A realistic renormalizable supersymmetric E₆ model
Bajc, Borut; Susič, Vasja
2014-01-01
A complete realistic model based on the supersymmetric version of E₆ is presented. It consists of three copies of matter 27, and a Higgs sector made of 2×(27+27⁻)+351´+351´⁻ representations. An analytic solution to the equations of motion is found which spontaneously breaks the gauge group into the Standard Model. The light fermion mass matrices are written down explicitly as non-linear functions of three Yukawa matrices. This contribution is based on Ref. [1].
Neutrino mass and proton lifetime in a realistic supersymmetric SO(10) model
NASA Astrophysics Data System (ADS)
Severson, Matthew
This work presents a complete analysis of fermion fitting and proton decay in a supersymmetric SO(10) model previously suggested by Dutta, Mimura, and Mohapatra. A key question in any grand unified theory is whether it satisfies the stringent experimental lower limits on the partial lifetimes of the proton. In more generic models, substantial fine-tuning is required among GUT-scale parameters to satisfy the limits. In the proposed model, the 10, 1¯2¯6¯, and 20 Yukawa couplings contributing to fermion masses have restricted textures intended to give favorable results for proton lifetime, while still giving rise to a realistic fermion sector, without the need for fine-tuning, even for large beta, and for either type-I or type-II dominance in the neutrino mass matrix. In this thesis, I investigate the above hypothesis at a strict numerical level of scrutiny; I obtain a valid fit for the entire fermion sector for both types of seesaw dominance, including theta13 in good agreement with the most recent data. For the case with type-II seesaw, I find that, using the Yukawa couplings fixed by the successful fermion sector fit, proton partial lifetime limits are readily satisfied for all but one of the pertinent decay modes for nearly arbitrary values of the triplet-Higgs mixing parameters, with the K+v¯ mode requiring a minor ∂(10--1) cancellation in order to satisfy its limit. I also find a maximum partial lifetime for that mode of τ( K+v¯) ˜ 1036,years. For the type-I seesaw case, I find that K+ v¯ decay mode is satisfied for any values of the triplet mixing parameters giving no major enhancement, and all other modes are easily satisfied for arbitrary mixing values; I also find a maximum partial lifetime for K+v¯ of nearly 1036years, which is largely sub-dominant to gauge boson decay channels.
Bosonic condensates in realistic supersymmetric GUT cosmic strings
NASA Astrophysics Data System (ADS)
Allys, Erwan
2016-04-01
We study the realistic structure of F-term Nambu-Goto cosmic strings forming in a general supersymmetric Grand Unified Theory implementation, assuming standard hybrid inflation. Examining the symmetry breaking of the unification gauge group down to the Standard Model, we discuss the minimal field content necessary to describe abelian cosmic strings appearing at the end of inflation. We find that several fields will condense in most theories, questioning the plausible occurrence of associated currents (bosonic and fermionic). We perturbatively evaluate the modification of their energy per unit length due to the condensates. We provide a criterion for comparing the usual abelian Higgs approximation used in cosmology to realistic situations.
Bosonic structure of realistic SO(10) supersymmetric cosmic strings
NASA Astrophysics Data System (ADS)
Allys, Erwan
2016-05-01
We study the bosonic structure of F -term Nambu-Goto cosmic strings forming in a realistic SO(10) implementation, assuming standard hybrid inflation. We describe the supersymmetric grand unified theory, and its spontaneous symmetry breaking scheme in parallel with the inflationary process. We also write the explicit tensor formulation of its scalar sector, focusing on the subrepresentations singlet under the standard model, which is sufficient to describe the string structure. We then introduce an ansatz for Abelian cosmic strings, discussing in details the hypothesis, and write down the field equations and boundary conditions. Finally, after doing a perturbative study of the model, we present and discuss the results obtained with numerical solutions of the string structure.
Bagger, J.A.
1984-09-01
We begin to construct the most general supersymmetric Lagrangians in one, two and four dimensions. We find that the matter couplings have a natural interpretation in the language of the nonlinear sigma model.
Non-tachyonic semi-realistic non-supersymmetric heterotic-string vacua
NASA Astrophysics Data System (ADS)
Ashfaque, Johar M.; Athanasopoulos, Panos; Faraggi, Alon E.; Sonmez, Hasan
2016-04-01
The heterotic-string models in the free fermionic formulation gave rise to some of the most realistic-string models to date, which possess N=1 spacetime supersymmetry. Lack of evidence for supersymmetry at the LHC instigated recent interest in non-supersymmetric heterotic-string vacua. We explore what may be learned in this context from the quasi-realistic free fermionic models. We show that constructions with a low number of families give rise to proliferation of a priori tachyon producing sectors, compared to the non-realistic examples, which typically may contain only one such sector. The reason being that in the realistic cases the internal six dimensional space is fragmented into smaller units. We present one example of a quasi-realistic, non-supersymmetric, non-tachyonic, heterotic-string vacuum and compare the structure of its massless spectrum to the corresponding supersymmetric vacuum. While in some sectors supersymmetry is broken explicitly, i.e. the bosonic and fermionic sectors produce massless and massive states, other sectors, and in particular those leading to the chiral families, continue to exhibit Fermi-Bose degeneracy. In these sectors the massless spectrum, as compared to the supersymmetric cases, will only differ in some local or global U(1) charges. We discuss the conditions for obtaining n_b=n_f at the massless level in these models. Our example model contains an anomalous U(1) symmetry, which generates a tadpole diagram at one-loop order in string perturbation theory. We speculate that this tadpole diagram may cancel the corresponding diagram generated by the one-loop non-vanishing vacuum energy and that in this respect the supersymmetric and non-supersymmetric vacua should be regarded on an equal footing. Finally we discuss vacua that contain two supersymmetry generating sectors.
Supersymmetric extensions of the standard model
NASA Astrophysics Data System (ADS)
Zwirner, Fabio
These four lectures are meant as an elementary introduction to the physics of realistic supersymmetric models. In the first lecture, after reviewing the motivations for low-energy supersymmetry and the recipe for the construction of supersymmetric lagrangians, we introduce the Minimal Supersymmetric extension of the Standard Model, and comment on possible alternatives. In the second lecture, we discuss what can be learnt by looking at such model as the low-energy limit of some unified theory, with emphasis at the implications of its renormalization group equations and at the possibility of a supersymmetric Grand Unification. The third lecture is devoted to the problem of supersymmetry breaking: we review some general features of the spontaneous breaking of global and local supersymmetry, and we compare the supergravity models with heavy and light gravitino. In the fourth lecture, we conclude with an overview of supersymmetric phenomenology: indirect effects of supersymmetric particles in electroweak precision tests and in flavour physics, as well as direct searches for the superpartners of ordinary particles.
Supersymmetric leptophilic Higgs model
Marshall, Gardner; Sher, Marc
2011-01-01
In the leptophilic model, one Higgs doublet couples to quarks and another couples to leptons. We study the supersymmetric version of this model, concentrating on the tightly constrained Higgs sector, which has four doublets. Constraints from perturbativity, unitarity, and LEP bounds are considered. It is found that the lightest Higgs, h, can have a mass well below 114 GeV, and for masses below 100 GeV will have a substantially enhanced branching ratio into {tau} pairs. For this region of parameter space, traditional production mechanisms (Higgs-strahlung, W fusion, and gluon fusion) are suppressed, but it may be produced in the decay of heavier particles. The second lightest Higgs has a mass of approximately 110 GeV for virtually all of parameter space, with standard model couplings, and thus an increase of a few GeV in the current lower bound on the standard model Higgs mass would rule out the model. The two heavier Higgs are both gauge phobic, one decays almost entirely into bb and can be produced via gluon fusion while the other decays almost entirely into {tau}{sup +}{tau}{sup -} but cannot be easily produced.
The Supersymmetric Standard Model
NASA Astrophysics Data System (ADS)
Fayet, Pierre
2016-10-01
The Standard Model may be included within a supersymmetric theory, postulating new sparticles that differ by half-a-unit of spin from their standard model partners, and by a new quantum number called R-parity. The lightest one, usually a neutralino, is expected to be stable and a possible candidate for dark matter. The electroweak breaking requires two doublets, leading to several charged and neutral Brout-Englert-Higgs bosons. This also leads to gauge/Higgs unification by providing extra spin-0 partners for the spin-1 W± and Z. It offers the possibility to view, up to a mixing angle, the new 125 GeV boson as the spin-0 partner of the Z under two supersymmetry transformations, i.e. as a Z that would be deprived of its spin. Supersymmetry then relates two existing particles of different spins, in spite of their different gauge symmetry properties, through supersymmetry transformations acting on physical fields in a non-polynomial way. We also discuss how the compactification of extra dimensions, relying on R-parity and other discrete symmetries, may determine both the supersymmetrybreaking and grand-unification scales.
A supersymmetric composite model of quarks and leptons
NASA Astrophysics Data System (ADS)
Luty, Markus A.; Mohapatra, Rabindra N.
1997-02-01
We present a class of supersymmetric models with complete generations of composite quarks and leptons using recent non-perturbative results for the low energy dynamics of supersymmetric QCD. In these models, the quarks arise as composite ``mesons'' and the leptons emerge as composite ``baryons''. The quark and lepton flavor symmetries are linked at the preon level. Baryon number violation is automatically suppressed by accidental symmetries. We give some speculations on how this model might be made realistic.
Supersymmetric Ruijsenaars-Schneider Model
NASA Astrophysics Data System (ADS)
Blondeau-Fournier, O.; Desrosiers, P.; Mathieu, P.
2015-03-01
An integrable supersymmetric generalization of the trigonometric Ruijsenaars-Schneider model is presented whose symmetry algebra includes the super Poincaré algebra. Moreover, its Hamiltonian is shown to be diagonalized by the recently introduced Macdonald superpolynomials. Somewhat surprisingly, the consistency of the scalar product forces the discreteness of the Hilbert space.
A Maximally Supersymmetric Kondo Model
Harrison, Sarah; Kachru, Shamit; Torroba, Gonzalo; /Stanford U., Phys. Dept. /SLAC
2012-02-17
We study the maximally supersymmetric Kondo model obtained by adding a fermionic impurity to N = 4 supersymmetric Yang-Mills theory. While the original Kondo problem describes a defect interacting with a free Fermi liquid of itinerant electrons, here the ambient theory is an interacting CFT, and this introduces qualitatively new features into the system. The model arises in string theory by considering the intersection of a stack of M D5-branes with a stack of N D3-branes, at a point in the D3 worldvolume. We analyze the theory holographically, and propose a dictionary between the Kondo problem and antisymmetric Wilson loops in N = 4 SYM. We perform an explicit calculation of the D5 fluctuations in the D3 geometry and determine the spectrum of defect operators. This establishes the stability of the Kondo fixed point together with its basic thermodynamic properties. Known supergravity solutions for Wilson loops allow us to go beyond the probe approximation: the D5s disappear and are replaced by three-form flux piercing a new topologically non-trivial S3 in the corrected geometry. This describes the Kondo model in terms of a geometric transition. A dual matrix model reflects the basic properties of the corrected gravity solution in its eigenvalue distribution.
Patterns of flavor signals in supersymmetric models
Goto, Toru; Okada, Yasuhiro; Shindou, Tetsuo
2008-05-01
Quark and lepton flavor signals are studied in four supersymmetric models, namely, the minimal supergravity model, the minimal supersymmetric standard model with right-handed neutrinos, SU(5) supersymmetric grand unified theory with right-handed neutrinos, and the minimal supersymmetric standard model with U(2) flavor symmetry. We calculate b{yields}s(d) transition observables in B{sub d} and B{sub s} decays, taking the constraint from the B{sub s}-B{sub s} mixing recently observed at the Tevatron into account. We also calculate lepton flavor violating processes {mu}{yields}e{gamma}, {tau}{yields}{mu}{gamma}, and {tau}{yields}e{gamma} for the models with right-handed neutrinos. We investigate possibilities to distinguish the flavor structure of the supersymmetry breaking sector with use of patterns of various flavor signals which are expected to be measured in experiments such as MEG, LHCb, and a future Super B factory.
The Minimal Supersymmetric Fat Higgs Model
Harnik, Roni; Kribs, Graham D.; Larson, Daniel T.; Murayama, Hitoshi
2003-11-26
We present a calculable supersymmetric theory of a composite"fat'" Higgs boson. Electroweak symmetry is broken dynamically through a new gauge interaction that becomes strong at an intermediate scale. The Higgs mass can easily be 200-450 GeV along with the superpartner masses, solving the supersymmetric little hierarchy problem. We explicitly verify that the model is consistent with precision electroweak data without fine-tuning. Gauge coupling unification can be maintained despite the inherently strong dynamics involved in electroweak symmetry breaking. Supersymmetrizing the Standard Model therefore does not imply a light Higgs mass, contrary to the lore in the literature. The Higgs sector of the minimal Fat Higgs model has a mass spectrum that is distinctly different from the Minimal Supersymmetric Standard Model.
Less minimal supersymmetric standard model
de Gouvea, Andre; Friedland, Alexander; Murayama, Hitoshi
1998-03-28
Most of the phenomenological studies of supersymmetry have been carried out using the so-called minimal supergravity scenario, where one assumes a universal scalar mass, gaugino mass, and trilinear coupling at M{sub GUT}. Even though this is a useful simplifying assumption for phenomenological analyses, it is rather too restrictive to accommodate a large variety of phenomenological possibilities. It predicts, among other things, that the lightest supersymmetric particle (LSP) is an almost pure B-ino, and that the {mu}-parameter is larger than the masses of the SU(2){sub L} and U(1){sub Y} gauginos. We extend the minimal supergravity framework by introducing one extra parameter: the Fayet'Iliopoulos D-term for the hypercharge U(1), D{sub Y}. Allowing for this extra parameter, we find a much more diverse phenomenology, where the LSP is {tilde {nu}}{sub {tau}}, {tilde {tau}} or a neutralino with a large higgsino content. We discuss the relevance of the different possibilities to collider signatures. The same type of extension can be done to models with the gauge mediation of supersymmetry breaking. We argue that it is not wise to impose cosmological constraints on the parameter space.
Supersymmetric cosmological FRW model and dark energy
Rosales, J. J.; Tkach, V. I.
2010-11-15
In this work we consider a flat cosmological model with a set of fluids in the framework of supersymmetric cosmology. The obtained supersymmetric algebra allowed us to take quantum solutions. It is shown that only in the case of a cosmological constant do we have a condition between the density of dark energy {rho}{sub {Lambda}} and density energy of matter {rho}{sub M}, {rho}{sub {Lambda}>}2{rho}{sub M}.
Quantum Supersymmetric Models in the Causal Approach
NASA Astrophysics Data System (ADS)
Grigore, Dan-Radu
2007-04-01
We consider the massless supersymmetric vector multiplet in a purely quantum framework. First order gauge invariance determines uniquely the interaction Lagrangian as in the case of Yang-Mills models. Going to the second order of perturbation theory produces an anomaly which cannot be eliminated. We make the analysis of the model working only with the component fields.
Supersymmetric extension of the quantum spherical model
NASA Astrophysics Data System (ADS)
Gomes, Pedro R. S.; Bienzobaz, P. F.; Gomes, M.
2012-06-01
In this work, we present a supersymmetric extension of the quantum spherical model, both in components and also in the superspace formalisms. We find the solution for short- and long-range interactions through the imaginary time formalism path integral approach. The existence of critical points (classical and quantum) is analyzed and the corresponding critical dimensions are determined.
Utilitarian supersymmetric gauge model of particle interactions
NASA Astrophysics Data System (ADS)
Ma, Ernest
2010-05-01
A remarkabale U(1) gauge extension of the supersymmetric standard model was proposed 8 years ago. It is anomaly free, has no μ term, and conserves baryon and lepton numbers automatically. The phenomenology of a specific version of this model is discussed. In particular, leptoquarks are predicted, with couplings to the heavy singlet neutrinos, the scalar partners of which may be components of dark matter. The Majorana neutrino mass matrix itself may have two zero subdeterminants.
Low-dimensional supersymmetric lattice models
Bergner, G. Kaestner, T. Uhlmann, S. Wipf, A.
2008-04-15
We study and simulate N=2 supersymmetric Wess-Zumino models in one and two dimensions. For any choice of the lattice derivative, the theories can be made manifestly supersymmetric by adding appropriate improvement terms corresponding to discretizations of surface integrals. In one dimension, our simulations show that a model with the Wilson derivative and the Stratonovich prescription for this discretization leads to far better results at finite lattice spacing than other models with Wilson fermions considered in the literature. In particular, we check that fermionic and bosonic masses coincide and the unbroken Ward identities are fulfilled to high accuracy. Equally good results for the effective masses can be obtained in a model with the SLAC derivative (even without improvement terms). In two dimensions we introduce a non-standard Wilson term in such a way that the discretization errors of the kinetic terms are only of order O(a{sup 2}). Masses extracted from the corresponding manifestly supersymmetric model prove to approach their continuum values much quicker than those from a model containing the standard Wilson term. Again, a comparable enhancement can be achieved in a theory using the SLAC derivative.
Phenomenology of the utilitarian supersymmetric standard model
NASA Astrophysics Data System (ADS)
Fraser, Sean; Kownacki, Corey; Ma, Ernest; Pollard, Nicholas; Popov, Oleg; Zakeri, Mohammadreza
2016-08-01
We study the 2010 specific version of the 2002 proposed U(1)X extension of the supersymmetric standard model, which has no μ term and conserves baryon number and lepton number separately and automatically. We consider in detail the scalar sector as well as the extra ZX gauge boson, and their interactions with the necessary extra color-triplet particles of this model, which behave as leptoquarks. We show how the diphoton excess at 750 GeV, recently observed at the LHC, may be explained within this context. We identify a new fermion dark-matter candidate and discuss its properties. An important byproduct of this study is the discovery of relaxed supersymmetric constraints on the Higgs boson's mass of 125 GeV.
The collider phenomenology of supersymmetric models
NASA Astrophysics Data System (ADS)
Muller, David J.
Scope and method of study. The purpose of this study is to investigate the phenomenology of various supersymmetric models. First, the Minimal Supersymmetric Standard Model (MSSM) is investigated. This model contains an extended Higgs sector that includes a charged boson. The effect that this charged Higgs boson has on the signatures for top quark pair production at the Tevatron is investigated. The rest of the work is devoted to the phenomenology of models with gauge mediated supersymmetry breaking (GMSB). In GMSB models, the lighter stau can be the next to lightest supersymmetric particle. The signals at hadronic colliders for GMSB models with minimal visible sector content are explored for this case. A GMSB model with non-minimal visible sector content is also explored. This is the left-right symmetric GMSB model which contains doubly charged bosons and fermions that could be light enough in mass to be produced at Run II of the Tevatron. Findings and conclusions. The presence of a charged Higgs boson that is lighter than the top quark is found to have a significant impact on the expected signatures for top quark pair production at the Tevatron. This is marked by an overall decrease in high pT electrons and muons in the final states. In addition, for tan beta less than about one, the three-body decay H+→bbW leads to final states that are not present in the Standard Model. For GMSB models with the lighter stau as the next to lightest supersymmetric particle, the signature at the Tevatron typically involves two or three tau-jets plus large missing transverse energy. This tau-jet signature can be even more pronounced in left-right symmetric GMSB models due to the production of light doubly charged fermions that may couple preferentially to the third generation of leptons. The left-right models can be distinguished from GMSB models with minimal visible sector content by the distribution in angle between the highest ET tau-jets when they come from same sign tau
Beyond the supersymmetric standard model
Hall, L.J.
1988-02-01
The possibility of baryon number violation at the weak scale and an alternative primordial nucleosynthesis scheme arising from the decay of gravitations are discussed. The minimal low energy supergravity model is defined and a few of its features are described. Renormalization group scaling and flavor physics are mentioned.
Supersymmetric chameleons and ultralocal models
NASA Astrophysics Data System (ADS)
Brax, Philippe; Rizzo, Luca Alberto; Valageas, Patrick
2016-07-01
Super-chameleon models where all types of matter belong to three secluded sectors, i.e. the dark, supersymmetry breaking and matter sectors, are shown to be dynamically equivalent to ultralocal models of modified gravity. In the dark sector, comprising both dark matter and dark energy, the interaction range between the dark energy field and dark matter is constrained to be extremely short, i.e. shorter than the inverse gravitino mass set by supersymmetry breaking. This realizes an extreme version of chameleon screening of the dark energy interaction. On the other hand, the baryonic matter sector decouples from the dark energy in a Damour-Polyakov way. These two mechanisms preclude the existence of any modification of gravity locally in the Solar System due to the presence of the super-chameleon field. On larger scales, the super-chameleon can have effects on the growth of structure and the number of dark matter halos. It can also affect the dynamics of galaxies where the fifth-force interaction that it induces can have the same order of magnitude as Newton's interaction.
Higgs boson masses in supersymmetric models
Berger, M.S.
1991-04-01
Imposing supersymmetry on a Higgs potential constrains the parameters that define the potential. In supersymmetric extensions to the stranded model containing only Higgs SU(2){sub L} doublets there exist Higgs boson mass sum rules and bounds on the Higgs masses at tree level. The prescription for renormalizing these sum rules is derived. An explicit calculation is performed in the minimal supersymmetric extension to the standard model (MSSM). In this model at tree level the mass sum rule is M{sub H}{sup 2} + M{sub h}{sup 2} = M{sub A}{sup 2} + M{sub Z}{sup 2}. The results indicate that large corrections to the sum rules may arise from heavy matter fields, e.g. a heavy top quark. Squarks significantly heavier than their fermionic partners contribute large contributions when mixing occurs in the squark sector. These large corrections result from squark-Higgs couplings that become large in this limit. Contributions to individual Higgs boson masses that are quadratic in the squark masses cancel in the sum rule. Thus the naturalness constraint on Higgs boson masses is hidden in the combination of Higgs boson masses that comprise the sum rule. 39 refs., 13 figs.
On supermatrix models, Poisson geometry, and noncommutative supersymmetric gauge theories
Klimčík, Ctirad
2015-12-15
We construct a new supermatrix model which represents a manifestly supersymmetric noncommutative regularisation of the UOSp(2|1) supersymmetric Schwinger model on the supersphere. Our construction is much simpler than those already existing in the literature and it was found by using Poisson geometry in a substantial way.
Simple supersymmetric strongly coupled preon model
NASA Astrophysics Data System (ADS)
Fajfer, S.; Tadić, D.
1988-08-01
This supersymmetric-SU(5) composite model is a natural generalization of the usual strong-coupling models. Preon superfields are in representations 5* and 10. The product representations 5*×10, 5×10, 5×5, and 5*×5 contain only those strongly hypercolor bound states which are needed in the standard electroweak theory. There are no superfluous quarklike states. The neutrino is massless. Only one strongly hypercolor bound singlet (10×10*) can exist as a free particle. At higher energies one should expect to see a plethora of new particles. Grand unification happens at the scale M~1014 GeV. Cabibbo mixing can be incorporated by using a transposed Kobayashi-Maskawa mixing matrix.
Area law violations in a supersymmetric model
NASA Astrophysics Data System (ADS)
Huijse, Liza; Swingle, Brian
2013-01-01
We study the structure of entanglement in a supersymmetric lattice model of fermions on certain types of decorated graphs with quenched disorder. In particular, we construct models with controllable ground-state degeneracy protected by supersymmetry and the choice of Hilbert space. We show that in certain special limits, these degenerate ground states are associated with local impurities and that there exists a basis of the ground-state manifold in which every basis element satisfies a boundary law for entanglement entropy. On the other hand, by considering incoherent mixtures or coherent superpositions of these localized ground states, we can find regions that violate the boundary law for entanglement entropy over a wide range of length scales. More generally, we discuss various criteria for constructing violations of the boundary law for entanglement entropy and discuss possible relations of our work to recent holographic studies.
A simple and realistic model of supersymmetry breaking
Nomura, Yasunori; Papucci, Michele
2007-09-25
We present a simple and realistic model of supersymmetry breaking. In addition to the minimal supersymmetric standard model, we only introduce a hidden sector gauge group SU(5) and three fields X, F and \\bar{F}. Supersymmetry is broken at a local minimum of the potential, and its effects are transmitted to the supersymmetric standard model sector through both standard model gauge loops and local operators suppressed by the cutoff scale, which is taken to be the unification scale. The form of the local operators is controlled by a U(1) symmetry. The generated supersymmetry breaking and mu parameters are comparable in size, and no flavor or CP violating terms arise. The spectrum of the first two generation superparticles is that of minimal gauge mediation with the number of messengers N_mess = 5 and the messenger scale 1011 GeV< M_mess< 1013 GeV. The spectrum of the Higgs bosons and third generation superparticles, however, can deviate from it. The lightest supersymmetric particle is the gravitino with a mass of order (1-10) GeV.
A tool box for implementing supersymmetric models
NASA Astrophysics Data System (ADS)
Staub, Florian; Ohl, Thorsten; Porod, Werner; Speckner, Christian
2012-10-01
We present a framework for performing a comprehensive analysis of a large class of supersymmetric models, including spectrum calculation, dark matter studies and collider phenomenology. To this end, the respective model is defined in an easy and straightforward way using the Mathematica package SARAH. SARAH then generates model files for CalcHep which can be used with micrOMEGAs as well as model files for WHIZARD and O'Mega. In addition, Fortran source code for SPheno is created which facilitates the determination of the particle spectrum using two-loop renormalization group equations and one-loop corrections to the masses. As an additional feature, the generated SPheno code can write out input files suitable for use with HiggsBounds to apply bounds coming from the Higgs searches to the model. Combining all programs provides a closed chain from model building to phenomenology. Program summary Program title: SUSY Phenomenology toolbox. Catalog identifier: AEMN_v1_0. Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEMN_v1_0.html. Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland. Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html. No. of lines in distributed program, including test data, etc.: 140206. No. of bytes in distributed program, including test data, etc.: 1319681. Distribution format: tar.gz. Programming language: Autoconf, Mathematica. Computer: PC running Linux, Mac. Operating system: Linux, Mac OS. Classification: 11.6. Nature of problem: Comprehensive studies of supersymmetric models beyond the MSSM is considerably complicated by the number of different tasks that have to be accomplished, including the calculation of the mass spectrum and the implementation of the model into tools for performing collider studies, calculating the dark matter density and checking the compatibility with existing collider bounds (in particular, from the Higgs searches). Solution method: The
Gauge extensions of supersymmetric models and hidden valleys
NASA Astrophysics Data System (ADS)
Luo, Mingxing; Zheng, Sibo
2009-04-01
Supersymmetric models with extended group structure beyond the standard model are revisited in the framework of general gauge mediation. Sum rules for sfermion masses are shown to depend genuinely on the group structure, which can serve as important probes for specific models. The left-right model and models with extra U(1) are worked out for illustrations. If the couplings of extra gauge groups are small, supersymmetric hidden valleys of the scale 10-100 GeV can be naturally constructed in companion of a TeV-scale supersymmetric visible sector.
Radiative neutralino production in low energy supersymmetric models
Basu, Rahul; Sharma, Chandradew; Pandita, P. N.
2008-06-01
We study the production of the lightest neutralinos in the radiative process e{sup +}e{sup -}{yields}{chi}-tilde{sub 1}{sup 0}{chi}-tilde{sub 1}{sup 0}{gamma} in low energy supersymmetric models for the International Linear Collider energies. This includes the minimal supersymmetric standard model as well as its extension with an additional chiral Higgs singlet superfield, the nonminimal supersymmetric standard model. We compare and contrast the dependence of the signal cross section on the parameters of the neutralino sector of the minimal and nonminimal supersymmetric standard model. We also consider the background to this process coming from the standard model process e{sup +}e{sup -}{yields}{nu}{nu}{gamma}, as well as from the radiative production of the scalar partners of the neutrinos (sneutrinos) e{sup +}e{sup -}{yields}{nu}-tilde{nu}-tilde*{gamma}, which can be a background to the radiative neutralino production when the sneutrinos decay invisibly. In low energy supersymmetric models radiative production of the lightest neutralinos may be the only channel to study supersymmetric partners of the standard model particles at the first stage of a linear collider, since heavier neutralinos, charginos, and sleptons may be too heavy to be pair produced at a e{sup +}e{sup -} machine with {radical}(s)=500 GeV.
On Newton's law in supersymmetric braneworld models
NASA Astrophysics Data System (ADS)
Palma, Gonzalo A.
2007-09-01
We study the propagation of gravitons within 5-D supersymmetric braneworld models with a bulk scalar field. The setup considered here consists of a 5-D bulk spacetime bounded by two 4-D branes localized at the fixed points of an S1/Bbb Z2 orbifold. There is a scalar field phi in the bulk which, given a superpotential W(phi), determines the warped geometry of the 5-D spacetime. This type of scenario is common in string theory, where the bulk scalar field phi is related to the volume of small compact extra dimensions. We show that, after the moduli are stabilized by supersymmetry breaking terms localized on the branes, the only relevant degrees of freedom in the bulk consist of a 5-D massive spectrum of gravitons. Then we analyze the gravitational interaction between massive bodies localized at the positive tension brane mediated by these bulk gravitons. It is shown that the Newtonian potential describing this interaction picks up a non-trivial contribution at short distances that depends on the shape of the superpotential W(phi). We compute this contribution for dilatonic braneworld scenarios W(phi) propto eαphi (where α is a constant) and discuss the particular case of 5-D Heterotic M-theory: It is argued that a specific footprint at micron scales could be observable in the near future.
Atomic model of supersymmetric Hubbard operators
NASA Astrophysics Data System (ADS)
Hopkinson, J.; Coleman, P.
2003-02-01
We apply the recently proposed supersymmetric Hubbard operators [P. Coleman, C. Pépin, and J. Hopkinson, Phys. Rev. B 63, 140411(R) (2001)] to an atomic model. In the limiting case of free spins, we derive exact results for the entropy which are compared with a mean-field + Gaussian corrections description. We show how these results can be extended to the case of charge fluctuations and calculate exact results for the partition function, free energy, and heat capacity of an atomic model for some simple examples. Wave-functions of possible states are listed. We compare the accuracy of large N expansions of the susy spin operators [P. Coleman, C. Pépin, and A. M. Tsvelik, Phys. Rev. B 62, 3852 (2000); Nucl. Phys. B 586, 641 (2000)] with those obtained using “Schwinger bosons” and “Abrikosov pseudofermions.” For the atomic model, we compare results of slave boson, slave fermion, and susy Hubbard operator approximations in the physically interesting but uncontrolled limiting case of N→2. For a mixed representation of spins, we estimate the accuracy of large N expansions of the atomic model. In the single box limit, we find that the lowest-energy susy saddle point reduces to simply either slave bosons or slave fermions, while for higher boxes this is not the case. The highest energy saddle point solution has the interesting feature that it admits a small region of a mixed representation, which bears a superficial resemblance to that observed experimentally close to an antiferromagnetic quantum critical point.
Neutralino dark matter in the left-right supersymmetric model
Demir, Durmus A.; Frank, Mariana; Turan, Ismail
2006-06-01
We study the neutralino sector of the left-right supersymmetric model. In addition to the possibilities available in the minimal supersymmetric model, the neutralino states can be superpartners of the U(1){sub B-L} gauge boson, the neutral SU(2){sub R} gauge boson, or of the Higgs triplets. We analyze neutralino masses and determine the parameter regions for which the lightest neutralino can be one of the new pure states. We then calculate the relic density of the dark matter for each of these states and impose the constraints coming from the {rho} parameter, the anomalous magnetic moment of the muon, b{yields}s{gamma}, as well as general supersymmetric mass bounds. The lightest neutralino can be the bino, or the right-wino, or the neutral triplet Higgsino, all of which have different couplings to the standard model particles from the usual neutralinos. A light bino satisfies all the experimental constraints and would be the preferred dark matter candidate for light supersymmetric scalar masses, while the right-wino would be favored by intermediate supersymmetric mass scales. The neutral triplet Higgs fermion satisfies the experimental bounds only in a small region of the parameter space, for intermediate to heavy supersymmetric scalar masses.
Challenging the minimal supersymmetric SU(5) model
Bajc, Borut; Lavignac, Stéphane; Mede, Timon
2014-06-24
We review the main constraints on the parameter space of the minimal renormalizable supersymmetric SU(5) grand unified theory. They consist of the Higgs mass, proton decay, electroweak symmetry breaking and fermion masses. Superpartner masses are constrained both from below and from above, giving hope for confirming or definitely ruling out the theory in the future. This contribution is based on Ref. [1].
Development of a realistic human airway model.
Lizal, Frantisek; Elcner, Jakub; Hopke, Philip K; Jedelsky, Jan; Jicha, Miroslav
2012-03-01
Numerous models of human lungs with various levels of idealization have been reported in the literature; consequently, results acquired using these models are difficult to compare to in vivo measurements. We have developed a set of model components based on realistic geometries, which permits the analysis of the effects of subsequent model simplification. A realistic digital upper airway geometry except for the lack of an oral cavity has been created which proved suitable both for computational fluid dynamics (CFD) simulations and for the fabrication of physical models. Subsequently, an oral cavity was added to the tracheobronchial geometry. The airway geometry including the oral cavity was adjusted to enable fabrication of a semi-realistic model. Five physical models were created based on these three digital geometries. Two optically transparent models, one with and one without the oral cavity, were constructed for flow velocity measurements, two realistic segmented models, one with and one without the oral cavity, were constructed for particle deposition measurements, and a semi-realistic model with glass cylindrical airways was developed for optical measurements of flow velocity and in situ particle size measurements. One-dimensional phase doppler anemometry measurements were made and compared to the CFD calculations for this model and good agreement was obtained. PMID:22558834
Taming the zoo of supersymmetric quantum mechanical models
NASA Astrophysics Data System (ADS)
Smilga, A. V.
2013-05-01
We show that in many cases nontrivial and complicated supersymmetric quantum mechanical (SQM) models can be obtained from the simple model describing free dynamics in flat complex space by two operations: (i) Hamiltonian reduction and (ii) similarity transformation of the complex supercharges. We conjecture that it is true for any SQM model.
Ellis, John; Olive, Keith A.; Savage, Christopher; Spanos, Vassilis C.
2010-04-15
We evaluate the neutrino fluxes to be expected from neutralino lightest supersymmetric particle (LSP) annihilations inside the Sun, within the minimal supersymmetric extension of the standard model with supersymmetry-breaking scalar and gaugino masses constrained to be universal at the grand unified theory scale [the constrained minimal supersymmetric standard model (CMSSM)]. We find that there are large regions of typical CMSSM (m{sub 1/2},m{sub 0}) planes where the LSP density inside the Sun is not in equilibrium, so that the annihilation rate may be far below the capture rate. We show that neutrino fluxes are dependent on the solar model at the 20% level, and adopt the AGSS09 model of Serenelli et al. for our detailed studies. We find that there are large regions of the CMSSM (m{sub 1/2},m{sub 0}) planes where the capture rate is not dominated by spin-dependent LSP-proton scattering, e.g., at large m{sub 1/2} along the CMSSM coannihilation strip. We calculate neutrino fluxes above various threshold energies for points along the coannihilation/rapid-annihilation and focus-point strips where the CMSSM yields the correct cosmological relic density for tan{beta}=10 and 55 for {mu}>0, exploring their sensitivities to uncertainties in the spin-dependent and -independent scattering matrix elements. We also present detailed neutrino spectra for four benchmark models that illustrate generic possibilities within the CMSSM. Scanning the cosmologically favored parts of the parameter space of the CMSSM, we find that the IceCube/DeepCore detector can probe at best only parts of this parameter space, notably the focus-point region and possibly also at the low-mass tip of the coannihilation strip.
Shell-model study on event rates of lightest supersymmetric particles scattering off 83Kr and 125Te
NASA Astrophysics Data System (ADS)
Pirinen, P.; Srivastava, P. C.; Suhonen, J.; Kortelainen, M.
2016-05-01
We investigate the elastic and inelastic scattering of lightest supersymmetric particle (LSP) dark matter off two possible target nuclei, 83Kr and 125Te. For the nuclear-structure calculations, we employ the nuclear shell model using recently generated realistic interactions. We have condensed the nuclear-physics contribution to a set of nuclear-structure factors that are independent of the adopted supersymmetric (SUSY) model. Total event rates are then easily calculated by combining the nuclear-structure factors with SUSY parameters of choice. In particular, 125Te shows promise as a detector material with both the elastic and inelastic channels yielding an appreciable nuclear response.
Invisible decays of Higgs bosons in supersymmetric models
Griest, K.; Haber, H.E.
1988-02-01
We point out that the dominant decay of the light scalar Higgs boson in a supersymmetric model may be into a pair of the lightest neutralinos (assumed to be the lightest supersymmetric particles), which would result in an invisible final state. Thus, in the search at the Stanford Linear Collider and the CERN collider LEP for a Higgs scalar produced in association with a real or virtual Z boson, it is important not to cut out events with significant missing energy recoiling against the Z.
Collective field theory of a singular supersymmetric matrix model
de Mello Koch, R.; Rodrigues, J.P.
1995-05-15
The supersymmetric collective field theory with the potential {ital v}{prime}({ital x})={omega}{ital x}{minus}{eta}/{ital x} is studied. Consistency with supersymmetry enforces a two band solution. A supersymmetric classical configuration is found, and interpreted in terms of the density of zeroes of certain Laguerre polynomials. The spectrum of the model is then studied and is seen to correspond to a massless scalar and a Majorana fermion. The {ital x} space eigenfunctions are constructed and expressed in terms of Chebyshev polynomials. Higher order interactions are also discussed.
Discrimination of supersymmetric grand unified models in gaugino mediation
Okada, Nobuchika; Hieu Minh Tran
2011-03-01
We consider supersymmetric grand unified theory (GUT) with the gaugino mediated supersymmetry breaking and investigate a possibility to discriminate different GUT models in terms of predicted sparticle mass spectra. Taking two example GUT models, the minimal SU(5) and simple SO(10) models, and imposing a variety of theoretical and experimental constraints, we calculate sparticle masses. Fixing parameters of each model so as to result in the same mass of neutralino as the lightest supersymmetric particle (LSP), giving the observed dark matter relic density, we find sizable mass differences in the left-handed slepton and right-handed down-type squark sectors in two models, which can be a probe to discriminate the GUT models realized at the GUT scale far beyond the reach of collider experiments.
BPS states in supersymmetric chiral models with higher derivative terms
NASA Astrophysics Data System (ADS)
Nitta, Muneto; Sasaki, Shin
2014-11-01
We study the higher derivative chiral models with four supercharges and Bogomol'nyi-Prasad-Sommerfield (BPS) states in these models. The off-shell Lagrangian generically includes higher powers of the auxiliary fields F , which causes distinct on-shell branches associated with the solutions to the auxiliary fields equation. We point out that the model admits a supersymmetric completion of arbitrary higher derivative bosonic models of a single complex scalar field, and an arbitrary scalar potential can be introduced even without superpotentials. As an example, we present a supersymmetric extension of the Faddeev-Skyrme model without four time derivatives, in contrast to the previously proposed supersymmetric Faddeev-Skyrme-like model containing four time derivatives. In general, higher derivative terms together with a superpotential result in deformed scalar potentials. We find that higher derivative corrections to 1 /2 BPS domain walls and 1 /2 BPS lumps are exactly canceled out, while the 1 /4 BPS lumps (as compact baby Skyrmions) depend on a characteristic feature of the higher derivative models. We also find a new 1 /4 BPS condition for domain wall junctions, which generically receives higher derivative corrections.
Realistic molecular model of kerogen's nanostructure.
Bousige, Colin; Ghimbeu, Camélia Matei; Vix-Guterl, Cathie; Pomerantz, Andrew E; Suleimenova, Assiya; Vaughan, Gavin; Garbarino, Gaston; Feygenson, Mikhail; Wildgruber, Christoph; Ulm, Franz-Josef; Pellenq, Roland J-M; Coasne, Benoit
2016-05-01
Despite kerogen's importance as the organic backbone for hydrocarbon production from source rocks such as gas shale, the interplay between kerogen's chemistry, morphology and mechanics remains unexplored. As the environmental impact of shale gas rises, identifying functional relations between its geochemical, transport, elastic and fracture properties from realistic molecular models of kerogens becomes all the more important. Here, by using a hybrid experimental-simulation method, we propose a panel of realistic molecular models of mature and immature kerogens that provide a detailed picture of kerogen's nanostructure without considering the presence of clays and other minerals in shales. We probe the models' strengths and limitations, and show that they predict essential features amenable to experimental validation, including pore distribution, vibrational density of states and stiffness. We also show that kerogen's maturation, which manifests itself as an increase in the sp(2)/sp(3) hybridization ratio, entails a crossover from plastic-to-brittle rupture mechanisms.
Realistic molecular model of kerogen's nanostructure
NASA Astrophysics Data System (ADS)
Bousige, Colin; Ghimbeu, Camélia Matei; Vix-Guterl, Cathie; Pomerantz, Andrew E.; Suleimenova, Assiya; Vaughan, Gavin; Garbarino, Gaston; Feygenson, Mikhail; Wildgruber, Christoph; Ulm, Franz-Josef; Pellenq, Roland J.-M.; Coasne, Benoit
2016-05-01
Despite kerogen's importance as the organic backbone for hydrocarbon production from source rocks such as gas shale, the interplay between kerogen's chemistry, morphology and mechanics remains unexplored. As the environmental impact of shale gas rises, identifying functional relations between its geochemical, transport, elastic and fracture properties from realistic molecular models of kerogens becomes all the more important. Here, by using a hybrid experimental-simulation method, we propose a panel of realistic molecular models of mature and immature kerogens that provide a detailed picture of kerogen's nanostructure without considering the presence of clays and other minerals in shales. We probe the models' strengths and limitations, and show that they predict essential features amenable to experimental validation, including pore distribution, vibrational density of states and stiffness. We also show that kerogen's maturation, which manifests itself as an increase in the sp2/sp3 hybridization ratio, entails a crossover from plastic-to-brittle rupture mechanisms.
Realistic molecular model of kerogen's nanostructure.
Bousige, Colin; Ghimbeu, Camélia Matei; Vix-Guterl, Cathie; Pomerantz, Andrew E; Suleimenova, Assiya; Vaughan, Gavin; Garbarino, Gaston; Feygenson, Mikhail; Wildgruber, Christoph; Ulm, Franz-Josef; Pellenq, Roland J-M; Coasne, Benoit
2016-05-01
Despite kerogen's importance as the organic backbone for hydrocarbon production from source rocks such as gas shale, the interplay between kerogen's chemistry, morphology and mechanics remains unexplored. As the environmental impact of shale gas rises, identifying functional relations between its geochemical, transport, elastic and fracture properties from realistic molecular models of kerogens becomes all the more important. Here, by using a hybrid experimental-simulation method, we propose a panel of realistic molecular models of mature and immature kerogens that provide a detailed picture of kerogen's nanostructure without considering the presence of clays and other minerals in shales. We probe the models' strengths and limitations, and show that they predict essential features amenable to experimental validation, including pore distribution, vibrational density of states and stiffness. We also show that kerogen's maturation, which manifests itself as an increase in the sp(2)/sp(3) hybridization ratio, entails a crossover from plastic-to-brittle rupture mechanisms. PMID:26828313
Supersymmetric U(1){sup '} model with multiple dark matters
Hur, Taeil; Lee, Hye-Sung; Nasri, Salah
2008-01-01
We consider a scenario where a supersymmetric model has multiple dark matter particles. Adding a U(1){sup '} gauge symmetry is a well-motivated extension of the minimal supersymmetric standard model (MSSM). It can cure the problems of the MSSM such as the {mu} problem or the proton decay problem with high-dimensional lepton number and baryon number violating operators which R parity allows. An extra parity (U parity) may arise as a residual discrete symmetry after U(1){sup '} gauge symmetry is spontaneously broken. The lightest U-parity particle (LUP) is stable under the new parity becoming a new dark matter candidate. Up to three massive particles can be stable in the presence of the R parity and the U parity. We numerically illustrate that multiple stable particles in our model can satisfy both constraints from the relic density and the direct detection, thus providing a specific scenario where a supersymmetric model has well-motivated multiple dark matters consistent with experimental constraints. The scenario provides new possibilities in the present and upcoming dark matter searches in the direct detection and collider experiments.
Flipped version of the supersymmetric strongly coupled preon model
NASA Astrophysics Data System (ADS)
Fajfer, S.; Mileković, M.; Tadić, D.
1989-12-01
In the supersymmetric SU(5) [SUSY SU(5)] composite model (which was described in an earlier paper) the fermion mass terms can be easily constructed. The SUSY SU(5)⊗U(1), i.e., flipped, composite model possesses a completely analogous composite-particle spectrum. However, in that model one cannot construct a renormalizable superpotential which would generate fermion mass terms. This contrasts with the standard noncomposite grand unified theories (GUT's) in which both the Georgi-Glashow electrical charge embedding and its flipped counterpart lead to the renormalizable theories.
Baby Skyrme model, near-BPS approximations, and supersymmetric extensions
NASA Astrophysics Data System (ADS)
Bolognesi, S.; Zakrzewski, W.
2015-02-01
We study the baby Skyrme model as a theory that interpolates between two distinct BPS systems. For this, a near-BPS approximation can be used when there is a small deviation from each of the two BPS limits. We provide analytical explanation and numerical support for the validity of this approximation. We then study the set of all possible supersymmetric extensions of the baby Skyrme model with N =1 and the particular ones with extended N =2 supersymmetries and relate this to the above mentioned almost-BPS approximation.
Target space supersymmetric sigma model techniques
de Boer, Jan; Skenderis, Kostas
1996-07-01
We briefly review the covariant formulation of the Green-Schwarz superstring by Berkovits, and describe how a detailed tree-level and one-loop analysis of this model leads, for the first time, to a derivation of the low-energy effective action of the heterotic superstring while keeping target-space supersymmetry manifest. The resulting low-energy theory is old-minimal supergravity coupled to tensor multiplet. The dilaton is part of the compensator multiplet.
R -parity conserving supersymmetric extension of the Zee model
NASA Astrophysics Data System (ADS)
Kanemura, Shinya; Shindou, Tetsuo; Sugiyama, Hiroaki
2015-12-01
We extend the Zee model, where tiny neutrino masses are generated at the one-loop level, to a supersymmetric model with R -parity conservation. It is found that the neutrino mass matrix can be consistent with the neutrino oscillation data thanks to the nonholomorphic Yukawa interaction generated via one-loop diagrams of sleptons. We find a parameter set of the model, where in addition to the neutrino oscillation data, experimental constraints from the lepton flavor violating decays of charged leptons and current LHC data are also satisfied. In the parameter set, an additional C P -even neutral Higgs boson other than the standard-model-like one, a C P -odd neutral Higgs boson, and two charged scalar bosons are light enough to be produced at the LHC and future lepton colliders. If the lightest charged scalar bosons are mainly composed of the SU (2 )L-singlet scalar boson in the model, they would decay into e ν and μ ν with 50% of a branching ratio for each. In such a case, the relation among the masses of the charged scalar bosons and the C P -odd Higgs in the minimal supersymmetric standard model approximately holds with a radiative correction. Our model can be tested by measuring the specific decay patterns of charged scalar bosons and the discriminative mass spectrum of additional scalar bosons.
Two Realistic Beagle Models for Dose Assessment.
Stabin, Michael G; Kost, Susan D; Segars, William P; Guilmette, Raymond A
2015-09-01
Previously, the authors developed a series of eight realistic digital mouse and rat whole body phantoms based on NURBS technology to facilitate internal and external dose calculations in various species of rodents. In this paper, two body phantoms of adult beagles are described based on voxel images converted to NURBS models. Specific absorbed fractions for activity in 24 organs are presented in these models. CT images were acquired of an adult male and female beagle. The images were segmented, and the organs and structures were modeled using NURBS surfaces and polygon meshes. Each model was voxelized at a resolution of 0.75 × 0.75 × 2 mm. The voxel versions were implemented in GEANT4 radiation transport codes to calculate specific absorbed fractions (SAFs) using internal photon and electron sources. Photon and electron SAFs were then calculated for relevant organs in both models. The SAFs for photons and electrons were compatible with results observed by others. Absorbed fractions for electrons for organ self-irradiation were significantly less than 1.0 at energies above 0.5 MeV, as expected for many of these small-sized organs, and measurable cross irradiation was observed for many organ pairs for high-energy electrons (as would be emitted by nuclides like 32P, 90Y, or 188Re). The SAFs were used with standardized decay data to develop dose factors (DFs) for radiation dose calculations using the RADAR Method. These two new realistic models of male and female beagle dogs will be useful in radiation dosimetry calculations for external or internal simulated sources. PMID:26222214
Supersymmetric sigma model of disordered, isotropic, elastic media
NASA Astrophysics Data System (ADS)
Photiadis, Douglas
The supersymmetry method proposed by Efetov in 1983 has been enormously successful at describing a broad range of phenomena involving disorder, providing a framework for understanding and going beyond the successes of random matrix theory and allowing a calculation of the slowing of diffusion as the Anderson transition is approached. The original model described the propagation of a scalar wave in a disordered medium, and subsequent work extended these ideas to classical waves, optical or elastic, with the approximation that the wave propagation can be similarly described by a scalar theory. Such a theory cannot however account correctly for scattering between different polarizations. A direct attempt to derive a supersymmetric model describing elastic waves results in a non-renormalizable field theory, and poses substantial difficulties. We have obtained a supersymmetric sigma model by considering the dual model which describes a generalized superstress field. The model enables one to fully account for the different wave types and polarizations in the medium. We will present our recent results in this area, including model predictions for the obtained diffusion constants, and the effects of renormalization to first order. This research was funded by the Office of Naval Research.
Vacuum fluctuations in a supersymmetric model in FRW spacetime
Bilic, Neven
2011-05-15
We study a noninteracting supersymmetric model in an expanding FRW spacetime. A soft supersymmetry breaking induces a nonzero contribution to the vacuum energy density. A short distance cutoff of the order of Planck length provides a scale for the vacuum energy density comparable with the observed cosmological constant. Assuming the presence of a dark energy substance in addition to the vacuum fluctuations of the field, an effective equation of state is derived in a self-consistent approach. The effective equation of state is sensitive to the choice of the cutoff but no fine-tuning is needed.
Electroweak baryogenesis in the exceptional supersymmetric standard model
Chao, Wei
2015-08-28
We study electroweak baryogenesis in the E{sub 6} inspired exceptional supersymmetric standard model (E{sub 6}SSM). The relaxation coefficients driven by singlinos and the new gaugino as well as the transport equation of the Higgs supermultiplet number density in the E{sub 6}SSM are calculated. Our numerical simulation shows that both CP-violating source terms from singlinos and the new gaugino can solely give rise to a correct baryon asymmetry of the Universe via the electroweak baryogenesis mechanism.
Novel symmetries in N=2 supersymmetric quantum mechanical models
Malik, R.P.; Khare, Avinash
2013-07-15
We demonstrate the existence of a novel set of discrete symmetries in the context of the N=2 supersymmetric (SUSY) quantum mechanical model with a potential function f(x) that is a generalization of the potential of the 1D SUSY harmonic oscillator. We perform the same exercise for the motion of a charged particle in the X–Y plane under the influence of a magnetic field in the Z-direction. We derive the underlying algebra of the existing continuous symmetry transformations (and corresponding conserved charges) and establish its relevance to the algebraic structures of the de Rham cohomological operators of differential geometry. We show that the discrete symmetry transformations of our present general theories correspond to the Hodge duality operation. Ultimately, we conjecture that any arbitrary N=2 SUSY quantum mechanical system can be shown to be a tractable model for the Hodge theory. -- Highlights: •Discrete symmetries of two completely different kinds of N=2 supersymmetric quantum mechanical models have been discussed. •The discrete symmetries provide physical realizations of Hodge duality. •The continuous symmetries provide the physical realizations of de Rham cohomological operators. •Our work sheds a new light on the meaning of the above abstract operators.
Inflation in Realistic D-Brane Models
NASA Astrophysics Data System (ADS)
Burgess, C. P.; Cline, J. M.; Stoica, H.; Quevedo, F.
2004-09-01
We find successful models of D-brane/anti-brane inflation within a string context. We work within the GKP-Bbb KLT class of type IIB string vacua for which many moduli are stabilized through fluxes, as recently modified to include `realistic' orbifold sectors containing standard-model type particles. We allow all moduli to roll when searching for inflationary solutions and find that inflation is not generic inasmuch as special choices must be made for the parameters describing the vacuum. But given these choices inflation can occur for a reasonably wide range of initial conditions for the brane and antibrane. We find that D-terms associated with the orbifold blowing-up modes play an important role in the inflationary dynamics. Since the models contain a standard-model-like sector after inflation, they open up the possibility of addressing reheating issues. We calculate predictions for the CMB temperature fluctuations and find that these can be consistent with observations, but are generically not deep within the scale-invariant regime and so can allow appreciable values for dns/dln k as well as predicting a potentially observable gravity-wave signal. It is also possible to generate some admixture of isocurvature fluctuations.
Comparing Realistic Subthalamic Nucleus Neuron Models
NASA Astrophysics Data System (ADS)
Njap, Felix; Claussen, Jens C.; Moser, Andreas; Hofmann, Ulrich G.
2011-06-01
The mechanism of action of clinically effective electrical high frequency stimulation is still under debate. However, recent evidence points at the specific activation of GABA-ergic ion channels. Using a computational approach, we analyze temporal properties of the spike trains emitted by biologically realistic neurons of the subthalamic nucleus (STN) as a function of GABA-ergic synaptic input conductances. Our contribution is based on a model proposed by Rubin and Terman and exhibits a wide variety of different firing patterns, silent, low spiking, moderate spiking and intense spiking activity. We observed that most of the cells in our network turn to silent mode when we increase the GABAA input conductance above the threshold of 3.75 mS/cm2. On the other hand, insignificant changes in firing activity are observed when the input conductance is low or close to zero. We thus reproduce Rubin's model with vanishing synaptic conductances. To quantitatively compare spike trains from the original model with the modified model at different conductance levels, we apply four different (dis)similarity measures between them. We observe that Mahalanobis distance, Victor-Purpura metric, and Interspike Interval distribution are sensitive to different firing regimes, whereas Mutual Information seems undiscriminative for these functional changes.
Nucleon electric dipole moments in high-scale supersymmetric models
NASA Astrophysics Data System (ADS)
Hisano, Junji; Kobayashi, Daiki; Kuramoto, Wataru; Kuwahara, Takumi
2015-11-01
The electric dipole moments (EDMs) of electron and nucleons are promising probes of the new physics. In generic high-scale supersymmetric (SUSY) scenarios such as models based on mixture of the anomaly and gauge mediations, gluino has an additional contribution to the nucleon EDMs. In this paper, we studied the effect of the CP -violating gluon Weinberg operator induced by the gluino chromoelectric dipole moment in the high-scale SUSY scenarios, and we evaluated the nucleon and electron EDMs in the scenarios. We found that in the generic high-scale SUSY models, the nucleon EDMs may receive the sizable contribution from the Weinberg operator. Thus, it is important to compare the nucleon EDMs with the electron one in order to discriminate among the high-scale SUSY models.
Phenomenological implications of supersymmetric family nonuniversal U(1){sup '} models
Everett, Lisa L.; Jiang Jing; Langacker, Paul G.; Liu Tao
2010-11-01
We construct a class of anomaly-free supersymmetric U(1){sup '} models that are characterized by family nonuniversal U(1){sup '} charges motivated from E{sub 6} embeddings. The family nonuniversality arises from an interchange of the standard roles of the two SU(5) 5{sup *} representations within the 27 of E{sub 6} for the third generation. We analyze U(1){sup '} and electroweak symmetry breaking and present the particle mass spectrum. The models, which include additional Higgs multiplets and exotic quarks at the TeV scale, result in specific patterns of flavor-changing neutral currents in the b{yields}s transitions that can accommodate the presently observed deviations in this sector from the standard model predictions.
Fractured shale reservoirs: Towards a realistic model
Hamilton-Smith, T.
1996-09-01
Fractured shale reservoirs are fundamentally unconventional, which is to say that their behavior is qualitatively different from reservoirs characterized by intergranular pore space. Attempts to analyze fractured shale reservoirs are essentially misleading. Reliance on such models can have only negative results for fractured shale oil and gas exploration and development. A realistic model of fractured shale reservoirs begins with the history of the shale as a hydrocarbon source rock. Minimum levels of both kerogen concentration and thermal maturity are required for effective hydrocarbon generation. Hydrocarbon generation results in overpressuring of the shale. At some critical level of repressuring, the shale fractures in the ambient stress field. This primary natural fracture system is fundamental to the future behavior of the fractured shale gas reservoir. The fractures facilitate primary migration of oil and gas out of the shale and into the basin. In this process, all connate water is expelled, leaving the fractured shale oil-wet and saturated with oil and gas. What fluids are eventually produced from the fractured shale depends on the consequent structural and geochemical history. As long as the shale remains hot, oil production may be obtained. (e.g. Bakken Shale, Green River Shale). If the shale is significantly cooled, mainly gas will be produced (e.g. Antrim Shale, Ohio Shale, New Albany Shale). Where secondary natural fracture systems are developed and connect the shale to aquifers or to surface recharge, the fractured shale will also produce water (e.g. Antrim Shale, Indiana New Albany Shale).
A realistic molecular model of cement hydrates
Pellenq, Roland J.-M.; Kushima, Akihiro; Shahsavari, Rouzbeh; Van Vliet, Krystyn J.; Buehler, Markus J.; Yip, Sidney; Ulm, Franz-Josef
2009-01-01
Despite decades of studies of calcium-silicate-hydrate (C-S-H), the structurally complex binder phase of concrete, the interplay between chemical composition and density remains essentially unexplored. Together these characteristics of C-S-H define and modulate the physical and mechanical properties of this “liquid stone” gel phase. With the recent determination of the calcium/silicon (C/S = 1.7) ratio and the density of the C-S-H particle (2.6 g/cm3) by neutron scattering measurements, there is new urgency to the challenge of explaining these essential properties. Here we propose a molecular model of C-S-H based on a bottom-up atomistic simulation approach that considers only the chemical specificity of the system as the overriding constraint. By allowing for short silica chains distributed as monomers, dimers, and pentamers, this C-S-H archetype of a molecular description of interacting CaO, SiO2, and H2O units provides not only realistic values of the C/S ratio and the density computed by grand canonical Monte Carlo simulation of water adsorption at 300 K. The model, with a chemical composition of (CaO)1.65(SiO2)(H2O)1.75, also predicts other essential structural features and fundamental physical properties amenable to experimental validation, which suggest that the C-S-H gel structure includes both glass-like short-range order and crystalline features of the mineral tobermorite. Additionally, we probe the mechanical stiffness, strength, and hydrolytic shear response of our molecular model, as compared to experimentally measured properties of C-S-H. The latter results illustrate the prospect of treating cement on equal footing with metals and ceramics in the current application of mechanism-based models and multiscale simulations to study inelastic deformation and cracking. PMID:19805265
NASA Astrophysics Data System (ADS)
Das, Debottam; Ellwanger, Ulrich; Teixeira, Ana M.
2012-03-01
The code NMSDECAY allows to compute widths and branching ratios of sparticle decays in the Next-to-Minimal Supersymmetric Standard Model. It is based on a generalization of SDECAY, to include the extended Higgs and neutralino sectors of the NMSSM. Slepton 3-body decays, possibly relevant in the case of a singlino-like lightest supersymmetric particle, have been added. NMSDECAY will be part of the NMSSMTools package, which computes Higgs, sparticle masses and Higgs decays in the NMSSM. Program summaryProgram title: NMSDECAY Catalogue identifier: AELC_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AELC_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 188 177 No. of bytes in distributed program, including test data, etc.: 1 896 478 Distribution format: tar.gz Programming language: FORTRAN77 Computer: All supporting g77, gfortran, ifort Operating system: All supporting g77, gfortran, ifort Classification: 11.1 External routines: Routines in the NMSSMTools package: At least one of the routines in the directory main (e.g. nmhdecay.f), all routines in the directory sources. (All software is included in the distribution package.) Nature of problem: Calculation of all decay widths and decay branching fractions of all particles in the Next-to-Minimal Supersymmetric Standard Model. Solution method: Suitable generalization of the code SDECAY [1] including the extended Higgs and neutralino sector of the Next-to-Minimal Supersymmetric Standard Model, and slepton 3-body decays. Additional comments: NMSDECAY is interfaced with NMSSMTools, available on the web page http://www.th.u-psud.fr/NMHDECAY/nmssmtools.html. Running time: On an Intel Core i7 with 2.8 GHZ: about 2 seconds per point in parameter space, if all flags flagqcd, flagmulti and flagloop are switched on.
Perturbative unification of gauge couplings in supersymmetric E6 models
NASA Astrophysics Data System (ADS)
Cho, Gi-Chol; Maru, Nobuhito; Yotsutani, Kaho
2016-07-01
We study gauge coupling unification in supersymmetric (SUSY) E6 models where an additional U(1)‧ gauge symmetry is broken near the TeV scale and a number of exotic matter fields from the 27 representations have O(TeV) mass. Solving the two-loop renormalization group equations (RGE) of gauge couplings and a kinetic mixing coupling between the U(1)‧ and U(1)Y gauge fields, we find that the gauge couplings fall into the non-perturbative regime below the grand unified theories (GUT) scale. We examine threshold corrections on the running of gauge couplings from both light and heavy ( ˜ GUT scale) particles and show constraints on the size of corrections to achieve the perturbative unification of gauge couplings.
Light Higgs boson scenario in the supersymmetric seesaw model
Asano, Masaki; Kubo, Takayuki; Matsumoto, Shigeki; Senami, Masato
2009-11-01
It is demonstrated that the light Higgs boson scenario, in which the lightest Higgs mass is less than the LEP bound, m{sub h}>114.4 GeV, is consistent with the supersymmetric seesaw model. With the assumptions of the universal right-handed neutrino mass and the hierarchical mass spectrum of the ordinary neutrinos, the bounds for the right-handed neutrino mass are investigated in terms of lepton flavor violating charged lepton decays. We also discuss the effect of the modification of renormalization group equations by the right-handed neutrinos on the b{yields}s{gamma} process and the relic abundance of dark matter in the light Higgs boson scenario.
Target space pseudoduality in supersymmetric sigma models on symmetric spaces
NASA Astrophysics Data System (ADS)
Sarisaman, Mustafa
We discuss the target space pseudoduality in supersymmetric sigma models on symmetric spaces. We first consider the case where sigma models based on real compact connected Lie groups of the same dimensionality and give examples using three dimensional models on target spaces. We show explicit construction of nonlocal conserved currents on the pseudodual manifold. We then switch the Lie group valued pseudoduality equations to Lie algebra valued ones, which leads to an infinite number of pseudoduality equations. We obtain an infinite number of conserved currents on the tangent bundle of the pseudo-dual manifold. Since pseudoduality imposes the condition that sigma models pseudodual to each other are based on symmetric spaces with opposite curvatures (i.e. dual symmetric spaces), we investigate pseudoduality transformation on the symmetric space sigma models in the third chapter. We see that there can be mixing of decomposed spaces with each other, which leads to mixings of the following expressions. We obtain the pseudodual conserved currents which are viewed as the orthonormal frame on the pullback bundle of the tangent space of G˜ which is the Lie group on which the pseudodual model based. Hence we obtain the mixing forms of curvature relations and one loop renormalization group beta function by means of these currents. In chapter four, we generalize the classical construction of pseudoduality transformation to supersymmetric case. We perform this both by component expansion method on manifold M and by orthonormal coframe method on manifold SO( M). The component method produces the result that pseudoduality transformation is not invertible at all points and occurs from all points on one manifold to only one point where riemann normal coordinates valid on the second manifold. Torsion of the sigma model on M must vanish while it is nonvanishing on M˜, and curvatures of the manifolds must be constant and the same because of anticommuting grassmann numbers. We obtain
Viable supersymmetric model with UV insensitive anomaly mediation
Ibe, Masahiro; Kitano, Ryuichiro; Murayama, Hitoshi
2005-04-01
We propose an electroweak model which is compatible with the UV insensitive anomaly-mediated supersymmetry breaking. The model is an extension of the next to minimal supersymmetric standard model (NMSSM) by adding vectorlike matter fields which can drive the soft scalar masses of the singlet Higgs field negative and the successful electroweak symmetry breaking is achieved. Viable parameter regions are found to preserve perturbativity of all the coupling constants up to the Planck scale. With this success, the model becomes a perfect candidate of physics beyond the standard model without the flavor changing neutral current and CP problem. The cosmology is also quite interesting. The lightest neutralino is the wino which is a perfect cold dark matter candidate assuming the nonthermal production from the gravitino decay. There is no gravitino problem because it decays before the big-bang nucleosynthesis era, and thus the thermal leptogenesis works. The cosmological domain wall problem inherent in the NMSSM is absent since the Z{sub 3} symmetry is broken by the QCD instanton effect in the presence of the vectorlike quarks. We also briefly comment on a possible solution to the strong CP problem a la the Nelson-Barr mechanism.
Higgs boson spectra in supersymmetric left-right models
NASA Astrophysics Data System (ADS)
Babu, K. S.; Patra, Ayon
2016-03-01
We present a comprehensive analysis of the Higgs boson spectra in several versions of the supersymmetric left-right model based on the gauge symmetry S U (3 )c×S U (2 )L×S U (2 )R×U (1 )B-L. A variety of symmetry breaking sectors are studied, with a focus on the constraints placed on model parameters by the lightest neutral C P even Higgs boson mass Mh. The breaking of S U (2 )R symmetry is achieved by Higgs fields transforming either as triplets or doublets, and the electroweak symmetry breaking is triggered by either bi-doublets or doublets. The Higgs potential is analyzed with or without a gauge singlet Higgs field present. Seesaw models of Type I and Type II, inverse seesaw models, universal seesaw models and an E6 inspired alternate left-right model are included in our analysis. Several of these models lead to the tree-level relation Mh≤√{2 }mW (rather than Mh≤mZ that arises in the MSSM), realized when the S U (2 )R symmetry breaking scale is of order TeV. With such an enhanced upper limit, it becomes possible to accommodate a Higgs boson of mass 126 GeV with relatively light stops that mix negligibly. In models with Higgs triplets, a doubly charged scalar remains light below a TeV with its mass arising entirely from radiative corrections. We carry out the complete one-loop calculation for its mass induced by the Majorana Yukawa couplings and show the consistency of the framework. We argue that these models prefer a low S U (2 )R breaking scale. Other theoretical and phenomenological implications of these models are briefly discussed.
Lepton flavor violation in predictive supersymmetric GUT models
Albright, Carl H.; Chen, M.-C.
2008-06-01
There have been many theoretical models constructed that aim to explain the neutrino masses and mixing patterns. While many of the models will be eliminated once more accurate determinations of the mixing parameters, especially sin{sup 2}2{theta}{sub 13}, are obtained, charged lepton flavor violation experiments are able to differentiate even further among the models. In this paper, we investigate various rare lepton flavor violation processes, such as l{sub i}{yields}l{sub j}+{gamma} and {mu}-e conversion, in five predictive supersymmetric (SUSY) SO(10) models and their allowed soft-SUSY breaking parameter space in the constrained minimal SUSY standard model. Utilizing the Wilkinson Microwave Anisotropy Probe dark matter constraints, we obtain lower bounds on the branching ratios of these rare processes and find that at least three of the five models we consider give rise to predictions for {mu}{yields}e+{gamma} that will be tested by the MEG Collaboration at PSI. In addition, the next generation {mu}-e conversion experiment has sensitivity to the predictions of all five models, making it an even more robust way to test these models. While generic studies have emphasized the dependence of the branching ratios of these rare processes on the reactor neutrino angle {theta}{sub 13} and the mass of the heaviest right-handed neutrino M{sub 3} we find very massive M{sub 3} is more significant than large {theta}{sub 13} in leading to branching ratios near to the present upper limits.
