritoneal cavity with tumors attached to multiple organs. In this study, interaction of ovarian tumor cells with the peritoneal tumor microenvironment was evaluated in a xenograft model based on intraperitoneal injection of fluorescent SKOV3.ip1 ovarian cancer cells. Intra-vital microscopy of mixed GFP-RFP cell populations injected into the peritoneum demonstrated that tumor cells aggregate and attach as mixed spheroids, emphasizing the importance of homotypic adhesion in tumor formation. Electron microscopy provided high resolution structural information about local attachment sites. Experimental measurements from the mouse model were used to build a three-dimensional cellular Potts ovarian tumor model (OvTM that examines ovarian tumor cell attachment, chemotaxis, growth and vascularization. OvTM simulations provide insight into the relative influence of tumor cell-cell adhesion, oxygen availability, and local architecture on tumor growth and morphology. Notably, tumors on the mesentery, omentum or spleen readily invade the open architecture, while tumors attached to the gut encounter barriers that restrict invasion and instead rapidly expand into the peritoneal space. Simulations suggest that rapid neovascularization of SKOV3.ip1 tumors is triggered by constitutive release of angiogenic factors in the absence of hypoxia. This research highlights the importance of cellular adhesion and tumor microenvironment in the seeding of secondary ovarian tumors on diverse organs within the peritoneal cavity. Results of the OvTM simulations indicate that invasion is strongly influenced by features underlying the mesothelial lining at different sites, but is also affected by local production of chemotactic factors. The integrated in vivo mouse model and computer simulations provide a unique platform for evaluating targeted therapies for ovarian cancer relapse.

Fluctuation relations for equilibrium states with broken discrete or continuous symmetries

International Nuclear Information System (INIS)

Lacoste, D; Gaspard, P

2015-01-01

Isometric fluctuation relations are deduced for the fluctuations of the order parameter in equilibrium systems of condensed-matter physics with broken discrete or continuous symmetries. These relations are similar to their analogues obtained for non-equilibrium systems where the broken symmetry is time reversal. At equilibrium, these relations show that the ratio of the probabilities of opposite fluctuations goes exponentially with the symmetry-breaking external field and the magnitude of the fluctuations. These relations are applied to the Curie–Weiss, Heisenberg, and XY models of magnetism where the continuous rotational symmetry is broken, as well as to the q-state Potts model and the p-state clock model where discrete symmetries are broken. Broken symmetries are also considered in the anisotropic Curie–Weiss model. For infinite systems, the results are calculated using large-deviation theory. The relations are also applied to mean-field models of nematic liquid crystals where the order parameter is tensorial. Moreover, their extension to quantum systems is also deduced. (paper)

Validation of mentorship model for newly qualified professional ...

African Journals Online (AJOL)

Newly qualified professional nurses (NQPNs) allocated to community health care services require the use of validated model to practice independently. Validation was done to adapt and assess if the model is understood and could be implemented by NQPNs and mentors employed in community health care services.

Ward identities for conformal models

International Nuclear Information System (INIS)

Lazzarini, S.; Stora, R.

1988-01-01

Ward identities which express the symmetry of conformal models are treated. Diffeomorphism invariance or locally holomorphic coordinate transformations are used. Diffeomorphism invariance is then understood in terms of Riemannian geometry. Two different sets of Ward identities expressing diffeomorphism invariance in a conformally invariant way are found for the free bosonic string. Using a geometrical argument, the correct invariance for a large class of conformal models is given

The Strategies of Modeling in Biology Education

Science.gov (United States)

Svoboda, Julia; Passmore, Cynthia

2013-01-01

Modeling, like inquiry more generally, is not a single method, but rather a complex suite of strategies. Philosophers of biology, citing the diverse aims, interests, and disciplinary cultures of biologists, argue that modeling is best understood in the context of its epistemic aims and cognitive payoffs. In the science education literature,…

The way I understood it, it wasn’t meant to be understood – when 6th grade reads Franz Kafka

DEFF Research Database (Denmark)

Johansen, Martin Blok

2017-01-01

In recent years, literacy problematics and different concepts (Cooperative Learning, Learning Styles) have taken up much of the school’s literature teaching. It has pushed discussions of the professional content into the background. This article takes up the content discussion for renewed debate......, but now also with the aim of discussing the literary texts one can present to children in school. The research questions posed are: Which texts can justifiably be presented to children as part of teaching in school? What will happen if 10 to 12-year-old Danish school pupils are presented with classical...... starting point in three concepts rooted in theory, i.e. unpredictability, defamiliarization and entitlement, which are subsequently used to get to grips with the empirical part of the study. The article does not attempt to depict a hard-and-fast picture of all children being equally enthusiastic about...

`Models of' versus `Models for'. Toward an Agent-Based Conception of Modeling in the Science Classroom

Science.gov (United States)

Gouvea, Julia; Passmore, Cynthia

2017-03-01

The inclusion of the practice of "developing and using models" in the Framework for K-12 Science Education and in the Next Generation Science Standards provides an opportunity for educators to examine the role this practice plays in science and how it can be leveraged in a science classroom. Drawing on conceptions of models in the philosophy of science, we bring forward an agent-based account of models and discuss the implications of this view for enacting modeling in science classrooms. Models, according to this account, can only be understood with respect to the aims and intentions of a cognitive agent (models for), not solely in terms of how they represent phenomena in the world (models of). We present this contrast as a heuristic— models of versus models for—that can be used to help educators notice and interpret how models are positioned in standards, curriculum, and classrooms.

RG flows in the D-series of minimal CFTs

International Nuclear Information System (INIS)

Klassen, T.R.; Melzer, E.

1993-01-01

Using results of the thermodynamic Bethe ansatz approach and conformal perturbation theory we argue that the φ 1,3 perturbation of a unitary minimal (1+1)-dimensional conformal field theory (CFT) in the D-series of modular invariant partition functions induces a renormalization group (RG) flow to the next-lower model in the D-series. An exception is the first model in the series, the three-state Potts CFT, which under the Z 2 -even φ 1,3 -perturbation flows to the tricritical Ising CFT, the second model in the A-series. We present arguments that in the A-series flow corresponding to this exceptional case, interpolating between the tetracritical and the tricritical Ising CFT, the IR fixed point is approached from 'exactly the opposite direction'. Our results indicate how (most of) the relevant conformal fields evolve from the UV to the IR CFT. (orig.)

Threat modeling and circumvention of Internet censorship

OpenAIRE

Fifield, David

2017-01-01

Research on Internet censorship is hampered by poor models of censor behavior. Censor models guide the development of circumvention systems, so it is important to get them right. A censor model should be understood not just as a set of capabilities—such as the ability to monitor network traffic—but as a set of priorities constrained by resource limitations.My research addresses the twin themes of modeling and circumvention. With a grounding in empirical research, I build up an abstract model ...

Rethinking exchange market models as optimization algorithms

Science.gov (United States)

Luquini, Evandro; Omar, Nizam

2018-02-01

The exchange market model has mainly been used to study the inequality problem. Although the human society inequality problem is very important, the exchange market models dynamics until stationary state and its capability of ranking individuals is interesting in itself. This study considers the hypothesis that the exchange market model could be understood as an optimization procedure. We present herein the implications for algorithmic optimization and also the possibility of a new family of exchange market models

Business Schools' Programs Turn Felons into Entrepreneurs

Science.gov (United States)

Mangan, Katherine

2013-01-01

Mike Potts was halfway through a five-year prison sentence outside Houston when he heard about a program that would help him start a business when even buddies with clean records were struggling to find work. The Prison Entrepreneurship Program, run by a nonprofit group of the same name, works with Baylor University's Hankamer School of Business…

International survey on current occupant modelling approaches in building performance simulation

NARCIS (Netherlands)

O'Brien, W.; Gaetani, I.; Gilani, S.; Carlucci, S.; Hoes, P.; Hensen, J.L.M.

2017-01-01

It is not evident that practitioners have kept pace with latest research developments in building occupant behaviour modelling; nor are the attitudes of practitioners regarding occupant behaviour modelling well understood. In order to guide research and development efforts, researchers,

Invasion from a cell aggregate—the roles of active cell motion and mechanical equilibrium

International Nuclear Information System (INIS)

Szabó, A; Varga, K; Czirók, A; Garay, T; Hegedűs, B

2012-01-01

Cell invasion from an aggregate into a surrounding extracellular matrix (ECM) is an important process during development disease, e.g., vascular network assembly or tumor progression. To describe the behavior emerging from autonomous cell motility, cell–cell adhesion and contact guidance by ECM filaments, we propose a suitably modified cellular Potts model. We consider an active cell motility process in which internal polarity is governed by a positive feedback from cell displacements, a mechanism that can result in highly persistent motion when constrained by an oriented ECM structure. The model allows us to explore the interplay between haptotaxis, matrix degradation and active cell movement. We show that for certain conditions the cells are able to both invade the ECM and follow the ECM tracks. Furthermore, we argue that enforcing mechanical equilibrium within a bulk cell mass is of key importance in multicellular simulations

Queueing models for token and slotted ring networks. Thesis

Science.gov (United States)

Peden, Jeffery H.

1990-01-01

Currently the end-to-end delay characteristics of very high speed local area networks are not well understood. The transmission speed of computer networks is increasing, and local area networks especially are finding increasing use in real time systems. Ring networks operation is generally well understood for both token rings and slotted rings. There is, however, a severe lack of queueing models for high layer operation. There are several factors which contribute to the processing delay of a packet, as opposed to the transmission delay, e.g., packet priority, its length, the user load, the processor load, the use of priority preemption, the use of preemption at packet reception, the number of processors, the number of protocol processing layers, the speed of each processor, and queue length limitations. Currently existing medium access queueing models are extended by adding modeling techniques which will handle exhaustive limited service both with and without priority traffic, and modeling capabilities are extended into the upper layers of the OSI model. Some of the model are parameterized solution methods, since it is shown that certain models do not exist as parameterized solutions, but rather as solution methods.

Wood-adhesive bonding failure : modeling and simulation

Science.gov (United States)

Zhiyong Cai

2010-01-01

The mechanism of wood bonding failure when exposed to wet conditions or wet/dry cycles is not fully understood and the role of the resulting internal stresses exerted upon the wood-adhesive bondline has yet to be quantitatively determined. Unlike previous modeling this study has developed a new two-dimensional internal-stress model on the basis of the mechanics of...

Learning Outcomes of 'Understanding Research' as understood by ...

African Journals Online (AJOL)

Simon Bhekumuzi

vision) for using Turnitin as a deterrent, in order to help learners to learn in the process. .... such as the American Psychological Association. (APA) ..... from other people. ..... and enduring concerns (2nd ed). ... Generations: The history of.

Learning Outcomes of 'Understanding Research' as understood by ...

African Journals Online (AJOL)

Simon Bhekumuzi

2015-11-23

Nov 23, 2015 ... Can Turnitin come to the rescue: From teachers' reflections? Simon Bheki Khoza ... In South Africa, however, there are very few schools that expose teachers to Turnitin in order to ... Turnitin program by John M. Barrie, when he was a graduate ... Questions. This article intended to explore and explain teach-.

Tip cell overtaking occurs as a side effect of sprouting in computational models of angiogenesis.

Science.gov (United States)

Boas, Sonja E M; Merks, Roeland M H

2015-11-21

During angiogenesis, the formation of new blood vessels from existing ones, endothelial cells differentiate into tip and stalk cells, after which one tip cell leads the sprout. More recently, this picture has changed. It has become clear that endothelial cells compete for the tip position during angiogenesis: a phenomenon named tip cell overtaking. The biological function of tip cell overtaking is not yet known. From experimental observations, it is unclear to what extent tip cell overtaking is a side effect of sprouting or to what extent it is regulated through a VEGF-Dll4-Notch signaling network and thus might have a biological function. To address this question, we studied tip cell overtaking in computational models of angiogenic sprouting in absence and in presence of VEGF-Dll4-Notch signaling. We looked for tip cell overtaking in two existing Cellular Potts models of angiogenesis. In these simulation models angiogenic sprouting-like behavior emerges from a small set of plausible cell behaviors. In the first model, cells aggregate through contact-inhibited chemotaxis. In the second model the endothelial cells assume an elongated shape and aggregate through (non-inhibited) chemotaxis. In both these sprouting models the endothelial cells spontaneously migrate forwards and backwards within sprouts, suggesting that tip cell overtaking might occur as a side effect of sprouting. In accordance with other experimental observations, in our simulations the cells' tendency to occupy the tip position can be regulated when two cell lines with different levels of Vegfr2 expression are contributing to sprouting (mosaic sprouting assay), where cell behavior is regulated by a simple VEGF-Dll4-Notch signaling network. Our modeling results suggest that tip cell overtaking can occur spontaneously due to the stochastic motion of cells during sprouting. Thus, tip cell overtaking and sprouting dynamics may be interdependent and should be studied and interpreted in combination. VEGF

Schumpeterian economic dynamics as a quantifiable model of evolution

Science.gov (United States)

Thurner, Stefan; Klimek, Peter; Hanel, Rudolf

2010-07-01

We propose a simple quantitative model of Schumpeterian economic dynamics. New goods and services are endogenously produced through combinations of existing goods. As soon as new goods enter the market, they may compete against already existing goods. In other words, new products can have destructive effects on existing goods. As a result of this competition mechanism, existing goods may be driven out from the market—often causing cascades of secondary defects (Schumpeterian gales of destruction). The model leads to generic dynamics characterized by phases of relative economic stability followed by phases of massive restructuring of markets—which could be interpreted as Schumpeterian business 'cycles'. Model time series of product diversity and productivity reproduce several stylized facts of economics time series on long timescales, such as GDP or business failures, including non-Gaussian fat tailed distributions and volatility clustering. The model is phrased in an open, non-equilibrium setup which can be understood as a self-organized critical system. Its diversity dynamics can be understood by the time-varying topology of the active production networks.

Stressor-response modeling using the 2D water quality model and regression trees to predict chlorophyll-a in a reservoir system

Science.gov (United States)

In order to control algal blooms, stressor-response relationships between water quality metrics, environmental variables, and algal growth should be understood and modeled. Machine-learning methods were suggested to express stressor-response relationships found by application of mechanistic water qu...

A matrix model for WZW

International Nuclear Information System (INIS)

Dorey, Nick; Tong, David; Turner, Carl

2016-01-01

We study a U(N) gauged matrix quantum mechanics which, in the large N limit, is closely related to the chiral WZW conformal field theory. This manifests itself in two ways. First, we construct the left-moving Kac-Moody algebra from matrix degrees of freedom. Secondly, we compute the partition function of the matrix model in terms of Schur and Kostka polynomials and show that, in the large N limit, it coincides with the partition function of the WZW model. This same matrix model was recently shown to describe non-Abelian quantum Hall states and the relationship to the WZW model can be understood in this framework.

Modelling hadronic interactions in HEP MC generators

CERN Document Server

Skands, Peter

2015-01-01

HEP event generators aim to describe high-energy collisions in full exclusive detail. They combine perturbative matrix elements and parton showers with dynamical models of less well-understood phenomena such as hadronization, diffraction, and the so-called underlying event. We briefly summarise some of the main concepts relevant to the modelling of soft/inclusive hadron interactions in MC generators, in particular PYTHIA, with emphasis on questions recently highlighted by LHC data.

Understanding organizational congruence: formal model and simulation framework.

NARCIS (Netherlands)

Dignum, M.V.; Dignum, F.P.M.

2007-01-01

Despite a large number of studies, the effect of organizational structure on the performance and the individual cognition of its members is still not well understood. Our research aims at developing tools and formalisms to model organizations and evaluate their performance under different

Towards a data assimilation system for morphodynamic modeling

NARCIS (Netherlands)

Garcia Triana, I.D.T.F.

2014-01-01

Currently, available models are not able to accurately predict the temporal evolution of coastal morphodynamic processes. The main reason for this, is that essential components governing this evolution are neither fully identified nor understood. Additionally, there is high uncertainty in some of

Models for map building and navigation

International Nuclear Information System (INIS)

Penna, M.A.; Jian Wu

1993-01-01

In this paper the authors present several models for solving map building and navigation problems. These models are motivated by biological processes, and presented in the context of artificial neural networks. Since the nodes, weights, and threshold functions of the models all have physical meanings, they can easily predict network topologies and avoid traditional trial-and-error training. On one hand, this makes their models useful in constructing solutions to engineering problems (problems such as those that occur in robotics, for example). On the other hand, this might also contribute to the ability of their models to explain some biological processes, few of which are completely understood at this time

The quantum-classical divide understood in terms of Bohm's holographic paradigm

Energy Technology Data Exchange (ETDEWEB)

Matarese, Vera [The University of Hong Kong (China)

2014-07-01

This paper aims to interpret the problem of the quantum-classical divide following Bohm's holographic model and to reformulate it as an indication of a new physical order. First of all I briefly outline the differences between the classical world and the quantum one (such as locality against nonlocality, determinism against indeterminism and continuity against discontinuity); then I claim that in order to understand the divide between the two domains we should start from what is common, and regard them as two abstractions and limiting cases of a general theory. In particular, following Bohm, I show that the central notion of this new theory is an undivided whole characterized by a general order consisting of a holomovement from an implicate order - the quantum domain - to an explicate order - in the classical domain. This part is explained with the aid of the structure of the hologram and is supported by a reflection on some key terms such as 'order', 'structure', 'implicate' and 'explicate'. Finally I propose that this movement of unfoldment and enfoldment can explain the apparent incompatibility of the two physical domains and the passage from one to the other.

Modeling of NAD+ analogues in horse liver alcohol dehydrogenase

NARCIS (Netherlands)

Beijer, N.A.; Buck, H.M.; Sluyterman, L.A.A.E.; Meijer, E.M.

1990-01-01

So far, the interactions of nicotinamide adenine dinucleotide (NAD+) derivatives with dehydrogenases are not very well understood. This hampers the introduction of NAD+ analogues with improved characteristics concerning industrial application. We have developed an AMBER molecular mechanics model in

Determinants of Academic Entrepreneurship Behavior: A Multilevel Model

Science.gov (United States)

Llano, Joseph Anthony

2010-01-01

It is well established that universities encourage the acquisition and dissemination of new knowledge among university community members and beyond. However, what is less well understood is how universities encourage entrepreneurial (opportunity discovery, evaluation, and exploiting) behavior. This research investigated a multilevel model of the…

(Tropical) soil organic matter modelling: problems and prospects

NARCIS (Netherlands)

Keulen, van H.

2001-01-01

Soil organic matter plays an important role in many physical, chemical and biological processes. However, the quantitative relations between the mineral and organic components of the soil and the relations with the vegetation are poorly understood. In such situations, the use of models is an

The Necker-Zeno model for bistable perception.

Science.gov (United States)

Atmanspacher, Harald; Filk, Thomas

2013-10-01

A novel conceptual framework for theoretical psychology is presented and illustrated for the example of bistable perception. A basic formal feature of this framework is the non-commutativity of operations acting on mental states. A corresponding model for the bistable perception of ambiguous stimuli, the Necker-Zeno model, is sketched and some empirical evidence for it so far is described. It is discussed how a temporal non-locality of mental states, predicted by the model, can be understood and tested. © 2013 Cognitive Science Society, Inc.

Agent-Based Modeling and Analysis of Socio-Technical Systems

NARCIS (Netherlands)

Sharpanskykh, O.

2011-01-01

Socio-technical systems are characterized by high structural and behavioral complexities, which impede understanding and modeling of such systems. In particular, reciprocal relations between diverse local system processes that determine global system dynamics are not well understood. In this article

21st Century Military Operations in a Complex Electromagnetic Environment

Science.gov (United States)

2015-07-01

Natalie Crawford RAND Corporation RDML Jon P. Cryer, USN (ret) Northrop Grumman Mr. Stephen Cummings Raytheon Dr. Eric Evans MIT Lincoln...Heyer U.S. Navy Ms. Leslie Litton U.S. Army Dr. Charles Perkins National Reconnaissance Office Mr. Marvin Potts U.S. Air Force Dr. Stephen ...Neil Fox Virginia Tech Applied Research Corporation Ms. Hannah Freeman Strategic Analysis, Inc. Mr. Marcus Hawkins Strategic Analysis, Inc. Dr

Consistent spectroscopy for a extended gauge model

International Nuclear Information System (INIS)

Oliveira Neto, G. de.

1990-11-01

The consistent spectroscopy was obtained with a Lagrangian constructed with vector fields with a U(1) group extended symmetry. As consistent spectroscopy is understood the determination of quantum physical properties described by the model in an manner independent from the possible parametrizations adopted in their description. (L.C.J.A.)

Spatio-temporal morphology changes in and quenching effects on the 2D spreading dynamics of cell colonies in both plain and methylcellulose-containing culture media.

Science.gov (United States)

Muzzio, N E; Pasquale, M A; Huergo, M A C; Bolzán, A E; González, P H; Arvia, A J

2016-06-01

To deal with complex systems, microscopic and global approaches become of particular interest. Our previous results from the dynamics of large cell colonies indicated that their 2D front roughness dynamics is compatible with the standard Kardar-Parisi-Zhang (KPZ) or the quenched KPZ equations either in plain or methylcellulose (MC)-containing gel culture media, respectively. In both cases, the influence of a non-uniform distribution of the colony constituents was significant. These results encouraged us to investigate the overall dynamics of those systems considering the morphology and size, the duplication rate, and the motility of single cells. For this purpose, colonies with different cell populations (N) exhibiting quasi-circular and quasi-linear growth fronts in plain and MC-containing culture media are investigated. For small N, the average radial front velocity and its change with time depend on MC concentration. MC in the medium interferes with cell mitosis, contributes to the local enlargement of cells, and increases the distribution of spatio-temporal cell density heterogeneities. Colony spreading in MC-containing media proceeds under two main quenching effects, I and II; the former mainly depending on the culture medium composition and structure and the latter caused by the distribution of enlarged local cell domains. For large N, colony spreading occurs at constant velocity. The characteristics of cell motility, assessed by measuring their trajectories and the corresponding velocity field, reflect the effect of enlarged, slow-moving cells and the structure of the medium. Local average cell size distribution and individual cell motility data from plain and MC-containing media are qualitatively consistent with the predictions of both the extended cellular Potts models and the observed transition of the front roughness dynamics from a standard KPZ to a quenched KPZ. In this case, quenching effects I and II cooperate and give rise to the quenched

Single-particle spectral density of the Hubbard model

NARCIS (Netherlands)

Mehlig, B.; Eskes, H.; Hayn, R.; Meinders, M.B.J.