Mixed axion/neutralino cold dark matter in supersymmetric models
Baer, Howard; Lessa, Andre; Rajagopalan, Shibi; Sreethawong, Warintorn E-mail: lessa@nhn.ou.edu E-mail: wstan@nhn.ou.edu
2011-06-01
We consider supersymmetric (SUSY) models wherein the strong CP problem is solved by the Peccei-Quinn (PQ) mechanism with a concommitant axion/axino supermultiplet. We examine R-parity conserving models where the neutralino is the lightest SUSY particle, so that a mixture of neutralinos and axions serve as cold dark matter (a Z-tilde {sub 1} CDM). The mixed a Z-tilde {sub 1} CDM scenario can match the measured dark matter abundance for SUSY models which typically give too low a value of the usual thermal neutralino abundance, such as models with wino-like or higgsino-like dark matter. The usual thermal neutralino abundance can be greatly enhanced by the decay of thermally-produced axinos (ã) to neutralinos, followed by neutralino re-annihilation at temperatures much lower than freeze-out. In this case, the relic density is usually neutralino dominated, and goes as ∼ (f{sub a}/N)/m{sub ã}{sup 3/2}. If axino decay occurs before neutralino freeze-out, then instead the neutralino abundance can be augmented by relic axions to match the measured abundance. Entropy production from late-time axino decays can diminish the axion abundance, but ultimately not the neutralino abundance. In a Z-tilde {sub 1} CDM models, it may be possible to detect both a WIMP and an axion as dark matter relics. We also discuss possible modifications of our results due to production and decay of saxions. In the appendices, we present expressions for the Hubble expansion rate and the axion and neutralino relic densities in radiation, matter and decaying-particle dominated universes.
Gauging N=2 supersymmetric nonlinear {sigma} models in the Atiyah-Ward space-time
Carvalho, M.; de Oliveira, M.W.
1997-06-01
We build up a class of N=2 supersymmetric nonlinear {sigma} models in an N=1 superspace based on the Atiyah-Ward space-time of (2+2)-signature metric. We also discuss the gauging of isometries of the associated hyper-K{umlt a}hlerian target spaces and present the resulting gauge-covariant supersymmetric action functional. {copyright} {ital 1997} {ital The American Physical Society}
Low scale nonuniversal, nonanomalous U(1){sub F}{sup '} in a minimal supersymmetric standard model
Chen Muchun; Huang Jinrui
2010-10-01
We propose a nonuniversal U(1){sub F}{sup '} symmetry combined with the minimal supersymmetric standard model. All anomaly cancellation conditions are satisfied without exotic fields other than three right-handed neutrinos. Because our model allows all three generations of chiral superfields to have different U(1){sub F}{sup '} charges, upon the breaking of the U(1){sub F}{sup '} symmetry at a low scale, realistic masses and mixing angles in both the quark and lepton sectors are obtained. In our model, neutrinos are predicted to be Dirac fermions and their mass ordering is of the inverted hierarchy type. The U(1){sub F}{sup '} charges of the chiral superfields also naturally suppress the {mu}-term and automatically forbid baryon number and lepton number violating operators. While all flavor-changing neutral current constraints in the down quark and charged-lepton sectors can be satisfied, we find that the constraint from D{sup 0}-D{sup 0} turns out to be much more stringent than the constraints from the precision electroweak data.
A Computational Framework for Realistic Retina Modeling.
Martínez-Cañada, Pablo; Morillas, Christian; Pino, Begoña; Ros, Eduardo; Pelayo, Francisco
2016-11-01
Computational simulations of the retina have led to valuable insights about the biophysics of its neuronal activity and processing principles. A great number of retina models have been proposed to reproduce the behavioral diversity of the different visual processing pathways. While many of these models share common computational stages, previous efforts have been more focused on fitting specific retina functions rather than generalizing them beyond a particular model. Here, we define a set of computational retinal microcircuits that can be used as basic building blocks for the modeling of different retina mechanisms. To validate the hypothesis that similar processing structures may be repeatedly found in different retina functions, we implemented a series of retina models simply by combining these computational retinal microcircuits. Accuracy of the retina models for capturing neural behavior was assessed by fitting published electrophysiological recordings that characterize some of the best-known phenomena observed in the retina: adaptation to the mean light intensity and temporal contrast, and differential motion sensitivity. The retinal microcircuits are part of a new software platform for efficient computational retina modeling from single-cell to large-scale levels. It includes an interface with spiking neural networks that allows simulation of the spiking response of ganglion cells and integration with models of higher visual areas. PMID:27354192
A Computational Framework for Realistic Retina Modeling.
Martínez-Cañada, Pablo; Morillas, Christian; Pino, Begoña; Ros, Eduardo; Pelayo, Francisco
2016-11-01
Computational simulations of the retina have led to valuable insights about the biophysics of its neuronal activity and processing principles. A great number of retina models have been proposed to reproduce the behavioral diversity of the different visual processing pathways. While many of these models share common computational stages, previous efforts have been more focused on fitting specific retina functions rather than generalizing them beyond a particular model. Here, we define a set of computational retinal microcircuits that can be used as basic building blocks for the modeling of different retina mechanisms. To validate the hypothesis that similar processing structures may be repeatedly found in different retina functions, we implemented a series of retina models simply by combining these computational retinal microcircuits. Accuracy of the retina models for capturing neural behavior was assessed by fitting published electrophysiological recordings that characterize some of the best-known phenomena observed in the retina: adaptation to the mean light intensity and temporal contrast, and differential motion sensitivity. The retinal microcircuits are part of a new software platform for efficient computational retina modeling from single-cell to large-scale levels. It includes an interface with spiking neural networks that allows simulation of the spiking response of ganglion cells and integration with models of higher visual areas.
Biophysically realistic minimal model of dopamine neuron
NASA Astrophysics Data System (ADS)
Oprisan, Sorinel
2008-03-01
We proposed and studied a new biophysically relevant computational model of dopaminergic neurons. Midbrain dopamine neurons are involved in motivation and the control of movement, and have been implicated in various pathologies such as Parkinson's disease, schizophrenia, and drug abuse. The model we developed is a single-compartment Hodgkin-Huxley (HH)-type parallel conductance membrane model. The model captures the essential mechanisms underlying the slow oscillatory potentials and plateau potential oscillations. The main currents involved are: 1) a voltage-dependent fast calcium current, 2) a small conductance potassium current that is modulated by the cytosolic concentration of calcium, and 3) a slow voltage-activated potassium current. We developed multidimensional bifurcation diagrams and extracted the effective domains of sustained oscillations. The model includes a calcium balance due to the fundamental importance of calcium influx as proved by simultaneous electrophysiological and calcium imaging procedure. Although there are significant evidences to suggest a partially electrogenic calcium pump, all previous models considered only elecrtogenic pumps. We investigated the effect of the electrogenic calcium pump on the bifurcation diagram of the model and compared our findings against the experimental results.
Realistic power output modeling of CPV modules
NASA Astrophysics Data System (ADS)
Steiner, Marc; Siefer, Gerald; Bösch, Armin; Hornung, Thorsten; Bett, Andreas W.
2012-10-01
In this work, we introduce a new model called YieldOpt, which calculates the power output of CPV modules. It uses SMARTS2 to model the spectral irradiance, a ray tracing program to model the optics and SPICE network simulation to model the electrical characteristic of triple-junction (3J) cells. The calculated power output is compared to data measured of five CPV modules operating in Freiburg, Germany during a period from October 2011 to March 2012. Four of the modules use lattice-matched 3J cells; one of these modules has also reflective secondary optics. In one of the five modules novel metamorphic 3J cells are used. The agreement of the predicted power output calculated by YieldOpt with the measured data is quantified using the normalized root mean square error. A good agreement between simulation and measurement is achieved. Moreover, the predicted energy yield derived from the new model is compared with the measured energy yield. A good agreement between the measured data and simulated data is achieved. In addition, a high accuracy in predicting the energy yield of different CPV modules is demonstrated. Finally, the new model is compared with three empirical models.
Particle spectroscopy of supersymmetric SO(10) with nonuniversal gaugino masses
Okada, Nobuchika; Raza, Shabbar; Shafi, Qaisar
2011-11-01
We examine the low scale particle spectroscopy of an SO(10) [or equivalently SU(5)] inspired supersymmetric model with nonuniversal gaugino masses. The model assumes minimal supergravity and contains the same number of fundamental parameters as the constrained minimal supersymmetric standard model. Realistic solutions compatible with dark matter and other applicable experimental constraints are shown to exist for both positive and negative signs of the minimal supersymmetric standard model parameter {mu}. We present several benchmark points which will be tested at the LHC and by the ongoing direct and indirect dark matter detection experiments.
Metastable cosmic strings in realistic models
Holman, R.; Hsu, S.; Vachaspati, T.; Watkins, R. |
1992-11-01
The stability of the electroweak Z-string is investigated at high temperatures. The results show that, while finite temperature corrections can improve the stability of the Z-string, their effect is not strong enough to stabilize the Z-string in the standard electroweak model. Consequently, the Z-string will be unstable even under the conditions present during the electroweak phase transition. Phenomenologically viable models based on the gauge group SU(2){sub L} {times} SU(2) {sub R} {times} U(1){sub B-L} are then considered, and it is shown that metastable strings exist and are stable to small perturbations for a large region of the parameter space for these models. It is also shown that these strings are superconducting with bosonic charge carriers. The string superconductivity may be able to stabilize segments and loops against dynamical contraction. Possible implications of these strings for cosmology are discussed.
Metastable cosmic strings in realistic models
Holman, R. . Dept. of Physics); Hsu, S. . Lyman Lab. of Physics); Vachaspati, T. . Dept. of Physics and Astronomy); Watkins, R. Fermi National Accelerator Lab., Batavia, IL )
1992-01-01
The stability of the electroweak Z-string is investigated at high temperatures. The results show that, while finite temperature corrections can improve the stability of the Z-string, their effect is not strong enough to stabilize the Z-string in the standard electroweak model. Consequently, the Z-string will be unstable even under the conditions present during the electroweak phase transition. Phenomenologically viable models based on the gauge group SU(2)[sub L] [times] SU(2) [sub R] [times] U(1)[sub B-L] are then considered, and it is shown that metastable strings exist and are stable to small perturbations for a large region of the parameter space for these models. It is also shown that these strings are superconducting with bosonic charge carriers. The string superconductivity may be able to stabilize segments and loops against dynamical contraction. Possible implications of these strings for cosmology are discussed.
Realistic model for SU(5) grand unification
Oshimo, Noriyuki
2009-10-01
A grand unified model based on SU(5) and supersymmetry is presented. Pairs of superfields belonging to 15 and 15 representations are newly introduced, two pairs with even and one pair with odd matter parity. Improper mass relations in the minimal model between charged leptons and d-type quarks are corrected. Neutrinos have nonvanishing masses, with large angles for generation mixings of the leptons being compatible with the small angles of the quarks. A new source for lepton-number generation in the early universe is provided.
Towards Realistic Modeling of Massive Star Clusters
NASA Astrophysics Data System (ADS)
Gnedin, O.; Li, H.
2016-06-01
Cosmological simulations of galaxy formation are rapidly advancing towards smaller scales. Current models can now resolve giant molecular clouds in galaxies and predict basic properties of star clusters forming within them. I will describe new theoretical simulations of the formation of the Milky Way throughout cosmic time, with the adaptive mesh refinement code ART. However, many challenges - physical and numerical - still remain. I will discuss how observations of massive star clusters and star forming regions can help us overcome some of them. Video of the talk is available at https://goo.gl/ZoZOfX
Recent developments for realistic solar models
NASA Astrophysics Data System (ADS)
Serenelli, Aldo M.
2014-05-01
The "solar abundance problem" has triggered a renewed interest in revising the concept of SSM from different perspectives: 1) constituent microphysics: equation of state, nuclear rates, radiative opacities; 2) constituent macrophysics: the physical processes impact the evolution of the Sun and its present-day structure, e.g. dynamical processes induced by rotation, presence of magnetic fields; 3) challenge the hypothesis that the young Sun was chemically homogeneous: the possible interaction of the young Sun with its protoplanetary disk. Here, I briefly review and then present a (personal) view on recent advances and developments on solar modeling, part of them carried out as attempts to solve the solar abundance problem.
Recent developments for realistic solar models
Serenelli, Aldo M.
2014-05-02
The 'solar abundance problem' has triggered a renewed interest in revising the concept of SSM from different perspectives: 1) constituent microphysics: equation of state, nuclear rates, radiative opacities; 2) constituent macrophysics: the physical processes impact the evolution of the Sun and its present-day structure, e.g. dynamical processes induced by rotation, presence of magnetic fields; 3) challenge the hypothesis that the young Sun was chemically homogeneous: the possible interaction of the young Sun with its protoplanetary disk. Here, I briefly review and then present a (personal) view on recent advances and developments on solar modeling, part of them carried out as attempts to solve the solar abundance problem.
[Realistic surgical training. The Aachen model].
Krones, C J; Binnebösel, M; Stumpf, M; Schumpelick, V
2010-01-01
The Aachen model is a practical mode in teaching and advanced training, which is closely geared to the areas of academic acquisition and training. During medical education optional student courses with constitutive curricula offer practical points of contact to the surgical department at all times. Besides improvement of manual training the aims are enhancing interests and acquisition of talents. This guided structure will be intensified with progression into advanced education. Next to the formal guidelines of the curriculum, education logbook and progression conversations, quality, transparency and reliability are particularly emphasized. An evaluation of both the reforms and the surgical trainers is still to be made. In addition procurement of an affirmative occupational image is essential.
Radiative Effects and Electroweak Symmetry Breaking in a Supersymmetric Preon Model
NASA Astrophysics Data System (ADS)
Kim, Jongbae
We construct the low energy effective theory of composite quarks, leptons, and Higgs bosons for a supersymmetric preon model and study the effects of renormalization-group based radiative corrections. The study on the evolution of scalar masses for avoiding color and charge breakings leads us to conclude that Yukawa couplings are bounded from above. The implementation of electroweak symmetry breaking requires that only the purely dynamical symmetry breaking should be needed for the model, but the combined scheme of dynamical and radiative symmetry breaking as well as the purely radiative symmetry breaking scheme be disfavored. Our analysis of (mb)/(m_τ ) including radiative effects shows that, should a discrepancy be found between the observed and the theoretical value of (mb)/(m_τ ) after experimental determination of supersymmetric particle masses, it would imply that the complete quark-lepton universality in the supersymmetric preon model does not hold either for the Yukawa couplings, or for the condensates, or for both.
Radiative breaking of the minimal supersymmetric left-right model
NASA Astrophysics Data System (ADS)
Okada, Nobuchika; Papapietro, Nathan
2016-05-01
We study a variation to the SUSY Left-Right symmetric model based on the gauge group SU (3)c × SU (2)L × SU (2)R × U(1)BL. Beyond the quark and lepton superfields we only introduce a second Higgs bidoublet to produce realistic fermion mass matrices. This model does not include any SU (2)R triplets. We calculate renormalization group evolutions of soft SUSY parameters at the one-loop level down to low energy. We find that an SU (2)R slepton doublet acquires a negative mass squared at low energies, so that the breaking of SU (2)R × U(1)BL → U(1)Y is realized by a non-zero vacuum expectation value of a right-handed sneutrino. Small neutrino masses are produced through neutrino mixings with gauginos. Mass limits on the SU (2)R × U(1)BL sector are obtained by direct search results at the LHC as well as lepton-gaugino mixing bounds from the LEP precision data.
Predictions for m{sub t} and M{sub W} in minimal supersymmetric models
Buchmueller, O.; Cavanaugh, R.; De Roeck, A.; Ellis, J. R.; Flaecher, H.; Heinemeyer, S.; Isidori, G.; Olive, Keith A.; Ronga, F. J.; Weiglein, G.
2010-02-01
Using a frequentist analysis of experimental constraints within two versions of the minimal supersymmetric extension of the standard model, we derive the predictions for the top quark mass, m{sub t}, and the W boson mass, M{sub W}. We find that the supersymmetric predictions for both m{sub t} and M{sub W}, obtained by incorporating all the relevant experimental information and state-of-the-art theoretical predictions, are highly compatible with the experimental values with small remaining uncertainties, yielding an improvement compared to the case of the standard model.
Towards a systematic construction of realistic D-brane models on a del Pezzo singularity
NASA Astrophysics Data System (ADS)
Dolan, Matthew J.; Krippendorf, Sven; Quevedo, Fernando
2011-10-01
A systematic approach is followed in order to identify realistic D-brane models at toric del Pezzo singularities. Requiring quark and lepton spectrum and Yukawas from D3 branes and massless hypercharge, we are led to Pati-Salam extensions of the Standard Model. Hierarchies of masses, flavour mixings and control of couplings select higher order del Pezzo singularities, minimising the Higgs sector prefers toric del Pezzos with dP 3 providing the most successful compromise. Then a supersymmetric local string model is presented with the following properties at low energies: (i) the MSSM spectrum plus a local B - L gauge field or additional Higgs fields depending on the breaking pattern, (ii) a realistic hierarchy of quark and lepton masses and (iii) realistic flavour mixing between quark and lepton families with computable CKM and PMNS matrices, and CP violation consistent with observations. In this construction, kinetic terms are diagonal and under calculational control suppressing standard FCNC contributions. Proton decay operators of dimension 4, 5, 6 are suppressed, and gauge couplings can unify depending on the breaking scales from string scales at energies in the range 1012-1016 GeV, consistent with TeV soft-masses from moduli mediated supersymmetry breaking. The GUT scale model corresponds to D3 branes at dP 3 with two copies of the Pati-Salam gauge symmetry SU(4) × SU(2) R × SU(2) L . D-brane instantons generate a non-vanishing μ-term. Right handed sneutrinos can break the B - L symmetry and induce a see-saw mechanism of neutrino masses and R-parity violating operators with observable low-energy implications.
NASA Astrophysics Data System (ADS)
Quinto, A. G.; Ferrari, A. F.; Lehum, A. C.
2016-06-01
In this work, we investigate the consequences of the Renormalization Group Equation (RGE) in the determination of the effective superpotential and the study of Dynamical Symmetry Breaking (DSB) in an N = 1 supersymmetric theory including an Abelian Chern-Simons superfield coupled to N scalar superfields in (2 + 1) dimensional spacetime. The classical Lagrangian presents scale invariance, which is broken by radiative corrections to the effective superpotential. We calculate the effective superpotential up to two-loops by using the RGE and the beta functions and anomalous dimensions known in the literature. We then show how the RGE can be used to improve this calculation, by summing up properly defined series of leading logs (LL), next-to-leading logs (NLL) contributions, and so on... We conclude that even if the RGE improvement procedure can indeed be applied in a supersymmetric model, the effects of the consideration of the RGE are not so dramatic as it happens in the non-supersymmetric case.
Impact of leptogenesis and muon g-2 on lepton flavour violation in supersymmetric seesaw models
Endo, Motoi; Shindou, Tetsuo
2009-04-17
The framework of supersymmetric see-saw models are considered. The successful leptogenesis scenarios which are due to a decay of the right-handed neutrinos tends to require rather heavy right-handed neutrinos. On the other hand, a discrepancy of the anomalous magnetic moment of the muon reported between the experimental and theoretical results implies lighter supersymmetric particles. In the light of successful leptogenesis scenarios, this anomaly of the anomalous magnetic moment of the muon leads to sizable lepton-flavour violations. It is shown that for a hierarchical right-handed neutrino mass spectrum, {mu}{yields}e{gamma} is expected to be observed in near future experiments.
A SPATIALLY REALISTIC MODEL FOR INFORMING FOREST MANAGEMENT DECISIONS
Spatially realistic population models (SRPMs) address a fundamental
problem commonly confronted by wildlife managers - predicting the
effects of landscape-scale habitat management on an animal population.
SRPMs typically consist of three submodels: (1) a habitat submodel...
On the quantum corrections to two-dimensional (1,0)-supersymmetric Abelian gauge models
Almeida, C.A.S.; De Oliveira, M.W. ); Kneipp, M.A.C. )
1991-05-30
In this paper the machinery of (1,0)-supergravity is employed to evaluate 1-loop corrections to the effective action and chiral symmetry supercurrent in the framework of an (1,0)-supersymmetric Abelian gauge model. As a by-product, a dynamically-generated mass is found out for the gauge (1,0)-superconductions.
Supercharges in the hyper-Kaehler with torsion supersymmetric sigma models
Smilga, A. V.
2012-12-15
We construct explicitly classical and quantum supercharges satisfying the standard N=4 supersymmetry algebra in the supersymmetric sigma models describing the motion over hyper-Kaehler with torsion manifolds. One member of the family of superalgebras thus obtained is equivalent to the superalgebra derived and formulated earlier in purely mathematical framework.
Acquisition of detailed laryngeal flow measurements in geometrically realistic models
Farley, Jayrin; Thomson, Scott L.
2011-01-01
Characterization of laryngeal flow velocity fields is important to understanding vocal fold vibration and voice production. One common method for acquiring flow field data is particle image velocimetry (PIV). However, because using PIV with models that have curved surfaces is problematic due to optical distortion, experimental investigations of laryngeal airflow are typically performed using models with idealized geometries. In this paper a method for acquiring PIV data using models with realistic geometries is presented. Sample subglottal, intraglottal, and supraglottal PIV data are shown. Capabilities and limitations are discussed, and suggestions for future implementation are provided. PMID:21877775
Dark Matter in Supersymmetric U(1){sub B-L} Model
Khalil, S.; Okada, H.
2009-04-17
We analyze the dark matter problem in the context of supersymmetric, U(1){sub B-L} model. In this model, the lightest neutalino can be B-L gaugino Z-tilde{sub B-L} or Higgsinos {chi}-tilde{sub 1,2} dominated. We examine the thermal relic abundance of these particles and discuss the prospects for their direct detection if they form part of our galactic halo.
Radiative symmetry breaking in supersymmetric B -L models with an inverse seesaw mechanism
NASA Astrophysics Data System (ADS)
Khalil, Shaaban
2016-10-01
We study the radiative symmetry breaking of B -L in supersymmetric models with an inverse seesaw mechanism. We show that for a wide region of parameter space, the radiative corrections can drive the squared mass of the extra Higgs boson from positive initial values at the GUT scale to negative values at the TeV scale, leading to the spontaneous breaking of the B -L symmetry. We also emphasize that in this class of models, unlike the supersymmetric B -L models with a type-I seesaw, the right-handed sneutrino cannot get a nonzero vacuum expectation value. Therefore, B -L can be radiatively broken, while R parity remains an exact symmetry.
Design for and efficient dynamic climate model with realistic geography
NASA Technical Reports Server (NTRS)
Suarez, M. J.; Abeles, J.
1984-01-01
The long term climate sensitivity which include realistic atmospheric dynamics are severely restricted by the expense of integrating atmospheric general circulation models are discussed. Taking as an example models used at GSFC for this dynamic model is an alternative which is of much lower horizontal or vertical resolution. The model of Heid and Suarez uses only two levels in the vertical and, although it has conventional grid resolution in the meridional direction, horizontal resolution is reduced by keeping only a few degrees of freedom in the zonal wavenumber spectrum. Without zonally asymmetric forcing this model simulates a day in roughly 1/2 second on a CRAY. The model under discussion is a fully finite differenced, zonally asymmetric version of the Heid-Suarez model. It is anticipated that speeds can be obtained a few seconds a day roughly 50 times faster than moderate resolution, multilayer GCM's.
The KM phase in semi-realistic heterotic orbifold models
Giedt, Joel
2000-07-05
In string-inspired semi-realistic heterotic orbifolds models with an anomalous U(1){sub X},a nonzero Kobayashi-Masakawa (KM) phase is shown to arise generically from the expectation values of complex scalar fields, which appear in nonrenormalizable quark mass couplings. Modular covariant nonrenormalizable superpotential couplings are constructed. A toy Z{sub 3} orbifold model is analyzed in some detail. Modular symmetries and orbifold selection rules are taken into account and do not lead to a cancellation of the KM phase. We also discuss attempts to obtain the KM phase solely from renormalizable interactions.
Time variability of α from realistic models of Oklo reactors
NASA Astrophysics Data System (ADS)
Gould, C. R.; Sharapov, E. I.; Lamoreaux, S. K.
2006-08-01
We reanalyze Oklo Sm149 data using realistic models of the natural nuclear reactors. Disagreements among recent Oklo determinations of the time evolution of α, the electromagnetic fine structure constant, are shown to be due to different reactor models, which led to different neutron spectra used in the calculations. We use known Oklo reactor epithermal spectral indices as criteria for selecting realistic reactor models. Two Oklo reactors, RZ2 and RZ10, were modeled with MCNP. The resulting neutron spectra were used to calculate the change in the Sm149 effective neutron capture cross section as a function of a possible shift in the energy of the 97.3-meV resonance. We independently deduce ancient Sm149 effective cross sections and use these values to set limits on the time variation of α. Our study resolves a contradictory situation with previous Oklo α results. Our suggested 2σ bound on a possible time variation of α over 2 billion years is stringent: -0.11≤Δα/α≤0.24, in units of 10-7, but model dependent in that it assumes only α has varied over time.
NASA Astrophysics Data System (ADS)
Banerjee, P.; Basu-Mallick, B.; Bondyopadhaya, N.; Datta, C.
2016-03-01
We derive the exact spectra as well as partition functions for a class of BCN type of spin Calogero models, whose Hamiltonians are constructed by using supersymmetric analogues of polarized spin reversal operators (SAPSRO). The strong coupling limit of these spin Calogero models yields BCN type of Polychronakos-Frahm (PF) spin chains with SAPSRO. By applying the freezing trick, we obtain an exact expression for the partition functions of such PF spin chains. We also derive a formula which expresses the partition function of any BCN type of PF spin chain with SAPSRO in terms of partition functions of several AK types of supersymmetric PF spin chains, where K ⩽ N - 1. Subsequently we show that an extended boson-fermion duality relation is obeyed by the partition functions of the BCN type of PF chains with SAPSRO. Some spectral properties of these spin chains, like level density distribution and nearest neighbor spacing distribution, are also studied.
Nonlocal charge of the CP/sup n/-1 model and its supersymmetric extension to all orders
Abdalla, E.; Abdalla, M.C.B.; Gomes, M.
1983-02-15
We prove that the conservation of quantum nonlocal charge of the CP/sup n/-1 model is spoiled by an anomaly calculable to all orders in the 1/n expansion, while for its supersymmetric extension it is restored.
Upper bound on the gluino mass in supersymmetric models with extra matters
NASA Astrophysics Data System (ADS)
Moroi, Takeo; Yanagida, Tsutomu T.; Yokozaki, Norimi
2016-09-01
We discuss the upper bound on the gluino mass in supersymmetric models with vector-like extra matters. In order to realize the observed Higgs mass of 125 GeV, the gluino mass is bounded from above in supersymmetric models. With the existence of the vector-like extra matters at around TeV, we show that such an upper bound on the gluino mass is significantly reduced compared to the case of minimal supersymmetric standard model. This is due to the fact that radiatively generated stop masses as well the stop trilinear coupling are enhanced in the presence of the vector-like multiplets. In a wide range of parameter space of the model with extra matters, particularly with sizable tan β (which is the ratio of the vacuum expectation values of the two Higgs bosons), the gluino is required to be lighter than ∼ 3 TeV, which is likely to be within the reach of forthcoming LHC experiment.
Impacts of supersymmetric higher derivative terms on inflation models in supergravity
Aoki, Shuntaro; Yamada, Yusuke E-mail: yuusuke-yamada@asagi.waseda.jp
2015-07-01
We show the effects of supersymmetric higher derivative terms on inflation models in supergravity. The results show that such terms generically modify the effective kinetic coefficient of the inflaton during inflation if the cut off scale of the higher derivative operators is sufficiently small. In such a case, the η-problem in supergravity does not occur, and we find that the effective potential of the inflaton generically becomes a power type potential with a power smaller than two.
Mass and mixing angle patterns in the Standard Model and its material Supersymmetric Extension
Ramond, P.
1992-01-01
Using renormalization group techniques, we examine several interesting relations among masses and mixing angles of quarks and lepton in the Standard Model of Elementary Particle Interactions as a functionof scale. We extend the analysis to the minimal Supersymmetric Extension to determine its effect on these mass relations. For a heavy to quark, and minimal supersymmetry, most of these relations, can be made to agree at one unification scale.
Impacts of supersymmetric higher derivative terms on inflation models in supergravity
Aoki, Shuntaro; Yamada, Yusuke
2015-07-14
We show the effects of supersymmetric higher derivative terms on inflation models in supergravity. The results show that such terms generically modify the effective kinetic coefficient of the inflaton during inflation if the cut off scale of the higher derivative operators is sufficiently small. In such a case, the η-problem in supergravity does not occur, and we find that the effective potential of the inflaton generically becomes a power type potential with a power smaller than two.
Family of fish-eye-related models and their supersymmetric partners
Makowski, Adam J.
2010-05-15
A large family of potentials related to the Maxwell fish-eye model is derived with the help of conformal mappings. It is shown that the whole family admits square-integrable E=0 solutions of the Schroedinger equation for discrete values of the coupling constant. A corresponding supersymmetric family of partner potentials to the preceding ones is derived as well. Some applications of the considered potentials are also discussed.
Towards Modeling Realistic Mobility for Performance Evaluations in MANET
NASA Astrophysics Data System (ADS)
Aravind, Alex; Tahir, Hassan
Simulation modeling plays crucial role in conducting research on complex dynamic systems like mobile ad hoc networks and often the only way. Simulation has been successfully applied in MANET for more than two decades. In several recent studies, it is observed that the credibility of the simulation results in the field has decreased while the use of simulation has steadily increased. Part of this credibility crisis has been attributed to the simulation of mobility of the nodes in the system. Mobility has such a fundamental influence on the behavior and performance of mobile ad hoc networks. Accurate modeling and knowledge of mobility of the nodes in the system is not only helpful but also essential for the understanding and interpretation of the performance of the system under study. Several ideas, mostly in isolation, have been proposed in the literature to infuse realism in the mobility of nodes. In this paper, we attempt a holistic analysis of creating realistic mobility models and then demonstrate creation and analysis of realistic mobility models using a software tool we have developed. Using our software tool, desired mobility of the nodes in the system can be specified, generated, analyzed, and then the trace can be exported to be used in the performance studies of proposed algorithms or systems.
Ferrer, Francesc; Krauss, Lawrence M.; Profumo, Stefano
2006-12-01
We explore the prospects for indirect detection of neutralino dark matter in supersymmetric models with an extended Higgs sector (next-to-minimal supersymmetric standard model, or NMSSM). We compute, for the first time, one-loop amplitudes for NMSSM neutralino pair annihilation into two photons and two gluons, and point out that extra diagrams (with respect to the minimal supersymmetric standard model, or MSSM), featuring a potentially light CP-odd Higgs boson exchange, can strongly enhance these radiative modes. Expected signals in neutrino telescopes due to the annihilation of relic neutralinos in the Sun and in the Earth are evaluated, as well as the prospects of detection of a neutralino annihilation signal in space-based gamma-ray, antiproton and positron search experiments, and at low-energy antideuteron searches. We find that in the low mass regime the signals from capture in the Earth are enhanced compared to the MSSM, and that NMSSM neutralinos have a remote possibility of affecting solar dynamics. Also, antimatter experiments are an excellent probe of galactic NMSSM dark matter. We also find enhanced two-photon decay modes that make the possibility of the detection of a monochromatic gamma-ray line within the NMSSM more promising than in the MSSM, although likely below the sensitivity of next generation gamma-ray telescopes.
Rapidly recomputable EEG forward models for realistic head shapes.
Ermer, J J; Mosher, J C; Baillet, S; Leah, R M
2001-04-01
With the increasing availability of surface extraction techniques for magnetic resonance and x-ray computed tomography images, realistic head models can be readily generated as forward models in the analysis of electroencephalography (EEG) and magnetoencephalography (MEG) data. Inverse analysis of this data, however, requires that the forward model be computationally efficient. We propose two methods for approximating the EEG forward model using realistic head shapes. The 'sensor-fitted sphere' approach fits a multilayer sphere individually to each sensor, and the 'three-dimensional interpolation' scheme interpolates using a grid on which a numerical boundary element method (BEM) solution has been precomputed. We have characterized the performance of each method in terms of magnitude and subspace error metrics, as well as computational and memory requirements. We have also made direct performance comparisons with traditional spherical models. The approximation provided by the interpolative scheme had an accuracy nearly identical to full BEM, even within 3 mm of the inner skull surface. Forward model computation during inverse procedures was approximately 30 times faster than for a traditional three-shell spherical model. Cast in this framework, high-fidelity numerical solutions currently viewed as computationally prohibitive for solving the inverse problem (e.g. linear Galerkin BEM) can be rapidly recomputed in a highly efficient manner. The sensor-fitting method has a similar one-time cost to the BEM method, and while it produces some improvement over a standard three-shell sphere, its performance does not approach that of the interpolation method. In both methods, there is a one-time cost associated with precomputing the forward solution over a set of grid points.
Electron percolation in realistic models of carbon nanotube networks
Simoneau, Louis-Philippe Villeneuve, Jérémie Rochefort, Alain
2015-09-28
The influence of penetrable and curved carbon nanotubes (CNT) on the charge percolation in three-dimensional disordered CNT networks have been studied with Monte-Carlo simulations. By considering carbon nanotubes as solid objects but where the overlap between their electron cloud can be controlled, we observed that the structural characteristics of networks containing lower aspect ratio CNT are highly sensitive to the degree of penetration between crossed nanotubes. Following our efficient strategy to displace CNT to different positions to create more realistic statistical models, we conclude that the connectivity between objects increases with the hard-core/soft-shell radii ratio. In contrast, the presence of curved CNT in the random networks leads to an increasing percolation threshold and to a decreasing electrical conductivity at saturation. The waviness of CNT decreases the effective distance between the nanotube extremities, hence reducing their connectivity and degrading their electrical properties. We present the results of our simulation in terms of thickness of the CNT network from which simple structural parameters such as the volume fraction or the carbon nanotube density can be accurately evaluated with our more realistic models.
Electron percolation in realistic models of carbon nanotube networks
NASA Astrophysics Data System (ADS)
Simoneau, Louis-Philippe; Villeneuve, Jérémie; Rochefort, Alain
2015-09-01
The influence of penetrable and curved carbon nanotubes (CNT) on the charge percolation in three-dimensional disordered CNT networks have been studied with Monte-Carlo simulations. By considering carbon nanotubes as solid objects but where the overlap between their electron cloud can be controlled, we observed that the structural characteristics of networks containing lower aspect ratio CNT are highly sensitive to the degree of penetration between crossed nanotubes. Following our efficient strategy to displace CNT to different positions to create more realistic statistical models, we conclude that the connectivity between objects increases with the hard-core/soft-shell radii ratio. In contrast, the presence of curved CNT in the random networks leads to an increasing percolation threshold and to a decreasing electrical conductivity at saturation. The waviness of CNT decreases the effective distance between the nanotube extremities, hence reducing their connectivity and degrading their electrical properties. We present the results of our simulation in terms of thickness of the CNT network from which simple structural parameters such as the volume fraction or the carbon nanotube density can be accurately evaluated with our more realistic models.
Modeling and Analysis of Realistic Fire Scenarios in Spacecraft
NASA Technical Reports Server (NTRS)
Brooker, J. E.; Dietrich, D. L.; Gokoglu, S. A.; Urban, D. L.; Ruff, G. A.
2015-01-01
An accidental fire inside a spacecraft is an unlikely, but very real emergency situation that can easily have dire consequences. While much has been learned over the past 25+ years of dedicated research on flame behavior in microgravity, a quantitative understanding of the initiation, spread, detection and extinguishment of a realistic fire aboard a spacecraft is lacking. Virtually all combustion experiments in microgravity have been small-scale, by necessity (hardware limitations in ground-based facilities and safety concerns in space-based facilities). Large-scale, realistic fire experiments are unlikely for the foreseeable future (unlike in terrestrial situations). Therefore, NASA will have to rely on scale modeling, extrapolation of small-scale experiments and detailed numerical modeling to provide the data necessary for vehicle and safety system design. This paper presents the results of parallel efforts to better model the initiation, spread, detection and extinguishment of fires aboard spacecraft. The first is a detailed numerical model using the freely available Fire Dynamics Simulator (FDS). FDS is a CFD code that numerically solves a large eddy simulation form of the Navier-Stokes equations. FDS provides a detailed treatment of the smoke and energy transport from a fire. The simulations provide a wealth of information, but are computationally intensive and not suitable for parametric studies where the detailed treatment of the mass and energy transport are unnecessary. The second path extends a model previously documented at ICES meetings that attempted to predict maximum survivable fires aboard space-craft. This one-dimensional model implies the heat and mass transfer as well as toxic species production from a fire. These simplifications result in a code that is faster and more suitable for parametric studies (having already been used to help in the hatch design of the Multi-Purpose Crew Vehicle, MPCV).
An Exactly Solvable Supersymmetric Model of Semimagic Nuclei
Balantekin, A. B.; Gueven, Nurtac; Pehlivan, Yamac
2008-11-11
A simple model of nucleons coupled to angular momentum zero (s-pairs) occupying the valance shell of a semi-magic nuclei is considered. The model has a separable, orbit dependent pairing interaction which dominates over the kinetic term. It is shown that such an interaction leads to an exactly solvable model whose (0{sup +}) eigenstates and energies can be computed very easily with the help of the algebraic Bethe ansatz method. It is also shown that the model has a supersymmetry which connects the spectra of some semimagic nuclei. The results obtained from this model for the semimagic Ni isotopes from {sup 58}Ni to {sup 68}Ni are given. In addition, a new and easier technique for calculating the energy eigenvalues from the Bethe ansatz equations is also presented.
Coleman-Weinberg mechanism in a three-dimensional supersymmetric Chern-Simons-matter model
Ferrari, A. F.; Gallegos, E. A.; Gomes, M.; Silva, A. J. da; Lehum, A. C.; Nascimento, J. R.; Petrov, A. Yu.
2010-07-15
Using the superfield formalism, we study the dynamical breaking of gauge symmetry and superconformal invariance in the N=1 three-dimensional supersymmetric Chern-Simons model, coupled to a complex scalar superfield with a quartic self-coupling. This is an analogue of the conformally invariant Coleman-Weinberg model in four spacetime dimensions. We show that a mass for the gauge and matter superfields are dynamically generated after two-loop corrections to the effective superpotential. We also discuss the N=2 extension of our work, showing that the Coleman-Weinberg mechanism in such model is not feasible, because it is incompatible with perturbation theory.
Higgs bosons of a supersymmetric U(1)' model
Ham, Seung Woo; Oh, Sun Kun
2008-11-23
The lightest scalar Higgs boson is predicted to be smaller than 162 GeV in the leptophobic {eta}-model, at the one-loop level, for a reasonable region of parameter space. In the NMSSM, the sum of the square of the normalized scalar Higgs coupling coefficients to a pair of Z bosons is unity, whereas the corresponding quantity in the leptophobic {eta}-model is less than unity. Thus, by measuring the scalar Higgs coupling coefficients at the ILC, the leptophobic {eta}-model might be distinguished from the NMSSM.
Sneutrino warm inflation in the minimal supersymmetric model
Bastero-Gil, Mar; Berera, Arjun
2005-11-15
The model of RH neutrino fields coupled to the MSSM is shown to yield a large parameter regime of warm inflation. In the strong dissipative regime, it is shown that inflation, driven by a single sneutrino field, occurs with all field amplitudes below the Planck scale. Analysis is also made of leptogenesis, neutrino mass generation and gravitino constraints. A new warm inflation scenario is purposed in which one scalar field drives a period of warm inflation and a second field drives a subsequent phase of reheating. Such a model is able to reduce the final temperature after inflation, thus helping to mitigate gravitino constraints.
Supersymmetric t - J model: An exact result for two dimensions
Cappon, K. Principia Microsystems Inc., 12 Caines Avenue, North York, Ontario, Canada M2M 1G2)
1991-04-01
The {ital t}-{ital J} model exhibits an additional symmetry at {ital J}=2{ital t}. The irreducible representations of this symmetry include states with different quantities of holes and total spin. This leads to degeneracies between systems with differing number of holes and gives an upper bound on the ground-state energy for one- and two-hole systems of arbitrary dimension. Also, it leads to an exact result for the difference in the ground-state energy for momenta {bold k}=(0,0) and {bold k}=({pi},{pi}) between the single-hole {ital t}-{ital J} model and the Heisenberg antiferromagnet in two dimensions.
Unsteady velocity measurements in a realistic intracranial aneurysm model
NASA Astrophysics Data System (ADS)
Ugron, Ádám; Farinas, Marie-Isabelle; Kiss, László; Paál, György
2012-01-01
The initiation, growth and rupture of intracranial aneurysms are intensively studied by computational fluid dynamics. To gain confidence in the results of numerical simulations, validation of the results is necessary. To this end the unsteady flow was measured in a silicone phantom of a realistic intracranial aneurysm. A flow circuit was built with a novel unsteady flow rate generating method, used to model the idealised shape of the heartbeat. This allowed the measurement of the complex three-dimensional velocity distribution by means of laser-optical methods such as laser doppler anemometry (LDA) and particle image velocimetry (PIV). The PIV measurements, available with high temporal and spatial distribution, were found to have good agreement with the control LDA measurements. Furthermore, excellent agreement was found with the numerical results.
Air-Flow Simulation in Realistic Models of the Trachea
Deschamps, T; Schwartz, P; Trebotich, D
2004-12-09
In this article we present preliminary results from a new technique for flow simulation in realistic anatomical airways. The airways are extracted by means of Level-Sets methods that accurately model the complex and varying surfaces of anatomical objects. The surfaces obtained are defined at the sub-pixel level where they intersect the Cartesian grid of the image domain. It is therefore straightforward to construct embedded boundary representations of these objects on the same grid, for which recent work has enabled discretization of the Navier- Stokes equations for incompressible fluids. While most classical techniques require construction of a structured mesh that approximates the surface in order to extrapolate a 3D finite-element gridding of the whole volume, our method directly simulates the air-flow inside the extracted surface without losing any complicated details and without building additional grids.
RADAR Realistic Animal Model Series for Dose Assessment
Keenan, Mary A.; Stabin, Michael G.; Segars, William P.; Fernald, Michael J.
2010-01-01
Rodent species are widely used in the testing and approval of new radiopharmaceuticals, necessitating murine phantom models. As more therapy applications are being tested in animal models, calculating accurate dose estimates for the animals themselves becomes important to explain and control potential radiation toxicity or treatment efficacy. Historically, stylized and mathematically based models have been used for establishing doses to small animals. Recently, a series of anatomically realistic human phantoms was developed using body models based on nonuniform rational B-spline. Realistic digital mouse whole-body (MOBY) and rat whole-body (ROBY) phantoms were developed on the basis of the same NURBS technology and were used in this study to facilitate dose calculations in various species of rodents. Methods Voxel-based versions of scaled MOBY and ROBY models were used with the Vanderbilt multinode computing network (Advanced Computing Center for Research and Education), using geometry and tracking radiation transport codes to calculate specific absorbed fractions (SAFs) with internal photon and electron sources. Photon and electron SAFs were then calculated for relevant organs in all models. Results The SAF results were compared with values from similar studies found in reference literature. Also, the SAFs were used with standardized decay data to develop dose factors to be used in radiation dose calculations. Representative plots were made of photon electron SAFs, evaluating the traditional assumption that all electron energy is absorbed in the source organs. Conclusion The organ masses in the MOBY and ROBY models are in reasonable agreement with models presented by other investigators noting that considerable variation can occur between reported masses. Results consistent with those found by other investigators show that absorbed fractions for electrons for organ self-irradiation were significantly less than 1.0 at energies above 0.5 MeV, as expected for many of
A viable supersymmetric model with UV insensitive anomaly mediation
Ibe, Masahiro; Kitano, Ryuichiro; Murayama, Hitoshi
2004-12-14
We propose an electroweak model which is compatible with the UV insensitive anomaly mediated supersymmetry breaking. The model is an extension of the NMSSM by adding vector-like matter fields which can drive the soft scalar masses of the singlet Higgs field negative and the successful electroweak symmetry breaking is achieved. Viable parameter regions are found to preserve perturbativity of all the coupling constants up to the Planck scale. With this success, the model becomes a perfect candidate of physics beyond the standard model without the FCNC and CP problem. The cosmology is also quite interesting. The lightest neutralino is the wino which is a perfect cold dark matter candidate assuming the non-thermal production from the gravitino decay. There is no gravitino problem because it decays before the BBN era, and thus the thermal leptogenesis works. The cosmological domain wall problem inherent in the NMSSM is absent since the Z_3 symmetry is broken by the QCD instanton effect in the presence of the vector-like quarks. We also briefly comment on a possible solution to the strong CP problem a la the Nelson-Barr mechanism.
Effect of relaxing grand-unification assumptions on neutralinos in the minimal supersymmetric model
Griest, K. ); Roszkowski, L. )
1992-10-15
We consider the phenomenological and cosmological properties of light neutralinos in the minimal supersymmetric model when grand-unification assumptions are relaxed. We show that substantial changes result in the mass and mixing properties of the neutralinos, in the interpretation of recent experimental restrictions on neutralino parameter space, and in the relic abundance of light-neutralino dark matter. Relaxation of the grand-unification assumptions is easily accomplished, even within the minimal supergravity model, and results in a larger neutralino parameter space and the viability of light-neutralino ({approx lt}10--20 GeV) dark matter.
Constraint on the scale-unifying supersymmetric preon model from ? - ? mixing
NASA Astrophysics Data System (ADS)
Kim, Jongbae
1997-06-01
We study the flavour changing neutral current process in 0954-3899/23/6/005/img3 - 0954-3899/23/6/005/img4 mixing in the supersymmetric preon model (SPM). Compared to the minimal supersymmetric standard model (MSSM), one distinguishing feature of 0954-3899/23/6/005/img3 - 0954-3899/23/6/005/img4 mixing in the SPM is that there are new contributions from box diagrams involving two vector-like families of quarks and their supersymmetric (SUSY) partners with masses of order 1 TeV. Another special feature of the process in the SPM, in contrast to the MSSM, is that left - right squark 0954-3899/23/6/005/img7 - 0954-3899/23/6/005/img8 mixing is highly suppressed owing to symmetries of the underlying model. We calculate the SUSY box diagrams for 0954-3899/23/6/005/img3 - 0954-3899/23/6/005/img4 mixing for the case of the SPM, using observed 0954-3899/23/6/005/img3 - 0954-3899/23/6/005/img4 mass splitting, and obtain the constraint of 0954-3899/23/6/005/img13 on the squark mass degeneracy in the model. This upper limit is smaller by about a factor of 3.6 than the corresponding limit for the MSSM. The difference arises because of the absence of 0954-3899/23/6/005/img7 - 0954-3899/23/6/005/img8 mixing in the the preon model.
Evolution of migration rate in a spatially realistic metapopulation model.
Heino, M; Hanski, I
2001-05-01
We use an individual-based, spatially realistic metapopulation model to study the evolution of migration rate. We first explore the consequences of habitat change in hypothetical patch networks on a regular lattice. If the primary consequence of habitat change is an increase in local extinction risk as a result of decreased local population sizes, migration rate increases. A nonmonotonic response, with migration rate decreasing at high extinction rate, was obtained only by assuming very frequent catastrophes. If the quality of the matrix habitat deteriorates, leading to increased mortality during migration, the evolutionary response is more complex. As long as habitat patch occupancy does not decrease markedly with increased migration mortality, reduced migration rate evolves. However, once mortality becomes so high that empty patches remain uncolonized for a long time, evolution tends to increase migration rate, which may lead to an "evolutionary rescue" in a fragmented landscape. Kin competition has a quantitative effect on the evolution of migration rate in our model, but these patterns in the evolution of migration rate appear to be primarily caused by spatiotemporal variation in fitness and mortality during migration. We apply the model to real habitat patch networks occupied by two checkerspot butterfly (Melitaea) species, for which sufficient data are available to estimate rigorously most of the model parameters. The model-predicted migration rate is not significantly different from the empirically observed one. Regional variation in patch areas and connectivities leads to regional variation in the optimal migration rate, predictions that can be tested empirically. PMID:18707258
Standard model and supersymmetric Higgs searches at CDF
Kilminster, Ben; /Ohio State U.
2005-10-01
We present the results on the searches for the SM and the MSSM Higgs boson production in proton-antiproton collisions at {radical}s = 1.96 GeV with the CDF detector. The Higgs bosons are searched for in various production and decay channels, with data samples corresponding to 400 pb{sup -1}. Using these measurements, we set an upper limit on the production cross section times branching fraction for the Standard Model Higgs as a function of the Higgs mass, and we obtain exclusion regions in the tan{beta} vs mass for the neutral MSSM Higgs, and branching fraction vs mass for the charged Higgs.
NASA Astrophysics Data System (ADS)
Orlova, Ksenia; Shprits, Yuri
2014-02-01
The outer radiation belt electrons in the inner magnetosphere show high variability during the geomagnetically disturbed conditions. Quasi-linear diffusion theory provides both a framework for global prediction of particle loss at different energies and an understanding of the dynamics of different particle populations. It has been recently shown that the pitch angle scattering of electrons due to wave-particle interaction with chorus waves modeled in a realistic magnetic field may be significantly different from those estimated in a dipole model. In this work, we present the lifetimes of 1 keV-2 MeV electrons computed in the Tsyganenko 89 magnetic field model for the night, dawn, prenoon, and postnoon magnetic local time (MLT) sectors for different levels of geomagnetic activity and distances. The lifetimes in the realistic field are also compared to those computed in the dipole model. We develop a realistic chorus lower band and upper band wave models for each MLT sector using the recent statistical studies of wave amplitude, wave normal angle, and wave spectral density distributions as functions of magnetic latitude, distance, and Kp index. The increase of plasma trough density with increasing latitude is also included. The obtained in the Tsyganenko 89 field electron lifetimes are parameterized and can be used in 2-D/3-D/4-D convection and particle tracing codes.
Realistic camera noise modeling with application to improved HDR synthesis
NASA Astrophysics Data System (ADS)
Goossens, Bart; Luong, Hiêp; Aelterman, Jan; Pižurica, Aleksandra; Philips, Wilfried
2012-12-01
Due to the ongoing miniaturization of digital camera sensors and the steady increase of the "number of megapixels", individual sensor elements of the camera become more sensitive to noise, even deteriorating the final image quality. To go around this problem, sophisticated processing algorithms in the devices, can help to maximally exploit the knowledge on the sensor characteristics (e.g., in terms of noise), and offer a better image reconstruction. Although a lot of research focuses on rather simplistic noise models, such as stationary additive white Gaussian noise, only limited attention has gone to more realistic digital camera noise models. In this article, we first present a digital camera noise model that takes several processing steps in the camera into account, such as sensor signal amplification, clipping, post-processing,.. We then apply this noise model to the reconstruction problem of high dynamic range (HDR) images from a small set of low dynamic range (LDR) exposures of a static scene. In literature, HDR reconstruction is mostly performed by computing a weighted average, in which the weights are directly related to the observer pixel intensities of the LDR image. In this work, we derive a Bayesian probabilistic formulation of a weighting function that is near-optimal in the MSE sense (or SNR sense) of the reconstructed HDR image, by assuming exponentially distributed irradiance values. We define the weighting function as the probability that the observed pixel intensity is approximately unbiased. The weighting function can be directly computed based on the noise model parameters, which gives rise to different symmetric and asymmetric shapes when electronic noise or photon noise is dominant. We also explain how to deal with the case that some of the noise model parameters are unknown and explain how the camera response function can be estimated using the presented noise model. Finally, experimental results are provided to support our findings.
NASA Astrophysics Data System (ADS)
Dubinin, M. N.; Petrova, E. Yu.
2016-07-01
Constraints on the parameter space of theMinimal Supersymmetric StandardModel (MSSM) that are imposed by the experimentally observed mass of the Higgs boson ( m H = 125 GeV) upon taking into account radiative corrections within an effective theory for the Higgs sector in the decoupling limit are examined. It is also shown that simplified approximations for radiative corrections in theMSSM Higgs sector could reduce, to a rather high degree of precision, the dimensionality of the multidimensionalMSSM parameter space to two.
Gravitational waves from domain walls in the next-to-minimal supersymmetric standard model
Kadota, Kenji; Kawasaki, Masahiro; Saikawa, Ken’ichi
2015-10-16
The next-to-minimal supersymmetric standard model predicts the formation of domain walls due to the spontaneous breaking of the discrete Z{sub 3}-symmetry at the electroweak phase transition, and they collapse before the epoch of big bang nucleosynthesis if there exists a small bias term in the potential which explicitly breaks the discrete symmetry. Signatures of gravitational waves produced from these unstable domain walls are estimated and their parameter dependence is investigated. It is shown that the amplitude of gravitational waves becomes generically large in the decoupling limit, and that their frequency is low enough to be probed in future pulsar timing observations.
Dynamical coarse grained models with realistic time dependence
NASA Astrophysics Data System (ADS)
Andersen, Hans
2015-03-01
Coarse grained (CG) models of molecular systems, with fewer mechanical degrees of freedom than an all-atom model, are used extensively in chemical physics. It is generally accepted that a coarse grained model that accurately describes equilibrium structural properties (as a result of having a well constructed CG potential energy function) does not necessarily exhibit appropriate dynamical behavior when simulated using conservative Hamiltonian dynamics for the CG degrees of freedom on the CG potential energy surface. Attempts to develop accurate CG dynamic models usually focus on replacing Hamiltonian motion by stochastic but Markovian dynamics on that surface, such as Langevin or Brownian dynamics. However, depending on the nature of the system and the extent of the coarse graining, a Markovian dynamics for the CG degrees of freedom may not be appropriate. We consider the problem of constructing dynamic CG models within the context of the Multi-Scale Coarse Graining (MS-CG) method of Voth and coworkers. We propose a method of converting an MS-CG model into a dynamic CG model by adding degrees of freedom to it in the form of a small number of fictitious particles that interact with the CG degrees of freedom in simple ways and that are subject to Langevin forces. The dynamic models are members of a class of nonlinear systems interacting with special heat baths that was studied by Zwanzig [R. Zwanzig, J. Stat. Phys. 9, 215 (1973)]. The dynamic models generate a non-Markovian dynamics for the CG degrees of freedom, but they can be easily simulated using standard molecular dynamics simulation programs. We present tests of this method on a series of simple examples that demonstrate that the method provides realistic dynamical CG models that have non-Markovian or close to Markovian behavior that is consistent with the actual dynamical behavior of the all-atom system used to construct the CG model. The dynamic CG models have computational requirements that are similar to
Improved transcranial magnetic stimulation coil design with realistic head modeling
NASA Astrophysics Data System (ADS)
Crowther, Lawrence; Hadimani, Ravi; Jiles, David
2013-03-01
We are investigating Transcranial magnetic stimulation (TMS) as a noninvasive technique based on electromagnetic induction which causes stimulation of the neurons in the brain. TMS can be used as a pain-free alternative to conventional electroconvulsive therapy (ECT) which is still widely implemented for treatment of major depression. Development of improved TMS coils capable of stimulating subcortical regions could also allow TMS to replace invasive deep brain stimulation (DBS) which requires surgical implantation of electrodes in the brain. Our new designs allow new applications of the technique to be established for a variety of diagnostic and therapeutic applications of psychiatric disorders and neurological diseases. Calculation of the fields generated inside the head is vital for the use of this method for treatment. In prior work we have implemented a realistic head model, incorporating inhomogeneous tissue structures and electrical conductivities, allowing the site of neuronal activation to be accurately calculated. We will show how we utilize this model in the development of novel TMS coil designs to improve the depth of penetration and localization of stimulation produced by stimulator coils.
Biochemical transport modeling, estimation, and detection in realistic environments
NASA Astrophysics Data System (ADS)
Ortner, Mathias; Nehorai, Arye
2006-05-01
Early detection and estimation of the spread of a biochemical contaminant are major issues for homeland security applications. We present an integrated approach combining the measurements given by an array of biochemical sensors with a physical model of the dispersion and statistical analysis to solve these problems and provide system performance measures. We approximate the dispersion model of the contaminant in a realistic environment through numerical simulations of reflected stochastic diffusions describing the microscopic transport phenomena due to wind and chemical diffusion using the Feynman-Kac formula. We consider arbitrary complex geometries and account for wind turbulence. Localizing the dispersive sources is useful for decontamination purposes and estimation of the cloud evolution. To solve the associated inverse problem, we propose a Bayesian framework based on a random field that is particularly powerful for localizing multiple sources with small amounts of measurements. We also develop a sequential detector using the numerical transport model we propose. Sequential detection allows on-line analysis and detecting wether a change has occurred. We first focus on the formulation of a suitable sequential detector that overcomes the presence of unknown parameters (e.g. release time, intensity and location). We compute a bound on the expected delay before false detection in order to decide the threshold of the test. For a fixed false-alarm rate, we obtain the detection probability of a substance release as a function of its location and initial concentration. Numerical examples are presented for two real-world scenarios: an urban area and an indoor ventilation duct.
Inter-Hemispherical Currents for Realistic Model of Ionospheric Conductivity
NASA Astrophysics Data System (ADS)
Lyatsky, S.; Khazanov, G. V.
2013-12-01
We present results of modeling of the global 3-D ionosphere-magnetosphere current system including in addition to the R1 and R2 field-aligned currents also inter-hemispherical currents. The inter-hemispherical currents flow between Northern and Southern conjugate ionospheres in case of a North-South asymmetry in ionospheric conductivity in two hemispheres. These currents link together the ionospheric currents in two hemispheres, so the currents observed in one hemisphere can provide us with information about currents in the opposite hemisphere, which is especially important when their magnitude can not be obtained from direct observation (e.g., in Antarctica). In this study, we investigate the generation of the inter-hemispherical currents for several distributions of ionospheric conductivity in two hemispheres including a simplified model of ionospheric conductivity, which is important for better understanding of the expected distribution and magnitude of these currents, and a more realistic model of ionospheric conductivity, which is observed during magnetospheric substorms, when the geometry of the inter-hemispherical currents is more complicated. Simulation results show that the inter-hemispherical currents during substorms could play a very significant role, and neglecting these currents does not allow obtaining the correct picture of 3-D magnetosphere-ionosphere current system. These currents are an important part of 3-D field-aligned current system, and they are especially strong during summer-winter months, when they are comparable in magnitude with the R2 currents (about ~0.5 MA). Inter-hemispherical currents map. Left panel is related to Northern hemisphere, right panel to Southern. R1 and R2 currents are not shown; their locations are indicated by the red and blue dashed circles, respectively. The inter-hemispherical currents appear inside the auroral zone in the region of conductivity gradient. The currents in both hemispheres are equal in magnitude and
Deformed matrix models, supersymmetric lattice twists and Script N = ¼ supersymmetry
NASA Astrophysics Data System (ADS)
Ünsal, Mithat
2009-05-01
A manifestly supersymmetric nonperturbative matrix regularization for a twisted version of Script N = (8,8) theory on a curved background (a two-sphere) is constructed. Both continuum and the matrix regularization respect four exact scalar supersymmetries under a twisted version of the supersymmetry algebra. We then discuss a succinct Script Q = 1 deformed matrix model regularization of Script N = 4 SYM in d = 4, which is equivalent to a non-commutative A4* orbifold lattice formulation. Motivated by recent progress in supersymmetric lattices, we also propose a Script N = ¼ supersymmetry preserving deformation of Script N = 4 SYM theory on Bbb R4. In this class of Script N = ¼ theories, both the regularized and continuum theory respect the same set of (scalar) supersymmetry. By using the equivalence of the deformed matrix models with the lattice formulations, we give a very simple physical argument on why the exact lattice supersymmetry must be a subset of scalar subalgebra. This argument disagrees with the recent claims of the link approach, for which we give a new interpretation.
Deformed Matrix Models, Supersymmetric Lattice Twists and N=1/4 Supersymmetry
Unsal, Mithat
2008-09-24
A manifestly supersymmetric nonperturbative matrix regularization for a twisted version of N = (8, 8) theory on a curved background (a two-sphere) is constructed. Both continuum and the matrix regularization respect four exact scalar supersymmetries under a twisted version of the supersymmetry algebra. We then discuss a succinct Q = 1 deformed matrix model regularization of N = 4 SYM in d = 4, which is equivalent to a non-commutative A*{sub 4} orbifold lattice formulation. Motivated by recent progress in supersymmetric lattices, we also propose a N = 1/4 supersymmetry preserving deformation of N = 4 SYM theory on R{sup 4}. In this class of N = 1/4 theories, both the regularized and continuum theory respect the same set of (scalar) supersymmetry. By using the equivalence of the deformed matrix models with the lattice formulations, we give a very simple physical argument on why the exact lattice supersymmetry must be a subset of scalar subalgebra. This argument disagrees with the recent claims of the link approach, for which we give a new interpretation.
Type II seesaw supersymmetric neutrino model for θ13≠0
NASA Astrophysics Data System (ADS)
Ahl Laamara, R.; Loualidi, M. A.; Saidi, E. H.
2016-06-01
Using the type II seesaw approach and properties of discrete flavor symmetry group representations, we build a supersymmetric A4×A3 neutrino model with θ13≠0 . After describing the basis of this model—which is beyond the minimal supersymmetric Standard Model—with a superfield spectrum containing flavons in A4×A3 representations, we first generate the tribimaximal neutrino mixing which is known to be in agreement with the mixing angles θ12 and θ23. Then, we give the scalar potential of the theory where the A3 discrete subsymmetry is used to avoid the so-called sequestering problem. We next study the deviation from the tribimaximal mixing matrix which is produced by perturbing the neutrino mass matrix with a nontrivial A4 singlet. Normal and inverted mass hierarchies are discussed numerically. We also study the breaking of A4 down to Z3 in the charged lepton sector, and use the branching ratio of the decay τ →μ μ e —which is allowed by the residual symmetry Z3—to get estimations on the mass of one of the flavons and the cutoff scale Λ of the model. Key words: Neutrino family symmetry, supersymmetry, deviation from TBM
Dark radiation and dark matter in supersymmetric axion models with high reheating temperature
Graf, Peter; Steffen, Frank Daniel E-mail: steffen@mpp.mpg.de
2013-12-01
Recent studies of the cosmic microwave background, large scale structure, and big bang nucleosynthesis (BBN) show trends towards extra radiation. Within the framework of supersymmetric hadronic axion models, we explore two high-reheating-temperature scenarios that can explain consistently extra radiation and cold dark matter (CDM), with the latter residing either in gravitinos or in axions. In the gravitino CDM case, axions from decays of thermal saxions provide extra radiation already prior to BBN and decays of axinos with a cosmologically required TeV-scale mass can produce extra entropy. In the axion CDM case, cosmological constraints are respected with light eV-scale axinos and weak-scale gravitinos that decay into axions and axinos. These decays lead to late extra radiation which can coexist with the early contributions from saxion decays. Recent results of the Planck satellite probe extra radiation at late times and thereby both scenarios. Further tests are the searches for axions at ADMX and for supersymmetric particles at the LHC.
de la Puente, Alejandro
2012-05-01
In this work, I present a generalization of the Next-to-Minimal Supersymmetric Standard Model (NMSSM), with an explicit μ-term and a supersymmetric mass for the singlet superfield, as a route to alleviating the little hierarchy problem of the Minimal Supersymmetric Standard Model (MSSM). I analyze two limiting cases of the model, characterized by the size of the supersymmetric mass for the singlet superfield. The small and large limits of this mass parameter are studied, and I find that I can generate masses for the lightest neutral Higgs boson up to 140 GeV with top squarks below the TeV scale, all couplings perturbative up to the gauge unification scale, and with no need to fine tune parameters in the scalar potential. This model, which I call the S-MSSM is also embedded in a gauge-mediated supersymmetry breaking scheme. I find that even with a minimal embedding of the S-MSSM into a gauge mediated scheme, the mass for the lightest Higgs boson can easily be above 114 GeV, while keeping the top squarks below the TeV scale. Furthermore, I also study the forward-backward asymmetry in the t¯t system within the framework of the S-MSSM. For this purpose, non-renormalizable couplings between the first and third generation of quarks to scalars are introduced. The two limiting cases of the S-MSSM, characterized by the size of the supersymmetric mass for the singlet superfield is analyzed, and I find that in the region of small singlet supersymmetric mass a large asymmetry can be obtained while being consistent with constraints arising from flavor physics, quark masses and top quark decays.
SuperLFV: An SLHA tool for lepton flavor violating observables in supersymmetric models
NASA Astrophysics Data System (ADS)
Murakami, Brandon
2014-02-01
We introduce SuperLFV, a numerical tool for calculating low-energy observables that exhibit charged lepton flavor violation (LFV) in the context of the minimal supersymmetric standard model (MSSM). As the Large Hadron Collider and MEG, a dedicated μ+→e+γ experiment, are presently acquiring data, there is need for tools that provide rapid discrimination of models that exhibit LFV. SuperLFV accepts a spectrum file compliant with the SUSY Les Houches Accord (SLHA), containing the MSSM couplings and masses with complex phases at the supersymmetry breaking scale. In this manner, SuperLFV is compatible with but divorced from existing SLHA spectrum calculators that provide the low energy spectrum. Hence, input spectra are not confined to the LFV sources provided by established SLHA spectrum calculators. Input spectra may be generated by personal code or by hand, allowing for arbitrary models not supported by existing spectrum calculators.
Bernhardt, M. A.; Das, S. P.; Dreiner, H. K.; Grab, S.
2009-02-01
We consider B{sub 3} minimal supergravity models where we have one lepton number violating L{sub i}Q{sub j}D{sub k} operator at the grand unification scale. This can alter the supersymmetric mass spectrum leading to a sneutrino as the lightest supersymmetric particle in a large region of parameter space. We take into account the restrictions from neutrino masses, the muon anomalous magnetic moment, b{yields}s{gamma}, and other precision measurements. We furthermore investigate existing restrictions from direct searches at LEP, the Tevatron, and the CERN pp collider. We then give examples for characteristic signatures at the LHC.
Natural h{yields}4g in supersymmetric models and R-hadrons at the LHC
Luty, Markus A.; Phalen, Daniel J.; Pierce, Aaron
2011-04-01
We construct a simple and natural supersymmetric model where the dominant Higgs decay is h{yields}aa followed by a{yields}gg. In this case m{sub h}
Schulze-Halberg, Axel E-mail: xbataxel@gmail.com; Wang, Jie
2015-07-15
We obtain series solutions, the discrete spectrum, and supersymmetric partners for a quantum double-oscillator system. Its potential features a superposition of the one-parameter Mathews-Lakshmanan interaction and a one-parameter harmonic or inverse harmonic oscillator contribution. Furthermore, our results are transferred to a generalized Pöschl-Teller model that is isospectral to the double-oscillator system.
Ma, J
2004-01-06
The authors searched for the light neutral scalar Higgs boson h{sup o} and the pseudoscalar Higgs boson A{sup o} of the Minimal Supersymmetric Extension of the Standard Model (MSSM) for the case tan {beta} < 1. The experiment was done with the SLD detector at the Stanford Linear Accelerator Center (SLAC). This analysis is based on the data set collected during the 1993 physics run which contained about 50,000 hadronic Z{sup o} events. After the event selection cuts for hadronic Z{sup 0} decays with CDC information, they select 27,560 events. The Monte Carlo (MC) simulated event distributions agree very well with the data. Good agreement is achieved between MC and the data on the number of events passing each of the event selection cuts.
Impact of future lepton flavor violation measurements in the minimal supersymmetric standard model
NASA Astrophysics Data System (ADS)
Ellis, Sebastian A. R.; Pierce, Aaron
2016-07-01
Working within the context of the minimal supersymmetric standard model, we compare current bounds from quark flavor changing processes with current and upcoming bounds on lepton flavor violation. We assume supersymmetry breaking approximately respects C P invariance. Under the further assumption that flavor violating insertions in the quark and lepton scalar masses are comparable, we explore when lepton flavor violation provides the strongest probe of new physics. We quote results both for spectra with all superpartners near the TeV scale and where scalars are multi-TeV. Constraints from quark flavor changing neutral currents are in many cases already stronger than those expected from future lepton flavor violation bounds, but large regions of parameter space remain where the latter could provide a discovery mode for supersymmetry.
New source for electroweak baryogenesis in the minimal supersymmetric standard model.
Cline, J M; Kainulainen, K
2000-12-25
One of the most experimentally testable explanations for the origin of the baryon asymmetry of the Universe is that it was created during the electroweak phase transition, in the minimal supersymmetric standard model. Previous efforts have focused on the current for the difference of the two Higgsino fields, H1-H2, as the source of biasing sphalerons to create the baryon asymmetry. We point out that the current for the orthogonal linear combination, H1+H2, is larger by several orders of magnitude. Although this increases the efficiency of electroweak baryogenesis, we nevertheless find that large CP-violating angles > or = 0.15 are required to get a large enough baryon asymmetry. PMID:11136036
Realizing the supersymmetric inverse seesaw model in the framework of R-parity violation
NASA Astrophysics Data System (ADS)
de S. Pires, C. A.; Rodrigues, J. G.; Rodrigues da Silva, P. S.
2016-08-01
If, on one hand, the inverse seesaw is the paradigm of TeV scale seesaw mechanism, on the other it is a challenge to find scenarios capable of realizing it. In this work we propose a scenario, based on the framework of R-parity violation, that realizes minimally the supersymmetric inverse seesaw mechanism. In it the energy scale parameters involved in the mechanism are recognized as the vacuum expectation values of the scalars that compose the singlet superfields NˆC and S ˆ . We develop also the scalar sector of the model and show that the Higgs mass receives a new tree-level contribution that, when combined with the standard contribution plus loop correction, is capable of attaining 125 GeV without resort to heavy stops.
Higgs bosons in a minimal R-parity conserving left-right supersymmetric model
Frank, Mariana; Korutlu, Beste
2011-04-01
We revisit the Higgs sector of the left-right supersymmetric model. We study the scalar potential in a version of the model in which the minimum is the charge-conserving vacuum state, without R-parity violation or additional nonrenormalizable terms in the Lagrangian. We analyze the dependence of the potential and of the Higgs mass spectrum on the various parameters of the model, pinpointing the most sensitive ones. We also show that the model can predict light neutral flavor-conserving Higgs bosons, while the flavor-violating ones are heavy and within the limits from K{sup 0}-K{sup 0}, D{sup 0}-D{sup 0}, and B{sub d,s}{sup 0}-B{sub d,s}{sup 0} mixings. We study variants of the model in which at least one doubly charged Higgs boson is light and show that the parameter space for such Higgs masses and mixings is very restrictive, thus making the model more predictive.
Prospects for Higgs boson searches with the tribottom channel in unified supersymmetric models
NASA Astrophysics Data System (ADS)
Baer, Howard; Kao, Chung; Sayre, Joshua
2012-02-01
We investigate the prospects for the discovery of a neutral Higgs boson produced in association with a b quark, followed by the Higgs decay into a pair of bottom quarks, pp→bϕ0→bbb¯+X, at the CERN Large Hadron Collider (LHC) within the framework of unified supersymmetric models. The Higgs boson ϕ0 can be a heavy scalar H0 or a pseudoscalar A0. Furthermore, this direct discovery channel is compared with the indirect Higgs searches in the rare decay Bs→μ+μ- at hadron colliders. Promising results are found for the minimal supergravity model, the anomaly-mediated supersymmetry breaking model, and the gauge-mediated supersymmetry breaking model. We find that the indirect search for B(Bs→μ+μ-)≥5×10-9 is complementary to the direct search for bϕ0→bbb¯ with s=14TeV and an integrated luminosity (L) of 300fb-1. In the anomaly-mediated supersymmetry breaking and gauge-mediated supersymmetry breaking models, bϕ0→bbb¯ with L=300fb-1 covers a larger area in the parameter space than B(Bs→μ+μ-)≥5×10-9. In addition, we present constraints from b→sγ and muon anomalous dipole moment (Δaμ) on the parameter space.
Supersymmetric model for dark matter and baryogenesis motivated by the recent CDMS result.
Allahverdi, Rouzbeh; Dutta, Bhaskar; Mohapatra, Rabindra N; Sinha, Kuver
2013-08-01
We discuss a supersymmetric model for cogenesis of dark and baryonic matter where the dark matter (DM) has mass in the 8-10 GeV range as indicated by several direct detection searches, including most recently the CDMS experiment with the desired cross section. The DM candidate is a real scalar field. Two key distinguishing features of the model are the following: (i) in contrast with the conventional weakly interacting massive particle dark matter scenarios where thermal freeze-out is responsible for the observed relic density, our model uses nonthermal production of dark matter after reheating of the Universe caused by moduli decay at temperatures below the QCD phase transition, a feature which alleviates the relic overabundance problem caused by small annihilation cross section of light DM particles and (ii) baryogenesis occurs also at similar low temperatures from the decay of TeV scale mediator particles arising from moduli decay. A possible test of this model is the existence of colored particles with TeV masses accessible at the LHC.
Nonzero θ13 for neutrino mixing in a supersymmetric B-L gauge model with T7 lepton flavor symmetry
NASA Astrophysics Data System (ADS)
Cao, Qing-Hong; Khalil, Shaaban; Ma, Ernest; Okada, Hiroshi
2011-10-01
We discuss how θ13≠0 is accommodated in a recently proposed renormalizable model of neutrino mixing using the non-Abelian discrete symmetry T7 in the context of a supersymmetric extension of the standard model with gauged U(1)B-L. We predict a correlation between θ13 and θ23, as well as the effective neutrino mass mee in neutrinoless double beta decay.
Ibrahim, Tarek; Nath, Pran
2010-09-01
The electric dipole moment (EDM) of the top quark is calculated in a model with a vector like multiplet which mixes with the third generation in an extension of the minimal supersymmetric standard model. Such mixings allow for new CP violating phases. Including these new CP phases, the EDM of the top in this class of models is computed. The top EDM arises from loops involving the exchange of the W, the Z as well as from the exchange involving the charginos, the neutralinos, the gluino, and the vector like multiplet and their superpartners. The analysis of the EDM of the top is more complicated than for the light quarks because the mass of the external fermion, in this case the top quark mass cannot be ignored relative to the masses inside the loops. A numerical analysis is presented and it is shown that the top EDM could be close to 10{sup -19} ecm consistent with the current limits on the EDM of the electron, the neutron and on atomic EDMs. A top EDM of size 10{sup -19} ecm could be accessible in collider experiments such as the International Linear Collider.
Krishna, S.; Shukla, A.; Malik, R.P.
2014-12-15
Using the supersymmetric (SUSY) invariant restrictions on the (anti-)chiral supervariables, we derive the off-shell nilpotent symmetries of the general one (0+1)-dimensional N=2 SUSY quantum mechanical (QM) model which is considered on a (1, 2)-dimensional supermanifold (parametrized by a bosonic variable t and a pair of Grassmannian variables θ and θ-bar with θ{sup 2}=(θ-bar){sup 2}=0,θ(θ-bar)+(θ-bar)θ=0). We provide the geometrical meanings to the two SUSY transformations of our present theory which are valid for any arbitrary type of superpotential. We express the conserved charges and Lagrangian of the theory in terms of the supervariables (that are obtained after the application of SUSY invariant restrictions) and provide the geometrical interpretation for the nilpotency property and SUSY invariance of the Lagrangian for the general N=2 SUSY quantum theory. We also comment on the mathematical interpretation of the above symmetry transformations. - Highlights: • A novel method has been proposed for the derivation of N=2 SUSY transformations. • General N=2 SUSY quantum mechanical (QM) model with a general superpotential, is considered. • The above SUSY QM model is generalized onto a (1, 2)-dimensional supermanifold. • SUSY invariant restrictions are imposed on the (anti-)chiral supervariables. • Geometrical meaning of the nilpotency property is provided.
LHC signals of a B -L supersymmetric standard model C P -even Higgs boson
NASA Astrophysics Data System (ADS)
Hammad, A.; Khalil, S.; Moretti, S.
2016-06-01
We study the scope of the Large Hadron Collider in accessing a neutral Higgs boson of the B -L supersymmetric standard model. After assessing the surviving parameter space configurations following the Run 1 data taking, we investigate the possibilities of detecting this object during Run 2. For the model configurations in which the mixing between such a state and the discovered standard-model-like Higgs boson is non-negligible, there exist several channels enabling its discovery over a mass range spanning from ≈140 to ≈500 GeV . For a heavier Higgs state, with mass above 250 GeV (i.e., twice the mass of the Higgs state discovered in 2012), the hallmark signature is its decay in two such 125 GeV scalars, h'→h h , where h h →b b ¯ γ γ . For a lighter Higgs state, with mass of order 140 GeV, three channels are accessible: γ γ , Z γ , and Z Z , wherein the Z boson decays leptonically. In all such cases, significances above discovery can occur for already planned luminosities at the CERN machine.
Bottom-tau unification in a supersymmetric model with anomaly-mediation
NASA Astrophysics Data System (ADS)
Chigusa, So; Moroi, Takeo
2016-08-01
We study the Yukawa unification, in particular, the unification of the Yukawa coupling constants of b and τ , in the framework of the supersymmetric (SUSY) model. We concentrate on the model in which the SUSY breaking scalar masses are of the order of the gravitino mass while the gaugino masses originate from the effect of anomaly mediation and hence are one-loop suppressed relative to the gravitino mass. We perform an accurate calculation of the Yukawa coupling constants of b and τ at the grand unified theory (GUT) scale, including relevant renormalization group effects and threshold corrections. In particular, we study the renormalization group effects, taking into account the mass splittings among sfermions, gauginos, and the standard model particles. We found that the Yukawa coupling constant of b at the GUT scale is about 70% of that of τ if there is no hierarchy between the sfermion masses and the gravitino mass. Our results suggest sizable threshold corrections to the Yukawa coupling constants at the GUT scale or significant suppressions of the sfermion masses relative to the gravitino mass.
NASA Astrophysics Data System (ADS)
Koehn, Michael; Trodden, Mark
2016-04-01
In supersymmetric theories, topological defects can have nontrivial behaviors determined purely by whether or not supersymmetry is restored in the defect core. A well-known example of this is that some supersymmetric cosmic strings are automatically superconducting, leading to important cosmological effects and constraints. We investigate the impact of nontrivial kinetic interactions, present in a number of particle physics models of interest in cosmology, on the relationship between supersymmetry and supercurrents on strings. We find that in some cases it is possible for superconductivity to be disrupted by the extra interactions.
GUT-inspired supersymmetric model for h → γ γ and the muon g - 2
Ajaib, M. Adeel; Gogoladze, Ilia; Shafi, Qaisar
2015-05-06
We study a grand unified theories inspired supersymmetric model with nonuniversal gaugino masses that can explain the observed muon g-2 anomaly while simultaneously accommodating an enhancement or suppression in the h→γγ decay channel. In order to accommodate these observations and mh≅125 to 126 GeV, the model requires a spectrum consisting of relatively light sleptons whereas the colored sparticles are heavy. The predicted stau mass range corresponding to Rγγ≥1.1 is 100 GeV≲mτ˜≲200 GeV. The constraint on the slepton masses, particularly on the smuons, arising from considerations of muon g-2 is somewhat milder. The slepton masses in this case are predicted tomore » lie in the few hundred GeV range. The colored sparticles turn out to be considerably heavier with mg˜≳4.5 TeV and mt˜₁≳3.5 TeV, which makes it challenging for these to be observed at the 14 TeV LHC.« less
Novel symmetries in an interacting 𝒩 = 2 supersymmetric quantum mechanical model
NASA Astrophysics Data System (ADS)
Krishna, S.; Shukla, D.; Malik, R. P.
2016-07-01
In this paper, we demonstrate the existence of a set of novel discrete symmetry transformations in the case of an interacting 𝒩 = 2 supersymmetric quantum mechanical model of a system of an electron moving on a sphere in the background of a magnetic monopole and establish its interpretation in the language of differential geometry. These discrete symmetries are, over and above, the usual three continuous symmetries of the theory which together provide the physical realizations of the de Rham cohomological operators of differential geometry. We derive the nilpotent 𝒩 = 2 SUSY transformations by exploiting our idea of supervariable approach and provide geometrical meaning to these transformations in the language of Grassmannian translational generators on a (1, 2)-dimensional supermanifold on which our 𝒩 = 2 SUSY quantum mechanical model is generalized. We express the conserved supercharges and the invariance of the Lagrangian in terms of the supervariables (obtained after the imposition of the SUSY invariant restrictions) and provide the geometrical meaning to (i) the nilpotency property of the 𝒩 = 2 supercharges, and (ii) the SUSY invariance of the Lagrangian of our 𝒩 = 2 SUSY theory.
Classifying BPS states in supersymmetric gauge theories coupled to higher derivative chiral models
NASA Astrophysics Data System (ADS)
Nitta, Muneto; Sasaki, Shin
2015-06-01
We study N =1 supersymmetric gauge theories coupled with higher derivative chiral models in four dimensions in the off-shell superfield formalism. We solve the equation of motion for the auxiliary fields and find two distinct on-shell structures of the Lagrangian that we call the canonical and noncanonical branches characterized by zero and nonzero auxiliary fields, respectively. We classify Bogomol'nyi-Prasado-Sommerfield (BPS) states of the models in Minkowski and Euclidean spaces. In Minkowski space, we find Abelian and non-Abelian vortices, vortex lumps (or gauged lumps with fractional lump charges) as 1 /2 BPS states in the canonical branch, and higher derivative generalization of vortices and vortex-(BPS)baby Skyrmions (or gauged BPS baby Skyrmions with fractional baby Skyrme charges) as 1 /4 BPS states in the noncanonical branch. In four-dimensional Euclidean space, we find Yang-Mills instantons trapped inside a non-Abelian vortex, intersecting vortices, and intersecting vortex-(BPS)baby Skyrmions as 1 /4 BPS states in the canonical branch but no BPS states in the noncanonical branch other than those in the Minkowski space.
Source of Kerr-Newman solution as supersymmetric bag model: 50 years of the problem
NASA Astrophysics Data System (ADS)
Burinskii, A.
The ultra extreme Kerr-Newman (KN) solution(a = J/m >> m) produces the gravitational and EM fields of the electron. It has a naked singular ring - a topological defect which may be regularized by a solitonic source forming the pseudo-vacuum bubble filled by Higgs condensate in a supersymmetric superconducting state. Structure and stability of this source is determined by Bogomolnyi equations as a BPS-saturated soliton. The Principal Null Congruences of the KN solution determine consistent embedding of the Dirac equation, which acquires the mass from the Higgs condensate inside the soliton, indicating that this soliton forms a bag model. Shape of this bag is unambiguously determined by BPS-bound. The bag turns out to be flexible and takes the form of a very thin disk, which is completed by a ring-string along its sharp boundary. The ring-string traveling waves generate extra deformations of the bag creating a circulating singular pole. Bag model of the KN source integrates the dressed and pointlike electron in a bag-string-quark system, which removes the conflict between gravity and the point-like electron of the Dirac theory.
Natural origin of inflation within a class of supersymmetric preon models
NASA Astrophysics Data System (ADS)
Cveti, Mirjam; Hübsch, Tristan; Pati, Jogesh C.; Stremnitzer, Hanns
1989-08-01
Derivation of a desired potential for implementing the idea of new inflation from an underlying theory of particle physics has so far remained a challenging task in that it requires unusually small quartic coupling (~10-13+/-1) and an even smaller mass term for the relevant field (the inflaton) in units of its true vacuum expectation value. It is shown that a class of viable locally supersymmetric preon models naturally give rise to the desired potential for a composite field ΔR commonly used as a Higgs field to break left-right symmetry and B-L, so that ΔR can serve as the inflaton. We show that both the quartic coupling and the mass of ΔR vanish in the limit of supersymmetry, U(1)X, U(1)V and gauge invariance. Radiative corrections, in the presence of soft supersymmetry-breaking mass terms, which arise dynamically in the model, give rise to a miniscule quartic coupling and a negligible mass for ΔR, just as desired. This turns out to be the case in spite of the fact that ΔR is a gauge nonsinglet.
Explanation of the masses of quarks and leptons in a supersymmetric preon model
NASA Astrophysics Data System (ADS)
Kim, Jongbae
1998-10-01
We have studied whether the radiative effects including gauge and Yukawa interaction corrections can improve the phenomenological consequences on the masses of quarks and leptons in the supersymmetric preon model. Our study shows that pure renormalization effects in the region from the metacolour scale to the electroweak scale produce quark-lepton distinction within a given family. They cannot, however, produce the desired up-down distinction or the expected quark-lepton asymmetry in the effective hierarchy parameter 0954-3899/24/10/006/img1 of the up, down and lepton sectors. It also shows that the pure radiative corrections cannot explain the `fine structure' effects exhibited by 0954-3899/24/10/006/img2. These lead us to conclude that the symmetry structure of the preon theory cannot strictly respect left-right, up-down and quark-lepton symmetries near and below the Planck scale. This subsequently implies the 0954-3899/24/10/006/img3 symmetry both as regards unification of couplings near the Planck scale in the model and as regards its possible origin from a superstring theory.
Neutralino dark matter in the minimal supersymmetric standard model with natural light Higgs sector
Kim, S.-G.; Maekawa, N.; Nagao, K. I.; Sakurai, K.; Yoshikawa, T.
2008-10-01
We study the neutralino relic density in the minimal supersymmetric standard model with natural light Higgs sector in which all Higgs masses, the supersymmetry (SUSY) breaking parameters, and the Higgsino mass parameter {mu} are of order the weak scale. To realize this situation we adopt nonuniversal Higgs masses at the grand unified scale. We show that in some parameter space in which the SUSY breaking parameters are comparatively small, not only the constraint from the observed relic density of dark matter but also the LEP Higgs bound and the constraint from the b{yields}s{gamma} process are satisfied. In most of the parameter space, the neutralino relic density becomes smaller than the observed relic density in contrast with the results in the constrained minimal SUSY standard model (CMSSM). The reason is that the neutralino coannihilation processes to Higgs bosons open even if the gaugino mass is small and the cross sections become large due to the small dimensionful parameters. Especially the small {mu} parameter and the light CP-odd Higgs, which are difficult to be realized in the CMSSM, are essential for the result.
Novel symmetries in an interacting 𝒩 = 2 supersymmetric quantum mechanical model
NASA Astrophysics Data System (ADS)
Krishna, S.; Shukla, D.; Malik, R. P.
2016-07-01
In this paper, we demonstrate the existence of a set of novel discrete symmetry transformations in the case of an interacting 𝒩 = 2 supersymmetric quantum mechanical model of a system of an electron moving on a sphere in the background of a magnetic monopole and establish its interpretation in the language of differential geometry. These discrete symmetries are, over and above, the usual three continuous symmetries of the theory which together provide the physical realizations of the de Rham cohomological operators of differential geometry. We derive the nilpotent 𝒩 = 2 SUSY transformations by exploiting our idea of supervariable approach and provide geometrical meaning to these transformations in the language of Grassmannian translational generators on a (1, 2)-dimensional supermanifold on which our 𝒩 = 2 SUSY quantum mechanical model is generalized. We express the conserved supercharges and the invariance of the Lagrangian in terms of the supervariables (obtained after the imposition of the SUSY invariant restrictions) and provide the geometrical meaning to (i) the nilpotency property of the 𝒩 = 2 supercharges, and (ii) the SUSY invariance of the Lagrangian of our 𝒩 = 2 SUSY theory.
Khoury, Justin; Lehners, Jean -Luc; Ovrut, Burt A.
2011-08-15
Galileon theories are of considerable interest since they allow for stable violations of the null energy condition. Since such violations could have occurred during a high-energy regime in the history of our universe, we are motivated to study supersymmetric extensions of these theories. This is carried out in this paper, where we construct generic classes of N = 1 supersymmetric Galileon Lagrangians. They are shown to admit non-equivalent stress-energy tensors and, hence, vacua manifesting differing conditions for violating the null energy condition. The temporal and spatial fluctuations of all component fields of the supermultiplet are analyzed and shown to bemore » stable on a large number of such backgrounds. In the process, we uncover a surprising connection between conformal Galileon and ghost condensate theories, allowing for a deeper understanding of both types of theories.« less
Khoury, Justin; Lehners, Jean -Luc
2011-08-15
Galileon theories are of considerable interest since they allow for stable violations of the null energy condition. Since such violations could have occurred during a high-energy regime in the history of our universe, we are motivated to study supersymmetric extensions of these theories. This is carried out in this paper, where we construct generic classes of N = 1 supersymmetric Galileon Lagrangians. They are shown to admit non-equivalent stress-energy tensors and, hence, vacua manifesting differing conditions for violating the null energy condition. The temporal and spatial fluctuations of all component fields of the supermultiplet are analyzed and shown to be stable on a large number of such backgrounds. In the process, we uncover a surprising connection between conformal Galileon and ghost condensate theories, allowing for a deeper understanding of both types of theories.
Berkooz, Micha; Chung, Daniel J H; Volansky, Tomer
2006-01-27
Nonperturbative preheating decay of postinflationary condensates often results in a high density, low momenta, nonthermal gas. In the case where the nonperturbative classical evolution also leads to Q balls, this effect shields them from instant dissociation, and may radically change the thermal history of the Universe. For example, in a large class of inflationary scenarios, motivated by the minimal supersymmetric standard model and its embedding in string theory, the reheat temperature changes by a multiplicative factor of 10(12). PMID:16486682
A description of the Galactic Center excess in the Minimal Supersymmetric Standard Model
NASA Astrophysics Data System (ADS)
Achterberg, Abraham; Amoroso, Simone; Caron, Sascha; Hendriks, Luc; Ruiz de Austri, Roberto; Weniger, Christoph
2015-08-01
Observations with the Fermi Large Area Telescope (LAT) indicate an excess in gamma rays originating from the center of our Galaxy. A possible explanation for this excess is the annihilation of Dark Matter particles. We have investigated the annihilation of neutralinos as Dark Matter candidates within the phenomenological Minimal Supersymmetric Standard Model (pMSSM) . An iterative particle filter approach was used to search for solutions within the pMSSM . We found solutions that are consistent with astroparticle physics and collider experiments, and provide a fit to the energy spectrum of the excess. The neutralino is a Bino/Higgsino or Bino/Wino/Higgsino mixture with a mass in the range 84-92 GeV or 87-97 GeV annihilating into W bosons. A third solutions is found for a neutralino of mass 174-187 GeV annihilating into top quarks. The best solutions yield a Dark Matter relic density 0.06 < Ω h2 <0.13. These pMSSM solutions make clear forecasts for LHC, direct and indirect DM detection experiments. If the pMSSM explanation of the excess seen by Fermi-LAT is correct, a DM signal might be discovered soon.
A description of the Galactic Center excess in the Minimal Supersymmetric Standard Model
Achterberg, Abraham; Amoroso, Simone; Caron, Sascha; Hendriks, Luc; Austri, Roberto Ruiz de
2015-08-03
Observations with the Fermi Large Area Telescope (LAT) indicate an excess in gamma rays originating from the center of our Galaxy. A possible explanation for this excess is the annihilation of Dark Matter particles. We have investigated the annihilation of neutralinos as Dark Matter candidates within the phenomenological Minimal Supersymmetric Standard Model (pMSSM). An iterative particle filter approach was used to search for solutions within the pMSSM. We found solutions that are consistent with astroparticle physics and collider experiments, and provide a fit to the energy spectrum of the excess. The neutralino is a Bino/Higgsino or Bino/Wino/Higgsino mixture with a mass in the range 84–92 GeV or 87–97 GeV annihilating into W bosons. A third solutions is found for a neutralino of mass 174–187 GeV annihilating into top quarks. The best solutions yield a Dark Matter relic density 0.06<Ωh{sup 2}<0.13. These pMSSM solutions make clear forecasts for LHC, direct and indirect DM detection experiments. If the pMSSM explanation of the excess seen by Fermi-LAT is correct, a DM signal might be discovered soon.
Supersymmetric moose models: An extra dimension from a broken deformed conformal field theory
NASA Astrophysics Data System (ADS)
Erlich, Joshua; Anly Tan, Jong
2006-09-01
We find a class of four dimensional deformed conformal field theories which appear extra dimensional when their gauge symmetries are spontaneously broken. The theories are supersymmetric moose models which flow to interacting conformal fixed points at low energies, deformed by superpotentials. Using a-maximization we give strong nonperturbative evidence that the hopping terms in the resulting latticized action are relevant deformations of the fixed-point theories. These theories have an intricate structure of RG flows between conformal fixed points. Our results suggest that at the stable fixed points each of the bulk gauge couplings and superpotential hopping terms is turned on, in favor of the extra-dimensional interpretation of the theory. However, we argue that the higher-dimensional gauge coupling is generically small compared to the size of the extra dimension. In the presence of a brane the topology of the extra dimension is determined dynamically and depends on the numbers of colors and bulk and brane flavors, which suggests phenomenological applications. The RG flows between fixed points in these theories provide a class of tests of Cardy’s conjectured a-theorem.
Supersymmetric moose models: An extra dimension from a broken deformed conformal field theory
Erlich, Joshua; Anly Tan, Jong
2006-09-15
We find a class of four dimensional deformed conformal field theories which appear extra dimensional when their gauge symmetries are spontaneously broken. The theories are supersymmetric moose models which flow to interacting conformal fixed points at low energies, deformed by superpotentials. Using a-maximization we give strong nonperturbative evidence that the hopping terms in the resulting latticized action are relevant deformations of the fixed-point theories. These theories have an intricate structure of RG flows between conformal fixed points. Our results suggest that at the stable fixed points each of the bulk gauge couplings and superpotential hopping terms is turned on, in favor of the extra-dimensional interpretation of the theory. However, we argue that the higher-dimensional gauge coupling is generically small compared to the size of the extra dimension. In the presence of a brane the topology of the extra dimension is determined dynamically and depends on the numbers of colors and bulk and brane flavors, which suggests phenomenological applications. The RG flows between fixed points in these theories provide a class of tests of Cardy's conjectured a-theorem.
Lepton flavor violation in the supersymmetric seesaw model after the LHC 8 TeV run
NASA Astrophysics Data System (ADS)
Goto, Toru; Okada, Yasuhiro; Shindou, Tetsuo; Tanaka, Minoru; Watanabe, Ryoutaro
2015-02-01
We study the lepton flavor violation in the supersymmetric seesaw model, taking into account recent experimental improvements, especially for the Higgs boson mass measurement, direct searches of superpartners, and the rare decay of Bs→μ+μ- at the LHC; the neutrino mixing angle of θ13 in the neutrino experiments; and the search of μ →e γ in the MEG experiment. We obtain the latest constraints on the parameters in the supersymmetry-breaking terms and study the effect on the lepton-flavor-violating decays of τ →μ γ and μ →e γ . In particular, we consider two kinds of assumption on the structures in the Majorana mass matrix and the neutrino Yukawa matrix. In the case of the Majorana mass matrix proportional to the unit matrix, allowing nonvanishing C P -violating parameters in the neutrino Yukawa matrix, we find that the branching ratio of τ →μ γ can be larger than 10-9 within the improved experimental limit of μ →e γ . We also consider the neutrino Yukawa matrix that includes the mixing only in the second and third generations, and we find that a larger branching ratio of τ →μ γ than 10-9 is possible while satisfying the recent constraints.
Realistic model of compact VLSI FitzHugh-Nagumo oscillators
NASA Astrophysics Data System (ADS)
Cosp, Jordi; Binczak, Stéphane; Madrenas, Jordi; Fernández, Daniel
2014-02-01
In this article, we present a compact analogue VLSI implementation of the FitzHugh-Nagumo neuron model, intended to model large-scale, biologically plausible, oscillator networks. As the model requires a series resistor and a parallel capacitor with the inductor, which is the most complex part of the design, it is possible to greatly simplify the active inductor implementation compared to other implementations of this device as typically found in filters by allowing appreciable, but well modelled, nonidealities. We model and obtain the parameters of the inductor nonideal model as an inductance in series with a parasitic resistor and a second order low-pass filter with a large cut-off frequency. Post-layout simulations for a CMOS 0.35 μm double-poly technology using the MOSFET Spice BSIM3v3 model confirm the proper behaviour of the design.
More-Realistic Digital Modeling of a Human Body
NASA Technical Reports Server (NTRS)
Rogge, Renee
2010-01-01
A MATLAB computer program has been written to enable improved (relative to an older program) modeling of a human body for purposes of designing space suits and other hardware with which an astronaut must interact. The older program implements a kinematic model based on traditional anthropometric measurements that do provide important volume and surface information. The present program generates a three-dimensional (3D) whole-body model from 3D body-scan data. The program utilizes thin-plate spline theory to reposition the model without need for additional scans.
Is Nigerian English a Realistic Model to Teach?
ERIC Educational Resources Information Center
Adeyanju, Thomas K.
Received Pronunciation (RP) has traditionally been presented as a teaching model in Nigeria though performance has not measured up to expectation. In recent years, there has been much confusion regarding the choice of an English teaching model in developing countries, especially since the emergence of local varieties. On the one hand, experts…
A Simple, Realistic Stochastic Model of Gastric Emptying
Yokrattanasak, Jiraphat; De Gaetano, Andrea; Panunzi, Simona; Satiracoo, Pairote; Lawton, Wayne M.; Lenbury, Yongwimon
2016-01-01
Several models of Gastric Emptying (GE) have been employed in the past to represent the rate of delivery of stomach contents to the duodenum and jejunum. These models have all used a deterministic form (algebraic equations or ordinary differential equations), considering GE as a continuous, smooth process in time. However, GE is known to occur as a sequence of spurts, irregular both in size and in timing. Hence, we formulate a simple stochastic process model, able to represent the irregular decrements of gastric contents after a meal. The model is calibrated on existing literature data and provides consistent predictions of the observed variability in the emptying trajectories. This approach may be useful in metabolic modeling, since it describes well and explains the apparently heterogeneous GE experimental results in situations where common gastric mechanics across subjects would be expected. PMID:27057750
A review of toxicity models for realistic atmospheric applications
NASA Astrophysics Data System (ADS)
Gunatilaka, Ajith; Skvortsov, Alex; Gailis, Ralph
2014-02-01
There are many applications that need to study human health effects caused by exposure to toxic chemicals. Risk analysis for industrial sites, study of population health impacts of atmospheric pollutants, and operations research for assessing the potential impacts of chemical releases in military contexts are some examples. Because of safety risks and the high cost of field trials involving hazardous chemical releases, computer simulations are widely used for such studies. Modelling of atmospheric transport and dispersion of chemicals released into the atmosphere to determine the toxic chemical concentrations to which individuals will be exposed is one main component of these simulations, and there are well established atmospheric dispersion models for this purpose. Estimating the human health effects caused by the exposure to these predicted toxic chemical concentrations is the other main component. A number of different toxicity models for assessing the health effects of toxic chemical exposure are found in the literature. Because these different models have been developed based on different assumptions about the plume characteristics, chemical properties, and physiological response, there is a need to review and compare these models to understand their applicability. This paper reviews several toxicity models described in the literature. The paper also presents results of applying different toxicity models to simulated concentration time series data. These results show that the use of ensemble mean concentrations, which are what atmospheric dispersion models typically provide, to estimate human health effects of exposure to hazardous chemical releases may underestimate their impact when toxic exponent, n, of the chemical is greater than one; the opposite phenomenon appears to hold when n < 1. The results also show that some toxicity models that disregard biological recovery processes may predict greater toxicity than the explicitly parameterised models. Despite
Towards realistic standard model from D-brane configurations
Leontaris, G. K.; Tracas, N. D.; Korakianitis, O.; Vlachos, N. D.
2007-12-01
Effective low energy models arising in the context of D-brane configurations with standard model (SM) gauge symmetry extended by several gauged Abelian factors are discussed. The models are classified according to their hypercharge embeddings consistent with the SM spectrum hypercharge assignment. Particular cases are analyzed according to their perspectives and viability as low energy effective field theory candidates. The resulting string scale is determined by means of a two-loop renormalization group calculation. Their implications in Yukawa couplings, neutrinos and flavor changing processes are also presented.
Flavor changing neutral currents in a realistic composite technicolor model
NASA Astrophysics Data System (ADS)
Carone, Christopher D.; Hamilton, Rowan T.
1993-03-01
We consider the phenomenology of a composite technicolor model proposed recently by Georgi. Composite technicolor interactions produce four-quark operators in the low energy theory that contribute to flavor changing neutral current processes. While we expect operators of this type to be induced at the compositeness scale by the flavor-symmetry breaking effects of the preon mass matrices, the Georgi model also includes operators from higher scales that are not GIM-suppressed. Since these operators are potentially large, we study their impact on flavor changing neutral currents and CP violation in the neutral K, B, and D meson systems. Notably, we find that this model gives rise to a typical value for {ɛ‧}/{ɛ} that is much smaller than most standard model estimates.
Constraints on realistic Gauge-Higgs unified models
Aranda, Alfredo; Wudka, Jose
2010-11-01
We investigate the general group structure of gauge-Higgs unified models. We find that a given embedding of the standard model gauge group will imply the presence of additional light vectors, except for a small set of special cases, which we determine; the arguments presented are independent of the compactification scheme. For this set of models we then find those that can both accommodate quarks and have a vanishing oblique T parameter at tree level. We show that none of the resulting models can have |s{sub w}|{approx}1/2 (the sine of the weak-mixing angle) at tree level and briefly discuss possible solutions to this problem.
Physically realistic camouflage net models for visualization and signature generation
NASA Astrophysics Data System (ADS)
Loyd, Jody S.; Sanders, Jeffrey S.
2001-09-01
The Virtual Targets Center (VTC) is a strategic alliance between the Targets Management Office within the US Army Simulation, Training, and Instrumentation Command (STRICOM) and the Systems Simulation and Development Directorate within the US Army Aviation and Missile Command (AMCOM). This center reduces duplication of effort by making DoD owned geometry models available for reutilization and supports the modeling and simulation community by redistributing or creating geometry models in formats applicable to a wide range of simulation activities. In addition to these activites, the VTC is developing methods and tools to enhance existing target models. A new software simulation exists at the VTC to automatically create facet models of camouflage netting by considering the netting as a 2D membrane that balances internal tensional stresses and the external force of gravity by assuming a minimum energy configuration - accurately replicating the draping of real netting. The geometric information of this virtual camouflage netting is exported to a file in a format commonly used for three-dimensional modeling, thereby making it available to workers in signature prediction and visualization.
Cirrus cloud model parameterizations: Incorporating realistic ice particle generation
NASA Technical Reports Server (NTRS)
Sassen, Kenneth; Dodd, G. C.; Starr, David OC.
1990-01-01
Recent cirrus cloud modeling studies have involved the application of a time-dependent, two dimensional Eulerian model, with generalized cloud microphysical parameterizations drawn from experimental findings. For computing the ice versus vapor phase changes, the ice mass content is linked to the maintenance of a relative humidity with respect to ice (RHI) of 105 percent; ice growth occurs both with regard to the introduction of new particles and the growth of existing particles. In a simplified cloud model designed to investigate the basic role of various physical processes in the growth and maintenance of cirrus clouds, these parametric relations are justifiable. In comparison, the one dimensional cloud microphysical model recently applied to evaluating the nucleation and growth of ice crystals in cirrus clouds explicitly treated populations of haze and cloud droplets, and ice crystals. Although these two modeling approaches are clearly incompatible, the goal of the present numerical study is to develop a parametric treatment of new ice particle generation, on the basis of detailed microphysical model findings, for incorporation into improved cirrus growth models. For example, the relation between temperature and the relative humidity required to generate ice crystals from ammonium sulfate haze droplets, whose probability of freezing through the homogeneous nucleation mode are a combined function of time and droplet molality, volume, and temperature. As an example of this approach, the results of cloud microphysical simulations are presented showing the rather narrow domain in the temperature/humidity field where new ice crystals can be generated. The microphysical simulations point out the need for detailed CCN studies at cirrus altitudes and haze droplet measurements within cirrus clouds, but also suggest that a relatively simple treatment of ice particle generation, which includes cloud chemistry, can be incorporated into cirrus cloud growth.
Model of Ni-63 battery with realistic PIN structure
NASA Astrophysics Data System (ADS)
Munson, Charles E.; Arif, Muhammad; Streque, Jeremy; Belahsene, Sofiane; Martinez, Anthony; Ramdane, Abderrahim; El Gmili, Youssef; Salvestrini, Jean-Paul; Voss, Paul L.; Ougazzaden, Abdallah
2015-09-01
GaN, with its wide bandgap of 3.4 eV, has emerged as an efficient material for designing high-efficiency betavoltaic batteries. An important part of designing efficient betavoltaic batteries involves a good understanding of the full process, from the behavior of the nuclear material and the creation of electron-hole pairs all the way through the collection of photo-generated carriers. This paper presents a detailed model based on Monte Carlo and Silvaco for a GaN-based betavoltaic battery device, modeled after Ni-63 as an energy source. The accuracy of the model is verified by comparing it with experimental values obtained for a GaN-based p-i-n structure under scanning electron microscope illumination.
Model of Ni-63 battery with realistic PIN structure
Munson, Charles E.; Voss, Paul L.; Ougazzaden, Abdallah; Arif, Muhammad; Salvestrini, Jean-Paul; Streque, Jeremy; El Gmili, Youssef; Belahsene, Sofiane; Martinez, Anthony; Ramdane, Abderrahim
2015-09-14
GaN, with its wide bandgap of 3.4 eV, has emerged as an efficient material for designing high-efficiency betavoltaic batteries. An important part of designing efficient betavoltaic batteries involves a good understanding of the full process, from the behavior of the nuclear material and the creation of electron-hole pairs all the way through the collection of photo-generated carriers. This paper presents a detailed model based on Monte Carlo and Silvaco for a GaN-based betavoltaic battery device, modeled after Ni-63 as an energy source. The accuracy of the model is verified by comparing it with experimental values obtained for a GaN-based p-i-n structure under scanning electron microscope illumination.
D-term spectroscopy in realistic heterotic-string models
NASA Astrophysics Data System (ADS)
Dedes, Athanasios; Faraggi, Alon E.
2000-07-01
The recent emergence of free fermionic heterotic string models with solely the MSSM charged spectrum below the string scale reinforces the motivation to investigate the pheneomelogical characteristics of this class of string models, which possess an underlying Z2×Z2 orbifold structure. An important property of the Z2×Z2 orbifold is the cyclic permutation symmetry between the three twisted sectors. If preserved in the three-generation models the cyclic permutation symmetry results in a family universal anomalous U(1)A, which is instrumental in explaining squark degeneracy, provided that the dominant component of supersymmetry breaking arises from the U(1)A D term. Interestingly, the contribution of the family-universal DA term to the squark masses may be intrafamily nonuniversal, and may differ from the usual (universal) boundary conditions assumed in the MSSM. We contemplate how DA-term spectroscopy may be instrumental in studying superstring models irrespective of our ignorance of the details of supersymmetry breaking. We examine the possible effect of the intrafamily nonuniversality on the resulting SUSY spectrum and the values of the strong coupling, effective weak mixing angle, and W-gauge boson mass, up to a two-loop accuracy, in the two models (universal and nonuniversal). We find that nonuniversality relaxes the constraint of color and charge breaking minima which appears in the universal case. In addition, it predicts a 3% smaller value of αs due to different threshold masses obtained in the latter scenario. Finally, we present the experimentally allowed predictions of the two models in an M0 and M1/2 parameter space.
Stochastic fire-diffuse-fire model with realistic cluster dynamics
NASA Astrophysics Data System (ADS)
Calabrese, Ana; Fraiman, Daniel; Zysman, Daniel; Ponce Dawson, Silvina
2010-09-01
Living organisms use waves that propagate through excitable media to transport information. Ca2+ waves are a paradigmatic example of this type of processes. A large hierarchy of Ca2+ signals that range from localized release events to global waves has been observed in Xenopus laevis oocytes. In these cells, Ca2+ release occurs trough inositol 1,4,5-trisphosphate receptors (IP3Rs) which are organized in clusters of channels located on the membrane of the endoplasmic reticulum. In this article we construct a stochastic model for a cluster of IP3R ’s that replicates the experimental observations reported in [D. Fraiman , Biophys. J. 90, 3897 (2006)10.1529/biophysj.105.075911]. We then couple this phenomenological cluster model with a reaction-diffusion equation, so as to have a discrete stochastic model for calcium dynamics. The model we propose describes the transition regimes between isolated release and steadily propagating waves as the IP3 concentration is increased.
Reaction Diffusion Modeling of Calcium Dynamics with Realistic ER Geometry
Means, Shawn; Smith, Alexander J.; Shepherd, Jason; Shadid, John; Fowler, John; Wojcikiewicz, Richard J. H.; Mazel, Tomas; Smith, Gregory D.; Wilson, Bridget S.
2006-01-01
We describe a finite-element model of mast cell calcium dynamics that incorporates the endoplasmic reticulum's complex geometry. The model is built upon a three-dimensional reconstruction of the endoplasmic reticulum (ER) from an electron tomographic tilt series. Tetrahedral meshes provide volumetric representations of the ER lumen, ER membrane, cytoplasm, and plasma membrane. The reaction-diffusion model simultaneously tracks changes in cytoplasmic and ER intraluminal calcium concentrations and includes luminal and cytoplasmic protein buffers. Transport fluxes via PMCA, SERCA, ER leakage, and Type II IP3 receptors are also represented. Unique features of the model include stochastic behavior of IP3 receptor calcium channels and comparisons of channel open times when diffusely distributed or aggregated in clusters on the ER surface. Simulations show that IP3R channels in close proximity modulate activity of their neighbors through local Ca2+ feedback effects. Cytoplasmic calcium levels rise higher, and ER luminal calcium concentrations drop lower, after IP3-mediated release from receptors in the diffuse configuration. Simulation results also suggest that the buffering capacity of the ER, and not restricted diffusion, is the predominant factor influencing average luminal calcium concentrations. PMID:16617072
Realistic thermal evolution models for Superearth Exo-solar planets
NASA Astrophysics Data System (ADS)
van den Berg, A.; Yuen, D.; Umemoto, K.; Wentzcovitch, R.; Jacobs, M.
2012-04-01
Massive superearth exoplanets in the range of one to ten times the Earth's mass have a much extended pressure regime compared to Earth, up to about 1 TPa, that may give rise to different material behavior. This has an impact on planetary evolution, and the evolution of a magnetic field and planetary atmosphere, and is therefore also relevant for habitability conditions. The material properties concerned include the mantle rheology where pressure affects both deep mantle viscosity and the brittle-ductile transition, both with a direct impact on lithosphere dynamics and the heat transport capacity of superearth mantle convection. Besides rheological considirations, other material properties also show strong variation with both pressure and temperature, in particular thermal expansivity and thermal conductivity. At ultra-high pressure they will exert a strong impact on the effectiveness of convective heat transport. The commonly used (extended) Boussinesq (EBA) convection model is not well suited for the pressure regime of superearth exoplanets becuase of the high value of the surface dissipation number involved, typically Di ~ 5 (van den Berg et al., Phys. Earth Planet. Inter.,178, 136-154). We therefore use a compressible convection model based on the anelastic liquid approximation and apply a selfconsistent model for the thermophysical properties based on ab-initio and lattice dynamics for relevant mantle silicates, perovskite, post-perovskite and periclase (Umemoto et al., Science,311, 983-986, 2006; Jacobs and van den Berg, Phys., Earth Planet. Inter.,186, 36-48, 2011). In particular our model includes, in a selfconsistent way, the significant temperature dependence of thermal expansivity, important in controlling the dynamics of cold downwellings in the upper mantle. We present results of convection modelling experiments exploring the forementioned model sensitivities on mantle heat transport both in transient cooling models and expressed in terms of Nusselt
Anisotropic, nonsingular early universe model leading to a realistic cosmology
Dechant, Pierre-Philippe; Lasenby, Anthony N.; Hobson, Michael P.
2009-02-15
We present a novel cosmological model in which scalar field matter in a biaxial Bianchi IX geometry leads to a nonsingular 'pancaking' solution: the hypersurface volume goes to zero instantaneously at the 'big bang', but all physical quantities, such as curvature invariants and the matter energy density remain finite, and continue smoothly through the big bang. We demonstrate that there exist geodesics extending through the big bang, but that there are also incomplete geodesics that spiral infinitely around a topologically closed spatial dimension at the big bang, rendering it, at worst, a quasiregular singularity. The model is thus reminiscent of the Taub-NUT vacuum solution in that it has biaxial Bianchi IX geometry and its evolution exhibits a dimensionality reduction at a quasiregular singularity; the two models are, however, rather different, as we will show in a future work. Here we concentrate on the cosmological implications of our model and show how the scalar field drives both isotropization and inflation, thus raising the question of whether structure on the largest scales was laid down at a time when the universe was still oblate (as also suggested by [T. S. Pereira, C. Pitrou, and J.-P. Uzan, J. Cosmol. Astropart. Phys. 9 (2007) 6.][C. Pitrou, T. S. Pereira, and J.-P. Uzan, J. Cosmol. Astropart. Phys. 4 (2008) 4.][A. Guemruekcueoglu, C. Contaldi, and M. Peloso, J. Cosmol. Astropart. Phys. 11 (2007) 005.]). We also discuss the stability of our model to small perturbations around biaxiality and draw an analogy with cosmological perturbations. We conclude by presenting a separate, bouncing solution, which generalizes the known bouncing solution in closed FRW universes.
NASA Astrophysics Data System (ADS)
Sasaki, Shin; Yamaguchi, Masahide; Yokoyama, Daisuke
2012-11-01
We discuss a supersymmetric version of DBI (Dirac-Born-Infeld) inflation, which is a typical inflation model in string cosmology. The supersymmetric DBI action together with a superpotential always leads to correction terms associated with the potential into the kinetic term, which drastically change the dynamics of DBI inflation. We find two significant features of supersymmetric DBI inflation. The first one is that ultra-relativistic motion is prohibited to cause inflation, which leads to order of unity sound velocity squared and hence small non-Gaussianities of primordial curvature perturbations. The second one is that the relation between the tensor-to-scalar ratio and the field variation is modified. Then, significant tensor-to-scalar ratio r≳0.01 is possible because the variation of the canonically normalized inflaton can be beyond the reduced Planck scale. These new features are in sharp contrast with those of the standard non-supersymmetric DBI inflation and hence have a lot of interest implications on upcoming observations of cosmic microwave background (CMB) anisotropies by the Planck satellite as well as direct detection experiments of gravitational waves like DECIGO and BBO.
Weakly-interacting massive particles in non-supersymmetric SO(10) grand unified models
NASA Astrophysics Data System (ADS)
Nagata, Natsumi; Olive, Keith A.; Zheng, Jiaming
2015-10-01
Non-supersymmetric SO(10) grand unified theories provide a framework in which the stability of dark matter is explained while gauge coupling unification is realized. In this work, we systematically study this possibility by classifying weakly interacting dark matter candidates in terms of their quantum numbers of SU(2) L ⊗ U(1) Y , B - L, and SU(2) R . We consider both scalar and fermion candidates. We show that the requirement of a sufficiently high unification scale to ensure a proton lifetime compatible with experimental constraints plays a strong role in selecting viable candidates. Among the scalar candidates originating from either a 16 or 144 of SO(10), only SU(2) L singlets with zero hypercharge or doublets with Y = 1 /2 satisfy all constraints for SU(4) C ⊗ SU(2) L ⊗ SU(2) R and SU(3) C ⊗ SU(2) L ⊗ SU(2) R ⊗ U(1) B- L intermediate scale gauge groups. Among fermion triplets with zero hypercharge, only a triplet in the 45 with intermediate group SU(4) C ⊗ SU(2) L ⊗ SU(2) R leads to solutions with M GUT > M int and a long proton lifetime. We find three models with weak doublets and Y = 1 /2 as dark matter candidates for the SU(4) C ⊗ SU(2) L ⊗ SU(2) R and SU(4) C ⊗ SU(2) L ⊗ U(1) R intermediate scale gauge groups assuming a minimal Higgs content. We also discuss how these models may be tested at accelerators and in dark matter detection experiments.
Coarse-grained theory of a realistic tetrahedral liquid model
NASA Astrophysics Data System (ADS)
Procaccia, I.; Regev, I.
2012-02-01
Tetrahedral liquids such as water and silica-melt show unusual thermodynamic behavior such as a density maximum and an increase in specific heat when cooled to low temperatures. Previous work had shown that Monte Carlo and mean-field solutions of a lattice model can exhibit these anomalous properties with or without a phase transition, depending on the values of the different terms in the Hamiltonian. Here we use a somewhat different approach, where we start from a very popular empirical model of tetrahedral liquids —the Stillinger-Weber model— and construct a coarse-grained theory which directly quantifies the local structure of the liquid as a function of volume and temperature. We compare the theory to molecular-dynamics simulations and show that the theory can rationalize the simulation results and the anomalous behavior.
A new model for realistic random perturbations of stochastic oscillators
NASA Astrophysics Data System (ADS)
Dieci, Luca; Li, Wuchen; Zhou, Haomin
2016-08-01
Classical theories predict that solutions of differential equations will leave any neighborhood of a stable limit cycle, if white noise is added to the system. In reality, many engineering systems modeled by second order differential equations, like the van der Pol oscillator, show incredible robustness against noise perturbations, and the perturbed trajectories remain in the neighborhood of a stable limit cycle for all times of practical interest. In this paper, we propose a new model of noise to bridge this apparent discrepancy between theory and practice. Restricting to perturbations from within this new class of noise, we consider stochastic perturbations of second order differential systems that -in the unperturbed case- admit asymptotically stable limit cycles. We show that the perturbed solutions are globally bounded and remain in a tubular neighborhood of the underlying deterministic periodic orbit. We also define stochastic Poincaré map(s), and further derive partial differential equations for the transition density function.
Modeling realistic breast lesions using diffusion limited aggregation
NASA Astrophysics Data System (ADS)
Rashidnasab, Alaleh; Elangovan, Premkumar; Dance, David R.; Young, Kenneth C.; Diaz, Oliver; Wells, Kevin
2012-03-01
Synthesizing the appearance of malignant masses and inserting these into digital mammograms can be used as part of a wider framework for investigating the radiological detection task in X-ray mammography. However, the randomness associated with cell division within cancerous masses and the associated complex morphology challenges the realism of the modeling process. In this paper, Diffusion Limited Aggregation (DLA), a type of fractal growth process is proposed and utilized for modeling breast lesions. Masses of different sizes, shapes and densities were grown by controlling DLA growth parameters either prior to growth, or dynamically updating these during growth. A validation study was conducted by presenting 30 real and 30 simulated masses in a random order to a team of radiologists. The results from the validation study suggest that the observers found it difficult to differentiate between the real and simulated lesions.
Nearly Supersymmetric Dark Atoms
Behbahani, Siavosh R.; Jankowiak, Martin; Rube, Tomas; Wacker, Jay G.
2011-01-01
Theories of dark matter that support bound states are an intriguing possibility for the identity of the missing mass of the Universe. This article proposes a class of models of supersymmetric composite dark matter where the interactions with the Standard Model communicate supersymmetry breaking to the dark sector. In these models, supersymmetry breaking can be treated as a perturbation on the spectrum of bound states. Using a general formalism, the spectrum with leading supersymmetry effects is computed without specifying the details of the binding dynamics. The interactions of the composite states with the Standard Model are computed, and several benchmarkmore » models are described. General features of nonrelativistic supersymmetric bound states are emphasized.« less
Nearly Supersymmetric Dark Atoms
Behbahani, Siavosh R.; Jankowiak, Martin; Rube, Tomas; Wacker, Jay G.; /SLAC /Stanford U., ITP
2011-08-12
Theories of dark matter that support bound states are an intriguing possibility for the identity of the missing mass of the Universe. This article proposes a class of models of supersymmetric composite dark matter where the interactions with the Standard Model communicate supersymmetry breaking to the dark sector. In these models supersymmetry breaking can be treated as a perturbation on the spectrum of bound states. Using a general formalism, the spectrum with leading supersymmetry effects is computed without specifying the details of the binding dynamics. The interactions of the composite states with the Standard Model are computed and several benchmark models are described. General features of non-relativistic supersymmetric bound states are emphasized.
A realistic model for quantum theory with a locality property
Eberhard, P.H.
1987-04-01
A model reproducing the predictions of relativistic quantum theory to any desired degree of accuracy is described in this paper. It involves quantities that are independent of the observer's knowledge, and therefore can be called real, and which are defined at each point in space, and therefore can be called local in a rudimentary sense. It involves faster-than-light, but not instantaneous, action at distance.
Modelling disease outbreaks in realistic urban social networks
NASA Astrophysics Data System (ADS)
Eubank, Stephen; Guclu, Hasan; Anil Kumar, V. S.; Marathe, Madhav V.; Srinivasan, Aravind; Toroczkai, Zoltán; Wang, Nan
2004-05-01
Most mathematical models for the spread of disease use differential equations based on uniform mixing assumptions or ad hoc models for the contact process. Here we explore the use of dynamic bipartite graphs to model the physical contact patterns that result from movements of individuals between specific locations. The graphs are generated by large-scale individual-based urban traffic simulations built on actual census, land-use and population-mobility data. We find that the contact network among people is a strongly connected small-world-like graph with a well-defined scale for the degree distribution. However, the locations graph is scale-free, which allows highly efficient outbreak detection by placing sensors in the hubs of the locations network. Within this large-scale simulation framework, we then analyse the relative merits of several proposed mitigation strategies for smallpox spread. Our results suggest that outbreaks can be contained by a strategy of targeted vaccination combined with early detection without resorting to mass vaccination of a population.
Quantitative description of realistic wealth distributions by kinetic trading models
NASA Astrophysics Data System (ADS)
Lammoglia, Nelson; Muñoz, Víctor; Rogan, José; Toledo, Benjamín; Zarama, Roberto; Valdivia, Juan Alejandro
2008-10-01
Data on wealth distributions in trading markets show a power law behavior x-(1+α) at the high end, where, in general, α is greater than 1 (Pareto’s law). Models based on kinetic theory, where a set of interacting agents trade money, yield power law tails if agents are assigned a saving propensity. In this paper we are solving the inverse problem, that is, in finding the saving propensity distribution which yields a given wealth distribution for all wealth ranges. This is done explicitly for two recently published and comprehensive wealth datasets.
Reliable modeling of the electronic spectra of realistic uranium complexes
NASA Astrophysics Data System (ADS)
Tecmer, Paweł; Govind, Niranjan; Kowalski, Karol; de Jong, Wibe A.; Visscher, Lucas
2013-07-01
We present an EOMCCSD (equation of motion coupled cluster with singles and doubles) study of excited states of the small [UO2]2+ and [UO2]+ model systems as well as the larger UVIO2(saldien) complex. In addition, the triples contribution within the EOMCCSDT and CR-EOMCCSD(T) (completely renormalized EOMCCSD with non-iterative triples) approaches for the [UO2]2+ and [UO2]+ systems as well as the active-space variant of the CR-EOMCCSD(T) method—CR-EOMCCSd(t)—for the UVIO2(saldien) molecule are investigated. The coupled cluster data were employed as benchmark to choose the "best" appropriate exchange-correlation functional for subsequent time-dependent density functional (TD-DFT) studies on the transition energies for closed-shell species. Furthermore, the influence of the saldien ligands on the electronic structure and excitation energies of the [UO2]+ molecule is discussed. The electronic excitations as well as their oscillator dipole strengths modeled with TD-DFT approach using the CAM-B3LYP exchange-correlation functional for the [UVO2(saldien)]- with explicit inclusion of two dimethyl sulfoxide molecules are in good agreement with the experimental data of Takao et al. [Inorg. Chem. 49, 2349 (2010), 10.1021/ic902225f].
Realistic modeling of clinical laboratory operation by computer simulation.
Vogt, W; Braun, S L; Hanssmann, F; Liebl, F; Berchtold, G; Blaschke, H; Eckert, M; Hoffmann, G E; Klose, S
1994-06-01
An important objective of laboratory management is to adjust the laboratory's capability to the needs of patients' care as well as economy. The consequences of management may be changes in laboratory organization, equipment, or personnel planning. At present only one's individual experience can be used for making such decisions. We have investigated whether the techniques of operations research could be transferred to a clinical laboratory and whether an adequate simulation model of the laboratory could be realized. First we listed and documented the system design and the process flow for each single laboratory request. These input data were linked by the simulation model (programming language SIMSCRIPT II.5). The output data (turnaround times, utilization rates, and analysis of queue length) were validated by comparison with the current performance data obtained by tracking specimen flow. Congruence of the data was excellent (within +/- 4%). In planning experiments we could study the consequences of changes in order entry, staffing, and equipment on turnaround times, utilization, and queue lengths. We conclude that simulation can be a valuable tool for better management decisions.
Realistic Representation of Trees in an Urban Canopy Model
NASA Astrophysics Data System (ADS)
Ryu, Young-Hee; Bou-Zeid, Elie; Wang, Zhi-Hua; Smith, James A.
2016-05-01
A single-layer urban canopy model that captures sub-facet heterogeneity and various hydrological processes is further developed to explicitly incorporate trees within the urban canyon. The physical processes associated with trees are shortwave/longwave radiation exchange, including mutual interception and shading by trees and buildings and multiple reflections, sensible heat and latent heat (through transpiration) exchange, and root water uptake. A computationally-efficient geometric approach is applied to the radiation exchanges, requiring a priori knowledge of view factors. These view factors are first obtained from independent Monte Carlo ray-tracing simulations, and subsequently simple relations, which are functions of canyon aspect ratio and tree-crown ratio, are proposed to estimate them. The developed model is evaluated against field observations at two urban sites and one suburban site, showing improved performance for latent heat flux compared to the previous version that only includes ground vegetation. The trees in the urban canopy act to considerably decrease sensible heat flux and increase latent heat flux, and these effects are found to be more significant in the more dense urban site. Sensitivity tests are then performed to examine the effects of tree geometry relative to canyon geometry. The results indicate that the tree-crown size relative to canyon width is the most influential parameter to decrease sensible heat flux and increase latent heat flux, resulting in cooling of the urban area.
Reliable Modeling of the Electronic Spectra of Realistic Uranium Complexes
Tecmer, Pawel; Govind, Niranjan; Kowalski, Karol; De Jong, Wibe A.; Visscher, Lucas
2013-07-21
We present an EOMCCSD (equation of motion coupled cluster with singles and doubles) study of excited states of the small [UO2]2+ and [UO2]+ model systems as well as the larger UV IO2(saldien) complex. In addition, the triples contribution within the EOMCCSDT and CR-EOMCCSD(T) (completely renormalized EOMCCSD with non-iterative triples) approaches for the [UO2]2+ and [UO2]+ systems as well as the active-space variant of the CR-EOMCCSD(T) method | CREOMCCSd(t) | for the UV IO2(saldien) molecule are investigated. The coupled cluster data was employed as benchmark to chose the "best" appropriate exchange--correlation functional for subsequent time-dependent density functional (TD-DFT) studies on the transition energies for closed-shell species. Furthermore, the influence of the saldien ligands on the electronic structure and excitation energies of the [UO2]+ molecule is discussed. The electronic excitations as well as their oscillator dipole strengths modeled with TD-DFT approach using the CAM-B3LYP exchange{correlation functional for the [UV O2(saldien)]- with explicit inclusion of two DMSOs are in good agreement with the experimental data of Takao et al. [Inorg. Chem. 49, 2349-2359, (2010)].
Multi-Dimensional Modeling of Nova with Realistic Nuclear Physics
Zingale, M; Hoffman, R D
2011-01-27
This contract covered the period from 03/09/2010 to 09/30/2010. Over this period, we adapted the low Mach number hydrodynamics code MAESTRO to perform simulations of novae. A nova is the thermonuclear runaway of an accreted hydrogen layer on the surface of a white dwarf. As the accreted layer grows in mass, the temperature and density at the base increase to the point where hydrogen fusion can begin by the CNO cycle - a burning process that uses carbon, nitrogen, and oxygen to complete the fusion of four hydrogen nuclei into one helium-4 nucleus. At this point, we are running initial models of nova, exploring the details of the convection. In the follow-on contract to this one, we will continue this investigation.
Optical Depth from Realistic Microlensing Models of M31
Gyuk, Geza; Crotts, Arlin
2000-06-01
We provide a set of microlensing optical depth maps for M31. Optical depths toward Andromeda were calculated on the basis of a four-component model of the lens and source populations: disk and bulge sources lensed by bulge, M31 halo, and Galactic halo lenses. We confirm the high optical depth and the strong optical depth gradient along the M31 minor axis due to a dark halo of lenses and also discuss the magnitude of the self-lensing due to the bulge. We explore how the shape of the optical depth maps to M31 vary with the halo parameters core radius and flattening. (c) 2000 The American Astronomical Society.
A Model of Biological Attacks on a Realistic Population
NASA Astrophysics Data System (ADS)
Carley, Kathleen M.; Fridsma, Douglas; Casman, Elizabeth; Altman, Neal; Chen, Li-Chiou; Kaminsky, Boris; Nave, Demian; Yahja, Alex
The capability to assess the impacts of large-scale biological attacks and the efficacy of containment policies is critical and requires knowledge-intensive reasoning about social response and disease transmission within a complex social system. There is a close linkage among social networks, transportation networks, disease spread, and early detection. Spatial dimensions related to public gathering places such as hospitals, nursing homes, and restaurants, can play a major role in epidemics [Klovdahl et. al. 2001]. Like natural epidemics, bioterrorist attacks unfold within spatially defined, complex social systems, and the societal and networked response can have profound effects on their outcome. This paper focuses on bioterrorist attacks, but the model has been applied to emergent and familiar diseases as well.
Realistic NLTE Radiative Transfer for Modeling Stellar Winds
NASA Technical Reports Server (NTRS)
Bennett, Philip D.
1999-01-01
This NASA grant supported the development of codes to solve the non-LTE multi-level spherical radiative transfer problem in the presence of velocity fields. Much of this work was done in collaboration with Graham Harper (CASA, University of Colorado). These codes were developed for application to the cool, low-velocity winds of evolved late-type stars. Particular emphasis was placed on modeling the wind of lambda Velorum (K4 lb), the brightest K supergiant in the sky, based on extensive observations of the ultraviolet spectrum with the HST/GHRS from GO program 5307. Several solution techniques were examined, including the Eddington factor Approach described in detail by Bennett & Harper (1997). An Eddington factor variant of Harper's S-MULTI code (Harper 1994) for stationary atmospheres was developed and implemented, although full convergence was not realized. The ratio of wind terminal velocity to turbulent velocity is large (approx. 0.3-0.5) in these cool star winds so this assumption of stationarity provides reasonable starting models. Final models, incorporating specified wind laws, were converged using the comoving CRD S-MULTI code. Details of the solution procedure were published by Bennett & Harper (1997). Our analysis of the wind of lambda Vel, based on wind absorption superimposed on chromospheric emission lines in the ultraviolet, can be found in Carpenter et al. (1999). In this paper, we compare observed wind absorption features to an exact CRD calculation in the comoving frame, and also to a much quicker, but approximate, method using the SEI (Sobolev with Exact Integration) code of Lamers, Cerruti-Sola, & Perinotto (1987). Carpenter et al. (1999) provide detailed comparisons of the exact CRD and approximate SEI results and discuss when SEI is adequate to use for computing wind line profiles. Unfortunately, the observational material is insufficient to unambiguously determine the wind acceleration law for lambda Vel. Relatively few unblended Fe II lines
Realistic uncertainties on Hapke model parameters from photometric measurement
NASA Astrophysics Data System (ADS)
Schmidt, Frédéric; Fernando, Jennifer
2015-11-01
The single particle phase function describes the manner in which an average element of a granular material diffuses the light in the angular space usually with two parameters: the asymmetry parameter b describing the width of the scattering lobe and the backscattering fraction c describing the main direction of the scattering lobe. Hapke proposed a convenient and widely used analytical model to describe the spectro-photometry of granular materials. Using a compilation of the published data, Hapke (Hapke, B. [2012]. Icarus 221, 1079-1083) recently studied the relationship of b and c for natural examples and proposed the hockey stick relation (excluding b > 0.5 and c > 0.5). For the moment, there is no theoretical explanation for this relationship. One goal of this article is to study a possible bias due to the retrieval method. We expand here an innovative Bayesian inversion method in order to study into detail the uncertainties of retrieved parameters. On Emission Phase Function (EPF) data, we demonstrate that the uncertainties of the retrieved parameters follow the same hockey stick relation, suggesting that this relation is due to the fact that b and c are coupled parameters in the Hapke model instead of a natural phenomena. Nevertheless, the data used in the Hapke (Hapke, B. [2012]. Icarus 221, 1079-1083) compilation generally are full Bidirectional Reflectance Diffusion Function (BRDF) that are shown not to be subject to this artifact. Moreover, the Bayesian method is a good tool to test if the sampling geometry is sufficient to constrain the parameters (single scattering albedo, surface roughness, b, c , opposition effect). We performed sensitivity tests by mimicking various surface scattering properties and various single image-like/disk resolved image, EPF-like and BRDF-like geometric sampling conditions. The second goal of this article is to estimate the favorable geometric conditions for an accurate estimation of photometric parameters in order to provide
Realistic many-body models for manganese monoxide under pressure
NASA Astrophysics Data System (ADS)
Tomczak, Jan M.; Miyake, T.; Aryasetiawan, F.
2010-03-01
In materials such as transition-metal oxides where electronic Coulomb correlations impede a description in terms of standard band theories, the application of genuine many-body techniques is inevitable. Interfacing the realism of density-functional-based methods with the virtues of Hubbard-type Hamiltonians, requires the joint ab initio construction of transfer integrals and interaction matrix elements (such as the Hubbard U ) in a localized basis set. In this work, we employ the scheme of maximally localized Wannier functions and the constrained random-phase approximation to create effective low-energy models for manganese monoxide and track their evolution under external pressure. We find that in the low-pressure antiferromagnetic phase, the compression results in an increase in the bare Coulomb interaction for specific orbitals. As we rationalized in recent model considerations [Phys. Rev. B 79, 235133 (2009)], this seemingly counterintuitive behavior is a consequence of the delocalization of the respective Wannier functions. The change in screening processes does not alter this tendency, and thus, the screened on-site component of the interaction, the Hubbard U of the effective low-energy system, increases with pressure as well. The orbital anisotropy of the effects originates from the orientation of the orbitals vis-à-vis the deformation of the unit cell. Within the high-pressure paramagnetic phase, on the other hand, we find the significant increase in the Hubbard U is insensitive to the orbital orientation and almost exclusively owing to a substantial weakening of screening channels upon compression.
Many light Higgs bosons in the next-to-minimal supersymmetric model
Dermisek, Radovan; Gunion, John F.
2009-03-01
The next-to-minimal supersymmetric model with a light doubletlike CP-odd Higgs boson and small tan{beta} can satisfy all experimental limits on Higgs bosons even with light superpartners. In these scenarios, the two lightest CP-even Higgs bosons, h{sub 1} and h{sub 2}, and the charged Higgs boson, h{sup +}, can all be light enough to be produced at CERN LEP and yet have decays that have not been looked for or are poorly constrained by existing collider experiments. The channel h{sub 1}{yields}a{sub 1}a{sub 1} with a{sub 1}{yields}{tau}{sup +}{tau}{sup -} or 2j is still awaiting LEP constraints for m{sub h{sub 1}}>86 or 82 GeV, respectively. LEP data may also contain e{sup +}e{sup -}{yields}h{sub 2}a{sub 1} events where h{sub 2}{yields}Za{sub 1} is the dominant decay, a channel that was never examined. Decays of the charged Higgs bosons are often dominated by H{sup {+-}}{yields}W{sup {+-}}{sup (}*{sup )}a{sub 1} with a{sub 1}{yields}gg, cc, and {tau}{sup +}{tau}{sup -}. This is a channel that has so far been ignored in the search for t{yields}h{sup +}b decays at the Tevatron. A specialized analysis might reveal a signal. The light a{sub 1} might be within the reach of B factories via {upsilon}{yields}{gamma}a{sub 1} decays. We study typical mass ranges and branching ratios of Higgs bosons in this scenario and compare these scenarios where the a{sub 1} has a large doublet component to the more general scenarios with arbitrary singlet component for the a{sub 1}.
Realistic Mathematics Learning Using Cooperative Strategy Model in Junior High School
ERIC Educational Resources Information Center
Dwiyana
2015-01-01
This study aims to develop a realistic mathematics learning model using cooperative strategy. This study applies research and development approach conducted at Junior High School "Laboratorium," State University of Malang. The implementation of this model is conducted through five stages: 1) previous study phase; 2) model planning phase;…
NASA Astrophysics Data System (ADS)
Aristovich, K. Y.; Khan, S. H.
2010-07-01
Realistic computer modelling of biological objects requires building of very accurate and realistic computer models based on geometric and material data, type, and accuracy of numerical analyses. This paper presents some of the automatic tools and algorithms that were used to build accurate and realistic 3D finite element (FE) model of whole-brain. These models were used to solve the forward problem in magnetic field tomography (MFT) based on Magnetoencephalography (MEG). The forward problem involves modelling and computation of magnetic fields produced by human brain during cognitive processing. The geometric parameters of the model were obtained from accurate Magnetic Resonance Imaging (MRI) data and the material properties - from those obtained from Diffusion Tensor MRI (DTMRI). The 3D FE models of the brain built using this approach has been shown to be very accurate in terms of both geometric and material properties. The model is stored on the computer in Computer-Aided Parametrical Design (CAD) format. This allows the model to be used in a wide a range of methods of analysis, such as finite element method (FEM), Boundary Element Method (BEM), Monte-Carlo Simulations, etc. The generic model building approach presented here could be used for accurate and realistic modelling of human brain and many other biological objects.