1995-01-01

We calculate the single-particle spectral function for the Hubbard model within the framework of a projection technique equivalent to the two-pole approximation. We show that the two-pole approximation can be well understood as an average characterization of the upper and the lower Hubbard bands,

SINGLE-PARTICLE SPECTRAL DENSITY OF THE HUBBARD-MODEL

NARCIS (Netherlands)

MEHLIG, B; ESKES, H; HAYN, R; MEINDERS, MBJ

1995-01-01

We calculate the single-particle spectral function for the Hubbard model within the framework of a projection technique equivalent to the two-pole approximation. We show that the two-pole approximation can be well understood as an average characterization of the upper and the lower Hubbard bands,

The 3-edge-colouring problem on the 4–8 and 3–12 lattices

International Nuclear Information System (INIS)

Fjærestad, J O

2010-01-01

We consider the problem of counting the number of 3-colourings of the edges (bonds) of the 4–8 lattice and the 3–12 lattice. These lattices are Archimedean with coordination number 3, and can be regarded as decorated versions of the square and honeycomb lattice, respectively. We solve these edge-colouring problems in the infinite-lattice limit by mapping them to other models whose solution is known. The colouring problem on the 4–8 lattice is mapped to a completely packed loop model with loop fugacity n = 3 on the square lattice, which in turn can be mapped to a 6-vertex model. The colouring problem on the 3–12 lattice is mapped to the same problem on the honeycomb lattice. The 3-edge-colouring problems on the 4–8 and 3–12 lattices are equivalent to the 3-vertex-colouring problems (and thus to the zero-temperature 3-state antiferromagnetic Potts model) on the 'square kagome' ('squagome') and 'triangular kagome' lattices, respectively

Health, trust, or "just understood": explicit and implicit condom decision-making processes among black, white, and interracial same-sex male couples.

Science.gov (United States)

Campbell, Chadwick K; Gómez, Anu Manchikanti; Dworkin, Shari; Wilson, Patrick A; Grisham, Kirk K; McReynolds, Jaih; Vielehr, Peter; Hoff, Colleen

2014-05-01

Among gay and bisexual men, primary partners are a leading source of HIV infection. Trust, intimacy, and advancements in HIV treatment may impact same-sex male (SSM) couples' decisions to engage in unprotected anal intercourse (UAI). This qualitative study explored how Black, White and interracial couples discussed, and made decisions regarding condoms. Qualitative interviews were conducted with 48 SSM couples in the New York and San Francisco metropolitan areas. Stratified purposive sampling was used to include Black (n = 16), White (n = 17), and interracial (Black-White) (n = 15) couples. Twenty-six couples were concordant HIV-negative and 22 were HIV-discordant. Interviews were recorded, transcribed, coded, and analyzed using a grounded theory approach. Some couples described explicit processes, which involved active discussion, while others described implicit processes, where condom-use decisions occurred without any explicit discussion. These processes also differed by race and HIV status. Black couples tended to report condom-use as "just understood." White, HIV-discordant couples decided not to use condoms, with some identifying the HIV-positive partner's suppressed viral load and high CD4 count as deciding factors. After an unplanned episode of UAI, White, HIV-negative couples tended to discontinue condom use while Black HIV-negative couples decided to revert to using condoms. HIV prevention efforts focused on same-sex, male couples must consider the explicit/implicit nature of condom decision-making processes. Understanding differences in these processes and considering relationship dynamics, across race and HIV status, can promote the development of innovative couple-level, HIV prevention interventions.

Computational challenges in modeling gene regulatory events.

Science.gov (United States)

Pataskar, Abhijeet; Tiwari, Vijay K

2016-10-19

Cellular transcriptional programs driven by genetic and epigenetic mechanisms could be better understood by integrating "omics" data and subsequently modeling the gene-regulatory events. Toward this end, computational biology should keep pace with evolving experimental procedures and data availability. This article gives an exemplified account of the current computational challenges in molecular biology.

The linear attenuation coefficients as features of multiple energy CT image classification

International Nuclear Information System (INIS)

Homem, M.R.P.; Mascarenhas, N.D.A.; Cruvinel, P.E.

2000-01-01

We present in this paper an analysis of the linear attenuation coefficients as useful features of single and multiple energy CT images with the use of statistical pattern classification tools. We analyzed four CT images through two pointwise classifiers (the first classifier is based on the maximum-likelihood criterion and the second classifier is based on the k-means clustering algorithm) and one contextual Bayesian classifier (ICM algorithm - Iterated Conditional Modes) using an a priori Potts-Strauss model. A feature extraction procedure using the Jeffries-Matusita (J-M) distance and the Karhunen-Loeve transformation was also performed. Both the classification and the feature selection procedures were found to be in agreement with the predicted discrimination given by the separation of the linear attenuation coefficient curves for different materials

How static media is understood and used by high school science teachers

Science.gov (United States)

Hirata, Miguel

The purpose of the present study is to explore the role of static media in textbooks, as defined by Mayer (2001) in the form of printed images and text, and how these media are viewed and used by high school science teachers. Textbooks appeared in the United States in the late 1800s, and since then pictorial aids have been used extensively in them to support the teacher's work in the classroom (Giordano, 2003). According to Woodward, Elliott, and Nagel (1988/2013) the research on textbooks prior to the 1970s doesn't present relevant work related to the curricular role and the quality and instructional design of textbooks. Since then there has been abundant research, specially on the use of visual images in textbooks that has been approached from: (a) the text/image ratio (Evans, Watson, & Willows, 1987; Levin & Mayer, 1993; Mayer, 1993; Woodward, 1993), and (b) the instructional effectiveness of images (Woodward, 1993). The theoretical framework for this study comes from multimedia learning (Mayer, 2001), information design (Pettersson, 2002), and visual literacy (Moore & Dwyer, 1994). Data was collected through in-depth interviews of three high school science teachers and the graphic analyses of three textbooks used by the interviewed teachers. The interview data were compared through an analytic model developed from the literature, and the graphic analyses were performed using Mayer's multimedia learning principles (Mayer, 2001) and the Graphic Analysis Protocol (GAP) (Slough & McTigue, 2013). The conclusions of this study are: (1) pictures are specially useful for teaching science because science is a difficult subject to teach, (2) due this difficulty, pictures are very important to make the class dynamic and avoid students distraction, (3) static and dynamic media when used together can be more effective, (4) some specific type of graphics were found in the science textbooks used by the participants, in this case they were naturalistic drawings, stylized

Stability patterns for a size-structured population model and its stage-structured counterpart

DEFF Research Database (Denmark)

Zhang, Lai; Pedersen, Michael; Lin, Zhigui

2015-01-01

In this paper we compare a general size-structured population model, where a size-structured consumer feeds upon an unstructured resource, to its simplified stage-structured counterpart in terms of equilibrium stability. Stability of the size-structured model is understood in terms of an equivale...... to the population level....

Chemical kinetics and modeling of planetary atmospheres

Science.gov (United States)

Yung, Yuk L.

1990-01-01

A unified overview is presented for chemical kinetics and chemical modeling in planetary atmospheres. The recent major advances in the understanding of the chemistry of the terrestrial atmosphere make the study of planets more interesting and relevant. A deeper understanding suggests that the important chemical cycles have a universal character that connects the different planets and ultimately link together the origin and evolution of the solar system. The completeness (or incompleteness) of the data base for chemical kinetics in planetary atmospheres will always be judged by comparison with that for the terrestrial atmosphere. In the latter case, the chemistry of H, O, N, and Cl species is well understood. S chemistry is poorly understood. In the atmospheres of Jovian planets and Titan, the C-H chemistry of simple species (containing 2 or less C atoms) is fairly well understood. The chemistry of higher hydrocarbons and the C-N, P-N chemistry is much less understood. In the atmosphere of Venus, the dominant chemistry is that of chlorine and sulfur, and very little is known about C1-S coupled chemistry. A new frontier for chemical kinetics both in the Earth and planetary atmospheres is the study of heterogeneous reactions. The formation of the ozone hole on Earth, the ubiquitous photochemical haze on Venus and in the Jovian planets and Titan all testify to the importance of heterogeneous reactions. It remains a challenge to connect the gas phase chemistry to the production of aerosols.

Mathematical modeling of solute transport in the subsurface

International Nuclear Information System (INIS)

Naymik, T.G.

1987-01-01

A review of key works on solute transport models indicates that solute transport processes with the exception of advection are still poorly understood. Solute transport models generally do a good job when they are used to test scientific concepts and hypotheses, investigate natural processes, systematically store and manage data, and simulate mass balance of solutes under certain natural conditions. Solute transport models generally are not good for predicting future conditions with a high degree of certainty, or for determining concentrations precisely. The mathematical treatment of solute transport far surpasses their understanding of the process. Investigations of the extent of groundwater contamination and methods to remedy existing problems show the along-term nature of the hazard. Industrial organic compounds may be immiscible in water, highly volatile, or complexed with inorganic as well as other organic compounds; many remain stable in nature almost indefinitely. In the worst case, future disposal of hazardous waste may be restricted to deep burial, as is proposed for radioactive wastes. For investigations pertinent to transport of radionuclides from a geologic repository, the process cannot be fully understood without adequate thermodynamic and kinetic data bases

Translations on Narcotics and Dangerous Drugs, Number 281.

Science.gov (United States)

1977-01-21

Mr F. Potts, said the State’s industry was of economic and national strategic importance. He said Australia would soon become one of the world’s...have their headquarters in those highly industrialized nations. These statements made by Pedro Ojeda Paullada (currently Secretary of Labor and...involved in the drug traffic. She lives on Tepanco Street, Parque San Andres District, Coyoacan where the marihuana was found. Jovita Ramirez Garcia

The star-triangle relation and the inversion relation in statistical mechanics

International Nuclear Information System (INIS)

Maillard, J.M.

1983-10-01

The plan of this paper is the following: we give a definition of the star-triangle relation (S.T.R.); we also define another very simple relation which occurs simultaneously with the S.T.R. for the two-dimensional (2-d) exact models: the inversion relation (I.R.); we study the connection between the S.T.R. and the I.R.: we see that the S.T.R. is deeply connected to the I.R., but, on the contrary, we see that the I.R. can exist even when no S.T.R. exists, as we show for the 2-d anisotropic Potts model by exhibiting an inverse functional equation satisfied by the partition function; having recognized the I.R. as an interesting concept, we use it by looking at the analytical consequences of this I.R. and, at last, we come back to the S.T.R., examining some consequences of the I.R. on the S.T.R

Process-Structure Linkages Using a Data Science Approach: Application to Simulated Additive Manufacturing Data

International Nuclear Information System (INIS)

Popova, Evdokia; Rodgers, Theron M.; Gong, Xinyi; Cecen, Ahmet; Madison, Jonathan D.; Kalidindi, Surya R.

2017-01-01

A novel data science workflow is developed and demonstrated to extract process-structure linkages (i.e., reduced-order model) for microstructure evolution problems when the final microstructure depends on (simulation or experimental) processing parameters. Our workflow consists of four main steps: data pre-processing, microstructure quantification, dimensionality reduction, and extraction/validation of process-structure linkages. These methods that can be employed within each step vary based on the type and amount of available data. In this paper, this data-driven workflow is applied to a set of synthetic additive manufacturing microstructures obtained using the Potts-kinetic Monte Carlo (kMC) approach. Additive manufacturing techniques inherently produce complex microstructures that can vary significantly with processing conditions. Using the developed workflow, a low-dimensional data-driven model was established to correlate process parameters with the predicted final microstructure. In addition, the modular workflows developed and presented in this work facilitate easy dissemination and curation by the broader community.

Two-dimensional fractal geometry, critical phenomena and conformal invariance

International Nuclear Information System (INIS)

Duplantier, B.

1988-01-01

The universal properties of critical geometrical systems in two-dimensions (2D) like the O (n) and Potts models, are described in the framework of Coulomb gas methods and conformal invariance. The conformal spectrum of geometrical critical systems obtained is made of a discrete infinite series of scaling dimensions. Specific applications involve the fractal properties of self-avoiding walks, percolation clusters, and also some non trivial critical exponents or fractal dimensions associated with subsets of the planar Brownian motion. The statistical mechanics of the same critical models on a random 2D lattice (namely in presence of a critically-fluctuating metric, in the so-called 2D quantum gravity) is also addressed, and the above critical geometrical systems are shown to be exactly solvable in this case. The new ''gravitational'' conformal spectrum so derived is found to satisfy the recent Knizhnik, Polyakov and Zamolodchikov quadratic relation which links it to the standard conformal spectrum in the plane

Growth modes of individual ferrite grains in the austenite to ferrite transformation of low carbon steels

International Nuclear Information System (INIS)

Li, D.Z.; Xiao, N.M.; Lan, Y.J.; Zheng, C.W.; Li, Y.Y.

2007-01-01

The mesoscale deterministic cellular automaton (CA) method and probabilistic Q-state Potts-based Monte Carlo (MC) model have been adopted to investigate independently the individual growth behavior of ferrite grain during the austenite (γ)-ferrite (α) transformation. In these models, the γ-α phase transformation and ferrite grain coarsening induced by α/α grain boundary migration could be simulated simultaneously. The simulations demonstrated that both the hard impingement (ferrite grain coarsening) and the soft impingement (overlapping carbon concentration field) have a great influence on the individual ferrite growth behavior. Generally, ferrite grains displayed six modes of growth behavior: parabolic growth, delayed nucleation and growth, temporary shrinkage, partial shrinkage, complete shrinkage and accelerated growth in the transformation. Some modes have been observed before by the synchrotron X-ray diffraction experiment. The mesoscopic simulation provides an alternative tool for investigating both the individual grain growth behavior and the overall transformation behavior simultaneously during transformation

Emotions are understood from biological motion across remote cultures.

Science.gov (United States)

Parkinson, Carolyn; Walker, Trent T; Memmi, Sarah; Wheatley, Thalia

2017-04-01

Patterns of bodily movement can be used to signal a wide variety of information, including emotional states. Are these signals reliant on culturally learned cues or are they intelligible across individuals lacking exposure to a common culture? To find out, we traveled to a remote Kreung village in Ratanakiri, Cambodia. First, we recorded Kreung portrayals of 5 emotions through bodily movement. These videos were later shown to American participants, who matched the videos with appropriate emotional labels with above chance accuracy (Study 1). The Kreung also viewed Western point-light displays of emotions. After each display, they were asked to either freely describe what was being expressed (Study 2) or choose from 5 predetermined response options (Study 3). Across these studies, Kreung participants recognized Western point-light displays of anger, fear, happiness, sadness, and pride with above chance accuracy. Kreung raters were not above chance in deciphering an American point-light display depicting love, suggesting that recognizing love may rely, at least in part, on culturally specific cues or modalities other than bodily movement. In addition, multidimensional scaling of the patterns of nonverbal behavior associated with each emotion in each culture suggested that similar patterns of nonverbal behavior are used to convey the same emotions across cultures. The considerable cross-cultural intelligibility observed across these studies suggests that the communication of emotion through movement is largely shaped by aspects of physiology and the environment shared by all humans, irrespective of differences in cultural context. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

How Self-Reliance Is Understood: Viewpoints from One Local ...

African Journals Online (AJOL)

DrNneka

intervention makes it easy to see why there is less commitment to ... funding for countries where crisis' stretch government ability to respond ... National agencies such as DfID (UK), Norad (Norway), USAID (USA) and GIZ .... This case study uses a qualitative research design consistent with DiCicco- ..... Swedish International.

Prevalence of obesity: A public health problem poorly understood

Science.gov (United States)

This review article discusses the Dietary Guidelines for Americans in support of a total diet approach to achieving diet and health goals, especially as they relate to the obesity epidemic. However, some scientists and organizations have identified one food, food group, or nutrient as the cause of t...

Inclusion understood from the perspectives of children with disability.

Science.gov (United States)

Spencer-Cavaliere, Nancy; Watkinson, E Jane

2010-10-01

This study explored the perspectives of children with disabilities regarding the concept of inclusion in physical activity. Participants were children (two girls, nine boys, Mage = 10 years, five months, age range: 8-12 years) with disabilities, including cerebral palsy, fine and gross motor delays, developmental coordination disorder, muscular dystrophy, nemaline myopathy, brachial plexus injury, and severe asthma. Children's perspectives on inclusion in physical activity (e.g., sports, games, and play) were explored through semistructured interviews. Interviews were digitally audio taped and transcribed verbatim. Data were analyzed through content analysis. Three themes emerged from the data: gaining entry to play, feeling like a legitimate participant, and having friends. These themes were associated with feeling included to varying degrees in sports, games, and play. In essence, it was the actions of others that were the prominent features identified by children that contributed to feeling more or less included in physical activity contexts. These results are discussed in relation to inclusion in physical education, recreation, and unstructured free play.

English in Dutch commercials: Not understood and not appreciated

NARCIS (Netherlands)

Gerritsen, M.; Korzilius, H.P.L.M.; Meurs, W.F.J. van; Gijsbers, I.

2000-01-01

Dutch consumers are increasingly exposed to English in commercials on television. Advertising agencies appear to use English because of financial and image reasons. This article investigates how often commercials that contain English occur in the Netherlands and whether consumers comprehend the

Happiness in Economics as Understood Across Ism and Religion

OpenAIRE

Abdul Ghafar Ismail; Nurfaradilla Haron

2014-01-01

The concept of happiness has been discussed long time ago by economists. Recently, it became the most related and important thing to be studied because of its impact in societies. Discussion about happiness basically interprets within two separate views. First, happiness related with economic variable, for instance, how money can create happiness. Second happiness is discussed within the context of religion. However, t...

Happiness in Economics as Understood Across Ism and Religion

Directory of Open Access Journals (Sweden)

Abdul Ghafar Ismail

2014-12-01

Full Text Available The concept of happiness has been discussed long time ago by economists. Recently, it became the most related and important thing to be studied because of its impact in societies. Discussion about happiness basically interprets within two separate views. First, happiness related with economic variable, for instance, how money can create happiness. Second happiness is discussed within the context of religion. However, the discussion did not combine both contexts, economic variable and religion, to interpret happiness. Therefore, it is important to highlight the concept of happiness in a different way such as in this article. Different cultures will have their own perspective on the determination of happiness. From just “individual perspective” of happiness, they then formed an ism through involvement of a big society from the same culture. Some isms such as hedonism and materialism are synonyms in characterizing the concept of happiness in this modern world. At the same time, the isms are actually working with the economic and non-economic indicators as elements to strengthen the ism itself. On the other hand, the concept of happiness from the perspective of religion will also be a part of discussion in this article. Therefore, this article will reveal that the meaning of happiness is different in terms of religion and ism. So, to carry out both ism and religion simultaneously in shaping a more intrinsic value of happiness is not an easy task. Furthermore, religion is always associated with spiritual value that makes it hard for some people to practice religion and their isms at the same time. Thus, this article will propose that the right interpretation of isms based on their faith in religion can contribute to the concept of genuine happiness.

On being understood: clarity and jargon in radiation protection.

Science.gov (United States)

Strom, Daniel J; Watson, Charles R

2002-03-01

While much of the language used to express the concepts of radiation protection works effectively, there are many ill-chosen names and phrases and much jargon that permeate our professional speech and writing. From the oxymoron "internal exposure" to the "snarl word" "decay," there is much room for improvement. This essay identifies many of the problems and suggests solutions. We examine the kinds of confusions that can result from using familiar words with unfamiliar meanings and the need for neology. We offer insights into specific and unambiguous naming of physical quantities and explore the seemingly unlimited kinds of "dose." We disaggregate exposure from irradiation following intakes, and unmask units like "gram rad per microcurie hour." We call for a definition of radiation weighting factor that doesn't result in a violation of the law of conservation of energy. We examine the subtleties of distinguishing between radiation and radioactive materials. Some words, such as "exposure," have multiple meanings, while at other times there are different words or phrases with the same meaning, such as "critical level" and "decision level" or "detection level" and "minimum detectable amount." Sometimes phrases are used whose meaning is unclear or not agreed upon, such as "lower limit of detection." Sometimes there are words that are simply not apt, such as "disintegration" applied to the emission of a subatomic particle from a nucleus.

An Indigenous Model of Career Satisfaction: Exploring the Role of Workplace Cultural Wellbeing

Science.gov (United States)

Haar, Jarrod M.; Brougham, Dave M.

2013-01-01

Despite career satisfaction models being well established, little is understood about the career satisfaction of indigenous employees. Using a sample of 172 Maori employees, the indigenous people of New Zealand, we tested a career satisfaction model with a cultural wellbeing factor over and above established factors of human capital,…

Universality classes for models of inflation

CERN Document Server

Binetruy, P.; Mabillard, J.; Pieroni, M.; Rosset, C.

2015-01-01

We show that the cosmological evolution of a scalar field in a potential can be obtained from a renormalisation group equation. The slow roll regime of inflation models is understood in this context as the slow evolution close to a fixed point, described by the methods of renormalisation group. This explains in part the universality observed in the predictions of a certain number of inflation models. We illustrate this behavior on a certain number of examples and discuss it in the context of the AdS/CFT correspondence.

Does Loading Influence the Severity of Cartilage Degeneration in the Canine Groove-Model of OA?

NARCIS (Netherlands)

Vos, Petra; Intema, Femke; van El, Benno; DeGroot, Jeroen; Bijlsma, J. W. J.; Lafeber, Floris; Mastbergen, Simon

2009-01-01

Many animal models are used to study osteoarthritis (OA). In these models the role of joint loading in the development of CA is not fully understood. We studied the effect of loading on the development of CIA in the canine Groove-model. In ten female beagle dogs OA was induced in one knee according

Increased GABAB receptor signaling in a rat model for schizophrenia

NARCIS (Netherlands)

Selten, M.M.; Meyer, F.; Ba, W.; Valles, A.; Maas, D.A.; Negwer, M.J.; Eijsink, V.D.; Vugt, R.W.M. van; Hulten, J.A; Bakel, N.H.M. van; Roosen, J.; Linden, R.J. van der; Schubert, D.; Verheij, M.M.M.; Nadif Kasri, N.; Martens, G.J.M.