Order Matters: Sequencing Scale-Realistic Versus Simplified Models to Improve Science Learning
NASA Astrophysics Data System (ADS)
Chen, Chen; Schneps, Matthew H.; Sonnert, Gerhard
2016-10-01
Teachers choosing between different models to facilitate students' understanding of an abstract system must decide whether to adopt a model that is simplified and striking or one that is realistic and complex. Only recently have instructional technologies enabled teachers and learners to change presentations swiftly and to provide for learning based on multiple models, thus giving rise to questions about the order of presentation. Using disjoint individual growth modeling to examine the learning of astronomical concepts using a simulation of the solar system on tablets for 152 high school students (age 15), the authors detect both a model effect and an order effect in the use of the Orrery, a simplified model that exaggerates the scale relationships, and the True-to-scale, a proportional model that more accurately represents the realistic scale relationships. Specifically, earlier exposure to the simplified model resulted in diminution of the conceptual gain from the subsequent realistic model, but the realistic model did not impede learning from the following simplified model.
Order Matters: Sequencing Scale-Realistic Versus Simplified Models to Improve Science Learning
NASA Astrophysics Data System (ADS)
Chen, Chen; Schneps, Matthew H.; Sonnert, Gerhard
2016-08-01
Teachers choosing between different models to facilitate students' understanding of an abstract system must decide whether to adopt a model that is simplified and striking or one that is realistic and complex. Only recently have instructional technologies enabled teachers and learners to change presentations swiftly and to provide for learning based on multiple models, thus giving rise to questions about the order of presentation. Using disjoint individual growth modeling to examine the learning of astronomical concepts using a simulation of the solar system on tablets for 152 high school students (age 15), the authors detect both a model effect and an order effect in the use of the Orrery, a simplified model that exaggerates the scale relationships, and the True-to-scale, a proportional model that more accurately represents the realistic scale relationships. Specifically, earlier exposure to the simplified model resulted in diminution of the conceptual gain from the subsequent realistic model, but the realistic model did not impede learning from the following simplified model.
Influence of atmospheric turbulence on OAM-based FSO system with use of realistic link model
NASA Astrophysics Data System (ADS)
Li, Ming; Yu, Zhongyuan; Cvijetic, Milorad
2016-04-01
We study the influence of atmospheric turbulence on OAM-based free-space optical (FSO) communication by using the Pump turbulence spectrum model which accurately characterizes the realistic FSO link. A comprehensive comparison is made between the Pump and Kolmogorov spectrum models with respect to the turbulence impact. The calculated results show that obtained turbulence-induced crosstalk is lower, which means that a higher channel capacity is projected when the realistic Pump spectrum is used instead of the Kolmogorov spectrum. We believe that our results prove that performance of practical OAM-based FSO is better than one predicted by using the original Kolmogorov turbulence model.
Order Matters: Sequencing Scale-Realistic versus Simplified Models to Improve Science Learning
ERIC Educational Resources Information Center
Chen, Chen; Schneps, Matthew H.; Sonnert, Gerhard
2016-01-01
Teachers choosing between different models to facilitate students' understanding of an abstract system must decide whether to adopt a model that is simplified and striking or one that is realistic and complex. Only recently have instructional technologies enabled teachers and learners to change presentations swiftly and to provide for learning…
Correcting electrode modelling errors in EIT on realistic 3D head models.
Jehl, Markus; Avery, James; Malone, Emma; Holder, David; Betcke, Timo
2015-12-01
Electrical impedance tomography (EIT) is a promising medical imaging technique which could aid differentiation of haemorrhagic from ischaemic stroke in an ambulance. One challenge in EIT is the ill-posed nature of the image reconstruction, i.e., that small measurement or modelling errors can result in large image artefacts. It is therefore important that reconstruction algorithms are improved with regard to stability to modelling errors. We identify that wrongly modelled electrode positions constitute one of the biggest sources of image artefacts in head EIT. Therefore, the use of the Fréchet derivative on the electrode boundaries in a realistic three-dimensional head model is investigated, in order to reconstruct electrode movements simultaneously to conductivity changes. We show a fast implementation and analyse the performance of electrode position reconstructions in time-difference and absolute imaging for simulated and experimental voltages. Reconstructing the electrode positions and conductivities simultaneously increased the image quality significantly in the presence of electrode movement.
The Collider Detector at Fermilab (CDF) is a Tevatron experiment at Fermilab. The Tevatron, a powerful particle accelerator, accelerates protons and antiprotons close to the speed of light, and then makes them collide head-on inside the CDF detector. The CDF detector is used to study the products of such collisions. The CDF Physics Group at Fermilab is organized into six working groups, each with a specific focus. The Higgs group searches for Standard Model and Supersymmetric Higgs bosons. Their public web page makes data and numerous figures available from both CDF Runs I and II.
NASA Astrophysics Data System (ADS)
Yamanaka, Nodoka
2012-10-01
We evaluate the Barr-Zee-type two-loop level contribution to the fermion electric and chromo-electric dipole moments with sfermion loop in R-parity violating supersymmetric models. It is found that the Barr-Zee-type fermion dipole moment with sfermion loop acts destructively to the currently known fermion loop contribution, and that it has small effect when the mass of squarks or charged sleptons in the loop is larger than or comparable to that of the sneutrinos, but cannot be neglected if the sneutrinos are much heavier than loop sfermions.
Exact solution of the one-dimensional super-symmetric t-J model with unparallel boundary fields
NASA Astrophysics Data System (ADS)
Zhang, Xin; Cao, Junpeng; Yang, Wen-Li; Shi, Kangjie; Wang, Yupeng
2014-04-01
The exact solution of the one-dimensional super-symmetric t-J model under generic integrable boundary conditions is obtained via the Bethe ansatz methods. With the coordinate Bethe ansatz, the corresponding R-matrix and K-matrices are derived for the second eigenvalue problem associated with spin degrees of freedom. It is found that the second eigenvalue problem can be transformed into that of the transfer matrix of the inhomogeneous XXX spin chain, which allows us to obtain the spectrum of the Hamiltonian and the associated Bethe ansatz equations by the off-diagonal Bethe ansatz method.
Supersymmetric biorthogonal quantum systems
Curtright, Thomas; Mezincescu, Luca; Schuster, David
2007-09-15
We discuss supersymmetric biorthogonal systems, with emphasis given to the periodic solutions that occur at spectral singularities of PT symmetric models. For these periodic solutions, the dual functions are associated polynomials that obey inhomogeneous equations. We construct in detail some explicit examples for the supersymmetric pairs of potentials V{sub {+-}}(z)=-U(z){sup 2}{+-}z(d/dz)U(z) where U(z){identical_to}{sigma}{sub k>0}{upsilon}{sub k}z{sup k}. In particular, we consider the cases generated by U(z)=z and z/(1-z). We also briefly consider the effects of magnetic vector potentials on the partition functions of these systems.
Cold and hot cognition: quantum probability theory and realistic psychological modeling.
Corr, Philip J
2013-06-01
Typically, human decision making is emotionally "hot" and does not conform to "cold" classical probability (CP) theory. As quantum probability (QP) theory emphasises order, context, superimposition states, and nonlinear dynamic effects, one of its major strengths may be its power to unify formal modeling and realistic psychological theory (e.g., information uncertainty, anxiety, and indecision, as seen in the Prisoner's Dilemma).
Duality in supersymmetric Yang-Mills theory
Peskin, M.E.
1997-02-01
These lectures provide an introduction to the behavior of strongly-coupled supersymmetric gauge theories. After a discussion of the effective Lagrangian in nonsupersymmetric and supersymmetric field theories, the author analyzes the qualitative behavior of the simplest illustrative models. These include supersymmetric QCD for N{sub f} < N{sub c}, in which the superpotential is generated nonperturbatively, N = 2 SU(2) Yang-Mills theory (the Seiberg-Witten model), in which the nonperturbative behavior of the effect coupling is described geometrically, and supersymmetric QCD for N{sub f} large, in which the theory illustrates a non-Abelian generalization of electric-magnetic duality. 75 refs., 12 figs.
Numerical modeling of Po-218 deposition in a physiologically realistic lung bifurcation model
NASA Astrophysics Data System (ADS)
Mously-Soroujy, Khalid Ahmad
Experimental data for lung bifurcations reveals complex geometries and distinct asymmetrical characteristic, which affects the localized distribution of particles deposited in the lung. This study is based on recently published numerical results for a symmetric physiological realistic bifurcation geometry Heistracher and Hofmann (1995) which has been extended here to the case of a asymmetric geometry. The asymmetric PRB model was used to study the flow field and the deposition of ultrafine particles for inspiratory and expiratory conditions. In the present study, we investigated the effect of different flow rates, representing human activity and deposition of different ultrafine particles representing radon daughter (Po-218), in the PRB model. Numerical results were compared with the limited available experimental and numerical data. The fluid dynamic computer program FIDAP was used for this purpose.
Pomeron in the N=4 supersymmetric gauge model at strong couplings
NASA Astrophysics Data System (ADS)
Kotikov, A. V.; Lipatov, L. N.
2013-09-01
We find the BFKL Pomeron intercept at N=4 supersymmetric gauge theory in the form of the inverse coupling expansion j0=2-2λ-λ-1+1/4λ+2(1+3ζ3)λ-2+O(λ) with the use of the AdS/CFT correspondence in terms of string energies calculated recently. The corresponding slope γ‧(2) of the anomalous dimension calculated directly up to the fifth order of perturbation theory turns out to be in an agreement with the closed expression obtained from the recent Basso results.
Realistic avatar eye and head animation using a neurobiological model of visual attention
NASA Astrophysics Data System (ADS)
Itti, Laurent; Dhavale, Nitin; Pighin, Frederic
2004-01-01
We describe a neurobiological model of visual attention and eye/head movements in primates, and its application to the automatic animation of a realistic virtual human head watching an unconstrained variety of visual inputs. The bottom-up (image-based) attention model is based on the known neurophysiology of visual processing along the occipito-parietal pathway of the primate brain, while the eye/head movement model is derived from recordings in freely behaving Rhesus monkeys. The system is successful at autonomously saccading towards and tracking salient targets in a variety of video clips, including synthetic stimuli, real outdoors scenes and gaming console outputs. The resulting virtual human eye/head animation yields realistic rendering of the simulation results, both suggesting applicability of this approach to avatar animation and reinforcing the plausibility of the neural model.
Realistic MHD Modeling of EUV Waves: Insight From a Coupled Observational and Modeling Analysis
NASA Astrophysics Data System (ADS)
Downs, C.; Roussev, I. I.; van der Holst, B.; Lugaz, N.; Sokolov, I.
2011-12-01
With the advent of modern computational tools it is now becoming the norm to employ detailed 3D computer models as empirical tools that directly account for the inhomogeneous nature of the Sun-Heliosphere environment. They key advantage of this approach is the ability to compare model results directly to observational data. Using EUV waves as the scientific driver, we show how the coupled analysis of observations and realistic model results can provide deep insight into the underlying physical nature of this phenomena. We motivate the discussion by overviewing the critical model development steps necessary to provide a realistic 3D thermodynamic and magnetic background in the low corona, as well as the important validation step of synthesizing observables for direct comparison to EUV imaging data. Once this link is established it becomes possible to use the model as an effective laboratory to test the plausibility of various physical scenarios for EUV waves (e.g. fast-mode wave, expanding current shell, reconnection front, non-linear modes, etc.) in not only their natural environment but one where the underlying 3D distribution of fundamental plasma parameters are known. Our latest effort involves a coupled modeling and observational analysis of the 2010 June 13 EUV wave observed by the AIA imager aboard the Solar Dynamics Observatory. With a model eruption that compares favorably with the observations, we focus on two main aspects: (a) the interpretation of the stark, unambiguous thermodynamic signatures in the multi-filter AIA data within the propagating EUV wave front. And (b) an in depth analysis of the time-dependent 3D simulation results and their implication with respect to EUV wave theories. Multiple aspects, including the relative phases of perturbed variables, suggest that the outer, propagating component of the EUV wave exhibits the characteristic behavior of a fast-mode wave. Additionally we find that this component becomes decoupled from the evolving
Realistic Image Rendition Using a Variable Exponent Functional Model for Retinex.
Dou, Zeyang; Gao, Kun; Zhang, Bin; Yu, Xinyan; Han, Lu; Zhu, Zhenyu
2016-01-01
The goal of realistic image rendition is to recover the acquired image under imperfect illuminant conditions, where non-uniform illumination may degrade image quality with high contrast and low SNR. In this paper, the assumption regarding illumination is modified and a variable exponent functional model for Retinex is proposed to remove non-uniform illumination and reduce halo artifacts. The theoretical derivation is provided and experimental results are presented to illustrate the effectiveness of the proposed model. PMID:27338379
Realistic Image Rendition Using a Variable Exponent Functional Model for Retinex
Dou, Zeyang; Gao, Kun; Zhang, Bin; Yu, Xinyan; Han, Lu; Zhu, Zhenyu
2016-01-01
The goal of realistic image rendition is to recover the acquired image under imperfect illuminant conditions, where non–uniform illumination may degrade image quality with high contrast and low SNR. In this paper, the assumption regarding illumination is modified and a variable exponent functional model for Retinex is proposed to remove non–uniform illumination and reduce halo artifacts. The theoretical derivation is provided and experimental results are presented to illustrate the effectiveness of the proposed model. PMID:27338379
Two-photon decay of the Higgs bosons in a supersymmetric model with a C P -violating potential
NASA Astrophysics Data System (ADS)
Oshimo, Noriyuki
2016-05-01
In the supersymmetric standard model which is not minimal, the Higgs potential does not conserve C P symmetry generally. Assuming that there exists an SU(2)-triplet Higgs field, we discuss resultant C P -violating effects on the Higgs bosons. The experimentally observed Higgs boson, which should be C P even in the standard model, could decay into two photons of C P -odd polarization state non-negligibly. For the second lightest Higgs boson, in a sizable region of parameter space, the dominant decay modes are different from those expected by the standard model. The two-photon decay could yield both even and odd C P final states at a ratio of the order of unity.
CP phases of neutrino mixing in a supersymmetric B-L gauge model with T7 lepton flavor symmetry
NASA Astrophysics Data System (ADS)
Ishimori, Hajime; Khalil, Shaaban; Ma, Ernest
2012-07-01
In a recently proposed renormalizable model of neutrino mixing using the non-Abelian discrete symmetry T7 in the context of a supersymmetric extension of the standard model with gauged U(1)B-L, a correlation was obtained between θ13 and θ23 in the case where all four parameters are real. Here we consider one parameter to be complex, thus allowing for one Dirac CP phase δCP and two Majorana CP phases α1,2. We find a slight modification to this correlation as a function of δCP. For a given set of input values of Δm212, Δm322, θ12, and θ13, we obtain sin22θ23 and mee (the effective Majorana neutrino mass in neutrinoless double beta decay) as functions of tanδCP. We find that the structure of this model always yields small |tanδCP|.
Enhancement of Br ( B d → μ + μ - ) / Br ( B s → μ + μ - ) in supersymmetric unified models
Dutta, Bhaskar; Mimura, Yukihiro
2015-05-14
We explain the 2.3σ deviation in the recent measurements of the neutral B meson decays into muon pairs from the standard model prediction in the framework of supersymmetric grand unified models using antisymmetric coupling as a new source of flavor violation. We show a correlation between the Bd→μ⁺μ⁻ decay and the CP phase in the Bd→J/ψK decay and that their deviations from the standard model predictions can be explained after satisfying constraints arising from various hadronic and leptonic rare decay processes, B-B¯, K-K¯ oscillation data, and electric dipole moments of electron and neutron. The allowed parameter space is typically representedmore » by pseudoscalar Higgs mass mA≤1 TeV and tanβH(≡vu/vd)≲20 for squark and gluino masses around 2 TeV.« less
Realistic micromechanical modeling and simulation of two-phase heterogeneous materials
NASA Astrophysics Data System (ADS)
Sreeranganathan, Arun
This dissertation research focuses on micromechanical modeling and simulations of two-phase heterogeneous materials exhibiting anisotropic and non-uniform microstructures with long-range spatial correlations. Completed work involves development of methodologies for realistic micromechanical analyses of materials using a combination of stereological techniques, two- and three-dimensional digital image processing, and finite element based modeling tools. The methodologies are developed via its applications to two technologically important material systems, namely, discontinuously reinforced aluminum composites containing silicon carbide particles as reinforcement, and boron modified titanium alloys containing in situ formed titanium boride whiskers. Microstructural attributes such as the shape, size, volume fraction, and spatial distribution of the reinforcement phase in these materials were incorporated in the models without any simplifying assumptions. Instrumented indentation was used to determine the constitutive properties of individual microstructural phases. Micromechanical analyses were performed using realistic 2D and 3D models and the results were compared with experimental data. Results indicated that 2D models fail to capture the deformation behavior of these materials and 3D analyses are required for realistic simulations. The effect of clustering of silicon carbide particles and associated porosity on the mechanical response of discontinuously reinforced aluminum composites was investigated using 3D models. Parametric studies were carried out using computer simulated microstructures incorporating realistic microstructural attributes. The intrinsic merit of this research is the development and integration of the required enabling techniques and methodologies for representation, modeling, and simulations of complex geometry of microstructures in two- and three-dimensional space facilitating better understanding of the effects of microstructural geometry
Multidimensional realistic modelling of Cepheid-like variables - II. Analysis of a Cepheid model
NASA Astrophysics Data System (ADS)
Mundprecht, Eva; Muthsam, Herbert J.; Kupka, Friedrich
2015-05-01
Non-local, time-dependent convection models have been used to explain the location of double-mode pulsations in Cepheids in the HR diagram as well as the existence and location of the red edge of the instability strip. These properties are highly sensitive to model parameters. We use 2D radiation-hydrodynamical simulations with realistic microphysics and grey radiative transfer to model a short-period Cepheid. The simulations show that the strength of the convection zone varies significantly over the pulsation period and exhibits a phase shift relative to the variations in radius. We evaluate the convective flux and the work integral as predicted by the most common convection models. It turns out that over one pulsation cycle the model parameter αc, has to be varied by up to a factor of beyond 2 to match the convective flux obtained from the simulations. To bring convective fluxes integrated over the He II convection zone and the overshoot zone below into agreement, this parameter has to be varied by a factor of up to ˜7.5 (Kuhfuß). We then present results on the energetics of the convection and overshoot zone by radially symmetric and fluctuating quantities. To successfully model this scenario by a static, 1D or even by a simple time-dependent model appears extremely challenging. We conclude that significant improvements are needed to make predictions based on 1D models more robust and to improve the reliability of conclusions on the convection-pulsation coupling drawn from them. Multidimensional simulations can provide guidelines for developing descriptions of convection then applied in traditional 1D modelling.
Harnik, Roni
2004-10-27
Supersymmetric models have traditionally been assumed to be perturbative up to high scales due to the requirement of calculable unification. In this note I review the recently proposed `Fat Higgs' model which relaxes the requirement of perturbativity. In this framework, an NMSSM-like trilinear coupling becomes strong at some intermediate scale. The NMSSM Higgses are meson composites of an asymptotically-free gauge theory. This allows us to raise the mass of the Higgs, thus alleviating the MSSM of its fine tuning problem. Despite the strong coupling at an intermediate scale, the UV completion allows us to maintain gauge coupling unification.
Cao, Junjie; Hikasa, Ken-ichi; Wang, Wenyu; Yang, Jin Min; Yu, Li-Xin
2010-09-01
Assuming the lightest neutralino solely composes the cosmic dark matter, we examine the constraints of the CDMS-II and XENON100 dark matter direct searches on the parameter space of the minimal supersymmetric standard model (MSSM) Higgs sector. We find that the current CDMS-II/XENON100 limits can exclude some of the parameter space which survive the constraints from the dark matter relic density and various collider experiments. We also find that in the currently allowed parameter space, the charged Higgs boson is hardly accessible at the LHC for an integrated luminosity of 30 fb{sup -1}, while the neutral non-SM (standard model) Higgs bosons (H,A) may be accessible in some allowed region characterized by a large {mu}. The future XENON100 (6000 kg-days exposure) will significantly tighten the parameter space in case of nonobservation of dark matter.
Non-standard charged Higgs decay at the LHC in Next-to-Minimal Supersymmetric Standard Model
NASA Astrophysics Data System (ADS)
Bandyopadhyay, Priyotosh; Huitu, Katri; Niyogi, Saurabh
2016-07-01
We consider next-to-minimal supersymmetric standard model (NMSSM) which has a gauge singlet superfield. In the scale invariant superpotential we do not have the mass terms and the whole Lagrangian has an additional Z 3 symmetry. This model can have light scalar and/or pseudoscalar allowed by the recent data from LHC and the old data from LEP. We investigate the situation where a relatively light charged Higgs can decay to such a singlet-like pseudoscalar and a W ± boson giving rise to a final state containing τ and/or b-jets and lepton(s). Such decays evade the recent bounds on charged Higgs from the LHC, and according to our PYTHIA-FastJet based simulation can be probed with 10 fb-1 at the LHC center of mass energy of 13 and 14 TeV.
Ding, Lei; Lai, Yuan; He, Bin
2005-01-01
It is of importance to localize neural sources from scalp recorded EEG. Low resolution brain electromagnetic tomography (LORETA) has received considerable attention for localizing brain electrical sources. However, most such efforts have used spherical head models in representing the head volume conductor. Investigation of the performance of LORETA in a realistic geometry head model, as compared with the spherical model, will provide useful information guiding interpretation of data obtained by using the spherical head model. The performance of LORETA was evaluated by means of computer simulations. The boundary element method was used to solve the forward problem. A three-shell realistic geometry (RG) head model was constructed from MRI scans of a human subject. Dipole source configurations of a single dipole located at different regions of the brain with varying depth were used to assess the performance of LORETA in different regions of the brain. A three-sphere head model was also used to approximate the RG head model, and similar simulations performed, and results compared with the RG-LORETA with reference to the locations of the simulated sources. Multisource localizations were discussed and examples given in the RG head model. Localization errors employing the spherical LORETA, with reference to the source locations within the realistic geometry head, were about 20-30 mm, for four brain regions evaluated: frontal, parietal, temporal and occipital regions. Localization errors employing the RG head model were about 10 mm over the same four brain regions. The present simulation results suggest that the use of the RG head model reduces the localization error of LORETA, and that the RG head model based LORETA is desirable if high localization accuracy is needed.
Diphoton resonances in a U (1 )B -L extension of the minimal supersymmetric standard model
NASA Astrophysics Data System (ADS)
Lazarides, G.; Shafi, Q.
2016-06-01
Inspired by the 750 GeV diphoton state recently reported by ATLAS and CMS, we propose a U (1 )B-L extension of the MSSM which predicts the existence of four spin zero resonance states that are degenerate in mass in the supersymmetric limit. Vectorlike fields, a gauge singlet field, as well as the MSSM Higgsinos are prevented from acquiring arbitrary large masses by a U (1 ) R symmetry. Indeed, these masses can be considerably lighter than the Z' gauge boson mass. Depending on kinematics, the resonance states could decay into right-handed neutrinos and sneutrinos, and/or MSSM Higgs fields and Higgsinos with total decay widths in the multi-GeV range.
A biologically realistic cortical model of eye movement control in reading.
Heinzle, Jakob; Hepp, Klaus; Martin, Kevan A C
2010-07-01
Reading is a highly complex task involving a precise integration of vision, attention, saccadic eye movements, and high-level language processing. Although there is a long history of psychological research in reading, it is only recently that imaging studies have identified some neural correlates of reading. Thus, the underlying neural mechanisms of reading are not yet understood. One very practical requirement of reading is that eye movements be precisely controlled and coordinated with the cognitive processes of reading. Here we present a biologically realistic model of the frontal eye fields that simulates the control of eye movements in human readers. The model couples processes of oculomotor control and cognition in a realistic cortical circuit of spiking neurons. A global rule that signals either "reading" or "not reading" switches the network's behavior from reading to scanning. In the case of reading, interaction with a cortical module that processed "words" allowed the network to read efficiently an array of symbols, including skipping of short words. Word processing and saccade buildup were both modeled by a race to threshold. In both reading and scanning, the network produces realistic distributions of fixation times when compared with human data.
Cao, Junjie; Xiong, Zhaohua; Yang, Jin Min
2002-03-18
In the framework of the minimal supersymmetric model we examine the Z-peak constraints on the scenario of one light bottom squark (sbottom) ( approximately 2-5.5 GeV) and light gluino (approximately 12-16 GeV), which has been successfully used to explain the excess of bottom quark production in hadron collisions. Such a scenario is found to be severely constrained by the CERN LEP Z-peak observables, especially by R(b), due to the large effect of gluino-sbottom loops. To account for the R(b) data in this scenario, the other mass eigenstate of sbottom, i.e., the heavier one, must be lighter than 125 (195) GeV at 2sigma(3sigma) level, which, however, is disfavored by CERN LEP II experiments. PMID:11909395
Realistic microwave breast models through T1-weighted 3-D MRI data.
Tunçay, Ahmet Hakan; Akduman, Ibrahim
2015-02-01
In this paper we present an effective method for developing realistic numerical three-dimensional (3-D) microwave breast models of different shape, size, and tissue density. These models are especially convenient for microwave breast cancer imaging applications and numerical analysis of human breast-microwave interactions. As in the recent studies on this area, anatomical information of the breast tissue is collected from T1-weighted 3-D MRI data of different patients' in prone position. The method presented in this paper offers significant improvements including efficient noise reduction and tissue segmentation, nonlinear mapping of electromagnetic properties, realistically asymmetric phantom shape, and a realistic classification of breast phantoms. Our method contains a five-step approach where each MRI voxel is classified and mapped to the appropriate dielectric properties. In the first step, the MRI data are denoised by estimating and removing the bias field from each slice, after which the voxels are segmented into two main tissues as fibro-glandular and adipose. Using the distribution of the voxel intensities in MRI histogram, two nonlinear mapping functions are generated for dielectric permittivity and conductivity profiles, which allow each MRI voxel to map to its proper dielectric properties. Obtained dielectric profiles are then converted into 3-D numerical breast phantoms using several image processing techniques, including morphologic operations, filtering. Resultant phantoms are classified according to their adipose content, which is a critical parameter that affects penetration depth during microwave breast imaging.
Nummenmaa, Aapo; Stenroos, Matti; Ilmoniemi, Risto J.; Okada, Yoshio C.; Hämäläinen, Matti S.; Raij, Tommi
2013-01-01
Objective MRI-guided real-time transcranial magnetic stimulation (TMS) navigators that apply electromagnetic modeling have improved the utility of TMS. However, their accuracy and speed depends on the assumed volume conductor geometry. Spherical models found in present navigators are computationally fast but may be inaccurate in some areas. Realistically-shaped boundary-element models (BEMs) could increase accuracy at a moderate computational cost, but it is unknown which model features have the largest influence on accuracy. Thus, we compared different types of spherical models and BEMs. Methods Globally and locally fitted spherical models and different BEMs with either one or three compartments and with different skull-to-brain conductivity ratios (1/1 – 1/80) were compared against a reference BEM. Results The one-compartment BEM at inner skull surface was almost as accurate as the reference BEM. Skull/brain conductivity ratio in the range 1/10 – 1/80 had only a minor influence. BEMs were superior to spherical models especially in frontal and temporal areas (up to 20 mm localization and 40% intensity improvement); in motor cortex all models provided similar results. Conclusions One-compartment BEMs offer a good balance between accuracy and computational cost. Significance Realistically-shaped BEMs may increase TMS navigation accuracy in several brain areas, such as in prefrontal regions often targeted in clinical applications. PMID:23890512
What Is the Most Realistic Single-Compartment Model of Spike Initiation?
Brette, Romain
2015-01-01
A large variety of neuron models are used in theoretical and computational neuroscience, and among these, single-compartment models are a popular kind. These models do not explicitly include the dendrites or the axon, and range from the Hodgkin-Huxley (HH) model to various flavors of integrate-and-fire (IF) models. The main classes of models differ in the way spikes are initiated. Which one is the most realistic? Starting with some general epistemological considerations, I show that the notion of realism comes in two dimensions: empirical content (the sort of predictions that a model can produce) and empirical accuracy (whether these predictions are correct). I then examine the realism of the main classes of single-compartment models along these two dimensions, in light of recent experimental evidence. PMID:25856629
Uncertainty Quantification of Tracer Dispersion with the PMVP Model under Realistic Conditions
NASA Astrophysics Data System (ADS)
Meyer, D. W.; Duenser, S.
2015-12-01
The polar Markovian velocity process (PVMP) model provides a computationally efficient method to propagate input uncertainty stemming from unknown permeability fields to output flow and transport statistics [Meyer and Tchelepi, WRR, 2010; Meyer, Jenny, and Tchelepi, WRR, 2010; Meyer et al., WRR, 2013]. Compared with classical Monte Carlo (MC) sampling, the PMVP model provides predictions of tracer concentration statistics at computing times that are three orders of magnitude smaller. Consequently, the PMVP model is as well significantly faster than accelerated sampling techniques such as multi-level MC or polynomial chaos expansions. In this work, we further evaluate the PMVP model performance by applying the model for tracer dispersion predictions in a setup derived from the well-known MADE field experiment [Boggs et al., WRR, 1992]. We perform detailed model validations against reference MC simulations and conclude that the model provides overall accurate dispersion predictions under realistic conditions.
Introducing a more realistic model for opinion formation considering instability in social structure
NASA Astrophysics Data System (ADS)
Salehi, Sajjad; Taghiyareh, Fattaneh
2016-06-01
Opinion formation is a process through which interactions of individuals and dynamism of their opinions in effect of neighbors are modeled. In this paper, in an effort to model the opinion formation more realistically, we have introduced a model that considers the role of network structure in opinion dynamics. In this model, each individual changes his opinion in a way so as to decrease its difference with the opinion of trusted neighbors while he intensifies his dissention with the untrusted ones. Considering trust/distrust relations as a signed network, we have defined a structural indicator which shows the degree of instability in social structure and is calculated based on the structural balance theory. It is also applied as feedback to the opinion formation process affecting its dynamics. Our simulation results show formation of a set of clusters containing individuals holding opinions having similar values. Also, the opinion value of each individual is far from the ones of distrusted neighbors. Since this model considers distrust and instability of relations in society, it can offer a more realistic model of opinion formation.
NASA Astrophysics Data System (ADS)
Hirvonen, Petri; Ervasti, Mikko M.; Fan, Zheyong; Jalalvand, Morteza; Seymour, Matthew; Vaez Allaei, S. Mehdi; Provatas, Nikolas; Harju, Ari; Elder, Ken R.; Ala-Nissila, Tapio
2016-07-01
We extend the phase field crystal (PFC) framework to quantitative modeling of polycrystalline graphene. PFC modeling is a powerful multiscale method for finding the ground state configurations of large realistic samples that can be further used to study their mechanical, thermal, or electronic properties. By fitting to quantum-mechanical density functional theory (DFT) calculations, we show that the PFC approach is able to predict realistic formation energies and defect structures of grain boundaries. We provide an in-depth comparison of the formation energies between PFC, DFT, and molecular dynamics (MD) calculations. The DFT and MD calculations are initialized using atomic configurations extracted from PFC ground states. Finally, we use the PFC approach to explicitly construct large realistic polycrystalline samples and characterize their properties using MD relaxation to demonstrate their quality.
A two-joint human posture control model with realistic neural delays.
Li, Yao; Levine, William S; Loeb, Gerald E
2012-09-01
During quiet standing, humans tend to sway with a distinctive pattern that has been difficult to capture with simple engineering models. We have developed a nonlinear optimal control model for posture regulation. The proposed model consists of two main components: body dynamics and performance measure. The body dynamics are those of a double inverted pendulum in the sagittal plane controlled by ankle and hip torques. The performance measure is nonlinear quartic in the center of pressure and quadratic in the controls. Realistic values for both sensory and motor delays are included in the dynamic model. This nonlinear quartic regulator problem is solved approximately by the model predictive control technique. The resulting feedback control replicates both the experimentally observed sway and the coordinated nonlinear response. It should also use less muscular energy than other comparable controls. The method can easily be extended to more complex models of posture regulation. PMID:22692939
Time-variability of alpha from realistic models of Oklo reactors
NASA Astrophysics Data System (ADS)
Gould, Chris; Sharapov, Eduard; Lamoreaux, Steve
2006-10-01
We reanalyze Oklo ^149Sm data using realistic models of the natural nuclear reactors. Disagreements among recent Oklo determinations of the time evolution of α, the electromagnetic fine structure constant, are shown to be due to different reactor models, which led to different neutron spectra used in the calculations. We use known Oklo reactor epithermal spectral indices as criteria for selecting realistic reactor models. Two Oklo reactors, RZ2 and RZ10, were modeled with MCNP. The resulting neutron spectra were used to calculate the change in the ^149Sm effective neutron capture cross section as a function of a possible shift in the energy of the 97.3-meV resonance. We independently deduce ancient ^149Sm effective cross sections, and use these values to set limits on the time-variation of α. Our study resolves a contradictory situation with previous Oklo α-results. Our suggested 2 σ bound on a possible time variation of α over two billion years is stringent: -0.11 <=δαα <=0.24, in units of 10-7, but model dependent in that it assumes only α has varied over time.
Realistic multi-cellular dosimetry for 177Lu-labelled antibodies: model and application
NASA Astrophysics Data System (ADS)
Marcatili, S.; Pichard, A.; Courteau, A.; Ladjohounlou, R.; Navarro-Teulon, I.; Repetto-Llamazares, A.; Heyerdahl, H.; Dahle, J.; Pouget, J. P.; Bardiès, M.
2016-10-01
Current preclinical dosimetric models often fail to take account of the complex nature of absorbed dose distribution typical of in vitro clonogenic experiments in targeted radionuclide therapy. For this reason, clonogenic survival is often expressed as a function of added activity rather than the absorbed dose delivered to cells/cell nuclei. We designed a multi-cellular dosimetry model that takes into account the realistic distributions of cells in the Petri dish, for the establishment of survival curves as a function of the absorbed dose. General-purpose software tools were used for the generation of realistic, randomised 3D cell culture geometries based on experimentally determined parameters (cell size, cell density, cluster density, average cluster size, cell cumulated activity). A mixture of Monte Carlo and analytical approaches was implemented in order to achieve as accurate as possible results while reducing calculation time. The model was here applied to clonogenic survival experiments carried out to compare the efficacy of Betalutin®, a novel 177Lu-labelled antibody radionuclide conjugate for the treatment of non-Hodgkin lymphoma, to that of 177Lu-labelled CD20-specific (rituximab) and non-specific antibodies (Erbitux) on lymphocyte B cells. The 3D cellular model developed allowed a better understanding of the radiative and non-radiative processes associated with cellular death. Our approach is generic and can also be applied to other radiopharmaceuticals and cell distributions.
Using coronal seismology to estimate the magnetic field strength in a realistic coronal model
NASA Astrophysics Data System (ADS)
Chen, F.; Peter, H.
2015-09-01
Aims: Coronal seismology is used extensively to estimate properties of the corona, e.g. the coronal magnetic field strength is derived from oscillations observed in coronal loops. We present a three-dimensional coronal simulation, including a realistic energy balance in which we observe oscillations of a loop in synthesised coronal emission. We use these results to test the inversions based on coronal seismology. Methods: From the simulation of the corona above an active region, we synthesise extreme ultraviolet emission from the model corona. From this, we derive maps of line intensity and Doppler shift providing synthetic data in the same format as obtained from observations. We fit the (Doppler) oscillation of the loop in the same fashion as done for observations to derive the oscillation period and damping time. Results: The loop oscillation seen in our model is similar to imaging and spectroscopic observations of the Sun. The velocity disturbance of the kink oscillation shows an oscillation period of 52.5 s and a damping time of 125 s, which are both consistent with the ranges of periods and damping times found in observations. Using standard coronal seismology techniques, we find an average magnetic field strength of Bkink = 79 G for our loop in the simulation, while in the loop the field strength drops from roughly 300 G at the coronal base to 50 G at the apex. Using the data from our simulation, we can infer what the average magnetic field derived from coronal seismology actually means. It is close to the magnetic field strength in a constant cross-section flux tube, which would give the same wave travel time through the loop. Conclusions: Our model produced a realistic looking loop-dominated corona, and provides realistic information on the oscillation properties that can be used to calibrate and better understand the result from coronal seismology. A movie associated with Fig. 1 is available in electronic form at http://www.aanda.org
Quantum Contextuality for a Three-Level System Sans Realist Model
NASA Astrophysics Data System (ADS)
Pan, A. K.; Mandal, K.
2016-08-01
Recently, an interesting form of non-classical effect which can be considered as a form of contextuality within quantum mechanics, has been demonstrated for a four-level system by discriminating the different routes that are taken for measuring a single observable. In this paper, we provide a simpler version of that proof for a single qutrit, which is also within the formalism of quantum mechanics and without recourse to any realist hidden variable model. The degeneracy of the eigenvalues and the L üder projection rule play important role in our proof.
Bray, O.H. |
1994-04-01
This paper describes a natural language based, semantic information modeling methodology and explores its use and value in clarifying and comparing political science theories and frameworks. As an example, the paper uses this methodology to clarify and compare some of the basic concepts and relationships in the realist (e.g. Waltz) and the liberal (e.g. Rosenau) paradigms for international relations. The methodology can provide three types of benefits: (1) it can clarify and make explicit exactly what is meant by a concept; (2) it can often identify unanticipated implications and consequence of concepts and relationships; and (3) it can help in identifying and operationalizing testable hypotheses.
Modeling short-term dynamics and variability for realistic interactive facial animation.
Stoiber, Nicolas; Breton, Gaspard; Seguier, Renaud
2010-01-01
Modern modeling and rendering techniques have produced nearly photorealistic face models, but truly expressive digital faces also require natural-looking movements. Virtual characters in today's applications often display unrealistic facial expressions. Indeed, facial animation with traditional schemes such as keyframing and motion capture demands expertise. Moreover, the traditional schemes aren't adapted to interactive applications that require the real-time generation of context-dependent movements. A new animation system produces realistic expressive facial motion at interactive speed. The system relies on a set of motion models controlling facial-expression dynamics. The models are fitted on captured motion data and therefore retain the dynamic signature of human facial expressions. They also contain a nondeterministic component that ensures the variety of the long-term visual behavior. This system can efficiently animate any synthetic face. The video illustrates interactive use of a system that generates facial-animation sequences.
Modeling the Earth's magnetospheric magnetic field confined within a realistic magnetopause
NASA Technical Reports Server (NTRS)
Tsyganenko, N. A.
1995-01-01
Empirical data-based models of the magnetosphereic magnetic field have been widely used during recent years. However, the existing models (Tsyganenko, 1987, 1989a) have three serious deficiencies: (1) an unstable de facto magnetopause, (2) a crude parametrization by the K(sub p) index, and (3) inaccuracies in the equatorial magnetotail B(sub z) values. This paper describes a new approach to the problem; the essential new features are (1) a realistic shape and size of the magnetopause, based on fits to a large number of observed crossing (allowing a parametrization by the solar wind pressure), (2) fully controlled shielding of the magnetic field produced by all magnetospheric current systems, (3) new flexible representations for the tail and ring currents, and (4) a new directional criterion for fitting the model field to spacecraft data, providing improved accuracy for field line mapping. Results are presented from initial efforts to create models assembled from these modules and calibrated against spacecraft data sets.
Modeling short-term dynamics and variability for realistic interactive facial animation.
Stoiber, Nicolas; Breton, Gaspard; Seguier, Renaud
2010-01-01
Modern modeling and rendering techniques have produced nearly photorealistic face models, but truly expressive digital faces also require natural-looking movements. Virtual characters in today's applications often display unrealistic facial expressions. Indeed, facial animation with traditional schemes such as keyframing and motion capture demands expertise. Moreover, the traditional schemes aren't adapted to interactive applications that require the real-time generation of context-dependent movements. A new animation system produces realistic expressive facial motion at interactive speed. The system relies on a set of motion models controlling facial-expression dynamics. The models are fitted on captured motion data and therefore retain the dynamic signature of human facial expressions. They also contain a nondeterministic component that ensures the variety of the long-term visual behavior. This system can efficiently animate any synthetic face. The video illustrates interactive use of a system that generates facial-animation sequences. PMID:20650728
Hoshi, Koki; Irisawa, Atsushi; Shibukawa, Goro; Yamabe, Akane; Fujisawa, Mariko; Igarashi, Ryo; Yoshida, Yoshitsugu; Abe, Yoko; Imbe, Koh
2016-01-01
Background and study aims: Trainees are required to learn EUS-FNA using a model before working with a patient. The aim of the current study was to validate a new training model developed for EUS-FNA. Patients and methods: Several fresh chicken tenderloins were embedded as target lesions in the submucosal layer of an isolated porcine stomach. The stomach was fixed to a plate with nails, and was placed in a tub filled with water. The primary endpoint was feasibility of the newly developed model for EUS-FNA training, evaluated as follows: 1) visualization of the target lesion with blinding for lesion location; 2) penetrability of the needle; 3) sampling rate of macroscopic specimen; and 4) ROSE capability. Secondary endpoints were its durability and utility for multiple EUS-FNA procedures during EUS-FNA training, and the ease and cost of preparing the model. Results: Six endoscopists (1 expert, 5 trainees) attempted EUS-FNA procedures using this model. The target lesion could be identified clearly, and EUS-FNA could be performed with realistic resistance felt. In addition, rapid on-site evaluation could be easily achieved. Based on 10 needlings by each endoscopist, adequate specimens for histology could be macroscopically taken with an average 85 % success rate. Visibility and maneuverability were maintained throughout all needlings. Preparation time for this model was less than 30 minutes with a total cost of $ 22. Conclusions: An easy-to-use and inexpensive training model with a realistic feel of needling was created. This model can potentially enable beginners to practice safe and effective EUS-FNA procedures. PMID:27652292
Hoshi, Koki; Irisawa, Atsushi; Shibukawa, Goro; Yamabe, Akane; Fujisawa, Mariko; Igarashi, Ryo; Yoshida, Yoshitsugu; Abe, Yoko; Imbe, Koh
2016-01-01
Background and study aims: Trainees are required to learn EUS-FNA using a model before working with a patient. The aim of the current study was to validate a new training model developed for EUS-FNA. Patients and methods: Several fresh chicken tenderloins were embedded as target lesions in the submucosal layer of an isolated porcine stomach. The stomach was fixed to a plate with nails, and was placed in a tub filled with water. The primary endpoint was feasibility of the newly developed model for EUS-FNA training, evaluated as follows: 1) visualization of the target lesion with blinding for lesion location; 2) penetrability of the needle; 3) sampling rate of macroscopic specimen; and 4) ROSE capability. Secondary endpoints were its durability and utility for multiple EUS-FNA procedures during EUS-FNA training, and the ease and cost of preparing the model. Results: Six endoscopists (1 expert, 5 trainees) attempted EUS-FNA procedures using this model. The target lesion could be identified clearly, and EUS-FNA could be performed with realistic resistance felt. In addition, rapid on-site evaluation could be easily achieved. Based on 10 needlings by each endoscopist, adequate specimens for histology could be macroscopically taken with an average 85 % success rate. Visibility and maneuverability were maintained throughout all needlings. Preparation time for this model was less than 30 minutes with a total cost of $ 22. Conclusions: An easy-to-use and inexpensive training model with a realistic feel of needling was created. This model can potentially enable beginners to practice safe and effective EUS-FNA procedures.
Causal effect models for realistic individualized treatment and intention to treat rules.
van der Laan, Mark J; Petersen, Maya L
2007-01-01
Marginal structural models (MSM) are an important class of models in causal inference. Given a longitudinal data structure observed on a sample of n independent and identically distributed experimental units, MSM model the counterfactual outcome distribution corresponding with a static treatment intervention, conditional on user-supplied baseline covariates. Identification of a static treatment regimen-specific outcome distribution based on observational data requires, beyond the standard sequential randomization assumption, the assumption that each experimental unit has positive probability of following the static treatment regimen. The latter assumption is called the experimental treatment assignment (ETA) assumption, and is parameter-specific. In many studies the ETA is violated because some of the static treatment interventions to be compared cannot be followed by all experimental units, due either to baseline characteristics or to the occurrence of certain events over time. For example, the development of adverse effects or contraindications can force a subject to stop an assigned treatment regimen.In this article we propose causal effect models for a user-supplied set of realistic individualized treatment rules. Realistic individualized treatment rules are defined as treatment rules which always map into the set of possible treatment options. Thus, causal effect models for realistic treatment rules do not rely on the ETA assumption and are fully identifiable from the data. Further, these models can be chosen to generalize marginal structural models for static treatment interventions. The estimating function methodology of Robins and Rotnitzky (1992) (analogue to its application in Murphy, et. al. (2001) for a single treatment rule) provides us with the corresponding locally efficient double robust inverse probability of treatment weighted estimator.In addition, we define causal effect models for "intention-to-treat" regimens. The proposed intention
Cao Qinghong; Khalil, Shaaban; Ma, Ernest; Okada, Hiroshi
2011-10-01
We discuss how {theta}{sub 13}{ne}0 is accommodated in a recently proposed renormalizable model of neutrino mixing using the non-Abelian discrete symmetry T{sub 7} in the context of a supersymmetric extension of the standard model with gauged U(1){sub B-L}. We predict a correlation between {theta}{sub 13} and {theta}{sub 23}, as well as the effective neutrino mass m{sub ee} in neutrinoless double beta decay.
NASA Astrophysics Data System (ADS)
Desai, Bipin R.; Xu, Guang-Hua
1990-04-01
Based on the idea that electromagnetism is responsible for mass differences within isotopic multiplets (e.g., pointlike neutron and proton or u and d quarks), we generalize an SU(2)×U(1) model in a toy field theory of vectors to a supersymmetric model and investigate the finite mass difference within the isotopic doublet. It is found that under soft-supersymmetry breaking, a positive n-p mass difference can be obtained under reasonable assumptions for the parameters involved.
Realistic texture extraction for 3D face models robust to self-occlusion
NASA Astrophysics Data System (ADS)
Qu, Chengchao; Monari, Eduardo; Schuchert, Tobias; Beyerer, Jürgen
2015-02-01
In the context of face modeling, probably the most well-known approach to represent 3D faces is the 3D Morphable Model (3DMM). When 3DMM is fitted to a 2D image, the shape as well as the texture and illumination parameters are simultaneously estimated. However, if real facial texture is needed, texture extraction from the 2D image is necessary. This paper addresses the possible problems in texture extraction of a single image caused by self-occlusion. Unlike common approaches that leverage the symmetric property of the face by mirroring the visible facial part, which is sensitive to inhomogeneous illumination, this work first generates a virtual texture map for the skin area iteratively by averaging the color of neighbored vertices. Although this step creates unrealistic, overly smoothed texture, illumination stays constant between the real and virtual texture. In the second pass, the mirrored texture is gradually blended with the real or generated texture according to the visibility. This scheme ensures a gentle handling of illumination and yet yields realistic texture. Because the blending area only relates to non-informative area, main facial features still have unique appearance in different face halves. Evaluation results reveal realistic rendering in novel poses robust to challenging illumination conditions and small registration errors.
Realistic Modeling of Multi-Scale MHD Dynamics of the Solar Atmosphere
NASA Technical Reports Server (NTRS)
Kitiashvili, Irina; Mansour, Nagi N.; Wray, Alan; Couvidat, Sebastian; Yoon, Seokkwan; Kosovichev, Alexander
2014-01-01
Realistic 3D radiative MHD simulations open new perspectives for understanding the turbulent dynamics of the solar surface, its coupling to the atmosphere, and the physical mechanisms of generation and transport of non-thermal energy. Traditionally, plasma eruptions and wave phenomena in the solar atmosphere are modeled by prescribing artificial driving mechanisms using magnetic or gas pressure forces that might arise from magnetic field emergence or reconnection instabilities. In contrast, our 'ab initio' simulations provide a realistic description of solar dynamics naturally driven by solar energy flow. By simulating the upper convection zone and the solar atmosphere, we can investigate in detail the physical processes of turbulent magnetoconvection, generation and amplification of magnetic fields, excitation of MHD waves, and plasma eruptions. We present recent simulation results of the multi-scale dynamics of quiet-Sun regions, and energetic effects in the atmosphere and compare with observations. For the comparisons we calculate synthetic spectro-polarimetric data to model observational data of SDO, Hinode, and New Solar Telescope.
Modeling wave propagation in realistic heart geometries using the phase-field method
NASA Astrophysics Data System (ADS)
Fenton, Flavio H.; Cherry, Elizabeth M.; Karma, Alain; Rappel, Wouter-Jan
2005-03-01
We present a novel algorithm for modeling electrical wave propagation in anatomical models of the heart. The algorithm uses a phase-field approach that represents the boundaries between the heart muscle and the surrounding medium as a spatially diffuse interface of finite thickness. The chief advantage of this method is to automatically handle the boundary conditions of the voltage in complex geometries without the need to track the location of these boundaries explicitly. The algorithm is shown to converge accurately in nontrivial test geometries with no-flux (zero normal current) boundary conditions as the width of the diffuse interface becomes small compared to the width of the cardiac action potential wavefront. Moreover, the method is illustrated for anatomically realistic models of isolated rabbit and canine ventricles as well as human atria.
A Madden-Julian oscillation event realistically simulated by a global cloud-resolving model.
Miura, Hiroaki; Satoh, Masaki; Nasuno, Tomoe; Noda, Akira T; Oouchi, Kazuyoshi
2007-12-14
A Madden-Julian Oscillation (MJO) is a massive weather event consisting of deep convection coupled with atmospheric circulation, moving slowly eastward over the Indian and Pacific Oceans. Despite its enormous influence on many weather and climate systems worldwide, it has proven very difficult to simulate an MJO because of assumptions about cumulus clouds in global meteorological models. Using a model that allows direct coupling of the atmospheric circulation and clouds, we successfully simulated the slow eastward migration of an MJO event. Topography, the zonal sea surface temperature gradient, and interplay between eastward- and westward-propagating signals controlled the timing of the eastward transition of the convective center. Our results demonstrate the potential making of month-long MJO predictions when global cloud-resolving models with realistic initial conditions are used.
More Realistic Face Model Surface Improves Relevance of Pediatric In-Vitro Aerosol Studies
Amirav, Israel; Halamish, Asaf; Gorenberg, Miguel; Omar, Hamza; Newhouse, Michael T.
2015-01-01
Background Various hard face models are commonly used to evaluate the efficiency of aerosol face masks. Softer more realistic “face” surface materials, like skin, deform upon mask application and should provide more relevant in-vitro tests. Studies that simultaneously take into consideration many of the factors characteristic of the in vivo face are lacking. These include airways, various application forces, comparison of various devices, comparison with a hard-surface model and use of a more representative model face based on large numbers of actual faces. Aim To compare mask to “face” seal and aerosol delivery of two pediatric masks using a soft vs. a hard, appropriately representative, pediatric face model under various applied forces. Methods Two identical face models and upper airways replicas were constructed, the only difference being the suppleness and compressibility of the surface layer of the “face.” Integrity of the seal and aerosol delivery of two different masks [AeroChamber (AC) and SootherMask (SM)] were compared using a breath simulator, filter collection and realistic applied forces. Results The soft “face” significantly increased the delivery efficiency and the sealing characteristics of both masks. Aerosol delivery with the soft “face” was significantly greater for the SM compared to the AC (p< 0.01). No statistically significant difference between the two masks was observed with the hard “face.” Conclusions The material and pliability of the model “face” surface has a significant influence on both the seal and delivery efficiency of face masks. This finding should be taken into account during in-vitro aerosol studies. PMID:26090661
Supersymmetrizing massive gravity
NASA Astrophysics Data System (ADS)
Malaeb, O.
2013-07-01
When four scalar fields with global Lorentz symmetry are coupled to gravity and take a vacuum expectation value, breaking diffeomorphism invariance spontaneously, the graviton becomes massive. This model is supersymmetrized by considering four N=1 chiral superfields with global Lorentz symmetry. The global supersymmetry is promoted to a local one using the rules of tensor calculus of coupling the N=1 supergravity Lagrangian to the four chiral multiplets. When the scalar components of the chiral multiplets zA acquire a vacuum expectation value, both diffeomorphism invariance and local supersymmetry are broken spontaneously. The global Lorentz index A becomes identified with the space-time Lorentz index, making the scalar fields zA vectors and the chiral spinors ψA spin-3/2 Rarita-Schwinger fields. We show that the spectrum of the model in the broken phase consists of a massive spin-2 field, two massive spin-3/2 fields with different mass and a massive vector.
Dynamic Rupture and Ground Motion Modeling on Realistically Complex Strike-Slip Faults
NASA Astrophysics Data System (ADS)
Lozos, Julian Charles
Faults are complex structures: they are geometrically complex, and have variable stress conditions and frictional behaviors along their length. In addition, faults exist in heterogeneous settings, in terms of surrounding geology, and in terms of regional and local stresses. These individual types of heterogeneity all contribute to complex dynamic rupture behaviors and ground motion distributions, as inferred from observational data and supported by previous modeling studies. In this study, we investigate the effects of individual types of complexity, and we combine different types of heterogeneity in order to enhance the realism of models of real-world faults. We use the finite element method to conduct dynamic rupture models of earthquakes on faults with complex geometry, initial stresses, frictional parameters, and surrounding geology, and with combinations of these factors, in order to investigate the effects of this complexity on fault interactions, rupture extent, and ground motion. In particular, we investigate the effect of critical weakening distance on the ability of rupture to propagate through a discontinuity in the fault trace, the effect of a small fault between the larger strands of a stepover on the ability of rupture to jump the stepover, and how zones of aseismic creep affect rupture through locked portions of the same fault. We also construct realistically complex models of the northern San Jacinto Fault, California, incorporating realistic geometry, velocity structure, and combined regional and stochastic stress fields. We find that the distribution of complexity of any type on the fault, which leads to heterogeneous fault strength, has the primary controlling effect on rupture behavior. The relative strength or weakness of the fault, rather than the actual value, is most important. We also find that the balance of the energy budget is crucial; if too much energy is redirected into fracture, rupture stops. Lastly, we find that each type of
The boundary layer over turbine blade models with realistic rough surfaces
NASA Astrophysics Data System (ADS)
McIlroy, Hugh M., Jr.
The impact of turbine blade surface roughness on aerodynamic performance and heat loads is well known. Over time, as the turbine blades are exposed to heat loads, the external surfaces of the blades become rough. Also, for film-cooled blades, surface degradation can have a significant impact on film-cooling effectiveness. Many studies have been conducted on the effects of surface degradation/roughness on engine performance but most investigations have modeled the rough surfaces with uniform or two-dimensional roughness patterns. The objective of the present investigation is to conduct measurements that will reveal the influence of realistic surface roughness on the near-wall behavior of the boundary layer. Measurements have been conducted at the Matched-Index-of-Refraction (MIR) Facility at the Idaho National Engineering and Environmental Laboratory with a laser Doppler velocimeter. A flat plate model of a turbine blade has been developed that produces a transitional boundary layer, elevated freestream turbulence and an accelerating freestream in order to simulate conditions on the suction side of a high-pressure turbine blade. Boundary layer measurements have been completed over a smooth plate model and over a model with a strip of realistic rough surface. The realistic rough surface was developed by scaling actual turbine blade surface data that was provided by U.S. Air Force Research Laboratory. The results indicate that bypass transition occurred very early in the flow over the model and that the boundary layer remained unstable throughout the entire length of the test plate; the boundary layer thickness and momentum thickness Reynolds numbers increased over the rough patch; and the shape factor increased over the rough patch but then decreased downstream of the patch relative to the smooth plate case; in the rough patch case the flow experienced two transition reversals with laminar-like behavior achieved by the end of the test plate; streamwise turbulence
LipidBuilder: A Framework To Build Realistic Models for Biological Membranes.
Bovigny, Christophe; Tamò, Giorgio; Lemmin, Thomas; Maïno, Nicolas; Dal Peraro, Matteo
2015-12-28
The physical and chemical characterization of biological membranes is of fundamental importance for understanding the functional role of lipid bilayers in shaping cells and organelles, steering vesicle trafficking and promoting membrane-protein signaling. Molecular dynamics simulations stand as a powerful tool to probe the properties of membranes at atomistic level. However, the biological membrane is highly complex, and closely mimicking its physiological constitution in silico is not a straightforward task. Here, we present LipidBuilder, a framework for creating and storing models of biologically relevant phospholipid species with acyl tails of heterogeneous composition. LipidBuilder also enables the assembly of these database-stored lipids into realistic bilayers featuring asymmetric distribution on layer leaflets and concentration of given membrane constituents as defined, for example, by lipidomics experiments. The ability of LipidBuilder to assemble robust membrane models was validated by simulating membranes of homogeneous lipid composition for which experimental data are available. Furthermore, taking advantage of the extensive lipid headgroup repertoire, we assembled models of membranes of heterogeneous nature as naturally found in viral (phage PRD1), bacterial (Salmonella enterica, Laurinavicius , S. ; Kakela , R. ; Somerharju , P. ; Bamford , D. H. ; Virology 2004 , 322 , 328 - 336 ) and plant (Chlorella kessleri, Rezanka , T. ; Podojil , M. ; J. Chromatogr. 1989 , 463 , 397 - 408 ) organisms. These realistic membrane models were built using a near-exact lipid composition revealed from analytical chemistry experiments. We suggest LipidBuilder as a useful tool to model biological membranes of near-biological complexity, and as a robust complement to the current efforts to characterize the biophysical properties of biological membrane using molecular simulation. PMID:26606666
Kang, Sin Kyu; Kato, Akina; Morozumi, Takuya; Yokozaki, Norimi
2010-01-01
We study the radiative electroweak symmetry breaking and the relic abundance of neutralino dark matter in the supersymmetric type I seesaw model. In this model, there exist threshold corrections to Higgs bilinear terms coming from heavy singlet sneutrino loops, which make the soft supersymmetry breaking (SSB) mass for up-type Higgs shift at the seesaw scale and thus a minimization condition for the Higgs potential is affected. We show that the required fine-tuning between the Higgsino mass parameter {mu} and the SSB mass for up-type Higgs may be reduced at the electroweak scale, due to the threshold corrections. We also present how the parameter {mu} depends on the SSB B-parameter for heavy singlet sneutrinos. Since the property of neutralino dark matter is quite sensitive to the size of {mu}, we discuss how the relic abundance of neutralino dark matter is affected by the SSB B-parameter. Taking the SSB B-parameter of order of a few hundreds TeV, the required relic abundance of neutralino dark matter can be correctly achieved. In this case, dark matter is a mixture of bino and Higgsino, under the condition that gaugino masses are universal at the grand unification scale.
NASA Astrophysics Data System (ADS)
Bandyopadhyay, Priyotosh; Corianò, Claudio; Costantini, Antonio
2015-12-01
We investigate the scalar sector in an extension of the Minimal Supersymmetric Standard Model (MSSM) containing a SU(2) Higgs triplet of zero hypercharge and a gauge singlet beside the SU(2) scalar doublets. In particular, we focus on a scenario of this model which allows a light pseudoscalar and/or a scalar below 100 GeV, consistent with the most recent data from the LHC and the earlier data from the LEP experiments. We analyze the exotic decay of the discovered Higgs ( h 125) into two light (hidden) Higgs bosons present in the extension. The latter are allowed by the uncertainties in the Higgs decay h 125 → WW ∗, h 125 → ZZ ∗ and h 125 → γγ. The study of the parameter space for such additional scalars/pseudoscalars decay of the Higgs is performed in the gluon fusion channel. The extra hidden Higgs bosons of the enlarged scalar sector, if they exist, will then decay into lighter fermion paris, i.e., boverline{b} , τ overline{τ} and μ overline{μ} via the mixing with the doublets. A detailed simulation using PYTHIA of the 2 b + 2 τ , ≥ 3 τ , 2 b + 2 μ and 2 τ + 2 μ final states is presented. From our analysis we conclude that, depending on the selected benchmark points, such decay modes can be explored with an integrated luminosity of 25 fb-1 at the LHC at a center of mass energy of 13 TeV.
Mordhorst, Mylena; Heidlauf, Thomas; Röhrle, Oliver
2015-01-01
This paper presents a novel multiscale finite element-based framework for modelling electromyographic (EMG) signals. The framework combines (i) a biophysical description of the excitation–contraction coupling at the half-sarcomere level, (ii) a model of the action potential (AP) propagation along muscle fibres, (iii) a continuum-mechanical formulation of force generation and deformation of the muscle, and (iv) a model for predicting the intramuscular and surface EMG. Owing to the biophysical description of the half-sarcomere, the model inherently accounts for physiological properties of skeletal muscle. To demonstrate this, the influence of membrane fatigue on the EMG signal during sustained contractions is investigated. During a stimulation period of 500 ms at 100 Hz, the predicted EMG amplitude decreases by 40% and the AP propagation velocity decreases by 15%. Further, the model can take into account contraction-induced deformations of the muscle. This is demonstrated by simulating fixed-length contractions of an idealized geometry and a model of the human tibialis anterior muscle (TA). The model of the TA furthermore demonstrates that the proposed finite element model is capable of simulating realistic geometries, complex fibre architectures, and can include different types of heterogeneities. In addition, the TA model accounts for a distributed innervation zone, different fibre types and appeals to motor unit discharge times that are based on a biophysical description of the α motor neurons. PMID:25844148
Malone, Emma; Jehl, Markus; Arridge, Simon; Betcke, Timo; Holder, David
2014-06-01
We investigate the application of multifrequency electrical impedance tomography (MFEIT) to imaging the brain in stroke patients. The use of MFEIT could enable early diagnosis and thrombolysis of ischaemic stroke, and therefore improve the outcome of treatment. Recent advances in the imaging methodology suggest that the use of spectral constraints could allow for the reconstruction of a one-shot image. We performed a simulation study to investigate the feasibility of imaging stroke in a head model with realistic conductivities. We introduced increasing levels of modelling errors to test the robustness of the method to the most common sources of artefact. We considered the case of errors in the electrode placement, spectral constraints, and contact impedance. The results indicate that errors in the position and shape of the electrodes can affect image quality, although our imaging method was successful in identifying tissues with sufficiently distinct spectra.
Modeling and Simulation for Realistic Propagation Environments of Communications Signals at SHF Band
NASA Technical Reports Server (NTRS)
Ho, Christian
2005-01-01
In this article, most of widely accepted radio wave propagation models that have proven to be accurate in practice as well as numerically efficient at SHF band will be reviewed. Weather and terrain data along the signal's paths can be input in order to more accurately simulate the propagation environments under particular weather and terrain conditions. Radio signal degradation and communications impairment severity will be investigated through the realistic radio propagation channel simulator. Three types of simulation approaches in predicting signal's behaviors are classified as: deterministic, stochastic and attenuation map. The performance of the simulation can be evaluated under operating conditions for the test ranges of interest. Demonstration tests of a real-time propagation channel simulator will show the capabilities and limitations of the simulation tool and underlying models.
Quark-lepton mass relation in a realistic A4 extension of the Standard Model
NASA Astrophysics Data System (ADS)
King, S. F.; Morisi, S.; Peinado, E.; Valle, J. W. F.
2013-07-01
We propose a realistic A4 extension of the Standard Model involving a particular quark-lepton mass relation, namely that the ratio of the third family mass to the geometric mean of the first and second family masses are equal for down-type quarks and charged leptons. This relation, which is approximately renormalization group invariant, is usually regarded as arising from the Georgi-Jarlskog relations, but in the present model there is no unification group or supersymmetry. In the neutrino sector we propose a simple modification of the so-called Zee-Wolfenstein mass matrix pattern which allows an acceptable reactor angle along with a deviation of the atmospheric and solar angles from their bi-maximal values. Quark masses, mixing angles and CP violation are well described by a numerical fit.
NASA Astrophysics Data System (ADS)
Ladeinde, Foluso; Alabi, Ken; Li, Wenhai
2015-11-01
The problem of generating design data for the operation of a farm of wind turbines for clean energy production is quite complicated, if properly done. Potential flow theories provide some models, but these are not suitable for the massive aerodynamic separation and turbulence that characterize many realistic wind turbine applications. Procedures, such as computational fluid dynamics (CFD), which can potentially resolve some of the accuracy problems with the purely theoretical approach, are quite expensive to use, and often prohibit real-time design and control. In our work, we seek affordable and acceptably-accurate models derived from the foregoing approaches. The simulation used in our study is based on high-fidelity CFD, meaning that we use high-order (compact-scheme based), mostly large-eddy simulation methods, with due regards for the proper treatment of the stochastic inflow turbulence data. Progress on the project described herein will be presented.
NASA Astrophysics Data System (ADS)
Khan, Saki
2016-06-01
We present a minimal renormalizable non-supersymmetric S O(10) grand unified model with a symmetry breaking sector consisting of Higgs fields in the 54H + 126H + 10H representations. This model admits a single intermediate scale associated with Pati-Salam symmetry along with a discrete parity. Spontaneous symmetry breaking, the unification of gauge couplings and proton lifetime estimates are studied in detail in this framework. Including threshold corrections self-consistently, obtained from a full analysis of the Higgs potential, we show that the model is compatible with the current experimental bound on proton lifetime. The model generally predicts an upper bound of few times 1035 yrs for proton lifetime, which is not too far from the present Super-Kamiokande limit of τp ≳ 1.29 × 1034 yrs. With the help of a Pecci-Quinn symmetry and the resulting axion, the model provides a suitable dark matter candidate while also solving the strong CP problem. The intermediate scale, MI ≈ (1013 - 1014) GeV which is also the B - L scale, is of the right order for the right-handed neutrino mass which enables a successful description of light neutrino masses and oscillations. The Yukawa sector of the model consists of only two matrices in family space and leads to a predictive scenario for quark and lepton masses and mixings. The branching ratios for proton decay are calculable with the leading modes being p → e+π0 and p →v ¯π+ . Even though the model predicts no new physics within the reach of LHC, the next generation proton decay detectors and axion search experiments have the capability to pass verdict on this minimal scenario.
Model of a realistic InP surface quantum dot extrapolated from atomic force microscopy results.
Barettin, Daniele; De Angelis, Roberta; Prosposito, Paolo; Auf der Maur, Matthias; Casalboni, Mauro; Pecchia, Alessandro
2014-05-16
We report on numerical simulations of a zincblende InP surface quantum dot (QD) on In₀.₄₈Ga₀.₅₂ buffer. Our model is strictly based on experimental structures, since we extrapolated a three-dimensional dot directly by atomic force microscopy results. Continuum electromechanical, [Formula: see text] bandstructure and optical calculations are presented for this realistic structure, together with benchmark calculations for a lens-shape QD with the same radius and height of the extrapolated dot. Interesting similarities and differences are shown by comparing the results obtained with the two different structures, leading to the conclusion that the use of a more realistic structure can provide significant improvements in the modeling of QDs fact, the remarkable splitting for the electron p-like levels of the extrapolated dot seems to prove that a realistic experimental structure can reproduce the right symmetry and a correct splitting usually given by atomistic calculations even within the multiband [Formula: see text] approach. Moreover, the energy levels and the symmetry of the holes are strongly dependent on the shape of the dot. In particular, as far as we know, their wave function symmetries do not seem to resemble to any results previously obtained with simulations of zincblende ideal structures, such as lenses or truncated pyramids. The magnitude of the oscillator strengths is also strongly dependent on the shape of the dot, showing a lower intensity for the extrapolated dot, especially for the transition between the electrons and holes ground state, as a result of a relevant reduction of the wave functions overlap. We also compare an experimental photoluminescence spectrum measured on an homogeneous sample containing about 60 dots with a numerical ensemble average derived from single dot calculations. The broader energy range of the numerical spectrum motivated us to perform further verifications, which have clarified some aspects of the experimental
Supersymmetric Higgs Bosons in Weak Boson Fusion
Hollik, Wolfgang; Plehn, Tilman; Rauch, Michael; Rzehak, Heidi
2009-03-06
We compute the complete supersymmetric next-to-leading-order corrections to the production of a light Higgs boson in weak-boson fusion. The size of the electroweak corrections is of similar order as the next-to-leading-order corrections in the standard model. The supersymmetric QCD corrections turn out to be significantly smaller than expected and than their electroweak counterparts. These corrections are an important ingredient to a precision analysis of the (supersymmetric) Higgs sector at the LHC, either as a known correction factor or as a contribution to the theory error.
Carena, Marcela; Hooper, Dan; Skands, Peter
2006-08-01
In regions of large tanbeta and small mAlpha, searches for heavy neutral minimal supersymmetric standard model (MSSM) Higgs bosons at the Tevatron are promising. At the same time, rates in direct dark matter experiments, such as CDMS, are enhanced in the case of large tanbeta and small mAlpha. As a result, there is a natural interplay between the heavy, neutral Higgs searches at the Tevatron and the region of parameter space explored by CDMS. We show that if the lightest neutralino makes up the dark matter of our universe, current limits from CDMS strongly constrain the prospects of heavy, neutral MSSM Higgs discovery at the Tevatron unless |mu| greater or approximately 400 GeV. The limits of CDMS projected for 2007 will increase this constraint to |mu| greater or approximately 800 GeV. If CDMS does observe neutralinos in the near future, however, it will make the discovery of Higgs bosons at the Tevatron far more likely. PMID:17026093
Dermisek, Radovan; Gunion, John F.; McElrath, Bob
2007-09-01
Completely natural electroweak symmetry breaking is easily achieved in supersymmetric models if there is a SM-like Higgs boson, h, with m{sub h} < or approx. 100 GeV. In the minimal supersymmetric model, such an h decays mainly to bb and is ruled out by LEP constraints. However, if the MSSM Higgs sector is expanded so that h decays mainly to still lighter Higgs bosons, e.g. h{yields}aa, with Br(h{yields}aa)>0.7, and if m{sub a}<2m{sub b}, then the LEP constraints are satisfied even if m{sub h} < or approx. 100 GeV. In this paper, we show that in the next-to-minimal supersymmetric model the above h and a properties (for the lightest CP-even and CP-odd Higgs bosons, respectively) imply a lower bound on Br({upsilon}{yields}{gamma}a) that dedicated runs at present (and future) B factories can explore.
Supersymmetric Higgs bosons and beyond
Carena, Marcela; Kong, Kyoungchul; Ponton, Eduardo; Zurita, Jose
2010-01-01
We consider supersymmetric models that include particles beyond the minimal supersymmetric standard model (MSSM) with masses in the TeV range, and that couple significantly to the MSSM Higgs sector. We perform a model-independent analysis of the spectrum and couplings of the MSSM Higgs fields, based on an effective theory of the MSSM degrees of freedom. The tree-level mass of the lightest CP-even state can easily be above the LEP bound of 114 GeV, thus allowing for a relatively light spectrum of superpartners, restricted only by direct searches. The Higgs spectrum and couplings can be significantly modified compared to the MSSM ones, often allowing for interesting new decay modes. We also observe that the gluon fusion production cross section of the SM-like Higgs can be enhanced with respect to both the standard model and the MSSM.
Supersymmetric Higgs Bosons and Beyond
Carena, Marcela; Kong, Kyoungchul; Ponton, Eduardo; Zurita, Jose; /Fermilab /Buenos Aires U.
2010-08-26
We consider supersymmetric models that include particles beyond the Minimal Supersymmetric Standard Model (MSSM) with masses in the TeV range, and that couple significantly to the MSSM Higgs sector. We perform a model-independent analysis of the spectrum and couplings of the MSSM Higgs fields, based on an effective theory of the MSSM degrees of freedom. The tree-level mass of the lightest CP-even state can easily be above the LEP bound of 114 GeV, thus allowing for a relatively light spectrum of superpartners, restricted only by direct searches. The Higgs spectrum and couplings can be significantly modified compared to the MSSM ones, often allowing for interesting new decay modes. We also observe that the gluon fusion production cross section of the SM-like Higgs can be enhanced with respect to both the Standard Model and the MSSM.
NASA Astrophysics Data System (ADS)
Dünser, Simon; Meyer, Daniel W.
2016-06-01
In most groundwater aquifers, dispersion of tracers is dominated by flow-field inhomogeneities resulting from the underlying heterogeneous conductivity or transmissivity field. This effect is referred to as macrodispersion. Since in practice, besides a few point measurements the complete conductivity field is virtually never available, a probabilistic treatment is needed. To quantify the uncertainty in tracer concentrations from a given geostatistical model for the conductivity, Monte Carlo (MC) simulation is typically used. To avoid the excessive computational costs of MC, the polar Markovian velocity process (PMVP) model was recently introduced delivering predictions at about three orders of magnitude smaller computing times. In artificial test cases, the PMVP model has provided good results in comparison with MC. In this study, we further validate the model in a more challenging and realistic setup. The setup considered is derived from the well-known benchmark macrodispersion experiment (MADE), which is highly heterogeneous and non-stationary with a large number of unevenly scattered conductivity measurements. Validations were done against reference MC and good overall agreement was found. Moreover, simulations of a simplified setup with a single measurement were conducted in order to reassess the model's most fundamental assumptions and to provide guidance for model improvements.
A neural model of how the brain computes heading from optic flow in realistic scenes.
Browning, N Andrew; Grossberg, Stephen; Mingolla, Ennio
2009-12-01
Visually-based navigation is a key competence during spatial cognition. Animals avoid obstacles and approach goals in novel cluttered environments using optic flow to compute heading with respect to the environment. Most navigation models try either explain data, or to demonstrate navigational competence in real-world environments without regard to behavioral and neural substrates. The current article develops a model that does both. The ViSTARS neural model describes interactions among neurons in the primate magnocellular pathway, including V1, MT(+), and MSTd. Model outputs are quantitatively similar to human heading data in response to complex natural scenes. The model estimates heading to within 1.5 degrees in random dot or photo-realistically rendered scenes, and within 3 degrees in video streams from driving in real-world environments. Simulated rotations of less than 1 degrees /s do not affect heading estimates, but faster simulated rotation rates do, as in humans. The model is part of a larger navigational system that identifies and tracks objects while navigating in cluttered environments.
Pulsations of rapidly rotating stars. II. Realistic modelling for intermediate-mass stars
NASA Astrophysics Data System (ADS)
Ouazzani, R.-M.; Roxburgh, I. W.; Dupret, M.-A.
2015-07-01
Context. Very high precision seismic space missions such as CoRoT and Kepler provide the means for testing the modelling of transport processes in stellar interiors. For some stars, such as δ Scuti, γ Doradus, and Be stars, the observed pulsation spectra are modified by rotation to such an extent that it prevents any fruitful interpretation. Aims: Our aim is to characterise acoustic pulsation spectra of realistic stellar models in order to be able to interpret asteroseismic data from such stars. Methods: The 2D oscillation code ACOR, which treats rotation in a non-perturbative manner, is used to study pulsation spectra of highly distorted evolved models of stars. Two-dimensional models of stars are obtained by a self-consistent method that distorts spherically averaged stellar models a posteriori, at any stage of evolution, and for any type of rotation law. Results: Four types of modes are calculated in a very dense frequency spectrum, among which are island modes. The regularity of the island modes spectrum is confirmed and yields a new set of quantum numbers, with which an échelle diagram can be built. Mixed gravito-acoustic modes are calculated in rapidly rotating models for the first time.
Ehrenfest urn revisited: Playing the game on a realistic fluid model
NASA Astrophysics Data System (ADS)
Scalas, Enrico; Martin, Edgar; Germano, Guido
2007-07-01
The Ehrenfest urn process, also known as the dogs and fleas model, is realistically simulated by molecular dynamics of the Lennard-Jones fluid. The key variable is Δz —i.e., the absolute value of the difference between the number of particles in one half of the simulation box and in the other half. This is a pure-jump stochastic process induced, under coarse graining, by the deterministic time evolution of the atomic coordinates. We discuss the Markov hypothesis by analyzing the statistical properties of the jumps and the waiting times between the jumps. In the limit of a vanishing integration time step, the distribution of waiting times becomes closer to an exponential and, therefore, the continuous-time jump stochastic process is Markovian. The random variable Δz behaves as a Markov chain and, in the gas phase, the observed transition probabilities follow the predictions of the Ehrenfest theory.
Turbulent transport measurements in a cold model of GT-burner at realistic flow rates
NASA Astrophysics Data System (ADS)
Gobyzov, Oleg; Chikishev, Leonid; Lobasov, Alexey; Sharaborin, Dmitriy; Dulin, Vladimir; Bilsky, Artur; Tsatiashvili, Vakhtang; Avgustinovich, Valery; Markovich, Dmitriy
2016-03-01
In the present work simultaneous velocity field and passive admixture concentration field measurements at realistic flow-rates conditions in a non-reacting flow in a model of combustion chamber with an industrial mixing device are reported. In the experiments for safety reasons the real fuel (natural gas) was replaced with neon gas to simulate stratification in a strongly swirling flow. Measurements were performed by means of planar laser-induced fluorescence (PLIF) and particle image velocimetry technique (PIV) at Reynolds number, based on the mean flow rate and nozzle diameter, ≈300 000. Details on experimental technique, features of the experimental setup, images and data preprocessing procedures and results of performed measurements are given in the paper. In addition to the raw velocity and admixture concentration data in-depth evaluation approaches aimed for estimation of turbulent kinetic energy (TKE) components, assessment of turbulent Schmidt number and analysis of the gradient closure hypothesis from experimental data are presented in the paper.
Realistic shell-model calculations and exotic nuclei around {sup 132}Sn
Covello, A.; Itaco, N.; Coraggio, L.; Gargano, A.
2008-11-11
We report on a study of exotic nuclei around doubly magic {sup 132}Sn in terms of the shell model employing a realistic effective interaction derived from the CD-Bonn nucleon-nucleon potential. The short-range repulsion of the latter is renormalized by constructing a smooth low-momentum potential, V{sub low-k}, that is used directly as input for the calculation of the effective interaction. In this paper, we focus attention on proton-neutron multiplets in the odd-odd nuclei {sup 134}Sb, {sup 136}Sb. We show that the behavior of these multiplets is quite similar to that of the analogous multiplets in the counterpart nuclei in the {sup 208}Pb region, {sup 210}Bi and {sup 212}Bi.
Study of airflow during respiratory cycle in semi-realistic model of human tracheobronchial tree
NASA Astrophysics Data System (ADS)
Elcner, Jakub; Zaremba, M.; Maly, M.; Jedelsky, J.; Lizal, F.; Jicha, M.
2016-06-01
This article deals with study of airflow under breathing process, which is characteristic by unsteady behavior. Simulations provided by computational fluid dynamics (CFD) was compared with experiments performed on similar geometry of human upper airways. This geometry was represented by mouth cavity of realistic shape connected to an idealized tracheobronchial tree up to fourth generation of branching. Commercial CFD software Star-CCM+ was used to calculate airflow inside investigated geometry and method of Reynolds averaging of Navier-Stokes equations was used for subscribing the turbulent behavior through model geometry. Conditions corresponding to resting state were considered. Comparisons with experiments were provided on several points through trachea and bronchial tree and results with respect to inspiratory and respiratory part of breathing cycle was discussed.
Modeling the plastic relaxation onset in realistic SiGe islands on Si(001)
Gatti, R.; Marzegalli, A.; Montalenti, F.; Miglio, Leo; Zinovyev, V. A.
2008-11-01
A detailed investigation of plastic relaxation onset in heteroepitaxial SiGe islands on Si(001) is presented. The strain field induced by a straight misfit-dislocation segment is modeled by finite-element-method (FEM) calculations in three dimensions, fully taking into account the interaction with the multifaceted free surfaces of realistic islands. The total elastic energies before and after the placement of a 60 deg. dislocation segment in the most favorable position are therefore evaluated by a full FEM approach, for different island sizes and compositions. The critical volumes with composition for inserting the dislocation are finally obtained and successfully compared with the data in a report by Marzegalli et al. [Phys. Rev. Lett. 99, 235505 (2007)], where experimental values are compared to a simpler approach.
Ab Initio No-Core Shell Model Calculations Using Realistic Two- and Three-Body Interactions
Navratil, P; Ormand, W E; Forssen, C; Caurier, E
2004-11-30
There has been significant progress in the ab initio approaches to the structure of light nuclei. One such method is the ab initio no-core shell model (NCSM). Starting from realistic two- and three-nucleon interactions this method can predict low-lying levels in p-shell nuclei. In this contribution, we present a brief overview of the NCSM with examples of recent applications. We highlight our study of the parity inversion in {sup 11}Be, for which calculations were performed in basis spaces up to 9{Dirac_h}{Omega} (dimensions reaching 7 x 10{sup 8}). We also present our latest results for the p-shell nuclei using the Tucson-Melbourne TM three-nucleon interaction with several proposed parameter sets.
NASA Astrophysics Data System (ADS)
Dobslaw, Henryk; Forootan, Ehsan; Bergmann-Wolf, Inga; Neumayer, Karl-Hans; Mayer-Gürr, Torsten; Kusche, Jürgen; Flechtner, Frank
2015-04-01
Recently completed performance studies of future gravity mission concepts arrived at sometimes contradicting conclusions about the importance of non-tidal aliasing errors that remain in the finally retrieved gravity field time-series. In those studies, typically a fraction of the differences between two different models of atmosphere and ocean mass variability determined the magnitude of the aliasing errors. Since differences among arbitrary pairs of the numerical models available might lead to widely different aliasing errors and thus conclusions regarding limiting error contributors of a candidate mission, we present here for the first time a version of a realistically perturbed de-aliasing model that is consistent with the updated ESA Earth System Model for gravity mission simulation studies (Dobslaw et al., 2015). The error model is available over the whole 12-year period of the ESA ESM and consists of two parts: (i) a component containing signals from physical processes that are intentionally omitted from de-aliasing models, as for a example, variations in global eustatic sea-level; and (ii) a series of true errors that consist of in total five different components with realistically re-scaled variability at both small and large spatial scales for different frequency bands ranging from sub-daily to sub-monthly periods. Based on a multi-model ensemble of atmosphere and ocean mass variability available to us for the year 2006, we will demonstrate that our re-scaled true errors have plausible magnitudes and correlation characteristics in all frequency bands considered. The realism of the selected scaling coefficients for periods between 1 and 30 days is tested further by means of a variance component estimation based on the constrained daily GRACE solution series ITSG-GRACE2014. Initial full-scale simulation experiments are used to re-assess the relative importance of non-tidal de-aliasing errors for the GRACE-FO mission, which might be subsequently expanded to
Mono-jet, -photon and - Z signals of a supersymmetric ( B - L) model at the Large Hadron Collider
NASA Astrophysics Data System (ADS)
Abdallah, W.; Fiaschi, J.; Khalil, S.; Moretti, S.
2016-02-01
Search for invisible final states produced at the Large Hadron Collider (LHC) by new physics scenarios are normally carried out resorting to a variety of probes emerging from the initial state, in the form of single-jet, -photon and - Z boson signatures. These are particularly effective for models of Supersymmetry (SUSY) in presence of R-parity conservation, owing to the presence in their spectra of a stable neutralino as a Dark Matter (DM) candidate. We assume here as theoretical framework the Supersymmetric version of the ( B - L) extension of the Standard Model (BLSSM), wherein a mediator for invisible decays can be the Z ' boson present in this scenario. The peculiarity of the signal is thus that the final state objects carry a very large (transverse) missing energy, since the Z ' is naturally massive and constrained by direct searches and Electro-Weak Precision Tests (EWPTs) to be at least in the TeV scale region. Under these circumstances the efficiency in accessing the invisible final state and rejecting the Standard Model (SM) background is very high. This somehow compensates the rather meagre production rates. Another special feature of this invisible BLSSM signal is its composition, which is often dominated by sneutrino decays (alongside the more traditional neutrino and neutralino modes). Sensitivity of the CERN machine to these two features can therefore help disentangling the BLSSM from more popular SUSY models. We assess in this analysis the scope of the LHC in establishing the aforementioned invisible signals through a sophisticated signal-to-background simulation carried out in presence of parton shower, hadronisation as well as detector effects. We find that significant sensitivity exists already after 300 fb-1 during Run 2. We find that mono-jet events can be readily accessible at the LHC, so as to enable one to claim a prompt discovery, while mono-photon and - Z signals can be used as diagnostic tools of the underlying scenario.
Draguhn, A; Pfeiffer, M; Heinemann, U; Polder, R
1997-12-30
A new hardware cell model for electrophysiological recording has been constructed which allows for the assessment of voltage clamp accuracy in different recording situations. Each compartment consists of a capacitor in parallel with a variable resistor and can be connected to other compartments by a variable axial resistance. The simulated membrane resistance can be changed extrinsically by a command voltage input which is optically coupled to the cell without any direct galvanic contact. Each compartment possesses a buffer amplifier which reads out the potential at the simulated membrane element, (e.g. 'somatic' or 'dendritic' potential). The model allows for the direct observation of typical situations and problems arising in electrophysiological experiments. We used the model to monitor deviations between the 'intracellular' and the command voltage, e.g. due to series resistance errors. We also used the model to simulate synaptic currents which were generated by triangular membrane conductance changes. The results demonstrate the strong influence of synaptic location and series resistance on voltage clamp fidelity. The cell model is a new and easy-to-handle tool for the observation of voltage control under realistic experimental conditions. PMID:9497006
Laganà, K; Dubini, G; Migliavacca, F; Pietrabissa, R; Pennati, G; Veneziani, A; Quarteroni, A
2002-01-01
This work was motivated by the problems of analysing detailed 3D models of vascular districts with complex anatomy. It suggests an approach to prescribing realistic boundary conditions to use in order to obtain information on local as well as global haemodynamics. A method was developed which simultaneously solves Navier-Stokes equations for local information and a non-linear system of ordinary differential equations for global information. This is based on the principle that an anatomically detailed 3D model of a cardiovascular district can be achieved by using the finite element method. In turn the finite element method requires a specific boundary condition set. The approach outlined in this work is to include the system of ordinary differential equations in the boundary condition set. Such a multiscale approach was first applied to two controls: (i) a 3D model of a straight tube in a simple hydraulic network and (ii) a 3D model of a straight coronary vessel in a lumped-parameter model of the cardiovascular system. The results obtained are very close to the solutions available for the pipe geometry. This paper also presents preliminary results from the application of the methodology to a particular haemodynamic problem: namely the fluid dynamics of a systemic-to-pulmonary shunt in paediatric cardiac surgery.
von Thienen, Wolfhard; Metzler, Dirk; Witte, Volker
2015-05-01
The emergence of self-organizing behavior in ants has been modeled in various theoretical approaches in the past decades. One model explains experimental observations in which Argentine ants (Linepithema humile) selected the shorter of two alternative paths from their nest to a food source (shortest path experiments). This model serves as an important example for the emergence of collective behavior and self-organization in biological systems. In addition, it inspired the development of computer algorithms for optimization problems called ant colony optimization (ACO). In the model, a choice function describing how ants react to different pheromone concentrations is fundamental. However, the parameters of the choice function were not deduced experimentally but freely adapted so that the model fitted the observations of the shortest path experiments. Thus, important knowledge was lacking about crucial model assumptions. A recent study on the Argentine ant provided this information by measuring the response of the ants to varying pheromone concentrations. In said study, the above mentioned choice function was fitted to the experimental data and its parameters were deduced. In addition, a psychometric function was fitted to the data and its parameters deduced. Based on these findings, it is possible to test the shortest path model by applying realistic parameter values. Here we present the results of such tests using Monte Carlo simulations of shortest path experiments with Argentine ants. We compare the choice function and the psychometric function, both with parameter values deduced from the above-mentioned experiments. Our results show that by applying the psychometric function, the shortest path experiments can be explained satisfactorily by the model. The study represents the first example of how psychophysical theory can be used to understand and model collective foraging behavior of ants based on trail pheromones. These findings may be important for other
Constraints on B and Higgs physics in minimal low energy supersymmetric models
Carena, Marcela; Menon, A.; Noriega-Papaqui, R.; Szynkman, A.; Wagner, C.E.M.; /Argonne /Chicago U., EFI
2006-03-01
We study the implications of minimal flavor violating low energy supersymmetry scenarios for the search of new physics in the B and Higgs sectors at the Tevatron collider and the LHC. We show that the already stringent Tevatron bound on the decay rate B{sub s} {yields} {mu}{sup +}{mu}{sup -} sets strong constraints on the possibility of generating large corrections to the mass difference {Delta} M{sub s} of the B{sub s} eigenstates. We also show that the B{sub s} {yields} {mu}{sup +}{mu}{sup -} bound together with the constraint on the branching ratio of the rare decay b {yields} s{gamma} has strong implications for the search of light, non-standard Higgs bosons at hadron colliders. In doing this, we demonstrate that the former expressions derived for the analysis of the double penguin contributions in the Kaon sector need to be corrected by additional terms for a realistic analysis of these effects. We also study a specific non-minimal flavor violating scenario, where there are flavor changing gluino-squark-quark interactions, governed by the CKM matrix elements, and show that the B and Higgs physics constraints are similar to the ones in the minimal flavor violating case. Finally we show that, in scenarios like electroweak baryogenesis which have light stops and charginos, there may be enhanced effects on the B and K mixing parameters, without any significant effect on the rate of B{sub s} {yields} {mu}{sup +}{mu}{sup -}.
NASA Astrophysics Data System (ADS)
Jeong, Woo Chul; Wi, Hun; Sajib, Saurav Z. K.; Oh, Tong In; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je
2015-08-01
Electromagnetic fields provide fundamental data for the imaging of electrical tissue properties, such as conductivity and permittivity, in recent magnetic resonance (MR)-based tissue property mapping. The induced voltage, current density, and magnetic flux density caused by externally injected current are critical factors for determining the image quality of electrical tissue conductivity. As a useful tool to identify bio-electromagnetic phenomena, precise approaches are required to understand the exact responses inside the human body subject to an injected currents. In this study, we provide the numerical simulation results of electromagnetic field mapping of brain tissues using a MR-based conductivity imaging method. First, we implemented a realistic three-dimensional human anisotropic head model using high-resolution anatomical and diffusion tensor MR images. The voltage, current density, and magnetic flux density of brain tissues were imaged by injecting 1 mA of current through pairs of electrodes on the surface of our head model. The current density map of anisotropic brain tissues was calculated from the measured magnetic flux density based on the linear relationship between the water diffusion tensor and the electrical conductivity tensor. Comparing the current density to the previous isotropic model, the anisotropic model clearly showed the differences between the brain tissues. This originates from the enhanced signals by the inherent conductivity contrast as well as the actual tissue condition resulting from the injected currents.
Investigations of sensitivity and resolution of ECG and MCG in a realistically shaped thorax model
NASA Astrophysics Data System (ADS)
Mäntynen, Ville; Konttila, Teijo; Stenroos, Matti
2014-12-01
Solving the inverse problem of electrocardiography (ECG) and magnetocardiography (MCG) is often referred to as cardiac source imaging. Spatial properties of ECG and MCG as imaging systems are, however, not well known. In this modelling study, we investigate the sensitivity and point-spread function (PSF) of ECG, MCG, and combined ECG+MCG as a function of source position and orientation, globally around the ventricles: signal topographies are modelled using a realistically-shaped volume conductor model, and the inverse problem is solved using a distributed source model and linear source estimation with minimal use of prior information. The results show that the sensitivity depends not only on the modality but also on the location and orientation of the source and that the sensitivity distribution is clearly reflected in the PSF. MCG can better characterize tangential anterior sources (with respect to the heart surface), while ECG excels with normally-oriented and posterior sources. Compared to either modality used alone, the sensitivity of combined ECG+MCG is less dependent on source orientation per source location, leading to better source estimates. Thus, for maximal sensitivity and optimal source estimation, the electric and magnetic measurements should be combined.
Investigations of sensitivity and resolution of ECG and MCG in a realistically shaped thorax model.
Mäntynen, Ville; Konttila, Teijo; Stenroos, Matti
2014-12-01
Solving the inverse problem of electrocardiography (ECG) and magnetocardiography (MCG) is often referred to as cardiac source imaging. Spatial properties of ECG and MCG as imaging systems are, however, not well known. In this modelling study, we investigate the sensitivity and point-spread function (PSF) of ECG, MCG, and combined ECG+MCG as a function of source position and orientation, globally around the ventricles: signal topographies are modelled using a realistically-shaped volume conductor model, and the inverse problem is solved using a distributed source model and linear source estimation with minimal use of prior information. The results show that the sensitivity depends not only on the modality but also on the location and orientation of the source and that the sensitivity distribution is clearly reflected in the PSF. MCG can better characterize tangential anterior sources (with respect to the heart surface), while ECG excels with normally-oriented and posterior sources. Compared to either modality used alone, the sensitivity of combined ECG+MCG is less dependent on source orientation per source location, leading to better source estimates. Thus, for maximal sensitivity and optimal source estimation, the electric and magnetic measurements should be combined.
Towards a large-scale biologically realistic model of the hippocampus.
Hendrickson, Phillip J; Yu, Gene J; Robinson, Brian S; Song, Dong; Berger, Theodore W
2012-01-01
Real neurobiological systems in the mammalian brain have a complicated and detailed structure, being composed of 1) large numbers of neurons with intricate, branching morphologies--complex morphology brings with it complex passive membrane properties; 2) active membrane properties--nonlinear sodium, potassium, calcium, etc. conductances; 3) non-uniform distributions throughout the dendritic and somal membrane surface of these non-linear conductances; 4) non-uniform and topographic connectivity between pre- and post-synaptic neurons; and 5) activity-dependent changes in synaptic function. One of the essential, and as yet unanswered questions in neuroscience is the role of these fundamental structural and functional features in determining "neural processing" properties of a given brain system. To help answer that question, we're creating a large-scale biologically realistic model of the intrinsic pathway of the hippocampus, which consists of the projection from layer II entorhinal cortex (EC) to dentate gyrus (DG), EC to CA3, DG to CA3, and CA3 to CA1. We describe the computational hardware and software tools the model runs on, and demonstrate its viability as a modeling platform with an EC-to-DG model. PMID:23366951
Primordial supersymmetric inflation
NASA Astrophysics Data System (ADS)
Ellis, John; Nanopoulos, D. V.; Olive, K. A.; Tamvakis, K.
1983-07-01
We discuss the motivations for reconsidering cosmological inflation in supersymmetric theories as contrasted with conventional GUTs. Radiative corrections to the effective potential can be made arbitrarily small in supersymmetric GUTs, removing some of the obstacles to inflation. We analyze general renormalizable potentials at the tree level and show that the required fine-tuning of parameters becomes less acute if inflation takes place before the grand unified phase transition, a hypothesis we term primordial inflation. We show how the grand unified monopole problem can be solved in supersymmetric GUTs embodying primordial inflation.
Supersymmetric oscillator in optics
NASA Technical Reports Server (NTRS)
Chumakov, Sergey M.; Wolf, Kurt Bernardo
1995-01-01
We show that the supersymmetric structure (in the sense of supersymmetric quantum mechanics) appears in Helmholtz optics describing light propagation in waveguides. For the case of elliptical waveguides, with the accuracy of paraxial approximation it admits a simple physical interpretation. The supersymmetry connects light beams of different colors. The difference in light frequencies for the supersymmetric beams is determined by the transverse gradient of the refractive index. These beams have the save wavelength in the propagation direction and can form a stable interference pattern.
Implications of introducing realistic fire response traits in a Dynamic Global Vegetation Model
NASA Astrophysics Data System (ADS)
Kelley, D.; Harrison, S. P.; Prentice, I. C.
2013-12-01
Bark thickness is a key trait protecting woody plants against fire damage, while the ability to resprout is a trait that confers competitive advantage over non-resprouting individuals in fire-prone landscapes. Neither trait is well represented in fire-enabled dynamic global vegetation models (DGVMs). Here we describe a version of the Land Processes and eXchanges (LPX-Mv1) DGVM that incorporates both of these traits in a realistic way. From a synthesis of a large number of field studies, we show there is considerable innate variability in bark thickness between species within a plant-functional type (PFT). Furthermore, bark thickness is an adaptive trait at ecosystem level, increasing with fire frequency. We use the data to specify the range of bark thicknesses characteristic of each model PFT. We allow this distribution to change dynamically: thinner-barked trees are killed preferentially by fire, shifting the distribution of bark thicknesses represented in a model grid cell. We use the PFT-specific bark-thickness probability range for saplings during re-establishment. Since it is rare to destroy all trees in a grid cell, this treatment results in average bark thickness increasing with fire frequency and intensity. Resprouting is a prominent adaptation of temperate and tropical trees in fire-prone areas. The ability to resprout from above-ground tissue (apical or epicormic resprouting) results in the fastest recovery of total biomass after disturbance; resprouting from basal or below-ground meristems results in slower recovery, while non-resprouting species must regenerate from seed and therefore take the longest time to recover. Our analyses show that resprouting species have thicker bark than non-resprouting species. Investment in resprouting is accompanied by reduced efficacy of regeneration from seed. We introduce resprouting PFTs in LPX-Mv1 by specifying an appropriate range of bark thickness, allowing resprouters to survive fire and regenerate vegetatively in
Ciesielski, Peter N.; Crowley, Michael F.; Nimlos, Mark R.; Sanders, Aric W.; Wiggins, Gavin M.; Robichaud, David; Donohoe, Bryon S.; Foust, Thomas D.
2014-12-09
Biomass exhibits a complex microstructure of directional pores that impact how heat and mass are transferred within biomass particles during conversion processes. However, models of biomass particles used in simulations of conversion processes typically employ oversimplified geometries such as spheres and cylinders and neglect intraparticle microstructure. In this study, we develop 3D models of biomass particles with size, morphology, and microstructure based on parameters obtained from quantitative image analysis. We obtain measurements of particle size and morphology by analyzing large ensembles of particles that result from typical size reduction methods, and we delineate several representative size classes. Microstructural parameters, including cell wall thickness and cell lumen dimensions, are measured directly from micrographs of sectioned biomass. A general constructive solid geometry algorithm is presented that produces models of biomass particles based on these measurements. Next, we employ the parameters obtained from image analysis to construct models of three different particle size classes from two different feedstocks representing a hardwood poplar species (Populus tremuloides, quaking aspen) and a softwood pine (Pinus taeda, loblolly pine). Finally, we demonstrate the utility of the models and the effects explicit microstructure by performing finite-element simulations of intraparticle heat and mass transfer, and the results are compared to similar simulations using traditional simplified geometries. In conclusion, we show how the behavior of particle models with more realistic morphology and explicit microstructure departs from that of spherical models in simulations of transport phenomena and that species-dependent differences in microstructure impact simulation results in some cases.
Ciesielski, Peter N.; Crowley, Michael F.; Nimlos, Mark R.; Sanders, Aric W.; Wiggins, Gavin M.; Robichaud, David; Donohoe, Bryon S.; Foust, Thomas D.
2014-12-09
Biomass exhibits a complex microstructure of directional pores that impact how heat and mass are transferred within biomass particles during conversion processes. However, models of biomass particles used in simulations of conversion processes typically employ oversimplified geometries such as spheres and cylinders and neglect intraparticle microstructure. In this study, we develop 3D models of biomass particles with size, morphology, and microstructure based on parameters obtained from quantitative image analysis. We obtain measurements of particle size and morphology by analyzing large ensembles of particles that result from typical size reduction methods, and we delineate several representative size classes. Microstructural parameters, includingmore » cell wall thickness and cell lumen dimensions, are measured directly from micrographs of sectioned biomass. A general constructive solid geometry algorithm is presented that produces models of biomass particles based on these measurements. Next, we employ the parameters obtained from image analysis to construct models of three different particle size classes from two different feedstocks representing a hardwood poplar species (Populus tremuloides, quaking aspen) and a softwood pine (Pinus taeda, loblolly pine). Finally, we demonstrate the utility of the models and the effects explicit microstructure by performing finite-element simulations of intraparticle heat and mass transfer, and the results are compared to similar simulations using traditional simplified geometries. In conclusion, we show how the behavior of particle models with more realistic morphology and explicit microstructure departs from that of spherical models in simulations of transport phenomena and that species-dependent differences in microstructure impact simulation results in some cases.« less
A realistic model of a wall-transpiration actuator for boundary layer control
NASA Astrophysics Data System (ADS)
Tilton, Nils; Cortelezzi, Luca
2008-11-01
Experimental studies of boundary layer control using continuously distributed wall-suction usually implement suction by applying a pressure gradient to a layer of porous material via an underlying plenum chamber. Theoretical studies, however, usually neglect the penetration of fluid into the porous layer and plenum chamber by forcing the base flow and velocity perturbations to vanish at the interface with the porous layer. We present a realistic model of a wall-transpiration actuator which implements suction through a fluid saturated, rigid, homogeneous, isotropic, porous layer stretched over a semi-infinite plenum chamber. We test our model on the asymptotic suction boundary layer (ASBL) and perform a linear stability analysis. We take account of the full coupling between the flow fields in the boundary layer, porous layer, and plenum chamber using boundary conditions derived by Ochoa-Tapia and Whitaker (Int. J. Heat Mass Transfer, Vol. 38, 1995, pp 2635-2646). We illustrate the impact of wall-permeability, porous layer thickness, and the plenum chamber on the critical Reynolds number and the stability of the Tollmien-Schlichting wave. We use our model to find the optimal operating conditions of an ASBL which minimize the skin friction drag and power required to apply the suction.
Meitav, Nizan; Shoham, Shy
2016-01-01
Abstract In recent years, optogenetics has become a central tool in neuroscience research. Estimating the transmission of visible light through brain tissue is of crucial importance for controlling the activation levels of neurons in different depths, designing optical systems, and avoiding lesions from excessive power density. The Kubelka–Munk model and Monte Carlo simulations have previously been used to model light propagation through rodents' brain tissue, however, these prior attempts suffer from fundamental shortcomings. Here, we introduce and study two modified approaches for modeling the distributions of light emanating from a multimode fiber and scattering through tissue, using both realistic numerical Monte Carlo simulations and an analytical approach based on the beam-spread function approach. We demonstrate a good agreement of the new methods' predictions both with recently published data, and with new measurements in mouse brain cortical slices, where our results yield a new cortical scattering length estimate of ∼47 µm at λ = 473 nm, significantly shorter than ordinarily assumed in optogenetic applications. PMID:26866055
Realistic modeling of the pulse profile of PSR J0737-3039A
Perera, B. B. P.; Kim, C.; McLaughlin, M. A.; Ferdman, R. D.; Kramer, M.; Freire, P. C. C.; Stairs, I. H.; Possenti, A.
2014-05-20
The Double Pulsar, PSR J0737-3039A/B, is a unique system in which both neutron stars have been detected as radio pulsars. As shown in Ferdman et al., there is no evidence for pulse profile evolution of the A pulsar, and the geometry of the pulsar was fit well with a double-pole circular radio beam model. Assuming a more realistic polar cap model with a vacuum retarded dipole magnetosphere configuration including special relativistic effects, we create synthesized pulse profiles for A given the best-fit geometry from the simple circular beam model. By fitting synthesized pulse profiles to those observed from pulsar A, we constrain the geometry of the radio beam, namely the half-opening angle and the emission altitude, to be ∼30° and ∼10 neutron star radii, respectively. Combining the observational constraints of PSR J0737-3039A/B, we are able to construct the full three-dimensional orbital geometry of the Double Pulsar. The relative angle between the spin axes of the two pulsars (Δ{sub S}) is estimated to be ∼(138° ± 5°) at the current epoch and will likely remain constant until tidal interactions become important in ∼85 Myr, at merger.
Atomistic surface erosion and thin film growth modelled over realistic time scales
NASA Astrophysics Data System (ADS)
Scott, Chris; Blackwell, Sabrina; Vernon, Louis; Kenny, Steven; Walls, Michael; Smith, Roger
2011-11-01
We present results of atomistic modelling of surface growth and sputtering using a multi-time scale molecular dynamics-on-the-fly kinetic Monte Carlo scheme which allows simulations to be carried out over realistic experimental times. The method uses molecular dynamics to model the fast processes and then calculates the diffusion barriers for the slow processes on-the-fly, without any preconceptions about what transitions might occur. The method is applied to the growth of metal and oxide materials at impact energies typical for both vapour deposition and magnetron sputtering. The method can be used to explain growth processes, such as the filling of vacancies and the formation of stacking faults. By tuning the variable experimental parameters on the computer, a parameter set for optimum crystalline growth can be determined. The method can also be used to model sputtering where the particle interactions with the surface occur at a higher energy. It is shown how a steady state can arise in which interstitial clusters are continuously being formed below the surface during an atom impact event which also recombine or diffuse to the surface between impact events. For fcc metals the near surface region remains basically crystalline during the erosion process with a pitted topography which soon attains a steady state roughness.
Flow in a Geometrically-Realistic, Vibrating Model of the Human Vocal Tract
NASA Astrophysics Data System (ADS)
Thomson, Scott; Seegmiller, Jayrin
2013-11-01
Airflow within the human vocal tract is an important component of voice quality. Understanding the nature of the airflow will help better understand voice production, potentially leading towards improved clinical diagnostics and treatments. An up-scaled experimental setup was developed to study three-dimensional flow features in a realistic model of the human larynx. The subglottal and supraglottal sections were made of clear silicone, with geometry derived from CT scan data. A cylindrically-shaped supraglottal section was also fabricated to compare flows with and without anatomically-accurate supraglottal sections. The glottal section consisted of two counter-rotating, mechanically-driven cams, covered by a silicone membrane, to approximate the alternating convergent-divergent profile of vibrating vocal folds. A mixture of water and glycerol was pumped through the system, the index of refraction matching that of the silicone for optical access into the sub- and supraglottal sections. Velocity fields throughout the glottal cycle were acquired using particle image velocimetry (PIV), giving particular attention to differences in flow features (e.g., jet skewing and axis switching) between models with CT-derived and cylindrically-shaped supraglottal geometry. In this presentation, the model design and characteristics will be given, and PIV flow results will be presented and discussed. Supported by NIH/NIDCD Grant R01 DC009616.
Time variation of the fine structure constant α from realistic models of Oklo reactors.
NASA Astrophysics Data System (ADS)
Gould, C. R.; Sharapov, E. I.; Lamoreaux, S. K.
2006-11-01
The topic of whether the fundamental constants of nature vary with time has been a subject of great interest since Dirac originally proposed the possibility that GN˜1/tuniverse. Recent observations of absorption spectra lines from distant quasars appeared to indicate a possible increase in the fine structure constant α over ten billion years. Contrarily, analyses of the time evolution of α from Oklo natural nuclear reactor data have yielded inconsistent results, some indicating a decrease over two billion years while others indicated no change. We have used known Oklo reactor epithermal spectral indices as criteria for selecting realistic reactor models. Reactors RZ2 and RZ10 were modeled with MCNP and the resulting neutron spectra were used to calculate the change in the ^149Sm capture cross section as a function of a possible shift in the energy of the 97.3-meV resonance. Our study resolves the contradictory situation with previous Oklo α-results. Our suggested 2 σ bound on a possible time variation of α over two billion years is stringent: -0.11 <=δαα <=0.24, in units of 10-7, but model dependent in that it assumes only α has varied over time.
Random vs realistic amorphous carbon models for high resolution microscopy and electron diffraction
Ricolleau, C. Alloyeau, D.; Le Bouar, Y.; Amara, H.; Landon-Cardinal, O.
2013-12-07
Amorphous carbon and amorphous materials in general are of particular importance for high resolution electron microscopy, either for bulk materials, generally covered with an amorphous layer when prepared by ion milling techniques, or for nanoscale objects deposited on amorphous substrates. In order to quantify the information of the high resolution images at the atomic scale, a structural modeling of the sample is necessary prior to the calculation of the electron wave function propagation. It is thus essential to be able to reproduce the carbon structure as close as possible to the real one. The approach we propose here is to simulate a realistic carbon from an energetic model based on the tight-binding approximation in order to reproduce the important structural properties of amorphous carbon. At first, we compare this carbon with the carbon obtained by randomly generating the carbon atom positions. In both cases, we discuss the limit thickness of the phase object approximation. In a second step, we show the influence of both carbons models on (i) the contrast of Cu, Ag, and Au single atoms deposited on carbon and (ii) the determination of the long-range order parameter in CoPt bimetallic nanoalloys.
Davtyan, Aram; Dama, James F.; Voth, Gregory A.; Andersen, Hans C.
2015-04-21
the method provides realistic dynamical CG models that have non-Markovian or close to Markovian behavior that is consistent with the actual dynamical behavior of the all-atom system used to construct the CG model. Both the construction and the simulation of such a dynamic CG model have computational requirements that are similar to those of the corresponding MS-CG model and are good candidates for CG modeling of very large systems.
NASA Astrophysics Data System (ADS)
Davtyan, Aram; Dama, James F.; Voth, Gregory A.; Andersen, Hans C.
2015-04-01
the method provides realistic dynamical CG models that have non-Markovian or close to Markovian behavior that is consistent with the actual dynamical behavior of the all-atom system used to construct the CG model. Both the construction and the simulation of such a dynamic CG model have computational requirements that are similar to those of the corresponding MS-CG model and are good candidates for CG modeling of very large systems.
NASA Astrophysics Data System (ADS)
Jain, Vaibhav; Maiti, Prabal K.; Bharatam, Prasad V.
2016-09-01
Computational studies performed on dendrimer-drug complexes usually consider 1:1 stoichiometry, which is far from reality, since in experiments more number of drug molecules get encapsulated inside a dendrimer. In the present study, molecular dynamic (MD) simulations were implemented to characterize the more realistic molecular models of dendrimer-drug complexes (1:n stoichiometry) in order to understand the effect of high drug loading on the structural properties and also to unveil the atomistic level details. For this purpose, possible inclusion complexes of model drug Nateglinide (Ntg) (antidiabetic, belongs to Biopharmaceutics Classification System class II) with amine- and acetyl-terminated G4 poly(amidoamine) (G4 PAMAM(NH2) and G4 PAMAM(Ac)) dendrimers at neutral and low pH conditions are explored in this work. MD simulation analysis on dendrimer-drug complexes revealed that the drug encapsulation efficiency of G4 PAMAM(NH2) and G4 PAMAM(Ac) dendrimers at neutral pH was 6 and 5, respectively, while at low pH it was 12 and 13, respectively. Center-of-mass distance analysis showed that most of the drug molecules are located in the interior hydrophobic pockets of G4 PAMAM(NH2) at both the pH; while in the case of G4 PAMAM(Ac), most of them are distributed near to the surface at neutral pH and in the interior hydrophobic pockets at low pH. Structural properties such as radius of gyration, shape, radial density distribution, and solvent accessible surface area of dendrimer-drug complexes were also assessed and compared with that of the drug unloaded dendrimers. Further, binding energy calculations using molecular mechanics Poisson-Boltzmann surface area approach revealed that the location of drug molecules in the dendrimer is not the decisive factor for the higher and lower binding affinity of the complex, but the charged state of dendrimer and drug, intermolecular interactions, pH-induced conformational changes, and surface groups of dendrimer do play an
Rapidly re-computable EEG (electroencephalography) forward models for realistic head shapes
Ermer, J. J.; Mosher, J. C.; Baillet, S.; Leahy, R. M.
2001-01-01
Solution of the EEG source localization (inverse) problem utilizing model-based methods typically requires a significant number of forward model evaluations. For subspace based inverse methods like MUSIC [6], the total number of forward model evaluations can often approach an order of 10{sup 3} or 10{sup 4}. Techniques based on least-squares minimization may require significantly more evaluations. The observed set of measurements over an M-sensor array is often expressed as a linear forward spatio-temporal model of the form: F = GQ + N (1) where the observed forward field F (M-sensors x N-time samples) can be expressed in terms of the forward model G, a set of dipole moment(s) Q (3xP-dipoles x N-time samples) and additive noise N. Because of their simplicity, ease of computation, and relatively good accuracy, multi-layer spherical models [7] (or fast approximations described in [1], [7]) have traditionally been the 'forward model of choice' for approximating the human head. However, approximation of the human head via a spherical model does have several key drawbacks. By its very shape, the use of a spherical model distorts the true distribution of passive currents in the skull cavity. Spherical models also require that the sensor positions be projected onto the fitted sphere (Fig. 1), resulting in a distortion of the true sensor-dipole spatial geometry (and ultimately the computed surface potential). The use of a single 'best-fitted' sphere has the added drawback of incomplete coverage of the inner skull region, often ignoring areas such as the frontal cortex. In practice, this problem is typically countered by fitting additional sphere(s) to those region(s) not covered by the primary sphere. The use of these additional spheres results in added complication to the forward model. Using high-resolution spatial information obtained via X-ray CT or MR imaging, a realistic head model can be formed by tessellating the head into a set of contiguous regions (typically the
NASA Astrophysics Data System (ADS)
Bui, Khoa; Papavassiliou, Dimitrios
2012-02-01
The effective thermal conductivity (Keff) of carbon nanotube (CNT) composites is affected by the thermal boundary resistance (TBR) and by the dispersion pattern and geometry of the CNTs. We have previously modeled CNTs as straight cylinders and found that the TBR between CNTs (TBRCNT-CNT) can suppress Keff at high volume fractions of CNTs [1]. Effective medium theory results assume that the CNTs are in a perfect dispersion state and exclude the TBRCNT-CNT [2]. In this work, we report on the development of an algorithm for generating CNTs with worm-like geometry in 3D, and with different persistence lengths. These worm-like CNTs are then randomly placed in a periodic box representing a realistic state, since the persistence length of a CNT can be obtained from microscopic images. The use of these CNT geometries in conjunction with off-lattice Monte Carlo simulations [1] in order to study the effective thermal properties of nanocomposites will be discussed, as well as the effects of the persistence length on Keff and comparisons to straight cylinder models. References [1] K. Bui, B.P. Grady, D.V. Papavassiliou, Chem. Phys. Let., 508(4-6), 248-251, 2011 [2] C.W. Nan, G. Liu, Y. Lin, M. Li, App. Phys. Let., 85(16), 3549-3551, 2006
A novel CPU/GPU simulation environment for large-scale biologically realistic neural modeling
Hoang, Roger V.; Tanna, Devyani; Jayet Bray, Laurence C.; Dascalu, Sergiu M.; Harris, Frederick C.
2013-01-01
Computational Neuroscience is an emerging field that provides unique opportunities to study complex brain structures through realistic neural simulations. However, as biological details are added to models, the execution time for the simulation becomes longer. Graphics Processing Units (GPUs) are now being utilized to accelerate simulations due to their ability to perform computations in parallel. As such, they have shown significant improvement in execution time compared to Central Processing Units (CPUs). Most neural simulators utilize either multiple CPUs or a single GPU for better performance, but still show limitations in execution time when biological details are not sacrificed. Therefore, we present a novel CPU/GPU simulation environment for large-scale biological networks, the NeoCortical Simulator version 6 (NCS6). NCS6 is a free, open-source, parallelizable, and scalable simulator, designed to run on clusters of multiple machines, potentially with high performance computing devices in each of them. It has built-in leaky-integrate-and-fire (LIF) and Izhikevich (IZH) neuron models, but users also have the capability to design their own plug-in interface for different neuron types as desired. NCS6 is currently able to simulate one million cells and 100 million synapses in quasi real time by distributing data across eight machines with each having two video cards. PMID:24106475
A novel CPU/GPU simulation environment for large-scale biologically realistic neural modeling.
Hoang, Roger V; Tanna, Devyani; Jayet Bray, Laurence C; Dascalu, Sergiu M; Harris, Frederick C
2013-01-01
Computational Neuroscience is an emerging field that provides unique opportunities to study complex brain structures through realistic neural simulations. However, as biological details are added to models, the execution time for the simulation becomes longer. Graphics Processing Units (GPUs) are now being utilized to accelerate simulations due to their ability to perform computations in parallel. As such, they have shown significant improvement in execution time compared to Central Processing Units (CPUs). Most neural simulators utilize either multiple CPUs or a single GPU for better performance, but still show limitations in execution time when biological details are not sacrificed. Therefore, we present a novel CPU/GPU simulation environment for large-scale biological networks, the NeoCortical Simulator version 6 (NCS6). NCS6 is a free, open-source, parallelizable, and scalable simulator, designed to run on clusters of multiple machines, potentially with high performance computing devices in each of them. It has built-in leaky-integrate-and-fire (LIF) and Izhikevich (IZH) neuron models, but users also have the capability to design their own plug-in interface for different neuron types as desired. NCS6 is currently able to simulate one million cells and 100 million synapses in quasi real time by distributing data across eight machines with each having two video cards.
NASA Astrophysics Data System (ADS)
Sourie, Aurélien; Oertel, Micaela; Novak, Jérôme
2016-04-01
We present a numerical model for uniformly rotating superfluid neutron stars in a fully general relativistic framework with, for the first time, realistic microphysics including entrainment. We compute stationary and axisymmetric configurations of neutron stars composed of two fluids, namely superfluid neutrons and charged particles (protons and electrons), rotating with different rates around a common axis. Both fluids are coupled by entrainment, a nondissipative interaction which in the case of a nonvanishing relative velocity between the fluids causes the fluid momenta to be not aligned with the respective fluid velocities. We extend the formalism put forth by Comer and Joynt in order to calculate the equation of state (EOS) and entrainment parameters for an arbitrary relative velocity as far as superfluidity is maintained. The resulting entrainment matrix fulfills all necessary sum rules, and in the limit of small relative velocity our results agree with Fermi liquid theory ones derived to lowest order in the velocity. This formalism is applied to two new nuclear equations of state which are implemented in the numerical model, which enables us to obtain precise equilibrium configurations. The resulting density profiles and moments of inertia are discussed employing both EOSs, showing the impact of entrainment and the dependence on the EOS.
Fate of supersymmetric flat directions and their role in reheating
Olive, Keith A.; Peloso, Marco
2006-11-15
We consider the role of supersymmetric flat directions in reheating the Universe after inflation. One or more flat directions can develop large vevs during inflation, which can potentially affect reheating by slowing down scattering processes among inflaton decay products or by coming to dominate the energy density of the Universe. Both effects occur only if flat directions are sufficiently long-lived. The computation of their perturbative decay rate, and a simple estimate of their nonperturbative decay have led to the conclusion that this is indeed the case. In contrast, we show that flat directions can decay quickly through nonperturbative channels in realistic models. The mass matrix for minimal supersymmetric standard model (MSSM) excitations around flat directions has nondiagonal entries, which vary with the phase of the (complex) flat directions. The quasiperiodic motion of the flat directions results in a strong parametric resonance, leading to the rapid depletion of the flat direction within its first few rotations. This may preclude any significant role for the flat directions in reheating the Universe after inflation in models in which the inflaton decays perturbatively.
Determining the regimes of cold and warm inflation in the supersymmetric hybrid model
Bastero-Gil, Mar; Berera, Arjun
2005-03-15
The SUSY hybrid inflation model is found to dissipate radiation during the inflationary period. Analysis is made of parameter regimes in which these dissipative effects are significant. The scalar spectral index, its running, and the tensor-scalar ratio are computed in the entire parameter range of the model. A clear prediction for strong dissipative warm inflation is found for n{sub S}-1{approx_equal}0.98 and a low tensor-scalar ratio much below 10{sup -6}. The strong dissipative warm inflation regime also is found to have no {eta} problem and the field amplitude much below the Planck scale. As will be discussed, this has important theoretical implications in permitting a much wider variety of SUGRA extensions to the basic model.
Successful N{sub 2} leptogenesis with flavour coupling effects in realistic unified models
Bari, Pasquale Di; King, Stephen F.
2015-10-02
In realistic unified models involving so-called SO(10)-inspired patterns of Dirac and heavy right-handed (RH) neutrino masses, the lightest right-handed neutrino N{sub 1} is too light to yield successful thermal leptogenesis, barring highly fine tuned solutions, while the second heaviest right-handed neutrino N{sub 2} is typically in the correct mass range. We show that flavour coupling effects in the Boltzmann equations may be crucial to the success of such N{sub 2} dominated leptogenesis, by helping to ensure that the flavour asymmetries produced at the N{sub 2} scale survive N{sub 1} washout. To illustrate these effects we focus on N{sub 2} dominated leptogenesis in an existing model, the A to Z of flavour with Pati-Salam, where the neutrino Dirac mass matrix may be equal to an up-type quark mass matrix and has a particular constrained structure. The numerical results, supported by analytical insight, show that in order to achieve successful N{sub 2} leptogenesis, consistent with neutrino phenomenology, requires a “flavour swap scenario” together with a less hierarchical pattern of RH neutrino masses than naively expected, at the expense of some mild fine-tuning. In the considered A to Z model neutrino masses are predicted to be normal ordered, with an atmospheric neutrino mixing angle well into the second octant and the Dirac phase δ≃20{sup ∘}, a set of predictions that will be tested in the next years in neutrino oscillation experiments. Flavour coupling effects may be relevant for other SO(10)-inspired unified models where N{sub 2} leptogenesis is necessary.
Successful N{sub 2} leptogenesis with flavour coupling effects in realistic unified models
Bari, Pasquale Di; King, Stephen F. E-mail: king@soton.ac.uk
2015-10-01
In realistic unified models involving so-called SO(10)-inspired patterns of Dirac and heavy right-handed (RH) neutrino masses, the lightest right-handed neutrino N{sub 1} is too light to yield successful thermal leptogenesis, barring highly fine tuned solutions, while the second heaviest right-handed neutrino N{sub 2} is typically in the correct mass range. We show that flavour coupling effects in the Boltzmann equations may be crucial to the success of such N{sub 2} dominated leptogenesis, by helping to ensure that the flavour asymmetries produced at the N{sub 2} scale survive N{sub 1} washout. To illustrate these effects we focus on N{sub 2} dominated leptogenesis in an existing model, the A to Z of flavour with Pati-Salam, where the neutrino Dirac mass matrix may be equal to an up-type quark mass matrix and has a particular constrained structure. The numerical results, supported by analytical insight, show that in order to achieve successful N{sub 2} leptogenesis, consistent with neutrino phenomenology, requires a ''flavour swap scenario'' together with a less hierarchical pattern of RH neutrino masses than naively expected, at the expense of some mild fine-tuning. In the considered A to Z model neutrino masses are predicted to be normal ordered, with an atmospheric neutrino mixing angle well into the second octant and the Dirac phase δ≅ 20{sup o}, a set of predictions that will be tested in the next years in neutrino oscillation experiments. Flavour coupling effects may be relevant for other SO(10)-inspired unified models where N{sub 2} leptogenesis is necessary.
SU(2) symmetry in a realistic spin-fermion model for cuprate superconductors
NASA Astrophysics Data System (ADS)
Kloss, T.; Montiel, X.; Pépin, C.
2015-05-01
We consider the pseudogap (PG) state of high-Tc superconductors in the form of a composite order parameter fluctuating between 2 pF -charge ordering and superconducting (SC) pairing. In the limit of linear dispersion and at the hot spots, both order parameters are related by a SU(2) symmetry, and the eight-hot-spot model of Efetov et al. [Nat. Phys. 9, 442 (2013), 10.1038/nphys2641] is recovered. In the general case, however, curvature terms of the dispersion will break this symmetry, and the degeneracy between both states is lifted. Taking the full momentum dependence of the order parameter into account, we measure the strength of this SU(2) symmetry breaking over the full Brillouin zone. For realistic dispersion relations including curvature we find generically that the SU(2) symmetry breaking is small and robust to the fermiology and that the symmetric situation is restored in the large paramagnon mass and coupling limit. Comparing the level splitting for different materials, we propose a scenario that could account for the competition between the PG and SC states in the phase diagram of high-Tc superconductors.
Kleimann, Jens; Fichtner, Horst; Röken, Christian; Heerikhuisen, Jacob E-mail: hf@tp4.rub.de E-mail: jacob.heerikhuisen@uah.edu
2016-01-01
Both physical arguments and simulations of the global heliosphere indicate that the tailward heliopause is flattened considerably in the direction perpendicular to both the incoming flow and the large-scale interstellar magnetic field. Despite this fact, all of the existing global analytical models of the outer heliosheath's magnetic field assume a circular cross section of the heliotail. To eliminate this inconsistency, we introduce a mathematical procedure by which any analytically or numerically given magnetic field can be deformed in such a way that the cross sections along the heliotail axis attain freely prescribed, spatially dependent values for their total area and aspect ratio. The distorting transformation of this method honors both the solenoidality condition and the stationary induction equation with respect to an accompanying flow field, provided that both constraints were already satisfied for the original magnetic and flow fields prior to the transformation. In order to obtain realistic values for the above parameters, we present the first quantitative analysis of the heliotail's overall distortion as seen in state-of-the-art three-dimensional hybrid MHD–kinetic simulations.
NASA Astrophysics Data System (ADS)
Kleimann, Jens; Röken, Christian; Fichtner, Horst; Heerikhuisen, Jacob
2016-01-01
Both physical arguments and simulations of the global heliosphere indicate that the tailward heliopause is flattened considerably in the direction perpendicular to both the incoming flow and the large-scale interstellar magnetic field. Despite this fact, all of the existing global analytical models of the outer heliosheath's magnetic field assume a circular cross section of the heliotail. To eliminate this inconsistency, we introduce a mathematical procedure by which any analytically or numerically given magnetic field can be deformed in such a way that the cross sections along the heliotail axis attain freely prescribed, spatially dependent values for their total area and aspect ratio. The distorting transformation of this method honors both the solenoidality condition and the stationary induction equation with respect to an accompanying flow field, provided that both constraints were already satisfied for the original magnetic and flow fields prior to the transformation. In order to obtain realistic values for the above parameters, we present the first quantitative analysis of the heliotail's overall distortion as seen in state-of-the-art three-dimensional hybrid MHD-kinetic simulations.
Underwriting information-theoretic accounts of quantum mechanics with a realist, psi-epistemic model
NASA Astrophysics Data System (ADS)
Stuckey, W. M.; Silberstein, Michael; McDevitt, Timothy
2016-05-01
We propose an adynamical interpretation of quantum theory called Relational Blockworld (RBW) where the fundamental ontological element is a 4D graphical amalgam of space, time and sources called a “spacetimesource element.” These are fundamental elements of space, time and sources, not source elements in space and time. The transition amplitude for a spacetimesource element is computed using a path integral with discrete graphical action. The action for a spacetimesource element is constructed from a difference matrix K and source vector J on the graph, as in lattice gauge theory. K is constructed from graphical field gradients so that it contains a non-trivial null space and J is then restricted to the row space of K, so that it is divergence-free and represents a conserved exchange of energy-momentum. This construct of K and J represents an adynamical global constraint between sources, the spacetime metric and the energy-momentum content of the spacetimesource element, rather than a dynamical law for time-evolved entities. To illustrate this interpretation, we explain the simple EPR-Bell and twin-slit experiments. This interpretation of quantum mechanics constitutes a realist, psi-epistemic model that might underwrite certain information-theoretic accounts of the quantum.
Modeling and Design of Realistic Si3N4-BASED Integrated Optical Programmable Power Splitter
NASA Astrophysics Data System (ADS)
Uranus, H. P.; Hoekstra, H. J. W. M.; Stoffer, R.
Controllable splitting of optical power with a large splitting ratio range is often required in an integrated optical chip, e.g. for the readout of phase-shift in a slow-light sensor. In this work, we report the modeling and design of an integrated optical programmable power splitter consisting of a Y-junction with a programmable phase-shifter cascaded to a directional coupler. We used a vectorial mode solver, and a combination of a transfer matrix method with a 3D vectorial coupled-mode theory (CMT) to compute the power transfer ratio of a realistic device structure made of Si3N4, TEOS, and SiO2 grown on a Si substrate. In the simulations, waveguide attenuation values derived from the measured attenuation of a prefabricated test wafer, have been taken into account. Vectorial modal fields of individual waveguides, as computed by a mode solver, were used as the basis for the CMT computation. In the simulation, an operational wavelength around 632.8 nm was assumed. Our simulations reveal that maximum power splitting ratio can be achieved when the directional coupler is operated as a 3-dB coupler with the phase-shifter set to produce a 90° phase-shift. The required coupler length for such desired operating condition is highly-dependent on the gap size. On the other hand, the inclusion of the waveguide loss and the non-parallel section of the directional coupler into the model only slightly affect the results.
Realistic modeling of seismic input for megacities and large urban areas
NASA Astrophysics Data System (ADS)
Panza, G. F.; Unesco/Iugs/Igcp Project 414 Team
2003-04-01
The project addressed the problem of pre-disaster orientation: hazard prediction, risk assessment, and hazard mapping, in connection with seismic activity and man-induced vibrations. The definition of realistic seismic input has been obtained from the computation of a wide set of time histories and spectral information, corresponding to possible seismotectonic scenarios for different source and structural models. The innovative modeling technique, that constitutes the common tool to the entire project, takes into account source, propagation and local site effects. This is done using first principles of physics about wave generation and propagation in complex media, and does not require to resort to convolutive approaches, that have been proven to be quite unreliable, mainly when dealing with complex geological structures, the most interesting from the practical point of view. In fact, several techniques that have been proposed to empirically estimate the site effects using observations convolved with theoretically computed signals corresponding to simplified models, supply reliable information about the site response to non-interfering seismic phases. They are not adequate in most of the real cases, when the seismic sequel is formed by several interfering waves. The availability of realistic numerical simulations enables us to reliably estimate the amplification effects even in complex geological structures, exploiting the available geotechnical, lithological, geophysical parameters, topography of the medium, tectonic, historical, palaeoseismological data, and seismotectonic models. The realistic modeling of the ground motion is a very important base of knowledge for the preparation of groundshaking scenarios that represent a valid and economic tool for the seismic microzonation. This knowledge can be very fruitfully used by civil engineers in the design of new seismo-resistant constructions and in the reinforcement of the existing built environment, and, therefore
ERIC Educational Resources Information Center
Shahbari, Juhaina Awawdeh; Peled, Irit
2015-01-01
This study investigates the effect of using a realistic situation with modeling characteristics in creating and resolving a cognitive conflict to promote understanding of a changing reference in fraction calculations. The study was conducted among 96 seventh graders divided into 2 experimental groups and 1 control group. The experimental groups…
NASA Astrophysics Data System (ADS)
Kamada, Ayuki; Kawasaki, Masahiro; Yamada, Masaki
2015-04-01
We show that the baryon-dark-matter coincidence problem can be solved in the constrained minimal supersymmetric model. Baryons and dark matter are generated simultaneously through the late-time decay of nontopological solitons, Q-balls, which are formed after the Affleck-Dine baryogenesis. A certain relation between the universal scalar mass m0 and the universal gaugino mass M1 /2 is required to solve the coincidence problem, marginally depending on the other parameters, and the result can be consistent with the observation of the 126-GeV Higgs boson. We also investigate the detectability in dark-matter direct-search experiments.
How realistic are flat-ramp-flat fault kinematic models? Comparing mechanical and kinematic models
NASA Astrophysics Data System (ADS)
Cruz, L.; Nevitt, J. M.; Hilley, G. E.; Seixas, G.
2015-12-01
Rock within the upper crust appears to deform according to elasto-plastic constitutive rules, but structural geologists often employ kinematic descriptions that prescribe particle motions irrespective of these physical properties. In this contribution, we examine the range of constitutive properties that are approximately implied by kinematic models by comparing predicted deformations between mechanical and kinematic models for identical fault geometric configurations. Specifically, we use the ABAQUS finite-element package to model a fault-bend-fold geometry using an elasto-plastic constitutive rule (the elastic component is linear and the plastic failure occurs according to a Mohr-Coulomb failure criterion). We varied physical properties in the mechanical model (i.e., Young's modulus, Poisson ratio, cohesion yield strength, internal friction angle, sliding friction angle) to determine the impact of each on the observed deformations, which were then compared to predictions of kinematic models parameterized with identical geometries. We found that a limited sub-set of physical properties were required to produce deformations that were similar to those predicted by the kinematic models. Specifically, mechanical models with low cohesion are required to allow the kink at the bottom of the flat-ramp geometry to remain stationary over time. Additionally, deformations produced by steep ramp geometries (30 degrees) are difficult to reconcile between the two types of models, while lower slope gradients better conform to the geometric assumptions. These physical properties may fall within the range of those observed in laboratory experiments, suggesting that particle motions predicted by kinematic models may provide an approximate representation of those produced by a physically consistent model under some circumstances.
Supersymmetric origin of matter
Balazs, C.; Carena, M.; Menon, A.; Morrissey, D.E.; Wagner, C.E.M.
2005-04-01
The minimal supersymmetric extension of the standard model (MSSM) can provide the correct neutralino relic abundance and baryon number asymmetry of the universe. Both may be efficiently generated in the presence of CP violating phases, light charginos and neutralinos, and a light top squark. Because of the coannihilation of the neutralino with the light stop, we find a large region of parameter space in which the neutralino relic density is consistent with WMAP and SDSS data. We perform a detailed study of the additional constraints induced when CP violating phases, consistent with the ones required for baryogenesis, are included. We explore the possible tests of this scenario from present and future electron electric dipole moment (EDM) measurements, direct neutralino detection experiments, collider searches and the b{yields}s{gamma} decay rate. We find that the EDM constraints are quite severe and that electron EDM experiments, together with stop searches at the Tevatron and Higgs searches at the LHC, will provide a definite test of our scenario of electroweak baryogenesis in the next few years.
Lesperance, Marielle; Inglis-Whalen, M.; Thomson, R. M.
2014-02-15
Purpose : To investigate the effects of the composition and geometry of ocular media and tissues surrounding the eye on dose distributions for COMS eye plaque brachytherapy with{sup 125}I, {sup 103}Pd, or {sup 131}Cs seeds, and to investigate doses to ocular structures. Methods : An anatomically and compositionally realistic voxelized eye model with a medial tumor is developed based on a literature review. Mass energy absorption and attenuation coefficients for ocular media are calculated. Radiation transport and dose deposition are simulated using the EGSnrc Monte Carlo user-code BrachyDose for a fully loaded COMS eye plaque within a water phantom and our full eye model for the three radionuclides. A TG-43 simulation with the same seed configuration in a water phantom neglecting the plaque and interseed effects is also performed. The impact on dose distributions of varying tumor position, as well as tumor and surrounding tissue media is investigated. Each simulation and radionuclide is compared using isodose contours, dose volume histograms for the lens and tumor, maximum, minimum, and average doses to structures of interest, and doses to voxels of interest within the eye. Results : Mass energy absorption and attenuation coefficients of the ocular media differ from those of water by as much as 12% within the 20–30 keV photon energy range. For all radionuclides studied, average doses to the tumor and lens regions in the full eye model differ from those for the plaque in water by 8%–10% and 13%–14%, respectively; the average doses to the tumor and lens regions differ between the full eye model and the TG-43 simulation by 2%–17% and 29%–34%, respectively. Replacing the surrounding tissues in the eye model with water increases the maximum and average doses to the lens by 2% and 3%, respectively. Substituting the tumor medium in the eye model for water, soft tissue, or an alternate melanoma composition affects tumor dose compared to the default eye model
Towards "realistic" fault zones in a 3D structure model of the Thuringian Basin, Germany
NASA Astrophysics Data System (ADS)
Kley, J.; Malz, A.; Donndorf, S.; Fischer, T.; Zehner, B.
2012-04-01
3D computer models of geological architecture are evolving into a standard tool for visualization and analysis. Such models typically comprise the bounding surfaces of stratigraphic layers and faults. Faults affect the continuity of aquifers and can themselves act as fluid conduits or barriers. This is one reason why a "realistic" representation of faults in 3D models is desirable. Still so, many existing models treat faults in a simplistic fashion, e.g. as vertical downward projections of fault traces observed at the surface. Besides being geologically and mechanically unreasonable, this also causes technical difficulties in the modelling workflow. Most natural faults are inclined and may change dips according to rock type or flatten into mechanically weak layers. Boreholes located close to a fault can therefore cross it at depth, resulting in stratigraphic control points allocated to the wrong block. Also, faults tend to split up into several branches, forming fault zones. Obtaining a more accurate representation of faults and fault zones is therefore challenging. We present work-in-progress from the Thuringian Basin in central Germany. The fault zone geometries are never fully constrained by data and must be extrapolated to depth. We use balancing of serial, parallel cross-sections to constrain subsurface extrapolations. The structure sections are checked for consistency by restoring them to an undeformed state. If this is possible without producing gaps or overlaps, the interpretation is considered valid (but not unique) for a single cross-section. Additional constraints are provided by comparison of adjacent cross-sections. Structures should change continuously from one section to another. Also, from the deformed and restored cross-sections we can measure the strain incurred during deformation. Strain should be compatible among the cross-sections: If at all, it should vary smoothly and systematically along a given fault zone. The stratigraphic contacts and
Supersymmetric Higgs singlet effects on FCNC observables
Hodgkinson, Robert N.