2016-01-01

Schizophrenia is a complex disorder that affects cognitive function and has been linked, both in patients and animal models, to dysfunction of the GABAergic system. However, the pathophysiological consequences of this dysfunction are not well understood. Here, we examined the GABAergic system in an

Opinion Dynamics on Complex Networks with Communities

International Nuclear Information System (INIS)

Ru, Wang; Li-Ping, Chi

2008-01-01

The Ising or Potts models of ferromagnetism have been widely used to describe locally interacting social or economic systems. We consider a related model, introduced by Sznajd to describe the evolution of consensus in the scale-free networks with the tunable strength (noted by Q) of community structure. In the Sznajd model, the opinion or state of any spins can only be changed by the influence of neighbouring pairs of similar connection spins. Such pairs can polarize their neighbours. Using asynchronous updating, it is found that the smaller the community strength Q, the larger the slope of the exponential relaxation time distribution. Then the effect of the initial up- spin concentration p as a function of the final all up probability E is investigated by taking different initialization strategies, the random node-chosen initialization strategy has no difference under different community strengths, while the strategies of community node-chosen initialization and hub node-chosen initialization are different in final probability under different Q, and the latter one is more effective in reaching final state

The link between physics and chemistry in track modelling

International Nuclear Information System (INIS)

Green, N.J.B.; Bolton, C.E.; Spencer-Smith, R.D.

1999-01-01

The physical structure of a radiation track provides the initial conditions for the modelling of radiation chemistry. These initial conditions are not perfectly understood, because there are important gaps between what is provided by a typical track structure model and what is required to start the chemical model. This paper addresses the links between the physics and chemistry of tracks, with the intention of identifying those problems that need to be solved in order to obtain an accurate picture of the initial conditions for the purposes of modelling chemistry. These problems include the reasons for the increased yield of ionisation relative to homolytic bond breaking in comparison with the gas phase. A second area of great importance is the physical behaviour of low-energy electrons in condensed matter (including thermolisation and solvation). Many of these processes are not well understood, but they can have profound effects on the transient chemistry in the track. Several phenomena are discussed, including the short distance between adjacent energy loss events, the molecular nature of the underlying medium, dissociative attachment resonances and the ability of low-energy electrons to excite optically forbidden molecular states. Each of these phenomena has the potential to modify the transient chemistry substantially and must therefore be properly characterised before the physical model of the track can be considered to be complete. (orig.)

Healing from Childhood Sexual Abuse: A Theoretical Model

Science.gov (United States)

Draucker, Claire Burke; Martsolf, Donna S.; Roller, Cynthia; Knapik, Gregory; Ross, Ratchneewan; Stidham, Andrea Warner

2011-01-01

Childhood sexual abuse is a prevalent social and health care problem. The processes by which individuals heal from childhood sexual abuse are not clearly understood. The purpose of this study was to develop a theoretical model to describe how adults heal from childhood sexual abuse. Community recruitment for an ongoing broader project on sexual…

The Norm Activation Model: An exploration of the functions of anticipated pride and guilt in environmental behaviour

NARCIS (Netherlands)

Onwezen, M.C.; Antonides, G.; Bartels, J.

2013-01-01

The Norm Activation Model (NAM; Schwartz, 1977) is a vested model that explains altruistic and environmentally friendly behaviour. Although research states that anticipated pride and guilt are associated with the NAM, these associations are not yet fully understood. The current study provides an

Universal Regularizers For Robust Sparse Coding and Modeling

OpenAIRE

Ramirez, Ignacio; Sapiro, Guillermo

2010-01-01

Sparse data models, where data is assumed to be well represented as a linear combination of a few elements from a dictionary, have gained considerable attention in recent years, and their use has led to state-of-the-art results in many signal and image processing tasks. It is now well understood that the choice of the sparsity regularization term is critical in the success of such models. Based on a codelength minimization interpretation of sparse coding, and using tools from universal coding...

A gentle introduction to Rasch measurement models for metrologists

International Nuclear Information System (INIS)

Mari, Luca; Wilson, Mark

2013-01-01

The talk introduces the basics of Rasch models by systematically interpreting them in the conceptual and lexical framework of the International Vocabulary of Metrology, third edition (VIM3). An admittedly simple example of physical measurement highlights the analogies between physical transducers and tests, as they can be understood as measuring instruments of Rasch models and psychometrics in general. From the talk natural scientists and engineers might learn something of Rasch models, as a specifically relevant case of social measurement, and social scientists might re-interpret something of their knowledge of measurement in the light of the current physical measurement models

Energy and enthalpy distribution functions for a few physical systems.

Science.gov (United States)

Wu, K L; Wei, J H; Lai, S K; Okabe, Y

2007-08-02

The present work is devoted to extracting the energy or enthalpy distribution function of a physical system from the moments of the distribution using the maximum entropy method. This distribution theory has the salient traits that it utilizes only the experimental thermodynamic data. The calculated distribution functions provide invaluable insight into the state or phase behavior of the physical systems under study. As concrete evidence, we demonstrate the elegance of the distribution theory by studying first a test case of a two-dimensional six-state Potts model for which simulation results are available for comparison, then the biphasic behavior of the binary alloy Na-K whose excess heat capacity, experimentally observed to fall in a narrow temperature range, has yet to be clarified theoretically, and finally, the thermally induced state behavior of a collection of 16 proteins.

Critical exponents for diluted resistor networks.

Science.gov (United States)

Stenull, O; Janssen, H K; Oerding, K

1999-05-01

An approach by Stephen [Phys. Rev. B 17, 4444 (1978)] is used to investigate the critical properties of randomly diluted resistor networks near the percolation threshold by means of renormalized field theory. We reformulate an existing field theory by Harris and Lubensky [Phys. Rev. B 35, 6964 (1987)]. By a decomposition of the principal Feynman diagrams, we obtain diagrams which again can be interpreted as resistor networks. This interpretation provides for an alternative way of evaluating the Feynman diagrams for random resistor networks. We calculate the resistance crossover exponent phi up to second order in epsilon=6-d, where d is the spatial dimension. Our result phi=1+epsilon/42+4epsilon(2)/3087 verifies a previous calculation by Lubensky and Wang, which itself was based on the Potts-model formulation of the random resistor network.

Episodic grammar: a computational model of the interaction between episodic and semantic memory in language processing

NARCIS (Netherlands)

Borensztajn, G.; Zuidema, W.; Carlson, L.; Hoelscher, C.; Shipley, T.F.

2011-01-01

We present a model of the interaction of semantic and episodic memory in language processing. Our work shows how language processing can be understood in terms of memory retrieval. We point out that the perceived dichotomy between rule-based versus exemplar-based language modelling can be

Modeling biology using relational databases.

Science.gov (United States)

Peitzsch, Robert M

2003-02-01

There are several different methodologies that can be used for designing a database schema; no one is the best for all occasions. This unit demonstrates two different techniques for designing relational tables and discusses when each should be used. These two techniques presented are (1) traditional Entity-Relationship (E-R) modeling and (2) a hybrid method that combines aspects of data warehousing and E-R modeling. The method of choice depends on (1) how well the information and all its inherent relationships are understood, (2) what types of questions will be asked, (3) how many different types of data will be included, and (4) how much data exists.

Modeling Control Situations in Power System Operations

DEFF Research Database (Denmark)

Saleem, Arshad; Lind, Morten; Singh, Sri Niwas

2010-01-01

for intelligent operation and control must represent system features, so that information from measurements can be related to possible system states and to control actions. These general modeling requirements are well understood, but it is, in general, difficult to translate them into a model because of the lack...... of explicit principles for model construction. This paper presents a work on using explicit means-ends model based reasoning about complex control situations which results in maintaining consistent perspectives and selecting appropriate control action for goal driven agents. An example of power system......Increased interconnection and loading of the power system along with deregulation has brought new challenges for electric power system operation, control and automation. Traditional power system models used in intelligent operation and control are highly dependent on the task purpose. Thus, a model...

The Norm Activation Model: An exploration of the functions of anticipated pride and guilt in pro-environmental behaviour

NARCIS (Netherlands)

Onwezen, M.C.; Antonides, G.; Bartels, J.

2013-01-01

The Norm Activation Model (NAM; Schwartz, 1977) is a vested model that explains altruistic and environmentally friendly behaviour. Although research states that anticipated pride and guilt are associated with the NAM, these associations are not yet fully understood. The current study provides an

Thermal Site Descriptive Model. A strategy for the model development during site investigations. Version 1.0

International Nuclear Information System (INIS)

Sundberg, Jan

2003-04-01

Site investigations are in progress for the siting of a deep repository for spent nuclear fuel. As part of the planning work, strategies are developed for site descriptive modelling regarding different disciplines, amongst them the thermal conditions. The objective of the strategy for a thermal site descriptive model is to guide the practical implementation of evaluating site specific data during the site investigations. It is understood that further development may be needed. The model describes the thermal properties and other thermal parameters of intact rock, fractures and fracture zones, and of the rock mass. The methodology is based on estimation of thermal properties of intact rock and discontinuities, using both empirical and theoretical/numerical approaches, and estimation of thermal processes using mathematical modelling. The methodology will be used and evaluated for the thermal site descriptive modelling at the Aespoe Hard Rock Laboratory

Modeling and Control of an Ornithopter for Non-Equilibrium Maneuvers

OpenAIRE

Rose, Cameron Jarrel

2015-01-01

Flapping-winged flight is very complex, and it is difficult to efficiently model the unsteady airflow and nonlinear dynamics for online control. While steady state flight is well understood, transitions between flight regimes are not readily modeled or controlled. Maneuverability in non-equilibrium flight, which birds and insects readily exhibit in nature, is necessary to operate in the types of cluttered environments that small-scale flapping-winged robots are best suited for. The advantages...

ASYMMETRIC PRICE TRANSMISSION MODELING: THE IMPORTANCE OF MODEL COMPLEXITY AND THE PERFORMANCE OF THE SELECTION CRITERIA

Directory of Open Access Journals (Sweden)

Henry de-Graft Acquah

2013-01-01

Full Text Available Information Criteria provides an attractive basis for selecting the best model from a set of competing asymmetric price transmission models or theories. However, little is understood about the sensitivity of the model selection methods to model complexity. This study therefore fits competing asymmetric price transmission models that differ in complexity to simulated data and evaluates the ability of the model selection methods to recover the true model. The results of Monte Carlo experimentation suggest that in general BIC, CAIC and DIC were superior to AIC when the true data generating process was the standard error correction model, whereas AIC was more successful when the true model was the complex error correction model. It is also shown that the model selection methods performed better in large samples for a complex asymmetric data generating process than with a standard asymmetric data generating process. Except for complex models, AIC's performance did not make substantial gains in recovery rates as sample size increased. The research findings demonstrate the influence of model complexity in asymmetric price transmission model comparison and selection.

Humanism in forensic psychiatry: the use of the tidal nursing model

DEFF Research Database (Denmark)

Jacob, Jean Daniel; Holmes, Dave; Buus, Niels

2008-01-01

The humanist school of thought, which finds resonance in many conceptual models and theories designed to guide nursing practice, needs to be understood in the context of the total institution, where the individual is subjected to a mortification of the self, and denied autonomy. This article will...

On 'Money' in ISLM and AD/AS Models

OpenAIRE

Thomas K. Rymes; Colin Rogers

2000-01-01

Hicks's ISLM model interpretation of Keynes's theory is subject to much controversy. In this paper, we focus upon the 'real balance' effect and its role in ISLM and AD/AS analyses. We shall argue that ISLM and AD/AS require 'nominal anchors'. We live in a world where, increasingly, the 'money' in the ISLM and AD/AS model no longer exists (as Keynes imperfectly understood in his TREATISE ON MONEy). There are no longer any nominal anchors, rather they have been replaced by discretionary policy....

Connecting the Kuramoto Model and the Chimera State

Science.gov (United States)

Kotwal, Tejas; Jiang, Xin; Abrams, Daniel M.

2017-12-01

Since its discovery in 2002, the chimera state has frequently been described as a counterintuitive, puzzling phenomenon. The Kuramoto model, in contrast, has become a celebrated paradigm useful for understanding a range of phenomena related to phase transitions, synchronization, and network effects. Here we show that the chimera state can be understood as emerging naturally through a symmetry-breaking bifurcation from the Kuramoto model's partially synchronized state. Our analysis sheds light on recent observations of chimera states in laser arrays, chemical oscillators, and mechanical pendula.

Responsibility modelling for civil emergency planning

OpenAIRE

Sommerville, Ian; Storer, Timothy; Lock, Russell

2009-01-01

This paper presents a new approach to analysing and understanding civil emergency planning based on the notion of responsibility modelling combined with HAZOPS-style analysis of information requirements. Our goal is to represent complex contingency plans so that they can be more readily understood, so that inconsistencies can be highlighted and vulnerabilities discovered. In this paper, we outline the framework for contingency planning in the United Kingdom and introduce the notion of respons...

Monte Carlo Study of the Fish-like Patterns of Anthracenes on Cu(111)

Science.gov (United States)

Kim, Kwangmoo; Einstein, T. L.; Sun, Dezheng; Kim, Dae-Ho; Bartels, Ludwig

2011-03-01

Using Monte Carlo calculations of the two-dimensional triangular lattice with a 2-component 3-state Potts model, we demonstrate a mechanism for the spontaneous formation of fish-like patterns of anthracene (AC) molecules on Cu(111) by sputtering and annealing, then cooling to ~ 80 K. The two components are an AC on a hollow site and another on a bridge site of Cu(111). The liquid crystal model with two separate parts, positional and orientational, only explains a part of the fish-like pattern, not the whole regular pattern. Our model fixes the positional order of AC's into the triangular lattice and the orientational order into three angles as observed in the experiments. The variation of the coverages of AC's is reflected in the change of the ratio of two components in our model. We also try to understand the compression of AC's with the introduction of Gaussian dispersion of AC's about their triangular lattice sites. Supported primarily by NSF Grants CHE 07-50334 with a secondary support from NSF-MRSEC at the University of Maryland, DMR05-20471. Work at UCR supported primarily by NSF CHE 07-49949.

Analytical evidence for the absence of spin glass transition on self-dual lattices

International Nuclear Information System (INIS)

Ohzeki, Masayuki; Nishimori, Hidetoshi

2009-01-01

We show strong evidence for the absence of a finite-temperature spin glass transition for the random-bond Ising model on self-dual lattices. The analysis is performed by an application of duality relations, which enables us to derive a precise but approximate location of the multicritical point on the Nishimori line. This method can be systematically improved to presumably give the exact result asymptotically. The duality analysis, in conjunction with the relationship between the multicritical point and the spin glass transition point for the symmetric distribution function of randomness, leads to the conclusion of the absence of a finite-temperature spin glass transition for the case of symmetric distribution. The result is applicable to the random-bond Ising model with ±J or Gaussian distribution and the Potts gauge glass on the square, triangular and hexagonal lattices as well as the random three-body Ising model on the triangular and the Union-Jack lattices and the four-dimensional random plaquette gauge model. This conclusion is exact provided that the replica method is valid and the asymptotic limit of the duality analysis yields the exact location of the multicritical point. (fast track communication)

Logarithmic conformal field theories as limits of ordinary CFTs and some physical applications

International Nuclear Information System (INIS)

Cardy, John

2013-01-01

We describe an approach to logarithmic conformal field theories as limits of sequences of ordinary conformal field theories with varying central charge c. Logarithmic behaviour arises from degeneracies in the spectrum of scaling dimensions at certain values of c. The theories we consider are all invariant under some internal symmetry group, and logarithmic behaviour occurs when the decomposition of the physical observables into irreducible operators becomes singular. Examples considered are quenched random magnets using the replica formalism, self-avoiding walks as the n → 0 limit of the O(n) model, and percolation as the limit Q → 1 of the Potts model. In these cases we identify logarithmic operators and pay particular attention to how the c → 0 paradox is resolved and how the b-parameter is evaluated. We also show how this approach gives information on logarithmic behaviour in the extended Ising model, uniform spanning trees and the O( − 2) model. Most of our results apply to general dimensionality. We also consider massive logarithmic theories and, in two dimensions, derive sum rules for the effective central charge and the b-parameter. (review)

Multichoice minority game

International Nuclear Information System (INIS)

Ein-Dor, Liat; Metzler, Richard; Kanter, Ido; Kinzel, Wolfgang

2001-01-01

The generalization of the problem of adaptive competition, known as the minority game, to the case of K possible choices for each player, is addressed, and applied to a system of interacting perceptrons with input and output units of a type of K-state Potts spins. An optimal solution of this minority game, as well as the dynamic evolution of the adaptive strategies of the players, are solved analytically for a general K and compared with numerical simulations

The Pill vs. the Sword: Additional Considerations; Comment on “The Pill Is Mightier Than the Sword”

Directory of Open Access Journals (Sweden)

Ilsa L. Lottes

2015-12-01

Full Text Available In this paper, I present additional information for policy-makers and researchers to consider in response to the view proposed by Potts et al that “the pill is mightier than the sword.” I identify states with both high rates of terrorism and a youth bulge and discuss correlates of both these societal characteristics. The research examined supports the view that factors other than access to family planning are more important in facilitating terrorism.

Wealth and Population Data in Africa

OpenAIRE

Brian Sturgess

2012-01-01

There are very good grounds for challenging much of the conventionally accepted UN and World Bank economic data relating to both the absolute and relative per capita income of many African countries and to their growth rates over time. A recent paper by Morton Jerven published in World Economics demonstrated the unreliability of much if not most African GDP data and a new paper published in this issue by Deborah Potts challenges the accuracy of African population estimates"

Animal models of tinnitus.

Science.gov (United States)

Brozoski, Thomas J; Bauer, Carol A

2016-08-01

motivational manipulation, but its sensitivity, reliability, mechanism, and optimal implementation are incompletely understood. While to date animal models have significantly expanded the neuroscience of tinnitus, they have been limited to examining sensory features. In the human condition, emotional and cognitive factors are also important. It is not clear that the emotional features of tinnitus can be further understood using animal models, but models may be applied to examine cognitive factors. A recently developed model is described that reveals an interaction between tinnitus and auditory attention. This research suggests that effective tinnitus therapy could rely on modifying attention to the sensation rather than modifying the sensation itself. This article is part of a Special Issue entitled . Copyright © 2015 Elsevier B.V. All rights reserved.

Pott's puffy tumor with cranial epidural and subdural abscesses ...

African Journals Online (AJOL)

A 16-year-old boy was admitted with fever, headache, and tender, fluctuant scalp swellings. A lumbar puncture was consistent with meningitis. Aspiration of the mass yielded purulent fluid and cultures yielded Staphylococcus aureus. Treatment with ceftriaxone and gentamicin was initiated. Unfortunately, the patient died ...

Multistage models of carcinogenesis and their implications for dose-response models and risk projections

International Nuclear Information System (INIS)

Hoel, D.G.

1992-01-01

Multistage models are used to both describe the biological steps in developing a cancer and as a mathematical description of the relationship of exposure to tumor incidence. With the rapid development of molecular biology the stages of tumor development are becoming understood. Specifically, the effect and role of proto-oncogenes and suppressor genes are exciting developments in the field of carcinogenesis. Mathematically the field has moved from the original Armitage-Doll multistage model to the more current cell kinetic models. These latter models attempt to describe both the rate of cell mutation and the birth-death process involved in clonal expansion. This then allows modeling of both initiation and promotion or cellular proliferation. The field of radiation carcinogenesis has a considerable body of data and knowledge. Unfortunately, relatively little work has been done with the cell kinetic models as to estimation of tumor incidence. This may be due to the newness of kinetic models in general. The field holds promise and it is essential if we are to develop better human risk estimates from exposure to ionizing radiation. (author)

Experimental study and modelling of transient boiling

International Nuclear Information System (INIS)

Baudin, Nicolas

2015-01-01

A failure in the control system of the power of a nuclear reactor can lead to a Reactivity Initiated Accident in a nuclear power plant. Then, a power peak occurs in some fuel rods, high enough to lead to the coolant film boiling. It leads to an important increase of the temperature of the rod. The possible risk of the clad failure is a matter of interest for the Institut de Radioprotection et de Securite Nucleaire. The transient boiling heat transfer is not yet understood and modelled. An experimental set-up has been built at the Institut de Mecanique des Fluides de Toulouse (IMFT). Subcooled HFE-7000 flows vertically upward in a semi annulus test section. The inner half cylinder simulates the clad and is made of a stainless steel foil, heated by Joule effect. Its temperature is measured by an infrared camera, coupled with a high speed camera for the visualization of the flow topology. The whole boiling curve is studied in steady state and transient regimes: convection, onset of boiling, nucleate boiling, critical heat flux, film boiling and rewetting. The steady state heat transfers are well modelled by literature correlations. Models are suggested for the transient heat flux: the convection and nucleate boiling evolutions are self-similar during a power step. This observation allows to model more complex evolutions, as temperature ramps. The transient Hsu model well represents the onset of nucleate boiling. When the intensity of the power step increases, the film boiling begins at the same temperature but with an increasing heat flux. For power ramps, the critical heat flux decreases while the corresponding temperature increases with the heating rate. When the wall is heated, the film boiling heat transfer is higher than in steady state but it is not understood. A two-fluid model well simulates the cooling film boiling and the rewetting. (author)

Weak diffusion limits of dynamic conditional correlation models

DEFF Research Database (Denmark)

Hafner, Christian M.; Laurent, Sebastien; Violante, Francesco

The properties of dynamic conditional correlation (DCC) models are still not entirely understood. This paper fills one of the gaps by deriving weak diffusion limits of a modified version of the classical DCC model. The limiting system of stochastic differential equations is characterized...... by a diffusion matrix of reduced rank. The degeneracy is due to perfect collinearity between the innovations of the volatility and correlation dynamics. For the special case of constant conditional correlations, a non-degenerate diffusion limit can be obtained. Alternative sets of conditions are considered...

Dual purpose use of preterm piglets as a model of pediatric GI disease

DEFF Research Database (Denmark)

Oosterloo, Berthe C; Premkumar, Muralidhar; Stoll, Barbara

2014-01-01

Necrotizing enterocolitis (NEC) is the most common gastrointestinal complication in human neonates, yet the pathogenesis of this disease remains poorly understood. A fundamental approach to understanding the etiology and underlying biology of NEC is the use of in vivo experimental animal models, ...

Classification and unification of the microscopic deterministic traffic models.

Science.gov (United States)

Yang, Bo; Monterola, Christopher

2015-10-01

We identify a universal mathematical structure in microscopic deterministic traffic models (with identical drivers), and thus we show that all such existing models in the literature, including both the two-phase and three-phase models, can be understood as special cases of a master model by expansion around a set of well-defined ground states. This allows any two traffic models to be properly compared and identified. The three-phase models are characterized by the vanishing of leading orders of expansion within a certain density range, and as an example the popular intelligent driver model is shown to be equivalent to a generalized optimal velocity (OV) model. We also explore the diverse solutions of the generalized OV model that can be important both for understanding human driving behaviors and algorithms for autonomous driverless vehicles.

Complex Networks in Psychological Models

Science.gov (United States)

Wedemann, R. S.; Carvalho, L. S. A. V. D.; Donangelo, R.

We develop schematic, self-organizing, neural-network models to describe mechanisms associated with mental processes, by a neurocomputational substrate. These models are examples of real world complex networks with interesting general topological structures. Considering dopaminergic signal-to-noise neuronal modulation in the central nervous system, we propose neural network models to explain development of cortical map structure and dynamics of memory access, and unify different mental processes into a single neurocomputational substrate. Based on our neural network models, neurotic behavior may be understood as an associative memory process in the brain, and the linguistic, symbolic associative process involved in psychoanalytic working-through can be mapped onto a corresponding process of reconfiguration of the neural network. The models are illustrated through computer simulations, where we varied dopaminergic modulation and observed the self-organizing emergent patterns at the resulting semantic map, interpreting them as different manifestations of mental functioning, from psychotic through to normal and neurotic behavior, and creativity.

Clinical application of the five-factor model.

Science.gov (United States)

Widiger, Thomas A; Presnall, Jennifer Ruth

2013-12-01

The Five-Factor Model (FFM) has become the predominant dimensional model of general personality structure. The purpose of this paper is to suggest a clinical application. A substantial body of research indicates that the personality disorders included within the American Psychiatric Association's (APA) Diagnostic and Statistical Manual of Mental Disorders (DSM) can be understood as extreme and/or maladaptive variants of the FFM (the acronym "DSM" refers to any particular edition of the APA DSM). In addition, the current proposal for the forthcoming fifth edition of the DSM (i.e., DSM-5) is shifting closely toward an FFM dimensional trait model of personality disorder. Advantages of this shifting conceptualization are discussed, including treatment planning. © 2012 Wiley Periodicals, Inc.

Particle production at large transverse momentum and hard collision models

International Nuclear Information System (INIS)

Ranft, G.; Ranft, J.

1977-04-01

The majority of the presently available experimental data is consistent with hard scattering models. Therefore the hard scattering model seems to be well established. There is good evidence for jets in large transverse momentum reactions as predicted by these models. The overall picture is however not yet well enough understood. We mention only the empirical hard scattering cross section introduced in most of the models, the lack of a deep theoretical understanding of the interplay between quark confinement and jet production, and the fact that we are not yet able to discriminate conclusively between the many proposed hard scattering models. The status of different hard collision models discussed in this paper is summarized. (author)

The future of subsidence modelling: compaction and subsidence due to gas depletion of the Groningen gas field in the Netherlands

NARCIS (Netherlands)

Thienen-Visser, K. van; Fokker, P.A.

2017-01-01

The Groningen gas field has shown considerable compaction and subsidence since starting production in the early 1960s. The behaviour is understood from the geomechanical response of the reservoir pressure depletion. By integrating surface movement measurements and modelling, the model parameters can

Opaque models: Using drugs and dreams to explore the neurobiological basis of mental phenomena.

Science.gov (United States)

Langlitz, Nicolas

2017-01-01

On the basis of four historical and ethnographic case studies of modeling in neuroscience laboratories, this chapter introduces a distinction between transparent and opaque models. A transparent model is a simplified representation of a real world phenomenon. If it is not patently clear, it is at least much better comprehended than its objects of representation. An opaque model, by contrast, looks at one only partially understood phenomenon to stand in for another partially understood phenomenon. Here, the model is often just as complex as its target. Examples of such opaque models discussed in this chapter are the use of hallucinogen intoxication in humans and animals as well as the dreaming brain as models of psychosis as well as the dreaming brain as a model of consciousness in general. Several functions of opaque models are discussed, ranging from the generation of funding to the formulation of new research questions. While science studies scholars have often emphasized the epistemic fertility of failures of representation, the opacity of hallucinogen intoxications and dreams seems to have diminished the potential to produce positive knowledge from the representational relationship between the supposed models and their targets. Bidirectional comparisons between inebriation, dreaming, and psychosis, however, proved to be generative on the level of basic science. Moreover, the opaque models discussed in this chapter implicated cosmologies that steered research endeavors into certain directions rather than others. © 2017 Elsevier B.V. All rights reserved.

Clinical governance; How been understood, what is needed? Nurses' perspective

Directory of Open Access Journals (Sweden)

Homayoun Sadeghi Bazargani

2015-07-01

Full Text Available Introduction: Clinical Governance (CG is an overarching concept, using organizational capacity, safeguards high standards of the health services and provides a safe care for patients.  The aim of this research was to study nurses’ perception about Clinical Governance. Materials and Methods: A qualitative study was done with Focus Group Discussions (FGD. Purposeful Sampling was used to select the objectives including 65 participants. Actually 7 FGD’s were held. Content analysis was used to extract the meaningful themes. Results:Nurses believed that patient centeredness and evidence based practice is the core of the CG concept. Also they mentioned that cultural change, staffs training, adequate financial and human resources are required to successfully implementation of CG in hospitals.  Conclusion: Spreading up a shared vision about CG and providing the required infrastructures in hospitals would be facilitate CG initiatives. Proper commitment of the managers and staff participation could lead an effective CG implementation.

Default options in the ICU: widely used but insufficiently understood

Science.gov (United States)

Hart, Joanna; Halpern, Scott D.

2015-01-01

Purpose of review Default options dramatically influence the behavior of decision makers and may serve as effective decision support tools in the ICU. Their use in medicine has increased in an effort to improve efficiency, reduce errors, and harness the potential of healthcare technology. Recent findings Defaults often fall short of their predicted influence when employed in critical care settings as quality improvement interventions. Investigations reporting the use of defaults are often limited by variations in the relative effect across sites. Preimplementation experiments and long-term monitoring studies are lacking. Summary Defaults in the ICU may help or harm patients and clinical efficiency depending on their format and use. When constructing and encountering defaults, providers should be aware of their powerful and complex influences on decision making. Additional evaluations of the appropriate creation of healthcare defaults and their resulting intended and unintended consequences are needed. PMID:25203352

How is evidence to be understood in modern coaching psychology?

DEFF Research Database (Denmark)

Spaten, Ole Michael; Løkken, Lillith Olesen

2015-01-01

The hunt for evidence in modern coaching psychology could be counter-productive, and possibly lead to a simplified approach to research, practice, searching for “definitive truths”. The article discuss a critical approach to evidence hierarchies, and the prevalent (medical) understanding...

Well Researched, Yet Little Understood: Young Adults and Physical Activity

Science.gov (United States)

Cothran, Donetta; Kulinna, Pamela Hodges

2005-01-01

The authors present two beginning studies. One investigated the teaching-style preferences of young adults, and the other looked at physical activity trends within this age group. One key to understanding young adults and physical activity is to recognize the importance of participant cognition on physical activity patterns. From this…

The bare parameters of Gribov's Langrangian are understood and determined

International Nuclear Information System (INIS)

Bishari, M.

1977-01-01

In the context of the ''1/N Dual Unitarization'' scheme, an explicit dynamical study of the triple bare pomeron mechanism which governs the interaction term in Gribov's Lagrangian is presented. Together with the previously established bare pomeron slope and intercept, controlling respectively, the kinetic and mass terms in Gribov's Lagrangian, this work demonstrates the viability of the ''1/N Dual Unitarization'' approach for a field theory of interaction bare pomerons. (author)

How Inclusive Education Is Understood by Principals of Independent Schools

Science.gov (United States)

Gous, Jennifer Glenda; Eloff, Irma; Moen, Melanie Carmen

2014-01-01

Inclusive education has become a practice that has been adopted by many schools across the globe and most usually in first-world countries. As a whole-school system, it occurs less frequently in developing countries including South Africa which unlike many developing countries has a sound infrastructure and many excellent schools in both the state…

Q Fever: An Old but Still a Poorly Understood Disease

Directory of Open Access Journals (Sweden)

Hamidreza Honarmand

2012-01-01

Full Text Available Q fever is a bacterial infection affecting mainly the lungs, liver, and heart. It is found around the world and is caused by the bacteria Coxiella burnetii. The bacteria affects sheep, goats, cattle, dogs, cats, birds, rodents, and ticks. Infected animals shed this bacteria in birth products, feces, milk, and urine. Humans usually get Q fever by breathing in contaminated droplets released by infected animals and drinking raw milk. People at highest risk for this infection are farmers, laboratory workers, sheep and dairy workers, and veterinarians. Chronic Q fever develops in people who have been infected for more than 6 months. It usually takes about 20 days after exposure to the bacteria for symptoms to occur. Most cases are mild, yet some severe cases have been reported. Symptoms of acute Q fever may include: chest pain with breathing, cough, fever, headache, jaundice, muscle pains, and shortness of breath. Symptoms of chronic Q fever may include chills, fatigue, night sweats, prolonged fever, and shortness of breath. Q fever is diagnosed with a blood antibody test. The main treatment for the disease is with antibiotics. For acute Q fever, doxycycline is recommended. For chronic Q fever, a combination of doxycycline and hydroxychloroquine is often used long term. Complications are cirrhosis, hepatitis, encephalitis, endocarditis, pericarditis, myocarditis, interstitial pulmonary fibrosis, meningitis, and pneumonia. People at risk should always: carefully dispose of animal products that may be infected, disinfect any contaminated areas, and thoroughly wash their hands. Pasteurizing milk can also help prevent Q fever.

A novel low-parameter computational model to aid in-silico glycoengineering

DEFF Research Database (Denmark)

Spahn, Philipp N.; Hansen, Anders Holmgaard; Hansen, Henning Gram

2015-01-01

benefit from computational models that would better meet the requirements for industrial utilization. Here, we introduce a novel approach combining constraints-based and stochastic techniques to derive a computational model that can predict the effects of gene knockouts on protein glycoprofiles while...... it does not follow any direct equivalent of a genetic code. Instead, its complex biogenesis in the Golgi apparatus (Figure 1A) integrates a variety of influencing factors most of which are only incompletely understood. Various attempts have been undertaken so far to computationally model the process...

Tailored model abstraction in performance assessments

International Nuclear Information System (INIS)

Kessler, J.H.

1995-01-01

Total System Performance Assessments (TSPAs) are likely to be one of the most significant parts of making safety cases for the continued development and licensing of geologic repositories for the disposal of spent fuel and HLW. Thus, it is critical that the TSPA model capture the 'essence' of the physical processes relevant to demonstrating the appropriate regulation is met. But how much detail about the physical processes must be modeled and understood before there is enough confidence that the appropriate essence has been captured? In this summary the level of model abstraction that is required is discussed. Approaches for subsystem and total system performance analyses are outlined, and the role of best estimate models is examined. It is concluded that a conservative approach for repository performance, based on limited amount of field and laboratory data, can provide sufficient confidence for a regulatory decision

Deterministic geologic processes and stochastic modeling

International Nuclear Information System (INIS)

Rautman, C.A.; Flint, A.L.

1992-01-01

This paper reports that recent outcrop sampling at Yucca Mountain, Nevada, has produced significant new information regarding the distribution of physical properties at the site of a potential high-level nuclear waste repository. consideration of the spatial variability indicates that her are a number of widespread deterministic geologic features at the site that have important implications for numerical modeling of such performance aspects as ground water flow and radionuclide transport. Because the geologic processes responsible for formation of Yucca Mountain are relatively well understood and operate on a more-or-less regional scale, understanding of these processes can be used in modeling the physical properties and performance of the site. Information reflecting these deterministic geologic processes may be incorporated into the modeling program explicitly using geostatistical concepts such as soft information, or implicitly, through the adoption of a particular approach to modeling

A Bayesian Interpretation of First-Order Phase Transitions

Science.gov (United States)

Davis, Sergio; Peralta, Joaquín; Navarrete, Yasmín; González, Diego; Gutiérrez, Gonzalo

2016-03-01

In this work we review the formalism used in describing the thermodynamics of first-order phase transitions from the point of view of maximum entropy inference. We present the concepts of transition temperature, latent heat and entropy difference between phases as emergent from the more fundamental concept of internal energy, after a statistical inference analysis. We explicitly demonstrate this point of view by making inferences on a simple game, resulting in the same formalism as in thermodynamical phase transitions. We show that analogous quantities will inevitably arise in any problem of inferring the result of a yes/no question, given two different states of knowledge and information in the form of expectation values. This exposition may help to clarify the role of these thermodynamical quantities in the context of different first-order phase transitions such as the case of magnetic Hamiltonians (e.g. the Potts model).

On the two-point correlation functions for the Uq[SU(2)]invariant spin one-half Heisenberg chain at roots of unity

International Nuclear Information System (INIS)

Hinrichsen, H.; Scheunert, M.

1993-10-01

Using U q [SU(2)] tensor calculus we compute the two-point scalar operators (TPSO), their averages on the ground-state give the two-point correlation functions. The TPSOs are identified as elements of the Temperley-Lieb algebra and a recurrence relation is given for them. We have not tempted to derive the analytic expressions for the correlation functions in the general case but got some partial results. For q=e iπ/3 , all correlation functions are (trivially) zero, for q=e iπ/4 , they are related in the continuum to the correlation functions of left-handed and right-handed Majorana fields in the half plane coupled by the boundary condition. In the case q=e iπ/6 , one gets the correlation functions of Mittag's and Stephen's parafermions for the three-state Potts model. A diagrammatic approach to compute correlation functions is also presented. (orig.)

Capillary network formation from dispersed endothelial cells: Influence of cell traction, cell adhesion, and extracellular matrix rigidity

Science.gov (United States)

Ramos, João R. D.; Travasso, Rui; Carvalho, João

2018-01-01

The formation of a functional vascular network depends on biological, chemical, and physical processes being extremely well coordinated. Among them, the mechanical properties of the extracellular matrix and cell adhesion are fundamental to achieve a functional network of endothelial cells, able to fully cover a required domain. By the use of a Cellular Potts Model and Finite Element Method it is shown that there exists a range of values of endothelial traction forces, cell-cell adhesion, and matrix rigidities where the network can spontaneously be formed, and its properties are characterized. We obtain the analytical relation that the minimum traction force required for cell network formation must obey. This minimum value for the traction force is approximately independent on the considered cell number and cell-cell adhesion. We quantify how these two parameters influence the morphology of the resulting networks (size and number of meshes).

Magnetic model for a horse-spleen ferritin with a three-phase core structure

Energy Technology Data Exchange (ETDEWEB)

Jung, J.H.; Eom, T.W. [Quantum Photonic Science Research Center, Department of Physics and Research Institute for Natural Sciences, Hanyang University, Seoul 133-791 (Korea, Republic of); Lee, Y.P., E-mail: yplee@hanyang.ac.kr [Quantum Photonic Science Research Center, Department of Physics and Research Institute for Natural Sciences, Hanyang University, Seoul 133-791 (Korea, Republic of); Rhee, J.Y. [Department of Physics, Sungkyunkwan University, Suwon (Korea, Republic of); Choi, E.H. [Kwangwoon University, Seoul (Korea, Republic of)

2011-12-15

The increasing interests in magnetic nanoparticles has prompted research on ferritin, which is naturally a well-defined iron-storage protein in most living organisms. However, the exact magnetic behavior of ferritin is not well understood, because the crystal structures of ferritin and ferrihydrite, its major component, are not fully understood. Briefly, we discuss the previous magnetization models of ferritin and ferrihydrite and we present a new model ({Sigma}3L) of the initial magnetization of ferritin, considering its different phases. The new model includes three Langevin-function terms, which represent three different magnetic moments provided by the likely hydroxide and oxide mineral phases in ferritin. Compared to previous models, our simple model fits the experimental data 12 times better in terms of the sum of least squares. The magnetic independence of each component supports the multi-phase compositional model of the mineral core of horse-spleen ferritin. This {Sigma}3L model gives a quantization of the amounts of the different phases within horse-spleen ferritins that matches other published experimental data: 60-80% ferrihydrite, 15-25% maghemite/magnetite, and 1-10% hematite. - Highlights: > We present a new model ({Sigma}3L) of the initial magnetization of ferritin, considering its different phases. > New model includes three Langevin-function terms, which represent three different magnetic moments provided by ferritin phases. > Compared to previous models, our simple model fits the experimental data 12 times better in terms of the sum of least square. > The magnetic independence of each component supports that ferritin and ferrihydrite are composed of different phases.

MaSTiS, microorganism and solute transport in streams, model documentation and user manual

Science.gov (United States)

In-stream fate and transport of solutes and microorganisms need to be understood to evaluate suitability of waters for agricultural, recreational, and household uses and eventually minimize surface water contamination. Concerns over safety of this water resulted in development of predictive models f...

Modeling Myeloid Malignancies Using Zebrafish

Directory of Open Access Journals (Sweden)

Kathryn S. Potts

2017-12-01

Full Text Available Human myeloid malignancies represent a substantial disease burden to individuals, with significant morbidity and death. The genetic underpinnings of disease formation and progression remain incompletely understood. Large-scale human population studies have identified a high frequency of potential driver mutations in spliceosomal and epigenetic regulators that contribute to malignancies, such as myelodysplastic syndromes (MDS and leukemias. The high conservation of cell types and genes between humans and model organisms permits the investigation of the underlying mechanisms of leukemic development and potential therapeutic testing in genetically pliable pre-clinical systems. Due to the many technical advantages, such as large-scale screening, lineage-tracing studies, tumor transplantation, and high-throughput drug screening approaches, zebrafish is emerging as a model system for myeloid malignancies. In this review, we discuss recent advances in MDS and leukemia using the zebrafish model.

A Physiologically-Based Pharmacokinetic (PBPK) Model With Metabolic Interactions of Chloroform (CHCL3) and Trichloroethylene

Science.gov (United States)

Exposure to mixtures is frequent, but biologic pathways such as metabolic inhibition, are poorly understood. CHCl3 and TCE are model volatiles frequently co-occurring; combined exposure results in less than additive hepatotoxicity. Here, we explore the underlying metabolic inte...

The Theory of Finance: A novel finance model being formed on the Internet

OpenAIRE

Magomet Yandiev

2015-01-01

The present paper argues that the present Internet conditions favour an entirely new finance model. Understood to soon supplement the existing ones (classical finance, corporate finance, and Islamic finance), it is argued that the new model will be defined by the destructive effect it is to have on the contemporary financial infrastructure of most countries, and the advent of the ‘future money value exceeds its present one’ principle.

Modeling Lolium perenne L. roots in the presence of empirical black holes

Science.gov (United States)

Plant root models are designed for understanding structural or functional aspects of root systems. When a process is not thoroughly understood, a black box object is used. However, when a process exists but empirical data do not indicate its existence, you have a black hole. The object of this re...

Thermodynamic analysis and numerical modeling of supercritical injection

OpenAIRE

Banuti, Daniel

2015-01-01

Although liquid propellant rocket engines are operational and have been studied for decades, cryogenic injection at supercritical pressures is still considered essentially not understood. This thesis intends to approach this problem in three steps: by developing a numerical model for real gas thermodynamics, by extending the present thermodynamic view of supercritical injection, and finally by applying these methods to the analysis of injection. A new numerical real gas thermodynamics mode...

A model of smooth muscle cell synchronization in the arterial wall

DEFF Research Database (Denmark)

Jacobsen, Jens Christian; Aalkjær, Christian; Nilsson, Holger

2007-01-01

Vasomotion is a rhythmic variation in microvascular diameter. Although known for more than 150 years, the cellular processes underlying initiation of vasomotion are not fully understood. In the present study a model of a single cell is extended by coupling a number of cells into a tube. The simul......Vasomotion is a rhythmic variation in microvascular diameter. Although known for more than 150 years, the cellular processes underlying initiation of vasomotion are not fully understood. In the present study a model of a single cell is extended by coupling a number of cells into a tube...... reticulum (SR) calcium, membrane depolarization and influx of extra-cellular calcium. Low [cGMP] is associated only with unsynchronized waves. At intermediate concentrations, cells display either waves or whole-cell oscillations, but these remain unsynchronized between cells. Whole-cell oscillations...... are associated with rhythmic variation in membrane potential and flow of current through gap junctions. The amplitude of these oscillations in potential grows with increasing [cGMP], and, past a certain threshold, they become strong enough to entrain all cells in the vascular wall, thereby initiating sustained...

Modeling and Deorphanization of Orphan GPCRs.

Science.gov (United States)

Diaz, Constantino; Angelloz-Nicoud, Patricia; Pihan, Emilie

2018-01-01

Despite tremendous efforts, approximately 120 GPCRs remain orphan. Their physiological functions and their potential roles in diseases are poorly understood. Orphan GPCRs are extremely important because they may provide novel therapeutic targets for unmet medical needs. As a complement to experimental approaches, molecular modeling and virtual screening are efficient techniques to discover synthetic surrogate ligands which can help to elucidate the role of oGPCRs. Constitutively activated mutants and recently published active structures of GPCRs provide stimulating opportunities for building active molecular models for oGPCRs and identifying activators using virtual screening of compound libraries. We describe the molecular modeling and virtual screening process we have applied in the discovery of surrogate ligands, and provide examples for CCKA, a simulated oGPCR, and for two oGPCRs, GPR52 and GPR34.

Randomized Controlled Study on Safety and Feasibility of Transfusion Trigger Score of Emergency Operations.

Science.gov (United States)

Liu, De-Xing; Liu, Jin; Zhang, Fan; Zhang, Qiu-Ying; Xie, Mian; Zhu, Zhao-Qiong

2015-07-05

Due to the floating of the guideline, there is no evidence-based evaluation index on when to start the blood transfusion for patients with hemoglobin (Hb) level between 7 and 10 g/dl. As a result, the trigger point of blood transfusion may be different in the emergency use of the existing transfusion guidelines. The present study was designed to evaluate whether the scheme can be safely and effectively used for emergency patients, so as to be supported by multicenter and large sample data in the future. From June 2013 to June 2014, patients were randomly divided into the experimental group (Peri-operative Transfusion Trigger Score of Emergency [POTTS-E] group) and the control group (control group). The between-group differences in the patients' demography and baseline information, mortality and blood transfusion-related complications, heart rate, resting arterial pressure, body temperature, and Hb values were compared. The consistency of red blood cell (RBC) transfusion standards of the two groups of patients with the current blood transfusion guideline, namely the compliance of the guidelines, utilization rate, and per-capita consumption of autologous RBC were analyzed. During the study period, a total of 72 patients were recorded, and 65 of them met the inclusion criteria, which included 33 males and 32 females with a mean age of (34.8 ± 14.6) years. 50 underwent abdomen surgery, 4 underwent chest surgery, 11 underwent arms and legs surgery. There was no statistical difference between the two groups for demography and baseline information. There was also no statistical differences between the two groups in anesthesia time, intraoperative rehydration, staying time in postanesthetic care unit, emergency hospitalization, postoperative 72 h Acute Physiologic Assessment and Chronic Health Evaluation II scores, blood transfusion-related complications and mortality. Only the POTTS-E group on the 1 st postoperative day Hb was lower than group control, P group was

Bayesian error analysis model for reconstructing transcriptional regulatory networks

OpenAIRE

Sun, Ning; Carroll, Raymond J.; Zhao, Hongyu

2006-01-01

Transcription regulation is a fundamental biological process, and extensive efforts have been made to dissect its mechanisms through direct biological experiments and regulation modeling based on physical–chemical principles and mathematical formulations. Despite these efforts, transcription regulation is yet not well understood because of its complexity and limitations in biological experiments. Recent advances in high throughput technologies have provided substantial amounts and diverse typ...