2008-11-23
Higgs singlet superflelds, usually present in extensions of the Minimal Supersymmetric Standard Model (MSSM) which address the {mu}-problem, such as the Next-to-Minimal Supersymmetric Standard Model (NMSSM) and the Minimal Nonminimal Supersymmetric Standard Model (mnSSM), can have significant contributions to B-meson flavour-changing neutral current observables for large values of tan{beta} > or approx. 50. Illustrative results are presented including effects on the B{sub s} and on the rare decay B{sub s}{yields}{mu}{sup +}{mu}{sup -}. In particular, we find that in the NMSSM, the branching ratio for B{sub s}{yields}{mu}{sup +}{mu}{sup -} can be enhanced or even suppressed with respect to the Standard Model prediction by more than one order of magnitude.
Acceleration modeling of moderate to large earthquakes based on realistic fault models
NASA Astrophysics Data System (ADS)
Arvidsson, R.; Toral, J.
2003-04-01
Strong motion is affected by distance to the earthquake, local crustal structure, focal mechanism, azimuth to the source. However, the faulting process is also of importance such as development of rupture, i.e., directivity, slip distribution on the fault, extent of fault, rupture velocity. We have modelled these parameters for earthquakes that occurred in three tectonic zones close to the Panama Canal. We included in the modeling directivity, distributed slip, discrete faulting, fault depth and expected focal mechanism. The distributed slip is based on previous fault models that we produced from the region of other earthquakes. Such previous examples show that maximum intensities in some cases coincides with areas of high slip on the fault. Our acceleration modeling also gives similar values to the few observations that have been made for moderate to small earthquakes in the range M=5-6.2. The modeling indicates that events located in the Caribbean might cause strong motion in the lower frequency spectra where high frequency Rayleigh waves dominates.
A realistic intersecting D6-brane model after the first LHC run
NASA Astrophysics Data System (ADS)
Li, Tianjun; Nanopoulos, D. V.; Raza, Shabbar; Wang, Xiao-Chuan
2014-08-01
With the Higgs boson mass around 125 GeV and the LHC supersymmetry search constraints, we revisit a three-family Pati-Salam model from intersecting D6-branes in Type IIA string theory on the T 6/(ℤ2 × ℤ2) orientifold which has a realistic phenomenology. We systematically scan the parameter space for μ < 0 and μ > 0, and find that the gravitino mass is generically heavier than about 2 TeV for both cases due to the Higgs mass low bound 123 GeV. In particular, we identify a region of parameter space with the electroweak fine-tuning as small as Δ EW ~ 24-32 (3-4%). In the viable parameter space which is consistent with all the current constraints, the mass ranges for gluino, the first two-generation squarks and sleptons are respectively [3, 18] TeV, [3, 16] TeV, and [2, 7] TeV. For the third-generation sfermions, the light stop satisfying 5 σ WMAP bounds via neutralino-stop coannihilation has mass from 0.5 to 1.2 TeV, and the light stau can be as light as 800 GeV. We also show various coannihilation and resonance scenarios through which the observed dark matter relic density is achieved. Interestingly, the certain portions of parameter space has excellent t- b- τ and b- τ Yukawa coupling unification. Three regions of parameter space are highlighted as well where the dominant component of the lightest neutralino is a bino, wino or higgsino. We discuss various scenarios in which such solutions may avoid recent astrophysical bounds in case if they satisfy or above observed relic density bounds. Prospects of finding higgsino-like neutralino in direct and indirect searches are also studied. And we display six tables of benchmark points depicting various interesting features of our model. Note that the lightest neutralino can be heavy up to 2.8 TeV, and there exists a natural region of parameter space from low-energy fine-tuning definition with heavy gluino and first two-generation squarks/sleptons, we point out that the 33 TeV and 100 TeV proton-proton colliders
Numerical simulation of wave propagation in a realistic model of the human external ear.
Fadaei, Mohaddeseh; Abouali, Omid; Emdad, Homayoun; Faramarzi, Mohammad; Ahmadi, Goodarz
2015-01-01
In this study, a numerical investigation is performed to evaluate the effects of high-pressure sinusoidal and blast wave's propagation around and inside of a human external ear. A series of computed tomography images are used to reconstruct a realistic three-dimensional (3D) model of a human ear canal and the auricle. The airflow field is then computed by solving the governing differential equations in the time domain using a computational fluid dynamics software. An unsteady algorithm is used to obtain the high-pressure wave propagation throughout the ear canal which is validated against the available analytical and numerical data in literature. The effects of frequency, wave shape, and the auricle on pressure distribution are then evaluated and discussed. The results clearly indicate that the frequency plays a key role on pressure distribution within the ear canal. At 4 kHz frequency, the pressure magnitude is much more amplified within the ear canal than the frequencies of 2 and 6 kHz, for the incident wave angle of 90° investigated in this study, attributable to the '4-kHz notch' in patients with noise-induced hearing loss. According to the results, the pressure distribution patterns at the ear canal are very similar for both sinusoidal pressure waveform with the frequency of 2 kHz and blast wave. The ratio of the peak pressure value at the eardrum to that at the canal entrance increases from about 8% to 30% as the peak pressure value of the blast wave increases from 5 to 100 kPa for the incident wave angle of 90° investigated in this study. Furthermore, incorporation of the auricle to the ear canal model is associated with centerline pressure magnitudes of about 50% and 7% more than those of the ear canal model without the auricle throughout the ear canal for sinusoidal and blast waves, respectively, without any significant effect on pressure distribution pattern along the ear canal for the incident wave angle of 90° investigated in this study. PMID
NASA Astrophysics Data System (ADS)
Gerya, Taras; Burov, Evgueni
2015-04-01
-branch junction formation and evolution by using high-resolution 3D numerical mechanical experiments that take into account realistic thermo-rheological structure and rheology of the lithosphere. We find that two major types of quadruple and triple junctions are formed under bi-directional or multidirectional far-field stress field: (i) plate rifting junctions are formed by the initial plate fragmentation and can be subsequently re-arranged into (ii) oceanic spreading junctions controlled by the new oceanic crust accretion. In particular, we document initial formation and destabilization of quadruple R-R-R-R junctions as initial plate rifting structures under bi-directional extension. In most cases, quadruple plate rifting junctions rapidly (typically within 1-2 Myr) evolve towards formation of two diverging triple oceanic spreading junctions connected by a linear spreading center lengthening with time. This configuration remains stable over long time scales. However, under certain conditions, quadruple junctions may also remain relatively stable. Asymmetric stretching results in various configurations, for example formation of "T-junctions" with trans-extensional components and combination of fast and slow spreading ridges. Combined with plume impingement, this scenario evolves in realistic patterns closely resembling observed plate dynamics. In particular, opening of the Red Sea and of the Afar rift system find a logical explanation within a single model. Numerical experiments also suggest that several existing oceanic spreading junctions form as the result of plate motions rearrangements after which only one of two plates spreading along the ridge become subjected to bi-directional spreading.
The Effect of Realistic Versus Imaginary Aggressive Models of Children's Interpersonal Play
ERIC Educational Resources Information Center
Hapkiewicz, Walter G.; Stone, Robert D.
1974-01-01
One hundred eighty elementary school children were randomly assigned to same sex pairs and randomly assigned to one of three treatment groups: real-life aggressive film, aggressive cartoon, or nonaggressive film. Results reveal that boys who viewed the realistic aggressive film were significantly more aggressive in play than boys who viewed the…
NASA Astrophysics Data System (ADS)
Fung, George S. K.; Segars, W. Paul; Veress, Alexander I.; Gullberg, Grant T.; Tsui, Benjamin M. W.
2009-02-01
A realistic 3D coronary arterial tree (CAT) has been developed for the heart model of the computer generated 3D XCAT phantom. The CAT allows generation of a realistic model of the location, size and shape of the associated regional ischemia or infarction for a given coronary arterial stenosis or occlusion. This in turn can be used in medical imaging applications. An iterative rule-based generation method that systematically utilized anatomic, morphometric and physiologic knowledge was used to construct a detailed realistic 3D model of the CAT in the XCAT phantom. The anatomic details of the myocardial surfaces and large coronary arterial vessel segments were first extracted from cardiac CT images of a normal patient with right coronary dominance. Morphometric information derived from porcine data from the literature, after being adjusted by scaling laws, provided statistically nominal diameters, lengths, and connectivity probabilities of the generated coronary arterial segments in modeling the CAT of an average human. The largest six orders of the CAT were generated based on the physiologic constraints defined in the coronary generation algorithms. When combined with the heart model of the XCAT phantom, the realistic CAT provides a unique simulation tool for the generation of realistic regional myocardial ischemia and infraction. Together with the existing heart model, the new CAT provides an important improvement over the current 3D XCAT phantom in providing a more realistic model of the normal heart and the potential to simulate myocardial diseases in evaluation of medical imaging instrumentation, image reconstruction, and data processing methods.
Bubbles of nothing and supersymmetric compactifications
NASA Astrophysics Data System (ADS)
Blanco-Pillado, Jose J.; Shlaer, Benjamin; Sousa, Kepa; Urrestilla, Jon
2016-10-01
We investigate the non-perturbative stability of supersymmetric compactifications with respect to decay via a bubble of nothing. We show examples where this kind of instability is not prohibited by the spin structure, i.e., periodicity of fermions about the extra dimension. However, such ``topologically unobstructed'' cases do exhibit an extra-dimensional analog of the well-known Coleman-De Luccia suppression mechanism, which prohibits the decay of supersymmetric vacua. We demonstrate this explicitly in a four dimensional Abelian-Higgs toy model coupled to supergravity. The compactification of this model to M3 × S1 presents the possibility of vacua with different windings for the scalar field. Away from the supersymmetric limit, these states decay by the formation of a bubble of nothing, dressed with an Abelian-Higgs vortex. We show how, as one approaches the supersymmetric limit, the circumference of the topologically unobstructed bubble becomes infinite, thereby preventing the realization of this decay. This demonstrates the dynamical origin of the decay suppression, as opposed to the more familiar argument based on the spin structure. We conjecture that this is a generic mechanism that enforces stability of any topologically unobstructed supersymmetric compactification.
Natural supersymmetric spectrum in mirage mediation
NASA Astrophysics Data System (ADS)
Asano, Masaki; Higaki, Tetsutaro
2012-08-01
The current results of LHC experiments exclude a large area of the light new particle region, namely, natural parameter space, in supersymmetric extension models. One of the possibilities for achieving the correct electroweak symmetry breaking naturally is the low-scale messenger scenario. Actually, the next-to-minimal supersymmetric standard model with TeV scale mirage mediation realizes the natural electroweak symmetry breaking with various mass spectra. In this paper, we show the possible mass spectrum in the scenario, e.g., the degenerate and/or hierarchical mass spectrum, and discuss these features.
Modeling of multi-dimensional impurity transport in a realistic tokamak geometry
NASA Astrophysics Data System (ADS)
Fukano, A.; Noritake, M.; Hoshino, K.; Yamazaki, R.; Hatayama, A.
2007-06-01
A 3D Monte Carlo transport code of heavy metal impurities is developed. The code includes most of important processes of heavy metal impurities, such as Larmor gyration, friction force, Coulomb collision, multi-step ionization and recombination process. The code outputs the 2D density profiles of tungsten impurity on realistic tokamak geometry. Calculations are made for given background plasma profiles for attached and detached plasma, which are the typical conditions in front of the divertor plate. In the attached plasma state, impurity tungsten particles are ionized to higher charge states near the divertor plate due to high background plasma electron temperature. On the other hand, in the detached plasma state, ions in higher charge states exist in the upstream of the divertor region mainly due to low background plasma electron temperature in front of the target plate. Although the code is still under development, it well describes the qualitative feature of impurity transport in the realistic tokamak geometry.
NASA Astrophysics Data System (ADS)
Morelli, S.; Casini, G.; Parmiggiani, F.
2009-04-01
Coastal polynyas are areas of open water (and/or very thin ice) which form adjacent to coasts or blocking feature in polar regions during the wintertime, when the sea water is expected to be ice covered. They are thought to be maintained by strong offshore winds blowing over these area and/or by ocean currents. Sea ice is removed as it forms and drifted offshore. In polynya areas a direct contact is established between the relatively warm sea water and the cold, dry atmosphere. As a consequence, the physical characteristics of the atmospheric boundary layer change. The work presented here concerns a real polynya event in the region of Terra Nova Bay (TNB), Antarctica, where a recurring coastal polynya occurs nearby the Italian Antarctic Base. The aim is the study of atmospheric response to the presence of a open water area of realistic size by three-dimensional numerical simulations. Atmospheric numerical modelling is a fundamental tool for the study of air - polynya interactions in the remote polar regions, where observational data are difficult. The numerical model used for the simulations is a recent version of ETA model (Mesinger et al., 2006), with the addition of a piecewise linear advection for the wind field. ECMWF and NCEP data provided the initial and boundary conditions. A previous version of the model had already been successfully used in the Antarctic area (De Carolis et al, 2006, Casini and Morelli, 2007). As a first step to analyze the polynya event, numerical simulation was performed for the period from 12 to 17 July 2006 in order to study the development of the katabatic wind (Morelli and Casini, 2008; Morelli, 2008). Daily satellite images, concerning the period, display that a sea ice free area formed on 15 and 16 July, reaching its maximum extension of about 4000 km2 on 16 July (Morelli et al.,2007). In order to gain insight on the atmospheric response to open water area within a sea ice field, ETA model runs were carried out from 15 to 17 July
Supersymmetric Ito equation: Bosonization and exact solutions
Ren Bo; Yu Jun; Lin Ji
2013-04-15
Based on the bosonization approach, the N=1 supersymmetric Ito (sIto) system is changed to a system of coupled bosonic equations. The approach can effectively avoid difficulties caused by intractable fermionic fields which are anticommuting. By solving the coupled bosonic equations, the traveling wave solutions of the sIto system are obtained with the mapping and deformation method. Some novel types of exact solutions for the supersymmetric system are constructed with the solutions and symmetries of the usual Ito equation. In the meanwhile, the similarity reduction solutions of the model are also studied with the Lie point symmetry theory.
Supersymmetric Ito equation: Bosonization and exact solutions
NASA Astrophysics Data System (ADS)
Ren, Bo; Lin, Ji; Yu, Jun
2013-04-01
Based on the bosonization approach, the N =1 N = 1 supersymmetric Ito (sIto) system is changed to a system of coupled bosonic equations. The approach can effectively avoid difficulties caused by intractable fermionic fields which are anticommuting. By solving the coupled bosonic equations, the traveling wave solutions of the sIto system are obtained with the mapping and deformation method. Some novel types of exact solutions for the supersymmetric system are constructed with the solutions and symmetries of the usual Ito equation. In the meanwhile, the similarity reduction solutions of the model are also studied with the Lie point symmetry theory.
Renormalizability of supersymmetric group field cosmology
NASA Astrophysics Data System (ADS)
Upadhyay, Sudhaker
2014-03-01
In this paper we consider the gauge invariant third quantized model of supersymmetric group field cosmology. The supersymmetric BRST invariance for such theory in non-linear gauge is also analysed. The path integral formulation to the case of a multiverse made up of homogeneous and isotropic spacetimes filled with a perfect fluid is presented. The renormalizability for the scattering of universes in multiverse are established with suitably constructed master equations for connected diagrams and proper vertices. The Slavnov-Taylor identities for this theory hold to all orders of radiative corrections.
Simulation and assessment of realistic breast lesions using fractal growth models.
Rashidnasab, A; Elangovan, P; Yip, M; Diaz, O; Dance, D R; Young, K C; Wells, K
2013-08-21
A new method of generating realistic three dimensional simulated breast lesions known as diffusion limited aggregation (DLA) is presented, and compared with the random walk (RW) method. Both methods of lesion simulation utilize a physics-based method for inserting these simulated lesions into 2D clinical mammogram images that takes into account the polychromatic x-ray spectrum, local glandularity and scatter. DLA and RW masses were assessed for realism via a receiver operating characteristic (ROC) study with nine observers. The study comprised 150 images of which 50 were real pathology proven mammograms, 50 were normal mammograms with RW inserted masses and 50 were normal mammograms with DLA inserted masses. The average area under the ROC curve for the DLA method was 0.55 (95% confidence interval 0.51-0.59) compared to 0.60 (95% confidence interval 0.56-0.63) for the RW method. The observer study results suggest that the DLA method produced more realistic masses with more variability in shape compared to the RW method. DLA generated lesions can overcome the lack of complexity in structure and shape in many current methods of mass simulation. PMID:23892735
Simulation and assessment of realistic breast lesions using fractal growth models
NASA Astrophysics Data System (ADS)
Rashidnasab, A.; Elangovan, P.; Yip, M.; Diaz, O.; Dance, D. R.; Young, K. C.; Wells, K.
2013-08-01
A new method of generating realistic three dimensional simulated breast lesions known as diffusion limited aggregation (DLA) is presented, and compared with the random walk (RW) method. Both methods of lesion simulation utilize a physics-based method for inserting these simulated lesions into 2D clinical mammogram images that takes into account the polychromatic x-ray spectrum, local glandularity and scatter. DLA and RW masses were assessed for realism via a receiver operating characteristic (ROC) study with nine observers. The study comprised 150 images of which 50 were real pathology proven mammograms, 50 were normal mammograms with RW inserted masses and 50 were normal mammograms with DLA inserted masses. The average area under the ROC curve for the DLA method was 0.55 (95% confidence interval 0.51-0.59) compared to 0.60 (95% confidence interval 0.56-0.63) for the RW method. The observer study results suggest that the DLA method produced more realistic masses with more variability in shape compared to the RW method. DLA generated lesions can overcome the lack of complexity in structure and shape in many current methods of mass simulation.
Spinon bases in supersymmetric CFTs
NASA Astrophysics Data System (ADS)
Fokkema, Thessa; Schoutens, Kareljan
2016-07-01
We present a novel way to organise the finite size spectra of a class of conformal field theories (CFT) with { N }=2 or (nonlinear) { N }=4 superconformal symmetry. Generalising the spinon basis of the {SU}{(n)}1 WZW theories, we introduce supersymmetric spinons ({φ }-,{φ }+), which form a representation of the supersymmetry algebra. In each case, we show how to construct a multi-spinon basis of the chiral CFT spectra. The multi-spinon states are labelled by a collection \\{{n}j\\} of (discrete) momenta. The state-content for given choice of \\{{n}j\\} is determined through a generalised exclusion principle, similar to Haldane's ‘motif’ rules for the {SU}{(n)}1 theories. In the simplest case, which is the { N }=2 superconformal theory with central charge c = 1, we develop an algebraic framework similar to the Yangian symmetry of the {SU}{(2)}1 theory. It includes an operator H 2, akin to a CFT Haldane-Shastry Hamiltonian, which is diagonalised by multi-spinon states. In all cases studied, we obtain finite partition sums by capping the spinon-momenta to some finite value. For the { N }=2 superconformal CFTs, this finitisation precisely leads to the so-called M k supersymmetric lattice models with characteristic order-k exclusion rules on the lattice. Finitising the c = 2 CFT with nonlinear { N }=4 superconformal symmetry similarly gives lattice model partition sums for spin-full Fermions with on-site and nearest neighbour exclusion.
Dynamical supersymmetric Dirac Hamiltonians
Ginocchio, J.N.
1986-01-01
Using the language of quantum electrodynamics, the Dirac Hamiltonian of a neutral fermion interacting with a tensor field is examined. A supersymmetry found for a general Dirac Hamiltonian of this type is discussed, followed by consideration of the special case of a harmonic electric potential. The square of the Dirac Hamiltonian of a neutral fermion interacting via an anomalous magnetic moment in an electric potential is shown to be equivalent to a three-dimensional supersymmetric Schroedinger equation. It is found that for a potential that grows as a power of r, the lowest energy of the Hamiltonian equals the rest mass of the fermion, and the Dirac eigenfunction has only an upper component which is normalizable. It is also found that the higher energy states have upper and lower components which form a supersymmetric doublet. 15 refs. (LEW)
Semiclassical Supersymmetric Quantum Gravity
NASA Astrophysics Data System (ADS)
Kiefer, Claus; Lück, Tobias; Vargas Moniz, Paulo
2008-09-01
We develop a semiclassical approximation scheme for the constraint equations of supersymmetric canonical quantum gravity. This is achieved by a Born-Oppenheimer type of expansion, in analogy to the case of the usual Wheeler-DeWitt equation. We recover at consecutive orders the Hamilton-Jacobi equation, the functional Schrödinger equation, and quantum gravitational correction terms to this Schrödinger equation. In particular, our work has the following implications: (i) the Hamilton-Jacobi equation and therefore the background spacetime must involve the gravitino, (ii) a (many fingered) local time parameter has to be present on Super Riem Σ (the space of all possible tetrad and gravitino fields), (iii) quantum supersymmetric gravitational corrections affect the evolution of the very early universe.
Dermisek, Radovan; Gunion, John F.
2006-06-01
We examine the LEP limits for the Zh{yields}Z+b's final state and find that the excess of observed events for m{sub h}{approx}100 GeV correlates well with there being an m{sub h}{approx}100 GeV Higgs boson with SM-like ZZh coupling that decays partly via h{yields}bb+{tau}{sup +}{tau}{sup -} [with B(h{yields}bb){approx}0.08] but dominantly via h{yields}aa [with B(h{yields}aa){approx}0.9], where m{sub a}<2m{sub b} so that a{yields}{tau}{sup +}{tau}{sup -} (or light quarks and gluons) decays are dominant. This type of scenario is precisely that predicted in the Next-to-Minimal Supersymmetric Model for parameter choices yielding the lowest possible fine-tuning.
NASA Astrophysics Data System (ADS)
Aad, G.; Abbott, B.; Abdallah, J.; Abdel Khalek, S.; Abdinov, O.; Aben, R.; Abi, B.; Abolins, M.; AbouZeid, O. S.; Abramowicz, H.; Abreu, H.; Abreu, R.; Abulaiti, Y.; Acharya, B. S.; Adamczyk, L.; Adams, D. L.; Adelman, J.; Adomeit, S.; Adye, T.; Agatonovic-Jovin, T.; Aguilar-Saavedra, J. A.; Agustoni, M.; Ahlen, S. P.; Ahmadov, F.; Aielli, G.; Akerstedt, H.; Åkesson, T. P. A.; Akimoto, G.; Akimov, A. V.; Alberghi, G. L.; Albert, J.; Albrand, S.; Alconada Verzini, M. J.; Aleksa, M.; Aleksandrov, I. N.; Alexa, C.; Alexander, G.; Alexandre, G.; Alexopoulos, T.; Alhroob, M.; Alimonti, G.; Alio, L.; Alison, J.; Allbrooke, B. M. M.; Allison, L. J.; Allport, P. P.; Aloisio, A.; Alonso, A.; Alonso, F.; Alpigiani, C.; Altheimer, A.; Alvarez Gonzalez, B.; Alviggi, M. G.; Amako, K.; Amaral Coutinho, Y.; Amelung, C.; Amidei, D.; Amor Dos Santos, S. P.; Amorim, A.; Amoroso, S.; Amram, N.; Amundsen, G.; Anastopoulos, C.; Ancu, L. S.; Andari, N.; Andeen, T.; Anders, C. F.; Anders, G.; Anderson, K. J.; Andreazza, A.; Andrei, V.; Anduaga, X. S.; Angelidakis, S.; Angelozzi, I.; Anger, P.; Angerami, A.; Anghinolfi, F.; Anisenkov, A. V.; Anjos, N.; Annovi, A.; Antonaki, A.; Antonelli, M.; Antonov, A.; Antos, J.; Anulli, F.; Aoki, M.; Aperio Bella, L.; Apolle, R.; Arabidze, G.; Aracena, I.; Arai, Y.; Araque, J. P.; Arce, A. T. H.; Arduh, F. A.; Arguin, J.-F.; Argyropoulos, S.; Arik, M.; Armbruster, A. J.; Arnaez, O.; Arnal, V.; Arnold, H.; Arratia, M.; Arslan, O.; Artamonov, A.; Artoni, G.; Asai, S.; Asbah, N.; Ashkenazi, A.; Åsman, B.; Asquith, L.; Assamagan, K.; Astalos, R.; Atkinson, M.; Atlay, N. B.; Auerbach, B.; Augsten, K.; Aurousseau, M.; Avolio, G.; Axen, B.; Azuelos, G.; Azuma, Y.; Baak, M. A.; Baas, A. E.; Bacci, C.; Bachacou, H.; Bachas, K.; Backes, M.; Backhaus, M.; Backus Mayes, J.; Badescu, E.; Bagiacchi, P.; Bagnaia, P.; Bai, Y.; Bain, T.; Baines, J. T.; Baker, O. K.; Balek, P.; Balli, F.; Banas, E.; Banerjee, Sw.; Bannoura, A. A. E.; Bansal, V.; Bansil, H. S.; Barak, L.; Baranov, S. P.; Barberio, E. L.; Barberis, D.; Barbero, M.; Barillari, T.; Barisonzi, M.; Barklow, T.; Barlow, N.; Barnes, S. L.; Barnett, B. M.; Barnett, R. M.; Barnovska, Z.; Baroncelli, A.; Barone, G.; Barr, A. J.; Barreiro, F.; Barreiro Guimarães da Costa, J.; Bartoldus, R.; Barton, A. E.; Bartos, P.; Bartsch, V.; Bassalat, A.; Basye, A.; Bates, R. L.; Batista, S. J.; Batley, J. R.; Battaglia, M.; Battistin, M.; Bauer, F.; Bawa, H. S.; Beattie, M. D.; Beau, T.; Beauchemin, P. H.; Beccherle, R.; Bechtle, P.; Beck, H. P.; Becker, K.; Becker, S.; Beckingham, M.; Becot, C.; Beddall, A. J.; Beddall, A.; Bedikian, S.; Bednyakov, V. A.; Bee, C. P.; Beemster, L. J.; Beermann, T. A.; Begel, M.; Behr, K.; Belanger-Champagne, C.; Bell, P. J.; Bell, W. H.; Bella, G.; Bellagamba, L.; Bellerive, A.; Bellomo, M.; Belotskiy, K.; Beltramello, O.; Benary, O.; Benchekroun, D.; Bendtz, K.; Benekos, N.; Benhammou, Y.; Benhar Noccioli, E.; Benitez Garcia, J. A.; Benjamin, D. 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2014-11-01
A search for the neutral Higgs bosons predicted by the Minimal Supersymmetric Standard Model (MSSM) is reported. The analysis is performed on data from proton-proton collisions at a centre-of-mass energy of 8 TeV collected with the ATLAS detector at the Large Hadron Collider. The samples used for this search were collected in 2012 and correspond to integrated luminosities in the range 19.5-20.3 fb-1. The MSSM Higgs bosons are searched for in the τ τ final state. No significant excess over the expected background is observed, and exclusion limits are derived for the production cross section times branching fraction of a scalar particle as a function of its mass. The results are also interpreted in the MSSM parameter space for various benchmark scenarios. [Figure not available: see fulltext.
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Schmitt, M; Stoynev, S; Velasco, M; Won, S; Antonelli, L; Berry, D; Hildreth, M; Jessop, C; Karmgard, D J; Kolb, J; Kolberg, T; Lannon, K; Luo, W; Lynch, S; Marinelli, N; Morse, D M; Pearson, T; Ruchti, R; Slaunwhite, J; Valls, N; Wayne, M; Ziegler, J; Bylsma, B; Durkin, L S; Gu, J; Hill, C; Killewald, P; Kotov, K; Ling, T Y; Rodenburg, M; Williams, G; Adam, N; Berry, E; Elmer, P; Gerbaudo, D; Halyo, V; Hebda, P; Hunt, A; Jones, J; Laird, E; Pegna, D Lopes; Marlow, D; Medvedeva, T; Mooney, M; Olsen, J; Piroué, P; Quan, X; Saka, H; Stickland, D; Tully, C; Werner, J S; Zuranski, A; Acosta, J G; Huang, X T; Lopez, A; Mendez, H; Oliveros, S; Vargas, J E Ramirez; Zatserklyaniy, A; Alagoz, E; Barnes, V E; Bolla, G; Borrello, L; Bortoletto, D; Everett, A; Garfinkel, A F; Gutay, L; Hu, Z; Jones, M; Koybasi, O; Kress, M; Laasanen, A T; Leonardo, N; Liu, C; Maroussov, V; Merkel, P; Miller, D H; Neumeister, N; Shipsey, I; Silvers, D; Svyatkovskiy, A; Yoo, H D; Zablocki, J; Zheng, Y; Jindal, P; Parashar, N; Boulahouache, C; Cuplov, V; Ecklund, K M; Geurts, F J M; Padley, B P; Redjimi, R; Roberts, J; Zabel, J; Betchart, B; Bodek, A; Chung, Y S; Covarelli, R; de Barbaro, P; Demina, R; Eshaq, Y; Flacher, H; Garcia-Bellido, A; Goldenzweig, P; Gotra, Y; Han, J; Harel, A; Miner, D C; Orbaker, D; Petrillo, G; Vishnevskiy, D; Zielinski, M; Bhatti, A; Ciesielski, R; Demortier, L; Goulianos, K; Lungu, G; Malik, S; Mesropian, C; Yan, M; Atramentov, O; Barker, A; Duggan, D; Gershtein, Y; Gray, R; Halkiadakis, E; Hidas, D; Hits, D; Lath, A; Panwalkar, S; Patel, R; Richards, A; Rose, K; Schnetzer, S; Somalwar, S; Stone, R; Thomas, S; Cerizza, G; Hollingsworth, M; Spanier, S; Yang, Z C; York, A; Asaadi, J; Eusebi, R; Gilmore, J; Gurrola, A; Kamon, T; Khotilovich, V; Montalvo, R; Nguyen, C N; Osipenkov, I; Pakhotin, Y; Pivarski, J; Safonov, A; Sengupta, S; Tatarinov, A; Toback, D; Weinberger, M; Akchurin, N; Bardak, C; Damgov, J; Jeong, C; Kovitanggoon, K; Lee, S W; Roh, Y; Sill, A; Volobouev, I; Wigmans, R; Yazgan, E; Appelt, E; Brownson, E; Engh, D; Florez, C; Gabella, W; Issah, M; Johns, W; Kurt, P; Maguire, C; Melo, A; Sheldon, P; Snook, B; Tuo, S; Velkovska, J; Arenton, M W; Balazs, M; Boutle, S; Cox, B; Francis, B; Hirosky, R; Ledovskoy, A; Lin, C; Neu, C; Yohay, R; Gollapinni, S; Harr, R; Karchin, P E; Lamichhane, P; Mattson, M; Milstène, C; Sakharov, A; Anderson, M; Bachtis, M; Bellinger, J N; Carlsmith, D; Dasu, S; Efron, J; Flood, K; Gray, L; Grogg, K S; Grothe, M; Hall-Wilton, R; Herndon, M; Klabbers, P; Klukas, J; Lanaro, A; Lazaridis, C; Leonard, J; Loveless, R; Mohapatra, A; Palmonari, F; Reeder, D; Ross, I; Savin, A; Smith, W H; Swanson, J; Weinberg, M
2011-06-10
A search for neutral minimal supersymmetric standard model (MSSM) Higgs bosons in pp collisions at the LHC at a center-of-mass energy of 7 TeV is presented. The results are based on a data sample corresponding to an integrated luminosity of 36 pb(-1) recorded by the CMS experiment. The search uses decays of the Higgs bosons to tau pairs. No excess is observed in the tau-pair invariant-mass spectrum. The resulting upper limits on the Higgs boson production cross section times branching fraction to tau pairs, as a function of the pseudoscalar Higgs boson mass, yield stringent new bounds in the MSSM parameter space.
Abazov V. M.; Abbott B.; Acharya B. S.; Adams M.; Adams T.; Alexeev G. D.; Alkhazov G.; Alton A.; Alverson G.; Aoki M.; Askew A.; Asman B.; Atkins S.; Atramentov O.; Augsten K.; Avila C.; BackusMayes J.; Badaud F.; Bagby L.; Baldin B.; Bandurin D. V.; Banerjee S.; Barberis E.; Baringer P.; Barreto J.; Bartlett J. F.; Bassler U.; Bazterra V.; Bean A.; Begalli M.; Belanger-Champagne C.; Bellantoni L.; Beri S. B.; Bernardi G.; Bernhard R.; Bertram I.; Besancon M.; Beuselinck R.; Bezzubov V. A.; Bhat P. C.; Bhatia S.; Bhatnagar V.; Blazey G.; Blessing S.; Bloom K.; Boehnlein A.; Boline D.; Boos E. E.; Borissov G.; Bose T.; Brandt A.; Brandt O.; Brock R.; Brooijmans G.; Bross A.; Brown D.; Brown J.; Bu X. B.; Buehler M.; Buescher V.; Bunichev V.; Burdin S.; Burnett T. H.; Buszello C. P.; Calpas B.; Camacho-Perez E.; Carrasco-Lizarraga M. A.; Casey B. C. K.; Castilla-Valdez H.; Chakrabarti S.; Chakraborty D.; Chan K. M.; Chandra A.; Chapon E.; Chen G.; Chevalier-Thery S.; Cho D. K.; Cho S. W.; Choi S.; Choudhary B.; Cihangir S.; Claes D.; Clutter J.; Cooke M.; Cooper W. E.; Corcoran M.; Couderc F.; Cousinou M. -C.; Croc A.; Cutts D.; Das A.; Davies G.; de Jong S. J.; De La Cruz-Burelo E.; Deliot F.; Demina R.; Denisov D.; Denisov S. P.; Desai S.; Deterre C.; DeVaughan K.; Diehl H. T.; Diesburg M.; Ding P. F.; Dominguez A.; Dorland T.; Dubey A.; Dudko L. V.; Duggan D.; Duperrin A.; Dutt S.; Dyshkant A.; Eads M.; Edmunds D.; Ellison J.; Elvira V. D.; Enari Y.; Evans H.; Evdokimov A.; Evdokimov V. N.; Facini G.; Ferbel T.; Fiedler F.; Filthaut F.; Fisher W.; Fisk H. E.; Fortner M.; Fox H.; Fuess S.; Garcia-Bellido A.; Garcia-Guerra G. A.; Gavrilov V.; Gay P.; Geng W.; Gerbaudo D.; Gerber C. E.; Gershtein Y.; Ginther G.; Golovanov G.; Goussiou A.; Grannis P. D.; Greder S.; Greenlee H.; Greenwood Z. D.; Gregores E. M.; Grenier G.; Gris Ph.; Grivaz J. -F.; Grohsjean A.; Gruenendahl S.; Gruenewald M. W.; Guillemin T.; Gutierrez G.; Gutierrez P.; Haas A.; Hagopian S.; Haley J.; Han L.; Harder K.; Harel A.; Hauptman J. M.; Hays J.; Head T.; Hebbeker T.; Hedin D.; Hegab H.; Heinson A. P.; Heintz U.; Hensel C.; Heredia-De La Cruz I.; Herner K.; Hesketh G.; Hildreth M. D.; Hirosky R.; Hoang T.; Hobbs J. D.; Hoeneisen B.; Hohlfeld M.; Hubacek Z.; Hynek V.; Iashvili I.; Ilchenko Y.; Illingworth R.; Ito A. S.; Jabeen S.; Jaffre M.; Jaminn D.; Jayasinghe A.; Jesik R.; Johns K.; Johnson M.; Jonckheere A.; Jonsson P.; Joshi J.; Jung A. W.; Juste A.; Kaadze K.; Kajfasz E.; Karmanov D.; Kasper P. A.; Katsanos I.; Kehoe R.; Kermiche S.; Khalatyan N.; Khanov A.; Kharchilava A.; Kharzheev Y. N.; Kohli J. M.; Kozelov A. V.; Kraus J.; Kulikov S.; Kumar A.; Kupco A.; Kurca T.; Kuzmin V. A.; Lammers S.; Landsberg G.; Lebrun P.; Lee H. S.; Lee S. W.; Lee W. M.; Lellouch J.; Li H.; Li L.; Li Q. Z.; Lietti S. M.; Lim J. K.; Lincoln D.; Linnemann J.; Lipaev V. V.; Lipton R.; Liu Y.; Lobodenko A.; Lokajicek M.; Lopes de Sa R.; Lubatti H. J.; Luna-Garcia R.; Lyon A. L.; Maciel A. K. A.; Mackin D.; Madar R.; Magana-Villalba R.; Malik S.; Malyshev V. L.; Maravin Y.; Martinez-Ortega J.; McCarthy R.; McGivern C. L.; Meijer M. M.; Melnitchouk A.; Menezes D.; Mercadante P. G.; Merkin M.; et al.
2012-04-20
We report results from searches for neutral Higgs bosons produced in p{bar p} collisions recorded by the D0 experiment at the Fermilab Tevatron Collider. We study the production of inclusive neutral Higgs boson in the {tau}{tau} final state and in association with a b quark in the b{tau}{tau} and bbb final states. These results are combined to improve the sensitivity to the production of neutral Higgs bosons in the context of the minimal supersymmetric standard model (MSSM). The data are found to be consistent with expectation from background processes. Upper limits on MSSM Higgs boson production are set for Higgs boson masses ranging from 90 to 300 GeV. We exclude tan {beta} > 20-30 for Higgs boson masses below 180 GeV. These are the most stringent constraints on MSSM Higgs boson production in p{bar p} collisions.
Chatrchyan, S; Khachatryan, V; Sirunyan, A M; Tumasyan, A; Adam, W; Bergauer, T; Dragicevic, M; Erö, J; Fabjan, C; Friedl, M; Frühwirth, R; Ghete, V M; Hammer, J; Hänsel, S; Hoch, M; Hörmann, N; Hrubec, J; Jeitler, M; Kasieczka, G; Kiesenhofer, W; Krammer, M; Liko, D; Mikulec, I; Pernicka, M; Rohringer, H; Schöfbeck, R; Strauss, J; Teischinger, F; Wagner, P; Waltenberger, W; Walzel, G; Widl, E; Wulz, C-E; Mossolov, V; Shumeiko, N; Suarez Gonzalez, J; Benucci, L; De Wolf, E A; Janssen, X; Maes, T; Mucibello, L; Ochesanu, S; Roland, B; Rougny, R; Selvaggi, M; Van Haevermaet, H; Van Mechelen, P; Van Remortel, N; Blekman, F; Blyweert, S; D'Hondt, J; Devroede, O; Gonzalez Suarez, R; Kalogeropoulos, A; Maes, J; Maes, M; Van Doninck, W; Van Mulders, P; Van Onsem, G P; Villella, I; Charaf, O; Clerbaux, B; De Lentdecker, G; Dero, V; Gay, A P R; Hammad, G H; Hreus, T; Marage, P E; Thomas, L; Vander Velde, C; Vanlaer, P; Adler, V; Cimmino, A; Costantini, S; Grunewald, M; Klein, B; Lellouch, J; Marinov, A; McCartin, J; Ryckbosch, D; Thyssen, F; Tytgat, M; Vanelderen, L; Verwilligen, P; Walsh, S; Zaganidis, N; Basegmez, S; Bruno, G; Caudron, J; Ceard, L; Cortina Gil, E; De Favereau De Jeneret, J; Delaere, C; Favart, D; Giammanco, A; Grégoire, G; Hollar, J; Lemaitre, V; Liao, J; Militaru, O; Ovyn, S; Pagano, D; Pin, A; Piotrzkowski, K; Schul, N; Beliy, N; Caebergs, T; Daubie, E; Alves, G A; Damiao, D De Jesus; Pol, M E; Souza, M H G; Carvalho, W; Da Costa, E M; Martins, C De Oliveira; De Souza, S Fonseca; Mundim, L; Nogima, H; Oguri, V; Da Silva, W L Prado; Santoro, A; Do Amaral, S M Silva; Sznajder, A; De Araujo, F Torres Da Silva; Dias, F A; Tomei, T R Fernandez Perez; Gregores, E M; Lagana, C; Marinho, F; Mercadante, P G; Novaes, S F; Padula, Sandra S; Darmenov, N; Dimitrov, L; Genchev, V; Iaydjiev, P; Piperov, S; Rodozov, M; Stoykova, S; Sultanov, G; Tcholakov, V; Trayanov, R; Vankov, I; Dimitrov, A; Hadjiiska, R; Karadzhinova, A; Kozhuharov, V; Litov, L; Mateev, M; Pavlov, B; Petkov, P; Bian, J G; Chen, G M; Chen, H S; Jiang, C H; Liang, D; Liang, S; Meng, X; Tao, J; Wang, J; Wang, J; Wang, X; Wang, Z; Xiao, H; Xu, M; Zang, J; Zhang, Z; Ban, Y; Guo, S; Guo, Y; Li, W; Mao, Y; Qian, S J; Teng, H; Zhang, L; Zhu, B; Zou, W; Cabrera, A; Moreno, B Gomez; Rios, A A Ocampo; Oliveros, A F Osorio; Sanabria, J C; Godinovic, N; Lelas, D; Lelas, K; Plestina, R; Polic, D; Puljak, I; Antunovic, Z; Dzelalija, M; Brigljevic, V; Duric, S; Kadija, K; Morovic, S; Attikis, A; Galanti, M; Mousa, J; Nicolaou, C; Ptochos, F; Razis, P A; Finger, M; Finger, M; Assran, Y; Khalil, S; Mahmoud, M A; Hektor, A; Kadastik, M; Müntel, M; Raidal, M; Rebane, L; Azzolini, V; Eerola, P; Fedi, G; Czellar, S; Härkönen, J; Heikkinen, A; Karimäki, V; Kinnunen, R; Kortelainen, M J; Lampén, T; Lassila-Perini, K; Lehti, S; Lindén, T; Luukka, P; Mäenpää, T; Tuominen, E; Tuominiemi, J; Tuovinen, E; Ungaro, D; Wendland, L; Banzuzi, K; Korpela, A; Tuuva, T; Sillou, D; Besancon, M; Choudhury, S; Dejardin, M; Denegri, D; Fabbro, B; Faure, J L; Ferri, F; Ganjour, S; Gentit, F X; Givernaud, A; Gras, P; de Monchenault, G Hamel; Jarry, P; Locci, E; Malcles, J; Marionneau, M; Millischer, L; Rander, J; Rosowsky, A; Shreyber, I; Titov, M; Verrecchia, P; Baffioni, S; Beaudette, F; Benhabib, L; Bianchini, L; Bluj, M; Broutin, C; Busson, P; Charlot, C; Dahms, T; Dobrzynski, L; Elgammal, S; de Cassagnac, R Granier; Haguenauer, M; Miné, P; Mironov, C; Ochando, C; Paganini, P; Sabes, D; Salerno, R; Sirois, Y; Thiebaux, C; Wyslouch, B; Zabi, A; Agram, J-L; Andrea, J; Bloch, D; Bodin, D; Brom, J-M; Cardaci, M; Chabert, E C; Collard, C; Conte, E; Drouhin, F; Ferro, C; Fontaine, J-C; Gelé, D; Goerlach, U; Greder, S; Juillot, P; Karim, M; Le Bihan, A-C; Mikami, Y; Van Hove, P; Fassi, F; Mercier, D; Baty, C; Beauceron, S; Beaupere, N; Bedjidian, M; Bondu, O; Boudoul, G; Boumediene, D; Brun, H; Chierici, R; Contardo, D; Depasse, P; El Mamouni, H; Fay, J; Gascon, S; Ille, B; Kurca, T; Le Grand, T; Lethuillier, M; Mirabito, L; Perries, S; Sordini, V; Tosi, S; Tschudi, Y; Verdier, P; Lomidze, D; Anagnostou, G; Edelhoff, M; Feld, L; Heracleous, N; Hindrichs, O; Jussen, R; Klein, K; Merz, J; Mohr, N; Ostapchuk, A; Perieanu, A; Raupach, F; Sammet, J; Schael, S; Sprenger, D; Weber, H; Weber, M; Wittmer, B; Ata, M; Bender, W; Dietz-Laursonn, E; Erdmann, M; Frangenheim, J; Hebbeker, T; Hinzmann, A; Hoepfner, K; Klimkovich, T; Klingebiel, D; Kreuzer, P; Lanske, D; Magass, C; Merschmeyer, M; Meyer, A; Papacz, P; Pieta, H; Reithler, H; Schmitz, S A; Sonnenschein, L; Steggemann, J; Teyssier, D; Tonutti, M; Bontenackels, M; Davids, M; Duda, M; Flügge, G; Geenen, H; Giffels, M; Ahmad, W Haj; Heydhausen, D; Kress, T; Kuessel, Y; Linn, A; Nowack, A; Perchalla, L; Pooth, O; Rennefeld, J; Sauerland, P; Stahl, A; Thomas, M; Tornier, D; Zoeller, M H
2011-06-10
A search for neutral minimal supersymmetric standard model (MSSM) Higgs bosons in pp collisions at the LHC at a center-of-mass energy of 7 TeV is presented. The results are based on a data sample corresponding to an integrated luminosity of 36 pb(-1) recorded by the CMS experiment. The search uses decays of the Higgs bosons to tau pairs. No excess is observed in the tau-pair invariant-mass spectrum. The resulting upper limits on the Higgs boson production cross section times branching fraction to tau pairs, as a function of the pseudoscalar Higgs boson mass, yield stringent new bounds in the MSSM parameter space. PMID:21770497
Oprisan, Sorinel A.; Buhusi, Catalin V.
2011-01-01
In most species, the capability of perceiving and using the passage of time in the seconds-to-minutes range (interval timing) is not only accurate but also scalar: errors in time estimation are linearly related to the estimated duration. The ubiquity of scalar timing extends over behavioral, lesion, and pharmacological manipulations. For example, in mammals, dopaminergic drugs induce an immediate, scalar change in the perceived time (clock pattern), whereas cholinergic drugs induce a gradual, scalar change in perceived time (memory pattern). How do these properties emerge from unreliable, noisy neurons firing in the milliseconds range? Neurobiological information relative to the brain circuits involved in interval timing provide support for an striatal beat frequency (SBF) model, in which time is coded by the coincidental activation of striatal spiny neurons by cortical neural oscillators. While biologically plausible, the impracticality of perfect oscillators, or their lack thereof, questions this mechanism in a brain with noisy neurons. We explored the computational mechanisms required for the clock and memory patterns in an SBF model with biophysically realistic and noisy Morris–Lecar neurons (SBF–ML). Under the assumption that dopaminergic drugs modulate the firing frequency of cortical oscillators, and that cholinergic drugs modulate the memory representation of the criterion time, we show that our SBF–ML model can reproduce the pharmacological clock and memory patterns observed in the literature. Numerical results also indicate that parameter variability (noise) – which is ubiquitous in the form of small fluctuations in the intrinsic frequencies of neural oscillators within and between trials, and in the errors in recording/retrieving stored information related to criterion time – seems to be critical for the time-scale invariance of the clock and memory patterns. PMID:21977014
Supersymmetric fifth order evolution equations
Tian, K.; Liu, Q. P.
2010-03-08
This paper considers supersymmetric fifth order evolution equations. Within the framework of symmetry approach, we give a list containing six equations, which are (potentially) integrable systems. Among these equations, the most interesting ones include a supersymmetric Sawada-Kotera equation and a novel supersymmetric fifth order KdV equation. For the latter, we supply some properties such as a Hamiltonian structures and a possible recursion operator.
Eastman, Clifford L.; Fender, Jason S.; Temkin, Nancy R.; D’Ambrosio, Raimondo
2015-01-01
Conventionally developed antiseizure drugs fail to control epileptic seizures in about 30% of patients, and no treatment prevents epilepsy. New etiologically realistic, syndrome-specific epilepsy models are expected to identify better treatments by capturing currently unknown ictogenic and epileptogenic mechanisms that operate in the corresponding patient populations. Additionally, the use of electrocorticography permits better monitoring of epileptogenesis and the full spectrum of acquired seizures, including focal nonconvulsive seizures that are typically difficult to treat in humans. Thus, the combined use of etiologically realistic models and electrocorticography may improve our understanding of the genesis and progression of epilepsy, and facilitate discovery and translation of novel treatments. However, this approach is labor intensive and must be optimized. To this end, we used an etiologically realistic rat model of posttraumatic epilepsy, in which the initiating fluid percussion injury closely replicates contusive closed-head injury in humans, and has been adapted to maximize epileptogenesis and focal non-convulsive seizures. We obtained week-long 5-electrode electrocorticography 1 month post-injury, and used a Monte-Carlo-based non-parametric bootstrap strategy to test the impact of electrode montage design, duration-based seizure definitions, group size and duration of recordings on the assessment of posttraumatic epilepsy, and on statistical power to detect antiseizure and antiepileptogenic treatment effects. We found that use of seizure definition based on clinical criteria rather than event duration, and of recording montages closely sampling the activity of epileptic foci, maximize the power to detect treatment effects. Detection of treatment effects was marginally improved by prolonged recording, and 24 h recording epochs were sufficient to provide 80% power to detect clinically interesting seizure control or prevention of seizures with small groups
Eastman, Clifford L; Fender, Jason S; Temkin, Nancy R; D'Ambrosio, Raimondo
2015-02-01
Conventionally developed antiseizure drugs fail to control epileptic seizures in about 30% of patients, and no treatment prevents epilepsy. New etiologically realistic, syndrome-specific epilepsy models are expected to identify better treatments by capturing currently unknown ictogenic and epileptogenic mechanisms that operate in the corresponding patient populations. Additionally, the use of electrocorticography permits better monitoring of epileptogenesis and the full spectrum of acquired seizures, including focal nonconvulsive seizures that are typically difficult to treat in humans. Thus, the combined use of etiologically realistic models and electrocorticography may improve our understanding of the genesis and progression of epilepsy, and facilitate discovery and translation of novel treatments. However, this approach is labor intensive and must be optimized. To this end, we used an etiologically realistic rat model of posttraumatic epilepsy, in which the initiating fluid percussion injury closely replicates contusive closed-head injury in humans, and has been adapted to maximize epileptogenesis and focal non-convulsive seizures. We obtained week-long 5-electrode electrocorticography 1 month post-injury, and used a Monte-Carlo-based non-parametric bootstrap strategy to test the impact of electrode montage design, duration-based seizure definitions, group size and duration of recordings on the assessment of posttraumatic epilepsy, and on statistical power to detect antiseizure and antiepileptogenic treatment effects. We found that use of seizure definition based on clinical criteria rather than event duration, and of recording montages closely sampling the activity of epileptic foci, maximize the power to detect treatment effects. Detection of treatment effects was marginally improved by prolonged recording, and 24h recording epochs were sufficient to provide 80% power to detect clinically interesting seizure control or prevention of seizures with small groups
Roques, Lionel; Bonnefon, Olivier
2016-01-01
We propose and develop a general approach based on reaction-diffusion equations for modelling a species dynamics in a realistic two-dimensional (2D) landscape crossed by linear one-dimensional (1D) corridors, such as roads, hedgerows or rivers. Our approach is based on a hybrid "2D/1D model", i.e, a system of 2D and 1D reaction-diffusion equations with homogeneous coefficients, in which each equation describes the population dynamics in a given 2D or 1D element of the landscape. Using the example of the range expansion of the tiger mosquito Aedes albopictus in France and its main highways as 1D corridors, we show that the model can be fitted to realistic observation data. We develop a mechanistic-statistical approach, based on the coupling between a model of population dynamics and a probabilistic model of the observation process. This allows us to bridge the gap between the data (3 levels of infestation, at the scale of a French department) and the output of the model (population densities at each point of the landscape), and to estimate the model parameter values using a maximum-likelihood approach. Using classical model comparison criteria, we obtain a better fit and a better predictive power with the 2D/1D model than with a standard homogeneous reaction-diffusion model. This shows the potential importance of taking into account the effect of the corridors (highways in the present case) on species dynamics. With regard to the particular case of A. albopictus, the conclusion that highways played an important role in species range expansion in mainland France is consistent with recent findings from the literature. PMID:26986201
Inflation in supersymmetric SU(5)
Khalil, S.; Rehman, M. U.; Shafi, Q.; Zaakouk, E. A.
2011-03-15
We analyze the adjoint field inflation in supersymmetric (SUSY) SU(5) model. In minimal SUSY SU(5) hybrid inflation monopoles are produced at the end of inflation. We therefore explore the nonminimal model of inflation based on SUSY SU(5), like shifted hybrid inflation, which provides a natural solution for the monopole problem. We find that the supergravity corrections with nonminimal Kaehler potential are crucial to realize the central value of the scalar spectral index n{sub s{approx_equal}}0.96 consistent with the 7 yr WMAP data. The tensor to scalar ratio r is quite small, taking on values r < or approx. 10{sup -5}. Because of R symmetry massless SU(3) octet and SU(2) triplet supermultiplets are present and could spoil gauge coupling unification. To keep gauge coupling unification intact, light vectorlike particles are added which are expected to be observed at LHC.
2016-01-01
We propose and develop a general approach based on reaction-diffusion equations for modelling a species dynamics in a realistic two-dimensional (2D) landscape crossed by linear one-dimensional (1D) corridors, such as roads, hedgerows or rivers. Our approach is based on a hybrid “2D/1D model”, i.e, a system of 2D and 1D reaction-diffusion equations with homogeneous coefficients, in which each equation describes the population dynamics in a given 2D or 1D element of the landscape. Using the example of the range expansion of the tiger mosquito Aedes albopictus in France and its main highways as 1D corridors, we show that the model can be fitted to realistic observation data. We develop a mechanistic-statistical approach, based on the coupling between a model of population dynamics and a probabilistic model of the observation process. This allows us to bridge the gap between the data (3 levels of infestation, at the scale of a French department) and the output of the model (population densities at each point of the landscape), and to estimate the model parameter values using a maximum-likelihood approach. Using classical model comparison criteria, we obtain a better fit and a better predictive power with the 2D/1D model than with a standard homogeneous reaction-diffusion model. This shows the potential importance of taking into account the effect of the corridors (highways in the present case) on species dynamics. With regard to the particular case of A. albopictus, the conclusion that highways played an important role in species range expansion in mainland France is consistent with recent findings from the literature. PMID:26986201
Thomas, Yoann; Dumas, Franck; Andréfouët, Serge
2014-01-01
Studying the larval dispersal of bottom-dwelling species is necessary to understand their population dynamics and optimize their management. The black-lip pearl oyster (Pinctada margaritifera) is cultured extensively to produce black pearls, especially in French Polynesia's atoll lagoons. This aquaculture relies on spat collection, a process that can be optimized by understanding which factors influence larval dispersal. Here, we investigate the sensitivity of P. margaritifera larval dispersal kernel to both physical and biological factors in the lagoon of Ahe atoll. Specifically, using a validated 3D larval dispersal model, the variability of lagoon-scale connectivity is investigated against wind forcing, depth and location of larval release, destination location, vertical swimming behavior and pelagic larval duration (PLD) factors. The potential connectivity was spatially weighted according to both the natural and cultivated broodstock densities to provide a realistic view of connectivity. We found that the mean pattern of potential connectivity was driven by the southwest and northeast main barotropic circulation structures, with high retention levels in both. Destination locations, spawning sites and PLD were the main drivers of potential connectivity, explaining respectively 26%, 59% and 5% of the variance. Differences between potential and realistic connectivity showed the significant contribution of the pearl oyster broodstock location to its own dynamics. Realistic connectivity showed larger larval supply in the western destination locations, which are preferentially used by farmers for spat collection. In addition, larval supply in the same sectors was enhanced during summer wind conditions. These results provide new cues to understanding the dynamics of bottom-dwelling populations in atoll lagoons, and show how to take advantage of numerical models for pearl oyster management.
Thomas, Yoann; Dumas, Franck; Andréfouët, Serge
2014-01-01
Studying the larval dispersal of bottom-dwelling species is necessary to understand their population dynamics and optimize their management. The black-lip pearl oyster (Pinctada margaritifera) is cultured extensively to produce black pearls, especially in French Polynesia's atoll lagoons. This aquaculture relies on spat collection, a process that can be optimized by understanding which factors influence larval dispersal. Here, we investigate the sensitivity of P. margaritifera larval dispersal kernel to both physical and biological factors in the lagoon of Ahe atoll. Specifically, using a validated 3D larval dispersal model, the variability of lagoon-scale connectivity is investigated against wind forcing, depth and location of larval release, destination location, vertical swimming behavior and pelagic larval duration (PLD) factors. The potential connectivity was spatially weighted according to both the natural and cultivated broodstock densities to provide a realistic view of connectivity. We found that the mean pattern of potential connectivity was driven by the southwest and northeast main barotropic circulation structures, with high retention levels in both. Destination locations, spawning sites and PLD were the main drivers of potential connectivity, explaining respectively 26%, 59% and 5% of the variance. Differences between potential and realistic connectivity showed the significant contribution of the pearl oyster broodstock location to its own dynamics. Realistic connectivity showed larger larval supply in the western destination locations, which are preferentially used by farmers for spat collection. In addition, larval supply in the same sectors was enhanced during summer wind conditions. These results provide new cues to understanding the dynamics of bottom-dwelling populations in atoll lagoons, and show how to take advantage of numerical models for pearl oyster management. PMID:24740288
Supersymmetric Lepton Flavor Violation
Ilakovac, Amon; Pilaftsis, Apostolos
2010-02-10
We study a new supersymmetric mechanism for lepton flavor violation in a minimal extension of the MSSM with low-mass heavy singlet neutrinos, which is fully independent of the flavour structure of the soft SUSY breaking sector. We find that l->l'gamma processes are forbidden in the SUSY limit, whilst the processes l->l'l{sub 1}l{sub 2} and mu->e conversion in nuclei can be enhanced well above the observable level, via large neutrino Yukawa-coupling effects.
Supersymmetric Quantum Mechanics
NASA Astrophysics Data System (ADS)
David, J.; Fernández, C.
2010-10-01
Supersymmetric quantum mechanics (SUSY QM) is a powerful tool for generating new potentials with known spectra departing from an initial solvable one. In these lecture notes we will present some general formulae concerning SUSY QM of first second order for one-dimensional arbitrary systems, we will illustrate the method through the trigonometric Pöschl-Teller potentials. Some intrinsically related subjects, as the algebraic structure inherited by the new Hamiltonians and the corresponding coherent states will be analyzed. The technique will be as well implemented for periodic potentials, for which the corresponding spectrum is composed of allowed bands separated by energy gaps.
Small numbers in supersymmetric theories of nature
Graesser, Michael L.
1999-05-01
The Standard Model of particle interactions is a successful theory for describing the interactions of quarks, leptons and gauge bosons at microscopic distance scales. Despite these successes, the theory contains many unsatisfactory features. The origin of particle masses is a central mystery that has eluded experimental elucidation. In the Standard Model the known particles obtain their mass from the condensate of the so-called Higgs particle. Quantum corrections to the Higgs mass require an unnatural fine tuning in the Higgs mass of one part in 10{sup {minus}32} to obtain the correct mass scale of electroweak physics. In addition, the origin of the vast hierarchy between the mass scales of the electroweak and quantum gravity physics is not explained in the current theory. Supersymmetric extensions to the Standard Model are not plagued by this fine tuning issue and may therefore be relevant in Nature. In the minimal supersymmetric Standard Model there is also a natural explanation for electroweak symmetry breaking. Supersymmetric Grand Unified Theories also correctly predict a parameter of the Standard Model. This provides non-trivial indirect evidence for these theories. The most general supersymmetric extension to the Standard Model however, is excluded by many physical processes, such as rare flavor changing processes, and the non-observation of the instability of the proton. These processes provide important information about the possible structure such a theory. In particular, certain parameters in this theory must be rather small. A physics explanation for why this is the case would be desirable. It is striking that the gauge couplings of the Standard Model unify if there is supersymmetry close to the weak scale. This suggests that at high energies Nature is described by a supersymmetric Grand Unified Theory. But the mass scale of unification must be introduced into the theory since it does not coincide with the probable mass scale of strong quantum gravity
Sperber, K R
2007-12-18
I agree with the authors that forecasting the Madden-Julian Oscillation (MJO) in a high resolution global model is important for numerous reasons, including improved weather forecast skill beyond 10 days, and resolving small scale features embedded in the MJO that coarse resolution ({approx}100-300km horizontal grid spacing) climate models do not (e.g., tropical cyclones). Unfortunately, the authors promote the (incorrect) overall impression that coarse resolution climate models cannot simulate the MJO by (a) only discussing aspects of works that indicate the poor ability of coarse resolution climate models to simulate the MJO, and (b) by promoting the use of higher resolution models, and the use of embedded two-dimensional cloud resolving models embedded in coarse resolution climate models as the principal methods for realistically representing the MJO because of the difficulty of coarse resolution models 'to estimate the vertical redistribution of heat and moisture by unresolved convective clouds'. Regarding items (a) and (b), I have co-authored two of the works cited by Miura et al. that bemoan the poor ability of coarse resolution climate models to simulate the MJO, and indeed simulating the MJO in coarse resolution climate models is a grand challenge. However, I would like to draw to their attention to work that has demonstrated that two different coarse resolution climate models, using conventional parameterizations of convection and clouds, can represent the MJO with high fidelity. In the later study, where more complete model diagnostics were available, important aspects of the MJO that were realistically represented included the relationship between convection and low-level moisture convergence, surface fluxes, the vertical structure of winds and divergence, and important air-sea interactions. Additionally, regarding item (b), convection is certainly of central importance in representing the MJO, but it is the interaction of convection (parameterized or
Hippelheuser, James E; Lauric, Alexandra; Cohen, Alex D; Malek, Adel M
2014-11-28
Most computational fluid dynamic (CFD) simulations of aneurysm hemodynamics assume constant (Newtonian) viscosity, even though blood demonstrates shear-thinning (non-Newtonian) behavior. We sought to evaluate the effect of this simplifying assumption on hemodynamic forces within cerebral aneurysms, especially in regions of low wall shear stress, which are associated with rupture. CFD analysis was performed for both viscosity models using 3D rotational angiography volumes obtained for 26 sidewall aneurysms (12 with blebs, 12 ruptured), and parametric models incorporating blebs at different locations (inflow/outflow zone). Mean and lowest 5% values of time averaged wall shear stress (TAWSS) computed over the dome were compared using Wilcoxon rank-sum test. Newtonian modeling not only resulted in higher aneurysmal TAWSS, specifically in areas of low flow and blebs, but also showed no difference between aneurysms with or without blebs. In contrast, for non-Newtonian analysis, bleb-bearing aneurysms showed significantly lower 5% TAWSS compared to those without (p=0.005), despite no significant difference in mean dome TAWSS (p=0.32). Non-Newtonian modeling also accentuated the differences in dome TAWSS between ruptured and unruptured aneurysms (p<0.001). Parametric models further confirmed that realistic non-Newtonian viscosity resulted in lower bleb TAWSS and higher focal viscosity, especially when located in the outflow zone. The results show that adopting shear-thinning non-Newtonian blood viscosity in CFD simulations of intracranial aneurysms uncovered hemodynamic differences induced by bleb presence on aneurysmal surfaces, and significantly improved discriminant statistics used in risk stratification. These findings underline the possible implications of using a realistic model of blood viscosity in predictive computational hemodynamics. PMID:25446269
NASA Astrophysics Data System (ADS)
Seo, Hyeon; Kim, Donghyeon; Jun, Sung Chan
2016-06-01
Electrical brain stimulation (EBS) is an emerging therapy for the treatment of neurological disorders, and computational modeling studies of EBS have been used to determine the optimal parameters for highly cost-effective electrotherapy. Recent notable growth in computing capability has enabled researchers to consider an anatomically realistic head model that represents the full head and complex geometry of the brain rather than the previous simplified partial head model (extruded slab) that represents only the precentral gyrus. In this work, subdural cortical stimulation (SuCS) was found to offer a better understanding of the differential activation of cortical neurons in the anatomically realistic full-head model than in the simplified partial-head models. We observed that layer 3 pyramidal neurons had comparable stimulation thresholds in both head models, while layer 5 pyramidal neurons showed a notable discrepancy between the models; in particular, layer 5 pyramidal neurons demonstrated asymmetry in the thresholds and action potential initiation sites in the anatomically realistic full-head model. Overall, the anatomically realistic full-head model may offer a better understanding of layer 5 pyramidal neuronal responses. Accordingly, the effects of using the realistic full-head model in SuCS are compelling in computational modeling studies, even though this modeling requires substantially more effort.
Seo, Hyeon; Kim, Donghyeon; Jun, Sung Chan
2016-01-01
Electrical brain stimulation (EBS) is an emerging therapy for the treatment of neurological disorders, and computational modeling studies of EBS have been used to determine the optimal parameters for highly cost-effective electrotherapy. Recent notable growth in computing capability has enabled researchers to consider an anatomically realistic head model that represents the full head and complex geometry of the brain rather than the previous simplified partial head model (extruded slab) that represents only the precentral gyrus. In this work, subdural cortical stimulation (SuCS) was found to offer a better understanding of the differential activation of cortical neurons in the anatomically realistic full-head model than in the simplified partial-head models. We observed that layer 3 pyramidal neurons had comparable stimulation thresholds in both head models, while layer 5 pyramidal neurons showed a notable discrepancy between the models; in particular, layer 5 pyramidal neurons demonstrated asymmetry in the thresholds and action potential initiation sites in the anatomically realistic full-head model. Overall, the anatomically realistic full-head model may offer a better understanding of layer 5 pyramidal neuronal responses. Accordingly, the effects of using the realistic full-head model in SuCS are compelling in computational modeling studies, even though this modeling requires substantially more effort. PMID:27273817
Seo, Hyeon; Kim, Donghyeon; Jun, Sung Chan
2016-01-01
Electrical brain stimulation (EBS) is an emerging therapy for the treatment of neurological disorders, and computational modeling studies of EBS have been used to determine the optimal parameters for highly cost-effective electrotherapy. Recent notable growth in computing capability has enabled researchers to consider an anatomically realistic head model that represents the full head and complex geometry of the brain rather than the previous simplified partial head model (extruded slab) that represents only the precentral gyrus. In this work, subdural cortical stimulation (SuCS) was found to offer a better understanding of the differential activation of cortical neurons in the anatomically realistic full-head model than in the simplified partial-head models. We observed that layer 3 pyramidal neurons had comparable stimulation thresholds in both head models, while layer 5 pyramidal neurons showed a notable discrepancy between the models; in particular, layer 5 pyramidal neurons demonstrated asymmetry in the thresholds and action potential initiation sites in the anatomically realistic full-head model. Overall, the anatomically realistic full-head model may offer a better understanding of layer 5 pyramidal neuronal responses. Accordingly, the effects of using the realistic full-head model in SuCS are compelling in computational modeling studies, even though this modeling requires substantially more effort. PMID:27273817
NASA Astrophysics Data System (ADS)
De Geeter, N.; Crevecoeur, G.; Leemans, A.; Dupré, L.
2015-01-01
In transcranial magnetic stimulation (TMS), an applied alternating magnetic field induces an electric field in the brain that can interact with the neural system. It is generally assumed that this induced electric field is the crucial effect exciting a certain region of the brain. More specifically, it is the component of this field parallel to the neuron’s local orientation, the so-called effective electric field, that can initiate neuronal stimulation. Deeper insights on the stimulation mechanisms can be acquired through extensive TMS modelling. Most models study simple representations of neurons with assumed geometries, whereas we embed realistic neural trajectories computed using tractography based on diffusion tensor images. This way of modelling ensures a more accurate spatial distribution of the effective electric field that is in addition patient and case specific. The case study of this paper focuses on the single pulse stimulation of the left primary motor cortex with a standard figure-of-eight coil. Including realistic neural geometry in the model demonstrates the strong and localized variations of the effective electric field between the tracts themselves and along them due to the interplay of factors such as the tract’s position and orientation in relation to the TMS coil, the neural trajectory and its course along the white and grey matter interface. Furthermore, the influence of changes in the coil orientation is studied. Investigating the impact of tissue anisotropy confirms that its contribution is not negligible. Moreover, assuming isotropic tissues lead to errors of the same size as rotating or tilting the coil with 10 degrees. In contrast, the model proves to be less sensitive towards the not well-known tissue conductivity values.