Human casualties in earthquakes: Modelling and mitigation

Science.gov (United States)

Spence, R.J.S.; So, E.K.M.

2011-01-01

Earthquake risk modelling is needed for the planning of post-event emergency operations, for the development of insurance schemes, for the planning of mitigation measures in the existing building stock, and for the development of appropriate building regulations; in all of these applications estimates of casualty numbers are essential. But there are many questions about casualty estimation which are still poorly understood. These questions relate to the causes and nature of the injuries and deaths, and the extent to which they can be quantified. This paper looks at the evidence on these questions from recent studies. It then reviews casualty estimation models available, and finally compares the performance of some casualty models in making rapid post-event casualty estimates in recent earthquakes.

Zebrafish models in neuropsychopharmacology and CNS drug discovery.

Science.gov (United States)

Khan, Kanza M; Collier, Adam D; Meshalkina, Darya A; Kysil, Elana V; Khatsko, Sergey L; Kolesnikova, Tatyana; Morzherin, Yury Yu; Warnick, Jason E; Kalueff, Allan V; Echevarria, David J

2017-07-01

Despite the high prevalence of neuropsychiatric disorders, their aetiology and molecular mechanisms remain poorly understood. The zebrafish (Danio rerio) is increasingly utilized as a powerful animal model in neuropharmacology research and in vivo drug screening. Collectively, this makes zebrafish a useful tool for drug discovery and the identification of disordered molecular pathways. Here, we discuss zebrafish models of selected human neuropsychiatric disorders and drug-induced phenotypes. As well as covering a broad range of brain disorders (from anxiety and psychoses to neurodegeneration), we also summarize recent developments in zebrafish genetics and small molecule screening, which markedly enhance the disease modelling and the discovery of novel drug targets. © 2017 The British Pharmacological Society.

High Throughput Exposure Modeling of Semi-Volatile Chemicals in Articles of Commerce (ACS)

Science.gov (United States)

Risk due to chemical exposure is a function of both chemical hazard and exposure. Near-field exposures to chemicals in consumer products are identified as the main drivers of exposure and yet are not well quantified or understood. The ExpoCast project is developing a model that e...

Modeling the C. elegans nematode and its environment using a particle system.

Science.gov (United States)

Rönkkö, Mauno; Wong, Garry

2008-07-21

A particle system, as understood in computer science, is a novel technique for modeling living organisms in their environment. Such particle systems have traditionally been used for modeling the complex dynamics of fluids and gases. In the present study, a particle system was devised to model the movement and feeding behavior of the nematode Caenorhabditis elegans in three different virtual environments: gel, liquid, and soil. The results demonstrate that distinct movements of the nematode can be attributed to its mechanical interactions with the virtual environment. These results also revealed emergent properties associated with modeling organisms within environment-based systems.

Controlling flow-induced vibrations of flood barrier gates with data-driven and finite-element modelling

NARCIS (Netherlands)

Erdbrink, C.D.; Krzhizhanovskaya, V.V.; Sloot, P.M.A.; Klijn, F.; Schweckendiek, T.

2012-01-01

Operation of flood barrier gates is sometimes hampered by flow-induced vibrations. Although the physics is understood for specific gate types, it remains challenging to judge dynamic gate behaviour for unanticipated conditions. This paper presents a hybrid modelling system for predicting vibrations

Cellular modeling of fault-tolerant multicomputers

Energy Technology Data Exchange (ETDEWEB)

Morgan, G

1987-01-01

Work described was concerned with a novel method for investigation of fault tolerance in large regular networks of computers. Motivation was to provide a technique useful in rapid evaluation of highly reliable systems that exploit the low cost and ease of volume production of simple microcomputer components. First, a system model and simulator based upon cellular automata are developed. This model is characterized by its simplicity and ease of modification when adapting to new types of network. Second, in order to test and verify the predictive capabilities of the cellular system, a more-detailed simulation is performed based upon an existing computational model, that of the Transputer. An example application is used to exercise various systems designed using the cellular model. Using this simulator, experimental results are obtained both for existing well-understood configurations and for more novel types also developed here. In all cases it was found that the cellular model and simulator successfully predicted the ranking in reliability improvement of the systems studied.

Mathematical models of soft tissue injury repair : towards understanding musculoskeletal disorders

OpenAIRE

Dunster, Joanne L.

2012-01-01

The process of soft tissue injury repair at the cellular lew I can be decomposed into three phases: acute inflammation including coagulation, proliferation and remodelling. While the later phases are well understood the early phase is less so. We produce a series of new mathematical models for the early phases coagulation and inflammation. The models produced are relevant not only to soft tissue injury repair but also to the many disease states in which coagulation and inflammation play a rol...

A Data-Driven Method for Selecting Optimal Models Based on Graphical Visualisation of Differences in Sequentially Fitted ROC Model Parameters

Directory of Open Access Journals (Sweden)

K S Mwitondi

2013-05-01

Full Text Available Differences in modelling techniques and model performance assessments typically impinge on the quality of knowledge extraction from data. We propose an algorithm for determining optimal patterns in data by separately training and testing three decision tree models in the Pima Indians Diabetes and the Bupa Liver Disorders datasets. Model performance is assessed using ROC curves and the Youden Index. Moving differences between sequential fitted parameters are then extracted, and their respective probability density estimations are used to track their variability using an iterative graphical data visualisation technique developed for this purpose. Our results show that the proposed strategy separates the groups more robustly than the plain ROC/Youden approach, eliminates obscurity, and minimizes over-fitting. Further, the algorithm can easily be understood by non-specialists and demonstrates multi-disciplinary compliance.

Effects of Chinese Formula Jueyin Granules on Psoriasis in an Animal Model

OpenAIRE

Ma, Tian; Jiang, Wen-cheng; Li, Xin; Chen, Jie; Wu, Tie-jun; Nian, Hua; Xu, Rong; Huang, Qian-yuan; Xiao, Qing-qing; Jian, Qiang; Li, Fu-lun; Li, Bin

2014-01-01

Although Traditional Chinese medicine (TCM) is known to be effective for psoriasis patients, the responsible mechanisms still remain poorly understood. In this study, we aimed to evaluate the effect of one formula, named Jueyin granules (JYG) in the mouse model of the vaginal epithelium and tail epidermis. Additionally, we also determined the anti-inflammatory effects of JYG in an imiquimod- (IMQ-) induced psoriasis-like skin mouse model. Our results show that JYG can attenuate the IMQ-induce...

A model of quarks with Δ(6N2) family symmetry

International Nuclear Information System (INIS)

Ishimori, Hajime; King, Stephen F.

2014-01-01

We propose a first model of quarks based on the discrete family symmetry Δ(6N 2 ) in which the Cabibbo angle is correctly determined by a residual Z 2 ×Z 2 subgroup, and the smaller quark mixing angles may be qualitatively understood from the model. The present model of quarks may be regarded as a first step towards formulating a complete model of quarks and leptons based on Δ(6N 2 ), in which the lepton mixing matrix is fully determined by a Klein subgroup. For example, the choice N=28 provides an accurate determination of both the reactor angle and the Cabibbo angle

Snowdrift – visualisation on an architectural model in wind tunnel testing

DEFF Research Database (Denmark)

Fiebig, Jennifer; Koss, Hans Holger Hundborg

2016-01-01

transport and deposition at and around buildings in comparison to the nature phenomenon. Although a number of studies performed the deposition on a test model with different snow substitutes, the scaling of the phenomenon is still not understood or inaccurate. The study is a visual method of the snow...... is an alternative approach hence the model design and the visual effect was primarily considered. Main aspects in the model design were different materials and sizes (matter of scale) which were photographed in picture series and time laps. The method indicates the aerodynamic phenomenon as a visual understanding...

Design of laser-generated shockwave experiments. An approach using analytic models

International Nuclear Information System (INIS)

Lee, Y.T.; Trainor, R.J.

1980-01-01

Two of the target-physics phenomena which must be understood before a clean experiment can be confidently performed are preheating due to suprathermal electrons and shock decay due to a shock-rarefaction interaction. Simple analytic models are described for these two processes and the predictions of these models are compared with those of the LASNEX fluid physics code. We have approached this work not with the view of surpassing or even approaching the reliability of the code calculations, but rather with the aim of providing simple models which may be used for quick parameter-sensitivity evaluations, while providing physical insight into the problems

MODELS OF INSULIN RESISTANCE AND HEART FAILURE

Science.gov (United States)

Velez, Mauricio; Kohli, Smita; Sabbah, Hani N.

2013-01-01

The incidence of heart failure (HF) and diabetes mellitus is rapidly increasing and is associated with poor prognosis. In spite of the advances in therapy, HF remains a major health problem with high morbidity and mortality. When HF and diabetes coexist, clinical outcomes are significantly worse. The relationship between these two conditions has been studied in various experimental models. However, the mechanisms for this interrelationship are complex, incompletely understood, and have become a matter of considerable clinical and research interest. There are only few animal models that manifest both HF and diabetes. However, the translation of results from these models to human disease is limited and new models are needed to expand our current understanding of this clinical interaction. In this review, we discuss mechanisms of insulin signaling and insulin resistance, the clinical association between insulin resistance and HF and its proposed pathophysiologic mechanisms. Finally, we discuss available animal models of insulin resistance and HF and propose requirements for future new models. PMID:23456447

Colouring and knot polynomials

International Nuclear Information System (INIS)

Welsh, D.J.A.

1991-01-01

These lectures will attempt to explain a connection between the recent advances in knot theory using the Jones and related knot polynomials with classical problems in combinatorics and statistical mechanics. The difficulty of some of these problems will be analysed in the context of their computational complexity. In particular we shall discuss colourings and groups valued flows in graphs, knots and the Jones and Kauffman polynomials, the Ising, Potts and percolation problems of statistical physics, computational complexity of the above problems. (author). 20 refs, 9 figs

Novel lean type 2 diabetic rat model using gestational low-protein programming

Science.gov (United States)

Type 2 diabetes (T2D) in lean individuals is not well studied and up to 26% of diabetes occurs in these individuals. Although the cause is not well understood, it has been primarily attributed to nutritional issues during early development. Our objective was to develop a lean T2D model using gestati...

Irradiation creep models - an overview

International Nuclear Information System (INIS)

Matthews, J.R.; Finnis, M.W.

1988-01-01

The modelling of irradiation creep is now highly developed but many of the basic processes underlying the models are poorly understood. A brief introduction is given to the theory of cascade interactions, point defect clustering and dislocation climb. The range of simple irradiation creep models is reviewed including: preferred nucleation of interstitial loops; preferred absorption of point defects by dislocations favourably orientated to an applied stress; various climb-enhanced glide and recovery mechanisms, and creep driven by internal stresses produced by irradiation growth. A range of special topics is discussed including: cascade effects; creep transients; structural and induced anisotropy; and the effect of impurities. The interplay between swelling and growth with thermal and irradiation creep is emphasized. A discussion is given on how irradiation creep theory should best be developed to assist the interpretation of irradiation creep observations and the requirements of reactor designers. (orig.)

Models and correlations of the DEBRIS Late-Phase Melt Progression Model

International Nuclear Information System (INIS)

Schmidt, R.C.; Gasser, R.D.

1997-09-01

The DEBRIS Late Phase Melt Progression Model is an assembly of models, embodied in a computer code, which is designed to treat late-phase melt progression in dry rubble (or debris) regions that can form as a consequence of a severe core uncover accident in a commercial light water nuclear reactor. The approach is fully two-dimensional, and incorporates a porous medium modeling framework together with conservation and constitutive relationships to simulate the time-dependent evolution of such regions as various physical processes act upon the materials. The objective of the code is to accurately model these processes so that the late-phase melt progression that would occur in different hypothetical severe nuclear reactor accidents can be better understood and characterized. In this report the models and correlations incorporated and used within the current version of DEBRIS are described. These include the global conservation equations solved, heat transfer and fission heating models, melting and refreezing models (including material interactions), liquid and solid relocation models, gas flow and pressure field models, and the temperature and compositionally dependent material properties employed. The specific models described here have been used in the experiment design analysis of the Phebus FPT-4 debris-bed fission-product release experiment. An earlier DEBRIS code version was used to analyze the MP-1 and MP-2 late-phase melt progression experiments conducted at Sandia National Laboratories for the US Nuclear Regulatory Commission

Human performance modeling for system of systems analytics.

Energy Technology Data Exchange (ETDEWEB)

Dixon, Kevin R.; Lawton, Craig R.; Basilico, Justin Derrick; Longsine, Dennis E. (INTERA, Inc., Austin, TX); Forsythe, James Chris; Gauthier, John Henry; Le, Hai D.

2008-10-01

A Laboratory-Directed Research and Development project was initiated in 2005 to investigate Human Performance Modeling in a System of Systems analytic environment. SAND2006-6569 and SAND2006-7911 document interim results from this effort; this report documents the final results. The problem is difficult because of the number of humans involved in a System of Systems environment and the generally poorly defined nature of the tasks that each human must perform. A two-pronged strategy was followed: one prong was to develop human models using a probability-based method similar to that first developed for relatively well-understood probability based performance modeling; another prong was to investigate more state-of-art human cognition models. The probability-based modeling resulted in a comprehensive addition of human-modeling capability to the existing SoSAT computer program. The cognitive modeling resulted in an increased understanding of what is necessary to incorporate cognition-based models to a System of Systems analytic environment.

A theoretical model for analysing gender bias in medicine.

Science.gov (United States)

Risberg, Gunilla; Johansson, Eva E; Hamberg, Katarina

2009-08-03

During the last decades research has reported unmotivated differences in the treatment of women and men in various areas of clinical and academic medicine. There is an ongoing discussion on how to avoid such gender bias. We developed a three-step-theoretical model to understand how gender bias in medicine can occur and be understood. In this paper we present the model and discuss its usefulness in the efforts to avoid gender bias. In the model gender bias is analysed in relation to assumptions concerning difference/sameness and equity/inequity between women and men. Our model illustrates that gender bias in medicine can arise from assuming sameness and/or equity between women and men when there are genuine differences to consider in biology and disease, as well as in life conditions and experiences. However, gender bias can also arise from assuming differences when there are none, when and if dichotomous stereotypes about women and men are understood as valid. This conceptual thinking can be useful for discussing and avoiding gender bias in clinical work, medical education, career opportunities and documents such as research programs and health care policies. Too meet the various forms of gender bias, different facts and measures are needed. Knowledge about biological differences between women and men will not reduce bias caused by gendered stereotypes or by unawareness of health problems and discrimination associated with gender inequity. Such bias reflects unawareness of gendered attitudes and will not change by facts only. We suggest consciousness-rising activities and continuous reflections on gender attitudes among students, teachers, researchers and decision-makers.

Constraining biogenic silica dissolution in marine sediments: a comparison between diagenetic models and experimental dissolution rates

NARCIS (Netherlands)

Khalil, K.; Rabouille, C.; Gallinari, M.; Soetaert, K.E.R.; DeMaster, D.J.; Ragueneau, O.

2007-01-01

The processes controlling preservation and recycling of particulate biogenic silica in sediments must be understood in order to calculate oceanic silica mass balances. The new contribution of this work is the coupled use of advanced models including reprecipitation and different phases of biogenic

A 3D co-culture microtissue model of the human placenta for nanotoxicity assessment

DEFF Research Database (Denmark)

Muoth, Carina; Wichser, Adrian; Monopoli, Marco

2016-01-01

and functionality of the placental tissue. The effects of NPs on the human placenta are not well studied or understood, and predictive in vitro placenta models to achieve mechanistic insights on NP-placenta interactions are essentially lacking. Using the scaffold-free hanging drop technology, we developed a well...

A Combined Electro-Thermal Breakdown Model for Oil-Impregnated Paper

Directory of Open Access Journals (Sweden)

Meng Huang

2017-12-01

Full Text Available The breakdown property of oil-impregnated paper is a key factor for converter transformer design and operation, but it is not well understood. In this paper, breakdown voltages of oil-impregnated paper were measured at different temperatures. The results showed that with the increase of temperature, electrical, electro-thermal and thermal breakdown occurred successively. An electro-thermal breakdown model was proposed based on the heat equilibrium and space charge transport, and negative differential mobility was introduced to the model. It was shown that carrier mobility determined whether it was electrical or thermal breakdown, and the model can effectively explain the temperature-dependent breakdown.

Aerosol numerical modelling at local scale

International Nuclear Information System (INIS)

Albriet, Bastien

2007-01-01

At local scale and in urban areas, an important part of particulate pollution is due to traffic. It contributes largely to the high number concentrations observed. Two aerosol sources are mainly linked to traffic. Primary emission of soot particles and secondary nanoparticle formation by nucleation. The emissions and mechanisms leading to the formation of such bimodal distribution are still badly understood nowadays. In this thesis, we try to provide an answer to this problematic by numerical modelling. The Modal Aerosol Model MAM is used, coupled with two 3D-codes: a CFD (Mercure Saturne) and a CTM (Polair3D). A sensitivity analysis is performed, at the border of a road but also in the first meters of an exhaust plume, to identify the role of each process involved and the sensitivity of different parameters used in the modelling. (author) [fr

From fracture mechanics to damage mechanics: how to model structural deterioration

International Nuclear Information System (INIS)

Nicolet, S.; Lorentz, E.; Barbier, G.

1998-01-01

Modelling of structural deteriorations of thermo-mechanical origin is highly enhanced when using damage mechanics. Indeed, the latter offers both a fine description of the material behaviour and an ability to deal with any loading conditions, moving away the current limits of fracture mechanics. But new difficulties can arise, depending on the examined problem: if forecasts of rack initiation are well mastered, the study of crack propagation remains more complex and needs sophisticated modelizations, which are nevertheless on the point of being well understood too. (authors)

Pervasive drought legacies in forest ecosystems and their implications for carbon cycle models

Science.gov (United States)

W. R. L. Anderegg; C. Schwalm; F. Biondi; J. J. Camarero; G. Koch; M. Litvak; K. Ogle; J. D. Shaw; E. Shevliakova; A. P. Williams; A. Wolf; E. Ziaco; S. Pacala

2015-01-01

The impacts of climate extremes on terrestrial ecosystems are poorly understood but important for predicting carbon cycle feedbacks to climate change. Coupled climate-carbon cycle models typically assume that vegetation recovery from extreme drought is immediate and complete, which conflicts with the understanding of basic plant physiology. We examined the recovery of...

Nonarteritic anterior ischemic optic neuropathy (NAION) and its experimental models

Science.gov (United States)

Bernstein, Steven L.; Johnson, Mary A.; Miller, Neil R.

2011-01-01

Anterior ischemic optic neuropathy (AION) can be divided into nonarteritic (NAION) and arteritic (AAION) forms. NAION makes up ~85% of all cases of AION, and until recently was poorly understood. There is no treatment for NAION, and its initiating causes are poorly understood, in part because NAION is not lethal, making it difficult to obtain fresh, newly affected tissue for study. In-vivo electrophysiology and post-mortem studies reveal specific responses that are associated with NAION. New models of NAION have been developed which enable insights into the pathophysiological events surrounding this disease. These models include both rodent and primate species, and the power of a `vertically integrated' multi-species approach can help in understanding the common cellular mechanisms and physiological responses to clinical NAION, and to identify potential approaches to treatment. The models utilize laser light to activate intravascular photoactive dye to induce capillary vascular thrombosis, while sparing the larger vessels. The observable optic nerve changes associated with rodent models of AION (rAION) and primate NAION (pNAION) are indistinguishable from that seen in clinical disease, including sectoral axonal involvement, and in-vivo electrophysiological data from these models are consistent with clinical data. Early post-infarct events reveal an unexpected inflammatory response, and changes in intraretinal gene expression for both stress response, while sparing outer retinal function, which occurs in AAION models. Histologically, the NAION models reveal an isolated loss of retinal ganglion cells by apoptosis. There are changes detectable by immunohistochemistry suggesting that other retinal cells mount a brisk response to retinal ganglion cell distress without themselves dying. The optic nerve ultimately shows axonal loss and scarring. Inflammation is a prominent early histological feature. This suggests that clinically, specific modulation of inflammation may

Small-χ behavior and patron staturation: A QCD model

International Nuclear Information System (INIS)

Mueller, A.H.

1990-01-01

A QCD model is defined to study questions of quark and gluon parton saturation at small χ-values. The model uses a source consisting of a nucleus of heavy quarkonium bound states, states well understood in QCD. Deeply inelastic scattering, using the currents j(χ)=1/4F a μν F a μν and j μ (χ)=ψγ μ ψ, is evaluated in Born and one-loop approximation in order to extract quark and gluon distributions. Quark distributions are observed to saturate while gluon distributions have a saturating and a nonsaturating component. (orig.)

CIMS: A FRAMEWORK FOR INFRASTRUCTURE INTERDEPENDENCY MODELING AND ANALYSIS

Energy Technology Data Exchange (ETDEWEB)

Donald D. Dudenhoeffer; May R. Permann; Milos Manic

2006-12-01

Today’s society relies greatly upon an array of complex national and international infrastructure networks such as transportation, utilities, telecommunication, and even financial networks. While modeling and simulation tools have provided insight into the behavior of individual infrastructure networks, a far less understood area is that of the interrelationships among multiple infrastructure networks including the potential cascading effects that may result due to these interdependencies. This paper first describes infrastructure interdependencies as well as presenting a formalization of interdependency types. Next the paper describes a modeling and simulation framework called CIMS© and the work that is being conducted at the Idaho National Laboratory (INL) to model and simulate infrastructure interdependencies and the complex behaviors that can result.

How much detail is needed in modeling a transcranial magnetic stimulation figure-8 coil: Measurements and brain simulations

OpenAIRE

Petrov, Petar I.; Mandija, Stefano; Sommer, Iris E. C.; van den Berg, Cornelis A. T.; Neggers, Sebastiaan F. W.

2017-01-01

Background: Despite TMS wide adoption, its spatial and temporal patterns of neuronal effects are not well understood. Although progress has been made in predicting induced currents in the brain using realistic finite element models (FEM), there is little consensus on how a magnetic field of a typical TMS coil should be modeled. Empirical validation of such models is limited and subject to several limitations. Methods: We evaluate and empirically validate models of a figure-of-eight TMS coil t...

Esophageal Cancer: Insights from Mouse Models

Directory of Open Access Journals (Sweden)

Marie-Pier Tétreault

2015-01-01

Full Text Available Esophageal cancer is the eighth leading cause of cancer and the sixth most common cause of cancer-related death worldwide. Despite recent advances in the development of surgical techniques in combination with the use of radiotherapy and chemotherapy, the prognosis for esophageal cancer remains poor. The cellular and molecular mechanisms that drive the pathogenesis of esophageal cancer are still poorly understood. Hence, understanding these mechanisms is crucial to improving outcomes for patients with esophageal cancer. Mouse models constitute valuable tools for modeling human cancers and for the preclinical testing of therapeutic strategies in a manner not possible in human subjects. Mice are excellent models for studying human cancers because they are similar to humans at the physiological and molecular levels and because they have a shorter gestation time and life cycle. Moreover, a wide range of well-developed technologies for introducing genetic modifications into mice are currently available. In this review, we describe how different mouse models are used to study esophageal cancer.

A Model of Amygdala-Hippocampal-Prefrontal Interaction in Fear Conditioning and Extinction in Animals

Science.gov (United States)

Moustafa, Ahmed A.; Gilbertson, Mark W.; Orr, Scott P.; Herzallah, Mohammad M.; Servatius, Richard J.; Myers, Catherine E.

2013-01-01

Empirical research has shown that the amygdala, hippocampus, and ventromedial prefrontal cortex (vmPFC) are involved in fear conditioning. However, the functional contribution of each brain area and the nature of their interactions are not clearly understood. Here, we extend existing neural network models of the functional roles of the hippocampus…

Usefulness of an equal-probability assumption for out-of-equilibrium states: A master equation approach

KAUST Repository

Nogawa, Tomoaki

2012-10-18

We examine the effectiveness of assuming an equal probability for states far from equilibrium. For this aim, we propose a method to construct a master equation for extensive variables describing nonstationary nonequilibrium dynamics. The key point of the method is the assumption that transient states are equivalent to the equilibrium state that has the same extensive variables, i.e., an equal probability holds for microscopic states in nonequilibrium. We demonstrate an application of this method to the critical relaxation of the two-dimensional Potts model by Monte Carlo simulations. While the one-variable description, which is adequate for equilibrium, yields relaxation dynamics that are very fast, the redundant two-variable description well reproduces the true dynamics quantitatively. These results suggest that some class of the nonequilibrium state can be described with a small extension of degrees of freedom, which may lead to an alternative way to understand nonequilibrium phenomena. © 2012 American Physical Society.

Usefulness of an equal-probability assumption for out-of-equilibrium states: A master equation approach

KAUST Repository

Nogawa, Tomoaki; Ito, Nobuyasu; Watanabe, Hiroshi

2012-01-01

We examine the effectiveness of assuming an equal probability for states far from equilibrium. For this aim, we propose a method to construct a master equation for extensive variables describing nonstationary nonequilibrium dynamics. The key point of the method is the assumption that transient states are equivalent to the equilibrium state that has the same extensive variables, i.e., an equal probability holds for microscopic states in nonequilibrium. We demonstrate an application of this method to the critical relaxation of the two-dimensional Potts model by Monte Carlo simulations. While the one-variable description, which is adequate for equilibrium, yields relaxation dynamics that are very fast, the redundant two-variable description well reproduces the true dynamics quantitatively. These results suggest that some class of the nonequilibrium state can be described with a small extension of degrees of freedom, which may lead to an alternative way to understand nonequilibrium phenomena. © 2012 American Physical Society.

Mesoscale Simulations of Pore Migration in a Nuclear Fuel

International Nuclear Information System (INIS)

Radhakrishnan, Balasubramaniam; Gorti, Sarma B.

2010-01-01

The evolution of pore and grain structure in a nuclear fuel environment is strongly influenced by the local temperature, and the temperature gradient. The evolution of pore and grain structure in an externally imposed temperature gradient is simulated for a hypothetical material using a Potts model approach that allows for porosity migration by mechanisms similar to surface, grain boundary and volume diffusion, as well as the interaction of migrating pores with stationary grain boundaries. First, the migration of a single pore in a single crystal in the presence of the temperature gradient is simulated. Next, the interaction of a pore moving in a temperature gradient with a grain boundary that is perpendicular to the pore migration direction is simulated in order to capture the force exerted by the pore on the grain boundary. The simulations reproduce the expected variation of pore velocity with pore size as well as the variation of the grain boundary force with pore size.

Psychological determinants of paying attention to eco-labels in purchase decisions: Model development and multinational validation

DEFF Research Database (Denmark)

Thøgersen, John

Environmental labels are useful from an environmental policy perspective only if they are noticed by the consumer in the shopping situation and next - and related - understood, trusted, and valued as a tool for decision-making. In this paper, a psychological model explaining variations in consumer...

Physically-Based Modelling of the Post-Fire Runoff Response of a Forest Catchment in Central Portugal

NARCIS (Netherlands)

Eck, Van Christel M.; Nunes, Joao P.; Vieira, Diana C.S.; Keesstra, Saskia; Keizer, Jan Jacob

2016-01-01

Forest fires are a recurrent phenomenon in Mediterranean forests, with impacts for human landscapes and communities, which must be understood before they can be managed. This study used the physically based Limburg Soil Erosion Model (LISEM) to simulate rainfall–runoff response, under soil water

Influence of fluid resuscitation on renal microvascular PO2 in a normotensive rat model of endotoxemia

NARCIS (Netherlands)

Johannes, Tanja; Mik, Egbert G.; Nohé, Boris; Raat, Nicolaas J. H.; Unertl, Klaus E.; Ince, Can

2006-01-01

INTRODUCTION: Septic renal failure is often seen in the intensive care unit but its pathogenesis is only partly understood. This study, performed in a normotensive rat model of endotoxemia, tests the hypotheses that endotoxemia impairs renal microvascular PO2 (microPO2) and oxygen consumption

Menyoal Elaboration Likelihood Model (ELM) dan Teori Retorika

OpenAIRE

Yudi Perbawaningsih

2012-01-01

Abstract: Persuasion is a communication process to establish or change attitudes, which can be understood through theory of Rhetoric and theory of Elaboration Likelihood Model (ELM). This study elaborates these theories in a Public Lecture series which to persuade the students in choosing their concentration of study. The result shows that in term of persuasion effectiveness it is not quite relevant to separate the message and its source. The quality of source is determined by the quality of ...

Solvable model for chimera states of coupled oscillators.

Science.gov (United States)

Abrams, Daniel M; Mirollo, Rennie; Strogatz, Steven H; Wiley, Daniel A

2008-08-22

Networks of identical, symmetrically coupled oscillators can spontaneously split into synchronized and desynchronized subpopulations. Such chimera states were discovered in 2002, but are not well understood theoretically. Here we obtain the first exact results about the stability, dynamics, and bifurcations of chimera states by analyzing a minimal model consisting of two interacting populations of oscillators. Along with a completely synchronous state, the system displays stable chimeras, breathing chimeras, and saddle-node, Hopf, and homoclinic bifurcations of chimeras.

Menyoal Elaboration Likelihood Model (ELM) Dan Teori Retorika

OpenAIRE

Perbawaningsih, Yudi

2012-01-01

: Persuasion is a communication process to establish or change attitudes, which can be understood through theory of Rhetoric and theory of Elaboration Likelihood Model (ELM). This study elaborates these theories in a Public Lecture series which to persuade the students in choosing their concentration of study. The result shows that in term of persuasion effectiveness it is not quite relevant to separate the message and its source. The quality of source is determined by the quality of the mess...

Improvements to the RADIOM non-LTE model

Science.gov (United States)

Busquet, M.; Colombant, D.; Klapisch, M.; Fyfe, D.; Gardner, J.

2009-12-01

In 1993, we proposed the RADIOM model [M. Busquet, Phys. Fluids 85 (1993) 4191] where an ionization temperature T z is used to derive non-LTE properties from LTE data. T z is obtained from an "extended Saha equation" where unbalanced transitions, like radiative decay, give the non-LTE behavior. Since then, major improvements have been made. T z has been shown to be more than a heuristic value, but describes the actual distribution of excited and ionized states and can be understood as an "effective temperature". Therefore we complement the extended Saha equation by introducing explicitly the auto-ionization/dielectronic capture. Also we use the SCROLL model to benchmark the computed values of T z.

Interaction effect in the Kondo energy of the periodic Anderson-Hubbard model

Science.gov (United States)

Itai, K.; Fazekas, P.

1996-07-01

We extend the periodic Anderson model by switching on a Hubbard U for the conduction band. The nearly integral valent limit of the Anderson-Hubbard model is studied with the Gutzwiller variational method. The lattice Kondo energy shows U dependence both in the prefactor and the exponent. Switching on U reduces the Kondo scale, which can be understood to result from the blocking of hybridization. At half filling, we find a Brinkman-Rice-type transition from a Kondo insulator to a Mott insulator. Our findings should be relevant for a number of correlated two-band models of recent interest.

Three-dimensional hydrological and thermal property models of Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Rautman, C.A.; McKenna, S.A.

1997-11-01

This report describes the creation of three-dimensional numerical models of selected rock-matrix properties for the region of the potential high-level nuclear waste repository site at Yucca Mountain, which is located in southern Nevada. The models have been generated for a majority of the unsaturated and shallow saturated zone within an area referred to within the Yucca Mountain Site Characterization project as the site area. They comprise a number of material properties of importance both to detailed process-level modeling activities and to more summary-style performance assessment modeling. The material properties within these models are both spatially variable (heterogeneous) and spatially correlated, as the rocks are understood from data obtained from site-characterization drill holes widely scattered across the site area

Efficient estimation of the robustness region of biological models with oscillatory behavior.

Directory of Open Access Journals (Sweden)

Mochamad Apri

Full Text Available Robustness is an essential feature of biological systems, and any mathematical model that describes such a system should reflect this feature. Especially, persistence of oscillatory behavior is an important issue. A benchmark model for this phenomenon is the Laub-Loomis model, a nonlinear model for cAMP oscillations in Dictyostelium discoideum. This model captures the most important features of biomolecular networks oscillating at constant frequencies. Nevertheless, the robustness of its oscillatory behavior is not yet fully understood. Given a system that exhibits oscillating behavior for some set of parameters, the central question of robustness is how far the parameters may be changed, such that the qualitative behavior does not change. The determination of such a "robustness region" in parameter space is an intricate task. If the number of parameters is high, it may be also time consuming. In the literature, several methods are proposed that partially tackle this problem. For example, some methods only detect particular bifurcations, or only find a relatively small box-shaped estimate for an irregularly shaped robustness region. Here, we present an approach that is much more general, and is especially designed to be efficient for systems with a large number of parameters. As an illustration, we apply the method first to a well understood low-dimensional system, the Rosenzweig-MacArthur model. This is a predator-prey model featuring satiation of the predator. It has only two parameters and its bifurcation diagram is available in the literature. We find a good agreement with the existing knowledge about this model. When we apply the new method to the high dimensional Laub-Loomis model, we obtain a much larger robustness region than reported earlier in the literature. This clearly demonstrates the power of our method. From the results, we conclude that the biological system underlying is much more robust than was realized until now.

Recent progress in the theory of noncritical strings

International Nuclear Information System (INIS)

Kazakov, V.A.; Migdal, A.A.

1988-01-01

We compare the results of analytical and numerical studies of lattice 2D quantum gravity, where the internal quantum metric is described by random (dynamical) triangulation, with the recent results of conformal approach developed by Knizhnik, Polyakov and Zamolodchikov. The remarkable agreement is underlined for the interactions of gravity with matter fields: Potts spins, D-dimensional Gaussian fields (bosonic string). Some new results are presented for D=1 discretized bosonic strings satisfying the predictions of conformal theory for the critical exponents: γ str =0, ν str =0, but with unusual logarithmic corrections. (orig.)

Examining effective use of data sources and modeling algorithms for improving biomass estimation in a moist tropical forest of the Brazilian Amazon

Science.gov (United States)

Yunyun Feng; Dengsheng Lu; Qi Chen; Michael Keller; Emilio Moran; Maiza Nara dos-Santos; Edson Luis Bolfe; Mateus Batistella

2017-01-01

Previous research has explored the potential to integrate lidar and optical data in aboveground biomass (AGB) estimation, but how different data sources, vegetation types, and modeling algorithms influence AGB estimation is poorly understood. This research conducts a comparative analysis of different data sources and modeling approaches in improving AGB estimation....

Laszlo Tisza and the two-fluid model of superfluidity

Science.gov (United States)

Balibar, Sébastien

2017-11-01

The "two-fluid model" of superfluidity was first introduced by Laszlo Tisza in 1938. On that year, Tisza published the principles of his model as a brief note in Nature and two articles in French in the Comptes rendus de l'Académie des sciences, followed in 1940 by two other articles in French in the Journal de physique et le Radium. In 1941, the two-fluid model was reformulated by Lev Landau on a more rigorous basis. Successive experiments confirmed the revolutionary idea introduced by Tisza: superfluid helium is indeed a surprising mixture of two fluids with independent velocity fields. His prediction of the existence of heat waves, a consequence of his model, was also confirmed. Then, it took several decades for the superfluidity of liquid helium to be fully understood.

Modelling radioactivity in the environment

International Nuclear Information System (INIS)

Scott, E.M.

2003-01-01

Just as an environmental model typically will be composed of a number of linked sub-models, representing physical, chemical or biological processes understood to varying degrees, this volume includes a series of linked chapters exemplifying the fundamental nature of environmental radioactivity models in all compartments of the environment. Modelling is an often misunderstood and maligned activity and this book can provide, to a broad audience, a greater understanding of modelling power but also some of the limitations. Modellers and experimentalists often do not understand and mistrust each other's work yet they are mutually dependent, in the sense that good experimental science can direct good modelling work and vice-versa. There is an increasing reliance on model results in environmental management, yet there is also often misuse and misrepresentation of these results. This book can help to bridge the gap between unrealistic expectations of model power and the realisation of what is possible, practicable and feasible in modelling of environmental radioactivity; and finally, - modelling tools, capacity and power have increased many-fold in a relatively short period of time. Much of this is due to the much-heralded computer revolution, but much is also due to better science. It is useful to consider what gap if any still remains between what is possible and what is necessary

Detection and quantification of flow consistency in business process models

DEFF Research Database (Denmark)

Burattin, Andrea; Bernstein, Vered; Neurauter, Manuel

2017-01-01

, to show how such features can be quantified into computational metrics, which are applicable to business process models. We focus on one particular feature, consistency of flow direction, and show the challenges that arise when transforming it into a precise metric. We propose three different metrics......Business process models abstract complex business processes by representing them as graphical models. Their layout, as determined by the modeler, may have an effect when these models are used. However, this effect is currently not fully understood. In order to systematically study this effect......, a basic set of measurable key visual features is proposed, depicting the layout properties that are meaningful to the human user. The aim of this research is thus twofold: first, to empirically identify key visual features of business process models which are perceived as meaningful to the user and second...

Asymptotic behavior of observables in the asymmetric quantum Rabi model

Science.gov (United States)

Semple, J.; Kollar, M.

2018-01-01

The asymmetric quantum Rabi model with broken parity invariance shows spectral degeneracies in the integer case, that is when the asymmetry parameter equals an integer multiple of half the oscillator frequency, thus hinting at a hidden symmetry and accompanying integrability of the model. We study the expectation values of spin observables for each eigenstate and observe characteristic differences between the integer and noninteger cases for the asymptotics in the deep strong coupling regime, which can be understood from a perturbative expansion in the qubit splitting. We also construct a parent Hamiltonian whose exact eigenstates possess the same symmetries as the perturbative eigenstates of the asymmetric quantum Rabi model in the integer case.

A theoretical model for analysing gender bias in medicine

Directory of Open Access Journals (Sweden)

Johansson Eva E

2009-08-01

Full Text Available Abstract During the last decades research has reported unmotivated differences in the treatment of women and men in various areas of clinical and academic medicine. There is an ongoing discussion on how to avoid such gender bias. We developed a three-step-theoretical model to understand how gender bias in medicine can occur and be understood. In this paper we present the model and discuss its usefulness in the efforts to avoid gender bias. In the model gender bias is analysed in relation to assumptions concerning difference/sameness and equity/inequity between women and men. Our model illustrates that gender bias in medicine can arise from assuming sameness and/or equity between women and men when there are genuine differences to consider in biology and disease, as well as in life conditions and experiences. However, gender bias can also arise from assuming differences when there are none, when and if dichotomous stereotypes about women and men are understood as valid. This conceptual thinking can be useful for discussing and avoiding gender bias in clinical work, medical education, career opportunities and documents such as research programs and health care policies. Too meet the various forms of gender bias, different facts and measures are needed. Knowledge about biological differences between women and men will not reduce bias caused by gendered stereotypes or by unawareness of health problems and discrimination associated with gender inequity. Such bias reflects unawareness of gendered attitudes and will not change by facts only. We suggest consciousness-rising activities and continuous reflections on gender attitudes among students, teachers, researchers and decision-makers.

Integrable lambda models and Chern-Simons theories

International Nuclear Information System (INIS)

Schmidtt, David M.

2017-01-01

In this note we reveal a connection between the phase space of lambda models on S 1 ×ℝ and the phase space of double Chern-Simons theories on D×ℝ and explain in the process the origin of the non-ultralocality of the Maillet bracket, which emerges as a boundary algebra. In particular, this means that the (classical) AdS 5 ×S 5 lambda model can be understood as a double Chern-Simons theory defined on the Lie superalgebra psu(2,2|4) after a proper dependence of the spectral parameter is introduced. This offers a possibility for avoiding the use of the problematic non-ultralocal Poisson algebras that preclude the introduction of lattice regularizations and the application of the QISM to string sigma models. The utility of the equivalence at the quantum level is, however, still to be explored.

Mathematical models for sleep-wake dynamics: comparison of the two-process model and a mutual inhibition neuronal model.

Directory of Open Access Journals (Sweden)

Anne C Skeldon

Full Text Available Sleep is essential for the maintenance of the brain and the body, yet many features of sleep are poorly understood and mathematical models are an important tool for probing proposed biological mechanisms. The most well-known mathematical model of sleep regulation, the two-process model, models the sleep-wake cycle by two oscillators: a circadian oscillator and a homeostatic oscillator. An alternative, more recent, model considers the mutual inhibition of sleep promoting neurons and the ascending arousal system regulated by homeostatic and circadian processes. Here we show there are fundamental similarities between these two models. The implications are illustrated with two important sleep-wake phenomena. Firstly, we show that in the two-process model, transitions between different numbers of daily sleep episodes can be classified as grazing bifurcations. This provides the theoretical underpinning for numerical results showing that the sleep patterns of many mammals can be explained by the mutual inhibition model. Secondly, we show that when sleep deprivation disrupts the sleep-wake cycle, ostensibly different measures of sleepiness in the two models are closely related. The demonstration of the mathematical similarities of the two models is valuable because not only does it allow some features of the two-process model to be interpreted physiologically but it also means that knowledge gained from study of the two-process model can be used to inform understanding of the behaviour of the mutual inhibition model. This is important because the mutual inhibition model and its extensions are increasingly being used as a tool to understand a diverse range of sleep-wake phenomena such as the design of optimal shift-patterns, yet the values it uses for parameters associated with the circadian and homeostatic processes are very different from those that have been experimentally measured in the context of the two-process model.

Atmospheric CH4 in the first decade of the 21st century: Inverse modeling analysis using SCIAMACHY satellite retrievals and NOAA surface measurements

NARCIS (Netherlands)

Bergamaschi, P.; Houweling, S.; Segers, A.; Krol, M.; Frankenberg, C.; Scheepmaker, R.A.; Dlugokencky, E.; Wofsy, S.C.; Kort, E.A.; Sweeney, C.; Schuck, T.; Brenninkmeijer, C.; Chen, H.; Beck, V.; Gerbig, C.

2013-01-01

The causes of renewed growth in the atmospheric CH4 burden since 2007 are still poorly understood and subject of intensive scientific discussion. We present a reanalysis of global CH4 emissions during the 2000s, based on the TM5-4DVAR inverse modeling system. The model is optimized using

Persuasion, Politeness and Relational Models

Directory of Open Access Journals (Sweden)

Jerzy Świątek

2017-06-01

Full Text Available Politeness Theory, just like Grice’s Cooperative Principle, points out that pragmatic analysis of language behaviour has to be grounded in extra-linguistic facts of social (or even biological nature. Additionally, despite the slightly misleading label, Politeness Theory provides a sound methodology to explain some persuasive as well as politeness phenomena. In the same vein, the so called Relational Model Theory provides another theoretical framework for the explanation of persuasive phenomena and persuasive language. Both Relational Model Theory and Politeness Theory show that persuasion is also to be understood as a rational response to not-so-rational social and biological needs. In the article an attempt is made to compare the two theories focusing on their explanatory power in reference to language choices aiming at enhancing the persuasive potential of a language message.

Challenges in modelling the random structure correctly in growth mixture models and the impact this has on model mixtures.