Pursuing realistic hydrologic model under SUPERFLEX framework in a semi-humid catchment in China
NASA Astrophysics Data System (ADS)
Wei, Lingna; Savenije, Hubert H. G.; Gao, Hongkai; Chen, Xi
2016-04-01
Model realism is pursued perpetually by hydrologists for flood and drought prediction, integrated water resources management and decision support of water security. "Physical-based" distributed hydrologic models are speedily developed but they also encounter unneglectable challenges, for instance, computational time with low efficiency and parameters uncertainty. This study step-wisely tested four conceptual hydrologic models under the framework of SUPERFLEX in a small semi-humid catchment in southern Huai River basin of China. The original lumped FLEXL has hypothesized model structure of four reservoirs to represent canopy interception, unsaturated zone, subsurface flow of fast and slow components and base flow storage. Considering the uneven rainfall in space, the second model (FLEXD) is developed with same parameter set for different rain gauge controlling units. To reveal the effect of topography, terrain descriptor of height above the nearest drainage (HAND) combined with slope is applied to classify the experimental catchment into two landscapes. Then the third one (FLEXTOPO) builds different model blocks in consideration of the dominant hydrologic process corresponding to the topographical condition. The fourth one named FLEXTOPOD integrating the parallel framework of FLEXTOPO in four controlled units is designed to interpret spatial variability of rainfall patterns and topographic features. Through pairwise comparison, our results suggest that: (1) semi-distributed models (FLEXD and FLEXTOPOD) taking precipitation spatial heterogeneity into account has improved model performance with parsimonious parameter set, and (2) hydrologic model architecture with flexibility to reflect perceived dominant hydrologic processes can include the local terrain circumstances for each landscape. Hence, the modeling actions are coincided with the catchment behaviour and close to the "reality". The presented methodology is regarding hydrologic model as a tool to test our
Confirmation of a realistic reactor model for BNCT dosimetry at the TRIGA Mainz
Ziegner, Markus; Schmitz, Tobias; Hampel, Gabriele; Khan, Rustam; Blaickner, Matthias; Palmans, Hugo; Sharpe, Peter; Böck, Helmuth
2014-11-01
Purpose: In order to build up a reliable dose monitoring system for boron neutron capture therapy (BNCT) applications at the TRIGA reactor in Mainz, a computer model for the entire reactor was established, simulating the radiation field by means of the Monte Carlo method. The impact of different source definition techniques was compared and the model was validated by experimental fluence and dose determinations. Methods: The depletion calculation code ORIGEN2 was used to compute the burn-up and relevant material composition of each burned fuel element from the day of first reactor operation to its current core. The material composition of the current core was used in a MCNP5 model of the initial core developed earlier. To perform calculations for the region outside the reactor core, the model was expanded to include the thermal column and compared with the previously established ATTILA model. Subsequently, the computational model is simplified in order to reduce the calculation time. Both simulation models are validated by experiments with different setups using alanine dosimetry and gold activation measurements with two different types of phantoms. Results: The MCNP5 simulated neutron spectrum and source strength are found to be in good agreement with the previous ATTILA model whereas the photon production is much lower. Both MCNP5 simulation models predict all experimental dose values with an accuracy of about 5%. The simulations reveal that a Teflon environment favorably reduces the gamma dose component as compared to a polymethyl methacrylate phantom. Conclusions: A computer model for BNCT dosimetry was established, allowing the prediction of dosimetric quantities without further calibration and within a reasonable computation time for clinical applications. The good agreement between the MCNP5 simulations and experiments demonstrates that the ATTILA model overestimates the gamma dose contribution. The detailed model can be used for the planning of structural
Dynamical screening in correlated electron systems—from lattice models to realistic materials
NASA Astrophysics Data System (ADS)
Werner, Philipp; Casula, Michele
2016-09-01
Recent progress in treating the dynamical nature of the screened Coulomb interaction in strongly correlated lattice models and materials is reviewed with a focus on computational schemes based on the dynamical mean field approximation. We discuss approximate and exact methods for the solution of impurity models with retarded interactions, and explain how these models appear as auxiliary problems in various extensions of the dynamical mean field formalism. The current state of the field is illustrated with results from recent applications of these schemes to U-V Hubbard models and correlated materials.
Effects of sutures and fontanels on MEG and EEG source analysis in a realistic infant head model.
Lew, Seok; Sliva, Danielle D; Choe, Myong-sun; Grant, P Ellen; Okada, Yoshio; Wolters, Carsten H; Hämäläinen, Matti S
2013-08-01
In infants, the fontanels and sutures as well as conductivity of the skull influence the volume currents accompanying primary currents generated by active neurons and thus the associated electroencephalography (EEG) and magnetoencephalography (MEG) signals. We used a finite element method (FEM) to construct a realistic model of the head of an infant based on MRI images. Using this model, we investigated the effects of the fontanels, sutures and skull conductivity on forward and inverse EEG and MEG source analysis. Simulation results show that MEG is better suited than EEG to study early brain development because it is much less sensitive than EEG to distortions of the volume current caused by the fontanels and sutures and to inaccurate estimates of skull conductivity. Best results will be achieved when MEG and EEG are used in combination.
NASA Astrophysics Data System (ADS)
Keyvanloo Shahrestanaky, Amirmohamad
The integration of a clinical linear accelerator (linac) with a magnetic resonance imaging (MRI) system would provide real-time tumor tracking. The magnetic fields of linac-MR systems modify the path of contaminant electrons in photon beams, which alters patient skin dose. In this work, we used Monte Carlo calculations that incorporate realistic 3D magnetic field models of longitudinal and transverse linac-MR systems to accurately quantify the changes in skin dose. The results show that fringe fields of realistic 3D B-fields decay rapidly and have a very small magnitude at the linac’s head. As a result, for longitudinal linac-MR systems only a small increase in the entrance skin dose is predicted. For transverse linac-MR systems, changes to the entrance skin dose are small for most scenarios. On the exit side, however, a fairly large increase is observed for perpendicular beams due to the electron return effect, but significantly drops for large oblique angles of incidence.
Toward more realistic projections of soil carbon dynamics by Earth system models
Luo, Y.; Ahlström, Anders; Allison, Steven D.; Batjes, Niels H.; Brovkin, V.; Carvalhais, Nuno; Chappell, Adrian; Ciais, Philippe; Davidson, Eric A.; Finzi, Adien; Georgiou, Katerina; Guenet, Bertrand; Hararuk, Oleksandra; Harden, Jennifer; He, Yujie; Hopkins, Francesca; Jiang, L.; Koven, Charles; Jackson, Robert B.; Jones, Chris D.; Lara, M.; Liang, J.; McGuire, Anthony; Parton, William; Peng, Changhui; Randerson, J.; Salazar, Alejandro; Sierra, Carlos A.; Smith, Matthew J.; Tian, Hanqin; Todd-Brown, Katherine E. O; Torn, Margaret S.; van Groenigen, Kees Jan; Wang, Ying; West, Tristram O.; Wei, Yaxing; Wieder, William R.; Xia, Jianyang; Xu, Xia; Xu, Xiaofeng; Zhou, T.
2016-01-01
Soil carbon (C) is a critical component of Earth system models (ESMs), and its diverse representations are a major source of the large spread across models in the terrestrial C sink from the third to fifth assessment reports of the Intergovernmental Panel on Climate Change (IPCC). Improving soil C projections is of a high priority for Earth system modeling in the future IPCC and other assessments. To achieve this goal, we suggest that (1) model structures should reflect real-world processes, (2) parameters should be calibrated to match model outputs with observations, and (3) external forcing variables should accurately prescribe the environmental conditions that soils experience. First, most soil C cycle models simulate C input from litter production and C release through decomposition. The latter process has traditionally been represented by first-order decay functions, regulated primarily by temperature, moisture, litter quality, and soil texture. While this formulation well captures macroscopic soil organic C (SOC) dynamics, better understanding is needed of their underlying mechanisms as related to microbial processes, depth-dependent environmental controls, and other processes that strongly affect soil C dynamics. Second, incomplete use of observations in model parameterization is a major cause of bias in soil C projections from ESMs. Optimal parameter calibration with both pool- and flux-based data sets through data assimilation is among the highest priorities for near-term research to reduce biases among ESMs. Third, external variables are represented inconsistently among ESMs, leading to differences in modeled soil C dynamics. We recommend the implementation of traceability analyses to identify how external variables and model parameterizations influence SOC dynamics in different ESMs. Overall, projections of the terrestrial C sink can be substantially improved when reliable data sets are available to select the most representative model structure
Borojeni, Azadeh A T; Noga, Michelle L; Martin, Andrew R; Finlay, Warren H
2015-07-16
This work describes in vitro measurement of the total pressure loss at varying flow rate through anatomically realistic conducting airway replicas of 10 children, 4 to 8 years old, and 5 adults. Experimental results were compared with analytical predictions made using published airway resistance models. For the adult replicas, the model proposed by van Ertbruggen et al. (2005. J. Appl. Physiol. 98, 970-980) most accurately predicted central conducting airway resistance for inspiratory flow rates ranging from 15 to 90 L/min. Models proposed by Pedley et al. (1970. J. Respir. Physiol. 9, 371-386) and by Katz et al. (2011. J. Biomech. 44, 1137-1143) also provided reasonable estimates, but with a tendency to over predict measured pressure loss for both models. For child replicas, the Pedley and Katz models both provided good estimation of measured pressure loss at flow rates representative of resting tidal breathing, but under predicted measured values at high inspiratory flow rate (60 L/min). The van Ertbruggen model, developed based on flow simulations performed in an adult airway model, tended to under predict measured pressure loss through the child replicas across the range of flow rates studied (2 to 60 L/min). These results are intended to provide guidance for selection of analytical pressure loss models for use in predicting airway resistance and ventilation distribution in adults and children.
NASA Astrophysics Data System (ADS)
Allahverdi, Rouzbeh; Dutta, Bhaskar; Sinha, Kuver
2012-11-01
If the lightest supersymmetric particle (LSP) is Higgsino-like, the thermal relic density is lower than the observed dark matter content for a LSP mass in the sub-TeV region. We outline constraints arising from the Fermi Gamma-ray Telescope data and LSP production from gravitino decay that must be satisfied by a successful nonthermal Higgsino scenario. We show that in a generic class of models where anomaly- and modulus-mediated contributions to supersymmetry breaking are of comparable size, Higgsino arises as the only viable sub-TeV dark matter candidate if gravitinos are heavy enough to decay before the onset of big bang nucleosynthesis. The correct relic density can be obtained via modulus decay in these models. As an explicit example, we consider a modulus sector in effective field theory (D=4, N=1 supergravitiy arising from type IIB Kachru-Kallosh-Linde-Trivedi compactification). Within this class of mirage mediation models, heaviness of the gravitino forces a sub-TeV Higgsino LSP and gives a Higgs mass around 125 GeV. In this example, the constraints from direct detection experiments are also satisfied.
Modeling and Control of Aggregated Air Conditioning Loads Under Realistic Conditions
Chang, Chin-Yao; Zhang, Wei; Lian, Jianming; Kalsi, Karanjit
2013-02-24
Demand-side control is playing an increasingly important role in smart grid control strategies. Modeling the dynamical behavior of a large population of appliances is especially important to evaluate the effectiveness of various load control strategies. In this paper, a high accuracy aggregated model is first developed for a population of HVAC units. The model efficiently includes statistical information of the population, systematically deals with heterogeneity, and accounts for a second-order effect necessary to accurately capture the transient dynamics in the collective response. Furthermore, the model takes into account the lockout effect of the compressor in order to represent the dynamics of the system under control more accurately. Then, a novel closed loop load control strategy is designed to track a desired demand curve and to ensure a stable and smooth response.
750 GeV diphoton excesses in a realistic D-brane model
NASA Astrophysics Data System (ADS)
Li, Tianjun; Maxin, James A.; Mayes, Van E.; Nanopoulos, Dimitri V.
2016-07-01
We study the diphoton excesses near 750 GeV recently reported by the ATLAS and CMS collaborations within the context of a phenomenologically interesting intersecting/magnetized D-brane model on a toroidal orientifold. It is shown that the model contains a Standard Model singlet scalar as well as vector-like quarks and leptons. In addition, it is shown that the singlet scalar has Yukawa couplings with vector-like quarks and leptons such that it may be produced in proton-proton collisions via gluon fusion as well as decay to diphotons through loops involving the vector-like quarks. Moreover, the required vector-like quarks and leptons may appear in complete S U (5 ) multiplets so that gauge coupling unification may be maintained. Finally, it is shown that the diphoton signal may be accommodated within the model.
Shell-Model Calculations of f p-shell Nuclei with Realistic NN Interactions
Qi, C.; Xu, F. R.
2010-05-12
Shell model calculations have been carried out to study the structure and decay properties of nuclei in the f p shell. The shell-model effective Hamiltonian is constructed from the high-precision CD-Bonn NN potential using the folded-diagram renormalization method without any empirical modification. The Hamiltonian gives a reasonable description of spectroscopic properties in nuclei around the N = Z line.
Anatomically realistic multiscale models of normal and abnormal gastrointestinal electrical activity
Cheng, Leo K; Komuro, Rie; Austin, Travis M; Buist, Martin L; Pullan, Andrew J
2007-01-01
One of the major aims of the International Union of Physiological Sciences (IUPS) Physiome Project is to develop multiscale mathematical and computer models that can be used to help understand human health. We present here a small facet of this broad plan that applies to the gastrointestinal system. Specifically, we present an anatomically and physiologically based modelling framework that is capable of simulating normal and pathological electrical activity within the stomach and small intestine. The continuum models used within this framework have been created using anatomical information derived from common medical imaging modalities and data from the Visible Human Project. These models explicitly incorporate the various smooth muscle layers and networks of interstitial cells of Cajal (ICC) that are known to exist within the walls of the stomach and small bowel. Electrical activity within individual ICCs and smooth muscle cells is simulated using a previously published simplified representation of the cell level electrical activity. This simulated cell level activity is incorporated into a bidomain representation of the tissue, allowing electrical activity of the entire stomach or intestine to be simulated in the anatomically derived models. This electrical modelling framework successfully replicates many of the qualitative features of the slow wave activity within the stomach and intestine and has also been used to investigate activity associated with functional uncoupling of the stomach. PMID:17457969
Cheng, Leo K; Komuro, Rie; Austin, Travis M; Buist, Martin L; Pullan, Andrew J
2007-03-01
One of the major aims of the International Union of Physiological Sciences (IUPS) Physiome Project is to develop multiscale mathematical and computer models that can be used to help understand human health. We present here a small facet of this broad plan that applies to the gastrointestinal system. Specifically, we present an anatomically and physiologically based modelling framework that is capable of simulating normal and pathological electrical activity within the stomach and small intestine. The continuum models used within this framework have been created using anatomical information derived from common medical imaging modalities and data from the Visible Human Project. These models explicitly incorporate the various smooth muscle layers and networks of interstitial cells of Cajal (ICC) that are known to exist within the walls of the stomach and small bowel. Electrical activity within individual ICCs and smooth muscle cells is simulated using a previously published simplified representation of the cell level electrical activity. This simulated cell level activity is incorporated into a bidomain representation of the tissue, allowing electrical activity of the entire stomach or intestine to be simulated in the anatomically derived models. This electrical modelling framework successfully replicates many of the qualitative features of the slow wave activity within the stomach and intestine and has also been used to investigate activity associated with functional uncoupling of the stomach.
Reliable, robust and realistic: the three R's of next-generation land-surface modelling
NASA Astrophysics Data System (ADS)
Prentice, I. C.; Liang, X.; Medlyn, B. E.; Wang, Y.-P.
2015-05-01
Land-surface models (LSMs) are increasingly called upon to represent not only the exchanges of energy, water and momentum across the land-atmosphere interface (their original purpose in climate models), but also how ecosystems and water resources respond to climate, atmospheric environment, land-use and land-use change, and how these responses in turn influence land-atmosphere fluxes of carbon dioxide (CO2), trace gases and other species that affect the composition and chemistry of the atmosphere. However, the LSMs embedded in state-of-the-art climate models differ in how they represent fundamental aspects of the hydrological and carbon cycles, resulting in large inter-model differences and sometimes faulty predictions. These "third-generation" LSMs respect the close coupling of the carbon and water cycles through plants, but otherwise tend to be under-constrained, and have not taken full advantage of robust hydrological parameterizations that were independently developed in offline models. Benchmarking, combining multiple sources of atmospheric, biospheric and hydrological data, should be a required component of LSM development, but this field has been relatively poorly supported and intermittently pursued. Moreover, benchmarking alone is not sufficient to ensure that models improve. Increasing complexity may increase realism but decrease reliability and robustness, by increasing the number of poorly known model parameters. In contrast, simplifying the representation of complex processes by stochastic parameterization (the representation of unresolved processes by statistical distributions of values) has been shown to improve model reliability and realism in both atmospheric and land-surface modelling contexts. We provide examples for important processes in hydrology (the generation of runoff and flow routing in heterogeneous catchments) and biology (carbon uptake by species-diverse ecosystems). We propose that the way forward for next-generation complex LSMs will
Reliable, robust and realistic: the three R's of next-generation land surface modelling
NASA Astrophysics Data System (ADS)
Prentice, I. C.; Liang, X.; Medlyn, B. E.; Wang, Y.-P.
2014-09-01
Land surface models (LSMs) are increasingly called upon to represent not only the exchanges of energy, water and momentum across the land-atmosphere interface (their original purpose in climate models), but also how ecosystems and water resources respond to climate and atmospheric environment, and how these responses in turn influence land-atmosphere fluxes of carbon dioxide (CO2), trace gases and other species that affect the composition and chemistry of the atmosphere. However, the LSMs embedded in state-of-the-art climate models differ in how they represent fundamental aspects of the hydrological and carbon cycles, resulting in large inter-model differences and sometimes faulty predictions. These "third-generation" LSMs respect the close coupling of the carbon and water cycles through plants, but otherwise tend to be under-constrained, and have not taken full advantage of robust hydrological parameterizations that were independently developed in offline models. Benchmarking, combining multiple sources of atmospheric, biospheric and hydrological data, should be a required component of LSM development, but this field has been relatively poorly supported and intermittently pursued. Moreover, benchmarking alone is not sufficient to ensure that models improve. Increasing complexity may increase realism but decrease reliability and robustness, by increasing the number of poorly known model parameters. In contrast, simplifying the representation of complex processes by stochastic parameterization (the representation of unresolved processes by statistical distributions of values) has been shown to improve model reliability and realism in both atmospheric and land-surface modelling contexts. We provide examples for important processes in hydrology (the generation of runoff and flow routing in heterogeneous catchments) and biology (carbon uptake by species-diverse ecosystems). We propose that the way forward for next-generation complex LSMs will include: (a
NASA Astrophysics Data System (ADS)
Arnold, B. W.; James, S. C.; Reimus, P. W.
2012-12-01
A series of adsorption, desorption, and column transport experiments were conducted to evaluate the transport of uranium (U) and neptunium (Np) through saturated volcanic tuffs. For potential high-level radioactive waste sites, these experiments demonstrate that slow radionuclide desorption processes, which are typically not accounted for in transport models implementing simple partition coefficients (Kd values), may dominate field-scale transport. A complimentary interpretive numerical model couples a simplified geochemical description of the system with transport calculations where heterogeneities are represented as an ensemble of sorption sites with characteristic adsorption and desorption rate constants that have widely varying values. Adsorption and desorption rate constants were estimated through inverse modeling such that reliable upscaled predictions of reactive transport in field settings could be simulated. The inverse modeling software, PEST, was also used to perform advanced uncertainty quantification. The multicomponent model/parameters matching the combined data sets suggest that over much longer time and distance scales the transport of U and Np under the experimental conditions would result in very little transport over field scales because even a small number of strong sorption sites will have an exaggerated retarding influence on the transport of a radionuclide plume. Modeling of combined sorption/desorption experiments and column transport experiments that involve both the measurement of column effluent breakthrough curves and the distribution of radionuclides remaining in the column at the conclusion of the experiments holds significant promise for supporting an improved approach to properly account for mineralogical heterogeneity over long time and distance scales in reactive radionuclide transport models. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed
General physically-realistic BRDF models for computing stray light from arbitrary isotropic surfaces
NASA Astrophysics Data System (ADS)
Greynolds, Alan W.
2015-09-01
Proposed twenty-five years ago specifically for stray light computations, a general BRDF model that automatically enforces continuity, positivity, reciprocity, and isotropic surface symmetry over all possible input/output directions has been implemented in commercial optical analysis codes. It was originally motivated by the need to fit (and possibly catalogue) measured BRDFs of everything from polished optical surfaces to rough diffuse blacks, reasonably extend inplane only data to out-of-plane, reduce hundreds or thousands of measurement points to a relatively small number of parameters (like glass dispersion formulas), and cleanup "sloppy" data or models that violate physical constraints. However, there is little attempt to relate the BRDF to any actual surface structure or statistics (the inverse problem). As application examples, the model successfully fits several thousand measured data points on a "glossy" anodized Aluminum sample to a 100-coefficient form and several dozen measured data points on Aeroglaze Z306 diffuse black paint to a general 20-coefficient form then probably the simplest 2-parameter model. Variations and other general BRDF models are also proposed.
Realistic Modeling of SDO/AIA-discovered Coronal Fast MHD Wave Trains in Active Regions
NASA Astrophysics Data System (ADS)
Ofman, Leon; Liu, Wei
2016-05-01
High-resolution EUV observations by space telescopes have provided plenty of evidence for coronal MHD waves in active regions. In particular, SDO/AIA discovered quasi-periodic, fast-mode propagating MHD wave trains (QFPs), which can propagate at speeds of ~1000 km/s perpendicular to the magnetic field. Such waves can provide information on the energy release of their associated flares and the magnetized plasma structure of the active regions. Before we can use these waves as tools for coronal seismology, 3D MHD modeling is required for disentangling observational ambiguities and improving the diagnostic accuracy. We present new results of observationally contained models of QFPs using our recently upgraded radiative, thermally conductive, visco-resistive 3D MHD code. The waves are excited by time-depended boundary conditions constrained by the spatial (localized) and quasi-periodic temporal evolution of a C-class flare typically associated with QFPs. We investigate the excitation, propagation, and damping of the waves for a range of key model parameters, such as the background temperature, density, magnetic field structure, and the location of the flaring site within the active region. We synthesize EUV intensities in multiple AIA channels and then obtain the model parameters that best reproduce the properties of observed QFPs. We discuss the implications of our model results for the seismological application of QFPs and for understanding the dynamics of their associated flares.
Can we trust climate models to realistically represent severe European windstorms?
NASA Astrophysics Data System (ADS)
Trzeciak, Tomasz M.; Knippertz, Peter; Pirret, Jennifer S. R.; Williams, Keith D.
2016-06-01
Cyclonic windstorms are one of the most important natural hazards for Europe, but robust climate projections of the position and the strength of the North Atlantic storm track are not yet possible, bearing significant risks to European societies and the (re)insurance industry. Previous studies addressing the problem of climate model uncertainty through statistical comparisons of simulations of the current climate with (re-)analysis data show large disagreement between different climate models, different ensemble members of the same model and observed climatologies of intense cyclones. One weakness of such evaluations lies in the difficulty to separate influences of the climate model's basic state from the influence of fast processes on the development of the most intense storms, which could create compensating effects and therefore suggest higher reliability than there really is. This work aims to shed new light into this problem through a cost-effective "seamless" approach of hindcasting 20 historical severe storms with the two global climate models, ECHAM6 and GA4 configuration of the Met Office Unified Model, run in a numerical weather prediction mode using different lead times, and horizontal and vertical resolutions. These runs are then compared to re-analysis data. The main conclusions from this work are: (a) objectively identified cyclone tracks are represented satisfactorily by most hindcasts; (b) sensitivity to vertical resolution is low; (c) cyclone depth is systematically under-predicted for a coarse resolution of T63 by both climate models; (d) no systematic bias is found for the higher resolution of T127 out to about three days, demonstrating that climate models are in fact able to represent the complex dynamics of explosively deepening cyclones well, if given the correct initial conditions; (e) an analysis using a recently developed diagnostic tool based on the surface pressure tendency equation points to too weak diabatic processes, mainly latent
Criticality and market efficiency in a simple realistic model of the stock market
NASA Astrophysics Data System (ADS)
Challet, Damien; Marsili, Matteo
2003-09-01
We discuss a simple model based on the minority game which reproduces the main stylized facts of anomalous fluctuations in finance. We present the analytic solution of the model in the thermodynamic limit. Stylized facts arise only close to a line of critical points with nontrivial properties, marking the transition to an unpredictable market. We show that the emergence of critical fluctuations close to the phase transition is governed by the interplay between the signal to noise ratio and the system size. These results provide a clear and consistent picture of financial markets, where stylized facts and verge of unpredictability are intimately related aspects of the same critical systems.
Bringing a Realistic Global Climate Modeling Experience to a Broader Audience
NASA Astrophysics Data System (ADS)
Sohl, L. E.; Chandler, M. A.; Zhou, J.
2010-12-01
EdGCM, the Educational Global Climate Model, was developed with the goal of helping students learn about climate change and climate modeling by giving them the ability to run a genuine NASA global climate model (GCM) on a desktop computer. Since EdGCM was first publicly released in January 2005, tens of thousands of users on seven continents have downloaded the software. EdGCM has been utilized by climate science educators from middle school through graduate school levels, and on occasion even by researchers who otherwise do not have ready access to climate model at national labs in the U.S. and elsewhere. The EdGCM software is designed to walk users through the same process a climate scientist would use in designing and running simulations, and analyzing and visualizing GCM output. Although the current interface design gives users a clear view of some of the complexities involved in using a climate model, it can be daunting for users whose main focus is on climate science rather than modeling per se. As part of the work funded by NASA’s Global Climate Change Education (GCCE) program, we will begin modifications to the user interface that will improve the accessibility of EdGCM to a wider array of users, especially at the middle school and high school levels, by: 1) Developing an automated approach (a “wizard”) to simplify the user experience in setting up new climate simulations; 2) Produce a catalog of “rediscovery experiments” that allow users to reproduce published climate model results, and in some cases compare model projections to real world data; and 3) Enhance distance learning and online learning opportunities through the development of a web-based interface. The prototypes for these modifications will then be presented to educators belonging to an EdGCM Users Group for feedback, so that we can further refine the EdGCM software, and thus deliver the tools and materials educators want and need across a wider range of learning environments.
Allhoff, K T; Ritterskamp, D; Rall, B C; Drossel, B; Guill, C
2015-06-04
The networks of predator-prey interactions in ecological systems are remarkably complex, but nevertheless surprisingly stable in terms of long term persistence of the system as a whole. In order to understand the mechanism driving the complexity and stability of such food webs, we developed an eco-evolutionary model in which new species emerge as modifications of existing ones and dynamic ecological interactions determine which species are viable. The food-web structure thereby emerges from the dynamical interplay between speciation and trophic interactions. The proposed model is less abstract than earlier evolutionary food web models in the sense that all three evolving traits have a clear biological meaning, namely the average body mass of the individuals, the preferred prey body mass, and the width of their potential prey body mass spectrum. We observed networks with a wide range of sizes and structures and high similarity to natural food webs. The model networks exhibit a continuous species turnover, but massive extinction waves that affect more than 50% of the network are not observed.
Lindstrom, F.T.; Cawlfield, D.E.; Donahue, M.E.; Emer, D.F.; Shott, G.J.
1992-12-31
US DOE Order 5820.2A (1988) requires that a performance assessment of all new and existing low-level radioactive waste management sites be made. An integral part of every performance assessment is the mathematical modeling of the transport and fate of noble gas radionuclides in the gas phase. Current in depth site characterization of the high desert alluvium in Area 5 of the Nevada Test Site (NTS) is showing that the alluvium is very very dry all the way to the water table (240 meters below land surface). The potential for radioactive noble gas (e.g. Rn-220 and Rn-222) transport to the atmosphere from shallow land burial of Thorium and Uranium waste is very high. Objectives of this modeling effort include: Construct a physics based sits specific noble gas transport model; Include induced advection due to barometric pressure changes at the atmospheric boundary layer (thin) - dry desert alluvium interface; User selected option for use of NOAA barometric pressure or a ``home brewed`` barometric pressure wave made up of up to 15 sinusoids and cosinusoids; Use the model to help make engineering decisions on the design of the burial pits and associated closure caps.
NASA Astrophysics Data System (ADS)
Allhoff, K. T.; Ritterskamp, D.; Rall, B. C.; Drossel, B.; Guill, C.
2015-06-01
The networks of predator-prey interactions in ecological systems are remarkably complex, but nevertheless surprisingly stable in terms of long term persistence of the system as a whole. In order to understand the mechanism driving the complexity and stability of such food webs, we developed an eco-evolutionary model in which new species emerge as modifications of existing ones and dynamic ecological interactions determine which species are viable. The food-web structure thereby emerges from the dynamical interplay between speciation and trophic interactions. The proposed model is less abstract than earlier evolutionary food web models in the sense that all three evolving traits have a clear biological meaning, namely the average body mass of the individuals, the preferred prey body mass, and the width of their potential prey body mass spectrum. We observed networks with a wide range of sizes and structures and high similarity to natural food webs. The model networks exhibit a continuous species turnover, but massive extinction waves that affect more than 50% of the network are not observed.
A Neural Model of How the Brain Computes Heading from Optic Flow in Realistic Scenes
ERIC Educational Resources Information Center
Browning, N. Andrew; Grossberg, Stephen; Mingolla, Ennio
2009-01-01
Visually-based navigation is a key competence during spatial cognition. Animals avoid obstacles and approach goals in novel cluttered environments using optic flow to compute heading with respect to the environment. Most navigation models try either explain data, or to demonstrate navigational competence in real-world environments without regard…
NASA Astrophysics Data System (ADS)
Nam, Jong-Hoon; Fettiplace, Robert
2011-11-01
The organ of Corti (OC) is believed to optimize the force transmission from the outer hair cell (OHC) to the basilar membrane and inner hair cell. Recent studies showed that the OC has complex modes of deformation. In an effort to understand the consequence of the OC deformation, we developed a fully deformable 3D finite element model of the OC. It incorporates hair bundle's mechano-transduction and the OHC electrical circuit. Geometric information was taken from the gerbil cochlea at locations with 18 and 0.7 kHz characteristic frequencies. Cochlear partitions of several hundred micrometers long were simulated. The model describes the signature 3D structural arrangement in the OC, especially the tilt of OHC and Deiters cell process. Transduction channel kinetics contributed to the system's mechanics through the hair bundle. The OHC electrical model incorporated the transduction channel conductance, nonlinear capacitance and piezoelectric properties. It also incorporated recent data on the voltage-dependent potassium conductance and membrane time constant. With the model we simulated (1) the limiting frequencies of mechano-transduction and OHC somatic motility and (2) OC transient response to impulse stimuli.
NASA Astrophysics Data System (ADS)
Scarella, Gilles; Clatz, Olivier; Lanteri, Stéphane; Beaume, Grégory; Oudot, Steve; Pons, Jean-Philippe; Piperno, Sergo; Joly, Patrick; Wiart, Joe
2006-06-01
The ever-rising diffusion of cellular phones has brought about an increased concern for the possible consequences of electromagnetic radiation on human health. Possible thermal effects have been investigated, via experimentation or simulation, by several research projects in the last decade. Concerning numerical modeling, the power absorption in a user's head is generally computed using discretized models built from clinical MRI data. The vast majority of such numerical studies have been conducted using Finite Differences Time Domain methods, although strong limitations of their accuracy are due to heterogeneity, poor definition of the detailed structures of head tissues (staircasing effects), etc. In order to propose numerical modeling using Finite Element or Discontinuous Galerkin Time Domain methods, reliable automated tools for the unstructured discretization of human heads are also needed. Results presented in this article aim at filling the gap between human head MRI images and the accurate numerical modeling of wave propagation in biological tissues and its thermal effects. To cite this article: G. Scarella et al., C. R. Physique 7 (2006).
An approach to creating a more realistic working model from a protein data bank entry
Brandon, Christopher J.; Martin, Benjamin P.; McGee, Kelly J.; Stewart, James J. P.; Braun-Sand, Sonja B.
2015-01-01
An accurate model of three-dimensional protein structure is important in a variety of fields such as structure-based drug design and mechanistic studies of enzymatic reactions. While the entries in the Protein Data Bank (http://www.pdb.org) provide valuable information about protein structures, a small fraction of the PDB structures were found to contain anomalies not reported in the PDB file. The semiempirical PM7 method in MOPAC2012 was used for identifying anomalously short hydrogen bonds, C–H···O/C–H···N interactions, non-bonding close contacts, and unrealistic covalent bond lengths in recently published Protein Data Bank files. It was also used to generate new structures with these faults removed. When the semiempirical models were compared to those of PDB_REDO (http://www.cmbi.ru.nl/pdb_redo/), the clashscores, as defined by MolProbity (http://molprobity.biochem.duke.edu/), were better in about 50 % of the structures. The semiempirical models also had a lower root-mean-square-deviation value in nearly all cases than those from PDB_REDO, indicative of a better conservation of the tertiary structure. Finally, the semiempirical models were found to have lower clashscores than the initial PDB file in all but one case. Because this approach maintains as much of the original tertiary structure as possible while improving anomalous interactions, it should be useful to theoreticians, experimentalists, and crystallographers investigating the structure and function of proteins. PMID:25605595
Can we trust climate models to realistically represent severe European windstorms?
NASA Astrophysics Data System (ADS)
Trzeciak, Tomasz M.; Knippertz, Peter; Owen, Jennifer S. R.
2014-05-01
Despite the enormous advances made in climate change research, robust projections of the position and the strength of the North Atlantic stormtrack are not yet possible. In particular with respect to damaging windstorms, this incertitude bears enormous risks to European societies and the (re)insurance industry. Previous studies have addressed the problem of climate model uncertainty through statistical comparisons of simulations of the current climate with (re-)analysis data and found that there is large disagreement between different climate models, different ensemble members of the same model and observed climatologies of intense cyclones. One weakness of such statistical evaluations lies in the difficulty to separate influences of the climate model's basic state from the influence of fast processes on the development of the most intense storms. Compensating effects between the two might conceal errors and suggest higher reliability than there really is. A possible way to separate influences of fast and slow processes in climate projections is through a "seamless" approach of hindcasting historical, severe storms with climate models started from predefined initial conditions and run in a numerical weather prediction mode on the time scale of several days. Such a cost-effective case-study approach, which draws from and expands on the concepts from the Transpose-AMIP initiative, has recently been undertaken in the SEAMSEW project at the University of Leeds funded by the AXA Research Fund. Key results from this work focusing on 20 historical storms and using different lead times and horizontal and vertical resolutions include: (a) Tracks are represented reasonably well by most hindcasts. (b) Sensitivity to vertical resolution is low. (c) There is a systematic underprediction of cyclone depth for a coarse resolution of T63, but surprisingly no systematic bias is found for higher-resolution runs using T127, showing that climate models are in fact able to represent the
Bergshoeff, E.A. ); Kallosh, R.; Ortin, T. )
1993-06-15
We present plane-wave-type solutions of the lowest-order superstring effective action which have unbroken space-time supersymmetries. They are given by a stringy generalization of the Brinkmann metric, dialton, axion, and gauge fields. Some conspiracy between the metric and the axion field is required. The [alpha][prime] stringy corrections to the effective on-shell action, to the equations of motion (and therefore to the solutions themselves), and to the supersymmetry transformations are shown to vanish for a special class of these solutions that we call supersymmetric string waves (SSW's). In the SSW solutions, there exists a conspiracy not only between the metric and the axion field, but also between the gauge fields and the metric, since the embedding of the spin connection in the gauge group is required.
The Classification of Highly Supersymmetric Supergravity Solutions
Gran, U.; Gutowski, J.; Papadopoulos, G.; Roest, D.
2009-02-02
The spinorial geometry method is an effective method for constructing systematic classifications of supersymmetric supergravity solutions. Recent work on analysing highly supersymmetric solutions in type IIB supergravity using this method is reviewed. It is shown that all supersymmetric solutions of IIB supergravity with more than 28 Killing spinors are locally maximally supersymmetric.
NASA Astrophysics Data System (ADS)
Zhang, Tianhe C.; Grill, Warren M.
2010-12-01
Deep brain stimulation (DBS) has emerged as an effective treatment for movement disorders; however, the fundamental mechanisms by which DBS works are not well understood. Computational models of DBS can provide insights into these fundamental mechanisms and typically require two steps: calculation of the electrical potentials generated by DBS and, subsequently, determination of the effects of the extracellular potentials on neurons. The objective of this study was to assess the validity of using a point source electrode to approximate the DBS electrode when calculating the thresholds and spatial distribution of activation of a surrounding population of model neurons in response to monopolar DBS. Extracellular potentials in a homogenous isotropic volume conductor were calculated using either a point current source or a geometrically accurate finite element model of the Medtronic DBS 3389 lead. These extracellular potentials were coupled to populations of model axons, and thresholds and spatial distributions were determined for different electrode geometries and axon orientations. Median threshold differences between DBS and point source electrodes for individual axons varied between -20.5% and 9.5% across all orientations, monopolar polarities and electrode geometries utilizing the DBS 3389 electrode. Differences in the percentage of axons activated at a given amplitude by the point source electrode and the DBS electrode were between -9.0% and 12.6% across all monopolar configurations tested. The differences in activation between the DBS and point source electrodes occurred primarily in regions close to conductor-insulator interfaces and around the insulating tip of the DBS electrode. The robustness of the point source approximation in modeling several special cases—tissue anisotropy, a long active electrode and bipolar stimulation—was also examined. Under the conditions considered, the point source was shown to be a valid approximation for predicting excitation
STEPS: efficient simulation of stochastic reaction–diffusion models in realistic morphologies
2012-01-01
Background Models of cellular molecular systems are built from components such as biochemical reactions (including interactions between ligands and membrane-bound proteins), conformational changes and active and passive transport. A discrete, stochastic description of the kinetics is often essential to capture the behavior of the system accurately. Where spatial effects play a prominent role the complex morphology of cells may have to be represented, along with aspects such as chemical localization and diffusion. This high level of detail makes efficiency a particularly important consideration for software that is designed to simulate such systems. Results We describe STEPS, a stochastic reaction–diffusion simulator developed with an emphasis on simulating biochemical signaling pathways accurately and efficiently. STEPS supports all the above-mentioned features, and well-validated support for SBML allows many existing biochemical models to be imported reliably. Complex boundaries can be represented accurately in externally generated 3D tetrahedral meshes imported by STEPS. The powerful Python interface facilitates model construction and simulation control. STEPS implements the composition and rejection method, a variation of the Gillespie SSA, supporting diffusion between tetrahedral elements within an efficient search and update engine. Additional support for well-mixed conditions and for deterministic model solution is implemented. Solver accuracy is confirmed with an original and extensive validation set consisting of isolated reaction, diffusion and reaction–diffusion systems. Accuracy imposes upper and lower limits on tetrahedron sizes, which are described in detail. By comparing to Smoldyn, we show how the voxel-based approach in STEPS is often faster than particle-based methods, with increasing advantage in larger systems, and by comparing to MesoRD we show the efficiency of the STEPS implementation. Conclusion STEPS simulates models of cellular
Supersymmetric mode converters
NASA Astrophysics Data System (ADS)
Heinrich, Matthias; Miri, Mohammad-Ali; Stützer, Simon; Nolte, Stefan; Szameit, Alexander; Christodoulides, Demetrios N.
2015-08-01
In recent years, the ever-increasing demand for high-capacity transmission systems has driven remarkable advances in technologies that encode information on an optical signal. Mode-division multiplexing makes use of individual modes supported by an optical waveguide as mutually orthogonal channels. The key requirement in this approach is the capability to selectively populate and extract specific modes. Optical supersymmetry (SUSY) has recently been proposed as a particularly elegant way to resolve this design challenge in a manner that is inherently scalable, and at the same time maintains compatibility with existing multiplexing strategies. Supersymmetric partners of multimode waveguides are characterized by the fact that they share all of their effective indices with the original waveguide. The crucial exception is the fundamental mode, which is absent from the spectrum of the partner waveguide. Here, we demonstrate experimentally how this global phase-matching property can be exploited for efficient mode conversion. Multimode structures and their superpartners are experimentally realized in coupled networks of femtosecond laser-written waveguides, and the corresponding light dynamics are directly observed by means of fluorescence microscopy. We show that SUSY transformations can readily facilitate the removal of the fundamental mode from multimode optical structures. In turn, hierarchical sequences of such SUSY partners naturally implement the conversion between modes of adjacent order. Our experiments illustrate just one of the many possibilities of how SUSY may serve as a building block for integrated mode-division multiplexing arrangements. Supersymmetric notions may enrich and expand integrated photonics by versatile optical components and desirable, yet previously unattainable, functionalities.
Dermisek, Radovan; Gunion, John F.
2007-11-01
We present an extended study of how the next-to-minimal supersymmetric model easily avoids fine-tuning in electroweak symmetry breaking for a SM-like light Higgs with mass in the vicinity of 100 GeV, as beautifully consistent with precision electroweak data, while escaping LEP constraints due to the dominance of h{yields}aa decays with m{sub a}<2m{sub b} so that a{yields}{tau}{sup +}{tau}{sup -} or jets. The residual {approx}10% branching ratio for h{yields}bb explains perfectly the well-known LEP excess at m{sub h}{approx}100 GeV. Details of model parameter correlations and requirements are discussed as a function tan{beta}. Comparisons of fine-tuning in the NMSSM to that in the MSSM are presented. We also discuss fine-tuning associated with scenarios in which the a is essentially pure singlet, has mass m{sub a}>30 GeV, and decays primarily to {gamma}{gamma} leading to an h{yields}aa{yields}4{gamma} Higgs signal.
NASA Astrophysics Data System (ADS)
Hopkins, Philip F.; Cox, Thomas J.; Hernquist, Lars; Narayanan, Desika; Hayward, Christopher C.; Murray, Norman
2013-04-01
We use hydrodynamic simulations with detailed, explicit models for stellar feedback to study galaxy mergers. These high-resolution (˜1 pc) simulations follow the formation and destruction of individual giant molecular clouds (GMC) and star clusters. We find that the final starburst is dominated by in situ star formation, fuelled by gas which flows inwards due to global torques. The resulting high gas density results in rapid star formation. The gas is self-gravitating, and forms massive (≲1010 M⊙) GMC and subsequently super star clusters (with masses up to 108 M⊙). However, in contrast to some recent simulations, the bulk of new stars which eventually form the central bulge are not born in super-clusters which then sink to the centre of the galaxy. This is because feedback efficiently disperses GMC after they turn several per cent of their mass into stars. In other words, most of the mass that reaches the nucleus does so in the form of gas. The Kennicutt-Schmidt law emerges naturally as a consequence of feedback balancing gravitational collapse, independent of the small-scale star formation microphysics. The same mechanisms that drive this relation in isolated galaxies, in particular radiation pressure from infrared photons, extend, with no fine-tuning, over seven decades in star formation rate (SFR) to regulate star formation in the most extreme starburst systems with densities ≳104 M⊙ pc-2. This feedback also drives super-winds with large mass-loss rates; however, a significant fraction of the wind material falls back on to the discs at later times, leading to higher post-starburst SFRs in the presence of stellar feedback. This suggests that strong active galactic nucleus feedback may be required to explain the sharp cut-offs in SFR that are observed in post-merger galaxies. We compare the results to those from simulations with no explicit resolution of GMC or feedback [`effective equation-of-state' (EOS) models]. We find that global galaxy properties
NASA Astrophysics Data System (ADS)
Kikuchi, Satoru; Saito, Kazuyuki; Takahashi, Masaharu; Ito, Koichi; Ikehira, Hiroo
This paper presents the computational electromagnetic dosimetry inside an anatomically based pregnant woman models exposed to electromagnetic wave during magnetic resonance imaging. The two types of pregnant woman models corresponding to early gestation and 26 weeks gestation were used for this study. The specific absorption rate (SAR) in and around a fetus were calculated by radiated electromagnetic wave from highpass and lowpass birdcage coil. Numerical calculation results showed that high SAR region is observed at the body in the vicinity of gaps of the coil, and is related to concentrated electric field in the gaps of human body such as armpit and thigh. Moreover, it has confirmed that the SAR in the fetus is less than International Electrotechnical Commission limit of 10W/kg, when whole-body average SARs are 2W/kg and 4W/kg, which are the normal operating mode and first level controlled operating mode, respectively.
NASA Technical Reports Server (NTRS)
Anderson, D. E., Jr.; Meier, R. R.; Hodges, R. R., Jr.; Tinsley, B. A.
1987-01-01
The H Balmer alpha nightglow is investigated by using Monte Carlo models of asymmetric geocoronal atomic hydrogen distributions as input to a radiative transfer model of solar Lyman-beta radiation in the thermosphere and atmosphere. It is shown that it is essential to include multiple scattering of Lyman-beta radiation in the interpretation of Balmer alpha airglow data. Observations of diurnal variation in the Balmer alpha airglow showing slightly greater intensities in the morning relative to evening are consistent with theory. No evidence is found for anything other than a single sinusoidal diurnal variation of exobase density. Dramatic changes in effective temperature derived from the observed Balmer alpha line profiles are expected on the basis of changing illumination conditions in the thermosphere and exosphere as different regions of the sky are scanned.
Zanlungo, Francesco; Ikeda, Tetsushi; Kanda, Takayuki
2012-01-01
We propose a way to introduce in microscopic pedestrian models a “social norm” in collision avoiding and overtaking, i.e. the tendency, shared by pedestrians belonging to the same culture, to avoid collisions and perform overtaking in a preferred direction. The “social norm” is implemented, regardless of the specific collision avoiding model, as a rotation in the perceived velocity vector of the opponent at the moment of computation of the collision avoiding strategy, and justified as an expectation that the opponent will follow the same “social norm” (for example a tendency to avoid on the left and overtake on the right, as proposed in this work for Japanese pedestrians). By comparing with real world data, we show that the introduction of this norm allows for a better reproduction of macroscopic pedestrian density and velocity patterns. PMID:23227202
Azcoiti, V.; Di Carlo, G.; Galante, A.; Grillo, A.F.; Laliena, V. Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, P.O. Box 13, Frascati Dipartimento di Fisica dell'Universita dell'Aquila, 67100 L'Aquila )
1994-12-01
The microcanonical fermionic average method has been used so far in the context of lattice models with phase transitions at finite coupling. To test its applicability to asymptotically free theories, we have implemented it in two-dimensional QED, i.e., the Schwinger model. We exploit the possibility, intrinsic to this method, of studying the whole [beta],[ital m] plane without extra computer cost, to follow constant physics trajectories and measure the [ital m][r arrow]0 limit of the chiral condensate. We recover the continuum result within three decimal places. Moreover, the possibility, intrinsic to the method, of performing simulations directly in the chiral limit allows us to compute the average plaquette energy at [ital m]=0, the result being in perfect agreement with the expected value.
Control of equine influenza: scenario testing using a realistic metapopulation model of spread.
Baguelin, M; Newton, J R; Demiris, N; Daly, J; Mumford, J A; Wood, J L N
2010-01-01
We present a metapopulation model of the spread of equine influenza among thoroughbred horses parametrized with data from a 2003 outbreak in Newmarket, UK. The number of horses initially susceptible is derived from a threshold theorem and a published statistical model. Two simulated likelihood-based methods are used to find the within- and between-yard transmissions using both exponential and empirical latent and infectious periods. We demonstrate that the 2003 outbreak was largely locally driven and use the parametrized model to address important questions of control. The chance of a large epidemic is shown to be largely dependent on the size of the index yard. The impact of poor responders to vaccination is estimated under different scenarios. A small proportion of poor responders strongly influences the efficiency of vaccine policies, which increases risk further when the vaccine and infecting strains differ following antigenic drift. Finally, the use of vaccinating in the face of an outbreak is evaluated at a global and individual management group level. The benefits for an individual horse trainer are found to be substantial, although this is influenced by the behaviour of other trainers.
Control of equine influenza: scenario testing using a realistic metapopulation model of spread
Baguelin, M.; Newton, J. R.; Demiris, N.; Daly, J.; Mumford, J. A.; Wood, J. L. N.
2010-01-01
We present a metapopulation model of the spread of equine influenza among thoroughbred horses parametrized with data from a 2003 outbreak in Newmarket, UK. The number of horses initially susceptible is derived from a threshold theorem and a published statistical model. Two simulated likelihood-based methods are used to find the within- and between-yard transmissions using both exponential and empirical latent and infectious periods. We demonstrate that the 2003 outbreak was largely locally driven and use the parametrized model to address important questions of control. The chance of a large epidemic is shown to be largely dependent on the size of the index yard. The impact of poor responders to vaccination is estimated under different scenarios. A small proportion of poor responders strongly influences the efficiency of vaccine policies, which increases risk further when the vaccine and infecting strains differ following antigenic drift. Finally, the use of vaccinating in the face of an outbreak is evaluated at a global and individual management group level. The benefits for an individual horse trainer are found to be substantial, although this is influenced by the behaviour of other trainers. PMID:19364721
Assessment of radiation dose in nuclear cardiovascular imaging using realistic computational models
Xie, Tianwu; Lee, Choonsik; Bolch, Wesley E.; Zaidi, Habib
2015-06-15
Purpose: Nuclear cardiology plays an important role in clinical assessment and has enormous impact on the management of a variety of cardiovascular diseases. Pediatric patients at different age groups are exposed to a spectrum of radiation dose levels and associated cancer risks different from those of adults in diagnostic nuclear medicine procedures. Therefore, comprehensive radiation dosimetry evaluations for commonly used myocardial perfusion imaging (MPI) and viability radiotracers in target population (children and adults) at different age groups are highly desired. Methods: Using Monte Carlo calculations and biological effects of ionizing radiation VII model, we calculate the S-values for a number of radionuclides (Tl-201, Tc-99m, I-123, C-11, N-13, O-15, F-18, and Rb-82) and estimate the absorbed dose and effective dose for 12 MPI radiotracers in computational models including the newborn, 1-, 5-, 10-, 15-yr-old, and adult male and female computational phantoms. Results: For most organs, {sup 201}Tl produces the highest absorbed dose whereas {sup 82}Rb and {sup 15}O-water produce the lowest absorbed dose. For the newborn baby and adult patient, the effective dose of {sup 82}Rb is 48% and 77% lower than that of {sup 99m}Tc-tetrofosmin (rest), respectively. Conclusions: {sup 82}Rb results in lower effective dose in adults compared to {sup 99m}Tc-labeled tracers. However, this advantage is less apparent in children. The produced dosimetric databases for various radiotracers used in cardiovascular imaging, using new generation of computational models, can be used for risk-benefit assessment of a spectrum of patient population in clinical nuclear cardiology practice.
A realistic age structured transmission model for dengue hemorrhagic fever in Thailand.
Pongsumpun, P; Tang, I M
2001-06-01
The influence of age structure in the susceptible class of the Susceptible-Infected Recovered (SIR) model used to describe the transmission of dengue hemorrhagic fever (DHF) was studied. This was done by first dividing all of the population classes into cohorts and then writing a set of coupled SIR equations for each cohort. The consequences of assuming different behavior of the transmission rates on the age structure in the DHF incidence rates were determined. In order for the predicted incidence rates to be similar to the DHF incidence patterns observed in several provinces in Thailand during the DHF epidemic in 1998, the transmission rates should be age dependent.
Ziraldo, Cordelia; Solovyev, Alexey; Allegretti, Ana; Krishnan, Shilpa; Henzel, M Kristi; Sowa, Gwendolyn A; Brienza, David; An, Gary; Mi, Qi; Vodovotz, Yoram
2015-06-01
People with spinal cord injury (SCI) are predisposed to pressure ulcers (PU). PU remain a significant burden in cost of care and quality of life despite improved mechanistic understanding and advanced interventions. An agent-based model (ABM) of ischemia/reperfusion-induced inflammation and PU (the PUABM) was created, calibrated to serial images of post-SCI PU, and used to investigate potential treatments in silico. Tissue-level features of the PUABM recapitulated visual patterns of ulcer formation in individuals with SCI. These morphological features, along with simulated cell counts and mediator concentrations, suggested that the influence of inflammatory dynamics caused simulations to be committed to "better" vs. "worse" outcomes by 4 days of simulated time and prior to ulcer formation. Sensitivity analysis of model parameters suggested that increasing oxygen availability would reduce PU incidence. Using the PUABM, in silico trials of anti-inflammatory treatments such as corticosteroids and a neutralizing antibody targeted at Damage-Associated Molecular Pattern molecules (DAMPs) suggested that, at best, early application at a sufficiently high dose could attenuate local inflammation and reduce pressure-associated tissue damage, but could not reduce PU incidence. The PUABM thus shows promise as an adjunct for mechanistic understanding, diagnosis, and design of therapies in the setting of PU.
Stress as necessary component of realistic recovery in animal models of experimental stroke
Walker, Frederick R; Jones, Kimberley A; Patience, Madeleine J; Zhao, Zidan; Nilsson, Michael
2014-01-01
Over the last decade there has been a considerable effort directed toward reformulating the standard approach taken to preclinically model stroke and stroke recovery. The principal objective of this undertaking has been to improve the success with which preclinical findings can be translated. Although several advancements have already been introduced, one potentially critical feature that appears to have been overlooked is psychological stress. Stroke is well recognized to produce high levels of stress in patients, and ongoing exposure to stress is recognized to deleteriously interfere with recovery. The presence of high levels of stress (distress) in stroke patients is also relevant because nearly all clinically deployed neurorestorative interventions occur against this background. Somewhat perplexingly, however, we could find no preclinical stroke studies concerned with investigating the efficacy of putative neurorestorative compounds that did so in the presence of stress. The following article will make the case that failure to recognize or compensate for the effects of ongoing stress in standard preclinical experimental models of recovery is likely to result in overestimation of the effectiveness of pharmacological or behavioral neurorestorative interventions. PMID:24326386
A realistic model for dark matter interactions in the neutrino portal paradigm
NASA Astrophysics Data System (ADS)
Macías, Vannia González; Illana, José I.; Wudka, José
2016-05-01
We discuss a simple extension of the Standard Model (SM) that provides an explicit realization of the dark-matter (DM) neutrino-portal paradigm. The dark sector is composed of a scalar Φ and a Dirac fermion Ψ, with the latter assumed to be lighter than the former. These particles interact with the SM through the exchange of a set of heavy Dirac fermion mediators that are neutral under all local SM symmetries, and also under the dark-sector symmetry that stabilizes the Ψ against decay. We show that this model can accommodate all experimental and observational constraints provided the DM mass is below ˜ 35 GeV or is in a resonant region of the Higgs or Z boson. We also show that if the dark scalar and dark fermion are almost degenerate in mass, heavier DM fermions are not excluded. We note that in this scenario DM annihilation in the cores of astrophysical objects and the galactic halo produces a monochromatic neutrino beam of energy m Ψ, which provides a clear signature for this paradigm. Other experimental signatures are also discussed.
Recovering evolutionary trees under a more realistic model of sequence evolution.
Lockhart, P J; Steel, M A; Hendy, M D; Penny, D
1994-07-01
We report a new transformation, the LogDet, that is consistent for sequences with differing nucleotide composition and that have arisen under simple but asymmetric stochastic models of evolution. This transformation is required because existing methods tend to group sequences on the basis of their nucleotide composition, irrespective of their evolutionary history. This effect of differing nucleotide frequencies is illustrated by using a tree-selection criterion on a simple distance measure defined solely on the basis of base composition, independent of the actual sequences. The new LogDet transformation uses determinants of the observed divergence matrices and works because multiplication of determinants (real numbers) is commutative, whereas multiplication of matrices is not,except in special symmetric cases. The use of determinants thus allows more general models of evolution with a symmetric rates of nucleotide change. The transformation is illustrated on a theoretical data set (where existing methods select the wrong tree) and with three biological data sets: chloroplasts, birds/mammals (nuclear), and honeybees ( mitochondrial ) . The LogDet transformation reinforces the logical distinction between transformations on the data and tree-selection criteria. The overall conclusions from this study are that irregular A,C,G,T compositions are an important and possible general cause of patterns that can mislead tree-reconstruction methods, even when high bootstrap values are obtained. Consequently, many published studies may need to be reexamined. PMID:19391266
Ziraldo, Cordelia; Solovyev, Alexey; Allegretti, Ana; Krishnan, Shilpa; Henzel, M. Kristi; Sowa, Gwendolyn A.; Brienza, David; An, Gary; Mi, Qi; Vodovotz, Yoram
2015-01-01
People with spinal cord injury (SCI) are predisposed to pressure ulcers (PU). PU remain a significant burden in cost of care and quality of life despite improved mechanistic understanding and advanced interventions. An agent-based model (ABM) of ischemia/reperfusion-induced inflammation and PU (the PUABM) was created, calibrated to serial images of post-SCI PU, and used to investigate potential treatments in silico. Tissue-level features of the PUABM recapitulated visual patterns of ulcer formation in individuals with SCI. These morphological features, along with simulated cell counts and mediator concentrations, suggested that the influence of inflammatory dynamics caused simulations to be committed to “better” vs. “worse” outcomes by 4 days of simulated time and prior to ulcer formation. Sensitivity analysis of model parameters suggested that increasing oxygen availability would reduce PU incidence. Using the PUABM, in silico trials of anti-inflammatory treatments such as corticosteroids and a neutralizing antibody targeted at Damage-Associated Molecular Pattern molecules (DAMPs) suggested that, at best, early application at a sufficiently high dose could attenuate local inflammation and reduce pressure-associated tissue damage, but could not reduce PU incidence. The PUABM thus shows promise as an adjunct for mechanistic understanding, diagnosis, and design of therapies in the setting of PU. PMID:26111346
Photo Realistic 3d Modeling with Uav: GEDİK Ahmet Pasha Mosque in AFYONKARAHİSAR
NASA Astrophysics Data System (ADS)
Uysal, M.; Toprak, A. S.; Polat, N.
2013-07-01
Many of the cultural heritages in the world have been totally or partly destroyed by natural events and human activities such as earthquake, flood and fire until the present day. Cultural heritages are legacy for us as well; it is also a fiduciary for next generation. To deliver this fiduciary to the future generations, cultural heritages have to be protected and registered. There are different methods for applying this registry but Photogrammetry is the most accurate and rapid method. Photogrammetry enables us to registry cultural heritages and generating 3D photo-realistic models. Nowadays, 3D models are being used in various fields such as education and tourism. In registration of complex and high construction by Photogrammetry, there are some problems in data acquisition and processing. Especially for high construction's photographs, some additional equipment is required such as balloon and lifter. In recent years The Unmanned Aerial Vehicles (UAV) are commonly started to be used in different fields for different goals. In Photogrammetry, The UAVs are being used for particularly data acquisition. It is not always easy to capture data due to the situation of historical places and their neighbourhood. The use of UAVs for documentation of cultural heritage will make an important contribution. The main goals of this study are to survey cultural heritages by Photogrammetry and to investigate the potential of UAVs in 3D modelling. In this purpose we surveyed Gedik Ahmet Pasha Mosque photogrammetricly by UAV and will produce photorealistic 3D model. Gedik Ahmet Pasha, The Grand Vizier of Fatih Sultan Mehmet, has been in Afyonkarahisar during the campaign to Karaman between the years of 1472-1473. He wanted Architect Ayaz Agha to build a complex of Bathhouse, Mosque and a Madrasah here, Afyon, due to admiration of this city. Gedik Ahmet Pasha Mosque is in the centre of this complex. Gedik Ahmet Pasha Mosque is popularly known as Imaret Mosque among the people of Afyon
Photo-realistic Terrain Modeling and Visualization for Mars Exploration Rover Science Operations
NASA Technical Reports Server (NTRS)
Edwards, Laurence; Sims, Michael; Kunz, Clayton; Lees, David; Bowman, Judd
2005-01-01
Modern NASA planetary exploration missions employ complex systems of hardware and software managed by large teams of. engineers and scientists in order to study remote environments. The most complex and successful of these recent projects is the Mars Exploration Rover mission. The Computational Sciences Division at NASA Ames Research Center delivered a 30 visualization program, Viz, to the MER mission that provides an immersive, interactive environment for science analysis of the remote planetary surface. In addition, Ames provided the Athena Science Team with high-quality terrain reconstructions generated with the Ames Stereo-pipeline. The on-site support team for these software systems responded to unanticipated opportunities to generate 30 terrain models during the primary MER mission. This paper describes Viz, the Stereo-pipeline, and the experiences of the on-site team supporting the scientists at JPL during the primary MER mission.
Lentz, Eric J; Mezzacappa, Anthony; Messer, Bronson; Liebendoerfer, Matthias; Hix, William Raphael; Bruenn, S. W.
2012-01-01
We have conducted a series of numerical experiments with the spherically-symmetric, general-relativistic neutrino radiation hydrodynamics code Agile-BOLTZTRAN to examine the effects of several approximations used in multidimensional core-collapse supernova simulations. Our code permits us to examine the effects of these approximations quantitatively by removing, or substituting for, the pieces of supernova physics of interest. These approximations include: (1) using Newtonian versus general-relativistic gravity, hydrodynamics, and transport; (2) using older weak interactions, including the omission of non-isoenergetic neutrino scattering, versus up-to-date weak interactions; and (3) omitting the velocity-dependent terms, or observer corrections, from the neutrino Boltzmann kinetic equation. We demonstrate that each of these changes has non-negligible effects on the outcomes of our simulations. Finally, we discuss the impact these results have for current, and future, multidimensional models.
Capture Conditions for Merging Trajectory Segments to Model Realistic Aircraft Descents
NASA Technical Reports Server (NTRS)
Zhao, Yiyuan; Slattery, Rhonda A.
1996-01-01
A typical commercial aircraft trajectory consists of a series of flight segments. An aircraft switches from one segment to another when certain specified variables reach their desired values. Trajectory synthesis for air traffic control automation must be consistent with practical pilot procedures. We examine capture conditions for merging trajectory segments to model commercial aircraft descent in trajectory synthesis. These conditions translate into bounds on measurements of atmospheric wind, pressure, and temperature. They also define ranges of thrust and drag feasible for a descent trajectory. Capture conditions are derived for the Center-TRACON Automation System developed at NASA Ames Research Center for automated air traffic control. Various uses of capture conditions are discussed. A Boeing 727-200 aircraft is used to provide numerical examples of capture conditions.
NASA Astrophysics Data System (ADS)
Saar, Steven; Dumusque, Xavier
2015-08-01
The radial velocity (RV) signature of starspots has been well-studied and methods to mitigate for them have been developed. The RV signature of magnetic plage is smaller, but more complex (since plage differs from its surroundings more by velocity than intensity) and less well understood. There are reasons however to expect that RV jitter from plage may be important, especially in low to moderate activity stars. We explore the RV effects of stellar plage by taking spatially resolved solar line bisectors in and out of plage at various limb angles to construct semi-empirical stellar intensity profiles profiles of different strengths. These lines are placed on model stars with various plage configurations, rotated, and disk-integrated. The resulting spectra are analyzed to yield the RV and various line and cross-correlation profile diagnostics as a function of rotational phase. We discuss the results and some ideas for mitigating the inferred RV signatures.
Lazy Updating of hubs can enable more realistic models by speeding up stochastic simulations
Ehlert, Kurt; Loewe, Laurence
2014-11-28
To respect the nature of discrete parts in a system, stochastic simulation algorithms (SSAs) must update for each action (i) all part counts and (ii) each action's probability of occurring next and its timing. This makes it expensive to simulate biological networks with well-connected “hubs” such as ATP that affect many actions. Temperature and volume also affect many actions and may be changed significantly in small steps by the network itself during fever and cell growth, respectively. Such trends matter for evolutionary questions, as cell volume determines doubling times and fever may affect survival, both key traits for biological evolution. Yet simulations often ignore such trends and assume constant environments to avoid many costly probability updates. Such computational convenience precludes analyses of important aspects of evolution. Here we present “Lazy Updating,” an add-on for SSAs designed to reduce the cost of simulating hubs. When a hub changes, Lazy Updating postpones all probability updates for reactions depending on this hub, until a threshold is crossed. Speedup is substantial if most computing time is spent on such updates. We implemented Lazy Updating for the Sorting Direct Method and it is easily integrated into other SSAs such as Gillespie's Direct Method or the Next Reaction Method. Testing on several toy models and a cellular metabolism model showed >10× faster simulations for its use-cases—with a small loss of accuracy. Thus we see Lazy Updating as a valuable tool for some special but important simulation problems that are difficult to address efficiently otherwise.
Vermeeren, Günter; Joseph, Wout; Martens, Luc
2013-04-01
Assessing the whole-body absorption in a human in a realistic environment requires a statistical approach covering all possible exposure situations. This article describes the development of a statistical multi-path exposure method for heterogeneous realistic human body models. The method is applied for the 6-year-old Virtual Family boy (VFB) exposed to the GSM downlink at 950 MHz. It is shown that the whole-body SAR does not differ significantly over the different environments at an operating frequency of 950 MHz. Furthermore, the whole-body SAR in the VFB for multi-path exposure exceeds the whole-body SAR for worst-case single-incident plane wave exposure by 3.6%. Moreover, the ICNIRP reference levels are not conservative with the basic restrictions in 0.3% of the exposure samples for the VFB at the GSM downlink of 950 MHz. The homogeneous spheroid with the dielectric properties of the head suggested by the IEC underestimates the absorption compared to realistic human body models. Moreover, the variation in the whole-body SAR for realistic human body models is larger than for homogeneous spheroid models. This is mainly due to the heterogeneity of the tissues and the irregular shape of the realistic human body model compared to homogeneous spheroid human body models.
Hao, Lei; Wang, Jun
2015-07-01
Superconductivity in the topological surface states is essential to both the surface spectrum of bulk superconducting state and the proximity-induced superconductivity of Bi2X3 (X is Se or Te) topological insulators. While previous theories were mostly based on simplified models for the bulk topological insulator and the surface states, the accumulating experiments stimulate us to make an analysis using realistic model for the normal state electronic structures, incorporating terms responsible for particle–hole asymmetry and hexagonal warping. An effective low-energy model for the topological surface states is derived first. Then we identify all the bulk time-reversal-invariant superconducting pairings in the topological insulator that can open a gap in the topological surface states. Many more pairings are found to be able to gap the topological surface states as compared to conclusions based on simplified models. The number of proximity-induced pairing channels in the topological surface states increases by one as a result of the hexagonal warping term, but is not changed by the particle–hole asymmetry term.
Ducrot, Virginie; Péry, Alexandre R. R.; Lagadic, Laurent
2010-01-01
Pesticide use leads to complex exposure and response patterns in non-target aquatic species, so that the analysis of data from standard toxicity tests may result in unrealistic risk forecasts. Developing models that are able to capture such complexity from toxicity test data is thus a crucial issue for pesticide risk assessment. In this study, freshwater snails from two genetically differentiated populations of Lymnaea stagnalis were exposed to repeated acute applications of environmentally realistic concentrations of the herbicide diquat, from the embryo to the adult stage. Hatching rate, embryonic development duration, juvenile mortality, feeding rate and age at first spawning were investigated during both exposure and recovery periods. Effects of diquat on mortality were analysed using a threshold hazard model accounting for time-varying herbicide concentrations. All endpoints were significantly impaired at diquat environmental concentrations in both populations. Snail evolutionary history had no significant impact on their sensitivity and responsiveness to diquat, whereas food acted as a modulating factor of toxicant-induced mortality. The time course of effects was adequately described by the model, which thus appears suitable to analyse long-term effects of complex exposure patterns based upon full life cycle experiment data. Obtained model outputs (e.g. no-effect concentrations) could be directly used for chemical risk assessment. PMID:20921047
Aumeunier, M.-H.; Travere, J.-M.
2010-10-15
In nuclear fusion experiments, the plasma facing components are exposed to high heat fluxes and infrared (IR) imaging diagnostics are routinely used for surveying their surface temperature for preventing damages. However the future use of metallic components in the ITER tokamak adds complications in temperature estimation. Indeed, low and variable emissivity of the observed surface and the multiple reflections of the light coming from hot regions will have to be understood and then taken into account. In this paper, a realistic photonic modeling based on Monte Carlo ray-tracing codes is used to predict the global response of the complete IR survey system. This also includes the complex vessel geometry and the thermal and optical surface properties using the bidirectional reflectivity distribution function that models the photon-material interactions. The first results of this simulation applied to a reference torus are presented and are used as a benchmark to investigate the validity of the global model. Finally the most critical key model parameters in the reflected signals are identified and their contribution is discussed.
Aumeunier, M-H; Travere, J-M
2010-10-01
In nuclear fusion experiments, the plasma facing components are exposed to high heat fluxes and infrared (IR) imaging diagnostics are routinely used for surveying their surface temperature for preventing damages. However the future use of metallic components in the ITER tokamak adds complications in temperature estimation. Indeed, low and variable emissivity of the observed surface and the multiple reflections of the light coming from hot regions will have to be understood and then taken into account. In this paper, a realistic photonic modeling based on Monte Carlo ray-tracing codes is used to predict the global response of the complete IR survey system. This also includes the complex vessel geometry and the thermal and optical surface properties using the bidirectional reflectivity distribution function that models the photon-material interactions. The first results of this simulation applied to a reference torus are presented and are used as a benchmark to investigate the validity of the global model. Finally the most critical key model parameters in the reflected signals are identified and their contribution is discussed.
NASA Astrophysics Data System (ADS)
Khosa, Charanjit K.; Pandita, P. N.