Science.gov (United States)

Gilthorpe, M S; Dahly, D L; Tu, Y K; Kubzansky, L D; Goodman, E

2014-06-01

Lifecourse trajectories of clinical or anthropological attributes are useful for identifying how our early-life experiences influence later-life morbidity and mortality. Researchers often use growth mixture models (GMMs) to estimate such phenomena. It is common to place constrains on the random part of the GMM to improve parsimony or to aid convergence, but this can lead to an autoregressive structure that distorts the nature of the mixtures and subsequent model interpretation. This is especially true if changes in the outcome within individuals are gradual compared with the magnitude of differences between individuals. This is not widely appreciated, nor is its impact well understood. Using repeat measures of body mass index (BMI) for 1528 US adolescents, we estimated GMMs that required variance-covariance constraints to attain convergence. We contrasted constrained models with and without an autocorrelation structure to assess the impact this had on the ideal number of latent classes, their size and composition. We also contrasted model options using simulations. When the GMM variance-covariance structure was constrained, a within-class autocorrelation structure emerged. When not modelled explicitly, this led to poorer model fit and models that differed substantially in the ideal number of latent classes, as well as class size and composition. Failure to carefully consider the random structure of data within a GMM framework may lead to erroneous model inferences, especially for outcomes with greater within-person than between-person homogeneity, such as BMI. It is crucial to reflect on the underlying data generation processes when building such models.

Making myself understood: perceived factors affecting the intelligibility of sung text.

Science.gov (United States)

Fine, Philip A; Ginsborg, Jane

2014-01-01

Singing is universal, and understanding sung words is thought to be important for many listeners' enjoyment of vocal and choral music. However, this is not a trivial task, and sung text intelligibility is probably affected by many factors. A survey of musicians was undertaken to identify the factors believed to have most impact on intelligibility, and to assess the importance of understanding sung words in familiar and unfamiliar languages. A total of 143 professional and amateur musicians, including singers, singing teachers, and regular listeners to vocal music, provided 394 statements yielding 851 references to one or more of 43 discrete factors in four categories: performer-related, listener-related, environment-related and words/music-related. The factors mentioned most frequently in each of the four categories were, respectively: diction; hearing ability; acoustic; and genre. In more than a third of references, the extent to which sung text is intelligible was attributed to the performer. Over 60% of respondents rated the ability to understand words in familiar languages as "very important," but only 17% when the text was in an unfamiliar language. Professional musicians (47% of the sample) rated the importance of understanding in both familiar and unfamiliar languages significantly higher than amateurs but listed fewer factors overall and fewer listener-related factors. The more important the respondents rated understanding, the more performer-related and environment-related factors they tended to list. There were no significant differences between the responses of those who teach singing and those who do not. Enhancing sung text intelligibility is thus perceived to be within the singer's control, at least to some extent, but there are also many factors outside their control. Empirical research is needed to explore some of these factors in greater depth, and has the potential to inform pedagogy for singers, composers, and choral directors.

Muslim fundamentalism: something to be understood or to be explained away?

NARCIS (Netherlands)

Bruinessen, M.M. van

1995-01-01

This article surveys various attempts to make sociological sense of the diverse Muslim movements often lumped together under the label of fundamentalism. Explanations of fundamentalism as a form of resistance to modernization or those reducing it to social and economic discontent may have some

Models of life: epigenetics, diversity and cycles

Science.gov (United States)

Sneppen, Kim

2017-04-01

This review emphasizes aspects of biology that can be understood through repeated applications of simple causal rules. The selected topics include perspectives on gene regulation, phage lambda development, epigenetics, microbial ecology, as well as model approaches to diversity and to punctuated equilibrium in evolution. Two outstanding features are repeatedly described. One is the minimal number of rules to sustain specific states of complex systems for a long time. The other is the collapse of such states and the subsequent dynamical cycle of situations that restitute the system to a potentially new metastable state.

Underwater noise modelling for environmental impact assessment

Energy Technology Data Exchange (ETDEWEB)

Farcas, Adrian [Centre for Environment, Fisheries and Aquaculture Science (Cefas), Pakefield Road, Lowestoft, NR33 0HT (United Kingdom); Thompson, Paul M. [Lighthouse Field Station, Institute of Biological and Environmental Sciences, University of Aberdeen, Cromarty IV11 8YL (United Kingdom); Merchant, Nathan D., E-mail: nathan.merchant@cefas.co.uk [Centre for Environment, Fisheries and Aquaculture Science (Cefas), Pakefield Road, Lowestoft, NR33 0HT (United Kingdom)

2016-02-15

Assessment of underwater noise is increasingly required by regulators of development projects in marine and freshwater habitats, and noise pollution can be a constraining factor in the consenting process. Noise levels arising from the proposed activity are modelled and the potential impact on species of interest within the affected area is then evaluated. Although there is considerable uncertainty in the relationship between noise levels and impacts on aquatic species, the science underlying noise modelling is well understood. Nevertheless, many environmental impact assessments (EIAs) do not reflect best practice, and stakeholders and decision makers in the EIA process are often unfamiliar with the concepts and terminology that are integral to interpreting noise exposure predictions. In this paper, we review the process of underwater noise modelling and explore the factors affecting predictions of noise exposure. Finally, we illustrate the consequences of errors and uncertainties in noise modelling, and discuss future research needs to reduce uncertainty in noise assessments.

Underwater noise modelling for environmental impact assessment

International Nuclear Information System (INIS)

Farcas, Adrian; Thompson, Paul M.; Merchant, Nathan D.

2016-01-01

Assessment of underwater noise is increasingly required by regulators of development projects in marine and freshwater habitats, and noise pollution can be a constraining factor in the consenting process. Noise levels arising from the proposed activity are modelled and the potential impact on species of interest within the affected area is then evaluated. Although there is considerable uncertainty in the relationship between noise levels and impacts on aquatic species, the science underlying noise modelling is well understood. Nevertheless, many environmental impact assessments (EIAs) do not reflect best practice, and stakeholders and decision makers in the EIA process are often unfamiliar with the concepts and terminology that are integral to interpreting noise exposure predictions. In this paper, we review the process of underwater noise modelling and explore the factors affecting predictions of noise exposure. Finally, we illustrate the consequences of errors and uncertainties in noise modelling, and discuss future research needs to reduce uncertainty in noise assessments.

Formal Definition of Measures for BPMN Models

Science.gov (United States)

Reynoso, Luis; Rolón, Elvira; Genero, Marcela; García, Félix; Ruiz, Francisco; Piattini, Mario

Business process models are currently attaining more relevance, and more attention is therefore being paid to their quality. This situation led us to define a set of measures for the understandability of BPMN models, which is shown in a previous work. We focus on understandability since a model must be well understood before any changes are made to it. These measures were originally informally defined in natural language. As is well known, natural language is ambiguous and may lead to misunderstandings and a misinterpretation of the concepts captured by a measure and the way in which the measure value is obtained. This has motivated us to provide the formal definition of the proposed measures using OCL (Object Constraint Language) upon the BPMN (Business Process Modeling Notation) metamodel presented in this paper. The main advantages and lessons learned (which were obtained both from the current work and from previous works carried out in relation to the formal definition of other measures) are also summarized.

OFFl Models: Novel Schema for Dynamical Modeling of Biological Systems.

Directory of Open Access Journals (Sweden)

C Brandon Ogbunugafor

Full Text Available Flow diagrams are a common tool used to help build and interpret models of dynamical systems, often in biological contexts such as consumer-resource models and similar compartmental models. Typically, their usage is intuitive and informal. Here, we present a formalized version of flow diagrams as a kind of weighted directed graph which follow a strict grammar, which translate into a system of ordinary differential equations (ODEs by a single unambiguous rule, and which have an equivalent representation as a relational database. (We abbreviate this schema of "ODEs and formalized flow diagrams" as OFFL. Drawing a diagram within this strict grammar encourages a mental discipline on the part of the modeler in which all dynamical processes of a system are thought of as interactions between dynamical species that draw parcels from one or more source species and deposit them into target species according to a set of transformation rules. From these rules, the net rate of change for each species can be derived. The modeling schema can therefore be understood as both an epistemic and practical heuristic for modeling, serving both as an organizational framework for the model building process and as a mechanism for deriving ODEs. All steps of the schema beyond the initial scientific (intuitive, creative abstraction of natural observations into model variables are algorithmic and easily carried out by a computer, thus enabling the future development of a dedicated software implementation. Such tools would empower the modeler to consider significantly more complex models than practical limitations might have otherwise proscribed, since the modeling framework itself manages that complexity on the modeler's behalf. In this report, we describe the chief motivations for OFFL, carefully outline its implementation, and utilize a range of classic examples from ecology and epidemiology to showcase its features.

OFFl Models: Novel Schema for Dynamical Modeling of Biological Systems.

Science.gov (United States)

Ogbunugafor, C Brandon; Robinson, Sean P

2016-01-01

Flow diagrams are a common tool used to help build and interpret models of dynamical systems, often in biological contexts such as consumer-resource models and similar compartmental models. Typically, their usage is intuitive and informal. Here, we present a formalized version of flow diagrams as a kind of weighted directed graph which follow a strict grammar, which translate into a system of ordinary differential equations (ODEs) by a single unambiguous rule, and which have an equivalent representation as a relational database. (We abbreviate this schema of "ODEs and formalized flow diagrams" as OFFL.) Drawing a diagram within this strict grammar encourages a mental discipline on the part of the modeler in which all dynamical processes of a system are thought of as interactions between dynamical species that draw parcels from one or more source species and deposit them into target species according to a set of transformation rules. From these rules, the net rate of change for each species can be derived. The modeling schema can therefore be understood as both an epistemic and practical heuristic for modeling, serving both as an organizational framework for the model building process and as a mechanism for deriving ODEs. All steps of the schema beyond the initial scientific (intuitive, creative) abstraction of natural observations into model variables are algorithmic and easily carried out by a computer, thus enabling the future development of a dedicated software implementation. Such tools would empower the modeler to consider significantly more complex models than practical limitations might have otherwise proscribed, since the modeling framework itself manages that complexity on the modeler's behalf. In this report, we describe the chief motivations for OFFL, carefully outline its implementation, and utilize a range of classic examples from ecology and epidemiology to showcase its features.

Hypercompetitive Environments: An Agent-based model approach

Science.gov (United States)

Dias, Manuel; Araújo, Tanya

Information technology (IT) environments are characterized by complex changes and rapid evolution. Globalization and the spread of technological innovation have increased the need for new strategic information resources, both from individual firms and management environments. Improvements in multidisciplinary methods and, particularly, the availability of powerful computational tools, are giving researchers an increasing opportunity to investigate management environments in their true complex nature. The adoption of a complex systems approach allows for modeling business strategies from a bottom-up perspective — understood as resulting from repeated and local interaction of economic agents — without disregarding the consequences of the business strategies themselves to individual behavior of enterprises, emergence of interaction patterns between firms and management environments. Agent-based models are at the leading approach of this attempt.

Pneumatic Artificial Muscle Actuation and Modeling

Science.gov (United States)

Leephakpreeda, Thananchai; Wickramatunge, Kanchana C.

2009-10-01

A Pneumatic Artificial Muscle (PAM) yields a natural muscle-like actuator with a high force to weight ratio, a soft and flexible structure, and adaptable compliance for a humanoid robot, rehabilitation and prosthetic appliances to the disabled, etc. To obtain optimum design and usage, the mechanical behavior of the PAM need to be understood. In this study, observations of experimental results reveal an empirical model for relations of physical variables, contraction and air pressure within the PAM, as compared to mechanical characteristics, such as stiffness or/and pulling forces of the PAM available now in market.

Energy-dissipation-model for metallurgical multi-phase-systems

Energy Technology Data Exchange (ETDEWEB)

Mavrommatis, K.T. [Rheinisch-Westfaelische Technische Hochschule Aachen, Aachen (Germany)

1996-12-31

Entropy production in real processes is directly associated with the dissipation of energy. Both are potential measures for the proceed of irreversible processes taking place in metallurgical systems. Many of these processes in multi-phase-systems could then be modelled on the basis of the energy-dissipation associated with. As this entity can often be estimated using very simple assumptions from first principles, the evolution of an overall measure of systems behaviour can be studied constructing an energy-dissipation -based model of the system. In this work a formulation of this concept, the Energy-Dissipation-Model (EDM), for metallurgical multi-phase-systems is given. Special examples are studied to illustrate the concept, and benefits as well as the range of validity are shown. This concept might be understood as complement to usual CFD-modelling of complex systems on a more abstract level but reproducing essential attributes of complex metallurgical systems. (author)

Energy-dissipation-model for metallurgical multi-phase-systems

Energy Technology Data Exchange (ETDEWEB)

Mavrommatis, K T [Rheinisch-Westfaelische Technische Hochschule Aachen, Aachen (Germany)

1997-12-31

Entropy production in real processes is directly associated with the dissipation of energy. Both are potential measures for the proceed of irreversible processes taking place in metallurgical systems. Many of these processes in multi-phase-systems could then be modelled on the basis of the energy-dissipation associated with. As this entity can often be estimated using very simple assumptions from first principles, the evolution of an overall measure of systems behaviour can be studied constructing an energy-dissipation -based model of the system. In this work a formulation of this concept, the Energy-Dissipation-Model (EDM), for metallurgical multi-phase-systems is given. Special examples are studied to illustrate the concept, and benefits as well as the range of validity are shown. This concept might be understood as complement to usual CFD-modelling of complex systems on a more abstract level but reproducing essential attributes of complex metallurgical systems. (author)

The development, validation and initial results of an integrated model for determining the environmental sustainability of biogas production pathways

NARCIS (Netherlands)

Pierie, Frank; van Someren, Christian; Benders, René M.J.; Bekkering, Jan; van Gemert, Wim; Moll, Henri C.

2016-01-01

Biogas produced through Anaerobic Digestion can be seen as a flexible and storable energy carrier. However, the environmental sustainability and efficiency of biogas production is not fully understood. Within this article the use, operation, structure, validation, and results of a model for the

Modeling gravity effects on water retention and gas transport characteristics in plant growth substrates

DEFF Research Database (Denmark)

Deepagoda Thuduwe Kankanamge Kelum, Chamindu; Jones, Scott B.; Tuller, Markus

2014-01-01

utilization to conserve energy and to limit transport costs, native materials mined on Moon or Mars are of primary interest for plant growth media in a future outpost, while terrestrial porous substrates with optimal growth media characteristics will be useful for onboard plant growth during space missions....... Due to limited experimental opportunities and prohibitive costs, liquid and gas behavior in porous substrates under reduced gravity conditions has been less studied and hence remains poorly understood. Based on ground-based measurements, this study examined water retention, oxygen diffusivity and air...... that estimates the gas percolation threshold based on the pore size distribution. The model successfully captured measured data for all investigated media and demonstrated the implications of the poorly-understood shift in gas percolation threshold with improved gas percolation in reduced gravity. Finally, using...

GENERAL REQUIREMENTS FOR SIMULATION MODELS IN WASTE MANAGEMENT

International Nuclear Information System (INIS)

Miller, Ian; Kossik, Rick; Voss, Charlie

2003-01-01

Most waste management activities are decided upon and carried out in a public or semi-public arena, typically involving the waste management organization, one or more regulators, and often other stakeholders and members of the public. In these environments, simulation modeling can be a powerful tool in reaching a consensus on the best path forward, but only if the models that are developed are understood and accepted by all of the parties involved. These requirements for understanding and acceptance of the models constrain the appropriate software and model development procedures that are employed. This paper discusses requirements for both simulation software and for the models that are developed using the software. Requirements for the software include transparency, accessibility, flexibility, extensibility, quality assurance, ability to do discrete and/or continuous simulation, and efficiency. Requirements for the models that are developed include traceability, transparency, credibility/validity, and quality control. The paper discusses these requirements with specific reference to the requirements for performance assessment models that are used for predicting the long-term safety of waste disposal facilities, such as the proposed Yucca Mountain repository

Roadmap for cardiovascular circulation model

Science.gov (United States)

Bradley, Christopher P.; Suresh, Vinod; Mithraratne, Kumar; Muller, Alexandre; Ho, Harvey; Ladd, David; Hellevik, Leif R.; Omholt, Stig W.; Chase, J. Geoffrey; Müller, Lucas O.; Watanabe, Sansuke M.; Blanco, Pablo J.; de Bono, Bernard; Hunter, Peter J.

2016-01-01

Abstract Computational models of many aspects of the mammalian cardiovascular circulation have been developed. Indeed, along with orthopaedics, this area of physiology is one that has attracted much interest from engineers, presumably because the equations governing blood flow in the vascular system are well understood and can be solved with well‐established numerical techniques. Unfortunately, there have been only a few attempts to create a comprehensive public domain resource for cardiovascular researchers. In this paper we propose a roadmap for developing an open source cardiovascular circulation model. The model should be registered to the musculo‐skeletal system. The computational infrastructure for the cardiovascular model should provide for near real‐time computation of blood flow and pressure in all parts of the body. The model should deal with vascular beds in all tissues, and the computational infrastructure for the model should provide links into CellML models of cell function and tissue function. In this work we review the literature associated with 1D blood flow modelling in the cardiovascular system, discuss model encoding standards, software and a model repository. We then describe the coordinate systems used to define the vascular geometry, derive the equations and discuss the implementation of these coupled equations in the open source computational software OpenCMISS. Finally, some preliminary results are presented and plans outlined for the next steps in the development of the model, the computational software and the graphical user interface for accessing the model. PMID:27506597

The Problem of Predecessors on Spanning Trees

Directory of Open Access Journals (Sweden)

V. S. Poghosyan

2011-01-01

Full Text Available We consider the equiprobable distribution of spanning trees on the square lattice. All bonds of each tree can be oriented uniquely with respect to an arbitrary chosen site called the root. The problem of predecessors is to find the probability that a path along the oriented bonds passes sequentially fixed sites i and j. The conformal field theory for the Potts model predicts the fractal dimension of the path to be 5/4. Using this result, we show that the probability in the predecessors problem for two sites separated by large distance r decreases as P(r ∼ r −3/4. If sites i and j are nearest neighbors on the square lattice, the probability P(1 = 5/16 can be found from the analytical theory developed for the sandpile model. The known equivalence between the loop erased random walk (LERW and the directed path on the spanning tree states that P(1 is the probability for the LERW started at i to reach the neighboring site j. By analogy with the self-avoiding walk, P(1 can be called the return probability. Extensive Monte-Carlo simulations confirm the theoretical predictions.

Modelling biogas production of solid waste: application of the BGP model to a synthetic landfill

Science.gov (United States)

Rodrigo-Ilarri, Javier; Segura-Sobrino, Francisco

2013-04-01

Production of biogas as a result of the decomposition of organic matter included on solid waste landfills is still an issue to be understood. Reports on this matter are rarely included on the engineering construction projects of solid waste landfills despite it can be an issue of critical importance while operating the landfill and after its closure. This paper presents an application of BGP (Bio-Gas-Production) model to a synthetic landfill. The evolution in time of the concentrations of the different chemical compounds of biogas is studied. Results obtained show the impact on the air quality of different management alternatives which are usually performed in real landfills.

Road networks as collections of minimum cost paths

Science.gov (United States)

Wegner, Jan Dirk; Montoya-Zegarra, Javier Alexander; Schindler, Konrad

2015-10-01

We present a probabilistic representation of network structures in images. Our target application is the extraction of urban roads from aerial images. Roads appear as thin, elongated, partially curved structures forming a loopy graph, and this complex layout requires a prior that goes beyond standard smoothness and co-occurrence assumptions. In the proposed model the network is represented as a union of 1D paths connecting distant (super-)pixels. A large set of putative candidate paths is constructed in such a way that they include the true network as much as possible, by searching for minimum cost paths in the foreground (road) likelihood. Selecting the optimal subset of candidate paths is posed as MAP inference in a higher-order conditional random field. Each path forms a higher-order clique with a type of clique potential, which attracts the member nodes of cliques with high cumulative road evidence to the foreground label. That formulation induces a robust PN -Potts model, for which a global MAP solution can be found efficiently with graph cuts. Experiments with two road data sets show that the proposed model significantly improves per-pixel accuracies as well as the overall topological network quality with respect to several baselines.

How much detail is needed in modeling a transcranial magnetic stimulation figure-8 coil : Measurements and brain simulations

NARCIS (Netherlands)

Petrov, Petar I.; Mandija, Stefano; Sommer, Iris E.C.; Van Den Berg, Cornelis A.T.; Neggers, Sebastiaan F.W.

2017-01-01

Background: Despite TMS wide adoption, its spatial and temporal patterns of neuronal effects are not well understood. Although progress has been made in predicting induced currents in the brain using realistic finite element models (FEM), there is little consensus on how a magnetic field of a

Towards an energy management maturity model

International Nuclear Information System (INIS)

Antunes, Pedro; Carreira, Paulo; Mira da Silva, Miguel

2014-01-01

Energy management is becoming a priority as organizations strive to reduce energy costs, conform to regulatory requirements, and improve their corporate image. Despite the upsurge of interest in energy management standards, a gap persists between energy management literature and current implementation practices. This gap can be traced to the lack of an incremental improvement roadmap. In this paper we propose an Energy Management Maturity Model that can be used to guide organizations in their energy management implementation efforts to incrementally achieve compliance with energy management standards such as ISO 50001. The proposed maturity model is inspired on the Plan-Do-Check-Act cycle approach for continual improvement, and covers well-understood fundamental energy management activities common across energy management texts. The completeness of our proposal is then evaluated by establishing an ontology mapping against ISO 50001. - Highlights: • Real-world energy management activities are not aligned with the literature. • An Energy Management Maturity Model is proposed to overcome this alignment gap. • The completeness and relevance of proposed model are validated

Building Better Ecological Machines: Complexity Theory and Alternative Economic Models

Directory of Open Access Journals (Sweden)

Jess Bier

2016-12-01

Full Text Available Computer models of the economy are regularly used to predict economic phenomena and set financial policy. However, the conventional macroeconomic models are currently being reimagined after they failed to foresee the current economic crisis, the outlines of which began to be understood only in 2007-2008. In this article we analyze the most prominent of this reimagining: Agent-Based models (ABMs. ABMs are an influential alternative to standard economic models, and they are one focus of complexity theory, a discipline that is a more open successor to the conventional chaos and fractal modeling of the 1990s. The modelers who create ABMs claim that their models depict markets as ecologies, and that they are more responsive than conventional models that depict markets as machines. We challenge this presentation, arguing instead that recent modeling efforts amount to the creation of models as ecological machines. Our paper aims to contribute to an understanding of the organizing metaphors of macroeconomic models, which we argue is relevant conceptually and politically, e.g., when models are used for regulatory purposes.

Using Service Scenarios to Model Business Services

DEFF Research Database (Denmark)

Bækgaard, Lars

The purpose of the paper is to present and evaluate the notion of service scenarios. A service is work done by a service executor in interaction with a service consumer. A service scenario is a model of a service system and the roles that are played by the actors participating and interacting...... during the execution of a service. The model represents the roles and the interactions between the participants. Service scenarios can be used to model specific services and roles played by human beings and IT systems in the execution of services. The use of service scenarios is demonstrated by means...... of a case study in a public library. The case study indicates that service systems should be understood as socio-technical systems in which service executors and service consumers co-create value in mutual interaction with each other and with a set of shared resources....

Integrable lambda models and Chern-Simons theories

Energy Technology Data Exchange (ETDEWEB)

Schmidtt, David M. [Departamento de Física, Universidade Federal de São Carlos,Caixa Postal 676, CEP 13565-905, São Carlos-SP (Brazil)

2017-05-03

In this note we reveal a connection between the phase space of lambda models on S{sup 1}×ℝ and the phase space of double Chern-Simons theories on D×ℝ and explain in the process the origin of the non-ultralocality of the Maillet bracket, which emerges as a boundary algebra. In particular, this means that the (classical) AdS{sub 5}×S{sup 5} lambda model can be understood as a double Chern-Simons theory defined on the Lie superalgebra psu(2,2|4) after a proper dependence of the spectral parameter is introduced. This offers a possibility for avoiding the use of the problematic non-ultralocal Poisson algebras that preclude the introduction of lattice regularizations and the application of the QISM to string sigma models. The utility of the equivalence at the quantum level is, however, still to be explored.

Tracing the Rationale Behind UML Model Change Through Argumentation

Science.gov (United States)

Jureta, Ivan J.; Faulkner, Stéphane

Neglecting traceability—i.e., the ability to describe and follow the life of a requirement—is known to entail misunderstanding and miscommunication, leading to the engineering of poor quality systems. Following the simple principles that (a) changes to UML model instances ought be justified to the stakeholders, (b) justification should proceed in a structured manner to ensure rigor in discussions, critique, and revisions of model instances, and (c) the concept of argument instantiated in a justification process ought to be well defined and understood, the present paper introduces the UML Traceability through Argumentation Method (UML-TAM) to enable the traceability of design rationale in UML while allowing the appropriateness of model changes to be checked by analysis of the structure of the arguments provided to justify such changes.

Visual Perceptual Learning and Models.

Science.gov (United States)

Dosher, Barbara; Lu, Zhong-Lin

2017-09-15

Visual perceptual learning through practice or training can significantly improve performance on visual tasks. Originally seen as a manifestation of plasticity in the primary visual cortex, perceptual learning is more readily understood as improvements in the function of brain networks that integrate processes, including sensory representations, decision, attention, and reward, and balance plasticity with system stability. This review considers the primary phenomena of perceptual learning, theories of perceptual learning, and perceptual learning's effect on signal and noise in visual processing and decision. Models, especially computational models, play a key role in behavioral and physiological investigations of the mechanisms of perceptual learning and for understanding, predicting, and optimizing human perceptual processes, learning, and performance. Performance improvements resulting from reweighting or readout of sensory inputs to decision provide a strong theoretical framework for interpreting perceptual learning and transfer that may prove useful in optimizing learning in real-world applications.

The Experience the Gift in a Model of Co-Therapy

Directory of Open Access Journals (Sweden)

Canna Paola

2014-07-01

Full Text Available The significant social and cultural transformations which took place in recent decades brought about significant changes in the way couples interact and deal with “the risk of bonding”. The vulnerability that characterizes the couple in post-modernity is the consequence of these changes. The application of a co-therapy model with couples in crisis is based on the premise of mutual gift, which has to be understood as both an exchange of expertise and professionalism to the benefit of the couple, and as a bond of unity between co-therapists. The work that follows suggests some reflections which originate from the co-therapy model.

An improved model for the reconstruction of past radon exposure.

Science.gov (United States)

Cauwels, P; Poffijn, A

2000-05-01

If the behavior of long-lived radon progeny was well understood, measurements of these could be used in epidemiological studies to estimate past radon exposure. Field measurements were done in a radon-prone area in the Ardennes (Belgium). The surface activity of several glass sheets was measured using detectors that were fixed on indoor glass surfaces. Simultaneously the indoor radon concentration was measured using diffusion chambers. By using Monte Carlo techniques, it could be proven that there is a discrepancy between this data set and the room model calculations, which are normally used to correlate surface activity and past radon exposure. To solve this, a modification of the model is proposed.

Laboratory astrophysics. Model experiments of astrophysics with large-scale lasers

International Nuclear Information System (INIS)

Takabe, Hideaki

2012-01-01

I would like to review the model experiment of astrophysics with high-power, large-scale lasers constructed mainly for laser nuclear fusion research. The four research directions of this new field named 'Laser Astrophysics' are described with four examples mainly promoted in our institute. The description is of magazine style so as to be easily understood by non-specialists. A new theory and its model experiment on the collisionless shock and particle acceleration observed in supernova remnants (SNRs) are explained in detail and its result and coming research direction are clarified. In addition, the vacuum breakdown experiment to be realized with the near future ultra-intense laser is also introduced. (author)

Certified Nursing Assistants’ Explanatory Models of Nursing Home Resident Depression

OpenAIRE

Piven, Mary Lynn; Anderson, Ruth A.; Colón-Emeric, Cathleen S.; Sandelowski, Margarete

2008-01-01

In this study, we explored how Certified Nursing Assistants (CNAs) understood resident depression. Interviews with 18 CNAs, working in two nursing homes were guided by Kleinman’s Explanatory Models of Illness framework. Interview data were content analyzed and CNAs’ descriptions of depression were compared to the MDS 2.0 Mood Screen and to DSM-IV-TR Depression Criteria. CNAs identified causes, signs, and symptoms of depression, but they were unsure about the duration and normalcy of depressio...

Organized versus self-organized criticality in the abelian sandpile model

OpenAIRE

Fey-den Boer, AC Anne; Redig, FHJ Frank

2005-01-01

We define stabilizability of an infinite volume height configuration and of a probability measure on height configurations. We show that for high enough densities, a probability measure cannot be stabilized. We also show that in some sense the thermodynamic limit of the uniform measures on the recurrent configurations of the abelian sandpile model (ASM) is a maximal element of the set of stabilizable measures. In that sense the self-organized critical behavior of the ASM can be understood in ...

Skeletal muscle repair in a mouse model of nemaline myopathy

OpenAIRE

Sanoudou, Despina; Corbett, Mark A.; Han, Mei; Ghoddusi, Majid; Nguyen, Mai-Anh T.; Vlahovich, Nicole; Hardeman, Edna C.; Beggs, Alan H.

2006-01-01

Nemaline myopathy (NM), the most common non-dystrophic congenital myopathy, is a variably severe neuromuscular disorder for which no effective treatment is available. Although a number of genes have been identified in which mutations can cause NM, the pathogenetic mechanisms leading to the phenotypes are poorly understood. To address this question, we examined gene expression patterns in an NM mouse model carrying the human Met9Arg mutation of alpha-tropomyosin slow (Tpm3). We assessed five d...

Modelling small groundwater systems - the role of targeted field investigations and observational data in reducing model uncertainty

Science.gov (United States)

Abesser, Corinna; Hughes, Andrew; Boon, David

2017-04-01

Coastal dunes are delicate systems that are under threat from a variety of human and natural influences. Groundwater modelling can provide a better understanding of how these systems operate and can be a useful tool towards the effective management of a coastal dune system, e.g. through predicting impacts from climatic change, sea level rise and land use management. Because of their small size, typically 10 - 100 km2, models representing small dune aquifer systems are more sensitive to uncertainties in input data, model geometry and model parameterisation as well as to the availability of observational data. This study describes the development of a groundwater flow model for a small (8 km2) spit dune system, Braunton Burrows, on the Southwest coast of England, UK. The system has been extensively studied and its hydrology is thought to be well understood. However, model development revealed a high degree of uncertainty relating to model structure (definition of model boundary conditions) and parameterisation (e.g., transmissivity distributions within the model domain). An iterative approach was employed, integrating (1) sensitivity analyses, (2) targeted field investigations and (3) Monte Carlo simulations within a cycle of repeated interrogation of the model outputs, observed data and conceptual understanding. Assessment of "soft information" and targeted field investigations were an important part of this iterative modelling process. For example, a passive seismic survey (TROMINO®) provided valuable new data for the characterisation of concealed bedrock topography and thickness of superficial deposits. The data confirmed a generally inclined underlying wave cut rock shelf platform (as suggested by literature sources), revealed a buried valley, and led to a more detailed delineation of transmissivity zones within the model domain. Constructing models with increasingly more complex spatial distributions of transmissivity, resulted in considerable improvements in

Mathematical modelling of performance of safety rod and its drive mechanism in sodium cooled fast reactor during scram action

International Nuclear Information System (INIS)

Rajan Babu, V.; Thanigaiyarasu, G.; Chellapandi, P.

2014-01-01

Highlights: • Mathematical modelling of dynamic behaviour of safety rod during scram action in fast reactor. • Effects of hydraulics, structural interaction and geometry on drop time of safety rod are understood. • Using simplified model, drop time can be assessed replacing detailed CFD analysis. • Sensitivities of the related parameters on drop time are understood. • Experimental validation qualifies the modelling and computer software developed. - Abstract: Performance of safety rod and its drive mechanism which are parts of shutdown systems in sodium cooled fast reactor (SFR) plays a major role in ensuring safe operation of the plant during all the design basis events. The safety rods are to be inserted into the core within a stipulated time during off-normal conditions of the reactor. Mathematical modelling of dynamic behaviour of a safety rod and its drive mechanism in a typical 500 MWe SFR during scram action is considered in the present study. A full-scale prototype system has undergone qualification tests in air, water and in sodium simulating the operating conditions in the reactor. In this paper, the salient features of the safety rod and its mechanism, details related to mathematical modelling and sensitivity of the parameters having influence on drop time are presented. The outcomes of the numerical analysis are compared with the experimental results. In this process, the mathematical model and the computer software developed are validated

A numerical solution model of the rewetting of a nuclear fuel rod

International Nuclear Information System (INIS)

Braz Filho, F.A.

1984-01-01

The study of thermal behaviour of a nuclear reactor fuel rod during the reflooding phase of the loss-of-coolant accident (LOCA) is presented. A mathematical model and a numerical scheme were proposed in order to solve the bidimensional heat conduction equation in cylindrical coordinates. The phenomenon of reflooding is not completely understood. One of the main difficulties is to estimate the heat transfer coefficient (h). For this reason two different models were elaborated: in the first three regions are considered and in each region h is considered constant; in the second the h profile is adjusted according to the boiling curve. The three region model yields satisfactory results at high and low mass flows while the 'boiling curve' model yields reasonable at low flows. (Author) [pt

Corporate Responsibility under the ECSI model: An application in the hotel sector

Directory of Open Access Journals (Sweden)

María-Ángeles Revilla-Camacho

2017-01-01

Full Text Available This article deals with the study of Corporate Responsibility (CR under the European Customer Satisfaction Index (ECSI. The methodology of this empirical study, conducted among 629 customers staying at hotels in the city of Seville, is based on structural equation modeling (PLS. The results obtained demonstrate the applicability of the European model to the hotel sector, although not all the relationships from the original model have been proven. The main contributions are derived from a better understanding of the model's components, a variable not studied before having been incorporated: the importance of Corporate Responsibility (CR. Moreover, it means to contribute to the field of research on CR as, despite the growing interest in the subject, the effects of this construct are still poorly understood.

Generative models of the human connectome.

Science.gov (United States)

Betzel, Richard F; Avena-Koenigsberger, Andrea; Goñi, Joaquín; He, Ye; de Reus, Marcel A; Griffa, Alessandra; Vértes, Petra E; Mišic, Bratislav; Thiran, Jean-Philippe; Hagmann, Patric; van den Heuvel, Martijn; Zuo, Xi-Nian; Bullmore, Edward T; Sporns, Olaf

2016-01-01

The human connectome represents a network map of the brain's wiring diagram and the pattern into which its connections are organized is thought to play an important role in cognitive function. The generative rules that shape the topology of the human connectome remain incompletely understood. Earlier work in model organisms has suggested that wiring rules based on geometric relationships (distance) can account for many but likely not all topological features. Here we systematically explore a family of generative models of the human connectome that yield synthetic networks designed according to different wiring rules combining geometric and a broad range of topological factors. We find that a combination of geometric constraints with a homophilic attachment mechanism can create synthetic networks that closely match many topological characteristics of individual human connectomes, including features that were not included in the optimization of the generative model itself. We use these models to investigate a lifespan dataset and show that, with age, the model parameters undergo progressive changes, suggesting a rebalancing of the generative factors underlying the connectome across the lifespan. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

On the interaction between the ground- and s-bands in the CHFB model

International Nuclear Information System (INIS)

Haakansson, H.B.

1980-01-01

The interaction between the ground configuration and the first excited 2 qp (s-) configuration in the isub 13/2 CHFB model is eliminated in order to investigate how the interaction is built up by the different terms in the Hamiltonian. The changes of sign of the interaction can be understood from the particle number projected wave functions. Oscillations are still present after projection. (author)

Nitrogen frost migration on Triton: A historical model

International Nuclear Information System (INIS)

Spencer, J.R.

1990-01-01

The author presents the results of numerical simulations of the seasonal migration of nitrogen frost on Triton, constrained by Voyager observations of atmospheric pressure, temperature, and albedo distribution. Most of the exposed nitrogen is probably seasonal frost, whose migration can produce major variations in atmospheric pressure. For instance, models explored here predict a tenfold pressure drop in the coming decade. The observed albedo patterns can be understood if fresh nitrogen frost is relatively dark butt brightens with increasing insolation in a manner analogous to the Martian southern CO 2 cap

Congenital tracheal defects: embryonic development and animal models

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Zenab Arooj Sher

2016-03-01

Full Text Available Tracheal anomalies are potentially catastrophic congenital defects. As a newborn begins to breathe, the trachea needs to maintain an appropriate balance of elasticity and rigidity. If the tracheal cartilages are disorganized or structurally weak, the airways can collapse, obstructing breathing. Cartilage rings that are too small or too rigid can also obstruct breathing. These anomalies are frequently associated with craniofacial syndromes, and, despite the importance, are poorly understood. In this review, we summarize the spectrum of pathological phenotypes of the trachea and correlate them with the molecular events uncovered in mouse models.

Full scale model studies of nuclear power stations for earthquake resistance

International Nuclear Information System (INIS)

Kirillov, A.P.; Ambriashvili, Ju. K.; Kozlov, A.V.

Behaviour of nuclear power plants and its equipments under seismic action is not well understood. In the absence of well established method for aseismic deisgn of nuclear power plants and its equipments, it is necessary to carry out experimental investigations on models, fragments and full scale structures. The present study includes experimental investigations of different scale models and on existing nuclear power stations under impulse and explosion effects simulating seismic loads. The experimental work was aimed to develop on model test procedure for nuclear power station and the evaluation of the possible range of dynamic stresses in structures and pipe lines. The results of full-scale investigations of the nuclear reactor show a good agreement of dynamic characteristics of the model and the prototype. The study confirms the feasibility of simulation of model for nuclear power plants. (auth.)

Toda theories, W-algebras, and minimal models

International Nuclear Information System (INIS)

Mansfield, P.; Spence, B.

1991-01-01

We discuss the classical W-algebra symmetries of Toda field theories in terms of the pseudo-differential Lax operator associated with the Toda Lax pair. We then show how the W-algebra transformations can be understood as the non-abelian gauge transformations which preserve the form of the Lax pair. This provides a new understanding of the W-algebras, and we discuss their closure and co-cycle structure using this approach. The quantum Lax operator is investigated, and we show that this operator, which generates the quantum W-algebra currents, is conserved in the conformally extended Toda theories. The W-algebra minimal model primary fields are shown to arise naturally in these theories, leading to the conjecture that the conformally extended Toda theories provide a lagrangian formulation of the W-algebra minimal models. (orig.)

The Birth of Model Theory Lowenheim's Theorem in the Frame of the Theory of Relatives

CERN Document Server

Badesa, Calixto

2008-01-01

Löwenheim's theorem reflects a critical point in the history of mathematical logic, for it marks the birth of model theory--that is, the part of logic that concerns the relationship between formal theories and their models. However, while the original proofs of other, comparably significant theorems are well understood, this is not the case with Löwenheim's theorem. For example, the very result that scholars attribute to Löwenheim today is not the one that Skolem--a logician raised in the algebraic tradition, like Löwenheim--appears to have attributed to him. In The Birth of Model Theory, Cali

Impact of bacterial activity on turnover of insoluble hydrophobic substrates (phenanthrene and pyrene)—Model simulations for prediction of bioremediation success

DEFF Research Database (Denmark)

Rein, Arno; Adam, Iris K.U.; Miltner, Anja

2016-01-01

Many attempts for bioremediation of polycyclic aromatic hydrocarbon (PAH) contaminated sites failed in the past, but the reasons for this failure are not well understood. Here we apply and improve a model for integrated assessment of mass transfer, biodegradation and residual concentrations...

A meta-proteomics approach to study the interspecies interactions affecting microbial biofilm development in a model community

DEFF Research Database (Denmark)

Herschend, Jakob; Damholt, Zacharias Brimnes Visby; Marquard, Andrea Marion

2017-01-01

Microbial biofilms are omnipresent in nature and relevant to a broad spectrum of industries ranging from bioremediation and food production to biomedical applications. To date little is understood about how multi-species biofilm communities develop and function on a molecular level, due to the co......Microbial biofilms are omnipresent in nature and relevant to a broad spectrum of industries ranging from bioremediation and food production to biomedical applications. To date little is understood about how multi-species biofilm communities develop and function on a molecular level, due...... to the complexity of these biological systems. Here we apply a meta-proteomics approach to investigate the mechanisms influencing biofilm formation in a model consortium of four bacterial soil isolates; Stenotrophomonas rhizophila, Xanthomonas retroflexus, Microbacterium oxydans and Paenibacillus amylolyticus...

Mediating objects: scientific and public functions of models in nineteenth-century biology.

Science.gov (United States)

Ludwig, David

2013-01-01

The aim of this article is to examine the scientific and public functions of two- and three-dimensional models in the context of three episodes from nineteenth-century biology. I argue that these models incorporate both data and theory by presenting theoretical assumptions in the light of concrete data or organizing data through theoretical assumptions. Despite their diverse roles in scientific practice, they all can be characterized as mediators between data and theory. Furthermore, I argue that these different mediating functions often reflect their different audiences that included specialized scientists, students, and the general public. In this sense, models in nineteenth-century biology can be understood as mediators between theory, data, and their diverse audiences.

Facility model for the Los Alamos Plutonium Facility

International Nuclear Information System (INIS)

Coulter, C.A.; Thomas, K.E.; Sohn, C.L.; Yarbro, T.F.; Hench, K.W.

1986-01-01

The Los Alamos Plutonium Facility contains more than sixty unit processes and handles a large variety of nuclear materials, including many forms of plutonium-bearing scrap. The management of the Plutonium Facility is supporting the development of a computer model of the facility as a means of effectively integrating the large amount of information required for material control, process planning, and facility development. The model is designed to provide a flexible, easily maintainable facility description that allows the faciltiy to be represented at any desired level of detail within a single modeling framework, and to do this using a model program and data files that can be read and understood by a technically qualified person without modeling experience. These characteristics were achieved by structuring the model so that all facility data is contained in data files, formulating the model in a simulation language that provides a flexible set of data structures and permits a near-English-language syntax, and using a description for unit processes that can represent either a true unit process or a major subsection of the facility. Use of the model is illustrated by applying it to two configurations of a fictitious nuclear material processing line

Nitrogen cycling models and their application to forest harvesting

Energy Technology Data Exchange (ETDEWEB)

Johnson, D.W.; Dale, V.H.

1986-01-01

The characterization of forest nitrogen- (N-) cycling processes by several N-cycling models (FORCYTE, NITCOMP, FORTNITE, and LINKAGES) is briefly reviewed and evaluated against current knowledge of N cycling in forests. Some important processes (e.g., translocation within trees, N dynamics in decaying leaf litter) appear to be well characterized, whereas others (e.g., N mineralization from soil organic matter, N fixation, N dynamics in decaying wood, nitrification, and nitrate leaching) are poorly characterized, primarily because of a lack of knowledge rather than an oversight by model developers. It is remarkable how well the forest models do work in the absence of data on some key processes. For those systems in which the poorly understood processes could cause major changes in N availability or productivity, the accuracy of model predictions should be examined. However, the development of N-cycling models represents a major step beyond the much simpler, classic conceptual models of forest nutrient cycling developed by early investigators. The new generation of computer models will surely improve as research reveals how key nutrient-cycling processes operate.

Modeling experiments using quantum and Kolmogorov probability

International Nuclear Information System (INIS)

Hess, Karl

2008-01-01

Criteria are presented that permit a straightforward partition of experiments into sets that can be modeled using both quantum probability and the classical probability framework of Kolmogorov. These new criteria concentrate on the operational aspects of the experiments and lead beyond the commonly appreciated partition by relating experiments to commuting and non-commuting quantum operators as well as non-entangled and entangled wavefunctions. In other words the space of experiments that can be understood using classical probability is larger than usually assumed. This knowledge provides advantages for areas such as nanoscience and engineering or quantum computation.

Women's Education and World Peace: A Feminist Dream Comes True: Comment on "The Pill Is Mightier Than the Sword".

Science.gov (United States)

Pillai, Vijayan K; Wang, Ya-Chien

2015-10-01

This commentary on Potts et al provides a critical view on their thesis that increasing the level of education among women is likely to reduce terrorism. Presence of a strong family planning program enables women to control family size resulting in women's public participation more likely and facilitating the emergence of small birth cohorts who are less likely to become unemployed. In spite of the several theoretical insights their paper offers, they have not adequately described the multiple social and economic linkages that may exist between fertility rates and lowering frequency of wars, terrorism, etc. © 2016 by Kerman University of Medical Sciences.

Interesting new record and further notes on the occurrence of marine fish in Nyamithi Pan, Ndumo Game Reserve, South Africa

Directory of Open Access Journals (Sweden)

R. Kyle

2002-12-01

Full Text Available Nyamithi Pan, situated in Ndumo Game Reserve, South Africa, is a floodplain pan near the confluence of the Usuthu and Pongolo rivers. It lies approximately 75 km from the Indian Ocean. The floodplain and its fish have been extensively surveyed (Coke & Pott 1970; Kok 1980; Merron et al 1993, 1994, 1994a, 1994b, 1994c, 1994d; Pooley 1975 and there are many records of the occurrence of marine fish in this and other pans of the Pongolo and Usuthu rivers. These are, however, usually isolated instances of individual fish being caught and attracting attention.