2016-06-01
We consider the measurement of the trilinear couplings of the neutral Higgs bosons in the minimal supersymmetric standard model (MSSM) at a high energy e+e‑ linear collider in the light of the discovery of a Higgs boson at the CERN Large Hadron Collider (LHC). We identify the state observed at the LHC with the lightest Higgs boson (h0) of the MSSM, and impose the constraints following from this identification, as well as other experimental constraints on the MSSM parameter space. In order to measure trilinear neutral Higgs couplings, we consider different processes where the heavier Higgs boson (H0) of the MSSM is produced in electron-positron collisions, which subsequently decays into a pair of lighter Higgs boson. We identify the regions of the MSSM parameter space where it may be possible to measure the trilinear couplings of the Higgs boson at a future electron-positron collider. A measurement of the trilinear Higgs couplings is a crucial step in the construction of the Higgs potential, and hence in establishing the phenomena of spontaneous symmetry breaking in gauge theories.
Enachescu, Cristian; Hauser, Andreas
2016-07-27
Here we reproduce the static and dynamical properties of spin-crossover complexes in the framework of the mechanoelastic model applied to triangular lattices. The switching processes between the high-spin and low-spin states are studied by combining the Monte Carlo method with the elastic lattice relaxation. The transition probabilities between the two states take into account intrinsic parameters, the values of which are approximated from experimental quantities (e.g., the energy gap, and the degeneracy ratio from the thermodynamic enthalpy and the entropy difference between the states), and the elastic force or elastic energy stored in the springs connecting the spin-changing centres. The value of the corresponding spring constant is estimated from the experimentally determined variation of the ligand-field strengths in the two spin states due to the cooperativity and the bulk modulus. Both simulated hysteresis loops and relaxation curves are in agreement with experimental data. Cooperativity related phenomena such as like-spin domain formation and the evolution of the interaction distribution with the HS fraction are also analysed.
NASA Astrophysics Data System (ADS)
Buckman, Stephen
2009-10-01
It is unlikely that anyone would dispute the important role that the availability of accurate data can play in the modeling and simulation of low temperature plasmas. Fundamental measurements of collision processes, from the relatively simple (eg. elastic scattering) to the complex (eg. molecular dissociation) are critical to developing an understanding of discharge and plasma behaviour. While there has been a healthy relationship between the data users and data gatherers at meetings such as GEC for many years, there are often misunderstandings about the capabilities that reside in each of these areas, and how best to maintain and strengthen the communication between them. This paper will attempt to summarise those electron-driven processes that are accessible, in a quantitative sense, in modern scattering experiments. Advances in treating reactive and excited species will also be discussed, as will the potential to push our measurement technologies further. An inescapable conclusion is that the collision community can best contribute through a strategic alliance between experiment and theory. Theory should be benchmarked against experiment for those processes and targets that are accessible, and used wisely for those processes where experiment cannot contribute.
Sun, Fubao Fuebiol; Hong, Jiapeng; Hu, Jinguang; Saddler, Jack N; Fang, Xu; Zhang, Zhenyu; Shen, Song
2015-11-01
The potential of cellulase enzymes in the developing and ongoing "biorefinery" industry has provided a great motivation to develop an efficient cellulase mixture. Recent work has shown how important the role that the so-called accessory enzymes can play in an effective enzymatic hydrolysis. In this study, three newest Novozymes Cellic CTec cellulase preparations (CTec 1/2/3) were compared to hydrolyze steam pretreated lignocellulosic substrates and model substances at an identical FPA loading. These cellulase preparations were found to display significantly different hydrolytic performances irrelevant with the FPA. And this difference was even observed on the filter paper itself when the FPA based assay was revisited. The analysis of specific enzyme activity in cellulase preparations demonstrated that different accessory enzymes were mainly responsible for the discrepancy of enzymatic hydrolysis between diversified substrates and various cellulases. Such the active role of accessory enzymes present in cellulase preparations was finally verified by supplementation with β-glucosidase, xylanase and lytic polysaccharide monooxygenases AA9. This paper provides new insights into the role of accessory enzymes, which can further provide a useful reference for the rational customization of cellulase cocktails in order to realize an efficient conversion of natural lignocellulosic substrates.
Enachescu, Cristian; Hauser, Andreas
2016-07-27
Here we reproduce the static and dynamical properties of spin-crossover complexes in the framework of the mechanoelastic model applied to triangular lattices. The switching processes between the high-spin and low-spin states are studied by combining the Monte Carlo method with the elastic lattice relaxation. The transition probabilities between the two states take into account intrinsic parameters, the values of which are approximated from experimental quantities (e.g., the energy gap, and the degeneracy ratio from the thermodynamic enthalpy and the entropy difference between the states), and the elastic force or elastic energy stored in the springs connecting the spin-changing centres. The value of the corresponding spring constant is estimated from the experimentally determined variation of the ligand-field strengths in the two spin states due to the cooperativity and the bulk modulus. Both simulated hysteresis loops and relaxation curves are in agreement with experimental data. Cooperativity related phenomena such as like-spin domain formation and the evolution of the interaction distribution with the HS fraction are also analysed. PMID:27406813
Lentz, Eric J.; Mezzacappa, Anthony; Hix, W. Raphael; Messer, O. E. Bronson; Liebendoerfer, Matthias; Bruenn, Stephen W. E-mail: mezzacappaa@ornl.gov
2012-03-01
We have conducted a series of numerical experiments with the spherically symmetric, general relativistic, neutrino radiation hydrodynamics code AGILE-BOLTZTRAN to examine the effects of several approximations used in multidimensional core-collapse supernova simulations. Our code permits us to examine the effects of these approximations quantitatively by removing, or substituting for, the pieces of supernova physics of interest. These approximations include: (1) using Newtonian versus general relativistic gravity, hydrodynamics, and transport; (2) using a reduced set of weak interactions, including the omission of non-isoenergetic neutrino scattering, versus the current state-of-the-art; and (3) omitting the velocity-dependent terms, or observer corrections, from the neutrino Boltzmann kinetic equation. We demonstrate that each of these changes has noticeable effects on the outcomes of our simulations. Of these, we find that the omission of observer corrections is particularly detrimental to the potential for neutrino-driven explosions and exhibits a failure to conserve lepton number. Finally, we discuss the impact of these results on our understanding of current, and the requirements for future, multidimensional models.
Supersymmetric quantum mechanics and paraquantization
Morchedi, O.; Mebarki, N.
2012-06-27
The paraquantum Hamiltonian of a free particle is shown to be supersymmetric. Depending on the space-time dimension, the corresponding N=1 and N=2 supercharges are constructed and the related Hamiltonians are derived.
NASA Astrophysics Data System (ADS)
Alimi, J.-M.; Füzfa, A.; Boucher, V.; Rasera, Y.; Courtin, J.; Corasaniti, P.-S.
2010-01-01
Quintessence has been proposed to account for dark energy (DE) in the Universe. This component causes a typical modification of the background cosmic expansion, which, in addition to its clustering properties, can leave a potentially distinctive signature on large-scale structures. Many previous studies have investigated this topic, particularly in relation to the non-linear regime of structure formation. However, no careful pre-selection of viable quintessence models with high precision cosmological data was performed. Here we show that this has led to a misinterpretation (and underestimation) of the imprint of quintessence on the distribution of large-scale structures. To this purpose, we perform a likelihood analysis of the combined Supernova Ia UNION data set and Wilkinson Microwave Anisotropy Probe 5-yr data to identify realistic quintessence models. These are specified by different model parameter values, but still statistically indistinguishable from the vanilla Λ cold dark matter (ΛCDM). Differences are especially manifest in the predicted amplitude and shape of the linear matter power spectrum though these remain within the uncertainties of the Sloan Digital Sky Survey data. We use these models as a benchmark for studying the clustering properties of dark matter haloes by performing a series of high-resolution N-body simulations. In this first paper, we specifically focus on the non-linear matter power spectrum. We find that realistic quintessence models allow for relevant differences of the dark matter distribution with respect to the ΛCDM scenario well into the non-linear regime, with deviations of up to 40 per cent in the non-linear power spectrum. Such differences are shown to depend on the nature of DE, as well as the scale and epoch considered. At small scales (k ~ 1-5hMpc-1, depending on the redshift), the structure formation process is about 20 per cent more efficient than in ΛCDM. We show that these imprints are a specific record of the cosmic
Veress, Alexander I.; Segars, W. Paul; Weiss, Jeffrey A.; Tsui,Benjamin M.W.; Gullberg, Grant T.
2006-08-02
The 4D NURBS-based Cardiac-Torso (NCAT) phantom, whichprovides a realistic model of the normal human anatomy and cardiac andrespiratory motions, is used in medical imaging research to evaluate andimprove imaging devices and techniques, especially dynamic cardiacapplications. One limitation of the phantom is that it lacks the abilityto accurately simulate altered functions of the heart that result fromcardiac pathologies such as coronary artery disease (CAD). The goal ofthis work was to enhance the 4D NCAT phantom by incorporating aphysiologically based, finite-element (FE) mechanical model of the leftventricle (LV) to simulate both normal and abnormal cardiac motions. Thegeometry of the FE mechanical model was based on gated high-resolutionx-ray multi-slice computed tomography (MSCT) data of a healthy malesubject. The myocardial wall was represented as transversely isotropichyperelastic material, with the fiber angle varying from -90 degrees atthe epicardial surface, through 0 degreesat the mid-wall, to 90 degreesat the endocardial surface. A time varying elastance model was used tosimulate fiber contraction, and physiological intraventricular systolicpressure-time curves were applied to simulate the cardiac motion over theentire cardiac cycle. To demonstrate the ability of the FE mechanicalmodel to accurately simulate the normal cardiac motion as well abnormalmotions indicative of CAD, a normal case and two pathologic cases weresimulated and analyzed. In the first pathologic model, a subendocardialanterior ischemic region was defined. A second model was created with atransmural ischemic region defined in the same location. The FE baseddeformations were incorporated into the 4D NCAT cardiac model through thecontrol points that define the cardiac structures in the phantom whichwere set to move according to the predictions of the mechanical model. Asimulation study was performed using the FE-NCAT combination toinvestigate how the differences in contractile function
A Framework for Realistic Modeling and Display of Object Surface Appearance
NASA Astrophysics Data System (ADS)
Darling, Benjamin A.
With advances in screen and video hardware technology, the type of content presented on computers has progressed from text and simple shapes to high-resolution photographs, photorealistic renderings, and high-definition video. At the same time, there have been significant advances in the area of content capture, with the development of devices and methods for creating rich digital representations of real-world objects. Unlike photo or video capture, which provide a fixed record of the light in a scene, these new technologies provide information on the underlying properties of the objects, allowing their appearance to be simulated for novel lighting and viewing conditions. These capabilities provide an opportunity to continue the computer display progression, from high-fidelity image presentations to digital surrogates that recreate the experience of directly viewing objects in the real world. In this dissertation, a framework was developed for representing objects with complex color, gloss, and texture properties and displaying them onscreen to appear as if they are part of the real-world environment. At its core, there is a conceptual shift from a traditional image-based display workflow to an object-based one. Instead of presenting the stored patterns of light from a scene, the objective is to reproduce the appearance attributes of a stored object by simulating its dynamic patterns of light for the real viewing and lighting geometry. This is accomplished using a computational approach where the physical light sources are modeled and the observer and display screen are actively tracked. Surface colors are calculated for the real spectral composition of the illumination with a custom multispectral rendering pipeline. In a set of experiments, the accuracy of color and gloss reproduction was evaluated by measuring the screen directly with a spectroradiometer. Gloss reproduction was assessed by comparing gonio measurements of the screen output to measurements of the
The gravitino problem in supersymmetric warm inflation
Sánchez, Juan C. Bueno; Bastero-Gil, Mar; Berera, Arjun; Dimopoulos, Konstantinos; Kohri, Kazunori E-mail: mbg@ugr.es E-mail: konst.dimopoulos@lancaster.ac.uk
2011-03-01
The warm inflation paradigm considers the continuous production of radiation during inflation due to dissipative effects. In its strong dissipation limit, warm inflation gives way to a radiation dominated Universe. High scale inflation then yields a high reheating temperature, which then poses a severe gravitino overproduction problem for the supersymmetric realisations of warm inflation. In this paper we show that, in a certain class of supersymmetric models, the dissipative dynamics of the inflaton is such that the field can avoid its complete decay after inflation. In some cases, the residual energy density stored in the inflaton field oscillations may come to dominate over the radiation bath at a later epoch. If the inflaton field finally decays much later than the onset of this matter dominated phase, the entropy produced from its decay may be sufficient to counteract the excess of gravitinos produced during the last stages of warm inflation.
A continuous family of realistic Susy SU(5) GUTs
NASA Astrophysics Data System (ADS)
Bajc, Borut
2016-06-01
It is shown that the minimal renormalizable supersymmetric SU(5) is still realistic providing the supersymmetric scale is at least few tens of TeV or large R-parity violating terms are considered. In the first case the vacuum is metastable, and different consistency constraints can give a bounded allowed region in the tan β - msusy plane. In the second case the mass eigenstate electron (down quark) is a linear combination of the original electron (down quark) and Higgsino (heavy colour triplet), and the mass ratio of bino and wino is determined. Both limits lead to light gravitino dark matter.
Guérin, Bastein; Fakhri, Georges El
2008-01-01
We have developed and validated a realistic simulation of random coincidences, pixelated block detectors, light sharing among crystal elements and dead-time in 2D and 3D positron emission tomography (PET) imaging based on the SimSET Monte Carlo simulation software. Our simulation was validated by comparison to a Monte Carlo transport code widely used for PET modeling, GATE, and to measurements made on a PET scanner. METHODS: We have modified the SimSET software to allow independent tracking of single photons in the object and septa while taking advantage of existing voxel based attenuation and activity distributions and validated importance sampling techniques implemented in SimSET. For each single photon interacting in the detector, the energy-weighted average of interaction points was computed, a blurring model applied to account for light sharing and the associated crystal identified. Detector dead-time was modeled in every block as a function of the local single rate using a variance reduction technique. Electronic dead-time was modeled for the whole scanner as a function of the prompt coincidences rate. Energy spectra predicted by our simulation were compared to GATE. NEMA NU-2 2001 performance tests were simulated with the new simulation as well as with SimSET and compared to measurements made on a Discovery ST (DST) camera. RESULTS: Errors in simulated spatial resolution (full width at half maximum, FWHM) were 5.5% (6.1%) in 2D (3D) with the new simulation, compared with 42.5% (38.2%) with SimSET. Simulated (measured) scatter fractions were 17.8% (21.3%) in 2D and 45.8% (45.2%) in 3D. Simulated and measured sensitivities agreed within 2.3 % in 2D and 3D for all planes and simulated and acquired count rate curves (including NEC) were within 12.7% in 2D in the [0: 80 kBq/cc] range and in 3D in the [0: 35 kBq/cc] range. The new simulation yielded significantly more realistic singles' and coincidences' spectra, spatial resolution, global sensitivity and lesion
Yona, Guy; Meitav, Nizan; Kahn, Itamar; Shoham, Shy
2016-01-01
In recent years, optogenetics has become a central tool in neuroscience research. Estimating the transmission of visible light through brain tissue is of crucial importance for controlling the activation levels of neurons in different depths, designing optical systems, and avoiding lesions from excessive power density. The Kubelka-Munk model and Monte Carlo simulations have previously been used to model light propagation through rodents' brain tissue, however, these prior attempts suffer from fundamental shortcomings. Here, we introduce and study two modified approaches for modeling the distributions of light emanating from a multimode fiber and scattering through tissue, using both realistic numerical Monte Carlo simulations and an analytical approach based on the beam-spread function approach. We demonstrate a good agreement of the new methods' predictions both with recently published data, and with new measurements in mouse brain cortical slices, where our results yield a new cortical scattering length estimate of ∼47 µm at λ = 473 nm, significantly shorter than ordinarily assumed in optogenetic applications.
Bethe Ansatz and supersymmetric vacua
Nekrasov, Nikita; Shatashvili, Samson
2009-05-14
Supersymmetric vacua of two dimensional N = 4 gauge theories with matter, softly broken by the twisted masses down to N = 2, are shown to be in one-to-one correspondence with the eigenstates of integrable spin chain Hamiltonians. Examples include: the Heisenberg SU(2)XXX spin chain which is mapped to the two dimensional U(N) theory with fundamental hypermultiplets, the XXZ spin chain which is mapped to the analogous three dimensional super-Yang-Mills theory compactified on a circle, the XYZ spin chain and eight-vertex model which are related to the four dimensional theory compactified on T{sup 2}. A consequence of our correspondence is the isomorphism of the quantum cohomology ring of various quiver varieties, such as cotangent bundles to (partial) flag varieties and the ring of quantum integrals of motion of various spin chains. The correspondence extends to any spin group, representations, boundary conditions, and inhomogeneity, it includes Sinh-Gordon and non-linear Schroedinger models as well as the dynamical spin chains like Hubbard model. Compactifications of four dimensional N = 2 theories on a two-sphere lead to the instanton-corrected Bethe equations.
Reinhardt, James W; Gooch, Keith J
2014-02-01
Agent-based modeling was used to model collagen fibrils, composed of a string of nodes serially connected by links that act as Hookean springs. Bending mechanics are implemented as torsional springs that act upon each set of three serially connected nodes as a linear function of angular deflection about the central node. These fibrils were evaluated under conditions that simulated axial extension, simple three-point bending and an end-loaded cantilever. The deformation of fibrils under axial loading varied <0.001% from the analytical solution for linearly elastic fibrils. For fibrils between 100 μm and 200 μm in length experiencing small deflections, differences between simulated deflections and their analytical solutions were <1% for fibrils experiencing three-point bending and <7% for fibrils experiencing cantilever bending. When these new rules for fibril mechanics were introduced into a model that allowed for cross-linking of fibrils to form a network and the application of cell traction force, the fibrous network underwent macroscopic compaction and aligned between cells. Further, fibril density increased between cells to a greater extent than that observed macroscopically and appeared similar to matrical tracks that have been observed experimentally in cell-populated collagen gels. This behavior is consistent with observations in previous versions of the model that did not allow for the physically realistic simulation of fibril mechanics. The significance of the torsional spring constant value was then explored to determine its impact on remodeling of the simulated fibrous network. Although a stronger torsional spring constant reduced the degree of quantitative remodeling that occurred, the inclusion of torsional springs in the model was not necessary for the model to reproduce key qualitative aspects of remodeling, indicating that the presence of Hookean springs is essential for this behavior. These results suggest that traction force mediated matrix
Neutral Supersymmetric Higgs Boson Searches
Robinson, Stephen Luke
2008-07-01
In some Supersymmetric extensions of the Standard Model, including the Minimal Supersymmetric Standard Model (MSSM), the coupling of Higgs bosons to b-quarks is enhanced. This enhancement makes the associated production of the Higgs with b-quarks an interesting search channel for the Higgs and Supersymmetry at D0. The identification of b-quarks, both online and offline, is essential to this search effort. This thesis describes the author's involvement in the development of both types of b-tagging and in the application of these techniques to the MSSM Higgs search. Work was carried out on the Level-3 trigger b-tagging algorithms. The impact parameter (IP) b-tagger was retuned and the effects of increased instantaneous luminosity on the tagger were studied. An extension of the IP-tagger to use the z-tracking information was developed. A new b-tagger using secondary vertices was developed and commissioned. A tool was developed to allow the use of large multi-run samples for trigger studies involving b-quarks. Offline, a neural network (NN) b-tagger was trained combining the existing offline lifetime based b-tagging tools. The efficiency and fake rate of the NN b-tagger were measured in data and MC. This b-tagger was internally reviewed and certified by the Collaboration and now provides the official b-tagging for all analyses using the Run IIa dataset at D0. A search was performed for neutral MSSM Higgs bosons decaying to a b{bar b} pair and produced in association with one or more b-quarks. Limits are set on the cross-section times the branching ratio for such a process. The limits were interpreted in various MSSM scenarios. This analysis uses the NN b-tagger and was the first to use this tool. The analysis also relies on triggers using the Level-3 IP b-tagging tool described previously. A likelihood discriminant was used to improve the analysis and a neural network was developed to cross-check this technique. The result of the analysis has been submitted to PRL and
Shi, Yunfei; Yao, Jiang; Young, Jonathan M.; Fee, Judy A.; Perucchio, Renato; Taber, Larry A.
2014-01-01
The morphogenetic process of cardiac looping transforms the straight heart tube into a curved tube that resembles the shape of the future four-chambered heart. Although great progress has been made in identifying the molecular and genetic factors involved in looping, the physical mechanisms that drive this process have remained poorly understood. Recent work, however, has shed new light on this complicated problem. After briefly reviewing the current state of knowledge, we propose a relatively comprehensive hypothesis for the mechanics of the first phase of looping, termed c-looping, as the straight heart tube deforms into a c-shaped tube. According to this hypothesis, differential hypertrophic growth in the myocardium supplies the main forces that cause the heart tube to bend ventrally, while regional growth and cytoskeletal contraction in the omphalomesenteric veins (primitive atria) and compressive loads exerted by the splanchnopleuric membrane drive rightward torsion. A computational model based on realistic embryonic heart geometry is used to test the physical plausibility of this hypothesis. The behavior of the model is in reasonable agreement with available experimental data from control and perturbed embryos, offering support for our hypothesis. The results also suggest, however, that several other mechanisms contribute secondarily to normal looping, and we speculate that these mechanisms play backup roles when looping is perturbed. Finally, some outstanding questions are discussed for future study. PMID:25161623
Ploix, Marie-Aude; Guy, Philippe; Chassignole, Bertrand; Moysan, Joseph; Corneloup, Gilles; El Guerjouma, Rachid
2014-09-01
Multipass welds made of 316L stainless steel are specific welds of the primary circuit of pressurized water reactors in nuclear power plants. Because of their strong heterogeneous and anisotropic nature due to grain growth during solidification, ultrasonic waves may be greatly deviated, split and attenuated. Thus, ultrasonic assessment of the structural integrity of such welds is quite complicated. Numerical codes exist that simulate ultrasonic propagation through such structures, but they require precise and realistic input data, as attenuation coefficients. This paper presents rigorous measurements of attenuation in austenitic weld as a function of grain orientation. In fact attenuation is here mainly caused by grain scattering. Measurements are based on the decomposition of experimental beams into plane-wave angular spectra and on the modeling of the ultrasonic propagation through the material. For this, the transmission coefficients are calculated for any incident plane wave on an anisotropic plate. Two different hypotheses on the welded material are tested: first it is considered as monoclinic, and then as triclinic. Results are analyzed, and validated through comparison to theoretical predictions of related literature. They underline the great importance of well-describing the anisotropic structure of austenitic welds for UT modeling issues.
Shi, Yunfei; Yao, Jiang; Young, Jonathan M; Fee, Judy A; Perucchio, Renato; Taber, Larry A
2014-01-01
The morphogenetic process of cardiac looping transforms the straight heart tube into a curved tube that resembles the shape of the future four-chambered heart. Although great progress has been made in identifying the molecular and genetic factors involved in looping, the physical mechanisms that drive this process have remained poorly understood. Recent work, however, has shed new light on this complicated problem. After briefly reviewing the current state of knowledge, we propose a relatively comprehensive hypothesis for the mechanics of the first phase of looping, termed c-looping, as the straight heart tube deforms into a c-shaped tube. According to this hypothesis, differential hypertrophic growth in the myocardium supplies the main forces that cause the heart tube to bend ventrally, while regional growth and cytoskeletal contraction in the omphalomesenteric veins (primitive atria) and compressive loads exerted by the splanchnopleuric membrane drive rightward torsion. A computational model based on realistic embryonic heart geometry is used to test the physical plausibility of this hypothesis. The behavior of the model is in reasonable agreement with available experimental data from control and perturbed embryos, offering support for our hypothesis. The results also suggest, however, that several other mechanisms contribute secondarily to normal looping, and we speculate that these mechanisms play backup roles when looping is perturbed. Finally, some outstanding questions are discussed for future study.
Nayak, Alok R; Pandit, Rahul
2014-01-01
We carry out an extensive numerical study of the dynamics of spiral waves of electrical activation, in the presence of periodic deformation (PD) in two-dimensional simulation domains, in the biophysically realistic mathematical models of human ventricular tissue due to (a) ten-Tusscher and Panfilov (the TP06 model) and (b) ten-Tusscher, Noble, Noble, and Panfilov (the TNNP04 model). We first consider simulations in cable-type domains, in which we calculate the conduction velocity θ and the wavelength λ of a plane wave; we show that PD leads to a periodic, spatial modulation of θ and a temporally periodic modulation of λ; both these modulations depend on the amplitude and frequency of the PD. We then examine three types of initial conditions for both TP06 and TNNP04 models and show that the imposition of PD leads to a rich variety of spatiotemporal patterns in the transmembrane potential including states with a single rotating spiral (RS) wave, a spiral-turbulence (ST) state with a single meandering spiral, an ST state with multiple broken spirals, and a state SA in which all spirals are absorbed at the boundaries of our simulation domain. We find, for both TP06 and TNNP04 models, that spiral-wave dynamics depends sensitively on the amplitude and frequency of PD and the initial condition. We examine how these different types of spiral-wave states can be eliminated in the presence of PD by the application of low-amplitude pulses by square- and rectangular-mesh suppression techniques. We suggest specific experiments that can test the results of our simulations. PMID:24959148
NASA Astrophysics Data System (ADS)
Carter-McAuslan, A.; Lelièvre, P. G.; Farquharson, C.
2012-12-01
Seismic methods provide high resolving potential for use in mineral exploration. Unfortunately, complicated hard-rock geology can make seismic data processing and interpretation difficult. It may help to overcome these difficulties by jointly inverting seismic tomography data with gravity data. We investigated the viability of deterministic minimum-structure style joint inversion of seismic traveltime and gravity data for the delineation of geological targets from the Voisey's Bay sulfide deposit in Labrador, Canada. These tests also assessed the potential of employing borehole gravity. A number of synthetic Earth models were created based on the geology of the Eastern Deeps zone of the Voisey's Bay deposit. These models were built on triangular (2D) and tetrahedral (3D) unstructured meshes, allowing for efficient generation of complicated, realistic geological structures. 2D models were based on conceptualized models of the Eastern Deeps. A detailed 3D model was built using information from extensive drilling. Single property and joint inversions were performed with seismic traveltimes and both ground-based and borehole gravity. There is a known relationship between seismic velocity and density for both silicate rocks and sulphide minerals for our study area; this lithological relationship was used to design an appropriate coupling strategy in the joint inversions. Joint inversions were able to successfully locate a buried high contrast target with a variety of survey designs. Experimentation with noise levels, mesh design, and various inversion parameters has lead to a better understanding of how to practically apply joint inversion of traveltimes and gravity data to this and similar exploration problems.
Patoul, Judith de; Foullon, Claire; Riley, Pete E-mail: c.foullon@exeter.ac.uk
2015-11-20
Knowledge of the electron density distribution in the solar corona put constraints on the magnetic field configurations for coronal modeling and on initial conditions for solar wind modeling. We work with polarized SOHO/LASCO-C2 images from the last two recent minima of solar activity (1996–1997 and 2008–2010), devoid of coronal mass ejections. The goals are to derive the 4D electron density distributions in the corona by applying a newly developed time-dependent tomographic reconstruction method and to compare the results between the two solar minima and with two magnetohydrodynamic models. First, we confirm that the values of the density distribution in thermodynamic models are more realistic than in polytropic ones. The tomography provides more accurate distributions in the polar regions, and we find that the density in tomographic and thermodynamic solutions varies with the solar cycle in both polar and equatorial regions. Second, we find that the highest-density structures do not always correspond to the predicted large-scale heliospheric current sheet or its helmet streamer but can follow the locations of pseudo-streamers. We deduce that tomography offers reliable density distributions in the corona, reproducing the slow time evolution of coronal structures, without prior knowledge of the coronal magnetic field over a full rotation. Finally, we suggest that the highest-density structures show a differential rotation well above the surface depending on how they are magnetically connected to the surface. Such valuable information on the rotation of large-scale structures could help to connect the sources of the solar wind to their in situ counterparts in future missions such as Solar Orbiter and Solar Probe Plus.
Rossner, Mike
2010-05-01
Nearly six years ago Ira Mellman, then Editor-in-Chief of the JCB, published an editorial entitled "Providing realistic access" (1). It described the Journal's efforts to reconcile its subscription-based business model with the goal of providing public access to scholarly journal content. Since then, developments in the public-access movement are bringing us closer to the ideal of universal public access. But will there still be a place for selective journals like the JCB when we achieve that objective? PMID:20375430
Xu, Jinyu; Deng, Benqiang; Fang, Yibin; Yu, Ying; Cheng, Jiyong; Wang, Shengzhang; Wang, Kuizhong; Liu, Jian-Min; Huang, Qinghai
2013-01-01
Adjusting hemodynamics via flow diverter (FD) implantation is emerging as a novel method of treating cerebral aneurysms. However, most previous FD-related hemodynamic studies were based on virtual FD deployment, which may produce different hemodynamic outcomes than realistic (in vivo) FD deployment. We compared hemodynamics between virtual FD and realistic FD deployments in rabbit aneurysm models using computational fluid dynamics (CFD) simulations. FDs were implanted for aneurysms in 14 rabbits. Vascular models based on rabbit-specific angiograms were reconstructed for CFD studies. Real FD configurations were reconstructed based on micro-CT scans after sacrifice, while virtual FD configurations were constructed with SolidWorks software. Hemodynamic parameters before and after FD deployment were analyzed. According to the metal coverage (MC) of implanted FDs calculated based on micro-CT reconstruction, 14 rabbits were divided into two groups (A, MC >35%; B, MC <35%). Normalized mean wall shear stress (WSS), relative residence time (RRT), inflow velocity, and inflow volume in Group A were significantly different (P<0.05) from virtual FD deployment, but pressure was not (P>0.05). The normalized mean WSS in Group A after realistic FD implantation was significantly lower than that of Group B. All parameters in Group B exhibited no significant difference between realistic and virtual FDs. This study confirmed MC-correlated differences in hemodynamic parameters between realistic and virtual FD deployment.
Neutrino masses in supersymmetric SU(3){sub c} x SU(3){sub L} x U(1){sub X} models
Rodriguez, J-Alexis; Duarte, J.
2008-11-23
The mass spectra and the superpotential of two different supersymetric models based on the gauge symmetry SU(3){sub C} x SU(3){sub L} x U(1){sub X}(331) without any exotic charges assigned to the fermionic spectra are studied. These two models have three families in different representations of the gauge group. In these kind of models, the diagonalization of the neutralino mass matrix allows that three light neutrinos get different mass values. Possible values for the neutrino masses are calculated covering the parameter space of the models. These values have to agree with the available data coming from the neutrino oscillations experiments. Therefore, a reduced space of parameters for the superpotential and the vacuum expectation values allowed in the framework of the 331 supersymetric models can be obtained.
Lee, Won Hee; Deng, Zhi-De; Kim, Tae-Seong; Laine, Andrew F; Lisanby, Sarah H; Peterchev, Angel V
2012-02-01
We present the first computational study investigating the electric field (E-field) strength generated by various electroconvulsive therapy (ECT) electrode configurations in specific brain regions of interest (ROIs) that have putative roles in the therapeutic action and/or adverse side effects of ECT. This study also characterizes the impact of the white matter (WM) conductivity anisotropy on the E-field distribution. A finite element head model incorporating tissue heterogeneity and WM anisotropic conductivity was constructed based on structural magnetic resonance imaging (MRI) and diffusion tensor MRI data. We computed the spatial E-field distributions generated by three standard ECT electrode placements including bilateral (BL), bifrontal (BF), and right unilateral (RUL) and an investigational electrode configuration for focal electrically administered seizure therapy (FEAST). The key results are that (1) the median E-field strength over the whole brain is 3.9, 1.5, 2.3, and 2.6 V/cm for the BL, BF, RUL, and FEAST electrode configurations, respectively, which coupled with the broad spread of the BL E-field suggests a biophysical basis for observations of superior efficacy of BL ECT compared to BF and RUL ECT; (2) in the hippocampi, BL ECT produces a median E-field of 4.8 V/cm that is 1.5-2.8 times stronger than that for the other electrode configurations, consistent with the more pronounced amnestic effects of BL ECT; and (3) neglecting the WM conductivity anisotropy results in E-field strength error up to 18% overall and up to 39% in specific ROIs, motivating the inclusion of the WM conductivity anisotropy in accurate head models. This computational study demonstrates how the realistic finite element head model incorporating tissue conductivity anisotropy provides quantitative insight into the biophysics of ECT, which may shed light on the differential clinical outcomes seen with various forms of ECT, and may guide the development of novel stimulation paradigms
The Supersymmetric origin of matter
Balazs, C.; Carena, M.; Menon, A.; Morrissey, D.E.; Wagner, C.E.M.; /Argonne /Chicago U., EFI
2004-12-01
The Minimal Supersymmetric extension of the Standard Model (MSSM) can provide the correct neutralino relic abundance and baryon number asymmetry of the universe. Both may be efficiently generated in the presence of CP violating phases, light charginos and neutralinos, and a light top squark. Due to the coannihilation of the neutralino with the light stop, we find a large region of parameter space in which the neutralino relic density is consistent with WMAP and SDSS data. We perform a detailed study of the additional constraints induced when CP violating phases, consistent with the ones required for baryogenesis, are included. We explore the possible tests of this scenario from present and future electron Electric Dipole Moment (EDM) measurements, direct neutralino detection experiments, collider searches and the b {yields} s{gamma} decay rate. We find that the EDM constraints are quite severe and that electron EDM experiments, together with stop searches at the Tevatron and Higgs searches at the LHC, will provide a definite test of our scenario of electroweak baryogenesis in the next few years.
Stop as a next-to-lightest supersymmetric particle in constrained MSSM
Huitu, Katri; Leinonen, Lasse; Laamanen, Jari
2011-10-01
So far the squarks have not been detected at the LHC indicating that they are heavier than a few hundred GeVs, if they exist. The lighter stop can be considerably lighter than the other squarks. We study the possibility that a supersymmetric partner of the top quark, stop, is the next-to-lightest supersymmetric particle in the constrained supersymmetric standard model. Various constraints, on top of the mass limits, are taken into an account, and the allowed parameter space for this scenario is determined. Observing stop which is the next-to-lightest supersymmetric particle at the LHC may be difficult.
NASA Astrophysics Data System (ADS)
Allanach, B. C.; Badziak, Marcin; Cottin, Giovanna; Desai, Nishita; Hugonie, Cyril; Ziegler, Robert
2016-09-01
We study the LHC phenomenology of the next-to-minimal model of gauge-mediated supersymmetry breaking, both for Run I and Run II. The Higgs phenomenology of the model is consistent with observations: a 125 GeV standard model-like Higgs which mixes with singlet-like state of mass around 90 GeV that provides a 2σ excess at LEP II. The model possesses regions of parameter space where a longer-lived lightest neutralino decays in the detector into a gravitino and a b-jet pair or a tau pair resulting in potential displaced vertex signatures. We investigate current bounds on sparticle masses and the discovery potential of the model, both via conventional searches and via searches for displaced vertices. The searches based on promptly decaying sparticles currently give a lower limit on the gluino mass 1080 GeV and could be sensitive up to 1900 GeV with 100 fb^{-1}, whereas the current displaced vertex searches cannot probe this model due to b-quarks in the final state. We show how the displaced vertex cuts might be relaxed in order to improve signal efficiency, while simultaneously applied prompt cuts reduce background, resulting in a much better sensitivity than either strategy alone and motivating a fully fledged experimental study.
Doubly Lopsided Models From SUSY SU(N)
Barr, S. M.
2008-11-23
It is shown that the doubly lopsided mass matrices, which are known to give realistic patterns of quark and lepton masses and mixings, arise naturally in the context of supersymmetric grand unified models based on SU(N) with N>5. An SU(7) model is presented as an illustration.
NASA Astrophysics Data System (ADS)
Blash, Derek M.
The region known as Low-Earth Orbit (LEO) has become populated with artificial satellites and space debris since humanities initial venture into the region. This has turned LEO into a hazardous region. Since LEO is very valuable to many different countries, there has been a push to prevent further buildup and talk of even deorbiting spent satellites and debris already in LEO. One of the more attractive concepts available for deorbiting debris and spent satellites is a Bare Electrodynamic Tether (BET). A BET is a propellantless propulsion technique in which two objects are joined together by a thin conducting material. When these tethered objects are placed in LEO, the tether sweeps across the magnetic field lines of the Earth and induces an electromotive force (emf) along the tether. Current from the space plasma is collected on the bare tether under the action of the induced emf, and this current interacts with the Earth's magnetic field to create a drag force that can be used to deorbit spent satellites and space debris. A Plasma Contactor (PC) is used to close the electrical circuit between the BET and the ionospheric plasma. The PC requires a voltage and, depending on the device, a gas flow to emit electrons through a plasma bridge to the ionospheric plasma. The PC also can require a plasma discharge electrode and a heater to condition the PC for operation. These parameters as well as the PC performance are required to build an accurate simulation of a PC and, therefore, a BET deorbiting system. This thesis focuses on the development, validation, and implementation of a simulation tool to model the effects of a realistic hollow cathode PC system model on a BET deorbit system.
NASA Technical Reports Server (NTRS)
Szallasi, Zoltan; Liang, Shoudan
2000-01-01
In this paper we show how Boolean genetic networks could be used to address complex problems in cancer biology. First, we describe a general strategy to generate Boolean genetic networks that incorporate all relevant biochemical and physiological parameters and cover all of their regulatory interactions in a deterministic manner. Second, we introduce 'realistic Boolean genetic networks' that produce time series measurements very similar to those detected in actual biological systems. Third, we outline a series of essential questions related to cancer biology and cancer therapy that could be addressed by the use of 'realistic Boolean genetic network' modeling.
Supersymmetric q-deformed quantum mechanics
Traikia, M. H.; Mebarki, N.
2012-06-27
A supersymmetric q-deformed quantum mechanics is studied in the weak deformation approximation of the Weyl-Heisenberg algebra. The corresponding supersymmetric q-deformed hamiltonians and charges are constructed explicitly.
Variational methods in supersymmetric lattice field theory: The vacuum sector
Duncan, A.; Meyer-Ortmanns, H.; Roskies, R.
1987-12-15
The application of variational methods to the computation of the spectrum in supersymmetric lattice theories is considered, with special attention to O(N) supersymmetric sigma models. Substantial cancellations are found between bosonic and fermionic contributions even in approximate Ansa$uml: tze for the vacuum wave function. The nonlinear limit of the linear sigma model is studied in detail, and it is shown how to construct an appropriate non-Gaussian vacuum wave function for the nonlinear model. The vacuum energy is shown to be of order unity in lattice units in the latter case, after infinite cancellations.
Bilinear approach to the supersymmetric Gardner equation
NASA Astrophysics Data System (ADS)
Babalic, C. N.; Carstea, A. S.
2016-08-01
We study a supersymmetric version of the Gardner equation (both focusing and defocusing) using the superbilinear formalism. This equation is new and cannot be obtained from the supersymmetric modified Korteweg-de Vries equation with a nonzero boundary condition. We construct supersymmetric solitons and then by passing to the long-wave limit in the focusing case obtain rational nonsingular solutions. We also discuss the supersymmetric version of the defocusing equation and the dynamics of its solutions.
NASA Astrophysics Data System (ADS)
Chifflard, Peter; Tilch, Nils
2010-05-01
Introduction Hydrological or geomorphological processes in nature are often very diverse and complex. This is partly due to the regional characteristics which vary over time and space, as well as changeable process-initiating and -controlling factors. Despite being aware of this complexity, such aspects are usually neglected in the modelling of hazard-related maps due to several reasons. But particularly when it comes to creating more realistic maps, this would be an essential component to consider. The first important step towards solving this problem would be to collect data relating to regional conditions which vary over time and geographical location, along with indicators of complex processes. Data should be acquired promptly during and after events, and subsequently digitally combined and analysed. Study area In June 2009, considerable damage occurred in the residential area of Klingfurth (Lower Austria) as a result of great pre-event wetness and repeatedly heavy rainfall, leading to flooding, debris flow deposit and gravitational mass movement. One of the causes is the fact that the meso-scale watershed (16 km²) of the Klingfurth stream is characterised by adverse geological and hydrological conditions. Additionally, the river system network with its discharge concentration within the residential zone contributes considerably to flooding, particularly during excessive rainfall across the entire region, as the flood peaks from different parts of the catchment area are superposed. First results of mapping Hydro(geo)logical surveys across the entire catchment area have shown that - over 600 gravitational mass movements of various type and stage have occurred. 516 of those have acted as a bed load source, while 325 mass movements had not reached the final stage yet and could thus supply bed load in the future. It should be noted that large mass movements in the initial or intermediate stage were predominately found in clayey-silty areas and weathered material
Haller, Jozsef; Raczkevy-Deak, Gabriella; Gyimesine, Katalin P.; Szakmary, Andras; Farkas, Istvan; Vegh, Jozsef
2014-01-01
Among the multitude of factors that can transform human social interactions into violent conflicts, biological features received much attention in recent years as correlates of decision making and aggressiveness especially in critical situations. We present here a highly realistic new model of human aggression and violence, where genuine acts of aggression are readily performed and which at the same time allows the parallel recording of biological concomitants. Particularly, we studied police officers trained at the International Training Centre (Budapest, Hungary), who are prepared to perform operations under extreme conditions of stress. We found that aggressive arousal can transform a basically peaceful social encounter into a violent conflict. Autonomic recordings show that this change is accompanied by increased heart rates, which was associated earlier with reduced cognitive complexity of perceptions (“attentional myopia”) and promotes a bias toward hostile attributions and aggression. We also observed reduced heart rate variability in violent subjects, which is believed to signal a poor functioning of prefrontal-subcortical inhibitory circuits and reduces self-control. Importantly, these autonomic particularities were observed already at the beginning of social encounters i.e., before aggressive acts were initiated, suggesting that individual characteristics of the stress-response define the way in which social pressure affects social behavior, particularly the way in which this develops into violence. Taken together, these findings suggest that cardiac autonomic functions are valuable external symptoms of internal motivational states and decision making processes, and raise the possibility that behavior under social pressure can be predicted by the individual characteristics of stress responsiveness. PMID:25374519
Ruffini, Giulio; Fox, Michael D; Ripolles, Oscar; Miranda, Pedro Cavaleiro; Pascual-Leone, Alvaro
2014-04-01
Recently, multifocal transcranial current stimulation (tCS) devices using several relatively small electrodes have been used to achieve more focal stimulation of specific cortical targets. However, it is becoming increasingly recognized that many behavioral manifestations of neurological and psychiatric disease are not solely the result of abnormality in one isolated brain region but represent alterations in brain networks. In this paper we describe a method for optimizing the configuration of multifocal tCS for stimulation of brain networks, represented by spatially extended cortical targets. We show how, based on fMRI, PET, EEG or other data specifying a target map on the cortical surface for excitatory, inhibitory or neutral stimulation and a constraint on the maximal number of electrodes, a solution can be produced with the optimal currents and locations of the electrodes. The method described here relies on a fast calculation of multifocal tCS electric fields (including components normal and tangential to the cortical boundaries) using a five layer finite element model of a realistic head. Based on the hypothesis that the effects of current stimulation are to first order due to the interaction of electric fields with populations of elongated cortical neurons, it is argued that the optimization problem for tCS stimulation can be defined in terms of the component of the electric field normal to the cortical surface. Solutions are found using constrained least squares to optimize current intensities, while electrode number and their locations are selected using a genetic algorithm. For direct current tCS (tDCS) applications, we provide some examples of this technique using an available tCS system providing 8 small Ag/AgCl stimulation electrodes. We demonstrate the approach both for localized and spatially extended targets defined using rs-fcMRI and PET data, with clinical applications in stroke and depression. Finally, we extend these ideas to more general
Lee, Won Hee; Deng, Zhi-De; Kim, Tae-Seong; Laine, Andrew F.; Lisanby, Sarah H.; Peterchev, Angel V.
2012-01-01
We present the first computational study investigating the electric field (E-field) strength generated by various electroconvulsive therapy (ECT) electrode configurations in specific brain regions of interest (ROIs) that have putative roles in the therapeutic action and/or adverse side effects of ECT. This study also characterizes the impact of the white matter (WM) conductivity anisotropy on the E-field distribution. A finite element head model incorporating tissue heterogeneity and WM anisotropic conductivity was constructed based on structural magnetic resonance imaging (MRI) and diffusion tensor MRI data. We computed the spatial E-field distributions generated by three standard ECT electrode placements including bilateral (BL), bifrontal (BF), and right unilateral (RUL) and an investigational electrode configuration for focal electrically administered seizure therapy (FEAST). The key results are that (1) the median E-field strength over the whole brain is 3.9, 1.5, 2.3, and 2.6 V/cm for the BL, BF, RUL, and FEAST electrode configurations, respectively, which coupled with the broad spread of the BL E-field suggests a biophysical basis for observations of superior efficacy of BL ECT compared to BF and RUL ECT; (2) in the hippocampi, BL ECT produces a median E-field of 4.8 V/cm that is 1.5–2.8 times stronger than that for the other electrode configurations, consistent with the more pronounced amnestic effects of BL ECT; and (3) neglecting the WM conductivity anisotropy results in E-field strength error up to 18% overall and up to 39% in specific ROIs, motivating the inclusion of the WM conductivity anisotropy in accurate head models. This computational study demonstrates how the realistic finite element head model incorporating tissue conductivity anisotropy provides quantitative insight into the biophysics of ECT, which may shed light on the differential clinical outcomes seen with various forms of ECT, and may guide the development of novel stimulation
Won Kim, Chang; Kim, Jong Hyo
2014-01-15
Purpose: Reducing the patient dose while maintaining the diagnostic image quality during CT exams is the subject of a growing number of studies, in which simulations of reduced-dose CT with patient data have been used as an effective technique when exploring the potential of various dose reduction techniques. Difficulties in accessing raw sinogram data, however, have restricted the use of this technique to a limited number of institutions. Here, we present a novel reduced-dose CT simulation technique which provides realistic low-dose images without the requirement of raw sinogram data. Methods: Two key characteristics of CT systems, the noise equivalent quanta (NEQ) and the algorithmic modulation transfer function (MTF), were measured for various combinations of object attenuation and tube currents by analyzing the noise power spectrum (NPS) of CT images obtained with a set of phantoms. Those measurements were used to develop a comprehensive CT noise model covering the reduced x-ray photon flux, object attenuation, system noise, and bow-tie filter, which was then employed to generate a simulated noise sinogram for the reduced-dose condition with the use of a synthetic sinogram generated from a reference CT image. The simulated noise sinogram was filtered with the algorithmic MTF and back-projected to create a noise CT image, which was then added to the reference CT image, finally providing a simulated reduced-dose CT image. The simulation performance was evaluated in terms of the degree of NPS similarity, the noise magnitude, the bow-tie filter effect, and the streak noise pattern at photon starvation sites with the set of phantom images. Results: The simulation results showed good agreement with actual low-dose CT images in terms of their visual appearance and in a quantitative evaluation test. The magnitude and shape of the NPS curves of the simulated low-dose images agreed well with those of real low-dose images, showing discrepancies of less than +/−3.2% in
Maximally Supersymmetric Yang-Mills Theory: The Story of N = 4 Yang-Mills Theory
NASA Astrophysics Data System (ADS)
Brink, Lars
The following sections are included: * History * Dual Models * Supersymmetric Field Theories and Supergravity * Maximally Supersymmetric Yang-Mills Theories * The Light-Cone Gauge Formulation of N = 4 Yang-Mills Theory * The Perturbative Finiteness N = 4 Yang-Mills Theory * References
ERIC Educational Resources Information Center
Affleck, James Q.; And Others
The manual, developed by the Realistic Transition Project in Washington State, reviews program experiences and recommended best practices for serving mildly handicapped students in their final years of school (ages 17-21). The project focused on employment with formal class teaching secondary to community work experience. A skills curriculum…
Enhanced lepton flavour violation in the supersymmetric inverse seesaw
NASA Astrophysics Data System (ADS)
Weiland, C.
2013-07-01
In minimal supersymmetric seesaw models, the contribution to lepton flavour violation from Z-penguins is usually negligible. In this study, we consider the supersymmetric inverse seesaw and show that, in this case, the Z-penguin contribution dominates in several lepton flavour violating observables due to the low scale of the inverse seesaw mechanism. Among the observables considered, we find that the most constraining one is the μ-e conversion rate which is already restricting the otherwise allowed parameter space of the model. Moreover, in this framework, the Z-penguins exhibit a non-decoupling behaviour, which has previously been noticed in lepton flavour violating Higgs decays.
Gunion, John F.; Haber, Howard E.; Moroi, Takeo
1996-06-24
We demonstrate that there are regions of parameter space in the next-to-minimal (i.e. two-Higgs-doublet, one-Higgs-singlet superfield) supersymmetric extension of the SM for which none of the Higgs bosons are observable either at LEP2 with $\\sqrt{s}=192 GeV$ and an integrated luminosity of $L=1000inverse pb$ or at the LHC with $L=600 inverse fb$.
Status of the minimal supersymmetric SO(10)
Dorsner, Ilja
2010-02-10
We discuss status of the minimal supersymmetric SO(10) in both low and split supersymmetry regime. To demonstrate viability of the model we present a good fit of the fermion masses and their mixings. The solution needs a strongly split supersymmetry with gauginos and higgsinos around 10{sup 2} TeV, sfermions close to 10{sup 14} GeV and a GUT scale of around 6x10{sup 15} GeV. It predicts fast proton decay rates, hierarchical neutrino masses and large leptonic mixing angle sin{theta}{sub 13}{approx_equal}0.1.
Abulencia, A; Acosta, D; Adelman, J; Affolder, T; Akimoto, T; Albrow, M G; Ambrose, D; Amerio, S; Amidei, D; Anastassov, A; Anikeev, K; Annovi, A; Antos, J; Aoki, M; Apollinari, G; Arguin, J-F; Arisawa, T; Artikov, A; Ashmanskas, W; Attal, A; Azfar, F; Azzi-Bacchetta, P; Azzurri, P; Bacchetta, N; Bachacou, H; Badgett, W; Barbaro-Galtieri, A; Barnes, V E; Barnett, B A; Baroiant, S; Bartsch, V; Bauer, G; Bedeschi, F; Behari, S; Belforte, S; Bellettini, G; Bellinger, J; Belloni, A; Ben-Haim, E; Benjamin, D; Beretvas, A; Beringer, J; Berry, T; Bhatti, A; Binkley, M; Bisello, D; Bishai, M; Blair, R E; Blocker, C; Bloom, K; Blumenfeld, B; Bocci, A; Bodek, A; Boisvert, V; Bolla, G; Bolshov, A; Bortoletto, D; Boudreau, J; Bourov, S; Boveia, A; Brau, B; Bromberg, C; Brubaker, E; Budagov, J; Budd, H S; Budd, S; Burkett, K; Busetto, G; Bussey, P; Byrum, K L; Cabrera, S; Campanelli, M; Campbell, M; Canelli, F; Canepa, A; Carlsmith, D; Carosi, R; Carron, S; Casarsa, M; Castro, A; Catastini, P; Cauz, D; Cavalli-Sforza, M; Cerri, A; Cerrito, L; Chang, S H; Chapman, J; Chen, Y C; Chertok, M; Chiarelli, G; Chlachidze, G; Chlebana, F; Cho, I; Cho, K; Chokheli, D; Chou, J P; Chu, P H; Chuang, S H; Chung, K; Chung, W H; Chung, Y S; Ciljak, M; Ciobanu, C I; Ciocci, M A; Clark, A; Clark, D; Coca, M; Connolly, A; Convery, M E; Conway, J; Cooper, B; Copic, K; Cordelli, M; Cortiana, G; Cruz, A; Cuevas, J; Culbertson, R; Cyr, D; Daronco, S; D'Auria, S; D'onofrio, M; Dagenhart, D; de Barbaro, P; De Cecco, S; Deisher, A; De Lentdecker, G; Dell'Orso, M; Demers, S; Demortier, L; Deng, J; Deninno, M; De Pedis, D; Derwent, P F; Dionisi, C; Dittmann, J; Dituro, P; Dörr, C; Dominguez, A; Donati, S; Donega, M; Dong, P; Donini, J; Dorigo, T; Dube, S; Ebina, K; Efron, J; Ehlers, J; Erbacher, R; Errede, D; Errede, S; Eusebi, R; Fang, H C; Farrington, S; Fedorko, I; Fedorko, W T; Feild, R G; Feindt, M; Fernandez, J P; Field, R; Flanagan, G; Flores-Castillo, L R; Foland, A; Forrester, S; Foster, G W; Franklin, M; Freeman, J C; Fujii, Y; Furic, I; Gajjar, A; Gallinaro, M; Galyardt, J; Garcia, J E; Garcia Sciveres, M; Garfinkel, A F; Gay, C; Gerberich, H; Gerchtein, E; Gerdes, D; Giagu, S; Giannetti, P; Gibson, A; Gibson, K; Ginsburg, C; Giolo, K; Giordani, M; Giunta, M; Giurgiu, G; Glagolev, V; Glenzinski, D; Gold, M; Goldschmidt, N; Goldstein, J; Gomez, G; Gomez-Ceballos, G; Goncharov, M; González, O; Gorelov, I; Goshaw, A T; Gotra, Y; Goulianos, K; Gresele, A; Griffiths, M; Grinstein, S; Grosso-Pilcher, C; Grundler, U; Guimaraes da Costa, J; Haber, C; Hahn, S R; Hahn, K; Halkiadakis, E; Hamilton, A; Han, B-Y; Handler, R; Happacher, F; Hara, K; Hare, M; Harper, S; Harr, R F; Harris, R M; Hatakeyama, K; Hauser, J; Hays, C; Hayward, H; Heijboer, A; Heinemann, B; Heinrich, J; Hennecke, M; Herndon, M; Heuser, J; Hidas, D; Hill, C S; Hirschbuehl, D; Hocker, A; Holloway, A; Hou, S; Houlden, M; Hsu, S-C; Huffman, B T; Hughes, R E; Huston, J; Ikado, K; Incandela, J; Introzzi, G; Iori, M; Ishizawa, Y; Ivanov, A; Iyutin, B; James, E; Jang, D; Jayatilaka, B; Jeans, D; Jensen, H; Jeon, E J; Jones, M; Joo, K K; Jun, S Y; Junk, T R; Kamon, T; Kang, J; Karagoz-Unel, M; Karchin, P E; Kato, Y; Kemp, Y; Kephart, R; Kerzel, U; Khotilovich, V; Kilminster, B; Kim, D H; Kim, H S; Kim, J E; Kim, M J; Kim, M S; Kim, S B; Kim, S H; Kim, Y K; Kirby, M; Kirsch, L; Klimenko, S; Klute, M; Knuteson, B; Ko, B R; Kobayashi, H; Kondo, K; Kong, D J; Konigsberg, J; Kordas, K; Korytov, A; Kotwal, A V; Kovalev, A; Kraus, J; Kravchenko, I; Kreps, M; Kreymer, A; Kroll, J; Krumnack, N; Kruse, M; Krutelyov, V; Kuhlmann, S E; Kusakabe, Y; Kwang, S; Laasanen, A T; Lai, S; Lami, S; Lammel, S; Lancaster, M; Lander, R L; Lannon, K; Lath, A; Latino, G; Lazzizzera, I; Lecci, C; Lecompte, T; Lee, J; Lee, J; Lee, S W; Lefèvre, R; Leonardo, N; Leone, S; Levy, S; Lewis, J D; Li, K; Lin, C; Lin, C S; Lindgren, M; Lipeles, E; Liss, T M; Lister, A; Litvintsev, D O; Liu, T; Liu, Y; Lockyer, N S; Loginov, A; Loreti, M; Loverre, P; Lu, R-S; Lucchesi, D; Lujan, P; Lukens, P; Lungu, G; Lyons, L; Lys, J; Lysak, R; Lytken, E; Mack, P; Macqueen, D; Madrak, R; Maeshima, K; Maksimovic, P; Manca, G; Margaroli, F; Marginean, R; Marino, C; Martin, A; Martin, M; Martin, V; Martínez, M; Maruyama, T; Matsunaga, H; Mattson, M E; Mazini, R; Mazzanti, P; McFarland, K S; McGivern, D; McIntyre, P; McNamara, P; McNulty, R; Mehta, A; Menzemer, S; Menzione, A; Merkel, P; Mesropian, C; Messina, A; von der Mey, M; Miao, T; Miladinovic, N; Miles, J; Miller, R; Miller, J S; Mills, C; Milnik, M; Miquel, R; Miscetti, S; Mitselmakher, G; Miyamoto, A; Moggi, N; Mohr, B; Moore, R; Morello, M; Movilla Fernandez, P; Mülmenstädt, J; Mukherjee, A; Mulhearn, M; Muller, Th; Mumford, R; Murat, P; Nachtman, J; Nahn, S; Nakano, I; Napier, A; Naumov, D; Necula, V; Neu, C; Neubauer, M S; Nielsen, J; Nigmanov, T; Nodulman, L; Norniella, O; Ogawa, T; Oh, S H; Oh, Y D; Okusawa, T; Oldeman, R; Orava, R; Osterberg, K; Pagliarone, C; Palencia, E; Paoletti, R; Papadimitriou, V; Papikonomou, A; Paramonov, A A; Parks, B; Pashapour, S; Patrick, J; Pauletta, G; Paulini, M; Paus, C; Pellett, D E; Penzo, A; Phillips, T J; Piacentino, G; Piedra, J; Pitts, K; Plager, C; Pondrom, L; Pope, G; Portell, X; Poukhov, O; Pounder, N; Prakoshyn, F; Pronko, A; Proudfoot, J; Ptohos, F; Punzi, G; Pursley, J; Rademacker, J; Rahaman, A; Rakitin, A; Rappoccio, S; Ratnikov, F; Reisert, B; Rekovic, V; van Remortel, N; Renton, P; Rescigno, M; Richter, S; Rimondi, F; Rinnert, K; Ristori, L; Robertson, W J; Robson, A; Rodrigo, T; Rogers, E; Rolli, S; Roser, R; Rossi, M; Rossin, R; Rott, C; Ruiz, A; Russ, J; Rusu, V; Ryan, D; Saarikko, H; Sabik, S; Safonov, A; Sakumoto, W K; Salamanna, G; Salto, O; Saltzberg, D; Sanchez, C; Santi, L; Sarkar, S; Sato, K; Savard, P; Savoy-Navarro, A; Scheidle, T; Schlabach, P; Schmidt, E E; Schmidt, M P; Schmitt, M; Schwarz, T; Scodellaro, L; Scott, A L; Scribano, A; Scuri, F; Sedov, A; Seidel, S; Seiya, Y; Semenov, A; Semeria, F; Sexton-Kennedy, L; Sfiligoi, I; Shapiro, M D; Shears, T; Shepard, P F; Sherman, D; Shimojima, M; Shochet, M; Shon, Y; Shreyber, I; Sidoti, A; Sill, A; Sinervo, P; Sisakyan, A; Sjolin, J; Skiba, A; Slaughter, A J; Sliwa, K; Smirnov, D; Smith, J R; Snider, F D; Snihur, R; Soderberg, M; Soha, A; Somalwar, S; Sorin, V; Spalding, J; Spinella, F; Squillacioti, P; Stanitzki, M; Staveris-Polykalas, A; St Denis, R; Stelzer, B; Stelzer-Chilton, O; Stentz, D; Strologas, J; Stuart, D; Suh, J S; Sukhanov, A; Sumorok, K; Sun, H; Suzuki, T; Taffard, A; Tafirout, R; Takashima, R; Takeuchi, Y; Takikawa, K; Tanaka, M; Tanaka, R; Tecchio, M; Teng, P K; Terashi, K; Tether, S; Thom, J; Thompson, A S; Thomson, E; Tipton, P; Tiwari, V; Tkaczyk, S; Toback, D; Tollefson, K; Tomura, T; Tonelli, D; Tönnesmann, M; Torre, S; Torretta, D; Tourneur, S; Trischuk, W; Tsuchiya, R; Tsuno, S; Turini, N; Ukegawa, F; Unverhau, T; Uozumi, S; Usynin, D; Vacavant, L; Vaiciulis, A; Vallecorsa, S; Varganov, A; Vataga, E; Velev, G; Veramendi, G; Veszpremi, V; Vickey, T; Vidal, R; Vila, I; Vilar, R; Vollrath, I; Volobouev, I; Würthwein, F; Wagner, P; Wagner, R G; Wagner, R L; Wagner, W; Wallny, R; Walter, T; Wan, Z; Wang, M J; Wang, S M; Warburton, A; Ward, B; Waschke, S; Waters, D; Watts, T; Weber, M; Wester, W C; Whitehouse, B; Whiteson, D; Wicklund, A B; Wicklund, E; Williams, H H; Wilson, P; Winer, B L; Wittich, P; Wolbers, S; Wolfe, C; Worm, S; Wright, T; Wu, X; Wynne, S M; Yagil, A; Yamamoto, K; Yamaoka, J; Yamashita, Y; Yang, C; Yang, U K; Yao, W M; Yeh, G P; Yoh, J; Yorita, K; Yoshida, T; Yu, I; Yu, S S; Yun, J C; Zanello, L; Zanetti, A; Zaw, I; Zetti, F; Zhang, X; Zhou, J; Zucchelli, S
2006-01-13
We present a search for neutral supersymmetric Higgs bosons decaying to tau pairs produced in pp collisions at square root of s = 1.96 TeV. The data, corresponding to 310 pb(-1) integrated luminosity, were collected with the Collider Detector at Fermilab in run II of the Tevatron. No significant excess above the standard model backgrounds is observed. We set exclusion limits on the production cross section times branching fraction to tau pairs for Higgs boson masses in the range from 90 to 250 GeV/c2.
Abulencia, A; Acosta, D; Adelman, J; Affolder, T; Akimoto, T; Albrow, M G; Ambrose, D; Amerio, S; Amidei, D; Anastassov, A; Anikeev, K; Annovi, A; Antos, J; Aoki, M; Apollinari, G; Arguin, J-F; Arisawa, T; Artikov, A; Ashmanskas, W; Attal, A; Azfar, F; Azzi-Bacchetta, P; Azzurri, P; Bacchetta, N; Bachacou, H; Badgett, W; Barbaro-Galtieri, A; Barnes, V E; Barnett, B A; Baroiant, S; Bartsch, V; Bauer, G; Bedeschi, F; Behari, S; Belforte, S; Bellettini, G; Bellinger, J; Belloni, A; Ben-Haim, E; Benjamin, D; Beretvas, A; Beringer, J; Berry, T; Bhatti, A; Binkley, M; Bisello, D; Bishai, M; Blair, R E; Blocker, C; Bloom, K; Blumenfeld, B; Bocci, A; Bodek, A; Boisvert, V; Bolla, G; Bolshov, A; Bortoletto, D; Boudreau, J; Bourov, S; Boveia, A; Brau, B; Bromberg, C; Brubaker, E; Budagov, J; Budd, H S; Budd, S; Burkett, K; Busetto, G; Bussey, P; Byrum, K L; Cabrera, S; Campanelli, M; Campbell, M; Canelli, F; Canepa, A; Carlsmith, D; Carosi, R; Carron, S; Casarsa, M; Castro, A; Catastini, P; Cauz, D; Cavalli-Sforza, M; Cerri, A; Cerrito, L; Chang, S H; Chapman, J; Chen, Y C; Chertok, M; Chiarelli, G; Chlachidze, G; Chlebana, F; Cho, I; Cho, K; Chokheli, D; Chou, J P; Chu, P H; Chuang, S H; Chung, K; Chung, W H; Chung, Y S; Ciljak, M; Ciobanu, C I; Ciocci, M A; Clark, A; Clark, D; Coca, M; Connolly, A; Convery, M E; Conway, J; Cooper, B; Copic, K; Cordelli, M; Cortiana, G; Cruz, A; Cuevas, J; Culbertson, R; Cyr, D; Daronco, S; D'Auria, S; D'onofrio, M; Dagenhart, D; de Barbaro, P; De Cecco, S; Deisher, A; De Lentdecker, G; Dell'Orso, M; Demers, S; Demortier, L; Deng, J; Deninno, M; De Pedis, D; Derwent, P F; Dionisi, C; Dittmann, J; Dituro, P; Dörr, C; Dominguez, A; Donati, S; Donega, M; Dong, P; Donini, J; Dorigo, T; Dube, S; Ebina, K; Efron, J; Ehlers, J; Erbacher, R; Errede, D; Errede, S; Eusebi, R; Fang, H C; Farrington, S; Fedorko, I; Fedorko, W T; Feild, R G; Feindt, M; Fernandez, J P; Field, R; Flanagan, G; Flores-Castillo, L R; Foland, A; Forrester, S; Foster, G W; Franklin, M; Freeman, J C; Fujii, Y; Furic, I; Gajjar, A; Gallinaro, M; Galyardt, J; Garcia, J E; Garcia Sciveres, M; Garfinkel, A F; Gay, C; Gerberich, H; Gerchtein, E; Gerdes, D; Giagu, S; Giannetti, P; Gibson, A; Gibson, K; Ginsburg, C; Giolo, K; Giordani, M; Giunta, M; Giurgiu, G; Glagolev, V; Glenzinski, D; Gold, M; Goldschmidt, N; Goldstein, J; Gomez, G; Gomez-Ceballos, G; Goncharov, M; González, O; Gorelov, I; Goshaw, A T; Gotra, Y; Goulianos, K; Gresele, A; Griffiths, M; Grinstein, S; Grosso-Pilcher, C; Grundler, U; Guimaraes da Costa, J; Haber, C; Hahn, S R; Hahn, K; Halkiadakis, E; Hamilton, A; Han, B-Y; Handler, R; Happacher, F; Hara, K; Hare, M; Harper, S; Harr, R F; Harris, R M; Hatakeyama, K; Hauser, J; Hays, C; Hayward, H; Heijboer, A; Heinemann, B; Heinrich, J; Hennecke, M; Herndon, M; Heuser, J; Hidas, D; Hill, C S; Hirschbuehl, D; Hocker, A; Holloway, A; Hou, S; Houlden, M; Hsu, S-C; Huffman, B T; Hughes, R E; Huston, J; Ikado, K; Incandela, J; Introzzi, G; Iori, M; Ishizawa, Y; Ivanov, A; 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2006-01-13
We present a search for neutral supersymmetric Higgs bosons decaying to tau pairs produced in pp collisions at square root of s = 1.96 TeV. The data, corresponding to 310 pb(-1) integrated luminosity, were collected with the Collider Detector at Fermilab in run II of the Tevatron. No significant excess above the standard model backgrounds is observed. We set exclusion limits on the production cross section times branching fraction to tau pairs for Higgs boson masses in the range from 90 to 250 GeV/c2. PMID:16486438
Determining Supersymmetric Parameters With Dark Matter Experiments
Hooper, Dan; Taylor, Andrew M.; /Oxford U.
2006-07-01
In this article, we explore the ability of direct and indirect dark matter experiments to not only detect neutralino dark matter, but to constrain and measure the parameters of supersymmetry. In particular, we explore the relationship between the phenomenological quantities relevant to dark matter experiments, such as the neutralino annihilation and elastic scattering cross sections, and the underlying characteristics of the supersymmetric model, such as the values of {mu} (and the composition of the lightest neutralino), m{sub A} and tan {beta}. We explore a broad range of supersymmetric models and then focus on a smaller set of benchmark models. We find that by combining astrophysical observations with collider measurements, {mu} can often be constrained far more tightly than it can be from LHC data alone. In models in the A-funnel region of parameter space, we find that dark matter experiments can potentially determine m{sub A} to roughly {+-}100 GeV, even when heavy neutral MSSM Higgs bosons (A, H{sub 1}) cannot be observed at the LHC. The information provided by astrophysical experiments is often highly complementary to the information most easily ascertained at colliders.
Liu, Quanying; Balsters, Joshua H.; Baechinger, Marc; van der Groen, Onno; Wenderoth, Nicole; Mantini, Dante
2016-01-01
Objective In electroencephalography (EEG) measurements, the signal of each recording electrode is contrasted with a reference electrode or a combination of electrodes. The estimation of a neutral reference is a long-standing issue in EEG data analysis, which has motivated the proposal of different re-referencing methods, among which linked-mastoid re-referencing (LMR), average re-referencing (AR) and reference electrode standardization technique (REST). In this study we quantitatively assessed the extent to which the use of a high-density montage and a realistic head